Enhancement of the electrochemical performance of the spinel structure LiNi0.5-xGaxMn1.5O4 cathode material by Ga doping

Lifang Lan,Fenghua Zhao,Shuaijun Xu,Si Huang,Lu Lu,Sheng Li,Chunyang Pan,Yan Lu,Jun Li

doi:10.1186/s11671-018-2666-3

Abstract

A sol-gel method was adopted to obtain LiNi0.5-xGaxMn1.5O4 (x = 0, 0.04, 0.06, 0.08, 0.1) samples. The effect of Ga doping on LiNi0.5Mn1.5O4 and its optimum content were investigated, and the electrochemical properties at room temperature and at a high temperature were discussed. The structural, morphological, and vibrational features of LiNi0.5-xGaxMn1.5O4 (x = 0, 0.04, 0.06, 0.08, 0.1) compounds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FT-IR). The XRD results demonstrate that all samples have a disordered spinel structure with a space group of Fd3m, and Ga doping restrains the formation of the LixNi1-xO secondary phase. FT-IR analysis reveals that Ga doping increases the degree of cation disorder. The SEM results reveal that all samples possess a fine spinel octahedron crystal. The electrochemical performance of the samples was investigated by galvanostatic charge/discharge tests, dQ/dV plots, and electrochemical impedance spectroscopy (EIS). The LiNi0.44Ga0.06Mn1.5O4 sample with the optimum content shows a superior rate performance and cycle stability after Ga doping, especially at a high discharge rate and high temperature. In addition, the LiNi0.44Ga0.06Mn1.5O4 sample retained 98.3% of its initial capacity of 115.7 mAhg−1 at the 3 C discharge rate after 100 cycles, whereas the pristine sample delivered a discharge capacity of 87.3 mAhg−1 at 3 C with a capacity retention of 80% at the 100th cycle. Compared with the pristine material, the LiNi0.44Ga0.06Mn1.5O4 sample showed a high capacity retention from 74 to 98.4% after 50 cycles at a 1 C discharge rate and 55 °C.

Highlights

With the increasing application of lithium-ion batteries, their requirements are increasing
The finding agrees with results reported previously, in which the formation of the LixNi1-xO secondary phase should be ascribed to high-temperature sintering, and it was considered to decrease the amount of active material [19]
No additional secondary phase was detected in the Ga-doped samples, suggesting that Ga doping could inhibit the formation of LixNi1-xO impure phases and provide a single phase

Summary

Introduction

With the increasing application of lithium-ion batteries, their requirements are increasing. Batteries with a long cycle life, high energy density, and low cost could meet the needs of consumers. Spinel LiNi0.5Mn1.5O4 (LNMO) has captured the attention of researchers in related fields [1] due to its high working potential [2], low cost [3], and high energy density [4]of 658 Wh kg−1. All of the advantages of LiNi0.5Mn1.5O4 are due to its three-dimensional lithium-ion diffusion path and high working voltage [5]. Spinel LiNi0.5Mn1.5O4 materials have several issues to be solved. A LixNi1-xO secondary phase forms during the preparation process of spinel LiNi0.5Mn1.5O4 materials [6]. The electrolyte is prone to decomposition at high working voltage (4.7 V) (vs Li/Li+) [1], which triggers a decrease in capacity and poor electrochemical performance

Methods

Results

Conclusion