A battery

Abstract

The present invention relates to the field of battery technology, and in particular to a battery. The battery includes a negative electrode sheet and an electrolyte, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on one or both sides of the negative electrode current collector, the surface of the negative electrode current collector has protruding particles, the height of the protruding average particles is A, and the unit is μm. The electrolyte includes 1,3-propane sultone, and the weight content of 1,3-propane sultone is Bwt% based on the total weight of the electrolyte. The battery satisfies the following relationship: 0.01≤B / A≤5. The battery of the present invention can enhance the adhesion between the negative electrode current collector and the negative electrode active material layer without losing or reducing energy density, thereby improving the rate performance of the battery.

Description

Technical Field

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

[0002] Lithium-ion batteries, with their high specific capacity, compact size, and lack of memory effect, have seen tremendous growth in recent years. Their practical applications are expanding, from batteries for small electronic devices to energy storage and power batteries for electric vehicles. These applications are driving increasing demands for higher energy density and rate performance. In the absence of significant breakthroughs in electrode material systems, researchers are working on improvements in current collectors, electrolytes, and separators to enhance the energy density and rate performance of lithium-ion batteries.

[0003] Copper is a good current collector material, but directly coating the copper current collector with the negative electrode active material can lead to poor adhesion. Battery manufacturers generally choose to pre-treat the copper current collector during processing—carbon coating. Using a gravure roller to apply carbon black slurry to the surface of the copper current collector significantly increases the adhesion between the foil and the active material, while also improving the rate performance of the battery cell. However, the carbon coating process not only increases the time and manufacturing costs of battery cell manufacturers, but also increases the overall thickness of the current collector, resulting in a loss of battery cell energy density. Furthermore, carbon-coated copper foil is prone to leaks and other issues. Summary of the Invention

[0004] The present invention provides a battery to address the problems of energy density loss, prone to coating leaks, and high costs associated with the carbon coating process in the prior art. The battery of the present invention achieves minimal or no energy density loss, eliminates the risk of coating leaks, and enhances the adhesion between the negative electrode current collector and the negative electrode active material layer, thereby improving the battery's rate discharge performance.

[0005] The present invention provides a battery, wherein the battery includes a negative electrode sheet and an electrolyte, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on one side or both sides of the negative electrode current collector, the surface of the negative electrode current collector has protruding particles, the average height of the protruding particles is A, and the unit is μm; the electrolyte includes 1,3-propane sultone, and the weight content of the 1,3-propane sultone is Bwt% based on the total weight of the electrolyte. Then, the battery satisfies the following relationship: 0.01≤B / A≤1.

[0006] Through the above technical solution, the present invention has at least the following advantages compared with the prior art:

[0007] The battery of the present invention, by defining the relationship between the height of the protruding particles on the surface of the negative electrode current collector and the content of 1,3-propane sultone in the electrolyte, can enable the negative electrode current collector and the negative electrode active material layer to be bonded in the form of rivets, thereby enhancing the adhesion between the negative electrode current collector and the negative electrode active material layer, improving the battery's rate performance, and reducing the loss of battery energy density, or even eliminating the loss of battery energy density.

[0008] Other features and advantages of the present invention will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Shown is a SEM image of the negative electrode current collector with protruding particles in the present invention.

[0010] Figure 2 Shown is the infrared spectrum of the protruding particles on the surface of the negative electrode current collector in the present invention.

[0011] Figure 3 The figure shows an optical microscope image of the negative electrode current collector after the negative electrode active material layer of the negative electrode sheet of Example 1 of the present invention is peeled off.

[0012] Figure 4 The figure shows an optical microscope image of the negative electrode current collector after the negative electrode active material layer of the negative electrode sheet of Comparative Example 1 of the present invention is peeled off.

[0013] Figure 5 The figure shows an optical microscope image of the negative electrode current collector after the negative electrode active material layer of the negative electrode sheet of Comparative Example 2 of the present invention is peeled off. DETAILED DESCRIPTION

[0014] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention. In this article, unless otherwise specified, data ranges include endpoints.

[0015] The present invention provides a battery, wherein the battery includes a negative electrode sheet and an electrolyte, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on one side or both sides of the negative electrode current collector, the surface of the negative electrode current collector has protruding particles, the average height of the protruding particles is A, and the unit is μm; the electrolyte includes 1,3-propane sultone, and the weight content of the 1,3-propane sultone is Bwt% based on the total weight of the electrolyte. Then, the battery satisfies the following relationship: 0.01≤B / A≤5.

[0016] The battery may satisfy the following relationship: 0.01≤B / A≤5 (e.g., 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5).

[0017] like Figure 1 As shown, the surface of the negative electrode current collector has protruding particles, which increase the physical contact sites on the surface of the negative electrode current collector. These contact sites can enter the negative electrode active material layer, so that the negative electrode current collector and the negative electrode active material layer are bonded in a riveted manner, thereby improving the adhesion between the negative electrode current collector and the negative electrode active material layer. At the same time, the protruding particles are beneficial to the exhaust and heat dissipation of the battery, thereby improving the safety performance of the battery. At the same time, after the battery is formed, the byproducts (for example, alkyl lithium carbonate) generated by 1,3-propane sultone in the electrolyte can be deposited between the negative electrode collector and the negative electrode active material. The byproduct can improve the adhesion between the negative electrode collector and the negative electrode active material, and the height of 1,3-propane sultone in the electrolyte and the protruding particles are limited to the above-mentioned specific relationship. On the one hand, the inclusion of 1,3-propane sultone in the electrolyte will increase the viscosity of the electrolyte, but because the surface of the negative electrode collector of the present invention has protruding particles, it is beneficial to the redistribution of the electrolyte, thereby increasing the lithium ion transmission performance and improving the battery's rate discharge performance. On the other hand, the inclusion of 1,3-propane sultone in the electrolyte will increase the impedance of the battery, but because the surface of the negative electrode collector of the present invention has protruding particles, the surface area of ​​the negative electrode collector is increased, thereby increasing the active sites during battery charging and discharging, thereby reducing the increase in impedance caused by the addition of 1,3-propane sultone. When B / A is lower than 0.01, the 1,3-propane sultone content in the electrolyte is too low or the height of the protruding particles is too high, which will cause the bonding performance between the negative electrode current collector and the negative electrode active material to deteriorate; when B / A is higher than 5, the 1,3-propane sultone content in the electrolyte is too high or the height of the protruding particles is too low, which will make the active sites increased by the protruding particles insufficient to reduce the impedance increase caused by the addition of 1,3-propane sultone, or even the reduction effect is not obvious, and at the same time, the bonding performance between the negative electrode current collector and the negative electrode active material deteriorates.

[0018] In this invention, by defining the specific relationship between the raised particles on the surface of the negative electrode current collector and 1,3-propane sultone in the electrolyte, the battery achieves higher rate capability and lower energy density loss than existing technologies. To further enhance this effect, one or more of these technical features may be further optimized.

[0019] In one example, 0.02≤B / A≤4.

[0020] In one example, 0.5 μm ≤ A μm ≤ 4 μm (eg, 0.5 μm, 0.6 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 3.9 μm, 4 μm).

[0021] In one example, 1 μm≤A μm≤3 μm.

[0022] In the present invention, the average height A of the raised particles can be obtained by testing in the following manner: bisecting the cross section of the negative electrode current collector, taking the dotted line in the middle as the baseline, the distance between the highest point and the lowest point of the protrusion on one side of the baseline is the height of the raised particles, and calculating the average height of the raised particles in the negative electrode current collector is the average height A of the raised particles.

[0023] In one embodiment, the protruding particles are compressible. The compressible protruding particles can reduce the cycle expansion rate of the battery during the charge and discharge process of the battery.

[0024] In one example, 0.01 wt% ≤ Bwt% ≤ 10 wt% (e.g., 0.26 wt%, 0.5 wt%, 1 wt%, 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt%, 9.5 wt%, 9.9 wt%).

[0025] In one example, 0.03 wt % ≤ B wt % ≤ 5 wt %.

[0026] According to a specific embodiment, 0.01≤B / A≤5, 1μm≤Aμm≤3μm, and 0.03wt%≤Bwt%≤5wt%. When B / A, A, and B are limited to the above specific ranges, the bonding performance between the negative electrode current collector and the negative electrode active material layer can be further improved, the loss of battery energy density can be further reduced, and the rate discharge performance of the battery can be improved.

[0027] In one embodiment, the median particle size D50 of the protrusions is 1 μm-10 μm (e.g., 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm). Limiting the median particle size D50 of the protrusions to the above-mentioned specific range can achieve a strong riveting effect between the negative electrode current collector and the negative electrode active material layer, and reduce or even eliminate the loss of energy density of the battery. When the median particle size of the protrusions is less than 1 μm or greater than 10 μm, the riveting effect will be poor.

[0028] In one embodiment, the median particle size D50 of the protruding particles is 3 μm-8 μm.

[0029] In the present invention, the median particle size D50 of the protruding particles represents the particle size corresponding to when the cumulative particle size distribution percentage in the sample reaches 50%, which can be obtained by testing in the following manner: it can be measured by a laser particle size distribution instrument.

[0030] It can be understood that, in the present invention, the average height A of the protruding particles is different from the median particle size D50 of the protruding particles, and the average height A of the protruding particles is less than the median particle size D50 of the protruding particles.

[0031] In one embodiment, any 2.5×10 -5 cm 2 Within the area of ​​the substrate, the number of protrusions with a particle size greater than 5 μm is N, where N is ≤ 3 (e.g., 3, 2, 1, or 0). When the particle size of the protrusions exceeds 5 μm, the protrusions with a larger median particle size will affect the riveting effect between the negative electrode current collector and the negative electrode active material layer to a certain extent. Therefore, by limiting the number of protrusions with a larger median particle size, the bonding performance between the negative electrode current collector and the negative electrode active material layer can be further improved.

[0032] When N=0, it means that any 2.5×10 -5 cm 2 Within the area range, there are no protruding particles with a particle size greater than 5μm.

[0033] In one embodiment, the surface of the negative electrode current collector includes oxygen-containing functional groups. After the battery is formed, 1,3-propane sultone in the electrolyte forms a byproduct (e.g., lithium alkyl carbonate) between the negative electrode current collector and the negative electrode active material. The oxygen-containing functional groups on the surface of the negative electrode current collector can form an intermolecular force with the byproduct, thereby further increasing the adhesion between the negative electrode current collector and the negative electrode active material layer, making the bond between the negative electrode current collector and the negative electrode active material closer, reducing the impedance of charge transfer during battery charging and discharging, thereby allowing more Li + Participating in electrochemical reactions is beneficial to fully releasing the capacity of active substances and improving the performance of the capacity of active substances.

[0034] In one example, the oxygen-containing functional group includes one or more of a hydroxyl group (—OH), a carboxyl group (—COOH), and a carbonyl group (—CO—).

[0035] In one embodiment, in the infrared spectrum of the protruding particles on the surface of the negative electrode current collector, at 1500 cm -1 -3600cm -1 (For example, -OH, -COOH, -CO-) have absorption peaks. Figure 2As shown, in the infrared spectrum of the protruding particles on the surface of the negative electrode current collector, at 1500 cm -1 -3600cm -1 The presence of the absorption peak indicates the presence of oxygen-containing functional groups on the surface of the negative electrode current collector.

[0036] In one embodiment, the oxygen-containing functional group is a hydroxyl group. Hydroxyl groups are typical polar groups that can form hydrogen bonds with water. Furthermore, the negative electrode binder in the negative electrode active material layer is a water-based binder. The negative electrode binder forms hydrogen bonds with the hydroxyl groups on the surface of the negative electrode current collector, further enhancing the bonding performance between the negative electrode current collector and the negative electrode active material layer. Thus, the negative electrode binder can not only play a bonding role between the negative electrode active materials, but also between the negative electrode current collector and the negative electrode active material layer.

[0037] In one embodiment, in the infrared spectrum of the protruding particles on the surface of the negative electrode current collector, at 3200 cm -1 -3600cm -1 (For example, 3200cm -1 、3300cm -1 3400cm -1 3500cm -1 3600cm -1 In the infrared spectrum of the protruding particles on the surface of the negative electrode current collector, at 3200 cm -1 -3600cm -1 The presence of an absorption peak surface indicates that hydroxyl groups exist on the surface of the negative electrode current collector.

[0038] According to a specific embodiment, the oxygen-containing functional group is a hydroxyl group, and in the infrared spectrum of the protruding particles on the surface of the negative electrode current collector, at 3200 cm -1 -3600cm -1 There is an absorption peak.

[0039] In one embodiment, the dyne value of the negative electrode current collector is D, and 20≤D≤80 (e.g., 20, 20.5, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 79, 80). Limiting the dyne value of the negative electrode current collector to the above-mentioned specific range can improve the spreading of the negative electrode active material layer on the surface of the negative electrode current collector. When the dyne value of the negative electrode current collector is lower than 20, the negative electrode current collector is prone to shrinkage, which is not conducive to the coating of the negative electrode active material layer on the surface of the negative electrode current collector and reduces the adhesion between the negative electrode current collector and the negative electrode active material layer.

[0040] In one example, 35≤D≤60.

[0041] In the present invention, the dyne value can be obtained by testing in the following manner: using a dyne pen of a certain specification to draw a line on the surface of the negative electrode current collector; if the negative electrode current collector does not shrink within 10 seconds, it indicates that the negative electrode current collector has reached the dyne value.

[0042] In one embodiment, where the tensile strength of the negative electrode current collector is E and the elongation at break of the negative electrode current collector is F, then C=E×F, and C is 100-2500 (e.g., 100, 300, 500, 700, 1000, 1200, 1500, 1800, 2000, 2200, 2500). When C is limited to the above specific range, the flexibility of the negative electrode current collector is better, which is conducive to the coating of the negative electrode active material layer on the surface of the negative electrode current collector, improves the adhesion between the negative electrode current collector and the negative electrode active material layer, and also improves the mechanical properties of the negative electrode current collector. When subjected to mechanical shock or heavy impact, the negative electrode current collector is not easily deformed, thereby improving the safety performance of the battery.

[0043] In one embodiment, C is 200-2000.

[0044] In the present invention, the tensile strength and the elongation at break can be obtained by testing in the following manner: a sample of a negative electrode current collector with a width of 15 mm and a length of 200 mm (this is the initial length L0) is taken, a tensile gauge is used, and the stretching speed is 50 mm / min. After the tensile gauge is broken, the tensile strength output by the tensile gauge is the tensile strength, and the length of the negative electrode current collector after breaking is measured and recorded as L1, then the elongation at break = (L1-L0) / L0.

[0045] In one embodiment, the negative electrode active material layer includes carbon. When the negative electrode current collector of the negative electrode sheet is peeled off from the negative electrode active material layer, a residual negative electrode active material layer remains on the surface of the negative electrode current collector after peeling. The weight content of carbon, Z, based on the total weight of the residual negative electrode active material layer, is 50 wt% ≤ Z wt% ≤ 95 wt% (e.g., 51 wt%, 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, 85 wt%, 89 wt%, 90 wt%, or 95 wt%). When Z satisfies the above-specified range, the adhesion between the surface negative electrode current collector and the negative electrode active material layer is strong, making peeling difficult.

[0046] In one example, 60 wt%≤Z wt%≤90 wt%.

[0047] In one example, the peel strength between the negative electrode current collector and the negative electrode active material layer is ≥0.8 N / m (e.g., 0.8 N / m, 0.85 N / m, 0.9 N / m, 0.95 N / m, 1 N / m, 1.05 N / m, 1.1 N / m, 1.2 N / m, 1.3 N / m, 1.4 N / m, 1.5 N / m).

[0048] In one example, 60 wt % ≤ Z ≤ 90 wt %, and the peel strength between the negative electrode current collector and the negative electrode active material layer is ≥ 0.8 N / m.

[0049] In the present invention, the peel strength can be obtained by the following test method: use tape to stick both sides of the negative electrode sheet, use a tensile gauge to test the tension required to peel the negative electrode sheet from one side of the current collector, and the output value of the tensile gauge is the peel strength.

[0050] In one embodiment, the negative electrode current collector comprises a copper foil that has been electroplated and / or solution treated. The copper foil that has been electroplated and / or solution treated may have raised particles formed on the surface of the copper foil, such as Figure 1 shown.

[0051] The electroplating method can be carried out in the following steps: first, a copper-containing substance is dissolved in a first solvent at room temperature to generate a copper-containing salt solution, and a copper foil with raised particles on the surface of a smooth cathode roller (such as a steel roller) is generated through an electrolytic reaction.

[0052] In one example, the first solvent includes one or more of a sulfuric acid solution, a hydrochloric acid solution, and a nitric acid solution.

[0053] In one example, the copper-containing substance includes one or more of copper, a copper-containing alloy, and copper oxide.

[0054] In one embodiment, the temperature of the electrolysis reaction is 10°C-100°C (e.g., 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C), and the time is 0.5h-3h (e.g., 0.5h, 1h, 1.5h, 2h, 2.5h, 3h).

[0055] The solution treatment method can be carried out by the following steps: taking copper ammonia solution treatment as an example, at room temperature, the untreated copper foil is completely immersed in the copper ammonia solution, wherein the pH of the copper ammonia solution is 8-12 (for example, 8, 9, 10, 11, 12), and the immersion time is 0.5h-3h (for example, 0.5h, 1h, 1.5h, 2h, 2.5h, 3h); then, the residual solution on the surface of the copper foil is washed with deionized water, and the copper foil is naturally dried at room temperature to remove moisture to obtain a copper foil with raised particles on the surface.

[0056] In one example, the negative electrode active material layer includes a negative electrode active material, a negative electrode binder, and a negative electrode conductor.

[0057] In one example, the negative electrode active material includes one or more of artificial graphite, natural graphite, mesocarbon microbeads, hard carbon, soft carbon, artificial graphite doped with silicon, and artificial graphite doped with silicon and oxygen.

[0058] In one example, the negative electrode binder includes one or more of lithiated polyacrylic acid (Li-PAA), sodium carboxymethyl cellulose, styrene-butadiene latex, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, and polyethylene oxide.

[0059] In one example, the negative electrode conductive agent includes one or more of conductive carbon black (SP), acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0060] In one example, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode active material is 90wt%-99.5wt% (for example, 90wt%, 91wt%, 92wt%, 93wt%, 94wt%, 95wt%, 96wt%, 97wt%, 98wt%, 99wt%, 99.5wt%), the weight content of the negative electrode binder is 0.5wt%-5wt% (for example, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%), and the weight content of the negative electrode conductor is 0wt%-5wt% (for example, 0wt%, 0.5wt%, 1wt%, 1.5wt%, 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%).

[0061] In one example, based on the total weight of the negative electrode active material layer, the weight content of the negative electrode active material is 95wt%-98.5wt%, the weight content of the negative electrode binder is 1.5wt%-2.5wt%, and the weight content of the negative electrode conductor is 0wt%-2.5wt%.

[0062] In one embodiment, the viscosity V of the electrolyte is 3 mPa·s-8 mPa·s (e.g., 3 mPa·s, 3.5 mPa·s, 4 mPa·s, 4.5 mPa·s, 5 mPa·s, 5.5 mPa·s, 6 mPa·s, 6.5 mPa·s, 7 mPa·s, 7.5 mPa·s, 8 mPa·s). When the viscosity of the electrolyte is limited to the above-mentioned specific range, the fluidity of the electrolyte can be improved, the transport capacity of lithium ions can be enhanced, and the protruding particles on the surface of the negative electrode current collector can play a certain disturbing role, thereby improving the dynamic performance of the battery.

[0063] In one example, V is 4 mPa·s to 7 mPa·s.

[0064] In one example, the electrolyte includes a lithium salt, an organic solvent, and an additive.

[0065] In one example, the lithium salt includes one or more of lithium tetrafluoroborate, lithium hexafluorophosphate, lithium nitrate, lithium difluorooxalatoborate, lithium perchlorate, lithium difluorophosphate, lithium bis(difluorosulfonyl imide), and lithium bis(trifluoromethylsulfonyl imide).

[0066] In one example, the organic solvent includes one or more of fluorinated or unsubstituted carbonates and fluorinated or unsubstituted carboxylates.

[0067] In one example, the carbonate includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate.

[0068] In one example, the carboxylic acid ester includes one or more of propyl acetate, n-butyl acetate, isobutyl acetate, n-amyl acetate, isoamyl acetate, propyl propionate, ethyl propionate, methyl butyrate, and ethyl n-butyrate.

[0069] In one example, the additive includes one or more of succinonitrile, adiponitrile, vinylene carbonate (VC), and 1,3,6-hexanetrinitrile.

[0070] In one example, based on the total weight of the electrolyte, the weight content of the lithium salt is 5wt%-15wt% (for example, 5wt%, 7wt%, 10wt%, 12wt%, 15wt%), the weight content of the organic solvent is 70wt%-89wt% (for example, 70wt%, 75wt%, 80wt%, 85wt%, 90wt%), and the weight content of the additive is 5wt%-15wt% (for example, 5wt%, 7wt%, 10wt%, 12wt%, 15wt%).

[0071] In one example, based on the total weight of the electrolyte, the weight content of the lithium salt is 6 wt %-12 wt %, the weight content of the organic solvent is 75 wt %-87 wt %, and the weight content of the additive is 6 wt %-13 wt %.

[0072] In one example, the battery includes a positive electrode sheet and a separator.

[0073] The positive electrode sheet can be a conventional positive electrode sheet in the art. For example, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one side or both sides of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a positive electrode conductor and a positive electrode binder.

[0074] In one example, the positive electrode current collector includes one or more of aluminum foil, nickel, stainless steel, and a composite current collector.

[0075] In one example, the positive electrode active material includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and transition metal lithium oxide.

[0076] In one embodiment, the chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O2, wherein -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo and Zr.

[0077] In one example, the positive electrode conductive agent includes one or more of conductive carbon black (SP), acetylene black, Ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, metal powder, and carbon fiber.

[0078] In one example, the positive electrode binder includes one or more of lithiated polyacrylic acid (Li-PAA), sodium carboxymethyl cellulose, styrene-butadiene latex, polyvinylidene fluoride (PVDF), polytetrafluoroethylene, and polyethylene oxide.

[0079] In one example, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material is 80wt%-99.8wt% (for example, 80wt%, 85wt%, 90wt%, 95wt%, 99wt%, 99.8wt%), the content of the positive electrode conductor is 0.1wt%-10wt% (for example, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%, 10wt%) and the content of the positive electrode binder is 0.1wt%-10wt% (for example, 0.1wt%, 0.5wt%, 1wt%, 3wt%, 5wt%, 7wt%, 10wt%).

[0080] In one example, based on the total weight of the positive electrode active material layer, the content of the positive electrode active material is 90 wt%-99.6 wt%, the content of the positive electrode conductor is 0.2 wt%-5 wt%, and the content of the positive electrode binder is 0.2 wt%-5 wt%.

[0081] The diaphragm may be a conventional diaphragm in the art, for example, the diaphragm includes one or more of a single-layer PE (polyethylene), a single-layer PP (polypropylene), a PP / PE / PP composite film and a composite ceramic diaphragm.

[0082] The present invention will be described in detail below through examples. The examples described in the present invention are only some examples of the present invention, not all examples. All other examples obtained by persons of ordinary skill in the art based on the examples of the present invention without creative work are within the scope of protection of the present invention.

[0083] The following examples illustrate the batteries of the present invention.

[0084] Example 1

[0085] (1) Negative electrode

[0086] Preparation of negative electrode current collector

[0087] 1) Prepare a copper ammonia solution: Dissolve copper sulfate in deionized water at a ratio of 1:80. Slowly add ammonia while stirring. A light blue precipitate will first precipitate. Continue adding ammonia until the precipitate dissolves and the solution becomes a clear blue liquid. Continue adding ammonia until the pH reaches 10. Then filter to remove the undissolved precipitate.

[0088] 2) At room temperature, the copper foil was completely immersed in the copper ammonia solution for 1 hour, and the residual solution on the surface of the copper foil was washed with deionized water; the water was naturally dried at room temperature to obtain a negative electrode current collector with raised particles on the surface.

[0089] Preparation of negative electrode active material slurry: 97.3% by mass of negative electrode active material (graphite), 0.5% by mass of negative electrode conductive agent (conductive carbon black), 1.3% by mass of binder (styrene-butadiene rubber) and 0.9% by mass of dispersant (sodium carboxymethyl cellulose) were mixed evenly, and then an appropriate amount of deionized water was added and dispersed evenly to prepare the negative electrode active material slurry.

[0090] The negative electrode active material layer slurry is coated on both sides of the negative electrode current collector to form a negative electrode active material layer, and the negative electrode sheet is obtained after baking and rolling.

[0091] Among them, from Figure 3 It can be seen from the figure that after the negative electrode active material layer is peeled off from the negative electrode sheet, a large amount of negative electrode active material remains on the negative electrode current collector.

[0092] (2) Positive electrode

[0093] Conductive carbon black and carbon nanotubes were added to a PVDF glue solution and stirred evenly. Lithium cobalt oxide was then added and stirred evenly to prepare a positive electrode active material slurry. The slurry was then coated on both sides of the positive current collector to form a positive electrode active material layer. After baking and roller pressing, the positive electrode sheet was obtained. The mass fraction of the positive electrode active material (lithium cobalt oxide) in the positive electrode active material layer was 97.6%, the mass fraction of the positive electrode binder (PVDF) was 1.05%, and the mass fraction of the positive electrode conductive agent (conductive carbon black and carbon nanotubes, with a carbon black to carbon nanotube mass ratio of 1:1) was 1.35%.

[0094] (3) Electrolyte

[0095] In an argon-filled glove box (H2O <0.1ppm, O2 <0.1ppm), the organic solvent is mixed thoroughly, and then fully dried lithium salt is quickly added. After dissolving, PS and additives are added to obtain the desired electrolyte. The electrolyte comprises 10 parts by weight of lithium hexafluorophosphate (LiPF), 1 part by weight of 1,3-propane sultone (PS), 85 parts by weight of organic solvents (40 parts by weight of ethylene carbonate (EC), 40 parts by weight of diethyl carbonate (DEC), and 5 parts by weight of fluoroethylene carbonate (FEC), and 4 parts by weight of the additive (vinylene carbonate (VC)).

[0096] (4) Diaphragm

[0097] The diaphragm is a PP / PE based diaphragm with ceramic coating on one side and PVDF adhesive coating on both sides. The base film thickness is 5μm, the ceramic layer thickness is 2μm, and the single-sided adhesive layer thickness is 1μm.

[0098] (5) Preparation of batteries

[0099] The negative electrode sheet of step (1), the positive electrode sheet of step (2) and the separator of step (4) are stacked in the order of positive electrode sheet, separator and negative electrode sheet, and then wound to obtain a battery cell; the battery cell is placed in an outer packaging aluminum foil, the electrolyte of step (3) is injected into the outer packaging, and a lithium ion battery is obtained through vacuum packaging, standing, forming, shaping, sorting and other processes.

[0100] Example 2

[0101] The same procedure was carried out as in Example 1, except that B% and A were changed. For details, see Table 1.

[0102] Example 3 group

[0103] This set of examples is used to illustrate the impact when B% changes.

[0104] This example group was carried out with reference to Example 1, except that B% was changed. Please refer to Table 1 for details.

[0105] Example 4 Group

[0106] This set of embodiments is used to illustrate the impact when A changes.

[0107] This embodiment group was carried out with reference to embodiment 1, except that A was changed. For details, see Table 1.

[0108] Example 5 Group

[0109] This set of examples is used to illustrate the effects produced when the D50 of the protruding particles changes.

[0110] This example group was carried out with reference to Example 1, except that the D50 of the protruding particles was changed. See Table 1 for details.

[0111] Example 6

[0112] This group of examples is used to illustrate the impact produced when the position of the absorption peak in the infrared spectrum of the protruding particles on the surface of the negative electrode current collector changes.

[0113] This embodiment group was carried out with reference to the embodiment 1, except that the position of the absorption peak in the infrared spectrum of the protruding particles on the surface of the negative electrode current collector was changed. See Table 1 for details.

[0114] Example 7 Group

[0115] This set of embodiments is used to illustrate the impact when D changes.

[0116] This embodiment group was carried out with reference to embodiment 1, except that D was changed. For details, see Table 1.

[0117] Example 8 Group

[0118] This set of examples is used to illustrate the impact when C changes.

[0119] This embodiment group was carried out with reference to embodiment 1, except that C was changed. For details, see Table 1.

[0120] Comparative Example 1

[0121] The same procedure was followed as in Example 1, except that the negative electrode current collector was changed to conventional copper foil. For details, see Table 1.

[0122] from Figure 4 It can be seen from the figure that after the negative electrode sheet peels off the negative electrode active material layer, less negative electrode active material remains on the negative electrode current collector.

[0123] Comparative Example 2

[0124] The same procedure was followed as in Example 1, except that the negative electrode current collector was changed to carbon-coated copper foil. For details, see Table 1.

[0125] from Figure 5 It can be seen from the figure that after the negative electrode active material layer is peeled off from the negative electrode sheet, a large amount of negative electrode active material remains on the negative electrode current collector.

[0126] Comparative Example 3

[0127] The process was carried out in accordance with Example 1, except that 1,3-propane sultone was not added to the electrolyte. For details, see Table 1.

[0128] Comparative Example 4

[0129] The same method was used as in Example 1, except that 1,3-propane sultone was replaced with DTD in the same weight portion. For details, see Table 1.

[0130] Comparative Example 5

[0131] The same procedure was followed as in Example 1, except that B% was changed to make B / A < 0.01. See Table 1 for details.

[0132] Comparative Example 6

[0133] The same procedure was carried out as in Example 1, except that A was changed to make B / A>5. For details, see Table 1.

[0134] Table 1

[0135]

[0136]

[0137] * indicates the same as Example 1;

[0138] - means it does not exist.

[0139] Test Case

[0140] The batteries obtained in the embodiment and the comparative example were respectively subjected to the following tests:

[0141] 1. Cycle performance test

[0142] The battery was placed in a constant temperature room at 45°C and discharged at 1C to the battery's lower voltage limit (3.0V). The battery was then charged at 1.5C to the battery's upper voltage limit (4.5V), and then discharged at 1C to the lower voltage limit. These three charge and discharge cycles constituted a test cycle. This cycle was repeated 800 times to calculate the battery's discharge capacity retention rate. The initial discharge capacity is Q1, and the discharge capacity after 800 cycles is Q2. The discharge capacity retention rate = (Q2 / Q1) * 100%.

[0143] 2. Rate performance test

[0144] Place the battery in a constant temperature room at the target temperature (25°C), discharge the battery at 1C to the battery's lower voltage limit, charge the battery at 1.5C to the battery's upper voltage limit, and then discharge the battery at 1C to the battery's lower voltage limit.

[0145] Rate discharge retention ratio = 1C discharge capacity / 0.2C discharge capacity * 100%.

[0146] 3. Energy density test

[0147] The battery was charged at a constant current rate of 0.2C to 4.5V, and then charged at a constant voltage rate of 0.025C to complete the full charge of the battery. Next, it was discharged at a constant current rate of 0.2C until the battery voltage dropped to 3V. The total capacity discharged during the discharge process was recorded as C, and the actual battery volume V was calculated.

[0148] ED (Energy Density) = Discharge Capacity C * Voltage Platform / Cell Volume V

[0149] The platform voltage of a 4.5V system is usually 3.9V.

[0150] ED loss rate (energy density loss rate) = ED difference / ED of the battery of comparative example 1*100%.

[0151] 4. Normal temperature cycle expansion rate

[0152] The battery was placed in a constant temperature room at 25°C and discharged at 1C to the battery's lower voltage limit (3.0V). The battery was then charged at 1.5C to the battery's upper voltage limit (4.5V). Then, the battery was discharged at 1C again to the lower voltage limit. These three charge and discharge cycles constituted a test cycle. This cycle was repeated 800 times to calculate the battery's discharge capacity retention rate. The initial battery thickness is H1, and the battery thickness after 800 cycles is H2. The cycle expansion rate = ((H2 - H1) / H1) * 100%.

[0153] 5. Low temperature discharge performance

[0154] After the battery is fully charged (100% SOC), the capacity of 0.2C discharge at room temperature (25°C) is C1. After the battery is fully charged and left to stand at -20°C for 4 hours, the capacity of 0.2C discharge is C2. The low-temperature discharge capacity retention rate = C2 / C1*100%.

[0155] The obtained results are recorded in Table 2.

[0156] Table 2

[0157]

[0158] As can be seen from Table 2, the comparative examples and the embodiments show that the 1C rate discharge capacity retention rate of the battery of the embodiment is improved, the capacity retention rate after 800 cycles at 45°C is improved, the ED loss is reduced, the expansion rate after 800 cycles at room temperature is reduced, and the low-temperature discharge capacity retention rate is improved. This shows that the battery of the present invention improves the rate performance and reduces the energy density loss by defining the specific relationship between the protruding particles on the surface of the negative electrode current collector in the battery and the protruding particles and 1,3-propane sultone in the electrolyte.

[0159] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, various simple variations of the technical solution of the present invention may be made, including combining the various technical features in any other appropriate manner. These simple variations and combinations should also be regarded as disclosed in the present invention and fall within the scope of protection of the present invention.

Claims

1. A battery, characterized in that: The battery includes a negative electrode sheet and an electrolyte. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer located on one or both sides of the negative electrode current collector. The negative electrode current collector is a copper foil having raised particles on the surface. The average height of the raised particles is A, in μm. The electrolyte includes 1,3-propane sultone. The weight content of the 1,3-propane sultone is Bwt% based on the total weight of the electrolyte. Then, the battery satisfies the following relationship: 0.01≤B / A≤5; the median particle size D50 of the raised particles is 1μm-10μm; and the raised particles are located at any 2.5×10 -5 cm 2 Within the area range, the number of the protruding particles with a particle size greater than 5 μm is N, and N≤3.

2. The battery according to claim 1, wherein 0.02≤B / A≤4.

3. The battery according to claim 2, wherein 0.5μm≤Aμm≤4μm.

4. The battery according to claim 3, wherein 1μm≤Aμm≤3μm.

5. The battery according to claim 2, wherein 0.01wt%≤Bwt%≤10wt%.

6. The battery according to claim 3, wherein 0.03wt%≤Bwt%≤5wt%.

7. The battery according to any one of claims 1 to 6, wherein The surface of the negative electrode current collector includes oxygen-containing functional groups, and the oxygen-containing functional groups include one or more of hydroxyl groups, carboxyl groups and carbonyl groups; And / or, in the infrared spectrum of the protruding particles on the surface of the negative electrode current collector, at 1500 cm -1 -3600cm -1 There is an absorption peak.

8. The battery according to claim 7, wherein The oxygen-containing functional group is a hydroxyl group; And / or, in the infrared spectrum of the protruding particles on the surface of the negative electrode current collector, at 3200 cm -1 -3600cm -1 There is an absorption peak.

9. The battery according to any one of claims 1 to 6, wherein The dyne value of the negative electrode current collector is D, and then 20≤D≤80.

10. The battery according to claim 9, wherein The dyne value D of the negative electrode current collector is 35≤D≤60.

11. The battery according to any one of claims 1 to 6, wherein The tensile strength of the negative electrode current collector is E, and the elongation at break of the negative electrode current collector is F, then C=E×F, and C is 100-2500.

12. The battery according to claim 11, wherein C is 200-2000.

13. The battery according to any one of claims 1 to 6, wherein The negative electrode active material layer includes carbon elements. The negative electrode current collector of the negative electrode sheet is peeled off from the negative electrode active material layer. After peeling, a residual negative electrode active material layer exists on the surface of the negative electrode current collector. Based on the total weight of the residual negative electrode active material layer, the weight content Zwt% of the carbon elements is 50wt%≤Zwt%≤95wt%; And / or, the peel strength between the negative electrode current collector and the negative electrode active material layer is ≥0.8 N / m.

14. The battery according to any one of claims 1 to 6, wherein: The negative electrode current collector is a copper foil that has been electroplated and / or solution-treated.

15. The battery according to any one of claims 1 to 6, wherein: The viscosity V of the electrolyte is 3 mPa·s-8 mPa·s.

16. The battery according to claim 15, wherein The viscosity V of the electrolyte is 4 mPa·s-7 mPa·s.

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