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

ABSTRACT 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.