A multi-component positive electrode active material, a lithium ion battery positive electrode, a preparation method thereof and a high-rate lithium ion battery

Abstract

The application discloses a multi-component positive electrode active material, a lithium ion battery positive electrode and a preparation method thereof and a high-rate lithium ion battery, and belongs to the technical field of lithium ion batteries. The multi-component positive electrode active material comprises lithium iron manganese phosphate, spinel-type oxide, superconducting carbon black, nano carbon fiber and nano Li2Al2B2O7 powder. By controlling the particle size ratio and mass proportion of different materials, the internal electronic conductance of the positive electrode material is improved in a particle gap filling mode, and a continuous three-dimensional conductive network is constructed, so that the problem of weak rate performance caused by low electronic conductance and ionic conductivity is solved, the conductivity of the three-dimensional conductive network is enhanced, the electrode polarization is reduced, and finally the large-rate discharge performance is realized.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to a multi-component positive electrode active material, a lithium-ion battery positive electrode and its preparation method, and a high-rate lithium-ion battery. Background Technology

[0002] Lithium manganese iron phosphate (LMFP) has become the preferred cathode material for high-rate batteries due to its combination of the high safety of lithium iron phosphate and the high voltage advantage of lithium manganese phosphate. However, two major bottlenecks remain: First, insufficient electron and ion conductivity. This is because LMFP itself has low electronic conductivity and a small lithium-ion diffusion coefficient, making it difficult for a single material to meet the charge transport requirements at high rates. Existing conductive agents (such as SP) are mostly added randomly, failing to form a continuous conductive network, resulting in high resistance to electron transport. Second, there is a design conflict between the compaction density and porosity of LMFP. Traditional LMFP cathodes have a compaction density of only 2.4 g / cm³ due to loose particle packing (mostly single-size or disordered mixtures). Forcibly increasing the compaction density can easily lead to excessively low porosity, preventing the electrolyte from fully wetting the battery and exacerbating ion transport resistance, ultimately resulting in excessive internal resistance and causing battery degradation. On the other hand, maintaining high porosity sacrifices energy density and increases the contact resistance between particles, creating a dilemma between rate and energy density.

[0003] In existing technologies, although there have been attempts to improve performance by using spinel oxides or adding metal powders, there are obvious drawbacks: First, there is no extreme matching design for particle size, and the spinel particles and LMFP particles are mismatched in size, so they cannot effectively fill the gaps; Second, there is a lack of synergistic design of "gap filling-high compaction-conduction network". Traditional designs only focus on material composition and ignore the impact of structure on performance, resulting in no significant increase in electronic conductivity after compaction. In fact, particle breakage may even increase the battery's internal resistance, reduce conductivity and cycle performance. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a multi-component positive electrode active material, a lithium-ion battery positive electrode and its preparation method, and a high-rate lithium-ion battery. By using a technical route of multi-component positive electrode gradation design and precise filling of particle gaps, a continuous electron-ion conduction network is constructed to improve electronic conductivity and ion conductivity, ultimately achieving high-rate discharge performance.

[0005] To address the above technical problems, according to one aspect of the present invention, a multi-component positive electrode active material is provided, comprising lithium manganese iron phosphate, spinel oxide, superconducting carbon black, carbon nanofibers, and nano-Li2Al2B2O7 powder; wherein the spinel oxide is LiMn2O4 or LiNi. 0.5 Mn 1.5At least one of O4;

[0006] The particle size ratio of lithium manganese iron phosphate, spinel oxide, and superconducting carbon black is 1:0.4-0.5:0.15-0.16, and the mass ratio is 60.0-60.5:4.5-5.0:0.23-0.24.

[0007] In a preferred embodiment, the particle size of the lithium manganese iron phosphate is 4~20 μm.

[0008] In a preferred embodiment, the particle size of the superconducting carbon black is 0.15~0.8μm.

[0009] In a preferred embodiment, the fiber diameter of the nanofiber is 20-100 nm, and the particle size of the nanoLi2Al2B2O7 powder is 0.01~0.2 μm.

[0010] As a preferred embodiment, the mass ratio of nano-carbon fiber to nano-Li2Al2B2O7 powder is 1:3.

[0011] According to another aspect of the present invention, a lithium-ion battery cathode is provided, comprising the multi-component cathode active material and binder described above.

[0012] According to another aspect of the present invention, a method for preparing the above-described lithium-ion battery cathode is provided, comprising:

[0013] Step 1: Disperse the components of the multi-component positive electrode active material to form a positive electrode material mixture;

[0014] Step 2: The positive electrode material mixture is mixed and dispersed with PVDF adhesive to form a slurry;

[0015] Step 3: The slurry is coated onto aluminum foil, dried, and sliced ​​to form the positive electrode of a lithium-ion battery.

[0016] As a preferred embodiment, the PVDF adhesive is mixed and stirred with N-methylpyrrolidone to form the PVDF adhesive solution described in step two.

[0017] According to another aspect of the present invention, the application of the above-described lithium-ion battery cathode in the preparation of lithium-ion batteries is provided.

[0018] According to another aspect of the present invention, a high-rate lithium-ion battery is provided, comprising a positive electrode, a separator, a liquid electrolyte, and a negative electrode, wherein the positive electrode is the positive electrode of the lithium-ion battery described above.

[0019] The positive electrode active material provided by this invention improves the internal electronic conductivity of the positive electrode material by controlling the particle size ratio and mass percentage of different materials and filling the particle gaps. Simultaneously, it constructs a continuous three-dimensional conductive network, solving the problem of weak rate performance caused by low electronic and ionic conductivity. This enhances the conductivity of the three-dimensional conductive network and reduces electrode polarization. The spinel-type composite oxide can suppress LMFP lattice distortion and optimize cycle performance.

[0020] The lithium-ion battery prepared according to the present invention improves high-rate performance without reducing cycle performance, and achieves a 10C discharge capacity retention rate of ≥90%, which is superior to the traditional LMFP battery (10C discharge capacity retention rate ≤60%).

[0021] The lithium-ion battery provided by this invention is suitable for fast-charging new energy vehicles, drones, emergency power supplies and other fields. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the particle distribution inside the positive electrode active material of the present invention;

[0023] Figure 2 This is a comparison of the rate performance of lithium-ion batteries prepared in Example 1 and Comparative Examples 1 and 2;

[0024] Figure 3 This is a comparison of the cycle performance of lithium-ion batteries prepared in Example 2 and Comparative Examples 3 and 4;

[0025] Figure 4 This is a comparison of the DC internal resistance performance of lithium-ion batteries prepared in Example 3 and Comparative Examples 5 and 6. Detailed Implementation

[0026] The basic concept of this invention is to adopt a multi-component positive electrode gradation design and a technical approach of precise filling of particle gaps. By controlling the particle size ratio, volume ratio and mass ratio of different materials, small particles are used to fill the gaps between large particles to improve compaction and shorten the contact distance between particles, thereby improving electronic and ionic conductivity. This further constructs a highly efficient three-dimensional conductive network. Combined with an improved battery pre-formation process to optimize the negative electrode SEI film, this invention addresses the high-rate bottleneck of LMFP-based batteries from a structural perspective.

[0027] Based on the above concept, a typical embodiment of the present invention provides a multi-component positive electrode active material that adopts a multi-component polarity design, including lithium manganese iron phosphate (LiMn). x Fe 1-x PO4 (0.4≤X≤0.6, abbreviated as LMFP), spinel-type oxides, superconducting carbon black (SP), carbon nanofibers, and nano-Li2Al2B2O7 powder; the spinel-type oxide is LiMn2O4 or LiNi. 0.5 Mn1.5 At least one of O4.

[0028] like Figure 1 As shown, this embodiment uses lithium manganese iron phosphate and spinel-type oxides (LiMn2O4 / LiNi) with spherical particle morphology and uniform particle size. 0.5 Mn 1.5 Using O4 as the main component, superconducting carbon black, carbon nanofibers and nano Li2Al2B2O7 powder with specific particle sizes are compounded. By controlling the particle size ratio, mass ratio and volume ratio of the above materials, dense packing between cathode powder particles is achieved.

[0029] In this embodiment, the particle size ratio of lithium manganese iron phosphate, spinel oxide, and superconducting carbon black is 1:0.4-0.5:0.15-0.16, and the mass ratio is 60.0-60.5:4.5-5.0:0.23-0.24.

[0030] Lithium manganese iron phosphate (LMFP) forms the large particle matrix, while spinel-type oxide materials fill the primary gaps between LMFP particles through a gap-filling mechanism. Superconducting carbon black fills the secondary gaps formed by the LMFP and spinel-type oxide materials, achieving dense packing of the cathode powder particles. The spinel-type composite oxide suppresses LMFP lattice distortion and optimizes cycle performance. Nanofiber carbon and nanoLi₂Al₂B₂O₇ powder fill the remaining tiny gaps, constructing a three-dimensional conductive network of electrons and ions, significantly improving the electronic and ionic conductivity of the electrode, and thus significantly enhancing the rate performance of the battery.

[0031] For example, the particle size ratio of lithium manganese iron phosphate, spinel oxide, and superconducting carbon black can be 1:0.4:0.15, 1:0.5:0.16, or 1:0.45:0.156; the mass ratio can be 60.0:4.5:0.23, 60.5:5.0:0.24, or 60.25:4.85:0.235.

[0032] For example, in a preferred embodiment, the particle size ratio of lithium manganese iron phosphate, spinel oxide, and superconducting carbon black is strictly controlled to be 1:0.414:0.154, and the mass ratio is 60.318:4.871:0.235, ensuring close packing of the three materials. At this point, the volume ratio of the three materials is 16.755:1.188:0.124. The lithium manganese iron phosphate has a particle size of 4~20 μm, ensuring it serves as the basis for the packing of the main particles. For example, the particle size of lithium manganese iron phosphate can be 4μm, 5μm, 6μm, 8μm, 10μm, 15μm, 18μm, or 20μm.

[0033] The spinel-type oxide material (LiMn2O4 / LiNi) 0.5 Mn 1.5 The particle size of O4 is 0.8~10μm, which meets the first-level gap filling requirements. For example, the particle size of spinel type oxide materials can be 0.8μm, 1.0μm, 1.2μm, 1.6μm, 2μm, 5μm, 8μm, or 10μm.

[0034] Among the spinel-type oxide materials, LiMn2O4 and LiNi 0.5 Mn 1.5 When O4 and O4 are combined, the preferred mass ratio is 1:1.

[0035] The superconducting carbon black has a particle size of 0.15~0.8μm and a conductivity ≥100S / m, enabling secondary gap filling and constructing a continuous electron conduction path. For example, the superconducting carbon black has particle sizes of 0.15μm, 0.2μm, 0.3μm, 0.5μm, and 0.8μm.

[0036] The diameter of the carbon nanofiber is 20-100nm. For example, the diameter of the carbon nanofiber can be 20nm, 30nm, 50nm, 80nm, or 100nm.

[0037] The particle size of nano Li2Al2B2O7 powder is 0.01~0.2μm. For example, the particle size of nano Li2Al2B2O7 powder can be 0.01μm, 0.05μm, 0.08μm, 0.1μm, 0.15μm, or 0.2μm.

[0038] The preferred mass ratio of carbon nanofibers to nano Li2Al2B2O7 powder is 1:3, which is used to improve electronic and ionic conductivity.

[0039] Another typical embodiment of the present invention provides a lithium-ion battery cathode prepared based on the multi-component active material described above, the preparation method of which includes the following steps:

[0040] Step 1: Prepare a mixture of cathode materials

[0041] The components of the multi-component positive electrode active material described in the above embodiments are mixed and dispersed to form a positive electrode material mixture.

[0042] In this step, lithium manganese iron phosphate and spinel oxide are first stirred and dispersed evenly to form a positive electrode active material; then superconducting carbon black, carbon nanofibers, and nano Li2Al2B2O7 powder are compounded and added to the evenly mixed positive electrode active material to form a positive electrode material mixture, which is then stirred and dispersed evenly.

[0043] Step 2: Prepare the positive electrode slurry

[0044] The positive electrode material mixture is mixed and dispersed with PVDF adhesive to form a slurry with a solid content of 50% to 65%.

[0045] The adhesive solution is prepared by mixing PVDF binder and N-methylpyrrolidone, with a preferred mass ratio of 6:94. The preferred mass ratio of the positive electrode material mixture to the PVDF adhesive solution is 96~99:1~4.

[0046] Step 3: Prepare the positive electrode for lithium-ion batteries

[0047] The positive electrode slurry is dried and sliced ​​on aluminum foil with a thickness of 10μm to 12μm to form the positive electrode of a lithium-ion battery.

[0048] Another typical embodiment of the present invention provides a lithium-ion battery, which includes a positive electrode, a separator, a liquid electrolyte, and a negative electrode.

[0049] The positive electrode is a lithium-ion positive electrode prepared based on multi-component positive electrode active materials according to the present invention.

[0050] Graphite, conductive agent, sodium carboxymethyl cellulose, and styrene-butadiene rubber are mixed in a certain proportion to form a uniform slurry. The slurry is then coated, rolled, dried, and sliced ​​on a 6-12μm copper foil to form a negative electrode.

[0051] The positive electrode, separator, and negative electrode are stacked in an alternating sequence of positive electrode, separator, negative electrode, and positive electrode, or the stacked separator, positive electrode, separator, and negative electrode are wound to form a battery cell. Then, the battery cell is subjected to tab welding and aluminum-plastic film encapsulation.

[0052] The purpose of baking the battery cell is to remove excess moisture inside. After baking, electrolyte is injected, and then the cell is left to stand after injection.

[0053] Finally, by performing pre-formation, high-temperature aging, OCV testing, and room-temperature aging on the battery cells, an improved battery sample can be obtained.

[0054] The pre-formation process described above involves using low-current regimes of 0.01C, 0.02C, 0.05C, and 0.1C to activate and charge the battery. The purpose is to form a dense SEI film in the early stages, which is beneficial for optimizing rate and cycle performance.

[0055] The technical solutions claimed in this invention will be further described below through some embodiments. However, the embodiments and comparative examples are for explaining the implementation schemes of this invention and do not exceed the scope of the subject matter of this invention. The scope of protection of this invention is not limited by the embodiments. Unless otherwise specified, the materials and reagents used in this invention are all available from commercially available products in the art.

[0056] Example 1

[0057] Step (1): LMFP and LiMn2O4 are stirred and dispersed evenly to form a positive electrode active material; then SP, nano carbon fiber and nano Li2Al2B2O7 powder are added to the evenly mixed positive electrode active material and stirred and dispersed evenly to obtain a positive electrode material mixture.

[0058] Step (2): Mix the PVDF binder with N-methylpyrrolidone to obtain a PVDF solution. Add the cathode material mixture to the PVDF solution and disperse it evenly for 5 hours to form a cathode slurry with a solid content of 55%.

[0059] The mass ratio of LMFP, LiMn2O4, SP, nano carbon fiber, nano Li2Al2B2O7 powder, and PVDF adhesive mentioned above is 60.25 : 4.85 : 0.235 : 8.0 : 24 : 2.665.

[0060] The particle size of LMFP is 4μm, that of LiMn2O4 is 1.6μm, and that of SP is 0.6μm; the fiber diameter of the nanofiber is 50nm, and the particle size of the nanoLi2Al2B2O7 powder is 0.1μm.

[0061] Step (3) involves coating the positive electrode slurry onto a 10 μm aluminum foil to achieve a double-sided areal density of 35.2 ± 0.6 mg / cm². 2 Positive electrode sheet of specified specifications; the dried positive electrode sheet is priced at 2.4 g / cm³. 3 The process involves rolling, followed by electrode slitting, punching, and baking.

[0062] Step (4): Graphite, SP, sodium carboxymethyl cellulose and styrene-butadiene rubber are mixed in proportion to form a uniform slurry, which is then coated on a 6μm copper foil, and then rolled, dried and sliced ​​to form a negative electrode sheet.

[0063] Step (5): The secondary lithium-ion battery cell pack is manufactured by winding, and the tabs are welded and sealed. The outer shell of the packaging can be an aluminum-plastic film shell. The cell is baked to remove excess moisture. After baking, electrolyte is injected and then the cell is allowed to stand after electrolyte injection.

[0064] Step (6) involves pre-forming, high-temperature aging, OCV testing, and room-temperature aging of the battery cell to obtain a lithium-ion battery sample, denoted as 1-a.

[0065] The pre-formation process is as follows: (1) Let stand for 5 minutes; (2) Perform 0.01C constant current charging for 2 hours, 0.02C constant current charging for 2 hours, and 0.05C constant current charging for 2 hours in sequence; (3) Charge to 4.2V with 0.1C constant current and constant voltage, and cut off the current at 0.05C; (4) Let stand for 5 minutes, and discharge to 3.0V with 0.1C constant current; (5) Charge to 3.6V with 0.2C constant current and constant voltage, and cut off the current at 0.05C; (6) Remove the battery from the production line.

[0066] Comparative Example 1

[0067] The difference from Example 1 is that LiMn2O4 is not added to the cathode material mixture provided in step (1). The remaining steps are the same, and the obtained lithium-ion battery sample is denoted as 1-b.

[0068] Comparative Example 2

[0069] The difference from Example 1 is that no nanofibers and nanoLi2Al2B2O7 powder are added to the cathode material mixture provided in step (1). The remaining steps are the same, and the obtained lithium-ion battery sample is denoted as 1-c.

[0070] The liquid lithium-ion battery samples prepared in Example 1 and Comparative Examples 1 and 2 were fully charged at a charge / discharge current of 1C within the range of 3.0-4.2V, and then rate-tested at discharge currents of 0.1C, 0.5C, 1C, 2C, 3C, and 10C. The comparative data are as follows: Figure 2 As shown, the liquid lithium-ion battery of the present invention obviously has better rate discharge performance, with a 10C rate discharge performance of ≥90%.

[0071] Example 2

[0072] Step (1) involves mixing LMFP and LiNi. 0.5 Mn 1.5 O4 is stirred and dispersed evenly to form a positive electrode active material; then SP, nano carbon fiber and nano Li2Al2B2O7 powder are compounded and added to the evenly mixed positive electrode active material and stirred and dispersed evenly to obtain a positive electrode material mixture.

[0073] Step (2): Mix the PVDF binder with N-methylpyrrolidone to obtain a PVDF solution. Add the cathode material mixture to the PVDF solution and disperse it evenly for 5 hours to form a cathode slurry with a solid content of 50%.

[0074] The above-mentioned LMFP, LiNi 0.5 Mn 1.5 The mass ratio of O4, SP, nano carbon fiber, nano Li2Al2B2O7 powder, and PVDF adhesive is 60.25 : 4.85 : 0.235 : 8.0 : 24 : 2.665.

[0075] The particle size of LMFP is 4μm, that of LiMn2O4 is 1.6μm, that of SP is 0.6μm, that of carbon nanofiber is 50nm, and that of nano Li2Al2B2O7 powder is 0.1μm.

[0076] Step (3) involves coating the positive electrode slurry onto a 12μm aluminum foil to achieve a double-sided areal density of 35.2±0.6 mg / cm². 2 Positive electrode sheet of specified specifications; the dried positive electrode sheet is priced at 2.4 g / cm³. 3 The process involves rolling, followed by electrode slitting, punching, and baking.

[0077] Step (4): Graphite, SP, sodium carboxymethyl cellulose and styrene-butadiene rubber are mixed in proportion to form a uniform slurry, which is then coated on a 12μm copper foil, and then rolled, dried and sliced ​​to form a negative electrode sheet.

[0078] Step (5): The secondary lithium-ion battery cell pack is manufactured by winding, and the tabs are welded and sealed. The outer shell of the packaging can be an aluminum-plastic film shell. The cell is baked to remove excess moisture. After baking, electrolyte is injected and then the cell is allowed to stand after electrolyte injection.

[0079] Step (6) involves pre-forming, high-temperature aging, OCV testing, and room-temperature aging of the battery cell to obtain a lithium-ion battery sample, denoted as 2-a.

[0080] The pre-formation process is as follows: (1) Let stand for 5 minutes; (2) Perform 0.01C constant current charging for 2 hours, 0.02C constant current charging for 2 hours, and 0.05C constant current charging for 2 hours in sequence; (3) Charge to 4.2V with 0.1C constant current and constant voltage, and cut off the current at 0.05C; (4) Let stand for 5 minutes, and discharge to 3.0V with 0.1C constant current; (5) Charge to 3.6V with 0.2C constant current and constant voltage, and cut off the current at 0.05C; (6) Remove the battery from the production line.

[0081] Comparative Example 3

[0082] The difference from Example 2 is that LiNi is not added to the cathode material mixture provided in step (1). 0.5 Mn 1.5 O4. The remaining steps are the same, and the resulting lithium-ion battery sample is denoted as 2-b.

[0083] Comparative Example 4

[0084] The difference from Example 2 is that no nanofibers and nanoLi2Al2B2O7 powder are added to the cathode material mixture provided in step (1). The remaining steps are the same, and the obtained lithium-ion battery sample is denoted as 2-c.

[0085] The liquid lithium-ion battery samples prepared in Example 2 and Comparative Examples 3 and 4 were fully charged and then cycled at a charge-discharge current of 1C within the range of 3.0-4.2V. The comparative data are as follows: Figure 3 As shown, the liquid lithium-ion battery of the present invention obviously has better room temperature cycle performance.

[0086] Example 3

[0087] Step (1) involves mixing LMFP, LiMn2O4 / LiNi 0.5 Mn 1.5 The O4 mixture (mass ratio of 1:1) is stirred and dispersed evenly to form the positive electrode active material; then SP, nano carbon fiber and nano Li2Al2B2O7 powder are compounded and added to the evenly mixed positive electrode active material and stirred and dispersed evenly to obtain the positive electrode material mixture.

[0088] Step (2): Mix the PVDF binder with N-methylpyrrolidone to obtain a PVDF solution. Add the cathode material mixture to the PVDF solution and disperse it evenly for 5 hours to form a cathode slurry with a solid content of 50%.

[0089] The above-mentioned LMFP, LiMn2O4 / LiNi 0.5 Mn 1.5 The mass ratio of O4 mixture, SP, nano carbon fiber, nano Li2Al2B2O7 powder, and PVDF adhesive is 60.25 : 4.85 : 0.235 : 8.0 : 24 : 2.665.

[0090] The particle size of LMFP is 4μm, that of LiMn2O4 is 1.6μm, that of SP is 0.6μm, that of carbon nanofiber is 50nm, and that of nano Li2Al2B2O7 powder is 0.1μm.

[0091] Step (3) involves coating the positive electrode slurry onto a 12μm aluminum foil to achieve a double-sided areal density of 35.2±0.6 mg / cm². 2 Positive electrode sheet of specified specifications; the dried positive electrode sheet is priced at 2.4 g / cm³. 3 The process involves rolling, followed by electrode slitting, punching, and baking.

[0092] Step (4): Graphite, SP, sodium carboxymethyl cellulose and styrene-butadiene rubber are mixed in proportion to form a uniform slurry, which is then coated on a 10μm copper foil, and then rolled, dried and sliced ​​to form a negative electrode sheet.

[0093] Step (5): The secondary lithium-ion battery cell pack is fabricated using a stacking method, and the tabs are welded and packaged. The packaging shell can be an aluminum-plastic film shell. The cell is baked to remove excess internal moisture. After baking, electrolyte is injected, and then the cell is allowed to stand after electrolyte injection.

[0094] Step (6) involves pre-forming, high-temperature aging, OCV testing, and room-temperature aging of the battery cell to obtain a lithium-ion battery sample, denoted as 3-a.

[0095] The pre-formation process is as follows: (1) Let stand for 5 minutes; (2) Perform 0.01C constant current charging for 2 hours, 0.02C constant current charging for 2 hours, and 0.05C constant current charging for 2 hours in sequence; (3) Charge to 4.2V with 0.1C constant current and constant voltage, and cut off the current at 0.05C; (4) Let stand for 5 minutes, and discharge to 3.0V with 0.1C constant current; (5) Charge to 3.6V with 0.2C constant current and constant voltage, and cut off the current at 0.05C; (6) Remove the battery from the production line.

[0096] Comparative Example 5

[0097] The difference from Example 3 is that LiMn2O4 / LiNi is not added to the cathode material mixture provided in step (1). 0.5 Mn 1.5 O4. The remaining steps are the same, and the resulting lithium-ion battery sample is designated as 3-b.

[0098] Comparative Example 6

[0099] The difference from Example 3 is that no nanofibers and nanoLi2Al2B2O7 powder are added to the cathode material mixture provided in step (1). The remaining steps are the same, and the obtained lithium-ion battery sample is denoted as 3-c.

[0100] The liquid lithium-ion battery samples prepared in Example 3 and Comparative Examples 5 and 6 were charged and discharged for 15 seconds at a charge-discharge current of 2C within the range of 3.0-4.2V. The comparative data are as follows: Figure 4 As shown, the liquid lithium-ion battery of the present invention obviously has a lower DC internal resistance.

[0101] The scope of protection claimed by this invention is not limited to the specific embodiments described above. For those skilled in the art, this invention can have various modifications and alterations. Any modifications, improvements, and equivalent substitutions made within the concept and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A multi-component positive electrode active material, characterized in that, It includes lithium manganese iron phosphate, spinel oxide, superconducting carbon black, carbon nanofibers, and nano-Li2Al2B2O7 powder; the spinel oxide is LiMn2O4 or LiNi. 0.5 Mn 1.5 At least one of O4; The particle size ratio of lithium manganese iron phosphate, spinel oxide, and superconducting carbon black is 1:0.4-0.5:0.15-0.16, and the mass ratio is 60.0-60.5:4.5-5.0:0.23-0.

24. The nanofiber has a fiber diameter of 20-100 nm, and the nanoLi2Al2B2O7 powder has a particle size of 0.01-0.2 μm; the mass ratio of nanofiber to nanoLi2Al2B2O7 powder is 1:

3. Lithium manganese iron phosphate forms the main body of large particles. Spinel-type oxide fills the primary gaps between lithium manganese iron phosphate particles through a gap-filling method. Superconducting carbon black fills the secondary gaps formed by lithium manganese iron phosphate and spinel-type oxide, achieving dense packing between cathode powder particles. Nanofiber and nanoLi2Al2B2O7 powder fill the remaining tiny gaps.

2. The multi-component positive electrode active material according to claim 1, characterized in that: The particle size of the lithium manganese iron phosphate is 4~20 μm.

3. The multi-component positive electrode active material according to claim 1, characterized in that: The particle size of the superconducting carbon black is 0.15~0.8μm.

4. A lithium-ion battery positive electrode, characterized in that: It includes the multi-component positive electrode active material and binder as described in any one of claims 1-3.

5. The method for preparing the lithium-ion battery cathode according to claim 4, characterized in that, include: Step 1: Disperse the components of the multi-component positive electrode active material to form a positive electrode material mixture; Step 2: The positive electrode material mixture is mixed and dispersed with PVDF adhesive to form a slurry; Step 3: The slurry is coated onto aluminum foil, dried, and sliced ​​to form the positive electrode of a lithium-ion battery.

6. The method for preparing the lithium-ion battery cathode according to claim 5, characterized in that: The PVDF adhesive is mixed and stirred with N-methylpyrrolidone to form the PVDF adhesive solution described in step two.

7. The application of the lithium-ion battery cathode according to claim 4 in the preparation of lithium-ion batteries.

8. A high-rate lithium-ion battery, comprising a positive electrode, a separator, a liquid electrolyte, and a negative electrode, characterized in that: The positive electrode is the positive electrode of the lithium-ion battery according to claim 4.

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