Economical cobalt-free single-crystal LiNi0.6Mn0.4O2 cathodes for high-performance lithium-ion batteries

With the scarcity of cobalt resources and soaring prices, the removal of cobalt from nickel-rich layered cathodes is now a priority to reduce the material costs and develop the sustainability of lithium-ion batteries (LIBs). In this work, we report a single-crystal cobalt-free LiNi0.6Mn0.4O2 (NM64) layered oxide cathode and compare it with single-crystal LiNi0.6Co0.1Mn0.3O2 (NCM613) cathode. On the one hand, NM64 exhibits competitive energy density to NCM613 and better long-term cycle stability under a high cutoff voltage of 4.5 V. Impressively, single-crystal NM64 not only could effectively suppress the microcrack formation, resulting in the excellent structural stability and long cycling lifespan even at the full delithiated state, but also, it has superior thermal stability to single-crystal NCM613, which is beneficial to achieve high operational safety of LIBs. On the other hand, due to the removal of expensive cobalt, the material cost of NM64 is only 2/3 of NCM613, which is conducive to significantly reducing the cost of LIBs. As a result, NM64 exhibits high energy density (765.27 Wh kg−1) and remarkable cycle stability (93.21 mA h g−1 after 200 cycles at a high charging voltage of 4.5 V). Considering the cost and electrochemical performance advantages, the NM64 cathode is highly expected to stand out in the next generation of cobalt-free LIBs.