阅读说明：本技术 一种功能隔膜、功能隔膜的制备方法及锂金属电池 (Functional diaphragm, preparation method of functional diaphragm and lithium metal battery ) 是由 杨杰 林久 许晓雄 崔言明 于 2020-11-24 设计创作，主要内容包括：本发明公开了一种功能隔膜、功能隔膜的制备方法及锂金属电池,其中功能隔膜包括基膜,还包括第一电子导电层、第二电子导电层和电子绝缘层,所述第一电子导电层和所述第二电子导电层分别位于所述基膜的两侧表面,所述电子绝缘层位于所述第一电子导电层的表面。实现了锂金属电池较慢的容量衰减,并能提前检测锂金属电池内部锂枝晶是否生长至能够刺穿隔膜的程度,从而有效避免隔膜被刺破而造成短路的情况。(The invention discloses a functional diaphragm, a preparation method of the functional diaphragm and a lithium metal battery, wherein the functional diaphragm comprises a base film, a first electronic conducting layer, a second electronic conducting layer and an electronic insulating layer, the first electronic conducting layer and the second electronic conducting layer are respectively positioned on the surfaces of two sides of the base film, and the electronic insulating layer is positioned on the surface of the first electronic conducting layer. The slow capacity attenuation of the lithium metal battery is realized, and whether the lithium dendrite inside the lithium metal battery grows to the extent of being capable of puncturing the diaphragm or not can be detected in advance, so that the situation of short circuit caused by the fact that the diaphragm is punctured is effectively avoided.)

1. A functional separator comprising a base film (1), characterized in that: the film is characterized by further comprising a first electronic conducting layer (2), a second electronic conducting layer (3) and an electronic insulating layer (4), wherein the first electronic conducting layer (2) and the second electronic conducting layer (3) are respectively located on the surfaces of two sides of the base film (1), and the electronic insulating layer (4) is located on the surface of the first electronic conducting layer (2).

2. The functional separator of claim 1, wherein: the base membrane (1) is one of a PP membrane, a PE membrane, a PP/PE/PP membrane, a polyvinylidene fluoride membrane, a polymethyl methacrylate membrane, a polyimide membrane, a polyetherimide membrane, a polycarbonate membrane, a aramid membrane, a non-woven fabric membrane, a cellulose membrane, a polyether-ether-ketone membrane and a perfluorosulfonic ether membrane.

3. The functional separator of claim 1, wherein: the conductive material of the first electronic conducting layer (2) and the second electronic conducting layer (3) comprises one or more of conductive graphite, conductive carbon black, acetylene black, Ketjen black, carbon nano tubes and graphene.

4. The functional separator of claim 1, wherein: the insulating material of the electronic insulating layer (4) comprises one of inorganic solid electrolyte powder, inorganic ceramic powder and organic polymer; the inorganic solid electrolyte powder is one of NASICON type solid electrolyte, perovskite type solid electrolyte, LICCON type solid electrolyte and garnet type solid electrolyte; the inorganic ceramic powder is one or a mixture of more of alumina, zirconia, titania and boehmite; the organic polymer is one or a mixture of PVDF, PVDF-HFP, PVDF-CTFE, PMMA, PAN, PEO, PVAc and PVC.

5. The functional separator of claim 4, wherein: the NASICON type solid electrolyte is Li_{1+ x}Ti_2-xM_x(PO₄)₃、Li_1+xGe_2-xM_x(PO₄)₃Wherein x is more than 0.1 and less than 0.7, and M is one of Al, Ga, In and Sc;

the perovskite type solid electrolyte is Li_3xLa_(2/3)-xTiO₃Wherein x is more than 0 and less than 0.16;

the LISICON type solid electrolyte is Li₁₄ZnGe₄O₁₆；

The garnet type solid electrolyte is Li₅La₃M₂O₁₂、Li₇La₃Zr₂O₁₂Wherein M is one of Ta and Nb.

6. A preparation method of a functional diaphragm is characterized by comprising the following steps: the method comprises the following steps:

step one, selecting a conductive material and an adhesive, mixing and dissolving the conductive material and the adhesive in NMP according to a mass ratio n:1 (n is more than 8 and less than 9), then uniformly mixing the conductive material and the adhesive by ball milling or sanding to form a first slurry, uniformly coating the obtained first slurry on two sides of a base film (1), and drying to obtain a first diaphragm with a first electronic conductive layer (2) and a second electronic conductive layer (3);

step two, when the insulating material adopts inorganic solid electrolyte powder or inorganic ceramic powder, mixing and dissolving the selected insulating material and a binder in NMP according to the mass ratio of m to 1 (m is more than 8 and less than 9), then uniformly mixing by ball milling or sanding to form slurry II, uniformly coating the obtained slurry II on the surface of the first electronic conducting layer (2) of the diaphragm I, and drying to obtain the functional diaphragm;

when the insulating material adopts an organic polymer, the selected organic polymer is directly dissolved in NMP to form slurry III, the obtained slurry III is uniformly coated on the surface of the first electronic conducting layer (2) of the diaphragm I, and the functional diaphragm is obtained after drying.

7. The method for producing a functional separator according to claim 6, characterized in that: the binder is one or more of sodium alginate, beta-cyclodextrin, carboxymethyl cellulose, polyacrylic acid, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-chlorotrifluoroethylene and ethylene-vinyl acetate copolymer.

8. The method for producing a functional separator according to claim 6, characterized in that: the drying temperature in the drying process in the first step and the second step is both 60 +/-5 ℃;

the coating mode in the first step and the second step is at least one of micro-concave coating, extrusion coating, transfer coating, screen printing, spraying, casting and 3D printing.

9. A lithium metal battery, characterized in that: comprising a positive electrode active material, a lithium negative electrode, and the functional separator according to any one of claims 1 to 5, which is located between the positive electrode active material and the lithium negative electrode, and in which the side of the functional separator having an insulating layer faces the positive electrode active material.

10. The lithium metal battery of claim 9, wherein: the positive active material comprises one of lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganese oxide and nickel cobalt aluminum; the material of the lithium negative electrode includes one of metallic lithium, a lithium alloy, and a lithium-containing mixed material.

Technical Field

The invention relates to the technical field of lithium metal batteries, in particular to a functional diaphragm, a preparation method of the functional diaphragm and a lithium metal battery.

Background

With the vigorous development of electronic products and the development of motorization of automobilesThe specific energy demand of society for battery energy storage devices is increasing day by day. In recent 20 years, graphite was used as the negative electrode, lithium cobaltate (LiCoO)₂) And lithium iron phosphate (LiFePO)₄) And lithium ion batteries in which the ternary material is the positive electrode have been widely used and developed. However, due to the lower theoretical specific capacity (372mAh g) of the traditional graphite anode material^-1) And a higher voltage platform, which causes that the traditional lithium ion battery can not further break through the specific energy bottleneck (260 Wh.kg)^-1). It is therefore desirable to further explore negative electrode materials with high theoretical specific capacities and low electrode potentials to achieve higher specific energies for batteries in battery material systems. In recent years, lithium metal has a high theoretical specific capacity (3860mAh g)^-1) And low electrode potential (-3.04V vs SHE), lithium metal cathodes have gained much attention from battery researchers.

In the seventy years of the last century, lithium secondary batteries used metallic lithium as a negative electrode, but were discarded due to serious safety problems. The lithium dendrite is a main problem in the use process of the lithium metal battery, the lithium dendrite continuously grows on the surface of the lithium metal due to the uneven deposition of lithium ions in the multiple charge-discharge cycle process of the battery, and the diaphragm is pierced due to the large stress of a large number of dendrites on the diaphragm, so that the thermal runaway problems of battery short circuit, ignition, gas production explosion and the like are caused, and the lithium metal battery is difficult to take in the practical application process, such as thin ice.

To alleviate the problem of lithium dendrites, researchers have primarily started with three aspects of the electrolyte, the lithium negative electrode surface, and the new form of lithium negative electrode. However, these methods are required to be carried out in a severe environment such as a glove box, are expensive, and are not suitable for industrial production. Therefore, a simple and easy method is urgently needed to realize uniform deposition of lithium ions, quickly detect and judge whether the lithium dendrite grows to pierce a diaphragm and cause the battery to have a micro short circuit, perform battery exception handling as soon as possible, avoid more serious safety problems such as fire, explosion and the like, and is of great importance to the practical application of the lithium metal battery.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a functional diaphragm, a preparation method of the functional diaphragm and a lithium metal battery, which realize the slow capacity attenuation of the lithium metal battery and can detect whether lithium dendrites in the lithium metal battery grow to the extent of being capable of piercing the diaphragm in advance, thereby effectively avoiding the situation of short circuit caused by piercing the diaphragm.

The technical scheme adopted by the invention for solving the technical problems is as follows:

a functional diaphragm comprises a base film, a first electronic conducting layer, a second electronic conducting layer and an electronic insulating layer, wherein the first electronic conducting layer and the second electronic conducting layer are respectively positioned on the two side surfaces of the base film, and the electronic insulating layer is positioned on the surface of the first electronic conducting layer.

Preferably, the base film is one of a PP film, a PE film, a PP/PE/PP film, a polyvinylidene fluoride film, a polymethyl methacrylate film, a polyimide film, a polyetherimide film, a polycarbonate film, a aramid film, a nonwoven fabric film, a cellulose film, a polyether ether ketone film, and a perfluorosulfonic acid ether film.

Preferably, the conductive material of the first and second electron conductive layers comprises one or more of conductive graphite, conductive carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene.

Preferably, the insulating material of the electronic insulating layer includes one of inorganic solid electrolyte powder, inorganic ceramic powder and organic polymer; the inorganic solid electrolyte powder is one of NASICON type solid electrolyte, perovskite type solid electrolyte, LICCON type solid electrolyte and garnet type solid electrolyte; the inorganic ceramic powder is one or a mixture of more of alumina, zirconia, titania and boehmite; the organic polymer is one or a mixture of PVDF, PVDF-HFP, PVDF-CTFE, PMMA, PAN, PEO, PVAc and PVC.

Preferably, the NASICON type solid electrolyte is Li_1+xTi_2-xM_x(PO₄)₃、Li_1+xGe_2-xM_x(PO₄)₃Wherein x is more than 0.1 and less than 0.7, and M is one of Al, Ga, In and Sc;

the perovskite type solid electrolyte is Li_3xLa_(2/3)-xTiO₃Wherein x is more than 0 and less than 0.16;

the LISICON type solid electrolyte is Li₁₄ZnGe₄O₁₆；

The garnet type solid electrolyte is Li₅La₃M₂O₁₂、Li₇La₃Zr₂O₁₂Wherein M is one of Ta and Nb.

A method for preparing a functional separator, comprising the steps of:

step one, selecting a conductive material and an adhesive, mixing and dissolving the conductive material and the adhesive in NMP according to a mass ratio n:1 (n is more than 8 and less than 9), then uniformly mixing the conductive material and the adhesive by ball milling or sanding to form a first slurry, uniformly coating the obtained first slurry on two sides of a base film, and drying to obtain a first diaphragm with a first electronic conductive layer and a second electronic conductive layer;

step two, when the insulating material is inorganic solid electrolyte powder or inorganic ceramic powder, mixing and dissolving the selected insulating material and a binder in NMP according to the mass ratio of m to 1 (m is more than 8 and less than 9), then uniformly mixing by ball milling or sanding to form slurry II, uniformly coating the obtained slurry II on the surface of the first electronic conducting layer of the diaphragm I, and drying to obtain the functional diaphragm;

when the insulating material is an organic polymer, the selected organic polymer is directly dissolved in NMP to form slurry III, the obtained slurry III is uniformly coated on the surface of the first electronic conducting layer of the diaphragm I, and the functional diaphragm is obtained after drying.

Preferably, the binder is one or a mixture of more of sodium alginate, beta-cyclodextrin, carboxymethyl cellulose, polyacrylic acid, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-chlorotrifluoroethylene and ethylene-vinyl acetate copolymer.

Preferably, the drying temperature in the drying process in the first step and the second step is both 60 +/-5 ℃;

the coating mode in the first step and the second step is at least one of micro-concave coating, extrusion coating, transfer coating, screen printing, spraying, casting and 3D printing.

A lithium metal battery comprises a positive electrode active material, a lithium negative electrode and the functional separator, wherein the functional separator is positioned between the positive electrode active material and the lithium negative electrode, and the side of the functional separator with an insulating layer faces the positive electrode active material.

Preferably, the positive electrode active material includes one of lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganese oxide and nickel cobalt aluminum; the material of the lithium negative electrode includes one of metallic lithium, a lithium alloy, and a lithium-containing mixed material.

Compared with the prior art, the functional diaphragm, the preparation method of the functional diaphragm and the lithium metal battery have the advantages that,

(1) the functional diaphragm is applied to a lithium metal battery, the second electronic conducting layer exposed outside the functional diaphragm can form a conducting network on the surface of a lithium negative electrode, and can induce lithium ions to be uniformly deposited, so that lithium dendrite is prevented from forming and growing on the surface of the lithium negative electrode, and the growth speed of the lithium dendrite on the surface of the lithium negative electrode can be effectively reduced; in addition, the conductive material can also absorb lithium ions, and can buffer the lithium ions under the condition of large-current charging and discharging, so that the current density on the surface of the lithium negative electrode is prevented from being instantly increased to prevent the growth of lithium dendrites;

(2) the first electronic conducting layer in the functional diaphragm electronic insulating layer has certain voltage with a lithium cathode of the lithium metal battery in the normal charging and discharging process of the lithium metal battery, when lithium dendrites growing on the surface of the lithium cathode sequentially pass through the second electronic conducting layer and the base film, the lithium dendrites can contact the first electronic conducting layer, the voltage between the first electronic conducting layer and the lithium cathode can be reduced to 0 at the moment, the lithium metal battery has micro short circuit and overcharge phenomena, so that the short circuit of the lithium metal battery is detected in advance, the battery exception handling is carried out as early as possible, meanwhile, the electronic insulating layer avoids the direct contact of the lithium dendrites and the anode, the safety problems of more serious ignition, explosion and the like can be effectively avoided, and the safety performance of the lithium metal battery is further improved;

(3) the method for preparing the functional diaphragm is low in cost, simple to manufacture and easy for mass production, and the lithium metal battery prepared by the functional diaphragm realizes the slow capacity attenuation of the lithium metal battery and the advanced detection of the short circuit of the lithium metal battery caused by the fact that the lithium dendrite grows to pierce the diaphragm.

Drawings

FIG. 1 is a schematic structural view of a functional separator according to the present embodiment;

FIG. 2 is a surface scanning electron micrograph of the functional separator prepared in this example 1, wherein (a) is an electron conductive layer; (b) an electron insulating layer;

fig. 3 is a surface scanning electron micrograph of the functional separator prepared in this example 2, in which (a) is an electron conductive layer; (b) an electron insulating layer;

in the figure, 1, a base film; 2. a first electron conducting layer; 3. a second electron conducting layer; 4. an electron insulating layer.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

A lithium metal battery includes a positive electrode active material, a lithium negative electrode, and a functional separator. The positive active material comprises one of lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganese oxide and nickel cobalt aluminum; the material of the lithium negative electrode includes one of metallic lithium, a lithium alloy, and a lithium-containing hybrid material.

The functional membrane, as shown in fig. 1, includes a base film 1, a first electronic conducting layer 2, a second electronic conducting layer 3 and an electronic insulating layer 4, wherein the first electronic conducting layer 2 and the second electronic conducting layer 3 are respectively coated on two side surfaces of the base film 1, and the electronic insulating layer 4 is coated on a surface of the first electronic conducting layer 2.

In the lithium metal battery, the functional separator is located between the positive electrode active material and the lithium negative electrode, and the side of the functional separator having the insulating layer faces the positive electrode active material.

Specifically, the base film 1 is one of a PP film, a PE film, a PP/PE/PP film, a polyvinylidene fluoride film, a polymethyl methacrylate film, a polyimide film, a polyetherimide film, a polycarbonate film, a aramid film, a nonwoven fabric film, a cellulose film, a polyether ether ketone film, and a perfluorosulfonic acid ether film.

The conductive material of the first electron-conductive layer 2 and the second electron-conductive layer 3 comprises one or more of conductive graphite, conductive carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene.

The insulating material of the electronic insulating layer 4 includes one of inorganic solid electrolyte powder, inorganic ceramic powder, and organic polymer.

Wherein the inorganic solid electrolyte powder is one of NASICON type solid electrolyte, perovskite type solid electrolyte, LISICON type solid electrolyte and garnet type solid electrolyte. The NASICON type solid electrolyte is Li_1+xTi_{2- x}M_x(PO₄)₃、Li_1+xGe_2-xM_x(PO₄)₃Wherein x is more than 0.1 and less than 0.7, and M is one of Al, Ga, In and Sc. The perovskite type solid electrolyte is Li_3xLa_(2/3)-xTiO₃Wherein x is more than 0 and less than 0.16. The LISICON type solid electrolyte is Li₁₄ZnGe₄O₁₆. Garnet-type solid electrolyte Li₅La₃M₂O₁₂、Li₇La₃Zr₂O₁₂Wherein M is one of Ta and Nb.

The inorganic ceramic powder is one or a mixture of more of alumina, zirconia, titania and boehmite.

The organic polymer is one or more of PVDF, PVDF-HFP, PVDF-CTFE, PMMA, PAN, PEO, PVAc and PVC.

The preparation method of the functional diaphragm comprises the following steps:

step one, selecting a conductive material and an adhesive, mixing and dissolving the conductive material and the adhesive in NMP according to a mass ratio n:1 (n is more than 8 and less than 9), then uniformly mixing the conductive material and the adhesive by ball milling or sanding to form a first slurry, uniformly coating the obtained first slurry on two sides of a base film 1, and drying the base film at a flood drying temperature of 60 +/-5 ℃ to obtain a first diaphragm with a first electronic conductive layer 2 and a second electronic conductive layer 3;

step two, when the insulating material is inorganic solid electrolyte powder or inorganic ceramic powder, mixing and dissolving the selected insulating material and a binder in NMP according to the mass ratio of m to 1 (m is more than 8 and less than 9), then uniformly mixing by ball milling or sanding to form slurry II, uniformly coating the obtained slurry II on the surface of the first electronic conducting layer 2 of the diaphragm I, and drying at the flood drying temperature of 60 +/-5 ℃ to obtain the functional diaphragm;

when the insulating material adopts an organic polymer, the selected organic polymer is directly dissolved in NMP to form slurry III, the obtained slurry III is uniformly coated on the surface of the first electronic conducting layer 2 of the diaphragm I, the flood drying temperature is 60 +/-5 ℃, and the functional diaphragm is obtained by drying.

The binder in the first step and the second step is one or a mixture of more of sodium alginate, beta-cyclodextrin, carboxymethyl cellulose, polyacrylic acid, polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-chlorotrifluoroethylene and ethylene-vinyl acetate copolymer.

The coating mode in the first step and the second step comprises at least one of micro-concave coating, extrusion coating, transfer coating, screen printing, spraying, casting and 3D printing.

Compared with the prior art, the functional diaphragm, the preparation method of the functional diaphragm and the lithium metal battery have the advantages that the functional diaphragm is applied to the lithium metal battery, the second electronic conducting layer 3 exposed outside the functional diaphragm can form a conducting network on the surface of the lithium negative electrode, and can induce lithium ions to be uniformly deposited, so that the formation and growth of lithium dendrites on the surface of the lithium negative electrode are hindered, and the growth speed of the lithium dendrites on the surface of the lithium negative electrode can be effectively reduced; in addition, the conductive material can also absorb lithium ions, and can buffer the lithium ions under the condition of large-current charging and discharging, so that the lithium dendrite growth caused by the instantaneous increase of the current density on the surface of the lithium negative electrode is prevented.

First electron conducting layer 2 in this function diaphragm electron insulating layer 4 has certain voltage between the normal charge-discharge in-process of lithium metal battery and the lithium negative pole of lithium metal battery, after lithium dendrite that grows out on lithium negative pole surface passes second electron conducting layer 3 and base film 1 in proper order, lithium dendrite can contact first electron conducting layer 2, voltage between first electron conducting layer 2 and the lithium negative pole can drop to 0 this moment, little short circuit appears in the lithium metal battery, overcharge phenomenon, with this short circuit that detects lithium metal battery in advance, make battery exception handling as early as possible, lithium dendrite and anodal direct contact have been avoided to electron insulating layer 4 simultaneously, can effectively avoid more serious ignition, safety problems such as explosion, further promote lithium metal battery's security performance.

The method for preparing the functional diaphragm is low in cost, simple to manufacture and easy for mass production, and the lithium metal battery prepared by the functional diaphragm realizes the slow capacity attenuation of the lithium metal battery and the advanced detection of the short circuit of the lithium metal battery caused by the fact that the lithium dendrite grows to pierce the diaphragm.

Examples 1,

The functional separator, in this embodiment, the base film 1 is a PE film, the conductive materials of the first electronic conducting layer 2 and the second electronic conducting layer 3 are both conductive carbon black, and the insulating material of the electronic insulating layer 4 is boehmite.

The preparation method of the functional film in the embodiment comprises the following steps:

A. dissolving conductive carbon black and polyvinylidene fluoride-hexafluoropropylene copolymer in a mass ratio of 9:1 in N-methyl pyrrolidone (NMP), uniformly mixing by ball milling to form a first slurry, uniformly coating the first slurry on the surfaces of two sides of a PE film in a micro-concave coating mode, and drying at 60 ℃ to obtain a first diaphragm;

B. and dissolving boehmite and polyvinylidene fluoride in N-methyl pyrrolidone (NMP) according to the mass ratio of 9:1, uniformly mixing by ball milling to form a second slurry, uniformly coating the second slurry on the surface of one side of the first diaphragm in a micro-concave coating mode, and drying at 60 ℃ to obtain the functional diaphragm.

A lithium metal battery including a positive active material, a functional separator, and a lithium negative electrode was prepared using the functional separator in this example, and the functional separator was located between the positive active material and the lithium negative electrode.

The positive active material of the lithium metal battery adopts a nickel cobalt lithium manganate ternary positive electrode, and the lithium negative electrode adopts a metal lithium foil.

The lithium metal battery obtained in the embodiment is subjected to a cyclic charge test, the charge cut-off voltage is 3.0-4.35V VS Li/Li +, and a cyclic performance test is performed at 0.3C, so that the lithium metal battery provided with the functional diaphragm shows good charge and discharge performance, the capacity retention rate is 83.51% after 88 cycles, and an overcharge phenomenon occurs. And the capacity retention rate of the battery provided with the common PE film is only 50.5 percent after 65 cycles.

Examples 2,

The functional separator, in this embodiment, the base film 1 is a polyimide film (PI film), the conductive materials of the first electronic conducting layer 2 and the second electronic conducting layer 3 are carbon nanotubes, and the insulating material of the electronic insulating layer 4 is PVDF.

The preparation method of the functional separator in the embodiment includes the following steps:

A. dissolving a carbon nano tube and a polyvinylidene fluoride-hexafluoropropylene copolymer in N-methyl pyrrolidone (NMP) according to a mass ratio of 9:1, uniformly mixing by sanding to form a first slurry, uniformly coating the first slurry on the surfaces of two sides of a PI film in a tape casting manner, and drying at 60 ℃ to obtain a first diaphragm;

B. and dissolving PVDF in N-methyl pyrrolidone (NMP) to obtain a third slurry, uniformly coating the third slurry on the surface of one side of the first diaphragm in a micro-concave coating mode, and drying at 60 ℃ to obtain the functional diaphragm.

A lithium metal battery including a positive active material, a functional separator, and a lithium negative electrode was prepared using the functional separator in this example, and the functional separator was located between the positive active material and the lithium negative electrode.

The positive electrode active material of the lithium metal battery adopts nickel-cobalt-aluminum NCA, and the lithium negative electrode adopts metal lithium foil.

The lithium metal battery obtained in the embodiment is subjected to a cyclic charge test, the charge cut-off voltage is 3.0-4.35V VS Li/Li +, and a cyclic performance test is performed at 0.3C, so that the lithium metal battery provided with the functional diaphragm shows good charge and discharge performance, the capacity retention rate is 82.4% after 110 cycles, and an overcharge phenomenon occurs. And the capacity retention rate of the battery provided with the common PI film is only 65.2 percent after 83 cycles.

Examples 3,

The functional separator, in this embodiment, the base film 1 is a PP film, the conductive material of the first electronic conducting layer 2 and the second electronic conducting layer 3 is graphene, and the insulating material of the electronic insulating layer 4 is aluminum oxide.

The preparation method of the functional separator in the embodiment includes the following steps:

A. dissolving graphene and polyvinylidene fluoride-hexafluoropropylene copolymer in a mass ratio of 9:1 in N-methyl pyrrolidone (NMP), uniformly mixing by sanding to form a first slurry, uniformly coating the first slurry on the surfaces of two sides of a PP film in a tape casting manner, and drying at 60 ℃ to obtain a first diaphragm;

B. and dissolving alumina and polyacrylic acid in N-methylpyrrolidone (NMP) according to the mass ratio of 8:1, uniformly mixing by ball milling to form a second slurry, uniformly coating the second slurry on the surface of one side of the first diaphragm in a micro-concave coating mode, and drying at 60 ℃ to obtain the functional diaphragm.

A lithium metal battery including a positive active material, a functional separator, and a lithium negative electrode was prepared using the functional separator in this example, and the functional separator was located between the positive active material and the lithium negative electrode.

The positive active material of the lithium metal battery adopts nickel cobalt lithium manganate, and the lithium negative electrode adopts metal lithium foil.

The lithium metal battery obtained in the embodiment is subjected to a cyclic charge test, the charge cut-off voltage is 3.0-4.35V VS Li/Li +, and a cyclic performance test is performed at 0.3C, so that the lithium metal battery provided with the functional diaphragm shows good charge and discharge performance, the capacity retention rate is 83.2% after 93 cycles, and an overcharge phenomenon occurs. And the capacity retention rate of the battery provided with the common PI film is only 54.1 percent after 71 cycles.

Examples 4,

Functional separator, in this embodiment, the base film 1 is a polyimide film (PI film), the conductive material of the first electronic conducting layer 2 and the second electronic conducting layer 3 is conductive carbon black, and the insulating material of the electronic insulating layer 4 is a garnet fast ion conductor LLZTO.

The preparation method of the functional separator in the embodiment includes the following steps:

A. dissolving conductive carbon black and polyvinylidene fluoride-hexafluoropropylene copolymer in a mass ratio of 9:1 in N-methyl pyrrolidone (NMP), uniformly mixing by ball milling to form a first slurry, uniformly coating the first slurry on the surfaces of two sides of a PI film in a micro-concave coating mode, and drying at 60 ℃ to obtain a first diaphragm;

B. and then dissolving the garnet type fast ion conductor LLZTO and polyvinylidene fluoride-chlorotrifluoroethylene in N-methyl pyrrolidone (NMP) according to the mass ratio of 9:1, uniformly mixing by ball milling to form slurry II, uniformly coating the slurry II on the surface of one side of the diaphragm I in a micro-concave coating mode, and drying at 60 ℃ to obtain the functional diaphragm.

A lithium metal battery including a positive active material, a functional separator, and a lithium negative electrode was prepared using the functional separator in this example, and the functional separator was located between the positive active material and the lithium negative electrode.

The positive electrode active material of the lithium metal battery adopts nickel-cobalt-aluminum NCA, and the lithium negative electrode adopts metal lithium foil.

The lithium metal battery obtained in the embodiment is subjected to a cyclic charge test, the charge cut-off voltage is 3.0-4.35V VS Li/Li +, and a cyclic performance test is performed at 0.3C, so that the lithium metal battery provided with the functional diaphragm shows good charge and discharge performance, the capacity retention rate is 84.4% after 125 cycles, and an overcharge phenomenon occurs. And the capacity retention rate of the battery provided with the common PI film is only 68.2 percent after 89 cycles.

First meter and cyclic charging test reference meter

And (3) cyclic charging conditions: the charge cut-off voltage is 3.0-4.35V VS Li/Li +, and the cycle performance test is carried out at 0.3C.

Although preferred embodiments of the present invention have been described in detail hereinabove, it should be clearly understood that modifications and variations of the present invention are possible to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.