Gel Polymer Electrolytes for Improved Safety
Another way to improve the safety of lithium ion batteries is to reduce the viscosity or "gel" the electrolyte. This prevents a battery from leaking flammable electrolyte if it is damaged while in use, thus significantly reducing the chance of a fire. A usual side effect of gelling an electrolyte is a reduction in performance due to reducing the mobility of the Li ions. This is especially detrimental in power applications, such as batteries for vehicles and power tools.
Novolyte has developed Gel Polymer Electrolyte (GPE) formulations that use standard electrolytes with monomer additives that can be polymerized in situ after a brief heat treatment. Once gelled, these electrolytes show very similar performance to their liquid electrolyte counterparts. The figure above shows similar performance between a Novolyte GPE and a liquid electrolyte using the same base formulation in a hybrid electric vehicle (HEV) type cell using a lithium iron phosphate (LFP) based cathode. Similar results are seen in other cell systems using various cathode chemistries.
Long-term testing was performed in 25Ah LiFePO4/synthetic graphite cylindrical cells at a 1C charge/discharge rate at room temperature.