24. Describe the designfeatures of an electrochemical cells an example of the construction of any power source.

An electrochemical battery consists of cathode, anode and electrolyte. When charging the battery, the accumulation of electrons at the anode, which creates a voltage potential between the anode and the cathode. In normal operation, as power supply current flows from the cathode to the anode through the load. When charging the battery the current flows in the opposite direction. The electrodes of the battery are connected in two different ways, the first is electric circuit through which electrons flow to feed the load and the second through the electrolyte, where ions move between the electrodes through the dielectric separator (separator). The electrode that releases electrons during a redox reaction is called the anode. The electric potential of the anode of a galvanic cell is negative relative to the cathode. A chemical reaction in the battery is a reversible process, and therefore, the polarity of the electrodes changes depending on the operation mode (charge/discharge), but the terminal marking is always constant. In tables 1, 2 , 3, 4 describes the structure and processes in lithium, lead, Nickel and alkaline batteries.

Тable 1. Composition and processes in Lithium-ion batteries

Li-ion battery	Cathode	Anode	Electrolyte
material composition of the elements	lithium metal oxides	carbon based	lithium salts in an organic solven
composition and processes in charged state	a metal oxide with an intercalation structure	migration of lithium ions to the anode
composition and processes in discharged state	lithium ions return to the positive electrode	mostly carbon based

Тable 2. Composition and processes in lead-acid batteries

Lead-acid battery	Cathode	Anode	Electrolyte
material composition of the elements	lead dioxide	gray spongy lead	hydrochloric acid
composition and processes in charged state	lead dioxide, the electrons join	lead, electrons are detached	strong sulphuric acid
composition and processes in discharged state	lead is converted to lead sulfide at the anode with the release of electrons, and attached at the cathode		weak sulfuric acid (diluted with water)

Table 3. Composition and processes in NiMH and NiCd batteries.

NiMH,NiCd	Cathode	Anode	Electrolyte
material composition of the elements	Ni	NiMH NiCd	potassium hydroxide

Table 4. Composition and processes in alkaline batteries.

Alkaline battery	Cathode	Anode	Electrolyte
material composition of the elements	manganese dioxide	zinc	an aqueous solution of alkali

When submerged unpressurized system the design of the battery, a liquid electrolyte flowing between two electrodes. In hermetic designs the electrolyte is usually in the role of impregnation of the separator to provide the movement of ions from anode to cathode and back when charging. Ions are atoms, which electrons have attached or lost. They acquire the ability to move between the electrodes through the separator.