Engineering the chemical environment of lithium manganese silicate by Mn ion substitution to boost the charge storage capacity for application in high efficiency supercapattery

Abstract

Polyanionic lithium manganese silicate (Li2MnSiO4) is a promising positive electrode material for lithium-ion batteries due to its low cost and high theoretical capacity. However, the Jahn-Teller distortion originating from Mn3+ centers destabilize the host structure and deteriorates the cycling life. In this work, a facile solvothermal approach was developed for the amelioration of the local environment and charge transfer kinetics of Li2MnSiO4 by Zn-doping, for the first time. X-ray diffraction confirmed crystalline and orthorhombic structural phases and skewed as well as bell-shaped particle size distributions of the nanocrystals were illustrated by small angle X-ray scattering studies. Electrochemical studies revealed superior performance of 4% Zn-doped Li2MnSiO4 (Li2Mn0.96Zn0.04SiO4) electrode material with a specific capacity of 80.46 C g−1 at 20 mV s−1. Supercapattery devices fabricated with activated carbon and Li2Mn1-xZnxSiO4 as the negative and positive electrodes, respectively delivered good capacitance retention and coulombic efficiencies over 3000 cycles. The AC//Li2Mn0.96Zn0.04SiO4 supercapattery device achieved a specific energy of 38.4 W h kg−1 at a specific power of 516 W kg−1 and up to 19.9 W h kg−1 was retained at specific power of 14,429 W kg−1. The enhanced electrochemical performance of the Zn-doped electrodes was ascribed to the high nucleation density and the pillar effect of Zn doping, as well as a slight reduction of high spin Mn3+ in the material, by substitution of Mn sites with Zn. These results show that the flexible strategy developed in this study can be used to boost the performance of various energy storage devices.