All-solid-state batteries (ASSBs) with Li metal anodes or Si anodes are promising candidates to achieve high energy density and improved safety, but they suffer from undesirable lithium dendrite growth or huge volume expansion, respectively. Here we synthesize a hard-carbon-stabilized Li–Si alloy anode in which sintering of Si leads to the transformation of micro-metre particles into dense continuum. A 3D ionic-electronic-conductive network composed of plastically deformable Li-rich phases (Li15Si4 and LiC6) that enlarges active area and relieves stress concentration is created in the anode, leading to improved electrode kinetics and mechanical stability. With the hard-carbon-stabilized Li-Si anode, full cells using LiCoO2 or LiNi0.8Co0.1Mn0.1O2 cathodes and Li6PS5Cl electrolyte achieve favourable rate capability and cycle stability. In particular, the ASSB with LiNi0.8Co0.1Mn0.1O2 at high loading of 5.86 mAh cm−2 delivers 5,000 cycles at 1 C (5.86 mA cm−2), demonstrating the potential of using hard-carbon-stabilized Li–Si alloy anodes for practical applications of ASSBs.
Si anodes could be an alternative to Li anodes in the application of solid-state batteries, but they suffer from issues such as severe volume expansion and sluggish kinetics. Here the researchers develop a Li–Si alloy anode that is stabilized by hard carbon, which leads to exceptional high-performance solid-state batteries.