Li-ion Hybrid Capacitors Research Articles

Advanced Li-ion hybrid capacitors based on the nanostructured ruthenium oxide on MWCNTs

Here, the porous ruthenium oxide/multi-walled carbon nanocomposite (RuO2/MWCNT) was prepared using a facile precipitation method. The RuO2/MWCNT showed high specific capacity, outstanding rate performance and long cycling stability under a Li-ion organic electrolyte. Thus, advanced Li-ion hybrid capacitors (LIHCs) were successfully constructed with RuO2/MWCNT anode and activated ployaniline derived carbon (APDC) cathode under a Li-ion organic electrolyte. The LIHCs exhibited a highest energy density of 146 Wh kg−1 and a highest power densities of 33 kW kg−1, with excellent cyclic stability (∼100% at 2.0 A g−1 after 15,000 cycles), which exhibited better performance than other LIHCs systems.

High-energy aqueous Li-ion hybrid capacitor based on metal-organic-framework-mimicking insertion-type copper hexacyanoferrate and capacitive-type graphitic carbon electrodes

A high-performance aqueous Li-ion hybrid capacitor (LHC) using sonochemically prepared copper hexacyanoferrate (Cu-HCF) and sodium alginate-derived graphitic carbon (GC) nanoparticles are capable of serving as positive and negative electrodes, respectively, is described in this report. The electrode materials were prepared in a cost-effective manner and characterized using X-ray diffraction (XRD) and Fourier transform-infrared spectroscopy (FT-IR). High-resolution transmission electron microscopy (HR-TEM) and surface area measurements revealed the formation of 30- to 60-nm Cu-HCF and 40- to 60-nm GC particles with specific surface areas of 48 and 802 m2g–1, respectively. Electrochemical studies including cyclic voltammetry (CV), galvanostatic charge-discharge (CD) analysis and electrochemical impedance spectroscopy (EIS) using a three-electrode configuration confirmed the presence of intercalative capacitance in the Cu-HCF electrode and double-layer capacitance in the GC electrode. Furthermore, the constructed Cu-HCF‖GC aqueous LHC system operates over a wide voltage window (2.2 V) and delivers a high capacitance (63.64 F g−1) and high energy density (42.78 Wh kg−1) with a good rate capability. These key features make the LHC system an ideal candidate for next-generation electrochemical energy storage devices.

Fabrication of high energy Li-ion hybrid capacitor using manganese hexacyanoferrate nanocubes and graphene electrodes

Herein, we demonstrated a facile sonochemical preparation of manganese hexacyanoferrate (Mn-HCF) and examined its use as an intercalative-type electrode for Li-ion hybrid capacitors (LHCs). The X-ray diffraction, field-emission scanning electron microscopy, and X-ray photoelectron spectroscopic analyses revealed the formation of Mn-HCF nanocubes. The electrochemical analyses revealed the presence of ion-intercalation pseudocapacitance in the Mn-HCF electrode with a specific capacity of 81.59mAhg−1. In the view of practical applications, we designed a Mn-HCF∥graphene LHC which delivered a high specific capacitance (79.52Fg−1) and energy density (44.18Whkg−1), respectively. Overall, our results highlight the significance of Mn-HCF towards cost-effective energy storage devices.

The orientation construction of S and N dual-doped discoid-like graphene with high-rate electrode property

The orientation construction of S and N dual-doped discoid-like graphene (labeled as SNDG) is achieved by regular arrangement of the polycyclic aromatics in pitch molecules using natural diatomites as templates. The superior electrochemical energy storage ability of SNDG is demonstrated by cathode and anode tests, respectively. The synergistic effects of the robust scaffold coupled with the hollow structure, unique porous structure, the excellent structural stability and the dual-doping of S and N lead to the electrode property enhancement in terms of rate capability and durability. The Li ion hybrid capacitor using SNDG as both anode and cathode, presents excellent long-term cycling stability and markedly energy and power densities (up to 143 Wh kg−1 and 13,548 W kg−1). This work provides a novel pathway to realize the mass production of high-rate electrode materials via the high value-added utilization of pitch.

Li2NiTiO4: A New Insertion type Pseudocapacitive Electrode for Aqueous Lithium-Ion Capacitors

Prabaharan et al first reported on the possibility of using a rocksalt type Li2NiTiO4 as a positive electrode for Li-Ion batteries and proven that the redox energy for the reaction Ni2+/4+ and Ti4+/3+ would favour facile redox reactions. We present here our first report on the possibility of using Li2NiTiO4 as pseudocapacitive electrode in Li based aqueous electrolyte and demonstrate the electrochemical properties of Li-Ion hybrid capacitor. Nanoparticles of Li2NiTiO4 have been synthesized by adopting a modified solvothermal process. The prepared Li2NiTiO4 nanoparticles were used as electrode material against a pure porous carbon electrode (AC) as Li-Ion capacitor couple, Li2NiTiO4//AC with a potential window of ∼1.6 V in aqueous electrolyte. Specific capacitance of Li2NiTiO4 was measured using a three electrode cell in Li+ alkaline electrolytes against Ag reference electrode. Electrochemical performance of the asymmetric capacitive couple was evaluated through constant current charge/discharge, cyclic voltammetry and ac impedance measurements. A hybrid Li-Ion capacitor Li2NiTiO4//AC was fabricated and studied for its capacitive performance. The electrochemical limitation of the potential window in aqueous medium < 1V is extended up to 1.6V by combining two different materials which predominantly enhances the energy density of the device. More specifically the asymmetric cell exhibits good cycling stability and high rate capability even at high scan rates.

In‐Plane Assembled Orthorhombic Nb2O5 Nanorod Films with High‐Rate Li+ Intercalation for High‐Performance Flexible Li‐Ion Capacitors

AbstractOrganic hybrid supercapacitors that consist of a battery electrode and a capacitive electrode show greatly improved energy density, but their power density is generally limited by the poor rate capability of battery‐type electrodes. In addition, flexible organic hybrid supercapacitors are rarely reported. To address the above issues, herein an in‐plane assembled orthorhombic Nb2O5 nanorod film anode with high‐rate Li+ intercalation to develop a flexible Li‐ion hybrid capacitor (LIC) is reported. The binder‐/additive‐free film exhibits excellent rate capability (≈73% capacity retention with the rate increased from 0.5 to 20 C) and good cycling stability (&gt;2500 times). Kinetic analyses reveal that the high rate performance is mainly attributed to the excellent in‐plane assembly of interconnected single‐crystalline Nb2O5 nanorods on the current collector, ensuring fast electron transport, facile Li‐ion migration in the porous film, and greatly reduced ion‐diffusion length. Using such a Nb2O5 film as anode and commercial activated carbon as cathode, a flexible LIC is designed. It delivers both high gravimetric and high volumetric energy/power densities (≈95.55 Wh kg−1/5350.9 W kg−1; 6.7 mW h cm−3/374.63 mW cm−3), surpassing previous typical Li‐intercalation electrode‐based LICs. Furthermore, this LIC device still keeps good electrochemical attributes even under serious bending states (30°–180°).

Design and Construction of Novel High-Performance Li-Ion Hybrid Supercapacitors Based on 3D Graphene Composites

Li-ion hybrid capacitors (LIHCs) as a novel and promising energy storage unit, consisting of a Li-ion battery type anode and an electrochemical double layer capacitance (EDLC) type cathode, has attracted enormous research attentions. However, it remains a significant challenge to obtain high-performance LIHCs due to most battery-type anodes with the sluggish kinetics of Li-ion storage and low specific capacitance of common capacitor-type cathodes. Thus, it is highly required to design and fabricate novel alternative high-performance battery type anode materials and capacitor-type cathode materials, able to deliver higher energies and power densities in organic electrolyte. In this work, a novel high-performance LIHCs is constructed by combining a Li-ion battery type anode (3D graphene/MoO3 nanocomposite) with a capacitor type cathode (3D graphene/PANI derived carbon material). Such a subtle design endow LIHCs with a wide voltage range of (3.8 V), a high energy density of 128.3 Wh·kg-1, and an ultra-long cycle life up to 3000 cycles with 87% capacity retention.

Improved flexible Li-ion hybrid capacitors: Techniques for superior stability

Flexible power devices play an increasingly crucial role in emerging flexible electronics. To improve the electrochemical performance of flexible power devices, novel electrode structures and new energy-storage systems should be designed. Herein, a novel flexible Li-ion hybrid capacitor (LIC) is designed based on an anode comprising Li4Ti5O12 nanoplate arrays coated on carbon textile (LTO/CT) and a cathode comprising a flexible N-doped graphene/carbon-nanotube composite (NGC) film. The LTO/CT anode is fabricated by directly growing Li4Ti5O12 nanoplates on CT with robust adhesion using a simple one-pot hydrothermal reaction. Considering the volume of a real-device flexible LIC, the NGC//LTO/CT configuration delivers high volumetric energy and power densities of 2 mWh·cm−3 and 185 mW·cm−3, respectively. Furthermore, the flexible LIC shows excellent flexibility and electrochemical stability, with extremely small capacity fluctuation under different bending states. This work demonstrates a scalable route to assemble flexible LICs as high-performance power devices.

Engineering layer structure of MoS2-graphene composites with robust and fast lithium storage for high-performance Li-ion capacitors

Two dimensional layered MoS2 has demonstrated great promise as an ideal alternative to graphite-based anodes for hybrid Li-ion capacitors and Li-ion batteries. Research effort on this material has focused mainly on synthesizing highly nanostructured MoS2 that allows reducing the dimensions into nanoscale to cross over the sluggish kinetics of Li-ion charge storage. Herein, we engineer the layer structure of MoS2 to preferentially expand the interlayer distance to increase atomic interface contact/interaction by successfully inserting amorphous carbon layer into adjacent MoS2 monolayers. This interlayer modified MoS2 is demonstrated to have the predominantly pseudocapacitive characteristics and can get further gains in Li-ion storage properties through incorporating reduced graphene oxide (RGO). Thus, a novel hybrid Li-ion capacitor is fabricated by employing this MoS2-RGO composite as the anode and activated carbon as the cathode, which exhibits an ultrahigh specific energy density of 188Whkg-1 at 200Wkg-1 and remains 45.3Whkg-1 even at a high specific power density of 40,000Wkg-1 as well as long cycle life. This work shows that engineering interlayer structure and introducing conductive graphene can significantly impact the Li-ion storage properties, enabling new opportunities for designing newly advanced MoS2 anodes for next-generation energy storage devices.

Nano-sized Mo- and Nb-doped TiO2 as anode materials for high energy and high power hybrid Li-ion capacitors

Nano-sized Mo-doped titania (Mo0.1Ti0.9O2) and Nb-doped titania (Nb0.25Ti0.75O2) were directly synthesized via a continuous hydrothermal flow synthesis process. Materials characterization was conducted using physical techniques such as transmission electron microscopy, powder x-ray diffraction, x-ray photoelectron spectroscopy, Brunauer–Emmett–Teller specific surface area measurements and energy dispersive x-ray spectroscopy. Hybrid Li-ion supercapacitors were made with either a Mo-doped or Nb-doped TiO2 negative electrode material and an activated carbon (AC) positive electrode. Cells were evaluated using electrochemical testing (cyclic voltammetry, constant charge discharge cycling). The hybrid Li-ion capacitors showed good energy densities at moderate power densities. When cycled in the potential window 0.5–3.0 V, the Mo0.1Ti0.9O2/AC hybrid supercapacitor showed the highest energy densities of 51 Wh kg−1 at a power of 180 W kg−1 with energy densities rapidly declining with increasing applied specific current. In comparison, the Nb0.25Ti0.75O2/AC hybrid supercapacitor maintained its energy density of 45 Wh kg−1 at 180 W kg−1 better, showing 36 Wh g−1 at 3200 W kg−1, which is a very promising mix of high energy and power densities. Reducing the voltage window to the range 1.0–3.0 V led to an increase in power density, with the Mo0.1Ti0.9O2/AC hybrid supercapacitor giving energy densities of 12 Wh kg−1 and 2.5 Wh kg−1 at power densities of 6700 W kg−1 and 14 000 W kg−1, respectively.

A novel high energy hybrid Li-ion capacitor with a three-dimensional hierarchical ternary nanostructure of hydrogen-treated TiO2 nanoparticles/conductive polymer/carbon nanotubes anode and an activated carbon cathode

Lithium ion capacitors (LICs) are considered to be high-performance energy storage devices that have stimulated intense attention to bridge the gap between lithium ion battery and supercapacitor. Currently, the major challenge for LICs has been to improve the energy density without sacrificing the high rate of power output performance. Herein, we designed a three-dimensional (3D) hierarchical porous nanostructure of hydrogen-treated TiO2 nanoparticles wrapped conducting polymer polypyrrole (PPy) framework with single-walled carbon nanotubes (SWCNTs) hybrid (denoted as, H-TiO2/PPy/SWCNTs) anode material for LICs through a conventional and green approach. Such a unique network can offer continuous electron transport and reduce the diffusion length of lithium ions. A greatly lithium storage specific capacity is achieved with reversible discharge capacity ∼213 mA h g−1 (based on the mass of TiO2) over 50 cycles (@ 0.1 A g−1), which is almostly three times compared with raw TiO2 (a commercial TiO2 nanoparticles powder). In addition, coupled with commercial activated carbon (AC) cathode, the fully assembled H-TiO2/PPy/SWCNTs//AC LICs delivers a maximum energy and power densities of 31.3 Wh kg−1 and 4 kW kg−1, a reasonably good cycling stability (∼77.8% retention after 3000 cycles) within the voltage range of 1.0–3.0 V.

A hybrid electrochemical device based on a synergetic inner combination of Li ion battery and Li ion capacitor for energy storage

Li ion battery (LIB) and electrochemical capacitor (EC) are considered as the most widely used energy storage systems (ESSs) because they can produce a high energy density or a high power density, but it is a huge challenge to achieve both the demands of a high energy density as well as a high power density on their own. A new hybrid Li ion capacitor (HyLIC), which combines the advantages of LIB and Li ion capacitor (LIC), is proposed. This device can successfully realize a potential match between LIB and LIC and can avoid the excessive depletion of electrolyte during the charge process. The galvanostatic charge-discharge cycling tests reveal that at low current, the HyLIC exhibits a high energy density, while at high current, it demonstrates a high power density. Ragone plot confirms that this device can make a synergetic balance between energy and power and achieve a highest energy density in the power density range of 80 to 300 W kg−1. The cycle life test proves that HyLIC exhibits a good cycle life and an excellent coulombic efficiency. The present study shows that HyLIC, which is capable of achieving a high energy density, a long cycle life and an excellent power density, has the potential to achieve the winning combination of a high energy and power density.

Eliminating pre-lithiation step for making high energy density hybrid Li-ion capacitor

Abstract Pre-lithiation is an indispensable step for making hybrid lithium-ion capacitors (LICs), its high cost and process complexity have greatly hindered the commercialization of LICs. Aiming to eliminate the pre-lithiation step, we propose an in-situ lithiation concept by introducing a Li + ion source material into the positive electrode to enable the lithiation to be completed in the formation cycle. In this paper we start with the fundamental principle of LICs to discuss the requirements for Li + ion source materials and demonstrate this concept by employing Li-rich Li 2 CuO 2 as the Li + ion source material, natural graphite and activated carbon (AC) as the negative and positive electrode materials. It is shown that the LICs made such behave as a pure capacitor with ability to deliver the same level of specific capacity and specific capacitance, i.e., 56 mAh g −1 and 143 F g −1 vs. the mass of AC in the voltage range between 2.8 V and 4.2 V, as those obtained from the counterpart Li/AC half-cell. The present concept is also applicable to other LICs with the negative electrode required to be pre-lithiated.

Preparation of a NbN/graphene nanocomposite by solution impregnation and its application in high-performance Li-ion hybrid capacitors

Freestanding NbN/graphene papers were used in Li-ion hybrid capacitors and exhibit high energy density and power density.

Engineering metal organic framework derived 3D nanostructures for high performance hybrid supercapacitors

A high-performance hybrid Li-ion capacitor was fabricated based on a metal–organic framework derived 3D porous carbon polyhedron and MoS2–ZIF nanostructures.

Fabrication of High‐Performance Aqueous Li‐Ion Hybrid Capacitor with LiMn2O4 and Graphene

AbstractIn this study, we fabricated an aqueous Li‐ion hybrid capacitor (LHC) by using LiMn2O4 and sonochemically reduced graphene as the positive and negative electrodes, respectively. The X‐ray diffraction pattern and Raman analyses were performed to identify the phase, crystallinity, and bonding nature of the prepared LiMn2O4 and sonochemically reduced graphene. Electrochemical characterization, such as cyclic voltammetry and electrochemical impedance spectroscopy, for the LiMn2O4 and graphene was performed by using a three‐electrode configuration. Furthermore, asymmetric LiMn2O4∥graphene LHC was fabricated and tested for its device performance. The galvanostatic charge‐discharge analysis shows that the fabricated LiMn2O4∥graphene LHC device delivered a high specific capacitance of 59.45 F g−1 at a constant discharge current density of 0.4 A g−1 with a better coulombic efficiency of 97.9 %. The LiMn2O4∥graphene LHC device delivered a high specific energy of 39.96 Wh kg−1 at a power of 440 W kg−1 with better capacitance retention of 90.24 % even after 1000 cycles.

Hierarchical Hydrogen Titanate Nanowire Arrays/Anatase TiO2 Heterostructures as Binder-Free Anodes for Li-ion Capacitors

Well-aligned hierarchical heterostructures composed of hydrogen titanate (H2Ti2O5·H2O, labeled as HTO) nanowire stems and anatase TiO2 nanoparticle branches (HTO/TiO2 NWAs) have been synthesized successfully on Ti-foil substrate as additive-free electrodes for hybrid Li-ion capacitors (LICs). The inner 3D HTO conductive scaffold consisted of vertically aligned nanowires and porous rooftop network is beneficial to large capacitance. Moreover, the countless anatase TiO2 particles on the surface of HTO nanowires can enrich electro-active sites, reduce the ion and electron resistance, shorten Li-ion transport pathways and enhance structural stability. Owning to the synergistic effects of HTO and anatase TiO2, the electrodes deliver large capacitance, superior rate capability and excellent cycle stability. The HTO/TiO2//AC (activated carbon) hybrid system presents fascinating energy density (84.7 Wh kg−1 at 0.5A g1) and ultralong lifespan (78.5% capacity retention after 10000 cycles at 10.0Ag−1 within 0.0-4.0V). Even at high power density of 20kWkg−1, an excellent energy density of 44.4 Wh kg−1 can be retained. Thus, the LIC assembled with HTO/TiO2 NWAs anode and AC cathode can be a potential candidate as high-performance energy storage application.

Electrochemical behavior and stability of a commercial activated carbon in various organic electrolyte combinations containing Li-salts

The fast development of Li-ion capacitor (LIC) technologies requires the use of low resistance and stable electrolytes. An electrolyte for a LIC not only has to provide Li for the intercalation/deintercalation of the battery-type materials, but it also needs to be compatible with the supercapacitor material. Before designing a hybrid Li-ion capacitor device containing Li-insertion and double layer-type materials, it is necessary to understand and separate the contribution of each electrode material to the resistance, capacity and stability in the chosen electrolyte. Due to the intensive research on Li-ion batteries, the interactions of Li-salt containing electrolytes combined with Li insertion materials have been extensively investigated, and a lot of literature is available on this field. In contrast, there is only little knowledge about the exclusive interaction and compatibility of Li containing electrolytes with supercapacitor-type electrode materials (in absence of battery materials). With this purpose, this paper explores the electrochemical performance of electrodes based on commercial activated carbon (AC) in various lithium salt-containing electrolytes. A standard electrolyte for Li-ion batteries (1M LiPF6 in EC:DMC, 1:1) is evaluated and compared with an electrolyte prepared with the same salt dissolved in propylene carbonate (1M LiPF6 in PC) which is a solvent typically used in commercial supercapacitors. Furthermore, two new electrolyte solutions are proposed, based on a blend of salts 0.8M LiPF6+0.2M NEt4BF4 in EC:DMC (1:1) as well as in pure PC. The effect of the electrolyte composition is evaluated in half and full cells. Resistances, rate capabilities, the electrochemical stability window (ESW) and cycling abilities of activated carbon electrodes are compared in different electrolytes using electrochemical impedance spectroscopy (EIS), cyclic voltammetry and galvanostatic cycling techniques. Among all electrolytes, 1M LiPF6 in PC displays the best performance with the widest ESW and an excellent cycling stability, retaining 75% of its initial capacitance after 20 000 cycles. However, due to its high viscosity, PC-based electrolytes show higher resistances in comparison to EC/DMC-based electrolytes. These results are the basis for further investigation on organic Li-salt containing electrolytes for the development of hybrid supercapacitor technology in which activated carbon and Li-insertion materials are combined together.

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 polyaniline-derived 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 143Whkg−1 at a working voltage of 1–4V. 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 0.5Ag−1.

Surfactant-free hydrothermal synthesis of hierarchically structured spherical CuBi2O4 as negative electrodes for Li-ion hybrid capacitors

Hierarchically structured spherical CuBi2O4 particles were prepared using a facile hydrothermal method without using a surfactant over various hydrothermal reaction periods. The prepared CuBi2O4 samples were examined via X-ray diffraction (XRD), which confirmed the formation of a tetragonal crystal structure. The morphological features were analyzed using field emission scanning electron microscopy (FESEM), which elucidated the construction of the hierarchical microspherical CuBi2O4 particles. The plausible growth mechanism of the hierarchical structure was explained in terms of a time-dependent synthesis process and its crystal structure. The uniform hierarchical CuBi2O4 microspheres were used to fabricate a Li-ion hybrid capacitor (Li-HC) along with activated carbon (AC), the generated device delivers a stable specific capacitance of 26.5Fg−1 over 1500 cycles at a high current density of 1000mAg−1 and a capacity retention of ∼86%. The AC/CB2 Li-ion hybrid cell exhibits high energy density and power density values of 24Whkg−1 and 300Wkg−1, respectively.