Research On High Specific Capacity NCA Cathode Materials For Lithium Ion Batteries

To achieve continuous supplement of green energy,the pace of researching and exploiting new energy storage,such as LIB,demands acceleration.Layered NCA materials,benefited from their high capacity,are considered one of the promising cathode materials for high energy density LIB.This paper aims at the NCA material,and through the optimization of carbonate co-precipitation along with the coating of AlPO4,the performance of NCA is improved.Furthermore,a gradient structured material is designed,synthesized and then studied on its character.The main content is as follows:1.Synthesis of NCA material through carbonate co-precipitationTaking LiNi0.80Co0.15Al0.05O2 for example with synthesis condition optimized.The temperature applied is 60℃.Under pH of 8.10 and material importing rate of 500mIL-1,the material is pumped in with continuous stirring for an hour.The precipitate is taken out,and after filtration,washing and drying,NCA precursor spheres with uniform size distribution are obtained.Then the precursor is mixed with LiOH with a ratio of 1:1.05,and the mixture is calcined in the air for a certain time to gain NCA material with good layered structure and electrochemical performance.2.Synthesis and character research of AIPO4 coated NCA mateirial.AIPO4 has been homogeneously coated on the surface of NCA via wet chemical method towards the target of protecting NCA from the attack of electrolyte.Compared with the bare NCA,NCA@AlPO4 electrode delivers high capacity without sacrificing the discharge capacity and excellent cycling stability.After 150 cycles at 0.5 C between 3.0-4.3 V,the capacity retention of the coated material is 86.9%,much higher than that of bare NCA(66.8%).Furthermore,the thermal stability of cathode is much improved due to the protection of the uniform coating layer on the surface of NCA.These results suggest that AIPO4 coated NCA materials could act as one promising candidate for next-generation LIBs with high energy density in the near future.3.Synthesis and character research of concentration-gradient cathode material.We present a concentration-gradient spherical particle with varied chemical composition from the inner end LiNi0.80Co0.15Al0.05O2(NCA)to the outer end LiNi1/3Co1/3Mnl1/3O2(NCM)of the structure.The method applied is carbonate co-precipitation.This cathode material shows excellent capacity retention of 99.8%at 0.5 C after 200 cycles with the merit of NCM concentration-gradient protection layer to the inner NCA core.Furthermore,the cathode material exhibits much improved thermal and air stability compared with bare NCA.These results could put new insights into the structure design of high-performance cathode materials for LIBs to meet the ever-increasing requirement for electric vehicles with high energy density,long life span and storage stability in the future.