High energy density achieved in all-solid-state batteries

Thursday, 04 April, 2019

High energy density achieved in all-solid-state batteries

Researchers from Japan’s Tohoku University and the High Energy Accelerator Research Organization (KEK) have developed a new complex hydride lithium superionic conductor that could result in all-solid-state batteries with the highest energy density to date. Their work has been published in the journal Nature Communications.

All-solid-state batteries incorporating a lithium metal anode are promising candidates for resolving the intrinsic drawbacks of current lithium-ion batteries, such as electrolyte leakage, flammability and limited energy density. Lithium metal is used as an anode material for all-solid-state batteries because it has the highest theoretical capacity (3860 mAh g−1) and the lowest potential (-3.04 V vs standard hydrogen electrode) among known anode materials.

Lithium-ion-conducting solid electrolytes are meanwhile a key component of all-solid-state batteries because the ionic conductivity and stability of the solid electrolyte determine battery performance. The problem is that most existing solid electrolytes have chemical/electrochemical instability and/or poor physical contact against lithium metal, inevitably causing unwanted side reactions at the interface. These side reactions result in an increase in interfacial resistance, greatly degrading battery performance during repeated cycling.

In order to combat this, the Japanese researchers created a new material, achieved by designing structures of hydrogen clusters (complex anions). This new solid electrolyte exhibits high ionic conductivity and high stability against lithium metal, and could therefore be a real breakthrough for all-solid-state batteries that use a lithium metal anode.

“Complex hydrides have received a lot of attention in addressing the problems associated with the lithium metal anode because of their outstanding chemical and electrochemical stability against the lithium metal anode,” said Sangryun Kim from Tohoku University.

“But because of their low ionic conductivity, using complex hydrides with the lithium metal anode has never been attempted in practical batteries. So we were very motivated to see if developing complex hydrides that exhibit lithium superionic conductivity at room temperature can enable the use of lithium metal anode. And it worked.

“We expect that this development will not only inspire future efforts to find lithium superionic conductors based on complex hydrides, but also open up a new trend in the field of solid electrolyte materials that may lead to the development of high-energy-density electrochemical devices.”

Image credit: ©stock.adobe.com/au/sdecoret

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