Synthesis Of Hydrogenated Carboxylated Nitrile Latex And Application In Lithium Batteries

With the rapid development of the global economy,the problems of energy crisis,environmental pollution and greenhouse effect are becoming more and more serious.While actively protecting our fragile environment,our country is paying more and more attention to sustainable development.The establishment of the dual carbon goal has promoted the rapid development of new energy sources and in order to achieve this goal earlier,firstly,we must reduce our dependence on fossil fuels such as coal and develop clean renewable energy sources,such as wind and water energy.However,the intermittent nature of renewable energy requires excellent energy storage systems that can be stored or released back to the grid on demand to maintain a steady supply of electricity for real life and production.Therefore,the storage and efficient utilization of energy sources become especially critical!This thesis explores the practical application value of HXNBR using hydrogenated carboxylated nitrile butadiene rubber as a binder for the anode and cathode of lithium ion batteries to further realize the significant improvement of lithium battery storage performance.The main research contents are as follows:（1）The introduction of carboxyl groups can improve the vulcanization characteristics and processing properties of the polymer.Therefore,after HNBR has been put into practical production applications,carboxylated butadiene rubber also hopes to improve its performance by virtue of hydrogenation technology.By investigating a new ruthenium-based catalyst,we successfully achieved direct hydrogenation of XNBR latex with good selectivity to effectively hydrogenate the carbon-carbon double bond on the molecular chain while retaining the cyano group.In addition,we also investigated the catalytic activity,the selectivity of the double bond of the catalyst,and the effects of reaction temperature and pressure on the hydrogenation rate of the latex.The results showed that the hydrogenation reaction time tended to decrease and then increase with the increase of reaction temperature;the hydrogenation rate occurred significantly with the increase of catalyst dosage as well as the increase of hydrogen pressure.Considering the safety of the reactor and the time and material cost of the actual industrial production,an optimal hydrogenation condition was determined:HXNBR products with more than 95%hydrogenation degree could be obtained at 1200psi hydrogen pressure and 140°C for 5 h when the catalyst accounted for 0.04%of the mass fraction of carboxylated nitrile rubber.（2）Silicon（Si）is considered to be one of the most promising anode materials of lithium batteries,but due to its huge volumetric fluctuations and instability of the interphase of the solid electrolyte,the capacity of Si anodes decrease rapidly,which limiting its application.Here,a new polymer network binder constructed by chemical cross-linking using hydrogenated nitrile butadiene rubber（HXNBR）and guar gum（GG）is used to solve the problem of deteriorating volume swelling of silicon anodes.Notably,this rigid-flexible binder（HX-GG）exhibited ideal electrochemical performance with a discharge capacity of up to 1402 m Ah g^-1 at 800 m Ah g^-1 for 500 cycles,and Si@HX-GG//Li Fe PO₄ full cells achieved an ultra-stable capacity of 115 m Ah g^-1 at 2 C for 2000cycles,both superior to most previously reported polymer binders.The excellent electrochemical performance is attributed to the buffer constructed by the flexible HXNBR and the rigid GG,the synergistic effect that effectively resists Si expansion and maintains the conductive network and mechanical integrity of the electrode.This work opens a new avenue for the discovery of potential binders for commercialization.（3）Due to the huge price fluctuation of PVDF in the market,we applied HXNBR as an alternative to PVDF for lithium-ion batteries cathode binder using our self-developed HXNBR latex by flocculation and dissolution.The electrode sheet coated with HXNBR has excellent adhesion and mechanical properties,and it can effectively restrain crack generation when coating with high load.It also exhibits excellent cycling stability in electrochemical tests.After 2000 cycles at 2 C,the LFP@HXNBR still showed a high capacity of 122 m Ah g^-1;after 5000 cycles at 4 C,the capacity was also as high as 86.4 m Ah g^-1.A stable specific capacity of 115.5 m Ah g^-1 can be achieved after 2000 cycles at 2 C using graphite（Gr）as the counter electrode to assemble the full cell.The experimental results are all similar to or even better than those of commercial PVDF binders.However,the adoption of low capacity performance at very large currents needs to be addressed urgently.