Tailoring Electrolyte Dehydrogenation with Trace Additives: Stabilizing the LiCoO₂ Cathode beyond 4.6 V

Abstract

Extending the charge cutoff voltage of cathode (e.g., LiCoO2) is a promising way to increase the energy density of Li-ion batteries, but critical challenges lie in the threats triggered by structural distortion and an unstable electrode/electrolyte interface. The general approach to enhance the stability of the cathode/electrolyte interface (CEI) consists of replacing the decomposition or sacrificing sources of carbonate solvents (e.g., EC) with concentrated or fluorinated electrolyte strategies. Herein, without following typical replacement strategies, we introduce a trace electrolyte additive and refine the dehydrogenation process of the original carbonate solvents, resulting in an enhanced CEI and long-term cycling stability of LiCoO2 up to 4.65 V. We demonstrate that cathode structure distortion, LiPF6 hydrolysis, and Co dissolution and shuttling have been simultaneously restrained. With the achievement of a long-life 250 and 270 Wh/kg pouch cells (assembled with a commercial graphite and SiO anodes), the refinement of the “old-school” electrolyte additive strategy opens up avenues toward the design of practical high-voltage full-cell systems.

Enabling interfacial stability of LiCoO2 batteries at an ultrahigh cutoff voltage ≥ 4.65 V via a synergetic electrolyte strategy

“…Aer 300 cycles, the LCO suffers accelerated growth of electrode over-potential and severe capacity decay in the baseline electrolyte at 1C (capacity of 41 mA h g −1 and retention of 18.4%). Although higher capacity (156 mA h g −1 ), retention (69.6%), and CE (99.3%) are evidenced with the optimized electrolyte, the LCO delivers the excellent cycling performance (capacity: 170 mA h g −1 ; retention: 75.9%; CE: 99.7%) under the same test condition with the upgraded electrolyte, which outperforms most electrolyte additives and recipes (Table S1 † [33][34][35]66 ) and the modication of the LCO material (Table S2 † 25,52,67,68 ) investigated for highvoltage LCO batteries, as summarized in Fig. 8d.…”

Interfacial Regulation and Hydrogen Fluoride Capture Enabled by Allyltrimethylsilane as Multifunctional Electrolyte Additive for Li/LiNi0.8Co0.1Mn0.1O2 Batteries

“…Obviously, the cell with ATMS exhibited a resistance lower than that of the counterpart without additive, confirming that the Li + deposition is facilitated by the ATMS-derived SEI film. Conclusively, the preferential oxidation/reduction of ATMS will affect the reactions of the carbonates due to the unsaturated carbon–carbon double bond (CC), and then the properties of the resulting CEI/SEI film are tuned. , …”

“…Conclusively, the preferential oxidation/ reduction of ATMS will affect the reactions of the carbonates due to the unsaturated carbon−carbon double bond (C�C), and then the properties of the resulting CEI/SEI film are tuned. 40,41…”

Lithium Difluorophosphate as a Widely Applicable Additive to Boost Lithium‐Ion Batteries: a Perspective

“…[1,2] Most state-of-the-art electrolyte additives are sacrificed during interlayer formation. [3][4][5] It is noted that the cyclic voltammetry (CV) used to detect the reduction of LiDFP should be conducted at a low sweep rate, e.g., 5 mV s −1 , or the reduction peak cannot be obtained and the wrong conclusion that no reduction occurs might result. [29] In addition, LiDFP can increase the solvent stability by increasing the LUMO energy of the carbonate solvent-DFPanion cluster through the electrostatic inductive effect in the solvent-anion cluster.…”