Search

The configuration of positive charge alignments in a poled-BaTiO3 functionalized separator, and the mechanism for anchoring polysulfides and accelerating Li-ion transportation.

Aqueous Zn metal batteries suffer from rapid cycling deterioration due to the severe water corrosion and dendrite growth on Zn anodes. Herein, a highly antiwater Zn

The growth of Zn dendrites and self-corrosion reaction during electrochemical cycling is a long-standing issue impeding the practical application of zinc-ion batteries. Although various surface engineering strategies have shown great promise in suppressing zinc dendrites, the protective layers unavoidably hinder Zn2+ diffusion, resulting in increased internal impedance/polarization. Therefore, constructing smart interface protective layers with fast Zn2+ transfer kinetics is highly desirable but remains a key challenge. Here, an Mg-Al layered double hydroxide (LDH)-based artificial solid electrolyte interface (SEI) with Zn-ion diffusion channels is proposed. The well-aligned interlayer channels in the Mg-Al LDH skeleton is proved to efficiently engineer the distribution of Zn2+ ions and facilitate Zn2+ diffusion between the electrode/electrolyte interface, thus giving rise to stable Zn deposition. Moreover, the mechanically robust Mg-Al LDH artificial SEI acts as an interfacial layer to constrain H2O-induced corrosion and hydrogen evolution reaction. Consequently, the Mg-Al LDH artificial SEI improves the Coulombic efficiency to 99.2% for more than 2000 cycles, and an ultralong lifespan of 1400 h has been achieved at 0.5 mA cm−2. Notably, the zinc-ion capacitors by pairing the Zn@LDH anode and high-loading active carbon cathode deliver outstanding cycling stability with a high capacity retention of 93.7% up to 10000 cycles at the high areal current density of 37.5 mA cm−2, portending the feasibility of practical applications.

Lithium-rich manganese-based layered oxides (LLOs) are considered to be the most promising cathode materials for next-generation lithium-ion batteries (LIBs) for their higher reversible capacity, higher operating voltage, and lower cost compared with those of other commercially available cathode materials. However, irreversible lattice oxygen release and associated severe structural degradation that exacerbate under high temperature and deep delithiation hinder the large-scale application of LLOs. Herein, we propose a strategy to stabilize the layered lattice framework and improve the thermal stability of cobalt-free Li1.2Mn0.53Ni0.27O2 by doping with 4d transition metal niobium (Nb). Detailed atomic-scale imaging, in situ characterization, and DFT simulations confirm that the induced strong Nb-O bonds stabilize the oxygen lattice framework and restrains the fracture of TM-O bonds, thereby inhibiting the release of lattice oxygen and the continuous migration of TM ions to the lithium layer during the cycle. Furthermore, Nb doping also promotes the surface rearrangement to form a Ni-enrichment layered/rocksalt heterogeneous interface to enhance surface structural stability. As a result, the Nb-doped material delivers a capacity of 181.7 mAh g-1 with retention of 85.5% after 200 cycles at 1C, extraordinary thermal stability with a capacity retention of 80.7% after 200 cycles at 50 °C, and superior rate capability.

Among various Zn-based batteries, transition metal compounds have been widely studied as cathode materials in alkaline electrolyte. However, the correlation between anion species and the electrochemical performance of corresponding compounds is still not well understood. Here, we construct a 3D-architecrured F doping Ni/Co hydroxides/oxides/phosphides (FNCA, A = H, O, P) as the model materials and deeply explore the effect of anion substitution on cathode material for Zn batteries. Electrochemical measurements are combined with theoretical calculations to reveal the mechanisms of FNCA delivering considerable dissimilarity in electrochemical properties. In-depth analysis suggests that the surface-dominated redox behaviors are greatly affected by the anion substitution, though the reversible capacity is just produced by the valence change of metal cations. The FNCP exhibits the highest capacity among three samples but an inferior cycling stability. As contrast, the FNCO shows a balanced characteristic of good capacity and superior cycling performance. Based on the understanding, we construct FNCA//Zn batteries. As expected, the FNCP//Zn batteries delivers the highest specific capacity of 318 mAh g−1 and a superior energy density of 532.7 Wh kg−1 at a power density of 1.673 kW kg−1, but an inferior cycling stability reserved from the individual FNCP electrode. This work provides a rational insight for deep understanding the behaviors that anions affect electrochemical energy storage but not participate in redox reactions, and offer more effective feasibility to design high capacity and durable cathode materials for aqueous Zn-based batteries.

All-solid-state batteries (ASSBs), particularly based on sulfide solid-state electrolytes (SSEs), are expected to meet the requirements of high-energy-density energy storage. However, the unstable interface between the ceramic pellets and lithium (Li) metal can induce unconstrained Li-dendrite growth with safety concerns. Herein, we design a carbon fluoride-silver (CF

Rechargeable aqueous zinc-ion batteries (ZIBs) are attractive candidates for next-generation batteries. However, the challenge of uneven zinc electroplating/electrostripping on bare Zn anodes has severely restrained the practical application of ZIBs. To address this problem, a straightforward strategy of sliver particle-coated zinc plate (designated as Zn@Ag) via the metallic replacement reaction as the zinc metal anode has been employed to facilitate uniform and stable Zn-plating/stripping. The newly formed AgZn3 alloy from silver particles at the first zinc-plating cycle with good zinc affinity can effectively lower the energy barrier of zinc nucleation and promote uniform electric field distribution for the flow of Zn ions, resulting in stable zinc deposition. Benefiting from the in situ formed alloy phase, the Zn@Ag anode achieves stable cycling for over 1700 h with a very low polarization voltage of about 21 mV at 0.25 mA cm−2 and 0.25 mA h cm−2, while the bare Zn anode just exhibits less than 150 cycles with large voltage fluctuation and polarization under same conditions. As a consequence, greatly improved performance of the Zn@Ag//CNT/MnO2 full-cell with twice the capacity (177 mA h g−1) than that of bare Zn//CNT/MnO2 full-cell (71 mA h g−1) after 400 cycles at 0.6 A g−1 can be realized. This work provides a facile and effective approach to regulate Zn deposition for the achievement of long-life rechargeable ZIBs.

Lithium-sulfur (Li-S) batteries are considered as a promising candidate of next generation lithium batteries by virtue of high theoretical energy density, low cost and eco-friendliness, yet their commercialization still suffers from undesirable polysulfide shuttling and uncontrollable Li dendrites growth. Herein, a dual-engineered separator is designed through double-side construction of ammonium alcohol polyvinyl phosphate/carbon black (AAPP/CB) constituted “polysulfide stockroom” and Li1.5Al0.5Ge1.5(PO4)3 (LAGP) based “ion guider” on a commercial polypropylene (PP) substrate. Such functional separator AAPP/CB@PP@LAGP enables highly robust, all-climate Li-S batteries, which is attributed to the efficient polysulfide-absorption/conversion function of the AAPP/CB layer and uniform Li ion distribution/transport capacity induced by the LAGP layer. It is anticipated that this work may provide a promising strategy for interface engineering of separators and promote the wide-temperature application of Li-S batteries.

Lithium-rich layered oxides (LLOs) are regarded as one of the most promising cathode materials for next generation Li-ion batteries (LIBs) due to their high energy density. However, the associated oxygen release and structure collapse resulting from the intrinsic anion and cation redox reactions lead to performance degradation, particularly the characteristic voltage fading which has prohibited the commercialization of LLOs for more than a decade. Herein, we have developed a dual-doping technique to overcome the longstanding structure and voltage instabilities of Co-free Li1.2Mn0.533Ni0.267O2, through the concurrent introduction of neodymium (Nd) and aluminum (Al) ions. Selective atomic substitution of Ni/Mn with Nd/Al ions and the preconstructed heteroepitaxial interface significantly enhance the voltage and capacity retention by regulating Ni ion activity and suppressing the phase transformation and Mn dissolution, thereby improving rate performance through tuning the electronic structure and promoting Li+ migration. The dual-doped material exhibits a superior cycling stability, with over 90% voltage retention and 82% capacity retention after 200 cycles, and excellent rate performance (150 mAh g−1 at 10 C).

Cathode materials have impeded the development of aqueous Zn batteries (AZBs) for a long time due to their low capacity and poor cycling stability. Here, a “two birds with one stone” strategy is devised to optimize the Ni–Co hydroxide cathode material (NCH) for AZBs, which plays an essential role in both composition adjustment and morphology majorization. The F-doped Ni–Co hydroxide (FNCH) exhibits a unique nanoarray structure consisting of the 2D flake-like unit, furnishing abundant active sites for the redox reaction. A series of analyses prove that FNCH delivers improved electrical conductivity and enhanced electrochemical activity. Contributing to the unique morphology and adjusted characteristics, FNCH presents a higher discharge-specific capacity, more advantageous rate capability and competitive cycling stability than NCH. As a result, an aqueous Zn battery assembled with a FNCH cathode and Zn anode exhibits a high capacity of 0.23 mAh cm−2 at 1 mA cm−2, and retains 0.10 mAh cm−2 at 10 mA cm−2. More importantly, the FNCH–Zn battery demonstrates no capacity decay after 3000 cycles with a conspicuous capacity of 0.15 mAh cm−2 at 8 mA cm−2, indicating a superior cycling performance. This work provides a facile approach to develop high-performance cathodes for aqueous Zn batteries.

The emerging inorganic CsPbI2Br perovskite is regarded as a promising candidate for future photovoltaics due to its superior photo-physical properties and thermal stability, but it usually requires a high fabrication temperature (>250 °C) and suffers from possible phase transition from a cubic α-phase to a non-perovskite δ-phase under ambient conditions, restricting its commercial applications. Herein, we demonstrated an additive-assisted hot solution spin coating route to simultaneously lower the fabrication temperature and stabilize the cubic phase structure. The incorporated biuret additive, consisting of functional amino and carbonyl groups, can strongly associate with the halide plumbates in the solution and generate optimal intermediate adducts of CsI–biuret–PbX2 to seed the large crystal growth, which can significantly reduce the perovskite formation energy and enable the low-temperature (120 °C) fabrication of α-phase CsPbI2Br. It was realized that the added biuret was mainly retained at the grain boundaries that effectively passivated antisite or under-coordinated defects, boosting the crystal quality with an improved photoluminescence quantum efficiency. In addition, the biuret molecules can act as anchors among the grains to stabilize the phase structure and prevent moisture permeation. As a result, a champion efficiency of 13.3% with improved ambient air stability was achieved in inverted all-inorganic perovskite solar cells, providing a cost-effective route to prepare high quality inorganic perovskites.

Understanding the complicated interplay of the continuously evolving electrode materials in their inherent 3D states during the battery operating condition is of great importance for advancing rechargeable battery research. In this regard, the synchrotron X-ray tomography technique, which enables non-destructive, multi-scale, and 3D imaging of a variety of electrode components before/during/after battery operation, becomes an essential tool to deepen this understanding. The past few years have witnessed an increasingly growing interest in applying this technique in battery research. Hence, it is time to not only summarize the already obtained battery-related knowledge by using this technique, but also to present a fundamental elucidation of this technique to boost future studies in battery research. To this end, this review firstly introduces the fundamental principles and experimental setups of the synchrotron X-ray tomography technique. After that, a user guide to its application in battery research and examples of its applications in research of various types of batteries are presented. The current review ends with a discussion of the future opportunities of this technique for next-generation rechargeable batteries research. It is expected that this review can enhance the reader's understanding of the synchrotron X-ray tomography technique and stimulate new ideas and opportunities in battery research.

Achieving non-dendritic Li deposition is generally believed to be a prerequisite for the successful commercialization of lithium metal batteries (LMBs). However, it is discussed here that eliminating the growth of the dendritic Li structure seems not to be sufficient to propel the LMB technology from laboratory research to practical applications. Other types of the electrochemically generated Li structure, besides the dendritic structure, must be further studied. It is suggested that considerable research effort be focused on studying the electrochemical nature of generated Li structures, in addition to finding novel strategies to eradicate them.

Lithium and oxygen activities can have substantial influences on the kinetics of ion and electron transport and the structural integrity of Li-rich layered oxide (LLO) cathodes, since reversible oxygen redox is ascribed to the extra capacity beyond the theoretical capacity from transition metal redox at high voltages. Herein, we demonstrate a liquid-solid interfacial reaction to generate a heteroepitaxial interface with tunable Li/O activities on LLOs using molten boric acid. The experimental and theoretical analyses indicate that the atomic scale interface is comprised of a disordered rock salt structure containing substantial Li/O vacancies along the layered structure, associated with a segregation tendency of Ni and Co. The formation of this heteroepitaxial interface with Li/O vacancies improves the ionic/electronic conduction and electrochemical/structural stability, leading to a high discharge capacity of 283 mA h g-1 with initial Coulombic efficiency of 91.7% (0.1 C, 2.0–4.7 V vs. Li+/Li), excellent rate performance (246 and 159.7 mAh g-1 at 1 C and 10 C, respectively) and enhanced cyclic performance with a capacity retention of 92% after 100 cycles. The findings highlight the importance of a well-engineered interface for the design of high performance layered cathode materials for Li storage.

The constantly increasing demands on sustainable and high-performance energy storage devices generate tremendous research attentions on novel battery systems. Rechargeable magnesium battery (RMB), which possesses the advantages of low cost, natural abundance, has emerged as a considerable candidate. The fascinating features of high volumetric capacity, dendrites free and earth abundance also made it more fascinating. However, owing to the strong polarization of Mg ions, the existing electrodes and electrolyte cannot fully facilitate the Mg2+ ion insertion/extraction. In this regard, finding suitable electrode materials and electrolytes with high Mg insertion kinetics, excellent reversibility and costless are still the challenges that hinder the practical application of RMB. In this review, we mainly attempt to accumulate the recently advances in the development of electrodes, as well as development of advanced hybrid RMB systems. The review specifically aimed to provide new perspectives on the construction of novel electrode materials. Moreover, the challenges and perspective of RMBs are also discussed to highlight the limitations and the future direction. These may inspire more efforts on future work and accelerate the development process.

Abrupt Li dendrite growth and the safety hazards caused by liquid electrolytes are generally acknowledged as major technical barriers for the practical application of Li metal batteries. Solid polymer electrolytes (SPEs) are promising to overcome these obstacles, but suffer from rigidity–conductivity inconsistency, ununiform ion distribution and inferior interfacial compatibility. Herein, an anion-immobilized SPE using vinylene carbonate as the rigid polymer backbone and flexible ether oxygen chains containing anion-trapping boron moieties is proposed, which facilitates the Li+ transport and adjusts the ion distribution. This ingenious design along with facile in situ preparation effectively integrates a favorable Young's modulus (2.41 GPa), high ionic conductivity (9.11 × 10−4 S cm−1 at 25 °C) and a high Li+ transference number (0.68), as well as achieving a stable solid electrolyte interface layer. As a result, these integrative properties enable dendrite-free LiFePO4/Li batteries with excellent rate capacity (8C, 98.3 mA h g−1) and superior long-term cyclability over 600 cycles at 30 °C, providing a new strategy for safe and high-energy all-solid-state energy storage systems.

Sodium-ion batteries (SIBs) hold great promise as power sources because of their low cost and decent electrochemical behavior. Nevertheless, the poor rate performance and long-term cycling capability of anode materials in SIBs still impede their practical application in smart grids and electric vehicles. Herein, we design a delicate method to embed WS2 nanosheets into lotus rhizome-like heteroatom-doped carbon nanofibers with abundant hierarchical tubes inside, forming WS2@sulfur and nitrogen-doped carbon nanofibers (WS2@S/N–C). The WS2@S/N–C nanofibers exhibit a large discharge capacity of 381 mA h g−1 at 100 mA g−1, excellent rate capacity of 108 mA h g−1 at 30 A g−1, and a superior capacity of 175 mA h g−1 at 5 A g−1 after 1000 cycles. The excellent performance of WS2@S/N–C is ascribed to the synergistic effects of WS2 nanosheets, contributing to larger interlayer spacing, and the stable lotus rhizome-like S/N–C nanofiber frameworks which alleviate the mechanical stress. Moreover, the WS2@S/N–C electrode shows obvious pseudocapacitive properties at 1 mV s−1 with a capacitive contribution of 86.5%. In addition, density functional theory calculations further indicate that the WS2@S/N–C electrode is very favorable for Na storage. This novel synthetic strategy is a promising method for synthesizing other electrode materials for rechargeable batteries in the future.

Low-cost Na-ion batteries (SIBs) are a promising alternative to Li-ion batteries (LIBs) for large-scale energy storage systems due to the abundant sodium resources and eco-friendliness. The volumetric changes of sodium anodes during the sodiation/desodiation processes, however, reduce the cycling life of Na-ion batteries. In order to solve the problem, we have used the electrospinning method to successfully fabricate mesoporous S/N-doped carbon nanofibers (S/N-C), which show a high capacity and high-rate capability in a Na-ion battery. The S/N-C nanofibers delivered a high reversible capacity of 552.5 and 355.3 mA h g−1 at 0.1 and 5 A g−1, respectively, because of the high S-doping (27.95%) in the carbon nanofibers. The introduction of N and S in S/N-C nanofibers increases the active sites for Na+ storage and reduces the energy required for Na+ transfer, as confirmed by in situ Raman spectroscopy and density functional theory (DFT) calculations. Moreover, the mesoporous S/N nanofibers are wetted by liquid electrolyte, which facilitates the Na+ transport and increases the rate performance, thus making them a suitable anode material for SIBs and other electrochemical energy storage devices.

The inevitable formation of dendrite-like morphology restricts the practical application of metallic lithium (Li) in secondary lithium metal batteries (LMBs) though it is regarded as a promising anode material for high-energy-density batteries. Achieving uniform Li plating is an essential strategy to address this issue; nevertheless, it is difficult to realize this on a commercial current collector. Herein, a nanostructured lithiophilic layer of vertically aligned NiO hexagonal nanoplates on Ni foil is formed by a simple hydrothermal strategy. The lithiophilic nature of NiO can effectively guide the homogeneous smooth deposition of metallic Li on Ni collector surface by reducing the nucleation barrier of the electrode. Such a structure of vertical NiO nanoplate arrays transforming into Ni/Li2O greatly decreases the local current inhomogeneity, facilitates the Li-ion kinetic transfer, and ensures good electron conduction between the lithiophilic layer and the conductive substrate. Benefiting from such a structure, the fabricated anode achieves a steady coulombic efficiency of 97% for 140 cycles (1 mA cm−2) and a prolonged lifespan of up to 600 hours (0.25 mA cm−2), confirming the effective suppression of volume change and dendrite morphology. This strategy provides an effective and facile way for obtaining a stable lithium metal anode.

Nano energy 82, 105762 (1-5) (2021). doi:10.1016/j.nanoen.2021.105762, From non-destructive and cross-sectional visualization by synchrotron X-ray tomography, we suggest a novel capacity decaying mechanism of all-solid-state Na batteries built with closo-borate electrolytes caused by electrochemically generated inactive Na electrodeposits., Published by Elsevier, Amsterdam [u.a.]

High energy density lithium metal batteries (LMBs) are promising next‐generation energy storage devices. However, the uncontrollable dendrite growth and huge volume change limit their practical applications. Here, a new Mg doped Li–LiB alloy with in situ formed lithiophilic 3D LiB skeleton (hereinafter called Li–B–Mg composite) is presented to suppress Li dendrite and mitigate volume change. The LiB skeleton exhibits superior lithiophilic and conductive characteristics, which contributes to the reduction of the local current density and homogenization of incoming Li+ flux. With the introduction of Mg, the composite achieves an ultralong lithium deposition/dissolution lifespan (500 h, at 0.5 mA cm−2) without short circuit in the symmetrical battery. In addition, the electrochemical performance is superior in full batteries assembled with LiCoO2 cathode and the manufactured composite. The currently proposed 3D Li–B–Mg composite anode may significantly propel the advancement of LMB technology from laboratory research to industrial commercialization., A Li–B–Mg composite with in situ formed 3D LiB fiber network shows a dendrite‐free morphology and less volume change during cycling. The symmetrical battery achieves a long and stable cycle lifespan of more than 500 h at 0.5 mA cm−2 due to the effect of skeleton and the addition of Mg. The full battery also displays improved electrochemical performance.

Nickel-rich layered oxides (NLOs) exhibit great potential to meet the ever-growing demand for further increases in the energy density of Li-ion batteries because of their high specific capacities. However, NLOs usually suffer from severe structural degradation and undesired side reactions when cycled above 4.3 V. These effects are strongly correlated with the surface structure and chemistry of the active NLO materials. Herein, we demonstrate a preformed cation-mixed ( Fm3 m) surface nanolayer (∼5 nm) that shares a consistent oxygen framework with the layered lattice through Zr modification, in which Ni cations reside in Li slabs and play the role of a "pillar". This preformed nanolayer alleviates the detrimental phase transformations upon electrochemical cycling, effectively enhancing the structural stability. As a result, the Zr-modified Li(Ni0.8Co0.1Mn0.1)0.985Zr0.015O2 material exhibits a high reversible discharge capacity of ∼210 mA h/g at 0.1 C (1 C = 200 mA/g) and outstanding cycling stability with a capacity retention of 93.2% after 100 cycles between 2.8 and 4.5 V. This strategy may be further extended to design and prepare other high-performance layered oxide cathode materials.

Li2MnSiO4-based cathode materials possess reasonable work potentials and high theoretical capacities, while the practical energy/power densities are constrained by their inferior kinetics of Li+ diffusion. In this work, the Pmn21-structure Li2FexMn1-xSiO4/C materials were synthesized via a solvothermal method and evaluated as Li-ion cathode materials, with notable morphological evolutions and tunable crystallographic habits observed after solvothermal process. The Li2Fe0.33Mn0.67SiO4/C material delivers an initial reversible capacity of 250.2 mAh g−1 at 0.1 C (~ 1.51 Li+ insertion/extraction, 1 C = 166 mA g−1), excellent high-rate capability (52.2 mAh g−1 at 5 C), and good long-term cyclability (64.6% after 196 cycles at 2 C). The enhanced electrochemical properties are attributed to the boosted ion/electron transports induced by preferred morphological and structural characteristics of Li2Fe0.33Mn0.67SiO4/C. Keywords: Electrochemistry, Silicates, Nanostructures, Enhanced kinetics, Li-ion battery

Li2TMSiO4 (TM = Mn, Fe, Co, etc.) is regarded as a new class of cathode materials for next generation Li-ion batteries because of the theoretical possibility of reversible deintercalation of two Li ions from the structure (ca. 330 mA hg−1). Nevertheless, the silicate cathode still suffers from low electronic conductivity, slow Li ion diffusion and structural instability upon deep cycling. To solve these problems, for the first time, we propose a rational design of mesocrystalline Li2FeSiO4 hollow discoids with an ordered single-crystal-like structure and highly exposed (001) facets. The Li2FeSiO4 mesocrystals display a near theoretical discharge capacity, superior rate capability and good cycling stability. The enhanced Li storage performance is ascribed to the unique structural features with a large surface area generated from the hollow mesocrystal structure and a shortened Li+ diffusion path along (001) exposed facets. This new facile, elegant synthesis method that enables the manipulation of crystal growth and subsequent improvements in the electronic and ionic kinetics and structural integrity should have a positive impact on the research and development of silicate materials as promising cathodes for next generation Li-ion batteries.

Limited ionic conduction and poor solid/solid interfacial stability are crucial characteristics that impede the practical application of solid polymeric electrolytes. Herein, a star-shaped solid composite electrolyte (SCE) containing multifunctional components, including anion-trapping boron moieties (B-PEGMA), poly(ethylene glycol)methyl ether methacrylate (PEGMEM) and octavinyl octasilsesquioxane (OV-POSS) nanofiller, was developed via a simple free radical polymerization method. The unique star-shaped structure induced by OV-POSS is beneficial to increasing the movement of polymer chains and forming continuously interconnected ion-conducting channels and the boron moieties can promote lithium salt dissociation and increase the effective transmission of Li+ in the electrolyte. This SCE exhibits an extremely high ionic conductivity of 3.44 × 10−4 S cm−1 and a high Li ion transference number of 0.58 at 25 °C, as well as excellent interfacial compatibility with the Li electrode leading to excellent rate performance and good cyclic stability in all-solid-state Li batteries.

Li2MnSiO4 has attracted significant attention as a cathode material for lithium ion batteries because of its high theoretical capacity (330 mA h g–1 with two Li+ ions per formula unit), low cost, and environmentally friendly nature. However, its intrinsically poor Li diffusion, low electronic conductivity, and structural instability preclude its use in practical applications. Herein, elongated hexagonal prism-shaped Li2MnSiO4 nanoplates with preferentially exposed {001} and {210} facets have been successfully synthesized via a solvothermal method. Density functional theory calculations and experimental characterization reveal that the formation mechanism involves the decomposition of solid precursors to nanosheets, self-assembly into nanoplates, and Ostwald ripening. Hydroxyl-containing solvents such as ethylene glycol and diethylene glycol play a crucial role as capping agents in tuning the preferential growth. Li2MnSiO4@C nanoplates demonstrate a near theoretical discharge capacity of 326.7 mA h g–1 at ...

The major hurdle of room temperature sodium-ion batteries (NIBs) for large-scale energy storage applications lies in developing new electrode materials with higher energy/power densities and improved durability. This work presents a novel Na-P3/Li 2 MnO 3 layered composite cathode with an alternating heteroepitaxial nanostructure fabricated by an in-situ composition modulation route. XRD structural refinement, synchrotron XAS and aberration-corrected HAADF-/ABF-STEM were employed to understand the structure evolution accompanying Li substitution. It is revealed that the in-situ formation of Li 2 MnO 3 (Li-O’3) changes the crystallographic and chemical features of the neighboring Na-P3 layered matrix significantly and leads to the alternating Na-P3/Li-O’3 heteroepitaxial nanostructure. This alternating heteroepitaxial nanostructure delivers an extremely high reversible capacity of ~ 210 mAh g −1 between 1.5 and 4.5 V vs. Na/Na + , much improved cycling stability and excellent electrode kinetics. Its enhanced electrochemical performance can be ascribed to the effective suppression of the P3-P3’’ phase transition and subsequent amorphization upon cycling to 4.5 V.

Aqueous Zn/MnO2 rechargeable batteries utilizing a near neutral electrolyte have demonstrated great potential for large-scale energy storage applications, due to their safe and sustainable nature. Nevertheless, the reaction chemistry and degradation process associated with the MnO2-based cathode is not yet fully understood. Herein, a novel reversible Zn/MnO2 battery with zinc hydroxide sulfate (Zn4(OH)6SO4·5H2O, ZHS) as the cathode has been designed, where active MnO2 is formed in situ during the initial charge process from the Mn(II)-containing ZnSO4 electrolyte. A combination of electrochemical and material characterizations reveal two-step redox reactions (Mn(II) ions ⇌ ZnMn2O4 spinel ⇌ layered Zn-birnessite) during the charge–discharge process. Excellent cycling stability with a capacity retention of 100% after 1500 cycles is achieved at 500 mA g−1. The mechanism for long-term capacity fading is also studied. Cycling reversibility is destroyed by the irreversible consumption of Mn(II) to form woodruffite with a tunnel structure and poor electrochemical activity.

Developing electrode materials with a full conversion reaction is an effective route to break through the capacity barriers, but this goal remains a great challenge. In this work, we report the synthesis of CoSe2 anodes with a quasi-reversible conversion reaction by uniformly encapsulating CoSe2 nanoparticles in nitrogen-doped carbon nanofibers (CoSe2/N-CNFs). The space-confined effect of CNFs effectively inhibits pulverization and amorphization of CoSe2 during charge and discharge and thus remarkably ensures the integrity of the crystal structure. Meanwhile, pseudocapacitive contributed by the size effect of CoSe2 nanodots and excellent conductivity due to doped nitrogen heteroatoms give the electrode outstanding electrochemical properties. When used as an anode, the CoSe2/N-CNFs achieved a reversible capacity of 371.8 mA h g−1 after 500 cycles at 0.2 A g−1. Even at a high current density of 2 A g−1, the discharge capacity of the CoSe2/N-CNFs still reached 308 mA h g−1 after 1000 cycles with excellent rate performance. The first principles calculations demonstrate that the heterointerfaces between CoSe2 and nitrogen-doped carbon can significantly enhance the stability of the structure and improve the storage/diffusion capability of Na+. Moreover, ex situ high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) reveal that the unique structure enables quasi-reversible crystalline-phase transformation of CoSe2, which leads to the superior cycling stability of the battery with high capacity retention.

Li metal is the ultimate anode material for Li based battery with high energy density. However, inhomogeneous charge distribution from the unbalanced ion/electron transport is usually generated at the electrode surface, leading to the uncontrollable dendrites with poor reversibility. Herein, interconnected Li3P@Cu ion/electron conductive interlayer activated from interfacial reaction between Cu3P arrays and metallic Li is efficiently constructed on Li foil surface through room-temperature mechanical rolling process for charge redistribution. Demonstrated by theoretic calculation, the diffusion barrier of Li+ is remarkably reduced from Li3P interphase with high ionic conductivity, while the electron-conductive Cu domains ensures well-dispersed current density, facilitating the uniform distribution of interfacial Li+ flux. Furthermore, the interconnected skeletons with extensive active channels significantly enhances the electrochemical kinetics and promotes the reversibility of Li plating/stripping processes. As expected, a prolonged lifespan of symmetrical cells over 1500 h with lower polarization is successfully achieved at 1 mA cm−2, further improving the rates and cycling performances of LiFePO4 based full cells in mass loading of 8.5 mg cm−2 with a capacity retention up to 91.7% after 300 cycles. This work proposed a rational interlayer design for interfacial charge redistribution and presents an efficient strategy to realize dendrite-free Li metal anode.

Nano energy 83, 105841 (2021). doi:10.1016/j.nanoen.2021.105841, Rechargeable potassium (K) batteries are a promising next-generation technology for low-cost grid scale energy storage applications. Nevertheless, the undesirable interfacial instabilities originating from the interplay between the employed separators and electrodes largely compromise the battery’s performance, and the underlying mechanism of which remains elusive. Herein, the interfacial stability between three types of commercial separators (Celgard 2325, Celgard 2400 and GF/D) and the K electrodeposits is investigated in K|K symmetric cells via in-situ Synchrotron X-ray tomography technique. It is demonstrated that the cell built with a Celgard 2400 separator can achieve a stable cycling performance due to its high mechanical strength and integrity along the thickness direction, thus alleviating the K dendrites growth. In contrast, a GF/D membrane of low mechanical cohesion and excessive porosity is found to be easily deformed and filled with deciduous potassium dendritic aggregates during battery cycling. Similarly, the tri-layer Celgard 2325 separators, which are weakly bonded by interlaminar forces, are found to be severely delaminated by the overgrowth of K dendrites. Furthermore, it is revealed that the delamination failure behaviors of Celgard 2325 is driven by the local stress induced by the spatially and heterogeneously formed "dead" K dendrites. Our work provides direct visualization of morphological evolvement of the separators in presence of potassium dendrites in K|K symmetric cells and highlights the significance of mechanical cohesion, porosity distribution and mechanical integrity of separators in dictating the battery’s performance under realistic battery operation conditions. As a result, these discoveries provide an in-depth understanding that is needed to design next-generation high performance separators to mitigate the formation of potassium dendrite in KMBs., Published by Elsevier, Amsterdam [u.a.]

Although chemical doping has been extensively employed to improve the electrochemical performance of Li-rich layered oxide (LLO) cathodes for Li ion batteries, the correlation between the electrochemical kinetics and local structure and chemistry of these materials after chemical doping is still not fully understood. Herein, gradient surface Si/Sn-doped LLOs with improved kinetics are demonstrated. The atomic local structure and surface chemistry are determined using electron microscopy and spectroscopy techniques, and remarkably, the correlation of local structure-enhanced kinetics is clearly described in this work. The experimental results suggest that Si/Sn substitution decreases the TMO2 slab thickness and enlarges the interslab spacing, and the concentration gradient of Si/Sn affects the magnitude of these structural changes. The expanded interslab spacing accounts for the enhanced Li+ diffusivity and rate performance observed in Si/Sn-doped materials. The improved understanding of the local structur...

Enhancing the conductivity of electrode materials is critically important for improving the high-rate performance of Na-ion batteries (NIBs). Herein, we report a multifaceted strategy for optimizing the conductivity and electrochemical properties of nickel cobalt selenides via the combination of fine component regulation and C coating. The electrical conductivity of C@Ni0.33Co0.67Se2/C nanofiber (CNF) (Co0.67) hybrids achieved in this study was 0.3733 S mm−1, a conductivity five-fold higher than that of selenides with a Ni/Co ratio of 2 : 1. Coupled with desirable three-dimensional (3D) nanobrush morphology and the 1D conducting path of CNFs, the Co0.67 electrode achieved a superior rate performance of 413.1 mA h g−1, even at 2 A g−1. Furthermore, the Co0.67 electrode exhibited an impressive cycling performance of 499 mA h g−1 after 100 cycles (exhibiting an 89.5% capacity retention of the second cycle). Finally, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry analysis at different sweep rates were conducted to demonstrate the Co0.67 electrode's fast charge/ion transport ability and increased electrode kinetics.

Li-rich layered oxides (LLOs) are promising cathode candidates for next generation Li-ion batteries, as they exhibit a higher reversible capacity (>250 mA h/g), enhanced safety and much lower cost. However, LLOs generally suffer from high first cycle irreversible capacity (IRC) loss, poor rate capability, and a substantial voltage decay over prolonged cycling. These major challenges are closely dependent on the surface structure and chemistry of LLO cathodes and, thus, different surfaces induce different irreversible reactions resulting in various levels of battery performance. This review presents the current understanding, as well as recent highlights, on the roles and fundamentals of surface structure in LLO cathodes, from a materials science perspective, concerning surface structural disorder in pristine LLO (antisites, composition segregation and crystallographic facets), the roles of surface structures on redox processes (oxygen evolution, cation activation and reversible anion redox reactions), surface structural evolution during the first cycle and long-term electrochemical operation, and surface modification strategies to stabilize the surface structure and to mitigate the performance degradation of LLOs. However, some fundamental problems remain yet ambiguous, especially with regard to characterization and understanding of the surface structure and chemistry in relation to synthesis conditions and composition, and charge transfer and ionic transport of the interfacial processes within LLOs. In order to exploit the potential of LLO cathodes, a clear understanding of these fundamental questions are essential to optimize the synthesis parameters and material properties.

Aqueous rechargeable Zn metal batteries have attracted widespread attention due to the intrinsic high volumetric capacity, low cost, and high safety. However, the low Coulombic efficiency and limited lifespan of Zn metal anodes resulting from uncontrollable growth of Zn dendrites impede their practical application. In this work, a 3D interconnected ZnF2 matrix is designed on the surface of Zn foil (Zn@ZnF2 ) through a simple and fast anodic growth method, serving as a multifunctional protective layer. The as-fabricated Zn@ZnF2 electrode can not only redistribute the Zn2+ ion flux, but also reduce the desolvation active energy significantly, leading to stable and facile Zn deposition kinetics. The results reveal that the Zn@ZnF2 electrode can effectively inhibit dendrites growth, restrain the hydrogen evolution reactions, and endow excellent plating/stripping reversibility. Accordingly, the Zn@ZnF2 electrode exhibits a long cycle life of over 800 h at 1 mA cm-2 with a capacity of 1.0 mAh cm-2 in a symmetrical cell test, the feasibility of which is also convincing in Zn@ZnF2 //MnO2 and Zn@ZnF2 //V2 O5 full batteries. Importantly, a hybrid zinc-ion capacitor of the Zn@ZnF2 //AC can work at an ultrahigh current density of ≈60 mA cm-2 for up to 5000 cycles with a high capacity retention of 92.8%.

Carbon coated SnS/SnO2 heterostructures wrapping on carbon nanofibers (C@SnS/SnO2@CNFs) was demonstrated to have excellent performance as an anode material for Li-ion batteries. C@SnS/SnO2@CNFs electrode delivers high reversible capacity of 826.8 mA h g–1 (500th cycle) at the current density of 1.0 A g–1. However, an interesting phenomenon of increasing capacity on cycling can be observed. According to the analysis of the evolution of structure and electrochemical property, C@SnS/SnO2@CNFs is demonstrated to experience the progress of conversion from nanowalls containing polycrystals into amorphous nanosheets with high porosity and larger surface upon cycling. The above lithiation-induced structural optimization provides larger effective surface areas and encourages the conversion reactions, which can promote charge transfer and also enhance the reversibility of the conversion reactions of SnS and SnO2 inducing the increasing reversible capacity. The study explains the progress of increasing capacity of C...

Hierarchical nanocomposite of ultrathin WS2 nanosheets uniformly attached on the surface of hollow nitrogen-doped carbon spheres (WS2@HNCSs) were successfully fabricated via a facile synthesis strategy. When evaluated as an anode material for LIBs, the hierarchical WS2@HNCSs exhibit a high specific capacity of 801.4 mA h g(-1) at 0.1 A g(-1), excellent rate capability (545.6 mA h g(-1) at a high current density of 2 A g(-1)), and great cycling stability with a capacity retention of 95.8% after 150 cycles at 0.5 A g(-1). The Li-ion storage properties of our WS2@HNCSs nanocomposite are much better than those of the previously most reported WS2-based anode materials. The impressive electrochemical performance is attributed to the robust nanostructure and the favorable synergistic effect between the ultrathin (3-5 layers) WS2 nanosheets and the highly conductive hollow N-doped carbon spheres. The hierarchical hybrid can simultaneously facilitate fast electron/ion transfer, effectively accommodate mechanical stress from cycling, restrain agglomeration, and enable full utilization of the active materials. These characteristics make WS2@HNCSs a promising anode material for high-performance LIBs.

Polyanion doping shows great potential to improve electrochemical performance of Li-rich layered oxide (LLO) materials. Here, by optimizing the doping content and annealing temperature, we obtained boron-doped LLO materials Li1.2Mn0.54Ni0.13Co0.13BxO2 (x = 0.04 and 0.06) with comprehensively improved performance (94% capacity retention after 100 cycles at 60 mA/g current density and a rate capability much higher compared to that of the pristine sample) at annealing temperatures of 750 and 650 °C, respectively, which are much lower than the traditional annealing temperature of similar material systems without boron. The scenario of the complex crystallization process was captured using Cs-corrected high-angle annular dark field scanning transmission electron microscopic (HAADF-STEM) imaging techniques. The existence of layered, NiO-type, and spinel-like structures in a single particle induced by boron doping and optimization of annealing temperature is believed to contribute to the remarkable improvement of cycling stability and rate capability.

Solid polymer electrolyte membranes (SPEMs) with star-shaped structure, consisting of octavinyl octasilsesquioxane (OV-POSS) with nanoscale organic/inorganic hybrid structure and poly(ethylene glycol) methyl ether methacrylate (PEGMEM), have been prepared by one-step free radical polymerization. OV-POSS with eight functional corner groups was used to produce star-shaped nanocomposites and PEGMEM was used as the polymer matrix to dissolve lithium ion. For comparison, SPEMs based on the corresponding linear copolymers, containing POSS moieties and PEGMEM segments, were also prepared. The SPEM with star-shaped structure containing 5.1 mol% POSS exhibits the highest ionic conductivity of 1.13×10−4 S cm−1 and Li+ transference number of 0.35 at 25 °C, which are about two times of that of SPEM with linear structure containing the same POSS content. Moreover, the Li/LiFePO4 cell assembled with such star-shaped SPEM delivers the highest discharge capacity of 137.1 mAh g−1 under a current density of 0.5 C at 25 °C. At an evaluated temperature of 80 °C, this cell exhibits an initial discharge capacity of 163.8 mAh g−1 at 0.5 C, and even at high discharging C-rates of 5 and 10 C, the discharge capacity of 75.6 and 45.7 mAh g−1 can still be obtained, respectively.