Battery-type Negative Electrode Research Articles

Comprehensive potentiodynamic analysis of electrodes performance in hybrid capacitors

A methodology which assesses the potentiodynamic characteristics of individual electrodes in hybrid capacitors (HCs) is introduced, using a Li-ion capacitor (LIC) as an example. Each electrode contribution was calculated from cyclic voltammetry (CV) measurements on a cell equipped with a reference electrode by adapting the procedure for electrical double-layer capacitors. It has been confirmed that, during the potentiodynamic analysis of a hybrid capacitor, the scan rate of the electrodes (dE+dt and dE-dt) is not constant in time. Furthermore, dE-dt tends to 0, while dE+dt aims to reach the rate of the voltage sweep (dUdt). By contrast, when the electrodes are analyzed separately at a constant potential scan rate, thevoltammogram of the battery-type negative electrode does not provide the same current response as ahybrid capacitor, where only the voltage ramp is controlled. The proposed methodology is fundamental for revealing any imbalance in the contributions of the electrodes and providing a correct representation of their current profiles during the potentiodynamic analysis of a hybrid cell.

Negative electrodes for supercapacitors with good performance using conductive bismuth-catecholate metal-organic frameworks.

Metal-organic frameworks (MOFs) have attracted increasing research interest in various fields. Unfortunately, the poor conductivity of most traditional MOFs considerably hinders their application in energy storage. Benefiting from the full charge delocalization in the atomic plane, two-dimensional conductive coordination frameworks achieve good electrochemical performance. In this work, π-π coupling conductive bismuth-catecholate nanobelts with tunable lengths, Bi(HHTP) (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene), are synthesized by a simple hydrothermal reaction and their length-dependent electrochemical properties are also investigated. The Bi(HHTP) nanobelts (about 10 μm in length) possess appropriate porosity, numerous redox active sites and good electrical conductivity. Being a negative electrode for supercapacitors, Bi(HHTP) nanobelts display a high specific capacitance of 234.0 F g-1 and good cycling stability of 72% after 1000 cycles. Furthermore, the mechanism of charge storage is interpreted for both battery-type and surface-capacitive behavior. It is believed that the results of this work will help to develop battery-type negative electrode materials with promising electrochemical performance using some newly designed π-π coupling conductive coordination frameworks.

An ultrahigh-energy-density lithium metal capacitor

Lithium-ion capacitors (LICs), shrewdly integrating a battery-type negative electrode and a capacitive-type carbon positive electrode, are expected to inherit simultaneously both the high specific energy of lithium-ion batteries (LIBs) and high specific power of electrochemical capacitors (ECs). However, state-of-the-art LICs are approaching their specific energy limits yet are still far away from that dictated by LIBs. Herein, we report an aprotic Li-metal capacitor (LMC) strategy to solve this problem through coupling a Li-metal negative electrode with a three-dimensional scaffold activated carbon (3D-SAC) positive electrode. The employment of metal Li negative electrode leads to an ultrahigh specific capacitance up to 280 F gpositive electrode−1 within high potential range from 1.5 to 4.3 V vs Li/Li+, giving a remarkable specific energy of 633 Wh kgpositive electrode−1. Combing with theoretical simulation and advanced characterizations, it is revealed that such a high capacitance is the contribution resulting from multiple electrical double-layer mechanisms on carbon positive electrode that involves the desorption of PF6− anions, the exchange between adsorbed PF6− anions and solvated cation clusters, and the adsorption of solvated cation clusters. The unique desolvation behavior and the electrochemical adsorption of desolvated Li+-related cations boost the specific capacitance and specific energy at low current rates. This is completely different from the reported LICs. This findings provide a new strategy for developing high-energy-and-power capacitors and batteries.

Construction of mesoporous bimetallic (Ni, Co) organic framework microspheres for lithium-ion capacitors

Rational design of appropriate negative electrode materials with high rates and long cycle life is essential to construct advanced lithium-ion capacitors (LICs). Herein, we solvothermally synthesize the bimetallic (Ni, Co) organic framework (NiCo-MOF) microspheres by using the polyvinylpyrrolidone as a structure-directing agent towards advanced LICs as a battery-type negative electrode. Benefiting from its rigid structure stability, high crystallinity, rich electroactive sites and high-content mesopores, the NiCo-MOF electrode obtains a large reversible capacity of ~557.1 mAh g−1 at 0.1 A g−1. Furthermore, the NiCo-MOF based LICs display a high SC of ~58.2 F g−1 at ~1.0 A g−1, along with an exceptional capacitance retention over 8500 cycles at 1.0 A g−1. More significantly, the contribution here will stimulate extensive development of versatile MOF microspheres for next-generation LICs and beyond.

Highly Reversible Na-Intercalation into Graphite Recovered from Spent Li-Ion Batteries for High-Energy Na-Ion Capacitor.

High-performance Na-ion capacitor (NIC) was constructed with graphite recovered from spent Li-ion batteries (LIBs) as battery-type negative electrode and high-surface-area activated carbon as a supercapacitor component. Unlike Li-insertion into graphite, Na-insertion into graphite is extremely limited; hence, a "solvent-co-intercalation" mechanism was proposed for high reversibility using ether family solvents. First, the Na-insertion properties were assessed in the half-cell assembly with 0.5 m NaPF6 in tetraethylene glycol dimethyl ether as an electrolyte solution and compared with the commercial graphite. The NIC comprised pre-sodiated graphite as a negative electrode and commercial activated carbon as a cathode. This fascinating NIC configuration displayed the maximum energy density of 59.93 Wh kg-1 with exceptional cyclability of 5000 cycles at ambient temperature with approximately 98 % retention. Interestingly, the electrode aging process in the presence of electrolyte resulted in approximately 19 % higher energy density than the routine electrode heat treatment. Further, the electrochemical activity of the NIC at various temperatures was studied, and it was found that the graphite recovered from spent LIBs could be effectively reused towards the construction of high-performance charge storage devices with exceptional performance.

High performance asymmetric supercapacitor based on vertical nanowire arrays of a novel Ni@Co–Fe LDH core@shell as negative and Ni(OH)2 as positive electrode

An efficient synthesis of the electrode material with abundant active sites is imperative for obtaining a flexible supercapacitor with excellent electrochemical performance. Herein, a novel flexible Ni@Co–Fe LDH core–shell nanowires supercapacitor negative electrode is synthesized using polycarbonate membrane on a copper substrate via an electrochemical deposition technique. The synthesized battery-type negative electrode exhibits remarkable specific capacitance of 1289 F g−1 at 1 A g−1 and excellent cycling stability with 76.66% capacitive retention after 5000 cycles. Furthermore, the Ni(OH)2//Ni@Co–Fe LDH nanowires based asymmetric supercapacitor exhibits excellent cycling stability of 90.49% after 1000 cycles with a highest energy density of 68 Wh kg−1 at 0.38 KW kg−1, and a good energy density of 31.8 Wh kg−1 is still attained at a high power density of 6 KW kg−1. For practical demonstration, a white LED of 3.3 V is lit by using two asymmetrical supercapacitor devices connected in series. The device offers a favorable and effective pathway for advanced energy storage.

High performance hybrid sodium-ion capacitor with tin phosphide used as battery-type negative electrode

A novel hybrid Na-ion capacitor (NIC), in which Sn4P3 is implemented as battery-type negative electrode together with activated carbon as positive electrical double-layer electrode, is disclosed. Sn4P3 was formed by high-energy ball milling in Ar atmosphere, which allows the Sn4P3-based electrodes to display the lowest irreversible capacity (80 mAh g−1) today reported. The NIC demonstrates stable performance in the voltage range from 2.2 V to 3.8 V, with 94% capacitance retention after 6500 galvanostatic cycles at 0.2 A g−1 (per total mass of electrodes). At specific power of 1 kW kg−1, it displays a specific energy of 39 Wh kg−1, against only 7 Wh kg−1 for the EDLC based on the same activated carbon electrodes. These metrics are superior to any of the values reported for NICs in the literature. Hence, the realized AC//Na–Sn4P3 NIC shows the possibility of developing a next-generation of low cost and safe high-power and energy storage devices.

The influence of electrode matching on capacity decaying of hybrid lithium ion capacitor

Hybrid lithium-ion capacitors (HyLICs), combining a battery-type negative electrode and a composite positive electrode, can display a more comprehensive performance than conventional lithium-ion capacitors (LICs), e.g. high energy density. However, owing to the coexisting of non-Faradaic and Faradaic energy storage mechanism in the composite positive electrode, the insufficient cycle stability of device becomes an urgent problem. In this paper, we discussed the influence of electrode matching on the cycling stability of HyLICs with a L30/HC@SLMP structure. The three L30/HC mass ratios were 0.8, 1.0 and 1.2, respectively. Three full cells with above ratios exhibit great difference in cycle stability when charging/discharging at a current density of 1 A g−1. Various methods, including galvanostatic charging/discharging, three-electrodes test and scanning electron microscopy, were used to analyze the performance of difference cells. It turns out that the poor rate performance of HC electrode is the main limited factor in HyLICs' cycling stability. Compared with the composite positive electrode, HC electrode is more sensitive to the current densities. Under high current density, solid electrolyte interface layers on the HC electrode surface accumulated fast, which leads to the increase in the impedance of HC electrode. From the Ragone plot, the best matching strategy of L30/HC electrode was achieved when the mass ratio of L30/HC was 1.0. Finally, the optimal HyLICs with L30/HC mass ratio of 1.0 were assembled and performed an excellent cycle stability of more than 80% retention after 62,000cycles in 40C, as well as better power and energy density compared with LICs.

Reduced graphene oxide decorated with SnO2 nanoparticles as negative electrode for lithium ion capacitors

The effort to increase the energy density of conventional electric double-layer capacitors (EDLCs) goes through the development of lithium-ion capacitors (LICs). Herein, we report a self-standing, binder-free composite as the battery-type negative electrode obtained by a low-cost and easily scalable method. Tin(IV) oxide nanoparticles (<10 nm) embedded in a reduced graphene oxide matrix (SnO2-rGO) were prepared by an in-situ synthetic approach that involves the freeze/freeze-drying of a graphene oxide suspension in the presence of a tin precursor and its subsequent thermal reduction under argon atmosphere. Physicochemical and electrochemical characterization confirmed the optimum nano-structuration of the composite showing ultrafast response at high current densities. Its coupling with a highly porous olive pits waste-derived activated carbon (AC) as the capacitor-type positive electrode, enables the fabrication of a LIC with an excellent energy density output. The newly designed LIC is able to deliver 60 Wh kg−1 at 2.9 kW kg−1 (tdischarge ≈ 1 min) and still 27 Wh kg−1 at 10.6 kW kg−1 (tdischarge ≈ 10 s).

(Invited) Redox-Active Carbon Positive Electrodes for High-Performance Hybrid Supercapacitors

Hybrid supercapacitors combine the advantages of lithium-ion batteries and electrochemical capacitors to achieve both high energy density and power density. However, the overall energy density is limited by the low capacity of the carbon-based positive electrodes. We have been trying to improve the energy density of the carbon-based positive electrodes by incorporating surface reactions into nanocarbon materials, including carbon nanotube and graphene. Recently, we have demonstrated the redox-active carbon positive electrodes by coating functional polymers on the surface of carbon nanotubes.1 ,2 This presentation introduces shape-controlled carbon materials with significantly enhanced charge storage performance. We also demonstrate high-performance hybrid supercapacitors by combining the redox-active carbon positive electrode with the battery-type negative electrode. References J. C. Bachman, R. Kavian, D. J. Graham, D. Y. Kim, S. Noda, D. G. Nocera, Y. Shao-Horn and S. W. Lee, Nature Communications, 6:7040 (2015).T. Liu, K. C. Kim, B. Lee, Z. Chen, S. Noda, S. S. Jang and S. W. Lee, Energy & Environmental Science, 10, 205 (2017).

Aqueous based solid battery-capacitor asymmetrical system for capacitive energy storage device

Battery-capacitor asymmetrical systems, using Zn as battery-type negative electrode and CNT as capacitor-type positive electrode are developed with both aqueous and solid polymer based electrolytes. The devices combine the merits of both electrodes: The Zn electrode contributed 1.6 V cell voltage, while the CNT electrode results in fast and reversible capacitive behavior. An all-solid asymmetrical system is demonstrated using a PVA-TEAOH polymer electrolyte and exhibit high power capability and long cycle life. The good capacitive behavior, excellent stability upon 10,000 cycles of charge and discharge, and high cell voltage suggest a promising system for thin film solid energy storage applications.

First prototypes of hybrid potassium-ion capacitor (KIC): An innovative, cost-effective energy storage technology for transportation applications

Hybrid supercapacitors, combining capacitive carbon-based positive electrode with a Li-ion battery-type negative electrode have been developed in the pursuit of increasing the energy density of conventional supercapacitor without impacting the power density. However, lithium-ion capacitors yet hardly meet the specifications of automotive sector. Herein we report for the first time the development of new hybrid potassium-ion capacitor (KIC) technology. Compared to lithium-ion capacitor (LIC) all strategic materials (lithium and copper) have been replaced. Excellent electrochemical performance have been achieved at a pouch cell scale, with cyclability superior to 55 000 cycles at high charge/discharge regime. For the same cell scale, the energy density is doubled compared to conventional supercapacitor up to high power regime (>1.5 kW kg−1). Finally, the technology was successfully scaled up to 18650 format leading to very promising prospects for transportation applications.

Capacitance of Fe3O4/rGO nanocomposites in an aqueous hybrid electrochemical storage device

Hybrid electrochemical storage devices comprising a capacitor-type positive electrode and a battery-type negative electrode are regarded as a promising concept combining high power density with high energy density. In this work Fe3O4/reduced graphene oxide (rGO) nanocomposite has been synthesized and applied as negative electrode in an electrochemical energy storage device being a serial internal hybrid of an alkaline battery and an electrochemical double layer capacitor (EDLC). Beneficial effect of graphene on the performance of magnetite electrode has been evidenced by means of cyclic voltammetry, galvanostatic cycling and electrochemical impedance spectroscopy techniques. Unlike in a vast majority of reports, magnetite capacitances have been determined in real electrochemical devices, against activated carbon as positive electrode. In three-electrode cells with activated carbon as the positive electrode magnetite has been found to exhibit from 65 to 83 F g−1 for the rGO content from 9.7 to 27.8 %. The maximum voltage of a capacitor with Fe3O4/rGO negative electrode has been established as 1.0 V, which is higher than typical value of 0.8 V known for the symmetrical carbon-based capacitors.

00/02597 Concrete decontamination and other D&D applications of electric pulse power technology

Hybrid supercapacitors, combining capacitive carbon-based positive electrode with a Li-ion battery-type negative electrode have been developed in the pursuit of increasing the energy density of conventional supercapacitor without impacting the power density. However, lithium-ion capacitors yet hardly meet the specifications of automotive sector. Herein we report for the first time the development of new hybrid potassium-ion capacitor (KIC) technology. Compared to lithium-ion capacitor (LIC) all strategic materials (lithium and copper) have been replaced. Excellent electrochemical performance have been achieved at a pouch cell scale, with cyclability superior to 55 000 cycles at high charge/discharge regime. For the same cell scale, the energy density is doubled compared to conventional supercapacitor up to high power regime (>1.5 kW kg−1). Finally, the technology was successfully scaled up to 18650 format leading to very promising prospects for transportation applications.