A polyanion-based composite cathode sheet and a method for preparing the same

Abstract

The application belongs to the technical field of sodium ion batteries, and particularly relates to a polyanion-based composite positive electrode sheet, a preparation method thereof and a sodium ion battery. The sheet is composed of a positive electrode current collector and an electrode material layer, and the electrode material layer contains an active material, a conductive agent and a binder. The mass percentage of the active material is as follows: 70% to 90% of sodium iron pyrophosphophosphate, 5% to 20% of P2-type layered oxide and 5% to 10% of sodium iron sulfate. In the preparation, the sodium iron pyrophosphophosphate and the sodium iron sulfate are first mixed by ball milling and then sintered under an inert atmosphere; then the P2-type layered oxide is ball-mixed and uniformly mixed with the composite active material and heated and dried under a vacuum atmosphere to obtain the composite active material. Then the composite active material is slurried with the conductive agent and the binder, coated on the surface of the aluminum foil current collector, dried, and roll-pressed to obtain the composite positive electrode sheet. The application can significantly improve the compaction density and the volume energy density of the positive electrode sheet, and improve the rate performance. The sodium ion battery comprises the composite positive electrode sheet.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a polyanion-based composite positive electrode, its preparation method, and a sodium-ion battery containing the electrode. Background Technology

[0002] Sodium-ion batteries have shown great potential in large-scale energy storage, and their volumetric energy density needs to be improved according to the requirements of practical applications. Sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7) is very promising due to its abundant raw materials and good safety, but its low specific capacity, operating voltage, and compaction density limit its further application. P2-type layered oxides have both a wide voltage operating range and high compaction density. Commercial sodium iron sulfate has good conductivity due to its high proportion of carbon nanotubes and graphene, and there are currently no reports on its use as a supplementary cathode in phosphate material systems.

[0003] To take into account the performance advantages of different cathode materials, composite cathodes have been applied in the field of lithium-ion batteries. For example, CN113346061A and CN120527367A disclose ternary / lithium iron phosphate composite cathode materials and high-nickel ternary / spinel lithium manganese oxide composite cathode materials, respectively; in the field of sodium-ion batteries, there are also reports on related patents concerning the composite of layered oxides and polyanionic materials.

[0004] Existing technologies such as CN117352707A and CN120824346A disclose composite cathode materials with "oxide as the main component and polyanion as the auxiliary component". Their thermal stability is determined by the high proportion of layered oxides, which is difficult to meet the requirements of energy storage scenarios with extremely high intrinsic safety requirements. CN120109146A mainly optimizes the process by improving the rheology of the slurry, but does not change the intrinsic crystal structure defects of the cathode material, and the improvement on the problem of low bulk compaction density of the material is still limited.

[0005] Existing technologies often employ composite methods with different active components, relying solely on the physical filling of high-specific-capacity or high-voltage components. However, this approach offers relatively limited improvement to the porous structure of the polyanion matrix. This strategy makes it difficult to simultaneously improve the three core indicators that determine volumetric energy density: specific capacity, voltage, and compaction density. Consequently, it limits further improvements in the volumetric energy density of polyanion-based batteries.

[0006] In summary, the present invention proposes a design scheme for a polyanion-based composite positive electrode sheet. By combining matrix densification with the construction of a multi-level particle size grading system, the tap density of the electrode material layer is increased; among them, sodium iron sulfate rich in carbon nanotubes and graphene can improve the particle packing state and interfacial transport conditions, and construct a continuous and efficient conductive network in the matrix. At the same time, taking advantage of the characteristics of P2-type layered oxides with a wide operating voltage range and high tap density, a composite positive electrode sheet scheme that兼顾基体致密化、放电比容量和工作电位提升 is developed to promote the development of sodium-ion batteries towards high electrode-level volumetric energy density. Summary of the Invention

[0007] Aiming at the technical problems of low tap density and limited volumetric energy density of polyanion-based positive electrode materials, the present invention provides a polyanion-based composite positive electrode sheet, its preparation method and a sodium-ion battery. The present invention uses sodium iron pyrophosphate as the main active component, and P2-type layered oxides and sodium iron sulfate as auxiliary components. First, the polyanion matrix is densified and repaired, and then the particle packing state of the electrode material layer is improved through a multi-phase particle size grading structure to further increase the tap density. At the same time, the P2-type layered oxides and sodium iron sulfate play a supplementary role in the discharge specific capacity and working voltage, and sodium iron sulfate can improve the conductivity of the composite system, making the obtained electrode sheet conducive to兼顾压实密度、放电比容量、工作电压和倍率性能 and improving the electrode-level volumetric energy density.

[0008] The technical solution adopted by the present invention is as follows:

[0009] In the first aspect, the present invention provides a polyanion-based composite positive electrode sheet, which includes a positive electrode current collector and an electrode material layer loaded on at least one surface of the positive electrode current collector; the electrode material layer includes an active material, a conductive agent and a binder, and the active material consists of the following components in mass percentage: 70% - 90% of sodium iron pyrophosphate, 5% - 20% of P2-type layered oxide, and 5% - 10% of sodium iron sulfate.

[0010] Preferably, the chemical general formula of the P2-type layered oxide is Na x MO2, where 0.6 < x ≤ 0.7, and M is Ni, Mn, optionally including at least one of Fe or Mg.

[0011] Preferably, the chemical general formula of the sodium iron sulfate is Na 2+2z Fe 2-z (SO4)3, where 0 ≤ z ≤ 0.3.

[0012] Preferably, the tap density of the electrode material layer ≥ 2.20 g cm -3 , and the tap density ρ It should be noted that there are some parts in the original text that seem to be incomplete or unclear in the description, such as "兼顾基体致密化、放电比容量和工作电位提升" which may need further clarification in the original Chinese context for a more accurate translation. Also, the "000000X" tags are kept as they are without further processing as per the requirements.It is calculated based on the mass and volume parameters of the electrode, and the calculation formula is as follows: ρ = m / ( S × h ),in, S The area (cm²) of the circular sheet punched from the rolled positive electrode sheet. 2 ); m The mass (g) of the electrode material layer; h The thickness (cm) of the electrode material layer. The rolling pressure was 29.43 MPa during the compaction density test.

[0013] Preferably, the conductive agent comprises conductive carbon black and carbon nanotubes, wherein the conductive carbon black accounts for 3-5 wt% of the electrode material layer by mass, and the carbon nanotubes account for 1-2 wt% of the electrode material layer by mass; the binder is polyvinylidene fluoride, and the binder accounts for 2-5 wt% of the electrode material layer by mass.

[0014] Secondly, the present invention provides a method for preparing the above-mentioned polyanion-based composite positive electrode sheet, comprising the following steps:

[0015] S1: Sodium ferric pyrophosphate and sodium ferric sulfate are mixed by first ball milling under dry grinding conditions;

[0016] S2: Sinter the mixture obtained in step S1 under nitrogen or argon protection;

[0017] S3: The material processed in step S2 is mixed with the P2 type layered oxide by a second ball milling under dry milling conditions;

[0018] S4: The material obtained in step S3 is heated and dried under vacuum;

[0019] S5: The composite active material and conductive agent obtained in step S4 are added to the binder solution, placed in a homogenizer and made into a slurry under vacuum conditions, and coated on the surface of the positive current collector. After drying and rolling, the polyanion-based composite positive electrode sheet is obtained.

[0020] Preferably, in step S1, the first ball milling is performed using a planetary ball mill with a milling speed of 300~600 rpm and a milling time of 1~3 hours.

[0021] Preferably, the sintering in step S2 is carried out under nitrogen or argon protection, with a heating rate of 0.5~2 °C / min. -1 The sintering temperature is 280~320 ℃, and the holding time is 0.5~1.5 hours.

[0022] Preferably, in step S3, the second ball milling speed is 200~400 rpm and the mixing time is 0.5~1.5 hours.

[0023] Preferably, the drying temperature in step S4 is 80~120 ℃, and the heating rate is 0.5~2 ℃ min. -1 The drying time is 0.5 to 1.5 hours.

[0024] Preferably, in step S5, the slurry mixing speed is 2000~4000 rpm, and the mixing time is 5~20 minutes. The mixed slurry is coated onto the surface of the positive electrode current collector, and the coated wet electrode is placed in a vacuum oven and first dried at 2 °C for 1 minute. -1 The temperature was increased from room temperature to 80 °C and dried at a constant temperature for 2 hours; then increased at 2 °C / min. -1 The heating rate was increased to 120℃, and the temperature was kept constant for 10-12 hours.

[0025] Thirdly, the present invention provides a sodium-ion battery comprising the above-mentioned polyanion-based composite positive electrode, negative electrode, separator, and electrolyte.

[0026] Compared with the prior art, the present invention has the following beneficial effects;

[0027] (1) Existing technologies mainly use layered oxides and supplemented by polyanionic materials, which still have limited effect on improving the loose structure inside the polyanionic matrix. This invention uses a combination of ball milling and sintering to densify and repair the polyanionic matrix composed of sodium iron pyrophosphate and sodium iron sulfate. Ball milling helps to break the loose structure in the original particles, and sintering helps to stabilize the rearrangement state of the particles after ball milling, remove adsorbed water and some volatile residues, and provide a basis for improving the compaction density of the electrode material.

[0028] (2) In this invention, sodium ferric pyrophosphate serves as the main active component, providing a structurally stable foundation. The P2-type layered oxide is primarily used to enhance the discharge specific capacity and operating voltage. Sodium ferric sulfate, as an auxiliary active component, helps improve the particle packing state and interfacial transport conditions of the composite system, thereby enhancing its conductivity. Simultaneously, sodium ferric sulfate, as a medium-to-high voltage active phase, supplements the improvement of the composite system's operating voltage. This invention is beneficial for increasing the lamination density of the electrode material while simultaneously considering discharge specific capacity, voltage, and rate performance. Attached Figure Description

[0029] Figure 1 Cyclic performance curves of sodium-ion batteries assembled in Example 1 and Comparative Example 2 of this invention.

[0030] Figure 2Charge-discharge curves of sodium-ion batteries assembled in Example 1 and Comparative Example 2 of this invention at a rate of 0.1C.

[0031] Figure 3 Rate performance curves of sodium-ion batteries assembled in Example 1 and Comparative Example 2 of this invention.

[0032] Figure 4 A comparison diagram of the AC impedance of the sodium-ion batteries assembled in Example 1 and Comparative Example 2 during the first cycle of charge and discharge.

[0033] Figure 5 A comparison diagram of the AC impedance of the sodium-ion batteries assembled in Example 1 and Comparative Example 2 after 100 cycles of charge and discharge.

[0034] Figure 6 XRD patterns of the active substances prepared in Example 1 and Comparative Example 2 of this invention.

[0035] Figure 7 Comparison of SEM morphology of the positive electrode sheet before cycling prepared in Example 1 and Comparative Example 2 of the present invention, wherein (a) is the SEM image of the positive electrode sheet before cycling prepared in Example 1; and (b) is the SEM image of the positive electrode sheet before cycling prepared in Comparative Example 2. Detailed Implementation

[0036] The technical solution of the present invention will be further described in detail below with reference to embodiments and comparative examples. It should be noted that the following embodiments and comparative examples are only used to illustrate the beneficial effects of the present invention and do not limit the scope of protection of the present invention. Conventional substitutions of materials and process parameters made by those skilled in the art without departing from the concept of the present invention are all within the scope of protection of the present invention.

[0037] Example 1

[0038] Before compounding, the particle size of the three active components was characterized, and the data are summarized in the table below:

[0039] Table 1

[0040] The median particle size D50 characterizes the secondary particle or aggregate size of the material at the macroscopic level. Na4Fe3(PO4)2P2O7 and Na 2.5 Fe 1.75 The median particle size D50 of (SO4)3 is 12.0 μm and 0.7 μm, and Na... 0.67 Ni 0.33 Mn 0.67The median particle size D50 of O2 is 3.0 μm, and the three active components exhibit significant differences in particle size gradient. In this embodiment, the composite active material contains Na4Fe3(PO4)2P2O7 and Na... 0.67 Ni 0.33 Mn 0.67 O2 and Na 2.5 Fe 1.75 The mass ratio of (SO4)3 is 7:2:1.

[0041] (1) First, weigh out 3.22 g of Na4Fe3(PO4)2P2O7 and Na 2.5 Fe 1.75 0.46 g of (SO4)3 was placed in a planetary ball mill. The grinding jar and grinding beads were both made of zirconium oxide, with a ball-to-material ratio of 10:1. The mixture was dry-milled at 500 rpm for 3 hours. It was then transferred to a tube furnace and milled under nitrogen protection at 2 °C for [time missing]. -1 The temperature was increased to 300 °C at a heating rate, held for 1 hour, and then cooled in the furnace to obtain a mixture for later use.

[0042] (2) Subsequently, weigh out Na 0.67 Ni 0.33 Mn 0.67 0.92 g of O2 and the mixture from step (1) were placed in a planetary ball mill and ball-milled at 300 rpm for 1 hour under dry grinding conditions. The resulting powder mixture was then transferred to a tube furnace and milled under vacuum at 2 °C for 1 minute. -1 The temperature was increased to 120 °C at a certain rate, and the mixture was dried at a constant temperature for 1 hour. The mixture was then cooled in the furnace to obtain the composite active substance for later use.

[0043] (3) Preparation of adhesive solution: Dissolve polyvinylidene fluoride powder in N-methylpyrrolidone solvent and stir at 500 rpm for 6 h to prepare an adhesive solution with a concentration of 4 wt% for later use.

[0044] (4) Prepare the mixture according to the mass percentage of composite active material, conductive carbon black, carbon nanotubes, and polyvinylidene fluoride as 92:4:1:3. Specifically, weigh out 0.46 g of composite active material, 0.02 g of conductive carbon black, and 0.005 g of carbon nanotubes. Add the above solid powder to 0.375 g of the polyvinylidene fluoride solution prepared in step (3). Then, place the mixture in a homogenizer and shear mix at high speed for 10 minutes under vacuum and a rotation speed of 3000 rpm. After high-speed shear mixing, a uniformly dispersed high-solids-content positive electrode slurry is obtained.

[0045] The above slurry was coated onto the surface of the aluminum foil positive electrode current collector, with the coating rate controlled at 5~30 mm / s.-1 The coated wet electrode sheet was placed in a vacuum oven and heated to 2 °C for 1 minute. -1 The temperature was increased from room temperature to 80 °C and dried at a constant temperature for 2 hours; then increased at 2 °C / min. -1 The heating rate was increased to 120 °C, and the mixture was dried at a constant temperature for 10-12 hours. After drying, the mixture was rolled and then punched into round sheets with a diameter of 12 mm to obtain the composite positive electrode sheet for sodium-ion batteries.

[0046] CR2032 coin cell half-cells were assembled in a glove box filled with high-purity argon gas. A sodium metal sheet was used as the negative electrode, and Whatman GF / D glass fiber was used as the separator. An electrolyte solution containing sodium perchlorate as the electrolyte and carbonate compounds as the solvent was used. The cells were activated for three cycles at 0.1C within a working voltage range of 2.0–4.3 V at 25 °C, followed by charge-discharge cycle performance testing at 1C, and the capacity retention rate was recorded. Unless otherwise stated, the discharge specific capacity, median discharge voltage, rate performance, and cycle performance described below were tested under the above conditions; the electrode-level volumetric energy density was determined according to the method described in

[0060] below.

[0047] Example 2 The preparation method of this embodiment is basically the same as that of Example 1, the only difference being: Na4Fe3(PO4)2P2O7, Na 0.67 Ni 0.33 Mn 0.67 O2 and Na 2.5 Fe 1.75 The mass ratio of (SO4)3 was adjusted to 8:1.5:0.5. The remaining steps and test conditions were the same as in Example 1.

[0048] Example 3 The preparation method of this embodiment is basically the same as that of Example 1, the only difference being: Na4Fe3(PO4)2P2O7, Na 0.67 Ni 0.33 Mn 0.67 O2 and Na 2.5 Fe 1.75 The mass ratio of (SO4)3 was adjusted to 8:1:1. The remaining steps and test conditions were the same as in Example 1.

[0049] Example 4 The preparation method of this embodiment is basically the same as that of Example 1, the only difference being: Na4Fe3(PO4)2P2O7, Na 0.67 Ni 0.33 Mn 0.67 O2 and Na 2.5 Fe 1.75The mass ratio of (SO4)3 was adjusted to 9:0.5:0.5. The remaining steps and test conditions were the same as in Example 1.

[0050] Comparative Example 1 The preparation method of this comparative example is basically the same as that of Example 1, except that: in steps (1), (2) and (4), only Na4Fe3(PO4)2P2O7 raw material is used as the positive electrode active material, and the other steps and test conditions are the same as those in Example 1.

[0051] Comparative Example 2 The preparation method of this comparative example is basically the same as that of Example 1, except that the ball milling and sintering process in steps (1) and (2) is omitted, and Na4Fe3(PO4)2P2O7 is directly used as the positive electrode active material. The remaining steps and test conditions are the same as those in Example 1.

[0052] Test Results and Analysis. To evaluate the effects of matrix modification, composite composition, and composition ratio on electrochemical performance and electrode-level volumetric energy density, Examples 1-4 and Comparative Examples 1-2 were compared and analyzed under the same test conditions. The test data are summarized in the table below. For ease of explanation, the test results of Example 1 and Comparative Example 2 are highlighted and analyzed in conjunction with particle size distribution, electrode morphology, and electrochemical test results.

[0053] The overall particle size distribution of the composite active material was tested, and the particle size distribution data after the first ball milling and sintering are summarized in the table below:

[0054] Table 2

[0055] The particle size distribution data after the second ball milling and drying are summarized in the table below:

[0056] Table 3

[0057] The median particle size of the original Na4Fe3(PO4)2P2O7 was approximately 12.0 μm. After the first ball milling, the Na4Fe3(PO4)2P2O7 / Na 2.5 Fe 1.75 The median particle size of the (SO4)3 mixture decreased significantly, indicating that the first ball milling process helped break down the loose aggregated structure in the polyanionic matrix. Further introduction of Na... 0.67 Ni 0.33 Mn 0.67 After O2 is applied, a multiphase particle size distribution is formed in the composite system. Combined with the morphology of the electrode coating, it can be seen that the various phase materials form a relatively dense particle packing structure in the electrode coating.

[0058] Table 4

[0059] Table 5

[0060] It should be noted that the electrode-level volumetric energy density described in this invention (…) E v Unit: Wh L -1 The calculation is based on the actual physical and electrochemical parameters of the electrode, and the calculation formula is as follows: Ev = C × V × ρ × w / 100 ， in, C The specific discharge capacity of the battery at a 0.1C rate (mAh g) -1 ); V The corresponding median discharge voltage (V); ρ The measured compaction density of the electrode material (g / cm³) -3 The compaction density of the electrode material layer is the compaction density calculated based on the electrode material layer after deducting the current collector; w The percentage (%) of the active material in the electrode material layer is used in the embodiments and comparative examples of this invention. w = 92. The compaction density of the electrode material layer is calculated based on the mass and volume of the electrode material layer.

[0061] The test results show that, comparative example 2 ( Figure 7 (b) The surface of the positive electrode coating has a relatively loose particle accumulation and many pores; in contrast, Example 1 ( Figure 7 The composite electrode coating in (a) exhibits a relatively dense packing morphology, with smaller particles distributed in the gaps between larger particles. Particle size distribution testing results show that, due to the introduction of small-particle-size auxiliary active components, the overall particle size distribution of the composite active material exhibits a smaller dimensional shift, indicating the formation of a multiphase particle size distribution structure within the system. Based on this particle size distribution structure, combined with... Figure 1-6 It can be seen that Na4Fe3(PO4)2P2O7 is the main active component, Na 0.67 Ni 0.33 Mn 0.67 O2 and Na 2.5 Fe 1.75 (SO4)3 serves as an auxiliary active component, contributing to the overall composite active substance. Among these components, Na4Fe3(PO4)2P2O7 helps maintain the structural stability and basic cycling performance of the composite system, while Na... 0.67 Ni 0.33 Mn 0.67O2 is mainly used to improve discharge specific capacity and operating voltage, while Na... 2.5 Fe 1.75 (SO4)3 helps improve the particle packing state and interfacial transport conditions of the composite system, enhancing its conductivity. Simultaneously, as a medium-to-high voltage active phase, it plays a supplementary role in improving the overall voltage. Specifically, as shown in Tables 4-5, the discharge specific capacity of Example 1 at 0.1C rate is 118.32 mAhg. -1 The median voltage is 3.14 V, and the discharge specific capacity at a 1C rate is 104.17 mAh g. -1 After 100 cycles, the capacity retention rate was 94.01%, and the discharge specific capacity at a 30C rate was 69.89 mAh g. -1 The electrode material has a laminated density of 2.40 g / cm³. -3 The electrode-level volumetric energy density reaches 820.3 Wh / L. -1 The above results demonstrate that the solution of the present invention is advantageous in balancing compaction density, discharge specific capacity, operating voltage, and rate performance, thereby improving the electrode-level volumetric energy density.

Claims

1. A polyanion-based composite positive electrode, characterized in that, The electrode includes a positive current collector and an electrode material layer loaded on at least one side of the positive current collector. The electrode material layer contains an active material, a conductive agent, and a binder. The active material contains the following components in mass percentage: sodium iron pyrophosphate 70%~90%; P2-type layered oxide 5%~20%; sodium iron sulfate 5%~10%. The active material in the electrode material layer is a composite active material, which is obtained by mixing sodium iron pyrophosphate and sodium iron sulfate through a first ball milling and sintering process, followed by mixing with P2-type layered oxide through a second ball milling process and vacuum drying.

2. The polyanion-based composite positive electrode according to claim 1, characterized in that, The general chemical formula of the P2-type layered oxide is Na. x MO2, wherein 0.6 < x ≤ 0.7, and M is Ni, Mn, and optionally includes at least one of Fe or Mg.

3. The polyanion-based composite positive electrode according to claim 1, characterized in that, The general chemical formula of the sodium ferric sulfate is Na. 2+2z Fe 2-z (SO4)3, where 0 ≤ z ≤ 0.

3.

4. The polyanion-based composite positive electrode sheet according to claim 1, characterized in that, The compaction density of the electrode material layer is ≥ 2.20 g cm⁻¹ -3 .

5. The polyanion-based composite positive electrode according to claim 1, characterized in that, The conductive agent includes conductive carbon black and carbon nanotubes, wherein the conductive carbon black accounts for 3-5 wt% of the electrode material layer by mass, and the carbon nanotubes account for 1-2 wt% of the electrode material layer by mass; the binder is polyvinylidene fluoride, and the binder accounts for 2-5 wt% of the electrode material layer by mass.

6. A method for preparing the polyanion-based composite positive electrode sheet as described in any one of claims 1 to 5: S1: Sodium ferric pyrophosphate and sodium ferric sulfate are mixed by first ball milling under dry grinding conditions; S2: Sinter the mixture obtained in step S1 under nitrogen or argon protection; S3: The material processed in step S2 is mixed with the P2 type layered oxide by a second ball milling under dry milling conditions; S4: The material obtained in step S3 is heated and dried under vacuum; S5: The composite active material and conductive agent obtained in step S4 are added to the binder solution, placed in a homogenizer and made into a slurry under vacuum conditions, and coated on the surface of the positive current collector. After drying and rolling, the polyanion-based composite positive electrode sheet is obtained.

7. The method for preparing the polyanion-based composite positive electrode sheet according to claim 6, characterized in that, In step S1, the first ball milling is performed using a planetary ball mill at a speed of 300-600 rpm for 1-3 hours; in step S2, the sintering is carried out under nitrogen or argon protection at a heating rate of 0.5-2 °C / min. -1 The sintering temperature is 280~320℃, and the holding time is 0.5~1.5 hours.

8. The method for preparing the polyanion-based composite positive electrode sheet according to claim 6, characterized in that, In step S3, the second ball milling speed is 200~400 rpm, and the mixing time is 0.5~1.5 hours; in step S4, the heating temperature for vacuum drying is 80~120 ℃, and the heating rate is 0.5~2 ℃ min. -1 The drying time is 0.5 to 1.5 hours.

9. The method for preparing the polyanion-based composite positive electrode sheet according to claim 6, characterized in that, In step S5, the slurry mixing speed is 2000~4000 rpm, and the mixing time is 5~20 minutes. The mixed slurry is then coated onto the surface of the positive electrode current collector. The coated wet electrode is then placed in a vacuum oven and preheated at 2 ℃ for 1 minute. -1 The temperature was increased from room temperature to 80 °C and dried at a constant temperature for 2 hours; then increased at 2 °C / min. -1 The heating rate was increased to 120 °C, and the temperature was kept constant for 10-12 hours.

10. A sodium-ion battery based on a composite cathode, characterized in that, The polyanion-based composite positive electrode sheet includes any one of claims 1 to 5.

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