Towards water based ultra-thick Li ion battery electrodes – A binder approach

Abstract

In this work, different water-soluble binder systems are investigated in view on their influence on adhesion, porosity and electrochemical performance of Li1Ni0.33Mn0.33Co0.33O2 composite cathodes, with the aim to establish a low viscosity binder system for ultra-thick electrodes.Different mixtures of sodium carboxymethylcellulose, polyacrylic acid and polyethylene oxide are used as binder in a fixed ratio of 3 wt.-% regarding the solid components.A ternary composition of carboxymethylcellulose/polyacrylic acid/polyethylene oxide is identified as superior binder candidate regarding electrode paste viscosity and electrode adhesion. Starting from 60 wt.-%, the solid content of the electrode paste is increased to 65 wt.-% using the new binder system. Applying solid contents, homogenous and crack free electrodes with an active mass loading of up to 60 mg cm−2 are produced. Cycled against graphite anodes, these cathodes show specific capacities of 85 mAh∙g−1 (5 mAh∙cm−2) at 0.2C (1.8 mA cm−2). In a further step, the capacity is successfully increased to 120 mAh∙g−1 (6 mAh∙cm−2) at 0.2C (1.5 mA cm−2) using carbon micro fibers as additive. Beyond that, the electrode paste based on carbon micro fibers shows superior performance in comparison to a polyvinylidene difluoride-based reference system.