Study Of Carboxymethyl Cellulose To Promote The Performance Of High Specific Capacity Silicon Anode Electrode For Lithium-ion Batteries

Binder is one of the key materials which affect the electrochemical performance of the Li-ion batteries such as energy density and cycling performance.Its main role is to make the electrode active material,electrode collector and conductive agent bonded together,which not only reduces the impedance of electrode,but also creates good processability and mechanical properties,so as to meet the needs of the actual production.Therefore,it is of great importance to select and optimize the binder for the development of Lithium-ion battery.Using microcrystalline cellulose,sodium hydroxide and sodium chloroacetate as raw materials,CMC with different DS was synthesized by a slurry method in large bath ratio.The process was divided into two steps(alkalization and etherification)and repeated in order to obtain CMC with required substitution.The raw materials and products were characterized with Fourier transform infrared spectroscopy(FT-IR),Carbon nuclear magnetic resonance(13C-NMR)and X-ray diffraction(XRD).A series of CMC with DS of 0.23,0.43,0.55,0.72 and 0.86 were prepared as silicon-based binder of cathode of lithium batteries to assemble button batteries.Electrical tests,including galvanostatic discharge-charge,cyclic voltammetry,AC impedance and rate capability were performed to evaluate the silicon-based cathode.Results showed that the discharging specific capacity of silicon-based cathode using CMC of DS=0.55 in the first and 50th cycle were 2917.0 mAh/g and 1607.6 mAh/g,and the electrochemical performance was superior to those using CMC with lower(0.23 and 0.43)or higher(0.72 and 0.86)DS.Secondly,we discussed the influence of some factors on the performance of lithium-ion battery,such as the ratio of CMC to deionized water and pressing technology.After the selection of the corresponding conditions,CMC(DS from 0.23 to 0.86)of low polymerization degree and commercial CMC of high polymerization degree were separately applied to silicon anode,the comparison of cyclic performance is carried out.And then,The electrode prepared with CMC(low polymerization degree)/SBR was subjected to a series of electrochemical performance tests.The experimental result showed that the electrochemical performance of CMC(low polymerization degree)was better than commercial CMC of high polymerization degree,the electrochemical performance of CMC/SBR electrode was inferior to that of electrode prepared with CMC alone.The relatively excellent electrochemical performance was realized without adding SBR when self-made CMC was used as binder,which shows the superiority of self-made CMC to commercial CMC in application to lithium-ion battery.Besides,free of SBR economizes materials cost and saves inner space of battery,thereby providing a good space for effective electrode materials.