Figure 2. The simulation of gas pressure resistance of the
thermal battery. (a) The schematics (2D) of the internal configuration
of Φ 83×83mm column thermal battery with 40 single-cells in the
series; (b) the simulation of the Von Mises Stress (MPa) brings to the
thermal battery stainless-steel shell under 0.3 MPa internal gas
pressure, according to the simulation, the highest stress brings to
stainless steel is about 220 MPa; (c) the relationships between thermal
battery internal gas pressure (aroused by the thermal decomposition of
binder), binder content in the cathode, and the proportion of volatiles
generated in binder thermal decomposition at 550 °C.
Commonly, the volatile products in polymer binder pyrolysis are small
molecules which with a similar average molecule weight. Here we
presumably set an M of 25 according to the volatile products of PVDF and
SBR binder in pyrolysis, as shown in Figure 1 (b) and
(c).[26,27] Combined with equation (1), we can
reach the quantitative relationship between Pb,χ, and ψ , as shown in Figure 2 (c). From Figure 2 (c), to
ensure the Pb lies in the security zones, the binders
with high ψ should have low χ , e.g., a binder with
a ψ of 80wt % the χ in the cathode should not
exceed 1.2wt %. In contrast, the binders with low ψ have a
wilder binder content space for choosing. e.g. binder with aψ of 40wt % the binder content limit is 2.3wt %.
From the simulation, we can get a guideline for selecting and designing
binders for thin-film TBs.