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The general trend of electrification is getting more and more intense. With the guidance and support of policies, China has become the world's largest market for new energy vehicles.
As we all know, the important bottleneck of new energy vehicles lies in the battery range. Under this background, the state introduced the action way for promote the development of automobile power lithium batteries, the energy saving and new energy automotive technology roadmap, encourage the use of high energy density batteries, recently the foreign investment industrial guidance catalogue (2017 years) policy put forward its all-electric joint venture company and cancel the auto electronic and power lithium battery shares of limits, This is also an important measure to promote the application of high-energy density batteries in the new energy vehicle market.
Battery is a very deep subject, because it has been widely used in our life since it was invented, such as 3C and energy storage.
Power lithium battery refers to the battery with large power capacity and output power that can be configured with the driving power of electric bicycles, electric vehicles, electric equipment and tools, usually including military (submarines, advanced intelligent robots, etc.) and the standing power of the communication command system of energy storage equipment used by enterprises and institutions. With the development and commercial production of emerging electric bicycles, electric vehicles, and the development of new submarines and unmanned underwater vehicles (UUV), the social demand for new green power lithium batteries has increased substantially. At present, the most widely used power lithium batteries in the world include lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, lithium ion batteries, fuel power batteries, solar cells. These power lithium batteries have their own advantages and have been widely used in different fields.
Types and performance of power lithium batteries
The lead-acid battery was developed in 1859 by Plant (R.G. Plante, is the earliest used battery. Plante battery uses two lead plates as electrodes and is placed in sulfuric acid solution for electrolysis. By constantly changing the direction of electrolysis current, the storage capacity of the lead plates is gradually increased, but the specific energy of the battery is very low.
The traditional lead-acid battery has two important disadvantages: one is during its service life, it needs constant water maintenance; Second, because the rich liquid has the danger of acid leakage can not be placed in any direction. After continuous research, in the middle of the 20th century, colloidal electrolyte technology and maintension-free sealing technology were invented: in 1955, German Sunshine Company first used gel electrolyte technology for lead-acid batteries and put it on the market. In the mid-1960s, the company developed the DryFit series of utility colloidal electrolyte sealed lead-acid batteries. In 1968 Desai filed the first patent describing a gas-sealed lead-acid battery, which was formally published in 1974. In 1972, D. McLelland and J.L.Devitt of Gates Corporation invented the adsorption type superfine glass fiber separator (AGM), which solved the problem of compound circulation of oxygen inside the battery from practice, and developed the cylindrical AGM type valve-controlled sealed lead-acid battery (VRLAB). The electrolyte of the battery is adsorbed in the glass fiber membrane, and the electrolyte cannot flow freely, which is related to the traditional liquid-rich lead-acid battery (the electrolyte can flow freely). The valve-controlled lead-acid battery is a liquid-poor battery. In the following 30 years, VRLAB batteries have developed rapidly and have been widely used in various professional sectors such as power, railway, shipping and communication. The emergence of VRLA technology has promoted the development of lead-acid battery, which has entered a period of prosperity.
Lead-acid battery is the most mature battery among all chemical power sources. It has the advantages of low price, high safety, good performance of large current discharge and high battery recovery rate. It has been widely used in electric bicycle, electric motorcycle, communication industry, power industry backup power supply, railway diesel locomotive and other fields. However, due to the shortcomings of low specific energy and not enough environmental protection, new materials, new structures and new technologies of lead-acid batteries are still being studied, such as corrosion-resistant lead-alloy positive grid, lead foam grid, carbon foam grid, new negative additive, super lead-acid batteries, etc.
Alkaline nickel - based batteries include nickel - cadmium batteries, nickel - zinc batteries and nickel - hydrogen batteries. Nickel-cadmium batteries have been widely used in many fields, but the risk of cadmium pollution in waste nickel-cadmium batteries greatly limits their application. European Union countries have banned the use of nickel-cadmium batteries for power lithium batteries, basically on the edge of elimination. During the charging of Ni-Zn battery, the negative zinc is prone to dendrite, which leads to septum puncture and affects the battery life. In contrast, nickel metal hydride battery is the best comprehensive performance of power lithium battery. Nickel-metal hydride batteries have been widely used in commercial electric vehicles.
Nickel hydride battery is composed of hydrogen ions and metal nickel battery, positive active material for nickel hydroxide, negative active material for hydrogen storage alloy, electrolyte using 6M potassium hydroxide solution. Its electrochemical formula can be expressed as:
(-) M/MH︱ KOH-Ni (OH) 2/NiOOH (+) When charged, the hydrogen ions (H+) in the KOH electrolyte are released and absorbed by the hydrogen storage alloy. The positive electrode changes from Ni (OH) 2 to NiOOH and H2O; The hydrogen is consumed at the negative electrode, and the positive electrode changes from NiOOH to Ni (OH) 2.
Nickel-metal hydride battery has the characteristics of high specific energy and high specific power, and its specific energy is three times higher than that of lead-acid battery. The specific power is nearly 10 times higher than that of lead-acid batteries. In addition, the nickel metal hydride battery also has good overcharge and discharge tolerance and thermal performance, so it has a high safety and reliability. Charging fast, environmental pollution, long life is also the advantages of nickel metal hydride battery.
However, because the raw material nickel and hydrogen storage alloy is very expensive, so the cost of nickel hydride battery is high, the price has become an important factor restricting the development of nickel hydride battery. The use of nickel-metal hydride batteries in electric vehicles has been limited.
Lithium-ion battery research began in 1990 Nagoura et al. developed a lithium ion battery with petroleum coke as the negative electrode and lithium cobalt acid as the positive electrode; In the same year, Japan's Sony and Canada's Moli announced plans to launch lithium-ion batteries with carbon as a negative electrode. In 1991, Sony Energy Technology Co., Ltd. and the battery department jointly developed a lithium ion battery with glycan alcohol pyrolytic carbon (PFA) as the negative electrode. Polymer lithium-ion batteries were first reported by Bellcore in 1993.
Lithium-ion battery is a kind of high-energy secondary battery in which Li+ is repeatedly embedded and disembedded in anode and cathode materials. It usually consists of the following components:
(1) the negative electrode, in the discharge of oxidation reaction, the application is more carbon materials;
(2) positive electrode, discharge reduction reaction occurs, using more transition metal oxides, such as LiCoO2;
(3) electrolyte to supply transport medium for ion movement;
(4) Diaphragm, providing electronic isolation for the positive and negative electrodes. Aluminium foil is usually used as the positive collector and copper foil as the negative collector.
Compared with other power lithium-ion batteries, lithium-ion batteries have obvious advantages:
1) High energy density, the volumetric energy and mass energy can reach 300Wh/cm3 and 125Wh/kg, respectively, and the maximum can reach 350Wh/cm3;
2) The average output voltage is high (about 3.9V), which is 3 times of that of Ni-CD and Ni-MH batteries;
3) Large output power;
4) the self-discharge is small, less than 10% per month, less than half of the Ni-CdNi-NH self-discharge;
5) It does not have the same memory effect as Ni-CDNi-NH batteries;
6) Fast charging and discharging;
7) High charging efficiency. Up to 100%;
8) Wide operating temperature range of -25CO ~ 70CO;
9) No environmental pollution, called green battery;
10) Long service life, up to about 1200 times, the longest up to 3000 times.
Therefore, lithium ion batteries are widely used in consumer electronic products, military products, aviation products, etc. However, with reports of lithium ion battery explosion, fire and other accidents, safety has become a key problem in the development of lithium ion battery technology. There are a series of potential exothermic reactions in lithium-ion batteries, which is the root cause of safety problems of lithium-ion batteries. Whether the safety problems caused by thermal runaway can be effectively solved has also become a key factor to promote or restrict the further development of lithium ion batteries.
Fuel powered cell
Fuel power cell is a kind of power generation device that converts chemical energy stored in fuel and oxidant directly into electric energy through electrochemical reaction. Like conventional batteries, fuel-powered cells are electricity-generating devices that operate on the principle of electrochemistry. The difference is that fuel-powered cells provide electricity continuously as long as the fuel is supplied continuously. There is no thermal process in the fuel power cell, that is, it is not restricted by the Carnot cycle, so the energy conversion efficiency is very high, and the reaction process does not appear any pollution, the product is only water.
There are many types of fuel power cell, which can be divided into proton exchange membrane fuel power cell, phosphoric acid fuel power cell, solid oxide fuel power cell, molten carbonate fuel power cell and alkaline fuel power cell based on the different properties of the electrolyte.
As a new generation technology, fuel-powered cells have the following characteristics:
1) High energy conversion efficiency: the fuel in the fuel power cell is directly converted into electric energy without combustion and is not restricted by the Carnot cycle. Therefore, the fuel power cell is more efficient than the ordinary heat engine. The theoretical energy conversion efficiency is up to more than 60%, and the actual service efficiency is 2-3 times that of the ordinary internal combustion engine.
2) Environment-friendly: The fuel directly goes through the electrochemical reaction of the fuel power cell, and water appears in the air. In this process, almost no environmental pollutants such as nitrogen oxides (NOx) and sulfur oxides (SOx) are emitted. Moreover, the fuel power cell has simple structure, no movable parts, and low noise and vibration level.
3) Fuel diversity: Fuel power cells have a wide range of fuel sources, including gaseous fuels such as hydrogen, natural gas and biogas, as well as liquid fuels such as gasoline, diesel, methanol, ethanol and formic acid, which is very consistent with the trend of energy diversification to cope with the increasing depletion of fossil energy such as oil and coal.
4) Wide application fields: Different from ordinary batteries, fuel power battery allows the power (determined by the size of fuel power battery) and capacity (determined by the fuel storage size) at random between scaling, can be easily levels from 1 w do MW, used in portable power supply, distributed and centralized power stations, power stations and also applied in aerospace, ships, cars and other vehicles.
Just because of these outstanding advantages, the research and development of fuel power cell technology is favored by governments and companies all over the world, which will trigger the green revolution of new energy and environmental protection in the 21st century. Fuel power battery for power supply is the most effective, the most environmentally friendly vehicle power, but to achieve fuel power battery is widely used, there are many problems to solve, such as a battery of high development costs (using precious metals such as platinum as catalyst, hydrogen storage transportation problem, and the problem of short service life of cell cycle.
These power lithium batteries have their own advantages and have been widely used in different fields. The important technical characteristics of common power lithium batteries are shown in Table 1
Power lithium battery technology analysis and application field
Market and application of power lithium batteries
Western countries such as Europe and the United States produce and sell electric bicycles earlier, Britain, the United States, France, Italy and other countries have production companies to launch electric bicycles. Japan Bicycle Promotion Association has a statistics show that the world's existing electric bicycle manufacturers more than 100, for its supporting the use of power lithium battery production companies are the most famous Sanyo Electric Co., Ltd., Toshiba Battery Co., Ltd., France's Safte Company, Germany's Warta Company, etc.
As a means of transportation for the development of our country, electric bicycle has also developed rapidly in recent years, especially in our country. Domestic e-bike production has been growing at an average annual rate of 40 per cent since 1998. The number of electric bikes in China reached 200 million in 2012. According to the authoritative forecast, by 2015, the output value of electric bikes in China will reach 100 billion yuan, among which the output value of supporting batteries will reach 16 billion yuan.
Motorcycles, as a flexible and convenient means of transportation, have a huge market in South China and some Southeast Asian countries. Although motorcycles have brought a lot of convenience to people, the exhaust pollution from motorcycles is considered to be one of the important air pollution sources in large and medium cities in China. A scooter is said to emit as much pollution as a Santana. Motorcycles have been banned in more than 60 Chinese cities in a bid to clean up the environment and ensure blue skies in cities.
Famous motorcycle manufacturers around the world are already actively developing electric scooters, including Yamaha and Honda in Japan.
Some motorcycle companies in China are also actively looking for more environmentally friendly power sources for their motorcycles. At present, the new continent, Chunlan, Chongqing Jialing and other motorcycle manufacturers have cast their eyes on the advantages of lithium ion power lithium battery, is working with power lithium battery manufacturers to jointly develop electric motorcycle. This situation has undoubtedly created unlimited business opportunities for the future market of power lithium batteries, and its brilliant market prospects are immeasurable.
Hybrid electric vehicle
Electric vehicle is a new type of vehicle powered by on-board battery and powered by high-power electric motor. Electric vehicles have the advantages of low pollution to no pollution, diversified power sources, high energy utilization rate, convenient use and maintenance, etc., and are considered as the most promising clean models in the 21st century, which are more and more recognized and favored by today's society. Generally, electric vehicles are divided into three categories: pure electric vehicles (EV), hybrid electric vehicles (HEV) and fuel-powered battery electric vehicles (FCEV). The EV is powered by a variety of batteries. The HEV is powered by two or more different energy sources, such as a storage battery and a gasoline or diesel engine. These energies can be used separately to power the car, or they can work together to power the car. HEVs can be classified as power-assisted (light hybrid), dual-mode (medium hybrid) and range-extended (high hybrid) based on the battery-related power ratio to the fuel engine. PHEVs are powered by fuel-powered cells. Battery and fuel two kinds of power mix degree is different, the battery requirements are different. The technical requirements of different types of electric vehicles for power lithium batteries are shown in Table 2.
Power lithium battery technology analysis and application field
At present, most of the power lithium batteries of electric vehicles use lead-acid batteries, nickel-metal hydride batteries, lithium ion batteries and fuel power batteries. Among them, lead-acid battery technology is the most mature, but its energy density and power density is not high, not suitable for the application of electric vehicles. In terms of the current technical level, the comprehensive advantages of nickel-metal hydride battery are the most obvious. Most of the well-known international automobile manufacturers, such as Toyota of Japan, General Motors of the United States and Volkswagen of Germany, choose nickel-metal hydride powered lithium battery as the power lithium battery of HEV, such as the Prius and other models that have been listed. This indicates that the technology of high-power nickel hydride powered lithium battery has been basically mature. Because of the advantages of light weight and high voltage of single battery, lithium-ion battery is recognized as the new development direction of power vehicle battery. At present, Panasonic, LG Chem, NEC and other Japanese and Korean companies are actively developing lithium manganese oxide ion batteries as power lithium batteries for electric vehicles; Companies such as Aystem123 and BYD are aiming for lithium-ion batteries powered by iron phosphate. Major car companies are focusing on lithium-ion batteries as a future development priority. At present, the listed car models installed with lithium ion batteries are shown in the following table. Lithium-ion batteries are promising and may replace nickel-metal hydride battery packs in the future, but there is still much work to be done in terms of safety, cycle stability and production cost.
In the military field
Due to the wide application of high technology in military, modern war has become a high-tech war dominated by digital and information weapons. This war mode makes the military energy with high efficiency, high specific energy density and fast filling fuel become the urgent need in the modern battlefield. Nowadays, the technology development of high-energy power lithium battery has been carried out in various countries, such as the use of new lead-acid battery, lithium ion battery and fuel power battery.
Lead acid battery is the underwater power source and auxiliary power source of conventional submarine, and also the emergency power source of nuclear submarine. Lead-acid battery is still the most widely used battery for conventional powered submarines in the world because of its obvious advantages such as mature technology, reliable performance and low manufacturing cost. However, lead-acid batteries used in modern submarines have some disadvantages, such as long charging time, low charging and discharging efficiency at high rate, and low specific energy and specific power. According to the requirements of the new generation of submarines, more advanced lead-acid batteries should be developed to meet the operational needs of mobile submarines and improve the tactical mission of conventional submarines.