CLASS OF CATHODE MATERIALS AND SECONDARY ION BATTERIES CONTAINING THESE CATHODE MATERIALS

Abstract

A class of cathode materials and secondary ion batteries containing these materials are provided. These cathode materials at least include a cathode active substance comprising a first active substance and a carrier. The first active substance is selected from alkali metal halide or alkali metal sulfite, alkaline earth metal halide or alkaline earth metal sulfite, aluminum halide, zinc halide and zinc sulfite. The carrier has a low-dimensional structure and is selected from a template and/or a second active substance. The first active substance of the cathode material has a relatively low molecular weight and a relatively high redox potential, and thus the secondary ion batteries have a relatively high specific capacity and voltage.

Claims

1. A class of cathode materials, at least including a cathode active substance comprising a first active substance and a carrier, wherein the first active substance is selected from alkali metal halide or sulfite, alkaline earth metal halide or sulfite, aluminum halide, zinc halide and zinc sulfite; the carrier has a low-dimensional structure and is selected from a template and/or a second active substance.

2. The cathode material according to claim 1, wherein in the cathode material, the first active substance may be uniformly distributed on the carrier or in the low-dimensional structure of the carrier; preferably, the low-dimensional structure comprises at least one of zero-dimensional, one-dimensional, two-dimensional, three-dimensional and multi-level structures; preferably, the low-dimensional structure may comprise a crystalline structure or an amorphous structure; preferably, the template and the second active substance have a zero-dimensional, one-dimensional, two-dimensional, three-dimensional or multi-level structure; preferably, at least a part of the halide or sulfite in the cathode material is in the low-dimensional structure; preferably, the carrier is selected from a template and/or a second active substance; preferably, the second active substance is selected from LiMn.sub.2O.sub.4, a ternary material, Na.sub.nCu.sub.xFe.sub.yMn.sub.zO.sub.2, Na.sub.nNi.sub.xFe.sub.yMn.sub.zO.sub.2, Na/K.sub.xPR(CN).sub.6 (P and R are Fe, Co, Ni or Mn), K.sub.0.5MnO.sub.2, LiFePO.sub.4, Na.sub.xFe.sub.y(PO.sub.4).sub.n, Na.sub.xFe.sub.y(SO.sub.4).sub.n, polypyrrole, polyaniline and so on; preferably, the second active substance is nanoparticle, which can further constitute a micron sphere.

3. The cathode material according to claim 1, wherein the alkali metal halide is selected from at least one of lithium chloride, lithium bromide, lithium iodide, sodium chloride, sodium bromide, sodium iodide, potassium chloride, potassium bromide and potassium iodide; preferably, the alkali metal sulfite is selected from at least one of lithium sulfite, sodium sulfite and potassium sulfite; preferably, the alkaline earth metal halide is selected from at least one of magnesium chloride, magnesium bromide, magnesium iodide, calcium chloride, calcium bromide and calcium iodide; preferably, the alkaline earth metal sulfite is selected from magnesium sulfite and/or calcium sulfite; preferably, the aluminum halide is selected from at least one of aluminum chloride, aluminum bromide and aluminum iodide; preferably, the zinc halide is selected from at least one of zinc chloride, zinc bromide, zinc iodide and so on.

4. The cathode material according to claim 1, wherein the first active substance accounts for 1%-99% of the mass of the cathode material, preferably 5%-90% preferably, the carrier accounts for 0.1%-95% of the mass of the cathode material, preferably 5%-90%; illustratively, in the carrier, the mass ratio of the template to the second active substance is (0.1-1):(0-10); preferably, the first active substance has the low-dimensional structure or a micro-nano grain structure; preferably, in the cathode material, when the first active substance is distributed in the low-dimensional structure, the first active substance also has the low-dimensional structure; preferably, when the first active substance is distributed on the carrier, the first active substance forms the micro-nano grain; preferably, the particle size of the micro-nano grain is in a range of 0.1-5 μm, preferably 0.5-5 μm; preferably, in the cathode material, the content of the low-dimensional structure in the first active substance is higher than the content of the micro-nano grain; preferably, the cathode material may be treated by carbonization, elution or other known methods to obtain a cathode material substantially comprising no template; illustratively, the cathode material comprises the first active substance and the carrier; the carrier comprises the second active substance; the first active substance and the second active substance are compounded to form the cathode material; for example, the first active substance is filled in the gaps among the nanoparticles or the micron spheres of the second active substance, and the two substances are compounded to form the cathode material.

5. A method for preparing the cathode material according to claim 1, wherein the method comprises: mixing the carrier and the first active substance, followed by compounding to obtain the cathode material; preferably, when the carrier is selected from a template and optionally comprises or does not comprise the second active substance, the mixing comprises: mixing the template and the first active substance, followed by adding with the second active substance; or, mixing the template and the second active substance, followed by adding with the first active substance; or, mixing the second active substance and the first active substance, followed by adding with the template; preferably, the method further comprises: optionally treating the cathode material after the compounding by any one of high-temperature carbonization, elution and so on; preferably, in the method for preparing, the carrier is pretreated to obtain any form of dispersion, foam, assembled film, powder, slurry and so on; preferably, the high-temperature carbonization specifically comprises: carbonizing the cathode material at a high temperature of 400-1000° C.; illustratively, the time for the carbonization is 1-10 h; preferably, the method for preparing the cathode material comprises the following steps: (1) ultrasonically dispersing the carrier to obtain a mixture, and then freeze drying to obtain a foam, (2) adding a solution containing the first active substance dropwise onto the foam obtained in step (1), and drying in the air to obtain a cathode material precursor. (3) carbonizing the cathode material precursor obtained in step (2) to a high-temperature treatment to obtain the cathode material; preferably, the concentration of the carrier in the mixture is 1-100 mg/g; preferably, step (2), optionally, further comprise slicing the foam; preferably, the solution containing the first active substance comprises the first active substance and a solvent; preferably, the solvent is selected from methanol, ethanol, acetone, dichloromethane and so on. Preferably, in the solution containing the first active substance, the concentration of the first active substance is 0.01-10 g/mL; preferably, the elution specifically comprises: adding the cathode material into an elution agent to remove all or a part of the template; preferably, the elution agent is selected from an organic solvent, such as concentrated acid or concentrated base; preferably, the method for preparing the cathode material comprises the following steps: (1) ultrasonically dispersing the first active substance and the carrier in the solvent to obtain a mixture, and drying to obtain a solid material; (2) adding the solid material obtained in step (1) into the elution agent to remove all or a part of the template to obtain an intermediate; and (3) drying the intermediate obtained in step (2) to obtain the cathode material.

6. A modified cathode material, wherein the modified cathode material is obtained by eluting the template in the cathode material according to claim 1, preferably, the modified cathode material substantially comprises no template.

7. Use of the cathode material according to claim 1 in secondary ion batteries.

8. The use according to claim 7, wherein the secondary ion battery is selected from at least one of aqueous secondary ion battery, organic secondary ion battery, organic/aqueous hybrid secondary ion battery, gel battery, quasi-solid battery and all-solid-state battery.

9. The use according to claim 7, wherein the secondary ion battery further comprises an anode material; the anode material is selected from a metal material and a carbon-based anode material; illustratively, the carbon-based anode material is selected from at least one of AC, graphite, hard carbon, soft carbon and so on; illustratively, the metal material is selected from at least one of lithium, sodium, potassium, magnesium, aluminum, zinc and so on.

10. The use according to claim 7, wherein the secondary ion battery further comprises an electrolyte solution, gel electrolyte or solid-state electrolyte; preferably, the electrolyte solution comprises an electrolyte and a solvent; preferably, in the electrolyte solution, the electrolyte is selected from at least one of lithium salt, sodium salt, potassium salt, magnesium salt, calcium salt, aluminum salt and zinc salt; preferably, the lithium salt is selected from at least one of lithium sulfate, lithium nitrate, lithium acetate, lithium perchlorate, lithium chloride, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium bis((trifluoromethyl)sulfonyl)imide and lithium bis(pentafluoroethanesulfonyl)imide; illustratively, the sodium salt is selected from at least one of sodium perchlorate, sodium acetate, sodium nitrate, sodium chloride, sodium sulfate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, sodium bis((trifluoromethyl)sulfonyl)imide and sodium bis(pentafluoroethanesulfonyl)imide; illustratively, the potassium salt is selected from at least one of potassium nitrate, potassium acetate, potassium sulfate, potassium chloride, potassium bis(fluorosulfonyl)imide, potassium trifluoromethanesulfonate, potassium bis((trifluoromethyl)sulfonyl)imide and potassium bis(pentafluoroethanesulfonyl)imide; illustratively, the zinc salt is selected from at least one of zinc trifluoromethanesulfonate, zinc sulfate, zinc chloride, zinc acetate and zinc bis((trifluoromethyl)sulfonyl)imide; illustratively, the magnesium salt is selected from at least one of magnesium trifluoromethanesulfonate, magnesium sulfate, magnesium chloride, magnesium acetate and magnesium bis((trifluoromethyl)sulfonyl)imide; preferably, the solvent is selected from, but not limited to, at least one of water or (and) an organic solvent such as ester, ether or nitrile; illustratively, the ester is selected from, but not limited to, at least one of propylene carbonate, diethyl carbonate and ethylene carbonate; illustratively, the ether is selected from ethylene glycol dimethyl ether; preferably, the electrolyte solution further includes a hybrid electrolyte solution comprising the electrolyte and a mixed solvent of an organic solvent and water; preferably, in the electrolyte solution, the concentration of the electrolyte is greater than or equal to 1-100 mol/L, preferably 5-70 mol/L; preferably, the gel electrolyte comprises a first polymer body material and an electrolyte solution, wherein the electrolyte solution is selected from the organic electrolyte solution; preferably, the first polymer body material is selected from at least one of polyvinyl alcohol, polyacrylic acid, polyacrylamide, sodium polyacrylate, polyethylene oxide, polypropylene carbonate, polyether ether ketone, ethylene glycol acrylonitrile block copolymer, poly(vinylidene fluoride-co-hexafluoropropylene) and the like; illustratively, the aqueous electrolyte is K(FSI).sub.0.55(OTf).sub.0.45.Math.0.9H.sub.2O electrolyte solution; illustratively, the organic electrolyte solution is selected from KFSI in propylene carbonate; preferably, the solid-state electrolyte is selected from at least one of a polymer electrolyte, an inorganic solid-state electrolyte and a composite solid-state electrolyte; preferably, the polymer electrolyte comprises a second polymer body and an electrolyte; preferably, the second polymer body comprises at least one of the first polymer body, polyethylene oxide, polypropylene oxide and so on; preferably, the inorganic solid-state electrolyte is selected from at least one of a sulfide solid-state electrolyte and an oxide solid-state electrolyte; preferably, the sulfide solid-state electrolyte comprises a sulfur-lithium superionic conductor, a sulfur-sodium superionic conductor and argyrodite such as Li.sub.3PS.sub.4, Na.sub.3PS.sub.4, Li.sub.6PS.sub.5Cl and so on; preferably, the oxide solid-state electrolyte is selected from at least one of perovskite, a sodium fast ionic conductor, a lithium fast ionic conductor and garnet such as La.sub.0.8Sr.sub.0.2Ga.sub.0.8Mg.sub.0.2O.sub.3, NaLaS.sub.2, La.sub.0.5Li.sub.0.5TiO.sub.3, Li.sub.7La.sub.3Zr.sub.2O.sub.12 and so on; preferably, the composite electrolyte comprises the polymer electrolyte and a second phase inorganic filler; the second inorganic filler is selected from at least one of a metal oxide nanoparticle such as TiO.sub.2, SiO.sub.2, Al.sub.2O.sub.3, ZrO.sub.2, MgO, ZnO.sub.x and so on, zeolite, montmorillonite and so on; preferably, the organic secondary ion battery has good cycle performance and relatively high energy density.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0101] FIG. 1 illustrates the microstructure of the KBr/rGO/AC composite according to Example 1-A; panel a: a scanning electron micrograph (SEM) image; panels b-d: energy spectrum analysis.

[0102] FIG. 2 is a charge/discharge curve of the aqueous battery according to Example 1-A.

[0103] FIG. 3 illustrates the cycle performance after 500 charge/discharge cycles of the aqueous battery according to Example 1-A.

[0104] FIG. 4 illustrates the microstructure of the KI/rGO/AC composite according to Example 1-B; panel a: SEM images; panels b-d: energy spectrum analysis; panels e and f: transmission electron microscope (TEM) images.

[0105] FIG. 5 is a TEM images of the KI/rGO/AC composite after 100 cycles according to Example 1-B.

[0106] FIG. 6 is a charge/discharge curve of the full battery according to Example 1-B.

[0107] FIG. 7 is a charge/discharge curve of the battery according to Examples 2-4.

[0108] FIG. 8 illustrates the cycle performance after 600 charge/discharge cycles of the battery according to Example 5.

[0109] FIG. 9 illustrates the cycle performance after 200 charge/discharge cycles of the battery according to Example 6-B.

[0110] FIG. 10 displays TEM images of the NaCl-based cathode material before (a) and after (b) elution of the template according to Example 7.

[0111] FIG. 11 illustrates the cycle performance after 300 charge/discharge cycles of the organic gel battery according to Example 9.

[0112] FIG. 12 illustrates the cycle performance after 10 charge/discharge cycles of the battery according to Comparative Example 2.

[0113] FIG. 13 illustrates the cycle performance after 100 charge/discharge cycles of the battery according to Comparative Example 3.

DETAILED DESCRIPTION

[0114] The present disclosure will be illustrated in further detail by the following description of specific embodiments. It should be understood that the following embodiments are merely exemplary illustration and explanation of the present disclosure, and should not be construed as limiting the protection scope of the present disclosure. All techniques implemented based on the content of the present disclosure described above are encompassed within the protection scope of the present disclosure.

[0115] Unless otherwise stated, the experimental methods used in the following examples are conventional methods. Unless otherwise stated, the reagents, materials and so on used in the following examples are commercially available.

[0116] In the following examples, the electrochemical performance of the batteries was tested at 25° C. unless otherwise stated.

Example 1-A. Potassium Ion Battery

[0117] 1. Preparation of Cathode Material:

[0118] (1) An aqueous dispersion containing graphene oxide (GO, 3 mg/g) and activated carbon (AC, 7 mg/g) was ultrasonicated for 2 h to obtain a mixture; 5 mL of the mixture was added into a culture dish with a diameter of 3.5 cm and froze for 2 h in a low-temperature refrigerator at −80° C. The mixture was frozen drying for 40 h at −60° C. to obtain a GO/AC foam.

[0119] (2) The GO/AC foam was punched into discs with a diameter of 11 mm; a 25 mg/mL KBr in methanol (200 μL) on each disc, and the round sheets were placed in a fume hood for 48 h to obtain a KBr/GO/AC sample after methanol was completely volatilized.

[0120] (3) The KBr/GO/AC sample prepared in step (2) was carbonized at a high temperature for 4 h in a 700° C. tube furnace to obtain KBr/reduced graphene oxide (rGO)/ACcomposite.

[0121] FIG. 1 illustrates the microstructure of the KBr/rGO/AC cathode. From the SEM image and energy spectrum analysis, it can be seen that KBr is evenly distributed in the foam. The average particle size of the micron grain is 1 μm.

[0122] 2. Preparation of aqueous battery: The full battery was assembled with the KBr/rGO/AC composite as the cathode, AC as the anode, 62 mol/kg aqueous K(FSI).sub.0.55(OTf).sub.0.45.Math.0.9H.sub.2O solution as the electrolyte solution and a glass fiber (GFF) as the separator. The mass of KBr in the cathode is 2 mg, and the mass of the anode AC is 12 mg. FIG. 2 illustrates the charge/discharge curve of the battery at a current density of 500 mA/g. The specific discharge capacity of the battery is 150 mAh/g and the capacity retention rate after 500 cycles is 86% (FIG. 3).

Example 1-B.

[0123] 1. Preparation of Cathode Material:

[0124] Steps (1)-(3) are the same as those in Example 1-A, wherein KBr in step (2) was replaced with KI to finally prepare the KI/rGO/AC composite.

[0125] FIG. 4 illustrates the microstructure of the KI/rGO/AC composite, in which KI was evenly distributed in the foam. In TEM image, the two-dimensional KI crystal has a lattice spacing of 0.35 nm, which corresponded to 200 crystal plane. According to the element analysis, the mass fraction of KI in the composite is 50%.

[0126] 2. Preparation of half-cell: A half-cell was assembled with the KI/rGO/AC material described above as the cathode, metallic potassium as the anode, 8 mol/L solution of KFSI in propylene carbonate as the electrolyte solution and GFF as the separator, wherein the mass of the cathode active substance KI is 3.7 mg. The half-cell still has a 94% capacity retention rate after 100 charge/discharge cycles at a current density of 100 mA/g. FIG. 5 illustrates a TEM image of the KI/rGO/AC cathode after 100 charge/discharge cycles and lattice distortion and lattice fringes of KI crystal can be observed.

[0127] 3. Preparation of full battery: A full battery was assembled with the KI/rGO/AC material described above as the cathode, pre-potassiated graphite as the anode, 8 mol/L KFSI in propylene carbonate as the electrolyte solution and GFF as the separator, wherein the mass of the cathode active substance KI is 3.7 mg, and the mass of the anode active substance is 3 mg. FIG. 6 is a charge/discharge curve of the full battery at a current density of 500 mA/g. The specific discharge capacity of the full battery is 113 mAh/g, and the full battery still has a 73% capacity retention rate after 800 charge/discharge cycles.

Example 2. Lithium-Ion Battery

[0128] 1. Preparation of cathode material: The preparation method in this example is the same as that of Example 1-A, except that solutions of LiCl, LiBr or LiI in methanol were added dropwise on the round sheets in step (2), and LiCl/rGO/AC composite, LiBr/rGO/AC composite and LiI/rGO/AC composite were prepared, respectively. The mass fractions of the active substances LiCl, LiBr and LiI in the composites are 45%, 51% and 48%, respectively.

[0129] 2. Assembly of battery: Half-cells were assembled with the LiCl/rGO/AC composite, the LiBr/rGO/AC composite or the LiI/rGO/AC composite in this example as the cathode, metallic lithium as the anode, 10 mol/L LiFSI in propylene carbonate as the electrolyte solution and GFF as the separator. In FIG. 7, panels a-c are charge/discharge curves of the three batteries described above at a current density of 100 mA/g, and the specific discharge capacities are 315 mAh/g, 153 mAh/g and 117 mAh/g, respectively.

Example 3. Sodium-Ion Battery

[0130] 1. Preparation of cathode material: The preparation method in this example is the same as that of Example 1-A, except that solutions of NaCl, NaBr or NaI in methanol or a mixture of water and methanol were added dropwise on the round sheets in step (2), and NaCl/rGO/AC composite, NaBr/rGO/AC composite and NaI/rGO/AC composite were prepared, respectively. The mass fractions of the active substances NaCl, NaBr and NaI in the composites are 52%, 46% and 48%, respectively.

[0131] 2. Assembly of battery: Half-cells were assembled with the NaCl/rGO/AC composite, the NaBr/rGO/AC composite or the NaI/rGO/AC composite in this example as the cathode, metallic sodium as the anode, 6 mol/L NaFSI in propylene carbonate as the electrolyte solution and GFF as the separator. In FIG. 7, panels d-f are charge/discharge curves of the three batteries at a current density of 100 mA/g, and the specific discharge capacities are 116 mAh/g, 156 mAh/g and 177 mAh/g, respectively.

[0132] Example 4. Zinc-Ion Battery

[0133] 1. Preparation of cathode material: The preparation method in this example is the same as that of Example 1-A, except that solutions of ZnCl.sub.2, ZnBr.sub.2 or ZnI.sub.2 in methanol were added dropwise on the round sheets in step (2), and ZnCl.sub.2/rGO/AC composite, ZnBr.sub.2/rGO/AC composite and ZnI.sub.2/rGO/AC composite were prepared, respectively. The mass fractions of the active substances ZnCl.sub.2, ZnBr.sub.2 and ZnI.sub.2 in the composites are 47%, 46% and 46%, respectively.

[0134] 2. Assembly of battery: Half-cells were assembled with the three materials in this example as the cathode, metallic zinc as the anode, 2 mol/L Zn(TFSI).sub.2 in acetonitrile as the electrolyte solution and GFF as the separator. In FIG. 7, panels g-i are charge/discharge curves of the three batteries described above at a current density of 100 mA/g, and the specific discharge capacities are 174 mAh/g, 163 mAh/g and 108 mAh/g, respectively.

Example 5. Sulfite

[0135] 1. Preparation of cathode material: The preparation method of the cathode material in this example is the same as that of Example 1-A, except that: in step (2), 0.1 g/mL K.sub.25O.sub.3 in a mixture of water and methanol was added dropwise on the round sheet; in step (3), the K.sub.2SO.sub.3/GO/AC sample was carbonized at a high temperature of 500° C. in a tube furnace for 4 h to prepare the

[0136] K.sub.2SO.sub.3/rGO/AC composite, wherein the average particle size of the K.sub.2SO.sub.3 micron grain is 3 μm. According to the element analysis, the mass fraction of K.sub.2SO.sub.3 in the K.sub.2SO.sub.3/rGO/AC composite is 45%.

[0137] 2. Assembly of aqueous battery: The preparation method in this example is the same as that of Example 1-A, except that the cathode is K.sub.2SO.sub.3/rGO/AC material, wherein the mass of the active substance K.sub.2SO.sub.3 of the cathode material is 2 mg. The battery still has an 82% capacity retention rate after 1000 charge/discharge cycles at a current density of 500 mA/g.

[0138] 3. Assembly of half-cell: The cathode was K.sub.2SO.sub.3/rGO/AC material, the anode was potassium, and the electrolyte solution was 6 mol/L KFSI in DME. FIG. 8 illustrates the cycle performance after 600 charge/discharge cycles of the battery, in which the battery still has an 88% capacity retention rate after 600 charge/discharge cycles at a current density of 100 mA/g.

Example 6-A. Addition of Second Active Substance

[0139] 1. Preparation of cathode material: (1) The 0.5 g of sodium iron manganese nickelate (NaNi.sub.1/3Fe.sub.1/3Mn.sub.1/3O.sub.2, the second active substance) with a microspheric microstructure was added into a 0.1 g/mL NaBr (the first active substance) in methanol (2 mL). The mixture was magnetically stirred for 12 h and then placed in a fume hood until the methanol completely evaporating. After that, the mixture was heated for 6 h in an air blast drier at 90° C. and the dried solid was ground for later use. By this method, NaBr could be filled in the gaps among the micron spheres to form NaBr/NaNi.sub.1/3Fe.sub.1/3Mn.sub.1/3O.sub.2 composite.

[0140] (2) The NaBr/NaNi.sub.1/3Fe.sub.1/3Mn.sub.1/3O.sub.2 composite, conductive carbon black and PVDF were mixed in a ratio of 8:1:1, and the slurry was applied on an aluminum foil current collector and dried. The material was punched into discs with a diameter of 11 mm for later use. The mass of the cathode active substance NaBr and NaNi.sub.1/3Fe.sub.1/3Mn.sub.1/3O.sub.2 are 1 mg and 2.5 mg, respectively.

[0141] 2. Assembly of battery: The battery was assembled with the composite described above as the cathode, sodium as the anode, 6 mol/L NaFSI in propylene carbonate as the electrolyte solution and GFF as the separator. The battery still has a capacity retention rate of up to 93.5% after 800 charge/discharge cycles at a current density of 500 mA/g.

[0142] Example 6-B. Addition of Second Active Substance

[0143] 1. Preparation of cathode material: The method is the same as that of Example 6-A, except that

[0144] NaNi.sub.1/3Fe.sub.1/3Mn.sub.1/3O.sub.2 was replaced with lithium iron phosphate (LiFePO.sub.4), and NaBr was replaced with LiBr.

[0145] 2. Assembly of half-cell: The half-cell was assembled with the LiFePO.sub.4/LiBr described above as the cathode, lithium as the anode, 10 mol/L LiFSI in propylene carbonate as the electrolyte solution and GFF as the separator, wherein the mass of the cathode active substance LiBr and LiFePO.sub.4 are 1.0 mg and 2.5 mg, respectively. FIG. 9 illustrates the cycle performance after 200 charge/discharge cycles of the battery at a current density of 100 mA/g, in which the battery still has a capacity retention rate of up to 98.6% after 200 charge/discharge cycles.

Example 7. Eluting Template

[0146] 1. Preparation of cathode material: (1) 0.1 g of TiO.sub.2 nanosheets was added to 100 mL of a 0.01 g/mL NaCl in a mixture of methanol and water (in a mass ratio of 1:1) and magnetically stirred for 12 h. The dispersion was heated to 50° C. until the solvent was completely evaporated and NaCl was uniformly deposited on the surface of TiO.sub.2 nanosheets partially in the form of nanoparticles due to electrostatic interaction (FIG. 10, panel a). The material was heated for 6 h in an air blast drier at 90° C. to obtain a solid, and the dried solid was added into concentrated hydrochloric acid. Since the TiO.sub.2 nanosheets were soluble while NaCl was insoluble in concentrated hydrochloric acid, the template was etched and only leaving low-dimensional NaCl. The elution of template didn't destroy the structure of NaCl, which is still partially in the state of nanoparticles, and the particle size did not change greatly before and after elution (FIG. 10, panel b). After the template was rinsed, the resulting NaCl solid was dried in vacuum at 90° C. for 6 h and then ground for later use.

[0147] (2) The step (1) was repeated for multiple times to obtain 0.5 g of the NaCl solid described above. NaCl, conductive carbon black and PVDF were mixed in a ratio of 7:2:1, and the slurry was applied on an aluminum foil current collector and dried. The material was punched into discs with a diameter of 11 mm for later use.

[0148] 2. Assembly of half-cell: The half-cell was assembled with the NaCl described above as the cathode, metallic sodium as the anode, 6 mol/L NaFSI in propylene carbonate as the electrolyte solution and GFF as the separator, wherein the mass of the cathode active substance NaCl was 1.8 mg. The half-cell still has a capacity retention rate of up to 93% after 600 charge/discharge cycles at a current density of 100 mA/g.

Example 8. Hydrogel Battery

[0149] 1. The preparation of hydrogel: The 0.05 mol of NaClO.sub.4 and 5 g of PVA were added to 5 mL of deionized water, and the mixture was stirred at room temperature for 20 min. Subsequently, the mixture was heated to 95° C. and continuously stirred for 2 h to give a homogeneous gel solution. The gel solution was added into a petri dish with a diameter of 6 cm and solidified in a refrigerator at −20° C. for 4 h to obtain a PVA-NaClO.sub.4 gel. The gel was shaped with a hole punch into discs with a diameter of 16 mm for later use.

[0150] 2. Assembly of full battery: A full battery was assembled with the NaI/rGO/AC composite prepared in Example 3 as the cathode, AC as the anode and PVA-NaClO.sub.4 as the gel electrolyte. The battery had a capacity retention rate of up to 95% after 100 charge/discharge cycles at a current density of 500 mA/g.

Example 9. Organic Gel Battery

[0151] 1. The preparation method of organic gel: The 0.3 g of polyethylene oxide (PEO) and 4.5 mL of 1 mol/L NaFSI in propylene carbonate were mixed and magnetically stirred for 12 h. The mixture was added to a petri dish with a diameter of 6 cm and let stand at room temperature for 7 days to give a PEO-NaFSI-PC organic gel electrolyte. The gel was punched into discs with a diameter of 16 mm for later use.

[0152] 2. Assembly of half-cell: The battery was assembled with the NaI/rGO/AC composite prepared in Example 3 as the cathode, metallic sodium as the anode and PEO-NaFSI-PC as the gel electrolyte. FIG. 11 illustrates the cycle performance of the battery, in which the battery still has an 86% capacity retention rate after 300 charge/discharge cycles at a current density of 100 mA/g.

Example 10. Organic/aqueous hybrid electrolyte battery

[0153] The battery was assembled with ZnI.sub.2/rGO/AC in Example 4 as the cathode, metallic zinc as the anode, 2 mol/L Zn(TFSI).sub.2 in a mixed solvent of acetonitrile and water (in a volume ratio of 10:1) as the electrolyte solution and GFF as the separator. The battery has a capacity retention rate of up to 89% after 200 charge/discharge cycles at a current density of 100 mA/g.

Example 11. All-Solid-State Battery

[0154] The preparation method of solid-state electrolyte: The 0.4 g of poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) was dissolved in 5 mL of anhydrous N,N-dimethylformamide, and the mixture was stirred well for 24 h. After then, 0.1 g of lithium bis((trifluoromethyl)sulfonyl)imide (LiTFSI) was added, and the mixture was further stirred for 24 h to obtain a homogeneous mixed solution. The well mixed slurry was quickly poured into a tetrafluoroethylene mold, and slowly vacuumized and dried for 48 h. The dried solid-state electrolyte film PVDF-HFP-LiTFSI was gently removed from the mold and quickly transferred to a glove box. The film was punched into sheets with a diameter of 16 mm for later use.

[0155] Assembly of half-cell: The solid battery was assembled using the above solid-state electrolyte with LiI/rGO/AC in Example 2 as the cathode and metallic lithium as the anode. The battery has a capacity retention rate of up to 89% after 800 charge/discharge cycles at a current density of 100 mA/g.

[0156] Comparative Example 1

[0157] 1. Preparation of KBr composite: KBr (AR), conductive carbon black and PVDF were mixed in a mass ratio of 8:1:1. The slurry was applied on an aluminum foil current collector and dried in a drying oven at 100° C. for 6 h to obtain discs with a diameter of 11 mm for later use, wherein the mass of KBr is 3 mg.

[0158] 2. Assembly of aqueous battery: An aqueous battery for testing was assembled with the KBr described above as the cathode, 62 mol/kg K(FSI).sub.0.55(OTf).sub.0.45.Math.0.9H.sub.2O aqueous solution as the electrolyte solution and GFF as the separator. The aqueous battery only has a 42% capacity retention rate after 50 charge/discharge cycles at a current density of 500 mA/g. The specific discharge capacity is 50 mAh/g, which is only 30% of that of Example 1-A.

[0159] Comparative Example 2

[0160] The battery was assembled with the NaNi.sub.1/3Fe.sub.1/3Mn.sub.1/3O.sub.2/NaBr composite in Example 6-A as the cathode, metallic sodium as the anode, 2 mol/L NaFSI in propylene carbonate as the electrolyte solution and GFF as the separator. FIG. 12 illustrates the cycle performance of the aqueous battery, in which the battery only has a 23.3% capacity retention rate after 10 charge/discharge cycles at a current density of 500 mA/g.

[0161] Comparative Example 3

[0162] 1. Preparation of cathode material: The preparation of the cathode material in this comparative example is different from that of Example 1-B in that the carrier was not added. K.sub.2SO.sub.3 as the first active substance was directly mixed with carbon black to obtain the K.sub.2SO.sub.3 composite through the following steps: K.sub.2SO.sub.3, conductive carbon black and PVDF were mixed in a mass ratio of 8:1:1. The slurry was applied on an aluminum foil current collector and dried in a drying oven at 100° C. for 6 h to obtain discs with a diameter of 11 mm for later use, wherein the mass of the active substance K.sub.2SO.sub.3 is 3 mg.

[0163] 2. Assembly of half-cell: The battery was assembled with the material in this comparative example as the cathode, metallic potassium as the anode, and 6 mol/L KFSI in DME as the electrolyte solution. FIG. 13 illustrates the cycle performance of the battery, in which the battery only has a 39% capacity retention rate after 100 charge/discharge cycles at a current density of 0.1 A/g. The specific discharge capacity of the battery is 105 mAh/g, which is only 55% of the specific discharge capacity of the half-cell in Example 5.

[0164] The embodiments of the present disclosure have been described above. However, the present disclosure is not limited the above embodiments. Any modification, equivalent, improvement and so on made without departing from the spirit and principle of the present disclosure shall fall within the protection scope of the present disclosure.