Positive pole piece, preparation method thereof and solid-state lithium battery
By using polyacrylonitrile and halide electrolytes in the positive electrode of solid-state lithium batteries, a highly efficient ion-electron conduction network is constructed, solving the problem of low ion conductivity of the positive electrode and improving the electrochemical performance and lifespan of the battery.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- PETROCHINA SHENZHEN NEW ENERGY RESEARCH INSTITUTE CO LTD
- Filing Date
- 2024-11-22
- Publication Date
- 2026-05-22
AI Technical Summary
The existing solid-state lithium battery cathode has low ionic conductivity, resulting in poor battery electrochemical performance.
Using polyacrylonitrile as a binder and lithium indium chloride or lithium zirconium chloride as a halide electrolyte, combined with positive electrode active materials such as nickel cobalt manganese, lithium cobalt oxide or lithium iron phosphate, an ion-electron conduction network is constructed through a specific preparation method.
It improves the ionic conductivity of the positive electrode, thereby enhancing the cycle stability and lifespan of the battery.
Smart Images
Figure CN122073218A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of lithium-ion battery technology, and in particular to a positive electrode sheet and its preparation method, and a solid-state lithium battery. Background Technology
[0002] As the application fields of lithium-ion batteries gradually expand, the requirements for their energy density and safety are also constantly increasing. Currently, commercially available lithium-ion batteries contain flammable organic electrolyte components, making them unstable. Therefore, high-energy-density lithium-ion batteries frequently experience spontaneous combustion and explosion accidents. Solid-state batteries have the advantages of high safety and potentially high energy density, which can be used to resolve the contradiction between energy density and safety in lithium-ion batteries.
[0003] In solid-state lithium batteries, the ion transport path changes from solid-solid transport to solid-liquid transport, resulting in significant interfacial impedance. This is especially true in high-energy-density solid-state batteries, where the thick electrode effect severely hinders ion transport within the electrode. To address this issue, existing Chinese invention patent application CN113130895B provides a solid-state lithium-ion battery and its preparation method. This method uses a polymer electrolyte doped into the positive electrode to improve its ionic conductivity. However, the polyacrylonitrile polymer electrolyte used has low ionic conductivity, and the use of polyvinylidene fluoride (PVDF) as a binder further reduces the electrode's ionic conductivity, thus failing to meet practical application requirements.
[0004] Therefore, existing cathode materials suffer from low ionic conductivity, resulting in poor electrochemical performance of the battery. There is an urgent need to provide a cathode material and its preparation method to improve these issues. Summary of the Invention
[0005] The main objective of this invention is to provide a positive electrode sheet and its preparation method, as well as a solid-state lithium battery, to solve the technical problem that the positive electrode sheet in the prior art has low ionic conductivity, resulting in poor electrochemical performance of the battery.
[0006] To achieve the above objectives, according to one aspect of the present invention, a positive electrode sheet is provided comprising: a positive electrode active material, a polymer binder, a lithium salt, and a halide electrolyte, wherein the polymer binder is polyacrylonitrile with a number-average molecular weight Mn of 1000 to 1000000 g / mol, and the halide electrolyte is lithium indium chloride and / or lithium zirconium chloride.
[0007] Furthermore, the weight of each component in the positive electrode sheet is as follows: 70-95 wt% positive electrode active material, 2-15 wt% polymer binder, 1-1.5 wt% lithium salt and 2-15 wt% halide electrolyte.
[0008] Furthermore, the positive electrode active material is selected from one or more of nickel cobalt manganese, lithium cobalt oxide, lithium manganese oxide, or lithium iron phosphate; preferably, the lithium salt is selected from one or more of LiPF6, LiBF4, LiTFSI, or LiFSI.
[0009] Furthermore, in the positive electrode active material, nickel, cobalt, and manganese are selected from one or more of the following: NCM111, NCM523, NCM622, NCM811, or NCM9055.
[0010] To achieve the above objectives, according to one aspect of the present invention, a method for preparing a positive electrode sheet is provided, the method comprising the following steps: Step S1, dissolving polyacrylonitrile in an organic solvent to obtain a polyacrylonitrile solution; Step S2, mixing positive electrode active material, lithium salt and halide electrolyte in an anhydrous environment, and then adding polyacrylonitrile solution to obtain a mixed solution; Step S3, diluting the mixed solution in an organic solvent until the viscosity of the mixed solution is 500-10000 Pa·s, and then sequentially coating, drying and rolling to obtain a positive electrode sheet.
[0011] Furthermore, by weight percentage, the weight ratio of polyacrylonitrile, positive electrode active material, lithium salt and halide electrolyte is (2-15):(70-95):(1-1.5):(2-15).
[0012] Further, the organic solvent is selected from one or more of N-methyl-2-pyrrolidone, chloroform, dichloromethane, acetonitrile, toluene, or xylene; preferably, in step S2, the mixing temperature is 15-60°C and the treatment time is 10-500 min.
[0013] Further, the coating process includes: uniformly coating the mixed solution onto the surface of the PET substrate film, adjusting the coating height by changing the doctor blade height, with the coating height being 1–50 μm.
[0014] Furthermore, the drying temperature is 60–150°C, and the processing time is 1–10 h; preferably, the rolling process is carried out in a rolling mill or a hot rolling mill, the rolling pressure is 1–500 MPa, more preferably 10–200 MPa, the processing temperature is 60–100°C, and the processing speed is 0.1–10 m / min.
[0015] According to another aspect of the present invention, a solid-state lithium battery is provided, comprising a halide electrolyte membrane obtained by the above-described method for preparing the halide electrolyte.
[0016] By applying the technical solution of this invention, an ion-electron transport network can be effectively constructed, improving ion conductivity. Moreover, when applied to batteries, it exhibits superior cycle stability and a longer service life. Attached Figure Description
[0017] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application. In the drawings:
[0018] Figure 1 An SEM image (magnification 3000x) of the positive electrode sheet prepared according to Example 1 of the present invention is shown. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0020] As described in the background section of this invention, existing positive electrode sheets suffer from low ionic conductivity, resulting in poor electrochemical performance of the battery. Based on this, this invention provides a positive electrode sheet comprising: a positive electrode active material, a polymer binder, a lithium salt, and a halide electrolyte. The polymer binder is polyacrylonitrile with a number-average molecular weight Mn of 1000–1000000 g / mol, and the halide electrolyte is lithium indium chloride and / or lithium zirconium chloride.
[0021] Compared to existing technologies where the positive electrode sheet has poor ionic conductivity due to the use of polyvinylidene fluoride (PVDF) as a binder, which reduces ionic conductivity, this invention uses polyacrylonitrile (PAF) as the polymer binder. Firstly, replacing PDF binder with PAF binder in existing technologies increases the content of the positive electrode active material while reducing the binder content. Secondly, the doping of the positive electrode sheet with PAF and halide electrolyte in this invention effectively constructs the ion-electron conduction network within the positive electrode sheet. This is because halide electrolytes have higher ionic conductivity and can increase the amorphous region content of PAF, thereby improving the ionic conductivity of the polymer electrolyte. Furthermore, both PAF and halide electrolytes are high-voltage stable materials, not easily oxidized by high-voltage positive electrode materials, thus improving the cycle stability and lifespan of solid-state batteries. In summary, the positive electrode sheet provided by this invention can effectively construct the ion-electron conduction network, improve ionic conductivity, and, when applied to batteries, also enhances battery cycle stability and lifespan.
[0022] In a preferred embodiment, the weight of each component in the positive electrode sheet is: 70-95 wt% positive electrode active material, 2-15 wt% polymer binder, 1-1.5 wt% lithium salt and 2-15 wt% halide electrolysis, thereby further improving the ionic conductivity and stability of the positive electrode sheet.
[0023] To further effectively construct the ion-electron conduction network in the positive electrode and improve ion conductivity, the preferred positive electrode active material is selected from one or more of nickel-cobalt-manganese, lithium cobalt oxide, lithium manganese oxide, or lithium iron phosphate. More preferably, the nickel-cobalt-manganese material is selected from one or more of NCM111, NCM523, NCM622, NCM811, or NCM9055. The preferred lithium salt is selected from one or more of LiPF6, LiBF4, LiTFSI, or LiFSI.
[0024] In another aspect, the present invention provides a method for preparing a positive electrode sheet, the method comprising the following steps: Step S1, dissolving polyacrylonitrile in an organic solvent to obtain a polyacrylonitrile solution; Step S2, mixing positive electrode active material, lithium salt and halide electrolyte in an anhydrous environment, and then adding polyacrylonitrile solution to obtain a mixed solution; Step S3, diluting the mixed solution in an organic solvent until the viscosity of the mixed solution is 500-10000 Pa·s, and then sequentially coating, drying and rolling to obtain a positive electrode sheet.
[0025] Those skilled in the art first dissolve polyacrylonitrile in an organic solvent to obtain a polyacrylonitrile solution. Then, the positive electrode active material, lithium salt, and halide electrolyte are mixed in an anhydrous environment, and the polyacrylonitrile solution is added to obtain a mixed solution. Finally, the mixed solution is diluted in an organic solvent until the viscosity of the mixed solution is 500–10000 Pa·s, and then coated, dried, and rolled to obtain the positive electrode sheet. This preparation method is simple, easy to operate, and has broad prospects for industrial application, making it suitable for large-scale production. The positive electrode sheet has high ionic conductivity, resulting in superior cycle stability and lifespan when used in solid-state lithium batteries.
[0026] In a preferred embodiment, the weight ratio of polyacrylonitrile, positive electrode active material, lithium salt and halide electrolyte is (2-15):(70-95):(1-1.5):(2-15) by weight percentage. By adding the above-mentioned raw materials in the preparation process of the positive electrode sheet, the ion-electron conduction network in the positive electrode sheet can be constructed more effectively, thereby improving the ion conductivity.
[0027] To further ensure that the raw materials are fully dissolved in the organic solution to obtain a homogeneous and stable mixed solution, the organic solvent is preferably selected from one or more of N-methyl-2-pyrrolidone, chloroform, dichloromethane, acetonitrile, toluene, or xylene. More preferably, the positive electrode active material, lithium salt, and halide electrolyte can be mixed evenly. The mixing temperature is preferably 15–60°C, and the processing time is preferably 10–500 min.
[0028] In a preferred embodiment, the coating process includes: uniformly coating the mixed solution onto the surface of a PET substrate film, adjusting the coating height by changing the doctor blade height, with the coating height being 1–50 μm, to prepare a high-performance positive electrode sheet; preferably, the drying temperature is 60–150°C, the drying time is 1–10 h, and the rolling process is carried out in a rolling mill or a hot rolling mill, with the rolling pressure being 1–500 MPa, more preferably 10–200 MPa, the processing temperature being 60–100°C, and the processing speed being 0.1–10 m / min.
[0029] In another aspect, the present invention provides a solid-state lithium battery, including a positive electrode sheet, which is obtained by the above-described method for preparing a positive electrode sheet.
[0030] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.
[0031] Example 1
[0032] Polyacrylonitrile (PAC) was dissolved in N-methyl-2-pyrrolidone (NMP) and stirred until homogeneous to obtain a PAC solution with a number-average molecular weight (Mn) of 100,000 g / mol. The positive electrode active material, lithium salt, and halide electrolyte were mixed in an anhydrous environment for 30 min at 25°C. The PAC solution was then added to obtain a mixed solution. The weight ratio of PAC, positive electrode active material, lithium salt, and halide electrolyte was 3:90:1.25:5.75. The mixed solution was then diluted in NMP to a viscosity of 4000 Pa·s. This solution was then uniformly coated onto the surface of a PET substrate film. The coating height was adjusted by changing the doctor blade height to 50 μm. The film was dried at 60°C for 10 h and then rolled in a roller press at a pressure of 50 MPa, a temperature of 80°C, and a speed of 10 m / min to obtain the positive electrode sheet. In this positive electrode, the halide electrolyte is lithium indium chloride, the positive electrode active material is nickel cobalt manganese NCM622, and the lithium salt is LiPF6. The weight percentages of the components in the positive electrode are: 90 wt% positive electrode active material, 5 wt% polymer binder, 1 wt% lithium salt, and 4 wt% halide electrolyte. A SEM image of this positive electrode is attached. Figure 1 As shown.
[0033] Example 2
[0034] The only difference from Example 1 is that the weight ratio of polyacrylonitrile, positive electrode active material, lithium salt and halide electrolyte is 5:88:1.25:5.75.
[0035] Example 3
[0036] The only difference from Example 1 is that the weight ratio of polyacrylonitrile, positive electrode active material, lithium salt and halide electrolyte is 1:92:1.25:5.75.
[0037] Example 4
[0038] The only difference from Example 1 is that the weight ratio of polyacrylonitrile, positive electrode active material, lithium salt and halide electrolyte is 3:90:1.25:5.75.
[0039] Example 5
[0040] The only difference from Example 1 is that the weight ratio of polyacrylonitrile, positive electrode active material, lithium salt and halide electrolyte is 3:85:1.25:10.75.
[0041] Comparative Example 1
[0042] The only difference from Example 1 is that no halide electrolyte is added to the raw materials, and the weight ratio of polyacrylonitrile, positive electrode active material, lithium salt and halide electrolyte is 3:95:2:0.
[0043] Comparative Example 2
[0044] The only difference from Example 1 is that the binder used is polyvinylidene fluoride (PVDF), and the weight ratio of PVDF, positive electrode active material, lithium salt and halide electrolyte is 3:95:2:5.
[0045] Performance testing
[0046] 1) The ionic conductivity was tested using a micrometer screw gauge and an electrochemical workstation. The testing method was as follows: ① The halide electrolyte membrane was cut into uniform circular pieces with a diameter R of 1 cm; ② The thickness d was measured using a micrometer screw gauge; ③ The intrinsic resistance R was measured using an electrochemical workstation. The formula for calculating the ionic conductivity is: б=d / (R×лR) 2 / 4).
[0047] 2) Electrode peel strength test, the test method is as follows:
[0048] ① Sample preparation: Place the adhesive tape sample in an environment of 23±1℃ and 50±5%RH for 24 hours for conditioning. Then, wipe the surface of the stainless steel plate with acetone 4 times and let it air dry for 10 minutes.
[0049] ② Sample cutting: Remove the four layers of adhesive tape from the surface of the sample, and cut a sample with a width of 24 mm and a length of 300 mm from the remaining sample using a cutter. Fold one end of the sample in half to form a folded layer of about 12 mm in length. Attach the other end of the sample to one end of the steel plate and roll it twice with an adhesive tape roller at a speed of 600 mm / min.
[0050] ③ Test Preparation: Peel approximately 25mm of adhesive tape from the steel plate at the folded end of the specimen, and clamp the steel plate at this end and the free end of the specimen in the upper and lower fixtures of the equipment, respectively. Set the test speed (300mm / min), specimen width (24mm), and other parameters. Click the test option to start the test. The equipment will automatically record the force value during the peeling process and report the peel strength of the specimen accordingly.
[0051] ④ Test repetition: Repeat the above sample cutting, preparation, and testing procedures to test the peel strength values of 3 samples.
[0052] Testing equipment: Commonly used equipment includes electronic tensile testing machines, which can automatically record the force values during the peeling process and calculate the peel strength of the sample. These machines typically feature a high-definition touchscreen for easy user control and display of real-time data and curves, and incorporate precision ball screw drives and force sensors for accurate displacement control and force measurement.
[0053] 3) Battery capacity degradation test results are as follows:
[0054] The positive electrode sheets prepared in the above examples and comparative examples were used to assemble solid-state batteries using lithium-indium alloy as the negative electrode for testing. Charge-discharge tests were conducted at room temperature at a rate of 0.3C using a Blue Electric charge-discharge test cabinet. The test was stopped when the capacity decayed to 80%. The test results are shown in Table 1.
[0055] Table 1
[0056]
[0057] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:
[0058] As shown in Table 1, the positive electrode sheet prepared by the method of this invention exhibits superior ionic conductivity and peel strength compared to the positive electrode sheet prepared in the comparative example, under the same conditions. Furthermore, when assembled into a battery, its cycle stability was tested, demonstrating superior stability and a longer service life. Moreover, the discharge specific capacity at its positive electrode active site is significantly higher than that of the comparative example, thus exhibiting superior electrochemical performance and overall superior performance.
[0059] In summary, the positive electrode sheet provided by this invention can effectively construct an ion-electron transport network, improve ion conductivity, and when applied to batteries, it can also improve the cycle stability and service life of the batteries.
[0060] While this specification contains numerous specific implementation details, these should not be construed as limiting the scope of any invention or the scope of the claims, but rather are primarily intended to describe features of specific embodiments of a particular invention. Certain features described in the various embodiments herein may also be implemented in combination in a single embodiment. Conversely, various features described in a single embodiment may also be implemented separately in various embodiments or in any suitable sub-combination. Furthermore, while features may function in certain combinations as described above and even initially claimed in this way, one or more features from a claimed combination may be removed from that combination in some cases, and a claimed combination may refer to a sub-combination or a variation thereof.
[0061] Similarly, although the operations are depicted in a specific order in the accompanying drawings, this should not be construed as requiring these operations to be performed in the specific order shown or sequentially, or requiring all illustrated operations to be performed to achieve the desired result. In some cases, multitasking and parallel processing may be advantageous. Furthermore, the separation of various system modules and components in the above embodiments should not be construed as requiring such separation in all embodiments, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products.
[0062] Thus, specific embodiments of the subject matter have been described. Other embodiments are within the scope of the appended claims. In some cases, the actions recited in the claims may be performed in a different order and still achieve the desired result. Furthermore, the processes depicted in the drawings are not necessarily shown in a specific order or sequence to achieve the desired result. In some implementations, multitasking and parallel processing may be advantageous.
[0063] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0064] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.
Claims
1. A positive electrode plate, characterized in that, The positive electrode comprises: a positive electrode active material, a polymer binder, a lithium salt, and a halide electrolyte. The polymer binder is polyacrylonitrile with a number-average molecular weight Mn of 1000-1000000 g / mol, and the halide electrolyte is lithium indium chloride and / or lithium zirconium chloride.
2. The positive electrode sheet according to claim 1, characterized in that, The weight of each component in the positive electrode sheet is as follows: 70-95 wt% of the positive electrode active material, 2-15 wt% of the polymer binder, 1-1.5 wt% of the lithium salt, and 2-15 wt% of the halide electrolyte.
3. The positive electrode sheet according to claim 1 or 2, characterized in that, The positive electrode active material is selected from one or more of nickel cobalt manganese, lithium cobalt oxide, lithium manganese oxide, or lithium iron phosphate; Preferably, the lithium salt is selected from one or more of LiPF6, LiBF4, LiTFSI or LiFSI.
4. The positive electrode sheet according to claim 3, characterized in that, In the positive electrode active material, the nickel, cobalt, and manganese are selected from one or more of the following: NCM111, NCM523, NCM622, NCM811, or NCM9055.
5. A method for preparing a positive electrode sheet according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: Step S1: Dissolve polyacrylonitrile in an organic solvent to obtain a polyacrylonitrile solution; Step S2: Take the positive electrode active material, lithium salt and halide electrolyte and mix them in an anhydrous environment, then add the polyacrylonitrile solution to obtain a mixed solution; Step S3: Dilute the mixed solution in an organic solvent until the viscosity of the mixed solution is 500-10000 Pa·s, and then perform coating, drying and rolling treatment in sequence to obtain the positive electrode sheet.
6. The preparation method according to claim 5, characterized in that, The weight percentage of the polyacrylonitrile, the positive electrode active material, the lithium salt and the halide electrolyte is (2-15):(70-95):(1-1.5):(2-15).
7. The preparation method according to claim 5, characterized in that, The organic solvent is selected from one or more of N-methyl-2-pyrrolidone, chloroform, dichloromethane, acetonitrile, toluene, or xylene; Preferably, in step S2, the temperature of the mixing process is 15–60°C, and the processing time is 10–500 min.
8. The preparation method according to claim 5, characterized in that, The coating process includes: uniformly coating the mixed solution onto the surface of a PET substrate film, adjusting the coating height by changing the doctor blade height, with the coating height being 1–50 μm.
9. The preparation method according to claim 5, characterized in that, The drying process is carried out at a temperature of 60–150°C for 1–10 hours. Preferably, the rolling process is carried out in a rolling mill or a hot rolling mill, the rolling pressure is 1 to 500 MPa, more preferably 10 to 200 MPa, the processing temperature is 60 to 100°C, and the processing speed is 0.1 to 10 m / min.
10. A solid-state lithium battery, comprising a positive electrode, characterized in that, The positive electrode sheet is obtained by the method for preparing the positive electrode sheet according to any one of claims 5 to 9.