Lithium battery bulge reason

The lithium battery basic structure of package resolution:

Lithium battery of main material: cathode materials, anode materials, electrolytes, diaphragm (isolation materials)

Simple cell structure

The anode

Form from the battery weight point of view, a large proportion of the anode materials (generally in 70% ~ 80%), because of the anode materials directly affects the performance lithium ion batteries performance and its cost is also directly determine the costs of batteries. The anode materials for lithium ion batteries cost 30% ~ 40%, also directly affect the energy density of lithium battery pack, and performance.

The cathode

Anode materials is formed by the positive potential relative to lower material, and has a high capacity and good cycle reversibility, thus in the process of embedded lithium keep good size (not) serious deformation and mechanical stability. Anode materials mainly influence on the performance of the lithium battery efficiency, circulation, etc., the performance of the anode materials has a direct impact on the performance of lithium battery, anode materials for lithium batteries cost about 10 ~ 20%.Types of anode materials, including carbon anode, no carbon cathode.

The electrolyte

Electrolyte between the positive and negative have the effect of transportation charge carrier) in the (similar to radio, has high ionic conductivity, general should reach 1 x10-3 x10-2 s/cm ~ 2.It affects the energy density of the lithium battery pack, wide application temperature, cycle life and power density, the safety performance.

The diaphragm

Diaphragm has certain pore size and porosity, guarantee the low resistance and high ionic conductivity, has good permeability to lithium ion, invasive of electrolyte and have enough liquid moisture absorption ability, keep the ionic conductivity, have electronic insulation at the same time, ensure mechanical isolation is negative, moreover should have enough puncture strength, tensile strength and other mechanical properties and resistance to corrosive electrolyte and electrochemical stability of the enough. Power battery higher request on the diaphragm, usually adopts the composite membrane.

Working principle of the lithium battery:

Is a kind of lithium-ion batteries rechargeable batteries, which rely on lithium ion between the positive and negative of embedding and embedded off back and forth to work, to achieve energy storage and release.

1, the charging process

Under the drive of lithium ion in electric field emergence from the positive lattice, through the electrolyte, embedded in the cathode in the lattice.

Voltage is lower than 3 v, have to be pre charge first, 1/10 of the charging current to set current, voltage to 3 v, in the process of charging standard. Standard charging process is: to set for constant current charging current and battery voltage rises to 4.20 V, the constant voltage charging and charging voltage of 4.20 V. At this point, the charging current is falling, when the current dropped to set up 1/10 of the charging current, charging is over. This is generally a process of lithium batteries, if lithium battery exists in intelligent devices, its charge mode will be intelligent equipment software control.

2, the discharge process

Discharge process is just the reverse of the charging process, lithium ion under the effect of electric field return to the anode, electrons are passed via external to the anode with lithium ion compound. Battery discharge on the cathode electron e running on to the anode through an external circuit is lithium ion Li + from the cathode "jump" in the electrolyte, "climb" diaphragm winding holes, "swimming" to the anode, and would have run to come over together.

By understanding the lithium battery charge and discharge process, we can understand from the microcosmic, battery capacity is actually contained in the amount of charge. The greater the current, the faster the discharge, battery for the shorter the time.

Why cells in normal use or there will be a long time without use bulge phenomenon?

In the process of charging and discharging, the phenomenon of the bulge has two kinds:

A.Overcharge caused bulge

Overcharge will lead to the anode material of lithium atom in all ran to the anode materials, lead to the anode was full of lattice deformation and collapse, which is, by a major reason for the lithium battery. In this process, more and more negative electrode of lithium ion, excessive accumulation makes lithium atoms grow stumps crystallization, makes the battery ballooning.

2.Put to bulge

In the process of liquid lithium ion battery charge and discharge for the first time, electrode materials and electrolyte reacts on the solid liquid interface and form a layer of coverage in the passivation layer on the surface of the electrode materials. Form the passivation layer film can effectively prevent the electrolyte molecules through, but Li + can freely through the passivation layer embedded and emergence, has the characteristics of the solid electrolyte, so this layer of passivation film is called "solid electrolyte interfacial film" (solid electrolyte interface), hereinafter referred to as SEI.SEI film on the anode materials can produce protective effect, make the material structure is not easy to collapse, and can increase the cycle life of electrode materials. SEI is not fixed, there will be a little change in the process of charging and discharging, mainly is the partial organic reversible change will happen. Makes the SEI film before and after the battery discharge excessively reversible damage, protect the cathode material of SEI destroyed after making anode materials, the collapse to form a bulge phenomenon.

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