Leaf-inspired design of mesoporous Sb_2S_3/N-doped Ti_3C_2T_x composite towards fast sodium storage

Owing to excellent conductivity and abundant surface terminals,MXene-based heterostructures have been intensively investigated as energy storage materials.However,elaborate design of the structure and composition of MXene-based hybrids towards superior electrochemical performance is still challenging.Herein,we present an ingenious leaf-inspired design for preparing a unique Sb_2S_3/nitrogen-doped Ti_3C_2T_x MXene (L-Sb_2S_3/Ti_3C_2) hybrid.In-situ TEM observations reveal that the leaflike Sb_2S_3 nanoparticles with numerous mesopores can well relieve the large volume changes via an inward pore filling mechanism with only 20%outward expansion,whereas highly conductive N-doped Ti_3C_2T_x nanosheets can serve as the robust mechanical support to reinforce the structural integrity of the hybrid.Benefiting from the structural and constituent merits,the L-Sb_2S_3/Ti_3C_2anode fabricated exhibits a fast sodium storage behavior in terms of outstanding rate capability (339.5 mA h g~(-1)at 2,000 mA g~(-1)) and high reversible capacity at high current density (358.2 mA h g~(-1)at 1,000 mA g~(-1)after 100 cycles).Electrochemical kinetic tests and theoretical simulation further manifest that the boosted electrochemical performance mainly arises from such a unique leaf-like Sb_2S_3 mesoporous nanostructure with abundant active sites,and enhanced Na~+ adsorption energy on the heterojunction formed between Sb_2S_3 nanoparticles and Ti_3C_2 matrix.     

Assembling Co_9S_8 nanoflakes on Co_3O_4 nanowires as advanced core/shell electrocatalysts for oxygen evolution reaction

Rational design of advanced cost-effective electrocatalysts is vital for the development of water electrolysis. Herein, we report a novel binder-free efficient Co_9S_8@Co_3O_4 core/shell electrocatalysts for oxygen evolution reaction(OER) via a combined hydrothermal-sulfurization method. The sulfurized net-like Co_9S_8 nanoflakes are strongly anchored on the Co_3O_4 nanowire core forming self-supported binder-free core/shell electrocatalysts. Positive advantages including larger active surface area of Co_9S_8 nanoflakes,and reinforced structural stability are achieved in the Co_9S_8@Co_3O_4 core/shell arrays. The OER performances of the Co_9S_8@Co_3O_4 core/shell arrays are thoroughly tested and enhanced electrocatalytic performance with lower over-potential(260 m V at 20 m A cm~(-2)) and smaller Tafel slopes(56 mV dec-1) as well as long-term durability are demonstrated in alkaline medium. Our proposed core/shell smart design may provide a new way to construct other advanced binder-free electrocatalysts for applications in electrochemical catalysis.     

Facile synthesis of free-standing nickel chalcogenide electrodes for overall water splitting

Developing high-performance noble metal-free and free-standing catalytic electrodes are crucial for overall water splitting. Here, nickel sulfide(Ni_3S_2) and nickel selenide(Ni Se) are synthesized on nickel foam(NF) with a one-pot solvothermal method and directly used as free-standing electrodes for efficiently catalyzing hydrogen evolution reaction(HER) and oxygen evolution reaction(OER) in alkaline solution.In virtue of abundant active sites, the Ni_3S_2/NF and the NiS e/NF electrodes can deliver a current density of 10 m A cm~(-2) at only 123 m V, 137 m V for HER and 222 m V, 271 m V for OER. Both of the hierarchical Ni_3S_2/NF and Ni Se/NF electrodes can serve as anodes and cathodes in electrocatalytic overall watersplitting and can achieve a current density of 10 m A cm~(-2) with an applied voltage of ~1.59 V and 1.69 V,respectively. The performance of as-obtained Ni_3S_2/NF||Ni_3S_2/NF is even close to that of the noble metalbased Pt/C/NF||IrO_2/NF system.     

γ-MnO_2 nanorods/graphene composite as efficient cathode for advanced rechargeable aqueous zinc-ion battery

Aqueous Zn//MnO_2 batteries are emerging as promising large-scale energy storage devices owing to their cost-effectiveness,high safety,high output voltage,and energy density.However,the MnO_2 cathode suffers from intrinsically poor rate performance and rapid capacity deterioration.Here,we remove the roadblock by compositing MnO_2 nanorods with highly conductive graphene,which remarkably enhances the electrochemical properties of the MnO_2 cathode.Benefiting from the boosted electric conductivity and ion diffusion rate as well as the structural protection of graphene,the Zn//MnO_2-graphene battery presents an admirable capacity of 301 mAh g~(-1) at 0.5 A g~(-1),corresponding to a high energy density of 411.6 Wh kg~(-1).Even at a high current density of 10 A g~(-1),a decent capacity of 95.8 mAh g~(-1) is still obtained,manifesting its excellent rate property.Furthermore,an impressive power density of 15 kW kg~(-1) is achieved by the Zn//MnO_2-graphene battery.     

Robust self-supported anode by integrating Sb_2S_3 nanoparticles with S,N-codoped graphene to enhance K-storage performance

Developing high-performance anode materials for potassium-ion batteries is significantly urgent. We here demonstrate Sb_2S_3 nanoparticles(~20 nm) homogeneously dispersed in porous S,N-codoped graphene framework(Sb_2S_3-SNG) as a self-supported anode material for potassium-ion batteries. The rational structure design of integrating Sb_2S_3 nanoparticles with S,N-codoped graphene contributes to high reactivity, strong affinity, good electric conductivity, and robust stability of the composite, enabling superior K-storage performance. Moreover, the self-supported architecture significantly decreases the inactive weight of the battery, resulting in a high energy density of a Sb_2S_3-SNG/KVPO_4 F-C full cell to ~166.3 W h kg~(-1).     

In-situ growth of vertically aligned nickel cobalt sulfide nanowires on carbon nanotube fibers for high capacitance all-solid-state asymmetric fiber-supercapacitors

Fiber-supercapacitors(FSCs)are promising power sources for miniature portable and wearable electronic devices.However,the development and practical application of these FSCs have been severely hindered by their low volumetric capacitance and narrow operating voltage.In this work,vertically aligned nickel cobalt sulfide(Ni Co_2S_4)nanowires grown on carbon nanotube(CNT)fibers were achieved through an in-situ two-step hydrothermal reaction method.The as-prepared Ni Co_2S_4@CNT fiber electrode exhibits a high volumetric capacitance of 2332 F cm~(-3),benefiting from its superior electric conductivity,large surface area,and rich Faradic redox reaction sites.Furthermore,a Ni Co_2S_4@CNT//VN@CNT(vanadium nitride nanosheets grown on CNT fibers)asymmetric fiber-supercapacitor(AFSC)was successfully fabricated.The device exhibits an operating voltage up to 1.6 V and a high volumetric energy density of 30.64m Wh cm~(-3).The device also possesses outstanding flexibility as evidenced by no obvious performance degradation under various bending angles and maintaining high capacitance after 5000 bending cycles.This work promotes the practical application of flexible wearable energy-storage devices.     

Electrodeposited NiSe_2 on carbon fiber cloth as a flexible electrode for high-performance supercapacitors

A flexible electrode of nickel diselenide/carbon fiber cloth(NiSe_2/CFC) is fabricated at room temperature by a simple and efficient electrodeposition method. Owing to NiSe_2 character of nanostructure and high conductivity, the as-synthesized electrodes possess perfect pseudocapacitive property with high specific capacitance and excellent rate capability. In three-electrode system, the electrode specific capacitance of the NiSe_2/CFC electrode varies from 1058 F g~(-1) to 996.3 F g~(-1) at 2 A g~(-1) to 10 A g~(-1) respectively, which shows great rate capability. Moreover, the NiSe_2 electrode is assembled with an active carbon(AC) electrode to form an asymmetric supercapacitor with an extended potential window of 1.6 V. The asymmetric supercapacitor possesses an excellent energy density 32.7 Wh kg~(-1) with a power density 800 W kg~(-1) at the current density of 1 A g~(-1). The nanosheet array on carbon fiber cloth with high flexibility, specific capacitance and rate capacitance render the NiSe_2 to be regarded as the promising material for the high performance superconductor.     

The design and fabrication of Co_3O_4/Co_3V_2O_8/Ni nanocomposites as high-performance anodes for Li-ion batteries

The Co_3O_4/Co_3V_2O_8/Ni nanocomposites were rationally designed and prepared by a two-step hydrothermal synthesis and subsequent annealing treatment. The one-dimensional(1D) Co_3O_4 nanowire arrays directly grew on Ni foam, whereas the 1D Co_3V_2O_8 nanowires adhered to parts of Co_3O_4 nanowires.Most of the hybrid nanowires were inlayed with each other, forming a 3D hybrid nanowires network.As a result, the discharge capacity of Co_3O_4/Co_3V_2O_8/Ni nanocomposites could reach 1201.8 mAh/g after100 cycles at 100 mA/g. After 600 cycles at 1 A/g, the discharge capacity was maintained at 828.1 mAh/g.Moreover, even though the charge/discharge rates were increased to 10 A/g, it rendered reversible capacity of 491.2 mAh/g. The superior electrochemical properties of nanocomposites were probably ascribed to their unique 3D architecture and the synergistic effects of two active materials. Therefore, such Co_3O_4/Co_3V_2O_8/Ni nanocomposites could potentially be used as anode materials for high-performance Li-ion batteries.     

In-situ conversion of Ni_2P/rGO from heterogeneous self-assembled NiO/rGO precursor with boosted pseudocapacitive performance

Two-dimensional(2 D) heterostructural Ni_2 P/rGO is successfully fabricated by in-situ phosphating selfassembled NiO/rGO composites and shows the enhanced electrochemical performances.In this design,the rGO sheets effectively reduce the lattice strain created during the phase transformation from NiO to Ni_2 P,thereby maintaining ultrathin nanostructures of Ni2 P.The resulting Ni_2 P/rGO layered heterostructure gives the composite plenty of pores or channels,good electrical conductivity and well-exposed active sites.Density functional theory(DFT) calculation further demonstrates that the Fermi energy level and electron localize of near Ni atoms in Ni_2 P is higher than that of NiO,which endow Ni_2 P with faster and more reversible redox reactivity in dynamic.Benefiting from their structural and compositional merits,the as-synthesized Ni2 P/rGO exhibits high specific discharge capacity and excellent rate performance.Furthermore,a hybrid supercapacitor built with Ni_2 P/rGO and activated carbon shows a high specific energy of 38.6 Wh/kg at specific power of 375 W/kg.     

A1掺杂量对正极材料LiNi_(1/3)Co_(2/3-x)A1_xO_2结构和电化学性能的影响

以共沉淀法合成的前驱体Ni_(1/3)Co_(2/3-x)Al_x(OH)_2与低共熔锂盐0.38LiOH·H_2O-0.62LiNO_3制备了锂离子电池正极材料LiNi_(1/3)Co_(2/3-x)Al_xO_2(x=1/12,1/3,1/2,7/12).采用X射线衍射(XRD)、扫描电镜(SEM)和电化学性能测试对其结构、形貌和电化学性质进行表征.结果表明,LiNi_(1/3)Co_(2/3-x)Al_xO_2在1/12≤x≤1/3范围内可以保持单一的六方层状a-NaFeO_2结构,当A1掺杂量(x)高于1/3时,会出现杂相.其中,LiNi_(1/3)Co_(1/3)Al_(1/3)O_2结晶程度最高,阳离子混排效应最小,并且颗粒小而均匀,振实密度可以达到2.88 g·cm~(-3),首次放电容量为151.5 mAh·g~(-1),循环50次后放电容量保持在91.4%,在1C和2C倍率下放电容量仍可达到133.7和120.9 mAh·g~(-1)     

LiNbO_3-coated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2 cathode with high discharge capacity and rate performance for all-solid-state lithium battery

In order to obtain high power density, energy density and safe energy storage lithium ion batteries(LIB)to meet growing demand for electronic products, oxide cathodes have been widely explored in all-solidstate lithium batteries(ASSLB) using sulfide solid electrolyte. However, the electrochemical performances are still not satisfactory, due to the high interfacial resistance caused by severe interfacial instability between sulfide solid electrolyte and oxide cathode, especially Ni-rich oxide cathodes, in charge-discharge process. Ni-rich LiNi_(0.8)Co_(0.1)Mn_(0.1)O_2(NCM811) material at present is one of the most key cathode candidates to achieve the high energy density up to 300 Wh kg~(-1) in liquid LIB, but rarely investigated in ASSLB using sulfide electrolyte. To design the stable interface between NCM811 and sulfide electrolyte should be extremely necessary. In this work, in view of our previous work, LiNbO_3 coating with about 1 wt%content is adopted to improve the interfacial stability and the electrochemical performances of NCM811 cathode in ASSLB using Li_(10)GeP_2S_(12) solid electrolyte. Consequently, LiNbO_3-coated NCM811 cathode displays the higher discharge capacity and rate performance than the reported oxide electrodes in ASSLB using sulfide solid electrolyte to our knowledge.     

Niobium oxyphosphate nanosheet assembled two-dimensional anode material for enhanced lithium storage

The development of high-capacity and high-rate anodes has become an attractive endeavor for achieving high energy and power densities in lithium-ion batteries(LIBs).Herein,a new-type anode material of reduced graphene oxide(rGO) supported niobium oxyphosphate(NbOPO_4) nanosheet assembled twodimensional composite material(NbOPO_4/rGO) is firstly fabricated and presented as a promising highperformance LIB anode material.In-depth electrochemical analyses and in/ex situ characterizations reveal that the intercalation-conversion reaction takes place during the first discharge process,followed by the reversible redox process between amorphous NbPO_4 and Nb which contributes to the reversible capacity in the subsequent cycles.Meanwhile,the lithiation-generated Li3 PO_4,behaving as a good lithium ion conductor,facilitates ion transport.The rGO support further regulates the structural and electron/ion transfer properties of NbOPO_4/rGO composite compared to neat NbOPO_4, resulting in greatly enhanced electrochemical performances.As a result,NbOPO_4/rGO as a new-type LIB anode material achieves a high capacity of 502.5 mAh g^-1 after 800 cycles and outstanding rate capability of 308.4 mAh g^-1 at 8 A g^-1.This work paves the way for the deep understanding and exploration of phosphate-ba sed high-efficiency anode materials for LIBs.     

Carbon-coated Li3VO4 with optimized structure as high capacity anode material for lithium-ion capacitors

Due to the high capacity, moderate voltage platform, and stable structure, Li₃VO₄ (LVO) has attracted close attention as feasible anode material for lithium-ion capacitor. However, the intrinsic low electronic conductivity and sluggish kinetics of the Li⁺ insertion process severely impede its practical application in lithium-ion capacitors (LICs). Herein, a carbon-coated Li₃VO₄ (LVO/C) hierarchical structure was prepared by a facial one-step solid-state method. The synthesized LVO/C composite delivers an impressive capacity of 435 mAh/g at 0.07 A/g, remarkable rate capability, and nearly 100% capacity retention after 500 cycles at 0.5 A/g. The superior electrochemical properties of LVO/C composite materials are attributed to the improved conductivity of electron and stable carbon/LVO composite structures. Besides, the LIC device based on activated carbon (AC) cathode and optimal LVO/C as anode reveals a maximum energy density of 110 Wh/kg and long-term cycle life. These results provide a potential way for assembling the advanced hybrid lithium-ion capacitors.     

超级电容电池

本文比较了超级电容器、锂离子电池和超级电容电池的结构、原理、研究现状和发展前景。超级电容电池的正极具有超级电容器电极的结构和双电层储能机制,负极具有类似锂离子电池负极的结构和快速电化学储能机制。超级电容器和锂离子电池的发展空间都很有限,而作为两者结合的产物的超级电容电池可兼具高比功率、高比能量、高放电电压和长循环寿命的优点,是未来储能电池的发展方向之一,但还面临缺乏具有高分解电压的电解液和高充电电压下电解液中离子枯竭的问题。     

Yolk-shell Si/C composites with multiple Si nanoparticles encapsulated into double carbon shells as lithium-ion battery anodes

The conceptual design of yolk-shell structured Si/C composites is considered to be an effective way to improve the recyclability and conductivity of Si-based anode materials. Herein, a new type of yolk-shell structured Si/C composite(denoted as TSC-PDA-B) has been intelligently designed by rational engineering and precise control. In the novel structure, the multiple Si nanoparticles with small size are successfully encapsulated into the porous carbon shells with double layers benefiting from the strong etching effect of HF. The TSC-PDA-B product prepared is evaluated as anode materials for lithium-ion batteries(LIBs).The TSC-PDA-B product exhibits an excellent lithium storage performance with a high initial capacity of 2108 mAh g~(-1) at a current density of 100 mA g~(-1) and superior cycling performance of 1113 mAh g~(-1) over 200 cycles. The enhancement of lithium storage performance may be attributed to the construction of hybrid structure including small Si nanoparticles, high surface area, and double carbon shells, which can not only increase electrical conductivity and intimate electrical contact with Si nanoparticles, but also provide built-in buffer voids for Si nanoparticles to expand freely without damaging the carbon layer.The present findings can provide some scientific insights into the design and the application of advanced Si-based anode materials in energy storage fields.     

煅烧温度对锂离子正极材料Li[Ni0.475 Mn0.475 Co0.05]O2结构和电化学性能的影响

应用高温固相合成法制备L i[N i0.475Mn0.475Co0.05]O2.XRD,SEM,循环伏安及充放电容量测试表明,在800℃下煅烧合成的样品具有较高的嵌锂容量和良好的循环稳定性,如在20 mA/g和2.3~4.6 V的电压范围内,其首次放电比容量为178.8 mAh/g,循环30周后放电比容量仍能达到150.2 mAh/g,容量损失16.0%.     

Nitrogen-doped carbon nanotubes by multistep pyrolysis process as a promising anode material for lithium ion hybrid capacitors

Lithium-ion hybrid capacitors (LIHCs) is a promising electrochemical energy storage devices which combines the advantages of lithium-ion batteries and capacitors. Herein, we developed a facile multistep pyrolysis method, prepared an amorphous structure and a high-level N-doping carbon nanotubes (NCNTs), and by removing the Co catalyst, opening the port of NCNTs, and using NCNTs as anode material. It is shows good performance due to the electrolyte ions enter into the electrode materials and facilitate the charge transfer. Furthermore, we employ the porous carbon material (APDC) as the cathode to couple with anodes of NCNTs, building a LIHCs, it shows a high energy density of 173 Wh/kg at 200 W/kg and still retains 53 Wh/kg at a high power density of 10 kW/kg within the voltage window of 0–4.0 V, as well as outstanding cyclic life keep 80% capacity after 5000 cycles. This work provides an opportunity for the preparation of NCNTs, that is as a promising high-performance anode for LIHCs.     

电解-电化学混合电容器的制备与性能

为解决电化学电容器工作电压过低的问题, 本文以钽电解电容器的烧结型钽块为阳极, 聚苯胺(PANI)/TiO₂电化学电容器复合电极为阴极, 成功制备了高能量密度、高工作电压的电解-电化学混合电容器. PANI/TiO₂复合电极是通过在多孔阳极氧化钛纳米管阵列中电化学聚合PANI 制得. 该阴极具有优良的倍率特性, 当平均功率密度为0.55 mW·cm^-2时, 对应的比容量仍达到10.0 mF·cm^-2. 由于与电解电容器复合, 该混合电容器的单元工作电压可高达100 V. 而且电化学电容器阴极的比容量远大于阳极, 故阴极所需尺寸远小于阳极, 节省的空间可用于增大阳极尺寸, 从而使混合电容器的比容量极大提高. 所制备的混合电容器体积能量密度和质量能量密度分别是钽电解电容器的4 倍和3 倍. 将该混合电容器在100 V下进行短路充放电实验, 循环10000 次后发现容量未衰减, 等效串联电阻未增加, 显示出极好的循环稳定性和功率特性. 计算表明其最大功率密度高达847.5 W·g^-1. 电化学阻抗谱显示其具有优良的阻抗特性和频率特性.     

Large-scale Ni-MOF derived Ni_3S_2 nanocrystals embedded in N-doped porous carbon nanoparticles for high-rate Na~+ storage

Metal organic framework(MOF) has been confirmed as the promising precursor to develop the conve rsion-typed anode mate rials of sodium-ion batteries(SIBs) because of the tunable structure design and simple functional modification.Here,we prepare the ultrasmall Ni_3S_2 nanocrystals embedded into N-doped porous carbon nanoparticles using the scalable Ni-MOF as precursor(denoted as Ni_3S_2@NPC).The ultrasmall size of Ni_3S_2 can work for accelerated electro n/ion transfer to facilitate the electrochemical reaction kinetics.Moreover,the robust conductivity network originated from N-doped porous carbon nanoparticles can not only improve the electron conductivity,but also enhance the electrode integrity and stability of the electrode/electrolyte interface.In addition,the N heteroatoms provide extra Na storage sites.Accordingly,the electrode delivers the obviously competitive capacities and high-power output with respect to the currently reported Ni_3S_2/C composites.This study provides a scalable and universal strategy to develop the advanced transition metal sulfides for practically feasible SIBs.     

Synthesis of Co-Ni oxide microflowers as a superior anode for hybrid supercapacitors with ultralong cycle life

Li-ion hybrid capacitors (LIHCs), composing of a lithium-ion battery (LIB) type anode and a supercapacitor (SC) type cathode, gained worldwide popularity due to harmonious integrating the virtues of high energy density of LIBs with high power density of SCs. Herein, nanoflakes composed microflower-like Co-Ni oxide (CoNiO) was successfully synthesized by a simple co-precipitation method. The atomic ratio of as-synthesized CoNiO is determined to be 1:3 through XRD and XPS analytical method. As a typical battery-type material, CoNiO and capacitor-type activated polyanilinederived carbon (APDC) were used to assemble LIHCs as the anode and cathode materials, respectively. As a result, when an optimized mass ratio of CoNiO and APDC was 1:2, CoNiO//APDC LIHC could deliver a maximum energy density of 143 Wh kg^-1 at a working voltage of 1-4 V. It is worth mentioning that the LIHC also exhibits excellent cycle stability with the capacitance retention of 78.2% after 15,000 cycles at a current density of 0.5 A g^-1.