| More than 90%international trade is completed by vessels of the oceans and inland.The marine environment and atmosphere is required to be protected by reducing the ship emissions which has caused more and more attention.Electric propulsion not only reduces emissions of the ship,but also increases on handing safety and maneuverability.For all this,stability status of ship power network and reliability of electric propulsion system,ship is need equiped with a large number stored energy battery.Lithium-ion batteries(LIBs)are assumed as promising ship energy storage system owing to their high capacity,long cycle life and environmental friendliness.The nickel-rich cathode materials have been considered as the most promising candidates to develop lithium-ion batteries of higher mass and volume specific capacity.However,some issues of these cathode materials and especially the production of high-Ni cathode material precursor has greatly limited their industrialization because of low productivity,high production cost,strict process control conditions and a poor electrochemical performances.Consequently,in this work,an improved co-precipitation and spray pyrolysis methods were designed to synthesize the cathode material precursors via a regulating second particles microstructure and the growth process.A series of scale-up tests and theoretical analysis have been carried out and a few suggestions and optimization strategy about industrialization of cathode materials have been proposed,for the purpose of lowering production costs,reducing waste water,reducing the process control difficulty and improveing the electrochemical properties.In this paper,an improved co-precipitation and spray pyrolysis methods have been used to synthesize three different precursors corresponding to high-performance cathode materials of LiNi0.5Co0.2Mno.3O2,LiNi0.6Co0.2Mn0.2O2 and LiNi0.8Co0.1Mn0.1O2,the secondary particles nucleation growth mechanism and rule is studied.And the samples' microstructures and electrochemical properties were investigated thoroughly,and characterized by SEM,XRD,TEM,CV and EIS,etc.High-efficiency and continuous synthesis methods have been explored and demonstrated by industrialized tests for mass production.Firstly,a semi-continuous nucleation filter product hydroxide co-precipitation methods(SNFHCP)has been used to synthesize the NCM5230H and NCM6220H cathode material precursors in 500 L reactor kettle.The precursor powders with suitable size-distributed region,long-period granularity and good morphology were obtained by means of controlling parameters of the cyclical nucleation filter product to regulate secondary particles'microstructure.XRD patterns of cathode materials sintered from the precursors with lithium salt shows that all peaks could be indexed to a well-defined hexagonal ?-NaFeO2 structure type and no extra peaks or impurities exist.It is believed that the process of co-precipitation is a process of nucleation and growth,and particle nucleation is mainly controlled by pH value,ammonia concentration and stirring rate,while growth is mainly controlled by pH value,reaction time,reaction temperature and aging time.LNCM523 and LNCM622 deliver an initial discharge capacity of 175 mAh/g and 187 mAh/g respectively,at 0.1 C(18 mA/g)in the voltage window of 2.8-4.3 V,and that LNCM622 could maintain 172 mAh/g with a capacity retention of 91%after 100 cycles.The technology has been applied into industrial production of the cathode material precursor(NCM6220H).Secondly,on the basis of previous study,an improved continuous hydroxide co-precipitation method(CHCP)has been employed to synthesize the spherical-like high-Ni cathode material precursor(NCM622OH)in 500 L chemical reactor by continuous stirring and feeding reaction solution.When the pH values of A kettle and B kettle are adjusted to 11.2 and the NH4OH concentration of A kettle is fixed at 0.5 M,stirring speed was controlled at above 40Hz,the temperature of the solution in the reactor was kept at 55±1?,and the solution was aged for 1 h,the NCM6220H cathode material precursor with excellent size distribution and morphology had been obtained in the 500 L system,which can work stably for a long time.The results show that as-prepared LiNCM622 powder presents a typical a-NaFeO2 lamellar structure.It delivers an initial discharge capacity of 208.5 mAh/g at 0.1 C(18 mA/g)with a capacity retention of 92.9%after 214 cycles in the voltage window of 2.8-4.3 V.Even after 1000 cycles charged at 10 C current density,the specific capacity stabilizes 101.1 mAh/g with a capacity loss of only 0.0105%per cycle.Practices show that the CHCP method is one of the most economical and effective approaches to prepare the high-Ni precursor,which can more greatly improve work efficiency,avoid stopping make,repeating kettle wash,adding base solution,heating and restarting the system in traditional batch process.The process and technology is reliable,steady,efficient,low cost and suitable for mass-scale production,which has been applied into pilot mass production.Moreover,in order to reduce cost,reduce discharge of wastwater and improve safety of the cathode materials further,one-step spray pyrolysis technology has been employed to synthesize single-crystal NCM622 oxide precursor materials.The optimized precursor soltuion is nickel,cobalt and manganese chloride solutions,the optimized pyrolysis temperature is 850?.The corresponding cathode material show better electrochemical performance,which delivers discharge capacity of 184 mAh/g at 0.1 C,and a capacity retention of 128 mAh/g after 100 cycles at 1 C,in the voltage window of 2.8-4.3 V.At last,two-step spray pyrolysis(spray drying and spray pyrolysis)method has been proposed to synthesize single-crystal NCM811 oxide precursor with controllable shape by prolonging the process of pyrolysis reaction and promoting the growth of single-crystal.The optimized drying temperature is 200?,the optimized pyrolysis temperature is 850 ?,the new method process can overcome the difficulty of morphology and flowing control.The results show that as-prepared LiNCM811 powder presents a typical a-NaFeO2 lamellar structure.It delivers an initial discharge capacity of 202 mAh/g at 0.1 C with a capacity retention of 181 mAh/g after 100 cycles in the voltage window of 2.8-4.3 V,These values are comparable with those of commercial materials synthesized by hydroxide co-precipitation method.Therefore,two-step spray pyrolysis method can be easily applied into scale production and exhibits great potential as a low cost technology of high-Ni single-crystal cathode material for high energy density LIBs in the future. |
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