LiNi0.5Co0.2Mn0.3O2掺混LiFe0.2Mn0.8PO4电池安全性能研究

Safety performance of Li-ion batteries with LiNi0.5Co0.2Mn0.3O2 cathode by blending LiFe0.2Mn0.8PO4

研究了LiNi0.5Co0.2Mn0.3O2(NCM523)中混掺LiFe0.2Mn0.8PO4(LFMP)的材料热稳定性及其电池安全性能,并对电池基础电性能进行了验证。采用差示扫描量热法(DSC)和加速量热法(ARC)对混掺正极材料(NCM523/LFMP)以及电池的热稳定性进行了对比测试,结果表明,NCM523/LFMP材料的放热温度比NCM523延后了50℃,同时,ARC测试结果显示NCM523/LFMP在SOC(荷电状态)为100%时的起始放热温度与NCM523材料在SOC为77%时的起始放热温度相似。LFMP的掺入提升了NCM523的放电平台,LFMP掺入前后,电池的倍率性能无明显变化,LFMP掺混前后,电池循环500次后容量保持率均大于80%。橄榄石结构的LFMP具有较高的热稳定性,可以减缓NCM523的热扩散,从而提高材料热稳定性,同时减少三元材料与铝箔的接触面积,提升了电池的安全性能。

We report the improvement of thermal stability and safety of cylindrical 18650 LIBs using NCM523 cathode blending LiFe0.2Mn0.8PO4(LFMP).Differential scanning calorimetry(DSC) and accelerating rate calorimetry(ARC) are used to study the mechanism of the improved thermal stability of the blended cathode and safety of the full cells.The exothermal temperature region of NCM523/LFMP composite cathode is 50℃ wider than that of NCM523 cathode.The ARC results demonstrate that the onset temperature of the 100% SOC with blended cathode is similar with that of pure NCM523 cathode at 77% SOC.The discharging voltage plateau is a little higher for the NCM523/LFMP cathode than that of pure NCM523.Both the NCM523/LFMP and the pure NCM 523 cathodes remain higher than80% of the capacity after 500 cycles.We demonstrate that olivine LFMP with higher thermal stability interrupt the thermal transferring of the NCM523 cathode,meanwhile,decreases the contact area between NCM523 and the aluminum foil,so it can improve the safety of the 18650 LIBs.