Enhancement of the High-Temperature Rate Performance of LiFePO4 Batteries via the Alteration of the Solvation Structure and Cathode–Electrolyte Interface Stability using Composite Lithium Salts

This dataset originates from the systematic experimental characterization, electrochemical evaluation, and theoretical simulation of a series of LiPF₆-based composite lithium salt electrolytes (CLSE, denoted as E1–E5) and their matching LiFePO₄ (LFP) half-cells, covering electrolyte physicochemical properties, electrochemical performance, interfacial micro-morphology, and solvation structure information. The data generation process is divided into four stages: first, the preparation of five groups of electrolytes with different LiTFSI/LiDFOB ratios and the assembly of corresponding Li||Li symmetric cells, Li||Cu asymmetric cells, and LFP/Li half-cells; second, the acquisition of physicochemical data including variable-temperature ionic conductivity, viscosity, and Li⁺ transference number (tLi⁺); third, the electrochemical testing of rate performance, long-cycle stability, electrochemical impedance spectroscopy (EIS), and distribution of relaxation times (DRT) at 30–60 °C; fourth, the microstructural and compositional characterization using NMR, SEM, TEM, AFM, ex-situ XPS, and molecular dynamics (MD) simulation.The data processing adopts standardized experimental and fitting methods: raw electrochemical data is collected in real time by the battery test system and electrochemical workstation, then imported into Origin 2023 for plotting and fitting; EIS data is fitted by ZView software with equivalent circuit model; XPS spectra are peak-fitted and analyzed by XPS Peak software; micro-morphology images are processed by ImageJ for dimensional and roughness statistics; MD simulation is carried out via GROMACS software to calculate the coordination number of Li⁺ solvation sheath, and ⁷Li NMR chemical shift data is calibrated and sorted by the supporting software of the NMR spectrometer. The experimental equipment and tools include a multi-channel battery test system, electrochemical workstation (for potentiostatic polarization and EIS/DRT testing), rotational rheometer (for viscosity test), conductivity meter, ⁷Li NMR spectrometer, scanning electron microscope (SEM), transmission electron microscope (TEM), atomic force microscope (AFM), X-ray photoelectron spectrometer (XPS), and molecular dynamics simulation platform.In terms of temporal and spatial information, the electrochemical performance data covers a temperature range of 30–60 °C with a temperature resolution of 10 °C; the long-cycle test includes 500 cycles at 5 C/60 °C and 300 h of Li||Li symmetric cell cycling at 1 mA cm⁻²; the micro-characterization data involves spatial scales from nanometer to micrometer, with TEM having a spatial resolution of ≤ 1 nm, AFM for surface roughness detection at the sub-nanometer scale, and SEM for observing electrode surface morphology at 1–5 μm scale. The tabular data mainly includes physicochemical parameter statistics and EIS fitting results, with a total of 5 groups of sample records (E1–E5), and the column labels are electrolyte number, ionic conductivity (mS cm⁻¹), viscosity (mPa·s), Li⁺ transference number (dimensionless), charge transfer resistance (Ω cm⁻²), activation energy (eV), capacity retention rate (%), etc., with clear international standard units.No data missing exists in this dataset, as all five electrolyte groups have completed the full-dimensional test and characterization without sample failure or test interruption. The experimental error is controlled within a reasonable range: all electrochemical tests are repeated with 3 parallel samples, and the relative error is less than 5%; the temperature control accuracy of the physicochemical test is ±0.1 °C, and the instrument system error of SEM/TEM/XPS is less than 3%, which is derived from the inherent accuracy of commercial testing equipment and has no impact on the conclusion of the study.The dataset consists of multiple types of files: raw electrochemical test files in .txt/.csv format (recording voltage, capacity, current, time and impedance data), micro-characterization spectrum files in .xy/.dat format (NMR chemical shift, XPS peak intensity, TEM/AFM size data), MD simulation data files in .xlsx format (coordination number statistics), and sorted summary tables in .xlsx format (physicochemical parameters and cycle performance). The data can be opened and processed by common scientific software such as Origin 2023, Microsoft Excel, ZView, ImageJ and GROMACS, all of which are official commercial or open-source scientific computing software.