Basic knowledge of lithium-ion batteries

1. What is a lithium-ion battery?

Lithium-ion batteries are rechargeable batteries that rely mainly on the movement of lithium ions between positive and negative electrodes to work. It has the advantages of high energy density, long cycle life, and low self-discharge rate, and is widely used in mobile phones, laptops, electric vehicles and other fields.

2. Composition of lithium-ion batteries

Lithium-ion batteries are mainly composed of the following parts:

• Positive electrode material: usually lithium transition metal oxides such as lithium cobalt oxide (LiCoO2), lithium iron phosphate (LiFePO4), etc. are used to provide lithium ions.
• Negative electrode material: usually graphite or other carbon materials are used to store and release lithium ions.
• Electrolyte: usually an organic solution of lithium salt is used to conduct lithium ions between the positive and negative electrodes.
• Separator: a porous film located between the positive and negative electrodes to prevent short circuits while allowing lithium ions to pass through.
• Casing: usually made of metal or plastic materials to encapsulate the internal components of the battery.

3. Working principle of lithium-ion battery

The working principle of lithium-ion battery can be simply summarized as a "rocking chair" charging and discharging process:

Charging process: Under the action of an external electric field, lithium ions are released from the positive electrode material, embedded in the negative electrode material through the electrolyte, and electrons flow from the positive electrode to the negative electrode through an external circuit.

Discharging process: Under the action of an external load, lithium ions are released from the negative electrode material, embedded in the positive electrode material through the electrolyte, and electrons flow from the negative electrode to the positive electrode through an external circuit.

4. Main parameters of lithium-ion batteries

• Voltage: The single cell voltage of different lithium batteries varies due to their different positive electrode materials, chemical systems and designs. The following is a comparison of the single cell voltage characteristics of common lithium battery types:

• Capacity: The unit is ampere-hour (Ah) or milliampere-hour (mAh), which indicates the battery's ability to store charge.
• Energy density: The unit is watt-hour/kilogram (Wh/kg) or watt-hour/liter (Wh/L), which indicates the energy stored in the battery per unit mass or volume.
• Power density: The unit is watts per kilogram (W/kg) or watts per liter (W/L), which indicates the power that a battery can output per unit mass or volume.
• Cycle life: Indicates the number of cycles that a battery can undergo before its capacity decays to a certain extent during the charge and discharge cycle.

5. Advantages and disadvantages of lithium-ion batteries

Advantages:

• High energy density
• Long cycle life
• Low self-discharge rate
• No memory effect
• Environmentally friendly

Disadvantages:

• High cost
• Safety risks (overcharge, overdischarge, high temperature, etc. may cause fire and explosion)
• Poor low temperature performance

6. Application of lithium-ion batteries

Lithium-ion batteries are widely used in the following fields:

1. Consumer electronics: mobile phones, laptops, tablets, digital cameras, etc.
2. Electric tools: electric drills, electric saws, lawn mowers, etc.
3. Electric vehicles: electric cars, electric bicycles, electric motorcycles, etc.
4. Energy storage systems: home energy storage, grid energy storage, etc.
5. So on

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