All-solid-state batteries were fabricated with lithium silicide anodes (Li4.4Si), sulfide-based glass electrolyte (Li2S-P2S5), and titanium disulfide (TiS2) cathodes. Two approaches were taken to improve the properties of the interface between anode and solid electrolyte, and between the anode and the current collector. First, the lithium silicide powder was ball-milled for particle-size reduction, to achieve higher utilization of the active material. Second, the anode layer was designed with gradient structure consisting of lithium silicide + solid electrolyte composite layer (for easy lithium ion transport from anode to electrolyte and vice versa) and lithium silicide layer (for easy electron transport from anode to current collector and vice versa). It was found that the additional ball milling step increased contact area between solid electrolyte and anode active material on the basis of GITT tests using a half cell. This effect was reflected in charge-discharge tests on a cell with the secondary ball-milled lithium silicide, resulting in higher capacities. A cell with the gradient-structured anode also showed 2–3-times higher capacities in comparison with a cell with conventional electrode design. Thus, the present work indicates why design of the electrode layers is a critical factor in determining the performance of solid state batteries.