Study On Application Of Graphene Conductive Additive For Lithium-ion Batteries

In order to meet the urgent demand for high energy density and high power performance for rapidly developing mobile digital battery and power battery,lithium-ion battery and their key materials need to be further improved in terms of high rate and high capacity performance.As cathode material of lithium ion battery is a semiconductor material with relatively poor electrical conductivity,it is necessary to add a conductive agent material to improve the ability of battery under high current charge and discharge condition.Graphene is composed of single-layer sp 2 carbon atoms,which has two-dimensional planar structure and large specific surface area.It is a new type of two-dimensional carbon nanomaterial with super-high electrical conductivity and excellent flexibility.In this paper,graphene as a conductive agent is added to cathode material of lithium cobalt oxide,lithium iron phosphate and NMC to explore its impact on processing performance and electrochemical performance.First,conductive agent comparison of graphene,carbon nanotube,and graphene and carbon black 5: 5 by applying in lithium cobalt oxide battery.Due to the two-dimensional sheet-like structure,it has shearing stress to improve solid content of slurry during mixing process.Graphene has the characteristics of ?thin and soft ?and flexible,which can significantly improve compaction density of battery material,at the same time,it can improve capacity performance of cathode electrode active material shown in test.Due to the process difficulty of easy to dust and difficult to disperse in graphene powder processing,graphene is made into slurry to effectively increase the degree of dispersion.In combination with conduction mechanism of conductive agents with different morphology,three graphene conductive composite slurry with different proportion are designed that GN/CNT/SP=3/2/1,3/1.5/1,3/ 1/1.They are applied in lithium cobalt oxide system for comparison in terms of electrode resistance rate,AC impedance,rate charge-discharge,high-low temperature discharge,cycle performance,etc.The conclusion makes that the best GN/CNT/SP ratio is 3/2/1.Second,according the application result of graphene in lithium cobalt oxide battery,the application field of the three graphene composite slurry are extended to lithium iron phosphate battery and NMC battery.Since lithium iron phosphate and NMC material have lower electrical conductivity than lithium cobalt oxide,GN/CNT/SP=3/2/1 battery with them have advantage in polarization resistance,AC resistance,large rate charge,low temperature and high current discharge,high temperature and high current discharge,2C cycle performance,1C long cycle.Therefore,it can be shown that,with the decrease of electrical conductivity of cathode material,performance advantage of GN/CNT/SP=3/2/1 conductive composite slurry is more obvious,and it is an excellent conductive slurry that can be commercially used in mass production.