Battery cell and battery

Abstract

The utility model provides a battery cell and battery, including first pole piece, second pole piece and diaphragm, said diaphragm is provided between the first pole piece and the second pole piece, the battery cell is formed by the first pole piece, diaphragm and second pole piece laminating and winding; the first pole piece comprises a first end and a second end, the first end is a winding starting point of the first pole piece, the second end is a winding end point of the first pole piece, the first pole piece comprises a first current collector, a first safety coating and a first active material layer, a first wall surface of the first current collector comprises a first part and a second part which are connected with each other, and the first wall surface of the first current collector comprises a second part. The first part is located on the side, close to the first end, of the second part. The first safety coating is arranged on the second part, the resistance of the first safety coating is greater than that of the first current collector, and the first active material layer is coated on the first safety coating; the first active material layer is also coated on the first portion. The problem that the battery cannot give consideration to both safety and energy density can be effectively solved.

Description

Technical Field

[0001] The utility model relates to the technical field of new energy, and in particular to a battery cell and a battery. Background Art

[0002] In modern soft-pack battery technology, the requirements for the battery life and safety performance of lithium-ion batteries are gradually increasing. However, to increase the energy density, the thickness of the substrate needs to be reduced. More active materials need to be stuffed into the same space, which leads to a significant reduction in the safety performance of lithium-ion batteries, especially the heavy object impact test, which high-energy-density batteries basically cannot pass. When the battery is impacted by gravity, the first current collector in the battery cell will be damaged or even broken, puncturing the diaphragm and causing a short circuit inside the battery. After a short circuit occurs inside the battery, a large amount of heat will be released quickly, causing the battery to catch fire, affecting the safety performance of the battery. Increasing the thickness of the first current collector or coating the first current collector with a full protective layer can improve the safety performance of the battery, but both will reduce the energy density of the battery cell. Therefore, it is necessary to provide a battery that is safer to use and has a higher energy density. Utility Model Content

[0003] The utility model aims to solve at least one of the technical problems existing in the prior art. To this end, the utility model proposes a battery cell that can effectively solve the problem that the battery cannot take into account both safety and energy density.

[0004] The utility model also provides a battery.

[0005] According to an embodiment of the first aspect of the utility model, a battery cell includes a first pole piece, a second pole piece and a diaphragm, the diaphragm is arranged between the first pole piece and the second pole piece, and the battery cell is formed by stacking and winding the first pole piece, the diaphragm and the second pole piece; the first pole piece includes a first end and a second end, the first end is the winding starting point of the first pole piece, and the second end is the winding end point of the first pole piece, the first pole piece includes a first current collector, a first safety coating and a first active material layer, the first current collector includes a first part and a second part connected to each other, the end of the first part facing away from the second part is the first end, and the end of the second part facing away from the first part is the second end; the first safety coating is arranged on the second part, the resistance of the first safety coating is greater than the resistance of the first current collector, and the first active material layer is coated on the first safety coating; the first active material layer is also coated on the first part.

[0006] A battery cell according to an embodiment of the first aspect of the utility model has at least the following beneficial effects: by setting a first safety coating on the first current collector, wherein the first safety coating has a large resistance. When the battery is impacted, the first current collector punctures the diaphragm and causes a short circuit inside the battery, the first safety coating separates the first current collector and the active material, and the current needs to pass through the first safety coating with a large resistance, thereby reducing the discharge power of the battery when it is short-circuited, reducing the speed at which the heat generated by the battery is avoided to prevent the battery from catching fire, and making the battery safer. When the battery cell is impacted, the outer pole piece is easily damaged, so the first safety coating is only set on the first current collector outside the battery cell, and more first active material layers are set on the first current collector inside the battery cell, thereby increasing the energy density of the battery cell.

[0007] According to some embodiments of the present invention, the length of the second portion is L1, the length of the first pole piece is L2, and 0.6≤L1 / L2≤0.9.

[0008] According to some embodiments of the present invention, the first pole piece is a positive pole piece.

[0009] According to some embodiments of the present invention, the first current collector of the positive electrode sheet is an aluminum foil, and the second current collector of the negative electrode sheet is a copper foil, and the thickness of the copper foil does not exceed 6 μm.

[0010] According to some embodiments of the present invention, a buffer layer is disposed on the outermost side of the battery core, and the material of the buffer layer is one of silicone, rubber or resin.

[0011] According to some embodiments of the present invention, the resistance of the first safety coating is not less than 0.2Ω and not more than 5Ω.

[0012] According to some embodiments of the present invention, the second pole piece includes a third end and a fourth end, the third end is the starting point of winding the second pole piece, and the fourth end is the end point of winding the second pole piece, the second pole piece includes a second current collector, a second safety coating and a second active material layer, the second current collector of the second pole piece includes a third part and a fourth part connected to each other, an end of the third part away from the fourth part is the third end, and an end of the fourth part away from the second part is the fourth end; the second safety coating is arranged on the fourth part, and the second active material layer is coated on the second safety coating; the second active material layer is also coated on the third part.

[0013] According to some embodiments of the present invention, the sum of the thickness of the first active material layer on the second part and the thickness of the first safety coating layer is equal to the thickness of the first active material layer on the first part.

[0014] According to some embodiments of the present invention, the thickness of the first safety coating is not less than 5 μm.

[0015] A battery according to an embodiment of the second aspect of the utility model comprises the battery cell described in any one of the above embodiments.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through the practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the battery cell of the utility model;

[0018] Figure 2 It is a schematic diagram of the structure of the pole piece of the utility model in the length direction;

[0019] Figure 3 It is a cross-sectional schematic diagram of the position of the first safety coating on the pole piece of the utility model.

[0020] Figure Number:

[0021] 1. First pole piece; 11. First current collector; 12. First active material layer; 13. First part; 14. Second part; 2. Second pole piece; 3. Diaphragm; 4. Buffer layer; 5. First safety coating. DETAILED DESCRIPTION

[0022] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0023] In the description of the present invention, it should be understood that the descriptions involving orientation, such as the orientation or positional relationship indicated as up, down, etc., are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0024] In the description of the present utility model, "a plurality" means more than two. If there is a description of "first" or "second", it is only for the purpose of distinguishing the technical features, and cannot be understood as indicating or implying the relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0025] In the description of the present invention, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in the present invention based on the specific content of the technical solution.

[0026] In modern technology, batteries, as key components for energy storage and supply, are widely used in various electronic devices, vehicles, and energy storage systems. In order to ensure the safety and stability of batteries, many protective measures have been taken in the prior art. However, despite these protective measures, batteries may still be impacted during actual use, and this impact may bring a series of serious consequences. First, from a physical perspective, after the battery is impacted, its shell may be dented, cracked, or deformed. This physical damage not only destroys the appearance of the battery, but more importantly, it may damage the integrity of the shell, making it possible for the chemical substances inside the battery to leak out. Once the substances inside the battery leak, they may react with substances in the external environment, causing environmental pollution or safety hazards. Secondly, the components inside the battery, such as the positive and negative electrodes, electrolytes, and separators, may also be displaced, deformed, or damaged due to the impact. This damage may directly affect the normal operation of the battery. For example, the contact between the positive and negative electrodes may become closer due to the impact, resulting in a decrease in the internal resistance of the battery, thereby increasing the risk of battery overheating. In addition, the leakage or damage of the electrolyte may cause an imbalance in the chemical reaction inside the battery, further increasing the risk of battery overheating, short circuit, etc. For some types of batteries, such as lithium-ion batteries, the impact of shock on the battery may be more serious. The chemical reaction inside the lithium-ion battery itself has a high energy density. Once the chemical reaction is out of control due to shock, a large amount of heat and gas may be generated rapidly. If this heat and gas cannot be dissipated and discharged in time, it may cause the battery to explode or fire. In actual cases, we can see that accidents caused by battery shock are common. For example, when an electric vehicle encounters a collision during driving, it may cause the on-board battery to be short-circuited, catch fire or even explode due to shock. In addition, portable electronic devices such as mobile phones and laptops may also be damaged by shock during transportation or use, which may lead to safety accidents. In order to reduce the risks of battery shock, we need to take a series of preventive measures. First, improve the strength and impact resistance of the battery shell so that it can maintain integrity when it is impacted and prevent the leakage of internal substances. Secondly, optimize the internal structure of the battery and the layout of components to reduce the impact on the internal components of the battery. In addition, shock detection and early warning functions can be added to the battery management system to detect and deal with potential safety hazards in a timely manner.

[0027] Reference Figure 1 , Figure 2 and Figure 3, a battery cell according to an embodiment of the first aspect of the utility model comprises a first pole piece 1, a second pole piece 2 and a diaphragm 3, wherein the diaphragm 3 is arranged between the first pole piece 1 and the second pole piece 2, and the battery cell is formed by stacking the first pole piece 1, the diaphragm 3 and the second pole piece 2 and then winding; the first pole piece 1 comprises a first end and a second end, wherein the first end is the winding starting point of the first pole piece 1, and the second end is the winding end point of the first pole piece 1; the first pole piece 1 comprises a first current collector, a first safety coating 5 and a first active material layer, and the first wall surface of the first current collector comprises a first part 13 and a second part 14 connected to each other, wherein the first part 13 is located on a side of the second part 14 close to the first end; the first safety coating 5 is arranged on the second part 14, the resistance of the first safety coating 5 is greater than the resistance of the first current collector, and the first active material layer is coated on the first safety coating 5; and the first active material layer is also coated on the first part 13. The first safety coating 5 is arranged on the first current collector, so that when the battery is impacted, after the first current collector pierces the diaphragm 3, the first safety coating 5 separates the first current collector from the active material on the other side of the diaphragm 3. When the active substances react and generate current, the current must pass through the first safety coating 5 to connect to the first current collector. The resistance of the first safety coating 5 is relatively large, so that when a short circuit occurs inside the battery, the current is reduced by the large resistance of the first safety coating 5, and the power of the battery to release electricity is reduced, so that the heating speed of the battery is slowed down, effectively avoiding the fire of the battery and enhancing the safety performance of the battery. The first safety coating 5 includes a binder, a safety substance and a conductive agent, wherein the binder can be mixed with one or more of polyvinylidene fluoride, acrylate, styrene-butadiene rubber, and polyethylene. The safety substance can be mixed with one or more of lithium iron phosphate, aluminum hydroxide, aluminum oxide, titanium oxide, zirconium oxide, and magnesium oxide, and the safety substance is selected from a substance with strong insulation or high resistance. The conductive agent can be mixed with one or more of carbon nanotubes, conductive carbon black, conductive graphite, and carbon fiber, wherein the conductive agent has good conductivity. The resistance of the first safety coating 5 is adjusted by adjusting the ratio between the conductive agent and the safety substance. Preferably, the thickness of the first safety coating 5 is not less than 5 μm. Ensuring the thickness of the first safety coating 5 can more easily ensure that the first safety coating 5 forms a more stable resistance, thereby providing more stable protection for the battery.

[0028] The first part 13 on the inner side of the battery cell, that is, the first pole piece 1, is not easily damaged when it is hit, so only the first active material layer is provided on the first part 13 without the first safety coating 5, so as to improve the energy density of the battery cell. The second part 14 on the first pole piece 1 is located outside the battery cell after winding, and the pole piece on the outside is easily damaged after a collision, resulting in a short circuit, so the first safety coating 5 is provided at the second part 14 to improve the safety of the battery cell.

[0029] Furthermore, the second pole sheet includes a third end and a fourth end, the third end is the starting point of winding the second pole sheet, and the fourth end is the end point of winding the second pole sheet, the second pole sheet includes a second current collector, a second safety coating and a second active material layer, the second current collector of the second pole sheet includes a third part and a fourth part connected to each other, the end of the third part facing away from the fourth part is the third end, and the end of the fourth part facing away from the second part is the fourth end; the second safety coating is arranged on the fourth part, and the second active material layer is coated on the second safety coating; the second active material layer is also coated on the third part, that is, the second safety coating is arranged on both the positive pole sheet and the negative pole sheet of the battery cell to protect the battery cell.

[0030] Increased battery internal resistance refers to the increase in the internal resistance value of the battery, which is usually caused by battery aging, long-term use, or changes in the internal structure of the battery. Increased battery internal resistance will bring a series of consequences: First, the operating voltage of the battery will decrease. Due to the increase in internal resistance, the battery needs to overcome greater resistance during discharge, resulting in a drop in voltage. This will directly affect the performance and efficiency of the battery, making the battery unable to provide enough energy to meet the needs of the device. Secondly, the increase in battery internal resistance will lead to an increase in battery self-heating. During the operation of the battery, the increase in internal resistance will cause more heat to be generated when the current passes through. This will not only increase the battery temperature, but may also cause safety problems such as battery thermal runaway. In addition, an increase in battery internal resistance will shorten the discharge time of the battery. Due to the increase in internal resistance, the battery voltage drops faster during discharge, resulting in a decrease in battery life. This will seriously affect the performance and reliability of devices that need to be used for a long time. In addition, an increase in battery internal resistance may also lead to a decrease in battery capacity. As the internal resistance increases, the amount of charge that the battery can store decreases, thereby reducing the battery capacity and energy density. This means that the battery will be used for a shorter time and will need to be charged or replaced more frequently. Finally, the increase in battery internal resistance will accelerate the battery aging process and shorten the battery life. The increase in internal resistance may lead to further deterioration of the internal structure of the battery and accelerate the decline of battery performance. This will cause the battery capacity to gradually decrease, and eventually make the battery unusable.

[0031] In summary, the increase of battery internal resistance has adverse effects on battery performance, safety, service life and life. Therefore, when using the battery, you should pay attention to monitoring the change of the battery's internal resistance and take timely measures to reduce the increase of internal resistance in order to extend the battery's service life and improve the battery's performance.

[0032] In addition to the consequences mentioned above, the increase in battery internal resistance may also cause other problems: First, the increase in battery internal resistance may affect the charging efficiency of the battery. Due to the increase in internal resistance, the battery needs to overcome greater resistance during the charging process, resulting in a slower charging speed. This not only prolongs the charging time, but may also increase the energy loss during the charging process, making the battery unable to be fully charged. Second, the increase in battery internal resistance may lead to uneven temperature distribution of the battery. When the battery is working, the increase in internal resistance will cause more heat to be generated inside the battery. If this heat cannot be dissipated evenly, it may cause local hot spots in the battery, increasing the risk of thermal runaway of the battery. In addition, the increase in battery internal resistance may also affect the cycle life of the battery. The increase in internal resistance may cause the battery to generate more stress during the charge and discharge cycle, accelerating the damage and aging of the battery. This will shorten the cycle life of the battery, require more frequent battery replacement, and increase the cost of use. In addition, the increase in battery internal resistance may also affect the safety of the battery. As the internal resistance increases, the heat and stress generated by the battery during operation may exceed its tolerance range, resulting in safety accidents such as thermal runaway and explosion of the battery. This may not only cause damage to the equipment, but also pose a threat to personal safety.

[0033] According to some embodiments of the utility model, the first safety coating 5 is arranged on two opposite sides of the first current collector 11. As a preferred solution, the first safety coating 5 is arranged only on two opposite sides of the first current collector 11. First, after the first safety coating 5 is arranged on the first current collector 11, the position where the short circuit occurs in the battery cell can be isolated and the resistance of the position can be increased. Secondly, compared with setting the second safety coating on the second current collector of the negative electrode, setting the first safety coating 5 on the first current collector 11 has less effect on the internal resistance of the battery cell during normal operation, and has less effect on the charging and discharging performance of the battery.

[0034] According to some embodiments of the utility model, the first current collector 11 as the positive electrode is an aluminum foil, and the second current collector as the negative electrode is a copper foil, and the thickness of the copper foil does not exceed 6μm. A buffer layer 4 is provided on the outside of the battery cell, and the material of the buffer layer 4 is silicone, rubber or resin. After the first safety coating 5 is provided, the first safety coating 5 can enhance the structural strength of the first current collector, so the second current collector can be set thinner. Among them, the negative electrode second current collector has a greater impact on the internal resistance of the battery cell during normal operation. Therefore, the negative electrode second current collector is set to a copper foil with better conductive effect, and because the copper foil has better ductility, the copper foil can be set thinner. And after the buffer layer 4 is provided on the outside of the battery cell, more impact force can be absorbed, so a thinner second current collector can be set, so that when the battery cell is impacted, the thinner second current collector will not break.

[0035] According to some embodiments of the present invention, the resistance of the first safety coating 5 is not less than 0.2Ω and not more than 5Ω. When the resistance of the first safety coating 5 is small, the effect of reducing the initial heat release of the battery cell is poor. When the resistance of the first safety coating 5 is large, the impact on the internal resistance of the battery cell is large. Therefore, the resistance of the first safety coating 5 is set between 0.2Ω and 5Ω.

[0036] According to some embodiments of the utility model, the first pole piece 1, the second pole piece 2 and the separator 3 are wound to form a battery cell, and the length of the first safety coating 5 along the length direction of the first current collector 11 does not exceed 90% and is not less than 60% of the length of the first current collector 11. In the area where the first safety coating 5 is not coated, the first active material layer can be directly connected to the first current collector, thereby greatly reducing the internal resistance of the battery cell.

[0037] According to some embodiments of the utility model, the first safety coating 5 is disposed at one end of the first current collector 11 wound on the outside of the battery cell. When the wound battery cell is impacted, usually only no more than 60% of the pole piece structure on the outside of the battery cell can be destroyed. Therefore, the first safety coating 5 is not disposed on a portion of the first current collector 11 close to the inside of the battery cell, which improves the energy density of the battery cell and reduces the overall internal resistance of the battery cell.

[0038] The copper foil of the second current collector serving as the negative electrode of the battery cell is more likely to break and deform when impacted, so the first safety coating 5 is only provided on the aluminum foil of the first current collector 11 of the positive electrode. The aluminum foil is less likely to deform than the copper foil, so the first safety coating 5 is more stable and will not be damaged due to the easy deformation of the first current collector, thereby causing the first safety coating 5 to fail to protect the battery cell.

[0039] Furthermore, the thickness of the first active material layer on the second part 14 and the thickness of the first safety coating 5 are equal to the thickness of the first active material layer on the first part, so that the side of the first active material layer on the first part 13 away from the first current collector is flush with the side of the first active material layer on the second part 14 away from the first current collector. This makes the surface of the first pole piece 1 more neat, effectively increasing the energy density of the battery cell.

[0040] A battery according to an embodiment of the second aspect of the utility model includes any one of the battery cells in the above embodiments, so that the battery has higher safety.

[0041] Specifically, in an embodiment of a battery, the first safety coating 5 is disposed on the first pole piece 1, the total length of the first pole piece 1 is 1131 mm, the length of the first safety coating 5 is 792 mm, and the width of the first safety coating 5 is equal to the width of the first current collector 11. The thickness of the second current collector on the second pole piece 2, i.e., the copper foil, is set to 6 μm, and a 20 μm thick silica gel buffer layer 4 is provided on the outside of the battery cell. The energy density of the battery is increased, and the safety performance of the battery in preventing fire is improved.

[0042] The embodiments of the present invention are described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A battery cell, characterized in that: The battery cell comprises a first pole piece, a second pole piece and a diaphragm, wherein the diaphragm is arranged between the first pole piece and the second pole piece, and the battery cell is formed by stacking the first pole piece, the diaphragm and the second pole piece and then winding them; The first pole piece includes a first end and a second end, the first end is a winding start point of the first pole piece, and the second end is a winding end point of the first pole piece, the first pole piece includes a first current collector, a first safety coating layer and a first active material layer, the first current collector includes a first part and a second part connected to each other, an end of the first part away from the second part is the first end, and an end of the second part away from the first part is the second end; The first safety coating is disposed on the second part, the resistance of the first safety coating is greater than the resistance of the first current collector, the first active material layer is coated on the first safety coating; the first active material layer is also coated on the first part.

2. A battery cell according to claim 1, characterized in that: The length of the second portion is L1, the length of the first pole piece is L2, and 0.6≤L1 / L2≤0.

9.

3. A battery cell according to claim 1, characterized in that: The first electrode is a positive electrode.

4. A battery cell according to claim 3, characterized in that: The first current collector of the positive electrode sheet is an aluminum foil sheet, the second electrode sheet is a negative electrode sheet, the second current collector of the negative electrode sheet is a copper foil sheet, and the thickness of the copper foil sheet does not exceed 6 μm.

5. A battery cell according to claim 1, characterized in that: A buffer layer is disposed on the outermost side of the battery core, and the material of the buffer layer is one of silica gel, rubber or resin.

6. A battery cell according to claim 1, characterized in that: The electrical resistance of the first safety coating is not less than 0.2Ω and not more than 5Ω.

7. A battery cell according to claim 1, characterized in that: The second pole piece includes a third end and a fourth end, the third end is the winding starting point of the second pole piece, and the fourth end is the winding end point of the second pole piece, the second pole piece includes a second current collector, a second safety coating layer, and a second active material layer, the second current collector of the second pole piece includes a third portion and a fourth portion connected to each other, an end of the third portion away from the fourth portion is the third end, and an end of the fourth portion away from the second portion is the fourth end; The second safety coating layer is disposed on the fourth portion, and the second active material layer is coated on the second safety coating layer; the second active material layer is also coated on the third portion.

8. A battery cell according to claim 1, characterized in that: A sum of a thickness of the first active material layer on the second portion and a thickness of the first safety coating layer is equal to a thickness of the first active material layer on the first portion.

9. A battery cell according to claim 8, characterized in that: The thickness of the first safety coating is not less than 5 μm.

10. A battery, characterized in that: A battery cell comprising any one of claims 1 to 9.

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