What is 18650 battery? In fact, 18650 is only a size model in the battery industry, 18 represents the diameter of the battery, 65 represents the height of the battery, 0 represents the cylindrical, that is, 18650 battery refers to the diameter of 18, the height of 65 cylindrical battery, this size has lithium batteries, there are other types of batteries, usually people say 18650 battery refers to 18650 lithium battery.
From the perspective of the internal material of the battery, the so-called lithium polymer battery refers to the use of polymer as the electrolyte of lithium-ion batteries, specifically divided into "semi-polymer" and "full polymer" two. The "semi-polymer" refers to a layer of polymer (usually PVDF) coated on the isolation film to make the cell more adhesive and the battery more rigid, while the electrolyte is still a liquid electrolyte. All-polymer" refers to the use of a polymer to form a gel network inside the cell, which is then injected into the electrolyte to form the electrolyte. Although "all-polymer" batteries still use liquid electrolyte, the amount is much less, which greatly improves the safety performance of lithium-ion batteries. As far as I know, only SONY is now mass-producing "all-polymer" lithium-ion batteries.
On the other hand, the polymer battery refers to the use of aluminum packaging film as the outer packaging of lithium-ion batteries, which is commonly known as soft pack batteries. This packaging film consists of three layers, PP layer, Al layer and nylon layer, because PP and nylon are polymers, so this kind of cell is called polymer battery.
1、High energy density. General 18650 battery capacity can do about 2200mAh, so the energy density is about 500Wh/L, while the energy density of polymer battery is close to 600Wh/L at this stage of mass production.
2. Good safety. We know that lithium-ion batteries in extreme conditions (such as overcharge, high temperature, etc.), the internal chemical reaction will be violent, generating a lot of gas. 18650 batteries use a metal shell, there is a certain strength, when the internal air pressure reaches a certain time the steel shell will rupture and explode, an extremely horrible safety accident. This is why the room where the 18650 battery is tested must generally be protected by layers, and absolutely no one can enter during the test. Polymer batteries do not have this problem, even in the same extreme case, due to the lower strength of the packaging film, as long as the air pressure is slightly higher will break, will not produce an explosion, the most egregious case is burning. So in terms of safety, polymer batteries are better than 18650 batteries.
3、Be able to design according to the customer's needs. This has already been said above, so I will not repeat.
4, the price is sold higher. The international price of 18650 is about 1USD/pcs, which is about 3RMB/Ah according to 2Ah, while the price of polymer lithium battery is 4RMB/Ah for low-end cottage factory, 5~7RMB/Ah for mid-end, and more than 7RMB/Ah for mid-end. Like ATL, Li Shen such, generally can be sold to about 10RMB/Ah, and you single small people are not willing to accept.
But polymer batteries also have their own drawbacks. The main is the higher cost, because you can design according to customer demand, which the research and development costs to be counted. And the shape is variable, a wide variety, resulting in the manufacturing process of a variety of fixtures are non-standard parts, but also correspondingly increase the cost. Polymer battery itself is poor versatility, which is also flexible design, often for so 1mm difference will need to redesign a customer, the cost of ah or cost.
It is generally believed that the no-load voltage of lithium batteries to 3.0V or less is considered to run out of electricity (the specific value needs to see the threshold value of the battery protection plate, such as low as 2.8V, there are also 3.2V). Most lithium batteries can not be discharged to the no-load voltage below 3.2V, otherwise excessive discharge will damage the battery (the general market lithium batteries are basically used with a protection board, so excessive discharge will also lead to the protection board can not detect the battery, thus unable to charge the battery).
4.2V is the maximum limit of the battery charging voltage, generally speaking, the lithium battery no-load voltage charged to 4.2V is considered full of electricity, battery charging process, the battery voltage in 3.7V gradually rise to 4.2V, lithium battery charging can not be no-load voltage charged to more than 4.2V, otherwise it will also damage the battery, this is the special place of lithium batteries, in general, 18650 lithium batteries have The following advantages.
A, 18650 battery characteristics
1、Wide range of use
Laptop computers, walkie-talkies, portable DVDs, instruments, audio equipment, models, toys, video cameras, digital cameras and other electronic equipment.
2、Series connection
Can be connected in series or parallel to form 18650 lithium battery pack.
3、Small internal resistance
The internal resistance of polymer cells is smaller than that of general liquid cells, and the internal resistance of domestic polymer cells can even be less than 35mΩ, which greatly reduces the self-consumption of the battery and extends the standby time of cell phones, and can completely reach the level of international standards. This support for large discharge current polymer lithium is the ideal choice for remote control models, becoming the most promising alternative to NiMH batteries.
4、No memory effect
No need to empty the remaining power before charging, easy to use.
5、High voltage
The voltage of 18650 lithium battery is generally at 3.6V, 3.8V and 4.2V, much higher than the 1.2V of NiCd and NiMH batteries.
6、High safety performance
18650 lithium battery has high safety performance, no explosion, no combustion; non-toxic, non-pollution, certified by RoHS trademark; various safety performance in one go, cycle times greater than 500 times; good high temperature resistance, discharge efficiency of 100% at 65 degrees. To prevent the short-circuit phenomenon of the battery, the positive and negative poles of 18650 lithium battery are separated. So the possibility of short circuit has been reduced to the extreme. You can add a protection plate to avoid overcharging and discharging the battery, which can also extend the service life of the battery.
7、Long service life
The service life of 18650 lithium battery is very long, and the cycle life can be more than 500 times in normal use, which is more than twice that of ordinary batteries.
8、Large capacity
18650 lithium battery capacity is generally 1200mah ~ 3600mah, while the general battery capacity is only about 800, if the combination of 18650 lithium battery into 18650 lithium battery pack, the 18650 lithium battery pack is casually can break through the 5000mah.
Second, 18650 lithium battery compared to polymer batteries
The so-called lithium polymer battery refers to the use of polymer as the electrolyte lithium-ion batteries, specifically divided into "semi-polymer" and "full polymer" two. The "semi-polymer" refers to a layer of polymer (usually PVDF) coated on the isolation film to make the cell more adhesive and the battery more rigid, while the electrolyte is still a liquid electrolyte. All-polymer" refers to the use of a polymer to form a gel network inside the cell, which is then injected into the electrolyte to form the electrolyte. Although "all-polymer" batteries still use liquid electrolyte, but the amount is much less, which has greatly improved the safety performance of lithium-ion batteries. As far as I know, only SONY is now in mass production of "all-polymer" lithium-ion batteries.
From another point of view, the polymer battery refers to the use of aluminum packaging film as the outer packaging of lithium-ion batteries, which is commonly known as soft pack batteries. This packaging film is composed of three layers, PP layer, Al layer and nylon layer, because PP and nylon are polymers, so this kind of battery is called polymer batteries.
1、Lower price
The international price of 18650 is about 1USD/pcs, which is about 3RMB/Ah according to 2Ah, while the price of polymer lithium battery is 4RMB/Ah for low-end cottage factory, 5~7RMB/Ah for mid-end, and more than 7RMB/Ah for mid-end. Like ATL, Lixin, generally can be sold to about 10RMB/Ah, and your single small people are not willing to accept.
2、Not customizable
SONY has always wanted to make lithium-ion batteries like alkaline batteries, there are certain industrial standards, just like the No. 5 battery, No. 7 battery, the world is basically the same. But because one of the advantages of lithium-ion batteries is that they can be designed according to customer demand for shape, it is impossible to have a unified standard, so now the lithium-ion battery industry is basically only 18650 this a standard model, the rest are designed according to customer demand.
3、Poor safety
We know that under extreme conditions (such as overcharging, high temperature, etc.), the lithium-ion battery will undergo a violent chemical reaction and produce a large amount of gas. 18650 batteries use a metal shell, which has a certain strength, and when the internal air pressure reaches a certain point the steel shell will rupture and explode, resulting in a horrible safety accident.
This is why the room where the 18650 battery is tested must generally be protected by layers, and absolutely no one can enter during the test. Polymer batteries do not have this problem, even in the same extreme case, due to the lower strength of the packaging film, as long as the air pressure is slightly higher will break, will not produce an explosion, the most egregious case is burning. So in terms of safety, polymer batteries are better than 18650 batteries.
4、Low energy density
General 18650 battery capacity can do about 2200mAh, so the energy density is about 500Wh/L, while the energy density of polymer battery can be close to 600Wh/L at this stage of mass production.
But polymer batteries also have their own disadvantages. Mainly, the cost is higher, because it can be designed according to customer needs, which the research and development costs have to be included. Moreover, the variety of shapes and types lead to non-standard fixtures in the manufacturing process, which also increases the cost accordingly. Polymer battery itself is poor in versatility, which is also brought about by flexible design, often for so 1mm difference will need to redesign a customer.
Third, the application of 18650 lithium battery
In the energy battery industry lithium secondary batteries are used thanks to their superior performance. With the continuous development of lithium secondary battery technology, has been widely used in our daily life; rechargeable batteries for multiple uses are increasingly favored by consumers. Focus on the energy battery industry, a full understanding of the battery so that we can do "for my use", the current 18650 lithium battery in the following areas have certain applications.
1、Energy storage
Mainly used in base station power supply, clean energy storage, grid power storage, home light storage system, etc.
2、Power class
Mainly refers to electric transportation, electric bicycle, new energy vehicles, etc.
3、Digital class
Cell phones, tablets, laptops, electric toys, MP3/MP4, headphones, rechargeable batteries, models, mobile power, etc.
Four, 18650 lithium battery classification
18650 lithium battery production are required to have a protective circuit to prevent the battery from being overcharged and overdischarged. Of course this is necessary for lithium batteries, which is also a general disadvantage of lithium batteries, because the materials used in lithium batteries are basically lithium cobaltate material, and lithium cobaltate material lithium batteries can not be discharged at high current, poor safety, from the classification of 18650 lithium batteries can be classified in the following way
1、Classification according to the practical performance of the battery
Power type battery and energy type battery. Energy type battery is characterized by high energy density, mainly used for high energy output; power type battery is characterized by high power density, mainly used for instantaneous high power output, output battery. The power-energy lithium battery is accompanied by the emergence of plug-in hybrid vehicles. It requires a higher energy stored in the battery to support a distance of pure electric driving, but also to have better power characteristics, and enter the hybrid mode at low power.
Simple understanding, energy type is similar to a marathon runner, to have endurance, is to require high capacity, high current discharge performance requirements are not high; then power type is a sprinter, the fight is burst power, but endurance must also have, or capacity is too small will not run far.
2、According to the electrolyte material
Lithium-ion batteries are divided into liquid lithium-ion batteries (LIB) and polymer lithium-ion batteries (PLB).
Liquid lithium-ion batteries use a liquid electrolyte (the current power battery is mostly such). Polymer Li-ion batteries are replaced by a solid polymer electrolyte, which can be either "dry" or "gel", and currently most use polymer gel electrolytes. About solid state battery, strictly speaking, it means that the electrode and electrolyte are solid state.
3、Classification by product appearance
Cylindrical, soft pack, square.
Cylindrical and square outer packaging is mostly steel or aluminum shell. Soft pack outer packaging for aluminum plastic film, in fact, soft pack is also a square, the market is used to aluminum plastic film packaging called soft pack, some people will be soft pack batteries called polymer batteries.
For cylindrical lithium-ion batteries, the model number is generally 5 digits. The first two digits are the diameter of the battery, and the middle two digits are the height of the battery. The unit is millimeter. For example, 18650 lithium battery, it has a diameter of 18 mm and a height of 65 mm.
4, according to the pole material classification
Anode material: lithium iron phosphate (LFP), lithium cobaltate (LCO), lithium manganate (LMO), (binary battery: lithium nickel manganate / lithium nickel cobaltate), (ternary: lithium nickel cobalt manganate (NCM), lithium nickel cobalt aluminum acid (NCA)).
Negative materials: lithium titanate (LTO), graphene battery, nano carbon fiber battery.
Regarding the graphene concept in the market, it mainly refers to graphene-based batteries, i.e. adding graphene slurry to the pole piece or adding graphene coating to the diaphragm. Lithium nickel-acid, magnesium-based batteries on the market basically does not exist.
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