Epoxidation Modification Of Natural Rubber And Its Application In Silicon Anode Binder

This work mainly consists of three parts.Firstly,epoxidized natural rubbers(ENR)with different degrees of modification were prepared by one-step and two-stage reaction processes;Secondly,on this basis,using ENR as the elastic component and reacting with aminated polyacrylic acid(PAG)to prepare double-crosslinked network binders.The mechanical properties,electrochemical properties,and interfacial stability of binders were studied;Finally,environment-friendly and low-cost natural polysaccharide chitosan(CTS)was selected to further react with ENR to prepare the double crosslinking network binders,and their properties have been systematically studied.1.Preparation of ENR and exploration of epoxidation conditionsControlled the temperature,hydrogen peroxide(H₂O₂)concentration,and formic acid(HCOOH)concentration as experimental variables to explore the effect of reaction conditions on the degree of modification,and used FTIR and ~1H NMR to characterize the structure of samples.The experimental results showed that the optimum temperature of the modification was 50?,and the epoxidation degree of samples increased with the increase of the concentration of H₂O₂and HCOOH.Then,ENR samples with different degrees of modification were prepared by one-step and two-stage modification processes under different reaction conditions,and their structures and heat resistance were tested.The results showed that the latex particle size,gel structure content,and glass transition temperature of ENR increased with the degree of epoxidation.Conversely,the initial thermal decomposition temperature of samples decreased with the increasing degree of epoxidation.2.Preparation and properties of ENR/PAG double-crosslinked network bindersFirstly,polyacrylic acid(PAA)was modified by glycinamide hydrochloride(GA)to obtain the product PAG.Subsequently,PAG and ENR were mixed with different mass ratios to prepare double-crosslinked network binders.The study found that when ENR and PAG were mixed in a mass ratio of 1:1,epoxy groups and primary amine groups could completely react,and the prepared PE55 film has excellent mechanical strength(5.51 MPa),elongation at break(87.4%),and adhesion(4.45 N).The PE55electrode prepared with this binder also had excellent electrochemical performance and interfacial stability.The PE55 electrode showed the first discharge specific capacity of 3548.6 m Ah g^-1.And the electrode exhibited excellent cycling stability(residual specific capacity of 2322.2 m Ah g^-1)after 100 cycles at a current density of1 A g^-1.In addition,a dense and smooth SEI film was formed on the surface of the cycled PE55 electrode,with a complete electrode structure and few side reaction products.3.Preparation and performance characterization of ENR/CTS double cross-linked network bindersThe green natural polysaccharide CTS was selected as the thickener and mixed with ENR latex to prepare a new type of double-crosslinked network binder,and the effect of ENR epoxidation degree on the comprehensive performance of the binder was explored.Firstly,FTIR was used to verify the success of the chemical cross-linking reaction.The results showed that EC-45 was the product of the complete reaction between ENR(epoxidation degree of 45%)and CTS,and had the highest degree of cross-linking.In addition,the EC-45 film had excellent mechanical properties,its mechanical strength could reach 12.74 MPa,and it had 63.4%elongation at break and 2.18 N adhesion,which could effectively inhibit and adapt to the volume expansion of Si particles.The Si anode prepared with this binder also had an excellent electrochemical performance.When the constant current charge-discharge test was carried out at room temperature,the EC-45 electrode had an initial discharge specific capacity of 3536.6 m Ah g^-1and the first-coulomb efficiency of 79.7%.After 100 cycles,the electrode still had a capacity remaining of 2000.5m Ah g^-1,showing good cycling stability.Finally,the structure of the EC-45 electrode remained intact after cycling,and a thin and smooth SEI film was formed on the surface,which could effectively isolate the electrolyte and active substances and prolong the service life of the electrode.