The demand for state-of-the-art high-energy-density lithium-ion batteries is increasing. However, the low specific capacity of electrode materials in conventional full-cell systems cannot meet the requirements. Ni-rich layered oxide cathodes such as Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) have a high theoretical specific capacity of 200 mAh g-1, but it is always accompanied by side reactions on the electrode/electrolyte interface. Phosphorus anode possesses a high theoretical specific capacity of 2596 mAh g-1, but it has a huge volume expansion (≈300%). Herein, a highly compatible and secure electrolyte is reported via introducing an additive with a narrow electrochemical window, Lithium difluoro(oxalato)borate (LiDFOB), into 1 m LiPF6 EC/DMC with tris (2,2,2-trifluoroethyl) phosphate (TFEP) as a cosolvent. LiDFOB participates in the formation of organic/inorganic hybrid electrode/electrolyte interface layers at both the cathode and anode sides. The side reactions on the surface of the NCM811 cathode and the volume expansion of the phosphorus anode are effectively alleviated. The NCM811//RP full cell in this electrolyte shows high capacity retention of 82% after 150 cycles at a 0.5C rate. Meanwhile, the electrolyte shows non-flammability. This work highlights the importance of manipulating the electrode/electrolyte interface layers for the design of lithium-ion batteries with high energy density.

Sodium-ion batteries (SIBs) have garnered significant attention as ideal candidates for large-scale energy storage due to their notable advantages in terms of resource availability and cost-effectiveness. However, there remains a substantial energy density gap between SIBs and commercially available lithium-ion batteries (LIBs), posing challenges to meeting the requirements of practical applications. The fabrication of high-energy cathodes has emerged as an efficient approach to enhancing the energy density of SIBs, which commonly requires cathodes operating in high-voltage regions. Layered oxide cathodes (LOCs), with low cost, facile synthesis, and high theoretical specific capacity, have emerged as one of the most promising candidates for commercial applications. However, LOCs encounter significant challenges when operated in high-voltage regions such as irreversible phase transitions, migration and dissolution of metal cations, loss of reactive oxygen, and the occurrence of serious interfacial parasitic reactions. These issues ultimately result in severe degradation in battery performance. This review aims to shed light on the key challenges and failure mechanisms encountered by LOCs when operated in high-voltage regions. Additionally, the corresponding strategies for improving the high-voltage stability of LOCs are comprehensively summarized. By providing fundamental insights and valuable perspectives, this review aims to contribute to the advancement of high-energy SIBs.

Sodium-ion batteries are competitive candidates for large-scale energy storage batteries due to the abundant sodium resource. However, the electrode interface in the conventional electrolyte is unstable, deteriorating the cycle life of the cells. Introducing functional electrolyte additives can generate stable electrode interfaces. Here, pentafluoro(phenoxy)cyclotriphosphazene (FPPN) serves as a functional electrolyte additive to stabilize the interfaces of the layered oxide cathode and the hard carbon anode. The fluorine substituting groups and the π-π conjugated ─PN─ structure decrease the lowest unoccupied molecular orbital and increase the highest occupied molecular orbital of FPPN, respectively, realizing the preferential reduction and oxidization of FPPN on the anode and cathode simultaneously, which results in the formation of a uniform, ultrathin, and inorganic-rich solid electrolyte interlayer and cathode electrolyte interphase. The sodium-ion pouch cells of 5 Ah capacity rather than coin cells are assembled to evaluate the effect of FPPN. It can retain a high capacity of 4.46 Ah after 1000 cycles, corresponding to a low decay ratio of 0.01% per cycle. The pouch cell also achieves a high energy density of 145 Wh kg-1 and a wide operating temperature of -20-60 °C. This work can attract more attention to the rational electrolyte design for practical applications.

Lithium-carbon dioxide (Li-CO2 ) battery technology presents a promising opportunity for carbon capture and energy storage. Despite tremendous efforts in Li-CO2 batteries, the complex electrode/electrolyte/CO2 triple-phase interfacial processes remain poorly understood, in particular at the nanoscale. Here, using in situ atomic force microscopy and laser confocal microscopy-differential interference contrast microscopy, we directly observed the CO2 conversion processes in Li-CO2 batteries at the nanoscale, and further revealed a laser-tuned reaction pathway based on the real-time observations. During discharge, a bi-component composite, Li2 CO3 /C, deposits as micron-sized clusters through a 3D progressive growth model, followed by a 3D decomposition pathway during the subsequent recharge. When the cell operates under laser (λ=405 nm) irradiation, densely packed Li2 CO3 /C flakes deposit rapidly during discharge. Upon the recharge, they predominantly decompose at the interfaces of the flake and electrode, detaching themselves from the electrode and causing irreversible capacity degradation. In situ Raman shows that the laser promotes the formation of poorly soluble intermediates, Li2 C2 O4 , which in turn affects growth/decomposition pathways of Li2 CO3 /C and the cell performance. Our findings provide mechanistic insights into interfacial evolution in Li-CO2 batteries and the laser-tuned CO2 conversion reactions, which can inspire strategies of monitoring and controlling the multistep and multiphase interfacial reactions in advanced electrochemical devices.

Ni-rich layered oxides have been intensively considered as promising cathode materials for next-generation Li-ion batteries. Nevertheless, the performance degradation caused by intergranular cracks and electrode/electrolyte interface parasitic reactions restricts their further application. Compared with secondary particles, single-crystal (SC) materials have better mechanical integrity and cycling stability. However, the preparation of ultrahigh-nickel layered SC cathode still remains a serious challenge. Herein, a novel LiOH-LiNO3 -H3 BO3 molten-salt method is proposed to synthesize SC LiNi0.92 Co0.06 Mn0.02 O2 with considerable crystallinity and uniformity. The critical impacts of calcination temperature and boric acid on the microstructure and electrochemical property of Ni-rich layered oxides are systematically investigated. The results show that the crystal growth is promoted and the stability of crystal structure is improved by this synthesis method. In particular, the optimal electrode demonstrates a superior initial discharge capacity of 214.8 mAh g-1 with a high capacity retention of 86.3% over 300 cycles as tested by pouch-type full cells at 45 ºC. This work not only prepares an ultrahigh-nickel layered CS cathode with superior electrochemical performances, but also provides a feasible method for the synthesis of other CS layered cathode materials.

Lithium (Li)-metal batteries (LMBs) with high-voltage cathodes and limited Li-metal anodes are crucial to realizing high-energy storage. However, functional electrolytes that are compatible with both high-voltage cathodes and Li anodes are required for their developments. In this study, the use of a moderate-concentration LiPF6 and LiNO3 dual-salt electrolyte composed of ester and ether co-solvents (fluoroethylene carbonate/dimethoxyethane, FEC/DME), which forms a unique Li+ solvation with aggregated dual anions, that is, PF6 - and NO3 - , is proposed to stabilize high-voltage LMBs. Mechanistic studies reveal that such a solvation sheath improves the Li plating/stripping kinetics and induces the generation of a solid electrolyte interphase (SEI) layer with gradient heterostructure and high Young\'s modulus on the anode, and a thin and robust cathode electrolyte interface (CEI) film. Therefore, this novel electrolyte enables colossal Li deposits with a high Coulombic efficiency (≈98.9%) for 450 cycles at 0.5 mA cm-2 . The as-assembled LiǁLiNi0.85 Co0.10 Al0.05 O2 full batteries deliver an excellent lifespan and capacity retention at 4.3 V with a rigid negative-to-positive capacity ratio. This electrolyte system with a dual-anion-aggregated solvation structure provides insights into the interfacial chemistries through solvation regulation for high-voltage LMBs.

Solid polymer electrolytes (SPEs)-based all-solid-state lithium-sulfur batteries (ASSLSBs) have attracted extensive research attention due to their high energy density and safe operation, which provide potential solutions to the increasing need for harnessing higher energy densities. There is little progress made, however, in the development of ASSLSBs to improve simultaneously energy density and long-term cycling life, mostly due to the \"shuttle effect\" of lithium polysulfide intermediates in the SPEs and the low interfacial compatibility between the metal lithium anode and the SPE. In this work, the issues of solid/solid interfacial architecturing through atomic layer deposition of Al2 O3 on poly(ethylene oxide)-lithium bis(trifluoromethanesulfonyl)imide SPE surface are effectively addressed. The Al2 O3 coating promotes the suppression of lithium dendrite formation for over 500 h. ASSLSBs fabricated with two layers of Al2 O3 -coated SPE deliver high gravimetric/areal capacity and Coulombic efficiency, as well as excellent cycling stability and extremely low self-discharge rate. This work provides not only a simple and effective approach to boost the electrochemical performances of SPE-based ASSLSBs, but also enriches the fundamental understanding regarding the underlying mechanism responsible for their performance.