Nonflammable Lithium Metal Full Cells with Ultra-high Energy Density Based on Coordinated Carbonate Electrolytes

Sung-Ju Cho; Dae-Eun Yu; Travis P Pollard; Hyunseok Moon; Minchul Jang; Oleg Borodin; Sang-Young Lee

doi:10.1016/j.isci.2020.100844

Nonflammable Lithium Metal Full Cells with Ultra-high Energy Density Based on Coordinated Carbonate Electrolytes

iScience. 2020 Feb 21;23(2):100844. doi: 10.1016/j.isci.2020.100844. Epub 2020 Jan 16.

Authors

Sung-Ju Cho¹, Dae-Eun Yu¹, Travis P Pollard², Hyunseok Moon¹, Minchul Jang³, Oleg Borodin⁴, Sang-Young Lee⁵

Affiliations

¹ Department of Energy Engineering, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea.
² Battery Science Branch, Energy and Biomaterials Division, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783, USA.
³ Battery R&D Center, LG Chem., Daejeon 34122, Korea.
⁴ Battery Science Branch, Energy and Biomaterials Division, Sensor and Electron Devices Directorate, U.S. Army Research Laboratory, Adelphi, MD 20783, USA. Electronic address: oleg.a.borodin.civ@mail.mil.
⁵ Department of Energy Engineering, School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea. Electronic address: syleek@unist.ac.kr.

Abstract

Coupling thin Li metal anodes with high-capacity/high-voltage cathodes such as LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) is a promising way to increase lithium battery energy density. Yet, the realization of high-performance full cells remains a formidable challenge. Here, we demonstrate a new class of highly coordinated, nonflammable carbonate electrolytes based on lithium bis(fluorosulfonyl)imide (LiFSI) in propylene carbonate/fluoroethylene carbonate mixtures. Utilizing an optimal salt concentration (4 M LiFSI) of the electrolyte results in a unique coordination structure of Li⁺-FSI^--solvent cluster, which is critical for enabling the formation of stable interfaces on both the thin Li metal anode and high-voltage NCM811 cathode. Under highly demanding cell configuration and operating conditions (Li metal anode = 35 μm, areal capacity/charge voltage of NCM811 cathode = 4.8 mAh cm^-2/4.6 V, and anode excess capacity [relative to the cathode] = 0.83), the Li metal-based full cell provides exceptional electrochemical performance (energy densities = 679 Wh kg_cell^-1/1,024 Wh L_cell^-1) coupled with nonflammability.

Keywords: Electrochemical Energy Engineering; Electrochemical Energy Storage; Electrochemical Materials Science.