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CN118173743A - Positive electrode material, preparation method and application thereof, positive electrode plate and battery - Google Patents

Positive electrode material, preparation method and application thereof, positive electrode plate and battery Download PDF

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Publication number
CN118173743A
CN118173743A CN202410344136.8A CN202410344136A CN118173743A CN 118173743 A CN118173743 A CN 118173743A CN 202410344136 A CN202410344136 A CN 202410344136A CN 118173743 A CN118173743 A CN 118173743A
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positive electrode
equal
electrode material
coating
coating layer
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宋艺
李惠东
高艳
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Huizhou Liwinon Energy Technology Co Ltd
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Huizhou Liwinon Energy Technology Co Ltd
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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
    • H01M4/362—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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
    • 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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
    • H01M4/602—Polymers
    • H01M4/604—Polymers containing aliphatic main chain polymers
    • 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

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Composite Materials (AREA)
  • Manufacturing & Machinery (AREA)
  • Inorganic Chemistry (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

The invention discloses a positive electrode material, a preparation method and application thereof, a positive electrode plate and a battery, wherein the positive electrode material has both anion doping and surface coating, can effectively improve the interface stability and capacity density of the positive electrode material, and has good alleviation effects on electrolyte decomposition and corrosion of the positive electrode material, so that the electrochemical performance of the positive electrode material under high voltage is improved. In addition, in the invention, the anion doping and the surface coating are both S elements, and other miscellaneous elements are not introduced; inhibition of the possible anion reduction reaction by cladding results in loss of S at the substituted O position in the lattice; the mass capacity density consumed by the surface coating material is compensated by anion doping. Finally, the invention improves the capacity density and long-cycle stability of the positive electrode material through the synergistic effect of lattice oxygen anion doping and CEI-like surface coating, and the obtained positive electrode material has better structural stability, thermal stability and electrochemical performance.

Description

Positive electrode material, preparation method and application thereof, positive electrode plate and battery
Technical Field
The invention relates to the technical field of batteries, in particular to a positive electrode material, a preparation method and application thereof, a positive electrode plate and a battery.
Background
In the field of sodium ion batteries, layered transition metal oxide materials have high specific energy and become ideal positive electrode materials for sodium ion batteries. However, due to its strong surface nucleophilicity, there are serious interfacial instability and capacity fade problems. For example, under the action of electrolyte, a crystal structure collapse easily occurs in Na xMnO2 (NMO) as a cathode material, and manganese ions are dissolved, so that an interface reaction is accelerated, and the service life of a sodium ion battery is further shortened. The same phenomenon is also present in other layered positive electrode material systems such as manganese-based oxides or manganese-based ternary materials, for example Nax(NiyMnz)O2(NNMO)、Nax(LiyMnz)O2(NLMO)、Nax(FeyMnz)O2(NFMO).
In the related art, reducing side reactions of the positive electrode and the electrolyte through interface engineering is a common modification method, for example, adding an additive into the electrolyte, and generating a positive electrode electrolyte interface (CEI) on the surface of the positive electrode through in-situ reaction. However, CEI instability results in poor electrolyte consumption and cycle life, accelerated manganese ion elution, deteriorated high-pressure cycle performance of layered transition metal oxide materials, and poor cycle stability of the prepared battery. While the increase of the capacity density of the sodium ion battery can be promoted by anion doping, the preparation process of the high-temperature solid-phase method synthesis is complex and takes a long time, and the method is not compatible with the common coprecipitation method for preparing the positive electrode matrix material, and the anion source loss is large.
Therefore, the problems of insufficient interface stability and capacity attenuation of the anode material are solved, and the improvement of the structural stability, the thermal stability and the electrochemical performance of the material is of great significance.
Disclosure of Invention
The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides a positive electrode material, a preparation method and application thereof, a positive electrode plate and a battery, and aims to solve the problems of insufficient interface stability and capacity attenuation of the current positive electrode material.
In a first aspect of the present invention, a positive electrode material is provided, including an inner core and a coating layer coated on at least a portion of a surface of the inner core; the inner core and the coating layer both contain an S element; the coating layer contains sulfonyl polymer.
The positive electrode material provided by the embodiment of the invention has at least the following beneficial effects: the invention provides a positive electrode material with a protective layer structure, which has two modification modes of anion doping and surface coating. Wherein, the anion (S 2-) doping can induce Mn 4+ to be partially reduced into Mn 3+ through charge neutrality, increase redox centers, and disturb the ordered structure of Na +, thereby promoting the increase of the capacity density of the sodium ion battery; the coating mainly takes the sulfonyl polymer as a main component, and the coating material forms a sulfonyl polymer coating layer with CEI-like protection function on the surface of the positive electrode material in an ex-situ manner, so that the contact interface of the positive electrode material and electrolyte can be well stabilized, the dissolution of manganese ions in the manganese-based material is inhibited, the volume expansion of the positive electrode material in the sodium removing process is effectively reduced, the interface stability of the positive electrode material is improved, meanwhile, the decomposition of the electrolyte and the corrosion of the positive electrode material are well relieved, and the circulation stability of the material is greatly improved, so that the electrochemical performance of the positive electrode material under high voltage is improved. Meanwhile, the coating layer can be directly characterized through testing, the thickness of the coating layer is controllable, the action result is more visual, and the action mechanism is more definite. In addition, in the invention, both the anion doping (S 2- doping) and the surface coating (sulfonyl polymer coating) are S elements, and other miscellaneous elements are not introduced; inhibition of the possible anion reduction reaction by cladding results in loss of S at the substituted O position in the lattice; the mass capacity density consumed by the surface coating material is compensated by anion doping. Finally, the invention improves the capacity density and long-cycle stability of the positive electrode material through the synergistic effect of lattice oxygen anion doping and CEI-like surface coating, and the obtained positive electrode material has better structural stability, thermal stability and electrochemical performance.
In some embodiments of the invention, the inner core comprises an S-doped manganese-based material. Anion (S 2-) doping is carried out in the manganese-based positive electrode material, and lattice oxygen anion doping can induce Mn 4+ to be partially reduced into Mn 3+ through charge neutrality, so that redox centers are increased, meanwhile, the ordered structure of Na + is disturbed, and the increase of the capacity density of the sodium ion battery is promoted.
In some embodiments of the invention, the thickness of the coating layer is 100-140 μm, for example, 100 μm, 200 μm, 300 μm, 400 μm may be used.
In some preferred embodiments of the invention, the thickness of the coating is 120 to 130 μm, more preferably about 120 μm.
In some preferred embodiments of the present invention, the S-doped manganese-based material comprises Na x(TMyMnz)O2-aSa, wherein 0.44.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0 < z.ltoreq.1, and y+z=1, 0 < a < 2, and TM is selected from at least one of Li, ni, fe. Specifically, the material may be Nax(NiyMnz)O2-aSa、Nax(LiyMnz)O2-aSa、Nax(FeyMnz)O2-aSa or another doped manganese-based ternary material, and may also be Na xMn O2-aSa or another doped manganese-based oxide (i.e., y=0, z=1).
In some more preferred embodiments of the present invention, 0.ltoreq.y.ltoreq.0.5, 0.5.ltoreq.z.ltoreq.1, and y+z=1. Specifically, na 0.88(Fe0.25Mn0.75)O2-aSa, 0 < a < 2, can be used.
In some embodiments of the invention, the sulfone-based polymer has the structural formula:
wherein R 1、R2 is independently selected from substituted or unsubstituted C1-C4 linear alkane, n is the polymerization degree of the sulfonyl polymer, and n is 10-10,000.
In some preferred embodiments of the invention, R 1、R2 is independently selected from substituted or unsubstituted C2-C5 linear alkanes, more preferably ethyl.
The coating layer takes the sulfonyl polymer as the main material, is a coating layer with CEI-like protection effect formed on the surface of the positive electrode material in an ex-situ manner by a thermal decomposition method, can well stabilize the contact interface between the positive electrode material and electrolyte, simultaneously inhibit the dissolution of manganese ions in the manganese-based material, and greatly improve the cycling stability of the material. The coating material of the present invention is often used as an electrolyte solvent rather than an electrolyte additive, and in the present invention, the coating material containing sulfone groups is used as an electrolyte additive to participate in the thermal decomposition reaction, and to participate in the formation of a CEI-like protective layer to protect the cathode material. Finally, the coating material of the invention forms a coating layer with CEI-like protection function on the surface of the positive electrode material of the sodium ion battery in an ex-situ manner by a thermal decomposition method, can well stabilize the contact interface between the positive electrode material and electrolyte, simultaneously inhibit the dissolution of manganese ions in the manganese-based material, and greatly improve the cycling stability of the material. Moreover, compared with the coating layer used as an electrolyte additive, the coating layer of the thermal decomposition method can be directly characterized through testing, the thickness of the coating layer is controllable, the action result is more visual, and the action mechanism is more definite.
In some embodiments of the present invention, the coating layer is polymerized from a coating material, the coating material including a sulfone-based compound having a structural formula as follows:
wherein R 1'、R2' is independently selected from H atom, substituted or unsubstituted C1-C10 straight-chain alkane, preferably H atom.
Specifically, the coating material is sulfolane (C 4H8O2 S, CAS: 126-0), and the structural formula is
The reduction decomposition of the coating material mainly comprises a sulfonyl polymer. The sulfonyl compound is decomposed by a thermal decomposition method through a reduction ring-opening reaction to obtain the coating layer of the sulfonyl polymer. The coating material is preferably sulfolane, which has good solubility, low volatility and high voltage stability, and is generally used as a solvent; however, its decomposition as a solvent in the electrolyte system is disadvantageous and should be avoided as much as possible. According to the invention, sulfolane is used as an electrolyte additive, so that the sulfolane is subjected to thermal decomposition reaction in a positive electrode, and participates in forming a CEI-like protective layer to protect a positive electrode material. Wherein, the operation conditions of the thermal decomposition reaction are as follows: mixing the matrix material and the coating material according to the mass ratio (solid-liquid mixing through ultrasonic and ball milling if solid-solid mixing), putting into a bottle after uniformly mixing, heating to 220-240 ℃ in an inert atmosphere through an oil bath, setting the heat preservation time (10 g about 2 h) according to the total mass of the matrix material and the coating material, and heating the solid-liquid mixture until the liquid disappears. When the temperature of sulfolane exceeds 220 ℃, the decomposition speed of the sulfolane is rapidly increased along with the increase of the temperature, so that the sulfolane is promoted to decompose to generate an organic polymer and sulfur dioxide, wherein the organic polymer coating layer can prevent the electrolyte from directly contacting with the anode material to a certain extent, so that the anode material is protected, the contact interface between the anode material and the electrolyte is stabilized, meanwhile, the dissolution of manganese ions in the manganese-based material is inhibited, and the cycle stability of the material is greatly improved. And compared with the coating layer used as the electrolyte additive, the coating layer of the thermal decomposition method can be directly characterized by testing, the thickness of the coating layer is controllable, the action result is more visual, and the action mechanism is more definite. In contrast, in situ CEI generation requires the addition of additives to the electrolyte, resulting in complex CEI compositions, which are dependent on factors such as the electrode, electrolyte, electrochemical window, etc. The organic/inorganic hybrid film formed during actual charge and discharge is not completely controllable, may crack, forms a non-uniform, thick CEI, results in low coulombic efficiency and short cycle life.
In some embodiments of the invention, the thickness of the coating layer is 100-140 μm, for example, 100 μm, 200 μm, 300 μm, 400 μm may be used.
In some preferred embodiments of the invention, the thickness of the coating is 120 to 130 μm, more preferably about 120 μm.
In a second aspect of the present invention, a method for preparing the above positive electrode material is provided, including the steps of:
S1, providing a matrix material, a coating material and an anion source containing S 2-;
S2, mixing the matrix material with the anion source and then reacting to obtain an S-doped inner core;
S3, mixing the inner core with the coating material, and then carrying out thermal decomposition reaction, wherein the coating material forms a coating layer containing sulfonyl polymers on at least part of the surface of the inner core, so as to obtain the positive electrode material.
The preparation method of the positive electrode material provided by the embodiment of the invention has at least the following beneficial effects: according to the preparation method, anions are doped into a matrix material to obtain the core, and then the doped core and the coating material are subjected to thermal decomposition to form the coating layer ex-situ. The coating material containing the sulfonyl is used as an electrolyte additive to participate in a thermal decomposition reaction, a sulfonyl polymer is formed through reduction and ring opening, and the coating material participates in forming a CEI-like protective layer to protect the positive electrode material, so that the contact interface of the positive electrode material and the electrolyte can be well stabilized, meanwhile, the dissolution of manganese ions in the manganese-based material is inhibited, and the cycling stability of the material is greatly improved. The coating obtained by the thermal decomposition method can be directly characterized by testing, the thickness of the coating is controllable, the action result is more visual, and the action mechanism is more definite. Moreover, the doping and coating process is simple, the reaction conditions are not harsh, the time consumption is short, the method is compatible with the common preparation method of the anode matrix material, and the loss of an anion source is reduced.
In some embodiments of the invention, the operating conditions for the thermal decomposition reaction are: mixing the matrix material and the coating material according to the mass ratio (solid-liquid mixing through ultrasonic and ball milling if solid-solid mixing), putting into a bottle after uniformly mixing, heating to 220-240 ℃ in an inert atmosphere through an oil bath, setting the heat preservation time (10 g about 2 h) according to the total mass of the matrix material and the coating material, and heating the solid-liquid mixture until the liquid disappears. Compared with the coating layer which is used as an electrolyte additive and formed in an ex-situ manner by a thermal decomposition method, the coating layer can be directly characterized by testing, the thickness of the coating layer can be controlled, the action result is more visual, and the action mechanism is more definite. In contrast, in situ CEI generation requires the addition of additives to the electrolyte, resulting in complex CEI compositions, which are dependent on factors such as the electrode, electrolyte, electrochemical window, etc. The organic/inorganic hybrid film formed during actual charge and discharge is not completely controllable, may crack, forms a non-uniform, thick CEI, results in low coulombic efficiency and short cycle life.
In some embodiments of the invention, the matrix material comprises a manganese-based material.
In some preferred embodiments of the present invention, the manganese-based material comprises Na x(TMyMnz)O2, wherein 0.44.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 0 < z.ltoreq.1, and y+z=1, and TM is selected from at least one of Li, ni, fe. Specifically, the material may be Nax(NiyMnz)O2(NNMO)、Nax(LiyMnz)O2(NLMO)、Nax(FeyMnz)O2(NFMO) or another doped manganese-based ternary material, and may also be Na xMn O2 (NMO) or another doped manganese-based oxide (i.e., y=0, z=1).
In some more preferred embodiments of the present invention, 0.ltoreq.y.ltoreq.0.5, 0.5.ltoreq.z.ltoreq.1, and y+z=1.
Preferably, the matrix material is Na 0.88(Fe0.25Mn0.75)O2, i.e. x=0.88, y=0.25, z=0.75.
In the invention, the value of x is 5/6 approximately equal to 0.83, which is favorable for forming a pure phase material of a P2 phase with high sodium content, and the P2 phase pure phase material has a specific P63/mmc crystal structure as a matrix material and has the meaning of stable structure. The value of y is 1/4 approximately equal to 0.25, because TM is Fe and is an active doping element, and a value of y larger than 0.4 can cause low Mn content, and TM occupies too many Mn sites to be beneficial to a stable structure formed by a MnO 6 framework; when y is less than 0.1, the content of doping elements is low, the occupied Mn site is small, and the value as a second redox center is low; through screening, the Fe: mn=1:3 structure is stable, the average valence state of TMyMnz is reduced by Fe, and Fe-O bond formation is favorable for S insertion into O sites to form nonmetallic element doping, so that the optimal material is finally determined to be 0.88 in x value, 1/4 in y value and 1-3/4 in z value.
In some embodiments of the invention, the anion source comprises S 2-. In the invention, the anion source is a compound containing S 2-, so that both anion doping and surface coating are S elements, and other hetero elements are not introduced. The loss of S at the substituted O position in the crystal lattice is caused by coating inhibition of possible anion reduction reaction, the mass capacity density consumed by the surface coating material is compensated by anion doping, and the capacity density and long-cycle stability of the positive electrode material are improved together by the synergistic effect of the lattice oxygen anion doping and the artificial CEI surface coating.
In some preferred embodiments of the invention, the anion source is selected from one or more of Na2S·9H2O(CAS:1313-84-4)、Na2S(CAS:1313-82-2)、H2Na2OS(CAS:27610-45-3)、H3NaOS(CAS:207683-19-0)、HNaS(CAS:16721-80-5)、K2S(CAS:1312-73-8)、KHS(CAS:1262770-73-9).
Preferably, the anion source is Na 2S·9H2 O.
In some embodiments of the invention, the sulfone-based polymer has the structural formula:
wherein R 1、R2 is independently selected from substituted or unsubstituted C1-C4 linear alkane, n is the polymerization degree of the sulfonyl polymer, and n is 10-10,000.
In some preferred embodiments of the invention, R 1、R2 is independently selected from substituted or unsubstituted C2-C5 linear alkanes, more preferably ethyl.
In some embodiments of the present invention, the coating layer is polymerized from a coating material, the coating material including a sulfone-based compound having a structural formula as follows:
wherein R 1'、R2' is independently selected from H atom, substituted or unsubstituted C1-C10 straight-chain alkane, preferably H atom.
Specifically, the coating material is sulfolane (C 4H8O2 S, CAS: 126-0), and the structural formula is
According to the preparation method, the sulfonyl compound is decomposed through a thermal decomposition method and a reduction ring-opening reaction, so that the coating layer of the sulfonyl polymer is obtained. The coating material is preferably sulfolane, and the sulfolane is used as an electrolyte additive to cause thermal decomposition reaction of the electrolyte additive in the positive electrode to participate in forming a CEI-like protective layer to protect the positive electrode material. When the temperature of sulfolane exceeds 220 ℃, the decomposition speed of the sulfolane is rapidly increased along with the increase of the temperature, so that the sulfolane is promoted to decompose to generate an organic polymer and sulfur dioxide, wherein the organic polymer coating layer can prevent the electrolyte from directly contacting with the anode material to a certain extent, so that the anode material is protected, the contact interface between the anode material and the electrolyte is stabilized, meanwhile, the dissolution of manganese ions in the manganese-based material is inhibited, and the cycle stability of the material is greatly improved. And compared with the coating layer used as the electrolyte additive, the coating layer of the thermal decomposition method can be directly characterized by testing, the thickness of the coating layer is controllable, the action result is more visual, and the action mechanism is more definite.
In some embodiments of the invention, the thickness of the coating layer is 100-140 μm, for example, 100 μm, 200 μm, 300 μm, 400 μm may be used.
In some preferred embodiments of the invention, the thickness of the coating is 120 to 130 μm, more preferably about 120 μm.
In some embodiments of the invention, the molar ratio of the matrix material to the anion source is 1 (0.01 to 0.20).
In some preferred embodiments of the invention, the molar ratio of the matrix material to the anion source is 1 (0.04 to 0.10).
In some embodiments of the invention, the mass ratio of the core to the cladding material is 1 (1-20). As the coating amount increases, the improvement in the cycle performance of the cathode material gradually increases. The coating layer positioned on the surface area of the particles effectively reduces the contact between the material and the electrolyte, reduces the dissolution of manganese, further prevents the phase change and improves the electrochemical performance of the anode material.
In some preferred embodiments of the invention, the mass ratio of the core to the cladding material is 1 (2-7).
The invention reasonably controls the doping amount of the anion source and the coating amount of the coating material. The solid molar mass of the anion source is 1-20% of that of the matrix material, and the mass of the coating material is 1-20 times of that of the doped matrix material (i.e. the inner core). The proportion can better balance coating and doping: the loss of S in the lattice, which has displaced the O sites, is caused by the reduction reaction of anions that may occur by cladding inhibition, the mass-to-volume density consumed by the surface cladding material being compensated by anion doping. And finally, the lattice oxygen anion doping and the artificial CEI surface coating are cooperated, and meanwhile, the capacity density and the long-cycle stability of the positive electrode material are improved.
In some embodiments of the present invention, step S2 specifically includes: and adding the anion source into the matrix material, immersing the matrix material in absolute ethyl alcohol, stirring and mixing in a vacuum environment to react, and vacuum drying after the reaction is finished to obtain the S-doped inner core.
Preferably, the stirring and mixing temperature is room temperature.
Preferably, the vacuum drying temperature is from 60℃to 120℃and more preferably about 120 ℃.
Preferably, the vacuum drying time is 12 to 24 hours, more preferably about 12 hours.
In some embodiments of the invention, the thermal decomposition reaction is carried out at a reaction temperature of 200 ℃ to 260 ℃, preferably about 240 ℃.
In some embodiments of the invention, the thermal decomposition reaction is carried out for a reaction time of 1 to 3 hours, preferably about 2 hours.
In a third aspect of the present invention, there is provided a positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, the positive electrode active material layer comprising the positive electrode material as described above or a positive electrode material prepared by the above-described preparation method.
The positive plate provided by the embodiment of the invention has at least the following beneficial effects: the positive electrode plate provided by the invention has the advantages that the positive electrode active material adopts the anion doped positive electrode material with the protective layer structure, the material can effectively inhibit the interfacial reaction caused by dissolution of manganese ions in the process of sodium intercalation removal of the manganese-based positive electrode material, the mass capacity density occupied by the coating layer is effectively reduced, the interfacial stability and the capacity density of the positive electrode material are improved, and meanwhile, the decomposition of electrolyte and the corrosion of the positive electrode material are well relieved, so that the electrochemical performance of the positive electrode plate under high voltage is improved.
In some embodiments of the present invention, the positive electrode current collector is a common positive electrode current collector in the art, such as, but not limited to, aluminum foil. The conductive agent, binder, etc. used for preparing the positive plate are all conventional materials in the art, and are not described herein.
In a fourth aspect of the present invention, a battery is provided that includes a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet as described above.
The battery according to the embodiment of the invention has at least the following beneficial effects: the battery provided by the invention adopts the positive plate prepared from the positive electrode material, so that the battery has at least all the beneficial effects brought by the technical scheme of the embodiment, namely, the obtained battery is more stable, the electrochemical performance is better, the gram capacity is higher, and the cycle capacity retention rate is better.
In some embodiments of the invention, the battery comprises a sodium ion battery, but is not limited thereto. The positive plate provided by the invention can also be used for energy storage devices such as super capacitors and hybrid super capacitors. The negative electrode, the separator, the electrolyte and the like of the assembled battery are not limited, and materials commonly used in the field can be reasonably adopted and are not repeated here.
In a fifth aspect of the present invention, an application of the above-mentioned positive electrode material or a positive electrode material prepared by using the above-mentioned preparation method in preparing an energy storage device, an electric device or an electronic device is provided.
Drawings
The invention is further described with reference to the accompanying drawings and examples, in which:
fig. 1 is a schematic view showing the X-ray diffraction (XRD) results of the positive electrode sheet produced in example 4 of the present invention.
Detailed Description
The conception and the technical effects produced by the present invention will be clearly and completely described in conjunction with the embodiments below to fully understand the objects, features and effects of the present invention. It is apparent that the described embodiments are only some embodiments of the present invention, but not all embodiments, and that other embodiments obtained by those skilled in the art without inventive effort are within the scope of the present invention based on the embodiments of the present invention.
In the description of the present invention, the descriptions of the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
In the description of the present invention, unless otherwise indicated, the numerical ranges "a-b" represent shorthand representations of any combination of real numbers between a and b, where a and b are both real numbers. Unless otherwise indicated, the various reactions or operational steps may or may not be performed sequentially. Preferably, the reaction process in the present invention is carried out sequentially.
The following examples are not to be construed as limiting the specific techniques or conditions described in the literature in this field or as per the product specifications. All reagents or equipment were commercially available as conventional products without the manufacturer's knowledge.
Example 1
1. Preparation of cathode Material
(1) The preparation method of the matrix material Na 0.88(Fe0.25Mn0.75)O2 powder comprises the following specific steps: high temperature solid phase synthesis, weighing Na 2CO3,Fe2O3 and Mn 2O3 according to a certain stoichiometric ratio, fully grinding and mixing, adding 5% sodium source to compensate instant sodium at high temperature, calcining the mixed powder in 900 deg.C air atmosphere for 15h to obtain the matrix material powder.
(2) And (3) adding an anion source Na 2S·9H2 O into the matrix material obtained in the step (1), and controlling the molar ratio of the matrix material to the solid of the anion source to be 1:0.04. And immersing the core in absolute ethyl alcohol, stirring and mixing the core in a room temperature vacuum environment, and drying the core for 12 hours at 120 ℃ in a vacuum oven to obtain the anion doped core.
(3) And (3) immersing the anion doped inner core obtained in the step (2) with coating material liquid, and controlling the mass ratio of the inner core powder to the liquid coating material to be 1:2. And (3) mixing and then carrying out thermal decomposition for 2 hours at 240 ℃ to obtain the positive electrode material.
Wherein the thickness of the coating layer is 120 mu m, the coating material is sulfolane (C 4H8O2 S, CAS: 126-33-0), the melting point is 27.4-27.8 ℃, and the coating material is in a liquid state in the preparation process.
2. Preparation of positive plate
And (3) fully stirring and uniformly mixing the prepared positive electrode material, the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) in an N-methyl pyrrolidone solvent system according to a mass ratio of 8:1:1, coating the mixture on an Al foil of a positive electrode current collector, drying the mixture at a vacuum temperature of 80 ℃, and cutting the mixture to obtain a positive electrode plate.
3. Preparation of electrolyte
In a glove box, naPF 6 is taken as sodium salt, fluoroethylene carbonate (FEC) with the mass percent of 5 percent is added into the solution according to the volume ratio of 1:1 (EC: PC) as electrolyte solvent, and sodium ion battery electrolyte is prepared according to the concentration of 1mol/L for standby.
4. Preparation of sodium ion button cell
The positive pole piece (the surface density is 2.5mg/cm 2) is adopted as the positive pole, sodium metal is adopted as the negative pole, PE membrane is adopted to assemble 2032 type layered oxide button cell, and the button cell is assembled from bottom to top in sequence: the negative electrode comprises a negative electrode shell, an elastic sheet, a stainless steel gasket, a sodium sheet, electrolyte, a PE diaphragm, electrolyte, a positive electrode material and a positive electrode shell.
Example 2
Consistent with the preparation of example 1, except that the molar ratio of matrix material to solids of the anion source in example 2 was 1:0.04; the mass ratio of the core powder to the liquid coating material sulfolane is 1:5.
Example 3
Consistent with the preparation of example 1, except that the molar ratio of matrix material to solids of the anion source in example 3 was 1:0.04; the mass ratio of the core powder to the liquid coating material sulfolane is 1:7.
Example 4
Consistent with the preparation of example 1, except that the molar ratio of matrix material to solids of the anion source in example 4 was 1:0.08; the mass ratio of the core powder to the liquid coating material sulfolane is 1:2.
Example 5
Consistent with the preparation of example 1, except that the molar ratio of matrix material to solids of the anion source in example 5 was 1:0.08; the mass ratio of the core powder to the liquid coating material sulfolane is 1:5.
Example 6
Consistent with the preparation of example 1, except that the molar ratio of matrix material to solids of the anion source in example 5 was 1:0.08; the mass ratio of the core powder to the liquid coating material sulfolane is 1:7.
Example 7
Consistent with the preparation of example 1, except that the molar ratio of matrix material to solids of the anion source in example 7 was 1:0.10; the mass ratio of the core powder to the liquid coating material sulfolane is 1:2.
Example 8
Consistent with the preparation of example 1, except that the molar ratio of matrix material to solids of the anion source in example 8 was 1:0.10; the mass ratio of the core powder to the liquid coating material sulfolane is 1:5.
Example 9
Consistent with the preparation of example 1, except that the molar ratio of matrix material to solids of the anion source in example 9 was 1:0.10; the mass ratio of the core powder to the liquid coating material sulfolane is 1:7.
Example 10
Consistent with the preparation of example 1, except that the molar ratio of matrix material to solids of the anion source in example 9 was 1:0.01; the mass ratio of the core powder to the liquid coating material sulfolane is 1:2.
Example 11
Consistent with the preparation of example 1, except that the molar ratio of matrix material to solids of the anion source in example 9 was 1:0.2; the mass ratio of the core powder to the liquid coating material sulfolane is 1:2.
Comparative example 1
The differences from the examples are: no anion doping nor coating is performed.
The preparation method of the positive electrode material in comparative example 1 is:
Directly immersing a matrix material Na 0.88(Fe0.25Mn0.75)O2 in absolute ethyl alcohol, drying for 12 hours at 120 ℃ in a vacuum oven, and then heating for 2 hours at 240 ℃ to obtain the positive electrode material.
Then the method for preparing the positive plate and the sodium ion button cell by using the positive electrode material is the same as that of the example 1.
Comparative example 2
The differences from the examples are: anion doping was performed without coating.
The preparation method of the positive electrode material in comparative example 2 is:
An anion source Na 2S·9H2 O is added into the matrix material Na 0.88(Fe0.25Mn0.75)O2, and the molar ratio of the matrix material to the anion source is controlled to be 1:0.08. And (3) immersing the cathode material in absolute ethyl alcohol, stirring and mixing the cathode material in a room temperature vacuum environment, and drying the cathode material for 12 hours at 120 ℃ in a vacuum oven to obtain the anion doped material which is not coated.
Then the method for preparing the positive plate and the sodium ion button cell by using the positive electrode material is the same as that of the example 1.
Comparative example 3
The differences from the examples are: the coating was performed without anion doping.
The preparation method of the positive electrode material in comparative example 3 is:
The coating material sulfolane is directly used for immersing the matrix material without doping, and the mass ratio of the matrix material to the liquid coating material is controlled to be 1:5. And (3) mixing and then carrying out thermal decomposition for 2 hours at 240 ℃ to obtain the positive electrode material.
Then the method for preparing the positive plate and the sodium ion button cell by using the positive electrode material is the same as that of the example 1.
Performance testing
(1) XRD testing
The positive electrode sheet prepared in example 4 was subjected to an X-ray diffraction (XRD) test. X-ray diffraction (XRD) is mainly used for researching the crystal structure inside a material, because X-rays have a wavelength similar to the interplanar spacing and have certain penetrability, one beam of X-rays passes through the crystal to diffract, and then the diffraction pattern is analyzed, so that phase identification and structural analysis can be performed on the X-rays. Test working conditions: cu K alpha radiation, working current of 250mA, continuous scanning, working voltage of 40kV, scanning range 2 theta of 10-80 degrees and scanning speed of 2 degrees min-1.
The XRD test results are shown in figure 1. As can be seen from the figure, a distinct and sharp strong diffraction peak is observed in the range of 10-20℃corresponding to the (002) diffraction crystal plane of the P2 pure phase. On the basis of pure-phase matrix materials, no impurity peak is found, which indicates that the doping of S in lattice O position does not affect the original lattice structure of the material, the polysulfone coating of the outer layer is artificial SEI, and the pure-phase structure of the matrix materials is not affected.
(2) Gram Capacity test
The sodium ion button cells in the comparative example and the example were each charged at a constant current of 0.1C rate to a voltage of 4.5V at normal temperature, and further charged at a constant voltage of 4.5V to a current of less than 0.05C to a full charge state of 4.5V. Then constant current discharge was performed at 0.1C magnification until the voltage was stopped at 2.0V.
(3) Cycle performance test
The sodium ion coin cells prepared in the comparative examples and examples were each taken 5 by repeating charge and discharge of the sodium ion coin cells by the following steps, and the cyclic capacity retention rate was calculated:
Firstly, carrying out first charge and discharge in an environment of 25 ℃, carrying out constant current and constant voltage charge under a charge current of 1C (namely, a current value of theoretical capacity is completely discharged in 1 h) until the upper limit voltage is 4.5V, then carrying out constant current discharge under a discharge current of 1C until the final voltage is 2V, and recording the discharge capacity of the first cycle; then, 100 charge and discharge cycles were performed, and the discharge capacity at the 100 th cycle was recorded.
Cycle capacity retention= (discharge capacity of the 100 th cycle/discharge capacity of the first cycle) ×100%.
Gram capacity test and cycle performance test data for examples 1-11 and comparative examples 1-3 are shown in Table 1:
TABLE 1
As can be seen from the comparison of the examples and the comparative examples, the S is adopted to dope the anions at the O site, so that the formed lattice oxygen anion doping can stabilize the anion reduction reaction of oxygen at high pressure, and meanwhile, the Na + diffusion is accelerated by disturbing the ordered structure of Na +, the increase of the capacity density of the sodium ion battery is promoted, the discharge gram capacity can be greatly improved, and the influence of the capacity retention rate is smaller; the sulfolane polymer coating layer is used for coating the sulfolane-decomposed artificial CEI polymer coating layer, so that the mechanical attenuation of the coating layer in the charge and discharge process is slowed down, the stability of the interface between the positive electrode material and the electrolyte is improved, and the cycle capacity retention rate of the battery is greatly improved. Comparative example 2 doped with anions alone greatly increases gram capacity while reducing cycle stability due to anion reduction reaction and the like; comparative example 3, which was coated alone, greatly improved the cycle stability, but the coating layer affected the gram capacity. When the doping and coating are used simultaneously, the gram capacity and the cycle stability of examples 1 to 11 can be improved simultaneously as compared with comparative example 1. Namely, the doped coated double-modified material can achieve a synergistic effect, and simultaneously, the gram capacity and the cycle stability of the material are improved.
The foregoing examples illustrate only a few embodiments of the invention and are described in detail herein without thereby limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention.

Claims (10)

1. The positive electrode material is characterized by comprising an inner core and a coating layer coated on at least part of the surface of the inner core;
The inner core and the coating layer both contain an S element;
wherein the coating layer contains a sulfonyl polymer.
2. The positive electrode material according to claim 1, wherein the structural formula of the sulfone-based polymer is as follows:
Wherein R 1、R2 is independently selected from substituted or unsubstituted C1-C4 linear alkane, n is the polymerization degree of the sulfonyl polymer, and n is 10-10,000;
preferably, the thickness of the coating layer is 100 to 140. Mu.m, preferably 120 to 130. Mu.m.
3. The positive electrode material of claim 1, wherein the core comprises an S-doped manganese-based material;
Preferably, the S-doped manganese-based material comprises Na x(TMyMnz)O2-aSa, wherein x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, y+z=1, a is more than 0 and less than 2, and TM is at least one of Li, ni and Fe;
preferably, 0.ltoreq.y.ltoreq.0.5, 0.5.ltoreq.z.ltoreq.1, and y+z=1.
4. A method for producing the positive electrode material according to any one of claims 1 to 3, comprising the steps of: providing a matrix material, a coating material, and an anion source comprising S 2-;
Mixing the matrix material with the anion source and then reacting to obtain an S-doped kernel;
And mixing the inner core with the coating material, and then carrying out thermal decomposition reaction, wherein the coating material forms a coating layer containing sulfonyl polymer on at least part of the surface of the inner core, so as to obtain the positive electrode material.
5. The method for producing a positive electrode material according to claim 4, wherein the base material comprises a manganese-based material; preferably, the manganese-based material comprises Na x(TMyMnz)O2, wherein x is more than or equal to 0.44 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and y+z=1, wherein TM is at least one of Li, ni and Fe;
preferably, y is more than or equal to 0 and less than or equal to 0.5, z is more than or equal to 0.5 and less than or equal to 1, and y+z=1;
Preferably, the anion source comprises S 2-;
Preferably, the anion source is selected from one or more of Na 2S·9H2O、Na2S、H2Na2OS、H3NaOS、HNaS、K2 S, KHS;
preferably, the structural formula of the sulfonyl polymer is as follows:
Wherein R 1、R2 is independently selected from substituted or unsubstituted C1-C4 linear alkane, n is the polymerization degree of the sulfonyl polymer, and n is 10-10,000;
Preferably, the coating material comprises a sulfonyl compound, the structural formula of the sulfonyl compound is
Wherein R 1'、R2' are each independently selected from H atoms, substituted or unsubstituted C1-C10 linear alkanes.
6. The method of producing a positive electrode material according to claim 4, wherein the molar ratio of the base material to the anion source is 1 (0.01 to 0.20), preferably 1 (0.04 to 0.10);
Preferably, the mass ratio of the inner core to the coating material is 1 (1-20), preferably 1 (2-7);
preferably, the thickness of the coating layer is 100 to 140. Mu.m, preferably 120 to 130. Mu.m.
7. The method according to claim 4, wherein the thermal decomposition reaction is carried out at a reaction temperature of 200 to 260 ℃ for a reaction time of 1 to 3 hours.
8. A positive electrode sheet comprising a positive electrode current collector and a positive electrode active material layer coated on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer comprises the positive electrode material according to any one of claims 1 to 3 or the positive electrode material prepared by the preparation method according to any one of claims 4 to 7.
9. A battery comprising a positive electrode sheet, a negative electrode sheet, and a separator interposed between the positive electrode sheet and the negative electrode sheet, wherein the positive electrode sheet is as claimed in claim 8.
10. Use of the positive electrode material according to any one of claims 1 to 3 or prepared by the preparation method according to any one of claims 4 to 7 in the preparation of an energy storage device, an electrical device or an electronic device.
CN202410344136.8A 2024-03-25 2024-03-25 Positive electrode material, preparation method and application thereof, positive electrode plate and battery Pending CN118173743A (en)

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