Characterization of a Lithium Ion Battery Based on Carbon-Coated Lithium Sulfide Cathode and Electrodeposited Silicon Based Anode

In the latest years there has been an increasing interest in the wide spread of electric vehicles (EVs) and hybrid vehicles (HEVs) with the final goal of the reduction of greenhouse gas emission and atmosphere pollution in large metropolitan areas. Clearly, the success of this operation depends on the availability of an efficient power source for the electric engine. Due to his high energy density, the lithium-ion battery is as an ideal candidate.¹ However, although appropriate for the consumer electronic market, the present lithium-ion battery technology is still inadequate for the electric road transportation one. Improvements in energy density and safety, as well as reduction in cost, are mandatory steps to meet the EV and HEV severe targets.² To achieve these operative improvements, battery chemistries alternative to intercalation are required.^3-4 A very promising example is provided by the lithium-sulfur battery, characterized by a conversion chemistry leading to high specific energy, i.e. of about 2600 Wh kg^-1,combined with the low cost of the earth abundant sulfur. However, several issues still prevent the practical development of this battery, including the solubility of polysulfides in the course of the discharge process and the high resistance, almost insulating nature of both reactants and products; furthermore the safety hazard associated with the use of lithium metal as anode. These issues have been recently addressed by modifying the electrolyte formulation and developing microstructured/nanostructured carbon conductive matrixes.⁵ Despite the replacement of the lithium metal anode with an alternative material is mandatory to assure the practical development of Li/S battery, surprisingly there are not many examples of efficient Li-ion sulfur batteries. In this work we report a new type of rechargeable lithium-ion battery based on the combination of a high capacity Si-O-C anode with a high-rate Li2S-MCMB (Mesophase Carbon Micro Beads) composite in a tetraglyme electrolyte. We show that this Si/Li2S battery operates around 1.4V, delivering a very stable capacity of about 280 mAh gLi₂S^-1 with a resulting theoretical energy density of the order 400 Wh kgLi₂S^-1.

[1] B. Scrosati, J. Garche, J. Power Sources 2010, 195, 2419

[2] M. Armand and J.M. Tarascon, Nat. 2008, 451, 652.

[3] K. Cai, M.K. Song, E.J. Cairns, Y. Zhang, Nano Lett. 2012, 12, 6474.

[4] Y.K. Sun, S.T. Myung, B.C. Park, J. Prakash, I. Belharouak, K. Amine, Nat. Mater. 2009, 8(4),

320.

[5] X. Ji, K.T. Lee, L.F. Nazar, Nat Mater. 2009, 8(6), 500.