Multifunctional composite binder with synergistic transport mechanism to achieve high performance all-solid-state batteries

All-solid-state batteries (ASSBs) using solid polymer electrolytes (SPEs) show a wide range of prospects in many aspects, but they do not perform well at high current densities. In order to solve the above problems, much effort has been spent on the improvement of electrolyte materials, but there is a lack of research on binders. This paper emphasizes the critical role played by the binder in the positive plates without any liquid infiltration,and an aqueous composite binder (CB) is designed by utilizing the characteristics of polyethylene oxide (PEO) and carboxymethyl cellulose lithium (CMC-Li) in lithium-ions transport. Electrochemical and Fourier transform infrared spectrometer (FTIR) tests demonstrate that the two polymers in the CB build a high-speed channel for migrating lithium-ions through synergistic action. The binder containing multiple reactive groups is tested to be highly competitive in both mechanical and electrochemical properties, which creates sufficient conditions for achieving high-performance ASSBs. The cells with CB as the binder are assembled which show a capacity of 65.5 mAh·g−1 at a current density of 3C while PVDF-based ASSBs exhibit only 3.3 mAh·g−1, and exhibit a capacity retention of 86.7% after 700 charge/discharge cycles at 0.5C (for comparison, PVDF-based ASSBs exhibit only 42.5%). This novel composite binder provides guidance for the further development of solid polymer batteries.