A LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material and preparation method

Abstract

The present invention discloses a LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material and a preparation method thereof. The chemical formula of the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material is Li 0.6 [Li 0.2 Mn x Ni 0.8‑x ]O2, wherein x is 0.5 to 0.7. Also disclosed are a method for preparing a positive electrode active material of a LMNO lithium-rich manganese-based all-solid-state lithium battery, a positive electrode of a LMNO lithium-rich manganese-based all-solid-state lithium battery, and a LMNO lithium-rich manganese-based all-solid-state lithium battery comprising the positive electrode. The present invention introduces Li and Ni into a P2 layered sodium-deficient precursor, and 2+ / Ni 4+ 、Mn 3+ / Mn 4+ and O 2‑ / O2 n‑ The complex charge compensation mechanism promoted by the redox couple effectively suppresses both lattice oxygen release and structural distortion, achieving high output capacity and excellent long-term stability of lithium-rich manganese-based solid-state batteries.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material and a preparation method thereof. Background Art

[0002] Lithium-ion batteries, as efficient and environmentally friendly energy storage devices, have been widely used in portable electronic devices, electric vehicles, and energy storage power stations. The performance of cathode materials, a core component of lithium-ion batteries, directly affects the battery's energy density, cycle life, and safety. In recent years, lithium-rich manganese-based cathode materials (xLi2MnO3·(1-x)LiMO2, where M = Ni, Co, Mn, etc.) have become a research hotspot for cathode materials for next-generation high-energy-density lithium-ion batteries due to their high specific capacity (>250 mAh / g), low cost, and high safety. However, these materials still face several challenges, including poor cycling stability and poor high-rate performance.

[0003] The oxygen lattice loss and derived structural distortion of lithium-rich manganese-based materials can lead to poor cycling stability and capacity loss. Summary of the Invention

[0004] The purpose of the present invention is to provide a LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material and a preparation method thereof, by Li, Ni co-doping combined with ion exchange, Li, Ni is introduced into the P2 layered Na y [A x Mn 1-x ]O2 matrix (where A includes electrochemically inert elements such as Li, Zn, and Cu), directly regulating the layered structure of the material, inhibiting oxygen release and structural distortion, simplifying the process, and eliminating the need for coating; and Ni doping synergistically with Ni 2+ / Ni 4+ 、Mn 3+ / Mn 4+ and O 2- / O2 n- The redox couple promotes a complex charge compensation mechanism, improving the charge compensation efficiency and enhancing the cycling stability of the material. In addition, the particle size is optimized through the annealing step to further improve the cycling stability.

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

[0006] In the first aspect, the present invention provides a LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material, the chemical formula of which is Li 0.6 [Li 0.2 Mn x Ni 0.8-x ]O2, where x is 0.5~0.7.

[0007] As some specific embodiments of the present invention, the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material Li 0.6 [Li 0.2 Mn x Ni 0.8-x ]O2 contains Ni 2+ / Ni 4+ 、Mn 3+ / Mn 4+ and O 2- / O2 n- Redox pair, where n is 1~2.

[0008] As some specific embodiments of the present invention, the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material is a P2-type layered metal oxide structure.

[0009] In a second aspect, the present invention provides a method for preparing the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material as described in any one of the above, comprising the following steps:

[0010] S1, press Na 0.6 [Li 0.2 Mn x Ni 0.8-x ] The raw materials lithium source, sodium source, MnO2, and NiCO3 are weighed and ball-milled until the powders are uniformly mixed, wherein x = 0.5~0.7;

[0011] S2, calcining the mixed powder in air;

[0012] S3, adding excess LiNO3 and LiCl to the calcined mixed powder, grinding and mixing uniformly;

[0013] S4, high temperature annealing to carry out ion exchange;

[0014] S5. Add deionized water to the powder for washing, centrifuge, filter, and dry to obtain the product.

[0015] As some specific embodiments of the present invention, in step S1, the lithium source is selected from at least one of Li2CO3, LiNO3, Li2SO4, and LiCl;

[0016] The sodium source is selected from at least one of Na2CO3, NaHCO3, NaOH, and Na2SO4.

[0017] As some specific embodiments of the present invention, in step S1, the raw materials are weighed into a ball mill jar, and the ball mill jar is loaded into a ball mill for ball milling; the speed of the ball mill is 300-400 rpm, and the time is 10-12 h.

[0018] As some specific embodiments of the present invention, in step S2, the ball-milled mixed powder is transferred from the ball mill to a crucible, and the crucible is placed in a muffle furnace for calcination; the calcination temperature is 600-800°C, the time is 20-24 h, and the heating rate is 3-5°C / min.

[0019] As some specific embodiments of the present invention, in step S3, the calcined mixed powder is transferred from the crucible to a mortar, and then an excess lithium source is added, the mass ratio of the lithium source to the mixed powder is 10~11:1, the lithium source is LiNO3 and LiCl, and the molar ratio of LiNO3 to LiCl is 0.88:0.12.

[0020] Li was converted to + and Ni 2+ Introduce into the P2 layered sodium-deficient precursor synthesized in step S2, replacing Na + , forming a stable interlayer structure. Li and Ni co-doping form strong metal-oxygen bonds (such as Ni-O), which inhibit the release of lattice oxygen.

[0021] As some specific embodiments of the present invention, in step S4, the high-temperature annealing is performed in a muffle furnace, the annealing temperature is 250-300°C, the time is 1-2 h, and the heating rate is 2-5°C / min.

[0022] As some specific embodiments of the present invention, in step S5, the centrifugal speed is 8000-10000 rpm, and the time is 2-4 min.

[0023] As some specific embodiments of the present invention, in step S5, the drying is performed in an oven at a temperature of 60-120° C. for a time of 8-12 h.

[0024] As some specific embodiments of the present invention, the preparation method further comprises:

[0025] S6. Place the dried material in a muffle furnace for annealing and calcining again until it cools to room temperature.

[0026] As some specific embodiments of the present invention, in step S6, the annealing temperature is 400-500°C, the holding time is 1 h-2 h, and the heating rate is 4-6°C / min.

[0027] In a third aspect, the present invention provides a LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode, comprising the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material described in any one of the above items, or the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material prepared by the preparation method described in any one of the above items.

[0028] As some specific embodiments of the present invention, the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode further includes a sulfide electrolyte and VGCF (vapor-grown carbon fiber as a conductive agent).

[0029] In a fourth aspect, the present invention provides a LMNO lithium-rich manganese-based all-solid-state lithium battery, comprising the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode described in any one of the above items, and also comprising a sulfide electrolyte and a battery negative electrode.

[0030] As some specific embodiments of the present invention, the sulfide electrolyte is selected from at least one of LPSC, LPS, and LGPS;

[0031] The battery negative electrode is selected from at least one of lithium silicon and lithium indium.

[0032] As some specific embodiments of the present invention, the lithium-rich manganese-based solid-state battery further includes current collectors on both sides of the positive electrode and the negative electrode of the battery. The current collector of the positive electrode is aluminum foil, and the current collector of the negative electrode is copper foil.

[0033] Only Mn 3+ / Mn 4+ When the redox pair is present, the stability of the material system is poor due to the John-Teller effect of the Mn base. 2+ / Ni 4+ Redox couples keep the material stable.

[0034] Compared with the prior art, the present invention has the following beneficial effects:

[0035] 1) The present invention introduces Li and Ni into the P2 layered sodium-deficient precursor by co-doping Li and Ni. 2+ / Ni 4+ 、Mn 3+ / Mn 4+ and O 2- / O2 n- The complex charge compensation mechanism promoted by the redox couple effectively suppresses both lattice oxygen release and structural distortion. 2+ Oxidized to Ni 4+ , Mn 3+ At the same time, it is oxidized to Mn 4+ , the oxidation of Ni and Mn provides the main source of electrons, significantly reducing the dependence on oxygen ion oxidation, thereby reducing the loss of lattice oxygen and avoiding the generation and escape of oxygen; at the same time, Ni doping forms a strong Ni-O bond, inhibiting the formation of oxygen vacancies; Mn 3+ / Mn 4+The oxidation of Mn regulates the activity of interlayer oxygen and maintains the stability of the oxygen sublattice. The charge compensation mechanism reduces the concentration of oxygen vacancies and avoids the irreversible transformation of the layered structure to the spinel phase or rock salt phase due to oxygen deficiency. The stable oxygen framework suppresses the Mn 3+ Low Jahn-Teller distortion. Achieves high output capacity and excellent long-term stability.

[0036] 2) Direct ball milling of nickel-containing lithium-rich manganese-based materials fails to insert lithium and nickel into the transition layer, resulting in uneven redox distribution. However, the present invention uses a simple ion exchange method to exchange lithium and nickel for sodium in the P2-type sodium-deficient precursor, thereby inserting lithium and nickel into the transition layer.

[0037] 3) The present invention also performs annealing and calcination after ion exchange to control the particle size and morphology of the material, achieving a more uniform particle distribution and appropriate particle size, allowing the material to be further formed. This helps increase the material's specific surface area and optimize the lithium ion diffusion path. Furthermore, after further annealing and calcination, both specific capacity and cycle stability are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0039] Figure 1 1 is a comparison chart of the electrochemical properties of the positive electrode active materials prepared in Example 1 and Comparative Example 1;

[0040] Figure 2 2500 times electron microscope photograph of LMNO prepared in Example 1;

[0041] Figure 3 5000x electron microscope photograph of LMNO prepared in Example 1;

[0042] Figure 4 50,000x electron microscope photograph of LMNO prepared in Example 1;

[0043] Figure 5 Elemental energy spectrum of LMNO prepared in Example 1;

[0044] Figure 6 Elemental composition diagram of LMNO prepared in Example 1. DETAILED DESCRIPTION

[0045] 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 are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0046] Example 1

[0047] (1) Press Na 0.6 [Li 0.2 Mn 0.65 Ni 0.15 Li2CO3, Na2CO3, MnO2, and NiCO3 raw materials were weighed and transferred to a ball mill jar. The raw materials were ball milled until the powders were uniformly mixed. The ball milling speed was 350 rpm and the time was 12 h to obtain a sodium-deficient precursor.

[0048] (2) Place the uniformly mixed precursor into a muffle furnace and calcine in air;

[0049] (3) Set the heating program with a heating rate of 4°C / min, keep the temperature at 700°C for 20 h, and then cool it down to room temperature naturally;

[0050] (4) After taking out the powder, put it into the glove box and add LiNO3 and LiCl with a molar ratio of 0.88:0.12, which is ten times the mass of the powder, into the mortar and grind by hand until the powder is evenly mixed;

[0051] (5) Place the mixed powder into a muffle furnace for ion exchange;

[0052] (6) Set the heating program with a heating rate of 4 °C / min, keep the temperature at 280 °C for 1 h, and then cool it down to room temperature naturally;

[0053] (7) After the ion exchange, remove and clean the product to remove all excess sodium salt. After filtration, dry it at 60°C overnight to obtain material 1.

[0054] Figure 2-Figure 4 The SEM images of the LMNO lithium-rich manganese-based positive electrode active material prepared in Example 1 at different rates are shown in FIG. Figure 2 It can clearly show that the particle size of LMNO is uniform. Figure 3 It can be seen that the material is gathered together in an interwoven manner. Figure 4 The material is shown to have a layered structure. Figure 5 and Figure 6 It can be seen that Ni has been uniformly inserted into the layered structure of the material.

[0055] Example 2

[0056] (1) Press Na 0.6 [Li 0.2 Mn 0.6 Ni 0.2] Li2CO3, Na2CO3, MnO2, and NiCO3 raw materials were weighed in an O2 stoichiometric ratio and transferred to a ball mill jar. The raw materials were ball milled until the powders were uniformly mixed. The ball milling speed was 350 rpm and the time was 12 h to obtain a sodium-deficient precursor.

[0057] (2) Place the uniformly mixed precursor into a muffle furnace and calcine in air;

[0058] (3) Set the heating program with a heating rate of 4°C / min, keep the temperature at 700°C for 20 h, and then cool it down to room temperature naturally;

[0059] (4) After taking out the powder, place it in a glove box and add ten times the mass of LiNO3 and LiCl into a mortar and grind by hand until the powder is evenly mixed;

[0060] (5) Place the mixed powder into a muffle furnace for ion exchange;

[0061] (6) Set the heating program with a heating rate of 4°C / min, keep the temperature at 280°C for 1 hour, and then cool it down to room temperature naturally;

[0062] (7) After the ion exchange, take out and wash, wash away all the excess sodium salt, filter and dry at 60℃ overnight to obtain material 2.

[0063] Example 3

[0064] (1) Press Na 0.6 [Li 0.2 Mn 0.55 Ni 0.25 Li2CO3, Na2CO3, MnO2, and NiCO3 raw materials were weighed in a stoichiometric ratio and transferred to a ball mill. The raw materials were then ball milled until the powders were uniformly mixed. The ball milling speed was 350 rpm for 12 h to obtain a sodium-deficient precursor.

[0065] (2) Place the uniformly mixed precursor into a muffle furnace and calcine in air;

[0066] (3) Set the heating program with a heating rate of 4°C / min, keep the temperature at 700°C for 20 h, and then cool it down to room temperature naturally;

[0067] (4) After taking out the powder, place it in a glove box and add ten times the mass of LiNO3 and LiCl into a mortar and grind by hand until the powder is evenly mixed;

[0068] (5) Place the mixed powder into a muffle furnace for ion exchange;

[0069] (6) Set the heating program with a heating rate of 4 °C / min, keep the temperature at 280 °C for 1 h, and then cool it down to room temperature naturally;

[0070] (7) After the ion exchange, take out and wash, wash away all the excess sodium salt, filter and dry at 60 °C overnight to obtain material 3.

[0071] Example 4

[0072] (1) Press Na 0.6 [Li 0.2 Mn 0.65 Ni 0.15 Li2CO3, Na2CO3, MnO2, and NiCO3 raw materials were weighed in a stoichiometric ratio and transferred to a ball mill. The raw materials were then ball milled until the powders were uniformly mixed. The ball milling speed was 350 rpm for 12 h to obtain a sodium-deficient precursor.

[0073] (2) Place the uniformly mixed precursor into a muffle furnace and calcine in air;

[0074] (3) Set the heating program with a heating rate of 4 °C / min, keep the temperature at 700 °C for 20 h, and then cool it down to room temperature naturally;

[0075] (4) After taking out the powder, place it in a glove box and add ten times the mass of LiNO3 and LiCl into a mortar and grind by hand until the powder is evenly mixed;

[0076] (5) Place the mixed powder into a muffle furnace for ion exchange;

[0077] (6) Set the heating program with a heating rate of 4°C / min, keep the temperature at 280°C for 1 hour, and then cool it down to room temperature naturally;

[0078] (7) After ion exchange, remove and clean the sample to remove all excess sodium salts, filter and dry at 60°C overnight;

[0079] (8) The dried material is placed in a muffle furnace for annealing and calcination;

[0080] (9) Set the heating program with a heating rate of 4°C / min, keep the temperature at 400°C for 1 h, and then cool it naturally to room temperature to obtain material 4.

[0081] Comparative Example 1

[0082] According to conventional practices in the prior art, direct ball milling is used to synthesize lithium-rich manganese-based materials containing Li and Ni. The process includes the following steps:

[0083] (1) Press Li 0.8 Mn 0.6 Ni0.2 O2 stoichiometric ratio Li2CO3, MnO2, and NiCO3 raw materials were weighed and transferred into a ball mill jar;

[0084] (2) Set the ball mill speed to 350 r / min, the ball milling time to 10 h, and the ball-to-material ratio to 20:1. Ball mill the powder until it is evenly mixed to obtain material 5.

[0085] Effect Example 1

[0086] The materials prepared in each example and comparative example were ground into composite positive electrodes with a sulfide electrolyte (Li6PS5Cl) and conductive carbon (VGCF) at a mass ratio of 70:26:4. A solid-state battery was assembled using 14 mg of the composite positive electrode, 100 mg of the sulfide electrolyte (Li6PS5Cl), 10 mg of the lithium-silicon negative electrode, and Al and Cu current collectors for performance testing. The results are shown in Table 1.

[0087] Table 1 Battery performance test results

[0088]

[0089] Figure 1 The electrochemical performance comparison diagram of the positive electrode active materials prepared in Example 1 and Comparative Example 1 is shown in Table 1 and Figure 1 It can be seen that by constructing a P2-type sodium-deficient precursor through the sintering method, and then introducing more lithium to replace unnecessary sodium through the ion exchange method, the alkaline metal layer is lithium-deficient, while the transition metal layer is lithium-excessive, thereby significantly improving the discharge capacity and cycle stability.

[0090] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material, characterized in that: Its chemical formula is Li 0.6 [Li 0.2 Mn x Ni 0.8-x ]O2, where x is 0.5~0.7; The LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material Li 0.6 [Li 0.2 Mn x Ni 0.8-x ]O2 contains Ni 2+ / Ni 4 + 、Mn 3+ / Mn 4+ and O 2- / O2 n- Redox pair, where n is 1 to 2; The preparation method of the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material comprises the following steps: S1, press Na 0.6 [Li 0.2 Mn x Ni 0.8-x ] The raw materials lithium source, sodium source, MnO2, and NiCO3 are weighed and ball-milled until the powders are uniformly mixed, wherein x = 0.5~0.7; S2, calcining the mixed powder in air; S3, adding an excess amount of lithium source to the calcined mixed powder, grinding and mixing uniformly; S4, high temperature annealing to carry out ion exchange; S5. Add deionized water to the powder for washing, centrifuge, filter, and dry; S6. Place the dried material in a muffle furnace for annealing and calcining again until it cools to room temperature; In step S1, the ball milling speed is 300-400 rpm and the time is 10-12 h; In step S1, the lithium source is selected from at least one of Li2CO3, LiNO3, Li2SO4, and LiCl; the sodium source is selected from at least one of Na2CO3, NaHCO3, NaOH, and Na2SO4; In step S2, the calcination temperature is 600-800°C, the time is 20-24 h, and the heating rate is 3-5°C / min; In step S4, the annealing temperature is 250-300°C, the time is 1-2 h, and the heating rate is 2-5°C / min; In step S6, the annealing temperature is 400-500°C, the holding time is 1-2 h, and the heating rate is 4-6°C / min.

2. The LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material according to claim 1, characterized in that: In step S3, the mass ratio of the lithium source to the mixed powder is 10-11:1, the lithium source is LiNO3 and LiCl, and the molar ratio of LiNO3 to LiCl is 0.88:0.

12.

3. The LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material according to claim 1, characterized in that: In step S5, the drying temperature is 60-120° C. and the drying time is 8-12 h.

4. A LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode, characterized in that: Comprising the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode active material according to any one of claims 1 to 3; The LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode also includes a sulfide electrolyte and VGCF.

5. A LMNO lithium-rich manganese-based all-solid-state lithium battery, characterized in that: The invention comprises the LMNO lithium-rich manganese-based all-solid-state lithium battery positive electrode as claimed in claim 4, and further comprises a sulfide electrolyte and a battery negative electrode; The sulfide electrolyte is selected from at least one of LPSC, LPS, and LGPS; The battery negative electrode is selected from at least one of lithium silicon and lithium indium.

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