High-voltage performance of concentration-gradient Li[Ni0 67Co0 15Mn0 18]O-2 cathode material for lithium-ion batteries

Abstract

A novel Li[Ni0 67Co0 15Mn0 18]O-2 cathode material encapsulated completely within a concentration-gradient shell was successfully synthesized via co-precipitation The Li[Ni0 67Co0 15Mn0 18]O-2 has a core of Li[Ni0 8Co0 15Mn0 05]O-2 that is rich in Ni a concentration-gradient shell having decreasing Ni concentration and increasing Mn concentration toward the particle surface and a stable outer-layer of Li[Ni0 57Co0 15Mn0 28]O-2 The electrochemical and thermal properties of the material were investigated and compared to those of the core Li[Ni0 8Co0 15Mn0 05]O-2 material alone The discharge capacity of the concentration-gradient Li[Ni0 67Co0 15Mn0 18]O-2 electrode increased with increasing upper cutoff voltage to 4 5 V and cells with this cathode material delivered a very high capacity 213 mAh/g with excellent cycling stability even at 55 C The enhanced thermal and lithium intercalation stability of the Li[Ni0 67Co0 15Mn0 18]O-2 was attributed to the gradual no ease in tetravalent Mn concentration and decrease in Ni concentration in the concentration-gradient shell layer .