Hydrothermally synthesized nanostructured LiMnxFe1\u2212xPO4 (x\u2009=\u20090\u20130.3) cathode materials with enhanced properties for lithium-ion\xa0batteries

Dung V Trinh,Hue T M Dang,Hang T T Le,Hoang V Tran,Chinh D Huynh,Huynh T N Le,Dung T Dang,Mai T T Nguyen

doi:10.1038/s41598-021-91881-1

Abstract

Nanostructured cathode materials based on Mn-doped olivine LiMnxFe1−xPO4 (x = 0, 0.1, 0.2, and 0.3) were successfully synthesized via a hydrothermal route. The field-emission scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analyzed results indicated that the synthesized LiMnxFe1−xPO4 (x = 0, 0.1, 0.2, and 0.3) samples possessed a sphere-like nanostructure and a relatively homogeneous size distribution in the range of 100–200 nm. Electrochemical experiments and analysis showed that the Mn doping increased the redox potential and boosted the capacity. While the undoped olivine (LiFePO4) had a capacity of 169 mAh g−1 with a slight reduction (10%) in the initial capacity after 50 cycles (150 mAh g−1), the Mn-doped olivine samples (LiMnxFe1−xPO4) demonstrated reliable cycling tests with negligible capacity loss, reaching 151, 147, and 157 mAh g−1 for x = 0.1, 0.2, and 0.3, respectively. The results from electrochemical impedance spectroscopy (EIS) accompanied by the galvanostatic intermittent titration technique (GITT) have resulted that the Mn substitution for Fe promoted the charge transfer process and hence the rapid Li transport. These findings indicate that the LiMnxFe1−xPO4 nanostructures are promising cathode materials for lithium ion battery applications.

Highlights

Nanostructured cathode materials based on Mn-doped olivine LiMnxFe1−xPO4 (x = 0, 0.1, 0.2, and 0.3) were successfully synthesized via a hydrothermal route
These studies shown that doping transition metal cations into L iFePO4 or L iMnPO4 causes a narrowing of the energy gap, which may improve the electrical conductivity of this material3,29. (iii) The Li-ion diffusion coefficient (DLi) of olivine cathode materials can be improved by reducing the particle size of the olivines to nanoscale, or changing their particle shapes
The electrochemical properties of the synthesized olivines were evaluated by cyclic voltammetry (CV) at a scan rate of 1 mV s−1, galvanostatic charge/discharge tests, and electrochemical impedance spectroscopy by using a VMP3 apparatus (BioLogic, France) in the frequency range 5 mHz to 105 Hz and 10 mV peak-to-peak excitation signal

Summary

Introduction

The results from electrochemical impedance spectroscopy (EIS) accompanied by the galvanostatic intermittent titration technique (GITT) have resulted that the Mn substitution for Fe promoted the charge transfer process and the rapid Li transport These findings indicate that the LiMnxFe1−xPO4 nanostructures are promising cathode materials for lithium ion battery applications. Previous works reported that cation mixing in LiMnxFe1−xPO4 orthophosphates is a great trade-off between the valuable capacity of L iFePO4 and the high potential of L iMnPO4 (voltage of oxidation pair compared with L i+/Li)[27,28,29] These studies shown that doping transition metal cations into L iFePO4 or L iMnPO4 causes a narrowing of the energy gap, which may improve the electrical conductivity of this material. The precipitation was collected by filtering, washing, and drying at 95 °C for 24 h

Methods

Results

Conclusion