CN110707294B - A three-dimensional fiber frame lithium battery anode co-doped with lithiophilic heteroatoms and metal oxides and its preparation - Google Patents

Abstract

A three-dimensional fiber frame lithium battery negative electrode co-doped with lithiophilic heteroatoms and metal oxides and preparation thereof belong to the technical field of lithium battery negative electrodes. Specific preparation: synthesize zinc hydroxide in gelatin solution to form a uniformly dispersed suspension; use electrospinning technology to spin the above suspension on the surface of copper foil to form an electrospinning fiber film, and then let stand at room temperature for After the solvent is evaporated, a copper foil with a gelatin spinning film is formed; heated to convert zinc hydroxide into zinc oxide; the modified copper foil and metal lithium sheet are assembled into a button battery, and after standing for 10 hours, the electrochemical The deposition method enables metal lithium to be deposited on the modified copper foil; the button battery is disassembled and the copper foil is taken out to obtain the desired metal lithium negative electrode. It solves the problem of the generation and growth of lithium dendrites in the lithium negative electrode during the battery cycle, and has excellent cycle stability.

Description

A three-dimensional fiber-framed lithium battery co-doped with lithiophilic heteroatoms and metal oxides Negative electrode and preparation

technical field

The invention relates to a design and preparation method of a three-dimensional fiber frame lithium battery negative electrode co-doped with lithiophilic heteroatoms and metal oxides, and the obtained lithium negative electrode, belonging to the fields of energy storage devices and energy materials.

Background technique

New types of renewable energy, such as the utilization of water energy and solar energy, the gradual marketization of electric vehicles, and the rapid development of various portable devices all require efficient and practical energy storage and transportation systems. While the device is concerned about its "greenness", the key to determining whether it is suitable for industrial applications is whether it has important indicators such as high power density and high energy density. New power systems, especially secondary batteries, are currently important "green" energy storage devices.

Since its first launch in the 1990s, lithium-ion batteries have been one of the mainstream products in the portable device market for more than 20 years and are one of the most common rechargeable power sources. Lithium metal has high electronegativity, At the same time, it has the lowest density among all metals, and therefore has the highest specific capacity (3861 mA hg ^-1 ), and is considered to be the best negative electrode for rechargeable batteries. However, there are serious problems in the use of lithium negative electrodes - the generation and growth of lithium dendrites. On the one hand, when the development and growth of lithium dendrites reach a certain level, they will separate from the negative electrode and enter the electrolyte to form "dead lithium". Therefore, the utilization rate of the negative electrode metal is reduced. On the other hand, when the lithium dendrite is large, it is easy to pierce the separator and make the positive and negative electrodes of the battery contact, resulting in a short circuit of the battery and a safety problem. The generation and development of lithium dendrites seriously hinder the long-term cycle stability and safety of lithium batteries. Therefore, it is urgent to develop a stable and safe lithium battery negative electrode to promote the development of the lithium battery industry.

Transition metal oxides, including: Fe ₂ O ₃ , ZnO, Mn ₃ O ₄ , NiCo ₂ O ₄ and CoFe ₂ O ₄ have high theoretical capacity and good lithiophilicity, and are very useful in lithium battery negative electrodes. good application prospects.

Gelatin is a natural polymer material, which is partially degraded from collagen in connective tissues such as animal skin and bone, so its structure is similar to that of biological tissues. Gelatin is mainly composed of more than 80% protein, and the rest is water and inorganic materials. Salt has good dispersibility, adhesion, etc. Under the current trend of pursuing environmental protection and green chemistry, using the polymer properties of gelatin and applying it to the production of batteries has a good application prospect.

SUMMARY OF THE INVENTION

In order to better meet the needs of social development for stable and safe secondary rechargeable lithium batteries, the present invention provides a design and preparation method of a three-dimensional fiber frame lithium battery negative electrode co-doped with lithiophilic heteroatoms and metal oxides, and the obtained Lithium anode to solve the problem of lithium dendrite generation and growth during battery cycling.

The preparation method of the lithium negative electrode provided by the present invention comprises the following steps:

(1) in the gelatin solution, zinc acetate dihydrate and lithium hydroxide monohydrate are reacted in situ to synthesize zinc hydroxide to form a uniformly dispersed suspension;

(2) using the electrospinning technology to spin the above-mentioned suspension on the surface of the copper foil to form an electrospinning fiber film, then stand at room temperature to make the solvent volatilize, and form a copper foil with a gelatin spinning film;

(3) heating the copper foil with the gelatin spinning film at 180°C to convert zinc hydroxide into zinc oxide;

(4) assembling the modified copper foil and metal lithium sheet into a button battery, and after standing for 10 hours, the metal lithium is deposited on the modified copper foil by an electrochemical deposition method;

(5) Disassemble the button battery and take out the copper foil to obtain the required metal lithium negative electrode.

Further, in step (1), the reaction of zinc acetate dihydrate and lithium hydroxide monohydrate is:

Zn(CH ₃ COO) ₂ ·2H ₂ O+2LiOH·H ₂ O→Zn(OH) ₂ +2Li(CH ₃ COO)+4H ₂ O

The mass concentration of the gelatin solution configured in step (1) is preferably 8-15wt%.

In step (1), the solvent of the gelatin solution is composed of water and trifluoroethanol in a mass ratio of 1:1.

The molar ratio of zinc acetate dihydrate and lithium hydroxide monohydrate is 1:2. The final Zn(OH) ₂ concentration was made to be 0.1wt%-1wt%.

In step (2), a gelatin fiber film (film thickness of 0.01-0.05 mm, preferably 0.02 mm) containing zinc hydroxide is prepared by electrospinning technology, and is attached to the surface of the copper foil.

Further, in step (3), zinc hydroxide is converted into zinc oxide through following reaction:

Zn(OH) ₂ →ZnO+H ₂ O

Further preferably, after the zinc hydroxide obtained by the reaction in step (1) is heated and dehydrated to obtain zinc oxide in step (3), zinc oxide/(zinc oxide+gelatin)=1.25% (mass fraction).

The copper foil with the gelatin electrospun film in step (3) was heated in a tube furnace filled with nitrogen.

In the step (3), the temperature range of the heating process is from room temperature to 180°C, the heating rate is 2°C/min, the holding time at 180°C is 5 hours, and the temperature is naturally cooled to 50°C after the heat preservation.

Further, the battery electrolyte used in step (4) is a common commercial lithium battery electrolyte, wherein the electrolyte solvent is DOL/DME=1:1 (volume ratio), including solutes 1M LiPF ₆ and 0.4M LiNO ₃ .

Further, the standing time of the button battery assembled in step (4) is 10 hours.

In step (4), the electrochemical deposition step is deposition under the condition of a current density of 0.2 mA/cm ² for 15-30 hours.

The invention also discloses a lithium negative electrode sheet prepared according to the foregoing method.

Compared with the prior art, the beneficial effects of the present invention are as follows:

The main material gelatin used in the present invention is a natural biopolymer, which has good physical and chemical properties such as dispersibility, cohesion, and processability, can disperse zinc oxide evenly, and the electrospinning film can well adhere to the surface .

The synergistic effect of abundant nitrogen atoms in gelatin and uniformly dispersed zinc oxide, coupled with the three-dimensional structure of the electrospinning film, allows lithium to be uniformly deposited on the copper foil, which can effectively avoid the generation of lithium dendrites during battery cycling and improve lithium Long-term cycle stability and safety of batteries.

Description of drawings

Fig. 1 is the cycle performance comparison diagram of the lithium pair battery composed of the lithium negative electrode prepared in Example 1 of the present invention and the ordinary lithium pair battery

Detailed ways

The present invention will be further described below in conjunction with specific embodiments, but the scope of the present invention is not limited to this, and any form modifications or changes made to the present invention should fall within the protection scope of the present invention.

The battery separator used in the examples is a common commercial separator—Celgard 2325.

Example 1

(1) Preparation of stable and safe lithium anode

Accurately weigh 5.0g of gelatin and fully dissolve it in 45.0g of solvent (wherein the mass ratio of water and trifluoroethanol is 1:1), then divide the solvent into two equal parts, and add 0.356g of acetic acid dihydrate to one part Zinc, add 0.136g of lithium hydroxide monohydrate to the other part, and after stirring evenly, add the solution containing lithium hydroxide monohydrate dropwise to the solution containing zinc acetate dihydrate, add dropwise and stir, and react for half an hour in total, Then, the electrospinning machine was used to spin it on the copper foil into a fiber film (the film thickness was 0.02mm). . Let it stand at room temperature for 24 hours.

The above-mentioned modified copper foil is heated in a tube furnace filled with nitrogen. The temperature range of the heating process is from room temperature to 180°C, the heating rate is 2°C/min, the holding time at 180°C is 5 hours, and the temperature is naturally lowered after the heat preservation. At 50°C, the material was taken out and cut into small discs with a diameter of 12 mm using a cutting machine.

The above-mentioned wafers and ordinary metal lithium sheets were assembled into a CR2025 button battery in a glove box, the separator was Celgard 2325, and the electrolyte was DOL/DME=1:1 (volume ratio) + 1M LiPF ₆ +0.4M LiNO ₃ . The assembled battery was allowed to stand for 10 hours.

The battery was discharged at a current density of 0.2 mA/cm ² for 25 hours to achieve the deposition of lithium on the modified copper foil, and then the lithium-deposited copper foil was taken out to obtain a lithium negative electrode.

(2) Preparation of lithium battery

Take two lithium negative electrodes prepared by the above steps and assemble them into a CR2025 button battery in a glove box. The diaphragm is Celgard 2325, and the electrolyte is DOL/DME=1:1 (volume ratio) + 1M LiPF ₆ +0.4M LiNO _3. Let the assembled battery stand for 10 hours.

Similarly, two ordinary lithium metal sheets were taken and assembled into a lithium pair battery as a control.

(3) Electrochemical performance test of lithium battery

The lithium battery was tested on the charging and discharging equipment, and the test conditions were as follows: the charging and discharging current density was 1.0 mA/cm ² , and the charging and discharging capacity was 1.0 mAh/cm ² . Figure 1 shows the cycle performance test results of the two. It can be seen from the data in the figure that the lithium pair battery assembled by using the lithium negative electrode prepared by the present invention has a smaller polarization voltage and a longer and more stable cycle period, indicating that the lithium negative electrode preparation method provided by the present invention and the obtained lithium negative electrode are feasible. of.

Those skilled in the art will recognize that, without departing from the scope of protection of the present invention, various modifications, changes and combinations can be made to the above-described embodiments, and such modifications, changes and combinations are considered to be original ideas within the range.

Claims (11)

1. A preparation method of a three-dimensional fiber framework lithium battery cathode codoped with lithium-philic heteroatoms and metal oxides is characterized by comprising the following steps:

(1) in-situ reacting zinc acetate dihydrate with lithium hydroxide monohydrate in a gelatin solution to synthesize zinc hydroxide to form uniformly dispersed suspension;

(2) spinning the suspension on the surface of a copper foil by using an electrostatic spinning technology to form an electrostatic spinning fiber film, and standing at room temperature to volatilize the solvent to form the copper foil with the gelatin spinning film;

(3) heating the copper foil with the gelatin spinning film at 180 ℃ to convert zinc hydroxide into zinc oxide;

(4) assembling the modified copper foil and a lithium metal sheet into a button battery, standing for 10 hours, and depositing lithium metal on the modified copper foil by using an electrochemical deposition method;

(5) and disassembling the button battery and taking out the copper foil to obtain the required lithium metal cathode.

2. The process according to claim 1, wherein the gelatin solution of step (1) has a mass concentration of 8 to 15 wt%.

3. The process according to claim 1, wherein in the step (1), the solvent of the gelatin solution is prepared from water and trifluoroethanol in a mass ratio of 1:1 under the condition of the formula (I).

4. The process according to claim 1, wherein the zinc acetate dihydrate and the oxyhydrogen monohydrateMolar ratio of lithium compound 1: 2; so that the final Zn (OH)₂The concentration of (B) is 0.1 wt% to 1 wt%.

5. The method of claim 1, wherein the gelatin fiber film containing zinc hydroxide is prepared in step (2) by an electrospinning technique to have a film thickness of 0.01 to 0.05mm and attached to the surface of the copper foil.

6. The production method according to claim 1, wherein the film thickness is 0.02 mm.

7. The production method according to claim 1, wherein the mass ratio of zinc oxide/(zinc oxide + gelatin) after the zinc hydroxide obtained by the reaction in step (1) is dehydrated by heating in step (3) to obtain zinc oxide is 1.25%.

8. The production method according to claim 1, wherein the copper foil with the gelatin electrostatic spinning film in step (3) is heated in a tube furnace filled with nitrogen gas; the temperature range of the heating process in the step (3) is from room temperature to 180 ℃, the heating rate is 2 ℃/min, the heat preservation time at 180 ℃ is 5 hours, and the temperature is naturally reduced to 50 ℃ after heat preservation.

9. The method of claim 1, wherein the battery electrolyte used in step (4) is a common commercial lithium battery electrolyte having a DOL/DME volume ratio of 1:1 and containing a solute of 1M LiPF₆And 0.4M LiNO₃。

10. The production method according to claim 1, wherein the electrochemical deposition step in the step (4) is carried out at a current density of 0.2mA/cm²Depositing for 15-30 hours under the condition.

11. The lithium-philic heteroatom and metal oxide co-doped three-dimensional fiber framework lithium battery negative electrode prepared by the method of any one of claims 1 to 10.

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