Dr. Yi Cui’s Latest, a Solid-state Electrolyte

Dean Sigler Electric Powerplants, Sustainable Aviation 0 Comments

Green Car Congress reports that, “Stanford researchers led by Professor Yi Cui have used ceramic nanowire fillers to enhance the ionic conductivity of polymer-based solid electrolyte by three orders of magnitude. The ceramic-nanowire filled composite polymer electrolyte also shows an enlarged electrochemical stability window.”

With solid-state batteries coming to the fore through efforts by Ann Marie Sastry at Sakti 3 and Qichao Hu at Solid Energy Systems, an improved solid electrolyte would seem to offer greater battery safety and stability “when compared with conventional liquid electrolytes.
Solid-state electrolyte provides safety and stability with much higher conductivity

Solid-state electrolyte provides safety and stability with much higher conductivity.   Note much higher energy conductivity for PAN-lithium Chlorate with titanium oxide nanowires, apparently varying little with temperature changes.  Diagrams on right show difference between unconnected nanoparticles and those connected with nanowires

The abstract for the Stanford researchers’ paper in the journal ACS Nano Letters explains that “Currently, the low mobility of lithium ions in solid electrolytes limits their practical application. The ongoing research over the past few decades on dispersing of ceramic nanoparticles into polymer matrix has been proved effective to enhance ionic conductivity although it is challenging to form the efficiency networks of ionic conduction with nanoparticles. In this work, we first report that ceramic nanowire fillers can facilitate formation of such ionic conduction networks in polymer-based solid electrolyte to enhance its ionic conductivity by three orders of magnitude. Polyacrylonitrile (PAN)-LiClO4 (lithium perchlorate) incorporated with 15 wt % Li0.33La0.557TiO3 (lithium oxide, lanthanium – a rare earth – oxide, titanium oxide) nanowire composite electrolyte exhibits an unprecedented ionic conductivity of 2.4 × 10–4 S cm–1 at room temperature, which is attributed to the fast ion transport on the surfaces of ceramic nanowires acting as conductive network in the polymer matrix. In addition, the ceramic-nanowire filled composite polymer electrolyte shows an enlarged electrochemical stability window in comparison to the one without fillers. The discovery in the present work paves the way for the design of solid ion electrolytes with superior performance.”

Green Car Congress reports, “They investigated the ionic conductivities of their solid electrolytes via AC impedance spectroscopy measurements with two stainless steel blocking electrodes.

“The composite electrolyte with 15 wt % LLTO nanowires displayed the highest conductivity of 2.4 × 10−4 S cm−1 at room temperature—about three orders of magnitude higher than that of PAN-LiClO4 without fillers (2.1 × 10−7 S cm−1).”

This jump in conductivity, coupled with materials already used in existing solid-state batteries, might lead to lighter, more energy dense cells that could be applicable in electric vehicles – in particular, light aircraft.

The Nano Letters paper concludes, “Our work opens the door for novel developments of one-dimensional Li+-conducting ceramic materials in solid electrolytes for lithium-ion batteries.”

Dr. Cui is a constant presence in the blog, having created batteries literally on paper, formed the experimental basis for technology that became Amprius, a Sunnyvale, California-based manufacturer of “high energy and high capacity lithium batteries,” and now working on solid-state batteries.  He will speak at the ninth annual Electric Airplane Symposium in Santa Rosa, California on May 2, 2015.

His talk, “Materials Design for Battery Breakthroughs: from Fundamental Science to Commercialization,” promises a great overview of his teams’ work.  He gives a preview in this synopsis.  “In the past two decades rechargeable batteries have been a great success in powering consumer electronics. There is a recent strong interest in applying rechargeable batteries to electrification of transportation, which present new challenges and opportunities for batteries including energy density, cost, safety and cycle life. There I present our breakthrough battery technology enabled by novel materials design. High-energy batteries examples include silicon and lithium metal anodes and sulfur cathodes, which have 10x charge storage capacity of current technology. We also designed smart separators which could enhance the battery safety significantly. The commercialization pathway of some of these breakthroughs will also be presented.”

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