Lithium Naphthalenide Research Articles

Uncovering Reduction Mechanisms of Fluoroethylene Carbonate

Energy storage plays an integral role in climate change mitigation, given that many promising alternatives to fossil fuel-based technologies rely on intermittent energy sources like the sun or wind. Particularly, lithium metal batteries (LMBs) are a promising technology due to lithium’s high theoretical specific capacity and low reduction potential, which can result in batteries with energy densities surpassing current state of the art lithium-ion batteries.1 Electrolyte design is a key strategy to improve the cycling stability and Coulombic efficiency of LMBs, where the highly reductive lithium metal anode reacts with the electrolyte during cycling, resulting in capacity loss. These reactions form a solid electrolyte interphase (SEI), and many successful electrolyte engineering strategies have involved tuning the SEI to be mechanically and chemically stable to prevent further reactions.In this research, we focus on fluoroethylene carbonate (FEC), a highly effective electrolyte solvent in LMBs.2 Although prior research has illuminated key reduction products of FEC2,3, including lithium fluoride (LiF), there remains a gap in understanding regarding the mechanism by which FEC and other similar fluorinated solvents are reduced to form an SEI. Furthermore, recent research has demonstrated that a preformed SEI comprised solely of LiF breaks down during cycling, illustrating that bulk chemical and mechanical properties of SEI components may not translate to their function within the SEI.4 In this work, we employ electron paramagnetic resonance (EPR) spectroscopy to study intermediate generation during FEC reduction. We pursued both a chemical reduction using lithium naphthalenide and an electrochemical approach to reduce FEC. The use of EPR with spin traps enables insight into the radical species formed during FEC reduction, which we hypothesize are precursors to cross-linked polymer networks that are key to a high performing SEI. Here, we employed conventional post-mortem SEI analysis like X-ray Photoelectron Spectroscopy (XPS) in addition to EPR to clarify reduction mechanisms of FEC and form a framework for studying electrolyte reduction intermediates. Ultimately, this approach affords insight into electrolyte breakdown mechanisms to form an effective SEI which can both accommodate volume expansion and inhibit parasitic electrolyte consumption. This will guide electrolyte design for high Coulombic efficiency LMBs in the future.References K. G. Gallagher et al., Energy Environ. Sci., 7, 1555–1563 (2014).X.-Q. Zhang, X.-B. Cheng, X. Chen, C. Yan, and Q. Zhang, Advanced Functional Materials, 27, 1605989 (2017).Y. Jin et al., J. Am. Chem. Soc., 139, 14992–15004 (2017).M. He, R. Guo, G. M. Hobold, H. Gao, and B. M. Gallant, Proceedings of the National Academy of Sciences, 117, 73–79 (2020).

Freestanding monolayer CrOCl through chemical exfoliation.

Magnetic two-dimensional (2D) materials are a unique class of quantum materials that can exhibit interesting magnetic phenomena, such as layer-dependent magnetism. The most significant barrier to 2D magnet discovery and study lies in our ability to exfoliate materials down to the monolayer limit. Therefore designing exfoliation methods that produce clean, monolayer sheets is crucial for the growth of 2D material research. In this work, we develop a facile chemical exfoliation method using lithium naphthalenide for obtaining 2D nanosheets of magnetic van der Waals material CrOCl. Using our optimized method, we obtain freestanding monolayers of CrOCl, with the thinnest measured height to date. We also provide magnetic characterization of bulk, intercalated intermediate, and nanosheet pellet CrOCl, showing that exfoliated nanosheets of CrOCl exhibit magnetic order. The results of this study highlight the tunability of the chemical exfoliation method, along with providing a simple method for obtaining 2D CrOCl.

Reactive Magnesium Nanoparticles to Perform Reactions in Suspension.

Zerovalent magnesium (Mg(0)) nanoparticles are prepared in the liquid phase (THF) by reduction of MgBr2 either with lithium naphthalenide ([LiNaph]) or lithium biphenyl ([LiBP]). [LiBP]-driven reduction results in smaller Mg(0) nanoparticles (10.3±1.7 nm) than [LiNaph]-driven reduction (28.5±4 nm). The as-prepared Mg(0) nanoparticles are monocrystalline (d101=245±5 pm) for both types of reduction. Their reactivity is probed by liquid-phase reaction (THF, toluene) in suspension near room temperature (20-120 °C) with 1-bromoadamantane (AdBr), chlortriphenylsilane (Ph3SiCl), trichlorphenylsilane (PhSiCl3), 9H-carbazole (Hcbz), 7-azaindole (Hai), 1,8-diaminonaphthalene (H4nda) and N,N'-bis(α-pyridyl)-2,6-diaminopyridine (H2tpda) as exemplary starting materials. The reactions result in the formation of 1,1'-biadamantane (1), [MgCl2(thf)2]×Ph6Si2 (2), [Mg9(thf)14Cl18] (3), [Mg(cbz)2(thf)3] (4), [Mg4O(ai)6]×1.5 C7H8 (5), [Mg4(H2nda)4(thf)4] (6) and [Mg3(tpda)3] (7) with 40-80 % yield. 1 and 2 show the reactivity of Mg(0) nanoparticles for C-C and Si-Si coupling reactions with sterically demanding starting materials. 3-7 represent new coordination compounds using sterically demanding N-H-acidic amines as starting materials. The formation of multinuclear Mg2+ complexes with multidentate ligands illustrates the potential of the oxidative approach to obtain novel compounds with Mg(0) nanoparticles in the liquid phase.

Capping Agents Enable Well-Dispersed and Colloidally Stable Metallic Magnesium Nanoparticles.

Mg nanoparticles are an emerging plasmonic material due to Mg's abundance and ability to sustain size- and shape-dependent localized surface plasmon resonances across a broad range of wavelengths from the ultraviolet to the near infrared. However, Mg nanoparticles are colloidally unstable due to their tendency to aggregate and sediment. Nanoparticle aggregation can be inhibited by the addition of capping agents that impart surface charges or steric repulsion. Here, we report that the common capping agents poly(vinyl) pyrrolidone (PVP), polyethylene glycol (PEG), cetyltrimethylammonium bromide (CTAB), and sodium dodecyl sulfate (SDS) interact differently and have varied effects on the aggregation and colloidal stability of Mg nanoparticles. Nanoparticles synthesized in the presence of PVP showed improvements in colloidal stability and reduced aggregation, as observed by electron microscopy and optical spectroscopy. The binding of PVP was confirmed through infrared and X-ray photoelectron spectroscopy. The influence of PVP on the reduction of di-n-butyl magnesium was evaluated through analysis of particle size distribution and Mg yield as a function of reaction time, reducing agent, and temperature. Furthermore, the presence of PVP drastically changes the growth pattern of metallic Mg structures obtained from the reduction of the Grignard reagents butylmagnesium chloride and phenylmagnesium chloride by lithium naphthalenide: large polycrystalline aggregates and well-separated faceted nanoparticles grow without and with PVP, respectively. This study provides new synthetic routes that generate colloidally stable and well-dispersed Mg nanoparticles for plasmonic and other applications.

B2,N4-Doped Heptacenes: Ambipolar Charge-Transfer Compounds with Deep LUMO Levels.

The B2,N4-doped heptacene H4 in which two N,N'-dihydrophenazine units are linked by two BMes bridges (Mes = mesityl) was synthesized via fourfold Buchwald-Hartwig coupling between 2,3,6,7-tetrachloro-9,10-dimesityl-9,10-dihydro-9,10-diboraanthracene and o-phenylenediamine (tBuXPhos-Pd-G3, DBU/NaOTf, 2-MeTHF, 50 °C, 16 h). Upon exposure to ambient air, H4 is oxidized to its N,N'-dihydro form H2; further oxidation with MnO2 furnishes the di(phenazine) derivative H0. Stirring under a blanket of H2 in the presence of Pd/C hydrogenates H0 back to H2 and ultimately H4. Yellow-colored H0 is a remarkably good electron acceptor with a LUMO-energy level of -3.9 eV; upon irradiation with a 405 nm LED in the presence of THF or 1,4-cyclohexadiene, H0 accepts two H atoms to furnish H2. One-electron reduction of H0 yields the isolable radical-anion salt Li[H0] (lithium naphthalenide, THF, -30 °C to rt). The ambipolar compounds H2 and H4 possess a navy blue and deep purple color, respectively, due to charge-transfer interactions from the electron-rich N,N'-dihydrophenazine donor(s) to the electron-accepting B2C4 core.

Chromium Metal Nanoparticles, Their Reactivity and Reactions

AbstractZerovalent chromium nanoparticles (2.2±0.2 nm in size) are prepared in the liquid phase (THF) by reduction of CrCl2 with lithium naphthalenide ([LiNaph]). The deep black Cr(0) nanoparticle suspensions in THF are colloidally and chemically highly stable. On the other hand, the Cr(0) nanoparticles are highly reactive, e. g., when in contact to O2, H2O, or other oxidizing agents. To probe the reactivity of the Cr(0) nanoparticles in the liquid phase near room temperature (50–80 °C), they are reacted with different coordinatively demanding, N−H, S−H or O−H acidic reactants. This includes the amines 2,2′‐dipyridylamine (HDPA), 2‐(1H‐imidazol‐2‐yl)pyridine (HImPy) and carbazole (HCbz), the thiol 2‐mercaptopyridine (HMPy), and benzoic acid (HBz) as a carboxylate. As a result, the five novel compounds [Cr(DPA)3], [Cr(ImPy)3] ⋅ HImPy, [Cr(MPy)3] ⋅ 0.5 Tol (Tol: toluene), [Na2Cr(Cbz)4(THF)3], and [Cr2(Bz)4(THF)2] are obtained. [Cr(DPA)3] and [Cr(ImPy)3] ⋅ HImPy show Cr(III) coordinated by nitrogen only; [Cr(MPy)3] ⋅ 0.5 Tol shows a coordination of Cr(III) by both N and S atoms. [Na2Cr(Cbz)4(THF)3] and [Cr2(Bz)4(THF)2] contain Cr(II) and exhibit an infinite chain‐like structure and pairs of chromium atoms with fourfold binding.

Preparation of Vinylic Lithium Reagents from Silyl Enolates of Alkyl Aryl Ketones Using Lithium Arenide

AbstractThe preparation of vinylic lithium reagents from vinylic halides is a common practice in organic synthesis. However, the preparation of vinylic halides is not always straightforward. In this study, we propose the use of silyl enolates of alkyl aryl ketones as a readily available and efficient alternative for generating vinylic lithium species. Treatment of triisopropylsilyl enolates of alkyl aryl ketones with lithium naphthalenide or lithium 4,4’‐di‐t‐butylbiphenylide affords the corresponding vinylic lithium species. This preparation represents a reductive transformation of electron‐rich silyl enolates, which had remained unexplored. This process provides an alternative to the Shapiro reaction and has great potential for various applications in organic synthesis.

Enantioselective Formal Total Synthesis of Damsin

AbstractEnantioselective formal total synthesis of damsin, which was isolated from Compositae Ambrosia maritima L., is described. The highly enantio- and diastereoselective catalytic Mukaiyama–Michael reaction and subsequent highly stereoselective epimerization shorten the synthetic steps. It is also reported that the enolate, which was formed by the reaction of β-keto sulfone with lithium naphthalenide, reacted with methyl cyanoformate to form a quaternary stereogenic center in high yield with high stereoselectivity. This finding extends the synthetic chemistry starting from β-keto sulfones.

Experimental and computational study of the exchange interaction between the V(III) centers in the vanadium-cyclal dimer.

[V2(HCyclal)2] is prepared by controlled oxidation of vanadium nanoparticles at 50 °C in toluene. The V(0) nanoparticles are synthesized in THF by reduction of VCl3 with lithium naphthalenide. They exhibit very small particle sizes of 1.2 ± 0.2 nm and a high reactivity (e.g. with air or water). By reaction of V(0) nanoparticles with the azacrown ether H4Cyclal, [V2(HCyclal)2] is obtained with deep green crystals and high yield. The title compound exhibits a V(III) dimer (V⋯V: 304.1(1) pm) with two deprotonated [HCyclal]3- ligands as anions. V(0) nanoparticles as well as the sole coordination of V(III) by a crown ether as the ligand and nitrogen as sole coordinating atom are shown for the first time. Magnetic measurements and computational results point to antiferromagnetic coupling within the V(III) couple, establishing an antiferromagnetic spin S = 1 dimer with the magnetic susceptibility determined by the thermal population of the total spin ranging from ST = 0 to ST = 2.

Improvement of Sulfur Cathode Reversibility by Specific Chemical Lithium Pre-doping Method

1.IntoroductionRecently, lithium-ion batteries (LIBs) have been required in terms of a high energy density for large-scale applications such as power supplies for electric vehicles. Lithium-sulfur (Li-S) batteries are, therefore, expected as next generation batteries because of their high energy density.Sulfur is utilized as cathode material for Li-S batteries because of a high specific capacity. However, sulfur has a low electric conductivity and a risk of dissolution into an electrolyte during a charge-discharge process [1]. L. Nazar et al. applied activated carbon as substrate for sulfur to help electric conduction and prevent dissolution of sulfur [2]. The activated carbon allows Li-S batteries to show high specific capacity with high reversibility. Even if these problems are solved, however, Li-S batteries have a further problem of excessive initial irreversible capacity during the first discharge process. Li pre-doping is a useful technique to cancel the large irreversible capacity in actual LIBs. Abe et al. reported a chemical lithium pre-doping method for a graphite using lithium naphthalenide [3]. Studies have been reported on the use of such pre-doping to improve the performance of Li-S batteries, for instance, with a sulfur-Ketjenblack composite cathode [4]. In our previous study, we have applied that method to a sulfur cathode composed of microporous activated carbon and sulfur before cell assembly and developed a Li2S cathode that suppressed the initial irreversible capacity during the first discharge process. However, the Li2S cathode showed an unignorable initial irreversible capacity and poor cycle life [5].This work attempts to improve the reversible capacity of the Li2S cathode by a specialized chemical lithium pre-doping method. Our report would lead to the proposal of novel cathode and anode options in Li-S batteries. Method 2-1. Fabrication of lithium naphthalenide solutionAs Li metal and Li2S are both sensitive to moisture in air, all the following synthesis processes were carried out in an Ar-filled glove box. Lithium naphthalenide, a dark green solution was prepared by mixing an equal mol amount of Li metal with naphthalene in a cyclic ether solvent.2-2. Fabrication of Li2S-AC cathodesEach sulfur cathode was prepared by mixing the S-AC (a composite of microporous activated carbon and sulfur), acetylene black, carboxymethyl cellulose, and styrene butadiene rubber at a respective weight ratio of 93: 3: 2: 2 and coating the resulting aqueous slurry on a carbon paper.The 1M lithium naphthalenide solution was dropped on the sulfur cathode. After 20 min reaction, the cathode was rinsed several times with 2–dimethoxyethane (DME) to remove the residues of reagents. The cathode was then dried under reduced pressure for 12 h. After that, the resulting Li2S cathode was impregnated with a mixture of vinylene carbonate (VC) and fluoroethylene carbonate (FEC) (VC: FEC = 1: 1 by weight). After 20 min impregnation, the cathode was dried under reduced pressure for 12 h.2-3. Assembling of cellsCells were assembled with the Li2S electrode and Li metal foil as an anode. Lithium bis(trifluorosulfonyl)imide (LiTFSI): tetraglyme (G4): 1,1,2,2–tetrafluoroethyl–2,2,3,3–tetrafluoropropyl ether (D2) at a respective ratio of 10: 8: 40 (by mol) was used as the electrolyte.3.Major results and discussionThe Li2S cathode without the VC/FEC impregnation showed an initial charge capacity of 1791 mAh g-1 and an initial discharge capacity of 1298 mAh g-1, indicating a large irreversible capacity. In contrast, the Li2S cathode with the VC/FEC impregnation showed 1446 mAh g-1 and 1422 mAh g-1, respectively. Thus, the impregnation with VC/FEC reduced the initial irreversible capacity and improved the initial charge capacity. According to these results, Li remaining in the sulfur cathode would be partially consumed to form a film by the impregnation with VC/FEC. In addition, the capacity retention of the Li2S cathode with and without the VC/FEC impregnation was 73 % and 64 % at the 30th cycle, respectively. This suggests that the Li2S cathode with the film leads to better cycle performance than that without the film.We will also report the results of surface composition analysis of the Li2S cathode with and without the VC/FEC impregnation by Hard X-ray Photoelectron Spectroscopy (HAXPES).

Synthesis of a Kinetically Stabilized 2,2-Dihydrosilene

Abstract An overcrowded 2,2-dihydrosilene bearing 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt) and 2,6-diisopropylphenyl (Dip) groups was synthesized as a stable compound both in the solid state and in solution for a long period of time. The newly generated 2,2-dihydrosilene was obtained by exhaustive reduction of the corresponding dibromosilane, Tbt(Dip)SiBr2, with an excess amount of lithium naphthalenide at −78 °C followed by addition of CH2Cl2. The formation of 1 was confirmed by multinuclear NMR studies and extensive theoretical calculations.

Li Pre-Doping into Si Negative Electrodes Using Li-Naphthalenide Solutions with Various Ether Solvents For Next-Generation Batteries

Four ethers were compared as solvents of lithium naphthalenide (Li-NTL) solutions to pre-dope Li into Si electrodes. The solvents of the Li-NTL solutions affected the stability and equilibrium potential (V eq). X-ray diffraction, thermodynamic characterization and ultraviolet-visible (UV–vis) spectroscopy were used to clarify the effects of the solvation structure, the lowest unoccupied molecular orbital (LUMO) energy of the solvent molecule and the ion pair structure between Li+ ions and naphthalenide radical anions ([NTL]·−) on doping capacity. A Li-NTL solution having a low V eq and sufficient stability under potentials as low as that of Li metal was found to provide the highest pre-doping capacity. In particular, a 2-methyltetrahydrofuran (MeTHF) solution exhibiting the lowest V eq showed a pre-doping capacity as high as 3250 mAh g−1 after 24 h. UV–vis spectra and Walden plots indicated that a Li-NTL solution using MeTHF provided less dissociation than a tetrahydrofuran (THF) solution. The doping capacity is evidently determined by the V eq of the Li-NTL solution as a consequence of the dissociation equilibrium of the ion pair of the solvated Li+ ion and [NTL]·− radical ions.

A Facile and Efficient Chemical Prelithiation of Graphite for Full Capacity Utilization of Li‐Ion Batteries

Chemical prelithiation is considered to be a facile and efficient strategy to compensate the initial irreversible capacity loss of anode materials for achieving full capacity utilization of Li‐ion batteries (LIBs). However, most of the prelithiation reagents reported so far are difficult to apply for commercially used graphite (Gr) anode due to their higher redox potentials than the formation potential of graphite–lithium compounds and the co‐intercalation behavior in the interlayers of Gr anode, causing the exfoliation and destruction of Gr structure during prelithiation process. Herein, a new prelithiation solution for Gr anode by using lithium naphthalenide as a lithiation reagent and 2‐methyl tetrahydrofuran as a reduction‐tolerant solvent is demonstrated. This prelithiation solution has a very low redox potential of 0.19 V and can controllably and efficiently prelithiate Gr anode to a required degree in a few minutes without the solvent co‐intercalation. Benefiting from these advantages, the Gr anode prelithiated for 3 min exhibits a high initial Coulombic efficiency of 100%, a better rate capability, and higher cycling capacity retention than conventional pristine Gr anode. Particularly, this prelithiation solution is low cost, easily synthesized, and recycled for industrial production, thus offering a practical convenience for LIBs manufacture.

Plastic Monolithic Mixed-Conducting Interlayer for Dendrite-Free Solid-State Batteries.

Solid‐state electrolytes (SSEs) hold a critical role in enabling high‐energy‐density and safe rechargeable batteries with Li metal anode. Unfortunately, nonuniform lithium deposition and dendrite penetration due to poor interfacial solid–solid contact are hindering their practical applications. Here, solid‐state lithium naphthalenide (Li‐Naph(s)) is introduced as a plastic monolithic mixed‐conducting interlayer (PMMCI) between the garnet electrolyte and the Li anode via a facile cold process. The thin PMMCI shows a well‐ordered layered crystalline structure with excellent mixed‐conducting capability for both Li+ (4.38 × 10–3 S cm–1) and delocalized electrons (1.01 × 10–3 S cm–1). In contrast to previous composite interlayers, this monolithic material enables an intrinsically homogenous electric field and Li+ transport at the Li/garnet interface, thus significantly reducing the interfacial resistance and achieving uniform and dendrite‐free Li anode plating/stripping. As a result, Li symmetric cells with the PMMCI‐modified garnet electrolyte show highly stable cycling for 1200 h at 0.2 mA cm–2 and 500 h at a high current density of 1 mA cm–2. The findings provide a new interface design strategy for solid‐state batteries using monolithic mixed‐conducting interlayers.

Constructing a Li-gradient in Li-Mn-O spinel for long-life lithium-ion batteries

Owing to the rapid Li ion extraction/insertion kinetics, Li-Mn-O spinels are promising candidates for high-power lithium-ion batteries that is required in electric vehicles. However, the Li-Mn-O spinel cathodes always suffer from poor cycling stability in practical due to the dissolution of Mn and Jahn-Teller distortion. Herein, we report on a new design of constructing a Li-gradient in Li-Mn-O spinel, which is achieved by surface treatment with lithium naphthalenide solution. The as-obtained Li1+xMn2-xO4 spinels exhibit a Li-gradient with decreasing Li concentration from surface to interior. Importantly, the highly doped surface ensures good cycle stability while the lightly doped bulk maintains a relatively high capacity. This work provides a new design for Li-Mn-O spinels to mitigate their stability problem.

Transient lithium metal plating on graphite: Operando7Li nuclear magnetic resonance investigation of a battery cell using a novel RF probe

The development of optimal fast charging protocols requires detailed information regarding lithium inventory in a battery. We built a parallel-plate resonator RF probe and a cartridge-type single layer cell of improved designs. The probe has excellent sensitivity and homogeneity of electromagnetic field, while the cartridge allows easy cell assembly, straight-forward multiplexing, and excellent cell-to-cell data reproducibility. Herein we present our findings from operando7Li NMR measurements on a graphite//NMC622 cell. The usual/expected sequencing of LixC6 phases from dilute to concentrated observed during charging at low (<C/5) rates is replaced at high (≥1C) rates by a direct transition to, and propagation of concentrated phases throughout the graphite electrode, with no evidence for dilute phases. Concurrently, a peak attributed to lithium naphthalenide appears at ∼20 ppm. Lithium therefore accumulates on graphite surfaces, facilitating Li metal plating under fast charge conditions. While some of the deposited Li metal can intercalate into graphite after cell charging, a significant fraction accumulates during consecutive cycles, creating a barrier for Li+ transport, which decreases the amount of recoverable Li, and its intercalation rate into graphite. Thus, Li plating not only can create safety hazards through dendrite growth, but also irreversibly impairs the fast charging capability of cells.

Synthesis of 6-tert-butyl-3-dicyanomethylene-5-silagermyl- and digermyl-1,2,4-triazines

Fragmentation of the Ge–Ph bond in 2-(6-tBu-5-triphenylgermyl-2-R-4,5-dihydro-1,2,4-triazin-3(2H)-ylidene)malononitriles (R = Me, nBu) using lithium naphthalenide and further electrophile trapping with H+, Ph3SiCl or Ph3GeBr furnished the corresponding 5-Ph2HGe–, Ph3Si–Ph2Ge– or Ph3Ge–Ph2Ge– derivatives. In the case of R = CH2CO2 tBu, metalation at the exocyclic methylene group was observed to give tert-butyl 7-amino-3-tBu-8-cyanopyrrolo[1,2-b][1,2,4]triazine-6-carboxylate as a result of cyclization/Ge atom elimination. Structures of the synthesized compounds were confirmed by spectral and XRD data.

Chemically Prelithiated Hard-Carbon Anode for High Power and High Capacity Li-Ion Batteries.

Hard carbons (HC) have potential high capacities and power capability, prospectively serving as an alternative anode material for Li-ion batteries (LIB). However, their low initial coulombic efficiency (ICE) and the resulting poor cyclability hinder their practical applications. Herein, a facile and effective approach is developed to prelithiate hard carbons by a spontaneous chemical reaction with lithium naphthalenide (Li-Naph). Due to the mild reactivity and strong lithiation ability of Li-Naph, HC anode can be prelithiated rapidly in a few minutes and controllably to a desirable level by tuning the reaction time. The as-formed prelithiated hard carbon (pHC) has a thinner, denser, and more robust solid electrolyte interface layer consisting of uniformly distributed LiF, thus demonstrating a very high ICE, high power, and stable cyclability. When paired with the current commercial LiCoO2 and LiFePO4 cathodes, the assembled pHC/LiCoO2 and pHC/LiFePO4 full cells exhibit a high ICE of >95.0% and a nearly 100% utilization of electrode-active materials, confirming a practical application of pHC for a new generation of high capacity and high power LIBs.

Preparation and reactions of 4,4-dilithiodithienogermole

The reaction of 4,4-dichloro-2,6-di(n-butyl)dithienogermole (DTGCl) with lithium naphthalenide yielded a dark blue solution, which was treated with methyl iodide to provide a 4,4-dimethylated product in 67% isolated yield, indicating the formation of 4,4-dilithio-2,6-di(n-butyl)dithienogermole (DTGLi). Similar treatment of the dark blue solution containing DTGLi with trimethylsilyl fluoride and water gave the corresponding 4,4-disubstituted products. When trimethylsilyl chloride was used, however, no silylated products were obtained, likely due to steric hindrance. The reaction of DTGLi with DTGCl gave poly[2,6-di(n-butyl)dithienogermole-4,4-diyl], whose UV–vis absorption spectra revealed a more extended conjugation than that of a previously prepared product from the Wurtz-type coupling of DTGCl with sodium. Reinvestigation of the electronic states of poly(dithienogermole-4,4-diyl) derivatives on the basis of crystal orbital calculations was also accomplished.

Reduction Reactions of Electrolyte Salts for Lithium Ion Batteries: LiPF6, LiBF4, LiDFOB, LiBOB, and LiTFSI

The reduction products of common lithium salts for lithium ion battery electrolytes, LiPF6, LiBF4, lithium bisoxalato borate (LiBOB), lithium difluorooxalato borate (LiDFOB), and lithium trifluorosulfonylimide (LiTFSI), have been investigated. The solution phase reduction of different lithium salts via reaction with the one electron reducing agent, lithium naphthalenide, results in near quantitative reactions. Analysis of the solution phase and head space gasses suggests that all of the reduction products are precipitated as insoluble solids. The solids obtained through reduction were analyzed with solution NMR, IR-ATR and XPS. All fluorine containing salts generate LiF upon reduction while all oxalate containing salts generate lithium oxalate. In addition, depending upon the salt other species including, LixPFyOz, LixBFy, oligomeric borates, and lithium bis[N-(trifluoromethylsulfonylimino)] trifluoromethanesulfonate are observed.