A kind of fast ion conductor coated all-solid-state lithium ion battery manganese-based positive electrode material and its preparation method

Abstract

This invention relates to a fast-ion conductor-coated all-solid-state manganese-based cathode material for lithium-ion batteries and its preparation method, belonging to the field of lithium-ion battery technology. It includes a lithium-rich manganese-based cathode material substrate and a fast-ion conductor coating layer (Li) covering the surface of the substrate. 1+2 / 3a Nb 1‑4 / 3a W a O3, 0.1≤a≤0.4; the coating layer is 0.5%~2% of the bulk mass, and the coating layer thickness is 5~20nm; it is obtained by adding the positive electrode material bulk to Nb-W sol and adding lithium salt, drying to form a gel-coated precursor powder, and then calcining. This invention uses Li 1+2 / 3a Nb 1‑4 / 3a W a The O3 fast ion conductor coating strategy modifies the interface of the cathode material, and significantly improves the overall performance of the all-solid-state lithium-ion battery by constructing a stable interface layer.

Description

Technical Field

[0001] This invention relates to a manganese-based cathode material for all-solid-state lithium-ion batteries coated with a fast-ion conductor and its preparation method, belonging to the field of lithium-ion battery technology. Background Technology

[0002] Currently, lithium-ion batteries are widely used in various electronic devices, such as smartphones, personal computers, wearable devices, and automotive electronic systems. With technological advancements and increasing user demands for device performance, higher requirements are being placed on the battery life and cycle life of lithium-ion batteries. However, traditional lithium-ion batteries pose significant safety hazards due to the flammability and gas generation properties of their organic electrolytes. In contrast, all-solid-state lithium-ion batteries not only possess higher energy density but also exhibit superior safety performance, thus being considered a crucial development direction for next-generation energy storage technology. In all-solid-state batteries, the cathode material is one of the key factors restricting energy density improvement. Currently, commercially available cathode materials mainly include lithium iron phosphate, lithium cobalt oxide, and nickel-rich layered cathode materials. Lithium-rich manganese-based cathode materials, with their high energy density and cost advantages, have become widely used cathode materials in the power battery field; however, when matched with sulfide-based solid electrolytes, problems such as contact failure, interfacial side reactions, and space charge layer effects still exist, severely restricting the performance and practical application of sulfide-based all-solid-state batteries.

[0003] Currently, there are many types of materials used for coating the cathode material of all-solid-state lithium-ion batteries, but most of these materials have problems such as low ionic conductivity and easy volume strain during charging and discharging, resulting in poor battery cycle stability and rate performance. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material and its preparation method. This invention uses Li... 1+2 / 3a Nb 1-4 / 3a W a The O3 fast ion conductor coating strategy modifies the interface of the cathode material, and significantly improves the overall performance of the all-solid-state lithium-ion battery by constructing a stable interface layer.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows.

[0006] A fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material includes a lithium-rich manganese-based cathode material substrate and a fast-ion conductor coating layer (Li) on the surface of the substrate. 1+2 / 3a Nb 1-4 / 3a W aO3, where 0.1 ≤ a ≤ 0.4; the coating layer accounts for 0.5% - 2% of the main body mass, and the thickness of the coating layer is 5 - 20 nm; it is obtained by adding the main body of the cathode material to Nb-W sol and adding a lithium salt, drying to form a gel-coated precursor powder, and then calcining.

[0007] Preferably, the chemical formula of the main body of the cathode material is Li 1+x Ni y Co z Mn 0.9-y-z O2, where 0.1 < x < 0.2, 0.1 < y < 0.9, 0.1 < z < 0.9, and y + z < 0.9.

[0008] Preferably, the coating layer accounts for 0.8% - 1.2% of the main body mass, and the thickness of the coating layer is 8 - 12 nm.

[0009] A preparation method of a manganese-based cathode material for a fast ion conductor-coated all-solid-state lithium-ion battery, the method steps include:

[0010] (1) Weigh niobium salt and tungsten salt according to the elemental stoichiometric ratio, and add them to a mixed solvent of water and ethanol, and dissolve to obtain a niobium salt solution and a tungsten salt solution; (2) Slowly drip the niobium salt solution obtained in step (1) into the tungsten salt solution, and add a complexing agent under continuous stirring to induce uniform complexation of niobium and tungsten ions at the molecular scale to obtain a uniform and stable Nb-W sol; (3) Add the main body of the cathode material to the Nb-W sol, ultrasonically disperse it, and add a lithium salt with an excess of 5% - 10% of the stoichiometric ratio under continuous stirring, stir for more than 1 h, and vacuum evaporate the mixed solvent to obtain a gel-coated precursor powder; (4) Place the gel-coated precursor powder in a tubular furnace, calcine it under an oxygen atmosphere, and cool it with the furnace to obtain a cathode material for a fast ion conductor-coated all-solid-state lithium-ion battery.

[0011] Preferably, in step (1), the niobium salt is one or more of niobium ethoxide, niobium isopropoxide, niobium butoxide, niobium oxalate, niobium acetate, and ammonium oxalate niobate.

[0012] Preferably, in step (1), the tungsten salt is one or more of tungsten ethoxide, tungsten isopropoxide, ammonium tungstate, ammonium metatungstate, and ammonium paratungstate.

[0013] Preferably, in step (1), in the mixed solvent of water and ethanol, the volume ratio of water to ethanol is 1:1 - 5.

[0014] Preferably, in step (2), the complexing agent is citric acid and / or oxalic acid.

[0015] Preferably, in step (2), the dropping rate is 0.1 - 10 mL min-1 .

[0016] Preferably, in step (3), the ultrasonic dispersion time is 30~180 min.

[0017] Preferably, in step (3), the stirring speed is 10~100 rpm and the stirring time is 1~6 h.

[0018] Preferably, in step (3), the lithium salt is one or more of lithium hydroxide, lithium carbonate, lithium oxalate and lithium acetate.

[0019] Preferably, in step (3), the vacuum evaporation temperature is 60~120℃.

[0020] Preferably, in step (4), the sample is first calcined at 400~500℃ for 1~3h, and then calcined at 600~800℃ for 2~6h.

[0021] Preferably, in step (4), the heating rate during calcination is 2~5℃ min. -1 .

[0022] A solid-state battery, wherein the positive electrode is a manganese-based positive electrode material for a solid-state lithium-ion battery coated with a fast ion conductor as described in this invention, and the electrolyte is a sulfide-based solid-state electrolyte.

[0023] Beneficial effects This invention provides a manganese-based cathode material for all-solid-state lithium-ion batteries coated with a fast-ion conductor, wherein the coating layer is Li₂, which has fast-ion conductivity and zero volumetric strain characteristics. 1+2 / 3a Nb 1-4 / 3a W a The O3 phase, with its excellent room-temperature ionic conductivity, can significantly reduce the conductivity of lithium ions in the cathode / sulfide solid electrolyte (such as Li₂). 5.5 PS 4.5 Cl 1.5 The high energy barrier and interfacial impedance at the interface enable lithium-ion transport rates to be increased by more than 30% compared to uncoated or traditionally coated systems. Even under 1C high-rate charge-discharge conditions, the cathode material can still stably release a high discharge specific capacity of over 111.3 mAh / g, fundamentally breaking through the technical bottleneck of "poor high-rate performance" in traditional all-solid-state batteries. Meanwhile, Li... 1+2 / 3a Nb 1-4 / 3a W a O3 exhibits near-zero volume strain performance during charge-discharge cycling: Addressing the typical 5%–8% volume expansion issue that easily occurs in lithium-rich manganese-based substrate cathode materials during cycling, this phase, with its extremely high structural stability, can effectively buffer the interfacial stress caused by volume changes, fundamentally avoiding risks such as coating cracking, delamination, and interfacial contact failure; Furthermore, Li…1+2 / 3a Nb 1-4 / 3a W a O3 can also physically isolate the nickel-rich cathode from direct contact with the sulfide solid electrolyte, significantly inhibiting Ni 3+ / Ni 2+ Restore, S 2- Oxidation, Li + / Ni 2+ Interfacial side reactions such as mixing are reduced by more than 90%, thereby effectively suppressing the irreversible collapse of the layered crystal structure of the cathode material. Ultimately, after 50 cycles at 0.2C, the all-solid-state battery still retains more than 95% of its capacity, significantly extending the battery's cycle life.

[0024] Compared with traditional Ti 4+ (3d) 0 Compared to W, 6+ (5d) 0 Ti exhibits significant advantages in controlling electronic structure. 4+ Although it is also d 0 The configuration is [WO6], but its 3d orbitals are relatively localized, and the conduction band width is limited. Due to its high electronegativity and broad 5d orbitals, W can significantly reduce the bottom conduction band energy level of the material after forming the [WO6] octahedron, effectively weakening the Li... + The electrostatic attraction between Li and the crystal lattice framework + The energy barrier that needs to be overcome for insertion / extraction decreases accordingly. (This is in contrast to Nb.) 5+ The synergistic effect allows for the formation of stable three-dimensional ion migration channels, which greatly promotes the migration dynamics of lithium ions. In Li 1+2 / 3a Nb 1-4 / 3a W a In the O3 crystal structure, W 6+ and Nb 5+ Together, they form a robust [B-O6] octahedral framework. The extremely strong WO covalent bonds give the crystal framework extremely high rigidity, making it less prone to lattice distortion during lithium-ion insertion / extraction. This invention utilizes Li... 1+2 / 3x Nb 1-4 / 3x W x The excellent fast ion conductivity of the O3 phase can significantly promote the rapid transport of lithium ions at the interface between the cathode and the electrolyte. At the same time, its lack of volume strain can effectively reduce the interfacial stress during the charging and discharging process. This effectively suppresses the interfacial side reactions and space charge layer effect between the lithium-rich manganese-based substrate cathode material and the sulfide solid electrolyte, inhibits the irreversible collapse of the layered structure of the cathode material matrix, and enables the cathode material to maintain structural stability during cycling. This significantly improves the electrochemical stability, cycle stability and rate performance of the cathode material. Attached Figure Description

[0025] Figure 1 This is a SEM image of the coated cathode material in Example 3 of the present invention.

[0026] Figure 2 This is the XRD pattern of the coated cathode material in Embodiment 3 of the present invention.

[0027] Figure 3 This is an interfacial impedance diagram between Embodiment 3 of the present invention and the uncoated positive electrode material.

[0028] Figure 4 This is a full-cell cycle diagram of Embodiment 3 of the present invention and the uncoated cathode material.

[0029] Figure 5 The above are charge-discharge curves of Embodiment 3 of the present invention at different rates. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments.

[0031] Example 1 The fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material and its preparation method described in this embodiment are specifically operated as follows: Weigh 0.0596 g of niobium oxalate and dissolve it in 10 mL of a water-ethanol mixture (volume ratio 1:1) and stir thoroughly. Weigh 0.0032 g of ammonium metatungstate and dissolve it in 10 mL of a water-ethanol mixture (volume ratio 1:1) and stir thoroughly. Slowly add the solution dropwise (5 mL / min). -1 Add 2g Li to the above niobium salt solution, then add 0.0476g citric acid to form a stable Nb-W sol. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was dispersed in the above sol and ultrasonically dispersed for 30 min. 0.0038 g of lithium hydroxide was added and the mixture was stirred vigorously at 600 rpm for 3 h to obtain a Li-Nb-WO coated precursor. After vacuum drying at 80 °C, the precursor was pre-sintered at 480 °C for 2 h and calcined at 600 °C for 4 h in an oxygen atmosphere in a tube furnace. The heating rate was set to 5 °C / min. After calcination in the tube furnace, a fully solid-state lithium-ion battery cathode material with a functional outer coating was obtained.

[0032] Example 2 The fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material and its preparation method described in this embodiment are specifically operated as follows: Weigh 0.0494 g of niobium oxalate and dissolve it in 10 mL of a water-ethanol mixture (volume ratio 1:1) and stir thoroughly. Weigh 0.0061 g of ammonium metatungstate and dissolve it in 10 mL of a water-ethanol mixture (volume ratio 1:1) and stir thoroughly. Then slowly add the solution dropwise (5 mL / min). -1 Add 2g Li to the above niobium salt solution, then add 0.0448g citric acid to form a stable Nb-W sol. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was dispersed in the above sol and ultrasonically dispersed. 0.0034 g of lithium hydroxide was added and the mixture was stirred vigorously at 600 rpm for 3 h to obtain a Li-Nb-WO coated precursor. After vacuum drying at 80 °C, the precursor was pre-sintered at 480 °C for 2 h and calcined at 600 °C for 4 h in an oxygen atmosphere in a tube furnace. The heating rate was set to 5 °C / min. After calcination in the tube furnace, a fully solid-state lithium-ion battery cathode material with a functional outer coating was obtained.

[0033] Example 3 The fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material and its preparation method described in this embodiment are specifically operated as follows: Weigh 0.00386 g of niobium oxalate and dissolve it in 10 mL of a water-ethanol mixture (volume ratio 1:1) and stir thoroughly. Weigh 0.0088 g of ammonium metatungstate and dissolve it in 10 mL of a water-ethanol mixture (volume ratio 1:1) and stir thoroughly. Then slowly add the solution dropwise (5 mL / min). -1 Add 2g Li to the above niobium salt solution, then add 0.0414g citric acid to form a stable Nb-W sol. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was dispersed in the above sol and ultrasonically dispersed. 0.0033 g of lithium hydroxide was added and the mixture was stirred vigorously at 600 rpm for 3 h to obtain a Li-Nb-WO coated precursor. After vacuum drying at 80 °C, the precursor was pre-sintered at 480 °C for 2 h and calcined at 600 °C for 4 h in an oxygen atmosphere in a tube furnace. The heating rate was set to 5 °C / min. After calcination in the tube furnace, a fully solid-state lithium-ion battery cathode material with a functional outer coating was obtained.

[0034] Example 4 The fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material and its preparation method described in this embodiment are specifically operated as follows: Weigh 0.0306 g of niobium oxalate and dissolve it in 10 mL of a water-ethanol mixture (volume ratio 1:1) and stir thoroughly. Weigh 0.0112 g of ammonium metatungstate and dissolve it in 10 mL of a water-ethanol mixture (volume ratio 1:1) and stir thoroughly. Slowly add (5 mL / min) -1 Add 2g Li to the above niobium salt solution, then add 0.0394g citric acid to form a stable Nb-W sol. 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 was dispersed in the above sol and ultrasonically dispersed. 0.0032g of lithium hydroxide was added and the mixture was stirred vigorously at 600rpm for 3h to obtain a Li-Nb-WO coated precursor. After vacuum drying at 80℃, the precursor was pre-sintered at 480℃ for 2h and calcined at 600℃ for 4h in an oxygen atmosphere in a tube furnace. The heating rate was set to 5℃ / min. After calcination in the tube furnace, a fully solid-state lithium-ion battery cathode material with a functional outer coating was obtained.

[0035] Comparative Example The comparative example is uncoated Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 cathode material.

[0036] The all-solid-state battery described in this comparative example is: Li-In alloy | Li 5.5 PS 4.5 Cl 1.5 Sulfide-based all-solid-state electrolyte | Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O2 positive electrode.

[0037] All-solid-state battery assembly: Weigh the above-mentioned cathode material and Li according to a mass ratio of 70:28:2. 5.5 PS 4.5 Cl 1.5 The composite cathode was prepared by grinding VGCF (vapor-grown carbon fiber) for 1 hour, and the anode was made of lithium indium alloy.

[0038] Inside an argon-filled glove box, all-solid-state lithium-ion batteries were assembled using PEEK (polyetheretherketone) molds. First, Li-ion batteries were pressed at 250 MPa. 5.5 PS 4.5 Cl 1.5 Solid electrolyte, forming dense Li 5.5 PS 4.5 Cl 1.5Solid electrolyte layer; then the composite positive electrode is evenly placed on one side of the solid electrolyte and a pressure of 500 MPa is applied; finally, the lithium indium alloy is placed on the other side of the solid electrolyte and the mold is tightened at 100 MPa.

[0039] All-solid-state battery testing: Test temperature 30℃, voltage range 2.8 - 4.3 V vs. Li + / Li.

[0040] Test results are as follows Figure 1-4 As shown in Table 1.

[0041] Table 1 shows the electrochemical performance of the all-solid-state lithium-ion batteries in Examples 1-4 and the comparative examples.

[0042] The Li prepared in Example 3 was tested and found to be... 1.2 Nb 0.6 W 0.3 The O3 fast ion conductor-coated cathode material exhibits a high discharge specific capacity (160 mAh g). -1 The capacity retention rate after 50 cycles at 0.2C is 95%, demonstrating the material's excellent cycling stability; it still retains 111.3 mAh g⁻¹ at 1C. -1 Its high discharge specific capacity and good high-rate discharge capability prove that its crystal structure is conducive to the rapid migration of lithium ions.

[0043] In summary, the invention includes, but is not limited to, the above embodiments. Any equivalent substitutions or partial improvements made under the spirit and principles of this invention shall be considered to be within the protection scope of this invention.

Claims

1. A manganese-based cathode material for all-solid-state lithium-ion batteries coated with a fast-ion conductor, characterized in that: Includes a lithium-rich manganese-based cathode material substrate and a fast ion conductor coating layer (Li) covering the surface of the substrate. 1+2 / 3a Nb 1-4 / 3a W a O3, 0.1≤a≤0.4; the coating layer is 0.5%~2% of the main body mass, and the coating layer thickness is 5~20nm; it is obtained by adding the positive electrode material main body to Nb-W sol and adding lithium salt, drying to form a gel-coated precursor powder, and then calcining.

2. The all-solid-state lithium-ion battery manganese-based cathode material coated with a fast-ion conductor as described in claim 1, characterized in that: The chemical formula of the main body of the positive electrode material is Li 1+x Ni y Co z Mn 0.9-y-z O2, where 0.1 < x < 0.2, 0.1 < y < 0.9, 0.1 < z < 0.9, and y + z < 0.

9.

3. The all-solid-state lithium-ion battery manganese-based cathode material coated with a fast-ion conductor as described in claim 1, characterized in that: The coating layer accounts for 0.8% to 1.2% of the main body mass, and the coating layer thickness is 8 to 12 nm.

4. A method for preparing a manganese-based cathode material for an all-solid-state lithium-ion battery coated with a fast-ion conductor as described in any one of claims 1 to 3, characterized in that: The method steps include: (1) Weigh niobium salt and tungsten salt according to the stoichiometric ratio of the elements, add them to a mixed solvent of water and ethanol respectively, dissolve them, and obtain niobium salt solution and tungsten salt solution; (2) The niobium salt solution obtained in step (1) is added dropwise to the tungsten salt solution, and a complexing agent is added while stirring continuously to obtain a uniform and stable Nb-W sol; (3) Add the cathode material to the Nb-W sol, disperse it by ultrasonication, and add an excess of 5%~10% stoichiometric lithium salt under continuous stirring. Stir for more than 1 hour, and then evaporate the mixed solvent under vacuum to obtain the gel-coated precursor powder. (4) The precursor powder coated with gel was placed in a tube furnace and calcined in an oxygen atmosphere. The furnace was then cooled to obtain a solid-state lithium-ion battery cathode material coated with a fast ion conductor.

5. The method for preparing a fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material as described in claim 4, characterized in that: In step (1), the niobium salt is one or more of niobium ethoxide, niobium isopropoxide, niobium n-butoxide, niobium oxalate, niobium acetate, and ammonium niobium oxalate; And / or, the tungsten salt is one or more of tungsten ethoxide, tungsten isopropoxide, ammonium tungstate, ammonium metatungstate, and ammonium paratungstate; And / or, in the water and ethanol mixed solvent, the volume ratio of water to ethanol is 1:1 to 5.

6. The method for preparing a fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material as described in claim 4, characterized in that: In step (2), the complexing agent is citric acid and / or oxalic acid; And / or, the dropping rate is 0.1~10 mL / min. -1 .

7. The method for preparing a fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material as described in claim 4, characterized in that: In step (3), the ultrasonic dispersion time is 30~180 min; And / or, the stirring speed is 10~100 rpm, and the stirring time is 1~6 hours; And / or, the vacuum evaporation temperature is 60~120℃.

8. The method for preparing a fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material as described in claim 4, characterized in that: In step (3), the lithium salt is one or more of lithium hydroxide, lithium carbonate, lithium oxalate and lithium acetate.

9. The method for preparing a fast-ion conductor-coated all-solid-state lithium-ion battery manganese-based cathode material as described in claim 3, characterized in that: In step (4), the sample is first calcined at 400~500℃ for 1~3h, and then calcined at 600~800℃ for 2~6h; And / or, the heating rate during calcination is 2~5℃ min. -1 .

10. An all-solid-state battery, characterized in that: The positive electrode of the battery is a manganese-based positive electrode material for a solid-state lithium-ion battery coated with a fast ion conductor as described in any one of claims 1 to 3, and the electrolyte is a sulfide-based solid-state electrolyte.

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