Lithium supplement agent and preparation method thereof, positive pole piece and secondary battery

Abstract

The invention relates to a lithium supplement agent and a preparation method thereof, a positive pole piece and a secondary battery. The lithium supplement agent comprises a compound with the following general formula: Li < x > Mo < 4 > O < 11 >, wherein 0 lt; and x < = 8. LixMo4O11 provided by the invention is used as a lithium supplement agent, and the following irreversible reaction occurs in the battery charging process: # imgabs0 #, so that active lithium is released, and the first-week coulombic efficiency and the battery capacity of the battery are improved; and meanwhile, LixMo4O11 is used as the lithium supplement agent and does not generate side reaction, so that gas production of the battery in the use process is reduced, bulging of the battery is inhibited, and the safety of the battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a lithium supplement and a preparation method thereof, a positive electrode sheet, and a secondary battery. Background Art

[0002] During the formation process of lithium-ion batteries, the formation of the negative electrode SEI film will consume a large amount of active lithium, especially when some high-capacity silicon-based negative electrode materials are added, resulting in a decrease in the coulombic efficiency and battery capacity of the battery in the first week.

[0003] Lithium supplement is a high lithium content compound that releases lithium during the charging process to form irreversible compounds to replenish the active lithium in the battery. Commonly used lithium supplements include lithium ferrite and lithium nickelate.

[0004] However, the above-mentioned lithium supplement easily generates gas during use, which causes the battery to swell and then causes the explosion-proof valve to burst, affecting the safety of the battery. Summary of the invention

[0005] Based on this, it is necessary to provide a lithium supplement and its preparation method, a positive electrode plate, and a secondary battery to replenish the active lithium in the battery, improve the battery's first-week coulomb efficiency and battery capacity, reduce the gas production of the battery during use, inhibit battery swelling, and improve battery safety.

[0006] The first aspect of the present application provides a lithium supplement, which includes a compound having the following general formula: Li x Mo4O 11 ; Among them, 0 <x≤8。

[0007] The second aspect of the present application provides a method for preparing a lithium supplement, the preparation method comprising the following steps: S1, preparing Mo4O 11 The material is prepared as a working electrode; S2, the working electrode is assembled with a counter electrode and an electrolyte into an electrolytic cell, wherein the electrolyte includes a lithium salt; S3, the electrolytic cell is discharged, and after the discharge, the precipitate on the working electrode is taken out, and the precipitate is post-processed to obtain a lithium supplement; wherein the lithium supplement includes Li x Mo4O 11 Compound, 0 <x≤8。

[0008] In some embodiments, step S1 specifically comprises: 11 Powder pressed into Mo4O 11 The conductor is then inserted into the Mo4O 11 In the block, a working electrode is obtained; or, Mo4O 11 The powder is pressed together with the conductor to obtain Mo4O with a conductor inserted inside. 11 The block is the working electrode.

[0009] In some embodiments, Mo4O 11 The particle size of the powder is D50<5μm.

[0010] In some embodiments, Mo4O 11 The compacted density of the powder is <3g / cm 3 .

[0011] In some embodiments, the volume of the conductor is about the same as that of Mo4O 11 The volume percentage of the block is 30% to 70%.

[0012] In some embodiments, in step S2, the concentration of the lithium salt in the electrolyte is 0.5 mol / L to 20 mol / L.

[0013] In some embodiments, the counter electrode is one of a lithium metal electrode, a lithium alloy electrode, and a lithium copper composite electrode.

[0014] In some embodiments, in step S3, the discharge cut-off voltage of the electrolytic cell is ≥1V.

[0015] In some embodiments, the post-processing includes pulverization, purification and drying.

[0016] The third aspect of the present application provides a positive electrode plate, which includes a positive electrode active material layer, and the positive electrode active material layer includes the lithium supplement provided by the first aspect above, or the lithium supplement prepared by the preparation method provided by the second aspect above.

[0017] In some embodiments, the mass percentage of the lithium supplement in the positive electrode active material layer is 0.5% to 5%.

[0018] A fourth aspect of the present application provides a secondary battery, which includes the positive electrode plate provided by the third aspect.

[0019] Compared with the traditional technology, this application has at least the following beneficial effects:

[0020] This application provides x Mo4O 11 As a lithium supplement, the following irreversible reaction occurs during battery charging: Li x Mo4O 11 -xe - →xLi + +Mo4O 11 , thereby releasing active lithium and improving the battery's first-week coulombic efficiency and battery capacity; at the same time, Li x Mo4O 11As a lithium supplement, no side reactions occur, thus reducing gas production during battery use, inhibiting battery swelling, and improving battery safety.

[0021] The preparation method of the lithium supplement provided in the present application comprises the steps of: 11 The working electrode, electrolyte and counter electrode of the material are assembled into an electrolytic cell, and the reaction is carried out on the working electrode, which can effectively control the lithium insertion process. Compared with the lithium supplement prepared by chemical methods, the electrochemical method can control the insertion of lithium ions, thereby accurately regulating the Li x Mo4O 11 The lithium content of the compound is high and the side reactions are less, so the prepared lithium supplement has higher purity and uniformity, which improves the consistency and stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of the process of preparing a lithium supplement in one embodiment of the present application.

[0023] Figure 2 Schematic diagram of the structure of the working electrode in one embodiment of the present application.

[0024] Figure 3 Schematic diagram of the structure of an electrolytic cell in one embodiment of the present application.

[0025] Figure 4 Li in Examples 1 to 4 of this application x Mo4O 11 With γ-Mo4O 11 XRD pattern of .

[0026] Reference numerals:

[0027] 1. Electrolytic cell;

[0028] 10. electrolytic cell; 11. electrolyte;

[0029] 20. Working electrode; 21. Mo4O 11 Block; 22, conductive rod; 23, conductor;

[0030] 30. Counter electrode;

[0031] 40. Power supply equipment. DETAILED DESCRIPTION

[0032] References to embodiments of the present application will now be provided in detail, one or more examples of which are described below. Each example is provided as an explanation rather than a limitation of the present application. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made to the present application without departing from the scope or spirit of the present application. For example, a feature described or described as part of one embodiment may be used in another embodiment to produce a further embodiment.

[0033] Therefore, it is intended that the present application covers such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features and aspects of the present application are disclosed in or are apparent from the following detailed description. It will be appreciated by those of ordinary skill in the art that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present application.

[0034] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0035] In this application, when it comes to numerical ranges, unless otherwise specified, the above numerical ranges are deemed to be continuous and include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Further, when a range refers to an integer, each integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0036] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0037] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0038] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0039] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0040] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0041] The first aspect of the present application provides a lithium supplement, which includes a compound having the following general formula: Li x Mo4O 11 ; Among them, 0 <x≤8。

[0042] This application provides x Mo4O 11 As a lithium supplement, the following irreversible reaction occurs during battery charging: Li x Mo4O 11 -xe - →xLi + +Mo4O 11 , thereby releasing active lithium and improving the battery's first-week coulombic efficiency and battery capacity; at the same time, Li x Mo4O 11 As a lithium supplement, no side reactions occur, thus reducing gas production during battery use, inhibiting battery swelling, and improving battery safety.

[0043] In addition, Li x Mo4O 11 After lithium replenishment, Mo4O is generated 11 , Mo4O 11 The lithium insertion potential of Mo4O is less than 2V, while the discharge voltage is generally higher than 2V. 11 Lithium insertion will not occur again, allowing the battery to maintain a lower voltage platform during discharge, thereby preventing the battery from over-discharge to a certain extent.

[0044] Furthermore, x satisfies: 1≤x≤7.

[0045] In some embodiments, Li x Mo4O 11 The specific surface area is <40m 2 / g.

[0046] In this article, "specific surface area" refers to the surface area per unit mass of a material, unit: m 2 / g.

[0047] The second aspect of the present application provides a method for preparing a lithium supplement, such as Figure 1 As shown, the preparation method comprises the following steps:

[0048] S1, Mo4O 11 The materials were prepared as working electrodes.

[0049] S2. Assemble the working electrode, the counter electrode and the electrolyte into an electrolytic cell, wherein the electrolyte includes a lithium salt.

[0050] S3, discharging the electrolytic cell, taking out the precipitate on the working electrode after the discharge, and post-treating the precipitate to obtain a lithium supplement.

[0051] Among them, lithium supplements include Li x Mo4O 11 Compound, 0 <x≤8。

[0052] The preparation method of the lithium supplement provided in the present application comprises the steps of: 11 The working electrode, electrolyte and counter electrode of the material are assembled into an electrolytic cell, and the reaction is carried out on the working electrode, which can effectively control the lithium insertion process. Compared with the lithium supplement prepared by chemical methods, the electrochemical method can control the insertion of lithium ions, thereby accurately regulating the Li x Mo4O 11 The lithium content of the compound is high, and the side reaction is less, so the prepared lithium supplement has high purity and uniformity, and the consistency and stability of the material are improved; the Li prepared by the preparation method x Mo4O 11 Lithium supplements improve the battery's first-week coulomb efficiency and battery capacity, while reducing gas production and battery swelling caused by side reactions, thereby improving the battery's safety and service life.

[0053] In some embodiments, step S1 specifically comprises: 11 Powder pressed into Mo4O 11 The conductor is then inserted into the Mo4O 11 Inside the block, a working electrode is obtained.

[0054] In some other embodiments, step S1 specifically comprises: 11 The powder is pressed together with the conductor to obtain Mo4O with a conductor inserted inside. 11 The block is the working electrode.

[0055] In this paper, "Mo4O 11The "block" can also be Mo4O 11 The thickness of the sheet depends on the pressing thickness.

[0056] In some embodiments, Mo4O 11 The particle size D50 of the powder is less than 5 μm. For example, Mo4O 11 The particle size D50 of the powder includes but is not limited to 0.1μm, 0.5μm, 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, and 4.5μm. Within the above particle size range, Mo4O 11 The particle size of the powder is small, which can increase the Mo4O 11 The specific surface area of ​​the material can be increased, thereby improving the activity of the electrochemical reaction, thereby increasing the rate of lithium ion embedding and improving the preparation efficiency of the lithium supplement.

[0057] In some embodiments, Mo4O 11 The compacted density of the powder is <3g / cm 3 Within the above compaction density range, the working electrode retains a certain porosity during compaction, providing a channel for the diffusion of lithium ions, reducing the resistance encountered by lithium ions during the embedding process, and improving the reaction efficiency of the working electrode; at the same time, it reserves space for pressing and conductor insertion.

[0058] In some embodiments, the volume of the conductor is about the same as that of Mo4O 11 The volume percentage of the block is 30% to 70%. For example, the conductor and Mo4O 11 The volume percentage of the block is 30%, 40%, 50%, 60%, and 70%. Within the above volume percentage range, the conductor can provide sufficient electrical conductivity, thereby improving the electrochemical performance of the electrolytic cell.

[0059] Herein, "volume of conductor" refers to the total volume of conductor used for the working electrode.

[0060] In some embodiments, the conductor includes one or more of a conductive rod, a conductive grid column, and a conductive wire; the number of the conductors can be one or more; when the number of the conductors is multiple, the multiple conductors are connected by wires. Figure 2 and Figure 3 As shown, the conductor is a conductive rod 22, and a plurality of conductive rods 22 are inserted into the Mo4O 11 A working electrode 20 is formed in the block 21 , and conductive rods 22 are connected by wires 23 .

[0061] In some embodiments, after step S2, the preparation method further comprises: infiltrating the working electrode with an electrolyte. 11The volume of the block is adjusted to adjust the infiltration time. Specifically, the infiltration time of the working electrode is 1h to 24h. In this embodiment, the infiltration of the electrolyte allows the pores in the working electrode to be fully filled with the electrolyte, thereby improving the transmission efficiency of lithium ions; 11 The volume of the block adjusts the wetting time to avoid over-wetting or under-wetting, thereby improving the reaction uniformity and stability of the electrode.

[0062] In some embodiments, in step S2, the concentration of lithium salt in the electrolyte is 0.5mol / L to 20mol / L, including but not limited to 0.5mol / L, 1mol / L, 2mol / L, 3mol / L, 4mol / L, 5mol / L, 6mol / L, 7mol / L, 8mol / L, 9mol / L, 10mol / L, 11mol / L, 12mol / L, 13mol / L, 14mol / L, 15mol / L, 16mol / L, 17mol / L, 18mol / L, 19mol / L, 20mol / L. Further, the concentration of lithium salt in the electrolyte is 0.5mol / L to 2mol / L. Within the above concentration range, sufficient lithium source is provided, and side reactions and lithium salt waste caused by excessive lithium salt concentration are avoided.

[0063] In some embodiments, the lithium salt includes one or more of lithium perchlorate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, and lithium hexafluorophosphate.

[0064] In some embodiments, the solvent of the electrolyte includes one or more of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, tetrahydrofuran and ethylene glycol dimethyl ether.

[0065] In some embodiments, the counter electrode is one of a lithium metal electrode, a lithium alloy electrode, and a lithium copper composite electrode.

[0066] In some embodiments, in step S3, the discharge cut-off voltage of the electrolytic cell is ≥1 V. In this embodiment, the lithium supplement agent is prepared by assembling an electrolytic cell, and the lithium content (i.e., Li x Mo4O 11 The smaller the discharge cut-off voltage of the electrolytic cell is, the higher the lithium content is. Further, the discharge cut-off voltage of the electrolytic cell is 1V to 2.5V. Further, the discharge cut-off voltage of the electrolytic cell is 1.6V to 2.3V.

[0067] In some embodiments, in step S3, the discharge current of the electrolytic cell is 1 mA to 1000 mA.

[0068] In some specific embodiments, Figure 3 As shown, the electrolytic cell 1 includes an electrolytic tank 10. The electrolytic tank 10 is provided with a working electrode 20, a counter electrode 30 and an electrolyte 11. The working electrode includes Mo4O 11 Materials and conductors. Exemplarily, the working electrode comprises Mo4O 11 Block 21 and inserted in Mo4O 11 The block 21 has a plurality of conductive rods 22, and the conductive rods 22 are connected by wires 23. The electrolytic cell 1 also includes a power supply device 40, which is electrically connected to the electrolytic cell 10 and is used to supply power to the electrolytic cell 10. Exemplarily, one end of the power supply device 40 is connected to the conductive rod 22 on the working electrode 20 through the wire 23, and the other end of the power supply device 40 is connected to the counter electrode 30 through the wire 23.

[0069] In some embodiments, the post-processing includes pulverizing, purifying and drying. x Mo4O 11 The particle size of the material is adjusted to the particle size range suitable for lithium supplementation standards to increase Li x Mo4O 11 The electrochemical reaction rate of the material as a lithium supplement in the battery. Purification treatment helps remove impurities in the precipitate and reduce side reactions during subsequent battery use. Drying treatment removes residual moisture and solvents in the lithium supplement and reduces side reactions during subsequent battery use.

[0070] In some embodiments, a ball mill is used to pulverize the material.

[0071] In some embodiments, during the purification process, the precipitate is washed one or more times; the solvent used in the washing is the same as the solvent of the electrolyte.

[0072] The third aspect of the present application provides a positive electrode plate, which includes a positive electrode active material layer, and the positive electrode active material layer is the lithium supplement provided by the first aspect, or the lithium supplement prepared by the preparation method provided by the second aspect.

[0073] In some embodiments, the mass percentage of the lithium supplement in the positive electrode active material layer is 0.5% to 5%, including but not limited to 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%. Further, the mass percentage of the lithium supplement in the positive electrode active material layer is 0.5% to 2%.

[0074] The positive electrode active material layer also includes a positive electrode active material. In some embodiments, the positive electrode active material layer is a single layer, and the positive electrode active material and the lithium replenisher are slurried to prepare the positive electrode active material layer. In other embodiments, the positive electrode active material layer includes a positive electrode material layer and a lithium replenisher layer, the positive electrode material layer includes the positive electrode active material, and the lithium replenisher layer includes the lithium replenisher.

[0075] In some embodiments, the positive electrode active material includes one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide, and lithium manganese oxide.

[0076] The fourth aspect of the present application provides a secondary battery, which includes the positive electrode plate provided by the third aspect above; the secondary battery also includes a negative electrode plate, and the negative electrode plate includes a negative electrode active material.

[0077] In some embodiments, the negative electrode active material includes one of a graphite material, a silicon-oxygen material, and a silicon-carbon composite material.

[0078] The present application will be further described below with reference to specific embodiments and comparative examples.

[0079] Example 1

[0080] Lithium supplements:

[0081] (1) The particle size D50 is 0.1 μm and the compaction density is 2 g / cm 3 Mo4O 11 Powder pressed into Mo4O 11 block, and then insert the conductive rod into the Mo4O 11 Inside the block, a working electrode is obtained.

[0082] Among them, the conductive rod and Mo4O 11 The volume percentage of the block is 50%.

[0083] (2) Assemble the working electrode, the counter electrode and the electrolyte into an electrolytic cell, and soak the working electrode in the electrolyte for 3 hours.

[0084] The counter electrode is a lithium metal electrode; the electrolyte is a 2 mol / L lithium perchlorate solution, and the solvent of the electrolyte is a mixed solution of ethylene carbonate and propylene carbonate.

[0085] (3) The electrolytic cell is discharged, the discharge cut-off voltage of the electrolytic cell is set to 1 V, and the discharge current is 100 mA to obtain Li8Mo4O 11 .

[0086] (4) After the discharge is completed, the precipitate on the working electrode is taken out, the precipitate is crushed by a ball mill, and the precipitate is washed three times with a mixed solution of ethylene carbonate and propylene carbonate. The precipitate is then vacuum dried to obtain a lithium supplement.

[0087] Positive electrode:

[0088] The positive electrode active material lithium iron phosphate, the above-mentioned lithium supplement, the binder PVDF, and the conductive agent SP are added to the solvent N-methylpyrrolidone in a mass ratio of 95:2:2:1 to make a slurry, and then coated on the positive electrode collector to form a positive electrode active material layer, and rolled to obtain a positive electrode sheet.

[0089] Negative electrode:

[0090] Artificial graphite (AG), Super-P, styrene-butadiene latex (SBR) and carboxymethyl cellulose (CMC) were mixed and stirred in a mass ratio of 96:0.7:2:1.3, and then evenly coated on the surface of copper foil. After vacuum drying at 120°C for 12 hours, the negative electrode was sliced.

[0091] Secondary battery:

[0092] The positive electrode sheet, the negative electrode sheet and the separator are assembled into a secondary battery, and then the electrolyte is injected for formation. The electrolyte used is 1 mol·L -1 The mixed organic solvent of LiPF6 is ethylene carbonate: diethyl carbonate (volume ratio 1:1), the separator is PE material, and the upper limit of the charging voltage is 3.65V.

[0093] Example 2

[0094] The preparation method of the lithium supplement, the positive electrode sheet, the negative electrode sheet and the secondary battery in this embodiment is basically the same as that in embodiment 1, except that:

[0095] In step (3), the discharge cut-off voltage of the electrolytic cell is set to 1.6 V to obtain Li7Mo4O 11 .

[0096] Example 3

[0097] The preparation method of the lithium supplement, the positive electrode sheet, the negative electrode sheet and the secondary battery in this embodiment is basically the same as that in embodiment 1, except that:

[0098] In step (3), the discharge cut-off voltage of the electrolytic cell is set to 2V to obtain Li3Mo4O 11 .

[0099] Example 4

[0100] The preparation method of the lithium supplement, the positive electrode sheet, the negative electrode sheet and the secondary battery in this embodiment is basically the same as that in embodiment 1, except that:

[0101] In step (3), the discharge cut-off voltage of the electrolytic cell is set to 2.3 V to obtain LiMo4O11 .

[0102] Example 5

[0103] The preparation method of the lithium supplement, the positive electrode sheet, the negative electrode sheet and the secondary battery in this embodiment is basically the same as that in embodiment 1, except that:

[0104] Lithium iron phosphate, lithium supplement agent, binder PVDF, and conductive agent SP were added to solvent N-methylpyrrolidone in a mass ratio of 96.5:0.5:2:1 to form a slurry, and then coated on the positive electrode collector to form a positive electrode active material layer, and rolled to obtain a positive electrode sheet.

[0105] Example 6

[0106] The preparation method of the lithium supplement, the positive electrode sheet, the negative electrode sheet and the secondary battery in this embodiment is basically the same as that in embodiment 1, except that:

[0107] Lithium iron phosphate, lithium supplement agent, binder PVDF, and conductive agent SP were added to solvent N-methylpyrrolidone in a mass ratio of 92:5:2:1 to form a slurry, and then coated on the positive electrode collector to form a positive electrode active material layer, and rolled to obtain a positive electrode sheet.

[0108] Comparative Example 1

[0109] Positive electrode:

[0110] The positive electrode active material lithium iron phosphate, the binder PVDF, and the conductive agent SP were added to the solvent N-methylpyrrolidone in a mass ratio of 97:2:1 to form a slurry, and then coated on the positive electrode collector to form a positive electrode active material layer, and rolled to obtain a positive electrode sheet.

[0111] Negative electrode:

[0112] Artificial graphite (AG), Super-P, styrene-butadiene latex (SBR) and carboxymethyl cellulose (CMC) were mixed and stirred in a mass ratio of 96:0.7:2:1.3, and then evenly coated on the surface of copper foil. After vacuum drying at 120°C for 12 hours, the negative electrode was sliced.

[0113] Secondary battery:

[0114] The positive electrode sheet, the negative electrode sheet and the separator are assembled into a secondary battery, and then the electrolyte is injected for formation. The electrolyte used is 1 mol·L -1 The mixed organic solvent of LiPF6 is ethylene carbonate: diethyl carbonate (volume ratio 1:1), the separator is PE material, and the upper limit of the charging voltage is 3.65V.

[0115] Comparative Example 2

[0116] Lithium supplements:

[0117] Commercially available Li5FeO4 material (manufacturer: Shenzhen Yanyi New Materials Co., Ltd.)

[0118] Positive electrode:

[0119] The positive electrode active material lithium iron phosphate, the above-mentioned lithium supplement, the binder PVDF, and the conductive agent SP are added to the solvent N-methylpyrrolidone in a mass ratio of 95:2:2:1 to make a slurry, and then coated on the positive electrode collector to form a positive electrode active material layer, and rolled to obtain a positive electrode sheet.

[0120] Negative electrode:

[0121] Artificial graphite (AG), Super-P, styrene-butadiene latex (SBR) and carboxymethyl cellulose (CMC) were mixed and stirred in a mass ratio of 96:0.7:2:1.3, and then evenly coated on the surface of copper foil. After vacuum drying at 120°C for 12 hours, the negative electrode was sliced.

[0122] Secondary battery:

[0123] The positive electrode sheet, the negative electrode sheet and the separator are assembled into a secondary battery, and then the electrolyte is injected for formation. The electrolyte used is 1 mol·L -1 The mixed organic solvent of LiPF6 is ethylene carbonate: diethyl carbonate (volume ratio 1:1), the separator is PE material, and the upper limit of the charging voltage is 4V.

[0124] The parameters of the above embodiments and comparative examples are summarized in Table 1 below.

[0125] Table 1

[0126]

[0127]

[0128] Test Example 1

[0129] The lithium supplements and γ-Mo4O of Examples 1 to 4 11 XRD test was performed, and the test results were as follows Figure 4 As shown, with the insertion of lithium ions, Li x Mo4O 11 As the lithium content x increases, the degree of crystallization gradually decreases.

[0130] Test Example 2

[0131] At 25° C., the secondary batteries of the above examples and comparative examples were charged at a rate of 1C to 4.0V, and then discharged at a rate of 1C to a cutoff of 2.5V.

[0132] First coulombic efficiency: calculate the ratio of the first discharge capacity to the first charge capacity.

[0133] Capacity retention rate test: At 25°C, the secondary batteries of the above embodiments and comparative examples were charged to 3.65V at a rate of 1C, and then discharged to 2.5V at a rate of 1C, which was considered one cycle. A total of 1000 cycles were performed, and the capacity retention rate of 1000 cycles was calculated.

[0134] The test results are shown in Table 2.

[0135] Test Example 3

[0136] Gas generation test: The secondary batteries of the above-mentioned embodiment and comparative example were subjected to a gas generation test using a drainage method. The test results are shown in Table 2.

[0137] Table 2

[0138]

[0139]

[0140] As shown in Table 2, by comparing Examples 1 to 6 and Comparative Examples 1 to 2, it can be seen that the lithium supplement, positive electrode plate and secondary battery provided in the present application supplement the active lithium in the battery, improve the first-week coulomb efficiency and battery capacity of the battery, reduce the gas production of the battery during use, inhibit the swelling of the battery, and improve the safety of the battery.

[0141] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0142] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the technical concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A lithium supplement, characterized in that: Includes compounds having the following general formula: Li x Mo4O 11 ; Among them, 0 <x≤8。 2. A method for preparing a lithium supplement, characterized in that: The following steps are involved: S1, Mo4O 11 The material is prepared as a working electrode; S2, assembling the working electrode, the counter electrode and an electrolyte into an electrolytic cell, wherein the electrolyte comprises a lithium salt; S3, discharging the electrolytic cell, taking out the precipitate on the working electrode after the discharge, and post-treating the precipitate to obtain a lithium supplement; wherein the lithium supplement comprises Li x Mo4O 11 Compound, 0 <x≤8。 3. The method for preparing a lithium supplement according to claim 2, characterized in that: The step S1 specifically includes: Mo4O 11 Powder pressed into Mo4O 11 The conductor is then inserted into the Mo4O 11 In the block, a working electrode is obtained; or, Mo4O 11 The powder is pressed together with the conductor to obtain a Mo4O 11 The block is the working electrode.

4. The lithium supplement according to claim 3, characterized in that: The Mo4O 11 The particle size of the powder is D50 < 5 μm; and / or, The Mo4O 11 The compacted density of the powder is <3g / cm 3 .

5. The method for preparing a lithium supplement according to claim 3, characterized in that: The volume of the conductor is similar to that of the Mo4O 11 The volume percentage of the block is 30% to 70%.

6. The method for preparing a lithium supplement according to claim 2, characterized in that: In the step S2, the concentration of the lithium salt in the electrolyte is 0.5 mol / L to 20 mol / L; and / or, The counter electrode is one of a lithium metal electrode, a lithium alloy electrode and a lithium-copper composite electrode.

7. The method for preparing a lithium supplement according to claim 2, characterized in that: In step S3, the discharge cut-off voltage of the electrolytic cell is ≥1V; and / or, The post-processing includes pulverization, purification and drying.

8. A positive electrode sheet, characterized in that: The invention comprises a positive electrode active material layer, wherein the positive electrode active material layer comprises the lithium supplement agent according to claim 1, or the lithium supplement agent prepared by the preparation method according to any one of claims 2 to 7.

9. The positive electrode sheet according to claim 8, characterized in that: The mass percentage of the lithium supplement in the positive electrode active material layer is 0.5% to 5%.

10. A secondary battery, characterized in that: Including the positive electrode sheet as described in claim 8 or 9.

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