Blow-Spinning Enabled Precise Doping and Coating for Improving High-Voltage Lithium Cobalt Oxide Cathode Performance.

Abstract

Lithium cobalt oxide (LiCoO₂) possesses an attractive theoretical specific capacity (274 mAh g^-1) and high discharge voltage (∼4.2 V vs Li⁺/Li). However, only a half of the theoretical capacity of LiCoO₂ is available in commercialized lithium ion batteries because of the intrinsic structural instability and detrimental interface of LiCoO₂ at the charging voltage over 4.2 V. Here, a facile blow-spinning synthetic method is developed to realize precise doping and simultaneous self-assembly coating of LiCoO₂ particles, achieving a record performance among present LiCoO₂ cathodes. Owing to the spatial confinement effect of microfibers fabricated by blow-spinning, homogeneously Mn and La doped in the LiCoO₂ host and uniformly Li-Ti-O segregated at the LiCoO₂ surface can be realized in every batch of samples. It is demonstrated that the Mn and La codoping can suspend the intrinsic instability and increase the Li⁺ diffusivity of the LiCoO₂ host, and the Ti-based coating can stabilize the interface of LiCoO₂ particles at the charging voltage up to 4.5 V. As a result, the obtained comodified LiCoO₂ cathode shows the best rate performance (1.85 mAh cm^-2 at 2C) and longest cycling stability under an areal capacity of 2.04 mAh cm^-2 (83% capacity retention over 300 cycles at 0.3C), in comparison to previously reported LiCoO₂ cathodes.