Superior electrochemical performance of quasi-concentration-gradient LiNi0.8Co0.15Al0.05O2 cathode material synthesized with multi-shell precursor and new aluminum source

Ni-rich LiNi0.8Co0.15Al0.05O2 (NCA) is considered as one of the most attractive cathode materials for Li-ion batteries. However, poor thermal stability and cycle performance for this material have to be faced. In this work, to promote the cycle and thermal stability of NCA cathode without lessening its discharge capacity, for the first time, quasi-concentration-gradient NCA cathode (QCG-NCA) is designed and synthesized with multi-shell precursor. The electrochemical properties and thermal stability of QCG-NCA are compared to homogeneous LiNi0.8Co0.15Al0.05O2 (HG-NCA), core material LiNi0.85Co0.15O2 (HG-NC) and the outer shell material LiNi0.6Co0.15Al0.25O2 (HG-NCA25). As expected, QCG-NCA exhibits higher discharge capacity (198.1 mA h g−1 at 20 mA g−1), higher capacity retention (87.8% at 0.2C after 200 cycles; 70.9% at 1C after 500 cycles) and better thermal stability than the homogeneous one. Reasons of these enhancements are investigated in this work. This strategy extends the concept of concentration-gradient structure and offers a new strategy suitable for practical application to modify the NCA cathode material.