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Large-capacitance and ultrahigh-rate electrochemical supercapacitors (UECs) with frequency response up to kilohertz (kHz) range are reported using light, thin, and flexible freestanding electrodes. The electrode is formed by perpendicularly edge oriented multilayer graphene/thin-graphite (EOG) sheets grown radially around individual fibers in carbonized cellulous paper (CCP), with cellulous carbonization and EOG deposition implemented in one step. The resulted ∼10 μm thick EOG/CCP electrode is light and flexible. The oriented porous structure of EOG with large surface area, in conjunction with high conductivity of the electrode, ensures ultrahigh-rate performance of the fabricated cells, with large areal capacitance of 0.59 mF cm −2 and 0.53 mF cm −2 and large phase angle of −83° and −80° at 120 Hz and 1 kHz, respectively. Particularly, the hierarchical EOG/CCP sheet structure allows multiple sheets stacked together for thick electrodes with almost linearly increased areal capacitance while maintaining the volumetric capacitance nearly no degradation, a critical merit for developing practical faraday-scale UECs. 3-layers of EOG/CCP electrode achieved an areal capacitance of 1.5 mF cm −2 and 1.4 mF cm −2 at 120 Hz and 1 kHz, respectively. This demonstration moves a step closer to the goal of bridging the frequency/capacitance gap between supercapacitors and electrolytic capacitors. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries (LIBs) play a crucial role in diverse applications, including electric vehicles, portable electronics, and grid energy storage, owing to their commendable features, such as high energy density, extended cycle life, and low self-discharge rates. Despite their widespread use, the growing market demands continuous efforts to enhance LIBs performance, particularly in terms of energy density and cycling stability. This paper details the development of a lithium nickel manganese oxide (LNMO - LiNi 0 · 5 Mn 1 · 5 O 4)/lithium iron phosphate (LFP - LiFePO 4) blended cathode for high-performance LIBs. The study investigates the impact of blending LFP and LNMO, examining morphological and electrochemical aspects. The usage of resonant acoustic mixing (RAM) technology is demonstrated to be a promising approach to improve the distribution of LFP and LNMO particles, leading to increased electrochemical performance. The blended LNMO/LFP cathode exhibits a specific capacity exceeding 125 mAh g−1 at C/10 and a capacity retention exceeding 80 % after 1000 cycles at 1C versus lithium. Moreover, in a full-cell configuration, the blended electrode displays a capacity retention close to 74 % after 100 cycles, showcasing a nearly 30 % improvement compared to the pure LNMO cathode. This research highlights the potential of blended cathode materials in advancing the capabilities of LIBs. [Display omitted] • Resonant acoustic mixing improves the LFP distribution on LNMO particle's surface. • LFP addition to LNMO increases the electrochemical performance of the cathode. • Low amount of LFP (2 wt%) improves the capacity retention in half and full-cell. • LFP compensates the lithium loss during cycling, acting as lithium donor. • Blended LNMO/LFP exhibits a capacity retention >80 % after 1000 cycles at 1C. [ABSTRACT FROM AUTHOR]

The heavy hybrid anion and cation redox contributes to high discharge capacity for Li-rich Mn-based cathode material, but also raises a number of issues including the low initial coulombic efficiency (ICE), rapid attenuation of capacity and voltage and so on, which have prevented its commercialization for more than a decade. Herein, solid-liquid impregnating is conducted to in-situ-build an artificial surface for Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 (FLLO) particles, which concurrently constructed a anion-redox-free LiMn 1.5 Ni 0.5 O 4 (LNMO) shell during FLLO synthesis process that completely encloses the FLLO lattice (A-2%-LNMO-FLLO), presents as solid solution structure between FLLO and LNMO coating interface and exhibits stronger bonding between coatings and FLLO cathode material. DSC, TEM and industry computed tomography (ICT) evidence that LNMO coatings is effectiveness in stabilizing the crystal structure of FLLO from macro and micro aspects, leading to the excellent electrochemical properties, such as A-2%-LNMO-FLLO exhibits a discharge capacity of 278mAh/g under 0.1C, and the capacity retention is 98.5 % after 200 cycles under 1C. Furthermore, the enhancement mechanism on electrochemical properties is investigated from aspects of reaction process and crystal structure stability. This paper can provide a theoretical and experimental support for the practical application of FLLO cathode material. [Display omitted] • LNMO shell was in-situ prepared on FLLO surface during synthesis. • The electrochemcial property was significantly improved. • The mechanism of artificial surface on enhancing cycle stability is studied. [ABSTRACT FROM AUTHOR]

This paper presents a methodology for understanding the phenomena that occur inside an actual electrode in a flow battery. We reconstruct the 3D microstructure of an electrode based on the real microstructure morphology to model the effect of mesopores on the electrode's electrochemical performance. In various reconstructed electrode structures, the presence of mesopores on carbon fibers has been shown to improve the performance compared to an electrode with no pores on the carbon fibers. This provides valuable insight for the preparation of a carbon electrode for a flow battery. In other words, the activity of carbon fibers with mesopores should be considered when preparing carbon paper, which will probably significantly improve the electrode performance. In addition, unlike the homogenous models in previous reports, simulation results showed the electrolyte flow and current density distribution in the pores and gap bridging pores. The pore interconnectivity and accessibility could be determined, which will provide significant guidance for electrode preparation to guarantee the utilization of a specific surface area. The approach proposed in this work sheds light on the phenomena inside the microstructure and provides detailed geometries for building the relationship between the structure and performance. • 3D microstructure of an actual electrode in a flow battery was reconstructed. • The previously existing homogenous models were improved. • The phenomena occurring inside an actual electrode was exhibited. • Carbon fibers constructing mesopores can improve electrode performance. • We provide valuable insight for the carbon electrode preparation. [ABSTRACT FROM AUTHOR]

Abstract The decay and lifetime of the graphite electrodes in lithium ion batteries are determined by coupling of deformation and lithium concentration. In this paper, lithium concentration and strain in graphite electrodes are investigated in-situ during an electrochemical process. We propose an experimental method to simultaneously measure the electrode concentration field and strain field in real time. A visual electrochemical simulation cell is developed, and a dual optical experimental system for in-situ image acquisition during electrochemical cycling is designed and built. On the basis of the relationship between the lithium concentration and color, we combine a color imaging technique to measure the concentration distribution. We also apply an improved digital image correlation technology to measure the strain field, and realize real time simultaneous measurements of the lithium concentration and strain distribution of graphite electrodes during the electrochemical lithiation process. It is founded that lithium concentration and strain in the graphite electrode show a nonlinear distribution along the direction of diffusion, and higher concentrations are associated with greater strain. This paper proposes a new experimental method to quantify the coupling relationship between the lithium concentration and strain, which provides an important experimental means for analyzing mechano-electrochemical coupling mechanisms. Highlights • An in-situ method is proposed to simultaneously measure Li concentration and strain. • A dual optical experiment acquisition system during electrochemical process is built. • Strain in graphite electrode is measured by the improved DIC technology. • Li concentration is successfully quantified through the electrode color. • The strain and concentration vary nonlinearly along the radial direction. [ABSTRACT FROM AUTHOR]

In this paper, we propose the design of a novel optimal strategy for charging the lithium-ion battery based on electrochemical battery model that is aimed at improved performance. A performance index that aims at minimizing the charging effort along with a minimum deviation from the rated maximum thresholds for cell temperature and charging current has been defined. The method proposed in this paper aims at achieving a faster charging rate while maintaining safe limits for various battery parameters. Safe operation of the battery is achieved by including the battery bulk temperature as a control component in the performance index which is of critical importance for electric vehicles. Another important aspect of the performance objective proposed here is the efficiency of the algorithm that would allow higher charging rates without compromising the internal electrochemical kinetics of the battery which would prevent abusive conditions, thereby improving the long term durability. A more realistic model, based on battery electro-chemistry has been used for the design of the optimal algorithm as opposed to the conventional equivalent circuit models. To solve the optimization problem, Pontryagins principle has been used which is very effective for constrained optimization problems with both state and input constraints. Simulation results show that the proposed optimal charging algorithm is capable of shortening the charging time of a lithium ion cell while maintaining the temperature constraint when compared with the standard constant current charging. The designed method also maintains the internal states within limits that can avoid abusive operating conditions. [ABSTRACT FROM AUTHOR]

The electrode, where electrochemical reactions are taken place, plays a vital role in the overall performance of vanadium flow batteries (VFBs). In this paper, a composite of manganese oxide and amorphous carbon was first synthesized from metal-organic frameworks and used as a catalyst to promote the electrochemical behavior of electrodes. The newly proposed catalyst was fabricated by a carbonization process of Mn-based metal-organic framework obtained by hydrothermal method. The morphology, composition, electrochemical activity and cell performance are respectively studied. The results show that: i) the catalyst carbonized at 900 °C possesses a smaller size, larger specific surface area, more oxygen-containing functional group and realizes superior electrochemical activity; ii) it helps the vanadium flow battery to increase its energy efficiency by 6% at 100 mA cm−2; iii) it is also beneficial to the working voltage, discharge capacity, high current density property and cycling performance of VFBs. Thus, this work can not only provide a new type of electrochemical catalyst for vanadium flow batteries, but also be significant to the improvement of the overall performance and conducive to the widespread application of vanadium flow batteries. • A composite catalyst of MnO and amorphous carbon was synthesized. • Carbon felt electrode was modified by MnO@C from metal-organic framework. • The composite carbonized at 900 °C characterizes superior electrochemical activity. • Energy efficiency of cell increases by 6% at 100 mA cm−2. [ABSTRACT FROM AUTHOR]

The rapid development and widespread use of lithium-ion batteries (LIBs) in electric vehicles and stationary energy storage systems has been stimulated by the global push toward carbon neutrality. Thus, recycling spent LIBs as an efficient way to cope with the resulting resource scarcity and environmental damage has attracted much attention. Herein, based on previous studies, a process for selective Li extraction from a recovered spent LiMn 2 O 4 (LMO) cathode with two-step molten salt treatments is proposed in this paper. The selective extraction of Li from the spent LMO cathode by (NH 4) 2 SO 4 molten salt is significantly promoted by mechanochemical treatment. Approximately 100% of the Li in the spent LMO is selectively extracted after step two of the molten salt treatment, and the Mn-containing phases in the spent LMO cathode are converted to Mn 2 O 3. A Li 2 SO 4 ·H 2 O product satisfying the requirements of Standard YS/T 1241–2018 is obtained from the purified Li 2 SO 4 water-leachate after crystallization and calcination. In addition, 93.65% Mn in the water-leaching residue of Mn 2 O 3 achieved sulfate conversion with (NH 4) 2 SO 4 molten salt reduction, and a first-grade product of MnSO 4 ·H 2 O satisfying the requirements of Standard HG/T 4823–2015 was obtained after water-leaching and crystallization. [Display omitted] • ∼100% Li in spent LMO is selectively extracted. • Molten salt lithium extraction is mechanochemically enhanced. • The process is acid and alkali free with no "three-waste" generation. • Li 2 SO 4 ·H 2 O and MnSO 4 ·H 2 O are obtained to meet the requirements of the national standard. [ABSTRACT FROM AUTHOR]

Abstract In this paper series of novel NaFe y Co 1-y O 2 (y = 0.1–1) cathode materials were synthesized and studied in terms of their structural properties, electrical conductivity and electrochemical performance in Na/Na+/Na x Fe y Co 1-y O 2 cells. The materials were fabricated by a high-temperature solid-state reaction. XRD measurements with Rietveld analysis confirmed the presence of an O3-type phase with R-3m symmetry for all compositions with the existence of the monophase region within 0.3 ≤ y ≤ 0.7 Fe substitution range. The linear variation of the unit cell parameters of the R-3m structure was found for the broad Fe concentration. The combined studies of thermogravimetric analysis, XPS and Mössbauer spectroscopy pointed at the formation of the oxygen vacancies along with spontaneous magnetization at low temperatures. The electrical conductivity of the NaFe y Co 1-y O 2 exhibits thermally activated character with low activation energies and decreases with the increasing of iron content. Electrochemical investigation of Na/Na+/Na x Fe y Co 1-y O 2 revealed changes in the character of discharge curve as a function of iron content and enabled us to select the NaFe 0.3 Co 0.7 O 2 as a material exhibiting optimal chemical composition assuring high, stable discharge capacity (180 mAh g−1) along with high operational potential. The EIS and GITT studies were performed in order to investigate the kinetics of the electrode processes. The relation between sodium diffusion coefficients and chemical composition confirmed enhanced performance in case of the NaFe 0.3 Co 0.7 O 2 material. Graphical abstract Image 1 Highlights • The phase diagram shows structural changing from P6 3 /mmc through R-3m to Pna2 1. • The substitution of Co3+ with Fe3+ increases the activation energy. • Oxygen evolution in NaFe y Co 1-y O 2 above 200 °C is shown. • NaFe 0.3 Co 0.7 O 2 was chosen as optimal composition for cathode in Na-ion batteries. [ABSTRACT FROM AUTHOR]

In this paper, the discharge performance of the Al–Mg–Sn alloy anodes with different Sn content for Al-air batteries is investigated in 4 mol L−1 NaOH solution, and their microstructure, corrosion behavior and discharge properties are discussed in detail. It shows that Sn-rich phases in the Al matrix act as cathode to promote the anode dissolution of the Al matrix and increase the electrochemical activity. The electrochemical impedance spectroscopy (EIS) results reveal that the value of hydroxide film resistance (R c) increases as Sn content increases to 0.5 wt%, indicating that Sn addition can improve the corrosion resistance and therefore reduce the hydrogen evolution rate (HER). As a result, the Al-0.6Mg-0.2Sn alloy shows good discharge performance at low current density and its peak energy density reaches 2858.6 mWh∙g−1 at 20 mA cm−2 with the discharge capacity of 2341.9 mAh∙g−1. The Al-0.6Mg-0.5Sn alloy presents good discharge performance at high current density and its peak anode efficiency reaches 93.21% at 40 mA cm−2. When Sn content is up to 0.8 wt%, excessive Sn-rich phases aggravate the hydrogen evolution corrosion and intergranular corrosion, which results in more weight loss. This is responsible for the unsatisfactory discharge performance of Al-0.6Mg-0.8Sn alloy at all current density. [Display omitted] • Moderate Sn-rich phases improve the discharge performance of Al–Mg–Sn alloy. • Excessive Sn-rich phases deteriorate the discharge performance of Al–Mg–Sn alloy. • Peak energy density of Al-0.6Mg-0.2Sn alloy reaches 2858.6 mWh∙g−1 at 20 mA cm−2. • Peak anode efficiency of Al-0.6Mg-0.5Sn alloy reaches 93.21% at 40 mA cm−2. [ABSTRACT FROM AUTHOR]

VO 2 is a good cathode material for aqueous zinc ion batteries (AZIBs). However, V4+ is not stable in weakly acidic aqueous electrolyte, while the voltage range of AZIBs with VO 2 as cathode in charge/discharge test is limited, usually below 1.5 V. In this paper, VO 2 is synthesized by solvothermal method and in situ electrochemically converted to Zn 2 V 2 O 7 as cathode material for AZIBs with superior performance, and the two drawbacks of narrow voltage range in charge/discharge test and easy dissolution of V4+ are solved. After 10 cycles, the VO 2 cathode offers a discharge specific capacity of 408.4 mAh g−1 from an initial discharge specific capacity of 329.8 mAh g−1 at a current density of 0.1 A g−1. After 124 cycles, the maximum discharge capacity is 271.7 mAh g−1, while the initial discharge capacity is 16.2 mA h g−1 at a current density of 10 A g−1. The results of XRD and XPS show that the VO 2 cathode is in situ electrochemically transformed into Zn 2 V 2 O 7 within the first few cycles. With its improved performance, high cycle stability under long cycles and high current density, the in-situ converted Zn 2 V 2 O 7 offers a new approach for the development of cathode materials for AZIBs. [Display omitted] • Solvothermal synthesis of VO 2 and in situ electrochemical transformation of Zn 2 V 2 O 7. • In situ converted VO 2 cathode with good electrochemical performance. • In-situ converted VO 2 cathode with larger charge/discharge range of voltage. [ABSTRACT FROM AUTHOR]

For the first time, we report a poly (2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA)-based organic electrode with 100 wt% active material loading. The electrochemical performance of the PTMA electrode for organic batteries was improved by replacing the aluminum current collector by graphite ones. The use of graphite current collector reduces the cell weight and increases its mechanical flexibility. The resulting battery with the new carbon conductor- and binder-free organic electrode with polyimide-based gel polymer electrolyte (GPE) displayed significantly higher increased energy density (470 Wh kg −1 vs . cell weight), which is essential for making organic batteries competitive with conventional Li ion batteries. [ABSTRACT FROM AUTHOR]

Excellent rate performance of Li 4+x Ti 5 O 12 (0 < x < 3, LTO) electrodes results from mixed Li site occupancy and facile Li ion exchange at 8a and 16c sites. In this paper, we reveal that inter-particle connectivity within LTO electrodes affects 8a and 16c site occupancies upon discharge and impacts Li ion diffusion. LTO electrodes of the same primary crystal structure but of different grain boundary structures were prepared and they showed significantly different electrochemical performance. LTO electrodes with a percolated 3D structural network and bridged grain boundaries offered balanced 8a-16c occupancy, Li ion exchange at 8a and 16c sites upon discharge, high ionic conductivities, and good rate performance. While LTO electrodes with isolated clusters of particles showed strong rate dependence of 8a-16c occupancy, a lack of Li ion exchange at 8a and 16c sites, large over-potential, and substantial capacity decay upon fast charging. Bridged grain boundaries in LTO secondary particles facilitate apparent solid-solution process during electrochemical cycling by maintaining Li site exchange and thus enhance the rate performance of LTO electrodes. [ABSTRACT FROM AUTHOR]

The aim of the paper is to present a promising approach for recycling high value-added metals from the cathode materials of spent LIBs. The synthesis process of NCM cathode material enlightened us to apply reduction roasting to break LiNi x Co y Mn z O 2 into simple compounds or metals. Accordingly, the effect of several factors such as temperature, carbon dosage and roasting time is assessed on the leaching efficiency of valuable metals. The roasted products are analyzed by XRD and SEM-EDS, and the results show that the cathode material after reduction roasting is primarily transformed into Li 2 CO 3 , Ni, Co and MnO. However, the solubility of Li 2 CO 3 is relatively low, so carbonated water leaching is used to treat the roasted products. Then the filtrate is evaporated for the preparation of pure Li 2 CO 3 , and residue is leached to recycle other metals with H 2 SO 4 . The results indicate that, after roasted at 650 °C for 3 h with 19.9% carbon dosage, 84.7% Li is preferentially recovered via carbonated water leaching, and more than 99% Ni, Co and Mn are recycled via acid leaching without adding reductant. Finally, the products of Li 2 CO 3 , NiSO 4 , CoSO 4 and MnSO 4 are obtained. The process have great potential for industrial-scale recycling from spent LIBs. [ABSTRACT FROM AUTHOR]

This paper presents a computational model of a single chamber, air-cathode MFC. The model considers losses due to mass transport, as well as biological and electrochemical reactions, in both the anode and cathode half-cells. Computational fluid dynamics and Monod-Nernst analysis are incorporated into the reactions for the anode biofilm and cathode Pt catalyst and biofilm. The integrated model provides a macro-perspective of the interrelation between the anode and cathode during power production, while incorporating microscale contributions of mass transport within the anode and cathode layers. Model considerations include the effects of pH (H + /OH − transport) and electric field-driven migration on concentration overpotential, effects of various buffers and various amounts of buffer on the pH in the whole reactor, and overall impacts on the power output of the MFC. The simulation results fit the experimental polarization and power density curves well. Further, this model provides insight regarding mass transport at varying current density regimes and quantitative delineation of overpotentials at the anode and cathode. Overall, this comprehensive simulation is designed to accurately predict MFC performance based on fundamental fluid and kinetic relations and guide optimization of the MFC system. [ABSTRACT FROM AUTHOR]

LiNi x Mn y Co z O 2 (x + y + z = 1, x > 0.6) Ni-rich layered structures are the most investigated and used cathode materials these days due to their high energy density. However, it is hard to avoid Li/Ni intermixing during synthesis and the charge/discharge cycle. This intermixing is known to degrade the cathode by inducing anisotropic stresses and phase transformations. On the other hand, some studies report that a certain amount of intermixing enhances electrochemical properties. Studying the detailed effect of the intermixing using an atomistic simulation may help in designing the cathode structure. In this paper, an interatomic potential for the Li–Ni–Mn–Co–O quinary system is developed by newly developing or modifying interatomic potentials for sub-unary, binary and ternary systems based on a second-nearest-neighbor modified embedded-atom method (2NNMEAM) formalism combined with a charge equilibration (Qeq) concept. This potential is used to analyze the effect of Li/Ni intermixing on Ni-rich cathode properties from three perspectives: lithium diffusion for rate properties, change in lattice parameter and internal stress for structural stability. The results show how the intermixing affects individual cathode properties and that controlling the intermixing will be particularly decisive in Ni-rich cathode materials. The Li–Ni–Mn–Co–O quinary potential also will be useful for analyzing and designing cathode materials. [Display omitted] • Develop a 2NNMEAM + Qeq interatomic potential for Li–Ni–Mn–Co–O quinary system. • Reproduce physical properties of the relevant quinary and sub-systems. • Analyze the effect of Li/Ni intermixing in Ni-rich layered cathode. • This potential can be used for further analyzing and designing cathode materials. [ABSTRACT FROM AUTHOR]

At present, the topic of building high-performance, miniaturized and mechanically flexible energy storage modules which can be directly integrated into textile based wearable electronics is a hotspot in the wearable technology field. In this paper, we reported a highly flexible fiber-shaped electrode fabricated through a one-step convenient hydrothermal process. The prepared graphene hydrogels/multi-walled carbon nanotubes-cotton thread derived from natural cotton thread is electrochemically active and mechanically strong. Fiber-shaped supercapacitor based on the prepared fiber electrodes and polyvinyl alcohol-H 3 PO 4 gel electrolyte exhibits good capacitive performance (97.73 μF cm −1 at scan rate of 2 mV s −1 ), long cycle life (95.51% capacitance retention after 8000 charge-discharge cycles) and considerable stability (90.75% capacitance retention after 500 continuous bending cycles). Due to its good mechanical and electrochemical properties, the graphene hydrogels/multi-walled carbon nanotubes-cotton thread based all-solid fiber-shaped supercapacitor can be directly knitted into fabrics and maintain its original capacitive performance. Such a low-cost textile thread based versatile energy storage device may hold great potential for future wearable electronics applications. [ABSTRACT FROM AUTHOR]

Electrochemical capacitor (EC) applications have broadened tremendously since EC energy storage devices were introduced in 1978. Then typical applications operated below 10 V at power levels below 1 W. Today many EC applications operate at voltages approaching 1000 V at power levels above 100 kW. This paper briefly reviews EC energy storage technology, shows representative applications using EC storage, and describes engineering approaches to design EC storage systems. Comparisons are made among storage systems designed to meet the same application power requirement but using different commercial electrochemical capacitor products. [ABSTRACT FROM AUTHOR]

Sulfur cathodes for lithium–sulfur batteries have been designed to be combined with conductive carbon because the insulating nature of sulfur causes low active material utilization and poor rate capability. This paper is the first to report that carbon can induce a phase transition in a sulfur cathode. The stable form of a sulfur crystal at ambient temperature is orthorhombic sulfur. We found that monoclinic sulfur becomes more stable than orthorhombic sulfur if carbon atoms penetrate into the sulfur at elevated temperatures and the carbon density exceeds a threshold of C 0.3 S 8 . The high stability of the carbon-containing monoclinic sulfur persists during lithiation and is attributed to locally formed linear SC 3 S chains with marked stability. This study provides a novel perspective on the role of carbon in the sulfur cathode and suggests control of the crystal phase of electrodes by composite elements as a new way of designing efficient electrode materials. [ABSTRACT FROM AUTHOR]

In this paper we present a three-dimensional computational formulation for electrode-electrolyte-electrode system of Li-Ion batteries. The physical consistency between electrical, thermal and chemical equations is enforced at each time increment by driving the residual of the resulting coupled system of nonlinear equations to zero. The formulation utilizes a rigorous volume averaging approach typical of multiphase formulations used in other fields and recently extended to modeling of supercapacitors [1] . Unlike existing battery modeling methods which use segregated solution of conservation equations and idealized geometries, our unified approach can model arbitrary battery and electrode configurations. The consistency of multi-physics solution also allows for consideration of a wide array of initial conditions and load cases. The formulation accounts for spatio-temporal variations of material and state properties such as electrode/void volume fractions and anisotropic conductivities. The governing differential equations are discretized using the finite element method and solved using a nonlinearly consistent approach that provides robust stability and convergence. The new formulation was validated for standard Li-ion cells and compared against experiments. Its scope and ability to capture spatio-temporal variations of potential and lithium distribution is demonstrated on a prototypical three-dimensional electrode problem. [ABSTRACT FROM AUTHOR]

Nanostructured silicon electrodes have attracted attention as a potential candidate for high capacity anode in lithium-ion batteries, thanks to their high specific capacity and their ability to accommodate silicon volume changes upon cycling. However, the silicon amount deposited on these nanostructured electrodes is generally low and leads to low surface capacities. Here, a new structure is proposed to increase the areal density of silicon on the electrode. A second growth of secondary nanowires on a silicon nanowires electrode leads to a “nano-tree” structure with surface capacities between 1.8 and 7.1 mAh cm −2 . These high loaded electrodes maintain very good rate capabilities and a rather stable cycling is observed for the intermediate loadings, with a capacity maintained above 2 mAh cm −2 after 100 cycles at C/5. This paper provides evidence of a successful synthesis of high loaded silicon electrodes for practical applications, of which the electrochemical performances outperform those of graphite commercial anodes. [ABSTRACT FROM AUTHOR]

A novel configuration of two electrodes containing electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) pressed into a bifunctional air electrode is designed for rechargeable Zn–air batteries. MOC/25BC carbon paper (MOC consisting of α-MnO 2 and XC-72 carbon black) and Fe 0.1 Ni 0.9 Co 2 O 4 /Ti mesh on this air electrode mainly serve as the cathode for the ORR and the anode for the OER, respectively. The morphology and physicochemical properties of Fe 0.1 Ni 0.9 Co 2 O 4 are investigated through scanning electron microscopy, inductively coupled plasma-mass spectrometry, and X-ray diffraction. Electrochemical studies comprise linear sweep voltammetry, rotating ring-disk electrode voltammetry, and the full-cell charge–discharge–cycling test. The discharge peak power density of the Zn–air battery with the unique air electrode reaches 88.8 mW cm −2 at 133.6 mA cm −2 and 0.66 V in an alkaline electrolyte under an ambient atmosphere. After 100 charge–discharge cycles at 10 mA cm −2 , an increase of 0.3 V between charge and discharge cell voltages is observed. The deep charge–discharge curve (10 h in each step) indicates that the cell voltages of discharge (1.3 V) and charge (1.97 V) remain constant throughout the process. The performance of the proposed rechargeable Zn–air battery is superior to that of most other similar batteries reported in recent studies. [ABSTRACT FROM AUTHOR]

Tin with a theoretical capacity of 993 mAh g −1 is considered as a promising anode material for lithium ion batteries (LIBs). However, under the intercalated-Li + state, large volume deformation in tin active materials may result in cracks and flakes that seriously affect the cycle stability of LIBs. In this paper, the indentation load-displacement behaviors of Li x Sn (0 ≤ x ≤ 4.4) alloys with various charge states are tested to determine their hardness, elastic modulus, yield strength and hardening exponent. In conjunction with finite element modeling and dimensional analysis, the stress–strain relationships of Li x Sn alloys are obtained by using a power-law hardening model. Furthermore, the evolution of stress–strain relationships is investigated as the change of charge states. [ABSTRACT FROM AUTHOR]

PEM fuel cells can be operated within a wide range of different operating conditions. In this paper, the special case of operating a PEM fuel cell with a dry cathode supply and without external humidification of the cathode, is considered. A deeper understanding of the water management in the cells is essential for choosing the optimal operation strategy for a specific system. In this study a theoretical model is presented which aims to predict the location in the flow field at which liquid water forms at the cathode. It is validated with neutron images of a PEM fuel cell visualizing the locations at which liquid water forms in the fuel cell flow field channels. It is shown that the inclusion of the GDL diffusion resistance in the model is essential to describe the liquid water formation process inside the fuel cell. Good agreement of model predictions and measurement results has been achieved. While the model has been developed and validated especially for the operation with a dry cathode supply, the model is also applicable to fuel cells with a humidified cathode stream. [ABSTRACT FROM AUTHOR]

Cobalt sulfides have become promising electrode materials for lithium ion batteries while their applications in rechargeable magnesium batteries are rarely reported. In this paper, we have done some research on the electrochemical properties of cobalt sulfide (CoS) as the cathode-active material for rechargeable magnesium batteries. Flower-like CoS with nanostructures is synthesized by a facile solvothermal route. The obvious redox peaks on the cyclic voltammetric curves confirm the possibility of applications. The galvanostatic charge–discharge tests display excellent cycle stability and high coulomb efficiency. Meanwhile, the possible mechanism of charge–discharge reactions is proposed and discussed. These results show that flower-like CoS is a promising candidate as cathode-active material for rechargeable magnesium batteries. [ABSTRACT FROM AUTHOR]

This paper is devoted to the study of composite cathodes of La 2 NiO 4+δ infiltrated into a Gd-doped ceria backbone. Porous Gd-doped ceria backbones are screen printed onto yttria-stabilized zirconia or Gd-doped ceria dense electrolytes, and infiltrated with a La and Ni nitrate solution (2:1 stoichiometry ratio). The influence of the preparation parameters on the polarization resistance, such as the concentration of the infiltration solution, the amount of infiltrated phase, the annealing temperature, the thickness of the electrode, and the nature of the electrolyte, is characterized by impedance spectroscopy performed on symmetrical cells. The optimization of these parameters results in a decrease of the polarization resistance down to 0.15 Ω cm 2 at 600 °C. Using the Adler-Lane-Steele model, the modelling of the impedance diagrams leads to the determination of the ionic conductivity as well as the surface exchange rate of the infiltrated electrode. [ABSTRACT FROM AUTHOR]

In the present paper, flower-like multimodal porous ZnCo 2 O 4 microspheres, comprised of numerous nanosheets, are synthesized through PVP assist solvothermal self-assembling process. The multimodal porous ZnCo 2 O 4 microspheres are characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). A possible formation mechanism of two steps self-assemble is proposed. The ZnCo 2 O 4 microspheres are then used as an anode material to fabricate lithium ion batteries. The results based on the evaluation of lithium ion batteries demonstrate that the porous microstructure offers the excellent electrochemical performance with high capacity and long-life cycling stability. It is found that a high reversible capacity of 940 and 919 mAh g −1 is maintained after 100 cycles at a low charge–discharge rate of 0.1C and 0.2C (100 and 200 mA g −1 ), respectively. Meanwhile, the remaining discharging capacity reaches as high as 856 mAh g −1 after 1000 cycles subject to the large current density up to 1C. [ABSTRACT FROM AUTHOR]

The manufacturing methods for liquid electrolyte-free Al polymer capacitors are introduced by using new materials like novel oxidants, separators and negative current collectors. The Al polymer capacitor is constructed by an Al foil as an anode, Al 2 O 3 as a dielectric, and poly(3, 4-ethylenedioxythiophene) (PEDOT) as a cathode. There are also various synthetic methods of 3, 4-ethylenedioxythiophene (EDOT) and the chemical polymerization of PEDOT from EDOT using iron benzenesulfonate as a new oxidant and dopant. Furthermore, various cathodic current collectors such as conventional Al foils, carbon and titanium dioxide deposited on Al foils or substrates, as well as various separators with manila-esparto paper and synthetic fibers (series of acryl, PET, etc.) are studied. The Al polymer capacitors with the newly introduced oxidant (iron benzenesulfonate), separator (aramid based synthetic fibers) and current collector (TiO 2 ) exhibit considerably enhanced capacitance values and the extremely low resistance (7 mΩ), so there is low power consumption and high reliability. Additionally, the newly developed Al polymer capacitor is guaranteed for 5,000 h at 125 °C, which means there is a long life time operation over ∼ 5 × 10 6 h at 65 °C. [ABSTRACT FROM AUTHOR]

Atomically thin graphene is a promising capacitor electrode material, but the cell voltages achieved so far with various electrolytes are too low for a typical capacitor's application. In this paper it is demonstrated that in a dicyanamide-based ionic liquid electrolyte a graphene electrode passivates at 10 V and at the same time the conductivity of the single-layer graphene sheet increases more than 5 times. The protective self-healing nanolayer formed is a new carbon–nitrogen material with dielectric constant value up to 9.8. In the cell voltage range from 4 to 10 V, capacitors with large surface area reduced graphene oxide electrodes outperform any commercial capacitor technology by better energy density. [ABSTRACT FROM AUTHOR]

Magnesium nickel hydride (Mg 2 NiH 4 ) used as negative electrode material in nickel-metal hydride (Ni-MH) secondary battery is modified by nano-nickel via mechanical milling. In this paper, we systematically investigate the microstructure and electrochemical properties of the modified system with different milling durations. X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analyses confirm the amorphous transformation of Mg 2 Ni-based hydride and a novel NiH 0.75 nanocrystalline with a diameter of about 5 nm embedding or covering on the surface of the base particle has been observed. Its formation mechanism and positive effects on electrochemical properties of the Mg 2 NiH 4 have also been elaborated. Electrochemical measurements show that the 5 h milled composite possesses markedly increased discharge capacity up to 896 mAh g −1 . With prolonging the milling duration from 5 h to 40 h, the discharge capacity at the 10th cycle increases from 99 mAh g −1 to 359 mAh g −1 . Besides, the discharging procedure changes from stepwise processes to one single-step process with increasing the milling duration. Tafel polarization test shows that the nano-nickel modified system exhibits a much better anti-corrosion ability during charging/discharging cycles. Meanwhile, both the charge-transfer reaction on the alloy surface and hydrogen diffusion inside the alloy bulk are enhanced with nano-nickel modification. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, a novel additive, calcium metaborate (CMB), is proposed to improve the high-temperature characteristics of the nickel electrodes for nickel–metal hydride batteries. As a soluble calcium salt, CMB can easily and uniformly be dispersed in the nickel electrodes. The effects of CMB on the nickel electrode are investigated via a combination of cyclability, capacity retention, electrochemical impedance spectroscopy, scanning electron microscope and X-ray diffraction. Compared with conventional nickel electrodes, the electrode containing 0.5 wt.% CMB exhibits superior electrode properties including enhanced discharge capacity, improved high-rate discharge ability and excellent cycle stability at an elevated temperature (70 °C). The improved cell performance of the nickel electrode containing CMB additives can be attributable to the increased oxygen evolution overvoltage and slower oxygen evolution rate. Compared with insoluble calcium salts, such as Ca(OH)2, CaCO3, and CaF2, CMB is more effective as a cathode additive to improve the high-temperature performance of Ni–MH batteries. [Copyright &y& Elsevier]

Abstract: This paper proposes a strategy to reduce the diffusion induced stress and enhance the capacity of a layered electrode by allowing the plastic deformation of current collector. Based on analytical formulations of the stress in whole electrode, three types of elastoplastic behaviors of current collector, i.e. pure elastic deformation, plastic shakedown and cyclic plasticity, are identified. Criterions separating the three cases are proposed. It is found applying a thin current collector and allowing it to plastically yield in the charge/discharge cycles is beneficial not only to capacity as more space can be provided for active materials but also to electrochemical stability because the stress in active layer is significantly reduced. Structural design corresponding to plastic shakedown shows good balance between the said improvements and structural safety, whereas the case of cyclic plasticity further enhances the improvements. Therefore, structural designing scheme is provided for the former case according to the criterion of plastic shakedown but for the latter one based on the Coffin–Manson relation with expected cycle life. [Copyright &y& Elsevier]

In the present paper, we demonstrate how modifications of the microstructure and the chemical composition can influence the electrochemical behavior of cathodes for molten carbonate fuel cells (MCFCs). Based on our experience, we designed new MCFC cathode microstructures combining layers made of porous silver, nickel oxide or nickel foam to overcome common issues with the internal resistance of the cell. The microstructures of the standard NiO cathode and manufactured cathodes were extensively investigated using scanning electron microscopy (SEM) and porosity measurements. The electrochemical behavior and overall cell performance were examined by means of electrochemical impedance spectroscopy and single-cell tests in operation conditions. The results show that a porous silver layer tape cast onto standard NiO cathode and nickel foam used as a support layer for tape cast NiO porous layer substantially decrease resistance components representing charge transfer and mass transport phenomena, respectively. Therefore, it is beneficial to combine them into a three-layer cathode since it facilitates separation of predominant physio-chemical processes of gas and ions transport in respective layers ensuring high efficiency. The superiority of the three-layer cathode has been proven by low impedance and high power density as compared to standard NiO cathode. • New layered MCFC cathodes were designed, manufactured and characterized. • Presence of porous silver layer decreases charge transfer resistance of MCFC cathode. • Presence of nickel foam decreases mass transfer resistance of MCFC cathode. • The combined effects of silver layer and nickel foam is demonstrated. [ABSTRACT FROM AUTHOR]

Taking into account the increasing global demand for sustainable energy storage in recent years, it is essential to find advanced environmentally-friendly energy storage systems with low cost and excellent performance. Rechargeable Zn-based batteries (RZBs) have attracted much attention owing to the safety, good reversibility, high theoretical capacity (820 mAh/g), and low redox potential (−0.763 V vs. the standard hydrogen electrode (SHE)) of metallic Zn. In addition, such technology has potential applications in electric vehicles, portable electronic devices, and other electrical systems. This paper first outlines the differences and connections between Zn-ion batteries (ZIBs) and Zn-air batteries (ZABs) and summarizes their reaction mechanisms, theoretical performance, and battery composition, among other properties. Secondly, the influence of the structure of the anode and the cathode materials on the electrochemical performance is summarized, and the bottlenecks encountered in the development of the technology and their corresponding solutions are described. Finally, the development and application potential of wearable batteries are reviewed, and suggestions for improving battery stability, safety, and efficiency are proposed. This review not only summarizes the current research status of ZIBs and ZABs but also provides new ideas for the design of high-performance RZBs. • The mechanisms of Zn-ion and Zn-air batteries are provided. • The factors of kinetics and stability of electrode materials are summarized. • The key issues for electrode materials of Zn-Based batteries are proposed. • Some perspective about high performance Zn-Based batteries are presented. [ABSTRACT FROM AUTHOR]

Electrolyte is the key to improve the safety, cycle performance and temperature adaptation of lithium batteries. In this paper, we introduce a novel electrolyte that based on ionic liquids (ILs) 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (PYR 14 -TFSI) and fluorinated solvent 1,1,1,3,3,3-hexafluoroisopropyl methyl ether (HFPM). HFPM can significantly reduce the viscosity of PYR 14 -TFSI and enhance the wettability with Celgard separators. In addition, the coordination of PYR 14 -TFSI and HFPM promotes the local dissolution of lithium nitrate and helps to form a stable cathode/anode interface film. The electrochemical test shows that the electrochemical window of the electrolyte can reach to 5.35 V. For the Li/LiNi 0.6 Co 0.2 Mn 0.2 O 2 half cells, the capacity retention is 94% and the Coulomb efficiency is 99.9% after 100 cycles at 0.5 C. The uniform and dense interface film is characterized and confirmed by scanning electron microscopy and X-ray photoelectron spectroscopy, etc. Furthermore, the half-cell also exhibits good thermal stability at high temperature. Considering ILs and fluoroether are non-flammable solvent, this work may pave the way for designing future generation high-performance electrolyte for lithium batteries. • A new electrolyte system for high voltage and safety batteries was developed. • Ionic liquids and HFPM regulate the cathode/anode interface simultaneously. • The HFPM enhances the electrochemical performance of Li/NCM622 half-cells. [ABSTRACT FROM AUTHOR]

In this paper, we present a neutral non-enzymatic glucose biofuel cell (GBFC) based on a Pt/Au nano-alloy anode. We synthesize Pt/Au alloy anodes by the electrochemical deposition of a Pt/Au nano-alloy on the surface of a thin polyethylene terephthalate membrane with a uniformly distributed microhemispheric array. The experimental results demonstrate that the proposed GBFC can generate a maximum power density of 0.32 mW/cm2, an open-circuit voltage (V oc) of 0.42 V, and a short-circuit current (I sc) density of 2.67 mA/cm2 with 5 mM of glucose in a 0.1-M PBS (pH 7.4) solution while the cathode is being supplied with 7% saturated oxygen. The synergistic effect of the Pt/Au bimetallic alloy is found to improve the performance of the proposed GBFC. The proposed neutral non-enzymatic GBFC shows promising feasibility as an implantable power supply system for the provision of continuous and consistent electricity to a continuous glucose monitoring system. Image 1 • We proposed a neutral non-enzymatic GBFC with a nanostructured Pt/Au alloy anode. • The proposed GBFC could produce a P max of 0.32 mW/cm2 and a V oc of 0.42 V. • The synergistic effect of the Pt/Au alloy improves the performance of the GBFC. • The proposed novel GBFC shows promising feasibility for implantable applications. [ABSTRACT FROM AUTHOR]

A binder-free LiNi 0.5(1-x) Mn 1.5(1-x/3) Cr x O 4 (Cr-doped LNMO)/carbon fiber (CF) cathode with carbon paper as the current collector is developed via a process that involves electrochemical deposition, hydrothermal reaction, and vacuum filtration. The composite material properties are thoroughly characterized using scanning electron microscopy/transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The Cr-doped LNMO active materials are composed of submicron particles with polyhedral and spinel crystal structures with good crystallinity. The LiNi 0.5(1-x) Mn 1.5(1-x/3) Cr x O 4 (x = 0.2) configuration is found to have a higher Mn4+/Mn3+ ratio and is capable of delivering a reversible capacity of ~137 mAh g−1 at 0.2 C, due to the active Ni2+/Ni3+/Ni4+ and Cr3+/Cr4+ redox reactions. Furthermore, it exhibits an enhanced rate capability with 118 mAh g−1 at 5 C. This is evidenced by a reduction in charge transfer resistance at the solid/electrolyte interface, and accelerated ion diffusion in the host material corresponding to a high degree of cation disordering in Cr-doped LNMO. Overall, the binder-free electrode, which integrates Cr-doped LNMO and a 3D CF-based framework, facilitates the electrochemical activity of the active material. This leads to improved cycling stability with 99% capacity retention over 200 cycles against high voltage (4.9 V vs. Li/Li+). Image 1 • A Cr-doped LNMO/CF/CP cathode is developed without binders and conductive agents. • The composite cathode shows prominent high-voltage cycling and rate performance. • Moderate Cr doping in LNMO contributes to structural stability under high voltage. • 3D binder-free CF-based electrode design leads to good high-voltage performance. [ABSTRACT FROM AUTHOR]

Among many promising cathode materials for SIBs, the transition metal oxides have attracted especially extensive attention for uncostly and environmental-friendly. In this paper, the Na 0 · 44 Mn 2/3 Co 1/6 Ni 1/6 O 2 tunnel cathode material with a hollow porous spherical structure is successfully prepared. Short distance for Na+ diffusion leads to good Na+ diffusion kinetics, so it has excellent rate performance, with the specific discharge capacity of 133 mAh g−1, 127 mAh g−1, 116 mAh g−1, 95 mAh g−1, and 72 mAh g−1 at charge and discharge rates of 0.1 C, 0.2 C, 0.5 C, 1 C, and 2 C (1 C = 120 mA g−1), respectively. The unique hollow porous structure ensures its excellent cycle stability. Therefore, designing a hollow and porous three-dimensional spherical structure is an effective method. Furthermore, it provides a reliable way for the modification of the cathode material for SIBs in the future. Image 1 • The novel micron hollow porous spherical NaMCNO-P cathode was synthesized. • NaMCNO-P hollow porous sphere reveals superior cycle stability and rate capability. • NaMCNO-P shortens the diffusion path of Na+ to obtain higher diffusion coefficient. [ABSTRACT FROM AUTHOR]

Ni-rich layered oxides LiNi x TM 1-x O 2 (TM = Co, Mn, Al, x > 0.6) cathode materials for lithium-ion batteries have an anisotropic volume change during lithium deintercalation process, which easily causes microcracks and rapid capacity decay. In the paper, carbonate precursor prepared by a urea-based hydrothermal method is lithiated at different temperatures of 750–850 °C to obtain agglomerate LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathode material with different primary sizes. The sample synthesized at 750 °C shows broadening diffraction peaks due to its near-nano grain size, which results in the merging of (006)/(012) and (018)/(110) peaks. The effect of anisotropic volume shrinkage is effectively weakened by fine grain range, which alleviates formation of intergranular crack that is commonly considered as an important reason for capacity decay of Ni-rich layered oxide cathode materials. In addition, two new types of intragranular microcracks are first identified in cyclic NCM811. One extends along the spinel phase and layered phase interface, and the other extends along the vertical (003) R crystal plane. The difference in atomic plane spacing during the electrochemical cycles plays a key role in the growth of intragranular microcracks. • Grain size refinement weakens the effect of anisotropic volume change. • The grain boundary misalignment induces generation of intergranular cracks. • Two new types of intragranular microcracks are first identified in cycled NCM811. [ABSTRACT FROM AUTHOR]

The operating temperature determines the energy consumption and lithium extraction rate of a pyrometallurgical process. This paper aims to employ a molten ammonium sulfate ((NH 4) 2 SO 4) assisted roasting approach to recovering and regenerating LiCoO 2 from spent lithium-ion batteries (LIBs) at 400 °C. First, cathode materials from the spent LIBs are converted to CoSO 4 and Li 2 SO 4 via a sulfation roasting approach. Both recovery rates of Li and Co reach over 98% at 400 °C for 2h and at an (NH 4) 2 SO 4 /(cathode materials) mass ratio of 4:1 in Ar atmosphere. Then, the obtained Co(OH) 2 and Li 2 CO 3 are used to regenerate LiCoO 2 that delivers a specific capacity of over 154 mAh g−1 at 1C with capacity retention of 94% after 100 cycles. Overall, the molten (NH 4) 2 SO 4 assisted roasting approach reduces the operating temperature to 400 °C while maintaining a high extraction rate of over 98% for both Li and Co, promising an energy-efficient approach to recovering various cathode materials from spent LIBs. Image 1 • LiCoO 2 is converted to Li 2 SO 4 and CoSO 4 by an (NH 4) 2 SO 4 roasting process. • The optimum roasting temperature is 400 °C. • The recovery rates are over 98% for both Li and Co. • No hazardous chemicals such as strong acids are employed. • LiCoO 2 is regenerated and shows good battery performances. [ABSTRACT FROM AUTHOR]

Storage of nickel-rich LiNi 1-x-y Mn x Co y O 2 positive active materials under improper environmental conditions brings about undesirable surface reactions causing poor Li-ion cell electrochemical performances and gas generation. In this paper, a detailed stepwise investigation of the increasing reactivity of 532, 622, 811 and 901 NMC materials towards a specific H 2 O/CO 2 atmosphere is reported. Water-soluble salts as lithium carbonate, hydroxide and sulfates are accurately quantified thanks to acid-base titration and inductively coupled plasma atomic emission spectroscopy techniques. On the other hand, the presence of insoluble species as transition metal oxyhydroxides and oxides is unveiled through a thermal decomposition study using thermogravimetric mass spectrometer coupling technique. Their formation and thermal decomposition mechanisms are proposed after careful analysis of the characteristic mass loss and O 2 , CO 2 and H 2 O evolution profile in the 50–500 °C region. Interestingly, the results also highlight an in situ lithiated layered oxide material reformation reaction. To assess their chemical reactivity towards LiPF 6 -based electrolyte, the latter was analyzed through 19F nuclear magnetic resonance after storage with various reference salts and 811 NMC. LiPO 2 F 2 is detected from storage tests with Li 2 CO 3 , Li 2 O and Li 2 SO 4 , and fluorophosphate-type molecules are detected from LiOH; this experiment can help discriminate between LiOH and Li 2 O as NMC surface species. • NMCs surface species composition before and after H 2 O/CO 2 exposure is elucidated. • Warder's titration method allows for an accurate quantification of OH− and CO 3 2−. • ICP-AES, IR and SEM/EDX data indicate the presence Li or Na sulfates. • The amount of basic species increases in Ni-rich NMCs surfaces. • Li 2 O is postulated instead of LiOH through 19F NMR analysis of the electrolyte. [ABSTRACT FROM AUTHOR]

Highly effective cathode materials are critical to improve existing Li–O 2 batteries. In this paper, we report a free-standing Co 3 O 4 @NiCo 2 O 4 sheet array cathode, which is prepared by in-situ growing an array of sword-like cobalt-based metal-organic framework (Co-MOF) sheets on a carbon cloth (CC) substrate, followed by impregnated with nickel nitrate solution and pyrolyzed in air flow. The Co 3 O 4 @NiCo 2 O 4 /CC cathode exhibits excellent ORR/OER bifunctional activity and high cathodic performance in a Li–O 2 battery, achieving a specific capacity of 10645 mAh g−1 and a stability of 225 cycles. We suggest the high performance of our cathode can be ascribed to its well-defined 3D sheet array structure, which can facilitate O 2 diffusion and electrolyte impregnation, provide sufficient space for the discharge products, and the synergistic effect between Co 3 O 4 and NiCo 2 O 4. This work provides an effective method for the rational design of electrode composition and structure. Image 1 • A sword-like Co 3 O 4 @NiCo 2 O 4 nanosheet array cathode for Li–O 2 battery is prepared. • The cathode exhibited enhanced bifunctional OER/ORR activities in Li–O 2 batteries. • The high performance can be ascribed to its hybrid and array structure. • A high specific capacity of 10645 mAh g−1 with stability of 225 cycles is achieved. [ABSTRACT FROM AUTHOR]

As an emerging energy storage technology, potassium-ion batteries (KIBs) are suitable for large-scale energy storage applications due to their abundant resources and low cost, but the known anode materials generally exhibit poor electrochemical performance. In this paper, synthesis of sulfur-doped bamboo charcoal (S-BC) anode materials are carried out to match the intercalation/deintercalation cycles of K+ by using biomass bamboo as a precursor and sulfur as a modifying element. Benefiting from the unique structure and composition formed during the activation, carbonization, and subsequently vulcanization at 700 °C, the S-BC materials exhibit stabilized electrochemical performance. The optimized S-BC-1 anode delivers a high specific capacity of 339.3 mAh g−1 at 50 mA g−1, a rate capacity of 124.2 mAh g−1 at 1 A g−1, and a cycling retention of 203.8 mAh g−1 at 200 mA g−1 after 300 cycles. It is indicated that the residual oxygen atoms and the doping sulfur in the BS can provide more active sites and increase the conductivity. The sustainable bamboo is demonstrated to be an environmentally friendly precursor to synthesize the high-performance anode material of KIBs. And it also provides a strategy to stabilize carbon-based anode materials by regulating their structure and composition in the synthetic process. Image 1 • Sulfur-doped bamboo charcoal (S-BC) is synthesized using sustainable bamboo. • The S-BC exhibits stable electrochemical performance as anode materials of KIBs. • The mechanism for the enhanced storage of potassium ions in the S-BC is analyzed. • This work provides a strategy to stabilize the performance of carbon-based anode. [ABSTRACT FROM AUTHOR]

High-energy, inexpensive and safe electrochemistries have been the main goals of lithium-ion battery research for many years. Historically, manganese-based cathodes have long been studied for their attractive cost and safety characteristics [1]. However, due to issues related to both surface and bulk instabilities, manganese-rich electrodes have yet to find substantial success in the high-energy lithium-ion battery market. With current trends in cathode chemistries leaning heavily toward Ni-rich compositions, the factors of cost and safety are again at the forefront of research and development efforts. This paper reports the recent progress made at Argonne National Laboratory (USA) to stabilize manganese-rich cathode structures and surfaces with a specific focus on composite materials with intergrown layered and spinel components; it presents an overview of their electrochemical properties in terms of capacity, energy, and cycle-life in cells with metallic lithium, graphite, and Li 4 Ti 5 O 12 anodes. These layered-spinel cathodes show promise as alternatives to highly nickel-rich electrode compositions, which bodes well for continued advances. • Mn-rich oxides show promise as competitive alternatives to Ni-rich cathodes. • Layered-layered-spinel electrodes offer high capacity and good rate capability. • Novel materials improve interfacial and cycling stability of Mn-rich cathodes. [ABSTRACT FROM AUTHOR]

Microbial fuel cells (MFCs) are one of the possible renewable energy supplies which microorganisms play an active role in bio-oxidize reactions of a substrate such as glucose. Electrode materials and surface modifications are highly effective tools in enhancing MFCs’ Performance. In this study, new composite anodes are fabricated. Bacterial cellulose (BC) is used as continuous phase and polyaniline (PANI) as dispersed one which is synthesized by in situ chemical oxidative polymerization on BC’s fibers. With hydrogel nature of BC as a novel feature and polyaniline conductivity there meet the favorable conditions to obtain an active microbial biofilm on anode surface. Maximum power density of 117.76 mW/m 2 in current density of 617 mA/m 2 is achieved for BC/PANI anode. The amounts demonstrate a considerable enhancement compared with graphite plate (1 mW/m 2 and 10 mA/m 2 ). [ABSTRACT FROM AUTHOR]