WO2023184133A1 - 负极极片、用于电化学装置中的负极极片、电化学装置及电子设备 - Google Patents

负极极片、用于电化学装置中的负极极片、电化学装置及电子设备 Download PDF

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WO2023184133A1
WO2023184133A1 PCT/CN2022/083578 CN2022083578W WO2023184133A1 WO 2023184133 A1 WO2023184133 A1 WO 2023184133A1 CN 2022083578 W CN2022083578 W CN 2022083578W WO 2023184133 A1 WO2023184133 A1 WO 2023184133A1
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negative electrode
silicon oxide
active material
material layer
oxide particles
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PCT/CN2022/083578
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English (en)
French (fr)
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任文臣
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宁德新能源科技有限公司
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Priority to CN202280014228.9A priority Critical patent/CN116918099A/zh
Priority to PCT/CN2022/083578 priority patent/WO2023184133A1/zh
Publication of WO2023184133A1 publication Critical patent/WO2023184133A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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 belongs to the technical field of electrochemistry, and specifically relates to a negative electrode piece, a negative electrode piece used in an electrochemical device, an electrochemical device and an electronic device.
  • Lithium-ion batteries are widely used in all aspects of today's life due to their advantages such as no memory effect, long cycle life, and environmental protection.
  • lithium-ion batteries have developed rapidly in the fields of new energy vehicles and large-scale energy storage.
  • carbon-based materials such as graphite have lower capacities, so the first-time efficiency of lithium-ion batteries is low.
  • Silicon-based materials are prone to expansion, resulting in poor cycle performance of lithium-ion batteries, which greatly limits their large-scale application in lithium-ion batteries.
  • the purpose of this application is to provide a negative electrode plate, a negative electrode plate used in an electrochemical device, an electrochemical device and an electronic device, aiming to improve the first Coulombic efficiency and cycle stability of the electrochemical device.
  • a first aspect of the present application provides a negative electrode sheet, including: a negative electrode current collector, and an active material layer disposed on at least one side of the negative electrode current collector.
  • the active material layer includes a negative electrode active material layer, and the negative electrode active material
  • the layer includes first silicon oxide particles, and a lithium metal layer is provided on a side of the negative active material layer away from the negative electrode current collector, wherein the first silicon oxide particles include silicon oxide doped with carbon element.
  • the mass percentage of the carbon element is 0.5% ⁇ ⁇ c1 ⁇ 7%.
  • the molar ratio of carbon atoms to silicon atoms in the first silicon oxide particles is 0.01:1 to 0.4:1, preferably 0.05:1 to 0.35:1.
  • the volume average particle size of the first silicon oxide particles is 3 ⁇ m ⁇ Dv50 ⁇ 20 ⁇ m, preferably 5 ⁇ m ⁇ Dv50 ⁇ 18 ⁇ m.
  • the thickness of the negative active material layer is 10 ⁇ m to 90 ⁇ m, preferably 15 ⁇ m to 85 ⁇ m.
  • the porosity of the negative active material layer is 21% to 28%, preferably 22% to 26%.
  • the mass percentage of the first silicon oxide particles is 0.2% to 60%, preferably 0.5% to 55%.
  • the negative active material layer further includes at least one of artificial graphite, natural graphite, mesocarbon microspheres, soft carbon, hard carbon, graphene, and carbon nanotubes.
  • the areal density of the lithium metal layer is 0.17 mg/cm 2 to 1.34 mg/cm 2 , preferably 0.20 mg/cm 2 to 1.30 mg/cm 2 .
  • the mass ratio of the first silicon oxide particles in the lithium metal layer and the negative active material layer is 0.10:1 to 0.19:1, preferably 0.12:1 to 0.17: 1.
  • the mass percentage content of the carbon element is 2% ⁇ ⁇ c1 ⁇ 7%.
  • the mass percentage of the carbon element is 2% ⁇ ⁇ c1 ⁇ 7%.
  • a second aspect of the present application provides a negative electrode sheet used in an electrochemical device, including: a negative electrode current collector, and an active material layer disposed on at least one side of the negative electrode current collector.
  • the active material layer includes nano silicon Second silicon oxide particles of crystal grains, wherein the particle size of the nano silicon crystal grains is d ⁇ 5nm.
  • the particle size of the nano silicon crystal particles is 1.4nm ⁇ d ⁇ 5nm.
  • the particle size of the nano silicon crystal particles is 1.4nm ⁇ d ⁇ 4.8nm.
  • the mass percentage of carbon element in the second silicon oxide particles is 2% ⁇ ⁇ c2 ⁇ 7%.
  • the particle size d of the nano-silicon crystal grains and the mass percentage content of carbon element ⁇ c2 in the second silicon oxide particles satisfy: 6.38 ⁇ d + 72 ⁇ c ⁇ 6.52.
  • a third aspect of this application provides an electrochemical device, including the negative electrode piece described in the first aspect of this application or the negative electrode piece described in the second aspect of this application.
  • a fourth aspect of the present application provides an electronic device, including the electrochemical device described in the third aspect of the present application.
  • Figure 1 is a TEM image of an embodiment of the second silicon oxide particles of the present application.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range.
  • each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • a list of items connected by the terms “at least one of,” “at least one of,” “at least one of,” or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase “at least one of A and B” means only A; only B; or A and B. In another example, if the items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B and C.
  • Item A may contain a single component or multiple components.
  • Item B may contain a single component or multiple components.
  • Item C may contain a single component or multiple components.
  • the inventor found that among the existing silicon-based anode materials (Si, SiO) for lithium-ion batteries, the carbon-doped silicon oxide (SiCO) material has Si-C bonds and O-C bonds inside. , thus weakening the number of Si-Si bonds formed after Si-O bonds are broken, and thus avoiding excessive stress in the Si-rich region causing particle expansion and rupture, thus significantly improving the cycle and expansion problems of silicon-based negative electrodes.
  • Si, SiO silicon-based anode materials
  • SiCO carbon-doped silicon oxide
  • the inventors have proposed a negative electrode piece that can fully suppress volume expansion and have high first efficiency and high cycle stability through extensive research.
  • a first aspect of the embodiment of the present application provides a negative electrode sheet, including: a negative electrode current collector, and an active material layer provided on at least one side of the negative electrode current collector, where the active material layer includes a negative electrode active material layer, so The negative active material layer includes first silicon oxide particles, and a lithium metal layer is provided on a side of the negative active material layer away from the negative electrode current collector, wherein the first silicon oxide particles include doped carbon elements.
  • the mass percentage content of the carbon element is 0.5% ⁇ ⁇ c1 ⁇ 7%.
  • the negative electrode sheet in this application includes a negative active material layer, the negative active material layer includes first silicon oxide particles, the first silicon oxide particles include a silicon oxide matrix doped with carbon element, and, A lithium metal layer is provided on the side of the negative active material layer away from the negative current collector. Since the silicon oxide matrix is uniformly doped with carbon element, the carbon element will form Si-C bonds and O-C bonds inside the first silicon oxide particles.
  • the carbon element in the silicon oxide matrix can reduce the number of Si-Si bonds formed after the Si-O bonds in the first silicon oxide particles are broken, thereby avoiding particle expansion and cracking caused by excessive stress in the Si-rich region, thus Improve the expansion and cycle performance of the negative electrode piece; since the lithium metal layer participates in the formation of the solid electrolyte film of the negative active material during the first charging process, it can reduce the consumption of lithium in the positive electrode material caused by side reactions during the first charging. This in turn can increase the capacity and first Coulomb efficiency of the battery.
  • the mass percentage of carbon element in the first silicon oxide particles is within an appropriate range, which is conducive to reducing the particle size of the nano-silicon grains formed after the reaction with metallic lithium, thereby reducing the negative electrode plate
  • the volume expansion during lithium insertion is beneficial to improving the battery's capacity retention rate.
  • the mass percentage of carbon element in the silicon oxide matrix has a meaning known in the art, and can be measured using instruments and methods known in the art.
  • the first silicon oxide particles are sprinkled on the copper foil of the conductive adhesive, cut into cross-sections, polished with a plasma polisher (Leica EM TIC 3X-Ion Beam Slope Cutter), and then placed in a scanning electron microscope (SEM) to search for The cut negative active material particles are cut along the vertical direction of the cross-section using a focused ion beam (FIB). After obtaining a thin section containing the cross section of the negative active material particles, a transmission electron microscope (TEM) and energy A spectrometer (EDS) measures the proportion of carbon elements in selected areas containing carbon, oxygen and silicon.
  • TEM transmission electron microscope
  • EDS energy A spectrometer
  • the first silicon oxide particles include a silicon oxide matrix doped with carbon element, and in the silicon oxide matrix, the mass percentage of the carbon element is 2% ⁇ ⁇ c1 ⁇ 7%.
  • the mass concentration of carbon element in the silica matrix refers to a powder composed of multiple silica matrix. The powder is randomly sampled, and the carbon element contained therein is relative to the total amount of the sample. The mass percentage of mass.
  • the mass concentration of carbon element in the silicon oxide matrix can be measured using the following method: add 0.8g of tungsten-tin-iron three-in-one flux at the bottom of the crucible so that it evenly covers the bottom of the crucible. Then add 0.5g of the first silicon oxide powder, and finally cover the sample surface evenly with 0.8g of tungsten-tin-iron three-in-one flux. Clamp the crucible and place it on the quartz crucible holder. Use a high-frequency infrared carbon and sulfur analyzer to test.
  • the pre-oxygen blowing time is 20s
  • the top oxygen blowing time is 50s
  • the oxygen blowing flow is 1.8L/min
  • the carbon cut-off voltage is 1.8L/min.
  • the level is 10%
  • the analysis time is 20s to 50s
  • the analysis oxygen flow is 2.0L/min.
  • the mass percentage of carbon element in the silicon oxide matrix is within an appropriate range, which is beneficial to reducing the particle size of nano silicon crystal grains formed after the reaction with metallic lithium, thereby Reduce the volume expansion of the negative electrode piece when lithium is embedded, thereby improving the capacity retention rate of the battery.
  • the molar ratio of carbon atoms to silicon atoms in the first silicon oxide particles is 0.01:1 to 0.4:1, for example, the molar ratio of carbon atoms to silicon atoms in the first silicon oxide particles The ratio is 0.05:1, 0.15:1, 0.20:1, 0.25:1, 0.30:1, 0.35:1 or within the range of any of the above values.
  • the molar ratio of carbon atoms to silicon atoms in the first silicon oxide particles is 0.05:1 to 0.35:1.
  • the molar ratio of carbon atoms to silicon atoms in the first silicon oxide particles is within an appropriate range, which is conducive to the formation of a sufficient number of Si-C bonds and O-C bonds in the first silicon oxide particles, thereby reducing Si
  • the number of Si-Si bonds formed after the -O bond is broken can avoid particle expansion and cracking caused by excessive stress in the Si-rich area, thereby improving the expansion and cycle performance of the negative electrode piece.
  • the molar ratio of carbon atoms to silicon atoms is within the above range, which is also beneficial to controlling the mass percentage of carbon element in the first silicon oxide particles between 2% and 7%.
  • the volume average particle diameter of the first silicon oxide particles is 3 ⁇ m ⁇ Dv50 ⁇ 20 ⁇ m.
  • the volume average particle diameter Dv50 of the first silicon oxide particles is 5 ⁇ m, 8 ⁇ m, 11 ⁇ m, 14 ⁇ m. , 17 ⁇ m, 20 ⁇ m or within the range of any of the above values.
  • the volume average particle size of the first silicon oxide particles is 5 ⁇ m ⁇ Dv50 ⁇ 18 ⁇ m.
  • the volume average particle diameters Dv50 and Dv10 of the first silicon oxide particles have meanings known in the art and can be measured using instruments and methods known in the art.
  • the volume average particle size of the first silicon oxide particles is within a suitable range, which can not only improve its diffusion efficiency in the electrolyte, but also reduce the contact area between the negative active material layer and the electrolyte, thus providing It is beneficial to improve the cycle performance of the negative electrode piece.
  • the thickness of the negative active material layer is 10 ⁇ m to 90 ⁇ m, for example, the thickness of the negative active material layer is 20 ⁇ m to 80 ⁇ m, 25 ⁇ m to 75 ⁇ m, 30 ⁇ m to 70 ⁇ m, 35 ⁇ m to 65 ⁇ m, 40 ⁇ m to 60 ⁇ m or 45 ⁇ m to 55 ⁇ m.
  • the thickness of the negative active material layer is 15 ⁇ m to 85 ⁇ m.
  • the thickness of the negative active material layer has a meaning known in the art, and can be measured using methods known in the art, such as using a multimeter (for example, Mitutoyo 293-100 type, with an accuracy of 0.1 ⁇ m).
  • the negative active material layer has a porosity of 21% to 28%, for example, the negative active material layer has a porosity of 22%, 24%, 26%, 28% or any value above. within the composed range.
  • the extremely active material layer has a porosity of 22% to 26%.
  • the porosity of the negative active material layer is within a suitable range, which is beneficial to improving the transmission efficiency of ions (such as lithium ions), thereby improving the cycle performance of the negative electrode piece.
  • the porosity of the negative active material layer has a meaning known in the art and can be tested using methods known in the art. For example, cut the reacted negative electrode into discs with a diameter of 10 mm, and use the gas replacement method to test the porosity of the negative active material layer.
  • the mass percentage of the first silicon oxide particles is 0.2% to 60% based on the total mass of the negative active material layer.
  • the mass percentage of the first silicon oxide particles is 0.2% to 60%.
  • the content is 1% to 55%, 5% to 50%, 10% to 45%, 15% to 40%, 20% to 35% or 25% to 30%.
  • the mass percentage of the first silicon oxide particles is 0.5% to 55%.
  • the mass percentage content of the first silicon oxide particles in the negative active material layer is within the above range, which is beneficial to promoting the synergistic effect between the first silicon oxide particles and graphite, so that the first silicon oxide particles have high capacity and low
  • the expansion and high first-efficiency performance can be more fully utilized, and it can also promote the highly conductive graphite to play a better role in the negative electrode active material layer, thereby enabling the negative electrode plate to have higher capacity, first-efficiency and rate performance.
  • the areal density of the lithium metal layer is 0.17 mg/cm 2 to 1.34 mg/cm 2 , for example, the areal density of the lithium metal layer is 0.20 mg/cm 2 to 1.30 mg/cm 2 , 0.30mg/cm 2 to 1.20mg/cm 2 , 0.40mg/cm 2 to 1.10mg/cm 2 , 0.50mg/cm 2 to 1.00mg/cm 2 , 0.60mg/cm 2 to 0.90mg/cm 2 or 0.70mg /cm 2 to 0.80mg/cm 2 .
  • the areal density of the lithium metal layer is 0.20 mg/cm 2 to 1.30 mg/cm 2 .
  • the area density of the lithium metal layer is within a suitable range, which can provide enough lithium for side reactions such as the formation of the solid electrolyte membrane during the first charging process, thereby reducing the irreversible consumption of lithium in the cathode material and improving the first Coulombic efficiency of the battery.
  • the mass ratio of the lithium metal layer to the negative active material layer is 0.10:1 to 0.19:1.
  • the mass ratio is 0.12:1, 0.14:1, 0.16: 1, 0.18:1 or within the range of any of the above values.
  • the mass ratio is 0.12:1 to 0.17:1.
  • the mass ratio of the lithium metal layer and the first silicon oxide particles is within the above range, which is beneficial to the first charging, so that the first silicon oxide particles can completely react with the lithium metal layer to generate lithium silicate and the solid electrolyte membrane, thereby avoiding consumption
  • the lithium in the cathode material can reduce the irreversible consumption of lithium in the cathode, thereby increasing the battery capacity and first Coulombic efficiency.
  • the lithium insertion reaction has already occurred in the particles, which is equivalent to the pre-expansion of the silicon oxide particles before the cycle of charge and discharge, which can reduce the negative electrode plate's full capacity.
  • the expansion rate during charging improves the cyclic expansion performance of the battery.
  • the material of the lithium metal layer is not particularly limited and can be selected according to actual needs, as long as it can provide lithium compensation for the first charge of the negative electrode plate.
  • the lithium metal layer may be a lithium metal material such as lithium foil, lithium powder or lithium wire.
  • a second aspect of the embodiment of the present application provides a negative electrode sheet used in an electrochemical device, including: a negative electrode current collector, and an active material layer provided on at least one side of the negative electrode current collector, the active material layer It includes second silicon oxide particles containing nano-silicon crystal grains, wherein the particle size of the nano-silicon crystal grains is d ⁇ 5nm.
  • the particle size of the nano silicon crystal particles is 1.4nm ⁇ d ⁇ 4.8nm.
  • the particle diameter of the nano silicon crystal grains is 1.5nm ⁇ d ⁇ 4.8nm, 2.0nm ⁇ d ⁇ 4.8nm, 2.5nm ⁇ d ⁇ 4.8nm, 3.0nm ⁇ d ⁇ 4.8nm, 3.5nm ⁇ d ⁇ 4.8 nm, 4.0nm ⁇ d ⁇ 4.8nm, 4.5nm ⁇ d ⁇ 4.8nm, 1.5nm ⁇ d ⁇ 4.5nm, 2.0nm ⁇ d ⁇ 4.5nm, 2.5nm ⁇ d ⁇ 4.5nm, 3.0nm ⁇ d ⁇ 4.5nm, 3.5nm ⁇ d ⁇ 4.5nm, 4.0nm ⁇ d ⁇ 4.5nm, 1.5nm ⁇ d ⁇ 4.0nm, 2.0nm ⁇ d ⁇ 4.0nm, 2.5nm ⁇ d ⁇ 4.0nm, 3.0nm ⁇ d ⁇ 4.0nm, 3.5nm ⁇ d ⁇ 4.0nm, 1.5nm ⁇ d ⁇ 3.5nm, 2.0nm ⁇ d ⁇ 3.5nm, 2.5nm ⁇ d ⁇ d ⁇ 4.0n
  • the second silicon oxide particles in this application are formed by the first silicon oxide particles described in the first aspect of this application and the lithium metal layer during the first charging reaction.
  • the inventor found through research that after the first charging reaction, as shown in Figure 1, nano-silicon grains will be produced in the second silicon oxide particles, and by controlling the particle size of the nano-silicon grains within the above range, subsequent results can be improved.
  • the volume expansion of the second silicon oxide particles during the cycle process improves the capacity retention rate and cycle stability of the battery.
  • the particle size of nano-silicon grains exceeds 5nm, during the cycle process, the larger size nano-silicon grains can easily cause the second silicon oxide particles to expand and break during the lithium intercalation process, thus affecting the battery cycle performance. .
  • the particle size of nano-silicon crystal particles has a meaning known in the art, and can be measured using methods known in the art. For example, gently scrape off the reacted negative electrode plate coating powder, plate the surface with Cr, select the second silicon oxide particles to be tested in a scanning electron microscope (SEM), and then use a focused ion beam (FIB) to The second silica particles are thinned, and finally the thinned sample is welded to a transmission electron microscope (TEM) sample holder.
  • SEM scanning electron microscope
  • FIB focused ion beam
  • the sample holder containing the second silicon oxide flake into the TEM sample introduction chamber for testing, measure the size of the lattice stripe area with a lattice spacing of 0.313nm to 0.329nm in the TEM test image, and place the lattice stripe area
  • the two points with the longest distance in the contour are determined as the particle size of the nano-silicon grains in the second silicon oxide particles.
  • the mass percentage of carbon element in the second silicon oxide particles is 2% ⁇ ⁇ c2 ⁇ 7%.
  • the mass percentage of the carbon element is 2.5% ⁇ c2 ⁇ 7%, 3% ⁇ c2 ⁇ 7%, 3.5% ⁇ c2 ⁇ 7%, 4% ⁇ c2 ⁇ 7%, 4.5% ⁇ c2 ⁇ 7%, 5% ⁇ ⁇ c2 ⁇ 7%, 5.5% ⁇ ⁇ c2 ⁇ 7%, 6% ⁇ ⁇ c2 ⁇ 7%, 6.5% ⁇ ⁇ c2 ⁇ 7%, 2.5% ⁇ ⁇ c2 ⁇ 6.5 %,3% ⁇ c2 ⁇ 6.5%,3.5% ⁇ c2 ⁇ 6.5%,4% ⁇ c2 ⁇ 6.5%,4.5% ⁇ c2 ⁇ 6.5%,5% ⁇ c2 ⁇ 6.5%,5.5% ⁇ ⁇ c2 ⁇ 6.5%, 6% ⁇ ⁇ c2 ⁇ 6.5%, 2.5% ⁇ ⁇ c2 ⁇ 6%,
  • the inventor further studied and found that during the first charging reaction between the first silicon oxide particles and the lithium metal layer to form the second silicon oxide particles, the mass percentage content of the carbon element will basically not change (that is, the carbon element will not change in the first charging reaction).
  • the mass percentage of the silicon monoxide particles is basically the same as the mass percentage of the second silicon oxide particles
  • the particle size of the nano-silicon crystal particles is related to the mass of the carbon element in the second silicon oxide particles.
  • the percentage content (or, in other words, the mass percentage of carbon element in the first silicon oxide particles) is related.
  • the inventor found that when the mass percentage of carbon in the first silicon oxide particles exceeds the above range, the second oxide formed during the first charging reaction with the lithium metal layer The particle size of the nano-silicon grains in the silicone particles will exceed 5nm; and when the mass percentage of carbon element in the first silicone oxide particles is controlled within the above range, the second silicone oxide particles formed will The carbon element and silicon element form a considerable number of Si-C bonds. These Si-C bonds can inhibit the growth of nano-silicon grains during the first charging reaction, thereby reducing the size of nano-silicon grains and controlling them. Within 5nm.
  • the particle size of the nano-silicon grains in the second silicon oxide particles exceeds 5 nm, the larger size nano-silicon grains may easily cause the second silicon oxide particles to expand and break during the lithium intercalation process. This in turn causes battery cycle performance to be affected.
  • the particle size of nano-silicon grains is controlled within 5 nm, the volume expansion problem of the second silicon oxide particles during subsequent cycles can be improved, thereby improving the capacity retention rate and cycle stability of the battery.
  • the particle diameter d of the nano silicon crystal particles and the mass percentage content of carbon element ⁇ c2 in the second silicon oxide particles satisfy: 6.38 ⁇ d+72 ⁇ c ⁇ 6.52.
  • the particle diameter d of the nano silicon crystal particles and the mass percentage content of carbon element ⁇ c2 in the second silicon oxide particles satisfy: 6.35 ⁇ d+72 ⁇ c ⁇ 6.52, 6.30 ⁇ d+72 ⁇ c ⁇ 6.52 ,6.25 ⁇ d+72 ⁇ c ⁇ 6.52,6.20 ⁇ d+72 ⁇ c ⁇ 6.52,6.15 ⁇ d+72 ⁇ c ⁇ 6.52,6.10 ⁇ d+72 ⁇ c ⁇ 6.52,6.05 ⁇ d+72 ⁇ c ⁇ 6.52,6.35 ⁇ d+ 72 ⁇ c ⁇ 6.50,6.30 ⁇ d+72 ⁇ c ⁇ 6.50,6.25 ⁇ d+72 ⁇ c ⁇ 6.50,6.20 ⁇ d+72 ⁇ c ⁇ 6.50,6.15 ⁇ d+72 ⁇ c ⁇ 6.50,6.10 ⁇ d+72 ⁇ c ⁇ 6.5
  • the inventor also found through research that when the particle size d of the nano-silicon crystal grains and the mass percentage of carbon element ⁇ c2 in the second silicon oxide particles satisfy the above relationship, by comparing the mass percentage of carbon in the above relationship Reasonable control of the content can keep the particle size of nano-silicon grains within a suitable range (d ⁇ 5nm), thereby reducing the volume expansion of the second silicon oxide particles during the cyclic lithium insertion process and improving the cycle stability of the battery.
  • other negative active materials other than the first silicon oxide particles and the graphite composition are not excluded from the active material layer.
  • the specific types of other negative active materials are not subject to specific restrictions and can be selected according to needs.
  • other negative active materials include, but are not limited to, natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO, Li-Sn alloy, Li-Sn -O alloy, Sn, SnO, SnO 2 , spinel structure Li 4 Ti 5 O 12 , and Li-Al alloy.
  • the active material layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the active material layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the active material layer optionally also includes other auxiliaries, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • auxiliaries such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • the present application is not limited to the above materials.
  • the negative electrode sheet of the present application can also use other well-known materials that can be used as negative active materials, conductive agents, binders and thickeners.
  • the negative electrode current collector has two surfaces opposite in its thickness direction, and the active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • a metal foil or porous metal plate can be used as the negative electrode current collector.
  • the negative electrode current collector is copper foil.
  • the negative electrode piece in this application can be prepared according to conventional methods in this field.
  • the first silicon oxide particles, optional other negative active materials, conductive agents, binders and thickeners contained in the negative electrode sheet described in the first aspect of the present application are dispersed in a solvent.
  • the solvent can be N-methylpyrrolidone (NMP) or deionized water to form a uniform negative electrode slurry.
  • NMP N-methylpyrrolidone
  • the negative electrode slurry is coated on the negative electrode current collector. After drying and cold pressing, the active material layer is obtained, and then the lithium metal is laminated. On the surface of the active material layer, a negative electrode piece is obtained.
  • the negative electrode sheet in this application does not exclude other additional functional layers in addition to the negative active material layer.
  • the negative electrode sheet of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the active material layer and disposed on the surface of the negative electrode current collector. ).
  • a third aspect of the embodiment of the present application provides an electrochemical device, including any device in which an electrochemical reaction occurs to convert chemical energy and electrical energy into each other, and specific examples thereof include all kinds of lithium primary batteries or lithium secondary batteries.
  • the lithium secondary battery includes a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery or a lithium ion polymer secondary battery.
  • the electrochemical device of the present application includes a positive electrode piece, a negative electrode piece, a separator and an electrolyte.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the electrochemical device of the present application also includes an outer package for packaging the electrode assembly and the electrolyte.
  • the outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc., or a soft bag, such as a bag-type soft bag.
  • the soft bag may be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PBS polybutylene succinate
  • the negative electrode sheet used in the electrochemical device of the present application is the negative electrode sheet of the first aspect of the embodiment of the present application or the negative electrode sheet used in the electrochemical device of the second aspect of the embodiment of the present application.
  • the material, composition and manufacturing method of the positive electrode piece used in the electrochemical device of the present application may include any technology known in the prior art.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive active material layer includes a positive active material.
  • the specific type of the positive active material is not specifically limited and can be selected according to requirements.
  • the cathode active material may include one or more of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds.
  • the above-mentioned modified compounds of each positive electrode active material may be doping modification, surface coating modification, or doping and surface coating modification of the positive electrode active material.
  • lithium transition metal oxides may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • the olivine-structured lithium-containing phosphate may include lithium iron phosphate, a composite material of lithium iron phosphate and carbon, a lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, a lithium manganese iron phosphate, a lithium manganese iron phosphate and carbon material.
  • the composite materials and their modified compounds One or more of the composite materials and their modified compounds. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • the positive active material layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive active material layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil can be used as the positive electrode current collector.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer may be selected from polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.
  • the positive electrode piece in this application can be prepared according to conventional methods in this field.
  • the positive electrode active material layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying, and cold pressing.
  • the cathode slurry is usually formed by dispersing the cathode active material, optional conductive agent, optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the positive electrode sheet of the present application does not exclude other additional functional layers in addition to the positive active material layer.
  • the positive electrode sheet of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the positive electrode current collector and the positive electrode active material layer and disposed on the surface of the positive electrode current collector. ).
  • the positive electrode sheet of the present application further includes a protective layer covering the surface of the positive electrode active material layer.
  • the electrolyte plays a role in conducting active ions between the positive electrode piece and the negative electrode piece.
  • the electrolyte solution that can be used in the electrochemical device of the present application can be an electrolyte solution known in the art.
  • the electrolyte solution includes an organic solvent, a lithium salt and optional additives.
  • organic solvent a lithium salt and optional additives.
  • the types of the organic solvent, lithium salt and additives are not specifically limited and can be selected according to needs.
  • the lithium salts include, but are not limited to, LiPF 6 (lithium hexafluorophosphate), LiBF 4 (lithium tetrafluoroborate), LiClO 4 (lithium perchlorate), LiFSI (lithium bisfluorosulfonimide) ), LiTFSI (lithium bistrifluoromethanesulfonimide), LiTFS (lithium trifluoromethanesulfonate), LiDFOB (lithium difluoromethanesulfonate), LiBOB (lithium difluoromethanesulfonate), LiPO 2 F 2 (difluorophosphoric acid Lithium), LiDFOP (lithium difluorodioxalate phosphate) and LiTFOP (lithium tetrafluorooxalate phosphate).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • LiClO 4 lithium perchlorate
  • LiFSI
  • the organic solvent includes, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), carbonic acid Dimethyl ester (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate Ester (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), Methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS)
  • EC ethylene carbon
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance. wait.
  • the additives include, but are not limited to, fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), vinyl sulfate (DTD), propylene sulfate, vinyl sulfite Ester (ES), 1,3-propene sultone (PS), 1,3-propene sultone (PST), sulfonate cyclic quaternary ammonium salt, succinic anhydride, succinonitrile (SN) , at least one of adiponitrile (AND), tris(trimethylsilane)phosphate (TMSP), and tris(trimethylsilane)borate (TMSB).
  • FEC fluoroethylene carbonate
  • VC vinylene carbonate
  • VEC vinyl ethylene carbonate
  • DTD vinyl sulfate
  • ES vinyl sulfite Ester
  • PS 1,3-propene sultone
  • PST 1,3-propene sultone
  • the electrolyte solution can be prepared according to conventional methods in the art.
  • the organic solvent, lithium salt, and optional additives can be mixed evenly to obtain an electrolyte.
  • the materials There is no particular restriction on the order in which the materials are added. For example, add lithium salt and optional additives to the organic solvent and mix evenly to obtain an electrolyte; or add lithium salt to the organic solvent first, and then add the optional additives.
  • the additives are added to the organic solvent and mixed evenly to obtain an electrolyte.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through.
  • isolation membrane There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, but is not limited to these.
  • the isolation film can be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different. In some embodiments, a ceramic coating or a metal oxide coating can also be provided on the isolation film.
  • a fifth aspect of the embodiment of the present application provides an electronic device, which includes the electrochemical device of the fourth aspect of the embodiment of the present application, wherein the electrochemical device can be used as a power source in the electronic device.
  • the electronic device of the present application is not particularly limited and may be used in any electronic device known in the art.
  • the electronic device may include, but is not limited to, a laptop computer, a pen computer, a mobile computer, an e-book player, a portable telephone, a portable fax machine, a portable copier, a portable printer, a stereo headset, a video recorder , LCD TV, portable cleaner, portable CD player, mini disc, transceiver, electronic notepad, calculator, memory card, portable recorder, radio, backup power supply, motor, automobile, motorcycle, power-assisted bicycle, bicycle, lighting Appliances, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries and lithium-ion capacitors, etc.
  • the composition of the first silicon oxide particles and graphite (wherein the mass ratio of the first silicon oxide particles to graphite is 15.5:84.5), the conductive agent acetylene black, and the binder sodium alginate are mixed in a mass ratio of 70:20: 10.
  • Mix add an appropriate amount of solvent deionized water, and obtain a negative electrode slurry under the action of a vacuum mixer; apply the negative electrode slurry evenly on both surfaces of the negative electrode current collector copper foil, and vacuum dry it at 70°C for 12 hours.
  • the metal is laminated on the coating formed by the negative electrode slurry, and the negative electrode pieces are obtained after being cut into strips.
  • cathode active material LiCoO 2 , conductive carbon black, and binder PVDF according to the mass ratio of 96.7:1.7:1.6, add an appropriate amount of solvent NMP, and use it in a vacuum mixer to obtain a cathode slurry; apply the cathode slurry evenly on the cathode on both surfaces of the current collector aluminum foil; then vacuum dried at 70°C for 12 hours, and then cut into strips to obtain the positive electrode piece.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • FEC fluoroethylene carbonate
  • PE porous film is used as the isolation membrane.
  • the lithium-ion battery is obtained through processes such as formation, degassing, and trimming.
  • the preparation method of the lithium-ion battery is similar to Example 1, except that the relevant parameters of the negative electrode plate are adjusted.
  • the specific parameters are shown in Table 1.
  • the mass percentage content of the carbon element in the silicon oxide matrix in the first silicon oxide particles is controlled.
  • “/” means that the lithium metal layer is not included (the lithium source is not replenished in advance).
  • “-” in Example 6 means that the first silicon oxide particle powder is soaked in 1 mol/L Li-PAH-THF organic lithium to pre-supply lithium, wherein the PAH is 9.9-dimethyl-9H-fluorene ( Flr), biphenyl (Bp) or naphthalene (Nap), THF is tetrahydrofuran.
  • First efficiency first discharge capacity/first charge capacity ⁇ 100%.
  • the test temperature is 25°C. Charge the lithium-ion battery to 4.48V at a constant current of 0.7C, and charge to 0.025C at a constant voltage. After leaving it alone for 5 minutes, discharge it to 3.0V at a rate of 0.5C; the capacity obtained in this step is the initial capacity. Conduct 500 cycles of 0.7C charge/0.5C discharge cycle test.
  • Capacity retention rate (%) after 500 cycles discharge capacity at the 500th cycle/first discharge capacity ⁇ 100%.
  • Table 2 gives the performance test results of Examples 1 to 6 and Comparative Examples 1 to 3.
  • a comparison between Examples 1-5 and Comparative Examples 1-3 shows that by adjusting the carbon content of the silicon oxide matrix in the first silicon oxide particles and the surface density of the lithium metal layer, the nanometer density after the reaction with metallic lithium can be effectively reduced.
  • the size of the silicon crystal grains, thereby reducing the volume expansion of the negative electrode plate when lithium is embedded, can not only reduce the volume expansion rate of the lithium-ion battery in the fully charged state, but also prevent the second silicon oxide particles from breaking when they expand, which can cause It is beneficial to improve the capacity retention rate of lithium-ion batteries.
  • Comparison of Examples 1-4 and 4-5 shows that by controlling the mass content of carbon elements between 2% and 7%, the size of nano-silicon grains can be limited to less than 5nm, and the capacity retention of lithium-ion batteries can be further improved. rate and expansion rate in fully charged state.
  • Example 6 shows that after introducing lithium metal on the surface of the negative electrode, the loss of lithium ions caused by the side reaction during the first charging of the negative electrode is compensated, and the first efficiency of the lithium-ion battery is increased from 76.1%. to 91.7%.
  • This may be due to the lithium insertion reaction of the second silicon oxide particles after the reaction between the negative electrode sheet and lithium metal, and the synergistic effect of the lithium metal layer and the evenly distributed doped carbon elements in the silicon oxide matrix before cycling charge and discharge.
  • Pre-expansion has already occurred in the silica particles, reducing the full-charge expansion rate of the lithium-ion battery from 8.5% to 7.0%.
  • the lithium replenishment method is replaced by organic lithium immersion from the lithium metal layer, the first efficiency of the battery is affected to a certain extent.
  • Comparison between Examples 1-3 and 4-6 illustrates that by adjusting the mass content of carbon element in the first silica particles and regulating the lithium supplementation method, the second silica particles satisfy 6.38 ⁇ d+ 72 ⁇ c ⁇ At 6.52, the capacity retention rate and expansion rate of the lithium-ion battery in the fully charged state are significantly improved.

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Abstract

本申请提供一种负极极片、用于电化学装置中的负极极片、电化学装置及电子设备。所述负极极片包括：负极集流体，和设置在所述负极集流体至少一侧的活性物质层，所述活性物质层包括负极活性材料层，所述负极活性材料层包括第一氧化亚硅粒子，所述负极活性材料层远离所述负极集流体的一侧设置有锂金属层，其中，所述第一氧化亚硅粒子包括掺杂有碳元素的氧化亚硅基体，所述氧化亚硅基体中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为0.5％≤ω c1≤7％。本申请提供的负极极片能够使电化学装置同时具有高容量、高首效和长循环寿命。

Description

负极极片、用于电化学装置中的负极极片、电化学装置及电子设备 技术领域
本申请属于电化学技术领域，具体涉及一种负极极片、用于电化学装置中的负极极片、电化学装置及电子设备。
背景技术
锂离子电池因无记忆效应、长循环寿命、绿色环保等优点，广泛应用在如今生活的各个方面。近年来，锂离子电池更是在新能源汽车和大规模储能领域得到了迅猛发展。然而，在传统商品化锂离子电池的负极材料中，石墨等碳基材料的容量较低，因而锂离子电池的首次效率较低。而硅基材料易膨胀，导致锂离子电池的循环性能较差，由此极大限制了它们在锂离子电池中的大规模应用。
发明内容
本申请的目的在于提供一种负极极片、用于电化学装置中的负极极片、电化学装置及电子设备，旨在提升电化学装置的首次库伦效率和循环稳定性。
本申请第一方面提供一种负极极片，包括：负极集流体，和设置在所述负极集流体至少一侧的活性物质层，所述活性物质层包括负极活性材料层，所述负极活性材料层包括第一氧化亚硅粒子，所述负极活性材料层远离所述负极集流体的一侧设置有锂金属层，其中，所述第一氧化亚硅粒子包括掺杂有碳元素的氧化亚硅基体，所述氧化亚硅基体中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为0.5％≤ω c1≤7％。
在本申请一种实施方式中，所述氧化亚硅基体的任意区域中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为0.5％≤ω c1≤7％。
在本申请一种实施方式中，所述第一氧化亚硅粒子中碳原子与硅原子的摩尔比为0.01:1至0.4:1，优选为0.05:1至0.35:1。
在本申请一种实施方式中，所述第一氧化亚硅粒子的体积平均粒径为3μm≤Dv50≤20μm，优选为5μm≤Dv50≤18μm。
在本申请一种实施方式中，所述负极活性材料层的厚度为10μm至90μm，优选为15μm至85μm。
在本申请一种实施方式中，所述负极活性材料层的孔隙率为21％至28％，优选为22％至26％。
在本申请一种实施方式中，基于所述负极活性材料层的总质量，所述第一氧化亚硅粒子的质量百分含量为0.2％至60％，优选为0.5％至55％。
在本申请一种实施方式中，所述负极活性材料层还包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、石墨烯、碳纳米管中的至少一种。
在本申请一种实施方式中，所述锂金属层的面密度为0.17mg/cm 2至1.34mg/cm 2，优选为0.20mg/cm 2至1.30mg/cm 2。
在本申请一种实施方式中，所述锂金属层与所述负极活性材料层中所述第一氧化亚硅粒子的质量比为0.10:1至0.19:1，优选为0.12:1至0.17:1。
在本申请一种实施方式中，所述氧化亚硅基体中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为2％≤ω c1≤7％。
在本申请一种实施方式中，所述氧化亚硅基体的任意区域中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为2％≤ω c1≤7％。
本申请第二方面提供一种用于电化学装置中的负极极片，包括：负极集流体，和设置在所述负极集流体至少一侧的活性物质层，所述活性物质层包括含有纳米硅晶粒的第二氧化亚硅粒子，其中，所述纳米硅晶粒的粒径为d<5nm。
在本申请一种实施方式中，所述纳米硅晶粒的粒径为1.4nm≤d<5nm。
在本申请一种实施方式中，所述纳米硅晶粒的粒径为1.4nm≤d≤4.8nm。
在本申请一种实施方式中，基于所述第二氧化亚硅粒子的总质量，所述第二氧化亚硅粒子中碳元素的质量百分含量为2％≤ω c2≤7％。
在本申请一种实施方式中，所述纳米硅晶粒的粒径d与所述第二氧化亚硅粒子中碳元素的质量百分含量ω c2满足：6.38≤d+72ω c≤6.52。
本申请第三方面提供一种电化学装置，包括本申请第一方面所述的负极极片或本申请第二方面所述的负极极片。
本申请第四方面提供一种电子设备，包括本申请第三方面所述的电化学装置。
附图说明
图1是本申请的第二氧化亚硅粒子的一实施例的TEM图。
具体实施方式
为使本申请的目的、技术方案和优点更加清楚，下面将结合实施例对本申请的技术方案进行清楚、完整地描述，显然，所描述的实施例是本申请一部分实施例，而不是全部的实施例。在此所描述的有关实施例为说明性质的且用于提供对本申请的基本理解。本申请的实施例不应该被解释为对本申请的限制。
为了简明，本文仅具体地公开了一些数值范围。然而，任意下限可以与任何上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的 点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
在本文的描述中，除非另有说明，“以上”、“以下”包含本数。
除非另有说明，本申请中使用的术语具有本领域技术人员通常所理解的公知含义。除非另有说明，本申请中提到的各参数的数值可以用本领域常用的各种测量方法进行测量(例如，可以按照在本申请的实施例中给出的方法进行测试)。
术语“中的至少一者”、“中的至少一个”、“中的至少一种”或其他相似术语所连接的项目的列表可意味着所列项目的任何组合。例如，如果列出项目A及B，那么短语“A及B中的至少一者”意味着仅A；仅B；或A及B。在另一实例中，如果列出项目A、B及C，那么短语“A、B及C中的至少一者”意味着仅A；或仅B；仅C；A及B(排除C)；A及C(排除B)；B及C(排除A)；或A、B及C的全部。项目A可包含单个组分或多个组分。项目B可包含单个组分或多个组分。项目C可包含单个组分或多个组分。
目前，随着电动汽车和电动工具等大功率设备的发展，人们对锂离子电池的能量密度要求越来越高。为了提升锂离子电池的能量密度，发明人发现在现有的锂离子电池硅基负极材料(Si、SiO)中，碳掺杂氧化亚硅(SiCO)材料由于内部存在Si-C键和O-C键，因而可减弱Si-O键在断裂后形成Si-Si键的数量，进而可以避免Si富集区应力过大导致颗粒膨胀破裂，由此可以显著改善硅基负极的循环和膨胀问题。
但碳掺杂氧化亚硅在首次充电过程中会因为形成硅酸锂和固体电解质膜(SEI膜)而消耗一部分锂，从而造成正极材料锂的损失，因而会降低锂离子电池的容量，使得电池的首次库伦效率较低。
为了解决上述问题，发明人通过大量研究提出了一种既能充分抑制体积膨胀，同时又具备高首效和高循环稳定性的负极极片。
负极极片
本申请实施方式的第一方面提供了一种负极极片，包括：负极集流体，和设置在所述负极集流体至少一侧的活性物质层，所述活性物质层包括负极活性材料层，所述负极活性材料层包括第一氧化亚硅粒子，所述负极活性材料层远离所述负极集流体的一侧设置有锂金属层，其中，所述第一氧化亚硅粒子包括掺杂有碳元素的氧化亚硅基体，所述氧化亚硅基体中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为0.5％≤ω c1≤7％。
进一步地，所述氧化亚硅基体的任意区域中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为0.5％≤ω c1≤7％。
本申请中的负极极片包括负极活性材料层，所述负极活性材料层包括第一氧化亚硅粒子，所述第一氧化亚硅粒子包括掺杂有碳元素的氧化亚硅基体，并且，所述负极活性材料层远离所述负极集流体的一侧设置有锂金属层。由于氧化亚硅基体中均匀地掺杂 有碳元素，所述碳元素在第一氧化亚硅粒子内部会形成Si-C键和O-C键，在与锂金属层的预膨胀反应中，均匀分布于氧化亚硅基体中的碳元素能够减少第一氧化亚硅粒子中Si-O键在断裂后形成的Si-Si键的数量，进而可以避免Si富集区应力过大导致的颗粒膨胀破裂，从而改善负极极片的膨胀和循环性能；由于在首次充电过程中，所述锂金属层参与负极活性材料固体电解质膜的形成，因而能够减少首次充电时副反应所导致的正极材料中锂的消耗，进而能够提升电池的容量及首次库伦效率。进一步地，本申请中第一氧化亚硅粒子中碳元素的质量百分含量在合适范围内，有利于降低其与金属锂反应后所形成的纳米硅晶粒的粒径，从而降低负极极片在嵌锂时的体积膨胀，进而有利于提升电池的容量保持率。
本申请中，氧化亚硅基体中碳元素的质量百分含量为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如，将第一氧化亚硅粒子洒在导电胶的铜箔上，裁剪成断面，采用等离子抛光机(Leica EM TIC 3X‐Ion Beam Slope Cutter)抛光，随后放入扫描电子显微镜(SEM)中寻找到切开的负极活性材料颗粒，采用采聚焦离子束(FIB)将上述负极活性材料颗粒沿断面的垂直方向切割，得到含有负极活性材料颗粒截面的薄片后，采用透射电子显微镜(TEM)和能谱仪(EDS)测量包含碳、氧和硅的选定区域中碳元素的比例。
在一些实施方式中，所述第一氧化亚硅粒子包括掺杂有碳元素的氧化亚硅基体，在所述氧化亚硅基体中，所述碳元素的质量百分含量为2％≤ω c1≤7％。
本申请中，氧化亚硅基体中碳元素的质量浓度，指的是基于多个氧化亚硅基体所组成的粉体，对所述粉体进行随机取样，其中所包含的碳元素相对于样品总质量的质量百分含量。
本申请中，氧化亚硅基体中碳元素的质量浓度可以采用如下方法测量：在坩埚底部加入0.8g钨锡铁三合一助熔剂，使其均匀覆盖坩埚底部。然后加入0.5g第一氧化亚硅粉末，最后在样品表面均匀覆盖0.8g钨锡铁三合一助熔剂。将坩埚夹夹住坩埚放在石英坩埚托上，用高频红外碳硫分析仪进行测试，预吹氧时间为20s，顶吹氧时间为50s，吹氧流量为1.8L/min，碳截止电平为10％，分析时间为20s至50s，分析氧流量为2.0L/min。
本申请中，第一氧化亚硅粒子中，氧化亚硅基体中碳元素的质量百分含量在合适范围内，有利于降低其与金属锂反应后所形成的纳米硅晶粒的粒径，从而降低负极极片在嵌锂时的体积膨胀，进而提升电池的容量保持率。
在一些实施方式中，所述第一氧化亚硅粒子中碳原子与硅原子的摩尔比为0.01:1至0.4:1，例如，所述第一氧化亚硅粒子中碳原子与硅原子的摩尔比为0.05:1，0.15:1，0.20:1，0.25:1，0.30:1，0.35:1或处于以上任何数值所组成的范围内。优选的，所述第一氧化亚硅粒子中碳原子与硅原子的摩尔比为0.05:1至0.35:1。
本申请中，第一氧化亚硅粒子中碳原子与硅原子的摩尔比在合适范围内，有利于第一氧化亚硅粒子内形成足够数量的Si-C键和O-C键，由此能够减少Si-O键在断裂后形 成的Si-Si键的数量，进而可以避免Si富集区应力过大导致的颗粒膨胀破裂，从而改善负极极片的膨胀和循环性能。而且所述碳原子与硅原子的摩尔比在上述范围内，也有利于将第一氧化亚硅粒子中碳元素的质量百分含量控制在2％至7％之间。
在一些实施方式中，所述第一氧化亚硅粒子的体积平均粒径为3μm≤Dv50≤20μm，例如，所述第一氧化亚硅粒子的体积平均粒径Dv50为5μm，8μm，11μm，14μm，17μm，20μm或处于以上任何数值所组成的范围内。优选的，所述为第一氧化亚硅粒子的体积平均粒径为5μm≤Dv50≤18μm。
本申请中，第一氧化亚硅粒子的体积平均粒径Dv50和Dv10为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如，可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer2000E型激光粒度分析仪。
本申请中，第一氧化亚硅粒子的体积平均粒径在合适范围内，既能够提升其在电解液中的扩散效率，又能够减小负极活性材料层与电解液的接触面积，由此有利于提升负极极片的循环性能。
在一些实施方式中，所述负极活性材料层的厚度为10μm至90μm，例如，所述负极活性材料层的厚度为20μm至80μm，25μm至75μm，30μm至70μm，35μm至65μm，40μm至60μm或45μm至55μm。优选的，所述负极活性材料层的厚度为15μm至85μm。负极活性材料层的厚度在合适范围内，能使负极极片在具备高充放电容量的前提下，还具有进一步提升的循环性能和倍率性能。
本申请中，负极活性材料层的厚度为本领域公知的含义，可采用本领域已知的方法测试，例如采用万分尺(例如Mitutoyo293-100型，精度为0.1μm)进行测试。
在一些实施方式中，所述负极活性材料层的孔隙率为21％至28％，例如，所述负极活性材料层的孔隙率为22％，24％，26％，28％或处于以上任何数值所组成的范围内。优选的，所述极活性材料层的孔隙率为22％至26％。负极活性材料层的孔隙率在合适范围内，有利于提升离子(例如锂离子)的传输效率，从而提高负极极片的循环性能。
本申请中，负极活性材料层的孔隙率为本领域公知的含义，可采用本领域已知的方法测试。例如，将反应后的负极极片裁成直径大小为10mm的圆片，采用气体置换法测试负极活性材料层的孔隙率，孔隙率的计算公式为：P＝(V-V0)/V×100％，其中P为孔隙率，V0为极片涂层真体积，V为极片涂层表观体积。
在一些实施方式中，基于所述负极活性材料层的总质量，所述第一氧化亚硅粒子的质量百分含量为0.2％至60％，例如，所述第一氧化亚硅粒子的质量百分含量为1％至55％，5％至50％，10％至45％，15％至40％，20％至35％或25％至30％。优选的，所述第一氧化亚硅粒子的质量百分含量为0.5％至55％。
负极活性材料层中第一氧化亚硅粒子的质量百分含量在上述范围内，有利于促进第一氧化亚硅粒子与石墨之间的协同效应，使第一氧化亚硅粒子的高容量、低膨胀以及 高首效性能得到更加充分的发挥，同时也能促进高导电性的石墨在负极活性材料层中起到更好的作用，从而使负极极片具备更高的容量、首效以及倍率性能。
在一些实施方式中，所述锂金属层的面密度为0.17mg/cm 2至1.34mg/cm 2，例如，所述锂金属层的面密度为0.20mg/cm 2至1.30mg/cm 2，0.30mg/cm 2至1.20mg/cm 2，0.40mg/cm 2至1.10mg/cm 2，0.50mg/cm 2至1.00mg/cm 2，0.60mg/cm 2至0.90mg/cm 2或0.70mg/cm 2至0.80mg/cm 2。优选的，所述锂金属层的面密度为0.20mg/cm 2至1.30mg/cm 2。
锂金属层的面密度在合适范围内，能够为首次充电过程中固体电解质膜的形成等副反应提供足够的锂，从而减少正极材料中不可逆锂的消耗，提升电池的首次库伦效率。
在一些实施方式中，所述锂金属层与所述负极活性材料层中所述的质量比为0.10:1至0.19:1，例如，所述质量比为0.12:1，0.14:1，0.16:1，0.18:1或处于以上任何数值所组成的范围内。优选的，所述质量比为0.12:1至0.17:1。
锂金属层与第一氧化亚硅粒子的质量比在上述范围内，有利于首次充电时，使第一氧化亚硅粒子能够完全与锂金属层反应生成硅酸锂以及固体电解质膜，而避免消耗正极材料中的锂，从而减少正极中不可逆锂的消耗，进而提升电池的容量及首次库伦效率。同时，第一氧化亚硅粒子与锂金属层发生反应后的粒子内已经进行了嵌锂反应，相当于在循环充放电之前氧化亚硅粒子已经发生了预膨胀，从而能够降低负极极片在满充时的膨胀率，提升电池的循环膨胀性能。
在一些实施方式中，锂金属层的材料没有特别的限制，可根据实际需求进行选择，只要能为负极极片的首次充电提供锂的补偿即可。例如，所述锂金属层可以为锂箔、锂粉或锂线等锂金属材料。
本申请实施方式的第二方面提供了一种用于电化学装置中的负极极片，包括：负极集流体，和设置在所述负极集流体至少一侧的活性物质层，所述活性物质层包括含有纳米硅晶粒的第二氧化亚硅粒子，其中，所述纳米硅晶粒的粒径为d<5nm。
在一些实施方式中，所述纳米硅晶粒的粒径为1.4nm≤d≤4.8nm。例如，所述纳米硅晶粒的粒径为1.5nm≤d≤4.8nm，2.0nm≤d≤4.8nm，2.5nm≤d≤4.8nm，3.0nm≤d≤4.8nm，3.5nm≤d≤4.8nm，4.0nm≤d≤4.8nm，4.5nm≤d≤4.8nm，1.5nm≤d≤4.5nm，2.0nm≤d≤4.5nm，2.5nm≤d≤4.5nm，3.0nm≤d≤4.5nm，3.5nm≤d≤4.5nm，4.0nm≤d≤4.5nm，1.5nm≤d≤4.0nm，2.0nm≤d≤4.0nm，2.5nm≤d≤4.0nm，3.0nm≤d≤4.0nm，3.5nm≤d≤4.0nm，1.5nm≤d≤3.5nm，2.0nm≤d≤3.5nm，2.5nm≤d≤3.5nm，3.0nm≤d≤3.5nm，1.5nm≤d≤3.0nm，2.0nm≤d≤3.0nm，2.5nm≤d≤3.0nm，1.5nm≤d≤2.5nm，2.0nm≤d≤2.5nm或1.5nm≤d≤2.0nm。
本申请中的第二氧化亚硅粒子，是通过本申请第一方面所述的第一氧化亚硅粒子与锂金属层在首次充电反应过程中形成的。发明人通过研究发现，在首次充电反应后，如图1所示，第二氧化亚硅粒子内会产生纳米硅晶粒，而且通过将纳米硅晶粒的粒径控制上述范围内，能够改善后续循环过程中第二氧化亚硅粒子的体积膨胀问题，进而提升电池的容量保持率和循环稳定性。当纳米硅晶粒的粒径超过5nm后，在循环过程中，粒径 较大的纳米硅晶粒易导致第二氧化亚硅粒子在嵌锂过程中的膨胀破碎，从而导致电池循环性能受到影响。
本申请中，纳米硅晶粒的粒径为本领域公知的含义，可采用本领域已知的方法测试。例如，将反应后的负极极片涂层粉末轻轻刮下，表面镀Cr处理后在扫描电子显微镜(SEM)中选取需要测试的第二氧化亚硅粒子，然后利用聚焦离子束(FIB)对第二氧化亚硅颗粒进行减薄处理，最后将减薄的样品焊在透射电子显微镜(TEM)样品架上。将载有第二氧化亚硅薄片的样品架上装入TEM进样室内进行测试，对TEM测试图像中晶格间距为0.313nm至0.329nm的晶格条纹区域进行尺寸测量，将晶格条纹区域轮廓中距离最长的两点定为第二氧化亚硅颗粒内纳米硅晶粒的粒径。
在一些实施方式中，在所述第二氧化亚硅粒子中，碳元素的质量百分含量为2％≤ω c2≤7％。例如，所述碳元素的质量百分含量为2.5％≤ω c2<7％,3％≤ω c2<7％,3.5％≤ω c2<7％,4％≤ω c2<7％,4.5％≤ω c2<7％,5％≤ω c2<7％,5.5％≤ω c2<7％,6％≤ω c2<7％,6.5％≤ω c2<7％,2.5％≤ω c2≤6.5％,3％≤ω c2≤6.5％,3.5％≤ω c2≤6.5％,4％≤ω c2≤6.5％,4.5％≤ω c2≤6.5％,5％≤ω c2≤6.5％,5.5％≤ω c2≤6.5％,6％≤ω c2≤6.5％,2.5％≤ω c2≤6％,3％≤ω c2≤6％,3.5％≤ω c2≤6％,4％≤ω c2≤6％,4.5％≤ω c2≤6％,5％≤ω c2≤6％,5.5％≤ω c2≤6％,2.5％≤ω c2≤5.5％,3％≤ω c2≤5.5％,3.5％≤ω c2≤5.5％,4％≤ω c2≤5.5％,4.5％≤ω c2≤5.5％,5％≤ω c2≤5.5％,2.5％≤ω c2≤5％,3％≤ω c2≤5％,3.5％≤ω c2≤5％,4％≤ω c2≤5％,4.5％≤ω c2≤5％,2.5％≤ω c2≤4.5％,3％≤ω c2≤4.5％,3.5％≤ω c2≤4.5％,4％≤ω c2≤4.5％,2.5％≤ω c2≤4％,3％≤ω c2≤4％,3.5％≤ω c2≤4％,2.5％≤ω c2≤3.5％,3％≤ω c2≤3.5％或2.5％≤ω c2≤3.5％。
发明人进一步研究发现，在第一氧化亚硅粒子与锂金属层经首次充电反应形成第二氧化亚硅粒子的过程中，碳元素的质量百分含量基本不会发生变化(即碳元素在第一氧化亚硅粒子中的质量百分含量，与其在第二氧化亚硅粒子中的质量百分含量基本相当)，而且纳米硅晶粒的粒径与第二氧化亚硅粒子中碳元素的质量百分含量(或者说，第一氧化亚硅粒子中碳元素的质量百分含量)相关。并非意在受限于任何理论，发明人发现，当第一氧化亚硅粒子中碳元素的质量百分含量超出上述范围时，其与锂金属层在首次充电反应过程中所形成的第二氧化亚硅粒子中的纳米硅晶粒的粒径将会超过5nm；而当第一氧化亚硅粒子中碳元素的质量百分含量控制在上述范围内时，所形成的第二氧化亚硅粒子中的碳元素与硅元素形成相当数量的Si-C键，这些Si-C键能抑制首次充电反应过程中纳米硅晶粒的生长，由此能够降低纳米硅晶粒的粒径，并将其控制在5nm以内。如果第二氧化亚硅粒子中的纳米硅晶粒的粒径超过5nm，则在循环过程中粒径较大的纳米硅晶粒易导致第二氧化亚硅粒子在嵌锂过程中的膨胀破碎，进而导致电池循环性能受到影响。当纳米硅晶粒的粒径被控制在5nm以内时，能够改善后续循环过程中第二氧化亚硅粒子的体积膨胀问题，进而提升电池的容量保持率和循环稳定性。
在一些实施方式中，所述纳米硅晶粒的粒径d与所述第二氧化亚硅粒子中碳元素的质量百分含量ω c2满足：6.38≤d+72ω c≤6.52。例如，所述纳米硅晶粒的粒径d与所述第二 氧化亚硅粒子中碳元素的质量百分含量ω c2满足：6.35≤d+72ω c≤6.52,6.30≤d+72ω c≤6.52,6.25≤d+72ω c≤6.52,6.20≤d+72ω c≤6.52,6.15≤d+72ω c≤6.52,6.10≤d+72ω c≤6.52,6.05≤d+72ω c≤6.52,6.35≤d+72ω c≤6.50,6.30≤d+72ω c≤6.50,6.25≤d+72ω c≤6.50,6.20≤d+72ω c≤6.50,6.15≤d+72ω c≤6.50,6.10≤d+72ω c≤6.50,6.05≤d+72ω c≤6.50,6.35≤d+72ω c≤6.45,6.30≤d+72ω c≤6.45,6.25≤d+72ω c≤6.45,6.20≤d+72ω c≤6.45,6.15≤d+72ω c≤6.45,6.10≤d+72ω c≤6.45,6.05≤d+72ω c≤6.45,6.35≤d+72ω c≤6.40,6.30≤d+72ω c≤6.40,6.25≤d+72ω c≤6.40,6.20≤d+72ω c≤6.40,6.25≤d+72ω c≤6.40,6.20≤d+72ω c≤6.40，6.15≤d+72ω c≤6.40，6.10≤d+72ω c≤6.40或6.05≤d+72ω c≤6.40。
发明人通过研究还发现，纳米硅晶粒的粒径d与第二氧化亚硅粒子中碳元素的质量百分含量ω c2满足上述关系式时，通过对上述关系式中碳元素的质量百分含量进行合理的调控，能够使纳米硅晶粒的粒径在合适范围内(d<5nm)，从而降低第二氧化亚硅粒子在循环嵌锂过程中的体积膨胀，提升电池的循环稳定性。
在一些实施方式中，所述活性物质层中并不排除除了第一氧化亚硅粒子与石墨组合物之外的其他负极活性材料。其他负极活性材料的具体种类不受到具体的限制，可根据需求进行选择。作为示例，其他负极活性材料包括但不限于天然石墨、人造石墨、中间相微碳球(MCMB)、硬碳，软碳、硅、硅-碳复合物、SiO、Li-Sn合金、Li-Sn-O合金、Sn、SnO、SnO 2、尖晶石结构的Li 4Ti 5O 12、Li-Al合金中的至少一种。
在一些实施方式中，活性物质层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，活性物质层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，活性物质层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
但本申请并不限定于上述材料，本申请的负极极片还可以使用可被用作负极活性材料、导电剂、粘结剂和增稠剂的其它公知材料。
在一些实施方式中，所述负极集流体具有在自身厚度方向相对的两个表面，活性物质层设置于负极集流体所述两个相对表面中的任意一者或两者上。
负极集流体可以使用金属箔材或多孔金属板，例如使用铜、镍、钛、铁等金属或它们的合金的箔材或多孔板。作为示例，负极集流体为铜箔。
本申请中负极极片可以按照本领域常规方法制备。例如，将本申请第一方面所述的负极极片中包含的第一氧化亚硅粒子，可选的其他负极活性材料，导电剂，粘结剂和增稠剂分散于溶剂中，溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，形成均匀的负 极浆料，将负极浆料涂覆在负极集流体上，经烘干、冷压后得到活性物质层，然后将锂金属层压在所述活性物质层的表面上，得到负极极片。
本申请中的负极极片并不排除除了负极活性材料层之外的其他附加功能层。例如，在某些实施方式中，本申请的负极极片还包括夹在负极集流体和活性物质层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。
电化学装置
本申请实施方式的第三方面提供一种电化学装置，包括其中发生电化学反应以将化学能与电能互相转化的任何装置，它的具体实例包括所有种类的锂一次电池或锂二次电池。特别地，锂二次电池包括锂金属二次电池、锂离子二次电池、锂聚合物二次电池或锂离子聚合物二次电池。
在一些实施方式中，本申请的电化学装置包括正极极片、负极极片、隔离膜和电解液。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
本申请的电化学装置还包括外包装，用于封装电极组件及电解液。在一些实施方式中，外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等，也可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)中的至少一种。
[负极极片]
本申请的电化学装置中使用的负极极片为本申请实施方式第一方面的负极极片或本申请实施方式第二方面的用于电化学装置中的负极极片。
[正极极片]
本申请的电化学装置中使用的正极极片的材料、构成和其制造方法可包括任何现有技术中公知的技术。
正极极片包括正极集流体以及设置在正极集流体至少一个表面上且包括正极活性材料的正极活性物质层。作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极活性物质层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，正极活性物质层包括正极活性材料，正极活性材料的具体种类不受到具体的限制，可根据需求进行选择。例如，正极活性材料可以包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。在本申请的电化学装置中，上述各正极活性材料的改性化合物可以是对正极活性材料进行掺杂改性、表面包覆改性、或掺杂同时表面包覆改性。
作为示例，锂过渡金属氧化物可以包括锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的一种或几种。作为示例，橄榄石结构的含锂磷酸盐可以包括磷酸铁锂、 磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其改性化合物中的一种或几种。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，正极活性物质层还可选的包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，正极活性物质层还可选的包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，正极集流体可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或几种。作为示例，高分子材料基层可选自聚丙烯、聚对苯二甲酸乙二醇酯、聚对苯二甲酸丁二醇酯、聚苯乙烯、聚乙烯等。
本申请中正极极片可以按照本领域常规方法制备。例如，正极活性物质层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。
本申请的正极极片并不排除除了正极活性物质层之外的其他附加功能层。例如，在一些实施方式中，本申请的正极极片还包括夹在正极集流体和正极活性物质层之间、设置于正极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施方式中，本申请的正极极片还包括覆盖在正极活性物质层表面的保护层。
[电解液]
电解液在正极极片和负极极片之间起到传导活性离子的作用。可用于本申请电化学装置的电解液可以为现有技术已知的电解液。
在一些实施方式中，所述电解液包括有机溶剂、锂盐和可选的添加剂，有机溶剂、锂盐和添加剂的种类均不受到具体的限制，可根据需求进行选择。
在一些实施方式中，作为示例，所述锂盐包括但不限于LiPF 6(六氟磷酸锂)、LiBF 4(四氟硼酸锂)、LiClO 4(高氯酸锂)、LiFSI(双氟磺酰亚胺锂)、LiTFSI(双三氟甲磺酰亚胺锂)、LiTFS(三氟甲磺酸锂)、LiDFOB(二氟草酸硼酸锂)、LiBOB(二草酸硼酸锂)、LiPO 2F 2(二氟磷酸锂)、LiDFOP(二氟二草酸磷酸锂)及LiTFOP(四氟草酸磷酸锂)中的至少一种。上述锂盐可以单独使用一种，也可以同时使用两种或两种以上。
在一些实施方式中，作为示例，所述有机溶剂包括但不限于碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的至少一种。上述有机溶剂可以单独使用一种，也可以同时使用两种或两种以上。可选地，上述有机溶剂同时使用两种或两种以上。
在一些实施方式中，所述添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
作为示例，所述添加剂包括但不限于氟代碳酸乙烯酯(FEC)、碳酸亚乙烯酯(VC)、乙烯基碳酸乙烯酯(VEC)、硫酸乙烯酯(DTD)、硫酸丙烯酯、亚硫酸乙烯酯(ES)、1,3-丙磺酸内酯(PS)、1,3-丙烯磺酸内酯(PST)、磺酸酯环状季铵盐、丁二酸酐、丁二腈(SN)、己二腈(AND)、三(三甲基硅烷)磷酸酯(TMSP)、三(三甲基硅烷)硼酸酯(TMSB)中的至少一种。
电解液可以按照本领域常规的方法制备。例如，可以将有机溶剂、锂盐、可选的添加剂混合均匀，得到电解液。各物料的添加顺序并没有特别的限制，例如，将锂盐、可选的添加剂加入到有机溶剂中混合均匀，得到电解液；或者，先将锂盐加入有机溶剂中，然后再将可选的添加剂加入有机溶剂中混合均匀，得到电解液。
[隔离膜]
隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯、聚偏氟乙烯中的一种或几种，但不仅限于这些。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料相同或不同。在一些实施例方式中，隔离膜上还可以设置陶瓷涂层、金属氧化物涂层。
电子设备
本申请实施方式的第五方面提供了一种电子设备，其包括本申请实施方式第四方面的电化学装置，其中，所述电化学装置可在所述电子设备中作为电源使用。
本申请的电子设备没有特别限定，其可以是用于现有技术中已知的任何电子设备。在一些实施方式中，电子设备可以包括但不限于，笔记本电脑、笔输入型计算机、移动电脑、电子书播放器、便携式电话、便携式传真机、便携式复印机、便携式打印机、头戴式立体声耳机、录像机、液晶电视、手提式清洁器、便携CD机、迷你光盘、收发机、 电子记事本、计算器、存储卡、便携式录音机、收音机、备用电源、电机、汽车、摩托车、助力自行车、自行车、照明器具、玩具、游戏机、钟表、电动工具、闪光灯、照相机、家庭用大型蓄电池和锂离子电容器等。
实施例
下述实施例更具体地描述了本发明公开的内容，这些实施例仅仅用于阐述性说明，因为在本发明公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于质量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
实施例1
第一氧化亚硅粒子的制备
将15kg SiO 2、7kg Si混合均匀后于置于乙炔气流中，控制反应体系以5℃/min的升温速率升温至1300℃，保温5h，得到第一氧化亚硅粒子。
负极极片的制备
将第一氧化亚硅粒子与石墨的组合物(其中，第一氧化亚硅粒子与石墨的质量比为15.5:84.5)、导电剂乙炔黑、粘结剂海藻酸钠按照质量比70:20:10进行混合，加入适量的溶剂去离子水，在真空搅拌机作用下获得负极浆料；将负极浆料均匀涂覆在负极集流体铜箔的两个表面上，经过70℃真空干燥12h后将锂金属层压在负极浆料形成的涂层之上，分条裁片后得到负极极片。
正极极片的制备
将正极活性材料LiCoO 2、导电炭黑、粘结剂PVDF按照质量比96.7:1.7:1.6进行混合，加入适量的溶剂NMP，在真空搅拌机作用获得正极浆料；将正极浆料均匀涂覆在正极集流体铝箔的两个表面上；然后经过70℃真空干燥12h，分条裁片后得到正极极片。
电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)及碳酸二乙酯(DEC)按照体积比为1:1:1进行混合，得到有机溶剂；将LiPF 6溶解在上述有机溶剂中，再加入氟代碳酸乙烯酯(FEC)混合均匀，得到电解液；其中，LiPF 6的浓度为1mol/L。
隔离膜的制备
采用PE多孔薄膜作为隔离膜。
锂离子电池的制备
将正极极片、隔离膜、负极极片依次叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到电极组件；将电极组件置于外包装中，注入配好的电解液后并封装，经过化成、脱气、切边等工艺流程得到锂离子电池。
实施例2至6和对比例1至3
锂离子电池的制备方法与实施例1类似，不同之处在于：调整了负极极片的相关参数，具体参数详见表1。
其中，通过调节乙炔气体的流速，控制第一氧化亚硅粒子中，氧化亚硅基体内碳元素的质量百分含量。
其中，“/”表示不包含锂金属层(不预先补充锂源)。实施例6中的“-”表示将第一氧化亚硅粒子粉末浸泡在1mol/L的Li-PAH-THF有机锂中进行预补锂，其中，PAH为9.9-二甲基-9H-芴(Flr)、联苯(Bp)或萘(Nap)，THF为四氢呋喃。
表1
Figure PCTCN2022083578-appb-000001
测试部分
(1)锂离子电池的首次效率测试
将未循环的锂离子电池以0.5C恒流充电至4.48V，再以4.48V恒压充电至0.1C，得到首次充电容量；以1C放电至3.0V，然后以0.5C放电至3.0V，最后以0.1C放电至3.0V，得到首次放电容量。
首次效率＝首次放电容量/首次充电容量×100％。
(2)锂离子电池循环性能测试
测试温度为25℃，将锂离子电池以0.7C恒流充电到4.48V，恒压充电到0.025C，静置5分钟后以0.5C放电到3.0V；以此步得到的容量为初始容量，进行500圈0.7C充电/0.5C放电循环测试。
循环500圈时容量保持率(％)＝第500圈的放电容量/首次放电容量×100％。
(3)锂离子电池满充膨胀率测试
将未循环的锂离子电池充电至50％Soc，用螺旋千分尺测试电池厚度，循环至500圈时，电池处于满充状态下，再用螺旋千分尺测试此时电池的厚度，与初始半充时新鲜电池的厚度对比，即可得此时满充电池膨胀率。
循环500圈时满充膨胀率＝第500圈时满充的电池厚度/首次充电至50％Soc时的电池厚度×100％。
表2给出实施例1至6和对比例1至3的性能测试结果。
表2
  首次效率(％) 循环500圈时容量保持率(％) 循环500圈时满充膨胀率(％)
实施例1 92.0 93.7 7.4
实施例2 91.7 93.4 7.0
实施例3 90.9 94.0 6.8
实施例4 91.2 92.9 7.8
实施例5 92.1 90.9 9.6
实施例6 84.8 91.3 8.3
对比例1 76.1 88.1 8.9
对比例2 92.0 87.0 11.0
对比例3 77.9 85.1 12.9
实施例1-5和对比例1-3对比说明，通过调整第一氧化亚硅粒子中氧化亚硅基体的碳元素含量，以及锂金属层的面密度，可以有效降低其与金属锂反应后纳米硅晶粒的尺寸，进而减小负极极片在嵌锂时的体积膨胀，不仅可降低锂离子电池在满充状态下的体积膨胀率，还可以避免第二氧化亚硅粒子膨胀时破碎，有利于提升锂离子电池的容量保持率。
实施例1-4和实施例4-5对比说明，通过把碳元素的质量含量控制在2％至7％，可以将纳米硅晶粒尺寸限制在5nm以下，并进一步提升锂离子电池的容量保持率及满充状态下的膨胀率。
实施例1、实施例6和对比例1对比说明，在负极极片表面引入锂金属后，负极在首次充电时副反应所导致的锂离子损失得到弥补，锂离子电池的首次效率由76.1％提升至91.7％。这可能是由于，负极极片和锂金属反应后第二氧化亚硅粒子发生嵌锂反应，在循环充放电前锂金属层与氧化亚硅基体中的均匀分布的掺杂碳元素协同作用，第二氧化亚硅粒子中就已经发生了预膨胀，使得锂离子电池的满充膨胀率由8.5％降低至7.0％。其中，将补锂方式由锂金属层替换为有机锂浸泡时，电池的首次效率受到一定程度的影响。
实施例1-6和对比例2对比说明，氧化亚硅基体内部不含有碳元素，在与锂金属反应时纳米硅晶粒的长大不受Si-C键约束，其尺寸可达到9.5nm，远超过5nm。过大的尺寸膨胀会使氧亚硅粒子破裂，因此由不含碳元素的氧亚硅粒子所形成的负极，其膨胀和循环性能受到明显影响。
实施例1-3和实施例4-6对比说明，通过调整第一氧化亚硅颗粒中碳元素的质量含量，并调控补锂方式，使得第二氧化亚硅颗粒满足6.38≤d+72ω c≤6.52时，锂离子电池的容量保持率及满充状态下的膨胀率得到显著改善。
以上所述，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，可轻易想到各种等效的修改或替换，这些修改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 (12)

  1. 一种负极极片，包括：
    负极集流体，和
    设置在所述负极集流体至少一侧的活性物质层，所述活性物质层包括负极活性材料层，所述负极活性材料层包括第一氧化亚硅粒子，所述负极活性材料层远离所述负极集流体的一侧设置有锂金属层，
    所述第一氧化亚硅粒子包括掺杂有碳元素的氧化亚硅基体，所述氧化亚硅基体中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为0.5％≤ω c1≤7％。
  2. 根据权利要求1所述的负极极片，其中，所述氧化亚硅基体的任意区域中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为0.5％≤ω c1≤7％。
  3. 根据权利要求1所述的负极极片，其中，所述第一氧化亚硅粒子满足以下条件中的至少一者：
    所述第一氧化亚硅粒子中碳原子与硅原子的摩尔比为0.01:1至0.4:1；
    所述第一氧化亚硅粒子的体积平均粒径为3μm≤Dv50≤20μm。
  4. 根据权利要求1所述的负极极片，其中，所述负极活性材料层满足以下条件中的至少一者：
    所述负极活性材料层的厚度为10μm至90μm；
    所述负极活性材料层的孔隙率为21％至28％；
    基于所述负极活性材料层的总质量，所述第一氧化亚硅粒子的质量百分含量为0.2％至60％。
  5. 根据权利要求1所述的负极极片，其中，所述负极活性材料层还包括人造石墨、天然石墨、中间相碳微球、软碳、硬碳、石墨烯、碳纳米管中的至少一种。
  6. 根据权利要求1所述的负极极片，其中，所述锂金属层满足以下条件中的至少一者：所述锂金属层的面密度为0.17mg/cm 2至1.34mg/cm 2；
    所述锂金属层与所述负极活性材料层中所述第一氧化亚硅粒子的质量比为0.10:1至0.19:1。
  7. 根据权利要求1所述的负极极片，其中，满足以下条件中的至少一者：
    所述锂金属层的面密度为0.20mg/cm 2至1.30mg/cm 2；
    所述锂金属层与所述负极活性材料层中所述第一氧化亚硅粒子的质量比为0.12:1至0.17:1；
    所述氧化亚硅基体中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为2％≤ω c1≤7％；
    所述氧化亚硅基体的任意区域中，基于碳、硅和氧的总质量，所述碳元素的质量百分含量为2％≤ω c1≤7％。
  8. 一种用于电化学装置中的负极极片，包括：
    负极集流体，和
    设置在所述负极集流体至少一侧的活性物质层，所述活性物质层包括含有纳米硅晶粒的第二氧化亚硅粒子，其中，所述纳米硅晶粒的粒径为d<5nm。
  9. 根据权利要求8所述的负极极片，其中，所述纳米硅晶粒的粒径为1.4nm≤d≤4.8nm。
  10. 根据权利要求8所述的负极极片，其中，所述第二氧化亚硅粒子满足以下条件的至少一者：
    基于所述第二氧化亚硅粒子的总质量，所述第二氧化亚硅粒子中碳元素的质量百分含量为2％≤ω c2≤7％；
    所述纳米硅晶粒的粒径d与所述第二氧化亚硅粒子中碳元素的质量百分含量ω c2满足：6.38≤d+72ω c≤6.52。
  11. 一种电化学装置，包括权利要求1-10中任一项所述的负极极片。
  12. 一种电子设备，包括权利要求11所述的电化学装置。
PCT/CN2022/083578 2022-03-29 2022-03-29 负极极片、用于电化学装置中的负极极片、电化学装置及电子设备 WO2023184133A1 (zh)

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