Flow batteries
流体电池

All pumped up
全都泵起来

Dec 16th 2009
From Economist.com

Batteries that can be “refuelled” quickly could give electric cars greater range
可以快速“中途加油”的电池可以使电动汽车跑得更远。


PROTOTYPES of new electric vehicles that are soon to go on sale show lots of promise. They are clean, quiet and provide nippy performance. But even with advances in power systems and improved lithium-ion batteries, their range on a single charge is limited—and recharging can take hours. However, a team of German engineers thinks it may be possible to produce a battery for an electric car which can be recharged in minutes, in a manner similar to refuelling a car with petrol.
新款电动车的原型很快就要上市并带给我们更多的承诺。他们清洁、安静并提供适宜的性能。但是即使是先进的动力系统和改善的锂离子电池，还是受到一次性充电 电池的限制-他们再充电的时候需要耗费数小时。然而，一个德国的工程师团队认为可以生产处一种类似汽车中途加油方式的电池，可以在几分钟内反复充电。

The technology that Jens Noack and his colleagues at the Fraunhofer Institute for Chemical Technology in Pfinztal are experimenting with is called a flow battery. All batteries work by converting electrical energy into chemical energy during charging, and then converting it back into electricity as the battery is discharged. Traditional batteries store the chemical energy in two solid electrodes; flow batteries store it in the liquid electrolyte in which the electrodes are immersed. The electrolyte is stored in an external tank and pumped through the battery’s cells to convert chemical energy into electricity. When the electrolyte has been discharged, it can be pumped back through again while a current is applied in order to recharge it.
位于Pfinztal 的Fraunhofer学院化学工艺系的Jens Noack和他的同事将所从事的实验称之为流体电池。所有电池是靠充电的同时通过将电能转换为化学能而工作，随后，当电池放电的时候，再将化学能转化为电 能。传统的电池是在两根固定电极中储存化学能的；而流体电池则将其储存在浸入电极，即液体电解质中。电解液储存在容器外然后泵过电池并将化学能转换为电 能。当电解液被释放的时候，它又可以再泵回来，此时产生的电流将被应用达到反复充电的目的。

There is, though, another way to recharge a flow battery: pump out the discharged electrolyte and replace it with a solution that has been recharged elsewhere. In a car, says Mr Noack, this process could be done at a garage in not much more time than it takes to fill up a conventional car with petrol.
然后，还有一种方法可以使流体电池重新充电：将释放电量的电解质溶液抽空，然后重新充入溶液。Noack先生说，这个过程比在加油站里给传统汽车加满汽油 比费不了多长时间。

Such batteries are already in use, but mainly in stationary applications. So-called “redox” flow batteries are sometimes used to balance grid power and store energy from wind turbines or solar panels. The term “redox” refers to the electrochemical potential between two different electrolytes. These are pumped through a cell, separated by a membrane. Ions passing through the membrane, as one solution is reduced and the other oxidised, create a current which powers an external circuit.
这种电池已经使用，但主要应用于静止设备中。这种所谓的“氧化还原”流体电池通常用来平衡并网发电以及从风力涡轮或太阳能板中储存电量。术语“氧化还原” 来自两种不同电解质之间的电化学电势。电势在电池间泵过，并被薄膜所分离。离子通过薄膜，此时一种溶液减少而另一种被氧化，便产生出了额外电流。

One of the most efficient redox flow batteries was developed in the 1980s at the University of New South Wales in Australia. It uses vanadium in both electrolytes. Vanadium can exist in solution in several different oxidation states. Using the same element in both electrolytes avoids contamination problems. Another advantage of a vanadium redox flow battery is that its capacity is limited only by the size of the tanks used to store its electrolytes.
20世纪80年代，xxx率的氧化还原流体电池在澳大利亚的New South Wales大学发展。当时两种电解质均使用了钒化合物。相同元素的使用避免了污染的问题。钒氧化还原流体电池的另外一个优点是：它的容量只受制于储存电解 质溶液容器的尺寸。

An electric car, however, cannot carry two large tanks. In practical terms, a redox flow battery would be capable of powering an electric car for only about a quarter of the distance of one using a fully charged lithium-ion battery. For some electric city cars that would amount to a range of just 25km. But the German researchers believe they can greatly increase that.
然而电动汽车是不能承载两个大油箱的。从实际情况看，一个装有氧化还原流体电池的汽车，其电量所能驱动的里程仅是充满电锂电池路程的四分之一。对于某些电 动城市汽车来说也就25km的样子。但是德国的研究者相信这种情况可以大大改观。

They are experimenting with other materials in their redox flow cell, including electrodes made from vanadium and bromide ions, and iron and chromium. Mr Noack says that, as a result of the work, he believes it is possible to build a redox flow battery that would provide a four- or five-fold increase in the range of an electric vehicle compared with one powered by an existing flow battery of a similar size. That would give such a vehicle a range equivalent to one running on a lithium-ion battery, but with the ability to be recharged either by being plugged into the mains or in minutes by swapping electrolytes.
他们在氧化还原流体电池中采用其它材料，包括钒、溴离子，以及铁和铬制成的电极。Noack说，他相信可以制造出电量是4-5倍于现在同等尺寸的流体电 池。这将使汽车所跑的路程和锂离子电池相当。但是具有反复充电能力的电池，要么插入电源，要么是快速交换电极。

The researchers hope to have a prototype flow battery for an electric car ready in about two years. By which time there should be enough electric cars on the road to enable a meaningful estimate to be made of the potential demand for a battery that is capable of being recharged both at home and at a filling station.
研究者希望在两年内可以制作出流体电池的原型。到那时，路上就应该有足够多的电动车并能够对具有同时在家和加油站反复充电能力的电池需求潜力做出有意义的 评估。