A Bifunctional Electrolyte Additive for High-Voltage LiNi_0.5Mn_1.5O₄ Positive Electrodes

Abstract

4-(Trimethylsiloxy)-3-pentene-2-one (TMSPO) is tested as an electrolyte additive to enhance Coulombic efficiency and cycle retention for the Li/ LiNi 0.5 Mn 1.5 O 4 (LNMO) half-cell and graphite/LNMO fullcell. TMSPO carries two functional groups, siloxane (−Si− O−) and carbon−carbon (CC) double bonds. It is found that the siloxane group reacts with hydrogen fluoride (HF), which is generated by hydrolysis of lithium hexafluorophosphate (LiPF 6 ) by impure water in the electrolyte solution, to produce 4-hydroxypent-3-ene-2-one (HPO). The as-generated HPO, as well as TMSPO itself, is electrochemically oxidized to form a protective surface film on the LNMO electrode, in which it is inferred that the carbon−carbon (CC) double bond initiates radical polymerization. The surface film derived from the TMSPO-added electrolyte shows a superior passivating ability to that generated from the pristine (TMSPO-free) electrolyte. The suppression of electrolyte oxidation enabled by the superior passivating ability offers two beneficial features to the half-cells and full-cells: the suppression of both HF generation and deposition of the resistive surface film on LNMO. As a result, the metal dissolution by HF attack on LNMO appears to be smaller by the addition of TMSPO. The cell polarization is also less significant because of the latter beneficial feature. In short, the bifunctional activity of TMSPO (HF scavenger and protective film former) allows an enhanced Coulombic efficiency and cycle retention to the half-cell and full-cell.

Organosilicon‐Based Functional Electrolytes for High‐Performance Lithium Batteries

“…Reproduced with permission. [44] Copyright 2019, American Chemical Society. Reproduced with permission.…”

“…[42,43] The effectiveness of organosilicon has been proved as a major component or merely an additive in liquid, gel polymer, and solid batteries. [44][45][46] Researchers from University of Wisconsin Madison conducted a lot of valuable researches on organosilicon electrolytes. They investigated the ionic conductivity, [47][48][49][50][51][52][53][54] security, [55][56][57] thermal and electrochemical stability [58][59][60][61] of organosilicon as the solvent and additive in electrolytes.…”

“…1) Chemical reaction, 2) possible electrochemical reaction (first charging), and 3) possible electrochemical reaction of TMSPO itself (first charging). Reproduced with permission [44]. Copyright 2019, American Chemical Society.…”

Enhancing the Electrochemical Performance of a High‐Voltage LiNi0.5Mn1.5O4 Cathode in a Carbonate‐Based Electrolyte with a Novel and Low‐Cost Functional Additive

“…[23] It is clearly seen that these peaks of LNMO cycled in STE + 0.5 wt %B Ab ecamew eaker than that in STE, which indicatest hat the intensity of PVDF signal is hided and the decomposition of LiPF 6 (LiPF 6 $LiF + PF 5 ,P F 5 + H 2 O! 2HF+ PF 3 O) [53,54] is suppressed with adding BA. The positive phenomenon suggestst hat CEI film has been formed on the LNMO surfacea fter cycled in STE + 0.5 wt %B A.…”

Regulation of Cathode‐Electrolyte Interphase via Electrolyte Additives in Lithium Ion Batteries

“…The working mechanism of bifunctional TMSPO is studied from two aspects: chemistry and electrochemistry (see Figure 8). [101] Studies have revealed that, on the one hand, as HF scavenger, TMSPO additive with bifunctional group can react with HF to generate HPO; on the other hand, the passivation protection layer derived from HPO and TMSPO can inhibit the continuous decomposition of electrolyte and the dissolution of transitional metal, thus improving the Coulomb efficiency and cycling performance of the battery. In addition, (pentafluorophenyl) diphenylphosphine (PFPDPP) as bifunctional additives was presented by Bolloju et.…”