The power batteries used in new energy vehicles mainly include lead-acid batteries, nickel hydrogen batteries, lithium batteries, and hydrogen fuel cells.
At present, lithium batteries have significant advantages in energy density, lifespan, and environmental performance, making them the preferred choice for power batteries.
The earliest use of lead-acid batteries in pure electric vehicles was lead-acid batteries, which were made of lead and its oxides as electrode materials, and sulfuric acid solution as electrolyte. This is now the power source for most electric vehicles, and low cost is its biggest advantage.
But it has two major drawbacks; Firstly, it has a lower specific energy, occupies too much mass and volume, and has a shorter driving range on a single charge; Another issue is the short service life and high usage cost.
Nickel hydrogen battery is a new type of green battery developed in the 1990s, which has the characteristics of high energy, long lifespan, and no pollution.
Compared to lead-acid batteries, nickel hydrogen batteries have significant improvements, and the electrolyte is non flammable with guaranteed safety. The manufacturing process is mature.
However, nickel hydrogen batteries have average charging efficiency and cannot be charged quickly under high voltage. Therefore, since lithium batteries have been widely used, there is a trend for nickel hydrogen batteries to be completely replaced in automobiles.
Lithium batteries are the mainstream choice for new energy vehicles at present. Lithium compounds (such as lithium manganese oxide and lithium iron phosphate) are used as electrode materials, while graphite is used as negative electrode material. Its advantages lie in light weight, large energy storage, no pollution, no memory effect, and long service life.
Under the same volume and weight conditions, the storage capacity of lithium batteries is 1.6 times that of nickel hydrogen batteries, and humans have only developed and utilized 20% to 30% of their theoretical electricity. The development prospects are very promising.
However, regardless of the type, all lithium battery packs will face the natural enemy of low temperatures.
Hydrogen fuel cell hydrogen is an ideal clean energy source.
The characteristics are pollution-free, noise free, and high efficiency. In terms of hydrogen itself, combustion can release a large amount of energy, with excellent low-temperature performance. The most important thing is the high efficiency of hydrogenation, which can travel over 600 kilometers in just 5 minutes.
And there is still room for improvement in this data, all of which are far superior to existing lithium batteries.
However, hydrogen fuel cell cars weigh over 200 kilograms and are more than 5 times more expensive than similar internal combustion engine cars.
Regarding the investment in hydrogen fuel cell vehicles, car companies in Japan and South Korea have long started researching and have now invested in their respective markets on a small scale.
The biggest cost of expanding information for new energy vehicles lies in the three major electrical systems of battery, motor, and electronic control, with the cost of power batteries being of utmost importance.
From the cost composition of new energy vehicles, the total proportion of power systems is about 50%, with batteries accounting for 38% and electronic control and motors accounting for about 12%.
At present, there are two main types of mainstream power batteries: ternary lithium batteries and lithium iron phosphate batteries.
However, the vast majority of newly launched electric vehicles on the market currently use ternary lithium batteries, mainly because the energy density of ternary lithium batteries is much higher than that of lithium iron phosphate.
However, from the perspectives of safety and reusability, the performance of lithium iron phosphate batteries is superior to that of ternary lithium batteries.
Among the 8 batches of 296 new energy passenger cars announced by the Ministry of Industry and Information Technology in 2017, 221 models used ternary lithium batteries, while only 33 models used lithium iron phosphate.
1. Lead acid batteries, as a relatively mature technology, are still the only electric vehicle batteries available for mass production due to their low cost and ability to discharge at high rates.
During the Beijing Olympics, there were 20 electric vehicles using lead-acid batteries to provide transportation services for the Olympics.
However, lead-acid batteries have low specific energy, specific power, and energy density, making it impossible for electric vehicles powered by them to have good speed and range.
2. Although nickel cadmium batteries and nickel hydrogen batteries perform better than lead-acid batteries, they contain heavy metals and can cause environmental pollution when discarded.
Nickel hydrogen power batteries have just entered a mature stage and are currently the only battery system used in hybrid vehicles that has been practically validated, commercialized, and scaled up. Currently, 99% of the market share of hybrid batteries is nickel hydrogen power batteries, with Toyota’s Prius being the representative of commercialization.
The main global automotive power battery manufacturers include Japan’s PEVE and Sanyo, with PEVE accounting for 85% of the global market share of nickel hydrogen batteries for Hybrid power vehicles. Currently, major commercial hybrid vehicles such as Toyota’s Prius, Alphard, and Estima, as well as Honda’s Civic and Insight, all use PEVE’s nickel hydrogen power battery packs.
In China, brands such as Changan Jiexun, Chery A5, FAW Pentium, and General Motors Grand Hyatt have already demonstrated their use of nickel hydrogen batteries. However, batteries are mainly purchased from abroad, and the application of domestic nickel hydrogen batteries in automobiles is still in the research and development matching stage.
3. Traditional lead-acid batteries, nickel cadmium batteries, and nickel hydrogen batteries have relatively mature technologies, but they have significant problems when used as power batteries in automobiles.
Currently, more and more car manufacturers are choosing to use lithium batteries as the power batteries for new energy vehicles.
Because lithium-ion power batteries have the following advantages: high operating voltage (three times that of nickel cadmium hydrogen nickel batteries); Higher specific energy (up to 165WH/kg, three times that of hydrogen nickel batteries); Small volume; Lightweight; Long cycle life; Low self discharge rate; No memory effect; No pollution, etc.
In terms of safety performance, due to the 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 for automotive power batteries, the working voltage of automotive power batteries is 12V or 24V.
The working voltage of a single power lithium-ion battery is 3.7V, so multiple batteries must be connected in series to increase the voltage. However, due to the difficulty of achieving completely uniform charging and discharging, a single battery in multiple battery packs connected in series may experience unbalanced charging and discharging.
Batteries may experience under charging and over discharging, which can lead to a sharp deterioration in battery performance, ultimately resulting in the inability of the entire set of batteries to function properly or even be scrapped, greatly affecting the battery’s service life and reliability performance.
The main types of power batteries used in new energy vehicles are lithium-ion batteries, nickel hydrogen batteries, fuel cells, lead-acid batteries, and supercapacitors.
1. Lead acid batteries: Lead acid batteries have a history of over 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 drawbacks; Firstly, it has a lower specific energy, occupies too much mass and volume, and has a shorter driving range on a single charge; Another issue is the short service life and high usage cost.
2. Nickel hydrogen batteries: Nickel hydrogen batteries belong to alkaline batteries, which have a longer cycle life and no memory effect, but are relatively expensive.
The main foreign companies producing nickel hydrogen batteries for electric vehicles are a joint venture between Ovonie, Toyota, and Panasonic.
Ovonie currently 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 over 600 times.
This type of battery has been tested on several types of electric vehicles, one of which can travel 345km on a single charge, and one vehicle has traveled over 80000 kilometers in a year.
Due to high prices, large-scale production has not yet been carried out.
55A · h and 100A · h unit batteries with a specific energy of 65 W · h/kg and a power density greater than 800 W/kg have been developed domestically.
3. Lithium ion batteries: As a new type of rechargeable battery with high voltage and high energy density, lithium-ion secondary batteries have unique physical and electrochemical properties and broad prospects for civil and national defense applications.
Its outstanding characteristics are: light weight, large energy storage, no pollution, no memory effect, and long service life.
Under 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. Moreover, humans have only developed and utilized 20% to 30% of their theoretical electricity, making the development prospects very promising.
At the same time, it is a truly green and environmentally friendly battery that will not cause pollution to the environment, and is currently the best battery that can be applied to electric vehicles.
China has been developing and utilizing lithium-ion batteries since the 1990s, and has made breakthrough progress to date, developing lithium-ion batteries that fully possess independent intellectual property rights.
4. Nickel cadmium batteries: The application of cadmium batteries is second only to lead-acid batteries, with a specific energy of up to 55W · h/kg and a specific power of over 190W/kg.
It can be charged quickly and has a longer cycle life, which is more than twice that of lead-acid batteries and can reach over 2000 times, but its price is 4-5 times that of lead-acid batteries.
Although its initial purchase cost is high, its long-term actual usage cost is not high due to its advantages in energy and service life.
The disadvantage is the memory effect, which can easily lead to a decrease in the available capacity of the battery due to poor charging and discharging.
After using it for about ten times, complete charging and discharging should be performed once. If there is already a “memory effect”, complete charging and discharging should be performed continuously for 3-5 times to release memory.
In addition, cadmium is toxic, and it is important to ensure proper recycling during use to avoid environmental pollution caused by cadmium.
5. Sodium sulfur battery: The advantages of sodium sulfur battery are: one is its high specific energy.
Its theoretical specific energy is 760W · h/kg, but in reality it has exceeded 100W · h/kg, which is 3-4 times that of lead-acid batteries; The other is capable of high current and high-power discharge.
Its discharge current density can generally reach 200-300A/mm2, and it can instantly release three times its inherent energy; Another factor is high charging and discharging efficiency.
Due to the use of solid electrolytes, there are no self discharge and side reactions commonly found in liquid electrolyte secondary batteries, and the charging and discharging current efficiency is almost 100%.
The disadvantage of sodium sulfur batteries is that their operating temperature is mainly between 300-350 ℃, so certain heating and insulation are required during battery operation.
However, high temperature corrosion is severe, and the battery life is relatively short.
High performance vacuum insulation technology has been adopted to effectively solve this problem.
There are also issues such as poor performance stability and usage safety.
1. Lead acid batteries, as a relatively mature technology, are still the only electric vehicle batteries available for mass production due to their low cost and ability to discharge at high rates. During the Beijing Olympics, there were 20 electric vehicles using lead-acid batteries to provide transportation services for the Olympics. However, lead-acid batteries have low specific energy, specific power, and energy density, making it impossible for electric vehicles powered by them to have good speed and range. 2. Although nickel cadmium batteries and nickel hydrogen batteries perform better than lead-acid batteries, they contain heavy metals and can cause environmental pollution when discarded. Nickel hydrogen power batteries have just entered a mature stage and are currently the only battery system used in hybrid vehicles that has been practically validated, commercialized, and scaled up. Currently, 99% of the market share of hybrid batteries is nickel hydrogen power batteries, with Toyota’s Prius being the representative of commercialization. The main global automotive power battery manufacturers include Japan’s PEVE and Sanyo, with PEVE accounting for 85% of the global market share of nickel hydrogen batteries for Hybrid power vehicles. Currently, major commercial hybrid vehicles such as Toyota’s Prius, Alphard, and Estima, as well as Honda’s Civic and Insight, all use PEVE’s nickel hydrogen power battery packs. In China, brands such as Changan Jiexun, Chery A5, FAW Pentium, and General Motors Grand Hyatt have already demonstrated their use of nickel hydrogen batteries. However, batteries are mainly purchased from abroad, and the application of domestic nickel hydrogen batteries in automobiles is still in the research and development matching stage. 3. Traditional lead-acid batteries, nickel cadmium batteries, and nickel hydrogen batteries have relatively mature technologies, but they have significant problems when used as power batteries in automobiles. Currently, more and more car manufacturers are choosing to use lithium batteries as the power batteries for new energy vehicles. Because lithium-ion power batteries have the following advantages: high operating voltage (three times that of nickel cadmium hydrogen nickel batteries); Higher specific energy (up to 165WH/kg, three times that of hydrogen nickel batteries); Small volume; Lightweight; Long cycle life; Low self discharge rate; No memory effect; No pollution, etc.
New energy vehicles refer to vehicles that use unconventional vehicle fuels as power sources (or use conventional vehicle fuels and new onboard power devices), integrate advanced technologies in vehicle power control and driving, and form advanced technical principles, new technologies, and new structures. New energy vehicles include four types: hybrid electric vehicles (HEVs), pure electric vehicles (BEVs, including solar powered vehicles), fuel cell electric vehicles (FCEVs), and other new energy vehicles (such as supercapacitors, flywheels, and other high-efficiency energy storage devices). The promotion of new energy vehicles is to meet the needs of environmental protection and oil crisis, and to reduce or abandon the current mainstream models of traditional gasoline or diesel driven internal combustion engines
