阅读说明：本技术 一种热电池薄膜正极的制备方法 (Preparation method of thermal battery thin film anode ) 是由 杨少华 任玥盈 李继龙 于 2021-07-30 设计创作，主要内容包括：本发明提供一种热电池薄膜正极的制备方法,包括如下步骤：(1)将正极活性原料二硫化铁、氧化锂高温锂化后与电解质混匀形成正极活性粉料；(2)将无机盐类粘合剂溶解于溶剂多元醇中,制得30-100mg/ml的无机盐类粘合剂-多元醇溶液。(3)将活性粉料与无机盐类粘合剂-多元醇溶液球磨均匀混合,制成正极活性浆料；(4)采用流延法进行涂膜,使活性浆料吸附至基体材料表面,干燥后即得热电池薄膜正极。本发明的热电池薄膜正极,克服了热电池电极现有粉末压片制备工艺带来的诸多弊端,轻松实现大面积或不规则形状电极片的制备,降低溶剂对正极材料活性的影响,同时提高电池的稳定性及其放电性能,具有较大的工业应用价值,具有非常好的应用前景。(The invention provides a preparation method of a thermal battery film anode, which comprises the following steps: (1) uniformly mixing the positive active raw materials of iron disulfide and lithium oxide after high-temperature lithiation with electrolyte to form positive active powder; (2) dissolving inorganic salt adhesive in solvent polyalcohol to obtain 30-100mg/ml inorganic salt adhesive-polyalcohol solution. (3) Uniformly mixing the active powder with an inorganic salt adhesive-polyalcohol solution by ball milling to prepare positive active slurry; (4) and coating by adopting a tape casting method, so that the active slurry is adsorbed to the surface of the base material, and drying to obtain the film anode of the thermal battery. The film anode of the thermal battery overcomes the defects caused by the conventional powder tabletting preparation process of the thermal battery electrode, easily realizes the preparation of large-area or irregular-shaped electrode slices, reduces the influence of a solvent on the activity of an anode material, improves the stability and the discharge performance of the battery, has higher industrial application value and has very good application prospect.)

1. A preparation method of a thin film anode of a thermal battery is characterized by comprising the following steps:

(1) uniformly mixing the positive active raw materials of iron disulfide and lithium oxide after high-temperature lithiation with electrolyte to form positive active powder;

(2) dissolving inorganic salt adhesive in solvent polyalcohol to obtain 30-100mg/ml inorganic salt adhesive-polyalcohol solution;

(3) uniformly mixing the active powder with an inorganic salt adhesive-polyalcohol solution by ball milling to prepare positive active slurry;

(4) and coating by adopting a tape casting method, so that the active slurry is adsorbed to the surface of the base material, and drying to obtain the film anode of the thermal battery.

2. The method for preparing the thin film positive electrode of the thermal battery according to claim 1, wherein the mass fraction of iron disulfide in the positive electrode active raw material in the step (1) is 98-99%, and the mass fraction of lithium oxide in the positive electrode active raw material is 1-2%; the dosage of the electrolyte is 5-15% of the total mass of the lithium compound and the electrolyte obtained after the raw material is lithiated.

3. The method for preparing the thin film positive electrode of the thermal battery according to claim 1, wherein the lithiation condition in the step (1) is as follows: lithiation temperature is 420-520 ℃, lithiation time is 3-5h, the active raw material is uniformly mixed with electrolyte after being lithiated at high temperature, and then the mixture is dried for 1-3 h in a vacuum drying oven at 180 ℃ to obtain active powder.

4. The method for preparing a thin film positive electrode of a thermal battery according to claim 1, wherein the electrolyte in the step (1) is one of binary, ternary eutectic and ternary full lithium electrolyte.

5. The method for preparing a thin film positive electrode of a thermal battery as claimed in claim 1, wherein the polyol in the step (2) is one of ethanol, ethylene glycol, glycerol, propylene glycol and butylene glycol.

6. The method for preparing a thin film anode of a thermal battery as claimed in claim 1, wherein the inorganic salt binder in step (2) is one or more of NaCl, KCl, LiCl, KCl, KBr and LiBr.

7. The method for preparing the thin-film positive electrode of the thermal battery according to claim 1, wherein the volume ratio of each component of the positive electrode active slurry in the step (3) is as follows: 70-80% of positive active powder and 20-30% of inorganic salt adhesive-polyalcohol solution.

8. The method for preparing the thin film positive electrode of the thermal battery according to claim 1, wherein the drying conditions in the step (4) are as follows: vacuum drying for 3-5h at 150-250 ℃.

9. The method for preparing a thin film positive electrode of a thermal battery as claimed in claim 1, wherein in the step (4), the base material is a porous conductive material or a flexible conductive material, the porous conductive material is one of foam or mesh carbon, chromium, titanium, nickel, silver, copper and alloys thereof, and the flexible conductive material comprises a flexible graphite product.

10. The thermal battery film anode is characterized by being prepared based on the preparation method of any one of claims 1 to 9, and the thermal battery film anode can be obtained into film anode plates with different specifications by cutting or punching a sheet machine.

Technical Field

The invention belongs to the technical field of thermal battery film electrodes, and particularly relates to a preparation method of a thermal battery film anode.

Background

The thermal battery is a storage type primary battery of molten salt electrolyte, the electrolyte of the thermal battery is a non-conductive anhydrous solid inorganic salt when stored at normal temperature, the hot molten salt is converted into an ionic conductor with high conductivity, and the battery can be activated and starts to discharge in a short time. The working temperature of a common lithium battery is only-20 ℃ to 60 ℃, but the thermal battery can work at the temperature of 350 ℃ to 550 ℃ as a high-temperature energy source.

The thermal battery has the advantages of excellent thermal stability and electrochemical performance, quick activation, long storage time, low manufacturing cost and the like, and can be suitable for strict working environments, so that the thermal battery has incomparable applicability to other chemical power sources in weaponry and some special fields. As thermal batteries continue to be explored, stable thermal battery systems have been developed, such as the most widely used LiSi/sulfide system. However, with the continuous progress of science and technology, the thermal battery needs to be miniaturized, high in voltage and high in specific capacity, and therefore, research on the high-potential positive electrode material of the thermal battery is urgent.

In the structure of the thermal battery, the electric pile is the most important component, and is formed by stacking the single batteries from bottom to top, and the thickness of the single batteries determines the height of the electric pile, thereby affecting the volume of the single batteries. With the continuous development of the field of weaponry, the requirements for the thermal battery are more and more strict, and besides the traditional safety and applicability problems, the shape and volume, and the energy density and capacity of the electric pile also become important directions for the development of the field of the thermal battery with urgent needs. The thickness of a single battery pressed by a traditional powder tabletting process is large, if the single battery is pressed to be thin, the impact resistance of an electrode plate is reduced, and the electrode plate is easy to crack, so that the safety problem is caused. Therefore, the special advantage is highlighted for the preparation of the film electrode, the positive electrode material is prepared into viscous slurry by mixing a proper binder and coated on a carrier material with excellent shock resistance and flexibility, so that the thickness of the prepared electrode plate is greatly reduced, the shape of the electrode plate can be freely changed according to actual requirements, and the safety is improved to a certain extent. Most importantly, the development requirements of the prior art on miniaturization, small volume and light weight of the thermal battery are met.

Iron disulfide (pyrite) is the most common cathode material in the lithium battery at present due to abundant natural reserves, low price and stable discharge performance. The traditional iron disulfide monomer battery that adopts the powder preforming technology to suppress thickness is great, if press and make very thin, can lead to the shock resistance of electrode slice to descend, the easy fracture of electrode slice to arouse the safety problem, can't satisfy the demand of thermal battery towards miniaturization, electrode film ization development.

Disclosure of Invention

The invention aims to overcome the defects of the prior art, and provides a preparation method of a thin-film anode of a thermal battery, which aims to solve the problem of poor preparation and forming of a ferrous disulfide powder electrode and meet the requirements of the thermal battery on the development of miniaturization and electrode thinning.

The technical scheme adopted by the invention for solving the technical problems is as follows: a preparation method of a thin film anode of a thermal battery comprises the following steps:

(1) uniformly mixing the positive active raw materials of iron disulfide and lithium oxide after high-temperature lithiation with electrolyte to form positive active powder;

(2) dissolving inorganic salt adhesive in solvent polyalcohol to obtain 30-100mg/ml inorganic salt adhesive-polyalcohol solution;

(3) uniformly mixing the active powder with an inorganic salt adhesive-polyalcohol solution by ball milling to prepare positive active slurry;

(4) and coating by adopting a tape casting method, so that the active slurry is adsorbed to the surface of the base material, and drying to obtain the film anode of the thermal battery.

Further, the mass fraction of iron disulfide in the positive active raw material in the step (1) is 98-99%, and the mass fraction of lithium oxide is 1-2%; the dosage of the electrolyte is 5-15% of the total mass of the lithium compound and the electrolyte obtained after the raw material is lithiated.

Further, the lithiation conditions in the step (1) are as follows: lithiation temperature is 420-520 ℃, lithiation time is 3-5h, the active raw material is uniformly mixed with electrolyte after being lithiated at high temperature, and then the mixture is dried for 1-3 h in a vacuum drying oven at 180 ℃ to obtain active powder.

Further, the electrolyte in the step (1) is one of binary, ternary low-melting and ternary full-lithium electrolyte.

Further, the electrolyte in the step (1) is specifically one of LiCl-KCl, LiCl-LiBr-KBr and LiCl-LiBr-LiF.

Further, in the step (2), the polyhydric alcohol is one of ethanol, ethylene glycol, glycerol, propylene glycol and butanediol.

Further, in the step (2), the inorganic salt binder is one or a plurality of compounds selected from NaCl, KCl, LiCl, KCl, KBr and LiBr.

Further, the volume ratio of each component of the positive active slurry in the step (3) is as follows: 70-80% of positive active powder and 20-30% of inorganic salt adhesive-polyalcohol solution.

Further, the drying conditions in the step (4) are as follows: vacuum drying for 3-5h at 150-250 ℃.

Further, in the step (4), the base material is a porous conductive material or a flexible conductive material, the porous conductive material is one of foam or mesh carbon, chromium, titanium, nickel, silver, copper and alloys thereof, and the flexible conductive material comprises a flexible graphite product.

The invention also provides a thermal battery film anode prepared based on the preparation method, and the thermal battery film anode can be cut or punched by a sheet punching machine to obtain film anode sheets with different specifications.

When the battery is assembled after the thin-film positive plate is prepared, the negative active material can be selected from lithium alloy, such as lithium boron alloy, lithium silicon alloy, lithium aluminum alloy and the like, and can also be selected from calcium, magnesium and alloys thereof and the like, and the thermal battery current collecting plate can be made of stainless steel, copper, nickel or other metal materials and flexible graphite.

Compared with the prior art, the invention has the beneficial effects that:

according to the invention, the positive electrode material is prepared into viscous slurry by adopting the binder and coated on the carrier material with excellent impact resistance and flexibility, so that the thickness of the prepared electrode plate can be greatly reduced; the positive electrode of the thermal battery film prepared by the invention is not limited by the area size and the shape, the preparation process is not limited by the environment humidity condition, the preparation can be carried out indoors, the printing times can be controlled according to the thickness of the required film, the shape of the electrode plate can be freely changed according to the actual requirement, the problems of large thickness and easy cracking of the single battery pressed by the traditional powder tabletting process are solved, the safety is also improved to a certain extent, and the most important thing is that the development requirements of the prior art on miniaturization, small volume and light weight of the thermal battery are met; in addition, the invention adopts novel solvent polyol, reduces the influence of the solvent on the activity of the material of the anode when preparing the film and ensures that the discharge performance is better.

Drawings

Fig. 1 is a schematic appearance diagram of a prepared iron disulfide film positive electrode, fig. 1(a) is a schematic appearance diagram of an entire iron disulfide film positive electrode without cutting, and fig. 1(b) is a schematic appearance diagram of an iron disulfide film positive electrode cut to a size required by a test;

FIG. 2 is a specific capacity discharge diagram of the positive electrode unit cell prepared by different processes in example 1;

FIG. 3 is a specific capacity discharge diagram of a positive electrode cell prepared according to different processes of example 2;

fig. 4 is a specific capacity discharge diagram of the positive single cell prepared by different processes in example 3.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

(1) Weighing and uniformly mixing iron disulfide and lithium oxide powder serving as positive active raw materials, wherein the mass fraction of the iron disulfide in the raw materials is 98%, and the mass fraction of the lithium oxide in the raw materials is 2%; lithiating the mixture in a lithiation furnace at the high temperature of 420 ℃ for 5 hours, and taking out a lithiation compound after the temperature is reduced to room temperature; uniformly mixing the lithiated compound with LiCl-LiBr-KBr electrolyte, and drying for 2 hours at 120 ℃ in a vacuum drying oven to form positive active powder, wherein the using amount of the electrolyte is 15% of the total mass of the lithiated compound and the electrolyte;

(2) dissolving LiCl and KCl in ethylene glycol according to the mass ratio of 9:11, uniformly mixing and dissolving to form 60mg/ml inorganic salt binder-polyalcohol solution, and uniformly mixing the positive active powder and the inorganic salt binder-polyalcohol solution by ball milling to obtain paste with certain viscosity, namely positive active slurry, wherein the volume ratio of the positive active powder in the positive active slurry is 80%, and the volume ratio of the inorganic salt binder-polyalcohol solution is 20%;

(3) coating with a scraper by adopting a tape casting method, so that the active slurry is uniformly distributed and adsorbed on the surface of the foam copper to prepare a film with uniformly distributed components, and the film has better repeatability and uniformity, and the substrate covered with the active substance is put into a vacuum drying oven to be dried for 3 hours at 190 ℃ in vacuum to obtain a large-area thermal battery film anode (as shown in figure 1 (a));

(4) under the protection of dry gas with relative humidity of 1%, using an electrode tablet press to flatly press the positive plate at 20MPa, and then using an electrode tablet press to punch to obtain a plurality of thin film positive plates with thickness of 0.4mm and diameter of 19mm (as shown in figure 1 (b)).

Under the protection of dry gas with the relative humidity of 1%, the prepared iron disulfide film positive plate of the thermal battery and LiCl-LiBr-KBr electrolyte powder are pressed into a sheet by using a hydraulic press, LiB alloy powder is pressed into a sheet by using the hydraulic press to serve as a negative electrode, and two electrode sheets are overlapped to form the monomer thermal battery. The prepared single battery of the thermal battery is placed in a specific clamp, and is placed in a tubular furnace which is pre-programmed to the test temperature, and high-purity argon is introduced as a protective gas in the whole test process, so that the test result is not interfered by the outside air. The test device is connected to a LAND-CT2001A battery test system to test the discharge performance of the single battery.

FIG. 2 shows the anode sheet prepared by the thin film process and the powder tabletting processThe specific capacity discharge diagram of the bulk battery is shown in the specification, wherein a curve A is an iron disulfide film anode in a film process by a tape casting method, a curve B is an iron disulfide anode in the existing powder tabletting process, and the discharge current density is 100mA/cm²The test result shows that the discharge performance of the single battery with the anode prepared by the thin film process is obviously superior to that of the single battery with the anode prepared by the powder tabletting process, the initial discharge voltage of the single battery with the anode prepared by the thin film process is 2.1339V, and the initial discharge voltage of the single battery with the anode prepared by the powder tabletting process is 2.1826V. The cut-off voltage is 1.5V, the specific capacity of the positive electrode monomer battery of the film process is 308.081mAh/g, and the specific capacity of the positive electrode monomer battery of the powder tabletting process is 203.803 mAh/g.

Example 2

(1) Weighing and uniformly mixing iron disulfide and lithium oxide powder serving as positive active raw materials, wherein the mass fraction of the iron disulfide in the raw materials is 98.3%, and the mass fraction of the lithium oxide in the raw materials is 1.7%; lithiating the mixture in a lithiation furnace at the high temperature of 450 ℃ for 4.5 hours, and taking out a lithiation compound after the temperature is reduced to room temperature; uniformly mixing the lithiated compound with LiCl-KCl electrolyte, and drying at 130 ℃ in a vacuum drying oven for 1.7 hours to form positive active powder, wherein the using amount of the electrolyte is 15% of the total mass of the lithiated compound and the electrolyte;

(2) dissolving LiCl in glycerol, uniformly mixing and dissolving to form 50mg/ml inorganic salt binder-polyalcohol solution, and uniformly mixing the positive active powder and the inorganic salt binder-polyalcohol solution by ball milling to obtain paste with certain viscosity, namely positive active slurry, wherein the volume ratio of the positive active powder in the positive active slurry is 80%, and the volume ratio of the inorganic salt binder-polyalcohol solution is 20%;

(3) coating with a scraper by adopting a tape casting method, so that the active slurry is uniformly distributed and adsorbed on the surface of the foamed nickel to prepare a film with uniformly distributed components, and the film has better repeatability and uniformity, and the substrate covered with the active substance is put into a vacuum drying oven to be dried for 4 hours at 180 ℃ in vacuum to obtain a large-area thermal battery film anode;

(4) under the protection of dry gas with the relative humidity of 1 percent, an electrode tablet press is adopted to carry out flat pressing on the positive plate at 20MPa, and then an electrode tablet press is used for punching to obtain a plurality of film positive plates with the thickness of 0.4mm and the diameter of 19 mm.

Under the protection of dry gas with the relative humidity of 1%, the prepared iron disulfide film positive plate of the thermal battery and LiCl-KCl electrolyte powder are pressed into a sheet by using a hydraulic machine, LiB alloy powder is pressed into a sheet by using the hydraulic machine to serve as a negative electrode, and the two electrode sheets are overlapped to form the monomer thermal battery. The prepared single battery of the thermal battery is placed in a specific clamp, and is placed in a tubular furnace which is pre-programmed to the test temperature, and high-purity argon is introduced as a protective gas in the whole test process, so that the test result is not interfered by the outside air. The test device is connected to a LAND-CT2001A battery test system to test the discharge performance of the single battery.

Fig. 3 is a specific capacity discharge diagram of the positive single battery prepared by the film process and the powder tabletting process. Curve a is the positive electrode of the iron disulfide film in the film process by the tape casting method, and curve B is the positive electrode of the iron disulfide in the existing powder tabletting process. The discharge current density was 100mA/cm²The test result shows that the discharge performance of the single battery with the anode prepared by the thin film process is obviously superior to that of the single battery with the anode prepared by the powder tabletting process, the initial discharge voltage of the single battery with the anode prepared by the thin film process is 2.146V, and the initial discharge voltage of the single battery with the anode prepared by the powder tabletting process is 2.1339V. The cut-off voltage is 1.5V, the specific capacity of the positive electrode monomer battery of the thin film process is 291.7mAh/g, and the specific capacity of the positive electrode monomer battery of the powder tabletting process is 203.8 mAh/g.

Example 3

(1) Weighing and uniformly mixing iron disulfide and lithium oxide powder serving as positive active raw materials, wherein the mass fraction of the iron disulfide in the raw materials is 99%, and the mass fraction of the lithium oxide in the raw materials is 1%; lithiating the mixture in a lithiation furnace at a high temperature of 500 ℃ for 4 hours, and taking out a lithiation compound after the temperature is reduced to room temperature; uniformly mixing the lithiated compound with LiCl-LiBr-KBr electrolyte, and drying for 1.5h at 150 ℃ in a vacuum drying oven to form positive active powder, wherein the using amount of the electrolyte is 15% of the total mass of the lithiated compound and the electrolyte;

(2) dissolving LiCl and KCl in ethylene glycol according to the mass ratio of 9:11, uniformly mixing and dissolving to form 40mg/ml inorganic salt binder-polyalcohol solution, and uniformly mixing the positive active powder and the inorganic salt binder-polyalcohol solution by ball milling to obtain paste with certain viscosity, namely positive active slurry, wherein the volume ratio of the positive active powder in the positive active slurry is 80%, and the volume ratio of the inorganic salt binder-polyalcohol solution is 20%;

(3) a doctor blade is used for coating by adopting a tape casting method, so that the active slurry is uniformly distributed and adsorbed to the surface of the foamed nickel, and a film with uniformly distributed components is prepared, and has better repeatability and uniformity; putting the substrate covered with the active substance into a vacuum drying oven, and vacuum-drying for 5 hours at 170 ℃ to obtain a large-area thermal battery thin film anode;

(4) under the protection of dry gas with the relative humidity of 1 percent, an electrode tablet press is adopted to carry out flat pressing on the positive plate at 20MPa, and then an electrode tablet press is used for punching to obtain a plurality of film positive plates with the thickness of 0.4mm and the diameter of 19 mm.

Under the protection of dry gas with the relative humidity of 1%, the prepared iron disulfide film positive plate of the thermal battery and LiCl-LiBr-KBr electrolyte powder are pressed into a sheet by using a hydraulic press, LiB alloy powder is pressed into a sheet by using the hydraulic press to serve as a negative electrode, and two electrode sheets are overlapped to form the monomer thermal battery. The prepared single battery of the thermal battery is placed in a specific clamp, and is placed in a tubular furnace which is pre-programmed to the test temperature, and high-purity argon is introduced as a protective gas in the whole test process, so that the test result is not interfered by the outside air. The test device is connected to a LAND-CT2001A battery test system to test the discharge performance of the single battery.

Fig. 4 is a specific capacity discharge diagram of the positive single battery prepared by the film process and the powder tabletting process. Curve a is the positive electrode of the iron disulfide film in the film process by the tape casting method, and curve B is the positive electrode of the iron disulfide in the existing powder tabletting process. The discharge current density was 100mA/cm²The test result shows that the discharge performance of the single battery with the anode prepared by the thin film process is obviously superior to that of the single battery with the anode prepared by the powder tabletting process, the initial discharge voltage of the single battery with the anode prepared by the thin film process is 2.1346V, and the initial discharge voltage of the single battery with the anode prepared by the powder tabletting process is 2.1339V. Cut-off voltage of 1.5V, positive film processThe specific capacity of the single battery of the anode is 224.7mAh/g, and the specific capacity of the single battery of the anode is 203.1mAh/g by a powder tabletting process.

From the above embodiment, it can be seen that: compared with the anode prepared by the conventional iron disulfide powder tabletting preparation process, the anode of the thermal battery film prepared by the iron disulfide film preparation process has higher initial discharge voltage, is stable in discharge level table in the discharge process, has better discharge performance than a single battery prepared by the conventional preparation process, has good wrapping property by using polyol with certain viscosity slurry as a solvent, is convenient for coating the film, greatly reduces the influence of the solvent on the activity of the material, and greatly improves the discharge specific capacity. And the thickness of the iron disulfide film positive electrode single battery is greatly reduced compared with the battery prepared by the traditional process, and the iron disulfide film positive electrode single battery can be more suitable for the requirement of high-power miniaturization development of a thermal battery.