Kinetic-Coordinated Mechano-Electrochemical Steady-State in All-Solid-State Si–Se Batteries

Abstract

Mechanical degradation induced by electrode volume fluctuations remains a fundamental barrier for all-solid-state lithium-ion batteries (ASSLBs). Here, a kinetic-coordinated mechano-electrochemical steady-state architecture is proposed for Li_xSi–Se ASSLBs. It dynamically counterbalances the Se cathode volumetric expansion with the continuous contraction of the Li_xSi anode during cycling. The conversion kinetics of Se promote temporal coordination with the anode, thereby mitigating transient mechanical imbalance. This volumetric and kinetic dual-matching results in a pressure change of −0.137 MPa at the discharge–charge transition in the 20th cycle. Its absolute magnitude is more than one order of magnitude lower than that of the Li–Se cell (−2.721 MPa). The mechanically stabilized interfaces suppress long-range cracking and help maintain continuous solid–solid contact. Consequently, the Li_xSi–Se system delivers excellent specific capacities of 579.1, 510.4, 369.4, 260.1, and 170.5 mAh g⁻¹ at 0.1, 0.2, 0.5, 1, and 2C, respectively. More importantly, scaled-up 10 × 10 cm² pouch cells achieve a high reversible capacity of 1.13 Ah. Their peak capacity of 1.16 Ah corresponds to a calculated gravimetric energy density of 274.15 Wh kg⁻¹ based on the combined masses of the cathode, solid-state electrolyte, and anode. This work establishes this dual-matching paradigm as a general design principle for overcoming interfacial mechanical failures in high-energy ASSLBs.