4. Experimental Section
Materials and electrode preparation: the acrylic acid derivative
terpolymer (LA136D, Chengdu Indigo, China), polyvinylidene fluoride
(PVDF) binder (Arkema, HSV900), butadiene-styrene rubber (SBR) emulsion
(JSR, 104A),
Fe0.5Co0.5S2, LiCl-KCl
molten electrolyte and LiB alloy were commercially available and used as
received. The LA136D-based cathode slurry was prepared by mixing LA136D
and Fe0.5Co0.5S2 cathode
materials in a planetary centrifugal mixer and stirred for 1.5 h, the
mass ratio of LA136D and
Fe0.5Co0.5S2 is
controlled at 1:99.The same procedure and material ratio are applied in
PVDF and SBR cathode slurry. The slurry was coated on graphite paper
current collector (100 μm) by blade casting. The electrode mass loading
was controlled at 35 mg cm-2 by adjusting the casting
thickness and solid content of the slurry. The thin film electrode
thickness after the calendar is about 100 μm. The contrast pellet
electrode was prepared by pressed-pellet technology with a thickness of
400 μm (including 100 μm graphite paper current collector).
Binder and thin film electrode characterization: the thermal
properties testing was conducted on a thermal analysis system with a
heating rate of 10 °C min−1 from 30 °C to 1000 °C in
N2. The Fourier Transform Infrared (FTIR) spectroscopy
test of LA136D before and after 550 °C treatment is conducted by using
Attenuated Total Reflection (ATR) model. The gaseous products of LA136D
were conducted on TG-FTIR with a heating rate of 10 °C
min−1 from 30 °C to 600 °C in N2. The
electrode peeling test was conducted. The microstructure morphology was
observed by SEM.
Electrochemical performance characterization: the thermal battery
single cells were assembled by using a pellet cathode and thin film
cathode respectively. The cathode material is
Fe0.5Co0.5S2, the molten
electrolyte is LiCl-KCl, and the anode material is LiB alloy. The
compressed pressure used for cell construction is about 0.5 t
cm−2. The single cells discharge test was conducted in
an Ar2 atmosphere environment, with a temperature of 500
°C and with a compress of 20 N cm−2. The discharge was
conducted by a LAND battery test system (Wuhan LAND, China). The current
used for single cells capacity characterization is controlled at 0.2 A
cm−2 and the cut-off voltage is 1.6 V. The pulse
discharge was conducted with a consistent current density of 0.1 A
cm−2 and a pulse current density of 1 A
cm−2. The thermal battery stacks was assembled in a
dry air room and a pulse discharge pattern of 0.05 A
cm−2 (15s)-0.2 A cm−2(5s)-0.05 A
cm−2(5s)-0.5 A cm−2(5s)-0.05 A
cm−2 (5s)-0.2 A cm−2(5s).
Thermal battery inner temperature and pressure characterization:the column thermal battery stainless steel shell was pre-processed with
two holes on the ends for signal transfer. The temperature sensor was
set on the thermal battery stack surface and can work normally at 600
°C. The pressure sensor was put at the ends of the column thermal
battery, outside the insulation layer. The holes were sealed by a
high-temperature ceramic binder after the battery assembly.