Battery and electric device

Abstract

The application relates to the technical field of new energy, and discloses a battery and a power utilization device, the battery comprising: a battery core, the battery core comprising a flat section and a bending section, the battery core comprising pole pieces and diaphragms between adjacent pole pieces; the pole piece comprising a bending part in a bending state, the bending part being located at the bending section of the battery core; the pole piece comprising a current collector layer and an active material layer coated on at least one side of the current collector layer; a protection unit, the protection unit comprising a glue layer and a base film, the protection unit being attached to the surface of the active material layer of the bending part through the glue layer; the air permeability of the protection unit being x; the proportion of the glue layer in the thickness of the protection unit being y; the compaction density of the active material layer on the pole piece attached by the protection unit being a; and 20<=x*y*a<=6290 being met. The battery provided by the application ensures that the battery core realizes efficient ion conduction and stable bonding under high safety, and improves the cycle life and use reliability.

Description

Technical Field

[0001] This invention relates to the field of new energy technology, specifically to a battery and an electrical device. Background Technology

[0002] The bending area of ​​a battery cell experiences significant stress, increasing the risk of active material shedding during use and potentially reducing the cell's energy density and lifespan. This risk is exacerbated by the increasing thickness of the electrode sheets as battery energy density improves, further increasing stress in the bending area and intensifying the risk of active material detachment. To address this, a protective layer can be added to the bending area to enhance protection of the active material and reduce shedding. However, the high resistance of this protective layer can lead to lithium ion deposition as lithium dendrites, compromising battery safety. Summary of the Invention

[0003] In view of this, the present invention provides a battery cell and an electrical device to solve the technical problem that the risk of lithium dendrite formation is easily increased after a protective layer is set in the bending area of ​​the battery cell.

[0004] In a first aspect, the present invention provides a battery comprising:

[0005] The battery cell includes a straight section and a bent section. The battery cell includes an electrode and a separator located between adjacent electrodes. The electrode includes a bent portion located in the bent section of the battery cell. The electrode includes a current collector layer and an active material layer coated on at least one side of the current collector layer.

[0006] The protective unit includes an adhesive layer and a base film. The protective unit is attached to the surface of the active material layer of the bent part through the adhesive layer.

[0007] The air permeability of the protective unit is xs / 100mL; the proportion of the adhesive layer to the thickness of the protective unit is y; the compaction density of the active material layer on the electrode to which the protective unit is attached is ag / cm³. 3 x, y, and a satisfy: 20 ≤ x·y·a ≤ 6290.

[0008] Beneficial effects: When the x·y·a formula is too small, the electrode compaction density is small, and the electrolyte can easily come into contact with the adhesive layer of the protection unit through the gaps between the active material particles. In addition, the proportion y of the adhesive layer to the thickness of the protection unit is too small, and the air permeability x of the protection unit is small. This can easily cause the adhesive layer to swell rapidly in the electrolyte and lose its adhesive force, resulting in the protection unit falling off. This can lead to material loss at the bending part 111, affecting the battery energy density.

[0009] When the x·y·a formula is too large, the permeability x of the protection unit is too large, which can easily lead to the obstruction of lithium ion transport. In addition, the compaction density a of the active material layer on the electrode is too large, making the active material particles too close together, which affects the electrolyte wetting and ion transport. At the same time, the adhesive layer of the protection unit is too thick, and liquid ingress affects ion transport, which increases the risk of lithium plating in the corresponding area of ​​the protection unit and affects the safety of battery use.

[0010] Secondly, the present invention also provides an electrical device, comprising: an electrical device body and a battery as described above, wherein the electrical device body is electrically connected to the battery.

[0011] Since the electrical device includes a battery and has the same effect as a battery, it will not be elaborated further here. Attached Figure Description

[0012] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0013] Figure 1 This is an exploded view of the battery of the present invention;

[0014] Figure 2 This is a cross-sectional schematic diagram of the battery cell of the present invention;

[0015] Figure 3 This is a detailed schematic diagram of the cross-sectional state of the battery cell of the present invention;

[0016] Figure 4 This is a cross-sectional view of the electrode sheet and the protection unit of the present invention being bonded together;

[0017] Figure 5 This is a cross-sectional view of another electrode sheet and protection unit being bonded together according to the present invention;

[0018] Figure 6 This is a schematic diagram of the protection unit of the present invention.

[0019] Explanation of reference numerals in the attached figures:

[0020] 1. Battery cell; 11. Electrode; 111. Bending section; 12. Separator; 1101. Current collector layer; 1102. Active material layer; 1103. Insulating layer;

[0021] 2. Protective unit; 21. Adhesive layer; 22. Base film; 221. Through hole;

[0022] 3. Shell;

[0023] 8. Straight section; 9. Bending section. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0026] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0028] During the use of wound battery cells, the bending area of ​​the cell experiences high stress, leading to a significant risk of active material shedding and consequently reducing the cell's energy density and lifespan. This risk is exacerbated by the increasing thickness of the electrodes in wound cells as battery energy density improves, further increasing stress in the bending area and intensifying the risk of active material detachment. To address this issue, a protective layer can be installed in the bending area to secure the active material, enhancing its protection and reducing shedding.

[0029] However, due to the high resistance of the protective layer, the ion transport rate inside the battery, especially in the area covered by the protective layer, decreases and the ion transport distance increases. This can lead to severe lithium deposition in the bending area of ​​the wound cell, which can cause lithium ions to precipitate in the form of lithium dendrites. These lithium dendrites can easily puncture the separator, causing an internal short circuit in the battery and affecting battery safety.

[0030] Studies have found that reducing the permeability of the protective layer can decrease the lithium-ion transport impedance in the corresponding positive and negative electrode regions, reducing the risk of lithium-ion deposition as lithium dendrites. However, a low-permeability protective layer increases the contact area between the adhesive layer and the electrolyte, leading to faster adhesive layer failure and increased risk of material loss. By adjusting the compaction density of the electrode where the protective layer is located, it is possible to prevent material loss at the cell's bending section 111, while also avoiding the formation of lithium dendrites and ensuring battery safety.

[0031] The following is combined with Figures 1 to 6 The following describes embodiments of the present invention.

[0032] According to an embodiment of the present invention, in one aspect, a battery is provided, comprising:

[0033] The battery cell 1 includes a straight section 8 and a bent section 9. The battery cell 1 includes an electrode 11 and a separator 12 located between adjacent electrode 11. The electrode 11 includes a bent portion 111 located in the bent section 9 of the battery cell 1. The electrode 11 includes a current collector layer 1101 and an active material layer 1102 coated on at least one side of the current collector layer 1101.

[0034] The protective unit 2 includes an adhesive layer 21 and a base film 22. The protective unit 2 is attached to the surface of the active material layer 1102 of the bent portion 111 through the adhesive layer 21.

[0035] The air permeability of the protective unit 2 is xs / 100mL; the proportion of the adhesive layer 21 to the thickness of the protective unit 2 is y; the compaction density of the active material layer 1102 on the electrode 11 to which the protective unit 2 is attached is ag / cm³. 3 It satisfies: 20≤x·y·a≤6290.

[0036] The battery in this embodiment includes a casing 3, which specifically includes a casing body and a cover plate. The casing body has an opening at at least one end along a first direction, and the cover plate is disposed at the opening to seal the casing body. An electrical connector is provided on the cover plate to enable the battery cell 1 to conduct electricity with an external circuit. During battery assembly, the battery cell 1 is inserted into the casing body along the first direction.

[0037] The battery cell 1 is specifically connected to the electrical connector by welding the tabs on the electrode plate 11. The electrical connector may include a terminal post and an adapter piece; the terminal post penetrates through the cover plate and is insulated from the cover plate. When the electrical connector only includes the terminal post, one end of the terminal post extends out of the cover plate for connection with an external circuit, and the other end extends into the housing and is welded to the tab of the battery cell 1; when the electrical connector also includes an adapter piece, one end of the adapter piece is welded to the tab and the other end is welded to the terminal post, thereby realizing the electrical connection.

[0038] The tabs of the battery cell 1 specifically include a positive tab and a negative tab. The positive tab and the negative tab can extend along a first direction and be located at the same end of the battery cell 1, or they can be located at opposite ends of the battery cell 1.

[0039] In this embodiment, the electrode 11 includes alternating layers of positive and negative electrode sheets, which are electrically isolated from each other by a separator 12. The active material layer 1102 includes positive and negative active materials, which are coated on the surface of the corresponding current collector layer 1101. The positive electrode sheet, separator 12, and negative electrode sheet are stacked sequentially and formed into a battery cell 1 by winding. During the forming process, the electrode 11 is partially bent to form a bent portion 111, which is concentrated in the bent section 9 area of ​​the battery cell 1. After winding, the battery cell 1 is compacted to form a racetrack-like structure, with its long axis extending along a second direction and its short axis extending along a third direction, and the length of the long axis being greater than the length of the short axis. The overall structure of the battery cell 1 forms a bent section 9 and a straight section 8. The straight section 8 is formed in the middle region of the battery cell 1, and the bent sections 9 are located on both sides of the straight section 8, with the bent sections 9 having an arc-shaped structure.

[0040] The electrode 11 includes a current collector layer 1101 and an active material layer 1102 coated on at least one side of the current collector layer 1101. The active material layer 1102 in the bending section 9, especially the active material layer 1102 in the inner circle of the bending section 9, is subjected to greater stress during the winding and compaction process, which poses a risk of cracking. In particular, during the charge and discharge cycle, repeated volume expansion and contraction can easily aggravate the generation of cracks, which can easily lead to the active material layer 1102 falling off.

[0041] To suppress cracking and detachment of the active material layer 1102, this embodiment further attaches a protective unit 2 to the surface of the active material layer 1102, thereby effectively covering the active material layer with the protective unit 2, alleviating stress concentration in the bending section 9, and fixing the active material layer 1102, thereby suppressing the risk of cracking and detachment of the active material layer 1102.

[0042] The protective unit 2 includes a base film 22 and an adhesive layer 21 attached to the base film 22. The base film 22 has high flexibility and can effectively resist stress deformation generated during bending. The adhesive layer 21 is coated on the surface of the base film 22 and is closely attached to the active material layer 1102 to enhance the interfacial bonding force.

[0043] When the protective unit 2 is attached to the surface of the active material layer 1102, the protective unit 2 will hinder the migration of lithium ions in the active material layer 1102, thereby affecting the ion conduction efficiency of the cell, and may even cause lithium plating, causing lithium ions to be deposited in the form of lithium dendrites. Lithium dendrites can easily pierce the separator, causing internal short circuits in the battery, which poses certain safety hazards.

[0044] To balance protection effectiveness and ion conduction performance, this embodiment adjusts the permeability of the protection unit 2 to reduce its hindering effect on lithium-ion migration and decrease the risk of lithium dendrite formation. Specifically, the permeability of the protection unit 2 can be adjusted by creating a through-hole ion channel structure on the protection unit 2 to construct a lithium-ion migration path and effectively reduce ion transport resistance.

[0045] The air permeability can be adjusted by creating through-holes that penetrate the thickness of the base membrane 22 in the protective unit 2, thereby reducing the air permeability value and increasing the air permeability of the protective unit 2. Furthermore, the air permeability of the protective unit can be adjusted by controlling the diameter of the through-holes and the spacing between adjacent through-holes. A larger through-hole diameter and a smaller spacing between adjacent through-holes result in a lower air permeability value.

[0046] In this embodiment, the specific method for measuring the air permeability of the protection unit 2 is as follows: The battery is discharged to the lower limit voltage at 0.33C. Then, the battery is disassembled, and the electrode with the protection unit 2 is removed. The protection unit 2 is then removed and a sample of 2.54cm × 2.54cm is prepared. The sample is immersed in DMC (dimethyl carbonate) for 4 hours and then dried at 60°C for 12 hours. The air permeability (Gurley number) of the separator is measured using a Gurley tester. The sample is placed in the Gurley tester, and the time required for a certain amount of test gas to pass through the 2.54cm × 2.54cm sample at a pressure of 1.22kPa is measured at room temperature. The unit is seconds (s). In this test, the test gas used is air, and the gas volume is 100mL. The timer calculates the air passage time. The shorter the time, the better the air permeability, and the easier it is for the gas to pass through the protection unit; the longer the time, the worse the air permeability, and the more difficult it is for the gas to pass through the protection unit. When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V. When the permeability x of protection unit 2 decreases, the shorter the time, the better the permeability. This reduces the resistance of lithium ions passing through protection unit 2, improves ion conduction efficiency, and helps reduce the risk of lithium plating. However, if the permeability x of protection unit 2 is too small, it increases the contact area between the electrolyte and the adhesive layer 21, causing the adhesive layer 21 to swell rapidly in the electrolyte and lose its adhesive strength, leading to the detachment of protection unit 2 and thus losing its protective function for the active material layer. Conversely, when the permeability x of protection unit 2 is too large, the longer the time, the worse the permeability. While this ensures the stability of the adhesive layer, it exacerbates the obstruction of ion transport, increasing the risk of lithium plating. Therefore, the permeability x of protection unit 2 needs to be controlled within a reasonable range to balance ion conduction efficiency and adhesion performance.

[0047] In this embodiment, the method for testing the proportion y of the adhesive layer 21 to the thickness of the protective unit 2 is as follows:

[0048] The battery was discharged at 0.33C to the lower limit voltage. Then, the battery was disassembled, and the electrode with protection unit 2 was removed. Protection unit 2 was then removed, and its total thickness was measured using a scanning electron microscope (SEM), denoted as m1 (μm). The thickness of the base film 22 of protection unit 2 was also measured using an SEM, denoted as m2 (μm). The thickness of the adhesive layer is calculated as m1 - m2. The value of y was calculated using the formula y = (m1 - m2) / m2. When the positive electrode active material is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V, and the lower limit voltage is 2.5V. When the positive electrode active material is lithium iron phosphate, the upper limit voltage is 3.6V, and the lower limit voltage is 2.5V. When the proportion y of the adhesive layer 21 to the thickness of the protective unit 2 increases, the adhesive layer 21 provides more complete coverage of the base film 22, and the interfacial bonding strength is correspondingly improved, which helps to enhance the adhesion stability between the protective unit 2 and the active material layer 1102. However, if the proportion y is too large, the adhesive layer 21 will be too thick, which will cause partial blockage of ion channels, increase the resistance to lithium ion migration, and thus affect the ion conduction efficiency, leading to an increased risk of lithium plating in the corresponding area of ​​the protective unit 2, affecting the safety of battery use. On the other hand, if the proportion y is too small, the bonding effect will be weakened, resulting in a weak bond between the protective unit 2 and the active material layer 1102. During bending or cycling of the cell 1, local peeling is likely to occur, thereby reducing the protective effect on the active material layer 1102. Therefore, the proportion y of the adhesive layer thickness needs to be controlled within an appropriate range to achieve a balance between bonding performance and ion conduction performance.

[0049] In this embodiment, the test method for the compaction density α of the active material layer 1102 on the electrode 11 to which the protection unit 2 is attached is as follows:

[0050] 1) Pretreatment: Discharge the battery to the lower limit voltage at 0.33C, disassemble the electrode with protection unit 2, remove protection unit 2, soak the electrode in dimethyl carbonate (DMC) solution for 4 hours; air dry. When the positive electrode active material of the battery is nickel-cobalt-manganese ternary, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V. 2) Use a punching machine to punch the pre-treated electrode sheet into circular pieces of fixed area, with an area of ​​S0 and a number of six circular pieces. Weigh them and calculate the average value as M1. At the same time, use a scanning electron microscope to measure the thickness of the active material layer in the six circular pieces (that is, the thickness after removing the current collector from the total thickness), take the average value and record it as H. Finally, add an appropriate amount of deionized water to each of the six circular pieces, gently wipe the coating on the circular pieces with lint-free paper to expose the current collector, let it stand at room temperature (or dry) for 10 minutes. After the current collector is dry, weigh the mass of the six current collectors, take the average value and record it as M0. Calculate the compaction density of the active material layer on the electrode where the protection unit is located according to the following formula: a = (M1-M0) / (H×S0).

[0051] When the compaction density 'a' of the active material layer 1102 on the electrode 11 to which the protection unit 2 is attached increases, although it can improve the energy density, the internal porosity of the electrode decreases, and the active material particles become too tightly packed, which can easily affect electrolyte wetting and thus ion transport. When the compaction density 'a' is too high, ion transport is severely hindered, which can easily lead to lithium plating and the formation of lithium dendrites, affecting battery safety. Conversely, when the compaction density 'a' is too low, although it is beneficial for electrolyte penetration and ion transport, it will result in a loose electrode structure, affecting the energy density. Furthermore, the electrolyte can easily come into contact with the adhesive layer 21 of the protection unit 2 through the gaps between the active material particles, increasing the risk of swelling of the adhesive layer 21, which may also cause the protection unit 2 to detach. Therefore, the compaction density 'a' of the active material layer 1102 on the electrode 11 needs to be controlled within a reasonable range to balance energy density, ion transport performance, and adhesive layer stability.

[0052] The method for adjusting the compaction density 'a' is to control the cold pressing pressure or the cold pressing rate during the electrode preparation process to adjust the compaction density of the electrode. The greater the cold pressing pressure and the slower the cold pressing rate, the greater the compaction density of the electrode. Conversely, the smaller the cold pressing pressure and the greater the cold pressing rate, the smaller the compaction density of the electrode.

[0053] The battery provided in this embodiment requires comprehensive consideration of the synergistic effect of air permeability x, thickness ratio y, and compaction density a to optimize the design parameters of the protection unit 2. This ensures that the battery achieves efficient ion conduction and stable adhesion under high safety conditions, thereby improving cycle life and reliability. When the air permeability x of the protection unit 2 decreases, the risk of lithium plating in the electrode area corresponding to the protection unit 2 decreases. At this time, the compaction density a of the active material layer 1102 on the electrode 11 to which the protection unit 2 is attached and the ratio y of the adhesive layer 21 to the thickness of the protection unit 2 can be increased. This ensures that the adhesion strength between the protection unit 2 and the active material layer 1102 of the electrode 11 is sufficient, preventing the protection unit 2 from easily detaching.

[0054] When the x·y·a formula is too small, the compaction density of the electrode 11 is small, and the electrolyte can easily come into contact with the adhesive layer 21 of the protection unit 2 through the gaps between the active material particles. Furthermore, the proportion y of the adhesive layer 21 to the thickness of the protection unit 2 is too small, and the air permeability x of the protection unit 2 is small. This can easily cause the adhesive layer 21 to swell rapidly in the electrolyte and lose its adhesive force, leading to the detachment of the protection unit 2. Consequently, the bending part 111 will lose material, affecting the battery energy density.

[0055] When the x·y·a formula is too large, the permeability x of the protection unit 2 is too large, which can easily lead to the obstruction of lithium ion transport. In addition, the compaction density a of the active material layer 1102 on the electrode 11 is too large, making the active material particles too close together, which affects the electrolyte wetting and ion transport. At the same time, the thickness of the adhesive layer 21 of the protection unit 2 is too thick, and the liquid ingress affects ion transport, which increases the risk of lithium plating in the corresponding area of ​​the protection unit 2 and affects the safety of battery use.

[0056] For example, in this embodiment, the value of x·y·a can be 20 or 80 or 100 or 200 or 450 or 870 or 1540 or 1997 or 2000 or 2400 or 3200 or 4100 or 5000 or 5400 or 6000 or 6290, etc., or it can be a range formed by any two of the above values.

[0057] Referring to Table 1 below, the battery was tested for the shedding rate of protection unit 2 and the lithium plating condition through several embodiments and comparative tests to verify its qualification.

[0058] Table 1

[0059]

[0060] Regarding Table 1 above, the explanation is as follows:

[0061] Performance 1 and protection unit 2 shedding rate test, the method is as follows:

[0062] Following the battery fabrication method described above, 200 lithium-ion batteries were prepared for each of the embodiments and comparative examples. The x and y values ​​of the protection unit 2 and the compaction density 'a' of the active material layer 1102 on the electrode where the protection unit 2 is located are shown in Table 1; all other structures are identical. The lithium-ion batteries of each embodiment and comparative example were subjected to cyclic testing at 25°C according to the following procedure, and the detachment of the protection unit was also tested.

[0063] For lithium iron phosphate lithium-ion batteries:

[0064] 1) Charge at a constant current rate of 1C to 3.65V, and then charge at a constant voltage until the current drops to 0.05C;

[0065] 2) Let it stand for 30 minutes;

[0066] 3) Discharge to 2.5V at a 1C rate;

[0067] 4) Let it stand for 30 minutes;

[0068] Repeat steps 1)-4) for 100 cycles.

[0069] For nickel-cobalt-manganese ternary lithium-ion batteries:

[0070] 1) Charge at a constant current rate of 1C to 4.35V, and then charge at a constant voltage until the current drops to 0.05C;

[0071] 2) Let it stand for 20 minutes;

[0072] 3) Discharge to 2.75V at a 1C rate;

[0073] 4) Let it stand for 20 minutes;

[0074] Repeat steps 1)-4) for 100 cycles.

[0075] After cycling, the lithium-ion battery was placed in a vibration table and subjected to random vibration in the Z / Y / X directions and sinusoidal fixed-frequency vibration under the conditions of GB38031-2020.8.2. The random vibration duration in each direction was 12 hours and the sinusoidal fixed-frequency vibration duration was 2 hours. Then, the lithium-ion battery was removed and disassembled. The electrode with the protection unit 2 was removed and the electrode was made into a sample of a specific size. The peel strength of the protection unit 2 in the sample was measured. The width of the protection unit 2 in the sample is the size of the protection unit 2 in the electrode unfolding direction, and the length of the protection unit 2 in the sample is the length of the protection unit 2 in the first direction. The peel strength test was performed using a universal tensile testing machine at 300 mm / min and a test angle of 180°. If the peel strength of the protection unit 2 is less than 0.5 N / cm, the protection unit 2 is considered to have detached; otherwise, the protection unit 2 is considered not to have detached. The number of lithium-ion batteries with the protection unit 2 detached was recorded as n. The percentage of batteries with detached protection unit 2 in different embodiments and comparative lithium-ion batteries is calculated using the formula (n / 200)×100%. This percentage is the detachment rate of protection unit 2. If the detachment rate is less than or equal to 5%, it is considered qualified; otherwise, it is considered unqualified.

[0076] In this test, the active material for the positive electrode of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder meets 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder meets 95:2:1:2.

[0077] Performance 2, Battery lithium plating test, the method is as follows:

[0078] Following the battery preparation method described above, corresponding lithium-ion batteries were prepared for each embodiment and comparative example. The x and y values ​​of the protection unit 2 and the compaction density 'a' of the active material layer 1102 on the electrode where the protection unit 2 is located are shown in Table 1. The remaining structures are the same. The lithium-ion battery was charged at room temperature (25°C) with a constant current of 0.33C to the upper limit voltage, then charged with a constant voltage until the current dropped to 0.05C. After standing for 5 minutes, the battery was discharged with a constant current of 0.33C to the lower limit voltage. This constitutes one cycle, and 2000 cycles were performed. Then, the lithium-ion battery was charged with 0.33C to the upper limit voltage, with the cutoff current less than or equal to 0.05C, resulting in a fully charged battery.

[0079] Disassemble the battery, then remove the electrodes and observe the lithium plating on the surface of the negative electrode in bending section 9. The part where the projection of a single protection unit coincides with the negative electrode is the first region. The lithium plating area of ​​the first region is measured and recorded as S1. The area of ​​a single protection unit attached to the active material layer of the bending part in the first region is recorded as S2. According to the formula, the percentage of the lithium plating area on the surface of the negative electrode bending section 9 is calculated as (S1 / S2)×100%. If the lithium plating area on the surface of the negative electrode bending section 9 is less than 10%, it is considered slight lithium plating; if the lithium plating area on the surface of the negative electrode bending section 9 is between 10% and 50%, it is considered moderate lithium plating; and if the lithium plating area on the surface of the negative electrode bending section 9 is greater than 50%, it is considered severe lithium plating. Severe lithium plating is unacceptable.

[0080] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary cathode, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V.

[0081] In this test, the positive electrode active material of the battery was selected from a nickel-cobalt-manganese ternary LiNi alloy. 0.6 Co 0.2 Mn 0.2 Taking O2 as an example, the mass ratio of positive electrode active material: conductive agent: binder satisfies 96:2:2; the negative electrode active material is selected from artificial graphite, and the ratio of negative electrode active material: conductive agent: thickener: binder satisfies 95:2:1:2.

[0082] Regarding the test results, referring to Table 1 above, the explanation is as follows:

[0083] As can be seen from Examples 1-16, the electrode polarity is positive. When the value of the formula x·y·a is within the range of 20-6290, the shedding rate of the protection unit is less than or equal to 5% after testing. The lithium plating condition of the battery is tested, and the lithium plating condition is no lithium plating, slight lithium plating, or moderate lithium plating, and no serious lithium plating is observed. The performance requirements are met.

[0084] In Comparative Examples 1, 3, and 5, the electrode polarity was positive, and the values ​​of x·y·a in the formula were below the lower limit. The protection unit shedding rate test showed a shedding rate greater than 5%, failing to meet performance requirements. In Comparative Examples 2 and 4, the electrode polarity was positive, and the values ​​of x·y·a in the formula exceeded the upper limit. The battery lithium plating test showed severe lithium plating, failing to meet performance requirements.

[0085] As can be seen from Examples 17-25, the electrode polarity is negative. When the formula x·y·a is within the range of 20-6290, the shedding rate of the protection unit is less than or equal to 5% after testing. The lithium plating of the battery is tested and found to be either non-existent or slightly plating, with no severe lithium plating observed. The performance requirements are met.

[0086] In Comparative Example 6, the electrode polarity was negative, and the value of x·y·a exceeded the upper limit. The lithium plating test showed severe lithium plating, failing to meet performance requirements. In Comparative Examples 7 and 8, the electrode polarity was negative, and the value of x·y·a was below the lower limit. The protection unit shedding rate test showed a shedding rate greater than 5%, also failing to meet performance requirements.

[0087] It should be noted that in this embodiment, the positive electrode is one of the core components in the battery that carries the positive electrode active material. During charging, metal ions (e.g., lithium ions) are released from the lattice of the positive electrode active material (oxidation reaction), migrate through the electrolyte, and intercalate into the negative electrode. During discharging, metal ions (e.g., lithium ions in a lithium battery) are released from the negative electrode and intercalated into the lattice of the positive electrode active material (reduction reaction), thus realizing the storage and release of lithium ions.

[0088] A positive electrode generally includes a positive current collector and a positive active material layer. The positive active material layer is coated on at least one surface of the positive current collector and includes: a positive active material, a conductive agent, and a binder. The positive current collector is a conductive metal foil, which can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium with a silver-plated surface; a composite current collector can also be used, which may include a polymer base material and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base film (such as a base film of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). The positive active material includes, but is not limited to, at least one of the following materials: lithium phosphate, lithium transition metal oxides and their respective modified compounds, or other conventional materials that can be used as positive active materials for batteries. These positive active materials can be used alone or in combination of two or more. The lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also known as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. Lithium transition metal oxides include, but are not limited to, at least one of lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their modified compounds. Conductive agents include, but are not limited to, one or more combinations of graphite, superconducting carbon, carbon black (such as acetylene black, Ketjen black, Super P, etc.), carbon nanotubes, graphene, and carbon nanofibers. The adhesive includes, but is not limited to, one or more of the following: polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, fluorinated acrylate resin, styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0089] It should be noted that during battery charging, active ions (such as Li) from the positive electrode are embedded in the negative electrode, while electrons from the positive electrode are transferred to the negative electrode through the external circuit to maintain charge balance. During discharging, active ions (such as lithium ions) previously embedded in the negative electrode can be released, while electrons from the negative electrode are transferred to the negative electrode through the external circuit to maintain charge balance, thus achieving energy storage and release.

[0090] The negative electrode sheet includes a negative electrode current collector and a negative electrode active layer disposed on at least one surface of the negative electrode current collector. The negative electrode current collector is a conductive metal foil, which can be made of stainless steel, copper, aluminum, nickel, carbon electrodes, or titanium with a silver-plated surface. A composite current collector may include a polymer base material and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, copper, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base film (such as a base film of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.). The negative electrode active layer includes a negative electrode active material, a conductive agent, and a binder. The negative electrode active material can be a carbon-based material such as graphite, porous carbon, hard carbon, soft carbon, or mesophase carbon microspheres, or a silicon-based material such as elemental silicon, silicon oxides, silicon-carbon composites, or silicon-nitrogen composites. The conductive agent can be conductive carbon black, carbon nanotubes, etc., and the binder can be styrene-butadiene rubber, polyacrylic acid, etc.

[0091] It should be noted that a battery cell is the component in a battery where electrochemical reactions occur; it is the smallest unit in a battery capable of performing electrochemical reactions such as charging and discharging. A battery cell is the basic unit of a battery and typically includes a positive electrode, a negative electrode, and a separator.12 Lithium-ion battery cells primarily function by the movement of lithium ions between the positive and negative electrodes. In cylindrical cells, the three-layer thin-film structure is wound into a cylindrical electrode assembly, while in cuboid cells, the thin-film structure is wound or stacked into an electrode assembly with a roughly cuboid shape.

[0092] It should be noted that the separator 12 is disposed between the positive and negative electrode plates to separate them and prevent short circuits caused by contact. The separator can be at least one of glass fiber, non-woven fabric, polyethylene (PE), polypropylene (PP), and polyvinylidene fluoride. A coating can also be provided on the surface of the separator. The coating can be an inorganic coating and / or an organic coating. The inorganic coating material includes at least one of alumina, silicon oxide, titanium oxide, magnesium oxide, zirconium oxide, and boehmite; the organic coating includes at least one of aramid coating and polyvinylidene fluoride (PVDF) coating.

[0093] It should be noted that the tab is located on one side of the positive / negative current collector and is separately / integrated with the current collector, electrically connected to the current collector to conduct the current on the corresponding current collector. The tab is made of a metal material with good conductivity (such as copper, aluminum, or nickel).

[0094] The protective unit 2 includes an adhesive layer 21 and a base film 22. It should be noted that the base film 22 of the protective unit 2 can be made of the following materials: polyvinyl chloride, polyethylene, polypropylene, polyvinylidene fluoride, or hexafluoropropylene. Vinylidene fluoride copolymer, tetrafluoropropylene Vinylidene fluoride copolymer, trifluorochloropropylene At least one of the following: vinylidene fluoride copolymer, polyethylene terephthalate, polyimide, polyetherimide, polycarbonate, polystyrene, polyphenylene sulfide, polyvinylidene fluoride, polyvinylidene fluoride copolymer, polyarylate, fiber, nylon, nonwoven fabric, etc.

[0095] The material of the adhesive layer 21 of the protective unit 2 can be selected from at least one of the following: acrylic-acrylate copolymer, butadiene-styrene copolymer, styrene-acrylic copolymer, styrene-acrylate copolymer, ethylene-vinyl acetate copolymer, acrylic-grafted polyethylene, maleic anhydride-grafted polyethylene, acrylic-grafted polypropylene, polyvinylidene fluoride, maleic anhydride-grafted polypropylene, carboxymethyl cellulose, polyimide, polyetherimide, styrene-isoprene-styrene copolymer rubber, polyethylene phthalate, ethylene-vinyl acetate copolymer bisphenol A type epoxy resin, ethylene-vinyl acetate copolymer bisphenol F type epoxy resin, glycerol ether type epoxy resin, glycerol ester type epoxy resin, silicone type resin, polyurethane, styrene-isoprene-styrene copolymer, etc.

[0096] The specific preparation process of the battery provided in the embodiments of the present invention is as follows:

[0097] (1) Preparation of the positive electrode:

[0098] The prepared positive electrode active material, conductive agent acetylene black, and binder PVDF are mixed, and solvent NMP is added. The mixture is stirred under vacuum until the system is homogeneous to obtain a positive electrode slurry. The positive electrode slurry is uniformly coated on both surfaces of the positive electrode current collector aluminum foil, air-dried at room temperature, and then transferred to an oven for further drying. Finally, it is cold-pressed and slit to obtain the positive electrode sheet. Specifically, the mass ratio of positive electrode active material: conductive agent: binder satisfies (92~98):(4~1):(4~1).

[0099] (2) Preparation of negative electrode:

[0100] The negative electrode active material, conductive agent acetylene black, thickener CMC, and binder SBR are mixed, and deionized water is added as a solvent. The mixture is stirred under vacuum until the system is homogeneous to obtain a negative electrode slurry. The negative electrode slurry is uniformly coated on both surfaces of the negative electrode current collector copper foil, air-dried at room temperature, and then transferred to an oven for further drying. After cold pressing and slitting, the negative electrode sheet is obtained. The ratio of negative electrode active material: conductive agent: thickener: binder satisfies (90~96): (4~2): (2~1): (4~1).

[0101] (3) Preparation of electrolyte:

[0102] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, fully dried lithium salt LiPF6 was dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0103] (4) Preparation of the diaphragm:

[0104] Polyethylene film is selected as the diaphragm.

[0105] (5) Preparation of lithium-ion batteries:

[0106] The positive electrode, separator, and negative electrode are stacked in sequence, and protective units 2 are attached to the bent sections of the electrodes. The resulting bare battery cell is then formed by winding. The bare cell is placed in a square battery casing. The battery is dried, injected with electrolyte, and then encapsulated, allowed to stand, formed, and volume-adjusted to obtain a lithium-ion battery.

[0107] The positive electrode active material can be selected from one or more lithium-containing positive electrode active materials, including lithium iron phosphate, ternary materials containing nickel, cobalt, and manganese, and lithium manganese iron phosphate; the negative electrode active material can be selected from one or more negative electrode active main materials, such as artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0108] In some embodiments, the compaction density of the active material layer 1102 on the electrode 11 to which the protection unit 2 is attached is ag / cm³. 3 The value range is: 0.9 g / cm³ 3 ≤ag / cm 3 ≤3.8g / cm 3 .

[0109] When the compaction density 'a' of the active material layer 1102 on the electrode 11 to which the protection unit 2 is attached is too high, ion transport is severely hindered, which can easily lead to lithium plating and the formation of lithium dendrites, affecting battery safety. Conversely, when the compaction density 'a' of the active material layer 1102 on the electrode 11 to which the protection unit 2 is attached is too low, although it is beneficial for electrolyte penetration and ion transport, it can result in a loose electrode structure, affecting energy density. Furthermore, the electrolyte can easily come into contact with the adhesive layer 21 of the protection unit 2 through the gaps between the active material particles, increasing the risk of swelling of the adhesive layer 21 and potentially causing the protection unit 2 to detach. Therefore, the compaction density 'a' of the active material layer 1102 on the electrode 11 needs to be controlled within a reasonable range to balance energy density, ion transport performance, and adhesive layer stability.

[0110] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary material, the compaction density is ag / cm³. 3 The value range is: 3.2 g / cm³ 3 ≤ag / cm 3≤3.8g / cm 3 When the positive electrode active material of the battery is lithium iron phosphate, the compaction density is ag / cm³. 3 The value range is: 2.45 g / cm³ 3 ≤ag / cm 3 ≤2.78g / cm 3 ;

[0111] When the negative electrode active material of the battery is graphite, the compaction density is ag / cm³. 3 The value range is: 1.2 g / cm³ 3 ≤ag / cm 3 ≤1.8g / cm 3 When the negative electrode active material of the battery is silicon-carbon, the compaction density is ag / cm³. 3 The value range is: 0.9 g / cm³ 3 ≤ag / cm 3 ≤1.1g / cm 3 .

[0112] For example, in this embodiment, ag / cm 3 The value can be 0.9 g / cm³. 3 or 1g / cm 3 Or 1.2g / cm 3 Or 1.5g / cm 3 Or 1.8g / cm 3 Or 2.1g / cm 3 Or 2.5g / cm 3 Or 2.8g / cm 3 Or 3g / cm 3 Or 3.2g / cm 3 Or 3.8g / cm 3 "etc." can also be the range formed by any two of the above values.

[0113] In some embodiments, the electrode 11 includes a positive electrode, and the compaction density of the active material layer 1102 on the electrode 11 to which the protection unit 2 is attached is ag / cm³. 3 The value range is: 2.4 g / cm³ 3 ≤ag / cm 3 ≤3.8g / cm 3 .

[0114] When electrode 11 is a positive electrode, controlling the compaction density of the positive electrode within a reasonable range facilitates electrolyte penetration, ensures smooth ion transport, and prevents excessive electrolyte from contacting the adhesive layer 21 of the protection unit 2 through the gaps between the active material particles. This reduces the risk of swelling and failure of the adhesive layer 21, ensuring stable adhesion of the protection unit 2. Furthermore, a reasonable compaction density can improve the energy density of the positive electrode.

[0115] In this embodiment, the areal density of the electrode 11 attached to the protection unit 2 ranges from 96 g / mm². 2 -292g / mm 2 ;

[0116] And / or, the thickness of the active material layer 1102 ranges from 30 μm to 210 μm.

[0117] When the areal density of the electrode 11 attached to the protection unit 2 is too high, the thickness of the active material layer 1102 is too large, which affects the electrolyte wetting rate, increases the ion transport resistance, and increases the risk of lithium plating. When the areal density is too low, the thickness of the active material layer 1102 is too small, and the electrolyte can easily come into contact with the adhesive layer 21 of the protection unit 2 through the gaps between the active material particles, which increases the risk of swelling of the adhesive layer 21. This may also cause the protection unit 2 to fall off, and it can easily reduce the battery's capacity per unit area, affecting the energy density.

[0118] For example, in this embodiment, the areal density of the electrode 11 to which the protection unit 2 is attached can be 96 g / mm². 2 Or 100g / mm 2 Or 125g / mm 2 Or 167g / mm 2 Or 196g / mm 2 Or 200g / mm 2 Or 224g / mm 2 Or 292g / mm 2 "etc." can also be the range formed by any two of the above values.

[0119] When the thickness of the active material layer 1102 is too large, the ion migration path is prolonged, which exacerbates the risk of lithium plating; while when the thickness is too small, the electrolyte can easily come into contact with the adhesive layer 21 of the protection unit 2 through the gaps between the active material particles, which increases the risk of swelling of the adhesive layer 21, and may also cause the protection unit 2 to fall off, and is not conducive to the improvement of energy density.

[0120] When the positive electrode active material of the battery is a nickel-cobalt-manganese ternary material, the thickness of the active material layer 1102 ranges from 30μm to 150μm; when the positive electrode active material of the battery is lithium iron phosphate, the thickness of the active material layer 1102 ranges from 70μm to 210μm.

[0121] For example, in this embodiment, the thickness of the active material layer 1102 can be 30μm, 50μm, 80μm, 110μm, 130μm, 160μm, 180μm, or 210μm, or it can be a range formed by any two of the above values.

[0122] In some embodiments, the electrode 11 includes a negative electrode, and the compaction density of the active material layer 1102 on the electrode 11 to which the protection unit 2 is attached is ag / cm³. 3 The value range is: 0.9 g / cm³ 3 ≤ag / cm 3 ≤1.8g / cm 3 .

[0123] When electrode 11 is a negative electrode, controlling the compaction density of the negative electrode within a reasonable range facilitates electrolyte penetration, ensures smooth ion transport, and prevents excessive electrolyte from contacting the adhesive layer 21 of the protection unit 2 through the gaps between the active material particles. This reduces the risk of swelling and failure of the adhesive layer 21, ensuring stable adhesion of the protection unit 2. Furthermore, a reasonable compaction density can increase the energy density of the negative electrode.

[0124] In this embodiment, the areal density of the electrode 11 attached to the protection unit 2 ranges from 36 g / mm². 2 -180g / mm 2 ;

[0125] And / or, the thickness of the active material layer 1102 ranges from 30 μm to 200 μm.

[0126] When the areal density of the electrode 11 attached to the protection unit 2 is too high, the thickness of the active material layer 1102 is too large, which affects the electrolyte wetting rate, increases the ion transport resistance, and increases the risk of lithium plating. When the areal density is too low, the thickness of the active material layer 1102 is too small, and the electrolyte can easily come into contact with the adhesive layer 21 of the protection unit 2 through the gaps between the active material particles, which increases the risk of swelling of the adhesive layer 21. This may also cause the protection unit 2 to fall off, and it can easily reduce the battery's capacity per unit area, affecting the energy density.

[0127] For example, in this embodiment, the areal density of the electrode 11 to which the protection unit 2 is attached can be 36 g / mm². 2 Or 55g / mm 2 Or 75g / mm 2 Or 99g / mm 2 Or 100g / mm 2 Or 120g / mm 2 Or 144g / mm 2 Or 180g / mm 2 "etc." can also be the range formed by any two of the above values.

[0128] Areal density can be adjusted by regulating the solid content of the slurry during electrode preparation. Increasing the solid content increases the areal density. It can also be adjusted by controlling the coating rate. The faster the coating rate, the lower the areal density.

[0129] When the thickness of the active material layer 1102 is too large, the ion migration path is prolonged, which exacerbates the risk of lithium plating; while when the thickness is too small, the electrolyte can easily come into contact with the adhesive layer 21 of the protection unit 2 through the gaps between the active material particles, which increases the risk of swelling of the adhesive layer 21, and may also cause the protection unit 2 to fall off, and is not conducive to the improvement of energy density.

[0130] When the negative electrode active material of the battery is graphite, the thickness of the active material layer 1102 ranges from 30μm to 200μm; when the negative electrode active material of the battery is silicon-carbon, the thickness of the active material layer 1102 ranges from 40μm to 160μm.

[0131] For example, in this embodiment, the thickness of the active material layer 1102 can be 30μm, 50μm, 80μm, 110μm, 130μm, 160μm, 180μm, or 200μm, or it can be a range formed by any two of the above values.

[0132] The test methods for the areal density of electrode 11 and the thickness of active material layer 1102 are as follows: 1) Pretreatment: Discharge the battery at 0.33C to the lower limit voltage, disassemble the electrode with protection unit 2, remove the protection unit 2, and soak the electrode in dimethyl carbonate (DMC) solution for 4 hours; then air dry. When the positive electrode active material of the battery is nickel-cobalt-manganese ternary, the upper limit voltage is 4.25V and the lower limit voltage is 2.5V. When the positive electrode active material of the battery is lithium iron phosphate, the upper limit voltage is 3.6V and the lower limit voltage is 2.5V. 2) Use a punching machine to punch the pretreated electrode into circular pieces of fixed area, with an area of ​​S0 and a quantity of six pieces. Weigh the pieces and calculate the average value, which is recorded as M1. At the same time, use a scanning electron microscope to measure the thickness of the active material layer in each of the six pieces (i.e., the total thickness after removing the current collector), and take the average value, which is recorded as H. H is the thickness of the active material layer 1102. Finally, add an appropriate amount of deionized water to each of the six pieces, gently wipe off the coating on the pieces with lint-free paper to expose the current collector, and let them stand at room temperature (or dry) for 10 minutes. After the current collector is dry, weigh the current collectors of the six pieces, take the average value, and record it as M0. Calculate the areal density of the active material layer on the electrode where the protection unit is located according to the following formula: (M1-M0) / S0.

[0133] In some embodiments, the particle size (D90) of the active material layer 1102 is... The range of D10 / D50 is 0.8-9.

[0134] It should be noted that particle size D50 refers to the particle size value corresponding to 50% of the cumulative volume percentage in the volumetric particle size distribution of the particle sample, while D90 and D10 are the particle size values ​​corresponding to 90% and 10% of the cumulative volume percentage in the volumetric particle size distribution of the particle sample, respectively.

[0135] The testing methods for D10, D50, and D90 are as follows:

[0136] 1) Pretreatment: Discharge the battery to the lower limit voltage at 0.33C, disassemble the electrode with protection unit 2, remove the protection unit 2, soak the electrode in dimethyl carbonate (DMC) solution for 4 hours, dry it at 60℃ for 12 hours, scrape off the powder, grind it to obtain a powder sample.

[0137] 2) Use a laser particle size distribution measuring instrument (Mastersizer 3000) to measure the particle size distribution of the powder sample according to the particle size distribution laser diffraction method (refer to GB / T19077-2016 for specific steps). The particle size corresponding to the cumulative particle size distribution percentage of 50% is D50; the particle size corresponding to the volume particle size distribution of 10% is D10; and the particle size corresponding to the volume particle size distribution of 90% is D90.

[0138] (D90 The value of D10 / D50 is used to characterize the breadth of the particle size distribution. When (D90) When the value of (D10) / D50 is too large, it indicates that the particle size distribution is too wide and the difference in particle gradation is greater, which may lead to local uneven porosity and low porosity. This affects the uniform wetting of the electrolyte, increases ion transport resistance, exacerbates the risk of lithium plating, and easily forms lithium dendrites, triggering the risk of internal short circuits. Conversely, when (D90) / D50 is too large... When the value of D10 / D50 is too small, the particle size distribution is too narrow and the porosity is too large, which leads to an increase in the contact area between the electrolyte and the adhesive layer 21. This can easily cause the adhesive layer 21 to swell and fall off, thereby affecting the bonding stability of the protection unit 2.

[0139] For example, in this embodiment, the particle size (D90) of the active material layer 1102 is... The value of D10 / D50 can be 0.8, 1, 1.5, 2, 3.5, 5, 6.7, 8.2, or 9, or it can be any range formed by any two of the above values.

[0140] The electrode 11 includes a positive electrode and a negative electrode, and the active material layer 1102 includes a positive active material and a negative active material. The positive active material can be lithium iron phosphate, ternary materials or lithium cobalt oxide, etc., and the negative active material can be graphite, silicon-carbon composite material, etc.

[0141] When the active material layer 1102 is the positive electrode active material, and the positive electrode active material is selected as a ternary material, its particle size (D90) The specific range of D10 / D50 is 1.5~8.5.

[0142] When the active material layer 1102 is the positive electrode active material, and the positive electrode active material is selected as lithium iron phosphate, its particle size (D90) The specific range of D10 / D50 is 3.5~9.

[0143] When the active material layer 1102 is the negative electrode active material, and the negative electrode active material is selected as a silicon-carbon composite material, its particle size (D90) The specific range of D10 / D50 is 1.5~4.2.

[0144] When the active material layer 1102 is the negative electrode active material, and the negative electrode active material is selected as graphite, its particle size (D90) The specific range of D10 / D50 is 0.8~1.5.

[0145] In some embodiments, the particle size D50 of the active material layer 1102 ranges from 0.2 μm to 30 μm.

[0146] When the particle size D50 of the active material layer 1102 is too large, it can easily lead to excessively large pore size, resulting in increased electrolyte retention and a larger contact area between the electrolyte and the adhesive layer 21. This increases the risk of swelling of the adhesive layer 21 and consequently affects the adhesion of the protection unit 2. On the other hand, when the particle size D50 of the active material layer 1102 is too small, the pore size is small, resulting in insufficient electrolyte wetting, which affects ion transport efficiency, exacerbates the risk of lithium plating, and easily leads to the formation of lithium dendrites, causing the risk of internal short circuits.

[0147] When the active material layer 1102 is the positive electrode active material, and the positive electrode active material is selected as a ternary material, the D50 of its particle size is specifically in the range of 2μm-20μm.

[0148] When the active material layer 1102 is the positive electrode active material, and the positive electrode active material is lithium iron phosphate, the D50 of its particle size is specifically in the range of 0.2μm-2μm.

[0149] When the active material layer 1102 is the negative electrode active material, and the negative electrode active material is selected as a silicon-carbon composite material, the D50 of its particle size is specifically in the range of 7μm-15μm.

[0150] When the active material layer 1102 is the negative electrode active material, and the negative electrode active material is selected as graphite, the D50 of its particle size is specifically in the range of 10μm-30μm.

[0151] For example, in this embodiment, the D50 value of the particle size of the active material layer 1102 can be 2μm, 5μm, 8μm, 10μm, 15μm, or 20μm, or it can be a range formed by any two of the above values.

[0152] In some embodiments, along the first direction, at least one end of the active material layer 1102 is spaced apart from the end of the current collector layer 1101 to form a spacer region; the protective unit 2 is at least partially bonded to the surface of the current collector layer 1101 in the spacer region, and the height of the overlap between the protective unit 2 and the spacer region is Bmm, satisfying 1mm≤Bmm≤10mm.

[0153] By at least partially bonding the protection unit 2 to the surface of the current collector layer 1101 in the spacer region, the bonding strength between the protection unit 2 and the electrode 11 can be improved, avoiding the problem of insufficient interfacial bonding caused by the protection unit 2 being directly bonded to the active material layer 1102.

[0154] If the overlap height B between the protection unit 2 and the spacer area is too large, it may reduce the height of the active material layer 1102, affecting the capacity of the electrode and reducing the lithium-ion transport area, making lithium plating more likely. Conversely, if the overlap height B between the protection unit 2 and the spacer area is too small, the bonding area between the protection unit 2 and the spacer area will be insufficient, which may lead to insufficient bonding strength between the protection unit and the current collector layer. During cell winding or use, the protection unit may easily fall off or lift up, affecting its protective effect on the active material layer 1102 and easily causing material loss.

[0155] For example, in this embodiment, the value of Bmm can be 1mm or 2mm or 4mm or 5mm or 6mm or 8mm or 10mm, or it can be any range formed by any two of the above values.

[0156] In some embodiments, the electrode 11 further includes an insulating layer 1103, the insulating layer 1103 is disposed in the spacer region, the protection unit 2 is at least partially bonded to the surface of the insulating layer 1103, and the value range of y satisfies: 0.12≤y≤0.7.

[0157] By setting the insulating layer 1103 in the interval area, the bonding stability between the protection unit 2 and the electrode 11 can be further improved, and the protection unit 2 can be prevented from falling off. At this time, the thickness of the adhesive in the protection unit 2 can be appropriately reduced to improve the lithium-ion transport rate and prevent lithium plating.

[0158] Meanwhile, the insulation layer 1103 can prevent the short circuit risk caused by direct contact between the current collector layer 1101 and the external structure.

[0159] It should be noted that the insulating layer 1103 is coated on at least one side of the current collector near the tab, or on at least one side of the tab surface, to prevent short circuit between the tab and the opposite electrode; it can also prevent the tab from breaking when bent during battery cell assembly.

[0160] In this embodiment, the insulating layer 1103 can specifically be tab adhesive. Tab adhesive mainly includes insulating materials such as PVDF (polyvinylidene fluoride), boehmite, polypropylene, and polyethylene.

[0161] In some embodiments, combined with Figure 5 As shown, along the first direction, the length of the insulating layer 1103 is C mm, which satisfies 1 mm ≤ C mm ≤ 10 mm.

[0162] When the length C of the insulating layer 1103 is too short, it cannot completely cover the exposed area of ​​the current collector layer 1101, resulting in insufficient insulation protection, a potential short circuit hazard, and an insufficient bonding area between the protection unit 2 and the insulating layer 1103, leading to low bonding strength and affecting the fixing effect of the protection unit 2, which in turn can easily cause the protection unit 2 to fall off. When the length C of the insulating layer 1103 is too long, it may cover part of the active material layer 1102, causing lithium ion transport to be too concentrated, increasing the risk of lithium plating and reducing the effective utilization rate of the electrode 11.

[0163] For example, in this embodiment, the value of Cmm can be 1mm or 2mm or 4mm or 5mm or 6mm or 8mm or 10mm, or it can be any range formed by any two of the above values.

[0164] In some embodiments, the ratio of the thickness of the insulating layer 1103 to the thickness of the active material layer 1102 ranges from 0.095 to 0.92.

[0165] Since both the insulating layer 1103 and the active material layer 1102 are coated on the surface of the current collector layer 1101, depending on the specific application environment, the thickness of the insulating layer 1103 can be thinner or thicker than the active material layer 1102.

[0166] When the ratio of the thickness of the insulating layer 1103 to the thickness of the active material layer 1102 is too large, the insulating layer 1103 becomes too thick, which may lead to uneven electrode thickness, affecting the adhesion between electrodes and thus affecting lithium-ion transport efficiency, resulting in lithium plating. Conversely, when the ratio of the thickness of the insulating layer 1103 to the thickness of the active material layer 1102 is too small, the insulating layer 1103 becomes too thin, which may cause a decrease in adhesion between the protection unit 2 and the insulating layer 1103, affecting the fixation reliability of the protection unit 2, causing the edges of the protection unit 2 to lift up, and thus causing the protection unit 2 to fall off, resulting in the active material layer 1102 falling off. At the same time, it reduces the insulation protection effect and increases the risk of short circuit.

[0167] For example, in this embodiment, the ratio of the thickness of the insulating layer 1103 to the thickness of the active material layer 1102 can be 0.095, 0.1, 0.5, 1, 1.1, 1.5, 2.3, 3, or 3.667, or it can be any range formed by any two of the above values.

[0168] In some embodiments, the air permeability xs / 100mL of the protection unit 2 is in the range of: 150s / 100mL≤xs / 100mL≤2000s / 100mL.

[0169] When the permeability x of the protection unit 2 is too small, the shorter the time, the better the permeability. This increases the contact area between the electrolyte and the adhesive layer 21, causing the adhesive layer 21 to swell rapidly in the electrolyte and lose its adhesive strength, leading to the detachment of the protection unit 2 and thus the loss of its protective function for the active material layer. Conversely, when the permeability x of the protection unit 2 is too large, the longer the time, the worse the permeability. Although this ensures the stability of the adhesive layer, it exacerbates the obstruction of ion transport and increases the risk of lithium plating. Therefore, the permeability x of the protection unit 2 needs to be controlled within a reasonable range to balance ion conduction efficiency and adhesive performance.

[0170] For example, in this embodiment, the value of xs / 100mL can be 150s / 100mL or 200s / 100mL or 400s / 100mL or 600s / 100mL or 900s / 100mL or 1200s / 100mL or 1400s / 100mL or 1700s / 100mL or 2000s / 100mL, or it can be any range formed by any two of the above values.

[0171] In some embodiments, combined with Figure 6 As shown, the base film 22 has through holes 221 that extend through the thickness direction of the base film 22, and the diameter of a single through hole 221 ranges from 10μm to 500μm.

[0172] By creating vias 221 on the base film 22, the unobstructed flow of ion transport channels can be effectively improved, reducing lithium-ion migration resistance. When the pore size of a single via 221 is too large, it increases the contact area between the electrolyte and the adhesive layer 21, causing the adhesive layer 21 to swell faster in the electrolyte, weakening the bonding reliability of the protection unit 2, and thus causing edge lifting or overall detachment. Conversely, when the pore size of a single via 221 is too small, although it can slow down the swelling of the adhesive layer, the ion transport path is restricted, ion transport is further hindered, and the risk of lithium plating increases.

[0173] For example, in this embodiment, the aperture of a single through hole 221 can be 10μm or 20μm or 70μm or 120μm or 200μm or 280μm or 330μm or 420μm or 500μm, or it can be a range formed by any two of the above values.

[0174] In some embodiments, combined with Figure 6 As shown, the through hole 221 is spaced apart from the edge of the protection unit 2, and the spacing is Lμm, which satisfies 500μm≤Lμm≤2000μm.

[0175] When the distance L between the through-hole 221 and the edge of the protection unit 2 is too small, the contact area between the edge of the protection unit 2 and the electrolyte increases. The electrolyte can easily seep into the adhesive layer 21 through the edge gaps, accelerating the swelling of the adhesive layer, reducing the interfacial adhesion strength, and thus causing the edge of the protection unit 2 to lift or partially peel off, thereby weakening the protective effect on the active material layer. When the distance L is too large, although it can effectively inhibit the electrolyte from seeping from the edge, it will significantly reduce the number of effective through-holes, resulting in uneven distribution of ion transport paths and an increased risk of lithium plating.

[0176] For example, in this embodiment, the value of Lμm can be 500μm, 700μm, 900μm, 1100μm, 1300μm, 1700μm, or 2000μm, or it can be any range formed by any two of the above values.

[0177] In some embodiments, the base film 22 has a through hole 221 that extends through the thickness direction of the base film 22, and the adhesive layer 21 has a clearance portion that is at least partially corresponding to the through hole 221.

[0178] By incorporating a clearance section, the adhesive layer 21 is prevented from completely covering the through-hole 221, thus preserving an effective ion transport channel. This further enhances lithium-ion transport capability and prevents lithium plating.

[0179] Meanwhile, the avoidance section can reduce the area of ​​direct contact between the electrolyte and the adhesive layer through the through hole 221, suppress excessive swelling of the adhesive layer, and improve the stability of the protection unit in the electrolyte environment.

[0180] In some embodiments, the ratio y of the adhesive layer 21 to the thickness of the protective unit 2 is in the range of 0.12≤y≤0.83.

[0181] When the proportion y of the adhesive layer 21 to the thickness of the protection unit 2 is too large, the excessive thickness of the adhesive layer 21 will partially block the ion channels, increase the resistance to lithium ion migration, and thus affect the ion conduction efficiency. This will increase the risk of lithium plating in the corresponding area of ​​the protection unit 2, affecting battery safety. Conversely, when the proportion y of the adhesive layer 21 to the thickness of the protection unit 2 is too small, the bonding effect will be weakened, resulting in a weak bond between the protection unit 2 and the active material layer 1102. This will make it prone to local peeling during bending or cycling of the cell 1, thereby reducing the protective effect on the active material layer 1102. Therefore, the proportion y of the adhesive layer thickness needs to be controlled within an appropriate range to achieve a balance between bonding performance and ion conduction performance.

[0182] For example, when the ratio of the thickness of the adhesive layer 21 to the thickness of the base film 22 is 3:10, the point value of y is 0.23.

[0183] For example, in this embodiment, the value of y can be 0.12 or 0.19 or 0.23 or 0.24 or 0.33 or 0.49 or 0.56 or 0.7 or 0.76 or 0.8 or 0.83, or it can be any range formed by any two of the above values.

[0184] In some embodiments, the thickness of the protection unit 2 is y1mm, satisfying 20mm≤y1mm≤120mm;

[0185] And / or, the thickness of adhesive layer 21 is y2mm, satisfying 10mm≤y2mm≤50mm.

[0186] When the thickness y1 of the protection unit 2 is too large, it will increase the overall thickness of the cell and affect the energy density; at the same time, it will reduce the controllability of the winding process and increase the risk of cell deformation; when the thickness y1 of the protection unit 2 is too small, its mechanical strength is insufficient, it is easy to crack or perforate, and it is difficult to effectively block the electrolyte penetration, thus losing the protective effect on the active material layer.

[0187] When the thickness y2 of the adhesive layer 21 is too large, it will increase the resistance to ion transport, thereby affecting the ion conduction efficiency, increasing the risk of lithium plating and affecting the safety of battery use; while when the thickness y2 of the adhesive layer 21 is too small, the adhesion is insufficient, which can easily lead to poor bonding between the protection unit 2 and the active material layer 1102, resulting in local peeling during cell bending or cycling, thereby weakening the protection effect on the active material layer.

[0188] For example, in this embodiment, the value of y1mm can be 20mm or 45mm or 59mm or 76mm or 97mm or 120mm, or it can be any range formed by any two of the above values.

[0189] For example, in this embodiment, the value of y2mm can be 10mm or 15mm or 19mm or 23mm or 32mm or 50mm, or it can be any range formed by any two of the above values.

[0190] In some embodiments, the electrode 11 includes a positive electrode and a negative electrode, the protective unit 2 is attached to the surface of the positive electrode, and / or the protective unit 2 is attached to the surface of the negative electrode.

[0191] By setting protection units 2 on the surfaces of both the positive and negative electrodes, the active material layer 1102 of the positive and negative electrodes can be fully protected, reducing the risk of material loss during the cycle and improving the cycle life and structural stability of the cell.

[0192] In some embodiments, the protection unit 2 is disposed within the range where the number of winding layers of the battery cell 1 is less than or equal to five layers.

[0193] When the number of winding layers is small, the bending curvature of the electrode 11 is large, and the stress concentration effect is significant. Setting the protection unit 2 can effectively alleviate the peeling of the active material layer 1102. When the number of winding layers exceeds five, the stress distribution tends to be uniform, and the protection unit 2 can be omitted to simplify the process.

[0194] Within the range of five or fewer winding layers, each layer can be equipped with a protection unit 2, or it can be set only on the inner one to three layers where stress concentration is most significant.

[0195] In some embodiments, combined with Figure 2 As shown, both ends of the straight section 8 along the second direction are provided with bent sections 9, and the surfaces of the active material layers 1102 corresponding to the bent sections 9 at both ends are attached with protective units 2.

[0196] By attaching protective units 2 to the surfaces of the active material layer 1102 corresponding to the bending sections 9 at both ends, the protective effect of the bending sections 9 can be effectively enhanced, preventing the active material layer 1102 from cracking or falling off.

[0197] In some embodiments, active material layers 1102 are provided on both sides of the current collector layer 1101, and protective units 2 are attached to the surface of the active material layers 1102 on both sides.

[0198] By attaching protective units 2 to the surfaces of the active material layers 1102 on both sides, the active materials on both sides of the current collector layer are protected simultaneously, avoiding cracking and peeling of the active material layer 1102 caused by uneven force on one side or local stress concentration, thereby improving the overall stability of the cell structure.

[0199] In some embodiments, when the electrode 11 is in the unfolded state and along the length direction of the electrode 11, the length of the protection unit 2 is 10mm to 30mm.

[0200] For example, in this embodiment, the length of the protection unit 2 can be 10mm, 15mm, 19mm, 23mm, 28mm, or 30mm, or it can be any range formed by any two of the above values.

[0201] In some embodiments, the electrode 11 has a crease in a portion of the bent section 9, and the protective unit 2 at least covers the crease of the electrode 11.

[0202] In this embodiment, the crease is formed when the electrode sheet in the bending section 9 of the inner winding is squeezed. The crease is the weakest area of ​​the electrode sheet in the wound cell. By making the protection unit 2 at least cover the crease of the electrode sheet 11, cracking and material loss at the crease are effectively suppressed, and the integrity of the cell structure and cycle life are improved.

[0203] In some embodiments, when the electrode 11 is unfolded and along the length direction of the electrode 11, the protection unit 2 extends beyond the crease and the extension distance is not less than 3mm. When the electrode 11 is unfolded, the length direction of the electrode 11 is perpendicular to the first direction.

[0204] By extending the protective unit 2 beyond the crease, the bonding area can be effectively expanded, further enhancing the support and fixation effect on the crease area, thereby reducing the risk of cracking of the electrode at the crease location. If the distance beyond the crease is too short, the bonding strength of the protective unit 2 will be insufficient, making it prone to detachment.

[0205] In some embodiments, the following condition is satisfied: 44≤x·y·a≤3660.

[0206] According to an embodiment of the present invention, in another aspect, an electrical device is also provided, comprising:

[0207] The electrical device body and the battery as described above, with the electrical device body and the battery being electrically connected.

[0208] In this embodiment, the battery can provide electrical energy to the main body of the electrical device. The battery device can be an electronic device, an electric vehicle, or an energy storage system. The electronic device includes a smartphone, a laptop or a tablet computer, the electric vehicle includes an electric car, an electric bicycle or an electric bus, and the energy storage system is used for grid peak shaving, distributed energy storage or emergency power supply.

[0209] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Although embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and all such modifications and variations fall within the scope defined by the present invention.

Claims

1. A battery, characterized in that, include: A battery cell (1) includes a straight section (8) and a bent section (9). The battery cell (1) includes an electrode (11) and a separator (12) located between adjacent electrodes (11). The electrode (11) includes a bent portion (111) in a bent state, the bent portion (111) being located in the bent section (9) of the battery cell (1). The electrode (11) includes a current collector layer (1101) and an active material layer (1102) coated on at least one side of the current collector layer (1101). The protective unit (2) includes an adhesive layer (21) and a base film (22). The protective unit (2) is attached to the surface of the active material layer (1102) of the bent portion (111) through the adhesive layer (21). The air permeability of the protective unit (2) is xs / 100mL; the ratio of the adhesive layer (21) to the thickness of the protective unit (2) is y; the compaction density of the active material layer (1102) on the electrode (11) to which the protective unit (2) is attached is ag / cm³. 3 x, y, and a satisfy: 20 ≤ x·y·a ≤ 6290.

2. The battery according to claim 1, characterized in that, The compaction density of the active material layer (1102) on the electrode (11) to which the protective unit (2) is attached is ag / cm³. 3 The value range is: 0.9 g / cm³ 3 ≤ag / cm 3 ≤3.8g / cm 3 .

3. The battery according to claim 2, characterized in that, The electrode (11) includes a positive electrode, and the compaction density of the active material layer (1102) on the electrode (11) to which the protective unit (2) is attached is ag / cm³. 3 The value range is: 2.4 g / cm³ 3 ≤ag / cm 3 ≤3.8g / cm 3 .

4. The battery according to claim 3, characterized in that, The areal density of the electrode (11) to which the protective unit (2) is attached ranges from 96 g / mm². 2 -292g / mm 2 ; And / or, the thickness of the active material layer (1102) ranges from 30 μm to 210 μm.

5. The battery according to claim 2, characterized in that, The electrode (11) includes a negative electrode, and the compaction density of the active material layer (1102) on the electrode (11) to which the protective unit (2) is attached is ag / cm³. 3 The value range is: 0.9 g / cm³ 3 ≤ag / cm 3 ≤1.8g / cm 3 .

6. The battery according to claim 5, characterized in that, The areal density of the electrode (11) to which the protective unit (2) is attached ranges from 36 g / mm². 2 -180g / mm 2 ; And / or, the thickness of the active material layer (1102) ranges from 30 μm to 200 μm.

7. The battery according to claim 1, characterized in that, The particle size (D90) of the active material layer (1102) The range of D10 / D50 is 0.8-9.

8. The battery according to claim 1, characterized in that, The particle size D50 of the active material layer (1102) ranges from 0.2 μm to 30 μm.

9. The battery according to claim 1, characterized in that, Along the first direction, at least one end of the active material layer (1102) is spaced apart from the end of the current collector layer (1101) to form a spacer area; the protective unit (2) is at least partially bonded to the surface of the current collector layer (1101) in the spacer area, and the height of the overlap between the protective unit (2) and the spacer area is Bmm, satisfying 1mm≤Bmm≤10mm.

10. The battery according to claim 9, characterized in that, The electrode (11) further includes an insulating layer (1103), the insulating layer (1103) is disposed in the interval area, the protection unit (2) is at least partially bonded to the surface of the insulating layer (1103), and the value range of y satisfies: 0.12≤y≤0.

7.

11. The battery according to claim 10, characterized in that, Along the first direction, the length of the insulating layer (1103) is C mm, which satisfies 1 mm ≤ C mm ≤ 10 mm.

12. The battery according to claim 10, characterized in that, The ratio of the thickness of the insulating layer (1103) to the thickness of the active material layer (1102) is in the range of 0.095-0.

92.

13. The battery according to any one of claims 1 to 12, characterized in that, The air permeability xs / 100mL of the protection unit (2) is in the range of: 150s / 100mL≤xs / 100mL≤2000s / 100mL.

14. The battery according to claim 1, characterized in that, The base film (22) has through holes (221) that extend through the thickness direction of the base film (22), and the adhesive layer (21) has a clearance portion that is at least partially corresponding to the through holes (221).

15. The battery according to any one of claims 1 to 12, characterized in that, The ratio y of the adhesive layer (21) to the thickness of the protective unit (2) is in the range of 0.12≤y≤0.

83.

16. The battery according to claim 15, characterized in that, The thickness of the protection unit (2) is y1mm, which satisfies 20mm≤y1mm≤120mm; And / or, the thickness of the adhesive layer (21) is y2mm, satisfying 10mm≤y2mm≤50mm.

17. The battery according to any one of claims 1 to 12, characterized in that, The electrode (11) includes a positive electrode and a negative electrode, and the protective unit (2) is attached to the surface of the positive electrode.

18. The battery according to any one of claims 1 to 12, characterized in that, The protection unit (2) is located within the range where the number of winding layers of the battery cell (1) is less than or equal to five.

19. The battery according to any one of claims 1 to 12, characterized in that, The straight section (8) is provided with the bent section (9) at both ends along the second direction, and the protective unit (2) is attached to the surface of the active material layer (1102) corresponding to the bent section (9) at both ends.

20. The battery according to any one of claims 1 to 12, characterized in that, The current collector layer (1101) has an active material layer (1102) on each of its opposite sides, and the protective unit (2) is attached to the surface of the active material layer (1102) on both sides.

21. The battery according to any one of claims 1 to 12, characterized in that, When the electrode (11) is in the unfolded state and along the length direction of the electrode (11), the length of the protection unit (2) is 10mm~30mm.

22. The battery according to any one of claims 1 to 12, characterized in that, The electrode (11) has a crease in a portion of the bending section (9), and the protective unit (2) covers at least the crease of the electrode (11).

23. The battery according to claim 22, characterized in that, When the electrode (11) is in the unfolded state and along the length direction of the electrode (11), the protective unit (2) extends beyond the crease and the extension distance is not less than 3mm.

24. The battery according to any one of claims 1 to 12, characterized in that, It satisfies: 44≤x·y·a≤3660.

25. An electrical appliance, characterized in that, include: The electrical device body and the battery as described in any one of claims 1 to 24, wherein the electrical device body is electrically connected to the battery.

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