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

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.