Air-Stable Li2S Cathodes Enabled by an In Situ-Formed Li+ Conductor for Graphite-Li2S Pouch Cells

Using Li2S cathodes instead of S cathodes presents an opportunity to pair them with Li-free anodes (e.g., graphite), thereby circumventing anode-related issues, such as poor reversibility and safety, encountered in Li-S batteries. However, the moisture-sensitive nature of Li2S causes the release of hazardous H2S and the formation of insulative by-products, increasing the manufacturing difficulty and adversely affecting cathode performance. Here, Li4SnS4, a Li+ conductor that is air-stable according to the hard-soft acid-base principle, is formed in situ and uniformly on Li2S particles because Li2S itself participates in Li4SnS4 formation. When exposed to air (20% relative humidity), the protective Li4SnS4 layer maintains its components and structure, thus contributing to the enhanced stability of the Li2S@Li4SnS4 composite. In addition, the Li4SnS4 layer can accelerate the sluggish conversion of Li2S because of its favorable interfacial charge transfer, and continuously confine lithium polysulfides owing to its integrity during electrochemical processes. A graphite-Li2S pouch cell containing a Li2S@Li4SnS4 cathode is constructed, which shows stable cyclability with 97% capacity retention after 100 cycles. Hence, combining a desirable air-stable Li2S cathode and a highly reversible Li-free configuration offers potential practical applications of graphite-Li2S full cells.

Electrolyte Regulation in Stabilizing the Interface of a Cobalt-Free Layered Cathode for 4.8 V High-Voltage Lithium-Ion Batteries

The cobalt-free layered oxide cathode of LiNi0.65Mn0.35O2 is promising for high-energy-density lithium-ion batteries (LIBs). However, under high-voltage conditions, severe side reactions between the Co-free cathode and electrolyte, as well as grain boundary cracks and pulverization of particles, hinder its practical applications. Herein, an electrolyte regulation strategy is proposed by adding fluoroethylene carbonate (FEC) and LiPO2F2 as electrolyte additives in carbonate-based electrolytes to address the above issues. As a result, a homogeneous and dense organic-inorganic hybrid cathode electrolyte interface (CEI) film is formed on the cathode surface. The CEI film consists of C-F, LiF, Li2CO3, and LixPOyFz species, which is proven to be highly conductive and effective in suppressing structure damage and alleviating the interfacial reactions between the cathode and electrolyte. With such a CEI film, the interfacial stability of the Co-free cathode and the high-voltage cycling performance of Li||LiNi0.65Mn0.35O2 are greatly improved. A reversible capacity of 155.1 mAh g-1 and a capacity retention of 81.3% over 150 cycles are attained at a 4.8 V charge cutoff voltage with the tamed electrolyte, whereas the cell without the additives only retains 76.1% capacity retention. Therefore, our work demonstrates the synergistic effect of FEC and LiPO2F2 in stabilizing the interface of Co-free cathode materials and provides an alternative strategy for the electrolyte design of high-voltage LIBs.

Regenerated Graphite Electrodes with Reconstructed Solid Electrolyte Interface and Enclosed Active Lithium toward > 100% Initial Coulombic Efficiency

Solid electrolyte interface (SEI) is arguably the most important concern in graphite anodes, which determines their achievable Coulombic efficiency (CE), energy density, and cycling stability. In spent graphite anodes, there are already-formed (yet loose and/or broken) SEIs and some residual active lithium, which, if could be inherited in the regenerated electrodes, are highly desired to compensate for the lithium loss due to SEI formation. However, current graphite regenerated approaches easily destroy the thin SEIs and residue active lithium, making their reuse impossible. Herein, we report a fast-heating strategy (e.g., 1900 K for ∼ 150 ms) to upcycle degraded graphite (incomplete discharging) via instantly converting the loose original SEI layer (∼ 100 nm thick) to a compact and mostly inorganic one (∼10-30 nm thick with a 26X higher Young's Modulus) and still retaining the activity of residual lithium. Thanks to the robust SEI and enclosed active lithium, the regenerated graphite exhibited 104.7% initial CE for half-cell and gifted the full cells with LiFePO4 significantly-improved initial CE (98.8% versus 83.2%) and energy density (309.4 versus 281.4 Wh kg-1 ), as compared with commercial graphite. The as-proposed upcycling strategy turns the "waste" graphite into high-value prelithiated ones, along with significant economic and environmental benefits. This article is protected by copyright. All rights reserved.

Phenylboronic Acid Functionalized Calix[4]pyrrole-Based Solid-State Supramolecular Electrolyte

Solid-state polymer electrolytes (SPEs) suffer from the low ionic conductivity and poor capability of suppressing lithium (Li) dendrites, which limits their utility in the preparation of all solid-state Li-metal batteries (LMBs). It is reported here a flexible solid supramolecular electrolyte that incorporates a new anion capture agent, namely a phenylboronic acid functionalized calix[4]pyrrole (C4P), into a poly(ethylene oxide) (PEO) matrix. The resulting solid-state supramolecular electrolyte demonstrates high ionic conductivity (1.9 × 10-3  S cm-1 at 60 °C) and a high Li+ transference number (t Li + ${t}_{{\mathrm{Li}}^{\mathrm{ + }}}$  = 0.70). Furthermore, the assembled Li|C4P-PEO-LiTFSI|LiFePO4 cell allows for stable cycling over 1200 cycles at 1 C at 60 °C, as well as good rate performance. The favorable performance of the C4P-PEO-LiTFSI SPE leads to suggest it can prove useful in the creation of high energy density solid-state LMBs.

Demystifying the Salt-Induced Li Loss: A Universal Procedure for the Electrolyte Design of Lithium-Metal Batteries

Lithium (Li) metal electrodes show significantly different reversibility in the electrolytes with different salts. However, the understanding on how the salts impact on the Li loss remains unclear. Herein, using the electrolytes with different salts (e.g., lithium hexafluorophosphate (LiPF6), lithium difluoro(oxalato)borate (LiDFOB), and lithium bis(fluorosulfonyl)amide (LiFSI)) as examples, we decouple the irreversible Li loss (SEI Li+ and "dead" Li) during cycling. It is found that the accumulation of both SEI Li+ and "dead" Li may be responsible to the irreversible Li loss for the Li metal in the electrolyte with LiPF6 salt. While for the electrolytes with LiDFOB and LiFSI salts, the accumulation of "dead" Li predominates the Li loss. We also demonstrate that lithium nitrate and fluoroethylene carbonate additives could, respectively, function as the "dead" Li and SEI Li+ inhibitors. Inspired by the above understandings, we propose a universal procedure for the electrolyte design of Li metal batteries (LMBs): (i) decouple and find the main reason for the irreversible Li loss; (ii) add the corresponding electrolyte additive. With such a Li-loss-targeted strategy, the Li reversibility was significantly enhanced in the electrolytes with 1,2-dimethoxyethane, triethyl phosphate, and tetrahydrofuran solvents. Our strategy may broaden the scope of electrolyte design toward practical LMBs.

Zinc-Contained Alloy as a Robustly Adhered Interfacial Lattice Locking Layer for Planar and Stable Zinc Electrodeposition

Stable zinc (Zn)/electrolyte interface is critical for developing rechargeable aqueous Zn-metal batteries with long-term stability, which requires the dense and stable Zn electrodeposition. Herein, an interfacial lattice locking (ILL) layer is constructed via the electro-codeposition of Zn and Cu onto the Zn electrodes. The ILL layer shows a low lattice misfit (δ = 0.036) with Zn(002) plane and selectively locks the lattice orientation of Zn deposits, enabling the epitaxial growth of Zn deposits layer by layer. Benefiting from the unique orientation-guiding and robustly adhered properties, the ILL layer enables the symmetric Zn||Zn cells to achieve an ultralong life span of >6000 h at 1 mA cm^-2 and 1 mAh cm^-2 , a low overpotential (65 mV) at 10 mAh cm^-2 , and a stable Zn plating/stripping for >90 h at an ultrahigh Zn depth of discharge (≈85%). Even with a limited Zn supply and a high current density (8.58 mA cm^-2 ), the ILL@Zn||Ni-doped MnO₂ cells can still survive for >2300 cycles.

Li2Se as a Cathode Prelithiation Additive for Lithium-Ion Batteries

In conventional lithium-ion batteries (LIBs), active lithium (Li) ions, which function as charge carriers and could only be supplied by the Li-containing cathodes, are also consumed during the formation of the solid electrolyte interphase. Such irreversible Li loss reduces the energy density of LIBs and is highly desired to be compensated by prelithiation additives. Herein, lithium selenide (Li₂Se), which could be irreversibly converted into selenide (Se) at 2.5-3.8 V and thus supplies additional Li, is proposed as a cathode prelithiation additive for LIBs. Compared with previously reported prelithiation reagents (e.g., Li₆CoO₄, Li₂O, and Li₂S), the delithiation of Li₂Se not only delivers a high specific capacity but also avoids gas release and incompatibility with carbonate electrolytes. The electrochemical characterizations show that with the addition of 6 wt % Li₂Se to the LiFePO₄ (LFP) cathodes, a 9% increase in the initial specific capacity in half Li||LFP cells and a 19.8% increase in the energy density (based on the total mass of the two electrodes' materials) could be achieved without sacrificing the other battery performance. This work demonstrates the possibility to use Li₂Se as a high-efficiency prelithiation additive for LIBs and provides a solution to the high-energy LIBs.

Solvation and Interfacial Engineering Enable -40 °C Operation of Graphite/NCM Batteries at Energy Density over 270 Wh kg-1

Li-ion batteries (LIBs) that can operate under low temperature (LT) conditions are essential for applications in orbital missions, subsea areas, and electric vehicles. Unfortunately, severe capacity loss is witnessed due to tremendous kinetic barriers that emerge at LT. Herein, to surmount such kinetic limitations, a low dielectric environment is tamed throughout the bulk electrolyte, which efficaciously brought the Li⁺ desolvation energy down to 30.76 kJ mol^-1 . At the meantime, the adoption of sodium cations (Na⁺ ) is proposed as a hetero-cation additive, and a Li-Na hybrid and fluoride-rich interphase is further identified via preferential reduction of Na⁺ -(solvent/anion) clusters, which is found to efficiently facilitate Li⁺ migration through the LiF/NaF grain boundaries. Based on a N/P ratio of 1.1, the graphite/LiNi_0.5 Co_0.2 Mn_0.3 O₂ (NCM) full cell (cathode loading of ≈18.5 mg cm^-2 ) delivers a capacity as high as 125.1 mAh g^-1 under -20 °C with prolonged cycling to 100 cycles. Finally, a 270 Wh kg^-1 graphite/NCM pouch cell is assembled, which affords a discharge capacity of 108.7 mAh g^-1 under -40 °C during the initial cycles. With an eye to both fundamental and practical aspects, this work will propel additional advancements and allow LIBs to fill more roles under extreme operation temperatures than ever before.

Electrochemical Reactivation of Dead Li2 S for Li-S Batteries in Non-Solvating Electrolytes

The use of non-solvating, or as-called sparingly-solvating, electrolytes (NSEs), is regarded as one of the most promising solutions to the obstacles to the practical applications of Li-S batteries. However, it remains a puzzle that long-life Li-S batteries have rarely, if not never, been reported with NSEs, despite their good compatibility with Li anode. Here, we find the capacity decay of Li-S batteries in NSEs is mainly due to the accumulation of the dead Li₂ S at the cathode side, rather than the degradation of the anodes or electrolytes. Based on this understanding, we propose an electrochemical strategy to reactivate the accumulated Li₂ S and revive the dead Li-S batteries in NSEs. With such a facile approach, Li-S batteries with significantly improved cycling stability and accelerated dynamics are achieved with diglyme-, acetonitrile- and 1,2-dimethoxyethane-based NSEs. Our finding may rebuild the confidence in exploiting non-solvating Li-S batteries with practical competitiveness.

A New Zinc Salt Chemistry for Aqueous Zinc-Metal Batteries

Aqueous zinc-ion batteries (ZIBs) are promising energy storage solutions with low cost and superior safety, but they suffer from chemical and electrochemical degradations closely related to the electrolyte. Here, a new zinc salt design and a drop-in solution for long cycle-life aqueous ZIBs are reported. The salt Zn(BBI)₂ with a rationally designed anion group, N-(benzenesulfonyl)benzenesulfonamide (BBI^- ), has a special amphiphilic molecular structure, which combines the benefits of hydrophilic and hydrophobic groups to properly tune the solubility and interfacial condition. This new zinc salt does not contain fluorine and is synthesized via a high-yield and low-cost method. It is shown that 1 m Zn(BBI)₂ aqueous electrolyte with a widened cathodic stability window effectively stabilizes Zn metal/H₂ O interface, mitigates chemical and electrochemical degradations, and enables both symmetric and full cells using a zinc-metal electrode.

Ultralean Electrolyte Li-S Battery by Avoiding Gelation Catastrophe

Due to the poor electronic conductivity of solid sulfur and sulfides, the dissolution of S^α- (α = 0, 2/8, 2/6, 2/4) into a liquid electrolyte and the vehicular diffusion of S^α- to carbon black are necessary for the electrochemical activity of a sulfur cathode in lithium-sulfur (Li-S) batteries. However, exactly how much dissolution and diffusion are required for high sulfur utilization and how this may control the minimum electrolyte/sulfur ratio, (E/S)_min, have not been quantitatively settled. In this work, we show experimentally that a dissolved polysulfide concentration which is too high (>10-20 MS) may gel the liquid electrolyte, leading to catastrophic loss of S^α- mobility, a failure mode that is especially susceptible in a high-donor-number (DN) electrolyte under a lean condition (low E/S), similar to a traffic jam, resulting in high electrochemical polarization and low sulfur utilization. In contrast, we show that a low-DN electrolyte, even with a low polysulfide solubility of 0.1-0.5 MS, will never encounter a gelation catastrophe even at extremely low E/S, leading to unprecedentedly high energy density. Specifically, high sulfur utilizations of 96% (1600 mAh g^-1) and 78% (1300 mAh g^-1) are reached in an electrolyte as lean as E/S = 2 and 1 μL mg^-1 Li-S coin cells when DME_1.6LiFSI-HFE of low solvation capability (DN = 13.9) is adopted, even paired against a high-sulfur-loading cathode (5 mg cm^-2).

Lanthanum nitrate as aqueous electrolyte additive for favourable zinc metal electrodeposition

Aqueous zinc batteries are appealing devices for cost-effective and environmentally sustainable energy storage. However, the zinc metal deposition at the anode strongly influences the battery cycle life and performance. To circumvent this issue, here we propose the use of lanthanum nitrate (La(NO3)3) as supporting salt for aqueous zinc sulfate (ZnSO4) electrolyte solutions. Via physicochemical and electrochemical characterizations, we demonstrate that this peculiar electrolyte formulation weakens the electric double layer repulsive force, thus, favouring dense metallic zinc deposits and regulating the charge distribution at the zinc metal|electrolyte interface. When tested in Zn||VS2 full coin cell configuration (with cathode mass loading of 16 mg cm-2), the electrolyte solution containing the lanthanum ions enables almost 1000 cycles at 1 A g-1 (after 5 activation cycles at 0.05 A g-1) with a stable discharge capacity of about 90 mAh g-1 and an average cell discharge voltage of ∼0.54 V.

High-Capacity and Long-Life Zinc Electrodeposition Enabled by a Self-Healable and Desolvation Shield for Aqueous Zinc-Ion Batteries

Artificial interfaces can alleviate the side reactions and the formation of the metallic (e.g. , Li, Na, and Zn) dendrites. However, the traditional ones always break down during the repeated plating/stripping and fail to regulate the electrodeposition behaviors of the electrodes. Herein, a self-healable ion regulator (SIR) is designed as a desolvation shield to protect the Zn electrodes and guide the Zn electrodeposition. Benefiting from the intermolecular hydrogen bonds, SIR shows a superb capability to in-situ repair the plating/stripping-induced creaks. Besides, the results of theoretical calculations and electrochemical characterizations show that the coating reduces water molecules in the solvated sheath of hydrated Zn2+ and restrains the random Zn2+ diffusion on the Zn surface. Even with a coating layer of only 360 nm, the SIR-modified Zn electrode exhibits excellent long-term stability for > 3500 h at 2 mAh cm-2 and > 950 h at an ultrahigh areal capacity of 20 mAh cm-2 .

Two-Plateau Li-Se Chemistry for High Volumetric Capacity Se Cathodes

For Li-Se batteries, ether- and carbonate-based electrolytes are commonly used. However, because of the "shuttle effect" of the highly dissoluble long-chain lithium polyselenides (LPSes, Li₂ Se_n , 4≤n≤8) in the ether electrolytes and the sluggish one-step solid-solid conversion between Se and Li₂ Se in the carbonate electrolytes, a large amount of porous carbon (>40 wt % in the electrode) is always needed for the Se cathodes, which seriously counteracts the advantage of Se electrodes in terms of volumetric capacity. Herein an acetonitrile-based electrolyte is introduced for the Li-Se system, and a two-plateau conversion mechanism is proposed. This new Li-Se chemistry not only avoids the shuttle effect but also facilitates the conversion between Se and Li₂ Se, enabling an efficient Se cathode with high Se utilization (97 %) and enhanced Coulombic efficiency. Moreover, with such a designed electrolyte, a highly compact Se electrode (2.35 g_Se  cm^-3 ) with a record-breaking Se content (80 wt %) and high Se loading (8 mg cm^-2 ) is demonstrated to have a superhigh volumetric energy density of up to 2502 Wh L^-1 , surpassing that of LiCoO₂ .

Semi-Flooded Sulfur Cathode with Ultralean Absorbed Electrolyte in Li-S Battery

Lean electrolyte (small E/S ratio) is urgently needed to achieve high practical energy densities in Li-S batteries, but there is a distinction between the cathode's absorbed electrolyte (AE) which is cathode-intrinsic and total added electrolyte (E) which depends on cell geometry. While total pore volume in sulfur cathodes affects AE/S and performance, it is shown here that pore morphology, size, connectivity, and fill factor all matter. Compared to conventional thermally dried sulfur cathodes that usually render "open lakes" and closed pores, a freeze-dried and compressed (FDS-C) sulfur cathode is developed with a canal-capillary pore structure, which exhibits high mean performance and greatly reduces cell-to-cell variation, even at high sulfur loading (14.2 mg cm-2) and ultralean electrolyte condition (AE/S = 1.2 µL mg-1). Interestingly, as AE/S is swept from 2 to 1.2 µL mg-1, the electrode pores go from fully flooded to semi-flooded, and the coin cell still maintains function until (AE/S)min ≈ 1.2 µL mg-1 is reached. When scaled up to Ah-level pouch cells, the full-cell energy density can reach 481 Wh kg-1 as its E/S ≈ AE/S ratio can be reduced to 1.2 µL mg-1, proving high-performance pouch cells can actually be working in the ultralean, semi-flooded regime.

Highly Rechargeable Lithium-CO2 Batteries with a Boron- and Nitrogen-Codoped Holey-Graphene Cathode

Metal-air batteries, especially Li-air batteries, have attracted significant research attention in the past decade. However, the electrochemical reactions between CO₂ (0.04 % in ambient air) with Li anode may lead to the irreversible formation of insulating Li₂ CO₃ , making the battery less rechargeable. To make the Li-CO₂ batteries usable under ambient conditions, it is critical to develop highly efficient catalysts for the CO₂ reduction and evolution reactions and investigate the electrochemical behavior of Li-CO₂ batteries. Here, we demonstrate a rechargeable Li-CO₂ battery with a high reversibility by using B,N-codoped holey graphene as a highly efficient catalyst for CO₂ reduction and evolution reactions. Benefiting from the unique porous holey nanostructure and high catalytic activity of the cathode, the as-prepared Li-CO₂ batteries exhibit high reversibility, low polarization, excellent rate performance, and superior long-term cycling stability over 200 cycles at a high current density of 1.0 A g^-1 . Our results open up new possibilities for the development of long-term Li-air batteries reusable under ambient conditions, and the utilization and storage of CO₂ .

Uniform Li2S precipitation on N,O-codoped porous hollow carbon fibers for high-energy-density lithium–sulfur batteries with superior stability

Long-term cycling stability with high-loading sulfur cathodes has been achieved using N,O-codoped carbon hollow fibers as the current collector and Li₂S₆ as the starting active material.

Sulfur-Doped Carbon with Enlarged Interlayer Distance as a High-Performance Anode Material for Sodium-Ion Batteries

S-doped carbon is investigated as a high-performance anode material for sodium-ion batteries. Due to the introduction of a high-content of S atoms, the as-obtained S-doped carbon shows an enlarged interlayer distance. As an anode, a high specific capacity of up to 303 mAh g-1 is achieved, even after 700 cycles at 0.5 A g-1.

VO2/TiO2 Nanosponges as Binder-Free Electrodes for High-Performance Supercapacitors

VO2/TiO2 nanosponges with easily tailored nanoarchitectures and composition were synthesized by electrostatic spray deposition as binder-free electrodes for supercapacitors. Benefiting from the unique interconnected pore network of the VO2/TiO2 electrodes and the synergistic effect of high-capacity VO2 and stable TiO2, the as-formed binder-free VO2/TiO2 electrode exhibits a high capacity of 86.2 mF cm(-2) (~548 F g(-1)) and satisfactory cyclability with 84.3% retention after 1000 cycles. This work offers an effective and facile strategy for fabricating additive-free composites as high-performance electrodes for supercapacitors.

Flexible membranes of MoS2/C nanofibers by electrospinning as binder-free anodes for high-performance sodium-ion batteries

A flexible membrane consisting of MoS₂/carbon nanofibers has been fabricated by a simple electrospinning method. MoS₂ nanosheets are uniformly encapsulated in the inter-connected carbon nanofibers with diameters of ~150 nm. When evaluated as a binder-free electrode for sodium-ion batteries, the as-obtained electrode demonstrates high performances, including high reversible capacity of 381.7 mA h g⁻¹ at 100 mA g⁻¹ and superior rate capability (283.3, 246.5 and 186.3 mA h g⁻¹ at 0.5, 1 and 2 A g⁻¹, respectively). Most importantly, the binder-free electrode made of MoS₂ and carbon nanofibers can still deliver a charge capacity of 283.9 mA h g⁻¹ after 600 cycles at a current density of 100 m A g⁻¹, indicating a very promising anode for long-life SIBs.

A facile layer-by-layer approach for high-areal-capacity sulfur cathodes

A layer-by-layer cathode is developed for high-areal-capacity Li-S batteries via a facile approach. Benefitting from the unique structure and favorable adsorption properties of the carbon layers, the fabricated cathodes display high capacity with superior rate and cycling performance. An areal capacity of as high as 11.3 mA h cm(-2) is achieved with a six-sulfur-layer cathode.

MOF-derived porous ZnO/ZnFe₂O₄/C octahedra with hollow interiors for high-rate lithium-ion batteries

Novel porous ZnO/ZnFe2O4/C octahedra with hollow interiors are fabricated by a facile self-sacrificing template method involving the refluxing synthesis of hollow, metal-organic framework octahedra in solution and subsequent thermal annealing in N2 . When evaluated as an anode material for lithium-ion batteries, these porous hollow ZnO/ZnFe2O4/C octahedra exhibit significantly enhanced electrochemical performances with high rate capability, high capacity, and excellent cycling stability.

Facile synthesis of sandwiched Zn2GeO4-graphene oxide nanocomposite as a stable and high-capacity anode for lithium-ion batteries

Traditional metal anode materials in lithium-ion batteries are plagued by instability upon discharge-charge cycling. We report that a unique sandwiched Zn2GeO4-graphene oxide nanocomposite has been synthesized on a large scale through a simple ion-exchange reaction, whereby Zn2GeO4 nanorods with lengths of 600 nm and widths of 40 nm are homogeneously sandwiched into the graphene oxide matrix. Compared with bare Zn2GeO4 nanorods, a dramatic improvement in the electrochemical performance of the resulting nanocomposite has been achieved. In the voltage window of 0.001-3 V, the electrode of the Zn2GeO4-graphene oxide nanocomposite delivers a specific capacity as high as 1150 mA h g(-1) at 200 mA g(-1) after 100 discharge-charge cycles. Even at a high current density of 3.2 A g(-1), a capacity of 522 mA h g(-1) can be retained. The unusual electrochemical performance including highly reversible capacity and excellent rate capability arise from synergetic chemical coupling effects between Zn2GeO4 and graphene oxide.

Controllable synthesis of hollow bipyramid β-MnO(2) and its high electrochemical performance for lithium storage

Three types of MnO2 nanostructures, viz., α-MnO2 nanotubes, hollow β-MnO2 bipyramids, and solid β-MnO2 bipyramids, have been synthesized via a simple template-free hydrothermal method. Cyclic voltammetry and galvanostatic charge/discharge measurements demonstrate that the hollow β-MnO2 bipyramids exhibit the highest specific capacity and the best cyclability; the capacity retains 213 mAh g(-1) at a current density of 100 mA g(-1) after 150 cycles. XRD patterns of the lithiated β-MnO2 electrodes clearly show the expansion of lattice volume caused by lithiation, but the structure keeps stable during lithium insertion/extraction process. We suggest that the excellent performance for β-MnO2 can be attributed to its unique electrochemical reaction, compact tunnel-structure and hollow architecture. The hollow architecture can accommodate the volume change during charge/discharge process and improve effective diffusion paths for both lithium ions and electrons.

Nitrogen-doped porous carbon nanofiber webs as anodes for lithium ion batteries with a superhigh capacity and rate capability

Nitrogen-doped carbon nanofiber webs (CNFWs) with high surface areas are successfully prepared by carbonization-activation of polypyrrole nanofiber webs with KOH. The as-obtained CNFWs exhibit a superhigh reversible capacity of 943 mAh g(-1) at a current density of 2 A g(-1) even after 600 cycles, which is ascribed to the novel porous nanostructure and high-level nitrogen doping.

Nonlinear elastic and viscoelastic deformation of the human red blood cell with optical tweezers

Studies of the deformation characteristics of single biological cells can offer insights into the connections among mechanical state, biochemical response and the onset and progression of diseases. Deformation imposed by optical tweezers provides a useful means for the study of single cell mechanics under a variety of well-controlled stress-states. In this paper, we first critically review recent advances in the study of single cell mechanics employing the optical tweezers method, and assess its significance and limitations in comparison to other experimental tools. We then present new experimental and computational results on shape evolution, force-extension curves, elastic properties and viscoelastic response of human red blood cells subjected to large elastic deformation using optical tweezers. Potential applications of the methods examined here to study diseased cells are also briefly addressed.

Characterization of the rat GRIK5 kainate receptor subunit gene promoter and its intragenic regions involved in neural cell specificity

The GRIK5 (glutamate receptor ionotropic kainate-5) gene encodes the kainate-preferring glutamate receptor subunit KA2. The GRIK5 promoter is TATA-less and GC-rich, with multiple consensus initiator sequences. Transgenic mouse lines carrying 4 kilobases of the GRIK5 5'-flanking sequence showed lacZ reporter expression predominantly in the nervous system. Reporter assays in central glial (CG-4) and non-neural cells indicated that a 1200-base pair (bp) 5'-flanking region could sustain neural cell-specific promoter activity. Transcriptional activity was associated with the formation of a transcription factor IID-containing complex on an initiator sequence located 1100 bp upstream of the first intron. In transfection studies, deletion of exonic sequences downstream of the promoter resulted in reporter gene activity that was no longer neural cell-specific. When placed downstream of the GRIK5 promoter, a 77-bp sequence from the deleted fragment completely silenced reporter expression in NIH3T3 fibroblasts while attenuating activity in CG-4 cells. Analysis of the 77-bp sequence revealed a functional SP1-binding site and a sequence resembling a neuron-restrictive silencer element. The latter sequence, however, did not display cell-specific binding of REST-like proteins. Our studies thus provide evidence for intragenic control of GRIK5 promoter activity and suggest that elements contributing to tissue-specific expression are contained within the first exon.

Herpes simplex virus entry is associated with tyrosine phosphorylation of cellular proteins

The initial step in herpes simplex virus (HSV) entry is binding of virion glycoprotein (g)C and/or gB to cell surface heparan sulfate. After this initial attachment, gD interacts with cell surface receptor or receptors, and the virion envelope fuses with the cell membrane. Fusion requires viral glycoproteins gB, gD, gL, and gH, but the cellular factors that participate in or the pathways activated by viral entry have not been defined. To determine whether signal transduction pathways are triggered by viral-cell fusion, we examined the association of viral entry with tyrosine phosphorylation of cellular proteins. Using immunoprecipitation and Western blotting, we found that at least three cytoplasmic host cell proteins, designated p80, p104, and p140, become tyrosine phosphorylated within 5-10 min after exposure to HSV-1 or HSV-2. However, no phosphorylation is detected when cells are exposed to a mutant virus deleted in gL that binds but fails to penetrate. Phosphorylation is restored when the gL-deletion virus is grown on a complementing cell line. Viral entry and the phosphorylation of p80, p104, and p140 are inhibited when cells are infected with virus in the presence of protein tyrosine kinase inhibitors. Taken together, these studies suggest that tyrosine phosphorylation of host cellular proteins is triggered by viral entry.

Identification of a Saccharomyces gene, LCB3, necessary for incorporation of exogenous long chain bases into sphingolipids

To identify genes necessary for sphingolipid synthesis in Saccharomyces cerevisiae we developed a procedure to enrich for mutants unable to incorporate exogenous long chain base into sphingolipids. We show here that a mutant strain, AG84-3, isolated by using the enrichment procedure, makes sphingolipids from endogenously synthesized but not from exogenously supplied long chain base. A gene termed LCB3 (YJL134W, GenBank designation X87371x21), which complements the long chain base utilization defect of strain AG84-3, was isolated from a genomic DNA library. The gene is predicted to encode a protein with multiple membrane-spanning domains and a COOH-terminal glycosylphosphatidylinositiol cleavage/attachment site. Deletion of the lcb3 gene in a wild type genetic background reduces the rate of exogenous long chain base incorporation into sphingolipids and makes the host strain more resistant to growth inhibition by long chain bases. Only one protein in current data bases, the S. cerevisiae open-reading frame YKR053C, whose function is unknown, shows homology to the Lcb3 protein. The two proteins are not, however, functional homologs because deletion of the YKR053C open reading frame does not impair long chain base utilization or enhance resistance of cells to growth inhibition by long chain bases. Based upon these data we hypothesize that the Lcb3 protein is a plasma membrane transporter capable of transporting sphingoid long chain bases into cells. It is the first candidate for such a transporter and the first member of what appears to be a new class of membrane-bound proteins.