Novel Lignin-Derived Water-Soluble Binder for Micro Silicon Anode in Lithium-Ion Batteries

Micro silicon is considered as the most prospective anode material for large-scale application of lithium-ion batteries (LIBs) due to its low production cost and diverse accessibilities. However, micro silicon anodes coupled with conventional binders generally show poor performances in LIBs. Therefore, developing new binders with high performance for micro silicon anode in LIBs is highly desirable. In this work, we report the first lignin-derived water-soluble binder (lignin-graft-sodium polyacrylate, PAL–NaPAA) for the micro silicon anodes. The PAL–NaPAA binder is obtained via a free radical graft copolymerization, followed by an alkaline hydrolysis. The electrochemical performance of PAL–NaPAA is compared with commercial binder carboxymethyl cellulose (CMC) for micro silicon anodes. The electrode using the PAL–NaPAA binder retains a capacity of 1914 mAh g–1 after 100 cycles at a constant current density of 840 mA g–1, which is superior to that of the electrode using the CMC binder (1544 mAh g–1). Additionally, the successful adhibition of PAL–NaPAA binder to commercial silicon–carbon anodes demonstrates great potential in practical applications in LIBs. It is also found that the lignin-derived binder can significantly accommodate the inevitable volume changes of silicon anode, while maintaining its excellent electrochemical performance. Our results provide a facile approach to utilize the abundant lignin biomass as a novel bind material and have paved the way to the industrial applications of micro silicon-based anodes in LIBs.