High-Voltage LiNi_0.5Mn_1.5O₄ Cathode Stability of Fluorinated Ether Based on Enhanced Separator Wettability

Abstract

Influence of separator wettability toward nonaqueous electrolyte was investigated in lithium-ion batteries using high-voltage LiNi 0.5 Mn 1.5 O 4 cathode. A fluorinated ether of 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE) was introduced as a co-solvent into the control electrolyte and polyolefin separator wettability toward nonaqueous electrolyte was effectively enhanced. Even though conductivity of the electrolyte bulk decreased after HFE was introduced, ionic conductivity of the electrolyte-soaking separator increased due to the enhanced separator wettability. From cycling stability of the half cells using high-voltage LiNi 0.5 Mn 1.5 O 4 cathode, all electrolytes containing 10%, 20% and 30% HFE have superiority to the control electrolyte, and the 20% HFE containing electrolyte is the optimal. Microscopical analysis revealed that oxidative decomposition of HFE-containing electrolyte on the LiNi 0.5 Mn 1.5 O 4 cathode was suppressed effectively with the thinner cathode electrolyte interface than that in the control electrolyte. In Li 4 Ti 5 O 12 |LiNi 0.5 Mn 1.5 O 4 full cells, the 20% HFE containing electrolyte exhibited the enhanced cycling stability and rate capability compared to the control of 1 mol L −1 LiPF 6 /propylene carbonate. This work here reveals the effect of fluorinated ether co-solvent on separator wettability and further the superior separator wettability is critical to the oxidation stability of the electrolyte in lithium-ion batteries using high-voltage cathode.

Synergistic Effect of Fluorinated Solvents for Improving High Voltage Performance of LiNi0.5Mn1.5O4 Cathode

“…One small but broad redox peak near 4.0 V corresponds to the Mn 4+ /Mn 3+ redox pair, and the sharp redox peak around 4.7 V is related to reversible conversion of Ni 4+ /Ni 2+ couple. 22,23 The discharge profiles of the LNMO/Li cell in various electrolytes deliver two voltage plateaus at around 4.0 and 4.75 V (Fig. 2b), which is well consistent with the above CV result.…”

High-Voltage-Compatible Dual-Ether Electrolyte for Lithium Metal Batteries

“…A comparative evaluation was performed with the optimal composition determined based on the above-mentioned results and the carbonate electrolyte, the FEC/DEC system, used in the current LIBs. Since the fluorinated ether has higher oxidative stability than linear carbonates and even FEC, and the compatibility with the lithium metal is much better in DME-based electrolyte systems than carbonates, − we believe that our dual-solvent electrolyte system will show better performance in the high-voltage lithium metal full cell than carbonate-based electrolytes. Figure shows the resistance change according to the state of charge (SOC) in the pouch-type LCO/Li full cell of the two electrolytes.…”

Composition Modulation of Ionic Liquid Hybrid Electrolyte for 5 V Lithium-Ion Batteries

“…This continuous and well-adhered protective layer is considered crucial for the great cycling stability of the electrode. The thin, compact, and robust CEI layer formed in the latter electrolyte can be attributed to less oxidative decomposition of the electrolyte and less LNMO dissolution, which led to less reaction products on the electrode surface. , In the figure inset, the lattice fringes of LNMO with a d -spacing of 0.47 nm (corresponding to (111)) can be clearly observed after 300 charge–discharge cycles, indicating that the spinel crystal structure was highly preserved.…”