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1. Polymer Precursor Derived LixPON Electrolytes: Toward Li−S Batteries

   https://doi.org/doi.org/10.1021/acsami.0c03341  

   Eleni Temeche, Xinyu Zhang ( May 2021 , ACS applied materials interfaces)

   null (Ed.)

   Efforts to develop polymer precursor electrolytes that offer properties anticipated to be similar or superior to (lithium phosphorus oxynitride, LiPON) glasses are reported. Such precursors offer the potential to be used to process LiPON-like thin glass/ceramic coatings for use in all solid state batteries, ASBs. Here, LiPON glasses provide a design basis for the synthesis of sets of oligomers/polymers by lithiation of OP(NH2)3−x(NH)x [from OP(NH)3],OP- (NH2)3‑x(NHSiMe3)x and [PN]3(NHSiMe3)6−x(NH)x. The resulting systems have degrees of polymerization of 5−20. Treatment with selected amounts of LiNH2 provides varying degrees of lithiation and Li+ conducting properties commensurate with Li+ content. Polymer electrolytes impregnated in/on Celgard exhibit Li+ conductivities up to ∼1 × 10−5S cm−1 at room temperature and are thermally stable to ∼150 °C. A Li−S battery assembled using a Li6SiPON composition polymer electrolyte exhibits an initial reversible capacity of 1500 mAh gsulfur −1 and excellent cycle performance at 0.25 and 0.5 C rate over 120 cycles at room temperature 

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2. Electrochemical Performance of LixSiON Polymer Electrolytes Derived from an Agriculture Waste Product, Rice Hull Ash

   https://doi.org/10.1021/acsapm.1c00192  

   Temeche, E. ; Zhang, X. ; Laine, R. M. ( March 2021 , ACS applied polymer materials)

   The electrochemical performance of LixSiON (x = 2, 4, and 6) polymer electrolytes derived from the agricultural waste, rice hull ash (RHA, 80−90 wt % SiO2), is reported. Silica can be extracted from RHA by base-catalyzed reaction with hexylene glycol forming the spirosiloxane [(C6H12O2)2Si, SP] that distills from the reaction solution. LixSiON polymer electrolytes form on reacting SP with xLiNH2, offering a low-cost, low- temperature, and green synthesis route. The effect of N and Li+ concentrations in the polymer electrolytes are correlated with ionic and electrical conductivity. X-ray photoelectron spectroscopy studies confirm that N and Li contents increase with increasing LiNH2 content. The amorphous nature and high Li+ contents of the Li6SiON electrolyte provide an optimal ionic conductivity (6.5 × 10−6) at ambient temperature when coated on Celgard. Furthermore, the LixSiON polymer electrolytes offer high Li+ transference numbers (∼0.75−1), enabling assembly of Li symmetric cells with high critical current densities (3.75 mA cm−2). Finally, Li-SPAN (sulfurized, carbonized polyacrylonitrile) half-cells with Li6SiON polymer electrolytes deliver discharge capacities of ∼765 and 725 mAh/g at 0.25 and 0.5 C rates over 50 cycles. 

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3. Polyphosphonates as ionic conducting polymers

   https://doi.org/10.1002/pol.20200561  

   Totsch, Timothy R. ; Popov, Ivan ; Stanford, Victoria L. ; Lucius, Aaron L. ; Foulger, Stephen H. ; Gray, Gary M. ( December 2020 , Journal of Polymer Science)

   Polyphosphonates, a class of polymers with the generic formula –[P(R)(X)–OR'O]_n–, exhibit a high degree of modularity due to the range of R, R', and X groups that can be incorporated. As such, these polymers may be designed with a polyethylene oxide (PEO) backbone (R' group) and employed as solid polymer electrolytes (SPEs). Two PEO‐containing polyphosphonate analogs (R = Ph; X = S or Se) were doped with LiPF₆and their conductivities were measured. Conductivities were similar (X = S) to or exceeding (X = Se) those of standard PEO systems (just below 10⁻⁴S/cm at 100°C). Binding models for Li⁺were generated using³¹P{¹H}NMR titration experiments. Binding of Li⁺by these polyphosphonates followed a positive cooperativity model, and varying the X group (S or Se) affected the observed cooperativity (Hill coefficient = 1.73 and 4.16, respectively). The presence of Se also leads to an increase in conductivity as temperature is raised above the T_g, which is likely an effect of reduced Columbic interactions. Because of their modularity and ease with which cation binding can be evaluated using³¹P{¹H} NMR titration experiments, polyphosphonates offer a unique approach for the modification of Li⁺ion battery technology.

    

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4. A flexible thin film lithium battery with a chemical vapor deposited organic complex cathode

   https://doi.org/10.1039/D1TA10867K  

   Li, Zhuo ; Hu, Fei ; Huo, Ni ; Tenhaeff, Wyatt E. ( March 2022 , Journal of Materials Chemistry A)

   Organic cathode materials have attracted significant research attention recently, yet their low electronic conductivity limits their application as solid-state cathodes in lithium batteries. This work describes the development of a novel organic cathode chemistry with significant intrinsic electronic conductivity for solid-state thin film batteries. A polymeric charge transfer complex (CTC) cathode, poly(4-vinylpyridine)-iodine monochloride (P4VP·ICl), was prepared by initiated chemical vapor deposition (iCVD). Critical chemical, physical, and electrochemical properties of the CTC complex were characterized. The complex was found to have an electronic conductivity of 4 × 10-7 S cm-1 and total conductivity of 2 × 10−6 S cm−1 at room temperature, which allows the construction of a 2.7 μm thick dense cathode. By fabricating a P4VP·ICl|LIPON|Li thin film battery, the discharge capacity of P4VP·ICl was demonstrated to be >320 mA h cm−3 on both rigid and flexible substrates. The flexible P4VP·ICl|LIPON|Li battery was prepared by simply replacing the rigid substrate with a flexible polyimide substrate and the as-prepared battery can be bent 180° while maintaining electrochemical performance. 

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5. Crosslinked Poly(tetrahydrofuran) as a Loosely Coordinating Polymer Electrolyte

   https://doi.org/10.1002/aenm.201800703  

   Mackanic, David G. ; Michaels, Wesley ; Lee, Minah ; Feng, Dawei ; Lopez, Jeffrey ; Qin, Jian ; Cui, Yi ; Bao, Zhenan ( July 2018 , Advanced Energy Materials)

   Solid polymer electrolytes (SPEs) promise to improve the safety and performance of lithium ion batteries (LIBs). However, the low ionic conductivity and transference number of conventional poly(ethylene oxide) (PEO)‐based SPEs preclude their widespread implementation. Herein, crosslinked poly(tetrahydrofuran) (xPTHF) is introduced as a promising polymer matrix for “beyond PEO” SPEs. The crosslinking procedure creates thermally stable, mechanically robust membranes for use in LIBs. Molecular dynamics and density functional theory (DFT) simulations accompanied by⁷Li NMR measurements show that the lower spatial concentration of oxygen atoms in the xPTHF backbone leads to loosened O–Li⁺coordination. This weakened interaction enhances ion transport; xPTHF has a high lithium transference number of 0.53 and higher lithium conductivity than a xPEO SPE of the same length at room temperature. It is demonstrated that organic additives further weaken the O–Li⁺interaction, enabling room temperature ionic conductivity of 1.2 × 10⁻⁴S cm⁻¹with 18 wt%N,N‐dimethylformamide in xPTHF. In a solid‐state LIB application, neat xPTHF SPEs cycle with near theoretical capacity for 100 cycles at 70 °C, with rate capability up to 1 C. The plasticized xPTHF SPEs operate at room temperature while maintaining respectable rate capability and capacity. The novel PTHF system demonstrated here represents an exciting platform for future studies involving SPEs.

    

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