Preparation Of One-dimensional Self-assembled Nanocomposites And Their Performance In Lithium-ion Batteries

Lithium-ion batteries(Li-ion batteries)have been widely used because of their advantages including high working voltage,small self-discharge,high energy-density,nonmemory effect,etc.With the increasing requirements on battery performance,it is of great significance to develop high-performance energy storage materials for Li-ion batteries,which has become a highly concerned research field in the world.Taking the anode materials as an example,many high-capacity anode candidates show largely volumetric change in charging and discharging,resulting in the rapid decay of capacity;the slow transportation kinetics of electrons and ions make it difficult to accelerate the charging speed of batteries;the cycling stability needs to be further improved,etc.In order to develop high performance Li-ion batteries energy-storage materials,this paper investigated the preparation methods of novel anode materials and energy-storage properties.The main research contents and novelties are as follows:(1)Nanoparticles were self-assembled into one-dimensional(1D)structure by a magnetic field assisted method,and multiple FeP nanospheres were encapsulated in FeP nanotubes to form a 1D nanosphere@nanotube composite.Moreover,nanosheets were grown on the surface of nanotubes by hydrothermal method and applied as Li-ion battery anode.The 1D structure improves the transportation of electrons and ions,enhancing rateperformance of the battery;the void in the structure accommodates the volumetric change,efficiently reducing the capacity decay;the nanosheet structure increases the specific surface area,which improving the electrochemical reactivity.The as-prepared 1D FeP anode exhibits a good electrochemical performance.After 1000 cycles at 2 A g-1,capacity remains 560 mAh g-1 and Coulombic efficiency reaches 99.8%.A recoverable rateperformance is also obtained after three rounds of tests.Furthermore,the capacities and Coulombic efficiencies remain stable at temperatures of-10℃ and 45℃,respectively,indicating good potential for use under different conditions.(2)Nanoneedle arrays were grown in-situ on the surface of self-assembled 1D nanotube by hydrothermal method,and the internal of the nanotube was coated with nanoparticles,thus forming a novel 1D "caterpillar-with-eggs" structured FeS2 anode.The voids alleviate the volumetric change in charge-discharge;the nanoarrays-assembled shell provides abundant rapidly transportation pathways for ions and electrons.The FeS2 anode exhibits a high capacity of 805.1 mAh g-1 after 500 cycles at 2 A g-1.When cycling at-10℃ and 45℃,the anode provides capacities of 754.5 and 744.4 mAh g-1 after 100 cycles at 1 A g1,respectively.The good electrochemical performance enables the special design to find broad applications for developing high-performance energy-storage materials and batteries.(3)A ternary 1D structure composite was prepared by in-situ growth of MoS2 nanosheets on SnP0.94 nanotube filled with Fe2P nanospheres by magnetic field-induced selfassembly.The mesostructure improves the diffusion performance of Li ions;the voids inside the composite and the nanosheets on the surface effectively alleviate the volumechange,realizing a long-term cycling stability.The Fe2P@SnP0.94@MoS2 anode displays a high capacity of 797.5 mAh g-1 after cycling 800 times at 2 A g-1,a Coulombic efficiency exceeding 99.4%,and a reversible rate-performance.The anode shows 908.7 and 987.6 mAh g-1 at different charge/discharge rates of 0.5/1 and 1/0.5 A g-1,respectively,and it has excellent energy-storage properties such as high capacity at different temperatures.