What is the difference between lithium polymer battery and li-ion polymer battery? Posted by benzoenergy.com
What is a lithium polymer battery?
Lithium
polymer battery ( Li-polymer battery ), is a chemical battery. Compared
with the previous battery, it has the characteristics of high energy,
miniaturization and light weight. Lithium polymer batteries have
ultra-thin features, and can be made into batteries of different shapes
and capacities to meet the needs of some products. The theoretical
minimum thickness can reach 0.5mm.
The
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
uses polymer materials. In the li-polymer battery
system, most of the polymer materials are used in the positive
electrode and electrolyte. The positive electrode material uses
conductive polymer or inorganic compounds used in general lithium ion
batteries, the negative electrode often uses lithium metal or
lithium-carbon intercalation compounds, and the electrolyte uses solid
or colloidal polymer electrolytes, or organic electrolytes. Since there
is no excess electrolyte in the lithium polymer, it is more reliable and
stable.
Characteristics of lithium polymer batteries
Lithium
polymer batteries use file alloys as positive electrodes, polymer
conductive materials, polyacetylene, polyaniline or poly-p-phenol as
negative electrodes, and organic solvents as electrolytes. The specific
energy of the 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 span is about 330 times.
Compared with lithium ion batteries, the characteristics of lithium polymer batteries are as follows:
1. Relatively, the problem of battery leakage is improved, but it has not been completely improved.
2. Can be made into a thin battery: With a capacity of 3.6V 250mAh, its thickness can be as thin as 0.5mm.
3. The battery can be designed into various shapes.
4.
It can be made into a single high voltage: the battery with liquid
electrolyte can only obtain high voltage by connecting several batteries
in series, while the polymer battery can be made into a multi-layer
combination within a single battery to achieve high voltage because
there is no liquid.
5. The discharge capacity is theoretically 10% higher than that of a lithium-ion battery of the same size.
Lithium
polymer batteries are packaged in aluminum plastic, and internal
problems can be immediately manifested through the outer packaging. Even
if there is a safety hazard, it will not explode, but will only swell.
In polymer batteries, the electrolyte plays the dual function of the
separator and the electrolyte: on the one hand, it separates the
positive and negative materials like a diaphragm to prevent
self-discharge and short circuit inside the battery. Conduct lithium
ions between. Polymer electrolyte not only has good conductivity, but
also has the characteristics of light weight, good elasticity, and easy
film formation that are unique to polymer materials. It also conforms to
the development trend of light weight, safety, efficiency and
environmental protection of chemical power sources.
Safety issues of lithium polymer batteries
All lithium-ion batteries, whether they are old or current, including polymer lithium-ion batteries,
lithium iron phosphate batteries, etc., are very afraid of internal
short-circuits, external short-circuits, and overcharge. Because the
chemical properties of lithium are very active and it is easy to burn.
When the battery is discharged and charged, the internal temperature of
the battery will continue to heat up. The gas generated during the
activation process expands, the internal pressure of the battery
increases, and the pressure reaches a certain level, it will rupture,
causing leakage, fire, or even explosion.
In
order to alleviate the danger of lithium-ion batteries, technicians
have added ingredients that can inhibit the activity of lithium elements
(such as cobalt, manganese, iron, etc.), but these do not essentially
change the danger of lithium-ion batteries.
When
ordinary lithium-ion batteries are overcharged, short circuited, etc.,
the battery may heat up, the positive electrode material decomposes, and
the negative electrode and electrolyte materials are oxidized, which
will cause gas expansion and increase the internal pressure of the
battery. When the pressure reaches a certain level After the degree, an
explosion may occur. The polymer lithium ion battery uses a colloidal
electrolyte, so it will not produce a large amount of gas due to the
boiling of the liquid, thereby preventing the possibility of a violent
explosion.
At present,
most of the polymer batteries on the market are only soft-pack
batteries, using aluminum plastic film as the outer shell, but the
electrolyte has not changed. This kind of battery can also be thinner,
and its low-temperature discharge characteristics are better than
polymer batteries, and the material energy density is basically the same
as that of liquid lithium batteries and ordinary polymer batteries, but
because of the use of aluminum plastic film, it is better than ordinary
liquid lithium batteries. In terms of safety, when the liquid just
boils, the aluminum-plastic film of the soft pack battery will naturally
bulge or rupture, and it will not explode.
It should be noted that the new battery may still burn or swell and crack, and safety is not foolproof.
Technical performance of lithium polymer battery
The
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. The sample of this lithium-ion
battery has been proved to be safe after collision test. To prevent
overcharge and overdischarge when multiple lithium polymer batteries are
connected in series, the fast charging performance of lithium polymer
batteries needs to be further addressed.
Lithium
polymer batteries can be divided into three categories according to the
electrolyte: (1) Gel polymer electrolyte lithium ion batteries, which
add additives to solid polymer electrolytes to improve ion conductivity,
so that the battery can be used at room temperature; (2) Solid polymer
electrolyte lithium ion battery, the electrolyte is a mixture of polymer
and salt, the ion conductivity is low at room temperature, suitable for
high temperature use; (3) Lithium ion battery with composite gel
polymer cathode material, conductive polymer as The positive electrode
material has a specific energy 3 times that of existing lithium-ion
batteries, and is the latest generation of lithium-ion batteries.
Comparison of ordinary lithium ion battery and lithium polymer battery
(1) The advantages of ordinary lithium-ion batteries:
①
The working voltage is high. The working voltage of Li-ion battery is
3.7V, which is three times that of Ni-Cd and Ni-MH batteries.
②
Higher specific energy. The specific energy of lithium-ion batteries
has reached 140Wh/kg, which is 3 times that of nickel-cadmium batteries
and 1.5 times that of nickel-hydrogen batteries.
③
Long cycle life. The cycle life of lithium-ion batteries has reached
more than 1,000 times, and can reach tens of thousands of times at low
depths of discharge, which exceeds that of other secondary batteries.
.
④
Small self-discharge. The monthly self-discharge rate of lithium-ion
batteries is only 6%-8%, which is far lower than nickel-cadmium
batteries (25%-30%) and nickel-hydrogen batteries (30%-40%).
⑤ No memory effect. It can be charged at any time as required without reducing battery performance.
⑥
No pollution to the environment. There are no harmful substances in
lithium-ion batteries, and they are veritable "green batteries".
(2) Advantages of lithium polymer battery
Lithium
polymer batteries are a new generation of batteries. Lithium polymer
batteries are basically the same as lithium ion batteries except that
the electrolyte is a solid polymer instead of a liquid electrolyte.
1. There is no battery leakage problem. The battery does not contain liquid electrolyte and uses colloidal solids.
2. Can be made into a thin battery: With a capacity of 3.6V 400mAh battery, its thickness can be as thin as 0.5mm.
3. The battery can be designed in various shapes.
4. The battery can be bent and deformed: the polymer battery can be bent about 90 degrees at most.
5.
It can be made into a single high voltage: the battery with liquid
electrolyte can only obtain high voltage by connecting several batteries
in series. Since polymer battery has no liquid itself, it can be made
into a multi-layer combination in a single battery to achieve high
voltage.
6. The capacity will be higher than a lithium-ion battery of the same size.
BENZO Energy Technology Co.,Ltd
UFine Technology Co., Ltd
Site: www.bz-battery.com / www.benzoenergy.com
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