Lithium ion batteries (LIB) are considered as prime candidates for electric vehicles. Among them, batteries with silicon nanoparticles (SiNPs) based negative electrode are very promising, thanks to their important energy storage capacity, ten times higher than the current ones. But their low cycling performance due to SiNPs degradation precludes further final applications. In this context, a breakthrough was recently achieved by researchers from INAC/SCIB and IMN Nantes. They have shown an impressive increase in the lifetime of these batteries by incorporating graphene as a carbon conductive matrix. By extensive and thorough characterizations, they have been able to understand the influence of graphene incorporation in the anode material. Indeed, SiNPs are readily destroyed by mechanical and chemical constrains associated to insertion-extraction of lithium and electrolyte decomposition during cycling processes. Graphene realizes a resilient wrapping of the SiNPs, keeping good electrical contacts whatever the volume changes. It also avoid direct contact with the electrolyte, limiting thus its degradation. The final result is an electrode with a very high capacity (2000 mAh/g) after more than 200 cycles, one of the best results ever published in the literature. Another essential advantage is that these results have been achieved with an active mass loading close to what is used on an industrial scale.
Figure 1. SEM images of Si-based composite electrodes using black carbon (a) and rGO (b) as a conductive additive; Charge - discharge capacity vs. cycle number for rGO battery as well as the variation of its mean discharge voltage.
Nguyen, B.P.N., Kumar, N.A., Gaubicher, J., Duclairoir, F., Brousse, T., Crosnier, O., Dubois, L., Bidan, G., Guyomard, D., Lestriez, B. Nanosilicon-Based Thick Negative Composite Electrodes for Lithium Batteries with Graphene as Conductive Additive » Adv. Energy Mater., 2013, DOI: 10.1002/aenm.201300330
Last update : 06/01 2016 (898)