Cation-disordered rocksalt transition metal oxides and oxyfluorides for high energy lithium-ion cathodes,Energy & Environmental Science

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Cation-disordered rocksalt transition metal oxides and oxyfluorides for high energy lithium-ion cathodes
Energy & Environmental Science ( IF 32.4 ) Pub Date : 2020/01/13 , DOI: 10.1039/c9ee02803j
R. J. Clément _{1,

2,

3,

4,

5} , Z. Lun _{1,

2,

3,

4,

6} , G. Ceder _{1,

2,

3,

4,

6}

Affiliation

For lithium-ion rechargeable batteries to meet society's ever-growing demands in electrical energy storage, e.g. for the electrification of transportation, for portable electronics and for grid storage applications, novel electrode materials with a large charge storage capacity and a high energy density are needed. Over the last five years, several experimental and theoretical studies have demonstrated the feasibility of disordered rocksalt (DRX) cathodes, that is, lithium transition metal oxide cathodes with a crystalline rocksalt structure but with a disordered arrangement of lithium and transition metal on the cation lattice. We provide here an overview of the current understanding of DRX materials, in terms of their structural and compositional characteristics, as well as their electrochemical properties. We also present important considerations for the design of high performance DRX cathodes and suggest future research directions. Because no specific order is needed, DRX compounds can be composed of a wide variety of transition metal species, which can create long-term benefits for the lithium battery industry by making it less reliant on scarce and expensive raw materials. While some DRX compositions can simply be synthesized at high temperature to induce thermal cation disorder, other compositions require mechanochemical methods to induce a disordered arrangement of cation species. Cation disorder leads to unique lithium transport properties, small volume changes during charge–discharge cycling and sloping electrochemical profiles. Fluorine substitution for oxygen and the incorporation of high-valent d⁰ transition metals in the bulk DRX structure are two strategies used to increase the lithium content in the material, improve lithium percolation and to keep the valence of redox-active metal species low so that high transition metal redox capacity can be obtained. Short-range cation order, which is affected by thermal treatment, metal composition and fluorine substitution, has a significant impact on electrochemical performance. Moreover, fluorine substitution for oxygen improves long-term capacity retention by significantly reducing anion-based charge compensation mechanisms during charge. Fluorinated DRXs have recently demonstrated reversible capacities >300 mA h g⁻¹ and extremely high energy densities approaching 1000 W h kg⁻¹, holding promise for a nearly two-fold increase in the energy density of commercial lithium-ion batteries.

中文翻译：

用于高能锂离子阴极的阳离子无序岩盐过渡金属氧化物和氟氧化物

锂离子充电电池可满足社会不断增长的电能存储需求，例如为了运输的电气化，便携式电子设备和网格存储应用，需要具有大电荷存储容量和高能量密度的新型电极材料。在过去的五年中，一些实验和理论研究证明了无序岩盐（DRX）阴极的可行性，即具有晶体岩盐结构但锂和过渡金属在阳离子晶格上无序排列的锂过渡金属氧化物阴极。在这里，我们从结构，组成特征以及电化学性能方面概述了对DRX材料的当前了解。我们还提出了高性能DRX阴极设计的重要考虑因素，并提出了未来的研究方向。由于不需要特定的顺序，DRX化合物可以由多种过渡金属组成，这可以使锂电池行业减少对稀缺和昂贵原材料的依赖，从而为锂电池行业创造长期利益。尽管一些DRX组合物可以简单地在高温下合成以引起热阳离子紊乱，但是其他组合物需要机械化学方法来引起阳离子物种的无序排列。阳离子异常导致独特的锂传输特性，在充放电循环和倾斜的电化学曲线中体积变化很小。氟取代氧气并引入高价d 通过减少对稀缺和昂贵原材料的依赖，可以为锂电池行业创造长期利益。尽管一些DRX组合物可以简单地在高温下合成以引起热阳离子紊乱，但是其他组合物需要机械化学方法来引起阳离子物种的无序排列。阳离子异常导致独特的锂传输特性，在充放电循环和倾斜的电化学曲线中体积变化很小。氟取代氧气并结合高价d 通过减少对稀缺和昂贵原材料的依赖，可以为锂电池行业创造长期利益。尽管一些DRX组合物可以简单地在高温下合成以引起热阳离子紊乱，但是其他组合物需要机械化学方法来引起阳离子物种的无序排列。阳离子异常导致独特的锂传输特性，在充放电循环和倾斜的电化学曲线中体积变化很小。氟取代氧气并结合高价d 阳离子异常导致独特的锂传输特性，在充放电循环和倾斜的电化学曲线中体积变化很小。氟取代氧气并结合高价d 阳离子异常导致独特的锂传输特性，在充放电循环和倾斜的电化学曲线中体积变化很小。氟取代氧气并结合高价d本体DRX结构中的⁰过渡金属是用于增加材料中锂含量，改善锂渗透和保持氧化还原活性金属的化合价低的两种策略，从而可以获得高的过渡金属氧化还原容量。受热处理，金属成分和氟取代影响的短程阳离子有序对电化学性能有重大影响。此外，氟取代氧可通过显着减少充电过程中基于阴离子的电荷补偿机制来改善长期容量保持能力。氟化DRX最近已证明可逆容量> 300 mA hg^-1，能量密度极高，接近1000 W h kg^-1有望使商用锂离子电池的能量密度提高近两倍。

更新日期：2020-02-19

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