I. Lead-acid battery
As a more mature technology, lead-acid batteries are still the only batteries available for mass production for electric vehicles because of their lower cost and ability to discharge at high rates. At the Beijing Olympic Games, there were 20 electric cars using lead-acid batteries to provide transportation services for the Olympic Games.
However, the specific energy, specific power and energy density of lead-acid batteries are very low, and it is impossible for electric vehicles with this as the power source to have good speed and range.
Second, nickel-cadmium batteries and nickel-metal hydride batteries
Although their performance is better than lead-acid batteries, they contain heavy metals and will cause pollution to the environment after being abandoned.
NiMH power battery has just entered the maturity period, is currently the only battery system used in hybrid cars have been actually verified and commercialized, the scale of the battery system, 99% of the existing hybrid battery market share for NiMH power battery, commercialized on behalf of Toyota's Prius. At present, the world's major automotive power battery manufacturers are mainly Japan's PEVE and Sanyo, PEVE occupies 85% of the global Hybrid power car NiMH battery market share, the current major commercial hybrid cars such as Toyota's Prius, Alphard and Estima, as well as Honda's Civic, Insight, etc. are using PEVE's NiMH power pack. In China, Changan Jiexun, Chery A5, FAW Pentium, GM Grand Hyatt and other brands of cars have been in demonstration operation, they are also using NiMH batteries, but the batteries are mainly purchased from foreign countries, the use of domestic NiMH batteries in cars is still at the stage of research and development matching.
Third, lithium batteries
Traditional lead-acid batteries, nickel-cadmium batteries and nickel-hydrogen batteries are relatively mature technology, but they are used in cars as a power battery is a bigger problem. At present, more and more car manufacturers choose to use lithium batteries as the power battery of new energy vehicles.
Because the lithium-ion power battery has the following advantages: high operating voltage (three times that of nickel-cadmium battery hydrogen-nickel battery); large specific energy (up to 165WH/㎏, three times that of hydrogen-nickel battery); small size; light quality; long cycle life; low self-discharge rate; no memory effect; no pollution, etc..
Currently many well-known car manufacturers are committed to the development of power lithium battery cars, such as the United States Ford, Chrysler, Japan Toyota, Mitsubishi, Nissan, South Korea Hyundai, France Courreges, Ventury, etc.. The domestic automakers BYD, Geely, Chery, Lifan, ZTE and other car companies have also been equipped with power lithium batteries in their own hybrid and pure electric vehicles.
The current bottleneck that hinders the development of power lithium-ion battery is: safety performance and automotive power battery management system. Safety performance, due to the lithium-ion power battery has a high energy density, high operating temperature, harsh working environment and other aspects, coupled with the human-centered safety concept, therefore, users put forward very high requirements for the safety of the battery. As for the management system of automotive power battery, since the working voltage of automotive power battery is 12V or 24V, and the working voltage of single power lithium-ion battery is 3.7V, the voltage must be increased by connecting multiple batteries in series, but since it is difficult to charge and discharge the batteries in a completely uniform manner, it leads to the unbalanced charging and discharging of individual batteries in multiple battery packs connected in series, and the batteries will be charged Undercharge and over-discharge phenomenon, and this situation will lead to a sharp deterioration in battery performance, eventually leading to the whole group of batteries can not work properly, or even scrap, thus greatly affecting the life and reliability of the battery performance.
Fourth, lithium iron phosphate batteries
Lithium iron phosphate battery is also a lithium battery, its specific energy is less than half of the lithium cobalt acid battery, but its high safety, cycle times can reach 2000 times, stable discharge, cheap, become a new choice for automotive power.
BYD proposed "iron battery", the industry believes that the possibility of lithium iron phosphate batteries.
Five, fuel cells
Simply put, fuel cell (Fuel Cell) is a kind of chemical energy present in the fuel and oxidizer directly into electricity generation device. Fuel and air are fed into the fuel cell separately, and electricity is produced wonderfully. It looks like a battery with positive and negative electrodes and electrolyte, but in essence it does not "store electricity" but is a "power plant".
The most promising one for automobiles is the proton exchange membrane fuel cell. It works as follows: hydrogen gas is sent to the negative electrode, and after the catalyst (platinum), two electrons in the hydrogen atom are separated out, and these two electrons are attracted to the positive electrode, and the current is generated by an external circuit. Since oxygen can be obtained from the air, the fuel cell can continuously provide electricity as long as hydrogen is continuously supplied to the negative electrode and water (steam) is carried away in time.
Because the fuel cell directly converts the chemical energy of the fuel into electrical energy without going through the combustion process in between, it is not limited by the Carnot cycle. The current fuel cell system has a fuel-electricity conversion efficiency of 45% to 60%, while the efficiency of thermal and nuclear power generation is about 30% to 40%.
