Unravelling binder chemistry in sodium/potassium ion batteries for superior electrochemical performances

Abstract

The binder chemistry in Na/K ion batteries is important to electrochemical performance. Here, commercial TiO₂ nanoparticles are employed as a model to illustrate the binder chemistry in ethers, with polyvinylidene difluoride (PVdF) and sodium carboxymethyl cellulose (CMC) as the examples. An electrode using CMC as the binder shows superior electrochemical performance to that using PVdF, especially in terms of initial coulombic efficiency (80.1% for CMC vs. 52.5% for PVdF). The worse performance of the electrode using PVdF is mainly due to electrochemical defluorination of PVdF, which leads to cleavage of C–F and the formation of NaF over the electrode. Last but not least, a similar improvement in the binder chemistry works for many anode materials in Na/K-ion batteries.