Typically, the sodium-sulfur battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator consisting of a housing, generally with the secondary battery (a lead-acid battery, a nickel cadmium battery, etc.) is different from a molten sodium-sulfur battery is a solid electrolyte and the electrode composition , the negative electrode active material of molten sodium metal, the positive electrode active material is a molten liquid sulfur and sodium polysulfide.
1. Fundamentals sodium-sulfur battery
Typically, the sodium-sulfur battery comprising a positive electrode, a negative electrode, an electrolyte, and a separator consisting of a housing, generally with the secondary battery (lead-acid batteries, nickel cadmium battery etc.), the sodium-sulfur battery is a melting electrode and the solid electrolyte composed of the negative electrode active material is molten sodium metal, liquid sulfur as a cathode active material and molten sodium polysulfide.
by a solid electrolyte and a separator operating temperature of 300 to 350 degrees. At operating temperature, sodium ions () through reversible reaction occurs between the separator and the electrolyte S, and forming a release of stored energy.
sodium-sulfur battery in the discharge process, electrons foreign routed through the anode (cathode to anode 0 (positive electrode), while binding to the solid electrolyte by a sodium polysulfide product is formed, and the electrode reaction during chargingOpposite discharge. The reaction between sodium and sulfur violent, so must be separated by a solid electrolyte between the two reactants, but it must be a solid electrolyte conductor of sodium ions.
The electrolyte material is present only at temperatures above 300 degrees Celsius, before having the good conductivity. Accordingly, in order to ensure the normal operation of the sodium-sulfur battery, operating temperature of the sodium-sulfur battery should be maintained at 300 to 350 degrees Celsius, the operating temperature of the sodium-sulfur battery as a car battery safety decreases, the electrolyte damaged, thereby causing security issues. .
2 sodium-sulfur battery main features
sodium-sulfur cells have many characteristics of the place: a high specific energy (i.e., unit mass or unit volume of the cell has an effective electrical energy). The theoretical specific energy of 760Wh / Kg, actually greater than 150Wh / Kg, is 3-4 times that of lead-acid batteries. The Tokyo Electric Power Company (TEPCO) and NGK companies to develop sodium-sulfur batteries as the energy storage battery, power plant targeting the application load leveling (i.e., play the role of clipping Pinggu the night excess electricity is stored in batteries, the daytime then release the power from the battery during peak out), UPS power supply emergency power and instant compensation, etc., and in 2002 entered the implementation phase of commercialization, the world’s largest (8MW) of sodium sulfur battery energy storage device has been built, as of 2005 October statistics, the annual output of the sodium-sulfur battery cell has more than 100MW, while overseas output to start.
Another is a high current, high power discharge. Discharge current density of generally up to 200-300mA / cm2, and the instantaneous release time can be three times asThe inherent energy; then a charge and discharge efficiency. As a result of the solid electrolyte, so that usually no liquid electrolyte secondary battery self-discharge and side reactions, charge and discharge current efficiency is almost 100 percentage. Of course, things are always divided into two, the sodium-sulfur batteries also have shortcomings, its working temperature at 300-350 deg.] C, therefore, requires a certain heat insulation during battery operation. However, high-performance vacuum thermal insulating techniques can effectively solve this problem.
3 sodium-sulfur battery main function
will be sodium and sulfur through a chemical reaction, the stored electrical energy, when the grid needs more power, it will convert chemical energy into electrical energy , released out of the sodium-sulfur battery “flood” performance is excellent, even if the current exceeds the rated power input of 5-10 times suddenly, it can withstand calm, and then released into a stable power grid – power which for large cities the smooth operation is particularly useful.
solar, wind and other new energy sources, although clean, but power generation is very unstable. Bring the unexpected “peak” This will give the entire grid. Energy storage power station will these “green electricity” first accept, then output according to power requirements.
sodium-sulfur battery is Na-beta- alumina (AL2O3) is an electrolyte and a separator, and metallic sodium are sodium polysulfide and a positive electrode and the negative electrode of the secondary battery. Sodium-sulfur battery has unique advantages for storage, mainly in the preparation of raw materials and low-cost, high energy and power density, high efficiency, without space constraints, easy maintenance and so on.
4. Brief History of sodium-sulfur batteries developed
sodium-sulfur battery as a high energy solid-electrolyte secondary battery was first invented in the mid-1960s, early studies main target applications for electric vehicles, comprising Ford US, Japan YUASA, Britain’s BBC and the railway laboratory, Germany’s ABB, American Mink companies, has assembled a sodium sulfur battery electric vehicles, and a long-term road test. When
However, long-term studies found that sodium-sulfur battery as the storage battery obvious advantages, but as a power source of electric vehicles or other mobile appliance, can not show its superiority, and early studies have not fully resolved sodium security and reliability of sulfur batteries, sodium sulfur batteries in the car and therefore ultimately abandoned by the application of energy people. However, due to the outstanding aspects of the advantages of its high specific energy and specific power, low cost raw material, temperature stability, and no self-discharge, so that the sodium-sulfur battery become the most promising market and dynamic storage battery.
a schematic view of the basic structural units of the sodium-sulfur battery is a sodium-sulfur battery cell, a cell for energy storage has reached the maximum capacity of 650 Ah, more power is 120 W, a combination of a plurality of unit cells after forming the power module, the module is typically tens of kilowatts may be used directly for storage. It can be formed of different power station according to the storage requirements of the specific power output of the module and then superimposed. Currently, commercial sodium-sulfur battery life can be achieved using the above 10 to 15 years.
Large-capacity tubular sodium-sulfur battery is a large-scale application of a static background storage. Since 1983, the Japanese company NGK and Tokyo Electric Power Company to develop such batteries, in 1992 realWhen the run is now a first exemplary sodium-sulfur battery energy storage power station so far, the production of a tubular sodium-sulfur battery cycle life, the percentage depth of discharge of 10 up to 42,000 times, 90 percent, from about 4,500 times, 100%, about 2,500 times.
At present NGK sodium sulfur battery energy storage has been successfully applied to the grid of the city, the sodium sulfur battery energy storage station more than 200 more than 500 kW of power, Japan and other countries into commercial demonstration operation, power plant the energy efficiency of 80% or more.
In addition to large-scale application outside Japan, has also been extended to the United States, Canada, Europe, West Asia and other countries and regions. Energy storage stations covering all sectors of commerce, industry, electricity, water, schools and hospitals.
In addition, the sodium-sulfur battery energy storage station is also applied to the storage of renewable energy power generation, wind power generation output is stable. As in Japan, octagonal island, a 400 kW sodium sulfur battery energy storage system with 500 kW wind power system facilities, to ensure that the wind power output is completely smooth, to achieve a safe docking with the grid.
is currently running wind with 34 MW sodium-sulfur battery energy storage stations and for stabilizing the maximum power output of the wind farm’s. Sodium sulfur batteries is expected to make the price of 32 cents / kWh, one of the most promising of the most economical energy storage battery.
NGK sodium-sulfur battery has been widely applied in the following areas:
① load shaving. During the low power energy storage and release electrical energy to meet the demand during the peak. Sodium-sulfur battery based demonstration projects to apply in this regard;
② renewable energy grid. In the sodium-sulfur battery supporting wind, solar power grid, power generation can be high when the power storage, energy release at the time of high-power electricity, improving power quality;
③ independent power system. Independent power system for remote areas, the island, and is typically combined with new energy;
④ industrial applications. Enterprise user using sodium-sulfur battery charging at night, daytime discharge to save electricity, it is also possible to provide an uninterruptible power supply and at the same time stabilize the quality of the electric power company; schematic sodium-sulfur battery module
⑤ transmission and distribution areas. For providing reactive power support, relieve transmission congestion, slow expansion and transmission and distribution equipment in the substation DC power supply, to improve the stability of the distribution network, intoEnhance power grid reliability and security.
2010 by NGK sodium-sulfur battery capacity increased by 50 percentage from 2009, to 150 MW. In 2009 the company NGK respectively with France and the UAE signed a 150 MW and 300 MW supply contract. In 2009 alone, NGK company’s contract orders reached 600 MW, currently NGK’s sodium-sulfur battery energy storage is the only access to large-scale commercial application of new energy storage technologies, products in short supply.
Sodium-sulfur batteries country to Shanghai Institute of Ceramics, Chinese Academy of Sciences as a representative, has successfully developed 6 kW sodium sulfur batteries for electric vehicles. In August 2006, the Shanghai Institute of Ceramics, and Shanghai Electric Power Company of cooperation, joint development of sodium sulfur battery energy storage applications. In January 2007 the successful development of a monomer capacity of 650 Ah sodium-sulfur batteries, and built a pilot line having an annual production capacity of 2 MW cell in 2009, may be continuously prepared capacity 650 Ah of the cell. Pilot line directed to various techniques and testing equipment hundred sets of sets, of which nearly 2/3 independent research, a number of independent intellectual property rights, the formation of evaluation technique has its own characteristics and the sodium-sulfur battery cell materials.
Currently the specific energy of the battery reaches 150 Wh / kg, the degradation rate of 200 cycles before the battery percentage 0.003 / second, the data level of advanced flat, the overall level of the current cell is close NGK company level. October 2011, Shanghai Electric Group, Shanghai Electric Power Company and the Shanghai Institute of Silicate formally established “sodium-sulfur battery industry companies”, the construction of a sodium-sulfur battery production line, 2015 is expected to sodium-sulfur battery production capacity to 50 MW, the world’s second largest sodium sulfur battery manufacturer.
Main technical difficulties sodium-sulfur battery is that the cell preparation beta- alumina ceramic solid electrolyte tube, is currently in automated mass production of high quality ceramic tube has been great progress, but its output is still limited the cost is still high.
Another important technical difficulties in the cell that the sealing of the battery pack, at home and abroad have initiated development of glass-ceramic materials with a ceramic thermal coefficient alfa- beta- or adapted as the sealing material, which is to reduce the cost of the cell in a new way. due toSulfur and sulphide are highly corrosive, one of the research focus electrode materials is the development of low-cost corrosion resistant single cell technology, we have successfully developed a number of corrosion resistant layer may be deposited for the collector electrode, as an inexpensive substrate carbide or ceramic material is deposited.
Further, to improve the interfacial polarization between the electrodes and the sodium-sulfur battery a solid ceramic electrolyte is an important aspect of improving the electrochemical cell performance and safety performance.
At present, the sodium-sulfur battery higher manufacturing cost, reliable long-term operation, the scale set of technologies which are major bottlenecks in large-scale applications. Thus, the sodium-sulfur battery technology key technologies including high quality ceramic tube sealing technology, the battery pack, corrosion resistant electrode material technology and scale set of technologies like.