Secondary battery and electric equipment

Abstract

The embodiment of the invention provides a secondary battery and electric equipment, and the secondary battery provided by the embodiment of the invention meets the following conditions: [100 * (logE) * (Pc)] / [(3Rc) 0.4] is more than or equal to 4.6 and less than or equal to 16.6; wherein Rc m omega is the diaphragm resistance of the positive pole piece; pc g / cc is the compaction density of the positive pole piece; e g / Ah is the liquid injection coefficient of the secondary battery. By matching the diaphragm resistance of the positive pole piece, the compaction density of the positive pole piece and the liquid injection coefficient of the secondary battery to meet the relationship, a pole piece conductive network is effectively constructed, and the ionic conductivity, the electronic conductivity and the cycle stability of the positive pole piece are improved, namely the discharge rate capability and the cycle performance of the battery are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery manufacturing, in particular to a secondary battery and electrical equipment. Background Art

[0002] Electric vehicles have placed higher requirements on the rapid discharge performance of secondary batteries. However, the rapid discharge performance of existing secondary batteries is poor and cannot effectively meet the demand for excellent rapid discharge of secondary batteries.

[0003] Therefore, there is an urgent need to provide a secondary battery with excellent kinetic performance. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a secondary battery and an electrical device to solve the problem of poor dynamic performance of existing secondary batteries.

[0005] In order to solve the above problems, the present invention is achieved through the following technical solutions:

[0006] The present invention provides a secondary battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material;

[0007] The secondary battery meets the following requirements: 4.6 ≤ [100×(logE)×(Pc)] / [(3Rc)^0.4] ≤ 16.6;

[0008] Wherein, Rc mΩ is the membrane resistance of the positive electrode plate;

[0009] Pc g / cc is the compaction density of the positive electrode sheet;

[0010] E g / Ah is the filling coefficient of the secondary battery.

[0011] Furthermore, in the secondary battery, the positive electrode active material has a pore structure, and the ratio K of open pores to closed pores of the positive electrode active material is 4-5.

[0012] Furthermore, in the secondary battery, the oil absorption value of the positive electrode active material is 20 to 30 mL / 100 g.

[0013] Furthermore, in the secondary battery, the sheet resistance Rc mΩ of the positive electrode sheet is 300-700 mΩ.

[0014] Furthermore, in the secondary battery, the compaction density Pc g / cc of the positive electrode sheet is 2.5 to 3.4 g / cc.

[0015] Furthermore, in the secondary battery, the filling coefficient E g / Ah of the secondary battery is 2.5 to 5.5 g / Ah.

[0016] Furthermore, the pH value of the positive electrode active material is less than 10.5.

[0017] Furthermore, in the secondary battery, the positive electrode active material comprises a sodium ion layered oxide, and the sodium ion layered oxide comprises a chemical formula of Na x A compound of MO2, wherein M is selected from at least one of Fe, Ni, Li, Cu, Zn, Co, Ti, and Mn, and 1.1>x>0.50.

[0018] Furthermore, in the secondary battery, the oil absorption value of the negative electrode active material is 50 to 70 mL / 100 g.

[0019] Furthermore, in the secondary battery, the negative electrode active material includes soft carbon, and the aspect ratio of the soft carbon is 1.4 to 3.5.

[0020] The present invention further provides an electric device, which includes the above-mentioned secondary battery, and the secondary battery serves as a power supply for the electric device.

[0021] The embodiments of the present invention include the following advantages:

[0022] In an embodiment of the present invention, a secondary battery provided includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode active material; the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material; the secondary battery meets: 4.6 ≤ [100×(logE)×(Pc)] / [(3Rc)^0.4] ≤ 16.6; wherein, Rc mΩ is the membrane resistance of the positive electrode sheet, Pc g / cc is the compaction density of the positive electrode sheet, and Eg / Ah is the injection coefficient of the secondary battery. In the embodiment of the present invention, by matching the membrane resistance of the positive electrode sheet, the compaction density of the positive electrode sheet and the injection coefficient of the secondary battery to satisfy the above relationship, the electrode sheet conductive network is effectively constructed, the ionic conductivity, electronic conductivity and cycle stability of the positive electrode sheet are improved, and the discharge rate performance of the secondary battery is effectively improved.

[0023] It should be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present application. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with specific implementation methods.

[0025] An embodiment of the present invention provides a secondary battery, which includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte, wherein the positive electrode plate includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, and the positive electrode active material layer includes a positive electrode active material; the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, and the negative electrode active material layer includes a negative electrode active material;

[0026] The secondary battery meets the following requirements: 4.6 ≤ [100×(logE)×(Pc)] / [(3Rc)^0.4] ≤ 16.6;

[0027] Among them, Rc mΩ is the membrane resistance of the positive electrode;

[0028] Pc g / cc is the compaction density of the positive electrode sheet;

[0029] E g / Ah is the filling coefficient of the secondary battery.

[0030] The applicant has found that the discharge rate performance of the battery is related to the performance of the positive electrode material, the design of the positive electrode sheet and the injection coefficient. The present invention makes reasonable design so that the membrane resistance of the positive electrode sheet of the battery, the compaction density of the positive electrode sheet and the injection coefficient meet the above relationship, which can effectively improve the discharge rate performance and cycle performance of the battery. Schematically, the value of [100×(logE)×(Pc)] / [(3Rc)^0.4] can be 4.6, 4.8, 5.5, 7.5, 8.9, 10, 13, 15, 16.6 or any two of the range values.

[0031] In the embodiment of the present invention, based on the interactive relationship between the diaphragm resistance, compaction density and filling coefficient of the positive electrode sheet, the diaphragm resistance of the positive electrode sheet, the compaction density of the positive electrode sheet and the filling coefficient of the secondary battery are matched to satisfy the above relationship, and the conductive network of the positive electrode sheet is effectively constructed, the ionic conductivity, electronic conductivity and cycle stability of the positive electrode sheet are improved, and it is ensured that the electrolyte can fully infiltrate the positive and negative electrode sheets and the diaphragm of the battery, reduce the battery ohmic resistance, effectively improve the discharge rate performance, and prepare a secondary battery with excellent kinetic performance.

[0032] Optionally, in one embodiment, the dibutyl phthalate oil absorption value of the above-mentioned positive electrode active material is 20-30 mL / 100 g, which can effectively ensure the wetting effect of the electrolyte on the positive electrode plate and achieve excellent fast charging performance, and can also avoid the problem of excessive exposure of the positive electrode plate interface to the electrolyte, resulting in excessive consumption of sodium ions in the film forming process, causing the battery capacity to decrease. In some embodiments, the dibutyl phthalate oil absorption value of the above-mentioned positive electrode active material is 20.0 mL / 100 g, 21.0 mL / 100 g, 22.0 mL / 100 g, 24.0 mL / 100 g, 25.0 mL / 100 g, 28.0 mL / 100 g, 30.0 mL / 100 g, or any two of the range values.

[0033] Optionally, in one embodiment, the pH value of the positive electrode active material is less than 10.5, which can slow down the decomposition of binders such as polyvinylidene fluoride and facilitate coating and processing to make positive electrode sheets. In one embodiment, the pH value of the positive electrode active material is 9.5-10.4; in one embodiment, the pH value of the positive electrode active material is 9.7-10.

[0034] Optionally, in one embodiment, the positive electrode active material comprises one or more crystals of P2 and O3 type layered oxides. The layered oxide comprises a chemical formula of Na x A compound of MO2, wherein M is selected from at least one of Fe, Ni, Li, Cu, Zn, Co, Ti, and Mn, and 1.1>x>0.5. When 1.1>x>0.9, the crystal structure of the layered positive electrode material is a single O3 type, when 0.9≥x≥0.7, the crystal structure of the layered positive electrode material is a mixed type of P2 and O3, and when 0.7>x>0.5, the crystal structure of the layered positive electrode material is a single P2 type.

[0035] In the range of 0.9≥x≥0.7, the ratio of P2-type layered oxide to O3-type layered oxide can be adjusted by the sodium content x. When x is larger, the ratio of O3 phase is larger, and when x is smaller, the ratio of P2 phase is larger.

[0036] Optionally, in a specific embodiment, the sodium ion layered oxide is a mixture of P2-type and O3-type sodium ion layered metal oxides, wherein the space group of the O3-type sodium ion layered metal oxide is R-3m, and its molar proportion in the mixed phase is 20-98%; the space group of the P2-type sodium ion layered metal oxide is P63 / mmc, and its molar proportion in the mixed phase is 2%-80%. In this way, both the energy density and cycle stability of the battery can be taken into account.

[0037] Optionally, in one embodiment, the positive electrode active material has a porous structure, and the ratio K of the open pores to the closed pores of the positive electrode active material is 4 to 5, so that the positive electrode active material has a rich porous structure, so that the active surface area of ​​the positive electrode active material is moderate, and the infiltration effect of the electrolyte is ensured, so that the first coulombic efficiency and rate performance of the battery can be effectively balanced. In some embodiments, the ratio K of the open pores to the closed pores of the positive electrode active material is 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, or any two of the range values.

[0038] In practical applications, the above K value can be obtained by adjusting the sintering temperature, the closed-pore porosity can be obtained by testing the closed-pore volume test method in GB / T10799-2008, and the open-pore porosity can be measured by a gas adsorption method.

[0039] Optionally, in one embodiment, the sheet resistance Rc mΩ of the positive electrode sheet is 300-700 mΩ, which can effectively take into account the compaction density of the positive electrode sheet and the DCR of the secondary battery, which is conducive to fast charging and ensuring the energy density of the battery. In some embodiments, the sheet resistance of the positive electrode sheet can be one of 300 mΩ, 320 mΩ, 350 mΩ, 380 mΩ, 400 mΩ, 500 mΩ, 600 mΩ, 700 mΩ or any two of the range values.

[0040] Optionally, in one embodiment, the compaction density Pc g / cc of the positive electrode sheet is 2.5 to 3.4 g / cc, which can effectively take into account the flexibility of the electrode sheet and the energy density of the battery, and is easy to process. In some embodiments, the compaction density of the positive electrode sheet is 2.5 g / cc, 2.6 g / cc, 2.7 g / cc, 2.8 g / cc, 2.9 g / cc, 3.0 g / cc, 3.1 g / cc, 3.2 g / cc, 3.3 g / cc, 3.4 g / cc, or any two of the range values.

[0041] In the embodiment of the present invention, the compaction density is controlled within the range of 2.5 to 3.4 g / cc by performing secondary coating and secondary rolling on the positive electrode sheet.

[0042] Optionally, in one embodiment, the injection coefficient E g / Ah of the secondary battery is 2.5 to 5.5 g / Ah, which can not only ensure that the battery has a high energy density, but also achieve a good electrolyte infiltration effect and excellent fast charging performance. In some embodiments, the injection coefficient of the secondary battery is 2.5 g / Ah, 2.6 g / Ah, 2.8 g / Ah, 3.0 g / Ah, 3.5 g / Ah, 4.0 g / Ah, 4.5 g / Ah, 5.5 g / Ah, or any two of the range values.

[0043] Optionally, in one embodiment, the positive electrode active material layer further includes a first conductive agent and a first binder.

[0044] The first conductive agent may include at least one of conductive carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, carbon fibers, and carbon microspheres.

[0045] Optionally, in one embodiment, the first binder includes at least one of styrene-butadiene latex, polytetrafluoroethylene, and polyvinylidene fluoride.

[0046] Optionally, in one embodiment, the positive electrode current collector includes at least one of copper foil, aluminum foil, carbon-coated copper foil, and carbon-coated aluminum foil.

[0047] In some embodiments, the positive electrode sheet is prepared as follows: the components for preparing the positive electrode sheet, such as the positive electrode active material including the positive electrode material, the first adhesive and the first conductive agent are dispersed in a solvent such as N-methylpyrrolidone to form a positive electrode slurry; the positive electrode slurry is coated on a positive electrode collector such as aluminum foil; after drying, rolling, die cutting and other processes, the positive electrode sheet can be obtained.

[0048] Optionally, in one embodiment, the dibutyl phthalate oil absorption value of the above-mentioned negative electrode active material is 50-70mL / 100g, which can effectively ensure the wetting effect of the electrolyte on the negative electrode plate and achieve excellent fast charging performance, and can also avoid the problem of excessive exposure of the negative electrode plate interface to the electrolyte, resulting in excessive consumption of sodium ions in the film formation process, causing the battery capacity to decrease. In some embodiments, the dibutyl phthalate oil absorption value of the above-mentioned negative electrode active material is 50mL / 100g, 55mL / 100g, 60mL / 100g, 65mL / 100g, 70mL / 100g, or any two of the range values.

[0049] Optionally, in a specific embodiment, the negative electrode active material is soft carbon, and the aspect ratio of the soft carbon is 1.4 to 3.5, so that the linearity of the negative electrode material is moderate, which can effectively form a 3D conductive network and improve the compaction density of the negative electrode sheet, thereby ensuring the mechanical properties of the battery. The aspect ratio of soft carbon is the ratio of the longest diameter passing through the inside of the soft carbon particle to the longest diameter perpendicular to it.

[0050] In some embodiments, the aspect ratio of the soft carbon may be in the range of one or any two of 1.4, 1.5, 1.8, 2.0, 2.5, 2.8, 3.0, 3.5.

[0051] Optionally, in one embodiment, the negative electrode active material layer further includes a second conductive agent and a second binder.

[0052] The second conductive agent is selected from at least one of conductive carbon black, Ketjen black, acetylene black, carbon nanotubes, and graphene.

[0053] The second binder is selected from at least one of styrene-butadiene latex, polytetrafluoroethylene, and polyvinylidene fluoride.

[0054] In some embodiments, the negative electrode sheet is prepared as follows: the components for preparing the negative electrode sheet, such as the negative electrode active material, the second adhesive and the second conductive agent, are dispersed in a solvent such as deionized water to form a negative electrode slurry; the negative electrode slurry is coated on both sides of a negative electrode collector such as copper foil; after baking, rolling, cutting and other processes, the negative electrode sheet can be obtained.

[0055] The secondary battery provided by the present invention also includes an electrolyte.

[0056] Among them, the electrolyte in the electrolyte plays the role of conducting ions between the positive electrode plate and the negative electrode plate.

[0057] It can be understood that the secondary battery provided in the embodiment of the present invention further includes a separator.

[0058] In practical applications, the negative electrode sheet, the separator and the positive electrode sheet are stacked in order and wound to obtain a core, the core is packaged to obtain a bare cell, and the bare cell is baked and then injected, formed, repackaged and sorted to obtain the above-mentioned secondary battery.

[0059] The present invention further provides an electric device, which includes the above-mentioned secondary battery, and the secondary battery serves as a power supply for the electric device.

[0060] For the above-mentioned electrical equipment embodiment, it includes the above-mentioned secondary battery and can achieve the same technical effect. In order to avoid repetition, it will not be described here. For relevant matters, please refer to the partial description of the positive electrode material embodiment.

[0061] In order to make the invention purpose, technical scheme and beneficial effect of the present invention clearer, the present invention is further described below in conjunction with embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0062] The present invention is described in detail below by way of examples.

[0063] (1) Diaphragm resistance Rc test:

[0064] The rolled positive electrode sheet was cut into a rectangular size of about 5cm×10cm and placed between the two electrodes of the membrane resistance meter. The test pressure was set to 25MPa and the pressure holding time was 15 seconds before starting the test. The software automatically read the membrane resistance.

[0065] (2) Positive electrode compaction density Pc test:

[0066] The coated and dried positive electrode sheet is placed in a roller press, and the positive electrode sheet is rolled under a roller pressure of 40 tons. Then, the density of the positive active material on the positive electrode sheet is tested, which is the compaction density of the positive electrode sheet.

[0067] (3) Injection coefficient E test:

[0068] At room temperature, a fully charged battery (voltage is 3.8V) is discharged to 1.5V at a current density of 0.33C. The capacity at this time is C1, and the injection coefficient E=m / C1, where m is the injection amount of the electrolyte.

[0069] (4) Discharge rate performance test:

[0070] At room temperature, the fully charged battery (voltage is 3.8V) is discharged to 1.5V at a current density of 0.33C, and the capacity is recorded as C1;

[0071] Then, at room temperature, the fully charged battery (voltage is 3.8V) is discharged to 1.5V at a current density of 5C, and the capacity is recorded as C2;

[0072] The capacity retention ratio C2 / C1 is calculated as a test indicator of the discharge rate performance.

[0073] (5) Cyclic performance test:

[0074] At room temperature, charge the battery to 3.8V at a current density of 1C, and then discharge it to 1.5V at a current density of 1C, and record the capacity C1 during the discharge process;

[0075] At room temperature, the battery was charged at a 1C rate and discharged at a 1C rate for a full charge and discharge cycle test with a voltage range of 1.5V to 3.8V. When the discharge capacity gradually decayed to 80%*C1, the test was stopped and the number of cycles was recorded as a test indicator of the cycle performance.

[0076] (6) Energy density test:

[0077] Connect the battery to the test channel in the test cabinet, charge it to 3.8V at a rate of 0.05C, and then discharge it to 1.5V at a rate of 0.33C. The energy during the discharge process is E2, and the mass of the battery is m, then the energy density = E2 / m.

[0078] Example 1

[0079] (1) Preparation of positive electrode sheet

[0080] The precursor (Ni 0.33 Fe 0.33 Mn 0.33 )OH2 and battery-grade sodium carbonate were put into a high-speed mixer and mixed at a speed of 1000r / min for 30min. After being mixed evenly, a mixture was prepared; the obtained mixture was sintered at high temperature in an atmosphere furnace, the sintering atmosphere was air, the sintering temperature was 1000℃, the sintering time was 10h, and the positive electrode active material NaNi was prepared after being cooled, crushed and sieved. 0.33 Fe 0.33 Mn 0.33 O2.

[0081] The obtained positive electrode active material NaNi 0.33 Fe 0.33 Mn 0.33 O2, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 85:7.5:7.5, and solvent NMP is added, and the positive electrode slurry is obtained by stirring under the action of a vacuum mixer; the positive electrode slurry is evenly coated on both sides of the positive electrode current collector aluminum foil, and after drying at room temperature, it is transferred to an oven at 100°C for further drying, and then rolled and cut under a roller pressure of 40 tons to obtain the positive electrode sheet.

[0082] (2) Preparation of negative electrode sheet

[0083] The negative electrode active material soft carbon (aspect ratio of 2.8), the conductive agent acetylene black (SuperP) and the binder PVDF are mixed evenly in a mass ratio of 97:1:2, and evenly dispersed in deionized water to form a uniform black slurry. The mixed slurry is coated on both sides of the copper foil, and then baked, rolled and cut into pieces to obtain the negative electrode sheet.

[0084] (3) Preparation of electrolyte

[0085] 1 mol / L NaPF6 was dissolved in a solution of propylene carbonate (PC), diethyl carbonate (DEC) and fluoroethylene carbonate (FEC) in a mixing volume ratio of 30:69:1, and the mixture was evenly mixed to prepare an electrolyte.

[0086] (4) Preparation of sodium ion batteries

[0087] The positive electrode sheet, the isolation film and the negative electrode sheet are stacked in sequence, then wound into a bare battery cell and loaded into a soft-pack shell. After top and side sealing, liquid injection, formation, sorting and other processes, a sodium ion battery is obtained.

[0088] Embodiment 2-3

[0089] The difference between Examples 2 to 3 and Example 1 is that in step (1), the amount of conductive agent, the electrode rolling pressure, and the amount of liquid injection are adjusted respectively.

[0090] Embodiment 4-5

[0091] The difference between Examples 4 to 5 and Example 1 is that in step (1), the amount of the conductive agent is adjusted to obtain positive electrode sheets with different positive electrode sheet resistances.

[0092] Embodiment 6-7

[0093] The difference between Examples 6 to 7 and Example 1 is that in step (1), the injection amount of the secondary battery is adjusted respectively to adjust the injection coefficient of the secondary battery.

[0094] Embodiments 8 to 9

[0095] The difference between Examples 8 to 9 and Example 1 is that in step (1), the electrode sheet rolling pressure is adjusted to obtain positive electrode sheets with different compaction densities.

[0096] Embodiments 10 to 15

[0097] The difference between Examples 10 to 15 and Example 1 is that in step (1), the type of precursor or the proportion of sodium carbonate in the preparation process of the positive electrode active material is adjusted to obtain different positive electrode active materials.

[0098] Embodiments 16 to 18

[0099] The difference between Examples 16 to 18 and Example 1 is that in step (2), soft carbon with different aspect ratios is used.

[0100] Embodiments 19 to 20

[0101] The difference between Examples 19 to 20 and Example 1 is that in step (1), the sintering temperature during the preparation of the positive electrode active material is adjusted to adjust the ratio of open pores to closed pores in the positive electrode active material.

[0102] Examples 21-22

[0103] The difference between Examples 21 to 22 and Example 1 is that in step (1), the mesh size of the positive electrode active material is adjusted to adjust the oil absorption value of the positive electrode active material.

[0104] Embodiments 23-24

[0105] The difference between Examples 23 to 24 and Example 1 is that in step (2), the oil absorption values ​​of the negative electrode active materials are adjusted to 50 mL / 100 g and 70 mL / 100 g, respectively.

[0106] Comparative Examples 1-2

[0107] The difference between Comparative Examples 1 and 2 and Example 1 is that in step (1), the amount of conductive agent, the electrode rolling pressure, and the amount of liquid injected into the battery cell are adjusted respectively. The specific parameters are shown in Table 1.

[0108] The battery characteristic parameters and material characteristic parameters of each embodiment and comparative example are shown in Table 1.

[0109] Table 1

[0110]

[0111]

[0112] Wherein, x = [100 × (logE) × (Pc)] / [(3Rc) ^ 0.4]; K is the ratio of open pores to closed pores of the positive electrode active material.

[0113] The positive electrode sheets prepared in each embodiment and comparative example were subjected to a membrane resistance test and a compaction density test, wherein the test data are shown in Table 1.

[0114] The batteries prepared in the embodiments and comparative examples were subjected to discharge rate performance test, cycle performance test and energy density test, wherein the test data are shown in Table 2.

[0115] Table 2

[0116]

[0117] To summarize, in this embodiment, based on the interaction and mutual influence relationship between the diaphragm resistance, compaction density and filling coefficient of the secondary battery of the positive electrode sheet, the diaphragm resistance of the positive electrode sheet, the compaction density of the positive electrode sheet and the filling coefficient of the secondary battery are matched to satisfy the above relationship, thereby effectively constructing a conductive network of the electrode sheet, improving the ionic conductivity, electronic conductivity and cycle stability of the positive electrode sheet, and effectively improving the discharge rate performance and cycle performance of the battery.

[0118] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the embodiments of the present invention.

[0119] The secondary battery and electrical equipment provided by the present invention are introduced in detail above. The principle and implementation mode of the present invention are explained by using specific examples in this article. The description of the above embodiments is only used to help understand the method and core idea of ​​the present invention. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A secondary battery, characterized in that: The invention comprises a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector, wherein the positive electrode active material layer comprises a positive electrode active material; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material; The secondary battery meets the following requirements: 4.6 ≤ [100×(logE)×(Pc)] / [(3Rc)^0.4] ≤ 16.6; Wherein, Rc mΩ is the membrane resistance of the positive electrode plate; Pc g / cc is the compaction density of the positive electrode sheet; E g / Ah is the filling coefficient of the secondary battery.

2. The secondary battery according to claim 1, characterized in that: The positive electrode active material has a pore structure, and a ratio K of open pores to closed pores of the positive electrode active material is 4-5.

3. The secondary battery according to claim 2, characterized in that: The dibutyl phthalate oil absorption value of the positive electrode active material is 20 to 30 mL / 100 g.

4. The secondary battery according to claim 1, characterized in that: The pH value of the positive electrode active material is less than 10.

5.

5. The secondary battery according to claim 1, characterized in that: The membrane resistance Rc mΩ of the positive electrode plate is 300-700 mΩ.

6. The secondary battery according to claim 1, characterized in that: The compaction density Pc g / cc of the positive electrode sheet is 2.5 to 3.4 g / cc.

7. The secondary battery according to claim 1, characterized in that: The secondary battery has a liquid injection coefficient E g / Ah of 2.5 to 5.5 g / Ah.

8. The secondary battery according to claim 1, characterized in that: The positive electrode active material includes a sodium ion layered oxide, wherein the sodium ion layered oxide includes a chemical formula of Na x A compound of MO2, wherein M is selected from at least one of Fe, Ni, Li, Cu, Zn, Co, Ti, and Mn, and 1.1>x>0.

5.

9. The secondary battery according to claim 1, characterized in that: The dibutyl phthalate oil absorption value of the negative electrode active material is 50 to 70 mL / 100 g.

10. The secondary battery according to claim 9, characterized in that: The negative electrode active material includes soft carbon, and the aspect ratio of the soft carbon is 1.4 to 3.

5.

11. An electrical device, characterized in that: It comprises the secondary battery according to any one of claims 1 to 10, wherein the secondary battery is used as a power supply for the electrical device.

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