Battery

Abstract

A battery. A positive electrode sheet comprises a positive electrode current collector, protective layers which are arranged on the surfaces of two sides of the positive electrode current collector, and a positive electrode active material layer which is arranged on the outer surface of at least one side of the positive electrode sheet, wherein the single-sided coating surface density of each protective layer is W1, and positive electrode tabs are arranged on the positive electrode sheet. The battery further comprises a negative electrode sheet, wherein negative electrode tabs are arranged on the negative electrode sheet. The sum of the number of positive electrode tabs and the number of negative electrode tabs is m; the number of folds of the battery is N; when m is a positive integer from 2 to 9, W1≥(0.05×m+0.9)×(0.2×N+1) is met, and when m is a positive integer from 10 to 100, W1≥(0.002×m+0.98)×(0.2×N+2) is met; and when the battery is a wound-type battery, the number N of folds is the number of straight sections of the positive electrode sheet, and when the battery is a laminated battery, the number N of folds is the number of positive electrode sheets. The battery has good safety performance in different battery systems.

Description

Battery Technical Field

[0001] The present disclosure relates to the field of battery technology, and in particular to batteries.

[0002] Background of the Invention

[0003] The safety performance of a battery is related to its folding number and structure. Batteries with different folding numbers or different structures have different heat generation rates and failure risks when an internal short circuit occurs. Taking the needle puncture test as an example, when the needle puncture causes a short circuit inside the battery, theoretically, there is a short circuit in each fold of the battery. Assuming that the short-circuit point of each fold is the same size, then for batteries with different folding numbers, the total short-circuit points are different, and the short-circuit resistance and heat generation rate of the battery are also different. In addition, when the folding number of the battery is the same (that is, the short-circuit point of the battery is the same), there are also differences between batteries with different structures: taking conventional wound batteries and multi-pole wound batteries as examples, the positive and negative poles of conventional wound batteries each have one pole tab, while the positive and negative poles of multi-pole wound batteries have multiple pole tabs, and the internal resistance of multi-pole batteries is smaller. When the short-circuit points are the same, the multi-pole battery generates heat faster and is therefore more prone to failure.

[0004] Therefore, it is very important to invent a battery that can take into account different folding ratios and different structures and has safety performance.

[0005] Summary of the Invention

[0006] In order to improve the deficiencies of the prior art, the present disclosure provides a battery, wherein the positive electrode sheet of the battery has a protective layer, and the single-sided coating density of the protective layer satisfies a specific relationship with the fold number of the battery and the number of tabs in the battery. Based on the above relationship, the battery of the present disclosure has excellent safety performance under different battery systems.

[0007] The present disclosure provides a battery, the battery comprising a positive electrode sheet, the positive electrode sheet comprising a positive electrode current collector, a protective layer disposed on both sides of the positive electrode current collector, and a positive electrode active material layer disposed on at least one outer surface of the protective layer; the single-sided coating density of the protective layer is W1, and the positive electrode sheet is provided with a positive electrode tab;

[0008] The battery further includes a negative electrode sheet, on which a negative electrode tab is provided; the sum of the number of the positive electrode tabs and the number of the negative electrode tabs is m, the fold number of the battery is N, and when m is a positive integer from 2 to 9, the following is satisfied: W1 ≥ (0.05 × m + 0.9) × (0.2 × N + 1);

[0009] When m is a positive integer from 10 to 100, W1≥(0.002×m+0.98)×(0.2×N+2) is satisfied.

[0010] Among them, when the battery is a wound battery, the fold number N is the number of straight sections of the positive electrode sheet; when the battery is a stacked battery, the fold number N is the number of the positive electrode sheets.

[0011] Through the above technical solution, the present disclosure has at least the following advantages compared with the prior art: in the battery of the present disclosure, the single-sided coating surface density of the protective layer of the positive electrode sheet satisfies a specific relationship with the fold number of the battery and the number of tabs in the battery. Based on the above relationship, the battery of the present disclosure can have excellent safety performance in different battery systems (different fold numbers and / or different structures). BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG1 is a schematic cross-sectional view of a positive electrode sheet according to an embodiment of the present disclosure.

[0013] FIG2 is a schematic diagram showing the structure of a battery according to an embodiment of the present disclosure.

[0014] FIG3 is a schematic cross-sectional view of the positive electrode sheet according to an embodiment of the present disclosure.

[0015] FIG4 is a schematic diagram showing the tab distribution of the positive electrode sheet in an example of the present disclosure. DETAILED DESCRIPTION

[0016] To make the objectives, technical solutions, and advantages of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the embodiments of the present disclosure. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments of the present disclosure, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present disclosure.

[0017] The present disclosure provides a battery, which may include a positive electrode sheet. The positive electrode sheet may include a positive electrode current collector, a protective layer disposed on both sides of the positive electrode current collector, and a positive electrode active material layer disposed on at least one outer surface of the protective layer. As shown in FIG1 , this is a cross-sectional schematic diagram of the positive electrode sheet in an example of the present disclosure, wherein FIG1(a) shows the case where the positive electrode active material layer is disposed on one side, and FIG1(b) shows the case where the positive electrode active material layer is disposed on both sides. In FIG1(a), the positive electrode sheet 1 includes a positive electrode current collector 11, a protective layer 12 disposed on both sides of the positive electrode current collector 11, and a positive electrode active material layer 13 disposed on one outer surface of the protective layer 12. In FIG1(b), the positive electrode sheet 1 includes a positive electrode current collector 11, a protective layer 12 disposed on both sides of the positive electrode current collector 11, and a positive electrode active material layer 13 disposed on both outer surfaces of the protective layer 12.

[0018] In the present disclosure, the outer surface of the protective layer refers to the surface of the protective layer away from the positive electrode current collector.

[0019] In the present disclosure, the single-sided coating density of the protective layer is W1 (unit: g / m 2 ), the positive electrode sheet may be provided with a positive electrode tab; the battery may further include a negative electrode sheet, and the negative electrode sheet may be provided with a negative electrode tab; the sum of the number of the positive electrode tabs and the number of the negative electrode tabs is m, the fold number of the battery is N, and when m is a positive integer from 2 to 9 (for example, 2, 3, 4, 5, 6, 7, 8 or 9), it satisfies: W1≥(0.05×m+0.9)×(0.2×N+1);

[0020] When m is a positive integer from 10 to 100 (e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100), W1 ≥ (0.002 × m + 0.98) × (0.2 × N + 2);

[0021] Among them, when the battery is a wound battery, the fold number N is the number of straight sections of the positive electrode sheet; when the battery is a stacked battery, the fold number N is the number of the positive electrode sheets.

[0022] In this disclosure, the terms "number of positive electrode tabs" and "number of negative electrode tabs" have conventional meanings in the art. For example, FIG2 shows a schematic diagram of the structure of a battery in one embodiment of this disclosure, wherein FIG2(a)-FIG2(c) show a wound structure, and FIG2(d) shows a laminated structure. In Figures 2(a) to 2(d), the battery includes a positive electrode sheet 1, a negative electrode sheet 2 and a separator 3, the positive electrode sheet 1 is provided with a positive electrode tab 14, and the negative electrode sheet 2 is provided with a negative electrode tab 21; in Figure 2(a), the number of the positive electrode tabs 14 is 1, and the number of the negative electrode tabs 21 is 1; in Figure 2(b), the number of the positive electrode tabs 14 is 2, and the number of the negative electrode tabs 21 is 1; in Figure 2(c), the number of the positive electrode tabs 14 is 5, and the number of the negative electrode tabs 21 is 5; in Figure 2(d), the number of the positive electrode tabs 14 is 6, and the number of the negative electrode tabs 21 is 5.

[0023] In the present disclosure, "the number of folds of the battery" has the conventional meaning in the field. For example, Figure 2(a) is a winding structure, which includes straight sections and arc sections. The number of folds of the battery refers to the number of straight sections of the positive electrode sheet 1, which is 5; Figure 2(d) is a stacked structure. In this stacked structure, the number of folds of the battery refers to the number of positive electrode sheets, which is 6.

[0024] The inventors of this disclosure discovered that when a battery mechanically fails, the short circuit between the positive current collector and the negative electrode sheet generates rapid heat, which can easily lead to fire and failure. Therefore, applying a protective layer on the surface of the positive current collector can effectively reduce the risk of short circuits between the positive current collector and the negative electrode sheet. The inventors of this disclosure further discovered that when the single-sided coating density of the protective layer satisfies a specific relationship with the total number of battery tabs and the number of folds, the battery can meet different battery systems and have superior safety performance.

[0025] In one embodiment, m is a positive integer from 2 to 6.

[0026] In one embodiment, m is a positive integer from 10 to 80.

[0027] In one embodiment, m is a positive integer from 2 to 4.

[0028] In one embodiment, m is a positive integer from 10 to 60.

[0029] In the above relational expressions of the present disclosure, each parameter is calculated using only its numerical part, and its unit part does not participate in the calculation.

[0030] In the present disclosure, the single-sided coating surface density of the protective layer can be tested by the following method, specifically: cutting the foil into a certain size, such as a length of a1 (unit: m) and a width of b1 (unit: m), using an electronic balance to weigh it, and recording its mass as m1 (unit: g); using the above-mentioned foil as a current collector, coating a protective layer slurry on its surface (both sides) (the protective layer slurry is a protective layer after drying) and drying it, cutting the current collector after coating the protective layer into a certain size, such as a length of a2 (unit: m) and a width of b2 (unit: m), using an electronic balance to weigh it, and recording its mass as m2 (unit: g), then the single-sided coating surface density of the protective layer W1 = [m2 / (a2×b2)-m1 / (a1×b1)]÷2.

[0031] The inventors of the present disclosure have discovered that when the fold number N of the battery is within a specific range, the battery has more excellent safety performance.

[0032] In one example, N≤50 (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, or 50).

[0033] In one embodiment, N is a positive integer ranging from 5 to 45.

[0034] In one embodiment, N is a positive integer from 10 to 40.

[0035] In the present disclosure, the single-sided coating density of the positive electrode active material layer is W2 (unit: g / m2 ), satisfying: W1 / W2≤0.15 (for example, W1 / W2 is equal to 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14 or 0.15).

[0036] In the present disclosure, the single-sided coating density of the positive electrode active material layer can be tested by the following method. Specifically, the foil is cut into a certain size, such as a length of a3 (unit: m) and a width of b3 (unit: m). The foil is used as a current collector, and a coating layer slurry is coated on its surface (both sides) (the protective layer slurry is dried to form a protective layer) and dried. The coating layer slurry is weighed using an electronic balance, and its mass is recorded as m3 (unit: g). The foil after drying is used to record the surface density of the positive electrode active material layer. The positive electrode active material layer slurry is coated on the surface (both sides) (the positive electrode active material layer slurry becomes the positive electrode active material layer after drying) and dried, and the current collector after coating the positive electrode active material layer is cut into a certain size, such as a length of a4 (unit: m) and a width of b4 (unit: m). Use an electronic balance to weigh it and record its mass as m4 (unit: g). The single-sided coating density of the positive electrode active material layer is W2 = [m4 / (a4×b4)-m3 / (a3×b3)]÷2.

[0037] In the present disclosure, when the length of the protective layer provided on the positive electrode current collector is greater than the length of the positive electrode active material layer provided on the protective layer (that is, in the length direction of the positive electrode current collector, the positive electrode active material layer does not completely cover the protective layer), the single-sided coating surface density of the protective layer and the positive electrode active material layer can also be obtained by testing by the following method. As shown in FIG3 , a cross-sectional schematic diagram of the positive electrode sheet in an example of the present disclosure is shown. In FIG3 , the positive electrode sheet 1 includes a positive electrode current collector 11, a protective layer 12 provided on both sides of the positive electrode current collector 11, and a positive electrode active material layer 13 provided on both sides of the outer surface of the protective layer 12, wherein in the length direction of the positive electrode current collector 11, the positive electrode active material layer 13 does not completely cover the protective layer 12. The test method for the single-sided coating surface density of the protective layer can be: along the dotted line in FIG3 , the positive electrode sheet is divided into two parts, left and right, and the single-sided coating surface density of the protective layer can be obtained by testing the right side part (the positive electrode current collector is coated with a protective layer on both sides). The testing method for the single-sided coating area density of the positive electrode active material layer can be: testing the above-mentioned left part (the positive electrode current collector is coated with a protective layer on both sides, and the surface of the protective layer is coated with a positive electrode active material layer), and the single-sided coating area density of the coating (positive electrode active material layer + protective layer) can be obtained, and then the single-sided coating area density of the protective layer measured above is subtracted to obtain the single-sided coating area density of the positive electrode active material layer.

[0038] The inventors of the present disclosure have discovered that the single-sided coating density of the protective layer and the single-sided coating density of the positive electrode active material layer have a specific relationship, which can improve the energy density of the battery.

[0039] In one example, W1 / W2≤0.1.

[0040] In one example, 0.02≤W1 / W2≤0.06.

[0041] In the present disclosure, W2 may be 100 g / m 2 -250g / m 2 , for example 100g / m 2 , 110g / m 2 , 120g / m 2 , 130g / m 2 , 140g / m 2 , 150g / m 2 , 160g / m 2 , 170g / m 2 , 180g / m 2 , 190g / m 2 , 200g / m 2 , 210g / m 2 , 220g / m 2 , 230g / m 2 , 240g / m 2 or 250g / m 2 .

[0042] In one embodiment, W2 is 150 g / m 2 -200g / m 2 .

[0043] In the present disclosure, the protection layer may include a filling material, and the filling material may include at least one of a first-type filling material, a second-type filling material, and a third-type filling material.

[0044] In the present disclosure, the filling materials can be divided into the first type of filling materials, the second type of filling materials and the third type of filling materials according to their conductive properties.

[0045] In one example, the type of filler material includes at least one of aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide, boehmite, cobalt oxide, iron phosphate, aluminum phosphate, iron metaphosphate, and aluminum metaphosphate.

[0046] In one example, the second type of filling material includes at least one of the following materials modified by a coating material, the material including at least one of aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide, boehmite, cobalt oxide, iron phosphate, aluminum phosphate, iron metaphosphate, aluminum metaphosphate, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide and lithium titanate; the coating material includes at least one of carbon black, carbon nanotubes, graphene, antimony-doped tin dioxide (ATO), fluorine-doped tin dioxide (FTO), tin-doped indium oxide (ITO) and aluminum-doped zinc oxide (AZO).

[0047] In the present disclosure, the antimony-doped tin dioxide (ATO), the fluorine-doped tin dioxide (FTO), the tin-doped indium oxide (ITO) and the aluminum-doped zinc oxide (AZO) have the conventional meanings in the art. It is generally believed that: the antimony doping amount in the "antimony-doped tin dioxide (ATO)" is 0.1%-20%; the fluorine doping amount in the "fluorine-doped tin dioxide (FTO)" is 0.1%-20%; the tin doping amount in the "tin-doped indium oxide (ITO)" is 0.1%-20%; and the aluminum doping amount in the "aluminum-doped zinc oxide (AZO)" is 0.1%-20%.

[0048] In one example, the three types of filling materials include at least one of antimony-doped tin dioxide (ATO), fluorine-doped tin dioxide (FTO), tin-doped indium oxide (ITO), and aluminum-doped zinc oxide (AZO).

[0049] The inventors of the present disclosure have discovered that when the filling material includes at least the three types of filling materials, the safety of the battery can be further improved.

[0050] In one example, the filling material includes at least one of the three types of filling materials.

[0051] In one example, the filling material includes at least antimony-doped tin dioxide (ATO) and / or aluminum-doped zinc oxide (AZO).

[0052] In the present disclosure, based on the total weight of the protective layer, the content of the filler material may be 70-99 wt%, for example, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, or 99 wt%.

[0053] In one example, based on the total weight of the protective layer, the content of the filler material is 85-96.5 wt %.

[0054] In the present disclosure, the protective layer may further include a first adhesive.

[0055] The first binder can be selected from the binders commonly used in the art. For example, the first binder includes at least one of polyvinylidene fluoride (PVDF), acrylic acid-modified polyvinylidene fluoride, acrylic polymers, polyacrylic acid, polyacrylate, polyimide, styrene-butadiene rubber and styrene-propylene rubber.

[0056] In one example, the acrylic polymer includes at least one of methyl acrylate, methyl 2-methacrylate, ethyl acrylate, and ethyl 2-methacrylate.

[0057] In one example, the polyacrylate includes at least one of lithium polyacrylate, sodium polyacrylate, and potassium polyacrylate.

[0058] In one example, the protective layer includes antimony-doped tin dioxide (ATO) and / or aluminum-doped zinc oxide (AZO) and polyvinylidene fluoride (PVDF).

[0059] In one example, based on the total weight of the protective layer, the content of the antimony-doped tin dioxide (ATO) and / or the aluminum-doped zinc oxide (AZO) is 85-96.5 wt %, and the content of the polyvinylidene fluoride (PVDF) is 3.5-15 wt %.

[0060] In the present disclosure, the protective layer may further include a first conductive agent.

[0061] In one example, the first conductive agent includes at least one of carbon black, carbon nanotubes, graphene, and carbon fibers.

[0062] In one example, the first conductive agent includes at least one of carbon black and carbon nanotubes.

[0063] In the present disclosure, based on the total weight of the protective layer, the content of the filler material can be 70-99 weight % (for example, 70, 75, 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, or 99 weight %), the content of the first binder can be 0.5-15 weight % (for example, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0.5 weight %), and the content of the first conductive agent can be 0.5-15 weight % (for example, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1 or 0.5 weight %).

[0064] In one example, based on the total weight of the protective layer, the content of the filling material is 85-96.5 weight %, the content of the first binder is 3-10 weight %, and the content of the first conductive agent is 0.5-5 weight %.

[0065] In the present disclosure, the minimum spacing L1 between the positive electrode tabs, the length L2 of the positive electrode sheet, and the number m1 of the positive electrode tabs satisfy: L1 ≥ L2 / (m1+3). The minimum spacing L3 between the negative electrode tabs, the length L4 of the negative electrode sheet, and the number m2 of the negative electrode tabs satisfy: L3 ≥ L4 / (m2+3).

[0066] The inventors of the present disclosure have discovered that when the minimum spacing between the positive electrode tabs and / or the minimum spacing between the negative electrode tabs satisfy the above relationship, it is beneficial to reduce the local current density of the battery, thereby reducing the temperature rise of the battery during high-rate discharge. The minimum spacing between the positive electrode tabs and / or the minimum spacing between the negative electrode tabs have a significant impact on the temperature rise of the battery. When the minimum spacing between the positive electrode tabs and / or the minimum spacing between the negative electrode tabs is small, the local current density of the battery is large, resulting in a higher temperature rise of the battery during discharge.

[0067] In the present disclosure, when the number of the positive electrode tabs is ≤5 (for example, the number of the positive electrode tabs is 2, 3, 4 or 5), the minimum spacing between the positive electrode tabs is 200 mm-800 mm, for example, 200 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm or 800 mm; when the number of the positive electrode tabs is >5 (for example, the number of the positive electrode tabs is 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45 or 50), the minimum spacing between the positive electrode tabs is 40 mm-150 mm, for example, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm or 150 mm. Similarly, when the number of the negative electrode tabs is ≤5 (for example, the number of the negative electrode tabs is 2, 3, 4 or 5), the minimum spacing between the negative electrode tabs is 200 mm-800 mm, for example, 200 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm or 800 mm; when the number of the negative electrode tabs is >5 (for example, the number of the negative electrode tabs is 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45 or 50), the minimum spacing between the negative electrode tabs is 40 mm-150 mm, for example, 40 mm, 50 mm, 60 mm, 70 mm, 80 mm, 90 mm, 100 mm, 110 mm, 120 mm, 130 mm, 140 mm or 150 mm.

[0068] In the present disclosure, the minimum spacing between positive electrode tabs refers to the shortest distance between the centers of two adjacent positive electrode tabs on one side of the positive electrode sheet in the width direction. FIG4 shows a schematic diagram of the tab distribution of a positive electrode sheet in an example of the present disclosure. As can be seen from the figure, the number of positive electrode tabs 14 in the positive electrode sheet 1 is 5. The minimum spacing between positive electrode tabs refers to the shortest distance d between the centers of two adjacent positive electrode tabs on one side of the positive electrode sheet in the width direction. Similarly, the minimum spacing between negative electrode tabs refers to the shortest distance between the centers of two adjacent negative electrode tabs.

[0069] The inventors of the present disclosure discovered that when the width of the positive electrode tab / the width of the battery (or the width of the negative electrode tab / the width of the battery) is less than 0.1, the current-carrying capacity of the positive electrode tab (or the negative electrode tab) is poor, resulting in more heat generation and higher temperature rise in the battery; when the width of the positive electrode tab / the width of the battery (or the width of the negative electrode tab / the width of the battery) is greater than 0.3, the positive electrode tab (or the negative electrode tab) occupies more battery space, resulting in a greater loss of battery energy density.

[0070] In the present disclosure, the width of the positive electrode tab / the width of the battery is 0.1-0.3, for example, 0.1, 0.15, 0.2, 0.25 or 0.3; similarly, the width of the negative electrode tab / the width of the battery is 0.1-0.3, for example, 0.1, 0.15, 0.2, 0.25 or 0.3.

[0071] In the present disclosure, the positive electrode active material layer may include a positive electrode active material. The positive electrode active material may be selected from positive electrode active materials commonly used in the art.

[0072] In one example, the positive electrode active material includes a lithium-containing transition metal oxide.

[0073] In one example, the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide, and lithium-rich manganese-based materials.

[0074] In the present disclosure, the positive electrode active material layer may further include a second binder and a second conductive agent. The second binder may be a binder commonly used in the art; the second conductive agent may be a conductive agent commonly used in the art.

[0075] In one example, the second binder includes at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, sodium carboxymethyl cellulose, and carboxymethyl cellulose.

[0076] In one example, the second conductive agent includes at least one of carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon fibers.

[0077] In the present disclosure, the positive electrode current collector may be selected from those conventionally used in the art, for example, at least one of aluminum foil, carbon-coated aluminum foil, and aluminum-polymer composite current collector.

[0078] In the present disclosure, the negative electrode sheet may further include a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material, a third binder, and a third conductive agent.

[0079] In the present disclosure, the negative electrode active material can be selected from those commonly used in the art, such as at least one of natural graphite, artificial graphite, soft carbon, hard carbon, carbon nanotubes, silicon-carbon materials, and silicon-oxygen materials. The third binder can be selected from those commonly used in the art, such as at least one of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber, polyacrylic acid, polyvinyl alcohol, sodium carboxymethyl cellulose, and carboxymethyl cellulose. The third conductive agent can be selected from those commonly used in the art, such as at least one of carbon black, acetylene black, Ketjen black, carbon nanotubes, graphene, and carbon fiber.

[0080] In the present disclosure, the preparation method of the battery and the materials other than the positive electrode sheet and the negative electrode sheet can be carried out according to the methods in the art, and both have excellent safety performance.

[0081] In the present disclosure, the battery may further include a separator, which may be selected from conventional separators in the art, such as polyethylene film. The battery may further include an electrolyte, which may be selected from conventional electrolytes in the art. For example, the electrolyte may include a solvent and a lithium salt, wherein the solvent includes at least one of a carbonate compound, a carboxylate compound, and a fluorocarbonate compound; and the lithium salt includes lithium hexafluorophosphate.

[0082] The battery disclosed herein can accommodate different battery systems (different folds and / or different structures) and all have excellent safety performance.

[0083] It should be noted that the numerical expressions such as "first" and "second" in the present disclosure are only used to distinguish different substances or usage methods, and do not represent a difference in order.

[0084] The present disclosure will be described in detail below through examples. The examples described in this disclosure are only a portion of the examples of the present disclosure, not all of the examples. Based on the examples in this disclosure, all other examples obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this disclosure.

[0085] In the following examples, unless otherwise specified, all materials used were commercially available analytical grade.

[0086] Example 1

[0087] Prepare the battery as follows:

[0088] (1) Preparation of protective layer slurry:

[0089] The filler material, the first binder and the optional first conductive agent are mixed in a certain mass ratio, and N-methylpyrrolidone (NMP) is added, wherein the solid content is 40%;

[0090] (2) Preparation of positive electrode active material layer slurry:

[0091] Lithium cobalt oxide, carbon black, carbon nanotubes and polyvinylidene fluoride were mixed uniformly in a mass ratio of 96:1:1:2, and N-methylpyrrolidone (NMP) was added, wherein the solid content was 70%;

[0092] (3) Preparation of positive electrode sheet:

[0093] The protective layer slurry obtained in step (1) is coated on both sides of the aluminum foil (the single-side coating density W1 of the protective layer is controlled as shown in Table 1), and then dried. The positive electrode active material layer slurry obtained in step (2) is then coated on the outer surface of the protective layer (the single-side coating density W2 of the positive electrode active material layer is controlled as shown in Table 1), and then dried. The positive electrode tabs are welded and rolled to the designed thickness using a roller press to obtain a positive electrode sheet, wherein the length of the positive electrode sheet is 1260 mm;

[0094] (4) Preparation of negative electrode sheet:

[0095] Artificial graphite, carbon black, styrene-butadiene rubber, and sodium carboxymethyl cellulose were uniformly mixed in a mass ratio of 96:1:1.5:1.5, and deionized water was added to obtain a negative electrode active material layer slurry having a solid content of 40%. The prepared negative electrode active material layer slurry was applied to both sides of a copper foil by an extrusion coating process, dried, welded to the negative electrode tabs, and rolled to a designed thickness using a roller press to obtain a negative electrode sheet having a length of 1386 mm.

[0096] (5) Preparation of batteries:

[0097] The positive electrode sheet prepared in step (3), the negative electrode sheet prepared in step (4) and the diaphragm (polyethylene film) are wound to obtain a roll core, and adhesive tape is affixed to fix the roll core; an aluminum-plastic film is punched out using a punching mold, and the roll core is packaged with the punched aluminum-plastic film. After baking until the moisture content is qualified, an electrolyte is injected (the solvent is ethylene carbonate, propylene carbonate and ethyl propionate mixed in a mass ratio of 50:30:20, and the lithium salt is 1 mol / L lithium hexafluorophosphate) to obtain a battery core; a formation device is used to charge and discharge the battery core to harden the battery core, and the capacity of the battery core is sorted; a secondary sealing is performed, and the edge is removed to obtain a battery, and an OCV test is performed on the battery to test the K value of the battery, and a battery with a qualified K value is selected, wherein the battery width is 60 mm.

[0098] Examples 2-13 and Comparative Examples 1-4 are carried out with reference to Example 1, except that the protective layer, the number of battery folds, the number of positive electrode tabs and the number of negative electrode tabs, the minimum spacing between the positive electrode tabs and the minimum spacing between the negative electrode tabs, the width of the positive electrode tabs and the width of the negative electrode tabs are changed, as shown in Table 1, wherein M1 in Table 1 is the calculation result of the formula (0.05×m+0.9)×(0.2×N+1), M2 is the calculation result of the formula (0.002×m+0.98)×(0.2×N+2), M3 is the calculation result of the formula L2 / (m1+3), and M4 is the calculation result of the formula L4 / (m2+3).

[0099] Table 1

[0100] Note: The carbon-coated lithium iron phosphate refers to lithium iron phosphate with a surface coated with 2% carbon material (2% means that the mass of the carbon material accounts for 2% of the mass of the lithium iron phosphate); the "lug width" in the "lug width / battery width" column refers to the width of the positive electrode lug or the width of the negative electrode lug, that is, the width of the positive electrode lug used in the embodiments of the present disclosure is the same as the width of the negative electrode lug. For example, in Example 1, the width of the positive electrode lug and the width of the negative electrode lug are both 6 mm; for another example, in Example 13a, the width of the positive electrode lug and the width of the negative electrode lug are both 12 mm.

[0101] Test Case

[0102] (1) Acupuncture test

[0103] The batteries prepared in the examples and comparative examples were subjected to a needle penetration test. The specific method is as follows: the batteries were fully charged and then placed on a test bench. A tungsten steel needle with a diameter of 3 mm and a needle tip length of 3.62 mm was inserted through the middle of the battery at a speed of 100 mm / s and penetrated the battery. The battery passed the test if it did not catch fire or explode. The number of batteries tested in each group was 30. The results are recorded in Table 2.

[0104] (2) Energy density loss test

[0105] Energy density loss = (initial energy density - safety energy density) / initial energy density;

[0106] Among them, the initial energy density is the energy density of the battery without a protective layer, and the safe energy density is the energy density of the battery with a protective layer.

[0107] The energy density test method is as follows: charge the battery to an upper voltage of 4.5V, then discharge it at 0.2C to a lower voltage of 3.0V. The discharge energy is recorded as E. The energy density of the battery is then calculated using the following formula:

[0108] Energy density = E / (battery length × width × height); the results are recorded in Table 2.

[0109] Table 2

[0110] As can be seen from Table 2, compared with the comparative example, the battery of the present disclosure significantly improves the pass rate of the needle penetration test while ensuring a low energy density loss.

[0111] (3) 1C discharge temperature rise test

[0112] The batteries prepared in Examples 1, 9, and 12-13 were subjected to a 1C discharge temperature rise test. The specific test method is as follows:

[0113] After fully charging the battery, place it in a 25°C environment and discharge it at the current corresponding to the rated capacity. For example, if the rated capacity of the battery is X mAh, the current corresponding to 1C is X mA. Attach temperature sensing wires to the positive and negative tabs of the battery. The maximum temperature monitored by the temperature sensing wires minus 25°C is the battery's 1C discharge temperature rise. Record the results in Table 3.

[0114] Table 3

[0115] As can be seen from Table 3, compared with Examples 1, 12a and 12b, and compared with Examples 9, 12d and 12e, in Example 12c, the spacing setting of the positive electrode tabs (or negative electrode tabs) has a greater influence on the temperature rise of the battery. The spacing between the positive electrode tabs (or negative electrode tabs) is too small, resulting in a higher temperature rise during battery discharge.

[0116] It can be seen from Tables 1 and 3 that when the width of the positive electrode tab / the width of the battery (or the width of the negative electrode tab / the width of the battery) is less than 0.1, the temperature rise is high when Example 13c is compared with Example 1, Example 13a and Example 13b, and when Example 13g is compared with Example 9, Example 13e and Example 13f; the energy density loss is larger when Example 13d is compared with Example 1, Example 13a and Example 13b, and when Example 13h is compared with Example 9, Example 13e and Example 13f.

[0117] The above describes the embodiments of the present disclosure. However, the present disclosure is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present disclosure shall be included in the scope of protection of the present disclosure.

Claims

1. A battery, characterized in that: The battery comprises a positive electrode sheet, the positive electrode sheet comprises a positive electrode current collector, a protective layer arranged on both sides of the positive electrode current collector, and a positive electrode active material layer arranged on at least one outer surface of the protective layer; the single-sided coating surface density of the protective layer is W1, and a positive electrode tab is arranged on the positive electrode sheet; The battery further comprises a negative electrode sheet, on which a negative electrode tab is disposed; the sum of the number of the positive electrode tabs and the number of the negative electrode tabs is m, the fold number of the battery is N, and when m is a positive integer from 2 to 9, the following conditions are satisfied: W1≥(0.05×m+0.9)×(0.2×N+1); When m is a positive integer from 10 to 100, it satisfies: W1≥(0.002×m+0.98)×(0.2×N+2); Among them, when the battery is a wound battery, the fold number N is the number of straight sections of the positive electrode sheet; when the battery is a stacked battery, the fold number N is the number of the positive electrode sheets.

2. The battery according to claim 1, wherein m is a positive integer from 2 to 6; or m is a positive integer from 10 to 80; Preferably, m is a positive integer of 2 to 4; or m is a positive integer of 10 to 60.

3. The battery according to claim 1 or 2, wherein: N≤50； Preferably, N is a positive integer from 5 to 45; Preferably, N is a positive integer from 10 to 40.

4. The battery according to any one of claims 1 to 3, wherein: The single-sided coating surface density of the positive electrode active material layer is W2, satisfying: W1 / W2≤0.15; Preferably, W1 / W2≤0.1; Preferably, 0.02≤W1 / W2≤0.

06.

5. The battery according to claim 4, wherein W2: 100g / m 2 -250g / m 2 ; Preferably, W2 is 150 g / m 2 -200g / m 2 .

6. The battery according to any one of claims 1 to 5, wherein The protective layer includes a filling material, and the filling material includes at least one of a first-class filling material, a second-class filling material, and a third-class filling material; The type of filler material includes at least one of aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide, boehmite, cobalt oxide, iron phosphate, aluminum phosphate, iron metaphosphate and aluminum metaphosphate; The second type of filling material includes at least one of the following materials modified by the coating material: The coating material comprises at least one of aluminum oxide, magnesium oxide, titanium oxide, zinc oxide, silicon oxide, boehmite, cobalt oxide, iron phosphate, aluminum phosphate, iron metaphosphate, aluminum metaphosphate, lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium cobalt oxide and lithium titanate, and the coating material comprises at least one of carbon black, carbon nanotubes, graphene, antimony-doped tin dioxide, fluorine-doped tin dioxide, tin-doped indium trioxide and aluminum-doped zinc oxide; The three types of filling materials include at least one of antimony-doped tin dioxide, fluorine-doped tin dioxide, tin-doped indium trioxide and aluminum-doped zinc oxide.

7. The battery according to claim 6, wherein The filling material includes at least one of the three types of filling materials; Preferably, the filling material includes at least one of antimony-doped tin dioxide and aluminum-doped zinc oxide.

8. The battery according to claim 6 or 7, wherein: Based on the total weight of the protective layer, the content of the filling material is 70-99 weight %; Preferably, based on the total weight of the protective layer, the content of the filling material is 85-96.5% by weight.

9. The battery according to any one of claims 1 to 8, wherein The protective layer further includes a first adhesive; Preferably, the first binder includes at least one of polyvinylidene fluoride, acrylic acid-modified polyvinylidene fluoride, acrylic ester polymer, polyacrylic acid, polyacrylic acid salt, polyimide, styrene-butadiene rubber and styrene-acrylic rubber.

10. The battery according to any one of claims 1 to 9, wherein The protective layer includes antimony-doped tin dioxide and / or aluminum-doped zinc oxide, and polyvinylidene fluoride; Preferably, based on the total weight of the protective layer, the content of the antimony-doped tin dioxide and / or the aluminum-doped zinc oxide is 85-96.5% by weight, and the content of the polyvinylidene fluoride is 3.5-15% by weight.

11. The battery according to any one of claims 1 to 10, wherein The protective layer also includes a first conductive agent; Preferably, the first conductive agent comprises at least one of carbon black, carbon nanotubes, graphene and carbon fiber; Preferably, the first conductive agent includes at least one of carbon black and carbon nanotubes.

12. The battery according to claim 11, wherein Based on the total weight of the protective layer, the content of the filling material is 70-99 weight %, the content of the first binder is 0.5-15 weight %, and the content of the first conductive agent is 0.5-15 weight %; Preferably, based on the total weight of the protective layer, the content of the filling material is 85-96.5% by weight, the content of the first binder is 3-10% by weight, and the content of the first conductive agent is 0.5-5% by weight.

13. The battery according to any one of claims 1 to 12, wherein The minimum spacing L1 of the positive electrode tabs, the length L2 of the positive electrode sheet and the number m1 of the positive electrode tabs satisfy: L1 ≥ L2 / (m1+3); And / or, the minimum spacing L3 of the negative electrode tabs, the length L4 of the negative electrode sheet and the number m2 of the negative electrode tabs satisfy: L3≥L4 / (m2+3).

14. The battery according to any one of claims 1 to 13, wherein The width of the positive electrode tab / the width of the battery is 0.1-0.3; And / or, the width of the negative electrode tab / the width of the battery is 0.1-0.

3.

15. The battery according to any one of claims 1 to 14, wherein The positive electrode active material layer includes a positive electrode active material; Preferably, the positive electrode active material comprises a lithium-containing transition metal oxide; Preferably, the positive electrode active material includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganese oxide and lithium-rich manganese-based materials.

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