A phase change temperature control flame-retardant current collector and a preparation method and application thereof

Abstract

The application provides a phase change temperature control flame-retardant current collector and a preparation method and application thereof. The current collector comprises a conductive coating layer and a temperature control flame-retardant layer, the conductive coating layer comprises a first conductive coating layer and a second conductive coating layer, and is used for loading an active material and encapsulating the temperature control flame-retardant layer, and the temperature control flame-retardant layer is arranged between the first conductive coating layer and the second conductive coating layer; the temperature control flame-retardant layer takes a porous copper film as a matrix, and the porous copper film is filled with a phase change material and a flame retardant agent. The phase change temperature control flame-retardant current collector has a volume specific latent heat greater than 100 J / cm 3 , a thermal conductivity greater than 150 W / m.K and a thickness between 10 and 50 mu m, and well solves the problems of low space utilization, low load and low thermal conductivity of the phase change material in the current temperature control diaphragm and temperature control electrode. In addition, the application has the characteristics of simple structure, high integration and low cost, and well meets the actual application requirements of the temperature control components in the battery.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium battery thermal management, in particular to a phase change temperature control flame-retardant current collector and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of lithium electric power and energy storage industry, it has become an urgent demand to pursue high specific energy density and high charge-discharge rate. However, the heat generation problem in the battery working process cannot be ignored. Once the temperature of the battery exceeds its working temperature threshold, it will seriously affect the cycle life and exacerbate the risk of thermal runaway. Therefore, how to reliably control the temperature of lithium ion battery in a suitable range is a major practical problem.

[0003] Currently, the battery thermal management system controls the temperature according to the thermocouple reading on the surface of the battery, and removes heat from the surface through a cooling medium (such as air, coolant or phase change material). With the development of internal temperature measurement technology for batteries, people are increasingly aware that the battery will generate a large temperature gradient under high rate operation, which is caused by the combination of rapid heat generation and low thermal conductivity of battery materials. Obviously, the external heat dissipation method can reduce the average temperature of the battery module to a certain extent, but it cannot directly solve the problem of heat accumulation and uneven temperature distribution inside the battery cell.

[0004] Combining organic phase change materials with internal components of the battery is a new type of internal temperature control method. Phase change materials spontaneously respond to high temperatures and absorb heat through phase transition, which is passive and efficient. Patent CN104201321A proposes to melt and mix phase change microcapsules and polyethylene and extrude them to prepare a separator with phase change temperature control function. In addition, patent CN111430709A also combines phase change microcapsules with the electrode layer to prepare a phase change temperature control type electrode. However, the porosity of the separator and the electrode layer is generally above 50% for absorbing electrolyte (high porosity is necessary to ensure the rapid transmission of lithium ions), plus the space occupation of the inherent materials of the separator and the electrode layer (such as polymer matrix, active material, conductive agent and binder) and the microcapsule shell, which leads to the problem of low space utilization and low loading of phase change materials in such technical solutions. In addition, the low thermal conductivity of organic phase change materials will limit their heat absorption efficiency. Under the trend of high integration and fast charging of batteries, it is necessary to develop high-thermal-conductivity internal temperature control components with more phase change materials.

[0005] Therefore, it is urgent to develop a new lithium battery internal temperature control assembly to solve the problem of the external thermal management system responding to the high temperature of the battery internally with a lag, so as to provide effective protection in the overheat state of the lithium battery and prevent the occurrence of thermal runaway and fire accidents. SUMMARY

[0006] Therefore, the application provides a phase change temperature control flame-retardant current collector, a preparation method and application thereof.

[0007] In a first aspect, the application provides a phase change temperature control flame-retardant current collector, comprising a conductive coating and a temperature control flame-retardant layer, wherein the conductive coating comprises a first conductive coating and a second conductive coating, the conductive coating is used to load active materials and encapsulate the temperature control flame-retardant layer, and the temperature control flame-retardant layer is arranged between the first conductive coating and the second conductive coating; the temperature control flame-retardant layer takes a porous copper film as a substrate, and the porous copper film is filled with phase change materials and flame retardants.

[0008] By adopting the above technical scheme, the application fills the phase change materials and the flame retardants in the porous copper film by taking the three-dimensionally interconnected porous copper film as the substrate of the temperature control flame-retardant layer, so that when the battery is overheated internally during operation, the phase change materials in the temperature control flame-retardant layer can quickly absorb the excess heat, ensuring that the battery is maintained within a suitable working temperature range. In addition, if the battery is in thermal runaway, the conductive coating will crack under the action of thermal shock, so that the flame retardants in the temperature control flame-retardant layer can be released, effectively reducing the risk of thermal runaway and avoiding secondary hazards caused by the phase change materials.

[0009] Further, the material of the first conductive coating and / or the second conductive coating is selected from one of aluminum, copper, silver, nickel or platinum; and the thickness of any of the conductive coatings is 1-5 μm.

[0010] Further, the thickness of the temperature control flame-retardant layer is 10-50 μm.

[0011] Further, the porosity of the porous copper film is 40-80%, the average pore size is 0.5-2.0 μm, and the thickness is 10-50 μm.

[0012] Further, the organic phase change material is one or more of paraffin, n-docosane, tetracosane, tetradecanol, hexadecanol, octadecanol, lauric acid, tetradecanoic acid, hexadecanoic acid and stearic acid; and the flame retardant is one or more of trimethyl phosphate, triethyl phosphate and triphenyl phosphate.

[0013] Further, the mass ratio of the phase change material to the flame retardant is 80:20-97:3.

[0014] In a second aspect, the present application also relates to a preparation method of the phase change temperature control flame retardant current collector, comprising the following steps:

[0015] S1: Preparing the porous copper film: placing the copper alloy foil in an acidic aqueous solution, heating and stirring, taking out after no bubbles are generated on the surface of the copper alloy foil, washing, drying, and obtaining the pretreated porous copper film;

[0016] S2: Adjusting the pores of the porous copper film: taking the porous copper film in step S1 as the anode, taking the phosphor copper sheet as the cathode, taking the mixed aqueous solution of sulfuric acid and copper sulfate as the electrolyte, and connecting a constant current power supply to electrochemically corrode the porous copper film; after the treatment, washing, drying, and obtaining the twice-treated porous copper film;

[0017] S3: Preparing the temperature control flame retardant layer: heating and stirring the phase change material and the flame retardant to form a liquid mixture; immersing the porous copper foil in step S2 in the liquid mixture and placing it in a constant temperature vacuum environment to obtain the porous copper film adsorbed with the phase change material and the flame retardant, placing it between polyethylene filter membranes, heat pressing, and cooling at room temperature to obtain the temperature control flame retardant layer;

[0018] S4: Preparing the phase change temperature control flame retardant current collector: depositing a conductive coating on both sides of the temperature control flame retardant layer in step S3 to obtain the phase change temperature control flame retardant current collector.

[0019] Based on the above technical scheme, preferably, in step S1 and / or step S2, the washing mode is that deionized water and anhydrous ethanol are used for washing at least three times, respectively.

[0020] Based on the above technical scheme, preferably, in step S4, the deposition mode is selected from one of evaporation plating, magnetron sputtering, electroplating, and chemical plating.

[0021] Based on the above technical scheme, in step S3, the purpose of the heat pressing treatment is to remove the residual liquid on the surface of the porous copper film.

[0022] In step S1 of the present application, the following steps are included:

[0023] Further, the copper alloy is one of copper-zinc alloy (brass), copper-nickel alloy (white copper), copper-zinc-nickel alloy (German white copper), copper-tin alloy (bronze), and copper-manganese alloy (manganese copper); in the copper alloy, the mass fraction of copper is 30-80%.

[0024] Further, the thickness of the foil is 10-50 μm.

[0025] Further, the temperature of the heating and stirring is 50-90 DEG C, and the stirring speed is 200-600 rpm.

[0026] Further, the acid used in the acid aqueous solution is one or more of sulfuric acid, hydrochloric acid, phosphoric acid and acetic acid, and the concentration is 0.1-1.0 mol / L.

[0027] In step S2 of the present application, it comprises:

[0028] Further, the reaction temperature of the chemical etching treatment is 50-90 DEG C, and the stirring speed is 200-600 rpm.

[0029] Further, the electrolyte used in the electrochemical etching treatment, wherein the concentration of sulfuric acid is 0.1-2.0 mol / L, and the concentration of copper sulfate is 0.1-0.6 mol / L.

[0030] Further, the conditions of the electrochemical etching treatment are: the current density is 0.5-2.0 mA / cm 2 , and the duration is 0.5-6 h.

[0031] In step S3 of the present application, it comprises:

[0032] Further, the temperature of the heating and stirring is 40-90 DEG C, the stirring speed is 200-600 rpm, and the duration is 0.5-4 h.

[0033] Further, the constant-temperature vacuum condition is: the vacuum degree is -0.6 to -0.8 MPa, the temperature is 50-80 DEG C, and the duration is 3-20 min.

[0034] Further, the hot-pressing condition is: the pressure is 0.02-0.5 MPa, the temperature is 50-90 DEG C, and the duration is 1-5 min.

[0035] In a third aspect, the present application also relates to the application of the above-mentioned phase change temperature control flame-retardant current collector in lithium batteries, which specifically realizes efficient thermal management and safety protection of lithium batteries under overheated conditions by integrating phase change materials and flame retardants. This design not only improves the thermal stability of lithium batteries, but also enhances their safety under extreme conditions.

[0036] Compared with the prior art, the present application has the following beneficial effects:

[0037] 1. The phase change temperature control flame-retardant current collector prepared by the present application can absorb heat in situ in the battery, quickly respond to the heat accumulated in the battery, and the addition of flame retardants solves the flammability risk of organic phase change materials, thereby improving the thermal safety of lithium batteries.

[0038] 2. The phase change temperature control flame-retardant current collector prepared by the present application has a latent heat of more than 100 J / cm 3 and a thermal conductivity of more than 150 W / m·K, compared with the thermal conductivity of most organic phase change materials, which is only 0.2 W / m·K. This is mainly due to the fact that the thermal resistance is greatly reduced by the thermal conductive network composed of the metal conductive coating and the porous copper matrix, and the porosity of the selected porous copper matrix is distributed between 40% and 80%, which significantly improves the space utilization of the phase change material and effectively increases the load of the phase change material.

[0039] 3. The phase change temperature control flame-retardant current collector prepared by the present application has a good encapsulation effect on the phase change material. The chemical corrosion and electrochemical corrosion double treatment makes the pore size of the porous copper film between 0.5 and 2.0 μm, compared with the pore size of more than 150 μm of commercial copper foam, and the small pore size significantly improves the capillary adsorption force on the phase change material. In addition, the conductive coating further prevents the leakage of the phase change material.

[0040] 4. The phase change temperature control flame-retardant current collector prepared by the present application has a thickness of 10 to 50 μm, so it has little negative impact on the energy density of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0042] Figure 1 is a structural schematic diagram of the phase change temperature control flame-retardant current collector of the present application; in the diagram, 1 is a conductive coating; 11 is a first conductive coating; 12 is a second conductive coating; 2 is a temperature control flame-retardant layer;

[0043] Figure 2 is a scanning electron microscope diagram of the phase change temperature control flame-retardant current collector obtained in Example 1 of the present application;

[0044] Figure 3 is a differential scanning calorimetry curve diagram of the phase change temperature control flame-retardant current collector obtained in Example 1 of the present application;

[0045] Figure 4 is a scanning electron microscope diagram of the porous copper film in Comparative Example 1 of the present application;

[0046] Figure 5 is a scanning electron microscope diagram of the porous copper film in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0048] As shown in Figure 1 The present application provides a phase change temperature control flame-retardant current collector, which comprises a conductive coating and a temperature control flame-retardant layer, wherein the conductive coating comprises a first conductive coating and a second conductive coating, the conductive coating is used for loading active materials and encapsulating the temperature control flame-retardant layer, and the temperature control flame-retardant layer is arranged between the first conductive coating and the second conductive coating; the temperature control flame-retardant layer takes a porous copper film as a substrate, and the porous copper film is filled with phase change materials and flame retardants inside.

[0049] The working principle of the phase change temperature control flame-retardant current collector is as follows: the phase change materials absorb and accumulate heat when the lithium battery is normally working, so as to maintain stable temperature; when the temperature of the lithium battery abnormally rises to a critical point, the encapsulated flame retardants are activated and released, so as to quickly suppress combustion, thereby effectively reducing the harm of thermal runaway and ensuring the safety of the lithium battery.

[0050] The present application is further described below in combination with specific embodiments, and the protection scope of the present application is not limited by the following embodiments. The materials mainly involved in the embodiments are all conventional commercially available products.

[0051] Embodiment 1

[0052] The phase change temperature control flame-retardant current collector provided in the embodiment is prepared by the following steps:

[0053] A 10cm*10cm*20μm H65 brass foil (the mass fractions of copper and zinc are 64% and 36% respectively) is placed in a 1L acidic aqueous solution for chemical corrosion treatment, the acidic aqueous solution is prepared by mixing 1.0M H2SO4 and 1.0M H3PO4, and the reaction is carried out at 80℃ and 200rpm for 24h. After the reaction is completed, the porous copper film is washed with deionized water and anhydrous ethanol for three times respectively, and then dried to obtain a primary processed porous copper film;

[0054] The primary processed porous copper film is used as an anode, a phosphor copper sheet cathode and an aqueous electrolyte are used to form an electrolytic cell, and the porous copper film is subjected to electrolytic corrosion treatment. The aqueous electrolyte is prepared by mixing 0.5M CuSO4 and 1.0M H2SO4, the current density of the electrochemical corrosion is 1.0mA / cm 2 , and the corrosion time is 4h. After the treatment is completed, the porous copper film is washed with deionized water and anhydrous ethanol for three times respectively, and then dried to obtain a secondary processed porous copper film;

[0055] Paraffin wax and triphenyl phosphate with a mass ratio of 95:5 were mixed at 60°C and 200 rpm for 4 hours, and the secondary treated porous copper film was immersed in the molten mixture and placed at 70°C and a vacuum of -0.6 MPa for 3 minutes. The porous copper film filled with phase change material and flame retardant was taken out, placed between two polyethylene filter membranes, and hot pressed to remove the residual liquid on the surface. The hot pressing conditions were a pressure of 0.05 MPa, a temperature of 70°C, and a duration of 3 minutes. After completion, it was cooled at room temperature to obtain a temperature-controlled flame retardant layer.

[0056] The temperature-controlled flame-retardant layer is used as the cathode, and an electrolytic cell is formed with a phosphor copper sheet anode and a commercial copper plating solution to perform surface electroplating on the flame-retardant phase change composite film. The current density of the surface electroplating treatment is 2.0 mA / cm 2 The duration was 1 hour, and the thickness of the electroplated layer was 2 μm. After completion, it was washed with deionized water and anhydrous ethanol three times each, and dried to obtain a phase change temperature control flame retardant current collector.

[0057] The phase change temperature control flame retardant current collector prepared in Example 1 was observed by electron microscope, and the following results were obtained: Figure 2 The scanning electron microscope image shown is Figure 2 It can be seen that the mixture of phase change material and flame retardant completely fills the pores of the porous copper film, and at the same time the electroplated copper layer is tightly combined with the temperature-controlled flame retardant layer, achieving good encapsulation of the phase change material and flame retardant.

[0058] The phase change temperature controlled flame retardant current collector prepared in Example 1 was subjected to differential scanning calorimetry, and the following results were obtained: Figure 3 The differential scanning calorimetry curve shown is Figure 3 It can be seen that the narrow and sharp peak represents the heat absorption and heat storage characteristics of the encapsulated phase change material, and the high volumetric latent heat of the phase change temperature-controlled flame-retardant current collector is due to the high filling rate of the phase change material.

[0059] Example 2

[0060] The phase-change temperature-controlled flame-retardant current collector provided in this embodiment is prepared by the following steps:

[0061] A 10cm x 10cm x 50μm H65 brass foil (copper and zinc content: 64% and 36%, respectively) was chemically etched in 1L of an acidic aqueous solution (1.0M H₂SO₄ + 1.0M H₃PO₄) at 90°C and 400rpm for 72 hours. After completion, the foil was rinsed three times with deionized water and three times with anhydrous ethanol, then dried to obtain the primary treated porous copper film.

[0062] The primary treated porous copper film is used as an anode to form an electrolytic cell with a phosphor copper sheet cathode and an aqueous electrolyte, and the porous copper film is subjected to electrolytic etching treatment. The aqueous electrolyte is prepared by mixing 0.5 M CuSO4 and 1.0 M H2SO4, and the current density of the electrochemical etching is 2.0 mA / cm 2 , and the etching time is 6 h. After completion, the porous copper film is washed with deionized water and anhydrous ethanol three times each, and dried to obtain a secondary treated porous copper film;

[0063] The paraffin and triphenyl phosphate with a mass ratio of 95:5 are mixed at 60 °C for 4 h at a stirring speed of 200 rpm, and the secondary treated porous copper film is immersed in the mixed melt and placed at 70 °C for 5 min under a vacuum degree of -0.8 MPa. The porous copper film filled with the phase change material and the flame retardant is taken out, placed between two polyethylene filter membranes, and subjected to hot pressing treatment to remove the liquid remaining on the surface. The hot pressing conditions are a pressure of 0.5 MPa, a temperature of 70 °C, and a duration of 3 min, and after completion, the temperature control flame retardant layer is cooled at room temperature to obtain a temperature control flame retardant layer;

[0064] The temperature control flame retardant layer is used as a cathode to form an electrolytic cell with a phosphor copper sheet anode and a commercial copper plating solution, and the surface of the flame retardant phase change composite film is subjected to electroplating treatment. The current density of the surface electroplating treatment is 2.0 mA / cm 2 , and the duration is 1.5 h, and the thickness of the electroplated layer formed is 3 μm. After completion, the porous copper film is washed with deionized water and anhydrous ethanol three times each, and dried to obtain a phase change temperature control flame retardant current collector.

[0065] Example 3

[0066] The phase change temperature control flame retardant current collector provided in this example is prepared by the following steps:

[0067] A 10 cm*10 cm*30 μm B45 cupronickel foil (the mass fractions of copper and nickel are 55% and 45%, respectively) is placed in 1 L of an acidic aqueous solution for chemical etching treatment. The acidic aqueous solution is prepared by mixing 1.0 M H2SO4 and 1.0 M H3PO4, and the reaction is carried out at 80 °C and a stirring speed of 200 rpm for 48 h. After completion of the reaction, the porous copper film is washed with deionized water and anhydrous ethanol three times each, and dried to obtain a primary treated porous copper film;

[0068] The primary treated porous copper film is used as an anode to form an electrolytic cell with a phosphor copper sheet cathode and an aqueous electrolyte, and the porous copper film is subjected to electrolytic etching treatment. The aqueous electrolyte is prepared by mixing 0.5 M CuSO4 and 1.0 M H2SO4, and the current density of the electrochemical etching is 1.5 mA / cm 2 , and the etching time is 3 h. After completion, the porous copper film is washed with deionized water and anhydrous ethanol three times each, and dried to obtain a secondary treated porous copper film;

[0069] The paraffin and triphenyl phosphate with a mass ratio of 97:3 were mixed at 60°C with stirring at a speed of 200 rpm for 1 h, and the twice-treated porous copper film was immersed in the molten mixture and placed at 70°C under a vacuum of -0.8 MPa for 4 min. The porous copper film filled with the phase change material and the flame retardant was taken out, placed between two pieces of polyethylene filter film, and subjected to heat pressing treatment to remove the liquid remaining on the surface. The heat pressing conditions were a pressure of 0.5 MPa, a temperature of 70°C, and a duration of 3 min, and after completion, the temperature was cooled at room temperature to obtain a temperature control flame retardant layer;

[0070] The temperature control flame retardant layer was used as a cathode, and an electrolytic cell was formed with a phosphor copper sheet anode and a commercial copper plating solution to perform surface electroplating treatment on the flame-retardant phase change composite film. The current density of the surface electroplating treatment was 2.0 mA / cm 2 , and the duration was 1 h, and the thickness of the electroplated layer formed was 2 μm. After completion, the flame-retardant phase change composite film was washed with deionized water and anhydrous ethanol three times each, and after drying, a phase change temperature control flame-retardant current collector was obtained.

[0071] Example 4

[0072] The phase change temperature control flame-retardant current collector provided in this example was prepared by the following steps:

[0073] A 10 cm*10 cm*20 μm BZn18-26 white copper foil (the mass fractions of copper, zinc, and nickel were 56%, 26%, and 18%, respectively) was placed in a 1 L acidic aqueous solution for chemical etching treatment. The acidic aqueous solution was prepared in a ratio of 1.0 M H2SO4+1.0 M HCl+1.0 M H3PO4, and the reaction was carried out at 70°C and a speed of 200 rpm for 24 h. After completion of the reaction, the porous copper film was washed with deionized water and anhydrous ethanol three times each, and after drying, a primary-treated porous copper film was obtained.

[0074] The primary-treated porous copper film was used as an anode, and an electrolytic cell was formed with a phosphor copper sheet cathode and an aqueous electrolyte to perform electrolytic etching treatment on the porous copper film. The aqueous electrolyte was prepared in a ratio of 0.5 M CuSO4+1.0 M H2SO4, and the current density of the electrochemical etching was 2.0 mA / cm 2 , and the etching time was 2 h. After completion, the porous copper film was washed with deionized water and anhydrous ethanol three times each, and after drying, a twice-treated porous copper film was obtained.

[0075] The paraffin and triphenyl phosphate with a mass ratio of 85:15 were mixed at 60 °C for 4 h at a stirring speed of 600 rpm, and the twice-treated porous copper film was immersed in the molten mixture and placed at 70 °C under a vacuum degree of -0.6 MPa for 3 min. The porous copper film filled with the phase change material and the flame retardant was taken out, placed between two polyethylene filter films, and subjected to heat pressing treatment to remove the liquid remaining on the surface. The heat pressing conditions were a pressure of 0.1 MPa, a temperature of 70 °C, and a duration of 3 min, and after completion, the temperature-control flame-retardant layer was obtained by cooling at room temperature.

[0076] A conductive copper layer was deposited on the surface of the temperature-control flame-retardant layer using a magnetron sputtering device to obtain the phase change temperature-control flame-retardant current collector. Each deposition was performed for 150 s, and after 50 depositions, the thickness of the copper layer was 1 μm.

[0077] Example 5

[0078] The phase change temperature-control flame-retardant current collector provided in this example was prepared by the following steps:

[0079] A 10 cm * 10 cm * 20 μm QAl10-4-4 aluminum bronze foil (the mass fractions of copper, aluminum, iron, and nickel were 78%, 11.0%, 5.5%, and 5.5%, respectively) was placed in a 1 L acidic aqueous solution for chemical etching treatment. The acidic aqueous solution was prepared by mixing 1.0 M H2SO4, 1.0 M HCl, and 1.0 M H3PO4. The reaction was performed at 60 °C and a stirring speed of 600 rpm for 24 h. After completion of the reaction, the primary-treated porous copper film was washed with deionized water and anhydrous ethanol three times each, and dried to obtain the primary-treated porous copper film.

[0080] The primary-treated porous copper film was used as an anode, and a phosphorized copper sheet was used as a cathode to form an electrolytic cell with an aqueous electrolyte. The aqueous electrolyte was prepared by mixing 0.5 M CuSO4 and 1.5 M H2SO4. The electrolytic etching was performed at a current density of 2.0 mA / cm2for 3 h. After completion, the twice-treated porous copper film was washed with deionized water and anhydrous ethanol three times each, and dried to obtain the twice-treated porous copper film. 2

[0081] The eicosane and trimethyl phosphate, triphenyl phosphate (the mass ratio of trimethyl phosphate to triphenyl phosphate was 2:3) with a mass ratio of 95:5 were mixed at 60 °C for 2 h at a stirring speed of 300 rpm, and the twice-treated porous copper film was immersed in the molten mixture and placed at 60 °C under a vacuum degree of -0.8 MPa for 5 min. The porous copper film filled with the phase change material and the flame retardant was taken out, placed between two polyethylene filter films, and subjected to heat pressing treatment to remove the liquid remaining on the surface. The heat pressing conditions were a pressure of 0.2 MPa, a temperature of 55 °C, and a duration of 5 min, and after completion, the temperature-control flame-retardant layer was obtained by cooling at room temperature. ​

[0082] The phase change temperature control flame-retardant current collector is prepared by using evaporation plating film deposition to deposit an aluminum layer, and the thickness of the aluminum layer is 1.5 μm.

[0083] Embodiment 6

[0084] The phase change temperature control flame-retardant current collector provided in the embodiment is prepared by the following steps:

[0085] A 10 cm*10 cm*20 μm QMn12-8-3-2 manganese copper foil (the mass fractions of copper, manganese, aluminum, iron and nickel are 71%, 14.0%, 8.5%, 4% and 2.5%, respectively) is placed in a 1 L acidic aqueous solution for chemical corrosion treatment, and the acidic aqueous solution is prepared by mixing 1.0 M H2SO4, 1.0 M CH3COOH and 1.0 M H3PO4. The reaction is carried out at 50°C and 400 rpm for 24 h. After the reaction is completed, the porous copper film is washed with deionized water and anhydrous ethanol for three times, and then dried to obtain a primary treated porous copper film.

[0086] The primary treated porous copper film is used as an anode, and a phosphorus copper sheet cathode and an aqueous electrolyte are used to form an electrolytic cell, and the porous copper film is subjected to electrolytic corrosion treatment. The aqueous electrolyte is prepared by mixing 0.5 M CuSO4 and 1.5 M H2SO4, and the current density of the electrochemical corrosion is 0.5 mA / cm 2 , and the corrosion time is 6 h. After the treatment is completed, the porous copper film is washed with deionized water and anhydrous ethanol for three times, and then dried to obtain a secondary treated porous copper film.

[0087] Hexadecanol and trimethyl phosphate, triethyl phosphate (the mass ratio of trimethyl phosphate to triethyl phosphate is 4:1) in a mass ratio of 90:10 are mixed at 60°C for 2 h at a stirring speed of 400 rpm, and the secondary treated porous copper film is immersed in the molten mixture and placed at 50°C under a vacuum degree of -0.6 MPa for 20 min. The porous copper film filled with the phase change material and the flame retardant is taken out, placed between two polyethylene filter membranes, and subjected to hot pressing treatment to remove the liquid remaining on the surface. The hot pressing conditions are a pressure of 0.02 MPa, a temperature of 80°C, and a duration of 1 min, and after the treatment is completed, the temperature control flame-retardant layer is obtained by cooling at room temperature.

[0088] The phase change temperature control flame-retardant current collector is prepared by using chemical plating to deposit copper, and the thickness of the copper layer is 3 μm.

[0089] Embodiment 7

[0090] The phase change temperature control flame-retardant current collector provided in the embodiment is prepared by the following steps:

[0091] A 10 cm*10 cm*30 pm B45 cupronickel foil (mass fraction of copper and nickel is 55% and 45% respectively) was placed in 1 L of an acidic aqueous solution for chemical etching treatment. The acidic aqueous solution was prepared by mixing 1.0 M H2SO4 and 1.0 M H3PO4. The reaction was carried out at 80 °C and 200 rpm for 48 h. After the reaction was completed, the porous copper film was washed with deionized water and anhydrous ethanol three times each, and then dried to obtain a primary treated porous copper film;

[0092] The primary treated porous copper film was used as an anode to form an electrolytic cell with a phosphorus copper sheet cathode and an aqueous electrolyte. The aqueous electrolyte was prepared by mixing 0.5 M CuSO4 and 1.0 M H2SO4. The current density for electrochemical etching was 1.0 mA / cm 2 , and the etching time was 3 h. After the reaction was completed, the porous copper film was washed with deionized water and anhydrous ethanol three times each, and then dried to obtain a secondary treated porous copper film;

[0093] Stearic acid and phosphoric acid trimethyl ester, phosphoric acid triethyl ester, and phosphoric acid triphenyl ester (mass ratio of 95:5:5, and mass ratio of phosphoric acid trimethyl ester, phosphoric acid triethyl ester, and phosphoric acid triphenyl ester is 2:2:1) were mixed at 85 °C and 400 rpm for 1 h. The secondary treated porous copper film was immersed in the molten mixture and placed at 50 °C under a vacuum of -0.8 MPa for 10 min. The porous copper film filled with the phase change material and the flame retardant was taken out, placed between two polyethylene filter membranes, and subjected to hot pressing to remove the liquid residue on the surface. The hot pressing conditions were a pressure of 0.2 MPa, a temperature of 60 °C, and a duration of 4 min. After the reaction was completed, the temperature control flame retardant layer was cooled at room temperature to obtain a temperature control flame retardant current collector.

[0094] The temperature control flame retardant layer was used as a cathode to form an electrolytic cell with a phosphorus copper sheet anode and a commercial copper plating solution. The surface of the flame retardant phase change composite film was subjected to electroplating treatment. The current density for surface electroplating treatment was 2.0 mA / cm 2 , and the duration was 1 h. The thickness of the electroplated layer formed was 2 pm. After the reaction was completed, the porous copper film was washed with deionized water and anhydrous ethanol three times each, and then dried to obtain a phase change temperature control flame retardant current collector.

[0095] Comparative Example 1

[0096] The difference between Example 1 and Comparative Example 1 is that step S1 is omitted.

[0097] During the experiment, the inventors found that, as shown in Figure 4 , the porous copper foil prepared in step S2 had a large pore size (>2 pm) and uneven distribution, and had weak adsorption to the mixture of the phase change material and the flame retardant, which could not effectively encapsulate them in the pores.

[0098] Comparative Example 2

[0099] The difference from Example 2 is that in step S2, the current density is 4 mA / cm 2 .

[0100] During the experiment, the inventors found that, as shown in Figure 5 , a large electrochemical corrosion current can cause the porous copper foil to produce super-large (>5 μm) and discontinuous pore structures, and the porous copper foil is brittle and fragile, and cannot be subjected to steps S3 and S4.

[0101] Comparative Example 3

[0102] The difference from Example 3 is that in step S3, the mass ratio of the phase change material to the flame retardant is 60:40.

[0103] During the experiment, the inventors found that when the mass ratio of the flame retardant is too high, the mixture of the phase change material and the flame retardant cannot be cured at room temperature, and thus is prone to leakage and contamination of the surface in step S4, resulting in failure of the deposition of the conductive coating.

[0104] Comparative Example 4

[0105] The difference from Example 4 is that in step S3, the mass ratio of the phase change material to the flame retardant is 99:1.

[0106] During the experiment, the inventors found that when the mass ratio of the flame retardant is too low, the flame retardation effect is poor, and the battery cannot be quickly released when it overheats, resulting in rapid overheating and fire of the battery.

[0107] Comparative Example 5

[0108] The difference from Example 5 is that the porous copper film adsorbed with the phase change material and the flame retardant is not subjected to heat pressing.

[0109] During the experiment, the inventors found that if the solidified phase change material and flame retardant remaining on the surface of the porous copper foil film are not removed by heat pressing, the deposition of the conductive coating in step S4 will fail.

[0110] Comparative Example 6

[0111] The difference from Example 6 is that a commercially available copper foam (purchased from Sanhe New Material Technology Co., Ltd.) is used instead of the porous copper film.

[0112] During the experiment, the inventors found that the commercially available copper foam has a pore size of more than 150 μm, and has weak adsorption and poor filling effect on the mixture of the phase change material and the flame retardant, and is extremely prone to leakage.

[0113] Performance Test:

[0114] The above Examples 1-7 are subjected to the following performance tests, including:

[0115] Thermal conductivity test: The thermal conductivity of the phase change temperature control flame-retardant current collector described in each example was tested according to ISO 22007-2 "Plastics - Determination of thermal conductivity and thermal diffusivity - Part 2: Transient plane source (hot disc) method" (this standard is applicable to thermal conductivity in the range of 0.01-500 W / m·K).

[0116] Phase change temperature and phase change enthalpy test: The phase change temperature and latent heat value of the phase change temperature control flame-retardant current collector described in each example were tested by differential scanning calorimetry (DSC) method.

[0117] The phase change materials obtained in the examples and comparative examples were tested according to the above test standards, and the test results are shown in Table 1 below:

[0118] Table 1 Thermal performance test results

[0119]

[0120] From the thermal performance test results in Table 1, it can be seen that due to the high thermal conductivity and high electrical conductivity of the deposited metal layer and the porous copper film, the phase change temperature control flame-retardant current collector obtained in the examples has good thermal conductivity and electrical conductivity, to meet the rapid heat absorption and normal operation of the battery. The thermal conductivity coefficient of the phase change temperature control flame-retardant current collector obtained in the examples is more than 150 W / m·K, which is three orders of magnitude higher than that of the paraffin phase change material (0.2 W / m·K) used, and is also higher than most existing phase change composite materials. In addition, the volumetric latent heat of the phase change temperature control flame-retardant current collector is more than 100 J / cm 3 , which is higher than that of the paraffin phase change material (168 J / cm 3 ) used, and has high volumetric utilization rate, so it has high practical application value. At the same time, the phase change temperature of the phase change temperature control flame-retardant current collector obtained in Example 1 is 42.6℃, and considering that the suitable working temperature of commercial lithium ion battery is 25-45℃, the phase change temperature control flame-retardant current collector is very suitable for temperature control inside the battery.

[0121] Taking Example 1 as an example, the 0.5 Ah lithium iron phosphate / graphite soft package battery was assembled by using Example 1 and commercial copper foil (material purchased from Kelude Technology Co., Ltd.) respectively, and the other components (positive electrode current collector, positive electrode, negative electrode, separator, electrolyte) of the battery were consistent. The battery was tested for the following performance:

[0122] (1) Cycle capacity retention rate

[0123] (2) Temperature rise after 3C discharge of the full charged battery

[0124] (3) Maximum temperature of thermal runaway

[0125] The test results are recorded in Table 2 below.

[0126] Table 2 Battery performance and thermal safety

[0127]

[0128] According to the results in Table 2, it can be seen that the 0.5 Ah LiFePO4 / graphite soft pack battery assembled using the phase change temperature control flame-retardant current collector has good cycle performance, the capacity retention rate is 94.9% at 25℃ after 100 cycles, and the capacity retention rate is 82.9% at 55℃ after 100 cycles, which is basically comparable to commercial copper foil. The stable cycle at 55℃ proves the good encapsulation of the phase change material and the flame retardant. After 3C rate discharge of the full state battery (SOC = 100%), the temperature rise of the battery using the phase change temperature control flame-retardant current collector is only 10.2℃, which is reduced by 9.3℃ compared with the commercial copper foil. In addition, the battery is subjected to thermal abuse to trigger thermal runaway, and the release of the flame retardant makes the maximum temperature of the battery only 181.4℃, which is far lower than the 486.2℃ of the commercial copper foil. Therefore, the phase change temperature control flame-retardant current collector effectively improves the thermal stability of the battery and suppresses thermal runaway.

[0129] The above description is merely preferred embodiments of the present application, but not to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for preparing a phase-change temperature-control flame-retardant current collector, wherein the phase-change temperature-control flame-retardant current collector comprises a conductive coating (1) and a temperature-control flame-retardant layer (2), wherein the conductive coating comprises a first conductive coating (11) and a second conductive coating (12), and wherein: The conductive coating (1) is used to load active materials and encapsulate the temperature-controlling flame-retardant layer (2), and the temperature-controlling flame-retardant layer (2) is arranged between the first conductive coating (11) and the second conductive coating (12); The temperature-controlling flame-retardant layer (2) is based on a porous copper film, and the porous copper film is filled with a phase change material and a flame retardant; The steps include: S1: Pre-preparation of a porous copper film: placing a copper alloy foil in an acidic aqueous solution, heating and stirring, and removing the copper alloy foil after no bubbles are generated on the surface, washing it, and drying it to obtain a pre-treated porous copper film; S2: Pore adjustment of the porous copper film: The porous copper film prepared in step S1 is used as the anode, the phosphor copper sheet is used as the cathode, and a mixed aqueous solution of sulfuric acid and copper sulfate is used as the electrolyte. A constant current power supply is connected to the porous copper film for electrochemical etching. After the treatment is completed, the porous copper film is cleaned and dried to obtain a secondary treated porous copper film. S3: Preparation of a temperature-controlled flame-retardant layer (2): heating and stirring a phase change material and a flame retardant to form a liquid mixture; immersing the porous copper foil in step S2 in the liquid mixture and placing it in a constant temperature vacuum environment to obtain a porous copper film adsorbed with the phase change material and the flame retardant, placing the porous copper film between polyethylene filter membranes, performing a hot pressing process, and cooling the film at room temperature to obtain a temperature-controlled flame-retardant layer (2); S4: Preparation of a phase-change temperature-controlled flame-retardant current collector: depositing a conductive coating (1) on both sides of the temperature-controlled flame-retardant layer (2) in step S3 to prepare a phase-change temperature-controlled flame-retardant current collector; The deposition method is selected from one of evaporation coating, magnetron sputtering, electroplating or chemical plating.

2. The method for preparing a phase-change temperature-controlled flame-retardant current collector according to claim 1, characterized in that: The material of the first conductive coating (11) and / or the second conductive coating (12) is selected from one of aluminum, copper, silver, nickel or platinum; the thickness of any one of the conductive coatings is 1 to 5 μm.

3. The method for preparing a phase-change temperature-controlled flame-retardant current collector according to claim 1, characterized in that: The temperature-controlling flame-retardant layer (2) has a thickness of 10 to 50 μm.

4. The method for preparing a phase-change temperature-controlled flame-retardant current collector according to claim 3, characterized in that: The porous copper film has a porosity of 40-80%, an average pore size of 0.5-2.0 μm, and a thickness of 10-50 μm; The phase change material is selected from one or more of paraffin, n-docosane, tetracosane, tetradecanol, hexadecanol, octadecanol, lauric acid, myristic acid, hexadecanoic acid and stearic acid; The flame retardant is selected from one or more of trimethyl phosphate, triethyl phosphate and triphenyl phosphate.

5. The method for preparing a phase-change temperature-controlled flame-retardant current collector according to claim 4, characterized in that: The mass ratio of the phase change material to the flame retardant is 80:20 to 97:

3.

6. The method for preparing a phase-change temperature-controlled flame-retardant current collector according to claim 1, characterized in that: In step S1, the copper alloy is selected from one of copper-zinc alloy, copper-nickel alloy, copper-zinc-nickel alloy, copper-tin alloy or copper-manganese alloy; in the copper alloy, the mass fraction of copper is 30-80%; The thickness of the foil is 10 to 50 μm; The acid used in the acidic aqueous solution is selected from one or more of sulfuric acid, hydrochloric acid, phosphoric acid and acetic acid, and the concentration is 0.1 to 1.0 mol / L; The heating and stirring temperature is 50-90° C., and the stirring speed is 200-600 rpm.

7. The method for preparing a phase-change temperature-controlled flame-retardant current collector according to claim 1, characterized in that: In step S2, in the electrolyte, the concentration of sulfuric acid is 0.1-2.0 mol / L, and the concentration of copper sulfate is 0.1-0.6 mol / L; The conditions of the electrochemical corrosion treatment are: the current density is 0.5-2.0 mA / cm 2 , the corrosion time is 0.5 to 6 hours.

8. The method for preparing a phase-change temperature-controlled flame-retardant current collector according to claim 1, characterized in that: In step S3, the heating and stirring temperature is 40-90° C., the stirring speed is 200-600 rpm, and the duration is 0.5-4 h; The constant temperature vacuum conditions are: vacuum degree -0.6 to -0.8 MPa, temperature 50 to 80°C, and duration 3 to 20 minutes; The hot pressing conditions are: pressure 0.02-0.5 MPa, temperature 50-90° C., and duration 1-5 min.

9. Use of the phase-change temperature-controlled flame-retardant current collector obtained by the preparation method according to any one of claims 1 to 8 in lithium batteries.

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