A rechargeable battery or secondary cell or storage battery is an electrical battery which can be charged, discharged into load and recharged many times, while non-rechargeable battery or primary battery is discarded when fully discharged. Though rechargeable batteries are costlier than the non-rechargeable ones, but they have much lower total cost of ownership and environmental impact. Rechargeable batteries are used in large number of applications ranging from automobiles, portable electronics devices to electric powered vehicles, grid energy storage and renewable energy use, for example storing power generated from photovoltaic arrays etc.

Some of the types of rechargeable batteries are Lithium ion (Li-ion) -made up of light weight lithium & carbon. Lithium is highly reactive meaning a lot of energy can be stored in its atomic bonds and hence offer very high energy density. A typical Li-ion battery can store 150 watt-hour of electricity in 1kg of battery.Nickel-metal hydride - NiMH battery can store typical of 60-70 watt hour per Kg. Lead Acid battery can store about 25 watt hours per Kg. Li-ion is a very fast growing battery system due to its light weight and high energy density. Also, it has a very small self discharging rate which is about 5% and can handle hundred of charge discharge cycles. It is used in cellular phones, portable electronics etc. Other popular battery in this segment is NiMH. Lead Acid Battery is far more economical but quite heavy due to its low energy density and is used in applications where weight of the battery is not a concern. It is used in automobiles, grid energy storage etc.

In this article however we are going to talk about new battery chemistry which is ultra fast charging, long lasting & inexpensive. It is a high performance aluminum battery invented at Standford University. It is a safe alternate to many commercial batteries in use today.

Aluminum Battery Chemistry

Aluminum has long been an attractive material for rechargeable batteries, mainly because of its low cost, low flammability and high-charge storage capacity. For decades, researchers have tried unsuccessfully to develop a commercially viable aluminum-ion battery. A key challenge has been finding materials capable of producing sufficient voltage after repeated cycles of charging and discharging. An aluminum-ion battery consists of two electrodes: a negatively charged anode made of aluminum and a positively charged cathode. For the experimental battery, Stanford team placed the aluminum anode and graphite cathode along with an ionic liquid electrolyte inside a flexible polymer- coated pouch. The electrolyte is basically a salt that's liquid at room temperature, so it's very safe. You can drill through the aluminum battery pouch, and it will continue working for a while without catching fire. Lithium-ion batteries on the other hand can be a fire hazard. Besides safety, the performance achieved from Aluminum battery is quite encouraging. According to the claims of the inventors, with their prototype charging time for Smartphone is reduced to 1 minute. Also it is more durable with their prototype withstanding 7500 charge cycles as compared to 1000 for Li-ion. Lastly, the battery can be bent or folded and hence has the potential to be used in flexible electronics.

There is variety of applications where this battery could be used. It can be used in electrical grid as grid requires long charge cycle life. It is more environments friendly and can be a good alternate to alkaline batteries.

By Abhishek Kansal,Student-ECE, Chitkara University ,Punjab

References
http://whatis.techtarget.com/definition/rechargeable-battery http://electronics.howstuffworks.com/everyday-tech/lithium-ion-battery.htm https://news.stanford.edu/news/2015/march/aluminum-ion-battery-033115.html