RECENT ADVANCES ON INSERTION MATERIALS FOR BETTER Li(Na)-ion BATTERIES

Rechargeable lithium ion batteries, because of their high energy density, have conquered most of today’s portable electronics and they stand as serious contenders for EV’s and grid applications. For the latter to happen, we still need to increase their energy density while making them greener and more sustainable. This is a formidable challenge. Electrode reactions in Li-based technologies are based on the reversible insertion/deinsertion of Li⁺ ions into a host material with the concomitant addition/removal of electrons. Such reactions being intrinsically limited to 1 e- per 3d-metal, there is a quest for new materials and new concepts, both of which will be addressed in this presentation.

Firstly, our strategy towards the design of novel high voltage polyanionic compounds ^[1] involving either Li or Na-based fluorosulfates, sulfates and oxysulfates such as Li₂CuO(SO₄)₂ will be described together with i) their electrochemical performance and ii) their ionic conductivities which will be discussed through the Bond Valence Energy Landscape approach.

Turning to new concepts, great hope is presently placed on the Li-rich Li[LixNiyCozMn1-x-y-z]O₂) layered electrodes, coined Li-rich NMC, which show staggering capacities of 280 mAh/g as compared to 15 mAh/g for LiCoO₂. We will show via the use of structurally related Li2Ru_1-ySn_yO3 materials^[2], combined with the use of complementary techniques (XPS, EPR)^[3], that this large capacity results from cumulative cationic and anionic redox processes, hence ending 25 years of belief that insertion reactions solely rely on cationic redox reactions. Lastly, pursuing our chemical substitution work we could design^[5] model compounds which enable, for the first time, the visualization, by both microscopy and neutron diffraction, of the perroxo (O-O) dimers involved in the reversible redox process.

Lastly, addressing the issue of sustainability, recent material advances in the field of rechargeable Na-ion batteries, an alternative to the Li-ion technology for grid applications will be presented. They will enlist among others, the elaboration via ball-milling of Na-enriched polyanionic or lamellar insertion compounds so as to develop advanced sodium ion batteries^[6]

1) G. Rousse, J.M. Tarascon, Chemistry of Materials, 26(1), 394, 2014.

2) M. Sathiya, G. Rousse, K. Ramesha, C.P. Laisa...and J.M. Tarascon J-M, Nature Materials, 12, 827, 2013.

3) M. Sathiya, J.B. Leriche, E. Salager, D. Gourier, J.M. Tarascon, and H. Vezin, Nature Communications, February 2015

4) M. Sathiya, A.M. Abakumov, D. Foix, G. Rousse… and J.M. Tarascon, Nature Materials 14, 230–238 (2015)

5) E. McCalla et al. Science December 2015. to be submitted

6) B. Zhang et al. Nature communication (In Press)