Lithium-ion Battery Technology Development and Assistance to Electric Vehicles
According to foreign media reports, a new generation of electric vehicles has appeared on the road since 10 years ago. Researchers at the Georgia Institute of Technology in the United States spent a year tracking the driving habits of nearly 500 American drivers in order to confirm whether electric vehicles are suitable for this type of population.
The researchers found that nearly one-third of the respondents said that they could use electric vehicles with a range of 100 miles (about 160 kilometers) to complete most of their travel activities. Only 6% of the cases involve longer travel distances, which may require users to fully charge before traveling, or renting a gasoline car.
Today, the development of electric vehicles is better. Many electric vehicles have a range of more than 200 miles (about 320 kilometers), and some large-scale, high-end models can even reach nearly 400 kilometers. After all, there are still many potential car buyers who worry that the vehicle will run out of power halfway. The long-life battery can relieve users' anxiety about electric vehicle mileage, but "there are still many pits to fill."
Many electric vehicles are equipped with lithium-ion batteries. This product is a battery design commercialized by Sony in 1991. The special feature of this type of battery is its high energy storage capacity. Currently, the energy density of on-board batteries for electric vehicles is usually 200wh / kg, and contemporary lithium-ion batteries can inject 200 watt-hours of electric potential into a 1 kg battery kit. This data is 5 times that of the old lead-acid batteries, and researchers are continuously researching and improving them to improve the performance of lithium-ion batteries.
The name of the lithium ion battery is taken from the lithium ion inside. But when this type of battery discharges, the anode produces lithium ions. Then, the lithium ions will pass through the battery separator (only lithium ions can pass) into the electrolyte, and then diffuse to the cathode. The electrons at the anode will disappear and enter the cathode along the external circuit. The current generated during this process will be used to drive the motor. At the cathode, ions and electrons recombine. This situation will continue until the user connects the vehicle to the charging device through the charging cable, and the entire process will be reversed.
For weight-sensitive applications such as vehicles, lithium metal is the lightest metal in the periodic table of chemical elements, but the metal's (chemical) reactivity is also higher. The construction of the battery cell needs to be very careful to avoid defects, otherwise it may cause a battery short circuit and even a battery fire accident. The anode is usually composed of a carbon-rich material, and the lithium metal in the cathode is usually easily oxidized partially to generate lithium cobalt oxide.
Cobalt metal is the most expensive battery material, battery manufacturers are trying to reduce the use of this material. Many cobalt mines are located in the Democratic Republic of the Congo, and the mining conditions are very bad, and even the use of child labor has occurred. The mainstream idea in the industry is to reduce the use of electric cobalt metal in lithium batteries, while increasing the amount of nickel and manganese to produce NMC batteries (ternary lithium batteries).
Last year, China ’s largest battery manufacturer, CATL, began mass production of NMC batteries with an energy density of 240wh / kg. Other companies such as Tesla hope to further reduce or even get rid of their dependence on cobalt metal, but Tesla keeps the details of its battery plan tight.
In order to reduce the cost of battery materials, as the production capacity of CATL, Tesla and other competitors increases, the price of such batteries will decline steadily. According to Bloomberg New Energy Finance, the average selling price of lithium batteries in 2012 was US $ 1160 / kWh (about 8204.68 yuan / kWh). By 2024, its price will be less than US $ 100 / kWh (about 707.3 yuan / kWh) (see chart). At that time, compared with diesel locomotives, electric vehicles will have a greater competitive advantage.