High-density crack-resistant Si-C microparticles for lithium ion batteries

Hollow-structured silicon-carbon composite particles are regarded as advanced anode materials for lithium-ion battery (LIBs) due to their superior expansion-buffering capability. However, the hollow structures compromise particle density and its benefits are diminished by the potential pore collapses due to electrode calendaring and cell operation. Herein, we report stuffed high-density Si-C particles that can suffice to be crack-resistant and deliver highly reversible Li-storage performances. This was achieved by implanting Si particles into a dual-layered carbon matrix comprised of a porous interior and a compact exterior. The compact exterior prevents electrolyte permeation, while the porous interior accommodates the Si expansion. Such structure allows an intraparticle "on-site voiding" mechanism, leading to anti-cracking and low swelling of Si-C electrode. The resulting Si-C particles possess high tap density (0.86 g/cc), low specific surface area (3.3 m2/g), and the Si-C/graphite mixture anode delivers capacity retention of 96.2% after 200 cycles. Paired with high-mass-loading LiFePO4, the full cells display 70.6% capacity retention over 200 cycles under industry-viable electrode metrics (1.20 g/cm3 for SiCG-600 and 2.40 g/cm3 for LFP, 1.88 mAh/cm2). This gives rise to 18.3% energy density improvement as compared to graphite || LiFePO4 battery. Herein, this study shed light on designing dense particles for practical high-energy LIBs.