China leading LiPo battery manufacturer

What is lithium polymer battery?

Lithium polymer battery is rechargeable lithium ion battery with pouch shape and soft aluminium foil plastic film package.According to original definition for lithium polymer battery, it is using solid or Gel electrolyte and soft external aluminum foil film. However, most of polymer batteries in the world now refers to pouch cell, a lithium ion battery which uses soft square package.

Lithium polymer battery cell

LiPo battery basic structure

• Name:Lithium polymer battery is also named lithium ion polymer battery,LiPo battery,Li-Poly battery,Li-Polymer battery.
• Basic structure: it is consist of mainly cathode,anode,separator, electrolyte.aluminum laminated film.
• Cathode structure: LiCoO2(Lithium cobalt oxide), conductive material,PVDF(adhesive), aluminum foil current collector.
• Anode structure: Graphite, conductive material,PVDF(adhesive), Copper foil current collector.
• Working principle : When the LiPo battery is charging, the Li ion move from cathode(positive) to anode(negative) where many caves are there in the graphite material, the ions entered the all the caves, then the battery is fully charged. When the battery is discharging, the Li ion move from graphite caves in the anode(negative) to cathode(positive) ,the ions left the all the caves, then the battery is fully discharged.

Lithium polymer battery working principle

Parameters of lithium polymer battery

To understand and use Lithium polymer battery better, we must know clearly about below parameters.

• Nominal Voltage: The stable operating voltage,during the full discharge and charge time of Lithium polymer battery, there is a stable 3.7 v voltage in the discharge charge curve, that is the nominal voltage for LiPo battery. This parameter is important for a rechargeable battery cell, with a higher value, less of cells will be needed to reach a suitable battery pack voltage, smaller size and less weight can be achieved.For example, to make a 3.6V battery, we need 3 pieces 1.2V NiCH battery cell while only one lithium polymer battery cell is enough to make it, this makes LiPo battery much more attractive when engineers look for battery solutions.
• Charging voltage: This is the output voltage required for charging a lithium polymer battery, the value is 4.2 v. 
• Charging cut off voltage: This is the protective setting to avoid over charging, it’s 4.25 v. It’s not allowed to charge the lithium polymer battery up to higher than 4.25 v. otherwise, it may cause danger and accident. The charging cut off function is always included in LiPo battery PCM, when the battery voltage rise up to 4.25V, this function will be activated and the circuit will be cut off.
• Nominal capacity: It’s the power that a battery can drain, let’s put it this way, if a LiPo battery discharge with a constant current of 1 A for 2 hours before it runs out of energy and cut off, then we can say the battery capacity is 2 Ah(1 A*2 Hours), its the calculation result of multiply of the discharge current and lasting time. 
• Discharging cut off voltage : Voltage at which the battery stop discharging. This is a value set by lithium ion battery protection IC to protect the lithium polymer battery from over discharging, for LiPo battery cell it’s always 2.75 v or 3.0 v. This voltage is a design that each lithium battery protection circuit must have, it protects the battery during discharging, otherwise, over discharging can damage the battery.
• C rate: C rate is the result of current divided by battery capacity. Let’s take an example, If a 200mAh LiPo battery is discharging @ 2000mA, then we can say that it’s discharge c rate is 10C(2000mA/200mAh).Compared to it’s capacity, the bigger the current is, the higher the C rate is. 
• Cycle life: We discharge the LiPo battery to cut off voltage, then we charge it @0.2C under room temperature 25C till it reaches 4.2V, and then we discharge it to 3.0V @0.2C, and keep it stay and wait for 5 minutes,this is called one cycle, then we repeat this process again and again, till the capacity become 80% of original value. The total cycle times we did before the battery capacity changed to 80% is the battery cycle life. Lithium polymer battery is 500 times.This is different from lifespan that we experience in daily life, but they both means similar things about a lipo battery life.

As the most popular rechargeable lithium battery in market, Lithium polymer battery has many unique advantages, especially because it can be made into different shapes according design needs, this is deadly attractive for many industries such as the field of consumer electronics,smart devices, wearable devices. This feature is a key success factor for lipo battery,but it is absolutely not enough, it’s high voltage, low weight and other more features made it together.

• High voltage.
• High energy density.
• Flexibility on shapes.
• Light weight
• Maintain free
• No memory effect
• Low self discharge rate
• Environmental friendly
• Great high drain discharge performance
• Long cycle life

LiPo battery is rechargeable lithium battery which is listed as dangerous goods for airway and sea way transport. Because fire accidents caused by transporting lithium ion batteries happened now and then, transport companies especially airlines and airports in all over the world released more and more strict regulations and limits to manage safe transporting of lithium ion batteries.With our professional service based on highly reliable battery quality management, as an experienced rechargeable lithium battery manufacturer and exporter, we have kept a good record of no accident in the past 15 years.

Why and which certificates are always needed?

To get access to markets of different countries, lithium polymer battery products are always required to prepare some certificates and get them ready. In China, 3C certificate is needed for electrical and electronics products, CE is the condition to enter EU market, For Korea market, it’s KC. Also for some specified industry,there are some new certificates are necessary.Many consumer electronics such as wearable devices and smart glass, mobile phones all require IEC62133,medical devices with battery power requires UL1624. And for safe transport, worldwide airports needs us to offer them UN38.3 or MSDS.

Can PD prepare certificates for customers?

PD can arrange samples testing by third-party labs and prepare lithium battery certificates mentioned above for customers.Even there is no stock of the battery cells, we can produce new samples for the certificates needs. So far, we have got CE, ROHS,UN38.3,IEC62133,KC,CB,REACH,UL,MSDS and so on.