Synergistic catalytic conversion and chemisorption of polysulfides from Fe/Fe3C/FeN0.0324 nanocubes modified separator for advanced Li-S batteries

Micro-mesoporous cobalt phosphosulfide (Co3S4/CoP/NC) nanowires for ultrahigh rate capacity and ultrastable sodium ion battery

The construction of heterostructure materials has been demonstrated as the promising approach to design high-performance anode materials for sodium ion batteries (SIBs). Herein, micro-mesoporous cobalt phosphosulfide nanowires (Co3S4/CoP/NC) with Co3S4/CoP hetero-nanocrystals encapsulating into N-doped carbon frameworks were successfully synthesized via hydrothermal reaction and subsequent phosphosulfidation process. The obtained micro-mesoporous nanowires greatly improve the charge transport kinetics from the facilitation of the charge transport into the inner part of nanowire. When evaluated as SIBs anode material, the Co3S4/CoP/NC presents outstanding electrochemical performance and battery properties owing to the synergistic effect between Co3S4 and CoP nanocrystals and the conductive carbon frameworks. The electrode material delivers outstanding reversible rate capacity (722.33 mAh/g at 0.1 A/g) and excellent cycle stability with 522.22 mAh/g after 570 cycles at 5.0 A/g. Besides, the Ex-situ characterizations including XRD, XPS, and EIS further revealed and demonstrated the outstanding sodium ion storage mechanism of Co3S4/CoP/NC electrode. These findings pave a promising way for the development of novel metal phosphosulfide anodes with unexpected performance for SIBs and other alkali ion batteries.

Bismuth oxychloride nanosheets anchored aramid separator with sponge-like structure for improved lithium-ion battery performance

Functional modification of inorganic particles is an effective approach to tackle the issue of Li+ transport and the lithium dendrites formation in lithium-ion batteries (LIBs). In this study, PMIA/BiOCl composite separators are prepared by nonsolvent induce phase separation (NIPS) method using P-type semiconductor bismuth oxychloride (BiOCl) functionalized poly (m-phenylene isophthalamide) (PMIA) separators. Compared with the polypropylene (PP) separator, PMIA has superior thermal stability and the addition of BiOCl further enhances its flame retardancy. And the prepared PMIA/BiOCl separator presents improved porosity (66.47 %), enhanced electrolyte uptake rate (863 %) and higher ionic conductivity (0.49 mS∙cm-1). Besides, the incorporation of BiOCl can anchor PF6- to the three-dimensional network skeleton of the PMIA/BiOCl separators, enabling the desolvation of Li+ and selectively facilitating Li+ transport (the Li+ transfer number is 0.79). Moreover, the uniform porous structure of the PMIA/BiOCl separators and the efficient transport of Li+ uniformly deposite Li+, and minimize the growth of lithium dendrites. Batteries assembled with PMIA/BiOCl separators have a discharge specific capacity of 124.4 mAh∙g-1 and capacity retention of 96.7 % after 200 cycles at 0.2C. Therefore, this work provides an effective route in the design strategy of separators for LIBs.

Cobalt Nitride Nanoparticles Encapsulated in N-Doped Carbon Nanotubes Modified Separator of Li-S Battery Achieving the Synergistic Effect of Restriction-Adsorption-Catalysis of Polysulfides

Although lithium-sulfur (Li-S) batteries have broad market prospects due to their high theoretical energy density and potential cost-effectiveness, the practical applications still face serious shuttle effects of polysulfides (LiPSs) and slow redox reactions. Therefore, in this paper, cobalt nitride nanoparticles encapsulated in nitrogen-doped carbon nanotube (CoN@NCNT) are prepared as a functional layer for the separator of high-performance Li-S batteries. Carbon nanotubes with large specific surface areas not only promote the transport of ions and electrons but also weaken the migration of LiPSs and confine the dissolution of LiPSs in electrolytes. The lithiophilic heteroatom N adsorbs LiPSs by strong chemical adsorption, and the CoN particles with high catalytic activity greatly improve the kinetics of the conversion between LiPSs and Li2S2/Li2S during the charge-discharge process. Due to these advantages, the battery with CoN@NCNT modified separator has superior rate performance (initial discharge capacity of 834.7 mAh g-1 after activation at 1 C) and excellent cycle performance (capacity remains 729.7 mAh g-1 after 200 cycles at 0.2 C). This work proposes a strategy that can give the separator a strong ability to confinement-adsorption-catalysis of LiPSs in order to provide more possibilities for the development of Li-S batteries.

Ultra-thin nanosheets decorated in-situ S-doped 3D interconnected carbon network as interlayer modified Li-S batteries separator for accelerating adsorption-catalytic synergistic process of LiPSs

The shuttle effect of soluble lithium polysulfides (LiPSs) is primarily responsible for the unstable performance of lithium-sulfur (Li-S) batteries, which has severely impeded their continued development. In order to solve this problem, a special strategy is proposed. Specifically, ultra-thin NiCo based layered double hydroxides (named LDH or NiCo-LDH) nanosheets are implanted into a pre-designed 3D interconnected carbon networks (SPC) to obtain porous composite materials (named SPC-LDH).During the operation of the battery, the 3D interconnected porous carbon mesh was the first to rapidly adsorb LiPSs, and then the LDH on the surface of the carbon mesh was used to realize the catalytic conversion of LiPSs. This facilitates the electrochemical conversion reaction between S substances while addressing the "shuttle effect". As a result, the battery maintains a discharge capacity of 1401.9, 1114.3, 975.5, 880.7, 760.4 and 679.6 mAh g-1 at the current densities of 0.1, 0.2, 0.5, 1, 2 and 3C, respectively. After 200 cycles at 2C, the battery's capacity stays at 732.9 mAh g-1, meaning that the average rate of capacity decay is only 0.007 % per cycle. Moreover, in-situ XRD demonstrates the critical function of PP/SPC-LDH separators in inhibiting LiPSs and encouraging Li2S transformation. The strong affinity of SPC-LDH for Li2S6 is also confirmed by density functional theory (DFT) calculation, offering more theoretical support for the synergistic adsorption process. This work offers a compelling method to develop modified separator materials that can counteract the "shuttle effect" in Li-S batteries.

Organic polymer coating induced multiple heteroatom-doped carbon framework confined Co1-xS@NPSC core-shell hexapod for advanced sodium/potassium ion batteries

Synthesis of advanced structure and multiple heteroatom-doped carbon based heterostructure materials are the key to the preparation of high-performance energy storage electrode materials. Herein, the hexapod-shaped Co1-xS@NPSC has been triumphantly prepared using hexapod ZIF-67 as the sacrificial template to prepare Co1-xS inner core and N, P, and S tri-doped carbon (NPSC) as the shell through the carbonization of the organic polymer precursor. When applied as anode for Na+ batteries (SIBs) and K+ batteries (PIBs), Co1-xS@NPSC presents the high reversible specific capability of 747.4 mAh/g at 1.0 A/g after 235 cycles and 387.8 mAh/g at 5.0 A/g after 760 cycles for SIBs, as well as 326.7 mAh/g at 1.0 A/g after 180 cycles for PIBs. The excellent storage capacity and rate capability of Co1-xS@NPSC is ascribed to hexapod structure of ZIF-67 unlike the common dodecahedron, which is constructed with interior porous and exterior framework repository, donating supplemental active sites, and doping of multiple heteroatoms forming organic polymer coating inhibiting the volume expansion and restrains the agglomeration of Co1-xS nanoparticles. This approach has paved a bright avenue to exploit promising anode materials with novel structure and hetero-atom doping for high-performance energy storage devices.

Cobalt-vanadium sulfide yolk-shell nanocages from surface etching and ion-exchange of ZIF-67 for ultra-high rate-capability sodium ion battery

Development of high-performance metal sulfides anode materials is a great challenge for sodium-ion batteries (SIBs). In this work, a cobalt-based imidazolate framework (ZIF-67) were firstly synthesized and applied as precursor. After the successive surface etching, ion exchange and sulfidation processes, the final cobalt-vanadium sulfide yolk-shell nanocages were obtained (CoS2/VS4@NC) with VS4 shell and CoS2 yolk encapsulated into nitrogen doped carbon frameworks. This yolk-shell nanocage structure effectively increases the specific surface area and provides enough space for inhibiting the volume change during charge/discharge processes. Besides, the nitrogen doped carbon skeleton greatly improves the ionic conductivity and facilitates ion transport. When used as the anode materials for SIBs, the yolk-shell nanocages of CoS2/VS4@NC electrode exhibits excellent rate capability and stable cycle performance. Notably, it displays a long-term cycling stability with excellent capacity of 417.28 mA h g-1 after 700 cycles at a high current density of 5 A/g. This developed approach here provides a new route for the design and synthesis of various yolk-shell nanocages nanomaterials from enormous MOFs with multitudinous compositions and morphologies and can be extended to the application into other secondary batteries and energy storage fields.

Synergistic enhancement of chemisorption and catalytic conversion in lithium-sulfur batteries via Co3Fe7/Co5.47N separator mediator

Lithium-sulfur batteries (LSBs) show considerable potential in next-generation high performance batteries, but the heavy shuttle effect and sluggish redox kinetics of polysulfide hinder their further applications. In this paper, to address these shortcomings of LSBs, Co3Fe7/Co5.47N heterostructure were prepared and constructed from their Fe-Co Prussian blue analogue precursors under the condition of high temperature pyrolysis. The obtained Co3Fe7/Co5.47N display excellent immobilization-diffusion-conversion performance for polysulfides by synergistic effect in successfully hindering the shuttle effect of polysulfides. When the Co3Fe7/Co5.47N heterostructure were applied to modify the commercial polypropylene (PP) separator, the batteries displayed fantastic rate capacity and cycling stability. Specifically, the Co3Fe7/Co5.47N-PP batteries exhibit an extremely satisfactory initial specific capacity of 1430 m Ah/g at 0.5C, wonderful rate capacity of around 780 m Ah/g at 3C and superior per cycle decaying rate of 0.08 % for 500 cycles at 0.5C. When the current density reaches to 2C, the batteries still exhibit 501 m Ah/g after 900 cycles with 0.015 % per cycle decay rate. Besides, even in the high loading of sulfur (3.0 mg cm-2) at 0.5C, the superior cycling stability (0.075 % per cycle decay rate after 200 cycles) and high specific capacity (741 mAh/g after 200 cycles) can still be performed. Thus, this work provides a facile method for high-powered and long-life Li-S batteries with eminent entrapping-conversion processes of polysulfides.

Construction of 2D sandwich-like Na2V6O16·3H2O@MXene heterostructure for advanced aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) have attained enormous attention in the last few years. The cathode materials of aqueous zinc ion batteries play a vital effect in their electrochemical and battery properties. In this manuscript, Sandwich-like MXene@Na2V6O16·3H2O (NVO@MXene) heterostructure was successfully prepared by the combination and cooperation of the layer lattice structure of Na2V6O16·3H2O and the high conductivity of MXene. When used as the cathode material for AZIBs, NVO@MXene demonstrates preeminent rate capability and excellent reversible capacity of 175 mAh/g after 3000 cycles at 5 A/g with a retention rate of 88.9 % of initial discharge capacity. The outstanding battery performance can be attributed to the MXene layers with high conductivity for accelerating the ion diffusion rate and reducing the agglomeration of Na2V6O16·3H2O nanowires during the (dis)charge process. Meanwhile, the stable layered structure of Na16V6O6·3H2O with wide interlamellar spacing (d = 7.9 Å) is also favorable for the s fast intercalation/deintercalation of Zn2+. Finally, ex-situ X-ray diffraction and X-ray photoelectron spectroscopy were applied to study and reveal the energy storage mechanism of this novel material for aqueous zinc ion batteries.

Modified separators boost polysulfides adsorption-catalysis in lithium-sulfur batteries from Ni@Co hetero-nanocrystals into CNT-porous carbon dual frameworks

In this manuscript, nickel/cobalt bimetallic nanocrystals confining into three-dimensional interpenetrating dual-carbon conductive structure (NiCo@C/CNTs) were successfully manufactured by annealing its core-shell structure (Ni-ZIF-67@ZIF-8) precursor under the high temperature. The results presented that the bimetallic nickel and cobalt nanocrystals with superior catalytic activity could quickly convert solid Li2S/Li2S2into soluble LiPSs and effectively decrease the energy barrier. While the hierarchical CNT-porous carbon dual frameworks can provide quick electron/ion transport because of their large specific surface area and the exposure of enough active sites. When used as the separator modifier for lithium sulfur batteries, the battery properties were significantly improved with high specific capacity, outstanding rate capability, and long-term cycle stability. Specifically, its initial specific capacity can achieve to 1038.51 mAh g-1 at 0.5C. At the high rate of 3C, it still delivers satisfactory discharge capacity of 555 mAhg-1 and the capacity decay rate is only 0.065% per cycle after 1000 cycles at 1C. Furthermore, even exposed to heavy sulfur loading (3.61 mg/cm2), they still maintain promising cycle stability. Therefore, such kinds of MOFs derivative with powerful chemical immobilization and catalytic conversion for polysulfides provides a novel guidance for the modification separator and the potential application in the field of high-performance Li-S batteries.

Topochemical and phase transformation induced Co9S8/NC nanosheets for high-performance sodium-ion batteries

In this paper, a cobalt-based sulfide nanosheet structure (Co9S8/NC) was successfully synthesized by topochemical and phase transformation processes from a dodecahedral cobalt-based imidazole skeleton (ZIF-67) as a self-template. The 2D sheet structure facilitates full contact of electrode materials with the electrolyte and shortens the diffusion distance for electrons and ions. In addition, the nitrogen-doped carbon framework derived from ZIF-67 promotes electron transfer and provides a reliable skeleton to buffer volume expansion during discharging and charging. Finally, Co9S8/NC exhibits excellent rate capability and stable cycling performance for the anode of a sodium ion battery, delivering a specific capacity remaining at 530 mA h g-1 after 130 cycles at a current density of 1 A g-1.

ZnSe@NPSC core-shell nanorods for super sodium ion storage induced from an organic polymer derived N, P, S tri-doped carbon framework

In this work, core-shell structured ZnSe@NPSC nanorods were prepared with a N, P, S hetero-doped carbon shell. The design of the core-shell structure is conducive to facilitating the transport of electrons and buffering the volume expansion during charge/discharge processes, which is favourable for improving the sodium ion storage properties of ZnSe@NPSC. Therefore, it can deliver capacities of 376.67 mA h g-1 after 150 cycles at 0.5 A g-1 and 359.1 mA h g-1 after cycling for 350 cycles at 1.0 A g-1, respectively.