WO2024103210A1 - 二次电池及含有其的用电装置 - Google Patents

二次电池及含有其的用电装置 Download PDF

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WO2024103210A1
WO2024103210A1 PCT/CN2022/131678 CN2022131678W WO2024103210A1 WO 2024103210 A1 WO2024103210 A1 WO 2024103210A1 CN 2022131678 W CN2022131678 W CN 2022131678W WO 2024103210 A1 WO2024103210 A1 WO 2024103210A1
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carbon
negative electrode
based material
secondary battery
electrode active
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PCT/CN2022/131678
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English (en)
French (fr)
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马宇
张欣欣
陈晓霞
欧阳楚英
成伟鸣
刘士坤
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/131678 priority Critical patent/WO2024103210A1/zh
Publication of WO2024103210A1 publication Critical patent/WO2024103210A1/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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx

Definitions

  • the present application relates to the field of batteries, and in particular to a secondary battery and an electrical device containing the secondary battery.
  • Secondary batteries are increasingly widely used due to their clean and renewable characteristics. They have the advantages of high energy density, low self-discharge, and excellent cycle performance.
  • the present application provides a secondary battery and an electrical device containing the same, aiming to improve the cycle performance of the secondary battery.
  • the first aspect of the present application provides a secondary battery, including a negative electrode plate, the negative electrode plate including a negative electrode collector and a negative electrode film layer arranged on at least one surface of the negative electrode collector, the negative electrode film layer including a negative electrode active material, and the negative electrode active material including a carbon-based material; in the negative electrode active material, the volume proportion of the first carbon-based material with a particle size less than or equal to 2 ⁇ m is greater than or equal to 15%.
  • the negative electrode active material of the negative electrode film layer in the negative electrode plate is controlled to contain a first carbon-based material in a specific particle size range, and its volume proportion in the negative electrode active material is regulated to increase the contact area between the negative electrode active particles, so that the negative electrode active particles are closely stacked, thereby improving the adhesion of the negative electrode plate, and further improving the cycle performance of the secondary battery.
  • the volume proportion of the first carbon-based material is 20% to 70%; optionally 30% to 60%.
  • the volume proportion of the first carbon-based material with a particle size of less than or equal to 2 ⁇ m is further adjusted to make it better compounded with other negative electrode active materials, further improving the cycle performance of the secondary battery.
  • the first carbon-based material satisfies at least one of the following conditions (1) to (7):
  • the volume distribution particle size Dv10 of the first carbon-based material is 0.2 ⁇ m to 0.5 ⁇ m;
  • the volume distribution particle size Dv50 of the first carbon-based material is 0.5 ⁇ m to 2 ⁇ m;
  • volume distribution particle size Dv90 of the first carbon-based material is ⁇ 2 ⁇ m
  • the specific surface area SSA of the first carbon-based material is 5 m 2 /g to 20 m 2 /g;
  • ID / IG 0.95 to 1.35
  • the powder compaction density of the first carbon-based material under a force of 50,000 N is 0.8 g/cm 3 to 1.1 g/cm 3 ;
  • the tap density of the first carbon-based material is 0.3 g/cm 3 to 0.8 g/cm 3 .
  • the volume proportion of the second carbon-based material with a particle size greater than 2 ⁇ m and less than or equal to 25 ⁇ m is 20% to 80%; optionally 50% to 60%.
  • the second carbon-based material satisfies at least one of the following conditions (I) to (VIII):
  • the volume distribution particle size Dv10 of the second carbon-based material is 2 ⁇ m to 4 ⁇ m;
  • the volume distribution particle size Dv50 of the second carbon-based material is 4 ⁇ m to 8 ⁇ m;
  • the volume distribution particle size Dv90 of the second carbon-based material is 8 ⁇ m to 20 ⁇ m;
  • V the volume distribution particle size Dv99 of the second carbon-based material is 20 ⁇ m to 25 ⁇ m;
  • the specific surface area SSA of the second carbon-based material is 1 m 2 /g to 10 m 2 /g;
  • the powder compaction density of the second carbon-based material under a force of 50,000 N is 0.92 g/cm 3 to 1.2 g/cm 3 ;
  • the tap density of the second carbon-based material is 0.6 g/cm 3 to 0.94 g/cm 3 .
  • the volume proportion of the third carbon-based material with a particle size greater than 40 ⁇ m and less than or equal to 100 ⁇ m is less than or equal to 10%; optionally, it may be less than or equal to 5%.
  • the third carbon-based material satisfies at least one of the following conditions (1) to (4):
  • the specific surface area SSA of the third carbon-based material is 1 m 2 /g to 10 m 2 /g;
  • ID / IG 0.95 to 1.35
  • the powder compaction density of the third carbon-based material under a force of 50,000 N is 0.7 g/cm 3 to 1 g/cm 3 ;
  • the tap density of the third carbon-based material is 0.5 g/cm 3 to 0.8 g/cm 3 .
  • the volume distribution particle size Dv50 of the negative electrode active material is less than or equal to 8 ⁇ m; optionally, the volume distribution particle size Dv50 of the negative electrode active material is 2 ⁇ m to 6 ⁇ m.
  • volume distribution particle size Dv50 of the negative electrode active material can further improve the initial efficiency of the secondary battery.
  • the volume distribution particle size of the negative electrode active material satisfies: 4 ⁇ m ⁇ Dv90 ⁇ 20 ⁇ m; optionally, 5 ⁇ m ⁇ Dv90 ⁇ 16 ⁇ m.
  • the volume distribution particle size Dv10 of the negative electrode active material satisfies: 0.2 ⁇ m ⁇ Dv10 ⁇ 2 ⁇ m; optionally, 0.5 ⁇ m ⁇ Dv10 ⁇ 1.8 ⁇ m.
  • the specific surface area SSA of the negative electrode active material is ⁇ 20 m 2 /g; optionally, SSA is ⁇ 10 m 2 /g.
  • ID / IG in the Raman spectrum test of the negative electrode active material, is 0.87 to 1.35; optionally, it is 0.91 to 1.25.
  • the interlayer spacing of the (002) crystal plane of the negative electrode active material is ⁇ 0.37nm, which can be optionally 0.37nm to 0.42nm.
  • the powder compaction density of the negative electrode active material under a force of 50000N is 0.90 g/cm 3 to 1.5 g/cm 3 ; optionally 0.95 g/cm 3 to 1.3 g/cm 3 .
  • the tap density of the negative electrode active material is 0.50 g/cm 3 to 0.97 g/cm 3 ; optionally 0.6 g/cm 3 to 0.94 g/cm 3 .
  • the carbon-based material includes a plurality of nanopore structures.
  • the carbon-based material includes a plurality of pore structures with a pore size of less than 10 nm.
  • the carbon-based material includes a hard carbon material.
  • the secondary battery is a sodium ion secondary battery.
  • a second aspect of the present application provides an electrical device, comprising the secondary battery of the first aspect of the present application.
  • FIG. 1 is a schematic diagram of one embodiment of a secondary battery.
  • FIG. 2 is an exploded view of FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of a battery pack.
  • FIG. 4 is an exploded view of FIG. 3 .
  • FIG. 5 is a schematic diagram of an embodiment of an electric device using a secondary battery as a power source.
  • FIG. 6 is an electron microscope image of the hard carbon particles before mixing in Example 1.
  • FIG. 7 is an electron microscope image of the mixed hard carbon particles in Example 1.
  • the term "and/or" is only a description of the association relationship of associated objects, indicating that three relationships may exist.
  • a and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone.
  • the character "/" in this article generally indicates that the associated objects before and after are in an "or" relationship.
  • multiple refers to more than two (including two).
  • multiple groups refers to more than two groups (including two groups), and “multiple pieces” refers to more than two pieces (including two pieces).
  • Secondary batteries mainly rely on the movement of active ions between the positive and negative electrodes to generate electrical energy.
  • the active ions are deintercalated from the positive electrode and embedded into the negative electrode through the electrolyte, and the opposite is true during discharge.
  • the embedding and extraction of active ions such as sodium ions, etc.
  • the expansion and contraction of the negative electrode sheet causing damage to the structure of the negative electrode material.
  • the instability of the negative electrode interface limits the improvement of the cycle performance of the secondary battery.
  • the interface stability of the negative electrode is often improved by improving the binder.
  • the binder generally needs to use a macromolecular resin, which will swell after long-term contact with the electrolyte, which will deteriorate the cycle performance of the secondary battery.
  • the technical personnel of this application has taken a different approach and creatively proposed to adjust the particle size of the negative electrode active material to improve the synergistic effect between the negative electrode active material particles, so as to improve the adhesion of the negative electrode sheet and thus improve the cycle performance of the secondary battery.
  • the technical personnel of this application obtained the technical solution of this application.
  • a secondary battery including a negative electrode plate, the negative electrode plate including a negative electrode collector and a negative electrode film layer provided on at least one surface of the negative electrode collector, the negative electrode film layer including a negative electrode active material, and the negative electrode active material including a carbon-based material; in the negative electrode active material, the volume proportion of the first carbon-based material with a particle size less than or equal to 2 ⁇ m is greater than or equal to 15%.
  • the negative electrode active material of the negative electrode film layer in the negative electrode plate is controlled to contain a first carbon-based material in a specific particle size range, and its volume proportion in the negative electrode active material is simultaneously regulated, thereby increasing the contact area between the negative electrode active particles and making the negative electrode active particles closely stacked, thereby improving the adhesion of the negative electrode plate, and then effectively improving the cycle performance of the secondary battery.
  • the volume proportion of the first carbon-based material is 20% to 70%; optionally 30% to 60%.
  • the volume proportion of the first carbon-based material with a particle size of less than or equal to 2 ⁇ m is further regulated to enable better compounding with other negative electrode active materials, thereby further improving the cycle performance of the secondary battery.
  • the values include the minimum and maximum values of the range, and every value between the minimum and maximum values.
  • Specific examples include but are not limited to the point values in the embodiment and the following point values: 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 36%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, or a range consisting of any two values, for example, 20% to 50%, 20% to 60%, 20% to 65%, 20% to 70%, 25% to 50%, 25% to 60%, 25% to 65%, 25% to 70%, 30% to 40%, 30% to 50%, 30% to 60%, 30% to 60%, 30% to 50%, 30% to 60%, 30% to 50%
  • the volume distribution particle size Dv10 of the first carbon-based material is 0.2 ⁇ m to 0.5 ⁇ m.
  • the volume distribution particle size Dv50 of the first carbon-based material is 0.5 ⁇ m to 2 ⁇ m.
  • the volume distribution particle size Dv90 of the first carbon-based material is ⁇ 2 ⁇ m.
  • the specific surface area SSA of the first carbon-based material is 5 m 2 /g to 20 m 2 /g.
  • ID / IG in a Raman spectrum test of the first carbon-based material, is 0.95 to 1.35.
  • the powder compaction density of the first carbon-based material under a force of 50000N is 0.8 g/cm 3 -1.1 g/cm 3 .
  • the tap density of the first carbon-based material is 0.3 g/cm 3 to 0.8 g/cm 3 .
  • the interlayer spacing of the (002) crystal plane of the negative electrode active material is 0.37nm to 0.42nm.
  • the volume proportion of the second carbon-based material with a particle size greater than 2 ⁇ m and less than or equal to 25 ⁇ m is 20% to 80%; optionally 50% to 60%.
  • the values include the minimum and maximum values of the range, as well as every value between the minimum and maximum values.
  • Specific examples include but are not limited to the point values in the embodiments and the following point values: 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 36%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%; or a range consisting of any two values, for example, 20% to 60%, 20% to 65%, 20%
  • the volume particle size distribution of the second carbon-based material is unimodal.
  • the volume distribution particle size Dv10 of the second carbon-based material is 2 ⁇ m to 4 ⁇ m.
  • the volume distribution particle size Dv50 of the second carbon-based material is 4 ⁇ m to 8 ⁇ m.
  • the volume distribution particle size Dv90 of the second carbon-based material is 8 ⁇ m to 20 ⁇ m.
  • the volume distribution particle size Dv99 of the second carbon-based material is 20 ⁇ m to 25 ⁇ m.
  • the specific surface area SSA of the second carbon-based material is 1 m 2 /g to 10 m 2 /g.
  • the powder compaction density of the second carbon-based material under a force of 50000N is 0.92 g/cm 3 -1.2 g/cm 3 .
  • the tap density of the second carbon-based material is 0.6 g/cm 3 to 0.94 g/cm 3 .
  • the interlayer spacing of the (002) crystal plane of the negative electrode active material is 0.37nm to 0.42nm.
  • the volume proportion of the third carbon-based material having a particle size greater than 40 ⁇ m is 0.
  • the particle composition in the negative electrode active material is regulated so that the volume proportion of carbon-based materials with a particle size greater than 40 ⁇ m is 0, that is, there is no carbon-based material with a particle size greater than 40 ⁇ m, so as to avoid the negative impact of larger particle sizes on the compounding effect.
  • the volume proportion of the third carbon-based material with a larger particle size can be further adjusted so that it can be better compounded with the carbon-based material with a smaller particle size to reduce the impact on the battery cycle performance.
  • the volume proportion of the third carbon-based material having a particle size greater than 40 ⁇ m is less than or equal to 10%; optionally, less than or equal to 5%.
  • the volume proportion of the third carbon-based material with a particle size greater than 40 ⁇ m can be selected as any one of 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or a range consisting of any two numbers; for example, it can be 0.1% to 5%, 0.1% to 4.5%, 0.1% to 4%, 0.1% to 3.5%, 0.1% to 3%, 0.1% to 2.5%, 0.1% to 2%, 0.1% to 1.5%, 0.1% to 1%, 0.1% to 0.5%, 1% to 5%, 1% to 4.5%, 1% to 4%, 1% to 3.5%, 2% to 4%, 3% to 5%.
  • the particle size of the third carbon-based material having a particle size greater than 40 ⁇ m is greater than 40 ⁇ m and less than or equal to 100 ⁇ m.
  • the specific surface area SSA of the third carbon-based material is 1 m 2 /g to 10 m 2 /g.
  • ID / IG in a Raman spectrum test of the third carbon-based material, is 0.95 to 1.35.
  • the powder compaction density of the third carbon-based material under a force of 50000N is 0.7 g/cm 3 -1 g/cm 3 .
  • the tap density of the third carbon-based material is 0.5 g/cm 3 to 0.8 g/cm 3 .
  • the interlayer spacing of the (002) crystal plane of the negative electrode active material is 0.37nm to 0.42nm.
  • the volume distribution particle size Dv50 of the negative electrode active material is less than or equal to 8 ⁇ m.
  • the volume distribution particle size Dv50 of the negative electrode active material is 1 ⁇ m to 8 ⁇ m.
  • the volume distribution particle size Dv50 of the negative electrode active material is 1 ⁇ m to 6 ⁇ m.
  • the volume distribution particle size Dv50 of the negative electrode active material is 2 ⁇ m to 6 ⁇ m.
  • volume distribution particle size Dv50 of the negative electrode active material can further improve the initial efficiency of the secondary battery.
  • the volume distribution particle size of the negative electrode active material satisfies: 4 ⁇ m ⁇ Dv90 ⁇ 20 ⁇ m; optionally, 5 ⁇ m ⁇ Dv90 ⁇ 16 ⁇ m.
  • the volume distribution particle size Dv10 of the negative electrode active material satisfies: 0.2 ⁇ m ⁇ Dv10 ⁇ 2 ⁇ m; optionally, 0.5 ⁇ m ⁇ Dv10 ⁇ 1.8 ⁇ m.
  • the above Dv10, Dv50 or Dv90 means: the particle size corresponding to the cumulative volume distribution percentage of the material reaching 10%, 50% or 90%, respectively, which can be measured by instruments and methods known in the art. For example, it can be conveniently measured by a laser particle size analyzer with reference to GB/T 19077-2016 particle size distribution laser diffraction method.
  • the test instrument can be the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Ltd., UK.
  • the specific surface area SSA of the negative electrode active material is ⁇ 20 m 2 /g; optionally, SSA is ⁇ 10 m 2 /g.
  • the specific surface area of the above-mentioned negative electrode active material is determined by referring to GB/T 19587-2004 gas adsorption BET method for determining the specific surface area of solid substances.
  • ID / IG in the Raman spectrum test of the negative electrode active material, is 0.87 to 1.35; optionally, it is 0.91 to 1.25.
  • ID / IG refers to the ratio of the peak intensities of the D peak and the G peak in the Raman spectrum of the material; wherein ID represents the D peak intensity of the Raman spectrum of the carbon material at 1350 ⁇ 50cm -1 , and IG represents the G peak intensity of the Raman spectrum of the carbon material at 1580 ⁇ 50cm -1 .
  • the carbon-based material includes a hard carbon material.
  • carbon materials are divided into graphite, soft carbon and hard carbon.
  • Hard carbon refers to carbon that is difficult to completely graphitize above 2800°C, and its disordered structure is difficult to eliminate at high temperatures.
  • the precursors for preparing hard carbon materials are not limited to mineral raw materials, but can include all compounds containing C, H, and O elements except for mineral raw materials that are particularly easy to graphitize.
  • the interlayer spacing of the (002) crystal plane of the negative electrode active material is ⁇ 0.37nm, and can be selected to be 0.37nm to 0.42nm.
  • the (002) crystal plane interlayer spacing is calculated using the Bragg formula.
  • the powder compaction density of the negative electrode active material under a force of 50000N is 0.90 g/cm 3 to 1.5 g/cm 3 ; optionally 0.95 g/cm 3 to 1.3 g/cm 3 .
  • the tap density of the negative electrode active material is 0.50 g/cm 3 to 0.97 g/cm 3 ; optionally 0.6 g/cm 3 to 0.94 g/cm 3 .
  • the carbon-based material includes a plurality of nanopore structures.
  • the carbon-based material includes a plurality of pore structures with a pore size of less than 10 nm.
  • the mass proportion of the negative electrode active material is 85 wt % to 95 wt %.
  • the negative electrode film layer further includes a negative electrode conductive agent and a negative electrode binder.
  • the above-mentioned negative electrode conductive agent can be a conductive material commonly used in the art, including but not limited to: at least one of graphite, carbon nanotubes, nanofibers, carbon black and graphene. Specifically, it can be selected from SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs and graphene and their composite conductive agents.
  • the weight ratio of the negative electrode conductive agent in the negative electrode film layer is 0 to 20 wt %.
  • the above-mentioned negative electrode binder can be a commonly used binder in the art, and can be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the weight ratio of the negative electrode binder in the negative electrode active layer is 0 to 30 wt %.
  • the negative electrode film layer may further include other additives, such as thickeners, such as sodium carboxymethyl cellulose (CMC-Na), etc. Based on the total weight of the negative electrode active layer, the weight ratio of other additives in the negative electrode active layer is 0-15wt%.
  • the current collector in the negative electrode plate may be a metal foil or a composite current collector.
  • copper foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the secondary battery can be prepared by a commonly used preparation method in the art.
  • the preparation method is exemplified here, but is not limited to the following preparation method.
  • the method for preparing the secondary battery comprises the following steps S10 to S30 to prepare a negative electrode sheet.
  • the raw materials used to prepare the negative electrode active material include a first carbon-based material, a second carbon-based material and a third carbon-based material, the particle size of the first carbon-based material is ⁇ 2 ⁇ m, the particle size of the second carbon-based material is greater than 2 ⁇ m and less than or equal to 25 ⁇ m, and the particle size of the third carbon-based material is greater than 40 ⁇ m.
  • first carbon-based material, the second carbon-based material and the third carbon-based material are configured according to the particle size volume ratio of the negative electrode active material.
  • the selection and parameter control of the first carbon-based material, the second carbon-based material and the third carbon-based material are the same as above and will not be repeated here.
  • the specific steps of preparing the negative electrode active material include the following steps:
  • the first carbon-based material, the second carbon-based material and the third carbon-based material are mixed to obtain a negative electrode active material.
  • the mixing time is 0.5h to 10h.
  • the above mixing step is carried out in a mixer.
  • the solid content of the negative electrode slurry is 30wt% to 70wt%, and the viscosity at room temperature is adjusted to 2000mPa ⁇ s to 10000mPa ⁇ s; the obtained negative electrode slurry is coated on the negative electrode current collector, and after a drying process, cold pressing such as rolling, a negative electrode sheet is obtained.
  • the negative electrode powder coating unit area density is 75mg/ m2 to 220mg/ m2
  • the negative electrode sheet compaction density is 1.2g/ m3 to 2.0g/ m3 .
  • the secondary battery further includes a positive electrode plate, an electrolyte and a separator.
  • the secondary battery may be a sodium ion battery, a lithium ion battery, or a potassium ion battery.
  • the secondary battery is a sodium ion battery.
  • the positive electrode plate includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the components of the positive electrode film layer include positive electrode active materials.
  • the current collector in the positive electrode sheet has two surfaces opposite to each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the current collector in the positive electrode plate may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a commonly used positive electrode active material in the present application, such as a lithium ion positive electrode active material or a sodium ion positive electrode active material.
  • the lithium ion active material may include at least one of the following materials: olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to , lithium cobalt oxide (such as LiCoO2 ), lithium nickel oxide (such as LiNiO2 ), lithium manganese oxide (such as LiMnO2 , LiMn2O4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide , lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523 ) , LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211 ), LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622 ), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi0.85Co0.15Mn0 .
  • olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), lithium manganese phosphate (such as LiMnPO 4 ), and lithium manganese iron phosphate.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • lithium manganese phosphate such as LiMnPO 4
  • lithium manganese iron phosphate lithium manganese iron phosphate.
  • the molecular formula of the lithium ion active material is: LiFe x Mn (1-x) PO 4 , where x is any number from 0 to 1.
  • LiFe x Mn (1-x) PO 4 is LiMnPO 4 lithium manganese phosphate
  • LiFePO 4 is LiFePO 4 lithium iron phosphate (LFP).
  • the sodium ion active material may include at least one of the following materials: at least one of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound.
  • a sodium transition metal oxide at least one of a sodium transition metal oxide, a polyanionic compound, and a Prussian blue compound.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.
  • the transition metal in the sodium transition metal oxide, includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the sodium transition metal oxide is, for example, Na x MO 2 , wherein M includes at least one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, and 0 ⁇ x ⁇ 1.
  • the polyanionic compound can be a class of compounds having sodium ions, transition metal ions and tetrahedral (YO 4 ) n- anion units.
  • the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y includes at least one of P, S and Si;
  • n represents the valence state of (YO 4 ) n- .
  • the polyanionic compound may also be a compound having sodium ions, transition metal ions, tetrahedral (YO 4 ) n- anion units and halogen anions.
  • the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y includes at least one of P, S and Si, and
  • n represents the valence state of (YO 4 ) n- ;
  • the halogen may be at least one of F, Cl and Br.
  • the polyanionic compound may also be a compound having sodium ions, tetrahedral (YO 4 ) n- anion units, polyhedral units (ZO y ) m+ and optional halogen anions.
  • Y includes at least one of P, S and Si, and n represents the valence state of (YO 4 ) n- ;
  • Z represents a transition metal, including at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, and m represents the valence state of (ZO y ) m+ ;
  • the halogen may be at least one of F, Cl and Br.
  • the polyanionic compound is, for example, at least one of NaFePO4 , Na3V2 ( PO4 ) 3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3 ( PO4 ) 2 ( P2O7 ), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3 ( VOy ) 2 ( PO4 )2F3-2y ( 0 ⁇ y ⁇ 1 ).
  • the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN - ).
  • the transition metal includes at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the Prussian blue compound is, for example, Na a Me b Me' c (CN) 6 , wherein Me and Me' each independently include at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 ⁇ a ⁇ 2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1.
  • the weight ratio of the positive electrode active material in the positive electrode film layer is 80 wt % to 100 wt %.
  • the components of the positive electrode film layer further include a positive electrode conductor and a positive electrode binder.
  • the positive electrode conductive agent can be a conductive agent commonly used in the art, including but not limited to: at least one of graphite, carbon nanotubes, nanofibers, carbon black and graphene. Specifically, it can be selected from SP, KS-6, acetylene black, branched Ketjen black ECP, SFG-6, vapor-grown carbon fiber VGCF, carbon nanotubes CNTs and graphene and their composite conductive agents.
  • the weight ratio of the positive electrode conductor in the positive electrode active layer is 0 to 20 wt %.
  • the binder of the above-mentioned positive electrode binder can be polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, hydrogenated nitrile rubber, styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), carboxymethyl chitosan (CMCS) and at least one of fluorine-containing acrylate resins.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE
  • the weight ratio of the positive electrode binder in the positive electrode active layer is 0 to 30 wt %.
  • the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • the solid content of the positive electrode slurry is 40wt% to 80wt%, and the viscosity at room temperature is adjusted to 5000mPa ⁇ s to 25000mPa ⁇ s.
  • the positive electrode slurry is coated on the surface of the positive electrode collector, and after drying, it is cold-pressed by a cold rolling mill to form a positive electrode sheet; the unit surface density of the positive electrode powder coating is 150 to 350mg/ m2 , and the compaction density of the positive electrode sheet is 3.0 to 3.6g/ cm3 , and can be optionally 3.3 to 3.5g/ cm3 .
  • the calculation formula of the compaction density is:
  • Compacted density coating surface density/(thickness of the electrode after extrusion - thickness of the current collector).
  • the electrolyte includes electrolyte salt and solvent
  • the electrolyte salt may be selected from electrolyte salts commonly used in the art, including lithium ion electrolyte salts and sodium ion electrolyte salts.
  • the lithium ion electrolyte salt is selected from: lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LIDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorobis(oxalatophosphate) (LIDFOP), Li(FSO 2 ) 2 N, LiCF 3 SO 3 and lithium tetrafluorooxalatophosphate (LiTFOP).
  • LiPF 6
  • the sodium ion electrolyte salt is selected from one or more of sodium hexafluorophosphate (NaPF 6 ), NaClO 4 , NaAIClh, NaFeClh, NaBF 4 , NaBClh, NaNO 3 , NaPOFA, NaSCN, NaCN, NaAsF 6 , NaCF 3 CO 2 , NaSbF 6 , NaC 6 HsCO 2 , Na(CH 3 )C 6 H 4 SO 3 , NaHSO 4 , and NaB(C 6 Hs) 4 .
  • NaPF 6 sodium hexafluorophosphate
  • NaPF 6 sodium hexafluorophosphate
  • the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), cyclopentane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sul
  • FEC fluoro
  • the concentration of the electrolyte salt is usually 0.5 mol/L to 15 mol/L.
  • the electrolyte may further optionally include additives.
  • the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet.
  • the present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the secondary battery further comprises a shell for packaging the positive electrode sheet, the negative electrode sheet, the separator and the electrolyte.
  • the shell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. It may also be a soft package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 4 of a square structure as an example.
  • the housing may include a shell 41 and a cover plate 43.
  • the shell 41 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate are enclosed to form a receiving cavity.
  • the shell 41 has an opening connected to the receiving cavity, and the cover plate 43 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the separator can be wound or laminated to form an electrode assembly 42.
  • the electrode assembly 42 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in the electrode assembly 42.
  • the number of electrode assemblies 42 included in the battery 4 can be one or more, which can be adjusted according to needs.
  • the present application also provides an electrical device, which includes the secondary battery mentioned above.
  • the secondary battery may exist in the form of a battery cell, or may be further assembled into a battery pack.
  • the battery pack 1 includes a battery box and one or more secondary batteries 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for the secondary batteries 4.
  • the plurality of secondary batteries 4 may be arranged in the battery box in any manner.
  • the secondary battery or the battery pack assembled therefrom can be used as a power source for an electrical device, or as an energy storage unit for an electrical device.
  • the above-mentioned electrical devices may be, but are not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • mobile devices such as mobile phones, laptops, etc.
  • electric vehicles such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.
  • electric trains ships and satellites, energy storage systems, etc.
  • Fig. 5 is an example of an electric device 5.
  • the electric device 5 is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack may be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • a device is usually required to be light and thin, and a battery may be used as a power source.
  • hard carbon particles including first hard carbon particles, second hard carbon particles and third hard carbon particles, wherein the particle sizes are T1, T2 and T3 respectively.
  • the Mastersizer 2000E laser particle size analyzer was used to measure the particle size-volume cumulative distribution curves of the first hard carbon particles, the second hard carbon particles and the third hard carbon particles according to the standard GB/T19077-2016, and the compaction density and tap density of the powder were measured. The specific parameters are shown in Table 1.
  • the hard carbon particles are mixed in a mixer according to a preset volume ratio for 4 hours to obtain mixed hard carbon particles.
  • the morphologies of the hard carbon particles before and after mixing were observed respectively.
  • the electron microscope image of the hard carbon particles before mixing is shown in Figure 6, wherein (a) is the electron microscope image of the first hard carbon particles before mixing, and (b) is the electron microscope image of the second hard carbon particles before mixing.
  • the electron microscope image of the hard carbon particles after mixing is shown in Figure 7.
  • the mixed hard carbon particles were tested by XRD and Raman.
  • the XRD results showed that the d002 peak position was 22° to 24°.
  • the Raman results showed that the peak intensity ratio of the D peak at 1350 ⁇ 50cm -1 to the G peak at 1580 ⁇ 50cm -1 was 0.9 to 1.35.
  • Both XRD and Raman showed that the mixed hard carbon particles still had the characteristic peaks of hard carbon, and the mixing process did not destroy the structure of hard carbon.
  • the particle size of the mixed hard carbon particles was tested by Mastersizer 2000E laser particle size analyzer in accordance with the standard GB/T19077-2016 to obtain its particle size-volume cumulative distribution curve.
  • the relevant parameter results are shown in Table 4. Taking the total volume peak area of the mixed hard carbon particles as the benchmark, the volume peak area proportions of carbon-based material hard carbon particles with a particle size of less than or equal to 2 ⁇ m, hard carbon particles with a particle size of greater than 2 ⁇ m and less than or equal to 25 ⁇ m, and hard carbon particles with a particle size of greater than 40 ⁇ m are recorded as D1, D2, and D3, respectively.
  • D1, D2, and D3 By adjusting the ratio of carbon particles at each level, the values of D1, D2, and D3 meet the relationship in Table 4.
  • the above-mentioned powder compaction density test is carried out under a pressure of 50000N with reference to the standard GB/T 24533-2009, and the above-mentioned tap density is carried out with reference to the standard GB/T 5162-2006.
  • the specific surface area of the mixed hard carbon particles was tested according to the standard GB/T 19587-2004 gas adsorption BET method for determining the specific surface area of solid substances. Please see Table 2 for specific results.
  • the mixed hard carbon particles, conductive agent carbon black, binder water-soluble unsaturated resin SR-1B (alkyd unsaturated polyester resin), and thickener sodium hydroxymethyl cellulose (CMC-Na) are mixed in a weight ratio of 95:1.74:2.3:0.96, and then dispersed in solvent deionized water to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, a negative electrode sheet can be obtained.
  • the unit area density of the negative electrode sheet is 50g/ m2
  • the compaction density of the negative electrode sheet is 1.2g/ m3 .
  • the compaction density and surface density of the above-mentioned pole piece are well-known in the art.
  • the weight of the active layer can be obtained by subtracting the weight of the current collector from the weight of the pole piece.
  • the compaction density of the above-mentioned pole piece refers to the ratio of the pole piece surface density to the thickness of the active layer, and is one of the reference indicators of the material energy density.
  • Test method Determine the surface density of the pole piece according to the above method, use a vernier caliper to measure the total thickness of the pole piece, and subtract the thickness of the current collector to calculate the thickness of the active layer. Based on the two parameters of surface density and thickness, the compaction density of the pole piece can be calculated.
  • the bonding strength and porosity of the prepared negative electrode sheet were tested.
  • the porosity was tested according to the standard GB/T 19587-2004.
  • the test steps for bonding strength are as follows:
  • buttons on the manual controller attached to the tensile testing machine to adjust the position of the upper clamp.
  • Turn on the dedicated computer connected to the tensile testing machine double-click the desktop software icon, and perform the test.
  • the stretching rate is 50m/min and the test distance is 50mm.
  • the software takes a data point every 10s. These data point values are the ordinate and the corresponding test distance is the abscissa. The ordinate reading gradually stabilizes, and the ordinate reading after stabilization is the bonding force.
  • Preparation of sodium positive electrode sheets Prussian white positive electrode active material, conductive agent carbon black, and polyvinylidene fluoride (PVDF) are dissolved in solvent N-methylpyrrolidone in a weight ratio of 95:5:5, and mixed evenly to prepare positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode collector copper foil at one time, and the sodium ion positive electrode sheets are obtained after drying, cold pressing, and cutting.
  • PVDF polyvinylidene fluoride
  • isolation membrane Polypropylene film is used as the isolation membrane.
  • the sodium ion positive electrode sheet and the negative electrode sheet are cut, shaped, assembled, shelled, injected with sodium ion battery electrolyte, and subjected to formation and aging steps in sequence to prepare a lithium ion battery.
  • the prepared sodium ion secondary battery was repeatedly charged and discharged, and the capacitance retention rate (capacity) after the cycle charge and discharge was calculated as follows:
  • the sodium ion battery prepared above was charged at a constant current of 1C to a charge cut-off voltage of 4.25V, then charged at a constant voltage to a current ⁇ 0.05C, allowed to stand for 5 min, and then discharged at a constant current of 0.33C to a discharge cut-off voltage of 2.8V, allowed to stand for 5 min, and the capacity C0 at this time was recorded. This is one charge and discharge cycle.
  • the battery was subjected to a cyclic charge and discharge test for 500 cycles, and the discharge capacity of each cycle was recorded.
  • Examples 2 to 12 are basically the same as Example 1, except that the volume ratio of each hard carbon particle during the mixing of the negative electrode active particles in step (1) is regulated so that some parameters of the mixed hard carbon particles in Examples 2 to 12 are different from those in Example 1. See Table 2 for details.
  • Examples 13 to 15 are basically the same as Example 1, except that: in step (1) of mixing the negative electrode active particles in Examples 13 to 15, the mixing time is 0.5 h, 2 h, and 8 h, respectively, so that some parameters of the mixed hard carbon particles in Examples 13 to 15 are different from those in Example 1. See Table 2 for details.
  • Comparative Example 1 is substantially the same as Example 1, except that the volume ratio of each hard carbon particle in the mixing of the negative electrode active particles in step (1) is adjusted so that some parameters of the mixed hard carbon particles in Comparative Example 1 are different from those in Example 1.
  • the parameters of the first hard carbon particles, the second hard carbon particles and the third hard carbon particles used in each embodiment and comparative example are shown in Table 1.
  • D1 represents: the volume peak area ratio of the first hard carbon particles with a particle size less than or equal to 2 ⁇ m
  • D2 represents: the volume peak area ratio of the second hard carbon particles with a particle size greater than 2 ⁇ m and less than or equal to 25 ⁇ m
  • D3 represents: the volume peak area ratio of the third hard carbon particles with a particle size greater than 40 ⁇ m.
  • the negative electrode active material of the negative electrode film layer in the negative electrode plate contains a carbon-based material with a specific particle size range, and its volume proportion in the negative electrode active material is regulated to increase the contact area between the negative electrode active particles, so that the negative electrode active particles are closely stacked, thereby improving the adhesion of the negative electrode plate, and further improving the initial efficiency and cycle performance of the secondary battery.

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Abstract

本申请提出一种二次电池及含有其的用电装置。该二次电池包括负极极片，所述负极极片包括负极集流体及设于所述负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料，所述负极活性材料包括碳基材料；在所述负极活性材料中，粒径小于等于2μm的第一碳基材料的体积占比大于等于15％，该二次电池的首效及循环性能优异。

Description

二次电池及含有其的用电装置 技术领域
本申请涉及电池领域，具体涉及一种二次电池及含有其的用电装置。
背景技术
二次电池因其清洁和可再生的特点得到日益广泛的应用，具有能量密度高、自放电小、循环性能优越等优点。
随着需求的提升，人们对二次电池的电化学性能的要求越来越高，尤其是随着锂资源的供应越来越紧张，钠资源储量更丰富、成本更低廉的钠离子二次电池进入人们的视线，而传统的钠离子电池的电化学性能难以满足人们的需求，有待进一步改进。
发明内容
鉴于上述问题，本申请提供一种二次电池及含有其的用电装置，旨在提高二次电池的循环性能。
为了实现上述目的，本申请的第一方面，提供了一种二次电池，包括负极极片，所述负极极片包括负极集流体及设于所述负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料，所述负极活性材料包括碳基材料；在所述负极活性材料中，粒径小于等于2μm的第一碳基材料的体积占比大于等于15％。
上述二次电池中，控制负极极片中的负极膜层的负极活性材料含有特定粒径范围的第一碳基材料，并调控其在负极活性材料中的体积占比，增加负极活性颗粒之间的接触面积，使负极活性颗粒之间紧密堆积，从而提高负极极片的粘结性，进而能提高二次电池的循环性能。
在本申请任意实施例中，在所述负极活性材料中，所述第一碳基材料的体积占比为20％～70％；可选为30％～60％。进一步调控粒径小于等于2μm的第一碳基材料的体积占比，使其与其他负极活性材料更好的复配，进一步提高二次电池的循环性能。
在本申请任意实施例中，所述第一碳基材料满足如下条件中(1)～(7) 的至少一个：
(1)所述第一碳基材料的体积分布粒径Dv10为0.2μm～0.5μm；
(2)所述第一碳基材料的体积分布粒径Dv50为0.5μm～2μm；
(3)所述第一碳基材料的体积分布粒径Dv90≤2μm；
(4)所述第一碳基材料的比表面积SSA为5m 2/g～20m 2/g；
(5)所述第一碳基材料的拉曼光谱测试中，I D/I G为0.95～1.35；
(6)所述第一碳基材料在50000N作用力下的粉体压实密度为0.8g/cm 3～1.1g/cm 3；
(7)所述第一碳基材料的振实密度为0.3g/cm 3～0.8g/cm 3。
在本申请任意实施例中，在所述负极活性材料中，粒径大于2μm、且小于等于25μm的第二碳基材料的体积占比为20％～80％；可选为50％～60％。
在本申请任意实施例中，所述第二碳基材料满足如下条件(Ⅰ)～(Ⅷ)中的至少一个：
(Ⅰ)所述第二碳基材料的体积粒径分布呈单峰分布；
(Ⅱ)所述第二碳基材料的体积分布粒径Dv10为2μm～4μm；
(Ⅲ)所述第二碳基材料的体积分布粒径Dv50为4μm～8μm；
(Ⅳ)所述第二碳基材料的体积分布粒径Dv90为8μm～20μm；
(Ⅴ)所述第二碳基材料的体积分布粒径Dv99为20μm～25μm；
(Ⅵ)所述第二碳基材料的比表面积SSA为1m 2/g～10m 2/g；
(Ⅶ)所述第二碳基材料在50000N作用力下的粉体压实密度为0.92g/cm 3～1.2g/cm 3；
(Ⅷ)所述第二碳基材料的振实密度为0.6g/cm 3～0.94g/cm 3。
在本申请任意实施例中，在所述负极活性材料中，粒径大于40μm、且小于等于100μm的第三碳基材料的体积占比小于等于10％；可选为小于等于5％。
在本申请任意实施例中，所述第三碳基材料满足如下条件中(1)～(4)的至少一种：
(1)所述第三碳基材料的比表面积SSA为1m 2/g～10m 2/g；
(2)所述第三碳基材料的拉曼光谱测试中，I D/I G为0.95～1.35；
(3)所述第三碳基材料在50000N作用力下的粉体压实密度为0.7g/cm 3～1g/cm 3；
(4)所述第三碳基材料的振实密度为0.5g/cm 3～0.8g/cm 3。
在本申请任意实施例中，所述负极活性材料的体积分布粒径Dv50小于等于8μm；可选地，所述负极活性材料的体积分布粒径Dv50为2μm～6μm。
进一步调控负极活性材料的体积分布粒径Dv50，使其具有特定的范围，可进一步提高二次电池的首效。
在本申请任意实施例中，所述负极活性材料的体积分布粒径满足：4μm≤Dv90≤20μm；可选地，5μm≤Dv90≤16μm。
在本申请任意实施例中，所述负极活性材料的体积分布粒径Dv10满足：0.2μm≤Dv10≤2μm；可选地，0.5μm≤Dv10≤1.8μm。
在本申请任意实施例中，所述负极活性材料的比表面积SSA≤20m 2/g；可选为SSA≤10m 2/g。
在本申请任意实施例中，所述负极活性材料的拉曼光谱测试中，I D/I G为0.87～1.35；可选为0.91～1.25。
在本申请任意实施例中，所述负极活性材料的X-ray射线衍射测试中，在22°～24°范围内具有(002)晶面峰，所述负极活性材料的(002)晶面的层间距≥0.37nm，可选为0.37nm～0.42nm。
在本申请任意实施例中，所述负极活性材料在50000N作用力下的粉体压实密度为0.90g/cm 3～1.5g/cm 3；可选为0.95g/cm 3～1.3g/cm 3。
在本申请任意实施例中，所述负极活性材料的振实密度为0.50g/cm 3～0.97g/cm 3；可选为0.6g/cm 3～0.94g/cm 3。
在本申请任意实施例中，所述碳基材料包括多个纳米孔结构，可选地，所述碳基材料包括多个孔径在10nm以下的孔结构。
在本申请任意实施例中，所述碳基材料包括硬碳材料。
在本申请任意实施例中，所述二次电池为钠离子二次电池。
本申请的第二方面，提供一种用电装置，包括本申请第一方面的二次电池。
上述说明仅是本申请技术方案的概述，为了能够更清楚了解本申请的 技术手段，而可依照说明书的内容予以实施，并且为了让本申请的上述和其它目的、特征和优点能够更明显易懂，以下特举本申请的具体实施方式。
附图说明
通过阅读对下文优选实施方式的详细描述，各种其他的优点和益处对于本领域普通技术人员将变得清楚明了。附图仅用于示出优选实施方式的目的，而并不认为是对本申请的限制。而且在全部附图中，用相同的附图标号表示相同的部件。在附图中：
图1是二次电池的一实施方式的示意图。
图2是图1的分解图。
图3是电池包的一实施方式的示意图。
图4是图3的分解图。
图5是二次电池用作电源的用电装置的一实施方式的示意图。
图6是实施例1中混合前的硬碳颗粒的电镜图。
图7是实施例1中混合后的硬碳颗粒的电镜图。
附图标记说明：
1、电池包；2、上箱体；3、下箱体；4、二次电池；41、壳体；42、电极组件；43、盖板；5、用电装置。
具体实施方式
下面将结合附图对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特 征的数量、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。本领域技术人员显式地和隐式地理解的是，本文所描述的实施例可以与其它实施例相结合。
在本申请实施例的描述中，术语“和/或”仅仅是一种描述关联对象的关联关系，表示可以存在三种关系，例如A和/或B，可以表示：单独存在A，同时存在A和B，单独存在B这三种情况。另外，本文中字符“/”，一般表示前后关联对象是一种“或”的关系。
在本申请实施例的描述中，术语“多个”指的是两个以上(包括两个)，同理，“多组”指的是两组以上(包括两组)，“多片”指的是两片以上(包括两片)。
在本申请实施例的描述中，技术术语“中心”“纵向”“横向”“长度”“宽度”“厚度”“上”“下”“前”“后”“左”“右”“竖直”“水平”“顶”“底”“内”“外”“顺时针”“逆时针”“轴向”“径向”“周向”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请实施例和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请实施例的限制。
在本申请实施例的描述中，除非另有明确的规定和限定，技术术语“安装”“相连”“连接”“固定”等术语应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或成一体；也可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请实施例中的具体含义。
二次电池主要依靠活性离子在正极和负极之间移动来产生电能，充电时，活性离子从正极脱嵌，经过电解液嵌入负极，放电时则相反。然而，二次电池在充放电过程中，活性离子(例如钠离子等)的嵌入和脱出会引起负极极片的膨胀和收缩，对负极材料结构造成破坏，且在循环充放电过 程中，电解液溶剂的共嵌、有机溶剂的还原以及大电流下的产气，均致使负极活性材料剥落，导致其界面不稳定性增加，造成负极活性物质损失及破坏固体电解质界面(SEI)膜，从而降低了电池的循环寿命。
综上所述，负极极片界面的不稳定性，限制了二次电池的循环性能的提升。传统技术中，常通过改进粘结剂，从而提高负极极片的界面稳定性，然而，粘结剂一般需要采用大分子树脂，其长期与电解液接触后，会发生膨胀，反而会恶化二次电池的循环性能。
基于此，本申请的技术人员另辟蹊径，创造性地提出对负极活性材料的粒径进行调控，提高负极活性材料颗粒之间的协同配合作用，以提高负极极片的粘结性，进而提高二次电池的循环性能。本申请的技术人员在经过大量实验探究之后，获得本申请的技术方案。
本申请一实施方式，提供了一种二次电池，包括负极极片，负极极片包括负极集流体及设于负极集流体至少一个表面上的负极膜层，负极膜层包括负极活性材料，负极活性材料包括碳基材料；在负极活性材料中，粒径小于等于2μm的第一碳基材料的体积占比大于等于15％。
上述二次电池中，控制负极极片中的负极膜层的负极活性材料含有特定粒径范围的第一碳基材料，并同步调控其在负极活性材料中的体积占比，增加了负极活性颗粒之间的接触面积，使负极活性颗粒之间紧密堆积，从而提高了负极极片的粘结性，进而有效改善二次电池的循环性能。
在本申请任意实施例中，在所述负极活性材料中，第一碳基材料的体积占比为20％～70％；可选为30％～60％。
进一步调控粒径小于等于2μm的第一碳基材料的体积占比，使其与其他负极活性材料更好的复配，进一步提高二次电池的循环性能。
上述“20％～70％”中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值及以下点值：20％、21％、22％、23％、24％、25％、26％、27％、28％、29％、30％、31％、32％、33％、34％、36％、36％、37％、38％、39％、40％、41％、42％、43％、44％、45％、46％、47％、48％、49％、50％、51％、52％、53％、54％、55％、56％、57％、58％、59％、60％、61％、62％、63％、64％、65％、66％、 67％、68％、69％、70％；或任意两个数值组成的范围，例如，可以为20％～50％、20％～60％、20％～65％、20％～70％、25％～50％、25％～60％、25％～65％、25％～70％、30％～40％、30％～50％、30％～60％、30％～65％、35％～55％、35％～60％、35％～65％、35％～70％、40％～60％、40％～65％、40％～70％、45％～60％、45％～65％、45％～70％、50％～60％、50％～65％、50％～70％、60％～70％、65％～70％。
在本申请任意实施例中，第一碳基材料的体积分布粒径Dv10为0.2μm～0.5μm。
在本申请任意实施例中，第一碳基材料的体积分布粒径Dv50为0.5μm～2μm。
在本申请任意实施例中，第一碳基材料的体积分布粒径Dv90≤2μm。
在本申请任意实施例中，第一碳基材料的比表面积SSA为5m 2/g～20m 2/g。
在本申请任意实施例中，第一碳基材料的拉曼光谱测试中，I D/I G为0.95～1.35。
在本申请任意实施例中，第一碳基材料在50000N作用力下的粉体压实密度为0.8g/cm 3～1.1g/cm 3。
在本申请任意实施例中，第一碳基材料的振实密度为0.3g/cm 3～0.8g/cm 3。
在本申请任意实施例中，第一碳基材料的X-ray射线衍射测试中，在22°～24°范围内具有(002)晶面峰，负极活性材料的(002)晶面的层间距为0.37nm～0.42nm。
在本申请任意实施例中，在所述负极活性材料中，粒径大于2μm、且小于等于25μm的第二碳基材料的体积占比为20％～80％；可选为50％～60％。
上述“20％～80％”中，取值包括该范围的最小值及最大值，以及这种最小值与最大值之间的每一个值，具体示例包括但不限于实施例中的点值及以下点值：20％、21％、22％、23％、24％、25％、26％、27％、28％、29％、30％、31％、32％、33％、34％、36％、36％、37％、38％、39％、40％、41％、42％、 43％、44％、45％、46％、47％、48％、49％、50％、51％、52％、53％、54％、55％、56％、57％、58％、59％、60％、61％、62％、63％、64％、65％、66％、67％、68％、69％、70％、71％、72％、73％、74％、75％、76％、77％、78％、79％、80％；或任意两个数值组成的范围，例如，可以为20％～60％、20％～65％、20％～70％、20％～75％、20％～80％、25％～60％、25％～65％、25％～70％、25％～75％、25％～80％、30％～60％、30％～65％、35％～70％、35％～75％、35％～80％、35％～60％、35％～65％、35％～70％、35％～75％、35％～80％、40％～60％、40％～65％、40％～70％、40％～75％、40％～80％、45％～60％、45％～65％、45％～70％、45％～75％、45％～80％、50％～60％、50％～65％、50％～70％、50％～75％、50％～80％、55％～65％、55％～75％、55％～80％、60％～70％、60％～75％、60％～80％、65％～70％、65％～75％、65％～80％、70％～80％。
在本申请任意实施例中，第二碳基材料的体积粒径分布呈单峰分布。
在本申请任意实施例中，第二碳基材料的体积分布粒径Dv10为2μm～4μm。
在本申请任意实施例中，第二碳基材料的体积分布粒径Dv50为4μm～8μm。
在本申请任意实施例中，第二碳基材料的体积分布粒径Dv90为8μm～20μm。
在本申请任意实施例中，第二碳基材料的体积分布粒径Dv99为20μm～25μm。
在本申请任意实施例中，第二碳基材料的比表面积SSA为1m 2/g～10m 2/g。
在本申请任意实施例中，第二碳基材料在50000N作用力下的粉体压实密度为0.92g/cm 3～1.2g/cm 3。
在本申请任意实施例中，第二碳基材料的振实密度为0.6g/cm 3～0.94g/cm 3。
在本申请任意实施例中，第二碳基材料的X-ray射线衍射测试中，在22°～24°范围内具有(002)晶面峰，负极活性材料的(002)晶面的层间距 为0.37nm～0.42nm。
在本申请任意实施例中，在负极活性材料中，粒径大于40μm的第三碳基材料的体积占比为0。
调控负极活性材料中的颗粒组成，使粒径大于40μm碳基材料的体积占比为0，即不存在粒径大于40μm碳基材料，以避免较大粒径的颗粒对复配效果产生负面影响。
进一步地，如果负极活性材料中存在粒径大于40μm的第三碳基材料时，可通过进一步调控较大粒径的第三碳基材料的体积占比，使其与较小粒径的碳基材料能较好复配，以降低对电池循环性能的影响。
在一些实施例中，在负极活性材料中，粒径大于40μm的第三碳基材料的体积占比小于等于10％；可选为小于等于5％。
在负极活性材料中，粒径大于40μm的第三碳基材料的体积占比可选为0.1％、0.5％、1％、1.5％、2％、2.5％、3％、3.5％、4％、4.5％、5％、5.5％、6％、6.5％、7％、7.5％、8％、8.5％、9％、9.5％、10％中的任一数或任意两个数组成的范围；例如，可以为0.1％～5％、0.1％～4.5％、0.1％～4％、0.1％～3.5％、0.1％～3％、0.1％～2.5％、0.1％～2％、0.1％～1.5％、0.1％～1％、0.1％～0.5％、1％～5％、1％～4.5％、1％～4％、1％～3.5％、2％～4％、3％～5％。
可选地，粒径大于40μm的第三碳基材料的粒径大于40μm、且小于等于100μm。
在本申请任意实施例中，第三碳基材料的比表面积SSA为1m 2/g～10m 2/g。
在本申请任意实施例中，第三碳基材料的拉曼光谱测试中，I D/I G为0.95～1.35。
在本申请任意实施例中，第三碳基材料在50000N作用力下的粉体压实密度为0.7g/cm 3～1g/cm 3。
在本申请任意实施例中，第三碳基材料的振实密度为0.5g/cm 3～0.8g/cm 3。
在本申请任意实施例中，第三碳基材料的X-ray射线衍射测试中，在22°～24°范围内具有(002)晶面峰，负极活性材料的(002)晶面的层间距为0.37nm～0.42nm。
在本申请任意实施例中，负极活性材料的体积分布粒径Dv50小于等于8μm。
可选地，负极活性材料的体积分布粒径Dv50为1μm～8μm。
可选地，负极活性材料的体积分布粒径Dv50为1μm～6μm。
可选地，负极活性材料的体积分布粒径Dv50为2μm～6μm。
进一步调控负极活性材料的体积分布粒径Dv50，使其具有特定的范围，可进一步提高二次电池的首效。
在本申请任意实施例中，负极活性材料的体积分布粒径满足：4μm≤Dv90≤20μm；可选地，5μm≤Dv90≤16μm。
在本申请任意实施例中，负极活性材料的体积分布粒径Dv10满足：0.2μm≤Dv10≤2μm；可选地，0.5μm≤Dv10≤1.8μm。
在本申请中，上述Dv10、Dv50或Dv90表示：材料累计体积分布百分数分别达到10％、50％或90％所对应的粒径，可以用本领域已知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定。测试仪器可以为英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
在本申请任意实施例中，负极活性材料的比表面积SSA≤20m 2/g；可选为SSA≤10m 2/g。
上述负极活性材料的比表面积参照GB/T 19587-2004气体吸附BET法测定固态物质比表面积测定。
在本申请任意实施例中，负极活性材料的拉曼光谱测试中，I D/I G为0.87～1.35；可选为0.91～1.25。
上述I D/I G是指在材料的拉曼光谱图中，D峰、G峰两个峰强度的比值；其中，I D表示碳材料的拉曼光谱在1350±50cm -1处的D峰强度，I G表示碳材料的拉曼光谱在1580±50cm -1处的G峰强度。
在本申请任意实施例中，上述碳基材料包括硬碳材料。
以石墨化难易程度分，碳材料分为石墨，软碳和硬碳，硬碳是指在2800℃以上难以完全石墨化的碳，在高温下其无序结构难以消除。进一步地，制备硬碳材料的前驱体不仅仅限于矿物质原料，可包括除特别容易石墨化的矿物质原料之外的所有含C、H、O元素的化合物。
在本申请任意实施例中，在22°～24°范围内具有(002)晶面峰，负极活性材料的(002)晶面的层间距≥0.37nm，可选为0.37nm～0.42nm。
具体地，负极活性材料的X-ray射线衍射测试中，(002)晶面层间距采用Bragg公式计算出。
在本申请任意实施例中，负极活性材料在50000N作用力下的粉体压实密度为0.90g/cm 3～1.5g/cm 3；可选为0.95g/cm 3～1.3g/cm 3。
进一步调控负极活性材料的粉体压实密度，提高负极片的粘结力，在提高二次电池的循环性能的同时，保持优异的首效。
在本申请任意实施例中，负极活性材料的振实密度为0.50g/cm 3～0.97g/cm 3；可选为0.6g/cm 3～0.94g/cm 3。
在本申请任意实施例中，碳基材料包括多个纳米孔结构，可选地，碳基材料包括多个孔径在10nm以下的孔结构。
在本申请任意实施方式中，基于负极膜层的总重量计，负极活性材料的质量占比为85wt％～95wt％。
在本申请任意实施方式中，上述负极膜层还包括负极导电剂及负极粘结剂。
在本申请任意实施方式中，上述负极导电剂可以采用本领域常用的导电材料，包括但不限于：石墨、碳纳米管、纳米纤维、炭黑和石墨烯中的至少一种。具体地，可选自SP、KS-6，乙炔黑、有支链结构的科琴黑ECP，SFG-6，气相生长碳纤维VGCF，碳纳米管CNTs和石墨烯及其复合导电剂中的至少一种。
基于负极膜层的总重量计，负极导电剂在负极膜层中的重量比为0～20wt％。
上述负极粘结剂可采用本领域常用的粘结剂，可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
基于负极膜层的总重量计，负极粘结剂在负极活性层中的重量比为0～30wt％。
在本申请任意实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂，如羧甲基纤维素钠(CMC-Na)等。基于负极活性层的总重量计，其他助剂在负极活性层中的重量比为0～15wt％。
在本申请任意实施方式中，负极极片中的集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
上述二次电池可采用本领域常用的制备方法制备，此处对制备方法进行示例说明，但不限于下述制备方法。
上述二次电池的制备方法，包括采用如下步骤S10～S30制备负极极片。
S10，配制上述负极活性材料。
S20，将负极活性材料制备成负极浆料。
S30，将负极浆料涂布在负极集流体的至少一个表面上形成负极膜层。
在本申请任意实施例中，配制负极活性材料采用的原料包括第一碳基材料、第二碳基材料和第三碳基材料，第一碳基材料的粒径≤2μm，第二碳基材料的粒径大于2μm、且小于等于25μm，第三碳基材料的粒径大于40μm。
可理解，采用上述第一碳基材料、第二碳基材料和第三碳基材料按照负极活性材料的粒径体积占比配置。
第一碳基材料、第二碳基材料和第三碳基材料的选择及参数控制同上，在此不再赘述。
在本申请任意实施例中，配制负极活性材料的具体步骤包括如下步骤：
将第一碳基材料、第二碳基材料和第三碳基材料混合，得到负极活性材料。
可选地，上述混合的步骤中，混料时间为0.5h～10h。
控制混料时间，在使物料混合均匀的同时，不破坏原始物料颗粒的结构。
具体地，上述混合的步骤在混料机中进行。
在本申请任意实施中，负极浆料固含量为30wt％～70wt％，室温下的粘度调整到2000mPa·s～10000mPa·s；将所得到的负极浆料涂覆在负极集流体上，经过干燥工序，冷压例如对辊，得到负极极片。负极粉末涂布单位面密度为75mg/m 2～220mg/m 2，负极极片压实密度1.2g/m 3～2.0g/m 3。
在本申请任意实施方式中，上述二次电池还包括正极极片、电解液及隔离膜。
可选地，上述二次电池可以是钠离子电池、锂离子电池、钾离子电池。
在一具体示例中，上述二次电池为钠离子电池。
下面对正极极片、电解液隔离膜进行举例说明，但不限于如下范围。
[正极极片]
正极极片包括正极集流体及设于正极集流体至少一个表面上的正极膜层，正极膜层的组分包括正极活性材料。
作为示例，正极极片中的集流体具有在其自身厚度方向相对的两个表面，正极活性材料层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在本申请任意实施方式中，正极极片中的集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
上述正极活性材料可采用本申请中的常用的正极活性材料，例如锂离子正极活性材料或钠离子正极活性材料。
进一步地，作为示例，锂离子活性材料可包括以下材料中的至少一种： 橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物(如LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))磷酸锰锂(如LiMnPO 4)、磷酸锰铁锂中的至少一种。
在本申请任意实施方式中，锂离子活性材料的分子式为：LiFe xMn (1-x)PO 4，x取0～1任一数。
可理解，当x取0时，LiFe xMn (1-x)PO 4即为LiMnPO 4磷酸锰锂，当x取1时，LiFePO 4即为LiFePO 4磷酸铁锂(LFP)。
作为示例，钠离子活性材料可包括以下材料中的至少一种：钠过渡金属氧化物、聚阴离子型化合物和普鲁士蓝类化合物中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作钠离子电池正极活性材料的传统公知的材料。
作为本申请可选的技术方案，钠过渡金属氧化物中，过渡金属至少包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。钠过渡金属氧化物例如为Na xMO 2，其中M至少包括Ti、V、Mn、Co、Ni、Fe、Cr及Cu中的一种或几种，0＜x≤1。
作为本申请可选的技术方案，聚阴离子型化合物可以是具有钠离子、过渡金属离子及四面体型(YO 4) n-阴离子单元的一类化合物。过渡金属至少包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y 至少包括P、S及Si中的至少一种；n表示(YO 4) n-的价态。
聚阴离子型化合物还可以是具有钠离子、过渡金属离子、四面体型(YO 4) n-阴离子单元及卤素阴离子的一类化合物。过渡金属至少包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y至少包括P、S及Si中的至少一种，n表示(YO 4) n-的价态；卤素可以是F、Cl及Br中的至少一种。
聚阴离子型化合物还可以是具有钠离子、四面体型(YO 4) n-阴离子单元、多面体单元(ZO y) m+及可选的卤素阴离子的一类化合物。Y至少包括P、S及Si中的至少一种，n表示(YO 4) n-的价态；Z表示过渡金属，至少包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种，m表示(ZO y) m+的价态；卤素可以是F、Cl及Br中的至少一种。
聚阴离子型化合物例如是NaFePO 4、Na 3V 2(PO 4) 3(磷酸钒钠，简称NVP)、Na 4Fe 3(PO 4) 2(P 2O 7)、NaM’PO 4F(M’为V、Fe、Mn及Ni中的一种或几种)及Na 3(VO y) 2(PO 4) 2F 3-2y(0≤y≤1)中的至少一种。
普鲁士蓝类化合物可以是具有钠离子、过渡金属离子及氰根离子(CN -)的一类化合物。过渡金属至少包括Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。普鲁士蓝类化合物例如为Na aMe bMe’ c(CN) 6，其中Me及Me’各自独立地至少包括Ni、Cu、Fe、Mn、Co及Zn中的至少一种，0＜a≤2，0＜b＜1，0＜c＜1。
基于正极膜层的总重量计，正极活性材料在正极膜层中的重量比为80wt％～100wt％。
在本申请任意实施方式中，正极膜层的组分还包括正极导电剂和正极粘结剂。
上述正极导电剂可以采用本领域常用的导电剂，包括但不限于：石墨、碳纳米管、纳米纤维、炭黑和石墨烯中的至少一种。具体地，可选自SP、KS-6，乙炔黑、有支链结构的科琴黑ECP，SFG-6，气相生长碳纤维VGCF，碳纳米管CNTs和石墨烯及其复合导电剂中的至少一种。
基于正极膜层的总重量计，正极导电剂在正极活性层中的重量比为0～20wt％。
在本申请任意实施方式中，上述正极粘结剂的粘结剂可以是聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物、氢化丁腈橡胶、丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)及含氟丙烯酸酯树脂中的至少一种。
基于正极膜层的总重量计，正极粘结剂在正极活性层中的重量比为0～30wt％。
在本申请任意实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在集流体上，经烘干、冷压等工序后，即可得到正极极片。正极浆料固含量为40wt％～80wt％，室温下的粘度调整到5000mPa·s～25000mPa·s，将正极浆料涂覆在正极集流体的表面，烘干后经过冷轧机冷压后形成正极极片；正极粉末涂布单位面密度为150～350mg/m 2，正极极片压实密度为3.0～3.6g/cm 3，可选为3.3～3.5g/cm 3。压实密度的计算公式为：
压实密度＝涂布面密度/(挤压后极片厚度-集流体厚度)。
[电解液]
电解液包括电解质盐及溶剂
在一些实施方式中，电解质盐可选自本领域常用的电解质盐，包括锂离子电解质盐和钠离子电解质盐。
作为示例，锂离子电解质盐选自：六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、高氯酸锂(LiClO 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LIDFOB)、二草酸硼酸锂(LiBOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LIDFOP)、Li(FSO 2) 2N、LiCF 3SO 3及四氟草酸磷酸锂(LiTFOP)中的一种或几种。
作为示例，钠离子电解质盐选自：六氟磷酸钠(NaPF 6)、NaClO 4，NaAIClh，NaFeClh，NaBF 4，NaBClh，NaNO 3，NaPOFA，NaSCN，NaCN，NaAsF 6，NaCF 3CO 2，NaSbF 6，NaC 6HsCO 2，Na(CH 3)C 6H 4SO 3，NaHSO 4，NaB(C 6Hs) 4中的一种或几种。
在本申请任意实施方式中，溶剂可选自氟代碳酸乙烯酯(FEC)、碳酸亚乙酯(EC)、碳酸亚丙基酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在本申请任意实施方式中，电解质盐的浓度通常为0.5mol/L～15mol/L。
在本申请任意实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
隔离膜设于正极极片和负极极片之间。
本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在其中一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
上述二次电池还包括外壳，用于包装正极极片、负极极片、隔离膜及电解液。
在其中一些实施方式中，上述外壳的可以是硬壳，例如硬塑料壳、铝 壳、钢壳等。也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池4。
在一些实施例中，参照图2，外壳可包括壳体41和盖板43。其中，壳体41可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体41具有与容纳腔连通的开口，盖板43能够盖设于所述开口，以封闭所述容纳腔。
正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件42。电极组件42封装于容纳腔。电解液浸润于电极组件42中。电池4所含电极组件42的数量可以为一个或多个，可根据需求来调节。
本申请还提供一种用电装置，该用电装置包括上述的二次电池。
进一步地，在上述用电装置中，二次电池可以电池单体的形式存在，也可以进一步组装成电池包的形式存在。
图3和图4是作为一个示例的电池包1。在电池包1中包括电池箱和设置于电池箱中的一个或多个二次电池4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于二次电池4的封闭空间。
多个二次电池4可以按照任意的方式排布于电池箱中。
上述二次电池或其组装成的电池包可以用作用电装置的电源，也可以作为用电装置的能量存储单元。
上述用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
图5是作为一个示例的用电装置5。该用电装置5为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置5对二次电池的高功率和高能量密度的需求，可以采用电池包形式。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用电池作为电源。
下面将结合具体的实施例对本发明进行了说明，但本发明并不局限于下述实施例，应当理解，所附权利要求概括了本发明的范围，在本发明构思的引导下本领域的技术人员应意识到，对本发明的各实施例所进行的一定的改变，都将被本发明的权利要求书的精神和范围所覆盖。
以下为具体实施例。
具体实施例
实施例1
(1)负极活性颗粒的混合：
提供硬碳颗粒，包括第一硬碳颗粒、第二硬碳颗粒和第三硬碳颗粒，其中，粒径分别为T1、T2及T3。
采用Mastersizer 2000E型激光粒度分析仪参照标准GB/T19077-2016分别测试得到第一硬碳颗粒、第二硬碳颗粒和第三硬碳颗粒的粒度-体积累积分布曲线，并测试其粉体压实密度和振实密度。具体参数如表1所示。
将上述硬碳颗粒按照预设体积比占比在混料机上进行混合，混料时间为4h，得到混合的硬碳颗粒。
分别对混合前后的硬碳颗粒的形貌进行观测，混合前的硬碳颗粒的电镜图如图6所示，图6中(a)为混合前的第一硬碳颗粒的电镜图，图6中(b)为混合前第二硬碳颗粒的硬碳颗粒电镜图，混合后的硬碳颗粒的电镜图如图7所示。
对混合后的硬碳颗粒进行XRD和Raman测试，XRD结果表明：d002峰峰位为22°～24°；Raman结果表明：在1350±50cm -1处的D峰和在1580±50cm -1处的G峰的峰强度之比I D/I G为0.9～1.35。XRD和Raman均表明：混合后的硬碳颗粒仍具有硬碳的特征峰，混合过程并未破坏硬碳的结构。
采用Mastersizer 2000E型激光粒度分析仪参照标准GB/T19077-2016对混合后的硬碳颗粒的粒度进行测试，获得其粒度-体积累积分布曲线，其相关参数结果请见表4。其中以混合后的硬碳颗粒的体积峰总面积为基准，粒径小于等于2μm的碳基材料硬碳颗粒、粒径大于2μm且小于等于25μm的硬碳 颗粒、粒径大于40μm的硬碳颗粒的体积峰面积占比分别记为D1、D2、D3，通过调节各级碳颗粒的配比，使D1、D2、D3的值满足表4中的关系
对混合后的硬碳颗粒的粉体压实密度和振实密度进行测试，具体结果请见表3。
上述粉体压实密度测试，参照标准GB/T 24533-2009在50000N的压力下进行，上述振实密度参照标准GB/T 5162-2006进行。
对混合后的硬碳颗粒的比表面积进行测试，参照标准GB/T 19587-2004气体吸附BET法测定固态物质比表面积进行，具体结果请见表2。
(2)负极极片的制备：
将上述混合后的硬碳颗粒、导电剂碳黑、粘结剂水溶性不饱和树脂SR-1B(醇酸不饱和聚酯树脂)、增稠剂羟甲基纤维素钠(CMC-Na)按照重量比为95：1.74：2.3：0.96混合，然后分散于溶剂去离子水中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。其中，负极极片涂布的单位面密度为50g/m 2，负极极片的压实密度为1.2g/m 3。
上述极片的压实密度和面密度为本领域公知的含义，极片的面密度是指：单位面积的极片负载的活性层的重量，单位面密度＝活性层的重量/活性层的面积。其中，活性层的重量可以采用的极片重量减去集流体的重量获得。
上述极片的压实密度是指极片面密度与活性层厚度的比值，是材料能量密度的参考指标之一。测试方法：根据上述方法确定极片的面密度，使用游标卡尺测量极片的总厚度，减去集流体的厚度就可以计算出活性层的厚度。根据面密度及厚度两个参数，就可以计算极片的压实密度。
对制得的负极极片的粘结力及孔隙率进行测试，参照标准GB/T 19587-2004对孔隙率进行测试，粘结力的测试步骤如下：
在25℃下，将负极极片用刀片截取宽30mm*长度为100-160mm的试样，将专用双面胶贴于钢板上，胶带宽度20mm*长度90-150mm，将截取的极片试样贴在双面胶上，测试面朝下，后用压辊沿同一个方向滚压三次，将宽度与极片等宽，长度大于试样长度80-200mm的纸带插入极片下方，并且用皱纹胶固定，打开拉力机电源，指示灯亮，调整限位块到合适位置，将钢板未贴 极片的一端用下夹具固定，将纸带向上翻折，用上夹具固定，利用拉力机附带的手动控制器上的“上行”和“下行”按钮调整上夹具的位置，打开与拉力机链接的专用电脑，双击桌面软件图标，进行测试，拉伸速率50m/min，测试距离50mm，软件每10s取一个数据点，以这些数据点值为纵坐标，以对应的测试距离为横坐标，纵坐标读数逐渐趋于稳定，读取稳定后的纵坐标读数即为粘结力。
具体测试结果请见表3。
(3)正极极片的制备：
钠子正极极片的制备：将普鲁士白正极活性材料、导电剂炭黑、聚偏二氟乙烯(PVDF)按照重量比为95：5：5溶于溶剂N-甲基吡咯烷酮中，混合均匀后制备成正极浆料；将正极浆料一次均匀涂覆在正极集流体铜箔上，经过烘干、冷压、分切得到钠离子正极极片。
(4)隔离膜的制备：以聚丙烯膜作为隔离膜。
(5)电解液的制备：
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将有机溶剂碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)按照体积比3：7混合均匀，加入NaPF 6盐溶解于有机溶剂中，搅拌均匀，得到NaPF 6盐浓度为12.5wt％的电解液。
(6)将钠离子正极极片、负极极片进行依次进行分切，整形，装配，入壳、注入钠离子电池电解液，化成、老化工序，制备得到锂离子电池。
(7)钠离子电池的循环性能测试：
于25℃下，对制得的钠离子二次电池重复进行充电和放电，计算其循环充放电n次(cycle)后的电容保持率(capacity)，具体如下：
在25℃下，将上述制备的钠离子电池以1C倍率恒流充电至充电截止电压4.25V，之后恒压充电至电流≤0.05C，静置5min，再以0.33C倍率恒流放电至放电截止电压2.8V，静置5min，记录此时的容量C0，此为一个充放电循环。
按照上述对电池进行循环充放电测试，循环500次，并记录每次循环的放电容量，循环500次时的容量记为C500，C500＝(C500/C0)×100％。具体结果请见表4。
(8)钠离子电池的首效性能测试：
在25℃下，将对应的电电池以0.05C恒流放电至5mV，再以50μA恒定电压放电至5mV，搁置1h，再以10μA放电至5mV，所得容量记为放电容量C0。再静置1h,然后以0.05C横流充电至2V，所得容量为充电容量C1，首次库伦效率P0＝C1/C0*100％。
具体结果请见表3。
实施例2～12
实施例2～12与实施例1基本相同，不同之处仅在于：调控步骤(1)负极活性颗粒的混合时各硬碳颗粒的体积占比，以使实施例2～12中混合后的硬碳颗粒的部分参数与实施例1不同。具体请见表2。
实施例13～15
实施例13～15与实施例1基本相同，不同之处仅在于：实施例13～15中步骤(1)负极活性颗粒的混合时，混料时间分别为0.5h、2h、8h，以使实施例13～15中混合后的硬碳颗粒的部分参数与实施例1不同。具体请见表2。
对比例1
对比例1与实施例1基本相同，不同之处仅在于：调控步骤(1)负极活性颗粒的混合时各硬碳颗粒的设体积比占比，以使对比例1中混合后的硬碳颗粒的部分参数与实施例1不同
具体请见表2。
各实施例及对比例中采用的第一硬碳颗粒、第二硬碳颗粒及第三硬碳颗粒的参数如表1所示。
表1
Figure PCTCN2022131678-appb-000001
Figure PCTCN2022131678-appb-000002
上述表中，“()”表示括号内的取值范围不能取两边端点值，“[]”表示括号内的取值范围能取两边端点值，“(]”或“[)”表示括号内的取值范围能取“[”一端的端点值，不能取“)”一端的端点值。
各实施例及对比例混合后的硬碳颗粒的参数请见表2，负极片参数、钠离子电池的性能测试结果如表3所示。
表2中，以混合后的硬碳颗粒的体积峰总面积为基准，D1代表：粒径小于等于2μm的第一硬碳颗粒的体积峰面积占比，D2代表：粒径大于2μm且小于等于25μm的第二硬碳颗粒，D3代表：粒径大于40μm的第三硬碳颗粒的体积峰面积占比。
表2
Figure PCTCN2022131678-appb-000003
Figure PCTCN2022131678-appb-000004
表3
Figure PCTCN2022131678-appb-000005
Figure PCTCN2022131678-appb-000006
由表3数据可知，控制负极极片中的负极膜层的负极活性材料含有特定粒径范围的碳基材料，并调控其在负极活性材料中的体积占比，增加负极活性颗粒之间的接触面积，使负极活性颗粒之间紧密堆积，从而提高负极极片的粘结性，进而能提高二次电池的首效及循环性能。
最后应说明的是：以上各实施例仅用以说明本申请的技术方案，而非对其限制；尽管参照前述各实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围，其均应涵盖在本申请的权利要求和说明书的范围当中。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (19)

  1. 一种二次电池，包括负极极片，所述负极极片包括负极集流体及设于所述负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料，所述负极活性材料包括碳基材料；
    在所述负极活性材料中，粒径小于等于2μm的第一碳基材料的体积占比大于等于15％。
  2. 如权利要求1所述的二次电池，其中，在所述负极活性材料中，所述第一碳基材料的体积占比为20％～70％；可选为30％～60％。
  3. 如权利要求1或2所述的二次电池，其中，所述第一碳基材料满足如下条件中(1)～(7)的至少一个：
    (1)所述第一碳基材料的体积分布粒径Dv10为0.2μm～0.5μm；
    (2)所述第一碳基材料的体积分布粒径Dv50为0.5μm～2μm；
    (3)所述第一碳基材料的体积分布粒径Dv90≤2μm；
    (4)所述第一碳基材料的比表面积SSA为5m 2/g～20m 2/g；
    (5)所述第一碳基材料的拉曼光谱测试中，I D/I G为0.95～1.35；
    (6)所述第一碳基材料在50000N作用力下的粉体压实密度为0.8g/cm 3～1.1g/cm 3；
    (7)所述第一碳基材料的振实密度为0.3g/cm 3～0.8g/cm 3。
  4. 如权利要求1～3任一项所述的二次电池，其中，在所述负极活性材料中，粒径大于2μm、且小于等于25μm的第二碳基材料的体积占比为20％～80％；可选为50％～60％。
  5. 如权利要求4所述的二次电池，其中，所述第二碳基材料满足如下条件(Ⅰ)～(Ⅷ)中的至少一种：
    (Ⅰ)所述第二碳基材料的体积粒径分布呈单峰分布；
    (Ⅱ)所述第二碳基材料的体积分布粒径Dv10为2μm～4μm；
    (Ⅲ)所述第二碳基材料的体积分布粒径Dv50为4μm～8μm；
    (Ⅳ)所述第二碳基材料的体积分布粒径Dv90为8μm～20μm；
    (Ⅴ)所述第二碳基材料的体积分布粒径Dv99为20μm～25μm；
    (Ⅵ)所述第二碳基材料的比表面积SSA为1m 2/g～10m 2/g；
    (Ⅶ)所述第二碳基材料在50000N作用力下的粉体压实密度为0.92 g/cm 3～1.2g/cm 3；
    (Ⅷ)所述第二碳基材料的振实密度为0.6g/cm 3～0.94g/cm 3。
  6. 如权利要求1～5任一项所述的二次电池，其中，在所述负极活性材料中，粒径大于40μm、且小于等于100μm的第三碳基材料的体积占比小于等于10％；可选为小于等于5％。
  7. 如权利要求6所述的二次电池，其中，所述第三碳基材料满足如下条件中(1)～(4)的至少一种：
    (1)所述第三碳基材料的比表面积SSA为1m 2/g～10m 2/g；
    (2)所述第三碳基材料的拉曼光谱测试中，I D/I G为0.95～1.35；
    (3)所述第三碳基材料在50000N作用力下的粉体压实密度为0.7g/cm 3～1g/cm 3；
    (4)所述第三碳基材料的振实密度为0.5g/cm 3～0.8g/cm 3。
  8. 如权利要求1～7任一项所述的二次电池，其中，所述负极活性材料的体积分布粒径Dv50小于等于8μm；可选地，所述负极活性材料的体积分布粒径Dv50为2μm～6μm。
  9. 如权利要求1～8任一项所述的二次电池，其中，所述负极活性材料的体积分布粒径满足：4μm≤Dv90≤20μm；可选地，5μm≤Dv90≤16μm。
  10. 如权利要求1～9任一项所述的二次电池，其中，所述负极活性材料的体积分布粒径Dv10满足：0.2μm≤Dv10≤2μm；可选地，0.5μm≤Dv10≤1.8μm。
  11. 如权利要求1～10任一项所述的二次电池，其中，所述负极活性材料的比表面积SSA≤20m 2/g；可选地，SSA≤10m 2/g。
  12. 如权利要求1～11任一项所述的二次电池，其中，所述负极活性材料的拉曼光谱测试中，I D/I G为0.87～1.35；可选为0.91～1.25。
  13. 如权利要求1～12任一项所述的二次电池，其中，所述负极活性材料的X-ray射线衍射测试中，在22°～24°范围内具有(002)晶面峰，所述负极活性材料的(002)晶面的层间距≥0.37nm，可选为0.37nm～0.42nm。
  14. 如权利要求1～13任一项所述的二次电池，其中，所述负极活性材料在50000N作用力下的粉体压实密度为0.90g/cm 3～1.5g/cm 3；可选为0.95g/cm 3～1.3g/cm 3。
  15. 如权利要求1～14任一项所述的二次电池，其中，所述负极活性材料的振实密度为0.50g/cm 3～0.97g/cm 3；可选为0.6g/cm 3～0.94g/cm 3。
  16. 如权利要求1～15任一项所述的二次电池，其中，所述碳基材料包括多个纳米孔结构，可选地，所述碳基材料包括多个孔径在10nm以下的孔结构。
  17. 如权利要求1～16任一项所述的二次电池，其中，所述碳基材料包括硬碳材料。
  18. 如权利要求1～17任一项所述的二次电池，其中，所述二次电池为钠离子二次电池。
  19. 一种用电装置，包括如权利要求1～18任一项所述的二次电池。
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CN113207313A (zh) * 2019-12-03 2021-08-03 宁德时代新能源科技股份有限公司 二次电池、装置、人造石墨及制备方法

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