My research aims to tackle the grand challenges in energy and electronics for a sustainable and smart future. Fundamental understanding through characterizations, materials/interfaces design in devices/applications, as well as development of advanced manufacturing methodologies, all of which form a positive feedback loop for advancing modern technologies. My past research accomplishments (primary author works) in these areas, namely, energy storage, electronics & devices, advanced characterizations, and advanced manufacturing, are summarized below.

Research Vision

 
 

Energy Storage (Solid-state Electrolyte)

Intrinsically safe, emerging all-solid-state batteries (ASSBs) can potentially provide an unmatched energy density compared with conventional energy storage systems. A notorious quandary between mechanical robustness, ionic resistance, and thickness exist in conventional solid-state electrolytes (SSE), preventing the practical utilization of ASSBs. My innovation of an ultrathin, ultralight polymer composite SSE, addressing such quandary, pointing out new research insights and directions from which to study ultra-lightweight SSEs for high energy/power density and safe ASSBs.

Phase field simulation of Li deposition behavior with nanochannels

Video of Phase field simulation: Li dendrite evolution/supression

The suppression come from a combined effect of hard/soft 

nanostructured SSE as well as space created from interlayer. 

Scheme, images, and MD simulation of the multifunctional

polymer composite SSE

Related Publications:

  • Nature Nanotech., 2019, 14, 705-711; 

  • Mater. Today Nano, 2018, 4, 1-16;

  • Nano Letters, 2020, In press

Flame test of a homemade all-solid-state battery with conventional solid polymer electrolyte 

(battery stopped functioning, red LED off with the flame) 

Flame test of a homemade all-solid-state battery with innovated solid polymer electrolyte

(battery remained functioning with flame,

red LED still on with the flame) 

Stab test in regular phone Li-ion battery with conventional liquid electrolyte (battery exploded) adopted from Youtube 

Conventional Solid Electrolyte

Innovated Solid Electrolyte

Dangerous Li-ion battery with conventional liquid electrolyte

My Design of Solid-state electrolyte

Conventional Liquid Electrolyte

Flame test of a homemade Li-ion battery with

conventional liquid electrolyte

(battery stopped functioning,

red LED off with the flame) 

Advanced Charaterizations

1. Operando Characterizations

2. In situ TEM

Accurate, operando characterizations in Li-ion batteries are very challenging, given the dynamic electrochemical process with reactive, fragile battery materials in a liquid (organic) electrolyte environment. I developed a planer micro-battery platform (same one from the 2D intercalation work) that allows advanced characterization (such as with operando Raman spectroscopy, Li diffusion kinetics, and resistance change of electrode materials) in batteries. 

Operando characterization platform that can couple with AFM, Raman, and Probe Station.

By in situ deposit Na metal on reduced graphene oxide inside a TEM chamber, I obtained the first experimental atomistic Na metal lattice HRTEM image (with extremely low electron dose rate). Direct observation of such a reactive material is almost impossible with regular TEM sample preparation/characterizations procedures. 

Video showing Na metal deposition inside a TEM chamber

Scheme and TEM images (low and high resolution ones) of in situ Na metal deposition on reduced graphene oxide nano sheets

Related Publications:

  • Nature Comm., 2014, 5, 4224; 

  • Adv. Energy Mater., 2015, 5, 1401742; 

  • Chem. Mater., 2016, 28, 6528-6535; 

  • Nano Letters, 2015, 15, 1018-1024

 

Electronics & Devices

1. Intercalation tuning

2. Paper electronics

I discovered a counter-intuitive phenomenon, where atomistically sandwiching Li (via electrochemical intercalation) in single flake, few-layer graphene made the host (graphene) more transparent (in the visible spectrum) and more conductive simultaneously (record performance of 92% transmittance at 550 nm and 3 ohm/sq sheet resistance in carbon materials). This interesting phenomenon is result from the ultrahigh charge transfer/doping of Li to carbon host as well as the unique bandstructure of few layered graphene. The electrochemical intercalation method provided a new paradigm in exploring unprecedented physical and chemical properties of 2D materials. 

Visible and IR images, sheet resistance changes, and band diagram of graphitic materials before and after Ion intercalation

Brief summary of tunable physical and chemical properties in layered materials via intercalation

I also developed electrochemical gatable transistors (with 2D materials) on flexible, ultraflat, bi-layer paper substrate. The paper was made from bio-degradable nanocellulose. This type of device can be utilized as building blocks for flexible electronics as well as biomedical devices.

Related Publications:

  • Nature Comm, 2014, 5, 4224;  

  • ACS Nano, 2017, 11, 788-796;

  • ACS Nano, 2014, 8, 10606-10612;

  • Nano Letters, 2015, 15, 3763-3769;

  • Nano Letters, 2015, 15, 7671-7677;

  • ACS Appl. Mater. Interfaces., 2016, 8, 11390-11395;

  • Extreme Mechanics Letters, 2019, Accepted

  • Chem. Soc. Rev., 2016, 45, 6742-6765

 

Advanced Manufacturing

1. Ultrafast manufacturing

2. Bio-inspired manufacturing

Nanoparticles/nanostructured are ubiquitously utilized from energy to biomedical applications. In many scenarios, direct exposure of surfaces are critical to realize the potential of nanoparticles.   However, stable, surfactant free nanoparticles are extremely difficult to obtain, due to their high surface energy thus easy to agglomerate. I innovated a unique methodology for ultrafast and facile nanomanufacturing that can overcome above problems. With ultrafast (as short as 1ms) and high temperature (as high as 3000K) shock, stable, surfactant free, uniformly distributed, and monodispersed metallic/semiconducting nanoparticles can be well synthesized. 3D printed filament was also developed for the ultrafast manufacturing.

I also developed a bio-inspired composite material (with wood and metal) that demonstrated extraordinary high electrically and thermally anisotropicity. The composite can be easily processed into different shapes. 

Application of such anisotropic wood composite material range from thermal management to body armor.

Video of metallic wood composite bullet test. It doubled the impact energy compared with natural wood, which show promise of such composites for body armor applications

IR video of heat conduction in metallic wood, with hot side on top. Wood/metal channels vertical to the ground 

IR video of heat conduction in metallic wood, with laser shining on top. Wood/metal channels parallel to the ground  

 

3. Printable nanoink manufacturing

Manufacturing of surfactant free nanoink not only allows fundamental studies of nanomaterials in vast applications (e.g. in situ TEM, in situ AFM), but also enabled scalable application of nano materials such as printed electronics, functional composite materials, and additive manufacturing.

Related Publications:

  • Nature Comm., 2016, 7, 12332; 

  • Adv. Mater., 2017, 29, 1703331;

  • Nano Letters, 2015, 15, 3763-3769

Photo images of printable graphene and graphene oxide inks, SEM image of one graphene flake on TEM grid .

​Schematics, pictures, and SEM images illustrating the ultrafast manufacturing process. Rapid heating is realized by rGO substrate, leading to instant nanoparticle manufacturing. 3D printed heating filament was also developed for this method.

Jiayu Wan

Department of Materials Science & Engineering

Stanford University

476 Lomita Mall, Rm 224

Stanford, CA, 94305

jwan16@stanford.edu

Copy Right © 2019, designed by Jiayu Wan