O2 Cathode Research Articles

A novel hybrid sodium ion capacitor based on Na [Ni0.60Mn0.35Co0.05] O2 battery type cathode and presodiated D-Ti3C2Tx pseudocapacitive anode

The combination of the high-power density of supercapacitors and the high energy density of batteries makes hybrid sodium-ion capacitors (HSICs) a promising device. HSICs can provide better performance characteristics by harnessing both ion adsorption/desorption in the capacitor-type electrode and sodium-ion intercalation in the battery-type electrode. Here, the synthesis of MXene (Ti3C2Tx), a two-dimensional (2D) carbide and nitride is reported. Delaminated MXene (D-Ti3C2Tx) is a promising candidate for anode material in HSIC due to its large surface area (∼ 42 m2/g) and good electronic conductivity. Electrochemical study indicates that D-Ti3C2Tx anode exhibits a high discharge capacity of ∼213 mAh/g at a current rate of 20 mA/g. Further the presodiated D-Ti3C2Tx anode is paired with Na [Ni0.60Mn0.35Co0.05] O2 (P2-NMC) cathode to obtain the configuration of HSIC. The HSIC exhibits good specific capacitance of ∼187 F/g and specific discharge capacity of ∼110 mAh/g at a current density of 10 mA/g, according to the electrochemical analysis. A notable improvement in specific energy density (∼ 256 Wh/kg) and specific power density (∼579 W/kg) is also demonstrated by the HSIC. With P2-NMC being used as the cathode material rather than traditional activated carbon, there has been a rise in specific energy density.

A General Strategy toward Enhanced Electrochemical and Mechanical Performance of Solid‐State Lithium Batteries through Constructing Covalently Bonded Electrode Materials/Electrolyte Interfaces

AbstractSolid‐state lithium batteries (SSLBs) offer inherent safety and high energy density for next‐generation energy storage, but the large interfacial resistance and poor physical connection between electrode materials and the solid electrolyte (SE) severely impede their practical applications. This work reports a general strategy to introduce covalent bonds between electrode materials and SE, not only reducing interfacial resistance but also enhancing electrochemical stability and mechanical robustness of SSLBs. The covalent bonding is accomplished by functionalizing electrode surfaces with C═C groups, enabling in situ copolymerization with telechelic polymers in the SE. This approach is applicable to various cathode/anode materials and SEs. Particularly, the SSLBs comprising LiFePO4 cathode, Li6.75La3Zr1.75Ta0.25O12/(polyethylene oxide (PEO)/lithium bis(trifluoromethylsulfonyl)imide (LiTFSI)/silk composite SE and metallic lithium anode exhibit a specific capacity of 158.4 mAh g−1 and can be cycled at 2 C for 2200 times with >80% retention. Additionally, the SSLBs containing the high nickel‐content LiNi0.96Co0.03Mn0.01O2 cathode can afford a high specific capacity of 201.8 mAh g−1. Comprehensive experimental examination and theoretical simulations confirm that the lowered interfacial resistance and intimately contacted electrode materials/electrolyte interfaces facilitate Li+ transport at different stages of charge. Furthermore, the covalently bonded electrode/electrolyte interfaces also endow SSLBs with outstanding mechanical stability, enabling flexible SSLB pouch cells to operate under various bending states without performance decay.

Dilute Electrolytes with Fluorine‐Free Ether Solvents for 4.5 V Lithium Metal Batteries

AbstractThe limited oxidation stability of ether solvents has posed significant challenges for their applications in high‐voltage lithium metal batteries (LMBs). To tackle this issue, the prevailing strategy either adopts a high concentration of fluorinated salts or relies on highly fluorinated solvents, which will significantly increase the manufacturing cost and create severe environmental hazards. Herein, an alternative and sustainable salt engineering approach is proposed to enable the utilization of dilute electrolytes consisting of fluorine (F)‐free ethers in high‐voltage LMBs. The proposed 0.8 M electrolyte supports stable lithium plating‐stripping with a high Coulombic efficiency of 99.47 % and effectively mitigates the metal dissolution, phase transition, and gas release issues of the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode upon charging to high voltages. Consequently, the 4.5 V high‐loading Li||NCM 811 cell shows a capacity retention of 75.2 % after 300 cycles. Multimodal experimental characterizations coupled with theoretical investigations demonstrate that the boron‐containing salt plays a pivotal role in forming the passivation layers on both anode and cathode. The present simple and cost‐effective electrolyte design strategy offers a promising and alternative avenue for using commercially mature, environmentally benign, and low‐cost F‐free ethers in high‐voltage LMBs.

Anion‐Reduction‐Catalysis Induced LiF‐Rich SEI Construction for High‐Performance Lithium‐Metal Batteries

AbstractThe practical application of lithium‐metal batteries (LMBs) remains impeded by uncontrollable Li dendrite growth and unstable solid‐state electrolyte interphase (SEI) on lithium‐metal anodes. Constructing the inorganic‐rich SEI is considered as an effective strategy to realize the dense Li deposition and inhibit interfacial side reactions, thereby improving the lifespans of LMBs. Herein, an anion‐reduction‐catalysis mechanism is proposed to design a LiF‐rich SEI utilizing 2D tellurium (Te) nanosheets as catalysts, which are homogenously implanted on the substrate. Lithiophilic Te nanosheets can induce uniform Li nucleation and deposition through in situ lithiation reactions, while the resulting product Li2Te can reduce the energy barrier for anion decomposition and promote the generation of LiF in the SEI. Consequently, Li dendrite growth and interfacial side reactions are effectively suppressed, enabling long‐cycle‐life LMBs. The Te‐modified electrode in half‐cells delivers superior cycle life exceeding 500 cycles and a high average Coulombic efficiency of 97.8% at 5 mAh cm−2. The high‐energy‐density (405 Wh kg−1) pouch cells pairing the Te‐modified Li anodes with high‐mass‐loading LiNi0.9Co0.05Mn0.05O2 (NCM90) cathodes exhibit stable cycling performance with a high average Coulombic efficiency of 99.3% in carbonate electrolytes. This work provides a promising anion catalyst design for LiF‐rich SEI and paves the way for developing high‐energy‐density LMBs.

Toward High-Energy-Density Initial-Anode-Free Lithium-Metal Batteries via Ultra-Thin Protective Ion-Transport-Promoting Interface Modification and Surface Prelithiation.

Anode-free lithium-metal batteries (AFLMBs) are desirable candidates for achieving high-energy-density batteries, while severe active Li+ loss and uneven Li plating/stripping behavior impede their practical application. Herein, a trilaminar LS-Cu (LiCPON + Si/C-Cu)current collector is fabricated by radio frequency magnetron sputtering, including a Si/C hybrid lithiophilic layer and a supernatant carbon-incorporated lithium phosphorus oxynitride (LiCPON) solid-state electrolyte layer. Joint experimental and computational characterizations and simulations reveal that the LiCPON solid-state electrolyte layer can decompose into an in situ stout ion-transport-promoting protective layer, which can not only regulate homogeneous Li plating/stripping behavior but also inhibit the pulverization and deactivation of Si/C hybrid lithiophilic layer. When combined with surface prelithiated Li1.2Ni0.13Co0.13Mn0.54O2 (Preli-LRM) cathode, the Preli-LRM||LS-Cu full cell delivers 896.1Wh kg-1 initially and retains 354.1Wh kg-1 after 50 cycles. This strategy offers an innovative design of compensating for active Li+ loss and inducing uniform Li plating/stripping behavior simultaneously for the development of AFLMBs.

An Utrastable Mg/Zr Modified P2‐Type Na2/3Ni1/3Mn2/3O2 Cathode Material for High‐Power Sodium‐Ion Batteries

AbstractP2‐Na2/3Ni1/3Mn2/3O2 demonstrates high energy density owing to its high specific capacity and high discharge voltage, but suffering from rapid performance decay due to severe structural degradation and aggravated surface side reaction during high‐voltage cycling. Herein, a Mg/Zr modified Na0.67Ni0.25Mg0.08Mn0.64Zr0.03O2 cathode is proposed with good structural stability and excellent cycling performance, showing reversible capacity of 123.2 mAh g−1 (0.1 C) and capacity retention of 99.1% after 100 cycles. The cycling stability is outstanding among P2‐type cathodes reported so far. In situ XRD analyses reveal a suppressed P2‐O2 phase transition after Mg modification, further incorporation of Zr greatly stabilizes the layered structure as some Zr ions reside in the Na layer providing a pinning effect to reduce the slide of TMO2 layer. First‐principles calculations suggest that oxygen loss in Na0.67Ni0.25Mg0.08Mn0.64Zr0.03O2 cathode is suppressed as Zr incorporation prevents the formation of oxygen vacancies. XPS analyses verify a Zr─O protective layer self‐segregated on particle surface during material synthesis. The expanded Na+ transport channel confirmed by the XRD analysis well explains the favored Na‐ion mobility verified by a high reversible capacity of 105.5 mAh/g at 20 C. This work sheds new light on providing a practical P2‐structured cathode material for high‐power sodium ion batteries.

Ultrafast and Highly Efficient Sodium Ion Storage in Manganese‐Based Tunnel‐Structured Cathode

AbstractNa0.44MnO2 with tunnel structure is considered a promising low‐cost cathode material for sodium‐ion batteries. However, the sluggish Na+ transport kinetics and low initial Coulombic efficiency restrict its practical applications in rechargeable sodium‐ion batteries. Herein, a manganese‐based tunnel‐structured cathode with high rate capability and high initial Coulombic efficiency is prepared by niobium doping and sodium compensation. Via materials characterizations and theoretical calculations, it is demonstrated that a proper amount of niobium doping in tunnel structure can effectively improve its structural stability and charge transport kinetics, resulting in outstanding rate capability (76.6% capacity retained from 0.5 to 30 C) and superior cycling performance (82.3% capacity retention after 800 cycles at 5 C) for the optimized Nb‐doped Na0.44MnO2 cathode (Na0.44Mn0.98Nb0.02O2). Furthermore, NaCrO2 is added into the Na0.44Mn0.98Nb0.02O2 cathode as a self‐sacrificing sodium compensation additive, and a high initial Coulombic efficiency close to 100% is achieved for the composite cathode. This work establishes a facile strategy to design advanced manganese‐based cathode materials for large‐scale energy storage applications.

Dilute Electrolytes with Fluorine-Free Ether Solvents for 4.5 V Lithium Metal Batteries.

The limited oxidation stability of ether solvents has posed significant challenges for their applications in high-voltage lithium metal batteries (LMBs). To tackle this issue, the prevailing strategy either adopts a high concentration of fluorinated salts or relies on highly fluorinated solvents, which will significantly increase the manufacturing cost and create severe environmental hazards. Herein, an alternative and sustainable salt engineering approach is proposed to enable the utilization of dilute electrolytes consisting of fluorine (F)-free ethers in high-voltage LMBs. The proposed 0.8 M electrolyte supports stable lithium plating-stripping with a high Coulombic efficiency of 99.47 % and effectively mitigates the metal dissolution, phase transition, and gas release issues of the LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode upon charging to high voltages. Consequently, the 4.5 V high-loading Li||NCM 811 cell shows a capacity retention of 75.2 % after 300 cycles. Multimodal experimental characterizations coupled with theoretical investigations demonstrate that the boron-containing salt plays a pivotal role in forming the passivation layers on both anode and cathode. The present simple and cost-effective electrolyte design strategy offers a promising and alternative avenue for using commercially mature, environmentally benign, and low-cost F-free ethers in high-voltage LMBs.

Achieving High-Capacity Cathode Presodiation Agent Via Triggering Anionic Oxidation Activity in Sodium Oxide.

Compensating for the irreversible loss of limited active sodium (Na) is crucial for enhancing the energy density of practical sodium-ion batteries (SIBs) full-cell, especially when employing hard carbon anode with initially lower coulombic efficiency. Introducing sacrificial cathode presodiation agents, particularly those that own potential anionic oxidation activity with a high theoretical capacity, can provide additional sodium sources for compensating Na loss. Herein, Ni atoms are precisely implanted at the Na sites within Na2O framework, obtaining a (Na0.89Ni0.05□0.06)2O (Ni-Na2O) presodiation agent. The synergistic interaction between Na vacancies and Ni catalyst effectively tunes the band structure, forming moderate Ni-O covalent bonds, activating the oxidation activity of oxygen anion, reducing the decomposition overpotential to 2.8V (vs Na/Na+), and achieving a high presodiation capacity of 710 mAh/g≈Na2O (Na2O decomposition rate >80%). Incorporating currently-modified presodiation agent with Na3V2(PO4)3 and Na2/3Ni2/3Mn1/3O2 cathodes, the energy density of corresponding Na-ion full-cells presents an essential improvement of 23.9% and 19.3%, respectively. Further, not limited to Ni-Na2O, the structure-function relationship between the anionic oxidation mechanism and electrode-electrolyte interface fabrication is revealed as a paradigm for the development of sacrificial cathode presodiation agent.

High-performance single crystal Ni-rich cathode with regulated lattice and interface constructed by separated lithiation and crystallization calcination

Incorporating high valence dopants, such as W6+ and Mo6+ has been verified to be effective for tuning the microstructure and grain boundary of polycrystal Ni-rich cathode. However, the hindered consolidation of primary particles induced by dopants during lithiation calcination limits the utilization of those dopants to crystalize single-crystal Ni-rich cathodes with stabilized lattice and surface. Herein, high performance single crystal LiNi0.84Co0.11Mn0.05O2 cathode with Al3+ and W6+ regulated lattice and boundary phase was construed based on commercial process with two-step calcination process containing separated lithiation and crystallization. The introduction of appropriate amount of Al3+ in the first lithiation calcination of 6 h endows the bulk of crystalline with enhanced lattice stability, while the incorporation of W6+ with stoichiometrical LiOH in the secondary crystallization calcination of 6 h renders uniformly distributed surface layer without hampering the growth of single-crystal. With the Al3+ doped bulk lattice, W6+ doped subsurface region and hetero-epitaxially grown Li2WO4, the cathode infused by two-step calcination exhibits high discharge capacity, rate performance, and cycling stability. Specifically, the modified LiNi0.84Co0.11Mn0.05O2 exhibits exceptional capacity retention, maintaining 88.98% of its initial capacity after 200 cycles at a rate of 1 C within a voltage window of 2.7–4.3 V at a temperature of 25 °C in half-cell. This performance is markedly superior to the capacity retention of 72.96% observed for pristine cathode. Even when subjected to a stringent test after 200 cycles at the same rate, the modified cathode sustains an impressive capacity retention of 82.41% at an elevated cut-off voltage of 4.5 V and a temperature of 30 °C.

Carbon-Binder-Domain porosity extraction through lithium-ion battery electrode impedance data

In the field of 3-D resolved computational modelling of Lithium-ion battery electrodes, the arrangement and properties of the Carbon-Binder-Domain (CBD) play a critical role in the ion and electron transport properties through their impact on the electrode tortuosity factor. However, until now, the CBD porosity value -its main descriptor in terms of transport properties and occupied volume- has been determined through educated guesses due to the lack of an experimental approach. Here, a novel methodology is reported for the determination of the CBD internal porosity through the combination of computational modelling and experimental electrochemical impedance spectroscopy (EIS). The methodology is based on the creation of a calibration curve that relates tortuosity factor with CBD porosity through digital stochastic generation of electrode microstructures and diffusivity characterization. The curve is then compared to the EIS experimental results and analyzed through a transmission line model, yielding a good estimation of the parameters. In this work, the usefulness and the identified limitation of this approach are demonstrated using three different formulations of LiNi0.3Mn0.3Co0.3O2 (NMC 111) cathodes. To the best of the authors’ knowledge, this is the first reported method for estimating CBD porosity.

Eliminating Hydrogen Fluoride through Piperidine-Doped Separators for Stable Li Metal Batteries with Nickel-Rich Cathodes.

Hydrofluoric acid (HF)-induced electrode and interfacial structure degeneration poses a significant challenge for high-voltage lithium metal batteries (LMBs). To address this issue, we propose a separator strategy that involves decorating a regular polyethylene (PE) separator with molecular sieves (TW) impregnated with piperidine (PI). The porous structure of the TW serves as a reaction chamber for PI and HF. As a result, the HF content in the controlled electrolyte with 500 ppm H2O (ELE-500) is notably reduced when using TW@PI-PE separators, thereby shielding nickel-rich cathodes from HF etching. Simultaneously, due to the hydrolysis of Li salts, and the inertness of PI towards H2O, a uniform lithium fluoride (LiF)-rich solid electrolyte interphase can form on the Li metal anode, further mitigating dendrite formation. The lifespan of the symmetric Li cell using the TW@PI-PE separator is doubled in ELE-500, exhibiting stable 500-hour cycles at 3 mA cm-2 and 3 mAh cm-2. Additionally, with the effective limitation of transition metal (TM) dissolution, the 4.6-V LMBs employing a LiNi0.8Co0.1Mn0.1O2 cathode maintain an 81% capacity retention over 100 cycles, even in ELE-1000. The innovative TW@PI system presented here offers a fresh perspective for future research aimed at eliminating HF in LMBs.

Solvation Regulation Reinforces Anion-Derived Inorganic-Rich Interphase for High-Performance Quasi-Solid-State Li Metal Batteries.

Solid-state polymer lithium metal batteries are an important strategy for achieving high safety and high energy density. However, the issue of Li dendrites and inherent inferior interface greatly restricts practical application. Herein, this study introduces tris(2,2,2-trifluoroethyl)phosphate solvent with moderate solvation ability, which can not only complex with Li+ to promote the in-situ ring-opening polymerization of 1,3-dioxolane (DOL), but also build solvated structure models to explore the effect of different solvation structures in the polymer electrolyte. Thereinto, it is dominated by the contact ion pair solvated structure with pDOL chain segments forming less lithium bonds, exhibiting faster kinetic process and constructing a robust anion-derived inorganic-rich interphase, which significantly improves the utilization rate of active Li and the high-voltage resistance of pDOL. As a result, it exhibits stable cycling at ultra-high areal capacity of 20 mAh cm-2 in half cells, and an ultra-long lifetime of over 2000h in symmetric cells can be realized. Furthermore, matched with LiNi0.9Co0.05Mn0.05O2 cathode, the capacity retention after 60 cycles is as high as 96.8% at N/P value of 3.33. Remarkably, 0.7 Ah Li||LiNi0.9Co0.05Mn0.05O2 pouch cell with an energy density of 461Wh kg-1 can be stably cycled for five cycles at 100% depth of discharge.

An Efficient and Eco-Friendly Recycling Route of Valuable Metals from Spent Ternary Li-Ion Batteries: Kinetics Evaluation of Chlorination Processes and Regeneration of LiNi0.8Co0.1Mn0.1O2 Cathode Materials.

The recycling of spent Li-ion batteries is urgent, and the effective recovery of valuable metals from spent cathode material is an economic and eco-friendly approach. In this study, Ni, Cu, Co, and Mn were extracted synchronously from spent LiNixCoyMn1-x-yO2 by chlorination and the complexation reaction of ammonium chloride at low temperatures. The kinetics of the chlorination process was investigated by nonisothermal thermal analysis to determine the rate equation of metal conversion, and the apparent activation energies were calculated to be 99.96 kJ·mol-1 for lithium and 146.70 kJ·mol-1 for nickel, cobalt, and manganese, respectively. The separation of valuable metals from polymetallic leaching solution and the regeneration of cathode materials were further investigated to promote the industrialization of the process. The recoveries of Ni, Co, Mn, and Li can reach 97.75, 99.99, 99.99, and 92.23%, respectively. The prepared LiNi0.8Co0.1Mn0.1O2 precursor is a multilayer spherical particle formed by stacking primary hexagonal nanosheets along the (010) crystal axis, the formation mechanism of which was discussed. The effect of temperature, time, and mixed lithium ratio on the performance of single crystal LiNi0.8Co0.1Mn0.1O2 cathode in the synthesis process was investigated to determine the optimum conditions. Compared with commercial materials, the prepared single crystal LiNi0.8Co0.1Mn0.1O2 cathode has a more regular crystal structure and higher initial discharge capacity (215.9 mAh·g-1 at 0.1 C).

Electrochemical and mechanical characterization of thermosets as fluorine‐free cathode binders for Li‐ion batteries

AbstractThis study demonstrates fluorine‐free cross‐linked (meth)acrylate polymers as alternatives to polyvinylidene fluoride (PVDF) in LiNi0.33Mn0.33Co0.33O2 (NMC111) cathodes. We determine the effects of thermal initiator content, polymer content, and curing environment for two polymer chemistries: a flexible acrylate polymer, and a stiff methacrylate polymer. Electrodes are manufactured and tested for final electrochemical performance and mechanical properties. The results show that the flexible acrylate polymer exhibits higher rate capability compared to the stiff methacrylate polymer because calendering fractures the brittle network of stiff polymer. Electrode adhesion to the current collector and cohesion between particles are found to be a strong function of thermal initiator ratio and oxygen inhibition. Furthermore, there exists an optimal binder concentration that maximizes rate capability performance. Under the right conditions, the two polymers exhibit comparable performance to PVDF electrodes. These results provide important implications for designing cross‐linked polymers as cathode binder alternatives to PVDF.

High-Performance Sheet-Type Sulfide All-Solid-State Batteries Enabled by Dual-Function Li4.4Si Alloy-Modified Nano Silicon Anodes.

The silicon-based anodes are one of the promising anodes to achieve the high energy density of all-solid-state batteries (ASSBs). Nano silicon (nSi) is considered as a suitable anode material for assembling sheet-type sulfide ASSBs using thin free-standing Li6PS5Cl (LPSC) membrane without causing short circuit. However, nSi anodes face a significant challenge in terms of rapid capacity degradation during cycling. To address this issue, dual-function Li4.4Si modified nSi anode sheets are developed, in which Li4.4Si serves a dual role by not only providing additional Li+ but also stabilizing the anode structure with its low Young's modulus upon cycling. Sheet-type ASSBs equipped with the Li4.4Si modified nSi anode, thin LPSC membrane, and LiNi0.83Co0.11Mn0.06O2 (NCM811) cathode demonstrate exceptional cycle stability, with a capacity retention of 96.16% at 0.5 C (1.18mA cm-2) after 100 cycles and maintain stability for 400 cycles. Furthermore, a remarkable cell-level energy density of 303.9Wh kg-1 is achieved at a high loading of 5.22 mAh cm-2, representing a leading level of sulfide ASSBs using electrolyte membranes at room temperature. Consequently, the chemically stable slurry process implemented in the fabrication of Li4.4Si-modified nSi anode sheet paves the way for scalable applications of high-performance sulfide ASSBs.

Mo-doped LiNi0.8Co0.1Mn0.1O2 cathode materials with improved performance for lithium ion batteries

The high nickel ternary LiNi[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2 (NCM811) cathode material has attracted much attention owing to its advantages of high capacity and low price. However, NCM811 suffers from surface side reactions and cation mixing, which results in an unstable crystal structure and lower Coulomb efficiency and capacity in lithium ion batteries. In this work, Mo-doped cathode material NCM811 is effectively synthesized by high-temperature solidification approach. The characterization results show that the doped NCM811 can form a coating layer on the surface, preventing electrolyte side reactions with the electrode. As the cathode for lithium ion batteries, the Mo-doped NCM811 electrode shows an initial discharge capacity of 185.21[Formula: see text]mAh/g and obtains 156.33[Formula: see text]mAh/g with a capacity retention of 84.5% after 100 cycles at 1C. This study provides a simple and reliable method of fabricating high-performance NCM811 cathode materials.

Enhancing Li-ion diffusivity of Li1.3Al0.3Ti1.7(PO4)3 through liquid-electrolytes-induced secondary crystallization

Solid electrolytes (SEs) offer promising avenues for improving both the energy density and safety of lithium-ion batteries (LIBs). However, the grain boundary resistance remains a significant hurdle that impact the performance of LIBs, particularly when utilizing SEs in powder form. In this study, we introduce a novel approach to reduce grain boundary resistance in Li1.3Al0.3Ti1.7(PO4)3 (LATP) via secondary crystallization induced by liquid electrolytes (LEs). By immersing nano-sized LATP powders in LiPF6/carbonates LEs, rapid aggregation and recrystallization into bulk micrometer-sized particles occur within minutes under ambient conditions. This secondary crystallization process alters the Li distribution within LATP bulk phase, substantially reducing the grain boundary resistance and enhancing Li-ion diffusivity. Consequently, the assembled LATP-modified commercial LiNi0.89Co0.07Mn0.04O2 cathode using LiPF6 electrolyte delivers a remarkable discharge capacity of 105.4 mAh g−1 at 4C, significantly superior to the bare electrode (44.7 mAh g−1). The recrystallized LATP enhances the transport properties and pathways of Li+ ions within the cathode material, especially at high current densities. Multinuclear and multi-dimensional solid-state NMR analysis reveal that active F− ions released from the hydrolysis of LiPF6 electrolytes act as mineralizing agent, facilitating rapid agglomeration and secondary growth of LATP grains. Our findings underscore the efficacy of secondary crystallization using LEs as a promising strategy for eliminating grain boundary resistance and facilitating fast Li-ion conduction of SEs, thereby advancing LIB performance.

Highly‐Dispersed Single‐Crystalline Ni‐Rich Cathodes with Low Li/O Loss for High‐Power and Long‐Life Li‐Ion Batteries

AbstractHighly‐dispersed single‐crystalline Ni‐rich cathodes with low Li/O loss are the key for high‐power Li‐ion batteries, but it is still a big challenge because an additional 60–110 °C higher synthesis temperature is required in comparison with the polycrystalline counterparts. Herein, a highly‐ordered and monodisperse single‐crystalline LiNi0.83Co0.12Mn0.05O2 (NCM83) cathode with an average size of 3.24 µm is reported by a Sr/Nb synergically controlling the grain surface energy strategy based on the Vegard's slopes of various ions. The solid‐phase lithiation temperature is reduced by ≈80 °C, greatly reducing Li/Ni disorder and oxygen vacancies with rapid Li‐ion diffusion kinetics and high structure stability. The introduced Sr/Nb ions remarkably increase the electron cloud density near the Fermi level, while alleviating the H2‐H3 phase transition with reduced lattice shrinkage. The as‐prepared single‐crystalline NCM83 cathode exhibits obvious increased capacity retention of 60% at 10C (vs. 0.1C) in coin‐type half‐cells and 89% after cycling 1000 times at 0.5C in pouch‐type full‐cells. The work sheds light on the low‐temperature synthesis of monodisperse and uniform single‐crystalline Ni‐rich cathodes for high‐power and long‐life Li‐ion batteries.

Mechanism of chromium poisoning on La0.5Sr0.5Co0.25Fe0.75O3 cathode and enhancing chromium tolerance using a novel anion doping strategy

Chromium poisoning the La1-xSrxCoyFe1-yO3(LSCF) cathode for solid oxide fuel cells is a severe issue that can lead to its electrochemical performance degradation. To clarify poisoning mechanism of chromium species and develop a novel anion doping strategy with enhancing chromium tolerance, the adsorption behavior of Cr species on LSCF and F-doping LSCF surface are explored by density functional theory (DFT) calculations. Our results indicate that CrO3 molecule prefers to be adsorbed on the La(Sr)O-terminated surface rather that the Co(Fe)O2-terminated LSCF(001) surface. The adsorption energies of CrO3 molecule are much larger than that of O2 molecules, implies that the CrO3 is more favorable to absorb on the LSCF surface. Bader charge analysis shows the CrO3 molecule behaves as an electron acceptor through an adsorption process. The adsorption of Cr atom is a weak physical adsorption for Sr site and La site and the Cr atom chemisorption is found to occur on hollow site and O site. In addition, F-doping efficiently improves chromium tolerance by weakening the adsorption strength of chromium species that poisons LSCF surface and this may be a feasible strategy to develop cathode for high performance solid oxide fuel cells.