High-voltage spinel cathodes for lithium-ion batteries: controlling the growth of preferred crystallographic planes through cation doping†
The high-voltage LiMn1.5Ni0.5O4 spinel cathode has become appealing for lithium-ion batteries as it offers fast, 3-dimesional Li-ion diffusion and high power. However, its commercialization is hampered by capacity fade during cycling due to the aggressive reaction between the cathode surface and the electrolyte and dissolution of the active material under the high-voltage operating conditions. We present here an investigation of the nucleation and growth of doped co-precipitated mixed-metal hydroxide precursor particles, and the resulting stabilization of preferred crystallographic surface planes in the final spinel samples. The samples are synthesized by a coprecipitation reaction of the mixed-metal hydroxide precursors with a scalable continuously stirred tank reactor (CSTR), followed by firing with lithium hydroxide. The synthesized samples are characterized by X-ray diffraction, electron microscopy, time-of-fight – secondary ion mass spectroscopy (TOF-SIMS), and electrochemical charge–discharge measurements. It is found that doping with certain cations stabilizes the growth of low-energy (111) surface planes, facilitating a long cycle life and fast high-rate performance.