Can liquid flow battery replace lithium ion battery?

A team of researchers at Harvard University has developed a new type of liquid flow battery. The liquid-flow battery could be used not only in smartphones, but also in new energy applications, including renewable energy, the team said.

In the mobile era, battery technology becomes the top priority. It can even be said that there will be no mobile era without battery. However, problems such as weak battery life exist in the batteries of mobile devices. Battery technology breakthrough has always been a cutting-edge problem, which restricts the further development of the mobile era. So researchers have been searching for more efficient sources of electricity to improve endurance.

In fact, fluid-flow batteries are not new, having been around since the 1960s. Liquid flow batteries do have some advantages over lithium batteries. However, this technology has been in the research and development stage, has not been put into practical application, the reason lies in its own limitations. Despite the obstacles, the quest continues, as humans continue to find cleaner sources of energy to improve battery technology while still using relatively safe new battery technologies.

First, the characteristics of liquid flow battery determine the advantages, some aspects are better than lithium battery

The harvard team is led by MichaelAziz, professor of materials and energy science, and RoyGordon, professor of chemistry and materials science. Their new liquid-flow battery, based on organic molecules in a neutral PH aqueous solution, is superior to current battery products in terms of safety and longevity.

In fact, the field of liquid-flow batteries is not a "wasteland". In the 1960s, iron-chromium REDOX batteries appeared, which can be regarded as the predecessor of all-vanadium liquid-flow batteries. After years of research and development, the technology has come a long way and is expected to be commercially available. Such liquid-flow batteries do have advantages over lithium-ion ones.

First, the scale can be large or small, and the design is flexible.

For energy storage systems, the most important factors are the quantity of electricity and power. Normally, the amount of power a vanadium flow battery can withstand depends on the size of the reactor, and the amount of charge is proportional to the size of the storage tank. Regardless of the requirements of an engineering project for an energy storage system, the designer can flexibly make corresponding designs and make adjustments at any time.

Liquid flow batteries instead of lithium ion batteries? There's a graphene in between

The figure above shows the structure of liquid flow battery

In contrast, lithium ion batteries are made by coating energy-storing materials on the surface of the collector fluid to form electrodes. The process and performance are fixed, which is difficult to be adjusted according to specific projects. In contrast, the advantages of liquid-flow batteries are obvious.

More importantly, the flow battery is scalable. No matter how much liquid flow battery is stored, its structure and control method are almost the same. As long as the energy-storing electrolyte is mixed evenly, the SOC (charging and discharging depth) can be guaranteed to be consistent.

To make a lithium battery of the same size, you need to stack the number of batteries and use a very complex BMS (battery management system) to manage the temperature and SOC of each battery. A little careless, overcharge, overdischarge, overheating will lead to the battery scrap and even cause danger, which is why smartphone batteries sometimes explode important reasons.

Second, the flow battery life is long.

The current lithium battery life on the market is about 1000~5000 times. Its main energy-storing mechanism is the insertion and uninsertion of solid electrodes, which can easily crack and end battery life.

The charging and discharging mechanism of liquid flow battery is based on the change of valence rather than the physical change of ordinary battery, so its service life is extremely long. Moreover, because the positive and negative electrodes of all-vanadium flow battery are separated by ion exchange membrane, the possibility of cross infection of positive and negative electrolytes due to mixing is avoided, and the battery life of all-vanadium flow battery is longer than that of other flow batteries.

Third, liquid flow batteries are extremely safe.

As mentioned in the first point, the characteristics of liquid flow batteries ensure their safety performance. There is no fire or explosion hazard, and there are no safety issues even with high current.

In addition, the energy efficiency of liquid flow battery is as high as 75%~80%, and the starting speed is only 0.02s. Moreover, most battery components are cheap carbon materials, without precious metals as catalysts.

At present, the global manufacturers of all-vanadium flow batteries mainly include UniEnergyTechnologies of the United States, Gildemeister of Austria, sumitomo electric of Japan and dalian rongke energy storage technology development co., LTD of China.

Among them, rongke energy storage co., ltd. has achieved a total installed capacity of vanadium liquid flow battery exceeding 12MW, accounting for 40% of the total installed capacity in the world. In addition, it also owns the world's first 5MW large-scale industrial energy storage device that is actually connected to the Internet. This means that China is at the leading international level in all indicators.

Although liquid flow battery has so many advantages and has a certain scale of production and application, it has not been put into commercial use and entered the consumer market on a large scale at present, because there are many limitations of liquid flow battery itself.

Two, the flow battery has not been commercially available, its own limitations

As an energy storage system, liquid-flow battery is still in the experimental stage in wind power and other large energy storage fields, which is difficult for commercial use. The new liquid-flow battery studied by Harvard University is also in the research and development stage, so we can first explore the limitations of the main vanadium series battery in the existing liquid-flow battery.

In theory, vanadium compounds could be used as additives in existing lithium batteries, similar to what graphene is used for.

However, vanadium pentavalent ions in the positive solution of a vanadium battery precipitate a highly toxic substance called vanadium pentoxide when the temperature is above 45 degrees. The deposition of this material can clog the flow channel, cover the carbon felt fiber, deteriorate the performance of the reactor, and eventually cause the battery to be scrapped. What's more, vanadium pentoxide, a highly toxic substance, can have serious consequences.

In addition, full vanadium flow batteries are extremely costly. For example, a 5kw liquid flow battery requires a total investment of 406,000 yuan in the cost of main materials, as well as additional investment in secondary materials and labor costs.

Finally, fluid-flow batteries have a very low energy density, about 40Wh/kg, and because they are liquid, they take up a lot of space.

Based on the above limitations, liquid flow battery is difficult to be applied on a large scale and commercialized.

The discovery of liquid-flow batteries represents a commitment to finding new sources of energy, but the technology is not yet mature enough. By contrast, graphene battery technology is relatively secure and is already used in smart devices, and humans are constantly looking for cleaner sources of energy to generate electricity.

Third, the availability of sound battery technology opens up more possibilities for the future

Among today's emerging battery technologies, graphene battery technology is relatively stable. Late last year, huawei unveiled the first lithium-ion battery using graphene technology at the 57th Japan battery conference. With the help of new high-temperature technology, the battery can increase the upper limit temperature of lithium ion battery by 10 degrees, and its service life is twice as long as that of ordinary lithium ion battery.

Graphene appears to be more reliable than the new liquid-flow batteries being developed. Graphene itself has its limitations, of course, but it is already used in smart devices.

So as things stand, graphene will be used more in the next phase to improve battery technology. On the road of battery technology development, it is impossible to achieve overnight success, but better results should be achieved through gradual transition of sound and mature technology.

This is not to say, of course, that the world of battery technology can rest on its laurels. On the contrary, in order to make battery technology no longer an obstacle to the development of the mobile era, it should be more bold to use all possible energy to power the progress of battery technology. There has been research, and progress has been made.

For example, a team from the university of Pennsylvania has developed a new way to generate electricity, using the difference between the carbon dioxide emitted by fossil fuel power plants and the concentration of carbon dioxide in the air. The device, called a "flow cell," produces an average power density of 0.82 watts per square meter, about 200 times higher than the previous approximation. The research is published in the latest issue of the journal environmental science and technology.

Similarly, Finnish scientists have made some progress in using kinetic energy, heat and solar energy to power their devices. Researchers have developed a ferroelectric material called KBNNO that converts heat and pressure into electricity. Researchers at the UniversityofOulu in Finland used perovskite crystal structures to extract energy from multiple sources and hope to collect even more.

The equipment is not complicated to make, and once the best materials are found, the technology could be ready for commercial use in the next few years. If this vision is realized, we may no longer need to plug our mobile devices into a socket to charge them, but instead get a continuous flow of electricity from natural energy to achieve real energy cleanness.

Based on the above results, we can make an optimistic prediction that in the future, there will be more new technologies in the field of battery, which can improve the efficiency of battery, battery life and other factors. In the development of battery technology and any kind of technology, we need both mature and bold innovation, the combination of the two can better promote the further development of the mobile era.

The page contains the contents of the machine translation.