Lithium ion battery and method of manufacturing the same
By using SPEEK-Li and PAA-Li as binders, the problems of high expansion rate and high resistivity of lithium-ion battery binders were solved, thereby improving the cycle life, rate performance and safety performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JINKO SOLAR CO LTD
- Filing Date
- 2025-02-25
- Publication Date
- 2026-06-16
AI Technical Summary
The binders commonly used in existing lithium-ion batteries have high expansion rates and high resistivity, which leads to a decrease in the efficiency of lithium-ion batteries.
SPEEK-Li and PAA-Li are used as binders. SPEEK-Li has lower electrolyte swelling and higher mechanical stability, while PAA-Li can supplement additional lithium sources and improve ionic conductivity through pre-lithiation. The combination of the two forms a dual lithium-ion transport channel, which promotes lithium-ion migration.
It improves the cycle life and rate performance of lithium-ion batteries, reduces the expansion rate of the negative electrode, enhances the liquid absorption rate and heat resistance of the negative electrode, and ensures the safety performance of the battery.
Smart Images
Figure CN120072940B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of lithium-ion battery technology, and in particular to a lithium-ion battery and its preparation method. Background Technology
[0002] Compared with traditional nickel-hydrogen batteries and lead-acid batteries, lithium-ion secondary batteries have advantages such as light weight, less environmental pollution, high operating voltage, high energy density, and long cycle life, and have been widely used in consumer electronics, electric vehicles, and energy storage.
[0003] Commonly used binders for lithium-ion batteries include polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), polyolefins (such as polypropylene and polyethylene), polyvinylidene fluoride (PVDF), modified styrene-butadiene rubber, fluorinated rubber, and polyurethane. As a crucial component of lithium-ion battery electrodes, the binder's main function is to ensure sufficient bonding strength between active material particles and between active particles and the current collector during battery use, while also facilitating the formation of the SEI film (Solid Electrolyte Interface membrane).
[0004] However, the binders commonly used in lithium-ion batteries currently have the problems of high expansion rate and high resistivity, which leads to a decrease in the efficiency of lithium-ion batteries. Summary of the Invention
[0005] This application provides a lithium-ion battery and its preparation method, which at least helps to improve the performance of the lithium-ion battery.
[0006] According to some embodiments of this application, one aspect of this application provides a method for preparing a lithium-ion battery, comprising: preparing a negative electrode sheet, the preparation steps including: weighing 85-99 parts of negative electrode active material, 0.35-8.1 parts of SPEEK-Li and 0.5-6 parts of conductive agent; adding the negative electrode active material, conductive agent and SPEEK-Li into a mixer for mixing, the mixing time being 20-40 minutes; adding 78-82 parts of deionized water for kneading and stirring, the mixing time being 120-130 minutes; adding 0.9-8.65 parts of an aqueous solution of PAA-Li, the total amount of SPEEK-Li and PAA-Li... The mass fraction is 0.5~9 parts, the mass ratio of SPEEK-Li to PAA-Li is (7~9):(3~1), and the concentration of the PAA-Li aqueous solution is 0.128mol / L~0.64mol / L. The stirring time is 110~120 minutes; defoaming stirring is performed for 20~30 minutes; the stirred slurry is coated onto the negative electrode current collector through a coating machine oven and dried to obtain a negative electrode sheet; a positive electrode sheet and a separator are provided, and the positive electrode sheet, separator and negative electrode sheet are wound or stacked and then placed into the casing. Electrolyte is injected into the casing to obtain a lithium-ion battery.
[0007] In some embodiments, before defoaming stirring, the method further includes: viscosity adjustment stirring, adjusting the viscosity of the mixed slurry to 3500 mPa·s to 9500 mPa·s and the solid content to 55% to 60%, and stirring for 30 to 40 minutes, wherein the stirring rate of defoaming stirring is lower than the stirring rate of viscosity adjustment stirring.
[0008] In some embodiments, the coating machine oven includes 5 sections with temperatures of 90℃~100℃, 100℃~105℃, 100℃~105℃, 105℃~110℃, and 105℃~110℃ respectively.
[0009] In some embodiments, the preparation steps of SPEEK-Li include: adding PEEK to concentrated sulfuric acid, wherein the mass ratio of PEEK to concentrated sulfuric acid is 1:(10~20), the concentration of concentrated sulfuric acid is 96%~98%, stirring at 60℃~100℃ for 20~30 hours, quenching the resulting mixture with cold water, filtering to obtain a white solid, dissolving the white solid in deionized water, neutralizing it with a 0.5M~1M aqueous solution of LiOH, and drying to obtain SPEEK-Li.
[0010] In some embodiments, before dissolving the white solid in deionized water and neutralizing it with an aqueous solution of 0.5M~1M LiOH, the process includes: dialysis purification of the white solid with a molecular cutoff of 1000 Da, followed by rotary evaporation to obtain the purified white solid.
[0011] In some embodiments, the preparation step of the PAA-Li aqueous solution includes: dissolving polyacrylic acid in deionized water to obtain an aqueous solution of polyacrylic acid, adding an aqueous solution of LiOH to the aqueous solution of polyacrylic acid to react and obtain an aqueous solution of PAA-Li, wherein the molar ratio of polyacrylic acid to LiOH is 1:(0.3~1), the concentration of the aqueous solution of polyacrylic acid is 0.14mol / L~0.69mol / L, and the concentration of the aqueous solution of LiOH is 1.22mol / L~2.44mol / L.
[0012] According to some embodiments of this application, another aspect of this application provides a lithium-ion battery, including: a casing, and a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte disposed in the casing and stacked thereon. The negative electrode sheet includes: a negative electrode current collector and a negative electrode material layer covering the surface of the negative electrode current collector. The mass parts of each substance in the negative electrode material layer are as follows: 85 to 99 parts of negative electrode active material, 0.5 to 9 parts of binder and 0.5 to 6 parts of conductive agent, wherein the binder is composed of PAA-Li and SPEEK-Li, and the mass ratio of SPEEK-Li to PAA-Li is (7 to 9): (3 to 1).
[0013] In some embodiments, the thickness of the negative electrode material layer is 140 μm to 150 μm.
[0014] In some embodiments, the average molecular weight of SPEEK-Li is greater than 1000.
[0015] In some embodiments, the average molecular weight of PAA-Li is 50,000 to 80,000.
[0016] The technical solution provided in this application has at least the following advantages:
[0017] The lithium-ion battery and its preparation method provided in this application embodiment include a negative electrode material layer comprising a negative electrode active material, a conductive agent, and a binder. The binder is composed of SPEEK-Li and PAA-Li. SPEEK-Li, as a binder, exhibits lower electrolyte swelling and higher mechanical stability. The SPEEK-Li main chain is linked with a large number of sulfonic acid side groups. Sulfonic acid groups possess excellent hydrophilicity and high-temperature resistance, which on the one hand can absorb a large amount of electrolyte, significantly increasing the liquid absorption rate of the negative electrode sheet, and on the other hand improves the heat resistance of the negative electrode sheet, ensuring the battery's safety performance. PAA-Li can supplement additional lithium sources to improve the initial coulombic efficiency and mitigate initial active lithium loss. Furthermore, both SPEEK-Li and PAA-Li undergo pre-lithiation, which increases ionic conductivity. The peristaltic movement of the binder molecular chains greatly promotes lithium-ion migration. The lithium-ion battery preparation method provided in this application provides a negative electrode sheet that, compared to conventional negative electrode sheets, can simultaneously meet the requirements of lithium-ion batteries for rate performance and long cycle life, thereby improving the cycle life and rate performance of lithium-ion batteries. SPEEK-Li and PAA-Li, as binders, improve the adhesion between the negative electrode sheet and the current collector and reduce the expansion rate of the negative electrode sheet. Attached Figure Description
[0018] One or more embodiments are illustrated by way of example with corresponding pictures in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the pictures in the accompanying drawings do not constitute a limitation on scale. In order to more clearly illustrate the technical solutions in the embodiments of this application or in the conventional technology, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0019] Figure 1 The flowchart corresponds to the preparation steps of the negative electrode sheet provided in the embodiments of this application. Detailed Implementation
[0020] As can be seen from the background technology, the binders commonly used in lithium-ion batteries currently have the problems of high expansion rate and high resistivity, which leads to a reduction in the efficiency of lithium-ion batteries.
[0021] This application provides a lithium-ion battery and its preparation method, which at least helps to improve the performance of the lithium-ion battery.
[0022] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0023] The embodiments of this application will now be described in detail with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been provided in the embodiments of this application to facilitate a better understanding of the application. However, the technical solutions claimed in this application can be implemented even without these technical details and various variations and modifications based on the following embodiments.
[0024] Figure 1 The flowchart corresponds to the preparation steps of the negative electrode sheet provided in the embodiments of this application.
[0025] According to some embodiments of this application, one aspect of this application provides a method for preparing a lithium-ion battery, including:
[0026] The negative electrode sheet is prepared using the steps S11~S16:
[0027] S11: Weigh 85-99 parts of negative electrode active material, 0.35-8.1 parts of SPEEK-Li and 0.5-6 parts of conductive agent.
[0028] Negative electrode active materials can be selected from graphite, silicon, and silicon-based composite materials. Graphite has advantages such as low cost, good cycle stability, high conductivity, and large specific capacity; silicon has a higher specific capacity and specific energy density than graphite, but its cycle stability and mechanical strength are problematic; silicon-based composite materials are composite materials composed of silicon and other materials, which can overcome the disadvantages of silicon while leveraging its advantages. Common silicon-based composite materials include silicon nanoparticles, nanoporous silicon materials, carbon-coated silicon, and nitrogen-coated silicon. In addition to the above materials, negative electrode active materials can also be selected from lithium titanate, lithium aluminum alloy, and other materials.
[0029] SPEEK-Li is a lithium-ionized sulfonated polyether ether ketone.
[0030] In some embodiments, the preparation steps of SPEEK-Li include: adding polyether ether ketone (PEEK) to concentrated sulfuric acid, wherein the mass ratio of PEEK to concentrated sulfuric acid is 1:(10~20), the concentration of concentrated sulfuric acid is 96%~98%, stirring at 60℃~100℃ for 20~30 hours, quenching the resulting mixture with cold water, filtering to obtain a white solid, dissolving the white solid in deionized water, neutralizing it with a 0.5M~1M aqueous solution of LiOH, and drying to obtain SPEEK-Li.
[0031] In some embodiments, before dissolving the white solid in deionized water and neutralizing it with an aqueous solution of 0.5M~1M LiOH, the process includes: dialysis purification of the white solid with a molecular cutoff of 1000 Da, followed by rotary evaporation to obtain the purified white solid.
[0032] The conductive agent can be selected from one or more of carbon black, conductive graphite, carbon nanotubes, graphene, acetylene black AB, Ketjen black KB, and vapor-grown carbon fiber (VGCF).
[0033] S12: Add the negative electrode active material, conductive agent and SPEEK-Li to the mixer and mix for 20-40 minutes.
[0034] S13: Add 78-82 parts of deionized water and knead and stir for 120-130 minutes.
[0035] S14: Add 0.9~8.65 parts of PAA-Li aqueous solution, the total mass fraction of SPEEK-Li and PAA-Li is 0.5~9 parts, the mass fraction ratio of SPEEK-Li to PAA-Li is (7~9):(3~1), and the concentration of PAA-Li aqueous solution is 0.128mol / L~0.64mol / L, and the stirring time is 110~120 minutes.
[0036] PAA-Li is lithium-modified polyacrylic acid.
[0037] In some embodiments, the preparation step of the PAA-Li aqueous solution includes: dissolving polyacrylic acid in deionized water to obtain an aqueous solution of polyacrylic acid, adding an aqueous solution of LiOH to the aqueous solution of polyacrylic acid to react and obtain an aqueous solution of PAA-Li, wherein the molar ratio of polyacrylic acid to LiOH is 1:(0.3~1), the concentration of the aqueous solution of polyacrylic acid is 0.14mol / L~0.69mol / L, and the concentration of the aqueous solution of LiOH is 1.22mol / L~2.44mol / L.
[0038] S15: Perform defoaming stirring for 20-30 minutes. The defoaming stirring rate can be 20±1 rpm.
[0039] In some embodiments, prior to defoaming stirring, the process further includes viscosity adjustment stirring, adjusting the viscosity of the mixed slurry to 3500 mPa·s~9500 mPa·s and the solid content to 55%~60%, with a stirring time of 30~40 minutes, wherein the stirring rate of defoaming stirring is lower than the stirring rate of viscosity adjustment stirring. The viscosity adjustment stirring rate is a revolution speed of 25±1 rpm.
[0040] The slurry is a solid-liquid mixture. To meet the requirements of subsequent coating processes, a suitable viscosity range is beneficial for the slurry to have good flowability, leveling, and rheological properties. Flowability can be assessed by agitating the slurry and allowing it to flow naturally, observing its continuity; a continuous flow indicates good flowability. Leveling affects the smoothness and uniformity of the coating. Rheological properties refer to the deformation characteristics of the slurry during flow, and their quality directly impacts the quality of the electrode sheet.
[0041] S16: The mixed slurry after stirring is coated onto the negative electrode current collector through a coating machine oven and dried to obtain the negative electrode sheet.
[0042] The material for the negative electrode current collector can be selected from copper foil.
[0043] In some embodiments, the coating machine oven includes 5 sections with temperatures of 90℃~100℃, 100℃~105℃, 100℃~105℃, 105℃~110℃, and 105℃~110℃ respectively.
[0044] A positive electrode and a separator are provided. The positive electrode, separator and negative electrode are wound or stacked and then placed into a housing. Electrolyte is injected into the housing to obtain a lithium-ion battery.
[0045] The positive electrode includes a positive current collector and a positive electrode material layer covering the surface of the positive current collector.
[0046] The material for the positive electrode current collector can be selected from aluminum foil.
[0047] The positive electrode material layer consists of positive electrode active material, conductive agent and binder.
[0048] The materials for positive electrode active materials can be selected from layered structure materials, spinel structure materials, polyanionic materials, etc. Layered structure materials include lithium cobalt oxide (LiCoO2) and lithium nickel cobalt manganese oxide (NCM); spinel structure materials include lithium manganese oxide (LiMn2O4); polyanionic materials include lithium iron phosphate (LiFePO4).
[0049] The conductive agent can be selected from one or more of carbon black, conductive graphite, carbon nanotubes, graphene, acetylene black AB, Ketjen black KB, and vapor-grown carbon fibers.
[0050] The adhesive can be selected from polyvinyl alcohol (PVA), polytetrafluoroethylene (PTFE), polyolefins (such as polypropylene, polyethylene, etc.), polyvinylidene fluoride (PVDF), modified styrene-butadiene rubber, fluorinated rubber, polyurethane, etc.
[0051] The diaphragm can be selected from polypropylene (PP) microporous diaphragms, polyethylene (PE) microporous diaphragms, PE / PP composite microporous diaphragms, copolymer diaphragms of propylene and ethylene, or polyethylene homopolymer diaphragms, etc.
[0052] The winding process involves stacking the positive electrode sheet, separator, and negative electrode sheet in sequence and winding them into a core coil in a specific order. It is mainly used to produce square and cylindrical lithium batteries.
[0053] Stacking is an assembly method for constructing battery cells by stacking components such as positive electrode sheets, separators, and negative electrode sheets layer by layer. Stacking processes can generally be divided into layering and folding. Compared with winding, the stacking winding process requires higher tension control. Stacking is mainly used for the manufacture of large square batteries, ultra-thin batteries, and irregularly shaped batteries.
[0054] The electrolyte comprises a solvent, a solute, and additives. The solvent can be selected from ethylene carbonate (EC), polycarbonate (PC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), sulfites, or carboxylic acid esters, etc.; the solute can be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, or lithium dioxaborate, etc.; the additives can be selected from film-forming additives, overcharge protection additives, high and low temperature additives, or flame retardant additives, etc.
[0055] Accordingly, another embodiment of this application also provides a lithium-ion battery, which can be manufactured using the lithium-ion battery preparation method provided in the above embodiments. For parts that are the same as or corresponding to the previous embodiment, please refer to the corresponding descriptions in the foregoing embodiments; detailed descriptions will not be repeated below.
[0056] The lithium-ion battery provided in this application includes: a casing, and a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte stacked inside the casing. The negative electrode sheet includes: a negative electrode current collector and a negative electrode material layer covering the surface of the negative electrode current collector. The mass parts of each substance in the negative electrode material layer are as follows: 85-99 parts of negative electrode active material, 0.5-9 parts of binder, and 0.5-6 parts of conductive agent. The binder is composed of PAA-Li and SPEEK-Li, and the mass ratio of SPEEK-Li to PAA-Li is (7-9):(3-1).
[0057] In some embodiments, the thickness of the negative electrode material layer is 140μm~150μm, specifically 140μm, 143μm, 146, 148μm or 150μm.
[0058] In some embodiments, the average molecular weight of SPEEK-Li is greater than 1000, specifically 1000, 1300, 1500 or 2000.
[0059] In some embodiments, the average molecular weight of PAA-Li is 50,000 to 80,000, specifically 50,000, 56,000, 60,000, 67,000, 70,000, 78,500 or 80,000.
[0060] The lithium-ion battery and its preparation method provided in this application embodiment include a negative electrode material layer comprising a negative electrode active material, a conductive agent, and a binder. The binder is composed of SPEEK-Li and PAA-Li. SPEEK-Li, as a binder, exhibits lower electrolyte swelling and higher mechanical stability. The SPEEK-Li main chain is linked with a large number of sulfonic acid side groups. Sulfonic acid groups possess excellent hydrophilicity and high-temperature resistance, which on the one hand can absorb a large amount of electrolyte, significantly increasing the liquid absorption rate of the negative electrode sheet, and on the other hand improves the heat resistance of the negative electrode sheet, ensuring the battery's safety performance. PAA-Li can supplement additional lithium sources to improve the initial coulombic efficiency and mitigate initial active lithium loss. Furthermore, both SPEEK-Li and PAA-Li undergo pre-lithiation, which increases ionic conductivity. The peristaltic movement of the binder molecular chains greatly promotes lithium-ion migration. The lithium-ion battery preparation method provided in this application provides a negative electrode sheet that, compared to conventional negative electrode sheets, can simultaneously meet the requirements of lithium-ion batteries for rate performance and long cycle life, thereby improving the cycle life and rate performance of lithium-ion batteries. SPEEK-Li and PAA-Li, as binders, improve the adhesion between the negative electrode sheet and the current collector and reduce the expansion rate of the negative electrode sheet.
[0061] SPEEK-Li, with its sulfonic acid group (-SO3H) forming -SO3Li after lithiation, exhibits high ionic conductivity. SPEEK-Li also possesses good mechanical strength and chemical stability, making it suitable as a matrix for electrolytes or electrode materials. PAA-Li, with its abundant lithium carboxylate groups (-COOLi), provides a large number of lithium ions. PAA-Li also exhibits excellent flexibility and interfacial compatibility, enabling good contact with electrode materials. SPEEK-Li provides high ionic conductivity and mechanical support, while PAA-Li provides a greater lithium ion source and better interfacial compatibility; their combination creates a complementary effect. The synergistic effect of SPEEK-Li and PAA-Li can form a dual lithium-ion transport channel (lithium sulfonate and lithium carboxylate), significantly improving the ionic conductivity of the electrolyte. Molecular dynamics simulations and experimental data demonstrate that the lithium-ion transference number (t) after their combination... + The combination of SPEEK-Li and PAA-Li enhances both the mechanical strength and electrical conductivity of the electrolyte. SPEEK-Li's high mechanical strength suppresses lithium dendrite growth, improving battery safety. PAA-Li's flexibility and interfacial compatibility allow it to form a stable interfacial layer with the electrode material, reducing interfacial impedance. This combination creates a "rigid-flexible" interfacial layer that suppresses lithium dendrite growth while reducing interfacial impedance, thus improving battery cycle stability. SPEEK-Li's chemical stability broadens the electrolyte's electrochemical window, making it suitable for high-voltage cathode materials. PAA-Li's high lithium-ion concentration improves the battery's rate performance. The combination of these two materials results in an electrolyte with both a wide electrochemical window and high ionic conductivity, significantly improving the battery's energy density and power density.
[0062] The following are specific embodiments of this application:
[0063] Example 1
[0064] Preparation of SPEEK-Li: PEEK was added to concentrated sulfuric acid at a mass ratio of 1:15 (concentration of 98%). The mixture was stirred at 80°C for 20 hours. The resulting mixture was quenched in cold water and filtered to obtain a white solid. The white solid was purified by dialysis and then by rotary evaporation. The molecular cutoff value of the purified solid was 1000 Da. The purified white solid was dissolved in deionized water, neutralized with 0.5 M LiOH aqueous solution, and dried to obtain SPEEK-Li.
[0065] Preparation of PAA-Li: Polyacrylic acid is dissolved in deionized water to obtain an aqueous solution of polyacrylic acid. An aqueous solution of LiOH is added to the aqueous solution of polyacrylic acid to react and obtain an aqueous solution of PAA-Li. The molar ratio of polyacrylic acid to LiOH is 1:0.6, the concentration of the aqueous solution of polyacrylic acid is 0.45 mol / L, the concentration of the aqueous solution of LiOH is 1.7 mol / L, and the molecular weight of PAA-Li is 50,000.
[0066] Preparation of the negative electrode sheet: Weigh 90 parts of graphite, 4 parts of the above-mentioned SPEEK-Li, and 3 parts of conductive carbon black SP; add graphite, SPEEK-Li, and SP to a mixer and stir for 30 minutes; add 80 parts of deionized water and knead and stir for 120 minutes; add 2 parts of PAA-Li aqueous solution with a concentration of 0.45 mol / L and stir for 120 minutes; adjust the viscosity of the mixed slurry to 6500 mPa·s~9500 mPa·s and the solid content to 58% for 40 minutes at a stirring speed of 25 rpm; perform defoaming stirring at a stirring speed of 20 rpm for 30 minutes; coat the stirred mixed slurry onto copper foil through a coating machine oven and dry to obtain the negative electrode sheet. The coating machine oven consists of 5 sections with temperatures of 90℃, 100℃, 100℃, 105℃, and 105℃ respectively.
[0067] Preparation of lithium-ion batteries: The positive electrode, separator and the negative electrode prepared above are wound and placed into the casing, and the electrolyte is injected into the casing to obtain a lithium-ion battery.
[0068] The difference between Examples 2, 3, and 5 and Example 1 is that the mass ratio of SPEEK-Li and PAA-Li is different; the difference between Comparative Examples 1 to 4 and Comparative Examples 6 to 8 and Example 1 is that the types of adhesives used are different, as detailed in Table 1.
[0069] Table 1. Types and proportions of adhesives used in different embodiments and comparative examples.
[0070]
[0071] The difference between Example 4 and Example 1 is that the molecular cutoff value of SPEEK-Li after dialysis purification is different; the difference between Comparative Example 10 and Example 1 is that SPEEK-Li was not purified by dialysis; the difference between Comparative Example 11 and Example 1 is that the average molecular weight of PAA-Li is different, as detailed in Table 2.
[0072] Table 2. Molecular cutoff values for different embodiments and comparative examples.
[0073]
[0074] Table 3 shows the test results of swelling ratio, liquid absorption rate, bonding strength, mechanical strength and resistivity of the negative electrode sheets of different embodiments and comparative examples; Table 4 shows the test results of initial coulombic efficiency, rate performance, cycle performance and reversible specific capacity of lithium-ion batteries of different embodiments and corresponding proportions.
[0075] Table 3. Swelling rate, liquid absorption rate, bond strength, mechanical strength, and resistivity for different embodiments and comparative examples.
[0076]
[0077] Table 4. Initial coulombic efficiency, rate performance, cycle performance, and reversible specific capacity of lithium-ion batteries of different embodiments and corresponding proportions.
[0078]
[0079] Referring to Examples 1 to 3 and Comparative Examples 1 to 9 in Table 3, it was found that when SPEEK-Li and PAA-Li are used synergistically as binders for the negative electrode, and the mass ratio of SPEEK-Li to PAA-Li is within a suitable range, the synergistic use of SPEEK-Li and PAA-Li as binders helps to reduce the swelling rate of the negative electrode, increase the liquid absorption rate of the negative electrode, and at the same time maintain the good mechanical stability and bonding strength of the negative electrode.
[0080] Referring to Examples 1 to 3 and Comparative Examples 1 to 4 in Table 4, it was found that, compared with conventional CMC binders and SBR binders, using SPEEK-Li and PAA-Li synergistically as binders with the mass ratio of SPEEK-Li and PAA-Li within a suitable range can improve the reversible specific capacity and cycle stability of lithium-ion batteries. Furthermore, the negatively charged nanochannels of SPEEK-Li and PAA-Li as binders can improve the initial coulombic efficiency and rate performance of lithium-ion batteries.
[0081] Referring to Examples 1, 4, Comparative Examples 10 and 11 in Table 3, it was found that the average molecular weight of SPEEK-Li and the average molecular weight of PAA-Li in the negative electrode sheet need to be within an appropriate range in order to maintain good adhesion strength and mechanical strength of the negative electrode sheet.
[0082] Referring to Examples 1, 4, Comparative Examples 10 and 11 in Table 4, it was found that the average molecular weight of SPEEK-Li and the average molecular weight of PAA-Li in the negative electrode need to be within an appropriate range, which is beneficial to maintaining the initial coulombic efficiency, rate performance, cycle performance and reversible specific capacity of the lithium-ion battery.
[0083] Those skilled in the art will understand that the above embodiments are specific examples of implementing this application, and in practical applications, various changes in form and detail can be made without departing from the spirit and scope of this application. Any person skilled in the art can make various alterations and modifications without departing from the spirit and scope of this application; therefore, the scope of protection of this application should be determined by the scope defined in the claims.
Claims
1. A method for preparing a lithium-ion battery, characterized in that, include: The preparation steps for the negative electrode include: Weigh out 85-99 parts of negative electrode active material, 0.35-8.1 parts of SPEEK-Li and 0.5-6 parts of conductive agent; The negative electrode active material, the conductive agent and the SPEEK-Li are added to a mixer and mixed for 20 to 40 minutes. Add 78-82 parts of deionized water and knead and stir for 120-130 minutes. Add 0.9 to 8.65 parts of an aqueous solution of PAA-Li, wherein the total mass fraction of SPEEK-Li and PAA-Li is 0.5 to 9 parts, the mass fraction ratio of SPEEK-Li to PAA-Li is (7 to 9):(3 to 1), and the concentration of the aqueous solution of PAA-Li is 0.128 mol / L to 0.64 mol / L, and the stirring time is 110 to 120 minutes; Perform defoaming stirring for 20-30 minutes; The stirred slurry is coated onto the negative electrode current collector through a coating machine oven and then dried to obtain the negative electrode sheet; A positive electrode and a separator are provided. The positive electrode, the separator and the negative electrode are wound or stacked and then placed into a housing. Electrolyte is injected into the housing to obtain the lithium-ion battery.
2. The method for preparing a lithium-ion battery according to claim 1, characterized in that, Before the defoaming stirring, the process further includes: viscosity adjustment stirring, adjusting the viscosity of the mixed slurry to 3500 mPa·s to 9500 mPa·s and the solid content to 55% to 60%, and stirring for 30 to 40 minutes, wherein the stirring rate of the defoaming stirring is lower than the stirring rate of the viscosity adjustment stirring.
3. The method for preparing a lithium-ion battery according to claim 1, characterized in that, The coating machine oven consists of 5 sections with temperatures ranging from 90℃ to 100℃, 100℃ to 105℃, 100℃ to 105℃, 105℃ to 110℃, and 105℃ to 110℃, respectively.
4. The method for preparing a lithium-ion battery according to claim 1, characterized in that, The preparation steps of the SPEEK-Li include: PEEK is added to concentrated sulfuric acid at a mass ratio of 1:(10-20), and the concentration of the concentrated sulfuric acid is 96%-98%. The mixture is stirred at 60℃-100℃ for 20-30 hours. The resulting mixture is then quenched in cold water and filtered to obtain a white solid. The white solid is dissolved in deionized water and neutralized with a 0.5M-1M LiOH aqueous solution. After drying, SPEEK-Li is obtained.
5. The method for preparing a lithium-ion battery according to claim 4, characterized in that, Before dissolving the white solid in deionized water and neutralizing it with a 0.5M to 1M aqueous solution of LiOH, the process includes: dialysis purification of the white solid with a molecular cutoff of 1000 Da, followed by rotary evaporation to obtain the purified white solid.
6. The method for preparing a lithium-ion battery according to claim 1, characterized in that, The preparation steps of the PAA-Li aqueous solution include: Polyacrylic acid is dissolved in deionized water to obtain an aqueous solution of polyacrylic acid. An aqueous solution of LiOH is added to the aqueous solution of polyacrylic acid to react and obtain an aqueous solution of PAA-Li. The molar ratio of polyacrylic acid to LiOH is 1:(0.3-1), the concentration of the aqueous solution of polyacrylic acid is 0.14 mol / L to 0.69 mol / L, and the concentration of the aqueous solution of LiOH is 1.22 mol / L to 2.44 mol / L.
7. A lithium-ion battery, characterized in that, include: A housing, and a positive electrode, a separator, a negative electrode, and an electrolyte stacked within the housing, wherein the negative electrode comprises: The negative electrode current collector and the negative electrode material layer covering the surface of the negative electrode current collector, wherein the mass parts of each substance in the negative electrode material layer are as follows: 85-99 parts of negative electrode active material, 0.5-9 parts of binder and 0.5-6 parts of conductive agent, wherein the binder is composed of PAA-Li and SPEEK-Li, and the mass ratio of SPEEK-Li to PAA-Li is (7-9):(3-1).
8. The lithium-ion battery according to claim 7, characterized in that, The thickness of the negative electrode material layer is 140μm to 150μm.
9. The lithium-ion battery according to claim 7, characterized in that, The average molecular weight of the SPEEK-Li is greater than 1000.
10. The lithium-ion battery according to claim 7, characterized in that, The average molecular weight of the PAA-Li is 50,000 to 80,000.