Metastable and Nanosized Li1.2Nb0.2V0.6O2 for High-Energy Li-ion Batteries (Supporting Information)

A Li-excess cation-disordered rocksalt oxide, Li1.2Nb0.2V0.6O2, with higher theoretical capacity than traditional stoichiometric and layered oxides, is synthesized and tested as positive electrode materials for battery applications. Although Li1.2Nb0.2V0.6O2 cannot be synthesized by conventional calcination method, a single phase and metastable oxide is successfully synthesized by high-energy mechanical milling. Electrode performance of metastable and nanosized Li1.2Nb0.2V0.6O2 is significantly improved by heat treatment at 600 °C. Heat treated Li1.2Nb0.2V0.6O2 with a partial cation ordered layered structure delivers a high reversible specific capacity of 320 mAh g−1 on the basis of highly reversible two-electron redox of V ions. Moreover, inferior cyclability originating from the dissolution of V ions is successfully improved by using concentrate electrolyte solution, and over 90 % capacity retention is achieved after 50 cycles. This finding opens a new way to design high-capacity metastable Li-excess oxides for advanced Li-ion batteries with higher energy density.

一种具有高于传统化学计量和层状氧化物的理论容量的Li-excess阳离子无序岩盐氧化物Li1.2Nb0.2V0.6O2，已被合成并测试作为电池应用的正极材料。尽管Li1.2Nb0.2V0.6O2不能通过常规的煅烧法合成，但通过高能机械球磨成功合成了单相和亚稳态氧化物。经过600°C热处理的亚稳态和纳米尺寸的Li1.2Nb0.2V0.6O2电极性能得到了显著提升。具有部分阳离子有序层状结构的经热处理Li1.2Nb0.2V0.6O2在基于V离子高度可逆的两电子氧化还原反应的基础上，实现了320 mAh g−1的高可逆比容量。此外，通过使用浓缩电解液成功改善了源自V离子溶解的较差循环性能，在经过50个循环后实现了超过90%的容量保持率。这一发现为设计具有更高能量密度的先进锂离子电池的高容量亚稳态Li-excess氧化物开辟了新的途径。