An Asymmetric Hybrid Nonaqueous Energy Storage Cell

Abstract

A nonaqueous asymmetric electrochemical cell technology is presented where the positive electrode stores charge through a reversible nonfaradaic or pseudocapacitive reaction of anions on the surface of an activated carbon positive electrode. The negative electrode is a crystalline intercalation compound which supports the fast reversible intercalation of lithium ions. Using a positive electrode material of activated carbon and newly developed negative electrode material of nanostructured Li 4 Ti 5 O 12 we obtain a cell which exhibits a sloping voltage profile from 3 to 1.5 V, 90% capacity utilization at 10C charge/discharge rates, and 10-15% capacity loss after 5000 cycles. Electrolyte oxidation on the activated carbon positive electrode was characterized in a Li metal asymmetric hybrid cell by cyclic voltammetry. Oxidation during the anodic scan was found to decrease significantly after surface passivation at high voltage and elevated temperatures. We also introduce the asymmetric hybrid technology in a bonded flat plate plastic cell configuration where packaged energy densities were calculated to be in excess of 20 Wh/kg. In addition, a practical method for three-electrode analysis of Li cells by use of a Ag quasi-reference electrode wire is discussed.

Non-aqueous energy storage devices using graphene nanosheets synthesized by green route

“…However, recently Kim et al 34 is mainly due to the usage of conventional Li-ion battery electrolytes, wherein the anionic size is also close to BF 4 -anions. 16 Figure 4 inset shows the plot of specific energy vs. specific power densities and the values are calculated based on the equation given in our previous reports. 32,35 TRGO based supercapacitor is capable of delivering maximum energy and power densities of 60.4 Wh kg -1 and 0.15 kW kg -1 , respectively.…”

“…10,[12][13][14][15][16] Poor cycleability in non-aqueous media results in the case of EDLC capacitors irrespective of carbon allotropes used. 7,8 Among the various forms of carbon, graphene is found to be a more attractive candidate to study the supercapacitive behaviour in nonaqueous media, however no extensive work has yet been carried out in such medium.…”

One-step, continuous synthesis of a spherical Li4Ti5O12/graphene composite as an ultra-long cycle life lithium-ion battery anode

“…[4][5][6][7][8] In addition, LTO possesses excellent Li ion insertion and removal reversibility with almost zero volume change during the charge/discharge process. 9,10 However, as demonstrated in previous studies, it is still a challenge to achieve good battery performance at high charge/discharge rates using LTO as the anode material because of the low electrical conductivity (o10 − 13 S cm − 1 ) of LTO, 11,12 and thus there have been many efforts to improve the rate capability and the cycling performance of LTO-based batteries. Commonly applied strategies include engineering the proper LTO structure to reduce the transport path length of Li ions and enhancing the electrical conductivity by surface coating or forming composites with carbon-based materials.…”

Electrochemical performance of lithium ion capacitors using aqueous electrolyte at high temperature

“…[1][2][3] According to the energy storage mechanism, 4,5 supercapacitors can be classified into three categories: electrochemical double layer capacitors (EDLCs), 6 in which electricity is stored by the electric double layer formed at the electrode/electrolyte interface and activated carbon (AC) with high specific area is normally used as electrode material; pseudocapacitive capacitors, 7 in which fast and reversible Faradic reactions (redox or ion intercalation) are utilized to store electricity; and hybrid capacitors, 8 in which a capacitor electrode (normally of activated carbon) and a battery electrode are employed.…”