Strategies for Limiting Gas Evolution in Li-Ion Batteries Applied to the Energy Storage System

Abstract

One of the promising approaches for limiting climate changes is to use alternatives and greener sources of energy (wind, solar, etc.). However, the production of electricity from these sources is fluctuant and needs a solution for storage thus, the advent of energy storage for wind power, solar plant, etc., requires a new generation of batteries in order to optimize the use of these alternative sources of energy. To do so, the development of a battery with a high rate of charging and discharging, a longer cycle life and safe is imperative. Esstalion Technologies was a joint-venture between Hydro-Québec and Sony Corp. (Murata) for the development of energy storage systems. Our division (Battery Materials Research) was dedicated on the elaboration of new materials for enhancing the cycle life, the safety and the performances of the Li-ion batteries. We devoted our efforts to develop LFP-LTO batteries; this presentation will highlight our strategies to limit the gas evolution in a battery; two strategies will be presented, the use of an additive in the cell for limiting the degradation of the electrolyte and the protection of the surface of the active inorganic particles by a hydrophobic polymeric coating before the production of the electrode. Formation of a solid-electrolyte-interface (SEI) during the operation of the battery is the most applicable for partially preventing degradation. Recently, we reported on the use of polymers as a protective layer; the thin film is in situ polymerized on the anode during cell operations or grafted on the surface of particles before manufacturing as electrodes. We demonstrated the efficient use of in situ Ring Opening Polymerization (ROP) of propylene carbonate for creating a protective film on the anode surface. By this method, we reduced gas evolution in the cell without increased of internal resistance. Moreover, two methods to graft polymers on particles (LTO) were applied with success for preventing degradation of LFP-LTO cells. Because battery environments are aggressive (HF formation, pH = 2), we developed a new robust method for grafting hydrophobic polymers on active particles (LTO) by Williamson Ether Synthesis, which is compatible with the manufacturing of electrodes, and prevents significant cell degradation over extensive cycling. These methods are valuable for large production because it is inexpensive and easy to scale-up. They are able to limit the degradation of the battery by increasing the capacity retention and stabilizing the resistance of the electrode with the accelerated aging.