Coupling NiCoP bimetallic phosphide nanoparticles with alkali-induced 3D crinkled Ti3C2 effectively enhances the structural stability and improved reaction kinetics of anodes for SIBs.

Taking advantage of zeolitic imidazolate framework (ZIF-8), ZnS-SbS@C core-double shell polyhedron structure is synthesized through a sulfurization reaction between Zn dissociated from ZIF-8 and S from thioacetamide (TAA), and subsequently a metal cation exchange process between Zn and Sb, in which carbon layer is introduced from polymeric resorcinol-formaldehyde to prevent the collapse of the polyhedron. The polyhedron composite with a ZnS inner-core and SbS/C double-shell as anode for sodium ion batteries (SIBs) shows us a significantly improved electrochemical performance with stable cycle stability, high Coulombic efficiency and specific capacity. Peculiarly, introducing a carbon shell not only acts as an important protective layer to form a rigid construction and accommodate the volume changes, but also improves the electronic conductivity to optimize the stable cycle performance and the excellent rate property. The architecture composed of ZnS inner core and a complex SbS/C shell not only facilitates the facile electrolyte infiltration to reduce the Na-ion diffusion length to improve the electrochemical reaction kinetics, but also prevents the structure pulverization caused by Na-ion insertion/extraction. This approach to prepare metal sulfides based on MOFs can be further extended to design other nanostructured systems for high performance energy storage devices.

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vehicles. In a typical electrochemical reaction, the discharge product of lithium peroxide (Li 2 O 2 ) can reversibly form and decompose on cathode side during oxygen reduction reaction (ORR) and subsequent oxygen evolution reaction (OER) processes, respectively (O 2 + 2Li + + 2e − ↔ Li 2 O 2 ). [1][2][3][4] Nevertheless, several critical barriers embracing unsatisfactory charge/discharge polarization, poor rate capability, and limited cycle life make the fantastic technology far from practical application, which can be mainly attributed to the intrinsic characteristic of discharge products including insulation property and insolubilization in aprotic electrolytes. During ORR process, Li 2 O 2 precipitations clog the eversmooth passageways of reactants and passivate electrode surfaces, deteriorating electrical connection between catalysts and efficient active sites, raising charge transfer impedance. In OER process, the insulating Li 2 O 2 precipitations are knotty to be composed, delivering unsatisfactory dynamic performance and triggering higher overpotential. [5][6][7][8][9][10] It has been well established that the morphology and distribution of Li 2 O 2 determined by different growth pathway during ORR govern the battery chemistry and hence the electrochemical performance. [11][12][13] Recent works demonstrate that large-sized Li 2 O 2 aggregations (large discs, [14,15] toroids, [16][17][18][19] spheres, [20,21] etc.) contribute to large discharge capacity output during ORR but at the cost of huge charge overpotential during OER, because large sized Li 2 O 2 products do not usually well contact with active sites and are not easily decomposed, thus resulting in a larger charging voltage gap and sluggish charging kinetics. On the contrary, the formation of conformal Li 2 O 2 films or small amorphous Li 2 O 2 particles during ORR can offer much smaller charge transfer resistance and thus improve kinetics performance obviously during the following charge process. [22][23][24][25] Unfortunately, under such condition, the exposed active sites of catalyst matrix would be inactivated quickly, hence leading to a lower discharge capacity. To alleviate this contradiction between large ORR capacity and small OER voltage gap, it mainly focuses on oxygen catalytic cathode to construct elaborate hierarchical porous structures and optimize microstructure of highly efficient dual-catalystThe critical challenges of Li-O 2 batteries lie in sluggish oxygen redox kinetics and undesirable parasitic reactions during the oxygen reduction reaction and oxygen evolution reaction processes, inducing large overpotential and inferior cycle stability. Herein, an elaborately designed 3D hierarchical heterostructure comprising NiCo 2 S 4 @NiO core-shell arrays on conductive carbon paper is first reported as a freestanding cathode for Li-O 2 batteries. The unique hierarchical array structures can build up multidimensional channels for oxygen diffusion and electrolyte impregnation. A built-in interfacial potential between NiCo 2 S 4 and NiO c...

To alleviate large volume change and improve poor electrochemical reaction kinetics of metal phosphide anode for sodium-ion batteries, for the first time, an unique Ni P@carbon/graphene aerogel (GA) 3D interconnected porous architecture is synthesized through a solvothermal reaction and in situ phosphorization process, where core-shell Ni P@C nanoparticles are homogenously embedded in GA nanosheets. The synergistic effect between components endows Ni P@C/GA electrode with high structural stability and electrochemical activity, leading to excellent electrochemical performance, retaining a specific capacity of 124.5 mA h g at a current density of 1 A g over 2000 cycles. The robust 3D GA matrix with abundant open pores and large surface area can provide unblocked channels for electrolyte storage and Na transfer and make fully close contact between the electrode and electrolyte. The carbon layers and 3D GA together build a 3D conductive matrix, which not only tolerates the volume expansion as well as prevents the aggregation and pulverization of Ni P nanoparticles during Na insertion/extraction processes, but also provides a 3D conductive highway for rapid charge transfer processes. The present strategy for phosphides via in situ phosphization route and coupling phosphides with 3D GA can be extended to other novel electrodes for high-performance energy storage devices.