The most important part of a lithium battery is the battery cell. It can be said that the battery cell is the core soul of the lithium battery. So what are the components of the lithium battery cell? What are the functions of the parts that make up the lithium battery cell? This article will take you to find out!
The lithium battery cell consists of five parts, namely the pole piece, the diaphragm, the pole ear, the electrolyte and the packaging film. These five parts are described below.
A pole piece generally refers to an electrode with a high potential that contains active species that undergo a reduction reaction upon discharge. The lithium battery pole piece is a coating composed of particles, which is uniformly coated on the metal current collector. Simply put, it is the core of the cell, one is positive and the other is negative, so that there is electricity, and then the electrodes are extended through the tabs, and the electrodes can be connected to other connections through the tabs.
The tab is a raw material for lithium battery products. The tabs are the metal conductors that lead out the positive and negative poles of the battery. In layman's terms, the ears of the positive and negative poles of the battery are the contact points during charging and discharging. This contact point is not the copper sheet we see on the outside of the battery, but a connection inside the battery.
The main function of the tab is to transfer the electrical energy of the internal positive and negative electrodes to the external circuit. The electrode of the polymer battery is made of aluminum tape for the positive electrode and a nickel tape for the negative electrode. Considering the sealing with the aluminum-plastic packaging film, a layer of electrode tape is placed on the sealing portion of the electrode. At the same time, since the positive aluminum strip is easy to break, special attention should be paid to protection during processing, transportation, storage, and use.
Electrolyte is the medium (with certain corrosiveness) used in chemical batteries, electrolytic capacitors, etc., to provide ions for their normal work. And to ensure that the chemical reactions that take place at work are reversible.
Lithium battery electrolyte is the carrier of ion transport in the battery. Generally composed of lithium salts and organic solvents. The electrolyte plays the role of conducting ions between the positive and negative electrodes of the lithium batteries, which is the guarantee for the lithium ion battery to obtain the advantages of high voltage and high specific energy. The electrolyte is generally prepared from high-purity organic solvents, electrolyte lithium salts, necessary additives and other raw materials under certain conditions and in a certain proportion.
In the structure of lithium batteries, the separator is one of the key inner layer components, which is a thin film used to separate the positive and negative electrodes to prevent energy loss from direct reaction in the electrolytic cell. The performance of the separator determines the interface structure and internal resistance of the battery, which directly affects the capacity, cycle and safety performance of the battery. The separator with excellent performance plays an important role in improving the overall performance of the battery. The main function of the separator is to separate the positive and negative electrodes of the battery to prevent short circuit due to contact between the two electrodes, and also has the function of allowing electrolyte ions to pass through.
The separator material is non-conductive, and its physical and chemical properties have a great impact on the performance of the battery. Different types of batteries use different separators. For the lithium battery series, since the electrolyte is an organic solvent system, a separator material resistant to organic solvents is required, and a high-strength thin-film polyolefin porous membrane is generally used.
The packaging film of lithium battery is generally aluminum-plastic film. Aluminum-plastic packaging film is a high-strength, high-barrier, electrolyte-resistant multi-layer composite film material composed of plastic, aluminum foil and adhesive, which is used for flexible packaging lithium battery packaging. It is divided into at least three layers: the middle layer is the aluminum layer, which acts to isolate moisture; the outer layer is the glue layer, which protects the aluminum from being oxidized by the external environment; the inner layer is the glue layer, which seals and prevents the electrolyte from corroding the aluminum layer. effect. The aluminum-plastic film is formed by stamping to make the required shell shape.
Aluminized composite film series products are suitable for moisture-proof, light-proof and vacuum packaging of chemical raw materials, pharmaceutical intermediates, and lithium iron phosphate cathode materials. It adopts two-layer structure, which has good toughness and good water and oxygen barrier functions. The size is not limited, and packaging bags of different specifications and styles can be customized, and can be made into flat pockets, three-dimensional bags and other styles. The product has been tested by GB standard and meets the requirements of environmental protection.
The pressure resistance of plastic film packaging is much worse than that of metal shell batteries, and the internal short circuit of the battery can easily cause inflation, and in severe cases, the seal will crack. Because of this, the safety performance of batteries packaged with aluminum-plastic film is better than that of metal shell batteries.