CN109888271B - Positive electrode active material and preparation method thereof, positive electrode sheet and lithium ion battery - Google Patents

Abstract

The present invention provides a positive electrode active material and a preparation method thereof, a positive electrode sheet and a lithium ion battery. The positive electrode active material includes: a crystal formed of Li _α [(Ni _x Co _y ) _(1-β) A _β ]O _z , wherein the A includes at least one of aluminum, boron, magnesium, titanium, and zirconium , 0.95≤α≤1.1, 0<β≤0.2, 0.75≤x≤0.95, 0.03≤y≤0.25, 1.9≤z≤2.1. The positive electrode active material has strong stability, can significantly improve the discharge capacity and cycle life of the lithium ion battery, and has low cost and easy industrialization.

Description

Positive electrode active material and preparation method thereof, positive electrode sheet and lithium ion battery

technical field

The present invention relates to the technical field of materials, in particular, to a positive electrode active material and a preparation method thereof, a positive electrode sheet and a lithium ion battery.

Background technique

Portable wireless electronic products are developing rapidly, and the demand for miniaturization, light weight and high energy density of their power sources is increasing day by day. In addition, in order to protect the environment, with the development and use of electric vehicles and hybrid vehicles, the demand for large and medium-sized lithium-ion batteries with good energy storage performance is also increasing. Therefore, the development of lithium-ion batteries with large capacity and long life is one of the technical problems to be solved urgently in related technologies. At present, in high-energy lithium-ion batteries, positive active materials include LiMn ₂ O ₄ with spinel structure, LiMnO ₂ with zigzag structure, LiCoO ₂ and LiNiO ₂ with rock salt structure, etc. Among them, LiNiO ₂ can make Lithium-ion batteries have high discharge capacity, so they are called cathode active materials that are widely studied at present. However, due to the poor stability of this material during charging, its cycle performance is poor, so it cannot fully meet the current demand for lithium-ion batteries. Requirements for the use of positive electrode active materials for ion batteries.

Thus, the related technologies of the existing cathode active materials still need to be improved.

SUMMARY OF THE INVENTION

The present invention aims to solve one of the technical problems in the related art at least to a certain extent. Therefore, an object of the present invention is to provide a positive electrode active material with strong stability, which can significantly improve the discharge capacity and cycle life of lithium ion batteries, lower cost, or be easy to industrialize.

In one aspect of the present invention, the present invention provides a positive electrode active material for a lithium ion battery. According to an embodiment of the present invention, the positive electrode active material includes: a _crystal formed of _Liα [( _NixCoy ) _{(1-β) Aβ ]} Oz, wherein the A includes aluminum, boron, magnesium, titanium and at least one of zirconium, 0.95≤α≤1.1, 0<β≤0.2, 0.75≤x≤0.95, 0.03≤y≤0.25, 1.9≤z≤2.1. The inventors found that the positive electrode active material has strong stability, can significantly improve the discharge capacity and cycle life of the lithium ion battery, and has low cost and easy industrialization.

According to an embodiment of the present invention, the A includes at least two of the aluminum, the boron, the magnesium, the titanium, and the zirconium.

According to an embodiment of the present invention, the A includes the aluminum, the boron, the magnesium, the titanium, and the zirconium.

According to an embodiment of the present invention, based on the total mass of the positive electrode active material, the A satisfies at least one of the following conditions: the mass percentage of the aluminum is greater than 0 and less than or equal to 1%; the mass of the boron The mass percentage of the magnesium is greater than 0 and less than or equal to 0.35%; the mass percentage of the magnesium is greater than 0 and less than or equal to 0.35%; the mass percentage of the titanium is greater than 0 and less than or equal to 0.5%; the zirconium The mass percentage is greater than 0 and less than or equal to 0.4%.

According to the embodiment of the present invention, α=1, β=0.1, x=0.9, y=0.1, z=2, and based on the total mass of the positive electrode active material, the mass percentage of the aluminum is 0.5%, The mass percentage content of boron is 0.02%, the mass percentage content of magnesium is 0.05%, the mass percentage content of titanium is 0.25%, and the mass percentage content of zirconium is 0.25%.

In another aspect of the present invention, the present invention provides a method for preparing the aforementioned positive electrode active material. According to an embodiment of the present invention, the method includes: mixing Ni _a Co _b (OH) ₂ and a lithium source to obtain a first premix, wherein a+b=1, and a>0, b>0; The first premix and the dopant are mixed to obtain a second premix, wherein the dopant contains the aforementioned A, and the second premix is carried out in an oxygen atmosphere After the calcination treatment, the temperature is naturally lowered to obtain the positive electrode active material. The inventors found that the method is simple, convenient, easy to implement, easy to industrialize production, and can effectively prepare a positive electrode active material with strong stability and significantly improved discharge capacity and cycle life of lithium ion batteries.

According to an embodiment of the present invention, the method satisfies at least one of the following conditions: the dopant includes Al(OH) ₃ , B ₂ O ₃ , Mg(OH) ₂ , TiO ₂ and Zr(OH) ₄ . at least one; the lithium source includes at least one of LiOH, LiNO ₃ , Li ₂ CO ₃ , Li ₃ PO ₄ , Li ₂ C ₂ O ₄ and CH ₃ COOLi; the Ni _a Co _b (OH) ₂ and the lithium source are mixed according to a molar ratio of 1:(1.005-1.05); the first premix and the dopant are mixed according to a weight ratio of 100:(1.1379-1.7747) mixed; at least one of the first premix and the second premix is a solid premix; the temperature of the calcination treatment is 500°C to 1000°C; the time of the calcination treatment is 5h～ 30h.

According to an embodiment of the present invention, the lithium source is LiOH.

According to an embodiment of the present invention, the temperature of the calcination treatment is 500°C to 850°C.

According to the embodiment of the present invention, the time of the calcination treatment is 4h-20h.

According to an embodiment of the present invention, after obtaining the positive electrode active material, the method further includes: subjecting the positive electrode active material to pulverization treatment and screening treatment, and The particle size of the positive electrode active material is not greater than 38 μm.

In yet another aspect of the present invention, the present invention provides a positive electrode sheet for a lithium ion battery. According to an embodiment of the present invention, the positive electrode sheet includes the aforementioned positive electrode active material. The inventors found that the positive electrode sheet can significantly improve the discharge capacity and cycle life of the lithium ion battery, the cost is low, the industrialization is easy, and it has all the features and advantages of the positive electrode active material described above, so it is not too much here. Repeat.

In yet another aspect of the present invention, the present invention provides a lithium ion battery. According to an embodiment of the present invention, the lithium ion battery includes: a negative electrode; a positive electrode, the positive electrode comprising the aforementioned positive electrode active material or the aforementioned positive electrode sheet; a battery separator; and an electrolyte. The inventors found that the lithium-ion battery has high discharge capacity and cycle life, low cost, easy industrialization, and has all the features and advantages of the aforementioned positive electrode active material or the aforementioned positive electrode sheet, which will not be discussed here. More to say.

Description of drawings

FIG. 1 shows a schematic flowchart of a method for preparing a positive electrode active material according to an embodiment of the present invention.

FIG. 2 shows a schematic flowchart of a method for preparing a positive electrode active material according to another embodiment of the present invention.

FIG. 3 shows a first charge-discharge curve diagram of the positive electrode active material of Example 1 of the present invention.

FIG. 4 shows a cycle charge-discharge curve diagram of the positive electrode active material of Example 1 of the present invention.

FIG. 5 is a graph showing the first charge-discharge curve of the positive electrode active material of Comparative Example 1 of the present invention.

FIG. 6 shows a cyclic charge-discharge graph of the positive electrode active material of Comparative Example 1 of the present invention.

7 shows the cycle capacity retention test results of the positive electrode active materials of Example 1 and Comparative Example 1 of the present invention.

Detailed ways

Embodiments of the present invention are described in detail below. The embodiments described below are exemplary, only for explaining the present invention, and should not be construed as limiting the present invention. If no specific technique or condition is indicated in the examples, the technique or condition described in the literature in the field or the product specification is used. The reagents or instruments used without the manufacturer's indication are conventional products that can be obtained from the market.

In one aspect of the present invention, the present invention provides a positive electrode active material for a lithium ion battery. According to an embodiment of the present invention, the positive electrode active material includes: a _crystal formed of _Liα [( _NixCoy ) _{(1-β) Aβ ]} Oz, wherein the A includes aluminum, boron, magnesium, titanium and at least one of zirconium, 0.95≤α≤1.1, 0<β≤0.2, 0.75≤x≤0.95, 0.03≤y≤0.25, 1.9≤z≤2.1. The inventors found that the positive electrode active material has strong stability, can significantly improve the discharge capacity and cycle life of the lithium ion battery, and has low cost and easy industrialization.

According to the embodiments of the present invention, the inventors have conducted a large number of careful investigations and experimental verifications on the components of the positive electrode active material and found that the positive electrode active material with the above-mentioned components has aluminum, boron, magnesium, titanium, At least one of zirconium can make the stability of the material strong, so that when the positive electrode active material is applied to a lithium ion battery, it is beneficial for lithium ions to move back and forth between the positive electrode and the negative electrode, thereby making the discharge capacity of the lithium ion battery and the negative electrode. Cycle life is significantly improved.

According to the embodiments of the present invention, the inventor found after extensive research that the aforementioned aluminum can improve the capacity of the positive electrode material; the aforementioned boron can improve the density of the material, thereby stabilizing the material structure; the aforementioned magnesium can Improve the cycle retention rate of the cathode material; the aforementioned titanium and zirconium can stabilize the structural stability of the cathode material. Therefore, the presence of at least one of aluminum, boron, magnesium, titanium, and zirconium in the positive electrode active material can make the material more stable, so that when the positive electrode active material is applied to a lithium ion battery, it is beneficial for the The back-and-forth movement between the positive electrode and the negative electrode can significantly improve the discharge capacity and cycle life of the lithium-ion battery.

According to the embodiment of the present invention, further, the positive electrode material may not only include at least one of aluminum, boron, magnesium, titanium, and zirconium, but also two or more of the five elements mentioned above. Can be used in combination. For example, A in the positive electrode active material can be aluminum and boron, or boron and zirconium, or aluminum, magnesium, and titanium, etc. The above five elements can be combined flexibly. In some embodiments of the present invention, A in the positive active material may be aluminum and magnesium; aluminum, magnesium and boron; titanium, aluminum and magnesium; zirconium, aluminum and magnesium; titanium, aluminum, magnesium and boron; Aluminum, magnesium and boron; zirconium, titanium, aluminum and boron; zirconium, titanium, aluminum, magnesium and boron, etc. As a result, the above elements cooperate with each other to play a synergistic role. For example, aluminum and magnesium can cooperate with each other to improve capacity and cycle retention, zirconium, titanium and aluminum can cooperate with each other to improve structural stability, zirconium, titanium, aluminum, magnesium and Boron can cooperate with each other to stabilize material properties and improve capacity and cycle retention rate, etc., which can further make the material more stable, so that when the positive active material is applied to lithium ion batteries, it is further beneficial for lithium ions to travel between the positive electrode and the negative electrode. mobile, which can further significantly improve the discharge capacity and cycle life of lithium-ion batteries.

According to an embodiment of the present invention, further, the A includes the aluminum, the boron, the magnesium, the titanium, and the zirconium. Therefore, the positive electrode active material contains all the above-mentioned elements, and the five elements of aluminum, boron, magnesium, titanium and zirconium play a synergistic effect. For example, aluminum can improve the capacity of the positive electrode material, and boron can improve the The compactness of the material, zirconium and titanium can improve the structural stability of the material, and magnesium can improve the cycle performance of the material, so that each component cooperates with each other, which can further make the material more stable, so that the positive electrode active material can be used in applications. When used in lithium ion batteries, it is further beneficial for lithium ions to move back and forth between the positive electrode and the negative electrode, which can further significantly improve the discharge capacity and cycle life of the lithium ion battery.

According to an embodiment of the present invention, in the chemical formula Li _α [(Ni _x Co _y ) _(1-β) A _β ]O _z of the positive electrode active material, the ranges of each parameter are 0.95≤α≤1.1, 0<β≤ 0.2, 0.75≤x≤0.95, 0.03≤y≤0.25, 1.9≤z≤2.1. In some embodiments of the present invention, α may be specifically 0.95, 0.98, 1, 1.02, 1.05, or 1.1, etc.; ; x can be specifically 0.75, 0.78, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, or 0.95, etc.; y can be specifically 0.03, 0.05, 0.08, 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22 Or 0.25, etc.; z can be specifically 1.9, 1.95, 2, 2.05 or 2.1, etc. Therefore, by adjusting the crystal structure of the positive electrode active material, the coordination between various atoms can be better, so that the A, Ni and Co can cooperate better with each other, and the various atoms can cooperate better with each other. The ratio of the positive electrode active material is an optimal ratio, thereby further enhancing the stability of the positive electrode active material crystal. When the positive electrode active material is applied to a lithium ion battery, it is further beneficial for lithium ions to move back and forth between the positive electrode and the negative electrode, which can further make The discharge capacity and cycle life of lithium-ion batteries are significantly improved; moreover, the contents of the above parameters α, β, x, y, and z are all suitable. If the content of aluminum is too high, the capacity of the positive active material will be reduced; If the content is too low, the cycle retention rate will be reduced; if the content of zirconium and titanium is too low, the structural stability of the positive electrode active material will be reduced; if the content of boron is too low, the compactness of the positive electrode active material will be poor.

According to an embodiment of the present invention, further, in the positive electrode active material, based on the total mass of the positive electrode active material, the mass percentage of the aluminum may be greater than 0 and less than or equal to 1%, specifically, may be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%, etc.; the mass percentage of boron can be greater than 0 and less than or equal to 0.35%, specifically ground, can be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3% or 0.35%, etc.; the mass percentage of magnesium can be greater than 0 and less than or equal to 0.35%, specifically, can be 0.05 %, 0.1%, 0.15%, 0.2%, 0.25%, 0.3% or 0.35%, etc.; the mass percentage of titanium can be greater than 0 and less than or equal to 0.5%, specifically, can be 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, or 0.5%, etc.; the mass percentage content of zirconium may be greater than 0 and less than or equal to 0.4%, specifically, may be 0.05 %, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35% or 0.4%, etc. Therefore, the inventors adjusted the ratio among the aluminum, the boron, the magnesium, the titanium, and the zirconium in the crystal structure of the positive electrode active material, so that the aluminum, the The boron, the magnesium, the titanium, and the zirconium are well coordinated with each other, the ratios between the various atoms are all optimal ratios, and the content of the various atoms in the positive electrode active material is also relatively high. Therefore, the stability of the positive electrode active material crystal is further enhanced. When the positive electrode active material is applied to a lithium ion battery, it is further conducive to the reciprocating movement of lithium ions between the positive electrode and the negative electrode, which can further increase the discharge capacity and the negative electrode of the lithium ion battery. The cycle life is significantly improved; moreover, the content of the above five elements, namely aluminum, boron, magnesium, titanium, and zirconium are all suitable, neither too high nor too low, if the aluminum content is too high, it will reduce the positive electrode The capacity of the active material; if the content of magnesium is too low, the cycle retention rate will be reduced; if the content of zirconium and titanium is too low, the structural stability of the positive active material will be reduced; if the content of boron is too low, the capacity of the positive active material will be reduced. The compactness is poor.

According to the embodiments of the present invention, further, the inventors have found, after a lot of careful investigation and experimental verification, that in the positive electrode active material of the present invention, when α=1, β=0.1, x=0.9, y= 0.1, z=2, and based on the total mass of the positive active material, the mass percentage of the aluminum is 0.5%, the mass percentage of the boron is 0.02%, and the mass percentage of the magnesium is 0.05%, the mass percentage of titanium is 0.25%, and the mass percentage of zirconium is 0.25%, the atoms in the positive electrode active material cooperate with each other better, thereby further enhancing the positive electrode activity The stability of the material crystal, when the positive active material is applied to a lithium ion battery, further facilitates the reciprocating movement of lithium ions between the positive electrode and the negative electrode, which can further significantly improve the discharge capacity and cycle life of the lithium ion battery.

In another aspect of the present invention, the present invention provides a method for preparing the aforementioned positive electrode active material. According to an embodiment of the present invention, referring to FIG. 1, the method includes the following steps:

S100: Mix Ni _a Co _b (OH) ₂ and a lithium source to obtain a first premix, wherein a+b=1, and a>0, b>0.

According to an embodiment of the present invention, in the Ni _a Co _b (OH) ₂ , as long as a+b=1 is satisfied, and a>0, b>0, the ratio between a and b is not particularly limited. Restriction, for example, in some embodiments of the present invention, the value of a may be 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, or 0.1, etc.; correspondingly, the value of b may be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, etc. As a result, the material sources are wide, easily available, and the cost is low, and a positive electrode active material with strong stability and significantly improving the discharge capacity and cycle life of the lithium ion battery can be effectively prepared.

According to an embodiment of the present invention, the lithium source may include LiOH, LiNO ₃ , Li ₂ CO ₃ , Li ₃ PO ₄ , Li ₂ C ₂ O ₄ , CH ₃ COOLi and the like. In some embodiments of the present invention, the lithium source may be specifically LiOH. As a result, the source of materials is wide, easy to obtain, and the cost is low. In the subsequent steps, there are fewer by-products, and too much gas will not be generated to affect the subsequent reaction, which is beneficial to the formation of the positive electrode active material, and can be further effectively prepared. A positive electrode active material with strong stability is obtained, which can further significantly improve the discharge capacity and cycle life of the lithium ion battery.

According to an embodiment of the present invention, the Ni _a Co _b (OH) ₂ and the lithium source are mixed in a molar ratio of 1:(1.005-1.05). In some embodiments of the present invention, the Ni _a Co _b (OH) ₂ and the lithium source are according to 1:1.005, 1:1.01, 1:1.015, 1:1.02, 1:1.025, 1:1.03, 1:1.035, 1:1.04, 1:1.045 or 1:1.05 molar ratios were mixed. Therefore, the ratio between the Ni _a Co _b (OH) ₂ and the lithium source is good, and the content of the total alkali (ie LiOH, Li ₂ CO ₃ ) on the surface of the positive electrode active material is not too high, and It will not be too low to lead to a lower capacity of the positive electrode active material, which is beneficial to the formation of the positive electrode active material, and can further effectively prepare a positive electrode active material with strong stability and can significantly improve the discharge capacity and cycle life of the lithium-ion battery. .

According to the embodiment of the present invention, the method for mixing Ni _a Co _b (OH) ₂ and the lithium source is dry mixing, which can make the ratio between the Ni _a Co _b (OH) ₂ and the lithium source Accurate, preventing the actual addition of lithium in the first premix due to dissolving the lithium source in the solvent.

S200: Mix the first premix and the dopant to obtain a second premix, wherein the dopant contains the aforementioned A, and make the second premix in an oxygen atmosphere After being calcined in the medium, the temperature is naturally lowered, so as to obtain the positive electrode active material.

According to the embodiment of the present invention, the material, type, and action mechanism of the A are the same as those described above, and will not be repeated here.

According to an embodiment of the present invention, the dopant includes at least one of Al(OH) ₃ , B ₂ O ₃ , Mg(OH) ₂ , TiO ₂ and Zr(OH) ₄ . As a result, the source of materials is wide, easy to obtain, and the cost is low, which is conducive to the formation of positive electrode active materials, and can further effectively prepare a positive electrode active material with strong stability, which can significantly improve the discharge capacity and cycle life of lithium-ion batteries.

According to an embodiment of the present invention, the first premix and the dopant are mixed in a weight ratio of 100:(1.1379-1.7747). In some embodiments of the present invention, the weight ratio of the first premix and the dopant may be 100:1.7747, 100:1.4716, or 100:1.4410, or the like. Therefore, it is beneficial to the formation of the positive electrode active material. In the obtained positive electrode active material, the coordination between various atoms is better, so that the A, Ni, and Co can be better coordinated with each other, and the various atoms are in good coordination. The ratio between the two is an optimal ratio, thereby further enhancing the stability of the positive electrode active material crystal. When the positive electrode active material is applied to a lithium ion battery, it is further beneficial for lithium ions to move back and forth between the positive electrode and the negative electrode, which can further A cathode active material that can significantly improve the discharge capacity and cycle life of lithium-ion batteries is obtained.

According to the embodiment of the present invention, the method for mixing the first premix and the dopant is dry mixing, which can make the ratio between the first premix and the dopant accurate, and prevent the After dissolving the first premix and the dopant in the solvent, there is an error between the actual addition amount of each material and the theoretical addition amount.

According to an embodiment of the present invention, the temperature of the calcination treatment is 500°C to 1000°C. In some embodiments of the present invention, the temperature of the calcination treatment may be 500°C, 600°C, 700°C, 800°C, 900°C, or 1000°C, and the like. Further, the temperature of the calcination treatment is 500°C to 850°C. As a result, the operation is simple, the reaction conditions are mild, and the industrial production is easy, which is beneficial to the formation of the positive electrode active material, and can further effectively prepare a positive electrode active material with strong stability, which can significantly improve the discharge capacity and cycle life of the lithium-ion battery; Moreover, the calcination temperature is neither too high to cause waste of resources, nor too low to cause the reaction to proceed slowly but with low production efficiency.

According to the embodiment of the present invention, the time of the calcination treatment is 5h-30h. In some embodiments of the present invention, the temperature of the calcination treatment may be 5h, 10h, 15h, 20h, 25h, or 30h, or the like. Further, the temperature of the calcination treatment is 4h-20h. Therefore, the operation is simple, the industrial production is easy, the formation of the positive electrode active material is favorable, and the positive electrode active material with strong stability can be further effectively prepared, and the discharge capacity and cycle life of the lithium ion battery can be further improved. The time will not be too long to lead to lower production efficiency, nor will it be too short to lead to the formation of positive active materials, although the reaction can be achieved, although it can achieve strong stability, the discharge capacity and cycle life of lithium-ion batteries can be significantly improved. However, other by-products will be contained in the positive electrode active material, which will lead to the reduction of effective components after the positive electrode is prepared.

In other embodiments of the present invention, referring to FIG. 2 , after obtaining the positive electrode active material, the method further includes the following steps:

S300: Perform pulverization and screening treatment on the positive electrode active material, and make the particle size of the positive electrode active material after the pulverization treatment and the screening treatment not greater than 38 μm.

According to the embodiment of the present invention, the specific conditions of the pulverizing treatment and the sieving treatment are not particularly limited, as long as the particle size of the positive electrode active material after the pulverizing treatment and the sieving treatment is not greater than 38 μm, that is, Can. In some embodiments of the present invention, a 400-mesh sieve can be used for sieving treatment. Specifically, the particle size of the positive electrode active material obtained through sieving treatment can be 30μm, 35μm or 38μm etc. As a result, impurities generated in the aforementioned steps and positive electrode active materials with large particle sizes that cannot be pulverized can be removed, which is beneficial to subsequent applications, and the positive electrode active materials with the above-mentioned particle sizes can further increase the discharge capacity of the lithium-ion battery. and cycle life is significantly improved.

In yet another aspect of the present invention, the present invention provides a positive electrode sheet for a lithium ion battery. According to an embodiment of the present invention, the positive electrode sheet includes the aforementioned positive electrode active material. The inventors found that the positive electrode sheet can significantly improve the discharge capacity and cycle life of the lithium ion battery, the cost is low, the industrialization is easy, and it has all the features and advantages of the positive electrode active material described above, so it is not too much here. Repeat.

According to the embodiments of the present invention, in addition to the positive electrode active material described above, those skilled in the art can understand that the positive electrode sheet may also include other components of conventional positive electrode sheets, such as a substrate, a conductive agent, a binder, and a thickening agent. agents, etc., which will not be repeated here.

In yet another aspect of the present invention, the present invention provides a lithium ion battery. According to an embodiment of the present invention, the lithium ion battery includes: a negative electrode; a positive electrode, the positive electrode comprising the aforementioned positive electrode active material or the aforementioned positive electrode sheet; a battery separator; and an electrolyte. The inventors found that the lithium-ion battery has high discharge capacity and cycle life, low cost, easy industrialization, and has all the features and advantages of the aforementioned positive electrode active material or the aforementioned positive electrode sheet, which will not be discussed here. More to say.

According to the embodiments of the present invention, in addition to the aforementioned structures, the shapes, structures, and manufacturing processes of other structures and components of the lithium-ion battery can be conventional shapes, structures, and manufacturing processes, which will not be repeated here. .

Embodiments of the present invention are described in detail below.

Example 1

Dry mixing Ni _0.9 Co _0.1 (OH) ₂ and LiOH according to a molar ratio of 1:1.02 to obtain a first premix; 100 parts by weight of the first premix, Al(OH) ₃ , B ₂ O ₃ , Mg(OH) ₂ , TiO ₂ and Zr(OH) ₄ in a total of 1.7747 parts by weight for dry mixing (wherein, Al(OH) ₃ is 1.0508 parts by weight; B ₂ O ₃ is 0.0163 parts by weight; Mg(OH) ₂ 0.0872 parts by weight; TiO ₂ is 0.3032 parts by weight; Zr(OH) ₄ is 0.3172 parts by weight) to obtain a second premix, and the second premix is carried out in an oxygen atmosphere at 750° C. After calcining for 30 hours, the temperature is naturally lowered to obtain a positive electrode active material, and the positive electrode active material is subjected to pulverization treatment and screening treatment, so that the particle size of the positive electrode active material after pulverization treatment and screening treatment is not greater than 38 μm.

Example 2

Dry mixing Ni _0.9 Co _0.1 (OH) ₂ and LiOH according to a molar ratio of 1:1.02 to obtain a first premix; 100 parts by weight of the first premix, Al(OH) ₃ , B ₂ O ₃ , Mg(OH) ₂ and Zr(OH) ₄ were dry mixed in a total of 1.4716 parts by weight (wherein, Al(OH) ₃ was 1.0508 parts by weight; B ₂ O ₃ was 0.0163 parts by weight; Mg(OH) ₂ was 0.0872 parts by weight parts; Zr(OH) ₄ is 0.3172 parts by weight) to obtain a second premix, and the second premix is calcined in an oxygen atmosphere at 750° C. for 30 hours and then naturally cooled to obtain a positive electrode activity The positive electrode active material is subjected to pulverization treatment and screening treatment, so that the particle size of the positive electrode active material after pulverization treatment and screening treatment is not greater than 38 μm.

Example 3

Dry mixing Ni _0.9 Co _0.1 (OH) ₂ and LiOH according to a molar ratio of 1:1.02 to obtain a first premix; 100 parts by weight of the first premix, Al(OH) ₃ , B ₂ O ₃ , 1.4410 parts by weight of Mg(OH) ₂ were dry mixed (wherein, Al(OH) ₃ was 1.3117 parts by weight; B ₂ O ₃ was 0.0204 parts by weight; Mg(OH) ₂ was 0.1089 parts by weight) to obtain the second premix, and the second premix is calcined in an oxygen atmosphere at 750°C for 30 hours and then cooled down naturally to obtain a positive electrode active material, and the positive electrode active material is crushed and sieved to make The particle size of the positive electrode active material after the pulverization treatment and the sieving treatment is not greater than 38 μm.

Comparative Example 1

Dry mixing Ni _0.9 Co _0.1 (OH) ₂ and LiOH according to a molar ratio of 1:1.02 to obtain a first premix; the first premix is calcined in an oxygen atmosphere at 750° C. After 30 hours of treatment, the temperature is naturally lowered to obtain a positive electrode active material, and the positive electrode active material is subjected to pulverization treatment and screening treatment, so that the particle size of the positive electrode active material after pulverization treatment and screening treatment is not greater than 38 μm.

The experimental method is as follows:

Button battery production: using the positive electrode active materials produced in the above-mentioned Examples 1 to 3 and Comparative Example 1, respectively, the positive electrode active materials, carbon black, PVDF (polyvinylidene fluoride) with a mass ratio of 95:2.5:2.5:5 were used. ) and NMP (N-methylpyrrolidone) were mixed uniformly to obtain a slurry. The slurry was coated on an aluminum foil with a thickness of 20-40um, vacuum-dried and rolled to make a positive electrode sheet, the metal lithium sheet was used as the negative electrode, and the electrolyte ratio was 1.15M LiPF ₆ /EC:DMC (volume ratio 1:1vol%), and assemble the button battery.

The blue battery test system was used to test at 45 °C, and the test voltage range was 3V ~ 4.5V; picture).

FIG. 3 and FIG. 5 , wherein, FIG. 3 is the first charge and discharge curve diagram of Example 1; FIG. 5 is the first charge and discharge curve diagram of Comparative Example 1. Figure 4 and Figure 6, wherein, Figure 4 is the charge-discharge cycle test curve of Example 1; Figure 6 is the charge-discharge cycle test curve of Comparative Example 1; Figure 7 is the 30-cycle cycle of Example 1 and Comparative Example 1 Capacity retention test results.

In Figures 4 and 6, a is the charge-discharge cycle curve of the positive electrode active material in the first cycle; b is the charge-discharge cycle curve of the positive electrode active material in the 10th cycle; c is the charge-discharge cycle of the positive electrode active material in the 20th cycle Graph; d is the 30th cycle charge-discharge cycle graph of the positive electrode active material. It should be noted that, in FIG. 4 , the charge-discharge cycle graphs of the positive electrode active material are basically overlapped (as shown in a and b).

Analysis of results:

It can be seen from Figure 3 and Figure 5 that the positive electrode active material of Example 1 of the present invention has a higher specific discharge capacity, and its first discharge specific capacity is as high as 213mAh/g; while the first discharge capacity of the positive electrode active material of Comparative Example 1 is only 203mAh. /g.

It can be seen from FIG. 4 , FIG. 6 and FIG. 7 that the positive electrode active material of Example 1 of the present invention can significantly improve the cycle life of the lithium ion battery. After 30 cycles of charge and discharge, the capacity retention rate was as high as 98.41%; while the positive active material in Comparative Example 1 only had a capacity retention rate of 50.47% after 30 cycles of charge and discharge.

In addition, the charge-discharge cycle test curves of Examples 2 and 3 are similar to those of Example 1, and their experimental results are better than those of Comparative Example 1.

In the description of the present invention, it should be understood that the terms "first" and "second" are only used for description purposes, and cannot be interpreted as indicating or implying relative importance or the number of indicated technical features. Thus, a feature defined as "first" or "second" may expressly or implicitly include one or more of that feature. In the description of the present invention, "plurality" means two or more, unless otherwise expressly and specifically defined.

In the description of this specification, description with reference to the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples", etc., mean specific features described in connection with the embodiment or example , structure, material or feature is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine and combine the different embodiments or examples described in this specification, as well as the features of the different embodiments or examples, without conflicting each other.

Although the embodiments of the present invention have been shown and described above, it should be understood that the above-mentioned embodiments are exemplary and should not be construed as limiting the present invention. Embodiments are subject to variations, modifications, substitutions and variations.

Claims (11)

1. A positive electrode active material for a lithium ion battery, comprising:

from Li_α[(Ni_xCo_y)_(1-β)A_β]O_zThe crystals that are formed are,

wherein, A comprises aluminum, boron, magnesium, titanium and zirconium, alpha is more than or equal to 0.95 and less than or equal to 1.1, beta is more than 0 and less than or equal to 0.2, x is more than or equal to 0.75 and less than or equal to 0.95, y is more than or equal to 0.03 and less than or equal to 0.25, and z is more than or equal to 1.9 and less than or equal to 2.1.

2. The positive electrode active material according to claim 1, wherein a satisfies at least one of the following conditions based on a total mass of the positive electrode active material:

the mass percentage of the aluminum is more than 0 and less than or equal to 1 percent;

the mass percentage of boron is more than 0 and less than or equal to 0.35 percent;

the mass percentage of the magnesium is more than 0 and less than or equal to 0.35 percent;

the mass percentage of the titanium is more than 0 and less than or equal to 0.5 percent;

the mass percentage of the zirconium is more than 0 and less than or equal to 0.4 percent.

3. The positive electrode active material according to claim 1, wherein α ═ 1, β ═ 0.1, x ═ 0.9, y ═ 0.1, and z ═ 2, and based on the total mass of the positive electrode active material, the mass percentage of aluminum is 0.5%, the mass percentage of boron is 0.02%, the mass percentage of magnesium is 0.05%, the mass percentage of titanium is 0.25%, and the mass percentage of zirconium is 0.25%.

4. A method for producing the positive electrode active material according to any one of claims 1 to 3, comprising:

mixing Ni_aCo_b(OH)₂And a lithium source to obtain a first premix, wherein a + b is 1, and a > 0, and b > 0;

and mixing the first premix and a doping agent to obtain a second premix, wherein the doping agent contains the A in any one of claims 1-3, and calcining the second premix in an oxygen atmosphere and then naturally cooling to obtain the cathode active material.

5. The method of claim 4, wherein at least one of the following conditions is satisfied:

the dopant includes Al (OH)₃、B₂O₃、Mg(OH)₂、TiO₂And Zr (OH)₄At least one of;

the lithium source comprises LiOH and LiNO₃、Li₂CO₃、Li₃PO₄、Li₂C₂O₄And CH₃At least one of COOLi;

the Ni_aCo_b(OH)₂And the lithium source is according to 1: (1.005-1.05) in a molar ratio;

the first pre-mixture and the dopant are mixed as per 100: (1.1379-1.7747) in parts by weight;

at least one of the first pre-mixture and the second pre-mixture is a solid pre-mixture;

the temperature of the calcination treatment is 500-1000 ℃;

the time of the calcination treatment is 5-30 h.

6. The method of claim 5, wherein the lithium source is LiOH.

7. The method according to claim 5, characterized in that the temperature of the calcination treatment is between 500 ℃ and 850 ℃.

8. The method according to claim 5, wherein the calcination treatment is carried out for a time ranging from 4 to 20 hours.

9. The method according to claim 4, further comprising, after obtaining the positive electrode active material:

subjecting the positive electrode active material to a pulverization treatment and a sieving treatment, and making the particle size of the positive electrode active material after the pulverization treatment and the sieving treatment not more than 38 [ mu ] m.

10. A positive electrode sheet for a lithium ion battery, comprising the positive electrode active material according to any one of claims 1 to 3.

11. A lithium ion battery, comprising:

a negative electrode;

a positive electrode comprising the positive electrode active material according to any one of claims 1 to 3 or the positive electrode sheet according to claim 10;

a battery separator; and

and (3) an electrolyte.

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