Aqueous battery pre-lithiation method, pre-lithiation positive electrode plate and aqueous lithium-ion battery

Abstract

The present invention provides an aqueous battery pre-lithiation method, a pre-lithiation positive electrode plate and an aqueous lithium-ion battery. The method comprises the following steps: mixing and grinding a transition metal pre-lithiation reagent with a mixed positive electrode material powder to obtain a pre-lithiation mixed positive electrode material powder; adding the pre-lithiation mixed positive electrode material powder into an organic solvent in which a binder is dissolved and stirring the mixture to obtain a mixed pre-lithiation positive electrode slurry; coating the mixed pre-lithiation positive electrode slurry on a metal foil to obtain a pre-lithiation positive electrode wet plate; and drying the pre-lithiation positive electrode wet plate in a blast oven to obtain a pre-lithiation positive electrode plate. During the first cycle of charging of the aqueous lithium-ion battery of the present invention, an electrochemical oxidation reaction of the transition metal pre-lithiation reagent occurs at the positive electrode, and the generated transition metal ions dissolve in the electrolyte. At the negative electrode, an SEI formation side reaction and a hydrogen evolution side reaction occur simultaneously, and the oxidation of the transition metal pre-lithiation reagent replaces the positive electrode active material to provide the first cycle of charging capacity for the side reactions.

Description

Technical Field

[0001] The invention relates to an aqueous battery pre-lithiation method, a pre-lithiation positive electrode plate and an aqueous lithium-ion battery, belonging to the field of lithium-ion batteries. Background Art

[0002] Lithium-ion batteries, as an emerging electrochemical energy storage device, offer advantages such as high energy density and high cycle efficiency, and are therefore widely used in small electronic devices and vehicles. However, because most lithium-ion batteries use flammable organic electrolytes, they pose a significant risk of internal short circuits or operation in extreme environments. Cases of battery explosions are common in various devices, and eliminating the safety hazards of lithium-ion batteries is an urgent issue. Therefore, developing safe and green aqueous lithium-ion batteries is one of the best solutions to improve battery safety.

[0003] Aqueous lithium-ion batteries (ALBs) have historically had low energy density and output voltage due to the narrow electrochemical stability window of the electrolyte solvent, water, making them a difficult research area. However, researchers have recently developed an aqueous LIB with a highly concentrated electrolyte. By using an electrolyte containing a high concentration of lithium salt, this LIB extends the electrochemical window from below 2V to above 3V. Furthermore, during cycling, this type of battery forms a solid electrolyte interphase (SEI) film on the negative electrode, which inhibits further side reactions. This allows the creation of aqueous LIBs with high output voltage, high efficiency, and high energy density. However, due to SEI formation and the accompanying hydrogen evolution side reaction during the first cycle, the first-cycle coulombic efficiency of aqueous LIBs is lower than that of traditional organic LIBs, and cyclability needs to be improved. Most researchers have attempted to improve the cycling performance of aqueous LIBs by using excess cathodes, but this significantly reduces the energy density of the electrodes, leaving them some distance from practical application.

[0004] To address the above issues, using pre-lithiation technology to pre-lithiate electrodes is an effective means to increase battery energy density, compensate for the loss of coulombic efficiency in the first cycle, and enhance the overall cyclability of the battery. However, widely used lithium-ion reagents in organic systems, such as LiH and Li3N, commonly used pre-lithiation additives in organic systems, will dissolve in aqueous electrolytes or undergo side reactions with aqueous electrolytes and produce gas, which will destroy the cyclability of aqueous batteries. Therefore, it is necessary to reconstruct the pre-lithiation method of aqueous lithium-ion batteries, screen out pre-lithiation reagents that are compatible with the various components of aqueous batteries, and have suitable pre-lithiation potentials and pre-lithiation specific capacities, and find a convenient, green, safe, and effective lithium supplementation method to improve the electrochemical performance of aqueous lithium-ion batteries. This is an urgent problem to be solved. Summary of the Invention

[0005] The present invention provides an aqueous battery pre-lithiation method, a pre-lithiation positive electrode plate and an aqueous lithium-ion battery. The pre-lithiation method breaks the limitation of traditional pre-lithiation additives that must contain lithium, and can be matched with aqueous electrolytes. The pre-lithiation operation is simple, and the pre-lithiation behavior will not have a negative impact on the working performance of the aqueous battery.

[0006] In a first aspect, an embodiment of the present invention provides a method for pre-lithiation of a positive electrode plate of an aqueous lithium-ion electrochemical battery, the method comprising:

[0007] Mixing and grinding the transition metal pre-lithiation reagent and the mixed cathode material powder to obtain the pre-lithiation mixed cathode material powder;

[0008] Adding pre-lithiation mixed positive electrode material powder into a solvent in which a binder is dissolved and stirring the mixture to obtain a mixed pre-lithiation positive electrode slurry;

[0009] coating the mixed pre-lithiated positive electrode slurry on a metal foil to obtain a pre-lithiated positive electrode wet plate;

[0010] Drying the pre-lithiated positive electrode wet plate in a blast oven to obtain a pre-lithiated positive electrode plate;

[0011] Wherein, the transition metal pre-lithiation reagent includes: metal powders of manganese, zinc, magnesium, aluminum, scandium, titanium, vanadium, chromium, copper, iron, cobalt, and nickel;

[0012] The mixed positive electrode material powder is a powder formed by mixing positive electrode material powder containing transition metal and a conductive agent;

[0013] The binder comprises at least one of fluorinated ethylene polymers, sodium alginate, sodium carboxymethyl cellulose, styrene-butadiene rubber, or acrylic acid ester multi-polymers;

[0014] The solvent includes one or more of water, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide, propylene carbonate, acetonitrile or tetrahydrofuran.

[0015] Preferably, the stirring speed of the stirring process is 1000-3000 r / min.

[0016] The transition metal pre-lithiation reagent is oxidized to form stable metal ions to provide a mass specific capacity greater than 500 mAh / g;

[0017] The redox potential of the transition metal pre-lithiation reagent electrochemically oxidized to metal ions is lower than 2.5V (vs. Li / Li + );

[0018] Furthermore, the metal powder should be air stable at 25°C and chemically stable in pure water and aqueous solutions of LiTFSI, LiOTF, LiFSI, LiNO3, LiClO4, CH3COOLi, and LiCl with a concentration of more than 5 mol / kg at 25°C.

[0019] Preferably, the mass ratio of the transition metal pre-lithiation agent to the mixed positive electrode material powder is not less than 1% and not more than 10%.

[0020] Preferably, the stirring time for preparing the mixed pre-lithiation positive electrode slurry is not less than 30 minutes.

[0021] Preferably, the drying temperature is 45°C-75°C.

[0022] Preferably, the conductive agent includes one or more of conductive carbon black, conductive graphite, super P or Ketjen black.

[0023] In a second aspect, an embodiment of the present invention provides a pre-lithiation positive electrode sheet prepared by the pre-lithiation method described in the first aspect.

[0024] In a third aspect, an embodiment of the present invention provides an aqueous lithium-ion battery, comprising the pre-lithiation positive electrode sheet described in the second aspect.

[0025] In a fourth aspect, an embodiment of the present invention provides a pre-lithiation method for an aqueous lithium-ion battery according to the third aspect, the method comprising:

[0026] In the initial state of the aqueous lithium-ion battery, the transition metal pre-lithiation reagent exists in the positive electrode sheet in the form of a single substance;

[0027] The battery is charged. As the charging process progresses, the battery voltage gradually increases, first reaching the electrochemical oxidation potential of the transition metal pre-lithiation reagent. The transition metal pre-lithiation reagent undergoes an electrochemical oxidation reaction at the positive electrode, and the generated transition metal ions dissolve in the electrolyte. At the negative electrode, a solid electrolyte interface (SEI) side reaction and a hydrogen evolution side reaction occur. The oxidation of the transition metal pre-lithiation reagent replaces the positive electrode active material to provide capacity for the side reactions, that is, to provide the first cycle charging capacity of the aqueous lithium-ion battery.

[0028] As the transition metal pre-lithiation reagent is consumed, the voltage of the positive electrode gradually increases, the SEI growth of the negative electrode ends, and the positive and negative electrodes enter the lithium desorption-lithiation working state.

[0029] In the pre-lithiation method of the present invention, the transition metal pre-lithiation reagent can provide capacity for the formation of negative electrode SEI, reduce the positive-negative electrode ratio of the aqueous lithium-ion battery, and improve the cyclability and energy density of the aqueous lithium-ion battery. The transition metal pre-lithiation reagent does not contain lithium element, which further reduces the material and synthesis costs. The transition metal pre-lithiation reagent is only responsible for providing the first-week charging capacity, and the lithium ions are provided by the electrolyte, which realizes the capacity-ion decoupling of the pre-lithiation process and broadens the path of pre-lithiation of the secondary battery. The transition metal pre-lithiation reagent itself is stably compatible with the electrolyte and the various components of the battery, and will not affect the normal operation of the battery. At the same time, it can provide a sufficiently high oxidation specific capacity in the first-week charging process to meet the pre-lithiation requirements. In addition, this method can be applied to aqueous sodium ion batteries and aqueous potassium ion batteries, and achieve the same alkali metal ion pre-embedding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The technical solutions of the embodiments of the present invention are further described in detail below through the accompanying drawings and examples.

[0031] Figure 1 Flow chart of a method for pre-lithiation of a positive electrode sheet of an aqueous lithium-ion electrochemical battery according to an embodiment of the present invention;

[0032] Figure 2 Schematic diagram of the principle of the pre-lithiation method of the positive electrode sheet of the aqueous lithium-ion electrochemical battery according to an embodiment of the present invention;

[0033] Figure 3 X-ray diffraction (XRD) patterns of the LiMn2O4 pre-lithiated positive electrode sheet containing 1.5% Mn metal powder provided in Example 1 of the present invention and the lithium manganate non-pre-lithiated positive electrode sheet provided in Comparative Example 1;

[0034] Figure 4 X-ray photoelectron spectroscopy (XPS) graphs of the negative electrode TiO2 pole piece of the pre-lithiation battery provided in Example 1 of the present invention and the non-pre-lithiation battery provided in Comparative Example 1 after 80 cycles;

[0035] Figure 5 Comparison of the capacity retention rates at 1C current density in the voltage range of 0.8-2.5V for an aqueous secondary lithium battery using TiO2 as a negative electrode material and a pre-lithiated mixed positive electrode material powder of LiMn2O4 containing 1.5% Mn metal powder as a positive electrode material provided in Example 1 of the present invention, an aqueous secondary lithium battery using TiO2 as a negative electrode material and a pre-lithiated mixed positive electrode material powder of LiMn2O4 containing 1.5% Mn metal powder as a positive electrode material provided in Experimental Example 3, and an aqueous secondary lithium battery using TiO2 as a negative electrode material and LiMn2O4 powder as a positive electrode material provided in Comparative Example 1;

[0036] Figure 6A comparison chart of the capacity retention rates at 1C current density in the voltage range of 0.8-2.5V for an aqueous secondary lithium battery using TiO2 as a negative electrode material and a pre-lithiated mixed positive electrode material powder of LiMn2O4 containing 1.5% Mn metal powder as a positive electrode material provided in Example 2 of the present invention, an aqueous secondary lithium battery using TiO2 as a negative electrode material and a pre-lithiated mixed positive electrode material powder of LiMn2O4 containing 1.5% Mn metal powder as a positive electrode material provided in Example 4, and an aqueous secondary lithium battery using TiO2 as a negative electrode material and LiMn2O4 powder as a positive electrode material provided in Comparative Example 2;

[0037] Figure 7 A comparison chart of the capacity retention rates of an aqueous secondary lithium battery provided in Example 5 of the present invention, in which TiO2 is used as the negative electrode material and LiMn2O4 pre-lithiation mixed positive electrode material powder containing 1.5% Zn metal powder is used as the positive electrode material, and an aqueous secondary lithium battery provided in Comparative Example 3, in which TiO2 is used as the negative electrode material and LiMn2O4 powder is used as the positive electrode material, at a current density of 1C in the voltage range of 0.8-2.5V. DETAILED DESCRIPTION

[0038] The present invention will be further described below through the accompanying drawings and specific embodiments, but it should be understood that these embodiments are only used for more detailed description and should not be understood as limiting the present invention in any form, that is, they are not intended to limit the scope of protection of the present invention.

[0039] The present invention provides a method for pre-lithiation of the positive electrode of an aqueous lithium-ion electrochemical battery. The main steps are as follows: Figure 1 As shown, including:

[0040] Step 110, mixing and grinding the transition metal pre-lithiation reagent and the mixed cathode material powder in a mortar to obtain a pre-lithiation mixed cathode material powder;

[0041] The transition metal pre-lithiation reagents include: metal powders of manganese, zinc, magnesium, aluminum, scandium, titanium, vanadium, chromium, copper, iron, cobalt, and nickel;

[0042] The mixed positive electrode material powder is a mixture of a positive electrode material powder containing a transition metal and a conductive agent; the conductive agent preferably includes one or more of conductive carbon black, conductive graphite, super P or Ketjen black;

[0043] In a specific embodiment, the mass ratio of the positive electrode material powder to the conductive carbon black in the mixed positive electrode material powder is preferably 7:1-8:1;

[0044] The mixing and grinding process in a mortar is preferably a mixing and grinding process, which is carried out in a mortar for a time of not less than 30 minutes;

[0045] The transition metal pre-lithiation reagent used in the present invention is oxidized to form stable metal ions to provide a mass specific capacity greater than 500 mAh / g; the redox potential of the transition metal pre-lithiation reagent electrochemically oxidized to form metal ions is lower than 2.5V (vs. Li / Li + );

[0046] Furthermore, the metal powder used as the transition metal pre-lithiation agent should be air-stable at 25°C, and chemically stable in pure water and LiTFSI, LiOTF, LiFSI, LiNO3, LiClO4, CH3COOLi, or LiCl aqueous solutions with a concentration of 5 mol / kg or more at 25°C.

[0047] In the pre-lithiation mixed positive electrode material powder, the mass ratio of the transition metal pre-lithiation agent to the mixed positive electrode material powder is not less than 1% and not more than 10%.

[0048] Step 120, adding the pre-lithiation mixed cathode material powder into a solvent in which a binder is dissolved and stirring the mixture to obtain a mixed pre-lithiation cathode slurry;

[0049] The binder used in the present invention includes at least one of fluorine-containing ethylene polymer substances, sodium alginate, sodium carboxymethyl cellulose, styrene-butadiene rubber or acrylic ester multi-polymer;

[0050] The solvent includes one or more of water, N-methylpyrrolidone (NMP), dimethylformamide (DMF), dimethyl sulfoxide, propylene carbonate, acetonitrile or tetrahydrofuran, and the binder is added to the solvent at a concentration of 20-100 mg / ml;

[0051] The stirring process is performed at a speed of 1000-3000 r / min for at least 30 minutes to uniformly mix the powder, thereby facilitating the uniform dispersion of the pre-lithiation agent to maximize its full capacity and enhance the cycling stability of the positive electrode material. The pre-lithiation agent in the mixed pre-lithiation positive electrode slurry obtained by the stirring process will remain in the form of a metal element in the pre-lithiation positive electrode sheet, and will not affect the uniform distribution of the positive electrode active material.

[0052] The above steps 110 and 120 may be executed in any order or in parallel.

[0053] Step 130 , coating the mixed pre-lithiated positive electrode slurry on a metal foil to obtain a pre-lithiated positive electrode wet plate;

[0054] The metal foil may specifically be common foil materials such as aluminum foil and copper foil.

[0055] Step 140, drying the pre-lithiated positive electrode wet plate in a blast oven to obtain a pre-lithiated positive electrode plate;

[0056] The drying temperature is 45°C-75°C.

[0057] In the process of preparing the mixed pre-lithiation positive electrode slurry, the powder of the transition metal pre-lithiation agent is mixed with the positive electrode material powder and the conductive additive in a certain mass ratio, and ground in a mortar for uniform mixing. The mixed powder is added to a solvent in which the binder is dissolved, and the mixed and defoamed by a blender. The obtained slurry is coated on a metal foil to form a pre-lithiation positive electrode plate, and assembled with the negative electrode plate to form a pre-lithiation battery. Before charging, the transition metal pre-lithiation agent exists in the positive electrode plate in the form of a single substance (such as Mn, Al, etc.). As the charging process begins, the voltage gradually increases, and first reaches the electrochemical oxidation potential of the transition metal pre-lithiation agent, so that the transition metal pre-lithiation agent first undergoes an electrochemical oxidation reaction in the positive electrode to generate the corresponding transition metal ions (such as Mn 2+ 、Al 3+ The SEI (e.g., ions) dissolve in the electrolyte and no longer participate in the reaction. Correspondingly, at the negative electrode, the SEI formation side reaction and the hydrogen evolution side reaction occur simultaneously. The oxidation of the transition metal pre-lithiation reagent replaces the positive electrode active material, providing the required capacity for the side reactions, that is, providing the first-cycle charging capacity of the aqueous lithium-ion battery. As the transition metal pre-lithiation reagent is consumed, the voltage of the positive electrode gradually increases, the SEI growth at the negative electrode basically ends, and the positive and negative electrodes begin normal lithium de-lithiation / lithiation reactions, and the battery returns to normal operating conditions.

[0058] The process principle can be seen in Figure 2 As shown. After the battery is assembled, the transition metal pre-lithiation reagent in the positive electrode, the transition metal element M, exists in its elemental form and does not undergo any reaction. After the first cycle charging process begins, as the positive electrode voltage gradually increases, it first reaches the oxidation potential of the transition metal element M in the positive electrode. M in the positive electrode undergoes an oxidation reaction, loses z electrons, and the oxidation product is M z+ The transition metal ions enter the electrolyte from the electrode. Simultaneously, the negative electrode voltage gradually decreases, reaching the potential for water molecule decomposition and SEI formation. The capacity provided by the oxidation of the transition metal pre-lithiation reagent M in the positive electrode compensates for the capacity required for the hydrogen evolution reaction during the water decomposition process at the negative electrode and the SEI formation reaction caused by the reduction of electrolyte anions. Furthermore, the excess oxidation capacity also provides some capacity for lithium ion pre-embedding in the negative electrode.

[0059] The ingenuity of the transition metal pre-lithiation reagent of the present invention lies in the fact that it does not contain lithium, reducing material and synthesis costs. The pre-lithiation reagent is only responsible for providing the initial charging capacity, while the lithium ions are provided by the electrolyte. This achieves capacity-ion decoupling during the pre-lithiation process and broadens the path for pre-lithiation of secondary batteries. The transition metal pre-lithiation reagent itself is stable and compatible with the electrolyte and various battery components, without affecting the normal operation of the battery. At the same time, it can provide a sufficiently high oxidation specific capacity during the initial charging process to meet the pre-lithiation requirements.

[0060] That is to say, in the present invention, the pre-lithiated aqueous lithium-ion battery assembled by pre-lithiated positive electrode sheets and corresponding negative electrode sheets has a different working principle from that of batteries assembled by traditional lithium-containing pre-lithiation reagents during the first week of charging. The transition metal pre-lithiation reagent in the pre-lithiated positive electrode sheet will be electrochemically oxidized to the corresponding cations and enter the electrolyte before the positive electrode sheet is delithiated. In this process, the oxidation capacity of the transition metal pre-lithiation reagent can make up for the capacity consumed by the formation of SEI and hydrogen evolution side reactions on the negative electrode sheet, while providing a small amount of capacity for lithium insertion in the negative electrode sheet, thus completing the pre-lithiation goal. In subsequent cycles, the transition metal pre-lithiation reagent exists in the electrolyte in the form of ions to play a conductive role and will not have a negative impact on the cycle performance of the entire battery.

[0061] In some embodiments of the present invention, the mass specific capacity provided by the oxidation of metal powder to stable metal ions is greater than 500 mAh / g. If the mass specific capacity provided by the electrochemical oxidation of metal powder is less than 500 mAh / g, it will affect the energy density of the full battery and fail to achieve a significant lithium replenishment effect.

[0062] In some embodiments of the present invention, the mass fraction of the transition metal pre-lithiation agent metal powder in the mixed positive electrode material powder should be greater than 1% and less than 10%. If the content of the transition metal pre-lithiation agent metal powder is too low, the lithium replenishment effect cannot be achieved; if the content of the transition metal pre-lithiation agent metal powder is too high, it will affect the normal cycle of the battery and change the electrolyte composition.

[0063] In some embodiments of the present invention, the redox potential of the transition metal pre-lithiation reagent metal powder electrochemically oxidized to metal ions should be lower than 2.5V (vs. Li / Li + If the redox potential of the metal powder electrochemically oxidized to metal ions is higher than 2.5V (vs. Li / Li + ), during the charge and discharge cycle of the battery, metal ions will be deposited on the negative electrode side, resulting in the inability to achieve the lithium replenishment effect.

[0064] In some embodiments of the present invention, the metal powder should be air-stable at 25° C. If the metal powder cannot remain stable in air, it may deteriorate during the preparation of the mixed pre-lithiated cathode slurry, resulting in failure to achieve the lithium replenishment effect.

[0065] In some embodiments of the present invention, the metal powder should maintain chemical stability in pure water or a LiTFSI aqueous solution with a concentration of 5 mol / kg or greater at 25°C. If the metal powder reacts with pure water or a LiTFSI aqueous solution with a concentration of 5 mol / kg or greater at 25°C, the resulting pre-lithiated positive electrode plate will chemically deactivate when it contacts the aqueous electrolyte during assembly into a pre-lithiated aqueous lithium-ion battery, resulting in failure to achieve lithium replenishment.

[0066] In a preferred embodiment, the mixed cathode material powder is added to a solvent in which the binder is dissolved and stirred in a stirrer. The stirring pre-lithiation time is 30 minutes and the stirring speed is 1000-3000 r / min.

[0067] In a preferred embodiment, the drying temperature of the pre-lithiated positive electrode plate in a blast oven should be 55° C., which has a good drying effect and ensures that the plate will not deteriorate.

[0068] It should be noted that while the present invention does not utilize lithium, it can still achieve the desired initial charge capacity. The oxidation capacity of the metal powder pre-lithiation reagent can offset the capacity consumed by SEI formation and hydrogen evolution side reactions on the negative electrode, achieving pre-lithiation. In subsequent cycles, the transition metal pre-lithiation reagent, present in ionic form in the electrolyte, still functions as a conductor.

[0069] The pre-lithiated positive electrode sheet prepared by the above method has the advantages of high surface density and sufficient lithium replenishment capacity. When used in lithium-ion batteries, it can not only reduce the ratio of positive electrode material to negative electrode material, increase the energy density of lithium-ion batteries, but also improve the cycle performance of lithium-ion batteries.

[0070] The pre-lithiated positive electrode plate of the present invention is applied in a pre-lithiated aqueous lithium-ion battery and has high energy density and high cycle performance.

[0071] The technical solutions of the present invention are further illustrated below with reference to specific examples. All reagents used in the examples are commercially available or synthesized according to conventional methods in the art, and all instruments used in the examples are commercially available. It should be understood that these examples are intended only to illustrate the present application and are not intended to limit the scope of protection claimed herein.

[0072] Example 1

[0073] This embodiment provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, comprising the following operations:

[0074] 1) Preparation of pre-lithiation cathode electrode

[0075] Preparation of mixed pre-lithiation positive electrode slurry: First, the binder polyvinylidene fluoride (PVDF) and the organic solvent N-methylpyrrolidone (NMP) are dissolved and stirred at 50 mg / ml to form a solution. The positive electrode active material lithium manganese oxide powder, conductive carbon black, and pre-lithiation agent Mn powder are mixed in a mass ratio of 78.5:10:1.5, and mixed and ground in a mortar for 30 minutes to obtain a pre-lithiation mixed positive electrode material powder. Then, the pre-lithiation mixed positive electrode material powder is mixed with the above solution in a mass ratio of 90:10 to PVDF (dissolved state), and stirred in a stirrer until the system is uniform to obtain a mixed pre-lithiation positive electrode slurry.

[0076] Preparation of pre-lithiated positive electrode sheets: Take a positive electrode current collector aluminum foil and adhere it to a glass plate with transparent tape. Use a four-sided preparation machine to evenly coat the mixed pre-lithiated positive electrode slurry on the aluminum foil. Place it in a forced air oven and dry it at an ambient temperature of 55°C to obtain a pre-lithiated positive electrode sheet. Use a sheet puncher to punch the obtained pre-lithiated positive electrode sheet into φ10 circular sheets for use as the positive electrode of aqueous lithium-ion batteries.

[0077] 2) Preparation of negative electrode sheet

[0078] Preparation of negative electrode slurry: First, dissolve the binder PVDF and the organic solvent NMP at 50 mg / ml and stir to mix evenly. Then, mix the negative electrode active materials titanium dioxide powder, conductive carbon black, and PVDF at a mass ratio of 7:2:1 and stir in a stirrer until the mixture is uniform to obtain the negative electrode slurry.

[0079] Preparation of the negative electrode sheet: Take a piece of negative electrode current collector aluminum foil and adhere it to a glass plate with transparent tape. Use a four-sided preparation machine to evenly coat the negative electrode slurry on the aluminum foil. Place it in a forced air oven and dry it at an ambient temperature of 55°C to obtain the negative electrode sheet. Use a sheet puncher to punch the resulting negative electrode sheet into φ10 circular pieces for use as the negative electrode of aqueous lithium-ion batteries.

[0080] 3) Preparation of drainage fluid

[0081] Preparation of positive electrode drain:

[0082] The polymer conductive carbon film was compacted on both sides on a 60-mesh titanium mesh to prepare a sandwich current collector, which was then sheared to prepare a positive electrode current collector.

[0083] Preparation of negative electrode drain:

[0084] A 40 μm thick aluminum foil was cut to prepare the negative electrode drain.

[0085] 4) The positive and negative electrodes are selected according to the net mass ratio of lithium manganese oxide in the positive electrode to titanium dioxide in the negative electrode of 1.4:1.

[0086] The positive electrode drain, pre-lithiation positive electrode plate, glass fiber separator, negative electrode plate and negative electrode drain were overlapped and placed in an aluminum-plastic film shell, 50μL 21mLiTFSI aqueous electrolyte was injected into the separator, and the edges were heat-sealed with a hot press to assemble the finished soft-pack battery.

[0087] 5) Allow the assembled soft-pack battery to rest at 25°C for two hours. Then, charge and discharge the soft-pack battery at a current of 1C within the voltage range of 0.8-2.5V. The soft-pack battery will automatically complete pre-lithiation during the first week of charging.

[0088] Example 2

[0089] This embodiment provides a method for preparing a positive electrode pre-lithiation aqueous lithium-ion battery, which is different from Experimental Example 1 in step 4);

[0090] In step 4), the positive and negative electrode sheets are selected according to the net mass ratio of lithium manganese oxide in the positive electrode sheet to titanium dioxide in the negative electrode sheet of 1.2:1.

[0091] Example 3

[0092] This embodiment provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, which is different from Experimental Example 1 in step 1);

[0093] In step 1), the mass ratio of the positive electrode active material lithium manganate powder, conductive carbon black, pre-lithiation agent Mn powder and PVDF (dissolved state) is 79:10:1:10.

[0094] Example 4

[0095] This embodiment provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, which differs from Experimental Example 1 in steps 1) and 4);

[0096] In step 1), the mass ratio of the positive electrode active material lithium manganate powder, conductive carbon black, pre-lithiation agent Mn powder and PVDF (dissolved state) is 79:10:1:10.

[0097] In step 4), the positive and negative electrode sheets are selected according to the net mass ratio of lithium manganese oxide in the positive electrode sheet to titanium dioxide in the negative electrode sheet of 1.2:1.

[0098] Example 5

[0099] This embodiment provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, which differs from Experimental Example 1 in steps 1) and 4);

[0100] In step 1), the mass ratio of the positive electrode active material lithium manganate powder, conductive carbon black, pre-lithiation agent Zn powder and PVDF (dissolved state) is 78.5:10:1.5:10.

[0101] In step 4), the positive and negative electrode sheets are selected according to the net mass ratio of lithium manganese oxide in the positive electrode sheet to titanium dioxide in the negative electrode sheet of 1.6:1.

[0102] Example 6

[0103] This embodiment provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, which is different from Experimental Example 1 in step 1);

[0104] In step 1), the binder is sodium carboxymethyl cellulose and styrene-butadiene rubber in a mass ratio of 1:1, and the solvent is water.

[0105] Example 7

[0106] This embodiment provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, which is different from Experimental Example 1 in step 1);

[0107] In step 1), the binder is polyvinylidene fluoride (PVDF) and the solvent is dimethylformamide (DMF).

[0108] Example 8

[0109] This embodiment provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, which is different from Experimental Example 1 in step 1);

[0110] In step 1), the binder is sodium alginate and the solvent is water.

[0111] Example 9

[0112] This embodiment provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, which is different from Experimental Example 1 in step 1);

[0113] In step 1), the binder is polyvinylidene fluoride (PVDF) and the solvent is tetrahydrofuran.

[0114] Comparative Example 1

[0115] This comparative example provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, which is different from Experimental Example 1 in step 1);

[0116] In step 1), the mass ratio of the positive electrode active material lithium manganate powder, conductive carbon black and PVDF (dissolved state) used in the preparation of the mixed pre-lithiation positive electrode slurry is 8:1:1.

[0117] The XRD diffraction patterns of the pre-lithiation positive electrode sheets prepared in Example 1 and Comparative Example 1 are as follows: Figure 3 As shown, compared with Comparative Example 1 in which no transition metal pre-lithiation agent is added, there is no significant difference in the diffraction peak shape of the materials of Example 1 and Comparative Example 1, which is consistent with the diffraction structure of lithium manganate, indicating that the added transition metal pre-lithiation agent does not change the crystal structure and lithium insertion / delithiation performance of the positive electrode material.

[0118] X-ray photoelectron spectroscopy (XPS) was used to analyze the changes in element valence states on the negative electrode TiO2 electrode of the pre-lithiation cell in Example 1 and the non-pre-lithiation cell provided in Comparative Example 1 after 80 cycles. The XPS spectra are as follows: Figure 4 As shown, no elemental manganese was found in the Mn2p spectrum, only divalent manganese oxide was contained, indicating that the metal element pre-lithiation agent of the positive electrode was oxidized and provided the first week capacity, and then existed in the electrolyte as an oxidized ion, and was not reduced at the negative electrode interface during the cycle, proving that the oxidation products of the metal element pre-lithiation agent will not undergo reversible redox reactions to affect the battery capacity.

[0119] The cycle comparison diagrams of Comparative Example 1, Example 1 and Example 3 are as follows: Figure 5 As shown in the figure, as the number of cycles increases, it can be seen that the capacity retention rate of comparative example 1 after 80 cycles is 87%; while the capacity retention rate of embodiment 1 after 80 cycles is 99%, and the capacity retention rate of embodiment 1 after 100 cycles is 97%, indicating that the addition of transition metal pre-lithiation agent Mn powder plays a role in oxidizing and replenishing lithium, thereby increasing the cycle life of the full battery.

[0120] The first charge specific capacity of the battery in Example 1 of the present invention can reach 156 mAh / g, which is 18.2% higher than the specific capacity of the battery in Comparative Example 1 without pre-lithiation.

[0121] Comparative Example 2

[0122] This comparative example provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, which differs from Experimental Example 1 in steps 1) and 4);

[0123] In step 1), the mass ratio of the positive electrode active material lithium manganate powder, conductive carbon black and PVDF (dissolved state) used in the preparation of the mixed pre-lithiation positive electrode slurry is 8:1:1.

[0124] In step 4), the positive and negative electrode sheets are selected according to the net mass ratio of lithium manganese oxide in the positive electrode sheet to titanium dioxide in the negative electrode sheet of 1.2:1.

[0125] The cycle comparison diagrams of Comparative Example 2, Example 2 and Example 4 are as follows: Figure 6 As shown in the figure, as the number of cycles increases, the capacity retention rate of comparative example 2 after 100 cycles is 70%; while the capacity retention rate of example 2 after 100 cycles is 93%, and the capacity retention rate of example 3 after 100 cycles is 86%, indicating that the addition of Mn metal powder can extend the cycle life of the battery with an extremely low positive and negative electrode mass ratio.

[0126] Comparative Example 3

[0127] This comparative example provides a method for preparing a positive electrode pre-lithiated aqueous lithium-ion battery, which differs from Experimental Example 1 in steps 1) and 4);

[0128] In step 1), the mass ratio of the positive electrode active material lithium manganate powder, conductive carbon black and PVDF (dissolved state) used in the preparation of the mixed pre-lithiation positive electrode slurry is 8:1:1.

[0129] In step 4), the positive and negative electrode sheets are selected according to the net mass ratio of lithium manganese oxide in the positive electrode sheet to titanium dioxide in the negative electrode sheet of 1.6:1.

[0130] The cycle comparison diagram of Comparative Example 3 and Example 5 is as follows Figure 7 As shown in FIG, as the number of cycles increases, the capacity retention rate after 100 cycles is 73%; while in Example 5, the capacity retention rate after 100 cycles is 90%, indicating that replacing Mn metal powder with Zn metal powder can also increase the cycle life.

[0131] The above examples illustrate that the present invention provides a pre-lithiation method for aqueous lithium-ion batteries using transition metal powder as a pre-lithiation agent. By uniformly mixing 1.5% by mass of Mn into the positive electrode material LiMn2O4 and combining it with the negative electrode material TiO2 to form a full cell, the battery exhibits an additional 18.2% first-cycle charge / discharge capacity at a current density of 1C and a low positive / negative electrode active material mass ratio of 1.4, with a capacity retention of 99% after 80 cycles.

[0132] The method of lithiation of aqueous lithium-ion batteries using transition metal powders as pre-lithiation agents offers advantages such as increased energy density, improved battery cycle performance, and reduced costs, broadening the path for the practical application of aqueous lithium-ion batteries. Furthermore, this pre-lithiation method is simple and fully meets the requirements of modern large-scale production, possessing enormous application prospects. Furthermore, this method can be extended to aqueous sodium-ion and potassium-ion batteries using the same operating method to achieve the same goal of alkali metal ion pre-lithiation.

[0133] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for pre-lithiation of an aqueous lithium-ion battery, characterized in that: The method comprises: Mixing and grinding a transition metal pre-lithiation agent with a mixed cathode material powder to obtain a pre-lithiation mixed cathode material powder; wherein the mass ratio of the transition metal pre-lithiation agent to the mixed cathode material powder is not less than 1% and not more than 10%; The pre-lithiation mixed cathode material powder is added to a solvent in which a binder is dissolved and stirred to obtain a mixed pre-lithiation cathode slurry; The mixed pre-lithiation positive electrode slurry is coated on a metal foil to obtain a pre-lithiation positive electrode wet plate; Drying the pre-lithiated positive electrode wet plate in a blast oven to obtain a pre-lithiated positive electrode plate; The pre-lithiation positive electrode plate is used for an aqueous lithium-ion battery; in the initial state of the aqueous lithium-ion battery, the transition metal pre-lithiation reagent exists in the positive electrode plate in the form of a single substance; During charging of the battery, the battery voltage gradually increases during the first cycle of charging, first reaching the electrochemical oxidation potential of the transition metal pre-lithiation reagent. The transition metal pre-lithiation reagent undergoes an electrochemical oxidation reaction at the positive electrode, and the generated transition metal ions dissolve in the electrolyte. At the negative electrode, a solid electrolyte interface SEI side reaction and a hydrogen evolution side reaction occur. The oxidation of the transition metal pre-lithiation reagent replaces the positive electrode active material to provide capacity for the solid electrolyte interface SEI side reaction and the hydrogen evolution side reaction, thereby providing the first cycle charging capacity of the aqueous lithium-ion battery. As the transition metal pre-lithiation reagent is consumed, the voltage of the positive electrode gradually increases, the SEI growth of the negative electrode ends, and the positive and negative electrodes enter the lithium desorption-lithiation working state; Wherein, the transition metal pre-lithiation reagent includes: metal powders of manganese, zinc, magnesium, aluminum, scandium, titanium, vanadium, chromium, copper, iron, cobalt, and nickel; The mixed positive electrode material powder is a powder formed by mixing positive electrode material powder containing transition metal and a conductive agent; The adhesive comprises: at least one of fluorinated ethylene polymers, sodium alginate, sodium carboxymethyl cellulose, styrene-butadiene rubber or acrylic acid ester multi-polymers; The solvent includes one or more of water, N-methylpyrrolidone, dimethylformamide, dimethyl sulfoxide, propylene carbonate, acetonitrile or tetrahydrofuran.

2. The pre-lithiation method according to claim 1, wherein The stirring speed of the stirring process is 1000-3000 r / min.

3. The pre-lithiation method according to claim 1, wherein The transition metal pre-lithiation reagent is oxidized to form stable metal ions to provide a mass specific capacity greater than 500 mAh / g; The redox potential of the transition metal pre-lithiation reagent electrochemically oxidized to metal ions is lower than 2.5V (vs. Li / Li + ); Furthermore, the metal powder should be air stable at 25°C and chemically stable in pure water and aqueous solutions of LiTFSI, LiOTF, LiFSI, LiNO3, LiClO4, CH3COOLi, and LiCl with a concentration of more than 5 mol / kg at 25°C.

4. The pre-lithiation method according to claim 1, wherein The stirring time for preparing the mixed pre-lithiation positive electrode slurry is not less than 30 minutes.

5. The pre-lithiation method according to claim 1, wherein The drying temperature is 45°C-75°C.

6. The pre-lithiation method according to claim 1, wherein The conductive agent includes one or more of conductive carbon black, conductive graphite, super P or Ketjen black.

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