Making Lithium Batteries Safer, Tougher & More Powerful

A pumpkin-shaped nanoparticle could help make lithium ion batteries less likely to explode while improving their performance at the same time.

AsianScientist (Jul. 20, 2015) – Researchers have developed a new lithium ion battery made from a porous solid which had greatly improved performance and lower overheating risks. Their results have been published in Chemical Communications.

Lithium ion batteries (LIBs) are a huge technological advancement from lead acid batteries which have existed since the late 1850’s. Thanks to their low weight, high energy density and slower loss of charge when not in use, LIBs have become the preferred choice for consumer electronics.

Unfortunately, current manufacturing technology is reaching the theoretical energy density limit for LIBs and overheating leading to thermal runaway i.e. “venting with flame” is a serious concern. Since 2002 there have been over 40 recalls in the US alone due to fire or explosion risk from LIBs used in consumer electronic devices.

Current LIB technology relies on intercalated lithium which functions well, but due to ever increasing demands from electronic devices to be lighter and more powerful, investigation of novel electrolytes is necessary in order.

In the present study, researchers at the Center for Self-assembly and Complexity, Institute for Basic Science (IBS), Department of Chemistry and Division of Advanced Materials Science at Pohang University, have tried a totally new approach to battery making. Instead of intercalated lithium, they used a porous, solid electrolyte built from a pumpkin-shaped molecule called cucurbit[6]uril (CB[6]).

CB[6] has an incredibly thin one dimensional-channel, averaging only 7.5 Å. In comparison, a single lithium ion is 0.76 Å, or 0.76 x 10-10 m. The physical structure of the porous CB[6] enables the lithium ions to battery to diffuse more freely than in conventional LIBs and exist without the separators found in other batteries.

In tests, the porous CB[6] solid electrolytes showed impressive lithium ion conductivity and mobility, with a lithium transference number of 0.7-0,8 compared to 0.2-0.5 of existing electrolytes. They also subjected the batteries to extreme temperatures of up to 373 K (99.85°C), above the 80°C typical upper temperature window for exiting LIBs.

The batteries showed no thermal runaway and hardly any change in conductivity after being cycled at temperatures between 298 K and 373 K (25° C and 99.85° C) for a duration of four days.

Various conventional liquid electrolytes can be incorporated into a porous CB[6] framework and converted to safer solid lithium electrolytes. Additionally, electrolyte usage is not limited to use only in LIBs, but a lithium air battery potentially feasible. What makes this new technique most exciting is that it is a new method of preparing a solid lithium electrolyte which starts as a liquid but no post-synthetic modification or chemical treatment is needed.

“It is possible for this lithium ion conduction following porous CB[6] to be safer than existing solid lithium electrolyte-based organic-molecular porous-materials utilizing the simple soaking method,” said study corresponding author Dr. Kim Kimoon from IBS.

The article can be found at: Park et al. (2015) Solid Lithium Electrolytes Based on an Organic Molecular Porous Solid.

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Source: Institute for Basic Science.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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