Positive electrode material for lithium ion battery and application

Abstract

To provide a positive electrode material for a lithium ion battery, in which drop of a capacity in a cycle of a lithium ion battery material, and the like can be prevented.SOLUTION: A positive electrode material of the invention has a porous structure, In which pore volume of mesoporous with pore diameter of 2 to 20 nm accounts for 90% or more of total pore volume. The positive electrode material is manufactured by sintering at least two times and crushing at least two times the raw material after mixing. Compared with conventional lithium-ion battery positive electrode materials, the lithium-ion battery positive electrode material of the present invention contains mainly mesopores, the pore diameter of the mesopores is mainly in a range of 2 to 20nm, there are hardly large pores inside the particles, a distribution of pores between particles is relatively reasonable, which can provide a channel for lithium ion transmission, thereby a high capacity can be provided and also an increase in impedance during a battery cycle is relatively small.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion batteries, and relates to a cathode material for lithium-ion batteries, a manufacturing method thereof, and uses thereof.

Background Art

[0002] In 2019, the new energy market underwent dramatic changes. With the continuous increase in electric vehicles, the needs for the energy density and cost-effectiveness of lithium-ion batteries have been on the rise. Among them, cobalt is a scarce resource in the lithium-cobalt-nickel-manganese ternary cathode material, and its price is high. Therefore, in order to improve the cost-effectiveness and ensure a high energy density, the content of nickel or manganese elements is appropriately increased to reduce the usage amount of cobalt. Increasing the nickel content can provide a high-capacity battery. However, when the nickel content increases, the structure of the material becomes unstable, it is easy to react with the electrolyte solution, and cracks occur in the cathode material due to repeated charge and discharge, shortening the cycle life of the lithium-ion battery, increasing the impedance, and reducing the capacity. Therefore, it is urgent to develop new materials or find new materials to replace cobalt, which is a scarce resource, or reduce the usage amount of cobalt in the material.

[0003] Chinese Patent CN102280636A discloses a cathode active material, a manufacturing method thereof, and a lithium secondary battery including the same. The cathode active material of the lithium secondary battery is obtained by preparing a precursor by a coprecipitation method and then mixing it with a lithium source and performing a firing process. The material includes pores having an average diameter of about 10 nm to about 60 nm, and the porosity of the material is about 0.5% to about 20%. Since the material has good particle strength, crushing after pressing is prevented or reduced. Since the material is difficult to react with the electrolyte and exhibits good thermal stability, it is possible to provide a high-capacity lithium secondary battery. However, the chemical formula of the material Li a Ni x Co y Mn z M kAs can be seen from O2 (where 0.45 ≦ x ≦ 0.65, 0.15 ≦ y ≦ 0.25, 0.15 < z ≦ 0.35), the cobalt content of the material is high and the capacity is insufficient, so the cost-effectiveness cannot meet the requirements.

[0004] Chinese Patent CN108123119A discloses a nickel-based active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including a positive electrode including the same. In this patent, a mixture of a lithium precursor and a metal hydroxide is heat-treated at a low temperature and then at a high temperature in an oxygen atmosphere to obtain a nickel-based active material. The material includes secondary particles including aggregates of two or more plate-like primary particles, and at least a part of the secondary particles includes a structure in which the plate-like primary particles are arranged radially. It is described that the outside of the secondary particles has a higher porosity (pore rate) than the inside of the secondary particles. However, this patent does not mention which field of problems is improved.

[0005] Chinese Patent CN1856890 discloses lithium composite oxide particles for a lithium secondary battery positive electrode material, a lithium secondary battery positive electrode using the particles, and a lithium secondary battery. This patent discloses lithium composite oxide particles for a lithium secondary battery electrode material and explains that it can improve the low-temperature load characteristics of the battery and the coating property in the manufacture of the positive electrode. The material must satisfy the following condition (A) in the measurement using the mercury intrusion method and at the same time satisfy at least one of the following conditions (B) and condition (C). Condition (A): In the mercury intrusion curve, when the pressure increases from 50 MPa to 150 MPa, the mercury intrusion volume is 0.02 cm 3 / g or less. Condition (B): In the mercury intrusion curve, when the pressure increases from 50 MPa to 150 MPa, the mercury intrusion volume is 0.01 cm 3 / g or more. Condition (C): The average pore radius is 10 - 100 nm, and the pore size distribution curve has a main peak with the upper end located at a pore radius of 0.5 - 50 μm and a sub-peak with the upper end located at a pore radius of 80 - 300 nm. This patent mainly focuses on low-temperature characteristics and does not consider high-temperature characteristics.

[0006] Chinese Patent CN104272520A discloses a non-aqueous electrolyte secondary battery and a method for manufacturing the same. In this patent, the positive electrode composite material layer constituting the positive electrode of the non-aqueous electrolyte secondary battery has, in the pore size distribution curve measured by a mercury porosimeter, a peak A of differential pore volume in the range of pore diameters from 0.05 μm to 2 μm and a peak B located on the smaller pore diameter side than the peak A. The pore size distribution curve has a minimum point C where the differential pore volume is at a minimum value between the peak A and the peak B. The differential pore volume X of the peak A A and the differential pore volume X of the peak B B Among them, the larger differential pore volume X of the two differential pore volumes L The differential pore volume X of the minimum point C C The ratio (X C / X L ) is described as being 0.6 or more. This patent mainly reduces problems such as gas generation in the battery by adding an overcharge additive in the process of manufacturing the battery.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The technical problem to be solved by the present invention is that in the prior art, since the pore diameter of the positive electrode material is too large, most of it is macroporous material. Due to the existence of macropores, the migration path of lithium ions is too long, so the lithium-ion battery cannot provide a high capacity. Moreover, in the process of repeatedly charging and discharging the lithium-ion battery, cracks occur in the positive electrode material particles, resulting in a decrease in the capacity of the lithium-ion battery during cycling, an increase in the internal resistance, and gas generation.

[0008] The present invention provides a cathode material for a lithium-ion battery in view of the drawbacks of the prior art. The cathode material contains mesopores with small diameters. These mesopores provide more paths for the movement of lithium ions and the paths are short. Therefore, the lithium-ion battery not only has a higher capacity, but also the cathode material for the lithium-ion battery manufactured by the method of the present invention hardly generates cracks in the cathode material during the charge and discharge process of the lithium-ion battery. Thus, problems such as capacity degradation during cycling of the lithium-ion battery material are prevented. The present invention further provides a method for manufacturing the cathode material for the lithium-ion battery and a lithium-ion battery including the cathode material for the lithium-ion battery. Furthermore, the present invention provides the use of the cathode material for the lithium-ion battery or the lithium-ion battery in the fields of digital batteries, power batteries or storage batteries.

Means for Solving the Problems

[0009] The technical solution of the present invention is as follows. The present invention provides a cathode material for a lithium-ion battery. The cathode material has a porous structure, and the pore volume of mesopores with pore diameters of 2 - 20 nm accounts for more than 90% of the total pore volume.

[0010] Preferably, the volume of pores with pore diameters of 3 - 20 nm accounts for more than 60% of the total volume of mesopores. Preferably, the volume of pores with pore diameters of 5 - 19 nm accounts for more than 40% of the total volume of mesopores.

[0011] Preferably, the specific surface area of the cathode material is 0.25 - 1.5 m 2 / g. Preferably, the Dv50 particle size of the cathode material is 2.00 - 6.00 μm. More preferably, the total amount of free lithium in the cathode material is less than 2000 ppm.

[0012] Preferably, the cathode material contains lithium element, nickel element and manganese element, and the content of nickel element in the cathode material is greater than the content of manganese element.

[0013] Preferably, the positive electrode material contains an elemental composition represented by Chemical Formula 1, wherein Chemical Formula 1 is 1+a Li x Ni y Mn z Co m A O2, provided that 0 ≤ a ≤ 0.25, 0.5 < x ≤ 0.97, 0 < y ≤ 0.42, 0 ≤ z ≤ 0.09, 0 ≤ m ≤ 0.03,

[0014] The present invention further provides a method for manufacturing the positive electrode material for a lithium ion battery, including a step of performing at least two firings and two grindings after mixing raw materials.

[0015] Preferably, the first firing temperature is 750 to 980 °C, the firing time is 8 to 40 hours, the second firing temperature is 650 to 920 °C, the firing time is 5 to 20 hours, and preferably, the firing atmosphere is air, oxygen, or a mixed gas of air and oxygen.

[0016] Preferably, the method for manufacturing the positive electrode material for a lithium ion battery further includes step (1) of mixing the ground material with a metal A source, and step (2) of firing and grinding the mixture of step (1).

[0017] Preferably, in step (2), the firing temperature is 300 to 780 °C, the firing time is 3 to 14 hours, and more preferably, the firing atmosphere is air, oxygen, or a mixed gas of air and oxygen.

[0018] Preferably, in the manufacturing method, the Li source is a lithium-containing oxide, a lithium-containing fluoride, or a lithium-containing salt. Preferably, the Li source is selected from one or more of anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, lithium acetate, and lithium fluoride.

[0019] The present invention further provides a positive electrode material for a lithium-ion battery manufactured by the manufacturing method.

[0020] The present invention further provides a lithium-ion battery positive electrode including a current collector and a positive electrode material supported on the current collector, wherein the positive electrode material is the positive electrode material for a lithium-ion battery.

[0021] The present invention further provides a lithium-ion battery including a positive electrode, a negative electrode, and a lithium salt-containing electrolyte, wherein the positive electrode is the lithium-ion battery positive electrode.

[0022] The present invention further provides the use of the positive electrode material for a lithium-ion battery, the lithium-ion battery positive electrode, or the lithium-ion battery in the fields of digital batteries, power batteries, or storage batteries.

Advantages of the Invention

[0023] The beneficial effects of the present invention are as follows. Compared with the conventional cathode material for lithium-ion batteries, the pores contained in the cathode material for lithium-ion batteries of the present invention are mainly mesopores, and the pore diameters of the mesopores are mainly in the range of 2 to 20 nm, and the percentage of the pore volume of the mesopores in the range of 2 to 20 nm in the total pore volume exceeds 90%. There are almost no macropores inside the particles, and the structure of the particles is relatively stable. Since the particles do not break even after repeated charge and discharge, it has good cycle characteristics. The pore distribution between the particles is relatively reasonable and can provide a channel for the transport of lithium ions. Therefore, it can provide a high capacity and the increase in impedance during the cycle of the battery is relatively small. If it exceeds the above range, the transport distance of lithium ions increases, the capacity decreases, and the impedance increases rapidly.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0025] In order to make the objectives, technical solutions and technical effects of the embodiments of the present invention clearer, the technical solutions according to the embodiments of the present invention will be clearly and completely described. The embodiments described below are not all the embodiments of the present invention, but are only a part of the embodiments of the present invention. If those skilled in the art obtain other embodiments from the embodiments of the present invention without performing any novel work, all of them belong to the protection scope of the present invention.

[0026] In the description of the present invention, the pore size distribution refers to the change in the ratio of the volume of pores with different pore sizes to the total pore volume with respect to the pore size.

[0027] In the description of the present invention, mesopores refer to pores with a pore size of 2 to 50 nm, that is, pores with a pore size of 2 nm or more and 50 nm or less. Micropores are pores with a pore size of less than 2 nm, and macropores are pores with a pore size exceeding 50 nm.

[0028] Hereinafter, in order to better understand the above technical solution, the present invention will be described in more detail.

[0029] The present invention provides a cathode material for a lithium-ion battery. The cathode material has a porous structure, and the pore volume of mesopores with a pore size of 2 to 20 nm accounts for 90% or more of the total pore volume.

[0030] In a preferred embodiment of the present invention, the volume of pores with a pore size of 3 to 20 nm accounts for 60% or more of the total volume of mesopores. Preferably, the volume of pores with a pore size of 5 to 19 nm accounts for 40% or more of the total volume of mesopores.

[0031] In another preferred embodiment of the present invention, the specific surface area of the cathode material is 0.25 to 1.5 m 2 / g. Preferably, the Dv50 particle size of the cathode material is 2.00 to 6.00 μm, and more preferably, the total amount of free lithium in the cathode material is less than 2000 ppm.

[0032] In another preferred embodiment of the present invention, the cathode material contains lithium element, nickel element and manganese element, and the content of nickel element in the cathode material is greater than the content of manganese element.

[0033] In another preferred embodiment of the present invention, the cathode material contains an element composition represented by Chemical Formula 1, wherein Chemical Formula 1 is Li 1+a Ni x Mn y Coz A m is O₂, provided that 0 ≦ a ≦ 0.25, 0.5 < x ≦ 0.97, 0 < y ≦ 0.42, 0 ≦ z ≦ 0.09, and 0 ≦ m ≦ 0.03. However, A is selected from one or more elements of Mn, Co, Al, Zr, Y, Rb, Cs, W, Ce, Mo, Ba, Ti, Mg, Ta, Nb, Ca, V, Sc, Sr, and B, or selected from phosphorus-containing compounds containing at least one element of Ti, Al, Mg, Zr, La, and Li.

[0034] The present invention further provides a method for manufacturing the positive electrode material for a lithium ion battery, including the step of performing at least two firings and two grindings after mixing the raw materials. However, the first firing temperature is 750 to 980 °C, the firing time is 8 to 40 hours, the second firing temperature is 650 to 920 °C, the firing time is 5 to 20 hours, and preferably, the firing atmosphere is air, oxygen, or a mixed gas of air and oxygen.

[0035] In a preferred embodiment of the present invention, the method for manufacturing the positive electrode material for a lithium ion battery further includes step (1) of mixing the ground substance with a metal A source, and step (2) of firing and grinding the mixture of step (1). However, in step (2), the firing temperature is 300 to 780 °C, the firing time is 3 to 14 hours, and more preferably, the firing atmosphere is air, oxygen, or a mixed gas of air and oxygen.

[0036] In another preferred embodiment of the present invention, in the manufacturing method, the Li source is a lithium-containing oxide, a lithium-containing fluoride, or a lithium-containing salt, and preferably, the Li source is selected from one or more of anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, lithium acetate, and lithium fluoride.

[0037] The present invention further provides a positive electrode material for a lithium-ion battery manufactured by the above manufacturing method.

[0038] In another preferred embodiment of the present invention, the positive electrode material for a lithium-ion battery of the present invention is manufactured from a manufacturing method including steps of performing at least two firings and two grindings after mixing raw materials. Preferably, in the positive electrode material for a lithium-ion battery of the present invention, the first firing temperature is 750 to 980 °C, the firing time is 8 to 40 hours, the second firing temperature is 650 to 920 °C, and the firing time is 5 to 20 hours.

[0039] Preferably, in the positive electrode material for a lithium-ion battery of the present invention, the manufacturing method of the positive electrode material for a lithium-ion battery further includes step (1) of mixing the material after grinding with a metal A source, step (2) of firing and grinding the mixture of step (1). Preferably, in the positive electrode material for a lithium-ion battery of the present invention, in step (2), the firing temperature is 300 to 780 °C and the firing time is 3 to 14 hours.

[0040] The present invention further provides a lithium-ion battery positive electrode including a current collector and a positive electrode material supported on the current collector, and the positive electrode material is the positive electrode material for a lithium-ion battery.

[0041] The present invention further provides a lithium-ion battery including a positive electrode, a negative electrode, and a lithium salt-containing electrolyte, characterized in that the positive electrode is the lithium-ion battery positive electrode.

[0042] The lithium-ion battery of the present invention further includes a separator and an aluminum laminate film. Specifically, its electrodes include a positive electrode and a negative electrode. The positive electrode is made of materials such as a positive electrode current collector, a positive electrode active material coated on the positive electrode current collector, an adhesive, and a conductive assistant. The positive electrode active material is the positive electrode material for the lithium-ion battery. The negative electrode is made of materials such as a current collector, a negative electrode active material coated on the current collector, an adhesive, and a conductive assistant. The separator is a PP / PE film generally used in the industry to isolate the positive electrode and the negative electrode from each other. The aluminum laminate film is a coating material for the positive electrode, the negative electrode, the separator, and the electrolyte.

[0043] The adhesive includes polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, poly(vinylidene fluoride), polyethylene, polypropylene, styrene-butadiene rubber, acrylate esterified styrene-butadiene rubber, epoxy resin, nylon, etc., and combinations thereof. Its role is to improve the adhesiveness between the positive electrode active material particles and between the positive electrode active material particles and the current collector.

[0044] The conductive assistant includes one or more of a carbon-based material, a metal-based material, and a conductive polymer. The carbon-based material is one or more of natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, and carbon fiber. The metal-based material is a metal powder or metal fiber of copper, nickel, aluminum, or silver. The conductive polymer is a polyphenylene derivative.

[0045] The present invention further provides the use of the positive electrode material for the lithium-ion battery, or the positive electrode of the lithium-ion battery, or the lithium-ion battery in the fields of digital batteries, power batteries, or storage batteries.

[0046] Hereinafter, the beneficial effects of the present invention will be further described with specific examples.

[0047] The information on the reagents and equipment used in the following examples is as shown in Table 1-1, Table 1-2 and Table 2.

[0048]

Table 1-1

[0049]

Table 1-2

[0050]

Table 2

[0051] (Example 1) Mixing of raw materials: Using a 200L plowshear mixer, start it and stir, add 46.11 kg of lithium hydroxide monohydrate, 0.256 kg of nano titanium dioxide and 100.0 kg of nickel-manganese precursor Ni 0.68 Mn 0.32 (for battery use, purchased from Guangdong Jiana Energy Technology Co., Ltd.) and stir for 2 hours in preparation for use. First firing: Using a 36-meter roller hearth kiln, set the firing temperature to 930 °C, flow in a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8 L / min), put the mixed raw materials into the device and conduct the first firing, set the constant temperature to 20 hours, cool the raw materials to room temperature, and grind them with a jet mill to obtain the semi-finished product of the first firing. Second firing: Using a 36-meter roller hearth kiln, set the firing temperature to 800 °C, flow in a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8 L / min), put the semi-finished product of the first firing into the 36-meter roller hearth kiln and conduct the second firing, set the constant temperature to 8 hours, cool the raw materials to room temperature, grind them with a jet mill, and then demagnetize them to obtain the semi-finished product of the second firing. Second mixing: The semi-finished product after the second firing was put into a mixer, started and stirred, and then 0.248 kg of nano-titanium dioxide was added and mixed for 30 minutes. Third firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 750 °C, and a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8 L / min) was introduced. The raw materials after the second mixing were put into the 36-meter roller hearth kiln for the third firing, with a constant temperature of 6 hours. The raw materials were cooled to room temperature, pulverized by a jet mill, demagnetized, and sieved to obtain the cathode material.

[0052] Digested with dilute hydrochloric acid and verified by ICP analysis, the chemical formula of the cathode material is LiNi 0.68 Mn 0.32 Ti 0.0063 O2.

[0053] (Example 2) Mixing of raw materials: Using a 200L plowshear mixer, start and stir, add 45.87 kg of lithium hydroxide monohydrate, 100 kg of nickel-manganese-cobalt precursor Ni 0.65 Co 0.1 Mn 0.25 (OH)2 (for batteries, purchased from Guizhou Zhongwei Zhengyuan New Materials Co., Ltd.) and stir for 2 hours in preparation for use. First firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 940 °C, and a mixed gas of air and oxygen (oxygen content 55%, gas flow rate 6 L / min) was introduced. The mixed raw materials were put into the device for the first firing, with a constant temperature of 13 hours. The raw materials were cooled to room temperature, pulverized by a jet mill to obtain the semi-finished product after the first firing. Second firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 850 °C, and a mixed gas of air and oxygen (oxygen content 55%, gas flow rate 6 L / min) was introduced. The semi-finished product after the first firing was put into the 36-meter roller hearth kiln for the second firing, with a constant temperature of 14 hours. The raw materials were cooled to room temperature, pulverized by a jet mill, and then demagnetized to obtain the semi-finished product after the second firing. Second mixing: The semi-finished product after the second firing was put into a mixer, started and stirred, and 4.43 kg of strontium carbonate was added to a 36-meter roller hearth kiln and mixed for 30 minutes. Third firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 780 °C, a mixed gas of air and oxygen (oxygen content 55%, gas flow rate 6 L / min) was introduced, and the raw materials after the second mixing were put into the 36-meter roller hearth kiln for the third firing. The constant temperature was set for 7 hours, the raw materials were cooled to room temperature, pulverized by a jet mill, demagnetized, and sieved to obtain a cathode material.

[0054] Digested with dilute hydrochloric acid and verified by ICP analysis, the chemical formula of the cathode material is LiNi 0.65 Co 0.1 Mn 0.25 Sr 0.03 O2.

[0055] (Example 3) Mixing of raw materials: Using a 200L plowshear mixer, start and stir, add 29.8 kg of anhydrous lithium hydroxide, 0.377 kg of aluminum oxide, and 100 kg of nickel-manganese precursor Ni 0.97 Mn 0.03 (OH)2 (for batteries, purchased from Guangdong Jiana Energy Technology Co., Ltd.) and stir for 2 hours in preparation for use. First firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 750 °C, oxygen (gas flow rate 10 L / min) was introduced, and the mixed raw materials were put into the device for the first firing. The constant temperature was set for 40 hours, the raw materials were cooled to room temperature, and pulverized by a jet mill to obtain a semi-finished product after the first firing. Second firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 650 °C, oxygen (gas flow rate 10 L / min) was introduced, and the semi-finished product after the first firing was put into the 36-meter roller hearth kiln for the second firing. The constant temperature was set for 5 hours, the raw materials were cooled to room temperature, pulverized by a jet mill, and then demagnetized to obtain a semi-finished product after the second firing. Second mixing: The semi-finished product after the second firing was put into a stirring tank, started and stirred, 200 kg of deionized water was added, and 0.614 kg of zirconium tetra-n-butoxide solution was added, and mixed for 50 minutes, and then filtered to obtain a cake. Third firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 550 °C, oxygen (oxygen flow rate 10 L / min) was introduced, the cake after the second mixing was put into the 36-meter roller hearth kiln for the third firing, the constant temperature was 4 hours, the raw material was cooled to room temperature, pulverized by a jet mill, demagnetized and sieved to obtain a cathode material.

[0056] Digested with dilute hydrochloric acid and verified by ICP analysis, the chemical formula of the cathode material is Li 1.15 Ni 0.97 Mn 0.03 Al 0.0037 Zr 0.0016 O2.

[0057] (Example 4) Mixing of raw materials: Using a 200 L plowshare mixer, start and stir, add 51.97 kg of lithium hydroxide monohydrate, 0.244 kg of boron oxide, 100 kg of nickel-manganese-cobalt precursor Ni 0.78 Co 0.07 Mn 0.15 (OH)2 (for batteries, Jingmen Greenway New Materials Co., Ltd.) was added and stirred for 2 hours in preparation for use. First firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 880 °C, oxygen (gas flow rate 8 L / min) was introduced, the mixed raw material was put into the device for the first firing, the constant temperature was 25 hours, the raw material was cooled to room temperature, pulverized by a jet mill to obtain a semi-finished product after the first firing. Second firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 800 °C, oxygen (gas flow rate 8 L / min) was introduced, the semi-finished product after the first firing was put into the 36-meter roller hearth kiln for the second firing, the constant temperature was 6 hours, the raw material was cooled to room temperature, pulverized by a jet mill, and then demagnetized to obtain a semi-finished product after the second firing. Second mixing: The semi-finished product after the second firing was put into a mixer, started and stirred, 0.104 kg of boron oxide was added, and mixed for 40 minutes. Third firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 500 °C, oxygen (gas flow rate 8 L / min) was introduced, the raw material after the second mixing was put into the 36-meter roller hearth kiln for the third firing, the constant temperature was 8 hours, the raw material was cooled to room temperature, pulverized by a jet mill, demagnetized, sieved, and the cathode material Li 1.14 Ni 0.78 Co 0.07 Mn 0.15 B 0.01 O2 was obtained.

[0058] Digested with dilute hydrochloric acid and verified by ICP analysis, the chemical formula of the cathode material is Li 1.14 Ni 0.77 Co 0.07 Mn 0.15 B 0.01 O2.

[0059] (Example 5) Mixing of raw materials: Using a 200 L plowshare mixer, started and stirred, 48.46 kg of lithium hydroxide monohydrate, 100 kg of nickel-manganese-cobalt precursor Ni 0.79 Co 0.02 Mn 0.19 (OH)2 (for batteries, Guangdong Jiana Energy Technology Co., Ltd.) was added and stirred for 2 hours in preparation for use. First firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 860 °C, oxygen (gas flow rate 7 L / min) was introduced, the mixed raw material was put into the apparatus for the first firing, the constant temperature was 25 hours, the raw material was cooled to room temperature, pulverized by a jet mill to obtain a semi-finished product after the first firing. Second firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 780 °C, oxygen (gas flow rate 7 L / min) was introduced, the semi-finished product after the first firing was put into the 36-meter roller hearth kiln for the second firing, the constant temperature was 7 hours, the raw material was cooled to room temperature, pulverized by a jet mill, and then demagnetized to obtain a semi-finished product after the second firing. Second mixing: The semi-finished product after the second firing was put into a stirring tank, started and stirred. 80 kg of deionized water was added and stirred for 30 minutes. Immediately after that, a solution containing phosphorus and aluminum elements was added (first, 0.23 kg of aluminum sulfate was weighed and dissolved in 2 kg of deionized water, and then 0.165 kg of ammonium dihydrogen phosphate was weighed and dissolved in 5 kg of deionized water), and mixed for 40 minutes, followed by filtration to obtain a cake. Third firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 300 °C, air (air flow rate 15 L / min) was introduced, the cake after the second mixing was put into the 36-meter roller hearth kiln for the third firing, with a constant temperature of 14 hours. The raw material was cooled to room temperature, ground by a jet mill, demagnetized and sieved to obtain the cathode material.

[0060] Digested with dilute hydrochloric acid and verified by ICP analysis, the chemical formula of the cathode material is Li 1.06 Ni 0.79 Co 0.02 Mn 0.19 Al 0.0013 P 0.0013 O2.

[0061] (Example 6) Mixing of raw materials: Using a 200 L plowshear mixer, started and stirred, 43.24 kg of lithium carbonate and 100 kg of nickel-manganese-cobalt hydroxide precursor Ni 0.62 Co 0.03 Mn 0.35 (for batteries, purchased from Guangdong Jiana Energy Technology Co., Ltd.) was added and stirred for 2 hours in preparation for use. First firing: Using a 36-meter roller hearth kiln, the firing temperature was set at 970 °C, air (air flow rate 15 L / min) was introduced, the mixed raw material was put into the device for the first firing, with a constant temperature of 8 hours. The raw material was cooled to room temperature and ground by a jet mill to obtain the semi-finished product after the first firing. Second firing: Using a 36-meter roller hearth kiln, set the firing temperature to 910 °C, introduce air (air flow rate 15 L / min), put the semi-finished product from the first firing into the 36-meter roller hearth kiln for the second firing, set the isothermal time to 20 hours, cool the raw material to room temperature, grind it with a jet mill, and then demagnetize it to obtain the cathode material. Digest with dilute hydrochloric acid and verify by ICP analysis. The chemical formula of the cathode material is Li 1.08 Ni 0.62 Co 0.03 Mn 0.35 O2.

[0062] (Example 7) Mixing of raw materials: Using a 200L plowshare mixer, start it and stir, add 43.24 kg of lithium carbonate, 100 kg of nickel-manganese-cobalt precursor Ni 0.62 Co 0.03 Mn 0.35 (OH)2 (for batteries, Guangdong Jiana Energy Technology Co., Ltd.), stir for 2 hours in preparation for use. First firing: Using a 36-meter roller hearth kiln, set the firing temperature to 970 °C, introduce air (air flow rate 15 L / min), put the mixed raw materials into the device for the first firing, set the isothermal time to 8 hours, cool the raw material to room temperature, and sieve it to obtain the cathode material.

[0063] Digest with dilute hydrochloric acid and verify by ICP analysis. The chemical formula of the cathode material is Li 1.08 Ni 0.62 Co 0.03 Mn 0.35 O2.

[0064] (Example 8) Mixing of raw materials: Using a 200L plowshare mixer, start it and stir, add 46.96 kg of lithium hydroxide monohydrate, 0.256 kg of nano-titanium dioxide, 100.0 kg of nickel-manganese precursor Ni 0.4 Mn 0.6 (OH)2 (for batteries, Guangdong Jiana Energy Technology Co., Ltd.), stir for 2 hours in preparation for use. First firing: Using a 36-meter roller hearth kiln, set the firing temperature to 930 °C, flow in a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8 L / min), put the mixed raw materials into the device for the first firing, set the constant temperature for 20 hours, cool the raw materials to room temperature, and grind them with a jet mill to obtain the semi-finished product of the first firing. Second firing: Using a 36-meter roller hearth kiln, set the firing temperature to 800 °C, flow in a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8 L / min), put the semi-finished product of the first firing into the 36-meter roller hearth kiln for the second firing, set the constant temperature for 8 hours, cool the raw materials to room temperature, grind them with a jet mill, and then demagnetize them to obtain the semi-finished product of the second firing. Second mixing: Put the semi-finished product of the second firing into a mixer, start it and stir, and add 0.248 kg of nano titanium dioxide and mix for 30 minutes. Third firing: Using a 36-meter roller hearth kiln, set the firing temperature to 750 °C, flow in a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8 L / min), put the raw materials after the second mixing into the 36-meter roller hearth kiln for the third firing, set the constant temperature for 6 hours, cool the raw materials to room temperature, grind them with a jet mill, demagnetize and sieve them to obtain the cathode material.

[0065] Digest with dilute hydrochloric acid and verify by ICP analysis. The chemical formula of the cathode material is LiNi 0.4 Mn 0.6 Ti 0.0063 O2.

[0066] (Test Example 1) For Examples 1 to 8 by the following method, the pore size distribution curve, specific surface area, particle size and total free lithium content were measured.

[0067] (1) Method for measuring the pore size distribution curve The desorption isotherm was measured using an automatic specific surface area and pore size distribution analyzer (TriStarII 3020). Next, using the desorption isotherm, the pore size distribution curve was calculated by the BJH method, with the horizontal axis representing the pore diameter and the vertical axis representing the pore volume ratio (the ratio of the volume of pores with different mesopore diameters to the total volume of mesopores). The results are shown in Figures 1 to 4. The ratios when the pore diameter is 2 to 20 nm (the ratio of the volume of pores with a pore diameter of 2 to 20 nm to the total pore volume), when the pore diameter is 3 to 20 nm (the ratio of the volume of pores with a pore diameter of 3 to 20 nm to the total mesopore volume), and when the pore diameter is 5 to 19 nm (the ratio of the volume of pores with a pore diameter of 5 to 19 nm to the total mesopore volume) are as shown in Table 3.

[0068] (2) Method for measuring specific surface area In the present invention, the specific surface area was measured using an automatic specific surface area and pore size distribution analyzer (TriStarII 3020) with reference to the gravimetric method of the gas adsorption BET method of GB / T 19587-2004. The test results are as shown in Table 3.

[0069] (3) Method for measuring particle size In the present invention, the particle size was measured using a Malvern Master Size 2000 laser particle size distribution analyzer with reference to the laser diffraction method for particle size distribution analysis of GB / T19077-2016. The test results are as shown in Table 3.

[0070] (4) Method for measuring total free lithium content Accurately weigh a 30 g ± 0.01 g sample, add the sample to a 250 mL Erlenmeyer flask, place a magnetic stirrer in it, and add 100 mL of deionized water. Place the Erlenmeyer flask on the magnetic stirrer, start the device, and stir for 30 minutes. Filter the mixed solution with qualitative filter paper and a funnel. Take out 50 mL of the filtrate with a 50 mL pipette and add it to a 100 mL beaker, and place a stir bar in it. Place the beaker on the magnetic stirrer, and add 2 drops of phenolphthalein indicator. Titrate with 0.05 mol / L hydrochloric acid standard solution until the color of the solution changes from red to colorless, and record the volume V1 (endpoint 1) of the 0.05 mol / L hydrochloric acid standard solution. Add 2 drops of methyl red indicator, and the color of the indicator changes from colorless to yellow. Titrate with 0.05 mol / L hydrochloric acid standard solution until the color of the solution changes from yellow to orange. Place the beaker on a heating furnace and heat until the solution boils (the color of the solution changes from orange to yellow). Remove the beaker and cool it to room temperature. Further place the beaker on the magnetic stirrer, and titrate with 0.05 mol / L hydrochloric acid standard solution until the color of the solution changes from yellow to light red, and record the volume V2 (endpoint 2) of the 0.05 mol / L hydrochloric acid standard solution. Calculate the total amount of free lithium according to the following formula, and the test results are as shown in Table 3.

[0071] Total amount of free lithium = V2 × 0.05 × 6.94 × 2 × 100% / (m × 1000), In the formula, the unit of the total amount of free lithium is mass percentage (%), m is the mass of the sample, and the unit is g, V2 is the second titration endpoint, and the unit is mL, 6.94 is the atomic weight of lithium.

[0072]

Table 3

[0073] (Test Example 2) Manufacture and performance evaluation of lithium-ion batteries: Manufacture the pouch cell 454261 by the following method. Manufacture of the positive electrode: The positive electrode material of the present invention, conductive carbon black (S.P), and adhesive polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) at a weight ratio of 94:3:3 (the weight ratio of the positive electrode material to NMP was 2.1:1), and thoroughly mixed and stirred to form a uniform slurry. The slurry was coated on an aluminum foil current collector, dried, and pressed to obtain a positive electrode plate.

[0074] Manufacture of the negative electrode: Artificial graphite for the negative electrode, conductive carbon black (S.P), carboxymethyl cellulose (CMC), and adhesive (SBR) were added to a sufficient amount of pure water at a weight ratio of 95:1:1:3, mixed, and stirred to form a uniform slurry. The slurry was coated on a copper foil current collector, dried, and pressed to obtain a negative electrode plate.

[0075] The separator was a PP / PE composite film material. After spot welding tabs to the pressed positive and negative electrode plates, inserting the separator, winding it up in a winder, putting it into a pouch jig, sealing the top and sides, then putting it into an oven for heating and drying. After that, 9 g of electrolyte solution was injected in an environment with a relative humidity of less than 1.5%. A mixed solvent with a mass ratio of EC:DEC:DMC = 1:1:1 was used as the electrolyte solution, and the electrolyte was 1 M lithium hexafluorophosphate. After injecting the solution and forming for 48 hours, it was evacuated and sealed. The cell model number was 454261.

[0076] The battery characteristic test was carried out on a battery tester (provided by Zhejiang Hangke Technology) by the following method.

[0077] 1) Capacity test The manufactured pouch cell was connected to a test track and the test program was started. The steps were set as follows. The test temperature was set to 25 °C, left standing for 4 hours, charged at a constant current and constant voltage for 4 hours (for example, charged to 4.2 V at 1 / 3C), stopped once, left standing, and discharged at a constant current (for example, discharged to a voltage of 3.0 V at 1 / 3C), and stopped once. It was left standing for 4 hours, charged at a constant current and constant voltage for 4 hours (for example, charged to 4.3 V at 1 / 3C), stopped once, left standing, and discharged at a constant current (for example, discharged to a voltage of 3.0 V at 1C), and stopped once. The above steps were repeated to obtain capacity data under different voltage conditions.

[0078] 2) Cycle test The battery that had undergone the capacity test was connected to a test track, the test program was started, and the steps were set as follows. The test temperature was set to 45 °C, left standing for 4 hours, charged at a constant current for 4 hours (for example, charged to 4.2 V at 1C or charged to 4.3 V at 1C), switched to a constant voltage for charging (for example, charged at 4.2 V for 2 hours or charged at 4.3 V for 2 hours), left standing for 5 minutes, and discharged at a constant current for 4 hours (for example, discharged to a voltage of 3.0 V at 1C), and left standing for 5 minutes. The steps starting from the constant current charging were repeated to conduct a cycle test to obtain the capacity retention rate at different cycle numbers under different voltage conditions.

[0079] 3) DCR increase test after cycling: In the cycle test steps of 2), before the constant current discharge, a step of discharging at a constant current for 30 seconds was added (the voltage difference within 30 seconds was recorded and divided by the current to obtain the DCR), and the rest was the same. The steps starting from the constant current charging were repeated to conduct a cycle test to obtain the DCR increase rate at different cycle numbers (the difference between the DCR after cycling and the DCR after the first cycle was divided by the DCR after the first cycle).

[0080] The test results are as shown in Table 4.

[0081]

Table 4

[0082] As can be seen from Table 3 and FIGS. 1 to 4, the pores contained in the cathode materials for lithium ion batteries manufactured in Examples 1 to 6 are mainly mesopores, and the pore diameters of the mesopores are mainly in the range of 2 to 20 nm, and the percentage of the pore volume of the mesopores in the range of 2 to 20 nm in the total pore volume all exceed 90%, and the percentage of the volume of pores in the range of 3 to 20 nm in the total volume of mesopores are all 80% or more, and the percentage of the volume of pores in the range of 5 to 19 nm in the total volume of mesopores are all 57% or more. The specific surface area of the cathode materials for lithium ion batteries manufactured in Examples 1 to 6 was as large as 0.48 to 1.5 m 2 / g, and the particle size was as small as 2.8 to 5.6 μm. The pores contained in the cathode materials manufactured in Examples 7 and 8 are mainly mesopores and macropores, and the mesopores within the range of 2 to 20 nm are relatively few, and the percentage of the pore volume of the mesopores in the range of 2 to 20 nm in the total pore volume are all less than 40%. The specific surface area of the cathode materials for lithium ion batteries manufactured in Examples 7 and 8 was as small as 0.25 to 0.32 m 2 / g, and the particle size was as large as 9.6 to 10.52 μm.

[0083] As can be seen from Table 4, compared with Example 7, the cathode materials for lithium ion batteries provided by Examples 1 to 6 had an increased capacity and improved cycle characteristics. In particular, the cycle characteristics were significantly improved under high voltage, and the increase rate of DCR after cycling was significantly reduced. In Example 7, since there were many and large macropores in the material, cracks were likely to occur during cycling, so the cycle characteristics were relatively poor and it was not suitable for use under high voltage. The capacity retention rate after 100 cycles under 4.3 V was only 55%, and the increase in DCR after cycling was large. In Example 8, since the manganese content exceeded the nickel content, compared with the material of Example 1, the capacity could not be exerted under low voltage, and the capacity could be exerted barely under high voltage, but since the capacity was too low, the requirement of energy density could not be met.

[0084] To summarize the above, the cathode material for lithium-ion batteries provided by the present invention has mesopores with pore diameters mainly in the range of 2 to 20 nm and a proportion greater than 90%. Since these mesopores provide more and shorter paths for the movement of lithium ions, the cathode material for lithium-ion batteries of the present invention has a higher capacity. Also, during charge and discharge of the lithium-ion battery, cracks are less likely to occur in the cathode material, thus preventing a decrease in capacity during cycling of the cathode material for lithium-ion batteries.

[0085] The above are only preferred embodiments related to the implementation of the present invention and are not any limitations to the present invention. Any modifications, equivalent substitutions, or improvements made without departing from the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0086] (Supplementary Note) (Supplementary Note 1) Having a porous structure, The pore volume of mesopores with pore diameters of 2 to 20 nm occupies 90% or more of the total pore volume, A cathode material for a lithium-ion battery, characterized by this.

[0087] (Supplementary Note 2) The volume of pores with pore diameters of 3 to 20 nm occupies 60% or more of the total volume of mesopores, A cathode material for a lithium-ion battery according to Supplementary Note 1, characterized by this.

[0088] (Supplementary Note 3) The specific surface area of the cathode material is 0.25 to 1.5 m 2 / g, A cathode material for a lithium-ion battery according to Supplementary Note 1, characterized by this.

[0089] (Supplementary Note 4) The Dv50 particle size of the cathode material is 2.00 to 6.00 μm, A cathode material for a lithium-ion battery according to Supplementary Note 1, characterized by this.

[0090] (Supplementary Note 5) The total amount of free lithium in the positive electrode material is less than 2000 ppm. The positive electrode material for a lithium-ion battery according to Addendum 1, characterized in that.

[0091] (Addendum 6) The positive electrode material contains lithium element, nickel element and manganese element, and the content of nickel element in the positive electrode material is greater than the content of manganese element. The positive electrode material for a lithium-ion battery according to Addendum 1, characterized in that.

[0092] (Addendum 7) It contains the element composition shown in Chemical Formula 1. The Chemical Formula 1 is Li 1+a Ni x Mn y Co z A m O2, provided that 0 ≦ a ≦ 0.25, 0.5 < x ≦ 0.97, 0 < y ≦ 0.42, 0 ≦ z ≦ 0.09, 0 ≦ m ≦ 0.03. However, A is selected from any one or two or more elements of Mn, Co, Al, Zr, Y, Rb, Cs, W, Ce, Mo, Ba, Ti, Mg, Ta, Nb, Ca, V, Sc, Sr and B, or selected from a phosphorus-containing compound containing at least one element of Ti, Al, Mg, Zr, La and Li. The positive electrode material for a lithium-ion battery according to Addendum 1, characterized in that.

[0093] (Addendum 8) It includes the step of performing at least two firings and two grindings after mixing the raw materials. The method for manufacturing a positive electrode material for a lithium-ion battery according to any one of Addenda 1 to 7, characterized in that.

[0094] (Addendum 9) The temperature of the first firing is 750 - 980 °C, the isothermal time is 8 - 40 hours, the temperature of the second firing is 650 - 920 °C, and the isothermal time is 5 - 20 hours. The manufacturing method according to Addendum 8, characterized in that.

[0095] (Appendix 10) The firing atmosphere is air, oxygen, or a mixed gas of air and oxygen, The manufacturing method according to Appendix 9, characterized in that.

[0096] (Appendix 11) The manufacturing method of the positive electrode material for the lithium ion battery, Step (1) of mixing the pulverized substance with a metal A source, And step (2) of firing and pulverizing the mixture of step (1), further comprising. The manufacturing method according to Appendix 8, characterized in that.

[0097] (Appendix 12) In step (2), the firing temperature is 300 to 780 ° C and the isothermal time is 3 to 14 hours, The manufacturing method according to Appendix 11, characterized in that.

[0098] (Appendix 13) The Li source is a lithium-containing oxide, a lithium-containing fluoride, or a lithium-containing salt, The manufacturing method according to Appendix 8, characterized in that.

[0099] (Appendix 14) The Li source is selected from one or more of anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, lithium acetate, and lithium fluoride, The manufacturing method according to Appendix 13, characterized in that.

[0100] (Appendix 15) Comprising a current collector and a positive electrode material supported on the current collector, wherein the positive electrode material is the positive electrode material for a lithium ion battery according to Appendix 1, The lithium ion battery positive electrode, characterized in that.

[0101] (Appendix 16) Comprising a positive electrode, a negative electrode, and a lithium salt-containing electrolyte, wherein the positive electrode is the lithium ion battery positive electrode according to Appendix 15, A lithium-ion battery characterized by [this].

Claims

1. It has a porous structure, the pore volume of mesopores with a pore diameter of 2 to 20 nm occupies 90% or more of the total pore volume, and the volume of pores with a pore diameter of 5 to 19 nm occupies 40% or more of the total volume of mesopores, contains the elemental composition shown in Chemical Formula 1, The chemical formula 1 is Li １＋ａ Ni ｘ Mn ｙ Co ｚ A ｍ O ２ where 0 ≦ a ≦ 0.25, 0.5 < x ≦ 0.97, 0 < y ≦ 0.42, 0 < z ≦ 0.09, 0 ≦ m ≦ 0.03, wherein A is any one or more elements selected from Mn, Co, Al, Zr, Y, Rb, Cs, W, Ce, Mo, Ba, Ti, Mg, Ta, Nb, Ca, V, Sc, Sr, and B, a cathode material for a lithium-ion battery, characterized by the above.

2. The volume of pores with a pore diameter of 3 to 20 nm occupies 60% or more of the total volume of mesopores, a cathode material for a lithium-ion battery according to Claim 1, characterized by the above.

3. The specific surface area of the positive electrode material is 0.25 to 1.5 m ２ / g. a cathode material for a lithium-ion battery according to Claim 1, characterized by the above.

4. The specific surface area of the positive electrode material is 0.48 to 1.5 m ２ / g, a cathode material for a lithium-ion battery according to Claim 1, characterized by the above.

5. The volume of pores with a pore diameter of 3 to 20 nm occupies 80% or more of the total volume of mesopores, a cathode material for a lithium-ion battery according to Claim 1, characterized by the above.

6. The volume of pores with a pore diameter of 5 to 19 nm occupies 57% or more of the total volume of mesopores, a cathode material for a lithium-ion battery according to Claim 1, characterized by the above.

7. The Dv50 particle size of the cathode material is 2.00 to 6.00 μm, a cathode material for a lithium-ion battery according to Claim 1, characterized by the above.

8. The total amount of free lithium in the cathode material is less than 2000 ppm, a cathode material for a lithium-ion battery according to Claim 1, characterized by the above.

9. It includes a current collector and a cathode material supported on the current collector, and the cathode material is the cathode material for a lithium-ion battery according to any one of Claims 1 to 8, a lithium-ion battery cathode, characterized by the above.

10. It includes a cathode, an anode, and a lithium salt-containing electrolyte, and the cathode is the lithium-ion battery cathode according to Claim 9, a lithium-ion battery, characterized by the above.

11. The cathode is made of a material including a cathode current collector, a cathode active material coated on the cathode current collector, an adhesive, and a conductive assistant, and the cathode active material is the cathode material for a lithium-ion battery according to any one of Claims 1 to 8, a lithium-ion battery according to Claim 10, characterized by the above.

12. The adhesive includes polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, poly(vinylidene fluoride), polyethylene, polypropylene, styrene-butadiene rubber, acrylic acid (ester) styrene-butadiene rubber, epoxy resin, nylon, etc., and combinations thereof. The lithium ion battery according to claim 11, characterized by the above.

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