In order to improve the electrical performance under extreme cold conditions, researchers reported in ACS central scientific journal that the traditional graphite anode in lithium-ion batteries was replaced with a rugged carbon based material, which can still maintain its rechargeable storage capacity at minus 31 ° f (-35 ° C).
Lithium ion battery is a kind of rechargeable battery. Lithium ion moves from the negative pole to the positive pole through electrolyte during discharge, and then returns when charging. Lithium ion batteries are very suitable for rechargeable electronic products because they can store a lot of energy and have a long life. However, when the temperature drops below the freezing point, the electrical performance of these energy sources will decline. When the conditions are cold enough, they may not be able to transfer any charge.
This is why some people living in the Midwest of the United States are troubled by their electric cars in the cold winter, and why using these batteries in space exploration is risky. Recently, scientists have determined that the flat direction of graphite in the anode is the reason for the decline of energy storage capacity of lithium-ion batteries in cold. Therefore, researchers modified the surface structure of a carbon based material to improve the charge transfer process of the anode.
To create this new material, researchers heated a cobalt containing zeolite imidazole framework (known as zif-67) at high temperatures. The resulting 12 sided carbon nanospheres have uneven surfaces and exhibit excellent charge transfer capability. Then, the research team tested the electrical properties of the material as an anode and lithium as a cathode in a coin shaped battery. The anode exhibits stable charging and discharging at temperatures from 77 ° f to -4 ° f (25 ° C to -20 ° C) and maintains 85.9% room temperature energy storage capacity below freezing point.
In contrast, lithium-ion batteries made with other carbon based anodes, including graphite and carbon nanotubes, have little electricity at freezing temperatures. When the researchers reduced the air temperature to -31 ° f (-35 ° C), the anode made of uneven nanospheres could still be charged, and almost 100% of the power put into the battery was released during the discharge process. The researchers said that the incorporation of rugged nanosphere materials into lithium-ion batteries could open up the possibility of using these energy sources at extremely low temperatures.