Battery safety has long been a critical pain point for the global energy storage and consumer electronics industries, and a team of Chinese researchers has now delivered a transformative solution that upends decades of conventional industry thinking. In a newly published study in *Nature Energy*, the team introduced an innovative liquid electrolyte that activates instantly when a battery overheats, forming a protective ‘firewall’ that stops catastrophic thermal runaway before it can begin. This work also marks the first time researchers have demonstrated full thermal runaway prevention in commercial-scale sodium-ion batteries, a milestone that could reshape the future of energy storage.