Brief Introduction Of Battery Principle

In a chemical battery, the direct conversion of chemical energy into electrical energy is the result of spontaneous chemical reactions such as oxidation and reduction inside the battery, which are carried out on the two electrodes respectively. The negative electrode active material is composed of reducing agents with relatively negative potential and stable in the electrolyte, such as active metals such as zinc, cadmium, and lead, and hydrogen or hydrocarbons. The positive electrode active material is composed of oxidants with positive potential and stable in the electrolyte, such as metal oxides such as manganese dioxide, lead dioxide, nickel oxide, oxygen or air, halogens and their salts, oxyacids and their salts, etc. Electrolyte is a material with good ion conductivity, such as acid, alkali, salt aqueous solution, organic or inorganic non-aqueous solution, molten salt or solid electrolyte, etc. When the external circuit is disconnected, although there is a potential difference (open circuit voltage) between the two poles, there is no current, and the chemical energy stored in the battery is not converted into electrical energy. When the external circuit is closed, current flows through the external circuit under the action of the potential difference between the two electrodes. At the same time, inside the battery, since there are no free electrons in the electrolyte, the transfer of charges must be accompanied by oxidation or reduction reactions at the interface between the two-pole active material and the electrolyte, as well as the material migration of reactants and reaction products. The transfer of charges in the electrolyte is also accomplished by the migration of ions. Therefore, the normal charge transfer and material transfer process inside the battery is a necessary condition to ensure the normal output of electric energy. When charging, the direction of the process of electricity and mass transfer inside the battery is just opposite to that of discharge; the electrode reaction must be reversible to ensure the normal progress of the process of mass and electricity transfer in the opposite direction. Therefore, the reversibility of the electrode reaction is a necessary condition for forming a battery. G is the Gibbs reaction free energy increment (Joule); F is the Faraday constant = 96500 library = 26.8 amp hours; n is the equivalent number of the battery reaction. This is the basic thermodynamic relationship between the electromotive force of the battery and the reaction of the battery, and it is also the basic thermodynamic equation for calculating the energy conversion efficiency of the battery. In fact, when the current flows through the electrode, the electrode potential will deviate from the thermodynamic equilibrium electrode potential, this phenomenon is called polarization. The greater the current density (current passing per unit electrode area), the more severe the polarization. Polarization is one of the important causes of battery energy loss.