Designing a Li-Metal Battery That Survives Practical Operating Conditions

Abstract

Rechargeable Li-metal batteries using LiNixCoyMn1-x-yO2 cathode (Li/NCM battery) have a great consideration as the most promising candidates for future high-energy batteries. Despite recent efforts, development of practical Li/NCM battery remains a enormous challenge due to the limited understanding of where efficiency improvements can be made. Herein, we propose the new customizing approach to realizing the practical Li/NCM battery. We suggest the novel methodology to maximize the Li-metal stability by forming a stable solid electrolyte (SEI) layer through in-situ and ex-situ route. The electrolyte comprises 1M LiPF6 and 0.05M lithium difluoro(oxalate)borate (LiDFOB) dissolved in the mixture of ethyl methyl carbonate (EMC) and fluoroethylene carbonate (FEC) solution induced robust and ion conductive inorganic-organic combination such as LiF, Li2CO3, and cross-linked oligomeric borate in SEI layer via in-situ electrochemical reaction. In addition, LiNO3 treatment on Li-metal anode induce Li2O-rich SEI layer via ex-situ route, providing the mechanical strength to maintain the SEI layer from breakdown against to dendritic Li growth at high current density. Finally, the rupture and pulverization issues of commercial Li[Ni0.6Co0.2Mn0.2]O2 cathode in practical loading of LMBs are surmounted by benchmarking a 2mol % Al-doped Ni-rich (Li[Ni0.73Co0.10Mn0.15Al0.02]O2) full concentration gradient (Al2-FCG75) cathode. As a result, the Li/CNM battery based on stabilized Li-metal anode with suitable electrolyte solution and Al2-FCG75 cathode delivers high areal capacity of 4.1 mAh cm-2 and the best cycling stability over 300 cycles at an extremely high current density of 3.6 mA cm-2 in reported LMBs to date.Reference S.-J. Park, J.-Y. Hwang, C. S. Yoon, H.-G. Jung andY.-K. Sun, ACS Appl. Mater. Interfaces 2018, 10, 17985.S. H. Lee, J.-Y. Hwang, S.-J. Park, G.-T. Park and Y.-K. Sun, Adv. Funct. Mater. 2019, 29, 1902496.S. H. Lee, J.-Y. Hwang, J. Ming, Z. Cao, H. A. Nguyen, H.-G. Jung, J. Kim and Y.-K. Sun, Adv. Energy Mater. 2020, 2000567