4.2 Electrochemical Measurements
Commercial 18650-type cylindrical batteries manufactured by Tianjin
LiShen Battery Co., Ltd were dismantled in an argon-filled glove box,
and pieces of the
LiNi0.5Co0.3Mn0.2O2(NCM532) cathodes were taken out. A bare Cu foil was cut into a 12 mm
diameter disc used as the anode current collector. A 2400-type Celgard
separator (25 μm thick) and a glass fiber separator were used as the
separator. Cu||Li half-cells and full AFLBs with
NCM532 cells were investigated in Swagelok cells with 75 μL of
electrolytes. The pure commercial electrolyte of LiPF6in EC/DEC/DMC 1:1:1 v/v/v ratio is denoted as E1 electrolyte. The
optimized electrolyte by adding 2 wt % LiAsF6 and FEC
into the pristine E1 electrolyte (LiPF6 in EC/DEC/DMC
1:1:1 v/v/v ratio) was named E2 electrolyte. All measurements were
performed in an argon-filled glove box (<0.1 ppm oxygen and
<0.1 ppm H2O). All electrochemical tests were
carried out in an MKF120 climate chamber (Binder, Germany) using a VMP3
potentiostat (Bio-Logic, France). The amount of Li metal to be plated
onto the copper surface was controlled by restricting the time. The
stripping was a voltage-controlled (0.1 V) process with a constant
current density of 0.5 mA·cm-2. Galvanostatic
(dis-)charge cycling of NCM532||Cu cells was performed
in the voltage range of 3.0–4.3 V at charge-discharge rates of 0.1C.
Cyclic voltammogram (CV) tests were operated in a voltage window of
3.0–4.3 V vs. Li+/Li at a scan rate of 0.1 mV
s–1. Electrochemical impedance spectroscopy (EIS)
tests were conducted with an amplitude of 10 mV in the frequency range
of 10–100 kHz.