CN111193010B - A lithium battery composite material - Google Patents

Abstract

The invention provides a lithium battery composite material which comprises a solid electrolyte and a metal mixed melt coating which is used as a cathode and coated on the surface of the solid electrolyte, wherein the metal mixed melt coating is a mixed melt of metal lithium, metal zinc and lithium oxide. According to the lithium battery composite material, the metal lithium, the metal zinc and the lithium oxide form a mixed melt and then are coated on the surface of the solid electrolyte to form a coating, so that the specific surface area difference between the cathode material and the contact surface of the solid electrolyte is reduced, the lithium battery composite material has smaller impedance and conductivity, and the charging and discharging performance is better.

Description

A lithium battery composite material

technical field

The invention relates to the field of battery materials, in particular to a lithium battery composite material.

Background technique

Lithium-ion batteries are widely used in numerous electronic products and power equipment sources. Since liquid organic lithium-ion batteries are prone to violent combustion when they are bumped or punctured, resulting in personal or property damage, all-solid-state lithium-ion batteries are energy storage devices with high safety. However, due to the huge specific surface energy of molten metal lithium and solid electrolyte, metal lithium cannot be spread in solid electrolyte, resulting in huge ion transport resistance of solid electrolyte and metal lithium, up to 2319Ωcm ^-2 , and leading to molten metal lithium and solid electrolyte. Poor interfacial contact results in uneven ion transport paths, resulting in excessive local current, accelerating lithium dendrite growth, and ultimately leading to short-circuiting of the battery. The invention patent of application number 201810210158.X describes an inorganic-organic composite solid electrolyte, but the current conductivity of organic solid electrolyte is one to two orders of magnitude lower than that of inorganic solid electrolyte, so the conductivity of this electrolyte is higher than that of inorganic solid electrolyte. In addition, due to the addition of organic substances, the electrolyte reduces the mechanical strength of the solid-state electrolyte, the overall density decreases, and is easily punctured by lithium dendrites, which can easily lead to short-circuit of the battery and cause serious accidents.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the shortcomings of the prior art and provide a lithium battery composite material.

In order to achieve the above purpose, the technical solution adopted in the present invention is: a lithium battery composite material, the lithium battery composite material includes a solid electrolyte and a metal mixed melt coating that is coated on the surface of the solid electrolyte as a cathode, so the The metal mixed melt coating is a mixed melt of metallic lithium, metallic zinc and lithium oxide.

The above-mentioned lithium battery composite material is coated on the surface of the solid electrolyte by forming a mixed melt of metal lithium, metal zinc and lithium oxide to form a coating, which reduces the specific surface area difference between the contact surface of the cathode material and the solid electrolyte, so that it contains The metal mixed melt coating of lithium metal adheres better to the surface of the solid electrolyte, and the zinc-lithium alloy is formed in the metal mixed melt coating formed by metal lithium, metal zinc and lithium oxide, which can form electron and lithium ion transport channels. The utilization rate of lithium in the negative electrode is large, and lithium oxide can be used as a buffer for the expansion and deformation of the negative electrode during the charging and discharging process, so that the above-mentioned lithium battery composite material has lower impedance and conductivity, and better charging and discharging performance.

Preferably, the weight ratio of the metallic lithium, metallic zinc and lithium oxide is 10:(1-1.20):(1-1.20).

The inventors have found through research that when the weight ratio of metal lithium, metal zinc and lithium oxide is 10:(1～1.20):(1～1.20) in the metal mixed melt coating coated on the surface of the solid electrolyte as the cathode ), the impedance of the lithium battery composite material is smaller, and the charge and discharge performance is better.

Preferably, the weight ratio of the metallic lithium, metallic zinc and lithium oxide is 10:(1-1.12):(1-1.12).

The inventors have found through research that when the weight ratio of metal lithium, metal zinc and lithium oxide is 10:(1～1.12):(1～1.12 ), the impedance of the lithium battery composite material is smaller, and the charge and discharge performance is better.

Preferably, the weight ratio of the metallic lithium, metallic zinc and lithium oxide is 10:1:1.11.

The inventors found through research that when the weight ratio of metal lithium, metal zinc and lithium oxide in the metal mixed melt coating coated on the surface of the solid electrolyte as the cathode is 10:1:1.11, the above lithium battery composite material The impedance is smaller and the charge and discharge performance is better.

Preferably, the solid electrolyte is lithium lanthanum zirconium oxygen.

Preferably, the preparation method of the lithium battery composite material comprises the following steps:

(1) After polishing the surface of the solid electrolyte, rinse it with an organic solvent and then dry it;

(2) heating lithium metal to 180-250° C. to obtain molten lithium metal A;

(3) adding metallic zinc and lithium oxide to metallic lithium melt A and stirring at 180-250° C. to obtain metallic mixed melt B;

(4) Coating the metal mixed melt B obtained in step (3) on the surface of the solid electrolyte to form a metal mixed melt coating to obtain the lithium battery composite material.

Preferably, in the step (2), the metal lithium is heated to 200° C. to obtain the metal lithium melt A.

The present invention also provides a lithium battery, the lithium battery comprising the lithium battery composite material described above.

The above-mentioned lithium battery application of any one of the above-mentioned lithium battery composite materials has better charge-discharge performance.

The beneficial effects of the present invention are as follows: the present invention provides a lithium battery composite material. The lithium battery composite material of the present invention forms a coating on the surface of a solid electrolyte by forming a mixed molten metal lithium, metal zinc and lithium oxide, and then coating it on the surface of the solid electrolyte. The specific surface area difference between the contact surface of the cathode material and the solid electrolyte is reduced, so that the metal mixed melt coating containing lithium metal can better adhere to the surface of the solid electrolyte. The metal formed by metal lithium, metal zinc and lithium oxide The zinc-lithium alloy formed in the mixed melt coating can form electron and lithium ion transport channels to increase the utilization rate of lithium in the negative electrode, and at the same time, lithium oxide can be used as a buffer for the expansion and deformation of the negative electrode during charging and discharging, so that the lithium The battery composite material has smaller impedance and conductivity, and better charge-discharge performance.

Description of drawings

FIG. 1 is a scanning electron microscope (SEM) image of the lithium battery composite materials of the examples and comparative examples of the present invention.

FIG. 2 is a graph showing the characterization performance of the lithium battery composite materials according to the embodiment of the present invention and the comparative example.

FIG. 3 is an AC impedance spectrum diagram of the lithium battery composite material of the embodiment and the comparative example of the present invention.

FIG. 4 is a graph showing the charge-discharge performance of the lithium battery composite materials according to the embodiment of the present invention and the comparative example.

Detailed ways

In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below with reference to specific embodiments.

Example 1

As a lithium battery composite material according to an embodiment of the present invention, the lithium battery composite material includes a solid electrolyte and a metal mixed melt coating as a cathode coated on the surface of the solid electrolyte, the metal mixed melt coating It is a mixed melt of metal lithium, metal zinc and lithium oxide, the weight ratio of the metal lithium, metal zinc and lithium oxide is 10:1:1, and the solid electrolyte is lithium lanthanum zirconium oxide (LLZTO).

The preparation method of the lithium battery composite material of the present embodiment includes the following steps:

(1) The lithium lanthanum zirconium oxide solid electrolyte with a diameter of 1 cm and a thickness of 1 mm is polished with 2000 mesh sandpaper, rinsed with ethanol and dried;

(2) heating 0.183 g of lithium metal to 200° C. to obtain molten lithium metal A;

(3) adding 0.0183g metal zinc and 0.0183g lithium oxide to the metal lithium melt A, stirring at 200° C. until the white powder completely disappears and removing surface impurities to obtain a metal mixed melt B;

(4) The metal mixed melt B obtained in step (3) is coated on the surface of the solid electrolyte to form a metal mixed melt coating, and the lithium battery composite material is obtained after cooling.

Example 2

As a lithium battery composite material of the embodiment of the present invention, the only difference between this embodiment and Embodiment 1 is that the weight ratio of the metal lithium, metal zinc and lithium oxide is 10:1.11:1.

Example 3

As a lithium battery composite material of an embodiment of the present invention, the only difference between this embodiment and Embodiment 1 is that the weight ratio of the metal lithium, metal zinc and lithium oxide is 10:1:1.11.

Comparative Example 1

As a lithium battery composite material as a comparative example of the present invention, the lithium battery composite material includes a solid electrolyte and a metal mixed melt coating as a cathode coated on the surface of the solid electrolyte, the metal mixed melt coating It is a mixed melt of metal lithium and zinc oxide, the weight ratio of the metal lithium and zinc oxide is 10:1, and the solid electrolyte is lithium lanthanum zirconium oxide (LLZTO).

The preparation method of the lithium battery composite material of this comparative example comprises the following steps:

(1) The lithium lanthanum zirconium oxide solid electrolyte with a diameter of 1 cm and a thickness of 1 mm is polished with 2000 mesh sandpaper, rinsed with ethanol and dried;

(2) heating 0.183 g of lithium metal to 200° C. to obtain molten lithium metal A;

(3) adding 0.0183g of zinc oxide to the molten lithium metal A and stirring at 200° C. until the white powder completely disappears and then removing surface impurities to obtain a mixed molten metal B;

(4) The metal mixed melt B obtained in step (3) is coated on the surface of the solid electrolyte to form a metal mixed melt coating, and the lithium battery composite material is obtained after cooling.

Comparative Example 2

As a lithium battery composite material as a comparative example of the present invention, the lithium battery composite material includes a solid electrolyte and a metal mixed melt coating as a cathode coated on the surface of the solid electrolyte, the metal mixed melt coating It is a mixed melt of metal lithium and metal zinc, the weight ratio of the metal lithium and metal zinc is 10:1.11, and the solid electrolyte is lithium lanthanum zirconium oxide (LLZTO).

The preparation method of the lithium battery composite material of this comparative example comprises the following steps:

(1) The lithium lanthanum zirconium oxide solid electrolyte with a diameter of 1 cm and a thickness of 1 mm is polished with 2000 mesh sandpaper, rinsed with ethanol and dried;

(2) heating 0.183 g of lithium metal to 200° C. to obtain molten lithium metal A;

(3) adding 0.0203 g of metallic zinc into the molten lithium metal A, stirring at 200° C. until the white powder completely disappears, and removing surface impurities to obtain a mixed molten metal B;

(4) The metal mixed melt B obtained in step (3) is coated on the surface of the solid electrolyte to form a metal mixed melt coating, and the lithium battery composite material is obtained after cooling.

Comparative Example 3

As a lithium battery composite material as a comparative example of the present invention, the lithium battery composite material includes a solid electrolyte and a metal melt coating as a cathode, which is coated on the surface of the solid electrolyte, and the metal melt coating is a metal Lithium melt, and the solid electrolyte is lithium lanthanum zirconium oxide (LLZTO).

The preparation method of the lithium battery composite material of this comparative example comprises the following steps:

(1) The lithium lanthanum zirconium oxide solid electrolyte with a diameter of 1 cm and a thickness of 1 mm is polished with 2000 mesh sandpaper, rinsed with ethanol and dried;

(2) heating 0.183 g of lithium metal to 200° C. to obtain molten lithium metal A;

(3) Coating the metal mixed melt A obtained in step (2) on the surface of the solid electrolyte to form a metal melt coating, and cooling to obtain the lithium battery composite material.

Effect example 1

Scanning electron microscopy, X-ray diffraction analysis, and charge-discharge performance tests were performed on the lithium battery composite materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3.

As shown in FIG. 1 , FIG. 1( a ) is a scanning electron microscope (SEM) image of the lithium battery composite material of Comparative Example 1, and FIG. 1( b ) is a scanning electron microscope (SEM) image of the lithium battery composite material of Comparative Example 2 Fig. 1(c) is a scanning electron microscope (SEM) image of the lithium battery composite material of Comparative Example 3, Fig. 1(d) is a scanning electron microscope (SEM) image of the lithium battery composite material of Example 1, Fig. 1 (e) is a scanning electron microscope (SEM) image of the lithium battery composite material of Example 2, and FIG. 1(f) is a scanning electron microscope (SEM) image of the lithium battery composite material of Example 3. It can be seen from Figure 1 that the roughness of the lithium battery composite materials of Examples 1 to 3 is better than that of the lithium battery composite materials of Comparative Examples 1 to 3, indicating that lithium oxide, zinc and lithium are combined to form a metal mixed melt coating tile. On the surface of the solid electrolyte, the current density of the lithium battery composite material can be reduced and the formation of lithium dendrites can be alleviated.

As shown in Fig. 2, Fig. 2(a) is a physical image of Comparative Example 3, and Fig. 2(a) shows that the molten lithium metal of Comparative Example 3 cannot spread on the surface of the solid electrolyte sheet, and Fig. 2(b) is an example 3, FIG. 2(c) is the SEM image of the lithium battery composite material of Example 3, and FIG. 2(d) is the infrared diffraction XRD pattern of the lithium battery composite material of Example 3. Figure 2(b) shows that the lithium battery composite material of Example 3 contains lithium-zinc alloy, lithium oxide and metal lithium, and Figures 2(c) and 2(d) illustrate the metal formed by metal lithium, metal zinc and lithium oxide The mixed melt coating (Li-ZnO) can be spread on the surface of the solid electrolyte (LLZTO) and tightly adhered to the solid electrolyte. It can be seen from FIG. 2(d) that the contact interface between the metal mixed melt coating and the solid electrolyte in the lithium battery composite material of Example 3 has no voids.

As shown in Figure 3, Figure 3(a) is the AC impedance diagram of the lithium battery composite material of Comparative Example 1, Figure 3(b) is the AC impedance diagram of the lithium battery composite material of Comparative Example 2, and Figure 3(c) is The AC impedance diagram of the lithium battery composite material of Comparative Example 3, FIG. 3(d) is the AC impedance diagram of the lithium battery composite material of Example 1, and FIG. 3(e) is the AC impedance diagram of the lithium battery composite material of Example 2 , Figure 3(f) is the AC impedance diagram of the lithium battery composite material of Example 3. The interface ion transfer impedance of the lithium battery composite material of Comparative Example 1 is 125Ωcm ^-2 , the interface ion transfer impedance of the lithium battery composite material of Comparative Example 2 is 250Ωcm ^-2 , and the interface ion transfer impedance of the lithium battery composite material of Comparative Example 3 is 2319Ωcm ^-2 , the interface ion transfer impedance of the lithium battery composite material of Example 1 is 80Ωcm ^{-2 , the interface ion transfer impedance of the lithium battery composite material of Example 2 is 85Ωcm -2 ,} and the interface of the lithium battery composite material of Example 3 The ion transfer impedance is 35Ωcm ^-2 , and the interface ion transfer impedance of the lithium battery composite materials of Examples 1 to 3 is much smaller than that of the lithium battery composite materials of Comparative Examples 1 to 3, indicating that lithium oxide, zinc and The combination of lithium to form a metal mixed melt coating spread on the surface of the solid electrolyte can reduce the AC impedance of the lithium battery composite. In addition, the comparative examples from Examples 1 to 3 found that the AC impedance of Example 3 is relatively lower, indicating that the weight ratio of metal lithium, metal zinc and lithium oxide is 10:1:1.11 The interface ion transfer resistance of the lithium battery composite material is lower .

As shown in Figure 4, Figure 4(a) is the charge-discharge performance diagram of the lithium battery composite material assembled into the counter electrode of Comparative Example 1, and Figure 4(b) is the charge and discharge performance of the lithium battery composite material assembled into the counter electrode of Comparative Example 2. Discharge performance diagram, Figure 4(c) is the charge and discharge performance diagram of the lithium battery composite material of Comparative Example 3 assembled into a counter electrode, and Figure 4(d) is the charge and discharge performance of the lithium battery composite material of Example 1 assembled into a counter electrode Figure 4(e) is a charge-discharge performance diagram of the lithium battery composite material of Example 2 assembled into a counter electrode, and Figure 4(f) is a charge-discharge performance diagram of the lithium battery composite material of Example 3 assembled into a counter electrode. It can be seen from Fig. 4 that at a current density of 0.1 mA cm ^-2 , the lithium battery composite material of Comparative Example 3 was assembled into a short circuit situation, indicating that the electrode assembled by the lithium battery composite material of Comparative Example 3 could not inhibit the formation of lithium dendrites. The voltage of Comparative Example 1, Comparative Example 3 and Examples 1 to 3 are all maintained at about 0.02V. When the current density rises to 0.2mAcm- ² , when the current density rises to 0.2mAcm ^-2 , Comparative Example 1 Compared with Comparative Example 2, the voltage instantly reached 0.12V, indicating that the interface of the lithium battery composite material in Comparative Example 1 and Comparative Example 2 also has a large ion transfer resistance, which corresponds to the result of the AC impedance spectrum, and then the voltage gradually decreases, indicating that Li dendrites start and gradually grow into the interior of Li dendrites, which reduces the ion transmission distance and the apparent voltage. The voltage of the lithium battery composite material of Example 2 gradually decreased from 0.04V, and there was fluctuation Crystal growth short-circuits the electrodes. The voltage of Example 3 is relatively stable, indicating that the lithium battery composite material of Example 3 has the best effect of inhibiting lithium dendrites.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that, The technical solutions of the present invention may be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims (7)

1. A lithium battery composite material, which is characterized by comprising a solid electrolyte and a metal mixed melt coating as a negative electrode, wherein the metal mixed melt coating is a mixed melt of metal lithium, metal zinc and lithium oxide; the weight ratio of the metal lithium to the metal zinc to the lithium oxide is 10: (1-1.20): (1-1.20).

2. The lithium battery composite material as claimed in claim 1, wherein the weight ratio of the metallic lithium, the metallic zinc and the lithium oxide is 10: (1-1.12): (1-1.12).

3. The lithium battery composite material as claimed in claim 1, wherein the weight ratio of the metallic lithium, the metallic zinc and the lithium oxide is 10: 1: 1.11.

4. the lithium battery composite of claim 1, wherein the solid state electrolyte is lithium lanthanum zirconium oxygen.

5. The lithium battery composite material as claimed in claim 1, wherein the preparation method of the lithium battery composite material comprises the steps of:

(1) polishing the surface of the solid electrolyte, washing with an organic solvent, and drying;

(2) heating the metal lithium to 180-250 ℃ to obtain a metal lithium melt A;

(3) adding metal zinc and lithium oxide into the metal lithium melt A, and stirring at 180-250 ℃ to obtain a metal mixed melt B;

(4) and (4) coating the metal mixed melt B obtained in the step (3) on the surface of a solid electrolyte to form a metal mixed melt coating, so as to obtain the lithium battery composite material.

6. The lithium battery composite material as claimed in claim 5, wherein in the step (2), the metallic lithium is heated to 200 ℃ to obtain the metallic lithium melt A.

7. A lithium battery, characterized in that it comprises a lithium battery composite as claimed in any one of claims 1 to 6.

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