Biomimetic plant-cell composite gel polymer electrolyte for boosting rate performance of lithium metal batteries

Unsatisfactory ionic conductivity and uncontrolled lithium dendritic propagation in the gel polymer electrolyte (GPE) battery system hinder cell operation, especially under high rate and long-cycling conditions. Herein, a biomimetic composite GPE (PVFH-PMC-PEGC) has been developed by incorporation of polymer microcapsule with polyethylene glycol chain and carboxylic acid group (PMC-PEGC) into poly(vinylidene fluoride-co-hexafluoropropylene) (PVFH) matrix, mimicking water retention and selective permeability mechanism in the plant cell. The large lumen of PMC can uptake liquid electrolytes, and the functional shell of PMC can conduct Li-ion and anchor anion. The PVFH-PMC-PEGC achieves a highly enhanced ionic conductivity of 2.7 mS cm−1 over one order of magnitude to the pure PVFH GPE. A desirable transference number of 0.77 can improve the homogeneous Li+ deposition. Meanwhile, the intrinsic advantage of organic/organic composite endows the composite GPE with highly enhanced mechanical strength, which can inhibit the propagation of lithium dendrite. Therefore, Li-Li cell assembled with PVFH-PMC-PEGC attains a high critical current density of 4 mA cm−2 and stable cycling for 300 h at 1 mA cm−2 (5 mAh cm−2). Different lithium metal batteries with the PVFH-PMC-PEGC, such as Li-LiFePO4, Li-LiNi0.6Co0.2Mn0.2O2, and even Li–S batteries, have demonstrated superior power density and excellent cycle stability.