Magnesium battery is a battery that uses magnesium cations as active charge transfer agent in solution and basic anode of electrochemical battery. The chemical properties of non rechargeable primary battery and rechargeable secondary battery were studied. Magnesium primary batteries have been commercialized and have been found to be used as backup batteries and general-purpose batteries.
Magnesium secondary battery is an active research topic, especially as a possible substitute or improvement of lithium-ion battery chemicals in some applications. A significant advantage of magnesium batteries is that they use solid magnesium anode. Compared with the battery design made of lithium, it allows higher energy density design. In many cases, lithium batteries need to be embedded with lithium anode. The insertion anode ("magnesium ion") was also studied.
Primary battery
Since the beginning of the 20th century, primary magnesium batteries have been developed. The chemical composition of many reserve battery types has been studied. Cathode materials include silver chloride, copper chloride (I), palladium chloride (II), copper iodide (I), copper thiocyanate (I), manganese dioxide and air (oxygen). For example, water activated silver chloride / magnesium reserve batteries began commercial production in 1943.
Ba-4386 magnesium dry battery has been fully commercialized, and the cost per unit is close to zinc battery - compared with the same zinc carbon battery, the battery has larger capacity and longer shelf life. Since 1968, ba-4386 has been widely used by the U.S. military until it was replaced by lithium thionyl chloride battery in 1984 [3] [4].
The theoretical working voltage of magnesium air fuel cell is 3.1V and the energy density is 6.8 kwh / kg. Ge produced a magnesium air fuel cell operating in neutral sodium chloride solution as early as the 1960s. Magnesium air battery is a primary battery, but it is possible to "refuel" by changing the anode and electrolyte. Magnesium air batteries have been commercialized and used as backup systems on land and seabed power, using seawater as electrolyte.
Secondary battery
summary
Magnesium is being studied and may replace or improve lithium-ion batteries in some applications. Compared with lithium as negative electrode material, the unit mass energy density of magnesium is (theoretically) less than half that of lithium (18.8 MJ / kg vs 42.3 MJ / kg), but the bulk energy density is about 50% (32.731 GJ / m3 vs 22.569 GJ / m3). Compared with metal lithium anode, magnesium anode does not show dendrite formation, which may allow metal magnesium to be used without intercalation compound; [Note 3] the ability to use magnesium anodes without intercalation increases the theoretical maximum relative volume energy density to about 5 times that of lithium-ion batteries. In addition, modeling and battery analysis show that magnesium based batteries may have a cost advantage over lithium due to the abundance of magnesium on the earth and the relative scarcity of lithium deposits.
As early as the 1990s, the potential use of magnesium based batteries based on V2O5, tis2 or ti2s4 cathode materials and metal magnesium anodes has been recognized. However, the instability of the observed discharge state and the uncertainty of the role of water in the electrolyte limit the progress. [10] [11] the first successful rechargeable battery was reported in 2000, based on chevrol type mo6s8 cathode and organic aluminum magnesium halide / THF based electrolyte.
As of 2018, secondary magnesium battery research has not produced commercially viable batteries, and the specific challenges are electrolyte and cathode materials. As of 2015, the obstacle to the production of commercially useful magnesium batteries is the lack of proven practical electrolytes and high energy density cathode materials for magnesium ions.
Research
Anode and electrolyte
A major disadvantage of using metal magnesium anode is that it is easy to form a passivation (non-conductive) layer during charging, which hinders further charging (opposite to the behavior of lithium); The passivation layer is considered to be derived from the decomposition of electrolyte during magnesium ion reduction. Common counter ions such as perchlorate and tetrafluoroboric acid were found to contribute to passivation, as were some common polar inorganic solvents such as carbonate and nitrile.
An early attempt to explore the use of a magnesium / magnesium alloy as an anode for reversible insertion (e.g., magnesium / bismuth based batteries). These have been shown to prevent passivation of the anode surface, but suffer anode damage due to the volume change during insertion and the slow dynamics of insertion.
Examples of the types of plug-in anodes studied include Sn and Mg2Sn.
Grignard based ether electrolytes have been shown not to be passivated; Organic magnesium borate also showed no passivation in electroplating. Compound Mg (bph2bu2) 2 was used in the rechargeable magnesium battery first shown, and its use was limited by electrochemical oxidation (i.e. low anode limit of voltage window). Other electrolytes studied by [21] include borohydride, phenol alkoxides, alkoxylates, amino based complexes (such as six methyl two silanes), carbon borane salts, fluorinated alkoxy borates, Mg (BH4) (NH2) solid electrolytes, and four polymer /PVDF containing Mg (AlCl2EtBu) 2.
The current wave of interest in magnesium metal batteries began in 2000, when an Israeli team reported reversible magnesium plating with a mixed solution of magnesium chloride and aluminum chloride in ethers such as THF. The main advantage of this electrolyte is that the positive limit of the voltage window is significantly greater than the previously reported magnesium plating electrolyte (therefore, the battery voltage is higher). Since then, several other magnesium salts have been reported, which are less corrosive than chlorides [26].
Compared with lithium, one disadvantage is that the charge of magnesium in the solution is high (+ 2), which often leads to the increase of viscosity and decrease of fluidity in the electrolyte. As of 2014, the movement of magnesium ions into the cathode lattice was very slow.
In 2018, a chlorine free electrolyte, together with a quinone based polymer cathode, showed promising performance, with a specific energy of 243 wh (870 kJ) per kilogram, a specific power of 3.4 kW / kg, and a retention rate of 87% in 2500 cycles. It is said that the absence of chloride in the electrolyte can improve ion dynamics, so as to reduce the use of electrolyte and improve performance.
A promising method is to combine magnesium anode with sulfur / carbon cathode. Therefore, there is a need for a non nucleophilic electrolyte that will not convert sulfur into sulfide just because of its reducibility. This electrolyte has been developed on the basis of chlorine containing [32] [33] [34] and chlorine free composite salts. The electrolyte in is a Mg salt containing Mg cation and two hexafluoroisopropyl boron groups as anions. This system is easy to synthesize. It shows similar ionic conductivity to lithium-ion battery. Its electrochemical stability window is as high as 4.5V. It is very stable in air and versatile for different solvents.
Cathode material
For cathode materials, the applicability of many different compounds has been studied, including those used in magnesium primary batteries. The new cathode materials studied or proposed include zirconium disulfide, cobalt oxide (II, III), tungsten selenide, vanadium pentoxide and vanadate based cathode. In 2000, the chelating phase form of mo6s8 was proved to have good applicability as a cathode. It lasted 2000 cycles with 15% loss under 100% discharge; The disadvantages are poor low temperature performance (the mobility of magnesium is reduced, which is compensated by replacing selenium) and low voltage. C. molybdenum disulfide cathode shows better voltage and energy density: 1.8V and 170mAh / g. Transition metal sulfides are considered as promising cathode candidates for magnesium ion batteries. In 2015, a mixed magnesium battery was reported, using a mixed magnesium / sodium electrolyte, and sodium was inserted into the nano iron disulfide cathode.
The cathode based on manganese dioxide shows good performance, but it will deteriorate in the cycle.
In 2014, a rechargeable magnesium battery was reported, using ion-exchanged olivine type mgfesio4 cathode and bis (trifluoromethylsulfonyl) imine / triethylene glycol electrolyte. The battery showed a capacity of 300mAh / g and a voltage of 2.4V.
In addition to non inorganic metal oxide / sulfide type cathode materials have also been studied: a cathode based on polymer containing anthraquinone was reported in 2015; Other organic and organic polymer cathode materials capable of redox reaction have also been studied, such as poly-2,2 '- dithiolidine.
In 2016, a porous carbon / iodine composite cathode was reported as a potential alternative to the Mg2 + plug-in cathode - the chemical reaction was reported as potentially suitable for rechargeable mobile batteries.
Commercialization
In October 2016, Honda and saitec (Saitama Industrial Technology Center) claimed to have a commercially available magnesium battery based on vanadium pentoxide / sulfur heteroalloy cathode. It also claims that the commercialization date is 2018.
In 2021, a design called wonderlight won an award at the Kansas Innovation Festival.
