La4NiLiO8-Shielded Layered Cathode Materials for Emerging High-Performance Safe Batteries.

Low theoretical capacities of the commercial cathode materials (olivine: ∼170 mA h g-1 and spinel: ∼140 mA h g-1) dictate the need for higher energy density alternates such as nickel-rich (denotes as NCM) materials with a theoretical capacity of ∼270 mA h g-1. However, low conductivity and the bulk degradation after direct contact with liquid electrolytes, especially at temperatures higher than 50 °C, are the biggest issues to resolve for safe use and confident commercialization of the NCM materials. In this context, we first report "La4NiLiO8 shields" to simultaneously boost charge conduction characteristics and circumvent the electrolytic degradation of NCM. Consequently, the La4NiLiO8-shielded LiNi0.5Co0.2Mn0.3O2 (LSN5) not only offers a 4.1× less charge transfer resistance and significantly higher discharge capacity (219.7 mA h g-1) than the nonshielded NCM (187 mA h g-1) and theoretical capacities of commercial cathode materials but also maintains more than 91.7% of capacity retention at 25 °C after 500 cycles and 84.2% at 60 °C after 200 cycles. In contrast, the nonshielded NCM cathodes can only provide 58.9 and 45.5% capacity retentions at corresponding test temperatures and performance cycles. The acquired excellent electrochemical performance and battery stability at both the ambient and high-temperature conductions infer great importance of the novel La4NiLiO8 shields in developing high-performance safe secondary batteries.