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In this study, a Ni-Co-Mn-Cd-based precursor was synthesized using a solvothermal method and the Li(Ni0.6Co0.2Mn0.2O2)xCd1-xO2 cathode materials were prepared using a high-temperature solid-phase method. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to determine the morphology, structure, elemental composition, and electronic state of the pristine and Cd-doped cathode materials. The electrochemical tests indicated that the Cd-doped samples exhibited better electrochemical performance than the pristine material; specifically, at a doping amount of 0.01 mol, the initial discharge capacity was 186.3 mAh g−1 with a capacity retention of 87.49% after 200 cycles at a current rate of 0.5 C and a capacity retention of 72.43% after 300 cycles at a current rate of 2 C, whereas the pristine material only had an initial capacity of 173.2 mAh g−1 and a capacity retention of 61.25% and 41.09% for the same current rate and cycle number, respectively. In addition, at 8 C, the discharge capacity was 129.8 mAh g−1 for the Cd-doped samples but only 119.6 mAh g−1 for the pristine material. The enhanced electrochemical performance was attributed to the in situ doping modification during the synthesis process of the precursor. This approach effectively stabilized the crystal structure, improved the electronic conductivity of the material, and reduced the impact of the hydrofluoric acid (HF) on the electrode surface due to the generation of CdF2 during the cycle process. [ABSTRACT FROM AUTHOR]

Herein, we present the use of lithium tetrafluoroborate (LiBF4) as an electrolyte salt for wide-temperature electrolytes in lithium-ion batteries. The research focused on the application of blend salts to exhibit their synergistic effect especially in a wide temperature range. In the study, LiCoO2 was employed as the cathode material; LiBF4 and lithium difluoro(oxalate)borate (LiODFB) were added to an electrolyte consisting of ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC). The electrochemical performance of the resulting electrolyte was evaluated through various analytical techniques. Analysis of the electrical conductivity showed the relationship among solution conductivity, the electrolyte composition, and temperature. Cyclic voltammetry (CV), charge-discharge cycling, and AC impedance measurements were used to investigate the capacity and cycling stability of the LiCoO2 cathode in different electrolyte systems and at different temperatures. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were applied to analyze the surface properties of the LiCoO2 cathode after cycling. The results indicated that the addition of a small amount of LiODFB into the LiBF4-based electrolyte system (LiBF4/LiODFB of 8:2) may enhance the electrochemical performance of the LiCoO2 cell over a relatively wide temperature range and improve the cyclability of the LiCoO2 cell at 60 °C. [ABSTRACT FROM AUTHOR]