Preferential growth of HT-LiCo1-xAlxO2 cathode micro-bricks via an intermediate-facilitated solid-solid-gas reaction

Abstract

Layered high-temperature LiCoO2 (HT-LiCoO2), a mature commercial cathode for 3C electronic devices, has been unable to satisfy the new and ever-growing battery demands due to its high price and the structural instability at high temperature or high voltage conditions. The practical strategies mainly conclude introducing even dopants and functional modifications to LiCoO2 crystals, but lacking explorations on the precise-control of non-equilibrium intermediates and preferred crystal planes during the solid-solid-gas (SSG) synthesis process. Here, the structure-optimal HT-LiCoO2 micro-bricks are synthesized via coherent pyrolysis followed by a SSG reaction from Co–Al-mixed oxalate precursors, forming layered phase, ideal crystal morphology and uniformly distributed Al-dopants. In particular, we observe both of the phase progression and morphology evolution during the synthesis process of LiCo1-xAlxO2 micro-bricks. Integrating the superiorities of the nanosized intermediates and Al-doping regulation, smaller crystalline size and less salt-rock defects are realized in the target cathodes, ultimately achieving promoted Li+ diffusion kinetic and electrochemical stability. Combined with the theory calculation, the optimized LiCo1-xAlxO2 with possible ion channels and the dopant-affected band gap have been simulated. These insights can help to guide the SSG synthesis of layered cathode materials with preferential orientations, precise doping and tailored phase compositions.