Zheng Jingxu, Kim Mun Sek, Tu Zhengyuan, Choudhury Snehashis, Tang Tian, Archer Lynden A
Department of Materials Science and Engineering, Cornell University, Ithaca, NY 14853, USA.
Chem Soc Rev. 2020 May 7;49(9):2701-2750. doi: 10.1039/c9cs00883g. Epub 2020 Mar 31.
Lithium, the lightest and most electronegative metallic element, has long been considered the ultimate choice as a battery anode for mobile, as well as in some stationary applications. The high electronegativity of Li is, however, a double-edged sword-it facilitates a large operating voltage when paired with essentially any cathode, promising a high cell-level energy density. It is also synonymous with a high chemical reactivity and low reduction potential. The interfaces a Li metal anode forms with any other material (liquid or solid) in an electrochemical cell are therefore always mediated by one or more products of its chemical or electrochemical reactions with that material. The physical, crystallographic, mechanical, electrochemical, and transport properties of the resultant new material phases (interphases) regulate all interfacial processes at a Li metal anode, including electrodeposition during battery recharge. This Review takes recent efforts aimed at manipulating the structure, composition, and physical properties of the solid electrolyte interphase (SEI) formed on an Li anode as a point of departure to discuss the structural, electrokinetic, and electrochemical requirements for achieving high anode reversibility. An important conclusion is that while recent reports showing significant advances in the achievement of highly reversible Li anodes, e.g. as measured by the coulombic efficiency (CE), raise prospects for as significant progress towards commercially relevant Li metal batteries, the plateauing of achievable CE values to around 99 ± 0.5% apparent from a comprehensive analysis of the literature is problematic because CE values of at least 99.7%, and preferably >99.9% are required for Li metal cells to live up to the potential for higher energy density batteries offered by the Li metal anode. On this basis, we discuss promising approaches for creating purpose-built interphases on Li, as well as for fabricating advanced Li electrode architectures for regulating Li electrodeposition morphology and crystallinity. Considering the large number of physical and chemical factors involved in achieving fine control of Li electrodeposition, we believe that achievement of the remaining ∼0.5% in anode reversibility will require fresh approaches, perhaps borrowed from other fields. We offer perspectives on both current and new strategies for achieving such Li anodes with the specific aim of engaging established contributors and newcomers to the field in the search for scalable solutions.
锂是最轻且电负性最强的金属元素，长期以来一直被视为移动设备以及某些固定应用中电池阳极的最终选择。然而，锂的高电负性是一把双刃剑——当与几乎任何阴极配对时，它有助于产生较大的工作电压，有望实现高电池级能量密度。它也意味着高化学反应性和低还原电位。因此，锂金属阳极在电化学电池中与任何其他材料（液体或固体）形成的界面总是由其与该材料发生化学或电化学反应的一种或多种产物介导。所得新材料相（界面相）的物理、晶体学、机械、电化学和传输特性调节锂金属阳极处的所有界面过程，包括电池充电期间的电沉积。本综述以最近旨在操纵锂阳极上形成的固体电解质界面（SEI）的结构、组成和物理性质的努力为出发点，讨论实现高阳极可逆性的结构、电动和电化学要求。一个重要的结论是，虽然最近的报告显示在实现高度可逆锂阳极方面取得了重大进展，例如通过库仑效率（CE）来衡量，但从对文献的综合分析来看，可实现的CE值稳定在约99±0.5%是有问题的，因为锂金属电池要充分发挥锂金属阳极提供的更高能量密度电池的潜力，需要至少99.7%，最好>99.9%的CE值。在此基础上，我们讨论了在锂上创建专用界面相以及制造用于调节锂电沉积形态和结晶度的先进锂电极结构的有前景的方法。考虑到实现锂电沉积精细控制涉及大量物理和化学因素，我们认为要实现阳极可逆性剩余的约0.5%，将需要新的方法，或许可以借鉴其他领域。我们针对实现此类锂阳极的当前和新策略提供观点，具体目的是促使该领域的现有贡献者和新进入者共同寻找可扩展的解决方案。
