As a new type of green energy, lithium batteries are widely used in portable electronic products, power tools, electric vehicles, energy storage systems and other fields. Lithium batteries have the characteristics of small size, light weight, high energy density and long cycle life, making them one of the most popular types of batteries in the world today. This article will introduce the working principle, classification, key parameters and application fields of lithium batteries in detail.
1. Composition of lithium batteries
Lithium batteries are mainly composed of two major parts, namely the battery cell and the protection board. The battery cell is equivalent to the heart of the lithium battery, responsible for storing and releasing energy; the protection board is equivalent to the brain of the lithium battery, managing and protecting the battery cell.
1. Battery cell
The battery cell is mainly composed of positive electrode material, negative electrode material, electrolyte, diaphragm and shell. The following are the functions of various materials:
(1) Positive electrode material: responsible for generating lithium ions during charging and accepting lithium ions during discharging. Common positive electrode materials include lithium cobalt oxide (LiCoO2), lithium manganese oxide (LiMn2O4), ternary lithium (LiNixCoyMnzO2) and lithium iron phosphate (LiFePO4).
(2) Negative electrode material: responsible for receiving lithium ions during charging and releasing lithium ions during discharging. Common negative electrode materials include carbon materials, silicon-carbon materials, etc.
(3) Electrolyte: responsible for transferring lithium ions between the positive and negative electrodes, and is the key medium for the operation of lithium batteries. Common electrolytes include liquid electrolytes used in lithium-ion batteries and gel electrolytes used in polymer lithium batteries.
(4) Diaphragm: prevents short circuits between the positive and negative electrodes while allowing lithium ions to pass through. Common diaphragm materials include polyethylene, polypropylene and ceramic materials.
(5) Shell: protects the battery from the influence of the external environment and prevents battery leakage, expansion and other phenomena.
2. Protection board
The protection board is mainly composed of protection chip, MOS tube, resistor, capacitor and PCB board. The following are the functions of each part:
(1) Protection chip: responsible for monitoring the charge and discharge status of the battery, and managing and protecting the battery. For example, preventing the battery from overcharging, over-discharging, over-current and over-temperature.
(2) MOS tube: cuts off the connection between the battery and the external circuit to realize the charging and discharging control of the battery. (3) Resistance and capacitance: filtering function, improving battery performance.
(4) PCB board: carrying other components and providing connection between battery and external circuit.
II. Working principle of lithium battery
1. Charging process
During the charging process, the positive electrode of the battery generates lithium ions, which are transferred to the negative electrode through the electrolyte. The lithium ions are embedded in the negative electrode, while the lithium ions in the positive electrode are reduced. The larger the charging current, the more lithium ions are embedded, and the higher the voltage and capacity of the battery.
2. Discharging process
During the discharge process, the lithium ions in the negative electrode are released and returned to the positive electrode. The more lithium ions are released, the higher the voltage and capacity of the battery. During the discharge process, the battery provides electrical energy to the outside to meet the power demand of external equipment.
3. Cycle life
The cycle life of a lithium battery refers to the number of times the battery is charged and discharged under certain conditions. Generally, the cycle life of a lithium battery is about 500-1000 times. The cycle life is affected by factors such as battery materials, charging and discharging parameters and environmental conditions.
3. Classification of lithium batteries
Lithium batteries can be divided into the following categories:
1. Disposable non-rechargeable batteries: such as lithium manganese dioxide batteries, lithium-sulfuramide batteries, etc.
2. Rechargeable batteries: divided into square lithium batteries, cylindrical lithium batteries, aluminum shell lithium batteries, steel shell lithium batteries, soft pack batteries, etc.
3. According to the positive electrode material: lithium cobalt oxide, lithium manganese oxide, ternary lithium, lithium iron phosphate, etc.
4. According to the state of the electrolyte: lithium ion batteries, polymer batteries, etc.
5. According to the purpose: ordinary batteries, power batteries, etc.
6. According to performance characteristics: high-capacity batteries, high-rate batteries, high-temperature batteries, low-temperature batteries, etc.
4. Key parameters of lithium batteries
1. Capacity: the amount of energy stored in the battery, in mAh or Wh.
2. Voltage: the potential difference of the battery, in V. The nominal voltage of a lithium battery is generally 3.6V or 3.7V.
3. Current: the rate at which the battery charges and discharges, in A. The charging current of lithium batteries is generally set between 0.2C and 1C.
4. Cycle life: the number of times a battery can be charged and discharged under certain conditions.
5. Safety: the ability of a battery to avoid short circuit, overcharge, overdischarge, overheating, etc. during the charging and discharging process.
5. Application fields of lithium batteries
Lithium batteries are widely used in various fields due to their high energy density, light weight and relatively low self-discharge rate. Here are some of the main application areas:
1. Mobile devices: Lithium batteries are widely used in mobile devices such as smartphones, tablets, laptops and portable audio/video devices. They provide high-performance energy storage solutions, allowing these devices to be used continuously for a long time.
2. Power tools: Power tools such as electric drills, electric saws, electric lawn mowers, etc. also use lithium batteries as their energy source. Lithium batteries provide sufficient power and have a longer service life and faster charging speed than other types of batteries.
3. Electric vehicles: Lithium batteries are widely used in vehicles such as electric cars, electric bicycles and electric scooters. They provide high energy density and reliable power support, providing long-range driving capabilities for electric vehicles.
4. Energy storage system: Lithium batteries are also used for energy storage in renewable energy systems such as solar and wind power. These systems are able to store energy collected during the day and release it to power when needed.
5. Aerospace: Lithium batteries are used in equipment such as drones, satellites and spacecraft in the aerospace field. Their high energy density and light weight are particularly important for these fields, helping to improve the performance and payload of equipment.
6. Medical equipment: Some portable medical devices, such as wearable health monitors, portable defibrillators, etc., also use lithium batteries as their power source.
7. Reserve power: Lithium batteries are used as backup or emergency power sources, such as emergency lighting systems or backup generators for power outages.
The above is an introduction to the working principle of lithium batteries. The working principle of lithium batteries relies on the reciprocating movement of lithium ions between the positive and negative electrodes. By selecting different positive and negative electrode materials, the performance of lithium batteries, such as capacity, voltage and cycle life, can be adjusted. In addition, lithium batteries also require a series of protection circuits to control the charging and discharging process to ensure their safe and reliable operation.
