Enhanced lithium storage performances of novel layered nickel germanate anodes inspired by the spatial arrangement of lotus leaves

Abstract

The rapid capacity degradation of Ge-based materials hinders their practical application for next generation lithium ion batteries, which could be solved by synthesizing Ge-containing ternary oxides, with new structures and hybridizing with carbon nanomaterials. Herein, novel Ni₃Ge₂O₅(OH)₄ nanosheets were synthesized and distributed in situ on reduced graphene oxide (RGO) sheets, with both flat-lying and vertically-grown spatial distributions to imitate the growth of lotus leaves. These two types of Ni₃Ge₂O₅(OH)₄ nanosheets enhance their efficient contact with RGO, and increase the mass loading of active materials. Furthermore, the interfacial bonds between RGO sheets and Ni₃Ge₂O₅(OH)₄ nanosheets are introduced to improve the diffusion rate of lithium ions. The RGO sheets act as a buffer matrix to sustain the volume change and prevent the nanosheets from aggregation. Consequently, the chemically bonded Ni₃Ge₂O₅(OH)₄/RGO hybrid delivers a high specific capacity of 863 mA h g⁻¹ over 75 cycles, which is much higher than those for neat Ni₃Ge₂O₅(OH)₄ nanosheets or the hybrid without the interfacial bonding. This study provides a novel perspective for designing high-performance Ge-based anode materials for advanced lithium ion batteries.