Cobalt-Free High-Capacity Ni-Rich Layered Li[Ni0.9Mn0.1]O2 Cathode

Li[Ni0.9Co0.1]O-2 (NC90), Li[Ni0.9Co0.05Mn0.05]O-2 (NCM90), and Li[Ni0.9Mn0.1]O-2 (NM90) cathodes are synthesized for the development of a Co-free high-energy-density cathode. NM90 maintains better cycling stability than the two Co-containing cathodes, particularly under harsh cycling conditions (a discharge capacity of 236 mAh g(-1) with a capacity retention of 88% when cycled at 4.4 V under 30 degrees C and 93% retention when cycled at 4.3 V under 60 degrees C after 100 cycles). The reason for the enhanced stability is mainly the ability of NM90 to absorb the strain associated with the abrupt anisotropic lattice contraction/extraction and to suppress the formation of microcracks, in addition to enhanced chemical stability from the increased presence of stable Mn4+. Although the absence of Co deteriorates the rate capability, this can be overcome as the rate capability of the NM90 approaches that of the NCM90 when cycled at 60 degrees C. The long-term cycling stability of NM90 is confirmed in a full cell, demonstrating that it is one of the most promising Co-free cathodes for high-energy-density applications. This study not only provides insight into redefining the role of Mn in a Ni-rich cathode, it also represents a clear breakthrough in achieving a commercially viable Co-free Ni-rich layered cathode.