Browsing by Author "Zhang, Weiran"
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Item ELECTROLYTE AND INTERFACE DESIGNATION FOR HIGH-PERFORMANCE SOLID-STATE LITHIUM METAL BATTERIES(2024) Zhang, Weiran; Wang, Chunsheng; Material Science and Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The demand for advanced battery technology is intensifying as electric energy becomes the foundation of modern technologies, such as smart devices, transportation, and artificial intelligence. Batteries play a crucial role in meeting our increasing energy demands and transitioning towards cleaner and more sustainable energy sources. However, range anxiety and safety concerns still hinder the widespread application of battery technology.Current Li-ion batteries, based on graphite anode, have revolutionized battery technology but are nearing the energy density limits. This necessitates the development of metal batteries, employing lithium metal as anode which eliminates host materials that do not contribute to capacity, thereby offering 10 times higher specific capacity. Recent research on lithium metal batteries has seen a significant surge, with growing knowledge transitioning from Li+ intercalation chemistry (graphite) to Li metal plating/stripping. The electrolyte, which was previously regarded as an inert material and acting as a Li+ ion transportation mediator, has gradually attracted researchers’ attention due to its significant impact on the solid electrolyte interphase (SEI) and the Li metal plating/stripping behaviors. Compared to the traditional liquid electrolytes, solid-state lithium metal batteries (SSLMB) have been regarded as the holy grail, the future of electric vehicles (EVs), due to their high safety and potential for higher energy density. However, there are notable knowledge gaps between liquid electrolytes and solid-state electrolytes (SSEs). The transition from liquid-solid contact to solid-solid contact poses new challenges to the SSLMB. As a result, the development of SSLMB is strongly hindered by interface challenges, including not only the Li/SSE interfaces and SSE/cathode interfaces but also SSE/SSE interfaces. In this dissertation, I detailed our efforts to highlight the role of electrolytes and interfaces and establish our understanding and fundamental criteria for them. Building on this understanding, we propose effective and facile engineering solutions that significantly enhance batterie metrics to meet real-world application demand. Rather than simply introducing new compositions or new designations, we are dedicated to introducing our understanding and mechanism behind it, we hope the scientific understanding, the practical solution, and the applicability to various systems can further guide and inspire the electrolyte and interface designation for next-generation battery technology.Item 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, ChunshengThe 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 mAhgItem High-Performance Lithium Metal Batteries Enabled by a Fluorinated Cyclic Ether with a Low Reduction Potential(Wiley, 2023-01-02) Wu, Min; Wang, Zeyi; Zhang, Weiran; Jayawardana, Chamithri; Li, Yue; Chen, Fu; Nan, Bo; Lucht, Brett L.; Wang, ChunshengElectrolyte engineering is crucial for developing high-performance lithium metal batteries (LMB). Here, we synthesized two cosolvents methyl bis(fluorosulfonyl)imide (MFSI) and 3,3,4,4-tetrafluorotetrahydrofuran (TFF) with significantly different reduction potentials and add them into LiFSI-DME electrolytes. The LiFSI/TFF-DME electrolyte gave an average Li Coulombic efficiency (CE) of 99.41 % over 200 cycles, while the average Li CEs for MFSI-based electrolyte is only 98.62 %. Additionally, the TFF-based electrolytes exhibited a more reversible performance than the state-of-the-art fluorinated 1,4-dimethoxylbutane electrolyte in both Li||Cu half-cell and anode-free Cu||LiNi0.8Mn0.1Co0.1O2 full cell. More importantly, the decomposition product from bis(fluorosulfonyl)imide anion could react with ether solvent, which destroyed the SEI, thus decreasing cell performance. These key discoveries provide new insights into the rational design of electrolyte solvents and cosolvents for LMB.Item 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, ChunshengThe 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.Item 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, ChunshengThe 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.