Positive electrode lithium supplementing material and preparation method and application thereof

Abstract

The invention relates to the technical field of batteries, in particular to a positive electrode lithium supplementing material and a preparation method and application thereof, the positive electrode lithium supplementing material is Li2Ni1-xMxO2, M is selected from Zn and / or Cu, and 0.01 * 0.1. The electronic structure of Li2NiO2 is regulated and controlled through heteroatom doping, a charge transfer item delta is reduced, a coulomb action item U is increased, the energy level of a non-bond O < 2 > p is close to the Fermi energy level, the oxidation activity of lattice oxygen is effectively excited, and the core problems that a traditional Li2NiO2 lithium supplementing material is low in lithium removal efficiency and insufficient in irreversible capacity are solved; and the preparation process is simple, the repeatability is high, and large-scale popularization is easy.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the technical field of batteries, in particular to a positive electrode lithium supplementing material and a preparation method and application thereof. BACKGROUND

[0002] Whether in the field of electric vehicles or in the field of large-scale power grid energy storage, lithium ion batteries play an irreplaceable role. Further improving the energy density and cycle life of lithium ion batteries can deepen the construction of electrification transformation and new power systems. Li2NiO2 is a lithium-rich transition metal oxide, which can release a large amount of active lithium during the first charge-discharge process to supplement the active lithium loss caused by the SEI film, thereby effectively improving the energy density and cycle life of lithium ion batteries.

[0003] However, the practical application of Li2NiO2 is still subject to two major bottlenecks: low delithiation efficiency and insufficient irreversible capacity. The Li2NiO2 crystal phase reported in the literature usually contains NiO impurities, which causes the actual delithiation capacity of Li2NiO2 to be mostly lower than 350 mAh·g -1 , far less than its theoretical specific capacity of 512 mAh·g -1 , and the irreversible capacity is less than 250 mAh·g -1 , hindering its further application. In order to improve the delithiation amount of Li2NiO2, existing research mainly focuses on optimizing the synthesis process to improve the phase purity. For example, Cho team used Li2CO3 as lithium source to successfully reduce NiO impurities, and the first delithiation capacity reached 420 mAh·g -1 . However, although the improvement of purity can improve the charge specific capacity, it does not change or even reduce the irreversible specific capacity, which is not conducive to the application as a lithium supplementing agent. In order to effectively improve the lithium compensation effect of Li2NiO2, the first coulombic efficiency should be greatly reduced, that is, the charge specific capacity should be improved and the discharge specific capacity should be reduced, so as to obtain greater irreversible capacity.

[0004] In summary, how to effectively improve the irreversible capacity of Li2NiO2 has become a problem to be solved at present. SUMMARY

[0005] In order to solve the above technical problems, the present disclosure provides a positive electrode lithium supplementing material and a preparation method and application thereof. The present disclosure overcomes the problems of low delithiation efficiency and insufficient irreversible capacity of the Li2NiO2 lithium supplementing material in the prior art by heteroatomic doping.

[0006] In a first aspect, the present disclosure provides a positive electrode lithium supplementing material, which is Li2Ni 1-x M x O2, wherein M is selected from Zn and / or Cu, 0.01 x 0.1.

[0007] Specifically, x can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1, but is not limited to the listed values; other unlisted values ​​within this range also apply.

[0008] This disclosure effectively modulates the electronic structure of Li₂NiO₂ by introducing specific heteroatoms (Zn, Cu). Specifically, it reduces the charge transfer term Δ and increases the coulombic interaction term U, bringing the non-bonded O 2p energy level closer to the Fermi level, thereby significantly activating the oxidation activity of lattice oxygen. This optimized electronic structure allows Li₂NiO₂ to release more active lithium during the first charge (high charge specific capacity). Furthermore, due to the irreversible structural changes after charging (such as the precipitation of lattice oxygen in the form of O₂), lithium-ion reintercalation is effectively suppressed, resulting in high irreversible capacity and greatly enhancing its effectiveness as a lithium replenisher.

[0009] However, the doping of heteroatoms should not be excessive, otherwise it will destroy the original crystal structure, hinder the migration of lithium ions, and reduce the amount of lithium replenished.

[0010] The following are preferred technical solutions of this disclosure, but are not intended to limit the technical solutions provided by this disclosure. The technical objectives and beneficial effects of this disclosure can be better achieved through the following technical solutions.

[0011] As a preferred technical solution in this disclosure, M is Cu, 0.03 x 0.07.

[0012] In this disclosure, the best performance is obtained when Cu is selected as the doping element.

[0013] As a preferred technical solution in this disclosure, M represents Zn, 0.03 x 0.07.

[0014] In this disclosure, when Zn is selected as the doping element, better results can be obtained by controlling its more suitable doping amount.

[0015] As a preferred technical solution of this disclosure, the charging specific capacity of the positive electrode lithium replenishment material 442 mAh·g -1 Irreversible capacity 355 mAh·g -1 .

[0016] Secondly, this disclosure provides a method for preparing a positive electrode lithium replenishment material as described in the first aspect, the method comprising the following steps: The lithium source, nickel source and dopant source are mixed and sintered to obtain the positive electrode lithium replenishment material.

[0017] As a preferred technical solution of this disclosure, the lithium source includes Li2CO3 and / or LiOH·H2O.

[0018] As a preferred technical solution of this disclosure, the nickel source includes NiO and / or Ni(OH)2.

[0019] As a preferred technical solution of this disclosure, the doping source includes ZnO and / or CuO.

[0020] As a preferred technical solution of this disclosure, the mixing method includes wet ball milling.

[0021] Preferably, the solvent used in the wet ball milling includes ethanol or deionized water.

[0022] Preferably, the wet ball milling time is 2-6 hours, such as 2 hours, 3 hours, 4 hours, 5 hours or 6 hours, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] In this disclosure, the ball milling method described above helps to achieve uniform mixing of raw materials and ensure the uniformity of doping.

[0024] As a preferred technical solution of this disclosure, the sintering temperature is 600-800℃, such as 600℃, 650℃, 700℃, 750℃ or 800℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, with 700-750℃ being the preferred temperature.

[0025] In this disclosure, a suitable sintering temperature can result in high purity of the synthesized Li2NiO2 phase, uniform heteroatom doping, and excellent lithium replenishment performance.

[0026] Preferably, the sintering time is 4-12 h, such as 4 h, 6 h, 8 h, 10 h or 12 h, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable, with 6-10 h being the preferred value.

[0027] Preferably, the sintering is carried out under an inert atmosphere.

[0028] Preferably, during the sintering process, the heating rate is 4-8℃ / min, such as 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min or 8℃ / min, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] In this disclosure, the heating rate during sintering should not be too fast, otherwise it will enter the nucleation stage too early, which is not conducive to the mixing of raw materials and affects the uniform doping of heteroatoms.

[0030] Thirdly, this disclosure provides a positive electrode sheet, including a positive current collector and a positive active layer located on at least one side surface of the positive current collector, wherein the positive active layer includes a positive lithium supplement material as described in the first aspect or a positive lithium supplement material prepared by the preparation method described in the second aspect, a positive active material, a conductive agent, and a binder.

[0031] Preferably, the mass ratio of the positive electrode lithium replenishment material, the positive electrode active material, the conductive agent, and the binder is (0.01-0.05):(0.75-0.94):(0.025-0.1):(0.025-0.1), for example, 0.01:094:0.25:0.25, 0.05:075:0.1:0.1, or 0.03:091:0.03:0.03, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0032] Preferably, the positive electrode active material includes lithium iron phosphate.

[0033] Preferably, the conductive agent includes acetylene black.

[0034] Preferably, the adhesive comprises polyvinylidene fluoride.

[0035] Fourthly, this disclosure provides a lithium battery, the lithium battery including the positive electrode as described in the third aspect.

[0036] The technical solution provided in this disclosure has the following advantages compared with the prior art: (1) This disclosure modulates the electronic structure of Li2NiO2 by heteroatomic doping, reducing the charge transfer term Δ and increasing the coulombic interaction term U, bringing the non-bonded O 2p energy level close to the Fermi level, effectively stimulating the oxidation activity of lattice oxygen, and solving the core problems of low delithiation efficiency and insufficient irreversible capacity of traditional Li2NiO2 lithium replenishment materials, so that the charging specific capacity of the lithium replenishment material reaches 442 mAh·g -1 The above irreversible capacity reaches 355 mAh·g -1 above; (2) The preparation process disclosed herein is simple, highly reproducible, and easy to promote on a large scale. Attached Figure Description

[0037] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments consistent with this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0038] To more clearly illustrate the technical solutions in the embodiments of this disclosure or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 The image shows the XRD pattern of the positive electrode lithium replenishment material described in Embodiment 1 of this disclosure.

[0040] Figure 2 The above are band structure comparison diagrams of the positive electrode lithium replenishment materials obtained in Examples 1-2 and Comparative Example 1 of this disclosure, calculated using first-principles calculations. Detailed Implementation

[0041] To better understand the above-mentioned objectives, features, and advantages of this disclosure, the solutions disclosed herein will be further described below. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0042] Numerous specific details are set forth in the following description in order to provide a full understanding of this disclosure, but this disclosure may also be implemented in other ways different from those described herein; obviously, the embodiments in the specification are only some, and not all, of the embodiments of this disclosure.

[0043] Example 1 This embodiment provides a positive electrode lithium replenishment material and its preparation method. The positive electrode lithium replenishment material is Li2Ni. 0.95 Cu 0.05 O2.

[0044] Its preparation method includes the following steps: (1) Weigh Li2CO3, NiO and CuO according to the molar ratio of Li:Ni:Cu=2:0.95:0.05, add them together with anhydrous ethanol into a ball mill jar, and ball mill at 300 rpm for 4 h to obtain a mixed slurry; (2) The mixed slurry was dried at 80°C for 12 h, and then placed in a muffle furnace. Under an argon atmosphere, the temperature was increased to 700°C at a heating rate of 5°C / min, and sintered at this temperature for 8 h. Then, it was cooled to room temperature with the furnace to obtain Cu-doped positive electrode lithium replenishment material.

[0045] The phase characterization of the Cu-doped cathode lithium supplementation material obtained in Example 1 is shown in the XRD pattern below. Figure 1 As shown. From Figure 1 As can be seen, its characteristic peaks are consistent with standard card #26-1175, corresponding to Li2NiO2, indicating that Li2NiO2 was successfully synthesized on the surface.

[0046] Example 2 This embodiment provides a positive electrode lithium replenishment material and its preparation method. The positive electrode lithium replenishment material is Li2Ni. 0.93 Zn 0.07 O2.

[0047] Its preparation method includes the following steps: (1) Weigh Li2CO3, NiO and ZnO according to the molar ratio of Li:Ni:Zn=2:0.93:0.07, add them together with anhydrous ethanol into a ball mill jar, and ball mill at 300 rpm for 4 h to obtain a mixed slurry; (2) The mixed slurry was dried at 80°C for 12 h, and then placed in a muffle furnace. Under an argon atmosphere, the temperature was increased to 750°C at a heating rate of 5°C / min, and sintered at this temperature for 7 h. Then, it was cooled to room temperature with the furnace to obtain Zn-doped positive electrode lithium replenishment material.

[0048] Example 3 This embodiment provides a positive electrode lithium replenishment material and its preparation method. The positive electrode lithium replenishment material is Li2Ni. 0.99 Zn 0.01 O2.

[0049] Its preparation method includes the following steps: (1) Weigh Li2CO3, NiO and ZnO according to the molar ratio of Li:Ni:Zn=2:0.99:0.01, add them together with anhydrous ethanol into a ball mill jar, and ball mill at 300 rpm for 4 h to obtain a mixed slurry; (2) The mixed slurry was dried at 80°C for 12 h, and then placed in a muffle furnace. Under an argon atmosphere, the temperature was increased to 600°C at a heating rate of 5°C / min, and sintered at this temperature for 12 h. Then, it was cooled to room temperature with the furnace to obtain Zn-doped positive electrode lithium replenishment material.

[0050] Example 4 This embodiment provides a positive electrode lithium replenishment material and its preparation method. The positive electrode lithium replenishment material is Li2Ni. 0.9 Cu 0.1 O2.

[0051] Its preparation method includes the following steps: (1) Weigh Li2CO3, NiO and CuO according to the molar ratio of Li:Ni:Cu=2:0.9:0.1, add them together with anhydrous ethanol into a ball mill jar, and ball mill at 300 rpm for 4 h to obtain a mixed slurry; (2) The mixed slurry was dried at 80°C for 12 h, and then placed in a muffle furnace. Under an argon atmosphere, the temperature was increased to 750°C at a heating rate of 5°C / min, and sintered at this temperature for 8 h. Then, it was cooled to room temperature with the furnace to obtain Cu-doped positive electrode lithium replenishment material.

[0052] Comparative Example 1 This comparative example provides a positive electrode lithium replenishment material and its preparation method, wherein the positive electrode lithium replenishment material is Li2NiO2.

[0053] The preparation method is the same as that in Example 1, except that no dopant source CuO is added.

[0054] Comparative Example 2 This comparative example provides a positive electrode lithium replenishment material and its preparation method, wherein the positive electrode lithium replenishment material is Li2Ni. 0.8 Cu 0.2 O2.

[0055] The preparation method is the same as that in Example 1, except that in step (1), Li2CO3, NiO and ZnO are weighed according to the molar ratio of Li:Ni:Zn=2:0.8:0.2.

[0056] Figure 2 This is a comparison of the band structures of the cathode lithium-ion supplementation materials obtained in Examples 1-2 and Comparative Example 1 of this disclosure, calculated using first-principles calculations. Figure 1 It can be seen that, compared with Li2NiO2 (i.e., Comparative Example 1), the introduction of Cu (i.e. Example 1) and Zn (i.e. Example 2) increases the U and decreases the Δ of the band structure, and the oxidation activity of lattice oxygen is significantly activated.

[0057] Lithium batteries for testing Preparation of a test lithium battery: Preparation of negative electrode sheet: lithium metal sheet.

[0058] Preparation of the positive electrode sheet: The positive lithium supplementation materials obtained in the various examples and comparative examples were mixed with acetylene black and polyvinylidene fluoride in an N-methylpyrrolidone solvent at a mass ratio of 8:1:1 to prepare a slurry with a viscosity of 4000-6000 mPa·s. This slurry was coated onto an aluminum foil with a thickness of 13 μm and dried to serve as the positive electrode sheet. The areal density of the positive electrode active layer was 3 mg / cm³. 2 The compacted density is 2.0-2.6 g / cm³. 3 .

[0059] Diaphragm: Celgard 2300.

[0060] Electrolyte: 1 mol LiPF6 dissolved in a solvent with a volume ratio of EC:DMC:DEC of 1:1:1; The above-mentioned positive electrode, separator, and negative electrode to be assembled are assembled into a CR2032 coin cell.

[0061] It should be noted that the lithium battery used for testing described above is only an example listed for testing the performance of the positive electrode lithium replenishment material. This disclosure is not limited to this type of battery. The raw materials (except for the positive electrode lithium replenishment material), proportions, parameters and processes can be replaced with other conventional raw materials, proportions, parameters and processes in the art to form a battery different from the lithium battery used for testing.

[0062] Performance testing Within a voltage range of 2.0-4.5 V and at a C rate of 0.1, the initial charge specific capacity and irreversible capacity (initial charge capacity - initial discharge capacity) were tested, and the test results are shown in Table 1. Table 1

[0063] As shown in Table 1, compared with Comparative Example 1, Examples 1-4 of this disclosure significantly improved the specific charging capacity and irreversible capacity of Li2NiO2 by heteroatomic doping, achieving a specific charging capacity of 442 mAh·g. -1 The above irreversible capacity reaches 355mAh·g -1 above.

[0064] In Comparative Example 2, the excessive amount of heteroatoms caused a sharp drop in lithium replenishment capacity.

[0065] The above description is merely a specific embodiment of this disclosure, enabling those skilled in the art to understand or implement it. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure is not to be limited to the embodiments described herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A positive electrode lithium replenishment material, characterized in that, The positive electrode lithium replenishment material is Li2Ni. 1-x M x O2, where M is selected from Zn and / or Cu, 0.01 x 0.

1.

2. The positive electrode lithium replenishment material according to claim 1, characterized in that, M is Cu, 0.03 x 0.

07.

3. A method for preparing a positive electrode lithium replenishment material as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: The lithium source, nickel source and dopant source are mixed and sintered to obtain the positive electrode lithium replenishment material.

4. The preparation method according to claim 3, characterized in that, The lithium source includes Li2CO3 and / or LiOH·H2O.

5. The preparation method according to claim 3 or 4, characterized in that, The nickel source includes NiO and / or Ni(OH)2.

6. The preparation method according to any one of claims 3-5, characterized in that, The doping source includes ZnO and / or CuO.

7. The preparation method according to any one of claims 3-6, characterized in that, The mixing method includes wet ball milling; Preferably, the solvent used in the wet ball milling includes ethanol or deionized water; Preferably, the wet ball milling time is 2-6 hours.

8. The preparation method according to any one of claims 3-7, characterized in that, The sintering temperature is 600-800℃, preferably 700-750℃; Preferably, the sintering time is 4-12 h, more preferably 6-10 h; Preferably, the sintering is carried out under an inert atmosphere; Preferably, the heating rate during the sintering process is 4-8℃ / min.

9. A positive electrode sheet, comprising a positive current collector and a positive active layer located on at least one side surface of the positive current collector, characterized in that, The positive electrode active layer comprises the positive electrode lithium replenishment material as described in claim 1 or 2, or the positive electrode lithium replenishment material prepared by the preparation method described in any one of claims 3-8, the positive electrode active material, the conductive agent, and the binder; Preferably, the mass ratio of the positive electrode lithium replenishment material, the positive electrode active material, the conductive agent, and the binder is (0.01-0.05):(0.75-0.94):(0.025-0.1):(0.025-0.1). Preferably, the positive electrode active material includes lithium iron phosphate; Preferably, the conductive agent includes acetylene black; Preferably, the adhesive comprises polyvinylidene fluoride.

10. A lithium battery, characterized in that, The lithium battery includes the positive electrode as described in claim 9.

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