Investigation On The Application Of Aqueous Binders In LiFePO₄ Based Cathode

Currently,the lithium-ion batteries with high energy density,long cycle life,low cost,and environment-friendliness are the research focus in energy storage and conversion field.Typically,binder is indispensable and also has a direct impact on the performance of lithium-ion batteries.The introduction of aqueous binders into the manufacturing process of lithium-ion batteries can be more environmentally friendly,and meanwhile decrease the manufacturing cost and bring great economic benefit by its development and application.Therefore,based on the present situation and properties,we investigated the application of aqueous binders in the LiFePO₄.We evaluated the application feasibility of various binders in the LiFePO₄ based electrodes by analyzing their oxidation.It was found that the oxidation potential of styrene-butadiene rubber?SBR?is 4.25 V,and that for polyacrylate binder is 4.65 V.Due to its higher oxidation potential,polyacrylate binder is more suitable for the cathode of lithium-ion batteries.In comparison with LA,the thermal stability of LB is better with a decompose temperature of LB 318?.The lithium ion diffusion coefficients for LA and LB are 6.2×10^-14 cm²·s^-1?1.8×10^-1414 cm²·s^-1,respectively.It proved the ion conductivity of LA chains which greatly decreased the total internal resistance from the ion diffusion.We systematically investigated the effect of LA and LB binders on the electrode manufacturing properties,the battery capacity,rate performance,and cycle life and obtained the optimized strategy for the application of aqueous binders in the LiFePO₄based electrodes.Typically,LB binder has a better processability while the LA exhibits a lower resistance.Besides the processability of the cathode and electrode adhesion property,low binder content and appropriate compaction density are help for reducing the internal resistance,improving the rate,cycle life,and comprehensive performance.The results indicated that 3%of the LA binder content,2.5%of the LB binder content,and 2.25 g/cm³ of the compaction density are the optimized condition for the batteries to obtain a best cycle life and comprehensive performance.Two aqueous binders were used to manufacture lithium-ion batteries in small batch production,which further proved and studied the performance of the LiFePO₄ based batteries with aqueous binders.The results illustrated that the LB has a better processability for the battery manufacture.The LA and LB both have excellent performances while the LA is even better.