Pushing Energy Density Limits: Anode‐Less Solid‐State Battery Integrated With Amorphous Lithium Vanadium Oxide Thin‐Film Cathode

ABSTRACT Anode‐less all‐solid‐state batteries offer a promising route to maximize stack‐level volumetric energy density by eliminating pre‐installed lithium (Li) and forming the anode in situ on a bare current collector. However, in thin‐film microbatteries, anode‐less operation is highly sensitive to Li loss, which occurs via interphase formation, dead‐Li isolation, and stripping‐induced contact loss. Here, we develop an anode‐less thin‐film battery platform using lithiated vanadium oxide (LVO) cathodes and a lithium phosphorus oxynitride solid electrolyte, targeting the critical challenge of stabilizing Li nucleation and stripping at the solid–solid anode interface. Systematic screening of ultrathin current–collector modifications, including carbon‐only, metal‐only, and metal/carbon bilayers (Au, Ag, Zn, Al, and Sn), identifies Sn/C as the most effective seed layer, yielding the lowest nucleation overpotential, reduced voltage hysteresis, improved galvanostatic stability, and the most uniform Li plating morphology. To further mitigate first‐cycle Li loss, a reversed‐structure prelithiation step introduces a controlled Li reservoir on the seeded collector, enabling gradual activation and stable cycling. The optimized anode‐less full cell with a 2‐µm‐thick LVO cathode achieves a volumetric energy density of 235.13 Wh L −1 at the 100 th cycle. These results establish practical guidelines for interlayer selection and interface engineering to enable durable anode‐less thin‐film batteries.