I. What Are Cylindrical Lithium Batteries?
1. Definition of Cylindrical Batteries
Cylindrical lithium batteries are categorized into different material systems: lithium iron phosphate (LFP), lithium cobalt oxide (LCO), lithium manganese oxide (LMO), cobalt-manganese hybrid, and ternary materials. Their casings are either steel or polymer. Batteries from different material systems offer distinct advantages. Currently, steel-cased cylindrical LiFePO₄ batteries dominate the market. These batteries exhibit high capacity, high output voltage, excellent charge/discharge cycle performance, stable output voltage, high-current discharge capability, stable electrochemical properties, operational safety, wide operating temperature range, and environmental friendliness. They are widely used in solar lighting, lawn lighting, backup power sources, power tools, and toy models.
2. Cylindrical Battery Structure
A typical cylindrical battery consists of: casing, end cap, positive electrode, negative electrode, separator, electrolyte, PTC element, gasket, safety valve, etc. The battery casing generally serves as the negative electrode, while the end cap functions as the positive electrode. The casing is typically made of nickel-plated steel plate.
3. Advantages of Cylindrical Lithium Batteries
Compared to pouch and prismatic lithium batteries, cylindrical lithium batteries have the longest development history, higher standardization, more mature manufacturing processes, higher yield rates, and lower costs.
Mature production processes, lower PACK costs, higher battery product yield rates, and superior heat dissipation performance.
Cylindrical batteries have established a series of internationally unified standard specifications and models with mature processes, making them suitable for large-scale continuous production.
The cylindrical shape provides a large specific surface area, enhancing heat dissipation.
Cylindrical batteries are typically sealed, eliminating maintenance concerns during use.
The battery casing exhibits high pressure resistance, preventing swelling issues common in prismatic or pouch cells.
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4. Cathode Materials for Cylindrical Batteries
Currently, mainstream commercial cathode materials for cylindrical batteries include lithium cobalt oxide (LiCoO₂), lithium manganese oxide (LiMn₂O₄), ternary compounds (NMC), and lithium iron phosphate (LiFePO₄). Batteries using different material systems exhibit distinct characteristics, as compared below:
| Project | Lithium cobalt oxide | LiNiCoMnO2 | LiMn2O4 | LiFePO4 |
| Bulk density（g/cm3） | (LiCoO2) | 2.0～2.3 | 2.2～2.4 | 1.0～1.4 |
| Specific surface area（m2/g） | 2.8～3.0 | 0.2～0.4 | 0.4～0.8 | 12～20 |
| Cubic capacity (mAh/g) | 0.4～0.6 | 140～180 | 90～100 | 130～140 |
| Voltage platform (V) | 135～140 | 3.5 | 3.8 | 3.2 |
| Cyclic performance | 3.7 | ≥500 times | ≥300 times | ≥2000 times |
| Transition metals | ≥500 times | Poverty | Rich | Very rich |
| Raw material cost | Poverty | High | Low-cost | Low-cost |
| Environmental protection | Very high | Nickel, cobalt-containing | Non-toxic | Non-toxic |
| Safety performance | Cobalt-containing | Better | Good | Excellent |
| Applicable field | Rarely | Small battery/small power battery | Power battery, low-cost battery | Power battery / ultra-high capacity power supply |
| Advantages | Small and medium-sized batteries | Electrochemical performance is stable, with good cycling performance. | Manganese resources are abundant, prices are low, and safety performance is good. | High safety, environmental protection, long lifespan |
| Shortcomings | Charging and discharging stability, simple production process; cobalt is expensive, and the cycle life is low. | Cobalt prices are expensive. | Low energy density, poor electrolyte compatibility | The low-temperature performance is poor, and the discharge voltage is low. |
If original equipment manufacturers (OEMs) of medical devices or instruments require ternary lithium-ion battery packs, you can review all lithium-ion battery pack models offered by TEFOO.
5. Cylindrical Battery Anode Materials
Cylindrical battery anode materials are broadly categorized into six types: carbon anodes, alloy anodes, tin-based anodes, lithium-containing transition metal nitride anodes, nanoscale materials, and nano-anodes.
1. Carbon Nanoscale Anode Materials: Currently, anode materials actually used in lithium-ion batteries are primarily carbon-based, such as artificial graphite, natural graphite, mesophase carbon microspheres, petroleum coke, carbon fiber, and pyrolytic resin carbon.
2. Alloy Anode Materials: These include tin-based alloys, silicon-based alloys, germanium-based alloys, aluminum-based alloys, antimony-based alloys, magnesium-based alloys, and other alloys. No commercial products are available at present.
3. Tin-based anode materials: Tin-based anodes can be categorized into tin oxides and tin-based composite oxides. Oxides refer to various valence states of metallic tin. No commercial products exist at present.
4. Lithium-containing transition metal nitride anode materials: No commercial products are currently available.
5. Nanoscale materials: Nanotubes, nano-alloy materials.
6. Nano anode materials: Nano-oxide materials.
II. Cylindrical Lithium-ion Battery Cells
1. Cylindrical Lithium-ion Cell Brands
Cylindrical lithium batteries are widely adopted by Japanese and South Korean battery manufacturers, with substantial domestic Chinese producers also entering this market. The earliest cylindrical lithium battery was invented by Sony Corporation of Japan in 1992.
Well-known cylindrical lithium-ion cell brands include: Sony, Panasonic, Sanyo, Samsung, LG, A123 Systems, BAK, Lishen, etc. TEFOO’s lithium-ion battery packs utilize Panasonic’s cylindrical lithium-ion cells.
2. Types of Cylindrical Lithium-Ion Cells
Cylindrical lithium-ion cells are typically denoted by a five-digit code. Counting from the left, the first and second digits indicate the cell diameter, the third and fourth digits denote the cell height, and the fifth digit signifies a cylindrical shape. Numerous cylindrical lithium battery models exist, with common types including 10400, 14500, 16340, 18650, 21700, 26650, and 32650. TEFOO’s lithium-ion battery packs exclusively utilize 18650 lithium-ion cells.
①10440 Battery
The 10440 battery is a lithium battery measuring 10mm in diameter and 44mm in height, identical in size to what we commonly refer to as a “AA battery.” This battery typically has a very small capacity, only a few hundred mAh, and is primarily used in miniature electronic devices. Examples include flashlights, mini speakers, and amplifiers.
②14500 Battery
The 14500 battery is a lithium battery with a diameter of 14mm and a height of 50mm. It typically operates at 3.7V or 3.2V, with a nominal capacity slightly larger than the 10440 battery, usually around 1600mAh. It offers superior discharge performance and is primarily used in consumer electronics such as wireless speakers, electric toys, and digital cameras.
③ 16340 Battery
The 16340 battery is a lithium-ion cell with a diameter of 16mm and a height of 34mm. Its relatively low profile and substantial capacity make it common in high-intensity flashlights, LED torches, headlamps, laser pointers, and lighting fixtures.
④ 18650 Battery
The 18650 battery is a lithium-ion cell with a diameter of 18mm and a height of 65mm. Its most notable feature is its exceptionally high energy density, reaching nearly 170 Wh/kg. making it a cost-effective choice. This is the most commonly seen battery type due to its mature technology and stable system performance. It is widely used in applications requiring around 10 kWh capacity, such as smartphones, laptops, and other small electronics.
⑤ 21700 Battery
The 21700 battery is a lithium-ion cell with a diameter of 21mm and height of 70mm. Its increased volume enhances space utilization, allowing for higher energy density in both individual cells and systems. Its volumetric energy density significantly surpasses that of the 18650 type. It is widely used in digital devices, electric vehicles, self-balancing scooters, solar-powered lithium streetlights, LED lighting, and power tools.
⑥ 26650 Battery
The 26650 battery is a lithium-ion cell with a diameter of 26mm and height of 65mm, featuring a nominal voltage of 3.2V and nominal capacity of 3200mAh. Characterized by excellent capacity and high consistency, it is increasingly replacing 18650 batteries and gaining favor in many power battery applications.
⑦ 32650 Battery
The 32650 battery is a lithium-ion cell with a diameter of 32mm and height of 65mm. Its strong continuous discharge capability makes it suitable for electric toys, backup power supplies, UPS batteries, wind power generation systems, and wind-solar hybrid power systems.
III. Market Development of Cylindrical Lithium Batteries
Technological advancements in cylindrical lithium-ion batteries primarily stem from innovations in key battery materials and their application progress. The development of new materials further enhances battery performance, improves quality, reduces costs, and enhances safety. To meet downstream applications’ demand for increased specific energy, efforts focus on two approaches: adopting high-capacity materials and utilizing high-voltage materials by raising charging voltages.
Cylindrical lithium-ion batteries have evolved from the 14500 format to Tesla’s 21700 cells. In the near-to-medium term, while optimizing existing lithium-ion power battery technologies to meet the scaling demands of new energy vehicles, the focus will be on developing novel lithium-ion power batteries. This involves enhancing critical technologies such as safety, consistency, and lifespan, while concurrently conducting forward-looking R&D on new battery systems.
For the medium-to-long-term development of cylindrical lithium-ion batteries, while continuously optimizing and improving new lithium-ion power batteries, the emphasis will be on developing new-system power batteries. This will significantly increase energy density, substantially reduce costs, and achieve the practical application and large-scale deployment of new-system power batteries.
IV. Comparison Between Cylindrical and Prismatic Lithium Batteries
1. Battery Shape: Prismatic batteries can be designed in any size, whereas cylindrical batteries cannot be scaled up.
2. Rate Discharge Characteristics: Due to manufacturing constraints in welding multiple tabs, cylindrical batteries exhibit slightly inferior rate discharge performance compared to prismatic batteries with multiple tabs.
3. Discharge Platform: Theoretically, lithium batteries using identical electrode materials and electrolytes should exhibit consistent discharge platforms. However, prismatic cells typically feature a slightly higher discharge platform.
4. Product Quality: Cylindrical battery manufacturing processes are more mature. The probability of secondary slitting defects in electrode sheets is low, and both winding process maturity and automation levels are relatively high. The laminated electrode process currently relies on semi-manual methods, which adversely affects battery quality.
5. Tab Welding: Cylindrical battery tabs are easier to weld than those of prismatic lithium batteries; prismatic lithium batteries are prone to cold soldering, affecting battery quality.
6. PACK Assembly: Cylindrical cells offer greater ease of use, resulting in simpler PACK technology and superior heat dissipation. PACKing prismatic cells requires effective thermal management solutions.
7. Structural Characteristics: Prismatic cells exhibit reduced chemical activity at their corners, leading to energy density degradation over extended use and shorter operational endurance.
V. Comparison Between Cylindrical Lithium Batteries and Pouch Lithium Batteries
1. Pouch Batteries
Pouch batteries offer superior safety performance. Structurally, they utilize aluminum-plastic film packaging. In the event of a safety issue, pouch batteries typically swell and rupture, unlike steel-cased or aluminum-cased cells that may explode. They outperform cylindrical lithium batteries in safety.
2. Pouch Batteries are Relatively Lighter: Pouch batteries weigh 40% less than steel-cased lithium batteries of equivalent capacity and 20% less than cylindrical aluminum-cased lithium batteries. They also feature lower internal resistance, significantly reducing self-discharge.
3. Pouch batteries exhibit superior cycle performance with extended cycle life. After 100 cycles, their capacity degradation is 4%–7% lower than that of cylindrical aluminum-cased batteries.
4. Flexible design: Pouch cells offer versatile shapes, enabling thinner profiles and customization to client specifications for new cell models—capabilities unavailable in cylindrical lithium batteries.
5. Limitations compared to cylindrical lithium batteries include lower consistency, higher costs, and susceptibility to electrolyte leakage. Cost can be mitigated through mass production, while leakage risks are addressed by enhancing aluminum-plastic composite film quality.
