All-solid-state passive direct methanol fuel cells with great orientation stability and high energy density based on solid methanol fuels

Passive direct methanol fuel cell (DMFC) is considered as a promising power source due to its high theory energy density. However, fuel, as the only non-solid part of the passive DMFC, has some disadvantages. Hence, we develop all-solid-state passive DMFCs based on solid methanol fuels. Solid methanol fuels prepared by combing methanol solution and absorbent material, different from liquid fuels and gaseous fuels, are employed as fuels on the anode side of passive DMFC. All-solid-state passive DMFC shows a great orientation stability. The average P-max (maximum power density) of the cell at five orientations is 17.2 mW cm(-2) with a standard deviation of 1.42 x 10(-4). Even when the anode is facing downward, P-max is only 1.4% lower than that of the cell with the anode facing up. The all-solid-state passive DMFC also reaches a power density of 20.5 mW cm(-2), which is 30.8% higher than that of the traditional liquid-feed passive DMFC. Besides, using the same weight of fuel, the discharge energy of all-solid-state passive DMFC is 88% higher than that of liquid-feed passive DMFC. Because of nonflowing properties of solid methanol, all-solid-state passive DMFCs avoid liquid leakage in the cells, which is safer and more portable.