Brief Introduction To The Principle Of Battery

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 in the battery, which are carried out on two electrodes respectively. The negative active material is composed of reducing agent with negative potential and stable in electrolyte, such as active metals such as zinc, cadmium, lead, hydrogen or hydrocarbons, etc. The positive active substance is composed of oxidants with positive potential and stable in the electrolyte, such as manganese dioxide, lead dioxide, nickel oxide and other metal oxides, oxygen or air, halogen and its salts, oxyacid and its salts, etc. Electrolytes are materials with good ionic conductivity, such as acid, alkali, salt aqueous solution, organic or inorganic nonaqueous solution, molten salt or solid electrolyte. 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, a current flows through the external circuit under the action of the potential difference between the two electrodes. At the same time, because there are no free electrons in the electrolyte inside the battery, the transfer of charge must be accompanied by the oxidation or reduction reaction between the bipolar active substances and the electrolyte interface, as well as the migration of reactants and reaction products. The transfer of charge in the electrolyte is also completed 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. During charging, the direction of power and mass transfer inside the battery is just opposite to that of discharge; The electrode reaction must be reversible to ensure the normal process of reverse mass transfer and electricity transfer. Therefore, reversibility of electrode reaction is a necessary condition to form a battery. G is the Gibbs reaction free energy increment (coke); F is Faraday constant=96500 storehouse=26.8 A · h; N is the equivalent number of battery reaction. This is the basic thermodynamic relationship between the battery electromotive force and the battery reaction, and 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, which is called polarization. The greater the current density (the current passing through the unit electrode area), the more serious the polarization. Polarization is one of the important reasons for energy loss of battery.