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.