Luo Yuting, Handy Joseph V, Das Tisita, Ponis John D, Albers Ryan, Chiang Yu-Hsiang, Pharr Matt, Schultz Brian J, Gobbato Leonardo, Brown Dean C, Chakraborty Sudip, Banerjee Sarbajit
Department of Chemistry, Texas A&M University, College Station, TX, USA.
Department of Materials Science and Engineering, Texas A&M University, College Station, TX, USA.
Nat Mater. 2024 Jul;23(7):960-968. doi: 10.1038/s41563-024-01842-y. Epub 2024 Mar 21.
Limitations in electrochemical performance as well as supply chain challenges have rendered positive electrode materials a critical bottleneck for Li-ion batteries. State-of-the-art Li-ion batteries fall short of accessing theoretical capacities. As such, there is intense interest in the design of strategies that enable the more effective utilization of active intercalation materials. Pre-intercalation with alkali-metal ions has attracted interest as a means of accessing higher reversible capacity and improved rate performance. However, the structural basis for improvements in electrochemical performance remains mostly unexplored. Here we use topochemical single-crystal-to-single-crystal transformations in a tunnel-structured ζ-VO positive electrode to illustrate the effect of pre-intercalation in modifying the host lattice and altering diffusion pathways. Furthermore, operando synchrotron X-ray diffraction is used to map Li-ion site preferences and occupancies as a function of the depth of discharge in pre-intercalated materials. Na- and K-ion intercalation 'props open' the one-dimensional tunnel, reduces electrostatic repulsions between inserted Li ions and entirely modifies diffusion pathways, enabling orders of magnitude higher Li-ion diffusivities and accessing higher capacities. Deciphering the atomistic origins of improved performance in pre-intercalated materials on the basis of single-crystal-to-single-crystal topochemical transformation and operando diffraction studies paves the way to site-selective modification approaches for positive electrode design.
电化学性能的局限性以及供应链挑战已使正极材料成为锂离子电池的关键瓶颈。目前最先进的锂离子电池无法达到理论容量。因此，人们对设计能更有效利用活性插层材料的策略有着浓厚兴趣。用碱金属离子进行预插层作为一种获得更高可逆容量和改善倍率性能的方法已引起关注。然而，电化学性能改善的结构基础大多仍未被探索。在此，我们利用隧道结构的ζ-VO正极中的拓扑化学单晶到单晶转变来说明预插层在修饰主体晶格和改变扩散途径方面的作用。此外，采用原位同步加速器X射线衍射来绘制预插层材料中锂离子的位置偏好和占有率随放电深度的变化情况。钠和钾离子的插层“撑开”了一维隧道，减少了插入锂离子之间的静电排斥，并完全改变了扩散途径，使锂离子扩散率提高了几个数量级，并能获得更高的容量。基于单晶到单晶的拓扑化学转变和原位衍射研究来解读预插层材料性能改善的原子起源，为正极设计的位点选择性修饰方法铺平了道路。
