Homogeneous Lithium Electrodeposition with Pyrrolidinium-Based Ionic Liquid Electrolytes

Abstract

In this study, we report on the electroplating and stripping of lithium in two ionic liquid (IL) based electrolytes, namely N-butyl-N-methylpyrrolidinium bis(fluorosulfonyl) imide (Pyr14FSI) and N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI), and mixtures thereof, both on nickel and lithium electrodes. An improved method to evaluate the Li cycling efficiency confirmed that homogeneous electroplating (and stripping) of Li is possible with TFSI-based ILs. Moreover, the presence of native surface features on lithium, directly observable via scanning electron microscope imaging, was used to demonstrate the enhanced electrolyte interphase (SEI)-forming ability, that is, fast cathodic reactivity of this class of electrolytes and the suppressed dendrite growth. Finally, the induced inhomogeneous deposition enabled us to witness the SEI cracking and revealed previously unreported bundled Li fibers below the pre-existing SEI and nonrod-shaped protuberances resulting from Li extrusion.

Exceptional long-life performance of lithium-ion batteries using ionic liquid-based electrolytes

“…[79][80][81] The higher SEI formation potential observed for the former electrolyte may be ascribed to the FSI anion decomposition known to have enhanced film-forming ability compared to TFSI. 82 The second cycle, reported in the lower panel, reveals the exclusive presence of reversible peaks in the 0.0-0.2 V vs. Li/Li + region associated with the lithium uptake in the carbon working electrode, 83 thus suggesting the formation of a stable solid electrolyte interface (SEI) film with all the investigated electrolytes which prevents any further decomposition process during the following cycles. The anodic stability of the electrolytes is evaluated by measuring the current evolution during a stepwise potential sweep, increasing by 0.1 V each one hour, (Fig.…”

Study of the Mechanisms of Internal Short Circuit in a Li/Li Cell by Synchrotron X-ray Phase Contrast Tomography

“…56 This is the first time that the amount of electrochemically deposited LmSs calculated from morphological information is directly correlated with the amount of external electron transfer measured electrochemically. Concerning the locations of preferential Li dissolution and LmS deposition during cycling it has been suggested that such locations are electrochemically more active 15 or possess a high local ionic conductivity. 27 It has been also suggested that a localized fracture in the SEI 58 Close-up inspection of morphological structures inside Li/Li-2 cell Apart from these findings, a close-up inspection of Figure 3 and 4 further demonstrates: 3) there are two different phases of electrodeposited LmSs, one being porous and the other solid and compact (both are shown in Figure 3b-e and 4c,f in light yellow and dark yellow, respectively, separated by a purple dotted line).…”

“…67 The above-observed results agree well with previous simulations. 15,[68][69] Additionally, the direct internal view of the electrochemically short circuited Li/Li-2 cell suggests that the shutdown mechanism proposed by the sandwich structure can hardly provide any protection from a real ISC, i.e. the considerable force accompanied by the growing LmSs and the ISC-induced high Joule heating easily destroy the trilayer separator that is made by laminating PP and PE layers together by adhesion or welding.…”

“…[1][2][3][4][5][6][7][8][9][10][11][12][13][14] For example, the most promising Li metal-based battery technologies such as lithium-sulphur and lithium-air batteries have not been successfully commercialized mainly because of the uncontrolled growth of lithium microstructures (LmSs) such as dendrites, fibers, whiskers, moss, etc., which can cause internal short circuit (ISC) of a cell and result in catastrophic fires or even explosions. [15][16][17] Recent field incidents such as fires on a Boeing 787 Dreamliner flight and in a Tesla electric vehicle (EV) or even in the Samsung Note 7 smartphone are believed to be closely linked to ISCs in LIBs. [18][19][20] Furthermore, the soaring number of EVs in use additionally adds tremendous weight to safety and reliability in presentand next-generation LIB technology.…”

Recent Advances in Designing High‐Capacity Anode Nanomaterials for Li‐Ion Batteries and Their Atomic‐Scale Storage Mechanism Studies

“…Besides carbon, boron nitride137 and graphene138 serve as chemical and physical stable barriers to restrict the reaction with Li metal. Moreover, utilization of solid‐state electrolytes (such as polymer membranes) and the electrolytes with various additives (such as vinylene carbonate, Cs + and Rb + , LiF, lithium polysulfide, and ionic liquids) can serve as protective layers that also suppress the growth of lithium dendrites by providing an effective way for suppressing 139, 140, 141, 142, 143…”