Improvement of electrochemical properties of P2-type Na2/3Mn2/3Ni1/3O2 sodium ion battery cathode material by water-soluble binders

摘要

P2-type Mn-based cathode materials present high reversible capacities and low cost, but still suffer the poor cycle ability. In this study, a water-stable cathode material was synthesized by simple solid-state method, and kinds of water-soluble natural biopolymers including guar gum, sodium alginate and xanthan gum were investigated as the binder for this typical P2-type cathode material. As the water-soluble binders contain a large amount of -OH and -COO- functional groups, they could result high adhesion between the particles and conductor, thus lead to a better conductivity. Indeed, an enhanced electrochemical performance was observed on these water-soluble binder, comparing with the commercialized PVDF binder. Among them, the P2-type cathode material with xanthan gum binder delivers the most significant improvement in cycling performance with the capacity retention of 77.6% at 40 mA g(-1) and 66% at 100 mA g(-1) after 80 and 200 cycle. The XPS depth profiles demonstrated that the dissolution of transition metal in this cathode materials, which lead to severe structural deformation and capacity fading during the repeated cycles, can be significant suppressed by the usage of the water-soluble binders. (C) 2018 Elsevier Ltd. All rights reserved.