Nb-Based Oxides As High Power Negative Electrode Materials

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 KTiNbO 5 will be discussed and proposed as efficient negative electrode materials for next generation of lithium ion batteries. The layered KTiNbO 5 with a two-dimensional framework represents a playground to produce a large range of closely related phases. [2] The protonated HTiNbO 5 analogue is obtained by ion exchange in acidic solution and it preserves a layered structure with a smaller interlayer distance. After dehydration of HTiNbO 5 at 400°C, the so-obtained Ti 2 Nb 2 O 9 phase displays a 2D arrangement with empty channels unlike tunnels of H(K)TiNbO 5 . In this work, all the synthesized phases were studied as negative electrode materials in lithium-ion batteries. Tested in 1M LiPF 6 in EC/DMC between 1.0V and 3.0V vs Li/Li + , these phases have shown different electrochemical behaviors. When HTiNbO 5 exhibits a typical plateau during the charge/discharge experiment corresponding to a biphasic phenomenon, lithiation of Ti 2 Nb 2 O 9 is governed by a solid—solution mechanism. For a better understanding of the charge storage mechanism, we have combined electrochemical experiments with in situ 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 (< 500 cycles) is in accordance with in situ XRD results showing a reversible behavior of the structure during cycling. Another synthesis method, using Chimie Douce techniques, leads to nanoparticules for both HTiNbO 5 and Ti 2 Nb 2 O 9 and allows an increase of the electrochemical performance of these materials. References : [1] Choi, C. et al, Nature Rev. Mat. 5, 5-19 (2020). [2] A. D. Wadsley, Acta Cryst. 623, 17-41 (1964).