A. James Clark School of Engineering

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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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Author: search.filters.author.Hou, Singyuk

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    Solvent-Free Electrolyte for High-Temperature Rechargeable Lithium Metal Batteries
    (Wiley, 2023-05-08) Phan, An L.; Jayawardana, Chamithri; Le, Phung ML; Zhang, Jiaxun; Nan, Bo; Zhang, Weiran; Lucht, Brett L.; Hou, Singyuk; Wang, Chunsheng
    The formation of lithiophobic inorganic solid electrolyte interphase (SEI) on Li anode and cathode electrolyte interphase (CEI) on the cathode is beneficial for high-voltage Li metal batteries. However, in most liquid electrolytes, the decomposition of organic solvents inevitably forms organic components in the SEI and CEI. In addition, organic solvents often pose substantial safety risks due to their high volatility and flammability. Herein, an organic-solvent-free eutectic electrolyte based on low-melting alkali perfluorinated-sulfonimide salts is reported. The exclusive anion reduction on Li anode surface results in an inorganic, LiF-rich SEI with high capability to suppress Li dendrite, as evidenced by the high Li plating/stripping CE of 99.4% at 0.5 mA cm−2 and 1.0 mAh cm−2, and 200-cycle lifespan of full LiNi0.8Co0.15Al0.05O2 (2.0 mAh cm−2) || Li (20 µm) cells at 80 °C. The proposed eutectic electrolyte is promising for ultrasafe and high-energy Li metal batteries.
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    Salt-in-Salt Reinforced Carbonate Electrolyte for Li Metal Batteries
    (Wiley, 2022-08-30) Liu, Sufu; Zhang, Weiran; Wan, Hongli; Zhang, Jiaxun; Xu, Jijian; Rao, Jiancun; Deng, Tao; Hou, Singyuk; Nan, Bo; Wang, Chunsheng
    The instability of carbonate electrolyte with metallic Li greatly limits its application in high-voltage Li metal batteries. Here, a “salt-in-salt” strategy is applied to boost the LiNO3 solubility in the carbonate electrolyte with Mg(TFSI)2 carrier, which enables the inorganic-rich solid electrolyte interphase (SEI) for excellent Li metal anode performance and also maintains the cathode stability. In the designed electrolyte, both NO3− and PF6− anions participate in the Li+-solvent complexes, thus promoting the formation of inorganic-rich SEI. Our designed electrolyte has achieved a superior Li CE of 99.7 %, enabling the high-loading NCM811||Li (4.5 mAh cm−2) full cell with N/P ratio of 1.92 to achieve 84.6 % capacity retention after 200 cycles. The enhancement of LiNO3 solubility by divalent salts is universal, which will also inspire the electrolyte design for other metal batteries.
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    Formation of LiF-rich Cathode-Electrolyte Interphase by Electrolyte Reduction
    (Wiley, 2022-04-08) Bai, Panxing; Ji, Xiao; Zhang, Jiaxun; Zhang, Weiran; Hou, Singyuk; Su, Hai; Li, Mengjie; Deng, Tao; Cao, Longsheng; Liu, Sufu; He, Xinzi; Xu, Yunhua; Wang, Chunsheng
    The capacityof transitionmetal oxide cathodefor Li-ionbatteriescan be furtherenhancedby increas-ing the chargingpotential.However,these high voltagecathodessufferfrom fast capacitydecaybecausethelargevolumechangeof cathodebreaksthe activematerialsand cathode-electrolyteinterphase(CEI),resultingin electrolytepenetrationinto brokenactivematerialsand continuousside reactionsbetweencath-ode and electrolytes.Herein,a robustLiF-richCEI wasformedby potentiostaticreductionof fluorinatedelec-trolyteat a low potentialof 1.7 V. By takingLiCoO2asa modelcathode,we demonstratethat the LiF-richCEImaintainsthe structuralintegrityand suppresseselectro-lyte penetrationat a high cut-offpotentialof 4.6 V. TheLiCoO2with LiF-richCEI exhibiteda capacityof198 mAhg
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    ELECTROLYTE DESIGN FOR HIGH-ENERGY METAL BATTERIES
    (2022) Hou, Singyuk; Wang, Chunsheng; Chemical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The demand for advanced batteries surged in the past decade because they are at the heart of several tactically important technologies, such as renewable electrification grids and electric vehicles (EVs). These technologies will progressively transform our energy consumption structure toward sustainability and alleviate the global climate crisis. Unlike consumer electronics, EVs require batteries with larger energy storage to avoid "range anxiety". According to the US Advanced Battery Consortium (USABC), breakthroughs are needed to double the battery energy density and reduce the price by 50% for EVs to be competitive in the automobile market. These stringent requirements are unlikely to be met by the Li-ion batteries (LIBs) because the charge storage limits have been reached. Metal batteries using metals as anodes require no host materials and have up to ten times higher charge storage capacities. When metals with low redox potentials (Mg, Ca, and Li) are used, new battery systems that benefit from larger capacities and high cell voltages result in over 100 % leap in energy density to satisfy the USABC's goals for EV applications. On the other hand, the scarcity of materials related to LIBs raises uncertainties and doubts in the transition to electric transportation. Metals such as Mg and Ca are highly abundant in the earth crust, which potentially ensures the reliability of the energy supply in the future.Despite the exciting prospects of metal batteries, there are knowledge gaps in understanding how the electrolyte changes the behaviors of metal plating/stripping. Although electrolytes are considered inert materials in batteries, they are indispensable in maintaining ionic transport, modulating interfacial reaction kinetics, and maintaining reversible electrode reactions through the formation of solid-electrolyte interphase (SEI). In this dissertation, I detailed our efforts to establish the microscopic understanding of the electrolyte structures, SEI components, nucleation, and growth of the electroplated metal with spectroscopic techniques and physical models. These understandings guided the design of electrolytes for reversible metal anodes in practical high-energy battery applications.
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    High-energy and low-cost membrane-free chlorine flow battery
    (Springer Nature, 2022-03-11) Hou, Singyuk; Chen, Long; Fan, Xiulin; Fan, Xiaotong; Ji, Xiao; Wang, Boyu; Cui, Chunyu; Chen, Ji; Yang, Chongyin; Wang, Wei; Li, Chunzhong; Wang, Chunsheng
    Grid-scale energy storage is essential for reliable electricity transmission and renewable energy integration. Redox flow batteries (RFB) provide affordable and scalable solutions for stationary energy storage. However, most of the current RFB chemistries are based on expensive transition metal ions or synthetic organics. Here, we report a reversible chlorine redox flow battery starting from the electrolysis of aqueous NaCl electrolyte and the as-produced Cl2 is extracted and stored in the carbon tetrachloride (CCl4) or mineral spirit flow. The immiscibility between the CCl4 or mineral spirit and NaCl electrolyte enables a membrane-free design with an energy efficiency of >91% at 10 mA/cm2 and an energy density of 125.7 Wh/L. The chlorine flow battery can meet the stringent price and reliability target for stationary energy storage with the inherently low-cost active materials (~$5/kWh) and the highly reversible Cl2/Cl− redox reaction.