Electrodes For Electrochemical Energy Storage Research Articles

Enhanced Methanol Electrooxidation and Supercapacitive Performance via Compositional Engineering of Colloidal Ni-Co Alloying Nanoparticles.

Among renewable energy technologies, particular attention is paid to electrochemically transforming methanol into valuable formate and storing energy into supercapacitors. In this study, we detailed a simple colloidal-based protocol for synthesizing a series of alloy nanoparticles with tuned Ni/Co atomic ratios, thereby optimizing their electrochemical performance. With the addition of 1 M methanol in 1 M KOH, the optimized composition was able to electrochemically produce formate at 0.149 mmol cm-2 h-1 with a Faradaic efficiency up to 95.1% at 0.6 V versus Hg/HgO within a 22-hour testing period. In 1 M KOH solution without methanol, the supercapacitive performance was achieved at a specific capacitance of over 1500 F g-1, and outstanding cycling stability with only approximately 20% decay after continuous 10000 charging-discharging cycles. These results underscore that the prepared Ni-Co alloy nanoparticles serve as multi-functional electrodes for electrochemical energy conversion and storage, particularly in the MOR and supercapacitors applications.

Design and Additive Manufacturing of Electrodes for Electrochemical Energy Storage

Supercapacitors exhibit rapid charge/discharge times and have attracted considerable attention within the automotive, aerospace, and telecommunication industries. The high electrical conductivity and surface area of porous carbons have been attractive for supercapacitor electrodes. Fabricating thick electrodes is one strategy to further increase energy density due to a higher volume fraction of active material. However, thick electrodes suffer from sluggish charged species transport. In this work, we investigate the use of computational optimization and additive manufacturing to design and fabricate thick porous electrodes with improved performance. Electrode performance was maximized by designing their morphologies via topology optimization and printing by projection micro stereolithography (PµSL) using commercial resin (PR48). The PR48 resin was then pyrolyzed (PR48-P) to create the final conductive electrode. The optimized PR48-P electrodes exhibited 99% improvement in capacitance compared to control electrodes printed with cubic lattice morphologies. To further improve performance, we formulated a resin combining graphene oxide (GO) and trimethylolpropane triacrylate (TMPTA). Electrodes printed with 3 wt% GO in TMPTA exhibited improved capacitance retention after pyrolysis compared to the PR48-P electrodes. This work demonstrates the enormous potential of leveraging topology optimization and additive manufacturing to resolve many challenges in the electrochemical storage and renewable energy regimes. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC Figure 1

Ammonium Persulfate Derived N,S-Dual-Doped Graphene─A Versatile Bifunctional Electrode for Electrochemical Energy Storage and Sensing

Ammonium Persulfate Derived N,S-Dual-Doped Graphene─A Versatile Bifunctional Electrode for Electrochemical Energy Storage and Sensing

Carbonization of bacterial cellulose with structure retention and Nitrogen/Sulfur/Oxygen doping for application in supercapacitors electrode

Bacterial cellulose (BC) presents great potential as an economical and sustainable biomass for the preparation of porous carbon electrodes for electrochemical energy storage. However, it is a challenge to maintain the natural structural advantages of BC and regulate the chemistry during the carbonization, significantly hindering the practical application. This study proposes a straightforward and efficient approach to rationally control the carbonization process of BC for improving structure retention and endowing multiple atomic doping, contributing an advanced electrode for supercapacitors. The addition of ammonium sulfate ((NH4)2SO4) is instrumental in promoting the early dehydration carbonization, forming a carbon layer with thermal insulation. This thermal barrier suppresses the volatile organic compound formation, resulting in the inhibition of volume shrinkage and boosted carbon yield. Moreover, the air activation combined with the addition of (NH4)2SO4 contributes to a Nitrogen/Sulfur/Oxygen-doped carbon electrode. The well-maintained hollow structure and diverse chemistry provide sufficient active sites and enhanced ion diffusion, resulting in a specific capacitance of 268.2 F/g at a current of 0.5 A/g and outstanding capacitance retention of 99.46 % after 10,000 cycles at 5 A/g. This work provides a deep insight into the development of cost-effective biomass in developing advanced carbon electrodes for efficient energy storage.

Carbon nanotube interweaved Fe7Se8 nanosheet/nanorod hybrids on expanded graphite for high-performance sodium storage

The construction of nano-micro scale hybrid structures by carbon materials is an effective strategy to address the issues of metal chalcogenides when used as anodes of sodium-ion batteries. Herein, we develop a carbon nanotube (CNT)-interweaved Fe7Se8/expanded graphite (EG) composite by means of a facile one-step gas-phase pyrolysis route with ferrocene, selenium and EG as the starting materials. The ex-situ monitoring of the pyrolysis process indicates that the selenium as a promoter facilitates the formation of CNTs and the carbon coated Fe7Se8 nanosheet/nanorod mixture. A competing reaction between CNT growth and the evolution of Fe7Se8 nanostructures occurs, which could be dominated by the concentration of selenium vapor. By optimizing the feeding ratio and the pyrolysis condition, the nanocomponents are homogeneously deposited on the surface of the EG matrix to realize a well-developed nano-micro hybrid configuration. The constructed three-dimensional conductive network, rich mesopores and high specific surface area (107.1 m2 g−1) contribute to substantially enhanced sodium-storage performance in ester electrolyte. Remarkably, the optimized composite electrode exhibits high reversible capacity retention of 97.5 % after 1000 cycles at 1.0 A g−1 and improved rate performance of 325 mAh g−1 at 2.0 A g−1. This study provides new avenues to develop high-performance metal chalcogenide electrodes for electrochemical energy storage.

The hierarchical dense structure induced high stability to NiCoB-based electrode for electrochemical energy storage

The construction of stable hierarchical surfaces through structural engineering is the key to improve reactive active sites and cycle stability to achieve high cycle performance of supercapacitors (SCs). In this work, the NiCo-LDH nanoflower as a structure guide agent was used to support NiCoB nanosheets to form a dense and stable hierarchical structure, thereby exposing more active sites and improving cycle stability. Due to the hierarchical stable surface structure, the NiCoB-0.3@NiCo-LDH-30 electrode has an excellent specific capacitance of 2710F g−1 at 1 A/g due to the excellent electrochemical active surface area (1259 mF cm−2), improving the OH– diffusion coefficient (2.4 × 10−9 cm2 s−1) and decreasing ionic diffusion barrier. After 5000 cycles, NiCoB-0.3@NiCo-LDH-30 electrode still has 92.6 % initial specific capacitance. In order to balance the energy density decrease caused by the capacitance imbalance between positive and negative electrodes, the cubed carbon (Co-C) derived from cobalt metal organic frameworks (Co-MOFs) as cathode with a good specific capacitance of 220F g−1 at 1 A/g is prepared. The assembled NiCoB-0.3@NiCo-LDH-30//Co-C hybrid SCs (HSCs), which are assembled with NiCoB-0.3@NiCo-LDH-30 electrode as anode and Co-C electrode as cathode, displays an energy density of 75 Wh kg−1 at a power density of 741 W kg−1.

Self-supported iron-doped nickel oxide multifunctional electrodes for highly efficient energy storage and overall water-splitting uses

Caused by complex synthesis processes, slow diffusion rates, and the formation of undesired nanostructures, it is tedious to produce a high-quality nickel oxide (NiO) electrodes for potential energy storage and water splitting applications. This paper introduces a novel chemical technique for producing self-supported iron-doped NiO electrodes having a high concentration of oxygen vacancies by utilizing different iron-based salts i.e. iron nitrate, iron chloride, iron ammonium sulfate, iron fumarate, and iron sulfate salts. After examining physical properties, the electrochemical energy storage and water splitting measurements were performed where iron nitrate precursor-mediated self-supporting Fe-NiO electrode confirms the optimum performance. Specifically, it exhibits a specific capacitance (SC) of 3302.5 Fg−1 at a current density of 5 Ag−1. The as-fabricated Fe-NiO-A//Bi2O3 asymmetric supercapacitor has a broad voltage range of 1.5 V, a remarkable volumetric-energy-density of 98.2 W hkg−1 at a power density of 900 Wkg−1, and a long-lasting cycling life with 92.6 % capacity retention after 5000 cycles at a current density of 15 Ag−1. A bifunctional Fe-NiO//Fe-NiO electrocatalyst demonstrates a current density of 10 mA cm−2 and remarkable long-term durability of 75 h without any degradation while operating at an ultra-low cell voltage of only 1.51 V, specifying importance of self-supported Fe-doped NiO electrodes for electrochemical energy storage and water splitting applications.

Porphyrin-Thiophene Based Conjugated Polymer Cathode with High Capacity for Lithium-Organic Batteries.

Organic electrode materials are promising for next-generation energy storage materials due to their environmental friendliness and sustainable renewability. However, problems such as their high solubility in electrolytes and low intrinsic conductivity have always plagued their further application. Polymerization to form conjugated organic polymers can not only inhibit the dissolution of organic electrodes in the electrolyte, but also enhance the intrinsic conductivity of organic molecules. Herein, we synthesized a new conjugated organic polymer (COPs) COP500-CuT2TP (poly [5,10,15,20-tetra(2,2'-bithiophen-5-yl) porphyrinato] copper (II)) by electrochemical polymerization method. Due to the self-exfoliation behavior, the porphyrin cathode exhibited a reversible discharge capacity of 420 mAh g-1, and a high specific energy of 900 Wh Kg-1 with a first coulombic efficiency of 96 % at 100 mA g-1. Excellent cycling stability up to 8000 cycles without capacity loss was achieved even at a high current density of 5 A g-1. This highly conjugated structure promotes COP500-CuT2TP combined high energy density, high power density, and good cycling stability, which would open new opportunity for the designable and versatile organic electrodes for electrochemical energy storage.

Porphyrin‐Thiophene Based Conjugated Polymer Cathode with High Capacity for Lithium‐Organic Batteries

AbstractOrganic electrode materials are promising for next‐generation energy storage materials due to their environmental friendliness and sustainable renewability. However, problems such as their high solubility in electrolytes and low intrinsic conductivity have always plagued their further application. Polymerization to form conjugated organic polymers can not only inhibit the dissolution of organic electrodes in the electrolyte, but also enhance the intrinsic conductivity of organic molecules. Herein, we synthesized a new conjugated organic polymer (COPs) COP500‐CuT2TP (poly [5,10,15,20‐tetra(2,2′‐bithiophen‐5‐yl) porphyrinato] copper (II)) by electrochemical polymerization method. Due to the self‐exfoliation behavior, the porphyrin cathode exhibited a reversible discharge capacity of 420 mAh g−1, and a high specific energy of 900 Wh Kg−1 with a first coulombic efficiency of 96 % at 100 mA g−1. Excellent cycling stability up to 8000 cycles without capacity loss was achieved even at a high current density of 5 A g−1. This highly conjugated structure promotes COP500‐CuT2TP combined high energy density, high power density, and good cycling stability, which would open new opportunity for the designable and versatile organic electrodes for electrochemical energy storage.

Harnessing enhanced lithium-ion storage in self-assembled organic nanowires for batteries and metal-ion supercapacitors

Organic materials are emerging as highly efficient, green and sustainable electrodes for electrochemical energy storage, however with often limited ion storage properties. In this study, we showcase that mesoscale engineering can dramatically...

Coaxial nickel cobalt selenide/nitrogen-doped carbon nanotube array as a three-dimensional self-supported electrode for electrochemical energy storage.

Herein, we propose a one-step urea pyrolysis method for preparing a nitrogen-doped carbon nanotube array grown on carbon fiber paper, which is demonstrated as a three-dimensional scaffold for constructing a nickel cobalt selenide-based coaxial array structure. Thanks to the large surface area, interconnected porous structure, high mass loading, as well as fast electron/ion transport pathway of the coaxial array structure, the nickel cobalt selenide/nitrogen-doped carbon nanotube electrode exhibits over 7 times higher areal capacity than that directly grown on carbon fiber paper, and better rate capability. The cell assembled by a nickel cobalt selenide/nitrogen-doped carbon nanotube positive electrode and an iron oxyhydroxide/nitrogen-doped carbon nanotube negative electrode delivers a volumetric capacity of up to 22.5 C cm-3 (6.2 mA h cm-3) at 4 mA cm-2 and retains around 86% of the initial capacity even after 10 000 cycles at 10 mA cm-2. A volumetric energy density of up to 4.9 mW h cm-3 and a maximum power density of 208.1 mW cm-3 are achieved, and is comparable to, if not better than, those of similar energy storage devices reported previously.

Sensor Absorbents for Heavy Metal Ions By Low-Cost Functionalization of Porous Carbons

Porous carbons are key materials in electrodes for electrochemical energy storage as well as in water purification. Methods to modify porous carbons to enhance their properties as charge storing or water purification materials have been explored during the past decades [1,2]. The main application fields if porous carbon, water purification and energy storage, are highly cost sensitive. For this reason, there is a need to develop low-cost methods to modify porous carbons. Here, the use of benzoxazine chemistry to modify porous carbons is explored. Benzoxazine chemistry can be considered a protection group strategy for phenols, where the phenols from which the benzoxazines are synthesized, are deprotected upon benzoxazine polymerization. Further, benzoxazine polymerization produces Mannich bridges located near phenol groups, motifs that can be used to capture heavy metal ions. More specifically, in the first step, the porous carbons are partially impregnated with benzoxazine monomers, from melt or solutions to afford powders impregnated far below the liquid saturation level of the particles. That is, the particles retain porosity after the impregnation but still have a dry appearance. After impregnation, the particles are heated over the polymerization temperature of the benzoxazine to afford the porous carbon with immobilized functionalities. As phenols can initiate benzoxazine polymerization and be incorporated in the polymer, this method offers a simple route to produce polymerized and immobilized structure at a carbon interface. Here, results on metal ion absorption and the electrochemical response after exposure are presented for carbons modified by impregnation-polymerization of benzoxazines with or without incorporation of phenols. Inks were manufactured from the modified carbons. The electrochemical characterizations were performed on printed arrays of electrochemical cells on a substrate having dimensions of well plates and intended for automatized testing and where the carbon inks were deposited on the working electrodes. This methodology has a potential of simplifying the development of sensor materials and absorbents and can be automatized and potentially be supported with machine learning schemes. The electrochemical responses of exposure of the modified carbon electrodes to metal salt solutions show that impregnation-polymerization of functional benzoxazine can produce absorbents responding electrochemically to metal ion absorption with a scalable process starting from low-cost materials.

EFFECT OF ELECTROPHORETIC DEPOSITION PARAMETERS ON COATING THICKNESS AND DEPOSIT YIELD OF NON-COLLOIDAL GRAPHITE PARTICLES

Electrophoretic Deposition (EPD) has become a method for fabricating and enhancing electrodes for electrochemical energy storage (EES) devices. This article explores the impact of dominant EPD parameters on the deposit yield and coating thickness of graphite produced from an organic-based graphite particle suspension. The deposit yield follows a linear Hamaker's law at voltages below 50 V, with a deposition time of up to 5 minutes and solid loading between 2.5 to 12.5 mg/mL. The study also demonstrates the successful deposition of negatively charged and non-colloidal sized graphite particles, which are previously dispersed in n-butylamine-acetone without the use of charging or binding additives. This later forms a coating with a relatively strong binding strength of graphite particles on the steel anode. EPD of graphite suspension with a concentration of 5 mg/mL at a deposition voltage of 10 V and 5 minutes deposition time is capable of producing a graphite coating thickness of 70 mm. This research demonstrates the high-yield capability of EPD of organic-based graphite particles on metal anode and provides valuable insight for future investigations into application of binderless graphite suspension particles for electrode materials in energy storage systems.

A Universal Cross-Synthetic Strategy for Sub-10nm Metal-Based Composites with Excellent Ion Storage Kinetics.

The sub-10nm metal-based nanomaterials (SMNs) show great potential for the electrochemical energy storage field. However, their ion storage capacity and stability suffer from severe agglomeration and interface problems. Herein, a universal strategy is reported to synthesize a wide range of SMNs (e.g., metal, nitride, oxide, and sulfides) embedded in free-standing carbon foam (SMN/FC-F) composite electrodes by crossing the interfacial confinement of NaCl self-assembly with the thermal-mechanical coupling of powder metallurgy. The pressure-enhanced NaCl self-assembly interfacial confinement is greatly beneficial to preventing SMN agglomeration and promoting SMNs embedded in FC-F which originate from the welding of carbon nanosheets. They are confirmed via a series of advanced characterizations including X-ray photoelectron spectroscopy, and spherical aberration-corrected scanning transmission electron microscopy, with theoretical computations. Benefiting from the unique structure, SMNs/FC-F delivers ultrafast and stable ion-storage kinetics. As a proof-of-concept demonstration, the MoS2 /FC-F shows excellent ion storage kinetics and superior long-term cycling performance for ion storage (e.g., Na3 V2 (PO4 )2 O2 F/C//MoS2 /FC-F sodium-ion batteries exhibit a high reversible capacity of 185mAhg-1 at 0.5Ag-1 with a decay rate of 0.05% per cycle.). This work provides a new opportunity to design and fabricate promising SMN-based free-standing working electrodes for electrochemical energy storage and conversion applications.

Marine predators optimization and ANFIS as an effective tools for maximization of specific capacity of G-NiO electrode for electrochemical energy storage

Marine predators optimization and ANFIS as an effective tools for maximization of specific capacity of G-NiO electrode for electrochemical energy storage

Sol-gel method preparation and high-rate energy storage of high-entropy ceramic (FeCoCrMnNi)C porous powder

Among the existing electrochemical capacitive energy storage electrode materials, the (TiNbTaZrHf)C, (VCrNbMoZr)2N, (CoCrFeMnNi)3O4, (FeCoCrMnMg)3O4 and (FeCoCrMnCuZn)3O4 all have excellent capacitive performance, but the energy density is limited due to the narrow potential window. In order to solve the problem of low energy density of electrochemical supercapacitor, a kind of high-entropy carbides (HEMCs) with broad potential window is designed from generalized analysis of electrochemical window of active elements. This high-entropy carbide contains five active elements of Fe, Co, Cr, Mn and Ni. The prepared HEMC-3 has abundant pores and a specific surface area of 417.8 m2 g−1. The large specific surface area makes the HEMCs have high-rate energy storage performance. Electrochemical tests show that the HEMC-3 presents a potential window of [-1.0, 0.6] versus Hg/HgO, and can obtain a specific capacitance of 169.7 F g−1 at a current density of 0.5 A g−1. Due to the designed wide potential window of the prepared HEMCs, the energy density has been greatly improved, which shows a new strategy for developing of electrochemical supercapacitor electrode materials.

Construction of 3D interconnected NiCo2S4/bio-carbon coated Ni foam as binder-free electrode for high-performance supercapacitor

Although transition metal hydroxides/sulfides are considered as promising potential electrode materials for supercapacitors due to their excellent electrochemical activity, the low electrical conductivity, easy agglomeration of nanomaterials and poor rate performance seriously hinder their practical applications. Herein, we construct 3D interconnected binder-free electrode NiCo2S4/bio-carbon coated nickel foam (NiCo2S4/GRCNF) by growing NiCo2S4 nanosheets on the surface of low-cost and highly conductive GRCNF substrate via a simple hydrothermal reaction followed with subsequent sulfidation. As suggested by systematic characterizations, the advantages of obtained NiCo2S4/GRCNF include that the ultrathin 3D interconnected network of NiCo2S4 can furnish massive electrochemically active sites for faradic reaction, and the highly conductive GRCNF substrate promotes electron transfer and meanwhile prevents the aggregation of NiCo2S4 nanosheets. With a high specific capacitance of 7.71 F cm−2 at 3 mA cm−2, NiCo2S4/GRCNF has a huge application advantage over the contrast samples Ni-Co LDH/NF (3.29 F cm−2) and Ni-Co LDH/GRCNF (5.97 F cm−2). In addition, NiCo2S4/GRCNF shows a much higher rate performance (82.1%) than Ni-Co LDH/NF (44.5%) and Ni-Co LDH/GRCNF (66.4%). Furthermore, hybrid supercapacitor NiCo2S4/GRCNF//GNPC which is assembled with NiCo2S4/GRCNF as the anode possesses an impressive energy density of 0.429 mWh cm−2 at a power density of 7.023 mW cm−2 and good cycling stability (82.3% over 5000 cycles). The outstanding electrochemical performance of NiCo2S4/GRCNF suggests that the reported strategy provides new inspiration for the design and preparation of new binder-free composite electrodes for electrochemical energy storage.

Facet Dependence and Vacancy-Controlled Reversibility of the Spinel-to-Rocksalt Phase Transformation at Co3O4 Surfaces

Transition-metal spinel oxides have attracted considerable interest as high-performance electrodes for electrochemical energy storage and conversion, where irreversible or reversible spinel–rocksalt (S–R) phase transformation at the oxide surface has been frequently observed, which sensitively controls their performance. Exploring key factors controlling the S–R transformation and its reversibility at the atomic scale is important for understanding the electrochemical performance of spinel oxides. Using Co3O4 nanoparticles as an example, which represent a promising electrocatalyst for the oxygen evolution reaction, we present in situ atomic-scale imaging of the S–R transformation by using aberration-corrected scanning transmission electron microscopy combined with the integrated differential phase contrast imaging technique to visualize oxygen anions and transition-metal cations simultaneously. We reveal that the S–R transformation is not only determined by the oxygen vacancy formation energy but also largely controlled by the surface polarity of the reconstructed rocksalt layer, leading to a faster S–R transformation at the (001) surface than the (111) surface. Moreover, cobalt and oxygen vacancies are directly identified at the spinel/rocksalt interface, leading to the formation of an intermediate defective rocksalt phase and a two-step S–R transformation process. The existence of the intermediate defective rocksalt phase or not decisively controls the reversibility of the two-step S–R transformation. The uncovered facet dependence and vacancy-controlled reversibility of the S–R transformation provide important insights into the shape-dependent reactivity and stability of spinel oxide electrodes for electrochemical energy applications.

Rational designed Cu-MOF@1D carbon nanofibers as free-standing and flexible electrode for robust electrochemical energy storage

The present study reported the performance of free-standing carbon nanofibers decorated with copper-metal-organic frameworks (Cu-MOFs). A green electrospinning technique was utilized to obtain nanofiber sheets that were carbonized and activated to produce activated carbon nanofiber sheets (ACNFs). These ACNFs consist of inherent oxygen functionalities of the lignin that can aid the growth of MOF structure on it in a single step, which motivated us to do this work. Cu-MOF particles were in-situ grown over the surface of ACNFs using a hydrothermal-assisted technique. The developed materials were characterized using FESEM, Raman Spectroscopy and BET analysis in order to identify morphological, porosity, and surface area transformations. Along with these, Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), and Galvanostatic Charge-Discharge (GCD) studies were performed to compare the electrochemical performance of the Cu-MOF, ACNF, and Cu-MOF@ACNF as electrode materials for supercapacitors. Among three electrodes, the Cu-MOF@ACNF sheet reveals a higher specific capacitance of 303.2 F/g compared to ACNF (203.3 F/g) and Cu-MOF (68.2 F/g) at the same current density of 1 A/g. Based on the higher performance of Cu-MOF@ACNF two types of symmetrical devices, i.e., aqueous (using electrolyte-impregnated filter paper) and solid-state devices (using a polymeric gel electrolyte), were fabricated. The all-solid-state supercapacitor device was found to feature high flexibility, stand-alone characteristics, and excellent performance as an electrode with a working potential window of 0–2.0 V. The device demonstrates a high energy density of 78.71 Wh/kg and a power density of 1050.0 W/kg, along with high coulombic efficiency (99.8 %) after 10,000 cycles. The achieved performance is superior to many published reports, revealing that the developed composite materials hold prospect for applications in green and high-performance flexible energy storage devices.

CuFeSe2/Cu2Se@C heterostructures as high-rate ultra-stable anodes for sodium ion half/full batteries

Transition metal selenides can be potentially implemented as a new generation of sodium storage anode owing to their abundance and high theoretical specific capacity. However, their practical applications are limited by large volume changes and slow kinetics. Therefore, the construction of transition metal selenide heterojunctions with long cycle stability and high capacity as anodes in sodium ion batteries remains challenging. In this study, carbon coated CuFeSe2/Cu2Se heterojunctions (CFS/CS@C) were successfully prepared via a simple aging and annealing strategy. The abundant heterojunction interfaces and carbon layers accelerated charge transfer, promoted the reaction kinetics, enhanced the electrical conductivity, and extended the cycle life. Consequently, the target material yielded ultra-long cycle stability (301.2 mAh/g at 10.0 A/g after 3000 cycles) and excellent rate performance (330.96 mAh/g at 20 A/g). The directly constructed full cell also exhibited remarkable cycling stability (138.6 mAh/g after 200 cycles at 0.5 A/g). Accordingly, this work demonstrated the construction of transition metal selenide composites as high-performance electrochemical energy storage electrodes.