Electrochemical Measurements

The electrochemical performance of NiCo₂S₄/N-CNT samples was evaluated in CR 2032 coin-type cells. To prepare the electrode slurry, 70 wt% of NiCo₂S₄/N-CNT composite, 15 wt% of carbon black (Super P), and 15 wt% of polyvinylidene fluoride (PVDF) binder were mixed in 1-methyl-2-pyrrolidinone (NMP). The slurry was uniformly spread onto a Cu foil using a doctor blade technique and then dried at 70 °C for 8 h in air. Circular disk electrodes were cut after drying, and the cells were assembled in a high-purity Ar-gas (99.9995%) filled glove box (MBraun). The mass loading of NiCo₂S₄/N-CNT in the electrodes was about 2 mg cm^–2. Pure Li foils were used as reference and counter electrodes, and microporous polypropylene Celgard 2300 was used as a separator. The electrolyte was 1 mol L^–1 LiPF₆ (Aladdin, CAS number: 21324-40-3) in a mixture of ethylene carbonate (EC, Aladdin, CAS number: 96-49-1) and dimethyl carbonate (DMC, CAS number: 616-38-6) with a volume ratio of 1:1. The galvanostatic charge/discharge measurements were conducted using a multichannel battery testing system (Neware BTS4000) at a potential window of 0.01–3.00 V (vs. Li⁺/Li). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were performed using an electrochemical workstation (Princeton, VersaState4).