March 14, 2024
What is a lithium polymer battery? Principles, features, and common applications explained
Lithium polymer battery (Li-Po), also known as lithium cell or polymer lithium-ion battery, is a type of lithium-ion battery that uses a polymer as the electrolyte or key structural component. Developed from traditional liquid lithium-ion batteries, it offers distinct advantages that make it widely used in portable electronic devices, electric vehicles, drones, and more. This article provides an in-depth exploration of the lithium polymer battery, including its development history, working principle, structure, types, advantages, applications, and usage precautions.
Table of Contents
Add a header to begin generating the table of contents
Development history
The evolution of lithium polymer battery closely linked to that of lithium-ion batteries. In the 1980s, scientists began intensive research into lithium-ion and lithium-metal batteries, laying the foundation for the birth of Li-Po batteries. Key milestones in their development include:
- 1991: Sony in Japan collaborated with its battery division to develop a lithium-ion battery using pyrolyzed polyalcohol carbon (PFA) as the anode, considered the commercial beginning of lithium polymer batteries.
- 1993: Bell Communications Research in the U.S. first reported a polymer lithium-ion battery (PLIB) using PVDF technology, marking a major breakthrough in polymer electrolyte technology.
- Late 1990s: Chinese manufacturers entered the field, gradually gaining a significant share of the global market.
How lithium polymer batteries work
Lithium polymer battery operates on a principle similar to liquid lithium-ion battery—based on the reversible movement of lithium ions between the anode and cathode. This is often referred to as the “rocking chair mechanism.”
Charging Process:
Lithium Ion Extraction: During charging, energy supplied by an external power source causes lithium ions to be extracted from the cathode (explore lithium battery state of charge).
Ion Migration: These lithium ions travel through the electrolyte (solid or gel-type polymer) toward the anode.
Lithium Intercalation: Upon reaching the anode, lithium ions embed into the anode material’s crystal structure. Electrons travel through the external circuit and combine with lithium ions to complete the reduction reaction.
Discharging Process:
Lithium Ion Extraction: When discharging, lithium ions are released from the anode (delithiation).
Ion Migration: These ions move through the electrolyte back to the cathode.
Lithium Intercalation: Lithium ions embed into the cathode material. Meanwhile, electrons flow through the external circuit to the cathode and complete the oxidation reaction.
This back-and-forth movement of lithium ions enables the conversion between chemical energy and electrical energy, thereby allowing the battery to charge and discharge.
Structure and components
The main components of a lithium polymer battery include the cathode, anode, electrolyte, and separator.
Cathode: Key to determining energy density, cycle life, and safety.
Anode: Stores lithium ions and supports charge/discharge processes.
Electrolyte: A defining feature of Li-Po batteries, responsible for lithium-ion transport. Unlike liquid lithium-ion batteries, Li-Po batteries use solid or gel-like electrolytes.
Separator: Positioned between the cathode and anode to prevent short circuits. Typically made from porous polymer films like polyethylene (PE), polypropylene (PP), or polyvinylidene fluoride (PVDF), offering excellent ion permeability, electrochemical stability, and mechanical strength.
Other supporting components include aluminum-plastic film casings, current collectors, and tabs. The outer casing is usually a flexible pouch (soft pack) that is thin, lightweight, and moldable.
Types of lithium polymer batteries
Based on structural design
Wound Type (Cylindrical Winding):
This type adopts a winding process similar to that used in traditional liquid lithium-ion battery manufacturing. The cathode, anode, and separator are rolled into a cylindrical or flat jelly-roll structure, then enclosed using laminated aluminum foil packaging. This structure is typically used in compact applications due to its high energy density and mature production process.
Stacked Type (Laminate Stacking):
In this design, the cathode, anode, and separator are cut into sheets of precise dimensions and stacked layer by layer using a hot-pressing technique. The stacked layers are then sealed in an aluminum-laminated pouch. This method offers better safety performance, structural stability, and efficient use of internal space, making it suitable for custom-shaped battery packs and high-power applications (explore lithium ion battery structure).
Based on the lithium polymer battery electrolyte
- Solid Polymer Electrolyte Batteries: Low conductivity at room temperature; suitable for high-temperature environments.
- Gel Polymer Electrolyte Batteries: Most widely used type today, capable of operating at room temperature due to improved ionic conductivity.
- Conductive Polymer Cathode Batteries: Use conductive polymers as cathode materials. Theoretically offer higher capacity but still face technical challenges in practical use.
Key features and advantages
Compared to traditional liquid lithium-ion batteries, Li-Po batteries offer the following significant advantages:
- Higher Energy Density: Advanced materials and compact design enable more energy storage. Energy density is 10–30% higher than liquid lithium batteries (explore what is energy density of a battery).
- Lightweight and Thin Design: The absence of a metal casing and the use of gel or solid electrolytes result in batteries that are 20–40% lighter. Thickness can go below 0.5mm.
- Flexible Shapes: Can be customized into various shapes and sizes—rectangular, round, curved, or irregular—to fit device designs.
- Improved Safety: Solid/gel electrolytes reduce leakage and fire risk. The flexible pouch can relieve internal pressure, enhancing safety further.
- Low Self-Discharge: Li-Po batteries retain charge better over time when idle.
- Longer Cycle Life: Capable of over 500 cycles under normal use, with no memory effect.
- Low Internal Resistance: Can reach as low as 35 mΩ, outperforming many liquid cell types (find lithium ion battery internal resistance).
Lithium polymer battery vs lithium-ion battery： Main difference
| Category | Lithium Polymer Battery (Li-Po) | Lithium-ion Battery (Li-ion) |
|---|---|---|
| Materials | Uses polymer materials in cathode, anode, or electrolyte | Uses active carbon, graphite, and organic electrolytes |
| Shape | Solid or gel-like electrolyte allows flexible and variable shapes | Liquid electrolyte requires rigid casing; shape is hard to change |
| Safety | Higher safety; less prone to explosion or combustion | Lower safety compared to Li-Po batteries |
| Voltage | Multi-layer cell structures can achieve high voltage using polymers | Standard cell voltage is 3.6V; needs to be connected in series for higher voltage |
| Capacity | No significant capacity improvement | Slightly higher capacity than Li-Po |
| Conductivity | Solid-state electrolytes have lower ionic conductivity | Stable conductivity, not affected by external materials |
| Manufacturing | Easier to produce thinner cells | Easier to manufacture thicker cells |
| Price | Generally more expensive than lithium-ion batteries | Lower cost than Li-Po batteries |
Application fields of lithium polymer batteries
Li-Po batteries are widely used in portable electronics such as smartphones, tablets, laptops, power banks, and medical devices. They are also increasingly adopted in electric vehicles, drones, and other applications where high energy density and compact size are required. As technology evolves and costs decline, their usage will continue to expand across industries.
Maintenance tips and usage precautions
To extend the lifespan of a Li-Po battery, follow these best practices:
- Avoid Overcharging and Overdischarging: Both can damage the battery. Use dedicated chargers and disconnect once fully charged. Do not wait until the battery is completely depleted before charging.
- Avoid Extreme Temperatures: High or low temperatures can degrade performance. Keep batteries away from direct sunlight, heaters, or freezing environments.
- Prevent Short Circuits: Contact with metal objects can cause short circuits, potentially leading to fire or explosion.
- Store at Half Charge: For long-term storage, charge to about 50% and store in a cool, dry place.
- Buy from Reputable Brands: Inferior batteries may pose safety risks. Always purchase from trusted manufacturers or vendors.
- Regularly Inspect Appearance: Check for swelling, leakage, or other abnormalities. Discontinue use and seek professional assistance if any issues are found.
Conclusion
With their unique advantages, the lithium polymer battery has become indispensable energy storage devices in modern life. As technological advancements continue, Li-Po batteries will keep improving in energy density, safety, cycle life, charging speed, and cost-efficiency—driving further adoption across consumer electronics, transportation, and industrial sectors.
Who we are
TYCORUN is a leading innovator in the battery swap industry, dedicated to delivering efficient and sustainable energy solutions for electric two-wheeled vehicles, including electric motorcycles, tricycles, and scooters. Our expertise lies in the research, development, and manufacturing of advanced battery swap stations and high-performance lithium-ion batteries.
Why Choose TYCORUN? Efficient Swapping; Sustainable Energy; Smart Battery Management; Long-lasting Performance… Choosing TYCORUN means choosing a smarter, greener future. Visit our official website to discover more about our battery swap solutions and join us in shaping the future of electric mobility!
Related post
October 2, 2023
September 19, 2023
Willow
Willow is a materials engineer with a Master’s degree in Materials Science and Engineering, specializing in lithium-ion battery materials and energy storage technologies.
Her work focuses on EV battery swapping solutions, battery innovation, and new energy industry trends, aiming to translate research insights into practical applications for sustainable transportation.
Leave a comment