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1. Solid-state rigid-rod polymer composite electrolytes with nanocrystalline lithium ion pathways

   https://doi.org/10.1038/s41563-021-00995-4  

   Wang, Ying; Zanelotti, Curt J.; Wang, Xiaoen; Kerr, Robert; Jin, Liyu; Kan, Wang Hay; Dingemans, Theo J.; Forsyth, Maria; Madsen, Louis A. (May 2021, Nature Materials)

   Dusastre, Vincent (Ed.)

   A critical challenge for next-generation lithium-based batteries lies in development of electrolytes that enable thermal safety along with use of high-energy-density electrodes. We describe molecular ionic composite (MIC) electrolytes based on an aligned liquid crystalline polymer combined with ionic liquids and concentrated Li salt. This high strength (200 MPa) and non-flammable solid electrolyte possesses outstanding Li+ conductivity (1 mS·cm-1 at 25 °C) and electrochemical stability (5.6 V vs Li|Li+) while suppressing dendrite growth and exhibiting low interfacial resistance (32 Ω·cm2) and overpotentials (≤ 120 mV @ 1 mA·cm-2) during Li symmetric cell cycling. A heterogeneous salt doping process modifies a locally ordered polymer-ion assembly to incorporate an inter-grain network filled with defective LiFSI & LiBF4 nanocrystals, strongly enhancing Li+ conduction. This modular material fabrication platform shows promise for safe and high-energy-density energy storage and conversion applications, incorporating the fast transport of ceramic-like conductors with the superior flexibility of polymer electrolytes. 

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2. Organic–inorganic hybrid electrolytes from ionic liquid-functionalized octasilsesquioxane for lithium metal batteries

   https://doi.org/10.1039/C7TA04599A  

   Yang, Guang; Chanthad, Chalathorn; Oh, Hyukkeun; Ayhan, Ismail Alperen; Wang, Qing (January 2017, Journal of Materials Chemistry A)

   The use of highly conductive solid-state electrolytes to replace conventional liquid organic electrolytes enables radical improvements in the reliability, safety and performance of lithium batteries. Here, we report the synthesis and characterization of a new class of nonflammable solid electrolytes based on the grafting of ionic liquids onto octa-silsesquioxane. The electrolyte exhibits outstanding room-temperature ionic conductivity (∼4.8 × 10 −4 S cm −1 ), excellent electrochemical stability (up to 5 V relative to Li + /Li) and high thermal stability. All-solid-state Li metal batteries using the prepared electrolyte membrane are successfully cycled with high coulombic efficiencies at ambient temperature. The good cycling stability of the electrolyte against lithium has been demonstrated. This work provides a new platform for the development of solid polymer electrolytes for application in room-temperature lithium batteries. 

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3. 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)

   Abstract 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⁻²at 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. 

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4. 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. 

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5. MOF-Enabled Ion-Regulating Gel Electrolyte for Long-Cycling Lithium Metal Batteries Under High Voltage

   https://doi.org/10.1002/smll.202106225  

   Fu, Xuewei; Hurlock, J. Matthew; Ding, Chenfeng; Li, Xiaoyu; Zhang, Qiang; Zhong, Wei-Hong (December 2021, Small)

   High-voltage lithium metal batteries (LMBs) are a promising high-energy density energy storage system. However, their practical implementations are impeded by short lifespan due to uncontrolled lithium dendrite growth, narrow electrochemical stability window, and safety concerns of liquid electrolytes. Here, a porous composite aerogel is reported as the gel electrolyte (GE) matrix, made of metal–organic framework (MOF)@bacterial cellulose (BC), to enable long-life LMBs under high voltage. The effectiveness of suppressing dendrite growth is achieved by regulating ion deposition and facilitating ion conduction. Specifically, two hierarchical mesoporous Zr-based MOFs with different organic linkers, that is, UiO-66 and NH2-UiO-66, are embedded into BC aerogel skeletons. The results indicate that NH2-UiO-66 with anionphilic linkers is more effective in increasing the Li+ transference number; the intermolecular interactions between BC and NH2-UiO-66 markedly increase the electrochemical stability. The resulting GE shows high ionic conductivity (≈1 mS cm−1), high Li+ transference number (0.82), wide electrochemical stability window (4.9 V), and excellent thermal stability. Incorporating this GE in a symmetrical Li cell successfully prolongs the cycle life to 1200 h. Paired with the Ni-rich LiNiCoAlO2 (Ni: Co: Al = 8.15:1.5:0.35, NCA) cathode, the NH2-UiO-66@BC GE significantly improves the capacity, rate performance, and cycle stability, manifesting its feasibility to operate under high voltage. 

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