What is the difference between 18650 and 21700 batteries? Which is better, 18650 or 21700? Posted by benzoenergy.com
Lithium-ion battery has a high energy density, its capacity is 1.5 to 2 times that of a nickel-hydrogen battery of the same weight, and it has a very low self-discharge rate. In addition, lithium-ion batteries have almost no "memory effect" and do not contain toxic substances. These advantages of lithium-ion batteries make it widely used in the field of new energy vehicles.
Nowadays, the more widely used cylindrical lithium-ion batteries are 18650 batteries and 21700 batteries.
18650 battery:
18650
batteries originally referred to nickel-metal hydride batteries and
lithium-ion batteries. As nickel-metal hydride batteries are now less
used, they now refer to lithium-ion batteries. 18, 65, 0 is the
originator of lithium-ion batteries --- a standard lithium-ion battery
model set by SONY in Japan in order to save costs, where 18 means a
diameter of 18mm, 65 means a length of 65mm, and 0 means Cylindrical
battery. Common 18650 batteries include ternary lithium-ion batteries
and lithium iron phosphate batteries.
Speaking
of 18650 batteries, Tesla has to be mentioned. When Tesla is developing
electric car batteries, it has tested many types of batteries, but in
the end, the target is locked on 18650 batteries, and 18650 batteries
are used as new energy electric car batteries. Technical route. It can
be said that the reason why Tesla is able to have performance that is
not inferior to traditional fuel vehicles, in addition to motor
technology, also benefits from Tesla's advanced battery technology. So
why did Tesla choose the 18650 battery as its source of power?
Mature technology, high consistency
Before
entering the field of new energy vehicles, 18650 batteries have been
widely used in electronic products. They are the earliest, most mature
and most stable lithium-ion batteries. After years of accumulated
experience, Japanese manufacturers have accumulated 18650 batteries in
consumer products. Advanced technology is extremely well applied in the
field of vehicle batteries. Panasonic is one of the world's largest
battery technology and scale companies. Compared with other
manufacturers, it has the fewest product defects and larger scale, and
it is also easy to select batteries with good consistency.
In
contrast, other batteries, such as laminated lithium-ion batteries, are
far from mature enough. Many products cannot even be unified in size
and size, and the production technology of battery manufacturers cannot
meet the conditions. In general, the consistency of the battery does not
reach the level of the 18650 battery. If the consistency of the battery
fails to meet the requirements, the management of a large number of
battery strings and battery packs formed in parallel and in serie will
not allow the performance of each battery to be better played, and 18650
batteries can solve this problem well.
High safety performance
The
18650 lithium battery has high safety performance, non-explosive,
non-combustible, non-toxic, non-polluting, and has passed RoHS trademark
certification; and has good high temperature resistance, and the
discharge efficiency is 100% at 65 degrees.
The
18650 battery is generally packaged in a steel shell. In extreme
situations such as a car collision, it can minimize the occurrence of
safety accidents and provide higher safety. In addition, the size of
each battery cell of the 18650 is small, and the energy of each cell can
be controlled in a smaller range. Compared with the use of large-size
battery cells, even if a unit of the battery pack fails, it can be
reduced The impact of the failure.
High energy density
The
capacity of 18650 lithium battery is generally between 1200mah~3600mah,
and the general battery capacity is only about 800mah. If combined into
a 18650 lithium battery pack, the 18650 lithium battery pack can exceed
5000mah. Its capacity is 1.5 to 2 times that of a nickel-hydrogen
battery of the same weight, and it has a very low self-discharge rate.
The energy density of 18650 batteries can currently reach the level of
250Wh/kg, which meets Tesla's high cruising range requirements.
Low cost, high cost performance
The
18650 lithium battery has a long service life, and the cycle life can
reach more than 500 times in normal use, which is more than twice that
of ordinary batteries. The 18650 product has a high degree of technical
maturity, and the structural design, manufacturing technology,
manufacturing equipment, and the derived 18650 module technology are all
mature, all of which reduce its operating and maintenance costs.
At
present, the 18650 battery, which is widely used, has a history of
development for many years. Although the technology is relatively mature
compared with other types of batteries, it still faces problems such as
high heat production, complex grouping, and inability to achieve fast
charging. In this context, 21700 cylindrical ternary batteries came into
being.
21700 battery:
The
battery 21, 70, 0 is the model of the cylindrical battery, which
specifically refers to: 21 - the outer diameter of the cylindrical
battery is 21mm; 70 - the height of the battery is 70mm, 0 refers to the
cylindrical battery.
This
is a new model developed to meet the requirements of electric vehicles
for longer mileage and to improve the effective utilization of vehicle
battery space. Compared with the common 18650 cylindrical lithium
battery with the same material, 21700 has a capacity of more than 35%
higher.
The new 21700 has four significant advantages:
(1).
The battery cell capacity is increased by 35%. Take the 21700 battery
produced by Tesla as an example. After switching from the 18650 model to
the 21700 model, the battery cell capacity can reach 3 to 4.8 Ah, a
significant increase of 35%.
(2).
The energy density of the battery system is increased by about 20%.
According to the data disclosed by Tesla, the energy density of the
18650 battery system used in the early days was about 250Wh/kg. Later,
the energy density of the 21700 battery system produced by it was about
300Wh/kg. The volumetric energy density of the 21700 battery was higher than the original 18650. Nearly 20%.
(3).
The cost of the system is expected to drop by about 9%. From the
analysis of battery price information disclosed by Tesla, the power
lithium battery system of the 21700 battery is priced at $170/Wh, and
the price of the 18650 battery system is $185/Wh. After using 21700
batteries on Model 3, the cost of the battery system alone can be
reduced by about 9%.
(4).
The weight of the system is expected to drop by about 10%. The overall
volume of 21700 is greater than 18650. As the capacity of the monomer
increases, the energy density of the monomer is higher, so the number of
battery cells required for the same energy can be reduced by about 1/3,
which will reduce the difficulty of system management and reduce the
number of batteries. The number of metal structural parts and electrical
accessories used in the bag further reduces the weight of the battery.
After Samsung SDI switched to a new set of 21700 batteries, it was found
that the weight of the system was reduced by 10% compared to the
current battery.
Maintaining
the high reliability and stable performance of the 18650 battery, the
performance of the 21700 battery is greatly improved compared to the
18650 in all aspects. In addition, compared to other battery models,
21700 is similar to the more mature 18650 battery in terms of battery
raw material selection, production process and technical process.
Therefore, most of the production lines of 18650 and 21700 are
compatible. Some companies have a safer way to make a fuss on the
production line and move the production line closer to the compatibility
of 21700 and 18650.
BENZO Energy Technology Co.,Ltd
UFine Technology Co., Ltd
Site: www.bz-battery.com / www.benzoenergy.com
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