Lithium-ion battery

Abstract

The present invention discloses a highly safe lithium-ion battery, comprising a battery connecting piece, wherein the battery connecting piece comprises a positive connecting piece and a negative connecting piece, wherein the positive connecting piece and / or the negative connecting piece have notches for a fuse protection function, wherein an electric conductor is embedded in the notches; wherein the electric conductor will not fuse within the normal operating temperature range of the lithium-ion battery, and when the temperature of the lithium-ion battery continues to rise due to abnormal operating conditions, the electric conductor will melt before the positive connecting piece and / or the negative connecting piece fuses. The present invention provides a notch for fuse protection on the battery connecting piece, and embeds a conductor in the notch, so that the battery connecting piece has both a fuse protection function and does not affect the overcurrent capacity.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a highly safe lithium ion battery. Background Art

[0002] With the development and popularization of lithium batteries, people have higher and higher requirements for the capacity, energy density and safety performance of lithium batteries. In order to meet the charging and discharging current requirements of large-capacity batteries, the connecting pieces inside the battery need to have a higher thickness and width to improve the overcurrent capacity. However, while improving the overcurrent capacity, it also reduces the fusing safety of the connecting piece itself. Specifically, when the battery is short-circuited, the fusing time is prolonged, resulting in excessive heat accumulation in the battery during long-term discharge, and there is a risk of thermal runaway. In addition, as the battery capacity increases, the energy released when thermal runaway occurs also increases, and there is still a lot of room for improvement in battery safety performance.

[0003] In the existing battery preparation technology, the connecting piece is either not provided with fuse protection, or a fuse area is set in the connecting piece by punching or other methods, such as "Secondary Battery and Connection Assembly Therefor" (China Patent Publication No. CN208256795U), which provides safety protection by setting a fuse area and an insulator inside the battery. This method only solves the problem of safe fuse without considering the loss of overcurrent capacity. In addition, the lower gasket of the battery in the prior art only plays an insulating or liquid absorbing role, such as "Lithium-ion Power Battery Lower Gasket Structure" (China Patent Publication No. CN202308077U), which uses polypropylene material as the lower gasket of the battery. This technology adds a conductor to the connecting piece to achieve fuse protection and retain overcurrent capacity at the same time, and in addition to the insulation function, the lower gasket also plays a role in slow release of electricity to improve safety in extreme cases.

[0004] In summary, in order to improve the battery's current capacity, existing battery manufacturing technology often adopts methods such as increasing the thickness of the connecting piece to reduce heat generation and increase the current area, but the fuse property of the connecting piece will be damaged; if the fuse area is set by punching, the current capacity will decrease. In addition, the gasket under the battery of the prior art usually only has the ability to insulate or absorb liquid. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies and defects of the prior art and provide a highly safe lithium-ion battery.

[0006] A highly safe lithium-ion battery comprises a battery connecting piece, wherein the battery connecting piece comprises a positive connecting piece and a negative connecting piece, and is characterized in that the positive connecting piece and / or the negative connecting piece have a notch for a fuse protection function, and an electric conductor is embedded in the notch; the electric conductor will not fuse within the normal operating temperature range of the lithium-ion battery, and will melt before the positive connecting piece and / or the negative connecting piece fuses when the temperature of the lithium-ion battery continues to rise due to an abnormal operating condition.

[0007] Wherein, the conductor is made of a low melting point metal or a conductive plastic. Preferably, the conductor is made of conductive modified polyethylene.

[0008] The notch is located between the pole welding area and the tab welding area, separating the pole welding area from the tab welding area.

[0009] The electrical conductor covers the groove surface of the notch.

[0010] Among them, the lithium-ion battery includes a lower gasket, which is located below the battery pole group and separates the battery pole group from the bottom of the battery shell; the lower gasket is composed of an insulating layer and a conductive layer; the insulating layer is located in the upper layer to form insulation to prevent the battery pole group from contacting the bottom of the battery shell and causing a short circuit, and the conductive layer is located in the lower layer and contacts the bottom of the battery shell. The lower gasket will not melt within the temperature range of normal operation of the lithium-ion battery. When the temperature of the lithium-ion battery continues to rise due to abnormal operating conditions, the lower gasket melts before the battery diaphragm is hot-melted.

[0011] Among them, the insulating layer is made of one or more of polyethylene, ethylene-vinyl acetate copolymer, and acrylonitrile-styrene copolymer; when the temperature of the lithium-ion battery continues to rise due to abnormal operating conditions, the insulating layer melts before the battery separator is hot-melted.

[0012] Wherein, the thickness of the insulating layer is 0.1-1 mm, preferably, the thickness is 0.2 mm.

[0013] Among them, the conductive layer adopts one or more of polyethylene, ethylene-vinyl acetate copolymer, and acrylonitrile-styrene copolymer modified by adding a conductive agent; when the temperature of the lithium-ion battery continues to rise due to abnormal operating conditions, the conductive layer melts before the battery separator is hot-melted.

[0014] Wherein, the thickness of the conductive layer is 0.1-1 mm, preferably, the thickness is 0.2 mm.

[0015] Wherein, the thickness of the lower gasket is 0.2-2 mm, preferably, the thickness is 0.4 mm.

[0016] The present invention provides a notch for fuse protection on the battery connecting piece and embeds a conductor in the notch, so that the battery connecting piece can form the function of fuse protection without affecting the overcurrent capacity.

[0017] The present invention retains the insulation capacity by providing a lower gasket composed of a low-melting-point insulating layer and a conductive layer. When the battery is overheated and there is a risk of thermal runaway, the lower gasket is melted first, and an internal micro-short circuit is formed through the conductive effect of the conductive layer, which slowly releases part of the electricity to improve safety.

[0018] Compared with conventional commercial lithium batteries that do not have fuse protection connectors, the battery has significantly improved safety performance such as short circuit, and the maximum temperature reached by the battery when thermal runaway is actively triggered is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic diagram of a lithium ion battery of the present invention.

[0020] Figure 2 It is a schematic diagram of the positive electrode connecting piece of the lithium ion battery of the present invention.

[0021] Figure 3 It is a schematic diagram of the negative electrode connecting piece of the lithium ion battery of the present invention.

[0022] Figure 4 It is a schematic diagram of the lower gasket of the lithium ion battery of the present invention.

[0023] Figure 5 This is the short circuit test result diagram of the experimental group.

[0024] Figure 6 This is the short circuit test result diagram of the control group.

[0025] Figure 7 This is a graph showing the temperature change results of the experimental group's rate charging test.

[0026] Figure 8 This is the result of the short circuit test of the control group 2.

[0027] Fig. 9 This is the heating test result diagram of the experimental group.

[0028] Fig.10 This is a graph of the three-heating test results for the control group.

[0029] Description of reference numerals:

[0030] 1- lithium battery upper gasket, 2- battery cover, 3- positive electrode connecting piece, 4- electrode group, 5- battery shell, 6- negative electrode connecting piece, 7- pole ear, 8- electrode group protective cover, 9- battery outer insulating film, 10- lower gasket;

[0031] 11-positive electrode column welding area, 12-notch of the positive electrode connecting piece, 13-electric conductor embedded in the notch of the positive connecting piece, 14-positive electrode ear welding area, 150 negative electrode column welding area, 16 notch of the negative electrode connecting piece, 17 electric conductor embedded in the notch of the negative connecting piece, 18 negative electrode ear welding area, 19-insulating layer, 20 positioning hole, 21-conductive layer. DETAILED DESCRIPTION

[0032] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0033] See also Figures 1 to 4 As shown, a high-safety lithium-ion battery includes a battery connecting piece, wherein the battery connecting piece includes a positive connecting piece and a negative connecting piece, and is characterized in that the positive connecting piece and / or the negative connecting piece have a notch for a fuse protection function, and an electric conductor is embedded in the notch; the electric conductor will not fuse within the normal operating temperature range of the lithium-ion battery, and when the temperature of the lithium-ion battery continues to rise due to an abnormal operating condition, the electric conductor melts before the positive connecting piece and / or the negative connecting piece fuses.

[0034] The current, time and fuse position required for fusing are controlled by controlling the width, depth and position of the notch to achieve the purpose of high current fusing protection. The shape and size of the notch can be changed according to actual needs, and the processing method can be etching, milling, etc. based on commercial connectors, but not limited to this. The notch position can be adjusted according to actual needs, preferably, it is located between the pole welding area and the pole ear welding area of ​​the positive connector. The shape, size, position, etc. of the notch of the positive connector and the negative connector are similar.

[0035] The principle of the fuse protection function involved in this application is that when the current passes through the notched connecting piece, according to the thermodynamic formula Q = I 2 Rt, R = ρ * L / S, Q = c * m * △ T, the temperature rise of the connecting piece can be obtained Where Q is heat generation, I is the current passing through the connecting piece, R is the resistance of the connecting piece at the notch, t is the time when the current passes through, ρ is the resistivity of the connecting piece, L is the width of the notch of the connecting piece, S is the cross-sectional area of ​​the connecting piece at the notch, c is the specific heat capacity of the connecting piece, m is the mass of the connecting piece at the notch, and △T is the temperature rise of the connecting piece at the notch; when the material and size of the connecting piece are certain, △T depends on the current I, the notch width L, the cross-sectional area S and the time t, and the melting point of the connecting piece is fixed, so the time required for melting under a certain current can be controlled by controlling the notch size.

[0036] In the present application, the resistivity of the selected conductor is low to improve the current carrying capacity of the notched connecting piece and avoid high heat generation of the connecting piece when the battery is working normally; the melting point of the selected conductor is higher than the normal working temperature range of the battery to ensure that the battery will not melt during operation and affect the electrical performance; the melting point of the selected conductor is much lower than that of the positive connecting piece. When the battery has abnormal operating conditions such as external short circuit, the conductor melts before the connecting piece melts, and then does not affect the effect of the notch melting of the connecting piece.

[0037] In the present application, the conductor embedded in the notch of the positive electrode connecting sheet and / or the negative electrode connecting sheet covers the surface of the groove of the notch, and its material must meet the requirements of not being easily embedded with lithium and not reacting with the electrolyte and other materials inside the battery to avoid failure due to chemical reactions. Its material can be low melting point metal, conductive plastic, etc. but is not limited thereto, preferably, conductive modified polyethylene.

[0038] Among them, the lithium-ion battery includes a lower gasket, which is located below the battery pole group. The lower gasket is provided with two positioning holes to separate the battery pole group from the bottom of the battery shell; the lower gasket is composed of an insulating layer and a conductive layer; the insulating layer is located in the upper layer to form insulation to prevent the battery pole group from contacting the bottom of the battery shell and causing a short circuit, and the conductive layer is located in the lower layer and contacts the bottom of the battery shell. The lower gasket will not melt within the temperature range of normal operation of the lithium-ion battery. When the temperature of the lithium-ion battery continues to rise due to abnormal operating conditions, the lower gasket melts before the battery diaphragm is hot-melted. In the present application, the lower gasket is located directly below the battery pole group. When the battery is operating normally, it prevents the pole group from contacting the battery shell and short-circuiting, and plays an insulating protection role. When the battery is in an abnormal operating condition, the low melting point is used to form a micro-short circuit inside the battery to release part of the electricity, thereby improving the battery safety performance.

[0039] The insulating layer is made of one or more of polyethylene, ethylene-vinyl acetate copolymer, and acrylonitrile-styrene copolymer; when the temperature of the lithium-ion battery continues to rise due to abnormal working conditions, the insulating layer melts before the battery separator is hot-melted. The melting point of the material selected for the insulating layer is higher than the normal working temperature of the battery to ensure normal working; the melting point of the selected material is lower than the melting point of the battery separator. When the temperature of the battery continues to rise due to abnormal working conditions such as external heating, external short circuit, internal short circuit, etc., it melts before the battery separator is hot-melted.

[0040] The thickness of the insulating layer is 0.1-1 mm to ensure insulation effectiveness, and preferably, the thickness is 0.2 mm.

[0041] Among them, the conductive layer adopts one or more of polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), and acrylonitrile-styrene copolymer (AS) modified by adding a conductive agent, preferably, conductive modified polyethylene (PE); when the temperature of the lithium-ion battery continues to rise due to abnormal operating conditions, the conductive layer melts before the battery separator is hot-melted.

[0042] In the present application, the selected material of the conductive layer is similar to that of the insulating layer, but the conductive agent is added to modify the conductivity, and the melting point is similar to that of the insulating layer. Since the conductive layer and the insulating layer are of similar materials, they can be compounded together. When the temperature of the battery continues to rise due to abnormal operating conditions such as external heating, external short circuit, internal short circuit, etc., the conductive layer also melts before the diaphragm is hot-melted. Under the conductive effect of the conductive layer material, micro short circuits such as the negative electrode sheet and the positive electrode sheet, the negative electrode sheet and the battery shell are caused, and part of the electricity is slowly released to avoid the occurrence of severe thermal runaway caused by rapid reaction and release of a large amount of heat in a very short time under abnormal conditions, thereby improving the safety performance of the battery.

[0043] The thickness of the conductive layer is 0.1-1 mm, so as to ensure that it can partially contact the negative electrode sheet to produce micro-conductivity after melting. Preferably, the thickness is 0.2 mm.

[0044] The thickness of the lower gasket is 0.4-2 mm, which reduces the space occupied by the battery while ensuring insulation. Preferably, the thickness is 0.4 mm.

[0045] Embodiment 1:

[0046] The conventional lithium-ion battery materials such as battery connectors with fuse protection, lithium-ion battery positive plates, negative plates, separators, electrolytes, square battery shell covers and other structural parts are made into square batteries by winding or stacking using commercial technology as the experimental group.

[0047] The battery connector with fuse protection includes a positive electrode connector with notches, an electric conductor embedded in the notches of the positive electrode connector, and a negative electrode connector with notches, an electric conductor embedded in the notches of the negative electrode connector. The electric conductor is made of conductive modified polyethylene and embedded in the notches of the negative electrode connector and the positive electrode connector.

[0048] A conventional battery connector without notches and a battery made of the same lithium-ion battery material and method were used as control group 1;

[0049] A battery connector with notches but no embedded conductor and a battery made of the same lithium-ion battery material and method were used as a second control group.

[0050] The experimental group and the control group 1 were subjected to short-circuit safety tests under the same test conditions, and the experimental group and the control group 2 were subjected to rate charging performance tests under the same test conditions. The test results are as follows: Figure 5 , 6 , 7, and 8.

[0051] In the short-circuit safety test, the voltage of the experimental group dropped to 0 within 6 seconds after the short circuit occurred, the battery connector melted, and the battery had no explosion-proof valve opening, leakage or thermal runaway. The explosion-proof valve of the control group opened 34 seconds after the short circuit occurred, and thermal runaway occurred later, and the voltage gradually dropped to 0 within the next 50 seconds.

[0052] In the rate charging performance test, the maximum temperature rise reached by the experimental group was 23°C, while the maximum temperature rise reached by the control group was 35°C, indicating that the short-circuit safety performance and overcurrent capability of the experimental group were better than those of the control group.

[0053] Embodiment 2:

[0054] The battery bottom gasket with a low melting point and conventional lithium-ion battery materials such as lithium-ion battery positive electrode, negative electrode, separator, electrolyte, square battery shell cover and other structural parts were made into square batteries by winding or stacking using commercial technical means as the experimental group; the low-melting point battery bottom gasket was composited with a 0.2 mm thick polyethylene insulating layer and a 0.2 mm thick conductive modified polyethylene conductive layer.

[0055] The conventional lower gasket and other batteries made of the same lithium-ion battery materials and methods were used as the control group; the experimental group and the control group were subjected to heating safety tests, and the test results were as follows Fig. 9 , 10 shown.

[0056] In the heating safety test, when the experimental group was heated to about 155°C, the voltage dropped uniformly at a certain rate, forming an internal micro-short circuit, triggering thermal runaway at about 175°C, and the maximum temperature was about 240°C; the control group three directly triggered thermal runaway at about 175°C, with a maximum temperature of about 330°C, indicating that the heat generated by the experimental group's battery when triggering thermal runaway was lower, thereby improving safety performance.

[0057] The basic principles and main features of the present invention and the advantages of the present invention are shown and described above. It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention.

[0058] Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is therefore intended that all changes falling within the meaning and range of equivalent elements of the claims are included in the present invention.

[0059] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A lithium-ion battery, comprising a battery connecting piece, wherein the battery connecting piece comprises a positive electrode connecting piece and a negative electrode connecting piece, characterized in that: The positive electrode connecting sheet and / or the negative electrode connecting sheet have notches for fuse protection, and an electrical conductor is embedded in the notches; the electrical conductor will not fuse within the normal operating temperature range of the lithium-ion battery, and will melt before the positive electrode connecting sheet and / or the negative electrode connecting sheet fuses when the temperature of the lithium-ion battery continues to rise due to abnormal operating conditions.

2. The lithium-ion battery according to claim 1, characterized in that: The conductor is made of a low melting point metal or a conductive plastic. Preferably, the conductor is made of conductive modified polyethylene.

3. The lithium-ion battery according to claim 2, characterized in that: The notch is located between the pole welding area and the tab welding area, separating the pole welding area from the tab welding area.

4. The lithium-ion battery according to claim 1, characterized in that: The electrical conductor covers the groove surface of the score.

5. The lithium ion battery according to any one of claims 1 to 4, characterized in that: It includes a lower gasket, which is located below the battery pole group and separates the battery pole group from the bottom of the battery shell; the lower gasket is composed of an insulating layer and a conductive layer; the insulating layer is located in the upper layer to form insulation to prevent the battery pole group from contacting the bottom of the battery shell and causing a short circuit, and the conductive layer is located in the lower layer and contacts the bottom of the battery shell. The lower gasket will not melt within the temperature range of normal operation of the lithium-ion battery. When the temperature of the lithium-ion battery continues to rise due to abnormal operating conditions, the lower gasket melts before the battery diaphragm is hot-melted.

6. The lithium-ion battery according to claim 5, characterized in that: The insulating layer is made of one or more of polyethylene, ethylene-vinyl acetate copolymer, and acrylonitrile-styrene copolymer; when the temperature of the lithium-ion battery continues to rise due to abnormal operating conditions, the insulating layer melts before the battery separator is hot-melted.

7. The lithium-ion battery according to claim 5, characterized in that: The thickness of the insulating layer is 0.1-1 mm, preferably 0.2 mm.

8. The lithium-ion battery according to claim 5, characterized in that: The conductive layer is made of one or more of polyethylene, ethylene-vinyl acetate copolymer, and acrylonitrile-styrene copolymer modified by adding a conductive agent; when the temperature of the lithium-ion battery continues to rise due to abnormal operating conditions, the conductive layer melts before the battery separator is hot-melted.

9. The lithium-ion battery according to claim 5, characterized in that: The thickness of the conductive layer is 0.1-1 mm, preferably 0.2 mm.

10. The lithium-ion battery according to claim 5, characterized in that: The thickness of the lower gasket is 0.2-2 mm, preferably 0.4 mm.

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