Chitosan binders for sustainable lithium-sulfur batteries: Synergistic effects of mechanical and polysulfide trapping properties

The lithium-sulfur (Li-S) system is a promising candidate for the next generation of lithium batteries; however, for practical applications, there are still problems to solve as the loss of active material due to polysulfides diffusion and migration (shuttle effect), passivation of interfaces of both electrodes by deposition of insulating species. Chitosan, as an abundant and sustainable biopolymer has been previously modified to solve issues related to polysulfides retention through biopolymer functionalization; however, the effect of such modifications on the mechanical properties, related to the structural modifications, has been poorly investigated; moreover, the coupled effects of both phenomena, polysulfide trapping capacity and mechanical properties, and its impact on battery capacity and cyclability has not been discussed. In order to determine those effects, in this work is proposed a new binder based on chitosan modified by Methanesulfonic Acid as a plasticizer in the fabrication of sulfur cathodes for Li-S batteries. The improvement in the overall performance of the system was investigated by C-Rate, deep cycling and tensile test, and the results were compared with those of the sulfur cathode using brittle and water-insoluble pristine chitosan as binder. Our results indicated that the Chitosan – Methanesulfonic Acid, ChMSA25 polymer network, is able to modulate the mechanical strength and binding performance of the system. Due to the aforementioned characteristics, the ChMSA25 based sulfur cathode exhibits a low-capacity fade (0.058% per cycle) at 1.0 C for 500 cycles. Therefore, the ChMSA25 binder is a promising candidate for the development of high-performance, water processable lithium-sulfur batteries.