Lithium ion cylindrical secondary battery and power utilization device

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion cylindrical secondary battery and a power utilization device, and the battery meets the following linear relation of lg m = A lg i-B in the discharge process at the discharge rate of 1C-10C, a ranges from 1.88 to 2.20, and B ranges from 2.1 to 2.5; i is the corresponding discharge current of the battery under different discharge rates, and m is the corresponding temperature rise coefficient of the battery under different discharge rates. Compared with a traditional battery, under the same discharge current, the temperature rise coefficient of the battery is relatively low, and the problem that the temperature rise of the battery is too fast in the using process can be effectively controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a lithium ion cylindrical secondary battery and an electrical device. Background Art

[0002] Nowadays, portable high-power electric tools are attracting attention, such as electric vacuum cleaners, electric lawn mowers, electric drills, electric planers, etc. While these tools bring convenience, they generally have the problem of poor battery performance. The batteries commonly used in these tools currently have the following technical problems: Battery temperature rise: During the use of power tools, especially under high-power discharge conditions, the battery temperature rises sharply due to the internal resistance of the battery; the greater the internal resistance of the battery, the faster the battery temperature rises. Frequent rapid temperature rise will continuously cause thermal shock to the battery, thus affecting the battery's service life and even the battery's safety performance.

[0003] Slow battery heat dissipation: To ensure the safety of tool use, the battery management system usually sets a temperature threshold (T 阈值1 ); When the surface temperature of the battery is lower than T 阈值1 After the high-power discharge is completed, the surface temperature of the battery is higher than T 阈值1 , you need to wait until the temperature drops to T 阈值1 If the heat dissipation of the battery is too slow, the user will have to wait longer. Furthermore, due to the temperature difference between the surface and the interior of the battery, if the heat dissipation of the battery is too slow, even if the surface temperature drops to T 阈值1 , the temperature inside the battery is still much higher than T 阈值1 If you start charging at this time, it will affect the battery life and even the battery safety performance.

[0004] The battery capacity cannot be fully utilized: In order to ensure the safety of tool use, the battery management system usually sets a temperature threshold (T 阈值2 ); During the operation of the tool, the battery discharges and generates heat, causing the battery temperature to rise. When the surface temperature of the battery reaches T 阈值2 , the system will cut off the current and the battery will stop working. During high-power discharge, due to the above-mentioned rapid temperature rise problem, the battery capacity cannot be fully released, triggering T 阈值2 , which limits the actual working time and also affects the user experience of the tool. The surface temperature of the battery also depends on the heat dissipation performance of the battery. If the heat dissipation performance is not good, the heat inside the battery cannot be quickly transferred to the outside of the battery. The battery continues to discharge and continues to generate heat, which easily causes heat accumulation.

[0005] Low battery energy density: This problem leads to insufficient battery life of power tools. Users need to charge frequently during use, which affects work efficiency and limits the use scenarios of power tools. Especially in outdoor environments, the problem of insufficient battery life is more prominent.

[0006] Poor battery safety performance: Due to problems with the battery's internal structure and materials, the battery temperature rises too quickly during use, which can easily lead to performance degradation due to heat. If short circuits, leakage, and other phenomena occur, it will pose a safety hazard to users and cause safety accidents.

[0007] The effective discharge of the battery is not high: the actual utilization efficiency of the battery is low and the performance of the power tool cannot be fully utilized.

[0008] The root of these problems is that battery technology is still at the level of traditional battery structure and chemical materials. In order to solve these problems, technicians began to seek improvements and innovations in both battery structure and battery material systems. The present invention improves and innovates lithium-ion cylindrical secondary battery technology to solve the above-mentioned technical problems existing in existing large power tool batteries, bringing users a more efficient and safer use experience. Summary of the invention

[0009] In order to solve the technical problems of excessively fast temperature rise and poor safety performance of existing batteries, the present invention provides a lithium-ion cylindrical secondary battery and an electrical device. The lithium-ion cylindrical secondary battery of the present invention can effectively control the problem of excessively fast temperature rise during battery use. Compared with traditional batteries, the temperature rise coefficient of the battery of the present invention is relatively low at the same discharge current. For example, at a discharge rate of 10C, the temperature rise coefficient of the 4.0Ah battery of the present invention is about 8 K / min, while the temperature rise coefficient of the traditional battery is close to 20 K / min.

[0010] To achieve the above objectives, the present invention is implemented through the following technical solutions: A lithium-ion cylindrical secondary battery, the battery comprising a winding core, the winding core is a battery cell formed by winding the positive electrode sheet inside the positive electrode sheet, a separator, a negative electrode sheet, and a separator stacked in sequence; The positive electrode sheet comprises a positive electrode current collector, and a first coating area and a first non-coating area arranged on the positive electrode current collector, wherein the first coating area is covered with a positive electrode active material; The negative electrode sheet comprises a negative electrode current collector, and a second coating area and a second non-coating area arranged on the negative electrode current collector, wherein the second coating area is coated with a negative electrode active material; The first non-coating area and the second non-coating area are cut, stacked or flattened to form a positive electrode tab and a negative electrode tab respectively; The battery satisfies the following linear relationship during discharge at a discharge rate of 1C-10C: y=Ax-B; Wherein A is the slope, and A is in the range of 1.88-2.20; B is the intercept, and B is in the range of 2.1-2.5; Wherein x=lg i, i is the discharge current corresponding to the battery at different discharge rates, and the unit of i is ampere; Where y=lg m, m is the temperature rise coefficient of the battery at different discharge rates, and the unit of m is K / min. The larger the B value, the lower the internal resistance of the battery. The B value of the battery with full-tabs of the present invention is increased by more than 20% compared with the B value in the traditional non-full-tabs battery relationship.

[0011] Furthermore, the radial cross-sectional area of ​​the battery is S1, and the area of ​​the second coating area is S2, which satisfies the following relationship: 0.35%≤S1 / S2≤0.45%. Controlling the ratio of the radial cross-sectional area S1 of the cylindrical battery to the area S2 of the second coating area (i.e., the negative electrode active material coating area on the copper foil of the negative electrode current collector) within this range can further reduce the heat generation of the battery and reduce energy loss.

[0012] Furthermore, the area of ​​the second coating region accounts for a percentage of 88%-98% of the total area of ​​the single negative electrode sheet. The coating area of ​​the negative electrode sheet of the present invention accounts for a percentage of 88%-98% of the total area of ​​a single electrode sheet, and there is no need to weld additional battery tabs on the electrode sheet, which can further reduce the internal resistance of the lithium-ion cylindrical secondary battery of the present invention, further reduce the operating temperature rise, and further improve the total energy throughput of the battery.

[0013] Furthermore, the battery also includes a shell and an electrolyte, wherein the shell accommodates the winding core and the electrolyte, and the electrolyte soaks the winding core; and also includes a top cover that seals the shell.

[0014] Furthermore, the winding core and the top cover are electrically connected by welding a current collecting sheet, the current collecting sheet includes a main body and a tail body, the main body is attached to the electrode end surface at the top of the winding core, and the end of the tail body is bent and abuts against the top cover; The tail body is provided with notches on both sides in the width direction, and the spacing between the notches on both sides is in the range of 40%-80% of the total width of the tail body (preferably in the range of 45%-65%). Providing a notch in the tail body of the current collector can play the role of a safety fuse. When the width of the notch accounts for more than 60%, it cannot play the role of a safety fuse. When the width accounts for less than 30%, the current collector is too fragile and cannot meet the safety use strength. The width of the notch will directly affect the distribution of the AC internal resistance R1 / R in the battery cell.

[0015] Furthermore, the tail body is bent to form a first bent portion and a second bent portion, the first bent portion is close to the end surface of the electrode, and the second bent portion is close to the top cover; Define R as the AC internal resistance between the battery top cover and the battery bottom; Define R1 as the AC internal resistance between the first bent portion and the bottom of the battery; The R is in the range of 2 milliohms to 10 milliohms, the R1 accounts for 80.8% to 85.5% of the R, and the difference between the R and the R1 is in the range of 0.57 to 0.75. Reducing the ratio of the winding core internal resistance to the total internal resistance of the battery is beneficial to reducing the heat generation of the battery and reducing the energy loss during the battery charging and discharging process. The size of R affects the size of the intercept B value.

[0016] Furthermore, the winding core and the shell are electrically connected by welding metal, and the welded metal material may be copper or a metal containing copper.

[0017] Furthermore, the negative electrode current collector is copper foil, and the copper content in the battery as a whole is controlled to be 7.9wt%-30wt%. By controlling the copper content in the battery as a whole to be ≥7.9wt%, the heat dissipation performance of the battery is improved, and by controlling the copper content in the battery as a whole to be ≤30wt%, it is avoided that excessive copper metal increases the overall weight of the battery, resulting in a decrease in the battery weight energy density, or occupies too much space inside the shell, resulting in the battery capacity being difficult to meet the design requirements.

[0018] Further, the electrolyte includes a solvent, a lithium salt and an additive; The solvent includes chain carbonates and cyclic carbonates, the cyclic carbonates include one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate, and the chain carbonates include one or more of methyl formate, ethyl acetate, and propyl propionate; The lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorooxalate phosphate, lithium difluorobisoxalate phosphate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate; The additive includes one or more of vinylene carbonate and propylene carbonate.

[0019] Furthermore, the diameter of the winding core is 15 mm-52 mm, the height is 33 mm-155 mm, and the ratio of the height to the diameter is greater than 1.65.

[0020] Further, the negative electrode active material at least includes the following materials in mass percentage: 94%-98.5% negative electrode active material, 0.5%-2% conductive agent, 0.5%-2% thickener, 0.5%-2% binder; the negative electrode active material is formed into a negative electrode slurry with a solid content of 30wt%-50wt% to form the second coating area; The negative electrode active material is selected from one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-carbon material, silicon-oxygen material, elemental silicon, and mesophase carbon microspheres. The silicon element contained in the negative electrode active material accounts for 0wt%-40wt% of the negative electrode active material. The more silicon content, the longer the pole piece can be designed, the larger the copper foil area of ​​the negative electrode current collector, and the faster the heat dissipation of the battery under the premise of the same volume energy density and capacity design target. During the discharge process, the heat can be exported to the surrounding environment more quickly to avoid heat accumulation; at the same time, the single-sided surface density of the positive and negative electrodes can also be reduced, and the internal resistance of the battery is reduced, thereby reducing the heat generation of the battery. The lower the battery temperature rise coefficient, the better, so that within the same temperature control range (25℃-80℃), the battery can discharge more electricity; similarly, within the same range of discharging the same amount of electricity, the battery temperature rise value is lower, and the electrical equipment is not easy to get hot, avoiding triggering the BMS battery management system alarm or even shutting down.

[0021] Furthermore, the positive electrode active material includes at least the following materials in mass percentage: 95%-98% positive electrode active material, 1%-3% conductive agent, and 0.5%-2% binder; the positive electrode active material is formed into a positive electrode slurry with a solid content of 35wt%-65wt% to form the first coating area; The positive electrode active material is selected from one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese iron phosphate, and the atomic proportion of nickel in the transition metal of the positive electrode active material is greater than or equal to 0.78. The positive electrode uses a ternary high-nickel material, and the negative electrode uses a graphite-doped silicon material, which can increase the battery specific energy to greater than or equal to 220Wh / kg.

[0022] Another aspect of the present invention provides an electric device comprising the lithium ion cylindrical secondary battery.

[0023] Beneficial technical effects: Since the battery structure and the selection of battery core materials have a great influence on the temperature rise coefficient, and it is well known that the greater the charge and discharge rate, the faster the battery temperature rises, the present invention, without limiting the precursor of the selection of battery core materials, through improved battery structure, such as full-ear design, current collector configuration, coating area ratio, etc., by limiting the regulation of the relationship between the temperature rise coefficient of the battery core and the discharge current, achieves high-rate discharge performance and excellent cycle performance of the battery, and greatly improves the high-rate fast charge and fast discharge cycle performance; The present invention adopts a full-ear design, which can greatly reduce resistance, thereby greatly reducing battery heat generation; the present invention adopts a current collector configuration with a notch tail. Under abnormal conditions of large current, the tail of the positive electrode current collector can be quickly fused at the notch to form a short circuit, thereby protecting the battery and meeting the safety intensity of use; the present invention designs the active material coating area within a specific range, which can reduce the resistance of the full-ear battery by at least 70%, reduce the operating temperature rise by at least 30%, increase the total energy throughput of the battery by at least 80%, and support a charging rate of ≥3C, with excellent technical effects; The battery of the present invention has good heat dissipation, high energy density, excellent high-rate fast-charge and fast-discharge cycle performance, and good safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of the current collector; L represents the length direction, and W represents the width direction; Figure 2 Schematic diagram of the structure of the positive electrode sheet and the negative electrode sheet; (a) is the positive electrode sheet, and (b) is the negative electrode sheet; Figure 3 A schematic diagram of the structure of winding a positive electrode sheet, a negative electrode sheet and a separator to form a winding core; Figure 4 It is a schematic diagram of the cross-sectional structure of the winding core; Figure 5 The figure is a schematic diagram of the installation of the current collector in the battery; Figure 6 This is a schematic diagram of the battery structure of the present invention; Figure 7 A linear relationship diagram of the logarithm of discharge current-logarithm of temperature rise coefficient of the 4Ah full-tab cylindrical battery of Example 2, the 5Ah full-tab cylindrical battery of Example 10, and the 4Ah traditional tab cylindrical battery of Comparative Example 3; Figure 8 The discharge current-temperature rise coefficient curves of the 4Ah full-tab cylindrical battery of Example 2, the 5Ah full-tab cylindrical battery of Example 10, and the 4Ah traditional tab cylindrical battery of Comparative Example 3; Fig. 9 Schematic diagram of the structure of the positive electrode sheet and the negative electrode sheet of the 4Ah traditional tab cylindrical battery of Comparative Example 3, wherein (c) represents the traditional positive electrode sheet and (d) represents the traditional negative electrode sheet; In the embodiment of the present invention Figures 1 to 6Meaning of the markings: 1-winding core, 2-shell, 3-top cover, 4-current collector, 11-positive electrode sheet, 12-negative electrode sheet, 13-diaphragm, 14-positive electrode tab, 15-negative electrode tab, 111-first coating area, 112-first non-coating area, 113-first cutting line, 121-second coating area, 122-second non-coating area, 123-second cutting line, 41-main body, 42-tail body, 421-notch, 422-first bending part, 423-second bending part; Comparative Example 3 Fig. 9 Meaning of the marks in the figure: 100-traditional positive electrode sheet, 1001-positive electrode collector coating area, 1002-positive electrode collector empty foil area, 1003-extra welded positive electrode tab, 200-traditional negative electrode sheet, 2001-negative electrode collector coating area, 2002-negative electrode collector empty foil area, 2003-extra welded negative electrode tab. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means intended to limit the present invention and its application or use. All other embodiments obtained by ordinary technicians in this field without creative work based on the embodiments of the present invention are within the scope of protection of the present invention.

[0026] Unless otherwise specifically stated, the numerical value set forth in these embodiments does not limit the scope of the present invention. The technology and method known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology and method should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as being merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments may have different values.

[0027] In addition, it should be noted that the use of terms such as "first" and "second" to limit the coating area is only to facilitate the distinction between the pole pieces. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0028] The experimental methods in the following examples without specifying specific conditions are usually measured in accordance with national standards; if there is no corresponding national standard, they are carried out in accordance with general standard requirements or general methods.

[0029] What needs to be noted about the expression of values ​​is that the expression “within the range of…” does not include the endpoint values; the expressions “the value is…”, “the value is…”, “the proportion is…”, “the percentage is…”, “the difference is…”, etc. include the endpoint values.

[0030] If the battery capacity is 4Ah, the discharge current at a discharge rate of 1C is 4 amperes, and the discharge current at a discharge rate of 10C is 40 amperes.

[0031] AC internal resistance test method: The AC internal resistance R between the battery top cover and the bottom of the battery steel shell is tested by an AC internal resistance tester at a frequency of 1000 Hz; the AC internal resistance R1 between the first bend of the lithium-ion cylindrical secondary battery and the bottom of the steel shell is tested by a multimeter.

[0032] The test method of temperature rise coefficient m corresponding to different discharge rates is as follows: at room temperature of 25°C, charge the battery at 1C to full charge SOC=100%, and charge at constant current and constant voltage until the current is less than 0.05C, and let it stand for 10 minutes. For example, use a discharge rate of 10C to discharge the battery to full discharge SOC=0%. When the temperature of the battery reaches 80°C during the monitoring discharge process, the discharge is directly cut off. Assuming that the total discharge time is t min, the difference between the battery temperature at the end of discharge and the battery temperature at room temperature is △T=55°C, and the temperature rise coefficient m=△T / t.

[0033] Example 1

[0034] This case is a 4Ah full-tab lithium-ion cylindrical secondary battery. The overall battery structure diagram is as follows Figure 6 As shown: The battery comprises a housing 2, a winding core 1 disposed in the housing, and a top cover 3 sealing the winding core 1 in the housing 2; The winding core 1 has a positive electrode tab 14 and a negative electrode tab 15 at both ends, respectively. The positive electrode tab 14 is electrically connected to the top cover 3 by welding through the current collector 4 arranged thereon, and the negative electrode tab is electrically connected to the bottom of the shell 2 by welding metal; The winding core 1 is formed by sequentially stacking a positive electrode sheet 11, a separator 13, a negative electrode sheet 12, and a separator 13 to form a battery cell by winding the positive electrode sheet 11 therein. The winding structure diagram is shown in FIG. Figure 3 and Figure 4 As shown; The structural schematic diagram of the positive electrode sheet 11 and the negative electrode sheet 12 is as follows Figure 2As shown, the positive electrode sheet 11 includes a positive electrode collector (aluminum foil), and a first coating area 111 and a first non-coating area 112 arranged on the positive electrode collector, the first coating area 111 is covered with a positive electrode active material, and the first non-coating area 112 is provided with a plurality of first cutting lines 113 that can be cut to the first coating area 111 along the width direction; the negative electrode sheet 12 includes a negative electrode collector (copper foil), and a second coating area 121 and a second non-coating area 122 arranged on the negative electrode collector, the second coating area 121 is covered with a negative electrode active material, and the second coating area 121 is provided with a plurality of second cutting lines 123 that can be cut to the second coating area 121 along the width direction, and the first cutting lines 113 and the second cutting lines 123 are directly formed into a positive electrode tab 14 and a negative electrode tab 15 respectively after cutting, folding and flattening; The structural schematic diagram of the current collecting sheet 4 is as follows Figure 1 As shown, the current collecting sheet 4 includes a main body 41 and a tail body 42 (the width of the tail body is 8 mm), and is welded and installed on the winding core 1. Figure 5 As shown, the main body 41 is attached to the upper surface of the positive electrode tab 14, and the end of the tail body 42 is bent to abut against the top cover 3; the tail body 42 is provided with notches 421 on both sides of the W width direction (the spacing between the notches on both sides is 4 mm), and the tail body 42 is bent to form a first bending portion 422 and a second bending portion 423, the first bending portion 422 is close to the end surface of the positive electrode tab 14, and the second bending portion 423 is close to the top cover 3; The assembly steps include: the negative electrode tab 15 is electrically connected to the bottom of the shell 2 by welding metal (the welded metal material is selected from copper); the tail 42 end of the current collector 4 is electrically connected to the top cover 3 by welding; the electrolyte is poured in; the top cover 3 and the shell 2 are sealed to form a battery. The diameter of the battery is 21mm, the height is 70mm, the copper content in the battery as a whole is 20wt%, and the electrolyte composition is ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and lithium salt LiPF is added 6 The electrolyte is configured to have a lithium salt concentration of 1 mol / L.

[0035] In addition, the percentage of the positive electrode active material, the negative electrode active material, the spacing of the notch portions 421 of the grooves on both sides in the total width of the tail body 42, and the percentage of the second coating area 121 in the area of ​​the negative electrode sheet 12 are shown in Table 1; The AC internal resistance R between the battery top cover 3 and the battery bottom, and the AC internal resistance R1 between the first bent portion 422 and the battery bottom are shown in Table 1; To test the temperature rise coefficient, a relationship curve is drawn with the discharge current i (i is in ampere) corresponding to the battery at different discharge rates as the horizontal coordinate and the temperature rise coefficient m (m is in K / min) corresponding to the battery at different discharge currents as the vertical coordinate; a linear relationship is obtained by drawing the logarithm of the discharge current lg i as the horizontal coordinate and the logarithm of the temperature rise coefficient lg m as the vertical coordinate.

[0036] The battery temperature rise performance is shown in Table 2.

[0037] Example 2-Example 9 Examples 2 to 9 are all 4Ah full-tab lithium-ion cylindrical secondary batteries, and the overall battery structure is the same as that of Example 1. The differences are shown in the parameters in Table 1, and the battery temperature rise performance is shown in Table 2.

[0038] The relationship between the discharge current and the temperature rise coefficient of the battery in Example 2 is shown in the figure below: Figure 7 and Figure 8 shown.

[0039] Example 10

[0040] This case is a 5Ah full-tab lithium-ion cylindrical secondary battery. The overall battery structure is the same as that of Example 1. The differences are shown in the parameters in Table 1, and the battery temperature rise performance is shown in Table 2.

[0041] The relationship between the discharge current and temperature rise coefficient of the battery in this case is shown in the figure below: Figure 7 and Figure 8 shown.

[0042] Embodiment 11

[0043] This case is a 2.5Ah full-tab lithium-ion cylindrical secondary battery (battery model is 18650). The overall battery structure is the same as that of Example 1. The differences are shown in the parameters in Table 1, and the battery temperature rise performance is shown in Table 2.

[0044] Comparative Example 1 The battery structure of this case is the same as that of Example 7, except that the spacing between the notches on both sides accounts for 35% of the total width of the tail body.

[0045] The battery temperature rise performance is shown in Table 2.

[0046] Comparative Example 2 The battery structure of this case is the same as that of Example 7, except that the spacing between the notches on both sides accounts for 80% of the total width of the tail body.

[0047] The battery temperature rise performance is shown in Table 2.

[0048] Comparative Example 3 The battery structure of this case is the same as that of Example 7, except that the tail of the current collector does not have notches on both sides and this case is a traditional pole ear. The structure of the traditional pole ear in this case is as follows: Fig. 9 As shown, according to the conventional size design, its structure includes: a traditional positive electrode sheet 100 and a traditional negative electrode sheet 200; the traditional positive electrode sheet 100 includes a large-area positive electrode collector coating area 1001 arranged on both sides and a small-area positive electrode collector empty foil area 1002 arranged in the middle empty part; the traditional negative electrode sheet 200 includes a large-area negative electrode collector coating area 2001 arranged in the middle and a small-area negative electrode collector empty foil area 2002 arranged in the two sides; and an additionally welded positive electrode tab 1003 and an additionally welded negative electrode tab 2003 are respectively arranged in the positive electrode collector empty foil area 1002 and the negative electrode collector empty foil area 2002.

[0049] The battery temperature rise performance is shown in Table 2.

[0050] Comparative Example 4 The battery structure of this case is the same as that of Example 9, except that the second coating area of ​​the negative electrode sheet accounts for 88% of the negative electrode sheet area. The battery temperature rise performance is shown in Table 2.

[0051] The relevant parameters of the batteries made in the above cases are shown in Table 1, and the temperature rise performance of each battery is shown in Table 2.

[0052] Table 1 Battery parameters for each case

[0053] Table 2 Battery temperature rise performance of each case

[0054] From Table 1 and Table 2 and Figure 7 and Figure 8 visible: (1) In Examples 1 to 4, the temperature rise coefficient of the negative electrode active material was reduced from 12.8 K / min to 5.4 K / min. The temperature rise performance of the battery increased with the increase of the silicon-oxygen content in the negative electrode active material, but the cycle retention rate of the 500-cycle performance decreased from 90.5% to 74.2%. The cycle performance decreased with the increase of the silicon-oxygen content in the negative electrode active material.

[0055] (2) Example 2, Example 5-Example 7 and Comparative Examples 1-3 all use the ratio of the spacing between the grooves and notches on both sides to the total width of the tail body as a variable (hereinafter referred to as the spacing ratio). The spacing ratio of 45%-65% can show excellent temperature rise performance. The battery temperature rise performance increases with the increase of the spacing (i.e., the spacing ratio increases) (the temperature rise coefficient decreases with the increase of the spacing); while the spacing ratio that is too small (the spacing ratio of Comparative Example 1 is 35%) or too large (the spacing ratio of Comparative Example 2 is 80%), although the temperature rise performance is acceptable, the external short-circuit test tab fuse ratio and the external short-circuit test pass ratio show poor technical effects. The possible reasons are: if the notch spacing ratio is too small, the internal resistance of the battery core is too large, resulting in an increase in the battery external short-circuit test and the current collector is prone to fuse ratio; if the notch spacing ratio is too large, when thermal runaway occurs inside the battery, the temperature rises sharply, and the current collector lacks the fuse function, resulting in the battery as a whole catching fire or exploding. In addition, the larger the R1 / R ratio, the higher the battery temperature rise coefficient, and the worse the battery temperature rise performance.

[0056] (3) In Example 2, Examples 8-9, and Comparative Example 4, the temperature rise coefficient increases with the increase of the area of ​​the second coating area, so the temperature rise performance of the battery decreases slightly with the increase of the area of ​​the second coating area; when the area of ​​the second coating area accounts for less than 90%, its cycle retention rate decreases significantly, and the technical effects of the external short-circuit test tab fuse ratio and the external short-circuit test pass ratio are poor.

[0057] (4) Examples 2, 10 and 11 are batteries designed with different capacities. It can be seen that the temperature rise performance and electrical performance of the batteries made with the structure and material selection of the present invention are better.

[0058] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A lithium-ion cylindrical secondary battery, characterized in that: The battery comprises a winding core, which is a battery cell formed by winding a positive electrode sheet, a separator, a negative electrode sheet, and a separator stacked in sequence; The positive electrode sheet comprises a positive electrode current collector, and a first coating area and a first non-coating area arranged on the positive electrode current collector, wherein the first coating area is covered with a positive electrode active material; The negative electrode sheet comprises a negative electrode current collector, and a second coating area and a second non-coating area arranged on the negative electrode current collector, wherein the second coating area is coated with a negative electrode active material; The first non-coating area and the second non-coating area are cut, stacked or flattened to form a positive electrode tab and a negative electrode tab respectively; The battery satisfies the following linear relationship during discharge at a discharge rate of 1C-10C: y=Ax-B; Wherein A is the slope, and A is in the range of 1.88-2.20; B is the intercept, and B is in the range of 2.1-2.5; Wherein x=lg i, i is the discharge current corresponding to the battery at different discharge rates, and the unit of i is ampere; Wherein y=lg m, m is the temperature rise coefficient of the battery at different discharge rates, and the unit of m is K / min.

2. A lithium-ion cylindrical secondary battery according to claim 1, characterized in that: The radial cross-sectional area of ​​the battery is S1, and the area of ​​the second coating area is S2, which satisfies the following relationship: 0.35%≤S1 / S2≤0.45%.

3. A lithium-ion cylindrical secondary battery according to claim 2, characterized in that: The percentage of the area of ​​the second coating region to the total area of ​​the single negative electrode sheet is in the range of 88%-98%.

4. A lithium-ion cylindrical secondary battery according to claim 1, characterized in that: The battery further includes a shell and an electrolyte, wherein the shell accommodates the winding core and the electrolyte, and the electrolyte soaks the winding core; and further includes a top cover for sealing the shell.

5. A lithium-ion cylindrical secondary battery according to claim 4, characterized in that: The winding core and the top cover are electrically connected by welding a current collecting sheet, wherein the current collecting sheet comprises a main body and a tail body, wherein the main body is attached to the electrode end surface at the top of the winding core, and the end of the tail body is bent and abuts against the top cover; The tail body is provided with notches on both sides in the width direction, and the spacing between the notches on both sides is within the range of 40%-80% of the total width of the tail body.

6. A lithium-ion cylindrical secondary battery according to claim 5, characterized in that: The tail body is bent to form a first bent portion and a second bent portion, wherein the first bent portion is close to the end surface of the electrode, and the second bent portion is close to the top cover; Define R as the AC internal resistance between the battery top cover and the battery bottom; Define R1 as the AC internal resistance between the first bent portion and the bottom of the battery; The R is in the range of 2 milliohms to 10 milliohms, the proportion of R1 in R is 80.8% to 85.5%, and the difference between R and R1 is in the range of 0.57 to 0.

75.

7. A lithium-ion cylindrical secondary battery according to claim 6, characterized in that: The winding core and the shell are electrically connected by welding metal, and the welding metal material is selected from copper or a metal containing copper.

8. A lithium-ion cylindrical secondary battery according to claim 7, characterized in that: The negative electrode current collector is copper foil, and the copper content in the battery as a whole is controlled to be 7.9wt%-30wt%.

9. A lithium-ion cylindrical secondary battery according to claim 4, characterized in that: The electrolyte comprises a solvent, a lithium salt and an additive; The solvent is selected from one or more of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl acetate, and propyl propionate; The lithium salt is selected from one or more of lithium hexafluorophosphate, lithium difluorooxalate phosphate, lithium difluorobisoxalate phosphate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalate borate; The additive is selected from one or more of vinylene carbonate and propylene carbonate.

10. A lithium ion cylindrical secondary battery according to any one of claims 1 to 9, characterized in that: The diameter of the winding core is 15 mm-52 mm, the height is 33 mm-155 mm, and the ratio of the height to the diameter is greater than 1.

65.

11. A lithium-ion cylindrical secondary battery according to claim 10, characterized in that: The negative electrode active material at least includes the following materials in a mass percentage of 100%: 94%-98.5% negative electrode active material, 0.5%-2% conductive agent, 0.5%-2% thickener, and 0.5%-2% binder; the negative electrode active material is formed into a negative electrode slurry with a solid content of 30wt%-50wt% to form the second coating area; The negative electrode active material is selected from one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-carbon material, silicon-oxygen material, elemental silicon, and mesophase carbon microspheres. The silicon element contained in the negative electrode active material accounts for 0wt%-40wt% of the negative electrode active material.

12. A lithium-ion cylindrical secondary battery according to claim 10, characterized in that: The positive electrode active material at least includes the following materials in 100% by mass: 95%-98% positive electrode active material, 1%-3% conductive agent, and 0.5%-2% binder; the positive electrode active material is formed into a positive electrode slurry with a solid content of 35wt%-65wt% to form the first coating area; The positive electrode active material is selected from one or more of lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, and lithium manganese iron phosphate. The atomic ratio of nickel element in the transition metal of the positive electrode active material is greater than or equal to 0.

78.

13. An electrical device, characterized in that: A lithium ion cylindrical secondary battery comprising any one of claims 1 to 12.

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