Using Polyisobutylene as a Non-Fluorinated Binder for Coated Lithium Powder (CLiP) Electrodes

Binder formulations based on N-methylpyrrolidone/polyvinylidene fluoride (NMP/PVdF) or water/carboxymethyl cellulose (H2O/CMC) are state of the art in the fabrication of anodes for lithium-ion battery (LIB) applications. However, in combination with metallic lithium these materials tend to degrade. Therefore, for the production and operation of anodes employing metallic lithium particles another binder system, which is flexible, chemically and electrochemically inert, inexpensive, commercially available and, especially for industrial applications, usable within a broad temperature range, is needed. Polyisobutylene (PIB) is able to fulfil these criteria. The advantages of this binder are its inert structure and its solubility in alkanes (e.g. heptane), which are inert against lithium metal, as well. In this work we will introduce heptane/PIB as a binder formulation for the preparation of electrodes from coated lithium powder (CLiP) particles. We demonstrate that CLiP electrodes fabricated with this binder system exhibit better electrochemical performance than electrodes made with NMP/PVdF or tetrahydrofuran (THF)/PVdF formulations. Furthermore, CLiP immersed in heptane/PIB show also better thermal stability compared to CLiP immersed in NMP/PVdF and THF/PVdF.