The hydrothermal method of production of high-power electrolytic manganese

April 25 [Wed], 2012, 17:34
Potassium content and pH potentiometric studies have shown that a EMD want to have the high power discharge performance, must have the following two conditions: First, the potassium content is low; First, the potentiometric pH. The so-called potentiometric pH refers to the voltage of the EMD measured at pH = 6. Want to emphasize is that this pH potentiometric determination of specialized methods (including impurities in potassium also have unique methods of measurement). PH potentiometric, a special article described [6], EMD's potential is divided into the the pH6 potentials, alkaline potentials and initial potential, in a different electrolyte, reference electrode and cathode composed of a different value.

In order to improve the potentiometric pH, are known to have three possible ways: (1) change of EMD electrolysis conditions, such as raising the acid concentration in the electrolyte; (2) electrolytic pickling of EMD; (3) the mother in the electrolyte solution is preferred raw materials, mainly to reduce the potassium content. Reduce the amount of potassium and also can increase the pH potentiometric

EMD in the potassium content of impurity into the crystal structure refers to the electrolysis process, the EMD crystal pores or adsorbed on the EMD surface potassium ions, without including electrolysis and in order to join, or with the cathode mixture or battery pack divided into contact with the potassium ion.

The results showed that EMD for high-power discharge in potassium content must be less than 2.510 ", preferably less than 1.510" or 310 "5; the pH6 potential should be greater than 0.86V (2.510" and 1.510 " potassium content of four different methods of measurement).

1A or 1.5A with these two conditions, EMD made LR6 batteries discharge, the discharge capacity is more commonly used EMD's battery can be increased by 15%, the results shown, such as 2. Visible, the potential of the high potassium content of low pH, high potassium, high pH potential, low potassium low pH potentiometric samples are not appropriate for high-power discharge.

Electronic paramagnetic spectroscopy (EPR) parameter method EMD in electronic paramagnetic (EPR) spectra of two kinds of signals A and B, respectively, the width of the two signal parameters-g factor and signal DB0. Of EMD different DB0 DB0 the greater, then the EMD of Mn3 + / Mn4 + and the greater; OH group is more, the defect structure, the greater the disorder, that is suitable for embedded in alkaline solution of H + [7] .

The hydrothermal method of production of high-power electrolytic manganese dioxide by hydrothermal method is essentially an autoclave method, at higher pressure electrolyzer temperature higher than 100 electrolysis. Hydrothermal method and control of certain electrolysis conditions to produce a certain porosity of the high power electrolytic manganese dioxide. Its best electrolysis conditions shown in Table 1. Electrolysis from the conditions in table 1 of EMD characteristics shown in Table 2.

It can be seen from Table 2, the characteristics of the sample in line with the 1.2 HPEMD should be with the features. BET surface area greater than 20m2 / g, microporous surface area greater than 8m2 / g, porosity of greater than 0.035%, the average radius of the large and medium-sized hole is greater than 3.2nm. LR6 batteries made with this sample is even put to 0.5A and 1.5A, closing voltage of 1.1V with a capacity of 500 $ 680mAh; cut-off voltage of 0.9V, the discharge capacity of 1500mAh and 1200mAh.

If the electrolyte solution is Mn2O3 as raw materials for the hydrothermal electrolysis [8], Mn2O3 acid in the formation of Mn2 + by disproportionation of dissolved precipitate MnO2. Will be different crystal samples at different temperature and different concentration of H2SO4.

To get the g-crystalline MnO2 was the following tends to: increase in temperature (1) reduce the concentration of H2SO4, can Dewolff defect structure increases; (2) lowering the temperature, but also reduce the concentration of H2SO4, can improve the g-MnO2 of Mn3 + Score (y); (3) lowering the temperature, increase the concentration of H2SO4, the vacancy fraction (x) allows g,-MnO2 was to improve.

Thus, the quality g-MnO2 stable phase is obtained under conditions of low temperature, low concentration of H2SO4, corresponding to the smallest vacancy fraction (x) the medium Dewolff structural defects (Pr) and twin (Tw ) values. This hydrothermal method under low temperature and acid concentration, the equipment likely to corrode, so it is safer.

Preparation of a suitable particle size, high power EMD conditions [4] To prepare a suitable particle size suitable for high power discharge of EMD, the key is to control the electrolysis conditions. Ti plate anode, cathode, graphite plates do electrolysis conditions shown in Table 3. Can be seen from the table, a $ 6 the nature of the sample are in line with the high power EMD of the two conditions: alkaline potentials above 270mV, while the density of more than 3.1g/cm3 density is the maximum diameter of 100mm below 1mm or smaller particle content of less than 15%, average 20 to $ 60mm in diameter, consistent with a high discharge potential, and high loading rates, and thus suitable for making high-power discharge battery. Sample 7 $ 8 do not comply with these conditions.

Change the regular electrolysis parameters Anderson et al [9,10] proposed a change often electrolysis parameters so that the EMD suitable for high power discharge method. The main measures are: use of high purity of the electrolyte solution; select the best electrolysis conditions: (1) Temperature: 95 $ 98; (2) current density J / (Acm "2): 26.9% J 37.7; (3) c (H2SO4) c (of MnSO4) is greater than 2, in order to obtain the best EMD crystal structure (g-e type), the surface area of ??the pore structure (balanced pore volume), suitable for the highest open circuit voltage (OCV). usual electrolytic the anode current density of 20 $ 100A/m2, bath temperature 90 to $ 99, c (of MnSO4) is approximately 1mol / L, and c (H2SO4) is about 0.3mol / L, we can see that the main difference in the c (H2SO4) and the ratio of c (of MnSO4). Table 4 shows some of the characteristics of the electrolytic parameters of the Act and its samples. can be seen from Table 1-4 samples using electrolysis conditions for change: of H2SO4 concentration in the 25 $ 40g / L of MnSO4 concentration between 5 $ 20g / L, J is the 26.9 $ 37.7A/m2. This results in a sample, its surface area in the 21 $ 29m2 / g, the compressed density 3.09 $ 3.21g/cm3, IOCV 1.62V above, the intrinsic capacity of 250mAh / g or more, while the XRD patterns of 220 and 370 peak than the Q values ??between 0.47 and 0.76. other electrolysis conditions such as sample 7-8 were not in the selected range, and thus its performance than six poor control sample (original sample 61). can be seen by the study, regardless of the hydrothermal method, or improved methods, EMD to make the system suitable for high-current discharge, the performance parameters of concern is basically the same.

LR6 battery thus obtained improved EMD samples obtained under 1W discharge rate of intrinsic discharge capacity 68.2mAh / g or more, while the original process only 63.4mAh / g,; 1W discharge energy of up to 755mWh The original process samples the only 637mWh.

The use of other methods to improve the large current discharge performance of alkaline manganese batteries cathode additives, TiO2 additives well known, in order to improve the discharge capacity of the alkaline manganese batteries, usually TiO2 in its cathode. TiO2 as the n-type semiconductor, the resistance is high, is not conducive to high-current discharge. Needs plus a modified additive, or use the hydrogen reduction of metal oxides. Have modified additives may enter the TiO2 crystal structure of the pore or partial replacement of the metal hydride lattice point formation the complex Ti1xMx-O2y, in order to reduce the resistivity of TiO2, and improve their ion exchange properties and reduce corrosion or the occurrence of the hydrogen evolution reaction. For example, the use of modified additives Nb2O5, the following complex reaction occurs at high temperatures [11]: (2) In this way, the resistivity of the additives greatly reduced, as shown in 3.

Ti1xO2y in the dopant M mole percent x: 0.01 mol% x 0.5% mole between the metal element M should have octagonal coordination structure. The amount of x-doped TiO2, 1000mA discharge, the cathode in the EMD and C mole ratio of 151 or (201), the amount of n-TiO2 for EMD amount of 1.6 mol%, while the modified dopant Nb2O5 TiO2 cation of 0.1 mol% (ie 10% of Nb2O5 in TiO2), the relative discharge time when the overflow semi-electrode discharge, such as 4.

Other modified TiO2-doped metal oxides are: NbO2, of Ta2O5 WO3, of GeO2 and ZrO2, ThO2, the In2O3, LiNiO2 and so on. Different doping modifiers, different mixing ratio, reaction temperature and time should also be different.

Conclusion In order to meet the requirements of electronic devices of digital high-current discharge, alkaline manganese batteries are still being explored in all aspects and research, and continue to make progress. Center of gravity to improve the performance of EMD, R & D emphasis on one single aspect, such as the definition of power factor is the definition of potentiometric pH alkaline potential and power factor in order to find the discharge performance of the EMD high voltage segment, similar to the Department; porosity and particle size distribution, optimization of the reaction area caused moderate electrolyte and out, in order to reduce the concentration polarization and reduce the reaction of blind spot; potassium content to minimize, in order to avoid a-MnO2 requires the formation of the g, e-type. If these factors together to consider the current rise of a combination of materials applied to the electrochemical combination of electrolysis, the electrolytic conditions optimized for high-current discharge of EMD, may be further progress.

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LiFePO4 battery's structure and working principle

April 25 [Wed], 2012, 17:32
Around it since the advent of lithium-ion battery research and development work has been carried out, has developed a lithium polymer battery in the late 1990s, after the 2002 introduction of the lithium iron phosphate battery.

Within the lithium-ion battery cathode, anode, electrolyte and diaphragm. Positive difference on the anode and the electrolyte of different materials and processes so that the battery performance, and have different names. Currently on the market lithium-ion battery cathode material of lithium cobalt oxide (LiCoO2), in addition to a small number of lithium manganese oxide (LiMn2O4) and lithium nickel oxide (LiNiO2) as cathode material for lithium-ion battery, generally two kinds of positive materials for lithium-ion battery called lithium-manganese battery and lithium-nickel batteries. The newly developed lithium iron phosphate power battery is lithium ion battery, the battery cathode material lithium iron phosphate (LiFePO4) it is a new family of lithium-ion battery.

The lithium-ion battery electrolyte is a liquid, and later developed a solid-state and gel-type polymer electrolyte, and claimed that this lithium-ion battery is a lithium polymer battery, its performance is superior to the liquid electrolyte lithium-ion battery.

The full name of the lithium iron phosphate lithium iron phosphate lithium-ion battery, this name is too long, referred to as lithium iron phosphate batteries. Its performance is particularly suitable for the application of the dynamic aspects of the word "power" in the name, that is, lithium iron phosphate battery. It was also known as lithium iron (LiFe) battery power.

Using LiFePO4 material for the positive significance of

Currently used as a lithium-ion battery cathode materials: LiCoO2, LiMn2O4, LiNiO2 of LiFePO4. Metal elements in the composition of the battery cathode materials, cobalt (Co) the most expensive, and not much storage, nickel (Ni), manganese (Mn) are cheaper, and iron (Fe) is the cheapest. The price of the cathode material is also consistent with these metals price quotes. Therefore, using the LiFePO4 cathode material made of lithium-ion battery is the cheapest. Another feature is the environmental pollution.

Rechargeable battery requirements are: high capacity, high output voltage, good charge-discharge cycle performance, output voltage, high current charge and discharge, electrochemical stability, the use of safety can (not due to over charge, over discharge and improper operation of a short circuit and cause a fire or explosion), wide operating temperature range, non-toxic or less toxic pollution to the environment. Using LiFePO4 for the positive electrode of lithium iron phosphate in these performance requirements are good, especially in a large discharge rate of discharge (5 to 10C discharge), stable discharge voltage on the security (no burning, no explosion), life (number of cycles ), environmental pollution, it is the best, the best high-current output power batteries.

LiFePO4 battery's structure and working principle

LiFePO4 battery, the internal structure shown in Figure 1. The left is olivine LiFePO4 as the cathode of the battery, connected by aluminum foil and battery cathode, in the middle of the polymer membrane, it is the anode and cathode are separated, but the lithium ion Li + by e-e-can not be the right by carbon (graphite) to form a battery anode, copper foil and the negative battery connection. Between the upper and lower side of the battery electrolyte of the battery and the battery sealed package from the metal shell.


Internal structure of LiFePO4 battery

LiFePO4 battery is charging, the positive electrode in lithium-ion Li + through the polymer membrane to the anode migrate; during the discharge process, the negative electrode in lithium ion Li + migration to the cathode through the diaphragm. Lithium-ion battery is lithium-ion migration back and forth in the charging and discharging named.



LiFePO4 battery performance

LiFePO4 battery nominal voltage is 3.2 V, and terminate the charging voltage is 3.6V, and the termination of discharge voltage is 2.0V. Will be some differences in performance due to the positive and negative electrode material, electrolyte material quality and process used by various manufacturers. For example, the same model (the same kind of package, standard battery), the capacity of their batteries have a greater difference (10% ~ 20%).

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Screen printing metal electrode

April 25 [Wed], 2012, 17:31
As we all know, the use of solar energy has many advantages, photovoltaic power generation will provide the main source of energy, but the current situation, to make solar power with a larger market, the majority of consumers, to improve the photoelectric conversion efficiency of solar cells for human reduce production costs should be our overriding goal, from the current development of the international solar cell process can be seen that the trend of monocrystalline silicon, polycrystalline silicon, ribbon silicon, thin film materials (including microcrystalline silicon thin film, film and dye compounds based film).

From the perspective of the development of industrialization, the focus has been single-crystal to the direction of the polycrystalline, mainly due to supply solar cell material end to end; [1] can be less and less; [2] in terms of solar cell, a square substrate cost-effective, direct casting method and the direct solidification method polysilicon square material; [3] of polysilicon production technology have made continuous progress, automatic casting furnace production cycle (50 hours) can produce more than 200 kg of silicon ingot. grain size up to centimeter level; [4] due to silicon process research and development in nearly a decade soon, which process is also used in the production of polycrystalline silicon cells, such as selective etching the emitter junction and back surface field, corrosion suede surface and bulk passivation, thin metal gate electrode, the width of the screen printing technology enables the gate electrode to less than 50 microns and a height of 15 microns or more, rapid thermal annealing for polysilicon production can greatly shorten the process time, single chip thermal process time can be completed within one minute, using the technology in the 100 cm2 silicon chip to make the cell conversion efficiency over 14%. According to reports, 50 to 60 micron polysilicon substrate produced more than 16% cell efficiency. Mechanical groove, screen printing technology more than 17% efficiency on 100 cm2 multi-crystal, mechanical groove efficiency of 16% in the same area, the use of the buried gate structure, mechanical groove 130 cm2 polycrystalline The cell efficiency of 15.8%.

The following two aspects to discuss the technology of polycrystalline silicon cells.

2 Laboratory of efficient battery technology

Laboratory techniques usually do not consider the cost of battery production and the possibility of large-scale production, just to study ways and means to achieve maximum efficiency and to provide specific materials and processes can reach the limit.

2.1 on the light absorption

Optical absorption is mainly:

(1) reduce the surface reflection;

(2) change the light path of the battery body;

(3) the back of the reflector.

For monocrystalline silicon, the application of anisotropic chemical etching method can be produced in the (100) surface structure of the pyramid-shaped suede, lower surface light reflection. Polysilicon crystal to deviate from the (100) surface, using the above method can not be made uniform suede, currently using the following methods:

[1] laser groove

Laser grooves in the surface of the polysilicon production of the inverted pyramid structure, in the 500 ~ 900nm wavelength range, the reflection rate of 4-6%, the production of double-layer antireflection coating and surface quite. Rate of 11% in the reflection (100) surface of monocrystalline silicon chemical production suede. Produced with a laser suede short circuit current than the smooth surface plated double-layer antireflection coating (ZnS/MgF2) increased by about 4%, the long waves (wavelength greater than 800nm) dipped into the cell. Problems in laser produced suede etching, surface damage caused by the introduction of some impurities, chemical treatment to remove surface damage layer. Solar cells made of the method is usually higher short-circuit current, open circuit voltage is too high, mainly due to the increase in cell surface area, causing the composite current increases.

[2] Chemical groove

Mask (Si3N4 or SiO2) isotropic corrosion, etching, acid etching solution, higher concentration of sodium hydroxide or potassium hydroxide solution, the method can not form a kind of anisotropic etching The cone-shaped structure. According to reports, the velvet formed the face of obvious antireflection spectral range of 700 to 1030 microns. The mask layer is generally formed at a higher temperature, causing the performance degradation of polysilicon materials, especially for lower quality polycrystalline materials, the minority carrier lifetime. Application of the technology in 225cm2 polysilicon made by cell conversion efficiency of 16.4%. The mask layer is also available screen printing form.

[3] reactive ion etching (RIE)

This method as a kind of mask etching process, formed by the suede reflection rate is particularly low, less than 2% of the reflectivity in the spectral range of 450 to 1000 microns. Only from the optical point of view, is an ideal method, but the problem is that the silicon surface damage is severe, the battery open circuit voltage and fill factor declined.

[4] produced antireflection film

For efficient solar cells, the most commonly used and most effective way is the evaporation ZnS/MgF2 double-layer antireflection film, the optimum thickness depends on the following oxide layer thickness and cell surface characteristics, for example, the surface is a smooth surface or suede deposition of Ta2O5 antireflection process, in PECVD deposition of Si3N3. ZnO conductive film can be used as anti-reflection material.

2.2 Metallization Technology

In the production of highly efficient batteries, metal electrode with the cell design parameters such as surface doping concentration, the PN junction depth, metal materials to match. The general area of ??the laboratory battery is relatively small (area less than 4cm2), so they need a thin metal gate line (less than 10 microns), the general method used for lithography, electron beam evaporation, electronic plating. Industrialization and mass production is also used in the plating process, evaporation and the lithography used in combination, does not belong to the low-cost technology.

[1] electron beam evaporation and plating

Typically, the positive photoresist stripping technology to reduce the series resistance caused by the metal electrode deposition of Ti / Pa / Ag multi-layer metal electrode, often need the metal layer is relatively thick (8-10 microns). Shortcomings caused by electron beam evaporation / passivation layer interface of the silicon surface damage, surface recombination improve the process, the use of short-term evaporation of Ti / Pa, layer in the process of evaporation of the silver layer. Another problem is that the metal and silicon contact surface will lead to minority carrier recombination velocity improve. Process, contact tunnel junction formed between the silicon and metal into a thin oxide layer (usually a thickness of 20 microns or so) the application of the work function of the lower metal (such as titanium, etc.) in the silicon surface sensing a stable electron accumulation layer (which can also introduce a fixed positive charge to enhance the anti-type). Another method is to open a small window in the passivation layer (less than 2 microns), and then deposited on a wide metal gate line (typically 10 microns), the formation of mushroom-like shaped electrode, the method in 4cm2 Mc -Si cell conversion efficiency of 17.3%. At present, the mechanical groove surface use Shallow, angle (oblique).

2.3 the PN junction formation technology

[1] the formation of the emitter and phosphorus gettering

Emitter for high efficiency solar cells to form generally used to select the diffusion in the metal electrode below the formation of shallow concentration of heavy impurities shallow concentration diffusion region between the electrodes, emitter diffusion which enhances the response of the batteries on the Blu-ray, but also so that the silicon surface easily passivated. The proliferation of two-step diffusion process, diffusion plus the corrosion process and buried diffusion process. Current diffusion, 15 × 15cm2 cell conversion efficiency of 16.4%, n + + n + region of the surface sheet resistance of 20Ω and 80Ω.

Mc-Si material, the expansion of phosphorus gettering on the battery has been widely studied, a longer period of time the phosphorus gettering process (usually 3 to 4 hours) can make some of the Mc-Si minority carrier diffusion length increase by two orders of magnitude. Gettering effect of substrate concentration, even high concentrations of contrast materials, the gettering can also get a larger minority carrier diffusion length (> 200 microns), the open circuit voltage of the battery is greater than 638mv The conversion efficiency of over 17%.

[2] the formation of the dorsal surface of the aluminum gettering

Mc-Si cell, back p + p junction by diffusion of aluminum or boron formed boron source in general for the BN, BBr, APCVD SiO2: B2O8, aluminum diffusion evaporation or screen printing aluminum 800 degrees sintering aluminum gettering carried out extensive research, are mixed with different phosphorus diffusion gettering, aluminum gettering at relatively low temperatures. Defects of which the body is also involved in the dissolution and deposition of impurities at higher temperatures, the impurities of the deposition easy to dissolve into the silicon, and have a negative impact on Mc-Si. To the current to the region back field has been applied to the process of monocrystalline silicon cells, but in the polysilicon, or application of the aluminum back surface field structure.

[3] double-sided Mc-Si battery

Mc-Si double-sided battery positive regular structure on the back for the N + and P + cross-cutting structure, so that a positive light but on the back near the photogenerated minority carriers by the back electrode to effectively absorb. Back electrode as an effective complement to the positive electrode, but also as an independent plant flow sub-collector on the back of the light and scattered light effect, It is reported that under AM1.5 conditions, the conversion efficiency of over 19%.

2.4 surface and bulk passivation techniques

Mc-Si, due to the presence of high grain boundary passivation of point defects (vacancies, interstitial atoms, metallic impurities, oxygen, nitrogen and their compounds) on the surface and in vivo defects is particularly important, in addition to the previously mentioned of the gettering techniques, the passivation process a variety of ways, by thermal oxidation of silicon dangling bond saturation is a commonly used method allows the Si-SiO2 interface recombination velocity is greatly decreased, the passivation effect depends on the emission region surface concentration, the interface state density and the electron and hole of floating cross section. Annealing in hydrogen atmosphere, allows the passivation effect is more pronounced. Using PECVD deposition of silicon nitride recent positive is very effective, because the hydrogenation effect in the film-forming process. The process can also be applied to large-scale production. Application Remote in PECVD of Si3N4 enable the surface recombination velocity of less than 20cm / s.

3 industrialized battery technology

Solar cells from the Laboratory to the factories, experimental study toward large-scale production is the road of development, they were able to achieve the characteristics of the industrial production should be:

[1] The production process of the battery to meet pipeline operations;

[2] to large-scale, modern production;

[3] to achieve efficient, low-cost.

Of course, its main goal is to reduce the production cost of solar cells. Polycrystalline silicon cells, the main direction of development towards large area, thin substrates. For example, the market can be seen on the 125 × 125mm2, 150 × 150mm2 or even large-scale single cell thickness from 300 microns is reduced to the current 250,200 and less than 200 microns. Efficiency has been greatly improved. Japan's Kyocera (Kyocera), small volume production of 150 × 150 battery photoelectric conversion efficiency of 17.1 percent, the company's production in 1998 amounted to 25.4MW.

(1) screen printing and related technologies

Large-scale production of polysilicon battery is widely used screen printing process, the process can be used for the printing of the diffusion source, positive electrode of the metal back contact electrode and antireflection coating, etc., with the improvement of the mesh material and the process raise the level of screen printing process in the production of solar cells will be more common applications.

the formation of a launching area

By screen printing to form a PN junction, instead of the conventional tube furnace diffusion process. Usually in the the polysilicon positive printing containing slurry, negative printing of aluminum-containing metal slurry. After printing, diffusion in the mesh belt furnace (usually the temperature at 900 degrees), printing, drying, diffusion can form a continuous production. Proliferation of screen printing technology of the emission region is usually relatively high surface concentration of surface photoinduced carrier Composite large, in order to overcome this shortcoming, the choice of the following emission technology on the process, so that the cell conversion efficiency further improved.

(b) Select the emitter technology

In the diffusion process of the polycrystalline silicon cells, select the emitter technology is divided into localized corrosion, or two-step diffusion method. Localized corrosion with a dry method (such as reactive ion corrosion) or chemical corrosion, heavy diffusion layer region between the metal electrode eroded. Initially, the the Solarex application of reactive ion etching method in the same device, the first large-response power eroded by the heavily doped layer between the metal electrode, and then the small power deposition of a layer of silicon nitride film, the film played antireflection and the dual role of cell surface passivation. 100cm2 polycrystalline make a conversion efficiency of over 13% of the battery. In the same area, the application of two diffusion method, the conversion efficiency of 16% is not the case for mechanical suede.

(c) back surface field formation

Dorsal PN junction by screen printing A slurry and the mesh belt furnace is usually formed after the thermal annealing process in the formation of the dorsal surface of the junction, the impurities in the polysilicon has a good suction in addition to the role of aluminum gettering process is generally The high-temperature section completed, the measurement results show that the minority carrier lifetime in polysilicon gettering role in bringing the front-high temperature process drops have been restored. Good back surface field can significantly increase the open circuit voltage of the battery.

(d) screen printing metal electrode

Screen printing process in large-scale production, compared with the vacuum evaporation of the metal plating process, but also has an advantage in the current process, a positive print materials are the common choice of silver-containing slurry, the main reason is that silver has a good conductivity, weldability and low diffusion in silicon performance. The conductive properties of the metal layer formed by screen printing, annealing depends on the chemical composition of the slurry, the vitreous content, coarse mesh worse, the sintering conditions and the thickness of the screen version. Eighty of the year early, screen printing has some defects, @) such as the width of the gate line, usually greater than 150 microns; ii) caused by shading, battery low fill factor; iii) is not suitable for surface passivation, the main The surface diffusion of the higher concentration, or contact resistance larger. Advanced screen printing stage gate line 50 microns wide, more than 15 microns thick, the sheet resistance of 2.5 ~ 4mΩ the parameters to meet the requirements of efficient battery. On Mc-Si, 15 × 15 cm square on the screen-printed electrodes and evaporation of the electrode made of solar cells compared to the parameters is almost no gap.

4 Conclusion

Production process of the polycrystalline silicon cells continue to move forward, to ensure the battery continuously improve the efficiency, cost reduction, with the deepening understanding of materials, device physics, optical properties, leading to cell structure is more reasonable, the laboratory level and the industrialization and mass production the distance is shrinking. Screen printing and buried gate process for high-performance, low-cost battery played a major role in the efficient Mc-Si battery components have been poured into the market, the current study is committed to the new film structure, the battery on cheap substrates, surface the user, we need to work to achieve greater volume, low-cost production, we would like to work harder to achieve this goal.

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Intermittent inkjet printing

April 25 [Wed], 2012, 17:27
First, the solar cell

(1) solar cells on the information identifies

Production of solar cells production line daily production of around 20,000 for the same batch, the product of the same production line in the production process directly printed logo, easy to manage the future product quality issues, which can find the which the production line, the day of production and the production of solar cells in which team have a problem. For these reasons, there is an urgent need to find a printing technology in the production process, marked on top of the solar cell. If the production line were randomly marked this information, only the use of inkjet printing in this way, this is because:

@ because the solar cell surface lighting, energy, and so need to be as large as possible to retain the area of ??light. Therefore, in the process of information marked on solar cells, require labeling information to occupy the smallest possible surface area of ??solar cells, about 2 ~ 3mm distance marked on 4 digital information, such as the date of production batch.

A required to label the information is constantly changing with the changes of the information to be recorded, so that direct control by the computer system.

B In addition to the two requirements above, but also the speed of annotation information coordinated with the rate of production of solar cells would like to achieve production on the assembly line.

C For the identity of the printing, also called solar cells sintered at high temperature of 800 ° C, identified by the instrument easy to distinguish.

D solar cells for identification information of the pigment is preferably printed electrode line in the production process, Silver, Silver particles the right size, you can use.

Two new solar cell electrode line printing

Currently used by screen printing a contact printing, the printing pressure to be able to print out the electrode line we need. If you are still using traditional screen printing solar cell technology continues to improve, its thickness is constantly reduced, there is the possibility of solar cells crushed in the production process, so for the quality of the product can not be guaranteed. Therefore, it requires us to find a new printing methods, printing pressure, need to touch to achieve the requirements of the solar cell electrode wire.

Electrode line requirements: a 15cm x 15cm square area, spray a lot of the electrode line, and asked the fineness of the lines of these electrodes in 90μm, height of 20μm, have a certain degree of cross-sectional area to ensure the flow of current. In addition, the requirements necessary to complete the printing of a solar cell electrode wire in one second.

Second, the inkjet printing technology

1 inkjet printing

Inkjet printing more than 20 kinds of basic principles are the first to have a small droplet, then the guide to set the location, can be broadly divided into continuous and intermittent. So-called continuous inkjet, regardless of stamped and non-image areas, ink droplets are generated in a sequential manner, then the non-image areas of the droplet recycling or distributed; intermittent inkjet ink droplets produce only in the stamped part .

@ continuous inkjet printing

To deviate from the droplet printing ink flows through the pressurized spray, vibration, broken down into small drops, after the electric field, due to electrostatic interactions, the small droplet over the fields that, whether charged or not, are straight before flight. By deviation from the electromagnetic field, the charge is large drops will be stronger attraction, which twists and turns large amplitude; the contrary, the deflection small. Instead of charged drops will actively set the ink trench recovery.

Not deviate from the droplet printing and these are very similar, the only difference is the deviation from the charge recovery, and not deviate from the charge it straight to the formation of stamped.

Droplet charge when not in use to split the ink flow is still pressure from a nozzle, but the pores are more slender, its diameter is about 10 ~ 15μm. Its pores fine spray droplet will be automatically broken down into those many very small droplets, so that these small drops through the same electrode charged ring. The droplet is quite small, because the charges repel each other's sake, these charged droplet is again split into the mist, then it loses the directionality can not be printed. On the contrary, without charge ink will not split the formation of stamped, can be used as a continuous tone printing.

A intermittent inkjet printing.

Pull to static electricity. As the static gravitational pull and inkjet printing inks in the nozzle at the formation of protruding half-moon, and then tied to an electrode plate protruding ink surface tension, will be the destruction of high-voltage parallel electrode board, thus droplet electrostatic Pull out. These droplets are charged with static electricity, can be offset to the vertical or horizontal direction, hitting the set position or shelter board recycling.

Thermal bubble inkjet. Instant heating the ink, so expansion of the gas in the vicinity of the resistor, there will be a small amount of ink into steam launch nozzle, squeeze the ink to make it on the flight to the paper to form stamped. Temperature of the ink droplet ejected immediately reduce temperature rapidly reduced within the cartridge, and then by the principle of capillary prominent ink back to the cartridge.

(2) the application of inkjet printing

Since the ink-jet printing is a non-contact, no pressure, no printed version of the digital printing, with the incomparable superiority of the traditional print. It has nothing to do with the material and shape of the substrates, In addition to the paper plates, such as metals, ceramics, glass, silk, textiles, and adaptable. Inkjet printing does not require film, bake, make-up, proofing processes are widely used in the printing field.

Ink control. Inkjet printing

Inkjet printing, in order to ensure results, the parameters of the printing ink to achieve a more appropriate control, printing control conditions.

@ In order to not block the ink jet head through a 0.2μm filter.

A sodium chloride content must be below 100ppm. Sodium chloride make the dye deposited, and sodium chloride containing corrosive, especially in the bubble jet system, it is easy to nozzle corrosion. Although the nozzle are made of titanium, sodium chloride corrosion therefrom at high temperatures.

B viscosity control 1 ~ 5cp (1cp = 1 × 10-3Pa · S), the viscosity of the Micro Piezo inkjet systems require a higher viscosity of the bubble jet system requirements are lower.

C surface tension of 30 60dyne/cm of (1dyne = 1 × 10-5N), the surface tension of the Micro Piezo inkjet system requirements are lower, the surface tension of the bubble jet systems require a higher

Just the D drying speed, too fast, easily clogged ink-jet head or the ink off, tend to spread too slow, so that the network overlapped.

E stability, the thermal stability of the dye used for bubble jet system is better, because the bubble jet ink is heated to 400 ° C high temperature, if the dye is not high temperature will be decomposed or discolored.

In the solar cell manufacturers to reduce costs, requiring more and more thin silicon solar cells selected, if the choice of traditional screen printing and silicon crushed under pressure, will. Belong to non-pressure printing and inkjet printing technology, the speed of production can be increased by increasing the inkjet head, inkjet printing technology in the near future in this area there will be a better development.

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Testing standards in the following table

April 25 [Wed], 2012, 17:23
With the "ultimate energy" and "green energy" known as lithium-ion battery, since its inception in the 1990s, button batteries from electronic products, mobile phones and digital products in the DC lithium batteries, electric vehicles battery power, are increasingly widely used in the production and life of the people. Compared with other batteries, lithium-ion batteries regardless of size, weight, or from the performance, have a lot of advantages.
To use lithium batteries within the range of reasonable voltage capacity

One-sided pursuit of large capacity, ultra-high voltage is wrong. First of all, everything goes through a simple to complex, from hard to easy process, and the like is also a flammable gas, effectively ensure the safety of the lighter is easier to act effectively to ensure the safety of the vehicle tank is much more difficult still not completely solved the crash when the car caught fire and exploded. The accumulation of energy in a limited volume, the more the more bad management, Suzhou star constant can only guarantee the safety of the largest-48V10Ah the battery packs. Second, the higher the voltage, the greater the capacity, protection circuit and the difficulty of the equalization circuit and the failure rate is greater, therefore Suzhou star constant advocate, does not support beyond 48V10Ah battery combination.

Depends on the lithium battery safety testing and certification

One, the UL certification

Today, most countries and regions in the world relating to safety, health, environmental protection product safety certification must be obtained before entering the market. The UL mark has become one of the world-renowned safety certification mark.

Testing standards are as follows:

1, shell

The lithium battery casing should be of sufficient strength and stiffness sufficient to resist abusive pressure, without causing the fire. User-replaceable lithium battery should be of sufficient strength and would not hurt people.

2, electrolyte

User-replaceable battery should not contain a pressure steam or emit toxic vapors and liquids damage the eyes, or battery casing under normal laboratory conditions (temperature 23 ℃) by the impact of leakage of liquid should be less than 5ml.

3, using the

The lithium battery should be taken when using measures to prevent the abnormal charge current, battery of tests to an acceptable charge current Ic, under abnormal conditions, protective measures should be in the end product.

4, leakage,

Leakage or leakage mass loss standard, the maximum loss of the quality of the batteries or the battery is not more than 1g0.5 1 ~ 5g0.2%> 5g0.1%.

5, mechanical tests

(1) squeeze: a diameter of 32mm hydraulic piston on the battery flat surface to exert pressure 13KN pressure 17.2Mpa, when the maximum pressure relief. Sample no fire, no explosion.

(2) impact on the sample center: diameter 15.8mm rod, so that the weight of 9.1Kg weight from 610mm height fell on the specimen. Sample no fire, no explosion.

(3) Acceleration: The battery is placed in the fixture, along three mutually perpendicular directions acceleration (acceleration requirements: the initial 3ms minimum average acceleration should reach 75g peak acceleration between 125-175g). Test temperature of 20 ± 5 ℃. Samples should be no fire, no explosion, another sample is not leaking.

(4) Vibration: cell is a simple tuning vibration along three mutually perpendicular directions, the vibration frequency 10-55Hz range, the rate of change of 1Hz/min restore back in the 90-100min, the amplitude is 0.8mm. The sample should be no fire, no explosion, no leakage.

(5) Heat shock: the sample heated in a natural convection or forced convection oven, the oven temperature to 5 ± 2 ° C / min rate of heating to 150 ° C, and maintain a stop after 10min. The sample should be no fire, no explosion.

(6) thermal cycling test: the battery is put to the test room and under the following cycle:

  @ The 30min to heat up to 70 ± 3 ° C, insulation 4h.
  A The 30min, cooled to 20 ± 3 ° C, insulation 2h.
  B within 30 min, heated to 40 ± 3 ° C, insulation 4h.
  C The 30min, cooled to 20 ± 3 ° C.
  D The nine repeat the cycle.
  (6) 10 cycles, the battery is placed seven days to be tested. The sample should be no fire, no explosion, no leakage.

Simulated altitude (7): The sample cell at an absolute pressure 11.6Kpa (1.68psi), 20 ± 3 ° C (68 ± 5 ° F) under the conditions of storage of six hours. The sample cell is not an explosion or fire, can not be a perforation or leak.

6, charge and discharge test

(1) charge and discharge cycles: the testing temperature of 25 ° C, in accordance with the requirements of the manufacturer, the batteries charge and discharge cycles, recycling capacity 25% of the initial nominal capacity of the continuous cycle of 90 days after termination. The sample should not be any security incidents.

(2) short circuit test: resistance less than 0.1Ω copper short connected to the battery positive and negative battery discharge until a fire or explosion, or until the battery is fully discharged, the shell temperature re-dropped at room temperature to stop (test at room temperature for 60 case ± 2 ℃). Samples should be no fire, no explosion, the shell or the battery case temperature does not exceed 150 ℃.

(3) non-normal charge test: normal discharge is completed, current charging three times the usual charge current. No fire, no explosion.

(4) forced discharge test: batteries at room temperature is completely discharged, after the new batteries in series with a certain number of the same model, the formation of the battery pack short-circuit test. The sample should be no fire, no explosion.

(5) over-charge: the battery to 3C under conditions of full power, 10V constant current, constant voltage battery charging, when the current reaches 100mA, converted to constant voltage charging for 48 hours.

7, logo

The battery shall identify the name of the manufacturer, trade name or trademark, style settings. The battery should identify the Warning, and the corresponding description.

Second, Extra Energy, the standard

Extra

Energy certification is a nonprofit organization, headquartered in the German tanks to take, main job is to focus on the global light electric vehicles, the neutrality of information, and provide value-added services, which are very strict, rigorous safety testing related to lithium batteries, to get recognized by most European customers.

Testing standards in the following table.

Safety standards before the state test in the test method test method

A non-normal charging at room temperature, air power, the original assembly. Removal of the protection circuit and the circuit, in the case of the battery pack fully charged, the battery pack 10A current overcharge to 1.5 times the nominal voltage.

No fire, no explosion; during the test battery case temperature less than 120 ° C; experimental wooden burning coke; release of toxic gases.

2 short-circuit

Room temperature, the original charger to full power, factory assembled.

Removal of the protection circuit and the circuit, in the case of the battery pack fully charged, the battery pack's positive and negative direct short circuit.

No fire, no explosion; during the test battery case temperature less than 120 ° C; experimental wooden burning coke; release of toxic gases.

3 heavy compression at room temperature, the original charger to full power, factory assembled. 15 cm diameter steel rollers, and extruded 10 tons of pressure on the battery pack.

No fire, no explosion; battery overflow of gas, non-toxic solid and liquid.

Third, the CE certification

In recent years, the commodities on the market in the European Economic Area (EU, European Free Trade Association member states, Switzerland excluded), the use of the CE certification mark more and more, affix the CE certification mark goods that meet the safety, health, environmental and consumer protection requirements of European directives to express.

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