LiNi0.8Co0.15Al0.05O2正极材料的电化学与热稳定性改善

Improvement of electrochemical performance and thermal stability of LiNi0.8Co0.15Al0.05O2 cathode material

锂离子电池正极材料LiNi0.8Co0.15Al0.05O2(NCA)面临着成本和安全稳定性挑战,为了降低成本,提高NCA的电化学与热稳定性能,加入LiMn2O4(LMO)和LiFePO4(LFP)制备成混合正极材料LMO/LFP/NCA。通过X射线衍射(XRD)和扫描电镜(SEM)表征了材料的结构和形貌,采用恒流充放电和电化学阻抗谱(EIS)测试电化学性能,使用差示扫描量热仪(DSC)测试了热稳定性。结果表明:简单物理混合后,NCA颗粒形貌保持完整,小颗粒的LMO和LFP材料均匀地分散在NCA二次颗粒表面和NCA颗粒之间的空隙中。所制备的混合正极材料LMO/LFP/NCA在45℃下循环50圈容量保持率为81.2%,明显优于单组分NCA材料(70.3%),热稳定性提高了16℃。说明LMO和LFP的加入,可以改善NCA正极材料的循环性能与热稳定性。

LiNi0.8Co0.15Al0.05O2(NCA)cathode materials are facing the challenges of high cost and low safety stability.In order to improve the electrochemical and thermal stability of NCA and reduce the cost,LiMn2O4(LMO)and LiFePO4(LFP)were added to prepare the blended cathode material NCA/LMO/LFP.X-ray diffraction(XRD)and scanning electron microscopy(SEM)were used to characterize the structure and morphology of the single and blended materials.The constant current charge-discharge test and electrochemical impedance spectroscopy(EIS)were performed to test electrochemical performance.Meanwhile,the differential scanning calorimeter(DSC)was used to study the thermal stability.The results show that the morphology of the NCA particles remains complete,and the small particles of LMO and LFP are uniformly dispersed on the surface of NCA secondary particles and in the gaps between NCA particles after simple physical mixing.The capacity retention rate of the blended NCA/LMO/LFP cathode material is 81.2%at 45℃after 50 cycles,which is obviously better than 70.3%of the single NCA material.And more importantly,the thermal stability of the blended NCA/LMO/LFP cathode material is improved by 16℃compared with the single NCA material.The results demonstrate that the cycle stability and thermal stability of NCA can be improved by adding LMO and LEP.