Internal battery overcharge protection

Ensuring battery safety during overcharge is pivotal for advancing these technologies from research to commercial deployment. While existing external overcharge protection strategies are effective, their dependence on intricate sensor networks and complex control systems escalates costs, increases system complexity, and introduces potential reliability issues, all of which constrain widespread adoption. Therefore, an internal overcharge protection approach has emerged as a promising alternative, utilizing redox reactions of preinstalled compounds within the battery to prevent overcharge, either complementing or replacing external strategies. This review categorizes these compounds into redox shuttle additives, electro-polymerization additives, and potential sensitive polymers based on their underlying protection mechanisms. A comprehensive analysis is conducted on the activation potentials, overcharge protection lifespans, and mechanisms within various battery systems. Furthermore, the compounds are systematically organized by core structures to elucidate the intrinsic relationships fostered by modified functional groups. The review delves into strategies for enhancing activation potential, solubility (for additives), and stability to prolong the efficacy of overcharge protection. Finally, the modification principles for these compounds, focusing on functional group adjustments that could extend their protective lifespan are summarized. These insights offer a roadmap for future design and development of internal overcharge protection strategies, with the potential to accelerate their commercial application.