Positive electrode sheet material, positive electrode sheet, and battery

Abstract

A positive electrode sheet material, a positive electrode sheet, and a battery. The positive electrode sheet material comprises a positive electrode active material, a conductive agent, and a binder; the positive electrode active material comprises manganese dioxide, and the specific surface area range of manganese dioxide is 10 g / cm2 to 26 g / cm2; the conductive agent comprises a first conductive agent, and the specific surface area range of the first conductive agent is 10 g / cm2 to 60 g / cm2.

Description

Positive electrode material, positive electrode and battery

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on February 4, 2024, with application number 202410157530.0. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery technology, and in particular to a positive electrode sheet material, a positive electrode sheet and a battery. Background Art

[0003] Currently, commercial lithium-manganese dioxide batteries have poor electrochemical performance after being stored at high temperatures (>85°C), resulting in the batteries being unable to meet the application requirements of some scenarios. To improve the electrical performance of batteries after high-temperature storage, researchers have conducted research on cathode processes, electrolytes, and other aspects. SUMMARY OF THE INVENTION

[0004] However, for higher temperatures (such as 100°C), the battery still has problems such as large weight loss rate, severe swelling, and a sharp increase in internal resistance after high-temperature storage. The poor high-temperature storage stability of the battery makes it unable to meet the performance requirements of product applications.

[0005] The present application provides a positive electrode sheet material. The positive electrode sheet material includes a positive electrode active material, a conductive agent, and a binder; wherein the positive electrode active material includes manganese dioxide, and the specific surface area of ​​manganese dioxide is in the range of 10 g / cm 2 ~26 g / cm 2 The conductive agent includes a first conductive agent, and the specific surface area of ​​the first conductive agent is in the range of 10 g / cm 2 ~60 g / cm 2 .

[0006] The present application also provides a positive electrode sheet, which includes a positive electrode current collector and a positive electrode sheet material coated on the positive electrode current collector.

[0007] The present application also provides a battery, which includes a battery housing, an electrolyte, a negative electrode sheet, a separator, and a positive electrode sheet located within the battery housing. Beneficial effects

[0008] The present application provides a positive electrode sheet material, a positive electrode sheet, and a battery. The positive electrode sheet material of the present application uses manganese dioxide with a low specific surface area as the positive electrode active material. Since the specific surface area of ​​the positive electrode active material manganese dioxide is small, the catalytic activity during high-temperature storage is low, which can inhibit side reactions in the electrolyte, reduce gas generation, and improve the swelling of the battery during high-temperature storage. Therefore, it can effectively improve the high-temperature storage stability of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] FIG1 is a battery discharge capacity curve diagram provided in this application. Modes for Carrying Out the Invention

[0010] The present application provides a positive electrode sheet material, which includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes manganese dioxide, and the specific surface area of ​​manganese dioxide is in the range of 10 g / cm 2 ~26 g / cm 2 The conductive agent includes a first conductive agent, and the specific surface area of ​​the first conductive agent is in the range of 10 g / cm 2 ~60 g / cm 2 .

[0011] Manganese dioxide is the positive electrode active material of the battery. Its physicochemical properties have a great influence on the electrical performance of the battery. Among them, the specific surface area characteristics of manganese dioxide can provide more active sites during the discharge process, thereby improving the discharge capacity of the battery. Because manganese dioxide itself has a certain catalytic activity, under high temperature environment, manganese dioxide with a large specific surface area provides more active sites to catalyze the side reactions of the electrolyte lithium salt in the battery, generating gas, causing the battery to swell, thereby affecting the electrical performance of the battery. In order to solve the above problems, the positive electrode sheet material of this application adopts a low specific surface area (10 g / cm 2 ~26 g / cm 2 ) as the positive electrode active material of the battery. Because the specific surface area of ​​the positive electrode active material manganese dioxide is small, the catalytic activity during high-temperature storage is low. It can inhibit the side reaction of organic solvents and lithium salts in the electrolyte, reduce gas generation, and improve the swelling of the battery during high-temperature storage. Therefore, the battery can still maintain its original electrical performance after high-temperature storage, which can effectively improve the high-temperature storage stability of the battery.

[0012] In the positive electrode sheet material of the present application, the mass ratio of the positive electrode active material, conductive agent, and binder is (85-90):(5-10):(5-10). That is, in terms of mass percentage, the total mass percentage of the positive electrode sheet material is 100%, of which the mass percentage of the positive electrode active material is 85%-90%, the mass percentage of the conductive agent is 5%-10%, and the mass percentage of the binder is 5%-10%. When the content of each component of the positive electrode sheet material of the battery is within the above range, the prepared battery has excellent high-temperature storage stability.

[0013] In some embodiments, the conductive agent of the present application further comprises a second conductive agent, and the specific surface area of ​​the second conductive agent is in the range of 350 g / cm 2 ~600 g / cm 2 .

[0014] In order to improve the high temperature storage stability of the battery, the positive electrode material of this application adopts manganese dioxide with low specific surface area, but compared with the manganese dioxide with large specific surface area commonly used in the related art (specific surface area is usually 28 g / cm 2 ~38 g / cm 2 ), the reduction in the specific surface area of ​​manganese dioxide may have a certain impact on the large current pulse performance of the battery. In order to improve the high-temperature storage stability of the battery while reducing the impact on the large current pulse performance of the battery, this embodiment further adds a second conductive agent with a larger specific surface area to the conductive agent of the battery positive electrode material, and utilizes the conductive agent with a large specific surface area to improve the large current pulse capability of the battery.

[0015] The conductive agent in this embodiment includes a first conductive agent and a second conductive agent. The specific surface area of ​​the first conductive agent is in the range of 10 g / cm 2 ~60 g / cm 2 The first conductive agent can be one or more of conductive graphite, conductive carbon black and acetylene black; the specific surface area of ​​the second conductive agent is in the range of 350 g / cm 2 ~600 g / cm 2 The second conductive agent can be one or more of Ketjen black, graphene, and carbon nanotubes. When the specific surface areas of the first and second conductive agents are within the aforementioned ranges, the resulting battery exhibits superior high-current pulse performance. However, when the specific surface areas of the first and second conductive agents are below or above the aforementioned ranges, the process becomes more difficult and may even reduce battery performance.

[0016] This embodiment uses manganese dioxide with a low specific surface area as the positive electrode active material in the positive electrode plate material, and at the same time adds a second conductive agent with a large specific surface area to the conductive agent, which improves the high-temperature storage stability of the battery without affecting the high-current pulse performance of the battery, thereby effectively improving the performance of the battery.

[0017] In the conductive agent of the present application, the mass ratio of the first conductive agent to the second conductive agent is (4.5-9.9): (0.1-0.5). That is, in terms of mass percentage, the total mass percentage of the positive electrode sheet material is 100%, of which the mass percentage of the positive electrode active material is 85%-90%, the mass percentage of the first conductive agent is 4.5%-9.9%, the mass percentage of the second conductive agent is 0.1%-0.5%, and the mass percentage of the binder is 5%-10%. When the content of the second conductive agent is within the above range, it can effectively improve the high-current pulse performance of the battery, minimize the impact on the battery stability, and improve the overall performance of the battery.

[0018] In the conductive agent of the present application, the first conductive agent, as a conventional conductive agent, may comprise one or two or more components. For example, the first conductive agent may include conductive carbon black (or acetylene black) and conductive graphite, wherein the mass ratio of conductive carbon black (or acetylene black) to conductive graphite may be (1-3):(3.5-6.9). In other embodiments, the second conductive agent, as a conductive agent with a large specific surface area, may also comprise one or two or more components. The specific design can be based on the battery's process and performance requirements.

[0019] The binder of the present application may be one or more of polytetrafluoroethylene, polyacrylic acid and polyacrylate, and the binder is used to increase the bonding performance of the positive electrode sheet material.

[0020] The present application also provides a positive electrode plate, which includes a positive electrode current collector and a positive electrode plate material coated on the positive electrode current collector.

[0021] The positive electrode sheet material includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes manganese dioxide, and the specific surface area of ​​manganese dioxide is in the range of 10 g / cm 2 ~26 g / cm 2 The conductive agent includes a first conductive agent, and the specific surface area of ​​the first conductive agent is in the range of 10 g / cm 2 ~60 g / cm 2 .

[0022] The material of the positive electrode current collector may be a metal, such as aluminum or copper, but is not limited thereto.

[0023] The positive electrode sheet is formed by coating a mixture slurry formed by the positive electrode sheet material on the surface of the positive electrode current collector, drying it, and rolling it.

[0024] In some embodiments, the positive electrode plate may also be a film layer formed of a positive electrode plate material.

[0025] The present application also provides a battery, which includes a battery casing and an electrolyte, a negative electrode plate, a separator and a positive electrode plate located in the battery casing.

[0026] The positive electrode sheet includes a positive electrode current collector and a positive electrode sheet material coated on the positive electrode current collector. The positive electrode sheet material includes a positive electrode active material, a conductive agent, and a binder. The positive electrode active material includes manganese dioxide, and the specific surface area of ​​manganese dioxide is in the range of 10 g / cm 2 ~26 g / cm 2 The conductive agent includes a first conductive agent, and the specific surface area of ​​the first conductive agent is in the range of 10 g / cm 2 ~60 g / cm 2 .

[0027] The battery casing includes a shell and a bottom cover. The shell and bottom cover enclose a cavity in which the negative electrode sheet, separator, and positive electrode sheet are stacked in sequence. The battery casing can be made of metal, such as steel or aluminum.

[0028] The negative electrode plate includes a negative electrode plate material, and the negative electrode plate material includes lithium-containing metal or lithium-containing compound. For example, the negative electrode plate can be metallic lithium, lithium alloy, etc., or it can be composed of a negative electrode current collector and a negative electrode plate material coated on the negative electrode current collector.

[0029] The electrolyte is contained in the containing cavity, and the electrolyte may be an organic electrolyte system, such as lithium perchlorate + propylene carbonate (PC) + ethylene glycol dimethyl ether (DME) + 1,3-dioxolane (DOL) system, but is not limited thereto.

[0030] In the present application, the battery may be a lithium-manganese dioxide battery, such as a CR2032 button-type lithium-manganese dioxide battery, but is not limited thereto.

[0031] The electrode material, positive electrode sheet and battery of the present application are described below through specific examples.

[0032] Experimental methods:

[0033] 1. Preparation of batteries

[0034] 1) Mix the positive electrode active material, conductive agent and binder used for the positive electrode sheet material to prepare the positive electrode slurry, evenly apply the positive electrode slurry to the positive electrode collector, dry and roll to obtain the positive electrode sheet;

[0035] 2) The negative electrode sheet, separator, and positive electrode sheet are stacked in sequence in the battery casing, the bottom cover is assembled, and the electrolyte is injected into the battery casing to obtain a CR2032 battery.

[0036] The positive electrode active material may be, but is not limited to, electrolytic manganese dioxide that has been subjected to high temperature heat treatment, and the specific surface area of ​​manganese dioxide is 10 g / cm 2 ~26 g / cm 2 between; the conductive agent can be one or more of conductive graphite, conductive carbon black, acetylene black, Ketjen black, graphene and carbon nanotubes; the binder can be one or more of polytetrafluoroethylene, polyacrylic acid and polyacrylate; the negative electrode plate can be but not limited to metallic lithium; the electrolyte can be but not limited to lithium perchlorate + propylene carbonate (PC) + ethylene glycol dimethyl ether (DME) + 1,3-dioxolane (DOL) system.

[0037] Example 1

[0038] The positive electrode sheet materials include manganese dioxide, conductive carbon black, conductive graphite and binder;

[0039] The specific surface area of ​​manganese dioxide is 10 g / cm 2 ;

[0040] The specific surface area of ​​conductive carbon black and conductive graphite is 10 g / cm 2 ~60 g / cm 2 ;

[0041] The mass ratio of manganese dioxide, conductive carbon black, conductive graphite, and binder is 86:3:4:7;

[0042] The positive electrode sheet material of Example 1 was prepared into a CR2032 battery according to the battery preparation method.

[0043] Example 2

[0044] The positive electrode sheet materials include manganese dioxide, conductive carbon black, conductive graphite and binder;

[0045] The specific surface area of ​​manganese dioxide is 15.5 g / cm 2 ;

[0046] The specific surface area of ​​conductive carbon black and conductive graphite is 10 g / cm 2 ~60 g / cm 2 ;

[0047] The mass ratio of manganese dioxide, conductive carbon black, conductive graphite, and binder is 86:3:4:7;

[0048] The positive electrode sheet material of Example 2 was prepared according to the battery preparation method to obtain a CR2032 battery.

[0049] Example 3

[0050] The positive electrode sheet materials include manganese dioxide, conductive carbon black, conductive graphite and binder;

[0051] The specific surface area of ​​manganese dioxide is 20.3 g / cm 2 ;

[0052] The specific surface area of ​​conductive carbon black and conductive graphite is 10 g / cm 2 ~60 g / cm 2 ;

[0053] The mass ratio of manganese dioxide, conductive carbon black, conductive graphite, and binder is 86:3:4:7;

[0054] The positive electrode sheet material of Example 3 was prepared according to the battery preparation method to obtain a CR2032 battery.

[0055] Example 4

[0056] The positive electrode sheet materials include manganese dioxide, conductive carbon black and binder;

[0057] The specific surface area of ​​manganese dioxide is 10 g / cm 2 ;

[0058] The specific surface area of ​​conductive carbon black is 10 g / cm 2 ~60 g / cm 2 ;

[0059] The mass ratio of manganese dioxide, conductive carbon black, and binder is 86:7:7;

[0060] The positive electrode sheet material of Example 4 was prepared according to the battery preparation method to obtain a CR2032 battery.

[0061] Example 5

[0062] The positive electrode sheet materials include manganese dioxide, conductive carbon black, graphene and binder;

[0063] The specific surface area of ​​manganese dioxide is 10 g / cm 2 ;

[0064] The specific surface area of ​​conductive carbon black is 10 g / cm 2 ~60 g / cm 2 , the specific surface area of ​​graphene is 500 g / cm 2 ~600 g / cm 2 ;

[0065] The mass ratio of manganese dioxide, conductive carbon black, graphene, and binder is 86:6.9:0.1:7;

[0066] The positive electrode sheet material of Example 5 was prepared according to the battery preparation method to obtain a CR2032 battery.

[0067] Comparative Example 1

[0068] The positive electrode sheet materials include manganese dioxide, conductive carbon black, conductive graphite and binder;

[0069] The specific surface area of ​​manganese dioxide is 32 g / cm 2 ;

[0070] The specific surface area of ​​conductive carbon black and conductive graphite is 10 g / cm 2 ~60 g / cm 2 ;

[0071] The mass ratio of manganese dioxide, conductive carbon black, conductive graphite, and binder is 86:3:4:7;

[0072] The positive electrode sheet material of Comparative Example 1 was prepared according to the battery preparation method to obtain a CR2032 battery.

[0073] Comparative Example 2

[0074] The positive electrode sheet materials include manganese dioxide, conductive carbon black, graphene and binder;

[0075] The specific surface area of ​​manganese dioxide is 10 g / cm 2 ; Graphene surface area > 600 g / cm 2 ;

[0076] The mass ratio of manganese dioxide, conductive carbon black, graphene, and binder is 86:6.9:0.1:7;

[0077] Comparative Example 2 uses the same ingredients as Example 5, but in Comparative Example 2, the specific surface area of ​​the graphene (second conductive agent) used is greater than 600 g / cm 2 This makes it difficult to form a film of the positive electrode sheet material, making it difficult to form a positive electrode sheet and impossible to proceed with subsequent battery preparation steps.

[0078] It should be noted that the binder in Examples 1 to 5 and Comparative Examples 1 and 2 may be polytetrafluoroethylene.

[0079] 2. High temperature storage experiment

[0080] CR2032 batteries prepared in Examples 1, 2, 3, 4, 5, and Comparative Example 1 were stored at 100°C for 80 days. The batteries were then subjected to a 15mA current pulse at room temperature to evaluate their pulse load capability. The change in battery height was used as a measure of battery swelling during storage. The changes in pulse load voltage, weight loss, and swelling of the batteries before and after 100°C storage are shown in Table 1.

[0081] Table 1 Pulse load voltage, weight loss rate, and expansion rate of batteries before and after 100℃ high-temperature storage

[0082]

[0083] Among them, the new power in Table 1 represents the battery before high-temperature storage at 100°C.

[0084] The results of Examples 1-4 and Comparative Example 1 indicate that Examples 1-4 are batteries prepared using low-surface-area manganese dioxide, while Comparative Example 1 is a battery prepared using conventional high-surface-area manganese dioxide. In Table 1, the pulse load voltage loss, weight loss, and expansion rate of the batteries of Examples 1-4 after 80 days of storage at 100°C are all lower than those of the battery of Comparative Example 1, demonstrating that low-surface-area manganese dioxide as the positive electrode active material can improve battery stability at high temperatures.

[0085] The results of Examples 1 to 3 and Comparative Example 1 show that the high current pulse load voltage of the new battery in Comparative Example 1 is higher than that in Examples 1 to 3, indicating that manganese dioxide with a low specific surface area will affect the high current pulse capability of the battery to a certain extent. This may be because the active sites of manganese dioxide with a low specific surface area are reduced during the discharge process, resulting in a weakening of the high current pulse capability of the battery and a decrease in the load voltage.

[0086] The results of Examples 4 and 5 show that: in Example 4, no second conductive agent with a large specific surface area was added, while in Example 5, a second conductive agent (graphene) with a large specific surface area was added. The large current pulse load voltage of Example 5 was higher than that of Example 4, indicating that the combination of manganese dioxide with a low specific surface area and a conductive agent with a large specific surface area can improve the large current pulse performance of the battery.

[0087] In summary, the results of Examples 1 to 5 and Comparative Example 1 show that the battery prepared by the positive electrode plate material using manganese dioxide with a low specific surface area of ​​the present application can effectively improve the high-temperature storage stability of the battery; the battery prepared by the positive electrode plate material using manganese dioxide with a low specific surface area and a second conductive agent with a large specific surface area of ​​the present application can improve the high-temperature storage stability of the battery while improving the large current pulse performance.

[0088] 3. Discharge capacity

[0089] Figure 1 shows a comparative diagram of the relationship between discharge capacity (mAh) and voltage (V) for Examples 1, 2, 3, and Comparative Example 1. As can be seen from Figure 1, the discharge capacity trends for Examples 1 through 3 are similar to those for Comparative Example 1, indicating that using low-surface-area manganese dioxide as the positive electrode active material has little effect on the battery's discharge capacity, specifically, on the capacity utilization of the manganese dioxide.

[0090] This application provides a positive electrode sheet material, a positive electrode sheet, and a battery. The positive electrode sheet material of this application uses low-specific-surface-area manganese dioxide as the positive electrode active material to improve the battery's electrical performance after high-temperature storage. A second conductive agent with a larger specific surface area is added to the positive electrode sheet material to enhance the battery's high-current pulse load capacity. By combining low-specific-surface-area manganese dioxide with a conductive agent with a larger specific surface area, this application effectively improves the battery's high-temperature storage stability and high-current pulse performance.

Claims

1. A positive electrode sheet material, comprising a positive electrode active material, a conductive agent and a binder; in, The positive electrode active material includes manganese dioxide, and the specific surface area of the manganese dioxide is in the range of 10 g / cm 2 ~26 g / cm 2 ; The conductive agent includes a first conductive agent, and the specific surface area of the first conductive agent is in the range of 10 g / cm 2 ~60 g / cm 2 .

2. The positive electrode sheet material according to claim 1, wherein: The mass ratio of the positive electrode active material, the conductive agent and the binder is (85-90): (5-10): (5-10).

3. The positive electrode sheet material according to claim 2, wherein: The conductive agent further includes a second conductive agent, and the specific surface area of the second conductive agent is in the range of 350 g / cm 2 ~600 g / cm 2 .

4. The positive electrode sheet material according to claim 3, wherein: In the conductive agent, the mass ratio of the first conductive agent to the second conductive agent is (4.5-9.9): (0.1-0.5).

5. The positive electrode sheet material according to any one of claims 1 to 4, wherein: The first conductive agent includes one or more of conductive graphite, conductive carbon black and acetylene black.

6. The positive electrode sheet material according to any one of claims 3 to 4, wherein: The second conductive agent includes one or more of Ketjen black, graphene, and carbon nanotubes.

7. The positive electrode sheet material according to any one of claims 1 to 4, wherein: The binder includes one or more of polytetrafluoroethylene, polyacrylic acid and polyacrylate.

8. A positive electrode sheet comprising a positive electrode current collector and the positive electrode sheet material according to any one of claims 1 to 7 coated on the positive electrode current collector.

9. A battery comprising a battery housing, an electrolyte, a negative electrode sheet, a separator and the positive electrode sheet according to claim 8 located in the battery housing.

10. The battery according to claim 9, wherein The negative electrode plate includes a negative electrode plate material, and the negative electrode plate material includes a lithium-containing metal or a lithium-containing compound.

11. The battery according to claim 9 or 10, wherein The pulse load voltage of the battery after being stored at a high temperature of 100° C. for 80 days is in the range of 2.3884 V to 2.8385 V.

12. The battery according to claim 9 or 10, wherein The weight loss rate of the battery after being stored at a high temperature of 100° C. for 80 days is in the range of 0.01% to 0.03%.

13. The battery according to claim 9 or 10, wherein The expansion rate of the battery after being stored at a high temperature of 100° C. for 80 days is in the range of 0.01% to 0.10%.

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