Preparation Of Nickel-based Compounds/carbon Composites And Their Applications In Lithium-ion Batteries

With the rapid development of electric vehicles and consumer electronics,the demand for lithium-ion batteries is also increasing dramatically.However,the commercial graphite anode materials are limited by their low theoretical capacity,which is difficult to meet the actual development needs.Therefore,the exploration of high-performance anode materials has become crucial.Among a large number of anode materials,nickel-based compounds are favored by researchers because of their high theoretical capacity,sufficient reserves,and environmental friendliness.In particular,NiO and NiS₂ materials show a very high theoretical capacity(>700 mAh g^-1)in lithium-ion batteries.However,the key issues of these two electrode materials are the inherent low electrical conductivity and severe volume change during the charge/discharge process.How to effectively alleviate the impact of these problems on electrode materials and give full play to the lithium storage potential of materials has become a joint goal of current researchers.A large of current studies have shown that the introduction of carbon-based materials as the matrix to construct composite materials with nanostructures has significantly improved the overall conductivity and stability of the active materials.Based on the comprehensive consideration of the above issues,here we designed a hybrid material of three-dimensional porous carbon skeleton and nickel-based compound to effectively improve the deficiencies of nickel-based materials in terms of electrical conductivity and structural stability by using SiO₂ as the template.?1?Using SiO₂ as the hard template,combined with hydrothermal treatment,high temperature annealing and chemical etching,the nickel oxide/hollow carbon spheres/reduced graphene oxide hybrid material?NiO/HCSs/rGO?was successfully prepared.The HCSs in the hybrid material can be used as a matrix for dispersing NiO nanoparticles uniformly,effectively avoiding their self-aggregation,and can also be in direct contact with NiO nanoparticles,thereby improving the overall conductivity of the electrode material.Moreover,the tiny NiO nanoparticles can not only ease the volume change during the cycle,but also expose more active sites of lithium storage,which is also conducive to the improvement of the cycling stability and the capacity of the electrode material.In addition,the introduction of graphene can provide a conductive network and effectively connect each NiO/HCSs unit,thereby further improving the overall conductivity of the hybrid material.Therefore,when it is used as an anode in lithium-ion batteries,the NiO/HCSs/rGO electrode shows good rate performance(257.7 mAh g^-1 at 10 A g^-1)and cycle stability(309.9 mAh g^-1 after 1000cycles at 5 A g^-1).?2?We first synthesized a composite of NiO nanoparticles anchored on helmet-like carbon shell?NiO/CNHs?using SiO₂ as a template,and then NiO/CNHs were sulfurized at high temperature to obtain the NiS₂/CNHs composite.The composite fully combines the high theoretical capacity of NiS₂ and the high conductivity and stability of carbon materials.The tiny NiS₂ nanoparticles are uniformly anchored on the open CNHs,which not only effectively relieves the volume change of NiS₂ during the charge/discharge process,but also helps to improve the overall conductivity of the hybrid material.Moreover,three-dimensional open and porous CNHs also provide more convenient channels for electrolyte diffusion and charge transfer.Benefiting from the above advantages,when tested as an anode in lithium-ion batteries,the NiS₂/CNHs exhibits excellent cycle stability(490 mAh g^-1 after 3000 cycles at 5 A g^-1)and superior rate performance(412 mAh g^-1 at 10 A g^-1),outperforming other NiS_x-based anode materials.