How long of lithium battery life for electric vehicles?

How long of lithium battery life for electric vehicles?

With the rapid spread of new energy vehicles, major auto manufacturers have also seem development prospects of electric vehicles. Many manufacturers have begun to introduce electric vehicles. However, as far as the current situation is concerned, there are still some problems to solve in electric vehicles. For example, how long the lithium battery life of an electric car? Slow charging, short cruising range, etc., but among these problems, there are important issues that generally overlooked by consumers - the life of electric vehicle batteries.

The Australian Commonwealth Scientific and Industrial Research Organization (CSIRO) published a research report yesterday saying that the agency scientists have invented a simpler method to extend the life of rechargeable lithium batteries, which the agency named the "salt bath."

It reported that the change method discovered by CSIRO in cooperation with the Royal Melbourne Institute of Technology and the Queensland University of Technology. According to CSIRO researchers, the material they use is an ionic liquid. This ionic liquid, also known as a normal temperature molten salt, is a transparent, colorless, odorless, and flame-retardant unique liquid that can applied to the electrode surface. A protective film formed to keep the battery stable during use. The process and principle of processing the battery is to immerse the lithium metal electrode in the mixed electrolyte containing the ionic liquid and the lithium salt before the battery assembled. After this treatment, the battery life can prolonged, and the battery life can extended. Time extended, and performance and security can enhanced.

At this stage, the batteries of electric vehicles that various manufacturers try to develop batteries (mainly lithium-ion batteries) and fuel cells. The fuel cell maintenance costs and maintenance costs are too high (the fuel cell maintenance cost is about three to four of the battery). It is not suitable for the development of electric vehicles at this stage. So, for the time being, do not mention it, just say the lithium battery that 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 reduced to less than 80% of the initial capacity, the driving range of the electric vehicle will significantly reduce. When the battery capacity reduced to less than 70%, the battery must replace. For many of today's pure electric vehicles, the cost of the battery is about 40% of the total cost of the car. Replacing the battery is equivalent to changing the car by half.

In nature, lithium is a light metal with a small atomic mass*, which has an atomic weight of 6.94 g/mol and ρ = 0.53 g/cm3. Lithium is chemically active, and it is easy to lose electrons to oxidize to Li+. Therefore, the standard electrode potential is *negative, -3.045V, and the electrochemical equivalent * is small, 0.26g/Ah. These characteristics of lithium determine that it is a kind of Very high-energy material. The ternary lithium battery refers to a lithium secondary battery using three kinds of transition metal oxides of nickel, cobalt and manganese as a positive electrode material. It fully integrates the good cycle performance of lithium cobalt ate, the high specific capacity of lithium nickelate and the high safety and low cost of lithium manganate. It synthesizes nickel by molecular level mixing, doping, coating and surface modification. A multi-element synergistic composite lithium intercalation oxide such as cobalt manganese. A lithium ion rechargeable battery has been widely studied and applied.

The so-called lithium battery life means that after the battery has been used for a period, the capacity is attenuated to 70% of the nominal capacity (room temperature 25 ° C, standard atmospheric pressure, and battery capacity discharged at 0.2 C), and the end of life can be considered. In the industry, the cycle life generally calculated by the number of cycles in which the lithium battery is fully charged. During the process of use, irreversible electrochemical reactions inside the lithium battery lead to a decrease in capacity, such as decomposition of the electrolyte, deactivation of the active material, collapse of the positive and negative structures, reduction in the number of lithium ion insertion and deintercalation, etc. Experiments have shown that higher rate discharges result in faster attenuation of the capacity. If the discharge current is lower, the battery voltage will approach the equilibrium voltage and release more energy.

The theoretical life of the battery pack of the ternary lithium battery in the field of street lamps is about 800 cycles, and the theoretical lifetime of the application in the base station of battery pack is more than 1600 times. In fact, the cycle life of the ternary lithium battery is more than 2000 times, and the capacity of more than 1000 times will reduced to 90% of the original capacity. It is among the best in the commercial rechargeable lithium battery. lithium iron phosphate is about 2000 times, and lithium titanate said to reach 10,000 cycles. At present, the mainstream battery manufacturers promise more than 500 times in the ternary battery specifications produced by them (charge and discharge under standard conditions), but after the batteries are assembled into battery packs, due to consistency problems, mainly voltage and internal the resistance cannot be the same, and its cycle life is about 400 times. The manufacturer recommends that the SOC use window be 10%~90%. It not recommended carry out deep charge and discharge. Otherwise, it will cause irreversible damage to the positive and negative structures of the battery. If it calculated by shallow charge and shallow release, the cycle life is at least 1000 times. In addition, if the lithium battery often discharged in a high rate and high temperature environment, the battery life will drop to less than 200 times.

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