Yolk-shell FeS@N-doped carbon nanosphere as superior anode materials for sodium-ion batteries.

Iron sulfides have shown great potential as anode materials for sodium-ion batteries (SIBs) because of their high sodium storage capacity and low cost. Nevertheless, iron sulfides generally exhibit unsatisfied electrochemical performance induced by sluggish electron/ion transfer and severe pulverization upon the sodiation/desodiation process. Herein, we constructed a yolk-shell FeS@NC nanosphere with an N-doped carbon shell and FeS particle core via a simple hydrothermal method, followed by in-situ polymerization and vulcanization. The FeS particles intimately coupled with N-doped carbon can accelerate the electron transfer, avoid severe volume expansion, and maintain structural stability upon repeated sodiation/desodiation process. Furthermore, the small particle size of FeS can shorten ion-diffusion distance and facilitate ion transportation. Therefore, the FeS@NC nanosphere shows excellent cycling performance and superior rate capability that it can deliver a high capacity of 520.1 mAh g-1 over 800 cycles at 2.0 A g-1 and a remarkable capacity of 625.9 mAh g-1 at 10.0 A g-1.

Interface engineering of metal sulfides-based composites enables high-performance anode materials for sodium-ion batteries.

Metal sulfides (MSs) have attracted much attention as anode materials for sodium-ion batteries (SIBs) due to their high sodium storage capacity. However, the unsatisfactory electrochemical performance induced by the huge volume change and sluggish kinetics hampered the practical application of SIBs. Herein, guided by the heterostructure interface engineering, novel multicomponent metal sulfide-based anodes, including SnS, FeS, and Fe3N embedded in N-doped carbon nanosheets (SnS/FeS/Fe3N/NC NSs), have been synthesized for high-performance SIBs. The as-prepared SnS/FeS/Fe3N/NC NSs with abundant heterointerfaces and high conductivity of N-doped carbon nanosheet matrix can shorten the Na+ diffusion path and promote reaction kinetics during the sodiation/desodiation process. Moreover, the presence of Fe3N can promote the reversible conversion of SnS and FeS during the cycling process. As a consequence, when evaluated as anode materials for SIBs, the SnS/FeS/Fe3N/NC NSs can maintain a high sodium storage capacity of 473.6 mAh g-1 after 600 cycles at 2.0 A g-1 and can still provide a high reversible capacity of 537.4 mAh g-1 even at 5.0 A g-1 This discovery offers a novel strategy for constructing metal sulfide-based anode materials for high-performance SIBs.

Well-Dispersed Bi nanoparticles for promoting the lithium storage performance of Si Anode: Effect of the bridging Bi nanoparticles.

Silicon (Si) is considered a promising anode material for lithium-ion batteries (LIBs) due to its high theoretical specific capacity of up to 4200 mAh/g. However, the poor cycling and rate performances of Si induced by the low intrinsic electronic conductivity and large volume expansion during the lithiation/delithiation process limit its practical application. Herein, a novel silicon/bismuth@nitrogen-doped carbon (Si/Bi@NC) composite with nanovoids was synthesized and investigated as an advanced anode material for LIBs. In such a structure, ultrafine bismuth nanoparticles coupled with an N-doped carbon layer were introduced to modify the surface of Si nanoparticles. Subsequently, the lithiated LixBi has excellent high ionic conductivity and acts as a fast transport bridge for lithium ions. The introduced carbon coating layer and nanovoids can buffer the volume expansion of Si during the lithiation/delithiation process, thus maintaining structural stability during the cycling process. As a result, the Si/Bi@NC composite exhibits excellent electrochemical performance, providing a relatively high capacity of 955.8 mAh/g at 0.5 A/g after 450 cycles and excellent rate performance with a high capacity of 477.8 mAh/g even at 10.0 A/g. Furthermore, the assembled full cell with LiFePO4 as cathode and pre-lithium Si/Bi@NC as anode can provide a high capacity of 138.8 mAh/g at 1C after 90 cycles, exhibiting outstanding cycling performance.

SiO2 bridged AlN/methylphenyl silicone resin composite with integrated superior insulating property, high-temperature resistance, and high thermal conductivity.

A high-temperature-resistance insulating layer with high thermal conductivity is the key component for fabricating the instant metal-based electric heating tube. However, it is still a challenge for materials to possess excellent high-temperature resistance, superior insulating property, and high thermal conductivity at the same time. Here, a novel SiO2 bridged AlN/MSR composite based on methylphenyl silicone resin (MSR) and AlN filler was reported. MSR with a high thermal decomposition temperature of 452.0 °C and a high withstand voltage of 5.6 kV was first synthesized by adjusting the contents of alkyl and phenyl groups. The superior high-temperature resistant insulating property is 3.7 and 2.4 times higher than the national standard requirement of 1.5 kV and commercial silicone resin, respectively. The hydrogen bonds formed between SiO2, AlN, and MSR and the electrostatic adsorption between SiO2 and AlN can remarkably improve the uniform dispersion of AlN in MSR and thus enhance the insulating property, thermal conductivity, and thermal stability. With the addition of 2 wt% SiO2 and 50 wt% AlN, the SiO2-AlN/MSR composite exhibits an extremely high withstand voltage of 7.3 kV, a high thermal conductivity of 0.553 W·m-1·K-1, and an enhanced decomposition temperature of 475 °C. The superior insulating property and thermal conductivity are 4.9 and 1.3 times higher than the national standard requirement and pure MSR, respectively. This novel composite shows great potential for application in the fields requiring integrated superior insulating property, high-temperature resistance, and high thermal conductivity.

Enhancing Structure Stability by Mg/Cr Co-Doped for High-Voltage Sodium-Ion Batteries.

P2-Na2/3Ni1/3Mn2/3O2 cathode materials have garnered significant attention due to their high cationic and anionic redox capacity under high voltage. However, the challenge of structural instability caused by lattice oxygen evolution and P2-O2 phase transition during deep charging persists. A breakthrough is achieved through a simple one-step synthesis of Cr, Mg co-doped P2-NaNMCM, resulting in a bi-functional improvement effect. P2-NaNMCM-0.01 exhibits an impressive capacity retention rate of 82% after 100 cycles at 1 C. In situ X-ray diffraction analysis shows that the "pillar effect" of Mg mitigates the weakening of the electrostatic shielding and effectively suppresses the phase transition of P2-O2 during the charging and discharging process. This successfully averts serious volume expansion linked to the phase transition, as well as enhances the Na+ migration. Simultaneously, in situ Raman spectroscopy and ex situ X-ray photoelectron spectroscopy tests demonstrate that the strong oxygen affinity of Cr forms a robust TM─O bond, effectively restraining lattice oxygen evolution during deep charging. This study pioneers a novel approach to designing and optimizing layered oxide cathode materials for sodium-ion batteries, promising high operating voltage and energy density.

Self-supporting network-structured MoS2/heteroatom-doped graphene as superior anode materials for sodium storage.

Layered graphene and molybdenum disulfide have outstanding sodium ion storage properties that make them suitable for sodium-ion batteries (SIBs). However, the easy and large-scale preparation of graphene and molybdenum disulfide composites with structural stability and excellent performance face enormous challenges. In this study, a self-supporting network-structured MoS2/heteroatom-doped graphene (MoS2/NSGs-G) composite is prepared by a simple and exercisable electrochemical exfoliation followed by a hydrothermal route. In the composite, layered MoS2 nanosheets and heteroatom-doped graphene nanosheets are intertwined with each other into self-supporting network architecture, which could hold back the aggregation of MoS2 and graphene effectively. Moreover, the composite possesses enlarged interlayer spacing of graphene and MoS2, which could contribute to an increase in the reaction sites and ion transport of the composite. Owing to these advantageous structural characteristics and the heteroatomic co-doping of nitrogen and sulfur, MoS2/NSGs-G demonstrates greatly reversible sodium storage capacity. The measurements revealed that the reversible cycle capacity was 443.9 mA h g-1 after 250 cycles at 0.5 A g-1, and the rate capacity was 491.5, 490.5, 453.9, 418.1, 383.8, 333.1, and 294.4 mA h g-1 at 0.1, 0.2, 0.5, 1, 2, 5 and 10 A g-1, respectively. Furthermore, the MoS2/NSGs-G sample displayed lower resistance, dominant pseudocapacitive contribution, and faster sodium ion interface kinetics characteristic. Therefore, this study provides an operable strategy to obtain high-performance anode materials, and MoS2/NSGs-G with favorable structure and excellent cycle stability has great application potential for SIBs.

Insights into the Conductive Network of Electrochemical Exfoliation with Graphite Powder as Starting Raw Material for Graphene Production.

Electrochemical exfoliation starting with graphite powder as the raw material for graphene production shows superiority in cost effectiveness over the popular bulk graphite. However, the crucial conductive network inside the graphite powder electrode along with its formation and influence mechanisms remains blank. Here, an adjustable-pressure graphite powder electrode with a sandwich structure was designed for this. Appropriate encapsulation pressure is necessary and conducive to constructing a continuous and stable conductive network, but overloaded encapsulation pressure is detrimental to the exfoliation and graphene quality. With an initial encapsulation pressure (IEP) of 4 kPa, the graphite powders expand rapidly to a final stable expansion pressure of 49 kPa with a final graphene yield of 46.3%, where 84% of the graphene sheets are less than 4 layers with ID/IG values between 0.22 and 1.24. Increasing the IEP to 52 kPa, the expansion pressure increases to 73 kPa, but the graphene yield decreases to 39.3% with a worse graphene quality including higher layers and ID/IG values of 1.68-2.13. In addition, small-size graphite powders are not suitable for the electrochemical exfoliation. With the particle size decreasing from 50 to 325 mesh, the graphene yield decreases almost linearly from 46.3% to 5.5%. Conductive network and electrolyte migration synergize and constrain each other, codetermining the electrochemical exfoliation. Within an encapsulated structure, the electrochemical exfoliation of the graphite powder electrode proceeds from the outside to the inside. The insights revealed here will provide direction for further development of electrochemical exfoliation of graphite powder to produce graphene.

Layered Metal Oxide Nanosheets with Enhanced Interlayer Space for Electrochemical Deionization.

Electrochemical deionization is regarded as one of the promising water treatment technologies. Here, CoAl-layered metal oxide nanosheets intercalated by sodium dodecyl sulfate (SDS) with an enhanced interlayer spacing from 0.76 to 1.33 nm are synthesized and used as an anode. The enlarged interlayer spacing provides an enhanced ion-diffusion channel and improves the utilization of the interlayer electroactive sites, while heat treatment, transferring layered double hydroxides to layered metal oxides (LMOs), offers additional active oxidation reaction sites to facilitate the electro-sorption rate, contributing to the high salt adsorption capacity (31.78 mg g-1 ) and average salt adsorption rate (3.75 mg g-1  min-1 ) at 1.2 V in 500 mg L-1 NaCl solution. In addition, the excellent long-term cycling stability (92.9%) after 40 cycles proves the strong electronic interaction between SDS and the host layer, which is validated by density functional theory calculations later on. Moreover, the electro-sorption mechanism of LMOs that originated from the reconstruction of the layered structure based on the "memory effect" is revealed according to the X-ray photoelectron spectroscopy peak shifts of Co element. This strategy of expanding the interlayer spacing combined with heat treatment makes LMOs a competitive candidate for electrochemical water deionization.

Constructing three-dimensional N-doped carbon coating silicon/iron silicide nanoparticles cross-linked by carbon nanotubes as advanced anode materials for lithium-ion batteries.

Silicon (Si), have been considered as promising anode material for lithium-ion batteries (LIBs), due to its high theoretical specific capacity of 4200 mAh g-1. However, the poor electrical conductivity and large volume change during lithiation/delithiation process, resulting in poor cycling stability, and seriously hindered the practical application in LIBs. Herein, a multiple Si/FexSiy@NC/CNTs composite is synthesized and investigated as advanced anode materials for LIBs via a simple one-step method. Such multiple Si/FexSiy@NC/CNTs composite has several merits including the FexSiy can not only accommodate the huge volume change of Si nanoparticles, but also enhance the conductivity upon discharge/charge process. Furthermore, the in-situ growth CNTs may help establish a long-range conductivity, and the Nitrogen-doped carbon (NC) layer can further improve the conductivity of Si, as well as inhibit the direct contract between electrolyte and Si during cycling process. Accordingly, the Si/FexSiy@NC/CNTs-1 exhibits excellent cycling stability (a high capacity of 994.4 mAh g-1 is maintained at 1.0 A g-1 after 600cycles) and outstanding rate capability (a suitable capacity of 441.7 mAh g-1 was obtained even at 5.0 A g-1). Moreover, the assembled full cell can achieve a capacity of 141.4 mAh g-1 after 65 cycles at 1.0C, exhibiting outstanding cycling stability. This work provides a prospective way for the commercial production of high-performance Si-based anode materials for LIBs.

Waste Lithium Ion Battery Evolves into Heteroatom Doped Carbon as Oxygen Reduction Electrocatalyst for Aqueous Al-Air Batteries.

Carbon based electrocatalysts prepared by recycling waste power batteries can not only realize the new utilization of waste energy materials, but also obtain cheap and efficient oxygen reduction electrocatalyst for metal-air battery. Based on the cathode carbon of waste LiFePO4 batteries, nitrogen doped carbon based catalyst NC-1000 is prepared by simple pyrolysis, acid dissolution of LiFePO4 and high temperature heteroatom doping. The catalyst is characterized by scanning electron microscope, transmission electron microscope and Raman spectrum, and the electrochemical performances of the catalyst and Al-air battery were tested. The results show that carbon based electrocatalyst NC-1000 is rich in structural defects and embedded with trace metal oxides. Compared with commercial 20 wt% Pt/C, it has higher electrocatalytic activity and faster kinetic with a half-wave potential of 0.828 V vs. RHE and the Tafel slope of 70.7 mV dec-1 . In addition, assembled into Al-air battery, the open circuit potential can reach 1.57 V along with the high power density of 141 mW cm-2 at 200 mA cm-2 . The discharge specific capacity at higher current of up to 100 mA cm-2 is even better than the commercial Pt/C. This study can not only improve the economic value of waste power batteries, but also obtain high-performance ORR electrocatalyst, which will greatly promote the commercial development of Al-air batteries.

SnS@C nanoparticles anchored on graphene oxide as high-performance anode materials for lithium-ion batteries.

Tin (II) sulfide (SnS) has been regarded as an attractive anode material for lithium-ion batteries (LIBs) owing to its high theoretical capacity. However, sulfide undergoes significant volume change during lithiation/delithiation, leading to rapid capacity degradation, which severely hinders its further practical application in lithium-ion batteries. Here, we report a simple and effective method for the synthesis of SnS@C/G composites, where SnS@C nanoparticles are strongly coupled onto the graphene oxide nanosheets through dopamine-derived carbon species. In such a designed architecture, the SnS@C/G composites show various advantages including buffering the volume expansion of Sn, suppressing the coarsening of Sn, and dissolving Li2S during the cyclic lithiation/delithiation process by graphene oxide and N-doped carbon. As a result, the SnS@C/G composite exhibits outstanding rate performance as an anode material for lithium-ion batteries with a capacity of up to 434 mAh g-1 at a current density of 5.0 A g-1 and excellent cycle stability with a capacity retention of 839 mAh g-1 at 1.0 A g-1 after 450 cycles.

Interlayer Spacing Regulation of NiCo-LDH Nanosheets with Ultrahigh Specific Capacity for Battery-Type Supercapacitors.

The transition metal-based layered double hydroxides (LDHs) have been extensively studied as promising functional nanomaterials owing to their excellent electrochemical activity and tunable chemical composition. In this work, using acetate anions (Ac-) as intercalating elements, the NiCo-LDH nanosheets arraying on Ni foam with different amounts of Ac- anion intercalation or volume of hydrothermal solution were prepared by a simple hydrothermal method. The optimized amount of Ac- anions expanded the interlayer space of LDH nanosheets from 0.8 to 0.94 nm. An ultrahigh specific capacity of 1200 C g-1 at 1 A g-1 (690 C g-1 without Ac- anions), an outstanding rate capability of 72.5% at 30 A g-1, and a cycle stability of 79.90% after 4500 cycles were mainly attributed to the higher interlayer spacing of Ac- anion intercalation. The enlarged interlayer spacing was beneficial for stabilizing the α-phase of LDHs and accelerating the electron transport and electrolyte penetration in the electrochemical reaction. This work sheds light on the mechanisms of the interlayer spacing regulation of NiCo-LDH nanosheets and offers a promising strategy to synthesize functional nanomaterials with excellent electrochemical performance via integrating their unique layered structure and interlayer anion exchange characteristics.

Functional Characterization of a Cucumber (Cucumis sativus L.) Vacuolar Invertase, CsVI1, Involved in Hexose Accumulation and Response to Low Temperature Stress.

Cucumber (Cucumis sativus L.), an important vegetable plant species, is susceptible to low temperature stress especially during the seedling stage. Vacuolar invertase (VI) plays important roles in plant responses to abiotic stress. However, the molecular and biochemical mechanisms of VI function in cucumber, have not yet been completely understood and VI responses to low temperature stress and it functions in cold tolerance in cucumber seedlings are also in need of exploration. The present study found that hexose accumulation in the roots of cucumber seedlings under low temperature stress is closely related to the observed enhancement of invertase activity. Our genome-wide search for the vacuolar invertase (VI) genes in cucumber identified the candidate VI-encoding gene CsVI1. Expression profiling of CsVI1 showed that it was mainly expressed in the young roots of cucumber seedlings. In addition, transcriptional analysis indicated that CsVI1 expression could respond to low temperature stress. Recombinant CsVI1 proteins purified from Pichia pastoris and Nicotiana benthamiana leaves could hydrolyze sucrose into hexoses. Further, overexpression of CsVI1 in cucumber plants could increase their hexose contents and improve their low temperature tolerance. Lastly, a putative cucumber invertase inhibitor was found could form a complex with CsVI1. In summary, these results confirmed that CsVI1 functions as an acid invertase involved in hexose accumulation and responds to low temperature stress in cucumber seedlings.

Phase Compatible NiFe2O4 Coating Tunes Oxygen Redox in Li-Rich Layered Oxide.

Li-rich layered oxides have attracted intense attention for lithium-ion batteries, as provide substantial capacity from transition metal cation redox simultaneous with reversible oxygen-anion redox. However, unregulated irreversible oxygen-anion redox leads to critical issues such as voltage fade and oxygen release. Here, we report a feasible NiFe2O4 (NFO) surface-coating strategy to turn the nonbonding coordination of surface oxygen into metal-oxygen decoordination. In particular, the surface simplex M-O (M = Ni, Co, Mn from MO6 octahedra) and N-O (N = Ni, Fe from NO6 octahedra) bonds are reconstructed in the form of M-O-N bonds. By applying both in operando and ex situ technologies, we found this heterostructural interface traps surface lattice oxygen, as well as restrains cation migration in Li-rich layered oxide during electrochemical cycling. Therefore, surface lattice oxygen behavior is significantly sustained. More interestingly, we directly observe the surface oxygen redox decouple with cation migration. In addition, the NFO-coating blocks HF produced from electrolyte decomposition, resulting in reducing the dissolution of Mn. With this strategy, higher cycle stability (91.8% at 1 C after 200 cycles) and higher rate capability (109.4 mA g-1 at 1 C) were achieved in this work, compared with pristine Li-rich layered oxide. Our work offers potential for designing electrode materials utilizing oxygen redox chemistry.

Stabilized Cathode Interphase for Enhancing Electrochemical Performance of LiNi0.5Mn1.5O4-Based Lithium-Ion Battery via cis-1,2,3,6-Tetrahydrophthalic Anhydride.

The continuous degradation of carbonate electrolytes and the dissolution of transition metal cations due to parasitic reactions on the cathode-electrolyte interphase (CEI) block the practical application of LiNi0.5Mn1.5O4-based lithium-ion batteries (LNMO-based LIBs) at a high voltage. cis-1,2,3,6-Tetrahydrophthalic anhydride (CTA) has been used as a functional additive in a carbonate baseline electrolyte (BE) for constructing the CEI film to enhance the cyclic stability of LNMO-based LIBs. The LNMO/Li cell with CTA exhibits a preponderant capacity retention of 83.3% compared with those of propionic anhydride (PA) (46.5%) and BE (13.6%) after 500 cycles at the current density of 1 C from 3.5 to 4.9 V. Additionally, the LNMO/graphite full cell with CTA still has a higher capacity retention of 95.46% even after 300 cycles at 1 C. By characterizations, it is reasonably demonstrated that CTA was oxidated to participate in the construction of a CEI film. An unsaturated aromatic group was introduced into the composition of the CEI film along with CTA in the formation process of the CEI film, which further improved the antioxidative activity of the CEI film under the influence of field-effect. Specifically, the CEI film obtains appreciable stability because of its higher antioxidative activity under the influence of field-effect. The stabilized CEI can significantly suppress the parasitic reactions of electrolytes, decrease the consumption of active-Li+, and protect the LNMO cathode structure, thereby enhancing the cyclic compatibility of LNMO-based LIBs with the carbonate electrolytes from 3.5 to 4.9 V.

A Vacuolar Invertase CsVI2 Regulates Sucrose Metabolism and Increases Drought Tolerance in Cucumis sativus L.

Vacuolar invertase (VI) can irreversibly degrade sucrose into glucose and fructose and involve in plants abiotic-stress-tolerance. Cucumber (Cucumis sativus L.) is susceptible to drought stress, especially during the seedling stage. To date, the involvement of VI in drought tolerance in cucumber seedlings is in urgent need of exploration. In the present study, a cucumber vacuolar invertase gene, CsVI2, was isolated and functionally characterized. The results showed that (1) CsVI2 showed vacuolar invertase activity both in vivo and in vitro; (2) the transcript level of CsVI2, along with VI activity, was significantly induced by drought stress. Moreover, the expression of sucrose synthase 3 (CsSUS3) was increased and that of sucrose phosphate synthase 1 (CsSPS1) was decreased after exposure to drought stress, which was followed by an increase in sucrose synthase activity and a decrease in sucrose phosphate synthase activity; (3) CsVI2-overexpressing transformed cucumber seedlings showed enhanced vacuolar invertase activity and drought tolerance and 4) protein-protein interaction modelling indicated that a cucumber invertase inhibitor, CsINVINH3, can interact with CsVI2. In summary, the results indicate that CsVI2 as an invertase can regulate sucrose metabolism and enhance drought stress in cucumber seedlings.

A green, efficient, closed-loop direct regeneration technology for reconstructing of the LiNi0.5Co0.2Mn0.3O2 cathode material from spent lithium-ion batteries.

Lithium nickel manganese cobalt oxide in the spent lithium ion batteries (LIBs) contains a lot of lithium, nickel, cobalt and manganese. However, how to effectively recover these valuable metals under the premise of reducing environmental pollution is still a challenge. In this work, a green, efficient, closed-loop direct regeneration technology is proposed to reconstruct LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode materials from spent LIBs. Firstly, the failure mechanism of NCM523 cathode materials in the spent LIBs is analyzed deeply. It is found that the spent NCM523 material has problems such as the dissolution of lithium and transition metals, surface interface failure and structural transformation, resulting in serious deterioration of electrochemical performance. Then NCM523 material was directly regenerated by supplementing metal ions, granulation, ion doping and heat treatment. Meanwhile, PO43- polyanions were doped into the regenerated NCM material in the recovery process, showing excellent electrochemical performance with discharge capacity of 189.8 mAh g-1 at 0.1 C. The recovery process proposed in this study puts forward a new strategy for the recovery various lithium nickel cobalt manganese oxide (e.g., LiNi1/3Co1/3Mn1/3O2, LiNi0.5Co0.2Mn0.3O2, LiNi0.6Co0.2Mn0.2O2 and LiNi0.8Co0.1Mn0.1O2) and accelerates the industrialization of spent lithium ion battery recycling.

FeSe2@C Microrods as a Superior Long-Life and High-Rate Anode for Sodium Ion Batteries.

Transition-metal selenides have emerged as promising anode materials for sodium ion batteries (SIBs). Nevertheless, they suffer from volume expansion, polyselenide dissolution, and sluggish kinetics, which lead to inadequate conversion reaction toward sodium and poor reversibility during the desodiation process. Therefore, the transition-metal selenides are far from long cycling stability, outstanding rate performance, and high initial Coulombic efficiency, which are the major challenges for practical application in SIBs. Here, an efficient anode material including an FeSe2 core and N-doped carbon shell with inner void space as well as high conductivity is developed for outstanding rate performance and long cycle life SIBs. In the ingeniously designed FeSe2@NC microrods, the N-doped carbon shell can facilitate mass transport/electron transfer, protect the FeSe2 core from the electrolyte, and accommodate volume variation of FeSe2 with the help of the inner void of the core. Thus, the FeSe2@NC microrods can maintain strong structural integrity upon long cycling and ensure a good reversible conversion reaction of FeSe2 during the discharge/charge process. As a result, the as-prepared FeSe2@NC microrods exhibit excellent sodium storage performance and ultrahigh stability, achieving an excellent rate capability (411 mAh g-1 at 10.0 A g-1) and a long-term cycle performance (401.3 mAh g-1 after 2000 cycles at 5.0 A g-1).

Structural Insight into the Abnormal Capacity of a Co-Substituted Tunnel-Type Na0.44MnO2 Cathode for Sodium-Ion Batteries.

Tunnel-type (T-type) Na0.44MnO2 (NMO) is a promising cathode material for sodium-ion batteries (SIBs) owing to its high rate performance and cycling stability compared to manganese-based layered oxides. However, the low specific capacity still restricts its practical applications. Herein, a Co-doped T-type NMO is synthesized through a facile solid-state reaction method and utilized as a cathode material for SIBs. A T-type Na0.44Mn0.9925Co0.0075O2 (NMO-3) electrode can deliver a high reversible capacity of 138 mAh g-1 at 0.1C, a superior rate capability (133, 130, 121, 106, and 93 mAh g-1 at 0.5, 1, 2, 5, and 10C, respectively), and excellent cycling stability (85.2% at 10C after 500 cycles). The substitution of Co3+ by Mn3+ leads to the enlargement of small and S-shaped tunnel spaces, which facilitates the insertion/deinsertion of Na+ into/from NMO-3 and greatly enhances its rate capability and cycling stability. Moreover, the reduced energy barriers for Na+ diffusion in small tunnels make the inactive Na+ easier to be deintercalated, which should be responsible for its high specific capacity that exceeds the theoretical capacity of T-type NMO.

Apoplastic maize fructan exohydrolase Zm-6-FEH displays substrate specificity for levan and is induced by exposure to levan-producing bacteria.

Fructan exohydrolases (FEHs) are structurally related to cell wall invertases. While the latter are ubiquitous in higher plants, the role of FEHs in non-fructan species has remained enigmatic. To explore possible roles of FEHs in maize, a full length putative Zm-6-FEH-encoding cDNA was cloned displaying high sequence similarity with cell wall invertases. For functional characterization, Zm-6-FEH protein was expressed in Picha pastoris and in Nicotiana benthamiana leaves. Enzyme activity of recombinant Zm-6-FEH protein showed a strong preference for levan as substrate. Expression profiling in maize seedlings revealed higher transcript amounts in the more mature leaf parts as compared to the growth zone at the base of the leaf, in good correlation with FEH enzyme activities. Subcellular localization analysis indicated Zm-6-FEH location in the apoplast. Noteworthy, incubation of leaf discs with levan and co-incubation with high levan-producing bacteria selectively up-regulated transcript levels of Zm-6-FEH, accompanied by an increase of 6-FEH enzyme activity. In summary, the results indicate that Zm-6-FEH, a novel fructan exohydrolase of a non-fructan species, may have a role in plant defense against levan-producing bacteria.