Enantioselective Synthesis of Phosphine Boranes via Crystallization-Induced Dynamic Resolution of Lithiated Intermediate by Understanding the Underlying Epimerization Process.

Described herein is the successful crystallization-induced dynamic resolution (CIDR) of an α-lithiated phosphine borane utilizing the easily accessible and inexpensive ligand (R,R)-TMCDA. Starting from the essential P-prochiral building block dimethyl phenyl phosphine borane we were able to obtain phosphine boranes in yields up to 80 % and e.r. up to 98 : 2 by crystallization of the lithiated intermediate prior to the trapping reaction. NMR-based deuterium labeling experiments indicate that the epimerization in solution is based on the intermolecular proton transfer between nonlithiated phosphine borane and the corresponding lithiated intermediate, rendering the presence of the remaining starting compound in an optimized solvent mixture the main factor for successful enantioselective synthesis. Quantum chemical calculations using different model systems based on solid state structures confirm these experimental results. By gaining insights into the epimerization mechanism, essential principles for CIDR of lithiated phosphine boranes are elucidated that may be expanded to other important P-stereogenic compounds and simple chiral amines.

Structural Characterization of the Metalized Radical Cations of Adenosine ([Ade+Li-H]•+ and [Ade+Na-H]•+) by Infrared Multiphoton Dissociation Spectroscopy and Theoretical Studies.

Nucleoside radicals are key intermediates in the process of DNA damage, and alkali metal ions are a common group of ions in living organisms. However, so far, there has been a significant lack of research on the structural effects of alkali metal ions on nucleoside free radicals. In this study, we report a new method for generating metalized nucleoside radical cations in the gas phase. The radical cations [Ade+M-H]•+ (M = Li, Na) are generated by the 280 nm ultraviolet photodissociation (UVPD) of the precursor ions of lithiated and sodiated ions of 2-iodoadenine in a Fourier transform ion cyclotron resonance (FT ICR) cell. Further infrared multiphoton dissociation (IRMPD) spectra of both radical cations were recorded in the region of 2750-3750 cm-1. By combining these results with theoretical calculations, the most stable isomers of both radicals can be identified, which share the common characteristics of triple coordination patterns of the metal ions. For both radical species, the lowest-energy isomers undergo hydrogen transfer. Although the sugar ring in the most stable isomer of [Ade+Li-H]•+ is in a (South, syn) conformation similar to that of [Ado+Na]+, [Ade+Na-H]•+ is distinguished by the unexpected opening of the sugar ring. Their theoretical spectra are in good agreement with experimental spectra. However, due to the flexibility of the structures and the complexity of their potential energy surfaces, the hydrogen transfer pathways still need to be further studied. Considering that the free radicals formed directly after C-I cleavage have some similar spectral characteristics, the existence of these corresponding isomers cannot be ruled out. The findings imply that the structures of nucleoside radicals may be significantly influenced by the attached alkali metal ions. More detailed experiments and theoretical calculations are still crucial.

Emerging Lithiated Organic Cathode Materials for Lithium-Ion Full Batteries.

Organic electrode materials have application potential in lithium batteries owing to their high capacity, abundant resources, and structural designability. However, most reported organic cathodes are at oxidized states (namely unlithiated compounds) and thus need to couple with Li-rich anodes. In contrast, lithiated organic cathode materials could act as a Li reservoir and match with Li-free anodes such as graphite, showing great promise for practical full-battery applications. Here we summarize the synthesis, stability, and battery applications of lithiated organic cathode materials, including synthetic methods, stability against O2 and H2 O in air, and strategies to improve comprehensive electrochemical performance. Future research should be focused on new redox chemistries and the construction of full batteries with lithiated organic cathodes and commercial anodes under practical conditions. This Minireview will encourage more efforts on lithiated organic cathode materials and finally promote their commercialization.

Micro-Mesoporous Carbons from Cyclodextrin Nanosponges Enabling High-Capacity Silicon Anodes and Sulfur Cathodes for Lithiated Si-S Batteries.

Manufactured globally on industrial scale, cyclodextrins (CD) are cyclic oligosaccharides produced by enzymatic conversion of starch. Their typical structure of truncated cone can host a wide variety of guest molecules to create inclusion complexes; indeed, we daily use CD as unseen components of food, cosmetics, textiles and pharmaceutical excipients. The synthesis of active material composites from CD resources can enable or enlarge the effective utilization of these products in the battery industry with some economical as well as environmental benefits. New and simple strategies are here presented for the synthesis of nanostructured silicon and sulfur composite materials with carbonized hyper cross-linked CD (nanosponges) that show satisfactory performance as high-capacity electrodes. For the sulfur cathode, the mesoporous carbon host limits polysulfide dissolution and shuttle effects and guarantees stable cycling performance. The embedding of silicon nanoparticles into the carbonized nanosponge allows to achieve high capacity and excellent cycling performance. Moreover, due to the high surface area of the silicon composite, the characteristics at the electrode/electrolyte interface dominate the overall electrochemical reversibility, opening a detailed analysis on the behavior of the material in different electrolytes. We show that the use of commercial LP30 electrolyte causes a larger capacity fade, and this is associated with different solid electrolyte interface layer formation and it is also demonstrated that fluoroethylene carbonate addition can significantly increase the capacity retention and the overall performance of our nanostructured Si/C composite in both ether-based and LP30 electrolytes. As a result, an integration of the Si/C and S/C composites is proposed to achieve a complete lithiated Si-S cell.

Soluble and Perfluorinated Polyelectrolyte for Safe and High-Performance Li-O2 Batteries.

The severe performance degradation of high-capacity Li-O2 batteries induced by Li dendrite growth and concentration polarization from the low Li+ transfer number of conventional electrolytes hinder their practical applications. Herein, lithiated Nafion (LN) with the sulfonic group immobilized on the perfluorinated backbone has been designed as a soluble lithium salt for preparing a less flammable polyelectrolyte solution, which not only simultaneously achieves a high Li+ transfer number (0.84) and conductivity (2.5 mS cm-1 ), but also the perfluorinated anion of LN produces a LiF-rich SEI for protecting the Li anode from dendrite growth. Thus, the Li-O2 battery with a LN-based electrolyte achieves an all-round performance improvement, like low charge overpotential (0.18 V), large discharge capacity (9508 mAh g-1 ), and excellent cycling performance (225 cycles). Besides, the fabricated pouch-type Li-air cells exhibit promising applications to power electronic equipment with satisfactory safety.

Studies on the Lithiation, Borylation, and 1,2-Metalate Rearrangement of O-Cycloalkyl 2,4,6-Triisopropylbenzoates.

A broad range of acyclic primary and secondary 2,4,6-triisopropylbenzoate (TIB) esters have been used in lithiation-borylation reactions, but cyclic TIB esters have not. We have studied the use of cyclic TIB esters in lithiation-borylation reactions and looked at the effect of ring size (3- → 6-membered rings) on the three key steps of the lithiation-borylation protocol: deprotonation, borylation and 1,2-metalate rearrangement. Although all rings sizes could be deprotonated, the cyclohexyl case was impractically slow, and the cyclopentyl example underwent α-elimination faster than deprotonation at -78 °C and so could not be used. Both cyclobutyl and cyclopropyl cases underwent rapid borylation, but only the cyclobutyl substrate underwent 1,2-metalate rearrangement. Thus, the cyclobutyl TIB ester occupies a "Goldilocks zone," being small enough for deprotonation and large enough to enable 1,2-migration. The generality of the reaction was explored with a broad range of boronic esters.

A Novel Lithiated Silicon-Sulfur Battery Exploiting an Optimized Solid-Like Electrolyte to Enhance Safety and Cycle Life.

Anovel lithiated Si-S battery exploiting an optimized solid-like electrolyte is presented. This electrolyte is fabricated by integrating ether-based liquid electrolyte with SiO2 hollow nanosphere layer to suppress the shuttle effect and fluoroethylene carbonate additive to optimize the anodic solid electrolyte interface. The prepared lithiated Si-S batteries exhibit enhanced cycle life, low flammability, and strong recovery ability against short-circuit.

Lithiated primary amine--a new material for hydrogen storage.

A facile method for synthesizing crystalline lithiated amines by ball milling primary amines with LiH was developed. The lithiated amines exhibit an unprecedented endothermic dehydrogenation feature in the temperature range of 150-250 °C, which shows potential as a new type of hydrogen storage material. Structural analysis and mechanistic studies on lithiated ethylenediamine (Li2EDA) indicates that Li may mediate the dehydrogenation through an α,ß-LiH elimination mechanism, creating a more energy favorable pathway for the selective H2 release.

Synthesis of new enantiopure poly(hydroxy)aminooxepanes as building blocks for multivalent carbohydrate mimetics.

New compounds with carbohydrate-similar structure (carbohydrate mimetics) are presented in this article. Starting from enantiopure nitrones and lithiated TMSE-allene we prepared three 1,2-oxazine derivatives which underwent a highly stereoselective Lewis acid-induced rearrangement to give bicyclic products in good yield. Subsequent reductive transformations delivered a library of new poly(hydroxy)aminooxepane derivatives. The crucial final palladium-catalyzed hydrogenolysis of the 1,2-oxazine moiety was optimized resulting in a reasonably efficient approach to a series of new seven-membered carbohydrate mimetics.

All-Solid-State Lithium-Sulfur Batteries of High Cycling Stability and Rate Capability Enabled by a Self-Lithiated Sn-C Interlayer.

All-solid-state lithium-sulfur batteries (ASSLSBs) have attracted intense interest due to their high theoretical energy density and intrinsic safety. However, constructing durable lithium (Li) metal anodes with high cycling efficiency in ASSLSBs remains challenging due to poor interface stability. Here, a compositionally stable, self-lithiated tin (Sn)-carbon (C) composite interlayer (LSCI) between Li anode and solid-state electrolyte (SSE), capable of homogenizing Li-ion transport across the interlayer, mitigating decomposition of SSE, and enhancing electrochemical/structural stability of interface, is developed for ASSLSBs. The LSCI-mediated Li metal anode enables stable Li plating/stripping over 7000 h without Li dendrite penetration. The ASSLSBs equipped with LSCI thus exhibit excellent cycling stability of over 300 cycles (capacity retention of ≈80%) under low applied pressure (<8 MPa) and demonstrate improved rate capability even at 3C. The enhanced electrochemical performance and corresponding insights of the designed LSCI broaden the spectrum of advanced interlayers for interface manipulation, advancing the practical application of ASSLSBs.

Ultralong Cycling and Interfacial Regulation of Bilayer Heterogeneous Composite Solid-State Electrolytes in Lithium Metal Batteries.

Under the background of "carbon neutral", lithium-ion batteries (LIB) have been widely used in portable electronic devices and large-scale energy storage systems, but the current commercial electrolyte is mainly liquid organic compounds, which have serious safety risks. In this paper, a bilayer heterogeneous composite solid-state electrolyte (PLPE) was constructed with the 3D LiX zeolite nanofiber (LiX-NF) layer and in-situ interfacial layer, which greatly extends the life span of lithium metal batteries (LMB). LiX-NF not only offers a continuous fast path for Li+, but also zeolite's Lewis acid-base interaction can immobilize large anions, which significantly improves the electrochemical performance of the electrolyte. In addition, the in-situ interfacial layer at the electrode-electrolyte interface can effectively facilitate the uniform deposition of Li+ and inhibit the growth of lithium dendrites. As a result, the Li/Li battery assembled with PLPE can be stably cycled for more than 2500 h at 0.1 mA cm-2. Meanwhile, the initial discharge capacity of the LiFePO4/PLPE/Li battery can be 162.43 mAh g-1 at 0.5 C, and the capacity retention rate is 82.74% after 500 cycles. These results emphasize that this bilayer heterogeneous composite solid-state electrolyte has distinct properties and shows excellent potential for application in LMB.

High-capacity dilithium hydroquinone cathode material for lithium-ion batteries.

Lithiated organic cathode materials show great promise for practical applications in lithium-ion batteries owing to their Li-reservoir characteristics. However, the reported lithiated organic cathode materials still suffer from strict synthesis conditions and low capacity. Here we report a thermal intermolecular rearrangement method without organic solvents to prepare dilithium hydroquinone (Li2Q), which delivers a high capacity of 323 mAh g-1 with an average discharge voltage of 2.8 V. The reversible conversion between orthorhombic Li2Q and monoclinic benzoquinone during charge/discharge processes is revealed by in situ X-ray diffraction. Theoretical calculations show that the unique Li-O channels in Li2Q are beneficial for Li+ ion diffusion. In situ ultraviolet-visible spectra demonstrate that the dissolution issue of Li2Q electrodes during charge/discharge processes can be handled by separator modification, resulting in enhanced cycling stability. This work sheds light on the synthesis and battery application of high-capacity lithiated organic cathode materials.

Stereodivergent synthesis of jaspine B and its isomers using a carbohydrate-derived alkoxyallene as C3-building block.

Herein we present the synthesis of the anhydrophytosphingosine jaspine B and three of its stereoisomers using a carbohydrate-derived alkoxyallene in order to obtain the products in enantiopure form. Key step of the reaction sequence is the addition of the lithiated alkoxyallene to pentadecanal, setting the configuration at the later C-2 of the ring system. This reaction step proceeds with moderate selectivity and therefore leads to a stereodivergent approach to the natural product and its enantiomer. The gold-catalyzed 5-endo-cyclization affords the corresponding dihydrofurans, which after separation, azidation of the enol ether moiety and two subsequent reduction steps give the natural product and its stereoisomers.

Carbohydrate-auxiliary assisted preparation of enantiopure 1,2-oxazine derivatives and aminopolyols.

An approach to enantiopure hydroxylated 2H-1,2-oxazine derivatives is presented utilizing the [3 + 3] cyclisation of lithiated alkoxyallenes and an L-erythrose-derived N-glycosyl nitrone as precursors. This key step proceeded only with moderate diastereoselectivity, but allowed entry into both enantiomeric series of the resulting 3,6-dihydro-2H-1,2-oxazines. Their enol ether double bond was then subjected to a hydroboration followed by an oxidative work-up, and finally the auxiliary was removed. The described three-step procedure enabled the synthesis of enantiopure hydroxylated 1,2-oxazines. Typical examples were treated with samarium diiodide leading to enantiopure acyclic aminopolyols. We also report on our attempts to convert these compounds into enantiopure hydroxylated pyrrolidine derivatives.

Synthesis of graphene and recovery of lithium from lithiated graphite of spent Li-ion battery.

Recycling of spent Li-ion batteries is crucial for achieving sustainable development of battery industry. Current recycling processes mainly focus on valuable metals but less attention has been paid to spent graphite, which generally ends up as secondary waste. In this study, a process for preparing graphene and recovering Li in anode as a by-product from spent graphite was developed. The key point was to re-charge the spent LIBs to generate lithium graphite intercalation compounds. The lithium graphite intercalation compounds were then subjected to a hydrolysis procedure and graphene could be produced through ultrasonic treatment via the expansion/micro-explosion mechanism. Experimental results demonstrated that 1-4 layered graphene could be efficiently produced when spent Li-ion batteries with beyond 50% capacity were re-charged. The prepared graphene showed high quantity containing few defects (ID/IG = 0.33, C/O = 13.2 by energy dispersive spectroscopy and C/O = 8.8 by X-ray photoelectron spectroscopy). In addition, Li was simultaneously recovered in the form of battery-grade lithium carbonate in the above process. Economic analysis indicated that the graphene production cost was extremely low ($540/ton) compared to that of commercial graphene.

Li-Nafion Membrane Plasticised with Ethylene Carbonate/Sulfolane: Influence of Mixing Temperature on the Physicochemical Properties.

The use of dipolar aprotic solvents to swell lithiated Nafion ionomer membranes simultaneously serving as electrolyte and separator is of great interest for lithium battery applications. This work attempts to gain an insight into the physicochemical nature of a Li-Nafion ionomer material whose phase-separated nanostructure has been enhanced with a binary plasticiser comprising non-volatile high-boiling ethylene carbonate (EC) and sulfolane (SL). Gravimetric studies evaluating the influence both of mixing temperature (25 to 80 °C) and plasticiser composition (EC/SL ratio) on the solvent uptake of Li-Nafion revealed a hysteresis between heating and cooling modes. Differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) revealed that the saturation of a Nafion membrane with such a plasticiser led to a re-organisation of its amorphous structure, with crystalline regions remaining practically unchanged. Regardless of mixing temperature, the preservation of crystallites upon swelling is critical due to ionomer crosslinking provided by crystalline regions, which ensures membrane integrity even at very high solvent uptake (≈200% at a mixing temperature of 80 °C). The physicochemical properties of a swollen membrane have much in common with those of a chemically crosslinked polymer gel. The conductivity of ≈10-4 S cm-1 demonstrated by Li-Nafion membranes saturated with EC/SL at room temperature is promising for various practical applications.

Superalkali-doped borazine and lithiated borazine complexes: diffuse excess electron and large first-hyperpolarizability.

A number of superalkali (M3O / M3S; M = Li, Na, K)-doped borazine and hexalithio borazine complexes are considered for the theoretical study of their electronic structure and quadratic polarizability. Electron-rich O/S atom of superalkali species remains very close to one boron atom of the ring through non-covalent interaction. The first-hyperpolarizability increases rather significantly upon superalkali doping. The chosen complexes possess diffuse excess electron which is located on the superpalkali moiety of borazine complexes and at the ring site of lithiated borazines. First-hyperpolarizability of M3O(S)@B3N3Li6 complexes are significantly larger than that of the corresponding M3O(S)@B3N3H6 complexes. The magnitude of first-hyperpolarizability of Li3S@B3N3Li6 is larger than that of Li3S@B3N3H6 by about three orders of magnitude.

Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans - an approach to carbohydrate mimetics.

A stereodivergent synthesis of enantiopure 3,6-dihydro-2H-pyrans is presented. The addition of lithiated enol ethers to carbohydrate-derived nitrones afforded syn- or anti-configured hydroxylamine derivatives 4a-d that were cyclized under Lewis acidic conditions to yield functionalized dihydropyrans cis- or trans-5a-d containing an enol ether moiety. This functional group was employed for a variety of subsequent reactions such as dihydroxylation or bromination. Bicyclic enol ether 19 was oxidatively cleaved to provide the highly functionalized ten-membered ring lactone 20. The synthesized enantiopure aminopyrans 24, 26, 28 and 30 can be regarded as carbohydrate mimetics. Trimeric versions of 24 and 28 were constructed via their attachment to a tricarboxylic acid core.

Growth of lithium hydride thin films from solutions: Towards solution atomic layer deposition of lithiated films.

Lithiated thin films are necessary for the fabrication of novel solid-state batteries, including the electrodes and solid electrolytes. Physical vapour deposition and chemical vapour deposition can be used to deposit lithiated films. However, the issue of conformality on non-planar substrates with large surface area makes them impractical for nanobatteries the capacity of which scales with surface area. Atomic layer deposition (ALD) avoids these issues and is able to deposit conformal films on 3D substrates. However, ALD is limited in the range of chemical reactions, due to the required volatility of the precursors. Moreover, relatively high temperatures are necessary (above 100 °C), which can be detrimental to electrode layers and substrates, for example to silicon into which the lithium can easily diffuse. In addition, several highly reactive precursors, such as Grignard reagents or n-butyllithium (BuLi) are only usable in solution. In theory, it is possible to use BuLi and water in solution to produce thin films of LiH. This theoretical reaction is self-saturating and, therefore, follows the principles of solution atomic layer deposition (sALD). Therefore, in this work the sALD technique and principles have been employed to experimentally prove the possibility of LiH deposition. The formation of homogeneous air-sensitive thin films, characterized by using ellipsometry, grazing incidence X-ray diffraction (GIXRD), in situ quartz crystal microbalance, and scanning electron microscopy, was observed. Lithium hydride diffraction peaks have been observed in as-deposited films by GIXRD. X-ray photoelectron spectroscopy and Auger spectroscopy analysis show the chemical identity of the decomposing air-sensitive films. Despite the air sensitivity of BuLi and LiH, making many standard measurements difficult, this work establishes the use of sALD to deposit LiH, a material inaccessible to conventional ALD, from precursors and at temperatures not suitable for conventional ALD.

Lithiated NiCo2O4 Nanorods Anchored on 3D Nickel Foam Enable Homogeneous Li Plating/Stripping for High-Power Dendrite-Free Lithium Metal Anode.

Lithium (Li) metal is one of the promising anode materials in the next-generation high-energy batteries, but Li dendrite growth and a big volume change during cycling result in low Coulombic efficiency (CE), short lifespan, and safety hazards, thereby impeding practical implementation of Li in rechargeable batteries. Herein, we report a highly stable and dendrite-free Li metal anode based on a three-dimensional (3D) conductive and lithiophilic scaffold comprising lithiated NiCo2O4 nanorods grown on nickel foam (LNCO/Ni). The nanorods grown on 3D Ni foam with a large surface area effectively reduce the averaged electrical current in the electrode, and the conformal Li2O coating produced in situ on the lithiated NiCo2O4 nanorods provides the surface lithiophilicity enabling stable Li plating/stripping without Li dendrite growth even at a high current density of 5 mA cm-2. The LNCO/Ni-Li anode shows a low voltage hysteresis of 16 mV, high CE of 98.7%, and stable cycling without obvious voltage fluctuation for over 500 cycles (1000 h) at a current density of 1 mA cm-2. Specifically, for a scalable Li loading of 20 mA h cm-2 on LNCO/Ni, no growth of Li dendrite and electrode thickness fluctuations are observed. The full cell consisting of the LNCO/Ni-Li anode and the LiFePO4 cathode exhibits a high rate capability and CE as high as 99.6% for more than 160 cycles. Our study reveals a new strategy to develop stable Li-metal anodes for high-energy batteries.