N. Berti, F. Cuevas, M. Latroche

CMTR – ICMPE, CNRS – UPEC UMR7182, 2-8, rue Henri Dunant, 94320 Thiais, France

Lithium-ion battery

Conclusions & Perspectives

MHx conversion reaction electrodes

Electrochemical properties

Galvanostatic measurements

The research leading to these results has received funding from the People Program (Marie Curie Actions) of the European Union's Seventh Framework Program FP7/2007-2013/ under REA grant agreement n° 607040 (Marie Curie ITN ECOSTORE) is thankfully acknowledged.

Nowadays Li-ion batteries are among the most used rechargeable batteries. Although the performance of these batteries has been improved considerably in the last decades, there is a common agreement that this technology is now close to its maximum efficiency unless new materials with higher storage capacity are found. Recently it has been demonstrated that many metal hydrides can react with lithium according to the general equation:

MHx + xLi+ + xe- M + xLiH

This conversion reaction can provide higher capacity than common graphite anodes (2000 mA∙h/g for MgH2 vs. 370 mA∙h/g for graphite) with low polarization. However, the commercial use of these compounds as electrodes for Li-ion batteries has been hindered to date by their short cycle life and sluggish kinetics at room temperature. Our aim is to better understand the reaction mechanisms between metal hydrides and lithium, and overcome hurdles for attaining long-term reversibility on cycling.

Negative electrodes based on metal hydrides for Li-ion batteries

MHx + xLi+ + xe- M + xLiH

0

0.2

0.4

0.6

Potential vs Li+/Li (V

) ZrH2

TiH2

NaH

MgH2

Synthesis and Characterization

MHx materials as negative electrodes for Li-ion batteries (M=Mg,Ti)

RBM of metal powder mixtures under high H2 pressure

0.5Mg-0.5Ti powders milled for 4 hours under 90 bar H2

Electrode formulation Three components (⅓ : ⅓ : ⅓ mass ratio)

- Active material: 0.5MgH2-0.5TiH2 - Carbon: Super P - Binder: Carboxymethyl cellulose (CMC)

Current collector: Nickel foam I: constant (C/50)

High theoretical capacity Low potential Low polarization

Pros - No memory loss - Low-discharge rate - Long cycle life - Lightweight

Cons - Cost issue - Low durability - Low capacity

• Efficient synthesis of nanohydride mixtures by RBM • Full conversion reaction on first charge

• Reduced reversibility on discharge • Issues on battery assembly and design

Improve electrode design: binders, current collectors, additives, etc. Increase reversibility of the redox reaction Find out novel synthesis routes and novel compounds Integration with other components (e.g. solid state electrolyte)

ZrH2

NaH

Graphite

TiH2

MgH2

Li-metal

Ref: Oumellal Y, Rougier A, Nazri G.A, Tarascon J.M, Aymard L. Metal hydrides for lithium-ion batteries. Nat Mater 2008;7:916e21.

H P N S O F

MgH2-Rutile TiH2-Fluorite

0.5MgH2-0.5TiH2

Graphite