Construction of a Stable LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) Cathode Interface by a Multifunctional Organosilicon Electrolyte Additive

Abstract

It is still a big challenge to stabilize a Ni-rich cathode interface at high current rate and a long-term cycle in the present Li-ion battery for electric vehicles. In this work, N,O-bis(trimethylsilyl)acetamide (BSA) is utilized as a multifunctional electrolyte additive to stabilize the LiNi 0.8 Co 0.1 Mn 0.1 O 2 cathode interface and enhance its electrochemical performance. After 200 cycles, the LiNi 0.8 Co 0.1 Mn 0.1 O 2 /Li cell at 1C rate with 0.5% BSA shows improved capacity retention of 86%, while it shows only 69.4% with the baseline electrolyte. When the discharge rate is increased to 2C, the LiNi 0.8 Co 0.1 Mn 0.1 O 2 /Li cell with BSA additive shows improved capacity retention of 72.6% after 400 cycles, while the counterpart is only 49.5%. The experimental results show that HF and H 2 O can be scavenged by BSA, and the hydrolysis of LiPF 6 is reduced. Moreover, the BSA additive can be preferentially oxidized during the charging process and form a robust, uniform electrode/electrolyte interface film on the NCM811 cathode surface. Consequently, a better CEI film can suppress the electrolyte decomposition, improve cathode interface stability, and alleviate transition metal ions dissolution.

Benzoic Anhydride as a Bifunctional Electrolyte Additive for Hydrogen Fluoride Capture and Robust Film Construction over High‐Voltage Li‐Ion Batteries

“…In order to investigate the HF capture ability of the BA additive in the electrolyte, 19 F and 31 P NMR spectra were recorded using the baseline and 1.0 wt % BA-containing electrolytes by adding 2000 ppm H 2 O after storing at 55°C for 96 h. Figure 1a,b shows the 19 F NMR spectra of electrolytes without and with 1.0 wt % BA. The main doublet peaks located at À 72 and À 73 ppm are attributed to LiPF 6 in both electrolytes.…”

“…Similarly, for 31 P NMR spectra, the peaks of PO 3 F 2À (À 5.7 and À 13.3 ppm) and PO 2 F 2 À (À 12.3, À 19.8, À 27.6 ppm) [18] recorded in baseline electrolyte disappeared in the electrolyte with BA (Figure 1c,d), in agreement with the 19 F NMR results. The thermodynamic reactivities of BA with H 2 O and HF are calculated by DFT method, [19] as displayed in Figure 1e. The Gibbs free energies (ΔG) for reactions of BA with H 2 O and HF are À 22.10 and À 18.84 kcal mol À 1 , respectively, indicating that H 2 O and HF can be rapidly eliminated by additive BA.…”

“…The 19 F and 31 P NMR spectroscopy (Advance 400, Bruker, Germany) study was conducted to analyze the chemical reactions between BA and baseline electrolyte with H 2 O (2000 ppm). The NCM811 cathode disassembled from the half-cells after 200 cycles was washed several times with dimethyl carbonate (DMC) to remove the residual electrolyte, and then dried in the glovebox overnight prior to characterization.…”

Dual‐Carbon Lithium‐Ion Capacitors: Principle, Materials, and Technologies

“…In this regard, the additives capable of scavenging H + and H 2 O formed by the oxidation of oxygen functional groups in the ACs and electrolyte solvents are expected to suppress capacity fade and gas generation, and beneficial to stabilizing LiPF 6 salt. The examples for such additives are, but not limited to, aromatic isocyanate, [40] trimethylsilyl isothiocyanate, [41] N,N‐diethylamino trimethylsilane, [42] and N,O‐bis(trimethylsilyl)acetamide [43] . The additives capable of forming robust SEI with the carbonaceous NEs are expected to stabilize capacity retention and suppress growth of the internal resistance and gas generation.…”

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

“…As the scavenger of HF and H 2 O hidden in electrolyte, BSA and the derived CEI protective layer can suppress the hydrolysis reaction of LiPF 6 and the decomposition of the electrolyte, thus the electrochemical stability can be improved. [89] In addition to self-sacrificing electrolyte additives, there is also an unconventional additive that has received great attention. Cui et.al reported an useful electrolyte additive for NCM 811 electrode, methyl diphenylphosphonate (MDPO).…”