High-stability high-specific-capacity ternary positive electrode material and lithium ion battery

Abstract

The application discloses a high-stability high-specific-capacity ternary positive electrode material and a lithium ion battery. a Co b Mn c O2, the core material is doped with carbonized thickening agent and conductive agent; the thickening agent is methyl cellulose and / or carboxymethyl cellulose; the conductive agent is conductive carbon black; and the coating layer is one or more of aluminum oxide, lanthanum oxide and yttrium oxide. The further-prepared lithium ion battery has the advantages of high specific capacity, good cycle performance, small thickness expansion rate and high energy density, and the preparation process operation flow is simple, which is beneficial to large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and specifically relates to a high-stability, high-specific-capacity ternary cathode material and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are widely used in small electronic devices such as mobile phones, laptops, cameras, and portable measuring instruments, and are showing broad application prospects in electric bicycles and automobiles. Improvements in lithium-ion battery performance often depend on the development and improvement of cathode materials. As the dominant material in lithium-ion batteries, the cathode material determines the battery's electrochemical performance and safety performance.

[0003] Modification measures for ternary cathode materials mainly involve coating the surface of secondary particles to form a coating layer. This coating layer, to some extent, suppresses side reactions between the material and the electrolyte, as well as irreversible phase transitions within the material itself. However, with increasing voltage, a large amount of Li is released from the cathode material during charging. + Afterwards, the layered structure of the cathode material will collapse, thereby deteriorating the material's cycle performance.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a ternary cathode material and its preparation method. By doping and coating the material, side reactions between the material and the electrolyte are suppressed, gas production during battery cycling is reduced, and the material has the advantages of high stability and high specific capacity, effectively improving the safety performance of the battery and thus improving the cycle stability of the battery.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] In a first aspect, the present invention provides a lithium nickel cobalt manganese oxide ternary cathode material, comprising the following components: a core material and a coating layer;

[0008] The chemical formula of the core material is LiNi. a Co b Mn c O2, where 0.6≤a≤0.9, 0.1≤b≤0.3, 0.1≤c≤0.4, and a+b+c=1;

[0009] The core material is doped with carbonized thickeners and conductive agents;

[0010] The thickener is methylcellulose (MC) and / or carboxymethylcellulose.

[0011] The conductive agent is conductive carbon black, preferably acetylene black;

[0012] The coating layer is one or more of aluminum oxide, lanthanum oxide, and yttrium oxide.

[0013] The physicochemical properties of the lithium nickel cobalt manganese oxide ternary cathode material are as follows:

[0014] Particle size D 50 The micrometer size is 3.5 ± 1.0 μm, preferably 3.5-3.59 μm;

[0015] Specific surface area is 0.4-0.8 m² 2 / g, preferably 0.60-0.65m 2 / g;

[0016] 1C discharge specific capacity ≥190mAh / g;

[0017] The tap density is 1.3-2.0 g / cm³. 3 The preferred concentration is 1.65-1.7 g / cm³. 3 .

[0018] Secondly, the present invention further provides a method for preparing the lithium nickel cobalt manganese oxide ternary cathode material, comprising the following steps:

[0019] S1. Mix nickel salt, cobalt salt, manganese salt, thickener and conductive agent, grind to obtain a mixture;

[0020] S2. Add deionized water and surfactant to the mixture, stir, add precipitant to react, and obtain ternary precursor;

[0021] S3. Dry the ternary precursor to obtain a solid powder;

[0022] S4. Mix the lithium source with the solid powder and nickel oxide, sinter, cool and then ball mill to obtain an intermediate product;

[0023] S5. The intermediate product is mixed with the coating agent, sintered twice, crushed and sieved to obtain the lithium nickel cobalt manganese oxide ternary cathode material.

[0024] In step S1, the nickel salt is one or more of nickel acetate, nickel carbonate, and nickel chloride.

[0025] The cobalt salt is one or more of cobalt acetate, cobalt carbonate, and cobalt chloride.

[0026] The manganese salt is one or more of manganese acetate, manganese carbonate, and manganese chloride.

[0027] Based on the total mass of the nickel salt, the cobalt salt, and the manganese salt, the amount of the thickener is 0.5-3.0%, preferably 1-1.5%; the amount of the conductive agent is 0.2-2%, preferably 0.8-1.5%.

[0028] The grinding conditions are as follows: a rotation speed of 500-1500 rpm, preferably 800-1000 rpm, and a grinding time of 2-5 hours, preferably 4 hours.

[0029] In step S2, the surfactant is sodium dodecylbenzenesulfonate.

[0030] Based on the mass of the mixture, the amount of surfactant used is 1-5%, preferably 1.5-2%.

[0031] The precipitant is oxalic acid, dimethyl oxalate, or an alkaline solution; wherein the alkaline solution is ammonia or sodium hydroxide solution.

[0032] Based on the mass of the lithium nickel cobalt manganese oxide ternary cathode material, the amount of the precipitant is 5%-10%, preferably 6-9%.

[0033] The reaction conditions are: temperature of 150-200℃, preferably 160-170℃, and time of 10-50h, preferably 24h.

[0034] In step S3, the drying conditions are: water bath or oil bath, temperature 60-90℃, preferably 80-90℃, time 8-12h, preferably 8-10h.

[0035] In step S4, the lithium source is one or more of lithium carbonate, lithium fluoride, lithium hydroxide, and lithium acetate.

[0036] The sintering conditions are: a temperature of 850-950℃, preferably 900℃, and a time of 5-12h, preferably 10h.

[0037] The conditions for ball milling are: rotation speed of 900-1300 rpm, preferably 1000-1100 rpm, and time of 2-5 hours, preferably 4 hours.

[0038] The particle size D of the intermediate product 50 The size is 10-15μm, preferably 13μm.

[0039] In step S5, based on the mass of the lithium nickel cobalt manganese oxide ternary cathode material, the amount of the coating agent is 0.05-1%.

[0040] The conditions for the secondary sintering are: a temperature of 850-950℃, preferably 900℃, and a time of 8-12h, preferably 10h.

[0041] The crushing method is roller crushing.

[0042] Thirdly, the present invention further provides a lithium-ion battery comprising: a positive electrode and a negative electrode; wherein the positive electrode is made of the lithium nickel cobalt manganese oxide ternary positive electrode material.

[0043] The beneficial effects achieved by this invention are as follows:

[0044] 1. This invention effectively controls grain growth through carbonization and coating with thickeners such as methyl cellulose, resulting in orderly and densely packed grains inside the material, thus maintaining the structural stability of the electrode material. Further surface coating with alumina allows it to react with excess lithium on the material surface, reducing its alkalinity. By combining these two treatment methods, the dopant and coating agent mutually promote each other, resulting in a ternary cathode material with advantages such as high specific capacity, good cycle performance, low thickness expansion, and high energy density.

[0045] 2. The raw materials used in this invention are inexpensive, readily available, safe, and environmentally friendly; the material synthesized after coating does not change the crystal structure and morphology of the ternary cathode material, and has a high cycle retention rate during cycling; the method is simple, easy to operate, and universal, and is easy to promote industrially. Attached Figure Description

[0046] Figure 1 The crystal structure of the ternary cathode material obtained in Example 1 is shown.

[0047] Figure 2 The morphology of the ternary cathode material obtained in Example 1 is shown. Detailed Implementation

[0048] The present invention will be further described below with reference to specific embodiments, but the present invention is not limited to the following embodiments.

[0049] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0050] Unless otherwise specified, all reagents, materials, instruments, etc. used in the following examples are commercially available.

[0051] Example 1

[0052] The specific operating steps are as follows:

[0053] (1) Weigh out 120g of hydrated nickel chloride, hydrated cobalt chloride and hydrated manganese chloride with the same molar mass, put them into the reactor, and then weigh out 1% of the total mass of the above substances, MC and acetylene black, grind them at 1000rpm for 4 hours to obtain a mixture.

[0054] (2) Add sodium dodecylbenzenesulfonate (2% of the total mass of the mixture) and an appropriate amount of deionized water to the above mixture. Sodium dodecylbenzenesulfonate is added in solution form. Stir to obtain a mixed solution. Then add 8g of oxalic acid. After stirring evenly, place in a drying oven at 160℃ for 24h and evaporate to dryness to obtain the ternary precursor.

[0055] (3) The ternary precursor was preheated and stirred in a water bath. The evaporation temperature was 80℃ and the stirring time was 8h to obtain solid powder.

[0056] (4) 15g of lithium carbonate, the above solid powder and 10g of nickel oxide were sintered at 900℃ for 10h, cooled and then ball-milled for 4h at 1100rpm to obtain a particle size D. 50 It is an intermediate product with a diameter of 13 μm.

[0057] (5) The intermediate product obtained above is mixed evenly with 0.8g of alumina, kept at 900℃ for 10 hours, and then crushed and sieved after natural cooling to obtain ternary cathode material.

[0058] Example 2

[0059] The specific operating steps are as follows:

[0060] (1) Weigh out 120g of hydrated nickel chloride, hydrated cobalt chloride and hydrated manganese chloride with the same molar mass, put them into the reactor, and then weigh out MC and acetylene black with a mass fraction of 1.5% of the total mass of the above substances. Grind them at high speed for 4 hours at a speed of 1000rpm to obtain a mixture.

[0061] (2) Add 1.5% sodium dodecylbenzenesulfonate and an appropriate amount of deionized water to the above mixture. Sodium dodecylbenzenesulfonate is added in solution form. Stir to obtain a mixed solution. Then add 10g of oxalic acid. After stirring evenly, place in a drying oven at 160℃ for 24h and evaporate to dryness to obtain the ternary precursor.

[0062] (3) The ternary precursor was preheated and stirred in a water bath. The evaporation temperature was 80℃ and the stirring time was 10h to obtain solid powder.

[0063] (4) 15g of lithium carbonate, the above solid powder, and 10g of nickel oxide were sintered at 900℃ for 10h, cooled, and then ball-milled for 4h at 1000rpm to obtain a particle size D. 50 It is an intermediate product with a diameter of 13 μm.

[0064] (5) The intermediate product obtained above is mixed evenly with 0.8g of alumina, kept at 900℃ for 10 hours, and then crushed and sieved after natural cooling to obtain ternary cathode material.

[0065] Comparative Example 1 (Methylcellulose MC was not added in step (1))

[0066] (1) Weigh out 120g of hydrated nickel chloride, hydrated cobalt chloride and hydrated manganese chloride with the same molar mass, put them into the reactor, and then weigh out acetylene black with a mass fraction of 1.5% of the total mass of the above substances. Grind at high speed for 4 hours to obtain a mixture.

[0067] (2) Add 2% of sodium dodecylbenzenesulfonate and an appropriate amount of deionized water to the above mixture. Sodium dodecylbenzenesulfonate is added in solution form. Stir to obtain a mixed solution. Then add 8g of oxalic acid. After stirring evenly, place in a drying oven at 150℃ for 24h and evaporate to dryness to obtain the ternary precursor.

[0068] (3) The ternary precursor was preheated and stirred in a water bath. The evaporation temperature was 60℃ and the stirring time was 8h to obtain solid powder.

[0069] (4) 15g of lithium carbonate, the above solid powder and 10g of nickel oxide were sintered at 900℃ for 10h, cooled and then ball-milled to obtain a particle size D. 50 It is an intermediate product with a diameter of 13 μm.

[0070] (5) The intermediate product obtained above is mixed evenly with 5g of alumina, kept at 900℃ for 10 hours, and then crushed and sieved after natural cooling to obtain ternary cathode material.

[0071] Comparative Example 2 (Sodium dodecylbenzenesulfonate was not added in step (2))

[0072] (1) Weigh out 120g of hydrated nickel chloride, hydrated cobalt chloride, and hydrated manganese chloride with the same molar mass, put them into the reactor, and then weigh out MC and acetylene black with a mass fraction of 1% of the total mass of the above substances. Grind them at high speed for 4 hours to obtain a mixture.

[0073] (2) Add an appropriate amount of deionized water to the above mixture, stir to obtain a mixed solution, then add 8g of oxalic acid, stir evenly and place in a drying oven at 150℃ for 24h, and evaporate to dryness to obtain the ternary precursor.

[0074] (3) The ternary precursor was preheated and stirred in a water bath. The evaporation temperature was 60℃ and the stirring time was 8h to obtain solid powder.

[0075] (4) 15g of lithium carbonate, the above solid powder and 10g of nickel oxide were sintered at 900℃ for 10h, cooled and then ball-milled to obtain a particle size D. 50 It is an intermediate product with a diameter of 13 μm.

[0076] (5) The intermediate product obtained above is mixed evenly with 5g of alumina, kept at 900℃ for 10 hours, and then crushed and sieved after natural cooling to obtain ternary cathode material.

[0077] Comparative Example 3 (no alumina was added in step (5))

[0078] (1) Weigh out 120g of hydrated nickel chloride, hydrated cobalt chloride and hydrated manganese chloride with the same molar mass, put them into the reactor, and then weigh out MC and acetylene black with a mass fraction of 1.5% of the total mass of the above substances. Grind them at high speed for 4 hours to obtain a mixture.

[0079] (2) Add 1.5% sodium dodecylbenzenesulfonate and an appropriate amount of deionized water to the above mixture. Sodium dodecylbenzenesulfonate is added in solution form. Stir to obtain a mixed solution. Then add 10g of oxalic acid. After stirring evenly, place in a drying oven at 160℃ for 24h and evaporate to dryness to obtain the ternary precursor.

[0080] (3) The ternary precursor was preheated and stirred in a water bath. The evaporation temperature was 80℃ and the stirring time was 8h to obtain solid powder.

[0081] (4) 15g of lithium carbonate, the above solid powder and 10g of nickel oxide were sintered at 900℃ for 10h, cooled and then ball-milled to obtain a particle size D. 50 It is an intermediate product with a diameter of 13 μm.

[0082] (5) The intermediate product obtained above is kept at 900°C for 10 hours, and after natural cooling, it is crushed and sieved to obtain ternary cathode material.

[0083] Effect verification

[0084] 1. Structural characterization

[0085] like Figure 1 , Figure 2 As shown, the crystal structure and morphology of the obtained material are not changed by the coating, and the growth of grains can be effectively controlled by the coating. The grains inside the material are arranged in an orderly manner and are packed relatively densely, which maintains the structural stability of the electrode material and thus has a high cycle retention rate during cycling.

[0086] 2. Physicochemical Indicators

[0087] Table 1. Physicochemical properties of materials obtained from the examples and comparative examples.

[0088] Example 1 3.58 0.62 1.70 Example 2 3.52 0.64 1.69 Comparative Example 1 3.42 0.78 1.43 Comparative Example 2 3.47 0.72 1.56 Comparative Example 3 3.50 0.66 1.68

[0089] As can be seen from the table above, the ternary cathode materials prepared in Examples 1 and 2 have moderate particle size and specific surface area, resulting in a larger tap density. Comparative Examples 1 and 2 did not add carbon coating agent and surface activator, respectively, and the particle size was smaller, resulting in a larger specific surface area and a smaller tap density.

[0090] 3. Performance Testing

[0091] Lithium-ion batteries were prepared and tested using the cathode materials obtained in the above embodiments and comparative examples. The specific preparation methods are as follows:

[0092] After mixing 0.5g of positive electrode material, 0.05g of organic binder (PVDF), and 1.25g of composite conductive agent (a mixture of conductive carbon black and multi-walled carbon nanotubes) evenly, the mixture was stirred at high speed for 6 hours using N-methylpyrrolidone (NMP) as a solvent. The slurry was then evenly coated onto aluminum foil and dried at 90°C for 2 hours. The electrode was then vacuum dried at 88°C for 6 hours. The moisture content was measured to be below 300ppm before proceeding to the next step. A lithium sheet was used as the negative electrode of the lithium-ion battery, a polypropylene / polyethylene (PP / PE) composite membrane was used as the separator, and a LiPF6 / EC:DEC (volume ratio 1:1) solution was used as the electrolyte. Button batteries were assembled in an anhydrous glove box under an argon atmosphere and allowed to stand for 12 hours for aging.

[0093] The following are the results of testing a full cell made from the prepared cathode material.

[0094] Table 2. Full Battery Test Results

[0095] Example 1 195.2 94.5 2.3 Example 2 194.9 95.8 2.8 Comparative Example 1 182.9 87.7 5.1 Comparative Example 2 180.8 86.5 5.3 Comparative Example 3 183.6 83.2 3.3

[0096] As can be seen from the test results in the table above, compared with Comparative Examples 1-3, Examples 1-2, through carbonization / doping of methyl cellulose and coating with alumina, resulted in ternary cathode materials with higher specific capacity, better cycle performance, smaller thickness expansion rate and higher energy density, which was verified to be ≥290Wh / kg.

[0097] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a lithium nickel cobalt manganese oxide ternary cathode material, characterized in that, Includes the following steps: S1. Mix nickel salt, cobalt salt, manganese salt, thickener and conductive agent, grind to obtain a mixture; S2. Add deionized water and surfactant to the mixture, stir, add precipitant to react, and obtain ternary precursor; S3. Dry the ternary precursor to obtain a solid powder; S4. Mix the lithium source with the solid powder and nickel oxide, sinter, cool, and ball mill to obtain an intermediate product; S5. The intermediate product is mixed with the coating agent, sintered twice, crushed, and sieved to obtain the lithium nickel cobalt manganese oxide ternary cathode material. The lithium nickel cobalt manganese oxide ternary cathode material comprises the following components: a core material and a coating layer; The chemical formula of the core material is LiNi. a Co b Mn c O2, where 0.6≤a≤0.9, 0.1≤b≤0.3, 0.1≤c≤0.4, and a+b+c=1; The core material is doped with carbonized thickeners and conductive agents; The coating layer is one or more of aluminum oxide, lanthanum oxide, and yttrium oxide; The thickener is methylcellulose and / or carboxymethylcellulose.

2. The method for preparing the lithium nickel cobalt manganese oxide ternary cathode material according to claim 1, characterized in that: In step S1, the nickel salt is one or more of nickel acetate, nickel carbonate, and nickel chloride; The cobalt salt is one or more of cobalt acetate, cobalt carbonate, and cobalt chloride; The manganese salt is one or more of manganese acetate, manganese carbonate, and manganese chloride; Based on the total mass of the nickel salt, the cobalt salt, and the manganese salt, the amount of the thickener is 0.5-3%, and the amount of the conductive agent is 0.2-2%. The grinding conditions are: a rotation speed of 500-1500 rpm and a grinding time of 2-5 hours.

3. The method for preparing the lithium nickel cobalt manganese oxide ternary cathode material according to claim 1, characterized in that: In step S2, the surfactant is sodium dodecylbenzenesulfonate; Based on the mass of the mixture, the amount of surfactant used is 1-5%; The precipitant is oxalic acid, dimethyl oxalate, or an alkaline solution; Based on the mass of the lithium nickel cobalt manganese oxide ternary cathode material, the amount of the precipitant is 5%-10%; The reaction conditions are: temperature 150-200℃, time 10-50h.

4. The method for preparing the lithium nickel cobalt manganese oxide ternary cathode material according to claim 1, characterized in that: In step S3, the drying conditions are: water bath or oil bath, temperature 60-90℃, time 8-12h.

5. The method for preparing the lithium nickel cobalt manganese oxide ternary cathode material according to claim 1, characterized in that: In step S4, the lithium source is one or more of lithium carbonate, lithium fluoride, lithium hydroxide, and lithium acetate; The sintering conditions are: temperature 850-950℃, time 5-12h; The conditions for ball milling are: rotation speed of 900-1300 rpm and time of 2-5 hours; The particle size D of the intermediate product 50 It is 10-15 μm.

6. The method for preparing the lithium nickel cobalt manganese oxide ternary cathode material according to claim 1, characterized in that: In step S5, based on the mass of the lithium nickel cobalt manganese oxide ternary cathode material, the amount of the coating agent is 0.05-1%; The conditions for the secondary sintering are: temperature of 850-950℃ and time of 8-12h.

7. The lithium nickel cobalt manganese oxide ternary cathode material obtained by the preparation method according to any one of claims 1-6.

8. The lithium nickel cobalt manganese oxide ternary cathode material according to claim 7, characterized in that: The conductive agent is conductive carbon black.

9. The lithium nickel cobalt manganese oxide ternary cathode material according to claim 7, characterized in that: The physicochemical properties of the lithium nickel cobalt manganese oxide ternary cathode material are as follows: Particle size D 50 It is 3.5±1.0μm; Specific surface area is 0.4-0.8 m² 2 / g; 1C discharge specific capacity ≥190mAh / g; The tap density is 1.3-1.6 g / cm³. 3 .

10. A lithium-ion battery, comprising: a positive electrode and a negative electrode; wherein the positive electrode is made of the ternary positive electrode material of lithium nickel cobalt manganese oxide as described in any one of claims 7-9.

Images