A Novel Cr2O3/MnO2-x Electrode for Lithium-Oxygen Batteries with Low Charge Voltage and High Energy Efficiency.

Zhaohuan Wei,Zhiyuan Zhang,Yaqi Ren,Hong Zhao

doi:10.3389/fchem.2021.646218

Abstract

A high energy efficiency, low charging voltage cathode is of great significance for the development of non-aqueous lithium-oxygen batteries. Non-stoichiometric manganese dioxide (MnO2-x) and chromium trioxide (Cr2O3) are known to have good catalytic activities for the discharging and charging processes, respectively. In this work, we prepared a cathode based on Cr2O3 decorated MnO2-x nanosheets via a simple anodic electrodeposition-electrostatic adsorption-calcination process. This combined fabrication process allowed the simultaneous introduction of abundant oxygen vacancies and trivalent manganese into the MnO2-x nanosheets, with a uniform load of a small amount of Cr2O3 on the surface of the MnO2-x nanosheets. Therefore, the Cr2O3/MnO2-x electrode exhibited a high catalytic effect for both discharging and charging, while providing high energy efficiency and low charge voltage. Experimental results show that the as-prepared Cr2O3/MnO2-x cathode could provide a specific capacity of 6,779 mA·h·g−1 with a terminal charge voltage of 3.84 V, and energy efficiency of 78%, at a current density of 200 mA·g−1. The Cr2O3/MnO2-x electrode also showed good rate capability and cycle stability. All the results suggest that the as-prepared Cr2O3/MnO2-x nanosheet electrode has great prospects in non-aqueous lithium-oxygen batteries.

Highlights

Non-aqueous lithium-oxygen batteries have been considered as a promising power source for portable devices and electric vehicles due to their high energy density (1.14 × 104 Wh kg−1) (Wang et al, 2019; Kwak et al, 2020)
Generated during the calcination and adsorption-calcination process can increase the electronic conductivity of the MnO2-x nanosheets, thereby reducing the ohmic resistance of the electrode material; 2) oxygen vacancies can improve the adsorption of oxygen species on the surface of the MnO2-based material, thereby obtaining good catalytic activity for oxygen reduction and lower charge transfer resistance; 3) the small amount of Cr2O3 is uniformly distributed on the MnO2-x nanosheets, thereby reducing the inhibitory effect of Cr2O3 on oxygen reduction to a minimum
We have prepared an electrode based on Cr2O3 decorated MnO2-x nanosheets as a non-carbon and binder-free cathode for lithium-oxygen batteries

Summary

Introduction

Non-aqueous lithium-oxygen batteries have been considered as a promising power source for portable devices and electric vehicles due to their high energy density (1.14 × 104 Wh kg−1) (Wang et al, 2019; Kwak et al, 2020). Chromium can be uniformly loaded on the surface of MnO2-x under low loading, which has two advantages: 1) the low Cr2O3 loading can minimize the inhibition effect to MnO2-x for the discharge process of lithium-oxygen batteries; and 2) uniform chromium distribution is conducive to achieve uniform contact with the discharge product, Li2O2, so as to achieve high catalytic effect in the charging process.

Results

Conclusion