CN115377356A - Three-dimensional vertical porous composite alkali metal cathode and preparation method and application thereof - Google Patents

Abstract

The invention discloses a three-dimensional vertical porous composite alkali metal cathode and a preparation method and application thereof, wherein a polymer and an organic solvent are mixed and fully stirred to obtain a precursor solution; coating the precursor solution on the surface of alkali metal in situ by a simple scraper blade coating method, drying at low temperature in an inert atmosphere, and obtaining the alkali metal containing the composite polymer layer after the organic solvent in the coating is completely volatilized; and punching the surface of the composite polymer layer by a mechanical punching method to obtain the three-dimensional vertical porous composite alkali metal cathode. The preparation method is simple in preparation process, low in cost and suitable for large-scale commercial production, and the densified deposition morphology is obtained by adjusting and controlling the growth mode of the dendritic deposition alkali metal through another method, so that the cycling stability of the battery is greatly improved, the application prospect is wide, and the breakthrough of high safety of the secondary alkali metal battery is facilitated.

Description

A three-dimensional vertical porous composite alkali metal negative electrode and its preparation method and application

technical field

The invention belongs to the technical field of metal battery preparation, and in particular relates to a three-dimensional vertical porous composite alkali metal negative electrode and its preparation method and application.

Background technique

Traditional secondary batteries are gradually difficult to meet the high energy density and safety requirements of large-scale energy storage devices such as electric vehicles and photovoltaic power stations that are rapidly developing. For example, for lithium-ion batteries based on ion intercalation/deintercalation reactions, the specific capacity of the anode has approached its theoretical limit (372mAh g ^-1 ), which severely limits further breakthroughs in the overall energy density of lithium-ion batteries. The high specific capacity negative electrode material of graphite is the trend of the times.

Using alkali metal materials instead of graphite materials directly as the negative electrode of secondary batteries has many advantages. On the one hand, the earth reserves of alkali metal resources such as lithium, sodium, and potassium are abundant, which can meet the requirements of large-scale applications. On the other hand, alkali metal negative electrodes generally have high specific capacity and low density, which can greatly improve the energy density of secondary batteries. For example, alkali metals are considered as negative electrode materials due to their extremely high theoretical specific capacity (3860mAh g ^-1 ), extremely low density (0.534g cm ^-3 ) and low electrochemical potential (-3.04V vs standard hydrogen electrode). The "Holy Grail".

However, using alkali metal directly as the negative electrode of secondary batteries will also bring many problems, which seriously limits its commercial application prospects. include:

(1) Due to the uneven surface and other reasons, the alkali metal anode is prone to dendritic deposition during the cycle, which leads to the piercing of the separator, and eventually causes serious safety problems such as fire and explosion due to internal short circuit.

(2) In addition, the alkali metal anode has a huge volume change during the cycle, which easily leads to the rupture of the SEI film on the electrode surface, and the exposed fresh alkali metal continues to react with the electrolyte, thereby aggravating the capacity fading.

(3) At the same time, the alkali metal negative electrode has high chemical activity and poor compatibility with the electrolyte or solid electrolyte. It is prone to corrosion or the formation of a passivation layer during the long cycle process, resulting in a sudden increase in interface impedance and polarization, and eventually the battery fails.

Therefore, in order to inhibit the growth of dendrites, limit the volume change of the alkali metal anode during the deposition/stripping process, and improve the safety performance of the secondary battery, a variety of modification methods have been proposed, including the use of electrolyte additives, solid electrolytes, and metal deposition frameworks. and composite metal anodes. However, most of these methods are complicated in process and high in cost, and cannot fundamentally prevent the formation of dendritic alkali metal deposition morphology, and the above problems will inevitably occur after long cycles. The main reasons include:

(1) The generation of dendritic alkali metal deposition is a complex random uncontrollable process, which is affected by many factors such as temperature, pressure, electric field strength, ion concentration and electrolyte performance.

(2) The introduced additives and interfacial layers will be exhausted or damaged after long cycle, and will fail, making it difficult to continue to function.

(3) There is almost no way to completely suppress the side reaction between lithium metal and electrolyte or solid electrolyte, and the products will eventually accumulate at the interface and affect the morphology of lithium deposition.

Therefore, it is particularly important to find a simple process to regulate the growth behavior of dendrites and greatly delay the separator puncture time when the dendrites have already been generated, which is particularly important for improving the safety of alkali metal batteries.

Contents of the invention

The technical problem to be solved by the present invention is to provide a three-dimensional vertical porous composite alkali metal negative electrode and its preparation method and application in order to solve the technical problems of low safety and poor cycle stability of alkali metal batteries. , it is possible to further control the growth behavior of dendritic metal deposition under the condition that dendritic metal deposition has already occurred, realize densified deposition and greatly reduce the probability of the separator being pierced, and achieve the purpose of improving the cycle life and safety of the metal battery.

The present invention adopts following technical scheme:

A three-dimensional vertical porous composite alkali metal negative electrode, including alkali metal, one side of the alkali metal is provided with a composite polymer layer, and three-dimensional vertical holes are arranged in an array on one side of the composite polymer layer, and the three-dimensional vertical holes are micron or submicron .

Specifically, the thickness of the composite polymer layer is 1-10 μm.

Specifically, the diameter of the three-dimensional vertical holes is 50-150 μm, the depth of the three-dimensional vertical holes is 70% to 90% of the thickness of the alkali metal negative electrode, and the area ratio of the three-dimensional vertical holes on the composite polymer layer is 30% to 70%. .

Another technical solution of the present invention is a method for preparing a three-dimensional vertical porous composite alkali metal negative electrode, comprising the following steps:

The polymer precursor solution is thinly coated on the surface of the alkali metal in situ, and the alkali metal containing the composite polymer layer is obtained by drying at a low temperature under an inert atmosphere; the composite polymer layer is formed on one side of the composite polymer layer by mechanical drilling. Holes are punched to obtain a three-dimensional vertical porous composite alkali metal negative electrode.

Specifically, the mass fraction of the polymer precursor solution is 5%-20%.

Further, the polymer is mixed with an organic solvent, and the polymer precursor solution is obtained through thorough stirring, and the polymer is polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polyamic acid and polyimide One or more of them, and the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide and acetonitrile.

Specifically, the polymer precursor solution is thinly coated on the surface of the alkali metal in situ by using a scraper coating method, and the height of the scraper is 20-50 μm higher than the thickness of the alkali metal.

Specifically, the temperature of the low-temperature drying treatment is 40-50° C., and the time is 3-5 hours.

Specifically, the alkali metal is one or more of lithium, sodium and potassium.

Another technical solution of the present invention is the application of the three-dimensional vertical porous composite alkali metal negative electrode in the alkali metal battery.

Compared with the prior art, the present invention has at least the following beneficial effects:

A three-dimensional vertical porous composite alkali metal negative electrode. On the one hand, the composite polymer coating confines the deposition of alkali metal in the hole due to its electronic insulating properties; It is beneficial to control the growth of dendritic metal deposition on the inner wall of the hole to the center of the hole along the horizontal direction; the three-dimensional vertical holes set in the array can effectively control the distribution of the negative electric field, so that the electric field in the hole changes vertically downward and deflects to the surrounding wall, and the outer edge of the hole The electric field changes vertically downward and deflects into the hole. Therefore, the alkali metal will grow upward from the vertical deposition on the bottom of the hole and the horizontal deposition on the wall to the center of the hole at the same time until they are in contact with each other. In the vertical array pore structure and polymer coating Under the double action of the layer, the final shape of the alkali metal deposition in the hole is dense and uniform, which reduces the probability of dendrites piercing the separator, and greatly improves the electrochemical stability and safety performance of the alkali metal secondary battery.

Further, the height of the scraper is adjusted so that the thickness of the final composite polymer layer is 1-10 μm, which can not only isolate electrons, but also prevent lithium ions from depositing on the surface of the polymer layer, confine it to the hole, and be ultra-thin. The thickness can try not to affect the energy density of the battery.

Further, according to the surface capacity of the matched positive electrode material, determine the surface deposition capacity required by the composite negative electrode, and then select the appropriate needle diameter, needle density and drilling depth; under the same needle density, the hole diameter and hole depth are appropriately increased, and the The larger the surface capacity of alkali metal deposition in the cave, the higher the positive electrode material with high active material surface loading can be matched; the larger the needle density and the more uniform the needle density, the more the alkali metal deposition surface capacity in the cave can be accommodated. Anode materials that can match the surface loading of high active materials.

A method for preparing a three-dimensional vertical porous composite alkali metal negative electrode. The alkali metal negative electrode with an organic interface layer has strong mechanical properties even after drilling to form a three-dimensional deposition structure. It is an ideal choice for the deposition support structure of the alkali metal negative electrode. Coating first The step setting of the preparation method for drying and forming the organic polymer coating can first increase the mechanical strength of the alkali metal negative electrode, so that the alkali metal negative electrode is not easy to be damaged during the subsequent mechanical drilling process.

Further, in order to avoid the slow volatilization of the solvent and the continuous side reaction of the alkali metal with it, the concentration of the precursor solution is determined according to the required height of the scraper and the thickness of the scraper. If the height of the scraper and the thickness of the scraper are small, the concentration of the precursor solution can also be appropriately reduced, that is, the proportion of the organic solvent can be higher; otherwise, the concentration of the precursor solution should be increased appropriately, that is, the proportion of the organic solvent should be reduced.

Furthermore, by dissolving the polymer in an organic solvent and then scraping it, not only can the adhesion between the polymer and the alkali metal be increased, but also an organic polymer coating with more uniform properties such as thickness and a smooth surface can be obtained.

Further, the organic polymer solution is applied to the surface of the alkali metal by the method of scraping with a scraper, which not only can change the height of the scraper more conveniently to obtain the required coating thickness, but also can reduce the amount of solvent on the surface of the alkali metal and increase the volatilization area to Inhibit the continued occurrence of side effects.

Further, the organic solvent is completely volatilized by thin coating of the polymer solution and rapid low-temperature drying treatment, so as to avoid continuous side reactions between it and the alkali metal. When the coating thickness is constant, the lower the low-temperature drying temperature, the time should be appropriately increased; when the low-temperature drying temperature is constant, the thicker the coating thickness, the time should be appropriately increased; The thicker the layer thickness, the lower the drying temperature should be appropriately increased, so that the organic solvent can be fully volatilized.

Further, alkali metals (such as: lithium, sodium, potassium, etc.) are abundant in earth resources, easy to obtain, generally have high theoretical capacity, low density and low electrochemical potential, and are expected to replace commercial graphite negative electrodes to improve battery energy. density.

To sum up, the preparation process of the present invention is simple, the cost is low, and it is suitable for large-scale commercial production. By adjusting the growth mode of dendritic deposited alkali metal to obtain a densified deposition morphology, the battery cycle is greatly improved. Stability, broad application prospects, and contribute to the breakthrough of high safety of secondary alkali metal batteries.

The technical solutions of the present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

Description of drawings

Figure 1 is the optical image of the alkali metal negative electrode prepared in Example 1, wherein (a) is the surface morphology of the alkali metal negative electrode containing only The surface morphology of the alkali metal negative electrode of the layer;

Fig. 2 is the mechanical punching tool with 100 μm diameter needle in embodiment 1, wherein (a) is the tool front view, (b) is the tool side view;

Figure 3 is the surface and cross-sectional scanning electron microscope images of the novel alkali metal negative electrode containing the vertical array hole structure and polymer coating prepared in Example 1, wherein (a) is the surface morphology of the novel alkali metal negative electrode, and (b) is Cross-sectional morphology of novel alkali metal anode;

Figure 4 is the results of the Comsol simulation of the negative electrode electric field distribution for a ternary full battery assembled with a new type of alkali metal negative electrode containing a vertical array of pore structures and a polymer coating;

Figure 5 is a comparison chart of the cycle performance of the ternary full battery assembled based on the alkali metal negative electrode containing only the insulating polymer coating and the new alkali metal negative electrode containing the insulating polymer coating and the vertical array of holes;

Fig. 6 Under the current density of 0.5mA cm ^-2 and different deposition capacities, the alkali concentration on the electrode surface of the lithium-lithium symmetric battery prepared in Example 1 contains a new type of alkali metal negative electrode assembly with a vertical array pore structure and a polymer coating Metal deposition scanning electron microscope image, where (a) is the surface morphology of the electrode after depositing 0.1mAh cm ^-2 of alkali metal, (b) is the surface morphology of electrode after depositing 0.3mAh cm ^-2 of alkali metal, (c ) is the electrode surface morphology after depositing 0.5mAh cm ^-2 of alkali metal, (d) is the electrode surface morphology after depositing 0.75mAh cm ^-2 of alkali metal;

Figure 7 Under the current density of 1mA cm ^-2 and the deposition capacity of 0.5mAh cm ^-2 , in the lithium-lithium symmetric battery assembled with the new alkali metal negative electrode containing the vertical array hole structure and polymer coating prepared in Example 1 , the optical photograph of the electrode surface;

Fig. 8 is a comparison chart of the cycle stability of the lithium-NCM811 ternary positive electrode full battery at 1C rate based on the new alkali metal containing the vertical array hole structure and the polymer coating prepared in Example 1 and the commercial lithium sheet respectively assembled;

Figure 9 is a comparison of the voltage-capacity curves of the assembled lithium-ternary positive electrode full battery at 2C rate, where (a) is the voltage- Capacity curve, (b) is the voltage-capacity curve of the lithium-NCM811 ternary positive electrode full battery assembled based on the new alkali metal negative electrode assembly containing the vertical array pore structure and polymer coating prepared in Example 1 at 2C rate;

Fig. 10 is a schematic diagram of the preparation of a novel alkali metal negative electrode containing a vertical array pore structure and a polymer coating according to the present invention.

Among them, 1. lithium sheet; 2. polymer precursor solution; 3. scraper; 4. mechanical punching tool.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below, and obviously, the described embodiments are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

In the present invention, unless otherwise specified, all the implementation modes and preferred implementation methods mentioned herein can be combined with each other to form new technical solutions.

In the present invention, if there is no special description, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

In the present invention, unless otherwise specified, percentage (%) or part refers to percentage by weight or part by weight relative to the composition.

In the present invention, unless otherwise specified, the various components involved or their preferred components can be combined with each other to form a new technical solution.

In the present invention, unless otherwise stated, the numerical range "a~b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "6-22" means that all the real numbers between "6-22" have been listed in this article, and "6-22" is just an abbreviated representation of the combination of these values.

The "ranges" disclosed herein may be in the form of lower limits and upper limits, and may refer to one or more lower limits and one or more upper limits, respectively.

In the present invention, the term "and/or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in sequence. Preferably, the reaction processes herein are performed sequentially.

Unless otherwise specified, professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the content described can also be applied in the present invention.

The invention provides a three-dimensional vertical porous composite alkali metal negative electrode and a preparation method thereof. The configured polymer precursor solution is thinly coated on the surface of the alkali metal side and dried at a low temperature. The surface capacity of the alkali metal deposition in the negative electrode hole is required, and then the diameter of the punching tool needle, the density of the pillow and the punching depth are determined. Under an inert atmosphere, mechanically punch holes on the surface of the composite polymer layer to obtain uniformly distributed micron or submicron Pores, that is, a new type of alkali metal negative electrode with a vertical array of pore structures and a polymer coating is obtained. The uniform vertical array of holes can effectively control the electric field intensity distribution of the negative electrode. On the one hand, the composite polymer layer has electronic insulation properties to limit the deposition of alkali metals in the holes, and on the other hand, because of its ion-adsorbing properties, it is beneficial to control the ion concentration at the edge of the holes; Ultimately, under the joint action of the vertical pore structure and the composite polymer layer, the dendrites will grow vertically upward from the bottom of the cave and horizontally from the wall to the center of the cave until they are in contact with each other and become dense and uniform, achieving improved dendrites. The cycle life of metal batteries and the purpose of safety.

Please refer to Fig. 10 , a three-dimensional vertical porous composite alkali metal negative electrode of the present invention includes a composite polymer layer arranged on the alkali metal, the thickness of the composite polymer layer is 1-10 μm, and there are several uniformly distributed layers on the composite polymer layer. Micron or submicron holes (holes account for 30% to 70% of the total surface area), micron or submicron holes are three-dimensional vertical holes, the diameter of the three-dimensional vertical holes is 50-150 μm, and the depth of the three-dimensional vertical holes is 70% to 90% of the thickness of alkali metal.

A method for preparing a three-dimensional vertical porous composite alkali metal negative electrode of the present invention comprises the following steps:

S1. Mix the polymer and the organic solvent, and stir thoroughly to obtain a polymer precursor solution with a mass fraction of 5% to 20%;

Among them, the polymer is selected from a polymer material with electronic insulation and certain ion adsorption, which is one of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polyamic acid and polyimide. one or more kinds, and the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide and acetonitrile.

S2. Thinly coat the polymer precursor solution on the surface of the alkali metal in situ by the scraper coating method, and dry it at 40-50°C for 3-5 hours in an inert atmosphere, and obtain a composite polymer containing compound after the organic solvent is completely volatilized. Alkali metal in the material layer;

The height of the scraper is 20-50 μm higher than the thickness of the alkali metal, and the thickness of the composite polymer layer is 1-10 μm.

Wherein, the alkali metal is one or more of lithium, sodium and potassium.

S3. Using a punching tool with a micron or submicron needle, punching holes on the surface of the composite polymer layer by a mechanical punching method to obtain a three-dimensional vertical porous composite alkali metal negative electrode.

The diameter of the needle used in the mechanical punching method is 50-150 μm, the density of the needle is 30%-70% (area ratio), and the punching depth is 70%-90% of the thickness of the alkali metal negative electrode.

Among them, the areal capacity of the alkali metal deposited in the hole required by the negative electrode is determined according to the areal capacity of the matched positive electrode material, and then the needle diameter, needle density and punching depth on the surface of the mechanical punching tool are determined according to the areal capacity of the alkali metal deposited in the hole required by the negative electrode , under the same hole density, the larger the hole diameter and hole depth, the more alkali metal deposition surface capacity in the hole can be accommodated; the larger the hole density and the more uniform hole density, the more alkali metal deposition surface capacity in the hole can be accommodated. The more capacity.

In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments It is a part of embodiments of the present invention, but not all embodiments. The components of the embodiments of the invention generally described and illustrated in the drawings herein may be arranged and designed in a variety of different configurations. Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1

Add 4,4'-diaminodiphenyl ether (ODA) into the organic solvent N, N-dimethylacetamide (DMAC) and stir until transparent and clear, then add the same molar number of pyromellitic dianhydride (PMDA ) was stirred, and after sufficient in-situ polymerization, a pale yellow clear polyamic acid (PAA) precursor solution was obtained, wherein the mass percentage of PAA polymer was 20%.

The polymer precursor solution 2 is scraped and coated on the metal surface of a commercial lithium sheet 1 with a thickness of 100 μm in situ with a scraper 3, the height of the scraper 3 is 50 μm higher than the thickness of the alkali metal, and it is baked at a low temperature of 40 ° C and an inert gas atmosphere After drying for 5 h, the alkali metal negative electrode containing only polymer coating was obtained as shown in Fig. 1(a).

The front and side optical photos of the selected mechanical punching tool 4 are shown in Figure 2 (a) and Figure 2 (b) respectively, it has a needle with a diameter of 80 μm, and the drilling depth is 70 μm (70% of the thickness of the alkali metal), The needle density is 30% (area ratio).

Scanning electron microscopy and optical observation were performed on the new alkali metal negative electrode with vertical array of holes and polymer coating obtained after mechanical drilling, as shown in Figure 3 and Figure 1(b), respectively. The diameter of the holes is 80 μm, and the hole density 30% (area ratio), the PAA polymer coating is smooth and flat without cracks, and the thickness is 10 μm.

The Comsol electric field simulation of the ternary full battery based on the new alkali metal negative electrode assembly with vertical array holes and polymer coating was carried out. The results are shown in Figure 4. The electric field at the outer edge turns vertically downward and deflects toward the inside of the hole. Therefore, the alkali metal will grow vertically upward on the bottom of the hole and grow horizontally toward the center of the hole at the same time, until they contact and squeeze each other to become dense and uniform.

Alkali metals containing only insulating polymer coatings and new alkali metals containing insulating polymer coatings and vertical array holes are used as negative electrodes, NCM811 material is used for positive electrodes, and polyethylene (PE) microporous diaphragms are used as separators, and 70 μL of commercial LiPF is added dropwise ₆ The full battery was assembled with electrolyte solution, and the charge-discharge cycle test was carried out at a rate of 1C. The specific capacity change of the active material is shown in Figure 5. The full battery assembled with a new type of alkali metal negative electrode containing vertical array holes and polymer coating was discharged in the first cycle. The specific capacity is 148.9mAh g ^-1 , and it can run stably for more than 600 cycles. After 600 cycles, the discharge specific capacity is 82.13% of the discharge specific capacity of the first cycle, and the full battery assembled with the alkali metal negative electrode containing only insulating polymer coating There is no discharge specific capacity, which proves that the PAA coating has electronic insulation, and alkali metals cannot be deposited on its surface.

A new type of alkali metal electrode containing a vertical array of holes and a polymer coating was used as the negative electrode, a commercial lithium sheet 1 was used as the positive electrode, and a polyethylene (PE) microporous diaphragm was used as the separator. A symmetrical battery was assembled by dropping 70 μL of commercial LiPF ₆ electrolyte. After charging at a current density of 0.5mAcm ^-2 for different periods of time, the battery was disassembled for scanning electron microscope testing. The results are shown in Figure 6. As the time increases, the deposited alkali metal gradually fills the entire hole densely. After charging for 0.5h at a current density of 1mA cm ^-2 , the battery was disassembled. The optical photo of the negative electrode is shown in Figure 7, which proves that the alkali metal cannot be deposited on the surface of the polymer layer, but can only be deposited and grown in the hole.

The newly prepared alkali metal and commercial lithium sheet 1 containing vertical array holes and polymer coating were used as the negative electrode, the NCM811 ternary material was used as the positive electrode, and the separator was made of polyethylene (PE) microporous separator, and 70 μL of commercial LiPF ₆ was added dropwise Electrolyte assembled full battery, charge-discharge cycle test at a rate of 1C, the specific capacity change trend of the positive active material is shown in Figure 8, the full battery assembled with a new type of alkali metal negative electrode containing vertical array holes and polymer coating is discharged in the first cycle The specific capacity is 148.9mAh g ^-1 , and it can run stably for more than 700 cycles. After 700 cycles, the discharge specific capacity is 75.49% of the discharge specific capacity of the first cycle, and the full battery assembled with commercial lithium sheets as the negative electrode is discharged after 700 cycles. The specific capacity is only 56.14% of the specific capacity of the first cycle discharge. It shows that under the joint action of the vertical hole structure and the polymer interface layer, the dendrites will grow vertically upward from the bottom of the hole and grow horizontally from the hole wall to the center of the hole until they are in contact with each other and become dense and uniform, so that the battery has Better cycle performance. In the charge-discharge cycle test at a rate of 2C, the voltage-capacity curve comparison chart is shown in Figure 9, which can prove that the composite alkali metal anode with a new structure can greatly improve the battery cycle stability and capacity retention.

Example 2

Add polyvinylidene fluoride (PVDF) into the organic solvent N, after stirring in N-dimethylacetamide (DMAC) until transparent and clear, obtain polymer precursor solution 2, wherein the mass percentage of PVDF polymer is 5% .

The polymer precursor solution 2 was scraped and coated on the surface of commercial sodium metal 1 with a thickness of 80 μm in situ with a scraper 3, the height of the scraper 3 was higher than the thickness of the sodium metal 20 μm, and dried at a low temperature of 50°C and an inert gas atmosphere for 3 hours Finally, the thickness of the PVDF coating was 1 μm, and finally a sodium metal anode with a polymer coating was obtained.

The selected mechanical punching tool 4 has a needle with a diameter of 100 μm, a drilling depth of 60 μm (75% of the thickness of the sodium metal negative electrode), and a needle density of 50% (area ratio). Layered novel sodium metal anode.

Example 3

Add polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) into the organic solvent anhydrous acetonitrile and stir until transparent and clear to obtain polymer precursor solution 2, wherein the mass percentage of PVDF-HFP polymer is 10%.

The polymer precursor solution 2 is scraped and coated on the alkali metal surface of a commercial lithium sheet 1 with a thickness of 100 μm in situ with a scraper 3, the height of the scraper 3 is 50 μm higher than the thickness of the alkali metal, and it is baked at a low temperature of 50 ° C and an inert gas atmosphere After drying for 3 hours, the thickness of the PVDF-HFP coating was 5 μm, and finally an alkali metal anode with a polymer coating was obtained.

The selected mechanical punching tool 4 has a needle with a diameter of 50 μm, a punching depth of 90 μm (90% of the thickness of the alkali metal negative electrode), and a needle density of 70% (area ratio). The final product contains a vertical array of holes and a polymer coating new alkali metal anode.

Example 4

Add polyacrylonitrile (PAN) into organic solvent N,N-dimethylformamide (DMF) and stir until transparent and clear to obtain polymer precursor solution 2, wherein the mass percentage of PAN polymer is 15%.

Apply the polymer precursor solution 2 in-situ with a scraper 3 on the alkali metal surface of a commercial lithium sheet 1 with a thickness of 100 μm. The height of the scraper 3 is 30 μm higher than the thickness of the alkali metal, and bake at a low temperature of 40° C. and in an inert gas atmosphere. After drying for 3 h, the thickness of the PAN coating was 10 μm, and finally an alkali metal anode with a polymer coating was obtained.

The selected mechanical punching tool 4 has a needle with a diameter of 150 μm, a punching depth of 90 μm (90% of the thickness of the alkali metal negative electrode), and a needle density of about 70% (area ratio). Coated novel alkali metal anode.

In summary, a three-dimensional vertical porous composite alkali metal negative electrode of the present invention and its preparation method and application are suitable for large-scale production. The introduced polymer coating not only does not greatly affect the energy density of the battery, but also combines vertical array holes The structure can regulate the growth behavior of alkali metal deposition, and finally the growth of alkali metal deposition is limited in the hole and the morphology is dense and uniform, which not only delays the time of separator piercing and improves safety performance, but also greatly improves the cycle stability and capacity retention of metal batteries Rate.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than limiting them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: It is still possible to modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the technical solutions of the various embodiments of the present invention. scope.

Claims (10)

1. The three-dimensional vertical porous composite alkali metal cathode is characterized by comprising an alkali metal, wherein a composite polymer layer is arranged on one side of the alkali metal, three-dimensional vertical holes are arranged on one side of the composite polymer layer in an array mode, and the three-dimensional vertical holes are in a micron-sized or submicron-sized mode.

2. The three-dimensional vertical porous composite alkali metal anode according to claim 1, wherein the composite polymer layer has a thickness of 1 to 10 μm.

3. The three-dimensional vertical porous composite alkali metal anode according to claim 1, wherein the diameter of the three-dimensional vertical pores is 50-150 μm, the depth of the three-dimensional vertical pores is 70-90% of the thickness of the alkali metal anode, and the area of the three-dimensional vertical pores on the composite polymer layer is 30-70%.

4. A method of making the three-dimensional vertical porous composite alkali metal anode of claim 1, 2 or 3 comprising the steps of:

in-situ thin coating the polymer precursor solution on the surface of alkali metal, and drying at low temperature in an inert atmosphere to obtain the alkali metal containing the composite polymer layer; and punching the surface of one side of the composite polymer layer by a mechanical punching method to obtain the three-dimensional vertical porous composite alkali metal cathode.

5. The preparation method of the three-dimensional vertical porous composite alkali metal cathode as claimed in claim 4, wherein the mass fraction of the polymer precursor solution is 5-20%.

6. The preparation method of the three-dimensional vertical porous composite alkali metal cathode according to claim 5, wherein a polymer and an organic solvent are mixed and fully stirred to obtain a polymer precursor solution, the polymer is one or more of polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene, polyacrylonitrile, polyamic acid and polyimide, and the organic solvent is one or more of N, N-dimethylformamide, N, N-dimethylacetamide and acetonitrile.

7. The method for preparing the three-dimensional vertical porous composite alkali metal cathode according to claim 4, wherein the polymer precursor solution is in-situ thinly coated on the surface of the alkali metal by using a doctor blade coating method, and the height of the doctor blade is 20-50 μm higher than the thickness of the alkali metal.

8. The preparation method of the three-dimensional vertical porous composite alkali metal cathode according to claim 4, wherein the temperature of the low-temperature drying treatment is 40-50 ℃ and the time is 3-5 h.

9. The method for preparing the three-dimensional vertical porous composite alkali metal cathode according to claim 4, wherein the alkali metal is one or more of lithium, sodium and potassium.

10. Use of the three-dimensional vertical porous composite alkali metal anode of any one of claims 1 to 3 in an alkali metal battery.

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