Synthesis and characterization of Co-free NMA cathodes for fast charging lithium-ion batteries

The new high nickel cathode LiNi _1−x−yMn _xAl _yO ₂ (NMA) has attracted the attention of researchers, but the high rate performance has shortcoming compared to the conventional cobalt-cathode. In this paper, NaAlO ₂ was used as the aluminum source to effectively inhibit the preferential precipitation of Al(OH) ₃ and the chemical composition was uniformly distributed in particles. LiNi _0.80Mn _0.1Al _0.1O ₂ (NMA80), LiNi _0.90Mn _0.05Al _0.05O ₂ (NMA90) and LiNi _0.95Mn _0.025Al _0.025O ₂ (NMA95) cobalt-free materials were synthesized by this optimized chemical co-precipitation method and calcinations and all three materials show high crystallinity and purity. The electrochemical performance and phase characterization analysis of Ni-Mn-Al materials were carried out and the effects of Al and Mn elements on the materials were investigated. The specific capacity of NMA95 is 210.6 mAh/g at 0.1 C under a voltage range of 2.75–4.30 V and NMA90 can also reach 201.1 mAh/g. In addition, NMA95 and NMA90 also have excellent specific capacity at 1 C, the discharge capacity are 195.3 and 183.2 mAh/g respectively. However, the cyclic stability of NMA95 at 1 C is slightly inadequate with 81.10% retention rate and NMA90 is the best with 95.52% retention rate. As for NMA80, the overall capacity is low. In particular, the rate performance of NMA90 is much higher than the other two materials. The discharge capacity of NMA90 can still reach 172.3 mAh/g at 5 C high discharge rate. Excellent specific capacity at high rate is promising for the development of fast charging technology. NaAlO ₂ effectively control the precipitation rate of Al, and the rate performance of the synthetic material is optimized. It is expected that performance of NMA for next-generation lithium-ion batteries could be improved by this process.