Thermally regenerative ammonia batteries (TRABs) show viable potential for harvesting abundant low-grade waste heat as high-power electricity. However, the ammonia brings about a large pH difference between the catholyte and anolyte, leading to self-discharge and severe energy decay. Here, an electrolyte decoupling strategy is proposed for ammonia batteries to restrain the self-discharge and enhance energy density as well as power generation at high temperatures. The self-discharge by ion cross contamination is observed visually as a colour evolution of the interlayer solution, and a transition of the principal cathodic reactant from Cu²⁺ to Cu(NH₃)₄ ²⁺ exists during discharging, which signals the beginning of performance degradation. The results demonstrate that decoupled Cu/Zn-TRABs with double and triple-membrane designs improve the energy density by 45–50%, mainly due to the delay of the transition region. The power density of the decoupled Cu/Zn-TRABs is reduced at high currents, but with concentration optimization or elevated temperatures, it is able to be promoted significantly. With an energy density of 1034 W h m⁻³ obtained by a decoupled Cu/Zn-TRAB with double-IEM (ion exchange membrane) design, a thermoelectric conversion efficiency of 1.86% (15.6% relative to the Carnot efficiency) is achieved at a condenser temperature of 16 °C.

For security issue of alkane used in Organic Rankine Cycle, a new model to evaluate the upper flammability limits for mixtures of alkanes, carbon dioxide and air has been proposed in present study. The linear relationship was found at upper flammability limits between molar fraction of diluent in alkane-CO2 mixture and calculated adiabatic flame temperature. The prediction ability of the variable calculated adiabatic flame temperature model that incorporated the linear relationship above is greatly better than the models that adopted the fixed calculated adiabatic flame temperature at upper flammability limit. The average relative differences between results predicted by the new model and observed values are less than 3.51% for upper flammability limit evaluation. In order to enhance persuasion of the new model, the observed values of n-butane-CO2 and isopentane-CO2 mixtures measured in this study were used to confirm the validity of the new model. The predicted results indicated that the new model possesses the capacity of practical application and can adequately provide safe non-flammable ranges for alkanes diluted with carbon dioxide.