Revealing Hidden Chemistry of Anode-Free Lithium Metal Battery

Abstract

Lithium metal batteries (LMBs) has been studied extensively over the past four decades and regained great attention then lithium-ion batteries (LIBs) recently due to its higher energy density and volumetric capacity. However, the inevitable formation of high surface area lithium (HSAL) [1,2], also known as dendrites, during the plating/stripping processes among cycling leads to poor capacity retention, low coulombic efficiency (CE), and potential safety concern. One of the major reasons causing serious dendrite formation is the usage of lithium foil as an anode electrode, owing to its soft texture and easily roughened surface. In addition, even if the lithium foil used is ultra-thin, the A/C ratio is still large than 1, which leads to unnecessary excess lithium and sacrifice of higher cathode loading within the cell. Anode-free lithium metal batteries (AFLMBs), using no excess metallic lithium at the initial state, enable potentially higher energy density than LMBs [3,4]. Nevertheless, the configuration possesses lowest safety risk among the cells with the involvement of metallic lithium due to fewest amount of plated lithium in the charged state. However, low plating/stripping efficiency of AFLMBs leads to rapid capacity decay and very short cycle life. Thus, AFLMBs are often considered having less potential than LMBs or recognized as a failure for this type of cell configuration. Here in, we fundamentally investigate different parameters which affect the performance of AFLMBs, comparing with LMBs, the hidden chemistry of AFLMBs is unveiled. Base on the obtained results, we tailor down different intrinsic reasons causing irreversible capacity and low CE, and the metallic lithium plating/stripping behavior. Thus, AFLMBs is able to provide extensive cycling performance evaluation, cycle life prediction of LMBs, and approaches to improve reversible lithium metal plating/stripping and suppress of dendrite formation. Reference: [1]: J.H. Cheng, A.A. Assegie, C.J. Huang, M.H. Lin, A.M. Tripathi, C.C. Wang, M.T. Tang, Y.F. Song, W.N. Su, and B.J. Hwang, J. Phys. Chem. C, 121, 7761–7766 (2017). [2]: A.M. Tripathi, W.N. Su and B.J. Hwang, Chem. Soc. Rev., 47, 736–851 (2018).