Cylindrical Lithium-Ion Batteries

Drone Battery

ENOV High-Energy drone batteries power industrial and commercial drones. Delivering 220–320 Wh/kg energy density, they enable long flight times (30+ mins) and support fast charging (2C). Perfect for aerial photography, surveillance, and delivery drones.

I. Definition and Classification

(I) Definition

A cylindrical lithium-ion battery is a rechargeable lithium-ion battery with a cylindrical shape. It uses lithium as the core energy storage carrier and is widely applied in various fields due to its long service life and high energy density. Its outer casing is mostly made of steel or aluminum alloy. Inside, it encapsulates key components such as the positive electrode, negative electrode, separator, and electrolyte. Some models are also equipped with safety structures like a safety valve and a PTC (Positive Temperature Coefficient) element, which ensure performance while enhancing safety during use.

(II) Classification

Based on the difference in positive electrode materials, cylindrical lithium-ion batteries can be divided into several systems, each with its own advantages, as detailed below:

• Lithium Iron Phosphate (LFP) System: It has high capacity, stable output voltage, excellent charge-discharge cycle performance, and can withstand high-current discharge. It also features stable electrochemical performance, a wide operating temperature range, and environmental friendliness. Currently, steel-cased cylindrical LFP batteries are widely used.

• Lithium Cobalt Oxide (LCO) System: It was widely used in the consumer electronics field in the early days. It has high energy density but relatively short cycle life and high cost. Special attention must be paid to its safety under specific conditions.

• Lithium Manganese Oxide (LMO) System: It has good low-temperature performance and rate capability, and low cost. However, its cycle stability and energy density are slightly inferior to those of some other systems.

• Cobalt-Manganese Mixed System: It combines some advantages of lithium cobalt oxide and lithium manganese oxide, achieving a certain balance between energy density and safety. It is suitable for scenarios with balanced performance requirements.

• Ternary Material System (NCM/NCA): It has high energy density, which can meet the long-endurance needs of equipment. However, its cost and safety need to be comprehensively considered based on specific formulas and application scenarios.

II. Core Structure

The structure of a cylindrical lithium-ion battery is sophisticated, and all components work together to realize the storage and release of electrical energy. It mainly includes the following parts:

• Outer Casing: Mostly made of nickel-plated steel or aluminum alloy. It not only provides solid mechanical support for the battery to resist external impact and vibration but also seals the electrolyte to prevent leakage. Meanwhile, the outer casing usually serves as the negative electrode of the battery.

• Cap: It acts as the positive electrode of the battery, and its design must ensure the stable output of current. Some caps are also integrated with structures such as a safety valve to enhance battery safety.

• Positive Electrode: Its core materials include lithium cobalt oxide, ternary materials (NCM/NCA), lithium iron phosphate, etc. It is the key part where the oxidation reaction occurs and lithium ions are released in the lithium-ion battery, directly affecting the battery’s energy density and output performance.

• Negative Electrode: The mainstream material is graphite, and some new-type batteries use silicon-based or silicon-carbon composite materials. Its main function is to receive and store lithium ions released from the positive electrode, and its performance has an important impact on the battery’s cycle life and charging speed.

• Separator: Generally, it is a polyolefin (PP/PE) porous membrane. It can effectively separate the positive and negative electrodes to avoid short circuits, while allowing lithium ions to pass through, ensuring the normal conduction of ions inside the battery.

• Electrolyte: It is prepared by dissolving lithium salts (such as LiPF₆) in organic solvents. It serves as an ion-conducting medium, providing a channel for the migration of lithium ions between the positive and negative electrodes. Its composition and performance affect the battery’s internal resistance, rate characteristics, and safety.

• Safety Valve: When the internal pressure of the battery is too high due to overcharging, short circuits, or other reasons, the safety valve will automatically release pressure to prevent the battery from exploding. It is an important component to ensure battery safety.

• PTC Element: Also known as a positive temperature coefficient thermistor. When the battery temperature is too high, its resistance increases sharply, limiting the passage of current and preventing the battery temperature from rising further, thus playing a role in overheating protection.

• Gasket: Mainly used for sealing and insulation to prevent electrolyte leakage, and at the same time, it ensures the stable relative position of various components inside the battery.

III. Common Models and Specifications

The model of a cylindrical lithium-ion battery is usually named after “diameter (mm) + height (mm)”. Different models vary significantly in capacity and applicable scenarios, as shown in the following table:

Model	Diameter (mm)	Height (mm)	Capacity Range (mAh)	Common Applications
10440	10	44	Several hundred	Miniature electronic products, such as flashlights, mini speakers, and amplifiers
14500	14	50	Approximately 1600	Consumer electronic products, such as wireless speakers, electric toys, and digital cameras
16340	16	34	Moderate	High-brightness flashlights, LED flashlights, headlamps, laser lights, and lighting fixtures
18650	18	65	1500-3500	Mobile phones, laptops, flashlights, some electric vehicles, and power tools
21700	21	70	3000-5000	Tesla vehicles, digital products, electric vehicles, balance bikes, solar lithium-ion battery street lamps, LED lights, and power tools
26650	26	65	4000-6000	Energy storage systems, electric two-wheelers, high-end flashlights, industrial equipment, and some power batteries
32650	32	65	6000-8000	Energy storage systems, industrial equipment, electric toys, backup power supplies, UPS batteries, wind power generation systems, and wind-solar hybrid power generation systems

IV. Performance Advantages and Disadvantages

(I) Advantages

• Mature Technology and Controllable Cost: With a long development history, it has formed internationally unified standard specifications and models, which is suitable for large-scale continuous production with a high yield rate. Not only the manufacturing cost is low, but also the subsequent PACK (battery assembly) cost is relatively affordable.

• Excellent Heat Dissipation Performance: The cylindrical structure gives it a large specific surface area, allowing heat to be distributed evenly and dissipated quickly. This effectively prevents the battery from being affected in performance or causing safety issues due to overheating during charge and discharge.

• High Mechanical Strength: The outer casing is made of steel or aluminum alloy, which has strong resistance to impact and vibration. During transportation, installation, and use, it can better protect internal components and is less likely to have bulging problems that are common in prismatic and pouch batteries.

• Convenient Use and Maintenance: Most of them are sealed storage batteries, which do not require additional maintenance during normal use, saving the trouble of frequent inspection and maintenance. At the same time, the battery has stable performance, and its reliability has been verified through long-term practice.

• Strong Combination Flexibility: Battery packs with different voltages and capacities can be formed through series and parallel connections, meeting the diverse power needs of different fields such as consumer electronics, electric vehicles, and energy storage systems.

(II) Disadvantages

• Low Space Utilization: The cylindrical structure leads to many gaps between multiple batteries when they are grouped. Compared with prismatic and pouch batteries, it is difficult to achieve higher energy storage in the same space, resulting in relatively low energy density.

• High Grouping Difficulty and BMS Requirements: The capacity of a single cell is small. To meet the needs of high-power and large-capacity equipment, a large number of cells need to be combined. This not only increases the complexity of grouping (such as the need for special brackets for fixation) but also places higher requirements on the Battery Management System (BMS). It is necessary to accurately monitor the status of each battery to ensure consistency and safety. For example, the early Tesla Model S used 7,000 18650 batteries, which had a very high dependence on the BMS.

• Limited Improvement in Energy Density: Compared with prismatic and pouch batteries, the structural design of cylindrical lithium-ion batteries faces more bottlenecks in improving energy density. Although improvements can be made through material innovation, the overall room for improvement is relatively small.

• High Cost of Some Models: Some cylindrical lithium-ion batteries that use new materials (such as high-nickel ternary materials and silicon-based negative electrodes) or have special performance (such as high-rate discharge) are relatively expensive due to high material costs and high production process requirements.

• Safety Risks Require Vigilance: Improper use, such as overcharging, over-discharging, physical damage (piercing, squeezing), or exposure to high-temperature environments, may cause thermal runaway, leading to liquid leakage, fire, or even explosion. Therefore, there are certain requirements for the use and storage conditions.

V. Application Fields

(I) Consumer Electronics Field

With its small size, stable performance, and moderate capacity, cylindrical lithium-ion batteries are widely used in the consumer electronics field. For example, portable devices such as mobile phones, laptops, and tablets often use batteries of models like 18650 and 14500; devices such as drones, handheld game consoles, and electric shavers also rely on them for continuous power supply; in addition, small electronic products such as mini speakers, amplifiers, high-brightness flashlights, and LED headlamps also mostly use cylindrical lithium-ion batteries of corresponding specifications.

(II) Electric Vehicle Field

Cylindrical lithium-ion batteries are one of the important power sources in electric vehicles. In terms of electric cars, many Tesla models have successively adopted batteries of models 18650, 21700, and 4680, and the early Nissan Leaf used 26650 batteries; for two-wheel electric vehicles such as electric bicycles and electric motorcycles, large-capacity batteries of models like 26650 and 32650 are often selected to meet the long-endurance needs; short-distance transportation tools such as balance bikes and electric scooters also mostly use batteries of models like 21700 to ensure power output.

(III) Power Tool Field

High-rate discharge cylindrical lithium-ion batteries (such as SONY VTC6) perform well in the power tool field. Power tools such as electric drills, electric saws, angle grinders, and electric hammers have high requirements for battery discharge speed and continuous power. Cylindrical lithium-ion batteries of appropriate specifications can meet their high-intensity work needs, ensuring sufficient power and stable performance during the use of the tools.

(IV) Energy Storage System Field

With the growth of energy storage demand, the application of cylindrical lithium-ion batteries in energy storage systems has gradually expanded. Household energy storage systems can use them to store solar energy or electricity during the off-peak period of the power grid and release it during the peak period of electricity consumption, realizing the rational use of energy; for backup power supplies of communication base stations and UPS (Uninterruptible Power Supply) systems, large-capacity batteries of models like 32650 and 26650 are often used to ensure rapid switching of power supply in case of power outages and guarantee the normal operation of equipment; in addition, the energy storage parts of outdoor lighting equipment such as solar lamps and lawn lamps, as well as the energy storage modules of wind power generation and wind-solar hybrid power generation systems, also mostly use cylindrical lithium-ion batteries.

(V) Industrial and Special Fields

In industrial production, some industrial equipment (such as testing instruments and portable equipment) relies on cylindrical lithium-ion batteries for power supply; electric toys (such as remote-controlled racing cars and large toy models, and Enovbattery also produces this type of battery) also select high-capacity cylindrical lithium-ion batteries to achieve complex movements and long playing time; at the same time, in some special fields, such as medical equipment (small portable medical instruments) and aerospace (power supply for some small equipment), cylindrical lithium-ion batteries with stable performance are also used under specific circumstances.

VI. Safety Precautions

(I) Avoid Overcharging and Over-Discharging

Overcharging (voltage exceeding 4.2V) or over-discharging (voltage lower than 2.5V) of the battery will seriously damage the battery performance and even cause thermal runaway. During use, a qualified Battery Management System (BMS) or a dedicated charger must be equipped to strictly monitor the charging and discharging processes and ensure that the voltage is within a safe range. The use of non-original or non-compliant chargers is prohibited.

(II) Keep Away from Extreme Temperature Environments

Long-term exposure to high-temperature environments (such as direct sunlight and proximity to heat sources) will accelerate battery aging, shorten its service life, and may cause electrolyte decomposition and increased internal pressure, leading to liquid leakage or fire; low-temperature environments will reduce battery capacity and discharge performance, affecting its use. The battery should be stored in a dry and well-ventilated environment with a temperature of 0-45℃ to avoid the impact of extreme temperatures.

(III) Prevent Physical Damage

When the battery is subject to physical damage such as piercing, squeezing, or impact, the internal separator may break, leading to a short circuit between the positive and negative electrodes and causing thermal runaway. During transportation, installation, and use, the battery should be handled with care to avoid external impact; throwing the battery into fire or performing destructive operations such as rolling and drilling is prohibited.

(IV) Correct Installation and Use

When installing the battery, attention should be paid to the polarity of the positive and negative electrodes to avoid short circuits caused by reverse connection; when multiple batteries are used in a group, the consistency of the cells must be ensured, and batteries of the same model, specification, and state should be selected. At the same time, dedicated brackets and connecting wires should be used to ensure firm connection and good contact, preventing sparks caused by poor contact.

(V) Regular Inspection and Maintenance

Regularly inspect the battery appearance. If abnormal conditions such as shell deformation, bulging, liquid leakage, or rust are found, the battery should be stopped using immediately; for batteries that are not used for a long time, they should be charged to 50%-60% capacity before storage, and supplementary charging should be performed every 3-6 months to prevent performance damage caused by deep discharge of the battery; at the same time, long-term idleness of the battery should be avoided to prevent affecting its service life.

(VI) Standardized Recycling and Disposal

Waste cylindrical lithium-ion batteries are hazardous wastes. Random disposal will pollute the environment and may pose safety hazards. Waste batteries should be handed over to professional recycling institutions for disposal in accordance with local environmental protection regulations. Unauthorized disassembly, incineration, or landfilling is prohibited to ensure the safety and environmental protection of the recycling process.

VII. Comparison with Other Types of Lithium-Ion Batteries

(I) Comparison with Prismatic Lithium-Ion Batteries

Comparison Dimension	Cylindrical Lithium-Ion Battery	Prismatic Lithium-Ion Battery
Shape and Size	Cylindrical, fixed models, standardized sizes	Flat shape, sizes can be arbitrarily designed according to needs, high flexibility
Rate Performance	Limited by tab welding technology, relatively poor rate performance	Better tab design, more excellent rate performance, suitable for high-power demand scenarios
Discharge Platform	When using the same positive and negative electrode materials and electrolyte, the discharge platform is slightly lower	The internal structure design is more conducive to ion conduction, and the discharge platform is slightly higher
Product Quality	Mature manufacturing technology, high automation level of winding process, low probability of secondary slitting defects of electrode sheets, good quality stability	The lamination process is mostly semi-manual, prone to quality fluctuations, and the probability of electrode sheet defects is relatively high
Tab Welding	Simple tab structure, easier welding operation, and easy control of welding quality	High difficulty in tab welding, prone to false welding, which affects battery quality and performance
PACK Grouping	Simple PACK process, no complex fixed structure required, and good heat dissipation effect	When grouping, it is necessary to solve the heat dissipation problem, usually requiring a dedicated heat dissipation structure, and the process is relatively complex
Structural Stability	Strong pressure resistance of the shell, not easy to bulge during long-term use, stable structure	The chemical activity of the corners is poor, the energy density is prone to attenuation after long-term use, and the battery life is relatively short
Energy Density	Low space utilization, relatively low energy density	High space utilization, higher energy density, and can store more electricity in the same volume

(II) Comparison with Pouch Lithium-Ion Batteries

Comparison Dimension	Cylindrical Lithium-Ion Battery	Pouch Lithium-Ion Battery
Safety Performance	The shell is made of metal material, and explosion may occur when safety problems arise, with relatively low safety	Encapsulated with aluminum-plastic film, when problems occur, it mostly releases gas due to expansion, and is not easy to explode, with better safety performance
Weight	The metal shell has a relatively large weight, and the overall battery weight is moderate	No metal hard shell, 40% lighter than cylindrical steel-cased lithium-ion batteries of the same capacity, and 20% lighter than cylindrical aluminum-cased lithium-ion batteries, with obvious weight advantage
Internal Resistance	Relatively large internal resistance due to internal structure and material characteristics	Smaller internal resistance, which can greatly reduce battery self-discharge and improve charge-discharge efficiency
Cycle Performance	Moderate cycle life, relatively large attenuation after 100 cycles	Longer cycle life, with attenuation after 100 cycles 4%-7% less than that of cylindrical aluminum-cased batteries
Design Flexibility	Fixed cylindrical shape, cannot be changed according to equipment needs, low design flexibility	Can be made into any shape and thickness according to the equipment space requirements, can adapt to unconventional spaces, with extremely high design flexibility
Consistency	Mature production process, high standardization level, good product consistency	Easily affected by factors such as process and materials during manufacturing, with relatively poor product consistency
Cost	Benefiting from large-scale production and mature technology, the cost is low	The aluminum-plastic film material cost and production process requirements are high, and the scale of large-scale production is relatively low, so the cost is high (but it can be reduced by expanding the production scale)
Liquid Leakage Risk	The metal shell has good sealing performance, and the risk of liquid leakage is low	If the aluminum-plastic film encapsulation process is improper or the material ages, liquid leakage is prone to occur, but it can be improved by improving the quality of the aluminum-plastic film

VIII. Selection, Maintenance, and Upkeep

(I) Selection Methods

• Clarify Equipment Requirements: First, determine the type of equipment that uses the battery. Different equipment has different requirements for battery voltage, capacity, and discharge rate. For example, for consumer electronic devices such as mobile phones and laptops, attention should be paid to voltage matching and moderate capacity; for power tools and electric vehicles, higher requirements are placed on discharge rate and capacity; for energy storage systems, cycle life and capacity should be the key considerations.

• Consider Usage Frequency and Endurance Needs: If the equipment is used frequently and requires frequent charging, a battery with a larger capacity should be selected to reduce the number of charges; if the equipment is used infrequently and only occasionally, a small-capacity battery can meet the needs, avoiding performance attenuation caused by long-term idleness of the battery.

• Match Equipment Size and Space: According to the reserved battery installation space of the equipment, select a cylindrical lithium-ion battery of appropriate size to ensure that the battery can be smoothly installed into the equipment without affecting the normal operation of other components of the equipment, and avoid being unusable or damaging the equipment due to improper size.

• Pay Attention to Battery Performance Parameters: In addition to voltage and capacity, attention should also be paid to battery parameters such as cycle life, discharge rate, and operating temperature range. For example, energy storage systems should select batteries with long cycle life (such as over 4,000 times, 8,000 times); high-power equipment needs to select high-rate discharge batteries; equipment used in extreme temperature environments should select batteries with a wide operating temperature range.

• Choose Regular Brands and Manufacturers: Priority should be given to brands and manufacturers with a good market reputation and formal production qualifications (such as Panasonic, CATL, Samsung SDI, etc.). Their products have better guarantees in terms of quality control, performance stability, and safety. The purchase of inferior or counterfeit batteries should be avoided to prevent safety problems during use.

(II) Maintenance and Upkeep Methods

• Keep the Battery Clean and Dry: Regularly clean the battery surface to remove dirt and debris, avoiding impurities affecting the battery contact performance; at the same time, ensure the battery is in a dry environment to prevent moisture, avoid electrolyte leakage or corrosion of internal components, and affect battery performance and service life.

• Regularly Check Battery Status: Frequently inspect the battery appearance, and check for abnormal conditions such as shell deformation, bulging, liquid leakage, rust, and electrode wear. If problems are found, the battery should be stopped using immediately to avoid safety accidents; at the same time, pay attention to the battery’s charge-discharge performance. If the charging speed is significantly slower and the endurance capacity is greatly reduced, it may be a sign of battery aging or damage, and the battery needs to be replaced in time.

• Control Storage and Use Temperature: Store the battery in an environment with a temperature of 0-45℃, avoid long-term exposure to high-temperature (such as direct sunlight, proximity to heat sources) or low-temperature environments. High temperature will accelerate battery aging, and low temperature will reduce battery performance; during use, avoid the battery working in extreme temperatures for a long time to reduce damage to the battery.

• Standardize Charge and Discharge Operations: Use the original or compliant charger, avoid overcharging (charging voltage not exceeding 4.2V) and over-discharging (discharging voltage not lower than 2.5V). Avoid long-term full-charge storage when charging, and it is recommended to charge to 80%-90%; for batteries not used for a long time, they should be charged to 50%-60% capacity first before storage, and supplementary charging should be performed every 3-6 months to prevent deep discharge of the battery.

•Avoid Physical Damage and Improper Use: When using and handling the battery, handle it with care to avoid impact, squeezing, or dropping the battery, and prevent battery shell damage and internal short circuits; throwing the battery into fire or water, or performing destructive operations such as disassembly and rolling is prohibited to avoid safety risks; at the same time, do not mix or connect batteries of different models, brands, and aging degrees in series/parallel into a group to prevent safety problems caused by inconsistent battery performance.