Lithium-ion cylindrical secondary battery and power-consuming device

Abstract

The present invention relates to the field of lithium-ion battery technology, and more specifically to a cylindrical lithium-ion secondary battery and an electrical device. During discharge at a discharge rate of 1C-10C, the battery satisfies the following linear relationship: lg m = Algi-B; A is in the range of 1.88-2.20, and B is in the range of 2.1-2.5; i is the discharge current corresponding to the battery at different discharge rates, and m is the temperature rise coefficient of the battery at different discharge rates. Compared to traditional batteries, the battery of the present invention has a relatively low temperature rise coefficient at the same discharge current, effectively controlling the problem of excessive temperature rise during battery use.

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] Portable, high-power power tools, such as electric vacuum cleaners, electric lawn mowers, electric drills, and electric planers, are gaining popularity these days. While these tools offer convenience, they also suffer from poor battery performance. The batteries currently used in these tools have the following technical issues:

[0003] Battery temperature rise: During power tool use, especially during high-power discharge, the battery's internal resistance causes the temperature to rise rapidly. The greater the internal resistance, the faster the battery's temperature rises. Frequent rapid temperature rises can cause continuous thermal shock to the battery, shortening its lifespan and even affecting its safety.

[0004] Battery heat dissipation is slow: In order 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 , the system allows charging. After the high power discharge is completed, due to the above-mentioned temperature rise problem, 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 much higher than T 阈值1 If you start charging at this time, it will affect the battery life and even the safety performance of the battery.

[0005] 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, which triggers T 阈值2 This limits the actual working time and also affects the user experience of the tool. The surface temperature of the battery also depends on the battery's heat dissipation performance. If the heat dissipation performance is poor, the heat inside the battery cannot be quickly transferred to the outside of the battery. The battery continues to discharge and generates heat, which can easily lead to heat accumulation.

[0006] 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.

[0007] Poor battery safety performance: Due to problems with the internal structure and materials of the battery, the battery temperature rises too quickly during use, which can easily lead to performance degradation due to heat. If short circuits, leakage, etc. occur, it will pose a safety hazard to users and cause safety accidents.

[0008] The battery's effective discharge of power is low: The actual battery usage efficiency is low, and the performance of the power tool cannot be fully utilized.

[0009] The root cause of these problems lies in the fact that battery technology remains stuck in traditional battery structure and chemical materials. To address these issues, researchers are seeking improvements and innovations in both battery structure and material systems. This invention improves and innovates lithium-ion cylindrical secondary battery technology to address these technical issues with existing large power tool batteries, providing users with a more efficient and safer experience. Summary of the Invention

[0010] To address the technical issues of rapid temperature rise and poor safety performance in 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 effectively controls the problem of rapid temperature rise during battery use. Compared with conventional batteries, the temperature rise coefficient of the present battery is relatively low at the same discharge current. For example, at a 10C discharge rate, the temperature rise coefficient of a 4.0Ah battery of the present invention is approximately 8 K / min, while the temperature rise coefficient of a conventional battery is closer to 20 K / min.

[0011] To achieve the above objectives, the present invention is implemented through the following technical solutions:

[0012] A lithium-ion cylindrical secondary battery, the battery comprising a winding core, wherein the winding core is a battery cell formed by winding the positive electrode sheet inside the winding core, which comprises a positive electrode sheet, a separator, a negative electrode sheet, and a separator stacked in sequence;

[0013] The positive electrode sheet includes a positive electrode current collector, and a first coating area and a first non-coating area provided on the positive electrode current collector, wherein the first coating area is covered with a positive electrode active material;

[0014] The negative electrode sheet includes a negative electrode current collector, and a second coating area and a second non-coating area provided on the negative electrode current collector, wherein the second coating area is coated with a negative electrode active material;

[0015] 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;

[0016] The battery satisfies the following linear relationship during discharge at a discharge rate of 1C-10C: y=Ax-B;

[0017] Wherein A is the slope, and the A is in the range of 1.88-2.20; B is the intercept, and the B is in the range of 2.1-2.5;

[0018] Wherein x=lg i, i is the discharge current corresponding to the battery at different discharge rates, and the unit of i is ampere;

[0019] Where y = lg m, where 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 to the B value in the relationship formula for conventional batteries without full tabs.

[0020] Furthermore, the radial cross-sectional area of the battery is S1, and the area of the second coating zone is S2, satisfying 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 zone (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 battery heat generation and energy loss.

[0021] Furthermore, the area of the second coating region accounts for 88%-98% of the total area of the negative electrode sheet. The present invention designs a negative electrode sheet with a coating region that accounts for 88%-98% of the total area of a single electrode sheet, eliminating the need to weld additional battery tabs to the electrode sheet. This can further reduce the internal resistance and operating temperature rise of the lithium-ion cylindrical secondary battery of the present invention, thereby further improving the battery's total energy throughput.

[0022] Furthermore, the battery further includes a shell and an electrolyte, wherein the shell accommodates the winding core and the electrolyte, and the electrolyte infiltrates the winding core; and further includes a top cover that seals the shell.

[0023] Furthermore, the winding core and the top cover are electrically connected by welding a current collecting sheet, the current collecting sheet comprising a main body and a tail body, the main body being attached to the electrode end surface at the top end of the winding core, and the tail body being bent so that its end abuts against the top cover;

[0024] The tail body is provided with notches on both sides of the width, with the spacing between the notches ranging from 40% to 80% of the total tail body width (preferably 45% to 65%). Providing notches in the tail body of the current collector can act as a safety fuse. If the notch width accounts for more than 60%, it will not function as a safety fuse. If the notch width accounts for less than 30%, the current collector will be too fragile and unable to meet the safety requirements. The width of the notch directly affects the distribution of the AC internal resistance R1 / R in the battery cell.

[0025] 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;

[0026] Define R as the AC internal resistance between the battery top cover and the battery bottom;

[0027] Define R1 as the AC internal resistance between the first bend and the bottom of the battery;

[0028] R is in the range of 2 milliohms to 10 milliohms, R1 accounts for 80.8% to 85.5% of R, and the difference between R and 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 helps reduce battery heat generation and energy loss during charging and discharging. The size of R affects the intercept B value.

[0029] Furthermore, the winding core and the shell are electrically connected by welding metal, and the welded metal material can be copper or a metal containing copper.

[0030] Furthermore, the negative electrode current collector is copper foil, and the copper content of the entire battery is controlled to be 7.9wt%-30wt%. By controlling the copper content in the battery to ≥7.9wt%, the battery's heat dissipation performance is improved. By controlling the copper content in the battery to ≤30wt%, the excess copper metal is prevented from increasing the overall weight of the battery, resulting in a decrease in the battery's weight energy density, or occupying too much space within the battery housing, resulting in a battery capacity that fails to meet design requirements.

[0031] Furthermore, the electrolyte includes a solvent, a lithium salt and an additive;

[0032] 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;

[0033] The lithium salt includes one or more of lithium hexafluorophosphate, lithium difluorooxalatephosphate, lithium difluorobisoxalatephosphate, lithium bisfluorosulfonyl imide, lithium difluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalateborate;

[0034] The additive includes one or more of vinylene carbonate and propylene carbonate.

[0035] 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.

[0036] Furthermore, the negative electrode active material includes at least the following materials in percentage by weight: 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;

[0037] The negative electrode active material is selected from one or more of artificial graphite, natural graphite, hard carbon, soft carbon, silicon-carbon materials, silicon-oxygen materials, elemental silicon, and mesophase carbon microbeads. The silicon content in the negative electrode active material ranges from 0% to 40% by weight. A higher silicon content allows for longer electrode lengths, a larger copper foil area for the negative electrode current collector, and faster heat dissipation during discharge, while maintaining the same volumetric energy density and capacity design targets. This reduces the battery's heat dissipation, allowing it to dissipate heat more quickly to the surrounding environment and prevent heat accumulation. Furthermore, the areal density of the positive and negative electrodes can be reduced, lowering the battery's internal resistance and thus reducing heat generation. A lower battery temperature rise coefficient (TCR) is preferred, allowing the battery to deliver more power within the same temperature range (25°C-80°C). Similarly, within the same power range, the battery's temperature rise is lower, minimizing overheating in electrical equipment and preventing triggering BMS alarms or even shutdowns.

[0038] Furthermore, the positive electrode active material includes at least the following materials in percentage by weight: 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;

[0039] 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 in the transition metals in the positive electrode active material is greater than or equal to 0.78. The use of a ternary high-nickel material for the positive electrode, combined with a graphite-doped silicon material for the negative electrode, can increase the battery's specific energy to greater than or equal to 220 Wh / kg.

[0040] Another aspect of the present invention provides an electrical device comprising the lithium-ion cylindrical secondary battery.

[0041] Beneficial technical effects:

[0042] 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 restricting the precursor of the battery core material selection, achieves high-rate discharge performance and excellent cycle performance of the battery by improving the battery structure, such as full-tab design, current collector configuration, coating area ratio, etc., and by limiting the regulation of the relationship between the temperature rise coefficient of the battery core and the discharge current, and greatly improves the high-rate fast charge and fast discharge cycle performance;

[0043] The present invention adopts a full-tab design, which can significantly reduce resistance and thus greatly reduce battery heat generation. The present invention adopts a current collector configuration with a notched tail. Under abnormal high current conditions, the tail of the positive electrode current collector can quickly fuse at the notch to form a short circuit, thereby protecting the battery and ensuring safe use. The present invention designs the active material coating area within a specific range, which can reduce the resistance of the full-tab battery by at least 70%, reduce the operating temperature rise by at least 30%, and increase the total energy throughput of the battery by at least 80%. It also supports a charging rate of ≥3C, with excellent technical effects.

[0044] The battery of the present invention has good heat dissipation, high energy density, excellent high-rate fast charge and discharge cycle performance, and good safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the structure of the current collector; L represents the length direction, and W represents the width direction;

[0046] 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;

[0047] Figure 3 A schematic diagram of the structure of winding the positive electrode sheet, the negative electrode sheet and the separator to form a winding core;

[0048] Figure 4 Schematic diagram of the cross-section structure of the winding core;

[0049] Figure 5 Schematic diagram of the installation of the current collector in the battery;

[0050] Figure 6 Schematic diagram of the battery structure of the present invention;

[0051] Figure 7This is a linear relationship graph of the logarithm of discharge current versus the logarithm of temperature rise coefficient for 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;

[0052] Figure 8 Graphs showing discharge current-temperature rise coefficient for 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;

[0053] Figure 9 Schematic diagram of the structure of the positive and negative electrodes of a 4Ah conventional tabbed cylindrical battery in Comparative Example 3, wherein (c) represents a conventional positive electrode and (d) represents a conventional negative electrode;

[0054] In the embodiment of the present invention Figures 1 to 6 Meaning of the markings: 1-winding core, 2-housing, 3-top cover, 4-current collector, 11-positive electrode sheet, 12-negative electrode sheet, 13-separator, 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 portion, 423-second bending portion;

[0055] Comparative Example 3 Figure 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-additionally welded positive electrode tab, 200-traditional negative electrode sheet, 2001-negative electrode collector coating area, 2002-negative electrode collector empty foil area, 2003-additionally welded negative electrode tab. DETAILED DESCRIPTION

[0056] The following will be combined with the embodiments of the present invention and the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0057] Unless otherwise specifically stated, the numerical value set forth in these embodiments does not limit the scope of the present invention. Technology and methods known to those of ordinary skill in the relevant art may not be discussed in detail, but in appropriate cases, the technology and methods should be considered as a part of the specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of exemplary embodiments can have different values.

[0058] In addition, it should be noted that the use of words such as "first" and "second" to limit the coating area is only for the convenience of distinguishing the electrodes. Unless otherwise stated, the above words have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0059] In the following examples, the experimental methods without specific conditions are generally measured according to national standards; if there is no corresponding national standard, the general standard requirements or general methods are used.

[0060] When expressing values, it should be noted that the expression "within the range of..." does not include the endpoint values; while expressions such as "the value is...", "the value is...", "the proportion is...", "the percentage is...", "the difference is...", etc. include the endpoint values.

[0061] 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.

[0062] AC internal resistance test method: The AC internal resistance R between the battery top cover and the bottom of the battery steel shell is measured 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 measured by a multimeter.

[0063] The test method for the temperature rise coefficient m corresponding to different discharge rates is as follows: at room temperature of 25°C, charge the battery at 1C to a full charge SOC = 100%, and charge it at constant current and constant voltage until the current is less than 0.05C. Let it stand for 10 minutes. For example, use a discharge rate of 10C to discharge the battery to a full charge SOC = 0%. When the battery temperature reaches 80°C during the 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.

[0064] Example 1

[0065] This case is a 4Ah full-tab lithium-ion cylindrical secondary battery. The overall battery structure diagram is as follows: Figure 6 As shown:

[0066] 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;

[0067] 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 provided thereon, and the negative electrode tab is electrically connected to the bottom of the shell 2 by welding metal;

[0068] 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 with the positive electrode sheet 11 wound inside. The winding structure diagram is shown in FIG. Figure 3 and Figure 4 As shown;

[0069] The structural diagram of the positive electrode sheet 11 and the negative electrode sheet 12 is as follows Figure 2 As shown, the positive electrode sheet 11 includes a positive electrode current collector (aluminum foil), and a first coating area 111 and a first non-coating area 112 provided on the positive electrode current collector, wherein 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 current collector (copper foil), and a second coating area 121 and a second non-coating area 122 provided on the negative electrode current collector, wherein 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. The first cutting lines 113 and the second cutting lines 123 are directly formed into the positive electrode tab 14 and the negative electrode tab 15 respectively after cutting, folding and flattening;

[0070] The structural diagram of the current collecting piece 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 the structural diagram of the current collecting sheet 4 being welded and mounted on the winding core 1 is shown in FIG. 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 the top cover 3; the tail body 42 is provided with notches 421 on both sides of the width direction W (the spacing between the notches on both sides is 4 mm), and the tail body 42 is bent to form a first bend 422 and a second bend 423, wherein the first bend 422 is close to the end surface of the positive electrode tab 14, and the second bend 423 is close to the top cover 3;

[0071] The assembly steps include: electrically connecting the negative electrode tab 15 to the bottom of the housing 2 by welding metal (the welded metal material is copper); electrically connecting the end of the tail 42 of the current collector 4 to the top cover 3 by welding; injecting electrolyte; and sealing the top cover 3 to the housing 2 to complete the battery. The battery has a diameter of 21 mm and a height of 70 mm. The copper content of the entire battery is 20 wt%. The electrolyte composition is an organic solvent composed of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) mixed in a volume ratio of 1:1:1, with lithium salt LiPF6 added to create a lithium salt concentration of 1 mol / L.

[0072] In addition, the ratio of the positive electrode active material, the negative electrode active material, the spacing of the notch portions 421 of the grooves on both sides to the total width of the tail body 42, and the percentage of the second coating area 121 to the area of the negative electrode sheet 12 are shown in Table 1;

[0073] 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;

[0074] To test the temperature rise coefficient, a relationship curve was plotted with the discharge current i (i in amperes) corresponding to the battery at different discharge rates as the horizontal axis and the temperature rise coefficient m (m in K / min) corresponding to the battery at different discharge currents as the vertical axis. A linear relationship was obtained by plotting the logarithm of the discharge current lg i as the horizontal axis and the logarithm of the temperature rise coefficient lg m as the vertical axis.

[0075] The battery temperature rise performance is shown in Table 2.

[0076] Example 2-Example 9

[0077] Examples 2 to 9 are all 4Ah full-tab lithium-ion cylindrical secondary batteries. The overall battery structure is the same as that of Example 1. The differences are shown in the parameters in Table 1. The battery temperature rise performance is shown in Table 2.

[0078] The relationship between the discharge current and temperature rise coefficient of the battery in Example 2 is shown in the figure below: Figure 7 and Figure 8 shown.

[0079] Example 10

[0080] 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. The battery temperature rise performance is shown in Table 2.

[0081] 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.

[0082] Example 11

[0083] 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. The battery temperature rise performance is shown in Table 2.

[0084] Comparative Example 1

[0085] 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.

[0086] The battery temperature rise performance is shown in Table 2.

[0087] Comparative Example 2

[0088] 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.

[0089] The battery temperature rise performance is shown in Table 2.

[0090] Comparative Example 3

[0091] 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 uses a traditional tab. The structure of the traditional tab in this case is as follows: Figure 9 As shown, according to 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; 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 additional welded positive electrode tab 1003 and an additional welded negative electrode tab 2003 are respectively provided in the positive electrode collector empty foil area 1002 and the negative electrode collector empty foil area 2002.

[0092] The battery temperature rise performance is shown in Table 2.

[0093] Comparative Example 4

[0094] The battery structure in this case is the same as that in 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.

[0095] 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.

[0096] Table 1 Battery parameters for each case

[0097]

[0098] Table 2 Battery temperature rise performance of each case

[0099]

[0100] From Table 1 and Table 2 and Figure 7 and Figure 8 visible:

[0101] (1) In Examples 1 to 4, the temperature rise coefficient of the negative electrode active material decreased 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.

[0102] (2) In Examples 2, 5-7, and Comparative Examples 1-3, the ratio of the spacing between the notches on both sides to the total width of the tail body is used 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 is too small (the spacing ratio is 35% in Comparative Example 1) or too large (the spacing ratio is 80% in Comparative Example 2). Although the temperature rise performance is acceptable, the external short circuit test tab melting ratio and the external short circuit test passing 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 melting 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 melting 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.

[0103] (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%, the cycle retention rate decreases significantly, and the technical effects of the external short-circuit test tab melting ratio and the external short-circuit test passing ratio are poor.

[0104] (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.

[0105] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A lithium-ion cylindrical secondary battery, characterized in that: The battery includes a roll core, which is a battery core formed by sequentially stacking a positive electrode sheet, a separator, a negative electrode sheet, and a separator in a wound form; The battery further includes a shell and an electrolyte, wherein the shell accommodates the winding core and the electrolyte, and the electrolyte infiltrates the winding core; and further includes a top cover for sealing the shell; The positive electrode sheet includes a positive electrode current collector, and a first coating area and a first non-coating area provided on the positive electrode current collector, wherein the first coating area is covered with a positive electrode active material; The negative electrode sheet includes a negative electrode current collector, and a second coating area and a second non-coating area disposed on the negative electrode current collector, wherein the second coating area is coated with a negative electrode active material; the area of the second coating area accounts for 90% to 96% of the total area of the negative electrode sheet; the negative electrode active material includes a negative electrode active material, wherein the negative electrode active material is a combination of graphite and silicon oxide material, and the silicon oxide material accounts for 0 wt % to 14 wt % of the 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 winding core and the top cover are electrically connected by welding a current collecting sheet, which 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 tail body is bent so that its end abuts the top cover. 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; the tail body is provided with notches on both sides in the width direction, wherein the notches on both sides are arranged between the first bent portion and the second bent portion and close to one side of the first bent portion, and the spacing between the notches on both sides is 45%-60% of the total width of the tail body; 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 bend and the bottom of the battery; The R is 3.03 milliohms to 4.74 milliohms, the proportion of R1 in R is 80.8% to 85.5%, and the difference between R and R1 is 0.61 to 0.72; The radial cross-sectional area of the battery is S1, and the area of the second coating area is S2, satisfying the following relationship: 0.41%≤S1 / S2≤0.45%; 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 the A is in the range of 1.88-2.20; B is the intercept, and the 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; Test method for temperature rise coefficient m corresponding to different discharge rates: At room temperature of 25°C, charge the battery at 1C to full charge SOC = 100%, and charge it at constant current and constant voltage until the current is less than 0.05C. Let it stand for 10 minutes, and discharge the battery to full charge SOC = 0% at different discharge rates. When the battery temperature reaches 80°C during the 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, then the temperature rise coefficient m=△T / t.

2. The lithium-ion cylindrical secondary battery according to claim 1, 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.

3. The lithium-ion cylindrical secondary battery according to claim 2, characterized in that: The negative electrode current collector is copper foil, and the copper content in the entire battery is controlled to be 7.9wt%-30wt%.

4. The lithium-ion cylindrical secondary battery according to claim 1, characterized in that: The electrolyte includes 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 difluorooxalatophosphate, lithium difluorodioxalatophosphate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate, lithium tetrafluoroborate, and lithium difluorooxalatoborate; The additive is selected from one or more of vinylene carbonate and propylene carbonate.

5. A lithium-ion cylindrical secondary battery according to any one of claims 1 to 4, characterized in that: The diameter of the winding core is 15 mm to 52 mm, and the height is 33 mm to 155 mm. The ratio of the height to the diameter is greater than 1.

65.

6. The lithium-ion cylindrical secondary battery according to claim 5, characterized in that: The negative electrode active material includes at least 100% by mass of the following materials: 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.

7. The lithium-ion cylindrical secondary battery according to claim 5, characterized in that: The positive electrode active material comprises at least 100% by weight of the following materials: 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, and lithium nickel cobalt aluminum oxide, and the atomic ratio of nickel in the transition metal of the positive electrode active material is greater than or equal to 0.

78.

8. An electrical device, characterized in that: A lithium-ion cylindrical secondary battery comprising the lithium-ion cylindrical secondary battery according to any one of claims 1 to 7.

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