An organic-inorganic compound thick electrode, a preparation method and application thereof

Abstract

The application belongs to the technical field of lithium batteries, and provides an organic-inorganic compound thick electrode, a preparation method and application thereof. The organic-inorganic compound thick electrode comprises a current collector and an active coating. The active coating comprises an active material, a composite conductive agent and a composite binder. The active material is SPAN and LVP. SPAN endows the electrode with high specific capacity characteristics, and can significantly improve the energy density of the battery. LVP effectively compensates for the defects of SPAN in conductivity and structural stability due to its excellent crystal structure stability, high ionic conductivity and nearly zero volume change in the cycle process. Through the synergistic compound design of organic-inorganic materials, the advantages of the two materials are complementary and synergistic, which not only solves the kinetic bottleneck of SPAN, but also strengthens the structural stability of the thick electrode, and further constructs a new electrode system with high energy density, long cycle life and excellent rate performance.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to an organic-inorganic composite thick electrode, its preparation method, and its application. Background Technology

[0002] With the rapid development of the new energy industry, the demand for lithium-ion batteries in electric vehicles, energy storage systems, and other fields continues to rise, placing higher demands on their energy density, cycle life, and safety. As the core of lithium-ion batteries, the performance of the cathode material directly determines the overall performance of the battery; therefore, the development of high-performance cathode materials and suitable electrode structures has become a research hotspot. Sulfated polyacrylonitrile (SPAN), as a highly promising organic cathode material, has attracted much attention due to its unique structural advantages. It stably fixes sulfur atoms within the polyacrylonitrile framework through sulfur-nitrogen covalent bonds, fundamentally solving the polysulfide shuttle problem of traditional sulfur cathodes through a solid-solid reaction mechanism, significantly improving cycle stability.

[0003] However, SPAN has two major drawbacks: firstly, its semiconductor properties result in a conductivity of only 10. -5 The low S / cm ratio severely limits the rate performance of the battery; secondly, the tap density is only about 0.4 g / cm³. 3 The difficulty in achieving high-activity material loading limits the improvement of volumetric energy density, especially in thick electrode designs.

[0004] In summary, the inherent semiconductor characteristics and low tap density of SPAN, coupled with the dual bottlenecks in current thick electrode fabrication technology regarding kinetic performance improvement and structural integrity assurance, have become the core obstacles restricting its commercialization. Against this backdrop, developing a composite material thick electrode that combines high specific capacity with high structural stability is of significant theoretical and practical value for overcoming current key performance bottlenecks in lithium-ion batteries, such as energy density and cycle life. Summary of the Invention

[0005] To overcome the shortcomings of existing technologies, this invention provides an organic-inorganic composite thick electrode, its preparation method, and its application. By using sulfurized polyacrylonitrile (SPAN) and lithium vanadium phosphate (LVP) as electrode active materials, the rate performance and cycle performance (such as capacity retention after long cycles) of the prepared lithium-ion battery are simultaneously and significantly improved.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides an organic-inorganic composite thick electrode, comprising a current collector and an active coating, wherein the active coating comprises an active material, a composite conductive agent, and a composite binder; the active material comprises vulcanized polyacrylonitrile (SPAN) and lithium vanadium phosphate (LVP); the composite conductive agent comprises at least three of Super P, Ketjen Black, acetylene black, aqueous carbon nanotube dispersion, and aqueous graphene dispersion; the composite binder comprises at least one of sodium alginate (SA), sodium carboxymethyl cellulose (CMC), styrene-butadiene rubber (SBR), polyacrylic acid (PAA), acrylonitrile copolymer (LA), polytetrafluoroethylene (PTFE), guar gum (GG), and polyvinylidene fluoride (PVDF).

[0007] Preferably, the mass ratio of the active material, the composite conductive agent, and the composite binder is 80-92:3-10:5-10.

[0008] Preferably, the amount of LVP added in the active material is 1%-25% based on the mass of SPAN.

[0009] Preferably, the composite conductive agent comprises acetylene black, aqueous carbon nanotube dispersion, and aqueous graphene dispersion in a mass ratio of 3-5:2-4:1-3.

[0010] Preferably, the binder is sodium alginate.

[0011] Preferably, the thickness of the thick electrode is 50-500 μm.

[0012] Preferably, the current collector is one of aluminum foil, carbon cloth, titanium mesh, or stainless steel mesh.

[0013] Secondly, the present invention provides a method for preparing the above-mentioned organic-inorganic composite thick electrode, comprising: (1) Preparation of active slurry by wet mixing method: The binder and solvent are mixed to obtain a binder solution, and then the composite conductive agent and active material are mixed to obtain a mixed slurry. Finally, the mixed slurry, binder solution and solvent are mixed to obtain an active slurry. The solvent is water.

[0014] (2) Coating: The active slurry is coated on the surface of the current collector at a coating speed of 5-20 m / min, and then the active slurry is dried at a temperature of 80-120°C with a wind frequency of 10-100 Hz to obtain an organic-inorganic composite thick electrode.

[0015] Thirdly, the present invention provides a lithium-ion battery comprising the above-mentioned organic-inorganic composite thick electrode and electrolyte.

[0016] Fourthly, the present invention provides the application of the above-mentioned organic-inorganic composite thick electrode in the preparation of lithium-ion batteries.

[0017] To address the inherent semiconductor properties and low tap density defects of sulfurized polyacrylonitrile (SPAN), coupled with the dual bottlenecks of existing thick electrode fabrication techniques in improving kinetic performance and ensuring structural integrity, this invention develops a composite thick electrode material that combines the high specific capacity of SPAN with the high structural stability of LVP. The conductivity of LVP reaches 10⁻⁶. -3 The density is S / cm, and the tap density reaches 1.4-1.8 g / cm³. 3 When combined, the network structure of LVP provides electron transport channels for SPAN, while the porous framework of SPAN can fill LVP particles, increasing the overall tap density to 1.2-1.5 g / cm³. 3 The polyanionic structure of LVP (Li3V2(PO4)3) possesses open three-dimensional ion channels, Li + The diffusion coefficient reaches 10 -10 cm 2 The LVP, with its olivine structure, complements the sulfur-based active sites of SPAN. When LVP is uniformly dispersed in the SPAN matrix as nanoparticles, its three-dimensional lithium-ion diffusion channels form a physical support network, suppressing the volume expansion of SPAN during lithium insertion / extraction. SPAN imparts high specific capacity to the electrode, significantly improving battery energy density; while LVP, with its excellent crystal structure stability, high ionic conductivity, and near-zero volume change during cycling, effectively compensates for the conductivity and structural stability deficiencies of SPAN. Through the synergistic design of organic-inorganic materials, not only is the complementary advantage and synergistic effect of the two materials achieved—solving the kinetic bottleneck of SPAN and enhancing the structural stability of thick electrodes—but also a novel electrode system with high energy density, long cycle life, and excellent rate performance is constructed.

[0018] The advantages and beneficial effects of this invention are as follows: (1) Compared to a single SPAN thick electrode, the organic-inorganic composite thick electrode prepared in this invention, while maintaining the same electrode thickness, utilizes the excellent tap density characteristics of LVP and the synergistic effect of densification of the two materials to increase the surface loading of active material by more than 10%. The surface loading of active material in this composite thick electrode can reach 35 mg cm⁻¹. -2This indicator far exceeds the upper limit of the surface load of conventional SPAN thick electrodes. It not only directly improves the lithium storage capacity per unit area of ​​the electrode, but also effectively solves the problem of insufficient volumetric energy density caused by low tap density of traditional SPAN electrodes. It provides key support for the development of lithium-ion batteries towards high volumetric energy density, and is especially suitable for portable electronic devices, power batteries and other scenarios with strict space requirements.

[0019] (2) The organic-inorganic composite thick electrode prepared by the present invention achieves synergistic improvement of "structure-performance" through precise composite of LVP and SPAN: On the one hand, the excellent crystal structure stability of LVP and the near-zero volume change characteristics during cycling can effectively suppress the volume expansion and contraction of SPAN during charging and discharging, avoid problems such as cracks and shedding of the electrode, and significantly enhance the structural integrity and long-term cycling reliability of the thick electrode; on the other hand, the high ionic conductivity of LVP can compensate for the semiconductor defects of SPAN, and the composite structure optimizes the ion transport path inside the electrode, greatly reducing the interface impedance and improving the ion transport efficiency.

[0020] The combination of these advantages enables a simultaneous and significant improvement in the rate performance (such as high-rate charge and discharge capability) and cycle performance (such as capacity retention after long cycles) of lithium-ion batteries. This effectively breaks through the current technical bottleneck of "difficulty in balancing high energy density and excellent dynamic performance" in thick electrode batteries, laying an important foundation for the industrial application of high-performance lithium-ion batteries. Attached Figure Description

[0021] Figure 1 The electronic conductivity of the SPAN / LVP composite thick electrodes prepared in Examples 1-8 is shown.

[0022] Figure 2 Rate performance of the SPAN / LVP composite thick electrodes prepared in Examples 1, 4-6 and Comparative Example 2.

[0023] Figure 3 Cyclic performance of the SPAN / LVP composite thick electrodes prepared in Examples 1, 4-6, 8 and Comparative Example 1. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0025] Example 1 This embodiment provides an organic-inorganic composite thick electrode, its preparation method, and its application, including the following steps: Step 1: Dry SPAN, LVP, and acetylene black at 100℃ for 12 hours; prepare a 15% sodium alginate (SA) aqueous solution. Step 2: Add SPAN, LVP, and acetylene black to the feed hopper of the air jet mill, and set the milling parameters as follows: working pressure 0.6 MPa, feed rate 10 g / min, and classifier speed 8000 rpm. Mill each raw material for 30 minutes, and collect the product through a 200-mesh sieve. Step 3: Weigh the following components according to the ratio of SPAN: composite conductive agent (acetylene black: carbon nanotube aqueous dispersion: graphene aqueous dispersion = 5:3:2): sodium alginate = 90:5:5. Based on the mass of SPAN, add 15% LVP; Step 4: Ball mill SPAN and LVP for 2 hours, then add acetylene black and dry mix to obtain the first mixed dry material; Step 5: Mix the first dry mixture with the conductive agent (aqueous carbon nanotube dispersion and aqueous graphene dispersion), stir and disperse to obtain the second slurry. Step 6: Add sodium alginate aqueous solution and a small amount of solvent (deionized water) to the second mixed slurry, and after mixing, stirring and dispersing, obtain the third mixed slurry; Step 7: Add an appropriate amount of solvent (deionized water) to the third mixed slurry, stir and disperse it under vacuum, and sieve it to obtain the electrode slurry.

[0026] Step 8: The electrode paste is coated on aluminum foil with a thickness of 500 μm and a coating speed of 5 m / min. Then, the active paste is dried at 100°C with a wind frequency of 50 Hz to obtain an organic-inorganic composite thick electrode, namely SPAN / LVP composite thick electrode.

[0027] Step 9: Roll and cut the above-mentioned SPAN / LVP composite thick electrode to obtain a circular electrode sheet with a diameter of 10mm. Then, using the SPAN / LVP composite thick electrode as the positive electrode and 14cm×500μm lithium metal as the negative electrode, a Celgard separator is matched and an electrolyte of 1M LiPF6in DEC:EC:FEC=9:9:2 Vol% is used. The battery is assembled into a 2032 type button cell in an argon glove box with a water and oxygen content of less than 0.01 ppm.

[0028] Example 2 This embodiment provides an organic-inorganic composite thick electrode and its preparation method and application, referring to Embodiment 1. The difference from Embodiment 1 is that a 1000μm scraper thickness is used instead of the 500μm scraper thickness in Embodiment 1, while the remaining raw material ratios and preparation methods are strictly consistent with Embodiment 1.

[0029] Example 3 This embodiment provides an organic-inorganic composite thick electrode and its preparation method and application, referring to Embodiment 1. The difference from Embodiment 1 is that a 1500μm scraper thickness is used instead of the 500μm scraper thickness in Embodiment 1, while the remaining raw material ratios and preparation methods are strictly consistent with Embodiment 1.

[0030] Example 4 This embodiment refers to Example 1 to provide an organic-inorganic composite thick electrode and its preparation method and application. The difference from Example 1 is that: based on SPAN mass, 0% LVP is added instead of 5% LVP in Example 1, while the remaining raw material ratios and preparation methods are strictly consistent with Example 1.

[0031] Example 5 This embodiment refers to Example 1 to provide an organic-inorganic composite thick electrode and its preparation method and application. The difference from Example 1 is that: based on the mass of SPAN, 5% LVP is added to replace the 5% LVP in Example 1, while the remaining raw material ratios and preparation methods are strictly consistent with Example 1.

[0032] Example 6 This embodiment refers to Example 1 to provide an organic-inorganic composite thick electrode and its preparation method and application. The difference from Example 1 is that: based on the mass of SPAN, 25% LVP is added to replace 5% LVP in Example 1, while the remaining raw material ratios and preparation methods are strictly consistent with Example 1.

[0033] Example 7 This embodiment provides an organic-inorganic composite thick electrode and its preparation method and application, referring to Embodiment 1. The difference from Embodiment 1 is that a composite binder (CMC:SBR=1:1) is used instead of SA in Embodiment 1, while the other raw material ratios and preparation methods are strictly consistent with Embodiment 1.

[0034] Example 8 This embodiment refers to Example 1 to provide an organic-inorganic composite thick electrode and its preparation method and application. The difference from Example 1 is that PVDF is used instead of SA in Example 1, NMP is used instead of deionized water, and carbon nanotube oil dispersion and graphene oil dispersion are used instead of aqueous carbon nanotube dispersion and aqueous graphene dispersion. The remaining raw material ratios and preparation methods are strictly consistent with those of Example 1.

[0035] Comparative Example 1 This embodiment refers to Example 1 to provide an organic-inorganic composite thick electrode and its preparation method and application. The difference from Example 1 is that: based on the mass of SPAN, 15% lithium iron phosphate (LFP) is added to replace 15% LVP in Example 1, while the remaining raw material ratios and preparation methods are strictly consistent with Example 1.

[0036] Comparative Example 2 This embodiment refers to Example 1 to provide an organic-inorganic composite thick electrode and its preparation method and application. The difference from Example 1 is that lithium vanadium phosphate (LVP) is used instead of the active material (SPAN+15%LVP) in Example 1, while the other raw material ratios and preparation methods are strictly consistent with Example 1.

[0037] Performance testing Performance tests were performed on the thick electrodes prepared in the examples and comparative examples: Electrode peel force test: The provided thick electrode was cut into dimensions of 61 mm wide and 75 mm long, and the electrode peel force was recorded. The test results are shown in Table 1.

[0038] Diaphragm resistance: The diaphragm resistance was recorded using an ACCFILM diaphragm resistance tester. The test results are shown in Table 1.

[0039] Electronic conductivity test: The resistance was recorded using a four-probe tester, and the electronic conductivity was calculated. The results are as follows: Figure 1 As shown.

[0040] Rate performance testing: Constant current charge-discharge tests were conducted on the 2032 model button batteries assembled in Examples 1, 4-6, and Comparative Example 2 using the LANHE battery testing system. The voltage range for the constant current charge-discharge tests was 1-3.5V, and rate performance tests were performed at 0.1C, 0.5C, and 1C. The results are as follows... Figure 2 As shown.

[0041] Cyclic performance testing: Cyclic performance testing was conducted on the 2032-type button batteries assembled in Examples 1, 4-6, 8, and Comparative Example 1. The voltage range for constant current charge-discharge testing was 1-3.5V, and cycle stability testing was performed using a current density of 1C (two cycles of 0.1C activation). The results are as follows: Figure 3 As shown.

[0042] Table 1 Performance results of thick electrodes in the examples and comparative examples

[0043] The thickness and surface loading of the organic-inorganic composite thick electrodes prepared in Examples 1-6 and Comparative Examples 1-2 were tested, and the results are shown in Table 2: Electrode thickness test: The thickness was recorded using a digital thickness gauge.

[0044] Active material surface load test: The weight is recorded by a balance and the surface load of the active material is calculated.

[0045] Table 2. Thickness and surface loading of active material in organic-inorganic composite thick electrodes of Examples 1-6 and Comparative Examples 1-2

[0046] Results analysis: (1) As shown in Table 1-2 and Figure 1-3 As shown, compared with Examples 4-8, the thick electrode provided in Example 1 has the characteristics of high peeling force and low film resistance. That is, the thick electrode provided in Example 1 has a stable structure, good conductivity and high ion transport efficiency.

[0047] (2) The electrode thickness of Example 1 was compared with that of Examples 2-3. The electrode thickness of Example 1 was 90 μm, and its surface loading of active material was 6.7 mg / cm². -2 The electrode thickness in Example 2 was 150 μm, and its surface loading of active material was 12.8 mg / cm². -2 The electrode thickness in Example 3 was 210 μm, and its surface loading of active material was 23.2 mg / cm². -2 .

[0048] (3) The different amounts of LVP added in Examples 1 and 4-6 were compared. Example 4 was a pure SPAN electrode without LVP, Example 5 had an LVP addition of 5%, Example 1 had an LVP addition of 15%, and Example 6 had an LVP addition of 25%. The experimental results showed that under this variable system, the electronic conductivity of the SPAN / LVP thick electrode showed a significant upward trend with the increase of LVP addition. This trend is due to the excellent electronic conduction properties of LVP itself. As an inorganic conductive phase, it can effectively compensate for the semiconductor defects of SPAN. With the increase of addition, the conductive network formed by LVP inside the electrode is more complete, thereby reducing the electron transport resistance and improving the overall electronic conductivity. Crucially, the addition of LVP demonstrated a significant optimization effect on the core indicator of active material areal loading: compared to the pure SPAN electrode in Example 4 (without LVP), the SPAN / LVP composite electrode in Example 1, with 15% LVP added, achieved a clear 28% increase in active material areal loading while maintaining the same electrode thickness. This improvement is attributed to the high tap density of LVP, which, when combined with SPAN, improves the overall density of the electrode, allowing for more active material to be accommodated within the same thickness space. This overcomes the areal loading bottleneck caused by the low tap density of the pure SPAN electrode, providing crucial support for improving the electrode's energy density.

[0049] (4) Comparing the different binders in Example 1 and Example 7, the SPAN / LVP composite thick electrode using sodium alginate as a binder exhibits stronger peel strength. Sodium alginate molecules are rich in hydroxyl (-OH) and carboxyl (-COOH) groups, which can react with hydroxyl groups and metal ions (Li) on the LVP surface. + V 3+ / V 4+ / V 5+ This results in stronger hydrogen and coordination bonds, as well as polar interactions with nitrogen and oxygen atoms in the SPAN molecular chain—a "multi-interface bonding" effect far superior to the single hydrogen bond interaction between CMC / SBR and the active material via carboxyl groups. This stronger interfacial bonding effectively suppresses the shedding of active material from SPAN during charge-discharge cycles due to sulfur species dissolution and volume expansion, while also preventing interfacial delamination between LVP particles and the current collector and conductive agent. This allows the SPAN / LVP composite thick electrode to maintain its intact microstructure even after long-term cycling, significantly reducing the capacity decay rate during cycling.

[0050] (5) The different slurry systems of Example 1 and Example 8 were compared. Example 1 used an aqueous wet coating process, while Example 8 used an oil-based wet coating process. Example 1 exhibited excellent rate performance and cycling performance. The core difference stemmed from the adverse effects of the solvent NMP in the oil-based system on the structure and electrochemical behavior of the SPAN material. Specifically, although the NMP used in the oil-based coating is a chemically inert solvent (does not react chemically with SPAN), its strong polarity affects the polymer skeleton of SPAN: during slurry preparation and subsequent processes, long-term immersion in NMP causes slight swelling of the SPAN skeleton. This swelling phenomenon directly disrupts the uniform dispersion of sulfur within the SPAN—and the high dispersion of sulfur is the key structural basis for SPAN to suppress the polysulfide shuttle effect. When the dispersion of sulfur is disrupted, the dissolution and migration of polysulfides (i.e., the shuttle effect) are aggravated, ultimately resulting in the electrochemical performance of Example 8 being significantly inferior to that of Example 1, which used an aqueous coating process.

[0051] (6) Compare Example 1 with the pure LVP of Comparative Example 1, such as Figure 3 As shown, the SPAN / LVP composite thick electrode exhibits high specific capacity and cycling stability. LVP has a limited ion diffusion rate and a relatively low specific capacity (<150 mAh·g). -1 Meanwhile, particle agglomeration and interfacial impedance accumulation are prone to occur during charge and discharge, resulting in poor cycle stability. However, when SPAN is combined with LVP, the electrochemical performance of the composite material is significantly and synergistically improved: on the one hand, as a sulfur-based active material, SPAN not only provides abundant SC≡N redox sites, contributing additional capacity to the composite material, but also increases the actual specific capacity of the composite cathode to 200-300 mAh·g. -1 On the other hand, the polymer network structure of SPAN can effectively encapsulate LVP particles, alleviating their volume expansion during charging and discharging. At the same time, the conjugated structure and sulfide components in SPAN can improve the electron transport efficiency inside the electrode, reduce the interface impedance, and synergistically improve cycle performance.

[0052] (7) Comparing Example 1 with Comparative Example 2's SPAN / LFP, the SPAN / LVP composite thick electrode exhibits superior high-rate charge-discharge capability compared to the SPAN / LFP composite system. The core reason is the significant difference in lithium-ion migration characteristics caused by the difference in crystal structure between LVP and LFP. LVP has an orthorhombic crystal structure with three-dimensional interconnected lithium-ion diffusion channels inside the crystal, resulting in smooth lithium-ion migration paths with low resistance. In contrast, LFP has an olivine-type structure, where lithium ions mainly diffuse through one-dimensional channels, and the diffusion process is easily hindered by lattice distortion and ion occupancy. The diffusion coefficient of LVP is significantly higher than that of LFP. With the assistance of the conductive network constructed by SPAN, the high lithium-ion migration rate advantage of LVP is fully utilized, enabling the SPAN / LVP composite thick electrode to maintain high lithium-ion transport and charge transfer efficiency at high rates (such as 5C and 10C).

[0053] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, technical solutions formed by substituting the above features with (but not limited to) technical features with similar functions disclosed in this application.

Claims

1. An organic-inorganic composite thick electrode, comprising a current collector and an active coating, characterized in that, The active coating comprises an active material, a composite conductive agent, and a binder in a mass ratio of 80-92:3-10:5-10; The active material is sulfurized polyacrylonitrile and lithium vanadium phosphate, wherein the amount of lithium vanadium phosphate added is 1%-25% of the mass of sulfurized polyacrylonitrile; The composite conductive agent comprises acetylene black, aqueous carbon nanotube dispersion, and aqueous graphene dispersion in a mass ratio of 3-5:2-4:1-3. The adhesive is sodium alginate.

2. The organic-inorganic composite thick electrode according to claim 1, characterized in that, The thickness of the thick electrode is 50-500 μm.

3. The organic-inorganic composite thick electrode according to claim 1, characterized in that, The current collector is one of aluminum foil, carbon cloth, titanium mesh, or stainless steel mesh.

4. A method for preparing an organic-inorganic composite thick electrode as described in any one of claims 1-3, characterized in that, include: (1) Preparation of active slurry by wet mixing method: The binder and solvent are mixed to obtain a binder solution, and then the composite conductive agent and active material are mixed to obtain a mixed slurry. Finally, the mixed slurry, binder solution and solvent are mixed to obtain an active slurry. (2) Coating: The active slurry is coated on the surface of the current collector at a coating speed of 5-20 m / min, and then the active slurry is dried at a temperature of 80-120°C and a wind frequency of 10-100 Hz to obtain an organic-inorganic composite thick electrode.

5. A lithium-ion battery, characterized in that, Includes the organic-inorganic composite thick electrode and electrolyte as described in any one of claims 1-3.

6. The application of an organic-inorganic composite thick electrode as described in any one of claims 1-3 in the preparation of lithium-ion batteries.

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