New electrode materials and battery design are required to improve the electrochemical performances of Li-ion batteries. Some metals like Al, Si or Sn can form alloys with Li by reversible electrochemical reactions and can be used as negative electrodes of high specific capacities (600 - 4000 Ah/kg) for high density Li-ion batteries. However, alloying reactions cause large volume variations resulting in the loss of electronic percolation and SEI instability at the origin of the usually observed poor cycle life of such materials. Different approaches were considered to overcome these problems based, for example, on the nanostructuration of the active material, the dispersion of the particles and the use of intermetallics or composites [1]. Recently, we have proposed a family of new composite materials formed by Si nanoparticles dispersed within a tin based intermetallic matrix Ni₃Sn₄ that exhibits high specific capacity and coulombic efficiency [2]. In order to improve the performances and reduce the cost of such composites, we propose now a new material with a lower tin content with the overall composition Ni_0.15Sn_0.14Si_0.26Al_0.04C_0.41.

In this communication, the synthesis method, the material characterization and the electrochemical performances are presented. We show that the composite is formed by Si nanoparticles embedded in a matrix composed of Ni₃Sn₂ and Ni₃Sn₄ particles (Figure 1). The specific capacity after 200 cycles is of about 500 Ah/kg (Figure 2), which is surprisingly close to that obtained by the Ni₃Sn₄ based composite. To understand this results, X-ray diffraction and ¹¹⁹Sn Mössbauer spectroscopy were combined to explore in situthe reaction mechanisms that reveal the electrochemical activities of the different components of the composite.

Figure 1 SEM image of Si/Ni₃Sn₂-Ni₃Sn₄/Al/C composite as negative electrode for Li-ion batteries.

Figure 2 Specific capacity and coulombic efficiency vs. cycle number for the Si/Ni₃Sn₂-Ni₃Sn₄/Al/C composite at C/10 galvanostatic regime

References

(1) D. Larcher, S. Beattie, M. Morcrette, K. Edström, J.C. Jumas, J.M. Tarascon, J. Mater. Chem. 17 (2007) 3759.

(2) Z. Edfouf, F. Cuevas, M. Latroche, C. Georges, C. Jordy, T. Hézèque, G. Caillon, J. C. Jumas, M.T.Sougrati,  J. Power Sources, 196 (2011) 4762.

Acknowledgments

The authors would like to thank the French National Research Agency for the funding of the project NEWMASTE under the grant N°ANR-13-PRGE-0010.