Battery cell and battery

Abstract

The utility model provides a battery cell and battery, including: positive pole piece, diaphragm and negative pole piece, positive pole piece, diaphragm and negative pole piece are laminated in proper order and wound into the battery cell, the battery cell includes bending area and straight area, the positive pole piece, diaphragm and negative pole piece have bending radian in the bending area, the straight area has bending radian in the straight area, the straight area has bending radian in the straight area, and the straight area has bending radian in the straight area. The positive plate, the diaphragm and the negative plate are straightly arranged in the straight area; the positive plate comprises a current collector, an active material layer and a resistive layer, the resistive layer is coated on the current collector and is arranged in the bending area, the active material layer is coated on the current collector and covers the resistive layer, and the resistance of the resistive layer is greater than that of the current collector. According to the battery cell provided by the utility model, the lithium precipitation phenomenon in the bending area of the battery cell can be effectively avoided.

Description

TECHNICAL FIELD

[0001] The utility model relates to new energy technology field especially, relate to a kind of electric core and battery. BACKGROUND

[0002] With the continuous progress and innovation of science and technology, people's demand for various intelligent devices is increasing, especially smart phones, computers and other electronic products. The popularity of these devices makes people have higher requirements for the performance and safety of intelligent products. Among many performance indicators, energy density and safety have become the focus of consumers and manufacturers. In order to meet these needs, higher coating weight and compaction are used, and the charging capacity of the system is increasingly challenged, so that the battery is more prone to lithium precipitation. In the winding process of high-density battery, the positive and negative plates will deform at the bending position of the plate, so that the volume of the plate inside the bend will be smaller than the volume of the plate outside the bend, so that the ratio of active material on the positive plate to active material on the negative plate changes, so that the lithium precipitation is more likely to occur at the bending position. Therefore, an electric core that can effectively prevent lithium precipitation at the bending position is needed. SUMMARY

[0003] The utility model aims at at least one of the technical problems existing in the prior art. To this end, the utility model provides an electric core, which can effectively prevent lithium precipitation in the bending area of the electric core.

[0004] The utility model further provides a battery.

[0005] According to the electric core of the first aspect of the utility model, the positive plate, the separator and the negative plate are sequentially stacked and wound to form an electric core, the electric core includes a bending area and a flat area, the positive plate, the separator and the negative plate have a bending radius in the bending area, and the positive plate, the separator and the negative plate are arranged flat in the flat area; the positive plate includes a current collector, an active material layer and a resistance layer, the resistance layer is coated on the current collector, and the resistance layer is arranged in the bending area, the active material layer is coated on the current collector and covers the resistance layer, and the resistance of the resistance layer is greater than the resistance of the current collector.

[0006] According to the electric core of the first aspect of the utility model, at least the following beneficial effects are achieved: when the electric core is charged, the current density of the positive plate in the bending area is reduced by the resistance layer, the lithium ion release efficiency of the active material in the bending area of the positive plate is reduced, the lithium ion in the bending area has more time to pass through the separator, and the lithium precipitation phenomenon in the bending area is effectively avoided.

[0007] According to some embodiments of the present application, the resistance layer is arranged on one side of the positive plate facing the outside of the battery cell.

[0008] According to some embodiments of the present application, the resistance layer comprises a non-metallic conductive agent and a binder, and the non-metallic conductive agent and the binder are mixed and coated on the positive plate to form the resistance layer.

[0009] According to some embodiments of the present application, the non-metallic conductive agent comprises one of conductive carbon black, conductive graphite sheet and conductive carbon nanotube.

[0010] According to some embodiments of the present application, the binder comprises one of polyvinylidene fluoride, acrylic modified PVDF, carboxylic acid modified PVDF, styrene butadiene rubber, acrylic modified styrene butadiene rubber, polymethyl methacrylate and polyimide.

[0011] According to some embodiments of the present application, the thickness of the active material layer on one side of the positive plate in the thickness direction of the positive plate is H, the thickness of the resistance layer in the thickness direction of the positive plate is D, and 0.25*H≤D≤0.5*H.

[0012] According to some embodiments of the present application, the width of the resistance layer in the width direction of the positive plate is E, and the width of the current collector is F, and 0.9*F≤E≤F.

[0013] According to some embodiments of the present application, the length of the resistance layer on the positive plate of the first layer of the battery cell winding in the winding direction of the positive plate is L, the thickness of the positive plate is A, the thickness of the negative plate is B, and the thickness of the diaphragm is C, the length of the resistance layer on the positive plate of the Nth layer of the battery cell winding in the winding direction of the positive plate is S, and S=L+π*[(N-1)*(A+B+2C)] / 2.

[0014] According to some embodiments of the present application, the positive plate has two resistance layers in the same layer of winding, and the lengths of the two resistance layers on the positive plate wound in the same layer are equal.

[0015] The battery according to the second aspect of the present application comprises the battery cell according to any one of the above embodiments.

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

[0017] Figure 1 It is a structural schematic view of a battery cell according to the present application.

[0018] Figure 2 is a partial enlarged schematic view of the positive plate of the battery cell; Figure 1

[0019] Figure 3 is a structural schematic view of the current collector of the positive plate of the battery cell.

[0020] Reference signs:

[0021] 1, positive plate; 11, current collector; 12, active material layer; 13, resistance layer; 2, negative plate; 3, diaphragm; 4, bending area; 5, flat area. DETAILED DESCRIPTION

[0022] The embodiments of the present application will be described in detail below, examples of which are shown in the drawings, wherein the same or similar reference signs represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application.

[0023] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, etc. is based on the orientation or position relationship shown in the drawings, and is only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as a limitation of the present application. The device or element indicated is necessarily constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

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

[0025] In the description of the present application, unless otherwise explicitly limited, the words such as setting, installing, connecting, etc. should be broadly understood, and the skilled in the art can reasonably determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0026] ​The winding process of the wound cell is to wind the positive plate, negative plate and separator film together through the winding needle mechanism of the winding machine to form the key step of the bare cell. The following is a detailed description of the process: first, before winding, it is necessary to ensure that the preparation work of the positive plate, negative plate and separator film has been completed. This includes mixing the positive or negative powder with other ingredients evenly and adjusting it into a paste, then uniformly coating the paste on the surface of the transmission current collector, drying to make the positive and negative plate rolls, and cold pressing to achieve the appropriate density and thickness. Then, the cold-pressed plate roll is cut into large pieces, and then divided into small strips of positive and negative plate. The winding process generally uses two winding needles to clamp two layers of separator film for pre-winding, and then sends the positive plate or negative plate in turn. The plate is clamped between the two layers of separator film for winding to ensure that the adjacent positive and negative plates are isolated by the separator film to avoid short circuit. During the winding process, it is necessary to ensure that the negative plate can completely cover the positive plate in the horizontal and vertical directions. The key components of the winding machine include the plate supply system, the separator unwinding system, the tension control system, the end adhesive system, the unloading transmission system, the foot switch and the human-machine interface. The plate supply system is responsible for conveying the positive and negative plates between the two layers of separator film along the guide rail; the separator unwinding system realizes the automatic continuous supply of the separator; the tension control system controls the constant tension of the separator during winding; the end adhesive system fixes the wound core after winding; the unloading transmission system automatically removes the wound core from the winding needle and transports it to the next process; the foot switch is used to control the normal operation of winding; the human-machine interface is used for parameter setting, manual debugging and alarm prompt, etc. After winding, the end adhesive paper is used for fixation to prevent the wound core from spreading out. At this time, the winding process of the wound cell is completed, and the bare cell is immediately transferred to the next process for further processing and detection. During the entire winding process, it is necessary to strictly control various parameters and conditions to ensure the quality and performance of the wound cell. At the same time, regular maintenance and maintenance of the winding machine are also needed to ensure its stable operation and prolong its service life.

[0027] Referring to Figure 1 , Figure 2 and Figure 3The utility model discloses the positive pole piece 1, diaphragm 3 and negative pole piece 2 of the electric core in the first embodiment of the utility model, the positive pole piece 1, diaphragm 3 and negative pole piece 2 are sequentially laminated and are wound out electric core, and the electric core includes bending area 4 and flat area 5, and the positive pole piece 1, diaphragm 3 and negative pole piece 2 have bending camber in bending area 4, and the positive pole piece 1, diaphragm 3 and negative pole piece 2 are straightly arranged in flat area 5. Wherein the positive pole piece 1 will have a part in bending area 4, and still will have a part positive pole piece 1 in flat area 5, and the positive pole piece 1 in bending area 4 has certain bending camber, and the positive pole piece 1 in flat area 5 is straightly arranged, that is, the part of positive pole piece 1 setting in flat area 5 and the part of positive pole piece 1 setting in flat area 5 are alternately arranged along the extension direction of positive pole piece 1. In the prior art, after winding the electric core is wound, the middle part of the winding electric core will form flat area 5, and the two ends of flat area 5 will form two bending areas 4. The positive pole piece 1 and negative pole piece 2 in bending area 4 are bent into semicircle. And the deformation of the positive pole piece 1 and negative pole piece 2 in bending area 4 will make the volume of active material on the pole piece inside the arc smaller than the volume of active material on the pole piece outside the arc, that is, the volume of active material on the positive pole piece 1 in bending area 4 is smaller than the volume of active material on the negative pole piece 2, so that lithium precipitation phenomenon is more likely to occur in bending area 4. It should be noted that the volume of active material on the entire positive pole piece 1 will not be smaller than the volume of active material on the entire negative pole piece 2, only the local part of the positive pole piece 1 in bending area 4 makes the volume of active material on the positive pole piece 1 smaller than the volume of active material on the negative pole piece 2, so when charging too fast, lithium ions in bending area 4 cannot be embedded in negative pole piece 2 in time, thereby causing lithium precipitation phenomenon.

[0028] The positive pole piece 1 includes current collector 11, active material layer 12 and resistance layer 13, the resistance layer 13 is coated on the current collector 11, and the resistance layer 13 is arranged in bending area 4, the active material layer 12 is coated on the current collector 11 and covers resistance layer 13, and the resistance of resistance layer 13 is greater than the resistance of current collector 11. By setting resistance layer 13 on the current collector 11 of positive pole piece 1, the current of current collector 11 of positive pole piece 1 in bending area 4 is smaller by setting resistance layer 13 with greater resistance. When the current in bending area 4 is smaller, the lithium ion release speed on the corresponding positive pole piece 1 will be smaller. At this time, lithium ions will have more sufficient time to pass through diaphragm 3 and embed into negative pole piece 2. Thus, lithium precipitation phenomenon in bending area 4 is effectively avoided. Meanwhile, the cycle number and service life of the electric core can be greatly improved.

[0029] According to some embodiments of the present application, the resistance layer 13 is arranged on the side of the positive plate 1 facing the outside of the battery cell. The side of the positive plate 1 facing the outside of the battery cell is more prone to lithium precipitation, so the resistance layer 13 is arranged on the side of the positive plate 1 facing the outside of the battery cell. Further, the resistance layer 13 can also be arranged on the side of the positive plate 1 facing the inside of the battery cell, so as to better prevent lithium precipitation in the bending area 4.

[0030] According to some embodiments of the present application, the resistance layer 13 comprises a non-metallic conductive agent and a binder, and the non-metallic conductive agent and the binder are mixed and coated on the positive plate 1 to form the resistance layer 13. Specifically, the non-metallic conductive agent comprises at least one of conductive carbon black, conductive graphite sheet, and conductive carbon nanotube, and the binder comprises at least one of polyvinylidene fluoride, acrylic modified PVDF, carboxylic acid modified PVDF, styrene butadiene rubber, acrylic modified styrene butadiene rubber, polymethyl methacrylate, and polyimide. The resistance of the resistance layer 13 is adjusted by selecting different types of non-metallic conductive agents and binders and the ratio between the non-metallic conductive agents and the binders.

[0031] According to some embodiments of the present application, the thickness of the active material layer 12 on the side of the positive plate 1 in the thickness direction of the positive plate 1 is H, and the thickness of the resistance layer 13 in the thickness direction of the positive plate 1 is D, and 0.25*H≤D≤0.5*H. When the thickness of the resistance layer 13 is too large, the energy density of the battery cell will be reduced, and the thickness of the resistance layer 13 being too large will also make the resistance of the resistance layer 13 too large, thereby affecting the charging and discharging rate of the battery cell. When the thickness of the resistance layer 13 is too small, the resistance added by the resistance layer 13 will be smaller, thereby failing to better prevent lithium precipitation in the bending area 4. Therefore, the thickness of the resistance layer 13 is limited within a certain range, which can not only ensure the energy density of the battery cell, but also effectively prevent lithium precipitation in the bending area 4.

[0032] According to some embodiments of the present application, the width of the resistance layer 13 in the width direction of the positive plate 1 is E, and the width of the current collector 11 is F, and 0.9*F≤E≤F. The part of the resistance layer 13 whose width exceeds the width of the positive plate 1 will reduce the energy density of the battery cell, so the width of the resistance layer 13 is limited to be smaller than the width of the positive plate 1. However, when the width of the resistance layer 13 is too small, the position of the current collector 11 in the bending area 4 where the resistance layer 13 is not arranged is prone to lithium precipitation. Therefore, the width of the resistance layer 13 is limited.

[0033] According to some embodiments of the utility model, the length of the resistance layer 13 on the positive plate 1 of the first layer of the electric core winding in the winding direction of the positive plate 1 is L, the thickness of the positive plate 1 is A, the thickness of the negative plate 2 is B, the thickness of the diaphragm 3 is C, the length of the resistance layer 13 on the positive plate 1 of the Nth layer of the electric core winding in the winding direction of the positive plate 1 is S, S = L + π * [(N-1) * (A + B + 2C)] / 2. When the electric core is wound, a semicircular shape is formed in the bending area 4, and the length of the positive plate 1 in the bending area 4 gradually increases with the increase of the winding layer number, that is, the winding radius increases, and the length of the winding also increases. Therefore, the length of the resistance layer 13 also needs to increase.

[0034] According to some embodiments of the utility model, the positive plate 1 has two resistance layers 13 in the same layer of winding, and the lengths of the two resistance layers 13 on the positive plate 1 wound in the same layer are equal. The positive plate 1 passes through the bending area 4 twice in the same layer of winding, the positive plate 1 in the same layer is provided with the resistance layer 13 in the two bending areas 4, and the lengths of the resistance layers 13 in the two bending areas 4 of the positive plate 1 wound in the same layer are equal, so that the performance of the electric core is more stable.

[0035] The battery according to the second aspect of the utility model comprises the electric core according to any one of the above embodiments.

[0036] The energy density of an electric cell refers to the amount of energy that can be stored per unit volume or mass of the cell. It is typically expressed in terms of watt-hours per liter (Wh / L) for volumetric energy density and watt-hours per kilogram (Wh / kg) for gravimetric energy density. Higher energy density means that the cell can store more electrical energy in the same volume or mass, which is crucial for applications such as portable electronic devices and electric vehicles. How is the energy density of an electric cell calculated? The energy density of an electric cell, which refers to the amount of energy that can be stored per unit volume or mass of the battery, is one of the key indicators of battery performance. It is influenced by a variety of complex factors that span a wide range of fields from material science to engineering design. First and foremost, the chemical composition of the cell is a core factor that affects energy density. Different cathode materials, such as lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide (NCM), or lithium iron phosphate (LFP), have different energy storage capabilities. Similarly, anode materials, such as graphite or silicon-based materials, also affect the overall energy density due to their different electrochemical properties. The choice of electrolyte and the material of the separator are also crucial, as they determine the efficiency and safety of ion transport within the battery. Design and manufacturing processes are also important aspects that affect energy density. The structural design of the battery, including the thickness of the electrodes, the loading amount of active materials, and the packaging method of the battery, can significantly affect the energy density. For example, thinner electrodes can reduce the use of non-active materials, thereby increasing the energy density per unit volume. The precision of manufacturing processes, such as the uniformity of coating, the compaction density, and the accuracy of assembly, can also affect the performance of the battery. In addition, the quality and purity of materials also have a non-negligible impact on energy density. High-purity materials can reduce side reactions within the battery and improve energy utilization. The microstructure of materials, such as particle size and distribution, can also affect the surface area of electrode materials and ion diffusion paths, thereby affecting the charge and discharge performance of the battery.

[0037] Battery lithium precipitation refers to the uneven deposition of lithium ions on the surface of the negative electrode during the charging process, eventually forming lithium metal dendrites. The presence of these dendrites poses a significant threat to the health of the battery. First, from a safety perspective, the growth of lithium dendrites is like a double-edged sword. It not only has the potential to pierce the internal separator of the battery, causing direct contact between the positive and negative electrodes, but this contact often leads to catastrophic consequences. Once a short circuit occurs, the temperature inside the battery will rise sharply, triggering a series of chain reactions that may ultimately lead to overheating, swelling, and even fire and explosion of the battery, posing a significant safety hazard to users. Second, the lifespan of the battery will also be greatly reduced due to the formation of lithium dendrites. The continuous growth of lithium dendrites will consume valuable lithium ion resources inside the battery. As the number of lithium ions decreases, the number of chargeable times and the capacity of the battery will gradually decrease. Users will find that the battery that was originally supposed to be used for several years may experience significant performance degradation in a short period of time. In addition, the charging and discharging efficiency of the battery will also be severely affected. The formation of lithium dendrites increases the internal resistance of the battery, making the flow of electrons inside the battery no longer smooth. This increase in resistance not only reduces the charging speed, but also affects the power output during discharging, thereby reducing the overall performance of the battery. Finally, the stability of the battery performance will also be affected by the uneven growth of lithium dendrites. The growth of lithium dendrites may cause voltage instability during battery use. This voltage fluctuation will directly affect the equipment powered by the battery, making it unstable and even causing unexpected shutdowns. Therefore, battery lithium precipitation is a phenomenon that must be strictly controlled and avoided in the design and use of lithium-ion batteries. Battery manufacturers and researchers have been working to reduce or eliminate the formation of lithium dendrites by improving battery materials, optimizing battery structure and charging strategies, and other methods to ensure the safety of the battery, extend its service life, and maintain its performance stability and reliability.

[0038] The embodiments of the utility model are explained in detail above in combination with the drawings, but the utility model is not limited to the above-mentioned embodiments, and various changes can be made within the knowledge range possessed by the ordinary skilled in the art without departing from the purpose of the utility model.

Claims

1. An electric cell, characterized by, The application relates to a battery cell. The battery cell comprises a positive electrode sheet, a separator and a negative electrode sheet, which are sequentially stacked and wound to form the battery cell, the battery cell comprises a bending area and a flat area, the positive electrode sheet, the separator and the negative electrode sheet are arranged in the bending area, and the positive electrode sheet, the separator and the negative electrode sheet are arranged in the flat area. The positive electrode sheet comprises a current collector, an active material layer and a resistance layer, the resistance layer is coated on the current collector and arranged in the bending area, the active material layer is coated on the current collector and covers the resistance layer, and the resistance layer has a resistance greater than that of the current collector.

2. The electric cell of claim 1, wherein, The resistance layer is arranged on one side of the positive electrode sheet facing the outside of the battery cell.

3. The electric cell of claim 1, wherein, The thickness of the active material layer on one side of the positive electrode sheet in the thickness direction of the positive electrode sheet is H, the thickness of the resistance layer in the thickness direction of the positive electrode sheet is D, and 0.25*H<=D<=0.5*H.

4. The electric cell of claim 1, wherein, The width of the resistance layer in the width direction of the positive electrode sheet is E, and the width of the current collector is F, and 0.9*F<=E<=F.

5. The electric cell of claim 1, wherein, The length of the resistance layer on the positive electrode sheet in the winding direction of the positive electrode sheet of the first layer of the battery cell is L, the thickness of the positive electrode sheet is A, the thickness of the negative electrode sheet is B, the thickness of the separator is C, the length of the resistance layer on the positive electrode sheet in the winding direction of the positive electrode sheet of the Nth layer of the battery cell is S, and S=L+pi*[(N-1)*(A+B+2C)] / 2.

6. The electric cell of claim 4, wherein, The positive electrode sheet has two resistance layers in the same layer of winding, and the lengths of the two resistance layers on the positive electrode sheet in the same layer of winding are equal.

7. A battery, characterized by The application further relates to a battery comprising the battery cell. The application further relates to a battery comprising the battery cell.

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