Preparing Of Aqueous Binders Of Si Anode For Lithium Ion Battery And Their Electrochemical Performances

Si is a promising anode material for next-generation high energy density lithium-ion batteries due to its high theoretical capacity,relatively low Li+ insert potential and nature abundance.However,Si anode has unstable cycle performance because of the huge volume change during charge/discharge processes.In this study,we have tried to improve the electrochemical properties of Si anode by preparing the binders with robust mechanical strength and developing new binders.We have prepared a series of hydrogel alginate binders?M-alg,M= Al,Ba,Mn,Zn?by coordinating alginate molecule chains with different cations,and have applied them on Si anodes respectively.Among these binders,Al-alg and Ba-alg binder exhibit superior mechanical properties.The Si anodes with Al-alg or Ba-alg both deliver the capacities near 2100 mAh g^-1 after 300 cycles at 420 mA g^-1,and present their capacities near 1770 mAh g^-1 after 500 cycles at 2100 mA g^-1.When the Si loading mass was elevated to 1.0 mg cm-2-1.2 mg cm-2,the electrodes with Al-alg or Ba-alg still have remarkable advantages.The morphology characterizations demonstrate that it is easier for the electrodes with more robust binders,Al-alg and Ba-alg,to keep integrity better than those electrodes with other weaker binders.Three natural polymers amylopectin,silk protein and egg white protein have been used as the binders for Si anode respectively.The amylopectin gel was prepared by string the heated amylopectin suspension.The silk protein was extracted from the cocoons by multiple chemical treatments.The egg white protein was prepared by drying egg white under vacuum.The electrode with amylopectin shows an initial charge capacity of 3547 mAh g^-1,an initial coulombic efficiency of 84.8%and remains a capacity of 1016 mAh g'1 after 100 cycles.The electrode with silk protein shows an initial charge capacity of 2717 mAh g^-1,an initial coulombic efficiency of 76.0%and a capacity of 1079 mAh g^-1 after 100 cycles.The electrode with egg white protein displays a capacity of 3006 mAh g^-1 and a coulombic efficiency of 77.9%at the first cycle,and it still keep a capacity of 1230 mAh g^-1 after 100 cycles.The charge/discharge capacity curves and cyclic voltammetry results proved that these three different binders have different effects during the charge/discharge processes.