Secondary battery and electric device

Abstract

Provided in the embodiments of the present disclosure are a secondary battery and an electric device. The secondary battery provided in the embodiments of the present disclosure comprises a jelly roll and an electrolyte, wherein the jelly roll comprises a positive electrode sheet, a separator and a negative electrode sheet that are sequentially stacked. The mass of the electrolyte that can be accommodated in a volume of 0.85 to 0.95 times the sum of the pore volume of the separator, the pore volume of the positive electrode sheet and the pore volume of the negative electrode sheet in the jelly roll is determined as a total retained electrolyte mass of the secondary battery, such that while electrolyte replenishment requirements of the secondary battery during charge-discharge cycling and storage are met, the risk of lithium plating at two sides of the jelly roll is reduced, and the capacity retention rate of the secondary battery during cycling is improved, thereby prolonging the cycle life of secondary batteries and improving the storage performance of the secondary batteries.

Description

A secondary battery and electrical device

[0001] This application claims priority to Chinese Patent Application No. 202411540332.9, filed on October 30, 2024, entitled "A Secondary Battery and Electrical Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to the field of secondary battery manufacturing technology, and in particular to a secondary battery and electrical equipment. Background Technology

[0003] Cylindrical batteries are one of the development trends of core components for new energy electric vehicles, and have received widespread attention from the industry due to their advantages such as high energy density, high safety performance, and high consistency.

[0004] Electrolyte is a crucial component of cylindrical batteries, significantly impacting not only their initial performance but also their long-term stability and lifespan. Currently, to ensure cylindrical batteries maintain good performance during extended use, the industry widely employs high electrolyte retention designs.

[0005] However, cylindrical battery casings have high strength, and the expansion force of the core during charge-discharge cycles is insufficient to cause significant casing expansion. Due to the constraint of the casing, cylindrical batteries cannot expand outwards during charge-discharge cycles, but instead expand inwards. This reduces the porosity of the positive and negative electrodes and the separator, decreasing the amount of electrolyte that can be stored in these areas. With a high electrolyte retention, a large amount of electrolyte is squeezed out of the porosity of the positive and negative electrodes and the separator during charge-discharge cycles and concentrates on both sides of the core. This results in a higher electrolyte concentration on the sides of the core, making lithium plating more likely. Consequently, the battery's cycle capacity retention rate decreases rapidly, severely impacting the battery's cycle life. Summary of the Invention

[0006] The technical problem to be solved by this disclosure is to provide a secondary battery and an electrical device to solve the problem of reduced cycle capacity retention and cycle life of existing high liquid-holding cylindrical batteries due to lithium plating on both sides of the core.

[0007] To solve the above problems, this disclosure provides the following technical solution: This disclosure proposes a secondary battery, comprising a core and an electrolyte, wherein the core comprises a positive electrode, a separator, and a negative electrode stacked sequentially; the secondary battery, at 0% SOC, satisfies: 0.85×(V0 / 1000)×ρ≤m≤0.95×(V0 / 1000)×ρ, where mg represents the electrolyte retention capacity of the secondary battery; V0mm 3This represents the total volume of pores in the core; the total volume of pores in the core is the sum of the pore volume of the diaphragm, the pore volume of the positive electrode sheet, and the pore volume of the negative electrode sheet; ρg / cm 3 This indicates the density of the electrolyte.

[0008] Furthermore, in the secondary battery, the ratio between the pore volume of the negative electrode sheet and the pore volume of the separator is 3.2 to 7.4.

[0009] Furthermore, in the secondary battery, the ratio between the pore volume of the negative electrode and the pore volume of the positive electrode is 1.2 to 4.3.

[0010] Furthermore, in the secondary battery, the porosity of the separator is 30% to 60%.

[0011] Furthermore, in the secondary battery, the porosity of the positive electrode sheet is 15% to 50%.

[0012] Furthermore, in the secondary battery, the positive electrode sheet includes a positive current collector, and a first positive electrode film layer and a second positive electrode film layer disposed on two opposite surfaces of the positive current collector; wherein, the porosity of the first positive electrode film layer is 15% to 50%, and the porosity of the second positive electrode film layer is 15% to 50%.

[0013] Furthermore, in the secondary battery, the absolute value of the difference between the porosity of the first positive electrode film layer and the porosity of the second positive electrode film layer is 0 to 5%.

[0014] Furthermore, in the secondary battery, the porosity of the negative electrode sheet is 30% to 60%.

[0015] Furthermore, in the secondary battery, the negative electrode sheet includes a negative current collector, and a first negative electrode film layer and a second negative electrode film layer disposed on two opposite surfaces of the negative current collector; wherein, the porosity of the first negative electrode film layer is 30% to 60%, and the porosity of the second negative electrode film layer is 30% to 60%.

[0016] Furthermore, in the secondary battery, the absolute value of the difference between the porosity of the first negative electrode film layer and the porosity of the second negative electrode film layer is 0 to 5%.

[0017] Furthermore, in the aforementioned secondary battery, the density of the electrolyte is 1.1 g / cm³. 3 ~1.5g / cm 3 .

[0018] Furthermore, the secondary battery includes a casing, which has a columnar structure.

[0019] This disclosure also proposes an electrical device, which includes the aforementioned secondary battery, serving as the power supply for the electrical device.

[0020] Compared with the prior art, the embodiments of this disclosure have the following advantages: In the embodiments of this disclosure, the electrolyte retention of the secondary battery at 0% SOC is less than the electrolyte that can be contained by the sum of the pore volumes of the separator, the positive electrode, and the negative electrode in the core. The total electrolyte retention of the secondary battery is determined to be the mass of electrolyte that can be contained by 0.85 to 0.95 times the sum of the pore volumes of the separator, the positive electrode, and the negative electrode in the core. While meeting the electrolyte replenishment requirements during the charge-discharge cycle and storage of the secondary battery, during the charge-discharge cycle, when the secondary battery expands inward due to the constraint of the casing, only a small amount of electrolyte or even no electrolyte is squeezed out to the sides of the core. This makes the electrolyte concentration at the sides of the core basically the same as the electrolyte concentration at other locations of the secondary battery, and the polarization is also basically the same. This reduces the risk of lithium plating at the sides of the core, improves the capacity retention rate of the secondary battery during cycles, and thus improves the cycle life and storage performance of the secondary battery.

[0021] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit this application. Attached Figure Description

[0022] Figure 1 is a schematic diagram of the core structure of a secondary battery provided in an embodiment of this disclosure;

[0023] Figure 2 is a schematic diagram of another secondary battery provided in an embodiment of this disclosure;

[0024] Figure 3 is a schematic diagram of the structure of a diaphragm provided in an embodiment of this disclosure;

[0025] Figure 4 is a schematic diagram of a positive electrode sheet provided in an embodiment of this disclosure; and

[0026] Figure 5 is a schematic diagram of the structure of a negative electrode sheet provided in an embodiment of this disclosure.

[0027] Explanation of reference numerals in the attached drawings: 10-Core; 100-Separator; 101-Negative electrode sheet; 1011-Negative current collector; 1012-First negative electrode film layer; 1013-Second negative electrode film layer; 102-Positive electrode sheet; 1021-Positive current collector; 1022-First positive electrode film layer; 1023-Second positive electrode film layer; 201-Negative current collector plate; 202-Cover plate; 203-Shell; 204-Positive current collector plate; 205-Insulating gasket; 206-Positive electrode post. Detailed Implementation

[0028] To make the above-mentioned objectives, features and advantages of this disclosure more apparent and understandable, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] The applicant of this disclosure discovered that, due to the high strength of the cylindrical secondary battery casing and the insufficient expansion force of the core during charge-discharge cycles to cause significant expansion of the casing, and the limited gas production during formation or normal use of the cylindrical secondary battery, the casing does not expand significantly. Therefore, during charge-discharge cycles, the cylindrical secondary battery cannot expand outward due to the constraint of the casing, but expands inward, which reduces the porosity of the positive electrode, the negative electrode, and the separator, and reduces the amount of electrolyte that can be stored in the positive electrode, the negative electrode, and the separator. When the electrolyte retention in a cylindrical secondary battery is high, a large amount of electrolyte is squeezed out from the positive electrode, negative electrode, and separator during charge-discharge cycles and concentrates on both sides of the core. This results in a higher electrolyte concentration on the sides of the core compared to other parts of the cylindrical secondary battery, increasing polarization and making lithium plating more likely. This leads to a rapid decline in the battery's cycle capacity retention, especially under high-rate fast charging conditions, where lithium plating occurs rapidly on the sides of the core, causing a sharp drop in capacity retention and severely impacting the cycle life of the cylindrical secondary battery. Conversely, when the electrolyte retention in a cylindrical secondary battery is low, the inability to replenish the electrolyte in a timely and effective manner during charge-discharge cycles and storage leads to lithium plating, decreased capacity retention, and lower storage capacity, affecting the cycle life and storage performance of the cylindrical secondary battery.

[0030] To address the aforementioned problems, this disclosure provides a secondary battery. Referring to Figure 1, the secondary battery includes a core 10 and an electrolyte. The core 10 includes a positive electrode 102, a separator 100, and a negative electrode 101 stacked sequentially. The secondary battery satisfies the following condition at 0% SOC (State of Charge): 0.85×(V0 / 1000)×ρ≤m≤0.95×(V0 / 1000)×ρ (1)

[0031] Where mg represents the electrolyte level of the secondary battery; V0mm 3 This represents the total volume of pores in the core 10; the total volume of pores in the core 10 is the sum of the pore volume of the diaphragm 100, the pore volume of the positive electrode 102, and the pore volume of the negative electrode 101; ρg / cm 3 This indicates the density of the electrolyte.

[0032] In this embodiment of the disclosure, the secondary battery is a cylindrical secondary battery.

[0033] The total volume of pores in the core 10 refers to the sum of the pore volumes of the diaphragm 100, the positive electrode 102, and the negative electrode 101 in the core 10; specifically, when the pore volume of the diaphragm 100 is V1, the pore volume of the positive electrode 102 is V2, and the pore volume of the negative electrode 101 is V3: V0=V1+V2+V3 (2)

[0034] When the electrolyte is injected into the core 10, the electrolyte will fill the pores of the separator 100, the pores of the positive electrode 102 and the pores of the negative electrode 101, so as to achieve timely replenishment of electrolyte during the charging and discharging process of the secondary battery and ensure the performance and storage performance of the secondary battery.

[0035] It should be noted that the positive electrode 102 includes a positive current collector and a positive electrode film layer disposed on the positive current collector. The pore volume of the positive electrode 102 refers to the volume of the pores in the positive electrode film layer disposed on the positive current collector. The negative electrode 101 includes a negative current collector and a negative electrode film layer disposed on the negative current collector. The pore volume of the negative electrode 101 refers to the volume of the pores in the negative electrode film layer disposed on the negative current collector.

[0036] It is understood that (V0 / 1000)×ρ in Formula 1 represents the mass of electrolyte contained in the total volume of the pores in the core 10. In this embodiment, the electrolyte retention capacity of the secondary battery is set within this range. While meeting the electrolyte replenishment requirements during the charge-discharge cycle and storage of the secondary battery, excessive electrolyte is not injected into the core 10. When the secondary battery expands inward during the charge-discharge cycle, only a small amount of electrolyte, or even no electrolyte, is squeezed out to the sides of the core 10. This makes the electrolyte concentration at the sides of the core 10 basically the same as the electrolyte concentration at other locations of the secondary battery, and the polarization is also basically the same. This reduces the risk of lithium plating at the sides of the core 10, improves the capacity retention rate of the secondary battery during cycles, and thus improves the cycle life and storage performance of the secondary battery.

[0037] In some embodiments, the liquid retention capacity m of the secondary battery can be a value within the range of one or any two of the following: 0.85×(V0 / 1000)×ρ, 0.87×(V0 / 1000)×ρ, 0.89×(V0 / 1000)×ρ, 0.91×(V0 / 1000)×ρ, 0.93×(V0 / 1000)×ρ, and 0.95×(V0 / 1000)×ρ.

[0038] In this embodiment, the electrolyte comprises an organic solvent, a lithium electrolyte salt, and additives, which are obtained by mixing and thoroughly stirring the above substances in a certain proportion under certain conditions. It is understood that electrolytes of different densities can be prepared by adjusting the proportions and types of the organic solvent, lithium electrolyte salt, and additives.

[0039] After the electrolyte is injected into the secondary battery, it is allowed to stand and soak before the first charge and discharge. The secondary battery is then sealed and weighed to determine the electrolyte retention.

[0040] Referring to Figure 2, the secondary battery provided in this embodiment includes a core 10, a negative current collector 201, a negative cover plate 202, a casing 203, a positive current collector 204, an insulating pad 205, and a positive terminal post 206.

[0041] The core 10 includes a positive electrode 102, a separator 100 and a negative electrode 101 stacked in sequence; both sides of the positive electrode 102 and the negative electrode 101 have empty foil as tabs. The positive electrode 102, the separator 100 and the negative electrode 101 are stacked in sequence and wound to form the core 10.

[0042] Shell 203 is a cylindrical shell.

[0043] Object 203 is a cylindrical shell.

[0044] The tab of the negative electrode 101 is connected to the negative current collector 201, the negative current collector 201 is connected to the cover plate 202, and the cover plate 202 is connected to the housing 203, thereby realizing the electrical connection of the negative electrode 101.

[0045] The tab of the positive electrode 102 is connected to the positive current collector 204, and the positive current collector 204 is connected to the positive electrode post 206, so as to realize the electrical connection of the positive electrode 102; wherein, the positive current collector 204 is insulated from the housing 203 by an insulating gasket 205, and the positive electrode post 206 is also insulated from the housing 203 by an insulating gasket 205.

[0046] Optionally, in some embodiments, the ratio between the pore volume of the negative electrode 101 and the pore volume of the separator 100 is 3.2 to 7.4.

[0047] Specifically:

[0048] In this embodiment of the present disclosure, the volume of the pores in the negative electrode film layer disposed on the negative electrode current collector in the negative electrode sheet 101 and the volume of the pores in the separator 100 can be adjusted so that the ratio between the pore volume of the negative electrode sheet 101 and the pore volume of the separator 100 satisfies 3.2 to 7.4.

[0049] The pore volume of the negative electrode sheet 101 can be adjusted by modifying the ratio between the negative electrode active material and the conductive agent in the negative electrode film layer, the content of the binder in the negative electrode film layer, the coating speed, coating thickness, coating uniformity, drying temperature and drying time of the negative electrode film layer, and compaction pressure.

[0050] Accordingly, the pore volume of the diaphragm 100 can be adjusted by modifying its constituent materials, stretching process, film-forming process, heat treatment process, and chemical treatment process.

[0051] In this embodiment, the ratio between the pore volume of the negative electrode 101 and the pore volume of the separator 100 is set to 3.2 to 7.4. This ensures that the negative electrode 101 has good electrolyte wetting effect, allowing for smoother movement of the lithium-ion battery between the separator and the negative electrode, thus improving the performance of the secondary battery. In some embodiments, the ratio between the pore volume of the negative electrode 101 and the pore volume of the separator 100 can be one or any two of the following values: 3.2, 3.4, 3.6, 3.8, 4.0, 4.2, 4.4, 4.6, 4.8, 5.0, 5.2, 5.4, 5.6, 5.8, 6.0, 6.2, 6.4, 6.6, 6.8, 7.0, 7.2, and 7.4.

[0052] Optionally, in some embodiments, the ratio between the pore volume of the negative electrode 101 and the pore volume of the positive electrode 102 is 1.2 to 4.3.

[0053] Specifically:

[0054] In this embodiment of the present disclosure, the volume of the pores in the negative electrode film layer disposed on the negative electrode current collector in the negative electrode 101 and the volume of the pores in the positive electrode film layer disposed on the positive electrode current collector in the positive electrode 102 can be adjusted so that the ratio between the pore volume of the negative electrode 101 and the pore volume of the positive electrode 102 satisfies 1.2 to 4.3.

[0055] The pore volume of the negative electrode sheet 101 can be adjusted by modifying the ratio between the negative electrode active material and the conductive agent in the negative electrode film layer, the content of the binder in the negative electrode film layer, the coating speed, coating thickness, coating uniformity, drying temperature and drying time of the negative electrode film layer, and compaction pressure.

[0056] Accordingly, the pore volume of the positive electrode sheet 102 can be adjusted by adjusting the ratio between the positive electrode active material and the conductive agent and binder in the positive electrode film layer, the coating speed, coating thickness, coating uniformity of the positive electrode film layer, the drying temperature and drying time of the positive electrode film layer, and the compaction pressure.

[0057] In this embodiment, the ratio of the pore volume of the negative electrode 101 to the pore volume of the positive electrode 102 is set to 1.2 to 4.3. This ensures that the negative electrode 101 has good electrolyte wetting effect and also ensures that the electric field distribution is uniform during the insertion / extraction process, thereby improving the performance of the secondary battery. In some embodiments, the ratio of the pore volume of the negative electrode 101 to the pore volume of the positive electrode 102 can be one or any two of the following: 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, and 4.3.

[0058] Optionally, in some embodiments, the porosity of the diaphragm 100 is 30% to 60%; exemplaryly, the porosity of the diaphragm 100 can be a range of one or any two of 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, and 60%.

[0059] The porosity of the diaphragm 100 refers to the ratio between the pore volume of the diaphragm 100 and the volume of the diaphragm 100.

[0060] Specifically, referring to Figure 3, when the length of the diaphragm 100 is L0, the width is W0, and the thickness is H0, the porosity S of the diaphragm 100 is:

[0061] Where S represents the porosity of membrane 100.

[0062] It is understandable that the porosity of the separator 100 directly affects its ability to absorb electrolyte. An appropriate porosity can ensure that the electrolyte fully wets the separator 100, improve the ion conduction efficiency, reduce the internal resistance of the secondary battery, and facilitate the rapid transport of ions in the secondary battery. At the same time, the porosity of the separator 100 is also closely related to its mechanical strength. In this embodiment, the porosity of the separator 100 is set to a range of 30% to 60%, which improves the separator's ability to absorb electrolyte while ensuring its mechanical strength.

[0063] Optionally, in some embodiments, the porosity of the positive electrode 102 is 15% to 50%; exemplaryly, the porosity of the positive electrode 102 can be a range of one or any two of 15%, 17%, 19%, 21%, 23%, 25%, 27%, 29%, 31%, 33%, 35%, 37%, 39%, 41%, 43%, 45%, 47%, and 50%.

[0064] In this embodiment, the positive electrode 102 includes a positive current collector and a positive electrode film layer disposed on the positive current collector. The positive current collector is generally an aluminum foil or a composite current collector. It is understood that, in order to ensure the conductivity of the current collector, the density of the aluminum foil and the density of the conductive layer in the composite current collector are generally high. In this embodiment, it is assumed that the positive current collector does not have the ability to absorb electrolyte, and the porosity of the positive electrode film layer in the positive electrode 102 can be determined as the porosity of the positive electrode 102.

[0065] It is understood that the porosity of the positive electrode 102 is related to the energy density and cycle life of the secondary battery. A higher porosity of the positive electrode 102 can provide more active sites, which is beneficial to the wetting of the electrolyte and the transport of ions, thereby improving the energy density and cycle life of the secondary battery. In this embodiment, the porosity of the positive electrode 102 is determined to be 15% to 50%. While ensuring the stability and reliability of the secondary battery, it can also improve the wetting effect of the electrolyte, thereby improving the energy density and cycle life of the secondary battery.

[0066] Optionally, referring to FIG4, the positive electrode 102 includes a positive current collector 1021, and a first positive electrode film layer 1022 and a second positive electrode film layer 1023 disposed on two opposite surfaces of the positive current collector 1021; wherein, the porosity of the first positive electrode film layer 1022 is 15% to 50%, and the porosity of the second positive electrode film layer 1023 is 15% to 50%.

[0067] The length of the first positive electrode film layer 1022 is L 11 Width is W 11 Thickness H 11 In the case of the first positive electrode film layer 1022, the porosity X a for:

[0068] Among them, X a V represents the porosity of the first positive electrode film layer 1022; 21 This represents the pore volume of the first positive electrode film layer 1022.

[0069] Accordingly, the length of the second positive electrode film layer 1023 is L 12 Width is W 12 Thickness H 12 In the case of the first positive electrode film layer 1022, the porosity X b for:

[0070] Among them, X b V represents the porosity of the second positive electrode film layer (1023); 22 Let V represent the pore volume of the second positive electrode film layer 1023. Then, the pore volume of the positive electrode sheet V2 = V21 +V 22 =X a ×L 11 ×W 11 ×H 11 +X b ×L 12 ×W 12 ×H 12 .

[0071] Optionally, in some embodiments, the absolute value of the difference between the porosity of the first positive electrode film layer 1022 and the porosity of the second positive electrode film layer 1023 is 0 to 5%, so that both the first positive electrode film layer 1022 and the second positive electrode film layer 1023 achieve the best electrolyte wetting effect, thereby improving the performance of the secondary battery; for example, the absolute value of the difference between the porosity of the first positive electrode film layer 1022 and the porosity of the second positive electrode film layer 1023 can be a range of one or any two of 0, 1%, 2%, 3%, 4%, and 5%.

[0072] Specifically, the absolute value of the difference between the porosity of the first positive electrode film layer 1022 and the porosity of the second positive electrode film layer 1023 can be expressed as: |X a -X b |≤5% (8)

[0073] Among them, |X a -X b | represents the absolute value of the difference between the porosity of the first positive electrode film layer 1022 and the porosity of the second positive electrode film layer 1023. In this embodiment, the difference between the porosity of the first positive electrode film layer 1022 and the porosity of the second positive electrode film layer 1023 is within the above range, indicating that the porosity of the first positive electrode film layer 1022 and the porosity of the second positive electrode film layer 1023 are highly consistent. This results in the first positive electrode film layer 1022 and the second positive electrode film layer 1023 having similar resistivity and ion transport rate, avoiding significant differences in ion insertion / extraction rates and electrochemical reactions on both sides of the positive electrode during cycling, and improving the cycle performance of the battery.

[0074] In this embodiment of the disclosure, the length L of the first positive electrode film layer 1022 is... 11 The length L of the second positive electrode film layer 1023 12 They can be equal or unequal, and this disclosure does not limit this.

[0075] Optionally, in some embodiments, the width W of the first positive electrode film layer 1022 is... 11 The width W of the second positive electrode film layer 1023 12 The thickness H of the first positive electrode film layer 1022 is equal to that of the other two films. 11 The thickness H of the second positive electrode film 1023 12 equal.

[0076] Optionally, in some embodiments, the porosity of the negative electrode 101 is 30% to 60%; exemplaryly, the porosity of the negative electrode 101 can be a range of one or any two of 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, and 60%.

[0077] In this embodiment, the negative electrode 101 includes a negative current collector and a negative electrode film layer disposed on the negative current collector. The negative current collector is generally a copper foil or a composite current collector. It is understood that, in order to ensure the conductivity of the current collector, the density of the copper foil and the density of the conductive layer in the composite current collector are generally high. In this embodiment, it is assumed that the negative current collector does not have the ability to absorb electrolyte, and the porosity of the negative electrode film layer in the negative electrode 101 can be determined as the porosity of the negative electrode 101.

[0078] It is understood that the porosity of the negative electrode 101 is related to the discharge capacity and cycle life of the secondary battery. In this embodiment, the porosity of the negative electrode 101 is set to 30% to 60%, which can improve the discharge capacity of the secondary battery while ensuring its stability and cycle life.

[0079] Optionally, referring to FIG5, the negative electrode sheet 101 includes a negative electrode current collector 1011, and a first negative electrode film layer 1012 and a second negative electrode film layer 1013 disposed on two opposite surfaces of the negative electrode current collector 1011; wherein, the porosity of the first negative electrode film layer 1012 is 30% to 60%, and the porosity of the second negative electrode film layer 1013 is 30% to 60%.

[0080] The length of the first negative electrode film layer 1012 is L 21 Width is W 21 Thickness H 21 In the case of the first negative electrode film layer 1012, the porosity Y a for:

[0081] Among them, Y a V represents the porosity of the first negative electrode film layer 1012; 31 This represents the pore volume of the first negative electrode film layer 1012.

[0082] Accordingly, the length of the second negative electrode film layer 1013 is L 22 Width is W 22 Thickness H 22 In the case of the second negative electrode film layer 1013, the porosity Y b for:

[0083] Among them, Y b V represents the porosity of the second negative electrode film layer (10¹³). 32 Let V represent the pore volume of the second negative electrode film layer 1013. Then, the pore volume of the negative electrode sheet V3 = V 31 +V 32 =Y a ×L 21 ×W 21 ×H 21 +Y b ×L 22 ×W 22 ×H 22 .

[0084] Optionally, in some embodiments, the absolute value of the difference between the porosity of the first negative electrode film layer 1012 and the porosity of the second negative electrode film layer 1013 is 0 to 5%, so that both the first negative electrode film layer 1012 and the second negative electrode film layer 1013 achieve the best electrolyte wetting effect, thereby improving the performance of the secondary battery; for example, the absolute value of the difference between the porosity of the first negative electrode film layer 1012 and the porosity of the second negative electrode film layer 1013 can be a range of one or any two of 0, 1%, 2%, 3%, 4%, and 5%.

[0085] Specifically, the absolute value of the difference between the porosity of the first negative electrode film layer 1012 and the porosity of the second negative electrode film layer 1013 can be expressed as:

[0086] |Y a -Y b |≤5% (11)

[0087] Among them, |Y a -Y b | represents the absolute value of the difference between the porosity of the first negative electrode film layer 1012 and the porosity of the second negative electrode film layer 1013. In this embodiment, the difference between the porosity of the first negative electrode film layer 1012 and the porosity of the second negative electrode film layer 1013 is within the above range, indicating that the porosity of the first negative electrode film layer 1012 and the porosity of the second negative electrode film layer 1013 are highly consistent. This results in the first negative electrode film layer 1012 and the second negative electrode film layer 1013 having similar resistivity and ion transport rate, avoiding significant differences in ion insertion / extraction rates and electrochemical reactions on both sides of the negative electrode sheet during cycling, which is beneficial for reducing local lithium plating on the negative electrode sheet. In this embodiment, the length L of the first negative electrode film layer 1012 is... 21 The length L of the second negative electrode film layer 1013 22 They can be equal or unequal, and this disclosure does not limit this.

[0088] Optionally, in some embodiments, the width W of the first negative electrode film layer 1012 is... 21 The width W of the second negative electrode film layer 1013 22 The thickness H of the first negative electrode film layer 1012 is equal to that of the other two layers. 21 The thickness H of the second negative electrode film 1013 22 equal.

[0089] Optionally, in some embodiments, the electrolyte density is 1.1 g / cm³. 3 1.5g / cm 3 For example, the density of the electrolyte can be 1.1 g / cm³. 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 and 1.5g / cm 3 The value is within one or both of the above ranges. When the electrolyte density is within the above range, the electrolyte penetration rate and the electromotive force of the secondary battery can be increased, which is beneficial to increasing the capacity of the secondary battery.

[0090] Optionally, in some embodiments, the diaphragm 100 includes a base membrane and a coating disposed on at least one surface of the base membrane. The base membrane includes at least one of polyethylene (PE), polypropylene (PP), and cellulose; the coating includes at least one of a ceramic coating and an adhesive layer.

[0091] Optionally, in some embodiments, the adhesive layer includes at least one of acrylic resin and polyurethane resin.

[0092] Optionally, in some embodiments, the thickness of the base film is 0.003 mm to 0.03 mm. A base film thickness within the above range can ensure that the separator has both high mechanical strength and good ion transport efficiency, which has a positive impact on the safety performance and cycle performance of the battery. In some embodiments, the thickness of the coating is 1 μm to 10 μm. A coating thickness within the above range can ensure that the separator has strong adhesion or thermal stability.

[0093] The aforementioned positive electrode 102 includes a positive current collector 1021 and a positive electrode film layer disposed on the positive current collector 1021. The positive electrode film layer includes a positive electrode active material, which includes a lithium-ion transition metal oxide. The lithium-ion transition metal oxide includes at least one of lithium cobalt oxide, lithium manganese oxide, and lithium nickel cobalt manganese oxide.

[0094] Optionally, in one embodiment, the positive electrode 102 further includes a conductive agent and a binder. The conductive agent may include at least one of conductive carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphene. The binder includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, and tetrafluoroethylene-hexafluoropropylene copolymer.

[0095] In some embodiments, the positive electrode sheet comprises a positive electrode active material, which includes lithium transition metal oxides of Ni, Mn, and Co.

[0096] In some embodiments, the molar ratio of Ni in the lithium transition metal oxide relative to the total amount of metal elements other than Li is 75% to 95%. A molar ratio of Ni within this range can improve the energy density of the battery and enhance its range.

[0097] In some embodiments, the molar ratio of Ni in the lithium transition metal oxide relative to the total amount of metal elements other than Li is 80% to 92%. In some embodiments, the molar ratio of Ni in the lithium transition metal oxide relative to the total amount of metal elements other than Li is 88% to 91%.

[0098] In some embodiments, the average particle size of the lithium transition metal oxide is 5–15 μm, for example, 5 μm, 8 μm, 10 μm, 12 μm, or 15 μm. An average particle size within this range is beneficial for increasing the compaction density of the positive electrode sheet, while also ensuring that the positive electrode sheet has suitable porosity, thereby improving the electrochemical performance of the battery.

[0099] In some embodiments, the positive electrode 102 is prepared as follows: the components used to prepare the positive electrode 102, such as the positive active material, binder and any other components, are dispersed in a solvent such as N-methylpyrrolidone to form a positive electrode slurry; the positive electrode slurry is coated on both sides of the positive electrode current collector 1021 such as aluminum foil; after baking, rolling, cutting and slitting, the positive electrode 102 can be obtained.

[0100] The secondary battery provided in this embodiment also includes a negative electrode 101, a separator 100, and an electrolyte.

[0101] The negative electrode 101 includes a negative current collector 1011 and a negative electrode film layer disposed on the negative current collector 1011. The negative electrode film layer can be a negative electrode active material used in batteries, such as a metal negative electrode material or a non-metal negative electrode material. The metal negative electrode material is preferably a metal foil or alloy compound such as sodium, sodium alloy, tin, or antimony. The non-metal negative electrode material is preferably any one or a combination of at least two of hard carbon, soft carbon, graphite, and silicon suboxide.

[0102] In some embodiments, the negative electrode sheet 101 is prepared as follows: the components used to prepare the negative electrode sheet 101, such as the negative electrode active material, binder and 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 the negative electrode current collector 1011 such as copper foil; after baking, rolling, cutting and slitting, the negative electrode sheet 101 can be obtained.

[0103] The electrolyte acts as a conductor of ions between the positive electrode 102 and the negative electrode 101. The electrolyte can be liquid, gel-like, or entirely solid. In some embodiments, the electrolyte is a liquid electrolyte comprising an electrolyte salt and a solvent. The electrolyte salt is a lithium salt, and the solvent includes cyclic ester solvents and chain ester solvents. In some embodiments, the cyclic ester solvent includes at least one of ethylene carbonate, propylene carbonate, butenyl carbonate, fluoroethylene carbonate, and γ-butyrolactone; the chain ester solvent includes at least one of dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, and diphenyl carbonate. In some embodiments, the organic solvent includes ethylene carbonate, propylene carbonate, and methyl ethyl carbonate.

[0104] In practical applications, the negative electrode 101, the separator 100 and the positive electrode 102 are stacked in sequence and wound to obtain the core 10. The core 10 is then packaged to obtain the bare cell. After baking, the bare cell is injected with electrolyte, formed, resealed and sorted to obtain the above-mentioned secondary battery.

[0105] This disclosure also proposes an electrical device, which includes the aforementioned secondary battery, serving as the power supply for the electrical device.

[0106] The above-described electrical equipment embodiment includes the aforementioned secondary battery and achieves the same technical effect. To avoid repetition, it will not be described again here. For relevant details, please refer to the description of the secondary battery embodiment.

[0107] To make the inventive objectives, technical solutions, and beneficial effects of this disclosure clearer, the present disclosure is further described below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure.

[0108] The present disclosure will now be described in detail through examples.

[0109] Example 1

[0110] (1) Preparation of positive electrode slurry

[0111] The positive electrode active material LiNi with an average particle size of 9.6 μm 0.9 Co 0.05 Mn 0.05 O2 (NCM90), conductive agent acetylene black, binder polyvinylidene fluoride and dispersant polyvinylpyrrolidone (PVP) are mixed evenly in a mass ratio of 97.5:1.2:1.2:0.1 and then uniformly dispersed in 1-methyl-2-pyrrolidone to form a uniform first positive electrode slurry.

[0112] (2) Preparation of positive electrode sheet

[0113] The first positive electrode slurry obtained in step (1) is uniformly coated on the first surface of the positive electrode current collector aluminum foil using a coating machine to obtain the first positive electrode coating; the first positive electrode slurry obtained in step (1) is uniformly coated on the second surface of the positive electrode current collector aluminum foil opposite to the first surface using a coating machine to obtain the second positive electrode coating; then it is placed in an oven and dried at a high temperature of 110°C, and the positive electrode sheet can be prepared by processes such as rolling, cutting, and slitting;

[0114] The positive electrode sheet comprises a first positive electrode coating with a compaction density of 3.55 g / cm³. 3 The compaction density of the first positive electrode film layer and the second positive electrode coating is 3.55 g / cm³. 3 The second positive electrode film layer; the first positive electrode film layer has a length of 6397 mm, a width of 83.8 mm, a thickness of 0.045 mm, a porosity of 35%, and a pore volume of 8443 mm². 3 The second positive electrode film has a length of 6397 mm, a width of 83.8 mm, a thickness of 0.045 mm, a porosity of 35%, and a pore volume of 8443 mm². 3 .

[0115] (3) Preparation of negative electrode slurry

[0116] A uniform first negative electrode slurry was prepared by mixing graphite (average particle size 12.5 μm), acetylene black (electrolyte), styrene-butadiene rubber (SBR) (binder), and carboxymethyl cellulose (CMC) (thickener) at a mass ratio of 96.5:1.5:1.8:0.2 and then dispersing the mixture evenly in deionized water.

[0117] (4) Preparation of negative electrode sheet

[0118] The first negative electrode slurry obtained in step (3) is uniformly coated on the first surface of the negative electrode current collector copper foil using a coating machine to obtain the first negative electrode coating; the first negative electrode slurry obtained in step (3) is uniformly coated on the second surface of the negative electrode current collector copper foil opposite to the first surface using a coating machine to obtain the second negative electrode coating; then it is placed in an oven and dried at a high temperature of 120°C, and the negative electrode sheet can be prepared by processes such as rolling, cutting, and slitting;

[0119] The negative electrode sheet comprises a first negative electrode coating with a compaction density of 1.55 g / cm³. 3 The compaction density of the first negative electrode film layer and the second negative electrode coating is 1.55 g / cm³. 3 The second negative electrode film layer; the first negative electrode film layer has a length of 6501 mm, a width of 86.3 mm, a thickness of 0.062 mm, a porosity of 45%, and a pore volume of 15653 mm². 3 The second negative electrode film has a length of 6501 mm, a width of 86.3 mm, a thickness of 0.062 mm, a porosity of 45%, and a pore volume of 15653 mm². 3 .

[0120] (5) Preparation of the diaphragm

[0121] A polyethylene polymer film with a porosity of 45% was selected as the base membrane for the separator, and a ceramic coating was applied to one side of the base membrane. The separator has a length of 13314 mm, a width of 88.3 mm, a thickness of 0.012 mm, and a pore volume of 6348 mm². 3 .

[0122] (6) Preparation of electrolyte

[0123] The organic solvent ethylene carbonate, the electrolyte lithium salt lithium hexafluorophosphate, and the additives (ethylene carbonate and fluoroethylene carbonate in a 1:1 mass ratio) were mixed in a mass ratio of 80:15:5 and stirred thoroughly under an inert atmosphere to obtain a density of 1.3 g / cm³. 3 The electrolyte.

[0124] (7) Preparation of secondary batteries

[0125] The positive electrode sheet prepared in step (2), the negative electrode sheet prepared in step (4), and the separator prepared in step (5) are wound in a predetermined order to prepare a bare cell. The bare cell is placed in an outer packaging aluminum-plastic film, baked to remove moisture, and then 63.8g of the electrolyte prepared in step (6) is injected. The cell is then vacuum-sealed to prepare a secondary battery.

[0126] Examples 2-3

[0127] The difference between Examples 2 and 3 and Example 1 is as follows:

[0128] In step (7), 60.3g and 67.4g of the electrolyte prepared in step (6) are injected into the bare battery respectively, and vacuum sealing is performed to prepare the secondary battery.

[0129] Examples 4-5

[0130] The difference between Examples 4 and 5 and Example 1 is that:

[0131] In step (5), polyethylene polymer films with porosities of 30% and 50% are selected as the base membranes of the separator, respectively; wherein, the pore volume of the separator using a polyethylene polymer film with a porosity of 30% as the base membrane is 4232 mm². 3 The pore volume of the membrane using a 50% porosity polyethylene polymer film as the base membrane is 8465 mm². 3 .

[0132] Examples 6-7

[0133] The difference between Examples 6 and 7 and Example 1 is that:

[0134] In step (4), while keeping the size of the first negative electrode film layer unchanged, the average particle size of the graphite is adjusted to adjust the compaction density of the first negative electrode film layer to 1.70 g / cm³. 3 and 1.40 g / cm 3 This is to form a first negative electrode film layer with porosities of 30% and 60%, respectively; wherein the compaction density is 1.70 g / cm³. 3 The pore volume of the first negative electrode film is 10435.5 mm². 3 The compacted density is 1.40 g / cm³. 3 The pore volume of the first negative electrode film layer is 20870.5 mm². 3 ;

[0135] In step (4), while keeping the size of the second negative electrode film unchanged, the average particle size of the graphite is adjusted to adjust the compaction density of the second negative electrode film to 1.70 g / cm³. 3 and 1.40 g / cm 3 This is to form a second negative electrode film layer with porosities of 30% and 60%, respectively; wherein the compaction density is 1.70 g / cm³. 3 The pore volume of the second negative electrode film is 10435.5 mm². 3 The compacted density is 1.40 g / cm³. 3 The pore volume of the second negative electrode film is 20870.5 mm². 3 .

[0136] Examples 8-9

[0137] The difference between Examples 8 and 9 and Example 1 is that:

[0138] In step (3), graphite, acetylene black, styrene-butadiene rubber, carboxymethyl cellulose, and other negative electrode active materials with particle sizes of 15.0 μm and 10.5 μm respectively are mixed evenly in a mass ratio of 96.5:1.5:1.8:0.2 and then evenly dispersed in deionized water to prepare uniform second and third negative electrode slurries.

[0139] In step (4), the second negative electrode slurry and the third negative electrode slurry obtained in step (3) are uniformly coated onto the second surface of the copper foil of the negative electrode current collector, opposite to the first surface, using a coating machine to obtain a second negative electrode coating, so that the second negative electrode coating forms a second negative electrode film layer with porosities of 40% and 50%, respectively; wherein, the pore volume of the second negative electrode film layer formed based on the second negative electrode slurry is 13914 mm. 3 The pore volume of the second negative electrode film layer formed based on the third negative electrode slurry is 17392 mm². 3 .

[0140] Examples 10-11

[0141] The difference between Examples 10 and 11 and Example 1 is that:

[0142] In step (2), while keeping the size of the first positive electrode film layer unchanged, the average particle size of NCM90 is adjusted to adjust the compaction density of the first positive electrode film layer to 3.70 g / cm³. 3 and 3.40 g / cm 3 This is to form a first positive electrode film layer with porosities of 15% and 50%, respectively, with a compaction density of 3.70 g / cm³. 3 The pore volume of the first positive electrode film is 3618.5 mm². 3 The compacted density is 3.40 g / cm³. 3 The pore volume of the first positive electrode film is 12061.5 mm². 3 ;

[0143] In step (2), while keeping the size of the second positive electrode film unchanged, the compaction density of the second positive electrode film is adjusted to 3.70 g / cm³ by adjusting the average particle size of NCM90. 3 and 3.40 g / cm 3 This is to form a second positive electrode coating with porosities of 15% and 50%, respectively; wherein the compaction density is 3.70 g / cm³. 3 The pore volume of the second positive electrode film is 3618.5 mm².3 The compacted density is 3.40 g / cm³. 3 The pore volume of the second positive electrode film is 12061.5 mm². 3 .

[0144] Examples 12-13

[0145] The difference between Examples 12-3 and Example 1 is that:

[0146] In step (1), positive electrode active materials LiNi with average particle sizes of 11.5 μm and 7.5 μm are used. 0.9 Co 0.05 Mn 0.05 O2 (NCM90), conductive agent acetylene black, binder polyvinylidene fluoride and dispersant polyvinylpyrrolidone are mixed evenly in a mass ratio of 97.5:1.2:1.2:0.1 and then evenly dispersed in 1-methyl-2-pyrrolidone to prepare uniform second and third positive electrode slurries;

[0147] In step (2), the second and third positive electrode slurries obtained in step (1) are uniformly coated onto the second surface of the positive electrode current collector aluminum foil opposite to the first surface using a coating machine to obtain a second positive electrode coating, so that the second positive electrode coating forms a second positive electrode film layer with porosities of 30% and 40%, respectively; wherein, the pore volume of the second positive electrode film layer formed based on the second positive electrode slurry is 7237 mm². 3 The pore volume of the second positive electrode film formed based on the second positive electrode slurry is 9649 mm². 3 .

[0148] Examples 14-15

[0149] The difference between Examples 14 and 15 and Example 1 is that:

[0150] In step (6), the organic solvent ethylene carbonate, the electrolyte lithium salt lithium hexafluorophosphate, and the additives (ethylene carbonate and fluoroethylene carbonate in a mass ratio of 1:1) are mixed at mass ratios of 85:10:5 and 75:20:5, respectively, and stirred thoroughly under an inert atmosphere to obtain a density of 1.1 g / cm³. 3 and 1.5g / cm 3 The electrolyte.

[0151] Examples 16-17

[0152] The difference between Examples 16 and 17 and Example 1 is that:

[0153] In step (5), the thicknesses of the diaphragms are 0.01 mm and 0.02 mm, respectively; wherein, the pore volume of the 0.01 mm thick diaphragm is 5290 mm².3 The pore volume of a 0.02 mm thick membrane is 7935 mm². 3 .

[0154] Example 18

[0155] The difference between Example 18 and Example 1 is:

[0156] In step (2), the width of both the first positive electrode film and the second positive electrode film is 75.5 mm, and the pore volume of both the first positive electrode film and the second positive electrode film is 7607 mm². 3 ;

[0157] In step (4), the width of both the first negative electrode film and the second negative electrode film is 78 mm, and the pore volume of both the first negative electrode film and the second negative electrode film is 14147.5 mm². 3 ;

[0158] In step (5), the width of the diaphragm is 80 mm, and the pore volume of the diaphragm is 5752 mm². 3 .

[0159] Example 19

[0160] The difference between Example 19 and Example 1 is:

[0161] In step (2), the width of the first positive electrode film is 111 mm, and the width of the second positive electrode film is 110.5 mm; the pore volume of the first and second positive electrode films is 11133 mm². 3 ;

[0162] In step (4), the width of the first negative electrode film and the second negative electrode film is 113 mm; the pore volume of the first negative electrode film and the second negative electrode film is 20495.5 mm². 3 ;

[0163] In step (5), the width of the diaphragm is 115 mm, and the pore volume of the diaphragm is 8268 mm². 3 .

[0164] Example 20

[0165] The difference between Example 20 and Example 1 is as follows:

[0166] In step (2), the lengths of both the first and second positive electrode films are 3045 mm; the pore volumes of both the first and second positive electrode films are 4019 mm². 3 ;

[0167] In step (4), the lengths of both the first and second negative electrode films are 3208 mm; the pore volumes of both the first and second negative electrode films are 7724 mm². 3 ;

[0168] In step (5), the length of the diaphragm is 6676 mm, and the pore volume of the diaphragm is 3183 mm². 3 .

[0169] Example 21

[0170] The difference between Example 21 and Example 1 is that:

[0171] In step (2), the lengths of both the first and second positive electrode films are 11345 mm; the pore volumes of both the first and second positive electrode films are 14973.5 mm². 3 ;

[0172] In step (4), the lengths of both the first and second negative electrode films are 11460 mm; the pore volumes of both the first and second negative electrode films are 27593 mm². 3 ;

[0173] In step (5), the length of the diaphragm is 23262 mm, and the pore volume of the diaphragm is 11092 mm². 3 .

[0174] Comparative Examples 1-2

[0175] The difference between Comparative Examples 1 and 2 and Example 1 is as follows:

[0176] In step (7), 56.7g and 70.9g of the electrolyte prepared in step (6) are injected into the bare battery respectively, and vacuum sealing is performed to prepare the secondary battery.

[0177] The components and parameters of the secondary batteries prepared in each embodiment and comparative example are shown in Table 1.

[0178] Table 1

[0179] It should be noted that L0, W0, H0, and L in Table 1... 11 W 11 H 11 L 12 W 12 H 12 L 21 W 21 H 21 L 22 W 22 H22 The unit is mm; the units for V0, V1, V2, and V3 are mm. 3 The unit of ρ is g / cm³. 3 The unit of m is g.

[0180] Test method:

[0181] (1) Cyclic test method for secondary batteries: In an environment of 25±3℃, step 1. rest for 30 minutes; step 2. charge at a constant current of 2.0C to the upper limit cutoff voltage, and then switch to constant voltage to 0.02C to end; step 3. rest for 30 minutes; step 4. discharge at a constant current of 1.0C to the lower limit cutoff voltage; repeat steps 1 to 4. When the discharge capacity of the Nth cycle divided by the discharge capacity of the first cycle is less than 80%, the number of cycles is recorded as N.

[0182] (2) Secondary battery storage test method: Step 1. First, place the battery in an environment of 25±3℃ for 30 minutes, then charge it at a constant current rate of 1 / 3C to the upper limit cutoff voltage; then switch to constant voltage to 0.02C; discharge it at a constant current rate of 1 / 3C to the lower limit cutoff voltage, and record the discharged capacity as the initial capacity; finally, charge it at a constant current rate of 1 / 3C to the upper limit cutoff voltage, then switch to constant voltage to 0.02C. Step 2. Place the battery in an environment of 60±3℃ for 300 days. Step 3. Place the battery in an environment of 25±3℃ for 30 minutes, then discharge it at a constant current rate of 1 / 3C to the lower limit cutoff voltage, and record the discharged capacity as the residual capacity. Divide the residual capacity by the initial capacity to record the residual capacity retention rate. Step 4. Charge the battery at a constant current rate of 1 / 3C to the upper limit cutoff voltage, then switch to constant voltage to 0.02C; discharge it at a constant current rate of 1 / 3C to the lower limit cutoff voltage, and record the discharged capacity as the recovered capacity. Divide the recovered capacity by the initial capacity to record the recovered capacity retention rate.

[0183] The lower and upper cutoff voltages mentioned above are 2.8V and 4.0V, respectively. The secondary batteries fabricated in each embodiment and comparative example were subjected to the above tests, and the test data are shown in Table 2.

[0184] Table 2

[0185] According to the test data above, compared with Comparative Example 1 and Comparative Example 2, Examples 1 to 21 provided in this disclosure control the liquid retention of the secondary battery between 0.85×(V0 / 1000)×ρ and 0.95×(V0 / 1000)×ρ, while maintaining the number of charge-discharge cycles of the secondary battery above 1000, and can also increase the residual storage capacity retention rate to above 40% and the storage recovery capacity retention rate to above 75%. Therefore, the total electrolyte capacity of the secondary battery is determined to be 0.85 to 0.95 times the mass of electrolyte that can be contained by the sum of the pore volumes of the separator, the positive electrode, and the negative electrode in the core. This satisfies the electrolyte replenishment requirements during the charge-discharge cycle and storage of the secondary battery. During the charge-discharge cycle, when the secondary battery expands inward due to the constraint of the casing, only a small amount of electrolyte, or even no electrolyte, is squeezed out to the sides of the core. This makes the electrolyte concentration at the sides of the core basically the same as the electrolyte concentration at other locations in the secondary battery, and the polarization is also basically the same. This reduces the risk of lithium plating at the sides of the core and improves the cycle life, cycle capacity retention, and storage performance of the secondary battery.

[0186] The above provides a detailed description of a secondary battery and electrical device provided by this disclosure. Specific examples have been used to illustrate the principles and implementation methods of this disclosure. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this disclosure. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this disclosure. Therefore, the content of this specification should not be construed as a limitation of this disclosure.

Claims

1. A secondary battery, comprising a winding core and an electrolyte, wherein the winding core comprises a positive electrode, a separator, and a negative electrode sequentially stacked; the secondary battery, at 0% SOC, satisfies: 0.85×(V0 / 1000)×ρ≤m≤0.95×(V0 / 1000)×ρ, in, mg represents the liquid content of the secondary battery; V0mm 3 This represents the total volume of pores in the core; the total volume of pores in the core is the sum of the pore volume of the diaphragm, the pore volume of the positive electrode sheet, and the pore volume of the negative electrode sheet; ρ g / cm 3 This indicates the density of the electrolyte.

2. The secondary battery according to claim 1, wherein the ratio between the pore volume of the negative electrode sheet and the pore volume of the separator is 3.2 to 7.

4.

3. The secondary battery according to claim 1, wherein the ratio between the pore volume of the negative electrode and the pore volume of the positive electrode is 1.2 to 4.

3.

4. The secondary battery according to claim 1, wherein the porosity of the separator is 30% to 60%.

5. The secondary battery according to claim 1, wherein the porosity of the positive electrode sheet is 15% to 50%.

6. The secondary battery according to claim 1, wherein the positive electrode sheet includes a positive current collector, and a first positive electrode film layer and a second positive electrode film layer disposed on two opposite surfaces of the positive current collector; in, The porosity of the first positive electrode film layer is 15% to 50%, and the porosity of the second positive electrode film layer is 15% to 50%.

7. The secondary battery according to claim 6, wherein the absolute value of the difference between the porosity of the first positive electrode film and the porosity of the second positive electrode film is 0 to 5%.

8. The secondary battery according to claim 1, wherein the porosity of the negative electrode sheet is 30% to 60%.

9. The secondary battery according to claim 1, wherein the negative electrode sheet includes a negative current collector, and a first negative electrode film layer and a second negative electrode film layer disposed on two opposite surfaces of the negative current collector; in, The porosity of the first negative electrode film layer is 30% to 60%, and the porosity of the second negative electrode film layer is 30% to 60%.

10. The secondary battery according to claim 9, wherein the absolute value of the difference between the porosity of the first negative electrode film and the porosity of the second negative electrode film is 0 to 5%.

11. The secondary battery according to claim 1, wherein the density of the electrolyte is 1.1 g / cm³. 3 ~1.5g / cm 3 .

12. The secondary battery according to any one of claims 1 to 11, wherein the secondary battery includes a casing, the casing being a columnar structure.

13. An electrical device comprising a secondary battery as described in any one of claims 1 to 12, wherein the secondary battery serves as a power supply for the electrical device.

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