Polymer Electrolytes for Shape-Adjustable, Fast Rate, Long Lifespan Lithium Batteries

Li metal is an ultimate anode for future high-energy-density rechargeable batteries, when in combination with high-capacity cathodes. However, commercial applications of Li metal batteries (LMBs) are impeded by critical issues triggered by dendritic growth of Li during plating/stripping processes. Therefore, the intrinsic chemical reactivity of Li metal, that reacts with almost all organic liquid electrolytes, make liquid electrolytes unsuitable in LMBs. Hence, finding effective strategies to suppress Li dendrites formation is critical for developing next generation high-energy-density Li batteries. Due to a key role of the electrolyte in enhancing the safety and functionality of LMBs, the main objective herein is to develop novel polymer electrolytes with high Li ions conductivity and stability against Li metal towards long lifespan LMBs. A novel lithophilic gel polymer electrolyte (GPE) for LMBs is demonstrated herein, enabling uniform and nondendritic Li electrodeposition, long cycle life, and high Columbic efficiency. The GPE is made by immobilization of one of the most widely used carbonate-based liquid electrolyte within a crosslinked polymer matrix. A stable Li/solid polymer electrolyte (SPE) interface is engineered via nitriding or phosphating of the solid electrolyte interphase (SEI) using a phosphazene additive. The new nitrogen- and phosphorus-containing compounds own a very high Li ions conductivity, mechanical strength and stability against the Li metal. The engineered interface enabled an extended lifespan for LMBs. The confinement effect of parallelly-aligned graphene oxide at Li metal surface is also demonstrated herein as an effective strategy to suppress the dendritic growth of electrochemically deposited Li. This nondendritic growth of Li enables fast charge/discharge capability of the Li batteries and their prolonged lifespan. A smart, flexible Li battery with shape memory function is designed and developed, which has ability to restore its shape against severe mechanical deformations, such as bending, twisting, rolling or elongation. The shape memory function is induced by integration of a shape-adjustable SPE. The shape memory SPE is engineered based on a semi-crystalline, crosslinkable polyethylene oxide, a Li salt, and tetraglyme additive. A flexible pouch-type all-solid-state Li battery could also recover its original shape (planar) against extreme mechanical deformations upon applying heat.