Polymer electrolytes and interfaces toward solid-state batteries: Recent advances and prospects

Solid-state batteries (SSBs) are considered to be promising next-generation energy storage devices owing to their enhanced safety and energy density. However, the practical application of SSBs has been hampered by the crucial solid-solid electrolyte-electrode interfacial issues, especially in inorganic solid electrolytes (ISEs) with high ionic conductivity. Compared to ISEs, polymer electrolytes (PEs) can alleviate the tough interface issues due to their inherently competitive interface property, and promote the real application of SSBs along with their enhanced ionic conductivity. Herein, from a polymer electrolyte perspective, an overall survey focused on the multi-functional applications of PEs and interface issues in SSBs is presented. Particularly, basic properties of PEs and strategies devoted to improving their ionic conductivity are highlighted. Then, recent advances in Li metal and beyond Li (Na, K, Zn, Mg, Al) based polymer batteries are summarized. Following that, the interface engineering progress for SSBs is reported with a focus on the anode/PE interface, cathode/PE interface and interfacial modification by polymer coatings. The advanced in-situ or ex-situ characterization techniques used to investigate solid-solid interfaces are also introduced. Finally, the foreseeable polymers designs and interface regulation strategies such as introducing specific polymer functional groups, constructing collaborative polymer microstructures, creating functional polymer interphase, and forming integrated electrode-electrolyte system are suggested.