PVD (Physical Vapor Deposition) modified positive electrode material as well as preparation method and application thereof

Abstract

The invention provides a PVD (Physical Vapor Deposition) modified positive electrode material as well as a preparation method and application thereof, and the preparation method comprises the following steps: (1) carrying out first PVD modification treatment on a positive electrode precursor by using a first lithium-containing compound target material to obtain a PVD modified positive electrode precursor; (2) mixing the PVD modified positive electrode precursor with a lithium source, and sintering to obtain a half-step positive electrode material; and (3) carrying out second PVD modification treatment on the half-step positive electrode material by using a second lithium-containing compound target material to obtain the PVD modified positive electrode material. The amorphous film is deposited on the surfaces of the positive electrode material particles through twice coating, so that the interface impedance in the solid-state battery can be remarkably reduced, and the charge-discharge capacity of the battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid-state batteries, and relates to a PVD-modified cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] Lithium secondary batteries are used as power sources in electronic devices such as mobile phones and personal computers due to their advantages such as high working voltage, high energy density, and long cycle time. In recent years, lithium secondary batteries have been applied to large-scale power storage systems such as electric vehicles and stationary batteries. Lithium secondary batteries require higher energy density and longer cycle performance. All-solid-state lithium secondary batteries using inorganic solid electrolytes are expected to be used as next-generation batteries, with higher safety, reliability, and energy density.

[0003] In order to improve the energy density applied to large devices, in-depth research has been carried out on bulk all-solid-state batteries with composite electrodes of powder mixtures of electrode active materials and solid electrolytes. Exploring solid electrolytes with high ionic conductivity is of great significance for improving the electrochemical performance of all-solid-state batteries.

[0004] CN118588939A discloses a composite cathode material, a cathode sheet containing the same, and a solid-state lithium ion battery. The composite cathode material includes cathode material particles and solid electrolyte particles; the cathode material particles include first cathode material particles and second cathode material particles; the first cathode material particles include a first cathode material core and a first coating layer; the second cathode material particles include a second cathode material core and a second coating layer; wherein, the first coating layer includes a MOF material; the second coating layer includes a metal oxide, and the solid electrolyte particles are sulfide solid electrolytes.

[0005] CN117638056A discloses a sulfide layered cathode material, a preparation method thereof, and an application in a lithium ion solid-state battery, and prepares a new sulfide layered cathode material Li 1.04 Ti 0.6 Fe 0.27 S 2 , which is a sulfide layered material.

[0006] Although the lithium-ion conductivity of sulfide solid electrolytes has reached or even exceeded that of liquid electrolytes, their cycling stability, rate performance, and battery capacity in all-solid-state sulfide lithium batteries are still lower than those of liquid lithium batteries. Among them, the interfacial problem between the NCM ternary cathode material and the sulfide solid electrolyte is the key problem restricting the performance of all-solid-state sulfide lithium batteries. Different from liquid lithium batteries, the contact mode between the NCM cathode material and the sulfide solid electrolyte in all-solid-state lithium batteries is solid-solid contact. The solid electrolyte cannot flow or penetrate, making the gaps and voids in all-solid-state lithium batteries unable to be effectively filled by ionic conduction media, resulting in poor physical contact between the cathode and the sulfide solid electrolyte. In addition, there are also a series of problems caused by chemical and electrochemical side reactions between the NCM ternary cathode and the sulfide electrolyte. In-depth study of the interfacial problem between the NCM cathode material and the sulfide solid electrolyte and finding a suitable solution are the keys to improving the performance of all-solid-state lithium batteries. Summary of the Invention

[0007] The purpose of the present invention is to provide a PVD-modified cathode material, its preparation method and application. Through two coatings, an amorphous thin film is deposited on the surface of the cathode material particles, which can significantly reduce the interfacial impedance inside the solid-state battery and improve the charge and discharge capacity of the battery.

[0008] To achieve the purpose of this invention, the following technical solutions are adopted:

[0009] In the first aspect, the present invention provides a preparation method of a PVD-modified cathode material, and the preparation method includes the following steps:

[0010] (1) Perform the first PVD modification treatment on the cathode precursor using the first lithium-containing compound target to obtain a PVD-modified cathode precursor;

[0011] (2) Mix the PVD-modified cathode precursor with a lithium source and perform a sintering treatment to obtain a semi-step cathode material;

[0012] (3) Perform the second PVD modification treatment on the semi-step cathode material using the second lithium-containing compound target to obtain a PVD-modified cathode material.

[0013] The present invention uses PVD (physical vapor deposition) to irradiate a laser on a lithium-containing compound target, so that the lithium-containing compound target is heated, melted, vaporized and turned into a plasma in a very short time. The generated plasma coats the surface of the cathode precursor and modifies the cathode precursor to obtain a PVD-modified cathode precursor. Mixing the PVD-modified cathode precursor with a lithium source and sintering is beneficial to the insertion of the lithium source. Then, perform the second PVD modification treatment on the semi-step cathode material, which is beneficial to reducing the interfacial impedance of the cathode material.

[0014] Preferably, the first lithium-containing compound target in step (1) and the second lithium-containing compound target in step (2) independently include any one or a combination of at least two of lithium niobate, lithium titanate, lithium silicate, lithium borate, or lithium phosphate. Typical but non-limiting combinations include the combination of lithium niobate and lithium phosphate, the combination of lithium niobate and lithium silicate, or the combination of lithium niobate and lithium titanate, etc.

[0015] Preferably, the cathode precursor in step (1) includes a ternary nickel-cobalt-manganese precursor.

[0016] Preferably, the first lithium-containing compound target and the second lithium-containing compound target in step (1) and step (2) are independently prepared by the following method:

[0017] The lithium-containing compound powder is pressed into a wafer under a pressure of 25 MPa to 35 MPa, such as 25 MPa, 28 MPa, 30 MPa, 32 MPa, or 35 MPa, etc. Not limited to the listed values, other unlisted values within this range are also applicable. After that, the wafer is sintered at 300 °C to 600 °C, such as 300 °C, 350 °C, 400 °C, 500 °C, or 600 °C, etc. Not limited to the listed values, other unlisted values within this range are also applicable, for 3 h to 6 h, such as 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, or 6 h, etc. Not limited to the listed values, other unlisted values within this range are also applicable, to obtain the lithium-containing compound target.

[0018] Preferably, during the first PVD modification treatment in step (1), the energy density at the first lithium-containing compound target is 1.5 J / cm 2 ~2.5 J / cm 2 , such as 1.5 J / cm 2 , 1.6 J / cm 2 , 1.7 J / cm 2 , 1.8 J / cm 2 , 1.9 J / cm 2 , 2.2 J / cm 2 or 2.5 J / cm 2 etc. Not limited to the listed values, other unlisted values within this range are also applicable.

[0019] Preferably, the time of the first PVD modification treatment in step (1) is 1 min to 10 min, such as 1 min, 2 min, 5 min, 8 min, or 10 min, etc. Not limited to the listed values, other unlisted values within this range are also applicable.

[0020] Preferably, the lithium source in step (2) includes lithium hydroxide and / or lithium carbonate.

[0021] Preferably, the molar ratio of the metal element in the PVD-modified cathode precursor to the lithium element in the lithium source is (3-10):1, such as 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0022] Preferably, the temperature of the sintering treatment in step (2) is 800°C - 1200°C, such as 800°C, 900°C, 1000°C, 1100°C or 1200°C, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0023] Preferably, the time of the sintering treatment in step (2) is 6h - 12h, such as 6h, 7h, 8h, 9h, 10h, 11h or 12h, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0024] Preferably, during the second PVD modification treatment in step (3), the energy density at the second lithium-containing compound target is 1.5 J / cm 2 ~2.5 J / cm 2 For example, 1.5 J / cm 2 、1.6 J / cm 2 、1.7 J / cm 2 、2 J / cm 2 、2.2 J / cm 2 or 2.5 J / cm 2 etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0025] Preferably, the time of the second PVD modification treatment in step (3) is 1 min - 10 min, such as 1 min, 2 min, 5 min, 8 min or 10 min, etc. It is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0026] In a second aspect, the present invention provides a PVD-modified cathode material, and the PVD-modified cathode material is prepared by the preparation method as described in the first aspect.

[0027] In a third aspect, the present invention provides a positive electrode sheet, and the positive electrode sheet contains the PVD-modified cathode material as described in the second aspect.

[0028] In a fourth aspect, the present invention provides a solid-state battery, and the solid-state battery contains the positive electrode sheet as described in the third aspect.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) Through two coatings, an amorphous thin film is deposited on the surface of the cathode material particles, which can significantly reduce the interfacial impedance inside the solid-state battery and improve the charge and discharge capacity of the battery.

[0031] (2) The 0.1C discharge capacity of the battery made of the PVD-modified cathode material of the present invention can reach more than 196.3 mAh / g, and the 1C discharge capacity can reach more than 174.5 mAh / g. Specific Embodiments

[0032] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0033] Embodiment 1

[0034] This embodiment provides a PVD-modified cathode material, and the preparation method of the PVD-modified cathode material is as follows:

[0035] (1) Take dry lithium niobate (LiNbO 3 ) target powder, press it into a 20-mm-diameter wafer under a pressure of 30 MPa by a tablet press, place it in a tube furnace, heat the furnace to 600 °C, and sinter for 6 h to obtain the required LiNbO 3 target. Place the LiNbO 3 target on the sample holder in the PVD equipment, and place Ni 0.9 Co 0.6 Mn 0.4 in the sample stage with a vibrator. The energy density at the LiNbO 3 target is 2 J / cm 2 , and the duration on the LiNbO 3 sample is 5 min. The target plasma vaporized by the laser adheres to the surface of the cathode precursor to obtain a PVD-modified cathode precursor;

[0036] (2) Mix the PVD-modified cathode precursor with lithium hydroxide in a ratio of 5:1, and sinter at 1000 °C for 10 h to obtain a semi-step cathode material;

[0037] (3) Place the semi-step cathode material in the sample stage with a vibrator, and use LiNbO 3 target. The energy density at the LiNbO 3 target is 2 J / cm 2 , and at LiNbO 3On the target material sample, for a duration of 5 minutes, the target material plasma vaporized by laser adheres to the surface of the semi-step cathode material to obtain the PVD-modified cathode material.

[0038] Example 2

[0039] This example provides a PVD-modified cathode material, and the preparation method of the PVD-modified cathode material is as follows:

[0040] (1) Take dry lithium titanate (Li 4 Ti 5 O 12 ) target material powder, press it into a 20-mm-diameter disc under a pressure of 35 MPa by a tablet press, place it in a tube furnace, heat the furnace to 500 °C, and sinter for 4 h to obtain the required Li 4 Ti 5 O 12 target material. Place the Li 4 Ti 5 O 12 target material on the sample holder in the PVD equipment, and place the Ni 0.9 Co 0.6 Mn 0.4 precursor material on the sample stage with a vibrator. The energy density at the Li 4 Ti 5 O 12 target material is 2.2 J / cm 2 . For a duration of 1 minute on the Li 4 Ti 5 O 12 target material sample, the target material plasma vaporized by laser adheres to the surface of the cathode precursor to obtain the PVD-modified cathode precursor;

[0041] (2) Mix the PVD-modified cathode precursor and lithium hydroxide in a ratio of 3:1, and sinter at 800 °C for 12 h to obtain the semi-step cathode material;

[0042] (3) Place the semi-step cathode material on the sample stage with a vibrator, use the Li 4 Ti 5 O 12 target material, and the energy density at the LiNbO 3 target material is 2.2 J / cm 2 . For a duration of 3 minutes on the target material Li 4 Ti 5 O 12 sample, the target material plasma vaporized by laser adheres to the surface of the semi-step cathode material to obtain the PVD-modified cathode material.

[0043] Example 3

[0044] This embodiment provides a PVD-modified cathode material, and the preparation method of the PVD-modified cathode material is as follows:

[0045] (1) Take dry lithium silicate (Li 4 SiO 4 ) target powder, press it into a 20-mm-diameter wafer under a pressure of 25 MPa by a tablet press, place it in a tube furnace, heat the furnace to 300 °C, and sinter for 6 h to obtain the required Li 4 SiO 4 target. Place the Li 4 SiO 4 target on the sample holder in the PVD equipment, and place the Ni 0.9 Co 0.6 Mn 0.4 precursor material on the sample stage with a vibrator. The energy density at the Li 4 SiO 4 target is 1.5 J / cm 2 , and the duration on the Li 4 SiO 4 target sample is 10 min. The target plasma vaporized by laser adheres to the surface of the cathode precursor to obtain a PVD-modified cathode precursor;

[0046] (2) Mix the PVD-modified cathode precursor and lithium hydroxide in a ratio of 10:1, and sinter at 1200 °C for 10 h to obtain a semi-step cathode material;

[0047] (3) Place the semi-step cathode material on the sample stage with a vibrator, use the Li 4 Ti 5 O 12 target, and the energy density at the Li 4 SiO 4 target is 2 J / cm 2 . The duration on the target Li 4 Ti 5 O 12 sample is 5 min. The target plasma vaporized by laser adheres to the surface of the semi-step cathode material to obtain the PVD-modified cathode material.

[0048] Example 4

[0049] The difference between this example and Example 1 is only that the laser energy density in step (1) is set to 1.5 J / cm 2 , and other conditions and parameters are exactly the same as those in Example 1.

[0050] Example 5

[0051] The difference between this embodiment and Embodiment 1 is only that the laser energy in step (1) is set to 2.5 J / cm 2 , and other conditions and parameters are exactly the same as those in Embodiment 1.

[0052] Embodiment 6

[0053] The difference between this embodiment and Embodiment 1 is only that the laser energy in step (2) is set to 1.5 J / cm 2 , and other conditions and parameters are exactly the same as those in Embodiment 1.

[0054] Embodiment 7

[0055] The difference between this embodiment and Embodiment 1 is only that the laser energy in step (2) is set to 2.5 J / cm 2 , and other conditions and parameters are exactly the same as those in Embodiment 1.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Embodiment 1 is only that PVD modification is not performed in step (1), and other conditions and parameters are exactly the same as those in Embodiment 1.

[0058] Comparative Example 2

[0059] The difference between this comparative example and Embodiment 1 is only that PVD modification is not performed in step (3), and other conditions and parameters are exactly the same as those in Embodiment 1.

[0060] Comparative Example 3

[0061] The difference between this comparative example and Embodiment 1 is only that neither step (1) nor step (3) uses coating modification by mixing and grinding with LiNbO 3 , and other conditions and parameters are exactly the same as those in Embodiment 1.

[0062] Performance Test:

[0063] The results of this test are all the test results of discharging the battery. The specific steps are as follows: Mix the PVD-treated cathode material and Li 2 S sulfide electrolyte in a mass ratio of 2:3; then, coat the slurry on aluminum foil with a coater and dry it in a vacuum drying oven at 80 °C for 8 h. Finally, punch the aluminum foil into a circle with a diameter of 1.13 cm 2 to obtain the cathode sheet. Use the obtained electrode sheet as the cathode and a lithium metal sheet as the counter electrode to assemble a CR2032 button battery in an argon glove box. Use a battery test system (BlueTEC CT2001A, Wuhan, China) to perform performance tests at a rate of 0.1C and 1C under the condition of 2.5V - 4.55V. The test results are shown in Table 1:

[0064] Table 1

[0065]

[0066]

[0067] As can be seen from Table 1, it can be obtained from Examples 1-7 that the 0.1C discharge capacity of the battery made of the PVD-modified cathode material of the present invention can reach more than 196.3 mAh / g, and the 1C discharge capacity can reach more than 174.5 mAh / g.

[0068] From the comparison between Example 1 and Examples 4-5, it can be obtained that during the preparation process of the PVD-modified cathode material of the present invention, the laser energy of the PVD modification in step (1) will affect its performance. Controlling the laser energy density of the PVD modification in step (1) at 1.8 J / cm 2 ~2.2 J / cm 2 , the performance of the PVD-modified cathode material prepared is better. If the laser energy density of the PVD modification in step (1) is too low, the vapor deposition layer is relatively thin. If the laser energy of the PVD modification in step (1) is too high, the vaporization speed is too fast, and the surface of the cathode material is not fully coated.

[0069] From the comparison between Example 1 and Examples 6-7, it can be obtained that during the preparation process of the PVD-modified cathode material of the present invention, the laser energy of the PVD modification in step (3) will affect its performance. Controlling the laser energy density of the PVD modification in step (3) at 1.8 J / cm 2 ~2.2 J / cm 2 , the performance of the PVD-modified cathode material prepared is better. If the laser energy of the PVD modification in step (3) is too low, the vapor deposition layer is relatively thin. If the laser energy of the PVD modification in step (3) is too high, the vaporization speed is too fast, and the surface of the cathode material is not fully coated.

[0070] From the comparison between Example 1 and Comparative Examples 1-2, it can be obtained that the present invention uses PVD (physical vapor deposition) to irradiate a lithium-containing compound target with a laser, so that the lithium-containing compound target is heated, melted, vaporized and turned into a plasma in a very short time. The generated plasma is coated on the surface of the cathode precursor to modify the cathode precursor, and a PVD-modified cathode precursor is obtained. Mixing and sintering the PVD-modified cathode precursor with a lithium source is beneficial to the insertion of the lithium source. Then, a second PVD modification treatment is performed on the semi-step cathode material, which is beneficial to reducing the interfacial impedance of the cathode material. The performance of the cathode material after two PVD modifications is significantly improved.

[0071] From the comparison between Example 1 and Comparative Example 3, it can be obtained that the present invention uses PVD to deposit LiNbO on the surface of the cathode material 3, the obtained coating layer has good uniformity, high density and stable structure, which is beneficial to the insertion of lithium while having low interfacial impedance, and the performance of the material is significantly improved.

[0072] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing a PVD-modified positive electrode material, characterized in that: The preparation method comprises the following steps: (1) performing a first PVD modification treatment on a positive electrode precursor using a first lithium-containing compound target to obtain a PVD-modified positive electrode precursor; (2) mixing the PVD-modified cathode precursor with a lithium source and sintering the mixture to obtain a half-step cathode material; (3) Using a second lithium-containing compound target material, the half-step positive electrode material is subjected to a second PVD modification treatment to obtain a PVD-modified positive electrode material.

2. The preparation method according to claim 1, characterized in that The first lithium-containing compound target material in step (1) and the second lithium-containing compound target material in step (3) independently include any one or a combination of at least two of lithium niobate, lithium titanate, lithium silicate, lithium borate or lithium phosphate; Preferably, the positive electrode precursor in step (1) comprises a ternary nickel-cobalt-manganese precursor.

3. The preparation method according to claim 1 or 2, characterized in that: The first lithium-containing compound target and the second lithium-containing compound target described in step (1) and step (2) are independently prepared by the following method: The lithium-containing compound powder is pressed into a disc at a pressure of 25 MPa to 35 MPa, and then the disc is sintered at 300° C. to 600° C. for 3 h to 6 h to obtain the lithium-containing compound target.

4. The preparation method according to any one of claims 1 to 3, characterized in that: The laser energy of the first PVD modification treatment in step (1) is 1.5 J / cm 2 ~2.5J / cm 2 ; Preferably, the time of the first PVD modification treatment in step (1) is 1 min to 10 min.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The lithium source in step (2) includes lithium hydroxide and / or lithium carbonate; Preferably, the molar ratio of the metal element in the PVD-modified positive electrode precursor to the lithium element in the lithium source in step (2) is (3-10):

1.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The sintering temperature in step (2) is 800° C. to 1200° C. Preferably, the sintering time in step (2) is 6 h to 12 h.

7. The preparation method according to any one of claims 1 to 6, characterized in that: Step (3) The laser energy of the second PVD modification treatment is 1.5 J / cm 2 ~2J / cm 2 ; Preferably, the time of the second PVD modification treatment in step (3) is 1 min to 10 min.

8. A PVD-modified positive electrode material, characterized in that: The PVD-modified positive electrode material is prepared by the preparation method according to any one of claims 1 to 7.

9. A positive electrode sheet, characterized in that: The positive electrode sheet comprises the PVD-modified positive electrode material as claimed in claim 8.

10. A solid-state battery, characterized in that: The solid-state battery comprises the positive electrode sheet as claimed in claim 9.

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