Lithium supplement reagent for negative electrode of lithium ion battery and application of lithium supplement reagent

Abstract

The invention belongs to the technical field of lithium battery negative electrode materials, and particularly relates to a lithium ion battery negative electrode lithium supplementing reagent and application thereof, and the lithium ion battery negative electrode lithium supplementing reagent comprises biphenyl, an antioxidant, a lithium elementary substance and an organic solvent; the reagent is applied to preparation of a pre-lithiated negative pole piece, and the preparation method specifically comprises the following steps: dissolving biphenyl and an antioxidant into an organic solution, and mixing to obtain a biphenyl solution; adding a lithium elementary substance into the biphenyl solution, and stirring until the lithium elementary substance is completely dissolved to obtain a biphenyl lithium solution; and spraying the biphenyl lithium solution on the surface of the negative pole piece, or completely soaking the negative pole piece into the biphenyl lithium solution, then taking out the negative pole piece, and completely volatilizing the organic solution on the surface of the negative pole piece to finally prepare the pre-lithiated negative pole piece. According to the invention, more active lithium sources are effectively supplemented to the negative electrode, so that the initial capacity of the battery is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of negative electrode materials for lithium batteries, and in particular, relates to a negative electrode lithium replenishing reagent for lithium ion batteries and an application thereof. Background Art

[0002] With the rapid development of modern science and technology, lithium-ion batteries, as an efficient and lightweight energy storage device, have been widely used in many fields, including but not limited to portable electronic devices (such as smartphones, laptops), electric vehicles, and renewable energy storage systems. The market's performance requirements for lithium-ion batteries are also constantly increasing, especially in terms of energy density, power density, cycle life, and safety. However, lithium-ion batteries face some key challenges in their development, which limit the further improvement of their performance.

[0003] During the first charge and discharge process of lithium-ion batteries, a series of complex electrochemical and chemical changes will occur at the negative electrode. Among them, an important issue is the formation of the solid electrolyte interface (SEI) film. The formation of the SEI film is necessary for the normal operation of the battery. It can prevent the electrolyte from further reacting with the negative electrode material and provide a channel for the transmission of lithium ions. However, the formation process of the SEI film will irreversibly consume a large amount of lithium ions, resulting in a decrease in the first coulombic efficiency of the negative electrode. For some new high-capacity negative electrode materials, such as silicon-based negative electrodes, this problem is more serious. The huge volume change of silicon during the charge and discharge process will destroy the SEI film, causing the SEI film to be continuously repaired and re-formed, further exacerbating the loss of lithium ions and seriously affecting the overall performance of the battery. At present, although some pre-lithiation agents have been developed, they each have corresponding problems. For example, although metal lithium powder has a high lithium content as a pre-lithiation agent, its activity is too high, which is easy to cause safety problems during use, such as the formation of lithium dendrites, which can cause battery short circuit and thermal runaway. Although some organic pre-lithiation reagents are relatively safe, they may have problems such as inappropriate decomposition potential, slow reaction kinetics, or poor solubility in the electrolyte.

[0004] Therefore, there is an urgent need to develop new and better-performing lithium-ion battery negative electrode pre-lithiation reagents to meet the needs of high-performance development of lithium-ion batteries, which is of vital importance to promoting the widespread application of lithium-ion battery technology in various fields. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a lithium-ion battery negative electrode lithium replenishing reagent and its application, which solves the technical problems of the prior art that the lithium-ion battery negative electrode lithium replenishing reagent has inappropriate decomposition potential, slow reaction kinetics, and poor solubility in electrolyte.

[0006] According to a first aspect of the present invention, a lithium-ion battery negative electrode lithium replenishing reagent is provided, comprising biphenyl, an antioxidant, lithium element, and an organic solvent.

[0007] Preferably, the mass fraction of the antioxidant is 0.001-5%, the mass fraction of biphenyl is 0.15-5%, the mass fraction of the organic solvent is 90%-95%, and the mass fraction of elemental lithium is 0.001-0.05%.

[0008] Preferably, the organic solvent is one or more of tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, ethylene glycol dimethyl ether or acetonitrile.

[0009] Preferably, the antioxidant is one or more of butylated hydroxyanisole, butylated hydroxytoluene, ascorbic acid or tocopherol.

[0010] According to another aspect of the present invention, a method for preparing a pre-lithiated negative electrode sheet is provided, which specifically comprises the following steps:

[0011] (1) dissolving biphenyl and an antioxidant in an organic solution and mixing them to obtain a biphenyl solution;

[0012] (2) adding lithium to the biphenyl solution and stirring until the lithium is completely dissolved to obtain a biphenyl lithium solution;

[0013] (3) Spraying the biphenyl lithium solution on the surface of the negative electrode plate, or completely immersing the negative electrode plate in the biphenyl lithium solution, then taking it out, and allowing the organic solution on the surface of the negative electrode plate to completely volatilize, finally obtaining a pre-lithiated negative electrode plate.

[0014] Preferably, the organic solvent is one or more of tetrahydrofuran, 2-methyltetrahydrofuran, ether, ethylene glycol dimethyl ether or acetonitrile; and the antioxidant is one or more of butylated hydroxyanisole, butylated hydroxytoluene, ascorbic acid or tocopherol.

[0015] Preferably, in the biphenyl lithium solution, the mass fraction of the antioxidant is 0.001-5%, the mass fraction of biphenyl is 0.15-5%, the mass fraction of the organic solvent is 90%-95%, and the mass fraction of elemental lithium is 0.001-0.05%.

[0016] Preferably, in step (3), when the spraying method is adopted, the spraying amount of the lithium biphenyl solution is 10 to 200 uL / cm 2 ; When the immersion method is used, the immersion time is 0.1 to 10 minutes.

[0017] Preferably, in step (2), the stirring is magnetic stirring, and the magnetic stirring time is 6 to 12 hours.

[0018] Preferably, the material of the negative electrode is one or more of silicon, carbon, lithium titanate, tin dioxide, molybdenum disulfide or tungsten disulfide.

[0019] In general, the above technical solution conceived by the present invention has the following technical advantages compared with the prior art:

[0020] 1. The lithium-ion battery negative electrode lithium replenishing reagent of the present invention can effectively compensate for the irreversible lithium ion loss caused by the formation of a solid electrolyte interface layer in the negative electrode material during the first charging process by pre-lithiation treatment, and reduce the lithium ion consumption during the first charging by adding an additional lithium source to the negative electrode material before battery assembly, thereby improving the first coulombic efficiency of the battery; the negative electrode lithium replenishing reagent reduces the electrochemical reaction energy of the electrode and promotes the improvement of the electrode reaction rate through its high conductivity and catalytic activity, which helps to improve the performance of the lithium-ion battery, so that it has a higher charging and discharging rate, thereby improving the overall performance of the battery; the negative electrode lithium replenishing reagent can further improve the energy density of the lithium-ion battery, so that it has a higher energy storage capacity, which is of great significance for improving the energy output of the battery and extending the service life.

[0021] 2. The negative electrode lithium replenishing reagent of the present invention has an anti-overcharge protection effect on lithium-ion batteries. Under high voltage, biphenyl will undergo an electrochemical polymerization reaction, and the generated conductive polymer can cause the overcharged battery to automatically discharge to a safer charged state. This mechanism helps to prevent safety problems caused by overcharging of the battery; at the same time, the addition of biphenyl can improve the stability and cycle life of the cathode material. Since the cycle life of a lithium-ion battery depends on the exchange rate between cations and anions, the addition of biphenyl lithium solution can make the electrochemical reaction more stable, reduce the degradation of the electrode material, and thus increase the cycle life of the battery.

[0022] 3. The negative electrode lithium replenishing reagent for lithium ion batteries prepared by the present invention can not only improve the anti-oxidation performance of the negative electrode material, but also improve its charge and discharge performance by adding an antioxidant. By reducing the oxidation reaction of the negative electrode during the charge and discharge process, the antioxidant helps to maintain the structural integrity and electrochemical activity of the negative electrode material, thereby improving the charge and discharge efficiency and capacity of the lithium ion battery; the added antioxidant can also improve the safety and stability of the storage of the negative electrode lithium replenishing reagent for lithium ion batteries.

[0023] 4. The special structure of biphenyl lithium in the lithium replenishing reagent of the present invention enables it to efficiently release lithium during the battery charging and discharging process. Compared with the existing common lithium replenishing reagents, the lithium replenishing efficiency can be increased to more than 100%, effectively replenishing more active lithium sources to the negative electrode, thereby significantly improving the initial capacity of the battery.

[0024] 5. The mass fraction of the antioxidant of the present invention is 0.001-5%, the mass fraction of biphenyl is 0.15-5%, the mass fraction of the organic solvent is 90%-95%, and the mass fraction of elemental lithium is 0.001-0.05%. This can not only achieve efficient lithium replenishment of the negative electrode of the lithium ion battery, but also the antioxidant can form a protective film on the surface of the electrode, inhibit the decomposition and redox reaction of the electrolyte on the surface of the electrode, reduce the side reactions on the surface of the electrode, thereby improving the stability of the electrode-electrolyte interface, facilitating the reversible shuttling of lithium ions between the electrode and the electrolyte, and thus improving the cycle performance of the battery.

[0025] 6. The present invention has good compatibility with the existing lithium-ion battery manufacturing process during preparation and application. The lithium-ion battery negative electrode lithium replenishing reagent can be introduced into the battery manufacturing process without changing the existing production line, thereby reducing production costs and process complexity.

[0026] 7. The present invention uses cheap metallic lithium, biphenyl and organic solvent as raw materials for lithium-ion battery negative electrode lithium replenishing reagent, which greatly reduces the preparation cost and can be used for large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic flow chart of a method for preparing a pre-lithiated negative electrode sheet of the present invention;

[0028] Figure 2 This is the first charge and discharge curve before pre-lithiation of the silicon-carbon composite negative electrode of the lithium-ion battery provided in Example 1 of the present invention;

[0029] Figure 3 This is the first charge and discharge curve after pre-lithiation of the silicon-carbon composite negative electrode of the lithium-ion battery provided in Example 1 of the present invention;

[0030] Figure 4 The electrochemical impedance spectrum of the lithium-ion battery silicon-carbon composite negative electrode before and after pre-lithiation provided in Example 1 of the present invention;

[0031] Figure 5 This is a first cycle cyclic voltammetry curve diagram of a lithium-ion battery silicon-carbon composite negative electrode before pre-lithiation provided by Example 1 of the present invention;

[0032] Figure 6 This is a first cycle cyclic voltammetry curve of the silicon-carbon composite negative electrode of the lithium ion battery after pre-lithiation in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Example 1

[0035] See also Figure 2 , Figure 3 , Figure 4 , Figure 5 and Figure 6 In the lithium-ion battery negative electrode lithium replenishing reagent in this embodiment, the antioxidant is ascorbic acid, the organic solvent is 2-methyltetrahydrofuran, the ratio of biphenyl, ascorbic acid and 2-methyltetrahydrofuran is 152g:1g:1000g, the ratio of metallic lithium and biphenyl in the biphenyl solution is 14g:1.52g, and the lithium-ion battery silicon-carbon composite negative electrode plate is immersed in the lithium-ion battery negative electrode lithium replenishing reagent for 5 minutes.

[0036] The process steps of this embodiment are as follows:

[0037] (1) 152 g of biphenyl and 1 g of anhydrous hemic acid were dissolved in 1000 g of 2-methyltetrahydrofuran and stirred with a magnetic stirrer for 10 minutes to obtain a biphenyl solution.

[0038] (2) 14 g of metallic lithium was added to the biphenyl solution and magnetically stirred for 10 hours until the metallic lithium was completely dissolved to obtain a biphenyl lithium solution.

[0039] (3) The lithium-ion battery silicon-carbon composite negative electrode plate is immersed in the lithium-ion battery negative electrode lithium replenishing reagent for 5 minutes, then taken out and waited for 1 hour until the organic solution on the surface of the negative electrode plate is completely volatilized, and finally a pre-lithiated lithium-ion battery silicon-carbon composite negative electrode plate is obtained.

[0040] The silicon-carbon composite negative electrode sheet of the lithium-ion battery before pre-lithiation and the silicon-carbon composite negative electrode sheet of the lithium-ion battery after pre-lithiation are respectively assembled into Li||Li + The lithium battery with silicon-carbon composite negative electrode was tested for its first cycle charge-discharge curve, electrochemical impedance spectrum and first cycle cyclic voltammetry curve. At room temperature, the pre-lithiation Li||Li + The first coulombic efficiency of lithium batteries with silicon-carbon composite negative electrode plates was increased from the initial 70.5% to 96.4%, the electrochemical impedance was effectively reduced, and the surface side reactions were greatly reduced.

[0041] Example 2

[0042] In the preparation and application of the lithium-ion battery negative electrode lithium replenishing reagent in this embodiment, the organic solvent is ethylene glycol dimethyl ether, the antioxidant is tocopherol, the ratio of biphenyl, tocopherol and ethylene glycol dimethyl ether is 152g:0.8g:1000g, the ratio of biphenyl in the metallic lithium and biphenyl solution is 10.5g:152g, and the lithium-ion battery silicon-carbon composite negative electrode plate is immersed in the lithium-ion battery negative electrode lithium replenishing reagent for 6 minutes.

[0043] The process steps of this embodiment are as follows:

[0044] (1) 152 g of biphenyl and 0.8 g of tocopherol were dissolved in 1000 g of ethylene glycol dimethyl ether and stirred with a magnetic stirrer for 15 minutes to obtain a biphenyl solution.

[0045] (2) 10.5 g of metallic lithium was added to the biphenyl solution and magnetically stirred for 6 hours until the metallic lithium was completely dissolved to obtain a biphenyl lithium solution.

[0046] (3) The lithium-ion battery silicon-carbon composite negative electrode plate is immersed in the lithium-ion battery negative electrode lithium replenishing reagent for 6 minutes, then taken out and waited for 3 hours until the organic solution on the surface of the negative electrode plate is completely volatilized, and finally a pre-lithiated lithium-ion battery silicon-carbon composite negative electrode plate is obtained.

[0047] Assemble the pre-lithiated lithium-ion battery silicon-carbon composite negative electrode plate into Li||Li + The lithium battery with silicon-carbon composite negative electrode plate is tested for its first cycle charge and discharge curve. At room temperature, the pre-lithiation Li||Li + The first coulombic efficiency of lithium batteries with silicon-carbon composite negative electrode plates was increased from the initial 70.5% to 94.4%.

[0048] Example 3

[0049] In the lithium-ion battery negative electrode lithium replenishing reagent and application in this embodiment, the organic solvent is acetonitrile, the antioxidant is butylated hydroxytoluene, the ratio of biphenyl, butylated hydroxytoluene and acetonitrile is 75g:1.2g:1200g, the ratio of biphenyl in the metallic lithium and biphenyl solution is 2.1g:75g, and the lithium-ion battery silicon-carbon composite negative electrode plate is immersed in the lithium-ion battery negative electrode lithium replenishing reagent for 5 minutes.

[0050] The process steps of this embodiment are as follows:

[0051] (1) 75 g of biphenyl and 1.2 g of butylated hydroxytoluene were dissolved in 1200 g of acetonitrile and stirred with a magnetic stirrer for 20 minutes to obtain a biphenyl solution.

[0052] (2) 2.1 g of metallic lithium was added to the biphenyl solution and magnetically stirred for 6 hours until the metallic lithium was completely dissolved to obtain a biphenyl lithium solution.

[0053] (3) The lithium-ion battery silicon-carbon composite negative electrode plate is immersed in the lithium-ion battery negative electrode lithium replenishing reagent for 10 minutes, then taken out and waited for 3 hours until the organic solution on the surface of the negative electrode plate is completely volatilized, and finally a pre-lithiated lithium-ion battery silicon-carbon composite negative electrode plate is obtained.

[0054] Assemble the pre-lithiated lithium-ion battery silicon-carbon composite negative electrode plate into Li||Li + The lithium battery with silicon-carbon composite negative electrode plate is tested for its first cycle charge and discharge curve. At room temperature, the pre-lithiation Li||Li + The first coulombic efficiency of lithium batteries with silicon-carbon composite negative electrode plates was increased from the initial 70.5% to 95.2%.

[0055] Example 4

[0056] Preparation and application of the lithium-ion battery negative electrode lithium replenishing reagent in this embodiment, the organic solvent is 2-methyltetrahydrofuran, the antioxidant is butylated hydroxyanisole, the ratio of biphenyl, butylated hydroxyanisole and 2-methyltetrahydrofuran is 152g:1.5g:1000g, the ratio of metallic lithium and biphenyl in the biphenyl solution is 14g:152g, the lithium-ion battery negative electrode lithium replenishing reagent is sprayed onto the lithium-ion battery silicon-carbon composite negative electrode plate, and the spraying amount is 50uL / cm 2 .

[0057] The process steps of this embodiment are as follows:

[0058] (1) 152 g of biphenyl and 1.5 g of butylated hydroxyanisole were dissolved in 1000 g of 2-methyltetrahydrofuran and stirred with a magnetic stirrer for 10 minutes to obtain a biphenyl solution.

[0059] (2) 14 g of metallic lithium was added to the biphenyl solution and magnetically stirred for 10 hours until the metallic lithium was completely dissolved to obtain a biphenyl lithium solution.

[0060] (3) Spray the lithium-ion battery negative electrode lithium replenishing reagent onto the lithium-ion battery silicon-carbon composite negative electrode plate, with a spraying volume of 50uL / cm 2 , wait for the organic solution on the surface to completely volatilize, and finally obtain the pre-lithiated lithium-ion battery silicon-carbon composite negative electrode.

[0061] Assemble the pre-lithiated lithium-ion battery silicon-carbon composite negative electrode plate into Li||Li + The lithium battery with silicon-carbon composite negative electrode plate is tested for its first cycle charge and discharge curve. At room temperature, the pre-lithiation Li||Li + The first coulombic efficiency of lithium batteries with silicon-carbon composite negative electrode plates was increased from the initial 70.5% to 94.3%.

[0062] Example 5

[0063] Preparation and application of lithium-ion battery negative electrode lithium replenishing reagent in this embodiment, the organic solvent is tetrahydrofuran, the antioxidant is ascorbic acid, the ratio of biphenyl, ascorbic acid and tetrahydrofuran is 152g:1.5g:1600g, the ratio of biphenyl in metallic lithium and biphenyl solution is 7g:152g, the lithium-ion battery negative electrode lithium replenishing reagent is sprayed onto the lithium-ion battery silicon-carbon composite negative electrode plate, and the spraying amount is 60uL / cm 2 .

[0064] The process steps of this embodiment are as follows:

[0065] (1) 152 g of biphenyl and 1.5 g of ascorbic acid were dissolved in 1600 g of 2-methyltetrahydrofuran and stirred with a magnetic stirrer for 5 minutes to obtain a biphenyl solution.

[0066] (2) 7 g of metallic lithium was added to the biphenyl solution and magnetically stirred for 8 hours until the metallic lithium was completely dissolved to obtain a biphenyl lithium solution.

[0067] (3) Spray the lithium-ion battery negative electrode lithium replenishing reagent onto the lithium-ion battery silicon-carbon composite negative electrode plate, with a spraying volume of 60uL / cm 2 , wait for the organic solution on the surface to completely volatilize, and finally obtain the pre-lithiated lithium-ion battery silicon-carbon composite negative electrode.

[0068] The pre-lithiation lithium-ion battery silicon-carbon composite negative electrode piece was assembled into a lithium battery with Li / / lithium-ion battery silicon-carbon composite negative electrode piece and its first cycle charge and discharge curve was tested. At room temperature, the first coulombic efficiency of the lithium battery with the pre-lithiation Li / / lithium-ion battery silicon-carbon composite negative electrode piece was increased from the initial 70.5% to 98.7%.

[0069] Example 6

[0070] Preparation and application of the lithium-ion battery negative electrode lithium replenishing reagent in this embodiment, the organic solvent is 2-methyltetrahydrofuran, the antioxidant is butylated hydroxytoluene, the ratio of biphenyl, butylated hydroxytoluene and 2-methyltetrahydrofuran is 152g:1g:1000g, the ratio of metallic lithium and biphenyl in the biphenyl solution is 7g:152g, the lithium-ion battery negative electrode lithium replenishing reagent is sprayed onto the graphite negative electrode of the lithium-ion battery, and the spraying amount is 10uL / cm 2 .

[0071] The process steps of this embodiment are as follows:

[0072] (1) 152 g of biphenyl and 1 g of butylated hydroxytoluene were dissolved in 1000 g of 2-methyltetrahydrofuran and stirred with a magnetic stirrer for 5 minutes to obtain a biphenyl solution.

[0073] (2) 7 g of metallic lithium was added to the biphenyl solution and magnetically stirred for 6 hours until the metallic lithium was completely dissolved to obtain a biphenyl lithium solution.

[0074] (3) Spray the lithium-ion battery negative electrode lithium replenishing reagent onto the lithium-ion battery graphite negative electrode plate, with a spraying amount of 10uL / cm 2 , wait for the organic solution on the surface to completely volatilize, and finally obtain the pre-lithiated lithium-ion battery hard carbon negative electrode.

[0075] Assemble the pre-lithiated graphite negative electrode sheet of lithium-ion battery into Li||Li + The lithium battery with graphite negative electrode plate is tested for its first cycle charge and discharge curve. At room temperature, the pre-lithiation Li||Li + The first coulombic efficiency of lithium batteries with graphite negative electrode sheets was increased from the initial 85.6% to 97.1%.

[0076] Example 7

[0077] Preparation and application of lithium-ion battery negative electrode lithium replenishing reagent in this embodiment, the organic solvent is ethylene glycol dimethyl ether, the antioxidant is tocopherol, the ratio of biphenyl, tocopherol and ethylene glycol dimethyl ether is 152g: 1g: 2000g, the ratio of metallic lithium and biphenyl in biphenyl solution is 14g: 152g, the lithium-ion battery negative electrode lithium replenishing reagent is sprayed onto the lithium-ion battery hard carbon negative electrode plate, and the spraying amount is 20uL / cm 2 .

[0078] The process steps of this embodiment are as follows:

[0079] (1) 152 g of biphenyl and 1 g of tocopherol were dissolved in 2000 g of ethylene glycol dimethyl ether and stirred with a magnetic stirrer for 16 minutes to obtain a biphenyl solution.

[0080] (2) 14 g of metallic lithium was added to the biphenyl solution and magnetically stirred for 20 hours until the metallic lithium was completely dissolved to obtain a biphenyl lithium solution.

[0081] (3) Spray the lithium-ion battery negative electrode lithium replenishing reagent onto the lithium-ion battery graphite negative electrode plate, with a spraying volume of 20uL / cm 2 , wait for the organic solution on the surface to completely volatilize, and finally obtain the pre-lithiated lithium-ion battery hard carbon negative electrode.

[0082] Assemble the pre-lithiated hard carbon negative electrode of lithium-ion battery into Li||Li + The first cycle charge and discharge curve of the lithium battery with hard carbon negative electrode is tested. At room temperature, the pre-lithiation Li||Li + The first coulombic efficiency of the lithium battery with hard carbon negative electrode was increased from the initial 76.2% to 91.1%.

[0083] Comparative Example 1

[0084] Preparation and application of lithium-ion battery negative electrode lithium replenishing reagent in this embodiment, the organic solvent is ethylene glycol dimethyl ether, the ratio of biphenyl to ethylene glycol dimethyl ether is 152g:2000g, the ratio of biphenyl in metallic lithium and biphenyl solution is 14g:152g, the lithium-ion battery negative electrode lithium replenishing reagent is sprayed onto the lithium-ion battery hard carbon negative electrode plate, and the spraying amount is 20uL / cm 2 .

[0085] The process steps of this embodiment are as follows:

[0086] (1) 152 g of biphenyl was dissolved in 2000 g of ethylene glycol dimethyl ether and stirred magnetically for 16 minutes to obtain a biphenyl solution.

[0087] (2) 14 g of metallic lithium was added to the biphenyl solution and magnetically stirred for 20 hours until the metallic lithium was completely dissolved to obtain a biphenyl lithium solution.

[0088] (3) Spray the lithium-ion battery negative electrode lithium replenishing reagent onto the lithium-ion battery graphite negative electrode plate, with a spraying volume of 20uL / cm 2 , wait for the organic solution on the surface to completely volatilize, and finally obtain the pre-lithiated lithium-ion battery hard carbon negative electrode.

[0089] Comparative Example 1 does not add an antioxidant, which makes the pre-lithiation reagent more susceptible to oxidation during storage and use, resulting in reduced stability. In addition, in the absence of an antioxidant, the pre-lithiation reagent will react with oxygen, moisture or other impurities in the air to produce by-products. These side reactions not only affect the purity of the sample, but also pose a safety hazard.

[0090] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A lithium-ion battery negative electrode lithium supplement reagent, characterized in that: Including biphenyl, antioxidant, lithium element and organic solvent.

2. A lithium-ion battery negative electrode lithium replenishing reagent according to claim 1, characterized in that: The mass fraction of the antioxidant is 0.001-5%, the mass fraction of biphenyl is 0.15-5%, the mass fraction of the organic solvent is 90%-95%, and the mass fraction of elemental lithium is 0.001-0.05%.

3. A lithium-ion battery negative electrode lithium replenishing reagent according to claim 1, characterized in that: The antioxidant is one or more of butylated hydroxyanisole, butylated hydroxytoluene, ascorbic acid or tocopherol.

4. A lithium-ion battery negative electrode lithium replenishing reagent according to claim 1, characterized in that: The organic solvent is one or more of tetrahydrofuran, 2-methyltetrahydrofuran, diethyl ether, ethylene glycol dimethyl ether or acetonitrile.

5. A method for preparing a pre-lithiated negative electrode sheet, comprising the following steps: (1) dissolving biphenyl and an antioxidant in an organic solvent and mixing them to obtain a biphenyl solution; (2) adding lithium to the biphenyl solution and stirring until the lithium is completely dissolved to obtain a biphenyl lithium solution; (3) coating the biphenyl lithium solution on the surface of the negative electrode plate, and waiting for the organic solvent on the surface of the negative electrode plate to completely volatilize, thereby finally obtaining a pre-lithiated negative electrode plate.

6. The method for preparing a pre-lithiated negative electrode sheet according to claim 5, characterized in that: The organic solvent is one or more of tetrahydrofuran, 2-methyltetrahydrofuran, ether, ethylene glycol dimethyl ether or acetonitrile; the antioxidant is one or more of butylated hydroxyanisole, butylated hydroxytoluene, ascorbic acid or tocopherol.

7. A method for preparing a pre-lithiated negative electrode sheet according to claim 5, characterized in that: In the biphenyl lithium solution, the mass fraction of the antioxidant is 0.001-5%, the mass fraction of biphenyl is 0.15-5%, the mass fraction of the organic solvent is 90%-95%, and the mass fraction of elemental lithium is 0.001-0.05%.

8. A method for preparing a pre-lithiated negative electrode sheet according to claim 5, characterized in that: The coating method in step (3) is selected from spraying or immersion; when the spraying method is adopted, the amount of the lithium biphenyl solution sprayed is 10 to 200 uL / cm 2 ; When the immersion method is used, the immersion time is 0.1 to 10 minutes.

9. A method for preparing a pre-lithiated negative electrode sheet according to claim 5, characterized in that: In step (2), the stirring is magnetic stirring, and the magnetic stirring time is 6 to 12 hours.

10. A method for preparing a pre-lithiated negative electrode sheet according to claim 5, characterized in that: The material of the negative electrode is one or more of silicon, carbon, lithium titanate, tin dioxide, molybdenum disulfide or tungsten disulfide.

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