Lithium-rich manganese-based solid-state battery positive active material as well as preparation method and application thereof

Abstract

The invention discloses a lithium-rich manganese-based solid-state battery positive electrode active material and a preparation method and application thereof, and the preparation method comprises the following steps: S1, taking a manganese salt, a cobalt salt and a nickel salt, and preparing a mixed salt solution; s2, adding an oxalic acid solution into the mixed salt solution, and stirring to form an oxalate precipitate; s3, carrying out vacuum drying and collecting precipitates to obtain an oxalic acid precursor; s4, mixing and uniformly grinding the oxalic acid precursor, LiOH and Li2WO4 to obtain mixed powder; and S5, pre-sintering the mixed powder, then calcining, and naturally cooling to room temperature to obtain the composite material. The invention also discloses the lithium-rich manganese-based solid-state battery positive electrode active material prepared by the preparation method, and a battery positive electrode and a solid-state battery comprising the active material. Li2WO4 is introduced into the lithium-rich manganese-based solid-state battery positive electrode material to construct a Li < + > / e <-> transmission channel, so that the initial specific capacity of the battery is increased; and a protective layer is formed on the surface of the positive electrode material to enhance the redox reversibility and improve the cycle stability of the battery.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and more specifically, to a cathode active material for a lithium-rich manganese-based solid-state battery, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, lithium-rich manganese-based cathode materials have become a promising material, mainly because of their advantages of large discharge capacity, high energy density, and environmental friendliness. These properties make lithium-rich manganese-based cathode materials an attractive choice for meeting the energy density and safety requirements of all-solid-state lithium electromagnetic devices. However, due to the existence of two nano-phases, LiTMO2 and Li2MnO3, in the lithium-rich manganese-based cathode, there is incompatibility at the interface between the cathode and the electrolyte, which limits the transport of lithium ions and prevents the full utilization of its high-capacity advantage. Secondly, the irreversibility of the anionic redox reaction of oxygen during long-term cycling leads to unsatisfactory rate capacity and voltage decay of the cathode.

[0003] Therefore, lithium-rich manganese-based cathode materials have problems such as poor conductivity, incompatibility with solid-state electrolytes (SEs) at the interface, irreversible redox, and severe voltage decay. Summary of the Invention

[0004] In order to solve the problems of poor conductivity of the above-mentioned lithium-rich manganese-based cathode materials, incompatibility with solid-state electrolytes (SEs) at the interface, irreversible redox, and severe voltage decay, the present invention provides a cathode active material for a lithium-rich manganese-based solid-state battery, a preparation method thereof, and an application thereof.

[0005] The object of the present invention is achieved by the following technical solutions:

[0006] In a first aspect, the present invention provides a preparation method for a lithium-rich manganese-based cathode active material, comprising the following steps:

[0007] S1. Take manganese salt, cobalt salt, and nickel salt to prepare a mixed salt solution;

[0008] S2. Add an oxalic acid solution to the mixed salt solution and stir to form an oxalate precipitate;

[0009] S3. Vacuum-dry and collect the precipitate to obtain an oxalic acid precursor;

[0010] S4. Mix and grind the oxalic acid precursor with LiOH and Li2WO4 evenly to obtain a mixed powder;

[0011] S5. Pre-sinter the mixed powder first, then calcine it, and let it cool naturally to room temperature to obtain the product.

[0012] As some specific embodiments of the present invention, in step S1, when taking manganese salt, cobalt salt and nickel salt, they are weighed according to the molar ratio of Mn / Co / Ni being 5.4:1.1 - 1.5:1.1 - 1.5. Preferably, it is 5.4:1.3:1.3.

[0013] As some specific embodiments of the present invention, in step S1, the manganese salt is selected from at least one of manganese sulfate, manganese nitrate, and manganese citrate; preferably MnSO4·H2O;

[0014] And / or, the cobalt salt is selected from at least one of cobalt sulfate, cobalt nitrate, and cobalt citrate; preferably CoSO4·7H2O;

[0015] And / or, the nickel salt is selected from at least one of nickel sulfate, nickel nitrate, and nickel citrate; preferably NiSO4·7H2O.

[0016] As some specific embodiments of the present invention, in step S1, the concentration of the mixed salt solution is 0.8 - 1.2 M; preferably 1.0 M.

[0017] As some specific embodiments of the present invention, in step S2, the concentration of the oxalic acid solution is 1.3 - 1.7 M; preferably 1.5 M; the volume ratio of the oxalic acid solution to the mixed salt solution is 1.3 - 1.7:1.

[0018] As some specific embodiments of the present invention, in step S2, a magnetic stirrer is used for stirring, the rotation speed of the stirring is 800 - 1200 rpm, and the time is 10 - 30 min.

[0019] The reaction in step S2 is carried out in a 100 mL beaker. By using excessive oxalic acid and vigorously stirring with a magnetic stirrer, the reaction is made sufficient to form oxalate precipitates of all metal ions.

[0020] As some specific embodiments of the present invention, in step S3, the vacuum drying is carried out in a vacuum oven, the temperature of the vacuum drying is 60 - 100 °C, and the time is 20 - 30 h. Preferably 80 °C, 24 h.

[0021] As some specific embodiments of the present invention, in step S4, the addition amount of LiOH and the molar ratio of Mn in the manganese salt is 10 - 12:5.4;

[0022] Then Li2WO4 is added according to the molar ratio of 3 - 7% of LiOH, preferably 5 wt%.

[0023] As some specific embodiments of the present invention, in step S4, the grinding is carried out in a mortar.

[0024] As some specific embodiments of the present invention, in step S5, the temperature of the pre-sintering is 450 - 550 °C, the time is 4 - 5 h, and the heating rate is 2 - 4 °C / min; preferably 500 °C, 5 h, 2 °C / min;

[0025] and / or, the temperature of the calcination is 800 - 900 °C, the time is 10 - 12 h, and the heating rate is 4 - 5 °C / min; preferably 900 °C, 12 h, 5 °C / min;

[0026] The pre-sintering and / or calcination is carried out in a muffle furnace in air.

[0027] In a second aspect, the present invention provides a cathode active material for a lithium-rich manganese-based solid-state battery, which is prepared by the preparation method described in any one of the above.

[0028] As some specific embodiments of the present invention, the cathode active material for the lithium-rich manganese-based solid-state battery is Li 1.2 Mn 0.54 Co y Ni z O2 wrapped by xLi2WO4, where x is the molar fraction of Li2WO4 relative to Li 1.2 Mn 0.54 Co y Ni z O2, 3% < x < 7%, 0.11 < y < 0.15, 0.11 < z < 0.15.

[0029] In a third aspect, the present invention provides a cathode for a lithium-rich manganese-based solid-state battery, which includes the cathode active material for the lithium-rich manganese-based solid-state battery described in any one of the above, and also includes an electrolyte and a conductive agent.

[0030] As some specific embodiments of the present invention, the electrolyte includes at least one of Li3InCl6, Li3InBr6, and LiNbOCl4;

[0031] and / or, the conductive agent includes at least one of vapor-grown carbon fiber (VGCF), carbon black conductive agent (SP), and carbon nanotubes (CNTs).

[0032] In a fourth aspect, the present invention provides a lithium-rich manganese-based solid-state battery, which includes the battery cathode described in any one of the above, and also includes an electrolyte and a battery anode.

[0033] As some specific embodiments of the present invention, the electrolyte includes at least one of Li3InCl6, Li3InBr6, and LiNbOCl4;

[0034] and / or, the battery anode includes at least one of a lithium sheet, a silicon-carbon composite material, and a lithium-silicon alloy.

[0035] In some specific embodiments of the present invention, current collectors are further included on both sides of the positive electrode and the negative electrode of the lithium-rich manganese-based solid-state battery. The current collector of the positive electrode is aluminum foil, and the current collector of the negative electrode is copper foil.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1) Through in-situ bulk / interface structure design, Li2WO4 is introduced into the positive electrode material of the lithium-rich manganese-based solid-state battery to construct a stable and fast Li + / e - transport channel. Li2WO4 has a cubic tunnel structure, which can reduce the Li + migration barrier, broaden the Li layer spacing, and enhance the bulk Li + diffusion kinetics, thereby accelerating the transport of lithium ions, increasing the initial specific capacity of the battery, and improving the cycle stability.

[0038] 2) Introducing Li2WO4 can form a protective layer on the surface of the positive electrode material, isolate the active part of the positive electrode from the electrolyte, inhibit side reactions, thereby inhibiting redox and protecting the material structure. During the charge and discharge process of the battery, oxygen in the positive electrode material may escape in the form of O2, resulting in structural collapse and capacity decay. The Li2WO4 protective layer coated on the surface of the present invention can inhibit oxygen escape, stabilize the surface oxygen structure, enhance the redox reversibility, improve the efficiency of the redox reaction required for the normal operation of the battery, and improve the cycle stability of the battery.

[0039] 3) Directly introducing lithium tungstate simplifies the experimental steps, and the chemical properties of lithium tungstate are stable. Its nucleation and growth processes are easier to control, and it can nucleate uniformly on the surface of the positive electrode material to form a dense and uniform continuous coating layer. Therefore, it can better protect the surface of the positive electrode material, reduce the occurrence of side reactions, and thus improve the electrochemical performance and cycle stability of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] By reading the detailed description of the non-limiting embodiments with reference to the following drawings, other features, objects, and advantages of the present invention will become more apparent:

[0041] Figure 1 It is a comparison chart of the 100-cycle performance of Example 2 and Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0042] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those of ordinary skill in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0043] Example 1

[0044] (1) Weigh MnSO4·H2O, CoSO4·7H2O and NiSO4·7H2O according to the molar ratio of Mn / Co / Ni being 5.4:1.3:1.3, and prepare a mixed salt solution with a total concentration of 1.0 M, which is placed in beaker A.

[0045] (2) Place beaker A on a magnetic stirrer at a rotation speed of 1000 rpm, add an oxalic acid solution with a concentration of 1.5 M, and the volume ratio of the oxalic acid solution to the mixed salt solution is 1.5:1. Continuously stir and react for 30 min.

[0046] (3) After drying in a vacuum oven at 80 °C for 24 hours, collect the precipitate to obtain an oxalic acid precursor.

[0047] (4) Add LiOH according to the molar ratio of Li / Mn being 12:5.4 with respect to LiOH and MnSO4·H2O in step (1), mix it with the oxalic acid precursor and put it into a mortar. Additionally, add Li2WO4 with 3% (molar ratio) of LiOH, and grind until the raw materials are evenly mixed to obtain a powder.

[0048] (5) Pre-sinter at 500 °C for 5 hours (heating rate is 2 °C / min), calcine in air at 900 °C for 12 hours (heating rate is 5 °C / min), and naturally cool to room temperature to obtain the final material.

[0049] Example 2

[0050] (1) Weigh MnSO4·H2O, CoSO4·7H2O and NiSO4·7H2O according to the molar ratio of Mn / Co / Ni being 5.4:1.3:1.3, and prepare a mixed salt solution with a total concentration of 1.0 M, which is placed in beaker A.

[0051] (2) Place beaker A on a magnetic stirrer at a rotation speed of 1000 rpm, add an oxalic acid solution with a concentration of 1.5 M, and the volume ratio of the oxalic acid solution to the mixed salt solution is 1.5:1. Continuously stir and react for 30 min.

[0052] (3) After drying in a vacuum oven at 80 °C for 24 hours, collect the precipitate to obtain an oxalic acid precursor.

[0053] (4) Add LiOH according to the molar ratio of Li / Mn being 12:5.4 with respect to LiOH and MnSO4·H2O in step (1), mix it with the oxalic acid precursor and put it into a mortar. Additionally, add Li2WO4 with 5% (molar ratio) of LiOH, and grind until the raw materials are evenly mixed to obtain a powder.

[0054] (5) Pre-sinter at 500 °C for 5 hours (heating rate: 2 °C / min), calcine in air at 900 °C for 12 hours (heating rate: 5 °C / min), and naturally cool to room temperature to obtain the final material.

[0055] Example 3

[0056] (1) Weigh MnSO4·H2O, CoSO4·7H2O, and NiSO4·7H2O according to the molar ratio of Mn / Co / Ni of 5.4:1.3:1.3, and prepare a mixed salt solution with a total concentration of 1.0 M, and place it in beaker A.

[0057] (2) Place beaker A on a magnetic stirrer at a rotation speed of 1000 rpm, add an oxalic acid solution with a concentration of 1.5 M, and the volume ratio of the oxalic acid solution to the mixed salt solution is 1.5:1, and continuously stir and react for 30 min.

[0058] (3) Dry in a vacuum oven at 80 °C for 24 hours and collect the precipitate to obtain the oxalic acid precursor.

[0059] (4) Add LiOH according to the molar ratio of Li / Mn of 12:5.4 with respect to LiOH and MnSO4·H2O in step (1), mix it with the oxalic acid precursor and put it into a mortar, and add Li2WO4 with 7% (molar ratio) of LiOH, and grind until the raw materials are evenly mixed to obtain a powder.

[0060] (5) Pre-sinter at 500 °C for 5 hours (heating rate: 2 °C / min), calcine in air at 900 °C for 12 hours (heating rate: 5 °C / min), and naturally cool to room temperature to obtain the final material.

[0061] Comparative Example 1

[0062] (1) Weigh MnSO4·H2O, CoSO4·7H2O, and NiSO4·7H2O according to the molar ratio of Mn / Co / Ni of 5.4:1.3:1.3, and prepare a mixed salt solution with a total concentration of 1.0 M.

[0063] (2) Place beaker A on a magnetic stirrer at a rotation speed of 1000 rpm, add an oxalic acid solution with a concentration of 1.5 M, and the volume ratio of the oxalic acid solution to the mixed salt solution is 1.5:1, and continuously stir and react for 30 min.

[0064] (3) Dry in a vacuum oven at 80 °C for 24 hours and collect the precipitate to obtain the oxalic acid precursor.

[0065] (4) Add LiOH according to the molar ratio of LiOH to MnSO4·H2O in step (1) with Li / Mn being 12:5.4, mix it with the oxalic acid precursor and put it into a mortar. Additionally, add 5% (molar ratio) of LiOH, and grind until the raw materials are evenly mixed to obtain a powder.

[0066] (5) Pre-sinter at 500 °C for 5 hours (heating rate: 2 °C / min), calcine in air at 900 °C for 12 hours (heating rate: 5 °C / min), and naturally cool to room temperature to obtain the final material.

[0067] Comparative Example 2

[0068] Compared with Example 1, the only difference is that in step (1), Na2WO4·2H2O is added according to the molar ratio of 2.5% of LiOH, and no tungsten source is added in step 4. Other operations and parameters are the same as those in Example 1, and the tests are carried out according to the method of Example 1. The results are shown in Table 1.

[0069] Effect Example 1

[0070] Assemble the cathode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 2 into batteries. The specific steps are as follows:

[0071] Weigh and grind the cathode material: Li3InCl6: VGCF according to the mass ratio of 64:33:3 as the battery cathode. The electrolyte is Li3InCl6, and the battery anode is a lithium sheet. Place the cathode on an aluminum foil and the anode on a copper foil, and assemble the battery in the glove box according to the battery assembly sequence.

[0072] Conduct performance tests on the assembled batteries above: Place the assembled batteries in the LAND2001CT battery test chamber for charge and discharge tests, and conduct tests under the conditions of 25 °C, 0.1C, and a cyclic voltage of 2.3 - 4.5V for 100 cycles. The test results can be seen Figure 1 and Table 1.

[0073] Table 1 Charge and Discharge Test Results of Batteries

[0074]

[0075]

[0076] According to Figure 1 and Table 1, it can be seen that at the 0.1C rate, the initial specific capacity of the batteries in each example is greater than that in each comparative example, and the specific capacity and capacity retention rate after 100 cycles are greater than those in each comparative example. Among them, Example 2 can reach 247.58 mAh / g, which indicates that the coating of lithium tungstate can construct a stable and fast Li + / e -The transmission channels are thus realized to achieve a higher initial specific capacity. The initial specific capacities of the batteries in each embodiment are all greater than that of Comparative Example 2, proving that directly coating lithium tungstate solves the problem of uneven distribution caused by the stepwise introduction of tungsten source and lithium source. Meanwhile, the capacity retention rate of Example 2 after 100 cycles at a rate of 0.1C is 95.22%, while that of Comparative Example 1 is only 86.91%, proving that the coating of lithium tungstate inhibits oxygen escape, stabilizes the material structure, and improves the capacity retention rate of the battery.

[0077] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various deformations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A preparation method of a cathode active material for a lithium-rich manganese-based solid-state battery, characterized in that, It includes the following steps: S1. Take manganese salts, cobalt salts and nickel salts to prepare a mixed salt solution; S2. Add an oxalic acid solution to the mixed salt solution and stir to form oxalate precipitates; S3. Vacuum dry and collect the precipitates to obtain an oxalic acid precursor; S4. Mix and grind the oxalic acid precursor with LiOH and Li2WO4 evenly to obtain a mixed powder; S5. First pre-sinter the mixed powder, then calcine it, and it can be obtained after naturally cooling to room temperature.

2. The preparation method according to claim 1, wherein, In step S1, when taking manganese salts, cobalt salts and nickel salts, they are weighed according to the molar ratio of Mn / Co / Ni of 5.4:1.1 - 1.5:1.1 - 1.5; The manganese salts are selected from at least one of manganese sulfate, manganese nitrate, and manganese citrate; the cobalt salts are selected from at least one of cobalt sulfate, cobalt nitrate, and cobalt citrate; the nickel salts are selected from at least one of nickel sulfate, nickel nitrate, and nickel citrate; The concentration of the mixed salt solution is 0.8 - 1.2M.

3. The preparation method according to claim 1, characterized in that, In step S2, the concentration of the oxalic acid solution is 1.3 - 1.7M; the volume ratio of the oxalic acid solution to the mixed salt solution is 1.3 - 1.7:

1.

4. The preparation method according to claim 1, wherein In step S2, the stirring speed is 800 - 1200 rpm and the time is 10 - 30 min.

5. The preparation method according to claim 1, characterized in that, In step S3, the temperature of the vacuum drying is 60 - 100 °C and the time is 20 - 30 h.

6. The preparation method according to claim 1, characterized in that, In step S4, the molar ratio of the addition amount of LiOH to Mn in the manganese salts is 10 - 12:5.4; Then add Li2WO4 according to the molar ratio of 3 - 7% of LiOH.

7. The preparation method according to claim 1, characterized in that, In step S5, the temperature of the pre-sintering is 450 - 550 °C, the time is 4 - 5 h, and the heating rate is 2 - 4 °C / min; And / or, the temperature of the calcination is 800 - 900 °C, the time is 10 - 12 h, and the heating rate is 4 - 5 °C / min.

8. A cathode active material for a lithium-rich manganese-based solid-state battery, prepared by the preparation method described in any one of claims 1-7, wherein the lithium-rich manganese-based solid-state battery cathode active material is Li 1.2 Mn 0.54 Co y Ni z O2, where x is the mole fraction of Li2WO4 relative to Li 1.2 Mn 0.54 Co y Ni z O2, 3% < x < 7%, 0.11 < y < 0.15, 0.11 < z < 0.

15.

9. A cathode for a lithium-rich manganese-based solid-state battery, comprising the cathode active material for a lithium-rich manganese-based solid-state battery as claimed in claim 8, and further comprising an electrolyte and a conductive agent; The electrolyte includes at least one of Li3InCl6, Li3InBr6, and LiNbOCl4; And / or, the conductive agent includes at least one of vapor-grown carbon fibers, carbon black conductive agents, and carbon nanotubes.

10. A lithium-rich manganese-based solid-state battery, comprising the battery cathode as claimed in claim 9, and further comprising an electrolyte and a battery anode; The electrolyte includes at least one of Li3InCl6, Li3InBr6, and LiNbOCl4; And / or, the battery anode includes at least one of a lithium sheet, a silicon-carbon composite material, and a lithium-silicon alloy.

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