What Are Lithium Polymer Batteries?

Lithium polymer battery (Li-polymer, also known as polymer lithium battery): Compared with the previous battery, it is a battery with high energy, small size and light weight, which is a chemical property.

Three elements of a general battery: positive electrode, negative electrode, and electrolyte. The so-called lithium polymer battery refers to a battery system in which at least one or more of the three elements use a polymer material. In lithium polymer battery systems, most polymer materials are used in the positive electrode and electrolyte. The positive electrode material uses a conductive polymer or an inorganic compound used in general lithium ion batteries. The negative electrode often uses lithium metal or lithium carbon interlayer compounds. The electrolyte is a solid or colloidal polymer electrolyte, or an organic electrolyte. Because there is no excess electrolyte in lithium polymers, it is more reliable and stable. ^[1]

A lithium polymer battery uses a file alloy as a positive electrode, a polymer conductive material, polyacetylene, polyaniline, or poly-p-phenol as a negative electrode, and an organic solvent as an electrolyte. The specific energy of lithium polyaniline battery can reach 350W.h / kg, but the specific power is only 50-60W / kg, the operating temperature is -40-70 degrees, and the life is about 330 times.

Relative to

All Lithium-Ion batteries, whether before or over the years, include:

A solid state maintenance-free lithium polymer battery was jointly developed by 3M Company in the United States and Hgdro-Quebec Company in Canada. The electrodes of the lithium battery are made of vanadium oxide (VOx) and graphite, and the electrolyte is Li (CFSO2) 2N. The lithium polymer battery has a special structure, which is composed of five layers of thin films. The first layer uses metal foil as a collector, the second layer is a negative electrode, the third layer is a solid electrolyte, the fourth layer uses a file foil as a positive electrode, the fifth layer is an insulating layer, and the total thickness of the five layers is 0.1 mm. This lithium polymer battery has an operating temperature of 60-100 degrees. In order to prevent the battery from overheating when a large current is momentarily output, the lithium polymer battery has a strict thermal management system to control its normal operating temperature. The main advantage of this lithium polymer battery is that it eliminates the liquid electrolyte, which can avoid pollution caused by electrolyte overflow when the battery fails.

Technical performance

In 1997, the technical performance of lithium polymer batteries jointly developed by 3M Corporation in the United States and Hgdro-Gabec in Canada is shown in Table 7-26.

The above lithium polymer battery electrolyte is a flexible solid polymer, and the metal file foil is sealed in the battery, and it can still work normally at a high temperature of 180 ° C. This

1.Ordinary lithium-ion battery

Lithium-ion batteries, commonly known as "lithium batteries", are currently the best battery system with comprehensive performance. The negative electrode of a lithium-ion battery is a carbon material, such as graphite. Positive electrode is a lithium-containing transition metal oxide

, Such as LiMn2O4.

(1) Advantages of lithium-ion batteries:

The operating voltage is high. The operating voltage of lithium-ion batteries is 3.7V, which is three times the operating voltage of nickel-cadmium and nickel-hydrogen batteries.

Higher specific energy. The specific energy of lithium-ion batteries has reached 140Wh / kg, which is three times that of nickel-cadmium batteries and 1.5 times that of nickel-hydrogen batteries.

Long cycle life. Lithium-ion batteries have a cycle life of more than 1,000 times and can reach tens of thousands of times at low discharge depths, surpassing several other secondary batteries.

Small self-discharge. The monthly self-discharge rate of lithium-ion batteries is only 6-8%, which is much lower than nickel-cadmium batteries (25-30%) and nickel-metal hydride batteries (30-40%).

No memory effect. It can be recharged at any time without degrading battery performance.

No pollution to the environment. Lithium-ion batteries do not contain harmful substances, and are truly "green batteries."

2.lithium polymer battery

Lithium polymer batteries are a newer generation of batteries that entered the market in large quantities in 1999. lithium polymer battery

It is basically the same as a lithium-ion battery except that the electrolyte is a solid polymer rather than a liquid electrolyte.

The polymer electrolyte material is a common thin film composed of a solution in which a host polymer such as polyethylene oxide is used as a non-moving solvent. The advantages of lithium polymer batteries are

It can be made into any shape and is lighter because it does not contain heavy metals and has a plastic case that keeps the electrolyte from leaking. Their performance is better, the ideal state of lithium polymer battery

It has a capacity of several thousand mAh and is more secure. The solid electrolyte is like a sealed gel and does not easily disintegrate during charging.

3. Comparison of two batteries

Both lithium polymer and lithium-ion battery technologies can replace Ni-Gd batteries. But the price is too high and the market has not fully accepted it, especially the lithium polymer technology. Analyst Brush of Darnell Group believes that polymer batteries will never be more expensive than lithium-ion batteries, and production is indeed much more expensive, which has promoted the development of lithium-ion battery technology. Lithium-ion batteries for laptops previously cost $ 41.42, and polymer batteries for laptops cost $ 60.80.

Lithium polymer batteries have larger capacity than lithium batteries in the same volume, and have no memory effect at all (lithium ion batteries still have memory effects, only relatively small).

Lithium polymer batteries are actually a gel-like substance that can be easily made into various shapes. It does not contain harmful heavy metal elements and is a "green battery."

1. There is no battery leakage problem. The battery contains no liquid electrolyte and uses a colloidal solid.

2. Can be made into a thin battery: with a capacity of 3.6V400mAh, its thickness can be as thin as 0.5mm.

3. The battery can be designed into various shapes

4. Battery can be deformed: polymer battery can be bent up to about 90 degrees

5. Can be made into a single high voltage: a battery with liquid electrolyte can only get a high voltage by connecting several batteries in series. Since a polymer battery has no liquid itself, it can be made into multiple layers in a single unit to achieve high voltage.

6. The capacity will be double that of the lithium-ion battery of the same size ^[3]

Lithium polymer battery industrialization status abroad

Lithium-ion batteries have been commercialized as early as 1992, and lithium polymer batteries have not been commercialized until seven years later. However, since the commercial production of Sony in 1999, the development of liquid lithium-ion batteries has lagged behind lithium polymerization. The speed of development of physical batteries. In 2002, 7% of the market share of lithium-ion batteries has been occupied by lithium polymer batteries. By 2005, it had roughly 9.3% of the market share, and by 2010 it had risen to about 30%. ^[1]

Although the sales volume of lithium polymer batteries is growing rapidly, its market share is still relatively low, and the gap between the market share of liquid lithium batteries is huge. Although polymer batteries on the market are generally higher than the price of liquid lithium batteries, it must also be recognized that the competition model of mobile appliances is slowly changing, and lithium polymer batteries are being used by more and more mobile phones and mobile phones. Designers such as DVDs recognize it, so polymer makers firmly believe that the era of polymers will come. According to the current development of mobile phones in the direction of miniaturization, ultra-thinness, personalization of mobile phone designs, artisticization, increasing use of color screens and mobile phone functions, etc., the development trend of lithium polymer batteries is also reflected from the side. ^[1]

In fact, laptops, Bluetooth headsets, PHS phones, mobile DVDs, and other appliances are all moving towards miniaturization and portability, with increasing functions and increasing LCD screens, all of which provide lithium polymer batteries. Unlimited development space and unlimited business opportunities. With the development of the economy, the number of cars in our country has also increased rapidly. From the perspective of protecting the environment and saving energy, it is imperative to develop new energy electric vehicles. As early as the "Tenth Five-Year Plan" period, China's electric vehicles were included in the "863" key projects. Today, with the rapid development of China, new energy vehicles are included in the strategic emerging industries in the "Twelfth Five-Year Plan" and We will actively support and promote the formulation and revision of important standards for electric vehicles, and work hard to establish a relatively complete standard system for electric vehicles in China to comprehensively support and accelerate future development needs. It is estimated that at the end of the "Twelfth Five-Year Plan", China will become the first country in the world to own electric vehicles. ^[1]

Developed countries around the world have formulated relevant policies to promote the development of electric vehicles, and establishing electric vehicles is one of the important ways to achieve energy security and a low-carbon economy. The United States proposes to popularize 1 million plug-in electric vehicles by 2015; Japan puts the development of electric vehicles at the core, and will promote electric vehicles as the mainstay of "next-generation vehicles" in 2020, with a planned number of 13.5 million; In August 2009, the German government released the "National Electric Vehicle Development Plan", which focuses on pure electric vehicles and plug-in electric vehicles, to achieve at least 1 million pure electric vehicles by 2020. ^[1]