Preparation Of Nano-LiNi_1/3Co_1/3Mn_1/3O₂ And Modification As Cathode Material For Li-ion Battery

Efficient energy storage of lithium-ion batteries plays a significant role across lots of sectors including consumer electronics,electric and hybrid electric vehicles and a smart grid accommodating intermittent renewable energy sources.The material's rate performance is one of the important parameters for measuring lithium ion battery as cathode materials.Additionally,the use of nanoscale materials is considered an effective way to ameliorate rate performance due to the larger contact area with electrolyte and the shorter Li⁺diffusion path.Nano-particles Li Ni_1/3Co_1/3Mn_1/3O₂material is expected to have the potential to diminish electrode polarization and improve battery capacity by the offered merits of nanostructure.However,the adverse effects of dissolution and corrosion behavior for Nano-particles Li Ni_1/3Co_1/3Mn_1/3O₂materials will be accelerated,accompanied with the large contact area between acid-containing electrolyte and cathode electrode.That is,to exert its superiority,we should first effectively prevent nanoparticles from being dissolved and corroded by acid-containing electrolyte.Therefore,the nano-sized Li Ni_1/3Co_1/3Mn_1/3O₂ needs to be modified,firstly,matching with electrolyte to improve the cycle performance,secondly the uniform carbon coating Li Ni_1/3Co_1/3Mn_1/3O₂ not only increases the conductivity,but also the cycle performance is improved.In this work,first of all,NCMa has been successfully synthesized via a facile chemistry method using a cheap chelating agent of acetic acid,creating a route to the mass production of NCMa at reduced price.the use of nanoscale materials is considered an effective way to ameliorate rate performance due to the larger contact area with electrolyte and the shorter Li⁺diffusion path.Charging and discharging test results showed that the discharge capacity and rate capacity of the sample obtained by acetic acid sol-gel method,is significantly higher than that of the sample obtained by conventional co-precipitation method.SEM results demonstrate that the sample has uniform particle size in the range of 100-300 nm and has little agglomerates.The specific surface area of NCMa is 5.2631 m² g^-1,which is significantly higher than that of NCMb(only 0.1932 m²g^-1).This nanostructure can significantly increase the active surface area of electrode and provide high interfacial area with electrolyte.In addition,to reduce the adverse effect caused by NCMa,lithium bis?oxalate?borate?Li BOB?instead of Li PF₆ has been used as electrolyte salt to enhance the cycling of NCMa,due to the fact that Li BOB will generate relatively little acid in electrolyte.By virtue of ICP,the content of the Mn ions in Li PF₆-based electrolyte?1.32 ppm of Mn ions?is significantly higher than that in Li BOB-based electrolyte?0.33 ppm of Mn ions?.The dissolution of the Mn ions is caused by the attack of protonic acids due to the catalytic decomposition of Li PF₆.Furthermore,it is interest to note that Li BOB leads to forming a relative stable passivation film on the surface of NCMa cathode.Hence,compared with Li PF₆,NCMa will generate remarkable electrochemical lithium storage properties in terms of high capacity,excellent rate capability and ultrastable long-term cycling performance.Secondly,we presented a green,novel,economic and controllable CVD method with sucrose as carbon source to coating NCM.By using this formula,the carbon layer has more uniform thickness and higher quality compared with the traditional HE.This way can be stretched to most low electronic conductivity materials.The acetic acid sol-gel synthesized NCM carbon coated using this formula show very high discharge capacity,extraordinary rate performance,high cycling performance.The thickness-optimized sample has a discharge capacity as high as 205 m Ah g^-11 and a discharge capacity for 104.5 m Ahg^-11 at 10 C.High capacity retentions of 94.29 and 94.78%after100 cycles for 0.1C,respectively.The work is a promising coating method for the surface modification of Li Ni_1/3Co_1/3Mn_1/3O₂,especially electric vehicles?EV?and hybrid electric vehicles?HEV?.