WO2023056636A1 - Matériau d'électrode positive en couches à base d'oxyde de lithium-cobalt, son procédé de fabrication et son utilisation - Google Patents

Matériau d'électrode positive en couches à base d'oxyde de lithium-cobalt, son procédé de fabrication et son utilisation Download PDF

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WO2023056636A1
WO2023056636A1 PCT/CN2021/122867 CN2021122867W WO2023056636A1 WO 2023056636 A1 WO2023056636 A1 WO 2023056636A1 CN 2021122867 W CN2021122867 W CN 2021122867W WO 2023056636 A1 WO2023056636 A1 WO 2023056636A1
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lithium
cobalt
positive electrode
electrode material
layer
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PCT/CN2021/122867
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Chinese (zh)
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潘锋
黄伟源
赵庆贺
张明建
李建元
林海
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北京大学深圳研究生院
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Priority to PCT/CN2021/122867 priority Critical patent/WO2023056636A1/fr
Priority to CN202180007620.6A priority patent/CN114938686B/zh
Publication of WO2023056636A1 publication Critical patent/WO2023056636A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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

Definitions

  • the present application relates to the field of lithium ion battery materials, in particular to a lithium cobalt oxide layered positive electrode material and its preparation method and application.
  • the limiting factor restricting the step-up of lithium cobalt oxide materials is mainly the severe structural phase transition around 4.5V.
  • This structural phase transition leads to drastic expansion/contraction of the lattice parameters, which reduces the electrochemical reaction kinetics; meanwhile, the incomplete reversibility of the phase transition leads to rapid capacity fading.
  • Excessive de-Li on the surface of lithium cobaltate materials under high pressure leads to a sharp increase in the reactivity of Co in the surface structure, and reacts with the electrolyte to overflow gas, accompanied by the dissolution of Co.
  • the oxidative decomposition products of the solid-liquid interface form a CEI film on the surface of lithium cobalt oxide, which greatly increases the internal resistance of the battery and intensifies the capacity fading process.
  • the purpose of this application is to provide a new lithium cobalt oxide layered positive electrode material and its preparation method and application.
  • One aspect of the present application discloses a lithium cobaltate layered positive electrode material, wherein the lithium layer of the crystal structure of the lithium cobaltate layered positive electrode material contains cobalt.
  • the lithium cobaltate layered positive electrode material refers to lithium cobaltate formed in a layered arrangement of cobalt layer, lithium layer and oxygen layer in the crystal structure of lithium cobaltate.
  • lithium layer and cobalt The layers are arranged according to the layered distribution, the lithium layer will not contain cobalt, and the cobalt layer will not contain lithium.
  • the present application found that by introducing Co into the Li layer of the lithium cobalt oxide crystal structure, more Li + can be reversibly intercalated and deintercalated from the lithium cobalt oxide material, which can be used at higher voltages, such as charging voltages. 4.65V, which improves the reversible charge-discharge capacity of lithium cobalt oxide positive electrode, and has high cycle stability.
  • the lithium cobalt oxide layered positive electrode material of the present application can effectively increase the voltage while ensuring the energy density and power density of the material.
  • the reversible charge-discharge capacity of the lithium cobalt oxide positive electrode is ⁇ 240mAh g -1 , as shown in Figure 1, and has a relatively high cycle Stability, as shown in Figure 2.
  • cobalt in the lithium layer in this application means that part of the lithium sites in the lithium layer in the microscopic crystal structure are replaced by cobalt, which is essentially different from the existing lithium cobalt oxide doping.
  • the research of this application found that for lithium cobalt oxide layered positive electrode materials, in order to ensure that the lithium layer will not collapse, only a small part of lithium in the lithium layer will be reversibly intercalated and deintercalated, which is the main factor limiting the boosting of lithium cobalt oxide materials.
  • the cobalt ions can support the stability of the lithium layer and avoid the collapse of the lithium layer, so it can support the reversible intercalation and extraction of more lithium ions and support higher charge and discharge voltages.
  • both the bulk phase of the crystal structure of the lithium cobaltate layered positive electrode material and the lithium layer in the surface interface region contain cobalt, and the cobalt and oxygen in the lithium layer in the surface interface region form a cobalt-oxygen link structure.
  • the cobalt in the lithium layer in the surface interface region and the cobalt oxygen in the cobalt layer are linked to each other, forming a connected network of cobalt oxygen structure on the surface of the lithium cobalt oxide layered positive electrode material.
  • the cobalt-oxygen structures in the crystal structure of the surface interface region are interconnected to form a connected network that runs through the phases and interfaces of the crystal structure.
  • the lithium layer in the bulk phase of the crystal structure contains 0.1%-5% cobalt.
  • the lithium layer in the bulk phase of the crystal structure contains no more than 3% cobalt.
  • the lithium layer in the surface interface region of the crystal structure contains not less than 30% cobalt.
  • the amount of cobalt contained in the lithium layer in the crystal structure gradually decreases from the interface to the bulk phase.
  • the research of this application found that the introduction of Co into the Li layer of the lithium cobalt oxide crystal structure can allow more Li + to be reversibly intercalated and deintercalated from the lithium cobalt oxide material; further, through the lithium layer at the interface Introduce a large amount of cobalt, such as cobalt that accounts for no less than 30% of the lithium layer, and a large number of cobalt-oxygen link structures in the surface area, which can conduct electricity and conduct lithium, and do not participate in redox reactions, further realizing the high-voltage lithium cobalt oxide. Reversible high energy density and high power density.
  • this optimization of the interface is further consolidated and realized by replacing the surface crystal framework with elements, and plays the role of isolating the electrolyte, avoiding the lithium cobaltate positive electrode material and the electrolyte.
  • Direct contact for example, after sintering the lithium cobalt oxide layered positive electrode material or the lithium cobalt oxide layered positive electrode material doped with metal elements in the crystal structure phase, further soaking in solution and heat treatment are used to make the lithium layer in the surface interface region Lithium and/or cobalt in are further replaced.
  • the lithium layer in the bulk domain crystal structure contains 0.1%-5% cobalt, preferably no more than 3%. With such a cobalt content, it can not only ensure that the total amount of reversible intercalation and deintercalation of Li + is not greatly affected, but also stabilize the structure of the lithium layer, allowing more Li + to be reversibly intercalated from the lithium cobalt oxide material. Escape effect.
  • the formed cobalt-oxygen two-dimensional link structure runs through the phase and interface of the crystal structure, which can better conduct electricity and lead lithium, and improve the overall performance of the battery.
  • lithium and/or cobalt in the lithium layer in the surface interface region are partially replaced by metal elements, and these metal elements are at least one of Mg, Al, B and Ti.
  • the lithium and/or cobalt in the lithium layer in the surface interface region are partially replaced by Mg, and the cobalt in the cobalt layer in the surface interface region is replaced by at least Al, B and Ti A partial replacement.
  • the proportion of metal elements replacing lithium and/or cobalt in the lithium layer in the surface interface region is not less than 40%.
  • the oxygen in the surface interface region of the crystal structure is partially or completely replaced by fluorine.
  • this application designs element substitution in the crystal structure of the surface region of the lithium cobaltate layered positive electrode material.
  • the purpose is to further realize the conduction and lithium conduction, and not participate in the redox reaction. , effectively isolate the electrolyte from the lithium cobalt oxide, and avoid direct contact between the lithium cobalt oxide cathode material and the electrolyte.
  • the thickness of the surface interface region of the lithium cobalt oxide layered positive electrode material is less than or equal to 5 nm.
  • the bulk phase of the crystal structure is doped with metal elements, the metal elements are doped in the lithium layer and/or the cobalt layer, and these metal elements are at least one of Mg, Al and Ti.
  • the proportion of metal elements doped in the bulk crystal structure does not exceed 1%.
  • lithium cobalt oxide positive electrode material is a technical solution that has been studied and reported in the prior art.
  • the lithium cobalt oxide layered positive electrode material of the present application can also be element doped according to requirements.
  • the specific element doping for the solution reference may be made to the prior art, and no specific limitation is made here.
  • the lithium cobalt oxide layered positive electrode material is primary micro-nano particles or secondary micro-nano particles.
  • the particle size of the lithium cobalt oxide layered positive electrode material is 0.5-40 microns.
  • the primary micro-nanoparticles in this application refer to nanoparticles or microparticles with a single crystal structure formed by the growth of crystal nuclei
  • the secondary micronanoparticles refer to particles formed by agglomeration of nanoparticles or microparticles with a single-crystal structure
  • the lithium cobalt oxide layered positive electrode material of the present application may be primary micro-nano particles or secondary micro-nano particles, which are not specifically limited here.
  • the other side of the present application discloses the preparation method of the lithium cobalt oxide layered positive electrode material of the present application, including mixing the lithium source and the cobalt source, and sintering at 750-950°C for 1-12 hours in an air atmosphere, and then, Microwave or quenching process is carried out to obtain the lithium cobalt oxide layered positive electrode material containing cobalt in the lithium layer of the crystal structure, especially the lithium cobalt oxide layered positive electrode material containing cobalt in the lithium layer of the bulk phase of the crystal structure.
  • the lithium cobaltate material sintered at high temperature for a certain period of time is quenched or treated with microwaves, so that the lithium layer of the crystal structure of the lithium cobaltate layered positive electrode material obtained by sintering contains cobalt, Thereby obtaining the lithium cobalt oxide layered positive electrode material of the present application.
  • the preparation method of the present application also includes mixing the metal element doped in the bulk phase of the crystal structure with the lithium source and the cobalt source and sintering to obtain the metal element doped in the bulk phase of the crystal structure.
  • Elemental lithium cobalt oxide layered cathode material is one implementation of the present application.
  • metal elements can be doped in the bulk phase of the crystal structure according to requirements, and the doping of metal elements in the bulk phase is mainly achieved through the sintering process.
  • the element replacement in the surface interface region it is mainly realized by solution immersion and subsequent heat treatment.
  • the element substitution at the interface and the element doping in the bulk phase are not carried out simultaneously; the element doping in the bulk phase is carried out during the sintering process of the lithium cobalt oxide material Formed;
  • the doping of Mg is generally in the lithium layer
  • the doping of B, Al, and Ti is generally in the cobalt layer.
  • Element substitution at the interface is formed during immersion and heat treatment, in which Al, B, and Ti partially replace cobalt in the cobalt layer, Mg partially replaces lithium and/or cobalt in the Li layer, and F completely or partially replaces cobalt in the lattice framework.
  • the preparation method of the present application also includes soaking the lithium cobaltate layered positive electrode material or the lithium cobaltate layered positive electrode material doped with metal elements in the crystal structure phase with a slightly acidic solution, After the immersion is completed, it is heat-treated to obtain lithium and/or cobalt in the lithium layer in the surface interface area is partially replaced by metal elements, cobalt in the cobalt layer in the surface interface area is partially replaced by metal elements, or oxygen is partially or completely replaced by fluorine Lithium cobalt oxide layered positive electrode material; wherein, the slightly acidic solution contains Li + , and at least one of Mg 2+ , Al 3+ , borate, Ti 4+ and F - ; the soaking condition is at 0-160 Soaking at °C for 0.1-48h, and maintaining a stirring speed of 50-1000r/min throughout the process; heat treatment conditions are heating at 200-700°C for 0.1-36h, and the atmosphere conditions for heat treatment are inert atmosphere or reducing
  • the lithium layer, cobalt layer and oxygen in the surface interface area can be further replaced by solution immersion and heat treatment; and, in the process of immersion and heat treatment, the surface interface area can also be realized
  • the increase of cobalt content in the lithium layer in fact, the cobalt in the lithium layer in the surface interface region of the crystal structure can be much higher than the cobalt in the bulk lithium layer, mainly through soaking and heat treatment, in this process, the surface Part of Li + in the lithium layer in the interface region will be lost, so that part of the cobalt in the cobalt layer will enter the lithium layer from the cobalt layer, thereby increasing the cobalt content in the lithium layer in the surface interface region to 30%-60%.
  • Another aspect of the present application discloses the application of the lithium cobalt oxide layered positive electrode material of the present application in the preparation of power lithium batteries, or lithium ion batteries for 3C consumer electronics products, drones or electronic cigarettes.
  • the lithium cobalt oxide layered positive electrode material of the present application has the advantages of high voltage, high reversible charge and discharge capacity, high energy density, high power density, and good stability, and can be better used in power lithium batteries, such as electric Cars or other medium and large electric equipment.
  • the lithium cobalt oxide layered positive electrode material of the present application can also be used in lithium-ion batteries of 3C consumer electronics products, drones or electronic cigarettes.
  • Another aspect of the present application discloses a lithium ion battery using the lithium cobalt oxide layered cathode material of the present application.
  • the lithium ion battery of the present application due to the use of the lithium cobalt oxide layered positive electrode material of the present application, makes the battery work at a higher charge and discharge voltage, and has a higher reversible charge and discharge capacity, and stability good.
  • the lithium ion battery of the present application can achieve high energy density and high power density at high voltage.
  • the lithium cobaltate layered positive electrode material of the present application contains cobalt in the lithium layer of its crystal structure, which realizes reversible structural phase transition and reversible oxygen valence change reaction in the process of charging and discharging at a high voltage greater than or equal to 4.5V, and improves the
  • the reversible lithium intercalation amount of the lithium cobalt oxide material increases the gram capacity, thus exhibiting excellent electrochemical performance under high-voltage charge-discharge conditions.
  • the lithium cobalt oxide layered positive electrode material of the present application has a simple preparation method for containing cobalt in the lithium layer, and is easy for large-scale industrial production.
  • Fig. 1 is the scanning electron microscope result figure of lithium cobalt oxide layered cathode material in the embodiment of the present application;
  • Fig. 2 is the Rietveld XRD refinement diagram of lithium cobalt oxide layered positive electrode material in the embodiment of the present application;
  • Fig. 3 is a high-resolution transmission electron microscopy result diagram of the bulk phase and surface area of the lithium cobalt oxide layered positive electrode material in the embodiment of the present application;
  • Fig. 4 is the charge-discharge curve of lithium cobalt oxide layered positive electrode material under 15mAg -1 electric current condition in the embodiment of the application;
  • Fig. 5 is the rate curve diagram of lithium cobalt oxide layered positive electrode material in the embodiment of the present application.
  • Fig. 6 is a graph showing the cycle stability of the lithium cobalt oxide layered positive electrode material at 5C and 10C current densities in the examples of the present application.
  • the study of this application shows that by controlling the sintering temperature and sintering time, combined with efficient material processing methods such as microwave and quenching, a new type of lithium cobalt oxide material containing cobalt in the bulk phase of the crystal structure and the lithium layer at the interface can be obtained.
  • This special bulk phase structure can not only allow more Li + to be extracted from the lithium layer under high voltage conditions, but also can effectively suppress the structural collapse of the Co-O layer of lithium cobalt oxide material during high voltage charging, so A very high reversible discharge capacity is obtained.
  • the gram capacity of the novel lithium cobalt oxide is ⁇ 240mAh g ⁇ 1 .
  • replacing the lithium, cobalt and oxygen in the crystal structure of the surface interface region of this new type of high-voltage lithium cobalt oxide material with other elements can further promote electrical conduction, lithium conduction, and inhibit the electrochemical side reaction process, which can further Obtain extremely high reversible discharge capacity.
  • This element replacement treatment within the surface micro-region not only physically blocks the direct contact between the high-valent Co catalytic active center on the surface of lithium cobaltate and the electrolyte under high voltage, suppresses the side reaction at the interface, but also ensures the reversible oxygen valence change reaction. , so that the new lithium cobalt oxide material exhibits excellent electrochemical performance.
  • this application creatively proposes a new lithium cobalt oxide layered positive electrode material containing cobalt in the lithium layer of the crystal structure.
  • the bulk phase Li layer and the interface of the crystal structure of the new lithium cobalt oxide positive electrode material Both Li layers contain Co.
  • the effect of Co contained in the bulk Li layer and the interface Li layer on improving capacity and cycle stability is that the Co contained in the bulk Li layer realizes the reversible intercalation/extraction of more Li + ions and improves the structure.
  • the reversibility of the phase transition increases the discharge capacity of lithium cobaltate; there is a large amount of cobalt in the lithium layer in the crystal structure of the lithium cobaltate interface region, and the replacement of effective elements in the surface micro-region can isolate the lithium cobaltate material from the lithium cobaltate to a certain extent.
  • the direct contact of the electrolyte reduces the side reactions at the interface under high voltage, and at the same time realizes the reversible oxygen valence change.
  • the new high-voltage lithium cobalt oxide material of this application exhibits excellent electrochemical performance under high-voltage charge and discharge conditions; in one implementation of this application, its reversible gram capacity exceeds 240mAh g -1 , which is the first report by humans .
  • the new high-voltage lithium cobalt oxide layered positive electrode material in this example contains 2% Co in the lithium layer of the crystal structure, and most of the Li and Co in the surface micro-region are replaced by Co and Al, respectively.
  • high-temperature sintering, solution immersion, and subsequent heat treatment were used to synthesize a new high-voltage lithium cobaltate cathode material containing 2% Co in the lithium layer. Specifically include:
  • Step 3 Subsequent heat treatment: put the lithium cobalt oxide sample obtained in step 2) in a rotary tube furnace for subsequent heat treatment. After 6 hours of heat preservation, the temperature was naturally lowered; the obtained material was sieved through a 100-mesh sieve, and was vacuum-packed and stored in an aluminum-plastic bag; the obtained material was named "LCO-LAO-1#".
  • Electrochemical test Using NMP as a solvent, LCO-LAO-1#, carbon black and PVDF were evenly mixed in a mass ratio of 8:1:1 to prepare a positive pole piece.
  • the active material loading of the pole piece was about It is 4.5mg cm -2 .
  • 1C 150mAh g -1 .
  • the results in Figure 5 show that the discharge capacity of the positive electrode material at 0.5C, 1C, 2C, 5C, 10C, 20C and 30C are 249.4, 244.2, 233.1, 216.1, 201.4, 176.6 and 159.3mAh g -1 , respectively. high rate performance.
  • the lithium layer contains 1.2% Co
  • the interface layer of Li-Co-Mg-O-F is formed in the surface area.
  • high-temperature sintering, immersion in a slightly acidic solution, and subsequent heat treatment were used in sequence to synthesize a new high-voltage lithium cobaltate cathode material containing 1.2% Co in the lithium layer. Specifically include:
  • the lithium cobaltate sample obtained in step 2) was placed in a rotary tube furnace for subsequent heat treatment.
  • the heat treatment conditions were: nitrogen atmosphere, the temperature was raised to 550 °C at a heating rate of 5 °C/min, and at 550 °C After 6 hours of heat preservation, the temperature was naturally lowered; the obtained material was sieved through a 200-mesh sieve, and was vacuum-packed and stored in an aluminum-plastic bag; the obtained material was named "LCO-LMO-900".
  • Electrochemical test Using NMP as a solvent, LCO-LMO-1#, carbon black and PVDF were uniformly mixed in a mass ratio of 8:1:1 to prepare a positive electrode sheet.
  • the active material loading of the electrode sheet was about It is 4.5mg cm -2 .
  • Use 2032 button cells to prepare half batteries with lithium sheet as negative electrode, use Celgard 2035 diaphragm and high voltage electrolyte (mass ratio LiPF 6 : EMC: FEC 15:55:30), this half battery is at 3-4.65V ( vs.
  • the N/P ratio of the full battery is about 1.15
  • the commercial graphite carbon microsphere (MCMB) anode material is provided by Shenzhen BTR New Energy Materials Company.
  • the pole pieces of LCO-LMOF-800 and LCO-LMOF-850 are also prepared by the same preparation process.
  • the analysis shows that the cobalt content in the surface Li layer is related to the solution immersion and subsequent heat treatment process, so there is little difference between the three; however, the cobalt content in the lithium layer in the bulk phase is related to the sintering preparation process, so the difference between the three Larger; in general, the lower temperature sintering process leads to an increase in the cobalt content in the lithium layer.
  • the charge-discharge curve results of the new high-voltage lithium cobaltate “LCO-LMO-900” cathode material at a current density of 0.1C between 3-4.65V (vs. Li/Li + ) show that the reversible discharge capacity is 251mAh g -1 .
  • the new high-voltage lithium cobalt oxide "LCO-LMO-900" cathode material has a capacity retention rate of 81.2% after 500 cycles of 5C cycles between 3-4.65V (vs. Li/Li + ), showing extremely high electrochemical stability.
  • the lithium layer contains 1.6% Co, and the surface area is a mixed area of Li, Co, B, and O elements.
  • high-temperature sintering, solution immersion, and subsequent heat treatment were used to synthesize a new high-voltage lithium cobaltate cathode material containing 1.6% Co in the lithium layer. Specifically include:
  • Step 3 Subsequent heat treatment: put the lithium cobalt oxide sample obtained in step 2) in a rotary tube furnace for subsequent heat treatment. After 12 hours of heat preservation, the temperature was naturally lowered; the obtained material was sieved through a 200-mesh sieve, and vacuum-packed and stored in an aluminum-plastic bag; the obtained material was named "LCO-LBO-1#".
  • Electrochemical test Using NMP as a solvent, LCO-LBO-1#, carbon black and PVDF were uniformly mixed in a mass ratio of 8:1:1 to prepare a positive pole piece.
  • the active material loading of the pole piece was about It is 4.5mg cm -2 .
  • MCMB commercial graphite carbon microsphere
  • the material has a reversible discharge capacity of 247mAh g -1 at a current density of 0.1C.
  • the new high-voltage lithium cobalt oxide “LCO-LBO-1#” positive electrode material has a capacity retention rate of 83.6% after 500 cycles of 5C cycles between 3-4.65V (vs. Li/Li + ), respectively. exhibited high electrochemical stability.
  • the sintering temperature in step 1) and the heat treatment temperature in step 3) are respectively controlled to prepare lithium cobalt oxide layered cathode materials with different cobalt contents in the lithium layer.
  • the specific parameters and test results of cobalt content are shown in Table 1.
  • the bulk lithium layer contains no more than 3% cobalt
  • the reversible discharge capacity obviously increases with the increase of cobalt content in the lithium layer; however, when the cobalt content exceeds 3%, the reversible discharge capacity decreases instead. Therefore, preferably, the bulk lithium layer contains no more than 3% cobalt.
  • the cobalt content in the lithium layer is 1.8%, and the surface area is a mixed element area containing Li, Co, Ti, O and F.
  • high-temperature sintering, solution immersion, and subsequent heat treatment were used to synthesize a new high-voltage lithium cobaltate cathode material containing 1.8% Co in the lithium layer. Specifically include:
  • Step 3 Subsequent heat treatment: put the lithium cobalt oxide sample obtained in step 2) in a rotary tube furnace for subsequent heat treatment. After 12 hours of heat preservation, the temperature was naturally lowered; the obtained material was sieved through a 200-mesh sieve, and vacuum-packed and stored in an aluminum-plastic bag; the obtained material was named "LCO-LTOF".
  • Electrochemical test Using NMP as a solvent, LCO-LTOF, carbon black and PVDF were uniformly mixed at a mass ratio of 8:1:1 to prepare a positive electrode sheet.
  • the active material loading of the electrode sheet was about 4.5mg cm -2 .
  • MCMB commercial graphite carbon microsphere
  • the analysis results of the "LCO-LTOF" prepared in this example by Rietveld XRD show that the bulk crystal structure of the material contains 1.8% cobalt in the lithium layer, and the XPS semi-quantitative results show that the cobalt content in the lithium layer in the surface area is about 45%. , while the thickness of the surface area is less than 5nm.
  • the new high-voltage lithium cobaltate “LCO-LTOF” cathode material has a reversible discharge capacity of 243mAh g -1 at a current density of 0.1C between 3-4.65V (vs. Li/Li + ).
  • the new high-voltage lithium cobalt oxide "LCO-LTOF-1#" positive electrode material has a capacity retention rate of 86.5% after 500 cycles at 5C between 3-4.65V (vs. Li/Li + ), respectively. exhibited high electrochemical stability.
  • the lithium cobalt oxide layered positive electrode material of the present application can be obtained by sintering at 750-950° C. for 1-12 hours, and then treated by microwave or quenching process. Further, in order to increase the replacement of the surface interface area of the crystal structure, immersion in slightly acidic solution and heat treatment process can be added.
  • the soaking solution contains Li + , and at least one of Mg 2+ , Al 3+ , borate, Ti 4+ and F - ; wherein, the solution contains Li + , mainly to ensure that the lithium layer in the surface interface region other elements are used to replace lithium and/or cobalt in the lithium layer in the surface interface region, cobalt in the cobalt layer, or oxygen.
  • the soaking condition is 0-160°C soaking for 0.1-48h, and the stirring speed is maintained at 50-1000r/min during the whole process.
  • the heat treatment condition is heating at 200-700°C for 0.1-36h in an inert atmosphere or a reducing atmosphere.
  • sintering conditions and heat treatment conditions are the key factors affecting the cobalt content in the lithium layer of the crystal structure bulk phase and surface interface; specifically, the sintering temperature directly affects the cobalt content of the bulk lithium layer.
  • the sintering temperature The lower the bulk phase lithium layer, the higher the cobalt content; the heat treatment temperature directly affects the cobalt content of the surface interface lithium layer, the higher the heat treatment temperature, the higher the cobalt content of the surface interface lithium layer.
  • the lithium layer in the bulk phase of the preferred crystal structure contains 0.1%-5% cobalt, and the lithium layer in the surface interface region contains not less than 30% cobalt cobalt.
  • the sintering process directly affects the elements of each layer of the crystal structure, and the solution immersion and heat treatment mostly affect the elements of the surface interface area of the crystal structure. Therefore, further, various metal elements can be doped in the bulk phase according to requirements, or replaced with other elements in the interface region. For example, other metal elements can be added during the sintering process to achieve bulk metal element doping.
  • This doping can be doped in the bulk lithium layer and/or cobalt layer, for example, the bulk lithium layer is doped with Mg, cobalt The layer is doped with Al and/or Ti.
  • the doping amount of the bulk metal element should not be too much.
  • the proportion of the doped metal element in the bulk phase should not exceed 1%.
  • the element replacement in the interface region it is mainly realized by solution immersion and heat treatment, for example, the lithium and/or cobalt in the lithium layer in the surface interface region are partially replaced by Mg, and the cobalt in the cobalt layer in the surface interface region is replaced by Al, B and At least one of Ti is partially substituted, and the oxygen in the surface interface region is partially or completely substituted by fluorine.
  • the role of the surface interface region is mainly to conduct electricity and guide lithium, and not to participate in redox reactions, and to isolate the electrolyte; therefore, on the one hand, the cobalt content in the lithium layer in the interface region can exceed 30%; on the other hand , the proportion of metal elements replacing lithium and/or cobalt can also exceed 40%.
  • the lithium layer in the interface area is replaced by a large amount of cobalt or metal elements, which can better conduct electricity, guide lithium, and isolate the electrolyte; of course, in order not to affect the reversible intercalation and extraction of Li + , the thickness of the surface interface area is generally less than Or equal to 5nm.

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  • Battery Electrode And Active Subsutance (AREA)

Abstract

L'invention concerne un matériau d'électrode positive en couches à base d'oxyde de lithium-cobalt, un procédé de fabrication et une utilisation de celui-ci Le cobalt est contenu dans une couche de lithium de la structure cristalline du matériau d'électrode positive en couches à base d'oxyde de lithium-cobalt ; une transition de phase structurelle réversible et une réaction de variation de valence de l'oxygène réversible, pendant un processus de charge et de décharge à haute tension, supérieur ou égal à 4,5 V, sont obtenus ; et la quantité d'intercalation de lithium réversible et la capacité par gramme du matériau d'oxyde de lithium-cobalt sont améliorées, de telle sorte que d'excellentes propriétés électrochimiques sont démontrées sous une condition de charge et de décharge à haute tension. De plus, le procédé de préparation du matériau d'électrode positive en couches à base d'oxyde de lithium-cobalt, contenant du cobalt dans la couche de lithium, est simple et facile pour une production industrielle à grande échelle.
PCT/CN2021/122867 2021-10-09 2021-10-09 Matériau d'électrode positive en couches à base d'oxyde de lithium-cobalt, son procédé de fabrication et son utilisation WO2023056636A1 (fr)

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CN116093298B (zh) * 2023-03-29 2023-06-30 江门市科恒实业股份有限公司 钴酸锂正极材料及其制备方法、锂离子电池和应用

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