Positive Active Material Research Articles

Highly redox active mesoporous Ni/Co-organic framework as a potential battery type electrode material for high energy density supercapattery

Designing potential electrochemically active metal-organic-framework (MOF) electrode materials with controllable structure and versatile nano-geometries are very pivotal to enable the forthcoming generation electrochemical energy storage systems. Among the hydrothermally synthesized materials; Nickel/MOF (NiMOF), Cobalt/MOF (CoMOF) and Nickel-Cobalt/MOF (Ni/CoMOF) with 1:1 of Ni/Co, the binary Ni/CoMOF shows excellent electrochemical performance compared to NiMOF and CoMOF, achieving a distinguished specific capacity of 594.24C g−1 at current density of 1 A g−1 in 3-electrode setup with 67.32 % remarkable rate capability at 10 A g−1 and excellent cyclic durability of 92.7 % after undergoing 5000 charge-discharge cycles. Further, Ni/CoMOF is employed as a positive active electrode material with Activated‑carbon (ActC) and reduced-graphene oxide (rGO) sequentially as negative capacitive type electrode materials to fabricate supercapattery devices. The high cyclically stable and novel Ni/CoMOF||rGO supercapattery unveils a striking specific capacity of 307.45C g−1 contrary to 222C g−1 of Ni/CoMOF||Act-C at 1 A g−1 and exhibits significantly increased energy density of 66.2 Wh kg−1 at power density of 775.13 kW kg−1. Overall, this synergy of Ni/CoMOF coupled with rGO in a hybrid configuration shows favorable energy storage features to fulfill the soaring renewable energy demands to power the digital world.

Control of Electrolyte Decomposition by Mixing Transition Metal Ions in Spinel Oxides as Positive Electrode Active Materials for Mg Rechargeable Batteries

The development of Mg rechargeable batteries is hindered by both oxidative and reductive electrolyte decomposition on the positive electrode, which results in poor cyclability. Although improving the stability of the electrolyte is one solution, we found that the oxidative decomposition of the electrolyte can be suppressed by introducing Fe ions to spinel oxides. Furthermore, the mechanism was clarified from the viewpoint of the electronic state of the spinel oxides, with MgFe2O4 exhibiting the lowest valence band maximum in our previous study. Here, by developing an interpretation of this mechanism, we demonstrated that the type of transition metal ions in spinel oxides has an effect on the reductive decomposition of the electrolyte. Based on the above knowledge, we synthesized mixed Co–Fe spinel oxides that exhibited a suppressive effect on both oxidative and reductive electrolyte decomposition and successfully improved the cyclability. This study provides guidelines for developing positive electrode active materials for Mg rechargeable batteries.

Synthesis and Application of an Aromatic Sulfonate Sodium Salt for Aqueous Sodium‐Ion Battery Electrolytes

The two‐step synthesis of sodium (2,3,5,6‐tetrafluorophenoxy) diethane sulfonate (Na‐TFP) is reported, starting from 2,3,5,6‐tetrafluorohydroquinone as the precursor. Compared with conventional aqueous electrolytes such as 0.5 m NaClO4 and Na2SO4, the 0.5 m aqueous solution of Na‐TFP provides higher ionic conductivity over a wide range of temperature (e.g., >60 mS cm−1 at 20 °C and >70 mS cm−1 at 30 °C) and a wider electrochemical stability window. Electrochemical cells with Na2VTi(PO4)3 as the positive electrode active material and a carbon‐based negative electrode provide a stable capacity for more than 450 cycles in 0.5 m Na‐TFP. Additionally, symmetric cells with Na2VTi(PO4)3 as the active material for the negative and positive electrode are studied. The cells employing 0.5 m Na‐TFP exhibit a good cycling stability at a high dis‐/charge rate of 5C for more than 50 cycles, which is superior to the performance of the cells employing 0.5 m aqueous solutions of NaClO4 and Na2SO4 as the electrolyte. The design of this bifunctional salt may trigger new ideas for the development of water‐based sodium‐ion battery electrolytes.

Making Aqueously Processed LiNi0.5Mn0.3Co0.2O2-Based Electrodes Competitive in Performance: Tailoring Distribution and Interconnection of Active and Inactive Electrode Materials through Paste Surfactants

Enabling aqueous processing of positive active materials to replace toxicologically critical N-methyl-2-pyrrolidone could significantly reduce the ecologic and economic footprint of lithium ion battery production. Processing additives are key to elevate the performance of aqueously processed electrodes beyond the state of the art. A mostly neglected factor during aqueous processing is electrostatic repulsion of active/inactive materials due to their ζ potentials, which can be compensated for by applying optimized amounts of surfactants like hexadecyltrimethylammonium bromide. The notably improved distribution and interconnection of active/inactive materials lead to superior rate capability and similar capacity retention during long-term cycling compared to state-of-the-art processing.

A medium-entropy transition metal oxide cathode for high-capacity lithium metal batteries

The limited capacity of the positive electrode active material in non-aqueous rechargeable lithium-based batteries acts as a stumbling block for developing high-energy storage devices. Although lithium transition metal oxides are high-capacity electrochemical active materials, the structural instability at high cell voltages (e.g., >4.3 V) detrimentally affects the battery performance. Here, to circumvent this issue, we propose a Li1.46Ni0.32Mn1.2O4-x (0 < x < 4) material capable of forming a medium-entropy state spinel phase with partial cation disordering after initial delithiation. Via physicochemical measurements and theoretical calculations, we demonstrate the structural disorder in delithiated Li1.46Ni0.32Mn1.2O4-x, the direct shuttling of Li ions from octahedral sites to the spinel structure and the charge-compensation Mn3+/Mn4+ cationic redox mechanism after the initial delithiation. When tested in a coin cell configuration in combination with a Li metal anode and a LiPF6-based non-aqueous electrolyte, the Li1.46Ni0.32Mn1.2O4-x-based positive electrode enables a discharge capacity of 314.1 mA h g−1 at 100 mA g−1 with an average cell discharge voltage of about 3.2 V at 25 ± 5 °C, which results in a calculated initial specific energy of 999.3 Wh kg−1 (based on mass of positive electrode’s active material).

Research for Electrochemical & Structural Properties of Recycling Cathode Materials for End of Life Lib

Demand for lithium-ion batteries (LIBs) has increased dramatically over the years due to the rapid market expansion of electric vehicles. However, many of the essential components of cathode materials, such as cobalt, nickel, manganese and lithium, are resource-limited and expensive[1]. Therefore, recycling of used LIB cathode materials is very important to conserve resources and the environment. Currently, the lithium secondary battery recycling technology mainly uses wet and dry smelting, but there is a disadvantage of high energy consumption due to the use of strong acid and the smelting process[2-3].In this study, the cathode active material was separated from a pouch-type lithium secondary battery separated from a portable tablet that was over 10 years old and the chemical, structural, and electrochemical characteristics thereof were investigated. The cathode active materials were dismantled from a pouch-type LIB, which was removed from the tablet produced in 2011. The pouch cell was in a swelling state and the OCV was 0V due to internal short is expected. As a result of TGA analysis, the electrode composition was confirmed to be 92wt% of the cathode active material, 3wt% of the conductive agent, and 3wt% of the binder, respectively. The recovery rate of the active material is the best when a mixed solvent including NMP, heating, and ultrasonic, respectively. Through SEM and EDS analysis, copper metal due to dissolution of the negative electrode current collector was found on the surface of the positive electrode. As shown in Fig. 1, It can be seen that the positive electrode active material recovered using the composite solvent is a positive electrode active material that is a mixture of NCM active material and LMO active material. The XRD results shows a well layered structure and a Co3O4 phase due to lithium deficiency. In order to examine the electrochemical characteristics of the recovered electrode, it was reassembled into a 2032 coin type cell and evaluated, and the discharge capacity of approximately 150mAh/g was recovered as shown in Fig. 2. The positive active material recovered according to the experimental results is estimated to be in a state of insufficient lithium, and a lithium compensation process is planned to be additionally performed in the future.

Strategies for formulation optimization of composite positive electrodes for lithium ion batteries based on layered oxide, spinel, and olivine-type active materials

Electrode processing and performance strongly depend on the active material. Maximizing the active material content of positive composite electrodes enables low cost and high energy density. However, this maximization cannot reach 100%, as composite electrodes additionally consist of binder to provide mechanical integrity and conductive additive to enhance electronic conductivity, which in combination create a flexible porous microstructure for appropriate electron and lithium transport. In this study, the influence of three positive active material classes, layered oxide LiNi0.6Mn0.2Co0.2O2, spinel-type LiMn2O4 and olivine-type carbon-coated LiFePO4, were investigated regarding the optimum amount of polyvinylidene difluoride as binder and carbon black as conductive additive to achieve high mechanical stability as well as high electronic and ionic conductivity within composite electrodes. Formulation optimization was conducted and compared to a reference electrode formulation with regard to physical, mechanical, electronic and electrochemical properties. In a first step, the binder amount was optimized for each active material class by varying the ratio of binder content to surface area of the solid electrode components. In a second step, the critical conductive additive content was determined. Overall, this strategy allows to decipher material class dependent optimized electrode formulations for high energy density composite electrodes with maximized active material content.

Comparison of Positive Electrode Separation by Electrical Pulsed Discharge in Underwater and Air Environments

This study presents a novel method to separate positive electrode active materials (PEAMs) and aluminum (Al) foil from positive electrodes (PEs) to enable more effective recycling processes. A pulsed current was applied to a PE sample that was prepared by manual dismantlement of spent lithium-ion batteries (LiBs). Joule heating caused the temperature of the Al foil to increase to be above the melting points of adhesion included in the PEAMs. The influence of the surrounding medium of the PE sample on the delamination phenomenon was investigated. PEAMs were peeled from the Al foil in water and air environments. High-speed visible imaging was employed to discuss separation processes. Differences in the size of the separated PEAMs and the amount of residual PEAM on the surface of the Al foil occurred due to the influence of the medium filled in the voids inside the PEAM layer.

Electrochemical Properties of Chitosan‐Modified PbO2 as Positive Electrode for Lead–Acid Batteries

The structure and properties of the positive active material PbO2 are key factors affecting the performance of lead–acid batteries. To improve the cycle life and specific capacity of lead–acid batteries, a chitosan (CS)‐modified PbO2–CS–F cathode material is prepared by electrodeposition in a lead methanesulfonate system. The microstructure and phase composition are characterized by scanning electron microscopy and X‐ray diffraction. The electrochemical activity of the cathode material is analyzed by cyclic voltammetry, linear sweep voltammograms, electrochemical impedance spectroscopy, and scanning electrochemical microscopy. The battery performance of laboratory lead–acid batteries assembled with the cathode material is analyzed by a battery tester. The results show that the PbO2–CS–F cathode material has the smallest grain size (21.879 nm), the highest oxygen evolution potential (2.237 V), and the highest exchange current density (3.788 × 10−7 A cm−2), smallest charge transfer resistance (5.359 Ω cm2), and highest chemical activity in the series of PbO2 cathode materials. The laboratory lead–acid battery assembled from PbO2–CS–F cathode material exhibist the best battery performance, with the first discharge capacities of 4257 mAh and the discharge‐specific capacity after 500 cycles is 196 mAh g−1.

Creating 3 dimensional foam morphology of lead dioxide on the polyaniline film for improving the performance of lead flow batteries

In the present study, we investigate the effect of polyaniline as a conductive surface modifier on the morphology of the lead dioxide, PbO2, as a positive active material of lead-acid redox flow batteries. We used cyclic voltammetry to electrodeposit PbO2 on the surface of the bare and polyaniline-modified graphite substrates. We characterized the morphology and crystal structure of the electrodeposited PbO2 film using X-ray diffraction and scanning electron microscopy. In addition, we used electrochemical polarization and electrochemical impedance spectroscopy techniques to investigate the kinetics of the lead dioxide charge transfer in the presence and absence of polyaniline. To analyze the effect of the polymer film on the battery performance, we discharged the cells at different rates, and studied the cycle life of the cells. The results show that lead dioxide adopts an interconnected 3D fiber-like morphology on the surface of the polyaniline-modified graphite, resulting in a higher surface area, a better cycle life, and a higher coulombic efficiency, along with a retarded short-circuit problem. Besides, polyaniline modification increased the electron transfer rate of lead dioxide, reduced the internal resistance, enhanced the discharge plateau with less oscillation in the voltage range from 1.4 to 1.6 V, and increased the average specific power up to 367 mWg−1, resulted in a generally boosted battery performance.

Mechanochemical synthesis of Na&lt;sub&gt;3&lt;/sub&gt;NbS&lt;sub&gt;4&lt;/sub&gt; metastable phase as positive electrode materials for all-solid-state sodium batteries

Transition metal sulfides have been reported to be active materials with high capacities by using anionic redox reactions. Modifying the structure to favor the extraction/insertion of sodium is beneficial in achieving the theoretical capacity of these sulfides. In this study, we synthesized three new phases of Na3NbS4 via a mechanochemical (MC) process. Under moderate MC conditions, amorphous Na3NbS4 was obtained. Under harsher MC conditions, metastable phases I and II of Na3NbS4 were obtained at different process times of 10 and 40 h, respectively. The conductivities of the three Na3NbS4 materials were higher than that of orthorhombic Na3NbS4. In particular, the metastable phase I of Na3NbS4 showed the highest conductivity of 3.2 × 10−6 S cm−1, and the all-solid-state sodium cells with metastable phase I as an electrode active material showed the highest capacity of 240 mAh g−1. Thus, the MC process is useful for synthesizing positive electrode active materials on transition metal sulfides with an advantageous structure to achieve a high capacity.

Surface modified Ni wire supported flexible asymmetric supercapacitor of Mn3O4// PEDOT-PSS-MWCNT and its solar charging for self-powered Cu-doped ZnO nanorods-based UV photodetector

Recently, wire-shaped supercapacitors (WSCs) with the benefits of being flexible, lightweight, and wearable, have attracted great attention as portable and wearable power sources, though still, they face critical challenges of inadequate energy density and electrochemical stability under mechanical deformations. Therefore, we report the fabrication of the asymmetric WSC constituting surface-modified Ni wire as current collectors, PVA-KOH electrolyte, and hydrothermally grown Mn3O4 nanoflakes and dip-coated PEDOT: PSS-MWCNT nanocomposites as positive and negative electrode active materials, respectively. Owing to surface modification of Ni wire and active materials with approximate mass matching, mesoporous nanostructured surface morphology, and improved surface areas, the twisted asymmetric WSC exhibits excellent volumetric capacitance of 7.55 F/cm3, 2.69 mWh/cm3 energy density, and 95 mW/cm3 power density at 25 μA with a 1.6 V voltage window. In addition, considering the recent trend of developing multi-functional self-powered systems integrating energy harvesters, storage entities, and functional components, ultraviolet photodetector (UV PD) in metal-semiconductor-metal (MSM) configuration was fabricated by hydrothermal growth of Cu-doped ZnO nanorods onto interdigitated electrode printed glass substrate, and hence for the first time a self-powered UV-light detection system with a fast response and high on/off ratio were successfully demonstrated by connecting solar-charged parallel asymmetric WSCs and UV PD.

Preparation of conductive Cu1.5Mn1.5O4 and Mn3O4 spinel mixture powders as positive active materials in rechargeable Mg batteries operative at room temperature

Preparation of conductive Cu1.5Mn1.5O4 and Mn3O4 spinel mixture powders as positive active materials in rechargeable Mg batteries operative at room temperature

Development of vanadium-based polyanion positive electrode active materials for high-voltage sodium-based batteries

Polyanion compounds offer a playground for designing prospective electrode active materials for sodium-ion storage due to their structural diversity and chemical variety. Here, by combining a NaVPO4F composition and KTiOPO4-type framework via a low-temperature (e.g., 190 °C) ion-exchange synthesis approach, we develop a high-capacity and high-voltage positive electrode active material. When tested in a coin cell configuration in combination with a Na metal negative electrode and a NaPF6-based non-aqueous electrolyte solution, this cathode active material enables a discharge capacity of 136 mAh g−1 at 14.3 mA g−1 with an average cell discharge voltage of about 4.0 V. Furthermore, a specific discharge capacity of 123 mAh g−1 at 5.7 A g−1 is also reported for the same cell configuration. Through ex situ and operando structural characterizations, we also demonstrate that the reversible Na-ion storage at the positive electrode occurs mostly via a solid-solution de/insertion mechanism.

Reinforcing the Li|Li1.3Al0.3Ti1.7(PO4)3 Interfacial Stability By an Ultrathin Multifunctional Polysiloxane-Based Single-Ion Conducting Polymer

Lithium metal is considered as one of the most promising anode candidates for high-energy batteries [1-3]. However, safety concerns induced by the formation of Li dendrites largely hinder the practical application of lithium-metal batteries [4]. It is anticipated that the use of non-flammable inorganic solid-state electrolytes can resolve these safety issues [5], but solid ceramic electrolytes generally suffer from poor physical contact with the electrode and poor electro-/chemical stability at the electrolyte|electrode interface [6].Herein, we report on a thin and flexible hybrid electrolyte composed of NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP), a polymer binder, and a small amount of an ionic liquid-based electrolyte. To reinforce the interfacial stability between LATP and Li, we coat an ultrathin polysiloxane-based single-ion conducting polymer (PSiO) on the Li metal surface via a simple dip-coating method. The implementation of PSiO-coated Li (PSiO@Li) in symmetric PSiO@Li||PSiO@Li cells enables a substantial extension of the cycle life, yielding >2,000 h of stable lithium stripping-plating. The full-cells comprising PSiO@Li as the negative electrode, LiNi0.88Co0.09Mn0.03O2 (NCM88) as the positive electrode active material, and the aforementioned hybrid electrolyte exhibit substantially enhanced rate capability at high dis-/charge rates above 0.5C and greatly prolonged cycle life at 1C. The superior performance achieved herein is mainly attributed to: (1) the prevented direct contact between LATP and Li, thus avoiding the reduction of LATP and the formation of mixed ion-electron conducting interphases; (2) the regulated Li+ flux at the electrode|electrolyte interface, ensuring homogeneous Li+ stripping-plating; and (3) the promoted intimate contact between PSiO and Li via the formation of Si−O−Li bonds.

Diagnosis and Prognosis of the Aging of LTO/NMC Li-Ion Cells Under Cycling Tests

Novel non-destructive analyses open up possibilities to delve into degradation mechanisms of Lithium-ion batteries and diagnose internal states without the inconvenience of post-mortem characterizations. Low-rate constant current charge or discharge measurements (pOCV(Q)) lower than C/20 give comprehensive information on the electrochemical reactions occurring within the cell. Then, the voltage spectroscopies (Differential Voltage Analysis - dV/dQ vs. Q (DVA) and Incremental Capacity Analysis - dQ/dV vs. V (ICA)) highlight the degradation mechanisms, linked up with the electrode states of health and the available lithium quantity. The aging mechanisms are gathered in four main degradation modes that can be quantified: the loss of lithium inventory (LLI), the loss of positive active materials (LAMPE), the loss of negative active materials (LAMNE) and the ohmic resistance increase (ORI). Estimating the aging laws of the modes enable to forecast the cell useful capacity and predict shifts into the aging trend through the upcoming electrode limitation changes.The diagnostic study is conducted on 28Ah prismatic Li4Ti5O12/Ni1-x-yMnxCoyO2 based cells for different electrical solicitations at 45°C. Cells are cycled between 70% and 100%SOC under 3C or 6C. A 45°C calendar aging test is performed on the mean of the cycling window (85%SOC) to observe the effects of resting at this temperature. No significant capacity fade can be seen in these aging tests, but changes into the cell internal states are expected as the different pOCV(Q) evolve and the resistances increase. Degradation modes are followed through the non-intrusive methods, and then used to make a prognosis on the future evolution of the cell capacity.The present investigation couples the differential methods with half-cell measurements of negative (LTO) and positive (NMC) electrode coin cells. From these data, a full cell model computed from the Alawa toolbox emulates the aging and design degradation maps to spot the focus of interest (FOI) points, i.e. the pOCV(Q) areas where the features of a specific degradation mode can easily be distinguished. The beginning of life cell design imposes that the negative electrode limits the cell operation both at the ends of charge and discharge. Thus, in the first part of the battery’s life, the negative electrode works between insertion rates close to 0 and 1, and its capacity is equivalent to the cell one. In the other hand, a clear FOI of the positive electrode appears on the ICA last shoulder at high voltage. From this knowledge, the positive and negative insertion rates can be described as a function of the cell voltage, and the possible changes into the electrode limitation can be predicted.This approach allows to precisely quantify the degradation modes LLI, LAMPE, LAMNE and ORI for the aging tests carried out. Diagnoses are conducted to find out the aging laws of each mode regarding the different conditions and determine the actual insertion rates that limit the cell operation window. Eventually, this non-intrusive method enables to forecast the next changes of electrode limitation that could affect the aging trend and the cell lifetime.

Hydro-thermal preparation of PbCO3/N-rGO nano-composites as positive additives to improve the performance of lead-acid batteries

Due to the expansion of the energy storage market, the demand for lead-acid batteries is also increasing. In order to improve the discharge specific capacity of lead-acid batteries, this paper uses graphene oxide (GO), Pb(Ac)2·3H2O, urea and other raw materials in the reactor. The PbCO3/N-rGO nanocomposite was prepared by a hydrothermal method as a positive electrode additive for lead-acid batteries. The material was characterized by XRD, STM, SEM, Raman, etc., and was doped into a simulated battery positive plate. The positive plate exhibits excellent electrochemical performance when the addition amount of the PbCO3/N-rGO nanocomposite in the positive plate is 1 wt%. In the simulated battery test, the initial discharge specific capacity reaches 166 mAh g−1, which is 52% higher than that of the blank control group, and a 2-fold improvement in HPRSoC cycle life at 1 C rate. The PbCO3/N-rGO enabled the battery to have a higher discharge specific capacity and the longest charge/discharge cycle life, this is due to the nanostructure and good electrical conductivity of the PbCO3/N-rGO nanocomposite improving the utilization of the positive active material (PAM).

Expanding the active charge carriers of polymer electrolytes in lithium-based batteries using an anion-hosting cathode

Ionic-conductive polymers are appealing electrolyte materials for solid-state lithium-based batteries. However, these polymers are detrimentally affected by the electrochemically-inactive anion migration that limits the ionic conductivity and accelerates cell failure. To circumvent this issue, we propose the use of polyvinyl ferrocene (PVF) as positive electrode active material. The PVF acts as an anion-acceptor during redox processes, thus simultaneously setting anions and lithium ions as effective charge carriers. We report the testing of various Li||PVF lab-scale cells using polyethylene oxide (PEO) matrix and Li-containing salts with different anions. Interestingly, the cells using the PEO-lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) solid electrolyte deliver an initial capacity of 108 mAh g−1 at 100 μA cm−2 and 60 °C, and a discharge capacity retention of 70% (i.e., 70 mAh g−1) after 2800 cycles at 300 μA cm−2 and 60 °C. The Li|PEO-LiTFSI|PVF cells tested at 50 μA cm−2 and 30 °C can also deliver an initial discharge capacity of around 98 mAh g−1 with an electrolyte ionic conductivity in the order of 10−5 S cm−1.

Regulating Polysulfide Diffusion and Deposition via Rational Design of Core-Shell Active Materials in Li-S Batteries.

Polar host materials with strong adsorption capacity of polysulfides are designed to limit the shuttle effect in sulfur cathodes. However, a critical problem is to control diffusion and deposition of lithium polysulfides during cycling, which significantly impacts cycling stability and sulfur utilization. Here, we report using a sequential adsorption-guided self-assembly to design two types of core-shell sulfur particles with opposite polysulfide adsorption gradients to explore quantitatively the regulation of polysulfide diffusion and deposition. We show that a positive core-shell design of sulfur particles (PCSD@SP), i.e., polysulfide adsorption capability decreasing from the interior to the exterior of the host, is more effective in restricting polysulfide diffusion and regulating polysulfide deposition than the negative core-shell counterpart (NCSD@SP). As a result, the PCSD@SP electrode with a sulfur loading of 7 mg cm-2 exhibits a stable areal capacity of 6 mAh cm-2 over 130 cycles at 0.2C. At intermittent discharge/charge, the PCSD@SP electrode retains excellent stability compared with the NCSD@SP. We conclude that rational design of positive core-shell active materials can be used to regulate polysulfide diffusion and deposition to boost electrochemical reaction dynamics and performance. The reported findings will be of immediate benefit to a range of researchers in the design of high-performance lithium-sulfur batteries.

Enabling fast-charging selenium-based aqueous batteries via conversion reaction with copper ions

Selenium (Se) is an appealing alternative cathode material for secondary battery systems that recently attracted research interests in the electrochemical energy storage field due to its high theoretical specific capacity and good electronic conductivity. However, despite the relevant capacity contents reported in the literature, Se-based cathodes generally show poor rate capability behavior. To circumvent this issue, we propose a series of selenium@carbon (Se@C) composite positive electrode active materials capable of delivering a four-electron redox reaction when placed in contact with an aqueous copper-ion electrolyte solution (i.e., 0.5 M CuSO4) and copper or zinc foils as negative electrodes. The lab-scale Zn | |Se@C cell delivers a discharge voltage of about 1.2 V at 0.5 A g−1 and an initial discharge capacity of 1263 mAh gSe−1. Interestingly, when a specific charging current of 6 A g−1 is applied, the Zn | |Se@C cell delivers a stable discharge capacity of around 900 mAh gSe−1 independently from the discharge rate. Via physicochemical characterizations and first-principle calculations, we demonstrate that battery performance is strongly associated with the reversible structural changes occurring at the Se-based cathode.