Zhang Jian, Shi Jiayan, Gordon Leo W, Shojarazavi Nastaran, Wen Xiaoyu, Zhao Yifan, Chen Jianjun, Su Chi-Cheung, Messinger Robert J, Guo Juchen
Materials Science and Engineering Program, University of California - Riverside, Riverside, California 92521, United States.
Department of Chemical and Environmental Engineering, University of California - Riverside, Riverside, California 92521, United States.
ACS Appl Mater Interfaces. 2022 Aug 17;14(32):36679-36687. doi: 10.1021/acsami.2c09267. Epub 2022 Aug 5.
Phosphorus pentoxide (PO) is investigated as an acid scavenger to remove the acidic impurities in a commercial lithium hexafluorophosphate (LiPF) carbonate electrolyte to improve the electrochemical properties of Li metal batteries. Nuclear magnetic resonance (NMR) measurements reveal the detailed reaction mechanisms of PO with the LiPF electrolyte and its impurities, which removes hydrogen fluoride (HF) and difluorophosphoric acid (HPOF) and produces phosphorus oxyfluoride (POF), OFP-O-PF anions, and ethyl difluorophosphate (CHOPOF) as new electrolyte species. The PO-modified LiPF electrolyte is chemically compatible with a Li metal anode and LiNiMnCoO (NMC622) cathode, generating a POF-rich solid electrolyte interphase (SEI) that leads to highly reversible Li electrodeposition, while eliminating transition metal dissolution and cathode particle cracking. The excellent electrochemical properties of the PO-modified LiPF electrolytes are demonstrated on Li||NMC622 pouch cells with 0.4 Ah capacity, 50 μm Li anode, 3 mAh cm NMC622 cathode, and 3 g Ah electrolyte/capacity ratio. The pouch cells can be galvanostatically cycled at C/3 for 230 cycles with 87.7% retention.
五氧化二磷（PO）被作为一种酸清除剂进行研究，以去除商用六氟磷酸锂（LiPF）碳酸酯电解质中的酸性杂质，从而改善锂金属电池的电化学性能。核磁共振（NMR）测量揭示了PO与LiPF电解质及其杂质的详细反应机理，该反应去除了氟化氢（HF）和二氟磷酸（HPOF），并产生了磷酰氟（POF）、OFP - O - PF阴离子和二氟磷酸乙酯（CHOPOF）作为新的电解质物种。PO改性的LiPF电解质与锂金属阳极和LiNiMnCoO（NMC622）阴极具有化学兼容性，生成富含POF的固体电解质界面（SEI），这导致锂的高度可逆电沉积，同时消除了过渡金属溶解和阴极颗粒开裂。在容量为0.4 Ah、锂阳极厚度为50 μm、NMC622阴极面积为3 mAh cm、电解质/容量比为3 g Ah的Li||NMC622软包电池上展示了PO改性LiPF电解质优异的电化学性能。该软包电池可以在C/3电流下恒电流循环230次，容量保持率为87.7%。
