Preparation Of Nickel Plated CNTs For Tin-based Anode Of Lithium Ion Battery

Lithium-ion battery is a hot research spot in new energy industry in recent years because of its superior performance. Currently, the main anode materials for commercial lithium-ion battery is carbon materials, but its theoretical specific capacity is 372 mAh/g, obviously cannot meet the growing demand of large capacity portable power. The theoretical specific capacity of tin anode materials reached 993mAh/g, three times of the graphite anode. However, tin anode materials will produce larger volume expansion in the process of repeated charge and discharge process,resulting in the material pulverization off and even failure. To solve this problem, this article added nickel plated carbon nanotubes(CNTs/Ni) to the tin film materials,prepared the Sn-CNTs/Ni-Cu(referred to as SCNC) composite electrode materials,effectively inhibited the volume change, improved cycle performance of the electrode.The main research contents and results were as follows:(1) In order to improve the adhesion strength of CNTs and the coating, and introduce nickel element into the plating, this article prepared CNTs/Ni powder materials by depositing nickel on the surface of CNTs through the method of chemical plating. Studied the effect of chemical plating parameters on the quality of coating,the experiments show that coating with high quality can be got under this conditions :the pH is 8.7, the temperature is 20 ℃ and the plating time is 90 minutes. The coating can be best optimized after annealing under the conditions of 500 ℃and 6 h. Material composition and structure were characterized by analysis of SEM, EDS and XRD.SEM photos showed that nickel particles were deposited on the surface of carbon nanotubes with the structure of string of pearls. XRD results showed that the diffraction peaks of CNTs/Ni powder materials mainly belong to carbon and nickel,containing about 26.27% of the nickel element, 73.73% of the carbon element.(2) In order to improve the cycle performance of tin anode, this article designed and prepared the SCNC composite electrode materials, the electrochemical properties were analyzed. With copper as the base, Sn and CNTs/Ni were deposited on the surface of it by the method of composite electroplating, so was the Sn-CNTs/Ni composite electrode material prepared. SEM photographs showed that, the electrode had irregular surface, with big tin particles and observable carbon nanotubes buried and embedded in the coating, the grain size of the SCNC electrode coating surfacedecreased after heat treatment. XRD results showed that the material composition are mainly from the basement of Cu current collector, active materials of Sn, carbon nanotubes and Ni element. After heat treatment, binary alloy such as Cu6Sn5 and ternary alloy such as CuNi2 Sn were formed in the electrode.(3) The electrochemical performance test results of the SCNC electrode showed that the electrode had large irreversible capacity of the first time, but after the first cycle, its discharge specific capacity became basically stable. For comparison, the second circulating specific capacity of Sn-CNTs electrode is 578 mAh/g, and decreased to 200 m Ah/g after 60 times of circulation, capacity remain at a rate of34.6%. The second circulating specific capacity of SCNC electrode is 601 mAh/g,and it remains 399.5 m Ah/g after 60 cycles, 66.5% of the discharge capacity is remained, proving that CNTs with nickel plating has better effect than the untreated CNTs when composited to tin based anode. In addition, the electrochemical performance of the electrode materials within nickel plated carbon nanotubes under500 ℃ annealing is the best.