Solid-state lithium batteries composed of hematite and oxide electrolyte

[Display omitted] •α-Fe2O3 was evaluated as anode of solid-state batteries using oxide electrolyte.•Smaller Fe2O3 particles showed better anode performance.•Contact area between Fe2O3 and the electrolyte was increased to improve performance.•Fe2O3 anode operated for the first time in oxide-based solid-state Li batteries. As Li-ion battery anode materials, two types of hematite (Fe2O3(big), Fe2O3(ultrafine)) were evaluated by using liquid electrolyte and oxide-based solid electrolyte. Although the anode using Fe2O3(ultrafine) with larger specific surface area showed a high initial reversible capacity in the liquid-electrolyte cell, there was a steep capacity decay in the cycling test. In the solid-electrolyte cell, we obtained very low reversible capacities of 40 mA h g−1 for the anode using Fe2O3(big) with smaller specific surface area. In contrast, the capacity of Fe2O3(ultrafine) anode was as high as 400 mA h g−1 at the 20th cycle. This is the first demonstration of charge–discharge reactions for Fe2O3 anode in oxide-based solid-state batteries. The Fe2O3(ultrafine) particles were dispersed relatively uniformly between solid electrolyte in the active layer, suggesting that the contact area between Fe2O3 and solid electrolyte becomes large. Consequently, Fe2O3(ultrafine) could benefit from larger contact area delivering the suitable reaction site for Li+ to improve the anode performance.