Liquid-solid phase separation-generated multifunctional light-weight modification layer of g-C3N4/carbon endowing 5 V cathode material graphite flakes with high capacity and cyclicability simultaneously

Abstract

Nowadays metal oxide coatings become one of the dominant ways to suppress electrolyte decomposition and consequantly improve cyclicability of high-voltage cathode materials for high energy-density batteries. However electrochemically inert nature and relatively high density of the metal oxides inevitably reduce cathode capacities. Meanwhile weak interfacial binding may induce desorption of the metal oxides during charge/discharge cycling. Herein a new strategy of light-weight g-C3N4/carbon coordinative modification of 5 V cathode material graphite flakes (GF) for dual-ion batteries is provided with aim to maintain graphite capacity and enhance interfacial binding strength simultaneously. Liquid-solid phase separation is utilized to generate multifunctional unique structure of the modification layer consisting of ultrafine g-C3N4 particles embedded homogeneously in carbon matrix, endowing the modified GF with high capacity and cyclicability for anion PF6─ storage simultaneously. A capacity enhancement of ~11% (1 C) is realized compared with that of TiO2/carbon modified GF, demonstrating superiority of the light-weight modification. Meanwhile capacity retention reaches 87% after 1500 charge/discharge cycles (5 C), exhibiting excellent cyclicability. The liquid-solid phase separation is an efficient way to generate homogeneous mixtures. Furthermore, the strategy of light-weight g-C3N4/carbon modification may provide a general way to improve capacity and cyclicability of other high-voltage cathode materials simultaneously.