Ultra-Thin Single-Particle-Layer Sodium Beta-Alumina-Based Composite Polymer Electrolyte Membrane for Sodium-Metal Batteries

摘要

Inorganic/organic composite polymer electrolytes (CPEs) with good flexibilityand electrode contact have been pursued for solid?state sodium-metal batteries.However, the application of CPEs for high energy density solid?statesodium-metal batteries is still limited by the low Na~+ conductivity, large thickness,and low ion transference number. Herein, an ultra-thin single-particlelayer(UTSPL) composite polymer electrolyte membrane with a thickness of≈20 μm straddled by a sodium beta?alumina ceramic electrolyte (SBACE) ispresented. A ceramic Na~+-ion electrolyte that bridges or percolates across anultra-thin and flexible polymer membrane provides: 1) the strength and flexibilityfrom the polymer membrane, 2) excellent electrolyte/electrode interfacialcontact, and 3) a percolation path for Na+-ion transfer. Owing to thisnovel design, the obtained UTSPL-35SBACE membrane exhibits a high Na+-ion conductivity of 0.19 mS cm~(-1) and a transference number of 0.91 at roomtemperature, contributing to long?term cycling stability of symmetric sodiumcells with a small overpotential. The assembled quasi-solid-state cell with theas?prepared UTSPL-35SBACE membrane displays superior cycling performancewith a discharge capacity of 105 mAh g~(-1) at 0.5 ℃ rate after 100 cyclesand excellent rate performance (82 mAh g~(-1) at 5 ℃ rate) at room temperaturewith the potassium manganese hexacyanoferrate (KMHCF)@CNTs/CNFscathode, where KMHCF refers to potassium manganese hexacyanoferrate.