Rational design of metal selenides nanomaterials for alkali metal ion(Li^(+)/Na^(+)/K^(+))batteries:current status and perspectives

Recently,metal selenides have obtained widespread attention as electrode materials for alkali(Li^(+)/Na^(+)/K^(+))batteries due to their promising theoretical capacity and mechanism.Nevertheless,metal selenides,similar to metal oxides and sulfides,also suffer from severe volume explosion during repeated charge/discharge processes,which results in the structure collapse and the following pulverization of electrode materials.Hence,it leads to poor cycle stability and influencing their further application.In order to solve these issues,some special strategies,including elemental doping,coupling with carbon materials,synthesis of the bimetal selenides with heterostructure,etc.,have been gradually applied to design novel electrode materials with outstanding electrochemical performance.Herein,the recent research progress on metal selenides as anodes for alkali ion batteries is summarized,including the regulation of crystal structure,synthesis strategies,modification methods,and electrochemical mechanisms and kinetics.Besides,the challenges of metal selenides and the perspective for future electrode material design are proposed.It is hoped to pave a way for the development of metal selenide electrode materials for the potential applications for alkali metal ion(Li^(+)/Na^(+)/K^(+))batteries.

Heterogeneous engineering of MnSe@NC@ReS_(2) core-shell nanowires for advanced sodium-/potassium-ion batteries

Sodium-ion batteries(SIBs) and potassium-ion batteries(PIBs) have been attracting great attentions and widely been exploited due to the abundant sodium/potassium resources.Hence,the preparation of high-powered anode materials for SIBs/PIBs plays a decisive role for the commercial applications of SIBs/PIBs in the future.Manganese selenides are a class of potential anode materials for SIBs/PIBs because of their small band gap and high electrical conductivity.In this work,MnSe and ReS_(2) core-shell nanowires connecting by polydopamine derived carbon nanotube(MnSe@NC@ReS_(2)) have been successfully synthesized from growing ReS_(2) nanosheets array on the surface of MnSe@NC nano wires,which present excellent Na^(+)/K^(+) storage performance.While applied as SIBs anode,the specific capacity of 300 mAh·g^(-1) was maintwined after 400 cycles at the current density of 1.0 A·g^(-1).Besides,it could also keep 120 mAh·g^(-1) specific capacity after 900 cycles at 1.0 A·g^(-1) for the anode of PIBs.These heterogeneous engineering and one-dimensional-two-dimensional(1D-2D) hybrid strategies could provide an ideal strategy for the synthesis of new hetero-structured anode materials with outstanding battery performance for SIBs and PIBs.

Super Na^(+)Half/Full Batteries and Ultrafast Na+Diffusion Kinetics of Cobalt-Nickel Selenide from Assembling Co_(0.5)Ni_(0.5)Se_(2)@NC Nanosheets into Cross-Stacked Architecture

Explorati on of adva need an ode materials for sodium-i on batteries(SIBs)is still a big challe nge due to the large radius of sodium.In this work,the hierarchical architectures assembled from N-doped carbon-coated Co_(0.5)Ni_(0.5)Se_(2)(Co_(0.5)Ni_(0.5)Se_(2)@NC)nanoparticles encapsulated into cross-stacked nano sheets have been successfully prepared from the cobalt-nickel bin ary-metal organic frameworks(CoNi-MOF)by two steps of the solid-state sele nizati on and carb on coating processes.Imports ntly,the resulta nt hierarchical Co0.5Nio:5Se2@NC architecture can achieve a satisfactory electrochemical performance,maintaining a high-rate capacity of 330 mA-h-g^(-1)1 at 3 A·g^(-1) and a stable cyclability of 100 cycles without obvious capacity decay at 0.2 A·g^(-1).The design of distinct superstructure can not only be applied to other electrode materials but also boost the forward development of energy storage systems.

Electrochemical and Pseudocapacitive Analysis of Rod-Like MoO_(2)@MoSe_(2)@NC Heterostructures for High-Performance Lithium Ion Batteries

A micro-scale rod-like heterostructure derived from molybdenum-based metal organic framework(Mo-MOF)has been successfully prepared via subsequent annealing treatment,which assembled from N-doped carbon encapsulated MoSe_(2) nanosheets grown on the surface of MoO_(2) microrod(named as MoO_(2)@MoSe_(2)@NC).For this novel heterostructure,the MoO_(2) nanoparticles assembled into rod core not only serve as supporting substrate for facilitating the fast kinetics of Li+cations inside the electrode but also protect the MoSe_(2) structure from restacking in the charge/discharge process.Moreover,the outer-layered MoSe2 nanosheets enable the fast lithium ion movement owing to its large interlayer spacing.Moreover,this unique rod-like core-shell structure composite could further effectively alleviate the structural strains caused by large volume expansion during charge/discharge process,thus leading to stable electrochemical performance when evaluated as anode material for lithium ion batteries.Electrochemical testing exhibits that the MoO_(2)@MoSe_(2)@NC heterostructure presents highly reversible capacity of 468 mAh g^(-1)at 0.5 A g^(-1)and superior rate capability(318 mAh g^(-1)even at 5.0 A g^(-1)),which is attributed to the synergistic effect of N-doped carbon encapsulated MoSe2 nanosheets and MoO_(2) nanoparticles.

Metal-organic framework(MOF)-derived selenidation strategy to prepare porous(Zn,Cu)CoSex micro/nanostructures for sodium-ion batteries

Owning to the wide distribution,low cost,and similar chemical-electrochemical properties with lithium,sodium-ion batteries(SIBs) have attracted much attention during recent years and may have the potential to replace the commercial lithium-ion batteries.Herein,facile and simple bottom-up approach has been rationally applied to fabricate carbon-encapsulated ZnSe@CoSe_(2)micro spheres and Cu_(2)Se@CoSe_(2)nanocubes.The as-prepared ZnSe@-CoSe_(2)microspheres and Cu_(2)Se@CoSe_(2)nanocubes composites inherited the original structure of ZnCo-MOF and CuCo-MOF,respectively.Herein,both ZnSe@CoSe_(2)micro spheres and Cu_(2)Se@CoSe_(2)nanocubes delivered excellent electrochemical performance when presented as anode materials for SIBs.Both ZnSe@CoSe2micro spheres and Cu_(2)Se@CoSe_(2)nanocubes electrode could display a long-term cycling stability with a reversible capacity of 525 and 423 mAh·g^(-1)at the current density of 1 A·g^(-1)after 500 cycles,respectively.Furthermore,even at a high current density of 5 A·g^(-1),ZnSe@CoSe_(2)microsphere could still maintain 520 mAh·g^(-1)after 500 cycles,demonstrating remarkable capacity and excellent cycling performance.Those high performances were beneficial from the unique hollow and porous structure of ZnSe@CoSe_(2)microspheres and Cu_(2)Se@CoSe_(2)nanocubes derived from the precursor which facilitate the transport of sodium ions,contributing to high capacity,improved excellent cycle stability and rate capability.

Rational design of heterostructured core-shell Co-Zn bimetallic selenides for improved sodium-ion storage

Bimetallic selenide with core-shell structure(CoSe_(2)/ZnSe/NC@ZnSe/NC)has been successfully prepared through facile carbonization and selenization processes of its core-shell metal-organic framework precursors,in which the precursor is synthesized by epitaxial growth of zinc-based zeolite imidazolate framework(ZIF-8)on the surface of cobalt-based and zinc-based zeolite imidazolate framework(ZIF-67@ZIF-8).The coreshell structure has the advantage of alleviating the volume expansion during repeated insertion and extraction of sodium ions which can effectively avoid structural collapse.Additionally,bimetallic selenides and heterostructure are effective strategies to greatly improve the rate capability of the material.Therefore,the core-shell structural CoSe2/ZnSe/NC@ZnSe/NC material can maintain the original dodecahedron structure and delivers a specific capacity of 308.6 mAh·g^(-1)at 1.0 A·g^(-1)after 300 cycles with the desirable capacity retention of 90%.With the synergistic effects of heterostructure and core-shell structure,CoSe_(2)/ZnSe/NC@ZnSe/NC exhibits better electrochemical performance than CoSe_(2)/ZnSe/NC and CoSe_(2)/NC.These prove that both core-shell structure and heterostructure have positive effects on improving the electrochemical properties of materials.

Freestanding and Ultra‑flexible PAN/ZIF‑67 Hybrid Membrane with Controlled Porosity for High‑Performance and High‑Safety Lithium Batteries Separator

Herein,a flexible ZIF-67/PAN hybrid membrane was successfully prepared by the incorporation of ZIF-67 nanoparticles and PAN nanofibers through electrospinning method.The hybrid membrane presented tomatoes on sticks structures with one single PAN fiber stringing series of ZIF-67 nanoparticles.The morphology,electrolyte wettability,heat resistance,flexibility,and electrochemical properties of the electrospun ZIF-67/PAN membranes were discussed.Among the membranes prepared with different percentage of ZIF-67,the 30% ZIF-67/PAN membrane exhibited outstanding heat shrinkage resistance(remained intact at 200℃ for 1 h),excellent electrolyte uptake(556.39%),wide electrochemical window(~5.25 V)and high ionic conductivity(2.98 mS cm^(−1)).When used as lithium-ion batteries(LIBs)separators,the cells assembled by 30% ZIF-67/PAN membrane presented excellent rate capacity and high capacity retention of 86.9% after 300 cycles at 1C.More importantly,the cells assembled with ZIF-67/PAN membranes repeated bent for 1000 times also exhibited high rate performance and maintained capacity retention of 92% after 100 cycles at 1 C.The characterization and the electrochemical testing suggest the electrospinning prepared ZIF-67/PAN flexible membranes can be expected to be used as potential separator for advanced batteries with high safety and high performance.

A N/Co co-doped three-dimensional porous carbon as cathode host for advanced lithium-selenium batteries

Selenium(Se)is a promising cathode material for lithium batteries due to its high volumetric energy density(2528 Wh·L^(-1)).However,its practical application is restricted by rapid capacity fading resulting from the shuttle effect and slow reaction kinetics.Herein,a N/Co co-doped three-dimensional porous carbon(Co-NC)is prepared and used as Se host for lithium-selenium batteries(LSeBs).Co-NC displays a high specific surface area of1201 m^(2)·g^(-1)which benefits from N and Co doping.The N and Co not only enhance the electrical conductivity of porous carbon but also possess an adsorption effect on polyselenide.Thus,Se/Co-NC electrode exhibits excellent cycling performance(a stable specific capacity of 480 mAh·g^(-1)after 200 cycles at 1.0C with a much lowcapacity decay of 0.028%per cycle)and outstanding rate performance(a high specific capacity of 414 mAh·g^(-1)at5.0C).This work inspires highly stable Se cathode design for LSeBs.