High-performance SiO electrodes for lithium-ion batteries: merged effects of a new polyacrylate binder and an electrode-maturation process

Abstract

SiO has been extensively studied as a high-capacity negative electrode material for lithium-ion batteries (LIBs). However, battery performance degradation caused by the large volume change during lithiation/delithiation hinders the practical application of SiO. To mitigate volume change degradation, we employed partially neutralized cross-linked sodium polyacrylate (CLPA) binders for fabricating carbon-coated SiO (SiO@C) composite electrodes and evaluated their electrochemical performance. We further synthesized new CLPA-based polymers with different amounts of the functional monomer (flexible additive), which was found to impart flexibility to the SiO composite layer. In addition, we employed “maturation” treatment for the fabricated composite electrode, in which the pre-dried SiO@C composite electrodes with CLPA-based binders on Cu foil were stored in 90% relative humidity for two days before drying. Among the non-matured electrodes, those with a CLPA-based binder with a 20% flexible additive (CLPA-20) exhibited the highest peel strength of 2.37 N cm⁻¹ and a reversible capacity of 1322 mA h g⁻¹ after 90 cycles. The maturation treatment further improved these properties (>5.8 N cm⁻¹ and 1598 mA h g⁻¹). Electron microscopy observations revealed that the dispersion condition of the CLPA binder and conductive carbon additives was clearly improved in the matured electrodes, implying the migration of carbon and binders during the maturation treatment. Matured electrodes not only exhibited enhanced electrochemical properties in Li cells and superior mechanical properties, but also showed better passivation, brought by the uniform and thin binder-coating on the SiO particles, as confirmed by surface analysis of the cycled electrodes.