Shenzhen Key Laboratory on Power Battery Safety and Shenzhen Geim Graphene Center, Tsinghua Shenzhen International Graduate School, Tsinghua University, Shenzhen 518055, China.
Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China.
ACS Nano. 2023 Jul 11;17(13):12040-12051. doi: 10.1021/acsnano.2c07061. Epub 2023 Jun 20.
Currently, the development of calcium-ion batteries (CIBs) is still in its infancy and greatly plagued by the absence of satisfactory cathode materials and compatible electrolytes. Herein, an acetonitrile-water hybrid electrolyte is first developed in CIB chemistry, in which, the strong lubricating and shielding effect of water solvent significantly boosts the swift transport of bulky Ca, thus contributing to large capacity storage of Ca in layered vanadium oxides (CaVO·HO, CVO). Meanwhile, the acetonitrile component noticeably suppresses the dissolution of vanadium species during repeated Ca-ion uptake/release, endowing the CVO cathode with a robust cycle life. More importantly, spectral characterization and molecular dynamics simulation confirm that the water molecules are well stabilized by the mutual hydrogen bonding with acetonitrile molecules (O-H···N), endowing the aqueous hybrid electrolyte with high electrochemical stability. By using this aqueous hybrid electrolyte, the CVO electrode shows a high specific discharge capacity of 158.2 mAh g at 0.2 A g, an appealing capacity of 104.6 mAh g at a high rate of 5 A g, and a capacity retention of 95% after 2000 cycles at 1.0 A g, which is a record-high performance for CIBs reported so far. A mechanistic study exemplifies the reversible extraction of Ca from the gap of VO polyhedral layers, which are accompanied by the reversible V-O and V-V skeleton change as well as reversible variation of layer spacing. This work constitutes a major advance in developing high-performance Ca-ion batteries.
目前，钙离子电池（CIBs）的发展仍处于起步阶段，其主要问题是缺乏令人满意的阴极材料和兼容的电解质。在此，我们首次在 CIB 化学中开发了一种乙腈-水混合电解质，其中，水溶剂的强润滑和屏蔽作用显著促进了大尺寸 Ca 的快速传输，从而有利于层状钒氧化物（CaVO·HO，CVO）中 Ca 的大容量存储。同时，乙腈组分明显抑制了钒物种在反复的 Ca 离子吸收/释放过程中的溶解，赋予 CVO 阴极具有稳健的循环寿命。更重要的是，光谱表征和分子动力学模拟证实了水分子通过与乙腈分子（O-H···N）的氢键相互作用而被很好地稳定，赋予了该混合电解质具有高电化学稳定性。使用这种混合电解质，CVO 电极在 0.2 A g 时表现出 158.2 mAh g 的高比放电容量，在 5 A g 的高倍率下具有 104.6 mAh g 的诱人容量，在 1.0 A g 下循环 2000 次后容量保持率为 95%，这是迄今为止报道的 CIBs 的最高性能。机理研究证明了 Ca 从 VO 多面体层的间隙中可逆提取，伴随着 V-O 和 V-V 骨架的可逆变化以及层间距的可逆变化。这项工作是开发高性能 Ca 离子电池的重大进展。
