The global electrification of transport, infrastructure and industry has positioned batteries as one of the defining technologies of the twenty-first century1. For decades, progress in battery science has been measured in terms of gravimetric and volumetric energy density, power density, lifetime and cost per kilowatt-hour. This optimization paradigm has delivered remarkable advances, particularly in lithium-ion chemistries, whose performance and scalable manufacturing have enabled mass-market electric vehicles and grid storage2. However, as electrified systems become increasingly weight-sensitive, space-constrained and carbon-limited, treating batteries as purely electrochemical devices is becoming a structural limitation.