High-Safety and Dendrite-Free Lithium Metal Batteries Enabled by Building a Stable Interface in a Nonflammable Medium-Concentration Phosphate Electrolyte

Abstract

Lithium metal anodes are promising for their high energy density and low working potential. However, high reactivity and dendrite growth of lithium metal lead to serious safety issues. Lithium dendrite may form "dead lithium" or pierce the separator, which will cause low efficiency and short-circuit inside the battery. A nonflammable phosphate-based electrolyte can effectively solve the flammability problem. Also, it shows poor compatibility with lithium metal anodes, resulting in an unstable solid electrolyte interface (SEI), which leads to dendrite growth and poor electrochemical performance. In this study, trimethyl phosphate is used to ensure the safety of lithium metal batteries. By adjusting the concentration of lithium salt and introducing fluoroethylene carbonate, a stable SEI layer is formed on the surface of the lithium metal anode and dendrite growth of the lithium metal anode is inhibited. Lithium metal batteries with a modified electrolyte achieved stable electrochemical plating/stripping, and the full cell has 93.4% capacity left and the coulombic efficiency is nearly 100%. In addition, the modified electrolyte can also enable reversible intercalation and de-intercalation of Li + in the commercial graphite anode. This work may provide an alternative direction for the development of lithium metal batteries with high safety and high energy density.

Synergistic Effect of Bis(2,2,2-trifluoroethyl) Carbonate and Succinonitrile in Suppressing the Dissolution of Nickel for Performance Improvement of Nickel-Rich Lithium Metal Batteries

“…42 As the XPS results of C 1s show in Figure 4d-f 43 Notably, the intensity and content of all the peaks in EC/DEC were much higher than that in SN/DEC electrolytes, which might be attributed to the catastrophic decomposition of the electrolyte due to the catalysis of Ni 2+ /Ni 3+ . 44,45 A similar phenomenon can also been observed in the O 1s spectrum. The intensity of the O− C�O peak at 531.4 eV corresponding to the generation of LiOR, LiCO 2 OR, and Li 2 CO is significantly higher, suggesting the formation of more O-containing species, 46 as shown in Figure 4g-i 4g originated from the side reactions between diffused TM ions, and the electrolyte on the anode/ electrode interface was much stronger than that in Figure 4h-i, supposing the stable passivation layer on the cathode surface has been constructed in hybrid electrolytes, thus preventing the dissolution of TM ions.…”

“…As the XPS results of C 1s show in Figure d-f, the characteristic peaks located at 284.7, 285.7, 286.5, and 288.3–288.5 eV were assigned to C–C/C–H, C–O, CO, and O–CO, respectively . Notably, the intensity and content of all the peaks in EC/DEC were much higher than that in SN/DEC electrolytes, which might be attributed to the catastrophic decomposition of the electrolyte due to the catalysis of Ni 2+ /Ni 3+ . , A similar phenomenon can also been observed in the O 1s spectrum. The intensity of the O–CO peak at 531.4 eV corresponding to the generation of LiOR, LiCO 2 OR, and Li 2 CO is significantly higher, suggesting the formation of more O-containing species, as shown in Figure g-i.…”

Effects of the Electrolyte Concentration on the Nature of the Solid Electrolyte Interphase of a Lithium Metal Electrode

“…Indeed, Zhang et al showed that adjusting the lithium salt concentration and introducing FEC as an additive in the electrolyte allow the formation of a stable solid electrolyte interphase (SEI) that favors a nondendritic lithium deposition over cycling. [ 13 ] The increase of salt concentration in the electrolyte tends to modify its properties as well as battery performance. For example, the flammability of carbonate liquid electrolytes has shown to be reduced just by increasing the lithium salt concentration from 1 to 4 M. [ 14 ] This effect can be attributed, in highly concentrated electrolytes, to the low amount of free solvent molecules, usually responsible of the electrolyte flammability, because many of them are engaged in Li + solvation.…”

“…Indeed, Zhang et al showed that adjusting the lithium salt concentration and introducing FEC as an additive in the electrolyte allow the formation of a stable solid electrolyte interphase (SEI) that favors a nondendritic lithium deposition over cycling. [13] The increase of salt concentration in the electrolyte tends to modify its properties as well as battery performance. DOI: 10.1002/ente.202201037…”

A trade-off-free fluorosulfate-based flame-retardant electrolyte additive for high-energy lithium batteries

“…Thermal stability issues, such as re and explosion through thermal runaway, are fundamentally caused by the use of volatile and ammable liquid electrolytes with linear or cyclic organocarbonate compounds. [1][2][3][4] Thermal runaway can be initiated by overcharging, external shock/cell defects, or excessive heat generation, which destabilizes the organic liquid electrolytes, resulting in overheating, heat accumulation, combustion, and eventual battery explosion. 5 Although a wide range of ame-retarding additives have been developed to avoid combustion and explosion, they involve a trade-off between ammability and electrochemical cell performance.…”