Long cycle ternary positive electrode material and preparation method and application thereof

Abstract

This invention discloses a long-cycle ternary cathode material, its preparation method, and its application, belonging to the field of battery material technology. This long-cycle ternary cathode material satisfies k1=Δ V / τ,k2=k1 / μ;Δ V =[(V1-V2) / V1]×100%, τ=(m2 / m1)×100%; k1≤20%, k2≤40%; μ is the mass percentage of nickel atoms in the ternary cathode material; Δ V The volume change rate of the ternary cathode material is given by τ, where V1 and V2 are the volumes of the ternary cathode material before and after delithiation under pressure P; τ is the percentage of delithiation of the ternary cathode material; and m1 and m2 are the lithium mass contained in the ternary cathode material before delithiation and the corresponding lithium mass removed after delithiation. This long-cycle ternary cathode material exhibits relatively small volume changes during repeated charge-discharge cycles, which helps mitigate crack formation, maintain structural stability, and extend service life.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and more specifically, to a long-cycle ternary cathode material, its preparation method, and its application. Background Technology

[0002] Ternary lithium-ion batteries have become important new energy power batteries due to their high energy density and excellent low-temperature performance, but their cycle performance is somewhat inferior to that of lithium iron phosphate batteries. Furthermore, during the continuous charging and discharging process, the ternary cathode material can develop secondary particle cracks due to volume changes. Once these cracks form, electrolyte can gradually seep in, accelerating side reactions and affecting the battery's cycle performance.

[0003] In view of this, the present invention is proposed. Summary of the Invention

[0004] The purpose of this invention is to provide a long-cycle ternary cathode material, its preparation method, and its application, so as to solve or improve the above-mentioned technical problems.

[0005] This invention can be implemented as follows:

[0006] In a first aspect, the present invention provides a long-cycle ternary cathode material, wherein the long-cycle ternary cathode material satisfies k1=Δ V / τ,k2=k1 / μ; ΔV =[(V1-V2) / V1]×100%, τ=(m2 / m1)×100%; k1≤20%, k2≤40%;

[0007] Wherein, μ is the content of nickel atoms in the long-cycle ternary cathode material, expressed as an atomic mass percentage; ΔV τ represents the volume change rate of the long-cycle ternary cathode material before and after delithiation; V1 is the volume of the long-cycle ternary cathode material after being compressed under pressure P before delithiation; V2 is the volume of the long-cycle ternary cathode material after being compressed under the same pressure P after delithiation; τ is the percentage of delithiation of the long-cycle ternary cathode material; m1 is the mass of lithium contained in the long-cycle ternary cathode material before delithiation; and m2 is the mass of lithium removed from the long-cycle ternary cathode material after delithiation.

[0008] In an optional implementation, the delithiation method includes immersing the long-cycle ternary cathode material in water.

[0009] In an optional implementation, k1 is 14% to 15.8%, and / or k2 is 25% to 37.5%.

[0010] In an optional embodiment, the long-cycle ternary cathode material has at least one of the following characteristics:

[0011] Feature 1: μ is 40%~57%;

[0012] Feature 2: ΔV The percentage is 1.8% to 4.3%;

[0013] Feature 3: τ is 12%~30%.

[0014] Secondly, the present invention provides a method for preparing a long-cycle ternary cathode material as described in any of the foregoing embodiments, comprising the following steps: complexing a mixed solution containing a nickel source, a cobalt source and a manganese source with a complexing agent; subjecting the complexed solution to spray pyrolysis and then calcining; mixing the calcined product with a lithium source and sintering it to obtain lithium nickel cobalt manganese oxide.

[0015] In an optional embodiment, the mixed solution includes at least one of the following characteristics:

[0016] Feature 4: The nickel source includes at least one of nickel chloride and nickel nitrate;

[0017] Feature 5: The cobalt source includes at least one of cobalt chloride and cobalt nitrate;

[0018] Feature 6: The manganese source includes at least one of manganese chloride and manganese nitrate;

[0019] Feature 7: The molar ratio of Ni, Co and Mn in the nickel source, cobalt source and manganese source is (0.5~0.98):(0.01~0.2):(0.01~0.3).

[0020] In an optional implementation, the complexation includes at least one of the following features:

[0021] Feature 8: The complexing agent is polyvinylphosphoric acid;

[0022] Feature 9: The ratio of the amount of complexing agent to the total amount of nickel, cobalt, and manganese is 0.1:1 to 0.5:1;

[0023] Feature 10: The complexation temperature is 50℃~90℃;

[0024] Feature 11: The pH value of the complex is 4~5;

[0025] Feature 12: The complexation time is 1h~3h.

[0026] In an optional embodiment, the spray pyrolysis temperature is 800℃~1200℃;

[0027] And / or, the calcination temperature is 800℃~1000℃, and the calcination time is 1h~5h.

[0028] In an optional embodiment, sintering includes a first-stage sintering at 600°C to 750°C for 0.5 to 2 hours, followed by a second-stage sintering at 750°C to 950°C for 20 to 30 hours.

[0029] Thirdly, the present invention provides a battery comprising the long-cycle ternary cathode material of any of the foregoing embodiments.

[0030] The beneficial effects of this invention include:

[0031] This invention creatively combines μ, ΔV In conjunction with τ, a specific relationship among the three was proposed, and a ternary cathode material that can simultaneously satisfy k1≤20% and k2≤40% was proposed. This material can exhibit small volume changes during charge and discharge, thereby reducing the generation of secondary particle cracks and improving the service life of the material during charge and discharge cycles. Detailed Implementation

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0033] The following is a detailed description of the long-cycle ternary cathode material, its preparation method, and its applications provided by this invention.

[0034] This invention provides a long-cycle ternary cathode material that satisfies k1=Δ V / τ,k2=k1 / μ; ΔV =[(V1-V2) / V1]×100%, τ=(m2 / m1)×100%; k1≤20%, k2≤40%.

[0035] Wherein, μ is the content of nickel atoms in the long-cycle ternary cathode material, expressed as an atomic mass percentage; ΔV τ represents the volume change rate of the long-cycle ternary cathode material before and after delithiation; V1 is the volume of the long-cycle ternary cathode material after being compressed under pressure P before delithiation; V2 is the volume of the long-cycle ternary cathode material after being compressed under the same pressure P after delithiation; τ is the percentage of delithiation of the long-cycle ternary cathode material; m1 is the mass of lithium contained in the long-cycle ternary cathode material before delithiation; and m2 is the mass of lithium removed from the long-cycle ternary cathode material after delithiation.

[0036] In some alternative embodiments, the delithiation method may include immersing the long-cycle ternary cathode material in water. For example, a certain mass (e.g., 10.000 g ± 0.010 g) of the long-cycle ternary cathode material is immersed in room temperature water for 0.5 h to 5 h at a certain solid-liquid ratio (by mass, e.g., 1:1 to 1:5) to leach some lithium ions from the crystal lattice into the water. Subsequently, solid-liquid separation is performed to obtain the delithiated material and a lithium-containing leaching solution.

[0037] Volumes V1 and V2 can be measured using a compaction density meter. V2 is actually the volume of the delithiated material after drying and pressing it into tablets under pressure P. For example, the value of P can be 50 MPa to 300 MPa.

[0038] m2 can be calculated by detecting the concentration of lithium ions in the leaching solution and then multiplying it by the volume of the leaching solution. m1 can be calculated from the initial weight of the long-cycle ternary cathode material used, based on the proportion of lithium in that long-cycle ternary cathode material.

[0039] In some alternative implementations, k1 can be 20%, 18%, 15%, 12%, 10%, 8%, 5%, or 2%, or other values ​​within the range of ≤20%. For example, k1 can be 14% to 15.8%, such as 14.1%, 14.3%, 14.6%, 15%, or 15.8%.

[0040] k2 can be 40%, 38%, 35%, 32%, 30%, 28%, 25%, 22%, 20%, 18%, 15%, 12%, 10%, 8%, 5%, or 2%, etc., or other values ​​within the range of ≤40%. For example, k2 can be 25%~37.5%, such as 25.3%, 30.6%, 34.9%, 36.4%, or 37.5%.

[0041] It should be noted that the volume change of the cathode material is directly related to lithium-ion insertion / extraction. During battery charging, lithium ions are extracted, causing the crystal structure of the cathode material to shrink; during battery discharging, lithium ions are inserted, causing the crystal structure of the cathode material to expand. Ternary cathode materials are polycrystalline materials composed of multiple single-crystal primary particles agglomerating into secondary particles to form spherical or near-spherical particles. Their main active element is nickel ions, and increasing the nickel ion content is usually achieved to improve energy density. However, the higher the nickel ion content in ternary cathode materials, the more likely it is to lead to a decrease in the stability of the crystal structure, resulting in a greater volume change during lithium insertion / extraction. Furthermore, the more lithium ions are extracted during lithium insertion / extraction, the greater the impact on the volume change of the ternary cathode material.

[0042] Based on this, the inventor creatively combined μ, ΔV In conjunction with τ, a specific relationship among the three was proposed, and a ternary cathode material that can simultaneously satisfy k1≤20% and k2≤40% was proposed. This ternary cathode material has a small volume change during charge and discharge, which can reduce the generation of secondary particle cracks and improve the service life of the material during charge and discharge cycles.

[0043] During the testing process, k1≤20% exhibits excellent electrochemical performance, thus limiting k1≤20%, while k2≤40% ensures the cycling performance advantage of lithium nickel cobalt manganese oxide.

[0044] In some alternative implementations, μ can be 40% to 57%, such as 40%, 40.2%, 40.3%, 51.8%, or 56.7%. μ within this range corresponds to a higher nickel content in the ternary cathode material without causing excessive volume changes.

[0045] In some alternative implementations, ΔV The concentration can range from 1.8% to 4.3%, such as 1.8%, 1.9%, 3.8%, or 4.3%. Within this range, the volume change rate of long-cycle ternary cathode materials before and after delithiation is relatively small, which is more conducive to improving cycle performance.

[0046] In some alternative implementations, τ can be 12% to 30%, such as 12%, 13.5%, 24% or 30%.

[0047] As described above, the long-cycle ternary cathode material provided by this invention exhibits small volume changes and fewer cracks in secondary particles during battery charging and discharging, effectively preventing and mitigating electrolyte ingress, thus enabling the battery to have better cycle performance.

[0048] Accordingly, the present invention also provides a method for preparing the above-mentioned long-cycle ternary cathode material, which may include the following steps: complexing a mixed solution containing a nickel source, a cobalt source and a manganese source with a complexing agent; spraying the complexed solution for pyrolysis and then calcining; mixing the calcined product with a lithium source and sintering it to obtain lithium nickel cobalt manganese oxide.

[0049] In some alternative embodiments, the nickel source in the mixed solution may include at least one of nickel chloride and nickel nitrate. The cobalt source may include at least one of cobalt chloride and cobalt nitrate. The manganese source may include at least one of manganese chloride and manganese nitrate.

[0050] The anions in the nickel, cobalt, and manganese sources described above can be volatilized and removed at high temperatures.

[0051] The molar ratio of Ni, Co and Mn in the nickel source, cobalt source and manganese source can be (0.5~0.98):(0.01~0.2):(0.01~0.3), such as 0.6:0.2:0.2, 0.5:0.2:0.3 or 0.98:0.01:0.01, etc.

[0052] In some alternative implementations, the complexing agent is polyvinylphosphoric acid.

[0053] Conventional ternary cathode material precursors are typically prepared using a co-precipitation method. Due to the different complexing abilities of nickel, cobalt, and manganese ions with ammonia, nickel ions tend to aggregate, while manganese ions have insufficient complexing ability. This results in uneven distribution of nickel, cobalt, and manganese ions within the ternary cathode material precursor, causing lithium ions to easily escape and consequently reducing battery cycle performance. The preparation method provided by this invention uses chlorides or nitrates of nickel, cobalt, and manganese as raw materials and employs polyvinyl phosphate organic complexing agent to complex the nickel, cobalt, and manganese cations. Based on the ability of polyvinyl phosphate to achieve indiscriminate complexation with divalent cations (nickel, cobalt, and manganese), a uniform complex is formed, effectively solving the problem of uneven distribution of nickel, cobalt, and manganese ions within the material. Furthermore, among ternary cathode materials, the (001) interface has the highest activity. Under conventional methods, crystal growth tends to occur along the (001) crystal plane. However, this application employs polyvinyl phosphate organic complexing agent, where the organic functional groups first act on the (001) crystal plane, hindering its growth. Therefore, the crystal plane tends to grow along the second most active crystal plane, effectively reducing the growth rate of the (001) crystal plane and minimizing its volume change during charging and discharging. In addition, polyvinyl phosphate exhibits a linear structure, meaning that the atoms constituting polyvinyl phosphate are mainly connected by covalent bonds to form a continuous "chain-like" framework. The atomic arrangement is relatively uniform, without obvious branches or ring structures. Therefore, polyvinyl phosphate is less prone to aggregation in solution, providing a linear morphological template for the oxidation of nickel, cobalt, and manganese, which is beneficial for the uniform distribution of nickel, cobalt, and manganese.

[0054] The ratio of the amount of complexing agent to the total amount of nickel, cobalt, and manganese is 0.1:1 to 0.5:1, such as 0.1:1, 0.2:1, 0.3:1, 0.4:1, or 0.5:1, or other values ​​within the range of 0.1:1 to 0.5:1.

[0055] If the amount of complexing agent is too small, it will not be conducive to the combination of complexing agent and nickel, cobalt and manganese ions; if the amount of complexing agent is too large, the organic content will be too high, and voids will be generated inside during the sintering process.

[0056] The complexation temperature can be between 50℃ and 90℃, such as 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, 85℃ or 90℃, or other values ​​within the range of 50℃ to 90℃.

[0057] If the complexation temperature is below 50℃, the complexation efficiency will be low and the complexation speed will be slow; if the temperature of the complexing agent is above 90℃, the complex will not be stable and precipitation will occur.

[0058] The pH value for complexation can be 4 to 5, such as 4, 4.2, 4.5, 4.8 or 5, or other values ​​within the range of 4 to 5.

[0059] If the pH value of the complex is below 4, it is easy to fail to complex; if the pH value of the complex is above 5, it is not conducive to the stability of the complex and precipitation will occur.

[0060] The complexation time can be 1h to 3h, such as 1h, 1.5h, 2h, 2.5h or 3h, or other values ​​within the range of 1h to 3h.

[0061] In some alternative embodiments, the spray pyrolysis temperature can be 800℃~1200℃, such as 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃, 1100℃, 1150℃ or 1200℃, or other values ​​within the range of 800℃~1200℃.

[0062] By performing spray pyrolysis under the above conditions, multiple polyvinylphosphoric acid complexed with metal ions can be formed into spherical or near-spherical particles, and the phosphate ions in polyvinylphosphoric acid can be reduced to phosphorus tetradecaoxide by carbon generated from polyvinyl at the above temperature.

[0063] In some alternative embodiments, the calcination temperature can be 800℃~1000℃, such as 800℃, 850℃, 900℃, 950℃ or 1000℃, or other values ​​within the range of 800℃~1000℃.

[0064] The calcination time can be 1h to 5h, such as 1h, 2h, 3h, 4h or 5h, or other values ​​within the range of 1h to 5h.

[0065] Under the above conditions, phosphorus decaoxide can sublimate and remove carbon materials.

[0066] In some alternative embodiments, after calcination, the calcined product is washed and dried to remove any residual chloride or nitrate ions, resulting in nickel-cobalt-manganese oxide with uniformly distributed nickel-cobalt-manganese and a uniformly distributed porosity inside.

[0067] In some alternative embodiments, the lithium source may be lithium hydroxide. The molar ratio of the calcined product to the lithium source may, for example, be from 1:1.02 to 1:1.05.

[0068] In some alternative embodiments, sintering includes a first sintering at 600°C to 750°C (e.g., 600°C, 650°C, 700°C, or 750°C) for 0.5h to 2h (e.g., 0.5h, 1h, 1.5h, or 2h), followed by a second sintering at 750°C to 950°C (e.g., 750°C, 800°C, 850°C, 900°C, or 950°C) for 20h to 30h (e.g., 20h, 25h, or 30h).

[0069] The first stage of sintering primarily decomposes lithium hydroxide into lithium oxide, while the second stage mainly involves the reaction of lithium oxide with metal salts to form lithium nickel cobalt manganese oxide. All sintering processes are carried out in an oxygen-rich atmosphere.

[0070] Lithium nickel cobalt manganese oxide (LCO) is formed by sintering a mixture of nickel, cobalt, and manganese oxides with lithium hydroxide, resulting in a lithium nickel cobalt manganese oxide material with uniform internal porosity and nickel, cobalt, and manganese element distribution. The uniform distribution of nickel, cobalt, and manganese in this LCO material ensures relatively uniform volume change during repeated charge-discharge cycles, which helps mitigate volume fluctuations. Furthermore, the uniform porous structure left by the carbon material also helps alleviate volume changes during lithium battery charge-discharge cycles, improving structural stability and thus extending the lifespan of the ternary cathode material.

[0071] It should be emphasized that the above method is only applicable if it can achieve the condition k1=Δ V This is one of the optional preparation methods for ternary cathode materials with / τ, k2=k2 / μ, k1≤20%, and k2≤40%. Alternatively, any other preparation method that can achieve the above parameters can be used depending on the actual situation.

[0072] In addition, the present invention also provides a battery cell whose positive electrode material includes the above-mentioned long-cycle ternary positive electrode material.

[0073] For example, the aforementioned battery cells can be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft.

[0074] The present invention also provides a battery comprising the above-described battery cells. This battery has good long-cycle performance and a long service life.

[0075] The present invention also provides an electrical device comprising the aforementioned battery cell and / or battery. As examples, the electrical device may include, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys may include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys; spacecraft may include airplanes, rockets, space shuttles, and spacecraft.

[0076] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0077] Example 1

[0078] This embodiment provides a long-cycle ternary cathode material, the preparation method of which includes:

[0079] Nickel chloride, cobalt chloride, and manganese chloride were mixed in a molar ratio of nickel, cobalt, and manganese of 0.6:0.2:0.2, and deionized water was added to obtain a mixed solution with a nickel ion concentration of 2 mol / L.

[0080] Polyvinylphosphoric acid was added to the above mixed solution as a complexing agent; the ratio of the complexing agent to the total amount of nickel, cobalt and manganese was 0.2:1 by molar amount; then complexation was carried out for 2 hours at pH 4 and temperature 70°C.

[0081] The solution obtained after complexation was subjected to spray pyrolysis at 1000℃. The spray pyrolysis material was then transferred to a rotary kiln and calcined under vacuum at 800℃ for 2 hours.

[0082] The calcined product obtained by vacuum calcination was washed and dried with water, and then mixed with lithium hydroxide at a molar ratio of 1:1.05. Under an oxygen atmosphere, the temperature was increased to 600℃ at a rate of 2℃ / min for a first-stage sintering of 1 hour, and then increased to 900℃ at a rate of 2℃ / min for a second-stage sintering of 20 hours. After the gas flow was broken up, the ternary cathode material of lithium nickel cobalt manganese oxide was obtained.

[0083] Example 2

[0084] This embodiment provides a long-cycle ternary cathode material, the preparation method of which includes:

[0085] Nickel chloride, cobalt chloride, and manganese chloride were mixed in a molar ratio of nickel, cobalt, and manganese of 0.8:0.1:0.1, and deionized water was added to obtain a mixed solution with a nickel ion concentration of 2 mol / L.

[0086] Polyvinylphosphoric acid was added to the above mixed solution as a complexing agent; the ratio of the complexing agent to the total amount of nickel, cobalt and manganese was 0.5:1 by molar amount; then complexation was carried out for 3 hours at pH 4 and temperature 80°C.

[0087] The solution obtained after complexation was subjected to spray pyrolysis at 1200℃. The spray-pyrolyzed material was then transferred to a rotary kiln and calcined under vacuum at 850℃ for 2 hours.

[0088] The calcined product obtained by vacuum calcination was washed and dried with water, and then mixed with lithium hydroxide at a molar ratio of 1:1.02. Under an oxygen atmosphere, the temperature was increased to 600℃ at a rate of 2℃ / min for a first-stage sintering of 1 hour, and then increased to 900℃ at a rate of 2℃ / min for a second-stage sintering of 25 hours. After airflow breakup, the ternary cathode material of lithium nickel cobalt manganese oxide was obtained.

[0089] Example 3

[0090] This embodiment provides a long-cycle ternary cathode material, the preparation method of which includes:

[0091] Nickel chloride, cobalt chloride, and manganese chloride were mixed in a molar ratio of nickel, cobalt, and manganese of 0.6:0.20:0.20, and deionized water was added to obtain a mixed solution with a nickel ion concentration of 3 mol / L.

[0092] Polyvinylphosphoric acid was added to the above mixed solution as a complexing agent; the ratio of the complexing agent to the total amount of nickel, cobalt and manganese was 0.3:1 by molar amount; then complexation was carried out for 1 hour at pH 4 and temperature 90°C.

[0093] The solution obtained after complexation was subjected to spray pyrolysis at 800°C. The spray-pyrolyzed material was then transferred to a rotary kiln and calcined under vacuum at 800°C for 2 hours.

[0094] The calcined product obtained by vacuum calcination was washed and dried with water, and then mixed with lithium hydroxide at a molar ratio of 1:1.05. Under an oxygen atmosphere, the temperature was increased to 650°C at a rate of 2°C / min for a first-stage sintering of 1 hour, and then increased to 850°C at a rate of 2°C / min for a second-stage sintering of 28 hours. After airflow breakup, the ternary cathode material of lithium nickel cobalt manganese oxide was obtained.

[0095] Example 4

[0096] This embodiment provides a long-cycle ternary cathode material, the preparation method of which includes:

[0097] Nickel nitrate, cobalt nitrate, and manganese nitrate were mixed in a molar ratio of nickel, cobalt, and manganese of 0.9:0.05:0.05, and deionized water was added to obtain a mixed solution with a nickel ion concentration of 3 mol / L.

[0098] Polyvinylphosphoric acid was added to the above mixed solution as a complexing agent; the ratio of the complexing agent to the total amount of nickel, cobalt and manganese was 0.1:1 by molar amount; then complexation was carried out for 3 hours at pH 4 and temperature 90°C.

[0099] The solution obtained after complexation was subjected to spray pyrolysis at 1100℃. The spray pyrolysis material was then transferred to a rotary kiln and calcined under vacuum at 900℃ for 2 hours.

[0100] The calcined product obtained by vacuum calcination was washed and dried with water, and then mixed with lithium hydroxide at a molar ratio of 1:1.05. Under an oxygen atmosphere, the temperature was increased to 750°C at a rate of 2°C / min for a first-stage sintering of 1 hour, and then increased to 850°C at a rate of 2°C / min for a second-stage sintering of 25 hours. After airflow breakup, the ternary cathode material of lithium nickel cobalt manganese oxide was obtained.

[0101] Example 5

[0102] This embodiment provides a long-cycle ternary cathode material, the preparation method of which includes:

[0103] Nickel chloride, cobalt chloride, and manganese chloride were mixed in a molar ratio of nickel, cobalt, and manganese of 0.5:0.2:0.3, and deionized water was added to obtain a mixed solution with a nickel ion concentration of 2 mol / L.

[0104] Polyvinylphosphoric acid was added to the above mixed solution as a complexing agent; the ratio of the complexing agent to the total amount of nickel, cobalt and manganese was 0.1:1 by molar amount; then complexation was carried out for 3 hours at pH 4 and temperature 90°C.

[0105] The solution obtained after complexation was subjected to spray pyrolysis at 900°C. The spray-pyrolyzed material was then transferred to a rotary kiln and calcined under vacuum at 800°C for 2 hours.

[0106] The calcined product obtained by vacuum calcination was washed and dried with water, and then mixed with lithium hydroxide at a molar ratio of 1:1.05. Under an oxygen atmosphere, the temperature was increased to 600℃ at a rate of 2℃ / min for a first-stage sintering of 1 hour, and then increased to 850℃ at a rate of 2℃ / min for a second-stage sintering of 30 hours. After airflow breakup, the ternary cathode material of lithium nickel cobalt manganese oxide was obtained.

[0107] Comparative Example 1

[0108] This comparative example provides a ternary cathode material, which is prepared using a conventional co-precipitation method, specifically including:

[0109] Nickel sulfate, cobalt sulfate, and manganese sulfate were mixed in a molar ratio of 0.8:0.1:0.1, and deionized water was added to obtain a mixed solution with a nickel ion concentration of 2 mol / L. Ammonia water (1 mol / L concentration; the amount of ammonia water added was twice the total amount of nickel, cobalt, and manganese) was added to the above mixed solution as a complexing agent, and sodium hydroxide (6 mol / L) was added as a precipitant to carry out a coprecipitation reaction. The coprecipitation reaction was carried out at pH 11 and a temperature of 70℃ for 5 hours. After the coprecipitation reaction was completed, the mixture was filtered, and the resulting material was dried at 120℃. The dried material was mixed with lithium hydroxide at a molar ratio of 1:1.05, and pre-calcined at 500℃ for 1 hour at a rate of 2℃ / min under an oxygen atmosphere, and then calcined at 900℃ for 20 hours at a rate of 2℃ / min. After airflow breakage, lithium nickel cobalt manganese oxide was obtained.

[0110] Comparative Example 2

[0111] The difference between this comparative example and Example 1 is that the complexation temperature is 40°C.

[0112] Comparative Example 3

[0113] The difference between this comparative example and Example 1 is that the complexation temperature is 95°C.

[0114] Comparative Example 4

[0115] The difference between this comparative example and Example 1 is that the pH value of the complexation is 3.5.

[0116] Comparative Example 5

[0117] The difference between this comparative example and Example 1 is that the pH value of the complexation is 5.5.

[0118] Comparative Example 6

[0119] The difference between this comparative example and Example 1 is that the ratio of the amount of complexing agent to the total amount of nickel, cobalt, and manganese is 0.05:1.

[0120] Comparative Example 7

[0121] The difference between this comparative example and Example 1 is that the ratio of the amount of complexing agent to the total amount of nickel, cobalt, and manganese is 0.8:1.

[0122] Comparative Example 8

[0123] The difference between this comparative example and Example 1 is that the complexing agent is replaced with ammonia.

[0124] Test case

[0125] The ternary cathode materials prepared in Examples 1-5 and Comparative Examples 1-8 were delithiated in the following manner, and according to k1=Δ V / τ,k2=k1 / μ;Δ V =[(V1-V2) / V1]×100%,τ=(m2 / m1)×100% to calculate the values ​​of k1 and k2, and the results are shown in Table 1.

[0126] Lithium removal method: Immerse the ternary cathode material in water. Specifically: Take 10g of ternary cathode material and immerse it in water at 20℃ for 1 hour at a solid-liquid ratio of 1:2 (by mass) to leach some lithium ions from the crystal lattice into the water. Then, separate the solid and liquid to obtain the delithiated material and the lithium-containing leaching solution.

[0127] Volumes V1 and V2 were measured using a compaction density meter. V1 is the volume of the ternary cathode material after being compressed under pressure P before delithiation; V2 is the volume of the delithiated material after being dried and compressed under pressure P, where P is 100 MPa.

[0128] m2 is calculated by multiplying the concentration of lithium ions in the leaching solution by an inductively coupled plasma atomic divergence spectrometer (ICP-AES) by the volume of the leaching solution. m1 is calculated by weighing the ternary cathode material using a weighing balance and then calculating the mass based on the percentage of lithium in the ternary cathode material.

[0129] The proportion of lithium and the content of nickel atoms μ were calculated using an inductively coupled plasma atomic divergence spectrometer according to YS / T 1006.2-2014.

[0130] Furthermore, the ternary cathode materials prepared in Examples 1-5 and Comparative Examples 1-8 were assembled into coin cells in the following manner, and the cycle performance of each cell was tested. The results are shown in Table 2.

[0131] The ternary cathode materials prepared in the above embodiments and comparative examples were respectively used to prepare electrodes and assembled into batteries. Specific methods included: mixing the ternary cathode material, conductive carbon black, and PVDF in an 8:1:1 mass ratio, adding them to NMP solvent, and magnetically stirring to form a uniform slurry; coating the slurry onto aluminum foil and vacuum drying at 100°C for 12 hours; cutting the prepared electrode sheet into 12mm circular slices using a slicer and weighing them; controlling the load of each electrode at 1.5 mg / cm². 2 ~3mg / cm 2Assemble a coin cell using this electrode in a glove box, with lithium metal as the negative electrode, Celgrad2400 as the separator, and a 1 mol / L LiPF6 organic solution (the solvent is a mixture of EC, DEC, and DMC in a volume ratio of EC:DEC:DMC=1:1:1) as the electrolyte to form a CR2032 coin cell.

[0132] Performance testing method: Constant current charge and discharge test was performed using a Blue Battery test cabinet; the test voltage range was 2.5V-4.2V, the charge and discharge rate was 1C, and the test temperature was 25℃.

[0133] Table 1. Performance Results of Ternary Cathode Materials

[0134]

[0135] As can be seen from Table 1, compared with the comparative example, under the same leaching ratio of τ, the ternary cathode material provided in the embodiments of the present invention has a smaller volume change before and after delithiation, that is, a smaller k1.

[0136] Table 2 Battery performance results

[0137]

[0138] As can be seen from Table 2, the ternary cathode material provided in the embodiments of the present invention can enable the corresponding battery to have better cycle performance.

[0139] In summary, the long-cycle ternary cathode material provided by this invention exhibits small volume changes and fewer cracks in secondary particles during battery charging and discharging, effectively preventing and mitigating electrolyte ingress, thus enabling the battery to have better cycle performance.

[0140] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A ternary cathode material, characterized in that, The ternary cathode material satisfies k1=Δ V / τ,k2=k1 / μ;Δ V =[(V1-V2) / V1]×100%, τ=(m2 / m1)×100%; k1 is 14%~15.8%, k2 is 25%~37.5%, Δ V The percentage is 1.8% to 4.3%; Wherein, μ represents the nickel atom content in the ternary cathode material, expressed as an atomic mass percentage; Δ V τ represents the volume change rate of the ternary cathode material before and after delithiation, V1 is the volume of the ternary cathode material after being compressed under pressure P before delithiation, and V2 is the volume of the ternary cathode material after being compressed under the same pressure P after delithiation; τ is the percentage of delithiation of the ternary cathode material, m1 is the mass of lithium contained in the ternary cathode material before delithiation, and m2 is the mass of lithium removed from the ternary cathode material after delithiation. The delithiation method includes: taking 10.000g±0.010g of ternary cathode material and soaking it in room temperature water for 0.5h~5h at a solid-liquid ratio of 1:1 to 1:5 by mass, so that some lithium ions in the crystal lattice are leached into the water, and then the solid and liquid are separated to obtain the delithiated material and the lithium-containing leaching solution. m2 is calculated by detecting the concentration of lithium ions in the leaching solution and then multiplying it by the volume of the leaching solution; m1 is calculated by the initial weight of the ternary cathode material used according to the proportion of lithium element in the ternary cathode material. The value of P ranges from 50 MPa to 300 MPa.

2. The ternary cathode material of claim 1, wherein, The ternary cathode material has at least one of the following characteristics: Feature 1: μ is 40%~57%; Feature 2: τ is 12%~30%.

3. A method for producing the ternary positive electrode material according to claim 1 or 2, characterized by, Includes the following steps: A mixed solution containing nickel, cobalt, and manganese sources is complexed with a complexing agent, and the complexed solution is then subjected to spray pyrolysis and calcination. The calcined product is mixed with a lithium source and sintered to obtain lithium nickel cobalt manganese oxide.

4. The production method according to claim 3, characterized by, The mixed solution includes at least one of the following characteristics: Feature 3: The nickel source includes at least one of nickel chloride and nickel nitrate; Feature 4: The cobalt source includes at least one of cobalt chloride and cobalt nitrate; Feature 5: The manganese source includes at least one of manganese chloride and manganese nitrate; Feature 6: The molar ratio of Ni, Co and Mn in the nickel source, the cobalt source and the manganese source is (0.5~0.98):(0.01~0.2):(0.01~0.3).

5. The preparation method according to claim 3, characterized in that, Complexation includes at least one of the following characteristics: Feature 7: The complexing agent is polyvinylphosphoric acid; Feature 8: The ratio of the amount of the complexing agent to the total amount of nickel, cobalt, and manganese is 0.1:1 to 0.5:1; Feature 9: The complexation temperature is 50℃~90℃; Feature 10: The pH value of the complex is 4~5; Feature 11: The complexation time is 1h~3h.

6. The preparation method according to claim 3, characterized in that, The spray pyrolysis temperature is 800℃~1200℃; And / or, the calcination temperature is 800℃~1000℃, and the calcination time is 1h~5h.

7. The preparation method according to claim 3, characterized in that, Sintering includes a first stage of sintering at 600℃~750℃ for 0.5h~2h, followed by a second stage of sintering at 750℃~950℃ for 20h~30h.

8. A battery, characterized by The battery comprises the ternary cathode material as described in claim 1 or 2.

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