Copper Phosphide Nanostructures Covalently Modified Ti3 C2 Tx for Fast Lithium-Ion Storage by Enhanced Kinetics and Pesudocapacitance

2D layer Ti3 C2 Tx material attracts enormous attention in lithium ion energy storage field owing to the unique surface chemistry properties, but the material still suffers from restacking issue and the restriction on capacity. Herein, copper phosphide (Cu3 P) nanostructures@Ti3 C2 Tx composites are prepared by the in situ generation of Cu-BDC precursor in the bulk material followed with phosphorization. The uniformly distributed copper phosphide nanostructures effectively expand the interlayer spacing promoting the structural stability, and achieves the effective connection with the bulk material accelerating the diffusion and migration of lithium ions. The electrochemical activity of Cu3 P also provides more lithium ion active sites for lithium storage. The X-ray photoelectron spectroscopy (XPS) analysis verifies that Ti─O─P bond with strong covalency allows the upper shift of maximum valence band and Fermi level, stimulating the charge transportation between Cu3 P and the bulk Ti3 C2 Tx for better electrode kinetics. 3Cu3 P@Ti3 C2 Tx exhibits excellent rate performance of 165.4 mAh g-1 at 3000 mA g-1 and the assembled 3Cu3 P@Ti3 C2 Tx //AC Lithium-ion hybrid capacitorsLIC exhibits superior energy density of 93.0 Wh kg-1 at the power density of 2367.3 W kg-1 . The results suggest that the interfacial modification of Ti3 C2 Tx with transition metal phosphides will be advantageous to its high energy density application in lithium-ion storage.

Explosion Strategy Engineering Oxygen-Functionalized Groups and Enlarged Interlayer Spacing of the Carbon Anode for Enhanced Lithium Storage

Amorphous carbon monoliths with tunable microstructures are candidate anodes for future lithium-based energy storage. Enhancing lithium storage capability and solid-state diffusion kinetics are the precondition for practical applications. Transforming intrinsic oxygen-rich defects into active sites and engineering enlarged interlayer spacing are of great importance. Herein, a novel explosion strategy is designed based on oxalate pyrolysis producing CO and CO₂ to successfully prepare lignin-derived carbon monolith (LSCM) with active carbonyl (C═O) groups and enlarged interlayer spacing. Explosion promotes the demethylation of methoxyl groups and cleavage of carboxyl groups to form C═O groups. CO₂ etches carbon atoms in a short time to improve the heteroatom level, expanding the interlayer spacing. ZnC₂O₄ is decomposed at 400 °C, simultaneously producing CO and CO₂, which constructs less C═O groups and large interlayer spacing. MgC₂O₄ is decomposed at 450 and 480 °C, staged-weakly producing CO and CO₂, which constructs more C═O groups and larger interlayer spacing. CaC₂O₄ is decomposed at 480 and 700 °C, staged-uniformly producing CO and CO₂, which constructs abundant C═O groups and largest interlayer spacing. The LSCM prepared by staged-uniform explosion exhibits high lithium storage capacity, superior rate capability, and cycling performance. The assembled lithium ion capacitor device achieves excellent energy/power densities of 78 Wh kg^-1/100 W kg^-1 and superior durability (capacitance retention of 8 4.6% after 20,000 cycles). This work gives a novel insight to engineer advanced oxygen-functionalized carbons for enhanced lithium storage.

Template-Directing Coupled with Chemical Activation Methodology-Derived Hexagon-like Porous Carbon Electrode with Outstanding Compatibility to Electrolytes and Low-Temperature Performance

The conversion of asphalt into hexagon-like porous carbon (HPC) with a micro-mesoporous structure is realized by the coupling of template-directing and chemical activation methodologies. The specific surface area of HPC can reach up to 1356 m² g^-1 even at such a low-proportioned dosage of activator (0.5-fold) and is also larger than those of template-directed carbon and activation-derived carbon, as it benefited from the coupling merits of template-directing and chemical activation. Excellent capacitive-energy-storage behavior with respect to rate capability, capacitance retention, and durability are delivered by HPC//HPC symmetric supercapacitors assembled with aqueous and organic electrolytes. This great compatibility for different kinds of electrolytes and electrode properties is owed to the robust hexagon-like microarchitecture feature associated with hierarchical pore structure, which not only hinders the stacking between each other but also provides a buffer function for the volume variation and sufficient active sites for the storage of electrolyte ions. The drastic temperature variation has almost no influence on the diffusion and transfer rate of electrolyte ions, further evidencing the advanced feature of the hierarchical pore structure. Additionally, HPC//Li₄Ti₅O₁₂ LIC assembled with the Li-based electrolyte also presents a superior Ragone performance. The coexistence of micro- and mesopores for the HPC makes it an attractive electrode material for various capacitive-energy-storage devices. This work provides a promising way to realize the plasticity of pore channels and mass production of high capacitive storage ability of electrode material via the combination of template-directing and chemical activation strategies.

3D Hierarchically Structured CoS Nanosheets: Li+ Storage Mechanism and Application of the High-Performance Lithium-Ion Capacitors

Lithium-ion capacitors possess excellent power and energy densities, and they can combine both of those advantages from supercapacitors and lithium-ion batteries, leading to novel generation hybrid devices for storing energy. This study synthesized one three-dimensional (3D) hierarchical structure, self-assembled from CoS nanosheets, according to a simple and efficient manner, and can be used as an anode for lithium ion capacitors. This CoS anode, based on a conversion-type Li⁺ storage mechanism dominated by diffusion control, showed a large reversible capacity, together with excellent stability for cycling. The CoS shows a discharge capacity ≈434 mA h/g at 0.1 A/g. The hybrid lithium-ion capacitor, which had the CoS anode as well as the biochar cathode, exhibits excellent electrochemical performance with ultrahigh energy and power densities of 125.2 Wh/kg and 6400 W/kg, respectively, and an extended cycling life of 81.75% retention after 40 000 cycles. The CoS with self-assembled 3D hierarchical structure in combination with a carbon cathode offers a versatile device for future applications in energy storage.

Great Enhancement of Carbon Energy Storage through Narrow Pores and Hydrogen-Containing Functional Groups for Aqueous Zn-Ion Hybrid Supercapacitor

The proton transfer mechanism on the carbon cathode surface has been considered as an effective way to boost the electrochemical performance of Zn-ion hybrid supercapacitors (SCs) with both ionic liquid and organic electrolytes. However, cheaper, potentially safer, and more environmental friendly supercapacitor can be achieved by using aqueous electrolyte. Herein, we introduce the proton transfer mechanism into a Zn-ion hybrid supercapacitor with the ZnSO₄ aqueous electrolyte and functionalized activated carbon cathode materials (FACs). We reveal both experimentally and theoretically an enhanced performance by controlling the micropores structure and hydrogen-containing functional groups (-OH and -NH functions) of the activated carbon materials. The Zn-ion SCs with FACs exhibit a high capacitance of 435 F g^-1 and good stability with 89% capacity retention over 10,000 cycles. Moreover, the proton transfer effect can be further enhanced by introducing extra hydrogen ions in the electrolyte with low pH value. The highest capacitance of 544 F g^-1 is obtained at pH = 3. The proton transfer process tends to take place preferentially on the hydroxyl-groups based on the density functional theory (DFT) calculation. The results would help to develop carbon materials for cheaper and safer Zn-ion hybrid SCs with higher energy.

A facile strategy for the synthesis of three-dimensional heterostructure self-assembled MoSe2 nanosheets and their application as an anode for high-energy lithium-ion hybrid capacitors

As energy storage devices, lithium-ion hybrid capacitors (LIHCs) are currently favored by researchers, because they combine the high energy density of lithium-ion batteries and the high power density as well as the long cycle life of electric double-layer capacitors. However, the reason that LIHCs are problematic for researchers and cannot be applied practically is the slow dynamic behavior of the battery type anode that leads to low magnification and cycle performance of the anode, furthermore, causing a dynamic imbalance between the Faraday embedded electrode and the capacitive electrode. Hence, it is imperative to find an anode material that can quickly intercalate/de-intercalate lithium. In this study, a novel anode material, MoSe2 nanoflowers, for LIHCs was incorporated through a facile solvothermal technique. The MoSe2 nanoflowers with a small volume change after Li+ insertion, conducive to a rapid kinetic layered heterostructure, result in extraordinary electrochemical performance. The prepared MoSe2 nanoflowers exhibit very good invertible capacity (641.4 mA h g-1 at 0.1 A g-1 after 200 cycles), superior velocity performance (380.3 mA h g-1 at 5 A g-1) and long-term cycling stability (214.6 mA h g-1 even after 1000 cycles at 1 A g-1) as anode materials for LIHCs. Benefiting from the reasonable nanometer size effect, locally fine charge transfers and low energy diffusion barriers, MoSe2 nanoflowers possess high rate pseudocapacitive behavior. In addition, the assembled MoSe2//AC (AC, activated carbon) LIHCs deliver a high energy density (78.75-39.1 W h kg-1) and high-power characteristic (150-3600 W kg-1). Besides, after 5000 cycles, the capacity retention rate is 70.28% under a broad potential window (0.5-3.5 V). This LIHC based on a transition metal selenide as an anode shows great potential for application in the fields of new energy electric vehicles and smart electronic products.

H0.92K0.08TiNbO5 Nanowires Enabling High-Performance Lithium-Ion Uptake

HTiNbO₅ has been widely investigated in many fields because of its distinctive properties such as good redox activity, high photocatalytic activity, and environmental benignancy. Here, this work reports the synthesis of one-dimensional H_0.92K_0.08TiNbO₅ nanowires via simple electrospinning followed by an ion-exchange reaction. The H_0.92K_0.08TiNbO₅ nanowires consist of many small "lumps" with a uniform diameter distribution of around 150 nm. Used as an anode for lithium-ion batteries, H_0.92K_0.08TiNbO₅ nanowires exhibit high capacity, fast electrochemical kinetics, and high performance of lithium-ion uptake. A capacity of 144.1 mA h g^-1 can be carried by H_0.92K_0.08TiNbO₅ nanowires at 0.5 C in the initial charge, and even after 150 cycles, the reversible capacity can remain at 123.7 mA h g^-1 with an excellent capacity retention of 85.84%. For H_0.92K_0.08TiNbO₅ nanowires, the diffusion coefficient of lithium ions is 1.97 × 10^-11 cm² s^-1, which promotes the lithium-ion uptake effectively. The outstanding electrochemical performance is ascribed to its morphology and the formation of a stable phase during cycling. In addition, the in situ X-ray diffraction and ex situ transmission electron microscopy techniques are applied to reveal its lithium storage mechanism, which proves the structure stability and electrochemical reversibility, thus achieving high-performance lithium-ion uptake. All these advantages demonstrate that H_0.92K_0.08TiNbO₅ nanowires can be a possible alternative anode material for rechargeable batteries.

Coprecipitation Reaction System Synthesis and Lithium-Ion Capacitor Energy Storage Application of the Porous Structural Bimetallic Sulfide CoMoS4 Nanoparticles

Lithium-ion capacitors (LICs) are noticed as a new-type of energy storage device with both capacitive mechanism and battery mechanism. The LICs own outstanding power density and energy density. In our work, an LIC was constructed by using a simple method to prepare a bimetallic sulfide of CoMoS₄ nanoparticles as the anode and a self-made biochar [fructus cannabis's shells (FCS)] with excellent specific surface area as the cathode. The CoMoS₄//FCS LIC demonstrated that the range of energy density is from 10 to 41.9 W h/kg and the range of power density is from 75 to 3000 W/kg in the meantime, and it also demonstrated a remarkable cycling performance with the capacitance retention of 95% after 10 000 cycles of charging-discharging at 1 A/g. The designed CoMoS₄//FCS LIC device exhibits a superior electrochemical performance because of the CoMoS₄ loose porous structure leading to excellent dynamic performance, which is conducive to the diffusion of electrolyte and lithium ion transport, and good electric double layer performance of biochar with large specific surface area could be achieved. Therefore, this bimetallic sulfide is a promising active material for LICs, which could be applied to electric vehicles in the future.

Electrode Materials, Electrolytes, and Challenges in Nonaqueous Lithium-Ion Capacitors

Among the various energy-storage systems, lithium-ion capacitors (LICs) are receiving intensive attention due to their high energy density, high power density, long lifetime, and good stability. As a hybrid of lithium-ion batteries and supercapacitors, LICs are composed of a battery-type electrode and a capacitor-type electrode and can potentially combine the advantages of the high energy density of batteries and the large power density of capacitors. Here, the working principle of LICs is discussed, and the recent advances in LIC electrode materials, particularly activated carbon and lithium titanate, as well as in electrolyte development are reviewed. The charge-storage mechanisms for intercalative pseudocapacitive behavior, battery behavior, and conventional pseudocapacitive behavior are classified and compared. Finally, the prospects and challenges associated with LICs are discussed. The overall aim is to provide deep insights into the LIC field for continuing research and development of second-generation energy-storage technologies.

High Capacitive Storage Performance of Sulfur and Nitrogen Codoped Mesoporous Graphene

Mesoporous graphene is synthesized based on the chemical vapor deposition methodology by using heavy MgO flakes as substrates in a fluidized-bed reactor. Subsequently, sulfur and nitrogen coincorporation into graphene frameworks is realized by the reaction between carbon atoms and thiourea molecules. The as-obtained sulfur and nitrogen codoped mesoporous graphene (SNMG) exhibits remarkable capacitive energy-storage behavior, as a result of well-developed pore channels, in terms of that in a symmetric supercapacitor and lithium-ion hybrid capacitor (LIHC). The ultrahigh durability of the SNMG/SNMG symmetric supercapacitor is demonstrated by long-term cycling, for which no capacitance decay is found after 20 000 cycles. A LIHC constructed from commercial Li₄ Ti₅ O₁₂ (LTO) as the anode and SNMG as the cathode is capable of delivering much enhanced lithium-storage ability and better rate capability than that of activated carbon (AC)/LTO LIHC. Moreover, SNMG/LTO LIHC exhibits maximum energy and power densities of 86.2 Wh kg^-1 and 7443 W kg^-1 and maintains 87 % capacitance retention after 2000 cycles.

Hybrid porous bamboo-like CNTs embedding ultrasmall LiCrTiO4 nanoparticles as high rate and long life anode materials for lithium ion batteries

Compared with Li₄Ti₅O₁₂, LiCrTiO₄ with the same spinel structure exhibits superior conductivity and Li⁺ diffusion properties. However, there has been no extensive study on LiCrTiO₄ as an anode material in lithium ion batteries, due to its pulverization, loss of electrical contact, and particle aggregation. A unique architecture based on hybrid porous CNTs embedding ultrasmall LiCrTiO₄ nanoparticles (6 ± 2 nm) was designed by using a facile sol-gel process combined with subsequent heat treatment. As an anode for lithium ion batteries, due to the absence of the aforementioned problems, the electrode exhibited high reversible capacity, excellent rate capability and superior long-term cycling stability at high current densities. Such nanocomposites should be competitive candidates to replace Li₄Ti₅O₁₂-based anode materials.

Exploration of Spinel LiCrTiO4 as Cathode Material for Rechargeable Mg-Li Hybrid Batteries

Mg-Li hybrid batteries have attracted wide interest in recent years because of their potential safety as well as their cost benefit and high volumetric capacity. However, slow kinetic properties strongly hinder their commercial application. In this study, we have prepared spinel LiCrTiO₄ by a solid-state reaction and have conducted a comprehensive study aimed at improving the performance of Mg-Li hybrid batteries by optimizing the dual-salt electrolyte. LiCrTiO₄ has been found to show reversible discharge/charge capacities of 178 and 169 mA h g^-1 in electrolytes of 1 m LiCl and 0.3 m APC (all-phenyl-complex), respectively. When the concentration of APC was increased to 0.4 m, LiCrTiO₄ showed a high capacity retention of 95 % after 30 cycles. In addition, no phase transition could be observed for an LiCrTiO₄ electrode in a dual-salt system, suggesting high electrochemical reversibility. Ex situ EDX and SEM studies have indicated that only Li⁺ ions are inserted into the cathode side, while Mg²⁺ ions are reversibly deposited on the surface of Mg metal without dendrite-like growth, indicative of good safety of the Mg-Li hybrid batteries.

Nonaqueous Hybrid Lithium-Ion and Sodium-Ion Capacitors

Hybrid metal-ion capacitors (MICs) (M stands for Li or Na) are designed to deliver high energy density, rapid energy delivery, and long lifespan. The devices are composed of a battery anode and a supercapacitor cathode, and thus become a tradeoff between batteries and supercapacitors. In the past two decades, tremendous efforts have been put into the search for suitable electrode materials to overcome the kinetic imbalance between the battery-type anode and the capacitor-type cathode. Recently, some transition-metal compounds have been found to show pseudocapacitive characteristics in a nonaqueous electrolyte, which makes them interesting high-rate candidates for hybrid MIC anodes. Here, the material design strategies in Li-ion and Na-ion capacitors are summarized, with a focus on pseudocapacitive oxide anodes (Nb₂ O₅ , MoO₃ , etc.), which provide a new opportunity to obtain a higher power density of the hybrid devices. The application of Mxene as an anode material of MICs is also discussed. A perspective to the future research of MICs toward practical applications is proposed to close.

Peapod-like Li3 VO4 /N-Doped Carbon Nanowires with Pseudocapacitive Properties as Advanced Materials for High-Energy Lithium-Ion Capacitors

Lithium ion capacitors are new energy storage devices combining the complementary features of both electric double-layer capacitors and lithium ion batteries. A key limitation to this technology is the kinetic imbalance between the Faradaic insertion electrode and capacitive electrode. Here, we demonstrate that the Li₃ VO₄ with low Li-ion insertion voltage and fast kinetics can be favorably used for lithium ion capacitors. N-doped carbon-encapsulated Li₃ VO₄ nanowires are synthesized through a morphology-inheritance route, displaying a low insertion voltage between 0.2 and 1.0 V, a high reversible capacity of ≈400 mAh g^-1 at 0.1 A g^-1 , excellent rate capability, and long-term cycling stability. Benefiting from the small nanoparticles, low energy diffusion barrier and highly localized charge-transfer, the Li₃ VO₄ /N-doped carbon nanowires exhibit a high-rate pseudocapacitive behavior. A lithium ion capacitor device based on these Li₃ VO₄ /N-doped carbon nanowires delivers a high energy density of 136.4 Wh kg^-1 at a power density of 532 W kg^-1 , revealing the potential for application in high-performance and long life energy storage devices.

High-Performance Li-Ion Capacitor Based on an Activated Carbon Cathode and Well-Dispersed Ultrafine TiO2 Nanoparticles Embedded in Mesoporous Carbon Nanofibers Anode

A novel Li-ion capacitor based on an activated carbon cathode and a well-dispersed ultrafine TiO₂ nanoparticles embedded in mesoporous carbon nanofibers (TiO₂@PCNFs) anode was reported. A series of TiO₂@PCNFs anode materials were prepared via a scalable electrospinning method followed by carbonization and a postetching method. The size of TiO₂ nanoparticles and the mesoporous structure of the TiO₂@PCNFs were tuned by varying amounts of tetraethyl orthosilicate (TEOS) to increase the energy density and power density of the LIC significantly. Such a subtle designed LIC displayed a high energy density of 67.4 Wh kg^-1 at a power density of 75 W kg^-1. Meanwhile, even when the power density was increased to 5 kW kg^-1, the energy density can still maintain 27.5 Wh kg^-1. Moreover, the LIC displayed a high capacitance retention of 80.5% after 10000 cycles at 10 A g^-1. The outstanding electrochemical performance can be contributed to the synergistic effect of the well-dispersed ultrafine TiO₂ nanoparticles, the abundant mesoporous structure, and the conductive carbon networks.

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 (Mo_0.1Ti_0.9O₂) and Nb-doped titania (Nb_0.25Ti_0.75O₂) 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 Mo_0.1Ti_0.9O₂/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 Nb_0.25Ti_0.75O₂/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 Mo_0.1Ti_0.9O₂/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.

Pillared Structure Design of MXene with Ultralarge Interlayer Spacing for High-Performance Lithium-Ion Capacitors

Two-dimensional transition-metal carbide materials (termed MXene) have attracted huge attention in the field of electrochemical energy storage due to their excellent electrical conductivity, high volumetric capacity, etc. Herein, with inspiration from the interesting structure of pillared interlayered clays, we attempt to fabricate pillared Ti₃C₂ MXene (CTAB-Sn(IV)@Ti₃C₂) via a facile liquid-phase cetyltrimethylammonium bromide (CTAB) prepillaring and Sn⁴⁺ pillaring method. The interlayer spacing of Ti₃C₂ MXene can be controlled according to the size of the intercalated prepillaring agent (cationic surfactant) and can reach 2.708 nm with 177% increase compared with the original spacing of 0.977 nm, which is currently the maximum value according to our knowledge. Because of the pillar effect, the assembled LIC exhibits a superior energy density of 239.50 Wh kg^-1 based on the weight of CTAB-Sn(IV)@Ti₃C₂ even under higher power density of 10.8 kW kg^-1. When CTAB-Sn(IV)@Ti₃C₂ anode couples with commercial AC cathode, LIC reveals higher energy density and power density compared with conventional MXene materials.

Agricultural waste-derived activated carbon for high performance lithium-ion capacitors

The optimized AC//LTO LIC is worth noting that our device outperformed most of the similar constructions concerning carbonaceous materials as cathode and LTO as anode and some other constructions.

Al doping effects on LiCrTiO4 as an anode for lithium-ion batteries

Al doping in LiCrTiO₄ showed apparently enhanced electrochemical performance at high temperature with slightly modification to crystal structure.

Applications of Novel Carbon/AlPO4 Hybrid-Coated H2Ti12O25 as a High-Performance Anode for Cylindrical Hybrid Supercapacitors

The hybrid supercapacitor using carbon/AlPO₄ hybrid-coated H₂Ti₁₂O₂₅/activated carbon is fabricated as a cylindrical cell and investigated against electrochemical performances. The hybrid coating shows that the conductivity for the electron and Li ion is superior and it prevented active material from HF attack. Consequently, carbon/AlPO₄ hybrid-coated H₂Ti₁₂O₂₅ shows enhanced rate capability and long-term cycle life. Also, the hybrid coating inhibits swelling phenomenon caused by gas generated as decomposition reaction of electrolyte. Therefore, the hybrid supercapacitor using carbon/AlPO₄ hybrid-coated H₂Ti₁₂O₂₅/activated carbon can be applied to an energy storage system that requires a long-term life.

Biomass-Derived Electrode for Next Generation Lithium-Ion Capacitors

We report the fabrication of a carbon-based high energy density Li-ion hybrid electrochemical capacitor (Li-HEC) from low cost and eco-friendly materials. High surface area (2448±20 m(2)  g(-1) ) activated carbon (AC) is derived from the environmentally threatening plant, Prosopis juliflora, and used as the positive electrode in a Li-HEC assembly. Natural graphite is employed as negative electrode and electrochemically pre-lithiated prior to the Li-HEC fabrication. The Li-HEC delivers a specific energy of 162.3 Wh kg(-1) and exhibits excellent cyclability (i.e., ∼79 % of initial capacity is retained after 7000 cycles). The superior electrochemical performance of Li-HEC benefits from the tube-like unique structural features of the AC. Also, the presence of a graphitic nanocarbon network improves the ion transport, and the formed micro- and meso-porous network acts as reservoir for the accommodation of charge carriers.

High power lithium-ion battery based on a LiMn2O4 nanorod cathode and a carbon-coated Li4Ti5O12 nanowire anode

LiMn₂O₄ nanorods and carbon-coated Li₄Ti₅O₁₂ nanowires were used to build a full cell that exhibits supercapacitor-like power performance, long life and high energy density.

A high energy and power Li-ion capacitor based on a TiO2 nanobelt array anode and a graphene hydrogel cathode

A novel hybrid Li-ion capacitor (LIC) with high energy and power densities is constructed by combining an electrochemical double layer capacitor type cathode (graphene hydrogels) with a Li-ion battery type anode (TiO(2) nanobelt arrays). The high power source is provided by the graphene hydrogel cathode, which has a 3D porous network structure and high electrical conductivity, and the counter anode is made of free-standing TiO(2) nanobelt arrays (NBA) grown directly on Ti foil without any ancillary materials. Such a subtle designed hybrid Li-ion capacitor allows rapid electron and ion transport in the non-aqueous electrolyte. Within a voltage range of 0.0-3.8 V, a high energy of 82 Wh kg(-1) is achieved at a power density of 570 W kg(-1). Even at an 8.4 s charge/discharge rate, an energy density as high as 21 Wh kg(-1) can be retained. These results demonstrate that the TiO(2) NBA//graphene hydrogel LIC exhibits higher energy density than supercapacitors and better power density than Li-ion batteries, which makes it a promising electrochemical power source.

TiNb2O7 nanoparticles assembled into hierarchical microspheres as high-rate capability and long-cycle-life anode materials for lithium ion batteries

As a competitor for Li4Ti5O12 with a higher capacity and extreme safety, monoclinic TiNb2O7 has been considered as a promising anode material for next-generation high power lithium ion batteries. However, TiNb2O7 suffers from low electronic conductivity and ionic conductivity, which restricts the electrochemical kinetics. Herein, a facile and advanced architecture design of hierarchical TiNb2O7 microspheres is successfully developed for large-scale preparation without any surfactant assistance. To the best of our knowledge, this is the first report on the one step solvothermal synthesis of TiNb2O7 microspheres with micro- and nano-scale composite structures. When evaluated as an anode material for lithium ion batteries, the electrode exhibits excellent high rate capacities and ultra-long cyclability, such as 258 mA h g(-1) at 1 C, 175 mA h g(-1) at 5 C, and 138 mA h g(-1) at 10 C, extending to more than 500 cycles.

Electrospun nanofibers: A prospective electro-active material for constructing high performance Li-ion batteries

The present review outlines high performance Li-ion cells fabricated with all one-dimensional materials as the cathode and anode, as well as a separator-cum-electrolyte prepared by an electrospinning technique.

Advanced hybrid supercapacitor based on a mesoporous niobium pentoxide/carbon as high-performance anode

Recently, hybrid supercapacitors (HSCs), which combine the use of battery and supercapacitor, have been extensively studied in order to satisfy increasing demands for large energy density and high power capability in energy-storage devices. For this purpose, the requirement for anode materials that provide enhanced charge storage sites (high capacity) and accommodate fast charge transport (high rate capability) has increased. Herein, therefore, a preparation of nanocomposite as anode material is presented and an advanced HSC using it is thoroughly analyzed. The HSC comprises a mesoporous Nb2O5/carbon (m-Nb2O5-C) nanocomposite anode synthesized by a simple one-pot method using a block copolymer assisted self-assembly and commercial activated carbon (MSP-20) cathode under organic electrolyte. The m-Nb2O5-C anode provides high specific capacity with outstanding rate performance and cyclability, mainly stemming from its enhanced pseudocapacitive behavior through introduction of a carbon-coated mesostructure within a voltage range from 3.0 to 1.1 V (vs Li/Li(+)). The HSC using the m-Nb2O5-C anode and MSP-20 cathode exhibits excellent energy and power densities (74 W h kg(-1) and 18,510 W kg(-1)), with advanced cycle life (capacity retention: ∼90% at 1000 mA g(-1) after 1000 cycles) within potential range from 1.0 to 3.5 V. In particular, we note that the highest power density (18,510 W kg(-1)) of HSC is achieved at 15 W h kg(-1), which is the highest level among similar HSC systems previously reported. With further study, the HSCs developed in this work could be a next-generation energy-storage device, bridging the performance gap between conventional batteries and supercapacitors.

High-power lithium-ion capacitor using LiMnBO3 -nanobead anode and polyaniline-nanofiber cathode with excellent cycle life

LiMnBO3 nanobeads (LMB-NB) with uniform size and distribution were synthesized using a urea-assisted microwave/solvothermal method. The potential application of LMB-NBs as an anode for a lithium-ion hybrid capacitor (Li-AHC) was tested with a polyaniline-nanofiber (PANI-NF) cathode in a nonaqueous LiPF6 (1 M)-ethylene carbonate/dimethyl carbonate electrolyte. Cyclic voltammetry (CV) and charge-discharge (C/DC) studies revealed that the PANI-NF/LMB-NB cell showed an exceptional capacitance behavior between 0-3 V along with a prolonged cycle life. A discharge capacitance of about 125 F g(-1) , and energy and power densities of about 42 Wh kg(-1) and 1500 W kg(-1) , respectively, could be obtained at a current density of 1 A g(-1) ; those Li-AHC values are higher relative to cells containing various lithium intercalation materials in nonaqueous electrolytes. In addition, the PANI-NF/LMB-NB cell also had an outstanding rate performance with a capacitance of 54 F g(-1) and a power density of 3250 W kg(-1) at a current density of 2.25 A g(-1) and maintained 94% of its initial value after 30000 cycles. This improved capacitive performance with an excellent electrochemical stability could be the result of the morphological features and inherent conductive nature of the electroactive species.

LiMnBO₃ nanobeads as an innovative anode material for high power lithium ion capacitor applications

A novel approach was made to fabricate lithium ion hybrid capacitor (Li-HC) having LiMnBO3 nanobead (LMB-NB) anode and polyaniline nanofiber (PANI) cathode in 1 M LiPF6 organic electrolyte. LMB-NB and PANI nanofibers were synthesized using urea assisted microwave-solvothermal method and chemical polymerization process, respectively. The PANI/LMB-NB cell showed improved electrochemical capacitive behavior as compared to activated carbon (AC)/LMB-NB cell due to the characteristic conductivity and the morphological feature of PANI as well as LMB-NB electrodes. A discharge capacitance (DCcell) of ∼125 F g(-1) was obtained at a current density of 1 A g(-1) between the potential range 0 and 3 V for PANI/LMB-NB cell, while AC/LMB-NB cell delivered only 77 F g(-1) at the same current density. Moreover, PANI/LMB-NB cell exhibited excellent rate performance with the DCcell of about 55 F g(-1) at 2.25 A g(-1) and still retained 94% of the initial value after 30 000 charge-discharge cycles. In addition, maximum energy and power densities of 42 Wh kg(-1) and 5350 W kg(-1), respectively, were achieved from PANI/LMB-NB cell. The obtained DCcell, energy, and power densities along with prolonged cyclic life for PANI/LMB-NB cell are some of the best ever reported values for Li-HC as compared to the cells constructed with various lithium intercalating materials.

Unveiling TiNb2 O7 as an insertion anode for lithium ion capacitors with high energy and power density

This is the first report of the utilization of TiNb2 O7 as an insertion-type anode in a lithium-ion hybrid electrochemical capacitor (Li-HEC) along with an activated carbon (AC) counter electrode derived from a coconut shell. A simple and scalable electrospinning technique is adopted to prepare one-dimensional TiNb2 O7 nanofibers that can be characterized by XRD with Rietveld refinement, SEM, and TEM. The lithium insertion properties of such electrospun TiNb2 O7 are evaluated in the half-cell configuration (Li/TiNb2 O7 ) and it is found that the reversible intercalation of lithium (≈3.45 mol) is feasible with good capacity retention characteristics. The Li-HEC is constructed with an optimized mass loading based on the electrochemical performance of both the TiNb2 O7 anode and AC counter electrode in nonaqueous media. The Li-HEC delivers very high energy and power densities of approximately 43 Wh kg(-1) and 3 kW kg(-1) , respectively. Furthermore, the AC/TiNb2 O7 Li-HEC delivers a good cyclability of 3000 cycles with about 84% of the initial value.