A lithium supplement additive, its preparation method and application

Abstract

The present application discloses a lithium supplement additive, a preparation method thereof, and an application. The lithium supplement additive of the present application has a core-shell structure, wherein the core material is a conductive carbon material and the shell material is lithium oxide. The lithium oxide is deposited on the surface of the conductive carbon material to form a nano-layer shell with nano-sized lithium oxide particles. For the lithium supplement additive of the present application, lithium oxide is compounded with the conductive carbon material, lithium supplement is carried out by using lithium oxide, and electrons are conducted by using the conductive carbon material, thereby improving the utilization rate of lithium oxide and enabling good lithium supplement for the positive electrode or the negative electrode. Moreover, after lithium deintercalation, the remaining conductive carbon material of the lithium supplement additive of the present application can be used as an electrode conductive material without introducing impurities. The lithium supplement additive of the present application is safe, environmentally friendly, and non-toxic, laying a foundation for the preparation of high-capacity lithium-ion batteries.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery materials, and particularly to a lithium supplement additive, a preparation method thereof, and an application thereof. Background Art

[0002] With the improvement of market demand, the energy density of lithium-ion batteries urgently needs to be increased, and finding anode and cathode materials with larger capacities has become one of the research hotspots in the current battery field. High-capacity electrode materials are often accompanied by a low initial efficiency. A large amount of lithium ions are consumed during the first discharge process to form irreversible content products, resulting in the reversible capacity of the battery being much lower than the theoretical value. For example, silicon, silicon oxide, and silicon carbide materials are a very typical type of new anode active materials with relatively high theoretical specific capacities. However, due to the low initial efficiency, the application of the lithium supplement process is particularly urgent. The most common current lithium supplement process is the lithium supplement method for the anode or cathode, that is, adding lithium-containing substances such as lithium powder to the electrode material to supplement the irreversible lithium lost by the electrode material during the first charging process. However, lithium metal is a very active metal and is extremely easy to oxidize in the air. It can react with a large number of inorganic and organic reagents, and has poor safety. In addition, in addition to providing a lithium source, the lithium supplement additive cannot introduce impurities into the electrode material. The existing lithium supplement additives generally have problems such as low utilization rate, generation of by-products or gases. Summary of the Invention

[0003] The purpose of this application is to provide a lithium supplement additive with a new formulation, a preparation method thereof, and an application thereof.

[0004] This application adopts the following technical solutions:

[0005] One aspect of this application discloses a lithium supplement additive. The lithium supplement additive has a core-shell structure, wherein the core material is a conductive carbon material and the shell material is lithium oxide; the lithium oxide is deposited on the surface of the conductive carbon material to form a nano-layer shell with nano-sized lithium oxide particles.

[0006] It should be noted that for the lithium supplement additive of this application, lithium oxide is used for lithium supplementation. Moreover, the lithium oxide is deposited on the surface of the conductive carbon material to form a composite material, which improves the overall conductivity of the composite material, thereby improving the utilization rate of lithium oxide, increasing the theoretical specific capacity to 1794 mAh / g, and further increasing the battery capacity.

[0007] It should also be noted that it is usually difficult to form nano-sized materials after the generation of inorganic lithium oxide. Through research, the present application finds that when used as a lithium supplement additive, the larger the size of the lithium oxide material, the lower its utilization rate. In the present application, lithium oxide is deposited on the surface of the conductive carbon material as a shell material, which is easier to maintain the nano-size of lithium oxide, thereby improving its utilization rate. Combining with the conductivity of the conductive carbon material, the overall conductivity of the lithium supplement additive of the present application is improved. It can be understood that in the lithium supplement additive of the present application, lithium oxide is the main active substance. The functions of the conductive carbon material are, first, to improve conductivity; second, to utilize its surface area to spread out lithium oxide to form a nano-sized lithium oxide layer. Therefore, it must be that lithium oxide is used as the shell layer and the conductive carbon material is used as the core layer; this is a completely different concept from the existing carbon-coated cathode materials.

[0008] The lithium supplement additive of the present application, wherein lithium oxide is coated on the surface of the conductive carbon material in the form of a nano-layer shell. Herein, the nano-layer shell is the commonly defined nano-film, and its thickness is about 1-100 nm.

[0009] Preferably, the conductive carbon material is at least one of conductive carbon black, conductive carbon nanotubes, conductive carbon nanofibers, conductive carbon spheres, and mesoporous carbon materials.

[0010] It should be noted that in principle, the conductive carbon material of the present application can adopt carbon materials sintered from various precursors as long as they have good conductivity. Among them, conductive carbon spheres are also called ball carbon, buckyballs, or fullerenes.

[0011] Another aspect of the present application discloses a preparation method of the lithium supplement additive of the present application, including the following steps:

[0012] (1) Mix the conductive carbon material and the lithium source evenly to make a mixture.

[0013] (2) Heat the mixture under reduced pressure for 30 min - 50 h. The conditions for heating under reduced pressure are that the vacuum degree is not higher than -60 KPa, and the heating temperature is 600 - 700 °C.

[0014] (3) After the heating under reduced pressure is completed, when the temperature naturally cools to 30 - 50 °C, introduce dry gas without carbon dioxide to break the vacuum.

[0015] (4) After breaking the vacuum, dry the product to obtain the lithium supplement additive.

[0016] Preferably, the lithium source is lithium hydroxide, lithium carbonate, or lithium peroxide; the conductive carbon material is at least one of conductive carbon black, conductive carbon nanotubes, conductive carbon nanofibers, conductive carbon spheres, and mesoporous carbon materials.

[0017] It should be noted that step (2) is slightly different when different lithium sources are used. When the lithium source is lithium hydroxide, the mixed material only needs to be placed under a carbon dioxide-free atmosphere and heated under reduced pressure; while when the lithium source is lithium carbonate or lithium peroxide, since carbon dioxide will be generated during the formation of lithium oxide, after reducing the pressure to the specified pressure, it is also necessary to intermittently evacuate to remove the carbon dioxide and maintain the reduced pressure condition.

[0018] Preferably, in step (1), the mixing is carried out by grinding method, ball milling method or dry stirring method.

[0019] It should be noted that in the preparation method of the lithium supplement additive of the present application, the conductive carbon material and the lithium source are directly mixed evenly for subsequent reactions. After being mixed evenly with the lithium source, during the subsequent reaction process, the generated lithium oxide is naturally and evenly deposited on the surface of the conductive carbon material, thereby obtaining the lithium supplement additive with a core-shell structure of the present application.

[0020] Another aspect of the present application discloses a positive electrode material for a lithium ion battery, and the positive electrode material contains the lithium supplement additive of the present application.

[0021] Preferably, in the positive electrode material, the dosage of the lithium supplement additive is less than or equal to 10% of the total weight of the positive electrode material.

[0022] Preferably, in the positive electrode material, the positive electrode active material of the positive electrode material includes but is not limited to at least one of LiCoO2, LiMnO2, LiFePO4, NCM and NCA. Among them, NCM is a nickel-cobalt-manganese ternary positive electrode material, and NCA is a nickel-cobalt-aluminum ternary positive electrode material.

[0023] It should be noted that the lithium supplement additive for the positive electrode of the lithium ion battery of the present application can be used for various positive electrode materials of lithium ion batteries to play the role of lithium supplement; LiCoO2, LiMnO2, LiFePO4, NCM and NCA are only several active materials that are currently commonly used. The lithium supplement additive for the positive electrode of the lithium ion battery of the present application is not limited to supplementing lithium for these positive electrode active materials.

[0024] Another aspect of the present application discloses a negative electrode material for a lithium ion battery, and the negative electrode material contains the lithium supplement additive of the present application.

[0025] Preferably, in the negative electrode material, the dosage of the lithium supplement additive is less than or equal to 10% of the total weight of the negative electrode material.

[0026] Preferably, in the negative electrode material, the active component is one or more of graphite, silicon, tin alloy, silicon oxide composite material or silicon-carbon composite material.

[0027] More preferably, the negative electrode of the lithium ion battery is silicon, a silicon oxide composite material or a silicon-carbon composite material.

[0028] Another aspect of the present application discloses an electrode paste, which is prepared by mixing an electrode material, the lithium supplement additive of the present application, and a non-aqueous binder; wherein, the electrode material is a positive electrode material or a negative electrode material.

[0029] It can be understood that the lithium supplement additive of the present application can be pre-added to the electrode material to prepare a suitable electrode paste for convenient use. Among them, the non-aqueous binder can refer to the water-free binder used in existing electrode pastes, such as organic solvent binders. The lithium supplement additive of the present application can supplement lithium to the positive electrode or the negative electrode. Therefore, the electrode material can be a positive electrode material or a negative electrode material, and accordingly, a positive electrode paste or a negative electrode paste can be prepared. The viscosity of the electrode paste can be determined according to the coating method or production process used, and no specific limitation is made here. In addition, other additives, such as viscosity regulators, can also be added to the electrode paste of the present application, which can refer to existing electrode pastes and no specific limitation is made here. The dosage of the lithium supplement additive in the electrode paste can refer to the dosage of the lithium supplement additive in the positive electrode material or negative electrode material of the present application.

[0030] Another aspect of the present application discloses a lithium-ion battery containing the lithium supplement additive of the present application, or using the positive electrode material or the negative electrode material of the present application.

[0031] The beneficial effects of the present application are as follows:

[0032] The lithium supplement additive of the present application combines lithium oxide with a conductive carbon material, uses lithium oxide to supplement lithium, and uses the conductive carbon material to conduct electrons, thereby improving the utilization rate of lithium oxide and enabling good lithium supplementation to the positive electrode or negative electrode. Moreover, after lithium deintercalation, the remaining conductive carbon material of the lithium supplement additive of the present application can be used as an electrode conductive material without introducing impurities. The lithium supplement additive of the present application is safe, environmentally friendly, and non-toxic, laying a foundation for the preparation of high-capacity lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic structural diagram of the lithium supplement additive obtained by combining lithium oxide and a conductive carbon material in an embodiment of the present application;

[0034] Figure 2 It is the first charge-discharge curve graph of the battery prepared by supplementing lithium to the negative electrode with the lithium supplement additive in an embodiment of the present application;

[0035] Figure 3 It is the first charge-discharge curve graph of the battery prepared by supplementing lithium to the positive electrode with the lithium supplement additive in an embodiment of the present application;

[0036] Figure 4 It is a transmission electron microscope of the lithium supplement additive obtained by combining lithium oxide and a conductive carbon material in an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] Due to its poor conductivity, lithium oxide has a low utilization rate when used as a lithium supplement additive. Therefore, lithium oxide is usually not used alone as a lithium supplement additive.

[0038] However, through a large number of experiments and studies, the inventors of this application found that if the conductivity problem of Li2O powder can be overcome, the electrochemical reaction equation when lithium peroxide is generated during battery charging is as follows:

[0039] 2Li2O → Li2O2 + 2Li + +2e - E0 = 2.87V vs.Li + / Li

[0040] At this time, the theoretical capacity is 897 mAh / g. When the charging voltage is further increased, the following reaction occurs:

[0041] Li2O2 → O2 + 2Li + +2e -

[0042] At this time, the theoretical specific capacity is as high as 1794 mAh / g. It can be seen that if Li2O is used as a lithium supplement additive, it has a very high theoretical specific capacity.

[0043] Based on the above research and findings, this application creatively proposes depositing lithium oxide on the surface of a conductive carbon material with excellent conductivity to form a composite material as a lithium supplement additive. Among them, the conductive carbon material has the advantages of low density, large specific surface area, high temperature resistance, etc. Combining lithium oxide with the conductive carbon material improves the conductivity of the composite material, thereby improving the utilization rate of lithium oxide as a lithium supplement additive, and further significantly improving the electrochemical performance of the lithium-ion battery. Moreover, the conductive carbon material formed after the composite material is de-lithiated can also be used as an electrode conductive material without introducing impurities.

[0044] The lithium supplement additive of this application has a core-shell structure, where the conductive carbon material is the core and the nano-thin layer formed by nano-lithium oxide is the shell. The shape of the lithium supplement additive depends on the conductive carbon material used. For example, as Figure 1 shown, in Figure 1, 1 is the lithium oxide shell and 2 is the conductive carbon material core. If the conductive carbon material is a conductive carbon sphere, the lithium supplement additive is spherical, Figure 1 Figure A; if the conductive carbon material is a carbon nanotube, the lithium supplement additive is nanotube-shaped, Figure 1 Figure B. The specific shape of the lithium supplement additive is not specifically limited in this application as long as it satisfies the core-shell structure of this application.

[0045] The present application will be further described in detail below through specific embodiments. The following embodiments are only for further illustration of the present application and should not be construed as a limitation of the present application.

[0046] Embodiment

[0047] In this example, three lithium sources, namely lithium hydroxide, lithium carbonate, and lithium peroxide, were used to prepare the lithium supplement additive. The lithium supplement additive was respectively added to the positive electrode material and the negative electrode material and used as the positive electrode lithium supplement additive and the negative electrode lithium supplement additive, respectively. The effects of adding the lithium supplement additive and not adding the lithium supplement additive on the first charge and discharge of the battery were respectively tested. Specifically as follows:

[0048] Preparation method 1 of the lithium supplement additive:

[0049] (1) After vacuum drying the carbon nanospheres, they were mixed evenly with anhydrous lithium hydroxide. The masses of the carbon nanospheres and lithium hydroxide were 30 g and 70 g respectively to form a mixture. The mixing method can be a grinding method, a ball milling method, or a dry stirring method. In this example, the ball milling method was specifically used.

[0050] (2) The mixture was wrapped with silver foil and placed in a nickel plate, and then transferred to a tube furnace. A gas without carbon dioxide was introduced for protection, sealed and heated under reduced pressure to 600 - 700 °C, and the temperature was controlled at a certain fixed value for a sufficient reaction time. Usually, the reaction time is greater than 30 min. Specifically in this example, the pressure was reduced to -100 KPa, and the reaction was carried out at 650 °C for 1 h.

[0051] (3) After the heating under reduced pressure was completed, the reduced pressure was stopped and it was allowed to cool naturally. When the temperature was about to reach 30 - 50 °C, dry air without carbon dioxide was slowly introduced to break the vacuum.

[0052] (4) After breaking the vacuum, the nickel plate was quickly transferred to a drying oven for drying to obtain the lithium supplement additive composed of lithium oxide and conductive carbon material.

[0053] Preparation method 2 of the lithium supplement additive:

[0054] (1) After vacuum drying the carbon nanospheres, they were mixed evenly with lithium carbonate. The masses of the carbon nanospheres and lithium carbonate were 30 g and 70 g respectively. The mixing method was a grinding method, a ball milling method, or a dry stirring method. In this example, the grinding method was specifically used.

[0055] (2) The mixture was placed in a platinum plate inside a porcelain tube, and the pressure was reduced to -100 kPa and kept constant. By means of intermittent vacuum pumping, the vacuum degree change range was kept not exceeding 1 kPa, and at the same time it was heated to 700 °C for decomposition and held for 50 h until it was checked that no more gas was generated. Among them, the judgment criterion for no more other generation is that the vacuum degree does not change without vacuum pumping.

[0056] (3) After the vacuum heating is completed, stop the vacuum, and let it cool naturally. When the temperature is about to reach room temperature, that is, when the temperature is between 30 - 50 °C, slowly introduce dry air without carbon dioxide to break the vacuum.

[0057] (4) After breaking the vacuum, quickly transfer the platinum plate to a drying oven for drying to obtain a lithium - supplementing additive composed of lithium oxide and conductive carbon material.

[0058] The third method for preparing the lithium - supplementing additive:

[0059] (1) After vacuum - drying carbon nanospheres, mix them evenly with lithium peroxide. The masses of the carbon nanospheres and lithium peroxide are 45 g and 55 g respectively. The mixing methods include grinding method, ball - milling method or dry - stirring method. In this example, the grinding method is specifically adopted.

[0060] (2) Place the mixture on a platinum plate inside a porcelain tube, reduce the pressure to - 100 kPa and keep it constant. By means of intermittent vacuum pumping, keep the vacuum degree change range not exceeding 1 kPa. At the same time, heat it to 700 °C for decomposition, and keep it warm for 50 h until it is checked that no more gas is generated.

[0061] (3) After the vacuum heating is completed, stop the vacuum, and let it cool naturally. When the temperature is about to reach room temperature, that is, when the temperature is between 30 - 50 °C, slowly introduce dry air without carbon dioxide to break the vacuum.

[0062] (4) After breaking the vacuum, quickly transfer the platinum plate to a drying oven for drying to obtain a lithium - supplementing additive composed of lithium oxide and conductive carbon material.

[0063] Using a transmission electron microscope (abbreviated as TEM) to observe the lithium - supplementing additives obtained by the above three methods, it can be clearly seen that the lithium - supplementing additive composed of lithium oxide and conductive carbon material has a core - shell structure, that is, the outer surface of the carbon nanospheres is wrapped with a nanolayer shell of lithium oxide; some results are as Figure 4 shown, Figure 4 is the lithium - supplementing additive composed of lithium oxide and conductive carbon material prepared by the first method.

[0064] The following introduces the application tests specifically as a lithium - supplementing additive for the positive electrode or negative electrode:

[0065] 1. Use as a negative - electrode lithium - supplementing additive

[0066] Use the lithium - supplementing additive obtained by the above first method as a negative - electrode lithium - supplementing additive. Specifically, during the preparation process of the negative - electrode slurry of the 18650 - type cylindrical battery A, add a lithium - supplementing additive accounting for 2.6% of the total weight of the negative - electrode slurry, and mix them evenly for standby.

[0067] The preparation process of the negative electrode slurry is as follows: 26 g of lithium supplement additive, 844 g of graphite, 50 g of PVDF, 80 g of super P conductive additive, and 1100 g of N-methylpyrrolidone are placed in a 2.5 L kettle and mechanically stirred for 4 hours for standby. Among them, the graphite is the graphite product of model S360-M from BETRAY Co., Ltd.

[0068] The preparation process of the positive electrode slurry is as follows: 780 g of ternary NCM811, 70 g of PVDF, 150 g of super P conductive additive, and 1100 g of N-methylpyrrolidone are placed in a 2.5 L kettle and mechanically stirred for 4 hours for standby.

[0069] Coating process: The positive electrode uses an aluminum foil with a thickness of 10 microns, and the negative electrode uses a copper foil with a thickness of 12 microns. The slurry is coated on the foil by a coater, and after single-sided coating, it is placed in an oven for drying. The drying temperature is 80 °C and the time is 4 hours. Then, coating is continued on the uncoated side and placed in the oven for drying. The drying temperature is 80 °C and the time is 4 hours. The areal densities of the positive and negative electrode materials are 33.6 mg / cm 2 、15.3 mg / cm 2 .

[0070] The pole pieces are slit, wound, injected with electrolyte, and encapsulated by using the automated 18650 cylindrical battery preparation equipment of BAK Battery Co., Ltd. to complete the battery production. The battery is marked as N-with additive. Among them, the separator model is Celgard 2340 separator, and the electrolyte model is LBC3033, which is purchased from Shenzhen Capchem Technology Co., Ltd.

[0071] As a comparison, the same negative electrode material is used at the same time, the lithium supplement additive is not added, and the same assembly method is adopted to assemble the same model of battery, which is marked as N-without additive.

[0072] The assembled batteries and the comparison samples are respectively subjected to charge and discharge tests by using a BlueTEC test system. The charge and discharge rate is 0.2C. The results of the first charge and discharge test are shown in Figure 2 . Figure 2Among them, the curve 1 marked as “—■—without additive-C(1)” is the charging curve of the comparative cell N-without additive, the curve 2 marked as “—●—without additive-D(2)” is the discharging curve of the comparative cell N-without additive, the curve 3 marked as “—△—with additive-C(3)” is the charging curve of the cell N-with additive prepared by adding a lithium supplement additive to the negative electrode in this example, and the curve 4 marked as “—▽—with additive-D(4)” is the discharging curve of the cell N-with additive prepared by adding a lithium supplement additive to the negative electrode in this example. Figure 2 The results show that, compared with the cell without the lithium supplement additive, the discharging capacity of the cell is significantly improved. The lithium supplement additive located at the negative electrode de-lithiumizes during the discharging process, increasing the total de-lithium amount of the negative electrode, thereby improving the initial efficiency. Figure 2 The horizontal axis represents the cell capacity. It can be seen that the cell with the lithium supplement additive has a higher charging capacity and discharging capacity than the one without the additive.

[0073] 2. Used as a lithium supplement additive for the positive electrode

[0074] Use the lithium supplement additive obtained by the previous method 1 as the lithium supplement additive for the positive electrode. Specifically, add the lithium supplement additive accounting for 2.6% of the total weight of the positive electrode slurry during the preparation process of the positive electrode slurry of the 18650 cylindrical cell A. After fully mixing and homogenizing, set it aside for use.

[0075] The preparation process of the positive electrode slurry is as follows: Put 26 g of the lithium supplement additive, 754 g of ternary NCM811, 70 g of PVDF, 150 g of super P conductive additive, and 1100 g of N-methylpyrrolidone into a 2.5 L kettle, and mechanically stir for 4 hours for standby.

[0076] The preparation process of the negative electrode slurry is as follows: Put 870 g of graphite, 50 g of PVDF, 80 g of super P conductive additive, and 1100 g of N-methylpyrrolidone into a 2.5 L kettle, and mechanically stir for 4 hours for standby. Among them, the graphite is the graphite product of model S360-M of BETRAY Co., Ltd.

[0077] Coating process: Use 10-micron-thick aluminum foil for the positive electrode and 12-micron-thick copper foil for the negative electrode. Use a coater to coat the slurry on the foil. After single-sided coating, place it in an oven for drying. The drying temperature is 80 °C and the time is 4 hours. Then continue to coat on the uncoated side and place it in an oven for drying. The drying temperature is 80 °C and the time is 4 hours. The surface densities of the positive and negative electrode materials are 33.6 mg / cm2 and 15.3 mg / cm2 respectively.

[0078] The electrode sheets are slit, wound, injected with electrolyte and encapsulated by the automated 18650 cylindrical battery preparation equipment of BAK Battery Co., Ltd. to complete the battery production. The battery is marked as P-with additive. Among them, the separator model is Celgard 2340 separator, and the electrolyte model is LBC3033, which is purchased from Shenzhen Capchem Technology Co., Ltd.

[0079] As a comparison, the same cathode material is used, without adding lithium supplement additive, and the same assembly method is adopted to assemble the same model of battery, marked as P-without additive.

[0080] The first charge-discharge tests are respectively carried out on the assembled batteries and the comparison samples by a BlueTEC test system at a charge-discharge rate of 0.2C. The results of the first charge-discharge tests are shown in Figure 3 . The test results are as Figure 3 shown. Figure 3 Among them, curve 1 marked as “—■—without additive-C(1)” is the charge curve of the comparison battery P-without additive, curve 2 marked as “—●—without additive-D(2)” is the discharge curve of the comparison battery P-without additive, curve 3 marked as “—△—with additive-C(3)” is the charge curve of the battery P-with additive prepared by adding the lithium supplement additive to the cathode in this example, and curve 4 marked as “—▽—with additive-D(4)” is the discharge curve of the battery P-with additive prepared by adding the lithium supplement additive to the cathode in this example. Figure 3 The results show that, compared with the battery without the lithium supplement additive, the capacity and efficiency of the battery with the lithium supplement additive are both significantly improved; it shows that the lithium supplement additive plays a role during the first charge-discharge process and effectively supplements the lithium source.

[0081] On the basis of the above tests, in this example, the lithium supplement additives prepared by method two and method three are respectively used as the cathode lithium supplement additive and the anode lithium supplement additive. The results show that the lithium supplement additives prepared by method two and method three have the same effect as the lithium supplement additive prepared by method one, and both can improve the first efficiency and the charge-discharge capacity, and have a good lithium supplement effect.

[0082] The above content is a further detailed description of the present application in combination with specific implementation manners. It cannot be determined that the specific implementation of the present application is only limited to these descriptions. For those of ordinary skill in the technical field to which the present application belongs, without departing from the concept of the present application, several simple deductions or substitutions can also be made.

Claims

1. A lithium supplement additive, characterized in that: The lithium supplement additive has a core-shell structure, where the core material is a conductive carbon material and the shell material is lithium oxide; the lithium oxide is deposited on the surface of the conductive carbon material to form a nano-layer shell composed of nano-sized lithium oxide particles. The preparation method of the lithium supplement additive includes the following steps. (1) Mix the conductive carbon material and the lithium source evenly to make a mixed material. (2) Subject the mixed material to reduced-pressure heating for 30 min to 50 h. The conditions for reduced-pressure heating are that the vacuum degree is not higher than -60 KPa and the heating temperature is 600 - 700 °C. (3) After the reduced-pressure heating is completed, when the temperature naturally cools to 30 - 50 °C, introduce a dry gas without carbon dioxide to break the vacuum. (4) After breaking the vacuum, dry the product to obtain the lithium supplement additive. The conductive carbon material is at least one of conductive carbon nanotubes, conductive carbon nanofibers, conductive carbon spheres, and mesoporous carbon materials.

2. The preparation method of the lithium supplement additive according to claim 1, characterized in that: It includes the following steps. (1) Mix the conductive carbon material and the lithium source evenly to make a mixed material. (2) Subject the mixed material to reduced-pressure heating for 30 min to 50 h. The conditions for reduced-pressure heating are that the vacuum degree is not higher than -60 KPa and the heating temperature is 600 - 700 °C. (3) After the reduced-pressure heating is completed, when the temperature naturally cools to 30 - 50 °C, introduce a dry gas without carbon dioxide to break the vacuum. (4) After breaking the vacuum, dry the product to obtain the lithium supplement additive. The conductive carbon material is at least one of conductive carbon nanotubes, conductive carbon nanofibers, conductive carbon spheres, and mesoporous carbon materials.

3. The preparation method according to claim 2, characterized in that: The lithium source is lithium hydroxide, lithium carbonate, or lithium peroxide.

4. The preparation method according to claim 2, characterized in that: In the step (1), the even mixing is achieved by grinding, ball milling, or dry stirring.

5. A cathode material for a lithium-ion battery, characterized in that: The positive electrode material contains the lithium supplement additive described in claim 1.

6. The cathode material according to claim 5, characterized in that: The dosage of the lithium supplement additive is less than or equal to 10% of the total weight of the positive electrode material.

7. An anode material for a lithium-ion battery, characterized in that: The negative electrode material contains the lithium supplement additive described in claim 1.

8. The negative electrode material according to claim 7, characterized in that: The dosage of the lithium supplement additive is less than or equal to 10% of the total weight of the negative electrode material.

9. An electrode paste, characterized in that: The electrode slurry is prepared by mixing an electrode material, the lithium supplement additive described in claim 1, and a non-aqueous binder solution; the electrode material is a positive electrode material or a negative electrode material.

10. A lithium-ion battery containing the lithium supplement additive described in claim 1, or using the positive electrode material described in claim 5 or 6, or using the negative electrode material described in claim 7 or 8.

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