Introduction of battery types The battery is the source of power for electric vehicles. At present, the key factor restricting the development of electric vehicles is the unsatisfactory power battery. The main performance indicators of electric vehicle batteries are specific energy, specific power and service life. To enable electric vehicles to compete with internal combustion engine vehicles, the key is to develop batteries with high specific energy, high specific power, long service life and low cost.
Lead-acid batteries have a history of more than 100 years and are widely used as the starting power source for internal combustion engine vehicles. It is also a mature electric vehicle battery, with good reliability, easy availability of raw materials, and low price; the specific power can basically meet the power requirements of electric vehicles. But it has two major shortcomings; one is low specific energy, the mass and volume occupied are too large, and the mileage is short on one charge; the other is short service life and high cost of use.
Ni-MH batteries are alkaline batteries. Ni-MH batteries have a long cycle life and no memory effect, but the price is relatively high. Although its initial purchase cost is high, its long-term actual use cost is not high due to its advantages in energy and service life. At present, foreign companies producing nickel-metal hydride batteries for electric vehicles are mainly a joint venture of Ovonie, Toyota and Panasonic. Ovonie has two types of unit batteries, 80A·h and 130A·h, with a specific energy of 75-80W·h/kg and a cycle life of more than 600 times. This kind of battery is installed on several electric vehicles for trial. One type of vehicle can travel 345km on a single charge, and one vehicle travels more than 80,000 kilometers in a year. Due to the high price, mass production is not yet available. Domestically, 55A·h and 100A·h unit batteries have been developed, with a specific energy of 65 W·h/kg and a power density greater than 800W/kg of nickel-hydrogen storage batteries.
Lithium Ion Battery
As a new type of high-voltage, high-energy density rechargeable battery, lithium-ion secondary batteries have unique physical and electrochemical properties and have a wide range of civilian and national defense applications. Its outstanding features are: light weight, large energy storage, no pollution, no memory effect, and long service life. In the case of the same volume and weight, the storage capacity of lithium batteries is 1.6 times that of nickel-hydrogen batteries and 4 times that of nickel-cadmium batteries. At present, human beings only use 20% to 30% of its theoretical power. The development prospects are very bright. . At the same time, it is a truly green battery that will not pollute the environment and is currently the best battery that can be applied to electric vehicles. my country began to develop and utilize lithium-ion batteries in the 1990s, and has made breakthroughs so far, and developed lithium-ion batteries with independent intellectual property rights.
The application range of nickel-cadmium batteries is second only to lead-acid batteries, with a specific energy of 55W•h/kg and a specific power of more than 190W/kg. It can be charged quickly and has a long cycle life. It is more than twice that of lead-acid batteries and can reach more than 2,000 times, but the price is 4 to 5 times that of lead-acid batteries. Although its initial purchase cost is high, its long-term actual use cost is not high due to its advantages in energy and service life. The disadvantage is that there is a "memory effect", which is likely to reduce the available capacity of the battery due to poor charging and discharging. It must be fully charged and discharged after about ten times of use. If there is a "memory effect", it should be fully charged and discharged continuously for 3 to 5 times to release the memory. In addition, cadmium is toxic, so pay attention to recycling during use to avoid environmental pollution caused by cadmium.
Advantages of sodium-sulfur batteries: One is higher than energy. Its theoretical specific energy is 760W•h/kg, which is actually greater than 100W•h/kg, which is 3 to 4 times that of lead-acid batteries; the other is high current and high power discharge. The discharge current density can generally reach 200～300mA/mm2, and can release 3 times its inherent energy in an instant; the other is the high charging and discharging efficiency. Due to the solid electrolyte, there is no self-discharge and side reactions that usually use liquid electrolyte secondary batteries, and the charge-discharge current efficiency is almost 100%. The disadvantages of sodium-sulfur batteries are that their operating temperature is between 300°C and 350°C. Therefore, a certain amount of heating and insulation is required when the battery is working. The high temperature corrosion is serious, and the battery life is short. Nowadays, high-performance vacuum insulation technology has been adopted, which can effectively solve this problem. There are also problems such as performance stability and unsatisfactory use safety. In the 1980s and 1990s, foreign countries focused on the development of sodium-sulfur batteries as fixed applications (such as energy storage in power stations), and they increasingly showed their superiority. In this regard, Japanese companies have made the most significant progress. As a generally promising electric vehicle battery in the near future, it has been listed as a mid-term development electric vehicle battery by the American Advanced Battery Consortium (USMABC). The B240K sodium-sulfur battery produced by ABB in Germany has a mass of 17.5kg and a storage capacity of 19.2Kw• h; The specific energy reaches 109W•h/kg, the cycle life is 1200 times, and the best vehicle drove 2300km without failure during the loading test.
Nickel zinc battery
The new sealed nickel-zinc battery has the advantages of high-quality performance, high-quality power and high-current discharge. This advantage enables nickel-zinc batteries to meet the energy requirements of electric vehicles in terms of one-time charging stroke, climbing and acceleration. The nickel-zinc battery is a product developed and produced by the National Energy Research Corporation (ERC) of the United States, and Xiamen Battery General Factory has cooperated with it to introduce this product. Nickel-zinc batteries are extremely competitive batteries. Its advantages: its specific energy reaches more than 50Wh/k, and its volumetric energy has exceeded that of nickel-cadmium batteries and is smaller than nickel-hydrogen batteries. High current discharge, the battery voltage will be balanced in a wide range, and has a long service life, cycle life ≥ 500 times. Charging time ≤3.5h, fast charging ≤1h. It is particularly worth mentioning that the self-discharge resistance to charge attenuation is very good. In one month at room temperature, the self-discharge is less than 30% of the rated charge. At a high temperature of 50°C, discharge at C/3, the battery charge attenuation is less than 10% of the rated charge, and at -15°C, C/3 discharge is less than 30%. Nickel-zinc batteries have good compatibility with lead-acid batteries. All vehicles currently using lead-acid batteries can be replaced with nickel-zinc batteries. Judging from the current price, nickel-zinc is still slightly more expensive, but it is believed that the price will naturally come down after its application volume increases. The compatibility with the outline of lead-acid batteries makes nickel-zinc batteries more convenient to replace lead-acid batteries and become an ideal power source for electric vehicles.
Zinc-air battery, also known as zinc-oxygen battery, is a type of metal-air battery. The theoretical value of the specific energy of the zinc-air battery is 1350W•h/kg, and the current specific energy has reached 230Wh/kg, which is almost 8 times that of the lead-acid battery. It can be seen that the development space of zinc-air batteries is very large. Zinc-air batteries can only be "mechanically charged" by replacing the zinc electrodes. The time to replace the electrode can be completed in 3 minutes. Replace with a new zinc electrode, the "charging" time is very short, very convenient. If this kind of battery has been developed, the construction of social security facilities such as charging stations has been eliminated. Zinc electrodes can be purchased in supermarkets, battery shops, auto parts stores, etc., which is very beneficial to the popularization of battery electric vehicles. This kind of battery has the advantages of small size, large charge capacity, small quality, normal operation in a wide temperature range, no corrosion, safe and reliable operation, and low cost. The charge capacity of the current test battery is only 5 times that of the lead-acid battery, which is not ideal. But 5 times the charge of lead-acid batteries has attracted the attention of the world. The United States, Mexico, Singapore and some European countries have been tested on postal vehicles, buses, and motorcycles. It is also a very promising electric vehicle. battery.
The flywheel battery is a new concept battery proposed in the 1990s. It breaks through the limitations of chemical batteries and uses physical methods to store energy. When the flywheel rotates at a certain angular velocity, it has a certain amount of kinetic energy. The flywheel battery converts its kinetic energy into electrical energy. High-tech flywheels are used to store electrical energy, much like standard batteries. There is a motor in the flywheel battery. When charging, the motor runs in the form of an electric motor. Driven by an external power source, the motor drives the flywheel to rotate at a high speed. That is, when electricity is used to "charge" the flywheel battery, it increases the speed of the flywheel and increases its function; , The motor runs as a generator, and it outputs electrical energy to the outside under the drive of the flywheel to complete the conversion of mechanical energy (kinetic energy) to electrical energy. When the flywheel battery is powered, the speed of the flywheel gradually decreases. The flywheel of the flywheel battery runs in a vacuum environment, and the speed is extremely high (200000r/min), and the bearings used are non-connected
Contact magnetic bearing. It is said that the flywheel battery has a specific energy of 150W•h/kg, a specific power of 5000～10000W/kg, a service life of up to 25 years, and can be used for electric vehicles to travel 5 million kilometers.