LiF添加剂改善含锂陶瓷隔膜与4.35 V LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)正极的界面稳定性

Enhancing interfacial stability between lithium-containing ceramic separator and 4.35 V LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)cathode through LiF additives

锂离子电池用LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)正极,具有较高比容量和较低成本的优点,但是其在高电压长循环时正极界面极不稳定、安全性能亟待提高。虽然锂快离子导体Li1.2Ca0.1Zr1.9(PO4)3制备的陶瓷隔膜在很大程度上可以解决电池的安全性问题,但是与NCM811正极界面稳定性差。本工作通过在陶瓷隔膜中添加具有稳定界面功能的氟化锂(LiF)的方法来解决此问题。采用扫描电子显微镜(SEM)、热重分析(TGA)、差示扫描量热法(DSC)、机械拉伸强度、热收缩、吸液率、电化学阻抗谱(EIS)、线性扫描伏安法(LSV)和充放电测试等方法进行表征。结果表明,当LiF占涂覆无机陶瓷颗粒总质量的10%时,得到的陶瓷隔膜性能最佳:具有良好的离子传输性能(室温离子电导率提高至9.5×10^(-4)S/cm)和最佳的界面稳定性。隔膜组装的Li||LiNi_(0.8)Co_(0.1)Ni_(0.1)O_(2)扣式电池在3.0~4.35 V的高电压范围以0.3 C倍率循环400次后,放电比容量从195.2 mAh/g减少到119.9 mAh/g,保持初始容量的61.4%,而没有添加LiF的陶瓷隔膜电池仅为32.7%。含LiF的陶瓷隔膜提升电池循环稳定性的原因是形成了高质量的高压正极/电解质界面膜,稳定了正极与陶瓷隔膜的界面,使正极材料在高电压下仍能保持结构的稳定。因此,本工作制备的陶瓷隔膜为NCM811正极在高电压锂离子电池中的商业化应用提供了一种便捷方法。

LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811)cathodes in lithium-ion batteries have the advantages of high specific capacity and relatively low cost.However,long-term cycling at high voltage poses challenges to the cathode interface,leading to instability and a need for improved safety performance.Although the lithium fast ion conductor Li1.2Ca0.1Zr1.9(PO4)3 ceramic separator can considerably enhance battery safety,it exhibits poor interface stability when paired with NCM811 cathode.Herein,a lithium fluoride(LiF)additive with a stable interface function is added to the ceramic separator to solve this problem.The LiF-modified ceramic separator was characterized using scanning electron microscopy,thermogravimetric analysis,differential scanning calorimetry,mechanical tensile strength,thermal shrinkage,electrolyte uptake ability,electrochemical impedance spectroscopy,linear sweep voltammetry,and charge-discharge testing.The results show that the ceramic separator performs best when LiF accounts for 10%of the total mass of coated inorganic ceramic particles.It exhibits improved ionic transport properties,with room temperature ionic conductivity of 9.5×10^(−4)S/cm and excellent interfacial stability.In a Li||LiNi_(0.8)Co_(0.1)Ni_(0.1)O_(2)coin cell operating in the high-voltage range of 3.0-4.35 V,the discharge-specific capacity decreases from 195.2 to 119.9 mAh/g at a 0.3 C rate after 400 cycles,while maintaining 61.4%of the initial capacity when using LiF contained ceramic separator.In contrast,the capacity retention of the cell without LiF is only 32.7%.The enhanced cycling stability of the battery using a LiF-contained ceramic separator can be ascribed to the formation of a high-quality,high-voltage cathode-electrolyte interface film,stabilizing the interface between the cathode and separator,thereby preserving the structural stability of the cathode material under high voltages.Therefore,the developed ceramic separator in this study provides a convenient method for commercializing NCM811 cathodes in high-voltage lithium-ion batteries by enhancing interfacial stability and cycling performance.