Cross-linked carboxymethyl cellulose–polyacrylic acid as a binder for thermally treated silicon–graphite@graphite based anodes: a multipronged approach towards realising silicon–graphite based anodes for lithium-ion cells

Abstract

Silicon–graphite (Si–Gr) composites are widely studied as a commercially feasible alternative to pure silicon (Si) anodes in lithium-ion (Li-ion) cells, as they enable effective utilization of silicon's high energy density while mitigating performance degradation associated with volume expansion during cycling. The present study adopts a multipronged approach to tackle the volume expansion by (1) employing a crosslinked carboxymethyl cellulose–polyacrylic acid (CMC–PAA) binder, (2) supporting the Si–Gr composite in a graphite (Gr) matrix, Si–Gr@Gr, and (3) thermal treatment of the active material. While the CMC–PAA binder helps form a three-dimensional matrix embedding the Si–Gr@Gr active material, the graphite support acts as an additional buffer for the Si–Gr composite material by alleviating the mechanical stress during expansion. The thermal treatment of Si–Gr@Gr leads to oxide formation and modification of particle morphology and d-spacing, thereby facilitating easy movement of Li-ions and particle integrity. The anode processed via this approach exhibited an initial specific capacity of 940 mA h g⁻¹ at a C/10 rate with a coulombic efficiency of 80.3% and demonstrated a specific capacity of 730 mA h g⁻¹ after 1000 charge–discharge cycles with 78% capacity retention.