阅读说明：本技术 锂镍钴复合氧化物、其制备方法和锂离子电池 (Lithium-nickel-cobalt composite oxide, preparation method thereof and lithium ion battery ) 是由 张弘旭 宋雄 罗亮 杨顺毅 杨才德 黄友元 于 2020-03-27 设计创作，主要内容包括：本发明公开了一种锂镍钴复合氧化物、其制备方法及二次锂电池。一种锂镍钴复合氧化物通式为Li-bNi-(1-x-y)Co-xM-yO-2,其中,0.95≤b≤1.05,0.08≤x≤0.15,0.025≤y≤0.040,M选自Al、Mn、Ti、Sr、Zr、Mg、W、Nb及B中的至少一种；附着于锂镍钴复合氧化物表面的锂化合物中的碳含量相对于所述锂镍钴复合氧化物的总量为0.01wt％～0.05wt％,附着于锂镍钴复合氧化物表面的锂化合物中的锂含量相对于所述锂镍钴复合氧化物的总量≤0.05wt％。该锂镍钴复合氧化物具有良好的加工性能、高温性能以及安全性能。(The invention discloses a lithium-nickel-cobalt composite oxide, a preparation method thereof and a secondary lithium battery. The general formula of the lithium nickel cobalt composite oxide is Li b Ni 1‑x‑y Co x M y O 2 Wherein B is more than or equal to 0.95 and less than or equal to 1.05, x is more than or equal to 0.08 and less than or equal to 0.15, y is more than or equal to 0.025 and less than or equal to 0.040, and M is selected from at least one of Al, Mn, Ti, Sr, Zr, Mg, W, Nb and B; the content of carbon in the lithium compound attached to the surface of the lithium nickel cobalt composite oxide is 0.01 wt% to 0.05 wt% with respect to the total amount of the lithium nickel cobalt composite oxide, and the content of lithium in the lithium compound attached to the surface of the lithium nickel cobalt composite oxide is not more than 0.05 wt% with respect to the total amount of the lithium nickel cobalt composite oxide. The lithium nickel cobalt composite oxide hasHas good processing performance, high temperature performance and safety performance.)

1. A lithium nickel cobalt complex oxide, characterized in that the general formula of the lithium nickel cobalt complex oxide is:

Li_bNi_1-x-yCo_xM_yO₂，

wherein B is more than or equal to 0.95 and less than or equal to 1.05, x is more than or equal to 0.08 and less than or equal to 0.15, y is more than or equal to 0.025 and less than or equal to 0.040, and M is selected from at least one of Al, Mn, Ti, Sr, Zr, Mg, W, Nb and B;

the carbon content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.01 wt% -0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide;

the lithium compound on the surface of the lithium nickel cobalt composite oxide contains lithium in an amount of 0.05 wt% or less relative to the total amount of the lithium nickel cobalt composite oxide.

2. The lithium nickel cobalt complex oxide according to claim 1,

the carbon content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.02 wt% -0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide; and/or

The lithium content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.02 wt% -0.04 wt% relative to the total amount of the lithium nickel cobalt composite oxide; and/or

The lithium nickel cobalt composite oxide is of an internal compact structure, the average particle size is 9-15 mu m, and D95 is more than 20 mu m; and/or

The specific surface area of the lithium nickel cobalt composite oxide was 1.0m²/g～2.0m²(ii)/g; and/or

The tap density of the lithium nickel cobalt composite oxide is more than or equal to 2.6g/cm³(ii) a And/or

The content of magnetic substances of the lithium nickel cobalt composite oxide is less than or equal to 40 ppb; and/or

The moisture content of the lithium nickel cobalt composite oxide is less than or equal to 400 ppm; and/or

The lithium nickel cobalt composite oxide has initial discharge capacity of more than 200mAh/g when being applied to a 2032 button cell.

3. A method for preparing a lithium nickel cobalt composite oxide is characterized by comprising the following steps:

sintering a raw material mixture including Ni to obtain a sintered product_1-x-yCo_xM_yAn oxide and a lithium source, wherein x is 0.08-0.15, y is 0.025-0.040, M is at least one selected from Al, Mn, Ti, Sr, Zr, Mg, W, Nb and B, and

washing the sintered material with water, and drying to obtain the lithium nickel cobalt composite oxide, wherein the washing temperature is 15-35 ℃, the concentration of the slurry during washing is 500-1500 g/L, and the washing time is 10-40 min;

the carbon content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.01 wt% -0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide;

the lithium compound on the surface of the lithium nickel cobalt composite oxide contains lithium in an amount of 0.05 wt% or less relative to the total amount of the lithium nickel cobalt composite oxide.

4. The production method according to claim 3,

the ratio of the total molar amount of Ni, Co and M in the raw material mixture to the molar amount of Li in the lithium source is 1:1 to 1: 1.1; and/or

The Ni_1-x-yCo_xM_yThe average particle diameter of the oxide is 9-15 μm, D95>20 μm; and/or

The Ni_1-x-yCo_xM_yThe tap density of the oxide is more than or equal to 2.0g/cm³(ii) a And/or

The sintering step is carried out in the temperature range of 650-780 ℃ under the atmosphere with the oxygen mass percent being more than or equal to 99%; and/or

The lithium source is at least one of lithium hydroxide and lithium carbonate; and/or

The average grain diameter of the lithium source is less than 15 mu m; and/or

The drying temperature is 100-300 ℃; and/or

The drying time is 12-48 h; and/or

The moisture content of the lithium nickel cobalt composite oxide is less than or equal to 400 ppm.

5. The production method according to claim 3,

the step of washing the burned product with water further comprises the following steps: crushing the calcined product to an average particle size of 9-15 μm, a D95 of more than 20 μm, and a specific surface area of 0.1m²/g～0.5m²(ii)/g; and/or

The step of washing the fired product with water and then drying to obtain the lithium nickel cobalt composite oxide further comprises the following steps: and demagnetizing the lithium nickel cobalt composite oxide until the content of magnetic substances is less than or equal to 40 ppb.

6. The production method according to claim 5,

the operation of the demagnetizing treatment is specifically as follows: and screening the dried lithium nickel cobalt composite oxide on a vibrating screen provided with a permanent magnet, and removing magnetic foreign matters in the lithium nickel cobalt composite oxide.

7. The production method according to any one of claims 3 to 6,

the Ni_1-x-yCo_xM_yThe oxide is prepared by sintering Ni at 400-600 deg.C_1-x-yCo_xM_y-aM and at least one of hydroxide and oxyhydroxide of (2)_aIs obtained by dehydrating at least one of the hydroxide and the oxyhydroxide, wherein a is 0. ltoreq. a.ltoreq.0.040.

8. The production method according to claim 7,

the Ni_1-x-yCo_xM_y-aThe average particle diameter of the hydroxide and the oxyhydroxide is 9-15 mu m, and D95 is more than 20 mu m; and/or

M_aThe average particle size of the hydroxides and oxyhydroxides of (4) is < 5 μm.

9. A lithium ion battery comprising the lithium nickel cobalt complex oxide according to any one of claims 1 to 2.

10. The lithium ion battery of claim 9, wherein the lithium ion battery is a button cell battery; and/or

The lithium ion battery is a 2032 button cell battery, and the lithium ion battery has an initial discharge capacity of more than 200 mAh/g.

Technical Field

The invention relates to the technical field of battery materials, in particular to a lithium nickel cobalt composite oxide, a preparation method thereof and a lithium ion battery.

Background

The anode material of the lithium ion battery is one of key materials for improving the cost performance of the lithium ion battery, and currently, LiCoO is widely used commercially₂A material. With LiCoO₂In contrast, the layered lithium-nickel composite oxide positive electrode material LiNi_xM_1-xO₂Wherein M is one or more elements of Co, Mn and Al, and x is more than or equal to 0.8 and less than 1. The discharge capacity of the material is high, can reach 250mAh/g and is obviously higher than that of LiCoO₂The discharge capacity is 140mAh/g, and the energy density advantage is obvious. Therefore, in recent years, a layered lithium nickel composite oxide positive electrode material has been studied.

Layered positive electrode material (LiNi)_xM_1-xO₂) Wherein Li atom is located at position 3a, transition metal atom is located at position 3b, and O atom is located at MO₆(M ═ Ni, Co, Mn or Al) at the 6c position of the octahedron. Due to the fact thatAndthe radii are very close, during the high-temperature sintering process, a trace amount of Li volatilizes, and part of Ni occupies the 3a position of Li in the crystal structure to form a tiny structure collapse area, which is called as lithium/nickel mixed discharge. The lithium/nickel mixed discharge enables more active oxygen and free lithium ions to be present on the surface of the positive electrode material, and further enables the active oxygen and the free lithium ions to be mixed with CO in the air₂And H₂O contact and react to generate free lithium compound (Li)₂CO₃And LiOH) impurities, which are attached to the surface of the positive electrode material, and the impurities easily absorb moisture, so that the pH value is increased, the material is jelly-like during size mixing, the processability is reduced, and the high-temperature performance and the storage performance of the battery are poor.

Disclosure of Invention

Therefore, it is necessary to provide a lithium nickel cobalt composite oxide with good processability, battery high-temperature performance and storage performance, a preparation method thereof and a lithium ion battery.

In a first aspect, the present invention provides a lithium nickel cobalt complex oxide, wherein the general formula of the lithium nickel cobalt complex oxide is:

Li_bNi_1-x-yCo_xM_yO₂

wherein b is more than or equal to 0.95 and less than or equal to 1.05, x is more than or equal to 0.08 and less than or equal to 0.15, y is more than or equal to 0.025 and less than or equal to 0.040, and M is selected from Al, Mn, Ti,

At least one of Sr, Zr, Mg, W, Nb and B;

the carbon content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.01 wt% -0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide;

the lithium compound on the surface of the lithium nickel cobalt composite oxide contains lithium in an amount of 0.05 wt% or less relative to the total amount of the lithium nickel cobalt composite oxide.

In one embodiment, the content of carbon in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.02 wt% to 0.05 wt% with respect to the total amount of the lithium nickel cobalt composite oxide.

In one embodiment, the lithium content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.02 wt% to 0.04 wt% with respect to the total amount of the lithium nickel cobalt composite oxide.

In one embodiment, the lithium nickel cobalt composite oxide is an internal compact structure, the average grain diameter is 9-15 μm, and D95 is more than 20 μm.

In one embodiment, the lithium nickel cobalt composite oxide has a specific surface area of 1.0m²/g～2.0m²/g。

In one embodiment, the lithium nickel cobalt complex oxygenThe tap density of the compound is more than or equal to 2.6g/cm³。

In one embodiment, the magnetic substance content of the lithium nickel cobalt composite oxide is less than or equal to 40 ppb.

In one embodiment, the moisture content of the lithium nickel cobalt composite oxide is less than or equal to 400 ppm.

In one embodiment, the lithium nickel cobalt composite oxide has an initial discharge capacity of 200mAh/g or more when applied to a 2032 button cell.

In a second aspect, the present invention provides a method for preparing a lithium nickel cobalt composite oxide, comprising the steps of:

sintering a raw material mixture including Ni to obtain a sintered product_1-x-yCo_xM_yAn oxide and a lithium source, wherein x is 0.08-0.15, y is 0.025-0.040, M is at least one selected from Al, Mn, Ti, Sr, Zr, Mg, W, Nb and B, and

washing the sintered material with water, and drying to obtain the lithium nickel cobalt composite oxide, wherein the washing temperature is 15-35 ℃, the concentration of the slurry during washing is 500-1500 g/L, and the washing time is 10-40 min;

the carbon content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.01 wt% -0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide;

the lithium compound on the surface of the lithium nickel cobalt composite oxide contains lithium in an amount of 0.05 wt% or less relative to the total amount of the lithium nickel cobalt composite oxide.

In one embodiment, the ratio of the total molar amount of Ni, Co and M in the raw material mixture to the molar amount of Li in the lithium source is 1:1 to 1: 1.1.

In one embodiment, the Ni_1-x-yCo_xM_yThe average particle diameter of the oxide is 9-15 μm, D95>20μm。

In one embodiment, the Ni_1-x-yCo_xM_yThe tap density of the oxide is more than or equal to 2.0g/cm³。

In one embodiment, the sintering step is carried out in an atmosphere with oxygen mass percent being more than or equal to 99% at the temperature of 650-780 ℃.

In one embodiment, the lithium source is at least one of lithium hydroxide and lithium carbonate.

In one embodiment, the lithium source has an average particle size < 15 μm.

In one embodiment, the drying temperature is 100 ℃ to 300 ℃.

In one embodiment, the drying time is 12h to 48 h.

In one embodiment, the moisture content of the lithium nickel cobalt composite oxide is less than or equal to 400 ppm.

In one embodiment, the step of washing the burned product with water further includes the following steps: crushing the calcined product to an average particle size of 9-15 μm, a D95 of more than 20 μm, and a specific surface area of 0.1m²/g～0.5m²/g。

In one embodiment, the step of washing the calcined product with water and then drying to obtain the lithium nickel cobalt composite oxide further includes the steps of: and demagnetizing the lithium nickel cobalt composite oxide until the content of magnetic substances is less than or equal to 40 ppb.

In one embodiment, the operation of the demagnetization process specifically includes: and screening the dried lithium nickel cobalt composite oxide on a vibrating screen provided with a permanent magnet, and removing magnetic foreign matters in the lithium nickel cobalt composite oxide.

In one embodiment, the Ni_1-x-yCo_xM_yThe oxide is prepared by sintering Ni at 400-600 deg.C_{1-x- y}Co_xM_y-aM and at least one of hydroxide and oxyhydroxide of (2)_aIs obtained by dehydrating at least one of the hydroxide and the oxyhydroxide, wherein a is 0. ltoreq. a.ltoreq.0.040.

In one embodiment, the Ni_1-x-yCo_xM_y-aThe average particle diameter of the hydroxide and the oxyhydroxide is 9 to 15 μm, and D95 is more than 20 μm.

In one of themIn one embodiment, M_aThe average particle size of the hydroxides and oxyhydroxides of (4) is < 5 μm.

In a third aspect, the invention provides a lithium ion battery, which comprises the above lithium nickel cobalt composite oxide.

In one embodiment, the lithium ion battery is a button cell battery.

In one embodiment, the lithium ion battery is a 2032 button cell battery, and the lithium ion battery has an initial discharge capacity of 200mAh/g or more.

Compared with the prior art, the invention has the following beneficial effects:

in the lithium nickel cobalt composite oxide provided by the invention, the lithium content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is controlled to be less than or equal to 0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide, the carbon content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is controlled to be 0.01 wt% -0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide, the processing performance, the high-temperature performance and the storage performance of the material can be improved, and the phase change of the lithium nickel cobalt composite oxide in the circulation process is effectively inhibited through the doping of the M element, so that the structural stability is improved. The lithium nickel cobalt composite oxide is applied to a lithium ion battery, the high-temperature cycle at 45 ℃ for 50 weeks can reach 95%, and the expansion rate of a soft package battery stored at 60 ℃ for 30 days is less than 15%.

In the preparation method provided by the invention, by controlling the water washing condition, the lithium content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is effectively controlled to be less than or equal to 0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide, and the carbon content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is controlled to be 0.01 wt% -0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide, so that the gas generation of the material can be inhibited, and the high temperature and storage performance can be improved; the specific surface area of the material can be controlled by controlling the washing condition, so that the thermal stability of the material is ensured while the capacity of the material meets the requirement.

Drawings

FIG. 1 is a graph showing the impedance comparison of the lithium nickel cobalt complex oxide obtained in example 1 and comparative example 1;

FIG. 2 is a DSC of the lithium nickel cobalt complex oxide obtained in example 1 and comparative example 1;

FIG. 3 is a SEM photograph of a cross section of the lithium nickel cobalt composite oxide obtained in example 1 after cycling at 45 ℃ and 1 ℃ for 100 weeks;

FIG. 4 is a SEM photograph of a cross section of the lithium nickel cobalt composite oxide obtained in comparative example 1 after cycling at 45 ℃ and 1 ℃ for 100 weeks.

Detailed Description

In order to better illustrate the present invention and facilitate the understanding of the technical solutions of the present invention, the present invention is further described in detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

One embodiment of the lithium nickel cobalt composite oxide has the general formula:

Li_bNi_1-x-yCo_xM_yO₂

wherein B is more than or equal to 0.95 and less than or equal to 1.05, x is more than or equal to 0.08 and less than or equal to 0.15, y is more than or equal to 0.025 and less than or equal to 0.040, and M is selected from at least one of Al, Mn, Ti, Sr, Zr, Mg, W, Nb and B;

the carbon content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.01 wt% -0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide;

the lithium compound on the surface of the lithium nickel cobalt composite oxide contains lithium in an amount of 0.05 wt% or less relative to the total amount of the lithium nickel cobalt composite oxide.

As known to those skilled in the art, the lithium compound on the surface of the lithium nickel cobalt composite oxide refers to: the residual lithium impurities (lithium carbonate and lithium hydroxide) adhering to the surface of the lithium nickel cobalt complex oxide are contained in an extremely small amount, and therefore, in the present embodiment, are considered to be contained in the lithium nickel cobalt complex oxide.

When the carbon content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is more than 0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide, the Li on the surface of the lithium nickel cobalt composite oxide₂CO₃The content is higher, and the battery is likely to generate gas in charge-discharge cycles, so that the battery expands; when the lithium nickel cobalt is compoundedWhen the content of carbon in the lithium compound on the surface of the complex oxide is less than 0.01 wt% relative to the total amount of the lithium nickel cobalt composite oxide, it means that the lithium nickel cobalt composite oxide is excessively washed with water, resulting in washing out of Li inside the lithium nickel cobalt composite oxide particles, resulting in a decrease in material capacity and cycle performance. In some embodiments, the carbon content of the lithium nickel cobalt composite oxide is 0.02 wt% to 0.05 wt%, such as 0.02 wt%, 0.025 wt%, 0.03 wt%, 0.035 wt%, 0.04 wt%, 0.05 wt%, relative to the total amount of the lithium nickel cobalt composite oxide.

LiOH and Li on the surface of the lithium nickel cobalt complex oxide when the lithium content in the lithium compound on the surface of the lithium nickel cobalt complex oxide is > 0.05 wt.% relative to the total amount of the lithium nickel cobalt complex oxide₂CO₃The content is higher, and the battery is likely to generate gas in charge-discharge cycles, so that the battery expands; when the lithium content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is less than 0.01 wt% relative to the total amount of the lithium nickel cobalt composite oxide, it means that the lithium nickel cobalt composite oxide is excessively washed with water, which causes Li in the interior of the lithium nickel cobalt composite oxide particles to be washed out, resulting in a decrease in the material capacity and cycle performance. In some embodiments, the lithium content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.02 wt% to 0.04 wt%, for example, 0.02 wt%, 0.025 wt%, 0.03 wt%, 0.035 wt%, relative to the total amount of the lithium nickel cobalt composite oxide.

In some embodiments, the lithium nickel cobalt composite oxide is an internal compact structure with an average particle size of 9 to 15 μm, D95>20 μm. The tap density of the lithium-nickel-cobalt composite oxide material can be controlled to be more than or equal to 2.6g/cm by controlling the internal structure and the particle size distribution³Thereby improving the energy density of the lithium nickel cobalt composite oxide. In some embodiments, the lithium nickel cobalt composite oxide has an average particle size of 10 μm to 14 μm. Of course, in another embodiment, the average particle diameter of the lithium nickel cobalt complex oxide may be 11 μm to 13 μm.

The specific surface area of the lithium nickel cobalt composite oxide was 1.0m²/g～2.0m²In g, e.g. 1.0m²/g、1.2m²/g、1.4m²/g、1.5m²/g、1.7m²/g、1.8m²/g、2.0m²/g。

The specific surface area of the lithium nickel cobalt composite oxide can influence the absorption of the material to the electrolyte, and when the specific surface area is less than 1.0m²When the concentration is/g, the lithium nickel cobalt composite oxide can not sufficiently absorb the electrolyte, so that the capacity and the cycle are reduced; when the specific surface area is more than 2.0m²(g) excessive absorption of electrolyte by the Li-Ni-Co composite oxide, Ni on the surface⁴⁺The electrolyte is easily oxidized, thereby causing an increase in gas generation and affecting the safety performance of the lithium nickel cobalt composite oxide.

In some embodiments, the tap density of the lithium nickel cobalt composite oxide is 2.6g/cm or more³。

The tap density of the lithium nickel cobalt composite oxide affects the energy density of the material, and the tap density is low, so that the high energy density requirement of the lithium ion battery cannot be met. The tap density is limited to be more than or equal to 2.6g/cm³The energy density of the lithium nickel cobalt composite oxide can be improved.

In some embodiments, the lithium nickel cobalt complex oxide has a magnetic material content of 40ppb or less.

When the content of the magnetic substance in the lithium nickel cobalt composite oxide is too high, the metal foreign matter in the material is excessive, and the metal foreign matter can puncture the diaphragm in the charge-discharge cycle process of the lithium ion battery, so that the safety performance of the lithium ion battery is seriously influenced. The content of the magnetic substance is less than or equal to 40ppb, and the metal foreign matters in the lithium nickel cobalt composite oxide can be effectively reduced, so that the safety performance of the lithium ion battery is ensured.

In some embodiments, the lithium nickel cobalt composite oxide has a moisture content of 400ppm or less.

In some embodiments, the lithium nickel cobalt composite oxide has an initial discharge capacity of 200mAh/g or greater for use in 2032 coin cells.

An embodiment provides a method for preparing the lithium nickel cobalt complex oxide, including the steps of:

sintering a raw material mixture including Ni to obtain a sintered product_1-x-yCo_xM_yOxidation by oxygenA substance and a lithium source, wherein x is not less than 0.08 and not more than 0.15, y is not less than 0.025 and not more than 0.040, M is selected from at least one of Al, Mn, Ti, Sr, Zr, Mg, W, Nb and B, and

washing the sintered material with water, and drying to obtain the lithium nickel cobalt composite oxide, wherein the washing temperature is 15-35 ℃, the concentration of the slurry during washing is 500-1500 g/L, and the washing time is 10-40 min;

the carbon content in the lithium compound on the surface of the lithium nickel cobalt composite oxide is 0.01 wt% -0.05 wt% relative to the total amount of the lithium nickel cobalt composite oxide;

the lithium compound on the surface of the lithium nickel cobalt composite oxide contains lithium in an amount of 0.05 wt% or less relative to the total amount of the lithium nickel cobalt composite oxide.

The water washing temperature is 15-35 ℃, and if the water washing temperature is lower than 15 ℃, the solubility of lithium compounds on the surface of the material is insufficient, so that the lithium content of the lithium-nickel-cobalt composite oxide is more than 0.05 wt% relative to the total amount, gas generation is easily caused, and the safety performance is influenced; if the washing temperature is higher than 35 ℃, lithium in the material is easy to be washed out, the structural stability of the material is influenced, and the capacity and the cycle performance of the material are reduced. In other embodiments, the water washing temperature may also be 20min to 30min, such as 20min, 25min, 30 min.

The concentration of the slurry is 500 g/L-1500 g/L, and when the concentration of the slurry is less than 500g/L, lithium in the material is easily washed out, the structural stability of the material is influenced, and the capacity and the cycle performance of the material are reduced; when the concentration of the slurry is more than 1500g/L, the slurry is easily excessively viscous, so that the water washing is insufficient, the lithium content of the lithium nickel cobalt composite oxide is more than 0.05 wt% relative to the total amount, the gas generation is easily caused, and the safety performance is influenced. In other embodiments, the slurry concentration may also be 600g/L to 1200g/L, such as 600g/L, 700g/L, 800g/L, 1000g/L, 1100g/L, 1200 g/L.

The washing time is 10-40 min, when the washing time is less than 10min, insufficient washing can be caused, the lithium content of the lithium-nickel-cobalt composite oxide is more than 0.05 wt% relative to the total amount, gas generation is easy to cause, and the safety performance is influenced; when the water washing time is more than 40min, lithium in the material is easy to be washed out, the structural stability of the material is influenced, and the capacity and the cycle performance of the material are reduced. In other embodiments, the washing time of the lithium nickel cobalt composite oxide may be 20min to 35min, for example, 20min, 25min, 30min, 35 min.

In some embodiments, the ratio of the total molar amount of Ni, Co, and M in the raw material mixture to the molar amount of Li in the lithium source is 1:1 to 1: 1.1.

In some embodiments, the Ni is_1-x-yCo_xM_yThe average particle diameter of the oxide is 9-15 μm, D95>20 μm. By optimizing Ni_1-x-yCo_xM_yThe particle size distribution of the oxide is such that the tap density is not less than 2.0g/cm³。

In some embodiments, the Ni is_1-x-yCo_xM_yThe tap density of the oxide is more than or equal to 2.0g/cm³. By controlling Ni_1-x-yCo_xM_yThe tap density of the oxide is ensured to be more than or equal to 2.6g/cm³。

In some embodiments, the sintering step is performed at a temperature ranging from 650 ℃ to 780 ℃ in an atmosphere with an oxygen mass percent of 99% or more. When the oxygen content is insufficient, the lithium content in the lithium compound on the surface of the material is more than 0.5 wt% relative to the total amount, so that the residual lithium compound on the surface of the material cannot be effectively removed in the subsequent water washing process, gas generation is easily caused, and the safety performance is influenced. In other embodiments, the oxygen content of the sintering atmosphere is 99.5% or more.

In some embodiments, the lithium source is at least one of lithium hydroxide and lithium hydroxide.

In some embodiments, the lithium source has an average particle size < 15 μm. Controlling the grain diameter of lithium source to be less than 15 μm to ensure that the lithium source and Ni are mixed_1-x-yCo_xM_yThe particle size of the oxide is equivalent, so that the two samples are mixed more uniformly in the mixing process, and the reaction is more complete.

In some embodiments, the drying temperature is from 100 ℃ to 300 ℃, e.g., 100 ℃, 200 ℃, 300 ℃.

In some embodiments, the drying time is 12h to 48h, e.g., 12h, 20h, 30h, 40h, 48 h.

When the drying temperature is less than 100 ℃ or the drying time is less than 12h, the moisture of the material is high, and Li on the surface of the material is increased₂CO₃And LiOH, which causes gas generation of the material and influences high-temperature performance, storage performance and safety performance; when the drying temperature is more than 300 ℃ or the drying time is more than 48 hours, the moisture content of the material cannot be further reduced, and energy consumption is wasted. In other embodiments, the drying conditions of the lithium nickel cobalt composite oxide may further be: drying at 150-250 deg.c for 20-30 hr.

In some embodiments, the lithium nickel cobalt composite oxide has a moisture content of 400ppm or less.

In some embodiments, the step of washing the calcined product with water further comprises the steps of: crushing the calcined product to an average particle size of 9-15 μm, a D95 of more than 20 μm, and a specific surface area of 0.1m²/g～0.5m²/g。

The particle diameter and the specific surface area of the crushed fired material were limited to ensure that the specific surface area of the lithium nickel cobalt composite oxide increased to 1.0m after the subsequent water washing²/g～2.0m²The specific surface area after washing is in the range, so that the material has good capacity and thermal stability, and if the specific surface area is too high, the material can react with the electrolyte violently in the circulation process, so that the thermal stability is reduced; if the specific surface area is too low, the capacity exertion of the material may be affected, and the cycle performance may be reduced.

The disruption step may be carried out using methods known to those skilled in the art, for example: mechanical crushing and air flow crushing.

In some embodiments, the step of washing the fired product with water and then drying the washed product to obtain the lithium nickel cobalt composite oxide further comprises the steps of: and demagnetizing the lithium nickel cobalt composite oxide until the content of magnetic substances is less than or equal to 40 ppb.

In some embodiments, the operation of the demagnetization process is specifically: and screening the dried lithium nickel cobalt composite oxide on a vibrating screen provided with a permanent magnet, and removing magnetic foreign matters in the lithium nickel cobalt composite oxide.

In some embodiments, the Ni is_1-x-yCo_xM_yThe oxide is prepared by sintering Ni at 400-600 deg.C_{1-x- y}Co_xM_y-aM and at least one of hydroxide and oxyhydroxide of (2)_aIs obtained by dehydrating at least one of the hydroxide and the oxyhydroxide, wherein a is 0. ltoreq. a.ltoreq.0.040.

In some embodiments, the Ni is_1-x-yCo_xM_y-aThe average particle diameter of the hydroxide and the oxyhydroxide is 9 to 15 μm, and D95 is more than 20 μm.

In some embodiments, M_aThe average particle size of the hydroxides and oxyhydroxides of (4) is < 5 μm.

An embodiment provides a lithium ion battery including the lithium nickel cobalt complex oxide.

In some embodiments, the lithium ion battery is a button cell battery.

In some embodiments, the lithium ion battery is a 2032 coin cell battery having an initial discharge capacity of 200mAh/g or greater.

The embodiments of the present invention are not limited to the above specific embodiments. The embodiments described above may be implemented with appropriate modifications and combinations within the scope of the main claims.

The embodiments of the present invention will be further described in the following with reference to the accompanying drawings.

Example 1:

(1) mixing Ni_0.88Co_0.09Al_0.03(OH)₂、Zr(OH)₄Sintering for 6h at 500 ℃ in air atmosphere to obtain Ni_0.88Co_0.09Al_0.025Zr_0.005O。

(2) Mixing Ni with a high-speed mixer according to the ratio of the molar weight of Li to the sum of the molar weights of Ni, Co, Al and Zr of 1.04_0.88Co_0.09Al_0.025Zr_0.005O and LiOH under the atmosphere that the oxygen content is more than or equal to 99.5 percent and at 74 percentSintering the mixture at 0 ℃ for 10h to obtain Li_1.03Ni_0.88Co_0.09Al_0.025Zr_0.005O₂And (4) firing the product.

(3) The sintered product is controlled to have an average particle size of 10 to 12 μm by a jet mill.

(4) And (3) preparing slurry from the calcined product and water according to 800g/L, and washing with water at the temperature of 20 ℃ for 25 min.

(5) And (4) carrying out filter pressing on the slurry after washing, wherein the filter pressing time is 1 h.

(6) Drying the filter cake obtained by filter pressing for 20h at 200 ℃ in a nitrogen atmosphere to obtain LiNi_0.88Co_0.09Al_0.025Zr_0.005O₂A lithium nickel cobalt composite oxide.

Example 2:

(1) mixing Ni_0.845Co_0.155(OH)₂、Al(OH)₃Sintering for 8 hours at 500 ℃ in air atmosphere to obtain Ni_0.815Co_0.15Al_0.035O。

(2) Mixing Ni with a high-speed mixer according to the ratio of the molar weight of Li to the sum of the molar weights of Ni, Co and Al of 1.05_0.815Co_0.15Al_0.035O and LiOH, sintering the mixture at 740 ℃ for 10 hours in the atmosphere with the oxygen content being more than or equal to 99.5 percent to obtain Li_1.04Ni_0.815Co_0.15Al_0.035O₂And (4) firing the product.

(3) The sintered product is controlled to have an average particle size of 10 to 12 μm by a jet mill.

(4) And (3) preparing slurry from the calcined product and water according to 800g/L, and washing with water at the temperature of 25 ℃ for 30 min.

(5) And (4) carrying out filter pressing on the slurry after washing, wherein the filter pressing time is 1 h.

(6) Drying the filter cake obtained by filter pressing for 25h at 200 ℃ in nitrogen atmosphere to obtain Li_1.01Ni_0.815Co_0.15Al_0.035O₂A lithium nickel cobalt composite oxide.

Example 3:

(1) mixing Ni_0.88Co_0.09Mn_.03(OH)₂、Zr(OH)₄Sintering for 8 hours at 500 ℃ in air atmosphere to obtain Ni_0.88Co_0.09Mn_0.025Zr_0.005O。

(2) Mixing Ni with a high-speed mixer according to the ratio of the molar weight of Li to the sum of the molar weights of Ni, Co, Mn and Zr of 1.04_0.88Co_0.09Mn_0.025Zr_0.005O and LiOH, sintering the mixture at 740 ℃ for 10 hours in the atmosphere with the oxygen content being more than or equal to 99.5 percent to obtain Li_1.03Ni_0.88Co_0.09Mn_0.025Zr_0.005O₂And (4) firing the product.

(3) The sintered product is controlled to have an average particle size of 10 to 12 μm by a jet mill.

(4) And preparing slurry from the sinter and water according to 1000g/L, and washing with water at the temperature of 20 ℃ for 15 min.

(5) And (4) carrying out filter pressing on the slurry after washing, wherein the filter pressing time is 1 h.

(6) Drying the filter cake obtained by filter pressing for 20h at 200 ℃ in a nitrogen atmosphere to obtain LiNi_0.88Co_0.09Mn_0.025Zr_0.005O₂A lithium nickel cobalt composite oxide.

Example 4:

(1) mixing Ni_0.88Co_0.09Al_0.03(OH)₂、WO₃、Sr(OH)₂Sintering for 8 hours at 500 ℃ in air atmosphere to obtain Ni_{0.8 8}Co_0.09Al_0.025W_0.003Sr_0.002O。

(2) Mixing Ni with high-speed mixer according to the ratio of the molar weight of Li to the sum of the molar weights of Ni, Co, Al, W and Sr of 1.02_0.88Co_0.09Al_0.025W_0.003Sr_0.002O and Li₂CO₃Sintering the mixture at 740 ℃ for 10h in an atmosphere with oxygen content not less than 99.5% to obtain Li_1.01Ni_0.88Co_0.09Al_0.025W_0.003Sr_0.002O₂And (4) firing the product.

(3) The sintered product is controlled to have an average particle size of 10 to 12 μm by a jet mill.

(4) And (3) preparing slurry from the calcined product and water according to 800g/L, and washing with water at the temperature of 25 ℃ for 10 min.

(5) And (4) carrying out filter pressing on the slurry after washing, wherein the filter pressing time is 1 h.

(6) Drying the filter cake obtained by filter pressing for 25h at 200 ℃ in nitrogen atmosphere to obtain Li_0.99Ni_0.88Co_0.09Al_{0.02 5}W_0.003Sr_0.002O₂A lithium nickel cobalt composite oxide.

Example 5:

(1) mixing Ni_0.90Co_0.10(OH)₂、Sr(OH)₂Sintering for 8 hours at 500 ℃ in air atmosphere to obtain Ni_0.88Co_0.09Sr_0.03O。

(2) Mixing Ni with high-speed mixer according to the ratio of the molar weight of Li to the sum of the molar weights of Ni, Co and Sr being 1.06_0.88Co_0.09Sr_0.03O and LiOH, sintering the mixture at 730 ℃ in an atmosphere with oxygen content not less than 99.5 percent for 10 hours to obtain Li_1.05Ni_0.87Co_0.096Sr_0.034O₂And (4) firing the product.

(3) The sintered product is controlled to have an average particle size of 10 to 12 μm by a jet mill.

(4) And (3) preparing slurry from the calcined product and water according to 1200g/L, and washing with water at the temperature of 20 ℃ for 30 min.

(5) And (4) carrying out filter pressing on the slurry after washing, wherein the filter pressing time is 1 h.

(6) Drying the filter cake subjected to filter pressing for 25h at 200 ℃ in nitrogen atmosphere to obtain Li_1.01Ni_0.87Co_0.096Sr_0.034O₂A lithium nickel cobalt composite oxide.

Comparative example 1:

comparative example 1 differs from example 1 only in that the water washing conditions were changed to: the washing time is 10min, and other steps are unchanged.

Comparative example 2:

comparative example 2 differs from example 4 only in that the water washing conditions were changed to: the concentration of the water-washed slurry is 2000g/L, and other steps are unchanged.

Comparative example 3:

comparative example 3 differs from example 4 only in that the water washing conditions were changed to: the washing time is 50min, and other steps are unchanged.

The results of the performance test on the lithium nickel cobalt complex oxide prepared in the examples and comparative examples are shown in tables 1 and 2.

Test method

Preparation of a 2032 type button cell: adding the lithium-nickel-cobalt composite oxide, the conductive carbon SP and the PVDF into NMP according to the ratio of 96:2:2, stirring to obtain slurry, coating the slurry on an aluminum foil, drying to obtain a positive plate, and taking the lithium plate as a negative electrode to prepare the 2032 type button cell.

Preparation of 554065 type pouch cell: the positive electrode slurry was prepared by mixing lithium nickel cobalt complex oxide: conductive graphite KS-6: conductive carbon SP: PVDF (96.8: 1.5:0.5: 1.2) is mixed, and the negative electrode is prepared according to the following proportion of natural graphite: dispersant CMC: and (3) preparing a binder SBR (styrene butadiene rubber) at a ratio of 96:1:3 to obtain positive and negative electrode slurry, coating the positive and negative electrode slurry on a current collector, drying, tabletting and winding to obtain the 554065 type soft package battery.

And (3) impedance testing: electrochemical impedance testing of 2032 type button cells was performed at 25 ℃ at 100% SOC using a multichannel potentiostat (Bio-Logic, VMP3) at a frequency of 1MHz to 1 mHz.

DSC test: the 2032 button cell was cycled twice at 0.1C and charged to 4.3V, the charged cell was disassembled in a glove box, the lithium nickel cobalt complex oxide was recovered from the current collector after the remaining electrolyte was removed, 3-5 mg of lithium nickel cobalt complex oxide and electrolyte were loaded into a sealed stainless steel crucible and measured using DSC 200pc (netzsch) at a temperature scan rate of 1 ℃/min.

DSC heat generation relative value test: the DSC calorific value of the lithium nickel cobalt composite oxide obtained in the examples and comparative examples was a percentage of the maximum value in the test results.

And (4) SEM test: the surface morphology of the material was tested by Hitachi S4800 scanning electron microscopy.

C content and Li content test: weighing 5.0000 +/-0.0010G of sample, adding the sample into 40mL of deionized water, stirring and carrying out ultrasonic treatment for 5min, filtering the solution to a 100mL volumetric flask, carrying out constant volume, dividing a certain volume, using 0.02M HCl as a titrant, and carrying out titration on a potentiometric titrator (Mettlerlitoduo G20S type automatic potentiometric titrator) by adopting an equivalent point titration mode to obtain LiOH and Li₂CO₃The C content and the Li content are calculated.

Specific surface area test: the method comprises the steps of testing by using a microphone Tristar3020 type specific surface area and pore size analyzer, weighing a certain mass of lithium nickel cobalt composite oxide, completely degassing under the conditions of vacuum air suction and heating at 300 ℃, and calculating the specific surface area of particles by absorbing nitrogen after removing surface adsorbates.

0.1C first week gram capacity and 50 week cycle retention test: charging/discharging a 2032 type button cell battery at 25 ℃ and between 2.5V and 4.3V at 0.1C/0.1C, and testing the capacity of the first week gram; the 2032 type button cell is charged/discharged at 0.5C/1C at 45 deg.C and 2.5V-4.3V, and the cycle performance is tested.

60 ℃/30 day storage swell ratio test: the prepared pouch batteries were stored at 60 ℃ for 30 days, and the swelling rates of the pouch batteries were measured.

The results of the above performance tests are as follows:

TABLE 1 physical Properties of lithium Nickel cobalt Complex oxides obtained in examples and comparative examples

Name (R)	C content (wt%)	Li content (wt%)	Specific surface area (m)2/g)
				Example 1	0.018％	0.044％	1.39
Example 2	0.019％	0.043％	1.18
				Example 3	0.021％	0.050％	1.17
Example 4	0.019％	0.049％	1.24
				Example 5	0.024％	0.046％	1.43
Comparative example 1	0.044％	0.068％	0.96
				Comparative example 2	0.052％	0.079％	0.85
Comparative example 3	0.021％	0.028％	2.33

TABLE 2 comparison of electrochemical properties of lithium nickel cobalt complex oxides obtained in examples and comparative examples

As can be seen from fig. 1, the carbon content and the lithium content in the lithium compound on the surface of the lithium/nickel-cobalt composite oxide obtained by the preparation method of the present invention are relatively low, which results in a substantial decrease in impedance and is beneficial to the improvement of the rate capability of the material.

As can be seen from fig. 2, the lithium nickel cobalt composite oxide obtained by the preparation method of the present invention controls the carbon content and the lithium content in the surface lithium compound and the specific surface area of the lithium nickel cobalt composite oxide by controlling the water washing conditions, thereby effectively improving the thermal stability of the material and improving the safety performance of the material.

As can be seen from the comparison between fig. 3 and fig. 4, the structure of the lithium nickel cobalt composite oxide obtained by the preparation method of the present invention is relatively complete after high temperature cycle, and the internal part of the material particle is cracked after high temperature cycle of the lithium nickel cobalt composite oxide obtained by the comparative example 1, which indicates that the material of this embodiment has more stable structure at high temperature.

As can be seen from the data of the examples in tables 1 and 2, the carbon content and the lithium content in the surface lithium compound of the lithium nickel cobalt composite oxide prepared by the present invention are effectively controlled, the capacity and the cycle of the compound are significantly improved, and the thermal stability and the storage performance of the material are improved.

As can be seen from comparison of the data of example 1 and comparative example 1, too short washing time leads to a significant increase in the carbon content and lithium content in the lithium compound on the surface of the material, and side reactions with the electrolyte during the cycle are accelerated, resulting in poor thermal stability.

As can be seen from the comparison of the data of example 1 and comparative example 2, the washing concentration is too high, which results in the significant increase of the carbon content and lithium content in the lithium compound on the surface of the material, the electrochemical performance is deteriorated, and the heat generation is increased.

As can be seen from the comparison of the data of example 1 and comparative example 3, the excessive washing time leads to the excessive specific surface area of the material, the lithium in the material is extracted, the capacity of the material is reduced from 212.5mAh/g to 204.1mAh/g, and the cycle retention rate at 45 ℃ is reduced from 95.3% to 83.2%.

The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.