Current collector of cathode-free metal battery, preparation method of current collector and cathode-free metal battery

Abstract

The invention relates to the technical field of battery materials, and discloses a current collector of a cathode-free metal battery, a preparation method of the current collector and the cathode-free metal battery. The current collector of the negative-electrode-free metal battery comprises a current collector base material and a three-dimensional network structure layer arranged on the surface of the current collector base material, and the three-dimensional network structure layer is provided with grids which are uniformly distributed and used for depositing metal sodium; the components of the three-dimensional network structure layer comprise a solid electrolyte and a binder. Due to the arrangement of the three-dimensional network structure layer on the surface of the current collector, the electrochemical performance is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and in particular, to a current collector for an anode-free metal battery, a preparation method thereof, and an anode-free metal battery. Background Art

[0002] An anode-free battery is a battery that uses a layered oxide material, a Prussian blue analogue material, or a polyanion as the positive electrode, and a coated carbon metal foil fluid as the negative electrode. It mainly uses ethers as solvents, and adds metal salts (such as fluorides, borates, and perchlorates, etc.) electrolytes and various additives (such as film-forming, flame-retardant, and overcharge protection types, etc.) to form an electrolyte solution. Although anode-free batteries have advantages such as good low-temperature performance, low cost, and high energy density, in anode-free metal batteries at higher energy densities, the growth of metal dendrites is more violent, and there is a risk of rapid short-circuit of the battery, which will seriously hinder the application of the battery. As a key component in the battery, the most common modification of the current collector is only to coat a conductive agent on the surface of the metal foil. Such a current collector is too traditional and may no longer be suitable for the obvious volume change characteristics of anode-free sodium batteries. In addition, the growth of metal dendrites on the plane of the metal foil is also likely to pierce the separator and cause more side reactions, which greatly reduces the cycle life of the battery.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] The purpose of the present invention is to provide a current collector for an anode-free metal battery, a preparation method thereof, and an anode-free metal battery, aiming to improve at least one problem mentioned in the background art.

[0005] The present invention is implemented as follows: In a first aspect, the present invention provides a current collector for an anode-free metal battery, including a current collector substrate and a three-dimensional network structure layer provided on the surface of the current collector substrate. The three-dimensional network structure layer has uniformly distributed grids for depositing metallic sodium. The thickness of the three-dimensional network structure layer is 3-10 μm. The components of the three-dimensional network structure layer include, by weight: 4-7 parts of solid electrolyte and 2 parts of binder.

[0006] In an optional embodiment, the components of the three-dimensional network structure layer further include 0.2-1.5 parts of an adsorbent capable of adsorbing gas.

[0007] In an optional embodiment, it further includes at least one of the following features (1) and (2): (1) The adsorbent is selected from at least one of molecular sieve, zeolite, and porous silica; (2) The particle size of the adsorbent is 200-1000 nm.

[0008] In an alternative embodiment, it further includes at least one of the following features (1) and (2): (1) The solid electrolyte is selected from at least one of lanthanum sodium zirconium oxide, sodium aluminum titanium phosphate, sodium aluminum oxide, poly(ethylene oxide), polyacrylonitrile, Na 3 PS 4 , Na 4 P 2 S 7 and Na 11 Sn 2 PS 12 ; (2) The particle size of the solid electrolyte is 200 - 500 nm.

[0009] In an alternative embodiment, the current collector substrate is carbon-coated aluminum foil.

[0010] In a second aspect, an embodiment of the present invention provides a method for preparing the above current collector, including: Coating the slurry onto the current collector substrate using a gravure roll with a grid pattern to form a three-dimensional network structure-like coating on the surface of the current collector substrate; Drying the current collector substrate with the three-dimensional network structure-like coating to volatilize the solvent in the coating, thereby forming the three-dimensional network structure layer on the current collector substrate.

[0011] In an alternative embodiment, the components of the slurry include effective components for forming the three-dimensional network structure layer, a dispersant, and the solvent; By weight, the slurry includes 6.2 - 10.5 parts of effective components and 0.5 - 1.5 parts of dispersant.

[0012] In an alternative embodiment, it includes at least one of the following technical features (1) - (3): (1) The dispersant is selected from at least one of sodium carboxymethyl cellulose, polyacrylic acid, and polyvinylpyrrolidone; (2) The solid content of the slurry is 60 - 80 wt%; (3) The solvent is water.

[0013] In a third aspect, an embodiment of the present invention provides a non-aqueous anode metal battery, including a positive electrode, a separator, the aforementioned current collector, and an electrolyte; The surface of the separator has an adhesive layer, and the three-dimensional network structure layer of the current collector is adhered to the adhesive layer on the surface of the separator.

[0014] In an alternative embodiment, it includes at least one of the following technical features (1) - (3): (1) The material of the adhesive layer is at least one of PVDF and PMMA; (2)The components of the electrolyte include a solvent and a salt, and the salt is a lithium salt or a sodium salt; (3)The preparation method of the non - negative - electrode metal battery includes: Press the stacked positive electrode sheet, separator, and current collector. When pressing, the pressure is 2 - 5T, the temperature is 60 - 95 °C, and the pressing time is 60 - 240s.

[0015] The present invention has the following beneficial effects: The uniform grid structure formed mainly by the solid - state electrolyte can provide a uniform fast - ion path, enabling ions to stably and uniformly pass through the path to reach the carbon - coated aluminum foil. Since both the grid structure and the separator have poor conductivity, metal ions will preferentially deposit on the current - collector substrate with excellent conductivity. Also, since there is no deposition space at the connection sites between the grid structure and the current - collector substrate, metal ions will transfer to the grid and deposit at the grid positions after reaching the aluminum foil. Therefore, the setting of the three - dimensional network structure layer provides space for the deposition of metal ions, reduces the disordered growth and accumulation of the deposited metal, and reduces the volume change of the battery. In addition, since metal ions tend to flow more in the ion path (solid - state electrolyte), the reaction rate is accelerated and the occurrence of side reactions is reduced. Therefore, after the current collector provided by the embodiments of the present invention is applied in the non - negative - electrode metal battery, compared with ordinary current collectors, it can improve the electrochemical performance of the battery and extend its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required in the embodiments. It should be understood that the following drawings only show some embodiments of the present invention, so they should not be regarded as limiting the scope. For those of ordinary skill in the art, without creative efforts, other related drawings can also be obtained based on these drawings.

[0017] Figure 1 It is a top - view schematic diagram of the three - dimensional network structure layer; Figure 2 It is a working principle diagram of the current collector. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those conditions not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0019] The current collector for the non - negative - electrode metal battery provided by the present invention, its preparation method, and the non - negative - electrode metal battery will be specifically described below with reference to specific embodiments.

[0020] As shown Figure 1 in the figure, the current collector of the non-aqueous anode metal battery provided by the embodiment of the present invention includes a current collector substrate and a three-dimensional network structure layer disposed on the surface of the current collector substrate. The three-dimensional network structure layer has grids uniformly distributed for depositing metallic sodium; The thickness of the three-dimensional network structure layer is 3-10 μm; The components of the three-dimensional network structure layer by weight include: 4-7 parts of solid electrolyte and 2 parts of binder.

[0021] For the current collector of the non-aqueous anode metal battery provided by the embodiment of the present invention, the uniform grid structure formed by the solid electrolyte as the main component can provide a uniform fast ion path, enabling ions to stably and uniformly pass through the path to reach the carbon-coated aluminum foil. Since both the grid structure and the separator have poor conductivity, metal ions will preferentially deposit on the current collector substrate with excellent conductivity. Also, since there is no deposition space at the connection sites between the grid structure and the current collector substrate, the metal ions will transfer to the grid and deposit at the grid positions after reaching the aluminum foil. Therefore, the setting of the three-dimensional network structure layer provides space for the deposition of metal ions, reduces the disordered growth and accumulation of the deposited metal, and reduces the volume change of the battery. In addition, since metal ions tend to flow in the ion path (solid electrolyte), the reaction is also accelerated, and the occurrence of side reactions is reduced. Therefore, after the current collector provided by the embodiment of the present invention is applied in the non-aqueous anode metal battery, it can improve the electrochemical performance of the battery and extend its service life compared with ordinary current collectors.

[0022] It should be noted that the thickness of the three-dimensional network structure layer needs to be within the range required by the present invention. If the thickness is too low, the improvement effect on the electrochemical performance of the current collector is not obvious. If the thickness is too high, the conductivity of the current collector decreases and the battery energy density decreases.

[0023] Optionally, the solid electrolyte can be an oxide-based solid electrolyte, a polymer-based solid electrolyte, and a sulfide-based solid electrolyte.

[0024] Specifically, the solid electrolyte is selected from at least one of lanthanum sodium zirconium oxide, sodium aluminum titanium phosphate, sodium aluminum oxide, polyethylene oxide, polyacrylonitrile, Na 3 PS 4 、Na 4 P 2 S 7 and Na 11 Sn 2 PS 12 .

[0025] Optionally, the particle size of the solid electrolyte is 200-500 nm.

[0026] Optionally, the components of the three-dimensional network structure layer further include 0.2 to 1.5 parts of an adsorbent capable of adsorbing gas.

[0027] As the metal is deposited, the grid-like skeleton will be wrapped therein, and the adsorbent in the skeleton can better play the role of adsorbing the gas generated by side reactions in the metal, further improving the performance of the battery.

[0028] It should be noted that the ratio of the adsorbent should be within the range required by the present invention. If the content is too high, the ability to conduct ions will decrease.

[0029] Optionally, the adsorbent is selected from at least one of molecular sieve, zeolite and porous silica. Its particle size is 200 to 1000 nm.

[0030] Optionally, the current collector substrate is copper foil or aluminum foil. Preferably, in order to make the current collector have better conductivity and further promote the deposition of metal ions, the current collector substrate is carbon-coated aluminum foil.

[0031] The preparation method of the current collector provided by the embodiment of the present invention includes: Coating the slurry onto the current collector substrate by using an intaglio roll with grid lines to form a three-dimensional network structure-like coating on the surface of the current collector substrate; Drying the current collector substrate with the three-dimensional network structure-like coating to volatilize the solvent in the coating, thereby forming a three-dimensional network structure layer on the current collector substrate.

[0032] The intaglio roll coating method can form a three-dimensional network structure-like coating on the surface of the current collector substrate, and after drying, a current collector with a three-dimensional network structure layer on the surface can be obtained.

[0033] Specifically, the roll coating equipment is a conventional roll coating equipment.

[0034] Start the roll coating equipment. The intaglio roll rotates in the slurry tank to pick up the slurry, and the doctor blade scrapes off the excess slurry on the roll surface. Subsequently, the intaglio roll contacts the carbon-coated aluminum foil substrate, and the slurry is transferred to the substrate to obtain a coating with a coating thickness of 3 to 10 μm; Send the substrate with the coating into the drying oven at 100 °C to volatilize the solvent in the slurry, and obtain a current collector with a three-dimensional network structure layer firmly adhered to the surface of the current collector substrate.

[0035] Specifically, the components of the slurry include effective components for forming the three-dimensional network structure layer, a dispersant and a solvent.

[0036] Further, by weight, the slurry includes 6.2 to 10.5 parts of effective components and 0.5 to 1.5 parts of a dispersant. The addition of the dispersant helps to mix the various components in the slurry evenly.

[0037] Optionally, the dispersant is selected from at least one of sodium carboxymethyl cellulose, polyacrylic acid, and polyvinylpyrrolidone.

[0038] Optionally, to ensure better viscosity and fluidity of the slurry, the solid content of the slurry is 60 - 80 wt%.

[0039] Optionally, the solvent is water.

[0040] A non - negative electrode metal battery provided by an embodiment of the present invention includes a positive electrode, a separator, a current collector provided by the embodiment of the present invention, and an electrolyte; The surface of the separator has an adhesive layer, and the three - dimensional network structure layer of the current collector is adhered to the adhesive layer on the surface of the separator.

[0041] Optionally, the positive electrode is formed by coating an active material (common materials for lithium / sodium batteries: polyanion materials, layered oxide materials, Prussian blue analog materials, etc.) on a copper foil or aluminum foil current collector with carbon coating.

[0042] Optionally, the material of the adhesive layer is at least one of PVDF and PMMA.

[0043] Specifically, the separator includes a base film and an adhesive layer coated on the surface of the base film. The material of the base film is polyethylene, polypropylene, glass fiber, etc.

[0044] Optionally, the components of the electrolyte include a solvent and a salt, and the salt is a lithium salt or a sodium salt.

[0045] Specifically, if the battery is a lithium battery, the salt is a lithium salt, and the lithium salt is a salt that has been publicly available for use in lithium battery electrolytes.

[0046] If the battery is a sodium battery, the salt is a sodium salt, and the sodium salt is a salt that has been publicly available for use in sodium battery electrolytes.

[0047] Specifically, the solvent can use a solvent that has been publicly available for use in electrolytes of lithium - ion or sodium - ion batteries, such as diethylene glycol dimethyl ether or ethylene glycol dimethyl ether, etc.

[0048] Optionally, the preparation method of the non - negative electrode metal battery includes: Press the stacked positive electrode sheet, separator, and current collector. When pressing, the pressure is 2 - 5T, the temperature is 60 - 95 °C, and the pressing time is 60 - 240s.

[0049] The features and properties of the present invention will be further described in detail below in conjunction with embodiments.

[0050] Example 1 Prepare a slurry: By weight, 5 parts of a solid electrolyte (sodium lanthanum zirconium oxide Na 7 La 3 Zr 2 O 12), 2 parts of binder (PVDF), 2 parts of dispersant (CMC), and 1 part of adsorbent (molecular sieve with a particle size of 200 - 500 nm) are mixed evenly with water to obtain a slurry with a solid content of 70%; Coating: Start the roll coating equipment. The gravure roll with a grid pattern on its surface rotates in the slurry tank to pick up the slurry, and the doctor blade scrapes off the excess slurry on the roll surface. Subsequently, the gravure roll contacts the carbon-coated aluminum foil substrate, and the slurry is transferred to the substrate to obtain a coating with a thickness of 5 μm; Drying: The substrate with the coating is sent into a drying oven at 100 °C to volatilize the solvent in the slurry, obtaining a current collector with a three-dimensional network structure layer firmly adhered to the surface of the current collector substrate.

[0051] Provide the positive electrode sheet: The carbon-coated aluminum foil serves as the current collector, and its surface is coated with an active layer. The active layer is composed of sodium iron pyrophosphate, PVDF, SP, and PVP with a mass ratio of 90:4:4:2; Provide the separator: A polyethylene-based film with a PVDF layer with a thickness of 2 μm coated on its surface.

[0052] Stack the positive electrode sheet, separator, and current collector in sequence, and then perform pressing. The pressure during pressing is 3T, the temperature is 75 °C, and the pressing time is 100 s. Then assemble it with the electrolyte into a battery. The electrolyte formula is: 1M NaPF 6 , and the solvent is diglyme.

[0053] Example 2 This example is basically the same as Example 1, except that the composition of the slurry is different, and the thickness of the three-dimensional network structure layer on the current collector is different.

[0054] The preparation method of the slurry in this example is as follows: By weight, 4 parts of solid electrolyte (sodium aluminum titanium phosphate NaAlTi(PO 4 ) 3 ), 2 parts of binder (PVDF), 0.5 part of dispersant (CMC), and 0.2 part of adsorbent (porous silica with a particle size of 200 - 500 nm) are mixed evenly with water to obtain a slurry with a solid content of 60%.

[0055] The thickness of the three-dimensional network structure layer on the current collector is 3 μm.

[0056] Example 3 This example is basically the same as Example 1, except that the composition of the slurry is different, and the thickness of the three-dimensional network structure layer on the current collector is different.

[0057] The preparation method of the slurry in this example is as follows: By weight, 7 parts of solid electrolyte (sodium aluminum oxide Na 2 O·11Al2 O 3 ), 2 parts of binder (PVDF), 1.5 parts of dispersant (CMC), and 1.5 parts of adsorbent (porous silica with a particle size of 200 - 500 nm) are mixed evenly with water to obtain a slurry with a solid content of 80%.

[0058] The thickness of the three - dimensional network structure layer on the current collector is 10 μm.

[0059] Example 4 This example is basically the same as Example 3, except that: the slurry does not contain an adsorbent, that is, the slurry formula is: 7 parts of solid electrolyte (sodium alumina Na 2 O·11Al 2 O 3 ), 2 parts of binder (PVDF), and 1.5 parts of dispersant (CMC).

[0060] Comparative Example 1 This comparative example is basically the same as Example 4, except that: the current collector substrate is directly used as the current collector.

[0061] Comparative Example 2 This comparative example is basically the same as Example 3, except that: the thickness of the three - dimensional network structure layer on the current collector is 15 μm.

[0062] Comparative Example 3 This comparative example is basically the same as Example 3, except that: in the slurry, an equal amount of adsorbent is used to replace the solid electrolyte, that is, the slurry formula is: 7 parts of adsorbent (porous silica with a particle size of 200 - 500 nm), 2 parts of binder (PVDF), and 1.5 parts of dispersant (CMC).

[0063] Example Test the electrochemical performance of the batteries in each example and comparative example, and test the exhaust volume. The test method for the exhaust volume is the drainage method. Specifically: Place a water tank on an electronic balance, and place the soft - pack battery in water so that it is just submerged in water. Principle: Archimedes, F 浮 =G 排 =ρ 水 gV 排 ρ 水 g = 10. V 排 =1 / 10 F 浮 = the weight shown on the electronic scale (g).

[0064] Record the test results in Table 1.

[0065] Table 1 Electrochemical performance of each example and comparative example

[0066] As can be seen from Table 1, the batteries prepared in the embodiments of the present invention have significantly improved cycle performance compared to Comparative Example 1; Comparing Comparative Example 2 with Example 3, the specific capacity, Coulomb efficiency, and capacity retention rate of Comparative Example 2 are significantly worse. This shows that if the thickness of the three-dimensional network structure layer is too thick, the specific capacity, Coulomb efficiency, and capacity retention rate will deteriorate due to reduced conductivity; Comparing Comparative Example 3 with Example 3, the Coulomb efficiency and capacity retention rate of Comparative Example 3 are poor. This shows that if there is no solid electrolyte in the slurry, there is no way to provide a path for sodium ions, and the reversibility of sodium metal deposition deteriorates; Comparing Example 4 with Example 3, the gas exhaust volume of Example 4 is higher than that of Example 3. This shows that the adsorbent added in Example 3 has an adsorption effect on the generated gas, can slow down the volume expansion of the battery, and thus achieve the effect of extending the service life of the battery.

[0067] In summary, for the current collector of the non-anode metal battery provided by the embodiments of the present invention, the setting of the three-dimensional network structure layer provides space for the deposition of metal ions, reducing the disordered growth and accumulation of the deposited metal. In addition, since metal ions tend to flow in the ion channels (solid electrolyte), the reaction is also accelerated, and the occurrence of side reactions is reduced. Therefore, after the current collector provided by the embodiments of the present invention is applied in a non-anode metal battery, compared with a common current collector, it can improve the electrochemical performance of the battery and extend its service life.

[0068] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A current collector for a negative electrode metal-free battery, characterized in that: It comprises a current collector substrate and a three-dimensional network structure layer arranged on the surface of the current collector substrate, wherein the three-dimensional network structure layer has a uniformly distributed grid for depositing metallic sodium; The thickness of the three-dimensional network structure layer is 3-10 μm; The components of the three-dimensional network structure layer include, by weight: 4 to 7 parts of solid electrolyte and 2 parts of binder.

2. The current collector according to claim 1, characterized in that: The components of the three-dimensional network structure layer also include 0.2 to 1.5 parts of an adsorbent capable of adsorbing gas.

3. The current collector according to claim 2, characterized in that: Also includes at least one of the following features (1) and (2): (1) The adsorbent is selected from at least one of molecular sieves, zeolites and porous silica; (2) The particle size of the adsorbent is 200~1000nm.

4. The current collector according to claim 1, characterized in that: Also includes at least one of the following features (1) and (2): (1) The solid electrolyte is selected from sodium lanthanum zirconium oxide, sodium aluminum titanium phosphide, sodium aluminum oxide, polyethylene oxide, polyacrylonitrile, Na3PS4, Na4P2S7 and Na 11 Sn2PS 12 At least one of the following; (2) The particle size of the solid electrolyte is 200~500nm.

5. The current collector according to claim 1, characterized in that: The current collector substrate is carbon-coated aluminum foil.

6. The method for preparing a current collector according to any one of claims 1 to 5, characterized in that: include: The slurry is applied to the current collector substrate using a gravure roller having a grid pattern, so that a three-dimensional network structure-like coating is formed on the surface of the current collector substrate; The current collector substrate having the three-dimensional network structure-like coating is dried to volatilize the solvent in the coating, thereby forming the three-dimensional network structure layer on the current collector substrate.

7. The preparation method according to claim 6, characterized in that: The components of the slurry include an effective component for forming the three-dimensional network structure layer, a dispersant and the solvent; The slurry comprises 6.2-10.5 parts of effective components and 0.5-1.5 parts of dispersant by weight.

8. The preparation method according to claim 6, characterized in that: It includes at least one of the following technical features (1) to (3): (1) The dispersant is selected from at least one of sodium carboxymethyl cellulose, polyacrylic acid and polyvinyl pyrrolidone; (2) The solid content of the slurry is 60-80wt%; (3) The solvent is water.

9. A negative electrode metal-free battery, characterized in that: Comprising a positive electrode, a separator, a current collector as claimed in any one of claims 1 to 5, and an electrolyte; The surface of the separator has an adhesive layer, and the three-dimensional network structure layer of the current collector is bonded to the adhesive layer on the surface of the separator.

10. The negative electrode-free metal battery according to claim 9, characterized in that: It includes at least one of the following technical features (1) to (3): (1) The material of the adhesive layer is at least one of PVDF and PMMA; (2) The components of the electrolyte include a solvent and a salt, and the salt is a lithium salt or a sodium salt; (3) The preparation method of the negative electrode metal-free battery includes: The stacked positive electrode sheet, separator and current collector are pressed at a pressure of 2-5T, a temperature of 60-95°C and a pressing time of 60-240s.

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