Lithium-ion batteries, as the core power source for modern electronic devices and electric vehicles, possess a series of distinctive characteristics and come in various types based on different classification methods . Below is a detailed explanation covering their features and classifications.
Characteristics of Lithium-Ion Batteries
Compared to other types of rechargeable batteries, lithium-ion batteries exhibit significant advantages but also have some limitations.
Core Advantages
- High Energy Density: They have high storage energy density, currently reaching 460-600 Wh/kg, which is about 6-7 times that of lead-acid batteries . The weight of a lithium-ion battery is half that of nickel-cadmium or nickel-metal hydride batteries of the same capacity, and its volume is 20-30% of nickel-cadmium and 35-50% of nickel-metal hydride .
- High Operating Voltage: The operating voltage of a single cell is as high as 3.7-3.8V (3.2V for Lithium Iron Phosphate), which is three times that of nickel-cadmium or nickel-metal hydride batteries . This makes it easier to form a battery pack with higher voltage.
- Long Cycle Life: Under normal conditions, the charge-discharge cycles of lithium-ion batteries can exceed 500 times, while Lithium Iron Phosphate batteries can reach over 2,000 times, and some can even be used up to 8,000 times .
- No Memory Effect: Lithium-ion batteries do not have the “memory effect” that plagues nickel-cadmium batteries and can be charged at any time without needing to be fully discharged first .
- Low Self-Discharge Rate: This is one of its most outstanding advantages. The self-discharge rate is generally less than 1% per month, which is less than 1/20th of nickel-metal hydride batteries .
- Fast Charging Capability: It supports fast charging. Using a constant current and constant voltage charger rated at 4.2V, a lithium-ion battery can be fully charged within 1.5 to 2.5 hours . Newly developed Lithium Iron Phosphate batteries can be charged to 90% of their nominal capacity in just 10 minutes .
- Environmental Friendliness: It does not contain any toxic or harmful heavy metals such as lead, mercury, or cadmium, making it known as a “green battery” .
- High and Low-Temperature Adaptability: It can be used in environments ranging from -20°C to 60°C and, after special processing, can be used in -45°C environments .
Main Disadvantages
- Safety Risks and Need for Protection Circuits: Lithium-ion batteries are not resistant to overcharging or over-discharging. Overcharging can damage the positive electrode structure, while over-discharging may cause the electrode material to collapse, both shortening the battery’s life . Therefore, a specialized protection circuit must be used to prevent overcharging and over-discharging .
- Aging: The capacity of a lithium-ion battery slowly decays with use and is also related to temperature. This aging phenomenon can manifest as reduced capacity or increased internal resistance .
- Higher Cost: Especially for batteries using cobalt-based positive electrode materials, the price is relatively expensive due to the scarcity of cobalt resources .
- Stringent Production Requirements: The production process requires high standards and comes with high costs .
Types of Lithium-Ion Batteries
Lithium-ion batteries can be divided into multiple categories based on different criteria such as internal materials, shape, packaging materials, and application scenarios .
Classification by Electrolyte Material
Based on the electrolyte material used, lithium-ion batteries are mainly divided into two categories :
- Liquid Lithium-Ion Battery (LIB): This type uses a liquid electrolyte (a mixture of lithium salt and organic solvent) and a separator to isolate the positive and negative electrodes. Currently, the majority of power batteries on the market are of this type . Its technology is mature and cost is low.
- Polymer Lithium-Ion Battery (PLB): This type uses a solid polymer electrolyte (which can be “dry” or “colloidal”) to replace the liquid electrolyte and separator . It can be made into various shapes with a soft packaging material (aluminum-plastic film), offering better safety and a lighter weight .
Additionally, solid-state batteries and semi-solid batteries (a transitional product where the electrolyte contains 5-10% liquid) currently under development are also extensions of this classification .
Classification by Shape and Packaging Material
Based on the external shape and packaging material, they are classified into three main types :
| Type | Shape Description | Packaging Material | Main Features |
|---|---|---|---|
| Cylindrical Battery | Fixed cylinder diameter and height, e.g., 18650, 26650. | Steel shell | High manufacturing consistency, mature process, low cost, but lower system energy density after grouping . |
| Prismatic Battery | Rectangular parallelepiped shape. | Aluminum shell or steel shell | High structural reliability, simple structure, high monomer energy density, and good grouping efficiency . |
| Pouch Battery | Rectangular shape. | Aluminum-plastic film (soft case) | Very light, high energy density, flexible shape (can be made into various shapes, even irregular ones), but the packaging film is easily damaged . |
Classification by Positive Electrode Material
This is the most common classification method, as different positive electrode materials directly determine the battery’s performance and application areas .
| Positive Electrode Material | Abbreviation | Key Features | Primary Applications |
|---|---|---|---|
| Lithium Cobalt Oxide (LiCoO₂) | LCO | High energy density, poor safety, short cycle life, high cost . | Consumer electronics like smartphones and laptops . |
| Lithium Manganese Oxide (LiMn₂O₄) | LMO | Good rate performance, easier preparation, lower cost, but cycling and high-temperature performance are average due to manganese dissolution . | Power tools, electric vehicles, medical equipment . |
| Lithium Iron Phosphate (LiFePO₄) | LFP | Excellent safety, very long cycle life (over 2,000 to 8,000 times), low cost, and abundant raw material resources, but lower energy density . | Electric buses, energy storage power stations, medium to low-end passenger cars . |
| Ternary Materials (NCM/NCA) | NCM/NCA | High energy density, good rate performance, and low-temperature performance. | Medium to high-end electric vehicles (long range), consumer electronics . |
Classification by Application
Based on application scenarios, they can be divided into three main categories :
- Consumer (Digital) Lithium-Ion Batteries: Used in smartphones, tablets, laptops, power banks, Bluetooth headphones, etc. These applications have relatively lower requirements for instantaneous current.
- Power Lithium-Ion Batteries: Used in new energy vehicles (EVs), electric bicycles, drones, power tools, etc. These applications require high instantaneous current and high power output, also known as “high-rate batteries” .
- Energy Storage Lithium-Ion Batteries: Used in base station power supplies, solar and wind energy storage, grid power storage, home solar storage systems, etc. These applications typically prioritize long cycle life, safety, and cost .
