CN110783529A - A metal lithium negative electrode for secondary battery and its preparation and application - Google Patents

Abstract

The invention belongs to the field of negative electrode materials for lithium secondary batteries, and specifically discloses a metal lithium negative electrode for secondary batteries, comprising a current collector, a lithium-bismuth alloy base layer compounded on the current collector, and a lithium-bismuth alloy base layer compounded on the surface of the lithium-bismuth alloy base layer. Lithium compound layer. The invention also discloses the preparation method of the metal lithium negative electrode for secondary battery. The bismuth compound, the conductive agent and the binder are slurried and compounded on the surface of the current collector, and then the bismuth compound compounded on the current collector is compounded on the surface of the current collector. The compound reacts with metallic lithium to prepare the metallic lithium negative electrode for secondary battery. The invention creatively finds that through the chemical reaction between the bismuth compound and metal lithium, an effective lithium-bismuth alloy is formed; the metal lithium is promoted to grow uniformly in the bismuth framework, and an effective SEI film is produced at the same time, which protects the metal lithium and avoids lithium Dendrites are generated, thereby improving the charge-discharge coulombic efficiency and cycle life of the lithium metal anode.

Description

A metal lithium negative electrode for secondary battery and its preparation and application

technical field

The invention belongs to the field of new energy devices, and in particular relates to a novel metal lithium negative electrode for secondary batteries.

Background technique

With the rise of the new energy field, battery materials have attracted more and more attention. Metal lithium is an ideal anode material in lithium batteries due to its high theoretical specific capacity (3860mAh/g), lowest electrode potential (-3.040V vs. SHE) and low density (0.53g/cm ³ ). However, the growth of lithium dendrites and the resulting safety hazards limit their commercial application. Due to the high activity of lithium metal, the growth of lithium dendrites during the charge-discharge cycle, resulting in short-circuit and low coulombic efficiency of the battery, restricts the application of metal lithium. At present, the main effective methods are: modification of electrolyte, application of 3D current collector, application of solid electrolyte, artificial SEI membrane and so on.

For example, Yang et al. prepared porous copper by dealloying Cu-Zn alloy as a 3D current collector, which also achieved good lithium storage performance, but only increased the specific surface area, so that more metal lithium was exposed in the electrolyte. Without the protection of the SEI film, it is not enough to achieve the excellent performance of the lithium anode [1]. Similarly, the design of artificial SEI film is as follows: Y Cao et al. uniformly coat Al2O3 on the surface of metal lithium by molecular deposition technology, which effectively protects metal lithium and inhibits the growth of lithium dendrites, but the internal resistance of the battery caused by artificial SEI film is relatively high. It is large and has many side reactions, so that the coulombic efficiency of the battery cannot be improved.

[1] YANG C-P, YIN Y-X, ZHANG S-F, et al.Accommodating lithium into 3Dcurrent collectors with a submicron skeleton towards long-life lithium metalanodes[J].2015, 6(8058)

[2] CaoY, Meng X, Elam JW. Atomic Layer Deposition of LixAlyS Solid-State Electrolytes for Stabilizing Lithium-Metal Anodes [J]. Chemelectrochem, 2016, 3(6): 858-863.

SUMMARY OF THE INVENTION

In order to solve the technical deficiencies of the existing lithium negative electrodes, the present invention starts with an alloyed metal lithium negative electrode, modifies the metal lithium negative electrode, and maintains a long cycle and high coulombic efficiency. The present invention provides a secondary battery metal lithium negative electrode ( The present invention is also abbreviated as negative electrode), which aims to improve its electrical properties, such as improving the cycle stability of the negative electrode.

The second object of the present invention is to provide the preparation method of the negative electrode.

The third object of the present invention is to provide the application of the metal lithium negative electrode.

A metal lithium negative electrode for a secondary battery (also referred to as a metal lithium negative electrode in the present invention) comprises a current collector, a lithium bismuth alloy base layer compounded on the current collector, and a lithium compound layer compounded on the surface of the lithium bismuth alloy base layer.

The metal lithium negative electrode of the present invention innovatively uses a lithium-bismuth alloy as a substrate, and a lithium compound layer is compounded on it. The composition and structure of the metal lithium negative electrode can promote the uniform growth of metal lithium in the bismuth skeleton, which is helpful for Avoid the generation of lithium dendrites, and at the same time, the in-situ SEI film formed on the surface of the lithium-bismuth alloy can stably exist in the electrolyte, block the contact between the metal lithium anode and the electrolyte, and effectively reduce the occurrence of side reactions, thereby improving the metal lithium anode. Charge and discharge coulombic efficiency and cycle life.

Preferably, the material of the lithium-bismuth alloy base layer is Li ₃ Bi and/or LiBi.

Preferably, the lithium compound layer is at least one of lithium oxide, sulfide, chloride, nitride, phosphide, and fluoride.

Further preferably, the lithium compound layer is at least one of Li ₂ O, LiCl, Li ₂ S, Li ₃ N, Li ₃ P, and LiF.

The current collector is a metal current collector, preferably at least one of copper, stainless steel, nickel and titanium.

Preferably, the thickness of the current collector is 10-20 microns, more preferably 15 microns.

Preferably, the thickness of the lithium-bismuth alloy base layer is 5 micrometers to 40 micrometers. Preferably, the thickness of the lithium compound layer is 5 nanometers to 500 nanometers.

The metal lithium negative electrode for a secondary battery also contains additional components that are allowed to be added to the existing metal lithium negative electrode, such as conductive agents, binders and other components. The conductive agent can be compounded in the lithium-bismuth alloy base layer.

The metal lithium negative electrode for secondary battery of the present invention includes a current collector and an active material compounded on the current collector, and the active material is a reaction product of a bismuth compound and metal lithium; wherein, the bismuth compound is preferably trioxide Bismuth (Bi ₂ O ₃ ), Bismuth Trichloride (BiCl ₃ ), Bismuth Trisulfide (Bi ₂ S ₃ ), Bismuth Disulfide (BiS ₂ ), Bismuth Phosphide (Bi ₃ P), Bismuth Fluoride ( BiF), at least one of bismuth nitride (Bi ₃ N).

Another innovation of the present invention is to provide a preparation method that can prepare a lithium-bismuth alloy substrate in one step and in-situ composite the lithium compound layer on the substrate. In the method for preparing a metal lithium negative electrode for a secondary battery, the bismuth compound, the conductive agent and the binder are slurried and compounded on the surface of the current collector, and then the bismuth compound compounded on the current collector is reacted with the metal lithium , to prepare the metal lithium negative electrode for secondary battery.

In the preparation method of the present invention, a bismuth compound is used as an active component, which is pre-coated on the current collector, and then subjected to an alloying reaction with metal lithium, and a lithium compound compounded on the alloy is formed in situ, so that The negative electrode composed of the structure can avoid the formation of lithium dendrites, and also has the function of in-situ SEI protection. The metal negative electrode material exhibits better charge-discharge coulombic efficiency and cycle life.

The conductive agent and the binder can adopt the well-known additive components in the industry that can be used for the metal lithium negative electrode.

Preferably, the conductive agent is at least one of acetylene black, carbon fiber cloth, graphite, activated carbon, graphene, acetylene black, carbon nanotubes, and Ketjen black.

Said binder is, for example, PVDF.

In the present invention, the conductive agent, the binder and the bismuth compound can be slurried with a solvent, and then compounded on the current collector by an existing method. The compounding method can be a well-known method in the industry such as coating.

In the slurry, the proportions of bismuth compound, conductive carbon and binder can be adjusted as required.

Preferably, in the slurry, the mass ratio of the bismuth compound, the conductive carbon and the binder is 10:1:1.

Preferably, the coating thickness of the slurry after slurrying is 1-300 μm; preferably: 20-50 μm.

The bismuth compound is in powder form, and the particle size is about 50-800 nm, preferably 50-300 nm. Under the preferred particle size, it is helpful to prepare a metal lithium negative electrode with excellent performance. The research also found that when the particle size of the bismuth compound is larger (for example, when the particle size is larger than the upper limit required by the present invention), the bismuth compound and the metal lithium The reaction is not sufficient; however, if the particles are small (for example, smaller than the lower limit required by the present invention), the lithium-bismuth alloy particles generated after the reaction have low binding force and are easy to pulverize.

Preferably, the compound of bismuth is at least one of oxide, chloride, sulfide, bismuth phosphide, bismuth fluoride and bismuth nitride of bismuth.

Further preferably, the compound of bismuth is at least one of bismuth trioxide, bismuth trichloride, bismuth trisulfide, bismuth disulfide, bismuth phosphide, bismuth fluoride and bismuth nitride; At least one of bismuth, bismuth phosphide, bismuth trichloride, and bismuth nitride.

Further preferably, the compound of bismuth is a mixture of bismuth fluoride and bismuth nitride. The present invention further innovatively finds that bismuth fluoride and bismuth nitride have excellent synergistic effects, and the combined use can significantly improve electrical performance and cycle stability unexpectedly.

Further preferably, the compound of bismuth is a mixture of bismuth fluoride and bismuth nitride with a mass ratio of 1-3:1-3.

Preferably, the mass of the bismuth compound on the current collector is: between 1 mg/cm ² and 6 mg/cm ² ; and preferably between 3 mg/cm ² and 5 mg/cm ² .

In the method of the present invention, the slurry of bismuth compound, conductive carbon and binder is mixed uniformly and coated on the surface of the current collector. After the slurry is dried, metal lithium is filled on the surface to make the metal lithium and bismuth The compound is fully reacted; the method of filling metal lithium can adopt the existing method.

Preferably, metal lithium is electroplated (electrodeposited) and/or filled with a bismuth compound compound on the current collector, and the metal lithium is reacted with the bismuth compound.

Preferably, the metal lithium is filled into the bismuth compound current collector by electrodeposition. Compared with other methods of filling lithium, using electrochemical deposition, the reaction between metal lithium and bismuth compounds is sufficient, and the reaction uniformity is better, the resulting lithium-bismuth alloy has strong binding force, high stability, and an in-situ SEI film on the surface. It can effectively protect the lithium-bismuth alloy. It is found in the present invention that the electrodeposition method is innovatively used to further improve the performance of the prepared metal lithium negative electrode, for example, to further improve the cycle performance of the negative electrode.

By supplying metallic lithium to the current collector of the compound compounded with bismuth, the alloying reaction is carried out, and the reaction mechanism is, for example:

Bi+Li=LiBi+Li ₃ Bi

Bi ₂ O ₃ +Li=LiBi+Li ₃ Bi+Li ₂ O

BiCl ₃ +Li=LiBi+Li ₃ Bi+LiCl

Bi ₂ S ₃ +Li=LiBi+Li ₃ Bi+Li ₂ S

BiS ₂ +Li=LiBi+Li ₃ Bi+Li ₂ S

Bi ₃ P+Li=LiBi+Li ₃ Bi+Li ₃ P

BiF+Li=LiBi+Li ₃ Bi+LiF

Bi ₃ N+Li=LiBi+Li ₃ Bi+Li ₃ N

The amount of metallic lithium is not less than 80% of the theoretical molar ratio for the complete reaction of the bismuth compound.

In the metal lithium negative electrode, the content of the filled metal lithium should not be lower than the amount of lithium lost during the first charge and discharge.

Preferably: in the metal lithium negative electrode, the content of metal lithium is 1mAh-8mAh.

The present invention also includes the metal lithium negative electrode prepared by the preparation method. The metal lithium negative electrode comprises a current collector, a lithium-bismuth alloy base layer compounded on the current collector, and a lithium compound layer compounded on the surface of the lithium-bismuth alloy base layer. The material of the lithium-bismuth alloy base layer is Li ₃ Bi and/or LiBi. The lithium compound layer is at least one of lithium oxide, sulfide, chloride, nitride, phosphide, and fluoride; preferably Li ₂ O, LiCl, Li ₂ S, Li ₃ N, Li ₃ At least one of P and LiF.

The invention also provides an application of the metal lithium negative electrode, which is used as a negative electrode to be assembled into a lithium ion battery, a lithium sulfur battery or a lithium air battery.

Preferably, the metal lithium negative electrode is used to assemble a button-type lithium ion battery.

In the present invention, the compound of bismuth can form a stable lithium-bismuth alloy with metal lithium, improve the stability of metal lithium, promote the stable deposition of metal lithium in the lithium-bismuth alloy, avoid the generation of lithium dendrites, and further improve the use of lithium Cycling stability and Coulombic efficiency of lithium anode with bismuth alloy as framework. And after the chemical reaction between metal lithium and bismuth compounds, the generated lithium compounds (Li ₂ O, LiCl, Li ₂ S, Li ₃ P, LiF, Li ₃ N) are effective SEI films, which can stabilize the surface of the lithium-bismuth alloy. , inhibit the occurrence of side reactions between the negative electrode and the electrolyte, protect the metal lithium negative electrode, and then help to significantly improve the cycle stability of the negative electrode.

In the invention, the metal bismuth compound is used as the substrate, and the metal lithium deposited on the metal bismuth compound reacts with the metal bismuth compound through an electrochemical method to generate an effective lithium bismuth compound and a corresponding SEI film. Lithium-bismuth as a current collector, coupled with effective SEI film protection on the surface, will achieve high Coulombic efficiency, long-cycle, and high-capacity-density metallic lithium anodes.

Beneficial effects:

It is proposed to use the chemical reaction of metal bismuth compounds with metal lithium to generate stable lithium-bismuth alloys and corresponding lithium-containing compounds, wherein the lithium-bismuth alloys can be used as lithium-precipitation sites, and metal lithium can be uniformly deposited on the lithium-precipitation sites. , and the lithium-containing compound can be used as an effective SEI film to separate the metal lithium and the electrolyte, reduce the occurrence of side reactions, and integrate the double protection of the lithium deposition site and the SEI film, which can effectively avoid the uneven deposition of lithium to produce lithium dendrites , so as to maintain the high specific capacity characteristics of the lithium metal anode during charge and discharge. It can effectively prevent the growth of lithium dendrites for a long time, and further improve the coulombic efficiency and cycle life of the lithium anode.

The present invention innovatively adopts the preparation method to obtain the metal lithium negative electrode in one step. Not only that, the present inventor innovatively found that, in the overall scheme of the present invention, the electrodeposition method can be used to significantly prepare the metal anode. Electrical properties of lithium anodes.

Under the preparation method, the present invention also innovatively finds that the combined use of bismuth fluoride and bismuth nitride can further improve the electrical properties of the prepared metal lithium negative electrode.

It is found that the cycle life of the negative electrode of the present invention is increased by more than 3 times compared with the existing metal lithium negative electrode; compared with the negative electrode of lithium bismuth alloy, the cycle performance is also increased by nearly 2 times.

Instruction drawings

Fig. 1 is the SEM image of the metal bismuth used in Example 1;

Fig. 2 is the metal bismuth and acetylene black used in Example 1, after the binder is smeared according to the mass ratio of 8: 1: 1, the current density is 1mA/cm ² and the area capacity is 1mAh/cm ² Under the cycle with copper foil The electrochemical performance comparison chart.

Fig. 3 is the SEM image of bismuth trioxide (Bi ₂ O ₃ ) used in Example 2;

Fig. 4 is the bismuth trioxide (Bi ₂ O ₃ ) and acetylene black used in Example 2, after the binder is smeared according to the mass ratio of 8: 1: 1, the current density is 1mA/em ² and the area capacity is 1mAh ^Graph of electrochemical performance with copper foil under cycling.

Fig. 5 is bismuth trichloride (BiCl ₃ ) and acetylene black used in Example 3, after the binder is smeared in a mass ratio of 8: 1: 1, the current density is 1mA/em ² and the area capacity is 1mAh/cm Electrochemical performance graph with copper foil under ² cycles.

6 is a diagram of the electrochemical performance of the full battery used in Example 4;

Fig. 7 is the electrochemical performance diagram of the half-cell used in Example 5;

Fig. 8 is the electrochemical performance diagram of the half-cell used in Comparative Example 1;

9 is a graph of the electrochemical performance of the half-cell used in Example 6. FIG.

Detailed ways

The following are specific descriptions of preferred embodiments of the present invention, which do not constitute any limitation to the present invention, that is, the present invention is not meant to be limited to the above-mentioned embodiments, and common modifications or alternative compounds in the technical field are included in the right of the application within the limits of the requirements.

Performance Testing

After the directional growth/dissolving lithium anode made by the present invention is assembled into a battery, a high-voltage cycle performance test is carried out, and the specific method and test results are as follows:

1. Assembly of the battery: The compound of bismuth is used as the active material, and it is mixed with acetylene black and PVDF according to the mass ratio of 8:1:1, and the mixture is uniformly dispersed into a slurry with NMP, which is coated on a 10-micron thick film. On the copper foil, dried in an oven at 80°C for 12h, punched into a pole piece negative electrode with a diameter of 13mm, using a metal lithium piece as the counter electrode, using 1M LiTFSI/DOL:DME (volume ratio = 1:1) containing 1% wt LiNO ₃ is the electrolyte, which is assembled with the lithium negative electrode prepared by the present invention to form a 2025 button-type lithium ion battery, and the diaphragm adopts GF/D glass fiber, and the charge-discharge cycle test is carried out. The charge-discharge cycle test was carried out with the compound of metal bismuth with the same structure as the active material.

Example 1

Commercially available Bi ₂ S ₃ powder was used as the active material (its microscopic morphology is shown in Figure 1), mixed with acetylene black and PVDF in a mass ratio of 8:1:1, and the mixture was uniformly dispersed into a slurry with NMP, and then coated with acetylene black and PVDF in a mass ratio of 8:1:1. It was clothed on a copper foil with a thickness of 10 microns, dried in an oven at 80 °C for 12 h, punched into a pole piece with a diameter of 13 mm, and a half-cell was assembled with a metal lithium lithium piece as the counter electrode. Under the same structure, an uncoated copper foil was used as the lithium negative electrode as a comparison sample. The test found that the cycle life of the lithium metal negative electrode of the present invention under the charge-discharge current density of 1mA/ ^cm2 and the charge-discharge area capacity of 1mAh/ ^cm2 was more than 2 times that of the smooth copper foil lithium negative electrode, and the average coulombic efficiency remained at 96.3 % above, the stable cycle is above 140 cycles (Figure 2).

Example 2

Compared with Example 1, the difference is that the bismuth compound adopted is Bi ₂ O ₃ , and the specific operations are as follows:

Commercially available bismuth oxide (Bi ₂ O ₃ ) powder was used as the active material (its microscopic morphology is shown in Figure 3), mixed with acetylene black and PVDF in a mass ratio of 8:1:1, and the mixture was uniformly dispersed with NMP as The slurry was coated on a copper foil with a thickness of 10 microns, dried in an oven at 80 °C for 12 h, punched into a pole piece with a diameter of 13 mm, and a half-cell was assembled with a metal lithium sheet as the counter electrode. Under the same structure, an uncoated copper foil was used as the lithium negative electrode as a comparison sample. The test found that the cycle life of the lithium negative electrode with bismuth oxide of the present invention under the charge-discharge current density of 1mA/ ^cm2 and the charge-discharge area capacity of 1mAh/ ^cm2 was more than 3 times that of the smooth copper foil lithium negative electrode, and the average Coulombic efficiency remained Above 96.7%, the stable cycle is above 140 cycles (Figure 4).

Example 3

Compared with Example 1, the difference is that the bismuth compound adopted is BiCl ₃ , and the specific operations are as follows:

Commercially available bismuth trichloride (BiCl ₃ ) powder is used as the active material (its microscopic morphology is shown in Figure 3), mixed with acetylene black and PVDF in a mass ratio of 8:1:1, and the mixture is uniformly dispersed with NMP as The slurry was coated on a copper foil with a thickness of 10 microns, dried in an oven at 80 °C for 12 h, punched into a pole piece with a diameter of 13 mm, and a half-cell was assembled with a metal lithium sheet as the counter electrode. Under the same structure, an uncoated copper foil was used as the lithium negative electrode as a comparison sample. The test found that the cycle life of the lithium anode with bismuth oxide of the present invention under the charge-discharge current density of 1mA/ ^cm2 and the charge-discharge area capacity of 1mAh/ ^cm2 was more than 3 times that of the smooth copper foil lithium anode, and the average Coulombic efficiency remained Above 97.0%, the stable cycle is above 150 cycles (Figure 5).

Example 4

Compared with Example 1, the difference is that the bismuth compound adopted is BiN ₃ , and the specific operations are as follows:

The commercial bismuth nitride (BiN ₃ ) powder is used as the active material, mixed with acetylene black and PVDF according to the mass ratio of 8:1:1, and the mixture is uniformly dispersed into a slurry with NMP, which is coated on a thickness of 10 microns. On the copper foil, dried in an oven at 80 °C for 12 h, punched into a pole piece with a diameter of 13 mm, and a half-cell was assembled with a metal lithium piece as the counter electrode. The half-cell for metal lithium was assembled. At a current density of 0.1 mA/cm ² , according to the amount of bismuth nitride, constant current deposition was carried out for about 10 hours, and all the reactions of bismuth nitride and metal lithium were realized, thereby preparing a lithium-bismuth alloy. It is an excellent metal lithium anode material coated with lithium nitride on the surface. Matching with commercial mature lithium cobalt oxide, assembling a full battery, stable cycling at 1C, the 200-cycle capacity retention rate reached 92.7%, and the lithium-bismuth alloy corresponding to the traditional metal bismuth as the negative electrode has a significant improvement effect.

Under the same structure, an uncoated copper foil was used as the lithium negative electrode as a comparison sample. The test found that the cycle life of the lithium negative electrode with bismuth oxide of the present invention at a charge-discharge current density of 1 mA/cm ² and a charge-discharge area capacity of 1 mAh/cm ² was more than 3 times that of the smooth copper foil lithium negative electrode (Fig. 6).

Example 5

Compared with Example 1, the difference is that the bismuth compound used is a bismuth fluoride (BiF) and bismuth nitride (Bi ₃ N) composite bismuth material, and the specific operations are as follows:

Bismuth fluoride (BiF) and bismuth nitride (Bi ₃ N) were uniformly mixed by ball milling at a mass ratio of 1:1 to obtain an active material, which was mixed with acetylene black and PVDF in a mass ratio of 8:1:1, and was mixed with NMP. The mixture was uniformly dispersed into a slurry, coated on a copper foil with a thickness of 10 microns, dried in an oven at 80 °C for 12 h, punched into a pole piece with a diameter of 13 mm, and a half-cell was assembled with a metal lithium sheet as the counter electrode. Under the same structure, an uncoated copper foil was used as the lithium negative electrode as a comparison sample. It is found in the test that using the ^two preferred metal bismuth compounds of the present invention for electrochemically depositing lithium half ^- cells can stably generate an SEI film with a thickness of 30 nanometers, and the cycle performance is good. The cycle life under the charge-discharge area capacity is more than 3 times that of the smooth copper foil lithium negative electrode, and the average Coulomb efficiency remains above 97.3%, and the stable cycle is more than 190 cycles. (Figure 7). Coulomb efficiency and number of cycles are significantly improved, and combined use can unexpectedly synergistically improve performance.

Comparative Example 1

Elemental metal bismuth was used as the active material, mixed with acetylene black and PVDF in a mass ratio of 8:1:1, and the mixture was uniformly dispersed into a slurry with NMP, which was coated on a copper foil with a thickness of 10 microns at 80 ° C. It was dried in an oven for 12 hours, punched into a pole piece with a diameter of 13 mm, and a half-cell was assembled with a metal lithium piece as the counter electrode. Under the same structure, an uncoated copper foil was used as the lithium negative electrode as a comparison sample. The test found that the cycle performance of the ^{half -} cell using metal bismuth for electrochemical deposition of lithium was improved compared with that of copper foil. It is more than 1.5 times that of the negative electrode, and the average Coulombic efficiency remains above 95%, and the stable cycle is more than 100 cycles (Figure 8). But without the compound of bismuth as the active material, the lithium-bismuth alloy negative electrode produced has excellent performance.

Example 6

Compared with Example 1, the difference is that the performance of the lithium-bismuth alloy negative electrode generated by molten lithium infiltration is as follows:

The bismuth oxide (Bi2O3) was mixed with acetylene black and PVDF as the active material according to the mass ratio of 8:1:1, and the mixture was uniformly dispersed into a slurry with NMP, which was coated on a copper foil with a thickness of 10 microns, and was placed at 80 μm. After drying in a ℃ oven for 12 hours, a pole piece with a diameter of 13 mm was punched out, in which the mass of active material bismuth oxide was 2 mg/cm ² , and the thickness was 10 microns; a half-cell was assembled with a metal lithium sheet as the counter electrode. Under the same structure, the bismuth oxide on the pole piece is completely converted into a metal lithium bismuth alloy (the lithium content of which is about 3mAh) by the method of infiltration with molten lithium. Cycling at 1 mA/cm ² charge-discharge current density and 1 mAh/cm ² charge-discharge area capacity. The test found that the negative polarity of the lithium-bismuth alloy prepared by molten lithium infiltration was slightly improved, but the negative electrode prepared without electrochemical deposition of metal lithium had a long life of only close to 100 cycles, and the coulombic efficiency was not as good as the negative electrode prepared by electrochemical deposition of metal lithium. high, only 94%. (Figure 9).

Claims (10)

1. A metal lithium negative electrode for a secondary battery, comprising a current collector, a lithium-bismuth alloy base layer compounded on the current collector, and a lithium compound layer compounded on the surface of the lithium-bismuth alloy base layer. 2 . The metal lithium negative electrode for a secondary battery according to claim 1 , wherein the material of the lithium-bismuth alloy base layer is Li ₃ Bi and/or LiBi. 3 . 3 . The lithium metal negative electrode for secondary batteries according to claim 1 , wherein the lithium compound layer is at least one of oxides, sulfides, chlorides, nitrides, phosphides, and fluorides of lithium. 4 . One; preferably at least one of Li ₂ O, LiCl, Li ₂ S, Li ₃ N, Li ₃ P, and LiF. 4. The lithium metal negative electrode for secondary batteries according to any one of claims 1 to 3, wherein the current collector used is a metal current collector, preferably at least one of copper, stainless steel, nickel, and titanium; The thickness of the fluid is preferably 10-20 microns; Preferably, the thickness of the lithium-bismuth alloy base layer is 5 microns to 40 microns; Preferably, the thickness of the lithium compound layer is 5 nanometers to 500 nanometers; Preferably, it includes a current collector and an active substance compounded on the current collector, and the active substance is a reaction product of a compound of bismuth and metallic lithium; wherein, the compound of bismuth is preferably bismuth trioxide, bismuth trichloride, trisulfide At least one of bismuth, bismuth disulfide, bismuth phosphide, bismuth fluoride, and bismuth nitride. 5. a preparation method of lithium metal negative electrode for secondary battery, it is characterized in that, compound on the surface of current collector after the compound of bismuth, conductive agent and binder is slurried, and then compound the bismuth on the current collector again. The compound reacts with metallic lithium to prepare the metallic lithium negative electrode for secondary battery. 6. The preparation method of lithium metal negative electrode for secondary battery as claimed in claim 5, wherein the compound of bismuth is bismuth oxide, chloride, sulfide, bismuth phosphide, bismuth fluoride, bismuth nitride at least one of; It is preferably at least one of bismuth trioxide, bismuth trichloride, bismuth trisulfide, bismuth disulfide, bismuth phosphide, bismuth fluoride and bismuth nitride. 7. The preparation method of lithium metal negative electrode for secondary battery as claimed in claim 6, wherein the compound of bismuth is a mixture of bismuth fluoride and bismuth nitride; preferably, the mass ratio is 1～3:1～ 3. A mixture of bismuth fluoride and bismuth nitride. 8. The method for preparing a lithium metal negative electrode for a secondary battery according to claim 5, wherein the mass of the bismuth compound on the current collector is between 1 mg/cm ² and 6 mg/cm ² ; The amount of metallic lithium is not less than 80% of the theoretical molar ratio for the complete reaction of the bismuth compound. 9. The method for preparing a metal lithium negative electrode for a secondary battery according to any one of claims 5 to 8, characterized in that, metal lithium is electrochemically deposited and/or fused on the current collector compounded with a bismuth compound, The metallic lithium is reacted with the compound of bismuth. 10. The application of the metal lithium negative electrode for secondary batteries according to any one of claims 1 to 4 or the metal lithium negative electrode for secondary batteries obtained by the preparation method of any one of claims 5 to 9, characterized in that: As a negative electrode, it is assembled into a lithium-ion battery, a lithium-sulfur battery or a lithium-air battery.

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