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Research Interests:

Non-aqueous electrolyte in state-of-the-art Li-ion batteries (LIBs) give rise to severe safety and environmental concerns, as they exhibit intrinsic drawbacks, including flammability, toxicity, and high sensitivity toward moisture. Aqueous batteries hold promise to address this issue, but are often maligned because of their low energy densities due to the narrow electrochemical stability window of water (1.23 V). Recently, we addressed this challenge and made ground-breaking efforts by expanding the ESW of water to >3.0 V when first introducing the concept of the “water-in-salt” electrolyte class (WiSE), based on highly or superconcentrated lithium salts (>21 mol/kg LiTFSI). After that, I dedicated last 4 years on fundamental understanding of this unique electrolyte system, including solvation structure, ionic transportation behavior, surface reaction behavior, etc. Based on this, I conducted a series of researches to push boundary of WiSE much further:

1. Highly reversible Li-sulfur chemistry was built on the nature of thermodynamically phase-separation between TFSI and polysulfide anions. High capacity sulfur anode left the energy density of aqueous battery from 80 Wh/kg up to 200 Wh/kg (material level). [Paper 4]
2. A flexible and wearable 3V-class aqueous symmetrical lithium-ion battery is developed using a single LiVPO₄F material as both cathode and anode in a “water-in-salt” gel polymer electrolyte, showing the high-safety and eco-friendly features of aqueous electrolyte. [Paper 3]
3. The strong hydrophobic passivation layer was developed to minimizes the competitive water reduction during interphase formation in WiSE, enabling a 4V-class aqueous Li-ion batteries with high efficiency and reversibility. Such aqueous Li-ion batteries offer energy densities approaching very closely to those of non-aqueous Li-ion batteries (~300 Wh/kg, material level), but without the safety concern of the latter. [Paper 2]
4. A brand new “halogen conversion-intercalation” cathode chemistry inside graphite was developed, based on a densely packed stage-I graphite intercalation compound, C3.5[Br0.5Cl0.5], forming reversibly in WiSE. By coupling it with a passivated graphite anode, this high capacity cathode blazed a trail for high-energy (>400 Wh/kg, material level) aqueous batteries. [Paper 1]

Successful Proposal and Grant: DoD Independent Research and Development (IR&D) Funds, subcontract from Johns Hopkins Applied Physics Lab (JHU/APL) ($48,000 USD), 2018

Leading Research Projects:

1. “High Energy Aqueous Lithium Ion Batteries”, DoE Advanced Research Projects Agency-Energy (ARPA-E)
2. Phantom Lord PLA “Improve the maturity of the 4.0 V aqueous flexible Li-ion battery technology”, subcontract from US Army Research Laboratory
3. Phantom Lord PLR “Improve the maturity for the Gel Polymer Electrolyte
4. (GPE) flexible aqueous battery from lab based to fieldable”, subcontract from US Army Research Laboratory
5. “Robust, Flexible, Aqueous Polymer Electrolyte Based Li-ion Batteries for Size and Weight Reduction”, ORION funded by Johns Hopkins Applied Physics Lab

All under supervision of Prof. Chunsheng Wang, Department of Chemical and Biomolecular Engineering, University of Maryland

Research Experience:

My academic career path has covered multiple areas of material science and engineering, including electron structure and transportation in thermoelectric materials, photo-induced minority carrier injection in photovaltaic materials, and electron-ion charge transfer in electrochemical materials, ect. These crossed experiences always give me a broader vision to design desired function material systems. My formal training also includes a systematic physics study, which makes me be passionate for electrochemistry – most quantifiable chemistry science and engineering. Hence, I joined Prof. Chunsheng Wang’s group and devoted myself to advanced battery research. Meanwhile, projects that I worked on were always close collaborations with large material characterization facilities: Argonne National Laboratory, Brookhaven national laboratory and NIST. As a result of these collaborations I have acquired invaluable and versatile experience in many research areas.

Teaching Experience and Interests:

Aside from my research career, I also have tried to seize any opportunity to gain teaching experience. I TAed “solid-state physics” course during my undergraduate period at Nanjing University. I guest-lectured graduate lecture “Advanced Fuel Cells and Batteries” in Department of Chemical and Biomolecular Engineering, University of Maryland. Meanwhile, I was very active in research mentorship and have advised 8 diverse students to-date, including 5 graduate students. As faculty, I am looking forward to teaching introductory and advanced courses on topics of physical chemistry, electrochemistry and solid physics and chemistry. I am especially interested in developing coursework that designs, synthesis, characterization, fabrication and application of materials for energy storage or harvest devices.

Future Direction:

As faculty I would like to continue developing advanced energy storage devices, which will mostly be focused on next-generation rechargeable batteries. Large-scale application of clean energy urgently demands new energy storage systems with higher energy density, higher safety and low cost. I believe innovate materials and fabrication strategies should be developed to build up new electrode chemistries to meet these requirements. I will also delicate to the fundamental understanding of electrolyte systems, which will give us huge advantages to manipulate their electrochemical stability and transport property.

Meanwhile, based on my previous research experiences of energy harvest materials, I will try to explore more possibility of devices or systems combining both energy harvest and storage. In many successful systems, especially electrochemical ones, they basically share the same principle or mechanism, but with different outputs or applications. Therefore, in the future, I foresee myself working on building more innovate systems, or potentially opening up new areas.

Selected Publications:

Papers: (citation: 4973; h-index: 33)

1. Yang, J. Chen, X. Ji, T. P. Pollard, X. Lü, C. Sun, S. Hou, Q. Liu, C. Liu, T. Qing, Y. Wang, O. Borodin, Y. Ren, K. Xu, C. Wang, Aqueous Li-ion Battery Enabled by Halogen Conversion-Intercalation Chemistry in Graphite, Nature, 2019, 569, 245–250.
2. Yang, J. Chen, T. Qing, J. Chen, X. Fan, W. Sun, A. v. Cresce, M. S. Ding, M. A. Schroeder, N. Eidson, C. Wang, K. Xu, 4.0 V Aqueous Li-ion Batteries, Joule (Cell press), 2017, 1, 122–132.
3. Yang, X. Ji, X. Fan, T. Gao, L. Suo, F. Wang, W. Sun, J. Chen, L. Chen, F. Han, L. Miao, K. Xu, K. Gerasopoulos, C. Wang, Flexible Aqueous Li-ion Battery with High Energy and Power Densities, Advanced Materials, 2017, 29, 1701972.
4. Yang, L. Suo, O. Borodin, F. Wang, W. Sun, T. Gao, X. Fan, S. Hou, Z. Ma, K. Amine, K. Xu, C. Wang, Unique aqueous Li-ion/sulfur chemistry with high energy density and reversibility, Proceedings of the National Academy of Sciences, 2017, 114, 6197-6202 (Direct Submission).
5. Yang, Z. Wang, T. Lin, H. Yin, X. Lv, D. Wan, T. Xu, C. Zheng, J. Lin, F. Huang, X. Xie, M. Jiang, Core-Shell Nanostructured “Black” Rutile Titania as Excellent Catalyst for Hydrogen Production Enhanced by Sulfur Doping, Journal of the American Chemical Society, 2013, 135, 17831–17838.
6. Lin, I-W. Chen, F. Liu, C. Yang, H. Bi, F. Xu, F. Huang, Nitrogen-doped mesoporous carbon of extraordinary capacitance for electrochemical energy storage, Science, 2015, 350, 1508-1513.

Key words: energy storage, Li-ion battery, aqueous electrolyte, electrochemistry