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

Accelerating catalytic conversion and chemisorption of polysulfides for advanced Li-S batteries from incorporating Fe0.64Ni0.36@Co5.47N hetero-nanocrystals into boron carbonitride nanotubes

With the rapid development of large-scale clean energy, lithium-sulfur (Li-S) batteries are considered to be one of the most promising energy storage devices. In this manuscript, the polymetallic hetero-nanocrystal of iron nickel@cobalt nitride encapsulating into boron carbonitride nanotubes (Fe0.64Ni0.36@Co5.47N@BCN) was designed and optimized for use as a modified material for commercial polypropylene (PP) separators. The prepared Fe0.64Ni0.36@Co5.47N@BCN-12 hybrid material presents strong chemisorption and catalytic conversion capabilities, which endows the Fe0.64Ni0.36@Co5.47N@BCN-12//PP separator with enhanced polysulfide shuttling inhibition. The assembled Li-S cells with Fe0.64Ni0.36@Co5.47N@BCN-12//PP separators have minimized charge transfer resistance and faster redox kinetics. Additionally, cells with Fe0.64Ni0.36@Co5.47N@BCN-12//PP separator provide high reversible capacity of 674 mAh/g for 400 cycles at 0.5C and excellent cyclability for 1000 cycles at 2C with a low decay rate of 0.05 % per cycle. Therefore, this study provides a feasible functionalization route for improving the electrochemical performance of Li-S batteries through separator modification.

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.

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.

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.