Solid state synthesis of extra phase-pure Li4Ti5O12 spinel

I Veljkovic,D Poleti,G Brankovic,Lj Karanovic,M Zdujic

doi:10.2298/sos1103343v

Abstract

Extra phase-pure Li4Ti5O12 spinel with particle sizes less than 500 nm was synthesized by solid state reaction of mechanochemicaly activated mixture of nano anatase and Li2CO3 for a very short annealing time, 4 h at 800?C. Structural and microstructural properties, the mechanism of solid state reaction between anatase and Li2CO3 as well as thermal stability of prepared spinel were investigated using XRPD, SEM and TG/DSC analysis. The mechanism of reaction implies decomposition of Li2CO3 below 250?C, formation of monoclinic Li2TiO3 as intermediate product between 400 and 600?C and its transformation to Li4Ti5O12 between 600-800?C. The spinel structure is stable up to 1000?C when it is decomposed due to Li2O evaporation.

Highlights

Lithium titanate, Li4Ti5O12, was presented in the 1990s as a prospective ‘‘zero-strain’’ Li-insertion material [1,2,3]. ‘‘Zero-strain’’ insertion of lithium considers that there is a negligible expansion and contraction of the material during intercalation/elimination of Li+ions
The intercalation/elimination process is based on the phase transition of spinel structured Li4Ti5O12 to NaCl structured Li7Ti5O12, permitting in that manner the reduction of 3Ti4+ ions out of 5, which corresponds to the theoretical capacity of 175 Ah kg–1.3 Detailed
In this work we report the synthesis of extra phase-pure Li4Ti5O12 via solid state route by annealing a high energy ball milling (HEBM) activated Li2CO3–anatase mixture for only 4 h at 800 oC

Summary

Introduction

Li4Ti5O12, was presented in the 1990s as a prospective ‘‘zero-strain’’ Li-insertion material [1,2,3]. ‘‘Zero-strain’’ insertion of lithium considers that there is a negligible expansion and contraction of the material during intercalation/elimination of Li+. The negligible structural changes during lithium insertion/extraction make Li4Ti5O12 an advanced anode material for long-cycle life battery applications. Many authors claim about low temperature sol-gel spinel synthesis, it was not difficult to notice that prepared samples were not really a phase-pure until long annealing times (often more than 12 h) at temperatures about or above 800 °C were applied. Wang et al synthesized Li4Ti5O12 by high energy ball milling (HEBM) of a mixture containing LiOH·H2O and anatase with subsequent annealing at 800 oC for 12 h and investigated the influence of milling time on morphology and electrochemical properties [14]. In this work we report the synthesis of extra phase-pure Li4Ti5O12 via solid state route by annealing a HEBM activated Li2CO3–anatase mixture for only 4 h at 800 oC. The influence of TiO2 particle size on the reaction, thermal properties and powder morphology of the products were examined

Experimental

Structural and microstructural properties

Conclusions