Composite positive electrode material and preparation method thereof, lithium ion battery and electrical equipment

Abstract

The present application provides a composite positive electrode material and its preparation method, lithium ion battery and electrical equipment, and relates to the field of new energy technology. The method of the present application is based on co-precipitation-solid phase reaction. By setting different chelating agent concentrations and rotation speeds in two stages of co-precipitation, a composite positive electrode material precursor is obtained. Then, in the subsequent solid phase sintering process, a flux is added to tightly coat the LLZO solid electrolyte on the surface of the high nickel ternary positive electrode material. The synchronously synthesized high nickel ternary / LLZO composite positive electrode material provided by the present application has a closer contact between the LLZO solid electrolyte and the high nickel ternary material, and a more uniform coating, which improves the lithium ion transfer kinetics while preventing the electrolyte from contacting the highly active Ni 4+ Direct contact reduces the generation of rock salt phase, and the garnet-type LLZO electrolyte can also enhance the phase change reversibility of high-nickel ternary materials through lithium replenishment strategy, thereby obtaining a composite positive electrode material with high rate performance and high cycle stability.

Description

Technical Field

[0001] The present application relates to the field of new energy technology, and in particular to a composite positive electrode material and a preparation method thereof, a lithium-ion battery and electrical equipment. Background Art

[0002] The positive electrode material is the key to the comprehensive performance of lithium-ion batteries. High nickel ternary positive electrode materials have the advantages of high working voltage and high discharge capacity. However, during the delithiation process, high nickel materials will produce Ni with strong oxidizing properties. 4+ , which is prone to side reactions with the electrolyte, affecting the structural stability of the positive electrode material, thereby reducing the battery cycle life and safety performance.

[0003] Garnet-type oxide LLZO (Li7La3Zr2O 12 ) has the advantages of wide electrochemical window (>5V), good chemical and thermal stability, and the lithium ion conductivity can reach 10 at room temperature. -4 S cm -1 , is a solid electrolyte material with great development potential.

[0004] Studies have shown that by co-firing the fast ion conductor LLZO with high-nickel positive electrode active materials, LLZO can be evenly coated on the surface of the high-nickel positive electrode active materials, which can effectively inhibit the interfacial side reactions between the high-nickel positive electrode materials and the electrolyte, thereby achieving the purpose of improving the battery's rate performance and cycle life.

[0005] However, the current synthesis of high-nickel ternary / LLZO composite positive electrode materials requires the separate synthesis of positive electrode materials and solid electrolytes, and then co-firing the two to form a composite. The process is cumbersome and complicated, and because the crystal phase formation temperatures of the two are quite different, the crystal phase composition of the composite positive electrode material is difficult to control, resulting in poor performance improvement. Summary of the Invention

[0006] The purpose of this application is to provide a composite positive electrode material and its preparation method, a lithium-ion battery and electrical equipment, aiming to solve the problems of complex preparation process and difficult control of crystal phase composition of existing high-nickel ternary / LLZO composite positive electrode materials.

[0007] To achieve the above objectives, the present application provides a method for preparing a composite positive electrode material, comprising:

[0008] A first mixed salt solution containing nickel, cobalt, and manganese, a first complexing agent, and an alkaline solution are introduced into the bottom liquid of the reaction kettle to perform a first coprecipitation reaction;

[0009] After the first coprecipitation reaction, a second mixed salt solution containing lanthanum and zirconium, a second complexing agent and an alkaline solution are introduced to perform a second coprecipitation reaction to obtain a precursor slurry;

[0010] Collecting the precipitate from the precursor slurry, washing it, and drying it to obtain a high-nickel ternary / LLZO composite precursor;

[0011] The high-nickel ternary / LLZO composite precursor is mixed with a lithium source and calcined to obtain a high-nickel ternary / LLZO composite positive electrode material.

[0012] In some embodiments, at least one of the following conditions is met:

[0013] A. the total metal ion concentration in the first mixed salt solution is 1.4-2.0 mol / L, and the total metal ion concentration in the second mixed salt solution is the same as that in the first mixed salt solution;

[0014] B. The total mass of the second mixed salt solution introduced is 0.5%-5% of the mass of the first mixed salt solution;

[0015] C. The first complexing agent and the second complexing agent are aqueous ammonia solutions, the concentration of the first complexing agent is 0.5-2 mol / L, and the concentration of the second complexing agent is 0.2-0.8 mol / L;

[0016] D. the alkali solution is a NaOH solution, and the concentration of the NaOH solution is 1-4 mol / L;

[0017] E. The bottom liquid of the reactor is an ammonia solution with a concentration of 9-11 g / L.

[0018] In some embodiments, at least one of the following conditions is met:

[0019] A. the pH value of the first coprecipitation reaction is 9-12;

[0020] B. the rotation speed of the first coprecipitation reaction is 400-900 rpm;

[0021] C. the temperature of the first coprecipitation reaction is 50-60°C;

[0022] D. the first coprecipitation reaction time is 8-12 h;

[0023] E. the rotation speed of the second coprecipitation reaction is 700-1200 rpm;

[0024] F. the pH value and reaction temperature of the second coprecipitation reaction are the same as those of the first coprecipitation reaction;

[0025] G. both the first coprecipitation reaction and the second coprecipitation reaction are carried out under a protective atmosphere;

[0026] H. The flow ratio of the mixed salt solution, complexing agent solution and alkaline solution in the two stages is the same;

[0027] Optionally, the flow ratio of the mixed salt solution, the complexing agent solution and the alkaline solution is 1:0.3:(0.5-2).

[0028] In some embodiments, the mixing and calcining of the high nickel ternary / LLZO composite precursor with a lithium source comprises:

[0029] The high nickel ternary / LLZO composite precursor is mixed with a lithium source and a flux, and then calcined.

[0030] In some embodiments, at least one of the following conditions is met:

[0031] A. The flux includes one or more of LiF, Li3PO4, and LiBiO3;

[0032] B. The amount of the flux added is 1%-5% of the molar number of the high nickel ternary / LLZO composite precursor;

[0033] C. The lithium source is one or more of lithium hydroxide, lithium carbonate, lithium chloride, lithium nitrate, lithium sulfate, lithium acetate, lithium phosphate and lithium oxalate.

[0034] In some embodiments, the calcination is divided into two stages: the first stage is heating to 400-600°C and keeping warm for 6-10 hours; the second stage is heating to 700-1000°C and keeping warm for 10 hours. The heating rate is 1-10°C / min. The whole calcination process is carried out in an oxygen atmosphere.

[0035] In some embodiments, the chemical formula of the high nickel ternary / LLZO composite precursor is: Ni a Co b Mn 1-a-b (OH)2·cLa3Zr2(OH) 17 The chemical formula of the high nickel ternary / LLZO composite cathode material is: LiNi a Co b Mn 1-a-b O2·cLi7La3Zr2O 12 , where a≥0.6, 0.1≤b≤0.3, 0.5wt% <c<5wt%。

[0036] The present application also provides a composite positive electrode material, which is prepared by the above-mentioned method for preparing the composite positive electrode material.

[0037] The present application also provides a lithium-ion battery comprising the above-mentioned composite positive electrode material.

[0038] The present application also provides an electrical device comprising the above-mentioned lithium-ion battery.

[0039] Compared with the prior art, the advantages of this application include:

[0040] The preparation method of the composite positive electrode material provided in this application simultaneously synthesizes a high-nickel ternary / LLZO composite precursor and a positive electrode material. Compared with the traditional composite positive electrode material synthesis method that requires the synthesis of high-nickel ternary and LLZO separately and then the two are compounded through other experiments, the method of this application is similar to the current ternary positive electrode material synthesis route, which greatly simplifies the production process of high-nickel ternary / LLZO composite positive electrode materials and reduces production costs. The method of this application is based on coprecipitation-solid phase reaction. By setting different complexing agent concentrations and rotation speeds in the two coprecipitation processes, a composite positive electrode material precursor is obtained. Then, in the subsequent solid phase sintering process, a flux is added to tightly coat the LLZO solid electrolyte on the surface of the high-nickel ternary positive electrode material.

[0041] The synchronously synthesized high nickel ternary / LLZO composite positive electrode material provided in this application has a closer contact and more uniform coating between the LLZO solid electrolyte and the high nickel ternary material, which improves the lithium ion transmission kinetics while preventing the electrolyte from contacting the highly active Ni 4+ Direct contact reduces the generation of rock salt phase, and the garnet-type LLZO electrolyte can also enhance the phase change reversibility of high-nickel ternary materials through lithium replenishment strategy, thereby obtaining a composite positive electrode material with high rate performance and high cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0043] Figure 1 Schematic diagram of the process for preparing the composite cathode material of the present application;

[0044] Figure 2 This is a schematic diagram of the operation flow of a specific embodiment of the method for preparing the composite positive electrode material of the present application;

[0045] Figure 3 LiNi prepared in Example 1 0.8 Co 0.1 Mn 0.1 SEM image of O2·2 wt.%LLZO composite cathode material;

[0046] Figure 4 LiNi prepared in Examples 1 and 2 0.8 Co 0.1 Mn 0.1 O2·2 wt.%LLZO composite cathode material and LiNi prepared in Comparative Example 1 0.8 Co0.1 Mn 0.1 XRD pattern of O2;

[0047] Figure 5 LiNi prepared in Example 1 0.8 Co 0.1 Mn 0.1 TEM image of O2·2 wt.%LLZO composite cathode material;

[0048] Figure 6 The rate performance diagram of the positive electrode materials prepared in Examples 1, 2, 3 and Comparative Example 1 at 0.1 C, 0.5 C, 1 C, 3 C, 5 C, and 10 C (1 C = 180 mAh / g) within the range of 2.7-4.3 V is shown;

[0049] Figure 7 1 C cycle performance diagram of the positive electrode materials prepared in Examples 1, 2, 3 and Comparative Example 1 within 2.7-4.3 V. DETAILED DESCRIPTION

[0050] As used herein:

[0051] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variations thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0052] The conjunction "consisting of" excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim, rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0053] When an amount, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values ​​and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value with any range lower limit or preferred value, regardless of whether the range is disclosed alone. For example, when a range of "1 to 5" is disclosed, the described range should be interpreted as including the range "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values ​​and all integers and fractions within the range.

[0054] In these examples, parts and percentages are by mass unless otherwise indicated.

[0055] "Parts by mass" refers to the basic unit of measurement used to express the mass ratio of multiple components. One part can represent any unit of mass, such as 1g or 2.689g. For example, if we say that the parts by mass of component A are a parts and the parts by mass of component B are b parts, this means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, we could say that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number representing a multiplication factor). It's important to note that, unlike parts by mass, the sum of the parts by mass of all components is not limited to 100 parts.

[0056] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0058] This application provides a method for preparing a composite positive electrode material. Figure 1 ,include:

[0059] S100: introducing a first mixed salt solution containing nickel, cobalt, and manganese, a first complexing agent, and an alkaline solution into the bottom liquid of the reactor to perform a first coprecipitation reaction;

[0060] S200: After the first coprecipitation reaction, a second mixed salt solution containing lanthanum and zirconium, a second complexing agent and an alkaline solution are introduced to perform a second coprecipitation reaction to obtain a precursor slurry;

[0061] S300: collecting the precipitate from the precursor slurry, washing it, and drying it to obtain a high nickel ternary / LLZO composite precursor;

[0062] S400: mixing a high nickel ternary / LLZO composite precursor with a lithium source and calcining the mixture to obtain a high nickel ternary / LLZO composite positive electrode material.

[0063] The preparation method of the composite positive electrode material provided in the present application simultaneously synthesizes a high-nickel ternary / LLZO composite precursor and a positive electrode material. Compared with the traditional synthesis method of composite positive electrode materials, which requires separately synthesizing high-nickel ternary and LLZO and then compounding the two through other experiments, the method of the present application is similar to the current synthesis route of ternary positive electrode materials, greatly simplifies the production process of high-nickel ternary / LLZO composite positive electrode materials, and reduces production costs.

[0064] The coprecipitation-solid phase method is widely used in the synthesis of ternary cathode materials. The hydroxide precursor is first prepared by coprecipitation, and then the cathode material is synthesized through a high-temperature sintering lithium process. After exploration, the coprecipitation-solid phase method can also be used to synthesize garnet-type solid electrolyte LLZO, but due to the solubility product constant (K sp ) with nickel hydroxide, cobalt hydroxide, manganese hydroxide K sp The gap is more than ten orders of magnitude, resulting in significant differences in the co-precipitation reaction conditions between the two, making it difficult to obtain a composite precursor through a one-step co-precipitation. The method of this application is based on co-precipitation-solid-phase reaction. By setting different complexing agent concentrations and rotation speeds in the two-stage co-precipitation process, a composite cathode material precursor is obtained. A lithium source is added during the solid-phase calcination process, thereby achieving the simultaneous preparation of high-nickel ternary / LLZO composite cathode materials, greatly simplifying the process flow of composite cathode materials.

[0065] In some embodiments, the total metal ion concentration in the first mixed salt solution in step S100 is 1.4-2.0 mol / L, for example, it can be 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L or any value between 1.4-2.0 mol / L; the first mixed salt solution can be one or more of sulfate, carbonate, chloride or nitrate.

[0066] In some embodiments, the total metal ion concentration in the second mixed salt solution in step S200 is the same as that in the first mixed salt solution; the total mass of the second mixed salt solution introduced is 0.5%-5% of the mass of the first mixed salt solution, for example, it can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5% or any value between 0.5% and 5%; the second mixed salt solution can be one or more of sulfate, carbonate, chloride or nitrate.

[0067] In some embodiments, the first complexing agent in step S100 and the second complexing agent in step S200 are aqueous ammonia solutions, the concentration of the first complexing agent is 0.5-2 mol / L, for example, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2 mol / L or any value between 0.5-2 mol / L, the concentration of the second complexing agent is 0.2-0.8 mol / L, for example, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, or any value between 0.2-0.8 mol / L.

[0068] In some embodiments, the alkali solution in step S100 and step S200 is a NaOH solution, and the concentration of the NaOH solution is 1-4 mol / L, for example, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or any value between 1-4 mol / L.

[0069] In some embodiments, the bottom liquid of the reactor in step S100 is an ammonia solution with a concentration of 9-11 g / L.

[0070] In some embodiments, the pH value of the first coprecipitation reaction in step S100 is 9-12, for example, it can be 9, 10, 11, 12 or any value between 9 and 12; the rotation speed of the first coprecipitation reaction is 400-900 rpm, for example, it can be 400 rpm, 450 rpm, 500 rpm, 550 rpm, 600 rpm, 650 rpm, 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm or any value between 400 and 900 rpm; the temperature of the first coprecipitation reaction is 50-60°C, for example, it can be 50°C, 55°C, 60°C or any value between 50 and 60°C; the time of the first coprecipitation reaction is 8-12 h, for example, it can be 8 h, 9 h, 10 h, 11 h, 12 h or any value between 8 and 12 h; the first coprecipitation reaction is carried out under a protective atmosphere.

[0071] In some embodiments, the rotation speed of the second coprecipitation reaction in step S200 is 700-1200 rpm, for example, it can be 700 rpm, 750 rpm, 800 rpm, 850 rpm, 900 rpm, 950 rpm, 1000 rpm, 1050 rpm, 1100 rpm, 1150 rpm, 1200 rpm or any value between 700-1200 rpm; the pH value and reaction temperature of the second coprecipitation reaction are the same as those of the first coprecipitation reaction; the second coprecipitation reaction is carried out under a protective atmosphere.

[0072] In some embodiments, the flow ratio of the mixed salt solution, the complexing agent solution and the alkaline solution in step S100 and step S200 is the same; optionally, the flow ratio of the mixed salt solution, the complexing agent solution and the alkaline solution is 1:0.3:(0.5-2), for example, it can be any ratio between 1:0.3:0.5, 1:0.3:1, 1:0.3:1.5, 1:0.3:2 or 1:0.3:(0.5-2).

[0073] In some embodiments, step S400 of mixing and calcining the high nickel ternary / LLZO composite precursor with a lithium source includes:

[0074] The high nickel ternary / LLZO composite precursor is mixed with a lithium source and a flux and calcined.

[0075] Since LLZO usually needs to be sintered at high temperatures (above 1000°C) to form a cubic phase with high ionic conductivity, and at this temperature, the lithium source volatilizes severely, which will lead to aggravated cation mixing in the high-nickel ternary cathode material, resulting in structural instability and reduced capacity. Therefore, the addition of a flux during the solid-phase sintering process effectively reduces the sintering temperature, enabling the simultaneous preparation of high-nickel ternary / LLZO composite cathode materials. This greatly simplifies the process flow of the composite cathode material and allows the LLZO solid electrolyte to be tightly coated on the surface of the high-nickel ternary cathode material, thereby suppressing the interfacial side reactions of the high-nickel ternary cathode material and improving the battery rate and cycle performance.

[0076] In some embodiments, the flux includes one or more of LiF, Li3PO4, and LiBiO3; the amount of the flux added is 1%-5% of the molar number of the high-nickel ternary / LLZO composite precursor, for example, it can be 1%, 2%, 3%, 4%, 5% or any value between 1% and 5%; the lithium source is one or more of lithium hydroxide, lithium carbonate, lithium chloride, lithium nitrate, lithium sulfate, lithium acetate, lithium phosphate and lithium oxalate.

[0077] In some embodiments, the calcination in step S400 is divided into two stages: the first stage is heating to 400-600°C and keeping warm for 6-10 hours; the second stage is heating to 700-1000°C and keeping warm for 10 hours. The heating rate is 1-10°C / min, and the entire calcination process is carried out in an oxygen atmosphere.

[0078] In some embodiments, the chemical formula of the high nickel ternary / LLZO composite precursor is: Ni a Co b Mn 1-a-b (OH)2·cLa3Zr2(OH) 17 The chemical formula of the high nickel ternary / LLZO composite cathode material is: LiNi a Co b Mn 1-a-b O2·cLi7La3Zr2O 12 , where a≥0.6, 0.1≤b≤0.3, 0.5wt% <c<5wt%。

[0079] For example, the operation flow diagram of a specific embodiment of the method for preparing the composite positive electrode material of the present application is as follows: Figure 2 As shown, a mixed sulfate solution A of nickel, cobalt and manganese is coprecipitated with a first complexing agent C and an alkali solution in one stage, and then a mixed nitrate solution B of lanthanum and zirconium and a second complexing agent D are added to carry out a second stage coprecipitation, and then the Ni 0.8 Co 0.1 Mn 0.1 (OH)2·La3Zr2(OH)17 The composite precursor is finally calcined with a lithium source and a flux to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2·2%LLZO composite cathode material.

[0080] The present application also provides a composite positive electrode material, which is prepared by the above-mentioned method for preparing the composite positive electrode material.

[0081] The synchronously synthesized high nickel ternary / LLZO composite positive electrode material provided in this application has a closer contact and more uniform coating between the LLZO solid electrolyte and the high nickel ternary material, which improves the lithium ion transmission kinetics while preventing the electrolyte from contacting the highly active Ni 4+ Direct contact reduces the generation of rock salt phase, and the garnet-type LLZO electrolyte can also enhance the phase change reversibility of high-nickel ternary materials through lithium replenishment strategy, thereby obtaining a composite positive electrode material with high rate performance and high cycle stability.

[0082] The present application also provides a lithium-ion battery comprising the above-mentioned composite positive electrode material.

[0083] The present application also provides an electrical device comprising the above-mentioned lithium-ion battery.

[0084] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present application and should not be considered as limiting the scope of the present application. In the examples, if specific conditions are not specified, the conditions are carried out according to conventional conditions or manufacturer recommendations. The reagents or instruments used are not specified by the manufacturer and are conventional products that can be purchased commercially.

[0085] Example 1

[0086] This embodiment provides a method for simultaneously preparing LiNi 0.8 Co 0.1 Mn 0.1 The method for preparing an O2·2 wt.% LLZO composite cathode material comprises the following steps:

[0087] Step 1: Prepare a mixed sulfate solution A of nickel, cobalt, and manganese, wherein the molar ratio of nickel:cobalt:manganese is 8:1:1 and the total metal ion molar concentration is 1.6 mol / L; prepare a mixed nitrate solution B of lanthanum and zirconium, wherein the molar ratio of lanthanum:zirconium is 3:2 and the total metal ion molar concentration is 1.6 mol / L, and the total amount of nitrate solution B introduced is 2% of the mass fraction of sulfate solution A; prepare ammonia complexing agent solution C with a molar concentration of 1 mol / L and ammonia complexing agent solution D with a concentration of 0.6 mol / L; prepare a sodium hydroxide solution with a molar concentration of 2 mol / L as an alkaline solution precipitant; and prepare an ammonia aqueous solution with a mass concentration of 10 g / L as the reactor bottom liquid.

[0088] Step 2: 1.6 L of the bottom liquid was added to the reactor, the reactor blade was turned on for stirring, and nitrogen was introduced into the reactor at a flow rate of 200 mL / min for more than 20 minutes to ensure the atmosphere in the reactor and prevent ion oxidation during the subsequent reaction process; the mixed sulfate solution A and the ammonia complexing agent solution C in step 1 were pumped into the reactor at flow rates of 2 mL / min and 0.6 mL / min, respectively, to carry out the first stage of coprecipitation reaction, and the pH value was maintained at 11 by the sodium hydroxide solution in the alkali tank. The stirring speed of the reactor was 700 rpm, and the temperature of the reactor system was 55°C. After the coprecipitation reaction was carried out for 10 hours, the mixed nitrate solution B was introduced, and the ammonia complexing agent solution C was replaced with the ammonia complexing agent solution D to carry out the second stage of coprecipitation reaction, and the speed was increased to 1000 rpm. The liquid flow rate, pH value and reaction temperature were kept the same as those in the first stage until the salt solution was completely consumed and the reaction was stopped.

[0089] Step 3: Reduce the speed to 100 rpm and age for 4 h. Collect the precipitate, wash it with deionized water, filter it for more than three times to remove sulfate ions and nitrate ions, and then dry it in a vacuum drying oven at 110 ° C for 20 h to obtain Ni 0.8 Co 0.1 Mn 0.1 (OH)2·La3Zr2(OH) 17 Composite precursor.

[0090] Step 4: The composite precursor, lithium source lithium hydroxide and flux LiF were mixed uniformly in a molar ratio of 1:1.15:0.02, and calcined in a tube furnace with an oxygen flow rate of 0.6 L / min. The temperature was first raised to 500°C for pre-calcination for 6 h, and then raised to 850°C for calcination for 10 h at a heating rate of 2°C / min. After cooling to room temperature, the LiNi 0.8 Co 0.1 Mn 0.1 O2·2%LLZO composite cathode material.

[0091] The SEM image of the composite cathode material obtained in Example 1 is as follows: Figure 3 As shown in the figure, the composite cathode material is a secondary particle sphere or spherical structure formed by the accumulation of primary particles, and the secondary particle size is about 10 μm; the XRD pattern is shown in Figure 4 As shown; TEM images are shown Figure 5 As shown in the figure, 0.19 nm is the specific crystal plane spacing of LLZO solid electrolyte, and 0.24 nm is the specific crystal plane spacing of NCM. It can be seen that LLZO solid electrolyte is tightly coated on the surface of high nickel ternary positive electrode material.

[0092] This embodiment also provides a lithium-ion battery, the preparation method of which includes the following steps:

[0093] The composite positive electrode material obtained in Example 1, acetylene black and polyvinylidene fluoride were mixed uniformly in a mass ratio of 8:1:1, and an appropriate amount of N-methylpyrrolidone was added to make a slurry. The slurry was evenly coated on an aluminum foil with a scraper, and vacuum dried at 80°C for 12 h. The slurry was then cut into discs with a diameter of 12 mm using a sheet puncher for use as positive electrode sheets.

[0094] Assembly of CR2025 button cells: A lithium metal sheet was used as the negative electrode, Celgard 2500 was used as the separator, and an electrolyte solution consisting of 1 M LiPF6 dissolved in ethyl methyl carbonate, dimethyl carbonate, and ethylene carbonate in a volume ratio of 1:1:1 was assembled into a half-cell for electrochemical performance testing.

[0095] Example 2

[0096] The difference between Example 2 and Example 1 is that the temperature of the second stage of calcination is adjusted to 1000°C, and other conditions remain unchanged to obtain the composite positive electrode material of Example 2. The XRD pattern is as follows: Figure 4 As shown, the electrochemical performance tests were carried out under the same conditions.

[0097] Example 3

[0098] The difference between Example 3 and Example 1 is that the temperature of the second stage of calcination is adjusted to 700° C., and other conditions remain unchanged to obtain the composite positive electrode material of Example 3, and the electrochemical performance test is carried out under the same conditions.

[0099] Example 4

[0100] The difference between Example 4 and Example 1 is that in step 1, the concentration of the ammonia complexing agent solution C is 0.5 mol / L, the concentration of the ammonia complexing agent solution D is 0.2 mol / L, and other conditions remain unchanged to obtain the composite positive electrode material of Example 4, and the electrochemical performance test is carried out under the same conditions.

[0101] Example 5

[0102] The difference between Example 5 and Example 1 is that in step 1, the concentration of the ammonia complexing agent solution C is 2 mol / L, the concentration of the ammonia complexing agent solution D is 0.8 mol / L, and other conditions remain unchanged to obtain the composite positive electrode material of Example 5, and the electrochemical performance test is carried out under the same conditions.

[0103] Example 6

[0104] The difference between Example 6 and Example 1 is that the stirring speed of the reactor in the first stage coprecipitation reaction in step 2 is 400 rpm, and the stirring speed of the reactor in the second stage coprecipitation reaction is 700 rpm. Other conditions remain unchanged to obtain the composite positive electrode material of Example 6, and the electrochemical performance test is carried out under the same conditions.

[0105] Example 7

[0106] The difference between Example 7 and Example 1 is that the stirring speed of the reactor in the first stage coprecipitation reaction in step 2 is 900 rpm, and the stirring speed of the reactor in the second stage coprecipitation reaction is 1200 rpm. Other conditions remain unchanged to obtain the composite positive electrode material of Example 7, and the electrochemical performance test is carried out under the same conditions.

[0107] Example 8

[0108] The difference between Example 8 and Example 1 is that the flux used in step 4 is Li3PO4, and other conditions remain unchanged to obtain the composite positive electrode material of Example 8, and the electrochemical performance test is carried out under the same conditions.

[0109] Example 9

[0110] The difference between Example 9 and Example 1 is that no flux is added in step 4, and other conditions remain unchanged to obtain the composite positive electrode material of Example 9, and the electrochemical performance test is carried out under the same conditions.

[0111] Comparative Example 1

[0112] The difference between Comparative Example 1 and Example 1 is that only the first stage high nickel ternary precursor coprecipitation reaction is carried out to synthesize pure phase high nickel ternary positive electrode material. The XRD pattern is as follows: Figure 4 The specific steps are as follows:

[0113] Step 1: Prepare a mixed sulfate solution A of nickel, cobalt, and manganese, wherein the molar ratio of nickel:cobalt:manganese is 8:1:1 and the total metal molar concentration is 1.6 mol / L; prepare an ammonia complexing agent solution C with a molar concentration of 1 mol / L; prepare a sodium hydroxide solution with a molar concentration of 2 mol / L as an alkaline solution precipitant; and prepare an ammonia solution with a concentration of 10 g / L as the reactor bottom liquid.

[0114] Step 2: Add the bottom liquid to the reactor, turn on the paddle stirring of the reactor, and introduce nitrogen into the reactor at a flow rate of 200 mL / min for more than 20 minutes to ensure the atmosphere in the reactor and prevent ion oxidation during the subsequent reaction process; pump the mixed sulfate solution A and ammonia complexing agent solution C in step 1 into the reactor at flow rates of 2 mL / min and 0.6 mL / min respectively for co-precipitation reaction, maintain the pH value at 11 by the sodium hydroxide solution in the alkali tank, stir the reactor at 700 rpm, and the reactor system temperature is 55°C. Stop the reaction after the co-precipitation reaction has been carried out for 10 hours.

[0115] Step 3: Reduce the speed to 100 rpm and age for 4 h. Collect the precipitate, wash it with deionized water, filter it three times or more to remove sulfate ions, and then dry it in a vacuum drying oven at 110 ° C for 20 h to obtain Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor.

[0116] Step 4: The precursor, lithium source lithium hydroxide and flux LiF were mixed evenly in a molar ratio of 1:1.15:0.02, and calcined in a tube furnace with an oxygen flow rate of 0.6 L / min. The temperature was first raised to 500 ° C for pre-calcination for 6 h, and then raised to 850 ° C for calcination for 10 h at a heating rate of 2 ° C / min. After cooling to room temperature, LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode material.

[0117] Comparative Example 2

[0118] Comparative Example 2 differs from Example 1 in that a high-nickel ternary precursor is prepared by coprecipitation, LLZO ceramic powder is prepared by solid-phase reaction, and the precursor and LLZO powder are then co-fired at 1100°C to synthesize a high-nickel ternary / LLZO composite cathode material. The specific steps are as follows:

[0119] Step 1: Prepare a mixed sulfate solution A of nickel, cobalt, and manganese, wherein the molar ratio of nickel:cobalt:manganese is 8:1:1 and the total metal molar concentration is 1.6 mol / L; prepare an ammonia complexing agent solution C with a molar concentration of 1 mol / L; prepare a sodium hydroxide solution with a molar concentration of 2 mol / L as an alkaline solution precipitant; and prepare an ammonia solution with a concentration of 10 g / L as the reactor bottom liquid.

[0120] Step 2: Add the bottom liquid to the reactor, turn on the paddle stirring of the reactor, and introduce nitrogen into the reactor at a flow rate of 200 mL / min for more than 20 minutes to ensure the atmosphere in the reactor and prevent ion oxidation during the subsequent reaction process; pump the mixed sulfate solution A and ammonia complexing agent solution C in step 1 into the reactor at flow rates of 2 mL / min and 0.6 mL / min respectively for co-precipitation reaction, maintain the pH value at 11 by the sodium hydroxide solution in the alkali tank, stir the reactor at 700 rpm, and the reactor system temperature is 55°C. Stop the reaction after the co-precipitation reaction has been carried out for 10 hours.

[0121] Step 3: Reduce the speed to 100 rpm and age for 4 h. Collect the precipitate, wash it with deionized water, filter it three times or more to remove sulfate ions, and then dry it in a vacuum drying oven at 110 ° C for 20 h to obtain Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor.

[0122] Step 4: Pour lithium hydroxide, lanthanum oxide, and zirconium oxide into a zirconia ball mill at a molar ratio of 7:3:2. Add an appropriate amount of isopropyl alcohol as a grinding medium. Yttrium-stabilized zirconia balls are added at a ball-to-material ratio of 10:1 (large, medium, and small balls, respectively). Mill the mixture at 400 rpm for 6 hours. The dried mixed powder is then placed in a magnesium oxide crucible and heated in a high-temperature resistance furnace at a rate of 5°C / min to 1200°C. Hold the temperature for 6 hours to obtain LLZO powder.

[0123] Step 5: The LLZO powder was ball-milled a second time. To further reduce the particle size, the second ball-milling time was increased to 8 hours. The milled slurry was then completely dried and oven-dried as in the previous step, then sieved through a 200-mesh sieve to obtain fine LLZO powder.

[0124] Step 6: Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor, lithium source lithium hydroxide, flux LiF and LLZO powder were mixed uniformly in a molar ratio of 1:1.15:0.02:0.02, and calcined in a tube furnace with an oxygen flow rate of 0.6 L / min. The temperature was first raised to 500°C for pre-calcination for 6 h, and then raised to 1100°C for calcination for 10 h at a heating rate of 2°C / min. After cooling to room temperature, LiNi2O3 of Comparative Example 2 was obtained. 0.8 Co 0.1 Mn 0.1 O2·2%LLZO composite cathode material.

[0125] Comparative Example 3

[0126] Comparative Example 3 differs from Example 1 in that a high-nickel ternary precursor is prepared by coprecipitation, LLZO ceramic powder is prepared by solid-phase reaction, and the precursor and LLZO powder are then co-fired at 700°C to synthesize a high-nickel ternary / LLZO composite cathode material. The specific steps are as follows:

[0127] Step 1: Prepare a mixed sulfate solution A of nickel, cobalt, and manganese, wherein the molar ratio of nickel:cobalt:manganese is 8:1:1 and the total metal molar concentration is 1.6 mol / L; prepare an ammonia complexing agent solution C with a molar concentration of 1 mol / L; prepare a sodium hydroxide solution with a molar concentration of 2 mol / L as an alkaline solution precipitant; and prepare an ammonia solution with a concentration of 10 g / L as the reactor bottom liquid.

[0128] Step 2: Add the bottom liquid to the reactor, turn on the paddle stirring of the reactor, and introduce nitrogen into the reactor at a flow rate of 200 mL / min for more than 20 minutes to ensure the atmosphere in the reactor and prevent ion oxidation during the subsequent reaction process; pump the mixed sulfate solution A and ammonia complexing agent solution C in step 1 into the reactor at flow rates of 2 mL / min and 0.6 mL / min respectively for co-precipitation reaction, maintain the pH value at 11 by the sodium hydroxide solution in the alkali tank, stir the reactor at 700 rpm, and the reactor system temperature is 55°C. Stop the reaction after the co-precipitation reaction has been carried out for 10 hours.

[0129] Step 3: Reduce the speed to 100 rpm and age for 4 h. Collect the precipitate, wash it with deionized water, filter it three times or more to remove sulfate ions, and then dry it in a vacuum drying oven at 110 ° C for 20 h to obtain Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor.

[0130] Step 4: Pour lithium hydroxide, lanthanum oxide, and zirconium oxide into a zirconia ball mill at a molar ratio of 7:3:2. Add an appropriate amount of isopropyl alcohol as a grinding medium. Yttrium-stabilized zirconia balls are added at a ball-to-material ratio of 10:1 (large, medium, and small balls, respectively). Mill the mixture at 400 rpm for 6 hours. The dried mixed powder is then placed in a magnesium oxide crucible and heated in a high-temperature resistance furnace at a rate of 5°C / min to 1200°C. Hold the temperature for 6 hours to obtain LLZO powder.

[0131] Step 5: The LLZO powder was ball-milled a second time. To further reduce the particle size, the second ball-milling time was increased to 8 hours. The milled slurry was then completely dried and oven-dried as in the previous step, then sieved through a 200-mesh sieve to obtain fine LLZO powder.

[0132] Step 6: The precursor, lithium source lithium hydroxide, flux LiF and LLZO powder were mixed in a molar ratio of 1:1.15:0.02:0.02, and calcined in a tube furnace with an oxygen flow rate of 0.6 L / min. First, the temperature was raised to 500 ° C for pre-calcination for 6 h, and then the temperature was raised to 700 ° C for calcination for 10 h at a heating rate of 2 ° C / min. After cooling to room temperature, LiNi 0.8 Co 0.1 Mn 0.1 O2·2%LLZO composite cathode material.

[0133] Comparative Example 4

[0134] Comparative Example 4 differs from Example 1 in that a high-nickel ternary precursor is prepared by coprecipitation, LLZO ceramic powder is prepared by solid-phase reaction, and the precursor and LLZO powder are then co-fired at 1200°C to synthesize a high-nickel ternary / LLZO composite cathode material. The specific steps are as follows:

[0135] Step 1: Prepare a mixed sulfate solution A of nickel, cobalt, and manganese, wherein the molar ratio of nickel:cobalt:manganese is 8:1:1 and the total metal molar concentration is 1.6 mol / L; prepare an ammonia complexing agent solution C with a molar concentration of 1 mol / L; prepare a sodium hydroxide solution with a molar concentration of 2 mol / L as an alkaline solution precipitant; and prepare an ammonia solution with a concentration of 10 g / L as the reactor bottom liquid.

[0136] Step 2: Add the bottom liquid to the reactor, turn on the paddle stirring of the reactor, and introduce nitrogen into the reactor at a flow rate of 200 mL / min for more than 20 minutes to ensure the atmosphere in the reactor and prevent ion oxidation during the subsequent reaction process; pump the mixed sulfate solution A and ammonia complexing agent solution C in step 1 into the reactor at flow rates of 2 mL / min and 0.6 mL / min respectively for co-precipitation reaction, maintain the pH value at 11 by the sodium hydroxide solution in the alkali tank, stir the reactor at 700 rpm, and the reactor system temperature is 55°C. Stop the reaction after the co-precipitation reaction has been carried out for 10 hours.

[0137] Step 3: Reduce the speed to 100 rpm and age for 4 h. Collect the precipitate, wash it with deionized water, filter it three times or more to remove sulfate ions, and then dry it in a vacuum drying oven at 110 ° C for 20 h to obtain Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor.

[0138] Step 4: Pour lithium hydroxide, lanthanum oxide, and zirconium oxide into a zirconia ball mill at a molar ratio of 7:3:2. Add an appropriate amount of isopropyl alcohol as a grinding medium. Yttrium-stabilized zirconia balls are added at a ball-to-material ratio of 10:1 (large, medium, and small balls, respectively). Mill the mixture at 400 rpm for 6 hours. The dried mixed powder is then placed in a magnesium oxide crucible and heated in a high-temperature resistance furnace at a rate of 5°C / min to 1200°C. Hold the temperature for 6 hours to obtain LLZO powder.

[0139] Step 5: The LLZO powder was ball-milled a second time. To further reduce the particle size, the second ball-milling time was increased to 8 hours. The milled slurry was then completely dried and oven-dried as in the previous step, then sieved through a 200-mesh sieve to obtain fine LLZO powder.

[0140] Step 6: The precursor, lithium source lithium hydroxide, flux LiF and LLZO powder were mixed in a molar ratio of 1:1.15:0.02:0.02, and calcined in a tube furnace with an oxygen flow rate of 0.6 L / min. First, the temperature was raised to 500 ° C for pre-calcination for 6 h, and then the temperature was raised to 1200 ° C for calcination for 10 h at a heating rate of 2 ° C / min. After cooling to room temperature, LiNi of Comparative Example 4 was obtained. 0.8 Co 0.1 Mn 0.1 O2·2%LLZO composite cathode material.

[0141] Figure 6 The rate performance diagram of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 at 2.7-4.3 V, 0.1 C, 0.5 C, 1 C, 3 C, 5 C, and 10 C (1 C = 180 mAh / g); Figure 7 The 1 C cycle performance diagram of the positive electrode materials prepared in Examples 1-3 and Comparative Example 1 within 2.7-4.3 V; the rate performance of the composite positive electrode materials of each Example and Comparative Example is shown in Table 1.

[0142] Table 1 Comparison of rate performance of composite cathode materials of various embodiments and comparative examples

[0143]

[0144] According to Table 1, Examples 1 to 8 of the present application simultaneously prepared high nickel ternary / LLZO composite positive electrode materials by segmented coprecipitation-solid phase method. The process is simple and can achieve uniform coating of high nickel ternary materials with garnet solid electrolyte, thereby improving lithium ion transfer kinetics while preventing electrolyte from interacting with highly active Ni. 4+Direct contact reduces the generation of rock salt phase, and the LLZO electrolyte can also enhance the phase change reversibility of high-nickel ternary materials through lithium replenishment strategy, thereby achieving a simultaneous improvement in rate performance and cycle stability.

[0145] In Example 9, no flux is added during the calcination process, and LLZO cannot form a cubic phase with high ionic conductivity. Therefore, the rate performance and cycle stability are not as good as those of Examples 1 to 8, but the cycle performance is slightly higher than the pure phase high nickel ternary positive electrode material of Comparative Example 1.

[0146] Comparative Examples 2 through 4 all first prepare a high-nickel ternary precursor via coprecipitation, and LLZO ceramic powder via a solid-phase reaction method. The high-nickel ternary precursor and LLZO powder are then co-fired to synthesize a high-nickel ternary / LLZO composite positive electrode material. It can be seen that the performance of the high-nickel ternary / LLZO composite positive electrode materials prepared in Comparative Examples 2 through 4 is even worse than that of the pure high-nickel ternary positive electrode material of Comparative Example 1. This is because LLZO, as an oxide solid electrolyte, has a very high temperature at which its high ionic conductivity crystalline phase (cubic phase) forms. Simply adding LLZO to the positive electrode material via a co-firing method prevents the formation of a targeted fast ion conductor coating on the surface of the positive electrode material crystals and also produces impurity crystalline phases, thus failing to achieve the desired effect of modifying the positive electrode material. Furthermore, since the co-firing temperature is higher than the solid-phase reaction synthesis temperature of conventional positive electrode materials, the crystal structure of the positive electrode material itself is somewhat disrupted, resulting in a decrease in performance. The present application uses a co-precipitation method to prepare NCM ternary / LLZO composite materials, which can directionally form an LLZO layer coating on the surface of the NCM ternary crystal, thereby improving the ion transmission performance between crystals and significantly improving the rate performance.

[0147] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

[0148] This application provides this technical solution, which promotes the application of high-nickel cathode materials in lithium-ion batteries and meets the needs of large-scale commercial promotion. The above is only a preferred embodiment of this application. It should be noted that there are many optional garnet electrolytes and high-nickel ternary components in this application. Although not listed one by one in the specific examples, all of them can achieve the purpose of this application.

[0149] Furthermore, those skilled in the art will appreciate that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and to form distinct embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is intended solely to enhance understanding of the overall background of this application and should not be construed as an admission or any implication that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a composite positive electrode material, characterized in that: include: A first mixed salt solution containing nickel, cobalt, and manganese, a first complexing agent, and an alkaline solution are introduced into the bottom liquid of the reaction kettle to perform a first coprecipitation reaction; After the first coprecipitation reaction, a second mixed salt solution containing lanthanum and zirconium, a second complexing agent and an alkaline solution are introduced to perform a second coprecipitation reaction to obtain a precursor slurry; Collecting the precipitate from the precursor slurry, washing it, and drying it to obtain a high-nickel ternary / LLZO composite precursor; The high nickel ternary / LLZO composite precursor is mixed with a lithium source and a flux, and calcined to obtain a high nickel ternary / LLZO composite positive electrode material; The first complexing agent and the second complexing agent are aqueous ammonia solutions, the concentration of the first complexing agent is 0.5-2 mol / L, and the concentration of the second complexing agent is 0.2-0.8 mol / L; The rotation speed of the first coprecipitation reaction is 400-900 rpm; The rotation speed of the second coprecipitation reaction is 700-1200 rpm; The flux includes one or more of LiF, Li3PO4, and LiBiO3; The amount of the flux added is 1%-5% of the molar number of the high nickel ternary / LLZO composite precursor.

2. The method for preparing a composite positive electrode material according to claim 1, wherein: At least one of the following conditions is met: A. the total metal ion concentration in the first mixed salt solution is 1.4-2.0 mol / L, and the total metal ion concentration in the second mixed salt solution is the same as that in the first mixed salt solution; B. The total mass of the second mixed salt solution introduced is 0.5%-5% of the mass of the first mixed salt solution; C. the alkali solution is a NaOH solution, and the concentration of the NaOH solution is 1-4 mol / L; D. The bottom liquid of the reactor is an ammonia solution with a concentration of 9-11 g / L.

3. The method for preparing a composite positive electrode material according to claim 1, wherein: At least one of the following conditions is met: A. the pH value of the first coprecipitation reaction is 9-12; B. the temperature of the first coprecipitation reaction is 50-60° C.; C. The first coprecipitation reaction time is 8-12 h; D. the pH value and reaction temperature of the second coprecipitation reaction are the same as those of the first coprecipitation reaction; E. both the first coprecipitation reaction and the second coprecipitation reaction are carried out under a protective atmosphere; F. The flow ratio of the mixed salt solution, complexing agent solution and alkaline solution in the two stages is the same; The flow ratio of the mixed salt solution, the complexing agent solution and the alkali solution is 1:0.3:(0.5-2).

4. The method for preparing a composite cathode material according to claim 1, wherein: The lithium source is one or more of lithium hydroxide, lithium carbonate, lithium chloride, lithium nitrate, lithium sulfate, lithium acetate, lithium phosphate and lithium oxalate.

5. The method for preparing a composite positive electrode material according to claim 1, wherein: The calcination is divided into two stages: the first stage is heating to 400-600°C and keeping warm for 6-10 hours; the second stage is heating to 700-1000°C and keeping warm for 10 hours. The heating rate is 1-10°C / min. The whole calcination process is carried out in an oxygen atmosphere.

6. The method for preparing a composite cathode material according to claim 1, wherein: The chemical formula of the high nickel ternary / LLZO composite precursor is: Ni a Co b Mn 1-a-b (OH)2·cLa3Zr2(OH) 17 The chemical formula of the high nickel ternary / LLZO composite cathode material is: LiNi a Co b Mn 1-a-b O2·cLi7La3Zr2O 12 , where a≥0.6, 0.1≤b≤0.3, 0.5wt% < c< 5wt%.

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