Showing papers by "Yi Cui published in 2016"
TL;DR: This review aims to summarize major developments in the field of lithium-sulfur batteries, starting from an overview of their electrochemistry, technical challenges and potential solutions, along with some theoretical calculation results to advance the understanding of the material interactions involved.
Abstract: Due to their high energy density and low material cost, lithium–sulfur batteries represent a promising energy storage system for a multitude of emerging applications, ranging from stationary grid storage to mobile electric vehicles. This review aims to summarize major developments in the field of lithium–sulfur batteries, starting from an overview of their electrochemistry, technical challenges and potential solutions, along with some theoretical calculation results to advance our understanding of the material interactions involved. Next, we examine the most extensively-used design strategy: encapsulation of sulfur cathodes in carbon host materials. Other emerging host materials, such as polymeric and inorganic materials, are discussed as well. This is followed by a survey of novel battery configurations, including the use of lithium sulfide cathodes and lithium polysulfide catholytes, as well as recent burgeoning efforts in the modification of separators and protection of lithium metal anodes. Finally, we conclude with an outlook section to offer some insight on the future directions and prospects of lithium–sulfur batteries.
1,816 citations
TL;DR: A composite lithium metal anode is reported that exhibits low dimension variation (∼20%) during cycling and good mechanical flexibility and a full-cell battery with a LiCoO2 cathode shows good rate capability and flat voltage profiles.
Abstract: Metallic lithium is a promising anode candidate for future high-energy-density lithium batteries. It is a light-weight material, and has the highest theoretical capacity (3,860 mAh g–1) and the lowest electrochemical potential of all candidates. There are, however, at least three major hurdles before lithium metal anodes can become a viable technology: uneven and dendritic lithium deposition, unstable solid electrolyte interphase and almost infinite relative dimension change during cycling. Previous research has tackled the first two issues, but the last is still mostly unsolved. Here we report a composite lithium metal anode that exhibits low dimension variation (∼20%) during cycling and good mechanical flexibility. The anode is composed of 7 wt% ‘lithiophilic’ layered reduced graphene oxide with nanoscale gaps that can host metallic lithium. The anode retains up to ∼3,390 mAh g–1 of capacity, exhibits low overpotential (∼80 mV at 3 mA cm–2) and a flat voltage profile in a carbonate electrolyte. A full-cell battery with a LiCoO2 cathode shows good rate capability and flat voltage profiles. Volumetric changes during cycling in lithium metal anodes can be largely suppressed by using a lithophilic carbonaceous host.
1,459 citations
TL;DR: In this paper, the authors explore the nucleation pattern of lithium on various metal substrates and unravel a substrate-dependent growth phenomenon that enables selective deposition of lithium metal, and design a nanocapsule structure for lithium metal anodes consisting of hollow carbon spheres with nanoparticle seeds inside.
Abstract: Lithium metal is an attractive anode material for rechargeable batteries, owing to its high theoretical specific capacity of 3,860 mAh g−1. Despite extensive research efforts, there are still many fundamental challenges in using lithium metal in lithium-ion batteries. Most notably, critical information such as its nucleation and growth behaviour remains elusive. Here we explore the nucleation pattern of lithium on various metal substrates and unravel a substrate-dependent growth phenomenon that enables selective deposition of lithium metal. With the aid of binary phase diagrams, we find that no nucleation barriers are present for metals exhibiting a definite solubility in lithium, whereas appreciable nucleation barriers exist for metals with negligible solubility. We thereafter design a nanocapsule structure for lithium metal anodes consisting of hollow carbon spheres with nanoparticle seeds inside. During deposition, the lithium metal is found to predominantly grow inside the hollow carbon spheres. Such selective deposition and stable encapsulation of lithium metal eliminate dendrite formation and enable improved cycling, even in corrosive alkyl carbonate electrolytes, with 98% coulombic efficiency for more than 300 cycles. Uncontrolled lithium deposition during cycling is a major concern in the development of lithium-based batteries. Here, the authors analyse the lithium nucleation pattern on various metal substrates and demonstrate that lithium can be selectively deposited in a nanoseed inside hollow carbon spheres.
1,375 citations
TL;DR: Cui et al. as discussed by the authors review the advantages and challenges of using nanomaterials in lithium-based rechargeable batteries and discuss the challenges caused by using them in batteries, including undesired parasitic reactions with electrolytes, low volumetric and areal energy density, and high costs from complex multi-step processing.
Abstract: Tremendous progress has been made in the development of lithium-based rechargeable batteries in recent decades. Discoveries of new electrode materials as well as new storage mechanisms have substantially improved battery performance. In particular, nanomaterials design has emerged as a promising solution to tackle many fundamental problems in conventional battery materials. Here we discuss in detail several key issues in batteries, such as electrode volume change, solid–electrolyte interphase formation, electron and ion transport, and electrode atom/molecule movement, and then analyse the advantages presented by nanomaterials design. In addition, we discuss the challenges caused by using nanomaterials in batteries, including undesired parasitic reactions with electrolytes, low volumetric and areal energy density, and high costs from complex multi-step processing, and their possible solutions. Nanomaterials design may offer a solution to tackle many fundamental problems in conventional batteries. Cui et al. review both the promises and challenges of using nanomaterials in lithium-based rechargeable batteries.
1,299 citations
TL;DR: In this paper, an oxide selection method was proposed to balance the optimization between sulfide-adsorption and diffusion on the oxides, which showed that better surface diffusion leads to higher sulfide species on electrodes.
Abstract: Lithium-sulfur batteries have attracted attention due to their six-fold specific energy compared with conventional lithium-ion batteries. Dissolution of lithium polysulfides, volume expansion of sulfur and uncontrollable deposition of lithium sulfide are three of the main challenges for this technology. State-of-the-art sulfur cathodes based on metal-oxide nanostructures can suppress the shuttle-effect and enable controlled lithium sulfide deposition. However, a clear mechanistic understanding and corresponding selection criteria for the oxides are still lacking. Herein, various nonconductive metal-oxide nanoparticle-decorated carbon flakes are synthesized via a facile biotemplating method. The cathodes based on magnesium oxide, cerium oxide and lanthanum oxide show enhanced cycling performance. Adsorption experiments and theoretical calculations reveal that polysulfide capture by the oxides is via monolayered chemisorption. Moreover, we show that better surface diffusion leads to higher deposition efficiency of sulfide species on electrodes. Hence, oxide selection is proposed to balance optimization between sulfide-adsorption and diffusion on the oxides.
1,062 citations
TL;DR: It is demonstrated that lithium-induced ultra-small NiFeOx nanoparticles are active bifunctional catalysts exhibiting high activity and stability for overall water splitting in base better than the combination of iridium and platinum as benchmark catalysts.
Abstract: Described here is a method for improving the catalytic activity of an electrocatalyst, comprising subjecting the electrocatalyst to 1-10 galvanostatic lithiation/delithiation cycles, wherein the electrocatalyst comprises at least one transition metal oxide (TMO) or transition metal chalcogenide (TMC). Also described here is an electrocatalyst and a water-splitting device comprising the electrocatalyst.
968 citations
TL;DR: A promising metallic lithium anode design is demonstrated by infusing molten lithium into a polymeric matrix, which successfully confines lithium within the matrix, realizing minimum volume change and effective dendrite suppression.
Abstract: Lithium metal is the ideal anode for the next generation of high-energy-density batteries. Nevertheless, dendrite growth, side reactions and infinite relative volume change have prevented it from practical applications. Here, we demonstrate a promising metallic lithium anode design by infusing molten lithium into a polymeric matrix. The electrospun polyimide employed is stable against highly reactive molten lithium and, via a conformal layer of zinc oxide coating to render the surface lithiophilic, molten lithium can be drawn into the matrix, affording a nano-porous lithium electrode. Importantly, the polymeric backbone enables uniform lithium stripping/plating, which successfully confines lithium within the matrix, realizing minimum volume change and effective dendrite suppression. The porous electrode reduces the effective current density; thus, flat voltage profiles and stable cycling of more than 100 cycles is achieved even at a high current density of 5 mA cm−2 in both carbonate and ether electrolyte. The advantages of the porous, polymeric matrix provide important insights into the design principles of lithium metal anodes. Lithium metal is a promising anode for batteries, but problems such as volume change and dendrite growth currently prevent it from practical usage. Here, the authors overcome these problems by infusing molten lithium into a polymeric matrix via a lithiophilic coating to make a stable nanoporous lithium electrode.
738 citations
TL;DR: A stable lithium–scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with “lithiophilic” coating, which possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling.
Abstract: Lithium metal-based battery is considered one of the best energy storage systems due to its high theoretical capacity and lowest anode potential of all. However, dendritic growth and virtually relative infinity volume change during long-term cycling often lead to severe safety hazards and catastrophic failure. Here, a stable lithium–scaffold composite electrode is developed by lithium melt infusion into a 3D porous carbon matrix with “lithiophilic” coating. Lithium is uniformly entrapped on the matrix surface and in the 3D structure. The resulting composite electrode possesses a high conductive surface area and excellent structural stability upon galvanostatic cycling. We showed stable cycling of this composite electrode with small Li plating/stripping overpotential (
717 citations
TL;DR: Much stronger chemical/mechanical interactions between monodispersed 12 nm diameter SiO2 nanospheres and poly(ethylene oxide) (PEO) chains were produced by in situ hydrolysis, which significantly suppresses the crystallization of PEO and thus facilitates polymer segmental motion for ionic conduction.
Abstract: High ionic conductivity solid polymer electrolyte (SPE) has long been desired for the next generation high energy and safe rechargeable lithium batteries. Among all of the SPEs, composite polymer electrolyte (CPE) with ceramic fillers has garnered great interest due to the enhancement of ionic conductivity. However, the high degree of polymer crystallinity, agglomeration of ceramic fillers, and weak polymer–ceramic interaction limit the further improvement of ionic conductivity. Different from the existing methods of blending preformed ceramic particles with polymers, here we introduce an in situ synthesis of ceramic filler particles in polymer electrolyte. Much stronger chemical/mechanical interactions between monodispersed 12 nm diameter SiO2 nanospheres and poly(ethylene oxide) (PEO) chains were produced by in situ hydrolysis, which significantly suppresses the crystallization of PEO and thus facilitates polymer segmental motion for ionic conduction. In addition, an improved degree of LiClO4 dissociati...
702 citations
TL;DR: A porous MoO2 nanosheet as an active and stable bifunctional electrocatalyst for overall water splitting, is presented and maintains its activity for at least 24 h in a two-electrode configuration.
Abstract: A porous MoO2 nanosheet as an active and stable bifunctional electrocatalyst for overall water splitting, is presented. It needs a cell voltage of only about 1.53 V to achieve a current density of 10 mA cm(-2) and maintains its activity for at least 24 h in a two-electrode configuration.
686 citations
TL;DR: In this paper, a graphene cage is grown conformally around the micro-silicon particles to improve their cycling stability, which is shown to improve the cycling stability of battery anodes.
Abstract: Micrometre-size silicon particles are desirable battery anode materials but are even more prone to structure degradation than nanoscale particles. Here, graphene cages grown conformally around the micro-silicon particles are shown to improve their cycling stability.
TL;DR: It is shown that few-layered vertically aligned MoS2 (FLV-MoS2) films can be used to harvest the whole spectrum of visible light (∼50% of solar energy) and achieve highly efficient water disinfection.
Abstract: Few-layered, vertically aligned MoS2 films can efficiently harvest visible light for photocatalytic water disinfection, allowing >99.999% bacteria to be rapidly inactivated.
TL;DR: It is shown that nanoporous polyethylene (nanoPE) is transparent to mid-infrared human body radiation but opaque to visible light because of the pore size distribution, and processed the material to develop a textile that promotes effective radiative cooling while still having sufficient air permeability, water-wicking rate, and mechanical strength for wearability.
Abstract: Thermal management through personal heating and cooling is a strategy by which to expand indoor temperature setpoint range for large energy saving. We show that nanoporous polyethylene (nanoPE) is transparent to mid-infrared human body radiation but opaque to visible light because of the pore size distribution (50 to 1000 nanometers). We processed the material to develop a textile that promotes effective radiative cooling while still having sufficient air permeability, water-wicking rate, and mechanical strength for wearability. We developed a device to simulate skin temperature that shows temperatures 2.7° and 2.0°C lower when covered with nanoPE cloth and with processed nanoPE cloth, respectively, than when covered with cotton. Our processed nanoPE is an effective and scalable textile for personal thermal management.
TL;DR: In this paper, the feasibility of a next-generation hybrid anode using silicon-nanolayer-embedded graphite/carbon was demonstrated, and the authors reported scalable synthesis of silicon-nolayer embedding graphite electrodes that display cycling stability at the industrial electrode density.
Abstract: Existing anode technologies are approaching their limits, and silicon is recognized as a potential alternative due to its high specific capacity and abundance. However, to date the commercial use of silicon has not satisfied electrode calendering with limited binder content comparable to commercial graphite anodes for high energy density. Here we demonstrate the feasibility of a next-generation hybrid anode using silicon-nanolayer-embedded graphite/carbon. This architecture allows compatibility between silicon and natural graphite and addresses the issues of severe side reactions caused by structural failure of crumbled graphite dust and uncombined residue of silicon particles by conventional mechanical milling. This structure shows a high first-cycle Coulombic efficiency (92%) and a rapid increase of the Coulombic efficiency to 99.5% after only 6 cycles with a capacity retention of 96% after 100 cycles, with an industrial electrode density of >1.6 g cm−3, areal capacity loading of >3.3 mAh cm−2, and <4 wt% binding materials in a slurry. As a result, a full cell using LiCoO2 has demonstrated a higher energy density (1,043 Wh l−1) than with standard commercial graphite electrodes. Silicon has long been recognized as a high-energy battery electrode but its commercialization faces significant barriers. Here the authors report scalable synthesis of silicon-nanolayer-embedded graphite electrodes that display cycling stability at the industrial electrode density.
TL;DR: A method for using battery electrode materials to directly and continuously control the lattice strain of platinum (Pt) catalyst and thus tune its catalytic activity for the oxygen reduction reaction (ORR) is reported.
Abstract: We report a method for using battery electrode materials to directly and continuously control the lattice strain of platinum (Pt) catalyst and thus tune its catalytic activity for the oxygen reduction reaction (ORR). Whereas the common approach of using metal overlayers introduces ligand effects in addition to strain, by electrochemically switching between the charging and discharging status of battery electrodes the change in volume can be precisely controlled to induce either compressive or tensile strain on supported catalysts. Lattice compression and tension induced by the lithium cobalt oxide substrate of ~5% were directly observed in individual Pt nanoparticles with aberration-corrected transmission electron microscopy. We observed 90% enhancement or 40% suppression in Pt ORR activity under compression or tension, respectively, which is consistent with theoretical predictions.
TL;DR: A bifunctional separator modified by black-phosphorus nanoflakes is prepared to overcome the challenges associated with the polysulfide diffusion in lithium-sulfur batteries.
Abstract: A bifunctional separator modified by black-phosphorus nanoflakes is prepared to overcome the challenges associated with the polysulfide diffusion in lithium-sulfur batteries. It brings the benefits of the entrapment of various sulfur species via the strong binding energy and re-activation of the trapped sulfur species due to its high electron conductivity as well as Li-ion diffusivity.
TL;DR: Here, high-efficiency polyimide-nanofiber air filters for the high temperature PM2.5 removal are developed that could effectively remove >99.5% PM particles from car exhaust at high temperature.
Abstract: Here, we developed high-efficiency (>99.5%) polyimide-nanofiber air filters for the high temperature PM2.5 removal. The polyimide nanofibers exhibited high thermal stability, and the PM2.5 removal efficiency was kept unchanged when temperature ranged from 25–370 °C. These filters had high air flux with very low pressure drop. They could continuously work for >120 h for PM2.5 index >300. A field-test showed that they could effectively remove >99.5% PM particles from car exhaust at high temperature.
TL;DR: A new strategy to address the issue of dendrite growth by a polyimide-coating layer with vertical nanoscale channels of high aspect ratio provides a novel approach and a significant step toward stabilizing Li metal anodes.
Abstract: The widespread implementation of high-energy-density lithium metal batteries has long been fettered by lithium dendrite-related failure Here we report a new strategy to address the issue of dendrite growth by a polyimide-coating layer with vertical nanoscale channels of high aspect ratio Smooth, granular lithium metal was deposited on the modified electrode instead of typical filamentary growths In a comparison with the bare planar electrode, the modified electrode achieved greatly enhanced Coulombic efficiency and longer cycle life Homogeneous Li+ flux distribution above the modified electrode from the nanochannel confinement can account for a uniform Li nucleation and a nondendrite growth We also demonstrated that the polyimide coating with microscale pores loses the confinement effects and fails to suppress lithium dendrites This strategy of spatially defined lithium growth in vertical-aligned nanochannels provides a novel approach and a significant step toward stabilizing Li metal anodes
TL;DR: A subzero-temperature cathode material is obtained by nucleating cubic prussian blue crystals at inhomogeneities in carbon nanotubes, providing a practical sodium-ion battery powering an electric vehicle in frigid regions.
Abstract: A subzero-temperature cathode material is obtained by nucleating cubic prussian blue crystals at inhomogeneities in carbon nanotubes. Due to fast ionic/electronic transport kinetics even at -25 °C, the cathode shows an outstanding low-temperature performance in terms of specific energy, high-rate capability, and cycle life, providing a practical sodium-ion battery powering an electric vehicle in frigid regions.
TL;DR: In this article, a nanoporous Mo-doped BiVO4 (Mo:BiVO4) was used for photoelectrochemical (PEC) water splitting, which achieved a high water-splitting photocurrent of 5.82 ± 0.36 mA cm−2 at 1.23 V versus the reversible hydrogen electrode under 1-sun illumination.
Abstract: Bismuth vanadate (BiVO4) has been widely regarded as a promising photoanode material for photoelectrochemical (PEC) water splitting because of its low cost, its high stability against photocorrosion, and its relatively narrow band gap of 2.4 eV. However, the achieved performance of the BiVO4 photoanode remains unsatisfactory to date because its short carrier diffusion length restricts the total thickness of the BiVO4 film required for sufficient light absorption. We addressed the issue by deposition of nanoporous Mo-doped BiVO4 (Mo:BiVO4) on an engineered cone-shaped nanostructure, in which the Mo:BiVO4 layer with a larger effective thickness maintains highly efficient charge separation and high light absorption capability, which can be further enhanced by multiple light scattering in the nanocone structure. As a result, the nanocone/Mo:BiVO4/Fe(Ni)OOH photoanode exhibits a high water-splitting photocurrent of 5.82 ± 0.36 mA cm−2 at 1.23 V versus the reversible hydrogen electrode under 1-sun illumination. We also demonstrate that the PEC cell in tandem with a single perovskite solar cell exhibits unassisted water splitting with a solar-to-hydrogen conversion efficiency of up to 6.2%.
TL;DR: A composite polymer electrolyte with oxygen-ion conductive nanowires that could address the challenges of all-solid-state LIBs is reported, demonstrating much higher ionic conductivity.
Abstract: Solid Li-ion electrolytes used in all-solid-state lithium-ion batteries (LIBs) are being considered to replace conventional liquid electrolytes that have leakage, flammability, and poor chemical stability issues, which represents one major challenge and opportunity for next-generation high-energy-density batteries. However, the low mobility of lithium ions in solid electrolytes limits their practical applications. Here, we report a solid composite polymer electrolyte with Y2O3-doped ZrO2 (YSZ) nanowires that are enriched with positive-charged oxygen vacancies. The morphologies and ionic conductivities have been studied systemically according to concentration of Y2O3 dopant in the nanowires. In comparison to the conventional filler-free electrolyte with a conductivity of 3.62 × 10–7 S cm–1, the composite polymer electrolytes with the YSZ nanowires show much higher ionic conductivity. It indicates that incorporation of 7 mol % of Y2O3-doped ZrO2 nanowires results in the highest ionic conductivity of 1.07 × ...
TL;DR: A backside-plating configuration is shown that enables long-term cycling of zinc metal batteries without shorting and can be applied to not only zinc metal systems but also other metal-based electrodes suffering from internal short circuits.
Abstract: Portable power sources and grid-scale storage both require batteries combining high energy density and low cost. Zinc metal battery systems are attractive due to the low cost of zinc and its high charge-storage capacity. However, under repeated plating and stripping, zinc metal anodes undergo a well-known problem, zinc dendrite formation, causing internal shorting. Here we show a backside-plating configuration that enables long-term cycling of zinc metal batteries without shorting. We demonstrate 800 stable cycles of nickel-zinc batteries with good power rate (20 mA cm(-2), 20 C rate for our anodes). Such a backside-plating method can be applied to not only zinc metal systems but also other metal-based electrodes suffering from internal short circuits.
TL;DR: This work demonstrates a high throughput method based on fast transfer of electrospun nanofiber film from roughed metal foil to a receiving mesh substrate that is 10 times faster and has better filtration performance at the same transmittance than the direct electrospinning method.
Abstract: Particulate matter (PM) pollution in air has become a serious environmental issue calling for new type of filter technologies. Recently, we have demonstrated a highly efficient air filter by direct electrospinning of polymer fibers onto supporting mesh although its throughput is limited. Here, we demonstrate a high throughput method based on fast transfer of electrospun nanofiber film from roughed metal foil to a receiving mesh substrate. Compared with the direct electrospinning method, the transfer method is 10 times faster and has better filtration performance at the same transmittance, owing to the uniformity of transferred nanofiber film (>99.97% removal of PM2.5 at ∼73% of transmittance). With these advantages, large area freestanding nanofiber film and roll-to-roll production of air filter are demonstrated.
TL;DR: In this article, a highly viscoelastic polymer was applied to the lithium metal electrode, and the morphology of the lithium deposition became significantly more uniform at a high current density of 5 mA/cm2.
Abstract: The future development of low-cost, high-performance electric vehicles depends on the success of next-generation lithium-ion batteries with higher energy density. The lithium metal negative electrode is key to applying these new battery technologies. However, the problems of lithium dendrite growth and low Coulombic efficiency have proven to be difficult challenges to overcome. Fundamentally, these two issues stem from the instability of the solid electrolyte interphase (SEI) layer, which is easily damaged by the large volumetric changes during battery cycling. In this work, we show that when a highly viscoelastic polymer was applied to the lithium metal electrode, the morphology of the lithium deposition became significantly more uniform. At a high current density of 5 mA/cm2 we obtained a flat and dense lithium metal layer, and we observed stable cycling Coulombic efficiency of ∼97% maintained for more than 180 cycles at a current density of 1 mA/cm2.
TL;DR: In this paper, high responsivity phototransistors based on few-layer rhenium disulfide (ReS2) are presented, where the maximum attainable photoresponsivity can reach as high as 88 600 A W−1, which is a record value compared to other individual 2D materials with similar device structures and two orders of magnitude higher than that of monolayer MoS2.
Abstract: 2D transition metal dichalcogenides are emerging with tremendous potential in many optoelectronic applications due to their strong light–matter interactions. To fully explore their potential in photoconductive detectors, high responsivity is required. Here, high responsivity phototransistors based on few-layer rhenium disulfide (ReS2) are presented. Depending on the back gate voltage, source drain bias and incident optical light intensity, the maximum attainable photoresponsivity can reach as high as 88 600 A W−1, which is a record value compared to other individual 2D materials with similar device structures and two orders of magnitude higher than that of monolayer MoS2. Such high photoresponsivity is attributed to the increased light absorption as well as the gain enhancement due to the existence of trap states in the few-layer ReS2 flakes. It further enables the detection of weak signals, as successfully demonstrated with weak light sources including a lighter and limited fluorescent lighting. Our studies underscore ReS2 as a promising material for future sensitive optoelectronic applications.
TL;DR: A programmable CRISPR-Cas9 based demethylase tool containing the deactivated Cas9 fused to the catalytic domain (CD) of Ten-Eleven Translocation dioxygenase1 (TET1CD) and TET1-dCas9 fusion proteins-mediated demethylation at a target region in BRCA1 gene promoter, a model tumour suppressor gene is examined.
Abstract: // Samrat Roy Choudhury 1 , Yi Cui 1 , Katarzyna Lubecka 2 , Barbara Stefanska 2,3 , Joseph Irudayaraj 1,3 1 Department of Agricultural & Biological Engineering, Bindley Bioscience Centre, Purdue University, West Lafayette, IN 47907, USA 2 Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA 3 Purdue Centre for Cancer Research, Purdue University, West Lafayette, IN 47907, USA Correspondence to: Barbara Stefanska, email: bstefanska@purdue.edu Joseph Irudayaraj, email: josephi@purdue.edu Keywords: CRISPR-dCas9, TET1, BRCA1, DNA demethylation, gene activation Received: March 10, 2016 Accepted: May 30, 2016 Published: June 23, 2016 ABSTRACT DNA hypermethylation at the promoter of tumour-suppressor genes is tightly correlated with their transcriptional repression and recognized as the hallmark of majority of cancers. Epigenetic silencing of tumour suppressor genes impairs their cellular functions and activates a cascade of events driving cell transformation and cancer progression. Here, we examine site-specific and spatiotemporal alteration in DNA methylation at a target region in BRCA1 gene promoter, a model tumour suppressor gene. We have developed a programmable CRISPR-Cas9 based demethylase tool containing the deactivated Cas9 (dCas9) fused to the catalytic domain (CD) of Ten-Eleven Translocation (TET) dioxygenase1 (TET1CD). The fusion protein selectively demethylates targeted regions within BRCA1 promoter as directed by the designed single-guide RNAs (sgRNA), leading to the transcriptional up-regulation of the gene. We also noticed the increment in 5-hydroxymethylation content (5-hmC) at the target DNA site undergoing the most profound demethylation. It confirms the catalytic activity of TET1 in TET1-dCas9 fusion proteins-mediated demethylation at these target sequences. The modular design of the fusion constructs presented here allows for the selective substitution of other chromatin or DNA modifying enzymes and for loci-specific targeting to uncover epigenetic regulatory pathways at gene promoters and other selected genomic regions.
TL;DR: A stretchable Li4 Ti5 O12 anode and a LiFePO4 cathode with 80% stretchability are prepared using a 3D interconnected porous polydimethylsiloxane sponge based on sugar cubes to achieve 82% and 91% capacity retention after 500 stretch-release cycles.
Abstract: A stretchable Li4 Ti5 O12 anode and a LiFePO4 cathode with 80% stretchability are prepared using a 3D interconnected porous polydimethylsiloxane sponge based on sugar cubes. 82% and 91% capacity retention for anode and cathode are achieved after 500 stretch-release cycles. Slight capacity decay of 6% in the battery using the electrode in stretched state is observed.
TL;DR: In this article, a fast and reversible thermoresponsive polymer switching material that can be incorporated inside batteries to prevent thermal runaway is reported, which consists of electrochemically stable graphene-coated spiky nickel nanoparticles mixed in a polymer matrix with a high thermal expansion coefficient.
Abstract: Safety issues have been a long-standing obstacle impeding large-scale adoption of next-generation high-energy-density batteries. Materials solutions to battery safety management are limited by slow response and small operating voltage windows. Here we report a fast and reversible thermoresponsive polymer switching material that can be incorporated inside batteries to prevent thermal runaway. This material consists of electrochemically stable graphene-coated spiky nickel nanoparticles mixed in a polymer matrix with a high thermal expansion coefficient. The as-fabricated polymer composite films show high electrical conductivity of up to 50 S cm−1 at room temperature. Importantly, the conductivity decreases within one second by seven to eight orders of magnitude on reaching the transition temperature and spontaneously recovers at room temperature. Batteries with this self-regulating material built in the electrode can rapidly shut down under abnormal conditions such as overheating and shorting, and are able to resume their normal function without performance compromise or detrimental thermal runaway. Our approach offers 103–104 times higher sensitivity to temperature changes than previous switching devices. Safety is a major issue in the development of lithium-ion batteries. Now, a thermoresponsive polymer composite embedded into electrodes is shown to rapidly shut down batteries at overheating but quickly resume function at normal conditions.
TL;DR: In this paper, a flexible all-solid state supercapacitor is provided that includes a first electrode and a second electrode, where the flexible nanofiber web connects the first electrode to the second electrode.
Abstract: A flexible all-solid state supercapacitor is provided that includes a first electrode and a second electrode, and a flexible nanofiber web, where the flexible nanofiber web connects the first electrode to the second electrode, where the flexible nanofiber web includes a plurality of flexible nanofibers, where the flexible nanofiber includes a hierarchal structure of macropores, mesopores and micropores through a cross section of the flexible nanofiber, where the mesopores and the micropores form a graded pore structure, where the macropores are periodically distributed along the flexible nanaofiber and within the graded pore structure.
TL;DR: In this article, a facile cathode prelithiation method with nanocomposites of conversion materials is demonstrated to compensate the initial lithium loss and improve the battery performance.
Abstract: Loss of lithium in the initial cycles appreciably reduces the energy density of lithium-ion batteries. Anode prelithiation is a common approach to address the problem, although it faces the issues of high chemical reactivity and instability in ambient and battery processing conditions. Here we report a facile cathode prelithiation method that offers high prelithiation efficacy and good compatibility with existing lithium-ion battery technologies. We fabricate cathode additives consisting of nanoscale mixtures of transition metals and lithium oxide that are obtained by conversion reactions of metal oxide and lithium. These nanocomposites afford a high theoretical prelithiation capacity (typically up to 800 mAh g−1, 2,700 mAh cm−3) during charging. We demonstrate that in a full-cell configuration, the LiFePO4 electrode with a 4.8% Co/Li2O additive shows 11% higher overall capacity than that of the pristine LiFePO4 electrode. The use of the cathode additives provides an effective route to compensate the large initial lithium loss of high-capacity anode materials and improves the electrochemical performance of existing lithium-ion batteries. There is an intensive research effort in suppressing the first-cycle lithium loss in lithium-ion batteries. Now, a cathode prelithiation method with nanocomposites of conversion materials is demonstrated to compensate the initial lithium loss and improve the battery performance.