Super capacitor / battery outline solution and application development trend

For some people in science and engineering, there may be more or less understanding of the capacitance. Even ordinary people may have seen the capacitor, because in our real life, the shadow of the capacitor can often be seen. However, supercapacitor batteries are not known to many people. Supercapacitor batteries are developed on the basis of supercapacitors. This type of battery has very remarkable characteristics. It is a battery that is more powerful than conventional batteries. In many aspects, there are many applications. For example, in new energy vehicles, trams, etc., you can see the shadow of super capacitor batteries. It can be said that the emergence and development of super capacitor batteries will definitely bring The industrial revolution once again greatly improved the operational capabilities of certain aspects.

Super capacitor battery

First, the type of capacitor

Due to the different insulation materials, the types of capacitors are different: According to the structure, it can be divided into: fixed capacitor, variable capacitor, and trimmer capacitor. According to the dielectric material can be divided into: gas dielectric capacitor, liquid dielectric capacitor, inorganic solid dielectric capacitor, organic solid dielectric capacitor electrolytic capacitor. Divided by polarity: there are polar capacitors and non-polar capacitors. The most common thing we get is electrolytic capacitors. In principle, it is divided into: non-polar variable capacitor, non-polar fixed capacitor, and polar capacitor. From the material can be divided into: CBB capacitor (polyethylene), polyester capacitor, ceramic capacitor, mica capacitor, monolithic capacitor, electrolytic capacitor, tantalum capacitor and so on.

1, electrolytic capacitor

Two pieces of aluminum strip and two layers of insulating film are laminated on each other, and are immersed in an electrolyte (acid-containing synthetic solution) after being bundled, and have a large capacity and a high frequency characteristic.

2, monolithic capacitor

The volume is smaller than CBB, and the other is the same as CBB.

3, mica capacitor

The mica sheet is coated with two layers of metal film, which is easy to produce, low in technical content, large in volume and small in capacity (almost useless).

4, ceramic capacitor

Using ceramic as a medium, a silver layer is sprayed on both sides of the ceramic substrate, and then fired into a silver film to form a plate. It is characterized by small volume, good heat resistance, low loss, high insulation resistance, but small capacity, suitable for use. In high frequency circuits.

5, the base layer capacitor

Ferroelectric ceramic capacitors have large capacity, but the loss and temperature coefficient are large, which is suitable for low frequency circuits. The thin porcelain sheet is made of silver on both sides of the metal film. It has small volume, high pressure resistance, low price and high frequency (there is a high frequency capacitor), which is fragile! Low capacity.

6, CBB capacitor

Two layers of polyethylene plastic and two layers of metal foil are alternately mixed and then bundled.

7, non-inductive CBB capacitor

2 layers of polypropylene plastic and 2 layers of metal foil are alternately mixed and then bundled, no feeling, high frequency characteristics, small volume, not suitable for large capacity, high price, poor heat resistance.

Second, the super capacitor is an upgrade of the traditional capacitor

The plate capacitor is composed of two metal electrode plates insulated from each other, and the capacitance is proportional to the area of ​​the electrode plate, and inversely proportional to the gap size between the electrode plates. The structure of the supercapacitor is similar to that of a flat-plate capacitor. The electrode is a porous carbon-based material. The porous structure of the material allows it to have a surface area of ​​several thousand square meters per gram of weight, and the distance between the capacitances of the capacitors is determined by the size of the ions in the electrolyte. The huge surface area plus the extremely small distance between the charges makes the supercapacitor have a large capacity, and the capacity of the supercapacitor can vary from 1 Farad to several thousand Farads.

Compared with the traditional battery, the super capacitor has many advantages: the charging speed is fast, it can be charged to more than 95% of its rated capacity in 10 seconds to 10 minutes; the power density is up to (102~104) W/kg, which is the lithium battery 10 Double times; high current discharge capacity; cycle usage up to 100,000 to 500,000 times, long life; high safety factor, long-term use maintenance-free. However, compared with mainstream sulfur batteries, it still faces the disadvantages of high cost and low energy density.

Third, super capacitors can be used as a substitute for batteries

In some applications, supercapacitors are a replacement for batteries; in some applications, supercapacitors support the battery. In some cases, the supercapacitor may not be able to store enough energy, so it is necessary to use the battery. For example, when the ambient energy source (such as the sun) is intermittent, such as at night, the stored energy is not only used to provide peak power, but also to support the application for a longer period of time.

If the required peak power exceeds the amount that the battery can provide (such as making a GSM call or low power transmission at low temperatures), the battery can charge the supercapacitor with low power, while the supercapacitor provides large pulse power. This structure also means that the battery never circulates deeply, thus extending battery life. Supercapacitors store physical charges, not chemical reactions like batteries, so supercapacitors actually have an infinite cycle life.

When a supercapacitor is charged from a battery to provide a peak power pulse, there is an important interval between the pulses. If the pulses are too close together, it is more efficient to have the supercapacitor always charged. But if the pulse spacing is not too close, the more energy efficient way is to charge the supercapacitor before the peak power event.

This spacing depends on a number of factors, including the capacitance that the supercapacitor absorbs before reaching the equilibrium leakage current, the self-discharge characteristics of the supercapacitor, and the charge that the circuit pulls out of the supercapacitor in order to provide a peak power event. This choice is valid only when you know in advance the peak power event, and not for reactions to unpredictable events such as battery failure or external stimuli.

Fourth, super capacitor batteries and super capacitors

Supercapacitor battery, also called electric double layer capacitor, is a new type of energy storage device. It has the characteristics of short charging time, long service life, good temperature characteristics, energy saving and environmental protection. Due to the shortage of petroleum resources in supercapacitors and the environmental pollution caused by the exhaust of diesel-burning internal combustion engines (especially in large and medium-sized cities), people are studying new energy devices that replace internal combustion engines.

Supercapacitors are electrochemical components that have been developed by polarizing electrolytes since the 1970s and 1980s. It is different from the traditional chemical power source. It is a kind of power source with special performance between the traditional capacitor and the battery. It mainly relies on the electric double layer and the redox dummy capacitor to store electric energy.

Five, the benefits of super capacitor battery

1, charging time

At present, the concept of charging piles is very hot, but it takes five hours to charge. This is the biggest problem that restricts lithium battery vehicles. The graphite giant super capacitor is surprisingly short. If combined with a charging post, this efficiency is at least not comparable to that of a lithium battery. According to the description of Zhuzhou Zhongqi, according to different capacity and rated working voltage, the 3 volt / 12000 Farad super capacitor can be fully charged in 30 seconds, and the charging time of 2.8 volt / 30000 Farad super capacitor is within 1 minute.

Compared with activated carbon supercapacitors, graphene/activated carbon composite electrode supercapacitors have higher energy and longer life. It is said that this technology represents the highest level of the world's super capacitor single-cell technology, and technology research and development continues to be at the forefront of the world.

2, security

The battery should be at risk of explosion. At present, all kinds of battery safety measures are very good, except for the counterfeit battery, the possibility of explosion is very low. In lithium-ion batteries, the biggest danger is the intermediate organic electrolyte solvent, with the most flammable ethers. When the battery is short-circuited for any reason, the energy in the battery will be released in the form of heat for a short period of time, igniting these ethers as solvents, causing an explosion.

Lithium-ion batteries are highly likely to explode or spontaneously ignite due to the high temperature inside the car in summer. Supercapacitor, after being fully charged, use a nail gun to make it short-circuit, and there is no reaction; if it is set on fire, the stainless steel casing will burn red quickly and there will be no explosion (a description by a netizen). It is similar to the description of Ning Dianbo, deputy director of the technology center of China CRRC Zhuzhou Machinery Co., Ltd., and is “no pollution, no explosion”.

3, cruising range

On December 26, 2014, US electric car manufacturer Tesla released an upgraded version of the first-generation Roadster that was discontinued two years ago, with a cruising range of 644 kilometers, 60% higher than the original. Tesla CEO Musk said that Tesla's high-performance graphene battery is nearly 70% larger than current capacity. A domestic website has also announced that it is expected to mass-produce graphene lithium batteries in the first half of 2015, but so far there is no following.

The result of a netizen's actual test is "Take the day we tested as an example. In the morning, we will start with full power and return to the car in the afternoon. Because of the fierce driving, we have only opened more than 140 kilometers, and the remaining power is only 20%. Left and right. I personally speculate that in the big cities like Beijing, its actual cruising range should be around 250-300km." According to Phoenix.com, an Israeli company, StoreDot, is aiming to invent a technology that allows electric vehicles to travel hundreds of miles after only 5 minutes of charging. It has been used on consumer phones and is expected to be used in future storage of StoreDot batteries on electric vehicles.

However, it may take longer to develop applications for electric vehicles. Even if everything goes well, StoreDot's battery is unlikely to complete the commercialization of its electric vehicle application for at least five years. According to the conclusion of a domestic paper, "If the material cost, production process, processability and electrochemical performance are comprehensively considered, the author believes that the possibility of using graphene or graphene composite materials for lithium battery anodes is small and the industrialization prospects are slim."

At the time when the graphite-lithium battery was not mass-produced, Graphite's super capacitor was introduced. The 3V/12000 Farad super capacitor is suitable for the main drive of the tram. The single-charge mileage can reach 6km, 2.8V/30000 Farad Super. The capacitor is suitable for the main drive of the trolley bus, and the mileage of the single charge can be increased from the current 4-6 km to 8-10 km. On the endurance ability, the supercapacitor energy density is low, and there is room for improvement, but it is more than enough to use on the bus. However, there is news on the Internet. Xie Yu'an, chairman of the board of directors of Zhongshang Automobile, said that the super capacitor can be charged for 20 minutes in about 3 minutes. This has not been experienced, there is no exact data on how much it can last.

Six, two capacitor forms of the super capacitor battery

In the practice process, in order to achieve the performance of improving the performance of the capacitor and reducing the cost, the tantalum capacitor electrode material and the electric double layer capacitor electrode material are often used in combination to form a so-called hybrid electrochemical capacitor. Hybrid electrochemical capacitors can be divided into two categories. One is that one electrode of the capacitor uses a tantalum capacitor material, and the other electrode is made of an electric double layer capacitor electrode material to make an asymmetric capacitor, which can widen the range of use voltage of the capacitor and improve Energy density; the other is a composite electrode composed of a tantalum capacitor electrode material and an electric double layer capacitor electrode material to prepare a symmetric capacitor.

1. Faraday tantalum capacitor

The Faraday tantalum capacitor, also called the Faraday quasi-capacitor, is in the two-dimensional or three-dimensional space in the living phase of the electrode surface. The electroactive material is subjected to underpotential deposition, and a highly reversible chemisorption or redox reaction occurs, which is related to the charge potential of the electrode. capacitance. The voltage of this electrode system varies linearly with the amount of charge transfer, exhibiting a capacitance characteristic, so it is called "quasi-capacitance", and is a complementary form of the electric double layer type capacitor. Original address: http://

The charging and discharging mechanism of the Faraday quasi-capacitor is: the ions in the electrolyte (generally H+ or OH-) diffuse into the solution to the electrode/solution interface under the action of an applied electric field, and then enter the electrode surface activity through the electrochemical reaction at the interface. In the bulk phase of the oxide; if the electrode material is an oxide having a large specific surface area, a considerable amount of such an electrochemical reaction occurs, and a large amount of charge is stored in the electrode. These ions entering the oxide return to the electrolyte during discharge, and the stored charge is released through the external circuit.

2, electric double layer capacitor

A pair of solid electrodes immersed in the electrolyte solution are redistributed and aligned under the action of an applied electric field on the surface of the electrode which is in contact with the electrolyte. As compensation, the positively charged positive electrode attracts negative ions in the electrolyte, and the negative electrode attracts positive ions in the electrolyte, thereby forming a compact electric double layer on the surface of the electrode, whereby the dust-generating capacitor is called an electric double layer capacitor. The electric double layer is composed of two opposite charge layers that are a small distance apart from the atomic size, and the two opposite charge layers are like the two plates of the plate capacitor. Helmholtz first proposed this model.

Energy is stored at the interface of the electrode material in the form of a charge. During charging, electrons flow from the positive electrode to the negative electrode through an external power source. At the same time, positive and negative ions are separated from the bulk phase of the solution and moved to the surface of the electrode to form an electric double layer. After charging, the positive and negative charges on the electrode are opposite to those in the solution. The ionic phase is attracted to stabilize the electric double layer, and a relatively stable potential difference is generated between the positive and negative electrodes. During discharge, electrons flow from the negative electrode to the positive electrode through the load, generating a current in the external circuit, and the positive and negative ions are released from the electrode surface into the liquid phase of the solution to be electrically neutral.

7. Leakage current phenomenon of super capacitor battery

When the supercapacitor is charged, the leakage current decays over time as ions in the carbon electrode diffuse into the pores. The leakage current settles at an equilibrium value that depends on capacitance, voltage, and time. The leakage current is proportional to the capacitor core. The empirical estimation algorithm for supercapacitor equalized leakage current is 1μA/F at room temperature. The 150 mF capacitor in Figure 6 has a leakage current of 0.2 μA and 0.3 μA after 160 hours. The leakage current increases exponentially with increasing temperature.

As the temperature increases, the time to stabilize to the equilibrium value decreases because the ions diffuse faster. Therefore, these capacitors require the least amount of time to charge from 0V. This current ranges from 5μA to 50μA depending on the supercapacitor. Designers should consider testing this minimum charging current when selecting a supercapacitor for an energy harvesting circuit.

Eight, super capacitor battery charging

A discharged supercapacitor is like a circuit that is shorted to an energy source. Fortunately, many energy harvesting sources (such as solar cells and micro-generators) can drive a short-circuited circuit that directly charges a supercapacitor from 0V. ICs that interface with various energy sources, such as piezoelectric or thermal power, must be able to drive a shorted circuit to charge the supercapacitor.

The industry has made great efforts in MPPT (Maximum Peak Power Tracking) to get the most efficient power from energy harvesting sources. This solution is feasible when the battery must be charged in a constant voltage manner. The battery charger is usually a dc/dc converter that is a constant power load to the energy source, so it makes sense to use MPPT to get energy at the most efficient point.

In contrast to batteries, supercapacitors do not need to be charged at a constant voltage, but are most efficient when charging at the maximum current that the power supply can provide. A simple and effective charging circuit for the case where the open circuit voltage of the solar cell array is less than the rated voltage of the super capacitor. The diode prevents the supercapacitor from recharging the solar cell in the absence of light. If the open circuit voltage of the energy is greater than the voltage of the super capacitor, the super capacitor needs to be overvoltage protected by a shunt regulator. The shunt regulator is an inexpensive and simple solution to overvoltage protection. Once the supercapacitor is fully charged, it does not matter whether it consumes too much energy.

The energy harvester is like a water pipe with unlimited water supply, filling a sink (like a super capacitor). If the sink is full, the water pipe is still open and the water will overflow. This is different from batteries, which have limited battery supply and therefore require a series regulator.

In the circuit, the super capacitor is 0V, and the short-circuit current is obtained from a solar cell. As the supercapacitor is charged, the current drops, depending on the voltage/current characteristics of the solar cell. But the supercapacitor always gets the maximum current possible, so it charges at the highest possible rate. The circuit uses the TLV3011 solar cell because it contains a voltage reference that requires only about 3μA of quiescent current, and it is an open-drain battery cell. When the regulator is turned off, the output is open. . The circuit uses a BAT54 diode because it has a low forward voltage drop at low currents, ie, a forward voltage of less than 0.1V at forward currents less than 10μA.

Micro-generators are well suited for industrial control applications, such as monitoring rotating machines because the machine vibrates while it is working. The voltage-current characteristic of a micro-generator is given, which is similar to a solar cell and can provide the maximum current for a short circuit. The micro-generator also has a diode bridge that prevents the supercapacitor from recharging the generator, which results in a simple charging circuit.

When the supercapacitor is charged, the leakage current decays over time as ions in the carbon electrode diffuse into the pores. The leakage current settles at an equilibrium value that depends on capacitance, voltage, and time. The leakage current is proportional to the capacitor core. The empirical estimation algorithm for supercapacitor equalized leakage current is 1μA/F at room temperature. The 150mF capacitor has a leakage current of 0.2μA and 0.3μA after 160 hours.

The leakage current increases exponentially with increasing temperature. As the temperature increases, the time to stabilize to the equilibrium value decreases because the ions diffuse faster. Therefore, these capacitors require the least amount of time to charge from 0V. This current ranges from 5μA to 50μA depending on the supercapacitor. Designers should consider testing this minimum charging current when selecting a supercapacitor for an energy harvesting circuit.

Nine, super capacitor battery drives the wind power revolution

As a new energy storage component, the super capacitor has the characteristics of long cycle life and fast charging and discharging time. In the closed and limited space hub control cabinet of the wind turbine, the super capacitor has a wide temperature range, small volume and large capacity. In the wind power equipment system, the super capacitor does not overcharge, the overdischarge affects the life, and the charging and discharging process is only a physical level change, which will not cause secondary pollution to the inside of the hub of the perennial closed space operation. The super capacitor maintains a stable DC voltage to ensure the normal operation of the pitch servo motor.

The basic working principle of the supercapacitor is the carbon-carbon double-layer principle. The storage process is reversible. The RC model is used for analysis, including the equivalent series internal resistance RESP of the ideal capacitor C. The equivalent parallel internal resistance REPR and RESP affect the supercapacitor charging and discharging efficiency. REPR affects the self-discharge of the capacitor, ie long-term stationary storage. The difference in stored charge is that the electric double layer capacitor stores energy in the form of an electrostatic charge on the electrode-electrolyte surface. This energy storage mode has the characteristics of fast charging/discharging capability, high reliability and long cycle life. Compared with lead-acid batteries, it is more advantageous for emergency pitch power supply in the case of variable wind conditions.

After replacing a part of the super capacitor, the wind power is random, the environment is bad, the temperature and humidity change greatly, and the salt spray pollution is serious, which affects the power supply module. It can be concluded that the supercapacitor is more stable than the lead-acid battery, and the practicability and feasibility are stronger. It can be expected that the application of the supercapacitor will gradually increase in the development of the more mature wind power generation technology. Therefore, supercapacitor is very feasible as a backup power source for wind turbines.

Ten, super capacitor battery revolutionary new energy vehicle

Supercapacitors mainly have three types of applications in new energy vehicles: First, as a power equipment, such as Shanghai No. 11 bus is a super capacitor bus. It takes only 30 seconds to charge the vehicle in the middle of operation, and can drive 5 to 8 kilometers on a single charge. It also takes into account the urban landscape; the second is the auxiliary drive of the engine, which provides a large driving current when the car is started quickly, reducing the fuel consumption and incomplete combustion pollution; the third is to recycle the braking energy, when the car needs to accelerate When these stored energy is released, the energy efficiency is improved.

XI, super capacitor battery outlook for the future of tram

According to incomplete statistics, there are currently more than 60 countries and 300 cities operating modern trams in the world; more than 50 cities in China have carried out the planning, construction and operation of trams. The supercapacitor energy storage tram project under construction in China: T1 line of tram in Dahanyang District, Wuhan, with a total length of 19km, has purchased 21 super capacitor vehicles; Ningbo Yinzhou District Tram Demonstration Line, with a total length of 8km , has purchased 10 super capacitor vehicles; Dongguan Songshan Lake Huawei Industrial Park line, a total length of 5km, has purchased 5 super capacitor vehicles; Shenzhen Longhua New District tram T1 line, total length of about 12km, plans to be equipped with super capacitor vehicles 15 columns; T1 and T2 lines of trams in Donghu High-tech Zone, Wuhan, with a total length of 16/19km, planned to be equipped with 26 super-capacitor vehicles; Guangzhou plans to build a 500-kilometer tram network before 2020, plans to be equipped with super-capacitor vehicles 500 columns and so on. Supercapacitor energy storage type tram project under construction in Hong Kong, Macao and Taiwan: Taiwan Kaohsiung tram line, with a total length of 22km, has purchased about 30 columns of supercapacitor vehicles (CAF); Qatar Doha tram line, with a total length of 12km , has purchased 18 super capacitor vehicles (SIEMENS).

The supercapacitor energy storage trams that have been operated or commissioned are: Guangzhou Haizhu (7.7km, already in operation); Jiangsu Huai'an (20.3km trial operation).

The world's first super capacitor energy storage modern tram line operation line - Guangzhou Haizhu line operation: operating hours: 9:00-21:00; on-line number: 4+1 columns on weekdays, 6+1 columns on weekends; operating mileage : 230 km (15 round trips per column); travel speed: 24km/h, 7.7km one-way 19 points; punctuality rate: 99.87%; daily passenger flow: maximum daily 20,000 tickets (7 trains); vehicle power consumption: "3 degrees / km ↓ 30%.

The supercapacitor energy storage tram has gradually integrated into the urban culture. It is not just a means of transportation, but a new way of life.

Twelve, super capacitor battery to help the development of hybrid vehicles

The origin of HEV is one from the energy crisis, on the other hand, environmental pollution, and the other is the relevant national policies. From these aspects, the hybrid demand is proposed. The classification of HEV now has different methods, and a lot has been introduced in the morning and afternoon. Working principle, I am not professional, I will not introduce more, mainly related to the theme, talk about our lithium titanate battery and super capacitor.

First of all, we must know the characteristics of HEV. At present, the first feature of HEV is the use of high frequency, frequent and shallow charge and discharge cycles. Second, the power requirements are relatively large, and the current and voltage are relatively large during the charging process. The change is the third; the third is the working environment, the actual working conditions are relatively complicated. In terms of temperature, the working temperature demand area is wider.

According to the above actual working characteristics, the requirements for power supply design of our HEV-related power supply are put forward. First, the cycle life, battery cycle life requirements are relatively high, it is best to continue to use for more than 15 years. The second is high power charge and discharge performance. Third, the work adapts to a wider temperature, and has a better charge and discharge capacity at 40 and 70 degrees. The fourth is the issue of safety and stability. There have been safety incidents in both pure electric and hybrid electric vehicles. This is a matter of great concern. The fifth is the charging and discharging efficiency. The cycle of energy in the power battery must pass the cycle of charging-discharging-charging. The high charging and discharging efficiency plays an important role in ensuring the efficiency of the whole vehicle.

At present, there are about ten kinds of matching battery solutions used in HEV, one is lead-acid battery; the other is traditional nickel-hydrogen battery; the third is lithium iron phosphate as cathode material, graphite or carbon as anode material; Lithium ternary nickel-cobalt-manganese hydride is used as the positive electrode material, graphite is the negative electrode material; fifth is the zinc-nickel battery; the sixth is the one I want to talk about today, the ternary material is used as the positive electrode, and the lithium titanate is used as the negative electrode, which is the titanic acid. Lithium battery, in fact, it is also a kind of our lithium-ion battery, but the negative electrode is different. Seven is the use of supercapacitors and other secondary batteries, used in hybrid electric vehicles. Of course, there are also flow batteries and fuel cells, iron-nickel batteries, etc., there are about a dozen.

Summary: The battery is the source of power, and the importance of the capacitor as the storage power is of course very important. If the characteristics of the capacitor and the battery can be combined, it is definitely very attractive. This is the largest of the super capacitor battery. Potential, so if this battery can be popularized, it will bring a revolution.

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