Cathodes with intrinsic redox overcharge protection: A new strategy towards safer Li-ion batteries

• A novel safety strategy to avoid overcharging, i.e. solid-state anti-overcharge additive, is proposed.
• The strategy can provide a high-potential and a long-period of anti-overcharge performance.
• The effectiveness of the solid-state anti-overcharge additives is confirmed in LiCoO2/C and LiMn2O4/C full cells.

Overcharge safety is the most crucial problem facing especially large-sized lithium-ion batteries (LIBs) packs owing to the inevitable inhomogeneity of charge-state for each cell. We propose a fresh safety strategy to avoid overcharging, i.e. the use of a solid-state anti-overcharge additive to perform an intrinsic overcharge protection. The mechanism is triggered from a solid-state composite cathode obtained by typically mixing a pre-selected transition-metal oxide with a certain cathodes thus constituting a composite cathode. The effectiveness of this strategy is demonstrated with an example of LiCoO2/CuO (95:5 by weight) composite, which exhibits high-potential (up to 5 V vs. Li+/Li) and long-period (month-level) anti-overcharge performance. It is found that the additive does not hurt the electrochemical cycling performance under normal operational conditions. This novel safety strategy is simple and flexible, which may open a new window to develop safer LIBs systems.