Aqueous solution lithium battery system.LR927 battery

　　A schematic structure of a rechargeable battery system is assembled. The water rechargeable lithium battery (ARLB) uses a coated lithium metal as the anode and lithium manganate as the cathode, and its CV curve has a scanning speed of 0.1 mV/s. There are two pairs of redox peaks, located at 4.14/3.80 and 4.28/3.93 V, respectively. From the above figure, the Redox is as follows: during the charging process, only one is in the anodic reaction. The transportation of Li+ions from aqueous electrolytes through the coating layer reduces the deposition of Li metal on the surface of the lithium metal. Two reactions were carried out on the cathode: the cations of Li+were de embedded into the sites from tetrahedron 8a and Octahedron 16c, and then two pairs of redox peaks were generated, similar to the behavior of organic electrolytes. During the discharge process, a reverse process occurs. Therefore, there are two pairs of redox peaks in the CV curve of our ARLB. This indicates that the lithium metal with a chemical coating of 0.5mol.L-1 Li2SO4/LiMn2O4 on our battery can generate an average output voltage of more than 3.8 V in a rechargeable battery with an aqueous electrolyte, which is much higher than the theoretical decomposition voltage of water, which is 1.229 V.

　　Figure 3: (1) Schematic diagram: The rechargeable lithium aqueous solution battery (ARLB) we designed uses a covered lithium metal as the anode, lithium manganate as the cathode, and 0.5mol.L-1 Li2SO4 aqueous solution as the electrolyte. (b) The scanning rate of the ARLB is 0.1 mV s-1. The potential variation of Li+ions in our design of ARLB is shown in Figure 4. Lithium metal has the lowest oxidation Reduction potential, -3.05 V (relative to Standard hydrogen electrode, SHE), and reacts rapidly with water to produce hydrogen and LiOH. In addition, the potential of lithium metal is much lower than that of hydrogen evolution, and hydrogen will be easily produced. However, in our example, the coating of lithium metal is very stable in aqueous electrolyte and without hydrogen evolution. The main reason is that Li+ions can cross the potential range of hydrogen evolution through the coating and directly reach the lithium metal. This intersection is similar to the potential changes between the two sides of the community membrane24. The sharp decrease in the potential of Li+ions in the coating ranges from positive to negative. The outer coating of Li+ions has a higher potential and is very stable. Li+ions do not come into contact with water inside the coating and cannot provide water for the production of hydrogen to the electron atom Li. By the way, water and protons cannot enter the internal coating, and they cannot reach a sufficiently low potential to produce hydrogen gas. As for the LiMn2O4 positive electrode, it is stable because its potential lies below water, which is much more favorable for oxygen evolution than for hydrogen evolution.

　　On the basis of the discharge voltage and capacity of Li metal anode and LiMn2O4 positive electrode, the ARLB discharge energy density based on the total mass of electrode material is 446 W/h kg-1, which is much higher than those previously reported in ARLBs (30-45 W/kg-1) 14, 15, 16, 17, 18, 19, 20, 21. Of course, it is higher than that used for lithium/M+aqueous solutions and other liquid flow batteries 3, 4, 5, 9, 12. Based on the manufacturing technology of half the energy density of lithium-ion batteries, almost available 7, 14 can be made, which means that the actual energy density is above 220 watt hours per kilogram-1, which is higher than about 80%, corresponding to the Li ion battery for electric vehicles (120 watt hours per kilogram-1 is C/organic electrolyte/LiMn2O4) 6, 7. This high energy density indicates that pure electric vehicles can run 200 to 400 kilometers on a single charge.

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