3D Interconnected Carbonaceous Network-Based Composite Materials As Advanced Anode For Constructing High-Performance Alkali Metal Ion Batteries

With the increasing demand for energy in modern society,alkali metal ion batteries have attracted extensive attention.Due to the large specific surface area and multi-channel structure,3D porous carbon materials can provide more active surfaces for the reaction and become a promising candidate for anode materials of alkali metal batteries.Unfortunately,compared with traditional carbon materials,the higher cost and poor cycling stability of 3D porous carbon materials hinder their practical development and application.Due to their high theoretical capacity and electronegativity matching with alkali metals,transition metal selenides（MSe_x,M=Co,Ni,Mn,etc.）have greatly attracted the attention of researchers.However,the drastic volume change of MSe_x in the charging and discharging process leads to the deterioration of its cycling stability and rate performance,which makes MSe_x difficult to be used in commercial applications.Because of the above problems,N-doped 3D interconnected carbon network（N-CN）is constructed by the sodium chloride sacrificial template strategy.Due to the structural advantages,N-CN carried out stable lithium/sodium/potassium energy storage.MSe_x@N-CN composites are further synthesized.The large specific surface area and many pores can provide active sites and rich paths for ion diffusion;the transition metal selenides can react with ions and provide high reversible capacity,reflecting the synergistic effect of porous carbon network and transition metal selenides.Thus,the cycling stability and lithium/sodium/potassium storage capacity are improved.The conclusions are as follows:（1）Because of the high cost of 3D carbon materials,we developed a sacrificial template method using environmentally friendly and low-cost raw materials to synthesize the 3D interconnected carbon network（CN）.Using glucose as the carbon source and sodium chloride as the template,the 3D interconnected carbon network is synthesized with the characteristics of 3D interconnection and multistage channels,showing good lithium/sodium/potassium energy storage performance.After nitrogen doping by urea,many defects are formed on the microscopic surface of N-CN.And the specific surface area and the number of mesopores are improved,providing more active sites for ion storage,and the energy storage capacity and cycling stability of N-CN are further improved.（2）Due to the low theoretical capacity,carbon materials are difficult to meet the increasing demand for energy storage.Thus,we designed a controllable immersion strategy of the metal aqueous solution to adsorb Co₃Se₄ on the nitrogen-doped 3D interconnected carbon network.By adjusting the concentration of transition metal in the aqueous solution to control the adsorption capacity of N-doped 3D interconnected carbon network for Co²⁺,to adjust the mass ratio of selenides in the composite material.Among different Co₃Se₄@N-CN,the composite synthesized with 0.1 M Co²⁺solution displays the best lithium/sodium energy storage performance.In the lithium-ion battery,the reversible capacity is 1314 m Ah g^-1 after 100 cycles at 0.1 A g^-1.The reversible capacity of the sodium-ion battery is 288 m Ah g^-1 after 800 cycles at 1.0 A g^-1.While maintaining good cycling stability and rate performance,the energy storage capacity of the composites has been greatly improved compared with that of N-CN,which reflects the superiority of the composite strategy of transition metal selenides and N-doped 3D interconnected carbon network.In addition,we found that the capacity of Co₃Se₄@N-CN increased during the lithium-ion battery cycling and verified that the formation of selenium may cause this phenomenon during the reaction process.（3）In consideration of the excellent lithium/sodium ion storage performance of MSe_x@N-CN,we further synthesized the high-performance anode material of Ni Se@N-CN for potassium ion battery.We analyzed the role of nitrogen doping in the combination of Ni Se and N-CN and its influence on the potassium ion storage mechanism.Ni Se@N-CN delivers a reversible capacity of 381 m Ah g^-1 after 300 cycles at 0.1 A g^-1 and a reversible capacity of 192 m Ah g^-1 after 3000 cycles even at the high current density of 5.0 A g^-1.We verified the anchoring effect of N doping,especially pyrrolic-and pyridinic-N-doping on Ni Se by comparative experiments and density functional theory.The results show that N doping can enhance the binding compactness of the material and improve the cycling stability.It can also enhance the adsorption capacity of Ni Se for potassium ions and reduce the energy barriers required for the reaction.The kinetic analysis confirms that the 3D interconnected carbon network is essential for rapid ion diffusion and electron transfer.