Safety type composite current collector manufacturing method, safety type composite current collector, pole piece, battery cell and battery

Abstract

The invention relates to the technical field of secondary batteries, and provides a safety type composite current collector manufacturing method, a safety type composite current collector, a pole piece, a battery cell and a battery, and the method comprises the following steps: manufacturing an isolation wire on the surface of the composite current collector based on the current direction of the battery cell; wherein the shielding wire is obtained by removing the metal layer in the composite current collector. The safety of the battery cell can be improved under the condition of maintaining the energy density of the battery cell.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a method for manufacturing a safe composite current collector, a safe composite current collector, a pole piece, a battery cell and a battery. Background Art

[0002] Due to the instability of lithium-ion power batteries in existing power vehicles, "safety" has become one of the concerns of people using electric vehicles. How to improve the safety of existing power batteries has become the focus of everyone's competition. At the same time, people are also very concerned about the energy density of lithium batteries. On the basis of not affecting the energy density, improving the safety of lithium batteries is also an important work direction for lithium battery engineers. In order to improve the safety of lithium batteries, the existing technology uses lithium iron phosphate with high stability as an active material or reduces the short circuit of the battery cell caused by burrs generated by the current collector. Lithium iron phosphate has higher thermal stability than ternary active materials. It is not easy to release oxygen after the internal or external short circuit of the battery cell rises, so the battery cell is not easy to burn, but its energy density is lower than that of ternary active materials, and it cannot meet the requirements of high safety and high energy density at the same time. The current collector generates burrs after the battery cell is deformed or punctured, causing the positive and negative short circuits, which is a major cause of heat release and fire in the battery cell. The safety primer of the current collector can effectively reduce the generation of burrs, thereby improving the safety of the battery cell. However, since the safety primer reduces the proportion of active materials in the electrode, the energy density of the battery cell is reduced. Similarly, applying a thicker solid electrolyte or other coating on the diaphragm can block burrs to a certain extent, but it also faces the problem of a decrease in the overall energy density of the battery cell due to an increase in the proportion of inactive substances.

[0003] Although the existing solutions can improve the safety of battery cells, the introduction of low energy density active materials or inactive materials into the battery cells is not conducive to the energy density of the battery cells. Therefore, how to improve the safety of battery cells while maintaining the energy density of the battery cells is a technical problem that needs to be solved urgently. Summary of the invention

[0004] In response to the above technical problems, the purpose of the present application is to provide a method for preparing a safe composite current collector, a safe composite current collector, a pole piece, a battery cell and a battery, aiming to improve the safety of the battery cell while maintaining the energy density of the battery cell.

[0005] In a first aspect, an embodiment of the present application provides a method for preparing a safe composite current collector, the method comprising:

[0006] Based on the direction of the battery cell current, an isolation line is made on the surface of the composite current collector; wherein the composite current collector includes a metal layer and a polymer layer, the polymer layer is located between two metal layers, and the isolation line is obtained by removing the metal layer in the composite current collector.

[0007] In one embodiment, the step of making an isolation line on the surface of the composite current collector based on the current direction of the battery cell includes:

[0008] If the composite current collector is a rectangular composite current collector, an isolation line parallel to the edge of the composite current collector is made substantially along the current direction of the battery cell in the current collector region where the current direction does not change significantly.

[0009] In one embodiment, the method further comprises:

[0010] An isolation line is made completely along the current direction of the battery cell in the current collector area close to the pole ear.

[0011] In one embodiment, the step of making an isolation line on the surface of the composite current collector based on the current direction of the battery cell includes:

[0012] An isolation line is made on the surface of the composite current collector completely along the current direction of the battery cell.

[0013] In one embodiment, the isolation line is obtained by removing the metal layer in the composite current collector by laser etching, chemical corrosion or mechanical method.

[0014] In one embodiment, on the same metal layer, the isolation lines on different metal layers are staggered.

[0015] In one embodiment, on the same metal layer, the ratio of the spacing between adjacent isolation lines to the width of the isolation lines is greater than 10:1.

[0016] In a second aspect, an embodiment of the present application provides a safe composite current collector, wherein an isolation line is arranged on the surface of the safe composite current collector, and the isolation line is made based on the current direction of the battery cell; wherein the isolation line is obtained by removing the metal layer of the composite current collector, and the composite current collector includes a metal layer and a polymer layer, and the polymer layer is located between the two metal layers.

[0017] In one embodiment, the isolation line is made completely along the current direction of the battery cell.

[0018] In one embodiment, if the composite current collector is a rectangular composite current collector, the isolation lines in the current collector region where the current direction does not change significantly are parallel lines and are parallel to the sides of the composite current collector.

[0019] In one embodiment, the isolation line is made completely along the current direction of the battery cell in the current collector region close to the tab.

[0020] In one embodiment, the isolation line is obtained by removing the metal layer in the composite current collector by laser etching, chemical corrosion or mechanical method.

[0021] In one embodiment, the ratio of the spacing between adjacent isolation lines to the width of the isolation lines is greater than 10:1.

[0022] In a third aspect, an embodiment of the present application provides a pole piece, comprising the safe composite current collector described in any one of the above items.

[0023] In one embodiment, the pole piece includes an active material layer, and the active material layer is coated on the metal layer of the safety composite current collector.

[0024] In one embodiment, the active material layer is also coated on the isolation line.

[0025] In a fourth aspect, an embodiment of the present application provides a battery cell, wherein the battery cell comprises a pole piece as described in any one of the above items.

[0026] In a fifth aspect, an embodiment of the present application further provides a battery, comprising the battery cell described in any one of the above items.

[0027] The present invention is based on the current direction of the battery cell, and makes an isolation line on the surface of the composite current collector by removing the metal layer. The isolation line formed after the metal layer is removed is electronically insulated, which changes the current distribution of the battery cell during a local short circuit, increases the short circuit impedance, and concentrates the energy released by the short circuit in the local current collector area, causing the local current collector to fuse, thereby achieving the effect of reducing the short circuit power and cutting off the discharge circuit, avoiding the danger of combustion or even explosion caused by the short-time high-power discharge of the entire battery cell, and improving the safety of the battery cell. In addition, the adopted current collector plus isolation line solution has a negligible change in the mass of the current collector, so the energy density of the existing battery cell can be maintained. In summary, the present invention can improve the safety of the battery cell while maintaining the energy density of the battery cell, thereby improving the safety of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solution of the present application, the drawings required for use in the implementation manner will be briefly introduced below. Obviously, the drawings described below are only some implementation manners of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0029] Figure 1 It is a schematic diagram of a process for preparing a safe composite current collector provided by one embodiment of the present invention;

[0030] Figure 2 is a partial schematic diagram of the composite current collector;

[0031] Figure 3 is a partial schematic diagram of a composite current collector with isolation lines provided in one embodiment of the present application;

[0032] Figure 4This is a schematic diagram of the working discharge current of a composite current collector battery cell with isolation lines provided in one embodiment of the present application;

[0033] Figure 5 It is a diagram of the local short-circuit current flow direction of a composite current collector cell without isolation wires;

[0034] Figure 6 It is a diagram of the local short-circuit current flow of a composite current collector cell with an isolation line;

[0035] Figure 7 is a design diagram of a current collector isolation line provided in another embodiment of the present application;

[0036] Figure 8 This is the overall side view of the existing common battery cell during acupuncture;

[0037] Fig. 9 yes Figure 8 A partial side view of

[0038] Fig.10 is with Figure 8 The corresponding overall top view;

[0039] Fig.11 This is an overall side view of the battery cell of the present invention during acupuncture;

[0040] Fig.12 yes Fig.11 A partial side view of

[0041] Fig.13 is with Fig.11 The corresponding overall top view;

[0042] Figure 14-18 This is a schematic diagram of the current direction of the battery cell corresponding to different pole ear positions and different pole piece length-to-width ratios;

[0043] Fig.19 It is a schematic diagram of arranging isolation lines on the composite current collector completely according to the direction of the battery cell current;

[0044] Fig. 20 The schematic diagram of the design is to arrange parallel isolation lines in the area where there is no obvious change in the current direction, and to arrange the isolation lines completely along the current direction of the battery cell in the current collector area close to the pole ear.

[0045] Figure ID:

[0046] 1. Metal layer; 2. Polymer layer; 3. Isolation line; 4. Steel needle; 5. Current collector area where the current direction does not change significantly; 6. Pole ear; 7. Current collector area close to the pole ear; 8. Current collector. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0048] It will be understood by those skilled in the art that, unless expressly stated, the singular forms "a", "an", "above", and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present application refers to the presence of features, integers, steps, operations, elements, modules, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, modules, components, and / or groups thereof. It should be understood that when we refer to an element as being "connected" or "coupled" to another element, it may be directly connected or coupled to the other element, or there may be an intermediate element. In addition, the "connection" or "coupling" used herein may include wireless connection or wireless coupling. The term "and / or" used herein includes all or any module and all combinations of one or more associated listed items.

[0049] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with those in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as here.

[0050] In order to facilitate understanding of the embodiments of the present invention, the battery structure is briefly described as follows:

[0051] The components of a battery include a cell, the components of a cell include a pole piece and a pole lug, the components of a pole piece include a current collector and an active material layer coated on the surface of the current collector, the active material layer is also called an electrode layer.

[0052] like Figure 1 The embodiment of the present application provides a method for preparing a safe composite current collector, the method comprising:

[0053] Based on the direction of the battery cell current, an isolation line is made on the surface of the composite current collector; wherein the composite current collector includes a metal layer and a polymer layer, the polymer layer is located between two metal layers, and the isolation line is obtained by removing the metal layer in the composite current collector.

[0054] In the embodiments of the present application, Figure 2As shown, the composite current collector includes a metal layer 1 and a polymer layer 2, and the polymer layer 2 is located between the two metal layers 1. In order to improve the safety of the battery cell, the present invention improves the composite current collector. The improved composite current collector is referred to as a safe composite current collector in this application, and the battery cell is manufactured based on the safe composite current collector. The composite current collector is improved. Specifically, based on the direction of the battery cell current, a safe composite current collector can be obtained by removing the metal layer to make an isolation line on the surface of the composite current collector. The battery cell current direction refers to the current direction of a battery cell composed of a composite current collector (which has not been improved by the present invention, that is, the composite current collector has no isolation line) in its current collector. The battery cell current direction in the current collector 8 is highly dependent on the shape of the pole piece, such as the aspect ratio, the position and width of the pole ear 6, and the shape. Schematically, as shown in FIG. Figure 14-18 Schematically, the position of the isolation line in the current collector 8 is as follows Figure 3 , 19 , as shown in Figure 20.

[0055] The present invention is based on the current direction of the battery cell, and makes an isolation line on the surface of the composite current collector by removing the metal layer. The isolation line formed after the metal layer is removed is electronically insulated, which changes the current distribution of the battery cell during a local short circuit, increases the short circuit impedance, and concentrates the energy released by the short circuit in the local current collector area, causing the local current collector to fuse, thereby achieving the effect of reducing the short circuit power and cutting off the discharge circuit, avoiding the danger of combustion or even explosion caused by the short-term high-power discharge of the entire battery cell, and improving the safety of the battery cell. In addition, the current collector plus isolation line solution adopted has a negligible change in the mass of the current collector, so the energy density of the existing battery cell can be maintained. In summary, the present invention can improve the safety of the battery cell while maintaining the energy density of the battery cell.

[0056] The present invention is applicable to liquid or solid lithium ion or sodium ion batteries.

[0057] In one embodiment, the step of making an isolation line on the surface of the composite current collector based on the current direction of the battery cell includes:

[0058] If the composite current collector is a rectangular composite current collector, an isolation line parallel to the edge of the composite current collector is made substantially along the current direction of the battery cell in the current collector region where the current direction does not change significantly.

[0059] In the embodiment of the present invention, the composite current collector may be rectangular or may be irregular (non-rectangular). Figure 2 The composite current collector shown is rectangular, wherein the middle layer is a polymer layer 2, and the two sides are metal layers 1, usually the positive electrode is aluminum, and the negative electrode is copper. When the composite current collector is a rectangular composite current collector, an isolation line parallel to the first side of the current collector can be made in the current collector area where the current direction does not change significantly, and the first side refers to the side that is basically consistent with the current direction of the battery cell, such as Figure 3 As shown, Figure 3 This is a partial schematic diagram of a composite current collector with isolation lines. Although the parallel line design can only ensure that the isolation lines and the current direction of the battery cell are basically consistent, it is easier to design and manufacture. The isolation lines are electronically insulated, which is obtained by removing the metal layer by laser etching, chemical corrosion or mechanical methods. Figure 4 This is a current direction diagram of a composite current collector with isolation lines (isolation lines are only present in areas where there is no obvious change in the current direction) when the battery cell is discharging normally. The arrow is the local current direction and mark 6 is the pole ear. Figure 5 Schematic diagram of the current direction of a composite current collector cell without isolation wire when it is locally short-circuited, where the circle is the short-circuit point of the cell, the arrow is the local current direction, and the mark 6 is the pole ear. Figure 5 The non-short-circuit area discharges to the short-circuit point via the shortest path. Figure 6 Schematic diagram of the current direction of a composite current collector cell with an isolation line when it is locally short-circuited, where the circle is the short-circuit point of the cell, the arrow is the local current direction, and the mark 6 is the pole ear. Figure 6 It can be seen that due to the electronic insulation of the isolation line, the current in the non-short-circuit area needs to move along the isolation line to the pole ear area and then return to the short-circuit point, where the electron propagation path is greatly lengthened, especially when all the discharge current is concentrated in the isolation line area where the short-circuit point is located. The metal layer of the composite current collector may melt quickly, thereby cutting off the discharge circuit, avoiding thermal runaway of the battery cell, and improving the safety of local short circuits in the battery cell.

[0060] In addition, if Figure 8-10 As shown, when the steel needle 4 pierces the ordinary laminated or wound battery, it is equivalent to an internal short circuit of the entire battery. The current of all electrodes will pass through the steel needle 4, thereby generating a large amount of heat. Assume that the resistance of the steel needle 4 is R m , the ohmic resistance of the battery is R c So the short circuit current i=U / (R m +R c ).

[0061] like Figure 11-13 As shown, Fig.11 In the battery shown, the electrode layer (active material layer) is only coated on the metal layer, but not on the isolation line. When it is specifically manufactured, the pole piece can be manufactured first, and then the electrode layer and the metal layer are removed together by laser etching, chemical corrosion or mechanical methods to form an isolation line. In batteries of other embodiments, the electrode layer is coated on both the metal layer and the isolation line. When it is specifically manufactured, the metal layer is first removed by laser etching, chemical corrosion or mechanical methods to form an isolation line, and then the active material is directly coated on the surface of the current collector, so that the active material is coated on both the metal layer and the isolation line, that is, the metal layer and the polymer layer are covered together.

[0062] like Figure 11-13 As shown, when the steel needle 4 is used for puncturing, each electrode layer can only be punctured by the steel needle 4 in one area. Assume that each electrode is isolated into N areas by an isolation line. Also, assume that the resistance of the steel needle 4 is R m , the ohmic impedance of the cell is R c When the steel needle 4 pierces, only the current in the pierced area can be short-circuited by the steel needle 4. At the same time, the entire battery circuit is transformed into N-1 areas connected in parallel and then connected in series with the pierced area and the steel needle 4 resistance. According to Ohm's law, the internal resistance of the pierced area is NR c , the internal resistance of N-1 regions connected in parallel is NR c / (N-1). The resistance of the entire loop is R = R m +NR c +NR c / (N-1)=R m +N 2 R c / (N-1)>R m +R c When N is larger, that is, the smaller the electrodes are divided by the isolation line, the greater the resistance generated by the short circuit, the smaller the current of the entire circuit, and thus the safer. Similarly, assuming that the resistance of steel needle 4 is R m , the ohmic resistance of the battery is R c When the internal resistance of the cell is M electrode layers (electrode layers are active material layers), each electrode layer is separated into N regions by isolation lines. During acupuncture, if there are P short-circuited electrode layers (P is an integer between 1 and M), the electrode layers that are not short-circuited are MP. Then the circuit will be transformed into MP non-short-circuited electrode layers connected in parallel (the resistance after parallel connection is NMR). c / (MP)), short-circuited with P electrode layers in series (PNMR c ) and connected in series with steel needle 4 (R m ), the total internal resistance is NMR c / (MP)+PNMR c +R m . This resistance is also greater than R c +R m , and the larger P is, the larger the value is, the smaller the current of the entire circuit is, and thus the safer it is.

[0063] In summary, the present invention changes the current distribution of the battery cell when a local short circuit occurs, increases the short-circuit impedance, and concentrates the energy released by the short circuit in the local current collector area, causing the local current collector to melt, thereby achieving the effect of reducing the short-circuit power and cutting off the discharge circuit, avoiding the risk of combustion or even explosion caused by short-time high-power discharge of the entire battery cell, improving the safety of the battery cell, and thus improving the safety of the battery.

[0064] In addition, the adopted current collector plus isolation wire solution has negligible change in the current collector mass, so the energy density of the existing battery cell can be maintained.

[0065] In summary, the present application can improve the safety of battery cells while maintaining the energy density of the battery cells.

[0066] In one embodiment, the method further comprises:

[0067] An isolation line is made completely along the current direction of the battery cell in the current collector area close to the pole ear.

[0068] In the embodiment of the present application, if the composite current collector is a rectangular current collector, in addition to making parallel isolation lines basically along the current direction of the battery cell, in the current collector area 5 where the current direction does not change significantly, it is also possible to further make isolation lines completely along the current direction of the battery cell in the current collector area 7 close to the tab, thereby improving the safety of the battery cell. Fig. 20 Generally, the isolation lines close to the tab region are arranged in a clustered pattern, and the specific shape can be obtained by a numerical simulation method, wherein the tab includes a multi-tab structure.

[0069] In one embodiment, an isolation line is made on the surface of the composite current collector completely along the current direction of the battery cell.

[0070] In the embodiments of the present application, Figure 7 As shown, Figure 7 This is a schematic diagram of designing isolation lines completely along the direction of the battery current. The solution of designing isolation lines completely along the direction of the battery current is better than Figure 4 The design of the parallel lines shown can completely design the isolation lines along the direction of the battery cell current, regardless of whether the battery cell pole pieces are irregular pole pieces or rectangular pole pieces (including wound or laminated batteries). Figure 4 The parallel line design can only ensure that the isolation line and the current direction in the composite current collector are basically consistent. It is simpler to design and manufacture, but the performance of the battery cell (rate, internal resistance, safety) is not as good as designing the isolation line completely according to the direction of the battery cell current. Making the isolation line completely along the direction of the battery cell current can minimize the contribution of the isolation line to the discharge impedance and improve the performance of the battery cell in rate, internal resistance and safety. Figure 4 The cell current direction does not need to be calculated in advance through mechanism simulation, but can be determined directly based on practical experience. If you want to make isolation lines on the surface of the composite current collector completely according to the cell current direction, you need to calculate the cell current direction in advance through mechanism simulation. The calculated cell current direction is the actual cell current direction. It should be noted that the current direction in the current collector is highly dependent on the shape of the pole piece, such as the aspect ratio, the position and width of the pole ear, and the shape.

[0071] In one embodiment, the isolation lines on different metal layers are staggered.

[0072] In the embodiment of the present application, isolation lines are made on both the upper and lower metal layers of the composite current collector, and the isolation lines on different metal layers are staggered. Of course, the isolation lines on different metal layers can also be aligned.

[0073] In one embodiment, on the same metal layer, the ratio of the spacing between adjacent isolation lines to the width of the isolation lines is greater than 10:1.

[0074] In the embodiment of the present application, at the same metal level, the ratio of the spacing between adjacent isolation lines to the width of the isolation lines is greater than 10:1. Specifically, at the same metal level, the ratio of the spacing between adjacent isolation lines to the width of the isolation lines is variable. For example, the ratio of the spacing between adjacent isolation lines to the width of the isolation lines is different in the current collector region where the current direction does not change significantly and the current collector region close to the tab. Of course, at the same metal level, the ratio of the spacing between adjacent isolation lines to the width of the isolation lines can also be the same.

[0075] In the embodiments of the present application, experiments show that when the direction of the isolation line is consistent or substantially consistent with the direction of the current, and the width of the isolation line is negligible relative to the distance between adjacent isolation lines, the presence of the isolation line has little effect on the proportion of the impedance of the current collector in the battery cell, and thus has little effect on the rate performance of the battery cell. Specifically, the ratio of the spacing between adjacent isolation lines and the width of the isolation line is set to be above 10:1, and some experimental data are shown in Table 1. The parallel line structure in Table 1 refers to the isolation line being parallel to the edge of the composite current collector, that is, the parallel line design described in the above embodiment, and the current direction structure refers to making the isolation line completely along the current direction of the battery cell; it can be seen from the experimental data that the energy density of the embodiment with isolation lines is improved compared with the embodiment without isolation lines, but the change is not large. In addition, the internal resistance of the battery cell with isolation lines is increased compared with that without isolation lines, but the change is very small, so the presence of isolation lines has little effect on the proportion of the impedance of the current collector in the battery cell, and thus has little effect on the rate performance of the battery cell. In addition, the needle puncture pass rate in the table refers to the proportion of batteries that do not catch fire or burn after needle puncturing multiple batteries.

[0076] Isolation line type Isolation line ratio Energy density improvement Internal resistance increases Acupuncture pass rate - No isolation line Ref. Ref. 0％ Parallel Line Structure 500：1 0.01％ 0.1％ 60％ Parallel Line Structure 100：1 0.05％ 0.5％ 90％ Parallel Line Structure 50：1 0.1％ 1％ 100％ Parallel Line Structure 10：1 0.5％ 5％ 100％ Current direction structure 500：1 0.01％ 0.1％ 80％ Current direction structure 100：1 0.05％ 0.5％ 100％

[0077] It can be seen that the isolation line solution of the embodiment of the present invention has little effect on the rate performance of the battery cell while not changing the energy density and increasing the safety.

[0078] In one embodiment, the safety composite current collector may be a positive electrode current collector or a negative electrode current collector.

[0079] An embodiment of the present application also provides a safe composite current collector, wherein an isolation line is arranged on the surface of the safe composite current collector, and the isolation line is made based on the current direction of the battery cell; wherein the isolation line is obtained by removing the metal layer of the composite current collector, and the composite current collector includes a metal layer and a polymer layer, and the polymer layer is located between the two metal layers.

[0080] The present invention is based on the current direction of the battery cell, and makes an isolation line on the surface of the composite current collector by removing the metal layer. The isolation line formed after the metal layer is removed is electronically insulated, which changes the current distribution of the battery cell during a local short circuit, increases the short circuit impedance, and concentrates the energy released by the short circuit in the local current collector area, causing the local current collector to fuse, thereby achieving the effect of reducing the short circuit power and cutting off the discharge circuit, avoiding the danger of combustion or even explosion caused by the short-time high-power discharge of the entire battery cell, and improving the safety of the battery cell. In addition, since the present invention does not change the material of the existing battery cell or reduce its content, including active substances and adding primers, the current collector plus isolation line solution used has negligible changes in the mass of the current collector, so the energy density of the existing battery cell can be maintained. In summary, the present invention can improve the safety of the battery cell while maintaining the energy density of the battery cell.

[0081] It should be noted that the embodiments of the present application can improve the safety of the battery cell while maintaining the energy density of the battery cell, which is the same as the principle of the above-mentioned method. Therefore, the explanation of the safety composite current collector in the above-mentioned embodiment method is also applicable to the embodiments of the present application. Therefore, the embodiments of the present application will not be repeated here.

[0082] In one embodiment, the isolation line is made completely along the current direction of the battery cell.

[0083] In one embodiment, if the composite current collector is a rectangular composite current collector, the isolation lines in the current collector region where the current direction does not change significantly are parallel lines and are parallel to the sides of the composite current collector.

[0084] In one embodiment, the isolation line is made completely along the current direction of the battery cell in the current collector region close to the tab.

[0085] In one embodiment, the isolation lines on different metal layers are staggered.

[0086] In one embodiment, the isolation line is obtained by removing the metal layer in the composite current collector by laser etching, chemical corrosion or mechanical method.

[0087] In one embodiment, on the same metal layer, the ratio of the spacing between adjacent isolation lines to the width of the isolation lines is greater than 10:1.

[0088] An embodiment of the present application also provides a pole piece, which includes the safe composite current collector described in any of the above embodiments.

[0089] In the embodiment of the present application, specifically, when the safety type composite current collector is a positive electrode current collector, the pole piece is a positive electrode pole piece. When the safety type composite current collector is a negative electrode current collector, the pole piece is a negative electrode pole piece.

[0090] In one embodiment, the pole piece includes an active material layer, and the active material layer is coated on the metal layer of the safety composite current collector.

[0091] In one embodiment, the active material layer is also coated on the isolation line.

[0092] An embodiment of the present application further provides a battery cell, which includes the pole piece described in any of the above embodiments.

[0093] In the embodiment of the present application, specifically, the battery cell includes a positive electrode sheet and a negative electrode sheet, and any one or both of the current collector of the positive electrode sheet and the current collector of the negative electrode sheet adopt the above-mentioned safe composite current collector. It should be understood that when the current collector of the positive electrode sheet is the safe composite current collector, the safe composite current collector is specifically the positive electrode current collector, and when the current collector of the negative electrode sheet is the safe composite current collector, the safe composite current collector is specifically the negative electrode current collector.

[0094] An embodiment of the present application also provides a battery, which includes the battery cell described in any of the above embodiments.

[0095] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, device, article or method including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, device, article or method. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the presence of other identical elements in the process, device, article or method including the element.

[0096] The above description is only a preferred embodiment of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A method for preparing a safe composite current collector, characterized in that: The method comprises: Based on the direction of the battery cell current, an isolation line is made on the surface of the composite current collector; wherein the composite current collector includes a metal layer and a polymer layer, the polymer layer is located between two metal layers, and the isolation line is obtained by removing the metal layer in the composite current collector.

2. The method for preparing a safe composite current collector according to claim 1, characterized in that: The step of making an isolation line on the surface of the composite current collector based on the current direction of the battery cell comprises: If the composite current collector is a rectangular composite current collector, an isolation line parallel to the edge of the composite current collector is made substantially along the current direction of the battery cell in the current collector region where the current direction does not change significantly.

3. The method for preparing a safe composite current collector according to claim 2, characterized in that: The method further comprises: An isolation line is made completely along the current direction of the battery cell in the current collector area close to the pole ear.

4. The method for preparing a safe composite current collector according to claim 1, characterized in that: The step of making an isolation line on the surface of the composite current collector based on the current direction of the battery cell comprises: An isolation line is made on the surface of the composite current collector completely along the current direction of the battery cell.

5. The method for preparing a safe composite current collector according to claim 1, characterized in that: The isolation line is obtained by removing the metal layer in the composite current collector by laser etching, chemical corrosion or mechanical method.

6. The method for preparing a safe composite current collector according to claim 1, characterized in that: The isolation lines on different metal layers are staggered.

7. The method for preparing a safe composite current collector according to any one of claims 1 to 6, characterized in that: On the same metal layer, the ratio of the spacing between adjacent isolation lines to the width of the isolation lines is greater than 10:

1.

8. A safe composite current collector, characterized in that: An isolation line is arranged on the surface of the safety composite current collector, and the isolation line is made based on the direction of the battery current; wherein the isolation line is obtained by removing the metal layer of the composite current collector, and the composite current collector includes a metal layer and a polymer layer, and the polymer layer is located between the two metal layers.

9. The safe composite current collector according to claim 8, characterized in that: The isolation line is made completely along the current direction of the battery cell.

10. The safe composite current collector according to claim 8, characterized in that: If the composite current collector is a rectangular composite current collector, the isolation lines in the current collector region where the current direction does not change significantly are parallel lines and are parallel to the sides of the composite current collector.

11. The safe composite current collector according to claim 10, characterized in that: The isolation line is made completely along the current direction of the battery cell in the current collector region close to the pole lug.

12. The safe composite current collector according to claim 8, characterized in that: The isolation line is obtained by removing the metal layer in the composite current collector by laser etching, chemical corrosion or mechanical method.

13. The method for preparing a safe composite current collector according to claim 8, characterized in that: The isolation lines on different metal layers are staggered.

14. The safe composite current collector according to any one of claims 8 to 13, characterized in that: On the same metal layer, the ratio of the spacing between adjacent isolation lines to the width of the isolation lines is greater than 10:

1.

15. A pole piece, characterized in that: The invention comprises the safe composite current collector as described in any one of claims 8 to 14.

16. The pole piece according to claim 15, characterized in that: The pole piece comprises an active material layer, and the active material layer is coated on the metal layer of the safety composite current collector.

17. The pole piece according to claim 15, characterized in that: The active material layer is also coated on the isolation line.

18. A battery cell, characterized in that: The battery cell comprises the pole piece described in any one of claims 15-17.

19. A battery, characterized in that: The battery comprises the battery cell according to claim 18.

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