Development of magnesium battery - applications and difficulties
How a magnesium battery works
Magnesium battery is a primary battery with magnesium as the anode electrode and some metal or non-metal oxides as the cathode electrode. Magnesium battery is a new type of secondary battery with great potential developed in recent years. Similar to the composition of lithium-ion batteries, magnesium batteries are mainly composed of four parts: cathode electrode, anode electrode, separator and electrolyte.
As shown in the figure, taking the discharge process as an example, generally, metal magnesium undergoes a dissolution reaction on the anode electrode side to form Mg2+, which is dissolved in the electrolyte. Mg2+ migrates to the cathode electrode side for an intercalation reaction, and electrons migrate from the anode electrode to the cathode electrode from the external circuit to complete the entire discharge reaction.
The charging process is the opposite.
Main categories of magnesium batteries
● Magnesium dry battery
● Magnesium secondary battery
● Magnesium solid state battery
● Magnesium reserve battery
● Magnesium fuel cell
● Magnesium air battery
Advantages of magnesium battery
Compared with lithium batteries, magnesium batteries have the following advantages:
(1) Magnesium resources are abundant. Magnesium resources are abundant in the earth’s crust and oceans, and the price is much cheaper than lithium. The cost is only 1/25-/150 of lithium, and it can be used for thousands of years;
(2) Magnesium batteries are not easy to grow dendrites and have high safety;
(3) Magnesium and its compounds have no environmental pollution;
(4) The magnesium battery theoretical energy density is comparable to that of lithium batteries. As a anode electrode, magnesium metal is a two-electron reaction, with a high mass energy density (2205 mAh·g-1), and its volume energy density (3833 mAh·cm-3) is even higher than that of lithium (2046 mAh·cm-3 ).
At the same time, magnesium has a relatively anode electrode potential (- 2.37 Vvs SHE), so when magnesium is used as the anode electrode, the battery will have a higher working voltage, which is conducive to improving the energy density of the battery;
(5) Unlike lithium metal, magnesium tends to form two-dimensional and three-dimensional structures during deposition, so magnesium metal anodes are safer than lithium metal anodes.
(6) Magnesium has a higher melting and boiling point (648°C/1170°C) than lithium, and its chemical properties are relatively inert and easy to process;
The specific capacity of the magnesium anode electrode is 6 times that of the existing commercial lithium battery anode electrode, reaching 2230mAh/g. The Prussian blue magnesium cathode has the characteristics of low cost, high voltage, and long life. The theoretical energy density exceeds 500wh/kg, and it is expected to replace lithium iron phosphate.
Application of magnesium battery
Recently, magnesium dry batteries are only used as power sources for military communication equipment. Due to the constraints of magnesium alloy anodes that are difficult to form, magnesium dry batteries have not been commercialized and commercialized so far.
With the development of the magnesium processing industry and the successful development of magnesium alloy battery plates, the birth of magnesium dry batteries will become a reality, which will bring a revolution to the battery industry.
Magnesium secondary batteries are considered to be a new type of green battery that is expected to be suitable for electric vehicles due to their potential advantages in heavy-load applications due to their safety and price factors.
Magnesium reserve batteries can be used in aerospace, military and biomedicine, such as underwater propulsion, submarines, buoys, missiles, space vehicles and biological microsystems, etc.
As a high-energy chemical power source, magnesium fuel cells have broad application prospects in mobile electronic device power, autonomous submersible vehicle power, marine underwater instrument power and backup power, etc. Magnesium-air battery is a kind of primary magnesium fuel cell. The cathode uses air, which is discharged through the redox reaction of cathode and anode. It is a clean, safe and efficient new energy battery.
Its energy density is more than 20 times that of lead-acid batteries, and it can provide power for TVs, lights, portable computers, mobile phones, GPS and other equipment. At present, they have cooperated with enterprises to start mass production.
Difficulties faced in the development of magnesium battery
Magnesium battery is still in the preliminary research stage, and there are many unresolved problems, which make magnesium battery far from being practical. The main problems hindering the development of magnesium batteries are as follows:
(1) Due to the chemical activity of magnesium, under neutral and acidic conditions, magnesium reacts violently with water and releases hydrogen gas, which reduces the utilization of the electrode and brings difficulties to the assembly of the battery.
(2) Lack of a suitable non-aqueous medium for conducting Mg;
(3)Due to the small size, high charge density and strong polarization of magnesium ions, it is difficult to insert into most matrices, and it is difficult to form embedded compounds. Therefore, the available cathode materials are limited.
(4) The metallographic structure of rolled or extruded anode magnesium alloy is very unfavorable to the corrosion resistance of the battery. With the in-depth research on the magnesium battery, it is expected to break through the above problems and develop a high-performance, low-cost, safe and environmentally friendly magnesium battery.
Future research on magnesium battery should mainly start from the following aspects:
(1) Improve the purity of anode materials, optimize alloy composition, and develop magnesium alloys with high activity and low corrosion rate;
(2) The previous solvents are limited to THF and ether, which are easy to absorb water, and the battery anode cannot be used in an environment with water, so a safe and cheap solvent should be found;
(3) In terms of cathode electrode embedded materials that match anode materials, nanotubes, rods, or doped materials can be made, and new embedded materials can also be developed, such as organic composite materials;
(4)Explore the processing and forming methods of magnesium as a anode electrode material to improve the performance of the magnesium battery.
The above is the introduction about the magnesium battery and areas that need improvement, China’s magnesium resource reserves rank first in the world, and the development and utilization of magnesium resources is of great strategic significance to the development of our country; It is expected to become a new generation of best rechargeable batteries in the future.