Soft-Pack Lithium 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.

1. Basic Definition and Core Characteristics

Soft-pack Lithium batteries, also known as pouch batteries or soft-pack cells, are a crucial category of Lithium batteries. Their core distinction from traditional hard-case batteries lies in the use of an aluminum-plastic composite film as the outer casing, rather than rigid materials such as steel or aluminum casings. By encapsulating core components, including positive electrodes, negative electrodes, separators, and electrolytes within a flexible casing, they form energy storage units that are both lightweight and highly adaptable, making them widely suitable for devices with strict requirements on volume and weight.

Their core characteristics are specifically manifested as follows:

• Flexible Encapsulation Design: The outer casing utilizes aluminum-plastic film as the core material, providing good flexibility. Its shape can be adjusted according to the needs of the device, breaking through the fixed structural limitations of traditional hard-case batteries.

• Significant Lightweight Advantage: Compared with hard-case batteries of the same capacity, they are lighter, being approximately 40% lighter than steel-cased batteries and about 20% lighter than aluminum-cased batteries, which can effectively improve the overall energy density of the device.

• Flexible Shape Customization: They can be designed in various forms, such as ultra-thin (with a minimum thickness of 0.5mm, far superior to the 4mm limit of aluminum-cased batteries), irregular shapes, and large sizes, adapting to the spatial layout requirements of different scenarios such as consumer electronics and automobiles.

• High Energy Density: Benefiting from the efficient use of internal space by the flexible encapsulation, under the same specification and size, their capacity is 10%-15% higher than that of steel-cased batteries and 5%-10% higher than that of aluminum-cased batteries. The energy density of some products can reach more than 300Wh/kg.

• Controllable Safety Performance: When safety hazards such as thermal runaway occur, energy is usually released in the form of bulging, cracking from the sealing edge, or gas exhaust, rather than the explosion that is prone to occur in hard-case batteries. However, attention should be paid to preventing the risk of the casing being punctured.

• Moderate Cycle Life: The number of cycles is usually 300-1000 times, depending on the material system (such as ternary, lithium iron phosphate, etc.). After 100 cycles, the capacity attenuation is 4%-7% less than that of aluminum-cased batteries, performing better than some hard-case batteries.

• Low Internal Resistance: The minimum internal resistance of a single cell can be less than 35mΩ, which greatly reduces the self-discharge of the battery pack, improves the discharge performance, and provides a guarantee for the stable operation of the device.

2. Structural Composition

(1) Internal Structure

The internal structure of a soft-pack Lithium battery consists of a positive electrode, a negative electrode, a separator, a positive tab, a negative tab, an insulating sheet, and an aluminum-plastic packaging film. All components work together to realize the storage and release of electrical energy:

The positive and negative electrodes are the core of electrical energy conversion. The separator is responsible for isolating the positive and negative electrodes to prevent short circuits while allowing ions to pass through.

The positive and negative tabs serve as the current output interfaces, and the insulating sheet prevents the risk of leakage between the tabs and the outer casing, as well as other components.

The aluminum-plastic packaging film is crucial for protecting the internal components and directly determines the sealing performance, safety, and durability of the battery.

(2) Structure and Function of Aluminum-Plastic Film

As the core packaging material of soft-pack Lithium batteries, the aluminum-plastic film usually adopts a three-layer composite structure, with each layer having a clear function:

• Outer Layer (Outer Barrier Layer): Mainly made of nylon (BOPA) or polyethylene terephthalate (PET), its core functions are to protect the middle layer, reduce scratches and stain adhesion, and ensure the intact appearance of the battery. Meanwhile, it blocks the penetration of air (especially oxygen) to maintain a stable internal environment of the battery. In addition, it ensures that the packaging aluminum foil has good deformability to adapt to the battery shape customization needs. If PET is used instead of nylon, the chemical resistance can be improved, but the punching pit depth of the aluminum-plastic film will be reduced.

• Middle Layer (Barrier Layer): Mainly made of aluminum foil with a certain thickness, it has excellent barrier performance, which can effectively block the penetration of water vapor and resist external impacts to protect the internal cells from damage. It is the key to ensuring the sealing performance and structural stability of the battery.

• Inner Layer (Multifunctional High Barrier Layer): Mainly made of polypropylene (PP) material, its core functions include packaging sealing, electrical insulation, and preventing the middle aluminum layer from directly contacting the electrolyte and undergoing chemical reactions, thus ensuring the stable electrochemical performance of the battery.

•Special Layer (Optional): In some scenarios, a matte layer (MATT layer) is added to the outer layer of PET or nylon to improve the gloss of the battery appearance, but this will significantly increase the production cost of the aluminum-plastic film.

3. Advantages and Disadvantages Analysis

(1) Advantages

• Better Safety Performance: Due to the flexible encapsulation design of the aluminum-plastic film, when a safety hazard occurs, energy is mostly released in the form of bulging, cracking, or gas exhaust, which greatly reduces the risk of explosion. Compared with hard-case batteries, it has better controllability over safety accidents.

• Outstanding Energy and Weight Advantages: It is lightweight and has a high capacity. For the same capacity, it is 40% lighter and has a 10%-15% higher capacity than steel-cased batteries, and 20% lighter and has a 5%-10% higher capacity than aluminum-cased batteries, which can effectively improve the battery life and portability of the device.

• Good Cycling and Discharge Performance: It has a relatively long cycle life, with a capacity attenuation of 4%-7% less than that of aluminum-cased batteries after 100 cycles. Its low internal resistance not only reduces self-discharge but also improves the discharge performance, making it suitable for high-power demand scenarios.

• Flexible Design and Adaptability: It can be customized into various shapes such as ultra-thin and irregular shapes, with a minimum thickness of 0.5mm. Its shape can be adjusted according to the spatial layout requirements of the device, providing higher freedom for product design, especially suitable for irregular devices such as wearable devices and foldable screen mobile phones.

• Good Heat Dissipation Performance: The flat structure is conducive to the uniform distribution of heat. With a reasonable heat dissipation design, the working temperature of the battery can be effectively controlled, reducing the impact of high temperatures on performance and service life.

(2) Disadvantages

• Weak Mechanical Strength: The aluminum-plastic film outer casing has poor puncture and impact resistance and is easily damaged by sharp objects or external pressure. Additional protective structures need to be added, which increases the application cost and complexity.

• Insufficient Sealing and Stability: During long-term use, electrolyte leakage may occur due to poor encapsulation technology. Under high-temperature or high-charge states, bulging (gas expansion) is prone to occur, which affects the battery performance and service life.

• Low Production Efficiency and High Cost: The variety of models leads to a lower degree of automation in the middle and later stages compared with cylindrical battery production lines, making it difficult to achieve large-scale production. The core material, aluminum-plastic film, mostly relies on imports, and the encapsulation process is complex. Combined with the cost of additional protective structures, the overall production cost is high.

• Difficulty in Consistency and Grouping: The low degree of production automation easily leads to poor battery performance consistency, increasing the safety risk during charging and discharging. During grouping, additional brackets, insulation, and heat dissipation structures need to be designed, resulting in high grouping costs and complex processes.

• Limitations in Cycle Life: Although it is better than some hard-case batteries, the electrolyte is prone to drying out after long-term use, and the cycle life is usually 300-1000 times, which is still inferior to some high-end hard-case batteries.

4. Application Fields

With its advantages of light weight, high energy density, and flexible design, soft-pack Lithium batteries are widely used in various fields. The specific scenarios are as follows:

• Consumer Electronic Products: They are the mainstream choice in the 3C field, including high-end mobile phones and tablets such as iPhone, iPad, and Samsung Galaxy series, laptops, Bluetooth headsets, smart watches, fitness trackers, and other wearable devices, as well as portable power banks. They can meet the needs of such devices for thinness, portability, and long battery life.

• UAVs and High-End Equipment: They are suitable for high-performance equipment such as unmanned aerial vehicles (e.g., some models of DJI drones) and remote control (RC) vehicles. The lightweight design can improve the battery life and load capacity of UAVs, and the high energy density meets the high-power requirements of high-end equipment.

• New Energy Vehicles: Some high-end vehicle models use soft-pack battery modules, such as some models of BYD (the “small blade cells” in DMI hybrid models), NIO (models such as ET7), and XPeng. They use their design flexibility to adapt to the layout of the vehicle battery compartment and improve the overall battery life of the vehicle.

• Energy Storage and Medical Fields: They are applied to portable energy storage devices to meet outdoor power supply needs. They can also be used in medical implantable devices (such as pacemakers). With the advantages of light weight and miniaturization, they reduce the impact of implantation on the human body.

• Military and Aerospace Fields: They are suitable for weight-sensitive equipment such as UAVs and satellite power supplies. The high energy density and lightweight design can meet the strict requirements of military and aerospace equipment for reliability and portability.

5. Comparison with Hard-Case Lithium Batteries

Hard-case Lithium batteries mainly include cylindrical and prismatic types, with outer casings made of steel, aluminum, or plastic. They have significant differences from soft-pack Lithium batteries in multiple dimensions, and the specific comparisons are as follows:

Comparison Dimension	Soft-Pack Lithium Batteries	Hard-Case Lithium Batteries (Cylindrical/Prismatic)
Encapsulation Structure	Flexible encapsulation with aluminum-plastic composite film	Rigid encapsulation with steel, aluminum, or plastic casings
Weight and Volume	Lightweight (40% lighter than steel-cased, 20% lighter than aluminum-cased), flexible volume customization, minimum thickness of 0.5mm	Heavy weight, fixed volume, minimum thickness of aluminum-cased batteries is 4mm, poor spatial adaptability
Energy Density	High (10%-15% higher than steel-cased, 5%-10% higher than aluminum-cased for the same size, up to over 300Wh/kg)	Moderate, lower space utilization than soft-pack batteries
Safety Performance	Mainly bulging and cracking, low explosion risk; but poor puncture resistance	Strong impact resistance; higher explosion risk than soft-pack batteries during thermal runaway
Design Flexibility	High, can be customized into ultra-thin and irregular shapes, adapting to a variety of devices	Low, fixed shape, only some can be customized, limited adaptability
Production and Cost	Low degree of automation, difficult mass production, aluminum-plastic film relies on imports, high cost	Mature and standardized technology, high degree of automation, low cost
Consistency and Grouping	Poor consistency, additional brackets and heat dissipation required for grouping, high cost	Better consistency than soft-pack batteries (prismatic type), relatively simple grouping process
Cycle Life	Moderate (300-1000 times), electrolyte prone to drying out	Moderate to high, some models have better cycle life than soft-pack batteries
Application Scenarios	Consumer electronics, UAVs, high-end automobiles, portable energy storage	New energy vehicles (mainstream), fixed energy storage, medical equipment, and aerospace