New Lithium Ion Battery isSafer, Tougher, and More Powerful

- SouthKorean scientists have developed a new high-performance lithium ion batterywhich is stable at high temperatures

July 3, 2015

Lithium ion batteries (LIBs) are ahuge technological advancement from lead acid batteries which have existedsince the late 1850’s.  Thanks to theirlow weight, high energy density and slower loss of charge when not in use, LIBshave become the preferred choice for consumer electronics.  Lithium-ion cells with cobalt cathodes holdtwice the energy of a nickel-based battery and four-times that of leadacid.  Despite being a superior consumerbattery, LIBs still have some drawbacks.Current manufacturing technology is reaching the theoretical energydensity limit for LIBs and overheating leading to thermal runaway i.e. “ventingwith flame” is a serious concern.

SouthKorean researchers at the Center for Self-assembly and Complexity, Institute forBasic Science (IBS), Department of Chemistry and Division of Advanced MaterialsScience at Pohang University, have created a new LIB made from a porous solidwhich greatly improves its performance as well as reducing the risks due tooverheating.

Since2002 there have been over 40 recalls in the US alone due to fire or explosionrisk from LIBs used in consumer electronic devices.  These types of batteries, in all of theirdifferent lithium-anode combinations, continue to be an essential part ofmodern consumer electronics despite their poor track record at hightemperatures.

TheKorean team tried a totally new approach in making the batteries.  According to Dr. Kimoon Kim at IBS, “we have already investigated high and highlyanisotropic [directionally dependent] proton conducting behaviors in porousCB[6] for fuel cell electrolytes. It is possible for this lithium ionconduction following porous CB[6] to be safer than existing solid lithiumelectrolyte -based organic-molecular porous-materials utilizing the simplesoaking method.” Current LIB technology relies on intercalated lithium whichfunctions well, but due to ever increasing demands from electronic devices tobe lighter and more powerful, investigation of novel electrolytes is necessaryin order.

(Above) Simple incorporation of various lithiumprecursor to porous CB[6] exhibits high lithium ion conductivities, mobilityand safer dried solid lithium electrolytes

Thenew 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 physicalstructure of the porous CB[6] enables the lithium ions to battery to diffusemore freely than in conventional LIBs and exist without the separators found inother batteries. 

Intests, the porous CB[6] solid electrolytes showed impressive lithium ionconductivity.  To compare this toexisting battery electrolytes, the team used a measurement of the lithiumtransference number (t_Li⁺) which was recorded at0.7-0.8 compared to 0.2-0.5 of existing electrolytes.  They also subjected the batteries to extremetemperatures of up to 373 K (99.85° C), well above the 80° C typical upper temperaturewindow for exiting LIBs.  In the tests,the batteries were cycled at temperatures between 298 K and 373 K ( 24.85° C and 99.85° C) for aduration of four days and after each cycle the results showed no thermalrunaway and hardly any change in conductivity.

Variousconventional liquid electrolytes can incorporate in a porous CB[6] frameworkand converted to safer solid lithium electrolytes. Additionally, electrolyte usage is not limitedto use only in LIBs, but a lithium air battery potentially feasible. What makes this new technique most exciting isthat it is a new method of preparing a solid lithium electrolyte which starts asa liquid but no post-synthetic modification or chemical treatment is needed.

- By DanielKopperud

Notes for editors

-References

JunHeuk Park,Kyungwon Suh,Md. Rumum Rohman,WooseupHwang, Minyoung Yoonand Kimoon Kim, (2015), “Solid lithiumelectrolytes based on an organic molecular porous solid”, The Royal Society ofChemistry, DOI: 10.1039/c5cc02581h

-MediaContact

For further information or to request mediaassistance, please contact: Mr. Shi Bo Shim, Head of Department ofCommunications, Institute for Basic Science (+82-42-878-8189; sibo@ibs.re.kr)or Ms. Sunny Kim, Department of Communications, Institute for Basic Science(+82-42-878-8135; Sunnykim@ibs.re.kr)

-Aboutthe Institute for Basic Science (IBS)
IBS was founded in 2011 by the government of the Republic of Korea with thesole purpose of driving forward the development of basic science in Korea Itcomprises a total of 50 research centers in all fields of basic science,including mathematics, physics, chemistry, life science, earth science andinterdisciplinary science.IBS has launched 24 research centers as ofJanuary 2015.There are eight physics, one mathematics, six chemistry, sevenlife science, and two interdisciplinary research centers.