CN115020673A - Modified nickel-cobalt-manganese ternary positive electrode material, its preparation method and lithium ion battery - Google Patents

Abstract

The invention provides a modified nickel-cobalt-manganese ternary positive electrode material, a preparation method thereof and a lithium ion battery. The preparation method includes: mixing an optional sodium source, a zinc source, a zirconium source, and a phosphorus source with a first solvent, and after pre-sintering treatment, a pre-sintered product is obtained, and the chemical formula of the pre-sintered product is Na _{2 (1-x)} Zn _x Zr ₄ (PO ₄ ) ₆ , wherein x is 0.5-1; the pre-sintered product is mixed with lithium source, nickel source, cobalt source, manganese source and the second solvent, and after calcination treatment, a modified nickel-cobalt-manganese ternary is obtained Positive electrode material; the molar ratio of lithium source, nickel source, cobalt source and manganese source is 1.012:a:b:c, where 0.5≤a≤0.8, 0.1≤b≤0.2, a+b＜1, c=1‑a ‑b. The modified nickel-cobalt-manganese ternary positive electrode material prepared by the above preparation method has high reactivity and structural stability, and is especially suitable for improving the high temperature cycle stability of lithium ion batteries.

Description

Modified nickel-cobalt-manganese ternary positive electrode material, its preparation method and lithium ion battery

technical field

The invention relates to the technical field of preparation of positive electrode materials, in particular to a modified nickel-cobalt-manganese ternary positive electrode material, a preparation method thereof and a lithium ion battery.

Background technique

As human society attaches great importance to energy and environmental protection issues, lithium-ion batteries have developed rapidly in recent years, and are widely used in mobile phones, computers, new energy vehicles and energy storage. In particular, driven by the explosive growth of the new energy vehicle market, it has driven the rapid development of lithium batteries, industry competition has become increasingly fierce, and local battery giants have gradually risen. Downstream new energy vehicles have entered a period of rapid growth. Factors such as the decline of subsidies and the improvement of technical performance requirements have intensified the survival of the fittest in the battery industry, and the market concentration has increased. In such a highly competitive environment, it is particularly important to improve the cost-effectiveness of materials. High capacity, long cycle, safety and stability are the main development directions of lithium-ion batteries in the future.

与Li⁺半径

非常接近，容易造成Li/Ni阳离子混排，导致锂离子电池的克容量和循环性能降低；其次，在首次充放电过程中，形成SEI膜的过程会消耗部分锂离子，这会导致首次库伦效率的降低；再次，在循环过程中，正极材料容易发生相变，晶体稳定性差导致的循环性能下降；最后，镍钴锰三元正极材料中镍含量高，Ni³⁺的比例也随之提高，然而Ni³⁺非常不稳定，当暴露在空气中时非常容易与空气中的水分和CO₂反应生成表面残碱，导致正极材料容量损失和循环性能损失；此外，过多的表面残碱会使得三元电池产气严重，影响其循环性能、安全性能等。The structure of the nickel-cobalt-manganese ternary cathode material is similar to that of LiCoO2, which is a layered structure of α _{- NaFeO2} . At present, the nickel-cobalt-manganese ternary cathode material has been industrialized on a large scale, but it still has some shortcomings. First, due to the Ni ²⁺ radius

with Li ⁺ radius

Very close, it is easy to cause the mixing of Li/Ni cations, resulting in a decrease in the gram capacity and cycle performance of Li-ion batteries; secondly, during the first charge and discharge process, the process of forming the SEI film will consume part of the lithium ions, which will lead to the first Coulomb efficiency Thirdly, during the cycle process, the cathode material is prone to phase transition, and the cycle performance is reduced due to poor crystal stability; finally, the nickel content in the nickel-cobalt-manganese ternary cathode material is high, and the proportion of Ni ³⁺ increases accordingly. However, Ni ³⁺ is very unstable, and when exposed to air, it is very easy to react with moisture and CO ₂ in the air to form surface residual alkali, resulting in the loss of cathode material capacity and cycle performance; in addition, too much surface residual alkali will make Ternary battery produces serious gas, which affects its cycle performance and safety performance.

In addition, studies on the synthesis of zirconium phosphate compounds by co-precipitation have been reported, but such materials have not been applied in the field of preparation of electrode materials for lithium ion batteries.

On this basis, it is necessary to research and develop a modified nickel-cobalt-manganese ternary cathode material and its preparation method, which is of great significance for improving the structural stability of the cathode material and improving the cycle stability of lithium-ion batteries.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a modified nickel-cobalt-manganese ternary positive electrode material, its preparation method and lithium ion battery, so as to solve the problem of poor structural stability of the nickel-cobalt-manganese ternary positive electrode material in the prior art and easy generation of surface residual alkali , resulting in problems such as poor cyclability of lithium-ion batteries.

In order to achieve the above purpose, one aspect of the present invention provides a method for preparing a modified nickel-cobalt-manganese ternary positive electrode material. , a zirconium source, a phosphorus source and a first solvent are mixed, and a pre-sintered product is obtained after pre-sintering treatment. The chemical formula of the pre-sintered product is Na _{2 (1-x)} Zn _x Zr ₄ (PO ₄ ) ₆ , wherein x is 0.5～ 1; Mix the pre-sintered product with a lithium source, a nickel source, a cobalt source, a manganese source and a second solvent, and obtain a modified nickel-cobalt-manganese ternary positive electrode material after calcination treatment; a lithium source, a nickel source, a cobalt source and a manganese source The molar ratio is 1.012:a:b:c, wherein 0.5≤a≤0.8, 0.1≤b≤0.2, a+b<1, c=1-ab.

Further, based on the total weight of the pre-sintered product, the lithium source, the nickel source, the cobalt source, the manganese source and the second solvent, the weight percentage of the pre-sintered product is 1-5 wt %; preferably, x in the pre-sintered product is 0.6 to 0.9.

Further, the vacuum degree of the pre-sintering treatment process is ^10-3 to ^10-4 Pa, the temperature is 400-600°C, and the time is 5-10h; preferably, the calcination temperature is 900-1000°C, and the time is 8- 12h; more preferably, the temperature of the pre-sintering process is positively correlated with the temperature of the calcination process.

Further, the preparation method of the modified nickel-cobalt-manganese ternary positive electrode material also includes: mixing the optional sodium source, zinc source, zirconium source, and phosphorus source with a first solvent to obtain a first mixed solution; The first ball milling treatment, the first drying treatment and the pre-sintering treatment are performed in sequence to obtain a pre-sintered product; the lithium source, the nickel source, the cobalt source, the manganese source and the second solvent are mixed to obtain a second mixed solution; the pre-sintered product is mixed with The second mixed solution is mixed and sequentially subjected to the second ball milling treatment, the second drying treatment and the calcination treatment to obtain a modified nickel-cobalt-manganese ternary positive electrode material; preferably, the solid contents of the first mixed solution and the second mixed solution are independent of each other. is selected from 30-60wt%, more preferably 40-50wt%; preferably, the ball milling speed of the first ball milling process and the second ball milling process is independently selected from 600-750rpm, and the ball milling time is independently selected from 1-4h .

Further, the temperature of the first drying process and the second drying process is independently selected from 90-120° C., and the time is independently selected from 4-6 h.

Further, when x is not 1, the sodium source is selected from one or more of the group consisting of sodium carbonate, sodium bicarbonate and sodium sulfate; the zinc source is selected from zinc sulfide; the zirconium source is selected from zirconia and/or Zirconium oxychloride; the phosphorus source is selected from ammonium dihydrogen phosphate and/or diammonium hydrogen phosphate.

Further, the first solvent and the second solvent are independently selected from absolute ethanol and/or water.

In order to achieve the above purpose, another aspect of the present invention also provides a modified nickel-cobalt-manganese ternary positive electrode material, the modified nickel-cobalt-manganese ternary positive electrode material is prepared by the above-mentioned preparation method of the modified nickel-cobalt-manganese ternary positive electrode material have to.

Further, the modified nickel-cobalt-manganese ternary cathode material includes an inner core and a modified material located on the surface of the inner core, and the inner core is LiNi _a Co _b Mn _c O ₂ (I), wherein 0.5≤a≤0.8, 0.1≤b≤0.2, a+b<1, c=1-ab; the modified material is Na _{2 (1-x)} Zn _x Zr ₄ (PO ₄ ) ₆ (II), wherein x is 0.5-1.

Another aspect of the present invention provides a lithium ion battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode, and the positive electrode comprises the above-mentioned preparation method for the modified nickel-cobalt-manganese ternary positive electrode material. The modified nickel-cobalt-manganese ternary positive electrode material, or the above-mentioned modified nickel-cobalt-manganese ternary positive electrode material.

By applying the technical scheme of the present invention, through the in-situ reaction method, the prepared pre-sintered product is coated on the surface of the inner core as a modified material, thereby obtaining a modified nickel-cobalt-manganese ternary positive electrode material. This can improve the stability of the positive electrode material, thereby effectively buffering the internal stress of the positive electrode material, and can effectively inhibit the mixing of cations to achieve the purpose of stabilizing the crystal structure, thereby inhibiting the degradation of the cycle stability and safety performance of the lithium-ion battery; It can effectively inhibit the dissolution of transition metal ions and improve the electrochemical performance of cathode materials.

In conclusion, the modified nickel-cobalt-manganese ternary cathode material prepared by the above preparation method has high reactivity and structural stability, and its application in lithium-ion batteries can achieve excellent comprehensive electrochemical performance. The nickel-cobalt-manganese ternary positive electrode material prepared by the above preparation method is especially suitable for improving the high temperature cycle stability of the lithium ion battery.

Description of drawings

The accompanying drawings forming a part of the present application are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached image:

FIG. 1 shows the high temperature (45° C.) cycle stability test curves (capacity retention rates corresponding to cycles 1 to 1350 cycles) of the lithium ion batteries prepared in Example 1 and Comparative Example 1, respectively.

Detailed ways

It should be noted that the embodiments in the present application and the features of the embodiments may be combined with each other in the case of no conflict. The present invention will be described in detail below with reference to the embodiments.

As described in the background art, the existing nickel-cobalt-manganese ternary positive electrode materials have poor structural stability and are prone to generate surface residual alkali, which in turn leads to problems such as poor cyclability of lithium ion batteries. In order to solve the above-mentioned technical problems, the present application provides a preparation method of a modified nickel-cobalt-manganese ternary positive electrode material. The preparation method of the modified nickel-cobalt-manganese ternary positive electrode material comprises: combining an optional sodium source, a zinc source, a The zirconium source, the phosphorus source and the first solvent are mixed, and a pre-sintered product is obtained after pre-sintering treatment. The chemical formula of the pre-sintered product is Na _2(1-x) Zn _x Zr ₄ (PO ₄ ) ₆ , wherein x is 0.5-1 ; Mix the pre-sintered product with lithium source, nickel source, cobalt source, manganese source and the second solvent, and obtain modified nickel-cobalt-manganese ternary positive electrode material after calcination treatment; lithium source, nickel source, cobalt source and manganese source The molar ratio is 1.012:a:b:c, wherein 0.5≤a≤0.8, 0.1≤b≤0.2, a+b<1, c=1-ab.

The optional sodium source, zinc source, zirconium source, and phosphorus source are mixed with the first solvent, and the pre-sintered product Na _{2 (1-x)} Zn _x Zr ₄ (PO ₄ ) ₆ can be obtained after pre-sintering. In the second solvent, a lithium source, a nickel source, a cobalt source and a manganese source in a specific molar ratio can combine to form a cathode material precursor crystal nucleus with a specific composition. During the process of the cathode material precursor crystal nucleus growing into a cathode material precursor , the pre-sintered product can be coated on the surface of the cathode material precursor in situ, and after calcination, it can form a core (or nickel-cobalt-manganese ternary cathode material) with a specific composition and a modified material located on the surface of the core, that is, modified nickel Cobalt manganese ternary cathode material.

Through an in-situ reaction method, the prepared pre-sintered product is used as a modified material to coat the surface of the inner core, thereby obtaining a modified nickel-cobalt-manganese ternary positive electrode material. This can improve the stability of the positive electrode material, thereby effectively buffering the internal stress of the positive electrode material, and can effectively inhibit the mixing of cations to achieve the purpose of stabilizing the crystal structure, thereby inhibiting the degradation of the cycle stability and safety performance of the lithium-ion battery; It can effectively inhibit the dissolution of transition metal ions and improve the electrochemical performance of cathode materials.

In conclusion, the modified nickel-cobalt-manganese ternary cathode material prepared by the above preparation method has high reactivity and structural stability, and its application in lithium-ion batteries can achieve excellent comprehensive electrochemical performance. The nickel-cobalt-manganese ternary positive electrode material prepared by the above preparation method is especially suitable for improving the high temperature cycle stability of the lithium ion battery.

The weight percentage of the pre-sintered product in the modified nickel-cobalt-manganese ternary cathode material will directly affect the coating effect. If the coating amount is too large, it will affect the Li ⁺ transport on the surface of the modified nickel-cobalt-manganese ternary cathode material, and it is difficult to play the core On the contrary, if the coating amount is too small, the surface of the inner core (unmodified nickel-cobalt-manganese ternary cathode material) will be partially exposed, which can be used in lithium-ion batteries for a long time. After being eroded by the electrolyte, it is easy to dissolve and fall off, which makes it difficult for the pre-sintered product located on the surface of the core to protect the core. In a preferred embodiment, based on the total weight of the pre-sintered product, the lithium source, the nickel source, the cobalt source, the manganese source and the second solvent, the weight percentage of the pre-sintered product is 1-5 wt %. The weight percent content of the pre-sintered product includes but is not limited to the above range, and limiting it within the above range is conducive to forming a coating layer with a suitable thickness, thereby improving the stability of the positive electrode material; at the same time, it is conducive to inhibiting the dissolution of transition metal ions, Improve the electrochemical performance of cathode materials.

In order to further exert the protective effect of the pre-sintered product on the inner core and further improve the structural stability of the inner core, preferably, x in the pre-sintered product is 0.6-0.9; more preferably 0.7-0.8.

In a preferred embodiment, the vacuum degree of the pre-sintering process is 10 ^-3 -10 ^-4 Pa, the temperature is 400-600° C., and the time is 5-10 h. The vacuum degree of the pre-sintering process includes but is not limited to the above range, and limiting it to the above range is beneficial to suppress the influence of impurities in the air on the pre-sintering process, thereby improving the purity of the pre-sintering product; at the same time, the pre-sintering process Limiting the temperature and time of the process within the above ranges is beneficial to improve the uniformity of the structure of the pre-sintered product, which in turn is beneficial to improve the high temperature (at 45°C) cycle stability and high temperature (55°C) shelf performance of the lithium ion battery.

In a preferred embodiment, the temperature of the calcination treatment is 900-1000° C., and the time is 8-12 hours. The temperature and time of the calcination treatment include but are not limited to the above-mentioned ranges. Limiting them to the above-mentioned ranges is conducive to further improving the structural stability of the modified nickel-cobalt-manganese ternary positive electrode material, which is not only conducive to suppressing the generation of surface residual alkali, but also It is beneficial to improve the cycle stability of lithium-ion batteries.

In a preferred embodiment, the temperature of the pre-sintering process is positively correlated with the temperature of the calcination process; more preferably, when the temperature of the pre-sintering process is 400-500°C, the temperature of the calcination process is 920-950°C , when the temperature of the pre-sintering process is 500-600°C, the temperature of the calcination process is 900-920°C. Compared with other ranges, the pre-sintered product obtained after the pre-sintering treatment under the conditions of the above preferred range is more suitable for the inner core formed after the calcination treatment, which is beneficial to make the modified material more closely cover the surface of the inner core, and then exert its position in the inner core. The role of modifying materials on the inner core surface.

In a preferred embodiment, the preparation method of the modified nickel-cobalt-manganese ternary positive electrode material further comprises: mixing the optional sodium source, zinc source, zirconium source, and phosphorus source with a first solvent to obtain a first mixed solution Perform the first ball milling treatment, the first drying treatment and the pre-sintering treatment on the first mixed solution to obtain a pre-sintered product; Mix the lithium source, the nickel source, the cobalt source, the manganese source and the second solvent to obtain the second mixed solution ; Mix the pre-sintered product with the second mixed solution and sequentially perform the second ball milling treatment, the second drying treatment and the calcining treatment to obtain a modified nickel-cobalt-manganese ternary positive electrode material.

The first ball milling treatment on the first mixed solution can reduce the particle size of the insoluble particles in the first mixed solution, and the first drying treatment can volatilize and remove the first solvent in the first mixed solution, so that the subsequent pre-sintering process can be smoothly performed. During the mixing process of the lithium source, the nickel source, the cobalt source, the manganese source and the second solvent, the positive electrode material precursor crystal nucleus of a specific composition can be formed by combining, and then the precursor particles of the nickel-cobalt-manganese ternary positive electrode material can be grown and formed. During the process, the pre-sintered product can simultaneously coat the surface of the positive electrode material precursor in situ, thereby forming a material with a composite structure.

The second ball milling treatment of the second mixed solution can make the pre-sintered product fully contact with the nickel-cobalt-manganese ternary cathode material precursor particles and coat the surface thereof. During the process, the pre-sintered product is transformed into a modified material and coated on the surface of the nickel-cobalt-manganese ternary positive electrode material (or inner core) to form a modified nickel-cobalt-manganese ternary positive electrode material.

If the solid content of the first mixed solution is too high or too low, the yield of the pre-sintered product will be reduced. At the same time, if the solid content of the second mixed solution is too high or too low, the coating effect of the modified material will be adversely affected. Reducing the yield of the modified nickel-cobalt-manganese ternary cathode material is not conducive to the improvement of its structural stability. In a preferred embodiment, the solid content of the first mixed solution and the second mixed solution independently includes, but is not limited to, 30-60 wt %, preferably 40-50 wt %.

In a preferred embodiment, the ball milling rotational speed of the first ball milling treatment and the second ball milling treatment process independently includes but not limited to 600-750 rpm, and the ball milling time includes but is not limited to 1-4 h, respectively.

The ball milling speed and ball milling time of the first ball milling treatment respectively include but are not limited to the above ranges. Limiting them to the above ranges is beneficial to reduce the particle size of the insoluble particles in the first mixed solution, and is also beneficial to make the sodium source, zinc source, The zirconium source and the phosphorus source are fully contacted and reacted to form a product to be pre-sintered, which is convenient for subsequent pre-sintering to obtain a more uniform Na _2(1-x) Zn _x Zr ₄ (PO ₄ ) ₆ pre-sintered product .

The ball-milling speed and ball-milling time of the second ball-milling treatment include but are not limited to the above-mentioned ranges, respectively. Limiting them within the above-mentioned ranges is conducive to improving the coating effect, which in turn is conducive to improving the inner core of the nickel-cobalt-manganese ternary positive electrode material and the modified nickel-cobalt-manganese The structural stability of the ternary cathode material, thereby improving the high temperature (45°C) cycle stability and high temperature (55°C) shelving performance of the modified nickel-cobalt-manganese ternary cathode material.

In a preferred embodiment, the temperature of the first drying process and the second drying process independently includes but is not limited to 90-120° C., and the time independently includes but is not limited to 4-6 hours.

The temperature and time of the first drying treatment respectively include but are not limited to the above-mentioned ranges. Limiting them to the above-mentioned ranges is beneficial to suppress the influence of the first solvent volatilization process on the crystal structure of the product, thereby helping to improve the modified nickel-cobalt-manganese ternary. The crystal structure of the cathode material improves its structural stability.

The optional sodium source, zinc source, zirconium source and phosphorus source in the present application can be commonly used in the field. In a preferred embodiment, when x is not 1, the sodium source includes but is not limited to one or more of the group consisting of sodium carbonate, sodium bicarbonate and sodium sulfate; the zinc source includes but is not limited to zinc sulfide ; Zirconium sources include but are not limited to zirconium oxide and/or zirconium oxychloride; Phosphorus sources include but are not limited to ammonium dihydrogen phosphate and/or diammonium hydrogen phosphate.

In the present application, the lithium source, nickel source, cobalt source and manganese source can be of common types in the field. In a preferred embodiment, the lithium source includes but is not limited to one or more of the group consisting of lithium hydroxide, lithium carbonate and lithium chloride; the nickel source includes but is not limited to nickel sulfate, nickel nitrate and chloride One or more of the group consisting of nickel; cobalt source includes but not limited to one or more of the group consisting of cobalt sulfate, cobalt nitrate and cobalt chloride; manganese source is manganese sulfate, manganese nitrate and manganese chloride one or more of the group consisting of.

In a preferred embodiment, the first solvent and the second solvent each independently include, but are not limited to, absolute ethanol and/or water. Compared with other solvents, the use of the above-mentioned preferred first solvent and second solvent is beneficial to the dispersion of each raw material component, thereby improving the dispersion uniformity of the raw materials in the first mixed solution and the second mixed solution.

The second aspect of the present application also provides a modified nickel-cobalt-manganese ternary positive electrode material, the modified nickel-cobalt-manganese ternary positive electrode material is prepared by the above-mentioned preparation method of the modified nickel-cobalt-manganese ternary positive electrode material provided by the present application.

The modified nickel-cobalt-manganese ternary cathode material provided in the present application has high reactivity and structural stability, and can achieve excellent comprehensive electrochemical performance when applied in a lithium-ion battery. The nickel-cobalt-manganese ternary cathode material prepared by the above preparation method is especially suitable for improving the high temperature (45°C) cycle stability and high temperature (55°C) shelf performance of lithium ion batteries.

In a preferred embodiment, the modified nickel-cobalt-manganese ternary cathode material includes an inner core and a modified material located on the surface of the inner core; the inner core is LiNi _a Co _b Mn _c O ₂ (I), where 0.5≤a≤0.8, 0.1≤b≤0.2, a+b<1, c=1-ab; the modified material is Na _2(1-x) Zn _x Zr ₄ (PO ₄ ) ₆ (II), where x is 0.5-1.

A third aspect of the present application also provides a lithium ion battery, comprising a positive electrode, a negative electrode, an electrolyte, and a separator disposed between the positive electrode and the negative electrode, the positive electrode comprising the modified nickel-cobalt-manganese ternary positive electrode material provided in the present application. The modified nickel-cobalt-manganese ternary positive electrode material prepared by the preparation method, or the above-mentioned modified nickel-cobalt-manganese ternary positive electrode material provided in this application. The above-mentioned lithium ion battery provided by the present application has excellent high temperature (45°C) cycle stability and high temperature (55°C) shelf performance.

The present application will be described in further detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present application.

Example 1

A preparation method of a modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material, comprising the following steps:

S1, weigh Na ₂ CO ₃ , ZnS, ZrO ₂ (average particle size not more than 50 nm) and NH ₄ H ₂ PO ₄ according to the molar ratio of Na:Zn:Zr:P of 1:0.5:4:6 and disperse them in In absolute ethanol, a first mixed solution is obtained, and the solid content of the first mixed solution is 45wt%;

S2, perform the first ball milling treatment on the first mixed solution, the ball milling speed is 750 rpm and the time is 2 h, dried at 100 ° C for 5 h, and under the condition of vacuum degree of 10 ^-3 Pa, pre-sintered at 500 ° C for 8 h, and then the pre-sintered solution is obtained. Sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ ;

S3, the molar ratio of Li:Ni:Co:Mn is 1.012:0.6:0.2:0.2 to weigh lithium hydroxide, anhydrous nickel sulfate, anhydrous cobalt sulfate, anhydrous manganese sulfate, and disperse them in dehydrated ethanol , obtain the second mixed solution, the solid content of this second mixed solution is 45wt%;

S4, adding the obtained pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution, and the weight ratio of the pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution is 0.025:1 ( That is, the weight percentage of the pre-sintered product is 2.5 wt%), and the second ball milling treatment is carried out. The ball milling speed is 750 rpm and the time is 2 h; drying at 100 ° C for 5 h; The modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material was obtained. In the final modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material, the weight percentage of the pre-sintered product in the modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material is 5wt%.

Example 2

A preparation method of a modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material, comprising the following steps:

S1, according to the mole ratio of Na:Zn:Zr:P is 1:0.5:4:6, weigh Na ₂ CO ₃ , ZnS, ZrO ₂ (average particle size does not exceed 50nm) and NH ₄ H ₂ PO ₄ dispersed in the In the water ethanol, a first mixed solution is obtained, and the solid content of the first mixed solution is 50wt%;

S2, perform the first ball milling treatment on the first mixed solution. The ball milling speed is 750 rpm and the time is 4 h, drying at 100 °C for 6 h, and under the condition of vacuum degree of 10 ^-4 Pa, pre-sintering at 600 ° C for 10 h to obtain pre-sintering Product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ ;

S3, the molar ratio of Li:Ni:Co:Mn is 1.012:0.6:0.2:0.2 to weigh lithium hydroxide, anhydrous nickel sulfate, anhydrous cobalt sulfate, anhydrous manganese sulfate, and disperse them in dehydrated ethanol , obtain the second mixed solution, the solid content of this second mixed solution is 50wt%;

S4, adding the obtained pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution, and the weight ratio of the pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution is 0.025:1, The second ball milling treatment was carried out, the ball milling speed was 750 rpm and the time was 4 h; drying at 120 °C for 6 h; calcination treatment at 950 °C for 12 h in an air atmosphere, and after natural cooling, the modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary cathode material was obtained .

Example 3

A preparation method of a modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material, comprising the following steps:

S1, weigh Na ₂ CO ₃ , ZnS, ZrO ₂ (average particle size not more than 50 nm) and NH ₄ H ₂ PO ₄ according to the molar ratio of Na:Zn:Zr:P of 1:0.5:4:6 and disperse them in In absolute ethanol, a first mixed solution is obtained, and the solid content of the first mixed solution is 40wt%;

S2, perform the first ball milling treatment on the first mixed solution, the ball milling speed is 600 rpm and the time is 1 h, dried at 90°C for 4h, and under the condition of vacuum degree of 10 ^-3 Pa, pre-sintered at 400°C for 5h, the pre-sintered solution is obtained. Sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ ;

S3, the molar ratio of Li:Ni:Co:Mn is 1.012:0.6:0.2:0.2 to weigh lithium hydroxide, anhydrous nickel sulfate, anhydrous cobalt sulfate, anhydrous manganese sulfate, and disperse them in dehydrated ethanol , obtain the second mixed solution, the solid content of this second mixed solution is 40wt%;

S4, adding the obtained pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution, and the weight ratio of the pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution is 0.025:1, The second ball milling treatment was carried out, the ball milling speed was 600 rpm and the time was 1 h; drying at 90 °C for 4 h; calcination treatment at 900 °C for 8 h in an air atmosphere, and after natural cooling, the modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary cathode material was obtained .

Example 4

A preparation method of a modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material, comprising the following steps:

S1, weigh ZnS, ZrO ₂ (average particle size not more than 50nm) and NH ₄ H ₂ PO ₄ and disperse in absolute ethanol according to the molar ratio of Zn:Zr:P as 1:4:6 to obtain the first mixture liquid, the solid content of the first mixed liquid is 45wt%;

S2, perform the first ball milling treatment on the first mixed solution, the ball milling speed is 750 rpm and the time is 2 h, dried at 100 ° C for 5 h, and under the condition of vacuum degree of 10 ^-3 Pa, pre-sintered at 500 ° C for 8 h, and then the pre-sintered solution is obtained. Sintered product ZnZr ₄ (PO ₄ ) ₆ ;

S3, the molar ratio of Li:Ni:Co:Mn is 1.012:0.6:0.2:0.2 to weigh lithium hydroxide, anhydrous nickel sulfate, anhydrous cobalt sulfate, anhydrous manganese sulfate, and disperse them in dehydrated ethanol , obtain the second mixed solution, the solid content of this second mixed solution is 45wt%;

S4, adding the obtained pre-sintered product ZnZr ₄ (PO ₄ ) ₆ to the second mixed solution, the weight ratio of the pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution is 0.025:1, and the first Two ball milling treatment, the ball milling speed is 750rpm and the time is 2h; drying at 100°C for 5h; calcination at 950°C for 10h in an air atmosphere, and after natural cooling, the modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary cathode material is obtained.

Example 5

A preparation method of a modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material, comprising the following steps:

S1, weigh Na ₂ CO ₃ , ZnS, ZrO ₂ (average particle size not more than 50 nm) and NH ₄ H ₂ PO ₄ according to the molar ratio of Na:Zn:Zr:P of 1:0.5:4:6 and disperse them in In absolute ethanol, a first mixed solution is obtained, and the solid content of the first mixed solution is 45wt%;

S2, perform the first ball milling treatment on the first mixed solution, the ball milling speed is 750 rpm and the time is 2 h, dried at 100 ° C for 5 h, and under the condition of vacuum degree of 10 ^-3 Pa, pre-sintered at 500 ° C for 8 h, and then the pre-sintered solution is obtained. Sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ ;

S3, the molar ratio of Li:Ni:Co:Mn is 1.012:0.6:0.2:0.2 to weigh lithium carbonate, anhydrous nickel sulfate, anhydrous cobalt sulfate, anhydrous manganese sulfate, and disperse in dehydrated ethanol, Obtain the second mixed solution, the solid content of this second mixed solution is 45wt%;

S4, adding the obtained pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution, and the weight ratio of the pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution is 0.025:1, The second ball milling treatment was carried out, the ball milling speed was 750 rpm and the time was 2 h; drying at 100 °C for 5 h; calcination treatment at 950 °C for 10 h in an air atmosphere, and after natural cooling, the modified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary cathode material was obtained .

Example 5

The difference from Example 1 is that the molar ratio of Na:Zn:Zr:P is 1:0.6:4:6, and the obtained pre-sintered product is Na _0.4 Zn _0.7 Zr ₄ (PO ₄ ) ₆ .

Example 6

The difference from Example 1 is that the molar ratio of Na:Zn:Zr:P is 1:0.7:4:6, and the obtained pre-sintered product is Na _0.4 Zn _0.7 Zr ₄ (PO ₄ ) ₆ .

Example 7

The difference from Example 1 is that the molar ratio of Na:Zn:Zr:P is 1:0.8:4:6, and the obtained pre-sintered product is Na _0.4 Zn _0.8 Zr ₄ (PO ₄ ) ₆ .

Example 8

The difference from Example 1 is that the molar ratio of Na:Zn:Zr:P is 1:0.9:4:6, and the obtained pre-sintered product is Na _0.4 Zn _0.8 Zr ₄ (PO ₄ ) ₆ .

Example 9

The difference from Example 1 is that the weight ratio of the pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution is 0.01:1, and the final pre-sintered product accounts for the modified nickel-cobalt-manganese ternary positive electrode material. The weight percent is 2wt%.

Example 10

The difference from Example 1 is that the weight ratio of the pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution is 0.05:1, and the final pre-sintered product accounts for the modified nickel-cobalt-manganese ternary positive electrode material. The weight percent is 10wt%.

Example 11

The difference from Example 1 is that the weight ratio of the pre-sintered product NaZn _0.5 Zr ₄ (PO ₄ ) ₆ to the second mixed solution is 0.005:1, and the final pre-sintered product accounts for the modified nickel-cobalt-manganese ternary positive electrode material. The weight percent is 1wt%.

Example 12

The difference from Example 1 is that the temperature of the pre-sintering process is 400° C. and the time is 10 h.

Example 13

The difference from Example 1 is that the temperature of the pre-sintering process is 600° C. and the time is 5 hours.

Example 14

The difference from Example 1 is that the temperature of the pre-sintering process is 300° C. and the time is 3 hours.

Example 15

The difference with Example 1 is: in step S3, the mol ratio of Li:Ni:Co:Mn is 1.012:0.5:0.2:0.3 to weigh lithium hydroxide, anhydrous nickel sulfate, anhydrous cobalt sulfate, anhydrous sulfuric acid. manganese, and dispersed in dehydrated ethanol to obtain a second mixed solution, and the solid content of the second mixed solution is 45wt%;

Finally, the modified LiNi _0.5 Co _0.2 Mn _0.3 O ₂ ternary cathode material was obtained.

Example 16

The difference with Example 1 is: in step S3, the mol ratio of Li:Ni:Co:Mn is 1.012:0.8:0.1:0.1 to weigh lithium hydroxide, anhydrous nickel sulfate, anhydrous cobalt sulfate, anhydrous sulfuric acid. manganese, and dispersed in dehydrated ethanol to obtain a second mixed solution, and the solid content of the second mixed solution is 45wt%;

Finally, the modified LiNi _0.8 Co _0.1 Mn _0.1 O ₂ ternary cathode material was obtained.

Example 17

The difference from Example 1 is that in step S4, the temperature of the calcination treatment is 1000°C.

Comparative Example 1

The difference from Example 1 is that the unmodified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary positive electrode material is prepared in Comparative Example 1, and the preparation process includes:

The molar ratio of Li:Ni:Co:Mn is 1.012:0.6:0.2:0.2, and lithium carbonate, anhydrous nickel nitrate, anhydrous cobalt nitrate, and anhydrous manganese nitrate are weighed, and dispersed in dehydrated ethanol to obtain The third mixed solution, the solid content of the third mixed solution is 45wt%; the third mixed solution is subjected to the first ball milling treatment, the ball milling speed is 750rpm and the time is 2h, dried at 100 ℃ for 5h, in an air atmosphere, 950 The temperature was kept constant for 10 h, and after natural cooling, an unmodified LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary cathode material was obtained.

Comparative Example 2

The difference from Example 1 is that the molar ratio of Na:Zn:Zr:P is 1:0.25:4:6, and the chemical formula of the obtained pre-sintered product is Na _1.5 Zn _0.25 Zr ₄ (PO ₄ ) ₆ , wherein x is 0.25.

The modified nickel-cobalt-manganese ternary positive electrode materials and unmodified nickel-cobalt-manganese ternary positive electrode materials prepared in all the examples and comparative examples of this application were assembled into lithium ion batteries, and the high temperature (45°C) cycle stability was carried out. and high temperature (55°C) shelf stability test.

The assembly process of the lithium-ion battery is as follows: the LiNi _0.6 Co _0.2 Mn _0.2 O ₂ ternary material is used as the positive electrode, the polyvinylidene fluoride is used as the binder, and the conductive carbon black is used as the conductive agent. The weight ratio of the three is 8:1:1. A lithium-ion battery is assembled by using a battery-grade lithium sheet as the negative electrode material, using an electrolyte whose main component is lithium hexafluorophosphate, and using a polymer polyethylene microporous film as a separator.

The test conditions are as follows: under the condition of 45 ℃, 0.33C constant current charge and discharge, the charge and discharge electrochemical window is 3.0 ~ 4.3V, and the capacity retention rate of the lithium ion battery is tested after 1350 cycles of cycling; the lithium ion battery is in a fully charged state (100 %SOC) and the capacity retention rate was tested after standing at 55°C for 28 days. The test results of the lithium-ion batteries prepared in all the examples and comparative examples of the present application are summarized in Table 1.

Table 1

From the above description, it can be seen that the above-mentioned embodiments of the present invention achieve the following technical effects:

Comparing the test results of Examples 1, 15 to 17 and Comparative Example 1, it can be seen that under the condition of 45°C, the capacity retention rate after 1350 cycles of cycling is 86%, and the lithium-ion battery is in a fully charged state (100% SOC) and at 55%. The capacity retention rate was 97.5% after being left at ℃ for 28 days; while the lithium-ion battery made of unmodified nickel-cobalt-manganese ternary cathode material in Comparative Example 1 maintained its capacity after 1350 cycles at 45℃. The rate is 83%, and the lithium-ion battery is in a fully charged state (100% SOC) and has a capacity retention rate of 92% after being left at 55°C for 28 days.

Comparing Examples 1 to 8 and Comparative Examples 1 and 2, it can be seen that by in-situ reaction method, the prepared pre-sintered product is used as a modified material to coat the surface of the inner core, thereby obtaining a modified nickel-cobalt-manganese ternary positive electrode material. This can improve the stability of the positive electrode material, thereby effectively buffering the internal stress of the positive electrode material, and can effectively inhibit the mixing of cations to achieve the purpose of stabilizing the crystal structure, thereby inhibiting the degradation of the cycle stability and safety performance of the lithium-ion battery; It can effectively inhibit the dissolution of transition metal ions and improve the electrochemical performance of cathode materials. In conclusion, the modified nickel-cobalt-manganese ternary cathode material prepared by the above preparation method provided in this application has high reactivity and structural stability, and its application in lithium ion batteries can achieve excellent comprehensive electrochemical performance. The nickel-cobalt-manganese ternary positive electrode material prepared by the above preparation method is especially suitable for improving the high temperature cycle stability of the lithium ion battery.

Comparing Examples 1, 9 to 11, it can be seen that the weight percentage of the pre-sintered product includes but is not limited to the preferred range of the present application, and limiting it to the preferred range of the present application is conducive to the formation of a coating layer with a suitable thickness, thereby improving the positive electrode material. At the same time, it is beneficial to inhibit the dissolution of transition metal ions and improve the electrochemical performance of cathode materials.

Comparing Examples 1, 12 to 14, it can be seen that limiting the temperature and time of the pre-sintering process to the preferred range of the present application is conducive to improving the uniformity of the structure of the pre-sintering product, which in turn is conducive to improving the high temperature (45°C condition of the lithium ion battery). Bottom) cycle stability and high temperature (55°C) shelf performance.

It should be noted that the terms "first", "second" and the like in the description and claims of the present application are used to distinguish similar objects, and are not necessarily used to describe a specific sequence or sequence. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein can, for example, be practiced in sequences other than those described herein.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. The preparation method of the modified nickel-cobalt-manganese ternary cathode material is characterized by comprising the following steps of:

mixing an optional sodium source, a zinc source, a zirconium source, a phosphorus source and a first solvent, and performing presintering treatment to obtain a presintering product, wherein the chemical formula of the presintering product is Na _2(1-x) Zn _x Zr ₄ (PO ₄ ) ₆ Wherein x is 0.5-1;

mixing the pre-sintered product with a lithium source, a nickel source, a cobalt source, a manganese source and a second solvent, and calcining to obtain the modified nickel-cobalt-manganese ternary cathode material; the molar ratio of the lithium source to the nickel source to the cobalt source to the manganese source is 1.012: a: b: c, wherein a is more than or equal to 0.5 and less than or equal to 0.8, b is more than or equal to 0.1 and less than or equal to 0.2, a + b is less than 1, and c is 1-a-b.

2. The preparation method of the modified nickel-cobalt-manganese ternary cathode material as claimed in claim 1, wherein the weight percentage of the pre-sintered product is 1-5 wt% based on the total weight of the lithium source, the nickel source, the cobalt source, the manganese source and the second solvent;

preferably, x in the presintered product is 0.6-0.9.

3. According to claimThe preparation method of the modified nickel-cobalt-manganese ternary cathode material in claim 1 or 2, wherein the degree of vacuum in the pre-sintering treatment process is 10 ^-3 ～10 ^-4 Pa, the temperature is 400-600 ℃, and the time is 5-10 h; preferably, the calcining treatment temperature is 900-1000 ℃, and the time is 8-12 h;

more preferably, the temperature of the pre-sintering treatment process is in positive correlation with the temperature of the calcination treatment.

4. The method for preparing a modified nickel-cobalt-manganese ternary positive electrode material according to any one of claims 1 to 3, further comprising:

mixing the optional sodium source, the optional zinc source, the optional zirconium source, the optional phosphorus source and the first solvent to obtain a first mixed solution;

sequentially carrying out first ball milling treatment, first drying treatment and presintering treatment on the first mixed solution to obtain a presintering product;

mixing the lithium source, the nickel source, the cobalt source, the manganese source and the second solvent to obtain a second mixed solution;

mixing the pre-sintered product with the second mixed solution, and sequentially carrying out second ball milling treatment, second drying treatment and calcination treatment to obtain the modified nickel-cobalt-manganese ternary cathode material;

preferably, the solid contents of the first mixed solution and the second mixed solution are respectively and independently selected from 30 to 60 wt%, and more preferably 40 to 50 wt%;

preferably, the ball milling rotation speed in the first ball milling treatment and the second ball milling treatment is respectively and independently selected from 600 to 750rpm, and the ball milling time is respectively and independently selected from 1 to 4 h.

5. The preparation method of the modified nickel-cobalt-manganese ternary cathode material as claimed in claim 4, wherein the temperatures of the first drying treatment and the second drying treatment are respectively and independently selected from 90 ℃ to 120 ℃, and the times are respectively and independently selected from 4h to 6 h.

6. The method for preparing the modified nickel-cobalt-manganese ternary positive electrode material according to claim 4, wherein when x is not 1, the sodium source is one or more selected from the group consisting of sodium carbonate, sodium bicarbonate and sodium sulfate; the zinc source is selected from zinc sulfide; the zirconium source is selected from zirconium oxide and/or zirconium oxychloride; the phosphorus source is selected from ammonium dihydrogen phosphate and/or diammonium hydrogen phosphate.

7. The method for preparing the modified nickel-cobalt-manganese ternary cathode material according to claim 4, wherein the first solvent and the second solvent are respectively and independently selected from anhydrous ethanol and/or water.

8. A modified nickel-cobalt-manganese ternary cathode material, which is prepared by the preparation method of the modified nickel-cobalt-manganese ternary cathode material according to any one of claims 1 to 7.

9. The modified nickel-cobalt-manganese ternary cathode material as claimed in claim 8, wherein the modified nickel-cobalt-manganese ternary cathode material comprises an inner core and a modified material located on the surface of the inner core; the inner core is LiNi _a Co _b Mn _c O ₂ (I) Wherein a is more than or equal to 0.5 and less than or equal to 0.8, b is more than or equal to 0.1 and less than or equal to 0.2, a + b is less than 1, and c is 1-a-b; the modified material is Na _2(1-x) Zn _x Zr ₄ (PO ₄ ) ₆ (II), wherein x is 0.5 to 1.

10. A lithium ion battery, comprising a positive electrode, a negative electrode, an electrolyte and a separator disposed between the positive electrode and the negative electrode, wherein the positive electrode comprises the modified nickel-cobalt-manganese ternary positive electrode material prepared by the method of any one of claims 1 to 7, or the modified nickel-cobalt-manganese ternary positive electrode material of claim 8 or 9.

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