A N-CoSe/CoSe_(2)-C@Cu hierarchical architecture as a current collector-integrated anode for potassium-ion batteries

The highly reversible insertion/extraction of large-radius K^+into electrode materials remains a tough goal,especially for con version-type materials.Herein,we design a current collector-integrated electrode(N-CoSe/CoSe_(2)-C@Cu) as an advanced anode for potassium-ion battery(PIBs).The conductive CoSe/CoSe_(2) heterojunction with rich Se vacancy defects,conductive sp^2 N-doped carbon layer,and the elastic copper foil matrix can greatly accelerate the electron transfer and enhance the structural stability.Consequently,the well-designed N-CoSe/CoSe_(2)-C@Cu current collector-integrated electrode displays enhanced potassium storage performance with regard to a high capacity(325.1 mAh·g^(-1) at 0.1 A·g^(-1) after 200cycles),an exceptional rate capability(223.5 mAh·g^(-1) at2000 mA·g^(-1)),and an extraordinary long-term cycle stability(a capacity fading of only 0.019% per cycle over1200 cycles at 2000 mA·g^(-1)).Impressively,ex situ scanning electron microscopy(SEM) characterizations prove that the elastic structure of copper foil is merged into the cleverly designed N-CoSe/CoSe_(2)-C@Cu heterostructure,which buffers the deformation of structure and volume and greatly promotes the cycle life during the potassium/depotassium process.

High-performance flexible self-powered strain sensor based on carbon nanotube/ZnSe/CoSe_(2) nanocomposite film electrodes

High-performance energy storage and sensing devices have been undergoing rapid development to meet the demand for portable and wearable electronic products,which require flexibility,extensibility,small volume and lightweight.In this study,we construct a lightweight and flexible self-powered sensing system by integrating a highly stretchable strain sensor with a high-performance asymmetric supercapacitor based on ZnSe/CoSe_(2)//ECNT(ECNT:electrochemically activated carbon nanotube film).The ZnSe/CoSe_(2) two-dimentional nanosheets on carbon nanotube(CNT)films are synthesized through a simple and efficient strategy derived from ZnCo-based metal-organic frameworks(MOFs).The density functional theory(DFT)simulations show the higher conductivity of the ZnSe/CoSe_(2)/CNT electrode than the CoSe_(2)/CNT electrode.Due to the synergistic properties of self-supported two-dimentional ZnSe/CoSe_(2) nanosheets with high specific surface area and the high pathway of one-dimention CNTs,the nanocomposite electrode provides efficient transmission and short paths for electron/ion diffusion.The asymmetric supercapacitor provides a stable output power supply to the sensors that can precisely respond to strain and pressure changes.The sensor can also be attached to a garment for measuring a variety of joint movements.

CoSe_(2)纳米颗粒修饰的碳纳米纤维硫宿主助力高性能锂硫电池

具有高理论容量和高能量密度的锂硫电池被认为是最具前景的储能器件,但其实用化进程受到了多硫化物穿梭效应和氧化还原动力学缓慢等问题的影响.本文将CoSe_(2)纳米颗粒修饰的碳纳米纤维/碳纳米管(CoSe_(2)@CNF/CNT)自支撑膜作为高性能锂硫电池硫宿主电极.其中,由氮掺杂多孔碳和CNF/CNT组成的导电碳网络能够促进电荷传输,并缓解硫在循环过程中的体积膨胀.CoSe_(2)纳米颗粒兼具化学吸附位点和电催化剂的功能,通过化学吸附锚定多硫化物并加速其氧化还原转换,从而抑制穿梭效应和提高性能.因此CoSe_(2)@CNF/CNT-S电极具有优异的电化学性能,1 C下能提供1098.8 mA h g^(−1)的放电比容量,循环500圈中每圈容量衰减率低至0.06%.这项工作为高能量密度锂硫电池的开发提供了一种新方案.

P-doped CoSe_(2)nanoparticles embedded in 3D honeycomb-like carbon network for long cycle-life Na-ion batteries

We report for the first time a Na-ion battery anode material composed of P-doped CoSe_(2)nanoparticles(P-CoSe_(2))with the size of 5–20 nm that are uniformly embed in a 3 D porous honeycomb-like carbon network.High rate capability and cycling stability are achieved simultaneously.The honeycomb-like carbon network is rationally designed to support high electrical conductivity,rapid Na-ion diffusion as well as the accommodation of the volume expansion from the active P-CoSe_(2)nanoparticles.In particular,heteroatom P-doping within CoSe_(2)introduces stronger P-Co bonds and additional P-Se bonds that significantly improve the structure stability of P-CoSe_(2)for highly stable sodiation/desodiation over long-term cycling.P-doping also improves the electrical conductivity of the CoSe_(2)nanoparticles,leading to highly elevated electrochemical kinetics to deliver high specific capacities at high current densities.Benefiting from the unique nanostructure and atomic-level P-doping,the P-CoSe_(2)(2:1)/C anode delivers an excellent cycle stability with a specific capacity of 206.9 mA h g^(-1)achieved at 2000 mA g^(-1)after 1000 cycles.In addition,this material can be synthesized using a facile pyrolysis and selenization/phosphorization approach.This study provides new opportunities of heteroatom doping as an effective method to improve the cycling stability of Na-ion anode materials.

Coral-like cobalt selenide/carbon nanosheet arrays attached on carbon nanofibers for high-rate sodium-ion storage

Cobalt selenide(CoSe_(2))has become a promising anode material for sodium-ion batteries(SIBs)due to its stable chemical properties,environmental friendliness,and high theoretical capacity.However,the undesirable rate capacity and cycle stability of the anode materials largely limit its applications for SIBs due to the relatively low electronic conductivity and huge volume change during the Na+insertion/extraction.In this study,electrostatic spinning combined with a wet chemical method is employed to synthesize coral-like composite material(CNF@c-CoSe_(2)/C),which is composed of CoSe_(2)/carbon nanosheet arrays(CoSe_(2)/C)and carbon nanofibers(CNFs).CoSe_(2)/C nanoflakes derived from metal-organic frameworks(MOFs)with high surface area and the porous structure can inhibit the pulverization and amorphization of CoSe_(2) during charge and discharge processes,thus significantly keeping the stability of the microstructure.CNF can limit the overgrowth of nanosheets and serve as a conductive skeleton.Compared to two-dimensional CoSe_(2)/C nanoflakes and pure CoSe_(2) nanoparticles,the composite can expose more active sites and effectively accelerate the diffusion of Na+,which displays enhanced rate capability(266.5 mAh·g^(-1) at 5.0 A·g^(-1))and cycling stability(268.3 mAh·g^(-1) after 100 cycles at 1.0 A·g^(-1)).Moreover,the rational preparation strategy for metal selenide-based heterostructure material presents a new way for high-performance SIB s.