Researches On Diamond Modified Assemblies And Improved Performances Of Ion Batteries

The excessive consumption of traditional fossil fuels and the resulting energy security issues have become significant challenges restricting social development.Sodium-ion batteries（SIBs）possess numerous favorable characteristics,such as abundant sodium reserves,environmental friendliness,and serve as promising applications in energy storage fields such as electric vehicles and smart grids.However,the limited energy density and rate performance have hindered its large-scale application.Therefore,improving the comprehensive electrochemical performance of SIBs through modifying the battery’s components is a hot topic in the research fields of SIBs at present.As the most critical components of batteries,rational modification and structural design of anode material,separator,and electrolyte can significantly enhance the electrochemical performance of batteries.Among them,the anode material determines the storage capacity and cycling stability of SIBs.Biomass carbon,with abundant resources,good conductivity,and rich microstructure,is a promising anode material for high-performance commercial SIBs.However,their theoretical capacity is relatively low.As a component that prevents direct contact between the cathode and anode,the separator avoids internal short circuits and provides channels for sodium ion（Na⁺）transport,playing a crucial role in the cycling performance and safety of batteries.The large interface and ion transport resistance of traditional glass fiber（GF）separators result in the low performance of SIBs.Optimizing the interface performance of the separator is crucial for enhancing the stability and safety of SIBs.The electrolyte serves as a carrier for ion transport and the basis for electrochemical reactions.The structure and content of the solid electrolyte interface（SEI）are determined by electrolyte.A high-quality SEI can separate the electrode material from the electrolyte,preventing continuous consumption of the electrolyte and electrode material,effectively reducing the generation of irreversible products in the electrode reaction,and improving the battery’s specific capacity and rate performance.In summary,the design and acquisition of high-capacity anode materials,separators with excellent ion transport,and controllable SEI interfaces in the electrolyte system are essential issues to be addressed in the fundamental research and application of SIBs.As carbon allotropes,nanodiamond（ND）possesses unique advantages such as size effects,superhardness,chemical stability,surface modifiability,and high ion adsorption capacity,and has been widely applied in lithium-ion batteries.In this study,ND has been researched and introduced into the bio-carbon anode material,GF separators,and electrolytes,significantly improving the comprehensive performance of SIBs.The specific research contents and results are listed as follows:1.The pinecone-derived bio-carbon（PBC）is prepared through high-temperature carbonization,and ND particles are introduced to form a composite anode material（PBC/ND）.Assembled into a SIB half-cell（with Na metal as the reference electrode,Na PF₆ electrolyte,and GF separators）,the PBC/ND anode exhibits a high capacity of520 m A h g^-1 after 100 cycles at 0.2 C(1C～279 m A h g^-1),which is significantly higher than the data of single PBC anode(302 m A h g^-1).The capacity is maintained at 170m A h g^-1 after 500 cycles at 2.0 C.The improvement of SIBs is caused by ND deposited in pine carbon,increasing the adsorption capacity,and its superhardness and chemical stability effectively increase the rate capability and cycling stability of the anode.2.Hydrogen-terminated nanodiamond is dispersed in ethanol solution through ultrasonic dispersion and spray-coated onto the surface of GF separators to obtain ND-modified GF separators（DGF）.The adsorption of ND can significantly enhance the Na⁺transport and reduce interfacial impedance.Assembled with DGF separators,the SIB half-cell exhibits a specific capacity of 480 m A h g^-1 after 100 cycles at a current density of 50 m A g^-1.After 1000 cycles at a current density of 1 A g^-1,the specific capacity of DGF-SIBs was maintained at 260 m A h g^-1,which is twice the data of GF-SIBs,demonstrating the favorable capacity and cycling performance.3.ND is added to Na PF₆ electrolyte to prepare ND composited electrolyte,combined with pinecone bio-carbon anode,and GF separators,the assembled SIB half-cells exhibit a capacity of 400 m A h g^-1at a current density of 100 m A g^-1.At a high current density of 5 A g^-1,the capacity maintains 180 m A h g^-1 after 1000 cycles,which is higher than the original electrolyte(85 m A h g^-1).The experimental results demonstrate that introducing ND into the electrolyte is beneficial for the transport of Na⁺.In addition,ND particles will migrate to the surface of SEI and the biochar anode,and their character-C=O functional group can promote the formation of inorganic substances in SEI.In addition,ND can provide abundant Na⁺adsorption/desorption sites,improving the capacity and long-term cycle stability of SIBs.The design of novel composite carbon anode materials,the preparation of membranes with high interfacial transport performance,and the construction of controllable solid electrolyte interfaces are of great research significance for enhancing the overall performance of SIBs.This study introduced ND into sodium-ion battery’s anode,separator,and electrolyte,taking advantage of its excellent chemical stability,large specific surface area,and strong Na⁺adsorption capacity.The preparation method is simple and compatible with commercial SIB production lines,providing new design ideas for promoting the industrial development and application of high-performance new sodium-ion batteries.