Effect Of TRIZIN Additive On Electrochemical Performance Of Lithium Ion Batteries

With the promotion of new energy vehicles through strong state subsidies,new energy vehicles have entered thousands of households and owned more and more them.new energy vehicles have exposed many problems in various practical applications,such as short endurance and low capacity at low temperature.Collision explosion and cyclic instability at high temperature and high pressure require further breakthrough and improvement of high capacity cathode and anode materials and functional electrolytes.The use of electrolyte additives for lithium-ion batteries is one of the most effective and economical methods to improve the performance of lithium-ion batteries.Only a small amount of additives can be added to the electrolyte to significantly improve some performance of the battery,such as the charge-discharge capacity of the battery,cycle performance,electrolyte conductivity,reversible capacity and so on.In this paper,charge-discharge test,cyclic voltammetry,electrochemical impedance spectroscopy（EIS）,scanning electron microscopy（SEM）and so on were used.The effect of boron trifluoride triazine,a high temperature and high pressure additive,on the electrochemical properties of ternary materials LiNi_0.5Co_0.3Mn_0.2O₂（NCM532）and LiNi_0.6Co_0.2Mn_0.2O₂（NCM622）electrodes was investigated.The results are as follows:（1）At 4.5 V cutoff voltage,the first cycle charge-discharge capacity of NCM532and NCM622 electrodes can be improved by adding additive TRIZIN,and the cycle stability can be improved.Among them,the concentration of 1%TRIZIN has the best effect.The results of CV show that the potential difference of redox peak in CV curve with 1%TRIZIN concentration is obviously smaller and the coincidence of the curve is better,which indicates that the addition of TRIZIN can inhibit the polarization of NCM532 and NCM622 cathode materials.The Coulomb efficiency and cyclic stability are improved.Through EIS and fitting results,it can be seen that the change of R_SEI and R_ct with 1%TRIZIN is more stable and the resistance value is smaller,and the surface of NCM532 and NCM622 electrode is smoother after 100 cycles by SEM.The results show that the addition of 1%TRIZIN additive can promote the formation of more uniform and thin SEI film and improve the electrochemical performance of NCM532and NCM622 electrodes at 4.5 V.（2）At 4.7 V cutoff voltage,the NCM622 charging platform moves to the x axis after 4.5 V,which may be due to the reversible redox of Ni³⁺/Ni⁴⁺inside the material when the voltage exceeds 4.5 V.However,the addition of TRIZIN additive can still improve the charge-discharge capacity and cycle performance of NCM532 and NCM622 electrodes at 4.7 V,among which the addition of 1%TRIZIN additive has the best electrochemical performance.NCM622 CV results show that there will be an additional oxidation peak after 4.5 V,corresponding to the decline of the charging platform.Similarly,the addition of 1%TRIZIN additive makes the potential difference of redox peak of NCM532 and NCM622 electrode smaller and more consistent with the coincidence,which indicates the polarization phenomenon inhibited by the addition of additive at 4.7 V potential.The Coulomb efficiency and cyclic stability are improved.The results of EIS and fitting show that the addition of 1%TRIZIN additive can obviously reduce the value of R_SEI and R_ct,which indicates that the addition of additive is beneficial to the formation of more stable and thin SEI film between NCM532 and NCM622 electrode at 4.7 V potential and the improvement of its electrochemical performance.（3）At 55℃,the capacity of NCM622 electrode decays rapidly,but the addition of TRIZIN additive can effectively curb the attenuation of capacity and improve the charge-discharge capacity and cycle stability.There are two oxidation peaks in the CV curve with 1%TRIZIN additive at about 3.75 V.it should be that the addition of the additive at high temperature makes the structure of the material transition from hexagonal to monoclinic.The potential difference of redox peak is obviously smaller than that of non-additive,which indicates that the addition of 1%TRIZIN additive can inhibit the polarization of NCM622 and improve the Coulomb efficiency and cycle stability at high temperature.The results of EIS and fitting show that the R_SEI and Rct values of 1%TRIZIN additives are lower than those of R_SEI and R_ct without additives,which improves the interfacial stability and is beneficial to the formation of stable and thin SEI,to improve the electrochemical performance of NCM622 at high temperature.