All-solid-state lithium-ion batteries (ASLBs) employing sulfide solid electrolytes are considered a promising alternative to conventional lithium-ion batteries (LIBs) from the perspectives of safety and high energy density. From a practical point of view, the development of sheet-type electrodes employing alternative electrode materials by scalable fabrication is of prime importance. While Si has been extensively studied for next-generation LIBs, reports on ASLBs are scarce. Herein, we fabricate sheet-type Si composite electrodes by infiltrating conventional LIB electrodes with solid electrolytes using a homogeneous Li6PS5Cl-ethanol solution. Further, we systematically investigate effects of the particle size (micro- vs. nano-Si) and polymeric binders (polyvinylidene fluoride vs. polyacrylic acid/carboxymethyl cellulose) on the electrochemical performance of ASLBs under varying external pressures (140, 20, and 5 MPa) upon cycling. Owing to intimate ionic contacts enabled by liquefied solid electrolytes, the Li6PS5Cl-infiltrated Si electrodes show higher capacities of over 3000 mA h g−1 at 0.25 mA cm−2 and 30 °C as compared with conventional dry-mixed electrodes. At 20 MPa, the Si electrodes using micro-Si and polyvinylidene fluoride show marginal degradation of performance. The high energy density of 338 W h kg−1 of LiCoO2/Si ASLBs fabricated using the Li6PS5Cl-infiltrated electrodes is demonstrated, highlighting the prospect of high-energy practical ASLBs.