MIT Develops Fast Charging Liquid Flow Batteries

An anonymous reader sends this from the MIT News office: "A radically new approach to the design of batteries, developed by researchers at MIT, could provide a lightweight and inexpensive alternative to existing batteries for electric vehicles and the power grid. The technology could even make 'refueling' such batteries as quick and easy as pumping gas into a conventional car (abstract). The new battery relies on an innovative architecture called a semi-solid flow cell, in which solid particles are suspended in a carrier liquid and pumped through the system. In this design, the battery’s active components — the positive and negative electrodes, or cathodes and anodes — are composed of particles suspended in a liquid electrolyte. These two different suspensions are pumped through systems separated by a filter, such as a thin porous membrane."

Nope, not a fuel cell. Nothing is consumed.

[IBitOBear]

A fuel cell basically "burns" (uses up) its reagent to make electricity directly.

This (according to the article) is a reversible reaction between two liquids, one acting as an anode and one acting as a cathode, where the reaction is bounded by a membrane. It is really more of the "capacitance gel" idea, only with two carries (which makes sense).

Think of it as two halves of a standard battery that can only interact when brought into proximity. While electrons (or maybe ions or something beyond my simple ability translate, not having seen the research or studied in the field) pass through the membrane by definition, the idea is that the charged medium is not part of the fixed assembly, so the fixed assembly (the reactor and membrane) is permanent while the charged part moves.

In a standard battery the anode and cathode are permanent parts of the battery. When the battery is discharged the whole battery is trashed. For instance, and alkaline battery is assembled in a charged state, the dissolving of the metals in the alkaline solution is what makes the voltage. Lead-acid batteries wear out because the lead is changed by the charging process (applying voltage in the presence of acid solution) and changed back by the discharge. This cycling slowly causes the lead to flake and degrade until there is either so much lead flakes in the battery that a cell shorts out because of the lead connecting the two parts, or the odd chemical impurities and available oxygen slowly make the lead into a chemical that will not react with the acid correctly any more.

In this arrangement the parts that would degrade are in the fluids, draining and replacing the fluids "assembles a new, fully charged battery". In this model the ideal of pulling into a service station and replacing your discharged battery pack with a new, charged one, becomes practical.

In the alternate, as a rechargeable battery the non-solid nature of the battery itself lets the battery be charged and cooled all at once. The anode and cathode material won't "flake" because it isn't sold to begin with. Plus nearly all of the anode and cathode material is used by weight, there is no "inner core" area acting as a superstructure. This should improve the energy density (how many kilowatt hours you can store per pound etc).

In the rechargeable battery usage the battery would probably need to be changed regularly, like an oil change, but _then_ one could probably use charged plates to separate/filter the degraded particles from the good ones, so the "battery" could be recycled in place instead of having to take it back to a factory.

There is a lot potential wins here, but it is _very_ unlike a fuel cell.