A Thermodynamic‐Decoupling‐Empowered Defect Engineering Guide: Uncovering the Substantial Yet Overlooked Stress Role in Electrode Potential Regulation

Defect chemistry for improving electrochemical potential and structural stability traditionally relies on chemical bonding and charge compensation. However, it reaches a bottleneck when the beneficial defect concentration saturates under the formation‐energy constraint, because defect‐induced lattice stress generally dissipates through volume expansion, obscuring its electrochemical contribution. Herein, we establish a defect‐engineering guide that thermodynamically decouples formation energy to extract an unprecedented stress dimension alongside traditional defect concentrations. Crucially, we develop a stepwise process driven by quantitative ligand‐field and stress descriptors to simultaneously screen both dimensions to their limits. We elucidate how universally expansive electrodes like silicon can maintain structural stability while suppressing passive stress release to mitigate expansion. Furthermore, targeting the extreme archetype of non‐expansive Li 4 Ti 5 O 12 electrodes, we uncover how confined stress can be transformed into a thermodynamic gain to lower their potentials. Among the 612 dual‐doping configurations, the optimal La‐Zr doping maximizes both the defect concentration and the strain energy, reducing the lithiation potential from 1.55 to 1.00 V (vs. Li/Li + ) while preserving intrinsic the zero‐strain characteristic. This work proposes a defect‐engineering guide rooted in a four‐quadrant panorama of thermodynamically decoupled concentration and stress dimensions, breaking optimization bottlenecks by harnessing stress upon formation‐energy‐constrained defect saturation to expand the boundaries of defect chemistry.