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All charged up in minutes flat

作者:易二    发布时间:2019-02-28 10:05:02    

By Helen Goss ONE of the principal problems facing electric car manufacturers is the long time – sometimes up to 12 hours – that it takes to recharge the vehicles’ batteries. Now a team of researchers has developed a battery that can be refilled at a service station in just a few minutes. The battery was designed by engineers and electrochemists at the University of New South Wales in Sydney. Like other batteries it relies on electrically conducting solutions called electrolytes. But the new battery has two electrolytes containing different solutions of vanadium sulphate and dilute sulphuric acid. When the solutions are spent, they can be pumped out and replaced. They can be recharged at the service station and made ready for the next driver who needs to fill up. The researchers have already developed a golf cart that is driven by the new battery. “We can demonstrate that the battery works,” says Maria Skyllas-Kazacos, who heads the research team. “But at the moment it’s too big to be used in cars. We need to reduce the size of the storage tanks holding the electrolyte.” At the moment, the battery needs two 280-litre storage tanks. This is fine for a bus or lorry, but not for the average family car. The team is working on reducing the tank size, by doubling the concentration of vanadium in the electrolyte solutions. According to Skyllass-Kazacos, this would provide enough energy to run an electric vehicle for 160 kilometres. The battery is called a vanadium redox flow battery. It has two tanks holding the vanadium solutions, which are linked to a stack of battery cells by two small pumps. The pumps replace spent solutions in the stack, for example, when the vehicle needs extra power to accelerate up hill. The researchers say that around 5 per cent of the energy from the battery goes on powering the pumps. The device uses vanadium ions in four different oxidation states. Each type of ion has a different amount of positive charge. When the battery is fully charged, one tank contains a solution of vanadium ions, each with five positive charges (vanadium V), while the other tank contains vanadium ions with just two charges (vanadium II). When connected, the potential difference between the two solutions drives electrons from one to the other, generating a current to power the vehicle. Although the solutions are physically separate, electrons can flow between them through a bipolar plastic electrode that divides them. Once the exchange is complete, the vanadium V ions have gained one electron each to become vanadium IV ions, while the ions in the vanadium II solution have each lost an electron to leave a solution of vanadium III ions. At this point, the battery is flat and the electroIytes must be recharged or replaced. When fully charged, each cell can generate a potential of about 1.5 volts. The cells can be stacked to give larger voltages. The amount of energy stored depends on how much vanadium is in the electrolytes, which can be increased or decreased by changing the size of the tanks or the concentration of the solutions. Skyllas-Kazacos says the battery is safer than other batteries because it works at ambient temperatures. Batteries tend to heat up as they are recharged, but in this case, the electrolytes act as coolants. The university has already granted two commercial licences for non-vehicle applications of the new battery. Thai Gypsum Products in Thailand is beginning trials of the batteries to provide back-up power for solar houses in remote areas,

 

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