Intraparticle alloying-plating reaction for high-performing lithium metal batteries with low volume expansion

Lithium metal anode is a key enabler for high-energy lithium-ion batteries, however solutions to achieve lithium metal anodes with stable charge–discharge cycling and low volume expansion have been lacking. Here, an intraparticle lithium-alloying-plating reaction offering high reversibility and low volume expansion is reported. A unique particle architecture, comprising a porous lithiophilic silicon core with a dual conductive seal, was constructed to concurrently achieve high porosity and low particle surface area. This hierarchically structured microparticle achieved intraparticle Li-storage with ultrahigh capacity (∼4,292 mAh/g_Si), greatly reduced electrode swelling and improved cycle life. Half-cells operating at ∼1 mA cm⁻² and ∼3mAh cm⁻² achieved coulombic efficiency > 99.3 % after 250 cycles in carbonate electrolyte, with the post-cycled electrodes showing well-preserved porosity and shielded-off electrolyte penetration. By contrast, porous silicon particles without the protective seal, experienced drastic side reactions and pulverization, with the electrodes experiencing severe swelling and capacity decay. Full pouch cells with LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811, ∼20.3 mg cm⁻²) retained ∼77.9 % capacity after 100 cycles, where the sealed porous silicon experienced minor expansion (∼12 %), much lower than a ∼20 μm lithium-metal anode (∼70 %). Furthermore, Z-stack full pouch cells adopting double-sided sealed porous microparticle anodes delivered a capacity retention of ∼95.7 % over 50 cycles.