1. Definition and Classification of Batteries
Classification of Batteries
- By working nature: Primary batteries (non-rechargeable), secondary batteries (rechargeable), and fuel cells.
- By electrolyte type: Acidic batteries, alkaline batteries, organic electrolyte batteries, and solid electrolyte batteries.
- By positive and negative electrode materials: Lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, lithium-ion batteries, etc.
2. Basic Composition of Batteries
- Positive electrode: Undergoes a reduction reaction and gains electrons.
- Negative electrode: Undergoes an oxidation reaction and loses electrons.
- Electrolyte: Conducts ions but is insulating to electrons.
- Separator: Isolates the positive and negative electrodes to prevent short circuits while allowing ions to pass through.
- Outer casing: Protects the internal structure of the battery.
3. Working Principle of Batteries
- Discharge process: Chemical energy is converted into electrical energy, and electrons flow from the negative electrode to the positive electrode through the external circuit.
- Charging process: Electrical energy is converted into chemical energy, and electrons flow from the positive electrode to the negative electrode through the external circuit.
4. Main Performance Indicators of Batteries
- Voltage: The potential difference between the positive and negative electrodes of the battery.
- Capacity: The ability of the battery to store electric charge, with the unit of ampere-hour (Ah).
- Energy density: The amount of energy stored per unit mass or volume of the battery, with the units of watt-hour per kilogram (Wh/kg) or watt-hour per liter (Wh/L).
- Power density: The amount of power that can be output per unit mass or volume of the battery, with the units of watt per kilogram (W/kg) or watt per liter (W/L).
- Cycle life: The number of times the battery can be repeatedly charged and discharged.
- Self-discharge rate: The rate at which the battery's capacity decreases during storage.
- Safety: The ability of the battery to avoid hazards under abusive conditions (such as overcharging, over-discharging, short circuit, high temperature, etc.).
