阅读说明：本技术 一种补锂负极片、锂离子电池及其制备方法 (Lithium-supplementing negative plate, lithium ion battery and preparation method of lithium-supplementing negative plate ) 是由 查惟伟 秦作路 孙伟 周建中 李明钧 佘伟华 郭平 于 2020-06-24 设计创作，主要内容包括：本发明属于锂离子电池技术领域,具体涉及一种补锂负极片的制备方法,包括将负极片,隔膜,正极片装配成电池；对电池进行一次恒流恒压充电,达到截至电压后,静置,再进行一次恒流放电,达到截至电压后,静置；拆解电池,正极片弃之,保留负极片；将保留的负极片使用有机溶剂浸泡清洗若干小时,真空干燥,得补锂负极片。本发明还提供了高能量密度锂离子电池的制备方法,包括所述补锂负极片,隔膜,新鲜正极片组装成电池,全电首效提高5～10％左右,进而提高了锂离子电池的能量密度。本发明制备的锂离子电池其质量能量密度高达300～320Wh/kg,基本电性能良好。(The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of a lithium-supplementing negative plate, which comprises the steps of assembling a negative plate, a diaphragm and a positive plate into a battery; performing primary constant-current and constant-voltage charging on the battery, standing after the voltage is cut off, performing primary constant-current discharging, and standing after the voltage is cut off; disassembling the battery, discarding the positive plate and keeping the negative plate; and soaking and cleaning the reserved negative plate for a plurality of hours by using an organic solvent, and drying in vacuum to obtain the lithium-supplement negative plate. The invention also provides a preparation method of the high-energy-density lithium ion battery, which comprises the step of assembling the lithium-supplement negative plate, the diaphragm and the fresh positive plate into the battery, so that the full electric first effect is improved by about 5-10%, and the energy density of the lithium ion battery is further improved. The lithium ion battery prepared by the invention has the mass energy density as high as 300-320 Wh/kg and good basic electrical property.)

1. The preparation method of the lithium-supplement negative plate is characterized by comprising the following steps:

s1, assembling a negative plate, a diaphragm and a positive plate into a battery;

s2, carrying out primary constant-current and constant-voltage charging on the S1 battery, standing after the voltage is cut off, carrying out primary constant-current discharging, and standing after the voltage is cut off;

s3, disassembling the battery S2, discarding the positive plate and keeping the negative plate;

s4, soaking and cleaning the negative plate reserved in the step S3 by using an organic solvent, and drying in vacuum to obtain a lithium-supplement negative plate;

the negative plate comprises a negative current collector and negative slurry coated on the negative current collector, wherein the negative slurry consists of negative active substances, a negative conductive agent and a negative binder in mass percentages of (95-96): (1-1.5): 2.5-4;

the positive plate comprises a negative current collector and positive slurry coated on the positive current collector, wherein the positive slurry consists of (95-97) mass percent, (1-2) mass percent, (2-3) mass percent of positive active material, a positive conductive agent and a positive binder.

2. The method for preparing a lithium-supplementing negative electrode sheet according to claim 1, wherein in step S1, the negative electrode active material is a silicon-oxygen-carbon composite material with a gram capacity of 650 to 800mAh/g, and the positive electrode active material is NCM811 with a gram capacity of 190 to 200 mAh/g.

3. The method for preparing a lithium-supplementing negative electrode sheet according to claim 1, wherein in step S1, the negative electrode conductive agent is one or more of SWCNT, MWCNT, VGCF; the negative binder is one or more of CMC, SBR, PMMA, PAA and PI.

4. The method of claim 1, wherein in step S1, the positive electrode conductive agent is one or more of SP, CNT, and VGCF, and the positive electrode binder is PVDF.

5. The method for preparing a lithium-supplementing negative electrode plate according to claim 1, wherein in step S2, the voltage is 3.65 to 3.85V for one constant-current constant-voltage charge, 2.0 to 2.4V for one constant-current discharge, the charging and discharging current is 0.1 to 0.3C, the current is 0.02 to 0.05C for one constant-voltage charge, and the standing time is 5 to 10 min.

6. The method for preparing the lithium-supplementing negative electrode plate as claimed in claim 1, wherein the step S3 is implemented by disassembling the battery in a low-humidity environment, and the dew point is less than or equal to-40 ℃.

7. The preparation method of the lithium-supplement negative electrode plate according to claim 1, wherein in the step S4, the organic solvent is one or more of EC, PC, DMC, DEC and EMC, the soaking time is 24-48 h, the vacuum drying temperature is 60-80 ℃, and the vacuum drying time is 12-24 h.

8. The lithium-supplementing negative plate prepared by the method of any one of claims 1 to 7.

9. The lithium ion battery prepared from the lithium-supplementing negative plate of claim 8.

10. A method of making the lithium ion battery of claim 9, comprising the steps of:

(1) assembling the lithium-supplementing negative plate, the diaphragm and the fresh positive plate into a battery;

(2) and (3) pressurizing the battery in the step (1) to form a lithium ion battery, and grading the capacity of the battery to obtain the lithium ion battery.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium-supplementing negative plate, a lithium ion battery and a preparation method thereof.

Background

The first coulombic efficiency of the conventional graphite cathode is higher and is about 92-94%, but the specific capacity is lower (less than 372mAh/g), so that the energy density improving space of a lithium ion battery using the graphite cathode material is very limited, and 300Wh/kg is difficult to break through. Since the silicon-based negative electrode material has very high gravimetric specific capacity and volumetric specific capacity, the energy density of the lithium ion battery is to be further improved, and therefore, the development of the silicon-based negative electrode is one of the most effective methods for improving the energy density of the lithium ion battery.

The aim of improving the capacity of the negative electrode is achieved by doping silicon or a silicon protoxide material into graphite in industry, however, as the doping amount of the silicon material is increased, the first effect is gradually reduced, and when the first effect of the silicon-based negative electrode is reduced to be smaller than that of the positive electrode material, the gram capacity of the positive electrode material cannot be fully exerted, so that the positive electrode material is wasted, and the capacity and the energy density of the lithium ion battery are not favorably improved. In order to realize that the energy density of a single power battery exceeds 300Wh/kg, the specific capacity of a silicon-based negative electrode at least reaches 650mAh/g, but the first effect of the full battery is only 75-80%, and the improvement of the energy density of the lithium ion battery by the silicon-based material is limited to a great extent.

At present, researchers have proposed a lot of solutions to solve the problem of low first-order efficiency of high silicon content negative electrodes of lithium ion batteries. Chinese patent CN109004304A discloses a lithium supplementing method for soft-package lithium ion battery, a lithium ion battery preparation method and a middle lithium supplementing battery, wherein lithium is supplemented to the negative plate through a lithium supplementing electrode, the method needs to redesign the battery structure, and the consistency of the negative electrode after lithium supplementation is difficult to ensure, the process is also very complex, and the operation is tedious. Chinese patent CN109713215A discloses a lithium-supplementing negative plate, a preparation method thereof and a lithium ion battery, wherein a lithium-supplementing composite layer formed by alloy lithium powder, ceramic powder and a binder is coated on the surface of the negative plate, the method is difficult to ensure uniform coating, and poor battery consistency can be caused.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a lithium supplement method for a lithium ion battery, which is simple to operate, has low requirements on process equipment and high safety and is easy to produce and apply on a large scale.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a preparation method of a lithium-supplement negative plate comprises the following steps:

s1, assembling a negative plate, a diaphragm and a positive plate into a battery;

s2, carrying out primary constant-current and constant-voltage charging on the S1 battery, standing after the voltage is cut off, carrying out primary constant-current discharging, and standing after the voltage is cut off;

s3, disassembling the battery S2, discarding the positive plate and keeping the negative plate;

s4, soaking and cleaning the negative plate reserved in the step S3 by using an organic solvent, and drying in vacuum to obtain a lithium-supplement negative plate;

the negative plate comprises a negative current collector and negative slurry coated on the negative current collector, wherein the negative slurry consists of negative active substances, a negative conductive agent and a negative binder in mass percentages of (95-96): (1-1.5): 2.5-4;

the positive plate comprises a negative current collector and positive slurry coated on the positive current collector, wherein the positive slurry consists of (95-97) mass percent, (1-2) mass percent, (2-3) mass percent of positive active material, a positive conductive agent and a positive binder.

Preferably, in step S1, the negative electrode active material is a silicon-oxygen-carbon composite material with a gram capacity of 650 to 800mAh/g, and the positive electrode active material is NCM811 with a gram capacity of 190 to 200 mAh/g.

Preferably, in step S1, the negative electrode conductive agent is one or more of SWCNT, MWCNT, VGCF; the negative binder is one or more of CMC, SBR, PMMA, PAA and PI.

Preferably, in step S1, the positive electrode conductive agent is one or more of SP, CNT, and VGCF, and the positive electrode binder is PVDF.

Preferably, in step S2, the voltage of the first constant current and constant voltage charging is 3.65-3.85V, the voltage of the first constant current discharging is 2.0-2.4V, the charging and discharging current is 0.1-0.3C, the current of the constant voltage charging is 0.02-0.05C, and the standing time is 5-10 min.

Preferably, step S3, disassembling the cell is performed in a low humidity environment with a dew point of ≦ 40 deg.C.

Preferably, in step S4, the organic solvent is one or more of EC, PC, DMC, DEC and EMC, the soaking time is 24-48 hours, the vacuum drying temperature is 60-80 ℃, and the vacuum drying time is 12-24 hours.

Based on one general inventive concept, another object of the present invention is to provide a lithium-supplement negative electrode sheet prepared by the above method, and a lithium ion battery prepared from the lithium-supplement negative electrode sheet, and a method for preparing the lithium ion battery, comprising the following steps:

(1) assembling the lithium-supplementing negative plate, the diaphragm and the fresh positive plate into a battery;

(2) and (3) pressurizing the battery obtained in the step (1) at high temperature to form the battery, and grading the battery to obtain the lithium ion battery.

Compared with the prior art, the invention has the following advantages and positive effects:

the lithium ion battery can overcome the obstacles brought by the traditional lithium supplement technology, can realize more accurate control of the lithium supplement amount and the lithium supplement uniformity of the negative plate by charging and discharging to cut off the voltage, improves the first coulombic efficiency and consistency of the battery, improves the full electric first effect by about 5-10%, and further improves the energy density of the lithium ion battery.

The lithium ion battery prepared by the invention has the mass energy density as high as 300-320 Wh/kg and good basic electrical property. The method for preparing the lithium-supplementing pole piece and the lithium ion battery is simple to operate, does not need to modify the existing production line, and is suitable for large-scale production.

Detailed Description

In order to make the aforementioned objects, features and advantages of the present invention more comprehensible, preferred embodiments accompanied with figures are described in detail below: