A Study on the Phosphoric Acid Modification Mechanism of Plasma‐Sprayed Aluminum Electrode and Its Application Characteristics in Composite Solid‐State Batteries

All‐solid‐state aluminum‐ion batteries offer a promising pathway toward safe, low cost, and high‐capacity energy storage. This study establishes a novel aluminum–carbon solid‐state battery system featuring three synergistically engineered components: a plasma‐sprayed Al–Si–Mg–Zn alloy anode modified by phosphoric acid, a porous magnesium silicate‐based solid electrolyte, and a sodium‐enriched graphite cathode. The aluminum anode, treated with phosphoric acid and annealed at 300°C, forms a partially crystalline AlPO 4 layer that enhances interfacial stability and ion transport, resulting in a specific capacity of 901 mAh g −1 —over 2.5 times higher than the untreated aluminum electrode. Similarly, the porous PB electrolyte, fabricated via PVA‐assisted casting, demonstrated superior cycle life (> 100 cycles) compared to the dense compressed Ingot‐B electrolyte (13 cycles), attributable to improved ion diffusion pathways and mechanical compliance. The sodium phosphate‐modified graphite cathode further increased interlayer spacing and facilitated reversible Al 3+ storage, leading to markedly enhanced capacity and durability. The optimized full‐cell configuration (S‐Al10SiMgZ(P)/PB/GFN) delivered an initial specific capacity of 6278 mAh g −1 and retained ~200 mAh g −1 after 40 cycles, with a total cycle life exceeding 100 cycles. This work demonstrates, for the first time, the successful integration of plasma‐sprayed alloy electrodes with interfacial phosphate engineering and porous ceramic electrolytes into a high‐performance solid‐state aluminum‐ion system, underscoring its potential for next‐generation energy storage and practical device integration.