Negative plate for improving charging capability and lithium ion battery

Abstract

The utility model relates to a negative pole piece capable of improving charging capability, which comprises a current collector and a negative pole piece prepared by drying an active material layer coated on the current collector, a plurality of parallel laser etching grooves are arranged on the active material layer through laser etching lines, the distance between the laser etching grooves is 0.5 mm-5 mm, and the distance between the laser etching grooves is 0.5 mm-5 mm. The depth of the laser etching groove is 2%-10% of the thickness of the active material layer, and the width of the laser etching groove is 4-10 times of the depth of the laser etching groove. And preparing the lithium ion battery by adopting the negative plate for improving the charging capability. According to the lithium ion battery, the negative pole piece is modified macroscopically, so that the liquid retention capacity of the battery can be effectively improved while the thickness of the battery cell is not influenced, and the charging capacity of the lithium ion battery under normal-temperature and low-temperature conditions is improved. The lithium ion battery prepared from the negative pole piece shows more excellent low-temperature cycle performance, and lithium is not separated out when the lithium ion battery is subjected to low-temperature cycle at a high charging rate.

Description

Technical Field

[0001] The utility model belongs to the technical field of lithium batteries, and in particular relates to a negative electrode sheet and a lithium ion battery with improved charging capacity. Background Art

[0002] As an important energy storage device, lithium-ion batteries play a key role in electric vehicles, mobile devices, and renewable energy. In order to further improve the endurance and standby time, it is necessary to develop lithium-ion batteries with higher energy density. Thick electrodes do not need to change the existing battery electrochemical system, but increase the energy density by increasing the proportion of electrochemically active substances in the battery cell, which is easier to apply and promote in actual production. However, the thick electrode makes the diffusion kinetics of lithium ions worse due to the thickening of the active material layer, especially at low temperature conditions and high charge and discharge rates, forming a lithium concentration gradient along the thickness of the film. At present, there are methods such as chemical etching, 3D printing, and sacrificial templates to construct fast charge transfer channels with low tortuosity, but the above methods are prone to damage to the graphite crystal structure, partial inactivation of active materials, and reduced energy density of the electrode. Laser etching technology causes little damage to the graphite crystal structure by ablating the electrode pole piece at high temperature, while improving the pole piece liquid absorption rate and battery charging capacity. The patent document with the authorization announcement number CN 203932198 U discloses a lithium-ion battery electrode sheet and a lithium-ion battery, wherein the electrode sheet includes a current collector and an active material layer coated on the current collector, wherein a groove is provided on the active material layer, wherein the width of the groove is 30 microns ≤ ≤ 100 microns, the depth of the groove is 10 microns ≤ ≤ 4 / 5 of the thickness of the active material layer, and the thickness of the active material layer is 50 to 300 microns. The lithium-ion battery electrode sheet can improve the rate performance of button batteries, but the groove depth is shallow and the line spacing is too narrow, which easily leads to a large loss of active materials and has limited improvement on the charging capacity of the battery cell. Utility Model Content

[0003] The purpose of the utility model is to overcome the shortcomings of the above-mentioned technology and provide a negative electrode sheet and a lithium-ion battery with improved charging capacity. The negative electrode sheet is modified to reduce the tortuosity of the electrode sheet while maintaining the overall structural stability of the graphite electrode sheet, increase the path for lithium ion transmission, and improve the porosity and liquid absorption rate of the electrode sheet.

[0004] In order to achieve the above-mentioned purpose, the utility model adopts the following technical scheme: a negative electrode sheet with improved charging capacity, including a current collector and an active material layer coated on the current collector, which is dried to form a negative electrode sheet, and a plurality of mutually parallel laser-etched grooves are made on the active material layer by laser scribing, wherein the spacing between the laser-etched grooves is 0.5mm-5mm, the depth of the laser-etched grooves is 2%-10% of the thickness of the active material layer, and the width is 4-10 times the depth of the laser-etched grooves.

[0005] Furthermore, the active material of the negative electrode plate includes one or more of graphite, carbon microspheres, graphene, silicon negative electrode and its composite material or tin negative electrode and its composite material.

[0006] Furthermore, the thickness of the negative electrode plate is 60-180 μm.

[0007] Furthermore, the laser scribing adopts one or more of gas laser, crystal laser, semiconductor laser or fiber laser.

[0008] Furthermore, the laser etching atmosphere is one or more of vacuum, nitrogen or air atmosphere.

[0009] Furthermore, the scanning rate of the laser scribing is 2000-5000 cm / s; the laser energy is 15-55%.

[0010] A lithium-ion battery made with a negative electrode sheet that improves charging capacity.

[0011] Beneficial effects: Compared with the prior art, the utility model modifies the negative electrode plate at a macroscopic level, which can effectively increase the battery liquid retention without affecting the thickness of the battery cell, and improve the charging capacity of lithium-ion batteries under normal and low temperature conditions. Compared with the traditional method of doping and coating active materials, which requires system development, it is simpler and easier to implement, and the preparation process is simple and controllable, which can achieve large-scale preparation and promotion; in addition, the method has a small loss of active materials, while maintaining the overall structural stability of the graphite electrode plate, reducing the tortuosity of the plate, increasing the path of lithium ion transmission, and improving the plate porosity and liquid absorption rate; the lithium-ion battery made of the negative electrode plate prepared by the utility model shows a more excellent low-temperature cycle performance, and there is no lithium precipitation in low-temperature cycling at a high charging rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 This is a structural front view of the three-dimensional negative electrode sheet of the utility model;

[0013] Figure 2 yes Figure 1 A top view of

[0014] Figure 3 It is the capacity retention curve after low temperature cycle of Example 1 and Comparative Example 1.

[0015] In the figure: A-active material layer width, B-etching line width, C-etching line depth. DETAILED DESCRIPTION

[0016] In order to more clearly understand the above-mentioned purposes, features and advantages of the utility model, the utility model is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other. In the following description, many specific details are set forth in order to fully understand the utility model, and the described embodiments are only part of the embodiments of the utility model, rather than all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the utility model. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by technicians in the technical field of the utility model. The terms used herein in the specification of the utility model are only for the purpose of describing specific embodiments and are not intended to limit the utility model.

[0017] In the various embodiments of the present invention, for the convenience of description rather than limitation of the present invention, the term "connection" used in the patent application specification and claims of the present invention is not limited to physical or mechanical connection, but may include electrical connection, whether direct or indirect. "Up", "down", "below", "left", "right", etc. are only used to indicate relative position relationship. When the absolute position of the described object changes, the relative position relationship also changes accordingly.

[0018] As shown in the accompanying drawings for details, this embodiment provides a negative electrode sheet with improved charging capacity, including a current collector and an active material layer coated on the current collector, which is dried to form a negative electrode sheet, and a plurality of mutually parallel laser-etched grooves are made on the active material layer by laser scribing, wherein the spacing between the laser-etched grooves is 0.5 mm-5 mm, the depth of the laser-etched grooves is 2%-10% of the thickness of the active material layer, and the width is 4-10 times the depth of the laser-etched grooves.

[0019] A preferred solution of this embodiment is that the active material of the negative electrode plate includes one or more of graphite, carbon microspheres, graphene, silicon negative electrode and its composite material or tin negative electrode and its composite material.

[0020] A preferred solution of this embodiment is that the thickness of the negative electrode plate is 60-180 μm.

[0021] A preferred solution of this embodiment is that the laser scribing adopts one or more of gas laser, crystal laser, semiconductor laser or fiber laser.

[0022] A preferred solution of this embodiment is that the laser etching atmosphere is one or more of vacuum, nitrogen or air atmosphere.

[0023] The preferred solution of this embodiment is that the scanning rate of the laser scribing is 2000-5000 cm / s; and the laser energy is 15-55%.

[0024] A lithium-ion battery made with a negative electrode sheet that improves charging capacity. Example

[0025] The thickness of the graphite negative electrode sheet is 160μm. After coating, baking and rolling, the electrode sheet is laser etched using a laser light source. The etching line depth is 15μm, the line width is 95μm, and the line-to-line spacing is 1.5 mm. The equipment parameters are a laser scanning rate of 3000cm / s and a laser energy of 30%. The resulting negative electrode sheet is C1.

[0026] The performance test cell is a 515974 soft-pack lithium-ion battery with a capacity of 4Ah. The positive electrode active material of the battery is high-voltage lithium cobalt oxide, and the negative electrode is the above-mentioned three-dimensional negative electrode sheet. The resulting battery is recorded as CC1. Example

[0027] The thickness of the graphite negative electrode sheet is 160μm. After coating, baking and rolling, the electrode sheet is laser etched using a laser light source. The etching line depth is 20μm, the line width is 100μm, and the line-to-line spacing is 2 mm. The equipment parameters are laser scanning rate of 2500cm / s and laser energy of 35%. The obtained negative electrode sheet is C2.

[0028] The performance test cell is a 515974 soft-pack lithium-ion battery with a capacity of 4Ah. The positive electrode active material of the battery is high-voltage lithium cobalt oxide, and the negative electrode is the above-mentioned three-dimensional negative electrode sheet. The resulting battery is recorded as CC2. Example

[0029] The thickness of the graphite negative electrode plate is 160μm. After coating, baking and rolling, the plate is laser etched using a laser light source. The etching line depth is 8μm, the line width is 80μm, and the line spacing is 1 mm. The equipment parameters are laser scanning rate of 4000cm / s and laser energy of 30%. The obtained negative electrode plate is C3.

[0030] The performance test cell is a 515974 soft-pack lithium-ion battery with a capacity of 4Ah. The positive electrode active material of the battery is high-voltage lithium cobalt oxide, and the negative electrode is the above-mentioned three-dimensional negative electrode sheet. The resulting battery is recorded as CC3.

[0031] Comparative Example 1

[0032] In this comparative example, the thickness of the graphite negative electrode sheet is 160 μm. After coating, baking and rolling, the obtained negative electrode sheet is recorded as C4. Subsequently, the negative electrode sheet and the positive electrode sheet separator are wound to form a 515974 soft-pack lithium-ion battery with a capacity of 4Ah. The obtained battery is recorded as CC4.

[0033] Test Method

[0034] 1. Pole end test

[0035] Liquid absorption capacity test: Use a micro-injector to quantify 1-10 μL of electrolyte injected into the battery cell. The timing starts when the electrolyte contacts the electrode and stops when the electrolyte droplet is completely absorbed. The results of the embodiment are shown in Table 1.

[0036] Powder loss test: weigh the pole piece before laser etching, recorded as m1, weigh the pole piece after laser etching as m2, powder loss = (m1-m2) / m1*100%.

[0037] Table 1

[0038] Pole Solution Absorption time (s) Powder loss (%) C1 112.1 1.01% C2 102.8 0.98% C3 119.2 1.00% C4 157.8 0

[0039] 2. Charging capacity test

[0040] Example 1 and Comparative Example 1 were charged at 0.5C, 0.6C, 0.7C, 0.8C, 0.9C, and 1C at 10 degrees Celsius, and discharged at 0.5C. The thickness expansion rate was shown in Table 2 after 25 cycles. The capacity retention rate of Example 1 and Comparative Example 1 under the conditions of charging to the maximum voltage at 0.7C and discharging at 0.5C was shown in Table 2. Figure 3 .

[0041] Table 2

[0042] Thickness expansion rate 0.5C 0.6C 0.7C 0.8C 0.9C 1C CC1 3.1% 3.2% 3.1% 3.1% 3.2% 3.8% CC4 2.9% 2.5% 4.4% 4.8% 5.1% 6.2%

[0043] In summary, it can be seen from Table 1 that the use of the negative electrode sheet of this patent has less powder loss and significantly improved liquid absorption capacity. It can be seen from Table 2 that the soft-pack battery prepared using the negative electrode sheet of this patent has less thickness expansion and significantly improved charging capacity, which can be increased from 0.6C charging rate to 0.9C, with stable capacity retention rate and no lithium precipitation during the cycle.

[0044] The detailed description of a negative electrode sheet and a lithium-ion battery with improved charging capacity with reference to the above-mentioned embodiments is illustrative rather than restrictive, and several embodiments can be listed according to the limited scope. Therefore, changes and modifications without departing from the overall concept of the utility model should fall within the scope of protection of the utility model.

Claims

1. A negative electrode sheet with improved charging capacity, comprising a current collector and an active material layer coated on the current collector, which is dried to form a negative electrode sheet, characterized in that: Several parallel laser-etched grooves are made on the active material layer by laser scribing. The spacing between the laser-etched grooves is 0.5 mm to 5 mm. The depth of the laser-etched grooves is 2% to 10% of the thickness of the active material layer, and the width is 4 to 10 times the depth of the laser-etched grooves.

2. The negative electrode sheet for improving charging capacity according to claim 1, characterized in that: The thickness of the negative electrode plate is 60-180 μm.

3. The negative electrode sheet for improving charging capacity according to claim 1, characterized in that: The laser scribing adopts one or more of gas laser, crystal laser, semiconductor laser or fiber laser.

4. The negative electrode sheet for improving charging capacity according to claim 3, characterized in that: The scanning rate of the laser scribing is 2000-5000 cm / s; the laser energy is 15-55%.

5. A lithium ion battery, characterized in that: The lithium-ion battery comprises a battery housing and an electrode group and an electrolyte sealed in the battery housing; the electrode group comprises a positive electrode sheet, a negative electrode sheet and a separator located between the positive electrode sheet and the negative electrode sheet, wherein the negative electrode sheet is a negative electrode sheet for improving charging capacity as described in any one of claims 1 to 4.

Images