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Lithium-ion batteries also have many defects: short cycle life, complicated charging circuit, and high requirements for internal protection circuits of batteries. Especially for lithium-ion batteries in fully sealed aluminum case, there is an extreme in the design of safety protection. Fatal flaws.
First, the resource shortage
The proportion of lithium in the earth's crust is about 0.0065%, and the total storage of lithium in seawater is 260 billion tons, but the concentration is too small and it is difficult to refine. The world's salt lake lithium resources are mainly distributed in Chile, Argentina, China and the United States. The granitic pegmatite lithium deposits are mainly distributed in Australia, Canada, Finland, China, Zimbabwe, South Africa and Congo. Pegmatite lithium deposits have also been discovered in India and France, but they are not commercially exploitable. Currently, only a few countries in the world have lithium resources that can be economically exploited.
Tang Yougen, director of the Institute of Chemical Power and Materials at Central South University, said that even if the cost and safety of lithium are all solved, if lithium batteries are used instead of gasoline in the future, they will not be able to meet all the needs, because this is equivalent to using a shortage. Resources replace another scarce resource.
Second, smelting pollution
Chemical substances such as lithium hexafluorophosphate and polypropylene glycol (alcohol) contained in lithium ion batteries cause organic pollution to the environment. The heavy metal elements such as cobalt may also cause harm to the environment, especially cobalt, which is relatively high in content and is a rare precious metal with high recovery value. Although the pollution of the lithium battery itself is not serious, the environmental pollution of lithium metal in the process of extraction and smelting is no less than the pollution caused by gasoline. The industrial production methods of metallic lithium mainly include molten salt electrolysis and vacuum thermal reduction. The molten salt electrolysis method uses lithium chloride as a raw material, and is decomposed into metallic lithium and chlorine gas during electrolysis in a molten electrolytic cell, lithium is precipitated at the cathode, and chlorine gas is precipitated at the anode. When electrolysis is performed, lithium chloride dissociates into lithium ions, moves toward the cathode, and discharges, and the formed metallic lithium gradually rises to the surface of the electrolytic cell or to the lithium collection chamber through the molten salt. The chlorine gas evolved at the anode is discharged to the outlet through the molten salt to be discharged or collected. The biggest disadvantage of this method is that the chlorine gas generated during electrolysis is seriously polluted, and the product quality is difficult to control and the production cost is high.
Third, security issues
Experts believe that high-capacity lithium batteries used in the market are prone to explosion and injury accidents due to differences in chemical composition. Relatively safe are nickel-metal hydride and nickel-cadmium batteries. Lithium is too active. It is not safe to use. It often burns and bursts during charging. Later, the improved lithium-ion battery incorporates components that inhibit lithium activity, thus improving the safety standards of lithium batteries. Efficient. In the development process of lithium batteries, because of the different positive and negative materials and their formulations, there are unsafe phenomena such as explosion and burning. Mainly the negative electrode uses metal lithium, which produces dendrites after cycling, causing short circuit and burning explosion. The positive electrode material adopts lithium cobaltate or nickel cobalt lithium, etc., and its chemical activity is high, in the case of graphite negative electrode, once it appears High temperature, easy to explode and burn. Although the actual probability of occurrence is one in 100,000 or more than one millionth, the number of electronic consumer products, such as mobile phones and notebook computers, is extremely large and the scope of use is extremely wide. People feel a lot. Since these electronic consumer goods are indispensable items in people's daily lives, once security problems occur, the impact is great. The safety design of lithium-ion batteries relies too much on their internal electronic safety protection chips without the necessary physical safety protection measures. In the process of charging and using, once the failure of its safety protection chip fails, the consequences are unimaginable. Lightly, the internal gas accumulation of the battery causes the battery body to rise, and the battery may be abnormal due to the internal short circuit of the battery. The tragedy of battery explosion occurred.
Fourth, the cost problem
Compared with lead-acid batteries, the high cost of lithium batteries for electric bicycles is a prominent feature, and it is also the key to affecting the large-scale replacement of lead-acid batteries for lithium-ion batteries for electric bicycles. The price of the main material such as the positive electrode material, the negative electrode material, the current collector, the separator, and the electrolyte of the lithium battery is much higher than that of the lead-acid battery, and the cost of assembling the auxiliary material and the external circuit system is hardly found in the lead-acid battery. Although lithium batteries have much higher energy than lead-acid batteries, the cost of raw and auxiliary materials per unit of power is not as large as the cost gap, but the material cost gap between the two does exist, and the gap is in multiples. Due to the manufacturing process, the labor cost of the lithium battery is relatively high. In the manufacturing cost, the labor cost of lithium batteries accounts for more than 40%, while the labor cost of lead-acid batteries is generally 10% to 20%. Most processes of lithium batteries are irreversible in production, and lead-acid batteries are reversible repair. Therefore, the overall pass rate of the lithium battery is low. The recovery value of lead-acid batteries after use is above 40%, while the recovery value of lithium batteries is almost zero.
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