CuS as Unique Cathode Material for Li Solid-State Batteries: Properties, Reaction Mechanism and Tomography

Abstract

Copper sulfide (CuS) is a naturally occurring mineral that reacts with lithium via a conversion reaction to form Li2S and Cu. The theoretical energy density of the reaction is 961 Wh/kg, the theoretical cell voltage is 1.96 V. Among all the conversion reactions, copper sulfide shows a unique behavior as large, µm-sized copper crystallites are formed during discharge. Some years ago, it was shown that the reaction can proceed reversibly in suitable electrolytes.[1] This presentation will discuss the behavior of copper sulfide as a cathode material in solid state batteries. In this context, the low cell voltage allows the use of Li3PS4 as a solid electrolyte, which is a major advantage. Despite the large volume expansion (+74%), the material can be cycled in solid state batteries at high contents (70 wt%), again forming large copper crystallites.[2] The size of the crystallites allows the reaction to be studied by 3D X-ray tomography.[3] In addition to phase transformations, crack formation can also be observed. The latter is strongly pressure dependent and can be minimized by increasing the pressure.[1] Birte Jache, Boris Mogwitz, Franziska Klein, Philipp Adelhelm (2014) Copper sulfides for rechargeable lithium batteries: Linking cycling stability to electrolyte composition Journal of Power Sources 247: 703-711.[2] Aggunda L Santhosha, N Nazer, Raimund Koerver, Simon Randau, Felix H Richter, Dominik A Weber, Joern Kulisch, Torben Adermann, Jürgen Janek, Philipp Adelhelm (2020) Macroscopic displacement reaction of copper sulfide in lithium solid-state batteries Advanced Energy Materials 2002394: .[3] Zhenggang Zhang, Kang Dong, Katherine A Mazzio, André Hilger, Henning Markötter, Fabian Wilde, Tobias Heinemann, Ingo Manke, Philipp Adelhelm (2022) Phase Transformation and Microstructural Evolution of CuS Electrodes in Solid-State Batteries Probed by in-situ 3D X-ray Tomography Advanced Energy Materials 2203143. Figure 1