Double-coated single-crystal positive electrode material and preparation method and application thereof

Abstract

The application relates to the field of solid-state battery materials, and discloses a double-coated single-crystal positive electrode material and a preparation method and application thereof. The method comprises the following steps: (1) first contact of a single-crystal positive electrode material with a fast ion conductor to obtain a positive electrode material I; (2) first heat treatment of the positive electrode material I at 300-800 DEG C in the presence of an oxygen-containing atmosphere to obtain a positive electrode material II; and (3) second heat treatment of the positive electrode material II and oxalic acid powder at 300-800 DEG C in the presence of a nitrogen-containing atmosphere to obtain a double-coated single-crystal positive electrode material. The double-coated single-crystal positive electrode material provided by the application can reduce the interface impedance of the positive electrode material during rapid charging, is more conducive to the transmission of lithium ions, and can effectively avoid the problem of excessive heat generation.

Description

Technical Field

[0001] This invention relates to the field of solid-state battery materials, specifically to a double-coated single-crystal cathode material, its preparation method, and its application. Background Technology

[0002] Currently, single-crystal high-voltage materials are among the most widely used materials on the market. Single-crystal high-voltage materials exhibit good thermal stability and, compared to high-nickel materials, are lower in cost and have better processing performance, thus gaining widespread application. However, this material also has certain drawbacks. Due to the relatively large primary particle size of single-crystal cathode materials, the lithium-ion transport distance within the material is longer. During fast charging, this results in an increased interfacial resistance (DCR) on the lithium-ion battery surface. Furthermore, the hydroxyl groups on the surface of single-crystal cathode materials readily react with solvents or additives in the electrolyte, generating more byproducts, which also increases the interfacial resistance and generates more heat during fast charging, thus affecting the battery's fast-charging performance.

[0003] However, in order to reduce the problems of high interfacial impedance and excessive heat generation during fast charging, the current industrial production method is to make the particle size of single-crystal cathode material as small as possible. However, making the particles of single-crystal cathode material smaller does not solve the problem of high interfacial impedance well, and it is also prone to particle agglomeration. The single-crystal cathode material is also prone to breakage during the rolling process.

[0004] Therefore, there is a need for a single-crystal cathode material that can improve lithium-ion conductivity, avoid excessive heat generation, and is less prone to agglomeration and breakage while addressing the issue of high DCR in single-crystal cathode materials under fast charging conditions, thereby better improving the fast charging performance of the battery. Summary of the Invention

[0005] The purpose of this invention is to overcome the problems of large DCR, low lithium-ion conductivity, and excessive heat generation in existing single-crystal cathode materials under fast charging conditions.

[0006] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a double-coated single-crystal cathode material, the method comprising: (1) making a first contact between the single-crystal cathode material and a fast ion conductor to obtain cathode material I; (2) The cathode material I is subjected to a first heat treatment at 300-800℃ in the presence of an oxygen-containing atmosphere to obtain cathode material II; (3) The cathode material II and oxalic acid powder are subjected to a second heat treatment at 300-800℃ in the presence of a nitrogen-containing atmosphere to obtain a double-coated single-crystal cathode material; The single-crystal cathode material is selected from at least one of lithium nickel cobalt manganese oxygen single crystal, lithium nickel manganese oxygen single crystal, and lithium nickel cobalt oxygen single crystal. The fast ion conductor is an inorganic solid electrolyte; The median particle size D of the oxalic acid powder 50 It ranges from 0.5 to 10 μm.

[0007] Preferably, the single-crystal cathode material is lithium nickel cobalt manganese oxygen single crystal and / or lithium nickel manganese oxygen single crystal.

[0008] In a preferred embodiment, the fast ion conductor is selected from at least one of lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, and lithium lanthanum zirconium titanium oxide.

[0009] Preferably, the median particle size D of the single-crystal cathode material is... 50 It ranges from 1.5 to 18 μm.

[0010] In a preferred embodiment, the median particle size D of the fast ion conductor is... 50 It ranges from 0.03 to 2.5 μm.

[0011] Preferably, in the nitrogen-containing atmosphere, the nitrogen content is 90-99.99 vol.

[0012] Preferably, in the oxygen-containing atmosphere, the oxygen content is 10-99.99 vol.

[0013] In a preferred embodiment, in step (1), the weight ratio of the single-crystal cathode material to the fast ion conductor is 50-200:1.

[0014] Preferably, in step (1), the operation of the first contact includes: dividing the single crystal cathode material and the fast ion conductor into 2-4 equal parts by mass, and then mixing them alternately to perform the first contact.

[0015] In a preferred embodiment, in step (1), the first contact is carried out under stirring conditions, and at least the following conditions are met: rotation speed is 100-5000 r / min, temperature is 20-80℃, and time is 0.1-10h.

[0016] In a preferred embodiment, in step (2), the duration of the first heat treatment is 1-10 hours.

[0017] Preferably, in step (3), the weight ratio of the single-crystal cathode material to the oxalic acid powder is 50-200:1.

[0018] In a preferred embodiment, in step (3), the second heat treatment time is 1-10 hours.

[0019] The second aspect of the present invention provides a double-coated single-crystal cathode material prepared by the method described in the first aspect.

[0020] The third aspect of this invention provides the application of the double-coated monocrystalline cathode material described in the second aspect in the field of solid-state battery materials.

[0021] Compared with existing technologies, the double-coated single-crystal cathode material provided by this invention can reduce the interfacial impedance of the cathode material during fast charging, improve the lithium-ion conductivity, facilitate lithium-ion transport, and effectively avoid the problem of excessive heat generation. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] As described above, the first aspect of the present invention provides a method for preparing a double-coated single-crystal cathode material, the method comprising: (1) The single-crystal cathode material is brought into first contact with the fast-ion conductor to obtain cathode material I; (2) The cathode material I is subjected to a first heat treatment at 300-800℃ in the presence of an oxygen-containing atmosphere to obtain cathode material II; (3) The cathode material II and oxalic acid powder are subjected to a second heat treatment at 300-800℃ in the presence of a nitrogen-containing atmosphere to obtain a double-coated single-crystal cathode material; The single-crystal cathode material is selected from at least one of lithium nickel cobalt manganese oxygen single crystal, lithium nickel manganese oxygen single crystal, and lithium nickel cobalt oxygen single crystal. The fast ion conductor is an inorganic solid electrolyte; The median particle size D of the oxalic acid powder 50 It ranges from 0.5 to 10 μm.

[0024] Preferably, the single-crystal cathode material is lithium nickel cobalt manganese oxygen single crystal and / or lithium nickel manganese oxygen single crystal.

[0025] In a preferred embodiment, the fast ion conductor is selected from at least one of lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconium oxide (LLZO), and lithium lanthanum zirconium titanium oxide (LLZTO).

[0026] Preferably, the median particle size D of the single-crystal cathode material is... 50 The interfacial impedance is 1.5-18 μm. The inventors discovered that, under this preferred condition, the interfacial impedance of the prepared double-coated single-crystal cathode material is even lower.

[0027] In a preferred embodiment, the median particle size D of the fast ion conductor is... 50 It ranges from 0.03 to 2.5 μm.

[0028] Preferably, in the nitrogen-containing atmosphere, the nitrogen content is 90-99.99 vol.

[0029] Preferably, in the oxygen-containing atmosphere, the oxygen content is 10-99.99 vol.

[0030] According to a preferred embodiment, the oxygen-containing atmosphere is air.

[0031] In a preferred embodiment, in step (1), the weight ratio of the single-crystal cathode material to the fast ion conductor is 50-200:1.

[0032] In a preferred embodiment, in step (1), the first contact is carried out under stirring conditions, and at least the following conditions are met: rotation speed is 100-5000 r / min, temperature is 20-80℃, and time is 0.1-10h.

[0033] Preferably, in step (1), the operation of the first contact includes: dividing the single-crystal cathode material and the fast-ion conductor into 2-4 equal parts by mass, and then mixing them alternately to perform the first contact. The inventors have found that, in this preferred case, the prepared double-coated single-crystal cathode material is more conducive to lithium-ion transport and can better improve the fast-charging capability of the single-crystal cathode material.

[0034] According to a preferred embodiment, the first contact is performed in a coating fusion machine.

[0035] Preferably, in this invention, the alternating mixing operation includes: under the conditions of the first contact, first adding any one portion of the single-crystal cathode material divided into 2-4 equal parts to the coating fusion machine, then adding any one portion of the fast ion conductor divided into 2-4 equal parts to the coating fusion machine for mixing, then adding any one portion of the remaining single-crystal cathode material to the coating fusion machine for mixing, and then adding any one portion of the remaining fast ion conductor to the coating fusion machine for mixing, and so on alternately until all the single-crystal cathode material and all the fast ion conductor are added to the coating fusion machine for the first contact to obtain the cathode material I; wherein, the mixing time for each step is independently 0.1-10h.

[0036] In a preferred embodiment, in step (2), the duration of the first heat treatment is 1-10 hours.

[0037] According to a preferred embodiment, the method of the present invention further includes: before performing the second heat treatment in step (3), first making the cathode material II into a second contact with the oxalic acid powder, and then performing the contact-mixed product into a second heat treatment under the conditions of the second heat treatment to obtain a double-coated single-crystal cathode material.

[0038] In a preferred embodiment, the second contact is carried out under stirring conditions, and at least the following conditions are met: rotation speed of 100-5000 r / min, temperature of 20-80℃, and time of 0.5-10 h.

[0039] In a preferred embodiment, the second heat treatment time is 1-10 hours.

[0040] Preferably, in step (3), the weight ratio of the single-crystal cathode material to the oxalic acid powder is 50-200:1.

[0041] As described above, the second aspect of the present invention provides a double-coated single-crystal cathode material prepared by the method described in the first aspect above.

[0042] As mentioned above, the third aspect of the present invention provides the application of the double-coated single-crystal cathode material described in the second aspect above in the field of solid-state battery materials.

[0043] The present invention will be described in detail below through examples. Unless otherwise specified, the raw materials used are all commercially available products and are of analytical grade.

[0044] Single-crystal cathode materials: Single-crystal cathode material I: is a lithium-nickel-cobalt-manganese-oxygen single crystal with the molecular formula LiNi. 0.65 Co 0.08 Mn 0.27 O2, median particle size D 50 It is 3.5um; Single-crystal cathode material II: is a lithium-nickel-manganese-oxygen single crystal with the molecular formula LiNi. 0.75 Mn 0.25 O2, median particle size D 50 It is 2.8um; Polycrystalline cathode material: LiNi cobalt manganese oxygen polycrystalline, with the molecular formula LiNi 0.65 Co 0.08 Mn 0.27 O2, median particle size D 50 It is 9.5um; Fast ion conductors: Fast ion conductor I: LATP, median particle size D 50 It is 0.03um; Fast ion conductor II: LLZO median particle size D 50It is 0.05um; Fast ion conductor III: LATP, median particle size D 50 It is 2.6um; Oxalic acid powder: Oxalic acid powder I: Median particle size D 50 It is 3um; Oxalic acid powder II: Median particle size D 50 It is 15um; Sodium oxalate: Median particle size D 50 It is 0.8um.

[0045] Example 1 This embodiment illustrates a preferred method for preparing a double-coated single-crystal cathode material provided by the present invention. The method is performed with reference to the substances, amounts, and parameters in Table 1, and the specific operations include: (1) First contact: At 35°C and a rotation speed of 2000 r / min, 1000 g of single crystal cathode material is divided into two equal parts. One part is added to the coating fusion machine. Then, 10 g of the fast ion conductor is divided into two equal parts. One part is added to the coating fusion machine and mixed for 0.5 h. Then, the remaining part of single crystal cathode material is added to the coating fusion machine and mixed for 0.5 h. Then, the remaining part of fast ion conductor is added to the coating fusion machine and mixed for 1 h to obtain the cathode material I. (2) The cathode material I is subjected to a first heat treatment in oxygen at 400°C for 4 hours to obtain cathode material II; (3) Under the stirring conditions of 30°C and 1000 r / min, the cathode material II was subjected to a second contact with 10 g of oxalic acid powder for 0.5 h, and then subjected to a second heat treatment at 500°C for 4 h in the presence of a nitrogen atmosphere (nitrogen content of 99.5 vol%) to obtain a double-coated single crystal cathode material, named P1.

[0046] Example 2 This embodiment uses the same method as Example 1, except that the types of materials, amounts, and parameter conditions are changed. See Table 1 for details. A double-coated single-crystal cathode material is obtained and named P2.

[0047] Example 3 This embodiment uses the same method as in Example 1, except that the same weight (10g) of fast ion conductor III is used instead of fast ion conductor I for the first contact, resulting in a double-coated single-crystal cathode material, named P3.

[0048] Comparative Example 1 This comparative example was conducted using the same method as in Example 1. The difference was that the same weight (1000g) of polycrystalline cathode material was used instead of single-crystal cathode material I for the first contact, resulting in cathode material named DP1.

[0049] Comparative Example 2 This comparative example was conducted using the same method as in Example 1. The difference was that a 1000g multi-element cathode material (composed of a single-crystal cathode material I and a polycrystalline cathode material with a weight ratio of 1:0.2) was used instead of the single-crystal cathode material I in Example 1 for the first contact, resulting in a cathode material named DP2.

[0050] Comparative Example 3 This comparative example was carried out using the same method as in Example 1, except that the same weight (10g) of oxalic acid powder II was used instead of oxalic acid powder I for the second heat treatment to obtain the positive electrode material, named DP3.

[0051] Comparative Example 4 This comparative example was carried out using the same method as Example 1, except that the same weight (10g) of sodium oxalate was used instead of oxalic acid powder I for the second heat treatment to obtain the positive electrode material, named DP4.

[0052] Comparative Example 5 This comparative example was conducted using a method similar to that of Example 1, except that a second heat treatment was performed first, followed by a first contact and heat treatment. Specific operations included: S1. Under stirring conditions of 30℃ and 1000r / min, 1000g of single crystal cathode material and 10g of oxalic acid powder are subjected to a second contact for 0.5h. Then, under a nitrogen atmosphere (nitrogen content of 99.5 vol%), a second heat treatment is carried out at 500℃ for 4h to obtain mixture I. S2. At 35℃ and a rotation speed of 2000 r / min, the mixture I obtained in S1 is divided into two equal parts. One part is added to the coating fusion machine. Then, 10g of fast ion conductor I is divided into two equal parts. One part is added to the coating fusion machine and mixed for 0.5h. Then, the remaining part of mixture I is added to the coating fusion machine and mixed for 0.5h. Finally, the remaining part of fast ion conductor I is added to the coating fusion machine and mixed for 1h to obtain mixture II. S3. Mixture II was subjected to a first heat treatment in oxygen at 400℃ for 4 hours to obtain the positive electrode material, named DP5.

[0053] Test Example 1 The DCR value and lithium-ion conductivity of the double-coated single-crystal cathode material and cathode material prepared in the above examples were tested. The test method was the same as that of HPPC (hybrid pulse power performance test). The results are shown in Table 2.

[0054] Table 1

[0055] Table 2

[0056] Table 2 (continued)

[0057] The results above show that the double-coated single-crystal cathode material provided by this invention improves the kinetic performance of lithium-ion transport and reduces the impedance of lithium-ion transport, thereby achieving the purpose of reducing the interface impedance of the cathode material during fast charging, improving lithium-ion transport, and effectively avoiding excessive heat generation.

[0058] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a double-coated single-crystal cathode material, characterized in that, The method includes: (1) making a first contact between a single-crystal cathode material and a fast-ion conductor to obtain cathode material I; the operation of the first contact includes: dividing the single-crystal cathode material and the fast-ion conductor into 2-4 equal parts by mass, and then mixing them alternately; (2) The cathode material I is subjected to a first heat treatment at 300-800℃ in the presence of an oxygen-containing atmosphere to obtain cathode material II; (3) The cathode material II and oxalic acid powder are subjected to a second heat treatment at 300-800℃ in the presence of a nitrogen-containing atmosphere to obtain a double-coated single-crystal cathode material; The single-crystal cathode material is selected from at least one of lithium nickel cobalt manganese oxygen single crystal, lithium nickel manganese oxygen single crystal, and lithium nickel cobalt oxygen single crystal. The fast ion conductor is an inorganic solid electrolyte; The median particle size D of the oxalic acid powder 50 It ranges from 0.5 to 10 μm.

2. The method according to claim 1, wherein, The single-crystal cathode material is lithium nickel cobalt manganese oxygen single crystal and / or lithium nickel manganese oxygen single crystal; and / or The fast ion conductor is selected from at least one of lithium aluminum titanium phosphate, lithium lanthanum zirconium oxide, and lithium lanthanum zirconium titanium oxide; and / or The median particle size D of the single-crystal cathode material 50 1.5-18µm; and / or The median particle size D of the fast ion conductor 50 0.03-2.5µm; and / or In the nitrogen-containing atmosphere, the nitrogen content is 90-99.99 vol%; and / or In the oxygen-containing atmosphere, the oxygen content is 10-99.99 vol.

3. The method according to claim 1 or 2, wherein, In step (1), the weight ratio of the single-crystal cathode material to the fast ion conductor is 50-200:

1.

4. The method according to claim 1 or 2, wherein, In step (1), the first contact is carried out under stirring conditions, and at least the following conditions are met: the rotation speed is 100-5000 r / min, the temperature is 20-80℃, and the time is 0.1-10h.

5. The method according to claim 1 or 2, wherein, In step (2), the first heat treatment lasts for 1-10 hours.

6. The method according to claim 1 or 2, wherein, In step (3), the weight ratio of the single-crystal cathode material to the oxalic acid powder is 50-200:

1.

7. The method according to claim 1 or 2, wherein, In step (3), the second heat treatment lasts for 1-10 hours.

8. The double-coated single-crystal cathode material prepared by the method according to any one of claims 1-7.

9. The application of the double-coated single-crystal cathode material as described in claim 8 in the field of solid-state battery materials.

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