Cyanoresin, cyanoresin/cellulose triacetate blends for thin film, dielectric capacitors

Non-brittle dielectric films are formed by blending a cyanoresin such as cyanoethyl, hydroxyethyl cellulose (CRE) with a compatible, more crystalline resin such as cellulose triacetate. The electrical breakdown strength of the blend is increased by orienting the films by uniaxial or biaxial stretching. Blends of high molecular weight CRE with high molecular weight cyanoethyl cellulose (CRC) provide films with high dielectric constants

Cellulose triacetate, thin film dielectric capacitor

Very thin films of cellulose triacetate are cast from a solution containing a small amount of high boiling temperature, non-solvent which evaporates last and lifts the film from the casting surface. Stretched, oriented, crystallized films have high electrical breakdown properties. Metallized films less than about 2 microns in thickness form self-healing electrodes for high energy density, pulsed power capacitors. Thicker films can be utilized as a dielectric for a capacitor

Cellulose triacetate, thin film dielectric capacitor

Very thin films of cellulose triacetate are cast from a solution containing a small amount of high boiling temperature, non-solvent which evaporates last and lifts the film from the casting surface. Stretched, oriented, crystallized films have high electrical breakdown properties. Metallized films less than about 2 microns in thickness form self-healing electrodes for high energy density, pulsed power capacitors. Thicker films can be utilized as a dielectric for a capacitor

Cyanoresin, cyanoresin/cellulose triacetate blends for thin film, dielectric capacitors

Non brittle dielectric films are formed by blending a cyanoresin such as cyanoethyl, hydroxyethyl cellulose (CRE) with a compatible, more crystalline resin such as cellulose triacetate. The electrical breakdown strength of the blend is increased by orienting the films by uniaxial or biaxial stretching. Blends of high molecular weight CRE with high molecular weight cyanoethyl cellulose (CRC) provide films with high dielectric constants

Electrolyte Optimization of a Substituted-LiCo 1-x Fe x PO 4 Cathode

Lithium cobalt phosphate (LiCoPO 4 ) is an attractive cathode material due to its high discharge potential (4.8 V vs. Li/Li + ) and specific capacity (167 mAh g -1 ), resulting in an impressive specific energy of ~802 Wh kg -1 . The development of LCP has proven difficult owing to the instability of the electrode and the tendency of the electrolyte to perpetually decompose (oxidize), leading to a highly resistive passivation layer. In this report, a substituted lithium cobalt iron phosphate (s-LiCo 1-x Fe x PO 4 or s-LCFP) cathode material was tested with various solvents and additives to find an optimized electrolyte that limits electrode polarization and improves cycle life. The s-LCFP cathode performed best with a 1M LiPF 6 solution of EC/EMC (3/7 wt%) with 2% of additive ARL1. Comparing ARL1 to the baseline electrolyte, the fade rate was reduced from 0.014% per cycle to 0.005% per cycle and the shift in charge voltage (due to polarization) was reduced from 39mV to 19mV through 50 cycles

Conductivity and Viscosity of PC-DEC and PC-EC Solutions of LiBOB

Conductivity of propylene carbonate-diethyl carbonate ͑PC-DEC͒ and propylene carbonate-ethylene carbonate ͑PC-EC͒ solutions of lithium bis͑oxalato͒borate ͑LiBOB͒ was experimentally determined at temperatures from 60 to Ϫ80°C, salt molalities m from 0.04 to 1.1 mol kg Ϫ1 , and solvent compositions w from 0 to 0.7 weight fraction of DEC and EC. Viscosity of LiBOB in PC-EC was studied through measuring its glass transition temperature T g in the same ranges of m and w. T g was found to rise with m and w of EC, indicating a concurrent change in the of the solution. The of the PC-DEC solution of LiBOB peaked in both m and w thus forming a ''dome'' in its 3D presentation in the coordinates of m and w, while that of the PC-EC solution peaked only in m resulting in an ''arch''-shaped surface. As the was lowered, these surfaces fell in height and shifted in the direction of low . These observations correlated well with the changes of dielectric constant of the solvents and of the solutions with the same set of variables. The measured (T) data for the PC-DEC solution was fitted with the Vogel-Tamman-Fulcher equation for an evaluation of its vanishing mobility temperature and apparent activation energy. The results of and of the LiBOB solutions were further compared with those of LiPF 6 solutions from a previous study. This report parallels two earlier ones 1,2 in both structure and content, those dealing with conductivities and viscosities of propylene carbonate-diethyl carbonate ͑PC-DEC͒ and propylene carobonate-ethylene carbonate ͑PC-EC͒ solutions of LiPF 6 and LiBF 4 , respectively; this report dealing with lithium bis͑oxalato͒bo-rate ͑LiBOB͒. 3 As such, this report, while giving full account of the new experimental results, skips over some of the detailed descriptions and explanations that can be found in previous reports. Also, although the measured properties of LiBOB are briefly compared with those of LiPF 6 in this report, a fuller comparison across all three salts and its discussion will be left to another report that is to follow. The aim of this report is mainly to provide a relatively complete picture for the change of conductivity with salt molality m and solvent weight fraction w at different temperatures ͑ symbolizes temperature in degrees centigrade and T in degrees of absolute temperature, K͒ 3 for PC-DEC and PC-EC solutions of LiBOB, denoted here as (LiBOB) m -PC 1Ϫw DEC w and (LiBOB) m -PC 1Ϫw EC w . It is felt that such a picture, together with what is already known of dielectric constant and viscosity of PC-DEC and PC-EC solvents and of and of their electrolytes of LiBF 4 and LiPF 6 , 1,2,4,5 could lead to a clear demonstration of the similarities and differences in the change of with m and w and with for the three important lithium salts in the carbonate solvents and to an elucidation of the mechanisms giving rise to these similarities and differences. As has been amply demonstrated, of an electrolyte of a particular salt is critically dependent on the of the solvent and the of the electrolyte:-rises with a high which promotes ion dissociation and with a low which facilitates ion movement. 6-9 For this reason, and of many solvents and and of many electrolytes have been measured as functions of w, m, and in regard to their application to lithium-ion batteries. 1,2 has been found to peak in both m and w for (LiPF 6 ) m -PC 1Ϫw DEC w and (LiBF 4 ) m -PC 1Ϫw DEC w thus forming a dome in the mw-coordinates but only in m for (LiPF 6 ) m -PC 1Ϫw EC w and (LiBF 4 ) m -PC 1Ϫw EC w thus forming an arch. 1,2 As is lowered, these surfaces lower their heights and shift their positions in the direction of low . 1,2,5 This series of investigation was continued with the work to be presented here, in which (LiBOB) m -PC 1Ϫw DEC w and (LiBOB) m -PC 1Ϫw EC w solutions were studied for their and . The choice for these materials was a result of the strong interest in and the wide use of these three lithium salts * Electrochemical Society Active Member. z E-mail: [email protected] Journal of The Electrochemical Society, 152 ͑1͒ A132-A140 ͑2005

Oxidative Stability and Initial Decomposition Reactions of Carbonate, Sulfone, and Alkyl Phosphate-Based Electrolytes

The oxidative stability and initial oxidation-induced decomposition reactions of common electrolyte solvents for batteries and electrical double layer capacitors were investigated using quantum chemistry (QC) calculations. The investigated electrolytes consisted of linear (DMC, EMC) and cyclic carbonate (EC, PC, VC), sulfone (TMS), sulfonate, and alkyl phosphate solvents paired with BF₄ ^–, PF₆ ^–, bis­(fluorosulfonyl)­imide (FSI^–), difluoro-(oxalato)­borate (DFOB^–), dicyanotriazolate (DCTA^–), and B­(CN)₄ ^– anions. Most QC calculations were performed using the M05-2X, LC-ωPBE density functional and compared with the G4MP2 results where feasible. The calculated oxidation potentials were compared with previous and new experimental data. The intrinsic oxidation potential of most solvent molecules was found to be higher than experimental values for electrolytes even after the solvation contribution was included in the QC calculations via a polarized continuum model. The presence of BF₄ ^–, PF₆ ^–, B­(CN)₄ ^–, and FSI^– anions near the solvents was found to significantly decrease the oxidative stability of many solvents due to the spontaneous or low barrier (for FSI^–) H- and F-abstraction reaction that followed the initial electron removal step. Such spontaneous H-abstraction reactions were not observed for the solvent complexes with DCTA^– or DFOB^– anions or for VC/anion, TMP/PF₆ ^– complexes. Spontaneous H-transfer reactions were also found for dimers of the oxidized carbonates (EC, DMC), alkyl phosphates (TMP), while low barrier H-transfer was found for dimers of sulfones (TMS and EMS). These reactions resulted in a significant decrease of the dimer oxidation potential compared to the oxidation potential of the isolated solvent molecules. The presence of anions or an explicitly included solvent molecule next to the oxidized solvent molecules also reduced the barriers for the oxidation-induced decomposition reaction and often changed the decomposition products. When a Li⁺ cation polarized the solvent in the EC_<i>n</i>/LiBF₄ and EC_<i>n</i>/LiPF₆ complexes, the complex oxidation potential was 0.3–0.6 eV higher than the oxidation potential of EC_<i>n</i>/BF₄ ^– and EC_<i>n</i>/PF₆ ^–