Cathode material, preparation method thereof and lithium ion battery

Abstract

The application relates to the technical field of lithium ion battery materials, in particular to a positive electrode material, a preparation method thereof and a lithium ion battery. The preparation method of the positive electrode material comprises the following steps: (a) under the action of a precipitant, carrying out a co-precipitation reaction on a mixed solution formed by a manganese source, a nickel source and a doped metal source to obtain a co-deposition precipitate; (b) calcining the co-deposition precipitate to obtain a precursor; (c) mixing the precursor with a lithium source, and then carrying out calcination in an oxygen-rich atmosphere to obtain the positive electrode material; wherein the molar ratio of the doped metal source and the manganese source is (0.001-0.08):1 in terms of doped metal elements and Mn. The positive electrode material prepared by the preparation method can realize the purpose of coating, doping and co-modification through one-step addition, improves the stability of the lithium nickel manganese oxide positive electrode material, greatly simplifies the production process, and is beneficial to large-scale commercial use of the material.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and in particular to a cathode material, its preparation method, and a lithium-ion battery. Background Technology

[0002] Lithium-ion batteries are widely used in numerous fields such as 3C electronic products, electric vehicles, and energy storage power stations due to their high energy density, low self-discharge, absence of memory effect, and long cycle life, making them a current research hotspot in new energy storage and conversion systems. The cathode material accounts for the highest cost and weight of the battery, thus significantly impacting its performance and cost. Spinel-structured lithium nickel manganese oxide (LiMO) materials have attracted widespread attention due to their ultra-high operating voltage, resulting in high energy density batteries assembled using them as electrode materials. However, at high voltages, the severe side reactions between the electrode material and the electrolyte significantly degrade the overall battery life, posing the biggest obstacle to the commercialization of LiMO materials. Therefore, improving the stability of LiMO is crucial to accelerating the commercialization of high-voltage LiMO materials.

[0003] Surface coating and element doping are conventional and effective methods to improve the stability of electrode materials, and they are also effective for lithium nickel manganese oxide. However, since lithium nickel manganese oxide has a higher working voltage than other cathode materials, and the presence of nickel and manganese further exacerbates the deterioration of the stability of the electrode material, a single modification strategy cannot completely improve the stability of the material. Moreover, conventional coating is often uneven, so the improvement in the stability of lithium nickel manganese oxide is not significant.

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

[0005] One objective of this invention is to provide a method for preparing a cathode material that simultaneously achieves doping and coating in a one-step process, thereby improving the stability of the cathode material.

[0006] Another objective of this invention is to provide a cathode material with good stability.

[0007] Another object of the present invention is to provide a lithium-ion battery comprising the above-mentioned positive electrode material.

[0008] To achieve the above-mentioned objectives of the present invention, one aspect of the present invention provides a method for preparing a cathode material, comprising the following steps:

[0009] (a) Under the action of a precipitant, a mixed solution formed by a manganese source, a nickel source and a doped metal source is subjected to a co-precipitation reaction to obtain a co-deposited precipitate;

[0010] (b) Calcining the co-deposited precipitate to obtain a precursor;

[0011] (c) The precursor is mixed with a lithium source and then calcined in an oxygen-rich atmosphere to obtain the cathode material;

[0012] The molar ratio of the doped metal source to the manganese source, calculated as doped metal element and Mn respectively, is (0.001~0.08):1.

[0013] Furthermore, the doped metal source includes at least one of titanium, aluminum, zinc, chromium, magnesium, zirconium, copper, and iron. Further, the titanium source includes at least one of tetrabutyl titanate, tetraethyl titanate, metatitanic acid, titanium oxysulfate, and titanium dioxide; the aluminum source includes at least one of alkyl aluminum, diethyl aluminum chloride, and aluminum silicate; the zinc source includes at least one of zinc acetate, zinc oxalate, zinc gluconate, zinc methionine, zinc lactate, zinc glycyrrhizinate, and zinc citrate; the chromium source includes at least one of dichromic acid, chromic anhydride, basic chromium sulfate, chromium nitrate, and chromium oxide green; the magnesium source includes at least one of magnesium ascorbate, magnesium monoperoxyphthalate hexahydrate, magnesium peroxide, magnesium monoethyl fumarate, magnesium rosinate, and magnesium nitrate; the zirconium source includes at least one of zirconium carboxylate, zirconium phosphate, zirconium nitrate, and zirconium 1-butoxide; the copper source includes at least one of copper nitrate, copper acetylene, phenyl copper, alkyl copper, copper acyl chloride, and cuprous acetate; and the iron source includes at least one of ferrous lactate, ferric citrate, ferrocene, potassium ferrocyanide, ferric glycinate, and ferrocene.

[0014] Furthermore, the doped metal source includes an organic doped metal source.

[0015] Furthermore, in the coprecipitation reaction, the pH of the system is controlled to be 5.75–6.1. Furthermore, the pH of the system is controlled by a slow-release agent; the slow-release agent includes at least one selected from sulfuric acid, phosphoric acid, and hydrochloric acid.

[0016] Further, the precipitant is an alkaline solution. Further, the precipitant includes at least one of an aqueous solution of a carbonate and an aqueous solution of a hydroxide.

[0017] Furthermore, the molar ratio of the manganese source and the nickel source, calculated as Mn and Ni respectively, is 1:(0.2 to 0.35).

[0018] Furthermore, the amounts of the manganese source, the nickel source, and the lithium source, respectively, calculated as Mn, Ni, and Li, satisfy the following: Li:(Mn+Ni)=1:(0.95~1.05).

[0019] Further, in step (b), the calcination temperature is 300–500°C, and the calcination time is 2–8 hours.

[0020] Further, in step (c), the calcination includes primary calcination and secondary calcination; the temperature of the primary calcination is 550–1100℃, and the time of the primary calcination is 8–24 h; the temperature of the secondary calcination is 450–800℃, and the time of the secondary calcination is 15–48 h.

[0021] Furthermore, in the first calcination, the temperature is increased to 550-1100℃ at a heating rate of 0.5-10℃ / min; in the second calcination, the temperature is decreased to 450-800℃ at a cooling rate of 0.5-2℃ / min.

[0022] Furthermore, the oxygen content in the oxygen-enriched atmosphere is 80% to 95%.

[0023] In another aspect, the present invention provides a cathode material prepared by any of the above-described cathode material preparation methods.

[0024] In another aspect, the present invention provides a lithium-ion battery comprising any of the above-described positive electrode materials.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] (1) The method for preparing the cathode material of the present invention uses a doped metal source as both a doping source and a coating source. During the co-precipitation process with nickel and manganese sources, the doped metal is doped into the nickel manganese oxide lattice. Then, during the calcination process with lithium sources, lithium nickel manganese oxide nucleates and grows. Part of the doped metal in the nickel manganese oxide lattice seeps out from the inside to the outer surface of the crystal nucleus. Since the calcination is carried out in an oxygen-rich atmosphere, the doped metal source will be rapidly oxidized to form metal oxide, thereby constructing a dense protective layer in situ on the surface of the lithium nickel manganese oxide crystal nucleus. The internal element doping improves the stability of the lattice structure, and the external in-situ construction of a protective layer avoids the occurrence of side reactions, thus greatly improving the stability of the lithium nickel manganese oxide material.

[0027] (2) The cathode material prepared by the preparation method of the present invention can achieve the purpose of coating doping and co-modification by adding it in one step, which improves the stability of lithium nickel manganese oxide cathode material and greatly simplifies the production process, which is conducive to the large-scale commercial use of the material. Attached Figure Description

[0028] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0029] Figure 1 The XRD patterns of lithium nickel manganese oxide cathode materials prepared in Example 1 and Comparative Example 2 of this invention are shown.

[0030] Figure 2 This is a SEM image of the lithium nickel manganese oxide cathode material prepared in Example 3 of the present invention. Detailed Implementation

[0031] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0032] This invention provides a method for preparing a positive electrode material, comprising the following steps:

[0033] (a) Under the action of a precipitant, a mixed solution formed by a manganese source, a nickel source and a doped metal source is subjected to a co-precipitation reaction to obtain a co-deposited precipitate;

[0034] (b) The co-deposited precipitate was calcined to obtain the precursor;

[0035] (c) The precursor is mixed with a lithium source and then calcined in an oxygen-rich atmosphere to obtain a cathode material;

[0036] The molar ratio of the doped metal source to the manganese source, calculated as doped metal element and Mn respectively, is (0.001~0.08):1.

[0037] The method for preparing the cathode material of this invention employs a doped metal source as both a dopant source and a coating source. During the co-precipitation process with nickel and manganese sources, the doped metal is incorporated into the nickel-manganese oxide lattice. Subsequently, during calcination with a lithium source, lithium nickel manganese oxide nucleates and grows. A portion of the doped metal in the nickel-manganese oxide lattice seeps out from the interior to the outer surface of the nucleus. Since calcination is carried out in an oxygen-rich atmosphere, the doped metal source rapidly oxidizes to form metal oxides, thereby constructing a dense protective layer in situ on the surface of the lithium nickel manganese oxide nucleus. Internal elemental doping improves the stability of the lattice structure, and the external in-situ construction of the protective layer more effectively suppresses manganese dissolution and electrolyte side reactions, greatly improving the electrochemical performance of lithium nickel manganese oxide and thus enhancing its electrochemical energy storage capabilities. Furthermore, the doping and coating processes of this invention are achieved in a one-step manner, effectively simplifying the production process, reducing production costs, and facilitating large-scale material production.

[0038] Research has shown that the doped metal source can partially diffuse out from the crystal lattice during calcination, thereby achieving simultaneous doping and coating modification. Simultaneous doping and coating modification require a sufficient amount of doped metal source and calcination in an oxygen-rich atmosphere. If the doped metal source content is insufficient, simultaneous doping and coating cannot be achieved. If calcination in step (c) is not carried out in an oxygen-rich atmosphere, but rather in an air atmosphere, the effect of converting the diffused metal into metal oxides is not ideal, and simultaneous doping and coating modification cannot be achieved.

[0039] By adjusting the amount of doped metal source within the above range, both the stability of the cathode material and its electrochemical performance can be improved. For example, in different embodiments, the molar ratio of the doped metal source to the manganese source, calculated by the doped metal element and Mn respectively, can be 0.001:1, 0.002:1, 0.005:1, 0.008:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, or any combination thereof.

[0040] In practice, step (a) may include: dissolving the manganese source, nickel source, and doped metal source in water in a specific ratio to obtain a mixed aqueous solution; then adding a certain amount of precipitant to the mixed aqueous solution to carry out a co-precipitation reaction, obtaining a co-precipitated precipitate. A certain amount of slow-release agent is added to the mixed system to ensure that the pH of the mixed system remains stable within a certain range. The amount of water used in the mixed aqueous solution can be adjusted according to the requirements of conventional co-precipitation reactions.

[0041] In steps (b) and (c), calcination can be carried out in a tube furnace. Before calcination in step (c), the mixture of precursor and lithium source can be ball-milled to ensure uniform dispersion.

[0042] In some specific embodiments of the present invention, the doped metal source includes at least one of titanium source, aluminum source, zinc source, chromium source, magnesium source, zirconium source, copper source and iron source. Further, the titanium source includes at least one of tetrabutyl titanate, tetraethyl titanate, metatitanic acid, titanium oxysulfate, and titanium dioxide; the aluminum source includes at least one of alkylaluminum, diethylaluminum chloride, and aluminum silicate; the zinc source includes at least one of zinc acetate, zinc oxalate, zinc gluconate, zinc methionine, zinc lactate, zinc glycyrrhizinate, and zinc citrate; the chromium source includes at least one of dichromic acid, chromic anhydride, basic chromium sulfate, chromium nitrate, and chromium oxide green; the magnesium source includes at least one of magnesium ascorbate, magnesium monoperoxyphthalate hexahydrate, magnesium peroxide, magnesium monoethyl fumarate, magnesium rosinate, and magnesium nitrate; the zirconium source includes at least one of zirconium carboxylate, zirconium phosphate, zirconium nitrate, and zirconium 1-butoxide; the copper source includes at least one of copper nitrate, copper acetylene, phenyl copper, alkyl copper, copper acyl chloride, and cuprous acetate; and the iron source includes at least one of ferrous lactate, ferric citrate, ferrocene, potassium ferrocyanide, iron glycinate, and ferrocene.

[0043] Alkyl aluminum includes, but is not limited to, triethylaluminum and / or triisobutylaluminum.

[0044] In some specific embodiments of the present invention, the doped metal source includes an organic doped metal source.

[0045] When the doping metal source includes an organic doping metal source, during high-temperature calcination, the organic source carbonizes and partially remains on the surface of lithium nickel manganese oxide, thus constructing an additional protective layer on the surface of lithium nickel manganese oxide. This achieves a three-in-one modification: internal elemental doping improves lattice structure stability, while the external in-situ constructed double-layer protective layer prevents side reactions, significantly improving the stability of lithium nickel manganese oxide materials. When an organic doping metal source is used, an additional carbon protective layer is formed. To ensure electrolyte wetting and ion diffusion, the thickness of the carbon layer is subject to certain requirements and cannot be too thick. Therefore, the organic doping metal source can be controlled within the aforementioned range.

[0046] By employing the aforementioned specific doped metal source, this invention can simultaneously ensure both doping and coating effects.

[0047] In some specific embodiments of the present invention, the manganese source includes at least one of manganese acetate, manganese nitrate, manganese sulfate, manganese carbonate, and manganese chloride; the nickel source includes at least one of nickel acetate, nickel carbonate, nickel nitrate, nickel sulfate, and nickel hydroxide; and the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium sulfate, lithium chloride, lithium phosphate, and lithium acetate.

[0048] The types of manganese, nickel, and lithium sources are not limited to those mentioned above; any other manganese, nickel, and lithium sources that can be used to prepare lithium nickel manganese oxide materials are acceptable.

[0049] In some specific embodiments of the present invention, the pH of the system is controlled to be 5.75–6.1 during the coprecipitation reaction. Further, the pH of the system is controlled by a slow-release agent; the slow-release agent includes at least one of sulfuric acid, phosphoric acid, and hydrochloric acid.

[0050] In the coprecipitation reaction, the pH of the system is controlled within the range of 5.75 to 6.2. In different embodiments, the pH of the system in the coprecipitation reaction can be controlled to be a range of 5.75, 5.8, 5.85, 5.9, 5.95, 6, 6.05, 6.1, or any combination thereof.

[0051] In practice, during the coprecipitation reaction, the pH of the system is preferably controlled within a stable value within the above range to further ensure the uniformity and stability of the coprecipitation reaction. Alternatively, the pH of the system can be controlled within a certain value within the above range to allow for small fluctuations due to the process.

[0052] In some specific embodiments of the present invention, the precipitant is an alkaline solution. Further, the precipitant includes at least one of an aqueous solution of a carbonate and an aqueous solution of a hydroxide.

[0053] In different embodiments, the precipitant may be one or more of sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide, including but not limited to sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide.

[0054] In some specific embodiments of the present invention, the molar ratio of the manganese source and the nickel source, respectively, calculated as Mn and Ni, is 1:(0.2 to 0.35).

[0055] In different embodiments, the molar ratio of the manganese source and the nickel source, respectively, calculated as Mn and Ni, can be 1:0.2, 1:0.22, 1:0.24, 1:0.25, 1:0.26, 1:0.28, 1:0.3, 1:0.32, 1:0.34, 1:0.35, or any combination thereof.

[0056] In some specific embodiments of the present invention, the amounts of manganese source, nickel source and lithium source, respectively, calculated as Mn, Ni and Li, satisfy: Li:(Mn+Ni)=1:(0.95~1.05).

[0057] In different implementations, Li:(Mn+Ni) can be a range of 0.95, 0.96, 0.97, 0.98, 0.99, 1.00, 1.01, 1.02, 1.03, 1.04, 1.05, or any combination thereof.

[0058] In some specific embodiments of the present invention, in step (b), the calcination temperature is 300-500°C and the calcination time is 2-8 hours.

[0059] In different embodiments, in step (b), the calcination temperature can be a range of 300°C, 320°C, 350°C, 380°C, 400°C, 420°C, 450°C, 480°C, 500°C or any combination thereof; the calcination time can be a range of 2h, 3h, 4h, 5h, 6h, 7h, 8h or any combination thereof.

[0060] In practice, the calcination in step (b) can be carried out in a normal air atmosphere.

[0061] In some specific embodiments of the present invention, step (c) includes calcination in the form of a first calcination and a second calcination; the temperature of the first calcination is 550-1100°C and the time of the first calcination is 8-24 h; the temperature of the second calcination is 450-800°C and the time of the second calcination is 15-48 h.

[0062] In different embodiments, in step (c), the temperature of the first calcination can be a range of 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, or any combination thereof; the time of the first calcination can be a range of 8h, 10h, 12h, 15h, 18h, 20h, 24h, or any combination thereof; the temperature of the second calcination can be a range of 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, or any combination thereof; and the time of the second calcination can be a range of 15h, 18h, 20h, 24h, 28h, 32h, 35h, 38h, 42h, 48h, or any combination thereof.

[0063] In some specific embodiments of the present invention, during the first calcination, the temperature is increased to 550-1100°C at a heating rate of 0.5-10°C / min; during the second calcination, the temperature is decreased to 450-800°C at a cooling rate of 0.5-2°C / min.

[0064] In different embodiments, during the first calcination, the heating rate to 550–1100°C can be 0.5°C / min, 1°C / min, 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, or any combination thereof; during the second calcination, the cooling rate to 450–800°C can be 0.5°C / min, 0.8°C / min, 1°C / min, 1.2°C / min, 1.5°C / min, 1.8°C / min, 2°C / min, or any combination thereof.

[0065] In some specific embodiments of the present invention, the oxygen content in the oxygen-enriched atmosphere is ≥80%, such as 80% to 99%. Here, the oxygen content refers to the volume fraction.

[0066] In different embodiments, the oxygen content in the oxygen-enriched atmosphere can be a range of 80%, 82%, 85%, 88%, 90%, 92%, 95%, 98%, 99%, or any combination thereof.

[0067] In another aspect, the present invention provides a cathode material prepared using any of the above-described cathode material preparation methods.

[0068] The cathode material of the present invention has a doped metal element inside the lithium nickel manganese oxide grains and a coating layer on the surface of the lithium nickel manganese oxide grains. The coating layer can be a single protective layer or a double coating layer. When the coating layer is a single protective layer, the coating layer is an oxide layer of the doped metal element. When the coating layer is a double protective layer, in addition to the oxide layer of the doped metal element, the coating layer may further include a carbon layer to form a double protective layer, further avoiding the occurrence of side reactions.

[0069] Another aspect of the present invention provides a lithium-ion battery comprising any of the above-mentioned cathode materials.

[0070] Example 1

[0071] This embodiment provides a method for preparing lithium nickel manganese oxide cathode material, including the following steps:

[0072] (1) Dissolve 0.064 mol of nickel sulfate and 0.192 mol of manganese sulfate in 400 mL of deionized water, and then add 0.001 mol of tetrabutyl titanate. Stir for 10 min to obtain a mixed aqueous solution. Under stirring conditions, add 256 mL of ammonia solution (mass fraction 25%) dropwise to the mixed aqueous solution, and then add 2600 mL of ammonium carbonate solution (mass fraction 10%) dropwise to precipitate metal ions. At the same time, add dilute sulfuric acid (mass fraction 5%) to stabilize the pH of the mixed aqueous solution at about 5.95. Collect the nickel-manganese precipitate by centrifugation after the reaction.

[0073] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in a tube furnace under an air atmosphere and calcined at 450°C for 8 hours to prepare the precursor.

[0074] (3) After the precursor obtained in step (2) and 0.13 mol of lithium carbonate are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 900°C for 12 h at an oxygen atmosphere and an oxygen flow rate of 300 mm / Hg (maintaining the oxygen content in the furnace ≥95%). Then, the temperature is lowered to 700°C for 30 h at a rate of 1°C / min. The modified lithium nickel manganese oxide cathode material is obtained by cooling down.

[0075] Example 2

[0076] This embodiment provides a method for preparing lithium nickel manganese oxide cathode material, including the following steps:

[0077] (1) Dissolve 0.032 mol of nickel acetate and 0.096 mol of manganese acetate in 200 mL of deionized water, then add 0.001 mol of zinc gluconate and stir for 10 min to obtain a mixed aqueous solution; under stirring conditions, add 112 mL of ammonia solution (mass fraction of 20%) dropwise to the mixed aqueous solution, and then add 1300 mL of ammonium carbonate solution (mass fraction of 12%) dropwise to precipitate metal ions. At the same time, add dilute sulfuric acid (mass fraction of 3%) to stabilize the pH of the mixed aqueous solution at about 6.0; collect the nickel-manganese precipitate by centrifugation after the reaction.

[0078] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in an air atmosphere in a tube furnace and calcined at 400°C for 12 hours to prepare the precursor.

[0079] (3) After the precursor obtained in step (2) and 0.07 mol of lithium hydroxide are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 1000℃ for 10 h at an oxygen atmosphere and an oxygen flow rate of 250 mm / Hg (maintaining the oxygen content in the furnace ≥90%). Then, the temperature is lowered to 750℃ for 8 h at a rate of 2℃ / min. After cooling, the modified lithium nickel manganese oxide cathode material is obtained.

[0080] Example 3

[0081] This embodiment provides a method for preparing lithium nickel manganese oxide cathode material, including the following steps:

[0082] (1) Dissolve 0.018 mol of nickel acetate and 0.054 mol of manganese acetate in 100 mL of deionized water, then add 0.0006 mol of zinc citrate and 0.0004 mol of triisobutylaluminum, stir for 10 min to obtain a mixed aqueous solution; under stirring conditions, add 56 mL of ammonia solution (mass fraction of 25%) dropwise to the mixed aqueous solution, then add 650 mL of ammonium carbonate solution (mass fraction of 10%) dropwise to precipitate metal ions, and at the same time, add dilute sulfuric acid (mass fraction of 2%) to stabilize the pH of the mixed aqueous solution at about 6.0; collect the nickel-manganese precipitate by centrifugation after the reaction.

[0083] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in an air atmosphere in a tube furnace and calcined at 400°C for 12 hours to prepare the precursor.

[0084] (3) After the precursor obtained in step (2) and 0.07 mol of lithium carbonate are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 900°C for 12 h at an oxygen atmosphere and an oxygen flow rate of 400 mm / Hg (maintaining the oxygen content in the furnace ≥98%). Then, the temperature is lowered to 700°C for 6 h at a rate of 3°C / min. The modified lithium nickel manganese oxide cathode material is obtained by cooling down.

[0085] Example 4

[0086] This embodiment provides a method for preparing lithium nickel manganese oxide cathode material, including the following steps:

[0087] (1) Dissolve 0.018 mol of nickel acetate and 0.054 mol of manganese acetate in 100 mL of deionized water, then add 0.0006 mol of tetrabutyl titanate and 0.0004 mol of magnesium monoethyl fumarate, stir for 10 min to obtain a mixed aqueous solution; under stirring conditions, add 56 mL of ammonia solution (mass fraction of 15%) dropwise to the mixed aqueous solution, then add 650 mL of ammonium carbonate solution (mass fraction of 15%) dropwise to precipitate metal ions, and at the same time, stabilize the pH of the mixed aqueous solution at about 6.0 by adding dilute sulfuric acid (mass fraction of 2.5%); collect the nickel-manganese precipitate by centrifugation after the reaction.

[0088] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in an air atmosphere in a tube furnace and calcined at 400°C for 12 hours to prepare the precursor.

[0089] (3) After the precursor obtained in step (2) and 0.07 mol of lithium sulfate are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 900°C for 12 h at an oxygen atmosphere and an oxygen flow rate of 300 mm / Hg (maintaining the oxygen content in the furnace ≥95%). Then, the temperature is lowered to 700°C for 6 h at a rate of 3°C / min. The modified lithium nickel manganese oxide cathode material is obtained by cooling down.

[0090] Example 5

[0091] This embodiment provides a method for preparing lithium nickel manganese oxide cathode material, including the following steps:

[0092] (1) Dissolve 0.018 mol of nickel acetate and 0.054 mol of manganese acetate in 100 mL of deionized water, then add 0.0006 mol of tetrabutyl titanate and 0.0004 mol of chromic anhydride, stir for 10 min to obtain a mixed aqueous solution; under stirring conditions, add 56 mL of ammonia solution (mass fraction of 25%) dropwise to the mixed aqueous solution, then add 650 mL of ammonium carbonate solution (mass fraction of 10%) dropwise to precipitate metal ions, and at the same time, add dilute sulfuric acid (mass fraction of 2%) to stabilize the pH of the mixed aqueous solution at about 6.0; collect the nickel-manganese precipitate by centrifugation after the reaction.

[0093] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in an air atmosphere in a tube furnace and calcined at 400°C for 12 hours to prepare the precursor.

[0094] (3) After the precursor obtained in step (2) and 0.07 mol of lithium sulfate are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 900℃ for 12 h at an oxygen atmosphere and an oxygen flow rate of 400 mm / Hg (maintaining the oxygen content in the furnace ≥98%). Then, the temperature is lowered to 700℃ for 6 h at 3℃ / min. The modified lithium nickel manganese oxide cathode material is obtained by cooling down.

[0095] Example 6

[0096] This embodiment provides a method for preparing lithium nickel manganese oxide cathode material, including the following steps:

[0097] (1) Dissolve 0.018 mol of nickel acetate and 0.054 mol of manganese acetate in 100 mL of deionized water, then add 0.001 mol of dicyclopentadienyl iron and stir for 10 min to obtain a mixed aqueous solution; under stirring conditions, add 56 mL of ammonia solution (mass fraction of 25%) dropwise to the mixed aqueous solution, and then add 650 mL of ammonium carbonate solution (mass fraction of 10%) dropwise to precipitate metal ions. At the same time, add dilute sulfuric acid (mass fraction of 2%) to stabilize the pH of the mixed aqueous solution at about 6.0; collect the nickel-manganese precipitate by centrifugation after the reaction.

[0098] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in an air atmosphere in a tube furnace and calcined at 400°C for 12 hours to prepare the precursor.

[0099] (3) After the precursor obtained in step (2) and 0.07 mol of lithium carbonate are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 900°C for 12 h at an oxygen atmosphere and an oxygen flow rate of 400 mm / Hg (maintaining the oxygen content in the furnace ≥98%). Then, the temperature is lowered to 700°C for 6 h at a rate of 3°C / min. The modified lithium nickel manganese oxide cathode material is obtained by cooling down.

[0100] Example 7

[0101] This embodiment provides a method for preparing lithium nickel manganese oxide cathode material, including the following steps:

[0102] (1) Dissolve 0.018 mol of nickel acetate and 0.054 mol of manganese acetate in 100 mL of deionized water, then add 0.001 mol of ferric citrate and stir for 10 min to obtain a mixed aqueous solution; under stirring conditions, add 56 mL of ammonia solution (mass fraction of 30%) dropwise to the mixed aqueous solution, and then add 650 mL of ammonium carbonate solution (mass fraction of 5%) dropwise to precipitate metal ions. At the same time, add dilute sulfuric acid (mass fraction of 3%) to stabilize the pH of the mixed aqueous solution at about 6.0; collect the nickel-manganese precipitate by centrifugation after the reaction.

[0103] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in an air atmosphere in a tube furnace and calcined at 400°C for 12 hours to prepare the precursor.

[0104] (3) After the precursor obtained in step (2) and 0.07 mol of lithium carbonate are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 900°C for 12 h at an oxygen atmosphere and an oxygen flow rate of 400 mm / Hg (maintaining the oxygen content in the furnace ≥98%). Then, the temperature is lowered to 700°C for 6 h at a rate of 3°C / min. The modified lithium nickel manganese oxide cathode material is obtained by cooling down.

[0105] Example 8

[0106] This embodiment provides a method for preparing lithium nickel manganese oxide cathode material, including the following steps:

[0107] (1) Dissolve 0.018 mol of nickel acetate and 0.054 mol of manganese acetate in 100 mL of deionized water, then add 0.0006 mol of tetrabutyl titanate and 0.0004 mol of magnesium nitrate, and stir for 10 min to obtain a mixed aqueous solution; under stirring conditions, add 56 mL of ammonia solution (mass fraction of 25%) dropwise to the mixed aqueous solution, and then add 650 mL of ammonium carbonate solution (mass fraction of 15%) dropwise to precipitate metal ions. At the same time, add dilute sulfuric acid (mass fraction of 3%) to stabilize the pH of the mixed aqueous solution at about 6.0; collect the nickel-manganese precipitate by centrifugation after the reaction.

[0108] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in an air atmosphere in a tube furnace and calcined at 400°C for 12 hours to prepare the precursor.

[0109] (3) After the precursor obtained in step (2) and 0.07 mol of lithium carbonate are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 900°C for 12 h at an oxygen atmosphere and an oxygen flow rate of 300 mm / Hg (maintaining the oxygen content in the furnace ≥95%). Then, the temperature is lowered to 700°C for 6 h at a rate of 3°C / min. The modified lithium nickel manganese oxide cathode material is obtained by cooling down.

[0110] Example 9

[0111] This embodiment refers to the preparation method of embodiment 3, the only difference being that the calcination temperature and time in steps (2) and (3) are different.

[0112] In this embodiment, the calcination temperature in step (2) is 300°C and the calcination time is 8 hours.

[0113] In step (3) of this embodiment, the first calcination is carried out at a heating rate of 0.5℃ / min to 550℃, and the first calcination time is 24h; the second calcination is carried out at a cooling rate of 0.5℃ / min to 450℃, and the second calcination time is 48h.

[0114] Example 10

[0115] This embodiment refers to the preparation method of embodiment 3, the only difference being that the calcination temperature and time in steps (2) and (3) are different.

[0116] In this embodiment, the calcination temperature in step (2) is 500°C and the calcination time is 2 hours.

[0117] In step (3) of this embodiment, the first calcination is carried out at a heating rate of 10℃ / min to 1100℃, and the first calcination time is 8h; the second calcination is carried out at a cooling rate of 2℃ / min to 800℃, and the second calcination time is 15h.

[0118] Comparative Example 1

[0119] Comparative Example 1 provides a method for preparing lithium nickel manganese oxide cathode material, comprising the following steps:

[0120] (1) Dissolve 0.018 mol of nickel acetate and 0.054 mol of manganese acetate in 100 mL of deionized water, then add 0.00001 mol of tetrabutyl titanate and 0.00001 mol of magnesium monoethyl fumarate, stir for 10 min to obtain a mixed aqueous solution; under stirring conditions, add 56 mL of ammonia solution (mass fraction of 25%) dropwise to the mixed aqueous solution, then add 650 mL of ammonium carbonate solution (mass fraction of 10%) dropwise to precipitate metal ions, and at the same time, stabilize the pH of the mixed aqueous solution at about 6.0 by adding dilute sulfuric acid (mass fraction of 3%); collect the nickel-manganese precipitate by centrifugation after the reaction.

[0121] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in an air atmosphere in a tube furnace and calcined at 400°C for 12 hours to prepare the precursor.

[0122] (3) After the precursor obtained in step (2) and 0.07 mol of lithium carbonate are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 900°C for 12 h at an oxygen atmosphere and an oxygen flow rate of 300 mm / Hg (maintaining the oxygen content in the furnace ≥95%). Then, the temperature is lowered to 700°C for 6 h at a rate of 3°C / min. The modified lithium nickel manganese oxide cathode material is obtained by cooling down.

[0123] Comparative Example 2

[0124] Comparative Example 2 provides a method for preparing lithium nickel manganese oxide cathode material, comprising the following steps:

[0125] (1) Dissolve 0.018 mol of nickel acetate and 0.054 mol of manganese acetate in 100 mL of deionized water, then add 0.0006 mol of tetrabutyl titanate and 0.0004 mol of magnesium monoethyl fumarate, stir for 10 min to obtain a mixed aqueous solution; under stirring conditions, add 56 mL of ammonia solution (mass fraction of 20%) dropwise to the mixed aqueous solution, then add 650 mL of ammonium carbonate solution (mass fraction of 10%) dropwise to precipitate metal ions, and at the same time, add dilute sulfuric acid (mass fraction of 3%) to stabilize the pH of the mixed aqueous solution at about 6.0; collect the nickel-manganese precipitate by centrifugation after the reaction.

[0126] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in an air atmosphere in a tube furnace and calcined at 400°C for 12 hours to prepare the precursor.

[0127] (3) After the precursor obtained in step (2) and 0.07 mol of lithium carbonate are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 900°C for 12 h under air at 1°C / min, and then calcined at 700°C for 6 h at 3°C / min. The modified lithium nickel manganese oxide cathode material is obtained by cooling.

[0128] Comparative Example 3

[0129] Comparative Example 3 provides a method for preparing lithium nickel manganese oxide cathode material, comprising the following steps:

[0130] (1) Dissolve 0.018 mol of nickel acetate and 0.054 mol of manganese acetate in 100 mL of deionized water, then add 0.002 mol of tetrabutyl titanate and 0.003 mol of magnesium monoethyl fumarate, and stir for 10 min to obtain a mixed aqueous solution; under stirring conditions, add 56 mL of ammonia solution (mass fraction of 15%) dropwise to the mixed aqueous solution, and then add 650 mL of ammonium carbonate solution (mass fraction of 20%) dropwise to precipitate metal ions. At the same time, add dilute sulfuric acid (mass fraction of 3%) to stabilize the pH of the mixed aqueous solution at about 6.0; collect the nickel-manganese precipitate by centrifugation after the reaction.

[0131] (2) The nickel-manganese precipitate obtained in step (1) was dried and placed in an air atmosphere in a tube furnace and calcined at 400°C for 12 hours to prepare the precursor.

[0132] (3) After the precursor obtained in step (2) and 0.07 mol of lithium carbonate are ball-milled and mixed evenly, the mixture is transferred to a tube furnace and calcined at 900°C for 12 h at an oxygen atmosphere and an oxygen flow rate of 300 mm / Hg (maintaining the oxygen content in the furnace ≥95%). Then, the temperature is lowered to 700°C for 6 h at a rate of 3°C / min. The modified lithium nickel manganese oxide cathode material is obtained by cooling down.

[0133] Experimental Example 1

[0134] Figure 1 The figures show the XRD patterns of lithium nickel manganese oxide cathode materials prepared in Example 1 and Comparative Example 2 of the present invention. As can be seen from the figures, the lithium nickel manganese oxide cathode material prepared in Example 1 of the present invention has better crystallinity. Figure 2 The image shows a SEM image of the lithium nickel manganese oxide cathode material prepared in Example 3 of the present invention. As can be seen from the image, the lithium nickel manganese oxide cathode material of the present invention has been successfully doped with the corresponding doping elements and formed the corresponding protective layer.

[0135] Experimental Example 2

[0136] To further illustrate the performance differences of the lithium nickel manganese oxide cathode material of the present invention, the lithium manganese iron phosphate composite electrode materials prepared in each embodiment and comparative example were applied to lithium-ion batteries to prepare coin cells. The specific steps are as follows:

[0137] ① Preparation of slurry: The lithium manganese iron phosphate composite electrode materials prepared in each example and comparative example were respectively ball-milled with SP (conductive carbon black), PVDF (polyvinylidene fluoride) and NMP (N-methylpyrrolidone) at a mass ratio of 93.5:2.5:4:100 for 4 hours at a speed of 360 r / min to obtain positive electrode slurry.

[0138] ② Coating of slurry: Adjust the scale of the scraper of the coating machine, and evenly coat the slurry after ball milling onto the aluminum foil. Place the coated electrode in a vacuum drying oven at 130℃ and bake for 3 hours.

[0139] ③ Roll pressing and stamping: Place the aluminum foil coated with slurry flat in the center of the roller and roll press the electrode sheet; then press the rolled electrode sheet with the front side tightly against the perforated area and stamp it sequentially; the compaction density of the electrode sheet is controlled at 2.0~2.4g / cm³. 3 The diameter is 14mm and the thickness is 0.05~0.10mm; the punched electrode is placed in a vacuum drying oven at 130℃ and baked for 3 hours;

[0140] ④ Assemble the button cell battery. In the glove box, assemble the negative electrode shell, spring, steel sheet, lithium sheet, separator, positive electrode sheet and positive electrode shell in sequence. During the process, inject 10μL of electrolyte. Then, use a sealing machine to seal the button cell battery to obtain the button cell battery corresponding to the positive electrode material provided in the examples and comparative examples.

[0141] The specific capacity, room temperature cycle performance, and 45℃ cycle performance of the button cells were tested respectively. The test results are shown in Table 1.

[0142] Table 1. Test results for different embodiments and comparative examples.

[0143] serial number Specific capacity (mAh / g) ambient temperature cycling performance 45℃ Cycling Performance Example 1 0.1C 132 / 1C 125 5C500 laps 91% 3C300 Circle 82% Example 2 0.1C 129 / 1C 122 5C500 laps 93% 3C300 Circle 84% Example 3 0.1C 131 / 1C 127 5C500 laps 90% 3C300 Circle 81% Example 4 0.1C 135 / 1C 130 5C500 laps 93% 3C300 Circle 85% Example 5 0.1C 133 / 1C 128 5C500 laps 89% 3C300 Circle 80% Example 6 0.1C 112 / 1C 108 5C500 laps 71% 3C300 Circle 39% Example 7 0.1C 124 / 1C 120 5C500 laps 76% 3C300 Circle 45% Example 8 0.1C 129 / 1C 125 5C500 laps 87% 3C300 Circle 71% Example 9 0.1C 126 / 1C 122 5C500 laps 88% 3C300 circles 76% Example 10 0.1C 128 / 1C 123 5C500 laps 85% 3C300 Circle 73% Comparative Example 1 0.1C 121 / 1C 112 5C500 laps 80% 3C300 Circle 56% Comparative Example 2 0.1C 115 / 1C 101 5C500 laps 78% 3C300 Circle 41% Comparative Example 3 0.1C 119 / 1C 105 5C500 laps 65% 3C300 Circle 21%

[0144] The test results above show that the present invention uses a doped metal source as both a doping source and a coating source. During the co-precipitation process with nickel and manganese sources, the doped metal is incorporated into the nickel-manganese oxide lattice. Subsequently, during the calcination process with a lithium source, lithium nickel manganese oxide nucleates and grows. Part of the doped metal in the nickel-manganese oxide lattice seeps out from the inside to the outer surface of the crystal nucleus. Since the calcination is carried out in an oxygen-rich atmosphere, the doped metal source is rapidly oxidized to form metal oxides, thereby constructing a dense protective layer in situ on the surface of the lithium nickel manganese oxide crystal nucleus. The internal elemental doping improves the stability of the crystal structure, and the external in-situ construction of the protective layer can more effectively suppress the dissolution of manganese and the occurrence of electrolyte side reactions, greatly improving the electrochemical performance of lithium nickel manganese oxide and thus enhancing its electrochemical energy storage.

[0145] Comparative Example 1 shows that when the amount of dopant metal source is insufficient, doping and coating cannot be achieved simultaneously, thus failing to achieve the desired effect. Comparative Example 2 shows that when calcination is carried out in an air atmosphere instead of an oxygen-enriched atmosphere, the conversion of the diffused metal into metal oxides is far from ideal, making simultaneous doping and coating impossible. Comparative Example 3 shows that when the amount of dopant metal source is too high, it leads to an excessively thick carbon layer. Due to the presence of the metal oxide coating layer, this excessively thick carbon layer affects electrolyte wetting and ion diffusion, thereby impacting electrochemical performance.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a positive electrode material, characterized in that, Includes the following steps: (a) Under the action of a precipitant, a mixed solution formed by a manganese source, a nickel source and a doped metal source is subjected to a co-precipitation reaction to obtain a co-deposited precipitate; (b) Calcining the co-deposited precipitate to obtain a precursor; (c) The precursor is mixed with a lithium source and then calcined in an oxygen-rich atmosphere to obtain a lithium nickel manganese oxide cathode material; the oxygen content in the oxygen-rich atmosphere is ≥80%, and the oxygen content refers to the volume fraction. The molar ratio of the doped metal source to the manganese source, calculated as doped metal element and Mn respectively, is (0.001~0.08):1; the molar ratio of the manganese source to the nickel source, calculated as Mn and Ni respectively, is 1:(0.2~0.35). In step (b), the calcination temperature is 300–500°C, and the calcination time is 2–8 hours; the calcination in step (b) is carried out in an air atmosphere. The doped metal source includes an organic doped metal source; the doped metal source serves as both a doping source and a coating source; during the calcination process with the lithium source, lithium nickel manganese oxide nucleates and grows, and some of the doped metal in the nickel manganese oxide lattice seeps out from the inside to the outer surface of the crystal nucleus; under an oxygen-rich atmosphere, the doped metal source is oxidized to form a metal oxide, and a dense protective layer is constructed in situ on the surface of the lithium nickel manganese oxide crystal nucleus.

2. The method for preparing the cathode material according to claim 1, characterized in that, The doped metal source includes at least one of titanium, aluminum, zinc, chromium, magnesium, zirconium, copper, and iron.

3. The method for preparing the cathode material according to claim 2, characterized in that, The titanium source includes at least one of tetrabutyl titanate and titanium oxysulfate.

4. The method for preparing the cathode material according to claim 2, characterized in that, The zinc source includes at least one of zinc gluconate, zinc methionine, zinc lactate, zinc glycyrrhizinate, and zinc citrate.

5. The method for preparing the cathode material according to claim 2, characterized in that, The chromium source includes chromium nitrate.

6. The method for preparing the cathode material according to claim 2, characterized in that, The magnesium source includes at least one of magnesium ascorbate, magnesium monoperoxyphthalate hexahydrate, magnesium peroxide, magnesium monoethyl fumarate, magnesium rosinate, and magnesium nitrate.

7. The method for preparing the cathode material according to claim 2, characterized in that, The zirconium source includes at least one of zirconium carboxylate, zirconium phosphate, zirconium nitrate, and zirconium 1-butoxide; the copper source includes at least one of copper nitrate, copper acetylene, phenyl copper, alkyl copper, copper acyl chloride, and cuprous acetate.

8. The method for preparing the cathode material according to claim 2, characterized in that, The iron source includes at least one of ferrous lactate, ferric citrate, and ferric glycine.

9. The method for preparing the positive electrode material according to claim 1, characterized in that, In the coprecipitation reaction, the pH of the system is controlled to be 5.75–6.

1.

10. The method for preparing the cathode material according to claim 9, characterized in that, The pH of the system is controlled by a slow-release agent; the slow-release agent is at least one of sulfuric acid, phosphoric acid, and hydrochloric acid.

11. The method for preparing the cathode material according to claim 1, characterized in that, The precipitant is an alkaline solution.

12. The method for preparing the cathode material according to claim 11, characterized in that, The precipitant includes at least one of an aqueous solution of a carbonate and an aqueous solution of a hydroxide.

13. The method for preparing the cathode material according to claim 11, characterized in that, The amounts of the manganese source, the nickel source, and the lithium source, respectively, calculated as Mn, Ni, and Li, satisfy the following: Li:(Mn+Ni)=1:(0.95~1.05).

14. The method for preparing the cathode material according to claim 1, characterized in that, In step (c), the calcination includes primary calcination and secondary calcination; the temperature of primary calcination is 550–1100℃, and the time of primary calcination is 8–24 h; the temperature of secondary calcination is 450–800℃, and the time of secondary calcination is 15–48 h.

15. The method for preparing the cathode material according to claim 14, characterized in that, In the first calcination, the temperature is increased to 550-1100℃ at a heating rate of 0.5-10℃ / min; in the second calcination, the temperature is decreased to 450-800℃ at a cooling rate of 0.5-2℃ / min.

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