Carbon fiber electrode, preparation method thereof and lithium ion battery

Abstract

The invention discloses a carbon fiber electrode, a preparation method thereof and a lithium ion battery, the carbon fiber electrode comprises a carbon fiber current collector, the surface of the carbon fiber current collector is coated with an electrode active material; the edge of the carbon fiber current collector extends outwards to form a tab connecting part, the surface of the tab connecting part is plated with a metal layer, and the carbon fiber electrode is connected with a tab through the metal layer. The conductivity of the metal layer is obviously higher than that of the conductive adhesive, so that compared with the existing carbon fiber electrode, the carbon fiber electrode provided by the invention has the advantages that the interface contact resistance between the carbon fiber electrode and the tab is obviously reduced, and the cycle performance and the capacity retention ratio of the lithium ion battery prepared from the carbon fiber electrode provided by the invention are relatively high.

Description

Technical Field

[0001] The present invention relates to the field of electrochemical technology, and in particular to a carbon fiber electrode, a preparation method thereof and a lithium ion battery. Background Art

[0002] Carbon fiber has excellent mechanical properties such as high specific strength and high modulus, as well as high specific surface area and excellent electrochemical stability, making it suitable as an electrode material for lithium-ion batteries. When carbon fiber is used as an electrode, several bundles of carbon fiber are usually woven together to form a carbon fiber electrode, and then a metal tab is connected to the edge of the carbon fiber electrode to introduce and extract the current.

[0003] Currently, the connection between carbon fiber electrodes and metal tabs is usually carried out using conductive glue. This connection method will increase the interface contact resistance between the electrode and the tab, and the cycle performance and capacity retention rate of lithium-ion batteries made with such electrodes are low. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problem that the cycle performance and capacity retention rate of lithium ion batteries made of existing carbon fiber electrodes are low.

[0005] In order to achieve the above-mentioned purpose, the present invention provides a carbon fiber electrode, comprising: a carbon fiber current collector, the surface of which is coated with an electrode active material; the edge of the carbon fiber current collector extends outward to form a pole ear connection portion, the surface of the pole ear connection portion is plated with a metal layer, and is connected to the pole ear through the metal layer.

[0006] Optionally, when the carbon fiber electrode is a positive electrode, the metal layer is an aluminum layer; when the carbon fiber electrode is a negative electrode, the metal layer is a copper layer.

[0007] Optionally, when the carbon fiber electrode is a positive electrode, the electrode active material includes at least one of lithium iron phosphate, lithium cobalt oxide, and lithium nickel cobalt manganese oxide. When the carbon fiber electrode is a negative electrode, the electrode active material includes at least one of graphite, silicon, and silicon dioxide.

[0008] Optionally, when the carbon fiber electrode is a positive electrode, the carbon fiber current collector is made of hydrophobic carbon fiber; when the carbon fiber electrode is a negative electrode, the carbon fiber current collector is made of hydrophilic carbon fiber.

[0009] Optionally, the length of the tab connection portion is 2 mm to 10 mm.

[0010] The present invention also provides a method for preparing the above-mentioned carbon fiber electrode, comprising:

[0011] Step 1: providing a carbon fiber current collector, wherein the carbon fiber current collector has an outwardly extending tab connection portion.

[0012] Step 2, coating the surface of the carbon fiber current collector with electrode active material, and after drying, plating a metal layer on the surface of the tab connection portion.

[0013] The plating method of the above-mentioned metal layer includes at least one of evaporation, electroplating, chemical plating and magnetron sputtering.

[0014] In the above step 2, the drying temperature is 150° C. to 200° C., and the drying time is 1 h to 3 h.

[0015] The present invention also provides a lithium ion battery, which comprises the carbon fiber electrode.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The present invention provides a carbon fiber electrode, which is plated with a metal layer at a pole ear connection portion and is connected to the pole ear through the metal layer. Since the conductivity of the metal layer is significantly higher than that of the conductive glue, compared with the existing carbon fiber electrode (the existing carbon fiber electrode does not contain a metal layer and can only be connected to the pole ear by conductive glue), the interface contact resistance between the carbon fiber electrode provided by the present invention and the pole ear is significantly reduced, and the lithium ion battery made by the present invention has higher cycle performance and capacity retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of the carbon fiber electrode of the present invention.

[0019] Figure 2 This is a physical picture of the carbon fiber electrode of the present invention.

[0020] Figure 3 This is an electron scanning micrograph of the carbon fiber electrode of the present invention.

[0021] Figure 4 This is a charge and discharge test diagram of the carbon fiber electrode of the present invention.

[0022] Figure 5 This is a cycle performance diagram of the carbon fiber electrode of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and embodiments.

[0024] like Figure 1 and Figure 2As shown, the present invention provides a carbon fiber electrode, comprising: a carbon fiber current collector 1, the surface of the carbon fiber current collector 1 is coated with an electrode active material; the edge of the carbon fiber current collector 1 extends outward to form a pole ear connection part 2, the surface of the pole ear connection part 2 is plated with a metal layer, and the carbon fiber electrode is connected to the pole ear through the metal layer. Since the conductivity of the metal layer is significantly higher than that of the conductive glue, compared with the existing carbon fiber electrode (the existing carbon fiber electrode does not contain a metal layer and can only be connected to the pole ear by conductive glue), the interface contact resistance between the carbon fiber electrode provided by the present invention and the pole ear is significantly reduced, and the lithium ion battery made by the present invention has a higher cycle performance and capacity retention rate.

[0025] In some embodiments, the connection method between the carbon fiber electrode and the metal pole ear 4 can be ultrasonic welding, and the welding part 3 is located on the surface of the metal layer. As a good conductive material, the metal layer can be tightly connected to the metal pole ear 4 by ultrasonic welding. The reason why the welding part 3 is located at the metal layer is that the metal layer has a certain toughness and hardness, which is suitable as a welding material for ultrasonic welding. If the welding part 3 is located at the carbon fiber current collector 1 coated with active material, the current collector can be easily crushed under ultrasonic conditions.

[0026] Generally, the metal tab can be connected to one or both sides of the carbon fiber electrode. The width of the metal tab should be greater than or equal to the width of the metal layer. If the width of the metal tab is too small, the contact area between the metal tab and the metal layer will be too small, increasing the interface contact resistance between the electrode and the tab.

[0027] In some embodiments, when the carbon fiber electrode is used as the positive electrode, the metal layer is made of aluminum; when the carbon fiber electrode is used as the negative electrode, the metal layer is made of copper. The reason for using aluminum and copper to prepare the metal layer is that both aluminum and copper have excellent conductivity and are relatively low in price, and are the preferred materials for the metal layer. Aluminum is used for the positive electrode because the positive electrode of the battery has a high potential and is corrosive to metals, and the surface of aluminum has an oxide layer that can protect aluminum. Copper is easily corroded at high potentials, so copper cannot be used in the positive electrode but can only be used in the negative electrode.

[0028] In some embodiments, the carbon fiber current collector 1 is usually woven from a plurality of bundles of carbon fibers. When the carbon fiber electrode of the present invention is used as a positive electrode, the carbon fiber current collector 1 is made of hydrophobic carbon fiber (purchased from Taiwan Carbon Energy Technology Co., Ltd.). When the carbon fiber electrode of the present invention is used as a negative electrode, the carbon fiber current collector 1 is made of hydrophilic carbon fiber (purchased from Taiwan Carbon Energy Technology Co., Ltd.).

[0029] The present invention also provides a method for preparing the above-mentioned carbon fiber electrode, comprising the following steps:

[0030] Step 1, providing a carbon fiber current collector 1, wherein the carbon fiber current collector 1 has a tab connecting portion 2 extending outward.

[0031] Step 2, coating the surface of the carbon fiber current collector 1 with electrode active material, and plating a metal layer on the surface of the tab connection portion 2 after drying.

[0032] In some embodiments, the metal layer can be prepared by at least one of evaporation, electroplating, chemical plating, and magnetron sputtering. Figure 3 As shown, since the carbon fiber current collector is woven with carbon fibers with gaps between the carbon fibers, the metal layer will not only cover the surface of the current collector during the plating process, but will also penetrate into the interior of the current collector, increasing the contact area between the current collector and the metal layer, and further reducing the interface contact resistance between the electrode and the tab.

[0033] In some embodiments, when the carbon fiber electrode of the present invention is used as a positive electrode, the electrode active material is made of at least one of lithium iron phosphate, lithium cobalt oxide, and lithium nickel cobalt manganese oxide. When the carbon fiber electrode of the present invention is used as a negative electrode, the electrode active material is made of graphite, silicon, silicon dioxide or its derivatives.

[0034] In some embodiments, when the carbon fiber electrode of the present invention is used as a positive electrode, the electrode tab used is an aluminum electrode tab, and when the carbon fiber electrode of the present invention is used as a negative electrode, the electrode tab used is a copper electrode tab.

[0035] The technical details are further illustrated below in conjunction with embodiments.

[0036] Example 1

[0037] This embodiment provides a method for preparing a carbon fiber electrode, which is used as a positive electrode and is prepared by the following steps:

[0038] S1, taking a carbon fiber current collector, wherein the carbon fiber current collector is made of hydrophobic carbon fiber.

[0039] S2, the electrode active material lithium nickel cobalt manganese oxide (purchased from Ningbo Rongbai New Energy Technology Co., Ltd., S96E) is coated on the carbon fiber current collector by spraying or transfer coating, leaving a portion of uncoated area for subsequent formation of the pole ear connection part.

[0040] S3, drying the electrode active material at 150°C to 200°C for 1h to 3h. Then punching the current collector according to the shape, so that the area not coated with the electrode active material is punched into a tab connection part, the length of the tab connection part is 10mm, and the width is 5mm. Then, an aluminum metal layer is plated on the surface of the tab connection part to obtain the carbon fiber electrode of this embodiment.

[0041] In this embodiment, the loading amount of the aluminum metal layer on the tab connection portion is 5 g / cm 2 .

[0042] The carbon fiber electrode and the lithium metal negative electrode of this embodiment are stacked to form a lithium metal battery, and the battery is subjected to charge and discharge tests. Figure 4 As shown, the charge and discharge curve of the carbon fiber electrode of this embodiment is normal, indicating that the carbon fiber electrode of this embodiment can play a normal charge and discharge characteristic. Figure 5 As shown, the battery is cycled 200 times at 0.2C and the capacity retention rate is still 90.1%, indicating that the carbon fiber electrode of this embodiment has good cycle performance and capacity retention rate.

[0043] In summary, the present invention provides a carbon fiber electrode, which is plated with a metal layer at the connecting portion of the pole lug, and is connected to the pole lug through the metal layer. Since the conductivity of the metal layer is significantly higher than that of the conductive glue, compared with the existing carbon fiber electrode (the existing carbon fiber electrode does not contain a metal layer and can only be connected to the pole lug using a conductive glue), the interface contact resistance between the carbon fiber electrode provided by the present invention and the pole lug is significantly reduced, and the cycle performance and capacity retention rate of the lithium ion battery made by the present invention are higher.

[0044] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A carbon fiber electrode, characterized in that: include: A carbon fiber current collector, the surface of which is coated with an electrode active material; The edge of the carbon fiber current collector extends outward to form a pole lug connecting portion, and the surface of the pole lug connecting portion is plated with a metal layer, and is connected to the pole lug through the metal layer.

2. The carbon fiber electrode according to claim 1, characterized in that: When the carbon fiber electrode is a positive electrode, the metal layer is an aluminum layer; when the carbon fiber electrode is a negative electrode, the metal layer is a copper layer.

3. The carbon fiber electrode according to claim 1, characterized in that: When the carbon fiber electrode is a positive electrode, the electrode active material includes at least one of lithium iron phosphate, lithium cobalt oxide, and lithium nickel cobalt manganese oxide.

4. The carbon fiber electrode according to claim 1, characterized in that: When the carbon fiber electrode is a negative electrode, the electrode active material includes at least one of graphite, silicon, and silicon monoxide.

5. The carbon fiber electrode according to claim 1, characterized in that: When the carbon fiber electrode is a positive electrode, the carbon fiber current collector is made of hydrophobic carbon fiber; when the carbon fiber electrode is a negative electrode, the carbon fiber current collector is made of hydrophilic carbon fiber.

6. The carbon fiber electrode according to claim 1, characterized in that: The length of the pole ear connecting portion is 2 mm to 10 mm.

7. A method for preparing a carbon fiber electrode according to any one of claims 1 to 6, characterized in that: include: Step 1, providing a carbon fiber current collector, wherein the carbon fiber current collector has an outwardly extending tab connection portion; Step 2, coating the surface of the carbon fiber current collector with electrode active material, and after drying, plating a metal layer on the surface of the tab connection portion.

8. The method for preparing a carbon fiber electrode according to claim 7, characterized in that: In step 2, the plating method of the metal layer includes at least one of evaporation, electroplating, chemical plating, and magnetron sputtering.

9. The method for preparing a carbon fiber electrode according to claim 7, characterized in that: In step 2, the drying temperature is 150° C. to 200° C., and the drying time is 1 h to 3 h.

10. A lithium ion battery, characterized in that: A carbon fiber electrode comprising any one of claims 1 to 6.

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