A dataset of Nitrile Solvent Structure induced Stable Solid Electrolyte Interphase for Wide-Temperature Lithium-ion Batteries

Sample preparationThe lithium salt LiPF6 and Electrolyte solvents EC, EP, FEC, AN, BN, VN, VC were purchased from Aladdin reagent network. All the solvents were mixed with molecule sieves to remove the trace water. The following electrolytes were prepared in the M. Braun MB-200MOD glovebox filled with Ar gas. EC group is 1.2 mol·L-1 LiPF6 in EC/EP/FEC with a volume ratio of 3:6:1 and with 1.5% of the weight ratio of VC added. Nitrile group is 1.2 mol·L-1 LiPF6 in nitrile /EP/FEC with a volume ratio of 3:6:1 and with 1.5% of the weight ratio of VC added. Electrochemical MeasurementsThe charge–discharge tests of LIBs were measured by the Neware CT-ZWJ-4’S-T-1U. The low-temperature and high-temperature electrochemical performance of full cells were measured in the constant temperature test box by high and low temperature alternating cycle test chamber. The graphite ||NCM523 pouch cell (no electrolyte) were provided by Hunan Boltpower New Energy Co., Ltd. The graphite and NCM523 were provided by Jilin Juneng Advanced Carbon Materials Co., Ltd. and Green Beauty (Wuxi) Energy Materials Co., Ltd., respectively. The anode is composed of 94.5% graphite, 2% SP, 3% LA133, 0.5% CMC, and the cathode is composed of 94.2% NCM523, 3% SP, 0.6% ECP-600JD, 2.2% PVDF. The mass loading of the anode was 8.6±0.1 mg·cm2, while that of the cathode was 17.6±0.2 mg·cm2. The electrolyte injection content of each full cell is 4.5 g. After electrolyte injection, the pouch cell was left to stand for 24 hours for formation. The formation process was as follows: charge at a constant current of 0.1C to 4.2V, followed by discharging to 3.0V. Material characterizationThe viscosity of the electrolyte was measured using a falling ball viscometer (Anton Paart Lovis 2000 M). Nuclear magnetic resonance (NMR) spectroscopy was performed on the electrolyte using a Bruker 600 MHz spectrometer in Germany. The ion diffusion coefficient of the electrolyte was obtained through the final processing of the NMR data. The ionic conductivity of the electrolyte was measured by the conductivity meter (LeiCi DDS-307A) at temperatures from 25℃ to -50°C. FT-IR spectra were collected by Thermo Scientific Nicolet iS50 FT-IR. XPS were tested by Kratos’s AXIS SUPRA+ (use Al target material, voltage 15kV, full spectrum current 5mA, power 75W, fine spectrum current 10mA, power 150W). SEM tests were collected by Jeol JSM-IT700HR. TEM images were collected by JEM-F200 from JEOL (shooting voltage: 200kv, high resolution magnification: 1.5 million times). Computational DetailDFT calculations were performed to optimize geometries of solvent molecules using Gaussian 16 package at B3LYP/6-311+G(d,p) level of theory. Atomic partial charges on were calculated using ChelpG method. Atomistic force field parameters are taken from ref53, and the cross-interactions between different atom types are obtained from Lorentz-Berthelot combination rule.Two modeling systems are constructed. Atomistic simulations were performed using GROMACS package with periodic boundary conditions. The atom motions were integrated using Verlet integration algorithm with a time step of 1.0 fs. A cutoff radius of 1.6 nm was set for short-range vdW interactions and electrostatic interactions. PME method was used to handle long range electrostatic interactions in reciprocal space. Simulation systems were energetically minimized and thereafter annealed from 600 to 300 K within 10 ns. These systems were equilibrated in NPT ensemble for 20 ns using a Nosé-Hoover thermostat and a Parrinello-Rahman barostat with time coupling constants of 0.4 and 0.2 ps, respectively. Atomistic simulations were further performed in a NVT ensemble for 50 ns for further structural and dynamical analysis.Representative structures extracted from atomistic simulations were adopted to perform DFT calculations using Gaussian 16 software at the same level of theory with Grimme’s-D3 dispersion correction to obtain LUMO-HOMO energies and de-solvation energies.