Engineering electrode–electrolyte interface for ultrastable Si-based solid-state batteries

Due to the plentiful supply and extremely high theoretical capacity, Silicon (Si) is acknowledged as a prospective anode material for solid-state batteries with high-energy. Nonetheless, the substantial increase in size of Si particles during cycling causes an unsteady interface, leading to a reduced initial coulombic efficiency (ICE) and inferior cycle longevity. To address this issue, we created a strong layer by applying a solid electrolyte (Li6.4La3Zr1.4Ta0.6O12, LLZTO) with excellent lithium-ion conductivity onto the Si electrode's exterior. The LLZTO coating forms a stable interface between the electrode and electrolyte by utilizing chemical bond cooperation between polyvinyl alcohol (PVA) binder in the LLZTO coating and polyacrylic acid (PAA) binder in the Si electrode. This guarantees excellent interface stability and rapid movement of lithium ions at the interface between the electrode and electrolyte. The Si@LLZTO electrode demonstrates excellent performance, achieving an ultrahigh ICE of 90 %. After 200 cycles, the composite electrode exhibits an outstanding capacity retention of 1363 mAh g−1 at a current density of 1 A g−1. Furthermore, when assembled into a solid-state battery, it exhibits outstanding cycling stability with remarkable capacity retention (386 mAh g−1) over 1000 cycles at 1.2 A g−1.