Li-ion Hybrid Capacitors Research Articles

Silica-assisted bottom-up synthesis of graphene-like high surface area carbon for highly efficient ultracapacitor and Li-ion hybrid capacitor applications

A silica-assisted method was developed to prepare graphene-like carbon displaying excellent capacitive charge storage.

Porous niobium nitride as a capacitive anode material for advanced Li-ion hybrid capacitors with superior cycling stability

Lithium-ion hybrid capacitors (LIHCs) are receiving intense interest because they can combine the distinctive advantages of Li-ion batteries and supercapacitors.

Nano-composite LiMnPO4 as new insertion electrode for electrochemical supercapacitors

Nano-composite olivine LiMnPO4 (nC-LMP) was found to exhibit facile pseudo-capacitive characteristics in aqueous as well as non-aqueous electrolytes. We demonstrated employing nC-LMP as positive electrode in hybrid electrochemical capacitors namely Li-Ion hybrid capacitors (LIC). Adapting a simple CVD technique, nano-crystallites of LiMnPO4 were coated with carbon monolayers of ∼2 nm thick to circumvent its poor intrinsic electronic conductivity. The novelty is that the single crystallites were intimately covered with carbon ring and networked to the neighboring crystallites via the continuous carbon wire-like connectivity as revealed from HRTEM analysis. Single electrode faradic capacitance of 3025 Fg−1 (versus standard calomel reference electrode) was deduced for carbon coated LMP, the highest reported hitherto in Li+ aqueous electrolytes. Employing nC-LMP as working electrode versus an activated carbon (AC), we obtained a high specific energy of 28.8 Wh kg−1 with appreciable stability in aqueous electrolytes whereas in nonaqueous electrolyte there is an obvious increase in energy density (35 Wh kg−1) due to wider potential window. That is, a full cell version of LIC, AC|Li+|LMP, was fabricated and demonstrated its facile cycling characteristics via removal/insertion of Li+ within nC-LMP (positive electrode) and the electrosorption of Li+ into mesoporous carbon (AC) (negative electrode). Such cells ensured a typical battery-like charging and EDLC-like discharging characteristics of LIC type electrochemical capacitors (ECs) which are desired to enhance safety and energy densities.

Temperature effect on electrochemical performances of Li-ion hybrid capacitors

Li-ion hybrid capacitor (LIC) is a type of energy storage device that bridge the gap between Li-ion battery and electrical double-layer capacitor. In the present work, LICs are assembled with activated carbon-based cathode and pre-lithiated hard carbon anode. The effect of temperature on the electrochemical properties of LIC is investigated by galvanostatic charge-discharge tests and electrochemical impedance analyses. The performances of LIC cells with different anode pre-lithiation degree and different cathode composition are comparatively studied. As the temperature decreases, the cell capacity decreases accordingly. The ambient temperature varies from −40 to +60 °C, and the working voltage window is 1.5–4.0 V. At the temperature of −20 and −40 °C, LIC cell can remain 77.7 and 33.8 % of the initial capacity at +25 °C, respectively. Some approaches to improving the low-temperature electrochemical performances of LIC have been proposed.

Fast and Large Lithium Storage in 3D Porous VN Nanowires–Graphene Composite as a Superior Anode Toward High‐Performance Hybrid Supercapacitors

Li‐ion hybrid capacitors (LIHCs), consisting of an energy‐type redox anode and a power‐type double‐layer cathode, are attracting significant attention due to the good combination with the advantages of conventional Li‐ion batteries and supercapacitors. However, most anodes are battery‐like materials with the sluggish kinetics of Li‐ion storage, which seriously restrict the energy storage of LIHCs at the high charge/discharge rates. Herein, vanadium nitride (VN) nanowire is demonstated to have obvious pseudocapacitive characteristic of Li‐ion storage and can get further gains in energy storage through a 3D porous architecture with the assistance of conductive reduced graphene oxide (RGO). The as‐prepared 3D VN–RGO composite exhibits the large Li‐ion storage capacity and fast charge/discharge rate within a wide working widow from 0.01–3 V (vs Li/Li+), which could potentially boost the operating potential and the energy and power densities of LIHCs. By employing such 3D VN–RGO composite and porous carbon nanorods with a high surface area of 3343 m2 g−1 as the anode and cathode, respectively, a novel LIHCs is fabricated with an ultrahigh energy density of 162 Wh kg−1 at 200 W kg−1, which also remains 64 Wh kg−1 even at a high power density of 10 kW kg−1.

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.

Porous NiCo2O4 as an anode material for 4.5 V hybrid Li-ion capacitors

A novel hybrid Li-ion capacitor has been constructed with a porous NiCo2O4 anode and an activated carbon cathode. The capacitor exhibits an ultrahigh working voltage of 4.5 V, good Ragone performance (39.4 W h Kg−1, 554 W Kg−1) and excellent cycling behavior (no energy loss after 2000 cycles).

Ester based electrolyte with lithium bis(trifluoromethane sulfonyl) imide salt for electrochemical storage devices: Physicochemical and electrochemical characterization

Esters co-solvent has been used in ternary system electrolytes for electrochemical storage using LiTFSI as salt. Three linear esters have been studied: methyl propanoate (MP), ethyl propanoate (EP) and ethyl butanoate (EB). The ionic conductivity, viscosity, and electrochemical performances of ethylene carbonate (EC)/ester/dimethyl carbonate (DMC) mixtures have been determined and compared to the reference ternary mixture: EC/propylene carbonate (PC)/DMC in proportion (1/1/3) by volume. These electrolytes have been tested in half cells of the type: Li | electrolyte | activated carbon (AC) or graphite (Gr). These active materials are designed to be used in hybrid Li-ion capacitors. Electrochemical results show that MP presents the best performances at the AC electrode in terms of capacitance, especially at low temperatures (−10°C). However, MP based electrolytes give the higher irreversible capacity when used with the Gr electrode, and are the most corrosive toward the aluminum current collector. This problem has been resolved by adding a small amount of LiPF6 (1% in mol) to the electrolyte solution as a passivating additive. Thus, MP based electrolytes exhibit the best performances in terms of capacity at the Gr electrode and capacitance at the AC electrode.