关键词: 钠离子电池, 负极材料, 双金属磷化物, 中空核壳结构, 氮掺杂碳, 拉曼光谱

Abstract:

With the increasing demand for large-scale energy storage, great progress has been made in discovering new advanced energy storage materials. Sodium-ion batteries (SIBs) have attracted much attention in recent years due to their use of abundant sodium resources and their comparable electrochemical capacity to lithium-ion batteries (LIBs). In this paper, we developed novel hollow core-shell Ni-Co bimetallic phosphide nanocubes with N-doped carbon coatings (Ni_1.2Co_0.8P@N-C) as the anode material for SIBs. The material was synthesized through a low-temperature phosphorization method using resorcinol formaldehyde (RF) resin coating with a Ni-Co Prussian blue analogue (PBA) as a template and a subsequent thermal annealing process. The size of the as-obtained nanocubes was about 310 nm with a 19 nm N-doped carbon shell. When used as the anode material of SIBs, Ni_1.2Co_0.8P@N-C exhibited the excellent electrochemical cycling stability and demonstrated an especially high coulombic efficiency of 99.3%, even after 200 cycles with current density of 100 mA·g^-1. Furthermore, in-situ Raman spectroscopy was used to investigate the electrode material in order to understand the electrochemical processes in the N-doped carbon shell of Ni_1.2Co_0.8P@N-C. The results showed that the intercalation and de-intercalation behavior of sodium ions in the N-doped carbon shell was almost reversible, providing valuable information about the charge and discharge processes in SIBs for the follow-up electrochemical studies.

Key words: sodium-ion batteries, anode material, bimetallic phosphide, hollow core-shell structure, N-doped carbon, Raman spectroscopy