CN109817968B

CN109817968B - Surface-coated lithium nickel manganese oxide particles and method for producing same

Info

Publication number: CN109817968B
Application number: CN201711167448.2A
Authority: CN
Inventors: 郭晓倩; 吴关; 高旭光; 柳娜
Original assignee: Contemporary Amperex Technology Co Ltd
Current assignee: Contemporary Amperex Technology Co Ltd
Priority date: 2017-11-21
Filing date: 2017-11-21
Publication date: 2021-06-25
Anticipated expiration: 2037-11-21
Also published as: CN109817968A

Abstract

The present invention relates to surface-coated lithium nickel manganese oxide particles and a method for producing the same. The lithium nickel manganese oxide has a chemical formula of LiNi_0.5Mn_1.5O₄At least part of the surface of the spinel type lithium nickel manganese oxide particles is coated with LiV_1‑xM_xOPO₄Wherein x is more than or equal to 0 and less than or equal to 0.9, and M is one or more doping metals selected from Y, Ca, Ce, K, Si, Mo, W, Mn, Fe, B, Mg, Al, Na, Zr and Ti. Because the surface of the lithium nickel manganese oxide is coated with the lithium vanadyl phosphate, the direct contact between the lithium nickel manganese oxide and the electrolyte can be prevented, and Mn is relieved³⁺Disproportionation and Mn⁴⁺The oxidation effect of the electrolyte can relieve the problem of battery core flatulence and improve the battery capacity and the first coulombic efficiency.

Description

Surface-coated lithium nickel manganese oxide particles and method for producing same

Technical Field

The invention relates to the field of lithium ion batteries, in particular to surface-coated lithium nickel manganese oxide particles and a manufacturing method thereof.

Background

In recent years, with the rapid development of pure electric vehicles and hybrid electric vehicles, the development of high-energy, long-life and low-cost chemical power supplies is particularly urgent, and lithium ion batteries are made in the field of chemical power supplies with unique advantages of high energy density, high power density, high working voltage, low self-discharge rate, no memory effect, long cycle life, no pollution and the like. Among positive electrode materials for lithium ion batteries, spinel-type lithium nickel manganese oxide (LiNi)_0.5Mn_1.5O₄) The lithium ion battery positive electrode material has the advantages of high voltage platform, good rate capability, high energy density, low cost and the like, and is considered to be one of the most promising and attractive lithium ion battery positive electrode materials. Compared with the ternary material of lithium cobaltate and nickel cobalt manganese, the lithium nickel manganese oxide has the advantages of high voltage, low cost, environmental friendliness and the like. Compared with lithium manganate, the high-temperature cycle stability of the lithium nickel manganate is greatly improved. Compared with lithium iron phosphate, the lithium nickel manganese oxide has higher energy density and good batch stability of production. Therefore, the lithium nickel manganese oxide is considered as a preferred positive electrode material of a future large-scale power battery.

However, because the lithium nickel manganese oxide material has a high voltage platform, Mn in the lithium nickel manganese oxide is in contact with the electrolyte³⁺Disproportionation reaction occurs and the catalyst migrates to the surface of the negative electrode to be catalyzedRegeneration of SEI film (solid electrolyte interface film), Mn⁴⁺Electrolyte can be oxidized to cause electrolyte decomposition, and the regeneration of the SEI film and the decomposition of the electrolyte can finally cause gas generation and expansion of the battery cell to influence the interface performance of the electrode.

Disclosure of Invention

One aspect of the present invention provides a surface-coated lithium nickel manganese oxide particle, wherein the lithium nickel manganese oxide is represented by the chemical formula LiNi_0.5Mn_1.5O₄At least part of the surface of the spinel type lithium nickel manganese oxide particles is coated with LiV_1-xM_xOPO₄Wherein x is more than or equal to 0 and less than or equal to 0.9, and M is one or more doping metals selected from Y, Ca, Ce, K, Si, Mo, W, Mn, Fe, B, Mg, Al, Na, Zr and Ti.

The nickel lithium manganate particles coated with the surfaces can be used as the positive active material of the lithium ion battery. When used as a battery positive electrode active material, the lithium nickel manganese oxide particles can realize at least one of the following functions:

because the surface of the lithium nickel manganese oxide is coated by the lithium vanadyl phosphate, the direct contact between the active substance of the lithium nickel manganese oxide and the electrolyte can be prevented or reduced, and the Mn in the lithium nickel manganese oxide is relieved³⁺Disproportionation and Mn⁴⁺The oxidation of the lithium nickel manganese oxide battery core can relieve the gas generation problem of the lithium nickel manganese oxide battery core.

In addition, the coated lithium vanadyl phosphate can also prevent Mn in lithium nickel manganese oxide³⁺The disproportionation reaction of the lithium ion battery can prevent the regeneration of an SEI film on the surface of the negative electrode, and can effectively reduce the loss of active lithium in the battery cell.

On the other hand, because the lithium vanadyl phosphate has a lithium ion transmission channel, the lithium ion diffusion resistance in a solid phase is correspondingly reduced due to the existence of the lithium vanadyl phosphate coating layer, the side reaction of the lithium nickel manganese oxide and the electrolyte is prevented, and the gram capacity and the first coulombic efficiency of the cathode material can be effectively increased.

Another aspect of the present invention provides a method for preparing surface-coated lithium nickel manganese oxide particles, comprising the steps of:

(A) providing a precursor mixture containing a manganese source material, a nickel source material, a lithium source material, a vanadium source material, a phosphorus source material and an optional doped metal source material, wherein the doped metal is selected from one or more of Y, Ca, Ce, K, Si, Mo, W, Mn, Fe, B, Mg, Al, Na, Zr and Ti, and the source material is used in an amount such that based on 1mol of Ni, the amount of Mn is 3 to 3.5mol, the amount of Li is 2 to 2.3mol, the amount of V is more than 0 to 0.2mol, the amount of P is more than 0 to 0.2mol, and the amount of doped metal is 0 to 0.2 mol; and

(B) and roasting the precursor mixture in an oxygen-containing atmosphere or an inert atmosphere.

The method can be used for manufacturing the nickel lithium manganate particles coated with the surfaces, and is low in process, equipment and control cost and beneficial to large-scale production.

In still another aspect of the present invention, there is provided a positive electrode active material comprising the surface-coated lithium nickel manganese oxide particles or the surface-coated lithium nickel manganese oxide particles obtained by the method.

In yet another aspect, the present invention provides a lithium ion battery cell comprising the surface-coated lithium nickel manganese oxide particles or the surface-coated lithium nickel manganese oxide particles obtained by the method.

In another aspect, the present invention provides a lithium ion battery comprising the surface-coated lithium nickel manganese oxide particles or the surface-coated lithium nickel manganese oxide particles obtained by the above method.

According to the positive active material, the lithium ion battery cell and the lithium ion battery, which are disclosed by the invention, due to the fact that the nickel lithium manganate particles coated with the surfaces are contained, the battery with improved capacity and first coulombic efficiency can be manufactured, and the problem of gas expansion of the cell can be effectively prevented and reduced.

Drawings

Features, advantages and technical effects of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is LiNi which is a positive electrode material of a lithium ion battery of a comparative example_0.5Mn_1.5O₂SEM picture of (1);

FIG. 2 shows LiNi, a positive electrode material for a lithium ion battery of example 5_0.5Mn_1.5O₄/LiV_0.92Na_0.08OPO₄SEM picture of (1);

fig. 3 is an experimental result of a swelling rate test performed on the battery cell of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantageous technical effects of the present invention more clear, the present invention is further described in detail with reference to the following embodiments. It should be understood that the examples described in this specification are for the purpose of illustration only and are not intended to limit the invention, and the formulation, proportions, etc. of the examples may be selected appropriately without materially affecting the results.

For the sake of brevity, only some numerical ranges are explicitly disclosed herein. However, any lower limit may be combined with any upper limit to form ranges not explicitly recited; and any lower limit may be combined with any other lower limit to form a range not explicitly recited, and similarly any upper limit may be combined with any other upper limit to form a range not explicitly recited. Also, although not explicitly recited, each point or individual value between endpoints of a range is encompassed within the range. Thus, each point or individual value can form a range not explicitly recited as its own lower or upper limit in combination with any other point or individual value or in combination with other lower or upper limits.

The above summary of the present invention is not intended to describe each disclosed embodiment or every implementation of the present invention. The following description more particularly exemplifies illustrative embodiments. At various points throughout this application, guidance is provided through a list of embodiments that can be used in various combinations. In each instance, the list serves only as a representative group and should not be construed as exhaustive.

Surface-coated lithium nickel manganese oxide particles

According to one aspect of the present invention, there is provided surface-coated lithium nickel manganese oxide particles, wherein the lithium nickel manganese oxide particles are of the formula LiNi_0.5Mn_1.5O₄At least part of the surface of the spinel type lithium nickel manganese oxide particles is coated with LiV_1-xM_xOPO₄Wherein x is more than or equal to 0 and less than or equal to 0.9, and M is one or more doping metals selected from Y, Ca, Ce, K, Si, Mo, W, Mn, Fe, B, Mg, Al, Na, Zr and Ti.

In the surface-coated lithium nickel manganese oxide particles, LiV_1-xM_xOPO₄The mass content of (b) may be determined in accordance with the desired properties of the electrode material, and may be selected from 100ppm to 50000 ppm.

Further, LiV in the particles_1-xM_xOPO₄The content of (b) can be measured by a qualitative analysis and/or quantitative analysis instrument for known elements such as ICP and ICP-MS.

In addition, the D50 (median diameter) of the surface-coated lithium nickel manganese oxide particles may be 0.1 to 20 μm. The D50 can be measured and/or calculated by well-known particle size measuring devices such as particle size measuring instruments. The particle size of the lithium nickel manganese oxide particles can be properly selected according to the performance of the required electrode active material and the process requirements. From the viewpoint of improving the performance of the lithium ion battery and not increasing the difficulty of the mixing and dispersing process, the thickness is preferably 0.1-10 μm.

In one embodiment of the invention, the specific surface area of the surface-coated lithium nickel manganese oxide particles can be 0.01-20 m²(ii) in terms of/g. The specific surface area can be measured by a known apparatus for measuring specific surface area.

The LiV is coated on the surface of the lithium nickel manganese oxide particles_1-xM_xOPO₄In other words, x is 0. ltoreq. x.ltoreq.0.9. From the viewpoint of improving the electron conductivity and the lithium ion diffusion conductivity, x is preferably 0.05. ltoreq. x.ltoreq.0.3.

The content ratio of each element in the particles is, for example, 3 to 3.04mol of Mn, 2.64 to 3.32mol of Li, 0.4 to 0.6mol of V, 0.4 to 0.6mol of P, and 0 to 0.04mol of doping metal element M with respect to 1mol of Ni.

The surface-coated nickel manganese acid of the present inventionThe surface of the lithium particles may be partially or completely coated with the lithium vanadyl phosphate. In order to better reduce Mn of lithium nickel manganese oxide⁴⁺The oxidation effect on the electrolyte can prevent Mn in the lithium nickel manganese oxide³⁺The disproportionation reaction of (a) is preferably completely coated from the viewpoint of reducing the loss of active lithium in the cell.

Method for producing surface-coated lithium nickel manganese oxide particles

According to an aspect of the present invention, there is provided a method for producing surface-coated lithium nickel manganese oxide particles, comprising the steps of:

(A) providing a precursor mixture comprising a manganese source material, a nickel source material, a lithium source material, a vanadium source material, a phosphorus source material and an optional doped metal source material, wherein the doped metal is selected from one or more of Y, Ca, Ce, K, V, Si, Mo, W, Mn, Fe, B, Mg, Al, Na, Zr and Ti, and the source material is used in an amount such that based on 1mol of Ni, the amount of Mn is 3 to 3.5mol, the amount of Li is 2 to 2.3mol, the amount of V is 0 to 0.2mol, the amount of P is 0 to 0.2mol and the amount of doped metal is 0 to 0.2 mol; and

According to one embodiment of the present invention, the step (a) may be a mixture which has been mixed in proportion in advance, or may be a mixture in which appropriate amounts of various source materials are uniformly mixed.

The "manganese source material", "nickel source material", "lithium source material", "vanadium source material", "phosphorus source material" and "doped metal source material" described in this specification mean that they contain "manganese", "nickel", "lithium", "vanadium", "phosphorus" and "doped metal", respectively, and can be converted into "manganese element", "nickel element", "lithium element", "vanadium element", "phosphorus element" and "doped metal element" in the target product by a predetermined treatment method. Preferably, other elements contained in the source material are decomposed into gas by calcination and separated from the product.

The above-mentioned materials may be selected from known commercially available materials or may be synthesized by known methods.

The manganese source material and the nickel source material can be selected as spinel LiNi_0.5Mn_1.5O₄Other manganese and nickel containing source materials may also be selected. Such as manganese or nickel oxides or hydroxides. To form spinel LiNi_0.5Mn_1.5O₄The molar ratio of the manganese or nickel element in the core, manganese or nickel oxide or hydroxide is preferably 1: 3. For example, Ni is preferably used_0.5Mn_1.5(OH)₄And Ni_0.5Mn_1.5O₂One or two of them, and spinel LiNi can be easily obtained by using these two nickel-manganese source materials_0.5Mn_1.5O₄A kernel.

The "lithium source material" may be a lithium-containing salt, hydroxide, or the like. For example, Li can be selected₂CO₃、LiOH·H₂O、LiNO₃And LiCl.

The "vanadium source material" may be a vanadium-containing salt, an oxide of vanadium, or the like. For example, VOPO can be selected₄ 2H₂O、V₂O₅、NH₄VO₃、VO(HPO₄)_0.5H₂One or more of O.

The "phosphorus source material" may be a phosphorus-containing salt. E.g. H₃PO₄、VO(HPO₄)_0.5H₂O、VOPO₄ 2H₂O、NH₄H₂PO₄、(NH₄)₂HPO₄The precursor of the dopant metal element M can be one or more of oxide, hydroxide, sulfate and carbonate of M.

The "doped metal source material" may be a substance containing the metal. Such as one or more of the metal's oxides, hydroxides, sulfates, carbonates, and the like. The doped metal M can change the arrangement of d-orbit electrons and reduce the extraction and insertion activation energy of lithium ions. In one embodiment of the present invention, Ti, Al, Mg, Na are preferred as the doping metal, and Mg (OH) is selected₂、Na₂CO₃、Al₂(CO₃)₃、Ti(OH)₄And the like.

In one embodiment, the source materials in step (a) may be the materials described in the previous section "materials" section, and the various source materials meeting the amounts described in step (a) are mixed in a mixer in the presence of a mixing medium.

In the case of mixing by a mixer, the mixing medium may be selected, for example, from one or more of deionized water or alcohols, such as one or more of ethanol, methanol, propanol, isopropanol. The mixing speed can be set according to the mixture and can be 100-10000 rpm, and the mixing time can be 2-100 h.

After mixing, drying may be carried out by a known drying method. In one embodiment of the invention, the mixture is dried by a spray drying device to form dry particles, the treatment temperature can be 50-300 ℃, and the rotating speed can be 1000-30000 rpm.

The amount of the source material may be calculated according to the chemical formula of the desired product and the content of the coated lithium vanadyl phosphate. Preferably, the amount of Mn element is 3 to 3.04mol, the amount of Li element is 2.64 to 3.32mol, the amount of V element is 0.4 to 0.6mol, the amount of P element is 0.4 to 0.6mol, and the amount of doping metal element M is 0 to 0.04mol, relative to 1mol of Ni element. By adopting the source material with the dosage range, the nickel lithium manganate particles with uniform coating can be obtained.

In addition, the calcination conditions in the step (B) may be carried out by a usual method. For example, in one embodiment, the temperature rising rate is 1-10 ℃/min, the sintering temperature is 400-1000 ℃, the sintering time is 1-20 h, and the introduced gas during the roasting is one or more of air, oxygen, nitrogen and argon.

In one embodiment, the product obtained in step (B) is directly ground and sieved to obtain the target product. In another embodiment, the product obtained by roasting is annealed in an oxygen-containing atmosphere or an inert atmosphere, and the annealed product is ground and sieved to obtain the target product. Through annealing treatment, the crystal structure can be improved, and disordered crystal forms are fewer and ordered crystal forms are more.

The annealing treatment can be performed by a known method. In one embodiment, the temperature reduction rate of the annealing treatment is 1-10 ℃/min, the sintering temperature is 500-700 ℃, and the sintering time is 1-15 h. The gas introduced during roasting can be one or more of air, oxygen, nitrogen and argon.

Positive electrode active material

According to an aspect of the present invention, there is provided a positive electrode active material comprising the surface-coated lithium nickel manganese oxide particles or the surface-coated lithium nickel manganese oxide particles produced by the production method.

The positive active material can be used for all batteries, particularly lithium ion batteries, and can effectively improve the performance characteristics of the positive electrode.

Examples of the "negative electrode active material" used in combination with the positive electrode active material in the present invention may be carbonaceous materials such as crystalline or amorphous carbon, or carbon composite materials (thermally decomposed carbon, coke, graphite), burned organic polymers, carbon fibers, tin oxide compounds, metallic lithium or lithium alloys.

Lithium ion battery core

The lithium ion battery cell comprises the surface-coated lithium nickel manganese oxide particles or the surface-coated lithium nickel manganese oxide particles prepared by the method.

The method of manufacturing the lithium ion battery cell is not particularly limited and may be manufactured by methods known in the art or produced in the future. In one embodiment, the lithium nickel manganese oxide particles provided by the invention are used as a positive active material, fully stirred and uniformly mixed with a conventional conductive agent and a binder in a solvent system according to a predetermined mass ratio, coated on a positive current collector, dried and cold-pressed to obtain a positive pole piece.

And (3) fully stirring and uniformly mixing the conventional negative active material, the conductive agent, the binder, the thickening agent and the like in a solvent system according to a preset mass ratio, coating the mixture on a negative current collector, drying and cold-pressing the mixture to obtain the negative pole piece.

And stacking the positive pole piece, the isolating membrane and the negative pole piece in sequence to enable the isolating membrane to be positioned between the positive pole and the negative pole to play an isolating role, and winding to obtain the bare cell. And placing the bare cell in an aluminum-plastic film bag, injecting the prepared electrolyte and performing hot-press packaging to obtain the cell.

In addition, the lithium ion battery cell adopts the surface-coated lithium nickel manganese oxide particles, so that Mn of the lithium nickel manganese oxide⁴⁺Oxidation of electrolyte and/or Mn in lithium nickel manganese oxide³⁺The disproportionation reaction of (a) is prevented, so that the loss of active lithium in the use of a cell can be reduced, and the problem of gas generation after storage of the cell can be improved.

According to the experiment of the inventor, when the storage days of the battery cell are 90 days, the expansion rate of the battery cell is below 30%. Further preferably, the swelling rate of the cell is 25% or less when the storage days are 90 days.

Lithium ion battery

According to an aspect of the present invention, there is provided a lithium battery comprising the surface-coated lithium nickel manganese oxide particles or the surface-coated lithium nickel manganese oxide particles obtained by the manufacturing method.

In one embodiment, the lithium ion battery comprises a positive electrode plate, a negative electrode plate and an electrolyte, wherein the surface-coated lithium nickel manganese oxide particles are used as a positive electrode active material layer and are arranged on a current collector.

The method for producing the lithium ion battery is not particularly limited, and any method known in the art or used in the future may be used. The battery core of the invention can be assembled into a battery after being dripped into a proper electrolyte.

In one embodiment, the lithium nickel manganese oxide particles are used as a positive electrode active material, fully stirred with a conductive agent and a binder in a solvent according to a predetermined weight, uniformly mixed, coated on a positive electrode current collector, dried and cold-pressed to obtain a positive electrode piece. And cutting the positive pole piece into small pieces to be used as a positive pole, a lithium piece as a negative pole, a PP porous polymer film as an isolating film, and dripping proper electrolysis to assemble the battery.

The lithium ion battery can be used as a power supply of any electric appliance or equipment, and the spinel type lithium nickel manganese oxide has the advantages of high voltage platform, good rate capability, high energy density, low cost and the like, and is preferably used as a battery of a large-scale power vehicle.

Furthermore, according to the lithium ion battery, the gram-capacity and the first coulombic efficiency of the battery are higher than those of a battery made of uncoated lithium nickel manganese oxide. According to the experiment of the inventor, the first coulombic efficiency of the lithium ion battery is more than 88%, and/or the gram capacity of the lithium ion battery is more than 130 mAh/g. Preferably, the lithium ion battery of the present invention has a first coulombic efficiency of 91% or more and/or a gram capacity of 132mAh/g or more.

Examples

The present disclosure is more particularly described in the following examples that are intended as illustrations only, since various modifications and changes within the scope of the present disclosure will be apparent to those skilled in the art. All parts, percentages, and ratios reported in the following examples are on a weight basis unless otherwise stated, and all reagents used in the examples are commercially available and can be used as is without further treatment unless otherwise stated.

Example 1

Preparation of surface-coated lithium nickel manganese oxide particles:

with Ni_0.5Mn_1.5(OH)₄Is a nickel-manganese precursor and takes Li₂CO₃As a lithium source, with VOPO₄ 2H₂And O is a vanadium source and a phosphorus source. Putting the precursor mixture into a mixer according to a molar ratio of 1:0.83:0.3, adding polyurethane balls and grinding medium water into the mixer, wherein the mixing speed is 5000rpm, and the mixing time is 24 h. And spheroidizing the mixed powder by a spray drying method, wherein the spray drying temperature is 100 ℃, and the spray rotating speed is 3000 rpm. Then the dried powder is ground properly and then placed in a muffle furnace for high-temperature roasting treatment, wherein the high-temperature treatment temperature is 850 ℃, the treatment time is 10 hours, and the temperature rise speed is 5 ℃/4And min, introducing air at the gas introduction speed of 0.8L/min. Grinding and sieving the roasted product to obtain the lithium nickel manganese oxide material LiNi coated with lithium vanadyl phosphate_0.5Mn_1.5O₄/LiVOPO₄。

Example 2

Preparation of surface-coated lithium nickel manganese oxide particles:

with Ni_0.5Mn_1.5O₂Is a nickel-manganese precursor and is made of Li₂CO₃As a source of lithium, with V₂O₅As a source of vanadium, with NH₄H₂PO₄Is a phosphorus source. Putting the powder into a mixer in a molar ratio of 1:0.72:0.1:0.2, and uniformly mixing. The rest experimental processes and parameters are the same as those of the embodiment 1, and the lithium ion battery cathode material LiNi is obtained after grinding and sieving_0.5Mn_1.5O₄/LiVOPO₄。

Example 3

Preparation of surface-coated lithium nickel manganese oxide particles:

the preparation method was the same as in example 1 except for the following conditions. With Ni_0.5Mn_1.5O₂Is a nickel-manganese precursor, LiOH is a lithium source and NH₄VO₃Is a vanadium source, NH₄H₂PO₄Is a source of phosphorus, Mg (OH)₂And adding a dopant species. The source materials are placed into a mixer in a molar ratio of 1:1.32:0.28:0.3:0.02, polyurethane balls and grinding medium methanol are added into the mixer, the mixing speed is 3000rpm, and the mixing time is 48 h. And carrying out spray drying spheroidization on the mixed powder, wherein the spray drying temperature is 150 ℃, and the spray rotating speed is 5000 rpm. Grinding and sieving the roasted product to obtain the lithium nickel manganese oxide material LiNi coated with lithium vanadyl phosphate_0.5Mn_1.5O₄/LiV_0.93Mg_0.07OPO₄。

Example 4

Preparation of surface-coated lithium nickel manganese oxide particles:

the preparation method was the same as in example 3 except for the following conditions. The doping metal is Al₂(CO₃)₃. Spray dryingThe high-temperature treatment temperature of the spheroidized powder is 900 ℃, the treatment time is 12 hours, the temperature rising speed is 3 ℃/min, the introduced atmosphere is oxygen, and the gas introduction speed is 1.0L/min. After roasting, the temperature is reduced to 650 ℃ at 3 ℃/min, and then the mixture is roasted for 10 h. Grinding and sieving the roasted product to obtain the lithium nickel manganese oxide material LiNi coated with lithium vanadyl phosphate_0.5Mn_1.5O₄/LiV_0.93Al_0.07OPO₄。

Example 5

Preparation of surface-coated lithium nickel manganese oxide particles:

the preparation method was the same as in example 3 except for the following conditions. With Ni_0.5Mn_1.5O₂Is nickel-manganese precursor, LiNO₃Is a lithium source, V₂O₅Is a vanadium source, (NH)₄)₂HPO₄Is a phosphorus source, Na₂CO₃Is a doped metal. The source materials were mixed in a mixer at a molar ratio of 1:1.35:0.13:0.2: 0.01. After roasting, the temperature is reduced to 700 ℃ at the speed of 2 ℃/min, and then the mixture is roasted for 6 h. Grinding and sieving to obtain the lithium nickel manganese oxide material LiNi coated with lithium vanadyl phosphate_0.5Mn_1.5O₄/LiV_0.92Na_0.08OPO₄。

Example 6

Preparation of surface-coated lithium nickel manganese oxide particles:

ni manganese precursor_0.5Mn_1.5O₂And Li as a lithium source₂CO₃Mixing in a mixer at a molar ratio of 1: 0.51. Adding polyurethane balls and grinding medium ethanol into a mixer, wherein the mixing speed is 5000rpm, and the mixing time is 24 hours. After the mixing is finished, spheroidization is carried out by a spray drying method, wherein the spray drying temperature is 150 ℃, and the spray rotating speed is 5000 rpm. And then, after being ground properly, the dried powder is placed in a muffle furnace for high-temperature roasting treatment, wherein the high-temperature treatment temperature is 850 ℃, the treatment time is 10 hours, and the temperature rise speed is 5 ℃/min. The introduced atmosphere is oxygen, and the gas introduction speed is 0.8L/min. Grinding and sieving after roasting to obtain uncoated lithium nickel manganese oxide material LiNi_0.5Mn_1.5O₄. Followed byThe synthesized LiNi_0.5Mn_1.5O₄With a source of lithium Li₂CO₃Vanadium source V₂O₅And a source of phosphorus NH₄H₂PO₄Putting the mixture into a mixer in a molar ratio of 1:0.012:0.01:0.02, and uniformly mixing, wherein the mixing speed is 5000rpm, and the mixing time is 24 h. And then placing the mixed powder in a muffle furnace for high-temperature roasting treatment. The high-temperature treatment temperature is 700 ℃, the treatment time is 10h, and the heating rate is 2 ℃/min. The atmosphere introduced is air, and the gas introduction speed is 0.8L/min. Grinding and sieving the roasted product to obtain the lithium nickel manganese oxide material LiNi coated with lithium vanadyl phosphate_0.5Mn_1.5O₄/LiVOPO₄。

Specific parameters are shown in table 1.

TABLE 1

Comparative example

Ni manganese precursor_0.5Mn_1.5O₂And Li as a lithium source₂CO₃Mixing in a mixer at a molar ratio of 1: 0.51. Adding polyurethane balls and grinding medium ethanol into a mixer, wherein the mixing speed is 5000rpm, the mixing time is 24 hours, and after the mixing is finished, performing spheroidization by a spray drying method. The spray drying temperature was 100 ℃ and the spray speed was 3000 rpm. And then, after being ground properly, the dried powder is placed in a muffle furnace for high-temperature roasting treatment, wherein the high-temperature roasting treatment temperature is 850 ℃, the treatment time is 10 hours, and the temperature rising speed is 5 ℃/min. The atmosphere introduced is air, and the gas introduction speed is 0.8L/min. Grinding and sieving after roasting to obtain uncoated lithium nickel manganese oxide material LiNi_0.5Mn_1.5O₄。

The specific parameters of the comparative examples are shown in table 2.

TABLE 2

Example of production of Battery cell

The lithium nickel manganese oxide particles prepared in examples 1, 5 and 6 and the comparative example were used as positive electrode active materials, and were mixed with acetylene black as a conductive agent and polyvinylidene fluoride (PVDF) as a binder in a mass ratio of 95: 2: and 3, fully stirring and uniformly mixing in an N-methyl pyrrolidone solvent system, coating on an aluminum foil, drying, and performing cold pressing to obtain the positive pole piece.

Preparing a negative electrode active material artificial graphite, a conductive agent acetylene black, a binder styrene butadiene rubber and a thickening agent sodium carboxymethyl cellulose according to a mass ratio of 90: 5: 2: 2: 1, fully stirring and uniformly mixing in a deionized water solvent system, coating on a copper foil, drying, and cold pressing to obtain the negative pole piece. The PE porous polymer film is used as a separation film.

The positive pole piece, the isolating film and the negative pole piece are sequentially stacked, so that the isolating film is positioned between the cathode and the anode to play an isolating role, and the anode and the cathode are wound to respectively obtain the bare cell 1, the bare cell 5 and the bare cell 6 and the comparison cell. Arrange naked electric core in the plastic-aluminum membrane bag, pour into the electrolyte (like high voltage electrolyte) of joining in marriage and carry out hot pressing encapsulation, obtain electric core 1, 5, 6 and contrast electric core.

Example of production of Battery

Taking the lithium nickel manganese oxide particles prepared in the examples 1-6 and the comparative example as positive electrode active materials, and mixing the positive electrode active materials with acetylene black serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to the weight ratio of 92: 4: and 4, adding the mixture into an N-methyl pyrrolidone solvent, fully stirring and uniformly mixing, coating the mixture on the surface of an aluminum foil, and then drying and cold pressing to obtain the positive pole piece. And cutting the positive pole piece into small pieces to be used as a positive pole, using the lithium piece as a negative pole, using the PP porous polymer film as a separation film, and dripping proper electrolysis to assemble the battery, wherein the battery is respectively marked as a battery 1-6 and a comparative battery.

Comparison of test results

(1) Photograph taken with an electron microscope

The spinel lithium nickel manganese oxide particles obtained in the examples and comparative examples were photographed by a Scanning Electron Microscope (SEM).

A scanning electron micrograph of the untreated spinel lithium nickel manganese oxide particles of the comparative example is shown in FIG. 1 (X30000). As can be seen from the SEM image, the uncoated lithium nickel manganese oxide particles have a regular crystal structure.

The scanning electron micrograph of the coated lithium nickel manganese oxide prepared in example 5 is shown in FIG. 2 (. times.30000). As can be seen from SEM electron microscope pictures, after the lithium vanadyl phosphate is coated, a layer of coating substance appears on the surface, and the surface of the material is not damaged.

(2) Comparison experiment of stored gas production

The cells 1, 5, and 6 prepared in the "cell manufacturing example" and the comparative cell were subjected to a storage gassing comparison experiment under the same conditions.

After the battery cells 1, 5 and 6 and the comparison battery cell are subjected to formation treatment, the full battery is fully charged, the full battery is placed in a thermostat at 60 ℃, the volume of the full battery is tested every 15 days, and a storage gas production comparison experiment is carried out.

The initial measured volume is V₀Volume measured on day 15 was V₁₅The volume measured at day 30 was V₃₀Volume measured at day 45 was V₄₅And so on, the volume measured on the nth day is V_n。

The cell expansion ratio was calculated as follows (1):

cell expansion ratio (%) - (V)_n-V₀)/V₀X 100% formula (1)

The measured expansion ratios were plotted in a graph to obtain the experimental results shown in fig. 3.

As can be seen from fig. 3, when the number of storage days is 15 days, the difference in expansion rates between the cells 1, 5, and 6 and the comparative cell is small, and the difference in expansion rates between the cells 1, 5, and 6 and the comparative cell increases as the storage time becomes longer. When the storage days were 90 days, the expansion rates of the cells 1, 5, and 6 and the comparative cell were 30% or less, the expansion rates of the cells 1 and 5 were 25% or less, and the expansion rate of the comparative cell exceeded 35%.

Therefore, after the lithium ion battery anode material prepared under the condition of the invention is assembled into a battery and then stored at high temperature, the expansion rate of the battery core is obviously reduced compared with that of a comparative example.

The volume expansion rate of cell 6 at the time of storage for 60 days and 90 days was higher than that of cells 1 and 5, and the following reasons are presumed. The pellets obtained in example 6 were used in the battery cell 6, and lithium nickel manganese oxide (LiNi) was used in example 6_0.5Mn_1.5O₄) For the nickel manganese source material, because the nickel lithium manganate is already formed into particles, when the nickel lithium manganate is roasted with the lithium vanadyl phosphate source material, the nickel lithium manganate particles as the inner core are large, and the lithium vanadyl phosphate is difficult to coat uniformly.

(3) Comparative experiment of gram capacity and first coulombic efficiency (first effect)

The batteries 1-6 prepared in the battery manufacturing example and a comparative battery are tested by adopting a blue electro-chemical workstation according to a standard method for testing gram capacity and first coulombic efficiency, the power-off test multiplying power is 0.1C, and the discharge voltage is 3.0-4.95V.

The experimental results obtained are shown in table 3.

TABLE 3

Item	Unit cell	Battery 1	Battery 2	Battery 3	Battery 4	Battery 5	Battery 6	Comparative battery
									Gram volume	mAh/g	133.4	132.9	132.7	134.4	135.7	131.3	125.5
First effect	％	92	91	92	93	93	88	86

Table 3 shows that the gram capacities of the batteries 1-6 are all more than 131, the first effect is more than 88%, and the first effect is higher than 125.5% and 86% of the comparative examples. The gram capacity of the batteries 1-5 is over 132, and the first effect is over 91%. That is, the capacity and primary efficiency of the batteries 1-6 are significantly improved over the comparative batteries.

As can be seen from the "examples of manufacturing batteries", the particles obtained in examples 1 to 6 and comparative example were used for batteries 1 to 6 and comparative battery, respectively. In combination with the experimental results of table 3, it can be presumed that: after the lithium vanadyl phosphate is coated, the contact area between the electrolyte and the cathode material containing the lithium nickel manganese oxide particles is reduced, the side reaction of the cathode interface is reduced, and the performance of the battery is improved.

In addition, the gram capacity and the first efficiency of the battery 6 are lower than those of the battery using nickel manganeseExamples 1 to 4 in which a substance other than lithium was used as the nickel manganese source material. Since the battery 6 used the pellets produced in example 6, lithium nickel manganese oxide (LiNi) was used in the example_0.5Mn_1.5O₄) As a source material of nickel manganese. It is therefore presumed that the reason why the performance of the battery 6 is lower than that of examples 1 to 4 is that lithium nickel manganese oxide (LiNi) is used_0.5Mn_1.5O₄) When the lithium nickel manganese oxide is used as a nickel manganese source material, the nickel lithium manganese oxide serving as a core is large in particle size, and lithium vanadyl phosphate is difficult to coat uniformly. When using, for example, Ni_0.5Mn_1.5(OH)₄、Ni_0.5Mn_1.5O₂Like the source material of nickel manganese, lithium nickel manganese oxide (LiNi)_0.5Mn_1.5O₄) The formation of lithium nickel manganese oxide (LiNi) is carried out simultaneously with the coating of lithium vanadyl phosphate_0.5Mn_1.5O₄) The core is smaller and the coating is more uniform.

In addition, gram capacity and first efficiency of the batteries 4 and 5 are superior to those of the batteries 1 to 3. Since the batteries 4 and 5 and the batteries 1 to 3 used the particles obtained in examples 4, 5 and 1 to 3, respectively, it is presumed that the reason why the batteries 4 and 5 were superior to the batteries 1 to 3 was that the annealing treatment was not performed after the source material was fired in examples 1 to 3, but the annealing treatment was performed in examples 4 and 5.

While the invention has been described with reference to a preferred embodiment, various modifications may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In particular, the technical features mentioned in the embodiments can be combined in any way as long as there is no structural conflict. It is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A method for preparing surface-coated lithium nickel manganese oxide particles is characterized by comprising the following steps:

(A) providing a catalyst containing Ni_0.5Mn_1.5(OH)₄And Ni_0.5Mn_1.5O₂One or two of a manganese-and nickel-containing source material, a lithium source material, a vanadium source material, a phosphorus source material, andoptionally a precursor mixture of a doped metal source material, wherein the doped metal is selected from one or more of Y, Ca, Ce, K, Si, Mo, W, Mn, Fe, B, Mg, Al, Na, Zr, Ti, and the source material is used in an amount such that based on 1mol of Ni, the amount of Mn is 3 to 3.5mol, the amount of Li is 2 to 2.3mol, the amount of V is more than 0 to 0.2mol, the amount of P is more than 0 to 0.2mol, and the amount of doped metal is 0 to 0.2 mol;

(A1) mixing the raw materials in the step (A) in a mixer in the presence of a mixing medium to form a precursor mixture; and

(B) and roasting the precursor mixture in an oxygen-containing atmosphere or an inert atmosphere, wherein the roasting condition is that the temperature rising speed is 1-10 ℃, the sintering temperature is 400-1000 ℃, and the sintering time is 1-20 h.

2. The method of claim 1, further comprising:

and annealing the product obtained by roasting in an oxygen-containing atmosphere or an inert atmosphere.

3. The method of claim 1,

the lithium source material is Li₂CO₃、LiOH·H₂O、LiNO₃One or more of LiCl and vanadium source material VOPO₄ 2H₂O、V₂O₅、NH₄VO₃、VO(HPO₄)_0.5H₂One or more of O, and H as phosphorus source material₃PO₄、VO(HPO₄)_0.5H₂O、VOPO₄ 2H₂O、NH₄H₂PO₄、(NH₄)₂HPO₄The precursor of the dopant metal element M is one or more of oxide, hydroxide, sulfate and carbonate of M.

4. The method of claim 3,

the source material is used in such an amount that, with respect to 1mol of Ni, the amount of Mn is 3 to 3.04mol, the amount of Li is 2.64 to 3.32mol, the amount of V is 0.4 to 0.6mol, the amount of P is 0.4 to 0.6 mol: the amount of the doped metal element M is 0 to 0.04 mol.

5. Surface-coated lithium nickel manganese oxide particles obtainable by the process according to any one of claims 1 to 4, wherein the lithium nickel manganese oxide is of the formula LiNi_0.5Mn_1.5O₄At least part of the surface of the spinel type lithium nickel manganese oxide particles is coated with LiV_1-xM_xOPO₄Wherein x is more than or equal to 0 and less than or equal to 0.9, and M is one or more doping metals selected from Y, Ca, Ce, K, Si, Mo, W, Mn, Fe, B, Mg, Al, Na, Zr and Ti.

6. The surface-coated lithium nickel manganese oxide particles according to claim 5, wherein LiV is contained in the surface-coated lithium nickel manganese oxide particles_1-xM_xOPO₄The mass content of (B) is 100 ppm-50000 ppm.

7. The surface-coated lithium nickel manganese oxide particles according to claim 5, wherein the surface-coated lithium nickel manganese oxide particles have a D50 of 0.1 to 20 μm and/or a specific surface area of 0.01 to 20m²/g。

8. The surface-coated lithium nickel manganese oxide particles according to claim 5, wherein x is 0.05. ltoreq. x.ltoreq.0.3.

9. The surface-coated lithium nickel manganese oxide particles according to claim 5, wherein M is one or more doping metals selected from the group consisting of Ti, Al, Mg, Na.

10. The surface-coated lithium nickel manganese oxide particles according to claim 5,

in the particles, relative to 1mol of Ni, the content of Mn is 3-3.04 mol, the content of Li is 2.64-3.32 mol, the content of V is 0.4-0.6 mol, the content of P is 0.4-0.6 mol, and the content of doped metal element M is 0-0.04 mol.

11. The surface-coated lithium nickel manganese oxide particles according to any one of claims 5 to 10, wherein the surfaces of the lithium nickel manganese oxide particles are completely coated with the lithium vanadyl phosphate.

12. A positive electrode active material comprising surface-coated lithium nickel manganese oxide particles produced by the method for producing surface-coated lithium nickel manganese oxide particles according to any one of claims 1 to 4, or comprising surface-coated lithium nickel manganese oxide particles according to any one of claims 5 to 11.

13. A lithium ion battery cell comprising the surface-coated lithium nickel manganese oxide particles prepared by the method of preparing surface-coated lithium nickel manganese oxide particles according to any one of claims 1 to 4, or comprising the surface-coated lithium nickel manganese oxide particles according to any one of claims 5 to 11.

14. The lithium ion battery cell of claim 13, wherein the lithium ion battery cell has a cell swell ratio of 30% or less on a 90 day storage day basis.

15. A lithium ion battery cell comprising the surface-coated lithium nickel manganese oxide particles prepared by the method of any one of claims 1 to 4, or comprising the surface-coated lithium nickel manganese oxide particles of any one of claims 5 to 11.