Battery and battery pack

Abstract

The application relates to the technical field of batteries, and discloses a battery and a battery pack, which comprise a shell and a battery cell; the shell comprises a shell main body and a cover plate, at least one end of the shell main body is provided with an opening, the cover plate is arranged on the opening and is electrically connected with the battery cell, the cover plate comprises a plurality of plate bodies arranged in a stack, along the stacking direction of the plate bodies, a plate body far from the battery cell is a first plate, and a plate body close to the battery cell is a second plate; the first plate comprises a metal element other than titanium, the second plate comprises a titanium element, the electrical conductivity of the metal element is greater than that of the titanium element, the ratio of the thickness d of the first plate to the thickness e of the second plate is a, the resistivity of the cover plate is b, the content of the titanium element in the second plate is c%, and 11<=c*b / a<=130 is satisfied. By controlling the content of titanium, the ratio of the thickness d of the first plate to the thickness e of the second plate and the relationship between the resistivity of the cover plate, the overcurrent capacity of the cover plate is improved, the resistance in the current transmission process is effectively reduced, and the temperature rise of the cover plate is avoided.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically to batteries and battery packs. Background Technology

[0002] A rechargeable battery is a type of battery that can recover its performance through a charging process after being discharged. Rechargeable batteries are widely used in consumer electronics (such as mobile phones, tablets, and digital cameras), electric vehicles, energy storage systems, and other fields.

[0003] Battery lightweighting is a crucial direction in current battery technology development, particularly in fields such as electric vehicles, portable electronic devices, and aerospace. With increasing demands for energy efficiency and portability, reducing battery weight while maintaining or increasing its energy density has become a research hotspot.

[0004] A battery consists of a casing and battery cells housed within the casing. The casing is made of materials such as titanium, which is beneficial for achieving a lightweight design and improving energy density. However, titanium casings have poor conductivity, affecting the battery's overcurrent capacity and thus negatively impacting battery performance and lifespan. Summary of the Invention

[0005] In view of this, the present invention provides a battery and a battery pack to solve the problem that the titanium casing affects the overcurrent capacity of the battery.

[0006] In a first aspect, the present invention provides a battery, comprising: a casing and a battery cell, the battery cell being disposed inside the casing; the casing comprising a casing body and a cover plate, at least one end of the casing body having an opening, the cover plate being disposed over the opening and electrically connected to the battery cell, the cover plate comprising a plurality of plates stacked together, the plate farther from the battery cell being a first plate along the stacking direction of the plurality of plates being a second plate, the first plate comprising a non-titanium metal element, the second plate comprising titanium element, the conductivity of the metal element being greater than the conductivity of the titanium element, the ratio of the thickness d of the first plate to the thickness e of the second plate being a, the resistivity of the cover plate being b in Ω·mm, and the titanium element content in the second plate being c%, satisfying 11≤c×b / a≤130.

[0007] Beneficial effects: By comprehensively controlling the relationship between the titanium content, the ratio of the thickness d of the first plate to the thickness e of the second plate, and the resistivity of the cover plate, the current carrying capacity of the cover plate can be improved, which can effectively reduce the resistance during current transmission and avoid the increase in cover plate temperature. At the same time, since titanium has a high specific strength, the overall structural strength of the cover plate can be improved, thus taking into account the structural strength of the cover plate and preventing the cover plate from easily deforming during battery charging and discharging, thereby improving the battery's resistance to deformation.

[0008] Secondly, the present invention also provides a battery pack, comprising: a plurality of the above-described batteries; a busbar connecting two adjacent batteries, the busbar being made of the same material as the first plate. Attached Figure Description

[0009] 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.

[0010] Figure 1 This is a perspective view of a battery according to an embodiment of the present invention;

[0011] Figure 2 for Figure 1 The sectional view of the cover plate shown;

[0012] Figure 3 This is a schematic diagram of the welding structure of the battery cell, current collector, cover plate and busbar according to an embodiment of the present invention;

[0013] Figure 4 This is a schematic diagram showing the area of ​​the second welding area and the current collector in an embodiment of the present invention;

[0014] Figure 5 This is a schematic diagram showing the area of ​​the first welding area and the electrode tab in an embodiment of the present invention;

[0015] Figure 6 This is a schematic diagram showing the area of ​​the pole and cover plate in an embodiment of the present invention.

[0016] Explanation of reference numerals in the attached figures:

[0017] 1. Shell body; 2. Cover plate; 201. First plate; 202. Second plate; 3. Battery cell; 301. Battery cell body; 302. Electrode; 4. Current collector; 5. First welding area; 6. Second welding area; 7. Terminal post; 8. Busbar; 9. Third welding area. Detailed Implementation

[0018] 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.

[0019] The following is combined with Figures 1 to 6 The following describes embodiments of the present invention.

[0020] According to an embodiment of the present invention, a battery is provided, comprising: a casing and a battery cell 3, wherein the battery cell 3 is disposed inside the casing; the casing includes a casing body 1 and a cover plate 2, wherein at least one end of the casing body 1 is provided with an opening, the cover plate 2 is disposed on the opening and electrically connected to the battery cell 3, the cover plate 2 includes a plurality of plates stacked together, wherein along the stacking direction of the plurality of plates, the plate farther away from the battery cell 3 is a first plate 201, and the plate closer to the battery cell 3 is a second plate 202, the first plate 201 includes a non-titanium metal element, the second plate 202 includes titanium element, the conductivity of the metal element is greater than the conductivity of the titanium element, the ratio of the thickness d of the first plate 201 to the thickness e of the second plate 202 is a, the resistivity of the cover plate 2 is b in Ω·mm, and the content of titanium element in the second plate 202 is c%, satisfying 11≤c×b / a≤130.

[0021] In the battery using this embodiment, since the cover plate 2 serves as the electrode output terminal and is electrically connected to the current collector 4, the cover plate 2 needs to transmit current. By comprehensively controlling the relationship between the titanium content, the ratio of the thickness d of the first plate 201 to the thickness e of the second plate 202, and the resistivity of the cover plate 2, the current carrying capacity of the cover plate 2 can be improved. This can effectively reduce the resistance during current transmission and prevent the temperature rise of the cover plate 2 from increasing. At the same time, since titanium has a high specific strength, the overall structural strength of the cover plate 2 can be improved, thereby taking into account the structural strength of the cover plate 2 and preventing the cover plate 2 from easily deforming during the charging and discharging process, thus improving the battery's resistance to deformation.

[0022] It is worth noting that if the value of c×b / a is too large, the current carrying capacity of cover plate 2 will be poor, and the impedance during current transmission will be too large when cover plate 2 acts as the current output terminal, resulting in excessive temperature rise of cover plate 2 during battery charging and discharging. If the value of c×b / a is too small, the structural strength of cover plate 2 will be weak, and cover plate 2 will be prone to deformation during battery charging and discharging.

[0023] Optionally, c×b / a can take any value from 11, 14, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, or a value between any two values.

[0024] Further preferred, the value of c×b / a satisfies 14≤c×b / a≤70.

[0025] Specifically, in one embodiment, the titanium content (c%) in the second plate 202 satisfies 90% ≤ c% ≤ 99.9%. By further controlling c% within the above range, the overall weight can be reduced while ensuring structural strength, which helps to enhance the mechanical strength and durability of the second plate 202, making it more resistant to external physical damage.

[0026] Optionally, c% can be any one of 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 99.9%, or a value between any two of them.

[0027] Further preferably, the value of c% satisfies 98.5% ≤ c% ≤ 99.9%.

[0028] Specifically, in one embodiment, the ratio a of the thickness d of the first plate 201 and the thickness e of the second plate 202 satisfies 0.2 ≤ a ≤ 0.7. By further limiting a to the above range, it helps to reduce resistance and improve current carrying efficiency, thereby enhancing the overall electrical performance of the battery; at the same time, it can increase the mechanical strength and durability of the entire cover plate 2, providing better physical protection and preventing external impacts from damaging the internal battery structure.

[0029] Optionally, the value of 'a' can be any one of 0.2, 0.25, 0.27, 0.28, 0.3, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, or 0.7, or a value between any two values.

[0030] Further preferred, the value of a satisfies 0.25≤a≤0.6.

[0031] Specifically, in one embodiment, the resistivity b of the cover plate 2 satisfies 0.077 Ω·mm ≤ b ≤ 0.298 Ω·mm. By further controlling b within the above range, energy loss during current flow can be reduced, thereby improving overall energy utilization and device operating time, while also helping to prevent local overheating and enhancing battery safety performance.

[0032] Optionally, the value of b can be any one of 0.077Ω·mm, 0.08Ω·mm, 0.1Ω·mm, 0.12Ω·mm, 0.15Ω·mm, 0.18Ω·mm, 0.2Ω·mm, 0.22Ω·mm, 0.25Ω·mm, 0.28Ω·mm, or 0.298Ω·mm, or a value between any two of these values.

[0033] Further preferred, the value of b satisfies 0.077Ω·mm≤b≤0.2Ω·mm.

[0034] It should be noted that the resistivity of cover plate 2 can be measured using a resistivity meter. Specifically, first, input the thickness and width of the sample into the instrument, then clamp the measuring clips to the ends of the sample, start the test, and the instrument will read the resistivity data.

[0035] Furthermore, in one embodiment, such as Figure 2As shown, the thickness d of the first plate 201 satisfies 0.2mm ≤ d ≤ 0.4mm. By further controlling d within the above range, the overcurrent resistance of the cover plate 2 is reduced while ensuring the energy density of the battery.

[0036] Optionally, d can be any value from 0.2mm, 0.22mm, 0.25mm, 0.28mm, 0.3mm, 0.32mm, 0.35mm, 0.38mm, 0.4mm, or a value between any two values.

[0037] Furthermore, in one embodiment, such as Figure 2 As shown, the thickness e of the second plate 202 satisfies 0.6mm ≤ e ≤ 0.8mm. By further controlling e within the above range, the energy density of the battery is guaranteed while ensuring the structural strength of the cover plate 2.

[0038] Optionally, the value of e can be any one of 0.6mm, 0.62mm, 0.65mm, 0.68mm, 0.7mm, 0.72mm, 0.75mm, 0.78mm, or 0.8mm, or a value between any two of these values.

[0039] In one embodiment, such as Figure 2 As shown, there are two plates, with the first plate 201 and the second plate 202 connected together. The value of 'a' satisfies 0.2 ≤ a ≤ 0.6. The cover plate 2 adopts a double-layer structure, which is simpler and avoids the need for welding multiple dissimilar metals and current collectors 4 in a multi-layer structure. This helps improve the reliability and consistency of the welding process, increases the current carrying capacity of the cover plate 2, and reduces energy loss. Therefore, the value of 'a' is further limited, thereby increasing the thickness of the second plate 202 and further enhancing the structural strength of the cover plate 2.

[0040] In one embodiment, such as Figure 2 As shown, the outer periphery of the second plate 202 extends beyond the outer periphery of the first plate 201, and the value of 'a' satisfies 0.25 ≤ a ≤ 0.7. The outer periphery of the first plate 201 and the outer periphery of the second plate 202 are spaced apart. The area of ​​the first plate 201 is limited, thus limiting the area available for subsequent welding to achieve flow passage, and limiting the improvement in the flow capacity of the cover plate 2. Therefore, by further controlling 'a' within the aforementioned range, the thickness of the first plate 201 can be further increased, thereby improving the flow capacity of the cover plate 2.

[0041] Furthermore, such as Figure 2As shown, the distance L1 between the outer periphery of the first plate 201 and the outer periphery of the second plate 202 satisfies 2mm ≤ L1 ≤ 5mm. By further keeping L1 within the above range, while ensuring the flow capacity of the cover plate 2, a certain space is reserved for welding the second plate 202 and the current collector 4, so that only the second plate 202 and the current collector 4 are welded, avoiding welding of more metal phases and affecting the welding effect, thereby ensuring the flow capacity.

[0042] Optionally, L1 can be any value from 2mm, 2.2mm, 2.6mm, 2.8mm, 3mm, 3.2mm, 3.5mm, 3.8mm, 4mm, 4.2mm, 4.5mm, 4.8mm, and 5mm, or a value between any two of these. Furthermore, along the circumferential direction of the first plate 201 and the second plate 202, the distance between the outer peripheral edges of the first plate 201 and the second plate 202 is the same. This arrangement ensures the uniformity of the overall structure of the cover plate 2 and further improves the overall structural strength of the cover plate 2.

[0043] It is understood that, in another embodiment, the outer peripheral edge of the first plate 201 is flush with the outer peripheral edge of the second plate 202, and the value of 'a' satisfies 0.2 ≤ a ≤ 0.65. When the edges of the first plate 201 and the second plate 202 are flush, the thickness of the cover plate 2 is consistent, and the structural strength of the cover plate 2 is high. Therefore, by further controlling 'a' within the above-mentioned range, the current-carrying capacity of the cover plate 2 can be further improved, and the conductivity of the cover plate 2 can be further guaranteed.

[0044] In one embodiment, such as Figure 3 As shown, the battery also includes a current collector 4, which is disposed between the cover plate 2 and the cell 3. The current collector 4 and the second plate 202 are welded together to form a second welding area 6. The orthographic projection of the second plate 202 is located between the outer peripheral edges of the first plate 201 and the second plate 202. The value of L1 satisfies 2.6mm≤L1≤5mm. By further limiting the value of L1, sufficient distance is maintained between the outer peripheral edges of the first plate 201 and the second plate 202, avoiding any impact on the welding of the current collector 4 and the cover plate 2, which would affect the current carrying capacity between the cell 3 and the cover plate 2.

[0045] In one embodiment, such as Figure 3 As shown, the distance between the outer periphery of the second welding area 6 and the second plate 202 is L2, and the value of L2 satisfies 3.35mm≤L2≤3.5mm. This setting ensures the welding area of ​​the second welding area 6, facilitates the welding process, and avoids the welding heat affecting other components of the battery cell 3.

[0046] Furthermore, in one embodiment, such as Figure 3 As shown, the distance between the second welding area 6 and the outer peripheral edge of the first plate 201 is L3, and the value of L3 satisfies 0.85mm≤L3≤1mm. This setting ensures the welding area of ​​the second welding area 6 while avoiding the large welding heat caused by the high melting point of titanium from affecting the first plate 201, thereby preventing damage to the first plate 201 and affecting the subsequent welding of the first plate 201 to the busbar 8.

[0047] Optionally, L2 can be any value from 3.35mm, 3.38mm, 3.4mm, 3.42mm, 3.45mm, 3.48mm, 3.5mm, or a value between any two of these values.

[0048] Optionally, L3 can be any value from 0.85mm, 0.88mm, 0.9mm, 0.92mm, 0.95mm, 0.98mm, 1mm, or a value between any two of these values.

[0049] In one embodiment, such as Figure 4 As shown, the ratio of the projected area S1 of the second welding region 6 on the second plate 202 to the projected area S2 of the current collector 4 on the second plate 202 satisfies 0.014 ≤ S1 / S2 ≤ 0.08. By further controlling S1 / S2 within the above range, the welding area between the current collector 4 and the cover plate 2 is guaranteed, thereby ensuring the current flow area between the current collector 4 and the cover plate 2, reducing the impedance of current transmission, and ensuring the current flow capacity. At the same time, it avoids the second welding region 6 from being too large and affecting the setting of the first welding region 5, and also reduces the impact of welding heat on the first plate 201, preventing damage to the first plate 201.

[0050] Optionally, the value of S1 / S2 can be any one of 0.014, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07, 0.075, or 0.08, or a value between any two of these values.

[0051] In one embodiment, such as Figure 5As shown, the battery cell 3 includes a battery cell body 301 and a tab 302 connected together. The tab 302 is welded to the current collector 4 to form a first welding area 5. The ratio of the projected area S3 of the first welding area 5 on the second plate 202 to the projected area S4 of the tab 302 on the second plate 202 satisfies 0.024 ≤ S3 / S4 ≤ 0.1. By further controlling S3 / S4 within the above range, the welding area between the current collector 4 and the tab 302 is guaranteed, thereby ensuring the current-carrying area between the current collector 4 and the tab 302, reducing the impedance of current transmission, ensuring the current-carrying capacity, and at the same time, avoiding the first welding area 5 from being too large and affecting the setting of the second welding area 6.

[0052] Optionally, the value of S3 / S4 can be any one of 0.024, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1, or a value between any two values.

[0053] In one embodiment, such as Figure 1 As shown, the casing is cylindrical, and the battery also includes terminals 7, which are disposed on the cover plate 2. The value of 'a' satisfies 0.25 ≤ a ≤ 0.7. Terminals 7 occupy a portion of the area of ​​the cover plate 2, reducing the area of ​​the cover plate 2 used for current flow. By controlling 'a' within the above range, the current flow capacity of the cover plate 2 is further guaranteed, avoiding the large area occupied by terminals 7 from affecting the current flow capacity of the cover plate 2, and improving the battery's transmission efficiency.

[0054] Furthermore, such as Figure 6 As shown, the battery has a plane perpendicular to the thickness direction of the cover plate 2. The ratio of the projected area S5 of the terminal post 7 on the plane to the projected area S6 of the cover plate 2 on the plane satisfies 0.15 ≤ S5 / S6 ≤ 0.155. By ensuring that S5 / S6 is within the above range, the current carrying capacity and structural strength of the cover plate 2 are guaranteed, avoiding the terminal post 7 occupying too large an area, which would seriously affect the current carrying capacity and structural strength of the cover plate 2. At the same time, the current carrying capacity of the terminal post 7 is guaranteed, reducing energy loss during charging and discharging, and improving the overall battery efficiency. Simultaneously, the welding area of ​​the terminal post 7 and the busbar 8 is guaranteed to ensure the current carrying capacity.

[0055] Optionally, the value of S5 / S6 can be any one of 0.15, 0.151, 0.152, 0.153, 0.154, 0.155 or a value between any two of them.

[0056] In one embodiment, the metallic element includes aluminum. This facilitates subsequent welding of the first plate 201 and the busbar 8, improves the welding effect, and thus enhances the current-carrying capacity of the cover plate 2 and the busbar 8.

[0057] According to an embodiment of the present invention, in another aspect, a battery pack is also provided, comprising: a plurality of batteries as described above and a busbar 8; the busbar 8 connects two adjacent batteries, and the material of the busbar 8 is the same as that of the first plate 201.

[0058] In one embodiment, the busbar 8 comprises aluminum, and the first plate 201 comprises aluminum. The presence of aluminum in both the busbar 8 and the first plate 201 improves the welding effect between them, ensures a reliable connection, reduces current transmission impedance, and enhances current carrying capacity.

[0059] In one embodiment, the outer peripheral edge of the second plate 202 extends beyond the outer peripheral edge of the first plate 201, the busbar 8 is welded to the cover plate 2 to form a third welding area 9, the battery has a plane perpendicular to the thickness direction of the cover plate 2, and the projection of the third welding area 9 in the plane is located inside the projection of the first plate 201 in the plane.

[0060] Furthermore, in one embodiment, such as Figure 3 As shown, the distance between the third welding area 9 and the outer peripheral edge of the first plate 201 is L4, and the value of L4 satisfies 1mm≤L4≤4.63mm. By limiting the value of L4, the welding area of ​​the third welding area 9 is guaranteed to ensure the current carrying capacity, while facilitating the welding process and reducing the welding difficulty.

[0061] Optionally, L4 can be any value from 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 4.63mm, or a value between any two of these values.

[0062] Furthermore, in one embodiment, such as Figure 3 As shown, the penetration depth f of the third welding area 9 and the thickness d of the first plate 201 satisfy f < d, 0.1 mm ≤ f ≤ 0.25 mm, and the value of a satisfies 0.28 ≤ a ≤ 0.7. This ensures that the penetration depth of the third welding area 9 is less than the thickness of the first plate 201, thus placing the third welding area 9 entirely within the first plate 201. Therefore, welding the busbar 8 to the second plate 202 is unnecessary, avoiding poor welding results caused by welding components of different materials. Furthermore, the value of the penetration depth f of the third welding area 9 is limited to ensure the welding strength between the first plate 201 and the busbar 8 while ensuring that the third welding area 9 remains within the first plate 201. At this point, the value of a is further limited to ensure that the first plate 201 has sufficient thickness to accommodate the third welding area 9.

[0063] Optionally, f can be any value among 0.1mm, 0.12mm, 0.15mm, 0.18mm, 0.2mm, 0.22mm, and 0.25mm, or a value between any two of these values.

[0064] In one embodiment, the battery is cylindrical, and the busbar 8 connects the terminals 7 or cover plates 2 of two adjacent batteries, with the value of 'a' satisfying 0.27 ≤ a ≤ 0.7. This allows for the series and parallel connection of multiple batteries within the battery pack.

[0065] Furthermore, the casing is located on the outermost side of the battery cell 3 to protect it. The casing material can be, but is not limited to, aluminum, steel, or aluminum alloy. Specifically, the casing material can be aluminum-manganese alloy, aluminum-magnesium alloy, stainless steel, nickel-plated steel, carbon steel, titanium, etc. In this embodiment, the casing is a titanium casing.

[0066] Furthermore, the current collector 4 is electrically connected to the electrode 302 and the cover plate 2 to realize current transmission; the current collector 4 can be a current collector bus or an adapter plate.

[0067] Furthermore, tab 302 serves as the current output terminal inside cell 3, and tab 302 is used for electrical connection with current collector 4, etc. Tab 302 can be cut from current collector or it can be a separately formed metal part. It can be understood that the positive tab is electrically connected to the positive electrode plate in cell 3, and the negative tab is electrically connected to the negative electrode plate in cell 3.

[0068] Furthermore, the battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator, with the separator disposed between the positive and negative electrode sheets. The positive electrode sheet, negative electrode sheet, and separator are stacked to form the battery cell. The positive electrode sheet includes a positive current collector and a positive active material layer, and the negative electrode sheet includes a negative current collector and a negative active material layer. There are no particular limitations on the positive current collector, as long as it is conductive and will not cause adverse chemical changes in the battery. For example, it can be made of stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc. The negative current collector can be made of copper, stainless steel, nickel, titanium, etc. In a specific embodiment, the positive electrode can be made of aluminum, and the negative electrode can be made of copper. The positive active material layer includes a positive active material, such as nickel-cobalt-manganese ternary materials, lithium iron phosphate materials, lithium manganese iron phosphate materials, etc.; the negative active material layer includes a negative active material, such as artificial graphite, natural graphite, silicon-based materials, etc.

[0069] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0070] The preparation of the example battery and the comparative battery includes the following steps:

[0071] (1) Preparation of the positive electrode:

[0072] 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 material: conductive agent: binder satisfies (92-98):(4-1):(4-1).

[0073] (2) Preparation of negative electrode:

[0074] The negative electrode active material graphite, 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 graphite: conductive agent: thickener: binder is (90-96): (4-2): (2-1): (4-1).

[0075] (3) Preparation of electrolyte:

[0076] 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.

[0077] (4) Preparation of the diaphragm:

[0078] Polyethylene film is selected as the diaphragm.

[0079] (5) Preparation of lithium-ion batteries:

[0080] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, and then wound or stacked to obtain a bare cell. The bare cell is placed in an outer packaging shell, dried, injected with electrolyte, and then packaged, left to stand, formed, and calibrated to obtain a lithium-ion battery.

[0081] 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 materials, including artificial graphite, natural graphite, silicon carbide, silicon oxide, and lithium titanate.

[0082] In this application, the positive electrode active material is selected from a nickel-cobalt-manganese ternary system with the structural formula LiNi0.9Co0.05Mn0.05O2, and the negative electrode material is selected from artificial graphite.

[0083] The difference between the batteries in each embodiment and the comparative battery lies in the values ​​of a, b, and c, as shown in Table 1.

[0084] The relevant performance and parameters of the batteries in the above embodiments and comparative examples were tested, and the test results are recorded in Table 1. The test methods are as follows:

[0085] 1. Cover plate temperature rise test:

[0086] The lithium-ion batteries prepared in the examples and comparative examples were tested at 25°C according to the following procedure.

[0087] (1) Connect the cover plate to the temperature sensor, charge it at a constant current of 4C to 4.25V, and charge it at a constant voltage until the current drops to 0.05C. Record the temperature of the cover plate area during the charging process.

[0088] (2) Obtain the highest temperature T of the cover plate area during the charging process. When the highest temperature T of the cover plate area is ≤ 45℃, it is good; when 45℃ < T ≤ 65℃, it is qualified; when T > 65℃, it is unqualified.

[0089] 2. Cover plate deformation test:

[0090] The degree of shell deformation was detected after cyclic testing.

[0091] The lithium-ion batteries prepared in the examples and comparative examples were subjected to cycle tests at 25°C according to the following procedure:

[0092] (1) Charge at a constant current rate of 1C to 4.25V, and charge at a constant voltage until the current drops to 0.05C;

[0093] (2) Let it stand for 10 minutes;

[0094] (3) Discharge to 2.5V at a 1C rate;

[0095] (4) Let stand for 10 minutes.

[0096] Perform 100 cycles of testing according to steps (1)-(4). Afterwards, measure the height of the protrusion at the point of maximum deformation of the cover plate, where:

[0097] No deformation: Deformation height is between 0-0.05mm;

[0098] Moderate deformation: Deformation height is greater than 0.05 mm and less than or equal to 0.1 mm;

[0099] Severe deformation: greater than 0.1 mm.

[0100] 3. The test method for the thickness of the first plate and the thickness of the second plate is not limited in this application. Specifically, the boundary between the first plate and the second plate can be identified first, and then the thickness of the first plate and the second plate can be measured with a micrometer.

[0101] 4. This application does not specify the testing method for Ti element content; specific methods may be used:

[0102] (1) Sample preparation: First, the shell sample needs to be properly treated to facilitate X-ray penetration and excitation of fluorescence. This may include steps such as cutting, grinding, and polishing to ensure that the sample surface is flat and free of contamination;

[0103] (2) X-ray excitation: High-energy X-rays are used to irradiate the sample surface, exciting the characteristic X-ray fluorescence of each element. The wavelength or energy characteristics of these fluorescence spectra correspond to the element types, thus allowing the determination of which elements are contained in the sample;

[0104] (3) Spectral collection and analysis: X-rays reflected from the sample surface and fluorescence spectra emitted are collected using a spectrometer. The type and content of elements can be determined by the position and intensity of characteristic spectral lines;

[0105] (4) Matrix effect correction: Due to the interaction between various elements in the shell (matrix effect), the collected spectral data needs to be corrected to eliminate the influence of this interaction on the analysis results and improve the accuracy of the analysis.

[0106] (5) Interpretation of results: Based on the corrected data, the content of each element in the shell can be calculated.

[0107] Table 1:

[0108]

[0109] Based on Examples 1-13 and Comparative Examples 1-3, it can be seen that when the value of c×b / a is within the range of 11-130, the temperature rise of cover plate 2 is less than or equal to 45°C, and the deformation of cover plate 2 is less than 0.1mm after 100 charge-discharge cycles. In Comparative Examples 1 and 2, the value of c×b / a is greater than 130. Due to the poor conductivity and weak overcurrent capacity of cover plate 2, the temperature rise of cover plate 2 is greater than 65°C, and the temperature rise test of cover plate 2 fails. In Comparative Example 3, the value of c×b / a is less than 11. After 100 charge-discharge cycles, the deformation of cover plate 2 is greater than 0.1mm, and cover plate 2 undergoes severe deformation.

[0110] As shown in Table 1, in Example 12, the value of 'a' is not within the range of 0.2 to 0.7 and is less than 0.2, resulting in relatively poor conductivity and weak overcurrent capacity of the cover plate 2 of the battery in Example 12. The temperature rise of the cover plate 2 is between 45°C and 55°C, indicating a slight increase in temperature. In Example 13, the value of 'c%' is not within the range of 90% to 99.9% and is less than 90%, and the value of 'a' is not within the range of 0.2 to 0.7 and is greater than 0.7, resulting in relatively weak structural strength of the cover plate 2 of the battery in Example 13. After 100 charge-discharge cycles, the deformation of the cover plate 2 is between 0.05 mm and 0.1 mm, indicating a slight increase in deformation and moderate deformation of the cover plate 2.

[0111] Although embodiments of the 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 invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A battery, characterized in that, include: The housing and the battery cell (3), wherein the battery cell (3) is disposed inside the housing; The housing includes a main body (1) and a cover plate (2). At least one end of the main body (1) is provided with an opening. The cover plate (2) is placed over the opening and electrically connected to the battery cell (3). The cover plate (2) includes a plurality of plates stacked together. Along the stacking direction of the plurality of plates, the plate away from the battery cell (3) is the first plate (201), and the plate close to the battery cell (3) is the second plate (202). The first plate (201) includes non-titanium metal elements, and the second plate (202) includes titanium elements. The conductivity of the metal elements is greater than that of the titanium elements. The ratio of the thickness d mm of the first plate (201) to the thickness e mm of the second plate (202) is a. The resistivity of the cover plate (2) is b Ω·mm. The content of the titanium elements in the second plate (202) is c% and satisfies 11≤c×b / a≤130. The titanium content c% in the second plate (202) satisfies 90%≤c%≤99.9%, the ratio a of the thickness d mm of the first plate (201) and the thickness e mm of the second plate (202) satisfies 0.2≤a≤0.7, and the resistivity b Ω·mm of the cover plate (2) satisfies 0.077Ω·mm≤b Ω·mm≤0.298Ω·mm.

2. The battery according to claim 1, characterized in that, The thickness d mm of the first plate (201) satisfies 0.2 mm ≤ d mm ≤ 0.4 mm, and the thickness e mm of the second plate (202) satisfies 0.6 mm ≤ e mm ≤ 0.8 mm.

3. The battery according to claim 1 or 2, characterized in that, The number of plates is two, the first plate (201) and the second plate (202) are connected, and the value of a satisfies 0.2≤a≤0.

6.

4. The battery according to claim 1, characterized in that, The outer periphery of the first plate (201) is flush with the outer periphery of the second plate (202), and the value of a satisfies 0.2≤a≤0.

65.

5. The battery according to claim 1, characterized in that, The outer periphery of the second plate (202) extends beyond the outer periphery of the first plate (201), and the value of a satisfies 0.25≤a≤0.

7.

6. The battery according to claim 5, characterized in that, The distance L1 mm between the outer peripheral edge of the first plate (201) and the outer peripheral edge of the second plate (202) satisfies 2mm≤L1 mm≤5mm.

7. The battery according to claim 5, characterized in that, Along the circumferential direction of the first plate (201) and the second plate (202), the distance between the outer peripheral edge of the first plate (201) and the outer peripheral edge of the second plate (202) is the same.

8. The battery according to claim 6, characterized in that, The battery also includes a current collector (4), which is disposed between the cover plate (2) and the cell (3). The current collector (4) and the second plate (202) are welded to form a second welding area (6). The projection of the second welding area (6) onto the second plate (202) is located between the outer peripheral edge of the first plate (201) and the outer peripheral edge of the second plate (202). The value of L1 mm satisfies 2.6 mm ≤ L1 mm ≤ 5 mm.

9. The battery according to claim 6, characterized in that, The battery also includes a current collector (4), which is disposed between the cover plate (2) and the cell (3). The current collector (4) is welded to the second plate (202) to form a second welding area (6). The orthographic projection of the second welding area (6) onto the second plate (202) is located between the outer peripheral edge of the first plate (201) and the outer peripheral edge of the second plate (202). The distance between the second welding area (6) and the outer peripheral edge of the second plate (202) is L2 mm, and the value of L2 mm satisfies 3.35 mm ≤ L2 mm ≤ 3.5 mm. The distance between the second welding area (6) and the outer peripheral edge of the first plate (201) is L3 mm, and the value of L3 mm satisfies 0.85 mm ≤ L3 mm ≤ 1 mm.

10. The battery according to claim 6, characterized in that, The battery also includes a current collector (4), which is disposed between the cover plate (2) and the battery cell (3). The current collector (4) is welded to the second plate (202) to form a second welding area (6). The orthographic projection of the second welding area (6) onto the second plate (202) is located between the outer peripheral edge of the first plate (201) and the outer peripheral edge of the second plate (202). The orthographic projection area of ​​the second welding area (6) onto the second plate (202) is S1 mm. 2 The projected area S2 mm of the current collector (4) on the second plate (202) is equal to that of the current collector (4). 2 The ratio satisfies 0.014≤S1 / S2≤0.

08.

11. The battery according to claim 8, characterized in that, The battery cell (3) includes a battery cell body (301) and a tab (302) connected together. The tab (302) is welded to the current collector (4) to form a first welding area (5). The first welding area (5) has a projected area of ​​S3 mm on the second plate (202). 2 The projected area of ​​the tab (302) on the second plate (202) is S4 mm. 2 The ratio satisfies 0.024≤S3 / S4≤0.

1.

12. The battery according to claim 1 or 2, characterized in that, The casing is cylindrical in shape, and the battery also includes a terminal (7), which is disposed on the cover plate (2). The value of a satisfies 0.25≤a≤0.

7.

13. The battery according to claim 12, characterized in that, The battery has a plane perpendicular to the thickness direction of the cover plate (2), and the projected area of ​​the electrode post (7) on the plane is S5 mm. 2 The projected area of ​​the cover plate (2) on the plane is S6 mm. 2 The ratio satisfies 0.15≤S5 / S6≤0.

155.

14. The battery according to claim 1 or 2, characterized in that, The metallic element includes aluminum.

15. A battery pack, characterized in that, include: The battery according to any one of claims 1 to 14; Busbar (8) connects two adjacent batteries and the material of the busbar (8) is the same as that of the first plate (201).

16. The battery pack according to claim 15, characterized in that, The busbar (8) includes aluminum, and the metal element of the first plate (201) includes aluminum.

17. The battery pack according to claim 16, characterized in that, The outer peripheral edge of the second plate (202) extends beyond the outer peripheral edge of the first plate (201). The busbar (8) is welded to the cover plate (2) to form a third welding area (9). The battery has a plane perpendicular to the thickness direction of the cover plate (2). The projection of the third welding area (9) in the plane is located inside the projection of the first plate (201) in the plane.

18. The battery pack according to claim 17, characterized in that, The distance between the third welding area (9) and the outer peripheral edge of the first plate (201) is L4 mm, and the value of L4 mm satisfies 1 mm ≤ L4 mm ≤ 4.63 mm.

19. The battery pack according to claim 17, characterized in that, The penetration depth f mm of the third welding area (9) and the thickness d mm of the first plate (201) satisfy f < d, 0.1 mm ≤ f mm ≤ 0.25 mm, and the value of a satisfies 0.28 ≤ a ≤ 0.

7.

20. The battery pack according to claim 15, characterized in that, The battery is cylindrical in shape, and the busbar (8) connects the terminals (7) or cover plates (2) of two adjacent batteries. The value of a satisfies 0.27≤a≤0.7.

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