Search

Abstract A facile one-step solid-phase synthesis strategy is developed for synthesizing a binder-free molybdenum disulfide/carbon fibers paper (MoS 2 /CFP) anode. The microstructure, composition, morphology and electrochemical performances were investigated. It is found that the thin MoS 2 layers are well anchored on the interlaced carbon fibers to form MoS 2 /CFP, which has mesoporous structure and large specific surface area of ∼18.8 m2g-1. As a result, the obtained MoS 2 /CFP anode exhibits a reversible capacity of 261 mAh·g−1 with 31.2% loading ratio of MoS 2. After subtracting the capacity of CFP, the MoS 2 in the composite anode delivers a reversible capacity of 539 mAh·g−1 and shows better cycle stability than commercial MoS 2 after 100 cycles at 100 mA g−1. The remarkable electrochemical performances could be attributed to the buffer space among carbon fibers for the volume changes of MoS 2 as well as the highly conductive carbon fibers network, suggesting that the MoS 2 /CFP is a promising binder-free anode for lithium-ion batteries. Graphical abstract Image 1 Highlights • A one-step solid-phase synthesis strategy is developed to fabricate MoS 2 /CFP anode. • The MoS 2 and the carbon matrix of MoS 2 /CFP composite were synthesized synchronously. • The MoS 2 /CFP anode exhibits enhanced cycling performance and high-rate capability. • The mechanism of the enhanced electrochemical properties was discussed for MoS 2 /CFP. [ABSTRACT FROM AUTHOR]

Toward achieving Li-ion batteries with high energy density, SWCNT/Sn composite paper was electrochemically prepared and the addition effect of formaldehyde (HCHO) and polyethylene glycol (PEG) on Sn electrodeposition morphology was studied. PEG improved the wettability of electroplating bath to enable inhomogeneous Sn embeddedness inside SWCNT paper, and HCHO delivered more nuclear growth. The synergetic effect resulted in a composite paper in which Sn particles with several-hundred nanometer order were distributed. Compared with a commercially-available Cu foil (18 μm-thickness) with 32 mg at 2 cm 2 ( φ 16 mm), the weight of the SWCNT paper (5 mg) is one sixth of that of the Cu foil. The dramatic reduction of the component greatly contributes to the increase in energy density of batteries. [ABSTRACT FROM AUTHOR]

In this paper, we synthesized Bi 2 Se 3 -NFs@rGO composite and analyzed electro chemical properties. Bi 2 Se 3 -NFs@rGO composite improved specific capacity, cycle stability and ion conductivity by rGO composite. [Display omitted] • The synthesis of Bi 2 Se 3 nanoflakes(NFs) by organic molecules as selenium precursor. • Synthesized homogenously nanoflakes by oleylamine as surfactant. • Bi2Se3-NFs@rGO composite exhibits high specific capacity compared to previous articles. • Analyzed the mechanism of Bi 2 Se 3 -NFs@rGO composite via Ex-situ TEM and Ex-situ XRD. Metal selenides have gained attention as alternative anode materials for lithium-ion batteries, with increasing demand for electro-vehicles and appliances. Bismuth selenide has significant potential as anode materials in lithium-ion batteries. Nevertheless, metal selenides have essential drawbacks, such as volume expansion and poor cycle performance. In this paper, bismuth selenide synthesized homogeneous morphology-like nanoflakes (NFs) using the wet chemical method. We combined these nanoflakes with reduced graphene oxide to improve their structural stability. The Bi 2 Se 3 -NFs@rGO composite showed enhanced specific capacity from 750 mAhg−1 to 1100 mAhg−1 at 100 mAg−1. Furthermore, at a current density of 500 mAg−1, it reached a specific capacity (819 mAhg−1) after 300 cycles and demonstrated a coulombic efficiency of 96 %. [ABSTRACT FROM AUTHOR]

The paper reports a results of series of interlaboratory comparisons of low impedance measurements at frequencies relevant for electrochemical impedance spectroscopy (EIS) of commercial lithium-ion cells. Two comparisons are presented. The first, bilateral comparison has focused on low impedance standards calibration in a full complex plane using digital sampling setups. The second comparison has focused on calibration and use of commercial 4-terminal battery EIS meters. Both comparisons have covered the impedance range from 50 μ ℧ to 100m℧ across the full complex plane in a frequency range from 0.01Hz up to 5kHz. Finally, the paper summarizes practices identified as critical for achieving measurement compatibility among various labs. • Relevant for electrochemical impedance measurements of lithium-ion battery cells. • First interlaboratory comparison of low impedances in full complex plane. • First interlaboratory comparison of low impedance at frequencies down to 0.01Hz. [ABSTRACT FROM AUTHOR]

Silicon/carbon (Si/C) composite shows great potential to replace graphite as lithium-ion battery (LIB) anode owing to its high theoretical capacity. Exploring low-cost scalable approach for synthesizing Si/C composites with excellent electrochemical performance is critical for practical application of Si/C anodes. In this study, we rationally applied a scalable in situ approach to produce Si-carbon nanotube (Si-CNT) composite via acid etching of commercial inexpensive micro-sized Al-Si alloy powder and CNT mixture. In the Si-CNT composite, ∼10 nm Si particles were uniformly deposited on the CNT surface. After combining with graphene sheets, a flexible self-standing Si-CNT/graphene paper was fabricated with three-dimensional (3D) sandwich-like structure. The in situ presence of CNT during acid-etching process shows remarkable two advantages: providing deposition sites for Si atoms to restrain agglomeration of Si nanoparticles after Al removal from Al-Si alloy powder, increasing the cross-layer conductivity of the paper anode to provide excellent conductive contact sites for each Si nanoparticles. When used as binder-free anode for LIBs without any further treatment, in situ addition of CNT especially plays important role to improve the initial electrochemical activity of Si nanoparticles synthesized from low-cost Al-Si alloy powder, thus resulting in about twice higher capacity than Si/G paper anode. The self-standing Si-CNT/graphene paper anode exhibited a high specific capacity of 1100 mAh g −1 even after 100 cycles at 200 mA g −1 current density with a Coulombic efficiency of >99%. It also showed remarkable rate capability improvement compared to Si/G paper without CNT. The present work demonstrates a low-cost scalable in situ approach from commercial micro-sized Al-Si alloy powder for Si-based composites with specific nanostructure. The Si-CNT/graphene paper is a promising anode candidate with high capacity and cycling stability for LIBs, especially for the flexible batteries application. [ABSTRACT FROM AUTHOR]

In this paper we present an all-solid-state lithium-ion battery (ASSB) model that considers electrochemistry and solid mechanics in a fully coupled manner. The model spatially resolves the three-dimensional microstructure of an ASSB cell and is based on non-linear continuum mechanics. The coupling of electrochemistry and solid mechanics is incorporated via lithiation-dependent volumetric changes of the active materials and the consistent formulation of the electrochemical governing equations on deformed geometries resulting in changed percolation paths. As the volumetric changes due to (de-)lithiation are reported to be large for several active materials, we introduce this effect using a multiplicative split of the deformation gradient. To also allow for large deformations in the mass conservation equation, an Arbitrary Lagrangian–Eulerian formulation is employed. Furthermore, we show the central steps to deduce the finite element formulation of our model as well as the adopted monolithic solution procedure to solve this strongly coupled non-linear problem. The linear solver used for large problem setups is adjusted from the advanced, physics-oriented preconditioning technique published in our previous work. In the numerical examples, we investigate three different geometries with up to about 1.3 million degrees of freedom and thereby prove that our approach is applicable to geometrically large and complex scenarios. Moreover, we show that our approach consistently introduces the mass and charge conservation on deformed meshes. Furthermore, the numerical examples demonstrate the high relevance to incorporate current collectors into the ASSB cell simulations. Finally, we show that solid mechanics and the coupling effects have indeed a large impact on the ASSB cell performance and their incorporation is therefore vital for precise results and predictions. [ABSTRACT FROM AUTHOR]

Highlights • K 0.8 Fe 0.8 Ti 1.2 was synthesized by hydrothermal method for the first time. • K 0.8 Fe 0.8 Ti 1.2 displays a platelike shape with the size of ∼3 μm in width and 50 nm in thickness. • The electrochemical performance of K 0.8 Fe 0.8 Ti 1.2 as lithium ion battery anode was explored for the first time. Abstract In this paper, the platelike K 0.8 Fe 0.8 Ti 1.2 O 4 particle with layered structure was synthesized in the hydrothermal system of TiO 2 , Fe(NO 3) 3 and KOH at 250 °C. The hydrothermal temperature and the KOH concentration are crucial in the formation of K 0.8 Fe 0.8 Ti 1.2 O 4 phase. The platelike K 0.8 Fe 0.8 Ti 1.2 O 4 particle had the size of ∼3 μm in width and 50 nm in thickness. Meanwhile, the electrochemical performance of K 0.8 Fe 0.8 Ti 1.2 O 4 as lithium ion battery anode materials was investigated for the first time. [ABSTRACT FROM AUTHOR]

Capacity fade induced by chemo-mechanical degradation during charge-discharge cycles is the bottleneck in the design of high-performance batteries, especially high-capacity electrode materials. In this paper, a flexible sigmoid function is used to create the two-phase electrochemical lithiation profile, describing a sharp phase boundary that separates the pristine core from the lithiated shell of an electrode particle. According to such a phase transition, an analytical solution of the stress evolution is obtained by introducing an electrochemical reaction layer into the plastic model. Finally, based on the theory of diffusion-induced stress and the energy principle, we determine the critical thickness of radius of a lithiated layer, at which fracture occurs. [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]

Porous tin films as anode for lithium-ion batteries are electrodeposited on graphite paper. Homogeneous tin films with significant void space accommodate the volume change during tin lithiation/delithiation. Through adjusting the electrodeposition currents and time, the morphologies and void space of tin films on graphite paper are controllable. At fixed electrodeposition current densities, the prolonged electrodeposition time plays the role in growing big tin particles and resulting the disappearance of void space among tin particles. The increased electrodeposition current plays the role to increase the quantity of tin seeds in thickness of tin film, and the void space among tin particles remains but the thick film limits its electrochemical performance. The tin films electrodeposited at an optimized current densities and for an optimized electrodeposition time, present the best electrochemical performance, because the tin nanoparticles are well dispersed on graphite substrate including void space. The tin film electrodeposited at 0.2 A cm −2 for 2 min shows the capacity of 1.0 mAh cm −2 after 50 charge/discharge cycles. The void space of tin film is very important for the best capacity and cyclic ability. The metallic tin film produced at 0.4 A cm −2 for 3 min remains the uniform and microporous structure after charge/discharge for 50 cycles. [ABSTRACT FROM AUTHOR]

To make a Lithium Ion Battery (LIB) reliably rechargeable over many cycles, its graphite-based negative electrode requires the solid electrolyte interphase (SEI) as a protection layer. The SEI is formed through chemical and particularly electrochemical side reactions of electrolyte components in the first charging cycle(s) after manufacturing of a LIB. The SEI ideally serves two purposes: (i) act as a sieve permeable to Li ions but not to other electrolyte components and (ii) passivate the electrode against further electrolyte decomposition. Core element of conventional SEI formation is a lengthy, low-current galvanostatic charging step, which due to its time consumption contributes heavily to cell manufacturing costs. Here, we report on some non-conventional SEI formation protocols for composite carbon electrodes, inspired by recent experimental findings at smooth model electrodes. Acknowledging that the SEI forms in two main steps, taking place in a high-potential and a low-potential region, respectively, we demonstrate that less time spent in the high-potential region not only makes the process faster but even yields SEIs with superior kinetic properties. We tentatively explain this via basic rules of thin film growth and the role of grain boundaries for ion transport. We also report on the positive influence of multi-frequency potential modulations applied between high-potential and low-potential formation. Given that any new cell chemistry in principle requires its own tailor-made formation process, technologic success of future LIB cells will benefit from a systematic, well-understood toolbox of formation protocols. This paper is meant as a first step, highlighting potentially low-hanging fruits, but also flagging the demand for further systematic studies on model systems and on commercially manufactured cells. [ABSTRACT FROM AUTHOR]

The growing interest in e-mobility and the increasing installation of renewable energy-based systems are leading to rapid improvements in lithium-ion batteries. In this context, battery manufacturers and engineers require advanced models in order to study battery performance accurately. A number of Li-ion battery models are based on the representation of physical phenomena by electrochemical equations. Although providing detailed physics-based information, these models cannot take into account all the phenomena for a whole battery, given the high complexity of the equations. Other models are based on equivalent circuits and are easier to design and use. However, they fail to relate these circuit parameters to physical properties. In order to take the best of both modeling techniques, we propose an equivalent circuit model which keeps a straight correlation between its parameters and the battery electrochemical principles. Consequently, this model has the required simplicity to be used in the simulation of a whole battery, while providing the depth of detail needed to identify physical phenomena. Moreover, due to its high accuracy, it can be used in a wide range of environments, as shown in the experimental validations carried out in the final section of this paper. [ABSTRACT FROM AUTHOR]

The LiV 1-x Co x PO 4 F/C (x = 0, 0.01, 0.03 and 0.05) composite cathode material for lithium ion batteries has been successfully prepared through the modified solid state method assisted by sonication and mechanical activation. Here, the influence of cobalt doping on the physical and electrochemical performances are investigated. In this paper, we adopted the X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM)/energy dispersive spectrometer (EDS), cycle voltammetry (CV), electrochemical impedance spectrum (EIS) and charge-discharge test to investigate the influence of cobalt doping on the different aspects of the materials, including the physical and electrochemical properties. Compared with the original simple, the cycle and rate performance of cobalt doped samples has increased to some extent. We found that the LiV 0.97 Co 0.03 PO 4 F/C sample showed the best electrochemical performance. The lithium ions diffusion constant (D Li+ ) of the LiV 0.97 Co 0.03 PO 4 F/C (1.86321 × 10 −13 cm 2 s −1 ) is much higher than that of LiVPO 4 F/C (2.06453 × 10 −14 cm 2 s −1 ). [ABSTRACT FROM AUTHOR]

The introduction of Li-ion batteries for grid applications has become evidence as the cost per kWh is continuously decreasing. Although the Li-ion battery is a mature technology for automotive applications and portable electronics, its use for stationary applications needs more validation. The Li-ion technology is considered safe enough for grid storage application, but its lifetime is generally evaluated to be around 10 years. Higher market penetration will be achieved if a longer lifespan could be demonstrated. Therefore, aging evaluation of the batteries becomes crucial. In this paper we investigated the effects of aging after a three years' standby field deployment of a 250 kW/500 kWh Li-ion battery integrated with the grid and solar farm under the harsh climate conditions of Qatar. The development of tools for acquisition and analysis of data from the battery management system (BMS) allows the assessment of the battery performance at the battery stack, string and cell levels. The analysis of the residual capacity after aging showed that the stack suffered from a low decrease of capacity, whereas some inconsistencies have been found between the strings. These inconsistencies are caused by misalignment of a small number of cells that underwent self-discharge during standby at high state of charge. [ABSTRACT FROM AUTHOR]

This paper presents a topology to passively balance two types of lithium-ion cells without using additional active electrical components or employing any algorithm based balancing management systems. We connect nickel-metal hydride or nickel-zinc cells in parallel to lithium-ion cells. The hydrogen/oxygen recombination process of the nickel-based cells can be used to balance lithium-ion cells. Two serially connected lithium iron phosphate cells, combined each with two serially connected nickel-zinc cells, show a successful balancing of 8% of the lithium iron phosphate cell's initial capacity. A lithium titanate cell connected in parallel to two nickel-metal hydride cells can be fully charged without suffering from over-voltage effects by constant current charging. [ABSTRACT FROM AUTHOR]

In this paper, LiTi 2 (PO 4 ) 3 @carbon composite as anode for aqueous lithium ion battery has been successfully synthesized by in-situ carbon coating method using oxalic acid and glucose as double carbon sources. XRD results confirm the rhombohedral NASICON-type LiTi 2 (PO 4 ) 3 structure of the as-prepared composite. The LiTi 2 (PO 4 ) 3 @carbon composite using double carbon sources (LTP-OG-10) disperses well, and the coated carbon layer has the appropriate thickness of 3–7 nm, which result in proper balance of the good electrical conductivity and the fast kinetics of diffusion of lithium ions. LTP-OG-10 exhibits better electrochemical performance compared with those using oxalic acid (LTP-O) or glucose (LTP-G) single carbon source. LTP-OG-10 anode delivers the discharge capacity of 112.5 mA h g −1 , 96.8 mA h g −1 , and 54.2 mA h g −1 at 0.2 C, 5 C and 20 C, respectively, much larger than that of LTP-O and LTP-G. Moreover, LTP-OG-10 demonstrated excellent cycling performance, with the capacity retention of 71.1% after 400 cycles at 0.2 C, 22.9% higher than that of LTP-G. The good electrochemical properties of LTP-OG-10 is mainly ascribed to the increase of defects, high-quality and appropriate thickness of carbon layer. Our study reveals that preparing LiTi 2 (PO 4 ) 3 @carbon composite using double carbon sources is an efficient approach to enhance its electrochemical properties. [ABSTRACT FROM AUTHOR]

Solidified lithium conducting hybrid electrolyte is designed and processed to realize the large scale and flexible solid state Li battery satisfying energy capability and safety issue. This paper presents a solidified inorganic-organic hybrid electrolyte to obtain commercially-acceptable ionic conductivity and a stable electrochemical window to prevent electrolyte decomposition in Li ion batteries. Li 3 PO 4 coated with solidified [Li][EMI][TFSI] ionic liquid is developed as hybrid electrolyte material. The material has high electrochemical stability on a high-voltage cathode and metallic anode, and the solid electrolyte has high ionic conductivity. This Li 3 PO 4 -[Li][EMI][TFSI] hybrid electrolyte has the advantages of long-term operation, safety and flexibility, so it may be suitable for use in high-voltage cathodes and Li anode. [ABSTRACT FROM AUTHOR]

Electrodes softening during lithium insertion may result in degeneration of their electrochemical performances. In this paper, based on a coupling multiple-slip crystal plasticity formulation with three (i.e., statistically-stored, geometrically-necessary and electrochemical reaction-induced) dislocation densities, a relationship is built up between hardness and the state of charge for electrodes in lithium-ion batteries, which can take into account the indentation size effect during charging and discharging progresses. It is shown that the relationship is helpful in monitoring the state of charge and providing new avenues for applications of high-performance rechargeable batteries. [ABSTRACT FROM AUTHOR]

This paper presents a large wound cell for in operando neutron diffraction (ND) from which high quality diffraction patterns are collected every 15 min while maintaining conventional electrochemical performance. Under in operando data collection conditions the oxygen atomic displacement parameters (ADPs) and cell parameters were extracted for Li 0.18 Sr 0.66 Ti 0.5 Nb 0.5 O 3 . Analysis of diffraction data collected under in situ conditions revealed that the lithium is located on the (0.5 0.5 0) site, corresponding to the 3 c Wyckoff position in the cubic perovskite unit cell, after the cell is discharged to 1 V. When the cell is discharged under potentiostatic conditions the quantity of lithium on this site increases, indicating a potential position where lithium becomes pinned in the thermodynamically stable phase. During this potentiostatic step the oxygen ADPs reduce significantly. On discharge, however, the oxygen ADPs were observed to increase gradually as more lithium is inserted into the structure. Finally, the rate of unit cell expansion changed by ∼44% once the lithium content approached ∼0.17 Li per formula unit. A link between lithium content and degree of mobility, disorder of the oxygen positions and changing rate of unit cell expansion at various stages during lithium insertion and extraction is thus presented. [ABSTRACT FROM AUTHOR]

The development of improved State-of-Health (SoH) diagnostic methods is a current research topic for battery-powered applications. For instance, the current rapid development of Electric Vehicles (EV) creates a strong demand for an accurate and reliable on-board SoH indicator during operation. Such an indicator is a key parameter required to optimize battery energy management and to track the degradation of the system performance. The electrochemical impedance spectrum (EIS) of an electrochemical system is a powerful lab-based diagnostic technique, usually measured using a frequency response analyzer. In this paper, we present an innovative diagnostic technique based on analysis of free voltage and current signals to give a so called “quasi-electrochemical impedance spectrum” (QEIS) and demonstrate its application on a Li-ion battery during a real EV duty cycle. It is worth noting that in our technique no additional signal is applied to the cell, since the current flowing into cells during use on-board is directly processed in the data treatment step. Commercial batteries (1.4 Ah cylindrical LiFePO 4 /graphite cell) were selected in this study to validate the diagnostic method in the framework of an applied case study related to an electric school bus demonstrator. In order to study the capability of QEIS measurements as a diagnostic tool for SoH of Li-ion cells, a test procedure including ageing phases has been defined to characterise Li-ion cells before and during ageing. Voltage and current signals were treated by Fast Fourier Transform (FFT) in order to determine the QEIS spectra of Li-ion cells under study. Then, SoH prediction algorithms have been obtained from a mathematical analysis of the impedance parameters sensitive to SoH. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries have been widely used as enabling energy storage in many industrial fields. Accurate modeling and state estimation play fundamental roles in ensuring safe, reliable and efficient operation of lithium-ion battery systems. A physics-based electrochemical model (EM) is highly desirable for its inherent ability to push batteries to operate at their physical limits. For state-of-charge (SOC) estimation, the continuous capacity fade and resistance deterioration are more prone to erroneous estimation results. In this paper, trinal proportional-integral (PI) observers with a reduced physics-based EM are proposed to simultaneously estimate SOC, capacity and resistance for lithium-ion batteries. Firstly, a numerical solution for the employed model is derived. PI observers are then developed to realize the co-estimation of battery SOC, capacity and resistance. The moving-window ampere-hour counting technique and the iteration-approaching method are also incorporated for the estimation accuracy improvement. The robustness of the proposed approach against erroneous initial values, different battery cell aging levels and ambient temperatures is systematically evaluated, and the experimental results verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

Supercapacitors with high power density and long cycle life are of interest to complement lithium-ion batteries. However it is necessary to increase the energy density of supercapacitors for its more widely practical application. In this paper, three-dimensional porous nitrogen-doped graphene hydrogel (N-RGOH) was investigated as supercapacitor electrodes in an ionic liquid electrolyte. The X-ray diffraction, electron microscopy and X-ray photoelectron spectroscopy results show that the N-RGOH displayed 3D porous structure, large specific surface (335.6 m 2 g −1 ) and high nitrogen content (10.8 at%). The electrochemical testing shows that the N-RGOH based supercapacitor device with 3.2 V working voltage delivered a specific capacitance of 48.6 F g −1 at 0.5 A g −1 resulting in a high energy density of 94.5 W h kg −1 . The N-RGOH also shows good rate and cycling performances. Our study demonstrates an effective combination of electrode and electrolyte to achieve high energy density supercapacitors for practical application. [ABSTRACT FROM AUTHOR]

Various yolk-shell structured particles designed for large volume expansion materials for lithium-ion storage have been reported, the cycle stability and coulombic efficiency can be effectively improved through such structure design. SnO 2 has high theoretical capacity of 1494 mA h g −1 and 1378 mA h g −1 for lithium and sodium storage, respectively. The large volume expansion problem of SnO 2 has long been considered as the primary reason for the capacity fading of SnO 2 based anode materials. In this paper, the yolk-shell structured SnO 2 porous nanowire has been designed, and this unique yolk-shell structure is reported as anode materials for lithium and sodium-ion storage for the first time. The yolk-shell structured porous nanowires deliver significantly improved cycle stability and coulombic efficiency as active material for both lithium and sodium-ion storage compared with that of pure SnO 2 porous nanowires. It exhibits a high and stable capacity of 1150 mA h g −1 at current density of 200 mA g −1 for lithium-ion storage, and a capacity of 401 mA h g −1 at current density of 50 mA g −1 after 50 cycles for sodium-ion storage. [ABSTRACT FROM AUTHOR]

Rechargeable lithium-ion batteries (LIBs) have been explored as competitive electrochemical power sources for various energy applications due to their high energy density. To meet to the development of high-performance electrode materials for LIBs, tin oxide (SnO 2 ) anodes demonstrate promising prospects for their high theoretical capacities. In this paper, novel hierarchical porous reduced graphene oxide/SnO 2 (rGO/SnO 2 ) networks that consist of porous SnO 2 anchored on graphene scaffold are constructed by a silica template assisted nanocasting process. The as-synthesized porous rGO/SnO 2 networks of improved electrical conductivity can facilitate the electron transport and also provide sufficient active sites for redox reactions, along with accommodating the large volume changes during cycling process. As an anode material for LIBs, such porous rGO/SnO 2 composite exhibits substantially enhanced cycling stability and rate capacity. In addition, the anode suggests highly stable cycling performance with the discharge capacities of 595 mAh g −1 (after 300 cycles) and 394 mAh g −1 (after 800 cycles) at 600 mA g −1 and 1000 mA g −1 , respectively. The strategy indicates a promising way to fabricate advanced anode materials for LIBs. [ABSTRACT FROM AUTHOR]

In this paper we propose a carbon-coated, nano-sized TiO 2 anode for application in lithium-ion batteries. The lithiation-delithiation process characteristic of this mixed anatase/rutile material has been investigated in detail, in order to define the optimal operating voltage range and to further enhance the electrode cycle life. Ex-situ x-ray diffraction measurements demonstrate that the rutile phase becomes electrochemically inactive toward lithium intercalation after the first cycle and remains inactive by cycles. The TiO 2 electrochemical behavior is studied by means of various techniques, including galvanostatic cycling and potentiodynamic cycling with galvanostatic acceleration. We show that the combination of the TiO 2 anode with a high-voltage, LiNi 0.5 Mn 1.5 O 4 spinel cathode results in an advanced li-ion battery able to exchange reversibly a capacity higher than 100 mAh/g for over 70 cycles at the high rate of 1C. Considering an average working voltage of about 2.9 V, the theoretical energy content of the cell here disclosed is about 300 Wh kg −1 . Taking into account the energy content and high safety level of the full cell, due to the use of a TiO 2 -based electrode, by operating at a voltage value well far from the one associated to the common electrolyte decomposition, i.e. about 1.7 V, we may propose the anode here studied as suitable material for advanced energy storage systems. [ABSTRACT FROM AUTHOR]

The OCV (open circuit voltage)-based method for SOC (state of charge) estimation by using the dual neural network fusion battery model is proposed in this paper. The weights of the constructed dual neural network fusion battery model can be used to describe the characteristics of the corresponding parameters of electrochemical model for the battery. The constructed dual neural network fusion battery model consists of two neural network models connected in series. The first part is a linear neural network battery model which can be used to identify parameters of the first-order electrochemical model or second-order electrochemical model for the battery, the second part is a BP (Back of Prorogation) neural network used for capturing the relationship between OCV and SOC. The DST (Dynamic Stress Test) data is adopted for training the dual neural network fusion battery model, by which the relationship between OCV and SOC is offline obtained. Under FUDS (Federal Urban Driving Schedule) condition, the experimental results show that the dual neural network fusion battery model can effectively estimate SOC based on the first-order electrochemical model or second-order electrochemical model. [ABSTRACT FROM AUTHOR]

Lithium ion batteries have attracted wide attention due to their high energy density, long cycle life, and environmental friendliness and are widely used in electrical vehicles. An accurate and reliable battery model is needed in battery management systems (BMS) to monitor battery operating conditions, including state of charge (SOC), state of health (SOH), etc. This paper presents a state-space model with non-integer order derivatives for electrochemical batteries with a constant phase element (CPE) in order to accurately describe battery dynamics. The proposed model is a combination of electrochemical impedance spectroscopy and the 1-RC model. The Oustaloup recursive approximation was selected for model parametric identification and potential implementation. A particle-swarm optimization (PSO) algorithm was used to identify three model parameters by using time-domain test data. The model accuracy and robustness were validated by using datasets from different driving cycles, aging levels and cells of the same chemistry. The proposed FOM showed good accuracy and robustness. It is suitable for research on battery reliability, including issues like SOC estimation, SOH prediction, and charging control. [ABSTRACT FROM AUTHOR]

A simple and scalable solution fabrication process preparing Li 4 Ti 5 O 12 /graphene anode material for lithium-ion batteries is the focus of this paper. The aforementioned graphene sheets are attached tightly to lithium titanate particles under the action of solvothermal treatments, which provide a highly conductive network for electron transportation. It is worth mentioning that the synthesis of graphene nanosheets from graphite oxide has been adapted to allow for a more cost-efficient, environmentally friendly, and scalable production method. Electrochemical tests reveal that electrodes with a graphene content of 3 wt% present a Li-ion storage specific capacity of 184 mA h/g at 0.1 C, and the specific capacity maintains at 158 mA h/g even after 50 cycles. Moreover, spinel-type Li 4 Ti 5 O 12 can also be fabricated via hydrothermal processes in a shorter time and at a lower temperature compared to solid-state synthesis. This low energy and environmentally friendly method of preparing Li 4 Ti 5 O 12 /graphene lends itself to a variety of applications, ranging from portable electronic devices to electric vehicles and energy storage devices. [ABSTRACT FROM AUTHOR]

The Distribution Function of Differential Capacity (DDC) is introduced as a supportive method for analyzing the capacitive tail in impedance spectra, which is related to the solid state diffusion of species into/out of battery electrodes. The DDC provides insight into the individual time-dependent utilization of differential capacity, as charging/discharging occurs in different electrode compositions, structures, particle sizes or blends thereof with different time constants. The aggregate differential capacity of an electrochemical system is decomposed by (i) measuring the electrode's impedance spectrum, (ii) computing the complex capacity spectrum, and, (iii) computing its distribution function DDC. This paper presents the mathematical derivation of the DDC and shows, using a simplified electrode model, how individual capacity contributions and associated time constants become accessible. [ABSTRACT FROM AUTHOR]

As more and more applications require high energy density electrochemical storage systems that deliver more than 200 Wh/kg, Lithium-ion batteries with silicon-based anodes provide promising electrochemical properties especially high specific capacity. In this paper, we present micro-grain structured silicon deposited by DC sputtering on special copper foil that serves as current collector. It is demonstrated that high-density silicon anodes are obtained with more than 2000 mAh g −1 and 2.0 mAh cm −2 that can be considered as a commercial value. In addition, irreversible capacity during the first galvanostatic cycle can be lower than 20% for such anodes. Finally, it is found that there exists a clear correlation between the grain-size and the texture of the amorphous silicon to the electrochemical performance of half-cells. [ABSTRACT FROM AUTHOR]

TiO 2 is one of the most promising anode candidates for novel lithium ion batteries which combines the advantage of state of art anode graphite and the safety of Li 4 Ti 5 O 12 . However, the low intrinsic conductivity limits its electrochemical properties. In this paper, a sol-gel based route is presented to produce nanosize TiO 2 /CNT core-shell composite fibers. Fiber diameter is 253 ± 63 nm as-spun and 126 ± 35 nm with subsequent calcination to obtain crystalline phase. Crystallite size is between 13–18 nm. The as-prepared core-shell fibers exhibited ∼1.5 time higher electronic conductivity, 1.6–3 times greater lithium diffusivity which resulted in 25% more galvanostatic capacity at C/10 compared to bare TiO 2 nanofibers. The enhancement in high-rate performance at 10C was over 80% which was crucial for fast charging applications. CNT additives were found to enhance the electronic conductivity, lithium diffusivity and electrochemical properties of the TiO 2 nanofibers by both providing an alternative electron and lithium ion conducting mechanism as well as synergistic effects, which were systematically reviewed. [ABSTRACT FROM AUTHOR]

Electrochemical models of lithium-ion batteries have been increasingly considered for online state of health estimation. These models can more accurately predict cell performance than traditional circuit models and can better relate physical degradation mechanisms to changes in model parameters. However, examples of state of health estimation algorithms that are validated with experimental data are scarce in the literature, particularly for cells with a composite electrode. The individual electrode active materials in a composite electrode may degrade at different rates and according to different physical mechanisms, and online estimation of this degradation facilitates more robust knowledge of how battery performance changes over its life. In this paper we use a reduced-order electrochemical model for a composite LiMn 2 O 4 -LiNi 1/3 Mn 1/3 Co 1/3 O 2 (LMO-NMC) electrode cell for online estimation of active material loss. Experimental data collected from composite electrode half cells that were aged under constant current cycling are used in an extended Kalman filter to estimate model parameters associated with loss of each active material. The capacity loss predicted by the online estimates agrees well with the measured capacity loss. Additionally, a differential capacity analysis demonstrates that active materials lose capacity at a similar rate, the same conclusion obtained from the online estimation algorithm. [ABSTRACT FROM AUTHOR]

Due to the suitability to balance the intermittency in decentralized systems with renewable sources, electrochemical energy storage possibilities have been analyzed in several studies, all highlighting the need for improvements in relevant techno-economic parameters. Particularly a reduction in the costs per cycle is much needed, which could either come from innovation in more cost-efficient manufacturing methods, a higher endurance of charge/discharge sequences or higher capacities. Looking at patent applications as a metric allows us to determine whether the necessary technological progress is indeed occurring, as the mandatory publication of the underlying inventions provides access to otherwise hidden R&D activities. Our paper contributes to the literature with a compilation of technological classes related to important battery types in the novel Cooperative Patent Classification (CPC), which can be used to identify relevant patent applications of the competing technologies. Using the worldwide patent statistical database (PATSTAT), we find that promising technologies have been showing increasing patent counts in recent years. For example, the number of patent applications related to regenerative fuel cells (e.g. redox flow batteries) doubled from 2009 to 2011. Nevertheless, the volume of patent filings in technologies related to lithium remains unchallenged. Patent applications in this area are still growing, which indicates that the introduction of improved modules will continue. Using citation analysis, we have identified important patents and organizations for relevant candidate technologies. Our study underlines that electrochemical storage, and in particular lithium-based technologies, will play an increasingly important role in future energy systems. [ABSTRACT FROM AUTHOR]

In this paper the preparation and electrochemical characterization of silicon nanowires for using as the anode of a lithium-ion battery are reported. The nanowires were synthesized by CVD and characterized by SEM. The nanostructured material was used as an electrode in a lithium cell and its electrochemical properties were investigated by galvanostatic charge–discharge cycles at various charge rates. The electrode was coupled with a LiFePO 4 cathode to fabricate a lithium-ion battery and the battery performance evaluated as a function of the discharge rate and cycle number. [ABSTRACT FROM AUTHOR]

Hierarchical assembly of hollow microstructures is of great scientificity and practical value. In this paper, a hydrothermal synthesis of Li 4 Ti 5 O 12 hollow microspheres assembled by nanosheets is introduced. Transmission electron microscopy (TEM) image shows that such Li 4 Ti 5 O 12 microspheres, with sizes of 2 μm in diameter, are composed of a hollow inner cavity and thin outer shell assembled by nanosheets. A possible growth mechanism of the structure is further expounded. The Li 4 Ti 5 O 12 hollow microspheres calcinated at 700 °C display extremely good electrochemical performance, including high capacity (147.3 mA h g −1 at 3 C), excellent cyclic stability (95.0% capacity retention after 100 cycles at 3 C) and remarkable rate capability (131.3 mA h g −1 at 20 C). [ABSTRACT FROM AUTHOR]

The operation of future microgrids will require the use of energy storage systems employing power electronics converters with advanced power management capacities. This paper presents the control scheme for a medium power lithium-ion battery bidirectional DC/AC power converter intended for microgrid applications. The switching devices of a bidirectional DC converter are commanded by a single sliding mode control law, dynamically shaped by a linear voltage regulator in accordance with the battery management system. The sliding mode controller facilitates the implementation and design of the control law and simplifies the stability analysis over the entire operating range. Control parameters of the linear regulator are designed to minimize the impact of commutation noise in the DC-link voltage regulation. The effectiveness of the proposed control strategy is illustrated by experimental results. [ABSTRACT FROM AUTHOR]

The formation of the solid electrolyte interface (SEI) layer on the surface of the anode electrode of a lithium ion battery prevents further electrolyte decomposition reaction. However, at certain battery operating conditions, the SEI breakdown leading to more electrolyte decomposition reactions that form several species on the anode electrode surface. This paper focuses on the effect of battery potential and charge rate on the decomposition side reaction on the anode electrode of a lithium ion polymer battery, as a result of the breakdown of the SEI layer. The results from this study indicate that raising the state of charge (SOC) increases the rate of the electrolyte decomposition side reaction that resulted in formation of a thick deposit layer at the electrolyte/electrolyte interface. This deposit layer contains lithium that can no longer participate in the reversible electrochemical reaction. In addition, at high cycling potential and charge rates the amount of lithium in the graphite after complete cell discharge increased due to the entrapment of lithium in the graphite. The amount of irreversible capacity loss for the batteries cycled at high potential and current correlates with the amount of trapped lithium in the graphite and the growth of the deposit layer thickness at the electrode/electrolyte interface. [ABSTRACT FROM AUTHOR]

In this paper, a facile and template-free solvothermal method has been developed to synthesize flower-like V 2 O 5 hierarchical architecture. The as-synthesized V 2 O 5 samples are composed of discrete and uniform micro-flower, which is further assembled from several nanosheets. Importantly, the as-synthesized flower-like V 2 O 5 hierarchical architecture exhibits an excellent electrochemical performance. At the rate of 0.1 C, these V 2 O 5 flowers deliver a high specific capacity of 285 mA h g −1 in the first discharge and retain reversible capacity of 249 mA h g −1 after 50 cycles. Meanwhile, even at a high rate of 5 C, they also exhibit a specific capacity of 152 mA h g −1 and the cycling retention rate is 86% after 50 cycles. [ABSTRACT FROM AUTHOR]

This paper presents extensive three-dimensional (3D) simulations of large LiFPO 4 pouch cells. 3D simulations of the Li-ion battery behavior are highly nonlinear and computationally demanding. Coupling electrochemical modeling to thermal models represents an important step towards accurate simulation of the Li-ion battery. Non-uniform temperature, potential and current density through the battery induce non-uniform use of the active material and can have a negative impact on cell performance and lifetime. Different pouch cell designs, with different tab locations, have been investigated in term of performance, current density, potential and heat distributions. The model is first validated with experimental data at different current discharge rates. Afterwards, the electrochemical, thermal and electrical behaviors over each cell design under high discharge rate (4 I t ) are compared between configurations. It has been shown that the designs with symmetrical configurations show uniform potential and current density gradient, which minimize the ohmic heat and lead to more uniform active material utilization and temperature distributions across the cell surface.Introduction [ABSTRACT FROM AUTHOR]

Abstract: Reducing the particle size and coating conductive materials are both effective ways to improve the performance of LFP (LiFePO4). In this paper, we synthesized LFP/C/CPO (LiFePO4/C/CePO4) composites and investigated the effects of CePO4 modification on the morphologies and electrochemical properties of LFP/C composites. The results demonstrated that introducing CePO4 nanoparticles via in situ method could reduce the particle size significantly and improve the electrochemical properties of LFP/C. [Copyright &y& Elsevier]

Abstract: Accurate models of lithium-ion batteries are important for analyzing and predicting battery dynamics and aging. This paper presents an electrochemistry-based impedance model for lithium-ion batteries to better understand the relationship between battery internal dynamics and external measurement. The proposed impedance model is a modified single particle model which balances between simplicity and accuracy. The model includes electrochemical impedance due to charge-transfer reaction, diffusion dynamics in the electrodes, effects of ion concentration, capacitance dispersion in the double layer, and anode insulating film growth, etc. The impedance tests for model validation were performed on two lithium-ion cells at ambient temperature and at different SOC levels. A particle swarm optimization method is employed to identify model parameters. The model accuracy under different conditions is compared with that of conventional Randles model and the parameter variations at different stage of the aging process are studied. [Copyright &y& Elsevier]

Abstract: In this paper the preparation of silicon nanowires and their electrochemical characterization as an anode in lithium batteries is reported. The nanowires were synthesized by CVD and characterized by XRD, SEM and EDS. The nanostructured materials were used as electrodes in lithium cells and their electrochemical properties were investigated by galvanostatic charge–discharge cycles at various discharge rates. To evaluate the dependence of the specific capacity and charge coefficient on the end charge potential this parameter was varied during the experimentation. The evolution of the charge transfer resistance, specific capacity, and charge coefficient as a function of the number of the cycles was also investigated. [Copyright &y& Elsevier]

Models that consistently couple particle, electrode, and battery level mechanics and electrochemistry are rare in literature. Within a battery, there are hundreds of layers of electrodes and the inherent multiscale structure of electrodes makes battery level simulations computationally very expensive. This paper presents a multiscale homogenization method that couples mechanics and electrochemistry at the particle, electrode, and battery scales. The method is divided into two parts. Firstly, an electrochemical/mechanical model for a one-dimensional periodic element is applied to determine particle and electrode layer swelling as functions of time and position. Secondly, the layered structure of the battery is homogenized by the use of three-dimensional laminate theory. The homogenized material model can be applied in finite element calculations on the battery level. Layer level stresses can in a second step be back-calculated. The accuracy and efficiency of the method are demonstrated by comparisons to detailed finite element computations where each layer is individually modeled. Predictions of electrode layer stresses are also favorably compared to impedance measurements of electrode layers at different electrode positions. It is furthermore demonstrated that the effects of external battery loadings like battery stacks, casings, and external pressure easily can be captured by the model. • A multiscale homogenization method is presented. • Application of three-dimensional laminate theory to battery modeling. • Layer level stresses are back-calculated from the homogenized model. • Good agreements to detailed finite element computations and experiments. • Efficient method for battery level simulations. [ABSTRACT FROM AUTHOR]

Transition metal phosphides (TMPs) are considered as one class of excellent energy storage materials. However, serious volume variation and agglomeration during charging and discharging hamper their development. In this paper, monodispersed Ni 2 P nanoparticles have been loaded on acid treated carbon nanotubes (Ni 2 P @ACNT(CTAB)) via a cationic surfactant-assisted hydrothermal synthesis approach. The resultant electrode can be used both in supercapacitors (SCs) and lithium/sodium-ion batteries (LIBs/SIBs) with excellent energy storage performance. Especially, the three-dimensional and omnidirectional conducting network of CNTs can provide open highways for electron/ion transport and promote electrode reaction kinetics. As a battery-type electrode for SCs, Ni 2 P@ACNT(CTAB) electrode has demonstrated a remarkable capacitance of 328.0 F·g−1 at 1 A·g−1. As an anode for LIBs, a significant capacity of 1475 mAh·g−1 can be delivered at 0.2 A·g−1 after 320 cycles, and a high capacity of 509.8 mAh·g−1 is achieved at 8 A·g−1. As an anode for SIBs, a significant capacity of 150.1 mAh·g−1 can be delivered at 0.1 A·g−1 after 100 cycles, and a high capacity of 104.8 mAh·g−1 is achieved at 4 A·g−1. The reaction mechanism is analyzed by Ex-situ XRD patterns. This design provides obvious advantages for the application of Ni 2 P based electrode materials for hybrid supercapacitors and batteries. [ABSTRACT FROM AUTHOR]

Fibrous carbon materials have a variety of dimensions and structures. However, these materials were earlier restricted for use as anode materials for lithium ion batteries due to their cost and performance. With the development of nanotechnology, some modified and new forms of carbon fibers have emerged, which show good performance as anode materials. This paper reviews recent domestic and foreign research progress on fibrous carbon materials as anode materials. The electrochemical performance and prospective use of graphite fibers, carbon fibers and carbon nanofibers for this purpose are summarized. Research has ranged from non-graphitized to graphitized carbon fibers, from micron to nanometer diameter, and has focused on the parameters of their preparation to the design of their microstructure. Fibrous carbon materials are likely to be important alternatives for carbon anode materials in the future based on their high capacity, high rate capability, low cost and ease of industrialization. [New Carbon Materials 2015, 30(1): 1–11] [ABSTRACT FROM AUTHOR]