The main function of the isolation cell membrane ion conduction electron, which is positive and negative electrodes in the batteries to prevent the direct electronic contact, but the free passage of ions. For lithium-ion battery separator, the basic requirements are as follows:

1. Thickness

For consumer-type lithium-ion battery (mobile phones, laptops, digital cameras, used in batteries), 25-micron membrane gradually became the norm. Membrane However, due to the increasing use of people with handheld devices, thin membranes, eg 20 microns, 18 microns, 16 microns, and even thinner started large-scale applications. For the Laptop battery power, because the requirements of mechanical assembly processes, often require thicker membrane, of course, with large batteries for power, security is also very important, while the membranes are often thicker also means better security.

2. Ventilation rate:

From academic point of view, the membrane is inert in the battery, that divide is not a necessary element of the stack, but only the production of industrial batteries. The existence of the membrane first encounter it does not deteriorate the electrochemical performance of the battery, mainly in the internal resistance. Electrolyte membrane containing the resistivity and the resistivity of the same electrolyte, the ratio between the numbers of known MacMullin. In general, consumption of lithium-ion batteries this value is close to 8, of course, this value is smaller, the better. In general, lithium-ion Dell Inspiron 6400 battery separator containing a parameter of the permeability, or called the number Gurley. This number is well defined, ie a certain amount of gas in certain pressure conditions, through a certain area, divide the time required, the volume of gas flow is generally 50cc, some companies will be marked 100cc with the final results will be twice as bad. Size should be 1 square inch pressure difference does not remember clearly. This value in a certain sense, and use their cell membrane of the internal resistance is proportional, that is, the higher the value, then the greater the resistance. However, a different membrane, the direct comparison of numbers does not make sense. Because the internal resistance of lithium-ion batteries and ionic conduction, while the ventilation rate and the spread of gases linked to two types of mechanism is not the same. In other words, the simple comparison of two different fracture Gurley number is meaningless, because she may divide two types of micro-structures are completely different, but the Gurley number of the same size of the membrane can be very good response from the size of the resistance, because the membrane is relatively the same micro-structure is identical or comparable.

3. Infiltration degrees:

To ensure internal resistance of the hp F2024A battery is not too demanding membrane is used in the electrolyte of the battery can be completely infiltrated. Government is not recognized testing standards. Can be roughly judged by the following experiment: Take a typical electrolyte (such as EC: DMC = 1:1.1 M LiPF 6), decreased membrane surface area, to see if the droplets will rapidly disappear by absorption the membrane, so it is essential to meet the infiltration requirements is illustrated. More accurate tests can be time-resolved ultra-high camera recording of the diaphragm into contact with droplets droplets disappear processes, computer time, the length of time to compare the two types of degree of membrane penetration. Infiltration degree one hand, a membrane material itself bound to another membrane on the surface and internal microstructure closely linked.

4. Chemical Stability:

In other words, is to make membranes in the electrochemical reaction is inert. After several years of industrial inspection, is generally considered that the current PE or PP separator material is chemically inert to meet the requirements.

5. Open:

In general, the membrane electrode particles to avoid direct contact, a very important point are to prevent the electrode particles directly through the diaphragm. Electrodes currently used in 10 micron particles in the general order of magnitude, while the use of BATBL50L6 conductive additives in the order of 10 nm, but had the chance to reunite the general carbon black particles tend to form large particles. In general, sub-micron pore size membrane enough to prevent particles directly by the electrodes, of course, does not exclude some of the surface of the electrode is not managed properly, leading to some of the dust over as micro-circuit short and so on.

6. Puncture Strength:

This parameter is not flat because the surface of the electrode, and the assembly process of limited technological level has applied, requiring considerable force perforated diaphragm. Tests for resistance to puncture is the industry standard to follow, usually within a certain speed (3-5 m per minute), so there is no sharp edge of a 1 mm diameter needle attached to the diaphragm ring to penetrate the membrane applied to the needle from the puncture strength of the strongest known. Similarly, because when the testing methods used and the actual situation of batteries vary considerably, the direct comparison of the two types of membrane puncture strength is not very reasonable, but in the micro-structure of certain circumstances, the strength of perforation relatively high rate of improper assembly is low. But the mere pursuit of power punching high, will inevitably lead to performance degradation of the membrane of another.

7. Thermal stability:

Diaphragms need to use the range of sony VGP-BPS2 battery temperature (-20C ~ 60C) to maintain thermal stability. Generally speaking, the current use of PE or PP is membrane materials to meet these requirements.

There is of course due to the electrolyte to water sensitive, and most manufacturers in the liquid injection around 80C before cooking, which is PP / PE membrane will not be a big problem there

8. Thermal Shutdown Temperature:

Contents of a more serious owing to security concerns, the current lithium-ion battery separator are generally able to provide an additional function, namely thermal shutdown. The general principles, we shall batteries (two flat electrodes sandwiching a diaphragm, using a common lithium-ion battery electrolyte) heating, where the resistance has increased three orders of magnitude when the temperature is called temperature thermal shutdown. This feature can be lithium-ion battery to provide extra security. Effectively close the temperature and the melting point of the matter itself closely related, such as the PE of about 135C. Of course, another micro-structure of the thermal shutdown temperature has an impact. But for small batteries, thermal shutdown mechanism for the role is very limited.

9. Rate of porosity:

Current form, the lithium-ion battery separator porosity of 40%. The pore size and the internal resistance of a certain relationship, but different types of membranes between the absolute value of the void fraction can be directly compared.