A heat-safe lithium-ion cylindrical battery and an electrical device

Abstract

The present invention relates to the technical field of lithium-ion batteries, and particularly to a hot-gas-safe lithium-ion cylindrical battery and an electrical device, comprising a winding assembly and a shell accommodating the winding assembly; further comprising a cover plate for sealing the shell, wherein a current safety device is provided in the structure of the cover plate; the winding assembly comprises a winding core, which is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet; the two ends of the winding core are flattened or cut and folded to form a positive electrode ear layer and a negative electrode ear layer respectively; the gas production of a cylindrical battery when placed in a constant temperature environment of 85°C for 24 hours is V1; the gas production of a cylindrical battery when overcharged for 6 hours at a set process of 0.2C and 5V at room temperature is V2; the internal gas production corresponding to the minimum pressure required for the cylindrical battery to activate the current safety device is Vs; and the following relationship is satisfied: V1<Vs≤V2; the present invention can achieve high performance and high safety characteristics by regulating the positive electrode chemical system and optimizing battery structural components.

Description

Technical Field

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

[0002] A CID, or Current Interrupt Device, is a safety device built into the battery. It's designed to cut off the current when an abnormal condition occurs, thereby preventing safety hazards such as overheating, short circuiting, and explosion. The CID operates primarily based on changes in the battery's internal pressure. When the internal pressure rises to a certain level due to overcharging, overheating, or other factors, the CID is triggered, rapidly cutting off the current and ensuring battery safety. CIDs are particularly widely used and crucial in lithium-ion batteries. Lithium-ion batteries are widely used in electric vehicles, electronic devices, and other fields due to their high energy density and long cycle life. However, lithium-ion batteries also pose safety risks such as overheating and short circuiting. Therefore, the CID plays a crucial role in lithium-ion batteries. The CID in a lithium-ion battery is often integrated with the battery's safety valve. If the internal pressure rises abnormally, the CID immediately cuts off the current and simultaneously opens the safety valve, releasing internal pressure and ensuring battery safety. Furthermore, some high-end lithium-ion batteries are equipped with multiple CID protections to provide an even higher level of safety.

[0003] Cylindrical batteries are widely used in various fields due to their high safety, high performance, and low cost. Compared to conventional batteries, cylindrical batteries have multiple safety valves to ensure safety. First, in the event of overheating, the diaphragm will block the circuit by closing the pores to provide protection. In the event of overcurrent or short circuit, a large amount of heat is generated inside the battery, and interfacial side reactions occur, thereby producing a large amount of gas. At this time, the accumulation of gas will continue to increase the internal pressure. When the internal pressure reaches the CID actuation pressure, it triggers another protection mechanism of the cylinder, forming a circuit breaker, thereby preventing the continued current from causing more heat and side reactions, leading to eventual loss of control.

[0004] However, the industry's current regulation of cylindrical thermal safety is still immature, especially in the case of some new technology iterations, such as full-tab, silicon-based negative electrode, quasi-solid state, etc., more and more systems are unable to achieve a thermal balance design, resulting in frequent battery failure. Summary of the Invention

[0005] In order to solve the technical problem of thermal imbalance in existing batteries, a thermally safe lithium-ion cylindrical battery is provided. The structural battery of the present invention can achieve both high performance and high safety.

[0006] In order to achieve the above objectives, the present invention is implemented through the following technical solutions:

[0007] A heat-safe lithium-ion cylindrical battery comprises a winding assembly and a housing for accommodating the winding assembly;

[0008] Also included is a cover plate for sealing the housing, wherein the cover plate is provided with a current safety device in its structure;

[0009] The winding assembly includes a winding core, which is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet; two ends of the winding core are flattened or cut and stacked to form a positive electrode ear layer and a negative electrode ear layer respectively;

[0010] The gas production of the cylindrical battery when placed in a constant temperature environment of 85°C for 24 hours is V1;

[0011] The gas production of the cylindrical battery under the condition of overcharging for 6 hours at 0.2C and 5V at room temperature is V2;

[0012] The internal gas production corresponding to the minimum pressure required for the cylindrical battery to cause the current safety device to be activated is Vs;

[0013] The following relationship is satisfied: V1<Vs≤V2, where the units of V1, V2, and Vs are milliliters.

[0014] Furthermore, the internal volume of the cylindrical battery shell is S1, the volume of the wound assembly is S2, and the space utilization coefficient S2 / S1 of the cylindrical battery is 86%-94%. For regular shell volumes, the volume is calculated by measuring the diameter and height of the battery; for irregular shell volumes, the volume is measured using a gas displacement method (Gas pycometer). The volume S2 of the wound assembly (including the positive electrode sheet, negative electrode sheet, separator, and current collector) inside the battery is measured using the water displacement method based on Archimedes' principle. The residual space inside a full-lug cylindrical lithium-ion battery refers primarily to the space remaining after the battery shell is installed with the battery core. If the residual space is too small, the gases generated by the chemical reaction inside the battery cannot be properly discharged, affecting the battery's safety performance. If the residual space is too large, the battery's space utilization rate is reduced, reducing the battery's energy density. The present invention controls the residual space value range of the full-tab cylindrical lithium-ion battery, so that the gas generated can be discharged normally and the battery safety performance is better. The control is mainly achieved by designing the axial size of the winding core, the thickness of the positive and negative electrode full-tab layer, and the thickness of the positive and negative electrode collector plates.

[0015] Furthermore, the density of the cylindrical battery is ρ g / cm 3 , the true density of the core is Td g / cm 3 , satisfying the following conditions: 0.3≤|Td-ρ|≤1.2.

[0016] Furthermore, the current safety device activates at a pressure of 0.8 MPa to 1.2 MPa. The current safety device is equipped with a bursting disc having a rupture pressure of 1.7 MPa to 2.1 MPa, preferably 1.9 MPa to 2 MPa. The bursting disc's rupture pressure and the current safety device's activation pressure are tested, for example, with reference to relevant standards such as GB 31241-2022, "Safety Technical Specification for Lithium-ion Batteries and Battery Packs for Portable Electronic Products," GB / T 31485-2015, "Safety Requirements and Test Methods for Power Batteries for Electric Vehicles," UL 1642, and GB 38031-2020, "Safety Requirements for Power Batteries for Electric Vehicles." The bursting disc's rupture pressure affects the current safety device's activation pressure, and thus, the battery's safety performance. The current safety device's activation pressure can be controlled by adjusting the bursting disc's notch depth to influence its rupture pressure. Optimization experiments can be performed to determine the matching bursting disc notch depth, its rupture pressure, and the current safety device's activation pressure.

[0017] Furthermore, the cylindrical battery also satisfies: T1>T2; T1 and T2 are defined as follows:

[0018] The cylindrical battery is fully charged with a current of 0.2C and placed in a hot box. The temperature is gradually increased to 130°C at a heating rate of 5°C / min and maintained for 20 minutes. Subsequently, the temperature is increased to 131°C at the same heating rate, maintained for 2 minutes, and this heating step is repeated with an interval of 1°C until the current safety device is activated. The temperature reached in the hot box at this time is T1;

[0019] At room temperature, the cylindrical battery is first fully discharged with a current of 0.2C, then left to stand at room temperature for 2 hours, and overcharged with a setting process of 2C and 6V is started until the overcharge test is completed. The battery temperature at this time is T2.

[0020] Furthermore, the positive electrode sheet includes a positive electrode current collector, and a positive electrode coating area and a positive electrode hollow foil area located on at least one surface of the positive electrode current collector, wherein a ceramic coating area is adjacently provided between the positive electrode coating area and the positive electrode hollow foil area; the positive electrode hollow foil area corresponds to forming the positive electrode lug;

[0021] The width of the ceramic coating area is 1.0%-5.5% of the width of the positive electrode sheet. The inorganic particulate material forming the ceramic coating area is selected from one or more of aluminum oxide, manganese dioxide, magnesium oxide, silicon dioxide, titanium dioxide, zirconium dioxide, zinc oxide, iron oxide, boehmite, gypsum, talc, and calcite, and the median diameter of the inorganic particulate material is 0.3 microns to 3.5 microns. Preferably, the inorganic particulate material is selected from a combination of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, and zinc oxide and is configured according to a mass ratio of 5-7:1-3:0.5-1.5:0.2-0.6:0.2-0.6.

[0022] Furthermore, the coating of the positive electrode coating area is formed by a positive electrode slurry, wherein the positive electrode slurry contains a positive electrode active material, a binder and a conductive agent;

[0023] The positive electrode active material is LiNi x Co y Mn z M j O2, wherein x is between 0.8 and 0.95, y = 0.05-0.1, z = 0.05-0.1, j = 1-xyz, M is selected from one or more of Al, Zr, Ti, Mg, Sr, Y, La, Ce, and V, and the positive electrode active material can be formed by conventional methods;

[0024] The positive electrode sheet further comprises F element and a characteristic element not higher than 1 wt %, wherein the content of F element in the positive electrode coating area is f, and the range of f is 0.8 wt % ≤ f ≤ 6.0 wt %, and the characteristic element not higher than 1 wt % is selected from one or more of B, P, and S;

[0025] The binder is selected from PVDF; the conductive agent is selected from one or more of acetylene black, carbon nanotubes, and graphene. The F, B, P, and S elements in the positive electrode sheet mainly come from the electrolyte and the positive electrode sheet binder PVDF;

[0026] Preferably, the positive electrode sheet meets one or more of the following conditions:

[0027] (1) The surface density of the positive electrode sheet is 10 mg / cm 2 -18 mg / cm 2 ;

[0028] (2) The compaction density of the positive electrode sheet is 3.35 g / cm 3 -3.65 g / cm 3 ;

[0029] (3) The surface capacity of the positive electrode is 2.1 mAh / cm 2 -2.5 mAh / cm2 ;

[0030] (4) The specific surface area of ​​the positive electrode sheet is 1m 2 / g -20m 2 / g;

[0031] (5) The porosity of the positive electrode sheet is 10%-50%.

[0032] Furthermore, the negative electrode sheet includes a negative electrode current collector, a negative electrode coating area and a negative electrode empty foil area located on at least one surface of the negative electrode current collector, and the negative electrode empty foil area forms the negative electrode ear.

[0033] The coating of the negative electrode coating area is formed by a negative electrode slurry, and the negative electrode slurry comprises at least the following solid materials: 94-98.5wt% of a negative electrode active material, 0.5-2wt% of a conductive agent, 0.5-2wt% of a dispersant, and 0.5-2wt% of a binder; the solvent in the negative electrode slurry is water and the solid content is 30-55wt%;

[0034] The negative electrode active material comprises one or more of artificial graphite, natural graphite, mesophase carbon microbeads, hard carbon, soft carbon, and silicon-based materials (silicon-oxygen materials, silicon-carbon materials), and the negative electrode active material contains 1-35 wt% of silicon-based materials;

[0035] The dispersant includes carboxymethyl cellulose (CMC), and the binder includes polyacrylate.

[0036] Preferably, the negative electrode sheet meets one or more of the following conditions:

[0037] (1) The surface density of the negative electrode sheet is 6.5 mg / cm 2 -9 mg / cm 2 ;

[0038] (2) The compaction density of the negative electrode sheet is 1.4 g / cm 3 -1.8 g / cm 3 ;

[0039] (3) The surface capacity of the negative electrode is 1.5 mAh / cm 2 -4.8 mAh / cm 2 ;

[0040] (4) The specific surface area of ​​the negative electrode sheet is 0.1m 2 / g -10m 2 / g;

[0041] (5) The porosity of the negative electrode sheet is 20%-60%.

[0042] Another aspect of the present invention provides an electrical device comprising any of the heat-safe lithium-ion cylindrical batteries described above.

[0043] Beneficial technical effects: The present invention realizes a lithium-ion cylindrical battery with excellent thermal balance, high performance and high safety characteristics by regulating the chemical system and optimizing the structural parts. The fundamental principle of the present invention is to regulate the residual space inside the cylindrical battery and adjust the rupture pressure of the explosion-proof disk in the current safety device. On this basis, by regulating the interface of the material chemical system, the rate of the interfacial reaction can be suppressed at high temperature, thereby achieving controllability. In the case of overcurrent, the interface can generate a large amount of gas accompanied by a small amount of heat, so that the current safety device can be quickly activated, achieving fast and accurate protection, and significantly improving the safety of the cylindrical battery. The present invention adopts 8 series or higher high-nickel positive electrode materials in combination with silicon-doped graphite negative electrode materials, which can achieve lithium-ion cylindrical battery energy density ≥300Wh / kg, continuous discharge rate ≥8C, instantaneous discharge rate ≥14C, cycle life ≥1000 times, and -40℃ discharge capacity retention rate ≥80%. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 This is a schematic diagram of the axial cross-sectional structure of a heat-safe cylindrical battery of the present invention;

[0045] Among them, 10-cover plate, 20-shell, 30-winding assembly;

[0046] Figure 2 A schematic diagram of the structure of the positive and negative electrodes of the heat-safe cylindrical battery of the present invention;

[0047] Among them, (a) represents the positive electrode sheet, (b) represents the negative electrode sheet, 101-positive electrode coating area, 102-positive electrode empty foil area, 103-ceramic coating area, 201-negative electrode coating area, 202-negative electrode empty foil area;

[0048] Figure 3 for Figure 1 Exploded view of the cover structure circled in the middle;

[0049] Among them, 1-lower end plate, 2-inner sealing ring, 3-explosion-proof disk, 4-top cover plate, 5-outer sealing ring. DETAILED DESCRIPTION

[0050] 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 embodiments described are only some embodiments of the present invention, rather than all 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.

[0051] 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.

[0052] 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.

[0053] The term "actuation" as used herein refers to the action of the explosion-proof disc in the current safety device turning over and cutting off the current.

[0054] The electrolyte used in the cylindrical battery described below 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 LiPF6 is added to prepare an electrolyte with a lithium salt concentration of 1 mol / L.

[0055] Example 1

[0056] A heat-safe lithium-ion cylindrical battery, the axial cross-sectional structure of which is as follows Figure 1 As shown, it includes a winding assembly 30 and a shell 20 for accommodating the winding assembly 30. The winding assembly 30 includes a winding core, which is injected with an electrolyte to impregnate the winding core and is accommodated in the shell 20. It also includes a cover plate 10 that seals the shell 20. One end of the cover plate 10 is the positive electrode of the lithium-ion cylindrical battery, and the other end is the negative electrode of the lithium-ion cylindrical battery.

[0057] The exploded view of the cover plate 10 structure is as follows Figure 3As shown, the structure of the cover plate 10 is provided with a current safety device, which is assembled with a top cover plate 4, a bursting disc 3, an inner sealing ring 2 and a lower end plate 1 in sequence from the outside to the inside. The top cover plate 4 and the lower end plate 1 are connected to form a cavity capable of accommodating the bursting disc 3. The edges of the bursting disc 3 are connected by the top cover plate 4 and the edges of the lower end plate 1. The cover plate 10 also includes an outer sealing ring 5, which wraps the top cover plate 4, bursting disc 3, inner sealing ring 2 and lower end plate 1 and seals the housing 20. The actuation pressure of the current safety device is 1.1 MPa.

[0058] The winding assembly 30 further includes a current collecting disk provided on the positive and negative electrode tab layers of the winding core. The positive electrode tab layer is electrically connected to the lower end plate 1 of the current safety device through the current collecting disk at this end, and the negative electrode tab layer is electrically connected to the bottom of the housing 20 through the current collecting disk at this end.

[0059] The winding core is formed by winding a positive electrode sheet (length 1532 mm × width 60 mm × thickness 90 mm), a separator (length 1665 mm × width 65 mm × thickness 12 mm), a negative electrode sheet (length 1590 mm × width 62 mm × thickness 110 mm), and a separator (length 1703 mm × width 65 mm × thickness 12 mm) in sequence.

[0060] The structure of the positive and negative electrodes is as follows Figure 2 As shown, Figure 2 In the figure, (a) represents a positive electrode sheet, and (b) represents a negative electrode sheet: the positive electrode sheet has a positive electrode hollow foil area at the top of the long side of one end, and the area is flattened or cut and stacked to form a positive electrode ear layer. The positive electrode sheet also includes a positive electrode current collector and a positive electrode coating area 101 located on both surfaces thereof. The coating of the positive electrode coating area 101 is obtained by coating with a positive electrode slurry. The uncoated area is the positive electrode hollow foil area 102. A ceramic coating area 103 is further provided in the area adjacent to the positive electrode coating area 101 and the positive electrode hollow foil area 102. The width of the ceramic coating area 103 is 1.2%-3.5% of the width of the positive electrode sheet. The inorganic particulate material forming the ceramic coating area 103 is a combination of aluminum oxide, silicon dioxide, titanium dioxide, zirconium dioxide, and zinc oxide in a mass ratio of 5:2:1:0.5:0.5, and the median diameter of the inorganic particulate material is 0.5-2.5 microns;

[0061] The negative electrode sheet has a negative electrode hollow foil area 202 at the top of one long side, which is flattened or cut to form a negative electrode ear layer. The negative electrode sheet includes a negative electrode current collector and negative electrode coating areas 201 located on both surfaces. The coating of the negative electrode coating area 201 is obtained by coating with a negative electrode slurry. The uncoated area is the negative electrode hollow foil area 202.

[0062] The negative electrode slurry includes 92 wt% artificial graphite, 4 wt% silicon oxide material, 1 wt% conductive agent acetylene black, and 3 wt% negative electrode binder polyacrylic acid. The surface density of the negative electrode sheet is set to 6.5 mg / cm 2 -9mg / cm 2 , compacted density is 1.4g / cm 3 -1.8 g / cm 3 , surface capacity is 1.5mAh / cm 2 -4.8 mAh / cm 2 , specific surface area is 0.1m 2 / g -10m 2 / g, porosity 20%-60%;

[0063] The positive electrode slurry includes 95.5 wt% of the positive electrode active material LiNi 0.8965 Co 0.05 Mn 0.05 Zr 0.003 Ti 0.0005 O2, 1.1 wt% carbon nanotube conductive agent, 1.9 wt% Super-P (conductive carbon black) conductive agent and 1.5 wt% polyvinylidene fluoride PVDF binder, the surface density of the positive electrode is 10 mg / cm 2 -18 mg / cm 2 , compacted density 3.35 g / cm 3 -3.65 g / cm 3 、Positive electrode surface capacity 2.1 mAh / cm 2 -2.5 mAh / cm 2 , positive electrode surface area 1 m 2 / g -20 m 2 / g, the porosity of the positive electrode sheet is 10%-50%; in addition, the injection of the electrolyte makes the F element content in the positive electrode sheet f=1.9wt% and one or more of B, P, and S not higher than 1wt%.

[0064] The above assembly forms a cylindrical battery, setting: the shell volume S1 = 24.4mL, the volume of the formed winding assembly S2 = 21.9mL, then the battery space utilization coefficient S2 / S1 = 89.75%; the true density of the winding core is set to Td = 2.95g / cm 3 The density of the resulting battery is ρ = 2.40 g / cm 3 .

[0065] The minimum pressure required for the cylindrical battery in this case to activate the current safety device corresponds to an internal gas production volume of Vs = 24.9 mL;

[0066] Five fresh lithium-ion cylindrical batteries were placed in a constant temperature environment of 85°C for 24 hours, and their gas production (average) was measured to be V1=13.2 mL. Another five fresh batteries were taken at room temperature, first fully discharged with a current of 0.2C, then left to stand at room temperature for 2 hours, and finally overcharged at a set process of 0.2C and 5V for 6 hours. The gas production (average) under the working conditions was V2=27.6 mL.

[0067] Five fresh lithium-ion cylindrical batteries were fully charged with a current of 0.2C and placed in a hot box. The temperature was gradually increased to 130°C at a heating rate of 5°C / min and maintained for 20 minutes. Subsequently, the temperature was increased to 131°C at the same heating rate, maintained for 2 minutes, and this heating step was repeated with an interval of 1°C until the battery's current safety device was activated. At this time, the temperature reached in the hot box was T1 = 133°C.

[0068] In addition, three fresh lithium-ion cylindrical batteries were taken at room temperature and fully discharged with a current of 0.2C. After that, the batteries were left to stand at room temperature for 2 hours and overcharged with a setting process of 2C and 6V until the overcharge test was completed. At this time, the maximum temperature of the batteries was T2=99℃.

[0069] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0070] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0071] Example 2

[0072] The structure of the lithium-ion cylindrical battery in this case is the same as that in Example 1, except that:

[0073] The positive electrode active material is LiNi 0.88 Co 0.05 Mn 0.05 Mg 0.002 O2;

[0074] The injection of electrolyte makes the F element content in the positive electrode f=5.9wt%;

[0075] The shell volume S1 = 23.9 mL, the volume of the wound assembly formed is S2 = 22.3 mL, then the space utilization coefficient of the battery is S2 / S1 = 93.31%; the true density of the core is set to Td = 2.53 g / cm 3 The density of the resulting battery is ρ = 2.35 g / cm 3 ;

[0076] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0077] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0078] Example 3

[0079] The structure of the lithium-ion cylindrical battery in this case is the same as that in Example 1, except that:

[0080] The positive electrode active material is LiNi 0.88 Co 0.05 Mn 0.05 Zr 0.003 Sr 0.0005 O2;

[0081] The pressure for the current safety device to operate is 1.2MPa;

[0082] The injection of electrolyte makes the F element content in the positive electrode f=2.1wt%;

[0083] The shell volume S1 = 24.7 mL, the volume of the wound assembly formed is S2 = 21.8 mL, then the space utilization coefficient of the battery is S2 / S1 = 88.26%; the true density of the core is set to Td = 2.96 g / cm 3 The density of the resulting battery is ρ = 2.42 g / cm 3 ;

[0084] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0085] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0086] Example 4

[0087] The structure of the lithium-ion cylindrical battery in this case is the same as that in Example 1, except that:

[0088] The positive electrode active material is LiNi 0.8955 Co 0.05 Mn 0.05 Al 0.004 La 0.0005 O2;

[0089] The pressure for the current safety device to operate is 1.0MPa;

[0090] The injection of electrolyte makes the F element content in the positive electrode f=2.1wt%;

[0091] The shell volume S1 = 24.1 mL, the volume of the wound assembly formed is S2 = 20.9 mL, then the space utilization coefficient of the battery is S2 / S1 = 86.72%; the true density of the core is set to Td = 2.93 g / cm 3 The density of the resulting battery is ρ = 2.41 g / cm 3 ;

[0092] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0093] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0094] Example 5

[0095] The structure of the lithium-ion cylindrical battery in this case is the same as that in Example 1, except that:

[0096] The positive electrode active material is LiNi 0.8928 Co 0.05 Mn 0.05 Al 0.007 Ti 0.0002 O2;

[0097] The pressure for the current safety device to operate is 0.9MPa;

[0098] The injection of electrolyte makes the F element content in the positive electrode f=1.8wt%;

[0099] The shell volume S1 = 24.8 mL, the volume of the wound assembly formed is S2 = 22.5 mL, then the battery space utilization coefficient is S2 / S1 = 90.73%; the true density of the core is set to Td = 2.89 g / cm 3 The density of the resulting battery is ρ = 2.39 g / cm 3 ;

[0100] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0101] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0102] Example 6

[0103] The structure of the lithium-ion cylindrical battery in this case is the same as that in Example 1, except that:

[0104] The positive electrode active material is LiNi 0.8965 Co0.05 Mn 0.05 Zr 0.003 Y 0.0005 O2;

[0105] The injection of electrolyte makes the F element content in the positive electrode f=0.9wt%;

[0106] The shell volume S1 = 24.3 mL, the volume of the wound assembly formed is S2 = 21.8 mL, then the space utilization coefficient of the battery is S2 / S1 = 89.71%; the true density of the core is set to Td = 2.99 g / cm 3 The density of the resulting battery is ρ = 2.41 g / cm 3 ;

[0107] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0108] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0109] Example 7

[0110] The structure of the lithium-ion cylindrical battery in this case is the same as that in Example 1, except that:

[0111] The positive electrode active material is LiNi 0.898 Co 0.05 Mn 0.05 V 0.001 Ti 0.001 O2;

[0112] The pressure for the current safety device to operate is 0.9MPa;

[0113] The injection of electrolyte makes the F element content in the positive electrode f=2.1wt%;

[0114] The shell volume S1 = 25 mL, the volume of the wound assembly formed is S2 = 22.2 mL, then the space utilization coefficient of the battery is S2 / S1 = 88.8%; the true density of the core is set to Td = 2.78 g / cm 3 The density of the resulting battery is ρ = 2.19 g / cm 3 ;

[0115] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0116] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0117] Comparative Example 1

[0118] The structure of the lithium-ion cylindrical battery in this case is the same as that in Example 1, except that:

[0119] The positive electrode active material is LiNi 0.9 Co 0.05 Mn 0.05 O2;

[0120] The injection of electrolyte makes the F element content in the positive electrode f=7.3wt%;

[0121] The shell volume S1 = 24.4 mL, the volume of the wound assembly formed is S2 = 21.8 mL, then the space utilization coefficient of the battery is S2 / S1 = 89.34%; the true density of the core is set to Td = 2.97 g / cm 3 The density of the resulting battery is ρ = 2.41 g / cm 3 ;

[0122] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0123] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0124] Comparative Example 2

[0125] The structure of the lithium-ion cylindrical battery in this case is the same as that in Example 1, except that:

[0126] The positive electrode active material is LiNi 0.9 Co 0.05 Mn 0.05 O2;

[0127] The pressure for the current safety device to operate is 1.7MPa;

[0128] The injection of electrolyte makes the F element content in the positive electrode f=3.3wt%;

[0129] The shell volume S1 = 23.9 mL, the volume of the wound assembly formed is S2 = 20.4 mL, then the space utilization coefficient of the battery is S2 / S1 = 85.36%; the true density of the core is set to Td = 2.97 g / cm 3 The density of the resulting battery is ρ = 2.46 g / cm 3 ;

[0130] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0131] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0132] Comparative Example 3

[0133] The structure of the lithium-ion cylindrical battery in this case is the same as that in Example 1, except that:

[0134] The positive electrode active material is LiNi 0.897 Co 0.05 Mn 0.05 Zr 0.003 O2;

[0135] The pressure for the current safety device to operate is 1.2MPa;

[0136] The injection of electrolyte makes the F element content in the positive electrode f=1.8wt%;

[0137] The shell volume S1 = 24.3 mL, the volume of the wound assembly formed is S2 = 23 mL, then the space utilization coefficient of the battery is S2 / S1 = 94.65%; the true density of the core is set to Td = 2.64 g / cm 3 The density of the resulting battery is ρ = 2.59 g / cm 3 ;

[0138] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0139] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0140] Comparative Example 4

[0141] The structure of the lithium-ion cylindrical battery in this case is the same as that in Example 1, except that:

[0142] The positive electrode active material is LiNi 0.8965 Co 0.05 Mn 0.05 Zr 0.003 Ti 0.0005 O2;

[0143] The pressure for the current safety device to operate is 0.6MPa;

[0144] The injection of electrolyte makes the F element content in the positive electrode f=0.6wt%;

[0145] The shell volume S1 = 24.3 mL, the volume of the wound assembly formed is S2 = 21.8 mL, then the space utilization coefficient of the battery is S2 / S1 = 89.71%; the true density of the core is set to Td = 2.91 g / cm3 The density of the resulting battery is ρ = 2.44 g / cm 3 ;

[0146] The above characteristic parameters S2 / S1, positive electrode active material, F element content f, |Td-ρ|, and the pressure at which the current safety device is activated are shown in Table 1.

[0147] The V1, V2, Vs, T1, and T2 results obtained from the lithium-ion cylindrical battery test in this case are shown in Table 2.

[0148] Table 1 Characteristic parameters of Examples and Comparative Examples

[0149]

[0150] Table 2 Battery test results

[0151]

[0152] As shown in Table 2, weak gas production during high-temperature testing prevents the current safety device from activating, indicating that the interfacial reaction is controllable. Furthermore, the hot box test exhibits a low temperature rise. Furthermore, in the event of overcharge, the gas production capacity enables the current safety device to activate and quickly disconnect the current, keeping the maximum battery temperature below 115°C and preventing explosion or fire. This demonstrates the high safety of the battery of the present invention.

[0153] In addition, the heat-safe lithium-ion cylindrical battery of the present invention can achieve a battery energy density of ≥300Wh / kg, a continuous discharge rate of ≥8C, an instantaneous discharge rate of ≥14C, a cycle life of ≥1000 times, and a -40°C discharge capacity retention rate of ≥80%.

[0154] 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 heat-safe lithium-ion cylindrical battery, characterized in that: comprising a winding assembly and a housing for accommodating the winding assembly; Also included is a cover plate for sealing the housing, wherein the cover plate is provided with a current safety device in its structure; The winding assembly includes a winding core, which is formed by winding a positive electrode sheet, a separator, and a negative electrode sheet; two ends of the winding core are flattened or cut and stacked to form a positive electrode ear layer and a negative electrode ear layer respectively; The gas production of the cylindrical battery when placed in a constant temperature environment of 85°C for 24 hours is V1; The gas production of the cylindrical battery under the condition of overcharging for 6 hours at 0.2C and 5V at room temperature is V2; The internal gas production corresponding to the minimum pressure required for the cylindrical battery to cause the current safety device to be activated is Vs; The following relationship is satisfied: V1<Vs≤V2, where the units of V1, V2, and Vs are milliliters; The inner volume of the cylindrical battery shell is S1, the volume of the winding assembly is S2, and the space utilization coefficient S2 / S1 of the cylindrical battery is 86%-94%; The density of the cylindrical battery is ρ g / cm 3 , the true density of the core is Td g / cm 3 , satisfying the following conditions: 0.3≤|Td-ρ|≤1.2; The pressure at which the current safety device is actuated is 0.8 MPa -1.2 MPa; The cylindrical battery also satisfies: T1>T2; T1 and T2 are defined as follows: The cylindrical battery is fully charged with a current of 0.2C and placed in a hot box. The temperature is gradually increased to 130°C at a heating rate of 5°C / min and maintained for 20 minutes. Subsequently, the temperature is increased to 131°C at the same heating rate, maintained for 2 minutes, and this heating step is repeated with an interval of 1°C until the current safety device is activated. The temperature reached in the hot box at this time is T1; At room temperature, the cylindrical battery is first fully discharged with a current of 0.2C, then left at room temperature for 2 hours, and overcharged with a setting process of 2C and 6V until the overcharge test is completed. The battery temperature at this time is T2; The positive electrode sheet includes a positive electrode current collector and a positive electrode coating area and a positive electrode blank foil area located on at least one surface of the positive electrode current collector. The coating of the positive electrode coating area is formed by a positive electrode slurry. The positive electrode slurry contains a positive electrode active material, F element, a binder and a conductive agent. The positive electrode active material is LiNi x Co y Mn z M j O2, wherein x is between 0.8 and 0.95, y = 0.05-0.1, z = 0.05-0.1, j = 1-xyz, and M is selected from one or more of Al, Zr, Ti, Mg, Sr, Y, La, Ce, and V; The positive electrode sheet also includes F element and characteristic elements not higher than 1wt%, wherein the content of F element in the positive electrode coating area is f, the range of f is 0.8 wt%≤f≤6.0 wt%, and the characteristic elements not higher than 1wt% are selected from one or more of B, P, and S.

2. The heat-safe lithium-ion cylindrical battery according to claim 1, characterized in that: A ceramic coating area is provided adjacent to the positive electrode coating area and the positive electrode hollow foil area; the positive electrode hollow foil area forms the positive electrode ear; The width of the ceramic coating area is 1.0%-5.5% of the width of the positive electrode sheet. The inorganic particulate material forming the ceramic coating area is selected from one or more of aluminum oxide, manganese dioxide, magnesium oxide, silicon dioxide, titanium dioxide, zirconium dioxide, zinc oxide, iron oxide, boehmite, gypsum, talc, and calcite, and the median diameter of the inorganic particulate material is 0.3 microns to 3.5 microns.

3. The heat-safe lithium-ion cylindrical battery according to claim 2, wherein: The binder is selected from PVDF; the conductive agent is selected from one or more of acetylene black, carbon nanotubes, and graphene.

4. The heat-safe lithium-ion cylindrical battery according to claim 2, characterized in that: The negative electrode sheet includes a negative electrode current collector, a negative electrode coating area and a negative electrode empty foil area located on at least one surface of the negative electrode current collector, and the negative electrode empty foil area corresponds to forming the negative electrode ear; The coating of the negative electrode coating area is formed by a negative electrode slurry, and the negative electrode slurry comprises at least the following solid materials: 94 wt%-98.5 wt% of a negative electrode active material, 0.5 wt%-2 wt% of a conductive agent, 0.5 wt%-2 wt% of a dispersant, and 0.5 wt%-2 wt% of a binder; The solvent in the negative electrode slurry is water and the solid content is 30 wt%-55 wt%; The negative electrode active material is selected from one or more of artificial graphite, natural graphite, mesophase carbon microbeads, hard carbon, soft carbon, and silicon-based materials, and the negative electrode active material contains 1 wt% to 35 wt% of silicon-based materials; The dispersant is selected from carboxymethyl cellulose, and the binder is selected from polyacrylate.

5. The heat-safe lithium-ion cylindrical battery according to claim 1, characterized in that: The positive electrode sheet meets one or more of the following conditions: (1) The surface density of the positive electrode sheet is 10 mg / cm 2 -18 mg / cm 2 ; (2) The compaction density of the positive electrode sheet is 3.35 g / cm 3 -3.65 g / cm 3 ; (3) The surface capacity of the positive electrode is 2.1 mAh / cm 2 -2.5 mAh / cm 2 ; (4) The specific surface area of ​​the positive electrode sheet is 1m 2 / g -20m 2 / g; (5) The porosity of the positive electrode sheet is 10%-50%.

6. The heat-safe lithium-ion cylindrical battery according to claim 1, characterized in that: The negative electrode sheet meets one or more of the following conditions: (1) The surface density of the negative electrode sheet is 6.5 mg / cm 2 -9 mg / cm 2 ; (2) The compaction density of the negative electrode sheet is 1.4 g / cm 3 -1.8 g / cm 3 ; (3) The surface capacity of the negative electrode is 1.5 mAh / cm 2 -4.8 mAh / cm 2 ; (4) The specific surface area of ​​the negative electrode sheet is 0.1m 2 / g -10m 2 / g; (5) The porosity of the negative electrode sheet is 20%-60%.

7. An electrical device comprising the heat-safe lithium-ion cylindrical battery according to any one of claims 1 to 6.

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