A lithium ion battery roll core and a preparation method and application thereof

Abstract

The application provides a lithium ion battery roll core and a preparation method and application thereof, the roll core comprises a positive electrode sheet, a diaphragm and a negative electrode sheet connected in sequence; raw materials of the positive electrode sheet comprise lithium manganate and lithium nickel cobalt aluminate, the particle size of the lithium nickel cobalt aluminate is greater than that of the lithium manganate; and raw materials of the negative electrode sheet comprise carbon-coated natural graphite and artificial graphite. The application improves the gram capacity of the positive electrode material and optimizes the lithium ion transmission path by mixing the two positive electrode materials, lithium nickel cobalt aluminate and lithium manganate; and the application effectively inhibits lithium dendrites in the 0 DEG C fast charging and discharging process, improves the cycle life and safety performance of the battery by mixing the carbon-coated natural graphite and the artificial graphite in the negative electrode material, adjusting the mixing ratio and compacting the negative electrode.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and in particular to a lithium-ion battery core, its preparation method, and its application. Background Technology

[0002] Currently, lithium-ion batteries are gradually becoming the mainstream in the market due to their advantages such as high energy density, long cycle life, low self-discharge, and environmental friendliness. However, at 0°C, the diffusion rate of lithium ions within the particles of both the positive and negative electrode materials slows down, leading to large-area lithium deposition on the negative electrode during fast charging, which severely affects battery life. For these reasons, fast charging of lithium-ion batteries at low temperatures has remained a challenging problem for the industry.

[0003] CN108767205A discloses a method for preparing artificial graphite-hard carbon anode material, the material itself, and its application. The mass percentage of spherical hard carbon material in the anode material is controlled between 2% and 60%. The anode material can be prepared simply by mixing the raw materials in sequence. The spherical hard carbon material is prepared from pyrolytic resin. However, this method has limited effect on improving the low-temperature discharge performance of the battery, and the preparation process is cumbersome and the raw materials are expensive.

[0004] CN101197457A discloses a lithium-ion battery suitable for low-temperature environments. The lithium-ion battery includes a battery casing, a heat-insulating layer tightly attached to the battery casing, a core disposed inside the battery casing, a control component consisting of a temperature control switch and a control circuit, and a heating component consisting of a heating element and a heat-conducting element. This allows the battery to automatically heat up at low temperatures, maintaining it within its normal operating temperature range. While this method achieves low-temperature operation by modifying the battery structure, assembling an automatically heating battery is costly.

[0005] CN105914394A discloses a low-temperature lithium-ion battery composite cathode material, a low-temperature lithium-ion battery cathode sheet, and a method for preparing the same. The composite cathode material is composed of the following components in the following mass ratio: lithium iron phosphate: carbon nanotube / polypropylene composite material: carbon nanofibers: lithium-containing compound = (90-94): (1-2): (1-2): (0.5-1). The low-temperature lithium-ion battery composite cathode material provided by this invention can effectively replenish the lithium ions consumed in forming the SEI film during the charging and discharging process of lithium-ion batteries, and provide more lithium ions for lithium-ion batteries during low-temperature charging, discharging, and cycling, thereby improving the low-temperature performance of lithium-ion batteries. However, the preparation process is complex and the raw materials are expensive.

[0006] Improving the low-temperature charge-discharge cycle life of lithium-ion batteries at a low cost is an important research direction in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a low-temperature fast-charging long-cycle-life lithium-ion battery core and its application. The preparation process is simple and the cost is low, and it significantly improves the low-temperature charge-discharge cycle life.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] One objective of this invention is to provide a lithium-ion battery core, the core comprising a positive electrode sheet, a separator, and a negative electrode sheet connected in sequence;

[0010] The raw materials for the positive electrode sheet include lithium manganese oxide and lithium nickel cobalt aluminum oxide, wherein the particle size of the lithium nickel cobalt aluminum oxide is larger than that of the lithium manganese oxide.

[0011] The raw materials for the negative electrode sheet include carbon-coated natural graphite and artificial graphite.

[0012] This invention utilizes a blend of two cathode materials, lithium nickel cobalt aluminum oxide and lithium manganese oxide. The lithium nickel cobalt aluminum oxide has a larger particle size than the lithium manganese oxide, ensuring a higher specific capacity and higher compaction of the cathode material, thus optimizing the lithium-ion transport path. The anode material is a blend of carbon-coated natural graphite and artificial graphite. By adjusting the blending ratio and the compaction of the anode, lithium dendrite formation during 0°C fast charging and discharging is effectively suppressed, improving the battery's cycle life and safety performance. The carbon-coated natural graphite used in the anode material consists of a layer of amorphous carbon coated on the graphite surface and is commercially available.

[0013] As a preferred embodiment of the present invention, the lithium nickel cobalt aluminum oxide accounts for 60-90% of the mass fraction of the raw material of the positive electrode sheet. The mass fraction of the lithium nickel cobalt aluminum oxide can be 60%, 62%, 65%, 67%, 70%, 72%, 75%, 77%, 80%, 82%, 85%, 87%, or 90%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0014] Preferably, the lithium manganese oxide has a particle size of 2 to 3 μm, wherein the particle size can be 2 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm or 3 μm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0015] Preferably, the lithium nickel cobalt aluminum oxide has a particle size of 30-35 μm, wherein the particle size can be 30 μm, 31 μm, 32 μm, 33 μm, 34 μm or 35 μm, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0016] As a preferred technical solution of the present invention, the carbon-coated natural graphite accounts for 50-80% of the mass fraction of the raw material of the negative electrode sheet. The mass fraction of the carbon-coated natural graphite can be 50%, 52%, 55%, 57%, 60%, 62%, 65%, 67%, 70%, 72%, 75%, 77%, or 80%, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] A second objective of this invention is to provide a method for preparing a lithium-ion battery core as described in the first aspect, the method comprising the following steps:

[0018] The raw materials for the positive electrode sheet are mixed and coated onto the first current collector to prepare the positive electrode sheet.

[0019] The raw materials for the negative electrode sheet are mixed and coated onto the second current collector to prepare the negative electrode sheet.

[0020] The positive electrode, the negative electrode, and the separator are wound together to obtain the core.

[0021] As a preferred embodiment of the present invention, the raw materials of the positive electrode sheet also include a conductive agent and a binder.

[0022] Preferably, the conductive agent includes Surpe-P and / or CNT.

[0023] Preferably, the adhesive comprises any one or a combination of at least two of PVDF, SBR, PAA, guar gum, or virgin gum. Typical but non-limiting examples of such combinations include combinations of PVDF and SBR, SBR and PAA, PAA and guar gum, guar gum and virgin gum, or PVDF and PAA.

[0024] As a preferred embodiment of the present invention, the first current collector comprises aluminum foil or carbon-coated aluminum foil.

[0025] As a preferred embodiment of the present invention, the raw materials of the negative electrode sheet further include conductive agent, binder and dispersant.

[0026] Preferably, the conductive agent includes Surpe-P and / or CNT.

[0027] Preferably, the adhesive comprises CMC and / or PVDF.

[0028] Preferably, the dispersant comprises SBR.

[0029] As a preferred embodiment of the present invention, the second current collector comprises copper foil or carbon-coated copper foil.

[0030] A third objective of this invention is to provide a lithium-ion battery, characterized in that the lithium-ion battery includes a lithium-ion battery core as described in one objective, and the lithium-ion battery is obtained by injecting electrolyte into the lithium-ion battery core and then encapsulating it.

[0031] As a preferred technical solution of the present invention, the solvent of the electrolyte includes any one or a combination of at least two of ethylene carbonate, methyl ethyl carbonate, dimethyl carbonate or propylene carbonate. Typical but non-limiting examples of such combinations include combinations of ethylene carbonate and methyl ethyl carbonate, combinations of methyl ethyl carbonate and dimethyl carbonate, combinations of dimethyl carbonate and propylene carbonate, or combinations of ethylene carbonate and dimethyl carbonate.

[0032] Preferably, the lithium salt of the electrolyte includes any one or a combination of at least two of LiFP6, LiClO4, LiBOB, LiFSI, LiODFB, LiTFSI, or LiBF4. Typical but non-limiting examples of such combinations include combinations of LiFP6 and LiClO4, LiClO4 and LiBOB, LiBOB and LiFSI, LiFSI and LiODFB, LiODFB and LiTFSI, or LiTFSI or LiBF4.

[0033] Preferably, the concentration of the lithium salt in the electrolyte is 1 to 3 mol / L, wherein the concentration can be 1 mol / L, 2 mol / L or 3 mol / L, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0034] Preferably, the electrolyte additives include any one or a combination of at least two of vinyl sulfate, vinylene carbonate, fluorovinyl carbonate, or ethylene ethylene carbonate. Typical but non-limiting examples of such combinations include combinations of vinyl sulfate and vinylene carbonate, combinations of vinylene carbonate and fluorovinyl carbonate, combinations of fluorovinyl carbonate and ethylene ethylene carbonate, or combinations of vinylene carbonate and ethylene ethylene carbonate.

[0035] Preferably, the additive accounts for 0.5% to 5% of the mass fraction of the electrolyte, wherein the mass fraction can be 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, 4.0%, 4.5%, or 5%, etc., but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) This invention effectively solves the problem of poor cycle life of lithium-ion batteries under low temperature conditions. The discharge capacity retention rate of lithium-ion batteries after 200 cycles at -20℃ / 0.33C can reach more than 94%.

[0038] (2) The preparation process of this invention is simple and the cost is low, making it highly competitive. Attached Figure Description

[0039] Figure 1 These are flowcharts of battery fabrication processes in Examples 1-7 and Comparative Examples 1-5 of the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0041] Example 1

[0042] This embodiment provides a method for preparing a lithium-ion battery core, the method comprising:

[0043] The positive electrode material consists of 35% lithium manganese oxide with a particle size of 2.5 μm and 65% lithium nickel cobalt aluminum oxide with a particle size of 32 μm. The positive electrode material, PVDF, and Surpe-P are mixed in a mass ratio of 96.5:1.5:2 and then coated onto aluminum foil to prepare a positive electrode sheet.

[0044] The negative electrode material consists of 65% carbon-coated natural graphite and 35% artificial graphite. The negative electrode material, PVDF and Surpe-P are coated on copper foil in a mass ratio of 96.5:1.5:2 to prepare a negative electrode sheet.

[0045] The positive electrode, the negative electrode, and the PP separator are wound together to obtain the core.

[0046] This embodiment also provides a method for preparing a lithium-ion battery, the method comprising:

[0047] After the winding core is inserted into the battery casing, liquid injection, sealing, and formation are performed to obtain the lithium-ion battery, wherein liquid injection includes:

[0048] With the electrolyte mass as 100%, the electrolyte composition is as follows: the organic solvent is ethylene carbonate, the lithium salt is 2 mol / L LiFP6, and the additive is 2.5% ethylene sulfate.

[0049] The preparation flowchart of this embodiment is as follows: Figure 1 As shown.

[0050] Example 2

[0051] This embodiment provides a method for preparing a lithium-ion battery core, the method comprising:

[0052] The positive electrode material consists of 40% lithium manganese oxide with a particle size of 2 μm and 60% lithium nickel cobalt aluminum oxide with a particle size of 30 μm. The positive electrode material, PVDF, and Surpe-P are mixed in a mass ratio of 96.5:1.5:2 and then coated onto aluminum foil to prepare the positive electrode sheet.

[0053] The negative electrode material consists of 50% carbon-coated natural graphite and 50% artificial graphite. The negative electrode material, PVDF and Surpe-P are coated on copper foil in a mass ratio of 96.5:1.5:2 to prepare a negative electrode sheet.

[0054] The positive electrode, the negative electrode, and the PE separator are wound together to obtain the core.

[0055] This embodiment also provides a method for preparing a lithium-ion battery, the method comprising:

[0056] After the winding core is inserted into the battery casing, liquid injection, sealing, and formation are performed to obtain the lithium-ion battery, wherein liquid injection includes:

[0057] With the electrolyte mass as 100%, the electrolyte composition is as follows: the organic solvent is ethylene carbonate, the lithium salt is 2 mol / L LiFP6, and the additive is 2.5% ethylene sulfate.

[0058] The preparation flowchart of this embodiment is as follows: Figure 1 As shown.

[0059] Example 3

[0060] This embodiment provides a method for preparing a lithium-ion battery core, the method comprising:

[0061] The positive electrode material consists of 10% lithium manganese oxide with a particle size of 3 μm and 90% lithium nickel cobalt aluminum oxide with a particle size of 35 μm. The positive electrode material, PVDF, and Surpe-P are mixed in a mass ratio of 96.5:1.5:2 and then coated onto carbon-coated aluminum foil to prepare the positive electrode sheet.

[0062] The negative electrode material consists of 80% carbon-coated natural graphite and 20% artificial graphite. The negative electrode material, PVDF and Surpe-P are coated on copper foil in a mass ratio of 96.5:1.5:2 to prepare a negative electrode sheet.

[0063] The positive electrode, the negative electrode, and the PP separator are wound together to obtain the core.

[0064] This embodiment also provides a method for preparing a lithium-ion battery, the method comprising:

[0065] After the winding core is inserted into the battery casing, liquid injection, sealing, and formation are performed to obtain the lithium-ion battery, wherein liquid injection includes:

[0066] With the electrolyte mass as 100%, the electrolyte composition is as follows: the organic solvent is ethylene carbonate, the lithium salt is 2 mol / L LiFP6, and the additive is 2.5% ethylene sulfate.

[0067] The preparation flowchart of this embodiment is as follows: Figure 1 As shown.

[0068] Example 4

[0069] In this embodiment, 65% of lithium nickel cobalt aluminum oxide by mass fraction is replaced with 40% lithium nickel cobalt aluminum oxide, and 35% of lithium manganese oxide is replaced with 60%. All other conditions are the same as in Example 1.

[0070] Example 5

[0071] In this embodiment, 65% of lithium nickel cobalt aluminum oxide by mass fraction is replaced with 95% lithium nickel cobalt aluminum oxide, and 35% of lithium manganese oxide is replaced with 5%. All other conditions are the same as in Example 1.

[0072] Example 6

[0073] In this embodiment, 65% of carbon-coated natural graphite by mass fraction is replaced with 40% carbon-coated natural graphite, and 35% of artificial graphite is replaced with 60% artificial graphite. All other conditions are the same as in Example 1.

[0074] Example 7

[0075] In this embodiment, 65% of carbon-coated natural graphite by mass fraction is replaced with 90% carbon-coated natural graphite, and 35% of artificial graphite is replaced with 10% artificial graphite. All other conditions are the same as in Example 1.

[0076] Comparative Example 1

[0077] The conditions for this comparative example are the same as those for Example 1, except that lithium manganese oxide is not added.

[0078] Comparative Example 2

[0079] The conditions for this comparative example are the same as those for Example 1, except that lithium nickel cobalt aluminum oxide is not added.

[0080] Comparative Example 3

[0081] In this comparative example, the conditions were the same as in Example 1, except that the lithium manganese oxide with a particle size of 2.5 μm was replaced with lithium manganese oxide with a particle size of 32 μm, and the lithium nickel cobalt aluminum oxide with a particle size of 32 μm was replaced with lithium nickel cobalt aluminum oxide with a particle size of 2.5 μm.

[0082] Comparative Example 4

[0083] The conditions for this comparative example are the same as those for Example 1, except that no carbon-coated natural graphite is added.

[0084] Comparative Example 5

[0085] The conditions for this comparative example are the same as those for Example 1, except that no artificial graphite is added.

[0086] The lithium-ion batteries of Examples 1-7 and Comparative Examples 1-5 were tested for low-temperature discharge capacity retention. The discharge capacity retention was tested after 200 cycles at -20℃ / 0.33C. The test results are shown in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] The results above show that in Examples 4-5, excessive or insufficient addition of lithium nickel cobalt aluminum oxide led to a decrease in the battery's discharge capacity retention rate. Similarly, in Examples 6 and 7, excessive or insufficient addition of carbon-coated natural graphite resulted in a decrease in the battery's discharge capacity retention rate. This indicates that the optimal electrochemical performance of the battery is achieved by using a specific mass ratio of lithium manganese oxide and lithium nickel cobalt aluminum oxide as the positive electrode material, combined with a specific mass ratio of carbon-coated natural graphite and artificial graphite as the negative electrode material. In Comparative Examples 1-2, only lithium manganese oxide or lithium nickel cobalt aluminum oxide was used as the positive electrode material. In Comparative Examples 4-5, only carbon-coated natural graphite or artificial graphite was used, resulting in a significant decrease in the electrochemical performance of the batteries. In Comparative Example 3, the particle size of lithium nickel cobalt aluminum oxide was smaller than that of lithium manganese oxide, leading to a poorer lithium-ion transport path and a decrease in electrochemical performance.

[0091] The applicant declares that the above description is only a specific embodiment 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 conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A lithium-ion battery core, characterized in that, The core comprises a positive electrode plate, a diaphragm, and a negative electrode plate connected in sequence. The positive electrode material of the positive electrode sheet includes lithium manganese oxide and lithium nickel cobalt aluminum oxide, wherein the particle size of the lithium nickel cobalt aluminum oxide is larger than that of the lithium manganese oxide. The lithium manganese oxide has a particle size of 2~3µm, and the lithium nickel cobalt aluminum oxide has a particle size of 30~35µm; The negative electrode material of the negative electrode sheet includes carbon-coated natural graphite and artificial graphite. The lithium nickel cobalt aluminum oxide accounts for 60-90% of the mass fraction of the cathode material; The carbon-coated natural graphite accounts for 50-80% of the mass fraction of the negative electrode material.

2. A method for preparing a lithium-ion battery core as described in claim 1, characterized in that, The preparation method includes the following steps: The raw materials of the positive electrode sheet are mixed and coated onto the first current collector to prepare the positive electrode sheet. The raw materials of the negative electrode sheet are mixed and coated onto the second current collector to prepare the negative electrode sheet. The positive electrode sheet, the negative electrode sheet and the separator are wound together to obtain the core.

3. The preparation method according to claim 2, characterized in that, The raw materials for the positive electrode sheet also include conductive agents and binders.

4. The preparation method according to claim 3, characterized in that, The conductive agent includes Surpe-P and / or CNT.

5. The preparation method according to claim 3, characterized in that, The adhesive includes any one or a combination of at least two of PVDF, SBR, PAA, guar gum, or virgin gum.

6. The preparation method according to claim 2, characterized in that, The first current collector includes aluminum foil or carbon-coated aluminum foil.

7. The preparation method according to claim 2, characterized in that, The raw materials for the negative electrode sheet also include conductive agents, binders, and dispersants.

8. The preparation method according to claim 7, characterized in that, The conductive agent includes Surpe-P and / or CNT.

9. The preparation method according to claim 7, characterized in that, The adhesive includes CMC and / or PVDF.

10. The preparation method according to claim 7, characterized in that, The dispersant includes SBR.

11. The preparation method according to claim 2, characterized in that, The second current collector includes copper foil or carbon-coated copper foil.

12. A lithium-ion battery, characterized in that, The lithium-ion battery includes the lithium-ion battery core as described in claim 1, and the lithium-ion battery is obtained by injecting electrolyte into the lithium-ion battery core and then encapsulating it.

13. The lithium-ion battery according to claim 12, characterized in that, The solvent of the electrolyte includes any one or a combination of at least two of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, or propylene carbonate.

14. The lithium-ion battery according to claim 12, characterized in that, The lithium salt in the electrolyte includes any one or a combination of at least two of LiFP6, LiClO4, LiBOB, LiFSI, LiODFB, LiTFSI, or LiBF4.

15. The lithium-ion battery according to claim 14, characterized in that, The concentration of the lithium salt in the electrolyte is 1~3 mol / L.

16. The lithium-ion battery according to claim 12, characterized in that, The electrolyte additives include any one or a combination of at least two of vinyl sulfate, vinylene carbonate, fluorovinylene carbonate, or ethylene ethylene carbonate.

17. The lithium-ion battery according to claim 16, characterized in that, The additive accounts for 0.5-5% of the mass fraction of the electrolyte.

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