Research on the Influence of Stray Parameters in the Circuit of the Hybrid Energy Storage
In the course of battery discharge in hybrid energy storage, overvoltage trends to appear at opposite ends of the IGBT (Insulated Gate Bipolar Transistor) when the IGBT is switched off, which is likely to cause overvoltage to damage the IGBT. To solve the problem, this paper has made analyses of the mechanism of capacitor when overvoltage caused by the IGBT failure, the stray inductance in the hybrid energy storage circuit and the inductance of switch-off current on the overvoltage. And the corresponding mathematical formula is derived. On the basis, a simulation model is established. The rational distribution and the addition of an absorption loop can reduce the peak value of overvoltage. It is found from simulations that the absorption circuit will lead to voltage oscillation in the main circuit. Aimed at this phenomenon, the design of the absorption loop is optimized. Simulations and experiments prove the proposed method to be effective.
Lithium fluoroalkylphosphates: a new class of conducting salts for electrolytes for high energy lithium-ion batteries
The effort to develop improved electrolytes that satisfy the requirements of lithium rechargeable batteries has intensified the search for new conducting salts having an improved chemical and electrochemical stability. With lithium fluoroalkylphosphates, we introduce a new class of conducting salts for electrolytes for high energy lithium-ion batteries. The results of electrochemical studies of Li[(C2F5)3PF3] in organic carbonates in comparison to LiPF6 including electrochemical stability and charge–discharge efficiency are reported. In addition, the influence of perfluorinated alkyl groups on stability towards hydrolysis is demonstrated.
Anodic dissolution of aluminium in organic electrolytes containing perfluoroalkylsulfonyl imides
Electrochemical dissolution of aluminium has been investigated in various solutions composed of organic solvents and 1 m lithium bis(perfluoroalkylsulfonyl) imide salts. Potentials of the onset of transpassive dissolution and repassivation as well as dissolution currents have been measured for several systems by using voltammetric methods. Empirical correlation between the composition of the solvent and the dissolution current has been established for mixtures of ethylene carbonate and ethylmethyl carbonate. The effect of the perfluoroalkyl chain length on the dissolution rate has also been studied and the result has been elucidated with the help of considerations on the structure of the ions. Mechanistic information obtained from electrochemical impedance spectra revealed that at least two adsorbed intermediates have to be included in the dissolution mechanism. Conditions of application of lithium perfluoroalkylsulfonyl imides in lithium ion batteries are briefly discussed.