Charge and discharge 700 times! Electric car mileage bottleneck is expected to break

Charge and discharge 700 times! Electric car mileage bottleneck is expected to break

Recently, an important research has greatly urged electrochemical energy storage.. A joint scientific research team from UNILENOSIISISATCHICAGO, UNIINOSISISATCHICAGO, UNIINENITINOISISATICAGO, UNENENENENATORY and CaliforniaStateuniversity, Northridge were published in the Nature magazine, successfully made A lithium air battery that can be circulated more than 700 times in an atmosphere similar to air.

Breaking the previous lithium air battery can only use pure oxygen, and the loop life is short, so that this battery has a battery with extremely high theoretical energy density. Replacing existing lithium ions, breaking through electric vehicle mileage bottlenecks. What is a lithium air battery? What is the difference between lithium air batteries and lithium-ion batteries? What is the breakthrough of the lithium air battery is important? This first should be tattaked from the lithium-ion battery.

. Lithium-ion battery is the most successful rechargeable battery. The reason why “lithium ion batteries” is called because in the battery, whether charging or discharging, is all between the two electrodes, to form a current.

. When the lithium ion reaches the electrodes, it is necessary to “deline” when “embedding” on its surface..

In order to ensure a good “embedded-deficed” reaction, the anode of the lithium-ion battery is usually graphite, and the cathode is typically a certain compound of lithium.. For example, in the cathode of the most popular “three-dimensional lithium” battery, in addition to lithium elements, nickel, cobalt, manganese, form a compound nickel-cobalt-manganese acid (lini0.

3CO0.3Mn0.3O2) And nickel, cobalt, manganese must be much more than lithium.

Therefore, in the lithium-ion battery, although one relative atomic mass is only 3 lithium ions (more than one-second weight of the atomic mass of one carbon atom), it can carry 1 unit charge, but its cathode is It is also more than a much more nickel, cobalt, manganese, iron, phosphorus, carbon, etc., etc. to “storage” this lithium ion.

. Leading to the positive charge of this one unit, only a “phenxue” that can be equipped with one relative molecular mass in the cathode..

Plus the weight of the anode and other materials and structures, the energy density of a lithium-ion battery will not do it.. This is also why, an electric car carrying a half-ton lithium-ion battery, the endless mileage is far less than the reasons for ordinary cars that only add tens of liter of gasoline.

. In a lithium ion battery, in order to stably “storage” carry charge-carrying lithium ions (gray spheres in the figure), there is a large number of other structural gates, such as lithium compounds (blue, red stereostructures) and graphite (Red layered structure), the relative atomic mass of these elements is much larger than lithium, resulting in a limited energy density of the lithium-ion battery. In the ideal lithium air battery, these elements don’t want it, as long as the lithium metal and the oxygen in the air are OK! And the lithium air battery is different.

. The compound and graphite to be lithium according to the lithium ion battery do different electrodes, and the lithium air battery can directly use lithium metal monomi (Li) and oxygen (O2) in the air as an electrode..

In the most ideal case, the battery is discharged, and the lithium oxide (Li2O2) is generated from the lithium oxygen, and a current is present in the outer circuit; and the lithium hydrate is decomposed into lithium and oxygen during charging.. There is no need for other elements of elements that are large with other quality, while the cathode can even directly use the weight and cost! Therefore, the lithium air battery can achieve much energy density than the lithium ion battery.

. In fact, since lithium is a metal element with the lightest quality of the atomic quality, while oxygen comes from air, the lithium air battery has the highest theoretical energy density in electrochemical cells – in other words, the quality of the unit quality Air batteries can store and release energy, more than all other electrochemical energy storage media. Non-liquid lithium-air battery theoretical energy density can reach 12KWh / kg, is 5 ~ 10 times the existing lithium-ion battery, which can be comparable to about 13kWh / kg of gasoline.

. If the lithium air battery can finally go to the market, the electric car will also have the same level of endurance with the gasoline car, which will completely break the life-ranking bottleneck due to the low energy density of lithium-ion batteries, and is important for the future development of clean energy. Meaning.

However, these are theoretical analysis. I want to achieve such an ideal situation, but it is not an easy thing..

Prior to this, claims to be a lithium air battery that can be cathode, relying on a pure oxygen environment.. This is because, in addition to oxygen, nitrogen, carbon dioxide, and water vapor in the air, make this process become more complicated.

. The oxidation of the anode, and the reaction of carbon dioxide and water vapor in the cathode lithium ion and the air in the air will generate undesirable by-products..

Due to other chemical reactions on electrodes, electrolyte, and the chemical properties of metal lithium and oxygen are more active, the cycle life of lithium air batteries has been very short. In addition, the pure oxygen environment requires lithium air to be equipped with an oxygen storage device, such as a huge oxygen cylinder, which makes the high energy density of the lithium air battery directly and heavy oxygen storage tanks, and the capacity of the battery Also rely on the capacity of the oxygen bottle. What’s more, if you want to use lithium air batteries on an electric car, the oxygen bottle will increase the weight of safety in addition to significant weight.

. In fact, if it is not because of the above defects, the lithium-ion battery will not take the complex electrode in remote use..

Since the lithium air battery directly using lithium metal is unable to obtain the desired oxygen in the air, some scientists even simply call the lithium air battery as “lithium oxygen battery”.. After years of development, these problems are like black clouds that have always been shrouded on the head of lithium air batteries.

Don’t say to market and lithium-ion batteries competition.. Until the Breakthrough of the Chicago University of Illinois, Agong National Labs and California State University Beiling Branch, only the brightness of this only in theory, the spiritual performance brings hope.

. If you want to solve the fatal defects of lithium-air batteries, you must want to prevent various chemicals-nitrogen, carbon dioxide, water vapor contained in the air..

These side reactions will affect the electrodes, lithium ions and electrolytes, and unbellive by-products. The researchers conducted an in-depth study of computer simulation (density function analysis) and experimental studies, and finally, they found an answer: add a protective layer on lithium metal electrodes..

The core of this technology is, in the anode, they add a layer of dense protective coating composed of lithium carbonate / carbon (LiCo3 / c) for lithium metal.. The process of coating is abnormal: directly by lithium metal and carbon dioxide through 10 charge and discharge cycles, chemical reactions on the surface of the electrode can be completed.

. Lithium carbonate prevents other compounds other than lithium ions from entering, thereby protecting the destruction of other components other than oxygen in the air..

In the atmospheric environment, lithium carbonate does not respond to the water vapor in the air, so this protective layer does not participate in the chemical reaction of the battery, nor will it be damaged. Under the protection of the coating, the lithium retention rate of a single cycle is as high as 99.97%, greatly exceeded the lithium air battery without coating.

. Figure 丨 Determinating anode protection layer (scale: 1 micrometer of the length of the green line) Figure 丨 丨 分 分 分 分 分 分 分 研究 分 分 分 分 分 分 分 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨 丨Diulfonated molybdenum disulfide (MOS2) nano sheet as a cathode, and adopt 1-ethyl-3-methylimidazoliolirate (1-ethyl-3-methylimidazoliumTrafluoroborate, EMIM-BF4) and dimethyl sulfoxide ( Dimethylsulfoxide, DMSO) Mixed mixture as electrolyte. Under the synergistic operation of the anode, cathode, electrolyte, the lithium air battery is placed in an simulated air environment – 79% nitrogen, 21% oxygen, 500 ppm relative humidity, temperature is 25 ° C.

. After testing, after 700 charge and discharge cycles, lithium air batteries do not have any failure..

This achievement exceeds many people’s expectations, and even has reached a circular life of a commercial battery (such as lead-acid batteries).. The research team thus concluded that “protected lithium anode, electrolyte mixture, and high-performance air cathode, working together under simulated air conditions, can effectively improve the number of cycles of lithium-air battery.

“And here, the Argon National Lab continues to respond to this battery to make computer simulation, in order to further understand the reaction mechanism, so that the performance of the battery in the future, support the future possible commercial supply theory support. It should be pointed out that although this study is still very far from commercial applications, its energy density is also a distance from the best existence, but it is undoubtedly a major advancement of lithium air battery development..

The research results prove that the lithium air battery can identify the interference of other gas, directly obtain oxygen from the gas environment of similar air, and get rid of the dependence on the oxygen storage device, and the cycle life is still very long.. This undoubtedly greatly enhances confidence in the future development of this revolutionary battery technology in the industry: Since most important troubles already have a clear solution, the rest may not be a fatal problem at all! It may not be used for more time, researchers can make new batteries that are much more energy density than existing lithium-ion battery technology, and this will undoubtedly change existing energy patterns.

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