Boosting the cycling stability of LixSi alloy microparticles through electroless copper deposition

Abstract

LixSi alloy as one of the most promising Li-containing anode candidates, but with the huge volumetric change and poor cyclability concerns, is still far away from its implementation. Nanostructuring has been proven effective to address these failure modes of Si-based anodes. However, issues of high cost and poor electrical connection of Si nanostructures are remained to be solved. Si microparticles as a low-cost alternative are feasible in practical applications. Here we report a novel LixSi/Cu alloy composites anode material synthesized through electroless copper deposition and thermal lithiation processes, using low-cost micrometer-sized Si starting materials. The sufficient Cu additives greatly enhance the electronic conductivity, and meanwhile, act as effective volumetric buffer maintaining the electrode structures during cycling. Consequently, the resultant LixSi/Cu composites (with traces of Ag, Sn, Pd) anode is able to maintain a stable structure and stable cycling in half cells (200 cycles with 74% capacity retention, ∼1100 mAh g−1 maintained). And the improved cycling stability is further demonstrated by symmetric cell tests. The anode is also paired with commercial LiFePO4 cathode to build practical battery, achieving a stable full-cell cycling (100 cycles, ∼92% capacity retention) with high Coulombic efficiency (99.5% at the third cycle and ∼99.8% for subsequent cycles).