Electric vehicle battery: lithium iron phosphate battery and lithium ternary battery
Lithium iron phosphate battery
It is a lithium ion battery with lithium iron phosphate as the positive electrode material. Its features are free of cobalt and other valuable elements, low raw material price and abundant phosphorus and iron resources in the earth, there will be no material supply problems. Its working voltage is moderate (3.2V), large capacity per unit weight (170mAh/g), high discharge power, fast charging and long cycle life, high stability in high temperature and high heat environment.
Advantages: Compared with lithium cobaltate and lithium manganate batteries, which are common on the market, lithium iron phosphate batteries have at least the following five advantages: higher security, longer service life, no heavy metals and rare metals (low raw material cost), fast charging support, and wide operating temperature range.
Disadvantages: lithium iron phosphate has some performance defects, such as low vibration density and compaction density, resulting in low energy density of lithium ion batteries; The material preparation cost and the battery manufacturing cost is higher, the battery yield is low, the consistency is poor; Poor product consistency; Intellectual property issues.
Ternary polymer lithium battery
Cathode material A lithium battery using a ternary cathode material called lithium Ni-Co manganate (Li (NiCoMn) O2). Ouyang Minggao of Tsinghua University explained that the "ternary" material in this investigation refers to the positive electrode is three, and the negative electrode is a "ternary power battery" as graphite is commonly referred to. And in the actual research and development application, there is a positive electrode is ternary, the negative electrode is lithium titanate, usually known as "lithium titanate", its performance is relatively safe, relatively long life, does not belong to the common said "ternary material."
Advantages: ternary lithium battery has high energy density and better cycle performance than normal lithium cobaltate. At present, with the continuous improvement of formula and structure, the nominal voltage of the battery has reached 3.7V, and the capacity has reached or exceeded the level of lithium cobalt acid battery.
Disadvantages: ternary material power lithium batteries mainly include nickel-cobalt-aluminate lithium batteries, nickel-cobalt-manganate lithium batteries, etc. Due to the unstable high-temperature structure of nickel-cobalt-aluminum, the high temperature safety is poor, and the high pH value is easy to make the monomer flatulence, which leads to danger, and the current high cost.
In contrast, ternary polymer lithium-ion batteries do have the characteristics of being superior to lithium iron phosphate batteries, but why has its development been hindered? The key to the development of new energy vehicles is also the key plaguing mobile digital products -- the development of batteries. How to ensure that battery technology can meet the growing needs of consumers under the condition of safety is not only the automotive technology related industry personnel, but also the pursuit of scientific research workers in the whole field.
When it comes to buying new energy vehicles, most consumers may think of "preferential policies" at the first time, although this is a little embarrassing but it is really quite a real reason. In the domestic sales environment, new energy vehicles to open the situation, not only because of the "environmental protection" such a heavy task and a long sense of mission. The advantages of new energy vehicles in selling price and maintenance cost do attract the majority of consumers at this stage still to the cost of the car.
However, the pace of some consumers may temporarily stop the curiosity of new energy vehicles for some reasons, because how many will be a variety of spontaneous combustion events of new energy vehicles. And that is why I am writing this article today. Must know do not understand the fundamental of the new energy vehicle - the advantages and disadvantages of the energy module, and do not understand the use of the need to pay attention to the matter, in fact, and buy a time bomb on the side and no different.
Lithium iron phosphate batteries: Mature but not enough
Lithium iron phosphate electrode material is currently the safest cathode material for lithium ion batteries, plus its cycle life of more than 2000 times, the standard charge (5-hour rate) use, can reach 2000 times of cycle characteristics, coupled with the maturity of the industry brought by the price and technical threshold and technology decline, so that many manufacturers will use lithium iron phosphate battery for various factors. It can be said that the rise of new energy vehicles, and lithium iron phosphate battery has an inseparable relationship.
However, lithium iron phosphate batteries have a fatal disadvantage: poor performance at low temperatures, which has not been solved even by nano - and carbon-coated batteries. Research shows that a 3500mAh battery, if working in the -10℃ environment, after less than 100 cycles of charge and discharge, the power will be sharply attenuated to 500mAh, basically scrapped. This is not a good thing for our comprehensive national conditions with vast territory and more low temperatures in winter.
In addition, the material preparation cost and the battery manufacturing cost is high, the battery yield is low, the consistency is poor, which is also an important reason for many pure electric vehicles can not reach the nominal value of endurance. Therefore, we can see that there are a lot of new energy vehicles in China (whether pure electric or hybrid electric), or some relatively cheap new energy vehicles, will choose lithium iron phosphate batteries for different reasons. It can be said that the use of lithium iron phosphate batteries plays an indelible role in laying the foundation for the mass production and promotion of new energy vehicles.
In contrast, ternary polymer lithium-ion batteries do have the characteristics of being superior to lithium iron phosphate batteries, but why has its development been hindered?
Ternary polymer lithium Battery: A restless future
Ternary polymer lithium battery refers to the lithium battery which uses ternary positive electrode material nickel-cobalt-manganate lithium (Li (NiCoMn) O2). The precursor product of ternary composite positive electrode material is nickel salt, cobalt salt and manganese salt as raw materials, and the ratio of nickel, cobalt and manganese in it can be adjusted according to actual needs. Ternary lithium batteries are more energy-dense, but their safety is often questioned.
The reason for this is that even though both materials break down at a certain temperature, lithium terpolymer breaks down at a lower temperature of around 200 degrees, and lithium iron phosphate at around 800 degrees. Moreover, the chemical reaction of ternary lithium materials is more intense, which will release oxygen molecules, and the electrolyte will burn rapidly under the action of high temperature, resulting in a chain reaction. To put it simply, ternary lithium is more likely to catch fire than lithium iron phosphate. It‘s important to note, though, that we‘re talking about materials, not finished batteries.
Because of the safety risks of ternary lithium materials, manufacturers are also trying to prevent accidents. According to the characteristics of easy pyrolysis of terpolymer lithium materials, manufacturers will make a lot of efforts in the aspects of over charge protection (OVP), over discharge protection (UVP), over temperature protection (OTP) and over current protection (OCP). Therefore, spontaneous combustion should be more about whether the manufacturer has implemented the functions in these links, rather than simply giving up eating for fear of choking.
So what is the status of these two batteries today? Let‘s focus on one set of statistics. In November last year, 64.9 percent of electric buses were equipped with lithium iron phosphate batteries, while only 27.6 percent were equipped with three-way lithium batteries. In contrast, in the pure electric passenger car market, three-way lithium batteries accounted for more than 76 percent of installed units in November last year.
It can be seen that the advantages of three-way lithium battery with greater energy density should be born as a new energy storage device for future vehicles. And now the occurrence of related safety incidents, in the popularity of new energy vehicles is still in the initial stage, can be called a good thing. In order to achieve the dual goals of occupying the market and obtaining policy support, many new-energy vehicle-related enterprises relax technical requirements and mass-produce energy components that cannot withstand repeated use for a long time. The working environment of automobile is strict, and the reasons for safety accidents will inevitably increase greatly if these parts are used for a long time.
Therefore, we can believe that Zhang Xiangmu, director general of the Equipment Department of the Ministry of Industry and Information Technology, announced to evaluate the safety performance of ternary lithium battery bus at the China Electric Vehicle 100 Meeting, indicating that relevant national departments intentionally defined a standard from the policy level, in order to promote the production of industry standards. Whether for consumers or manufacturers, in the future has a very positive significance. Therefore, there is no need to hesitate because of the one-sided information on the Internet to see the safety accident of three-way lithium battery, materials are dangerous, the key is how to firmly control.
Batteries of different types of new energy vehicles: unified requirements
Finished the situation of the battery, the author thinks that for the situation of new energy vehicles, we also need to briefly introduce the role of the battery in the vehicle. After all, consumers who buy pure electric cars still account for a minority, and more friends are concerned about hybrid electric cars. And hybrids can technically be divided into three types: regular hybrids, plug-in hybrids and extended-range hybrids.
The range of battery capacity in the above three types of vehicles from small to large happens to be ordinary hybrid vehicles < plug-in hybrid vehicles ≤ extended-range hybrid vehicles. The battery of ordinary hybrid electric vehicle is not rechargeable, and the battery is used for starting and rapid acceleration. Plug-in hybrid electric vehicle battery on the basis of ordinary hybrid electric vehicle battery increased capacity and rechargeable, with better acceleration ability and fuel saving ability; The engine of an extended-range hybrid is used to drive a motor to generate electricity, which is more likely to be pure electric vehicles.
These three hybrid electric vehicle modes have their own advantages and disadvantages. At the present stage, the main force is also ordinary hybrid and plug-in hybrid. It is precisely because the characteristics of the three hybrid electric vehicles have the same characteristics in terms of battery life and working environment. Therefore, no matter what model of hybrid electric vehicle is purchased, consumers should pay attention to relevant parameters, such as battery material, operating environment and optimal working condition. At the same time, manufacturers should also strictly control the battery quality and related safety Settings during the design process to ensure the safe and efficient use.
The key to the development of new energy vehicles lies in whether their use experience can match or even surpass the traditional internal combustion engine vehicles, and whether they have more outstanding advantages in the purchase and after-sales links. In the author‘s opinion, the key to the development of new energy vehicles is also the key plaguing mobile digital products -- the development of batteries. How to ensure that battery technology can meet the growing needs of consumers under the condition of safety is not only the automotive technology related industry personnel, but also the pursuit of scientific research workers in the whole field.
