Jul
8
Lithium ion are low weight, have high energy density and a slower loss of charge when not in use, a huge technological advancement over lead acid batteries. Lithium ion cells with cobalt cathodes hold twice the energy of a nickel-based and four-times that of lead acid batteries making them the top consumer choice.
But current manufacturing technology is reaching the theoretical energy density limit for lithium ion batteries and overheating leading to thermal runaway known as “venting with flame” remains a serious concern.
Since 2002 there have been over 40 recalls in the U.S. alone due to fire or explosion risk from lithium ion batteries used in consumer electronic devices. These types of batteries, in all of their different lithium-anode combinations, continue to be an essential part of modern consumer electronics despite their poor track record at high temperatures.
![Porous Solid Battery Molecules of CB[6]. Simple incorporation of various lithium precursor to porous CB[6] exhibits high lithium ion conductivities, mobility and safer dried solid lithium electrolytes. Image Credit: Institute for Basic Science. Click image for the largest view.](https://newenergyandfuel.com/wp-content/uploads/2015/07/Porous-Solid-Battery-Molecules-of-CB6.jpg)
Porous Solid Battery Molecules of CB[6]. Simple incorporation of various lithium precursor to porous CB[6] exhibits high lithium ion conductivities, mobility and safer dried solid lithium electrolytes. Image Credit: Institute for Basic Science. Click image for the largest view.
The team’s study paper has been published in the journal Chemical Communications.
The new battery is built from pumpkin-shaped molecules called cucurbit[6]uril (CB[6]) which are organized in a honeycomb-like structure. The molecules have an incredibly thin 1D-channel, only averaging 7.5 Å [a single lithium ion is 0.76 Å, or .76 x 10-10 m] that runs through them. The physical structure of the porous CB[6] enables the lithium ions to diffuse more freely than in conventional lithium ion batteries and exist without the separators found in other batteries.
In tests, the porous CB[6] solid electrolytes showed impressive lithium ion conductivity. To compare this to existing battery electrolytes, the team used a measurement of the lithium transference number (tLi+) which was recorded at 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), well above the 80° C typical upper temperature window for exiting lithium ion batteries. In the tests, the batteries were cycled at temperatures between 298 K and 373 K (24.85° C and 99.85° C) for a duration of four days and after each cycle the results showed no thermal runaway and hardly any change in conductivity.
Various conventional liquid electrolytes can incorporate in a porous CB[6] framework and converted to safer solid lithium electrolytes. Additionally, electrolyte usage is not limited to use only in lithium ion batteries, with lithium air battery technology potentially feasible as well. 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.
Lithium ion batteries have made products possible that were only dreams a few years ago in spite of the horrifying risk of a battery self igniting. We aren’t hearing much anymore about battery fires, but new battery constructions without the fire risks could well bring more products that are better, last longer and have longer life spans.
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