The core component of a new energy vehicle is the vehicle power battery, which is the energy source of the new energy vehicle, which directly determines the cruising range of the vehicle.
Ternary batteries and lithium iron phosphate batteries are the dominant applications in the field of passenger cars and commercial vehicles. At present, passenger car batteries are dominated by ternary batteries, and commercial vehicle batteries are dominated by 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 battery for electric vehicles that can be mass-produced due to their low cost and high-rate discharge capability. 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 a good speed and cruising range.
2. NiCd and NiMH batteries
Although its performance is better than that of lead-acid batteries, it contains heavy metals, which will pollute the environment after being used and abandoned.
Ni-MH power battery has just entered the mature stage, and it is the only battery system that has been actually verified and commercialized and scaled in the current hybrid electric vehicle. The representative of this is Toyota’s Prius. At present, the world’s major automotive power battery manufacturers mainly include Japan’s PEVE and Sanyo. PEVE occupies 85% of the global market share of nickel-metal hydride batteries for hybrid power vehicles. At present, the main commercialized hybrid vehicles such as Toyota’s Prius, Alphard and EsTIma, And Honda’s Civic, Insight, etc. all use PEVE’s nickel-metal hydride power battery pack. In my country, Changan Jiexun, Chery A5, FAW Bestune, GM Grand Hyatt and other brand sedans are already in demonstration operation. They also use nickel-hydrogen batteries, but the batteries are mainly purchased from abroad, and domestic nickel-hydrogen batteries are used in automobiles. Still in the R&D matching stage.
3. Lithium battery
Traditional lead-acid batteries, nickel-cadmium batteries and nickel-metal hydride batteries are relatively mature in technology, but there are major problems when they are used as power batteries in automobiles. At present, more and more car manufacturers choose to use lithium batteries as power batteries for new energy vehicles.
Because lithium-ion power batteries have the following advantages:
High working voltage (three times that of nickel-cadmium batteries); high specific energy (up to 165WH/kg, three times that of nickel-hydrogen batteries);
light in mass;
Long cycle life;
Low self-discharge rate;
no memory effect;
No pollution, etc.
The current bottlenecks hindering the development of power lithium-ion batteries are: safety performance and the management system of automotive power batteries.
In terms of safety performance, due to the reasons of high energy density, high working temperature and harsh working environment of lithium-ion power batteries, coupled with the people-oriented safety concept, users have put forward very high requirements for the safety of batteries. In terms of the management system of the automobile power battery, since the working voltage of the automobile power battery is 12V or 24V, and the working voltage of a single power lithium-ion battery is 3.7V, the voltage must be increased by connecting multiple batteries in series. The charge and discharge are completely uniform, so that the single battery in the multiple battery packs connected in series will be unbalanced in charge and discharge, the battery will be undercharged and overdischarged, and this situation will lead to a sharp deterioration of the battery performance. As a result, the entire battery pack cannot work normally or even be scrapped, thus greatly affecting the service life and reliable performance of the battery.
4. Lithium iron phosphate battery
Lithium iron phosphate battery is also a kind of lithium battery, its specific energy is less than half of that of lithium cobalt oxide battery, but its safety is high, the number of cycles can reach 2000 times, the discharge is stable, and the price is cheap. It has become a new choice for vehicle power.
The “iron battery” proposed by BYD, the industry believes that it is more likely to be a lithium iron phosphate battery.
5. Fuel cells
Fuel Cell is a power generation device that converts chemical energy in fuel and oxidant directly into electrical energy.
The fuel and air are fed separately into the fuel cell, and electricity is magically produced. It looks like a battery from the outside with positive and negative electrodes and electrolytes, but in essence it cannot “storage electricity” but a “power plant”.
The most promising for automotive use are proton exchange membrane fuel cells.
Its working principle is: hydrogen is sent to the negative electrode, and through the action of a catalyst (platinum), two electrons in the hydrogen atom are separated, and these two electrons are attracted by the positive electrode to generate current through an external circuit, and the hydrogen that loses electrons The ions (protons) can pass through the proton exchange membrane (i.e. the 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 hydrogen is continuously supplied to the negative electrode and water (steam) is taken away in time, the fuel cell can continuously provide electricity.
Because the fuel cell directly converts the chemical energy of the fuel into electrical energy, without going through the combustion process, it is not limited by the Carnot cycle. At present, the fuel-electricity conversion efficiency of the fuel cell system is 45% to 60%, while the efficiency of thermal power generation and nuclear power is about 30% to 40%.
6. Solid State Battery
The solid-state battery has also entered the field of vision of most people. In fact, it is the same as the current liquid lithium battery in principle. The biggest difference is that the electrolyte becomes a solid state, and more charged ions are gathered in the density and structure advantages. At one end, a larger current can be conducted, so the battery capacity is greatly improved.
There are two most notable features of solid-state batteries. One is high energy density. Many laboratories have achieved 300-400Wh/kg, which is 2.5-3 times that of traditional lithium batteries. It avoids the burning hazard caused by accidents such as battery rupture or high temperature.
Solid-state batteries also have shortcomings, that is, the overall low conductivity, large internal resistance, and slow charging speed. As for how the American Fisker car can charge for 1 minute and have a range of 800 kilometers, that is its core secret.
New energy battery: deep cycle lithium iron phosphate battery