A few days ago, Harvard University's research team developed a new type of flow battery. The team said that this type of flow battery can be used not only in the smart phone field, but also in new energy applications including renewable energy. In the mobile era, battery technology has become a top priority. It can even be said that there is no mobile era without batteries. However, problems such as weak endurance are present in the batteries of mobile devices, and breakthroughs in battery technology have always been cutting-edge problems, thus constraining the further development of the mobile era. Therefore, researchers have been exploring more efficient power generation in order to increase their endurance.
In fact, the flow battery is not a new technology, as it has appeared since the 1960s. Compared with lithium batteries, flow batteries do have some advantages. However, this technology has been in the research and development stage and has not been put into practical use. The reason is its own limitations. In spite of obstacles, exploration continues. Humans are using relatively safe new battery technologies and are constantly looking for cleaner energy to improve battery technology.
First, the flow battery characteristics determine advantages, some aspects are better than lithium batteries
The Harvard team is led by Michael Aziz, Professor of Materials and Energy Technology, and Roy Gordon, Professor of Chemistry and Materials Science. The new flow cell they studied is based on organic molecules in a neutral PH aqueous solution for power generation, and their safety and longevity are better than current battery products.
In fact, the field of flow batteries is not considered as a "wasteland." In the 1960s, redox batteries for iron-chromium systems had emerged, which could be considered as precursors to all-vanadium flow batteries. After years of research and development, the technology has made great progress and is expected to be put into commercial use. Compared with lithium-ion batteries, this flow battery does have advantages.
First, its size can be varied and its design is flexible.
For energy storage systems, the most important factors are power and power. Under normal circumstances, the vanadium flow battery can withstand the power depends on the size of the stack, and the amount of electricity is proportional to the size of the tank. No matter what kind of requirements the engineering project puts on the energy storage system, designers can flexibly make corresponding designs and can make adjustments at any time.
The picture above shows the flow battery structure
In contrast, lithium-ion batteries are coated with energy storage materials on the surface of the collector to form electrodes, and their process and performance are fixed. It is difficult to adjust according to specific projects. In contrast, the advantage of flow batteries is obvious.
More importantly, the flow battery is expandable. Regardless of the amount of storage, the flow battery has almost the same structure and control method. If the energy storage electrolyte is mixed uniformly, the SOC (charge-discharge depth) can be guaranteed.
If you want to make lithium batteries of the same size, you need to stack the number of batteries while using an extremely complicated BMS (Battery Management System) to manage the temperature and SOC of each battery. Inadvertently, overcharging, overdischarging, and overheating can cause the battery to be scrapped or even cause danger. This is an important reason why smart phone batteries sometimes explode.
Second, the flow battery has a long life.
Lithium battery life on the market is currently about 1000 to 5000 times. Its main energy storage principle is the embedding and de-embedding on the solid-state electrode. This way can easily produce cracks and end the battery life.
The charge-discharge mechanism of the flow battery is based on the change in valence, rather than the physical change of the ordinary battery, and therefore the service life is extremely long. In addition, all-vanadium flow batteries have an ion-exchange membrane between the positive and negative electrodes, which avoids the possibility of cross-infection due to mixing of positive and negative electrolytes, and have a longer life than other flow batteries.
Third, the flow battery is extremely safe.
As mentioned in the first point, the characteristics of the flow battery ensure its safety performance. There is no fire or explosion hazard, and there will be no safety problems even with large currents.
In addition, the energy efficiency of the flow battery is as high as 75% to 80%, and the starting speed is only 0.02 s. The battery components are mostly cheap carbon materials, and noble metals are not required as a catalyst.
At present, the global production of vanadium-based flow battery companies mainly include the United States UniEnergy Technologies, Austria Gildemeister Corporation, Japan's Sumitomo Electric Corporation and China's Dalian Branch Energy Storage Technology Development Co., Ltd..
Among them, Rongke Energy Storage Company has cumulatively installed more than 12MW of all-vanadium flow battery capacity, which accounts for 40% of the world's total installed capacity. It also has the world's first 5MW large-scale industrial energy storage device that is actually connected to the grid. This means that all Chinese indicators are at the leading international level.
Although the flow battery has so many advantages, and has a certain scale of production and application, it has not yet seen its large-scale commercial application and entry into the consumer market. The reason is that the current battery itself has many limitations.
Second, the flow battery has not been able to commercial use, and its limitations are more
As an energy storage system, flow batteries are still in the experimental stage in large-scale energy storage fields such as wind power, and commercialization is even more difficult to reach. The new flow battery researched by Harvard University above is also in the research and development stage, and it can be first explored the limitations of the current vanadium batteries in existing flow batteries.
In theory, vanadium compounds can be used as additives in existing lithium batteries, which is similar to the use of graphene.
However, in the case of vanadium-battery positive-electrode solutions, pentavalent vanadium ions, at a temperature higher than 45 degrees, will precipitate a highly toxic substance called vanadium pentoxide. Precipitation of this material will block the flow channel, cover the carbon felt fiber, deteriorate the performance of the stack, and ultimately render the battery scrap. More importantly, vanadium pentoxide, a highly toxic substance, can have serious consequences.
In addition, all-vanadium flow batteries need to be invested at a very high cost. For example, a 5 kW flow battery requires a total of 406,000 main material costs, plus additional material and labor costs.
Finally, the flow battery has an extremely low energy density of only about 40 Wh/kg. This, combined with the fact that the battery is liquid, covers a large area.
Due to the above limitations, the flow battery is difficult to apply on a large scale, and it is more difficult to realize commercialization.
The exploration of the flow battery represents the determination of mankind to continuously search for new energy. However, this technology is still not mature enough. In contrast, graphene battery technology is relatively safe and has been applied in smart devices, and humans are constantly looking for cleaner energy for power generation.
Third, secure battery technology is commercially available, and more possibilities exist in the future
In today's emerging battery technology, graphene battery technology is relatively safe. At the end of last year, Huawei introduced the first lithium-ion battery with graphene technology at the 57th Japan Battery Conference. The battery uses a new high-temperature technology, can increase the maximum temperature of lithium-ion battery 10 degrees, and its service life is also up to 2 times that of ordinary lithium-ion batteries.
Compared to the new flow battery in research and development, graphene seems to be more reliable. Of course, graphene itself also has some limitations, but after all, it has been applied in smart devices.
Therefore, as far as the current situation is concerned, graphene will be used more in the next phase in upgrading battery technology. On the road to the development of battery technology, it will not work at once, and gradual transition through sound and mature technology will achieve better results.
Of course, this does not mean that the battery technology field can be stagnant for the sake of stability. On the contrary, in order for battery technology to no longer be a resistance to the development of the mobile era, it should be bolder to use all possible sources of energy to power battery technology. There are already relevant studies and progress has been made.
For example, the research team of the University of Pennsylvania recently developed a new power generation method that uses the difference in concentration of carbon dioxide emitted by fossil fuel power plants and carbon dioxide in the air to generate electricity. This device, called a "flow unit," produces an average power density of 0.82 watts per square meter, which is about 200 times higher than the value obtained from previous approximations. The research results have been published in the latest edition of the journal Environmental Science and Technology.
Not coincidentally, Finnish scientists are also studying how to use kinetic energy, thermal energy and solar energy to provide power for equipment. Researchers have developed a ferroelectric material called KBNNO that converts heat and pressure into electricity. Researchers at the University of Oulu in Finland have used perovskite crystal structures to extract energy from multiple energy sources and hope to collect more energy through research.
The manufacturing process of this equipment is not complicated. Once the best materials are found, it is possible to put this technology into commercial use in the next few years. If this idea is realized, we may not need to plug the mobile device into the socket to recharge it. Instead, we can obtain continuous power from natural energy and achieve true energy cleansing.
The above results can be used to make optimistic predictions. In the future, more new technologies will emerge in the field of batteries. They can improve the utilization of batteries, battery life and other factors. In the development of battery technology and even any kind of technology, it is necessary to move forward steadily and maturely, as well as bold and avant-garde innovations. The combination of the two may better promote the further development of the mobile era.
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