A carbonate-free, sulfone-based electrolyte for high-voltage Li-ion batteries. Issue 4 (May 2018)

• Record Type: Journal Article
• Authors: Alvarado, Judith; Schroeder, Marshall A.; Zhang, Minghao; Borodin, Oleg; Gobrogge, Eric; Olguin, Marco; Ding, Michael S.; Gobet, Mallory; Greenbaum, Steve; Meng, Ying Shirley; Xu, Kang
• Is Part Of: Materials today. Volume 21:Issue 4(2018)
• Page Start: 341
• Page End: 353
• Publication Date: 2018-05
• Subjects: Lithium-ion battery -- Electrolyte -- Sulfolane -- 5V-class -- LiFSI; Materials science -- Periodicals; Metallurgy -- Periodicals; Metal-work -- Periodicals; Biomedical and Dental Materials -- Periodicals; Manufactured Materials -- Periodicals; Metals -- Periodicals; 620.11
• DOI: 10.1016/j.mattod.2018.02.005
• Languages: English
• ISSNs: 1369-7021

Abstract

Graphical abstract: Abstract: Practical implementation of next-generation Li-ion battery chemistries is to a large extent obstructed by the absence of an electrolyte that is capable of simultaneously supporting reversible electrochemical reactions at two extreme electrochemical potentials—above 4.5 V at the positive electrode and near 0 V vs. Li at the negative electrode. Electrolytes based on carbonate esters have been reliable in satisfying state-of-the-art Li-ion battery (LIB) chemistries below <4.2 V; however, it is the intrinsic thermodynamic tendency of these carbonates to decompose at potentials well below the thermodynamic threshold required for reversible reactions of high-voltage systems (>4.4 V), releasing CO2 . In this work, we explore a carbonate-free electrolyte system based on a single sulfone solvent, in which a newly discovered synergy between solvent and salt simultaneously addresses the interfacial requirements of both graphitic anode and high-voltage cathode (LiNi0.5 Mn1.5 O4 (LNMO)). Experimental measurements, quantum chemistry (QC) calculations, and molecular dynamics simulations reveal the system's fast ion conduction, stability over a wide temperature range, and non-flammability. At the anode, a LiF-rich interphase generated by early-onset reduction of the salt anion effectively suppresses solvent co-intercalation and subsequent graphite exfoliation, enabling unprecedented and highly reversible graphite cycling in a pure sulfone system. Under oxidative conditions, QC calculations predict that high salt concentration promotes complex/aggregate formation which slow the decomposition of sulfolane and leads to polymerizable rather than gaseous products—a fundamental improvement over carbonate solvents. These predictions are corroborated by X-ray photoelectron spectroscopy (XPS), cryogenic-transmission electron microscopy (TEM), and electron energy loss spectroscopy (EELS) experiments, which revealed the presence of a thin, conformal, sulfur-based cathode electrolyte interphase (CEI). Together, the functional interphases (SEI/CEI) generated by this electrolyte system supported long term operation of a high-voltage (4.85 V) LNMO/graphite full cell, which retained ∼70% of its original first-cycle discharge capacity after the 1000th cycle. Based on these results, this new carbonate-free electrolyte system, supported by the mechanistic understanding of its behavior, presents a promising new direction toward unlocking the potential of next generation Li-ion battery electrodes.