Preparation method of pole piece for high-rate lithium ion battery and pole piece

Abstract

The invention discloses a preparation method of a pole piece for a high-rate lithium ion battery and the pole piece. The preparation method comprises the following steps: uniformly mixing an active material and a metal nanowire through a slurry mixing process to prepare mixed slurry; coating a current collector with the mixed slurry to prepare a pole piece prefabricated member; and performing surface scanning treatment on the pole piece prefabricated part by adopting plasma jet, completing welding between the metal nanowires in the pole piece prefabricated part and between the metal nanowires and the current collector, and constructing the pole piece with an integrated three-dimensional nano network structure in which a substrate layer shape and an active layer net shape are combined. The metal nanowire is used as the current collector in the electrode of the lithium ion battery to coat the active material, so that direct conduction of electrons between active material particles and the current collector is realized, the electron conductivity of the electrode material is improved, and the rate capability of the lithium ion battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and more specifically, relates to a method for preparing a pole piece for a high-rate lithium ion battery and a pole piece. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, good safety performance, long cycle life, and low self-discharge, and have been widely used in various fields such as civil, national defense, and aerospace. At present, the research hotspots on lithium-ion batteries are mostly focused on improving energy density. In some application fields, especially some national defense fields, the demand for high-rate performance lithium-ion batteries is more urgent.

[0003] There are many ways to improve the rate performance of lithium-ion batteries, including carbon coating on the surface of active materials, morphology optimization, doping modification, etc. However, these existing methods all have their own problems. It is difficult to obtain a uniform coating layer by surface carbon coating, and the coated carbon is mostly an amorphous carbon structure, which has limited improvement on the conductivity of the electrode. The most commonly used method for morphology optimization is nano-sizing, which increases the migration rate of lithium ions in active materials, but also reduces the tap density of electrode materials, and loses the battery energy density and cycle performance. As for doping modification, the doping mechanism and the mechanism of improving performance have not been thoroughly studied so far, and no unified conclusion has been reached. Summary of the invention

[0004] In view of the above defects or improvement needs of the prior art, the present invention provides a method for preparing a pole piece and a pole piece that can greatly improve the rate performance of a lithium-ion battery.

[0005] To achieve the above object, the present invention provides a method for preparing a pole piece for a high-rate lithium-ion battery, which comprises the following steps:

[0006] 1) uniformly mixing the active material and the metal nanowires through a slurrying process to form a mixed slurry;

[0007] 2) coating the mixed slurry onto the current collector to form a pole piece preform;

[0008] 3) The pole piece preform is subjected to surface scanning treatment by using a plasma jet to complete the welding between the metal nanowires inside the pole piece preform and between the metal nanowires and the current collector, so as to construct a pole piece with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh.

[0009] Preferably, in step 1), the active material is a positive electrode active material, the metal nanowire is an aluminum nanowire, and the current collector is an aluminum foil to make a positive electrode sheet preform.

[0010] The mass of the aluminum nanowires is 0.5-1.5% of the mass of the positive electrode active material, for example, 0.5%, 0.8%, 1%, 1.2% or 1.5%, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. If the mass proportion of the aluminum nanowires is too high, it will affect the energy density of the electrode, and if it is too low, it will affect the rate performance of the electrode.

[0011] The positive electrode active material includes various types of lithium battery positive electrode materials, such as lithium iron phosphate positive electrode, ternary positive electrode, lithium cobalt oxide positive electrode, lithium manganese oxide positive electrode, but is not limited to the listed electrode material types, and other unlisted electrode types are also applicable.

[0012] Preferably, in step 1), the active material is a negative electrode active material, the metal nanowires are copper nanowires, and the current collector is copper foil to form a negative electrode sheet preform.

[0013] The mass of the copper nanowires is 1-2% of the mass of the negative electrode active material, for example, 1%, 1.2%, 1.4%, 1.6%, 1.8% or 2%, but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. If the mass proportion of the copper nanowires is too high, it will affect the energy density of the electrode, and if it is too low, it will affect the rate performance of the electrode.

[0014] The negative electrode active material includes various types of lithium battery negative electrode materials, such as lithium titanate negative electrode, graphite negative electrode, silicon carbon negative electrode, but is not limited to the listed electrode material types, and other unlisted electrode types are also applicable.

[0015] Preferably, the plasma jet is a room temperature and normal pressure pulsed plasma jet, and the discharge working gas of the plasma jet is helium.

[0016] Preferably, the vertical distance between the plasma jet outlet and the positive electrode preform is 10-20 mm, for example, 10 mm, 12 mm, 14 mm, 16 mm, 18 mm or 20 mm, but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the speed of the plasma jet surface sweeping the positive electrode preform is 20-40 mm / s, for example, 20 mm / s, 25 mm / s, 30 mm / s, 35 mm / s or 40 mm / s, but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the distance between the plasma jet and the positive electrode preform is too close, which may cause the pole piece to burn, and too far will lead to incomplete optimization of the pole piece; the plasma jet surface sweep speed is too slow to affect the pole piece processing efficiency, and too fast will lead to incomplete optimization of the pole piece. .

[0017] Preferably, the vertical distance between the plasma jet outlet and the negative electrode preform is 5 to 10 mm, for example, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm or 10 mm, but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable; the rate at which the plasma jet surface scans the negative electrode preform is 10 to 30 mm / s, for example, 10 mm / s, 15 mm / s, 20 mm / s, 25 mm / s or 30 mm / s, but not limited to the listed values, and other values ​​not listed in the numerical range are also applicable. If the distance between the plasma jet and the negative electrode is too close, it may cause the electrode to burn, and if it is too far, the optimization treatment of the electrode will not be thorough; if the plasma jet surface scan speed is too slow, it will affect the efficiency of the electrode processing, and if it is too fast, the optimization treatment of the electrode will not be thorough. Compared with the positive electrode, the distance between the plasma jet and the negative electrode is closer and the scanning rate is slower, because the copper nanowires in the negative electrode have a higher melting point than the aluminum nanowires in the positive electrode.

[0018] The present invention also provides a pole piece for a high-rate lithium-ion battery, wherein the pole piece is prepared by the above method.

[0019] Conventional current collectors are only present as substrates below the active materials of lithium batteries, and are in direct contact with only the bottom active materials. Therefore, during charging and discharging, electrons need to be conducted layer by layer through active materials with low electronic conductivity. In the present invention, the integrated three-dimensional nanopole sheet structure obtained by room temperature and atmospheric pressure pulsed plasma jet treatment can realize direct conduction of electrons between active material particles and current collectors, improve the electronic conductivity of electrode materials, and thus improve the rate performance of lithium-ion batteries.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) The present invention uses metal nanowires as internal current collectors of lithium-ion battery electrodes to coat active materials. The metal nanowire current collectors have the following advantages: high conductivity, which greatly reduces the ohmic impedance of the battery; small mass ratio, small battery capacity loss; large porosity, which will not hinder the embedding and de-embedding of lithium ions.

[0022] 2) The present invention utilizes room temperature and atmospheric pressure pulsed plasma jet technology to realize the welding of metal nanowires in the active material of lithium-ion batteries, and constructs an integrated three-dimensional nano-network structure electrode sheet combining the electrode substrate layer and the active layer mesh, which can greatly improve the rate performance of lithium-ion batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the plasma jet used in the present invention to treat a lithium-ion battery pole piece;

[0024] Figure 2It is a schematic diagram of the mixing of active material particles and metal nanowires in the lithium ion battery electrode of the present invention;

[0025] Figure 3 This is a schematic diagram of the welding of metal nanowires inside the lithium-ion battery electrode of the present invention;

[0026] Figure 4 It is a schematic diagram of welding between metal nanowires inside the lithium-ion battery electrode and the metal substrate of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] The method for preparing a pole piece for a high-rate lithium-ion battery of the present invention comprises the following steps:

[0029] 1) The positive electrode active material and the aluminum nanowires are uniformly mixed through a slurrying process to form a positive electrode mixed slurry, and the negative electrode active material and the copper nanowires are uniformly mixed through a slurrying process to form a negative electrode mixed slurry; the mass of the aluminum nanowires is 0.5-1.5% of the mass of the positive electrode active material, and the mass of the copper nanowires is 1-2% of the mass of the negative electrode active material.

[0030] 2) coating the positive electrode mixed slurry onto the positive electrode current collector to form a positive electrode sheet preform; coating the negative electrode mixed slurry onto the negative electrode current collector to form a negative electrode sheet preform;

[0031] 3) The positive electrode preform is subjected to surface scanning treatment by using a plasma jet (the discharge working gas is helium) to complete the welding between the metal nanowires inside the positive electrode preform and between the metal nanowires and the current collector, and to construct a positive electrode with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh;

[0032] Similarly, a plasma jet (the discharge working gas is helium) is used to perform surface scanning on the negative electrode preform to complete the welding between the metal nanowires inside the negative electrode preform and between the metal nanowires and the current collector, thereby constructing a negative electrode preform with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh.

[0033] The vertical distance between the plasma jet outlet and the positive electrode preform is 10-20 mm, and the speed at which the plasma jet surface sweeps the positive electrode preform is 20-40 mm / s; the vertical distance between the plasma jet outlet and the negative electrode preform is 5-10 mm, and the speed at which the plasma jet surface sweeps the negative electrode preform is 10-30 mm / s.

[0034] Finally, it is assembled into a high-rate lithium-ion battery.

[0035] Figure 1 It is a schematic diagram of a three-dimensional nano-network structure electrode piece constructed by scanning a battery electrode piece with a plasma jet in the method of the present invention, and is composed of a high-voltage electrode 1, a quartz tube 2, a plasma jet 3, an active material 4, and a current collector 5. Figure 2 Schematic diagram of a battery electrode, including a current collector 5, metal nanowires 6, and active material particles 7. Figure 3 This is a schematic diagram of the welding of metal nanowires inside the electrode. Through the treatment of plasma jets with different discharge parameters, the positive electrode aluminum nanowires and the negative electrode copper nanowires are welded at the contact points. Figure 4 This is a schematic diagram of the welding between the metal nanowires in the electrode and the base metal foil. The contact points between the positive electrode aluminum nanowires and the aluminum foil, and the contact points between the negative electrode copper nanowires and the copper foil are all welded.

[0036] In order to explain the method of the present invention in more detail, the following is described in conjunction with embodiments:

[0037] Example 1

[0038] 1) The lithium iron phosphate positive electrode active material and the aluminum nanowires are uniformly mixed through a slurrying process to form a positive electrode mixed slurry, and the graphite negative electrode active material and the copper nanowires are uniformly mixed through a slurrying process to form a negative electrode mixed slurry; the mass of the aluminum nanowires is 1% of the mass of the positive electrode active material, and the mass of the copper nanowires is 1% of the mass of the negative electrode active material.

[0039] 2) coating the positive electrode mixed slurry onto the positive electrode current collector to form a positive electrode sheet preform; coating the negative electrode mixed slurry onto the negative electrode current collector to form a negative electrode sheet preform;

[0040] 3) The positive electrode preform is subjected to surface scanning treatment by using a plasma jet (the discharge working gas is helium) to complete the welding between the metal nanowires inside the positive electrode preform and between the metal nanowires and the current collector, and to construct a positive electrode with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh;

[0041] Similarly, a plasma jet (the discharge working gas is helium) is used to perform surface scanning on the negative electrode preform to complete the welding between the metal nanowires inside the negative electrode preform and between the metal nanowires and the current collector, thereby constructing a negative electrode preform with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh.

[0042] The vertical distance between the plasma jet outlet and the positive electrode preform is 18 mm, and the rate at which the plasma jet surface sweeps the positive electrode preform is 30 mm / s; the vertical distance between the plasma jet outlet and the negative electrode preform is 6 mm, and the rate at which the plasma jet surface sweeps the negative electrode preform is 15 mm / s.

[0043] Assemble high-rate performance lithium iron phosphate / graphite batteries and test rate performance.

[0044] Example 2

[0045] 1) The lithium iron phosphate positive electrode active material and the aluminum nanowires are uniformly mixed through a slurrying process to form a positive electrode mixed slurry, and the graphite negative electrode active material and the copper nanowires are uniformly mixed through a slurrying process to form a negative electrode mixed slurry; the mass of the aluminum nanowires is 1.5% of the mass of the positive electrode active material, and the mass of the copper nanowires is 2% of the mass of the negative electrode active material.

[0046] 2) coating the positive electrode mixed slurry onto the positive electrode current collector to form a positive electrode sheet preform; coating the negative electrode mixed slurry onto the negative electrode current collector to form a negative electrode sheet preform;

[0047] 3) The positive electrode preform is subjected to surface scanning treatment by using a plasma jet (the discharge working gas is helium) to complete the welding between the metal nanowires inside the positive electrode preform and between the metal nanowires and the current collector, and to construct a positive electrode with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh;

[0048] Similarly, a plasma jet (the discharge working gas is helium) is used to perform surface scanning on the negative electrode preform to complete the welding between the metal nanowires inside the negative electrode preform and between the metal nanowires and the current collector, thereby constructing a negative electrode preform with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh.

[0049] The vertical distance between the plasma jet outlet and the positive electrode preform is 10 mm, and the rate at which the plasma jet surface sweeps the positive electrode preform is 20 mm / s; the vertical distance between the plasma jet outlet and the negative electrode preform is 10 mm, and the rate at which the plasma jet surface sweeps the negative electrode preform is 30 mm / s.

[0050] Assemble high-rate performance lithium iron phosphate / graphite batteries and test rate performance.

[0051] Example 3

[0052] 1) The 523 series ternary positive electrode active material and aluminum nanowires are uniformly mixed through a slurrying process to form a positive electrode mixed slurry, and the graphite negative electrode active material and copper nanowires are uniformly mixed through a slurrying process to form a negative electrode mixed slurry; the mass of the aluminum nanowires is 1% of the mass of the positive electrode active material, and the mass of the copper nanowires is 2% of the mass of the negative electrode active material.

[0053] 2) coating the positive electrode mixed slurry onto the positive electrode current collector to form a positive electrode sheet preform; coating the negative electrode mixed slurry onto the negative electrode current collector to form a negative electrode sheet preform;

[0054] 3) The positive electrode preform is subjected to surface scanning treatment by using a plasma jet (the discharge working gas is helium) to complete the welding between the metal nanowires inside the positive electrode preform and between the metal nanowires and the current collector, and to construct a positive electrode with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh;

[0055] Similarly, a plasma jet (the discharge working gas is helium) is used to perform surface scanning on the negative electrode preform to complete the welding between the metal nanowires inside the negative electrode preform and between the metal nanowires and the current collector, thereby constructing a negative electrode preform with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh.

[0056] The vertical distance between the plasma jet outlet and the positive electrode preform is 18 mm, and the rate at which the plasma jet surface sweeps the positive electrode preform is 30 mm / s; the vertical distance between the plasma jet outlet and the negative electrode preform is 6 mm, and the rate at which the plasma jet surface sweeps the negative electrode preform is 15 mm / s.

[0057] Assemble high-rate performance ternary / graphite batteries and test rate performance.

[0058] Example 4

[0059] 1) The 523 series ternary positive electrode active material and aluminum nanowires are uniformly mixed through a slurrying process to form a positive electrode mixed slurry, and the graphite negative electrode active material and copper nanowires are uniformly mixed through a slurrying process to form a negative electrode mixed slurry; the mass of the aluminum nanowires is 1.5% of the mass of the positive electrode active material, and the mass of the copper nanowires is 2% of the mass of the negative electrode active material.

[0060] 2) coating the positive electrode mixed slurry onto the positive electrode current collector to form a positive electrode sheet preform; coating the negative electrode mixed slurry onto the negative electrode current collector to form a negative electrode sheet preform;

[0061] 3) The positive electrode preform is subjected to surface scanning treatment by using a plasma jet (the discharge working gas is helium) to complete the welding between the metal nanowires inside the positive electrode preform and between the metal nanowires and the current collector, and to construct a positive electrode with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh;

[0062] Similarly, a plasma jet (the discharge working gas is helium) is used to perform surface scanning on the negative electrode preform to complete the welding between the metal nanowires inside the negative electrode preform and between the metal nanowires and the current collector, thereby constructing a negative electrode preform with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh.

[0063] The vertical distance between the plasma jet outlet and the positive electrode preform is 10 mm, and the rate at which the plasma jet surface sweeps the positive electrode preform is 20 mm / s; the vertical distance between the plasma jet outlet and the negative electrode preform is 10 mm, and the rate at which the plasma jet surface sweeps the negative electrode preform is 30 mm / s.

[0064] Assemble high-rate performance ternary / graphite batteries and test rate performance.

[0065] Comparative Example 1

[0066] The method is the same as Example 1 except that in step 1), no aluminum nanowires are added to the positive electrode slurry and no copper nanowires are added to the negative electrode slurry.

[0067] Comparative Example 2

[0068] The method is the same as Example 3 except that in step 1), no aluminum nanowires are added to the positive electrode slurry and no copper nanowires are added to the negative electrode slurry.

[0069] The rate performance test results are shown in Table 1:

[0070] Table 1

[0071] Example / Comparative Example Rate capability Example 1 50C Example 2 50C Example 3 60C Example 4 60C Comparative Example 1 20C Comparative Example 2 30C

[0072] From Table 1, we can see the following points:

[0073] (1) It can be seen from Examples 1 to 4 that the amount of metal nanowires mixed in step 1) of the method has a great influence on the final electrode rate performance.

[0074] (2) It can be seen from Example 1 and Comparative Example 1 that the mixing of metal nanowires in the method and the welding effect of the plasma jet on the metal nanowires have a significant effect on improving the rate performance of the lithium iron phosphate battery electrode.

[0075] (3) It can be seen from Example 3 and Comparative Example 2 that the mixing of metal nanowires in the method and the welding effect of the plasma jet on the metal nanowires have a significant effect on improving the rate performance of the ternary battery electrode.

[0076] In summary, in the method of the present invention, an integrated three-dimensional nano-network structure current collector combining a substrate layer surface and an active layer mesh is constructed, and metal nanowires are used as internal current collectors of lithium-ion battery electrodes to coat active materials, thereby achieving direct conduction of electrons between active material particles and current collectors, thereby improving the electronic conductivity of the electrode material and thus improving the rate performance of lithium-ion batteries.

[0077] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a pole piece for a high-rate lithium-ion battery, characterized in that: It includes the following steps: 1) uniformly mixing the active material and the metal nanowires through a slurrying process to form a mixed slurry; 2) coating the mixed slurry onto the current collector to form a pole piece preform; 3) The pole piece preform is subjected to surface scanning treatment by using a plasma jet to complete the welding between the metal nanowires inside the pole piece preform and between the metal nanowires and the current collector, so as to construct a pole piece with an integrated three-dimensional nano-network structure combining the substrate layer surface and the active layer mesh.

2. The method for preparing a pole piece for a high-rate lithium-ion battery according to claim 1, characterized in that: In the step 1), the active material is a positive electrode active material, the metal nanowire is an aluminum nanowire, and the current collector is an aluminum foil to prepare a positive electrode sheet preform.

3. The method for preparing a pole piece for a high-rate lithium-ion battery according to claim 2, characterized in that: The mass of the aluminum nanowires is 0.5-1.5% of the mass of the positive electrode active material.

4. The method for preparing a pole piece for a high-rate lithium-ion battery according to claim 1, characterized in that: In the step 1), the active material is a negative electrode active material, the metal nanowire is a copper nanowire, and the current collector is a copper foil to prepare a negative electrode sheet preform.

5. The method for preparing a pole piece for a high-rate lithium-ion battery according to claim 4, characterized in that: The mass of the copper nanowires is 1-2% of the mass of the negative electrode active material.

6. The method for preparing a pole piece for a high-rate lithium-ion battery according to claim 1, characterized in that: The plasma jet is a room temperature and normal pressure pulsed plasma jet.

7. The method for preparing a pole piece for a high-rate lithium-ion battery according to claim 1 or 6, characterized in that: The discharge working gas of the plasma jet is helium.

8. The method for preparing a pole piece for a high-rate lithium-ion battery according to claim 2, characterized in that: The vertical distance between the plasma jet outlet and the positive electrode plate preform is 10 to 20 mm; the speed at which the plasma jet surface sweeps the positive electrode plate preform is 20 to 40 mm / s.

9. The method for preparing a pole piece for a high-rate lithium-ion battery according to claim 4, characterized in that: The vertical distance between the plasma jet outlet and the negative electrode piece preform is 5 to 10 mm; the speed at which the plasma jet surface sweeps the negative electrode piece preform is 10 to 30 mm / s.

10. A pole piece for a high-rate lithium-ion battery, characterized in that: The pole piece is prepared by the preparation method according to any one of claims 1 to 8.

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