CN115911324A - Positive electrode material, secondary battery, and electric device - Google Patents
Positive electrode material, secondary battery, and electric device Download PDFInfo
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- CN115911324A CN115911324A CN202211483250.6A CN202211483250A CN115911324A CN 115911324 A CN115911324 A CN 115911324A CN 202211483250 A CN202211483250 A CN 202211483250A CN 115911324 A CN115911324 A CN 115911324A
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- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
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Images
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a positive electrode material, a secondary battery and an electric device. The positive electrode material comprises a positive electrode active material, a lithium supplement layer arranged on the surface of the positive electrode active material and a first carbon material layer arranged on the surface of the lithium supplement layer, wherein the lithium supplement layer comprises a lithium-containing material. Providing a lithium-supplementing layer on the surface enables Li in the layer to be present as compared to a bare positive electrode active material + Is taken out and participates in the formation of an SEI film, thereby reducing the first irreversible capacity loss of the secondary battery during the first cycle. The first carbon material layer is coated on the surface of the lithium supplement layer, so that the interface conductivity of the anode material can be improved, and the energy density of the battery can be improved; meanwhile, the structural stability of the anode material can be improved, so that the cycle stability of the secondary battery is improved.
Description
Technical Field
The invention relates to the technical field of secondary battery materials, in particular to a positive electrode material, a secondary battery and electric equipment.
Background
During the first charging process of the lithium ion battery, a passivation film, i.e., an SEI film, composed of various lithium salts (lithium carbonate, lithium fluoride, lithium oxide, etc.) is formed on the surface of the negative electrode, and the loss of irreversible capacity is also caused while lithium is consumed. When graphite is used as a negative electrode, the initial irreversible capacity loss can reach 10%, and for new negative electrode materials with higher capacities (silicon, silicon-carbon composite materials, silicon oxide, tin oxide and the like), the irreversible capacity loss can even reach 30%. The first irreversible capacity loss greatly limits the increase of the energy density of the lithium ion battery. In order to improve the first effect and compensate for the active lithium loss caused by the negative electrode SEI formation in the first charge and discharge process, the development and application of lithium supplementation technology is urgent.
The positive electrode lithium supplementing technology has high safety and convenience, does not need to change the existing battery manufacturing process and equipment, and has wide application prospect. The existing anode lithium supplement agent has three lithium supplement modes: adding a lithium supplement agent during preparation of the positive electrode slurry; (2) Coating the slurry containing the lithium supplementing material on a current collector, and then coating the positive electrode slurry; and (3) coating the lithium supplement material slurry on the surface of the positive pole piece. However, the above three methods do not allow the lithium supplement agent to selectively and specifically exist on the surface of the positive active material. The lithium supplementing agent is converted into an inert substance which does not conduct the ionic ions after supplementing lithium, and the electron transmission in the pole piece is influenced, so that the impedance of the pole piece is increased, and the multiplying power and the long-term cycle performance of the battery are deteriorated. In addition, the traditional positive electrode lithium supplement agent has the problems of large residual alkali, poor conductivity, sensitivity to environmental humidity and the like.
Therefore, research and development of a positive electrode material having a lithium supplement function and having good conductivity and stability are important for improving the electrochemical capacity and the cycle stability of the secondary battery.
Disclosure of Invention
The invention mainly aims to provide a positive electrode material, a secondary battery and electric equipment, so as to solve the problems that the positive electrode material in the prior art is difficult to simultaneously meet the requirements of lithium supplement function and has good conductivity and structural stability.
In order to achieve the above object, an aspect of the present invention provides a positive electrode material including a positive electrode active material, a lithium supplement layer disposed on a surface of the positive electrode active material, and a first carbon material layer disposed on a surface of the lithium supplement layer; the lithium supplement layer comprises a lithium-containing material.
Further, the weight of the lithium supplement layer accounts for 0.5-3 wt% of the positive electrode active material.
Further, the weight of the first carbon material layer accounts for 0.1-2 wt% of the positive electrode active material.
Further, the lithium-containing material includes doped or undoped Li 2 NiO 2 、Li 5 FeO 4 、Li 6 CoO 6 、Li 2 S and Li 4 SiO 4 One or more of the group consisting of.
Further, the lithium-containing material comprises Li doped with a first doping element 2 NiO 2 、Li 5 FeO 4 、Li 6 CoO 6 、Li 2 S and Li 4 SiO 4 One or more of the group consisting of Al, cr, sr, Y, W, zr, ti, la, nb, S and Mo; the content of the first doping element is 500 to 5000ppm based on the total weight of the lithium supplement layer and the positive electrode active material.
Further, the particle surface of the lithium-containing material is also provided with a first oxide coating layer, the first oxide coating layer comprises an oxygen-containing compound formed by a first coating element, and the first coating element comprises one or more of the group consisting of Al, ti, B, sr, Y and W; and/or the content of the first coating element is 1500-3000 ppm based on the total weight of the lithium supplement layer and the positive electrode active material.
Further, the positive electrode active material contains a second doping element doped or undoped Li a CoO 2 、Li a Ni x Co y Mn z O 2 、Li a Ni x Co y Al z O 2 、Li a Mn 2 O 4 And Li a FePO 4 0.95 is not less than 1.05,0 is not less than x is not less than 1,0 is not less than y is not less than 1,0 is not less than z is not less than 1; and/or the second doping element comprises one or more of the group consisting of Cr, sr, Y, W, zr, al, ti, la, nb and Mo; and/or the content of the second doping element is 500-5000 ppm based on the total weight of the lithium supplement layer and the positive electrode active material.
Further, the surface of the positive electrode active material is provided with a second oxide coating layer, the second oxide coating layer contains an oxygen-containing compound formed by a second coating element, and the second coating element comprises one or more of the group consisting of Al, ti, B, sr, Y and W; and/or the content of the second coating element is 1000-3000 ppm based on the total weight of the lithium supplement layer and the positive electrode active material.
Further, when the positive active material includes doped or undoped Li a FePO 4 When the positive electrode active material is used, the surface of the positive electrode active material is also provided with a second carbon material layer, and the weight of the second carbon material layer accounts for 0.5-5 wt% of the positive electrode active material.
Furthermore, the first carbon material layer is made of carbon nano tubes, the average tube diameter of the carbon nano tubes is 4-100 nm, and the specific surface area is more than or equal to 20m 2 (ii)/g; and/or the thickness of the lithium supplement layer is 30-50 nm; the thickness of the first carbon material layer is 10-20 nm.
In order to achieve the above object, another aspect of the present invention further provides a secondary battery, including a positive electrode plate, a negative electrode plate, a separator and an electrolyte, where the positive electrode plate includes the above positive electrode material provided in this application.
Another aspect of the present invention provides an electric device including the above-described secondary battery provided herein.
By applying the technical scheme of the invention, the surface of the positive active material is sequentially coated with the lithium supplement layer and the first carbon material layer. Compared with an uncoated naked positive active material, the lithium supplement layer is arranged on the surface of the positive active material, so that lithium ions in the lithium supplement layer can be extracted and participate in the formation process of the SEI film, the SEI film can play a lithium supplement function, and the first irreversible capacity loss caused by the formation of the SEI film in the first circulation process of the secondary battery can be reduced.
The first carbon material coating layer is coated on the surface of the lithium supplement coating layer, so that on one hand, the conductive performance of the carbon material can be exerted, the conductive loss caused by the lithium supplement layer is compensated, the effect of improving the interface conductivity of the cathode material is achieved, and the energy density of the secondary battery can be improved; on the other hand, the lithium ion battery can also play a role in isolation, so that the internal positive active material is not directly contacted with air and/or electrolyte, and the structural stability of the positive material is further improved, and the cycle stability of the secondary battery is further improved.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate embodiment(s) of the invention and together with the description serve to explain the invention and not to limit the invention. In the drawings:
fig. 1 shows a transmission electron micrograph (TEM image) of the positive electrode material produced in example 1 of the present application.
Detailed Description
It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict. The present invention will be described in detail with reference to examples.
As described in the background art, the conventional positive electrode material has the problems that the lithium supplement function is difficult to satisfy and the conductivity and the structural stability are good. In order to solve the above technical problem, the present application provides a positive electrode material, including a positive electrode active material, a lithium supplement layer disposed on a surface of the positive electrode active material, and a first carbon material layer disposed on a surface of the lithium supplement layer; the lithium supplement layer comprises a lithium-containing material.
In the anode material, the surface of the anode active material is sequentially coated with a lithium supplement layer and a carbon material layer. Compared with an uncoated naked positive active material, the lithium supplement layer is arranged on the surface of the positive active material, so that lithium ions in the lithium supplement layer can be extracted and participate in the formation process of an SEI film, the SEI film can play a lithium supplement function, and the first irreversible capacity loss caused by the SEI film formation in the first cycle process of the secondary battery can be reduced.
The first carbon material layer is coated on the surface of the lithium supplement layer, so that on one hand, the conductivity of the carbon material can be exerted, the conductivity loss caused by the lithium supplement layer is compensated, the effect of improving the interface conductivity of the cathode material is achieved, and the energy density of the secondary battery can be further improved; on the other hand, the lithium ion battery can also play a role in isolation, so that the internal positive active material is not directly contacted with air and/or electrolyte, and the structural stability of the positive material is further improved, and the cycle stability of the secondary battery is further improved.
In a preferred embodiment, the positive electrode material satisfies at least one of the following conditions: (1) The weight of the lithium supplement layer accounts for 0.5-3 wt% of the positive active material; (2) The weight of the first carbon material layer accounts for 0.1-2 wt% of the positive electrode active material. The use amounts of the lithium supplement layer and the first carbon material layer are respectively limited in the range, so that the lithium supplement function of the first carbon material layer can be better exerted, and further, the first irreversible capacity loss can be reduced; and meanwhile, the conductivity of the anode material is improved, so that the energy density of the secondary battery is improved, and the structural stability of the anode material is improved, so that the cycle stability of the secondary battery is improved.
In a preferred embodiment, the lithium-containing material includes, but is not limited to, doped or undoped Li 2 NiO 2 、Li 5 FeO 4 、Li 6 CoO 6 、Li 2 S and Li 4 SiO 4 One or more of the group consisting of. Compared with other lithium-containing materials, the lithium-containing material is beneficial to better playing a lithium supplementing function, so that the capacity loss of the secondary battery caused by the formation of an SEI (solid electrolyte interphase) film in the first cycle process is reduced, and the energy density of the secondary battery is improved; compared with undoped lithium-containing materials, doping is beneficial to relieving irreversible phase change in the lithium removal process, and the doped lithium-containing materials have better structural stability and thermal stability, so that the lithium-supplementing gram capacity of the secondary battery is improved, and the safety performance of the secondary battery is improved.
In order to further improve the structural stability of the lithium-containing material and the lithium supplement layer and facilitate better lithium supplement function, in a preferred embodiment, the lithium-containing material comprises first doping element doped Li 2 NiO 2 、Li 5 FeO 4 、Li 6 CoO 6 、Li 2 S and Li 4 SiO 4 One or more of the group consisting of the first doping elementBut are not limited to, one or more of the group consisting of Al, cr, sr, Y, W, zr, ti, la, nb, S, and Mo.
In a preferred embodiment, the content of the first doping element is 500 to 5000ppm, specifically 500ppm, 1500ppm, 3000ppm, 5000ppm, based on the total weight of the lithium supplement layer and the positive electrode active material. The content of the first doping element includes, but is not limited to, the above range, and limiting the content to the above range is beneficial to further relieving the irreversible phase change in the lithium removal process, so as to be beneficial to further improving the structural stability and the thermal stability of the lithium-containing material, and further beneficial to further improving the structural stability of the lithium supplement layer and improving the safety performance; and meanwhile, the conductivity loss caused by the lithium supplement layer is further reduced, and the capacity loss of the anode material is further reduced.
In a preferred embodiment, the lithium-supplementing layer comprises particles of a lithium-containing material, the surface of the particles of the lithium-containing material is further provided with a first oxide coating layer, the first oxide coating layer comprises an oxygen-containing compound formed by a first coating element, and the first coating element comprises one or more of the group consisting of, but not limited to, al, ti, B, sr, Y and W. The first oxide coating layer is arranged on the surface of the lithium-containing material particles, so that the particles of the lithium-containing material can be isolated from air and moisture, and the surface residual alkali amount of the lithium-containing material can be reduced; the first coating element includes, but is not limited to, the above-mentioned species, and it is advantageous to further improve the stability of the lithium-containing material to carbon dioxide and moisture within the above-mentioned preferred species range, thereby further reducing the surface residual alkali amount of the lithium-containing material.
In a preferred embodiment, the content of the first coating element is 1500 to 3000ppm, specifically 1500ppm, 2000ppm, 2500ppm, 3000ppm, based on the total weight of the lithium supplement layer and the positive electrode active material. The content of the first coating element includes, but is not limited to, the above range, and it is advantageous to further improve the stability of the lithium-containing material to carbon dioxide and moisture, thereby further reducing the surface residual alkali amount of the lithium-containing material.
In a preferred embodiment, the positive electrode active materialIncluding but not limited to Li doped or undoped with a second doping element a CoO 2 、Li a Ni x Co y Mn z O 2 、Li a Ni x Co y Al z O 2 、Li a Mn 2 O 4 And Li a FePO 4 0.95 is not less than 1.05,0 is not less than x is not less than 1,0 is not less than y is not less than 1,0 is not less than z is not less than 1. It should be noted that the values of a, x, y and z should satisfy the valence balance, and when two positive electrode active materials are contained, a, x, y and z are independent. The positive electrode active material is beneficial to improving the electrochemical capacity of the positive electrode material.
In order to improve the structural stability of the positive electrode active material while improving its electrical conductivity, in a preferred embodiment, the second doping element includes, but is not limited to, one or more of the group consisting of Cr, sr, Y, W, zr, al, ti, la, nb, and Mo.
In a preferred embodiment, the content of the second doping element is 500 to 5000ppm, specifically 500ppm, 1000ppm, 1500ppm, 2000ppm, 5000ppm based on the total weight of the lithium supplement layer and the positive electrode active material. The content of the second doping element includes, but is not limited to, the above range, and limiting the content to the above range is beneficial to improving the structural stability of the positive electrode active material and inhibiting the precipitation of the transition metal element therein, so that the structural stability of the positive electrode material is improved, and the cycle stability is beneficial to being improved.
In a preferred embodiment, the surface of the positive electrode active material is provided with a second oxide coating layer comprising an oxygen-containing compound formed from a second coating element including, but not limited to, one or more of the group consisting of Al, ti, B, sr, Y, W. The second oxide coating layer is coated on the surface of the positive electrode active material, so that the crystal structure of the positive electrode active material is more stable, and the precipitation of valuable metal ions such as transition metal ions is inhibited, so that the cycle stability of the positive electrode material is improved; the second coating element includes, but is not limited to, the above-mentioned species, and it is advantageous to define it within the above-mentioned preferred species range to obtain a second oxide coating layer having a more stable structure, thereby contributing to an improvement in the structural stability of the positive electrode active material.
In a preferred embodiment, the content of the second coating element is 1000 to 3000ppm, specifically 1000ppm, 2000ppm, 2500ppm, 3000ppm based on the total weight of the lithium supplement layer and the positive electrode active material. The content of the second coating element includes, but is not limited to, the above range, and limiting the content to the above range is beneficial to improving the structural stability of the positive electrode active material and inhibiting the precipitation of the transition metal element therein, thereby improving the structural stability of the positive electrode material and being beneficial to improving the cycle stability.
In a preferred embodiment, when the positive electrode active material includes doped or undoped Li a FePO 4 When the positive electrode active material is used, the surface of the positive electrode active material is also provided with a second carbon material layer, and the weight of the second carbon material layer accounts for 0.5-5 wt% of the positive electrode active material. Compared with other ranges, the second carbon material layer with the dosage within the range is arranged on the surface of the positive electrode active material, so that the conductivity of the positive electrode active material is improved, and the energy density of the positive electrode material is improved.
In a preferred embodiment, the material of the first carbon material layer comprises carbon nanotubes, the average diameter of the carbon nanotubes is 4-100 nm, and the specific surface area is more than or equal to 20m 2 (ii) in terms of/g. Compared with other types of carbon materials, the carbon nano tube has higher conductivity, and the effect of improving the non-conductivity of the lithium supplement agent is better, so that the lithium supplement effect of the lithium supplement agent is promoted. In addition, the carbon nano tube has the characteristic of a multi-dimensional long-range conductive agent, and can effectively improve the electron conduction among broken particles under the condition that polycrystalline particles are broken after high compaction and long circulation, so that the lithium supplement efficiency is improved, and the increase of cyclic DCR is reduced. Meanwhile, compared with other ranges, the carbon nano tube with the granularity and the specific surface area is favorable for further improving the interface conductivity of the cathode material and further making up the conductivity loss caused by the lithium supplement layer, so that the energy density of the secondary battery is further improved.
In a preferred embodiment, the carbon nanotubes include, but are not limited to, single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
In a preferred embodiment, the thickness of the lithium supplement layer is 30 to 50nm; the thickness of the first carbon material layer is 10-20 nm. The thickness of the lithium supplement layer and the thickness of the first carbon material layer include, but are not limited to, the above ranges, and limiting the thicknesses within the above ranges is beneficial to better exert the lithium supplement function, so as to reduce the first irreversible capacity loss; meanwhile, the conductivity of the anode material is improved, so that the energy density of the secondary battery is improved, and the structural stability of the anode material is improved, so that the cycle stability of the secondary battery is improved.
In a preferred embodiment, the positive electrode material comprises a single crystal or a polycrystal.
In a preferred embodiment, the positive electrode material has an average particle size of 1 to 15 μm and a specific surface area of 0.1 to 11m 2 /g。
The second aspect of the present application also provides a method for preparing a positive electrode material, which includes: carrying out first ball milling treatment on the lithium-containing material to obtain a first ball milling system; mixing the first ball-milling system with a positive electrode active material and carrying out second ball-milling treatment to obtain the positive electrode active material with a lithium supplement layer on the surface; and mixing the positive electrode active material with the lithium supplement layer arranged on the surface with the material of the first carbon material layer, and carrying out third ball milling treatment to obtain the positive electrode material.
Carrying out first ball milling treatment on the lithium-containing material to uniformly disperse the lithium-containing material to obtain a first ball milling system; mixing the first ball milling system and the positive active material, and carrying out second ball milling treatment to coat the lithium-containing material dispersed in the first ball milling system on the surface of the positive active material so as to obtain the positive active material with a lithium supplement layer on the surface; and mixing the positive electrode active material with the lithium supplement layer arranged on the surface with the material of the first carbon material layer, and carrying out third ball milling treatment to coat the material of the first carbon material layer on the surface to obtain the positive electrode material.
In a preferred embodiment, the weight of the lithium-containing material is 0.5 to 3wt% of the weight of the positive electrode active material, and the weight of the material of the first carbon material layer is 0.1 to 2wt% of the weight of the positive electrode active material. Limiting the weight parts of the lithium-containing material and the first carbon material layer to the above range is beneficial to better playing the lithium supplementing function of the lithium-containing material and further beneficial to reducing the first irreversible capacity loss; meanwhile, the conductivity of the anode material is improved, so that the energy density of the secondary battery is improved, and the structural stability of the anode material is improved, so that the cycle stability of the secondary battery is improved.
In a preferred embodiment, the rotating speed in the first ball milling treatment process is 500-1000 rpm, and the time is 1-3 h; the rotating speed in the second ball milling treatment process is 300-500 rpm, and the time is 0.5-2 h; the rotating speed in the third ball milling treatment process is 200-400 rpm, and the time is 10-30 min. The rotating speed and time in the first ball milling treatment and the second ball milling treatment include but are not limited to the ranges, and limiting the rotating speed and time in the ranges is beneficial to enabling the lithium-containing material to be dispersed more uniformly, enabling the lithium-containing material to be coated on the surface of the positive electrode active material more uniformly, and improving the thickness uniformity of the lithium supplementing layer, so that the first irreversible capacity loss is further reduced. The rotation speed and time in the third ball milling process include, but are not limited to, the above ranges, and limiting the rotation speed and time within the above ranges is advantageous for improving the thickness uniformity of the first carbon material layer, thereby further exerting its effect on improving the conductivity of the cathode material and increasing the energy density of the secondary battery.
In a preferred embodiment, a ball milling medium is also introduced during the first ball milling treatment, the second ball milling treatment and the third ball milling treatment, and the preferred ball milling medium includes, but is not limited to, high manganese steel balls. In order to disperse the lithium-containing material more uniformly and further improve the ball milling effect, the content of manganese element in the high manganese steel ball is preferably more than or equal to 13%.
The third aspect of the present application also provides a method for preparing a lithium-containing material, including:
performing a first sintering of a first precursor, an oxygen-containing oxide of an optional first doping element, and lithium oxideObtaining a first sintering product; carrying out second sintering on the oxygen-containing compound formed by the first coating element and the first sintering product to obtain a lithium-containing material; wherein the first precursor includes but is not limited to NiO and Fe 2 O 3 、Co 2 O 3 、Li 2 S、SiO 2 One or more of; the first doping element and the first cladding element have the same definitions as above.
In a preferred embodiment, the temperature of the first sintering is 600-1000 ℃ and the time is 12-24 h; the temperature of the second sintering is 200-600 ℃, and the time is 6-12 h.
In a preferred embodiment, the first sintering and/or the second sintering process is carried out in a nitrogen atmosphere.
The fourth aspect of the present application also provides a method for preparing a positive electrode active material, including:
performing third sintering on the oxygen-containing oxide formed by the second precursor and the second doping element and the lithium source to obtain a third sintering product; wherein the second precursor includes but is not limited to Ni x Co y Mn z (OH) 2 、MnCO 3 X, y, z have the same definitions as before, and the second doping element has the same definition as before;
carrying out fourth sintering on an oxygen-containing compound formed by the second coating element and a third sintering product to obtain a positive electrode active material; wherein the second cladding element has the same definition as before.
In a preferred embodiment, the temperature of the third sintering process is 600-1000 ℃ and the time is 12-24 h; the temperature of the fourth sintering process is 200-600 ℃, and the time is 6-12 h.
In a preferred embodiment, the lithium source includes, but is not limited to, lithium hydroxide.
In a preferred embodiment, when the second precursor is Ni x Co y Mn z (OH) 2 Or MnCO 3 In this case, the third sintering and/or the fourth sintering process is performed in an oxygen atmosphere.
In an alternative embodiment, the second precursor may also be FePO 4 And when the second precursor is FePO 4 And then, the third sintering process and/or the fourth sintering process are/is carried out in a nitrogen atmosphere, and the raw material of the third sintering product also comprises a carbon source, wherein the carbon source comprises one or more of glucose, sucrose, acetylene black and carbon nano tubes.
The fifth aspect of the present application further provides a secondary battery, which includes a positive electrode plate, a negative electrode plate, a diaphragm and an electrolyte, wherein the positive electrode plate includes the above positive electrode material provided by the present application. The cathode active material provided by the present application has excellent conductivity and stability, and a secondary battery including the same has excellent energy density and cycle stability.
The fifth aspect of the present application further provides an electric device, which includes the above-mentioned secondary battery provided by the present application.
The present application is described in further detail below with reference to specific examples, which should not be construed as limiting the scope of the invention as claimed.
It should be noted that, in the embodiments of the present application, the contents of the first doping element and the second doping element, and the contents of the first coating element and the second coating element are calculated by taking the total weight of the lithium supplement layer and the positive electrode active material as 100%.
The surface residual lithium test methods in the examples and comparative examples of the present application are as follows: mixing the anode material prepared by the method with water, wherein the solid-to-liquid ratio of the anode material to the water is 0.3g/mL, stirring for 30min, carrying out suction filtration, and titrating CO by using 0.1mol/L HCl 3 2- And OH - The concentration of ions, and thus the total lithium concentration at the surface.
Preparation of cathode material
Example 1
1.1 a method of preparing a lithium-containing material, comprising:
for the first precursors NiO and Li in nitrogen 2 O is subjected to first sintering to obtain a first sintering product Li 2 NiO 2 (ii) a For Al in nitrogen 2 O 3 And Li 2 NiO 2 Performing a second sintering to obtainA lithium-containing material; wherein the temperature of the first sintering is 600 ℃, and the time is 15h; the temperature of the second sintering is 500 ℃ and the time is 8h.
The lithium-containing material prepared by the method is Al 2 O 3 Coated Li 2 NiO 2 Particles, denoted as Li 2 NiO 2 @Al 2 O 3 Wherein the content of the first coating element Al element is 2000ppm. The lithium-containing material has an average particle diameter of 2.5 μm and a specific surface area of 0.7m 2 /g。
1.2 a method for preparing a positive electrode active material, comprising:
ni for second precursor in oxygen 0.5 Co 0.2 Mn 0.3 (OH) 2 、Zr 2 O 5 And LiOH is subjected to third sintering to obtain a third sintered product; in oxygen to Y 2 O 3 And performing fourth sintering on the third sintering product to obtain the positive electrode active material. Wherein the temperature of the third sintering process is 1000 ℃, and the time is 24h; the temperature of the fourth sintering process is 60 ℃, and the time is 12h.
The positive electrode active material in example 1 was Y 2 O 3 Coated LiNi doped with Zr element 0.5 Co 0.2 Mn 0.3 O 2 Wherein the second doping element is Zr with the content of 1000ppm; meanwhile, the content of the second coating element Y is 2000ppm; the positive electrode active material was represented by Li (Ni) 0.5 Co 0.2 Mn 0.3 ) 0.999 Zr 0.001 O 2 @Y 2 O 3 。
1.3A preparation method of the cathode material comprises the following steps:
(1) Li-containing material prepared by the method 2 NiO 2 @Al 2 O 3 Adding the mixture into a ball mill for carrying out first ball milling treatment, setting the rotating speed of the ball mill to be 1000rpm, and carrying out ball milling for 3 hours to obtain a first ball milling system;
(2) Mixing the first ball milling system with the positive electrode active material Li (Ni) 0.5 Co 0.2 Mn 0.3 ) 0.999 Zr 0.001 @Y 2 O 3 Mixing and carrying out secondary ball milling, setting the rotating speed of the ball mill to be 500rpm, and carrying out the time of 30min to obtainA positive electrode active material having a lithium-supplementing layer provided on the surface thereof;
(3) The anode active material with the lithium supplementing layer arranged on the surface and single-walled carbon nanotubes (SWCNTs, the average tube diameter is 4nm, and the specific surface area is 22 m) 2 And/g) mixing and carrying out third ball milling, setting the rotating speed of the ball mill to be 200rpm, and carrying out the time to be 30min to obtain the cathode material. The positive electrode material is represented by: positive electrode active material @ lithium supplement layer @ first carbon material layer, wherein the weight of the lithium supplement layer is 3wt% of the weight of the positive electrode active material, and the weight of the first carbon material layer is 0.1wt% of the weight of the positive electrode active material.
The cathode material prepared in this example was in the form of a single crystal with an average particle size of 4 μm. As can be seen from the TEM image shown in fig. 1, the thickness of the lithium supplement layer was 15nm, and the thickness of the first carbon material layer was 10nm. The specific surface area of the positive electrode material was 0.7m 2 G, tap density of 2.5g/cm 3 The amount of residual lithium on the surface was 300ppm.
Example 2
2.1 a method of preparing a lithium-containing material, comprising:
for the first precursor Fe in nitrogen 2 O 3 、TiO 2 And Li 2 Performing first sintering on O to obtain a first sintering product Li 5 FeO 4 (ii) a For Al in nitrogen 2 O 3 And Li 5 FeO 4 Performing second sintering to obtain a lithium-containing material; wherein the temperature of the first sintering is 900 ℃, and the time is 20h; the temperature of the second sintering is 600 ℃, and the time is 12h.
The lithium-containing material prepared by the method is Al 2 O 3 Coated Ti doped Li 5 FeO 4 Particles, noted as Li 5 Fe 0.999 Ti 0.001 O 4 @Al 2 O 3 . Wherein, the content of Al in the first coating element is 2000ppm, and the content of Ti in the first doping element is 500ppm. The lithium-containing material has an average particle diameter of 1 μm and a specific surface area of 1.2m 2 /g。
2.2 a positive electrode active material was prepared in the same manner as in example 1, except that:
example 2 where the second precursor was Ni 0.6 Co 0.2 Mn 0.2 (OH) 2 The second doping elements are Sr and Ti, and the second cladding elements are B and Al.
The positive active material prepared in example 2 was B 2 O 3 And WO 3 Coated Sr and Ti element-doped LiNi 0.6 Co 0.2 Mn 0.2 O 2 Is denoted by Li (N) i0.6 Co 0.2 Mn 0.2 ) 0.99 Sr 0.004 Ti 0.006 O 2 @B 2 O 3 -WO 3 . Wherein the second doping element is Sr and Ti, the Sr content is 4000ppm, and the Ti content is 3000ppm; meanwhile, the second coating element is B and Al, and the material of the second oxide coating layer is B 2 O 3 And WO 3 And the content of B was 2000ppm and the content of Al was 2000ppm.
2.3A method for preparing a positive electrode material, comprising:
(1) Li-containing material prepared by the above method 5 Fe 0.999 Ti 0.001 O 4 @Al 2 O 3 Adding the mixture into a ball mill for primary ball milling treatment, setting the rotating speed of the ball mill to be 800rpm, and performing ball milling for 2 hours to obtain a first ball milling system;
(2) Mixing the first ball milling system with the positive electrode active material Li (N) i0.6 Co 0.2 Mn 0.2 ) 0.99 Sr 0.004 Ti 0.006 O 2 @B 2 O 3 -WO 3 Mixing and carrying out secondary ball milling treatment, setting the rotating speed of a ball mill to be 400rpm, and carrying out time 1h to obtain the positive active material with the surface provided with the lithium supplement layer;
(3) The positive active material with the lithium-supplementing layer arranged on the surface and a multi-walled carbon nanotube (MWCNTs, the average tube diameter is 5nm, and the specific surface area is 25 m) 2 And/g) mixing and carrying out third ball milling treatment, setting the rotating speed of the ball mill to be 300rpm, and carrying out ball milling for 10min to obtain a positive electrode material, wherein the positive electrode material is represented as: positive electrode active material @ lithium supplement layer @ first carbon material layer, wherein the weight of the lithium supplement layer is 2wt% of the weight of the positive electrode active material, and the weight of the first carbon material layer is 0.5wt% of the weight of the positive electrode active material.
The cathode material prepared in this example was single-crystal morphology, the average particle size was 3.8 μm, the thickness of the lithium-supplement layer was 15nm, and the thickness of the first carbon material layer was 30nm. The specific surface area of the positive electrode material was 0.8m 2 The tap density is 2.4g/cm 3 The amount of residual lithium on the surface was 600ppm.
Example 3
3.1A method for preparing a lithium-containing material, comprising:
for the first precursor Fe in nitrogen 2 O 3 And Li 2 Performing first sintering on O to obtain a first sintering product Li 5 FeO 4 (ii) a For Al in nitrogen 2 O 3 And Li 5 FeO 4 Performing second sintering to obtain a lithium-containing material; wherein the temperature of the first sintering is 800 ℃, and the time is 12h; the temperature of the second sintering is 200 ℃ and the time is 12h.
The lithium-containing material prepared by the method is Al 2 O 3 Coated Li 5 FeO 4 The content of particles, i.e., al as the first coating element, was 2500ppm. The lithium-containing material is denoted as Li 5 FeO 4 @Al 2 O 3 Average particle diameter of 1.5 μm and specific surface area of 1.1m 2 /g。
3.2 the preparation method of the positive electrode active material was the same as example 1 except that:
the second precursor is Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 The second doping elements are W and Ti, and the second cladding elements are W and Ti.
The positive electrode active material in example 3 was WO 3 And TiO 2 2 Coated and W and Ti element doped LiNi 0.8 Co 0.1 Mn 0.1 O 2 . Namely, the second doping elements are W and Ti, the content of W is 1000ppm, and the content of Ti is 500ppm; meanwhile, the second coating elements are W and Ti, the content of W is 2000ppm, and the content of Ti is 500ppm. The positive electrode active material was represented by Li (Ni) 0.8 Co 0.1 Mn 0.1 ) 0.9985 W 0.0005 Ti 0.001 O 2 @WO 3 -TiO 2 。
3.3A method for preparing a cathode material, comprising:
(1) Li prepared as above 5 FeO 4 @Al 2 O 3 Adding the mixture into a ball mill for carrying out first ball milling treatment, setting the rotating speed of the ball mill to be 500rpm, and carrying out ball milling for 2 hours to obtain a first ball milling system;
(2) Mixing the first ball milling system and the positive electrode active material Li (Ni) 0.8 Co 0.1 Mn 0.1 ) 0.9985 W 0.0005 Ti 0.001 O 2 @WO 3 -TiO 2 Mixing and carrying out secondary ball milling treatment, setting the rotating speed of a ball mill to be 500rpm, and carrying out time 2h to obtain the positive active material with the surface provided with the lithium supplement layer;
(3) Mixing the positive electrode active material with lithium-supplementing layer on the surface and MWCNTs (average diameter of 5nm, specific surface area of 25 m) 2 /g) and carrying out third ball milling treatment, setting the rotating speed of the ball mill to be 400rpm, and setting the rotating speed of the ball mill to be 20min to obtain a positive electrode material, wherein the positive electrode material is expressed as: positive electrode active material @ lithium supplement layer @ first carbon material layer, wherein the weight of the lithium supplement layer is 1wt% of the weight of the positive electrode active material, and the weight of the first carbon material layer is 2wt% of the weight of the positive electrode active material.
The cathode material prepared in this example was polycrystalline, with an average grain size of 4 μm, a lithium supplement layer of 15nm thickness, and a first carbon material layer of 50nm thickness. The specific surface area of the positive electrode material was 0.6m 2 (ii)/g, tap density 2.7g/cm 3 The amount of residual lithium on the surface was 1000ppm.
Example 4
4.1 the lithium-containing material was prepared in the same manner as in example 1, except that: the content of Al element was 1500ppm.
The lithium-containing material prepared in example 4 was Al 2 O 3 Coated Li 2 NiO 2 Particles, denoted as Li 2 NiO 2 @Al 2 O 3 And the first coating element is Al with a content of 1500ppm. The lithium-containing material has an average particle diameter of 1 μm and a specific surface area of 1.5m 2 /g。
4.2 the preparation method of the positive electrode active material was the same as example 1, except for the difference from example 1:
the second precursor is Ni 0.8 Co 0.1 Mn 0.1 (OH) 2 The second doping element is W, and the second cladding element is B and W.
The positive electrode active material prepared in example 4 was B 2 O 3 And WO 3 Coated W element doped LiNi 0.8 Co 0.1 Mn 0.1 O 2 Namely, the second doping element is W, and the content of the W element is 1000ppm; meanwhile, the second coating elements are B and W, and the material of the second oxide coating layer is B 2 O 3 And WO 3 The content of the element B is 500ppm, and the content of the element W is 500ppm; the positive electrode active material was represented by Li (Ni) 0.8 Co 0.1 Mn 0.1 ) 0.9995 W 0.0005 O 2 @B 2 O 3 -WO 3 。
4.3A preparation method of the cathode material comprises the following steps:
(1) The lithium-containing material Li 2 NiO 2 @Al 2 O 3 Adding the mixture into a ball mill for carrying out first ball milling treatment, setting the rotating speed of the ball mill to be 1000rpm, and carrying out ball milling for 3 hours to obtain a first ball milling system;
(2) Mixing the first ball milling system with the positive electrode active material Li (Ni) 0.8 Co 0.1 Mn 0.1 ) 0.9995 W 0.0005 O 2 @B 2 O 3 -WO 3 Mixing and carrying out secondary ball milling treatment, setting the rotating speed of a ball mill to be 300rpm and the time to be 30min, and obtaining the positive electrode active material with the surface provided with the lithium supplement layer;
(3) Mixing the positive electrode active material with lithium-supplementing layer on the surface and the MWCNTs (average tube diameter of 10nm, specific surface area of 22 m) 2 /g) and carrying out third ball milling treatment, setting the rotation speed of the ball mill to be 400rpm and the time to be 10min, and obtaining the cathode material, wherein the cathode material is represented as follows: positive electrode active material @ lithium supplement layer @ first carbon material layer, wherein the weight of the lithium supplement layer is 2wt% of the weight of the positive electrode active material, and the weight of the first carbon material layer is 1.5wt% of the weight of the positive electrode active material.
The cathode material prepared in this example was in a polycrystalline morphology with an average grain size of 10 μm, a lithium supplement layer of 10nm thick, and a first carbon material layer of 40nm thick. The specific surface area of the positive electrode material was 0.4m 2 (ii)/g, tap density 2.2g/cm 3 The amount of residual lithium on the surface was 1100ppm.
Example 5
5.1A method for preparing a lithium-containing material, comprising:
subjecting the first precursor Co to nitrogen 2 O 3 、Nb 2 O 3 、MoO 3 、Li 2 O is subjected to first sintering to obtain a first sintering product Li 6 CoO 6 (ii) a For Al in nitrogen 2 O 3 、B 2 O 3 And Li 6 CoO 6 Performing second sintering to obtain a lithium-containing material; wherein the temperature of the first sintering is 1000 ℃, and the time is 20h; the temperature of the second sintering is 600 ℃, and the time is 12h.
The lithium-containing material prepared by the method is Al 2 O 3 And B 2 O 3 Coated Nb and Mo doped Li 6 CoO 6 The particles, namely the first coating elements are Al and B, the content of Al is 2000ppm, and the content of B is 500ppm; meanwhile, the contents of the first doping elements Nb and Mo are respectively 500ppm and 1000ppm. The lithium-containing material is denoted as Li 6 Co 0.997 Nb 0.001 Mo 0.002 O 4 @B 2 O 3 -Al 2 O 3 Having an average particle diameter of 1 μm and a specific surface area of 1.3m 2 /g。
5.2 a positive electrode active material was prepared in the same manner as in example 1, except that:
the second precursor is Ni 0.9 Co 0.05 Mn 0.05 (OH) 2 The second doping element is Nb, and the second cladding element is Ti and W.
The positive electrode active material in example 5 was TiO 2 And WO 3 Coated Nb-doped LiNi 0.9 Co 0.05 Mn 0.05 O 2 That is, the content of the second doping element Nb is 1500ppm; meanwhile, the content of the second coating element Ti is 500ppm,the W content was 1000ppm; the positive electrode active material is represented by Li (Ni) 0.9 Co 0.05 Mn 0.05 ) 0.998 Nb 0.002 O 2 @TiO 2 -WO 3 。
5.3A preparation method of the cathode material comprises the following steps:
(1) The lithium-containing material Li 6 Co 0.997 Nb 0.001 Mo 0.002 O 4 @B 2 O 3 -Al 2 O 3 Adding the mixture into a ball mill for first ball milling, wherein the rotating speed of the ball mill is 900rpm, and the ball milling time is 3 hours, so as to obtain a first ball milling system;
(2) Mixing the first ball milling system with the positive electrode active material Li (Ni) 0.9 Co 0.05 Mn 0.05 ) 0.998 Nb 0.002 O 2 @TiO 2 -WO 3 Mixing and carrying out secondary ball milling treatment, setting the rotating speed of a ball mill to be 500rpm, and carrying out time 1h to obtain the positive active material with the surface provided with the lithium supplement layer;
(3) Mixing the positive electrode active material with lithium-supplementing layer on the surface and the MWCNTs (average diameter of 5nm, specific surface area of 25 m) 2 /g) and carrying out third ball milling treatment, setting the rotating speed of the ball mill to be 200rpm, and setting the time to be 20min to obtain the cathode material, wherein the cathode material is expressed as: positive electrode active material @ lithium supplement layer @ first carbon material layer, wherein the weight of the lithium supplement layer is 0.5wt% of the weight of the positive electrode active material, and the weight of the first carbon material layer is 0.5wt% of the weight of the positive electrode active material.
The cathode material prepared in this example was polycrystalline, with an average grain size of 9 μm, a lithium supplement layer of 20nm thickness, and a first carbon material layer of 20nm thickness. The specific surface area of the positive electrode material was 0.4m 2 (ii)/g, tap density 2.3g/cm 3 The amount of residual lithium on the surface was 1200ppm.
Example 6
6.1 the lithium-containing material was prepared in the same manner as in example 1, except that:
the lithium-containing material in example 6 was B 2 O 3 Coated Li doped with Sr element 2 S particles, i.e. of the first coating element BThe content is 1000ppm; meanwhile, the content of the first doping element Sr is 3000ppm. The lithium-containing material is denoted as Li 2 Sr 0.001 S 0.999 @B 2 O 3 The average particle diameter was 0.5 μm and the specific surface area was 1.9m 2 /g。
6.2 the preparation method of the positive electrode active material was the same as example 1 except that:
the positive electrode active material in example 6 was WO 3 And Y 2 O 3 Coated LiCoO doped with Al and Mo elements 2 Namely, the second doping elements are Al and Mo, and the content of the Al and the content of the Mo are respectively 1000ppm; meanwhile, the second coating elements are W and Y, and the material of the second oxide coating layer is WO 3 And Y 2 O 3 And the contents of W and Y elements are respectively 1000ppm; the positive electrode active material was noted as LiCo 0.996 Al 0.003 Mo 0.001 O 2 @WO 3 -Y 2 O 3 。
6.3A preparation method of the cathode material comprises the following steps:
(1) Mixing Li with the above lithium-containing material 2 Sr 0.001 S 0.999 @B 2 O 3 Adding the mixture into a ball mill for carrying out first ball milling treatment, setting the rotating speed of the ball mill to 700rpm, and carrying out ball milling for 3 hours to obtain a first ball milling system;
(2) Mixing the first ball milling system with the positive electrode active material LiCo 0.996 Al 0.003 Mo 0.001 O 2 @WO 3 -Y 2 O 3 Mixing and carrying out secondary ball milling treatment, setting the rotating speed of a ball mill to be 400rpm, and carrying out time 2h to obtain the positive active material with the surface provided with the lithium supplement layer;
(3) Mixing the positive electrode active material with lithium-supplementing layer on the surface and MWCNTs (average tube diameter of 4nm, specific surface area of 25 m) 2 /g) and carrying out third ball milling treatment, setting the rotating speed of the ball mill to be 400rpm, and carrying out 30min time to obtain a positive electrode material, wherein the positive electrode material is represented as: positive electrode active material @ lithium supplement layer @ first carbon material layer, wherein the weight of the lithium supplement layer is 1.5wt% of the weight of the positive electrode active material, and the weight of the first carbon material layer is the weight of the positive electrode1wt% of active material weight.
The cathode material prepared in this example was single-crystal in morphology, with an average particle size of 8 μm, a lithium-supplement layer of 10nm thick, and a first carbon material layer of 10nm thick. The specific surface area of the positive electrode material was 0.6m 2 (ii)/g, tap density 2.6g/cm 3 The surface residual lithium content was 200ppm.
Example 7
7.1 the lithium-containing material was prepared in the same manner as in example 1, except that:
example 7 lithium containing Material is Y 2 O 3 Coated Al and S doped Li 4 SiO 4 Particles, denoted as Li 4 Si 0.998 Al 0.002 O 3.99 S 0.01 @Y 2 O 3 Wherein the content of the first coating element Y is 1500ppm; meanwhile, the content of the first doping element Al is 500ppm, and the content of S is 3000ppm. The lithium-containing material has an average particle diameter of 1 μm and a specific surface area of 1.5m 2 /g。
7.2 the preparation method of the positive electrode active material was the same as example 1 except that:
the positive electrode active material in example 7 was Al 2 O 3 Coated Ti element doped LiMn 2 O 4 Namely, the second doping element is Ti, and the content of the Ti element is 500ppm; meanwhile, the content of a second coating element Al element is 2000ppm; the positive electrode active material is recorded as LiMn 1.998 Ti 0.002 O 4 @Al 2 O 3 。
7.3A preparation method of the cathode material comprises the following steps:
(1) The lithium-containing material Li 4 Si 0.998 Al 0.002 O 4 /S@Y 2 O 3 Adding the mixture into a ball mill for primary ball milling treatment, setting the rotating speed of the ball mill to be 600rpm, and performing ball milling for 3 hours to obtain a first ball milling system;
(2) Mixing the first ball milling system with the positive electrode active material LiMn 1.998 Ti 0.002 O 4 @Al 2 O 3 Mixing and carrying out secondary ball milling, setting the rotating speed of the ball mill to be 500rpm, lasting for 2 hours, and obtaining the positive active material with the surface provided with the lithium supplement layer;
(3) Mixing the positive electrode active material with lithium-supplementing layer on the surface and the SWCNTs (average tube diameter of 10nm and specific surface area of 21 m) 2 /g) and carrying out third ball milling at a ball mill rotation speed of 200rpm for 15min to obtain the cathode material, wherein the cathode material is represented as: positive electrode active material @ lithium supplement layer @ first carbon material layer, wherein the weight of the lithium supplement layer is 1.5wt% of the weight of the positive electrode active material, and the weight of the first carbon material layer is 0.5wt% of the weight of the positive electrode active material.
The cathode material prepared in this example was single-crystal in morphology, with an average grain size of 13 μm, a lithium-doped layer of 15nm thickness, and a first carbon material layer of 25nm thickness. The specific surface area of the positive electrode material was 0.5m 2 G, tap density of 2.1g/cm 3 The surface residual lithium content was 50ppm.
Example 8
8.1 the lithium-containing material was prepared in the same manner as in example 1, except that:
the lithium-containing material in example 8 was Al 2 O 3 Coated Li 2 S particles, i.e. Al as the first cladding element and Al as the material of the first oxide cladding 2 O 3 And the content of Al element was 2000ppm. The lithium-containing material is denoted as Li 2 S@Al 2 O 3 The average particle diameter was 0.5 μm and the specific surface area was 1.8m 2 /g。
8.2 the preparation method of the positive electrode active material was the same as example 1 except that:
second precursor FePO in nitrogen 4 、TiO 2 Glucose, li 2 CO 3 And carrying out third sintering to obtain the positive electrode active material. Wherein the temperature of the third sintering process is 1000 ℃, and the time is 20h;
the positive active material in example 8 was carbon-coated LiFePO doped with Ti element 4 The content of Ti element is 2000ppm, and the content of C element is 5wt%; the positive electrode active material is noted as LiFe 0.994 Ti 0.006 PO 4 @C。
8.3A preparation method of the cathode material comprises the following steps:
(1) Mixing the above Li 2 S@Al 2 O 3 Adding the mixture into a ball mill for carrying out first ball milling treatment, setting the rotating speed of the ball mill to be 1000rpm, and carrying out ball milling for 2 hours to obtain a first ball milling system;
(2) Mixing the first ball milling system with the positive electrode active material LiFe 0.994 Ti 0.006 PO 4 Mixing @ C, and carrying out secondary ball milling treatment, wherein the rotating speed of a ball mill is set to be 500rpm, and the time is 2h, so that the positive active material with the lithium supplement layer arranged on the surface is obtained;
(3) Mixing the positive electrode active material with lithium-supplementing layer on the surface and MWCNTs (average tube diameter of 5nm, specific surface area of 25 m) 2 /g) and carrying out third ball milling treatment, setting the rotating speed of the ball mill to be 400rpm, and carrying out 30min time to obtain a positive electrode material, wherein the positive electrode material is represented as: the positive electrode active material @ lithium supplement layer @ second carbon material layer, wherein the weight of the lithium supplement layer was 2wt% of the weight of the positive electrode active material, and the weight of the first carbon material layer was 1.5wt% of the weight of the positive electrode active material.
The cathode material prepared in this example was in a polycrystalline morphology, with an average grain size of 1 μm, a lithium supplement layer of 10nm thick, and a first carbon material layer of 10nm thick. The specific surface area of the positive electrode material was 10.4m 2 G, tap density of 0.9g/cm 3 The amount of residual lithium on the surface was 400ppm.
Example 9
The difference from example 2 is that: in the preparation method of the lithium-containing material, the content of the first doping element Ti is 2000ppm.
Example 10
The difference from example 2 is that: in the preparation method of the lithium-containing material, the content of the first doping element Ti is 5000ppm.
Example 11
The difference from example 2 is that: in the preparation method of the lithium-containing material, the content of the first doping element Ti is 10000ppm.
Example 12
The difference from example 1 is that: in the method for producing the lithium-containing material, the content of the first coating element Al is 1500ppm.
Example 13
The difference from example 1 is that: in the preparation method of the lithium-containing material, the content of the first coating element Al is 3000ppm.
Example 14
The difference from example 1 is that: in the preparation method of the lithium-containing material, the content of the first coating element Al is 200ppm.
Example 15
The difference from example 1 is that: in the positive electrode active material, the content of the second doping element Zr was 500ppm.
Example 16
The difference from example 1 is that: in the positive electrode active material, the content of the second doping element Zr was 5000ppm.
Example 17
The difference from example 1 is that: in the positive electrode active material, the content of the second doping element Zr was 8000ppm.
Example 18
The difference from example 1 is that: in the positive electrode active material, the content of the second coating element was 1000ppm.
Example 19
The difference from example 1 is that: in the positive electrode active material, the content of the second coating element was 3000ppm.
Example 20
The difference from example 1 is that: in the positive electrode active material, the content of the second coating element was 500ppm.
Table 1 summarizes the kinds and contents of the first coating element, the first doping element, the second coating element, and the second doping element in the lithium-containing material and the positive electrode active material in examples 1 to 20.
TABLE 1
Example 21
The difference from example 1 is that: the first carbon material layer is made of acetylene black conductive agent.
Example 22
The difference from example 1 is that: the first carbon material layer is made of graphene conductive agent.
Comparative example 1
The difference from example 1 is that: the positive electrode material is Li (Ni) 0.5 Co 0.2 Mn 0.3 ) 0.999 Zr 0.001 O 2 @Y 2 O 3 That is, the positive electrode material in comparative example 1 did not contain the lithium supplement layer and the first carbon material layer.
Comparative example 2
The difference from example 2 is that: the positive electrode material is LiNi 0.6 Co 0.2 Mn 0.2 O 2 That is, the positive electrode material in comparative example 2 did not contain the lithium supplement layer and the first carbon material layer.
Comparative example 3
The difference from example 3 is that: the positive electrode material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 That is, the positive electrode material in comparative example 3 did not contain the lithium supplement layer and the first carbon material layer.
Comparative example 4
The difference from example 4 is that: the positive electrode material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 That is, the positive electrode material in comparative example 4 did not contain the lithium supplement layer and the first carbon material layer.
Comparative example 5
The difference from example 5 is that: the positive electrode material is LiNi 0.9 Co 0.05 Mn 0.05 O 2 That is, the positive electrode material in comparative example 5 did not contain the lithium supplement layer and the first carbon material layer.
Comparative example 6
The difference from example 6 is that: the anode material is LiCoO 2 That is, the positive electrode material in comparative example 6 did not contain the lithium supplement layer and the first carbon material layer.
Comparative example 7
The difference from example 7 is that: the anode material is LiMn 2 O 4 That is, the positive electrode material in comparative example 7 did not containThere is a lithium supplement layer and a first carbon material layer.
Comparative example 8
The difference from example 8 is that: the anode material is LiFePO 4 That is, the positive electrode material in comparative example 8 did not contain the lithium supplement layer and the second carbon material layer.
Comparative example 9
The difference from example 3 is that: the cathode material is prepared by adopting a wet processing technology, and particularly provides a cathode material with a surface coated with C and Li 5 FeO 4 In-situ lithium-supplementing LiNi 0.8 Co 0.1 Mn 0.1 O 2 The preparation method of the cathode material comprises the following steps:
(1) Adding lithium nitrate and ferric nitrate into a 5mmol/L glucose solution (carbon source), and stirring to obtain a mixed solution, wherein the molar ratio of the Li element to the Fe element is 6:1;
(2) Mixing LiNi 0.8 Co 0.1 Mn 0.1 O 2 Immersing the positive electrode material into the mixed solution obtained in the step (1), taking out the positive electrode material after immersing the positive electrode material in the mixed solution at the room temperature of 25 ℃ for 30min, then centrifugally drying the positive electrode material, and repeating the immersing step and the centrifugal drying for 4 times respectively;
(3) Putting the centrifugally dried anode material in the step (2) into a furnace chamber, heating to 350 ℃ at the speed of 5 ℃/min, pre-sintering for 1h, then adding to 850 ℃ at the speed of 5 ℃/min, sintering for 24h, and naturally cooling to room temperature to obtain the anode material with the surface coated with C and Li 5 FeO 4 In-situ lithium-supplementing LiNi 0.8 Co 0.1 Mn 0.1 O 2 A positive electrode material, wherein LiNi 0.8 Co 0.1 Mn 0.1 O 2 As core, carbon and Li 5 FeO 4 Coating LiNi 0.8 Co 0.1 Mn 0.1 O 2 Of the surface of (a).
Li in the prepared in-situ lithium supplement cathode material 5 FeO 4 The weight of (a) is 2wt% of the positive electrode material.
Comparative example 10
The differences from example 4 are: comparative example 10 provides a high-nickel ternary cathode material with a core-shell structure, and the core material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 The shell material is Li 2 Ni 0.8 Co 0.1 Mn 0.1 O 2 The mol ratio of the core material to the shell material is 1.06, the radius of the core material is 3.9 μm, the thickness of the shell material is 0.1 μm, and the nano coating layer is nano Al 2 O 3 (the amount added is 0.5wt% of the total weight of the core and shell materials). The preparation method comprises the following steps:
(1) Reacting LiNi 0.8 Co 0.1 Mn 0.1 O 2 Adding the particles and water into a reaction kettle, and dissolving for 10min to obtain slurry;
(2) Carrying out solid-liquid separation on the slurry obtained in the step (1) by adopting a centrifugal machine, transferring the obtained solid material to a 150 ℃ double-cone drying agent for drying, and obtaining a dried material;
(3) Mixing the dried material with lithium salt (LiOH. H) 2 O) is placed into a mixer (the molar ratio of the dried material to the lithium salt is 1.11);
(4) Carrying out solid-phase reaction on the mixed intermediate product prepared in the step (3) at 680 ℃ in a nitrogen atmosphere, crushing and sieving after 24h of reaction, and carrying out coating on nano Al in the nitrogen atmosphere by using a coating machine 2 O 3 And (the average particle size is 50 nm) to form a nano coating layer, so as to obtain the high-nickel ternary cathode material with the core-shell structure.
Comparative example 11
Comparative example 11, lithium-containing Material Li 2 NiO 2 @Al 2 O 3 MWCNTs and positive electrode active material Li (Ni) 0.8 Co 0.1 Mn 0.1 ) 0.9995 W 0.0005 O 2 @B 2 O 3 -WO 3 Respectively, as in example 4.
The difference from example 4 is that: in the preparation method of the anode material, the three materials are simultaneously added into a ball mill for ball milling treatment; the lithium-supplementing material and carbon in the finally prepared positive electrode material are coated on the surface of the positive electrode active material at the same time, and the lithium-containing material Li 2 NiO 2 @Al 2 O 3 The weight of the MWCNTs is 1.5wt% of the above positive electrode active material.
Assembly of lithium ion batteries
Preparing a positive pole piece: mixing the positive electrode materials in examples 1 to 22 and comparative examples 1 to 11 with acetylene black serving as a conductive agent and PVDF serving as a binder according to a mass ratio of 90.
Preparing a negative pole piece: mixing a negative electrode active material, a conductive agent acetylene black, a thickening agent CMC and a binder SBR according to a mass ratio of 96. Among them, the negative active materials of the lithium ion batteries manufactured in examples 1 to 4 and examples 9 to 22 were graphite, the negative active materials of the lithium ion batteries manufactured in examples 5 to 8 were Si/C composite materials (weight ratio of 1:4), the negative active materials of the lithium ion batteries manufactured in comparative examples 1 to 4 and comparative examples 9 to 11 were graphite, and the negative active materials of the lithium ion batteries manufactured in comparative examples 5 to 8 were Si/C composite materials (weight ratio of 1:4).
The positive pole piece, the diaphragm and the negative pole piece are sequentially stacked, the isolating film is positioned between the positive pole piece and the negative pole piece and plays an isolating role, then the bare cell is obtained by winding, the bare cell is placed in an outer packaging shell, electrolyte is injected after drying, and the lithium ion battery is obtained through the processes of vacuum packaging, standing, formation, shaping and the like. The lithium ion batteries composed of the cathode materials obtained in examples 1 to 22 were numbered S1 to S22, and the lithium ion batteries composed of the cathode materials obtained in comparative examples 1 to 11 were numbered C1 to C11. Wherein the electrolyte is LiPF with the concentration of 1mol/L 6 (the solvent is EC and EMC, the volume ratio is 1:1), the diaphragms are all PP films, the thickness is 12 mu m, and the porosity is 40%.
Electrochemical performance testing of lithium ion batteries
The capacity test is carried out on the lithium ion batteries with the numbers from S1 to S22 and from C1 to C11 at room temperature, and the test method comprises the following steps: and carrying out constant current charging to the upper voltage limit at a multiplying power of 0.33C, then carrying out constant voltage charging to a multiplying power of less than 0.05C under the upper voltage limit, standing for 5min, then carrying out discharging to the lower voltage limit at the multiplying power of 0.33C, obtaining the first discharge capacity and calculating the first efficiency. The first efficiency is calculated as follows: primary efficiency = primary discharge capacity/primary charge capacity × 100%.
During the charging and discharging process, lithium cobaltate LiCoO is added 2 And ternary materials (LiNi) 0.5 Co 0.2 Mn 0.3 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.8 Co 0.1 Mn 0.1 O 2 Or LiNi 0.9 Co 0.05 Mn 0.05 O 2 The charge-discharge voltage range of the lithium ion battery corresponding to the anode material is set to be 2.8-4.2V, and the cycle test voltage range is set to be 2.8-4.2V; lithium manganate LiMn 2 O 4 Setting the charge-discharge voltage range of the lithium ion battery corresponding to the anode material to be 3-4.3V, and setting the cycle test voltage range to be 3-4.3V; lithium iron phosphate LiFePO 4 The first charge and discharge voltage range of the anode material is set to be 2.5-4.2V, and the cycle test voltage range is set to be 2.5-3.65V.
In the cycle performance test process, the cycle test charging and discharging multiplying power is 1C, and the cycle is 500 circles. And (3) calculating to obtain the 500 th capacity retention rate, wherein the calculation formula is as follows: capacity retention ratio (%) at 500 th time = 500 th turn capacity/first turn capacity × 100%.
The electrochemical capacity and cycle performance test results of the lithium ion batteries in all examples and comparative examples of the present application are shown in table 2.
TABLE 2
Number of | First charge capacity/mAh | First discharge capacity/mAh | First coulombic efficiency/%) | Capacity retention after 500 cycles% |
S1 | 4111 | 3470 | 84.4 | 99.5 |
S2 | 4093 | 3450 | 84.3 | 98.8 |
S3 | 4089 | 3455 | 84.5 | 97.2 |
S4 | 4056 | 3480 | 85.8 | 97.9 |
S5 | 4130 | 3404 | 82.4 | 94.3 |
S6 | 4290 | 3608 | 84.1 | 93.5 |
S7 | 4298 | 3623 | 84.3 | 93.7 |
S8 | 2521 | 2100 | 83.3 | 93.5 |
S9 | 4093 | 3450 | 84.3 | 98.8 |
S10 | 4088 | 3448 | 84.3 | 98.6 |
S11 | 4095 | 3400 | 83.0 | 97.2 |
S12 | 4110 | 3475 | 84.5 | 99.2 |
S13 | 4115 | 3472 | 84.4 | 99.1 |
S14 | 4100 | 3405 | 83.0 | 97.2 |
S15 | 4115 | 3475 | 84.4 | 99.2 |
S16 | 4118 | 3477 | 84.4 | 99.2 |
S17 | 4001 | 3380 | 84.5 | 97.1 |
S18 | 4155 | 3468 | 83.5 | 98.9 |
S19 | 4122 | 3460 | 83.9 | 98.8 |
S20 | 4050 | 3350 | 82.7 | 97.5 |
S21 | 4000 | 3310 | 82.8 | 98.0 |
S22 | 3950 | 3300 | 83.5 | 97.5 |
C1 | 3948 | 3310 | 83.8 | 98.8 |
C2 | 3945 | 3300 | 83.7 | 98.2 |
C3 | 3965 | 3305 | 83.4 | 96.7 |
C4 | 3906 | 3322 | 85.0 | 97.2 |
C5 | 3889 | 3224 | 81.3 | 92.3 |
C6 | 4081 | 3348 | 82.0 | 93.2 |
C7 | 4149 | 3362 | 81.0 | 92.2 |
C8 | 2409 | 1980 | 82.2 | 92.4 |
C9 | 4043 | 3370 | 83.4 | 95.2 |
C10 | 4041 | 3380 | 83.6 | 94.1 |
C11 | 3350 | 2803 | 83.7 | 96.1 |
From the above description, it can be seen that the above-described embodiments of the present invention achieve the following technical effects:
as can be seen by comparing the electrochemical properties of the lithium ion batteries prepared in examples 1 to 8 and comparative examples 1 to 8, the first charge capacity, the first discharge capacity, and the capacity retention rate after 500 cycles of the lithium ion battery numbered S1 are respectively higher than those of the lithium ion battery numbered C1; similar results were obtained by comparing S2 and C2, S3 and C3, S4 and C4, S5 and C5, S6 and C6, S7 and C7, and S8 and C8 in this order. Compared with an uncoated bare positive active material, the positive active material has the advantages that the lithium supplementing layer arranged on the surface of the positive active material can play a lithium supplementing function of the lithium supplementing layer, so that the initial irreversible capacity loss can be reduced, and the gram capacity can be improved; meanwhile, the first carbon material layer is coated on the surface of the lithium supplement layer, so that on one hand, the conductive performance of the carbon material can be exerted, the conductive loss caused by the lithium supplement layer is compensated, and the effect of improving the interface conductivity of the anode material is achieved; on the other hand, the lithium ion battery can also play a role in isolation, so that the internal positive active material is not directly contacted with air and/or electrolyte, and the structural stability of the positive material is further improved, thereby improving the cycle stability of the lithium ion battery.
In addition, especially for the negative electrode material containing silicon, compared with the uncoated naked positive electrode active material, the positive electrode material containing the lithium supplement layer and the first carbon material layer has more obvious effect of improving gram capacity and cycle performance of the lithium ion battery.
Comparing S3 prepared in example 3 with C9 prepared in comparative example 9, and comparing S4 prepared in example 4 with C10 prepared in comparative example 10, respectively, it can be seen that the positive electrode material prepared by the preparation method provided by the present application has a better lithium supplementing effect and the prepared lithium ion battery has a higher gram capacity and capacity retention rate than other positive electrode materials prepared by other preparation methods different from the positive electrode material provided by the present application.
Comparing S4 prepared in example 4 with C11 prepared in comparative example 11, it can be seen that, compared to a method of directly mixing a lithium-containing material, a carbon nanotube, and a positive active material to prepare a positive electrode slurry, the positive electrode material prepared by the method of preparing a positive electrode material provided in the present application can achieve higher discharge capacity and capacity retention rate when applied to a lithium ion battery.
As can be seen from comparative examples 2 and 9 to 11, the content of the first doping element includes, but is not limited to, the above range, and limiting the content to the preferred range of the present application is advantageous to further alleviate the irreversible phase transformation during the lithium removal process, thereby further improving the structural stability and thermal stability of the lithium-containing material, further improving the structural stability of the lithium supplement layer and improving the safety performance; and meanwhile, the conductive loss caused by the lithium supplement layer is reduced, and the capacity loss of the anode material is further reduced.
As can be seen from comparative examples 1 and 12 to 14, the content of the first coating element includes, but is not limited to, the above range, and limiting the content to the preferred range of the present application is advantageous for further improving the stability of the lithium-containing material to carbon dioxide and moisture, thereby further reducing the surface residual alkali amount of the lithium-containing material, and further improving the gram capacity and the long-term cycle performance.
As can be seen from comparison of examples 1 and 15 to 17, the content of the second doping element, including but not limited to the above range, is limited to the preferred range of the present application, and is advantageous in improving the structural stability of the positive electrode active material, suppressing the precipitation of the transition metal element therein, improving the structural stability of the positive electrode material, and improving the cycle stability.
As is apparent from comparative examples 1 and 18 to 20, the content of the second coating element, including but not limited to the above range, is limited to the preferable range of the present application, and is advantageous in improving the structural stability of the positive electrode active material, suppressing the precipitation of the transition metal element therein, improving the structural stability of the positive electrode material, and improving the cycle stability.
It is known from comparison among examples 1, 21, and 22 that the carbon nanotubes have higher conductivity than other types of carbon materials, and can effectively improve the problem of non-conductivity of the lithium supplement agent and enhance the lithium supplement effect of the lithium supplement agent. In addition, the carbon nano tube has the characteristic of a multi-dimensional long-range conductive agent, and can effectively improve the electron conduction among broken particles under the condition that polycrystalline particles are broken after high compaction and long circulation, so that the lithium supplement efficiency is improved, and the increase of the circulating DCR is reduced; meanwhile, the carbon nano tube with the granularity and the specific surface area range is favorable for further improving the interface conductivity of the anode material and further making up the conductivity loss caused by the lithium supplement layer, so that the energy density of the lithium ion battery is further improved.
It should be noted that the terms "first," "second," and the like in the description and in the claims of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances such that the embodiments of the application described herein are, for example, capable of operation in sequences other than those described or illustrated herein.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The positive electrode material is characterized by comprising a positive electrode active material, a lithium supplement layer arranged on the surface of the positive electrode active material and a first carbon material layer arranged on the surface of the lithium supplement layer, wherein the lithium supplement layer comprises a lithium-containing material.
2. The positive electrode material according to claim 1, wherein the positive electrode material satisfies at least one of the following conditions:
(1) The weight of the lithium supplement layer accounts for 0.5-3 wt% of the positive active material;
(2) The weight of the first carbon material layer accounts for 0.1-2 wt% of the positive electrode active material.
3. The positive electrode material of claim 1, wherein the lithium-containing material comprises doped or undoped Li 2 NiO 2 、Li 5 FeO 4 、Li 6 CoO 6 、Li 2 S and Li 4 SiO 4 One or more of the group consisting of.
4. The cathode material of claim 3, wherein the lithium-containing material comprises Li doped with a first doping element 2 NiO 2 、Li 5 FeO 4 、Li 6 CoO 6 、Li 2 S and Li 4 SiO 4 One or more of the group consisting of Al, cr, sr, Y, W, zr, ti, la, nb, S and Mo; and/or the like, and/or,
the content of the first doping element is 500 to 5000ppm based on the total weight of the lithium supplement layer and the positive electrode active material.
5. The positive electrode material according to claim 1, wherein the lithium-containing material surface is further provided with a first oxide coating layer containing an oxygen-containing compound formed of a first coating element including one or more of the group consisting of Al, ti, B, sr, Y, and W; and/or the like, and/or,
the content of the first coating element is 1500-3000 ppm based on the total weight of the lithium supplement layer and the positive electrode active material.
6. The positive electrode material according to any one of claims 1 to 5, wherein the positive electrode active material contains Li doped or undoped with a second doping element a CoO 2 、Li a Ni x Co y Mn z O 2 、Li a Ni x Co y Al z O 2 、Li a Mn 2 O 4 And Li a FePO 4 0.95-1.05,0-1,0-1,0-z 1; and/or the presence of a catalyst in the reaction mixture,
the second doping element comprises one or more of the group consisting of Cr, sr, Y, W, zr, al, ti, la, nb and Mo; and/or the like, and/or,
the content of the second doping element is 500 to 5000ppm based on the total weight of the lithium supplement layer and the positive electrode active material.
7. The positive electrode material according to claim 6, wherein a surface of the positive electrode active material is provided with a second oxide coating layer containing an oxygen-containing compound formed of a second coating element including one or more of the group consisting of Al, ti, B, sr, Y, and W; and/or the like, and/or,
the content of the second coating element is 1000 to 3000ppm based on the total weight of the lithium supplement layer and the positive electrode active material.
8. The cathode material as claimed in claim 1, wherein the material of the first carbon material layer comprises carbon nanotubes, the average diameter of the carbon nanotubes is 4-100 nm, and the specific surface area is not less than 20m 2 (iv) g; and/or the presence of a catalyst in the reaction mixture,
the thickness of the lithium supplement layer is 30-50 nm; the thickness of the first carbon material layer is 10-20 nm.
9. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet comprises the positive electrode material according to any one of claims 1 to 8.
10. An electric device comprising the secondary battery according to claim 9.
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