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1. Investigating miscibility and lithium ion transport in blends of poly(ethylene oxide) with a polyanion containing precisely-spaced delocalized charges

   https://doi.org/10.1039/D2PY00605G  

   Nguyen, Nam ; Blatt, Michael Patrick ; Kim, Kyoungmin ; Hallinan, Daniel T. ; Kennemur, Justin G. ( July 2022 , Polymer Chemistry)

   A novel precision single-ion conductor with phenylsulfonyl(trifluoromethylsulfonyl)imide lithium salt covalently bound to every fifth carbon of a polyethylene backbone, p5PhTFSI-Li, was synthesized via ring opening metathesis polymerization (ROMP) followed by post polymerization modification. The conversion of poly(4-phenylcyclopentene), bearing 94% sulfonate anions, to trifluoromethanesulfonimide (TFSI) anions was highly efficient (∼90%) as determined by 19 F NMR analysis and corroborated through other spectroscopic methods. The flexible hydrocarbon backbone combined with a bulky TFSI anion led to an observable glass transition temperature of 199 °C even at these high levels of ionization. A high thermal stability up to 375 °C was also observed. Blending of p5PhTFSI-Li with poly(ethylene oxide) at various compositions was performed to investigate electrochemical performance and transference numbers with respect to the lithium electrode using a combination of impedance and polarization methods. At 90 °C and a 50 : 50 wt% blend composition, this system displayed the highest reported conductivity (2.00 × 10 −4 S cm −1 ) of a system with a demonstrated lithium-ion transference number near unity. Such performance is also atypical of single ion conductors produced through post-polymerization modification, which we attribute to the high yield of TFSI conversion. Investigations into the complex miscibility and phase behavior of thesemore »blends at various compositions was also probed by a combination of microscopy and differential scanning calorimetry, which is discussed with reference to computational predictions of how charge correlations affect polymer blend phase behavior.« less
2. Comparison of Single-Ion Conducting Polymer Gel Electrolytes for Sodium, Potassium, and Calcium Batteries: Influence of Polymer Chemistry, Cation Identity, Charge Density, and Solvent on Conductivity

   https://doi.org/10.3390/batteries6010011  

   Ford, Hunter O. ; Cui, Chuanchuan ; Schaefer, Jennifer L. ( March 2020 , Batteries)

   From the standpoint of material diversification and sustainability, the development of so-called “beyond lithium-ion” battery chemistries is important for the future of energy storage. Na, K, and Ca are promising as the basis for battery chemistries in that these elements are highly abundant. Here, a series of single-ion conducting polymer electrolytes (SIPEs) for Na, K, and Ca batteries are synthesized and investigated. The two classes of metal cation neutralized SIPEs compared are crosslinked poly(ethylene glycol) dimethacrylate-x-styrene sulfonate (PEGDMA-SS) and poly(tetrahydrofuran) diacrylate-x-4-styrenesulfonyl (trifluoromethylsulfonyl)imide (PTHFDA-STFSI); three cation types, three charge densities, and four swelling states are examined. The impact on conductivity of all of these parameters is studied, and in conjunction with small angle X-ray scattering (SAXS), it is found that promoting ion dissociation and preventing the formation of dense ionic aggregates facilitates ion transport. These results indicate many of the lessons learned from the Li SIPE literature can be translated to beyond Li chemistries. At 25 °C, the best performing Na/K and Ca exchanged polymers yield active cation conductivity on the order of 10−4 S/cm and 10−6 S/cm, respectively, for ethylene carbonate:propylene carbonate gelled SIPEs, and 10−5 S/cm and 10−7 S/cm, respectively, for glyme gelled SIPEs.
3. Designing electrolytes with polymerlike glass-forming properties and fast ion transport at low temperatures

   https://doi.org/10.1073/pnas.2004576117  

   Zhao, Qing ; Liu, Xiaotun ; Zheng, Jingxu ; Deng, Yue ; Warren, Alexander ; Zhang, Qiyuan ; Archer, Lynden ( October 2020 , Proceedings of the National Academy of Sciences)

   In the presence of Lewis acid salts, the cyclic ether, dioxolane (DOL), is known to undergo ring-opening polymerization inside electrochemical cells to form solid-state polymer batteries with good interfacial charge-transport properties. Here we report that LiNO₃, which is unable to ring-open DOL, possesses a previously unknown ability to coordinate with and strain DOL molecules in bulk liquids, completely arresting their crystallization. The strained DOL electrolytes exhibit physical properties analogous to amorphous polymers, including a prominent glass transition, elevated moduli, and low activation entropy for ion transport, but manifest unusually high, liquidlike ionic conductivities (e.g., 1 mS/cm) at temperatures as low as −50 °C. Systematic electrochemical studies reveal that the electrolytes also promote reversible cycling of Li metal anodes with high Coulombic efficiency (CE) on both conventional planar substrates (1 mAh/cm²over 1,000 cycles with 99.1% CE; 3 mAh/cm²over 300 cycles with 99.2% CE) and unconventional, nonplanar/three-dimensional (3D) substrates (10 mAh/cm²over 100 cycles with 99.3% CE). Our finding that LiNO₃promotes reversibility of Li metal electrodes in liquid DOL electrolytes by a physical mechanism provides a possible solution to a long-standing puzzle in the field about the versatility of LiNO₃salt additives for enhancing reversibility of Li metal electrodes in essentially any aprotic liquidmore »electrolyte solvent. As a first step toward understanding practical benefits of these findings, we create functional Li||lithium iron phosphate (LFP) batteries in which LFP cathodes with high capacity (5 to 10 mAh/cm²) are paired with thin (50 μm) lithium metal anodes, and investigate their galvanostatic electrochemical cycling behaviors.

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4. Highly‐Cyclable Room‐Temperature Phosphorene Polymer Electrolyte Composites for Li Metal Batteries

   https://doi.org/10.1002/adfm.201910749  

   Rojaee, Ramin ; Cavallo, Salvatore ; Mogurampelly, Santosh ; Wheatle, Bill K. ; Yurkiv, Vitaliy ; Deivanayagam, Ramasubramonian ; Foroozan, Tara ; Rasul, Md Golam ; Sharifi‐Asl, Soroosh ; Phakatkar, Abhijit H. ; et al ( June 2020 , Advanced Functional Materials)

   Despite significant interest toward solid-state electrolytes owing to their superior safety in comparison to liquid-based electrolytes, sluggish ion diffusion and high interfacial resistance limit their application in durable and high-power density batteries. Here, a novel quasi-solid Li+ ion conductive nanocomposite polymer electrolyte containing black phosphorous (BP) nanosheets is reported. The developed electrolyte is successfully cycled against Li metal (over 550 h cycling) at 1 mA cm(-2) at room temperature. The cycling overpotential is dropped by 75% in comparison to BP-free polymer composite electrolyte indicating lower interfacial resistance at the electrode/electrolyte interfaces. Molecular dynamics simulations reveal that the coordination number of Li+ ions around (trifluoromethanesulfonyl)imide (TFSI-) pairs and ethylene-oxide chains decreases at the Li metal/electrolyte interface, which facilitates the Li+ transport through the polymer host. Density functional theory calculations confirm that the adsorption of the LiTFSI molecules at the BP surface leads to the weakening of N and Li atomic bonding and enhances the dissociation of Li+ ions. This work offers a new potential mechanism to tune the bulk and interfacial ionic conductivity of solid-state electrolytes that may lead to a new generation of lithium polymer batteries with high ionic conduction kinetics and stable long-life cycling.
5. High-performance all-solid-state batteries enabled by salt bonding to perovskite in poly(ethylene oxide)

   https://doi.org/10.1073/pnas.1907507116  

   Xu, Henghui ; Chien, Po-Hsiu ; Shi, Jianjian ; Li, Yutao ; Wu, Nan ; Liu, Yuanyue ; Hu, Yan-Yan ; Goodenough, John B. ( September 2019 , Proceedings of the National Academy of Sciences)

   Flexible and low-cost poly(ethylene oxide) (PEO)-based electrolytes are promising for all-solid-state Li-metal batteries because of their compatibility with a metallic lithium anode. However, the low room-temperature Li-ion conductivity of PEO solid electrolytes and severe lithium-dendrite growth limit their application in high-energy Li-metal batteries. Here we prepared a PEO/perovskite Li 3/8 Sr 7/16 Ta 3/4 Zr 1/4 O 3 composite electrolyte with a Li-ion conductivity of 5.4 × 10 −5 and 3.5 × 10 −4 S cm −1 at 25 and 45 °C, respectively; the strong interaction between the F − of TFSI − (bis-trifluoromethanesulfonimide) and the surface Ta 5+ of the perovskite improves the Li-ion transport at the PEO/perovskite interface. A symmetric Li/composite electrolyte/Li cell shows an excellent cyclability at a high current density up to 0.6 mA cm −2 . A solid electrolyte interphase layer formed in situ between the metallic lithium anode and the composite electrolyte suppresses lithium-dendrite formation and growth. All-solid-state Li|LiFePO 4 and high-voltage Li|LiNi 0.8 Mn 0.1 Co 0.1 O 2 batteries with the composite electrolyte have an impressive performance with high Coulombic efficiencies, small overpotentials, and good cycling stability.