A pvd modified positive electrode material and a preparation method and application thereof

Abstract

The application provides a PVD modified positive electrode material and a preparation method and application thereof, and the preparation method comprises the following steps: (1) using a first lithium-containing compound target to perform first PVD modification treatment on a positive electrode precursor to obtain a PVD modified positive electrode precursor; (2) mixing the PVD modified positive electrode precursor with a lithium source, and performing sintering treatment to obtain a semi-step positive electrode material; and (3) using a second lithium-containing compound target to perform second PVD modification treatment on the semi-step positive electrode material to obtain the PVD modified positive electrode material. Through twice coating, an amorphous thin film is deposited on the surface of the positive electrode material particles, the interface impedance in the solid-state battery can be significantly reduced, and the charge and discharge capacity of the battery is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid-state batteries, and relates to a PVD modified positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Lithium secondary batteries are used as power sources in electronic devices such as mobile phones and personal computers due to their high operating voltage, high energy density, long cycle time and other advantages. 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 need higher energy density and longer cycle performance. All-solid-state lithium secondary batteries using inorganic solid electrolytes are expected to be used as the next generation of batteries, with higher safety, reliability and energy density.

[0003] In order to improve the energy density applied to large-scale devices, block-shaped all-solid-state batteries using a powder mixture of electrode active materials and solid electrolytes have been intensively studied. Exploring solid electrolytes with high ionic conductivity is of great significance to improve the electrochemical performance of all-solid-state batteries.

[0004] CN118588939A discloses a composite positive electrode material, a positive electrode sheet containing the same, and a solid-state lithium ion battery. The composite positive electrode material includes positive electrode material particles and solid electrolyte particles; the positive electrode material particles include first positive electrode material particles and second positive electrode material particles; the first positive electrode material particles include a first positive electrode material inner core and a first coating layer; the second positive electrode material particles include a second positive electrode material inner 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 positive electrode material, a preparation method and application in lithium ion solid-state batteries, which prepares a new sulfide layered positive electrode material Li 1.04 Ti 0.6 Fe 0.27 S2, which is a sulfide layered material.

[0006] Although the sulfide solid electrolyte has reached or even exceeded the level of the liquid electrolyte in lithium ion conductivity, its cycle stability, rate performance and battery capacity in the full solid sulfide lithium battery are still lower than those of the liquid lithium battery. The interface problem between the NCM ternary positive electrode material and the sulfide solid electrolyte is the key problem that limits the performance of the full solid sulfide lithium battery. Unlike the liquid lithium battery, the contact mode of the NCM positive electrode material and the sulfide solid electrolyte in the full solid lithium battery is solid-solid contact, and the solid-state electrolyte cannot flow or penetrate, so that the gaps and voids in the full solid lithium battery cannot be effectively filled by the ion conductive medium, resulting in poor physical contact between the positive electrode and the sulfide solid electrolyte. In addition, there are a series of problems caused by chemical and electrochemical side reactions between the NCM ternary positive electrode and the sulfide electrolyte. Therefore, it is necessary to further study the interface problem between the NCM positive electrode material and the sulfide solid electrolyte and find a suitable solution to improve the performance of the full solid lithium battery. SUMMARY

[0007] The purpose of the present application is to provide a PVD modified positive electrode material and its preparation method and application. The present application deposits an amorphous thin film on the surface of the positive electrode material particles through twice coating, which can significantly reduce the interface impedance in the solid-state battery and improve the charge and discharge capacity of the battery.

[0008] To achieve the purpose of the present application, the following technical solutions are adopted:

[0009] In a first aspect, the present application provides a preparation method of a PVD modified positive electrode material, which comprises the following steps:

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

[0011] (2) mixing the PVD modified positive electrode precursor with a lithium source and performing sintering treatment to obtain a semi-step positive electrode material;

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

[0013] In the present application, PVD (physical vapor deposition) is used to irradiate the lithium-containing compound target with laser, so that the lithium-containing compound target is heated, melted, gasified and even turned into plasma in a very short time. The generated plasma is coated on the surface of the positive electrode precursor to modify the positive electrode precursor, and the PVD modified positive electrode precursor is mixed with the lithium source for sintering, which is beneficial to the embedding of the lithium source. Then the semi-step positive electrode material is subjected to second PVD modification treatment, which is beneficial to reducing the interface impedance of the positive electrode material.

[0014] Preferably, the first lithium-containing compound target of step (1) and the second lithium-containing compound target of step (2) independently comprise 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 a combination of lithium niobate and lithium phosphate, a combination of lithium niobate and lithium silicate, or a combination of lithium niobate and lithium titanate, etc.

[0015] Preferably, the positive electrode precursor of step (1) comprises a ternary nickel-cobalt-manganese precursor.

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

[0017] The lithium-containing compound powder is pressed into a round sheet at a pressure of 25 MPa to 35 MPa, for example: 25 MPa, 28 MPa, 30 MPa, 32 MPa or 35 MPa, etc., not limited to the listed values, other values not listed within this range are also applicable, and then the round sheet is sintered at 300°C to 600°C, for example: 300°C, 350°C, 400°C, 500°C or 600°C, etc., not limited to the listed values, other values not listed within this range are also applicable, for 3h to 6h, for example: 3h, 3.5h, 4h, 4.5h, 5h, 5.5h or 6h, etc., not limited to the listed values, other values not listed within this range are also applicable, to obtain the lithium-containing compound target.

[0018] Preferably, during the first PVD modification treatment of step (1), the energy density at the first 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 , 1.8 J / cm 2 , 1.9 J / cm 2 , 2.2 J / cm 2 or 2.5 J / cm 2 , not limited to the listed values, other values not listed within this range are also applicable.

[0019] Preferably, the time of the first PVD modification treatment of step (1) is 1 min to 10 min, for example: 1 min, 2 min, 5 min, 8 min or 10 min, etc., not limited to the listed values, other values not listed 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, for example: 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1, etc., and is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0022] Preferably, the sintering temperature in step (2) is 800℃~1200℃, for example: 800℃, 900℃, 1000℃, 1100℃ or 1200℃, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0023] Preferably, the sintering time in step (2) is 6h to 12h, for example: 6h, 7h, 8h, 9h, 10h, 11h or 12h, etc., not limited to the listed values, and other unlisted values ​​within this range are also 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 / cm². 2 ~2.5J / cm 2 For example: 1.5J / cm 2 1.6J / cm 2 1.7J / cm 2 2J / cm 2 2.2J / cm 2 Or 2.5J / cm 2 The term "etc." is not limited to the listed values; it also applies to other unlisted values ​​within the range.

[0025] Preferably, the time for the second PVD modification treatment in step (3) is 1 min to 10 min, for example: 1 min, 2 min, 5 min, 8 min or 10 min, etc., not limited to the listed values, and other unlisted values ​​within this range are also applicable.

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

[0027] Thirdly, the present invention provides a positive electrode sheet comprising the PVD-modified positive electrode material as described in the second aspect.

[0028] Fourthly, the present invention provides a solid-state battery comprising a positive electrode as described in the third aspect.

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

[0030] (1) The present application can significantly reduce the interface impedance in the solid-state battery by depositing an amorphous thin film on the surface of the positive electrode material particles through twice coating, thereby improving the charge and discharge capacity of the battery.

[0031] (2) The 0.1C discharge capacity of the battery made of the PVD modified positive electrode material according to the present application can reach 196.3mAh / g or more, and the 1C discharge capacity can reach 174.5mAh / g or more. DETAILED DESCRIPTION

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

[0033] Example 1

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

[0035] (1) Take dry lithium niobate (LiNbO3) target powder, press into a round sheet with a diameter of 20mm under a pressure of 30MPa by a tablet press, and place it in a tube-type sintering furnace. Heat the sintering furnace to 600℃ and sinter for 6h to obtain the required LiNbO3 target. Place the LiNbO3 target on a sample holder in a PVD device, and place Ni 0.9 Co 0.6 Mn 0.4 on a sample table with a vibrator. The energy density at the LiNbO3 target is 2J / cm 2 , and the duration on the target LiNbO3 sample is 5min. The target plasma attached to the surface of the positive electrode precursor by laser gasification, and a PVD modified positive electrode precursor is obtained.

[0036] (2) Mix the PVD modified positive electrode precursor with lithium hydroxide according to a ratio of 5:1, and sinter at 1000℃ for 10h to obtain a half-step positive electrode material.

[0037] (3) Place the half-step positive electrode material on a sample table with a vibrator, and use a LiNbO3 target. The energy density at the LiNbO3 target is 2J / cm 2 , and the duration on the LiNbO3 target sample is 5min. The target plasma attached to the surface of the half-step positive electrode material by laser gasification, and the PVD modified positive electrode material is obtained.

[0038] Example 2

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

[0040] (1) Take dried lithium titanate (Li4Ti5O) 12 The target powder was pressed into 20mm diameter discs using a tablet press at 35MPa. These discs were then placed in a tube sintering furnace, which was heated to 500℃ and sintered for 4 hours to obtain the desired Li4Ti5O. 12 Target material, Li4Ti5O 12 The target material is placed on the sample holder in the PVD equipment, and Ni is then applied. 0.9 Co 0.6 Mn 0.4 The precursor material is placed in a sample stage equipped with a vibrator. Li₄Ti₅O 12 The energy density at the target is 2.2 J / cm². 2 In Li4Ti5O 12 The target sample was subjected to laser-vaporized target plasma for 1 minute, which was then attached to the surface of the cathode precursor to obtain a PVD-modified cathode precursor.

[0041] (2) After mixing the PVD modified cathode precursor with lithium hydroxide at a ratio of 3:1, the mixture was sintered at 800℃ for 12h to obtain a semi-step cathode material.

[0042] (3) Place the half-step cathode material in a sample stage equipped with a vibrator, and use Li4Ti5O 12 The energy density at the LiNbO3 target is 2.2 J / cm². 2 In the target material Li4Ti5O 12 The plasma from the target material, vaporized by laser, adheres to the surface of the half-step cathode material for a duration of 3 minutes, thus obtaining 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 (Li4SiO4) target powder, press it into a disc with a diameter of 20 mm using a tablet press at 25 MPa, place it in a tube sintering furnace, heat the sintering furnace to 300℃, and sinter for 6 h to obtain the desired Li4SiO4 target. Place the Li4SiO4 target on the sample holder in the PVD equipment, and then apply Ni... 0.9 Co 0.6 Mn 0.4The precursor material was placed in a sample holder with a vibrator. The energy density at the Li4SiO4 target was 1.5 J / cm 2 The PVD modified anode precursor was mixed with lithium hydroxide at a ratio of 10:1 and sintered at 1200°C for 10 h to obtain a half-step anode material.

[0046] (2) The PVD modified anode precursor was mixed with lithium hydroxide at a ratio of 10:1 and sintered at 1200°C for 10 h to obtain a half-step anode material.

[0047] (3) The half-step anode material was placed in a sample holder with a vibrator. The Li4Ti5O 12 target was used, and the energy density at the Li4SiO4 target was 2 J / cm 2 The PVD modified anode material was obtained by laser vaporization of the target plasma onto the surface of the half-step anode material for a duration of 5 min on the target Li4Ti5O 12 sample.

[0048] Example 4

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

[0050] Example 5

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

[0052] Example 6

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

[0054] Example 7

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

[0056] Comparative Example 1

[0057] The only difference between this example and Example 1 is that step (1) was not PVD modified, and the other conditions and parameters were exactly the same as in Example 1.

[0058] Comparative Example 2

[0059] The comparative example is different from example 1 only in that step (3) is not modified by PVD, and other conditions and parameters are completely same as example 1.

[0060] Comparative example 3

[0061] The comparative example is different from example 1 only in that step (1) and step (3) are not modified by mixing and grinding with LiNbO3, and other conditions and parameters are completely same as example 1.

[0062] Performance test:

[0063] The results of the test are the test results of the discharged battery. The specific steps are as follows: the PVD treated positive electrode material and Li2S sulfide electrolyte are mixed according to the mass ratio of 2:3; then, the slurry is coated on the aluminum foil by a coater, and dried in a vacuum drying oven at 80℃ for 8h. Finally, the aluminum foil is punched into a 1.13cm 2 diameter to obtain a positive electrode sheet. The obtained electrode sheet is used as a positive electrode, and a lithium metal sheet is used as a counter electrode to assemble a CR2032 button battery in an argon glove box. The battery test system (Lantian CT2001A, Wuhan, China) is used to test the performance at a rate of 0.1C and 1C under the condition of 2.5V-4.55V, and the test results are shown in table 1:

[0064] Table 1

[0065]

[0066]

[0067] As can be seen from table 1, according to examples 1-7, the 0.1C discharge capacity of the battery made of the PVD modified positive electrode material of the application can reach 196.3mAh / g or more, and the 1C discharge capacity can reach 174.5mAh / g or more.

[0068] As can be seen from the comparison of example 1 and examples 4-5, in the preparation process of the PVD modified positive electrode material of the application, the laser energy of step (1) PVD modification will affect its performance. The laser energy density of step (1) PVD modification is controlled at 1.8J / cm 2 ~2.2J / cm 2 , and the performance of the PVD modified positive electrode material is better. If the laser energy density of step (1) PVD modification is too low, the gasification deposition layer is too thin, and if the laser energy of step (1) PVD modification is too high, the gasification speed is too fast, and the surface of the positive electrode material is not fully coated.

[0069] From the comparison of Example 1 and Examples 6-7, it can be seen that in the preparation process of the PVD modified positive electrode material of the present application, the laser energy of the PVD modification in step (3) will affect the performance, and the laser energy density of the PVD modification in step (3) is controlled at 1.8 J / cm 2 ~2.2 J / cm 2 , the performance of the PVD modified positive electrode material is better, if the laser energy of the PVD modification in step (3) is too low, the gasification deposition layer is too thin, if the laser energy of the PVD modification in step (3) is too high, the gasification speed is too fast, and the surface coating of the positive electrode material is insufficient.

[0070] From the comparison of Example 1 and Comparative Examples 1-2, it can be seen that the present application uses PVD (physical vapor deposition) to irradiate the lithium-containing compound target with laser, so that the lithium-containing compound target is heated, melted, gasified and changed into plasma in a very short time, the generated plasma is coated on the surface of the positive electrode precursor, the positive electrode precursor is modified, the PVD modified positive electrode precursor is obtained, and the PVD modified positive electrode precursor is mixed with lithium source and sintered, which is beneficial to the embedding of the lithium source. Then the semi-step positive electrode material is subjected to a second PVD modification treatment, which is beneficial to reducing the interface impedance of the positive electrode material. The performance of the positive electrode material after two times of PVD modification is obviously improved.

[0071] From the comparison of Example 1 and Comparative Example 3, it can be seen that the present application uses PVD to deposit LiNbO3 on the surface of the positive electrode material, and the obtained coating layer has good uniformity, high density and stable structure, which is beneficial to the embedding of lithium and has low interface impedance, and the performance of the material is obviously improved.

[0072] The applicant declares that the above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and those skilled in the art should understand that any changes or replacements within the technical scope disclosed by the present application can be easily thought of by those skilled in the art, and all fall within the protection scope and disclosure scope of the present application.

Claims

1. A method for preparing a PVD-modified cathode material, characterized in that, The preparation method includes the following steps: (1) The cathode precursor is subjected to first PVD modification treatment using a first lithium-containing compound target to obtain a PVD-modified cathode precursor; (2) The PVD-modified cathode precursor is mixed with a lithium source and sintered to obtain a semi-step cathode material; (3) The second lithium-containing compound target is used to perform a second PVD modification on the half-step cathode material to obtain a PVD-modified cathode material; 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, and the positive electrode precursor in step (1) includes a ternary nickel-cobalt-manganese precursor. Step (1) The laser energy for the first PVD modification treatment is 1.5 J / cm. 2 ~2.5J / cm 2 In step (3), the laser energy for the second PVD modification treatment is 1.5 J / cm². 2 ~2.5J / cm 2 .

2. The preparation method according to claim 1, characterized in that, The first lithium-containing compound target material described in step (1) and the second lithium-containing compound target material described in step (3) are independently prepared by the following methods: After pressing lithium compound powder into discs under a pressure of 25 MPa to 35 MPa, the discs are sintered at 300°C to 600°C for 3 to 6 hours to obtain the lithium compound target material.

3. The preparation method according to claim 1, characterized in that, Step (1) The time for the first PVD modification treatment is 1 min to 10 min.

4. The preparation method according to claim 1, characterized in that, The lithium source in step (2) includes lithium hydroxide and / or lithium carbonate.

5. The preparation method according to claim 1, characterized in that, In step (2), 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.

6. The preparation method according to claim 1, characterized in that, The sintering temperature in step (2) is 800℃~1200℃.

7. The preparation method according to claim 1, characterized in that, The sintering process in step (2) takes 6 to 12 hours.

8. The preparation method according to claim 1, characterized in that, Step (3) The second PVD modification treatment time is 1 min to 10 min.

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

10. A positive electrode plate, characterized in that, The positive electrode sheet comprises the PVD-modified positive electrode material as described in claim 9.

11. A solid-state battery, characterized in that, The solid-state battery includes the positive electrode as described in claim 10.

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