A polymer binder with amine-facilitated lithium-ion transfer, enabling high-loading silicon-based anodes

Abstract

High-energy silicon (Si)-anode lithium (Li)-ion batteries require anodes with high mass loadings and areal capacities. However, they often suffer from poor utilization of active materials due to an inadequate Li-ion transport network and electrode breakdown resulting from a lack of mechanical strength. We introduce an amine-containing polymer binder, poly(acrylic acid)–g-n-(2-aminoethyl)piperazine (PAA–AEP), which enhances Li-ion transfer within high-loading electrodes and provides durable mechanical strength during cycling. In this polymer, amine groups bind with Li ions, facilitating their transfer, while carboxyl groups interact with the silicon surface to maintain structural integrity. Additionally, hexatomic ring structures provide additional mechanical strength to accommodate the volume expansion of silicon. At a high mass loading of 2.8 mg cm⁻² and an impressive areal capacity of 4.5 mA h cm⁻², the electrodes show high ionic conductivity and low resistance. Spectroscopic and microscopic studies confirm a stable and intact electrode structure, successfully reducing SiO anode expansion by over 50%. A SiO|NCM811 pouch cell (4.5 mA h cm⁻²) demonstrates a capacity retention of 89.0% over 700 cycles. Our findings provide an effective way to utilize amine-based polymers for practical, high-energy density batteries based on silicon anodes.