Positive electrode active layer material of lithium ion battery, positive electrode plate and lithium ion battery

Abstract

The invention relates to a lithium ion battery positive electrode active layer material, a positive electrode plate and a lithium ion battery. The lithium ion battery positive electrode active layer material comprises a positive electrode material, a conductive agent, a binder, an inorganic solid electrolyte and [3-(trimethoxysilyl) propyl] succinic anhydride. Water and acidic substances in the electrolyte are removed through the [3-(trimethoxysilyl) propyl] succinic anhydride, corrosion of the acidic substances in the electrolyte to the positive electrode material is avoided, and the [3-(trimethoxysilyl) propyl] succinic anhydride and the inorganic solid electrolyte can form an interfacial film on the surface of the positive electrode material, so that the positive electrode material is prevented from being damaged. Therefore, the electrolyte is further prevented from damaging the positive electrode material, the long-term stability of the lithium ion battery is improved, meanwhile, the inorganic solid electrolyte can also improve the ionic conductivity of the positive electrode surface, and the rate capability of the lithium ion battery is improved. Therefore, the lithium ion battery positive electrode active layer material can improve the rate capability and the high-temperature storage performance of the lithium ion battery at the same time.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials, and in particular relates to a lithium-ion battery positive electrode active layer material, a positive electrode sheet and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries have the advantages of high operating voltage, light weight, no memory effect, low self-discharge rate, long cycle life, and high energy density. They are currently widely used in mobile phones, computers, electric vehicles, etc. In recent years, out of consideration for environmental protection, electric vehicles have been rapidly developed under the promotion of governments and automobile manufacturers, and lithium-ion secondary batteries have become the ideal power source for the new generation of electric vehicles with their excellent performance.

[0003] At present, based on the fast charging demand of lithium-ion batteries, researchers have developed niobium-based negative electrode materials, especially niobium titanium oxide materials. However, the voltage platform of niobium titanium oxide negative electrode materials is greater than 1V. When niobium titanium oxide negative electrode materials are matched with conventional lithium iron phosphate or nickel-cobalt-manganese ternary materials, the overall voltage platform of lithium-ion batteries drops significantly, and the energy density is not competitive. Therefore, it is necessary to develop high-voltage positive electrode materials to match them.

[0004] Lithium nickel manganese oxide is a high-voltage positive electrode material that is currently being studied more. Its cost and thermal stability are better than those of nickel-cobalt-manganese ternary materials. However, the acidic substances produced in lithium-ion batteries will corrode lithium nickel manganese oxide, resulting in irreversible loss of lithium nickel manganese oxide positive electrode materials, causing more positive electrode surfaces to be exposed to the electrolyte to oxidize the electrolyte, and also causing the lithium nickel manganese oxide positive electrode materials to dissolve manganese ions. The dissolved manganese ions migrate to the electrolyte and the negative electrode to participate in more side reactions, thereby causing the rapid attenuation of lithium ion capacity during the cycle and storage process. In addition, the high-voltage lithium nickel manganese oxide has a large particle size, which is not conducive to the high-rate cycle performance of lithium-ion batteries. Summary of the invention

[0005] In order to solve the above problems existing in the prior art, the present invention provides a lithium ion battery positive electrode active layer material, a positive electrode sheet and a lithium ion battery. The technical problem to be solved by the present invention is achieved by the following technical solutions:

[0006] The first aspect of the present invention provides a positive electrode active layer material for a lithium ion battery, comprising: a positive electrode material, a conductive agent, a binder, an inorganic solid electrolyte and [3-(trimethoxysilyl)propyl]succinic anhydride.

[0007] In one achievable manner, the inorganic solid electrolyte comprises an inorganic compound having a perovskite structure, an inorganic compound having a LISICON structure, a Li-ion having a NASICON framework structure, 1+x Al x Ti 2-x(PO4)3、Li 3.6 Si 0.6 PO4, amorphous Li 2.9 PO 3.3 N 0.46 , lithium calcium zirconium oxide, Li7La3Zr2O with garnet structure 12 One or more of , where 0.1≤x≤0.4.

[0008] In one achievable manner, the content of the inorganic solid electrolyte in the positive electrode active layer material is 0.2-2 wt %.

[0009] In one achievable manner, the content of the [3-(trimethoxysilyl)propyl]succinic anhydride in the positive electrode active layer material is 0.1 to 1 wt %.

[0010] In one achievable manner, the positive electrode material includes spinel-type lithium nickel manganese oxide doped with a doping element;

[0011] The doping elements include one or more of Al, Mg, Fe, Co, Y, Sc, Ru, Cu, Mo, Ce, W, Nb, Ta, Zr, Ca, P, S, F, B, Si and Sr.

[0012] In one achievable manner, the conductive agent includes: one or more of carbon black, carbon nanotubes, graphene, and conductive graphite.

[0013] In one achievable manner, the binder includes: one or more of PVDF, CMC, PAA, polyacrylate, polyacrylonitrile, and nitrile rubber.

[0014] The second aspect of the present invention provides a lithium ion battery positive electrode sheet, comprising: a current collector and the lithium ion battery positive electrode active layer material provided by the first aspect of the present invention;

[0015] The positive electrode active layer material is coated on the surface of the current collector.

[0016] The third aspect of the present invention provides a lithium ion battery, comprising: an electrolyte, a separator, a negative electrode plate and the positive electrode plate provided by the second aspect of the present invention;

[0017] The separator is disposed between the negative electrode sheet and the positive electrode sheet, and the separator, the negative electrode sheet and the positive electrode sheet are all located in the electrolyte.

[0018] In one achievable manner, the electrolyte includes a solvent, an electrolyte salt and an additive;

[0019] The electrolyte salt includes: one or more of LiPF6, LiClO4, LiFSI, LiTFSI or LiBF4;

[0020] The negative electrode plate includes niobium titanium oxide negative electrode material.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The positive electrode active layer material of the lithium ion battery provided by the present invention removes water and acidic substances in the electrolyte through [3-(trimethoxysilyl)propyl]succinic anhydride, thereby preventing the acidic substances in the electrolyte from corroding the positive electrode material, and [3-(trimethoxysilyl)propyl]succinic anhydride and the inorganic solid electrolyte can form an interface film on the surface of the positive electrode material to further prevent the electrolyte from damaging the positive electrode material, thereby improving the long-term stability of the lithium ion battery, and at the same time, the inorganic solid electrolyte can also improve the ionic conductivity of the positive electrode surface, thereby improving the rate performance of the lithium ion battery. Therefore, the positive electrode active layer material of the lithium ion battery can simultaneously improve the rate performance and high temperature storage performance of the lithium ion battery. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto.

[0024] A first aspect of the present embodiment provides a positive electrode active layer material for a lithium-ion battery, comprising: a positive electrode material, a conductive agent, a binder, an inorganic solid electrolyte and [3-(trimethoxysilyl)propyl]succinic anhydride (TPSA).

[0025] Specifically, [3-(trimethoxysilyl)propyl]succinic anhydride has a good dehydration and deacidification effect, which can inhibit the damage of water acid in the electrolyte to the positive electrode material, and [3-(trimethoxysilyl)propyl]succinic anhydride can be well attached to the surface of the positive electrode material through Si-O bonds to form a dense and long-term stable interface film, thereby improving the high temperature storage performance of lithium-ion batteries; inorganic solid electrolytes can be wrapped on the surface of the positive electrode material through physical action to form an interface film, protect the positive electrode interface to inhibit the oxidation and decomposition of the electrolyte, and at the same time, inorganic solid electrolytes can also improve the ionic conductivity of the positive electrode surface and improve the rate performance of lithium-ion batteries. Therefore, under the dehydration and deacidification effect of [3-(trimethoxysilyl)propyl]succinic anhydride, [3-(trimethoxysilyl)propyl]succinic anhydride and inorganic solid electrolytes form an interface film through chemical and physical actions respectively to protect the positive electrode material and improve the ionic conductivity of the positive electrode surface, thereby simultaneously improving the rate performance and high temperature storage performance of lithium-ion batteries.

[0026] In this embodiment, the inorganic solid electrolyte includes: an inorganic compound with a perovskite structure, an inorganic compound with a LISICON (lithium super ion conductor) structure, and a Li-ion electrolyte with a NASICON (sodium super ion conductor) skeleton structure. 1+ x Al x Ti 2-x (PO4)3、Li 3.6 Si 0.6 PO4, amorphous Li 2.9 PO 3.3 N 0.46 , lithium calcium zirconium oxide, Li7La3Zr2O with garnet structure 12 One or more of, wherein 0.1≤x≤0.4. Furthermore, the inorganic solid electrolyte comprises the above substances and their coated doped derivatives. The content of the inorganic solid electrolyte in the positive electrode active layer material is 0.2-2wt%. The content of [3-(trimethoxysilyl)propyl]succinic anhydride in the positive electrode active layer material is 0.1-1wt%.

[0027] In this embodiment, the positive electrode material includes spinel lithium nickel manganese oxide (LiNi 0.5 Mn 1.5 O4), doping elements include: one or more of Al, Mg, Fe, Co, Y, Sc, Ru, Cu, Mo, Ce, W, Nb, Ta, Zr, Ca, P, S, F, B, Si and Sr. Conductive agents include: one or more of carbon black, carbon nanotubes, graphene, and conductive graphite. Binders include: one or more of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polyacrylic acid (PAA), polyacrylate, polyacrylonitrile, and nitrile rubber.

[0028] The second aspect of this embodiment provides a lithium-ion battery positive electrode plate, comprising: a current collector and the lithium-ion battery positive electrode active layer material provided by the first aspect of this embodiment, wherein the positive electrode active layer material is coated on the surface of the current collector.

[0029] The third aspect of this embodiment provides a lithium-ion battery, comprising: an electrolyte, a diaphragm, a negative electrode plate and the positive electrode plate provided by the second aspect of this embodiment, wherein the diaphragm is arranged between the negative electrode plate and the positive electrode plate, and the diaphragm, the negative electrode plate and the positive electrode plate are all located in the electrolyte.

[0030] In the present embodiment, the negative electrode plate includes a niobium titanium oxide negative electrode material. The diaphragm can be a conventional electrochemical battery diaphragm that can isolate electrons and allow metal ions (such as lithium ions) to pass through; it can also be any one of an organic polymer diaphragm or an inorganic diaphragm. Exemplarily, the diaphragm can be selected from any one of a polyethylene porous membrane, a polypropylene porous membrane, a polyethylene-polypropylene double-layer porous membrane, a polypropylene-polyethylene-polypropylene three-layer porous membrane, a glass fiber porous membrane, a non-woven porous membrane, an electrospun porous membrane, a PVDF-HFP porous membrane, and a polyacrylonitrile porous membrane. Furthermore, the non-woven diaphragm can be listed as polyimide nanofiber non-woven fabric, polyethylene terephthalate (PET) nanofiber non-woven fabric, cellulose nanofiber non-woven fabric, aramid nanofiber non-woven fabric, nylon nanofiber non-woven fabric, and polyvinylidene fluoride (PVDF) nanofiber non-woven fabric. Examples of the electrospun porous membrane include polyimide electrospun membranes, polyethylene terephthalate electrospun membranes, and polyvinylidene fluoride electrospun membranes.

[0031] In this embodiment, the electrolyte includes a solvent, an electrolyte salt and an additive. Furthermore, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) or lithium tetrafluoroborate (LiBF4). The negative electrode plate includes a niobium titanium oxide negative electrode material.

[0032] In an achievable manner, the solvent includes: one or more of fluorocarbonate, fluorocarboxylate, fluoroether, nitrile, and sulfone. Preferably, the solvent includes: one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, bisfluoroethylene carbonate, trifluoromethylethylene carbonate, pentafluoroethylethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methylpropyl carbonate, methyl trifluoromethyl carbonate, methyl trifluoroethyl carbonate, ethyl trifluoroethyl carbonate, di(2,2,2-trifluoroethyl) carbonate, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, or 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0033] In one achievable manner, the additive includes: one or more of lithium difluorooxalatoborate, lithium difluorophosphate, 1,3-propane sultone, 1,3-propylene sultone, fluoroethylene carbonate, vinyl sulfate, succinonitrile, adiponitrile, 1,3,6-hexanetrinitrile, tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, and tris(trimethylsilyl)phosphite.

[0034] The method for preparing the positive electrode active layer material of a lithium ion battery provided in this embodiment comprises:

[0035] The positive electrode material, the binder, the conductive agent, the inorganic solid electrolyte and TPSA are mixed according to a certain proportion, and N-methylpyrrolidone (NMP) is added and stirred to prepare the positive electrode active layer material.

[0036] The method for preparing the positive electrode sheet of a lithium-ion battery provided in this embodiment includes:

[0037] The positive electrode active layer material is then evenly coated on the surface of the aluminum foil current collector. The coated aluminum foil current collector is dried at room temperature and then transferred to a 130°C oven for drying. It is then cold pressed, trimmed, cut into pieces, and striped, and the tabs are welded to make positive electrode sheets.

[0038] The method for preparing a lithium-ion battery provided in this embodiment includes:

[0039] Preparation of negative electrode sheet: The negative electrode materials niobium titanium oxide (TiNb2O7), polyvinylidene fluoride, and conductive carbon black are dissolved in N-methylpyrrolidone (NMP) at a mass ratio of 95:2:3 and mixed evenly to form a negative electrode slurry. The negative electrode slurry is then evenly coated on the current collector copper foil, then dried at 130°C, and then cold pressed, trimmed, cut, and striped, and the tabs are welded to form a negative electrode sheet.

[0040] Preparation of electrolyte: In a glove box, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) were mixed in a mass ratio of 2:2:3:3 to obtain a mixed solvent, and electrolyte salt (LiPF6) was slowly added to the mixed solvent and mixed evenly to prepare an electrolyte. The mass content of the electrolyte salt in the electrolyte was 14%.

[0041] The positive electrode sheet, negative electrode sheet and separator are wound into a bare battery cell and then loaded into an aluminum-plastic film. Then, they are baked at 100°C to remove water, and then the electrolyte is injected and sealed. After standing, hot and cold pressing, formation, exhaust, and capacity separation, a lithium-ion battery is obtained.

[0042] Furthermore, in this embodiment, polyvinylidene fluoride is used as a binder, conductive carbon black is used as a conductive agent, spinel type lithium nickel manganese oxide is used as a positive electrode material, and Li 1+x Al x Ti 2-x(PO4)3(LATP) is an inorganic solid electrolyte, and the contents of the positive electrode material, binder, conductive agent, LATP and TPSA in the positive electrode active layer material of the lithium ion battery are changed, and several groups of positive electrode active layer materials of lithium ion batteries are prepared by the above preparation method, which are recorded as Examples 1 to 7. A control group is set up and recorded as Comparative Examples 1 to 3. The contents of each component in Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Table 1, and the positive electrode active layer materials of lithium ion batteries shown in Examples 1 to 7 and Comparative Examples 1 to 3 are prepared into lithium ion batteries according to the above preparation method, and the following performance tests are performed:

[0043] (1) Lithium-ion battery 25°C 3C / 3C cycle test:

[0044] First, let the lithium-ion battery stand for 30 minutes at 25°C, discharge it to 1.5V at a constant current of 1C, and then stand for 5 minutes; then charge it to 3.6V at a constant current of 3C, further charge it to a current of 0.1C at a constant voltage of 3.6V, and then stand for 5 minutes, and then discharge it to 1.5V at a constant current of 3C. This is a charge and discharge cycle process, and the obtained discharge capacity is the discharge capacity Ca of the lithium-ion battery. After that, 300 charge and discharge cycles are performed, and the discharge capacity of the 300th cycle is recorded as Cb. 25°C 3C / 3C cycle capacity retention rate (%) = Cb / Ca.

[0045] (2) Lithium-ion battery 60°C storage test:

[0046] First, let the lithium-ion battery stand at 25°C for 30 minutes; charge it to 3.6V at a constant current of 1C, and further charge it to 0.1C at a constant voltage of 3.6V; then test the volume of the battery using the drainage method, which is the volume before storage V A The lithium-ion battery was then stored at 60°C and the volume of the test battery was taken out every 10 days. It was then charged to 3.6V at a constant current of 1C and further charged to a current of 0.1C at a constant voltage of 3.6V. The battery was taken out after 60 days of storage at 60°C and the volume of the test battery was V B . Lithium-ion battery storage volume expansion rate at 60°C (%) = (V B -V A ) / V A .

[0047] After being stored at 60°C for 60 days, the test battery was taken out and its volume was measured, and then the battery SOC was adjusted to the full discharge state; then the battery was disassembled, the negative electrode active plate was taken out, and the content of metallic manganese in the negative electrode plate was tested by the ICP method.

[0048] The performance test results of Examples 1 to 7 and Comparative Examples 1 to 3 are shown in Table 2.

[0049] Table 1: Content of each component in Examples 1 to 7 and Comparative Examples 1 to 3

[0050] Group Positive electrode material content (%) Conductive agent content (%) Binder content (%) LATP content (%) TPSA content (%) Example 1 90.0 5.3 4.0 0.2 0.5 Example 2 90.0 4.5 4.0 1.0 0.5 Example 3 90.0 3.5 4.0 2.0 0.5 Example 4 90.0 2.5 4.0 3.0 0.5 Example 5 90.0 4.9 4.0 1.0 0.1 Example 6 90.0 4.0 4.0 1.0 1.0 Example 7 90.0 3.0 4.0 1.0 2.0 Comparative Example 1 90.0 6.0 4.0 / / Comparative Example 2 90.0 5.0 4.0 1.0 / Comparative Example 3 90.0 5.5 4.0 / 0.5

[0051] Table 2: Lithium-ion battery performance test results

[0052]

[0053]

[0054] It can be concluded from Comparative Examples 1, 2 and 3 that, compared with the cases where no LATP and TPSA are added to the positive electrode active layer material, after LATP and TPSA are added to the positive electrode active layer material respectively, the 25°C rate cycling, 60°C storage volume expansion and metal ion deposition are improved to varying degrees. LATP has a more obvious improvement on the 25°C rate cycling due to its ability to improve conductivity, while TPSA has a more obvious improvement on the 60°C storage due to the stability of the interface film and the effect of removing water and acid.

[0055] It can be concluded from Comparative Example 2, Comparative Example 3 and Example 2 that after adding LATP and TPSA at the same time, the 25°C rate cycle and 60°C storage performance are significantly improved compared to adding only LATP or TPSA.

[0056] It can be concluded from Examples 1 to 4 and Comparative Example 3 that as the LATP content increases, various properties are improved. However, when the content increases to a certain amount, especially at 25°C rate cycling, obvious attenuation occurs. It is speculated that when the LATP content is too high, the thick wrapping of the positive electrode material will also hinder the transmission channel of lithium ions.

[0057] It can be concluded from Example 2, Examples 5 to 7 and Comparative Example 2 that as the TPSA content increases, various performances are improved to varying degrees. However, when the content is too high, the 25°C rate cycle also shows obvious attenuation. It is speculated that when there is too much TPSA, the interfacial impedance formed at the positive electrode is significantly increased, thereby hindering the rapid transmission of lithium ions.

[0058] The positive electrode active layer material of the lithium ion battery provided in this embodiment removes water and acidic substances in the electrolyte through [3-(trimethoxysilyl)propyl]succinic anhydride to avoid corrosion of the positive electrode material by the acidic substances in the electrolyte, and [3-(trimethoxysilyl)propyl]succinic anhydride and the inorganic solid electrolyte can form an interface film on the surface of the positive electrode material to further avoid the electrolyte from damaging the positive electrode material and improve the long-term stability of the lithium ion battery. At the same time, the inorganic solid electrolyte can also improve the ionic conductivity of the positive electrode surface and improve the rate performance of the lithium ion battery. Therefore, the positive electrode active layer material of the lithium ion battery provided in this embodiment can simultaneously improve the rate performance and high temperature storage performance of the lithium ion battery.

[0059] The above contents are further detailed descriptions of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as falling within the protection scope of the present invention.

Claims

1. A lithium ion battery positive electrode active layer material, characterized in that: include: Positive electrode material, conductive agent, binder, inorganic solid electrolyte and [3-(trimethoxysilyl)propyl]succinic anhydride.

2. The lithium-ion battery positive electrode active layer material according to claim 1, characterized in that: The inorganic solid electrolyte includes: an inorganic compound with a perovskite structure, an inorganic compound with a LISICON structure, and a Li with a NASICON skeleton structure. 1+x Al x Ti 2-x (PO4)3、Li 3.6 Si 0.6 PO4, amorphous Li 2.9 PO 3.3 N 0.46 , lithium calcium zirconium oxide, Li7La3Zr2O with garnet structure 12 One or more of , where 0.1≤x≤0.

4.

3. The lithium-ion battery positive electrode active layer material according to claim 1, characterized in that: The content of the inorganic solid electrolyte in the positive electrode active layer material is 0.2-2 wt %.

4. The lithium-ion battery positive electrode active layer material according to claim 1, characterized in that: The content of [3-(trimethoxysilyl)propyl]succinic anhydride in the positive electrode active layer material is 0.1 to 1 wt %.

5. The lithium-ion battery positive electrode active layer material according to claim 1, characterized in that: The positive electrode material includes spinel-type lithium nickel manganese oxide doped with a doping element; The doping elements include one or more of Al, Mg, Fe, Co, Y, Sc, Ru, Cu, Mo, Ce, W, Nb, Ta, Zr, Ca, P, S, F, B, Si and Sr.

6. The lithium-ion battery positive electrode active layer material according to claim 1, characterized in that: The conductive agent includes: one or more of carbon black, carbon nanotubes, graphene, and conductive graphite.

7. The lithium-ion battery positive electrode active layer material according to claim 1, characterized in that: The binder includes: one or more of PVDF, CMC, PAA, polyacrylate, polyacrylonitrile, and nitrile rubber.

8. A positive electrode plate for a lithium-ion battery, characterized in that: include: A current collector and a positive electrode active layer material for a lithium ion battery according to any one of claims 1 to 7; The positive electrode active layer material is coated on the surface of the current collector.

9. A lithium ion battery, characterized in that: include: An electrolyte, a separator, a negative electrode sheet and a positive electrode sheet as claimed in claim 8; The separator is disposed between the negative electrode sheet and the positive electrode sheet, and the separator, the negative electrode sheet and the positive electrode sheet are all located in the electrolyte.

10. The lithium ion battery according to claim 9, characterized in that: The electrolyte comprises a solvent, an electrolyte salt and an additive; The electrolyte salt includes one or more of LiPF6, LiClO4, LiFSI, LiTFSI or LiBF4; The negative electrode plate includes niobium titanium oxide negative electrode material.

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