How to distinguish so-called "soft-pack lithium batteries" and "polymer batteries"

In both digital and application in power market,Soft package battery is becoming a very important technical route.

Soft pack batteries, it is to use the batteries of aluminum-plastic packaging film as packing material.Relatively speaking,Lithium ion batteries packaging can be divided into two categories, one kind is soft package of batteries, one kind is metal shell batteries.Metal case batteries also include steel shell and aluminum shell, etc., in recent years due to the special need some batteries, the use of plastic shell, can also be classified as such.

The difference between the two in addition to the shell material, determines its encapsulation mode is also different.Soft package of batteries used hot encapsulation, and metal shell welding, laser welding) commonly used batteries.Soft package of batteries can be used in a hot encapsulation is the cause of its use of aluminum-plastic packaging film this material.

Lu: su packaging film

Aluminum-plastic packaging film (hereinafter referred to as aluminum-plastic film) structure as shown in figure, based on its cross section composed of three layers: nylon layer, Al layer and PP.

Three layers of each have each function, the first is to make sure the shape of the aluminum composite membrane, nylon layer in manufacturing into lithium ion battery before the membrane deformation will not occur.

Al layer is a layer of metal Al composition, its role is to prevent the infiltration of water.Lithium ion battery is very afraid of water, water content of general requirement sheet was in PPM level, so packaging film must be able to block moisture infiltration.Nylon is not waterproof, can't protect.Al and metal at room temperature will react with the oxygen in air to produce a dense layer of oxide film, prevent moisture from infiltration, protect the internal batteries.Al layer at the time of aluminum-plastic film forming also provides hole is plastic, this can be found in the 3 point.

PP is the abbreviation of polypropylene, the characteristics of this material is occurs in more than one hundred degrees Celsius temperature melting, and the viscosity.So the battery thermal encapsulation is largely PP layer on the head under the action of heat to melt together, and then head removed, cooling solidification cohere.

Aluminum-plastic film looks very simple, actually do, how to put the three layers of material evenly, firmly together is not so easy.Unfortunately, now good quality aluminum composite membrane are imported from Japan, basically not domestic, but the quality remains to be improved.

Lu: su film forming process

Soft package of batteries can be designed according to the needs of customers into different size, design good after, when the overall size will need to issue the corresponding mold, aluminum-plastic film forming.Molding process is also called scouring pit (actually people think it should be "spear pit", but everyone write and then do so), as the name implies, is to use molding under the condition of the heating, aluminum-plastic film on roll core hole, rushed out of a can a detailed below.

Aluminum-plastic film ran well and cut out after forming, generally known as the Pocket bag, as shown below.In batteries commonly thinner when choose single crater (below left) and the batteries thicker when choose double hole (below right) and because one side of the deformation caused by too much breakthrough aluminum-plastic film deformation limit rupture.

According to the needs of design, sometimes in the position of air pocket of a small pit, again in order to enlarge the volume of air pocket.

Top side sealing process

Finally talk about the topic (how great you are carried away!, top side sealing process is mild package lithium-ion batteries of the first line of encapsulation process.Top side sealing actually contains the two processes, top and side sealing.Must first put good winding core winding in good pit, then will packaging film folded along the dotted line position, as shown in the figure below.

This figure is aluminous model membrane into the core winding, need encapsulation several places, including the top sealing area, lateral sealing area, an area with two sealing area.The following is described respectively.

Put the roll core in the pit, he put the whole aluminum composite membrane can be in the fixture, at the top of the top side in the sealing machine for sealing and side sealing.Top side sealing machine is like this:

Diagram of this kind of top side sealing machine with four fixtures, the location is on the left, on the right side of the station is the lateral sealing.The two pieces of the yellow metal is on the head, there are a head, encapsulation when two head with a certain temperature (generally at about 180 ℃), closed when the pressure on the aluminum composite membrane, aluminum-plastic film layers of PP melt then stick together, thus encapsulation to OK.

Lateral sealing nothing much to say (what side voltage pull too far not speak), mainly, said the top sealing, sealing area diagram as shown in the figure below.Top sealing to seal a ear, ear is very metal (aluminum anode and the cathode nickel), how to PP packaged together?It relies on a widget on the ears - pole ear glue to complete.Very ear rubber concrete structure is not very clear to me, hope to have a knowledgeable person to complement.I only know that it also has the cost of PP, that is to say, when heated to melt bond.In very ear as shown in the circle part of the package below.Encapsulation, pole ear glue of PP and aluminum-plastic film layer PP melt bond, to form the effective encapsulation structure.

Filler, seal process

Soft package batteries after top side, you need to do to X - ray examination of its core winding parallel, then went into the dry room in addition to water vapour.Let stand for some time, in a dry room into the liquid injection and the sealing process.

Through the above introduction we know, the batteries in the top side is completed, will be left with air pocket on the other side of an opening, the opening is used for filler.After the completion of a filler, need to immediately take air pocket edge sealing, also called a letter.After completion of an encapsulation, batteries, in theory, the interior is completely cut off from the external environment.An encapsulation of the principle of the same as the top side, here is not here.

Let stand for, into, clamp plastic process

In liquid injection and after completion of a letter, you first need to will let stand for batteries, according to the process of different can is divided into the high temperature static and let stand at room temperature and let stand for the purpose of the injection of electrolyte is fully infiltrates pole piece.And then batteries can take into.

Pictured above is soft package of batteries into the ark, is actually a charge and discharge device, I find for a long time didn't find the picture of the batteries, you think about the batteries in the picture above with respect to OK.Is recharging the batteries for the first time, but not to use the highest voltage, charging current is very small.

Into is for the purpose of the electrode surface to form stable SEI film, which is equivalent to a process of the batteries "activate".In the process, will produce a certain amount of gas, which is why aluminum-plastic film to reserve an air pocket.Some factories process will use jig into that put the batteries in the fixture (sometimes figure is simple with the glass plate, and then Shanghai clip) on ark into again, a gas that will be fully into the bag, at the same time into the electrode interface also is better.

After into some batteries, especially heavy batteries, due to internal stress is bigger, may produce a certain amount of deformation.So some factories will set a fixture after into plastic process, also called jig baking (baked).

Second sealing process

Said just now turned to produce gas in the process, so we have to take out gas and then on the second encapsulation.Here some companies into two processes: Degassing (exhaust) and two letters, and then cut a bag of working procedure, here I am general together are referred to as the second.

Two letters, the first by the blade airbags will prick, vacuum at the same time, so that the gases in the air pocket and a small portion of the electrolyte can be pulled out.Then in the second sealing area are two sealing head encapsulation, ensure batteries air tightness.Finally cut the packaging of the batteries to air pocket, a basic forming soft package of batteries.Second sealing is lithium ion battery last encapsulation process, the heat in front of the principle or encapsulation, no longer here.

The follow-up process

Because of the Lord to ask is encapsulation, behind with encapsulation is not big, so the two sealing process I said together.

2 after seal cut the bag need to be cutting edge and frilled edge, is an edge with the two sealing the linesman to appropriate width, then folded up, ensure that the width of the batteries do not overweight.After folding batteries can points let ark of capacity, is really a capacity test, see the capacity of the batteries have to meet the minimum value.In principle, all the batteries before the factory need to do a points test, to ensure that the capacity of unqualified batteries will not sent to the hands of customers.But at the time of batteries, large quantity, some companies will do part of the capacity, using statistical probability to determine the qualified rate of the batch capacity of batteries.

Points after capacity, capacity of qualified batteries will enter after the process, including inspection appearance, stick to cement, side voltage testing, pole ear through welding, etc., can increase or decrease in number of process according to customer requirements.Is the final OQC inspection, then the packaged goods.

The page contains the contents of the machine translation.