Rechargeable battery is largely about the environmental performance of electric vehicles and vehicle costs. Car rechargeable batteries not only need to meet the energy capacity of the vehicle farther from the decision, the instantaneous current input and output, as well as to prevent abnormal heat and fire safety requirements, and also need to meet in order to make electric cars that can be accepted by ordinary consumers, cost requirements, being the fierce competition in the development for enterprises. The development of the lithium-ion rechargeable batteries in the future will focus on the following three elements: (1) reduce the cost of energy per unit of capacity; (2) to ensure security; (3) inhibition of charging and discharging a result of deterioration. Especially inhibiting the deterioration of charge and discharge causes, relationship to the user the feeling of use of electric vehicles, and contains the total cost of the maintenance costs, including, therefore important factor can not be ignored.
The Cathode Material choices vary
The performance and cost of the battery depends on the material, structure, and control, of which the most important is the choice of materials. Battery manufacturers must make the optimal choice from a variety of candidate materials. Are already in production or plan the next 1 to 2 years of mass production of lithium-ion rechargeable battery cathode material, in accordance with the different material combinations with lithium, divided into four kinds the ternary manganese, NCA and iron phosphate class (Figure 1). Cathode materials are generally of the conventional lithium battery using lithium cobalt oxide (LiCoO2). But the use of a positive electrode of lithium cobaltate when charging the crystal structure is not stable enough to use in the vehicle-mounted battery, the existence of the security issue. Develop in-vehicle lithium battery technology to try and develop a new material instead of lithium cobalt oxide.
Be referred to as a ternary material of lithium cobalt oxide part of the cobalt, nickel and manganese is substituted by cobalt, nickel, manganese, three components, to improve the stability of the material. Ternary [Li (Ni-Mn-Co) O2] battery materials manufacturers including the announcement of the shallow the Suzuki extended-range electric vehicle supply lithium batteries, Sanyo Electric, and developed for Honda PHEV supply battery GS soup with Honda joint venture company Blue Energy Japan.
The NCA based material NCA is nickel, cobalt, aluminum, three word prefix abbreviation. NCA class of materials made of aluminum instead of manganese ternary material. NCA class material [Li (Ni-Co-Al) O2] is the joint venture of Toyota and Panasonic Primearth EV Energy with its production of lithium battery is equipped in the Prius plug-in hybrid. NCA class lithium generally has excellent energy density, but there are still to be solved in terms of safety. Primearth EV Energy Company in order to improve the lithium-ion rechargeable battery security, improve the heat resistance of coated ceramic layer on the negative measures, so as to strengthen the safety performance.
The manganese-based material using lithium manganese oxide (LiMn2O4). Such materials have been widely adopted by the battery manufacturers in Japan, South Korea and the United States is now the mainstream car battery. Major manufacturers including Automotive Energy Supply to supply batteries Nissan LEAF (Chinese name: hear the wind) for the the Mitsubishi iMiEV supply battery Lithium Energy Japan, LG Chem to supply batteries for GM's Volt, as well as Daimler, BMW and Beijing Automotive supply batteries, Johnson Controls-Saft (Johnson Controls-Saft), etc.. The manganese-based material compared with the ternary and NCA based material, in theory, the energy capacity density is lower, but the lithium atoms, manganese atoms, and an oxygen atom capable of forming a solid crystal structure, and therefore thermal stability is excellent, safe. In addition, manganese, cobalt and nickel, compared the prices of raw materials cheaper cost advantage. The prices of raw materials in descending order of the cobalt, nickel, manganese, if the price of cobalt is seen as 10 words, then nickel is 5, and manganese is less than 1.
The material of ferrous phosphate (LiFePO4) cathode materials for Chinese manufacturers to use more. Such material tightly due to phosphorus (P) and oxygen (O), even when the battery internal heat, the crystal structure also difficult destruction is therefore highly safe. Ago due to low electrical conductivity of the iron phosphate-based material, there is a problem, but difficult to improve the output power supply in the cathode material coated fine CFC improved characteristics, greatly promote the process of practical. The advantage of such materials in addition to the safety, another advantage in that the cost of materials. Raw material prices of iron manganese also cheap, estimated about only manganese fraction of. But there are also technical personnel noted that the process for manufacturing of such material are high cost, so it is difficult to play out the cost advantages of the material itself. Due to the need to create prevent iron oxidation manufacturing environment, but also for the cathode material coated with carbon quality management process also takes manpower and resources, and therefore contain manufacturing costs, including the total cost is not necessarily cheaper.
Cost target is 20,000 yen / kWh reduced consumer products with lithium batteries quite
Currently, the Japanese manufacturer of car lithium battery costs about 10 to 12 million yen / kWh, Chinese manufacturers for its half. GM's Volt battery costs 100,000 yen / kWh to calculate the cost of electric car battery with 16kwh battery for 1.6 million yen, The Nissan LEAF with 24kwh battery for 2.4 million yen (Figure 2). Only the cost of the battery is equivalent to the price of a car. In other words, EV and REV (modified EV) compared with the same level of gasoline cars, the cost will be twice as high. To promote the popularization of electric vehicles, battery costs must be reduced.
Car lithium battery cost targets consumer products is reduced to the level of lithium batteries. Consumer products with lithium batteries cost about 20,000 yen / kWh. 20,000 yen / kWh, the Volt's battery costs 320,000 yen, LEAF 480,000 yen. Battery costs can be reduced by 1.28 million yen and 1.92 million yen. The cost of the battery will decrease reflected in vehicle prices, then, to the Volt price can be reduced to 2 million yen, LEAF can be reduced to 1.85 million yen. If the cost can be reduced to this level, the electric car will be able to achieve the average consumer can afford the price.
20,000 yen / kWh cost is also consistent with the target value of the Japanese and Chinese car lithium battery development blueprint. Preparation of the car in Japan's New Energy and Industrial Technology Development Organization (NEDO) rechargeable battery development blueprint, the cost target for 2015 dropped to 30,000 yen / kWh 20,000 yen / kWh in 2020 for year three. In electric vehicle technology blueprint released by the Chinese government in 2015, China's battery cost target value of $ 1,500 / kWh (about 18,000 yen) (Figure 3).
The attitude of the battery suppliers for car battery cost 20,000 yen / kWh support the possibility of this goal. Nissan joint venture between NEC executives in an interview with Reuters in September 2010, said the company is promoting the development of lithium-ion rechargeable battery, the goal is to have 2017, its price compared with the products now halved performance doubled. Half the price doubled the performance dropped to a quarter of the current means the price per kWh. Assuming the current cost of the battery for 100,000 yen / kWh, the 2017 cost is 25,000 yen / kWh. In addition, LG Chemical Company executives said in February 2011 at the International Conference on the price of the company that will be mass produced lithium-ion rechargeable battery 350 to $ 400 / kWh (about 28,000 to 32,000 yen). LG Chem said 350 to 400 U.S. dollars / kWh prices considering the cost of the company will be reduced.
A driving force to reduce the prices of the battery unit capacity is a high capacity, and improve production efficiency. High capacity, consumer products, energy density lithium nearing 250Wh/kg, the and car lithium battery is only about 100Wh/kg. Car lithium battery, there is scope to improve the energy density. Battery Unit another driving force is reduced to improve production efficiency, it may be mainly adopted to expand the scale to obtain the mass-production effect, to improve the process and reduce the cost of production equipment and other measures to achieve. Automotive Energy Supply Company regarding its future car rechargeable battery production plans, 50,000 EV battery unit available for mass production from 2011, the increase in production by 2013 will amount to 500,000 EV
The deterioration of the battery performance problems can not be ignored
Car lithium battery elements can not be ignored is the deterioration of the battery problem. Buy a new car to the scrap car to use a minimum of 10 years. If the battery obvious deterioration during this period, the user is forced to replace the batteries of electric vehicles, it will damage the user experience, the user will increase the economic burden.
The rechargeable battery using the electrochemical reaction of charge and discharge, and therefore it is inevitable to cause deterioration due to repeated use. EV users must be aware of in advance of the: EV 5 years after the deterioration of the battery may cause the battery capacity is reduced by 20 to 30%. With a capacity of 25kWh battery, can travel 150km of EV example, the battery capacity decline may lead to shorten the travel distance of 30 ~~ 50km. Perhaps the user wants the performance deterioration of the battery replaced, in this case, even if the battery is priced at 20,000 yen / kWh battery replacement costs 500,000 yen. Assume that every 5 years would cost 500,000 yen replace the battery, then the annual cost burden is 100,000 yen, the user needs to be considered in advance EV maintenance fees.
As mentioned above, the battery life is directly related to the user's EV cost of ownership, so it will become a key element in the car charging battery development. Future, widespread popularity EV and PEHV standing with costs, but also reduce the user's vehicle to the point of view of the cost of ownership and cost assessment, on-board lithium battery. Concern as a strong anti-deterioration performance car lithium battery is a the negative lithium titanate battery. The negative electrode of lithium batteries generally use graphite, but the durability can be improved using the lithium titanate. Toshiba experimental results show that the lithium titanate negative electrode of the lithium battery life when compared with the use of graphite in the traditional lithium may be extended to 6 times. In this case, you do not need during the life of the vehicle due to the deterioration of the battery and replace the battery, it will not cause the user's vehicle with rising costs. Toshiba is currently in mass production car lithium battery using lithium titanate addition to Mitsubishi Motors of this battery will be on the company's EV, Honda is also considering for the company developed the Fit EV.
The lithium-ion rechargeable battery technology is still in its development stage enterprises in order to further technological progress in the fierce competition. In the future, companies develop in-vehicle lithium battery, not only in energy capacity, cost, and security there is often a shift in the relationship between the elements of the (Trade-off) aspects to achieve optimization, but also stand the impact of performance degradation, and contains maintenance fees, including the cost of ownership perspective, comprehensive performance evaluation of the battery.
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