Positive electrode sheet, battery and electronic device

Abstract

To provide a positive electrode sheet, a battery and an electronic apparatus.SOLUTION: A first aspect of the present invention provides a positive electrode sheet. The positive electrode sheet includes a positive electrode current collector and a positive electrode active layer that includes a positive electrode active material and that is provided on at least one surface of the positive electrode current collector. In a plane composed of a length direction and a thickness direction of the positive electrode sheet, particles of the positive electrode active material have a longest distance a in the length direction of the positive electrode sheet, and have a longest distance b in the thickness direction of the positive electrode sheet, and in a region of 25 μm*25 μm or more, the number of the particles of the positive electrode active material meeting a / b≥3 is N, where N≥2. The positive electrode active material provided by the present invention has a relatively regular morphological structure and is easy to form an accordion stacking structure, which is helpful to improve structural integrity of the positive electrode active material, thereby improving compaction density of the positive electrode sheet and cycle performance of the battery.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a positive electrode sheet, a battery and an electronic device, and relates to the field of electrochemical technology. [Background technology]

[0002] As consumer electronic products such as mobile phones and tablets become thinner, the requirements for battery energy density are also increasing. In order to improve the energy density of a battery, improving the end-of-charge voltage of the battery and the packing density of the positive electrode sheet is one of the effective methods. As a conventional positive electrode active material, the structure of lithium cobalt oxide is irregular spheres, and there is a limit to improving the packing density. When the charging voltage is ≧4.55V (vs.Li), lithium cobalt oxide undergoes an irreversible phase change, that is, an irreversible phase change from O3 phase to H1-3 phase, and the ionic conductivity and electronic conductivity of the H1-3 phase are poor, which accelerates the decay of the capacity of lithium cobalt oxide, thereby accelerating the destruction of the lithium cobalt oxide structure and affecting the cycle performance of the battery. How to improve the packing density of the positive electrode sheet and the cycle performance of the battery is a technical problem that must be solved by those skilled in the art. Summary of the Invention [Problem to be solved by the invention]

[0003] The present invention provides a positive electrode sheet, which is used to improve the packing density of the positive electrode sheet and the cycle performance of the battery.

[0004] The present invention further provides a battery and an electronic device comprising the above-mentioned positive electrode sheet. [Means for solving the problem]

[0005] In a first aspect of the present invention, there is provided a positive electrode sheet, the positive electrode sheet including a positive electrode current collector and a positive electrode active layer provided on at least one surface of the positive electrode current collector, the positive electrode active layer including a positive electrode active material; In a plane consisting of the longitudinal and thickness directions of the positive electrode sheet, the longest distance of the particles of the positive electrode active material in the longitudinal direction of the positive electrode sheet is a, the longest distance of the particles of the positive electrode active material in the thickness direction of the positive electrode sheet is b, and the number of particles of the positive electrode active material that satisfies a / b≧3 within an area of ​​25 μm*25 μm or more is N, where N≧2.

[0006] The present invention provides a positive electrode sheet, and after processing the positive electrode sheet using CP (cross-section) technology, a SEM imaging test is performed. FIG. 1 is a CP-SEM image of a positive electrode sheet provided in one embodiment of the present invention. As can be seen from FIG. 1, the positive electrode sheet includes a positive electrode current collector 100 and a positive electrode active layer provided on the surface of the positive electrode current collector 100. The positive electrode active layer includes some positive electrode active material particles 200. In FIG. 1, two positive electrode particles are circled. Taking the active material particles as an example, the positive electrode active material is elongated, the longest distance of the positive electrode active material particles in the longitudinal direction of the positive electrode sheet is a, the longest distance of the positive electrode active material particles in the thickness direction of the positive electrode sheet is b, and a sample with a size of 25 μm*25 μm or more is taken from any position on the plane, and the number of particles of the positive electrode active material that satisfy a / b≧3 is N, and the number of particles N of the positive electrode active material that satisfies a / b≧3 within the sample range is 2 or more. The positive electrode active material provided by the present invention has a relatively regular morphological structure and is easy to form an accordion laminated structure, which is helpful in improving the structural integrity of the positive electrode active material, and further improves the compaction density of the positive electrode sheet and the cycle performance of the battery.

[0007] In a specific embodiment, the positive electrode active material is lithium cobalt oxide, whose structural formula is Li n-x Na x Co 1-y Me yO2 (where 0.70 ≤ n ≤ 1, 0 < x ≤ 0.15, 0 ≤ y ≤ 0.15, and Me is one or more selected from Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, W, Sc, Ce, P, Nb, V, Ta, Te). Note that for the cathode active material, the value of n is different in different lithium - deintercalated states. Before forming the cathode sheet and performing the capacity test, the value of n in the cathode active material (powder state) is 1. After forming the cathode sheet and performing the capacity test, when the operating voltage of the battery including the cathode sheet is 3.6 - 4.0V, the value of n decreases to 0.70 - 1. This is mainly because during the first charge - discharge of the battery, some lithium ions are used to form the CEI film and SEI film, which are the protective layers on the surfaces of the positive and negative electrodes, resulting in + irreversible loss of a part of Li, so the Li content of the cathode active material in the cathode sheet after formation and capacity test decreases.

[0008] As can be seen from the XRD test on the cathode active material, the lithium cobaltate provided in the present invention has characteristic peaks different from those of general lithium cobaltate. Specifically, the X - ray diffraction pattern of the cathode active material has a 002 peak corresponding to the 002 crystal plane, a 102 peak corresponding to the 102 crystal plane, and a 103 peak corresponding to the 103 crystal plane. The lithium cobaltate having the above crystal phase structure has a lower platform voltage compared to general lithium cobaltate, and has multiple platform voltages. At the same end - of - charge voltage, it has a higher discharge capacity per gram and a relatively stable structure, which helps to improve the capacity and cycle performance of the battery.

[0009] Furthermore, the diffraction angle 2θ of the 002 crystal plane is 18.6° ± 0.5°, the diffraction angle 2θ corresponding to the 102 peak is 41.7° ± 0.5°, and the diffraction angle 2θ corresponding to the 103 peak is 47.1° ± 0.5°.

[0010] The X-ray diffraction pattern of the positive electrode active material further has a 101 peak corresponding to the 101 crystal plane and a 004 peak corresponding to the 004 crystal plane, and the peak intensity ratio between the 101 peak and the 004 peak is m. When m is 1.5 or more, it is helpful to further improve the structural stability of the positive electrode material, which is more favorable for desorption and absorption of lithium ions; otherwise, the structural stability of the positive electrode material may be deteriorated, and the electrochemical performance may be deteriorated due to an incomplete reaction or poor crystallinity.

[0011] The particle size of the positive electrode active material is 6 to 18 μm as measured by a Malvern laser granulometer, the particle size being the size of the particles of the positive electrode active material.

[0012] Based on the special structure of the positive electrode active material provided by the present invention, the positive electrode active material provided by the present invention has a conductivity of ≧1E under a force of ≧4KN. -4 S / cm, and under a force of ≧30KN, the compaction density is ≧3.75g / cm 3 The specific test method is as follows: the powdered positive active material is placed in a container, and compressed by a certain external force, and then the conductivity and compaction density are tested, and the four-point probe principle is used for the powder conductivity test, which indicates that the positive active material provided in the present invention has good conductivity performance and is useful for improving the compaction density of the positive sheet.

[0013] In order to increase the number N of particles of the positive electrode active material per unit area, the compaction density of the positive electrode sheet is ≧4.0 g / cm 3 It is.

[0014] The test results show that the capacity per gram of the positive electrode material is ≧196mAh / g (3.0-4.5V, vs. Li), and when the battery is initially charged and discharged at 0.1C under a voltage of 3.0-4.5V, the discharge capacity per gram obtained is defined as C0mAh / g, the discharge capacity per gram from the start of discharge to 4.4V is C1mAh / g, the capacity per gram within the voltage range of 3.8V-3.7V is C2mAh / g, and C1 / C0≧9%, C2 / C0≧25%.

[0015] In the present invention, further provided is a method for manufacturing the above positive electrode active material. Specifically, a compound containing at least Co and Na elements, Na x Step 1 of manufacturing CoO2(0.68 < x < 0.74), and a compound containing Co and Na, Na x CoO2 and a compound containing lithium element are dispersed in deionized water, and an ion exchange reaction is carried out to replace a part of the Na ions in Na x CoO2 with Li ions to obtain a positive electrode material, including Step 2.

[0016] In one specific embodiment, the manufacturing of the positive electrode material specifically includes Step 1-1, Step 1-2, and Step 2.

[0017] In Step 1-1, after weighing a compound containing Co element and a compound containing sodium element in a required stoichiometric ratio, one of the mixing devices such as a high-speed mixing device, a sand mill device, a ball mill device, a colter mixing device, and an inclined mixing device is used to mix them sufficiently until they become uniform to obtain a mixed material. During the mixing, water, alcohol, or other solvents can be added, and after uniform mixing, it can be dried.

[0018] Here, the compound containing cobalt element can be one or more of cobalt hydroxide, tricobalt tetraoxide, doped tricobalt tetraoxide, cobalt oxide, cobalt oxyhydroxide, cobalt nitrate, and cobalt sulfate. The compound containing sodium can be one or more of sodium-containing oxides, sodium carbonate, sodium nitrate, sodium hydroxide, sodium bicarbonate, and sodium sulfate. In addition, a compound containing a doping element Me can be further added. The doping element Me includes one or more of Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, W, Sc, Ce, P, Nb, V, Ta, and Te. Specifically, it can be a compound containing a doping element such as basic magnesium carbonate, magnesium hydroxide, zirconium oxide, aluminum oxide, yttrium oxide, and lanthanum oxide. Furthermore, the cobalt-containing compound, sodium-containing compound, and Me-containing compound follow Na:Co:Me = x:(1 - y):y, where 0.68 < x < 0.74 and 0 ≤ y ≤ 0.15. To ensure sufficient mixing until the compound becomes uniform, the mixing time is at least 4 h, and those skilled in the art can observe the mixing state of the compound with an SEM electron microscope.

[0019] In Step 1-2, after loading the mixed material produced in Step 1-1 into a crucible, it is placed in a high-temperature sintering apparatus such as a muffle furnace, tunnel furnace, roller hearth kiln, tubular furnace, etc., and high-temperature sintering is carried out in an air or oxygen atmosphere to obtain the first compound Na x Co 1-y Me y O2, where 0.68 < x < 0.74 and 0 ≤ y ≤ 0.15.

[0020] Furthermore, the sintering temperature is 700 - 900 °C, and the time is 8 - 50 h.

[0021] In Step 2, the first compound synthesized and obtained in Step 1-2 and the lithium-containing compound are mixed in a required ratio and dispersed in deionized water, and an ion exchange reaction is carried out. Due to the free migration and diffusion of sodium ions and lithium ions in the aqueous solution, most of the Na ions in the first compound are replaced by Li ions. After the reaction is completed, the reaction product is washed and dried to obtain the cathode material.

[0022] The lithium element-containing compound can be one or more of lithium carbonate, lithium chloride, lithium bromide, lithium iodide, lithium nitrate, lithium hydroxide, and lithium fluoride. If necessary, several carbon-containing compounds or fast ion conductor compounds can be added to improve the conductivity of the cathode material.

[0023] The mass ratio of the lithium-containing compound to the first compound is ≥1, and further 1 - 3. The mass ratio of the solvent to the first compound is ≥5, and further 20 - 150.

[0024] The reaction equipment used includes sealed vessel equipment with sealing function and stirring ability, such as wet coating reaction equipment, coprecipitation reaction equipment, etc., the stirring speed during the reaction is 10-200 rpm, the reaction temperature is 70-125°C, and the reaction time is ≧5H, and the reaction time is 10-15H; The equipment used for drying, such as blower oven, vacuum drying oven, rotary kiln, box dryer, etc., has a drying temperature of 80-180℃ and a drying time of ≥ 10H.

[0025] After preparing the above positive electrode active material, a positive electrode active layer slurry is prepared by combining an adhesive and a conductive agent, and the slurry is applied to at least one surface of a positive electrode current collector to obtain a positive electrode active layer. Finally, a positive electrode sheet is obtained by drying and rolling, where the positive electrode current collector can be an aluminum foil, the adhesive is one or more selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), and lithium polyacrylate (PAALi), the conductive agent is one or more selected from conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotubes, single-arm carbon nanotubes, and multi-arm carbon nanotubes, and the mass ratio of the positive electrode active material, the conductive agent, and the adhesive is (70 to 99): (0.5 to 15): (0.5 to 15), and further, the mass ratio of the positive electrode active material, the conductive agent, and the adhesive is (80 to 98): (1 to 10): (1 to 10).

[0026] In a second aspect of the present invention, there is provided a battery including any of the positive electrode sheets described above.

[0027] Specifically, the battery provided by the present invention is obtained by incorporating the above-mentioned positive electrode sheet together with a negative electrode sheet, a separator and an electrolyte, wherein the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer provided on the surface of the negative electrode current collector, the negative electrode active layer includes a negative electrode active material, a conductive agent and an adhesive, the negative electrode active material is one or more selected from artificial graphite, natural graphite, hard carbon, mesocarbon microbeads, lithium titanate, silicon carbon and silicon oxide, the types of the conductive agent and the adhesive are the same as those of the positive electrode active layer, the mass ratio of the negative electrode active material, the conductive agent and the adhesive is (70-99):(0.5-15):(0.5-15), and further, the mass ratio of the negative electrode active material, the conductive agent and the adhesive is (80-98):(1-10):(1-10).

[0028] During the preparation of the negative electrode sheet, the above-mentioned negative electrode active material, conductive agent and adhesive are mixed in a certain ratio, and then dispersed in a solvent to obtain a negative electrode active layer slurry, which is then applied to the surface of a negative electrode current collector to obtain a negative electrode sheet, and the negative electrode current collector may be a copper foil.

[0029] The separator may be any material common in the art, such as a polypropylene based material, or an adhesive coated separator with a ceramic coating on one or both sides in addition.

[0030] The electrolyte is a common material in the art and includes an organic solvent including ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and fluoroethylene carbonate (FEC), a lithium salt, and an additive having the structure shown in the following formula, the weight of which is 0.1-10% of the total weight of the electrolyte: [ka]

[0031] The positive electrode active material provided by the present invention is applied to a high voltage battery, and the operating voltage of the battery is specifically 3.0 to 4.5 V. Under the voltage condition, the positive electrode active material has high capacity per gram and structural stability, so that the battery including the positive electrode active material also has good capacity and cycle performance.

[0032] In a third aspect of the present application, there is further provided an electronic device comprising the battery provided in the second aspect of the present invention. The battery can be used as a power source or energy storage unit for the electronic device. The electronic device may be, but is not limited to, a mobile device (e.g., a mobile phone, a tablet computer, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), etc.

[0033] Electronic devices such as mobile phones, tablet computers, and notebook computers are typically required to be thin, and can use lithium-ion batteries as their power source. Effect of the Invention

[0034] Implementation of the present invention has at least the following advantages: 1. The positive electrode active material provided in the present invention has a relatively regular shape structure, which is easy to form an accordion laminate structure, which is helpful in improving the compaction density of the positive electrode sheet and the cycle performance of the battery. 2. The positive electrode active material provided in the present invention has a lower platform voltage and multiple platform voltages than common lithium cobalt oxide, and at the same end voltage, it has a higher discharge capacity per gram and a relatively stable structure, which is helpful in improving the capacity and cycle performance of the battery. 3. The battery provided in the present invention has good capacity and cycle performance. [Brief description of the drawings]

[0035] [Figure 1] FIG. 2 is a CP-SEM image of a positive electrode sheet provided in one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] In order to make the objectives, technical solutions and advantages of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the embodiments of the present invention, and obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative labor, all belong to the protection scope of the present invention.

[0037] Unless otherwise specified, the experimental methods used in the following examples are all common methods, and the reagents, materials, etc. used in the following examples are all commercially available, unless otherwise specified. Example 1

[0038] The method for producing the positive electrode material provided in this embodiment includes the following steps (1) to (4).

[0039] (1) Weigh out 3.656 kg of sodium carbonate powder and 29.105 kg of cobalt nitrate hexahydrate powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. After that, take out the mixture and check that there are no small white dots of white sodium carbonate in the mixture. After that, the materials are deemed to be uniformly mixed.

[0040] (2) 30g of the mixture was taken and loaded into a ceramic crucible, and then a pit-type muffle furnace, model number of which is VBF-1200X, was used for high-temperature sintering. The temperature rise rate of the sintering temperature rise graph was 5℃ / min. When the temperature rose to 750℃, constant-temperature sintering was carried out for 10 hours. After sintering, the temperature was naturally lowered to room temperature, and then the sample was taken out to determine the cobalt- and sodium-containing compound Na after sintering. 0.69 Obtain CoO2.

[0041] (3) 200 ml of deionized water, 10.49 g of lithium hydroxide monohydrate, and 10.59 g of lithium chloride were added to a reaction vessel, and the mixture was stirred for 5 minutes at a water temperature of 78°C and a rotation speed of 20 rpm. Then, 10 g of the cobalt- and sodium-containing compound Na obtained in step 2 was added. 0.69CoO2 is weighed out and the reaction is continued for 8 hours at 78°C and a rotation speed of 20 rpm.

[0042] (4) After the reaction was completed, the reaction product was taken out, sucked, filtered, and washed with deionized water three times, and then dried in a 90°C blower oven for 8 hours to obtain the positive electrode material. Example 2

[0043] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0044] (3) 200 ml of deionized water, 10.49 g of lithium hydroxide monohydrate, and 21.71 g of lithium bromide were added to a reaction vessel, and the mixture was stirred for 5 minutes at a water temperature of 78°C and a rotation speed of 20 rpm. Then, 10 g of the cobalt- and sodium-containing compound Na obtained in step 2 was added. 0.69 CoO2 is weighed out and the reaction is continued for 8 hours at 78°C and a rotation speed of 20 rpm. Example 3

[0045] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0046] (3) 200 ml of deionized water, 10.49 g of lithium hydroxide monohydrate, and 33.46 g of lithium iodide were added to a reaction vessel, and the mixture was stirred for 5 minutes at a water temperature of 78°C and a rotation speed of 20 rpm. Then, 10 g of the cobalt- and sodium-containing compound Na obtained in step 2 was added. 0.69 CoO2 is weighed out and the reaction is continued for 8 hours at 78°C and a rotation speed of 20 rpm. Example 4

[0047] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0048] (3) 200 ml of deionized water, 10.49 g of lithium hydroxide monohydrate, and 6.48 g of lithium fluoride were added to a reaction vessel, and the mixture was stirred for 5 minutes at a water temperature of 78° C. and a rotation speed of 20 rpm. Then, 10 g of the cobalt- and sodium-containing compound Na obtained in step 2 was added. 0.69 CoO2 is weighed out and the reaction is continued for 8 hours at 78°C and a rotation speed of 20 rpm. Example 5

[0049] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0050] (3) Add 200 ml of deionized water, 16.78 g of lithium hydroxide monohydrate, and 3.69 g of lithium carbonate to a reaction vessel, and stir for 5 minutes at a water temperature of 78°C and a rotation speed of 20 rpm. Then, add 10 g of the cobalt- and sodium-containing compound Na obtained in step 2. 0.69 CoO2 is weighed out and the reaction is continued for 8 hours at 78°C and a rotation speed of 20 rpm. Example 6

[0051] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0052] (3) Add 200 ml of deionized water, 16.78 g of lithium hydroxide monohydrate, and 16.96 g of lithium chloride to a reaction vessel, and stir for 5 minutes at a water temperature of 78°C and a rotation speed of 20 rpm. Then, add 10 g of the cobalt- and sodium-containing compound Na obtained in step 2. 0.69 CoO2 is weighed out and the reaction is continued for 8 hours at 78°C and a rotation speed of 20 rpm. Example 7

[0053] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0054] (3) Add 200 ml of deionized water, 16.78 g of lithium hydroxide monohydrate, and 4.24 g of lithium chloride to a reaction vessel, and stir for 5 minutes at a water temperature of 78°C and a rotation speed of 20 rpm. Then, add 10 g of the cobalt- and sodium-containing compound Na obtained in step 2. 0.69 CoO2 is weighed out and the reaction is continued for 8 hours at 78°C and a rotation speed of 20 rpm. Example 8

[0055] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0056] (3) 200 ml of deionized water, 10.49 g of lithium hydroxide monohydrate, and 10.59 g of lithium chloride were added to a reaction vessel, and the mixture was stirred for 5 minutes at a water temperature of 78°C and a rotation speed of 30 rpm. Then, 10 g of the cobalt- and sodium-containing compound Na obtained in step 2 was added. 0.69 CoO2 is weighed out and the reaction is continued for 8 hours under conditions of 78°C and a rotation speed of 30 rpm. Example 9

[0057] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0058] (1) Weigh out 2.138 kg of sodium oxide powder and 29.105 kg of cobalt nitrate hexahydrate powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium oxide in the mixture. After that, the materials are deemed to be uniformly mixed. Example 10

[0059] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0060] (1) Weigh out 3.656 kg of sodium carbonate powder and 7.493 kg of cobalt oxide, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium oxide in the mixture. The materials are deemed to be uniformly mixed. Example 11

[0061] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0062] (1) Weigh out 3.656 kg of sodium carbonate powder and 9.293 kg of cobalt hydroxide powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium carbonate in the mixture. The materials are deemed to be uniformly mixed. Example 12

[0063] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0064] (1) Weigh out 3.656 kg of sodium carbonate powder and 8.026 kg of tricobalt tetroxide powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. After that, take out the mixture and check that there are no small white dots of white sodium carbonate in the mixture. After that, the materials are deemed to be uniformly mixed. Example 13

[0065] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0066] (1) Weigh out 3.656 kg of sodium carbonate powder, 9.200 kg of cobalt hydroxide powder, and 50.98 g of nano alumina powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium carbonate in the mixture. The materials are deemed to be uniformly mixed. Example 14

[0067] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0068] (1) Weigh out 3.656 kg of sodium carbonate powder, 9.014 kg of cobalt hydroxide powder, and 152.94 g of nano alumina powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium carbonate in the mixture. After that, the materials are deemed to be uniformly mixed. Example 15

[0069] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0070] (1) Weigh out 3.656 kg of sodium carbonate powder, 8.828 kg of cobalt hydroxide powder, and 254.9 g of nano alumina powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium carbonate in the mixture. After that, the materials are deemed to be uniformly mixed. Example 16

[0071] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0072] (1) Weigh out 3.656 kg of sodium carbonate powder, 9.200 kg of cobalt hydroxide powder, and 40.30 g of nano magnesium oxide powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium carbonate in the mixture. The materials are deemed to be uniformly mixed. Example 17

[0073] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0074] (1) Weigh out 3.656 kg of sodium carbonate powder, 9.014 kg of cobalt hydroxide powder, and 120.91 g of nano magnesium oxide powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium carbonate in the mixture. The materials are deemed to be uniformly mixed. Example 18

[0075] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0076] (1) Weigh out 3.656 kg of sodium carbonate powder, 8.828 kg of cobalt hydroxide powder, and 201.52 g of nano magnesium oxide powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium carbonate in the mixture. The materials are deemed to be uniformly mixed. Example 19

[0077] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0078] (1) Weigh out 2.138 kg of sodium oxide powder and 9.293 kg of cobalt hydroxide powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium oxide in the mixture. The materials are deemed to be uniformly mixed. Example 20

[0079] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0080] (1) Weigh out 2.138 kg of sodium oxide powder, 9.200 kg of cobalt hydroxide powder, and 50.98 g of nano alumina powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium oxide in the mixture. After that, the materials are deemed to be uniformly mixed. Example 21

[0081] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0082] (1) Weigh out 2.138 kg of sodium oxide powder, 9.014 kg of cobalt hydroxide powder, and 152.94 g of nano alumina powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium carbonate in the mixture. After that, the materials are deemed to be uniformly mixed. Example 22

[0083] The manufacturing method of the positive electrode material provided in this embodiment can refer to Example 1, with the following differences:

[0084] (1) Weigh out 2.138 kg of sodium oxide, 8.828 kg of cobalt hydroxide powder, and 254.9 g of nano alumina powder, put them into a high-speed mixer, mix at 300 rpm for 3 minutes, mix at 500 rpm for 5 minutes, and then mix at 1000 rpm for 10 minutes. Then, take out the mixture and check that there are no small white dots of white sodium oxide in the mixture. After that, the materials are deemed to be uniformly mixed. Comparative Example 1

[0085] The positive electrode material provided in this comparative example is a general non-doped lithium cobalt oxide, whose chemical composition is Li 1.003 The compound is CoO2, and the production method includes the following steps (1) to (4).

[0086] (1) Weigh out lithium carbonate in a molar ratio of Li:Co=100.3:100 and common undoped spherical Co3O4 particles purchased on the market. Use the same stirring equipment as in the embodiment to mix the two substances at 300 rpm for 3 minutes, then at 500 rpm for 5 minutes, and finally at 1000 rpm for 10 minutes. Take out the mixture and confirm that there are no small white dots of white lithium carbonate in the mixture. The materials are deemed to be uniformly mixed.

[0087] (2) Take 30g of the mixture, load it into a ceramic crucible, and use a pit-type muffle furnace with the model number VBF-1200X to carry out high-temperature sintering. The temperature rise rate of the sintering temperature rise graph is 5℃ / min. When the temperature rises to 1050℃, constant temperature sintering is carried out for 10 hours. After sintering, the temperature is naturally lowered to room temperature, and then the sample is taken out to determine the cobalt-lithiated compound Li after sintering. 1.003 Obtain CoO2.

[0088] (3) The sintered lithium cobalt oxide was crushed and polished, and then the powder was placed in a muffle furnace and sintered at 950°C for 8 hours. The sintered product was then crushed to obtain Li with no doping coating and a D50 of 15.2μm. 1.003 Obtain CoO2. Comparative Example 2

[0089] The positive electrode material provided in this comparative example is a high-voltage doped lithium cobalt oxide, the chemical composition of which is Li 1.0028 Co 0.982 Al 0.014 Mg 0.002 La 0.002 It's O2.

[0090] The method for producing the positive electrode material includes steps (1) to (3).

[0091] (1) Weigh out lithium carbonate and spherical Co3O4 particles doped with general Al and La purchased on the market in a molar ratio of Li:Co:Mg=100.28:98.2:0.2, and the stoichiometric ratio of the Co3O4 particles is Co:Al:La=98.2:1.4:0.2. Using the same stirring equipment as in the example, mix the two substances at 300 rpm for 3 minutes, then at 500 rpm for 5 minutes, and finally at 1000 rpm for 10 minutes. After removing the mixture, check that there are no small white dots of white lithium carbonate in the mixture, and the materials are deemed to be uniformly mixed.

[0092] (2) Take 30g of the mixture, load it into a ceramic crucible, and use a pit-type muffle furnace with the model number VBF-1200X to perform high-temperature sintering. The temperature rise rate of the sintering temperature rise graph is 5℃ / min. When the temperature rises to 1030℃, constant temperature sintering is performed for 10 hours. After sintering, the temperature is naturally lowered to room temperature, and then the sample is taken out to obtain the cobalt-sodium-containing compound Li after sintering. 1.0028 Co 0.982 Al 0.014 Mg 0.002 La 0.002 Get O2.

[0093] (3) After the lithium cobalt oxide obtained by sintering is ground and polished, it is weighed with titanium dioxide in a molar ratio of Co:Ti=98.2:0.2. Then, the two materials are put into a high-speed mixer and the material mixing process is set to mix at 300 rpm for 3 minutes, then at 500 rpm for 5 minutes, and finally at 1000 rpm for 10 minutes. Then, the mixed material is taken out and the powder is placed in a muffle furnace again and sintered at 950°C for 8 hours. Then, the sintered product is ground to obtain a doped-coated high-voltage lithium cobalt oxide material with a D50 of 14.8μm. 1.0028 Co 0.982 Al 0.014 Mg 0.002 La 0.002 Ti 0.002 Get O2. Comparative Example 3

[0094] The manufacturing method of the positive electrode material provided in this Comparative Example can refer to Example 1, and the differences are as follows:

[0095] (3) 10.49 g of lithium hydroxide monohydrate, 10.59 g of lithium chloride, and 10 g of the cobalt- and sodium-containing compound Na obtained in step 2 0.69 CoO2 is weighed out, put into a mixer, and mixed uniformly, and then sintered at high temperature at 300℃ for 5 hours. Comparative Example 4

[0096] The manufacturing method of the positive electrode material provided in this comparative example can refer to Example 1, and the differences are as follows:

[0097] (3) 10.49 g of lithium hydroxide monohydrate, 10.59 g of lithium chloride, and 10 g of the cobalt- and sodium-containing compound Na obtained in step 2. 0.69 CoO2 is weighed out and placed in a mixer. After uniform mixing, the mixture is sintered at high temperature at 250℃ for 5 hours.

[0098] The positive electrode materials provided in Examples 1 to 22 and Comparative Examples 1 to 4 were subjected to XRD test, electrical conductivity test and compaction density test. The diffraction angle of the crystal plane, peak intensity ratio and electrical conductivity obtained in the XRD test, and the compaction density test results are shown in Table 1.

[0099] [Table 1-1] [Table 1-2]

[0100] From the data in Table 1, compared with Comparative Examples 1 and 2, the positive electrode active materials provided by the present invention all have characteristic peaks corresponding to the 002 crystal plane, the 102 crystal plane, and the 103 crystal plane, and the electrical conductivity is ≧1E under an acting force of 8 KN. -4 S / cm, and the compaction density is ≧3.75g / cm under a force of 30KN. 3 It has been found that the positive electrode active material provided by the present invention has better discharge capacity per gram, structural stability, and conductive performance, and is also easily compacted, which is helpful in improving the compaction density of the positive electrode sheet.

[0101] As can be seen from the XRD data provided in Examples 1-12 in Table 1, different manufacturing raw materials and proportional relationships have certain effects on the peak position and peak intensity of the phase of the positive electrode material. As can be seen from the XRD data provided in Examples 13-22, with the increase in the content of doping element, the peak intensity ratio of the 101 crystal plane and the 004 crystal plane in the positive electrode material increases significantly. As can be seen from Comparative Examples 3-4, compared with the ion exchange reaction using the sintering method, the peak intensity ratio m of the 101 crystal plane / 004 crystal plane of the positive electrode material prepared by the solution method provided in the present invention increases significantly.

[0102] The positive electrode active materials provided in Examples 1 to 22 and Comparative Examples 1 to 4 were subjected to a button battery capacity test, and the manufacturing method of the button battery is as follows: The positive electrode active material, conductive carbon black (SP) and PVDF are mixed in a weight ratio of 8:1:1 and dispersed in a solvent to obtain a positive electrode active layer slurry, which is applied to an aluminum foil current collector and rolled to manufacture a positive electrode sheet, which is then punched into a mini-wafer with a diameter of 12 mm using a mold, dried and weighed, and then, in a glove box under an Ar protective atmosphere, a 2025 button battery case is used to make a negative electrode with a Li metal wafer, and a button battery is assembled together with a general high-voltage lithium cobalt oxide electrolyte. After the button battery was manufactured, it was left for 4 hours in a normal environment, and then an initial charge and discharge capacity test was performed. The test conditions were: charge at 0.1C to 4.5V, charge at a constant voltage to 0.025C, terminate, leave for 3 minutes, and discharge at 0.1C to 3.0V. The initial discharge gram capacity C0mAh / g was recorded, and the discharge capacity per gram within the voltage termination range from the start of discharge to 4.4V was defined as C1mAh / g. In terms of discharge capacity, the capacity per gram discharged within the discharge voltage range of 3.8V to 3.7V was C2mAh / g, and C1 / C0 and C2 / C0 were calculated. The results are shown in Table 2.

[0103] The positive electrode active materials provided in Examples 1 to 22 and Comparative Examples 1 to 2 are amplified by a certain amount, and then mixed with conductive carbon black and PVDF in a weight ratio of 96:2:2, and dispersed in a solvent to prepare a positive electrode active layer slurry. The slurry is applied to the surface of a positive electrode aluminum collector, and rolled according to the compaction density shown in Table 2 to prepare a positive electrode sheet. The positive electrode sheet is subjected to CP treatment, and then an SEM imaging test is performed. When the amplification factor is 5000 (i.e., the sampling area is 25 μm*25 μm), the particle number N of the positive electrode active material with a / b≧3 is calculated, and the statistical result is shown in Table 2.

[0104] The positive electrode sheet is assembled with the negative electrode sheet, a separator and an electrolyte to obtain a lithium-ion battery, and the negative electrode sheet is manufactured by mixing artificial graphite, styrene-diene rubber (SBR), sodium carboxymethyl cellulose and conductive carbon black in a weight ratio of 94:3:2:1, dispersing the mixture in water, and mixing with a revolution-rotation mixer to obtain a negative electrode active layer slurry, which is then applied to the negative electrode copper current collector to obtain the negative electrode sheet.

[0105] The electrolyte contains an organic solvent including ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC) and fluoroethylene carbonate (FEC) and an additive having the structure: [ka]

[0106] Next, the cycle performance of the lithium-ion battery was tested, and the cycle performance test process was as follows: at 25°C, constant current charging at a charge rate of 1C to 4.50V, constant voltage charging at a charge rate of 0.05C to 4.50V, and then discharging at a discharge rate of 1C to 3.0V, and this charge / discharge cycle was repeated 500 times, and the discharge capacity at the first cycle and the discharge capacity at the 500th cycle were measured, and the capacity retention rate after cycling was calculated as follows: Capacity retention rate after cycling = (Discharge capacity at the 500th cycle) / (Discharge capacity at the first cycle) * 100%, and the results are shown in Table 2.

[0107] [Table 2-1] [Table 2-2]

[0108] As can be seen from Table 2, the positive electrode sheet made by the positive electrode active material provided by the present invention can be applied to high compaction density, and due to the accordion laminated structure of the positive electrode sheet, the particle number N that satisfies a / b≧3 within the same region is significantly increased, the particle regularity of the positive electrode active material is improved, and with the increase in the content of doping element, the particle number that satisfies this condition is also significantly increased; as can be seen from Examples 13 to 22, with the increase in the content of doping element in the positive electrode active material, the particle number N is also increased, and the particle regularity is significantly improved, which is helpful to improve the cycle performance of lithium-ion batteries.

[0109] As can be seen from Table 2, the capacity per gram of the positive electrode active material provided by the present invention is significantly increased, specifically, C1 / C0≧9%, C2 / C0≧25%, which explains that the positive electrode active material with special structure provided by the present invention has more charge / discharge platforms and can achieve higher capacity per gram. In addition, because the positive electrode active material has a lower platform voltage, it has very good structural stability, so that the capacity retention rate after 500 cycles of the lithium ion battery is all above 80%, and it has good cycle performance under high voltage.

[0110] In summary, the positive electrode active material provided by the present invention enables a lithium ion battery to have a high discharge capacity per gram and excellent cycle performance at high voltage, and to meet the requirement for thin lithium ion batteries.

[0111] Finally, it should be understood that the above embodiments are only used to explain the technical solutions of the present invention, and are not limiting. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art may modify the technical solutions described in the above embodiments or make equivalent substitutions for part or all of the technical features, and such modifications or substitutions do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. [Explanation of symbols]

[0112] 100… Positive current collector 200… Positive electrode active material

Claims

1. A positive electrode sheet, the positive electrode sheet including a positive electrode current collector and a positive electrode active layer including a positive electrode active material and provided on at least one surface of the positive electrode current collector; In a plane consisting of the longitudinal direction and thickness direction of the positive electrode sheet, the longest distance of the particles of the positive electrode active material in the longitudinal direction of the positive electrode sheet is denoted by a, the longest distance of the particles of the positive electrode active material in the thickness direction of the positive electrode sheet is denoted by b, and the number of particles of the positive electrode active material that satisfies a / b≧3 within any region of 25 μm×25 μm or more is denoted by N, where N≧2; The positive electrode active material is Li ｎ－ｘ Na ｘ Co １－ｙ Me ｙ O ２ (0.70≦n≦1, 0<x≦0.15, 0≦y≦0.15, and Me is one or more selected from Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, W, Sc, Ce, P, Nb, V, Ta, and Te); the X-ray diffraction pattern of the positive electrode active material has a 002 peak corresponding to a 002 crystal plane, a 102 peak corresponding to a 102 crystal plane, and a 103 peak corresponding to a 103 crystal plane; The diffraction angle 2θ of the 002 crystal plane is 18.6°±0.5°, the diffraction angle 2θ corresponding to the 102 peak is 41.7°±0.5°, and the diffraction angle 2θ corresponding to the 103 peak is 47.1°±0.5°, The X-ray diffraction pattern of the positive electrode active material has a 101 peak corresponding to a 101 crystal plane and a 004 peak corresponding to a 004 crystal plane, and the peak intensity ratio of the 101 peak to the 004 peak is m, m being ≧1.5; The positive electrode sheet, wherein the positive electrode active material has a conductivity of ≧1E −4 S / cm under an applied force of ≧4 KN, and a compaction density of ≧3.75 g / cm 3 under an applied force of ≧30 KN.

2. 2. The positive electrode sheet according to claim 1, wherein the particle size of the positive electrode active material is 6 to 18 μm.

3. The compaction density of the positive electrode sheet is ≧4.0 g / cm ３ The positive electrode sheet according to claim 1 ,

4. A battery comprising the positive electrode sheet according to any one of claims 1 to 3.

5. An electronic device comprising the battery according to claim 4.

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