Cyclability of tin and tin-based intermetallic compounds on carbon paper current collector-substrate

Although lithium-ion battery technology is well consolidated, research efforts have been greatly active in attempts to ameliorate the performance of these batteries. In particular, the research on negative electrodes has been not only focused on the optimization of carbonaceous materials but also on alternative materials, such as lithium-metal alloys, which are very attractive for their specific capacity. However, their high volume changes during the lithiation/delithiation processes cause materials pulverization and, consequently, loss of electrical contact among particles, determining poor cycle life. The strategies of the intermetallic compounds and of morphological conversion toward nanomaterials to buffer the volume changes, although beneficial, have been not conclusive to overcome this drawback. To improve the cyclability performance of nanometric lithium-metal alloys we regarded the electrode materials as a whole with the current collector and we focused our efforts on the carbon paper (CP) as an alternative substrate-current collector to the conventional copper. The CP, with its three-dimensional interconnected conductive fibers, was able to host the metals and intermetallic materials and to guarantee a good electric contact without addition of carbon as conducting agent, providing a significantly improved cycling stability of these electrodes. To get an insight into the effective role of CP on the cycling stability of lithium-metal alloy/CP electrodes we compared the electrochemical and structural behavior over repeated lithiation/delithiation cycles of different types of tin-based materials on CP such as Sn, Cu6Sn5 and Sn2Mn and the results of this study are presented and discussed in this contribution.