Interfacial fracture energy as the missing descriptor in solid-state batteries: coordination-chemistry origins of manufacturing-induced mechanical memory and pressure-lean cycling

Solid-state batteries are routinely optimized through ionic conductivity, electrochemical stability, elastic modulus, interfacial resistance, and externally applied stack pressure, but these descriptors do not directly quantify resistance to propagation of damage at internal solid-solid or composite interfaces. This review develops a coordination-chemistry-centered, fracture-aware framework in which retained interfacial integrity is interpreted through competition between a state-dependent effective interfacial fracture resistance, G c,eff , and a local electrochemical-mechanical crack-driving energy, G drive . Importantly, G c,eff is treated as an operational descriptor rather than a universally established material constant: direct battery-relevant fracture-energy measurements remain scarce, so adhesion, modulus, impedance, critical current density, morphology, and cycling are classified as proxy evidence unless they are explicitly connected to crack extension. The review links coordination chemistry, dynamic solid-electrolyte interphase (SEI), cathode-electrolyte interphase (CEI), and solid-liquid electrolyte interphase (SLEI) reconstruction, manufacturing-induced mechanical memory (MIMM), contact retention, and pressure requirements. A structured evidence hierarchy distinguishes direct fracture measurements, state-resolved chemo-mechanical fields, mechanical proxies, and computational interpretations. We further define the boundary conditions and measurement routes required to estimate G c,eff and G drive , propose the Interface Survival Number, Ψ IF = G c,eff /G drive , as a testable but non-universal conceptual descriptor, and identify where fatigue, creep, mixed-mode fracture, and evolving interphases require extensions beyond an instantaneous scalar ratio. The resulting framework shifts the design target from pressure-supported contact toward intrinsically durable interfacial integrity.