Pu Riley Zhang is a materials science grad student, advised by Dr. Yi Cui and Dr. Johanna Nelson Weker. She focuses on self-discharge behaviors of lithium-sulfur batteries, chemical corrosion of lithium, and scaleable alkaline water electrolysis. She received her BS in NanoEngineering from UC San Diego in 2019, where she was advised by Dr. Zheng Chen on synthesizing PtIr nanocatalysts for Ethanol Oxidation and Pd nanocrystals for Oxygen Reduction Reaction.
Contact: puzhang AT stanford.edu
- High-entropy electrolytes for practical lithium metal batteries NATURE ENERGY 2023
Ultrahigh-loading Manganese-based Electrode for Aqueous Battery via Polymorph Tuning.
Advanced materials (Deerfield Beach, Fla.)
Manganese-based aqueous batteries utilizing Mn2+ /MnO2 redox reactions are promising choices for grid-scale energy storage due to their high theoretical specific capacity, high power capability, low-cost, and intrinsic safety with water-based electrolytes. However, the application of such systems is hindered by the insulating nature of deposited MnO2 , resulting in low normalized areal loading (0.0050.05 mAh cm-2 ) during charge/discharge cycle. In this work, we investigated the electrochemical performance of various MnO2 polymorphs in Mn2+ /MnO2 redox reactions and determined ɛ-MnO2 with low conductivity to be the primary electrochemically deposited phase in normal acidic aqueous electrolyte. We found that increasing the temperature can change the deposited phase from ɛ-MnO2 with low conductivity to gamma-MnO2 with two orders of magnitude increase in conductivity. We demonstrated that the highly conductive gamma-MnO2 could be effectively exploited for ultrahigh areal loading electrode, and a normalized areal loading of 33 mAh cm-2 was achieved. At a mild temperature of 50 °C, cells were cycled with an ultrahigh areal loading of 20 mAh cm-2 (1-2 orders of magnitude higher than previous studies) for over 200 cycles with only 13% capacity loss. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/adma.202211555
View details for PubMedID 37149287
Hydrogen-substituted graphdiyne-assisted ultrafast sparking synthesis of metastable nanomaterials.
Metastable nanomaterials, such as single-atom and high-entropy systems, with exciting physical and chemical properties are increasingly important for next-generation technologies. Here, we developed a hydrogen-substituted graphdiyne-assisted ultrafast sparking synthesis (GAUSS) platform for the preparation of metastable nanomaterials. The GAUSS platform can reach an ultra-high reaction temperature of 3,286K within 8ms, a rate exceeding 105Ks-1. Controlling the composition and chemistry of the hydrogen-substituted graphdiyne aerogel framework, the reaction temperature can be tuned from 1,640 K to 3,286K. We demonstrate the versatility of the GAUSS platform with the successful synthesis of single atoms, high-entropy alloys and high-entropy oxides. Electrochemical measurements and density functional theory show that single atoms synthesized by GAUSS enhance the lithium-sulfur redox reaction kinetics in all-solid-state lithium-sulfur batteries. Our design of the GAUSS platform offers a powerful way to synthesize a variety of metastable nanomaterials.
View details for DOI 10.1038/s41565-022-01272-4
View details for PubMedID 36585516
- An Interdigitated Li-Solid Polymer Electrolyte Framework for Interfacial Stable All-Solid-State Batteries ADVANCED ENERGY MATERIALS 2022
All-Solid-State Lithium-Sulfur Batteries Enhanced by Redox Mediators.
Journal of the American Chemical Society
Redox mediators (RMs) play a vital role in some liquid electrolyte-based electrochemical energy storage systems. However, the concept of redox mediator in solid-state batteries remains unexplored. Here, we selected a group of RM candidates and investigated their behaviors and roles in all-solid-state lithium-sulfur batteries (ASSLSBs). The soluble-type quinone-based RM (AQT) shows the most favorable redox potential and the best redox reversibility that functions well for lithium sulfide (Li2S) oxidation in solid polymer electrolytes. Accordingly, Li2S cathodes with AQT RMs present a significantly reduced energy barrier (average oxidation potential of 2.4 V) during initial charging at 0.1 C at 60 °C and the following discharge capacity of 1133 mAh gs-1. Using operando sulfur K-edge X-ray absorption spectroscopy, we directly tracked the sulfur speciation in ASSLSBs and proved that the solid-polysulfide-solid reaction of Li2S cathodes with RMs facilitated Li2S oxidation. In contrast, for bare Li2S cathodes, the solid-solid Li2S-sulfur direct conversion in the first charge cycle results in a high energy barrier for activation (charge to 4 V) and low sulfur utilization. The Li2S@AQT cell demonstrates superior cycling stability (average Coulombic efficiency 98.9% for 150 cycles) and rate capability owing to the effective AQT-enhanced Li-S reaction kinetics. This work reveals the evolution of sulfur species in ASSLSBs and realizes the fast Li-S reaction kinetics by designing an effective sulfur speciation pathway.
View details for DOI 10.1021/jacs.1c07754
View details for PubMedID 34677957
- Wheat Bran Derived Carbon toward Cost-Efficient and High Performance Lithium Storage ACS SUSTAINABLE CHEMISTRY & ENGINEERING 2020; 8 (42): 15898–905
Incorporating the nanoscale encapsulation concept from liquid electrolytes into solid-state lithium-sulfur batteries.
Lithium-sulfur (Li-S) batteries are attractive due to their high specific energy and low-cost prospect. Most studies in the past decade are based on these batteries with liquid electrolytes, where many exciting material/structural designs are realized at the nanoscale to address problems of Li-S chemistry. Recently, there is a new promising direction to develop Li-S batteries with solid polymer electrolytes, although it is unclear whether the concepts from liquid electrolytes are applicable in the solid state to improve battery performance. Here we demonstrate that the nanoscale encapsulation concept based on Li2S-TiS2 core-shell particles, originally developed in liquid electrolytes, is very effective in solid polymer electrolytes. Using in situ optical cell measurement and sulfur K-edge X-ray absorption near edge spectroscopy, we find that polysulfides form and are well trapped inside individual particles by the nanoscale TiS2 encapsulation. This TiS2 encapsulation layer also functions to catalyze the oxidation reaction of Li2S to sulfur, even in solid-state electrolytes, proved by both experiments and density functional theory calculations. A high cell-level specific energy of 427 W∙h∙kg-1 at 60 °C (including the mass of the anode, cathode, and solid-state electrolyte, but excluding the current collector and packaging) is achieved by integrating TiS2 encapsulated Li2S cathode with ultrathin polyethylene oxide-based solid polymer electrolyte (10~20 m) and lithium metal anode. The solid-state cells show excellent stability over 150 charge/discharge cycles at 0.8 C at 80 °C. This study points to the fruitful direction of borrowing concepts from liquid electrolytes into solid-state Li-S batteries.
View details for DOI 10.1021/acs.nanolett.0c02033
View details for PubMedID 32515973
Promoting H2O2 production via 2-electron oxygen reduction by coordinating partially oxidized Pd with defect carbon.
2020; 11 (1): 2178
Electrochemical synthesis of H2O2 through a selective two-electron (2e-) oxygen reduction reaction (ORR) is an attractive alternative to the industrial anthraquinone oxidation method, as it allows decentralized H2O2 production. Herein, we report that the synergistic interaction between partially oxidized palladium (Pdδ+) and oxygen-functionalized carbon can promote 2e- ORR in acidic electrolytes. An electrocatalyst synthesized by solution deposition of amorphous Pdδ+ clusters (Pd3δ+ and Pd4δ+) onto mildly oxidized carbon nanotubes (Pdδ+-OCNT) shows nearly 100% selectivity toward H2O2 and a positive shift of ORR onset potential by ~320 mV compared with the OCNT substrate. A high mass activity (1.946 A mg-1 at 0.45 V) of Pdδ+-OCNT is achieved. Extended X-ray absorption fine structure characterization and density functional theory calculations suggest that the interaction between Pd clusters and the nearby oxygen-containing functional groups is key for the high selectivity and activity for 2e- ORR.
View details for DOI 10.1038/s41467-020-15843-3
View details for PubMedID 32358548
View details for PubMedCentralID PMC7195490
Production of activated carbons from four wastes via one-step activation and their applications in Pb2+ adsorption: Insight of ash content.
2019; 245: 125587
Natural biomass is a renewable source for precursors of porous carbon. Four agriculture wastes of corn cob (CC), wheat bran (WB), rice husk (RH), and soybean shell (SS) were applied to produce activated carbons (ACs) via one-step activation by sodium hydroxide. The effects of ash contents and NaOH dosage ratio (1-5) on surface area for ACs were investigated. Owing to ash etching, the high ash precursor (like RH) exhibited less alkali consumption and larger surface area than low ash one (like CC). All four ACs expressed developed pore structure and outstanding surface area of 2500m2g-1. During adsorption of lead ions in simulated wastewater, RH-based AC revealed superior capture capacity of 492±15mgg-1. One-step activation had the potential to deliver savings around 1/3 of energy consumption, enabling the cost performance of high ash RH-based AC reaching 194±12gPb2+$-1, 76% larger than low ash CC-based AC. High ash biomass is a promising candidate to obtain eco-friendly carbon products.
View details for DOI 10.1016/j.chemosphere.2019.125587
View details for PubMedID 31864062
Enhancing C–C Bond Scission for Efficient Ethanol Oxidation using PtIr Nanocube Electrocatalysts
View details for DOI 10.1021/acscatal.9b02039