Lithium supplement additive for positive electrode of lithium ion battery as well as preparation method and application of lithium supplement additive

Abstract

The invention discloses a lithium supplement additive for a positive electrode of a lithium ion battery as well as a preparation method and application thereof. The preparation method of the lithium ion battery positive electrode lithium supplement additive comprises the following steps: S1, mixing a nickel source, a lithium source and a tantalum source, sintering, and crushing to obtain an LNTO base material; s2, the LNTO base material obtained in the step S1 is added into an absolute ethyl alcohol solution of NH4F for ultrasonic treatment, a material obtained through suction filtration is annealed in the hydrogen and inert atmosphere, and a LiF-coated LNTO material with the high oxygen vacancy concentration is obtained; and S3, mixing the LiF-coated LNTO material and NH4H2PO4 in ethanol / isopropanol, stirring the obtained slurry, carrying out suction filtration, and calcining in an inert atmosphere to obtain the lithium ion battery positive electrode lithium supplement additive. The positive electrode lithium supplement additive is low in initial efficiency, high in irreversible capacity and better in material performance, the preparation method is simple and easy to control, the cost is low, and industrial production is facilitated.

Description

Technical Field

[0001] The present invention relates to a lithium supplement additive for the positive electrode of a lithium-ion battery, its preparation method and application, belonging to the technical field of lithium-ion batteries. Background Art

[0002] Due to its characteristics of high energy density and long cycle life, lithium-ion batteries are widely used in various electronic products. At the same time, with the rapid development of electric vehicles, drones and energy storage devices, higher requirements are put forward for the capacity and power of the batteries. However, during the first charging process of lithium-ion batteries, part of the lithium released from the positive electrode will form an irreversible lithium-containing passivation film SEI on the surface of the negative electrode, resulting in the loss of active lithium and reducing the reversible capacity of the battery.

[0003] To address this problem, the most common current improvement measure is to pre-lithiate the positive electrode or negative electrode of the battery. Compared with negative electrode lithiation, positive electrode lithiation does not require changing the existing battery production process, and has the characteristics of low cost, simplicity and high safety. Positive electrode lithiation generally mixes the lithium supplement material with the positive electrode material in a certain proportion. For the battery cell prepared using the mixed positive electrode material, during the first charging process, the lithium supplement agent releases excessive lithium to make up for the lithium consumed in forming the SEI film on the surface of the negative electrode, thus completing the lithium supplementation. Therefore, the positive electrode lithium supplement agent needs to have the characteristics of low first efficiency and high irreversible capacity to achieve a better lithium supplementation effect.

[0004] Existing preparation methods for positive electrode lithium supplement agent materials have problems such as complex process, high cost, and the prepared positive electrode lithium supplement agent materials having a high first efficiency and a low irreversible capacity. Therefore, there is a need to provide a positive electrode lithium supplement additive with a simple, green preparation process, low first efficiency and high irreversible capacity. Summary of the Invention

[0005] The purpose of the present invention is to provide a lithium supplement additive for the positive electrode of a lithium-ion battery. This positive electrode lithium supplement additive has a low first efficiency, a high irreversible capacity, better material properties, and a simple and easy-to-control preparation method, low cost, which is conducive to industrial production.

[0006] The preparation method of the lithium supplement additive for the positive electrode of a lithium-ion battery provided by the present invention includes the following steps:

[0007] S1. Mix the nickel source, lithium source and tantalum source and sinter them, then crush to obtain the LNTO matrix material;

[0008] S2. Add the LNTO matrix material obtained in step S1 to an anhydrous ethanol solution of NH4F for ultrasonic treatment, and anneal the filtered material in a hydrogen and inert atmosphere to obtain the LNTO material coated with LiF with a high oxygen vacancy concentration;

[0009] S3. Mix the LiF-coated LNTO material with NH4H2PO4 in ethanol / isopropanol. After stirring the obtained slurry, filter it by suction, and then calcine it in an inert atmosphere to obtain the lithium supplement additive for the positive electrode of the lithium-ion battery.

[0010] Preferably, the nickel source is at least one of nickel oxide, nickel acetate, nickel chloride, nickel nitrate, and nickel sulfate;

[0011] The lithium source is at least one of lithium hydroxide, lithium hydride, lithium oxide, lithium peroxide, lithium carbonate, lithium oxalate, lithium acetate, and lithium citrate;

[0012] The tantalum source is at least one of tantalum oxide and tantalum chloride.

[0013] Preferably, in step S1, the molar ratio of lithium element in the lithium source, nickel element in the nickel source, and tantalum element in the tantalum source is 1.8 - 2.4:1 - x:x, where x is a number between 0 and 1.

[0014] Preferably, in step S1, the sintering is carried out in an inert atmosphere, heated to 600 - 900 °C at a rate of 2 - 5 °C / min, and held for 8 - 5 h;

[0015] Crush and screen the sintered product. The mesh number of the sieve used for screening is 300 - 400 meshes, and the particle size D50 is 5.0 - 9.0 μm.

[0016] Preferably, in step S2, the concentration of the anhydrous ethanol solution of NH4F is 0.1 - 1 mol / L;

[0017] The solid content of the slurry obtained by adding the LNTO matrix material is 5 - 30%;

[0018] The conditions for the ultrasonic treatment are: temperature is 40 - 70 °C, and time is 0.5 - 3 h.

[0019] Preferably, in step S2, the annealing conditions are as follows:

[0020] The heating rate is 1 - 10 °C / min, the temperature is 400 - 700 °C, and the time is 0.5 - 5 h;

[0021] The gas is a mixed gas of H2 and Ar. Among them, the volume of H2 accounts for 0.5% - 5% of the volume of the mixed gas, and the total gas flow rate is 1000 - 3000 sccm.

[0022] Preferably, in step S3, the mass ratio of the LiF-coated LNTO material to the NH4H2PO4 is 10 - 30:1;

[0023] The solid content of the slurry is 5 - 30%;

[0024] The stirring rate is 100 - 300 rpm;

[0025] The calcination conditions are as follows: the temperature is 100°C - 500°C, and the time is 0.5 - 6 h.

[0026] Based on the lithium - supplementing additive for the positive electrode of the lithium - ion battery, the present invention also provides a positive electrode material for a lithium - ion battery, which includes a high - nickel positive electrode material and the lithium - supplementing additive for the positive electrode of the lithium - ion battery;

[0027] The mass of the lithium - supplementing additive for the positive electrode of the lithium - ion battery is 0.5% - 5% of the mass of the positive electrode material for the lithium - ion battery;

[0028] The high - nickel positive electrode material is LiNi x’ Co y M (1-x’-y) O2, where 0.65 ≤ x’ < 1, 0 < y ≤ 0.2, (x’ + y) < 1, and M is one or more of Al, Mn, Mg, such as Li(Ni 0.88 Co 0.095 Mn 0.025 )O2.

[0029] The present invention also provides a lithium - ion battery, which includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. The positive electrode plate includes a current collector and the positive electrode material for the lithium - ion battery provided on the current collector.

[0030] The total residual alkali amount of the lithium - supplementing additive for the positive electrode of the lithium - ion battery provided by the present invention is < 3%; maintaining a constant temperature of 25°C, a voltage range of 2.8 - 4.35 V, charging at a constant current and constant voltage of 0.2C, testing the charging specific capacity of the CR2016 type button cell, calculating the irreversible capacity, the first - charge specific capacity is 420 - 460 mAh / g, the first - efficiency is 3% - 28%, and the irreversible capacity is 300 - 446 mAh / g.

[0031] [[ID=3,4]]The present invention improves the structural stability of LNO and the migration barrier of Li by doping with Ta elements; through NH4F pretreatment, F - partially replaces O 2- , promotes the ordering of oxygen vacancies during the annealing process, provides a fast lithium - extraction path during the first - charge process, and captures part of Li + during the first - discharge process to form a local potential well to inhibit Li + back - insertion. The LiF coating layer and Li3PO4 coating layer outside LNTO not only limit the back - insertion of Li + but also inhibit the side reaction between LNTO and the electrolyte.

[0032] Compared with the prior art, in the present invention, by doping with Ta element, the structural stability of LNO and the migration barrier of Li are improved; through NH4F pretreatment, F - partially replaces O 2- , promotes the ordering of oxygen vacancies during the annealing process, provides a fast lithium extraction path during the first charge process, and captures part of Li during the first discharge process + to form a local potential well and inhibit Li + back-insertion. The LiF coating layer and Li3PO4 coating layer outside LNTO not only limit the back-insertion of Li + , but also inhibit the side reactions existing between LNTO and the electrolyte. The method of the present invention not only greatly improves the irreversible capacity of Li2NiO2, but also improves the stability of Li2NiO2, and has a simple process, which is conducive to industrial production.. Description of the Drawings

[0033] Figure 1 Figure 16 is a cross-sectional SEM image of the lithium supplement additive LNTO for the positive electrode of the lithium-ion battery prepared in Example 4

[0034] Figure 2 Figure 20 is an XRD pattern of the lithium supplement additive LNTO for the positive electrode of the lithium-ion battery prepared in Example 4

[0035] Figure 3 Figure 24 is a charge-discharge curve of the lithium supplement additive LNTO for the positive electrode of the lithium-ion battery prepared in Example 4 Detailed Embodiments

[0036] Unless otherwise specified, the experimental methods used in the following examples are all conventional methods

[0037] Unless otherwise specified, the materials, reagents, etc. used in the following examples can all be obtained from commercial channels

[0038] Example 1: Preparation of the lithium supplement additive for the positive electrode

[0039] Under a N2 atmosphere, lithium oxide, nickel oxide and tantalum oxide are fully mixed according to the molar ratio of metal elements of 1.92:0.95:0.5, transferred into a tube furnace for sintering, heated to 700 °C at a rate of 2 °C / min, held for 12 h, and cooled naturally. After crushing the material with a stone mortar, it is sieved once with a 300-mesh sieve to obtain the primary sintered material of the lithium supplement additive LNTO for the positive electrode

[0040] The LNTO primary sintered material is added to a 1 mol / L NH4F absolute ethanol solution, and the solid content is controlled to be 15%. Ultrasonic treatment is carried out at 60 °C for 1 h. After the ultrasonic treatment is completed, the obtained material is annealed at 550 °C for 3 h under a mixed gas atmosphere of H2:Ar = 3:97 with a total gas flow rate of 2000 sccm, and then naturally cooled to obtain the LNTO material coated with LiF with a high oxygen vacancy concentration.

[0041] The LNTO material coated with LiF with a high oxygen vacancy concentration and NH4H2PO4 are added to absolute ethanol at a ratio of 20:1, and the solid content is controlled to be 20%. After sealing, magnetic stirring is carried out at 200 rpm for 2 h. After the stirring is completed, suction filtration is carried out. The obtained material is calcined at 350 °C for 5 h in a nitrogen atmosphere to obtain a lithium supplement additive for the positive electrode of a lithium-ion battery.

[0042] Example 2. Preparation of a lithium supplement additive for the positive electrode

[0043] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide are fully mixed according to the molar ratio of metal elements of 1.96:0.95:0.5, and the other conditions are the same as in Example 1.

[0044] Example 3. Preparation of a lithium supplement additive for the positive electrode

[0045] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide are fully mixed according to the molar ratio of metal elements of 2.0:0.95:0.5, and the other conditions are the same as in Example 1.

[0046] Example 4. Preparation of a lithium supplement additive for the positive electrode

[0047] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide are fully mixed according to the molar ratio of metal elements of 2.04:0.95:0.5, and the other conditions are the same as in Example 1.

[0048] From Figure 1 it can be seen that there is a uniform coating layer on the surface of LNTO.

[0049] From Figure 2 it can be seen that the NiO impurity phase peak in LNTO is very low and there are no other impurity phases.

[0050] Example 5. Preparation of a lithium supplement additive for the positive electrode

[0051] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide are fully mixed according to the molar ratio of metal elements of 2.08:0.95:0.5, and the other conditions are the same as in Example 1.

[0052] Example 6. Preparation of a lithium supplement additive for the positive electrode

[0053] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to a molar ratio of metal elements of 2.04:0.96:0.4, and the remaining conditions were the same as in Example 1.

[0054] Example 7. Preparation of a cathode lithium supplement additive

[0055] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to a molar ratio of metal elements of 2.04:0.94:0.6, and the remaining conditions were the same as in Example 1.

[0056] Example 8. Preparation of a cathode lithium supplement additive

[0057] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to a molar ratio of metal elements of 2.04:0.95:0.5, transferred to a tube furnace for sintering, heated to 650 °C at 2 °C / min, held for 12 h, and cooled naturally. The remaining conditions were the same as in Example 1.

[0058] Example 9. Preparation of a cathode lithium supplement additive

[0059] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to a molar ratio of metal elements of 2.04:0.95:0.5, transferred to a tube furnace for sintering, heated to 750 °C at 2 °C / min, held for 12 h, and cooled naturally. The remaining conditions were the same as in Example 1.

[0060] Example 10. Preparation of a cathode lithium supplement additive

[0061] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to a molar ratio of metal elements of 2.04:0.95:0.5, transferred to a tube furnace for sintering, heated to 700 °C at 2 °C / min, held for 12 h, and cooled naturally. After crushing the material using a stone mortar, it was sieved once through a 300-mesh sieve to obtain the primary sintered material of the cathode lithium supplement additive LNTO.

[0062] The primary sintered LNTO material was added to a 1 mol / L NH4F absolute ethanol solution, the solid content was controlled to be 15%, and ultrasonic treatment was carried out at 60 °C for 1 h. After the ultrasonic treatment was completed, the obtained material was annealed at 500 °C for 3 h in a mixed gas atmosphere of H2:Ar2 = 3:97 with a total gas flow rate of 2000 sccm and then cooled naturally to obtain the LNTO material coated with LiF with a high oxygen vacancy concentration.

[0063] The LiF-coated LNTO material with a high oxygen vacancy concentration and NH4H2PO4 were added to absolute ethanol at a ratio of 20:1, and the solid content was controlled to be 20%. After sealing, it was magnetically stirred at 200 rpm for 2 h. After the stirring was completed, suction filtration was carried out. The obtained material was calcined in a nitrogen atmosphere at 350 °C for 5 h to obtain a lithium-ion battery cathode lithium supplement additive.

[0064] Example 11. Preparation of a cathode lithium supplement additive

[0065] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to the molar ratio of metal elements of 2.04:0.95:0.5, transferred to a tube furnace for sintering, heated to 700 °C at 2 °C / min, held for 12 h, and cooled naturally. After crushing the material with a stone mortar mill, it was sieved once with a 300-mesh sieve to obtain the LNTO primary sintered material of the cathode lithium supplement additive.

[0066] The LNTO primary sintered material was added to a 1 mol / L NH4F absolute ethanol solution, and the solid content was controlled to be 15%. Ultrasonic treatment was carried out at 60 °C for 1 h. After the ultrasonic treatment was completed, the obtained material was annealed in a mixed gas atmosphere of H2:Ar2 = 3:97 at a total gas flow rate of 2000 sccm at 600 °C for 3 h and then cooled naturally to obtain the LiF-coated LNTO material with a high oxygen vacancy concentration.

[0067] The LiF-coated LNTO material with a high oxygen vacancy concentration and NH4H2PO4 were added to absolute ethanol at a ratio of 20:1, and the solid content was controlled to be 20%. After sealing, it was magnetically stirred at 200 rpm for 2 h. After the stirring was completed, suction filtration was carried out. The obtained material was calcined in a nitrogen atmosphere at 350 °C for 5 h to obtain a lithium-ion battery cathode lithium supplement additive.

[0068] Example 12. Preparation of a cathode lithium supplement additive

[0069] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to the molar ratio of metal elements of 2.04:0.95:0.5, transferred to a tube furnace for sintering, heated to 700 °C at 2 °C / min, held for 12 h, and cooled naturally. After crushing the material with a stone mortar mill, it was sieved once with a 300-mesh sieve to obtain the LNTO primary sintered material of the cathode lithium supplement additive.

[0070] The LNTO primary sintered material was added to a 1 mol / L NH4F absolute ethanol solution, and the solid content was controlled to be 15%. Ultrasonic treatment was carried out at 60 °C for 1 h. After the ultrasonic treatment was completed, the obtained material was annealed in a mixed gas atmosphere of H2:Ar2 = 3:97 at a total gas flow rate of 2000 sccm at 550 °C for 3 h and then cooled naturally to obtain the LiF-coated LNTO material with a high oxygen vacancy concentration.

[0071] The LiF-coated LNTO material with a high oxygen vacancy concentration and NH4H2PO4 were added to absolute ethanol at a ratio of 10:1, and the solid content was controlled to be 20%. After sealing, it was magnetically stirred at 200 rpm for 2 h. After stirring, suction filtration was carried out. The obtained material was calcined in a nitrogen atmosphere at 350 °C for 5 h to obtain the lithium-ion battery cathode lithium supplement additive of the present invention.

[0072] Example 13. Preparation of cathode lithium supplement additive

[0073] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to the molar ratio of metal elements of 2.04:0.95:0.5, transferred to a tubular furnace for sintering, heated to 700 °C at 2 °C / min, held for 12 h, and cooled naturally. After crushing the material with a stone mortar mill, it was sieved once with a 300-mesh sieve to obtain the LNTO primary sintered material of the cathode lithium supplement additive.

[0074] The LNTO primary sintered material was added to a 1 mol / L NH4F absolute ethanol solution, and the solid content was controlled to be 15%. It was ultrasonically treated at 60 °C for 1 h. After ultrasonic treatment, the obtained material was annealed in a mixed gas atmosphere of H2:Ar2 = 3:97 at a total gas flow rate of 2000 sccm at 550 °C for 3 h and then cooled naturally to obtain the LiF-coated LNTO material with a high oxygen vacancy concentration.

[0075] The LiF-coated LNTO material with a high oxygen vacancy concentration and NH4H2PO4 were added to absolute ethanol at a ratio of 30:1, and the solid content was controlled to be 20%. After sealing, it was magnetically stirred at 200 rpm for 2 h. After stirring, suction filtration was carried out. The obtained material was calcined in a nitrogen atmosphere at 350 °C for 5 h to obtain the lithium-ion battery cathode lithium supplement additive.

[0076] Comparative Example 1

[0077] Under an N2 atmosphere, lithium oxide and nickel oxide were fully mixed according to the molar ratio of metal elements of 2.04:1, transferred to a tubular furnace for sintering, heated to 700 °C at 2 °C / min, held for 12 h, and cooled naturally. After crushing the material with a stone mortar mill, it was sieved once with a 300-mesh sieve to obtain the LNO primary sintered material of the cathode lithium supplement additive.

[0078] Comparative Example 2. Without doping Ta and without Li3PO4 coating layer

[0079] Under an N2 atmosphere, lithium oxide and nickel oxide were thoroughly mixed at a metal element molar ratio of 2.04:1, transferred into a tube furnace for sintering, heated to 700 °C at a rate of 2 °C / min, held for 12 h, and then cooled naturally. After crushing the material using a mortar mill, it was sieved once through a 300-mesh sieve to obtain the primary sintered material of the cathode lithium supplement additive LNO.

[0080] The primary sintered material of LNTO was added to a 1 mol / L NH4F absolute ethanol solution, the solid content was controlled to be 15%, and ultrasonic treatment was carried out at 60 °C for 1 h. After the ultrasonic treatment was completed, the obtained material was annealed at 550 °C for 3 h in a mixed gas atmosphere of H2:Ar2 = 3:97 with a total gas flow rate of 2000 sccm and then cooled naturally to obtain the LNO material coated with LiF with a high oxygen vacancy concentration.

[0081] Comparative Example 3: Without Ta doping and without LiF coating layer

[0082] Under an N2 atmosphere, lithium oxide and nickel oxide were thoroughly mixed at a metal element molar ratio of 2.04:1, transferred into a tube furnace for sintering, heated to 700 °C at a rate of 2 °C / min, held for 12 h, and then cooled naturally. After crushing the material using a mortar mill, it was sieved once through a 300-mesh sieve to obtain the primary sintered material of the cathode lithium supplement additive LNO.

[0083] The primary sintered material of LNO and NH4H2PO4 were added to absolute ethanol at a ratio of 20:1, the solid content was controlled to be 20%, sealed and magnetically stirred at 200 rpm for 2 h. After stirring, suction filtration was carried out, and the obtained material was calcined at 350 °C for 5 h in a nitrogen atmosphere to obtain the cathode lithium supplement agent LNO coated with Li3PO4.

[0084] Comparative Example 4: Without Ta doping

[0085] Under an N2 atmosphere, lithium oxide and nickel oxide were thoroughly mixed at a metal element molar ratio of 2.04:1, transferred into a tube furnace for sintering, heated to 700 °C at a rate of 2 °C / min, held for 12 h, and then cooled naturally. After crushing the material using a mortar mill, it was sieved once through a 300-mesh sieve to obtain the primary sintered material of the cathode lithium supplement additive LNO.

[0086] The primary sintered material of LNTO was added to a 1 mol / L NH4F absolute ethanol solution, the solid content was controlled to be 15%, and ultrasonic treatment was carried out at 60 °C for 1 h. After the ultrasonic treatment was completed, the obtained material was annealed at 550 °C for 3 h in a mixed gas atmosphere of H2:Ar2 = 3:97 with a total gas flow rate of 2000 sccm and then cooled naturally to obtain the LNO material coated with LiF with a high oxygen vacancy concentration.

[0087] The LiF-coated LNO material with a high oxygen vacancy concentration and NH4H2PO4 were added to absolute ethanol at a ratio of 20:1, and the solid content was controlled to be 20%. After sealing, it was magnetically stirred at 200 rpm for 2 h. After the stirring was completed, suction filtration was carried out. The obtained material was calcined at 350 °C for 5 h in a nitrogen atmosphere to obtain the cathode lithium supplement agent LNO co-coated with LiF and Li3PO4.

[0088] Comparative Example 5, without LiF and Li3PO4 coating layers

[0089] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to the molar ratio of metal elements of 2.04:0.95:0.5, transferred to a tubular furnace for sintering, heated to 700 °C at 2 °C / min, held for 12 h, and naturally cooled. After crushing the material with a stone mortar mill, it was sieved once with a 300-mesh sieve to obtain the primary sintered material of the cathode lithium supplement additive LNTO.

[0090] Comparative Example 6, without Li3PO4 coating layer

[0091] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to the molar ratio of metal elements of 2.04:0.95:0.5, transferred to a tubular furnace for sintering, heated to 700 °C at 2 °C / min, held for 12 h, and naturally cooled. After crushing the material with a stone mortar mill, it was sieved once with a 300-mesh sieve to obtain the primary sintered material of the cathode lithium supplement additive LNTO.

[0092] The primary sintered LNTO material was added to a 1 mol / L NH4F absolute ethanol solution, and the solid content was controlled to be 15%. Ultrasonic treatment was carried out at 60 °C for 1 h. After the ultrasonic treatment was completed, the obtained material was annealed at 550 °C for 3 h in a mixed gas atmosphere of H2:Ar2 = 3:97 with a total gas flow rate of 2000 sccm and then naturally cooled to obtain the LiF-coated LNTO material with a high oxygen vacancy concentration.

[0093] Comparative Example 7, without LiF coating layer

[0094] Under an N2 atmosphere, lithium oxide, nickel oxide, and tantalum oxide were fully mixed according to the molar ratio of metal elements of 2.04:0.95:0.5, transferred to a tubular furnace for sintering, heated to 700 °C at 2 °C / min, held for 12 h, and naturally cooled. After crushing the material with a stone mortar mill, it was sieved once with a 300-mesh sieve to obtain the primary sintered material of the cathode lithium supplement additive LNTO.

[0095] The LNTO primary sintered material and NH4H2PO4 were added to absolute ethanol at a ratio of 20:1, and the solid content was controlled to be 20%. After sealing, it was magnetically stirred at 200 rpm for 2 h. After stirring, suction filtration was carried out. The obtained material was calcined in a nitrogen atmosphere at 350 °C for 5 h to obtain a lithium-ion battery cathode lithium supplement additive.

[0096] Example 14

[0097] The lithium-ion battery cathode lithium supplement additive prepared by the examples and comparative examples of the present invention was used as the cathode to assemble a CR2016 button battery.

[0098] LNTO / LNO, carbon black SuperP, and polyvinylidene fluoride (Solvey5130) were mixed at a mass ratio of 95:5:5. Using N-methylpyrrolidone as a solvent, a slurry with a mass fraction of 5% was prepared and uniformly coated on the surface of an aluminum foil sheet. After rolling, a positive electrode sheet was obtained; then, a lithium sheet was used as the negative electrode sheet, a 1 mol / L solution of lithium hexafluorophosphate in ethylene carbonate (EC) and dimethyl carbonate (DMC) (the mass ratio of EC to DMC was 1:1) was used as the electrolyte, and cell gard2300 was used as the separator, and it was assembled in a glove box to obtain a lithium-ion half-cell.

[0099] An electrochemical tester was used to test the electrochemical performance of the lithium-ion half-cell. The test voltage range was 2.8 - 4.35 V, and the test temperature was 25 °C. The test results are shown in Table 1.

[0100] The charge-discharge curve of the lithium-ion battery cathode lithium supplement additive prepared in Example 4 is shown in Figure 3 .

[0101] Table 1 Data comparison between examples and comparative examples

[0102]

[0103]

[0104] From Table 1 and Figure 3 it can be seen that the lithium-ion battery cathode lithium supplement additive LNTO prepared by the method of Example 4 has a lower first efficiency and a higher irreversible capacity.

[0105] From the comparison results of Examples 1 - 13 and Comparative Examples 2 - 7 in Table 1, it can be seen that the Ta-doped, LiF and Li3PO4 co-coated lithium supplement additive prepared by the present invention has a higher irreversible capacity and a lower first efficiency. Among them, the residual alkali content of the lithium supplement agent in Comparative Example 1 is very high, resulting in gelation during the positive electrode slurry mixing, and the test cannot be carried out normally.

[0106] Example 15

[0107] Using a high-nickel cathode material Li(Ni 0.88 Co 0.095 Mn 0.025 )O2 as the cathode, adding the lithium-ion battery cathode lithium supplement additive LNTO prepared in Example 4 of the present invention to the cathode material, and the addition amount of the lithium supplement additive is 2 wt% of the mass of the cathode active material, to prepare a composite cathode active material, and assembling a CR2016 button cell.

[0108] Mix the composite cathode active material, carbon black SuperP, and polyvinylidene fluoride (Solvey5130) according to a mass ratio of 95:5:5, use N-methylpyrrolidone as the solvent, prepare a slurry with a mass fraction of 5%, uniformly coat it on the surface of the aluminum foil, and obtain the positive electrode sheet after rolling; then, use a lithium sheet as the negative electrode sheet, a 1 mol / L solution of lithium hexafluorophosphate in ethylene carbonate (EC) and dimethyl carbonate (DMC) (the mass ratio of EC to DMC is 1:1) as the electrolyte, and cell gard2300 as the separator, and assemble in a glove box to obtain a lithium-ion half cell.

[0109] Use an electrochemical tester to perform electrochemical performance tests on the lithium-ion half cell. The test voltage range is 2.8 - 4.35 V, and the test temperature is 25°C. The test results are shown in Table 2.

[0110] Comparative Example 8,

[0111] Using a high-nickel cathode material Li(Ni 0.88 Co 0.095 Mn 0.025 )O2 as the cathode, and assembling a CR2016 button cell.

[0112] Mix the cathode active material, carbon black SuperP, and polyvinylidene fluoride (Solvey5130) according to a mass ratio of 95:5:5, use N-methylpyrrolidone as the solvent, prepare a slurry with a mass fraction of 5%, uniformly coat it on the surface of the aluminum foil, and obtain the positive electrode sheet after rolling; then, use a lithium sheet as the negative electrode sheet, a 1 mol / L solution of lithium hexafluorophosphate in ethylene carbonate (EC) and dimethyl carbonate (DMC) (the mass ratio of EC to DMC is 1:1) as the electrolyte, and cell gard2300 as the separator, and assemble in a glove box to obtain a lithium-ion half cell.

[0113] Use an electrochemical tester to perform electrochemical performance tests on the lithium-ion half cell. The test voltage range is 2.8 - 4.35 V, and the test temperature is 25°C. The test results are shown in Table 2.

[0114] Table 2 Comparison of Example Data

[0115] Sample Charge capacity at 0.2C mAh / g Discharge capacity at 0.2C mAh / g Initial efficiency % Comparative Example 8 248.1 216.9 87.4 Example 15 258.3 213.7 82.7

[0116] As can be seen from Table 2, for the lithium-ion battery cathode lithium supplement additive LNTO prepared by the method of Example 4, when it is applied to a lithium-ion half-cell with a high-nickel ternary as the cathode material, compared with the lithium-ion half-cell without the cathode lithium supplement additive LNTO, the charging capacity at 0.1C is significantly improved, while the initial efficiency is significantly reduced.

Claims

1. A preparation method of a lithium supplement additive for a lithium-ion battery cathode, comprising the following steps: S1. Mix a nickel source, a lithium source and a tantalum source, then sinter and crush them to obtain an LNTO matrix material; S2. Add the LNTO matrix material obtained in step S1 to an anhydrous ethanol solution of NH4F for ultrasonic treatment. The filtered material is annealed in a hydrogen and inert atmosphere to obtain an LNTO material coated with LiF with a high oxygen vacancy concentration; S3. Mix the LiF-coated LNTO material and NH4H2PO4 in ethanol / isopropanol. The obtained slurry is stirred and then filtered, and then calcined in an inert atmosphere to obtain the lithium supplement additive for the lithium-ion battery cathode.

2. The preparation method according to claim 1, wherein: The nickel source is at least one of nickel oxide, nickel acetate, nickel chloride, nickel nitrate and nickel sulfate; The lithium source is at least one of lithium hydroxide, lithium hydride, lithium oxide, lithium peroxide, lithium carbonate, lithium oxalate, lithium acetate and lithium citrate; The tantalum source is at least one of tantalum oxide and tantalum chloride.

3. The preparation method according to claim 1 or 2, characterized in that: In step S1, the molar ratio of lithium element in the lithium source, nickel element in the nickel source to tantalum element in the tantalum source is 1.8 - 2.4:1 - x:x, where x is a number between 0 and 1.

4. The preparation method according to claim 1 or 2, characterized in that: In step S1, the sintering is carried out in an inert atmosphere, heated to 600 - 900°C at a rate of 2 - 5°C / min, and held for 8 - 5 h; Crush and screen the sintered product. The mesh number of the sieve used for screening is 300 - 400 meshes, and the particle size D50 is 5.0 - 9.0 um.

5. The preparation method according to claim 1 or 2, characterized in that: In step S2, the concentration of the anhydrous ethanol solution of NH4F is 0.1 - 1 mol / L; The solid content of the slurry obtained by adding the LNTO matrix material is 5 - 30%; The conditions of the ultrasonic treatment are: temperature is 40 - 70°C, and time is 0.5 - 3 h.

6. The preparation method according to claim 1 or 2, characterized in that: In step S2, the annealing conditions are as follows: The heating rate is 1 - 10°C / min, the temperature is 400 - 700°C, and the time is 0.5 - 5 h; The gas is a mixed gas of H2 and Ar. Among them, the volume of H2 accounts for 0.5% - 5% of the volume of the mixed gas, and the total gas flow rate is 1000 - 3000 sccm.

7. The preparation method according to claim 1 or 2, characterized in that: In step S3, the mass ratio of the LiF-coated LNTO material to the NH4H2PO4 is 10 - 30:1; The solid content of the slurry is 5 - 30%; The stirring rate is 100 - 300 rpm; The calcination conditions are: temperature is 100°C - 500°C, and time is 0.5 - 6 h.

8. A lithium supplement additive for a lithium-ion battery cathode prepared by the method according to any one of claims 1 - 7.

9. A lithium-ion battery cathode material, comprising a high-nickel cathode material and the lithium supplement additive for a lithium-ion battery cathode according to claim 8; The mass of the lithium supplement additive for a lithium-ion battery cathode is 0.5% - 5% of the lithium-ion battery cathode material.

10. A lithium-ion battery, comprising a positive electrode plate, a negative electrode plate, a separator and an electrolyte. The positive electrode plate comprises a current collector and the lithium-ion battery cathode material according to claim 9 provided on the current collector.

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