Nanostructured SnCo anode for li-ion batteries

Currently, lithium-ion batteries (LIBs) can be considered the most effective response to the growing demand of portable energy supply both for their lightweight and powerful. Therefore, worldwide efforts are oriented to increase the performances of LIBs, also improving safety, electrolyte stability, and specific energy that are mandatory requirements for battery use in fields like automotive traction, where very high power density together with low recharge times and long life are required.


In this highly competitive scenario, CrMoSS has recently reached exciting results based on the development of nanostructured materials for negative electrodes. In the last year, CrMoSS has synthesized a nanostructured tin binary alloy (SnCo) which can store capacity higher than that of carbonaceous materials usually used. Carbonaceous materials have a specific theoretical capacity of about 372 mAh g-1, while tin stores up to 994 mAh g-1 when Li4.4Sn is formed. The synthesis procedure is based on an electrochemical technique, that is fast, cheap, environmentally friendly, and very easy to scale-up.



Advantages

The most interesting result is the overcoming of the mechanical instability, the main drawback in using tin (like silicon, germanium and other lithium hosts). During lithium alloying and de-alloying, tin is subjected to large volume expansion and contraction leading to a rapid failure of the electrode. In order to prevent this occurrence, usually, solid electrolyte interface (SEI) promoter, or stabilizers are used. In some cases, new electrolyte has been tailored for the special anode. The patented method developed by CrMoSS discloses a new and cheap electrochemical way toward Sn-based anode production at about room-temperature. The procedure allows the growth of the nanostructured alloy directly on copper current collector, without using either binders or additional conductive promoters , making a ready-to-use anode for LIB. Preliminary electrochemical tests conducted in a half cell, with lithium foils as counter and reference electrodes. At a C-rate of 1C a residual capacity higher than 600 mAh g-1Sn after 100 cycles was reached with CSC-60, while CSC-50 at C/2 showed that these anodes can store about the theoretical specific capacity of tin. These findings can be attributed to the particular morphology of our anode and to the physical characteristics of tin. In particular, the values of lithium ion diffusion, and tin Young’s modulus allows to obtain better performances than with silicon. It is worthwhile to underline that these results have been achieved looking carefully at the engineering of the material, and without any addition of SEI stabilizers or other additives.