Lithium‐rich layered oxides with the capability to realize extraordinary capacity through anodic redox as well as classical cationic redox have spurred extensive attention. However, the ...oxygen‐involving process inevitably leads to instability of the oxygen framework and ultimately lattice oxygen release from the surface, which incurs capacity decline, voltage fading, and poor kinetics. Herein, it is identified that this predicament can be diminished by constructing a spinel Li4Mn5O12 coating, which is inherently stable in the lattice framework to prevent oxygen release of the lithium‐rich layered oxides at the deep delithiated state. The controlled KMnO4 oxidation strategy ensures uniform and integrated encapsulation of Li4Mn5O12 with structural compatibility to the layered core. With this layer suppressing oxygen release, the related phase transformation and catalytic side reaction that preferentially start from the surface are consequently hindered, as evidenced by detailed structural evolution during Li+ extraction/insertion. The heterostructure cathode exhibits highly competitive energy‐storage properties including capacity retention of 83.1% after 300 cycles at 0.2 C, good voltage stability, and favorable kinetics. These results highlight the essentiality of oxygen framework stability and effectiveness of this spinel Li4Mn5O12 coating strategy in stabilizing the surface of lithium‐rich layered oxides against lattice oxygen escaping for designing high‐performance cathode materials for high‐energy‐density lithium‐ion batteries.
A heterostructured spinel Li4Mn5O12 encapulated lithium‐rich layered oxide cathode is designed by the controlled KMnO4 oxidiation strategy. Spinel Li4Mn5O12 is chosen due to its lattice stability against oxygen release as well as a 3D lithium diffusion framework with minimal Jahn–Teller distortion. Such uniform coating can suppress lattice oxygen release, associated phase transformation, and catalytic side reactions, consequently ensuring improved electrochemical performance.
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The key issue holding back the application of solid polymeric electrolytes in high‐energy density lithium metal batteries is the contradictory requirements of high ion conductivity and mechanical ...stability. In this work, self‐healable solid polymeric electrolytes (SHSPEs) with rigid‐flexible backbones and high ion conductivity are synthesized by a facile condensation polymerization approach. The all‐solid Li metal full batteries based on the SHSPEs possess freely bending flexibility and stable cycling performance as a result of the more disciplined metal Li plating/stripping, which have great implications as long‐lifespan energy sources compatible with other wearable devices.
Solid but flexible: A self‐healing solid polymer electrolyte (featuring fast self‐healing within 60 s after a deep cut with a blade) endows solid Li metal full batteries with freely bending flexibility and superior cycling stability as demonstrated by the small capacity decay of 0.1 % per cycle over 100 cycles.
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A hybrid solid/liquid electrolyte with superior security facilitates the implementation of high‐energy‐density storage devices, but it suffers from inferior chemical compatibility with cathodes. ...Herein, an optimal lithium difluoro(oxalato)borate salt was introduced to build in situ an amorphous cathode electrolyte interphase (CEI) between Ni‐rich cathodes and hybrid electrolyte. The CEI preserves the surface structure with high compatibility, leading to enhanced interfacial stability. Meanwhile, the space‐charge layer can be prominently mitigated at the solid/solid interface via harmonized chemical potentials, acquiring promoted interfacial dynamics as revealed by COMSOL simulation. Consequently, the amorphous CEI integrates the bifunctionality to provide an excellent cycling stability, high Coulombic efficiency, and favorable rate capability in high‐voltage Li‐metal batteries, innovating the design philosophy of functional CEI strategy for future high‐energy‐density batteries.
The CEI's advantage: An amorphous cathode electrolyte interphase (CEI) with superior chemical compatibility and plasticity was formed via in situ LiDFOB conversion. It endows high‐voltage hybrid solid/liquid batteries with significantly enhanced interfacial stability, durability, and dynamics.
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Solid polymer electrolytes (SPEs) are promising candidates for developing high‐energy‐density Li metal batteries due to their flexible processability. However, the low mechanical strength as well as ...the inferior interfacial regulation of ions between SPEs and Li metal anode limit the suppress ion of Li dendrites and destabilize the Li anode. To meet these challenges, interfacial engineering aiming to homogenize the distribution of Li+/electron accompanied with enhanced mechanical strength by Mg3N2 layer decorating polyethylene oxide is demonstrated. The intermediary Mg3N2 in situ transforms to a mixed ion/electron conducting interlayer consisting of a fast ionic conductor Li3N and a benign electronic conductor Mg metal, which can buffer the Li+ concentration gradient and level the nonuniform electric current distribution during cycling, as demonstrated by a COMSOL Multiphysics simulation. These characteristics endow the solid full cell with a dendrite‐free Li anode and enhanced cycling stability and kinetics. The innovative interface design will accelerate the commercial application of high‐energy‐density solid batteries.
An in situ formed mixed ion/electron conducting interlayer formed from an intermediary Mg3N2 layer decorated on polyethylene oxide is designed. The as‐synthesized electrolyte manipulates ion and electron distributions on the surface of the Li anode, endowing the solid full cell with a dendrite‐free Li anode and enhanced cycling stability and kinetics.
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Herein, a composite polymer electrolyte with a viscoelastic and nonflammable interface is designed to handle the contact issue and preclude Li dendrite formation. The composite polymer electrolyte ...(cellulose acetate/polyethylene glycol/Li1.4Al0.4Ti1.6P3O12) exhibits a wide electrochemical window of 5 V (vs Li+/Li), a high Li+ transference number of 0.61, and an excellent ionic conductivity of above 10−4 S cm−1 at 60 °C. In particular, the intimate contact, low interfacial impedance, and fast ion‐transport process between the electrodes and solid electrolytes can be simultaneously achieved by the viscoelastic and nonflammable layer. Benefiting from this novel design, solid lithium metal batteries with either LiFePO4 or LiCoO2 as cathode exhibit superior cyclability and rate capability, such as a discharge capacity of 157 mA h g−1 after 100 cycles at C/2 and 97 mA h g−1 at 5C for LiFePO4 cathode. Moreover, the smooth and uniform Li surface after long‐term cycling confirms the successful suppression of dendrite formation. The viscoelastic and nonflammable interface modification of solid electrolytes provides a promising and general strategy to handle the interfacial issues and improves the operative safety of solid lithium metal batteries.
A strategy to stabilize and improve the electrode–electrolytes interface, via a viscoelastic interface design, is developed. The viscoelastic and nonflammable ionic liquids interface can construct an effective Li+ transport pathway in the cathode and maintain the interface stability at both anode and cathode. This finding provides a practical and promising strategy for optimizing the solid electrolytes‐electrode interface.
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Layered Ni‐rich lithium transition metal oxides are promising battery cathodes due to their high specific capacity, but their poor cycling stability due to intergranular cracks in secondary particles ...restricts their practical applications. Surface engineering is an effective strategy for improving a cathode's cycling stability, but most reported surface coatings cannot adapt to the dynamic volume changes of cathodes. Herein, a self‐adaptive polymer (polyrotaxane‐co‐poly(acrylic acid)) interfacial layer is built on LiNi0.6Co0.2Mn0.2O2. The polymer layer with a slide‐ring structure exhibits high toughness and can withstand the stress caused by particle volume changes, which can prevent the cracking of particles. In addition, the slide‐ring polymer acts as a physicochemical barrier that suppresses surface side reactions and alleviates the dissolution of transition metallic ions, which ensures stable cycling performance. Thus, the as‐prepared cathode shows significantly improved long‐term cycling stability in situations in which cracks may easily occur, especially under high‐rate, high‐voltage, and high‐temperature conditions.
A slide‐ring polymer featuring high elasticity and self‐adaptive ability is designed to improve the performance of lithium‐ion batteries via relieving the cracks of cathode particles and retarding parasitic interfacial side reactions during cycling.
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Graphite has been serving as the key anode material of rechargeable Li‐ion batteries, yet is difficultly charged within a quarter hour while maintaining stable electrochemistry. In addition to a ...defective edge structure that prevents fast Li‐ion entry, the high‐rate performance of graphite could be hampered by co‐intercalation and parasitic reduction of solvent molecules at anode/electrolyte interface. Conventional surface modification by pitch‐derived carbon barely isolates the solvent and electrons, and usually lead to inadequate rate capability to meet practical fast‐charge requirements. Here we show that, by applying a MoOx−MoNx layer onto graphite surface, the interface allows fast Li‐ion diffusion yet blocks solvent access and electron leakage. By regulating interfacial mass and charge transfer, the modified graphite anode delivers a reversible capacity of 340.3 mAh g−1 after 4000 cycles at 6 C, showing promises in building 10‐min‐rechargeable batteries with a long operation life.
Application of a MoOx−MoNx (MoON) layer onto the conventional graphite (Gr) surface enables formation of a Li+‐permeable, solvent‐/electron‐repelled anode‐electrolyte interface in a rechargeable Li‐ion battery, which is beneficial for achieving “kinetically stable” mass and charge transfer across the interface during fast Li‐ion (de)intercalation and building of a 10‐min‐rechargeable battery with a long cycle life.
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Rechargeable lithium‐metal batteries (RLBs), which employ the Li‐metal anode to acquire notably boosted specific energy at cell level, represent the “Holy Grail” for “beyond Li‐ion” electrochemical ...energy storage technology. Currently, the practical use of RLBs is impeded by poor cycling and safety performance, which are derived from high chemical reactivity of metallic Li and uncontrollable formation and propagation of metal dendrites during repeated Li plating/stripping. In this study, a new strategy is demonstrated to stabilize the anode electrochemistry of RLBs by applying a Mg3N2‐decorated functional separator onto the Li‐metal surface. An in situ conversion‐alloying reaction occurring at Li‐separator interface assists formation of a mixed ion/electron conducting layer that consists mainly of Li3N and Li‐Mg solid‐solution. The inorganic interlayer effectively suppresses parasitic reactions at Li‐electrolyte interface while simultaneously homogenizes Li+/e‐ flux across the interface and therefore, contributes to dendrite‐free operation of Li‐metal anode. A Li||LiNi0.6Co0.2Mn0.2O2 battery based on the functional separator delivers a reversible capacity of 129 mAh g‐1 after 600 cycles at 0.5 C, which corresponds to a capacity retention of 75.9%. The preparation of functional separator is scalable and adaptive to battery manufacture, which brings new opportunities to realize high‐energy RLBs with long cycle life and improved safety.
A mixed ion/electron conducting layer is in situ formed at the interface between Li‐metal anode and Mg3N2‐supported functional separator, which enables fast Li+ diffusion, uniform Li plating, and inhibits interfacial parasitic reactions for dendrite‐free operation of high‐energy rechargeable Li‐metal batteries.
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In overcoming the Li+ desolvation barrier for low‐temperature battery operation, a weakly‐solvated electrolyte based on carboxylate solvent has shown promises. In case of an organic‐anion‐enriched ...primary solvation sheath (PSS), we found that the electrolyte tends to form a highly swollen, unstable solid electrolyte interphase (SEI) that shows a high permeability to the electrolyte components, accounting for quickly declined electrochemical performance of graphite‐based anode. Here we proposed a facile strategy to tune the swelling property of SEI by introducing an inorganic anion switch into the PSS, via LiDFP co‐solute method. By forming a low‐swelling, Li3PO4‐rich SEI, the electrolyte‐consuming parasitic reactions and solvent co‐intercalation at graphite‐electrolyte interface are suppressed, which contributes to efficient Li+ transport, reversible Li+ (de)intercalation and stable structural evolution of graphite anode in high‐energy Li‐ion batteries at a low temperature of −20 °C.
Inclusion of difluorophosphate anion in the primary solvation sheath of a weakly‐solvated electrolyte helps to switch the swelling properties of solid electrolyte interphase (SEI) on a graphite (Gr) composite anode. By forming a low‐swelling, Li3PO4‐enriched SEI, reversible Li+ (de)intercalation was enabled at a stable Gr‐electrolyte interface, contributing to improved low‐temperature electrochemical performance of a Li‐ion battery.
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Silicon oxide‐graphite (SiOx‐G) composites are promising anode materials for building practical high‐energy Li‐ion batteries. To acquire long and safe operation of battery, extensive efforts are made ...to maintain stable Li storage of SiOx‐G against materials aging and the accompanied performance fade. While previous studies mostly focus on the cycling aging, the calendar aging occurred during battery storage at a high state of charge or high temperature has not received sufficient attention. In this work, a mechanism study on the calendar aging chemistry of fully lithiated SiOx‐G electrodes in half‐cells both at ambient and high temperature (60 °C) is performed. Unmodified SiOx is employed as active materials to inspect the change of thermodynamics properties in the bulk and at interfaces. By excluding the interference from cathode, it is revealed that besides aggravated parasitic reactions happening at interface, Li migration from the lithiated graphite to the vicinal SiOx particles is also responsible for calendar aging of SiOx‐G electrodes, and high‐temperature storage notably accelerates the aging process. This work enriches the fundamental understandings about the multifactor‐coupled aging process of anode materials and sheds lights on rational materials design toward improved calendar life of a high‐energy rechargeable battery.
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