Ultrahigh-nickel positive electrode composite material, preparation method thereof and application of ultrahigh-nickel positive electrode composite material in all-solid-state battery

Abstract

The invention relates to the field of lithium ion batteries, and discloses an ultrahigh-nickel positive electrode composite material, a preparation method thereof and an application of the ultrahigh-nickel positive electrode composite material in an all-solid-state battery. The ultra-high nickel positive electrode composite material comprises an ultra-high nickel positive electrode material and LYZO coated outside the ultra-high nickel positive electrode material, wherein the chemical general formula of the ultrahigh nickel positive electrode material is LiNixCoyMnzO2, x is greater than or equal to 0.9, y is greater than or equal to 0 and less than or equal to 0.1, z is greater than or equal to 0 and less than or equal to 0.1, and x + y + z = 1; the LYZO is Li < 4 > ZrO < 4 > doped with Y2O3. According to the invention, LYZO is rich in oxygen vacancies, the LYZO is used as a coating material to meet the characteristics of selective ion conduction channels and oxygen vacancy buffering, and the ultrahigh nickel positive electrode composite material obtained after coating is relatively good in matching property with solid electrolyte and relatively good in cycling stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular to a super-high nickel positive electrode composite material, a preparation method thereof and application thereof in all-solid-state batteries. BACKGROUND

[0002] With the rapid development of new energy vehicles, large-scale energy storage systems and portable electronic devices, the market has increasingly stringent requirements for the energy density, cycle life and safety of lithium ion batteries. As the core component of the battery, the performance of the positive electrode material directly determines the overall performance of the battery. Currently, high-nickel layered oxides (such as LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.9 Co 0.05 Al 0.05 O2, etc.) are considered as key materials for breaking through the energy density bottleneck due to their high specific capacity (≥200 mAh / g) and low cost advantage.

[0003] However, the increase in nickel content (Ni content ≥90%) leads to multiple challenges for the material: ① structural instability: lattice distortion is intensified during charging and discharging, causing irreversible phase transition (such as H2→H3 phase transition), leading to particle micro-cracks and capacity decay. ② Interface side reaction: high activity surface is prone to interface side reaction with solid-state electrolyte, accelerating impedance rise. ③ Thermal safety risk: oxygen release is intensified at high temperature (thermal decomposition onset temperature <200℃), and the reaction with solid-state electrolyte releases heat, inducing thermal runaway.

[0004] The main modification methods and their limitations for the above problems currently include: ① bulk doping (such as Al, Mg, Ti, etc.): although it can alleviate structural stress, it is difficult to precisely control the doping sites, which may lead to deterioration of lithium ion diffusion kinetics. ② Traditional coating technology (such as Al2O3, Li3PO4 coating): passive physical isolation effect is limited, and rigid coating layer is prone to breakage and failure under volume expansion; some coating materials (such as metal oxides) have poor electronic conductivity, increasing the interface impedance. ③ Process complexity: most coating methods (such as atomic layer deposition) require high-temperature annealing or complex equipment, which is difficult to realize industrialized low-cost preparation.

[0005] Therefore, the prior art still needs to be improved and developed. SUMMARY

[0006] In view of the deficiencies of the prior art, the purpose of the present application is to provide a super-high nickel positive electrode composite material, a preparation method thereof and application thereof in all-solid-state batteries, by designing a multifunctional composite coating layer with "selective ion conduction channel, oxygen vacancy buffer", which can inhibit interface side reaction while improving ion transport efficiency, thereby breaking through the key barriers of commercial application of super-high nickel positive electrode.

[0007] The technical scheme of the present application is as follows:

[0008] In a first aspect, an ultra-high nickel positive electrode composite material is provided, comprising: an ultra-high nickel positive electrode material and LYZO coated on the outside of the ultra-high nickel positive electrode material; wherein the chemical general formula of the ultra-high nickel positive electrode material is LiNi x Co y Mn z O2, x≥0.9, 0≤y≤0.1, 0≤z≤0.1, x+y+z=1; and the LYZO is Y2O3-doped Li4ZrO4.

[0009] In a preferred technical scheme, the molar ratio of Y2O3 and Li4ZrO4 is 1:(20-30).

[0010] In a preferred technical scheme, the mass ratio of the ultra-high nickel positive electrode material and LYZO is 100:(1-5).

[0011] In a second aspect, a preparation method of the ultra-high nickel positive electrode composite material according to the first aspect is provided, comprising the following steps:

[0012] (1) uniformly mixing Y2O3 and Li4ZrO4 powders to obtain a first mixture;

[0013] (2) uniformly mixing the first mixture and LiNi x Co y Mn z O2 powders to obtain a second mixture;

[0014] (3) performing heat treatment on the second mixture under oxygen and then cooling to obtain the ultra-high nickel positive electrode composite material.

[0015] The particle size of the Y2O3 and Li4ZrO4 powders is 20-100 nm, and the particle size of the LiNi x Co y Mn z O2 powders is 5-20 μm.

[0016] In a preferred technical scheme, the flow rate of the oxygen is 1-3 L / min.

[0017] In a preferred technical scheme, the heat treatment conditions include: increasing the temperature to 500-900 ℃ at a temperature increasing rate of 1-5 ℃ / min and then maintaining the temperature for 2-6 h;

[0018] The cooling conditions include: decreasing the temperature to 10-30 ℃ at a temperature decreasing rate of 3-8 ℃ / min.

[0019] Preferably, in step (2), the first mixture and LiNi x Co y Mn z O2 are mixed uniformly by mechanical fusion, and the mechanical fusion is performed under the conditions of a rotation speed of 1000-3000 rpm and a time of 2-10 min.

[0020] In a third aspect, the application provides use of the ultra-high nickel positive electrode composite material in the first aspect in preparation of a full solid-state battery.

[0021] In a fourth aspect, the application provides a full solid-state battery, comprising a positive electrode, a solid-state electrolyte and a negative electrode, wherein the positive electrode comprises the ultra-high nickel positive electrode composite material in the first aspect.

[0022] Compared with the prior art, the application has the following beneficial effects:

[0023] (1) The ultra-high nickel positive electrode composite material provided by the application uses a lithium fast ion conductor (such as Li4ZrO4) with oxygen vacancies (oxygen vacancies are generated by doping an oxide of a low-valence element such as Y2O3 into a high-valence metal lithium salt) to coat an ultra-high nickel positive electrode material, which has good compatibility with a solid-state electrolyte and can more effectively promote Li + transport and has better cycle stability.

[0024] (2) The preparation method of the ultra-high nickel positive electrode composite material provided by the application adopts dry coating, which is simpler and more environmentally friendly than the method of synthesizing by wet chemical method and then heat treatment in the prior art.

[0025] (3) The preparation method of the ultra-high nickel positive electrode composite material provided by the application has simple operation steps, readily available raw materials, low cost, is easy to industrialize, has high production efficiency, is suitable for large-scale industrial production, has broad commercial application prospects, and has great theoretical and practical significance. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a graph of XRD test results of LYZO@NCM96 of an embodiment of the application and NCM96 of a comparative example.

[0027] Figure 2 is a graph of EPR test results of LYZO@NCM96 of an embodiment of the application and NCM96 of a comparative example.

[0028] Figure 3 is a graph of SEM test results of LYZO@NCM96 of an embodiment of the application and NCM96 of a comparative example.

[0029] Figure 4Figure of the half-cell cycle test results of the NCM96 assembled by the LYZO@ NCM96 of the embodiment of the application and the NCM96 of the comparative example. DETAILED DESCRIPTION

[0030] The application provides an ultrahigh-nickel positive electrode composite material, a preparation method thereof and application thereof in a full-solid-state battery.

[0031] The technical scheme of the application is as follows:

[0032] The application provides an ultrahigh-nickel positive electrode composite material, which comprises an ultrahigh-nickel positive electrode material and LYZO coated outside the ultrahigh-nickel positive electrode material; wherein the structural general formula of the ultrahigh-nickel positive electrode material is LiNi x Co y Mn z O2, x is greater than or equal to 0.9, y is greater than or equal to 0 and less than or equal to 0.1, z is greater than or equal to 0 and less than or equal to 0.1, and x+y+z is equal to 1; and the LYZO is Y2O3-doped Li4ZrO4.

[0033] Specifically, in the LYZO, Y 3+ partially replaces Zr in Li4ZrO4 4+ To maintain the charge conservation of the system, oxygen vacancies are formed. The LYZO is rich in oxygen vacancies and has a selective ion conduction channel, and when it is used as a coating material, the ion transmission efficiency can be improved while the interface side reaction is inhibited, thereby solving the problem of interface side reaction of the ultrahigh-nickel positive electrode material in application and breaking through the key barrier of commercial application of the ultrahigh-nickel positive electrode.

[0034] In an embodiment, the molar ratio of Y2O3 to Li4ZrO4 is 1:(20-30); for example, it can be 1:20, 1:23, 1:25, 1:27 or 1:30, and is preferably 1:25, but is not limited thereto.

[0035] In an embodiment, the mass ratio of the ultrahigh-nickel positive electrode material to the LYZO is 100:(1-5); for example, it can be 100:1, 100:2, 100:3, 100:4, 100:5, and is preferably 100:3, but is not limited thereto.

[0036] In an embodiment, the XRD diffraction peak main peak crystal face of the ultrahigh-nickel positive electrode material is (003); and specifically, the chemical formula of the ultrahigh-nickel positive electrode material can be LiNi 0.96 Co 0.02 Mn 0.02 O2.

[0037] In an embodiment, the XRD diffraction peak main peak of the LYZO is located at 2theta=23.1°.

[0038] The present application provides a preparation method of the ultra-high nickel positive electrode composite material as described above, comprising the steps of:

[0039] (1) mixing Y2O3 and Li4ZrO4 powders uniformly to obtain a first mixture;

[0040] (2) mixing the first mixture and LiNi x Co y Mn z O2 powders uniformly to obtain a second mixture;

[0041] (3) performing heat treatment on the second mixture under oxygen and cooling to obtain the ultra-high nickel positive electrode composite material.

[0042] In an embodiment, the particle size of the Y2O3 and Li4ZrO4 powders is 20-100 nm; for example, it can be 20 nm, 50 nm, 50 nm or 100 nm, preferably 50 nm, but is not limited thereto.

[0043] In an embodiment, the particle size of the LiNi x Co y Mn z O2 powders is 5-20 μm; for example, it can be 5 μm, 10 μm, 15 μm or 20 μm, preferably 10 μm, but is not limited thereto.

[0044] In an embodiment, the flow rate of the oxygen is 1-3 L / min; for example, it can be 1 L / min, 1.5 L / min, 2 L / min, 2.5 L / min or 3 L / min, preferably 1.5 L / min, but is not limited thereto.

[0045] In an embodiment, the heat treatment condition comprises: heating at a heating rate of 1-5 ℃ / min to 500-900 ℃ and then holding for 2-6 h; preferably, heating at a heating rate of 2 ℃ / min to 700 ℃ and then holding for 4 h, but is not limited thereto.

[0046] In an embodiment, the cooling condition comprises: cooling at a cooling rate of 3-8 ℃ / min to 10-30 ℃; preferably, cooling at a cooling rate of 5 ℃ / min to 25 ℃, but is not limited thereto.

[0047] In an embodiment, in step (1), the uniform mixing of Y2O3 and Li4ZrO4 is performed by grinding, and the grinding is performed in a mortar, and the grinding time is 20-40 min; preferably, the grinding time is 30 min, but is not limited thereto.

[0048] In an embodiment, in step (2), the first mixture and LiNi x Co y Mn z The mixing of the second mixture is performed by mechanical fusion, and the conditions of the mechanical fusion include a rotation speed of 1000-3000 rpm and a time of 2-10 min; preferably, the rotation speed is 1500 rpm and the time is 5 min, but are not limited thereto.

[0049] In an embodiment, in step (3), the second mixture is cooled after the heat treatment in the muffle furnace.

[0050] The present application provides an application of the ultra-high nickel positive electrode composite material as described above in the preparation of a full solid-state battery.

[0051] The present application provides a full solid-state battery, comprising a positive electrode, a solid-state electrolyte and a negative electrode, wherein the positive electrode comprises the ultra-high nickel positive electrode composite material as described in the first aspect.

[0052] In an embodiment, the material of the solid-state electrolyte is lithium indium chloride (Li3InCl6, LIC), and the material of the negative electrode is a lithium indium (LiIn) alloy.

[0053] The present application is further described below through specific embodiments.

[0054] Embodiment

[0055] The present embodiment provides an ultra-high nickel positive electrode composite material prepared by coating an ultra-high nickel positive electrode material with LYZO, and the specific steps are as follows:

[0056] 1 mol of yttrium trioxide (Y2O3) powder (50 nm in particle size) and 25 mol of lithium zirconium acid lithium (Li4ZrO4) powder (50 nm in particle size) are weighed and mixed in a mortar for 30 min to obtain a LYZO mixed precursor. The target mass of LiNi 0.96 Co 0.02 Mn 0.02 O2 (10 μm in particle size) and the LYZO mixed precursor are placed in a mechanical fusion machine (wherein the total mass of the LiNi 0.96 Co 0.02 Mn 0.02O2 is 100 g, and the LYZO precursor is 3 g. The mechanical fusion machine is set to rotate at 1500 rpm, and the mixing time is 5 min. The mixture is placed in a quartz tube, and the tube is placed in a muffle furnace. Oxygen is introduced at a rate of 1.5 L / min, the temperature is raised at a rate of 2°C / min to 700°C, and the material is heat-treated for 4 h. The cooling rate is 5°C / min. The burned material is ground in a mortar for 10 min to obtain the LYZO-coated ultra-high nickel positive electrode material, i.e., the ultra-high nickel positive electrode composite (LYZO@NCM96).

[0057] Comparative Example

[0058] The present comparative example provides an ultra-high nickel positive electrode material, and the specific steps are as follows:

[0059] The target mass of LiNi 0.96 Co 0.02 Mn 0.02 O2 is 100 g, and the LYZO precursor is 3 g. The mechanical fusion machine is set to rotate at 1500 rpm, and the mixing time is 5 min. The mixture is placed in a quartz tube, and the tube is placed in a muffle furnace. Oxygen is introduced at a rate of 1.5 L / min, the temperature is raised at a rate of 2°C / min to 700°C, and the material is heat-treated for 4 h. The cooling rate is 5°C / min. The burned material is ground in a mortar for 10 min to obtain the LYZO-coated ultra-high nickel positive electrode material, i.e., the ultra-high nickel positive electrode composite (LYZO@NCM96).

[0060] Performance Test

[0061] (1) XRD test: The LYZO@NCM96 of the example and the NCM96 of the comparative example were subjected to X-ray diffraction (XRD) test, as shown in Figure 1 , the LYZO@NCM96 has (003), (104) main characteristic peaks, and LYZO characteristic peaks appear at 2θ = 23.1°, which indicates that the LYZO in LYZO@NCM96 is successfully coated on the ultra-high nickel positive electrode material.

[0062] (2) EPR test: The LYZO@NCM96 of the example and the NCM96 of the comparative example were subjected to electron paramagnetic resonance (EPR) test, as shown in Figure 2 , the EPR spectrum of LYZO@NCM96 has a relatively high intensity, confirming that its total oxygen vacancy content is higher than that of the unmodified NCM96 positive electrode material.

[0063] (3) SEM test: The LYZO@NCM96 of the example and the NCM96 of the comparative example were subjected to scanning electron microscope (SEM) test, as shown in Figure 3 , after LYZO surface modification, a large number of nano-sized LYZO particles are observed on the surface of the material and are uniformly dispersed.

[0064] (4) Secondary battery stability test: The positive electrode was prepared by using the LYZO@NCM96 of the example and the NCM96 of the comparative example, and the half battery was assembled for stability test, and the test results were as shown in Table 2. Figure 4 The solid-state electrolyte material used for test was LIC, and the negative electrode was LiIn alloy. It can be concluded from Table 2 that the cycle stability of the half battery assembled by using the ultra-high nickel positive electrode composite material (LYZO@NCM96) of the present application is better than that of the half battery assembled by using the unmodified ultra-high nickel positive electrode material (NCM96). Figure 4

[0065] It should be understood that the application of the present application is not limited to the above examples, and those skilled in the art can make improvements or changes according to the above description, and all these improvements and changes shall belong to the protection scope of the appended claims of the present application.​

Claims

1. An ultrahigh nickel positive electrode composite, characterized by, Comprising: An ultra-high nickel positive electrode material and LYZO coated outside the ultra-high nickel positive electrode material; wherein the chemical general formula of the ultra-high nickel positive electrode material is LiNi x Co y Mn z O2, x>0.9, 0y0.1, 0z0.1, x+y+z=1; the LYZO is Y2O3 doped Li4ZrO4.

2. The ultra-high nickel positive electrode composite of claim 1, wherein, The molar ratio of Y2O3 and Li4ZrO4 is 1:(20-30).

3. The ultra-high nickel positive electrode composite of claim 1, wherein the nickel is present in an amount of 50-90 wt%. The mass ratio of the ultra-high nickel positive electrode material and LYZO is 100:(1-5).

4. A method for producing the ultra-high nickel positive electrode composite material according to any one of claims 1 to 3, characterized by, Comprising steps: (1) uniformly mixing Y2O3 and Li4ZrO4 powders to obtain a first mixture; (2) mixing the first mixture with LiNi x Co y Mn z O2 powder uniformly to obtain a second mixture; (3) after heat treatment of the second mixture under oxygen and cooling, the ultra-high nickel positive electrode composite material is obtained.

5. The preparation method according to claim 4, characterized in that, The particle size of the Y2O3 and Li4ZrO4 powders is 20-100 nm, the particle size of the LiNi x Co y Mn z The particle size of the O2 powder is 5-20 μm.

6. The preparation method according to claim 4, characterized in that, The flow rate of the oxygen is 1-3 L / min.

7. The preparation method according to claim 4, characterized in that, The heat treatment conditions include: heating at a rate of 1-5 ℃ / min to 500-900 ℃ and holding for 2-6 h; The cooling conditions include: cooling at a rate of 3-8 ℃ / min to 10-30 ℃.

8. The preparation method according to claim 4, characterized in that, In step (2), the first mixture and LiNi x Co y Mn z The powder mixture is mixed uniformly by mechanical fusion, the conditions of which include a rotation speed of 1000-3000 rpm and a time of 2-10 min.

9. Use of the ultra-high nickel positive electrode composite material according to any one of claims 1-3 in the preparation of a full solid-state battery.

10. An all-solid battery, characterized by, Comprising: A positive electrode, a solid-state electrolyte and a negative electrode, the positive electrode comprising the ultra-high nickel positive electrode composite material according to any one of claims 1-3.

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