Effects Of TiN And Graphene-CNTs Electrical Conductors On The Electrochemical Performance Of Lithium-ion Batteries

Lithium-ion batteries with the properties of long cycle life,high energy density,portability,and high security,have become energy storage devices that are being closely concerned and developed in the contemporary world.Electrode materials include cathode materials:lithium iron phosphate(LiFePO4)and ternary materials(LiNixCoyMn1xyO2),anode electrode materials such as lithium titanate(Li4Ti5O12)and so on.However,these electrode materials have the obvious problems of low conductivity,poor conductivity,etc.Adding appropriate conductive agent in the process of preparing electrode material is particularly important.The conductive agent is utilized to increase the conductivity of electrode material and improve the charge and discharge performance of battery.In the process of electrode preparation,a certain amount of conductive materials is usually added to reduce the internal resistance of electrode and accelerate the mobility of electrons.This article attempts to use titanium nitride(TiN)as a conductive agent with high stability and high conductivity and examine its electrochemical performance for lithium iron phosphate(LiFeP04),ternary(LiNixCoyMn1xyO2),and lithium titanate(Li4Ti5O12)cells.The Graphene-CNTs composite conductive paste prepared in the laboratory is used as a conductive agent,which is also explore its impact on the electrochemical performance of lithium iron phosphate(LiFePO4),ternary materials(LiNixCoyMn1XyO2),lithium titanate(Li4Ti5O12)batteries.The details are as follows:1.When TiN is used as a conductive agent,it can be obtained by compounding and adding different proportions of conventional conductive agent:the optimal proportion of conductive agent is S+T(7:3)when the active material is lithium iron phosphate,which can obtain the most excellent rate and cycle performance.The initial discharge specific capacity is 164.5 mAh·g-1 at 0.1C current density,and the Coulomb efficiency is 97.63%.After 200 cycles measurement at 1C,the capacity retention rate is 108.4%;When the active material is lithium nickel-cobalt-manganese oxide,the electrode shows the best rate performance during the ratio of the conductive agent is S+T(7:3).The initial discharge specific capacity was 150.5 mAh·g-1,and the Coulomb efficiency was 85.23%.For the cycle performance,the conventional conductive agent owns good cycle performance.However,the addition of TiN can not improve the cycle performance of nickel-cobalt-manganese.when the active material is lithium titanate,the optimal ratio of conductive agent is S+T(7:3).The electrode material exhibits the best rate performance and cycle performance.The initial discharge specific capacity is 163.5 mAh·g-1 at 0.1C,and the Coulomb efficiency is 101.3%.TiN has no significant effect on the cycling performance of lithium titanate materials.2.When graphene-CNTs composite conductive paste is used as a conductive agent,it is obtained by compounding with different proportions of conventional conductive agents.The optimal proportion of conductive agent is:GC has the best rate performance and cycle performance when the active material is lithium iron phosphate.The initial discharge specific capacity is 146.5 mAh·g-1 at 0.1C,and the Coulomb efficiency is 88.26%.The initial discharge specific capacity was 127.5 mAh·g-1 at 1C.After 200 cycles,the discharge specific capacity was 129.7 mAh·g-1,and the capacity retention rate was 101.7%.When the active material was nickel-cobalt-manganese oxide,the optimal ratio of conductive agent is S+K+GC(1:1:2).The electrode material has the best rate performance and cycle performance.The first discharge specific capacity is 144.1mAh·g-1 and the coulomb efficiency is 84.76%,Meanwhile,the initial discharge specific capacity was 118.3 mAh·g-1 at 1C.After 200 cycles,the discharge specific capacity was 112.3 mAh·g-1,and the capacity retention rate was 94.9%.In the case of lithium titanate,the conductivity of the material is GC.The material shows the most excellent rate performance and cycle performance.The first discharge specific capacity is 166.5 mAh·g-1,and the Coulomb efficiency is 97.60.%.The initial discharge specific capacity was 162.7 mAh·g-1 at 1C.After 200 cycles,the discharge specific capacity was 161.1 mAh·g-1,and the capacity retention rate was 98.9%.In the graphene-CNTs composite conductive paste,the carbon nanotubes can provide channels for electrolyte,which is beneficial to improve the permeability so that the electrolyte and the electrode contact each other more sufficiently.Moreover,graphene owns the high electron mobility,which can greatly enhance the electrochemical performance of electrode materials.