Effect of AlF3-Coated Li4Ti5O12 on the Performance and Function of the LiNi0.5Mn1.5O4||Li4Ti5O12 Full Battery—An in-operando Neutron Powder Diffraction Study

Gemeng Liang,Chia-Ming Chang,Jin-Ming Chen,Cheng-Zhang Lu,Shih-Chieh Liao,Chia-Erh Liu,Zaiping Guo,Anoop Somanathan Pillai,Wei Kong Pang,Vanessa K Peterson,Kuan-Yu Ko

doi:10.3389/fenrg.2018.00089

Abstract

The LiNi0.5Mn1.5O4 ||Li4Ti5O12 (LMNO||LTO) battery possesses relatively-high energy density and cycle performance, with further enhancement possible by application of an AlF3 coating on the LTO electrode particles. We measure the performance enhancement to the LMNO||LTO battery achieved by a AlF3 coating on the LTO particles through electrochemical testing and use in-operando neutron powder diffraction to study the changes to the evolution of the bulk crystal structure during battery cycling. We find that the AlF3 coating along with parasitic Al doping slightly increases capacity and greatly increases rate capability of the LTO electrode, as well as significantly reducing capacity loss on cycling, facilitating a gradual increase in capacity during the first 50 cycles. Neutron powder diffraction reveals a structural response of the LTO and LNMO electrodes consistent with a greater availability of lithium in the battery containing AlF3-coated LTO. Further, the coating increases the rate of structural response of the LNMO electrode during charge, suggesting faster delithiation and enhanced Li diffusion. This work demonstrates the importance of studying such battery performance effects within full configuration batteries.

Highlights

Lithium ion batteries (LIBs) are the main choice of power source for portable electronic devices, including emerging electric vehicle (EV) and hybrid electric vehicle (HEV) technologies, as a result of their low cost, high energy/power density, and relatively long cycle life (Wang and Cao, 2008; Choi and Aurbach, 2016; Li et al, 2017a,b)
The morphology and particle size of LTO and AlF3-coated LTO as characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) are shown in Figures 1a,c and Figures S2a,b, revealing that the secondary particles of both LTO and AlF3-coated LTO are highly porous microspheres with a diameter of 3–10 μm and composed of primary particles of ∼50 nm in diameter
We identify the parasitic doping of Al into the LTO structure in our crystallographic analysis, which was not performed in previous studies of AlF3-coated electrodes (Sun et al, 2007; Tron et al, 2016), despite Al doping in LTO

Summary

Introduction

Lithium ion batteries (LIBs) are the main choice of power source for portable electronic devices, including emerging electric vehicle (EV) and hybrid electric vehicle (HEV) technologies, as a result of their low cost, high energy/power density, and relatively long cycle life (Wang and Cao, 2008; Choi and Aurbach, 2016; Li et al, 2017a,b). We performed a comparative study to investigate how an AlF3 coated LTO enhances the electrochemical performance of a LNMO||LTO full-configuration battery using high-resolution and in-operando neutron powder diffraction (NPD).

Results

Conclusion