Integrating dry-processing and pre-sodiation enables high-energy sodium ion batteries

Abstract

Sacrificial sodium-rich salts pre-sodiation is a safe and promising approach to supplement sodium-ion batteries with additional capacity for energy density enhancement. However, high-cost from additional solvent and low-utilization-ratio caused by loose electrical contact limit its practical application in slurry-coated electrodes. Herein, we demonstrate a dry-processing method to enable complete sodium oxalate decomposition and solvent-free production of thick electrodes. Distinct to particle aggregation in slurry-coated electrodes, a homogenous mixture of Na2C2O4 and conductive agents is generated and wraps Na3V2(PO4)3 particles after high-speed shear-mixing and hot-calendaring of dry-processing method, constructing intimate and durable electronic pathways, thus realizing theoretical decomposition capacity of Na2C2O4 in thick electrodes (54 mg cm-2). This strategy increases the lifespan by 200 cycles and energy density by 82.5% for all-dry-processing sodium-ion batteries with areal capacity of 5.4 mAh cm-2, which highlights the vital role of exploiting mechanical and thermal effects of dry-processing method in sustainable fabrication of high-energy sodium-ion batteries.