Spinel‐Layered Core‐Shell Cathode Materials for Li‐Ion Batteries

Abstract

In an attempt to overcome the problems associated with LiNiO 2, the solid solution series of lithium nickel‐metal oxides, Li[Ni 1–x M x]O 2 (with M = Co, Mn, Al, Ti, Mg, etc.), have been investigated as favorable cathode materials for high‐energy and high‐power lithium‐ion batteries. However, along with the improvement in the electrochemical properties in Ni‐based cathode materials, the thermal stability has been a great concern, and thus violent reaction of the cathode with the electrolyte needs to be avoided. Here, we report a heterostructured Li[Ni 0.54 Co 0.12 Mn 0.34]O 2 cathode material which possesses both high energy and safety. The core of the particle is Li[Ni 0.54 Co 0.12 Mn 0.34]O 2 with a layered phase (R3‐m) and the shell, with a thickness of < 0.5 μm, is a highly stable Li 1+x[CoNi x Mn 2–x]2 O 4 spinel phase (Fd‐3m). The material demonstrates reversible capacity of 200 mAhg‐1 and retains 95% capacity retention under the most severe test condition of 60 °C. In addition, the amount of oxygen evolution from the lattice in the cathode with two heterostructures is reduced by 70%, compared to the reference sample. All these results suggest that the bulk Li[Ni 0.54 Co 0.12 Mn 0.34]O 2 consisting of two heterostructures satisfy the requirements for hybrid electric vehicles, power tools, and mobile electronics.