WO2021179219A1 - 阳极极片及其制备方法、采用该极片的电池及电子装置 - Google Patents

阳极极片及其制备方法、采用该极片的电池及电子装置 Download PDF

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WO2021179219A1
WO2021179219A1 PCT/CN2020/078856 CN2020078856W WO2021179219A1 WO 2021179219 A1 WO2021179219 A1 WO 2021179219A1 CN 2020078856 W CN2020078856 W CN 2020078856W WO 2021179219 A1 WO2021179219 A1 WO 2021179219A1
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lithium
porous carbon
anode
pole piece
active layer
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PCT/CN2020/078856
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English (en)
French (fr)
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陈茂华
谢远森
杜鹏
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宁德新能源科技有限公司
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Priority to CN202080096492.2A priority Critical patent/CN115088101A/zh
Priority to JP2022551684A priority patent/JP7465362B2/ja
Priority to PCT/CN2020/078856 priority patent/WO2021179219A1/zh
Priority to EP20924188.4A priority patent/EP4120393A4/en
Priority to KR1020227031292A priority patent/KR20220130825A/ko
Publication of WO2021179219A1 publication Critical patent/WO2021179219A1/zh
Priority to US17/941,124 priority patent/US20230006215A1/en

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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
    • H01M4/13—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
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/665—Composites
    • H01M4/667—Composites in the form of layers, e.g. coatings
    • 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
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • This application relates to the field of batteries, in particular to an anode pole piece and a preparation method thereof, a battery and an electronic device using the pole piece.
  • Lithium-ion batteries have the characteristics of large specific energy, high working voltage, low self-discharge rate, small size, light weight, etc., and have a wide range of applications in the field of consumer electronics. With the rapid development of electric vehicles and portable electronic devices, people have higher and higher performance requirements for lithium-ion batteries. For example, lithium-ion batteries are required to have higher energy density, safety, and cycle performance.
  • the prior art adopts anode framework technology, which uses carbon materials to construct a porous carbon framework on the anode pole pieces, so that during the battery discharge process, lithium metal is stripped from the anode and embedded In the cathode material, the carbon skeleton can maintain its own shape, so the volume of the anode electrode piece will not decrease; during the battery charging process, the lithium metal is peeled off from the cathode and deposited on the anode electrode piece, and lithium can be stored in the carbon skeleton.
  • the carbon skeleton can also disperse the current and reduce the local current density, thereby improving the deposition morphology, reducing the lithium dendrites, increasing the lithium deposition density, and improving the performance of lithium-ion batteries. Purpose.
  • the carbon material itself has a relatively large binding energy for lithium, about -1 eV
  • the deposition position of the existing carbon skeleton anode electrode during the lithium metal deposition process is uncontrollable, resulting in uneven lithium metal deposition.
  • due to lithium The metal deposition is not uniform, and the volume of the anode pole piece changes greatly during the cycle, so that the performance of the lithium ion battery manufactured based on the existing carbon skeleton anode pole piece also needs to be improved.
  • the purpose of this application is to provide an anode pole piece and a preparation method thereof, a battery and an electronic device using the pole piece, so as to improve the uniformity of lithium metal deposition.
  • the specific technical solutions are as follows:
  • the first aspect of the present application provides an anode electrode sheet, which includes a current collector and an active layer, the active layer including a porous carbon framework and silicon nanoparticles and lithium metal in the porous carbon framework.
  • the sum of the volume of the porous carbon framework and the silicon nanoparticles accounts for 10% to 60% of the total volume of the active layer.
  • the overall product ratio of the porous carbon skeleton to the silicon nanoparticles is 5:1 to 100:1.
  • the content of the lithium metal in the active layer is 0.001 to 3 mg/cm 2 .
  • the thickness of the active layer is 1 to 100 ⁇ m.
  • the strength of the porous carbon skeleton is not less than 200 GPa.
  • the porosity of the porous carbon skeleton is 40% to 90%.
  • the material of the current collector includes: at least one of copper, nickel, titanium, molybdenum, iron, zinc, stainless steel and alloys thereof, or carbon and graphene.
  • the second aspect of the present application provides a method for preparing the anode pole piece as described in the first aspect, including:
  • the active layer is placed on a current collector, and the active layer and the current collector are combined by hot pressing to prepare an anode pole piece.
  • the deposition time of the nano silicon particles is controlled to be 5 to 120 minutes.
  • the third aspect of the present application provides a lithium ion battery, including: a cathode electrode piece;
  • isolation film located between the cathode electrode piece and the anode electrode piece;
  • the anode pole piece is the anode pole piece described in the first aspect.
  • a third aspect of the present application provides an electronic device, and the electronic device includes the lithium ion battery as described in the third aspect.
  • the present application provides an anode pole piece.
  • the anode pole piece includes a current collector and an active layer.
  • the active layer includes a porous carbon framework, silicon nanoparticles and lithium metal.
  • the silicon nanoparticles and lithium metal are located in the porous carbon framework.
  • Fig. 1 is a schematic diagram of the structure of the anode framework of the prior art
  • FIG. 2 is a schematic diagram of the structure of an anode pole piece according to an embodiment of the application
  • FIG. 3 is a schematic diagram of the structure of an anode pole piece according to another embodiment of the application.
  • FIG. 4 is a schematic diagram of the structure of an anode pole piece according to another embodiment of the application.
  • anode materials for lithium-ion batteries for example, graphite and other materials
  • lithium ions exist in the graphite layer structure in the form of intercalation during charging.
  • the graphite layer is similar to the framework structure and provides storage space for lithium.
  • Lithium-ion batteries with metal electrodes do not have such a framework structure. Therefore, the anode pole pieces will undergo drastic volume changes during charging and discharging.
  • the thickness of the anode pole pieces usually varies from 8 to 200 ⁇ m, which leads to a decrease in the cycle performance of the battery.
  • lithium will be deposited on the surface of the current collector of the anode electrode.
  • lithium dendrites Due to the uneven current density and the concentration of lithium ions in the electrolyte, the deposition rate of certain sites will be too fast during the deposition process. This part of lithium grows from the main body of lithium metal in the form of a synapse, and continues to grow and even bifurcate, eventually forming sharp lithium dendrites. The presence of lithium dendrites will greatly reduce the deposition density, which reduces the energy density of the battery. For example, in some lithium ion batteries, the actual deposition density of lithium metal is about 0.2 g/cm 3 , which is much smaller than the true density of lithium metal of 0.534 g/cm 3 . Due to the loose deposition of lithium metal, the energy density of the battery will be reduced by more than 100Wh/L. In addition, lithium dendrites may also pierce the isolation membrane to form a short circuit, causing battery failure and affecting battery safety.
  • this application provides an anode electrode piece, see Figures 2 and 3, where Figure 2 is a top view of an anode electrode piece according to an embodiment of the application, and Figure 3 is an embodiment of the application
  • the silicon nanoparticles 4 and the lithium metal 5 may be discretely distributed in the porous carbon framework 3 or continuously distributed in the porous carbon framework 3. This application does not exclude a small part of the silicon nanoparticles 4 and lithium metal 5 on the surface of the porous carbon framework.
  • the active layer 2 may be composed of a porous carbon skeleton 3, silicon nanoparticles 4, and lithium metal 5.
  • the porous carbon skeleton 3 may be a sheet-like structure with a large number of pores.
  • the pores in 3 can be microporous or other shapes of pores.
  • the porous carbon skeleton 3 has sufficient strength, for example, the strength of the porous carbon skeleton 3 is not less than 200 GPa, so as to maintain a stable morphology and internal space.
  • the porous carbon skeleton 3 can provide a stable space, allowing lithium metal to be deposited in a large number of pores of the porous carbon skeleton 3; and during discharge, the porous carbon skeleton 3 can be formed in the process of decreasing lithium in the anode.
  • the stable structure and internal space prevent the anode from shrinking violently.
  • the porous carbon skeleton 3 is a carbon-based material, which has good ionic and electronic conductivity, so it can provide a conductive channel.
  • the porous carbon skeleton 3 has a high specific surface area, so it can effectively disperse the charge and discharge process.
  • the electric current reduces the current density and forms a more uniform electric field, thereby improving the uniformity of lithium deposition and inhibiting the growth of lithium dendrites.
  • the active layer of the present application also includes silicon nanoparticles 4, and the silicon nanoparticles are located in the porous carbon skeleton 3.
  • the silicon nanoparticles 4 can spontaneously undergo an alloying reaction with lithium metal, and the alloy potential can reach about 0.2V. Therefore, it can provide the required sites for lithium metal deposition, thereby effectively regulating the deposition position of lithium metal, so that the lithium metal can be deposited during the cycle. It is preferentially deposited in the pores of the porous carbon skeleton 3, rather than on the surface of the anode pole piece.
  • the active layer of the present application may also include pre-filled lithium metal 5.
  • lithium metal 5 is an anode active material. Since lithium metal has a higher specific capacity relative to materials such as carbon and silicon, the specific capacity of lithium metal is 3860mAh/g, the specific capacity of silicon is 3600mAh/g, and the specific capacity of carbon is The specific capacity is only 372mAh/g, so the battery using this anode electrode will also have a higher energy density.
  • the above-mentioned lithium metal 5 may be pre-replenished during the preparation of the anode electrode sheet, or may be all transferred from the cathode, of course, it may also be obtained jointly by the pre-replenished lithium and the cathode transferred lithium.
  • the silicon nanoparticles 4 may be attached to the porous carbon skeleton 3, and the lithium metal 5 may be filled in the porous carbon skeleton 3.
  • the sum of the volume of the porous carbon framework and the silicon nanoparticles accounts for 10% to 60% of the total volume of the active layer. After being made into a lithium ion battery, it has a lower volume expansion rate and a higher number of cycles.
  • the total volume ratio of the porous carbon skeleton to the silicon nanoparticles may be 5:1 to 100:1, that is, in the active layer 2, the total volume of the porous carbon skeleton and the total volume of the silicon nanoparticles The ratio between the total volume is 5:1 to 100:1.
  • the silicon nanoparticles have insufficient guidance for the deposition of lithium metal. Therefore, part of the lithium metal is deposited on the anode electrode.
  • the lithium metal is deposited inside the anode electrode, and the volume expansion of the anode electrode is smaller; however, when the silicon nanoparticles are active When there is too much in the layer, since the silicon nanoparticles themselves do not participate in the reaction during the cycle, too much silicon nanoparticles will affect the deposition of lithium metal instead. Controlling the volume of silicon nanoparticles in the active layer within the above range in terms of volume ratio can make the anode pole piece have a lower volume expansion rate and a higher number of cycles after being made into a lithium ion battery .
  • the content of lithium metal in the active layer is 0.001 to 3 mg/cm 2
  • the content of pre-replenished lithium is too small to improve the cycle performance of the battery
  • the content of pre-replenished lithium is too large , It may lead to reduced security.
  • the thickness of the active layer is 1 to 100 ⁇ m.
  • the porosity of the porous carbon skeleton is 40% to 90%.
  • the material of the current collector of the present application is not particularly limited, and materials well known to those skilled in the art can be used.
  • the material of the current collector may include, but is not limited to: copper, nickel, titanium, molybdenum, iron, zinc, stainless steel and alloys thereof.
  • nano-silicon can spontaneously undergo an alloying reaction with lithium metal from the cathode, it can provide sites required for lithium deposition, thereby effectively regulating the deposition position of lithium.
  • lithium is preferentially deposited in the pores, so that the deposition of lithium metal is more uniform, thereby reducing the volume change of the anode pole piece during the cycle, and inhibiting the growth of lithium dendrites.
  • This application also provides a method for preparing an anode pole piece, which includes the following steps:
  • porous carbon skeleton flakes are placed in a CVD device, and a silane-containing gas is introduced to deposit nano-silicon particles to obtain the deposited porous carbon skeleton flakes.
  • the porous carbon skeleton flakes can be prepared by carbonizing a glucose solution in advance, and the silane gas can be monosilane, disilane, or the like.
  • the molten lithium metal is brought into contact with the deposited porous carbon framework flakes, so that the lithium metal is filled into the pores of the deposited porous carbon framework flakes to prepare an active layer.
  • the protective gas atmosphere may refer to an atmosphere in argon with a water content of less than 1 ppm and an oxygen content of less than 1 ppm.
  • the active layer is placed on the current collector, and the active layer and the current collector are combined by hot pressing to prepare an anode pole piece. After the anode pole piece is made, the anode pole piece can be punched into a size of 40*60mm for assembling a laminated battery.
  • the lithium metal deposition of the anode pole piece during cycling is made more uniform, and the volume change of the anode pole piece during the cycle is reduced, and the lithium metal is pre-filled so that The battery adopting the anode electrode piece of the present application has higher cycle performance.
  • An embodiment of the present application also provides a lithium ion battery, including: a cathode electrode piece, an anode electrode piece, a separator, and an electrolyte, wherein the separator film is located between the cathode electrode piece and the anode electrode piece.
  • the anode pole piece is the anode pole piece described in any of the above embodiments.
  • the nano-silicon in the anode electrode piece can spontaneously undergo an alloying reaction with the lithium metal from the cathode, it can provide the sites required for lithium deposition, thereby effectively regulating the deposition position of lithium.
  • lithium is preferentially deposited in the pores to make the lithium metal deposition more uniform, thereby reducing the volume change of the anode pole piece during the cycle, inhibiting the growth of lithium dendrites, and improving the safety of the lithium ion battery.
  • An embodiment of the present application also provides an electronic device, including the lithium ion battery described in the above embodiment.
  • the lithium ion battery used has a more uniform lithium metal deposition, thereby reducing anodes.
  • the volume change of the sheet during the cycle inhibits the growth of lithium dendrites, so that the electronic device has higher safety.
  • the cathode sheet in this application is not particularly limited, and any cathode sheet known in the art can be used.
  • a cathode electrode piece containing lithium cobalt oxide a cathode electrode piece containing lithium manganate, a cathode electrode piece containing lithium iron phosphate, or a cathode electrode piece containing lithium nickel cobalt manganate or lithium nickel cobalt aluminate.
  • the isolation film of the present application is not particularly limited, and any isolation film known in the art can be used, for example, a PE (polyethylene) diaphragm, a PP (polypropylene) diaphragm, and the like.
  • the electrolyte is not particularly limited, and any electrolyte known in the art can be used, for example, organic solvents DOL (dioxolane) and DME (dimethyl ether) and LiFSI (bis(fluorosulfonyl) )
  • organic solvents DOL dioxolane
  • DME dimethyl ether
  • LiFSI bis(fluorosulfonyl)
  • an electrolyte prepared from organic solvents DMC (dimethyl carbonate), EMC (ethyl methyl carbonate) and LiPF 6 etc.
  • the framework flakes have a porosity of 70%.
  • porous carbon framework sheet into a CVD (chemical vapor deposition) equipment pass in a gas containing silane, the flow rate of the silane gas is 100sccm/min, the pressure of the CVD equipment is 30torr, and the deposition is at 500 degrees Celsius for 30 minutes to obtain the
  • the porous carbon skeleton flakes after the deposition treatment have an average particle diameter of 20 nm of silicon nanoparticles in the porous carbon skeleton flakes after the deposition treatment.
  • the obtained active layer was placed on a nickel current collector with a thickness of 15 ⁇ m, and the active layer was combined with the nickel current collector by a hot pressing method, where the hot pressing temperature was controlled to 300 degrees Celsius and the hot pressing pressure It is 100kg to obtain the anode pole piece, and then the anode pole piece is punched into a size of 40*60mm for later use.
  • the cathode active material LiFePO 4 lithium iron phosphate
  • conductive carbon black conductive carbon black
  • PVDF polyvinylidene fluoride
  • NMP N-methylpyrrolidone
  • the slurry is uniformly stirred, and the solid content of the slurry is 75%.
  • the slurry is evenly coated on an aluminum foil current collector with a thickness of 15 ⁇ m, and dried at 90 degrees Celsius to obtain a cathode electrode piece.
  • the loading amount of the cathode active material on the fluid is 1 mg/cm 2. After the coating is completed, the cathode electrode piece is cut into a size of 38mm*58mm for use.
  • the addition amount of LiFSI in the mixed solvent is 1 mol/L
  • the addition amount of LiNO 3 in the mixed solvent is 1 wt%.
  • a PE film polyethylene with a thickness of 15 ⁇ m is selected as the isolation film, a cathode electrode piece is placed on each side of the anode electrode piece, and a layer of isolation film is placed between the cathode electrode piece and the anode electrode piece to form a laminate, and then the whole The four corners of the laminated structure are fixed, placed in an aluminum plastic film, and after top-side sealing, electrolyte injection, and packaging, a lithium metal laminated battery is obtained.
  • the loading amount of lithium in the active layer is controlled to 0.2 mg/cm 2 by reducing the amount of pre-supplemented lithium, the rest is the same as in Example 1.
  • the loading amount of lithium in the active layer is controlled to 1 mg/cm 2 by increasing the amount of pre-supplemented lithium, the rest is the same as in Example 1.
  • the loading amount of lithium in the active layer is controlled to 3 mg/cm 2 by increasing the amount of pre-supplemented lithium, the rest is the same as in Example 1.
  • the lithium ion battery was prepared by the same method as in Example 1, except that the charge rate was 0.2C when the performance test of the prepared lithium ion battery was performed.
  • the lithium ion battery was prepared by the same method as in Example 1, except that the charging rate was 0.4C when the performance test of the prepared lithium ion battery was performed.
  • the average particle size of the silicon nanoparticles in the deposited porous carbon framework flakes is controlled to 5 nm by reducing the deposition temperature, etc., the rest is the same as in Example 1.
  • the average particle size of the silicon nanoparticles in the deposited porous carbon framework flakes is controlled to 50 nm by increasing the deposition temperature, and the rest is the same as in Example 1.
  • the porosity of the porous hard carbon framework is controlled to 40% by lowering the carbonization temperature, and the rest is the same as in Example 1.
  • the thickness of the porous carbon skeleton sheet is reduced to 20 microns by reducing the amount of glucose, and the rest is the same as in Example 1.
  • the thickness of the porous carbon skeleton sheet is increased to 75 microns by increasing the amount of glucose, and the rest is the same as in Example 1.
  • the thickness of the porous carbon skeleton sheet is increased to 100 microns by increasing the amount of glucose, and the rest is the same as in Example 1.
  • the commercially available lithium-clad copper foil is punched into a size of 40*60mm for assembling laminated batteries. Among them, the thickness of the lithium-clad copper foil is 30 ⁇ m.
  • Example 2 The same method as in Example 1 was used to prepare a porous carbon skeleton.
  • the metallic lithium In a dry argon atmosphere, the metallic lithium is placed in a stainless steel crucible and heated to 300 degrees Celsius to melt the solid metallic lithium into a liquid state, and the deposited porous carbon framework flakes are brought into contact with the molten lithium.
  • the anode pole piece was prepared using the same anode pole piece preparation method as in Example 1.
  • silicon powder particles with an average particle size of 80nm and lithium metal are mixed in a volume ratio of 1:10, and then the silicon powder particles and lithium metal are combined by hot pressing to control the hot pressing
  • the temperature is 150 degrees Celsius
  • the pressure is 100 kg
  • the anode pole piece is obtained.
  • the average thickness of the anode pole piece is 30 ⁇ m, and then the anode pole piece is punched into a size of 40*60 mm for assembling the laminated battery.
  • the composite process of the porous carbon skeleton and nano-silicon is the same as in Example 1, to obtain the porous carbon skeleton flakes after the deposition treatment.
  • the porous carbon skeleton flakes are not subjected to the pre-replenishing lithium treatment and directly use the anode electrode preparation method of embodiment 1 to obtain Anode pole piece.
  • the silicon nanoparticles, polyacrylic acid and conductive carbon are mixed in water at a mass ratio of 80:10:10 and stirred evenly to obtain a mixed solution, and then the mixed solution is coated on a nickel current collector and dried at 180 degrees Celsius. Obtain the anode pole piece.
  • the load of silicon in the anode pole piece is 1.1 mg/cm 2 , and then the anode pole piece is punched into a size of 40*60 mm for assembling a laminated battery.
  • Example 1 The method of Example 1 was used to prepare a porous hard carbon skeleton, and the porous hard carbon skeleton was used as an anode electrode piece.
  • the nickel current collector is directly used as the anode pole piece.
  • the metallic lithium In a dry argon atmosphere, the metallic lithium is placed in a stainless steel crucible and heated to 300 degrees Celsius to melt the solid metallic lithium into a liquid state, and the nickel current collector is in contact with the molten lithium, and a small amount of lithium adheres to the surface of the nickel current collector.
  • the anode electrode piece was prepared by the same method as that of Comparative Example 8. The difference from Comparative Example 8 was that the lithium ion battery made from the anode electrode piece was charged with a charge rate of 0.4C.
  • Example 2 to 14 the same method as in Example 1 for preparing the lithium ion battery was used to prepare a lithium ion battery.
  • the lithium-ion battery prepared in each example was turned into a circle at a charge and discharge rate of 0.1C under the condition of 60 degrees Celsius, and then the charge and discharge cycle was performed at room temperature.
  • the current in the constant current charging stage was 1C and the cut-off voltage was 3.8 V, the cut-off current of the constant voltage charging stage is 0.05C, the constant current discharge rate is 1C, and the cut-off voltage is 2.7V.
  • the lithium ion battery prepared in Comparative Example 9 was charged with a charge rate of 0.4C.
  • the cathode electrode pieces and anode electrode pieces of each example and comparative example were cut into 10mm ⁇ 5mm size respectively, and put into an ion grinding polisher to polish the cross-section of each electrode piece, and then the obtained electrode piece was transferred to the scanning In an electron microscope (SEM), observe the cross-section of the pole piece after polishing at a suitable magnification, and measure the corresponding thickness. Then, the thickness of the cathode electrode piece, the anode electrode piece and the diaphragm are respectively added to obtain the thickness of the battery core, which does not consider the packaging.
  • SEM electron microscope
  • volume expansion rate (t( 100%)-t(0%))/t(0%).
  • Examples 9 and 10 used different charging magnifications when performing performance tests on the prepared lithium-ion batteries, but compared with Comparative Examples 1 to 9, the volume expansion rate was obviously reduced, and the number of cycles was also significantly increased.
  • Example 15 when the thickness of the porous carbon flakes is relatively low relative to the loading amount of the cathode active material (as in Example 15), the internal pores of the pole pieces are not enough to carry all the pre-replenished lithium and deposited lithium. Part of the lithium is deposited on the surface of the pole piece, resulting in an increase in volume change and deterioration of circulation.
  • the thickness is increased to 75 micrometers and 100 micrometers, due to the increase of the thickness itself, the volume expansion will be slightly improved at the expense of energy density; on the other hand, due to the increase of the specific surface area, the circulation will be reduced. Therefore, the optimum thickness should be adapted from the perspective of energy density, volume expansion and number of cycles, combined with the cathode load, and comprehensive considerations.
  • Comparative Example 1 the battery prepared using only the lithium-coated copper foil anode electrode piece, compared with the batteries prepared in Examples 1 to 17, the volume expansion rate was significantly increased, and the circulation circle was significantly decreased.
  • Comparative Example 2 when the anode pole piece does not contain silicon nanoparticles, compared with the batteries prepared in Examples 1 to 17, the volume expansion rate is significantly increased, and the number of cycles is significantly reduced.
  • Comparative Example 3 when the anode electrode piece contains silicon particles but does not contain a carbon skeleton, compared with the batteries prepared in Examples 1 to 17, the volume expansion rate is significantly increased, and the number of cycles is significantly reduced.
  • Comparative Example 4 when the anode plate contains silicon particles, but not silicon nanoparticles prepared by the SVD method, and does not contain pre-replenished lithium, compared with the batteries prepared in Examples 1 to 17, the volume expansion rate is There is little change, but the number of cycles has dropped significantly.
  • Comparative Example 5 when only silicon particles (non-CVD method) are contained in the anode pole piece, without carbon skeleton and pre-replenished lithium, the volume expansion rate is significantly higher than that of the batteries prepared in Examples 1 to 17. , But the number of cycles has dropped significantly.
  • Comparative Example 6 when the anode pole piece contains only the porous carbon skeleton and does not contain pre-replenished lithium, compared with the batteries prepared in Examples 1 to 17, the volume expansion rate does not change much, and the number of cycles decreases significantly. .
  • Comparative Example 7 when only the current collector is contained in the anode pole piece, and the carbon skeleton and pre-replenished lithium are not included, the volume expansion rate is significantly higher than that of the batteries prepared in Examples 1 to 17, and the number of cycles Significantly decreased.
  • Comparative Example 8 when the anode pole piece contains only the current collector and pre-replenished lithium, compared with the batteries prepared in Examples 1 to 17, the volume expansion rate is significantly increased, and the number of cycles is significantly reduced.

Abstract

一种阳极极片及其制备方法、采用该极片的电池及电子装置，其中阳极极片包括集流体（1）和活性层（2），活性层（2）包括多孔碳骨架（3）和位于多孔碳骨架（3）中的硅纳米颗粒（4）和锂金属（5）。采用该极片的电池能够减少阳极极片在循环过程中的体积变化，抑制锂枝晶的生长，提高锂离子电池的安全性，并能够使得采用该阳极极片的电池具有更高的能量密度。

Description

阳极极片及其制备方法、采用该极片的电池及电子装置 技术领域
本申请涉及电池领域，具体涉及一种阳极极片及其制备方法、采用该极片的电池及电子装置。
背景技术
锂离子电池具有比能量大、工作电压高、自放电率低、体积小、重量轻等特点，在消费电子领域具有广泛的应用。随着电动汽车和可移动电子设备的高速发展，人们对锂离子电池的性能需求也越来越高，例如，需要锂离子电池具有更高的能量密度、安全性、循环性能等。
为了提高锂离子电池的性能，如图1所示，现有技术采用阳极骨架技术，即使用碳材料在阳极极片上构建多孔的碳骨架，这样在电池放电过程中，锂金属从阳极剥离并嵌入到阴极材料中，碳骨架能够维持本身的形状不变，因此阳极极片的体积不会减少；在电池充电过程中，锂金属从阴极剥离并沉积到阳极极片上，锂可以储存在碳骨架的孔洞中，从而维持阳极极片体积的稳定性，并且，碳骨架还可以分散电流，降低局部电流密度，从而改善沉积形貌，减少锂枝晶，提高锂沉积密度，达到提高锂离子电池性能的目的。
但是，由于碳材料本身对锂的结合能较大，约为-1eV，现有的碳骨架阳极极片在锂金属沉积过程中沉积位置不可控，导致锂金属沉积不均匀，进一步地，由于锂金属沉积不均匀，阳极极片在循环过程中体积变化大，使得这种基于现有碳骨架阳极极片制造的锂离子电池的能也有待提高。
发明内容
本申请的目的在于提供一种阳极极片及其制备方法、采用该极片的电池及电子装置，以提高锂金属沉积均匀性。具体技术方案如下：
本申请的第一方面提供了一种阳极极片，其包括集流体和活性层，所述活性层包括多孔碳骨架和位于所述多孔碳骨架中的硅纳米颗粒和锂金属。
在本申请的一种实施方案中，所述多孔碳骨架和硅纳米颗粒的体积之和，占所述活性层总体积的10％至60％。
在本申请的一种实施方案中，所述多孔碳骨架与所述硅纳米颗粒的总体 积比为5：1至100：1。
在本申请的一种实施方案中，所述锂金属在所述活性层中的含量为0.001至3mg/cm 2。
在本申请的一种实施方案中，所述活性层的厚度为1至100μm。
在本申请的一种实施方案中，所述多孔碳骨架的强度不低于200GPa。
在本申请的一种实施方案中，所述多孔碳骨架的孔隙率为40％至90％。
在本申请的一种实施方案中，所述集流体的材料包括：铜、镍、钛、钼、铁、锌、不锈钢及其合金或碳、石墨烯中的至少一种。
本申请的第二方面提供了一种如上述第一方面所述的阳极极片的制备方法，包括：
将多孔碳骨架薄片置于CVD设备中，通入含硅烷的气体，进行纳米硅颗粒的沉积得到沉积后的多孔碳骨架薄片；
在保护气体氛围下，将熔融态锂金属与所述沉积后的多孔碳骨架薄片相接触，使锂金属填充至所述沉积后的多孔碳骨架薄片的孔隙中，制得活性层；
将所述活性层放置在集流体上，热压使所述活性层和集流体相结合，制得阳极极片。
在本申请的一种实施方案中，纳米硅颗粒的沉积时间控制为5至120min。
本申请的第三方面提供了一种锂离子电池，包括：阴极极片；
阳极极片；
隔离膜，所述隔离膜位于所述阴极极片和所述阳极极片之间；以及
电解液；
其中，所述阳极极片为上述第一方面所述的阳极极片。
本申请的第三方面提供了一种电子装置，所述电子装置包括如上述第三方面所述的锂离子电池。
本申请提供一种阳极极片，阳极极片包括集流体和活性层，其中活性层中包括：多孔碳骨架、硅纳米颗粒以及锂金属，硅纳米颗粒和锂金属位于多孔碳骨架的中，在循环过程中，由于纳米硅能够自发地与来自阴极的锂金属发生合金化反应，因此可以提供锂沉积所需的位点，从而有效地调控锂的沉积位置，使循环过程中锂优先沉积在孔隙中，使锂金属沉积更加均匀，从而 减少阳极极片在循环过程中的体积变化，抑制锂枝晶的生长。
附图说明
为了更清楚地说明本申请实施例和现有技术的技术方案，下面对实施例和现有技术中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图获得其他的技术方案。
图1为现有技术阳极骨架的结构示意图；
图2为本申请的一种实施方案的阳极极片的结构示意图；
图3为本申请的另一种实施方案的阳极极片的结构示意图；
图4为本申请的再一种实施方案的阳极极片的结构示意图。
具体实施方式
为使本申请的目的、技术方案、及优点更加清楚明白，以下参照附图和实施例，对本申请进一步详细说明。显然，所描述的实施例仅仅是本申请一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有做出创造性劳动前提下所获得的所有其他技术方案，都属于本申请保护的范围。
现有的锂离子电池阳极材料，例如，石墨等材料，在充电时锂离子以嵌入的形式存在于石墨层结构中，石墨层类似于骨架结构，为锂提供了储存空间，而对于具有纯锂金属电极的锂离子电池，并不存在这样的骨架结构，因此在充放电过程中阳极极片会出现剧烈的体积变化，通常阳极极片厚度变化范围为8至200μm，导致电池的循环性能下降。并且，在充电过程中，锂会在阳极极片的集流体表面沉积，由于电流密度以及电解液中锂离子浓度的不均匀性，沉积过程中会出现某些位点沉积速度过快的现象，这部分锂以类似突触的形式从锂金属主体中长出，并持续生长甚至分叉，最终形成尖锐的锂枝晶。锂枝晶的存在会导致沉积密度大大降低，使得电池的能量密度降低。例如，在一些锂离子电池中，锂金属的实际沉积密度为0.2g/cm 3左右，远小于锂金属的真密度0.534g/cm 3。由于锂金属的疏松沉积，电池的能量密度将会降低100Wh/L以上。此外，锂枝晶还可能会刺穿隔离膜形成短路，导致电池失效，影响电池安全性。
有鉴于此，本申请提供了一种阳极极片，参见图2和图3，其中，图2为本申请的一种实施方案的阳极极片的俯视图，图3为本申请的一种实施方案的阳极极片的截面图，包括：集流体1和活性层2，其中，活性层2包括多孔碳骨架3和位于多孔碳骨架3中的硅纳米颗粒4和锂金属5。可以理解，硅纳米颗粒4和锂金属5可以离散分布于多孔碳骨架3中，也可以连续分布于多孔碳骨架3中。本申请中并不排除少部分硅纳米颗粒4和锂金属5处于多孔碳骨架表面上。
本申请的一种实施方案中，活性层2可以由多孔碳骨架3、硅纳米颗粒4以及锂金属5组成，其中，多孔碳骨架3可以是具有大量孔隙的膜片状结构，该多孔碳骨架3中的孔隙可以为微孔状，或者是其它形状的孔洞。并且，多孔碳骨架3具有足够的强度，例如，该多孔碳骨架3的强度不低于200GPa，从而保持稳定的形貌和内部空间。在充电时，多孔碳骨架3可以提供稳定的空间，使锂金属沉积在多孔碳骨架3的大量孔隙中；而放电时，在阳极的锂不断变少的过程中，多孔碳骨架3又能形成稳定的结构和内部空间，使得阳极不会发生剧烈的收缩。另一方面，多孔碳骨架3为碳基材料，具有良好的离子和电子导电性，因此可以提供导电通道，进一步地，多孔碳骨架3具有高比表面积，因此可以有效地分散充放电过程中的电流，减小电流密度，形成更加均匀的电场，从而改善锂沉积的均匀性，抑制锂枝晶的生长。
但是发明人研究发现，只有锂金属沉积位置得到有效的控制，多孔碳骨架3的作用才能最大限度地发挥出来。若锂金属沉积在阳极极片表面，则阳极极片在循环过程中，仍然会有剧烈的体积变化，因而多孔碳骨架3难以发挥出本身的作用。
因此，本申请的活性层还包括硅纳米颗粒4，硅纳米颗粒位于多孔碳骨架3中。硅纳米颗粒4可以自发地与锂金属发生合金化反应，合金电位达到0.2V左右，因此可以提供锂金属沉积所需的位点，从而有效地调控锂金属的沉积位置，使循环过程中锂金属优先沉积在多孔碳骨架3的孔隙中，而不是阳极极片的表面。
本申请的活性层还可以包括预补的锂金属5。可以理解，锂金属5是阳极活性物质，由于锂金属相对于碳、硅等材料具有更高的比容量，锂金属的比 容量为3860mAh/g，硅的比容量为3600mAh/g，而碳的比容量仅为372mAh/g，因此采用该阳极极片的电池也将具有更高的能量密度。当然，上述锂金属5可以是在制备阳极极片时预补充的，也可以全部由阴极转移而来的，当然还可以是预补锂和阴极转移锂共同得到的。
本申请的一种实施方案中，硅纳米颗粒4可以附着在多孔碳骨架3中，锂金属5可以填充在多孔碳骨架3中。
本申请的一种实施方案中，多孔碳骨架和硅纳米颗粒的体积之和，占活性层总体积的10％至60％，通过上述多孔碳骨架和硅纳米颗粒的比例制得的阳极极片在制成锂离子电池后，具有更低的体积膨胀率和更高的循环圈数。
本申请的一种实施方案中，多孔碳骨架与硅纳米颗粒的总体积比可以为5：1至100：1，即，在活性层2中，多孔碳骨架的总体积，以及硅纳米颗粒的总体积之间的比例为5：1至100：1，当硅纳米颗粒在活性层中较少的时，硅纳米颗粒对锂金属沉积的引导作用不足，因此，部分锂金属沉积在了阳极极片表面，导致阳极极片体积膨胀较大；而当硅纳米颗粒在活性层中适中时，锂金属沉积在了阳极极片内部，阳极极片体积膨胀较小；但是，当硅纳米颗粒在活性层中过多时，由于在循环过程中硅纳米颗粒本身并不参与反应，因此过多的硅纳米颗粒反而会影响锂金属的沉积。将硅纳米颗粒在活性层中所占的体积以体积比的方式控制在上述范围内，可以使阳极极片在制成锂离子电池后，具有更低的体积膨胀率和更高的循环圈数。
本申请的一种实施方案中，锂金属在活性层中的含量为0.001至3mg/cm 2，预补锂的含量太小，不能起到提高电池循环性能的作用；预补锂的含量太大，则可能会导致安全性降低。
本申请的一种实施方案中，活性层的厚度为1至100μm。
本申请的一种实施方案中，多孔碳骨架的孔隙率为40％至90％。
本申请的集流体的材料没有特别限制，可以采用本领域技术人员熟知的材料，例如集流体的材料可以包括但不限于：铜、镍、钛、钼、铁、锌、不锈钢及其合金中的至少一种，或者使用导电无机材料，例如，碳或石墨烯。这些材料可以单独使用一种，也可以两种以上组合使用。
本申请提供的阳极极片，在循环过程中，由于纳米硅能够自发地与来自 阴极的锂金属发生合金化反应，因此可以提供锂沉积所需的位点，从而有效地调控锂的沉积位置，使循环过程中锂优先沉积在孔隙中，使锂金属沉积更加均匀，从而减少阳极极片在循环过程中的体积变化，抑制锂枝晶的生长。
本申请还提供了一种阳极极片的制备方法，包括以下步骤：
多孔碳骨架与硅纳米颗粒的复合：
将多孔碳骨架薄片置于CVD设备中，通入含硅烷的气体，进行纳米硅颗粒的沉积得到沉积后的多孔碳骨架薄片。其中，多孔碳骨架薄片可以预先通过葡萄糖溶液经碳化后制得，硅烷气体可以为甲硅烷，或者乙硅烷等。
预补锂：
在保护气体氛围下，将熔融态锂金属与沉积后的多孔碳骨架薄片相接触，使锂金属填充至沉积后的多孔碳骨架薄片的孔隙中，制得活性层。其中，保护气体氛围可以指在氩气中，且水含量低于1ppm，氧含量低于1ppm的氛围。当熔融态锂金属与经沉积处理后的多孔碳骨架薄片相接触时，锂会自发地填充进薄片的孔隙中。
阳极极片的制备：
将活性层放置在集流体上，热压使活性层和集流体相结合，制得阳极极片。制得阳极极片后，可以将阳极极片冲切成40*60mm的尺寸，用于组装叠片电池。
本申请中，通过在多孔碳骨架薄片上沉积硅纳米颗粒，使阳极极片在循环时锂金属沉积更加均匀，减少阳极极片在循环过程中的体积变化，并且，通过预补锂金属，使得采用本申请阳极极片的电池具有更高的循环性能。
本申请的一种实施方案中还提供了一种锂离子电池，包括：阴极极片，阳极极片，隔离膜，以及电解液，其中，隔离膜位于阴极极片和阳极极片之间，上述阳极极片是上述任一实施例所述的阳极极片。
本申请的锂离子电池中，由于阳极极片中的纳米硅能够自发地与来自阴极的锂金属发生合金化反应，因此可以提供锂沉积所需的位点，从而有效地调控锂的沉积位置，使循环过程中锂优先沉积在孔隙中，使锂金属沉积更加均匀，从而减少阳极极片在循环过程中的体积变化，抑制锂枝晶的生长，提高锂离子电池的安全性。
本申请的一种实施方案中还提供了一种电子装置，包括上述实施方案中所述的锂离子电池，该电子装置中，所使用的锂离子电池，锂金属沉积更加均匀，从而减少阳极极片在循环过程中的体积变化，抑制锂枝晶的生长，使得该电子装置具有更高的安全性。
本申请中的阴极极片没有特别限制，可以采用本领域公知的任何阴极极片。例如，含有钴酸锂的阴极极片，含有锰酸锂的阴极极片，含有磷酸铁锂的阴极极片，或含有镍钴锰酸锂或镍钴铝酸锂的阴极极片。
本申请的隔离膜没有特别限制，可以采用本领域公知的任何隔离膜，例如，PE(聚乙烯)隔膜，PP(聚丙烯)隔膜等。
本申请中，所述电解液没有特别限制，可以使用本领域公知的任何电解液，例如，由有机溶剂DOL(二氧戊环)和DME(二甲醚)以及LiFSI(双(氟代磺酰)亚胺锂)和LiNO 3(硝酸锂)制得的电解液；或者，由有机溶剂DMC(碳酸二甲酯)、EMC(碳酸甲乙酯)和LiPF 6制得的电解液等。
以下，举出实施例及比较例来对本申请的实施方式进行更具体地说明。各种的试验及评价按照下述的方法进行。另外，只要无特别说明，“份”、“％”为重量基准。
实施例1
<活性层的制备>
a)多孔硬碳骨架的制备
将葡萄糖粉末放置在模具中，在10吨的压力下压成葡萄糖薄片，然后在氩气气氛的保护下加热到800摄氏度10h，进行碳化，最终得到厚度为50微米的硬碳骨架，即多孔碳骨架薄片，其孔隙率为70％。
b)多孔碳骨架与纳米硅复合
将多孔碳骨架薄片放入CVD(chemical vapor deposition，化学气相沉积)设备中，通入含硅烷的气体，硅烷气体流速为100sccm/min，CVD设备压强为30torr，在500摄氏度下沉积30min，得到经沉积处理后的多孔碳骨架薄片，经沉积处理后的多孔碳骨架薄片中硅纳米颗粒的平均粒径为20nm。
c)预补锂
在干燥的氩气气氛中，将金属锂置于不锈钢坩埚中并加热至300摄氏度， 使固态金属锂熔融成液态，将经沉积处理后的多孔碳骨架薄片与熔融态锂相接触，锂金属自发地填充至经沉积处理后的多孔碳骨架薄片的孔隙中，制得活性层。其中，上述氩气气氛中，水含量低于1ppm，氧含量低于1ppm，活性层中锂负载量为0.5mg/cm 2。
<阳极极片的制备>
在干燥的氩气气氛中，将得到的活性层放置在厚度为15μm镍集流体上，通过热压方法使活性层与镍集流体相结合，其中，控制热压温度为300摄氏度，热压压力为100kg，得到阳极极片，然后将阳极极片冲切成40*60mm的大小待用。
<阴极极片的制备>
将阴极活性材料LiFePO 4(磷酸铁锂)、导电炭黑、PVDF(聚偏二氟乙烯)按照重量比97.5:1.0:1.5进行混合，然后加入NMP(N-甲基吡咯烷酮)作为溶剂，调配成浆料，并搅拌均匀，浆料的固含量为75％，然后，将浆料均匀涂覆在厚度为15μm的铝箔集流体上，90摄氏度条件下烘干，得到阴极极片，其中，铝箔集流体上阴极活性材料的负载量为1mg/cm 2，涂覆完成后，将阴极极片裁切成38mm*58mm的规格待用。
<电解液的制备>
在干燥氩气气氛中，将有机溶剂DOL和DME以体积比DOL:DME＝1:1混合，得到混合溶剂，然后向混合溶剂中加入LiFSI和LiNO 3，溶解并混合均匀后制得电解液。其中，LiFSI在混合溶剂中的添加量为1mol/L，LiNO 3在混合溶剂中的添加量为1wt％。
<锂离子电池的制备>
选用厚度15μm的PE膜(聚乙烯)作为隔离膜，阳极极片的两面分别放置一片阴极极片，阴极极片与阳极极片之间放置一层隔离膜，组成叠片，然后用胶带将整个叠片结构的四个角固定好，置入铝塑膜中，经顶侧封、注电解液、封装后，得到锂金属叠片电池。
实施例2
除了多孔碳骨架薄片在CVD设备中的沉积时间为5min以外，其余与实施例1相同。
实施例3
除了多孔碳骨架薄片在CVD设备中的沉积时间为120min以外，其余与实施例1相同。
实施例4
除了在制备活性层时通过减少预补锂的添加量，使活性层中锂负载量控制为0.2mg/cm 2以外，其余与实施例1相同。
实施例5
除了在制备活性层时通过增加预补锂的添加量，使活性层中锂负载量控制为1mg/cm 2以外，其余与实施例1相同。
实施例6
除了在制备活性层时通过增加预补锂的添加量，使活性层中锂负载量控制为3mg/cm 2以外，其余与实施例1相同。
实施例7
除了阳极极片的集流体材料使用钛以外，其余与实施例1相同。
实施例8
除了阳极极片的集流体材料使用铜以外，其余与实施例1相同。
实施例9
采用与实施例1相同的方法制备锂离子电池，不同之处在于，在对所制得的锂离子电池进行性能测试时的充电倍率为0.2C。
实施例10
采用与实施例1相同的方法制备锂离子电池，不同之处在于，在对所制得的锂离子电池进行性能测试时的充电倍率为0.4C。
实施例11
除了在制备沉积后的多孔碳骨架薄片时，通过降低沉积温度等方式使沉积后的多孔碳骨架薄片中硅纳米颗粒的平均粒径控制为5nm以外，其余与实施例1相同。
实施例12
除了在制备沉积后的多孔碳骨架薄片时，通过提高沉积温度使沉积后的多孔碳骨架薄片中硅纳米颗粒的平均粒径控制为50nm以外，其余与实施例1 相同。
实施例13
除了在制备多孔硬碳骨架时，通过降低碳化温度使多孔硬碳骨架的孔隙率控制为40％以外，其余与实施例1相同。
实施例14
除了在制备多孔硬碳骨架时，通过提高碳化温度等方式使多孔硬碳骨架的孔隙率控制为90％以外，其余与实施例1相同。
实施例15
除了在制备多孔硬碳骨架时，通过减少葡萄糖的用量使多孔碳骨架薄片的厚度降低为20微米外，其余与实施例1相同。
实施例16
除了在制备多孔硬碳骨架时，通过增加葡萄糖的用量使多孔碳骨架薄片的厚度提高到75微米外，其余与实施例1相同。
实施例17
除了在制备多孔硬碳骨架时，通过增加葡萄糖的用量使多孔碳骨架薄片的厚度提高到100微米外，其余与实施例1相同。
对比例1
<制备覆锂铜箔阳极极片>
将市售覆锂铜箔冲切成40*60mm的大小，用于组装叠片电池。其中，覆锂铜箔的厚度为30μm。
对比例2
<制备含有多孔碳骨架、预补锂、不含硅纳米颗粒的阳极极片>
a)多孔碳骨架的制备
使用与实施例1相同的方法制备多孔碳骨架。
b)预补锂
在干燥的氩气气氛中，将金属锂置于不锈钢坩埚中并加热至300摄氏度，使固态金属锂熔融成液态，将经沉积处理后的多孔碳骨架薄片与熔融态锂相接触。
然后使用与实施例1的相同的阳极极片制备方法制备阳极极片。
对比例3
<制备不含碳骨架但含硅颗粒(非CVD法)的阳极极片>
在干燥的氩气气氛中，将平均粒径为80nm的硅粉颗粒与锂金属以1:10的体积比混合，然后，通过热压的方法使硅粉颗粒与锂金属相结合，控制热压温度为150摄氏度，压力为100kg，得到阳极极片，该阳极极片的平均厚度为30μm，然后将阳极极片冲切成40*60mm的大小，用于组装叠片电池。
对比例4
<制备含多孔碳骨架、含硅颗粒(CVD法)但不预补锂的阳极极片>
多孔碳骨架的制备过程与实施例1相同。
多孔碳骨架与纳米硅复合过程与实施例1相同，得到经沉积处理后的多孔碳骨架薄片，该多孔碳骨架薄片不进行预补锂处理，直接使用实施例1的阳极极片制备方法，得到阳极极片。
对比例5
<制备仅含硅颗粒(非CVD法)的阳极极片>
将硅纳米颗粒与聚丙烯酸和导电碳以质量比80：10：10的比例在水中混合并搅拌均匀，得到混合液，然后将混合液涂布在镍集流体上在180摄氏度条件下烘干，得到阳极极片。其中硅在阳极极片中的负载量为1.1mg/cm 2，然后将阳极极片冲切成40*60mm的大小，用于组装叠片电池。
对比例6
<制备仅含多孔碳骨架的阳极极片>
使用实施例1的方法制备多孔硬碳骨架，将该多孔硬碳骨架作为阳极极片。
对比例7
<制备仅含集流体的阳极极片>
将镍集流体直接作为阳极极片。
对比例8
<制备仅含集流体和预补锂的阳极极片>
在干燥的氩气气氛中，将金属锂置于不锈钢坩埚中并加热至300摄氏度，使固态金属锂熔融成液态，将镍集流体与熔融态锂相接触，少量锂附着于镍 集流体表面。
对比例9
<制备仅含集流体和预补锂的阳极极片>
采用与对比例8相同的方法制备阳极极片，与对比例8不同处在于，使用0.4C的充电倍率对由该阳极极片制得的锂离子电池进行充电。
在实施例2至14及对比例1至9制得阳极极片后，使用与实施例1制备锂离子电池相同的方法制备锂离子电池。
<性能测试>
使用下述方法对实施例1至8，实施例11至14，以及对比例1至8制得的锂离子电池进行测试：
将各实施例制得的锂离子电池在60摄氏度条件下，以0.1C的充电和放电倍率化成一圈，然后在常温进行充放电循环，其中恒流充电阶段的电流为1C，截止电压为3.8V，恒压充电阶段的截止电流为0.05C，恒流放电的倍率为1C，截止电压为2.7V。
使用0.2C的充电倍率对实施例9制得的锂离子电池进行充电；
使用0.2C的充电倍率对实施例10制得的锂离子电池进行充电；
使用0.4C的充电倍率对对比例9制得的锂离子电池进行充电。
使用如下方法对各实施例和对比例的体积膨胀率进行测试和计算：
将各实施例和对比例的阴极极片和阳极极片分别裁切成10mm×5mm的大小，放入离子研磨抛光机中对各极片的横截面进行抛光，然后将所得极片转移到扫描电子显微镜(SEM)中，在合适的放大倍率下观测抛光后极片的横截面，并测量相应的厚度。然后将阴极极片、阳极极片和隔膜的厚度分别相加，得到电芯的厚度，该电芯的厚度不考虑封装。采用上述方法分别测量0％电荷状态和100％电荷状态的电芯厚度，分别记为t(0％)和t(100％)，并根据如下公式计算体积膨胀率：体积膨胀率＝(t(100％)-t(0％))/t(0％)。
实施例1至14和对比例1至9的测试参数以及相应的实验结果如下表1所示：
表1各实施例及对比例的测试参数以及相应的实验结果
Figure PCTCN2020078856-appb-000001
如表1所示，虽然实施例1至3中硅纳米颗粒沉积量不同，但与对比例1-3、5、及7-9相比，其体积膨胀率明显降低；与对比例1至9相比，其循环圈数明显升高。
虽然实施例4至6中预补锂的添加量不同，但与对比例1至9相比，其循环圈数明显升高，尤其是实施例5，其体积膨胀率显著降低，循环圈数显著提高。
虽然实施例7和8使用的集流体材料不同，但与对比例1至9相比，其体积膨胀率明显降低，循环圈数明显提高。
实施例9和10在对所制得的锂离子电池进行性能测试时采用不同的充电 倍率，但与对比例1至9相比，其体积膨胀率明也显降低，循环圈数也明显提高。
虽然实施例11和12的硅纳米颗粒的平均粒径不同，但与对比例1至9相比，其体积膨胀率明显降低，循环圈数明显提高。
虽然实施例13和14中，多孔硬碳骨架的孔隙率不同，但与对比例1至9相比，其体积膨胀率明显降低，循环圈数明显提高。
实施例15至17中，当多孔碳薄片厚度相对于阴极活性材料负载量而言较低时(如实施例15)，极片内部孔隙不足以承载所有的预补锂和沉积锂，此时会出现部分锂沉积在了极片表面，导致体积变化增大，同时循坏恶化。当厚度提高至75微米和100微米时，由于本身厚度增加，在牺牲能量密度的前提下，会略微改善体积膨胀；另一方面，由于比表面积增加，循环会有所减少。因此，应该从能量密度、体积膨胀和循环圈数角度，结合阴极负载量，综合考虑，适配最佳的厚度。
在对比例1中，仅使用覆锂铜箔阳极极片制备的电池，与实施例1至17制备的电池相比，体积膨胀率明显升高，循环圈明明显下降。
在对比例2中，当阳极极片中不含硅纳米颗粒时，与实施例1至17制备的电池相比，体积膨胀率明显升高，循环圈数明显下降。
在对比例3中，当阳极极片中虽含有硅颗粒，但不含碳骨架时，与实施例1至17制备的电池相比，体积膨胀率明显升高，循环圈数明显下降。
在对比例4中，当阳极极片中虽含有硅颗粒，但不是由SVD法制备的硅纳米颗粒，且不含预补锂时，与实施例1至17制备的电池相比，体积膨胀率变化不大，但循环圈数明显下降。
在对比例5中，当阳极极片中仅含硅颗粒(非CVD法)，而不含碳骨架和预补锂时，与实施例1至17制备的电池相比，体积膨胀率明显升高，但循环圈数明显下降。
在对比例6中，当阳极极片中仅含多孔碳骨架时，而不含预补锂时，与实施例1至17制备的电池相比，体积膨胀率变化不大，循环圈数明显下降。
在对比例7中，当阳极极片中仅含集流体时，而不含碳骨架和预补锂时，与实施例1至17制备的电池相比，体积膨胀率明显升高，循环圈数明显下降。
在对比例8中，当阳极极片中仅含集流体和预补锂时，与实施例1至17制备的电池相比，体积膨胀率明显升高，循环圈数明显下降。
在对比例9中，当阳极极片中仅含集流体和预补锂，并使用0.4C的充电倍率充电时，与实施例1至17制备的电池相比，体积膨胀率明显升高，循环圈数明显下降。
以上所述仅为本申请的较佳实施例，并不用以限制本申请，凡在本申请的精神和原则之内，所做的任何修改、等同替换、改进等，均应包含在本申请保护的范围之内。

Claims (10)

  1. 一种阳极极片，其包括集流体和活性层，所述活性层包括多孔碳骨架和位于所述多孔碳骨架中的硅纳米颗粒和锂金属。
  2. 根据权利要求1所述的阳极极片，所述多孔碳骨架和硅纳米颗粒的体积之和，占所述活性层总体积的10％至60％。
  3. 根据权利要求1或2所述的阳极极片，所述多孔碳骨架与所述硅纳米颗粒的总体积比为5：1至100：1。
  4. 根据权利要求1所述的阳极极片，所述锂金属在所述活性层中的含量为0.001至3mg/cm 2。
  5. 根据权利要求1所述的阳极极片，所述活性层的厚度为1至100μm。
  6. 根据权利要求1所述的阳极极片，所述多孔碳骨架的强度不低于200GPa。
  7. 根据权利要求1所述的阳极极片，所述多孔碳骨架的孔隙率为40％至90％。
  8. 根据权利要求1所述的阳极极片，所述集流体的材料包括铜、镍、钛、钼、铁、锌、不锈钢、碳或石墨烯中的至少一种。
  9. 一种锂离子电池，包括：阴极极片；
    阳极极片；
    隔离膜，所述隔离膜位于所述阴极极片和所述阳极极片之间；以及
    电解液；
    其中，所述阳极极片为权利要求1至8任一项所述的阳极极片。
  10. 一种电子装置，所述电子装置包括权利要求9所述的锂离子电池。
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