Construction Of 3D Network Binders For Silicon Anodes In Lithium-ion Batteries Based On Hydrogen Bonding

Since the"14th Five-Year Plan"period,the new energy industry,which focuses on the development of"carbon peaking and carbon neutral",has been developing rapidly,and the development of high-efficiency,high-energy and high-safety energy storage systems is imminent.Rechargeable lithium-ion batteries（LIBs）,which have many characteristics such as high energy density,long life and portability,are widely used in energy storage devices.Silicon anode materials have gained a lot of attention and extensive research because of their high specific capacity,low electrical potential,abundant raw materials and environmental friendliness,and are expected to replace carbon anode materials as the new anode materials.However,silicon anode materials can generate high internal stresses during battery cycling leading to cracking of the active material,continuous growth of unstable surface solid electrolyte interface（SEI）film structures and severe electrode structure collapse,resulting in a significant reduction in the electrochemical performance of the silicon cathode and a curtailment of cycle life.In addition,the poor electrical conductivity and low Li⁺diffusion rate of the silicon anode result in high internal resistance and poor multiplier performance.The polymer binder is a key component in ensuring the structural integrity of the electrode.The rational design of the binder structure can improve the long cycle stability,multiplicative performance and irreversible capacity loss of the silicon anode.The design of the binder can also improve the long cycle stability,multiplier performance and irreversible capacity loss of the silicon anode.Although some progress has been made in improving the cycling performance of batteries with the new binders studied,they are still difficult to commercialize due to their relatively high cost and the poor mechanical properties of most of them.Based on the above issues,the main studies are as follows:（1）A three-dimensional network of water-soluble elastomers was prepared by physico-mechanical mixing of konjac glucomannan（KGM）and Dopamine hydrochloride（DOP）,which can withstand large volume changes of the active material,has excellent mechanical properties and bonding ability,and is an effective binder for silicon anodes.3D networks formed by reversible hydrogen bonding between KGM,PDA and the active material will contribute to the formation of reversible recovery forces during battery The 3D network formed by the reversible hydrogen bonds between the KGM,PDA and active materials will help to generate reversible recovery forces during the charge/discharge cycle,while providing multiple sites of action,which can effectively inhibit the mechanical behavior of the active materials,conductive particles and collector fluid,and help to stabilize the formation of the solid electrolyte interface film（SEI film）and improve the performance of the silicon anode.The KD-1-1 anode had the highest initial embedded lithium specific capacity(3594 m Ah·g^-1),which is almost close to the theoretical specific capacity of the silicon anode material,and after50 cycles at 0.3 C,it has an initial Coulomb efficiency of 84%and retains a high specific capacity of 1345 m Ah·g^-1.（2）The currently commonly used polyvinylidene fluoride（PVDF）is based on weak van der Waals force interactions formed by F atoms,which are not sufficient to buffer the expansion and shrinkage deformation of the active material during battery operation.Therefore,a ternary polymer（IDD）was prepared by a two-step polyurethane reaction using 2,2-dihydroxymethylpropionic acid（DMPA）,isophorone diisocyanate（IPDI）and PDAamine hydrochloride（DOP）as monomers and di-morpholine diethyl ether as initiator,which was used to co-modify PVDF to prepare an IP binder to improve the electrochemical stability of PVDF for silicon-carbon composite anodes.The IP anode was charged and discharged 20times at 0.3 C,and its discharge specific capacity was 50 m Ah·g^-1 higher than that of the PVDF anode,with a capacity retention of nearly 250 m Ah·g^-1 and a higher reversible specific capacity at high current densities than that of the PVDF anode.In summary,this thesis is based on the study of 3D network adhesives for lithium-ion batteries constructed by dynamic hydrogen bonding The prepared adhesives successfully improved the electrochemical performance of lithium-ion batteries and contributed to the development of lithium-ion batteries and the research aspect of adhesives.