阅读说明：本技术 一种锂离子电池负极极片及其制备方法 (Lithium ion battery negative pole piece and preparation method thereof ) 是由 张立君 陈慧龙 段恒志 *** 王念贵 王瑛 于 2019-09-30 设计创作，主要内容包括：本申请公开了一种锂离子电池负极极片,所述负极极片包括集流体,以及喷涂在所述集流体上的补锂材料,所述补锂材料包括纺丝纤维状的石墨烯和均匀分布于所述石墨烯内部及表面的金属锂,分布于所述石墨烯表面的所述金属锂还包覆有碳层。本发明采用静电纺丝技术直接在负极极片上纺丝实现补锂,获得的锂离子电池负极复合补锂极片性能稳定,材料与极片之间粘结度高,安全性能优异,可以实现均匀补锂,而纤维状的石墨烯,使得大部分锂是包覆在纤维内的,在电池循环过程中可以持续提供锂补充,进而提高电池的循环保持率,有效提高了锂离子电池的首次效率及能量密度,保证了锂离子电池的长循环性能。(The application discloses lithium ion battery negative pole piece, negative pole piece includes the mass flow body, and the spraying is in mend lithium material on the mass flow body, mend lithium material including the fibrous graphite alkene of spinning and evenly distributed in the inside and surperficial metal lithium of graphite alkene, distribute in graphite alkene surface metal lithium still has the carbon-layer in the cladding. According to the invention, the lithium is directly spun on the negative pole piece by adopting an electrostatic spinning technology to realize lithium supplement, the obtained lithium ion battery negative pole composite lithium supplement pole piece has stable performance, the adhesion between the material and the pole piece is high, the safety performance is excellent, and uniform lithium supplement can be realized, and most of lithium is wrapped in the fiber by the fibrous graphene, so that the lithium supplement can be continuously provided in the battery circulation process, the circulation retention rate of the battery is further improved, the primary efficiency and the energy density of the lithium ion battery are effectively improved, and the long circulation performance of the lithium ion battery is ensured.)

1. The utility model provides a lithium ion battery negative pole piece, its characterized in that, negative pole piece includes that the mass flow body and spraying are in mend lithium material on the mass flow body, mend lithium material including the fibrous graphite alkene of spinning and evenly distributed in the inside and surperficial lithium metal of graphite alkene, distribute in graphite alkene surface lithium metal still has the cladding to have the carbon-layer.

2. The negative electrode plate of the lithium ion battery as claimed in claim 1, wherein the spraying thickness of the lithium supplement material on the current collector is 0.5-3 μm; in the lithium supplement material, the mass ratio of the graphene to the metal lithium is 1: 0.7-3.5.

3. The preparation method of the lithium ion battery negative electrode plate according to the claims 1 to 2, characterized by comprising the following steps:

1) dispersing graphene in an organic solvent to obtain a dispersion liquid;

2) adding an organic lithium solution into the dispersion liquid to obtain a spinning solution;

3) carrying out electrostatic spinning on the spinning solution, and directly spraying spinning fibers obtained by the electrostatic spinning on a current collector to obtain a lithium-supplement pole piece;

4) and calcining the lithium supplement electrode sheet at a high temperature to coat carbon.

4. The preparation method according to claim 3, wherein the step 1) specifically comprises: adding the graphene sheets into an organic solvent under an inert atmosphere, and sequentially carrying out ultrasonic dispersion and magnetic stirring.

5. The method of claim 4, wherein the inert atmosphere is selected from one or more of nitrogen, argon; the organic solvent is selected from one of n-hexane, cyclohexane and tetrahydrofuran; the ultrasonic dispersion time is 90-180 min; the temperature of the magnetic stirring is 40-80 ℃, and the stirring time is 12-24 h.

6. The method of claim 3, wherein the organolithium solution is selected from one or more of a butyl lithium solution, a tert-butyl lithium solution, or a phenyl lithium solution.

7. The method according to claim 3, wherein the concentration of the organolithium solution is 0.1 to 5 mol/L.

8. The method according to claim 3, wherein the electrospinning voltage is 10 to 20kV, and the spraying speed is 0.01 to 0.03 mm/s.

9. The method of claim 3, wherein the carbon-coated carbon source is selected from one or more of methane, ethane, propane, and ethylene.

10. The preparation method of claim 3, wherein the temperature rise rate of the high-temperature calcination is 1-5 ℃/min, the calcination temperature is 600-900 ℃, and the calcination time is 2-4 h.

Technical Field

The application relates to the technical field of lithium ion batteries, in particular to a lithium ion battery negative pole piece and a preparation method thereof.

Background

The lithium ion battery has the characteristics of high working voltage, large specific energy, small volume, light weight, long cycle life and the like, so that the lithium ion battery becomes the focus of development and competition of the automobile industry. With the continuous development of lithium ion batteries in the fields of portable electronic devices, electric bicycles and electric automobiles, the requirements on the energy density and other properties of the lithium ion batteries are higher and higher.

In the first charge-discharge process of the lithium ion battery, the electrode material reacts with the electrolyte at a solid-liquid interface to form a Solid Electrolyte Interface (SEI) passive film, and a large amount of active lithium ions are consumed, so that the first irreversible coulombic efficiency is low, and the energy density and performance of the battery are reduced.

Lithium metal or a lithium-containing compound is added into the negative electrode material, so that lithium ions consumed by the first charge and discharge of the lithium ion battery can be supplemented, the first efficiency of the battery is improved, lithium consumed by the formation of an SEI film is supplemented, the transmission rate of the lithium ions is improved, and the cycle performance of the battery is improved. At present, common lithium supplement methods include in-situ doping lithium supplement, electrochemical lithium supplement and chemical lithium pre-supplement methods, but the methods have high requirements on the environment and potential safety hazards such as flammability and the like, so that the further popularization and application of each method are limited.

CN110010860A provides a composite negative electrode material for lithium ion battery, which comprises a silicon/carbon nanotube composite fiber cloth and a carbon layer formed on the surface of the cloth, but the material does not contain lithium ions, so that the material cannot achieve the effect of lithium supplement although the material has a high capacity residual rate after cycling. CN105914343A provides a lithium ion battery negative plate, and this scheme adopts the electrostatic spinning technique to distribute the solution that contains lithium compound evenly on the negative plate surface and dry, but still need to add surfactant in order to guarantee even lithium supplementation, but the charge-discharge efficiency of the electrode material that contains surfactant among the prior art can't reach the practical level. CN109301188A provides a highly dispersed lithium-ion battery lithium supplement material and a preparation method thereof, the lithium supplement material is a graphene sheet with metal lithium particles uniformly dispersed on the surface, the surface of the metal lithium particles is coated with a carbon layer, but in the scheme, lithium on the surface of the single-sheet graphene can be crushed and separated from the surface of the graphene in the circulation process, so that dead lithium is caused, and the effectiveness of the material is greatly reduced.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a lithium ion battery negative electrode composite lithium supplement pole piece and a preparation method of the pole piece, and develops the lithium ion battery negative electrode composite lithium supplement pole piece with good metal lithium dispersion and excellent electrochemical performance.

In one aspect, the invention provides a lithium ion battery negative electrode plate, which comprises a current collector and a lithium supplement material sprayed on the current collector, wherein the lithium supplement material comprises a spinning fibrous graphene and a compound of metal lithium uniformly distributed in the graphene and on the surface of the graphene, and the metal lithium distributed on the surface of the graphene is further coated with a carbon layer.

Further, the spraying thickness of the lithium supplement material on the current collector is 0.5-3 μm; in the lithium supplement material, the mass ratio of the graphene to the metal lithium is 1: 0.7-3.5, preferably 1: 1-10, and more preferably 1: 7. Metallic lithium is to be understood as meaning, among others, metallic lithium particles.

Further, the current collector may be a copper foil or an aluminum foil, preferably a copper foil.

On the other hand, the invention also provides a preparation method of the lithium ion battery negative pole piece, which comprises the following steps:

1) dispersing graphene in an organic solvent to obtain a dispersion liquid;

2) adding an organic lithium solution into the dispersion liquid to obtain a spinning solution;

3) carrying out electrostatic spinning on the spinning solution, and directly spraying spinning fibers obtained by the electrostatic spinning on a current collector to obtain a lithium-supplement pole piece;

4) and calcining the lithium supplement electrode sheet at a high temperature to coat carbon.

When graphene and an organic lithium solution are subjected to a mixing reaction, lithium ions can be reduced into metallic lithium and uniformly distributed in and on the surface of the graphene spinning fiber carrier.

Further, the method can be prepared by using a laboratory electrostatic spinning device, and the spinneret of the electrostatic spinning device can be various medical metal needles with the diameter of 0.6-1.6 mm. Preferably, the diameter of the spinneret may be 0.6mm, 1.0mm or 1.6 mm.

Further, the step 1) specifically includes: adding the graphene sheets into an organic solvent under an inert atmosphere, and sequentially carrying out ultrasonic dispersion and magnetic stirring.

Further, the inert atmosphere is selected from one or more of nitrogen and argon; the organic solvent is selected from one of n-hexane, cyclohexane and tetrahydrofuran; the ultrasonic dispersion time is 90-180 min; the temperature of the magnetic stirring is 40-80 ℃, and the stirring time is 12-24 h.

Further, the organic lithium solution is selected from one or more of a butyl lithium solution, a tert-butyl lithium solution or a phenyl lithium solution.

Further, the concentration of the organic lithium solution is 0.1 to 5mol/L, preferably 1 mol/L.

Further, the electrostatic spinning voltage is 10-20kV, preferably 20 kV; the spraying speed is 0.01-0.03mm/s, preferably 0.02 mm/s.

Further, the carbon-coated carbon source is selected from one or more of methane, ethane, propane and ethylene. Preferably, the carbon source is methane.

Further, the heating rate of the high-temperature calcination is 1-5 ℃/min, preferably 5 ℃/min; the calcination temperature is 600-900 ℃, preferably 700 ℃; the calcination time is 2-4h, preferably 3 h.

Further, the high temperature calcination is performed in a muffle furnace.

In one embodiment, the preparation method of the lithium ion battery negative electrode plate comprises the following steps:

(1) adding graphene sheets into a normal hexane solution, and sequentially carrying out ultrasonic dispersion and magnetic stirring to obtain a graphene dispersion solution;

(2) adding an organic lithium solution into the dispersion liquid obtained in the step (1) in an inert atmosphere, and uniformly dispersing to obtain a spinning solution;

(3) putting the spinning solution obtained in the step (2) into a 10mL disposable injector, putting the injector into an electrostatic spinning instrument, performing electrostatic spinning, and directly spraying the nanofiber obtained by electrostatic spinning on a negative electrode plate to obtain a composite negative electrode lithium-supplement plate;

(4) and (4) placing the composite negative electrode lithium supplement electrode piece obtained in the step (3) in a muffle furnace, and calcining at high temperature by taking methane gas as a carbon source to coat carbon, so as to obtain the negative electrode piece of the lithium ion battery.

On the other hand, the invention also provides application of the lithium ion battery cathode composite lithium supplement material in improving the cycle performance of the lithium ion battery. Preferably, the residual capacity of the lithium ion battery after charge-discharge cycles is increased.

This application can bring following beneficial effect:

1. according to the invention, the lithium is directly spun on the negative pole piece by adopting an electrostatic spinning technology to realize lithium supplement, the obtained lithium ion battery negative pole composite lithium supplement pole piece has stable performance, the adhesion between the material and the pole piece is high, the safety performance is excellent, and uniform lithium supplement can be realized, and the fibrous graphene is spun, so that most of lithium is wrapped in the fiber, and lithium supplement can be continuously provided in the battery circulation process, thereby improving the circulation retention rate of the battery, effectively improving the primary efficiency and energy density of the lithium ion battery, and ensuring the long circulation performance of the lithium ion battery.

2. The preparation method of the lithium ion battery negative pole piece is simple in process, easy to implement and high in safety.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

fig. 1 is a schematic structural diagram of a lithium supplement material loaded on a lithium ion battery negative electrode composite lithium supplement electrode sheet provided by the invention;

in the figure: 1. a graphene sheet; 2. the lithium particles are carbon coated.

Detailed Description

In order to more clearly explain the overall concept of the present application, the following detailed description is given by way of example. In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present application. It will be apparent, however, to one skilled in the art, that the present application may be practiced without one or more of these specific details. In other instances, well-known features of the art have not been described in order to avoid obscuring the present application.

The starting materials in the following examples are all commercially available, unless otherwise specified.