The Preparation And Application Of NiCoS Cathode Material Of Lithium Sulfur Battery Derived From Prussian Blue

With the coming of 2020s,the world situation has entered a new stage of development.The development and competition of energy around the world is becoming more and more intense,so that the oil price is soaring,and many fuel vehicle owners have expressed the helplessness of"filling up 95 and going bankrupt".To this end,it is an urgent need to develop power battery vehicles.On the other hand,with the rapid development of 3C electronic devices and the needs of the future intelligent society,higher performance requirements are put forward for energy storage devices such as portable batteries.Therefore,it is necessary to develop large-capacity,long-lasting,fast-charging and discharging,safe and cheap batteries to meet people’s demand for energy storage devices in the future.Lithium-sulfur batteries（LSBs）due to their excellent high theoretical specific capacity(1675 mAh·g^-1),high theoretical energy density(2567 Wh·Kg^-1)and cheap and environmentally friendly sulfur cathodes,have become one of the most promising commercialized batteries for next-generation energy storage devices after lithium-ion batteries（LIBs）.However,the electrode insulation,the"shuttle effect"during the charge and discharge process,and the electrode expansion during the charging and discharging process have led to huge challenges in the commercialization of lithium-sulfur batteries.In view of the above problems,the development and design of battery electrodes with good electrical conductivity,high adsorption and catalytic activity has become the key research in the development of lithium-sulfur batteries.In this paper,the MOF-like porous structure NiCoPrussian blue analogue（NiCo-PBA）is used as the precursor,then the NiCoalloy exposed on the surface of the nanocube is vulcanized by a mild pyrolysis method to obtain a mixed vulcanization of NiCoalloy and NiCoS synthesized on the surface of the nitrogen-doped carbon matrix（NiCo-NiCoS/NC）.The high-rate and long-cycle performance of lithium-sulfur batteries was achieved by using NiCo-NiCoS/NC with good conductivity and synergistic effect as the sulfur cathode for lithium-sulfur batteries.The specific research process is as follows:（1）Optimization of the heterostructures:Various carbon-based heterostructures were prepared by adjusting the pyrolysis temperature and vulcanization time,and XRD,TGA,SEM,BET,and other characterization methods are used to determine the optimal pyrolysis temperature and vulcanization time to ensure that the morphology of NiCo-PBA cubes is not damaged during the pyrolysis process and that the NiCometal elements inside NiCo-PBA can be fully obtained on the surface of nanocubes to make the final heterostructures well distributed.（2）Analysis of the underlying mechanism:The NiCo-NiCoS/NC materials synthesized with different vulcanization time were served as sulfur hostand their electrochemical tests,such as Cyclic voltammetry（CV）measurements,Electrochemical impedance spectroscopy（EIS）spectra,the responding current of Symmetric electrodes and the response time of Li₂S nucleation,were systematically investigated.Combined with the adsorption,catalytic,and Li ion diffusion tests,the synergistic effect between the NiCoalloys and the NiCoS were revealed.Finally the optimal pyrolysis temperature was determined to be 500℃,and the NiCo-NiCoS/NC obtained after 6h vulcanization was served as sulfur cathode material of lithium-sulfur batterieswith the most excellent electrical conductivity.And the synergistic adsorption and catalytic performance of NiCo-NiCoS/NC can be fully exerted,which greatly suppress the influence of the"shuttle effect"on the battery performance during the charging and discharging process.The specific capacity of the battery reaches 692.1 mAh g^-1 at a high current density of 5C,and it has an ultra-stable life of more than 1500 cycles at a current density of 1.0 C,with a capacity decay of only 0.055%per cycle.