High‐energy‐density Li‐rich layered oxides (LLOs) as promising cathodes for Li‐ion batteries suffer from the dissolution of transition metals (especially manganese) and severe side reactions in conventional electrolytes, which greatly deteriorate their electrochemical performance. Herein, an in situ “anchoring + pouring” synergistic cathode–electrolyte interphase (CEI) construction is realized by using 1,3,6‐hexanetricarbonitrile (HTCN) and tris(trimethylsilyl) phosphate (TMSP) electrolyte additives to alleviate the challenges of an LLO (Li1.13Mn0.517Ni0.256Co0.097O2). HTCN with three nitrile groups can tightly anchor transition metals by coordinative interaction to form the CEI framework, and TMSP will electrochemically decompose to reshape the CEI layer. The uniform and robust in situ constructed CEI layer can suppress the transition metal dissolution, shield the cathode against diverse side reactions, and significantly improve the overall electrochemical performance of the cathod with a discharge voltage decay of only 0.5 mV cycle−1. Further investigations based on a series of experimental techniques and theoretical calculations have revealed the composition of in situ constructed CEI layers and their distribution, including the enhanced HTCN anchoring effect after lattice densification of LLOs. This study provides insights into the in situ CEI construction for enhancing the performance of high‐energy and high‐voltage cathode materials through effective, convenient, and economical electrolyte approaches.

To boost the use of electronic devices and driving mileage of electric vehicles, it is urgent to develop lithium-ion batteries (LIBs) with higher energy density and longer life. High-voltage and high-capacity cathode materials, such as LiCoO 2 , LiNi 0.5 Mn 1.5 O 4 , Ni-rich layered oxides, and lithium-rich layered oxides, are critically important for LIBs to obtain high energy density. Among various forms of these materials, "single-crystal" cathodes (SCCs) have shown many advantages over other forms for industrial applications, including good crystallinity, high mechanical strength, high reaction homogeneity, small specific surface area, excellent structural stability, and high thermal stability, which can noticeably improve the cycling performance and safety of SCCbased batteries. Therefore, SCCs have received wide attention from academic to industrial communities and have been applied to the liquid-based and solid-state batteries in recent years. In this paper, the advantages, progress, and challenges of SCCs for highvoltage cathode materials are reviewed. Moreover, we summarize the efforts for improving the electrochemical performance of SCCs, intending to provide insights into the development of high-performance cathodes for practical LIBs.

No abstract

The strong market incentives and pressing environmental preservation call for high-energy, eco-friendly, and highsafety batteries. Lithium-ion batteries (LIBs) are still the most

Lithium-rich layered oxides have been considered as the most promising candidate for offering a high specific capacity and energy density for lithium-ion batteries. However, their practical applications are still suffered by the cycle instability and also closely related thermal stability. Here, microsized crystalline grains with good dispersion of lithium-rich layered oxides are prepared by a molten-salt method, while a spinel structure is also introduced on a grain surface by following chemical oxidation and annealing process, and their thermal performance with different cutoff voltages during the charge process is systematically studied using differential scanning calorimetry method. Results have shown that thermal stability of microsized crystalline grains is better than that of spherical secondary agglomerates, the spinel structure introduction on the grain surface of microsized crystalline grains can contribute obviously to their thermal stability, in which the onset temperature of the exothermic peak has been increased by 103 °C, and the thermal release value can be reduced as much as about 40% when the battery was charged to 4.8 V. Furthermore, the electrochemical performance, especially cycle stability under a high temperature, has also been enhanced for spinel-modified microsized crystalline grains. This work not only develops the microsized crystalline grains with good dispersion of lithium-rich layered oxides, confirming the advantages of these materials compared to spherical secondary agglomerates, but also reveals the method to improve their thermal stability by grain surface structure modification, opening the way to optimize the comprehensive performance of electrode materials for batteries.