2.3. Electrochemistry testsFor the

2.3. Electrochemistry testsFor the electrochemical test, 70wt % of active material, 10wt % of acetylene black (AB) and 20wt % of polyvinylidene fuoride (PVDF) were first mixed evenly in N-methyl-2-pyrrolidinone (NMP). The obtained blended slurry was then cast onto a copper foil current collector and dried for>10h (110°C) in vacuum. The electrode sheet was tailored into disks of Ф10 mm and assembled in CR2032 coin-type cells with lithium metal as the counter electrode in an Ar-filled glove box. The loading mass of the active material in the electrode was 1–1.5mg (area of 0.785cm2). The mixed solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (1: 1: 1 by volume) containing 1M LiPF6 was used as the electrolyte. A Celgard 2400 microporous membrane served as the separator. Galvanostatic charge/discharge measurements were carried out in the voltage window of 0.01–3V (vs. Li/Li+) using a battery test system (CT2001A, Land). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were performed on a Bio-Logic VSP electrochemical workstation. CV curves were recorded with increasing scanning rates from 0.1 to 1mVs−1 (0.01–3V). EIS were collected at open circuit voltage (OCV) of 2V after three cycles of activation in the frequency range of 100 kHz–0.01Hz (amplitude of 10mV). All the electrochemical tests were performed at ambient temperature (∼25°C).