Interface pretreatment liquid for pre-lithiated positive electrode, and lithium supplementing battery and preparation method therefor

Abstract

The present application relates to the technical field of lithium ion batteries, and discloses an interface pretreatment liquid for a pre-lithiated positive electrode, and a lithium supplementing battery and a preparation method therefor. The interface pretreatment liquid comprises a solute which is one or a mixture of more of lithium polysulfide, hydrobromic acid, and hydroiodic acid. In mass percent, the interface pretreatment liquid comprises: a solute: 0.1%-10% and a solvent: 90%-99.9%, wherein the solvent is one or a mixture of more of N-methyl-2-pyrrolidone, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, methyl formate, ethyl formate, methyl acetate, ethyl acetate, ethyl propionate, propyl propionate, ethyl butyrate, propyl butyrate, dimethyl sulfoxide, and dimethyl sulfide. A preparation method for the interface pretreatment liquid of the present application is simple, and the usage method is simple. In the application process, a lithium supplementing positive electrode sheet only needs to be immersed in the interface pretreatment liquid, the immersing time is short, the action effect is good, the production efficiency is high, and the present application is suitable for industrial production.

Description

An interfacial pretreatment solution for prelithiated cathodes, a lithium supplement battery and its preparation method Technical Field

[0001] This application relates to the technical field of lithium-ion batteries, and particularly to an interfacial pretreatment solution for prelithiated cathodes, a lithium supplement battery and its preparation method. Background Art

[0002] As one of the most promising high-energy density storage devices, silicon lithium-ion batteries have the advantages of high energy density, long cycle life, high safety, environmental friendliness, etc., and are widely used in fields such as electronic products, electric vehicles, aerospace, and large-scale energy storage power stations. With the rapid development of new energy vehicles and the improvement of the cruising range, higher requirements are put forward for the energy density of batteries.

[0003] To further improve the energy density of lithium-ion batteries, lithium supplementation for the cathode or anode is an effective method. Compared with lithium supplementation for the anode, the lithium supplementation process for the cathode is simple, has relatively low requirements for equipment and the environment, is safer during use, and has relatively low costs. Some patents have studied this.

[0004] Chinese Patent with application number CN201710867438.3 discloses a lithium supplementation additive for the cathode of a lithium-ion battery and its application. The lithium supplementation additive for the cathode of this application is a conductive metal-doped lithium oxide powder. By doping copper in the lithium oxide powder, the conductivity of the lithium oxide powder is improved, enabling it to be used as a lithium supplementation additive.

[0005] Chinese Patent with application number CN201410707478.8 discloses a cathode, its preparation method and a lithium secondary battery using this cathode. The cathode includes a conductive substrate, a cathode active material layer, and a lithium supplementation layer disposed between the conductive substrate and the cathode active material layer. The lithium supplementation layer contains at least one lithium-containing compound, at least one conductive agent, and at least one binder. The lithium-containing compound is selected from the group consisting of compounds represented by the formula LixA, where A is O, P, S or N, and 0 < x ≤ 3. The cathode of this application has a lithium supplementation function and can effectively compensate for the irreversible capacity loss during the charge and discharge process of the lithium secondary battery, improving the energy density of the battery.

[0006] However, as a lithium supplementation additive for the cathode, although lithium oxide has a high lithium supplementation specific capacity of 1794 mAh / g, its chemical properties are active, and it is easy to absorb moisture and CO2 in the air and deteriorate into LiOH and Li2CO3. On the one hand, this leads to a low specific capacity performance and poor lithium supplementation effect on the cathode; on the other hand, side reactions with the electrolyte cause serious gas generation, affecting the battery performance, and there are limitations in improving the capacity and first charge-discharge efficiency of lithium-ion secondary batteries. Summary of the Invention

[0007] In response to the deficiencies in the prior art, the present application provides an interface pretreatment liquid for a pre-lithiated positive electrode, a lithium-supplementing battery, and a preparation method thereof. By selecting the types of solvent and solute, and matching the dosages of solute and solvent, the solvent of the present application can fully infiltrate the internal pores of the lithium-supplementing positive electrode sheet, and the solute can react with the pre-lithiated positive electrode material lithium oxide, thereby improving the air stability of the positive electrode surface and the stability of the positive electrode interface film (CEI film), thereby synergistically improving the battery capacity and initial charge and discharge efficiency.

[0008] Specifically, in order to achieve the above technical solution, in the first aspect, the present application provides an interface pretreatment liquid for pre-lithiation of the positive electrode, which comprises 0.1% to 10% of a solute and 90% to 99.9% of a solvent in percentage by mass; the solute is a mixture of one or more of lithium polysulfide, hydrobromic acid and hydroiodic acid; the solvent is a mixture of one or more of N-methylpyrrolidone, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, methyl formate, ethyl formate, methyl acetate, ethyl acetate, ethyl propionate, propyl propionate, ethyl butyrate, propyl butyrate, dimethyl sulfoxide, ethylene glycol dimethyl ether, 1,3-dioxolane, diethylene glycol dimethyl ether and dimethyl sulfoxide.

[0009] Preferably, the solute comprises 0.5% to 8% and the solvent comprises 92% to 99.5% by mass.

[0010] Preferably, the solute comprises 1% to 5% and the solvent comprises 95% to 99% by mass.

[0011] Preferably, the solvent is selected from a mixed solvent of one or more of ethylene glycol dimethyl ether, 1,3-dioxolane, diethylene glycol dimethyl ether and dimethyl sulfide.

[0012] Preferably, the lithium polysulfide is prepared from sulfur and lithium sulfide in a molar ratio of 6 to 10:1.

[0013] In a second aspect, the present application provides a method for preparing a lithium-supplemented battery, comprising the following steps:

[0014] A positive electrode slurry containing a positive electrode active material is coated on the surface of the positive electrode current collector, and after drying, an initial positive electrode sheet with a positive electrode membrane disposed on the surface of the positive electrode current collector is obtained, and then a layer of lithium oxide is further disposed on the surface of the positive electrode membrane to obtain a lithium-supplemented positive electrode sheet;

[0015] A negative electrode slurry containing a negative electrode active material is applied to the surface of the negative electrode current collector, and after drying, a negative electrode sheet having a negative electrode film provided on the surface of the negative electrode current collector is obtained;

[0016] In an inert gas atmosphere, the water content is controlled to be less than 1 ppm, and the oxygen content is controlled to be less than 1 ppm. The lithium-supplemented positive electrode sheet is immersed in an interface pretreatment solution for a pre-lithiation positive electrode for 1 to 25 minutes, and then dried in an inert environment at room temperature for 1 to 3 hours to obtain a positive electrode material.

[0017] Assemble the positive electrode material, separator and negative electrode sheet into a lithium-supplemented battery cell;

[0018] The lithium-supplemented battery cell is placed in a battery packaging shell, injected with electrolyte and packaged to obtain a lithium-supplemented battery.

[0019] Preferably, the lithium-supplemented positive electrode sheet is immersed in the interface pretreatment solution for 2 minutes to 15 minutes.

[0020] Preferably, the lithium-supplemented positive electrode sheet is immersed in the interface pretreatment solution for 5 minutes to 10 minutes.

[0021] In a third aspect, the present application provides a lithium-supplemented battery, which is prepared by a method for preparing a lithium-supplemented battery provided in any embodiment of the present application.

[0022] The present application has the following beneficial effects: the interface pretreatment liquid provided by the present application is selected by matching the ratio between the solute and the solvent, and the specific solute and solvent are selected. The specific solvent has good chemical stability, strong solubility, and moderate surface tension. Using these reagents as the solvent of the interface pretreatment liquid can fully infiltrate the internal pores of the lithium-replenishing positive electrode sheet; the specific solute can react with lithium oxide to obtain products with good stability. These products have good mechanical properties and electrochemical stability, can effectively inhibit the occurrence of side reactions, and make the CEI film formed on the surface of the pre-lithiation positive electrode more stable, thereby improving the capacity and initial charge and discharge efficiency of the battery; compared with the prior art, the preparation method of the interface pretreatment liquid of the present application is simple, and the use method is simple. During the application process, the lithium-replenishing positive electrode sheet only needs to be immersed in the interface pretreatment liquid. The immersion time is short, the effect is good, the production efficiency is high, and it is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings that constitute a part of this application are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute an improper limitation on this application.

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] FIG1 is a schematic flow chart of a method for preparing a lithium-supplemented battery according to Example 1 of the present application. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application; it is obvious that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0027] The present invention is further described below with reference to specific embodiments. Example

[0028] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0029] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0030] 1% lithium polysulfide and 99% ethylene glycol dimethyl ether; lithium polysulfide is prepared by sulfur and lithium sulfide in a molar ratio of 7:1.

[0031] (2) The preparation method of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0032] In an argon atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, ethylene glycol dimethyl ether was added to an aluminum-plastic bottle, and then sulfur and lithium sulfide were added to the aluminum-plastic bottle in a molar ratio of 7:1. The mixture was stirred for 1 hour until the sulfur and lithium sulfide were completely dissolved to prepare an interface pretreatment liquid with a solute of lithium polysulfide and a solute mass fraction of 1wt%.

[0033] (3) Preparation of lithium-ion battery: Referring to FIG1 , a preferred embodiment, this embodiment provides a method for preparing a lithium-ion battery, comprising the following steps:

[0034] S1: Prepare the positive electrode sheet; 0 .8 Co 0 .1 Mn 0 .1 O2, conductive carbon black, carbon nanotubes and polyvinylidene fluoride binder were mixed in a mass ratio of 97:0.5:0.5:2, and N-methylpyrrolidone solvent was added. The mixture was stirred and mixed thoroughly to obtain a positive electrode slurry, which was then coated on both surfaces of the positive electrode current collector aluminum foil. The coating mass of the positive electrode slurry was 1.524 g / 76.2 cm 2 (single side, based on the mass of the solid component excluding the solvent), and then dried and cold pressed to obtain a positive electrode sheet.

[0035] S2: Prepare lithium-replenishing positive electrode sheet; mix lithium oxide and conductive carbon black SP in a mass ratio of 1:1, stir and mix thoroughly to obtain lithium-replenishing slurry, and then apply it on both surfaces of the positive electrode sheet with a coating surface density of 14.6 g / m 2 (double-sided, based on the mass of the solid component excluding the solvent), and then dried and cold pressed to obtain a lithium-supplemented positive electrode sheet.

[0036] S3: Perform interface pretreatment on the lithium-supplemented positive electrode sheet; in an argon atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, soak the cut lithium-supplemented positive electrode sheet in the interface pretreatment solution of this embodiment for 5 minutes, and then dry it at room temperature for 2 hours under an argon atmosphere to obtain a negative electrode material.

[0037] S4: preparing an electrolyte; in an argon atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, ethylene carbonate, diethyl carbonate, ethyl methyl carbonate, and fluoroethylene carbonate are mixed in weight percentages of 20%, 30%, 40%, and 10% to obtain a mixed organic solvent, and then dried lithium hexafluorophosphate is dissolved in the above mixed organic solvent. The concentration of lithium hexafluorophosphate is 1 mol / L. In addition, vinylene carbonate is added as an additive in an amount of 1% by weight of the electrolyte, and the electrolyte is obtained after stirring evenly.

[0038] S5: preparing a diaphragm; a polyethylene porous membrane coated with alumina ceramic on both sides is used as the diaphragm.

[0039] S6: Prepare the battery; stack the positive electrode sheet, separator, and negative electrode material in order, so that the separator is located between the positive and negative electrodes to play an isolating role, to obtain a lithium-supplemented battery cell, place the lithium-supplemented battery cell in a battery packaging shell, and then inject the prepared electrolyte and package it to obtain a lithium-supplemented battery. Example

[0040] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0041] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0042] 2% lithium polysulfide and 98% ethylene glycol dimethyl ether; lithium polysulfide is prepared by sulfur and lithium sulfide in a molar ratio of 7:1.

[0043] (2) The preparation method of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0044] In an argon atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, ethylene glycol dimethyl ether was added to an aluminum-plastic bottle, and then sulfur and lithium sulfide were added to the aluminum-plastic bottle in a molar ratio of 7:1. The mixture was stirred for 1 hour until the sulfur and lithium sulfide were completely dissolved to obtain an interface pretreatment liquid with a solute of lithium polysulfide and a solute mass fraction of 2wt%.

[0045] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0046] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0047] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0048] 3% lithium polysulfide and 97% ethylene glycol dimethyl ether; lithium polysulfide is prepared by sulfur and lithium sulfide in a molar ratio of 7:1.

[0049] (2) The preparation method of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0050] In an argon atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, ethylene glycol dimethyl ether was added to an aluminum-plastic bottle, and then sulfur and lithium sulfide were added to the aluminum-plastic bottle in a molar ratio of 7:1. The mixture was stirred for 1 hour until the sulfur and lithium sulfide were completely dissolved to obtain an interface pretreatment liquid with a solute of lithium polysulfide and a solute mass fraction of 3wt%.

[0051] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0052] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0053] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0054] Hydrobromic acid 1% and ethylene glycol dimethyl ether 99%.

[0055] The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this embodiment is as follows: in an argon atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm, ethylene glycol dimethyl ether and hydrobromic acid are added to an aluminum-plastic bottle in sequence, and stirred for 1 hour until the hydrobromic acid is completely dissolved to prepare an interface pretreatment liquid with a solute mass fraction of 1 wt%.

[0056] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0057] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0058] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0059] Hydrobromic acid 2% and ethylene glycol dimethyl ether 98%.

[0060] The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this embodiment is as follows:

[0061] ppm, in an argon atmosphere glove box with an oxygen content of <1 ppm, ethylene glycol dimethyl ether and hydrobromic acid were added to an aluminum-plastic bottle in sequence, and stirred for 1 h until the hydrobromic acid was completely dissolved to prepare an interface pretreatment solution with a solute mass fraction of 2 wt%.

[0062] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0063] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0064] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is: 3% hydrobromic acid and 97% ethylene glycol dimethyl ether.

[0065] (2) The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this embodiment is as follows: in an argon atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm, ethylene glycol dimethyl ether and hydrobromic acid are added to an aluminum-plastic bottle in sequence, and stirred for 1 hour until the hydrobromic acid is completely dissolved to prepare an interface pretreatment liquid with a solute mass fraction of 3 wt%.

[0066] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0067] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0068] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0069] Hydroiodic acid 2% and ethylene glycol dimethyl ether 98%.

[0070] (2) The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this embodiment is as follows: in an argon atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm, ethylene glycol dimethyl ether and hydroiodic acid are added to an aluminum-plastic bottle in sequence, and stirred for 1 hour until the hydroiodic acid is completely dissolved to prepare an interface pretreatment liquid with a solute mass fraction of 2 wt%.

[0071] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0072] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0073] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is: 2% hydroiodic acid and 98% ethylene glycol dimethyl ether.

[0074] The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this embodiment is as follows: in an argon atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm, ethylene glycol dimethyl ether and hydroiodic acid are added to an aluminum-plastic bottle in sequence, and stirred for 1 hour until the hydroiodic acid is completely dissolved to prepare an interface pretreatment liquid with a solute mass fraction of 2 wt%.

[0075] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0076] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0077] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is: 2% hydroiodic acid and 98% ethylene glycol dimethyl ether.

[0078] (2) The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this embodiment is as follows: in an argon atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm, ethylene glycol dimethyl ether and hydroiodic acid are added to an aluminum-plastic bottle in sequence, and stirred for 1 hour until the hydroiodic acid is completely dissolved to prepare an interface pretreatment liquid with a solute mass fraction of 2 wt%.

[0079] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0080] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0081] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0082] 2% lithium polysulfide and 98% 1,3-dioxolane; lithium polysulfide is prepared by sulfur and lithium sulfide in a molar ratio of 7:1.

[0083] (2) The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this embodiment is as follows: in an argon atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm, 98% of 1,3-dioxolane is added to an aluminum-plastic bottle, and then sulfur and lithium sulfide are added to the aluminum-plastic bottle in a molar ratio of 7:1, and stirred for 1 hour until the sulfur and lithium sulfide are completely dissolved, to prepare an interface pretreatment liquid in which the solute is lithium polysulfide and the solute mass fraction is 2 wt%.

[0084] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0085] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0086] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiated positive electrode in this embodiment is: 2% lithium polysulfide and 98% polyethylene glycol dimethyl ether; lithium polysulfide is prepared by molar ratio of sulfur and lithium sulfide.

[0087] (2) The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this embodiment is specifically as follows: in an argon atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, diethylene glycol dimethyl ether is added to an aluminum-plastic bottle, and then sulfur and lithium sulfide are added to the aluminum-plastic bottle in a molar ratio of 7:1, and stirred for 1 hour until the sulfur and lithium sulfide are completely dissolved, to prepare an interface pretreatment liquid in which the solute is lithium polysulfide and the solute mass fraction is 2wt%.

[0088] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0089] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0090] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0091] 2% lithium polysulfide and 98% dimethyl sulfide; lithium polysulfide is prepared by sulfur and lithium sulfide in a molar ratio of 7:1.

[0092] (2) The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this embodiment is specifically as follows: in an argon atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm, dimethyl sulfide is added to an aluminum-plastic bottle, and then sulfur and lithium sulfide are added to the aluminum-plastic bottle in a molar ratio of 7:1, and stirred for 1 hour until the sulfur and lithium sulfide are completely dissolved, to prepare an interface pretreatment liquid in which the solute is lithium polysulfide and the solute mass fraction is 2 wt%.

[0093] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0094] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0095] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0096] 0.5% lithium polysulfide and 99.5% ethylene glycol dimethyl ether; lithium polysulfide is prepared by sulfur and lithium sulfide in a molar ratio of 8:1.

[0097] (2) The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this comparative example is as follows: in an argon atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm, ethylene glycol dimethyl ether is added to an aluminum-plastic bottle, and then sulfur and lithium sulfide are added to the aluminum-plastic bottle in a molar ratio of 8:1, and stirred for 1 hour until the sulfur and lithium sulfide are completely dissolved, to prepare an interface pretreatment liquid in which the solute is lithium polysulfide and the solute mass fraction is 0.5 wt%.

[0098] (3) The preparation process of the lithium-ion battery is the same as that in Example 1. Example

[0099] This embodiment provides an interface pretreatment solution for a pre-lithiation positive electrode, a preparation method thereof, and an application thereof.

[0100] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this embodiment is:

[0101] 8% lithium polysulfide and 92% ethylene glycol dimethyl ether; lithium polysulfide is prepared by sulfur and lithium sulfide in a molar ratio of 8:1.

[0102] (2) The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this comparative example is as follows: in an argon atmosphere glove box with a water content of <1ppm and an oxygen content of <1ppm, ethylene glycol dimethyl ether is added to an aluminum-plastic bottle, and then sulfur and lithium sulfide are added to the aluminum-plastic bottle in a molar ratio of 8:1, and stirred for 1 hour until the sulfur and lithium sulfide are completely dissolved, to prepare an interface pretreatment liquid in which the solute is lithium polysulfide and the solute mass fraction is 8wt%.

[0103] (3) The preparation process of the lithium-ion battery is the same as that in Example 1.

[0104] Comparative Example 1

[0105] The lithium-ion battery of this comparative example is the same as that of Example 1 except that the interface pretreatment of the lithium-supplemented positive electrode sheet is not performed.

[0106] Comparative Example 2

[0107] The interface pretreatment liquid for pre-lithiation of the positive electrode provided in this comparative example is ethylene glycol dimethyl ether, and the preparation process of the lithium ion battery is the same as that of Example 1.

[0108] Comparative Example 3

[0109] The interface pretreatment liquid for the pre-lithiation positive electrode provided in this comparative example is 1,3-dioxolane, and the preparation process of the lithium ion battery is the same as that of Example 1.

[0110] Comparative Example 4

[0111] The interface pretreatment liquid for pre-lithiation of the positive electrode provided in this comparative example is polyethylene glycol dimethyl ether, and the preparation process of the lithium ion battery is the same as that of Example 1.

[0112] Comparative Example 5

[0113] The interface pretreatment liquid for pre-lithiation of the positive electrode provided in this comparative example is dimethyl sulfide, and the preparation process of the lithium ion battery is the same as that of Example 1.

[0114] Comparative Example 6

[0115] This comparative example provides an interface pretreatment solution for a pre-lithiation positive electrode, and a preparation method and application thereof.

[0116] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this comparative example is: 2% dilute hydrochloric acid and 98% ethylene glycol dimethyl ether.

[0117] (2) The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this comparative example is as follows: in an argon atmosphere glove box with a water content of <1 ppm and an oxygen content of <1 ppm, ethylene glycol dimethyl ether and dilute hydrochloric acid are added to an aluminum-plastic bottle in sequence, and stirred for 1 hour until the dilute hydrochloric acid is completely dissolved to prepare an interface pretreatment liquid with a solute mass fraction of 2 wt%.

[0118] (3) The preparation process of the lithium-ion battery is the same as that in Example 1.

[0119] Comparative Example 7

[0120] This comparative example provides an interface pretreatment solution for a pre-lithiation positive electrode, and a preparation method and application thereof.

[0121] (1) In terms of mass percentage, the composition of the interface pretreatment solution for the pre-lithiation positive electrode in this comparative example is: 2% dilute silicic acid and 98% ethylene glycol dimethyl ether.

[0122] (2) The preparation method of the interface pretreatment liquid for the pre-lithiation positive electrode in this comparative example is as follows: in an argon atmosphere glove box with a water content of less than 1 ppm and an oxygen content of less than 1 ppm, ethylene glycol dimethyl ether and dilute silicic acid are added to an aluminum-plastic bottle in sequence, and stirred for 1 hour until the dilute silicic acid is completely dissolved to prepare an interface pretreatment liquid with a solute mass fraction of 2 wt%.

[0123] (3) The preparation process of the lithium-ion battery is the same as that in Example 1.

[0124] The compositions of the interface pretreatment solutions in Examples 1 to 14 and Comparative Examples 1 to 7 are shown in Table 1.

[0125] Table 1: Composition of interface pretreatment solutions in Examples 1 to 14 and Comparative Examples 1 to 7

[0126] No. Solvent Solute Example 1 Ethylene glycol dimethyl ether lithium polysulfide 1% (sulfur and lithium sulfide molar ratio 7:1) Example 2 Ethylene glycol dimethyl ether lithium polysulfide 2% (sulfur and lithium sulfide molar ratio 7:1) Example 3 Ethylene glycol dimethyl ether lithium polysulfide 3% (sulfur and lithium sulfide molar ratio 7:1) Example 4 Ethylene glycol dimethyl ether hydrobromic acid 1% Example 5 Ethylene glycol dimethyl ether hydrobromic acid 2% Example 6 Ethylene glycol dimethyl ether hydrobromic acid 3% Example 7 Ethylene glycol dimethyl ether hydroiodic acid 1% Example 8 Ethylene glycol dimethyl ether hydroiodic acid 2% Example 9 Ethylene glycol dimethyl ether hydroiodic acid 3% Example 10 1,3-Dioxolane lithium polysulfide 2% (sulfur and lithium sulfide molar ratio 7:1) Example 11: Diethylene glycol dimethyl ether lithium polysulfide 2% (sulfur and lithium sulfide molar ratio 7:1) Example 12: Dimethyl sulfide lithium polysulfide 2% (sulfur and lithium sulfide molar ratio 7:1) Example 13: Ethylene glycol dimethyl ether lithium polysulfide 0.5% (sulfur and lithium sulfide molar ratio 7:1) Example 14: Ethylene glycol dimethyl ether lithium polysulfide 6% (sulfur and lithium sulfide molar ratio 7:1) Comparative Example 1 - Comparative Example 2: Ethylene glycol dimethyl ether - Comparative Example 3: 1,3-Dioxolane - Comparative Example 4: Diethylene glycol dimethyl ether - Comparative Example 5: Dimethyl sulfide - Comparative Example 6: Ethylene glycol dimethyl ether diluted hydrochloric acid 2% Comparative Example 7: Ethylene glycol dimethyl ether diluted silicic acid 2%

[0127] The batteries of Examples 1 to 14 and Comparative Examples 1 to 7 were tested respectively:

[0128] At 25°C, the battery was first charged at a constant current of 0.02C to a voltage of 3.9V, then charged at a constant current of 0.2C to a voltage of 4.25V. After standing for 5 minutes, the battery was discharged at a constant current of 0.2C to a voltage of 2.5V. This is the first charge and discharge process. The first charge and discharge test results of the lithium-ion batteries of the embodiment and the comparative example are shown in Table 2.

[0129] Table 2: Performance test results of Examples 1 to 14 and Comparative Examples 1 to 7

[0130] No. First cycle discharge capacity Ah First charge and discharge efficiency Example 1 4.36 87.1% Example 2 4.38 87.5% Example 3 4.38 87.6% Example 4 4.32 86.3% Example 5 4.34 86.8% Example 6 4.35 87.0% Example 7 4.35 87.0% Example 8 4.37 87.3% Example 9 4.37 87.4% Example 10 4.36 87.2 % Example 114.3787.4% Example 124.3687.1% Example 134.2084.0% Example 144.2384.6% Comparative Example 14.0581.0% Comparative Example 24.0681.2% Comparative Example 34.0981.8% Comparative Example 44.0781.4% Comparative Example 54.0881.5% Comparative Example 64.0981.8% Comparative Example 74.0881.6%

[0131] As can be seen from Table 2, the initial charge and discharge efficiency and cycle performance of the lithium-ion batteries of Examples 1 to 14 are significantly better than those of the comparative example. It can be seen that by performing interface pretreatment on the lithium-supplemented positive electrode sheet, the interface film formation of the pre-lithiated positive electrode can be significantly improved, thereby effectively improving the initial charge and discharge efficiency; in Comparative Example 1, since the interface pretreatment of the lithium-supplemented positive electrode sheet was not performed, the CEI film formed on the surface of the pre-lithiated positive electrode was not stable enough, aggravating the side reaction between the electrolyte and the electrolyte, thereby affecting the initial charge and discharge efficiency of the battery; the composition and structure of the CEI film were not improved, and thermodynamically and kinetically unstable substances such as alkyl lithium carbonate and alkyl lithium were subsequently generated, resulting in insufficient CEI stability, thereby affecting the initial charge and discharge efficiency of the battery.

[0132] In Comparative Examples 6 and 7, the solute reacted with lithium oxide to form an unstable substance, which did not improve the interfacial film formation of the pre-lithiated positive electrode and had a certain impact on the initial charge and discharge efficiency of the lithium-ion secondary battery. Therefore, it is necessary to add a suitable solute to react with lithium oxide to form a thermodynamically and kinetically stable interfacial layer.

[0133] The above are only preferred specific implementations of this application; however, the scope of protection of this application is not limited thereto. Any person skilled in the art who, within the technical scope disclosed in this application, makes equivalent substitutions or modifications based on the technical solutions and improved concepts of this application shall be covered by the scope of protection of this application.

Claims

1. An interface pretreatment solution for a pre-lithiation positive electrode, characterized in that: The invention comprises, by mass percentage, 0.1% to 10% of solute and 90% to 99.9% of solvent; the solute is a mixture of one or more of lithium polysulfide, hydrobromic acid and hydroiodic acid; the solvent is a mixture of one or more of N-methylpyrrolidone, ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, γ-butyrolactone, methyl formate, ethyl formate, methyl acetate, ethyl acetate, ethyl propionate, propyl propionate, ethyl butyrate, propyl butyrate, dimethyl sulfoxide, ethylene glycol dimethyl ether, 1,3-dioxolane, diethylene glycol dimethyl ether and dimethyl sulfoxide.

2. The interface pretreatment solution for pre-lithiation positive electrode according to claim 1, characterized in that Calculated by mass percentage, it comprises 0.5% to 8% of solute and 92% to 99.5% of solvent.

3. The interface pretreatment solution for pre-lithiation positive electrode according to claim 2, characterized in that: Calculated by mass percentage, it includes 1% to 5% of solute and 95% to 99% of solvent.

4. An interface pretreatment solution for pre-lithiation positive electrode according to claim 1 or 2, characterized in that The solvent is selected from a mixed solvent of one or more of ethylene glycol dimethyl ether, 1,3-dioxolane, diethylene glycol dimethyl ether and dimethyl sulfide.

5. The interface pretreatment solution for pre-lithiation positive electrode according to claim 1, characterized in that: The lithium polysulfide is prepared from sulfur and lithium sulfide in a molar ratio of 6 to 10:

1.

6. A method for preparing a lithium-supplemented battery, characterized in that: The steps include: A positive electrode slurry containing a positive electrode active material is coated on the surface of the positive electrode current collector, and after drying, an initial positive electrode sheet with a positive electrode membrane disposed on the surface of the positive electrode current collector is obtained, and then a layer of lithium oxide is further disposed on the surface of the positive electrode membrane to obtain a lithium-supplemented positive electrode sheet; A negative electrode slurry containing a negative electrode active material is applied to the surface of the negative electrode current collector, and after drying, a negative electrode sheet having a negative electrode film provided on the surface of the negative electrode current collector is obtained; In an inert gas atmosphere, the water content is controlled to be less than 1 ppm, and the oxygen content is controlled to be less than 1 ppm. The lithium-supplemented positive electrode sheet is immersed in an interface pretreatment solution for a pre-lithiation positive electrode for 1 to 25 minutes, and then dried in an inert environment at room temperature for 1 to 3 hours to obtain a positive electrode material. Assemble the positive electrode material, separator and negative electrode sheet into a lithium-supplemented battery cell; The lithium-supplemented battery cell is placed in a battery packaging shell, injected with electrolyte and packaged to obtain a lithium-supplemented battery.

7. The method for preparing a lithium-supplemented battery according to claim 6, characterized in that: The lithium-supplemented positive electrode sheet is immersed in the interface pretreatment solution for 2 minutes to 15 minutes.

8. The method for preparing a lithium-supplemented battery according to claim 7, characterized in that: The lithium-supplemented positive electrode sheet is immersed in the interface pretreatment solution for 5 minutes to 10 minutes.

9. A lithium supplement battery, characterized in that: The lithium-supplemented battery is prepared by the method for preparing a lithium-supplemented battery according to any one of claims 6 to 8.

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