Ternary lithium battery cycle life

Mar 27, 2019   Pageview:234

 Energy is the cornerstone of social science and technology development. At present, with the increasing global pollution, energy conservation and environmental protection has become the top priority of social development. At present, China vigorously promotes environmental protection and has introduced some related policies. Therefore, environmental protection in the market has more and more equipment. Including the reduction of gasoline vehicles, the market launch of new energy vehicles, and products such as charging treasures are all environmentally friendly batteries. That is, lithium batteries, lithium batteries, compared with the traditional lead acid point, have a short charging time, long cycle life, energy saving and environmental protection, no pollution, light weight, long service life and other characteristics. Said that it has a long life, can it be several years?


 The ternary lithium battery is a lithium battery with a positive electrode material of three yuan. The lithium iron phosphate crystal has stable chemical properties, and in actual use, it will not be hot or explode even in the case of over-charging or high temperature. The cycle life of lead-acid batteries can also reach 500 times, and the cycle life of ternary lithium batteries can reach more than 1000 times, which far exceeds that of lead-acid batteries.


 Calculated according to the battery cycle of ternary battery for 1000 times, the battery is fully charged and discharged in three days, and the service life reaches 8.3 years. Even if there is a loss process, it can reach more than 7 years.


 The depreciation rate of lead-acid batteries is fast and requires constant maintenance. * Long-term use time is no more than one and a half years. In contrast, the life of a ternary lithium battery can reach 7 years under the same conditions. The ternary lithium battery adapts to a wide operating temperature, and its electric heating peak can reach 350 ° C -500 ° C. Compared with ordinary lead-acid batteries, its energy storage capacity is stronger, and its materials are relatively lighter.


The ternary lithium battery does not contain any rare earth metals and heavy metals, and is environmentally friendly. It is a new type of green battery. However, ternary lithium batteries also have their own shortcomings, such as poor performance in low temperature environment, volume is greater than the lead-acid battery under the same conditions, so there must be a big gap in the development of micro-batteries.


 As a rechargeable lithium battery, the ternary lithium battery has stable output voltage, high output voltage, stable performance, large capacity, long service life, wide operating temperature range, good safety and environmental protection, so it has a future development path for lithium batteries. There is a lot of room for improvement, but it needs to be continuously researched in order to achieve the goal of improving its own defects.


 Lithium iron phosphate battery: refers to a lithium ion battery using lithium iron phosphate as a positive electrode material. Its characteristic is that it does not contain precious elements such as cobalt. The raw material price is low and phosphorus and iron are abundant in the earth's resources, and there is no problem of feeding. Its working voltage is moderate (3.2V), its capacity per unit weight is large (170mAh/g), high discharge power, fast charging and long cycle life, high stability under high temperature and high heat environment.


 Advantages Compared with the more common lithium cobalt oxide and lithium manganate batteries currently on the market, lithium iron phosphate batteries have at least five advantages: higher safety, longer service life, and no heavy metals and rare metals ( Low raw material cost), fast charging and wide operating temperature range.


 Disadvantages Lithium iron phosphate has some performance defects, such as low tap density and compaction density, resulting in low energy density of lithium ion battery; material preparation cost and battery manufacturing cost are high, battery yield is low, consistent Poor sex; poor product consistency; intellectual property issues.


 Ternary polymer lithium battery: A lithium battery of a lithium lanthanum manganese oxide (Li(NiCoMn)O2) ternary positive electrode material is used as a positive electrode material. According to Tsinghua University Ouyang Minggao: The "three yuan" material referred to in this survey refers to the "three- dimensional power battery" in the usual saying that the positive electrode is ternary and the negative electrode is graphite . In actual research and development applications, there is also a positive electrode is ternary, the negative electrode is lithium titanate, commonly known as "lithium titanate", its performance is relatively safe, long life, not the common saying "three yuan material."


 Advantages The ternary lithium battery has high energy density and better cycle performance than normal lithium cobaltate. At present, with the continuous improvement of the formula and the perfect structure, the nominal voltage of the battery has reached 3.7V, and the capacity has reached or exceeded the level of lithium cobalt oxide battery.


 Disadvantages ternary material power lithium battery mainly includes nickel-cobalt-aluminum lithium battery, nickel-cobalt-manganese lithium battery, etc., due to the high temperature structure of nickel-cobalt aluminum, the high-temperature safety is poor, and the pH value is too high, so that the monomer is flatulent. This raises danger and is currently costly.


 In contrast, the ternary polymer lithium battery does have a better quality than the lithium iron phosphate battery, but why is its development hindered? The key to the development of new energy vehicles is also the key to the mobile digital products - the development of batteries. How to ensure that battery technology can meet the growing needs of consumers in a safe situation, not only in the automotive industry-related industry, but also in the pursuit of scientific research workers in the whole field.


 When it comes to buying new energy vehicles, most consumers may think of "policy concessions" for the first time. Although this is a bit embarrassing, it is indeed quite a real reason. In the domestic sales environment, new energy vehicles need to open up the situation, not only because of the long-term mission of “environmental protection”. The advantages of new energy vehicles in terms of selling price and maintenance cost have indeed attracted most of the consumers who still use car-based costs at this stage.


 However, some consumers may stop their curiosity about new energy vehicles for some reason, because it will be overwhelmed by the various spontaneous combustion events of new energy vehicles. And this is why I wrote this article today. You must know that you don't understand the fundamentals of new energy vehicles - the advantages and disadvantages of energy modules, and if you don't understand the things you need to pay attention to during use, it is no different from buying a time bomb.


 Lithium iron phosphate battery: mature but not enough


 Lithium iron phosphate electrode material is currently the safest lithium ion battery cathode material, and its cycle life is more than 2000 times. Standard charging (5 hour rate) can be used to achieve 2000 cycles, coupled with industrial maturity. The resulting price threshold and technology decline have led many manufacturers to use lithium iron phosphate batteries for various reasons. It can be said that the rise of new energy vehicles has an inseparable relationship with lithium iron phosphate batteries.


 However, lithium iron phosphate batteries have a fatal disadvantage, that is, poor low temperature performance, even if they are nano-sized and carbon coated, this problem is not solved. Studies have shown that a battery with a capacity of 3500 mAh, if operated in a -10 ° C environment, after less than 100 charge and discharge cycles, the power will be abruptly attenuated to 500 mAh, basically scrapped. This is indeed not a good thing for China, which has a vast territory and a relatively low temperature in winter.


 In addition, the preparation cost of the material and the manufacturing cost of the battery are high, the battery yield is low, and the consistency is poor, which is also an important reason that the endurance of many pure electric vehicles cannot reach the nominal value. Therefore, we can see that there are quite a few new energy vehicles in China (whether pure electric or hybrid electric), or some relatively cheap new energy vehicles, which will choose lithium iron phosphate batteries for different reasons. It can be said that the use of lithium iron phosphate batteries has an indelible foundation for the mass production and promotion of new energy vehicles.


 In contrast, the ternary polymer lithium battery does have a better quality than the lithium iron phosphate battery, but why is its development hindered?


Ternary polymer lithium battery: the future of restlessness


The ternary polymer lithium battery refers to a lithium battery using a nickel-cobalt-manganese hydride (Li(NiCoMn)O2) ternary positive electrode material for the positive electrode material, and a ternary composite positive electrode material precursor product, which is a nickel salt, a cobalt salt, and a manganese salt. As raw materials, the ratio of nickel-cobalt-manganese can be adjusted according to actual needs. Ternary lithium batteries have higher energy density, but safety is often suspect.


 The reason for this is that even if both materials decompose when they reach a certain temperature, the ternary lithium material will decompose at a lower temperature of about 200 degrees, and the lithium iron phosphate material is around 800 degrees. Moreover, the chemical reaction of the ternary lithium material is more intense, and oxygen molecules are released, and the electrolyte rapidly burns under the action of high temperature, and a chain reaction occurs. To put it simply, the ternary lithium material is more likely to catch fire than the lithium iron phosphate material. However, it should be noted that we are referring to materials, not batteries that have become finished products.


 Because ternary lithium materials have such safety hazards, manufacturers are also trying to stop the direction of accidents. According to the easy pyrolysis characteristics of ternary lithium materials, manufacturers will have a lot of problems in over-charge protection (OVP), over-discharge protection (UVP), over-temperature protection (OTP), and over-current protection (OCP). Therefore, the spontaneous combustion incident should be more about whether the function of the manufacturers in these links is in place, rather than simply squandering food.


 So what is the current use of these two batteries? Let's focus on a set of data. In November last year, the installed capacity of electric bus for lithium iron phosphate battery accounted for 64.9%, and the installed capacity for ternary lithium battery was only 27.6%. In contrast, in the pure electric passenger vehicle market, the installed capacity of the ternary lithium battery in November last year exceeded 76%.


 It can be seen that the advantage of the higher energy density of the ternary lithium battery itself should be born as a new energy storage device for the future automobile. Now that the relevant security incidents occur, it is a good thing when the popularity of new energy vehicles is still in its infancy. In order to achieve the dual goals of seizing the market and obtaining policy support, many new energy vehicle-related enterprises have relaxed technical requirements and mass-produced energy components that cannot withstand repeated use for a long time. The environment in which a car works is harsh. When these parts are used for a long time, the cause of a safety accident is inevitably greatly increased.


 Therefore, we can think that Zhang Xiangmu, director of the Equipment Department of the Ministry of Industry and Information Technology, has issued an assessment on the safety performance of the ternary lithium battery bus. It is the intention of the relevant state departments to define a standard from the policy level. To promote the emergence of industry standards. Whether it is for consumers or manufacturers, it has a very positive meaning in the future. Therefore, there is no need to see the safety accident news of the ternary lithium battery on the Internet one-sidedly, the materials are dangerous, the key is how to firmly control.


 Batteries for different types of new energy vehicles: uniform requirements


 After talking about the battery, I believe that for the situation of new energy vehicles, we need to briefly introduce the role of the battery in the vehicle. After all, consumers who buy pure electric vehicles still account for a small number, and more friends are concerned about hybrid vehicles. Hybrid vehicles can be divided into three types: ordinary hybrid vehicles, plug-in hybrid vehicles and extended-range hybrid vehicles.


 In the above three types of cars, the arrangement of the battery capacity from small to large is just an ordinary hybrid vehicle < plug-in hybrid vehicle extended-range hybrid vehicle. The batteries of ordinary hybrid vehicles are not rechargeable, the batteries are used for starting and rapid acceleration; the batteries of plug-in hybrid vehicles are increased in capacity and rechargeable on the basis of ordinary hybrid vehicle batteries, with better acceleration and fuel economy. Capability; while the engine of the extended-mix hybrid car is used to drive the motor to generate electricity, and is more inclined to pure electric vehicles.


 These three hybrid vehicle models have their own advantages and disadvantages. At this stage, the main force is also based on ordinary hybrid power and plug-in hybrid power. Because the characteristics of the three hybrid vehicles have something in common for battery life and working environment, consumers should pay attention to relevant parameters, such as battery material and environment, regardless of the model of hybrid vehicle. And the best working conditions, etc. At the same time, manufacturers should strictly control battery quality and related security settings during the design process to ensure safe and efficient use.


 The key to the development of new energy vehicles is whether their experience can rival or even surpass the traditional internal combustion engine vehicles, and whether there is a better advantage in the purchase and after-sales links. In my opinion, the key to the development of new energy vehicles is also the key to the development of mobile digital products - the development of batteries. How to ensure that battery technology can meet the growing needs of consumers in a safe situation is not only the automotive industry-related industry personnel, but also the pursuit of scientific research workers in the whole field.