WO2026012016A1 - 一种电化学装置及电子装置 - Google Patents

一种电化学装置及电子装置

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Publication number
WO2026012016A1
WO2026012016A1 PCT/CN2025/098976 CN2025098976W WO2026012016A1 WO 2026012016 A1 WO2026012016 A1 WO 2026012016A1 CN 2025098976 W CN2025098976 W CN 2025098976W WO 2026012016 A1 WO2026012016 A1 WO 2026012016A1
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Prior art keywords
positive electrode
material layer
electrode material
electrochemical device
active material
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PCT/CN2025/098976
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English (en)
French (fr)
Inventor
谭功谦
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Ningde Amperex Technology Ltd
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Ningde Amperex Technology Ltd
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Publication of WO2026012016A1 publication Critical patent/WO2026012016A1/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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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 electrochemical technology, and in particular to an electrochemical device and an electronic device.
  • Electrochemical devices such as lithium-ion batteries
  • safety issues such as external force puncturing the batteries have arisen at the user end, leading to growing concerns about their safety performance. This is especially true given the ongoing series of mobile phone explosion incidents, which have prompted users, after-sales service providers, and lithium-ion battery manufacturers to demand new safety standards for lithium-ion batteries.
  • the purpose of this application is to provide an electrochemical device and an electronic device that enable the electrochemical device to achieve both high energy density and good safety and cycle performance.
  • the specific technical solution is as follows:
  • the first aspect of this application provides an electrochemical device comprising a positive electrode and a negative electrode.
  • the positive electrode comprises a positive current collector and a positive electrode material layer.
  • the positive electrode material layer comprises a first positive electrode material layer and a second positive electrode material layer.
  • the first positive electrode material layer is disposed between the positive current collector and the second positive electrode material layer.
  • the first positive electrode material layer comprises a first active material.
  • the delithiation product of the first active material comprises at least one of Li 5-x FeO 4-y , Li 5-x CoO 4-y , Li 2-z MnO 2 , Li 1.2-r Ni 0.13 Fe 0.13 Mn 0.54 O 2 or Li 1-t FePO 4 , wherein 4 ⁇ x ⁇ 5, 2 ⁇ y ⁇ 3, 1.6 ⁇ z ⁇ 2, 1 ⁇ r ⁇ 1.2, and 0.8 ⁇ t ⁇ 1.
  • the second positive electrode material layer includes a second active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, or lithium manganese oxide.
  • the negative electrode includes a negative electrode material layer containing silicon, with the silicon content ranging from 1% to 50% based on the mass of the negative electrode material layer.
  • the mass of the delithiation product of the first active material in the positive electrode is A mg/1540 mm2
  • the mass of silicon in the negative electrode is B mg/1540 mm2 , with 29% ⁇ A/B ⁇ 230%.
  • the electrochemical device includes a positive electrode and a negative electrode with the above characteristics, and the mass percentage of silicon and the A/B value are controlled within the above range.
  • the negative electrode material layer has a high specific capacity, and the use of the first active material for lithium replenishment helps reduce the irreversible capacity loss of the second active material during the first charge, improves the first coulombic efficiency of the second active material, and thus improves the energy density and cycle performance of the secondary battery. Meanwhile, the delithiation products of the first active material, being the aforementioned substances, enable the positive electrode sheet to possess suitable resistivity and bonding properties, thus improving the safety performance of the electrochemical device. Therefore, by satisfying these characteristics, the electrochemical device can achieve a balance of high energy density, good safety performance, and good cycle performance.
  • 39% ⁇ A/B ⁇ 200% 39% ⁇ A/B ⁇ 200%. Adjusting the value of A/B within the above range can enable the electrochemical device to have high energy density, better safety performance, and better cycle performance.
  • the delithiation products of the first active material include at least one selected from LiFeO2 , CoO2 , MnO2 , Ni0.13Fe0.13Mn0.54O2 , FePO4 , FeO2 , Fe2O3 , or FeO .
  • the inclusion of the aforementioned materials in the delithiation products of the first active material in the first cathode material layer allows the first cathode material layer to possess suitable resistivity and good adhesion properties, enabling the electrochemical device to achieve high energy density while improving its safety and cycle performance.
  • the mass percentage of delithiation products of the first active material is 30% to 96% based on the mass of the first cathode material layer. Adjusting the mass percentage of delithiation products of the first active material within the above range allows the first cathode material layer to have suitable resistivity and bonding properties, enabling the electrochemical device to have high energy density while improving its safety and cycle performance.
  • the mass of the second active material in the positive electrode is C mg/1540 mm2 , and 0.45% ⁇ A/C ⁇ 6%, preferably 0.9% ⁇ A/C ⁇ 4.5%. Adjusting the value of A/C within the above range can enable the electrochemical device to have high energy density while improving its safety and cycle performance.
  • the silicon element content is 1% to 20% by mass, based on the mass of the negative electrode material layer, which can enable the electrochemical device to have a high energy density while improving its safety performance.
  • the electrochemical device satisfies at least one of the following characteristics: (1) 1 mg/1540 mm2 ⁇ A ⁇ 14 mg/1540 mm2 ; (2) 3 mg/1540 mm2 ⁇ B ⁇ 12 mg/1540 mm2 ; (3) 200 mg/1540 mm2 ⁇ C ⁇ 300 mg/1540 mm2 . Satisfying the above characteristics allows the electrochemical device to have high energy density while improving its safety and cycle performance.
  • the first positive electrode material layer further includes inorganic materials, including at least one of alumina, lithium lanthanum zirconium oxide, lithium lanthanum titanate, lithium titanium aluminum phosphate, antimony-doped tin oxide, or titanium oxide; the mass percentage of the inorganic materials is 5% to 60% based on the mass of the first positive electrode material layer.
  • inorganic materials including at least one of alumina, lithium lanthanum zirconium oxide, lithium lanthanum titanate, lithium titanium aluminum phosphate, antimony-doped tin oxide, or titanium oxide; the mass percentage of the inorganic materials is 5% to 60% based on the mass of the first positive electrode material layer.
  • the specific capacity of the first positive electrode material layer is from 130 mAh/g to 780 mAh/g. Because the first active material has a high specific capacity, ensuring the specific capacity of the first positive electrode material layer is within the aforementioned range, during the first charge of the electrochemical device, it can mitigate the loss of active lithium caused by the formation of the solid electrolyte interphase (SEI) film, reduce irreversible capacity loss and the decrease in initial coulombic efficiency, thereby enabling the electrochemical device to achieve high energy density while further improving its cycle performance.
  • SEI solid electrolyte interphase
  • the specific capacity of the first positive electrode material layer is greater than or equal to the specific capacity of the second positive electrode material layer.
  • the specific capacities of the first and second positive electrode material layers satisfying the aforementioned relationship are more conducive to leveraging the lithium replenishment effect of the first active material during the initial charge-discharge cycle, reducing the loss of active lithium in the second positive electrode material layer, reducing irreversible capacity loss of the electrochemical device, and minimizing the decrease in initial coulombic efficiency. This results in the electrochemical device possessing high energy density while further improving its cycle performance.
  • the first active material comprises at least one of the following compounds: Li5QO4 or Li5QO6 , where Q comprises at least one of Ni, Co, Fe, Sn, or Mn, and the valence state of the Q element is lower than its highest oxidation state; Li2qFe0.5 (1+q) PO4 , 1 ⁇ q ⁇ 5; Li2-abcdNi2aRbMncMdO2 - f , 0 ⁇ a ⁇ 0.35, 0 ⁇ b ⁇ 0.5, 0.3 ⁇ c ⁇ 0.6 , 0 ⁇ d ⁇ 0.05, 0.7 ⁇ a+b+c+d ⁇ 0.9, 0 ⁇ f ⁇ 0.2, where R comprises at least one of Fe or Co, and M comprises at least one of Mg, Al, Ti, V, Cr, Cu, Y, Zr, Nb, Mo, La , or W; Li1 + eMn1- pXpO2- sYs The range is defined as follows: -0.1 ⁇ e ⁇ 0.2,
  • the first active material within this range exhibits high specific capacity and low initial coulombic efficiency, which helps reduce initial coulombic efficiency and irreversible capacity loss.
  • the aforementioned first active material also possesses good stability, enabling the electrochemical device to exhibit good cycle performance.
  • the positive electrode has suitable resistivity, and the positive electrode material layer exhibits high adhesion to the positive electrode current collector, further improving the safety performance of the electrochemical device. Therefore, selecting the aforementioned materials allows the electrochemical device to possess high energy density, good safety performance, and good cycle performance.
  • the first active material includes at least one selected from Li5FeO4 , Li5CoO4 , Li2MnO2 , Li1.2Ni0.13Fe0.13Mn0.5O2 , or LiFePO4 . Selecting the aforementioned first active material is more conducive to leveraging its lithium replenishment function, enabling the electrochemical device to achieve high energy density while further improving its safety and cycle performance.
  • the negative electrode material layer includes a negative electrode active material, which includes at least one of silicon, silicon-carbon, or silicon-oxygen. These materials have high specific capacity, and including them in the negative electrode active material enables the electrochemical device to have high energy density.
  • the negative electrode active material further includes at least one of graphite, hard carbon, soft carbon, or mesophase microcarbon spheres.
  • the resistivity of the positive electrode material layer is ⁇ m, where 44 ⁇ 155.
  • the resistivity of the positive electrode material layer being within this range indicates that the positive electrode material layer has suitable impedance, which can reduce the probability of internal short circuits in the electrochemical device and reduce the heat generated during internal short circuits, thereby further improving the safety performance of the electrochemical device.
  • the second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application.
  • the electrochemical device provided in the first aspect of this application has high energy density, good safety performance, and good cycle performance, thus the electronic device of this application has good performance and a long service life.
  • the electrochemical device includes a positive electrode and a negative electrode.
  • the positive electrode includes a positive current collector and a positive electrode material layer.
  • the positive electrode material layer includes a first positive electrode material layer and a second positive electrode material layer.
  • the first positive electrode material layer is disposed between the positive current collector and the second positive electrode material layer.
  • the first positive electrode material layer includes a first active material.
  • the delithiation products of the first active material include Li 5-x FeO 4-y , Li 5-x CoO 4-y , Li 2-z MnO 2 , Li 1.2-r Ni 0.13 Fe 0.13 Mn 0.54 O 2 , or Li 1-t FePO
  • the second positive electrode material layer comprises a second active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, or lithium manganese oxide
  • the negative electrode comprises a negative electrode material layer, which includes silicon, and the mass percentage of silicon is 1% to 50% based on the mass of the negative electrode material layer;
  • the mass of the delithiation product of the first active material in the positive electrode is A mg/1540 mm2
  • the mass of silicon in the negative electrode is B mg/1540 mm2 , with 29% ⁇ A/B ⁇ 230%.
  • An electrochemical device comprising a positive electrode and a negative electrode having the above characteristics, and by controlling the mass percentage
  • Figure 1 is a schematic diagram of the structure of the positive electrode sheet in one embodiment of this application.
  • positive electrode 10 first positive electrode material layer 11, second positive electrode material layer 12, positive electrode current collector 13.
  • a lithium-ion battery is used as an example of an electrochemical device to explain this application; however, the electrochemical device of this application is not limited to lithium-ion batteries.
  • the specific technical solution is as follows:
  • the first aspect of this application provides an electrochemical device comprising a positive electrode and a negative electrode.
  • the positive electrode includes a positive current collector and a positive electrode material layer.
  • the positive electrode material layer includes a first positive electrode material layer and a second positive electrode material layer, with the first positive electrode material layer disposed between the positive current collector and the second positive electrode material layer.
  • the first positive electrode material layer includes a first active material, and the delithiation product of the first active material includes at least one of Li 5-x FeO 4-y , Li 5-x CoO 4-y , Li 2-z MnO 2 , Li 1.2-r Ni 0.13 Fe 0.13 Mn 0.54 O 2 , or Li 1-t FePO 4 , wherein 4 ⁇ x ⁇ 5, 2 ⁇ y ⁇ 3, 1.6 ⁇ z ⁇ 2, 1 ⁇ r ⁇ 1.2, and 0.8 ⁇ t ⁇ 1.
  • the second positive electrode material layer includes a second active material, which includes at least one of lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, or lithium manganese oxide; the negative electrode sheet includes a negative electrode material layer, which includes silicon element.
  • the mass percentage content of silicon element is 1% to 50%, preferably 1% to 20%; for example, the mass percentage content of silicon element can be 1%, 2.2%, 5%, 8%, 10%, 12.2%, 14.2%, 17%, 20%, 23%, 26%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, or a range consisting of any two of these values.
  • the mass of the delithiation product of the first active material in the positive electrode is A mg/1540 mm2
  • the mass of silicon in the negative electrode is B mg/1540 mm2 , with 29% ⁇ A/B ⁇ 230%, preferably 39% ⁇ A/B ⁇ 200%.
  • the value of A/B can be 29%, 34%, 39%, 45%, 47%, 50%, 55%, 58%, 60%, 62%, 69%, 70%, 75%, 78%, 80%, 85%, 88%, 92%, 95%, 100%, 105%, 110%, 114%, 116%, 130%, 150%, 160%, 175%, 190%, 210%, 215%, 230%, or a range of any two of these values.
  • the electrochemical device can achieve a higher energy density.
  • Using the aforementioned second active material as the main positive electrode material allows the electrochemical device to exhibit better cycle performance and a higher initial coulombic efficiency.
  • SEI solid electrolyte interphase
  • the first active material undergoes delithiation to obtain a delithiation product of the first active material.
  • the first active material undergoes delithiation, yielding a delithiation product.
  • the lithium ions released from the first active material can replace those released from the second active material in the negative electrode film formation.
  • the minimal lithium ion re-intercalation after the initial delithiation helps reduce irreversible capacity loss during the first charge of the second active material, improving its initial coulombic efficiency and thus enhancing the initial coulombic efficiency and cycle performance of the secondary battery.
  • these characteristics allow for a suitable resistivity in the positive electrode and high adhesion between the positive electrode material layer and the positive current collector, thereby improving the safety performance of the electrochemical device. Therefore, combining the first active material (using the delithiation product) with the second active material and a silicon-containing negative electrode allows for high energy density while simultaneously improving cycle performance and safety. If the A/B ratio is too low, for example, less than 29%, the formation of the SEI film will consume lithium ions in the second active material, reducing active lithium and causing a decrease in the initial coulombic efficiency and irreversible capacity loss of the electrochemical device. This also negatively impacts the safety performance of the lithium-ion battery.
  • the combination of the first active material and silicon is unreasonable. Simultaneously, excessive side reactions occur between the first active material, the negative electrode material layer, and the electrolyte, significantly impacting the electrical performance of the electrochemical device. Capacity decay is rapid during cycling, which is detrimental to improving the device's cycle performance. Therefore, by selecting a second active material and the delithiation product as the first active material, and by including silicon in the negative electrode material layer and controlling its mass percentage and A/B ratio within the aforementioned range, the electrochemical device can simultaneously possess high energy density, good safety performance, and good cycle performance.
  • the initial charging process described above can be as follows: at 45°C, first charge at a constant current of 0.1 times (C) for 10 minutes, then charge at a constant current of 0.5C to a voltage Q (Q ⁇ 4.45V), and then charge at a constant voltage until the current is less than or equal to 0.05C.
  • Q can be 4.45V, 4.48V, 4.5V, 4.53V, 4.6V, 4.7V, or a range of any two of these values.
  • the initial charging process described above can be a formation process.
  • the positive electrode 10 in this application includes a first positive electrode material layer 11, a second positive electrode material layer 12, and a positive electrode current collector 13.
  • the first positive electrode material layer 11 is disposed between the positive electrode current collector 13 and the second positive electrode material layer 12, which can improve the protection of the positive electrode current collector and the interlayer adhesion of the positive electrode material layer, reduce the probability of internal short circuit and internal short circuit Joule heating caused by external mechanical damage, and make it more conducive to the electrochemical device having high energy density and good safety performance.
  • the delithiation products of the first active material include at least one of LiFeO2 , CoO2, MnO2 , Ni0.13Fe0.13Mn0.54O2 , FePO4 , FeO2 , Fe2O3 , or FeO .
  • the delithiation products of the first active material in the first positive electrode material layer include the aforementioned materials.
  • the lithium ions delithiated from the first active material can be consumed in place of the lithium ions delithiated from the second active material at the negative electrode to form a film.
  • the low rate of lithium ion re-intercalation after the initial delithiation helps reduce the irreversible capacity loss of the second active material during the first charge, improving the initial coulombic efficiency of the second active material. This, in turn, improves the initial coulombic efficiency and cycle performance of the secondary battery.
  • the first positive electrode material layer possesses suitable resistivity and good adhesion properties, enabling the electrochemical device to achieve high energy density while simultaneously improving its safety and cycle performance.
  • the mass percentage of the delithiation product of the first active material is 30% to 96%.
  • the mass percentage of the delithiation product of the first active material can be 30%, 36%, 40%, 45%, 50%, 55%, 58%, 60%, 62%, 69%, 70%, 75%, 78%, 80%, 85%, 88%, 92%, 96%, or a range consisting of any two of these values.
  • a mass percentage of the delithiation product of the first active material within the above range is beneficial for fully utilizing the lithium replenishment function of the first active material.
  • the first cathode material layer possesses suitable resistivity and good adhesion properties, enabling the electrochemical device to achieve high energy density while improving its safety and cycle performance.
  • the mass percentage of delithiation products of the first active material can be adjusted by changing the mass percentage of the first active material in the first positive electrode material layer during the preparation process. With other conditions remaining constant, increasing the mass percentage of the first active material increases the mass percentage of the delithiation products; conversely, decreasing the mass percentage of the first active material decreases the mass percentage of the delithiation products.
  • This application does not impose any particular limitation on the mass percentage of the first active material in the first cathode material layer.
  • the mass percentage of the delithiation product of the first active material can be adjusted according to the actual needs, as long as the purpose of this application can be achieved.
  • the mass of the second active material in the positive electrode is C mg/1540 mm2 , with 0.45% ⁇ A/C ⁇ 6%, preferably 0.9% ⁇ A/C ⁇ 4.5%.
  • the value of A/C can be 0.45%, 0.5%, 0.8%, 1%, 1.4%, 1.8%, 2%, 2.5%, 2.8%, 3%, 3.4%, 3.8%, 4%, 4.5%, 4.8%, 5%, 5.2%, 5.6%, 6%, or a range consisting of any two of these values. Adjusting the A/C value within the above range reduces side reactions between the first active material, the negative electrode material layer, and the electrolyte, which is beneficial for the positive electrode material layer to have both high specific capacity and good cycle stability. This results in the electrochemical device having high energy density while improving its safety and cycle performance.
  • A can be 1 mg/1540 mm2 , 3 mg/1540 mm2 , 5 mg/1540 mm2 , 6 mg/1540 mm2 , 8 mg/1540 mm2 , 10 mg/1540 mm2 , 12 mg/1540 mm2 , 13 mg/1540 mm2 , 14 mg/1540 mm2 , or a range of any two of these values;
  • B can be 3 mg/1540 mm2 , 4 mg/1540 mm2, 6 mg/1540 mm2 , 8 mg/1540 mm2 , 9 mg/1540 mm2 , 10 mg/1540 mm2 , 12 mg/1540 mm2 , or a range of any two of these values;
  • C can be 200 mg/1540 mm2 , 220 mg/1540 mm2, etc.
  • the values are 240 mg/1540 mm2 , 250 mg/1540 mm2 , 280 mg/1540 mm2 , 300 mg/1540 mm2 , or any two of these values. Meeting these characteristics allows the electrochemical device to achieve high energy density while improving its safety and cycle performance.
  • the negative electrode material layer includes a negative electrode active material, which includes at least one of silicon, silicon-carbon, or silicon-oxygen.
  • a negative electrode active material which includes at least one of silicon, silicon-carbon, or silicon-oxygen.
  • the aforementioned silicon-containing materials have high specific capacity, and including these silicon-containing materials in the negative electrode active material enables the electrochemical device to have high energy density.
  • the negative electrode active material further includes at least one of graphite, hard carbon, soft carbon, or mesophase microcarbon spheres.
  • the graphite mentioned above includes at least one of artificial graphite or natural graphite.
  • the mass percentage content of the aforementioned carbon material can be from 0.7% to 97.2%.
  • the silicon element in the negative electrode material layer is derived from silicon, silicon-carbon, or silicon-oxygen-containing materials. Based on the mass of the negative electrode material layer, the mass percentage of the silicon-containing material can range from 2% to 98.5%. Typically, the mass percentage of silicon and the value of B can be adjusted by changing the mass percentage of the silicon-containing material in the negative electrode material layer and the coating weight of the negative electrode material layer. With other conditions remaining constant, increasing the mass percentage of the silicon-containing material in the negative electrode material layer increases the mass percentage of silicon and the value of B; decreasing the mass percentage of the silicon-containing material in the negative electrode material layer decreases the mass percentage of silicon and the value of B. With other conditions remaining constant, increasing the coating weight of the negative electrode material layer increases the value of B; decreasing the coating weight of the negative electrode material layer decreases the value of B.
  • the value of A can be adjusted by changing the coating weight of the first positive electrode material layer and the mass percentage of the first active material in the first positive electrode material layer. With other conditions remaining constant, increasing the coating weight of the first positive electrode material layer increases A, and decreasing the coating weight decreases A. Similarly, with other conditions remaining constant, increasing the mass percentage of the first active material increases A, and decreasing the mass percentage of the first active material decreases A.
  • the value of C can be adjusted by changing the coating weight of the second positive electrode material layer and the mass percentage of the second active material in the second positive electrode material layer. With other conditions remaining constant, increasing the coating weight of the second positive electrode material layer increases C, and decreasing the coating weight decreases C. Similarly, with other conditions remaining constant, increasing the mass percentage of the second active material increases C, and decreasing the mass percentage of the second active material decreases C.
  • the coating weight of the first positive electrode material layer can be 3mg/ 1540mm2 to 20mg / 1540mm2
  • the coating weight of the second positive electrode material layer can be 200mg/1540mm2 to 300mg/ 1540mm2 .
  • the first cathode material layer further includes an inorganic material, which includes at least one of alumina, lithium lanthanum zirconium oxide, lithium lanthanum titanate, lithium titanium aluminum phosphate, antimony-doped tin oxide, or titanium oxide; based on the mass of the first cathode material layer, the mass percentage content of the inorganic material is 0.2% to 60%, preferably 5% to 60%.
  • the mass percentage content of the inorganic material can be 0.2%, 2%, 3%, 5%, 8%, 10%, 12.2%, 14.2%, 17%, 20%, 23%, 26%, 30%, 33%, 35%, 37%, 40%, 43%, 45%, 47%, 50%, 60%, or a range consisting of any two of these values.
  • the first positive electrode material layer includes the aforementioned inorganic materials, and by controlling its mass percentage content within the aforementioned range, the stability of the positive electrode material layer can be improved, enabling the first positive electrode material layer to have good adhesion properties and suitable resistivity, reducing the probability of internal short circuits and the heat generated by internal short circuits, thereby further improving the safety performance of the electrochemical device.
  • the specific capacity of the first positive electrode material layer is between 130 mAh/g and 780 mAh/g.
  • the specific capacity of the first positive electrode material layer can be 130 mAh/g, 150 mAh/g, 160 mAh/g, 180 mAh/g, 200 mAh/g, 250 mAh/g, 300 mAh/g, 350 mAh/g, 400 mAh/g, 500 mAh/g, 600 mAh/g, 700 mAh/g, 780 mAh/g, or a range of any two of these values. Because the first active material has a high specific capacity, the specific capacity of the first positive electrode material layer can be within the above range.
  • the specific capacity of the first positive electrode material layer is greater than or equal to the specific capacity of the second positive electrode material layer.
  • the specific capacity of the first cathode material layer is within the scope of this application, the specific capacities of the first cathode material layer and the second cathode material layer satisfy the above relationship, which is more conducive to reducing the loss of active lithium in the second cathode material layer during the first charge and discharge, giving full play to the lithium replenishment role of the first active material, reducing the irreversible capacity loss of the electrochemical device and the reduction of the first coulombic efficiency, thereby enabling the electrochemical device to have high energy density while further improving its cycle performance.
  • the specific capacity of the second cathode material layer can be from 130 mAh/g to 280 mAh/g.
  • the specific capacity of the second cathode material layer can be 130 mAh/g, 150 mAh/g, 170 mAh/g, 186 mAh/g, 192 mAh/g, 200 mAh/g, 220 mAh/g, 245 mAh/g, 260 mAh/g, 280 mAh/g, or a range of any two of these values.
  • a specific capacity of the second cathode material layer within the above range allows the electrochemical device to have a high energy density.
  • the specific capacity of the first positive electrode material layer can be adjusted by changing the type and mass percentage of active materials in the first positive electrode material layer. With other conditions remaining constant, using a first positive electrode material with a high specific capacity or increasing the mass percentage of active materials in the first positive electrode material layer increases the specific capacity of the first positive electrode material layer; using a first positive electrode material with a low specific capacity or decreasing the mass percentage of active materials in the first positive electrode material layer decreases the specific capacity of the first positive electrode material layer.
  • the specific capacity of the second positive electrode material layer can be adjusted by changing the type and mass percentage of active materials in the second positive electrode material layer.
  • using a second positive electrode material with a high specific capacity or increasing the mass percentage of active materials in the second positive electrode material layer increases the specific capacity of the second positive electrode layer; using a second positive electrode material with a low specific capacity or decreasing the mass percentage of active materials in the second positive electrode material layer decreases the specific capacity of the second positive electrode material layer.
  • the first active material comprises at least one of the following compounds: Li5QO4 or Li5QO6 , where Q comprises at least one of Ni, Co, Fe, Sn, or Mn, and the valence state of the Q element is lower than its highest oxidation state; Li2qFe0.5 (1+q) PO4 , 1 ⁇ q ⁇ 5; Li2-abcdNi2aRbMncMdO2 - f , 0 ⁇ a ⁇ 0.35, 0 ⁇ b ⁇ 0.5, 0.3 ⁇ c ⁇ 0.6 , 0 ⁇ d ⁇ 0.05, 0.7 ⁇ a+b+c+d ⁇ 0.9, 0 ⁇ f ⁇ 0.2, where R comprises at least one of Fe or Co, and M comprises at least one of Mg, Al, Ti, V, Cr, Cu, Y, Zr, Nb, Mo, La , or W; Li1 + eMn1- pXpO2- sYs The range is defined as follows: -0.1 ⁇ e ⁇ 0.2,
  • the first active material within this range exhibits high specific capacity and low initial coulombic efficiency, which helps reduce initial coulombic efficiency and irreversible capacity loss.
  • the aforementioned first active material also possesses good stability, enabling the electrochemical device to exhibit good cycle performance.
  • the positive electrode has suitable resistivity, and the positive electrode material layer exhibits high adhesion to the positive electrode current collector, further improving the safety performance of the electrochemical device. Therefore, selecting the aforementioned materials allows the electrochemical device to possess high energy density, good safety performance, and good cycle performance.
  • the first active material includes at least one selected from Li5FeO4 , Li5CoO4 , Li2MnO2 , Li1.2Ni0.13Fe0.13Mn0.5O2 , or LiFePO4 . Selecting the aforementioned first active material is more conducive to leveraging its lithium replenishment function, enabling the electrochemical device to achieve high energy density while further improving its safety and cycle performance.
  • the resistivity of the positive electrode material layer is ⁇ m, where 44 ⁇ 155.
  • the value of ⁇ can be 44, 50, 58, 65, 72, 84, 95, 100, 114, 130, 135, 148, 150, 155, or a range of any two of these values. Adjusting the resistivity of the positive electrode material layer within the above range allows the positive electrode material layer to have suitable impedance, reducing the probability of internal short circuits in the electrochemical device and reducing the heat generated during internal short circuits, thereby further improving the safety performance of the electrochemical device.
  • the resistivity of the first positive electrode material layer can be from 40 ⁇ m to 130 ⁇ m
  • the resistivity of the second positive electrode material layer can be from 2 ⁇ m to 50 ⁇ m.
  • the first positive electrode material layer of this application may further include a conductive agent.
  • a conductive agent does not impose any particular limitation on the conductive agent; for example, it may include, but is not limited to, at least one of conductive carbon black or carbon nanotubes.
  • This application does not impose any particular limitation on its mass percentage content; those skilled in the art can select it according to actual needs, as long as the purpose of this application is achieved.
  • the mass percentage content of the conductive agent can be from 0% to 5%.
  • the first positive electrode material layer may further include a binder.
  • This application does not particularly limit the type of binder, as long as it achieves the purpose of this application.
  • This application also does not particularly limit the mass percentage content of the binder, as long as it achieves the purpose of this application.
  • the mass percentage content of the binder can be from 3% to 15%.
  • the second positive electrode material layer may further include a conductive agent and a binder.
  • a conductive agent and a binder.
  • This application does not particularly limit the types of these agents, as long as they achieve the purpose of this application.
  • This application does not particularly limit the mass percentage content of the second active material, conductive agent, and binder in the second positive electrode material layer, as long as the purpose of this application is achieved.
  • the mass percentage content of the second active material can be 90% to 99%
  • the mass percentage content of the conductive agent can be 0.2% to 5%
  • the mass percentage content of the binder can be 0.2% to 5%.
  • the aforementioned binder may include, but is not limited to, at least one of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, lithium polyacrylate, polyimide, polyvinyl alcohol, carboxymethyl cellulose, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, polyamide-imide, styrene-butadiene rubber, or polyvinylidene fluoride.
  • the aforementioned conductive agent may include, but is not limited to, at least one of conductive carbon black (Super P), carbon nanotubes (CNTs), carbon fibers, flake graphite, graphene, metallic materials, or conductive polymers.
  • the aforementioned carbon nanotubes may include, but are not limited to, single-walled carbon nanotubes and/or multi-walled carbon nanotubes.
  • the aforementioned carbon fibers may include, but are not limited to, vapor-grown carbon fibers (VGCF) and/or carbon nanofibers.
  • the aforementioned metallic materials may include, but are not limited to, metal powders and/or metal fibers; specifically, the metal may include, but is not limited to, at least one of copper, nickel, aluminum, or silver.
  • the aforementioned conductive polymer may include, but is not limited to, at least one of polyphenylene derivatives, polyaniline, polythiophene, polyacetylene, or polypyrrole.
  • the positive electrode material layer is disposed on at least one surface of the positive electrode current collector. That is, the positive electrode material layer can be disposed on one surface or two surfaces in the thickness direction of the positive electrode current collector. It should be noted that the "surface” here can be the entire area of the surface of the positive electrode current collector or a part of the surface of the positive electrode current collector. This application has no particular limitation, as long as the purpose of this application can be achieved.
  • the positive electrode current collector may comprise aluminum foil, aluminum alloy foil, or a composite current collector (e.g., an aluminum-carbon composite current collector).
  • This application does not impose any particular limitation on the thickness of the positive electrode current collector, as long as it achieves the purpose of this application.
  • the thickness of the positive electrode current collector may be 5 ⁇ m to 20 ⁇ m.
  • the thickness of the first positive electrode material layer and the second positive electrode material layer may be 30 ⁇ m to 120 ⁇ m.
  • the positive electrode sheet can be prepared by the following method: a first positive electrode material layer slurry is uniformly coated onto one surface of the positive electrode current collector and dried; then, a second positive electrode material layer slurry is uniformly coated onto the surface of the first positive electrode material layer, and after drying, a positive electrode sheet with a single-sided positive electrode material layer is obtained. The above coating steps are repeated on the other surface of the positive electrode current collector, and after drying, a positive electrode sheet with a double-sided positive electrode material layer is obtained. After coating, the positive electrode sheet is obtained by cold pressing and cutting.
  • the first positive electrode material layer slurry described above can be prepared by the following steps: mixing a first active material and a binder, optionally adding an inorganic material or mixing an inorganic material and a conductive agent, adding N-methylpyrrolidone (NMP) and stirring until homogeneous, to obtain a first positive electrode material layer slurry with a solid content of 40 wt% to 85 wt%.
  • NMP N-methylpyrrolidone
  • the second positive electrode material layer slurry described above can be prepared by the following steps: mixing a second active material, a binder, and a conductive agent, adding N-methylpyrrolidone (NMP) and stirring until homogeneous, to obtain a second positive electrode material layer slurry with a solid content of 65 wt% to 85 wt%.
  • NMP N-methylpyrrolidone
  • the negative electrode sheet of this application also includes a negative electrode current collector.
  • a negative electrode material layer is disposed on at least one surface of the negative electrode current collector.
  • the negative electrode material layer can be disposed on one surface or two surfaces along the thickness direction of the negative electrode current collector.
  • surface here can refer to the entire area of the negative electrode current collector or only a portion thereof; this application has no particular limitation, as long as the purpose of this application is achieved.
  • the thickness of the negative electrode current collector and the negative electrode material layer is 30 ⁇ m to 160 ⁇ m.
  • the negative electrode material layer of this application may further include a conductive agent, a binder, and a thickener.
  • This application does not impose any particular limitation on the conductive agent and binder, as long as they achieve the purpose of this application; for example, they may be at least one of the aforementioned conductive agents and binders.
  • the thickener may include at least one of sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, or carboxymethyl cellulose. Based on the mass of the negative electrode material layer, the mass percentage content of the conductive agent may be 0.5% to 5%, the mass percentage content of the binder may be 0.2% to 2%, and the mass percentage content of the thickener may be 0.1% to 2%.
  • the preparation method of the negative electrode sheet there are no particular limitations on the preparation method of the negative electrode sheet, as long as it can achieve the purpose of this application.
  • it can be prepared by the following method: mixing negative electrode active material, conductive agent, binder, and thickener, adding deionized water and stirring evenly to obtain a negative electrode slurry with a solid content of 40wt% to 75wt%.
  • the negative electrode slurry is uniformly coated on one surface of the negative electrode current collector, and after drying, a negative electrode sheet with a single-sided negative electrode material layer is obtained. Then, the above coating steps are repeated on the other surface of the negative electrode current collector, and after drying, a negative electrode sheet with a double-sided negative electrode material layer is obtained. After coating, the negative electrode sheet is obtained by cold pressing and cutting.
  • the secondary battery of this application also includes an electrolyte, which comprises a lithium salt and a non-aqueous solvent.
  • the lithium salt may include at least one of LiPF6 , LiNO3 , LiBF4 , LiClO4 , LiB( C6H5 ) 4 , LiCH3SO3 , LiCF3SO3 , LiN( SO2CF3 ) 2 , LiC( SO2CF3 ) 3 , Li2SiF6 , lithium bis( oxalato )borate (LiBOB) , lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), or lithium difluoroborate.
  • the non-aqueous solvent may include, but is not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents.
  • the aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds or cyclic carbonate compounds.
  • the aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, or methyl ethyl carbonate.
  • the aforementioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate, propylene carbonate (PC), butylene carbonate, or vinylethylene carbonate.
  • the aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, ⁇ -butyrolactone, decanolactone, valproic acid lactone, or caprolactone.
  • the aforementioned ether compounds may include, but are not limited to, at least one of dimethyl ether, dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran.
  • the other organic solvents mentioned above may include, but are not limited to, at least one of dimethyl sulfoxide, 1,3-dioxolane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.
  • This application does not limit the mass percentage of lithium salt and non-aqueous solvents, as long as the purpose of this application is achieved.
  • the electrochemical device of this application also includes a separator membrane.
  • the material of the separator membrane may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid.
  • the type of separator membrane may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.
  • the separator membrane may include a substrate layer and a surface treatment layer.
  • the substrate layer may be a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide.
  • a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used.
  • a surface treatment layer is disposed on at least one surface of the substrate layer.
  • the surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by a mixture of polymer and inorganic materials.
  • the inorganic layer includes inorganic particles and a binder.
  • the inorganic particles may include at least one of alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate.
  • the binder may be at least one of the binders described above.
  • the polymer layer includes a polymer
  • the polymer material includes at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).
  • the thickness of the separator there is no particular limitation on the thickness of the separator, as long as it can achieve the purpose of this application.
  • the thickness of the separator can be from 3 ⁇ m to 30 ⁇ m.
  • the electrochemical device also includes a housing for accommodating the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of electrochemical devices.
  • a housing for accommodating the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of electrochemical devices.
  • This application does not limit the scope of these other components.
  • This application does not impose any particular limitation on the housing; it can be a housing known in the art, as long as it achieves the purpose of this application.
  • the housing can be a rigid housing or a flexible housing.
  • the material of the rigid housing can be metal; this application does not limit the type of metal and can use known metal rigid housings, as long as they achieve the purpose of this application.
  • the flexible housing can be a metal-plastic film, such as aluminum-plastic film, steel-plastic film, etc.
  • electrochemical devices may include, but are not limited to: lithium-ion batteries, sodium-ion batteries, lithium polymer secondary batteries, and lithium-ion polymer secondary batteries.
  • the preparation process of the electrochemical device described in this application is well known to those skilled in the art, and this application does not impose any particular limitations.
  • the preparation process of the electrochemical device may include, but is not limited to, the following steps: stacking the positive electrode, the separator, and the negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the electrochemical device.
  • overcurrent protection elements, conductive plates, etc. may be placed in the housing as needed to prevent pressure rise and overcharging/discharging inside the electrochemical device.
  • the second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application.
  • the electrochemical device provided in the first aspect of this application has high energy density, good safety performance, and good cycle performance, thus the electronic device of this application has good performance and a long service life.
  • the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.
  • Disassembly process under full charge The lithium-ion batteries prepared in each embodiment and comparative example were charged at a constant current of 0.2C to the upper voltage limit setting value, reaching the full charge state. After disassembly, the positive and negative electrode plates were removed, cleaned with dimethyl carbonate, and dried at 60°C to obtain positive and negative electrode plate samples.
  • the above-mentioned upper voltage limit setting value is determined by the type of second active material.
  • the above-mentioned upper voltage limit setting value is 4.53V; when the second active material is lithium nickel cobalt manganese oxide, the above-mentioned upper voltage limit setting value is 4.25V; when the second active material is lithium iron phosphate, the above-mentioned upper voltage limit setting value is 4.3V; when the second active material is lithium nickel cobalt aluminum oxide, the above-mentioned upper voltage limit setting value is 4.2V; and when the second active material is lithium manganese oxide, the above-mentioned upper voltage limit setting value is 4.3V.
  • Disassembly process under full discharge condition The lithium-ion batteries prepared in each embodiment and comparative example were discharged at a constant current of 0.2C to the lower voltage limit setting value to reach the full discharge state. After disassembly, the positive and negative electrode sheets were removed, cleaned with dimethyl carbonate, and dried at 60°C to obtain positive and negative electrode sheet samples.
  • the aforementioned lower voltage limit setting value is determined by the type of the second active material.
  • the aforementioned lower voltage limit setting value is 3V; when the second active material is lithium nickel cobalt manganese oxide, the aforementioned lower voltage limit setting value is 3.2V; when the second active material is lithium iron phosphate, the aforementioned lower voltage limit setting value is 2.4V; when the second active material is lithium nickel cobalt aluminum oxide, the aforementioned lower voltage limit setting value is 2.8V; and when the second active material is lithium manganese oxide, the aforementioned lower voltage limit setting value is 2.4V.
  • a positive electrode sample was obtained by disassembling a lithium-ion battery in a fully discharged state.
  • the positive electrode material layer was scraped off from the surface of the positive electrode current collector.
  • Powder from the first positive electrode material layer was scraped off from the side that was originally close to the positive electrode current collector.
  • the sample was placed in a muffle furnace and sintered at 500°C for 6 hours.
  • the calcined powder sample was collected and then the following elemental analysis was performed.
  • the composition and structure information of the delithiation product of the first active material were obtained by X-ray diffraction (XRD) and Raman spectroscopy, thereby deducing its chemical formula and calculating its mass percentage content.
  • Elemental analysis 0.4 g of the above powder sample was digested with 10 mL of aqua regia, which was obtained by mixing concentrated nitric acid and concentrated hydrochloric acid in a 1:1 volume ratio. The volume was then adjusted to 100 mL, and the content of each element in the solution was measured using an inductively coupled plasma optical emission spectrometer (ICP).
  • ICP inductively coupled plasma optical emission spectrometer
  • the powder samples were subjected to XRD tests using an X-ray diffractometer (Bruker D8 ADVANCE).
  • the XRD pattern of the first cathode material layer was obtained.
  • the phase composition of the delithiation products of the first active material could be obtained.
  • Cu K ⁇ rays were used.
  • Raman spectroscopy analysis The above powder sample was subjected to Raman testing using a Raman spectrometer (LabRAM HR Evolution) to obtain the Raman spectrum of the first cathode material layer. By comparing the characteristic peaks with the standard spectrum, the material metal bond structure information of the delithiation products of the first active material can be obtained.
  • a negative electrode sample was obtained by disassembling a lithium-ion battery in a fully discharged state.
  • the negative electrode material layer powder on the surface of the negative electrode current collector was scraped off. 1g of the powder sample was taken, and the mass percentage of silicon in the negative electrode material layer was determined by ICP.
  • a positive electrode sample was obtained by disassembling a lithium-ion battery under full charge.
  • the positive electrode material layer was scraped off from the surface of the positive electrode current collector.
  • Powder of the first positive electrode material layer in the positive electrode sample was scraped from the side originally close to the positive electrode current collector (i.e., within a range of 0 to 2 ⁇ m from the surface of the positive electrode current collector, parallel to the thickness direction of the current collector). Its mass was weighed as M1 mg, and the area of the positive electrode current collector was measured as S1 mm2 . Then, the mass percentage w1 of the delithiation product of the first active material was measured using a thermogravimetric analyzer. Therefore, the mass of the delithiation product of the first active material in the positive electrode is calculated as M1 ⁇ w1 ⁇ 1540/ S1 , in mg/1540 mm2 .
  • a lithium-ion battery was disassembled in a fully discharged state to obtain a negative electrode sample.
  • the negative electrode material layer powder on the surface of the negative electrode current collector was scraped off and weighed as M 2 mg.
  • the area of the current collector of the negative electrode sample was measured as S 2 mm 2.
  • the mass percentage of silicon in the negative electrode material layer, w 2 was determined using ICP. Therefore, the mass of silicon in the negative electrode is calculated as M 2 ⁇ w 2 ⁇ 1540 / S 2 , in mg/1540 mm 2 .
  • a positive electrode sample was obtained by disassembling a lithium-ion battery in a fully discharged state.
  • the positive electrode material layer was scraped off from the surface of the positive electrode current collector.
  • Powder of the second positive electrode material layer was scraped from the side of the positive electrode sample away from the positive electrode current collector (i.e., within a range of 0 to 20 ⁇ m from the surface of the positive electrode sheet, parallel to the thickness direction of the current collector). Its mass was weighed as M 3 mg, and the area of the positive electrode current collector was measured as S 3 mm 2.
  • the first positive electrode material layer slurry was prepared according to the slurry ratios in the various embodiments and comparative examples.
  • the slurry of the first positive electrode material layer was coated onto the positive electrode current collector, and after drying and cold pressing, a positive electrode sheet with a single-sided thickness of 12.6 ⁇ m was obtained.
  • the mass of the positive electrode current collector and the positive electrode sheet were weighed, and the mass of the positive electrode current collector per unit area and the mass of the positive electrode sheet per unit area were calculated.
  • the mass of the first positive electrode material layer per unit area was calculated to be M4.
  • the above-mentioned positive electrode sheet, separator, and lithium sheet were stacked sequentially, and an electrolyte was injected to obtain a coin cell.
  • the above-mentioned positive electrode current collector, separator, and electrolyte are the same as in Example 1.
  • the coin cell was charged to 4.58V at a constant current rate of 0.05C, and the initial charge capacity was recorded.
  • the specific capacity ⁇ 1 of the first positive electrode material layer is equal to the initial charge capacity / M4, in mAh/g.
  • the second positive electrode material layer slurry was prepared according to the slurry ratios in the various embodiments and comparative examples.
  • the slurry of the second positive electrode material layer was coated onto the positive electrode current collector, and after drying and cold pressing, a positive electrode sheet with a single-sided thickness of 53.6 ⁇ m was obtained.
  • the mass of the positive electrode current collector and the positive electrode sheet were weighed, and the mass of the positive electrode current collector per unit area and the mass of the positive electrode sheet per unit area were calculated.
  • the mass of the second positive electrode material layer per unit area was calculated to be M5.
  • the above-mentioned positive electrode sheet, separator, and lithium sheet were stacked sequentially, and an electrolyte was injected to obtain a coin cell.
  • the above-mentioned positive electrode current collector, separator, and electrolyte were the same as in Example 1.
  • the coin cell was charged to 4.58V at a constant current rate of 0.05C, and the initial charge capacity was recorded.
  • the specific capacity ⁇ 2 of the second positive electrode material layer is calculated as: initial charge capacity / M5, in mAh/g.
  • the positive electrode sheet was obtained by disassembling a lithium-ion battery in a fully discharged state. Positive electrode material was scraped off from one surface of the positive current collector. A positive electrode sheet sample with a width of 20 mm and a length of 160 mm was then cut. The sample was adhered to a steel plate with a width of 20 mm and a length of 300 mm using double-sided tape with the positive current collector facing the steel plate. A paper strip of the same width and length as the positive electrode sheet, 200 mm long, was connected and fixed to a section of the sample strip. The sample was then tested using a high-speed rail AI-3000 tensile testing machine.
  • the test sample was fixed on the test table, the paper strip was folded upwards 180° and secured with clamps, and then the tensile testing machine began pulling the paper strip at a speed of 50 mm/min.
  • the tensile displacement was 50 mm.
  • the adhesion force F between the first positive electrode material layer and the positive current collector was calculated when the curve flattened and the displacement was greater than 10 mm.
  • the unit is N/m.
  • a positive electrode sample is obtained by disassembling a lithium-ion battery in a fully charged state.
  • the total thickness of the positive electrode is measured, and then the resistance R of the positive electrode is measured using a film resistivity meter (PPM), where the probe area of the PPM is S.
  • PPM film resistivity meter
  • the positive electrode material layer is then scraped off, and the thickness of the positive electrode current collector is measured.
  • the thickness h of the positive electrode material layer is calculated.
  • the lithium-ion battery was charged at a constant current rate of 3C to 4.53V, then charged at a constant voltage rate until the current was less than or equal to 0.05C, and then discharged at a constant current rate of 0.5C to 3V. This constitutes one charge-discharge cycle.
  • the discharge capacity of the lithium-ion battery in the first cycle was recorded.
  • the lithium-ion battery was charged and discharged in the same manner, and the discharge capacity of each cycle was recorded, until the discharge capacity of the lithium-ion battery decreased to 80% of the discharge capacity of the first cycle. The number of charge-discharge cycles was recorded.
  • the lithium-ion battery was placed in a 25°C constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. The battery was then charged at a constant current of 0.5C to a voltage of 4.53V, followed by constant voltage charging at 4.53V to a current of 0.025C, resulting in a fully charged lithium-ion battery. The fully charged battery was transferred to a nail-piercing tester. Maintaining the test environment temperature at 25°C ⁇ 2°C, a 4mm diameter steel nail was driven through the center of the battery at a constant speed of 30mm/s for 300s. The battery was considered to have passed if it did not catch fire or explode. Ten lithium-ion batteries were tested in each embodiment or comparative example. The nail-piercing test pass rate (N/10) was used as an indicator to evaluate the safety performance of the lithium-ion battery, where N is the number of lithium-ion batteries that passed the nail-piercing test.
  • the lithium-ion battery was placed in a 25°C constant temperature chamber and left to stand for 30 minutes to allow it to reach a constant temperature. The battery was then charged at a constant current of 0.5C to a voltage of 4.53V, followed by constant voltage charging at 4.53V to a current of 0.05C, and finally discharged at 0.5C to a voltage of 3.0V. The discharge energy (in Wh) was recorded.
  • the volumetric energy density VED discharge energy / (length ⁇ width ⁇ thickness of lithium-ion battery), in Wh/L.
  • length, width, and thickness refer to the length, width, and thickness of the packaged lithium-ion battery.
  • the first active material Li5FeO4 and the binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 97:3, and N-methylpyrrolidone (NMP) was added as a solvent. After stirring evenly, a first cathode material slurry with a solid content of 45wt% was prepared.
  • the second active material lithium cobalt oxide ( LiCoO2 ), conductive carbon black, carbon nanotubes, and binder polyvinylidene fluoride were mixed in a mass ratio of 97.4:0.5:0.5:1.4. NMP was added as a solvent, and the mixture was stirred evenly to prepare a second cathode material slurry with a solid content of 75wt%.
  • LiCoO2 lithium cobalt oxide
  • conductive carbon black conductive carbon black
  • carbon nanotubes carbon nanotubes
  • binder polyvinylidene fluoride binder polyvinylidene fluoride
  • the prepared first positive electrode material slurry was uniformly coated onto one surface of a 10 ⁇ m thick aluminum foil for the positive electrode current collector. After drying, a positive electrode sheet with a single-sided first positive electrode material layer was obtained. Then, a second positive electrode material slurry was uniformly coated onto the surface of the first positive electrode material layer, and dried to obtain a positive electrode sheet with both a single-sided first and second positive electrode material layer. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. The sheet was then vacuum-dried at 120°C for 6 hours, followed by cold pressing, cutting, and welding of tabs to obtain a positive electrode sheet with dimensions of 74 mm ⁇ 867 mm for later use.
  • the thickness of the single-sided first positive electrode material layer was 2.6 ⁇ m, and the coating weight was 5 mg/1540 mm2 .
  • the thickness of the single-sided second positive electrode material layer was 43.6 ⁇ m, and the coating weight was 230 mg/1540 mm2 .
  • a mixture of silicon carbide and artificial graphite (negative electrode active material), polyacrylic acid binder, sodium carboxymethyl cellulose thickener, and conductive carbon black conductive agent was prepared in a mass ratio of 20:77.5:1.5:0.5.
  • Deionized water was added as a solvent to prepare a slurry with a solid content of 45 wt%.
  • the slurry was stirred evenly in a vacuum mixer to obtain the negative electrode slurry.
  • the negative electrode slurry was uniformly coated onto one surface of a 6 ⁇ m thick copper foil current collector and dried at 120°C to obtain a single-sided coated negative electrode sheet with a coating weight of 105 mg/1540 mm2 .
  • the above steps were repeated on the other surface of the copper foil to obtain a double-sided coated negative electrode sheet. After drying at 120°C for 6 hours, the sheet was cold-pressed, cut, and had tabs welded to obtain a negative electrode sheet with a size of 78 mm ⁇ 875 mm for later use.
  • the thickness of the single-sided negative electrode layer was 35.5 ⁇ m.
  • a 16 ⁇ m thick polyethylene film (supplied by Celgard) was used as the separator.
  • lithium salt LiPF6 was added to the non-aqueous solvent and mixed thoroughly to obtain the electrolyte.
  • concentration of lithium salt was 1.15 mol/L.
  • the prepared positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets to provide isolation.
  • the electrode assembly is then wound to obtain the electrode assembly.
  • the electrode assembly is placed in an aluminum-plastic film packaging bag and dried in an 85°C vacuum oven for 12 hours to remove moisture.
  • the prepared electrolyte is then injected, and the lithium-ion battery is obtained through vacuum sealing, settling, formation, degassing, and edge trimming.
  • the formation process involves charging the lithium-ion battery at a constant current rate of 0.1C for 10 minutes at 45°C, followed by constant current charging at a constant current rate of 0.5C to 4.53V, and then constant voltage charging to a current of 0.05C.
  • the coating weight of the first positive electrode material layer can be adjusted to make A as shown in Table 1
  • the coating weight of the negative electrode material layer can be adjusted to make B as shown in Table 1.
  • the mass percentage of the delithiation products of the first active material is adjusted by controlling its mass percentage content.
  • the mass percentage content of the binder changes accordingly, and the sum of the mass percentage contents of the three is 100%.
  • the mass percentage of the delithiation product of the first active material is adjusted by controlling its mass percentage content.
  • the mass percentage content of the binder changes accordingly, and the sum of the mass percentage contents of the three is 100%.
  • the second cathode material slurry was prepared using the process described in Example 1.
  • the prepared second positive electrode material slurry was uniformly coated onto one surface of a 10 ⁇ m thick aluminum foil used as a positive electrode current collector. After drying, a positive electrode sheet with a single-sided second positive electrode material layer was obtained. The above steps were then repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided second positive electrode material layer. This was then vacuum dried at 120°C for 6 hours, followed by cold pressing, cutting, and welding of tabs to obtain a positive electrode sheet with dimensions of 74 mm ⁇ 867 mm for later use.
  • the thickness of the single-sided second positive electrode material layer was 46.2 ⁇ m, and the coating weight of the second positive electrode material layer was 235 mg/1540 mm2 .
  • the second cathode material slurry was prepared using the process described in Example 1.
  • Inorganic material Al2O3 and binder polyvinylidene fluoride (PVDF) were mixed at a mass ratio of 95:5, and N-methylpyrrolidone (NMP) was added as a solvent. After stirring evenly, a first cathode material slurry with a solid content of 45 wt% was prepared.
  • the prepared first positive electrode material slurry was uniformly coated onto one surface of a 10 ⁇ m thick aluminum foil for the positive electrode current collector. After drying, a positive electrode sheet with a single-sided first positive electrode material layer was obtained. Then, a second positive electrode material slurry was uniformly coated onto the surface of the first positive electrode material layer, and dried to obtain a positive electrode sheet with both a single-sided first and second positive electrode material layer. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided positive electrode material layer. The sheet was then vacuum-dried at 120°C for 6 hours, followed by cold pressing, cutting, and welding of tabs to obtain a positive electrode sheet with dimensions of 74 mm ⁇ 867 mm for later use.
  • the thickness of the single-sided first positive electrode material layer was 2.6 ⁇ m, and the coating weight was 5 mg/1540 mm2 .
  • the thickness of the single-sided second positive electrode material layer was 43.6 ⁇ m, and the coating weight was 230 mg/1540 mm2 .
  • Inorganic material Al2O3 , conductive agent conductive carbon black (SP), and binder polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 93:2:5 , and N-methylpyrrolidone (NMP) was added as a solvent. After stirring evenly, a first cathode material slurry with a solid content of 45wt% was prepared.
  • Example 10 Except for adjusting the relevant parameters as shown in Table 1, the rest is the same as in Example 10.
  • the positive electrode material layer can have a suitable resistivity, and the first positive electrode material layer and the current collector have a high bonding force.
  • the lithium-ion battery simultaneously exhibits higher volumetric energy density, pin penetration rate, and more cycle times, indicating that the lithium-ion battery simultaneously possesses higher energy density, better safety performance, and better cycle performance.
  • no first positive electrode material layer was provided.
  • the composition of the first positive electrode material layers in Comparative Examples 2 and 3 is not within the scope of this application.
  • Comparative Examples 4 to 7 at least one of the A/B ratio or the mass percentage of silicon is not within the scope of this application.
  • the lithium-ion batteries in Comparative Examples 1, 3 to 7 cannot simultaneously achieve high volumetric energy density, pin penetration rate, and a large number of cycle times, indicating poor overall performance. Because the resistivity of the first positive electrode material layer in Comparative Example 2 is too high, the lithium-ion battery cannot operate, and no relevant performance data was measured.
  • the type of the first active material and its delithiation products typically affect the energy density, safety performance, and cycle performance of a lithium-ion battery.
  • the lithium-ion battery can simultaneously possess higher volumetric energy density, pin penetration rate, and more cycle life, indicating that the lithium-ion battery simultaneously exhibits higher energy density, better safety performance, and better cycle performance.
  • A/B and A/C typically affect the energy density, safety performance, and cycle performance of lithium-ion batteries. As can be seen from Examples 10 to 14, adjusting the values of A/B and A/C within the scope of this application can enable lithium-ion batteries to simultaneously possess higher volumetric energy density, pin penetration rate, and more cycle counts, indicating that lithium-ion batteries simultaneously exhibit higher energy density, better safety performance, and better cycle performance.
  • the mass percentage of silicon typically affects the energy density, safety performance, and cycle performance of lithium-ion batteries.
  • lithium-ion batteries can simultaneously have higher volumetric energy density, pin penetration rate, and more cycle times, indicating that lithium-ion batteries simultaneously have higher energy density, better safety performance, and better cycle performance.
  • the mass percentage of delithiation products in the first active material typically affects the energy density, safety performance, and cycle performance of lithium-ion batteries. As can be seen from Examples 1, 12, and 18, adjusting the mass percentage of delithiation products in the first active material within the scope of this application can enable lithium-ion batteries to simultaneously possess higher volumetric energy density, pin penetration rate, and more cycle life, indicating that lithium-ion batteries simultaneously exhibit higher energy density, better safety performance, and better cycle performance.
  • the mass percentage of inorganic materials typically affects the energy density, safety performance, and cycle performance of lithium-ion batteries. As can be seen from Examples 19 to 23, by adjusting the mass percentage of inorganic materials within the scope of this application, lithium-ion batteries can simultaneously exhibit higher volumetric energy density, pin penetration rate, and more cycle times, indicating that lithium-ion batteries simultaneously possess higher energy density, better safety performance, and better cycle performance.
  • inorganic material typically affects the energy density, safety performance, and cycle performance of lithium-ion batteries. As can be seen from Examples 19 to 23, selecting inorganic materials within the scope of this application can enable lithium-ion batteries to simultaneously possess higher volumetric energy density, pin penetration rate, and more cycle life, indicating that lithium-ion batteries simultaneously exhibit higher energy density, better safety performance, and better cycle performance.
  • the type of second active material typically affects the energy density, safety performance, and cycle performance of lithium-ion batteries. As can be seen from Examples 12, 26, and 27, selecting the second active material within the scope of this application can enable lithium-ion batteries to simultaneously possess higher volumetric energy density, pin penetration rate, and more cycle life, indicating that lithium-ion batteries simultaneously exhibit higher energy density, better safety performance, and better cycle performance.

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Abstract

一种电化学装置及电子装置。电化学装置包括正极极片和负极极片，正极极片包括第一活性材料，第一活性材料的脱锂产物包括Li 5-xFeO 4-y、Li 5-xCoO 4-y、Li 2-zMnO 2、Li 1.2-rNi 0.13Fe 0.13Mn 0.54O 2或Li 1-tFePO 4中的至少一种；负极极片包括负极材料层，负极材料层包括硅元素，基于负极材料层的质量，硅元素的质量百分含量为1％至50％；正极极片中第一活性材料的脱锂产物的质量为A mg/1540mm 2，负极极片中硅元素的质量为Bmg/1540mm 2，29％≤A/B≤230％。具有上述特征，可以使电化学装置具有高能量密度、良好的安全性能和循环性能。

Description

一种电化学装置及电子装置
本申请要求于2024年07月09日提交中国国家知识产权局专利局、申请号为202410916811.X发明名称为“一种电化学装置及电子装置”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及电化学技术领域，特别是涉及一种电化学装置及电子装置。
背景技术
电化学装置，例如锂离子电池，已伴随着科技的进步及环保要求的提高进入了我们日常的生活。随着锂离子电池的大量普及，在用户端会出现因外力刺破锂离子电池导致的安全问题等，其安全性能越来越受到人们的重视，尤其是一些手机爆炸事件的持续发酵，使得包括使用者、售后端及锂离子电池生产厂商都对锂离子电池的安全性能提出了新的要求。
目前改善锂离子电池安全性能的方法多是以牺牲其能量密度和循环性能为代价，因此，急需提供一种在较高能量密度的条件下，能够提高锂离子电池的安全性能和循环性能的技术手段。
发明内容
本申请的目的在于提供一种电化学装置及电子装置，以使得电化学装置兼顾高能量密度以及良好的安全性能和循环性能。具体技术方案如下：
本申请的第一方面提供了一种电化学装置，其包括正极极片和负极极片，正极极片包括正极集流体和正极材料层，正极材料层包括第一正极材料层和第二正极材料层，第一正极材料层设置于正极集流体和第二正极材料层之间，第一正极材料层包括第一活性材料，第一活性材料的脱锂产物包括Li5-xFeO4-y、Li5-xCoO4-y、Li2-zMnO2、Li1.2-rNi0.13Fe0.13Mn0.54O2或Li1-tFePO4中的至少一种，其中，4≤x≤5，2≤y≤3，1.6≤z≤2，1≤r≤1.2，0.8≤t≤1。第二正极材料层包括第二活性材料，第二活性材料包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂或锰酸锂中的至少一种；负极极片包括负极材料层，负极材料层包括硅元素，基于负极材料层的质量，硅元素的质量百分含量为1％至50％。正极极片中第一活性材料的脱锂产物的质量为A mg/1540mm2，负极极片中硅元素的质量为B mg/1540mm2，29％≤A/B≤230％。电化学装置包括具有上述特征的正极极片和负极极片，并调控硅元素的质量百分含量以及A/B的值在上述范围内，负极材料层具有较高的克容量，同时采用第一活性材料进行补锂，有利于减少第二活性材料首次充电不可逆容量的损失，提高第二活性材料首次库伦效率，从而可以提高二次电池的能量密度和循环性能。同时，第一活性材料的脱锂产物为上述物质可以使得正极极片具有合适的电阻率和粘结性能，因此还能够提高电化学装置的安全性能。从而，满足上述特征，可以使得电化学装置兼顾高能量密度、良好的安全性能和循环性能。
在本申请的一些实施方案中，39％≤A/B≤200％。调控A/B的值在上述范围内，可以使得电化学装置具有高能量密度、更好的安全性能和循环性能。
在本申请的一些实施方案中，第一活性材料的脱锂产物包括LiFeO2、CoO2、MnO2、Ni0.13Fe0.13Mn0.54O2、FePO4、FeO2、Fe2O3或FeO中的至少一种。第一正极材料层中的第一活性材料的脱锂产物包括上述材料，可以使得第一正极材料层具有合适的电阻率和良好的粘结性能，可以使得电化学装置具有高能量密度的同时提高其安全性能和循环性能。
在本申请的一些实施方案中，基于第一正极材料层的质量，第一活性材料的脱锂产物的质量百分含量为30％至96％。调控第一活性材料的脱锂产物的质量百分含量在上述范围内，可以使得第一正极材料层具有合适的电阻率和粘结性能，可以使得电化学装置具有高能量密度的同时提高其安全性能和循环性能。
在本申请的一些实施方案中，正极极片中，第二活性材料的质量为C mg/1540mm2，0.45％≤A/C≤6％，优选0.9％≤A/C≤4.5％，调控A/C的值在上述范围内，可以使得电化学装置具有高能量密度的同时提高其安全性能和循环性能。
在本申请的一些实施方案中，基于所述负极材料层的质量，所述硅元素的质量百分含量为1％至20％，可以使得电化学装置具有较高能量密度的同时提高其安全性能。
在本申请的一些实施方案中，电化学装置满足以下特征中的至少一者：(1)1mg/1540mm2/≤A≤14mg/1540mm2；(2)3mg/1540mm2≤B≤12mg/1540mm2；(3)200mg/1540mm2≤C≤300mg/1540mm2。满足上述特征，可以使得电化学装置具有高能量密度的同时提高其安全性能和循环性能。
在本申请的一些实施方案中，第一正极材料层还包括无机材料，无机材料包括氧化铝、锂镧锆氧、钛酸镧锂、磷酸钛铝锂、掺锑氧化锡或氧化钛中的至少一种；基于第一正极材料层的质量，无机材料的质量百分含量为5％至60％。第一正极材料层包括上述无机材料，并调控其质量百分含量在上述范围内，可以提高第一正极材料层的稳定性，使得第一正极材料层具有良好的粘结性能以及合适的电阻率，降低内部短路发生的概率以及内部短路产生的热量，从而有利于进一步提高电化学装置的安全性能。
在本申请的一些实施方案中，第一正极材料层的比容量为130mAh/g至780mAh/g。由于第一活性材料具有较高的比容量，使得第一正极材料层的比容量在上述范围内，在电化学装置的首次充电时，可以改善因固态电解质界面膜(SEI膜)的形成造成的活性锂损失，减少电化学装置的不可逆容量损失以及首次库伦效率的降低，从而使得电化学装置具有高能量密度的同时进一步提高其循环性能。
在本申请的一些实施方案中，第一正极材料层的比容量大于或等于第二正极材料层的比容量。第一正极材料层和第二正极材料层的比容量满足上述关系，更有利于在首次充放电时，发挥第一活性材料的补锂作用，减少第二正极材料层的活性锂损失，减少电化学装置的不可逆容量损失以及首次库伦效率的降低，从而使得电化学装置具有高能量密度的同时进一步提高其循环性能。
在本申请的一些实施方案中，第一活性材料包括以下化合物中的至少一种：Li5QO4或Li5QO6，Q包括Ni、Co、Fe、Sn或Mn中的至少一种，Q元素的价态低于其自身的最高氧化价态；LiqFe0.5(1+q)PO4，1≤q≤5；Li2-a-b-c-dNiaRbMncMdO2-f，0≤a＜0.35，0＜b＜0.5，0.3＜c≤0.6，0≤d＜0.05，0.7＜a+b+c+d＜0.9，0≤f＜0.2，R包括Fe或Co中的至少一种，M包括Mg、Al、Ti、V、Cr、Cu、Y、Zr、Nb、Mo、La或W中的至少一种；Li1+eMn1-pXpO2-sYs，-0.1＜e＜0.2，0≤p＜0.2，0≤s＜0.2，X包括Fe、Co、Ni、Ti、Zn、Mg、Al、V、Cr或Zr中的至少一种，Y包括S、N、F、Cl或Br中的至少一种。上述范围内的第一活性材料具有较高的比容量和较低的首次库伦效率，有利于减少首次库伦效率以及不可逆容量的损失。上述第一活性材料具有良好的稳定性，可以使得电化学装置具有良好的循环性能。同时，正极极片具有合适的电阻率、正极材料层与正极集流体之间具有较高的粘结力，还能够提高电化学装置的安全性能。因此，选用上述材料，可以使得电化学装置具有高能量密度、良好的安全性能和循环性能。
在本申请的一些实施方案中，第一活性材料包括Li5FeO4、Li5CoO4、Li2MnO2、Li1.2Ni0.13Fe0.13Mn0.54O2或LiFePO4中的至少一种。选用上述第一活性材料，更有利于发挥第一活性材料的补锂作用，使得电化学装置具有高能量密度的同时进一步提高其安全性能和循环性能。
在本申请的一些实施方案中，负极材料层包括负极活性材料，负极活性材料包括硅、硅碳或硅氧中的至少一种。上述材料具有较高的克容量，负极活性材料包括上述材料，可以使得电化学装置具有较高的能量密度。
在本申请的一些实施方案中，负极活性材料还包括石墨、硬碳、软碳或中间相微碳球中的至少一种。
在本申请的一些实施方案中，正极材料层的电阻率为ρΩ·m，44≤ρ≤155。正极材料层的电阻率在上述范围内，说明正极材料层具有合适的阻抗，可以降低电化学装置内部短路发生的概率以及减少内部短路时产生的热量，从而有利于进一步提高电化学装置的安全性能。
本申请的第二方面提供了一种电子装置，其包括本申请第一方面提供的电化学装置。本申请第一方面提供的电化学装置具有高能量密度、良好的安全性能和循环性能，从而本申请的电子装置具有良好的使用性能和较长的使用寿命。
本申请提供了一种电化学装置及电子装置。电化学装置包括正极极片和负极极片，正极极片包括正极集流体和正极材料层，正极材料层包括第一正极材料层和第二正极材料层，第一正极材料层设置于正极集流体和第二正极材料层之间，第一正极材料层包括第一活性材料，第一活性材料的脱锂产物包括Li5-xFeO4-y、Li5-xCoO4-y、Li2-zMnO2、Li1.2-rNi0.13Fe0.13Mn0.54O2或Li1-tFePO4中的至少一种，第二正极材料层包括第二活性材料，第二活性材料包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂或锰酸锂中的至少一种；负极极片包括负极材料层，负极材料层包括硅元素，基于负极材料层的质量，硅元素的质量百分含量为1％至50％；正极极片中第一活性材料的脱锂产物的质量为A mg/1540mm2，负极极片中硅元素的质量为B mg/1540mm2，29％≤A/B≤230％。电化学装置包括具有上述特征的正极极片和负极极片，并调控硅元素的质量百分含量以及A/B的值在上述范围内，可以使得电化学装置具有高能量密度、良好的安全性能和循环性能。
当然，实施本申请的任一产品或方法并不一定需要同时达到以上所述的所有优点。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述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，还可以根据这些附图获得其他的实施例。
图1为本申请的一种实施方式中的正极极片的结构示意图。
附图标记：正极极片10，第一正极材料层11，第二正极材料层12，正极集流体13。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，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。本领域技术人员基于本申请所获得的所有其他实施例，都属于本申请保护的范围。
需要说明的是，本申请的具体实施方式中，以锂离子电池作为电化学装置的例子来解释本申请，但是本申请的电化学装置并不仅限于锂离子电池。具体技术方案如下：
本申请的第一方面提供了一种电化学装置，其包括正极极片和负极极片，正极极片包括正极集流体和正极材料层，正极材料层包括第一正极材料层和第二正极材料层，第一正极材料层设置于正极集流体和第二正极材料层之间。第一正极材料层包括第一活性材料，第一活性材料的脱锂产物包括Li5-xFeO4-y、Li5-xCoO4-y、Li2-zMnO2、Li1.2-rNi0.13Fe0.13Mn0.54O2或Li1-tFePO4中的至少一种，其中，4≤x≤5，2≤y≤3，1.6≤z≤2，1≤r≤1.2，0.8≤t≤1。第二正极材料层包括第二活性材料，第二活性材料包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂或锰酸锂中的至少一种；负极极片包括负极材料层，负极材料层包括硅元素，基于负极材料层的质量，硅元素的质量百分含量为1％至50％，优选1％至20％；例如硅元素的质量百分含量可以为1％、2.2％、5％、8％、10％、12.2％、14.2％、17％、20％、23％、26％、30％、33％、35％、37％、40％、43％、45％、47％、50％或为其中任意两个数值组成的范围。正极极片中第一活性材料的脱锂产物的质量为A mg/1540mm2，负极极片中硅元素的质量为B mg/1540mm2，29％≤A/B≤230％，优选为39％≤A/B≤200％。例如A/B的值可以为29％、34％、39％、45％、47％、50％、55％、58％、60％、62％、69％、70％、75％、78％、80％、85％、88％、92％、95％、100％、105％、110％、114％、116％、130％、150％、160％、175％、190％、210％、215％、230％或为其中任意两个数值组成的范围。
负极材料层包括硅元素并调控硅元素的质量百分含量在上述范围内，可以使得电化学装置具有更高的能量密度。选用上述第二活性材料作为正极主材，可以使得电化学装置具有较好的循环性能和较高的首次库伦效率。在电化学装置的首次充电时，含硅负极表面的固态电解质界面膜(SEI膜)的形成会消耗大量正极脱出的活性锂，造成电化学装置的首次库伦效率降低以及不可逆的容量损失。发明人发现，采用第一活性材料进行补锂，第一活性材料具有较高的比容量和较低的首次库伦效率。在电化学装置首次充电后，上述第一活性材料脱锂后得到第一活性材料的脱锂产物。在充电过程中，第一活性材料脱锂，得到第一活性材料的脱锂产物，第一活性材料脱出的锂离子可以在负极代替第二活性材料脱出的锂离子消耗成膜，并且在首次脱锂后锂离子回嵌少，有利于减少第二活性材料首次充电时不可逆容量的损失，提高第二活性材料的首次库伦效率，从而有利于提高二次电池的首次库伦效率和循环性能。同时，具有上述特征，可以使得正极极片具有合适的电阻率、正极材料层与正极集流体之间具有较高的粘结力，因此还能够提高电化学装置的安全性能。从而，采用脱锂产物为上述物质的第一活性材料与上述第二活性材料以及含硅的负极极片进行搭配，有利于可以使得电化学装置具有高能量密度的同时提高其循环性能和安全性能。A/B的值过小时，例如小于29％，SEI膜的形成会消耗第二活性材料中的锂离子，使得活性锂减少，造成电化学装置的首次库伦效率降低以及不可逆的容量损失，同时也不利于提高锂离子电池的安全性能。A/B的值过大时，例如大于230％，第一活性材料和硅元素搭配不合理，同时，第一活性材料与负极材料层以及电解液之间发生过多副反应，会对电化学装置的电性能影响较大，在循环过程中容量衰减较快，不利于改善电化学装置的循环性能。因此，选用第二活性材料以及脱锂产物为上述物质的第一活性材料，负极材料层包括硅元素并调控其质量百分含量以及A/B的值在上述范围内，可以使得电化学装置同时具有高能量密度、良好的安全性能和循环性能。
在一些实施方案中，上述首次充电过程的流程可以为：在45℃下，首先以0.1倍率(C)恒流充电10min，随后以0.5C恒流充电至电压Q(Q≥4.45V)，再恒压充电至电流小于等于0.05C。例如Q可以为4.45V、4.48V、4.5V、4.53V、4.6V、4.7V或为其中任意两个数值组成的范围。在需要进行化成的电化学装置中，上述首次充电流程可以为化成过程。
本申请中，如图1所示，正极极片10包括第一正极材料层11、第二正极材料层12和正极集流体13，第一正极材料层11设置于正极集流体13和第二正极材料层12之间，可以使得对正极集流体的保护性以及正极材料层的层间粘结更好，减少外部机械破坏引起的内短路概率和内短路焦耳热，更有利于使得电化学装置具有高能量密度的同时具有良好的安全性能。
在本申请的一些实施方案中，第一活性材料的脱锂产物包括LiFeO2、CoO2、MnO2、Ni0.13Fe0.13Mn0.54O2、FePO4、FeO2、Fe2O3或FeO中的至少一种。第一正极材料层中的第一活性材料的脱锂产物包括上述材料，第一活性材料脱出的锂离子可以在负极代替第二活性材料脱出的锂离子消耗成膜，并且在首次脱锂后锂离子回嵌少，有利于减少第二活性材料首次充电时不可逆容量的损失，提高第二活性材料的首次库伦效率，从而可以提高二次电池的首次库伦效率和循环性能，同时第一正极材料层具有合适的电阻率和良好的粘结性能，可以使得电化学装置具有高能量密度的同时提高其安全性能和循环性能。
在本申请的一些实施方案中，基于第一正极材料层的质量，第一活性材料的脱锂产物的质量百分含量为30％至96％，例如第一活性材料的脱锂产物的质量百分含量可以为30％、36％、40％、45％、50％、55％、58％、60％、62％、69％、70％、75％、78％、80％、85％、88％、92％、96％或为其中任意两个数值组成的范围。第一活性材料的脱锂产物的质量百分含量在上述范围内，有利于充分发挥第一活性材料的补锂作用，同时第一正极材料层具有合适的电阻率和良好的粘结性能，可以使得电化学装置具有高能量密度的同时提高其安全性能和循环性能。
通常情况下，可以通过改变制备过程中第一正极材料层中第一活性材料的质量百分含量调整第一活性材料的脱锂产物的质量百分含量。其他条件不变的情况下，第一活性材料的质量百分含量增大，第一活性材料的脱锂产物的质量百分含量增大；第一活性材料的质量百分含量减小，第一活性材料的脱锂产物的质量百分含量减小。
本申请对第一正极材料层中第一活性材料的质量百分含量没有特别限制，可以根据实际需要的第一活性材料的脱锂产物的质量百分含量进行调整，只要能实现本申请的目的即可。
在本申请的一些实施方案中，正极极片中，第二活性材料的质量为C mg/1540mm2，0.45％≤A/C≤6％，优选0.9％≤A/C≤4.5％；例如A/C的值可以为0.45％、0.5％、0.8％、1％、1.4％、1.8％、2％、2.5％、2.8％、3％、3.4％、3.8％、4％、4.5％、4.8％、5％、5.2％、5.6％、6％或为其中任意两个数值组成的范围。调控A/C的值在上述范围内，第一活性材料与负极材料层和电解液之间的副反应较少，有利于使得正极材料层具有较高的比容量的同时具有良好的循环稳定性，从而使得电化学装置具有高能量密度的同时提高其安全性能和循环性能。
在本申请的一些实施方案中，1mg/1540mm2≤A≤14mg/1540mm2，3mg/1540mm2≤B≤12mg/1540mm2，200mg/1540mm2≤C≤300mg/1540mm2。例如A可以为1mg/1540mm2、3mg/1540mm2、5mg/1540mm2、6mg/1540mm2、8mg/1540mm2、10mg/1540mm2、12mg/1540mm2、13mg/1540mm2、14mg/1540mm2或为其中任意两个数值组成的范围，B可以为3mg/1540mm2、4mg/1540mm2、6mg/1540mm2、8mg/1540mm2、9mg/1540mm2、10mg/1540mm2、12mg/1540mm2或为其中任意两个数值组成的范围，C可以为200mg/1540mm2、220mg/1540mm2、240mg/1540mm2、250mg/1540mm2、280mg/1540mm2、300mg/1540mm2或为其中任意两个数值组成的范围。满足上述特征，可以使得电化学装置具有高能量密度的同时提高其安全性能和循环性能。
在本申请的一些实施方案中，负极材料层包括负极活性材料，负极活性材料包括硅、硅碳或硅氧中的至少一种。上述含硅材料具有较高的克容量，负极活性材料包括上述含硅材料，可以使得电化学装置具有较高的能量密度。
在本申请的一些实施方案中，负极活性材料还包括石墨、硬碳、软碳或中间相微碳球中的至少一种。上述石墨包括人造石墨或天然石墨中的至少一种。本申请中，基于负极材料层的质量，上述碳材料的质量百分含量可以为0.7％至97.2％。
在一些实施方案中，负极材料层中的硅元素来源于上述硅、硅碳或硅氧等含硅材料。基于负极材料层的质量，含硅材料的质量百分含量可以为2％至98.5％。通常情况下，可以通过改变负极材料层中上述含硅材料的质量百分含量以及负极材料层的涂布重量来调整硅元素的质量百分含量和B的值。其他条件不变的情况下，增加负极材料层中含硅材料的质量百分含量，硅元素的质量百分含量和B的值增大；减少负极材料层中含硅材料的质量百分含量，硅元素的质量百分含量和B的值减小。其他条件不变的情况下，增加负极材料层的涂布重量，B的值增大；减少负极材料层的涂布重量，B的值减小。
通常情况下，可以通过改变第一正极材料层的涂布重量和第一正极材料层中第一活性材料的质量百分含量来调整A的值。其他条件不变的情况下，增大第一正极材料层的涂布重量，A增大，减少第一正极材料层的涂布重量，A减小。其他条件不变的情况下，增大第一活性材料的质量百分含量，A增大，减少第一活性材料的质量百分含量，A减小。
通常情况下，可以通过改变第二正极材料层的涂布重量和第二正极材料层中第二活性材料的质量百分含量来调整C的值。其他条件不变的情况下，增大第二正极材料层的涂布重量，C增大，减少第二正极材料层的涂布重量，C减小。其他条件不变的情况下，增大第二活性材料的质量百分含量，C增大，减少第二活性材料的质量百分含量，C减小。
本申请中，对第一正极材料层的涂布重量和第二正极材料层的涂布重量没有特别限制，只要能实现本申请的目的即可，例如，第一正极材料层的涂布重量可以为3mg/1540mm2至20mg/1540mm2，第二正极材料层的涂布重量可以为200mg/1540mm2至300mg/1540mm2。
在本申请的一些实施方案中，第一正极材料层还包括无机材料，无机材料包括氧化铝、锂镧锆氧、钛酸镧锂、磷酸钛铝锂、掺锑氧化锡或氧化钛中的至少一种；基于第一正极材料层的质量，无机材料的质量百分含量为0.2％至60％，优选5％至60％。例如无机材料的质量百分含量可以为0.2％、2％、3％、5％、8％、10％、12.2％、14.2％、17％、20％、23％、26％、30％、33％、35％、37％、40％、43％、45％、47％、50％、60％或为其中任意两个数值组成的范围。第一正极材料层包括上述无机材料，并调控其质量百分含量在上述范围内，可以提高正极材料层的稳定性，使得第一正极材料层具有良好的粘结性能以及合适的电阻率，降低内部短路发生的概率以及内部短路产生的热量，从而有利于进一步提高电化学装置的安全性能。
在本申请的一些实施方案中，第一正极材料层的比容量为130mAh/g至780mAh/g。例如，第一正极材料层的比容量可以为130mAh/g、150mAh/g、160mAh/g、180mAh/g、200mAh/g、250mAh/g、300mAh/g、350mAh/g、400mAh/g、500mAh/g、600mAh/g、700mAh/g、780mAh/g或为其中任意两个数值组成的范围。由于第一活性材料具有较高的比容量，可以使得第一正极材料层的比容量在上述范围内，从而在电化学装置的首次充电时，可以改善因SEI膜的形成造成的活性锂损失，减少电化学装置的不可逆容量损失以及首次库伦效率的降低，从而使得电化学装置具有高能量密度的同时进一步提高其循环性能和安全性能。在本申请的一些实施方案中，优选第一正极材料层的比容量大于或等于第二正极材料层的比容量。第一正极材料层的比容量在本申请范围内的同时，第一正极材料层和第二正极材料层的比容量满足上述关系，更有利于在首次充放电时，减少第二正极材料层的活性锂损失，发挥第一活性材料的补锂作用，减少电化学装置的不可逆容量损失以及首次库伦效率的降低，从而使得电化学装置具有高能量密度的同时进一步提高其循环性能。
在一些实施方案中，第二正极材料层的比容量可以为130mAh/g至280mAh/g，例如，第二正极材料层的比容量可以为130mAh/g、150mAh/g、170mAh/g、186mAh/g、192mAh/g、200mAh/g、220mAh/g、245mAh/g、260mAh/g、280mAh/g或为其中任意两个数值组成的范围。第二正极材料层的比容量在上述范围内，可以使得电化学装置具有较高的能量密度。
通常情况下，可以通过调整第一正极材料层活性物质种类和质量百分比来调整第一正极材料层的比容量。其他条件不变的情况下，使用高比容量的第一正极材料或增加第一正极材料层活性物质质量百分比，第一正极材料层的比容量增加，使用低比容量的第一正极材料或减少第一正极材料层活性物质质量百分比，第一正极材料层的比容量减小。可以通过调整第二正极材料层活性物质种类和质量百分比来调整第二正极材料层的比容量。其他条件不变的情况下，使用高比容量的第二正极材料或增加第而正极材料层活性物质质量百分比，第二正极材料层的比容量增加，使用低比容量的第二正极材料或减少第二正极材料层活性物质质量百分比，第二正极材料层的比容量减小。
在本申请的一些实施方案中，第一活性材料包括以下化合物中的至少一种：Li5QO4或Li5QO6，Q包括Ni、Co、Fe、Sn或Mn中的至少一种，Q元素的价态低于其自身的最高氧化价态；LiqFe0.5(1+q)PO4，1≤q≤5；Li2-a-b-c-dNiaRbMncMdO2-f，0≤a＜0.35，0＜b＜0.5，0.3＜c≤0.6，0≤d＜0.05，0.7＜a+b+c+d＜0.9，0≤f＜0.2，R包括Fe或Co中的至少一种，M包括Mg、Al、Ti、V、Cr、Cu、Y、Zr、Nb、Mo、La或W中的至少一种；Li1+eMn1-pXpO2-sYs，-0.1＜e＜0.2，0≤p＜0.2，0≤s＜0.2，X包括Fe、Co、Ni、Ti、Zn、Mg、Al、V、Cr或Zr中的至少一种，Y包括S、N、F、Cl或Br中的至少一种。上述范围内的第一活性材料具有较高的比容量和较低的首次库伦效率，有利于减少首次库伦效率以及不可逆容量的损失。上述第一活性材料具有良好的稳定性，可以使得电化学装置具有良好的循环性能。同时，正极极片具有合适的电阻率、正极材料层与正极集流体之间具有较高的粘结力，还能够提高电化学装置的安全性能。因此，选用上述材料，可以使得电化学装置具有高能量密度、良好的安全性能和循环性能。
在本申请的一些实施方案中，第一活性材料包括Li5FeO4、Li5CoO4、Li2MnO2、Li1.2Ni0.13Fe0.13Mn0.54O2或LiFePO4中的至少一种。选用上述第一活性材料，更有利于发挥第一活性材料的补锂作用，使得电化学装置具有高能量密度的同时进一步提高其安全性能和循环性能。
在本申请的一些实施方案中，正极材料层的电阻率为ρΩ·m，44≤ρ≤155。例如ρ的值可以为44、50、58、65、72、84、95、100、114、130、135、148、150、155或为其中任意两个数值组成的范围。调控正极材料层的电阻率在上述范围内，可以使得正极材料层具有合适的阻抗，降低电化学装置内部短路发生的概率以及减少内部短路时产生的热量，从而有利于进一步提高电化学装置的安全性能。
本申请对第一正极材料层和第二正极材料层的电阻率没有特别限制，只要二者之和在上述范围内即可。例如，第一正极材料层的电阻率可以为40Ω·m至130Ω·m，第二正极材料层的电阻率可以为2Ω·m至50Ω·m。
在一些实施方案中，本申请的第一正极材料层还可以包括导电剂，本申请对导电剂没有特别限制，例如，可以包括但不限于导电碳黑或碳纳米管中的至少一种。本申请对其质量百分含量没有特别限制，本领域技术人员可以根据实际需要进行选择，只要能实现本申请的目的即可。例如，基于第一正极材料层的质量，导电剂的质量百分含量可以为0％至5％。
本申请中，第一正极材料层还可以包括粘结剂，本申请对粘结剂的种类没有特别限制，只要能实现本申请的目的即可。本申请对粘结剂的质量百分含量没有特别限制，只要能实现本申请的目的即可。例如，基于第一正极材料层的质量，粘结剂的质量百分含量可以为3％至15％。
在一些实施方案中，第一正极材料层包括第一活性材料的脱锂产物和粘结剂，在另一些实施方案中，第一正极材料层包括第一活性材料的脱锂产物、无机材料和粘结剂。在又一些实施方案中，第一正极材料层包括第一活性材料的脱锂产物、无机材料、粘结剂和导电剂。
本申请中，第二正极材料层还可以包括导电剂和粘结剂，本申请对其种类没有特别限制，只要能实现本申请的目的即可。本申请对第二正极材料层中第二活性材料、导电剂和粘结剂的质量百分含量没有特别限制，只要能够实现本申请目的即可。例如，基于第二正极材料层的质量，第二活性材料的质量百分含量可以为90％至99％，导电剂的质量百分含量可以为0.2％至5％，粘结剂的质量百分含量可以为0.2％至5％。
上述粘结剂可以包括但不限于聚丙烯酸、聚丙烯酸钠、聚丙烯酸钾、聚丙烯酸锂、聚酰亚胺、聚乙烯醇、羧甲基纤维素、羧甲基纤维素钠、羧甲基纤维素锂、聚酰胺酰亚胺、丁苯橡胶或聚偏二氟乙烯中的至少一种。上述导电剂可以包括但不限于导电炭黑(Super P)、碳纳米管(CNTs)、碳纤维、鳞片石墨、石墨烯、金属材料或导电聚合物中的至少一种。上述碳纳米管可以包括但不限于单壁碳纳米管和/或多壁碳纳米管。上述碳纤维可以包括但不限于气相生长碳纤维(VGCF)和/或纳米碳纤维。上述金属材料可以包括但不限于金属粉和/或金属纤维，具体地，金属可以包括但不限于铜、镍、铝或银中的至少一种。上述导电聚合物可以包括但不限于聚亚苯基衍生物、聚苯胺、聚噻吩、聚乙炔或聚吡咯中的至少一种。
本申请中，正极材料层设置于正极集流体至少一个表面上，即正极材料层可以设置于正极集流体厚度方向上的一个表面上，也可以设置于正极集流体厚度方向上的两个表面上。需要说明，这里的“表面”可以是正极集流体表面的全部区域，也可以是正极集流体表面的部分区域，本申请没有特别限制，只要能实现本申请目的即可。
本申请对正极集流体没有特别限制，只要能够实现本申请目的即可。例如，正极集流体可以包含铝箔、铝合金箔或复合集流体(例如铝碳复合集流体)等。本申请对正极集流体的厚度没有特别限制，只要能够实现本申请目的即可。例如，正极集流体的厚度为5μm至20μm。本申请对第一正极材料层和第二正极材料层的厚度没有特别限制，只要能够实现本申请目的即可。例如，第一正极材料层的厚度为2μm至5μm，第二正极材料层的厚度为30μm至120μm。
本申请中，对正极极片的制备方法没有特别限制，只要能实现本申请的目的即可。在一些实施方案中，正极极片可以通过以下方法制备：将第一正极材料层浆料均匀涂覆于正极集流体的一个表面上晾干，然后将第二正极材料层浆料均匀涂覆于第一正极材料层表面，烘干后得到单面涂覆正极材料层的正极极片。在正极集流体的另一个表面上重复以上涂布步骤，烘干后得到双面涂布正极材料层的正极极片，涂布完成后，经冷压、裁切得到正极极片。
上述第一正极材料层浆料可以通过以下步骤制备：将第一活性材料、粘结剂混合，可选地加入无机材料或者无机材料和导电剂混合，加入N-甲基吡咯烷酮(NMP)搅拌均匀，获得固含量为40wt％至85wt％的第一正极材料层浆料。上述第二正极材料层浆料可以通过以下步骤制备：将第二活性材料、粘结剂、导电剂混合，加入N-甲基吡咯烷酮(NMP)搅拌均匀，获得固含量为65wt％至85wt％的第二正极材料层浆料。
本申请的负极极片还包括负极集流体，负极材料层设置于负极集流体的至少一个表面上，在本申请中，负极材料层可以设置于负极集流体厚度方向上的一个表面上，也可以设置于负极集流体厚度方向上的两个表面上。需要说明，这里的“表面”可以是负极集流体的全部区域，也可以是负极集流体的部分区域，本申请没有特别限制，只要能实现本申请目的即可。在本申请中，对负极集流体和负极材料层的厚度没有特别限制，只要能够实现本申请目的即可。例如，负极集流体的厚度为4μm至12μm，单面负极材料层的厚度为30μm至160μm。
本申请的负极材料层还可以包含导电剂、粘结剂和增稠剂。本申请对导电剂和粘结剂没有特别限制，只要能够实现本申请目的即可，例如可以是上述导电剂和上述粘结剂中的至少一种。增稠剂可以包括羧甲基纤维素钠、羧甲基纤维素锂或羧甲基纤维素中的至少一种。基于负极材料层的质量，导电剂的质量百分含量可以为0.5％至5％，粘接剂的质量百分含量可以为0.2％至2％，增稠剂的质量百分含量可以为0.1％至2％。
本申请中，对负极极片的制备方法没有特别限制，只要能实现本申请的目的即可，例如可以通过以下方法制备：将负极活性材料、导电剂、粘结剂、增稠剂混合，加入去离子水搅拌均匀，获得固含量为40wt％至75wt％的负极浆料。将负极浆料均匀涂覆于负极集流体的一个表面上，烘干后得到单面涂覆负极材料层的负极极片。然后在负极集流体的另一个表面上重复以上涂布步骤，烘干后得到双面涂布负极材料层的负极极片，涂布完成后，经冷压、裁切得到负极极片。
本申请的二次电池还包括电解液，电解液包括锂盐和非水溶剂。锂盐可以包括LiPF6、LiNO3、LiBF4、LiClO4、LiB(C6H5)4、LiCH3SO3、LiCF3SO3、LiN(SO2CF3)2、LiC(SO2CF3)3、Li2SiF6、双草酸硼酸锂(LiBOB)、双三氟甲磺酰亚胺锂(LiTFSI)或二氟硼酸锂中的至少一种。非水溶剂可以包括但不限于碳酸酯化合物、羧酸酯化合物、醚化合物或其它有机溶剂中的至少一种。上述碳酸酯化合物可以包括但不限于链状碳酸酯化合物或环状碳酸酯化合物中的至少一种。上述链状碳酸酯化合物可以包括但不限于碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯或碳酸甲乙酯中的至少一种。上述环状碳酸酯可以包括但不限于碳酸乙烯酯、碳酸丙烯酯(PC)、碳酸亚丁酯或碳酸乙烯基亚乙酯中的至少一种。上述羧酸酯化合物可以包括但不限于甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸正丙酯、乙酸叔丁酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、γ-丁内酯、癸内酯、戊内酯或己内酯中的至少一种。上述醚化合物可以包括但不限于二甲醚、二丁醚、四甘醇二甲醚、二甘醇二甲醚、1,2-二甲氧基乙烷、1,2-二乙氧基乙烷、1-乙氧基-1-甲氧基乙烷、2-甲基四氢呋喃或四氢呋喃中的至少一种。上述其它有机溶剂可以包括但不限于二甲亚砜、1,3-二氧环戊烷、环丁砜、甲基环丁砜、1,3-二甲基-2-咪唑烷酮、N-甲基-2-吡咯烷酮、二甲基甲酰胺、乙腈、磷酸三甲酯、磷酸三乙酯或磷酸三辛酯中的至少一种。本申请对锂盐和非水溶剂的质量百分含量不做限定，只要能实现本申请的目的即可。
本申请的电化学装置还包括隔离膜。本申请对隔离膜没有特别限制，只要能够实现本申请目的即可。例如，隔离膜的材料可以包括但不限于聚乙烯(PE)、聚丙烯(PP)为主的聚烯烃(PO)类、聚酯(例如，聚对苯二甲酸二乙酯(PET)膜)、纤维素、聚酰亚胺(PI)、聚酰胺(PA)、氨纶或芳纶中的至少一种。隔离膜的类型可以包括织造膜、非织造膜、微孔膜、复合膜、碾压膜或纺丝膜中的至少一种。在一些实施方案中，隔离膜可以包括基材层和表面处理层。基材层可以为具有多孔结构的无纺布、膜或复合膜，基材层的材料可以包括聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯或聚酰亚胺中的至少一种。任选地，可以使用聚丙烯多孔膜、聚乙烯多孔膜、聚丙烯无纺布、聚乙烯无纺布或聚丙烯-聚乙烯-聚丙烯多孔复合膜。任选地，基材层的至少一个表面上设置有表面处理层，表面处理层可以是聚合物层或无机物层，也可以是混合聚合物与无机物所形成的层。在一些实施方案中，无机物层包括无机颗粒和粘结剂。本申请对无机颗粒没有特别限制，例如无机颗粒可以包括氧化铝、氧化硅、氧化镁、氧化钛、二氧化铪、氧化锡、二氧化铈、氧化镍、氧化锌、氧化钙、氧化锆、氧化钇、碳化硅、勃姆石、氢氧化铝、氢氧化镁、氢氧化钙或硫酸钡中的至少一种。本申请对粘结剂没有特别限制，例如粘结剂可以是上述粘结剂中的至少一种。在本申请的一些实施方案中，聚合物层包括聚合物，聚合物的材料包括聚酰胺、聚丙烯腈、丙烯酸酯聚合物、聚丙烯酸、聚丙烯酸盐、聚乙烯吡咯烷酮、聚乙烯醚或聚偏二氟乙烯或聚(偏二氟乙烯-六氟丙烯)中的至少一种。在本申请中，隔离膜的厚度没有特别限制，只要能实现本申请的目的即可，例如隔离膜的厚度可以为3μm至30μm。
电化学装置还包括壳体，用于容纳正极极片、隔离膜、负极极片和电解液，以及电化学装置领域中已知的其它部件，本申请对上述其它部件不做限定。本申请对壳体没有特别限制，可以为本领域公知的壳体，只要能够实现本申请目的即可。例如，壳体可以为硬壳壳体或柔性壳体。硬壳壳体的材料可以为金属，本申请对金属的种类不做限定，可以采用本领域已知的金属硬壳壳体，只要能实现本申请的目的即可。柔性壳体可以为金属塑膜，例如铝塑膜、钢塑膜等。
本申请对电化学装置的种类没有特别限制，其可以包括发生电化学反应的任何装置。例如，电化学装置可以包括但不限于：锂离子电池、钠离子电池、锂聚合物二次电池、锂离子聚合物二次电池。
本申请的电化学装置的制备过程为本领域技术人员所熟知的，本申请没有特别的限制，例如，电化学装置的制备过程可以包括但不限于以下步骤：将正极极片、隔离膜和负极极片按顺序堆叠，并根据需要将其卷绕、折叠等操作得到卷绕结构的电极组件，将电极组件放入壳体内，将电解液注入壳体并封口，得到电化学装置。或者，将正极极片、隔离膜和负极极片按顺序堆叠，然后用胶带将整个叠片结构的四个角固定好得到叠片结构的电极组件，将电极组件置入壳体内，将电解液注入壳体并封口，得到电化学装置。此外，也可以根据需要将防过电流元件、导板等置于壳体中，从而防止电化学装置内部的压力上升、过充放电。
本申请的第二方面提供了一种电子装置，其包括本申请第一方面提供的电化学装置。本申请第一方面提供的电化学装置具有高能量密度、良好的安全性能和循环性能，从而本申请的电子装置具有良好的使用性能和较长的使用寿命。
本申请对电子装置的种类没有特别限定，其可以是用于现有技术中已知的任何电子装置。在一些实施例中，电子装置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
以下，举出实施例及对比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”、“％”为质量基准。
测试方法和设备：
正极极片和负极极片的取样方法：
满放状态拆解过程：将各个实施例和对比例制得的锂离子电池以0.2C恒流充电到电压上限设定值，达到满充状态，拆解后取出正极极片和负极极片，用碳酸二甲酯将正极极片和负极极片清洗干净后，60℃烘干得到正极极片样品和负极极片样品。上述电压上限设定值由第二活性材料的种类决定，当第二活性材料为钴酸锂时，上述电压上限设定值为4.53V；当第二活性材料为镍钴锰酸锂时，上述电压上限设定值为4.25V；当第二活性材料为磷酸铁锂时，上述电压上限设定值为4.3V；当第二活性材料为镍钴铝酸锂时，上述电压上限设定值为4.2V；当第二活性材料为锰酸锂时，上述电压上限设定值为4.3V。
满放状态拆解过程：将各个实施例和对比例制得的锂离子电池以0.2C恒流放电到电压下限设定值，达到满放状态，拆解后取出正极极片和负极极片，用碳酸二甲酯将正极极片和负极极片清洗干净后，60℃烘干得到正极极片样品和负极极片样品。上述电压下限设定值由第二活性材料的种类决定，当第二活性材料为钴酸锂时，上述电压下限设定值为3V；当第二活性材料为镍钴锰酸锂时，上述电压下限设定值为3.2V；当第二活性材料为磷酸铁锂时，上述电压下限设定值为2.4V；当第二活性材料为镍钴铝酸锂时，上述电压下限设定值为2.8V；当第二活性材料为锰酸锂时，上述电压下限设定值为2.4V。
第一活性材料的脱锂产物的测定：
取锂离子电池处于满放状态下拆解得到正极极片样品，将正极材料层从正极集流体表面刮下，在原先靠近正极集流体一侧刮取在第一正极材料层的粉末，置于马弗炉中500℃烧结6h，收集煅烧后的粉末样品，然后进行如下元素分析，采用X-射线衍射(XRD)测试以及拉曼测试得到第一活性材料的脱锂产物的组成结构信息，从而反推出其化学式，并计算得到其质量百分含量。
元素分析：取0.4g上述粉末样品，用10mL王水进行消解，王水由浓硝酸与浓盐酸按照体积比1:1混合得到。然后定容至100mL，使用电感耦合等离子光谱发生仪(ICP)测得溶液中的各个元素的含量。
XRD分析：采用X-射线衍射仪(仪器型号为布鲁克Bruker D8 ADVANCE)对上述粉末样品进行XRD测试，得到第一正极材料层的XRD谱图，分析XRD谱图，根据衍射峰的位置、强度和形状与标准谱图对比，可以得到第一活性材料的脱锂产物的物相组成。其中，采用Cu Kα射线。
拉曼光谱分析：采用拉曼光谱仪(仪器型号为LabRAM HR Evolution)对上述粉末样品进行拉曼测试，得到第一正极材料层的拉曼光谱，其特征峰与标准谱图对比，可以得到第一活性材料的脱锂产物的物质金属键结构信息。
硅元素的质量百分含量(Y)测试：
取锂离子电池处于满放状态下拆解得到负极极片样品，刮下负极集流体表面的负极材料层粉末，取上述粉末样品1g，然后使用ICP测得负极材料层中硅元素的质量百分含量。
正极极片中第一活性材料的脱锂产物的质量(A)测试：
取锂离子电池处于满充状态下拆解得到正极极片样品，将正极材料层从正极集流体表面刮下，在原先靠近正极集流体一侧(即沿平行于集流体厚度方向，距离正极集流体表面0至2μm范围内)刮取正极极片样品中的第一正极材料层的粉末，称量其质量为M1 mg，并测试正极集流体的面积为S1 mm2。然后使用热重分析仪测得第一活性材料的脱锂产物的质量百分含量w1，则正极极片中第一活性材料的脱锂产物的质量＝M1×w1×1540/S1，单位为mg/1540mm2。
负极极片中硅元素的质量(B)测试：
取锂离子电池处于满放状态下拆解得到负极极片样品，刮下上述样品的负极集流体表面的负极材料层粉末，称量其质量为M2 mg，并测试负极极片样品集流体的面积为S2 mm2。然后使用ICP测得负极材料层中硅元素的质量百分含量w2，则负极极片中硅元素的质量＝M2×w2×1540/S2，单位为mg/1540mm2。
正极极片中第二活性材料的质量(C)测试：
取锂离子电池处于满放状态下拆解得到正极极片样品，将正极材料层从正极集流体表面刮下，在原先远离正极集流体一侧(即沿平行于集流体厚度方向，距离正极极片表面0至20μm范围内)刮取正极极片样品中的第二正极材料层的粉末，称量其质量为M3mg，并测试正极集流体的面积为S3 mm2。然后使用热重分析仪测得第二活性材料的质量百分含量w3，则正极极片中第二活性材料的质量＝M3×w3×1540/S3，单位为mg/1540mm2。
第一正极材料层的比容量(θ1)测试：
按照各个实施例和对比例中的浆料配比制得第一正极材料层浆料，将第一正极材料层的浆料涂覆在正极集流体上，干燥冷压后得到单面厚度为12.6μm的第一正极材料层的正极极片。制备过程中称量正极集流体的质量和正极极片的质量，计算单位面积正极集流体质量和单位面积正极极片质量，计算得到单位面积第一正极材料层的质量为M4。将上述正极极片、隔离膜、锂片依次叠置，注入电解液得到扣式电池。上述正极集流体、隔离膜和电解液与实施例1中相同。
将扣式电池以0.05C倍率恒流充电到4.58V，记录首次充电容量。第一正极材料层的比容量θ1＝首次充电容量/M4，单位为mAh/g。
第二正极材料层的比容量(θ2)测试：
按照各个实施例和对比例中的浆料配比制得第二正极材料层浆料，将第二正极材料层的浆料涂覆在正极集流体上，干燥冷压后得到单面厚度为53.6μm的第二正极材料层的正极极片。在扣式电池的制备过程中称量正极集流体的质量和正极极片的质量，计算单位面积正极集流体质量和单位面积正极极片质量，计算得到单位面积第二正极材料层的质量为M5。将上述正极极片、隔离膜、锂片依次叠置，注入电解液得到扣式电池。上述正极集流体、隔离膜和电解液与实施例1中相同。
将扣式电池以0.05C倍率恒流充电到4.58V，记录首次充电容量。第二正极材料层的比容量θ2＝首次充电容量/M5，单位为mAh/g。
粘结力(F)测试：
取锂离子电池处于满放状态下拆解得到正极极片，刮下正极集流体一个表面的正极材料。然后裁取宽度为20mm、长度为160mm的正极极片试样。用宽度为20mm、长度为150mm双面胶将正极极片试样粘贴于宽度为20mm、长度为300mm的钢板上，正极集流体面向钢板粘贴，将与正极极片等宽、长度为200mm的纸带与制样样条的一段进行连接固定，使用高铁AI-3000拉力机进行测试。将测试样品固定于测试台上，将纸带180°向上翻折，并通过夹具固定，随后拉力机以50mm/min的速度开始拉动纸带，拉伸位移为50mm，取曲线走平且位移大于10mm时拉力值计算第一正极材料层和正极集流体之间的粘结力F，单位：N/m。
电阻率(ρ)测试方法：
取锂离子电池处于满充状态下拆解得到正极极片样品，测试正极极片的总厚度，然后通过膜片电阻仪测试正极极片的电阻R，其中膜片电阻仪的测试探头面积为S。然后刮下正极材料层，测试正极集流体的厚度，计算得到正极材料层的厚度h。本申请中，正极集流体的电阻忽略不计，膜片电阻仪测试正极极片的电阻R可表示正极材料层的电阻。则正极材料层的电阻率ρ＝R×S/h，单位为Ω·m。
循环性能测试：
在25℃下，将锂离子电池以3C倍率恒流充电至4.53V，再恒压充电至电流小于等于0.05C，再以0.5C倍率恒流放电至3V，此为一个充放电循环，记录锂离子电池第一次循环的放电容量。将锂离子电池按照上述方法进行充放电循环，记录每一次循环的放电容量，直至锂离子电池的放电容量衰减至第一次循环的放电容量的80％，记录充放电循环次数。
安全性能测试：
将锂离子电池置于25℃恒温箱中，静置30分钟，使锂离子电池达到恒温。将达到恒温的锂离子电池以0.5C恒流充电至电压为4.53V，然后以4.53V恒压充电至电流为0.025C，得到满充锂离子电池。将满充锂离子电池转移至穿钉测试机上，保持测试环境温度25℃±2℃，用直径为4mm的钢钉，以30mm/s的速度匀速穿过锂离子电池中心，保留300s，锂离子电池不起火不爆炸记为通过。每个实施例或对比例测试10块锂离子电池，以穿钉测试通过率(N/10)作为评价锂离子电池安全性能的指标，N为通过穿钉测试的锂离子电池数量。
体积能量密度测试：
将锂离子电池置于25℃恒温箱中，静置30分钟，使锂离子电池达到恒温。将达到恒温的锂离子电池以0.5C恒流充电至电压为4.53V，然后以4.53V恒压充电至电流为0.05C，再0.5C放电至电压为3.0V，记录放电能量(单位Wh)，体积能量密度VED＝放电能量/(锂离子电池长度×宽度×厚度)，单位为Wh/L。其中，长度、宽度、厚度均指包装后的锂离子电池的长度、宽度、厚度。
实施例1
<正极极片的制备>
将第一活性材料Li5FeO4、粘结剂聚偏氟乙烯(PVDF)按照质量比97:3进行混合加入N-甲基吡咯烷酮(NMP)作为溶剂，搅拌均匀后调配成固含量为45wt％的第一正极材料层浆料。
将第二活性材料钴酸锂(LiCoO2)导电炭黑、碳纳米管、粘结剂聚偏二氟乙烯按照质量比97.4:0.5:0.5:1.4进行混合，加入NMP作为溶剂，搅拌均匀后调配成固含量为75wt％的第二正极材料层浆料。
将上述制备好的第一正极材料层浆料均匀涂覆在厚度为10μm的正极集流体铝箔的一个表面上，烘干得到单面涂布第一正极材料层的正极极片，然后将第二正极材料层浆料均匀涂覆在第一正极材料层的表面上，烘干得到单面涂布第一正极材料层和第二正极材料层的正极极片，然后在铝箔的另一个表面上重复以上步骤，即得到双面涂布正极材料层的正极极片，120℃条件下真空干燥6h，再经冷压、裁片、焊接极耳，得到规格为74mm×867mm的正极极片待用。其中，单面第一正极材料层的厚度为2.6μm，第一正极材料层的涂布重量为5mg/1540mm2，单面第二正极材料层的厚度为43.6μm，第二正极材料层的涂布重量为230mg/1540mm2。
<负极极片的制备>
将负极活性材料硅碳和人造石墨、粘结剂聚丙烯酸、增稠剂羧甲基纤维素钠、导电剂导电炭黑按照质量比20:77.5:1.5:0.5:0.5进行混合，加入去离子水作为溶剂，调配成固含量为45wt％的浆料，真空搅拌机搅拌均匀后得到负极浆料。将负极浆料均匀涂覆于厚度为6μm的负极集流体铜箔的一个表面上，120℃条件下烘干，得到单面涂布负极材料层的负极极片，负极材料层的涂布重量为105mg/1540mm2。然后在铜箔的另一个表面上重复以上步骤，即得到双面涂布负极材料层的负极极片。120℃条件下干燥6h，再经冷压、裁片、焊接极耳，得到规格为78mm×875mm的负极极片待用。其中，单面负极材料层的厚度为35.5μm。
<隔离膜的制备>
采用厚度为16μm的聚乙烯薄膜(Celgard公司提供)作为隔离膜。
<电解液的制备>
在含水量小于10ppm的环境下，将碳酸乙烯酯和碳酸丙烯酯按照质量比为50:50混合得到非水溶剂，然后向非水溶剂中加入锂盐LiPF6，混合均匀，得到电解液。其中，锂盐的浓度为1.15mol/L。
<锂离子电池的制备>
将制备的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正极极片和负极极片中间起到隔离的作用，然后卷绕得到电极组件。将电极组件装入铝塑膜包装袋中，放置在85℃真空烘箱中干燥12h脱去水分，注入上述配好的电解液，经过真空封装、静置、化成、脱气、切边等工序得到锂离子电池。其中化成过程为：在45℃下，将锂离子电池以0.1C倍率恒流充电10min，随后以0.5C倍率恒流充电至4.53V，再恒压充电至电流0.05C。
实施例2至实施例9
除了调整相关参数如表1所示以外，其余与实施例1相同。其中，可以通过调控第一正极材料层的涂布重量使得A如表1所示，调控负极材料层的涂布重量使得B如表1所示。
实施例10至实施例14
除了在第一正极材料层中进一步引入无机材料，并调整相关参数如表1所示以外，其余与实施例1相同。其中，通过调控第一活性材料的质量百分含量调整第一活性材料的脱锂产物的质量百分含量，当第一活性材料和/或无机材料的质量百分含量改变时，粘结剂的质量百分含量随之改变，三者的质量百分含量之和为100％。
实施例15至实施例17
除了调整硅碳的质量百分含量使得硅元素的质量百分含量以及B的值如表1所示以外，其余与实施例12相同。其中，当硅碳的质量百分含量改变时，人造石墨的质量百分含量随之改变，粘结剂、增稠剂以及导电剂的质量百分含量保持不变。
实施例18至实施例27
除了调整相关参数如表1所示以外，其余与实施例10相同。其中，通过调控第一活性材料的质量百分含量调整第一活性材料的脱锂产物的质量百分含量，当第一活性材料和/或无机材料的质量百分含量改变时，粘结剂的质量百分含量随之改变，三者的质量百分含量之和为100％。
对比例1
除了采用以下<正极极片的制备>制得正极极片以外，其余与实施例1相同。
<正极极片的制备>
采用实施例1的过程制得第二正极材料层浆料。
将上述制备好的第二正极材料层浆料均匀涂覆在厚度为10μm的正极集流体铝箔的一个表面上，烘干得到单面涂布第二正极材料层的正极极片，然后在铝箔的另一个表面上重复以上步骤，即得到双面涂布第二正极材料层的正极极片，120℃条件下真空干燥6h，再经冷压、裁片、焊接极耳，得到规格为74mm×867mm的正极极片待用。其中，单面第二正极材料层的厚度为46.2μm，第二正极材料层的涂布重量为235mg/1540mm2。
对比例2
除了采用以下<正极极片的制备>制得正极极片以外，其余与实施例1相同。
采用实施例1的过程制得第二正极材料层浆料。
将无机材料Al2O3、粘结剂聚偏氟乙烯(PVDF)按照质量比95:5进行混合加入N-甲基吡咯烷酮(NMP)作为溶剂，搅拌均匀后调配成固含量为45wt％的第一正极材料层浆料。
将上述制备好的第一正极材料层浆料均匀涂覆在厚度为10μm的正极集流体铝箔的一个表面上，烘干得到单面涂布第一正极材料层的正极极片，然后将第二正极材料层浆料均匀涂覆在第一正极材料层的表面上，烘干得到单面涂布第一正极材料层和第二正极材料层的正极极片，然后在铝箔的另一个表面上重复以上步骤，即得到双面涂布正极材料层的正极极片，120℃条件下真空干燥6h，再经冷压、裁片、焊接极耳，得到规格为74mm×867mm的正极极片待用。其中，单面第一正极材料层的厚度为2.6μm，第一正极材料层的涂布重量为5mg/1540mm2，单面第二正极材料层的厚度为43.6μm，第二正极材料层的涂布重量为230mg/1540mm2。
对比例3
除了采用以下步骤制得第一正极材料层浆料以外，其余与对比例2相同。
将无机材料Al2O3、导电剂导电炭黑(SP)、粘结剂聚偏氟乙烯(PVDF)按照质量比93:2:5进行混合加入N-甲基吡咯烷酮(NMP)作为溶剂，搅拌均匀后调配成固含量为45wt％的第一正极材料层浆料。
对比例4至对比例7
除了调整相关参数如表1所示以外，其余与实施例10相同。
各实施例和各对比例的相关参数及性能如表1所示。

从实施例1至实施例27、对比例1至对比例7可以看出，采用本申请范围内的正极极片和负极极片，并调控硅元素的质量百分含量以及A/B的值在本申请范围内，可以使得正极材料层具有合适的电阻率，第一正极材料层和集流体之间具有较高的粘结力，锂离子电池同时具有更高的体积能量密度、穿钉通过率以及更多的循环次数，说明锂离子电池同时具有更高的能量密度、更好的安全性能和循环性能。对比例1中未设置第一正极材料层，对比例2和对比例3的第一正极材料层的组成未在本申请范围内，对比例4至对比例7中，A/B的值或者硅元素的质量百分含量中的至少一者未在本申请范围内，上述对比例1、对比例3至对比例7的锂离子电池无法兼顾较高的体积能量密度、穿钉通过率以及较多的循环次数，从而说明其综合性能较差。由于对比例2的第一正极材料层的电阻率过大，锂离子电池无法工作，未测得相关性能数据。
第一活性材料和第一活性材料的脱锂产物的种类通常会影响锂离子电池的能量密度、安全性能和循环性能。从实施例1至实施例9可以看出，选用本申请范围内的第一活性材料，其脱锂产物如表1所示，可以使得锂离子电池同时具有更高的体积能量密度、穿钉通过率以及更多的循环次数，说明锂离子电池同时具有更高的能量密度、更好的安全性能和循环性能。
A/B和A/C的值通常会影响锂离子电池的能量密度、安全性能和循环性能。从实施例10至实施例14可以看出，调控A/B和A/C的值在本申请范围内，可以使得锂离子电池同时具有更高的体积能量密度、穿钉通过率以及更多的循环次数，说明锂离子电池同时具有更高的能量密度、更好的安全性能和循环性能。
硅元素的质量百分含量通常会影响锂离子电池的能量密度、安全性能和循环性能。从
实施例10、实施例15至实施例17可以看出，调控硅元素的质量百分含量在本申请范围内，可以使得锂离子电池同时具有更高的体积能量密度、穿钉通过率以及更多的循环次数，说明锂离子电池同时具有更高的能量密度、更好的安全性能和循环性能。
第一活性材料的脱锂产物的质量百分含量通常会影响锂离子电池的能量密度、安全性能和循环性能。从实施例1、实施例12和实施例18可以看出，调控第一活性材料的脱锂产物的质量百分含量在本申请范围内，可以使得锂离子电池同时具有更高的体积能量密度、穿钉通过率以及更多的循环次数，说明锂离子电池同时具有更高的能量密度、更好的安全性能和循环性能。
无机材料的质量百分含量通常会影响锂离子电池的能量密度、安全性能和循环性能。从实施例19至实施例23可以看出，调控无机材料的质量百分含量在本申请范围内，可以使得锂离子电池同时具有更高的体积能量密度、穿钉通过率以及更多的循环次数，说明锂离子电池同时具有更高的能量密度、更好的安全性能和循环性能。
无机材料的种类通常会影响锂离子电池的能量密度、安全性能和循环性能。从实施例19至实施例23可以看出，选用本申请范围内的无机材料，可以使得锂离子电池同时具有更高的体积能量密度、穿钉通过率以及更多的循环次数，说明锂离子电池同时具有更高的能量密度、更好的安全性能和循环性能。
第二活性材料的种类通常会影响锂离子电池的能量密度、安全性能和循环性能。从实施例12、实施例26至实施例27可以看出，选用本申请范围内的第二活性材料，可以使得锂离子电池同时具有更高的体积能量密度、穿钉通过率以及更多的循环次数，说明锂离子电池同时具有更高的能量密度、更好的安全性能和循环性能。
需要说明的是，在本文中，诸如第一和第二等之类的关系术语仅仅用来将一个实体或者操作与另一个实体或操作区分开来，而不一定要求或者暗示这些实体或操作之间存在任何这种实际的关系或者顺序。而且，术语“包括”、“包含”或者其任何其他变体意在涵盖非排他性的包含，从而使得包括一系列要素的过程、方法或者物品不仅包括那些要素，而且还包括没有明确列出的其他要素，或者是还包括为这种过程、方法或者物品所固有的要素。
本说明书中的各个实施例均采用相关的方式描述，各个实施例之间相同相似的部分互相参见即可，每个实施例重点说明的都是与其他实施例的不同之处。
以上所述仅为本发明的较佳实施例，并非用于限定本发明的保护范围。凡在本发明的精神和原则之内所作的任何修改、等同替换、改进等，均包含在本发明的保护范围内。

Claims (17)

  1. 一种电化学装置，其包括正极极片和负极极片，所述正极极片包括正极集流体和正极材料层，所述正极材料层包括第一正极材料层和第二正极材料层，所述第一正极材料层设置于所述正极集流体和所述第二正极材料层之间；
    所述第一正极材料层包括第一活性材料，所述第一活性材料的脱锂产物包括Li5-xFeO4-y、Li5-xCoO4-y、Li2-zMnO2、Li1.2-rNi0.13Fe0.13Mn0.54O2或Li1-tFePO4中的至少一种，其中，4≤x≤5，2≤y≤3，1.6≤z≤2，1≤r≤1.2，0.8≤t≤1；
    所述第二正极材料层包括第二活性材料，所述第二活性材料包括钴酸锂、镍钴锰酸锂、镍钴铝酸锂、磷酸铁锂或锰酸锂中的至少一种；
    所述负极极片包括负极材料层，所述负极材料层包括硅元素，基于所述负极材料层的质量，所述硅元素的质量百分含量为1％至50％；
    所述正极极片中所述第一活性材料的脱锂产物的质量为A mg/1540mm2，所述负极极片中所述硅元素的质量为B mg/1540mm2，29％≤A/B≤230％。
  2. 根据权利要求1所述的电化学装置，其中，39％≤A/B≤200％。
  3. 根据权利要求1所述的电化学装置，其中，所述第一活性材料的脱锂产物包括LiFeO2、CoO2、MnO2、Ni0.13Fe0.13Mn0.54O2、FePO4、FeO2、Fe2O3或FeO中的至少一种。
  4. 根据权利要求1所述的电化学装置，其中，基于所述第一正极材料层的质量，所述第一活性材料的脱锂产物的质量百分含量为30％至96％。
  5. 根据权利要求1至4中任一项所述的电化学装置，其中，所述正极极片中所述第二活性材料的质量为C mg/1540mm2，0.45％≤A/C≤6％。
  6. 根据权利要求5所述的电化学装置，其中，0.9％≤A/C≤4.5％。
  7. 根据权利要求1至4中任一项所述的电化学装置，其中，基于所述负极材料层的质量，所述硅元素的质量百分含量为1％至20％。
  8. 根据权利要求5所述的电化学装置，其满足以下特征中的至少一者：
    (1)1mg/1540mm2≤A≤14mg/1540mm2；
    (2)3mg/1540mm2≤B≤12mg/1540mm2；
    (3)200mg/1540mm2≤C≤300mg/1540mm2。
  9. 根据权利要求1至4中任一项所述的电化学装置，其中，所述第一正极材料层还包括无机材料，所述无机材料包括氧化铝、锂镧锆氧、钛酸镧锂、磷酸钛铝锂、掺锑氧化锡或氧化钛中的至少一种；
    基于所述第一正极材料层的质量，所述无机材料的质量百分含量为5％至60％。
  10. 根据权利要求1至4中任一项所述的电化学装置，其中，所述第一正极材料层的比容量为130mAh/g至780mAh/g。
  11. 根据权利要求10所述的电化学装置，其中，所述第一正极材料层的比容量大于或等于所述第二正极材料层的比容量。
  12. 根据权利要求1至4中任一项所述的电化学装置，其中，所述第一活性材料包括以下化合物中的至少一种：
    Li5QO4或Li5QO6，Q包括Ni、Co、Fe、Sn或Mn中的至少一种，Q元素的价态低于其自身的最高氧化价态；
    LiqFe0.5(1+q)PO4，1≤q≤5；
    Li2-a-b-c-dNiaRbMncMdO2-f，0≤a＜0.35，0＜b＜0.5，0.3＜c≤0.6，0≤d＜0.05，0.7＜a+b+c+d＜0.9，0≤f＜0.2，R包括Fe或Co中的至少一种，M包括Mg、Al、Ti、V、Cr、Cu、Y、Zr、Nb、Mo、La或W中的至少一种；
    Li1+eMn1-pXpO2-sYs，-0.1＜e＜0.2，0≤p＜0.2，0≤s＜0.2，X包括Fe、Co、Ni、Ti、Zn、Mg、Al、V、Cr或Zr中的至少一种，Y包括S、N、F、Cl或Br中的至少一种。
  13. 根据权利要求10所述的电化学装置，其中，所述第一活性材料包括Li5FeO4、Li5CoO4、Li2MnO2、Li1.2Ni0.13Fe0.13Mn0.54O2或LiFePO4中的至少一种。
  14. 根据权利要求1至4中任一项所述的电化学装置，其中，所述负极材料层包括负极活性材料，所述负极活性材料包括硅、硅碳或硅氧中的至少一种。
  15. 根据权利要求14所述的电化学装置，其中，所述负极活性材料还包括石墨、硬碳、软碳或中间相微碳球中的至少一种。
  16. 根据权利要求1至4中任一项所述的电化学装置，其中，所述正极材料层的电阻率为ρΩ·m，44≤ρ≤155。
  17. 一种电子装置，其包括权利要求1至16中任一项所述的电化学装置。
PCT/CN2025/098976 2024-07-09 2025-06-04 一种电化学装置及电子装置 Pending WO2026012016A1 (zh)

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