Resolving the Mechano-Electrochemical Dilemma in Structural Batteries via In Situ Entropy Engineering

Structural batteries (SBs) offer a revolutionary approach to massless energy storage, but suffer from severe capacity degradation and mechanical failure due to coupled electrochemical and mechanical stresses, particularly when employing high-energy layered cathodes. Herein, an in situ entropy engineering strategy is pioneered to construct a highly robust, nickel-rich structural cathode (SC). Multi-element co-doping induces a strong lattice pinning effect, which thermodynamically suppresses lattice oxygen escape and intrinsically mitigates internal anisotropic strain during continuous lithiation/delithiation. Integrated onto carbon fiber current collectors, the resulting SBs exhibit an exceptional balance of energy and load-bearing metrics. They deliver a superior specific capacity of 122.34 mAh g⁻¹ at 0.3C with 82.25% capacity retention over 200 cycles, significantly outperforming conventional NCM811 benchmarks. Furthermore, the SBs withstand macroscopic external stresses, yielding a tensile strength of 206.05 MPa and a flexural strength of 122.35 MPa, while demonstrating near-zero capacity degradation under sustained static in situ mechanical loads. Experimental and theoretical insights jointly confirm that entropy-driven lattice stabilization bridges the critical gap between high energy density and mechanical robustness, propelling the practical development of massless energy storage.