Ti and Nb-Based Oxides as Negative Electrode Materials for High Power Batteries

Today, one of the main challenges of lithium-ion batteries is to have the ability to charge faster and to provide high power during longer periods, thus allowing a larger development of intermittent electric power sources ^[1]. The actual negative electrode materials (graphite and silicon mainly) cannot sustain such high rate capabilities. In this work, we are therefore investigated some materials of the plentiful family of niobium-based oxides. A presentation of old and interesting structures will be briefly reviewed. As an example, the case of KTiNbO₅ will be discussed and proposed as efficient negative electrode materials for next generation of lithium ion batteries.<br/>The layered KTiNbO₅ with a two-dimensional framework represents a playground to produce a large range of closely related phases.^[2] The protonated HTiNbO₅ analogue is obtained by ion exchange in acidic solution and it preserves a layered structure with a smaller interlayer distance. After dehydration of HTiNbO₅at 400°C, the so-obtained Ti₂Nb₂O₉ phase displays a 2D arrangement with empty channels unlike tunnels of H(K)TiNbO₅.<br/>In this work, all the synthesized phases were studied as negative electrode materials in lithium-ion batteries. Tested in 1M LiPF₆ in EC/DMC between 1.0V and 3.0V vs Li/Li⁺, these phases have shown different electrochemical behaviors. When HTiNbO₅ exhibits a typical plateau during the charge/discharge experiment corresponding to a biphasic phenomenon, lithiation of Ti₂Nb₂O₉ is governed by a solid—solution mechanism. For a better understanding of the charge storage mechanism, we have combined electrochemical experiments with <i>in situ</i> XRD measurements. We have shown that multielectron redox and corner/edge sharing system of Ti/Nb octaedra are at the origin of an interesting capacity of more than 100 mAh.g^-1 at a rate of 0.2 A.g^-1. A good observed cyclability (&lt; 500 cycles) is in accordance with <i>in situ</i> XRD results showing a reversible behavior of the structure during cycling. Another synthesis method, using <i>Chimie Douce</i> techniques, leads to nanoparticules for both HTiNbO₅ and Ti₂Nb₂O₉ and allows an increase of the electrochemical performance of these materials.<br/><b>References :</b><br/>[1] Choi, C. et al, Nature Rev. Mat. 5, 5-19 (2020).<br/>[2] A. D. Wadsley, Acta Cryst. 623, 17-41 (1964).