Comparison of Electrochemical Characteristics of Thin-Film Batteries with a Si@O@Al Composite Anode and Lithium Metal Formed by In Situ Method

The electrochemical characteristics of solid-state thin-film lithium-ion batteries with two different structures: Ti/Anode/LiPON/LiCoO₂/Ti (with an anode) and Ti/LiPON/LiCoO₂/Ti (anode-free) are intercompared. Si@O@Al composite anode with thicknesses of 154 and 15 nm, as well as pre-lithiated Li_xSi@O@Al composite with a thickness of 192 nm, were used as anodes. In anode-free batteries, the lithium anode was formed by the in-situ method. Batteries with 154 nm-thick Si@O@Al and Li_xSi@O@Al anodes have good cyclability due to their moderate volume change during lithium-ion insertion/extraction and reliable adhesion to the LiPON solid electrolyte. These batteries are promising in terms of high energy density due to the lithium anode in-situ formation, although they have poor cycling performance due to peeling of the upper current collector. The introducing of a Si@O@Al thin film with a thickness of ~15 nm between the LiPON and the current collector allows maintaining the high energy density that is inherent in batteries with lithium anodes, while also improving their cyclability.