Lithium Battery Basics
A polymer battery refers to a lithium-ion battery that uses polymer as the electrolyte. Specifically, it is further divided into two types: “semi-polymer” and “full-polymer”.The “semi-polymer” type means coating a layer of polymer (usually PVDF) on the separator, which makes the bonding force of the cell stronger and the battery can be made harder. Its electrolyte is still liquid electrolyte. The “full-polymer” type refers to using polymer to form a gel network inside the cell, and then injecting electrolyte to form the electrolyte. Although the “full-polymer” battery still needs to use liquid electrolyte, the amount is much less, which greatly improves the safety performance of the lithium-ion battery. As far as the author knows, currently only SONY is mass-producing “full-polymer” lithium-ion batteries. From another perspective, a polymer battery refers to a lithium-ion battery that uses an aluminum-plastic packaging film as the outer packaging, also commonly known as a soft-pack battery. This packaging film is composed of three layers, namely the PP layer, the Al layer, and the nylon layer. Because PP and nylon are polymers, this type of cell is called a polymer battery.
Differences between lithium polymer batteries and ordinary lithium - ion batteries:
1. Different Raw Materials
Lithium-ion batteries use liquid or colloidal electrolytes as raw materials.
lithium polymer batteries adopt electrolytes including solid or gel-state polymer electrolytes and organic electrolytes.
Supplementary note: The polymer electrolyte enables better flexibility in structural design, while organic electrolytes in polymer batteries still maintain ion conductivity similar to traditional lithium-ion batteries.
2. Varying Safety Performance
Lithium-ion batteries are prone to explosion under high-temperature or high-pressure conditions due to their liquid electrolyte and rigid casing.
Polymer lithium batteries use aluminum-plastic films as casings. Even when using organic electrolytes, they will not explode even if the internal temperature rises, as the flexible casing can relieve pressure without causing violent rupture.
Supplementary note: The aluminum-plastic film casing also reduces the risk of electrolyte leakage compared to metal casings in lithium-ion batteries.
3. Diverse Shaping Capabilities
Polymer batteries can achieve thin-form, large-area, and arbitrary shape designs because their electrolytes exist in solid or gel states (instead of liquid), eliminating the need for a rigid container.
Lithium-ion batteries use liquid electrolytes, requiring a sturdy casing as secondary packaging to contain the electrolyte, which limits their shape flexibility.
Supplementary note: This characteristic makes polymer batteries ideal for thin electronic devices (e.g., foldable phones), while lithium-ion batteries are more commonly used in cylindrical or prismatic formats for electric vehicles.
4. Different Cell Voltages
Polymer batteries can achieve high voltage through multi-layer combinations within the cell due to their polymer materials, with typical nominal voltages ranging from 3.7V to 4.35V (depending on cathode materials).
Lithium-ion batteries have a nominal cell voltage of 3.6V (e.g., NCM/NCA cells). To achieve high voltage in practical applications, multiple cells must be connected in series to form a sufficient high-voltage working platform.
Supplementary note: Series connection of lithium-ion cells increases system complexity, while polymer batteries can simplify circuit design through internal voltage stacking.
5. Distinct Manufacturing Processes
Polymer batteries are easier to produce in thinner formats, while lithium-ion batteries are more efficiently manufactured in thicker structures, allowing lithium-ion batteries to expand into more application fields (e.g., large-scale energy storage systems).
Supplementary note: The thin-film manufacturing process of polymer batteries requires precise control of electrolyte viscosity, whereas lithium-ion battery production benefits from mature winding or stacking processes for thick electrodes.
6. Capacity Differences
The capacity of polymer batteries has not been effectively improved; in fact, it is slightly lower than that of standard-capacity lithium-ion batteries under the same volume.
Supplementary note: This is mainly due to the lower energy density of polymer electrolytes compared to liquid electrolytes, though advancements in high-capacity cathode materials (e.g., NCM811) are gradually narrowing this gap.
Advantages and Disadvantages of Polymer Lithium Batteries
Advantages of Polymer Lithium Batteries
1. Excellent Safety Performance
Polymer lithium batteries adopt an aluminum-plastic soft package structure, differing from the metal casing of liquid cells. In case of safety hazards, liquid lithium-ion cells are prone to explosion, while polymer cells only swell or burn at most, significantly reducing the risk of explosion.
2. Ultra-thin Design with Minimal Thickness
Extreme Thinness: The thickness can be reduced to less than 1mm, allowing integration into credit cards or other ultra-thin devices.
Technical Limitations of Traditional Batteries: Conventional liquid lithium batteries face technical bottlenecks in reducing thickness below 3.6mm, and 18650 batteries are constrained by their standardized volume.
3. Lightweight and High Capacity
Weight Advantage: Batteries with polymer electrolytes eliminate the need for metal casings as protective outer packaging. When having the same capacity, they are 40% lighter than steel-cased lithium batteries and 20% lighter than aluminum-cased batteries.
Capacity Advantage: For the same volume, polymer batteries have approximately 30% higher capacity, demonstrating superior energy density.
4. Customizable Shape
The thickness of polymer battery cells can be adjusted according to practical needs. For example, a new laptop model from a renowned brand uses a trapezoidal polymer battery to fully utilize the internal space, optimizing structural design flexibility.
Disadvantages of Polymer Lithium Batteries
1. Higher Costs
Custom designs tailored to client needs add to research and development expenses. Moreover, the wide variety of shapes and sizes means production relies on non-standard fixtures and tools, which further pushes up manufacturing costs—unlike standardized options such as 18650 batteries that benefit from mass production efficiencies.
2. Poor Universality
The flexibility in design comes with a downside: even a 1mm difference in thickness often requires a completely new custom cell. This lack of standardization means polymer batteries have little cross-device compatibility, making them less versatile than more uniform battery types.
3. Fragility and Reliance on Protection Systems
A single fault typically renders the entire battery unusable, as there are no replaceable components. Additionally, overcharging or over-discharging can permanently damage the internal chemical structure, severely shortening lifespan. This makes strict oversight by a Battery Management System (BMS) essential.
4. Shorter Lifespan and Inferior High-Current Performance
Polymer batteries usually offer 300–500 charge-discharge cycles, which is shorter than the 500–1000 cycles of 18650 batteries. They also perform less effectively under high-current discharge—such as in power tools or drones—due to electrolyte limitations, trailing behind the cylindrical 18650s in these scenarios.
——End——
Canrd Brief Introduce： Canrd use high battery R&D technology(core members are from CATL) and strong Chinese supply chain to help many foreign companies with fast R&D.
We provide lab materials, electrodes, custom dry cells, material evaluation, perfomance and test, coin/pouch/cylindrical cell equipment line, and other R&D services.
Email:Eden@canrd.com
Phone/Wechat/WhatsApp/Skype:+86 13713092381
Website : www.canrud.com
Comments
Post a Comment