Quasi-mono-solar lithium-ion battery -Lithium - Ion Battery Equipment

Quasi-mono-solar lithium-ion battery -Lithium - Ion Battery Equipment

1. Introduction to quasi-single crystal technology

1.1 Traditional monocrystalline and polycrystalline silicon technology
We understand that single crystal silicon is generally prepared by the Czochralski method (CZ method), seeding with a single crystal seed crystal of a specific crystal orientation, and then rotating and pulling to obtain a single crystal silicon rod of the target crystal orientation. The obtained product only contains A die with low defects and high conversion efficiency. At present, the conversion efficiency of large-scale production of monocrystalline silicon cells has reached 18%, but this method has high requirements on raw materials and operations, and has less single feeding, high product cost, and large solar cell attenuation. Polycrystalline silicon is mainly produced by directional solidification method. It has the characteristics of large single feeding amount, easy operation and low cost. The attenuation of cell chips is much smaller than that of single crystal silicon wafers. It often contains a large number of grain boundaries and defects, which makes the conversion efficiency of polycrystalline silicon solar cells about 1.5% to 2% lower than that of monocrystalline silicon cells.(Lithium - Ion Battery Equipment)

1.2 Quasi-single crystal technology
The core of quasi-single crystal technology is single crystal ingot technology. Products similar to single crystal or even full single crystal produced by ingot casting process combine the advantages of single crystal silicon and polycrystalline silicon. Compared with polycrystalline, quasi-monocrystalline silicon wafers have fewer grain boundaries and lower dislocation density; the conversion efficiency of solar cells is as high as 17.5%. Compared with single crystal silicon wafers, the light-induced attenuation of quasi-single crystal cells is about 1/4-1/2 lower; the charging charge is large, the production efficiency is high, the slicing process is simple, and the cost is low.

2. Quasi-single crystal ingot technology

2.1 Implementation method
There are two ways to realize ingot single crystal, as follows:

(1) Seedless ingot. The seedless guided ingot casting process has high requirements on the initial growth control process of the crystal nucleus. One method is to use a crucible with a slotted bottom. The point of this method is to precisely control the temperature gradient and crystal growth rate during directional solidification to increase the size of the polycrystalline grains. The size of the grooves and the cooling rate determine the size of the grains. The grooves help to increase the grain size. . The seedless ingot casting process is particularly difficult because there are so many parameters to control.

(2) There is a seed crystal ingot. Most of the mass-produced quasi-single crystal technologies are seeded ingots. In this technology, the seed crystal and silicon material doping elements are first placed in the crucible. The seed crystal is generally located at the bottom of the crucible, and then the silicon material is heated and melted to keep the seed crystal from being completely melted. Finally, the temperature is controlled to adjust the temperature of the solid and liquid phases. The temperature gradient ensures that the single crystal grows from the seed position.

2.2 Temperature control and process control
Quasi-single crystal ingots put high demands on temperature control and process control. In order to meet the requirements of quasi-single crystal ingot, the ingot furnace must have strict temperature gradient and solidification rate control, suitable interface shape, nucleation or single crystal control, and flow control. At present, many manufacturers can supply quasi-single crystal ingot casting equipment, such as Shaoxing Jinggong JJL500/JJL660/JJL800(G6), American GTDSS450Hp/DSS650(G5), Beijing Jingyuntong JZ460/JZ660(G6), Germany ALDSCU450/SCU800 , French Cyberstar650/800. In addition, European, American and Japanese manufacturers such as REC (ALD improved type), SchottSolar (VGF), and Kyocera (VGF type) have specially designed furnaces with good results.

Among them, ALD has developed equipment for Bpsolar products in the early stage. As early as 2006, Bpsolar has done a lot of work on the subject of single crystal casting, and developed MONO2 products, and its patent US2007/0169684A1 reported a variety of methods. One of the methods is to separate the seed crystal from the silicon material, and pour the molten silicon liquid into the container covered with the seed crystal for crystal growth. Later, Bpsolar discontinued the research on ingot single crystal due to its parent company's focus on fossil fuels.



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