The Preparation And Performance Of LiNi_0.82Co_0.1Al_0.08O₂ Cathode Materials And Prelithiation Materials For Lithium Ion Batteries

In recent years,lithium ion batteries have received extensive attention in the fields of new energy vehicles and power grid scale energy storage.LiNi0.82Co0.1Al0.08O2 is one of the most promising cathode materials,but it has problems such as poor structural stability and poor cycle performance,which affects its practical application.In addition,the irreversible capacity loss is a common problem during the charge and discharge for lithium ion batteries.This is mainly due to the formation of solid electrolyte interphase（SEI）at the anode surface,which consumes approximately 10-20%of active lithium from the cathode,resulting in low first cycle coulombic efficiency and cycling performance and lower energy density.Therefore,this paper mainly takes LiNi0.82Co0.1Al0.08O2 cathode material and Fe/Li2O prelithiation material as the research objects,and study the preparation conditions and electrochemical properties of each respectively.LiNi0.82Co0.1Al0.08O2 cathode material is successfully prepared by co-precipitation,high temperature solid phase method.The effects of different aluminum sources and aluminum source addition methods on the electrochemical properties of LiNi0.82Co0.1Al0.08O2 are studied.It is found that the initial discharge specific capacity of LiNi0.82Co0.1Al0.08O2 sample prepared by using Al（OH）3 as aluminum source can reach 179.8 mAh·g^-1 at the rate of 0.1C,which is better than that of LiNi0.82Co0.1Al0.08O2 prepared by using Al（OH）2（CH3COO）and Al（OCH（CH3）2）3 as aluminum source.An experimental study on the preparation of LiNi0.82Co0.1Al0.08O2 by aluminum compensation is carried out.LiNi0.82Co0.1Al0.08O2sample is prepared in the molar ratio of NaAlO2:Al（OH）3=3:5,and has an initial discharge specific capacity of 162.3 mAh·g^-1,and its capacity retention rate is 88.2%after 50 cycles.In addition,the sample has a discharge capacity of 143.2 mAh·g^-1 at5C rate,exhibiting good rate performance.This is because aluminum compensation method helps aluminum elements evenly distributed in the interior of the particles to enhance the structural stability;In addition,some aluminum elements can form a protective shell on the surface of particles to slow down the erosion of electrolyte,thus making the sample shows better rate performance.In order to improve the structural stability and cycle performance of LiNi0.82Co0.1Al0.08O2,an experimental study on Mn-doped LiNi0.82Co0.1Al0.08O2 is carried out.LiNi0.82Co0.1Al0.06Mn0.02O2 sample has a first discharge capacity of 183.8mAh·g^-1 at 0.1C rate,and a first discharge capacity of 164.9 mAh·g^-1 at 1C rate,and its capacity retention rate is 94.1%after 50 cycles.In addition,the sample exhibits a discharge capacity of 136.5 mAh·g^-1 at 5C rate,showing good cycle performance and rate performance.This is mainly because that doping an appropriate amount of Mn can increase the lithium vacancy in the material,which can conduce to improve the electrical conductivity and the structural reversibility of the material,and thus improving the electrochemical properties of the material.In order to alleviate the irreversible capacity loss in the first cycle for lithium ion batteries,the prelithiation material Fe/Li2O is studied.The Fe/Li2O composites are successfully prepared by in situ solid phase method.The effects of calcination temperature,holding time and Li/Fe molar ratio on the Fe/Li2O composites performance are compared.The experiment exhibit that Fe/Li2O as a cathode prelithiation additive has a high prelithiation specific capacity of 447.3 mAh·g^-1 at1/40C rate during charging,and the first charge capacity of LiNi0.6Co0.2Mn0.2O2 with7.5%Fe/Li2O additive can be improved by 9.1%at 0.05C rate and its cycling stability is increased from 86.9%to 90.2%at 0.2C after 70 cycles.In addition,LiNi0.82Co0.1Al0.08O2 with 7.5%Fe/Li2O additive is 7.2%higher first charge capacity than that of the pristine LiNi0.82Co0.1Al0.08O2 at 0.05C,and its cycling stability is increased from 84.7%to 87.5%at 0.1C after 60 cycles.The Fe/Li2O prelithiation additive remarkably enhanced the content of active lithium during the initial delithiation process,contributing the formation of solid electrolyte interphase on the anode surface and better cycling stability.