Endowing an Intrinsic High‐Capacity Primary Thin‐Film Cathode With Cyclability

The rapid development of the Internet of Things (IoT) urgently demands high-performance and process-compatible integrated micro-power sources. All-solid-state thin-film batteries (ATFBs), which combine an all-solid-state architecture with on-chip integration capability, are regarded as an ideal on-chip power solution. However, their practical application is constrained by the low capacity of conventional cathode materials and the high-temperature annealing process (>500°C) required for crystallization, which is incompatible with temperature-sensitive integration processes. This study presents an annealing-free Ag₂O/V₂O₅ composite thin-film cathode, fabricated at room temperature by magnetron co-sputtering, in which the nanoconfinement effect of the amorphous V₂O₅ matrix effectively suppresses Ag₂O particle agglomeration to endow the electrode with satisfactory cycling stability. The composite thin-film cathode demonstrates excellent lithium storage performance, delivering an initial discharge capacity as high as 171.0 µAh cm⁻² µm⁻¹ (406.5 µWh cm⁻² µm⁻¹), which is approximately 2-3 times that of LiCoO₂, while maintaining 73% capacity retention after 1000 cycles. When integrated into ATFBs, this cathode achieves 71% retention over 400 cycles and can successfully power an LED sensor and a motion sensor. This work provides a new pathway to overcome the challenges of energy density and process compatibility in microelectronic applications.