High-Performance Silicon-Rich Microparticle Anodes for Lithium-Ion Batteries Enabled by Internal Stress Mitigation

The Sn and Sb incorporation boosts the electronic conductivity and lithium diffusivity of Si anodes, thereby reducing the stress due to lithium concentration gradient.The lithiation of modified electrode mimics isotropic solid solution reaction, rather than the original anisotropic two-phase reaction of Si, effectively weakening the stress concentration.The silicon-rich particles exhibit a capacity of over 1.9 Ah g-1 after 100 cycles at 0.1 A g-1 and maintain the excellent cyclic stability at 3 A g-1. Si is a promising anode material for Li ion batteries because of its high specific capacity, abundant reserve, and low cost. However, its rate performance and cycling stability are poor due to the severe particle pulverization during the lithiation/delithiation process. The high stress induced by the Li concentration gradient and anisotropic deformation is the main reason for the fracture of Si particles. Here we present a new stress mitigation strategy by uniformly distributing small amounts of Sn and Sb in Si micron-sized particles, which reduces the Li concentration gradient and realizes an isotropic lithiation/delithiation process. The Si8.5Sn0.5Sb microparticles (mean particle size: 8.22 mu m) show over 6000-fold and tenfold improvements in electronic conductivity and Li diffusivity than Si particles, respectively. The discharge capacities of the Si8.5Sn0.5Sb microparticle anode after 100 cycles at 1.0 and 3.0 A g-1 are 1.62 and 1.19 Ah g-1, respectively, corresponding to a retention rate of 94.2% and 99.6%, respectively, relative to the capacity of the first cycle after activation. Multicomponent microparticle anodes containing Si, Sn, Sb, Ge and Ag prepared using the same method yields an ultra-low capacity decay rate of 0.02% per cycle for 1000 cycles at 1 A g-1, corroborating the proposed mechanism. The stress regulation mechanism enabled by the industry-compatible fabrication methods opens up enormous opportunities for low-cost and high-energy-density Li-ion batteries.

Automated summary

The incorporation of Sn and Sb in Si anodes enhances the electronic conductivity and lithium diffusivity, reducing stress and improving the performance. Si8.5Sn0.5Sb microparticles exhibit improved conductivity and diffusivity, achieving high capacity and cycling stability.