Positive electrode materials for lithium-ion batteries and their applications

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 relates to the technical field of lithium ion batteries, and to a positive electrode material for lithium ion batteries, a manufacturing method thereof, and applications thereof. [Background technology]

[0002] The new energy market experienced dramatic changes in 2019, and the continued rise in electric vehicles has driven increasing demand for energy density and cost-effectiveness in lithium-ion batteries. Among these, lithium-cobalt-nickel-manganese ternary cathode materials contain cobalt, a rare and expensive resource. To improve cost-effectiveness and ensure high energy density, the nickel or manganese content must be appropriately increased to reduce cobalt usage. While increasing the nickel content can provide higher capacity batteries, excessive nickel content can also lead to structural instability and increased reactivity with the electrolyte. Repeated charging and discharging can lead to cracks in the cathode material, shortening the cycle life of lithium-ion batteries, increasing impedance, and reducing capacity. Therefore, there is an urgent need to develop or discover new materials to replace or reduce the amount of cobalt used in materials, which is a rare resource.

[0003] Chinese Patent CN102280636A discloses a positive electrode active material, its manufacturing method, and a lithium secondary battery containing the same. The positive electrode active material for the lithium secondary battery is obtained by preparing a precursor by coprecipitation, then mixing it with a lithium source and calcining it. The material contains pores with an average diameter of about 10 nm to about 60 nm, and the porosity of the material is about 0.5% to about 20%. The material has good particle strength, preventing or reducing crushing after pressing. The material is not easily reactive with electrolytes and exhibits good thermal stability, making it possible to provide high-capacity lithium secondary batteries. However, the chemical formula of the material is 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 in an oxygen atmosphere and then heat-treated at a high temperature to obtain a nickel-based active material. The material includes secondary particles including aggregates of two or more plate-shaped primary particles, and at least a part of the secondary particles includes a structure in which the plate-shaped primary particles are radially arranged. The outside of the secondary particles has a larger 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, 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 least one of the following conditions (B) and condition (C). Condition (A): In the mercury intrusion curve, when the pressure increases from 5 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 from 10 to 100 nm, and the pore size distribution curve has a main peak with the upper end located at a pore radius of 0.5 to 50 μm and a sub-peak with the upper end located at a pore radius of 80 to 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 manufacturing method thereof. In this patent, the positive electrode composite layer constituting the positive electrode of the non-aqueous electrolyte secondary battery has, in a pore distribution curve measured with a mercury porosimeter, a differential pore volume peak A in the pore diameter range of 0.05 μm to 2 μm and a peak B located on the smaller pore diameter side than the peak A, and the pore distribution curve has a minimum point C between the peak A and the peak B where the differential pore volume is a minimum value, and the differential pore volume X of the peak A is A and the differential pore volume X of the peak B B The larger differential pore volume of L The differential pore volume X at the minimum point C C Ratio to (X C / X L ) is 0.6 or more. The patent mainly focuses on reducing problems such as gas generation in batteries by adding an overcharge additive during the battery manufacturing process. Summary of the Invention [Problem to be solved by the invention]

[0007] The technical problem that the present invention aims to solve is that in conventional technologies, the pore diameter of the positive electrode material is too large, and most of the materials are macroporous. The existence of macropores makes the path for lithium ions too long, which not only makes it impossible to provide high capacity to lithium ion batteries, but also causes cracks in the positive electrode material particles during repeated charging and discharging of the lithium ion battery, resulting in a decrease in capacity, an increase in internal resistance, and gas generation during the lithium ion battery cycle.

[0008] In response to the shortcomings of the prior art, the present invention provides a positive electrode material for lithium ion batteries, which contains mesopores with small diameters, and these mesopores provide more and shorter paths for lithium ion migration, resulting in higher capacity for lithium ion batteries. Furthermore, the positive electrode material for lithium ion batteries produced by the method of the present invention is free from cracks during charging and discharging, preventing capacity loss during cycling of the lithium ion battery material. The present invention also provides a method for producing the positive electrode material for lithium ion batteries, and a lithium ion battery comprising the positive electrode material for lithium ion batteries. Furthermore, the present invention provides uses of the positive electrode material for lithium ion batteries or lithium ion batteries in the fields of digital batteries, power batteries, and storage batteries. [Means for solving the problem]

[0009] The technical solution of the present invention is as follows: The present invention provides a positive electrode material for a lithium ion battery, the positive electrode material having a porous structure, The pore volume of mesopores with pore diameters of 2 to 20 nm accounts for 90% or more of the total pore volume.

[0010] Preferably, the volume of the pores having a pore diameter of 3 to 20 nm accounts for 60% or more of the total volume of the mesopores, and preferably, the volume of the pores having a pore diameter of 5 to 19 nm accounts for 40% or more of the total volume of the mesopores.

[0011] Preferably, the specific surface area of ​​the positive electrode material is 0.25 to 1.5 m 2 / g, preferably the Dv50 particle size of the positive electrode material is 2.00 to 6.00 μm, and more preferably the total amount of free lithium of the positive electrode material is less than 2000 ppm.

[0012] Preferably, the positive electrode material contains lithium, nickel, and manganese elements, and the content of nickel in the positive electrode material is greater than the content of manganese.

[0013] Preferably, the positive electrode material comprises an elemental composition shown in Chemical Formula 1, The formula 1 is Li 1+a Ni x Mn y Co z A m O2, where 0≦a≦0.25, 0.5 <x≦0.97、0<y≦0.42、0≦z≦0.09、0≦m≦0.03であり、 Here, A is 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, or is selected from phosphorus-containing compounds containing at least one element of Ti, Al, Mg, Zr, La, and Li.

[0014] The present invention further provides a method for producing the positive electrode material for a lithium ion battery, comprising the steps of mixing the raw materials and then performing firing at least twice and grinding at least twice.

[0015] Preferably, the first firing temperature is 750 to 980°C and 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, and the firing atmosphere is preferably air, oxygen, or a mixed gas of air and oxygen.

[0016] Preferably, the method for producing a positive electrode material for a lithium ion battery comprises: (1) mixing the ground material with a metal A source; The method further includes step (2) of calcining and pulverizing the mixture of step (1).

[0017] Preferably, in step (2), the firing temperature is 300 to 780° C. and 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 production method, the Li source is a lithium-containing oxide, a lithium-containing fluoride, or a lithium-containing salt, and preferably, the Li source is one or more selected from 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 produced by the above-mentioned production method.

[0020] The present invention further provides a lithium ion battery positive electrode comprising a current collector and a positive electrode material supported on the current collector, the positive electrode material being the positive electrode material for a lithium ion battery described above.

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

[0022] The present invention further provides the use of said lithium ion battery cathode material, or said lithium ion battery cathode, or said lithium ion battery in the field of digital batteries, power batteries or storage batteries. [Effects of the Invention]

[0023] The beneficial effects of the present invention are as follows: Compared with conventional lithium-ion battery positive electrode materials, the pores contained in the lithium-ion battery positive electrode material of the present invention are mainly mesopores, with mesopore diameters mainly in the range of 2 to 20 nm, and the pore volume of mesopores in the 2 to 20 nm range accounts for more than 90% of the total pore volume. The particles are almost free of macropores, resulting in a relatively stable particle structure and resistance to particle breakdown during repeated charge and discharge, and good cycle performance. The pore distribution between particles is relatively reasonable, providing channels for lithium ion transport, resulting in high capacity and a relatively small increase in impedance during battery cycling. Exceeding this range increases the lithium ion transport distance, resulting in a decrease in capacity and a rapid increase in impedance. [Brief explanation of the drawings]

[0024] [Figure 1] FIG. 1 is a pore size distribution curve diagram of the positive electrode material for a lithium ion battery produced in Example 1. [Figure 2] FIG. 2 is a pore size distribution curve diagram of the positive electrode material for a lithium ion battery produced in Example 2. [Figure 3] FIG. 3 is a pore size distribution curve diagram of the positive electrode material for a lithium ion battery produced in Example 6. [Figure 4] FIG. 4 is a pore size distribution curve diagram of the positive electrode material for a lithium ion battery produced in Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0025] In order to make the purpose, technical solution and technical effect of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention are clearly and completely described. The embodiments described below are not all the embodiments, but only a part of the embodiments of the present invention. If a person skilled in the art derives other embodiments from the embodiments of the present invention without making any novel work, they all fall within the protection scope of the present invention.

[0026] In the context of the present invention, pore size distribution refers to the change in the ratio of the volume of pores of different pore sizes to the total pore volume as a function of pore size.

[0027] In the description of the present invention, mesopores refer to pores with a pore diameter of 2 to 50 nm, i.e., pores of 2 nm or more and 50 nm or less, micropores are pores with a pore diameter of less than 2 nm, and macropores are pores with a pore diameter of more than 50 nm.

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

[0029] The present invention provides a positive electrode material for a lithium ion battery, the positive electrode material having a porous structure, The pore volume of mesopores with pore diameters 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 having a pore diameter of 3 to 20 nm accounts for 60% or more of the total volume of mesopores, and preferably, the volume of pores having a pore diameter 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 positive electrode material is 0.25 to 1.5 m 2 / g, preferably the Dv50 particle size of the positive electrode material is 2.00 to 6.00 μm, and more preferably the total amount of free lithium of the positive electrode material is less than 2000 ppm.

[0032] In another preferred embodiment of the present invention, the positive electrode material comprises lithium, nickel, and manganese elements, and the content of nickel in the positive electrode material is greater than the content of manganese.

[0033] In another preferred embodiment of the present invention, the positive electrode material comprises an elemental composition shown in Chemical Formula 1, The formula 1 is Li 1+a Ni x Mn y Coz A m O2, where 0≦a≦0.25, 0.5 <x≦0.97、0<y≦0.42、0≦z≦0.09、0≦m≦0.03であり、 Here, A is 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, or is 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 producing the positive electrode material for a lithium ion battery, comprising the steps of mixing the raw materials and then performing firing at least twice and grinding at least twice. However, the first firing temperature is 750 to 980°C and 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, 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 producing a positive electrode material for a lithium ion battery further comprises: (1) mixing the ground material with a metal A source; and step (2) of calcining 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 production method, the Li source is a lithium-containing oxide, a lithium-containing fluoride, or a lithium-containing salt, and preferably, the Li source is one or more selected from the group consisting 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 produced by the above-mentioned production method.

[0038] In another preferred embodiment of the present invention, the positive electrode material for a lithium ion battery of the present invention is produced by a production method including the steps of mixing raw materials and then performing firing at least twice and grinding at least twice. Preferably, in the positive electrode material for a lithium ion battery of the present invention, the first firing temperature is 750 to 980°C and the firing time is 8 to 40 hours, and 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 method for producing the positive electrode material for a lithium ion battery further comprises: (1) mixing the ground material with a metal A source; and step (2) of calcining and grinding the mixture of step (1). Preferably, in the positive electrode material for a lithium ion battery of the present invention, the firing temperature in step (2) 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 comprising a current collector and a positive electrode material supported on the current collector, the positive electrode material being the positive electrode material for a lithium ion battery described above.

[0041] The present invention further provides a lithium ion battery comprising a positive electrode, a negative electrode, and a lithium salt-containing electrolyte, wherein the positive electrode is the positive electrode of the lithium ion battery.

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

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

[0044] The conductive additive includes one or more of a carbon-based material, a metal-based material, and a conductive polymer, wherein 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, and the conductive polymer is a polyphenylene derivative.

[0045] The present invention further provides the use of said lithium ion battery cathode material, or said lithium ion battery cathode, or said lithium ion battery in the field of digital batteries, power batteries or storage batteries.

[0046] The beneficial effects of the present invention are further illustrated by the following specific examples.

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

[0048] [Table 1-1]

[0049] [Table 1-2]

[0050] [Table 2]

[0051] Example 1 Mixing of raw materials: Using a 200L plowshare mixer, start and mix 46.11 kg of lithium hydroxide monohydrate, 0.256 kg of nano-titanium dioxide, and 100.0 kg of nickel-manganese hydroxide precursor Ni 0.68 Mn 0.32 (OH)2 (battery grade, purchased from Guangdong Jianna Energy Technology Co., Ltd.) was added and stirred for 2 hours before use. First firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 930°C, a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8L / min) was poured in, the mixed raw materials were put into the device and the first firing was carried out, the temperature was kept constant for 20 hours, the raw materials were cooled to room temperature and pulverized in a jet mill to obtain the first fired semi-finished product. Second firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 800°C, and a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8L / min) was poured in. The first fired semi-finished product was then put into the 36-meter roller hearth kiln for the second firing, and the temperature was kept constant for 8 hours. The raw material was then cooled to room temperature, crushed in a jet mill, and demagnetized to obtain the second fired semi-finished product. Second mixing: The second fired semi-finished product was placed in a mixer, which was started to stir, and 0.248 kg of nano titanium dioxide was added thereto, followed by mixing for 30 minutes. Third firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 750°C, and a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8L / min) was poured in. The raw materials after the second mixing were fed into the 36-meter roller hearth kiln for the third firing, which was held at a constant temperature for 6 hours. The raw materials were then cooled to room temperature, crushed in a jet mill, demagnetized, and sieved to obtain the positive electrode material.

[0052] After digestion with dilute hydrochloric acid and verification by ICP analysis, the chemical formula of the positive electrode material is LiNi 0.68 Mn 0.32 Ti 0.0063 It was O2.

[0053] Example 2 Mixing of raw materials: Using a 200L plowshare mixer, start and mix 45.87 kg of lithium hydroxide monohydrate, 100 kg of nickel-manganese-cobalt hydroxide precursor Ni 0.65 Co 0.1 Mn 0.25 (OH)2 (battery grade, purchased from Guizhou Zhongwei Zhengyuan New Material Co., Ltd.) was added and stirred for 2 hours before use. First firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 940°C, a mixed gas of air and oxygen (oxygen content 55%, gas flow rate 6 L / min) was poured in, the mixed raw materials were fed into the equipment and the first firing was carried out, the temperature was kept constant for 13 hours, the raw materials were cooled to room temperature and pulverized in a jet mill to obtain the first fired semi-finished product. Second firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 850°C, and a mixed gas of air and oxygen (oxygen content 55%, gas flow rate 6L / min) was poured in. The first fired semi-finished product was then put into the 36-meter roller hearth kiln for the second firing, and the temperature was kept constant for 14 hours. The raw material was then cooled to room temperature, crushed in a jet mill, and demagnetized to obtain the second fired semi-finished product. Second mixing: The second calcined semi-finished product was placed in the mixer, which was started to mix, and 4.43 kg of strontium carbonate was added to the 36-meter roller hearth kiln and mixed for 30 minutes. Third firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 780°C, and a mixed gas of air and oxygen (oxygen content 55%, gas flow rate 6L / min) was poured in. The raw materials after the second mixing were fed into the 36-meter roller hearth kiln for the third firing, which was held at a constant temperature for 7 hours. The raw materials were then cooled to room temperature, crushed in a jet mill, demagnetized, and sieved to obtain the positive electrode material.

[0054] After digestion with dilute hydrochloric acid and verification by ICP analysis, the chemical formula of the positive electrode material is LiNi 0.65 Co 0.1 Mn 0.25 Sr 0.03 It was O2.

[0055] Example 3 Mixing of raw materials: Using a 200L plowshare mixer, start and mix 29.8 kg of anhydrous lithium hydroxide, 0.377 kg of aluminum oxide, and 100 kg of nickel-manganese hydroxide precursor Ni. 0.97 Mn 0.03 (OH)2 (battery grade, purchased from Guangdong Jianna Energy Technology Co., Ltd.) was added and stirred for 2 hours before use. First firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 750°C, oxygen (gas flow rate 10 L / min) was introduced, and the mixed raw materials were placed into the equipment for the first firing. The temperature was kept constant for 40 hours, and the raw materials were cooled to room temperature and pulverized in a jet mill to obtain the first fired semi-finished product. Second firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 650°C, oxygen (gas flow rate 10 L / min) was introduced, and the first fired semi-finished product was placed in the 36-meter roller hearth kiln for the second firing, and the temperature was kept constant for 5 hours. The raw material was cooled to room temperature, crushed in a jet mill, and then demagnetized to obtain the second fired semi-finished product. Second mixing: The second calcined semi-finished product was placed in a stirring tank, stirred under start, and 200 kg of deionized water was added, followed by 0.614 kg of zirconium tetra-n-butoxide solution. The mixture was mixed for 50 minutes and filtered to obtain a cake. Third firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 550°C, oxygen (oxygen flow rate 10 L / min) was flowed in, and the cake after the second mixing was placed into the 36-meter roller hearth kiln for the third firing, which was held at a constant temperature for 4 hours.The raw material was then cooled to room temperature, pulverized in a jet mill, demagnetized, and sieved to obtain the positive electrode material.

[0056] After digestion with dilute hydrochloric acid and verification by ICP analysis, the chemical formula of the positive electrode material is Li 1.15 Ni 0.97 Mn 0.03 Al 0.0037 Zr 0.0016 It was O2.

[0057] Example 4 Mixing of raw materials: Using a 200L plowshare mixer, start and mix 51.97 kg of lithium hydroxide monohydrate, 0.244 kg of boron oxide, and 100 kg of nickel-manganese-cobalt hydroxide precursor Ni. 0.78 Co 0.07 Mn 0.15 (OH)2 (battery grade, Jingmen Green Mei New Materials Co., Ltd.) was added and stirred for 2 hours before use. First firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 880°C, oxygen (gas flow rate 8 L / min) was introduced, and the mixed raw materials were placed into the equipment for the first firing, which was carried out at a constant temperature for 25 hours. The raw materials were then cooled to room temperature and pulverized in a jet mill to obtain the first fired semi-finished product. Second firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 800°C, oxygen (gas flow rate 8L / min) was introduced, and the first fired semi-finished product was placed in the 36-meter roller hearth kiln for the second firing, at a constant temperature for 6 hours. The raw material was cooled to room temperature, crushed in a jet mill, and then demagnetized to obtain the second fired semi-finished product. Second mixing: The second calcined semi-finished product was placed in a mixer, which was started to stir, and 0.104 kg of boron oxide was added, followed by mixing for 40 minutes. Third firing: A 36-meter roller hearth kiln is used, the firing temperature is set to 500°C, oxygen (gas flow rate 8L / min) is introduced, and the raw materials after the second mixing are fed into the 36-meter roller hearth kiln for the third firing. The temperature is kept constant for 8 hours, and the raw materials are cooled to room temperature, crushed in a jet mill, demagnetized, and sieved to obtain the positive electrode material Li. 1.14 Ni 0.78 Co 0.07 Mn 0.15 B 0.01 Got O2.

[0058] After digestion with dilute hydrochloric acid and verification by ICP analysis, the chemical formula of the positive electrode material is Li 1.14 Ni 0.77 Co 0.07 Mn 0.15 B 0.01 It was O2.

[0059] Example 5 Mixing of raw materials: Using a 200L plowshare mixer, start and mix 48.46 kg of lithium hydroxide monohydrate, 100 kg of nickel-manganese-cobalt hydroxide precursor Ni 0.79 Co 0.02 Mn 0.19 (OH)2 (battery grade, Guangdong Jianna Energy Technology Co., Ltd.) was added and stirred for 2 hours before use. First firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 860°C, oxygen (gas flow rate 7 L / min) was introduced, and the mixed raw materials were placed into the equipment for the first firing, which was carried out at a constant temperature for 25 hours. The raw materials were then cooled to room temperature and pulverized in a jet mill to obtain the first fired semi-finished product. Second firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 780°C, oxygen (gas flow rate 7L / min) was introduced, and the first fired semi-finished product was placed in the 36-meter roller hearth kiln for the second firing, at a constant temperature for 7 hours. The raw material was cooled to room temperature, crushed in a jet mill, and then demagnetized to obtain the second fired semi-finished product. Second mixing: The second calcined semi-finished product was placed in a stirring tank, started to stir, and 80 kg of deionized water was added. After stirring for 30 minutes, a solution containing phosphorus and aluminum was immediately 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). The mixture was mixed for 40 minutes and filtered to obtain a cake. Third firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 300°C, and air (air flow rate 15 L / min) was introduced. The cake after the second mixing was then fed into the 36-meter roller hearth kiln for the third firing, which was held at a constant temperature for 14 hours. The raw material was then cooled to room temperature, pulverized in a jet mill, demagnetized, and sieved to obtain the positive electrode material.

[0060] After digestion with dilute hydrochloric acid and verification by ICP analysis, the chemical formula of the positive electrode material is Li 1.06 Ni 0.79 Co 0.02 Mn 0.19 Al 0.0013 P 0.0013 It was O2.

[0061] Example 6 Mixing of raw materials: Using a 200L plowshare mixer, start and mix 43.24 kg of lithium carbonate, 100 kg of nickel-manganese-cobalt hydroxide precursor Ni 0.62 Co 0.03 Mn 0.35 (OH)2 (battery grade, purchased from Guangdong Jianna Energy Technology Co., Ltd.) was added and stirred for 2 hours before use. First firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 970°C, air (air flow rate 15 L / min) was flowed in, and the mixed raw materials were fed into the device for the first firing, held at a constant temperature for 8 hours. The raw materials were then cooled to room temperature and pulverized in a jet mill to obtain the first fired semi-finished product. Second firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 910°C, and air (air flow rate 15 L / min) was flowed in. The first fired semi-finished product was then placed in the 36-meter roller hearth kiln for the second firing, which was carried out at a constant temperature for 20 hours. The raw material was then cooled to room temperature, pulverized in a jet mill, and demagnetized to obtain a positive electrode material. After digestion with dilute hydrochloric acid and verification by ICP analysis, the chemical formula of the positive electrode material is Li 1.08 Ni 0.62 Co 0.03 Mn 0.35 It was O2.

[0062] Example 7 Mixing of raw materials: Using a 200L plowshare mixer, start and mix 43.24 kg of lithium carbonate, 100 kg of nickel-manganese-cobalt hydroxide precursor Ni 0.62 Co 0.03 Mn 0.35 (OH)2 (battery grade, Guangdong Jianna Energy Technology Co., Ltd.) was added and stirred for 2 hours before use. First firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 970°C, air (air flow rate 15 L / min) was introduced, and the mixed raw materials were placed into the device for the first firing, which was held at a constant temperature for 8 hours. The raw materials were then cooled to room temperature and sieved to obtain the positive electrode material.

[0063] After digestion with dilute hydrochloric acid and verification by ICP analysis, the chemical formula of the positive electrode material is Li 1.08 Ni 0.62 Co 0.03 Mn 0.35 It was O2.

[0064] Example 8 Mixing of raw materials: Using a 200L plowshare mixer, start and mix 46.96 kg of lithium hydroxide monohydrate, 0.256 kg of nano-titanium dioxide, and 100.0 kg of nickel-manganese hydroxide precursor Ni. 0.4 Mn 0.6 (OH)2 (battery grade, Guangdong Jianna Energy Technology Co., Ltd.) was added and stirred for 2 hours before use. First firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 930°C, a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8L / min) was poured in, the mixed raw materials were put into the device and the first firing was carried out, the temperature was kept constant for 20 hours, the raw materials were cooled to room temperature and pulverized in a jet mill to obtain the first fired semi-finished product. Second firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 800°C, and a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8L / min) was poured in. The first fired semi-finished product was then put into the 36-meter roller hearth kiln for the second firing, and the temperature was kept constant for 8 hours. The raw material was then cooled to room temperature, crushed in a jet mill, and demagnetized to obtain the second fired semi-finished product. Second mixing: The second fired semi-finished product was placed in a mixer, which was started to stir, and 0.248 kg of nano titanium dioxide was added thereto, followed by mixing for 30 minutes. Third firing: A 36-meter roller hearth kiln was used, the firing temperature was set to 750°C, and a mixed gas of air and oxygen (oxygen content 60%, gas flow rate 8L / min) was poured in. The raw materials after the second mixing were fed into the 36-meter roller hearth kiln for the third firing, which was held at a constant temperature for 6 hours. The raw materials were then cooled to room temperature, crushed in a jet mill, demagnetized, and sieved to obtain the positive electrode material.

[0065] After digestion with dilute hydrochloric acid and verification by ICP analysis, the chemical formula of the positive electrode material is LiNi 0.4 Mn 0.6 Ti 0.0063 It was O2.

[0066] (Test Example 1) The pore size distribution curve, specific surface area, particle size, and total amount of free lithium were measured for Examples 1 to 8 by the following methods.

[0067] (1) Pore size distribution curve measurement method The desorption isotherm was measured using an automatic specific surface area and pore size distribution analyzer (TriStar II 3020). Next, the desorption isotherm was used to perform calculations using the BJH method to obtain pore size distribution curves, with the pore size on the horizontal axis and the pore volume ratio (the ratio of the volume of pores with different mesopore sizes to the total volume of mesopores) on the vertical axis. These curves are shown in Figures 1 to 4. The test results for the ratio of pore sizes of 2 to 20 nm (the ratio of the volume of pores with a pore size of 2 to 20 nm to the total pore volume), the ratio of pore sizes of 3 to 20 nm (the ratio of the volume of pores with a pore size of 3 to 20 nm to the total mesopore volume), and the ratio of pore sizes of 5 to 19 nm (the ratio of the volume of pores with a pore size of 5 to 19 nm to the total mesopore volume) are shown in Table 3.

[0068] (2) Measurement method of specific surface area In the present invention, the specific surface area was measured by the gravimetric method of the gas adsorption BET method in accordance with GB / T 19587-2004 using an automatic specific surface area and pore distribution analyzer (TriStar II 3020). The test results are shown in Table 3.

[0069] (3) Particle size measurement method In the present invention, the particle size is measured by a Malvern Master Size 2000 laser particle size analyzer in accordance with GB / T19077-2016 particle size distribution analysis - laser diffraction method, and the test results are shown in Table 3.

[0070] (4) Measurement method for total free lithium Accurately weigh 30 g ± 0.01 g of sample and place it in a 250 mL Erlenmeyer flask. Place a magnetic stirrer and stir for 30 minutes. The mixture was filtered through a qualitative filter and a funnel. Using a 50 mL pipette, 50 mL of the filtrate was added to a 100 mL beaker and a stir bar was added. The beaker was placed on the magnetic stirrer and two drops of phenolphthalein indicator were added. The solution was titrated with 0.05 mol / L hydrochloric acid standard solution until the solution changed from red to colorless. The volume of the 0.05 mol / L hydrochloric acid standard solution, V1 (endpoint 1), was recorded. Two drops of methyl red indicator were added, and the indicator color changed from colorless to yellow. The solution was titrated with 0.05 mol / L hydrochloric acid standard solution until the solution changed from yellow to orange. The beaker was placed in a heating furnace and heated until the solution boiled (the color of the solution changed from orange to yellow). The beaker was removed and allowed to cool to room temperature. The beaker was then placed on a magnetic stirrer and titrated with 0.05 mol / L hydrochloric acid standard solution until the color of the solution changed from yellow to pale red. The volume V2 of the 0.05 mol / L hydrochloric acid standard solution (endpoint 2) was recorded. The total amount of free lithium was calculated using the following formula, and the test results are shown in Table 3.

[0071] Total free lithium = V2 × 0.05 × 6.94 × 2 × 100% / (m × 1000), where the total amount of free lithium is in mass percent (%), m is the mass of the sample in g, V2 is the second titration endpoint in mL; 6.94 is the atomic weight of lithium.

[0072] [Table 3]

[0073] (Test Example 2) Lithium-ion battery fabrication and characterization: Pouch cell 454261 was manufactured in the following manner. Preparation of positive electrode: The positive electrode material of the present invention, conductive carbon black (SP), and adhesive polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) in 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 then coated onto an aluminum foil current collector, dried, and pressed to obtain a plate.

[0074] Negative electrode preparation: Artificial graphite for the negative electrode, conductive carbon black (SP), carboxymethyl cellulose (CMC), and adhesive (SBR) were mixed in a weight ratio of 95:1:1:3 with a sufficient amount of pure water, and stirred to form a uniform slurry. This was then coated onto a copper foil current collector, dried, and pressed to obtain a plate.

[0075] The separator was a PP / PE composite film material. Tabs were spot-welded to the pressed positive and negative plates, and the separator was inserted. The battery was then wound up on a winder and placed in a pouch jig. The top and sides were sealed, and the battery was then placed in an oven for heating and drying. After that, 9 g of electrolyte (a 1M lithium hexafluorophosphate electrolyte, a 1:1:1 EC:DEC:DMC mixed solvent) was injected in an environment with a relative humidity of less than 1.5%. The electrolyte was a 1M lithium hexafluorophosphate solution. After 48 hours of formation, the battery was vacuumed and sealed. The cell model number was 454261.

[0076] The battery characteristics were tested using a battery tester (provided by Zhejiang Hang Ke Technology) using the following method.

[0077] 1) Capacity test The fabricated pouch cell was connected to a test rack, and a test program was initiated. The following steps were set: the test temperature was set to 25°C, the battery was left standing for 4 hours, the battery was charged at a constant current and constant voltage for 4 hours (e.g., charged to 4.2 V at 1 / 3 C), stopped, left standing, discharged at a constant current (e.g., discharged at 1 / 3 C to a voltage of 3.0 V), and stopped. The battery was left standing for 4 hours, the battery was charged at a constant current and constant voltage for 4 hours (e.g., charged to 4.3 V at 1 / 3 C), stopped, left standing, discharged at a constant current (e.g., discharged at 1 C to a voltage of 3.0 V), and stopped. 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 rack, and a test program was launched with the following steps: the test temperature was set to 45°C, the battery was allowed to stand for 4 hours, the battery was charged at a constant current for 4 hours (e.g., charged to 4.2 V at 1 C, or charged to 4.3 V at 1 C), the battery was switched to a constant voltage and charged (e.g., charged at 4.2 V for 2 hours, or charged at 4.3 V for 2 hours), the battery was allowed to stand for 5 minutes, the battery was discharged at a constant current for 4 hours (e.g., discharged to a voltage of 3.0 V at 1 C), and the battery was allowed to stand for 5 minutes. The steps starting with the constant current charge were repeated to perform a cycle test, and the capacity retention rate at different cycle numbers under different voltage conditions was obtained.

[0079] 3) Post-cycle DCR increase test: In the cycle test step 2), a constant current 30-second discharge step was added before the constant current discharge (the voltage difference within 30 seconds was recorded and divided by the current to obtain the DCR). The cycle test was performed by repeating the steps starting with the constant current charge, and the DCR increase rate at different cycle numbers was obtained (the difference between the DCR after the cycle and the DCR after the first cycle was divided by the DCR after the first cycle).

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

[0081] [Table 4]

[0082] As can be seen from Table 3 and Figures 1 to 4, the pores contained in the lithium-ion battery positive electrode materials produced in Examples 1 to 6 were mainly mesopores, and the pore diameters of the mesopores were mainly in the range of 2 to 20 nm. The percentage of the pore volume of mesopores in the 2 to 20 nm range to the total pore volume was always over 90%, the percentage of the volume of pores with a diameter of 3 to 20 nm to the total mesopore volume was always 80% or more, and the percentage of the volume of pores with a diameter of 5 to 19 nm to the total mesopore volume was always 57% or more. The specific surface area of ​​the lithium-ion battery positive electrode materials produced in Examples 1 to 6 was 0.48 to 1.5 m 2 / g, and the particle size was small, ranging from 2.8 to 5.6 μm. The pores contained in the positive electrode materials produced in Examples 7 and 8 were mainly mesopores and macropores, and the number of mesopores in the range of 2 to 20 nm was relatively small, with the percentage of the pore volume of mesopores in the range of 2 to 20 nm to the total pore volume being less than 40% in both cases. The specific surface area of ​​the positive electrode materials for lithium ion batteries produced in Examples 7 and 8 was 0.25 to 0.32 m 2 / g, and the particle size was large, ranging from 9.6 to 10.52 μm.

[0083] As can be seen from Table 4, compared with Example 7, the lithium-ion battery cathode materials provided by Examples 1 to 6 had increased capacity and improved cycle characteristics, especially at high voltages, with a significant improvement in cycle characteristics and a significantly reduced increase in DCR after cycling. Example 7 had many large macropores, which made it prone to cracking during cycling, resulting in relatively poor cycle characteristics and making it unsuitable for use at high voltages. After 100 cycles at 4.3 V, the capacity retention rate was only 55%, and the DCR increase after cycling was significant. Because the manganese content of Example 8 exceeded the nickel content, compared with the material of Example 1, it was unable to demonstrate capacity at low voltages and, although it could demonstrate capacity at high voltages, its capacity was too low to meet the energy density requirements.

[0084] In summary, the positive electrode material for lithium ion batteries provided by the present invention has mesopores whose pore sizes are mainly within the range of 2 to 20 nm and account for more than 90% of the total. These mesopores provide more and shorter paths for the migration of lithium ions, so the positive electrode material for lithium ion batteries of the present invention has a higher capacity. Furthermore, cracks are less likely to occur in the positive electrode material during charging and discharging of lithium ion batteries, so that the capacity of the positive electrode material for lithium ion batteries during cycling is prevented from decreasing.

[0085] The above-mentioned are merely preferred embodiments of the present invention, and are not intended to limit the present invention in any way. Any modifications, equivalent replacements, or improvements made without departing from the spirit and principles of the present invention shall fall within the scope of protection of the present invention.

[0086] (Addendum) (Appendix 1) It has a porous structure, The pore volume of mesopores with pore diameters of 2 to 20 nm accounts for more than 90% of the total pore volume. A positive electrode material for a lithium ion battery.

[0087] (Appendix 2) The volume of the pores having a pore diameter of 3 to 20 nm accounts for 60% or more of the total volume of the mesopores. 2. The positive electrode material for a lithium ion battery according to claim 1,

[0088] (Appendix 3) The specific surface area of ​​the positive electrode material is 0.25 to 1.5 m 2 / g, 2. The positive electrode material for a lithium ion battery according to claim 1,

[0089] (Appendix 4) The positive electrode material has a Dv50 particle size of 2.00 to 6.00 μm. 2. The positive electrode material for a lithium ion battery according to claim 1,

[0090] (Appendix 5) The total free lithium content of the positive electrode material is less than 2000 ppm; 2. The positive electrode material for a lithium ion battery according to claim 1,

[0091] (Appendix 6) The positive electrode material includes lithium, nickel, and manganese, and the content of nickel in the positive electrode material is greater than the content of manganese. 2. The positive electrode material for a lithium ion battery according to claim 1,

[0092] (Appendix 7) Contains the elemental composition shown in Chemical Formula 1, The formula 1 is Li 1+a Ni x Mn y Co z A m O2, where 0≦a≦0.25, 0.5 <x≦0.97、0<y≦0.42、0≦z≦0.09、0≦m≦0.03であり、 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 is selected from phosphorus-containing compounds containing at least one element of Ti, Al, Mg, Zr, La and Li. 2. The positive electrode material for a lithium ion battery according to claim 1,

[0093] (Appendix 8) The raw materials are mixed, followed by at least two firings and two grindings. 8. A method for producing a positive electrode material for a lithium ion battery according to any one of claims 1 to 7.

[0094] (Appendix 9) The first firing temperature is 750 to 980°C, and the constant temperature time is 8 to 40 hours. The second firing temperature is 650 to 920°C, and the constant temperature time is 5 to 20 hours. 9. The method of claim 8,

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

[0096] (Appendix 11) The method for producing the positive electrode material for a lithium ion battery includes: (1) mixing the ground material with a metal A source; and (2) calcining and grinding the mixture of step (1). 9. The method of claim 8,

[0097] (Appendix 12) In step (2), the firing temperature is 300 to 780°C, and the constant temperature time is 3 to 14 hours. 12. The method of claim 11,

[0098] (Appendix 13) the Li source is a lithium-containing oxide, a lithium-containing fluoride, or a lithium-containing salt; 9. The method of claim 8,

[0099] (Appendix 14) the Li source is one or more selected from the group consisting of anhydrous lithium hydroxide, lithium hydroxide monohydrate, lithium carbonate, lithium nitrate, lithium acetate, and lithium fluoride; 14. The method of claim 13,

[0100] (Appendix 15) 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 described in Appendix 1; A lithium-ion battery positive electrode characterized by:

[0101] (Appendix 16) a positive electrode, a negative electrode, and a lithium salt-containing electrolyte, wherein the positive electrode is the lithium ion battery positive electrode described in Appendix 15; A lithium-ion battery characterized by:

Claims

1. It has a porous structure, the pore volume of mesopores having a pore diameter of 2 to 20 nm accounts for 90% or more of the total pore volume, and the volume of pores having a pore diameter of 5 to 19 nm accounts for 40% or more of the total mesopore volume; Contains the elemental composition shown in Chemical Formula 1, The 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, and 0≦m≦0.03; However, A is 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 positive electrode material for a lithium ion battery.

2. the volume of the pores having a pore diameter of 3 to 20 nm accounts for 60% or more of the total volume of the mesopores; The positive electrode material for a lithium ion battery according to claim 1 .

3. The specific surface area of ​​the positive electrode material is 0.25 to 1.5 m ２ / g, The positive electrode material for a lithium ion battery according to claim 1 .

4. The specific surface area of ​​the positive electrode material is 0.48 to 1.5 m ２ / g, The positive electrode material for a lithium ion battery according to claim 1 .

5. the volume of the pores having a pore diameter of 3 to 20 nm accounts for 80% or more of the total volume of the mesopores; The positive electrode material for a lithium ion battery according to claim 1 .

6. the volume of the pores having a pore diameter of 5 to 19 nm accounts for 57% or more of the total volume of mesopores; The positive electrode material for a lithium ion battery according to claim 1 .

7. The positive electrode material has a Dv50 particle size of 2.00 to 6.00 μm; The positive electrode material for a lithium ion battery according to claim 1 .

8. 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 claim 1 .

9. A positive electrode material for a lithium ion battery according to any one of claims 1 to 8, comprising a current collector and a positive electrode material supported on the current collector. A lithium-ion battery positive electrode characterized by:

10. A lithium ion battery 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 claim 9. A lithium-ion battery characterized by:

11. The positive electrode is made from a material including a positive electrode current collector, a positive electrode active material coated on the positive electrode current collector, an adhesive, and a conductive additive, and the positive electrode active material is the positive electrode material for a lithium ion battery according to any one of claims 1 to 8.

11. The lithium ion battery of claim 10.

12. The adhesive includes polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymers, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, poly(vinylidene fluoride), polyethylene, polypropylene, styrene butadiene rubber, acrylated styrene butadiene rubber, epoxy resin, nylon, and the like, and combinations thereof.

12. The lithium ion battery of claim 11.

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