Solid Polymer Electrolytes in Lithium Batteries: Challenges and Opportunities for High Specific Energy

Abstract

Besides enhanced safety aspects, solid polymer electrolytes (SPEs) offer the opportunity to increase the specific energy of secondary batteries by enabling lithium metal as negative electrode in all-solid-state lithium batteries (ASSLB). Therefore, the SPE needs to provide sufficient mechanical strength to prevent short circuits caused by lithium dendrite penetration especially favoured at high current densities.[1] In order to obtain the maximum specific energy of ASSLBs, lithium metal negative electrodes are combined with high voltage positive electrodes, e.g. LiNi0.6Mn0.2Co0.2O2 (NMC622).[2]In the frame of this work, a novel SPE is applied to NMC622 based ASSLB cells and studied regarding energy limits on battery cell and pack level. In a first step, the active mass loading is systematically increased revealing the specific energy limit on battery cell level. Additionally, the chosen system is applied to a bipolar (serial) stacking aiming towards further energy improvements on battery pack level.[3] In sum, this work reveals remaining challenges but still points towards opportunities enabling the aimed energy increase of ASSLBs.[1] G. Homann, L. Stolz, J. Nair, I. C. Laskovic, M. Winter and J. Kasnatscheew, Sci Rep, 10, 4390 (2020).[2] J. Kasnatscheew, M. Evertz, R. Kloepsch, B. Streipert, R. Wagner, I. Cekic Laskovic and M. Winter, Energy Technology, 5, 1670-1679 (2017).[3] G. Homann, P. Meister, L. Stolz, J. P. Brinkmann, J. Kulisch, T. Adermann, M. Winter and J. Kasnatscheew, ACS Appl. Energy Mater., 3, 4, 3162–3168 (2020). Figure 1