Semi-Interpenetrating Polymer Network Electrolytes Based On A Spiro-Twisted Benzoxazine For All-Solid-State Lithium-Ion Batteries

A spiro-twisted benzoxazine, namely, 6,6'-(6,6,6',6'-tetramethyl-6,6',7,7'-tetrahydro-2H, 2'H-8,8'-spirobi [indeno[5,6-e] [1,3]oxazin]-3,3'(4H,4'H)-diyl)bis(hexan-1-ol) (TSBZ6D), was successfully developed as a semi-interpenetrating polymer network (s-IPN) matrix for solid polymer electrolytes (SPEs). The designed spiro-twisted molecular structure of TSBZ6D constitutes an SPE matrix with a high fractional free volume that facilitates the transport of lithium ions. In the meantime, its cross-linking network structure enables a remarkable enhancement in the mechanical properties of SPEs. When combined with polyethylene oxide) (PEO) electrolytes, the TSBZ6D s-IPN imparts an enhancement of >300 and 1100% in tensile stress and in tensile strain, respectively, to the PEO-TSBZ6D (PT) composite SPEs over the PEO/lithium salt sample. Electrochemical testing of symmetric Li/PT/Li cells indicates the effectiveness of PT SPEs in mitigating the short-circuiting problem caused by Li dendrite formation. We demonstrated that a specific capacity of 166 mAh g(-1) (0.1 C) at 80 degrees C and a promising cycle stability have been achieved by an all-solid-state LiFePO4/PT/Li.