High-rate Cycling Research Articles

Engineering eutectic network for regulating the stability of polyiodides towards high rate and long cycling zinc-iodine batteries

Despite aqueous Zn-iodine batteries have gained enormous research interests, their development is restricted by disproportionation and diffusion of polyiodides. Herein, for the first time, we propose a distinct electrolyte engineering strategy for regulating the performance of Zn-iodine batteries. A hydrated eutectic electrolyte composed of zinc tetrafluoroborate hydrate (ZBF) and succinonitrile (SN) forms the unique SNH2O eutectic network, which breaks the H2OH2O hydrogen network, strengthens OH bond in H2O and constrains the freedom of water molecules. Consequently, the disproportionation and diffusion of polyiodides are suppressed. The investigation for the solvation structure based on the spectroscopy results and molecular dynamics simulations demonstrate the relatively weak solvation effect of the organic ligand SN with Zn2+, which enables superior ion conductivity and high transference number. As a result, the as-assembled Zn-iodine battery based on optimized eutectic electrolyte delivers a high capacity of 202 mAh g−1 at 0.5 A g−1 with 99.5% coulombic efficiency, superior rate performance (capacity retention of 60% at 20 A g−1) and outstanding cycling stability (over 10,000 cycles). Benefiting from its anti-freezing ability, the hydrated eutectic electrolyte enables Zn-iodine battery to work stably at a low-temperature of -20°C. The paradigm provides an encouraging strategy to construct the stable aqueous Zn-halogen batteries through electrolyte engineering.

Carrageenan as A Sacrificial Binder for 5V LiNi0.5 Mn1.5 O4 Cathodes in Lithium-Ion Batteries.

5V-class LiNi0.5 Mn1.5 O4 (LNMO) with its spinel symmetry is a promising cathode material for lithium-ion batteries. However, the high-voltage operation of LNMO renders it vulnerable to interfacial degradation involving electrolyte decomposition, which hinders long-term and high-rate cycling. Herein, we overcome this longstanding challenge presented by LNMO by incorporating a sacrificial binder, namely, λ-carrageenan (CRN), a sulfated polysaccharide. This binder not only uniformly covers the LNMO surface via hydrogen bonding and ion-dipole interaction but also offers an ionically conductive cathode-electrolyte interphase layer containing LiSOx F, a product of the electrochemical decomposition of the sulfate group. Taking advantage of these two auspicious properties, the CRN-based electrode exhibited cycling and rate performance far superior to that of its counterparts based on the conventional poly(vinylidene difluoride) and sodium alginate binders. This study introduces a new concept, namely "sacrificial" binder, for battery electrodes known to deliver superior electrochemical performance but be adversely affected by interfacial instability. This article is protected by copyright. All rights reserved.

Facile preparation of CoSb2O6/rGO composite as the anode material of lithium-ion batteries

CoSb2O6/rGO composite was prepared by sol–gel and evaluated for the first time as anode material for lithium-ion batteries (LIBs). The ex-situ XRD revealed the lithium storage mechanism of CoSb2O6, indicating that its capacity is mainly provided by the conversion reaction. The results show that CoSb2O6/rGO has better cycling stability and higher cycling rate than pristine CoSb2O6, with a reversible capacity of 693.0 mAh/g after 100 cycles at a current density of 0.1 A/g. This is due to the introduction of reduced graphene oxide (rGO), which can effectively buffer the volume expansion during lithiation/delithiation and maintain the the structural stability of the electrode, and facilitate the transfer of lithium ions and electrons during the cycling process. Based on these results, the CoSb2O6/rGO has the potential to be used as anode material for LIBs.

Constructing Wide-Temperature Lithium-Sulfur Batteries by Using a Covalent Organic Nanosheet Wrapped Carbon Nanotube.

Lithium-sulfur (Li-S) batteries hold the superiority of eminent theoretical energy density (2600Wh kg-1 ). However, the ponderous sulfur reduction reaction and the issue of polysulfide shuttling pose significant obstacles to achieving the practical wide-temperature operation of Li-S batteries. Herein, a covalent organic nanosheet-wrapped carbon nanotubes (denoted CON/CNT) composite is synthesized as an electrocatalyst for wide-temperature Li-S batteries. The design incorporates the CON skeleton, which contains imide and triazine functional units capable of chemically adsorbing polysulfides, and the underlaid CNTs facilitate the conversion of captured polysulfides enabled by enhanced conductivity. The electrocatalytic behavior and chemical interplay between polysulfides and the CON/CNT interlayer are elucidated by in situ X-ray diffraction detections and theoretical calculations. Resultantly, the CON/CNT-modified cells demonstrate upgraded performances, including wide-temperature operation ranging from 0 to 65 °C, high-rate performance (625 mAh g-1 at 5.0 C), exceptional high-rate cyclability (1000 cycles at 5.0 C), and stable operation under high sulfur loading (4.0mg cm-2 ) and limited electrolyte (5µL mgs -1 ). These findings might guide the development of advanced Li-S batteries.

Boosting the high-rate performance and cycling life of NaTi2(PO4)3 anode by forming N-doped carbon coating derived from polyacrylonitrile

Boosting the high-rate performance and cycling life of NaTi2(PO4)3 anode by forming N-doped carbon coating derived from polyacrylonitrile

Synergized oxygen vacancies with Mn2O3@CeO2 heterojunction as high current density catalysts for Li–O2 batteries

The application of Li–O2 batteries (LOBs) with ultra-high theoretical energy density is limited due to the slow redox kinetics and serious side reactions, especially in high-rate cycles. Herein, CeO2 is constructed on the surface of Mn2O3 through an interface engineering strategy, and Mn2O3@CeO2 heterojunction with good activity and stability at high current density is prepared. The interfacial properties of catalyst and formation mechanism of Li2O2 are deeply studied by density functional theory (DFT) and experiments, revealing the charge-discharge reaction mechanism of LOBs. The results show that the strong electron coupling between Mn2O3 and CeO2 can promote the formation of oxygen vacancies. Heterojunction combined with oxygen vacancy can improve the affinity for O2 and LiO2 reaction intermediates, inducing the formation of thin-film Li2O2 with low potential and easy decomposition, thus improving the cycle stability at high current density. Consequently, it achieved a high specific capacity of 12545 at 1000 mA g−1 and good cyclability of 120 cycles at 4000 mA g−1. This work thus sheds light on designing efficient and stable catalysts for LOBs under high current density.

Deciphering the Degradation Mechanism of High‐Rate and High‐Energy‐Density Lithium–Sulfur Pouch Cells

AbstractLithium–sulfur (Li–S) batteries are widely regarded as promising next‐generation battery systems due to their impressive theoretical energy density of 2600 Wh kg−1. However, practical high‐energy‐density Li–S pouch cells suffer from rapid performance degradation under high working rates. Herein, the performance degradation mechanism of 400 Wh kg−1 Li–S pouch cells is systematically investigated under a high cycling rate of 0.2 C. Focusing on the reduced specific capacity and increased cell polarization, the sluggish cathodic sulfur redox kinetics under lean‐electrolyte and high‐rate conditions is identified as the main limitation. Further polarization decoupling indicates the cathodic activation polarization contributes dominantly to the increased cell polarization. Accordingly, a delicately designed electrolyte using dimethyl diselenide as the kinetic promoter is proposed to enable the Li–S pouch cells to work at 0.2 C with reduced cell polarization. This work clarifies the sluggish cathodic interfacial charge transfer kinetics as the main challenge for high‐energy‐density Li–S batteries at high rates and is expected to inspire rational strategy design for achieving advanced Li–S batteries.

Interfacial friction enabling ≤ 20 μm thin free-standing lithium strips for lithium metal batteries

A practical high-specific-energy Li metal battery requires thin (≤20 μm) and free-standing Li metal anodes, but the low melting point and strong diffusion creep of lithium metal impede their scalable processing towards thin-thickness and free-standing architecture. In this paper, thin (5 to 50 μm) and free-standing lithium strips were achieved by mechanical rolling, which is determined by the in situ tribochemical reaction between lithium and zinc dialkyldithiophosphate (ZDDP). A friction-induced organic/inorganic hybrid interface (~450 nm) was formed on Li with an ultra-high hardness (0.84 GPa) and Young’s modulus (25.90 GPa), which not only enables the scalable process mechanics of thin lithium strips but also facilitates dendrite-free lithium metal anodes by inhibiting dendrite growth. The rolled lithium anode exhibits a prolonged cycle lifespan and high-rate cycle stability (in excess of more than 1700 cycles even at 18.0 mA cm−2 and 1.5 mA cm−2 at 25 °C). Meanwhile, the LiFePO4 (with single-sided load 10 mg/cm2) ||Li@ZDDP full cell can last over 350 cycles with a high-capacity retention of 82% after the formation cycles at 5 C (1 C = 170 mA/g) and 25 °C. This work provides a scalable approach concerning tribology design for producing practical thin free-standing lithium metal anodes.

Influence of Backbone on the Performance of Pendant Polymer Electrode Materials in Li-ion Batteries.

Pendant polymers are a promising class of electrode materials due to their synthetic simplicity, derivation from sustainable feedstocks, and potentially benign synthesis. These materials consist of a redox-active pendant tethered to a polymer backbone, which mitigates dissolution during electrode cycling. To date, an extensive number of pendant groups have been studied within the context of metal-ion batteries. However, the choice of the polymer backbone and its impact on the electrode performance have been relatively understudied. In this work, we use a postpolymerization modification approach to synthesize a series of viologen-bearing redox-active pendant polymers with similar molecular weights but three distinct chemical backbones, namely, polyacrylamide, polymethacrylamide, and polystyryl. By evaluating the polymers in lithium-ion batteries, we show that the polymer backbone has a significant influence on electrode performance and behavior. Specifically, the polymethacrylamide displays slower kinetics than the other two polymers, resulting in lower capacities, particularly at high cycling rates. Furthermore, the charge storage mechanism is dependent on the nature of the backbone: the polyacrylamide shows a significant capacitive contribution to charge storage, while the polystyryl does not. The difference in performance between the polymer electrode materials is ascribed to a difference in chain mobility and packing within the electrode films. Overall, this work shows that the fundamental properties of the polymer backbone are critical to the design of high-performance polymer electrodes.

Improvements in the Electrochemical Performance of Sodium Manganese Oxides by Ti Doping for Aqueous Mg-Ion Batteries.

In recent times, the research on cathode materials for aqueous rechargeable magnesium ion battery has gained significant attention. The focus is on enhancing high-rate performance and cycle stability, which has become the primary research goal. Manganese oxide and its derived Na-Mn-O system have been considered as one of the most promising electrode materials due to its low cost, non-toxicity and stable spatial structure. This work uses hydrothermal method to prepare titanium gradient doped nano sodium manganese oxides, and uses freeze-drying technology to prepare magnesium ion battery cathode materials with high tap density. At the initial current density of 50 mA g-1 , the NMTO-5 material exhibits a high reversible capacity of 231.0 mAh g-1 , even at a current density of 1000 mA g-1 , there is still 122.1 mAh g-1 . It is worth noting that after 180 cycles of charging and discharging at a gradually increasing current density such as 50-1000 mA g-1 , it can still return to the original level after returning to 50 mA g-1 . Excellent electrochemical performance and capacity stability show that NMTO-5 material is a promising electrode material.

Anti-Shedding Nickel-Protection-Layer Boosting an Ultrahigh Loading Carbon Fiber@Co-NiSx Electrode to Deliver Superior Areal/Volumetric/Gravimetric Capacitance.

Challenges remain to show good capacitive performance while achieving high loadings of active materials for supercapacitors. Trying to realize this version, a nickel-protecting carbon fiber paper@Co-doped NiSx (Ni-CP@Co-NiSx) electrode with high specific gravimetric, areal, and volumetric capacitance is reported in this work. This free-standing electrode is prepared by an electroplating-hydrothermal-electroplating (EHE) three-step method to achieve a high loading of almost 26.7 mg cm-2. The cobalt-doping and nickel-protection strategies effectively decrease the impedance and inhibit the active material dropping from the electrode resulting from the expansion stress, which endows the Ni-CP@Co-NiSx electrode with a high rate and good cycling performance, especially with an ultrahigh specific areal/volumetric/gravimetric capacitance of 53.3 F cm-2/2807 F cm-3/1997 F g-1 at 5 mA cm-2, respectively. Employing activated carbon functionalized with riboflavin (AC/VB2) as a negative electrode, the asymmetric supercapacitor device delivers a very high energy density of up to 60.4 W h kg-1. This work demonstrates that electrodes with a high loading density and excellent performance can be obtained by the combination of the EHE method to adjust the internal conductivity and external structural stability.

Molten Sodium Batteries – Lewis Acidity of AlCl3/NaI Catholyte Impedes NaSICON Interface

Low temperature molten sodium batteries with sodium metal anodes, NaSICON solid-state separators, and sodium halide salt catholytes are low cost, earth-abundant technologies for grid-scale energy storage.1-3 We compared batteries with NaI/AlCl3-based molten salt catholytes of differing Lewis acidities at 110 °C. Batteries with >50 mol% AlCl3 (acidic catholytes) experienced a linear decline in energy efficiency during cycling, whereas batteries with >50 mol% NaI (basic catholytes) maintained 95% energy efficiency for 100 cycles (5 months) at 2.5 mA cm-2. A 3-electrode cell was developed, enabling electrochemical identification of the NaSICON-catholyte interface as the source of increased impedance. Complementary physical and chemical characterization of the NaSICON exposed to acidic and basic catholytes showed no changes in crystallinity, bulk morphology, or bulk chemical composition, but surface sensitive X-ray photoelectron spectroscopy (XPS) revealed subtle changes in the local NaSICON surface chemistry. In addition, Raman spectroscopy indicated that basic catholytes lack the dimer species Al2Cl6I- present in acidic catholytes. These results suggest that one means to enable efficient and stable battery cycling is maintaining Lewis-basic NaI/AlCl3, which avoids deleterious interactions at the NaSICON-catholyte interface. Recent progress towards achieving high cycling rates in these molten salt systems will also be shared.References L. J. Small, A. Eccleston, J. Lamb, A. C. Read, M. Robins, T. Meaders, D. Ingersoll, P. G. Clem, S. Bhavaraju and E. D. Spoerke, J. Power Sources, 360, 569 (2017).S. J. Percival, L. J. Small and E. D. Spoerke, J. Electrochem. Soc., 165, A3531 (2018).M. M. Gross, S. J. Percival, L. J. Small, J. Lamb, A. S. Peretti and E. D. Spoerke, ACS Appl. Energy Mater., 3, 11456 (2020). Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

(Invited) Addressing Energy/Power Tradeoffs in Composite Solid-State Battery Electrodes

Solid-state batteries (SSBs) have seen a dramatic increase in research in recent years because of their ability to address safety challenges associated with flammable liquid electrolytes, and the potential to enable Li metal anodes. However, SSBs present unique challenges, including high interfacial impedances, accommodation of mechanical stresses due to solid-solid interfacial contact, and (electro)chemical instabilities that can evolve during dynamic cycling conditions. Furthermore, a significant challenge facing the scale-up of SSBs is to improve our understanding of processing science needed to enable manufacturing.While a significant amount of attention has been paid recently to the Li metal anode/electrolyte interface, there has been significantly less work on the cathode side of the SSB. In SSBs, the cathodes are typically composites of the active material and solid electrolyte (SE) phases, which experience rate limitations. Analogous to porous electrodes with liquid electrolytes, the rate capability of these composite solid-state electrodes is strongly dependent on electrode thickness (electrode capacity) and electrode composition/microstructure. These results in tradeoffs between energy and power density, which are exacerbated at high charging rates.To address these challenges, we have recently applied operando optical microscopy to directly observe state-of-charge (SoC) gradients in composite solid-state electrodes, using graphite as a model active material [1]. To describe mass transport in these composite electrodes, continuum-scale modeling was performed, which illustrates the critical role of the electrode microstructure and tortuosity on rate capability. These in situ observations are consistent with ex situ measurements of Li-graphite half-cells, where we quantify the rate capability as a function of areal capacity.To overcome these limitations, we engineered composite SSB electrodes with controlled microstructure and 3-D architectures. These electrodes showed improved homogeneity in the local SOCs throughout the electrode thickness, enabling high-rate cycling capabilities. Overall, the insights presented here will enable new strategies to overcome power/energy tradeoffs in SSBs with composite electrodes.[1] A. L. Davis, V. Goel, D. W. Liao, M. N. Main, E. Kazyak, J. Lee, K. Thornton, N. P. Dasgupta, ACS Energy Lett. 6, 2993 (2021)

Self-Assembled 2D VS2 /Ti3 C2 Tx MXene Nanostructures with Ultrafast Kinetics for Superior Electrochemical Sodium-Ion Storage.

Constructing nanostructures with high structural stability and ultrafast electrochemical reaction kinetics as anodes for sodium-ion batteries (SIBs) is a big challenge. Herein, the robust 2D VS2 / Ti3 C2 Tx MXene nanostructures with the strong Ti─S covalent bond synthesized by a one-pot self-assembly approach are developed. The strong interfacial interaction renders the material of good structural durability and enhanced reaction kinetics. Meanwhile, the enlarged and few-layered MXene nanosheets can be easily obtained according to this interaction, providing a conductive network for sufficient electrolyte penetration and rapid charge transfer. As predicted, the VS2 /MXene nanostructures exhibit an extremely low sodium diffusion barrier confirmed by DFT calculations and small charge transfer impedance evidenced by electrochemical impedance spectroscopy (EIS) analysis. Therefore, the SIBs based on the VS2 /MXene electrode present first-class electrochemical performance with the ultrahigh average initial columbic efficiency of 95.08% and excellent sodium-ion storage capacity of 424.6mAhg-1 even at 10Ag-1 . It also shows an outstanding sodium-ion storage capacity of 514.2mAhg-1 at 1Ag-1 with a capacity retention of nearly 100% within 500 times high-rate cycling. Such impressive performance demonstrates the successful synthesis strategy and the great potential of interfacial interactions for high-performance energy storage devices.

2D-Layer-Structure Bi to Quasi-1D-Structure NiBi3 : Structural Dimensionality Reduction to Superior Sodium and Potassium Ion Storage.

Layer-structured bismuth (Bi) is an attractive anode for Na-ion and K-ion batteries due to its large volumetric capacity and suitable redox potentials. However, the cycling stability and rate capability of the Bi anode are restricted by the large volume expansion and sluggish Na/K-storage kinetics. Herein, a structural dimensionality reduction strategy is proposed and developed by converting2D-layer-structured Bi into a quasi-1D structured NiBi3 with enhanced reaction kinetics and reversibility to realize high-rate and stable cycling performance for Na/K-ion storage. As a proof of concept, the quasi-1D intermetallic NiBi3 with low formation energy, metallic conductivity, and 3D Na/K-ion diffusion pathways delivers outstanding capacity retention of 94.1% (332 mAh g-1 ) after 15000 cycles for Na-ion storage, and high initial coulombic efficiency of 93.4% with improved capacity retention for K-ion storage. Moreover, investigations on the highly reversible Na/K-storage reaction mechanisms and cycling-driven morphology reconstruction further reveal the origins of the high reversibility and the accommodation to volume expansion. The finding of this work provides a new strategy for high-performance anode design by structural dimensionality manipulation and cycling-driven morphology reconstruction.

An investigation of the lattice parameter and micro-strain behaviour of LiMn2O4 coated with LiMn1.5Ni0.5O4 to attain high-rate capability and cycling stability

This research provides new insights on the lattice parameters, development of micro strain, and electrochemical properties of uniquely-designed core-shell structure of the LiMn2O4@LiMn1.5Ni0.5O4 composite. The investigation of lattice expansion and contraction during cycling, and evolution of micro strain, provided a better mechanistic understanding of Li+ diffusion. The LiMn2O4 (LMO) was successfully interfaced with LiMn1.5Ni0.5O4 (LMNO) to modify the surface of spinel LiMn2O4 particles through solution combustion and Pluronic polymer assisted composite synthesis. The unique synthesis approach significantly enhanced the rate capability. The LMO@LMNO composite was characterized using XRD, XPS, TEM, CV and charge/discharge characterization. The material characterization results confirmed that the LMO@LMNO composite had slightly larger lattice parameter (8.24027 Å) compared to the pristine LMO (8.2402 Å) and LMNO (8.18511 Å). The micro-strain of the composite is 2.1 × 10−3 μm/m (LMO@LMNO); this is higher than the individual components 1.28 × 10−3 μm/m (LMO), and 1.22 × 10−3 μm/m (LMNO). As expected, the micro-strain of the composite increased during composite formation which induces defects and microscopic stresses. The LMO@LMNO sample exhibited superior electrochemical properties at all current rates as compared LMO. The LMNO delivered a low capacity for high current rates compared to LMO and LMO@LMNO samples; this was attributed to the unique synthesis approach. The first cycle capacities of LMO, LMNO, and LMO@LMNO, were 101 mAh g−1, 125 mAh g−1, 123 mAh g−1 (0.2C). As expected, the discharge capacities for LMO, LMNO, and LMO@LMNO reduced after 120 cycles to 95 mAh g−1 (94 %), 122 mAh g−1 (97.3 %) and 119 mAh g−1 (96.2 %), respectively. In brief, composite LMO@LMNO core-shell structure exhibited superior electrochemical properties due to the higher Ni ratios coupled with the formation a surface layer.

Growing Electrocatalytic Conjugated Microporous Polymers on Self-Standing Carbon Nanotube Films Promotes the Rate Capability of Li-S Batteries.

Lithium-sulfur (Li-S) batteries hold great promise for widespread application on account of their high theoretical energy density (2600Wh kg-1 ) and the advantages of sulfur. Practical use, however, is impeded by the shuttle effect of polysulfides along with sluggish cathode kinetics. it is reported that such deleterious issues can be overcome by using a composite film (denoted as V-CMP@MWNT) that consists of a conjugated microporous polymer (CMP) embedded with vanadium single-atom catalysts (V SACs) and a network of multi-walled carbon nanotubes (MWNTs). V-CMP@MWNT films are fabricated by first electropolymerizing a bidentate ligand designed to coordinate to V metals on self-standing MWNT films followed by treating the CMP with a solution containing V ions. Li-S cells containing a V-CMP@MWNT film as interlayer exhibit outstanding performance metrics including a high cycling stability (616mA h g-1 at 0.5 C after 1000 cycles) and rate capability (804mA h g-1 at 10 C). An extraordinary area-specific capacity of 13.2mA h cm-2 is also measured at a high sulfur loading of 12.2mg cm-2 . The underlying mechanism that enables the V SACs to promote cathode kinetics and suppress the shuttle effect is elucidated through a series of electrochemical and spectroscopic techniques.

Highly Conductive Polyoxanorbornene-Based Polymer Electrolyte for Lithium-Metal Batteries.

This present study illustrates the synthesis and preparation of polyoxanorbornene-based bottlebrush polymers with poly(ethylene oxide) (PEO) side chains by ring-opening metathesis polymerization for solid polymer electrolytes (SPE). In addition to the conductive PEO side chains, the polyoxanorbornene backbones may act as another ion conductor to further promote Li-ion movement within the SPE matrix. These results suggest that these bottlebrush polymer electrolytes provide impressively high ionic conductivity of 7.12 × 10-4 S cm-1 at room temperature and excellent electrochemical performance, including high-rate capabilities and cycling stability when paired with a Li metal anode and a LiFePO4 cathode. The new design paradigm, which has dual ionic conductive pathways, provides an unexplored avenue for inventing new SPEs and emphasizes the importance of molecular engineering to develop highly stable and conductive polymer electrolytes for lithium-metal batteries (LMB).

Dual-vapour-thermal engineering evoking bound water pathways of vanadium oxide for high-rate and durable zinc-ion storage

Vanadium oxides have attracted extensive attention as promising cathode materials for aqueous zinc-ion batteries (AZIBs) owing to their variable valences and laminar structures. However, the strong interaction between divalent Zn2+ and the [VOn] host lattice limits its application. In this study, a facile dual-vapour-thermal engineering strategy was proposed for the first time to reconstruct V2O5 as an advanced cathode for AZIBs. Synchrotron radiation X-ray adsorption and photoelectron spectroscopies revealed that the high pressure and thermal environments of the ethanol/water dual-vapour phase trigger the fast formation of oxygen-deficient vanadium oxide hydrates (VPH-VO) containing rich bound water pathways. The in situ Raman spectra verified that these bound water pathways shield the electrostatic interaction within the lamellar [VOn] host, providing a more favourable environment for Zn2+ diffusion. The VPH-VO cathode delivered an outstanding capacity of 452 mA h g−1 at 0.5 A/g and an excellent high-rate cycling stability of 242 mA h g−1 after 2000 cycles at 10 A/g. Density functional theory calculation disclosed the highly reversible Zn2+ adsorption/desorption and low zinc-ion migration barrier in the bound water pathways of VPH-VO. This pioneering dual-vapour-thermal engineering is an efficient fabrication approach for superior lamellar cathode materials for high-performance AZIBs.

Atomic Layer Deposition of Alumina-Coated Thin-Film Cathodes for Lithium Microbatteries.

This work shows the electrochemical performance of sputter-deposited, binder-free lithium cobalt oxide thin films with an alumina coating deposited via atomic layer deposition for use in lithium-metal-based microbatteries. The Al2O3 coating can improve the charge-discharge kinetics and suppress the phase transition that occurs at higher potential limits where the crystalline structure of the lithium cobalt oxide is damaged due to the formation of Co4+, causing irreversible capacity loss. The electrochemical performance of the thin film is analysed by imposing 4.2, 4.4 and 4.5 V upper potential limits, which deliver improved performances for 3 nm of Al2O3, while also highlighting evidence of Al doping. Al2O3-coated lithium cobalt oxide of 3 nm is cycled at 147 µA cm-2 (~2.7 C) to an upper potential limit of 4.4 V with an initial capacity of 132 mAh g-1 (65.7 µAh cm-2 µm-1) and a capacity retention of 87% and 70% at cycle 100 and 400, respectively. This shows the high-rate capability and cycling benefits of a 3 nm Al2O3 coating.