How long can the lithium battery be used in electric car?

During the sintering process in the preparation of lithium iron phosphate, iron oxide is likely to be reduced to elemental iron under a high temperature reducing atmosphere. Elemental iron can cause micro short circuit of the battery, which is the most taboo substance in the battery. This is also the main reason why Japan has not used this material as a positive electrode material for a lithium-ion battery . 2. There are some performance defects in lithium iron phosphate, such as low tap density and compaction density, resulting in low energy density of lithium ion batteries. Low temperature performance is poor, even if it is nano-sized and carbon coated, this problem is not solved. 3. The preparation cost of the material and the manufacturing cost of the electricity are high, the battery yield is low, and the consistency is poor. The nano-crystallization and carbon coating of lithium iron phosphate, while improving the electrochemical performance of the material, also brings other problems such as a decrease in energy density, an increase in synthesis cost, poor electrode processing performance, and environmentally demanding problems. Although the chemical elements Li, Fe and P in lithium iron phosphate are abundant and the cost is low, the cost of the prepared lithium iron phosphate product is not low, even if the previous research and development cost is removed, the process cost of the material is higher. The cost of preparing the battery will make the cost of the final unit of stored energy higher. 4. Poor product consistency. At present, there is no domestic lithium iron phosphate material factory that can solve this problem. From the viewpoint of material preparation, the synthesis reaction of lithium iron phosphate is a complex heterogeneous reaction, which has solid phase phosphate, iron oxide and lithium salt, a carbon precursor and a reducing gas phase. In this complex reaction process, it is difficult to ensure the consistency of the reaction. However, the PO bond in the lithium iron phosphate crystal is stable and difficult to decompose, and does not collapse or heat like a lithium cobaltate or form a strong oxidizing substance even at a high temperature or overcharge, and thus has good safety. It has been reported that in the actual operation, a small part of the sample was found to have a burning phenomenon in the acupuncture or short circuit test, but there was no explosion event. In the overcharge experiment, a high voltage charge that was several times higher than the self-discharge voltage was used, and it was found that there was still Explosion phenomenon. Even so, its overcharge safety has been greatly improved compared to the ordinary liquid electrolyte lithium cobalt oxide battery . In addition, lithium iron phosphate battery generally considered to be free of any heavy metals and rare metals (Ni-MH batteries need rare metals), non-toxic, non-polluting, in line with European RoHS regulations, is an absolute green battery certificate. Since 2015, there have been eight spontaneous electric buses and hybrid buses in the country, and the problem of battery safety has once again been pushed to the cusp. In the existing battery safety incidents reported, there are many reasons for this: there are various factors such as battery leakage, battery short circuit, overcharge and so on. Battery safety should not only be for lithium iron phosphate or ternary batteries. The types are discussed. Tesla uses aluminum cobalt oxide. The safety characteristics of materials are evaluated from the material point of view. It is worse than the ternary batteries produced by many domestic manufacturers, but Tesla guarantees the safe use of the battery system from the battery PACK level. Proof is also ok, so safety is to be evaluated from multiple dimensions. From the perspective of the vehicle system, it can be considered that the safety of the PACK level is more reasonable and objective than the safety of the material system of the battery itself. From the perspective of industrial guidance, the application of advanced technology should be encouraged. Only the emergence of better cost-effective batteries with better power density characteristics and energy density characteristics can better support the development of the new energy automobile industry. To improve the energy density of lithium-ion batteries, there are the following methods: 1. Increase the proportion of positive active materials: lithium ions as an energy carrier, lithium ions can cross the separator to the negative electrode to participate in the reaction, but the proportion of lithium ions in the positive electrode is less than 1%. The rest are lithium oxides, so it is necessary to increase the proportion of the positive active material. 2. Increasing the ratio of the active material of the negative electrode: in order to cope with the increase in the concentration of the lithium ion of the positive electrode, the irreversible chemical reaction is avoided to cause the energy density to decay. 3. Increasing the reactivity of the positive electrode material: increasing the proportion of the positive electrode lithium ion participating in the negative electrode chemical reaction, however, the ratio of the positive electrode active material has an upper limit, so the study of a new positive electrode material is a method for increasing the reactivity of the material. 4. Improve the reactivity of the anode material: This is not the main solution, but it can solve the problem of the quality of the anode material. The anode is mostly graphite, which can be changed to a new anode material or a carbon nanotube to enhance the efficiency of the reaction. . 5. Other parts of the weight loss to improve efficiency. As for the improvement of the charge and discharge rate, the method is as follows: 1. Improve the diffusion ability of the positive and negative ions: the positive and negative active materials are as thin as possible, and have sufficient and uniform pores inside the active material to facilitate the passage of ions. 2. Improve the ionic conductivity of the electrolyte: to speed up the exchange of lithium ions between the positive and negative electrodes. 3. Reduce the internal resistance of the battery. The factors affecting the lifespan of various types of lithium batteries are similar. Finally, there are two points for everyone to think about. First, the needs of consumers are endless. It is best to be a fool, as long as we give us the best battery. Second, the battery must first improve the "positive material" to think, to get to the bottom. It is still the best solution in the "interface".

With electric vehicles every day, do you know how long the life of electric vehicle lithium batteries is? Lithium-ion battery can only charge and discharge 500 times, right? I believe that most consumers have heard that the life of lithium batteries is "500 times" and 500 times of charge and discharge. More than this number of times, the battery will be "dying down". Many friends are trying to extend the life of the battery every time. Charging when the battery is completely exhausted, does this really extend the life of the battery? The answer is negative. The life of a lithium battery is "500 times", which means not the number of times of charging, but a period of charging and discharging.

A charge cycle means that all of the battery's charge is from full to empty, and then from empty to full, which is not the same as charging. For example, a lithium battery used only half of the power on the first day, and then charged it slowly. If it is still the next day, it will be charged in half, and it will be charged twice in total. This can only be counted as one charging cycle, not two. Therefore, it is usually possible to complete a cycle after several charges. The battery capacity is reduced a little every time a charge cycle is completed. However, this amount of power is very small, and high-quality batteries will retain 80% of the original capacity after many cycles. Many lithium-powered products will still be used after two or three years. Of course, the lithium battery life needs to be replaced after the end. The so-called 500 times means that the manufacturer has achieved 625 times of chargeable times at a constant depth of discharge, reaching 500 charge cycles. Due to the various effects of real life, especially the depth of discharge during charging is not constant, the "500 charging cycles" can only be used as a reference battery life.

The life of lithium-ion batteries on ordinary electronic products is about 5 to 20 years, with an average of 8 years. At the current state of the art, lithium-ion batteries have a service life of only about 3-5 years on electric vehicles. When the battery capacity on the electric vehicle is reduced to less than 80% of the initial capacity, the driving range of the electric vehicle will be significantly reduced. When the battery capacity is reduced to less than 70%, the battery must be replaced. For many of today's pure electric vehicles, the cost of the battery is about 40% of the total cost of the car. That is to say, replacing the battery is equivalent to changing the car by half. The reason why the battery life of electric vehicles is short is due to the influence of working environment and large-scale charging and discharging. In terms of working environment, the operation of electric vehicle batteries in high temperature or low temperature will have an impact on the life of lithium batteries. This effect is generally uncontrollable. After all, the external environment of driving is less selective.

The Australian Commonwealth Scientific and Industrial Research Organization published a research report saying that a simple method to extend the life of rechargeable lithium batteries, the agency named this method "salt bath." According to the researchers, the material they use is an ionic liquid, also known as a normal temperature molten salt. It is a transparent, colorless, odorless, and flame retardant liquid that forms a surface on the electrode surface. It is a protective film that keeps the battery stable during application. The process and principle of processing the battery is that the lithium metal electrode is immersed in the mixed electrolyte containing the ionic liquid and the lithium salt before the battery is assembled. After this treatment, the battery life can be prolonged, and the battery life can be extended. Time is extended, and performance and security can be enhanced.

At the stage, the batteries of electric vehicles that various manufacturers try to develop are basically batteries (mainly lithium-ion batteries) and fuel cells. The cost of maintenance and maintenance of fuel cells is too high (the maintenance cost of fuel cells is about three to four times that of batteries or so), not suitable for the development of electric vehicles at this stage. So for the time being, don't mention it, just say the lithium battery that is commonly used now.

The life of lithium-ion batteries on ordinary electronic products is about 5 to 20 years, with an average of 8 years. At the current state of the art, lithium-ion batteries have a service life of only about 3-5 years on electric vehicles. When the battery capacity on the electric vehicle is reduced to less than 80% of the initial capacity, the driving range of the electric vehicle will be significantly reduced. When the battery capacity is reduced to less than 70%, the battery must be replaced. For many of today's pure electric vehicles, the cost of the battery is about 40% of the total cost of the car. That is to say, replacing the battery is equivalent to changing the car by half.

The reason why the battery life of electric vehicles is short is due to the influence of working environment and large-scale charging and discharging.

In terms of working environment, the operation of electric vehicle batteries in high temperature or low temperature will have an impact on the life of lithium batteries. This effect is generally uncontrollable. After all, the external environment of driving is less selective.

Lithium battery life of electric vehicles: charging

In terms of charging and discharging, the current charging mode of electric vehicles is basically two types - household charging piles and charging piles for quick charging. For example, Tesla, the world's best-known electric car, is super-charged. It can charge half of the car in 20 minutes. The charging peak can reach the charging speed of more than 500 kilometers per hour. The charging power is the highest. There are 120 kilowatts.

This kind of charging has a significant impact on the life of the battery. According to foreign statistics, Tesla's battery decay efficiency is about 1% of the 10,000-kilometer recession. If the long-term use of "fast charge" declines, the efficiency will be faster, and Most electric vehicle manufacturers, including Tesla, are not covered by the warranty milestones, so the impact of battery life on the car is enough to attract users' attention.