Aluminum battery may become the preferred solution for new energy storage
- Aluminum batteries have many advantages over lithium batteries
- Aluminum batteries still have shortcomings
- Aluminum batteries have great practical application prospects
Nowadays, lithium-ion batteries also play a very important role in the battery industry, but the content of lithium in the earth’s crust is low, so it is important to find elements that can replace lithium to prepare high-performance secondary rechargeable batteries.
As a substitute for lithium, aluminum is abundant in the earth’s crust, but its chemical properties are very active, and it is easy to form a dense oxide layer, and it is also prone to aluminum dendrites as a negative electrode, resulting in short circuit of the battery, so it is difficult to realize industrialization.
Recently, scientists have developed a low melting point molten salt electrolyte composed of inorganic chlorides (sodium chloride-potassium chloride-aluminum chloride) to replace the currently commonly used ionic liquid electrolytes.
According to the data, the aluminum electrode in the sodium chloride-potassium chloride-aluminum chloride electrolyte has the characteristics of anti-dendritic growth, and the electrode surface presents a clear cut surface without sharp dendrites. This provides new ideas for the development of aluminum batteries in the future.
Aluminum batteries have many advantages over lithium batteries
The aluminum battery uses metal aluminum as the negative electrode, chloroaluminate-based molten salt or ionic liquid as the electrolyte, aluminum deposition/stripping occurs on the negative electrode, and chloroaluminate ion or aluminum ion insertion/extraction or conversion reaction occurs on the positive electrode.
“Aluminum batteries have the advantages of high battery capacity, high safety and long service life.” Experts said that compared with traditional lithium batteries, aluminum batteries have many advantages, because the theoretical mass specific capacity of aluminum is 2.98 Ah/g , second only to lithium. The theoretical volumetric specific capacity is 8.05Ah/cm3, ranking first among all metals, so the battery capacity of aluminum batteries has a high theoretical upper limit.
And because the negative metal aluminum of the aluminum battery has stable properties and the electrolyte is not flammable, the aluminum battery will not burn, explode and other dangerous phenomena even if it is punctured and short-circuited.
Experts have developed a new type of non-aqueous aluminum battery with room temperature ionic liquid as the electrolyte, graphite as the positive electrode, and aluminum as the negative electrode. This battery system has a discharge voltage of up to 2 V, and has excellent cycle stability and rate performance, showing great practical potential. Since then, non-aqueous aluminum batteries have gradually become a research hotspot in the field of energy storage worldwide.
However, due to the strong acidity of the ionic liquid electrolyte, high-capacity cathode materials dissolved in the electrolyte usually have the problem of short cycle life. In addition, the ionic liquid electrolyte is extremely easy to absorb water, has poor air stability, and is easy to decompose. The development has become an important research direction of non-aqueous aluminum batteries.
“This latest research, by using a low-melting inorganic chloride molten salt electrolyte, successfully replaced the currently commonly used ionic liquid electrolyte, and achieved high-rate operation, low-voltage polarization and high energy efficiency of aluminum batteries.” Expert said that due to the high thermal stability and non-flammability of the low melting point molten salt electrolyte, it solves the difficult problem of large-scale integrated system safety.
Aluminum batteries still have shortcomings
Although aluminum batteries have good application prospects and have made significant breakthroughs in recent years, their shortcomings, such as insufficient reaction kinetics, low energy density, and severe capacity fading in some systems, still need to be improved.
According to the data, in the aluminum battery system using ionic liquid electrolyte, the graphite material based on the intercalation/deintercalation reaction mechanism has limited reversible capacity, which will lead to a low overall energy density of the battery. Cathode materials such as sulfur based on a conversion-type reaction mechanism operate at lower temperatures and exhibit high specific capacity.
However, they have slow battery reaction kinetics, large charge-discharge voltage polarization, poor charge-discharge rate performance, Short cycle life and other shortcomings will greatly reduce the energy efficiency of the battery.
“Non-aqueous rechargeable aluminum-ion battery cathode materials usually face the problems of low electrical conductivity and structural disintegration.” Experts say that the volume change of intercalated materials during cycling, in addition to making the material’s electrical conductivity worse, will also Lead to swelling and disintegration of electrodes, pulverization of active materials, etc.
In addition, intercalated transition metal compounds still have the problems of low discharge voltage, low capacity, and rapid capacity decay, which are much more serious than li-ion batteries.
Conversion materials generally face the problems of irreversible reaction and low coulombic efficiency (the percentage of charge released during battery discharge to the number of charges input during charging under given conditions), and the discharge capacity of the battery is low in the first few cycles. After a sharp decline, it exhibits rapid capacity fading and poor cycling stability.
At the same time, aluminum as a negative electrode material has a passivation layer on the electrode surface, which will reduce the voltage and efficiency of the battery; severe corrosion of aluminum will also lead to irreversible aluminum consumption, thereby reducing the utilization rate of aluminum electrodes; and during the cycle process. The growth of aluminum dendrites will also reduce the safety and cycle life of the battery.
In non-aqueous rechargeable aluminum-ion batteries, the role of binders has been ignored, so by There is also less research on the modification of existing binder systems and the development of new binders to improve battery performance.
Aluminum batteries have great practical application prospects
It is understood that energy storage technology is closely connected with new energy applications and the development of power grids, which can effectively improve energy utilization efficiency and solve problems such as power supply in remote areas. Therefore, energy storage technology is a key link that cannot be avoided in the development of new energy.
Industry insiders believe that the future of energy storage batteries should be in the wind power and optoelectronic industries, especially the wind power industry that has already been deployed in large numbers. Although the wind power industry has developed rapidly in recent years, it has been plagued by grid integration due to the instability of wind resources. The application of energy storage technology can help wind farms output smoothly.
The advantages of aluminum batteries are high safety, good stability, and excellent wide temperature performance. Therefore, experts believe that aluminum batteries will be inseparable from battery energy storage system, special equipment and other industries in the future.
According to estimates, by 2025, the power scale of China’s electrochemical energy storage market alone will reach 28.6 GW, and the market share will reach 128.7 billion RMB. The market scale of the entire industry has a trillion-level market potential.
Electrochemical energy storage technology has become the first choice for grid application of energy storage technology to solve new energy access due to its short construction period, low operating cost, and no impact on the environment. Currently, lithium-ion batteries dominate the electrochemical energy storage technology due to their high energy density. However, high cost, limited lithium resources, and safety issues greatly limit its large-scale energy storage applications.
Due to the low cost of aluminum anode, high content of crustal elements, and high specific capacity, aluminum batteries are considered to be a promising battery for practical applications other than lithium-ion batteries. More importantly, the aluminum battery system has high safety, and the new aluminum battery will solve the problem of large-scale integrated system safety after it is put into production.