WO2024078053A1 - 负极材料及其制备方法、二次电池和用电设备 - Google Patents

负极材料及其制备方法、二次电池和用电设备 Download PDF

Info

Publication number
WO2024078053A1
WO2024078053A1 PCT/CN2023/104986 CN2023104986W WO2024078053A1 WO 2024078053 A1 WO2024078053 A1 WO 2024078053A1 CN 2023104986 W CN2023104986 W CN 2023104986W WO 2024078053 A1 WO2024078053 A1 WO 2024078053A1
Authority
WO
WIPO (PCT)
Prior art keywords
negative electrode
electrode material
shell
layer
shell layer
Prior art date
Application number
PCT/CN2023/104986
Other languages
English (en)
French (fr)
Inventor
沙玉静
陈小雪
龚萌
孙永明
夏圣安
Original Assignee
华为技术有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 华为技术有限公司 filed Critical 华为技术有限公司
Publication of WO2024078053A1 publication Critical patent/WO2024078053A1/zh

Links

Classifications

    • 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
    • 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
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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 batteries, and in particular to a negative electrode material and a preparation method thereof, a secondary battery and an electrical device.
  • Graphite and silicon-based materials are the most studied negative electrode materials at present.
  • the existing coating layer on the surface of graphite is mainly structured as amorphous carbon, which enables rapid transmission of electrons between the interface and the bulk phase, thereby improving the fast charging ability of graphite.
  • the theoretical specific capacity of silicon is 4200mAh/g, which is the negative electrode material with the highest theoretical capacity.
  • the structure of the silicon negative electrode is unstable.
  • the silicon surface will continuously produce a new SEI film with the electrolyte, which will cause the electrolyte to be exhausted and the battery capacity to decay rapidly.
  • the silicon negative electrode material is usually coated to reduce the occurrence of side reactions between the silicon material and the electrolyte and improve the stability of the SEI film.
  • Existing coating methods generally include liquid phase coating, nanoparticle heterogeneous coating and ALD/CVD precision coating. The above method can be used to form a negative electrode material with a core-shell structure.
  • the outer shell layer usually includes a transition metal compound layer to improve the interface stability between the silicon-based material and the electrolyte.
  • the coating layer is usually a crystalline structure with a relatively thick thickness, generally 25nm or more. On the one hand, the coating layer of this thickness will reduce the energy density of the negative electrode material. On the other hand, during long-term charge and discharge cycles, it is easy to cause cracking of the coating layer, which can easily cause a sudden drop in battery capacity.
  • the present application provides a negative electrode material and a preparation method thereof, a secondary battery and an electrical device, so as to improve the structural stability of the negative electrode material, reduce the probability of cracking of the coating layer, and at the same time maintain a high energy density of the negative electrode material.
  • the present application provides a negative electrode material for a secondary battery, wherein the negative electrode material is a core-shell structure, comprising an inner core and an outer shell; wherein the inner core is a negative electrode active material; the outer shell comprises a first shell layer coated on the surface of the inner core and a second shell layer coated on the surface of the first shell layer, wherein the first shell layer is a dense transition metal compound layer, and the second shell layer is a conductive layer, wherein the first shell layer comprises at least a transition metal compound with a layered structure, wherein the maximum thickness of the transition metal compound layer is less than or equal to 10 nm, and the total thickness of the outer shell is less than or equal to 15 nm.
  • the negative electrode material of the present application is a core-shell structure, wherein the core is a negative electrode active material, and the shell is a double-layer structure, including a first shell and a second shell, wherein the first shell is coated on the surface of the core, and the second shell is coated on the surface of the first shell.
  • the first shell includes at least a transition metal compound, and the crystal structure of the transition metal compound is layered. When the transition metal compound is dispersed in a medium or ground at high speed, it is easy to form a very small structure and wrap on the surface of the core to form a dense amorphous structure of the first shell, so as to provide more active ion transmission channels and improve the conductivity of the negative electrode material to active ions.
  • the second shell can improve the interface conduction electron ability of the negative electrode material, in order to enhance the functionality of the second shell in addition to the interface conduction electron ability.
  • the total thickness of the first shell and the second shell is less than or equal to 15nm, which is an ultra-thin structure.
  • the shell formed thereby can be used as an artificial SEI film.
  • the shell When the volume of the negative electrode active material of the core changes, the shell can have a strong skin effect, which can significantly improve the structural stability of the negative electrode material. When used in a secondary battery, it can effectively improve the cycle stability of the secondary battery and reduce the consumption of the electrolyte.
  • the second shell layer includes at least one of carbon, a conductive polymer, a mixture of carbon and a transition metal compound, and a mixture of a conductive polymer and a transition metal compound.
  • the second shell layer material is not limited to an amorphous carbon negative electrode, and also includes carbon nanofibers, nanotubes, graphene, etc. The stacking and connection of one-dimensional and two-dimensional carbon materials can enhance the strength of the shell layer.
  • the second shell layer material also includes a conductive polymer.
  • the second shell formed by the conductive polymer can have a certain elasticity, so that the outer shell layer has better compliance when the core material expands/contracts during charging and discharging.
  • the second shell layer material also includes a mixture of a conductive material and a transition metal compound. Compared with a simple conductive layer, it can have both electronic and ion conduction capabilities after mixing with a transition metal compound, and form a natural transition structure of a transition metal compound between the second shell layer and the first shell layer, thereby improving the structural stability between the first shell layer and the second shell layer.
  • the pore size of the first shell layer is no greater than 5 nm to form a dense transition metal compound layer.
  • the composition of the transition metal compound layer includes transition metal oxides, transition metal carbides, transition At least one of metal nitrides and transition metal carbonitrides, or a mixture of two or more types.
  • a mixture of multiple transition metals can undergo a certain degree of fusion during high temperature treatment to improve the compactness of the first shell.
  • the composition formula of the transition metal compound layer is MXn(Ym), M is a transition metal element, X is a non-metallic element, Y is a functional group, and Y includes at least one of O, F, or OH; wherein n>0, m ⁇ 0.
  • M includes at least one of V, Mo, Ti or Al.
  • X includes at least one of O, C or N.
  • the transition metal compound layer can be electrochemically inert or non-inert.
  • MXn (Ym) is non-electrochemically inert
  • its lithium insertion potential is higher than that of the negative electrode active material in the core.
  • the negative electrode active material acts as a "resource pool" for active ion storage and transmission, reducing the direct contact between the electrolyte and the surface of the negative electrode active material at low potential, and avoiding the interfacial side reactions.
  • the double-layer shell structure formed by the synergistic effect of the dense MXn (Ym) layer and the outer conductive layer has high interface stability, ion conduction and charge exchange capabilities, so that when the negative electrode material of the present application is applied to a secondary battery, the secondary battery can have a higher first coulomb efficiency and better cycle stability.
  • the lithium insertion potential of the first shell is higher than the lithium insertion potential of the core, the lithium desorption potential of the first shell is greater than 1 V, and the lithium desorption capacity of the first shell within 1 V accounts for less than 30% of the lithium desorption capacity of the first shell within 3 V. In this way, a first shell with higher electrochemical stability can be obtained.
  • the mass proportion of the transition metal element in the first shell layer in the negative electrode material is less than or equal to 5%.
  • the mass proportion of the second shell layer in the negative electrode material is less than or equal to 5%.
  • the negative electrode active material includes at least one of a carbon-based negative electrode material, a silicon-based negative electrode material, a tin-based negative electrode material, and a phosphorus-based negative electrode material.
  • the carbon-based negative electrode material includes at least one of graphite, soft carbon, hard carbon, and amorphous carbon
  • the silicon-based material includes at least one of pure silicon, silicon oxygen, magnesium-doped silicon oxygen, lithium-doped silicon oxygen or silicon carbon
  • the phosphorus-based negative electrode material includes at least one of red phosphorus, white phosphorus, black phosphorus, blue phosphorus, phosphorus-containing complexes, and phosphorus-containing mixtures.
  • the present application provides a method for preparing a negative electrode material, which comprises: mixing a negative electrode active material with a layered transition metal compound, and obtaining a negative electrode material coated with a first shell layer after ball milling; mixing the negative electrode material coated with the first shell layer with a conductive agent, and obtaining a negative electrode material coated with a double shell layer after drying.
  • the mixing method includes solid phase stirring, high-speed dispersion, wet mixing and drying, or spray drying.
  • the ball milling speed is 200-800 rpm, and the ball milling time is 0.5-24 h.
  • the mass ratio of the negative electrode material coated with the single-layer shell to the carbon source is 100:0.5-20.
  • the carbonization temperature of the carbonization treatment is 350-900° C., and the carbonization time is 1-10 h.
  • the carbon source includes at least one of methanol, ethanol, benzene, methane, acetylene, tri-butadiene or polyvinyl alcohol.
  • the data in the above-mentioned possible implementation methods of the present application such as the transition metal compound with layered structure, the total thickness of the outer shell, the mass proportion of the first shell layer, the mass proportion of the second shell layer, the ball milling speed, the ball milling time, the lithium insertion potential and other data, when measuring, the values within the scope of engineering measurement error should be understood to be within the range specified in the present application.
  • the present application also provides a secondary battery, which includes a positive electrode, a negative electrode, and an electrolyte between the positive electrode and the negative electrode, wherein the negative electrode includes a negative electrode collector and a negative electrode material layer, and the negative electrode material layer includes the negative electrode material of the first aspect of the present application.
  • the present application further provides an electrical device, comprising an electrical component and the secondary battery of the present application, wherein the secondary battery is electrically connected to the electrical component to provide power to the electrical component.
  • the electrical equipment includes but is not limited to mobile phones, computers, electric vehicles, energy storage systems, electric work tools, etc.
  • FIG1 is a schematic diagram of the working principle of a lithium battery
  • FIG2 is a schematic diagram of the structure of a negative electrode material according to an embodiment
  • FIG3 is a schematic diagram of a ball milling process of a negative electrode active material and a transition metal compound
  • FIG4 is a SEM image of Example 1
  • FIG5 is an XRD diagram of Example 2.
  • FIG. 6 is an EDS graph of Example 2.
  • references to "one embodiment” or “some embodiments” etc. described in this specification mean that a particular feature, structure or characteristic described in conjunction with the embodiment is included in one or more embodiments of the present application.
  • the phrases “in one embodiment”, “in some embodiments”, “in some other embodiments”, “in some other embodiments”, etc. appearing in different places in this specification do not necessarily all refer to the same embodiment, but mean “one or more but not all embodiments", unless otherwise specifically emphasized in other ways.
  • the terms “including”, “comprising”, “having” and their variations all mean “including but not limited to”, unless otherwise specifically emphasized in other ways.
  • FIG1 is a schematic diagram of the working principle of a lithium battery.
  • the lithium battery may include a positive electrode 11, a negative electrode 12, an electrolyte 14, a separator 13, and corresponding connecting accessories and circuits.
  • the active materials in the positive electrode 11 and the negative electrode 12 can deintercalate lithium ions to achieve energy storage and release.
  • the electrolyte 14 is a carrier for the transmission of lithium ions between the positive and negative electrodes.
  • the separator 13 can pass lithium ions and block electrons, thereby achieving lithium ion conduction and preventing short circuits between the positive and negative electrodes.
  • the active materials in the positive and negative electrodes are the main parts that play the role of energy storage, and directly affect the energy density, cycle performance and safety performance of the battery cell.
  • mainstream commercial graphite does not have a mature strategy to improve interface stability and cycle life.
  • the capacity of the negative electrode 12 is crucial to the improvement of the energy density of the entire battery cell.
  • the actual gram capacity of commercial graphite anode is 355mAh/g, which is close to its theoretical value (372mAh/g). Therefore, it is imperative to accelerate the commercialization of silicon-based materials.
  • FIG2 is a schematic diagram of the structure of a negative electrode material of an embodiment.
  • the negative electrode material is a core-shell structure, including a core 121 and an outer shell 122.
  • the core 121 is a granular negative electrode material 125.
  • the negative electrode material 125 may be, for example, at least one of a carbon-based negative electrode material, a silicon-based negative electrode material, a tin-based negative electrode material, and a phosphorus-based negative electrode material.
  • the carbon-based negative electrode material includes at least one of graphite, soft carbon, hard carbon, and amorphous carbon.
  • the silicon-based material includes at least one of pure silicon, silicon oxygen, magnesium-doped silicon oxygen, lithium-doped silicon oxygen, or silicon carbon.
  • the phosphorus-based negative electrode material includes at least one of red phosphorus, white phosphorus, black phosphorus, blue phosphorus, a phosphorus-containing compound, and a phosphorus-containing mixture.
  • the shell 122 is a double-layer shell structure, including a first shell 123 and a second shell 124, wherein the first shell 123 is coated on the surface of the core 121, that is, coated on the surface of the negative electrode material 125 particles, and is a transition metal compound layer, wherein the composition of the amorphous transition metal compound layer includes but is not limited to at least one of transition metal oxides, transition metal carbides, transition metal nitrides, and transition metal carbonitrides.
  • the general formula of the composition of the amorphous transition metal compound layer can be expressed as MXn(Ym), where M is a transition metal element, and M includes but is not limited to at least one of V, Mo, Ti, Zr, Nb, or Al.
  • X is a non-metallic element, including but not limited to at least one of O, C, S, or N.
  • Y is a functional group, including but not limited to at least one of O, F, Cl, or OH; wherein n>0, m ⁇ 0.
  • the first shell layer 123 includes at least a dense transition metal compound layer, and on the surface of the core 121, a dense transition metal compound layer can be formed by bridging tiny particles, and the thickness is less than or equal to 10nm.
  • the mass proportion of the first shell layer 123 in the negative electrode material can be less than or equal to 5%.
  • the layered structure in this application refers to the ordered, layered arrangement of metal atoms and non-metal atoms in the crystal structure of the transition metal compound.
  • the lithium insertion potential of the first shell 123 is higher than the lithium insertion potential of the core 121, the lithium desorption potential of the first shell 123 is greater than 1V, and the lithium desorption capacity of the first shell 123 within 1V accounts for less than 30% of the lithium desorption capacity of the first shell 123 within 3V.
  • the structure is more stable.
  • the lithium insertion potential of the transition metal compound layer is higher than that of the negative electrode material 125 of the core 121. Due to its lithium insertion ability, it can provide a better lithium ion transmission channel for the negative electrode material 125 of the core 121 at the same time.
  • the lithium insertion potential is higher than that of the negative electrode material 125 of the core 121, and it can also avoid the electrolyte 14 from decomposing at the interface of the negative electrode material at a low potential to form a large amount of SEI film, thereby improving the interface stability between the negative electrode material and the electrolyte 14 and reducing the occurrence of side reactions.
  • the surface of the first shell layer 123 is also coated with a second shell layer 124, and the second shell layer 124 is a conductive layer.
  • the material of the second shell layer 124 includes but is not limited to carbon, a conductive polymer, a mixture of carbon and a transition metal compound, a conductive polymer and a transition metal compound, or at least one of carbon, a polymer and a transition metal compound.
  • the total thickness of the first shell layer 123 and the second shell layer 124 is less than or equal to 15nm.
  • the mass proportion of the metal element of the second shell layer 124 in the negative electrode material may be less than or equal to 5%.
  • the coating of the second shell layer 124 on the basis of the first shell layer 123 can further enhance the interfacial charge conduction capability of the negative electrode material 125 and the interfacial stability with the electrolyte 14.
  • the double-shell shell 122 formed by the amorphous dense MXn (Ym) layer and the carbon layer can be used as an artificial SEI membrane.
  • the SEI membrane has high interface stability, ion conduction and charge exchange capabilities, so that the negative electrode material of the present application can have the advantages of higher first coulomb efficiency and better cycle stability when used in lithium batteries.
  • the method for preparing the negative electrode material of the embodiment of the present application may include the following steps S11 and S12:
  • the layered transition metal compound 126 is easier to achieve thin layer exfoliation and nano-sizing, so that it can be dispersed and coated on the surface of the particles of the negative electrode material 125, and it is easier to form bridges between the particles, thereby forming a denser and thinner first shell layer 123.
  • FIG3 is a schematic diagram of a ball milling process of a negative electrode active material and a transition metal compound 126.
  • the negative electrode material 125 and the transition metal compound 126 are mixed in a certain proportion and placed in a ball milling jar.
  • the gas in the jar needs to be replaced with an inert gas.
  • a certain amount of ball milling beads 15 are put in, and the negative electrode material 125 and the transition metal compound 126 are mixed at a certain speed.
  • the structure of the transition metal compound 126 is relatively softer, it is easy to undergo interlayer peeling and fragmentation under mechanical energy conditions.
  • the peeled sheet material forms a coating layer of a bridging structure on the particle surface of the negative electrode material 125, thereby making it easier to achieve a dense, uniform and ultra-thin coating effect, and finally achieve a dense coating on the outer layer of the particles of the negative electrode material 125.
  • the ball milling speed can be 200-800rpm
  • the ball milling time can be 0.5-24h.
  • the mass ratio of the single-layer shell structure negative electrode material to the conductive agent can be 100:0.5-20.
  • the carbonization temperature of the carbonization treatment can be 350-800°C, and the carbonization time can be 1-10h.
  • the first shell layer 123 can be kept in an amorphous coating state while forming a carbon layer.
  • the carbon coating method includes but is not limited to solid phase method, liquid phase method and gas phase method, and its carbon source includes but is not limited to sugars, aromatics, low molecular weight liquid carbon sources or gas carbon sources.
  • low molecular weight carbon sources and gas carbon sources are preferred, such as at least one of methanol, ethanol, benzene, methane, acetylene, tributylene or polyvinyl alcohol.
  • the interfacial stability between the negative electrode material and the electrolyte can be further improved.
  • VO 2 -Si silicon negative electrode material
  • VO 2 -Si powder was placed in a tube furnace, evacuated and protected with N 2 atmosphere. After heating to 750°C, a methane/hydrogen mixed gas (volume ratio 1:10) was introduced for 15min, and the ventilation was stopped and switched to N 2 protective gas. After keeping warm for 3h, it was naturally cooled to room temperature to obtain a silicon negative electrode material with a double-shell artificial SEI membrane structure, which was recorded as VO 2 -Si-C-1.
  • a silicon negative electrode material VO 2 -Si 0.15g of vanadium dioxide VO 2 and 3.88g of silicon powder were mixed evenly in a glove box and placed in a ball mill. Mechanical ball milling was performed under the setting conditions of a rotation speed of 300rpm and a total duration of 2.5h to prepare a silicon negative electrode material VO 2 -Si with a core-shell structure.
  • 0.5g of polyvinyl alcohol (PVA) was dispersed in 50ml of ultrapure aqueous solution, heated and stirred until PVA was completely dissolved, 0.5g of VO 2 -Si prepared in step (1) was added to the PVA aqueous solution, and heating and stirring were continued until a wet gel was formed.
  • PVA polyvinyl alcohol
  • the gel was placed in an 80°C forced air drying oven for overnight drying, and then placed in a tubular furnace, a protective atmosphere of Ar was introduced, and the temperature was raised to 650°C. After being kept warm for 3h, it was naturally cooled to room temperature to obtain a double-shell artificial SEI.
  • the silicon negative electrode material with a film structure is denoted as VO 2 -Si-C-2.
  • Mxene powder Ti 2 CF 2 and 3g of silicon powder were mixed evenly in a glove box and placed in a ball mill. Mechanical ball milling was performed under the setting conditions of a rotation speed of 600rpm and a total duration of 2h to prepare a silicon negative electrode material TiCF 2 -Si with a core-shell structure. The material was soaked in a toluene solution for 6h and filtered. The filter residue was placed in a blast drying oven at 80°C for overnight drying. After being taken out, it was placed in a tube furnace, and a protective atmosphere of Ar was introduced.
  • the temperature was raised to 680°C, and after being kept warm for 3h, it was naturally cooled to room temperature to obtain a silicon negative electrode material with a double-shell artificial SEI membrane structure, which was recorded as Ti 2 CF 2 -Si-C-3.
  • the silicon negative electrode material obtained in Example 2 and graphite were mixed in a mass ratio of 15:85 to prepare a composite electrode.
  • the specific operation was as follows: 0.12 g of the silicon negative electrode material VO 2 -Si-C-2 in Example 2 and 0.68 g of the graphite material were weighed and mixed in a mortar to obtain a composite electrode material.
  • 0.1g of Mxene powder Ti 2 CF 2 and 3g of silicon powder were mixed evenly in a glove box and placed in a ball mill. Mechanical ball milling was performed under the setting conditions of a rotation speed of 600rpm and a total duration of 2h to prepare a silicon negative electrode material TiCF 2 -Si with a core-shell structure. The material was placed in a mixed solution of toluene, graphene sheets and TiCF 2 and soaked for 6h and filtered. The filter residue was placed in a blast drying oven at 80°C for overnight drying. After being taken out, it was placed in a tube furnace, and a protective atmosphere of Ar was introduced.
  • the temperature was raised to 680°C, and after being kept warm for 3h, it was naturally cooled to room temperature to obtain a silicon negative electrode material with a double-shell artificial SEI membrane structure, which was recorded as Ti 2 CF 2 -Si-C/Graphene/Ti 2 CF 2 -4.
  • 0.5 g of vanadium dioxide VO 2 and 5 g of silicon powder were mixed evenly in a glove box and placed in a ball milling jar, and mechanical ball milling was performed under the setting conditions of a rotation speed of 300 rpm and a total duration of 2.5 h to prepare a silicon negative electrode material VO 2 -Si with a core-shell structure.
  • PVA polyvinyl alcohol
  • the thickness of the VO2 layer formed on the surface of the silicon particles is much larger than the true 0.15 nm.
  • 0.2g of vanadium dioxide VO2 and 5g of silicon powder were mixed evenly in a glove box and placed in a ball mill. Mechanical ball milling was performed under the setting conditions of a rotation speed of 300rpm and a total duration of 2.5h to prepare a silicon negative electrode material VO2 -Si with a core-shell structure.
  • 0.5g of polyvinyl alcohol (PVA) was dispersed in 50ml of ultrapure aqueous solution, heated and stirred until PVA was completely dissolved, 0.5g of VO2 -Si prepared in step (1) was added to the PVA aqueous solution, and heating and stirring were continued until a wet gel was formed.
  • PVA polyvinyl alcohol
  • the mixture was placed in an 80°C forced air drying oven for overnight drying, and then placed in a tubular furnace, a protective atmosphere of Ar was introduced, and the temperature was raised to 1000°C. After being kept warm for 3h, it was naturally cooled to room temperature to obtain a double-shell artificial SEI.
  • the silicon negative electrode material with a film structure is denoted as VO 2 -Si-C-4.
  • the carbonization temperature is 1000°C
  • the particles in the VO2 layer are crystalline structures and an amorphous VO2 layer is not formed.
  • the structural information of the negative electrode material was measured by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS), wherein FIG4 shows the SEM image of Example 1, FIG5 shows the XRD image of Example 2, and FIG6 shows the EDS image of Example 2.
  • SEM scanning electron microscopy
  • XRD X-ray diffraction
  • EDS energy dispersive x-ray spectroscopy
  • the surface of the negative electrode material sample of Example 1 is clean and flat, without self-agglomerates of the coating.
  • obvious characteristic diffraction peaks of silicon can be observed, but there are no obvious characteristic diffraction peaks of VO2 , indicating that the amorphization treatment of VO2 has been successfully achieved in the ball milling process of the synthesis process.
  • the particle interface of the silicon-based material has an obvious shell structure. Through the EDS energy spectrum test of different elements, it is found that there are obvious double shells of V and C elements on the surface of the silicon-based material, corresponding to VO2 and C, respectively.
  • the double shell thickness of VO2 /C at two points is 12nm and 13.5nm, respectively. It shows that each embodiment of the present application can successfully achieve relatively uniform double shell coating, and the coating thickness is ⁇ 15nm.
  • Button-type lithium-ion batteries were assembled using the negative electrode materials of the embodiments and comparative examples, and the initial effective capacity and cycle performance of the corresponding lithium-ion batteries were tested. The test results are listed in Table 1.
  • the double-shell coated negative electrode materials of Examples 1-4 of the present application all showed higher first charge specific capacity and coulombic efficiency, indicating that the double-shell coating structure effectively improves the interface performance of the silicon-based material.
  • Comparative Example 2 only the first shell coating is performed. Although the first charge capacity and coulomb efficiency are improved to a certain extent compared with the uncoated silicon, the cycle stability of the corresponding button battery is significantly reduced compared with that of Comparative Example 1, which may be related to the poor charge conduction ability of the first shell VO2 coating layer.
  • Comparative Example 3 is only coated with an outer layer.
  • its first charge specific capacity is the highest among all samples, but the first coulombic efficiency and 100-cycle capacity retention rate are still lower than those of the double-shell related embodiments.
  • the outer shell carbon layer coating improves the interfacial charge exchange capacity, the carbon layer is more stable than the silicon-based material and can be used as an interfacial stabilizing layer to reduce the complex reaction between the electrolyte and the silicon-based material.
  • the carbon layer formed during the cracking process inevitably has pores, and the structural capacity of carbon is relatively weak, so its interfacial side reaction is still higher than that of the double-shell structure, and its stability is lower than that of the double-shell structure.
  • Comparative Example 4 can prove that when the total thickness of the outer shell layer is above 15nm, the performance of the corresponding negative electrode material is slightly lower.
  • Comparative Example 5 when the first shell layer formed is a non-amorphous layer, the performance of the corresponding negative electrode material is also lower than that of the embodiments of the present application. This may be because, when the first shell layer is an amorphous layer and the thickness is less than 15nm, the obtained first shell layer has a better skin effect, and when the silicon-based material undergoes a volume change due to lithium insertion and detachment, the negative electrode material of the present application has a higher structural stability.
  • Comparative Example 6 when the MoS2 layer is used as the first shell layer, the interface stability is worse than that of Examples 1 and 2. This is because transition metal sulfides easily form polysulfides in the battery, causing a polysulfide ion shuttle effect, which leads to rapid cycle decay.
  • Example 5 proves that although the reversible capacity of graphite after coating has decreased to a certain extent (the coating layer accounts for the overall mass of the negative electrode material), the first coulombic efficiency of graphite is significantly improved, indicating that the decomposition of the interfacial electrolyte and the side reactions are significantly reduced. Moreover, the capacity retention rate after 100 cycles is also significantly improved, indicating that the coating layer effectively improves the interfacial reaction during the long-term cycle process.
  • Example 6 is based on Example 3, in which graphene and Ti 2 CF 2 are introduced into the carbon of the second shell layer.
  • the graphene sheet structure and the Ti 2 CF 2 sheet structure are stacked on each other. After drying and dehydration, the hydrogen bonds between the graphene and Ti 2 CF 2 sheets and between the graphene and Ti 2 CF 2 sheets and the first shell layer make the second shell layer tightly wrap around the surface of the first shell layer, avoiding the problem of weak bonding between pure amorphous carbon and the first shell layer.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Battery Electrode And Active Subsutance (AREA)
  • Secondary Cells (AREA)

Abstract

本申请提供了一种负极材料及其制备方法、二次电池和用电设备。本申请的负极材料为核壳结构，包括内核和外壳；其中，内核为负极活性材料；外壳包括包覆于内核表面的第一壳层和包覆在第一壳层表面的第二壳层，第一壳层为过渡金属化合物层，第二壳层为导电层，第一壳层的最大厚度小于或等于10nm，第二壳体为碳层；外壳的总厚度小于或等于15nm。利用该负极材料可提高负极材料的结构稳定性，降低包覆层开裂的几率，同时使负极材料保持较高的能量密度。

Description

负极材料及其制备方法、二次电池和用电设备
相关申请的交叉引用
本申请要求在2022年10月10日提交中国专利局、申请号为202211237095.X、申请名称为“负极材料、二次电池和用电设备”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电池领域，具体涉及一种负极材料及其制备方法、二次电池和用电设备。
背景技术
随着人们对储能电池寿命要求提升，电池中负极在充放电过程中的界面稳定性亟需改善。石墨、硅基材料是目前研究最多的负极材料。石墨表面的现有包覆层主要结构为无定型碳，实现电子在界面和体相之间快速传输，从而提升石墨快充能力。但对提升石墨界面稳定性和长循环寿命方面，仍没有较好方案。硅的理论比容量为4200mAh/g，是理论容量最高的负极材料。但是硅负极的结构不稳定，硅在充放电过程中，硅表面会与电解液不断产生新的SEI膜，从而导致电解液消耗殆尽，电池容量迅速衰减。为改善该问题，通常对硅负极材料进行包覆，以减少硅材料与电解液的副反应的发生，提高SEI膜的稳定性。现有包覆方法通常包括液相包覆、纳米颗粒非均相包覆以及ALD/CVD精密包覆，利用上述方法可形成具有核壳结构的负极材料。由于过渡金属化合物能够有效抵挡硅基材料与电解液之间副反应的发生，因此，在现有核壳结构的负极材料中，外壳层通常包括过渡金属化合物层，以提高硅基材料与电解液之间的界面稳定性。但是现有具有包覆层的硅基材料中，包覆层通常为晶体结构，其厚度较厚，一般在25nm及以上，该厚度的包覆层，一方面会降低负极材料的能量密度，另一方面，在长周期的充放电循环过程中，容易造成包覆层的开裂，进而易于引起电池容量骤减。
发明内容
本申请提供了一种负极材料及其制备方法、二次电池和用电设备，以提高负极材料的结构稳定性，降低包覆层开裂的几率，同时使负极材料保持较高的能量密度。
第一方面，本申请提供一种二次电池用负极材料，负极材料为核壳结构，包括内核和外壳；其中，内核为负极活性材料；外壳包括包覆于内核表面的第一壳层和包覆在第一壳层表面的第二壳层，第一壳层为致密的过渡金属化合物层，第二壳层为导电层，第一壳层中至少包括层状结构的过渡金属化合物，过渡金属化合物层的最大厚度小于或等于10nm，外壳的总厚度小于或等于15nm。
本申请的负极材料为核壳结构，其中，内核为负极活性材料，外壳为双层结构，包括第一壳层和第二壳层，第一壳层包覆在内核的表面，第二壳层包覆在第一壳层的表面。第一壳层中至少包括过渡金属化合物，过渡金属化合物的晶体结构是层状的，当过渡金属化合物在介质中分散或者高速研磨时，容易行成非常小的结构并包裹在内核表面从而形成致密的无定形结构的第一壳体，以便于提供更多的活性离子传输通道，提高负极材料对活性离子的传导能力。第二壳层可以提高负极材料的界面导电子能力，为提升第二壳层在具备界面导电子能力外的功能性。第一壳层和第二壳层的总厚度小于或等于15nm，为超薄结构，由此形成的外壳可作为人工SEI膜，当内核的负极活性材料发生体积变化时，该外壳可具有较强的趋肤效应，可显著提高负极材料的结构稳定性，用于二次电池时，可有效提高二次电池的循环稳定性，减少电解液的消耗。
在一种可选的实现方式中，所述第二壳层包括碳、导电聚合物、碳与过渡金属化合物的混合物、导电聚合物与过渡金属化合物的混合物中的至少一种。第二壳层材料不限于无定型碳负极，还包括碳纳米纤维、纳米管、石墨烯等，一维、二维碳材料堆积和连接可以增强壳层的强度。第二壳层材料还包括导电聚合物，利用导电聚合物形成的第二壳体可具备一定弹性，使内核材料在充放电膨胀/收缩时外壳层具备更好的随变性。第二壳层材料还包括导电材料和过渡金属化合物的混合物，相比单纯的导电层，与过渡金属化合物混合后可以同时具备电子传导和离子传导能力，并在第二壳层与第一壳层之间形成过渡金属国合物的自然过渡结构，提升第一壳层和第二壳层之间的结构稳定性。
在一种可选的实现方式中，所述第一壳层的孔径尺寸不大于5nm，以形成致密的过渡金属化合物层。
在一种可选的实现方式中，过渡金属化合物层的成分包括过渡金属氧化物、过渡金属碳化物、过渡 金属氮化物、以及过渡金属碳氮化物中的至少一种，或者两种及以上种类的混合物。多种过渡金属混合物可以在高温处理过程中发生一定融合，提升第一壳层的致密性。其中，过渡金属化合物层的成分通式为MXn(Ym)，M为过渡金属元素，X为非金属元素，Y为官能团，Y包括O、F、或OH中的至少一种；其中，n>0，m≥0。示例性地，M包括V、Mo、Ti或Al中的至少一种。X包括O、C或N中的至少一种。
其中，过渡金属化合物层可为电化学惰性或非惰性，MXn(Ym)为非电化学惰性时，其嵌锂电位高于内核的负极活性材料，负极活性材料作为活性离子存储和传输的“资源池”，减少低电位下电解液与负极活性材料的表面直接接触，避免产生的界面副反应。相比单一碳界面或单一无机化合物界面，致密MXn(Ym)层与外导电层协同作用形成的双层壳层结构，同时具备高的界面稳定性、离子传导及电荷交换能力，使得本申请的负极材料应用于二次电池时可使二次电池具有更高的首次库伦效率和较好的循环稳定性。
在一种可选的实现方式中，第一壳层的嵌锂电位高于内核的嵌锂电位，第一壳层的脱锂电位大于1V，且第一壳层在1V以内的脱锂容量占第一壳层在3V以内脱锂容量的30％以下。这样，可获得电化学稳定性更高的第一壳层。
在一种可选的实现方式中，第一壳层中过渡金属元素在负极材料中的质量占比为小于等于5％。
在一种可选的实现方式中，第二壳层在负极材料中的质量占比为小于等于5％。
在一种可选的实现方式中，负极活性材料包括碳基负极材料、硅基负极材料、锡基负极材料、以及磷基负极材料中的至少一种。
其中，所述碳基负极材料包括石墨、软炭、硬炭、以及无定型碳中至少一种，所述硅基材料包括纯硅、硅氧、镁掺杂硅氧、锂掺杂硅氧或硅碳中的至少一种，所述磷基负极材料包括红磷、白磷、黑磷、蓝磷、含磷复合物、以及含磷混合物中的至少一种。
第二方面，本申请提供一种负极材料的制备方法，该制备方法包括：将负极活性材料与层状过渡金属化合物混合，经球磨后得到具有第一壳层包覆的负极材料；将第一壳层包覆的负极材料与导电剂混合，干燥后得到具有双层壳层包覆的负极材料。
在一种可选的实现方式中，所述混合方法包括固相搅拌、高速分散、湿法混合干燥、或喷雾干燥。
在一种可选的实现方式中，球磨中，球磨转速为200-800rpm，球磨时间为0.5-24h。
在一种可选的实现方式中，单层壳层包覆的负极材料与碳源的质量比为100:0.5-20。
在一种可选的实现方式中，碳化处理的碳化温度为350-900℃，碳化时间为1-10h。
在一种可选的实现方式中，碳源包括甲醇、乙醇、苯、甲烷、乙炔、一三丁二烯或聚乙烯醇中的至少一种。
其中，本申请上述各可能实现方式中的数据，例层状结构的过渡金属化合物、外壳的总厚度、第一壳层的质量占比、第二壳层的质量占比、球磨转速、球磨时间、嵌锂电位等数据，在测量时，工程测量误差范围内的数值均应理解为在本申请所限定的范围内。
第三方面，本申请还提供一种二次电池，该二次电池包括正极、负极、介于正极和负极之间的电解质，负极包括负极集流体和负极材料层，负极材料层包括本申请第一方面的负极材料。
第四方面，本申请还提供一种用电设备，包括用电元件和本申请的二次电池，其中，二次电池与用电元件电连接，以为用电元件提供电力。
其中，所述用电设备包括但不限于手机、电脑、电动车、储能***、电动工装具等。
上述第二方面至第四方面可以达到的技术效果，可以参照上述第一方面中的相应效果描述，这里不再重复赘述。
附图说明
图1为一种锂电池的工作原理示意图；
图2为一种实施例的负极材料的结构示意图；
图3为一种负极活性材料与过渡金属化合物的球磨过程示意图；
图4为实施例1的SEM图；
图5为实施例2的XRD图；
图6为实施例2的EDS图。
附图标记：
11-正极；12-负极；13-隔膜；14-电解液；121-内核；122-外壳；123-第一壳层；
124-第二壳层；125-负极材料；126-过渡金属化合物；15-球磨珠。
具体实施方式
为了使本申请的目的、技术方案和优点更加清楚，下面将结合附图对本申请作进一步地详细描述。
以下实施例中所使用的术语只是为了描述特定实施例的目的，而并非旨在作为对本申请的限制。如在本申请的说明书和所附权利要求书中所使用的那样，单数表达形式“一个”、“一种”、“所述”、“上述”、“该”和“这一”旨在也包括例如“一个或多个”这种表达形式，除非其上下文中明确地有相反指示。
在本说明书中描述的参考“一个实施例”或“一些实施例”等意味着在本申请的一个或多个实施例中包括结合该实施例描述的特定特征、结构或特点。由此，在本说明书中的不同之处出现的语句“在一个实施例中”、“在一些实施例中”、“在其他一些实施例中”、“在另外一些实施例中”等不是必然都参考相同的实施例，而是意味着“一个或多个但不是所有的实施例”，除非是以其他方式另外特别强调。术语“包括”、“包含”、“具有”及它们的变形都意味着“包括但不限于”，除非是以其他方式另外特别强调。
图1为一种锂电池的工作原理示意图，如图1所示，锂电池可包括正极11、负极12、电解液14、隔膜13以及相应的连通辅件和回路。正极11和负极12中的活性材料可以脱嵌锂离子从而实现能量的存储和释放，电解液14是锂离子在正负极之间传输的载体，隔膜13可透过锂离子而阻隔电子，从而实现锂离子的导通，并防止正负极短路。其中，正负极中的活性材料是发挥储能功效的主体部分，直接影响电芯的能量密度、循环性能及安全性能。一方面主流商用石墨没有成熟的提升界面稳定性和循环寿命的策略。另一方面，在当前商用正极11材料钴酸锂达到其使用最高极限时(4.4V，压实4.2g/cm3)，负极12的容量发挥对于整个电芯的能量密度的提升显得至关重要。然而，目前商用石墨负极实际使用克容量355mAh/g，已接近其理论值(372mAh/g)。因此，加快硅基材料的商用势在必行，在维持硅基材料的高克容量的前提下，解决硅基材料与电解液的界面不稳定问题，有利于提升电池长循环稳定性、以及对电池中活性锂离子和电解液的不可逆消耗速度，在提升电池能量密度的同时提升电子产品的寿命和安全，从而提高产品整体竞争力。
为解决负极材料125与电解液14的界面问题，本申请提供一种负极材料，图2为一种实施例的负极材料的结构示意图，如图2所示，该负极材料为核壳结构，包括内核121和外壳122。其中，内核121为颗粒状的负极材料125。
负极材料125例如可为碳基负极材料、硅基负极材料、锡基负极材料、以及磷基负极材料中的至少一种。其中，所述碳基负极材料包括石墨、软炭、硬炭、以及无定型碳中至少一种。所述硅基材料包括纯硅、硅氧、镁掺杂硅氧、锂掺杂硅氧或硅碳中的至少一种。所述磷基负极材料包括红磷、白磷、黑磷、蓝磷、含磷复合物、以及含磷混合物中的至少一种。
继续参照图2，在本申请一种实施例中，外壳122为双层壳结构，包括第一壳层123和第二壳层124，其中，第一壳层123包覆在内核121的表面，即包覆在负极材料125颗粒的表面，其为过渡金属化合物层，其中，无定形过渡金属化合物层的成分包括但不限于过渡金属氧化物、过渡金属碳化物、过渡金属氮化物、以及过渡金属碳氮化物中的至少一种。无定形过渡金属化合物层的成分通式可表示为MXn(Ym)，M为过渡金属元素，M包括但不限于V、Mo、Ti、Zr、Nb或Al中的至少一种。X为非金属元素，包括但不限于O、C、S或N中的至少一种。Y为官能团，包括但不限于O、F、Cl或OH中的至少一种；其中，n>0，m≥0。当X和Y元素不同时，可能形成具备层间离子传输能力和结构重塑能力更强的片层状材料如Ti3C2(T)，其中T为OH或F。并且片层结构的堆叠效果更好，可以进一步减小第一壳层中的空隙。
其中，第一壳层123中至少包括致密的过渡金属化合物层，在内核121的表面，可通过微小颗粒的桥接形成致密结构的过渡金属化合物层，厚度小于等于10nm。在一种可选实施例中，第一壳层123在负极材料中的质量占比可小于等于5％。可以理解的是，本申请中的层状结构是指过渡金属化合物的晶体结构中金属原子和非金属原子的有序、层状排列。
第一壳层123的嵌锂电位高于内核121的嵌锂电位，第一壳层123的脱锂电位大于1V，且第一壳层123在1V以内的脱锂容量占第一壳层123在3V以内脱锂容量的30％以下。由此，可使第一壳层123 的结构更稳定。过渡金属化合物层的嵌锂电位高于内核121的负极材料125，由于具备嵌锂能力，因此能同时为内核121的负极材料125提供较好的锂离子传输通道，而且嵌锂电位比内核121负极材料125高，还可以避免电解液14低电位下在负极材料界面分解形成大量SEI膜，从而可提高负极材料和电解液14之间的界面稳定性，减少副反应的发生。
继续参照图2，第一壳层123的表面还包覆有第二壳层124，第二壳层124为导电层，第二壳层124的材料包括但不限于碳、导电聚合物、碳与过渡金属化合物的混合物、导电聚合物与过渡金属化合物、或者碳与聚合物与过渡金属化合物中的至少一种。其中，第一壳层123和第二壳层124的总厚度小于等于15nm。在一种可选实施例中，第二壳层124金属元素在负极材料中的质量占比可小于等于5％。在第一壳层123的基础上进行第二壳层124的包覆，可进一步提升负极材料125的界面电荷传导能力和与电解液14的界面稳定性。
相比单一碳界面或单一的无机化合物界面，无定形致密MXn(Ym)层与碳层形成的双层壳层的外壳122，可作为人造SEI膜，该SEI膜同时具备高的界面稳定性、离子传导及电荷交换能力，使得本申请的负极材料在应用于锂电池时能够兼具较高的首次库伦效率和较好的循环稳定性的优点。
以上对负极材料的结构和材料组成做了说明，下面将做对其制备方法做解释说明。
本申请实施例的负极材料的制备方法，可包括如下步骤S11和步骤S12：
S11、将负极活性材料与层状结构过渡金属化合物126混合，经球磨后得到具有单层壳层包覆的负极材料。
经研究发现，层状结构的过渡金属化合物126更容易实现薄层剥离、纳米化，从而在负极材料125的颗粒表面分散、包覆，颗粒与颗粒之间更易于形成桥接，从而形成更致密、更薄的第一壳层123。
图3为一种负极活性材料与过渡金属化合物126的球磨过程示意图。如图3所示，将负极材料125和过渡金属化合物126按照一定比例混合，放入球磨罐中，同时为了避免球磨过程中负极材料125的过度氧化造成容量和首效降低，需要将罐中气体置换为惰性气体。投入一定量球磨珠15，在一定转速下对负极材料125和过渡金属化合物126进行混合。同时，因为过渡金属化合物126的结构相对更软，容易在机械能情况下发生层间剥离和碎片化，剥离后的片层材料在负极材料125的颗粒表面形成桥接结构的包覆层，由此，更容易实现致密均匀且超薄的包覆效果，最终在负极材料125的颗粒外层实现致密包覆。其中，在球磨过程中，球磨转速可为200-800rpm，球磨时间可为0.5-24h。
S12、将单层壳层结构负极材料与导电剂混合，经干燥后得到具有双层壳层结构的负极材料。其中，单层壳层结构负极材料与导电剂的质量比可为100:0.5-20。作为示例性说明，碳化处理的碳化温度可为350-800℃，碳化时间可为1-10h。利用上述碳化工艺，可在形成碳层的同时，使第一壳层123保持无定形的包覆状态。
其中，本申请实施例中，碳包覆方法包括但不限于固相法、液相法和气相法，其碳源包括但不限于糖类、芳香类、低分子量液体碳源或气体碳源，为实现薄层包覆优选低分子量碳源和气体碳源，如甲醇、乙醇、苯、甲烷、乙炔、一三丁二烯或聚乙烯醇中的至少一种。
通过引入碳源进一步碳化形成双层壳层的人造SEI膜，可进一步提高负极材料与电解液的界面稳定性。
以下将结合具体实施例对本申请的负极材料的性能做进一步详细说明。
实施例1
取0.12g二氧化钒VO2与5g硅粉末在手套箱中混合均匀并放置于球磨罐中，在转速为300rpm，总持续时间为2.5h的设定条件下进行机械球磨，制备得具有核壳结构的硅负极材料VO2-Si。取VO2-Si粉至管式炉中，抽真空后用N2进行气氛保护，升温至750℃后通入甲烷/氢气混合气体(体积比1：10)15min，停止通气，并切换为N2保护气，保温3h后自然冷却至室温，得到具有双壳层人造SEI膜结构的硅负极材料，记为VO2-Si-C-1。
实施例2
取0.15g二氧化钒VO2与3.88g硅粉末在手套箱中混合均匀并放置于球磨罐中，在转速为300rpm，总持续时间为2.5h的设定条件下进行机械球磨，制备得具有核壳结构的硅负极材料VO2-Si。取0.5g聚乙烯醇(PVA)分散到50ml的超纯水溶液中，加热搅拌至PVA完全溶解，在PVA水溶液中加入0.5g步骤(1)所制备的VO2-Si，继续加热搅拌至形成湿凝胶，放入80℃的鼓风干燥箱隔夜干燥，取出后置于管式炉中，通入保护气氛Ar，升温至650℃，保温3h后自然冷却至室温，得到具有双壳层人造SEI 膜结构的硅负极材料，记为VO2-Si-C-2。
实施例3
取0.1g Mxene粉末Ti2CF2与3g硅粉末在手套箱中混合均匀并放置于球磨罐中，在转速为600rpm，总持续时间为2h的设定条件下进行机械球磨，制备得具有核壳结构的硅负极材料TiCF2-Si。取材料放入甲苯溶液中浸泡6h并过滤后将滤渣放入80℃的鼓风干燥箱隔夜干燥，取出后置于管式炉中，通入保护气氛Ar，升温至680℃，保温3h后自然冷却至室温，得到具有双壳层人造SEI膜结构的硅负极材料，记为Ti2CF2-Si-C-3。
实施例4
将实施例2获得的硅负极材料与石墨按照质量比为15:85进行混合制备复合电极，具体操作如下：称取0.12g实施例2的硅负极材料VO2-Si-C-2与0.68g的石墨材料于研钵中混合均匀得到复合电极材料。
实施例5
取10ml MoO3纳米粒子墨水(西格玛采购)与20g石墨粉体进行混合研磨分散，并转移到球磨罐中，在转速为350rpm的条件下球磨30min，在石墨表面形成第一层过渡金属氧化物MoO3包覆。取出低温烘烤，将墨水中的乙醇烘干。将完成第一层包覆的样品与CNT浆料进行分散混合、搅拌、过滤、低温烘干，从而在外表面形成具有电子传导能力的CNT纳米线缠绕结构，记为G-MoO3-CNT。
实施例6
取0.1g Mxene粉末Ti2CF2与3g硅粉末在手套箱中混合均匀并放置于球磨罐中，在转速为600rpm，总持续时间为2h的设定条件下进行机械球磨，制备得具有核壳结构的硅负极材料TiCF2-Si。取材料放入甲苯、石墨烯片和TiCF2的混合溶液中浸泡6h并过滤后将滤渣放入80℃的鼓风干燥箱隔夜干燥，取出后置于管式炉中，通入保护气氛Ar，升温至680℃，保温3h后自然冷却至室温，得到具有双壳层人造SEI膜结构的硅负极材料，记为Ti2CF2-Si-C/Graphene/Ti2CF2-4。
对比例1
取5g硅粉末在手套箱中放置于球磨罐中，在转速为300rpm，总持续时间为2.5h的设定条件下进行机械球磨，制备得未经包覆处理的硅负极材料，记为Si。
对比例2
取0.12g二氧化钒VO2与3.88g硅粉末在手套箱中混合均匀并放置于球磨罐中，在转速为300rpm，总持续时间为2.5h的设定条件下进行机械球磨，制备得具有核壳机构的硅负极材料，其中，核层为硅颗粒，壳层为二氧化钒层，记为VO2-Si。
对比例3
取0.5g聚乙烯醇(PVA)分散到50ml的超纯水溶液中，加热搅拌至PVA完全溶解，在PVA水溶液中加入0.5g对比实施例1所得的硅负极材料Si，继续加热搅拌至形成湿凝胶，放入80℃的鼓风干燥箱隔夜干燥，取出后置于管式炉中，通入保护气氛Ar，升温至650℃，保温3h后自然冷却至室温，制备得具有核壳结构的硅负极材料，其中，核层为硅颗粒，壳层为碳层，记为Si-C。
对比例4
取0.5g二氧化钒VO2与5g硅粉末在手套箱中混合均匀并放置于球磨罐中，在转速为300rpm，总持续时间为2.5h的设定条件下进行机械球磨，制备得具有核壳结构的硅负极材料VO2-Si。取0.5g聚乙烯醇(PVA)分散到50ml的超纯水溶液中，加热搅拌至PVA完全溶解，在PVA水溶液中加入0.5g步骤(1)所制备的VO2-Si，继续加热搅拌至形成湿凝胶，放入80℃的鼓风干燥箱隔夜干燥，取出后置于管式炉中，通入保护气氛Ar，升温至650℃，保温3h后自然冷却至室温，得到具有双壳层人造SEI膜结构的硅负极材料，记为VO2-Si-C-3。
该对比例中，由于VO2的添加量要远大于本申请限定的比例，在制备过程中，形成在硅颗粒表面的VO2层的厚度要远大于真0.15nm。
对比例5
取0.2g二氧化钒VO2与5g硅粉末在手套箱中混合均匀并放置于球磨罐中，在转速为300rpm，总持续时间为2.5h的设定条件下进行机械球磨，制备得具有核壳结构的硅负极材料VO2-Si。取0.5g聚乙烯醇(PVA)分散到50ml的超纯水溶液中，加热搅拌至PVA完全溶解，在PVA水溶液中加入0.5g步骤(1)所制备的VO2-Si，继续加热搅拌至形成湿凝胶，放入80℃的鼓风干燥箱隔夜干燥，取出后置于管式炉中，通入保护气氛Ar，升温至1000℃，保温3h后自然冷却至室温，得到具有双壳层人造SEI 膜结构的硅负极材料，记为VO2-Si-C-4。
该对比例中，由于碳化温度为1000℃，在该碳化温度下，VO2层中的颗粒为晶体结构，并未形成无定形的VO2层。
对比例6
取4g硅粉末，投入50ml钼酸铵和硫脲的混合溶液中，钼酸铵浓度为8mg/ml，硫脲浓度为32mg/ml。将溶液放入反应釜180℃反应24h，自然冷却后降温至常温，洗涤干燥，得到MoS2包覆的硅材料。置于管式炉中，通入保护气氛Ar，升温至800℃，保温3h后自然冷却至室温，得到具有双壳层人造SEI膜结构的硅负极材料，记为MoS2-Si-C。
通过扫描电子显微镜(scanning electron microscop，SEM)、X射线衍射(diffraction of x-rays，XRD)和X射线能谱(energy dispersive x-ray spectroscopy，EDS)测量负极材料的结构信息，其中，图4所示为实施例1的SEM图，图5所示为实施例2的XRD图，图6为实施例2的EDS图。
如图4所示，实施例1的负极材料样品表面干净平整，无包覆物的自团聚体。如图5所示，可观察到明显的硅特征衍射峰，但无明显的VO2特征衍射峰，说明在合成过程的球磨处理中成功实现了对VO2的无定形化处理。一并参照图6，表明硅基材料的颗粒界面有明显的壳层结构，通过对不同元素的EDS能谱测试发现，硅基材料表面有明显V、C元素的双壳层，分别对应VO2和C。通过对负极材料颗粒的EDS线扫可以发现，VO2/C的两点双壳层厚度分别为12nm和13.5nm。说明本申请各实施例可成功实现相对均匀的双壳层包覆，且包覆厚度<15nm。
对比例7
取5g石墨在转速为350rpm的条件下球磨30min，制备得未经包覆处理的石墨负极材料，记为G。
分别利用各实施例和对比例的负极材料组装扣式锂离子电池，测试对应锂离子电池的首效容量以及循环性能，测试结果列于表1。
表1
如表1所示，与未包覆的对比例1以及仅单壳层包覆的对比例2和对比例3相比，本申请实施例1-4的双壳层包覆的负极材料均显示出更高的首次充电比容量和库伦效率，说明双壳层包覆结构有效改善了硅基材料的界面性能。
对比例2仅做第一壳层包覆，虽然首次充电容量和库伦效率相比未包覆的硅得到一定改善，但其对应的扣式电池的循环稳定性相比对比例1下降明显，可能与第一壳层VO2包覆层的电荷传导能力较差有关。
对比例3仅作外层包覆，由表1数据可知，其首次充电比容量是所有样品中最高的，但首次库伦效率和100圈循环容量保持率仍低于双壳层的相关实施例，这是因为虽然外壳层碳层包覆提高了界面电荷交换能力，而且碳层相比硅基材料更稳定，可以作为界面稳定层减少电解液与硅基材料的复反应。但因 为裂解过程中形成的碳层不可避免有孔隙，而且碳的结构能力较弱，所以其界面副反应仍高于双壳层结构，且稳定性低于双壳层结构。
对比例4的数据可证明，当外壳层的总厚度在15nm以上时，相应的负极材料的性能要略低。对比例5中，当形成的第一壳层为非无定形层时，相应的负极材料的性能也要低于本申请的各实施例。这可能是因为，当第一壳层为无定形层且厚度小于15nm时，所获得的第一壳层具有较好的趋肤效应，当硅基材料因嵌锂脱离发生体积变化时，本申请的负极材料具有更高的结构稳定性。对比例6中，MoS2层作为第一壳层时，界面稳定性方面相比实施例1和实施例2会较差，这是因为过渡金属硫化物容易在电池中形成多硫化物造成多硫离子穿梭效应，从而导致循环快速衰减。
实施例5数据证明，虽然包覆后石墨的可逆容量有一定下降(包覆层占负极材料整体质量)，但石墨首次库伦效率明显提升，说明界面电解液分解和副反应明显减小。而且循环100周容量保持率也明显提升，说明包覆层有效改善的长期循环过程的界面反应。
实施例6在实施例3的基础上，在第二壳层的碳中引入了石墨烯和Ti2CF2，石墨烯的片层结构和Ti2CF2片层结构相互堆叠，干燥脱水后，石墨烯和Ti2CF2片层相互之间、以及和第一壳层之间的氢键作用使第二壳层紧紧包覆在第一壳层表面，避免了纯无定型碳与第一壳层之间的结合力不强问题。
以上，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (16)

  1. 一种二次电池用负极材料，其特征在于，所述负极材料为核壳结构，包括内核和外壳；其中，所述内核为负极活性材料；所述外壳包括包覆于所述内核表面的第一壳层和包覆在所述第一壳层表面的第二壳层，所述第一壳层为过渡金属化合物层，所述第二壳体为导电层，所述过渡金属化合物层的最大厚度小于或等于10nm，所述外壳的总厚度小于或等于15nm。
  2. 根据权利要求1所述的负极材料，其特征在于，所述第二壳层包括碳、导电聚合物、碳与过渡金属化合物的混合物、导电聚合物与过渡金属化合物的混合物中的至少一种。
  3. 根据权利要求1或2所述的负极材料，其特征在于，所述第一壳层的孔径尺寸不大于5nm。
  4. 根据权利要求1-3任一项所述的负极材料，其特征在于，所述过渡金属化合物层的成分通式为MXn(Ym)，M为过渡金属元素，X为非金属元素，Y为官能团，Y包括O、F、Cl或OH中的至少一种；其中，n>0，m≥0。
  5. 根据权利要求4所述的负极材料，其特征在于，所述M包括V、Mo、Ti、Zr、Nb或Al中的至少一种。
  6. 根据权利要求4所述的负极材料，其特征在于，所述X包括O、C或N中的至少一种。
  7. 根据权利要求4所述的负极材料，其特征在于，所述第一壳层的嵌锂电位高于所述内核的嵌锂电位，所述第一壳层的脱锂电位大于1V，且所述第一壳层在1V以内的脱锂容量占所述第一壳层在3V以内脱锂容量的30％以下。
  8. 根据权利要求1-7任一项所述的负极材料，其特征在于，所述第一壳层中过渡金属元素在所述负极材料中的质量占比小于等于5％。
  9. 根据权利要求1-8任一项所述的负极材料，其特征在于，所述第二壳层在所述负极材料中的质量占比小于等于5％。
  10. 根据权利要求1-9任一项所述的负极材料，其特征在于，所述负极活性材料包括碳基负极材料、硅基负极材料、锡基负极材料、以及磷基负极材料中的至少一种；
    所述碳基负极材料包括石墨、软炭、硬炭、以及无定型碳中至少一种；
    所述硅基材料包括纯硅、硅氧、镁掺杂硅氧、锂掺杂硅氧或硅碳中的至少一种；
    所述磷基负极材料包括红磷、白磷、黑磷、蓝磷、含磷复合物、以及含磷混合物中的至少一种。
  11. 一种如权利要求1-10任一项所述的负极材料的制备方法，其特征在于，包括：
    将负极活性材料与层状结构过渡金属化合物混合，得到具有单层壳层包覆的负极材料；
    将单层壳层包覆的负极材料与导电剂混合，干燥后得到具有双层壳层包覆的负极材料。
  12. 根据权利要求11所述的制备方法，其特征在于，所述混合方法包括固相搅拌、高速分散、湿法混合干燥、或喷雾干燥。
  13. 根据权利要求11任一项所述的制备方法，其特征在于，所述热处理的温度为150-900℃，时间为0.5-10h。
  14. 根据权利要求11所述的制备方法，其特征在于，所述碳源包括甲醇、乙醇、苯、甲烷、乙炔、一三丁二烯或聚乙烯醇中的至少一种。
  15. 一种二次电池，其特征在于，包括正极、负极、介于所述正极和所述负极之间的电解质，所述负极包括负极集流体和负极材料层，所述负极材料层包括如权利要求1-10任一项所述的负极材料。
  16. 一种用电设备，其特征在于，包括用电元件和如权利要求15所述的二次电池，其中，所述二次电池与所述用电元件电连接，以为所述用电元件提供电力。
PCT/CN2023/104986 2022-10-10 2023-06-30 负极材料及其制备方法、二次电池和用电设备 WO2024078053A1 (zh)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
CN202211237095.XA CN117878260A (zh) 2022-10-10 2022-10-10 负极材料、二次电池和用电设备
CN202211237095.X 2022-10-10

Publications (1)

Publication Number Publication Date
WO2024078053A1 true WO2024078053A1 (zh) 2024-04-18

Family

ID=90579831

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2023/104986 WO2024078053A1 (zh) 2022-10-10 2023-06-30 负极材料及其制备方法、二次电池和用电设备

Country Status (2)

Country Link
CN (1) CN117878260A (zh)
WO (1) WO2024078053A1 (zh)

Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103094551A (zh) * 2012-08-24 2013-05-08 中国科学院上海硅酸盐研究所 一种石墨/氧化亚锰复合电极材料及其制备方法
CN104733699A (zh) * 2015-03-20 2015-06-24 常州大学 一种制备二氧化钼包覆钛酸锂负极材料的方法
JP2015125817A (ja) * 2013-12-25 2015-07-06 株式会社豊田自動織機 複合負極活物質体、非水電解質二次電池用負極および非水電解質二次電池
CN105810912A (zh) * 2016-05-10 2016-07-27 武汉理工大学 三维分级碳包覆NaTi2(PO4)3/C微米花电极材料及其制备方法和应用
CN107623104A (zh) * 2017-09-25 2018-01-23 常州市宇科不绣钢有限公司 一种多重缓冲结构硅基负极材料及其制备方法
CN108682812A (zh) * 2018-05-10 2018-10-19 山东大学 一种MXene包覆硅的复合电极材料及其制备方法
CN109346681A (zh) * 2018-08-17 2019-02-15 福建翔丰华新能源材料有限公司 一种核壳结构纳米硅-MXene复合负极材料及其制备方法
CN109888253A (zh) * 2019-03-29 2019-06-14 华南理工大学 一种二氧化钛包覆三氧化钼材料及其制备方法与应用
CN110212190A (zh) * 2019-06-18 2019-09-06 清华大学 一种网状包覆结构的复合电极材料及其制备方法与应用
CN112786887A (zh) * 2021-01-14 2021-05-11 广东凯金新能源科技股份有限公司 一种高温用石墨负极材料及其制备方法
CN113113606A (zh) * 2021-04-08 2021-07-13 昆山宝创新能源科技有限公司 负极材料及其制备方法、极片、锂离子电池
CN115000403A (zh) * 2021-03-01 2022-09-02 华为技术有限公司 负极材料、复合负极材料及其制备方法、二次电池与终端设备

Patent Citations (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103094551A (zh) * 2012-08-24 2013-05-08 中国科学院上海硅酸盐研究所 一种石墨/氧化亚锰复合电极材料及其制备方法
JP2015125817A (ja) * 2013-12-25 2015-07-06 株式会社豊田自動織機 複合負極活物質体、非水電解質二次電池用負極および非水電解質二次電池
CN104733699A (zh) * 2015-03-20 2015-06-24 常州大学 一种制备二氧化钼包覆钛酸锂负极材料的方法
CN105810912A (zh) * 2016-05-10 2016-07-27 武汉理工大学 三维分级碳包覆NaTi2(PO4)3/C微米花电极材料及其制备方法和应用
CN107623104A (zh) * 2017-09-25 2018-01-23 常州市宇科不绣钢有限公司 一种多重缓冲结构硅基负极材料及其制备方法
CN108682812A (zh) * 2018-05-10 2018-10-19 山东大学 一种MXene包覆硅的复合电极材料及其制备方法
CN109346681A (zh) * 2018-08-17 2019-02-15 福建翔丰华新能源材料有限公司 一种核壳结构纳米硅-MXene复合负极材料及其制备方法
CN109888253A (zh) * 2019-03-29 2019-06-14 华南理工大学 一种二氧化钛包覆三氧化钼材料及其制备方法与应用
CN110212190A (zh) * 2019-06-18 2019-09-06 清华大学 一种网状包覆结构的复合电极材料及其制备方法与应用
CN112786887A (zh) * 2021-01-14 2021-05-11 广东凯金新能源科技股份有限公司 一种高温用石墨负极材料及其制备方法
CN115000403A (zh) * 2021-03-01 2022-09-02 华为技术有限公司 负极材料、复合负极材料及其制备方法、二次电池与终端设备
CN113113606A (zh) * 2021-04-08 2021-07-13 昆山宝创新能源科技有限公司 负极材料及其制备方法、极片、锂离子电池

Also Published As

Publication number Publication date
CN117878260A (zh) 2024-04-12

Similar Documents

Publication Publication Date Title
US9843045B2 (en) Negative electrode active material and method for producing the same
JP5302456B1 (ja) 非水二次電池
JP5180211B2 (ja) リチウムイオン電池の珪素・炭素複合陰極材料及びその製造方法
JP4974597B2 (ja) リチウムイオン二次電池用負極及び負極活物質
JP4944974B2 (ja) チタン酸リチウムナノ粒子とカーボンの複合体、その製造方法、この複合体からなる電極材料、この電極材料を用いた電極及び電気化学素子
CN114975980A (zh) 负极材料及使用其的电化学装置和电子装置
JP2009272041A (ja) リチウムイオン二次電池
KR20150006703A (ko) 리튬이차전지용 음극 활물질, 이를 포함하는 음극용 조성물 및 리튬이차전지
JP2013054958A (ja) 非水電解質二次電池用負極材、リチウムイオン二次電池及び電気化学キャパシタ
WO2022121281A1 (zh) 一种自填充包覆硅基复合材料、其制备方法及其应用
CN114464909A (zh) 一种纳米化复合正极补锂浆料以及正极
CN101355150B (zh) 锂离子电池用石墨碳纳米管复合电极材料的制备方法
WO2023208058A1 (zh) 负极极片及其制备方法、电池、及负极材料的制备方法
CN113889594A (zh) 一种硼掺杂锆酸镧锂包覆石墨复合材料的制备方法
CN113196524B (zh) 负极材料、负极极片、电化学装置和电子装置
KR101470090B1 (ko) 리튬이차전지용 양극 활물질 복합체, 이의 제조방법 및 이를 이용한 리튬이차전지
WO2020105598A1 (ja) 複合炭素粒子、その製造方法及びリチウムイオン二次電池
WO2024078053A1 (zh) 负极材料及其制备方法、二次电池和用电设备
KR102473745B1 (ko) 실리콘／탄소나노튜브／그래핀 복합체 제조방법 및 이를 이용한 이차전지 제조방법
JP5318921B2 (ja) リチウムイオン二次電池用黒鉛粒子
CN101728524A (zh) 一种锂离子电池/电容器电极材料及其制备方法
WO2021128208A1 (zh) 负极材料及包含其的电化学装置和电子装置
CN116759563B (zh) 一种多孔结构的锂电池复合负极材料、其制备方法及锂电池
CN117038941B (zh) 一种多孔硅碳负极材料及其制备方法与应用
WO2023002758A1 (ja) 負極活物質、負極材料、および電池

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 23876262

Country of ref document: EP

Kind code of ref document: A1