Low-Volatile Binder Enables Thermal Shock-Resistant Thin-Film Cathodes for Thermal Batteries

Manufacturing thin-film components is crucial for achieving high-efficiency and high-power thermal batteries (TBs). However, developing binders with low-gas production at the operating temperature range of TBs (400-550 degree celsius) has proven to be a significant challenge. Here, we report the use of acrylic acid derivative terpolymer (LA136D) as a low-volatile binder for thin-film cathode fabrication and studied the chain scission and chemical bond-breaking mechanisms in pyrolysis. It is shown LA136D defers to random-chain scission and cross-linking chain scission mechanisms, which gifts it with a low proportion of volatile products (psi, psi = 39.2 wt%) at even up to 550 degree celsius, well below those of the conventional PVDF (77.6 wt%) and SBR (99.2 wt%) binders. Surprisingly, LA136D contributes to constructing a thermal shock-resistant cathode due to the step-by-step bond-breaking process. This is beneficial for the overall performance of TBs. In discharging test, the thin-film cathodes exhibited a remarkable 440% reduction in polarization and 300% enhancement in the utilization efficiency of cathode materials, while with just a slight increase of 0.05 MPa in gas pressure compared with traditional "thick-film" cathode. Our work highlights the potential of LA136D as a low-volatile binder for thin-film cathodes and shows the feasibility of manufacturing high-efficiency and high-power TBs through polymer molecule engineering.