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Summary With an extremely high theoretical energy density, solid-state lithium-sulfur (Li-S) batteries (SSLSBs) are emerging as one of the most feasible chemistries; however, their energy efficiency and long-term cyclability are severely hampered by the lithium metal (Li°) dendrite formation during repeated discharge/charge cycles and the shuttling of aggressive polysulfide intermediates between two electrodes. Herein, we report (difluoromethanesulfonyl) (trifluoromethanesulfonyl)imide anion [N(SO2CF2H)(SO2CF3)]−, hereafter DFTFSI−, as a designer anion for high-performance polymer-based SSLSBs. In contrast to the widely used bis(trifluoromethanesulfonyl)imide anion [N(SO2CF3)2]− (TFSI−), DFTFSI-based SSLSBs provide superior interfacial stability against Li°, extremely high discharge and areal capacities, very high Coulombic efficiency, and long-term cyclability, surpassing the reported literature values, in terms of gravimetric energy density. This work opens a new door for accelerating the practical deployment of SSLSBs in the future.

Machine learning (ML) algorithms are gaining importance in the processing of chemical information and modeling of chemical reactivity problems. In this work, we have developed a perturbation-theory and machine learning (PTML) model combining perturbation theory (PT) and ML algorithms for predicting the yield of a given reaction. For this purpose, we have selected Parham cyclization, which is a general and powerful tool for the synthesis of heterocyclic and carbocyclic compounds. This reaction has both structural (substitution pattern on the substrate, internal electrophile, ring size, etc.) and operational variables (organolithium reagent, solvent, temperature, time, etc.), so predicting the effect of changes on substrate design (internal elelctrophile, halide, etc.) or reaction conditions on the yield is an important task that could help to optimize the reaction design. The PTML model developed uses PT operators to account for perturbations under experimental conditions and/or structural variables of all the molecules involved in a query reaction, compared to a reaction of reference. Thus, a dataset of100 reactions has been collected for different substrates and internal electrophiles, under different reaction conditions, with a wide range of yields (0-98%). The best PTML model found using General Linear Regression (GLR) has R = 0.88 in training and R = 0.83 in external validation series for 10 000 pairs of query and reference reactions. The PTML model has a final R = 0.95 for all reactions using multiple reactions of reference. We also report a comparative study of linear versus nonlinear PTML models based on artificial neural network (ANN) algorithms. PTML-ANN models (LNN, MLP, RBF) with R ≈ 0.1-0.8 do not outperform the first PMTL model. This result confirms the validity of the linearity of the model. Next, we carried out an experimental and theoretical study of nonreported Parham reactions to illustrate the practical use of the PTML model. A 500 000-point simulation and a Hammett analysis of the reactivity space of Parham reactions are also reported.

Inverse vulcanization copolymers (p(S-DVB)) from the radical polymerization of elemental sulfur and divinylbenzene (DVB) have been studied as cathode active materials in poly(ethylene oxide) (PEO)-based all-solid-state Li-S cells. The Li-S cell comprising the optimized p(S-DVB) cathode (80:20 w/w S/DVB ratio) and lithium bis(fluorosulfonyl)imide/PEO (LiFSI/PEO) electrolyte shows high specific capacity (ca. 800 mAh g −1 ) and high Coulombic efficiency for 50 cycles. Most importantly, polysulfide (PS) shuttle is highly mitigated due to the strong interactions of PS species with polymer backbone in p(S-DVB). This is demonstrated by the stable cycling of the p(S-DVB)-based cell using lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)/PEO electrolyte, where successful charging cannot be achieved even at the first cycle with plain elemental S-based cathode material due to the severe PS shuttle phenomenon. These results suggest that inverse vulcanization copolymers are promising alternatives to elemental sulfur for enhancing the electrochemical performance of PEO-based all-solid-state Li-S cells.

Nanocomposite solid polymer electrolytes (NSPEs) comprising lithium salt based on two representative sulfonylimide anions (i.e., bis(fluorosulfonyl)imide ([N(SO2F)2]−, FSI−) and bis(trifluoromethanesulfonyl)imide ([N(SO2CF3)2]−, TFSI−)) have been prepared by simply dissolving the corresponding lithium salt in poly(ethylene oxide) matrix in the presence of inert nano-sized Al2O3 fillers. The physicochemical and electrochemical properties of the FSI- and TFSI-based NSPEs are investigated, in terms of phase transition, ion transport behavior, chemical and electrochemical compatibility with Li metal. With the addition of nano-sized Al2O3 fillers, a significant improvement in chemical and electrochemical compatibility with Li metal has been observed in both the FSI- and TFSI-based NSPEs. Particularly, the symmetric cell using the FSI-based NSPE can be continuously cycled for > 1000 h at 70 °C. The Li | LiFePO4 cell with the FSI-based NSPEs shows good cycling stability and capacity retention. These promising results make them attractive electrolytes for safe and stable rechargeable Li metal batteries.

New synthesis route of polysalt with single ion conductivity based on functionalization of polyacrylic acid is reported for all solid state lithium metal batteries. Poly[(trifluoromethyl)sulfonyl acrylamide] PA–LiTFSI was synthesized in two steps reaction. The degree of functionalization of the polymer backbone by anion of lithium salt bis(trifluoromethane)sulfonimide (LiTFSI) was confirmed by ICP analysis. An ionic conductivity equal 1,77 10 −5 S cm −1 at 80 °C of polysalt blended with PEO is reported. Easy process-able polysalt blended with PEO exhibits good mechanical properties and high transference number.

We report a simple synthesis route towards a new type of comb polymer material based on polyether amines oligomer side chains (i.e., Jeffamine® compounds) and a poly(ethylene-alt-maleic anhydride) backbone. Reaction proceeds by imide ring formation through the NH2 group allowing for attachment of side chains. By taking advantage of the high configurational freedoms and flexibility of propylene oxide/ethylene oxide units (PO/EO) in Jeffamine® compounds, novel polymer matrices were obtained with good elastomeric properties. Fully amorphous solid polymer electrolytes (SPEs) based on lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and Jeffamine®-based polymer matrices show low glass transition temperatures around −40 °C, high ionic conductivities and good electrochemical stabilities. The ionic conductivities of Jeffamine-based SPEs (5.3 × 10−4 S cm−1 at 70 °C and 4.5 × 10−5 S cm−1 at room temperature) are higher than those of the conventional SPEs comprising of LiTFSI and linear poly(ethylene oxide) (PEO), due to the amorphous nature and the high concentration of mobile end-groups of the Jeffamine-based polymer matrices rather than the semi-crystalline PEO The feasibility of Jeffamine-based compounds in lithium metal batteries is further demonstrated by the implementation of Jeffamine®-based polymer as a binder for cathode materials, and the stable cycling of Li|SPE|LiFePO4 and Li|SPE|S cells using Jeffamine-based SPEs.

The ion interactions in two novel ionic liquids containing the asymmetric sulfonimide anion, (difluoromethanesulfonyl)(trifluoromethanesulfonyl)imide (DFTFSI), are investigated using 1H–19F Heteronuclear Overhauser Effect Spectroscopy (HOESY) nuclear magnetic resonance (NMR) in combination with relaxation measurements, and molecular dynamics (MD) simulations. These methods provide insights into how the different end groups of the anion interact with different regions of the IL cations. The 1H–19F cross-relaxation rates (σ) between different pairs of nuclei measured by HOESY are interpreted based on inter/intra molecular distances and dynamics. The results show that the protonated end of the DFTFSI anion (i.e., the CF2H group) preferentially interacts with the IL cations, while the MD simulations also show evidence of C-H…O hydrogen bonding interactions between DFTFSI and the methoxy-functionalised cation C2O1mpyr, thereby explaining the observed lower ionic conductivity and higher density in this IL as compared to the C3mpyr DFTFSI system.

© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. Suppressing the mobility of anionic species in polymer electrolytes (PEs) is essential for mitigating the concentration gradient and internal cell polarization, and thereby improving the stability and cycle life of rechargeable alkali metal batteries. Now, an ether-functionalized anion (EFA) is used as a counter-charge in a lithium salt. As the salt component in PEs, it achieves low anionic diffusivity but sufficient Li-ion conductivity. The ethylene oxide unit in EFA endows nanosized self-agglomeration of anions and trapping interactions between the anions and its structurally homologous matrix, poly(ethylene oxide), thus suppressing the mobility of negative charges. In contrast to previous strategies of using anion traps or tethering anions to a polymer/inorganic backbone, this work offers a facile and elegant methodology on accessing selective and efficient Li-ion transport in PEs and related electrolyte materials (for example, composites and hybrid electrolytes).