Solvent-free lithium-ion battery electrodes with ultrahigh loading using a reactive epoxy nanobinder

Abstract

Currently, the manufacturing of lithium-ion battery (LIB) electrodes relies strongly on the slurry-coating process, which severely restricts the fabrication of thick electrodes and inevitably leaves electrochemically harmful solvents in electrodes. Herein, we demonstrate a novel dry process for electrodes using reactive epoxy nanospheres (EPs) as dry binders. Reactive EPs, with an average particle size of 103.3 nm, are successfully prepared and provide strong bonding to Li₄Ti₅O₁₂ through covalent bonds formed by curing cross-linking reactions. The structural integrity and electrochemical performance of the fabricated dry electrodes significantly surpass those of traditional slurry-coated electrodes. Moreover, EPs exhibit unique advantages in the preparation of high-loading dry electrodes (HDEs). A series of HDEs with gradient mass loadings were prepared, achieving a maximum mass loading of 31 mg cm⁻², corresponding to an areal capacity of 3.6 mA h cm⁻². Compared to the commonly used polyvinylidene fluoride (PVDF) dry binders, HDEs-EPs (17 mg cm⁻²) demonstrate more stable cycling performance, retaining 72.4% capacity after 350 cycles at 1C. We believe that EPs will drive the dry process as a promising solution for the scalable fabrication of solvent-free LIB electrodes due to their reactive bonding mode, stable solid state, and low cost.