With the rapid increase in the production and sales of new energy vehicles, my country's power lithium battery industry has made considerable progress. The core component of a new energy vehicle is the automobile power lithium battery, which is the energy source of a new energy vehicle, which directly determines the car's cruising range.
Ternary batteries and lithium iron phosphate batteries are the dominant applications in passenger cars and commercial vehicles. At present, passenger car batteries are mainly ternary batteries, and commercial vehicle batteries are mainly lithium iron phosphate batteries.
Classification of new energy batteries:
1. Lead-acid battery
As a relatively mature technology, lead-acid batteries are still the only batteries for electric vehicles that can be mass-produced because of their lower cost and ability to discharge at a high rate. During the Beijing Olympics, there were 20 electric vehicles using lead-acid batteries to provide transportation services for the Olympics.
However, the specific energy, specific power and energy density of lead-acid batteries are very low, and electric vehicles using this as a power source cannot have good speed and cruising range.
2. Nickel-cadmium batteries and nickel-metal hydride batteries
Although it has better performance than lead-acid batteries, it contains heavy metals, which will pollute the environment after being used and abandoned.
Ni-MH power lithium batteries have just entered a mature stage, and are currently the only battery system that has been practically verified, commercialized, and large-scale in the battery system used in hybrid electric vehicles. The current 99% of the market share of the existing hybrid lithium batteries is nickel-metal hydride power lithium. The representative of battery commercialization is Toyota's Prius. At present, the world’s important automotive power lithium battery manufacturers include Japan’s PEVE and Sanyo. PEVE occupies 85% of the global market share of nickel-hydrogen batteries for hybrid power vehicles. At present, important commercial hybrid vehicles such as Toyota’s Prius, Alphard and Estima , And Honda's Civic, Insight, etc. all use PEVE's nickel-hydrogen power lithium battery pack. In my country, Changan Jiexun, Chery A5, FAW Pentium, GM Grand Hyatt and other brand cars have been in demonstration operation. They also use nickel-metal hydride batteries. However, the batteries are mainly purchased from abroad. The use of domestic nickel-metal hydride batteries in automobiles It is still in the R&D matching stage.
3. Lithium-ion battery
Traditional lead-acid batteries, nickel-cadmium batteries and nickel-metal hydride batteries have relatively mature technologies, but their use in automobiles as power lithium batteries has major problems. At present, more and more automobile manufacturers choose to use lithium-ion batteries as the power lithium batteries for new energy vehicles.
Because lithium-ion power lithium batteries have the following advantages: high working voltage (3 times that of nickel-cadmium batteries, hydrogen-nickel batteries); large specific energy (up to 165WH/kg, which is 3 times that of nickel-hydrogen batteries); small size; quality Light; long cycle life; low self-discharge rate; no memory effect; no pollution, etc.
At present, many well-known automakers are committed to the development of power lithium-ion battery vehicles, such as Ford and Chrysler in the United States, Toyota, Mitsubishi, Nissan, Hyundai in South Korea, Courreges and Venture in France. Domestic automakers BYD, Geely, Chery, Lifan, ZTE and other automakers have also equipped their hybrid and pure electric vehicles with power lithium-ion batteries.
The current bottleneck hindering the development of power lithium-ion batteries is: safety performance and the management system of automotive power lithium batteries. In terms of safety performance, due to the high energy density, high working temperature, and harsh working environment of lithium-ion power lithium batteries, coupled with the people-oriented safety concept, users have put forward very high requirements for battery safety. Regarding the management system of automobile power lithium battery, since the working voltage of the automobile power lithium battery is 12V or 24V, and the working voltage of a single power lithium ion battery is 3.7V, it is necessary to increase the voltage by connecting multiple batteries in series, but it is difficult for the battery Achieve completely uniform charging and discharging, so that a single battery in multiple battery packs connected in series will experience unbalanced charging and discharging, and the battery will experience under-charge and over-discharge, and this situation will cause rapid deterioration of battery performance , Eventually lead to the entire set of batteries not working properly, or even scrapped, which greatly affects the service life and reliability of the battery.
Fourth, lithium iron phosphate battery
Lithium iron phosphate battery is also a kind of lithium ion battery, its specific energy is less than half of lithium cobalt oxide battery, but its safety is high, the cycle number can reach 2000 times, the discharge is stable, the price is cheap, and it has become a new vehicle power choose.
The "iron battery" proposed by BYD, the industry believes that it is more likely to be a lithium iron phosphate battery.
Five, fuel power battery
Simply put, a fuel cell (FuelCell) is a power generation device that directly converts the chemical energy in the fuel and oxidizer into electrical energy. Fuel and air are fed into the fuel power cell separately, and electricity is magically produced. It looks like an accumulator with positive and negative poles and electrolytes from the outside, but in fact it cannot "storage" but is a "power plant".
The most promising one for automobiles is the proton exchange membrane fuel power cell. Its working principle is: send hydrogen to the negative electrode, after the use of a catalyst (platinum), two electrons in the hydrogen atom are separated, and these two electrons are attracted by the positive electrode, and a current flows through the external circuit, and the hydrogen loses the electrons. Ions (protons) can pass through the proton exchange membrane (solid electrolyte) and recombine with oxygen atoms and electrons to form water at the positive electrode. Since oxygen can be obtained from the air, as long as the negative electrode is continuously supplied with hydrogen and the water (steam) is taken away in time, the fuel power cell can continuously supply electric energy.
Because the fuel power cell directly converts the chemical energy of the fuel into electrical energy, without going through the combustion process, it is not restricted by the Carnot cycle. At present, the fuel-electricity conversion efficiency of the fuel power battery system is 45% to 60%, while the efficiency of thermal power and nuclear power is about 30% to 40%.