WO2024011509A1 - 二次电池、电池模块、电池包和用电装置 - Google Patents

二次电池、电池模块、电池包和用电装置 Download PDF

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WO2024011509A1
WO2024011509A1 PCT/CN2022/105752 CN2022105752W WO2024011509A1 WO 2024011509 A1 WO2024011509 A1 WO 2024011509A1 CN 2022105752 W CN2022105752 W CN 2022105752W WO 2024011509 A1 WO2024011509 A1 WO 2024011509A1
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negative electrode
secondary battery
ferroelectric
layer
film layer
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PCT/CN2022/105752
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English (en)
French (fr)
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游兴艳
吴益扬
白文龙
武宝珍
王育文
吴凯
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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/CN2022/105752 priority Critical patent/WO2024011509A1/zh
Priority to CN202280007457.8A priority patent/CN117716574A/zh
Publication of WO2024011509A1 publication Critical patent/WO2024011509A1/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
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/409—Separators, membranes or diaphragms characterised by the material
    • H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of batteries, and specifically to a secondary battery, a battery module, a battery pack and an electrical device.
  • Secondary batteries have the characteristics of high capacity and long life, so they are widely used in electronic equipment, such as mobile phones, laptop computers, battery cars, electric cars, electric airplanes, electric ships, electric toy cars, electric toy ships, electric toy airplanes and electric tools etc. As the range of battery applications becomes more and more extensive, the performance requirements for secondary batteries are becoming increasingly stringent, such as requiring fast charging capabilities.
  • This application was made in view of the above-mentioned problems, and its purpose is to provide a secondary battery, a battery module, a battery pack, and an electrical device.
  • the first aspect of the present application provides a secondary battery.
  • the secondary battery includes a positive electrode plate, a negative electrode, an isolation film, and a ferroelectric layer; the negative electrode plate includes a negative electrode film layer containing a negative active material; and the isolation film is provided Between the positive electrode piece and the negative electrode piece; a ferroelectric layer is provided on at least one surface of the isolation film, the ferroelectric layer includes ferroelectric particles, wherein the compaction of the negative electrode film layer The density is P g/cm 3 ; the coating weight of the negative electrode film layer is CW g/1540.25mm 2 ; the thickness of the ferroelectric layer is H ⁇ m; the volume average particle size Dv50 of the ferroelectric particles is D ⁇ m, the secondary battery satisfies:
  • this application regulates the compaction density P of the negative electrode film layer, the coating weight of the negative electrode film layer, the thickness H of the ferroelectric layer, and the volume average particle size Dv50 of the ferroelectric particles to meet the above ranges, and the secondary battery is charged At this time, it can ensure that the ferroelectric particles in the ferroelectric layer fully exert the ferroelectric effect, and can evenly distribute the metal ions between the negative electrode active material and the electrolyte interface, thereby ensuring the lithium embedding ability of the negative electrode sheet and improving the performance of the secondary battery. Cycle performance.
  • the thickness H ⁇ m of the ferroelectric layer satisfies: 2 ⁇ H ⁇ 10; optionally, 4 ⁇ H ⁇ 6.
  • the ferroelectric layer can fully exert the ferroelectric effect and further balance the distribution of metal ions, making the distribution of metal ions more uniform; and the ferroelectric layer may not be able to Provides capacity for the secondary battery, so the ferroelectric layer in the above thickness range will not occupy too much space and will not excessively occupy the space in the secondary battery, thereby ensuring the space occupied by the negative active material, thus ensuring the secondary battery
  • the energy density and capacity of the secondary battery give the secondary battery the advantage of long battery life; in addition, the moderate thickness of the ferroelectric layer can effectively inhibit the vertical growth of metal ions, and can effectively reduce the internal occurrence of secondary battery when the secondary battery is charged at a high rate. The risk of short circuit is thereby guaranteed to ensure the high-rate charging performance of the secondary battery.
  • the volume average particle diameter Dv50 of the ferroelectric particles satisfies: 0.08 ⁇ D ⁇ 1; optionally, 0.1 ⁇ D ⁇ 0.8.
  • the volume average particle size Dv50 of the ferroelectric particles satisfies the above range, which is beneficial to even distribution in the ferroelectric layer.
  • the mass content a of the ferroelectric particles satisfies: 90% ⁇ a ⁇ 98%; optionally, 95% ⁇ a ⁇ 98%.
  • the ferroelectric particles can be more evenly distributed on the surface of the negative electrode film layer, and the reverse electric field generated is more uniform; and the ferroelectric layer containing ferroelectric particles will not Thick, thus ensuring the occupied volume of the negative active material and ensuring the energy density of the secondary battery.
  • the ferroelectric particles include one or more selected from the group consisting of perovskite structure oxides, tungsten bronze-type compounds, and bismuth oxide-type layered structure compounds; optionally, the calcium Titanium structure oxides include one or more of barium titanate BTO, lead zirconate titanate PZT, lead metaniobate, lead barium lithium niobate PBLN and lead titanate PT.
  • the above types of ferroelectric particles can effectively exert the ferroelectric effect to improve the degree of uniform distribution of metal ions.
  • the dielectric constant of the ferroelectric particles satisfies: 100 ⁇ 100000; optionally, 1000 ⁇ 10000.
  • the dielectric constant of ferroelectric particles is within the above range, it can quickly migrate metal ions, thereby ensuring the migration rate of metal ions.
  • the compacted density P g/cm 3 of the negative electrode film layer and the coating weight CW g/1540.25mm 2 of the negative electrode film layer satisfy:
  • the ferroelectric layer can affect the overall structure of the pole piece, including the structure of the lower layer of the pole piece; and the pole piece has appropriate pores, and the electrolyte can fully infiltrate the pole piece, which is conducive to the migration of lithium ions.
  • the compacted density P g/cm 3 of the negative electrode film layer satisfies: 1.1 ⁇ P ⁇ 1.85; optionally, 1.3 ⁇ P ⁇ 1.8.
  • the secondary battery can have a higher energy density.
  • the compaction density within an appropriate range the negative electrode film layer can also have a strong ability to maintain the pore structure during circulation. As a result, the negative electrode sheet has better electrolyte wettability and can better Improve the cycle performance of secondary batteries.
  • the coating weight of the negative electrode film layer CW g/1540.25mm 2 satisfies: 0.1 ⁇ CW ⁇ 0.3; optionally, 0.14 ⁇ CW ⁇ 0.2.
  • the thickness L ⁇ m of the negative electrode film layer satisfies: 30 ⁇ m ⁇ L ⁇ 200 ⁇ m; optionally, 35 ⁇ m ⁇ L ⁇ 190 ⁇ m.
  • the negative active material includes one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.
  • a second aspect of the application also provides a battery module, including the secondary battery according to any embodiment of the first aspect of the application.
  • a third aspect of the present application also provides a battery pack, including the battery module according to the embodiment of the second aspect of the present application.
  • the fourth aspect of the present application also provides an electrical device, including a secondary battery as in any embodiment of the first aspect of the present application, a battery module as in the second embodiment of the present application, or a third embodiment of the present application. battery pack.
  • Figure 1 is a schematic diagram of an electrode assembly according to an embodiment of the present application.
  • Figure 2 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • Figure 3 is an exploded view of the secondary battery according to an embodiment of the present application shown in Figure 2;
  • FIG. 4 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 6 is an exploded view of the battery pack according to an embodiment of the present application shown in Figure 5;
  • Figure 7 is a schematic diagram of an electrical device according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) can be added to the method in any order.
  • the method may include steps (a), (b) and (c), and may also include step (a). , (c) and (b), and may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • the secondary battery may include a lithium-ion battery, a lithium-sulfur battery, a sodium-lithium-ion battery, a sodium-ion battery or a magnesium-ion battery, etc., which are not limited in the embodiments of this application.
  • the secondary battery includes an electrode assembly and an electrolyte.
  • the electrode assembly consists of a positive electrode plate, a negative electrode plate and a separator. Secondary batteries work mainly by relying on the movement of metal ions between the positive electrode piece, which includes the positive active material, and the negative electrode piece, which includes the negative active material.
  • the metal ions can be lithium ions, sodium ions, etc.; next, the metal ions are lithium ions to illustrate the charging process.
  • the electrode kinetics process usually includes the following steps.
  • Lithium ion extraction step Lithium ions are extracted from the positive electrode active material and migrate to the electrolyte phase;
  • Liquid phase mass transfer step in the electrolyte phase The solvated lithium ions in the electrolyte diffuse to the surface of the negative electrode active material Transfer;
  • Surface conversion step During the first charge, the solvated lithium ions are adsorbed on the surface of the negative active material and react to form a solid electrolyte interface (SEI) film. During subsequent charging, the solvated lithium ions are adsorbed on the surface of the SEI film and undergo deionization.
  • SEI solid electrolyte interface
  • lithium ions reach the surface of the negative active material; (4) charge exchange step: lithium ions obtain electrons from the surface of the negative active material and form a lithium-insertion product; (5) solid-phase mass transfer step of the lithium-insertion product: lithium insertion The product solid-phase diffuses from the surface of the negative active material to the interior, completing the charging process.
  • lithium ions are extracted from the cathode active material too quickly, and the current density and lithium ion concentration distribution in the electrolyte phase may be uneven, making it easy for lithium ions in the electrolyte phase to
  • the surface of the negative active material is locally enriched.
  • the lithium ions detached from the positive active material cannot be embedded in the negative active material in equal amounts.
  • the lithium ions that cannot be embedded in the negative active material gain electrons on the surface of the negative active material, thereby forming silvery white metallic lithium. Elemental substance, namely "lithium dendrite".
  • lithium dendrites not only reduces the performance of the secondary battery, such as shortening the cycle life, but in severe cases, it can form sharp shapes that pierce the isolation film and cause a short circuit within the secondary battery, which may cause catastrophic consequences such as combustion and explosion.
  • the continuously deposited metallic lithium elements will also fall off the surface of the negative active material, thus forming "dead lithium" that cannot continue to participate in the reaction, resulting in a reduction in the energy density of the secondary battery.
  • the inventor has improved the separation film and proposed a separation film containing a ferroelectric layer, which can enable metal ions such as lithium ions to be evenly embedded in the negative active material, thereby improving "lithium dendrites" and “death” "Lithium” problem, improve the cycle performance of secondary batteries containing negative electrode plates, and improve the fast charging performance of the negative electrode plates.
  • the present application provides a secondary battery.
  • the secondary battery is also called a rechargeable battery or a storage battery, which refers to a battery that can activate active materials by charging and continue to be used after the battery is discharged.
  • a secondary battery includes an electrode assembly and an electrolyte.
  • the electrode assembly 52 generally includes a positive electrode piece 522 , a negative electrode piece 521 , an isolation film 523 and a ferroelectric layer 5213 .
  • the isolation film 523 is disposed between the positive electrode piece 522 and the negative electrode piece 521, and mainly functions to prevent the positive electrode and the negative electrode from being short-circuited and allows metal ions to pass through.
  • the electrolyte plays a role in conducting metal ions between the positive electrode piece 522 and the negative electrode piece 521 .
  • the secondary battery of the present application may be a lithium secondary battery, a sodium-ion battery, or the like, and in particular, may be a lithium-ion secondary battery.
  • the isolation film 523 includes two surfaces opposite to each other in its own thickness direction, and the ferroelectric layer 5213 may be disposed on any one or both of the two opposite surfaces of the isolation film 523 .
  • the ferroelectric layer 5213 may be disposed on both surfaces of the isolation film 523; optionally, the ferroelectric layer 5213 may be disposed on the surface of the isolation film 523 facing the negative electrode piece 521; the ferroelectric layer 5213 It not only homogenizes the metal ion concentration but also ensures the energy density of the secondary battery.
  • the ferroelectric layer 5213 and the negative electrode piece 521 may not be in direct contact.
  • the ferroelectric effect generated by the ferroelectric layer 5213 can be used to uniformly distribute metal ions, which can reduce the impact of the ferroelectric layer 5213 on the negative electrode piece 521 when it is disposed on the negative electrode piece 521.
  • the negative electrode diaphragm or the negative electrode current collector is damaged, thereby ensuring the structural stability of the negative electrode plate 521 .
  • the ferroelectric layer 5213 includes ferroelectric particles, and of course may also include other additives such as binders.
  • the ferroelectric particles can be directly disposed on the surface of the isolation film 523; when the ferroelectric layer 5213 also includes other additives, the ferroelectric particles can be placed on the surface of the isolation film 523 through a binder or the like. provided on the surface of the isolation film 523.
  • the inventor found that the secondary battery of the present application has good kinetic properties, can effectively alleviate the metal precipitation phenomenon, and can improve the fast charging capability of the secondary battery.
  • the ferroelectric effect of ferroelectric particles causes spontaneous polarization under the action of an external electric field, generating a reverse electric field, balancing the electron density near lithium dendrites, and inhibiting the vertical growth of lithium dendrites. .
  • an internal electric field between the positive electrode piece and the negative electrode piece 521.
  • the positive and negative charge centers inside the ferroelectric particles may be excited to shift, resulting in Reverse electric field, the reverse electric field can uniformly enrich electrons at the tips of lithium dendrites, forming reversible lithium deposition.
  • the vertical growth of lithium dendrites is inhibited, reducing the risk of metal precipitation due to local enrichment of metal ions, and reducing the risk of metal precipitation.
  • the loss of ions can ensure the cycle performance of the secondary battery.
  • This application can reduce the risk of local precipitation of metal ions. Taking the metal ion as lithium ion as an example, the risk of lithium ion precipitation is reduced, and the risk of lithium dendrites can be reduced, thereby reducing the risk of lithium dendrites piercing the isolation film and causing secondary The risk of internal short circuit of the secondary battery improves the safety performance of the secondary battery.
  • the ferroelectric layer 5213 is disposed on the isolation film 523, which can reduce the impact on the negative electrode film during the formation of the ferroelectric layer 5213, thereby effectively protecting the negative electrode film; and will not affect the cooling of the negative electrode film. Compression molding process.
  • This application regulates the compaction density P of the negative electrode film layer, the coating weight of the negative electrode film layer, the thickness H of the ferroelectric layer 5213, and the volume average particle size Dv50 of the ferroelectric particles to meet the above ranges.
  • the secondary battery When the secondary battery is charged, it can It is ensured that the ferroelectric particles in the ferroelectric layer 5213 can fully exert the ferroelectric effect and fully homogenize the metal ions at the interface between the negative active material and the electrolyte, thereby ensuring the lithium embedding ability of the negative electrode sheet 521 and improving the cycle of the secondary battery. performance.
  • isolation membrane 523 has no particular limitation on the type of isolation membrane 523 , and any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane 523 may include one or a combination of one or more selected from fiberglass, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different.
  • the positive electrode piece 522, the isolation film 523 and the negative electrode piece 521 can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the thickness H ⁇ m of the ferroelectric layer 5213 satisfies: 2 ⁇ H ⁇ 10.
  • the ferroelectric layer 5213 can fully exert the ferroelectric effect and further balance the distribution of metal ions, making the distribution of metal ions more uniform; but the ferroelectric layer 5213 may not be able to provide capacity for the secondary battery, so the ferroelectric layer 5213 in the above thickness range occupies a moderate volume and will not excessively occupy the space in the secondary battery, thus ensuring the space occupied by the negative active material in the negative electrode plate 521 , in order to ensure the energy density and capacity of the secondary battery, so that the secondary battery has the advantage of long battery life; the thickness of the ferroelectric layer 5213 is moderate, which can effectively inhibit the vertical growth of metal ions, and can be effective when the secondary battery is charged at a high rate.
  • the thickness of the ferroelectric layer 5213 satisfies: 4 ⁇ H ⁇ 6.
  • the thickness of the ferroelectric layer 5213 may be 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m or 10 ⁇ m; or a range consisting of any two of the above values.
  • the thickness of the ferroelectric layer 5213 can also be measured directly using tomography.
  • the details are as follows: 1. Sample preparation: a. Use ceramic scissors to cut the diaphragm into a size of 6mm*6mm and stick it on a sample stage coated with paraffin. On the top, just make the sample slightly protrude ( ⁇ 1mm) from the edge of the sample stage; b. The sample is sprayed with gold for 60S; c. Set the polishing voltage and time for polishing (150um thick negative electrode piece, 100min at 7.5KV); 2. Morphology analysis: Use a scanning electron microscope to move the sample position about 50 times until it is clear. Mark the thickness of 5213 at 12 positions. After the end, take the average value to get the thickness of 5213.
  • the volume average particle diameter Dv50 of the ferroelectric particles is D ⁇ m, 0.08 ⁇ D ⁇ 1.
  • each ferroelectric particle will basically stimulate the ferroelectric effect to generate a reverse electric field. Since the volume average particle size Dv50 of the ferroelectric particles meets the above range, two adjacent ferroelectric particles generate The reverse electric fields will basically not interfere with each other, ensuring the intensity of the electric field of each ferroelectric particle, thereby ensuring the role of the ferroelectric particles in uniformizing the metal ions; and is conducive to even distribution in the ferroelectric layer 5213, which is further conducive to uniformity Chemically distribute metal ions.
  • the ferroelectric particles with the above-mentioned volume average particle size are easy to prepare and shape, the process is simple, and the cost is relatively high.
  • D ⁇ m can be 0.08 ⁇ m, 0.09 ⁇ m, 0.10 ⁇ m, 0.15 ⁇ m, 0.20 ⁇ m, 0.25 ⁇ m, 0.30 ⁇ m, 0.35 ⁇ m, 0.40 ⁇ m, 0.50 ⁇ m, 0.60 ⁇ m, 0.70 ⁇ m, 0.80 ⁇ m, 0.90 ⁇ m or 1 ⁇ m; or a range consisting of any two of the above values.
  • the volume average particle size Dv50 of the material is a well-known meaning in the art. It represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%. It can be tested using instruments and methods known in the art. For example, you can refer to the GB/T 19077-2016 particle size distribution laser diffraction method and use a laser particle size analyzer to conveniently test, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the United Kingdom.
  • the mass content a of the ferroelectric particles satisfies: 90% ⁇ a ⁇ 98%; optionally, 95% ⁇ a ⁇ 98%.
  • the ferroelectric particles can be more evenly distributed on the surface of the isolation film. If there are too many ferroelectric particles, the adhesion to the isolation film will decrease, and the ferroelectric particles may fall off. The risk is that the ferroelectric content is too low and the effect of inhibiting lithium evolution is limited. Within a suitable range, it can homogenize the metal ions at the interface between the negative active material and the electrolyte.
  • a ferroelectric slurry containing ferroelectric particles can be used, the ferroelectric slurry is disposed on the surface of the isolation film 523, and solidified to form the ferroelectric layer 5213; thus, the ferroelectric slurry can be adjusted by adjusting the ferroelectric slurry.
  • the solid content of the ferroelectric particles in the material is adjusted to adjust the mass content a of the ferroelectric particles in the ferroelectric layer 5213.
  • ferroelectric particles there is no particular restriction on the type of ferroelectric particles in this application, and any well-known ferroelectric particles with good chemical stability and mechanical stability can be selected.
  • the ferroelectric particles include one or a combination of more selected from the group consisting of perovskite structure oxides, tungsten bronze-type compounds, and bismuth oxide-type layered structure compounds. More optionally, the ferroelectric particles 103 are selected from perovskite structure oxides.
  • the perovskite structure oxide has a molecular formula Ba 1-x A x Ti 1-y By O 3 .
  • A includes one or more combinations selected from Pb, Sr, Ca, K, Na and Cd
  • B includes one or more combinations selected from Sn, Hf, Zr, Ce, Nb and Th, 0 ⁇ x ⁇ 1, 0 ⁇ y ⁇ 1.
  • the perovskite structure oxide may include BaTiO 3 , Ba 1-x1 Sr x1 TiO 3 (0 ⁇ x1 ⁇ 1), SrTiO 3 , PbTiO 3 , PbZr y1 Ti 1-y1 O 3 (0 ⁇ y1 ⁇ 1), one or a combination of BaZr y2 Ti 1-y2 O 3 (0 ⁇ y2 ⁇ 1), KNbO 3 and NaNbO 3 .
  • the ferroelectric particles include one or more of barium titanate BTO, lead zirconate titanate PZT, lead metaniobate, lead barium lithium niobate PBLN and lead titanate PT. The above types of ferroelectric particles can effectively exert the piezoelectric effect to improve the degree of uniform distribution of metal ions.
  • the tungsten bronze type compound may have the molecular formula MzWO3 .
  • M includes one or a combination of more selected from Na, K, Rb and Cs, 0 ⁇ z ⁇ 1.
  • the tungsten bronze compound may include one or a combination of more selected from Na z1 WO 3 (0 ⁇ z1 ⁇ 1), K z2 WO 3 (0 ⁇ z2 ⁇ 1).
  • the bismuth oxide type layered structure compound has a molecular formula (Bi 2 O 2 ) (C n-1 D n O 3n+1 ).
  • C includes one or more combinations selected from Na, K, Ba, Sr, Pb, Ca, Ln and Bi
  • D includes selected from Zr, Cr, Nb, Ta, Mo, W, Fe, Ti and V One or a combination of more of them, 2 ⁇ n ⁇ 5.
  • the bismuth oxide type layered structure compound may be one or a combination of more of SrBi 2 Nb 2 O 9 , SrBi 2 Ta 2 O 9 , SrBi 2 Nb 2 O 9 , and Bi 4 Ti 3 O 12 .
  • the dielectric constant of the ferroelectric particles satisfies: 100 ⁇ 100000.
  • the dielectric constant of ferroelectric particles When the dielectric constant of ferroelectric particles is within the above range, it can quickly migrate metal ions, thereby ensuring the migration rate of metal ions.
  • the dielectric constant of the ferroelectric particles may be 100 to 50000, 100 to 25000, 100 to 10000, 100 to 5000, 100 to 4000, 100 to 3000, 100 to 2000, 100 to 1000, 100 to 500, 150 to 50000, 150 to 25000, 150 to 10000, 150 to 5000, 150 to 4000, 150 to 3000, 150 to 2000, 150 to 1000, 150 to 500, 200 to 50000, 200 to 25000, 200 to 10000, 200 to 5000, 200 to 4000, 200 to 3000, 200 to 2000 or 200 to 1000.
  • the dielectric constant of ferroelectric particles refers to the dielectric constant at room temperature (25 ⁇ 5°C), which has a well-known meaning in the art and can be tested using instruments and methods known in the art.
  • C represents the capacitance, in Farad (F);
  • d represents the sample thickness, in cm;
  • A represents the sample area, in cm 2 ;
  • the test conditions can be 1KHz, 1.0V, 25 ⁇ 5°C.
  • the test standard can be based on GB/T 11297.11-2015.
  • the ferroelectric layer 5213 also includes an adhesive, which may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer , one or more of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer one or more of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene cop
  • the ferroelectric layer 5213 also includes a dispersant, which may include one or more of sodium carboxymethylcellulose, polyvinylpyrrolidone, and Hypermer KD-1.
  • the negative electrode sheet 521 includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector; the negative electrode film layer includes a negative electrode active material.
  • the compacted density P g/cm 3 of the negative electrode film layer and the coating weight CW g/1540.25mm 2 of the negative electrode film layer satisfy:
  • the ferroelectric layer can affect the overall structure of the pole piece, including the structure of the lower layer of the pole piece; and the pole piece has appropriate pores, and the electrolyte can fully infiltrate the pole piece, which is conducive to the migration of lithium ions.
  • the compacted density P g/cm 3 of the negative electrode film layer satisfies: 1.1 ⁇ P ⁇ 1.85.
  • the secondary battery can have a higher energy density.
  • the compaction density within an appropriate range the negative electrode film layer can also have a strong ability to maintain the pore structure during circulation. As a result, the negative electrode piece 521 has better electrolyte wettability and can better Improve the cycle performance of secondary batteries.
  • P g/cm 3 can be 1.1g/cm 3 , 1.2g/cm 3 , 1.3g/cm 3 , 1.4g/cm 3 , 1.5g/cm 3 , 1.6g/cm 3 , 1.7g/cm 3 or 1.8g/cm 3 ; or the value of P is within any two of the above ranges.
  • the compacted density of a material is a meaning known in the art, and can be tested using instruments and methods known in the art.
  • An exemplary test method is as follows: weigh 1g of material, add it to a mold with a bottom area of 1.327cm2 , pressurize it to 2000kg (equivalent to 20000N), hold the pressure for 30s, then release the pressure, hold it for 10s, then record and calculate the material's Compaction density under 20000N force.
  • the coating weight of the negative electrode film layer CW g/1540.25mm 2 satisfies: 0.1 ⁇ CW ⁇ 0.3.
  • CW g/1540.25mm 2 can be 0.1g/1540.25mm 2 , 0.12g/1540.25mm 2 , 0.13g/1540.25mm 2 , 0.14g/1540.25mm 2 , 0.15g/1540.25mm 2 , 0.16g/1540.25mm 2 , 0.17g/1540.25mm 2 , 0.18g/1540.25mm 2 or 0.19g/1540.25mm 2 ; or a combination of any two of the above values.
  • the base material is punched with an area of 1540.25mm2 and weighed on a balance; the small discs (area: 1540.25mm2) are punched and weighed, and the weight of the active material coating is obtained by subtracting the weight of the base material;
  • the thickness L ⁇ m of the negative electrode film layer satisfies: 30 ⁇ m ⁇ L ⁇ 200 ⁇ m.
  • the thickness L of the negative electrode film layer within an appropriate range, on the one hand, the quality of the negative electrode active material can be ensured, thereby ensuring the energy density of the secondary battery; on the other hand, it can be matched with the ferroelectric layer 5213 to make the ferroelectric layer 5213 can give full play to the piezoelectric effect and promote the uniform distribution of metal ions in the negative electrode film layer.
  • 35 ⁇ m ⁇ L ⁇ 190 ⁇ m. L can be 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 120, 140, 150, 160, 180, 190 or 200; or it can be composed of any two of the above values range.
  • the thickness of the negative electrode film layer has a well-known meaning in the art, and can be measured using instruments and methods known in the art.
  • a micrometer can be used to measure the thickness of the negative electrode piece 521 at at least 12 different positions along the thickness direction of the negative electrode piece 521, and then the average value is taken as the thickness h1 of the negative electrode piece 521; and then the thickness of the negative electrode current collector is subtracted. The thickness of the negative electrode film.
  • the thickness of the negative electrode film layer can also be measured directly using tomography, as follows:
  • the coating weight can be measured using ion polishing scanning 1.
  • Sample preparation a. Use ceramic scissors to cut the electrode piece into 6mm*6mm size, stick it on the sample stage coated with paraffin, and make the sample slightly protrude ( ⁇ 1mm) from the edge of the sample stage.
  • b. Set the polishing voltage and time for polishing (150um negative electrode plate with a thickness of 100min at 7.5KV); 2.
  • Morphology analysis Use a scanning electron microscope to move the sample position about 50 times until it is clear. Mark the thickness of 5212 at 12 positions. After the end, take the average value to get the thickness of 5212.
  • the negative electrode film layer may include negative electrode active materials for secondary batteries that are well known in the art.
  • the negative active material includes one or a combination of more selected from natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material may include one or a combination of one or more selected from the group consisting of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitride composite and silicon alloy material.
  • the tin-based material may include one or a combination of more selected from elemental tin, tin oxide and tin alloy materials.
  • the negative active material includes a silicon-carbon composite.
  • the silicon in the silicon-carbon composite may expand in volume, and the expanded silicon may give a certain compressive stress to the ferroelectric particles. , thereby further stimulating the piezoelectric effect of ferroelectric particles and improving their ability to homogenize the concentration of metal ions.
  • the negative electrode film layer optionally further includes a negative electrode conductive agent.
  • a negative electrode conductive agent may include selected from the group consisting of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and One or a combination of carbon nanofibers.
  • the mass percentage of the negative electrode conductive agent is less than 5%.
  • the negative electrode film layer optionally further includes a negative electrode binder.
  • the negative electrode binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid).
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • acrylic resin for example, polyacrylic acid.
  • PAA poly(methacrylate PMAA), poly(sodium acrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA) and carboxymethyl chitosan (CMCS). combination of species.
  • PAA poly(methacrylate PMAA)
  • PAAS poly(sodium acrylate PAAS)
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • CMCS carboxymethyl chitosan
  • the mass percentage of the negative electrode binder is less than 5%.
  • the negative electrode film layer optionally includes other additives.
  • other auxiliaries may include thickeners, such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like.
  • CMC-Na sodium carboxymethylcellulose
  • PTC thermistor materials such as sodium carboxymethylcellulose (CMC-Na), PTC thermistor materials, and the like.
  • the mass percentage of other additives is less than 2%.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil or copper alloy foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver. and a combination of one or more silver alloys.
  • the polymer material base layer may include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate ( One or a combination of one or more of PBT), polystyrene (PS) and polyethylene (PE).
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the negative electrode plate 521 does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode sheet 521 of the present application also includes a conductive undercoat layer (for example, composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector. ).
  • the negative electrode piece 521 of the present application also includes a protective layer covering the surface of the negative electrode film layer.
  • the above various parameter tests for the negative electrode sheet 521 are explained by taking the negative electrode active material as a test sample.
  • the sample can be tested before coating the negative electrode slurry, or the negative electrode film layer can be tested after cold pressing. Sampling test.
  • the sampling can be carried out as follows: randomly select a cold-pressed negative electrode film layer, and sample the negative electrode active material (for example, you can Use a blade scraper for powder sampling); place the collected negative active material powder in deionized water, then filter and dry it, and then sinter the dried negative active material at a certain temperature and time (for example, 400°C , 2h), remove the binder and conductive agent, and obtain the negative active material test sample.
  • a certain temperature and time for example, 400°C , 2h
  • sampling and testing can be performed before curing the ferroelectric slurry, or after curing the ferroelectric slurry.
  • the positive electrode sheet 522 includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector.
  • the positive electrode current collector has two surfaces opposite in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material
  • the positive electrode active material may be a positive electrode active material known in the art for secondary batteries.
  • the cathode active material may include one or a combination of more selected from the group consisting of lithium transition metal oxides, olivine-structured lithium-containing phosphates, and their respective modified compounds.
  • the lithium transition metal oxide may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide , lithium nickel cobalt aluminum oxide and a combination of one or more of their respective modified compounds.
  • Examples of the lithium-containing phosphate with an olivine structure may include lithium iron phosphate, a composite material of lithium iron phosphate and carbon, a lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, a lithium manganese iron phosphate, a lithium manganese iron phosphate and A composite material of carbon and a combination of one or more of its respective modifying compounds.
  • the cathode active material may include a combination of one or more of the lithium transition metal oxide and its modified compounds shown in Formula 1.
  • M includes Mn, Al, Zr , a combination of one or more of Zn, Cu, Cr, Mg, Fe, V, Ti and B, A includes a combination of one or more selected from N, F, S and Cl.
  • the above-mentioned modified compounds of each cathode active material may be doping modification or surface coating modification of the cathode active material.
  • the positive electrode film layer optionally further includes a positive electrode conductive agent.
  • a positive electrode conductive agent includes superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon.
  • the mass percentage of the cathode conductive agent is less than 5%.
  • the positive electrode film layer optionally further includes a positive electrode binder.
  • the positive electrode binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene One or more combinations of terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the mass percentage of the cathode binder is less than 5% based on the total mass of the cathode film layer.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil or aluminum alloy foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver. and a combination of one or more silver alloys.
  • the polymer material base layer may include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate ( One or a combination of one or more of PBT), polystyrene (PS) and polyethylene (PE).
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying and cold pressing.
  • the cathode slurry is usually formed by dispersing the cathode active material, optional conductive agent, optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • the electrolyte solution of the present application can be an electrolyte solution known in the art and used for secondary batteries.
  • the electrolyte includes lithium salt and organic solvent.
  • the lithium salt may include lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonimide (LiFSI), lithium bistrifluoromethanesulfonimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonate borate (LiDFOB), lithium dioxalatoborate (LiBOB), lithium difluorophosphate (LiPO 2 F 2 ), one or more combinations of lithium difluorodioxalate phosphate (LiDFOP) and lithium tetrafluorooxalate phosphate (LiTFOP).
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium tetrafluoroborate
  • the organic solvent may include ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dimethyl carbonate, Propyl ester (DPC), methylpropyl 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 - One or a combination of butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).
  • EC
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the soft bag may be made of plastic, such as one or a combination of polypropylene (PP), polybutylene terephthalate (PBT) and polybutylene succinate (PBS).
  • FIG. 2 shows an example of a square-structured secondary battery 5 .
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and can be adjusted according to needs.
  • the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte may be assembled to form a secondary battery.
  • the positive electrode sheet, isolation film, and negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process.
  • the electrode assembly is placed in an outer package, dried, and then injected with electrolyte. After vacuum packaging, standing, and Through processes such as formation and shaping, secondary batteries are obtained.
  • the secondary batteries according to the present application can be assembled into a battery module.
  • the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 4 is a schematic diagram of the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having an accommodation space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application provides an electrical device.
  • the electrical device includes at least one of a secondary battery, a battery module and a battery pack of the present application.
  • Secondary batteries, battery modules and battery packs can be used as power sources for power-consuming devices, and can also be used as energy storage units for power-consuming devices.
  • Electric devices can 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, and electric golf balls). vehicles, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electrical device can select secondary batteries, battery modules or battery packs according to its usage requirements.
  • FIG. 7 is a schematic diagram of an electrical device as an example.
  • the electric device 6 is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, or the like.
  • a battery pack 1 or a battery module can be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electrical device is usually required to be light and thin, and secondary batteries can be used as power sources.
  • this application also proposes a method for preparing a secondary battery, which method can be used to prepare the secondary battery according to any embodiment of the first aspect of this application.
  • the methods include:
  • the negative electrode plate includes a negative electrode film layer containing negative electrode active material
  • the compacted density of the negative electrode film layer is P g/cm 3 ;
  • the coating weight of the negative electrode film layer is CW g/1540.25mm 2 ;
  • the thickness of the ferroelectric layer is H ⁇ m
  • the volume average particle size Dv50 of ferroelectric particles is D ⁇ m
  • the secondary battery satisfies:
  • the method of the embodiment of the present application has a simple preparation process, and only needs to continue to form the ferroelectric layer on the isolation film. There is no need to change the original production process route, and the operation is convenient;
  • step S200 based on the total mass of the ferroelectric layer, the mass content b of the ferroelectric particles satisfies: 90% ⁇ a ⁇ 98%; optionally, 95% ⁇ a ⁇ 98%.
  • Various processes can be used to place the ferroelectric slurry on the isolation film, such as gravure process, coating process, etc.
  • the ferroelectric slurry can be placed in the gravure plate.
  • the gravure roller carries the ferroelectric slurry through the roller gap and rolls it on the isolation film.
  • the ferroelectric layer can be controlled by adjusting the size of the roller gap. thickness.
  • the ferroelectric slurry When the mass of the ferroelectric slurry is small, the ferroelectric slurry may partially cover the isolation film, and the ferroelectric layer formed by solidification may be in a continuous state or may be in a discontinuous state. As the mass of the ferroelectric slurry increases, the ferroelectric slurry may completely cover the isolation film, and the ferroelectric layer formed by solidification may present a continuous whole-layer structure, with the entire layer covering the isolation film.
  • the ferroelectric layer covering the isolation film refers to the projection of the ferroelectric layer along its own thickness direction covering the isolation film.
  • the quality of the ferroelectric particles can be adjusted by adjusting the mass content b of the ferroelectric particles in the ferroelectric slurry.
  • the mass content b of the ferroelectric particles is in the above range, the bonding strength between the ferroelectric layer and the isolation film is high, the ferroelectric layer is not easy to peel off, and the ferroelectric layer is easy to exert the piezoelectric effect and uniformize the distribution of metal ions.
  • An aluminum foil with a thickness of 13 ⁇ m was used as the positive electrode current collector.
  • the coke raw material is pretreated to remove impurities, and pyrolyzed and granulated to obtain secondary particles with a Dv50 of 11 ⁇ m; then graphitized at 3000°C for 23 hours, and then coated with asphalt; and high-temperature carbonized at 1000°C for 16 hours to obtain artificial graphite. .
  • a copper foil with a thickness of 8 ⁇ m was used as the negative electrode current collector.
  • the barium titanate slurry is coated on the surface of the isolation film facing the negative electrode piece. After drying at 110°C, the barium titanate slurry is solidified on the isolation film to form a ferroelectric layer.
  • the above-mentioned positive electrode piece, isolation film and negative electrode piece in order so that the isolation film is between the positive electrode piece and the negative electrode piece to play an isolation role, and then wind it to obtain the electrode assembly; place the electrode assembly in the outer packaging shell After drying, the electrolyte is injected, and through processes such as vacuum packaging, standing, formation, and shaping, a lithium-ion battery is obtained.
  • Example 1 What is different from Example 1 is that the "thickness H of the ferroelectric layer" was adjusted in Examples 2-1 to 2-4.
  • Comparative Example 2 adjusted the "thickness H of the ferroelectric layer".
  • the negative electrode slurry of Comparative Example 3 mixed the negative active material and ferroelectric particles; specifically, the negative active material, ferroelectric particles BaTiO 3 , and binder styrene-butadiene rubber (SBR) , thickener sodium carboxymethyl cellulose (CMC-Na), and conductive agent carbon black are fully stirred and mixed in an appropriate amount of solvent deionized water according to the mass ratio of 97:1:1:1 to form a uniform negative electrode slurry; The slurry is evenly coated on the surface of the negative electrode current collector copper foil, and after drying and cold pressing, the negative electrode piece is obtained.
  • SBR styrene-butadiene rubber
  • CMC-Na thickener sodium carboxymethyl cellulose
  • Example 1 The parameters of Example 1, Example 2, and Comparative Examples 1 to 3 are as shown in Table 1:
  • Example 1 The parameters of Example 1, Example 3-1 to Example 3-4 are as shown in Table 2:
  • Example 4 Different from Example 1, in Examples 4-1 to 4-4, the mass content a% of the ferroelectric particles was adjusted.
  • Example 1 The parameters of Example 1, Example 4-1 to Example 4-4 are as shown in Table 3:
  • Example 5-1 to Example 5-5 Different from Example 1, in Examples 5-1 to 5-5, the compaction density P and coating weight of the negative electrode film layer were adjusted.
  • the parameters of Example 1, Example 5-1 to Example 5-5 are as shown in Table 4:
  • Comparative Example 4 replaces ferroelectric particles with alumina particles.
  • Example 1 The parameters of Example 1, Example 6-1 to Example 6-2 and Comparative Example 4 are as shown in Table 5:
  • the compaction of the negative electrode film layer can be obtained by the coating weight CW of the film layer and the thickness L of the negative electrode film layer.
  • the Dv90, Dv50 and Dv10 of a material have well-known meanings in the art and can be measured using instruments and methods well-known in the art. For example, you can refer to the GB/T 19077-2016 particle size distribution laser diffraction method and use a laser particle size analyzer to conveniently test, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the United Kingdom.
  • Dv90 is the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 90%;
  • Dv50 is the particle size corresponding to the cumulative volume distribution percentage of the material reaches 50%;
  • Dv10 is the particle size corresponding to the cumulative volume distribution percentage of the material reaches 10% .
  • the lithium ion battery prepared in the Examples and Comparative Examples was fully charged at a rate of 0.33C and fully discharged at a rate of 0.33C for 3 cycles.
  • the discharge energy (E) of the last cycle was taken and the lithium was weighed using an electronic balance.
  • the mass of the ion battery (m), W E/m.
  • the lithium ion battery prepared in the Examples and Comparative Examples is fully charged to 97% state of charge (SOC), stored at 60°C, and the capacity decays to 80% cutoff.
  • SOC state of charge
  • the storage time at this time is recorded, where the target storage time is 280 days.
  • the lithium-ion batteries prepared in the Examples and Comparative Examples were charged at a 3C rate, discharged at a 1C rate, and subjected to a 3%-97% SOC cycle test until the capacity of the lithium-ion battery was less than 80% of the initial capacity, and recorded Number of cycles.
  • Example 1 5.5C 2100 97.0% 310
  • Example 2-1 5.1C 1900 99.0% 300
  • Example 2-2 5.6C 2200 96.0% 320
  • Example 2-3 5.7C 2400 95.0% 325
  • Example 2-4 5.8C 2450 92.0% 328
  • Comparative example 1 4.0C 1700 100.0% 280
  • Comparative example 2 5.9C 2500 85.5% 260
  • Comparative example 3 4.5C 1800 99.5% 290
  • Example 1 5.5C 2100 97.0% 310
  • Example 3-1 5.4C 2050 97.0% 308
  • Example 3-2 5.2C 2000 97.0% 305
  • Example 3-3 5.1C 1950 97.0% 300
  • Example 3-4 4.9C 1900 97.0% 290
  • Example 1 5.5C 2100 97.0% 310
  • Example 5-1 4.2C 1800 90.0% 300
  • Example 5-2 4.5C 1850 92.0% 305
  • Example 5-3 5C 1950 95.0% 308
  • Example 5-4 5.1C 1940 96.0%
  • Example 5-5 5.2C 1950 98.0% 320
  • the ferroelectric layer can affect the overall structure of the pole piece including the structure of the lower layer of the pole piece; and the pole piece has a suitable The pores allow the electrolyte to fully infiltrate the pole piece, which is conducive to the migration of lithium ions and optimizes the charging capacity and energy density of the battery cell.
  • Example 1 5.5C 2100 97.0% 310
  • Example 6-1 5.4C 2101 97.0% 311
  • Example 6-2 5.5C 2101 97.0% 309
  • Comparative example 4 4.0C 1700 100.0% 280

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Abstract

本申请提供了一种二次电池、电池模块、电池包和用电装置。所述二次电池包括正极极片、负极积极、隔离膜、铁电层；负极极片包括含有负极活性材料的负极膜层；隔离膜设置于所述正极极片和所述负极极片之间；铁电层设置于所述隔离膜的至少一个表面，所述铁电层包括铁电体颗粒，其中，所述负极膜层的压实密度为P g/cm3；所述负极膜层的涂布重量为CW g/1540.25mm2；所述铁电层的厚度为H μm；所述铁电体颗粒的体积平均粒径Dv50为D μm，所述二次电池满足：式（I）。本申请的二次电池能够兼顾改善二次电池的快充性能和循环性能。

Description

二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及电池领域，具体涉及一种二次电池、电池模块、电池包和用电装置。
背景技术
二次电池具有容量高、寿命长等特性，因此广泛应用于电子设备，例如手机、笔记本电脑、电瓶车、电动汽车、电动飞机、电动轮船、电动玩具汽车、电动玩具轮船、电动玩具飞机和电动工具等等。随着电池应用范围越来越广泛，对二次电池性能的要求也逐渐严苛，比如要求其具有快充能力。
但是在改善二次电池的快充能力的同时，可能伴随着析锂等风险，从而降低二次电池的循环性能。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种二次电池、电池模块、电池包和用电装置。
本申请的第一方面提供了一种二次电池，所述二次电池包括正极极片、负极积极、隔离膜、铁电层；负极极片包括含有负极活性材料的负极膜层；隔离膜设置于所述正极极片和所述负极极片之间；铁电层设置于所述隔离膜的至少一个表面，所述铁电层包括铁电体颗粒，其中，所述负极膜层的压实密度为P g/cm 3；所述负极膜层的涂布重量为CW g/1540.25mm 2；所述铁电层的厚度为H μm；所述铁电体颗粒的体积平均粒径Dv50为D μm，所述二次电池满足：
Figure PCTCN2022105752-appb-000001
可选地，
Figure PCTCN2022105752-appb-000002
由此，本申请调控负极膜层的压实密度P、负极膜层的涂布重量、铁电层的厚度H、铁电体颗粒的体积平均粒径Dv50满足上述范围，在二次电池进行充电时，能够保证铁电层中的铁电体颗粒充分发挥铁电效应，能够将负极活性材料和电解质界面间的金属离子均匀化分布，从而保证负极极片的嵌锂能力，改善二次电池的循环性能。
在一些实施方式中，所述铁电层的厚度H μm满足：2≤H≤10；可选地，4≤H≤6。铁电层的厚度H满足上述范围时，在二次电池充电过程中，铁电层能够充分发挥铁电效应，能够进一步均衡金属离子分布，使得金属离子的分布更均匀；且铁电层可能无法为二次电池提供容量，故上述厚度范围的铁电层的占用体积不会过大，不会过度侵 占二次电池内的空间，从而能够保证负极活性材料的占用空间，以此保证二次电池的能量密度和容量，使得二次电池具有长续航的优势；此外，铁电层的厚度适中，可以有效抑制金属离子垂直生长，在二次电池进行大倍率充电时能够有效降低二次电池内部发生短路的风险，由此保证二次电池大倍率充电性能。
在一些实施方式中，所述铁电体颗粒的体积平均粒径Dv50满足：0.08≤D≤1；可选地，0.1≤D≤0.8。铁电体颗粒的体积平均粒径Dv50满足上述范围，有利于均匀分布于铁电层。
在一些实施方式中，基于所述铁电层的总质量计，所述铁电体颗粒的质量含量a满足：90％≤a≤98％；可选地，95％≤a≤98％。铁电体颗粒的质量含量a满足上述范围时，铁电体颗粒能够更均匀地分布于负极膜层的表面，产生的反向电场更加均匀；并且包含铁电体颗粒的铁电层不会过厚，从而能够保证负极活性材料的占用体积，保证二次电池的能量密度。
在一些实施方式中，所述铁电体颗粒包括选自钙钛矿结构氧化物、钨青铜型化合物和铋氧化物型层状结构化合物中的一种或多种；可选地，所述钙钛矿结构氧化物包括钛酸钡BTO、锆钛酸铅PZT、偏铌酸铅、铌酸铅钡锂PBLN和钛酸铅PT中的一种或多种。上述种类的铁电体颗粒能够有效发挥铁电效应，以提高金属离子的均匀化分布的程度。
在一些实施方式中，所述铁电体颗粒的介电常数满足：100≤ε≤100000；可选地，1000≤ε≤10000。铁电体颗粒的介电常数在上述范围时，可以起到快速迁移金属离子的作用，从而保证金属离子的迁移速率。
在一些实施方式中，所述负极膜层的压实密度P g/cm 3、所述负极膜层的涂布重量CW g/1540.25mm 2之间满足：
Figure PCTCN2022105752-appb-000003
负极膜层的压实密度P和涂布重量CW满足上述范围时，可以保证负极膜层在适当的厚度范围内，以此保证二次电池的能量密度；在二次电池充电过程中Z在上述范围时，铁电层可以影响极片整体结构包括极片下层的结构；并且极片具有合适的孔隙，电解液可以充分浸润极片，有利于锂离子的迁移。
在一些实施方式中，所述负极膜层的压实密度P g/cm 3满足：1.1≤P≤1.85；可选地，1.3≤P≤1.8。通过调节负极膜层的压实密度在合适的范围内，能够使得二次电池具有较高的能量密度。此外，通过调节压实密度在合适的范围内，还能使负极膜层在循环过程中具有较强的维持孔道结构的能力，由此负极极片的电解液浸润性更好，能更好地提升二次电池的循环性能。
在一些实施方式中，所述负极膜层的涂布重量CW g/1540.25mm 2满足：0.1≤CW≤0.3；可选地，0.14≤CW≤0.2。通过调节负极膜层的涂布重量CW在合适的范围内，能够保证电芯的能量密度以及铁电层对负极膜层的效果。
在一些实施方式中，所述负极膜层的厚度Lμm满足：30μm≤L≤200μm；可选地，35μm≤L≤190μm。通过调节负极膜层的厚度L在合适的范围内，一方面能够保证负 极活性材料的质量，从而保证二次电池的能量密度；另一方面可以与铁电层相配合，以使铁电层能够充分发挥铁电效应，促进负极膜层中的金属离子均匀化分布。
在一些实施方式中，所述负极活性材料包括天然石墨、人造石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂中的一种或多种。
本申请的第二方面还提供了一种电池模块，包括如本申请第一方面任一实施方式的二次电池。
本申请的第三方面还提供了一种电池包，包括如本申请第二方面实施方式的电池模块。
本申请第四方面还提供了一种用电装置，包括如本申请第一方面任一实施方式的二次电池、如本申请第二方面实施方式的电池模块或如本申请第三方面实施方式的电池包。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍，显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请一实施方式的电极组件的示意图；
图2是本申请一实施方式的二次电池的示意图；
图3是图2所示的本申请一实施方式的二次电池的分解图；
图4是本申请一实施方式的电池模块的示意图；
图5是本申请一实施方式的电池包的示意图；
图6是图5所示的本申请一实施方式的电池包的分解图；
图7是本申请一实施方式的用电装置的示意图；
附图未必按照实际的比例绘制。
附图标记说明如下：
1、电池包；2、上箱体；3、下箱体；4、电池模块；
5、二次电池；51、壳体；52、电极组件；521、负极极片；522、正极极片；523、隔离膜；
5213、铁电层；
53、盖板；
6、用电装置。
具体实施方式
以下，详细说明具体公开了本申请的二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的 事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，方法包括步骤(a)和(b)，表示方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
在本申请中，术语“多个”、“多种”是指两个或两种以上。
本申请中，二次电池可以包括锂离子电池、锂硫电池、钠锂离子电池、钠离子电池或镁离子电池等，本申请实施例对此并不限定。
二次电池包括电极组件和电解液，电极组件由正极极片、负极极片和隔离膜组成。二次电池主要依靠金属离子在正极极片和负极极片之间移动来工作，正极极片包括正极活性材料，负极极片包括负极活性材料。在本文中金属离子可以为锂离子、钠离子等；接下来以金属离子为锂离子说明其充电过程。
在二次电池充电过程中，电极动力学过程通常包括以下几个步骤。
(1)锂离子脱出步骤：锂离子从正极活性材料中脱出，向电解质相中迁移；(2)电解质相中的液相传质步骤：电解液中的溶剂化锂离子向负极活性材料表面扩散传递；(3)表面转化步骤：首次充电时溶剂化锂离子吸附在负极活性材料表面发生反应并形成固体电解质界面(SEI)膜，后续充电过程中溶剂化锂离子吸附在SEI膜表面，经过去溶剂化过程后锂离子达到负极活性材料表面；(4)电荷交换步骤：锂离子从负极活性材料表面得到电子并形成嵌锂生成物；(5)嵌锂生成物固相传质步骤：嵌锂生成物从负极活性材料表面固相扩散至内部，完成充电过程。
随着充电倍率的提高，锂离子过快地从正极活性材料中脱出，且电流密度和电解质相中的锂离子浓度分布可能会存在不均匀的现象，由此使得电解质相中的锂离子容易在局部的负极活性材料表面富集，从正极活性材料脱出的锂离子无法等量地嵌入负极活性材料中，无法嵌入负极活性材料的锂离子在负极活性材料表面得电子，从而形成银白色的金属锂单质，即“锂枝晶”。锂枝晶的形成不仅使二次电池性能下降，例如循环寿命缩短等，而且严重时会形成尖锐形貌刺穿隔离膜导致二次电池内短路，从而有可能引起燃烧、爆炸等灾难性后果。同时不断沉积的金属锂单质还会从负极活性材料表面脱落，由此形成不能继续参与反应的“死锂”，导致二次电池能量密度降低。
鉴于此，发明人对隔离膜进行了改进，提出了一种包含铁电层的隔离膜，其能够使得金属离子例如锂离子均匀嵌入负极活性材料中，由此改善“锂枝晶”和“死锂”的问题，提高包含负极极片的二次电池的循环性能，并能够提高负极极片的快充性能。
二次电池
第一方面，本申请提供了一种二次电池，二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
所述二次电池包括正极极片、负极极片和隔离膜以及铁电层；负极极片包括含有负极活性材料的负极膜层；隔离膜设置于正极极片和负极极片之间；铁电层设置于隔离膜的至少一个表面，铁电层包括铁电体颗粒；其中，负极膜层在的压实密度为P g/cm 3＝CW/极片厚度/1540.25；负极膜层的涂布重量为CW g/1540.25mm 2；铁电层的厚度为H μm；铁电体颗粒的体积平均粒径Dv50为D μm，P、CW、H和D之间满足：
Figure PCTCN2022105752-appb-000004
可选地，
Figure PCTCN2022105752-appb-000005
为便于说明，将
Figure PCTCN2022105752-appb-000006
在一些实施方式中，二次电池包括电极组件和电解液。
如图1所示，电极组件52通常包括正极极片522、负极极片521和隔离膜523以及铁电层5213。隔离膜523设置在正极极片522和负极极片521之间，主要起到防止正极和负极短路的作用，同时可以使金属离子通过。电解液在正极极片522和负极极片521之间起到传导金属离子的作用。本申请的二次电池可为锂二次电池、钠离子电池等，特别地，可为锂离子二次电池。
隔离膜523包括在其自身厚度方向上彼此相对的两个表面，铁电层5213可以设置为隔离膜523的两个相对表面中的任意一者或两者上。在一些实施方式中，铁电层 5213可以设置在隔离膜523的两个表面上；可选地，铁电层5213可以设置在隔离膜523的面向负极极片521的表面上；铁电层5213起到均匀化金属离子浓度的同时还可以保证二次电池的能量密度。铁电层5213和负极极片521可以不直接接触，利用铁电层5213所产生的铁电效应均匀化分布金属离子，能够降低铁电层5213设置于负极极片521时对负极极片521的负极膜片或负极集流体造成损伤，由此能够保证负极极片521的结构稳定性。
铁电层5213包括铁电体颗粒，当然也可以还包括其他的助剂例如粘结剂等。在铁电层5213包括铁电体颗粒时，可以将铁电体颗粒直接设置于隔离膜523的表面；在铁电层5213还包括其他助剂时，可以通过粘结剂等将铁电体颗粒设置于隔离膜523的表面。
虽然机理尚不明确，但发明人发现本申请的二次电池具有良好的动力学性能，能够有效缓解金属析出现象，且能够提升二次电池的快速充电能力。
发明人推测作用机理如下：铁电体颗粒的铁电效应，使得其在外场电场作用下，可发生自发极化，产生反向电场，均衡锂枝晶附近的电子密度，抑制锂枝晶垂直生长。在本申请中，在二次电池充电过程中，正极极片和负极极片521之间具有内部电场，在内部电场作用下，可能激发铁电体颗粒内部的正负电荷中心发生偏移，产生反向电场，反向电场能够均匀锂枝晶尖端的电子富集，形成可逆的锂沉积，锂枝晶的垂直生长受到抑制，降低因局部富集金属离子而导致发生金属析出的风险，降低金属离子的损失，从而能够保证二次电池的循环性能。本申请能够降低金属离子在局部析出的风险，以金属离子为锂离子进行举例说明，锂离子析出的风险降低，能够降低锂枝晶发生的风险，从而能够降低锂枝晶刺破隔离膜导致二次电池内部短路的风险，提高二次电池的安全性能。
本申请将铁电层5213设置于隔离膜523上，能够降低在形成铁电层5213的过程中对负极膜层的影响，从而能够有效地防护负极膜层；且不会影响负极膜层的冷压成型过程。
本申请调控负极膜层的压实密度P、负极膜层的涂布重量、铁电层5213的厚度H、铁电体颗粒的体积平均粒径Dv50满足上述范围，二次电池进行充电时，能够保证铁电层5213中的铁电体颗粒充分发挥铁电效应，能够将负极活性材料和电解质界面间的金属离子充分均匀化，从而保证负极极片521的嵌锂能力，改善二次电池的循环性能。
[隔离膜]
本申请对隔离膜523的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施例中，隔离膜523的材质可以包括选自玻璃纤维、无纺布、聚乙烯、聚丙烯和聚偏二氟乙烯中的一种或多种的组合。隔离膜可以是单层薄膜，也可以是多层复合薄膜。当隔离膜为多层复合薄膜时，各层的材料相同或不同。
在一些实施例中，正极极片522、隔离膜523和负极极片521可通过卷绕工艺 或叠片工艺制成电极组件52。
[铁电层]
在一些实施例中，铁电层5213的厚度Hμm满足：2≤H≤10。
铁电层5213的厚度H满足上述范围时，在二次电池充电过程中，铁电层5213能够充分发挥铁电效应，能够进一步均衡金属离子分布，使得金属离子的分布更均匀；但铁电层5213可能无法为二次电池提供容量，故上述厚度范围的铁电层5213的占用体积适中，不会过度侵占二次电池内的空间，从而能够保证负极极片521中的负极活性材料的占用空间，以此保证二次电池的能量密度和容量，使得二次电池具有长续航的优势；铁电层5213的厚度适中，可以有效抑制金属离子垂直生长，在二次电池进行大倍率充电时能够有效降低二次电池内部发生短路的风险，由此保证二次电池大倍率充电性能。可选地，铁电层5213的厚度满足：4≤H≤6。示例性地，铁电层5213的厚度可以为2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm或10μm；或者是上述任意两个数值组成的范围。
铁电层5213的厚度H为本领域公知的含义，可以采用本领域公知的测试仪器和测试方法进行测定。例如可以采用万分尺沿隔离膜523(不包含铁电层5213)的厚度方向测量至少12个不同位置的隔离膜523的厚度，然后取平均值作为隔离膜523的厚度h1。然后采用万分尺沿隔离膜523(包含铁电层5213)的厚度方向测量至少12个不同位置的隔离膜523的厚度，然后取平均值作为隔离膜523的厚度h2，铁电层5213的厚度H＝h2-h1。
铁电层5213的厚度还可以采用断层扫描，直接测定铁电层5213的厚度，具体如下：1.制样：a.用陶瓷剪刀将隔膜剪成6mm*6mm大小，贴在涂抹石蜡的样品台上，将样品略突出(＜1mm)样品台边缘即可；b.样品进行60S喷金；c.设置抛光电压和时间抛光(厚度150um负极极片7.5KV下100min)；2.形貌分析：采用扫描电子显微镜，50倍左右移动样品位置，直至清晰为止，分别取12个位置标记5213的厚度，结束后取平均值，即可得到5213的厚度。
在一些实施例中，铁电体颗粒的体积平均粒径Dv50为D μm，0.08≤D≤1。
在二次电池充电过程中，各铁电体颗粒基本均会激发铁电效应产生反向电场，鉴于铁电体颗粒的体积平均粒径Dv50满足上述范围，相邻的两个铁电体颗粒产生的反向电场基本不会相互干涉，保证各铁电体颗粒的电场的强度，从而能够保证铁电体颗粒均匀化金属离子的作用；且有利于均匀分布于铁电层5213，从而进一步利于均匀化分布金属离子。此外，上述体积平均粒径的铁电体颗粒易于制备成型，工艺简单，成本相对较高。可选地，0.1≤D≤0.8；示例性地，Dμm可以为0.08μm、0.09μm、0.10μm、0.15μm、0.20μm、0.25μm、0.30μm、0.35μm、0.40μm、0.50μm、0.60μm、0.70μm、0.80μm、0.90μm或1μm；或者是上述任意两个数值组成的范围。
在本申请中，材料的体积平均粒径Dv50为本领域公知的含义，其表示材料累计体积分布百分数达到50％时所对应的粒径，可以用本领域公知的仪器及方法进行测试。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 测试，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
在一些实施例中，基于铁电层5213的总质量计，铁电体颗粒的质量含量a满足：90％≤a≤98％；可选地，95％≤a≤98％。
铁电体颗粒的质量含量a满足上述范围时，铁电体颗粒能够更均匀地分布于隔离膜的表面，铁电体过多，对隔离膜的粘接力下降，铁电体有掉粉的风险，铁电体含量过低，抑制析锂的效果受限，在合适范围内能够对负极活性材料和电解质界面间的金属离子起到均匀化作用的目的。
在制备铁电层5213时，可以采用包含铁电体颗粒的铁电浆料，将铁电浆料设置于隔离膜523的表面，并固化形成铁电层5213；由此可以通过调整铁电浆料中的铁电体颗粒的固含量，以调整铁电层5213中的铁电体颗粒的质量含量a。
本申请对铁电体颗粒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铁电体颗粒。
在一些实施例中，铁电体颗粒包括选自钙钛矿结构氧化物、钨青铜型化合物、铋氧化物型层状结构化合物中的一种或多种的组合。更可选地，铁电体颗粒103选自钙钛矿结构氧化物。
可选地，钙钛矿结构氧化物具有分子式Ba 1-xA xTi 1-yB yO 3。A包括选自Pb、Sr、Ca、K、Na和Cd中的一种或多种的组合，B包括选自Sn、Hf、Zr、Ce、Nb和Th中的一种或多种的组合，0≤x≤1，0≤y≤1。例如，钙钛矿结构氧化物可以包括选自BaTiO 3、Ba 1-x1Sr x1TiO 3(0≤x1≤1)、SrTiO 3、PbTiO 3、PbZr y1Ti 1-y1O 3(0≤y1≤1)、BaZr y2Ti 1-y2O 3(0<y2<1)、KNbO 3、NaNbO 3中的一种或多种的组合。进一步地，铁电体颗粒包括钛酸钡BTO、锆钛酸铅PZT、偏铌酸铅、铌酸铅钡锂PBLN和钛酸铅PT中的一种或多种。上述种类的铁电体颗粒能够有效发挥压电效应，以提高金属离子的均匀化分布的程度。
可选地，钨青铜型化合物可具有分子式M zWO 3。M包括选自Na、K、Rb和Cs中的一种或多种的组合，0＜z＜1。例如，钨青铜型化合物可以包括选自Na z1WO 3(0<z1<1)、K z2WO 3(0<z2<1)中的一种或多种的组合。
可选地，铋氧化物型层状结构化合物具有分子式(Bi 2O 2)(C n-1D nO 3n+1)。C包括选自Na、K、Ba、Sr、Pb、Ca、Ln和Bi中的一种或多种的组合，D包括选自Zr、Cr、Nb、Ta、Mo、W、Fe、Ti和V中的一种或多种的组合，2≤n≤5。例如，铋氧化物型层状结构化合物可以为SrBi 2Nb 2O 9、SrBi 2Ta 2O 9、SrBi 2Nb 2O 9、Bi 4Ti 3O 12中的一种或多种的组合。
在一些实施例中，铁电体颗粒的介电常数满足：100≤ε≤100000。
铁电体颗粒的介电常数在上述范围时，可以起到快速迁移金属离子的作用，从而保证金属离子的迁移速率。可选地，1000≤ε≤10000；示例性地，铁电体颗粒的介电常数可以为100至50000，100至25000，100至10000，100至5000，100至4000，100至3000，100至2000，100至1000，100至500，150至50000，150至25000，150至10000，150至5000，150至4000，150至3000，150至2000，150至1000，150至500， 200至50000，200至25000，200至10000，200至5000，200至4000，200至3000，200至2000或200至1000。
在本申请中，铁电体颗粒的介电常数是指室温(25±5℃)下的介电常数，其具有本领域公知的含义，可以用本领域已知的仪器及方法进行测试。例如可以将铁电体颗粒制备成圆形试样后，采用LCR测试仪测试电容量C并根据公式：介电常数ε＝(C×d)/(ε 0×A)计算得到。C表示电容量，单位为法拉(F)；d表示试样厚度，单位为cm；A表示试样面积，单位为cm 2；ε 0表示真空介电常数，ε 0＝8.854×10 -14F/cm。在本申请中，测试条件可以为1KHz、1.0V、25±5℃。测试标准可依据GB/T 11297.11-2015。制备试样时可参考中国专利申请CN114217139A。
在一些实施例中，铁电层5213还包括粘接剂，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的一种或多种。
在一些实施例中，铁电层5213还包括分散剂，分散剂可以包括羧甲基纤维素钠、聚乙烯吡咯烷酮、Hypermer KD-1中的一种或多种。
[负极极片]
负极极片521包括负极集流体、设置于负极集流体的至少一个表面的负极膜层；负极膜层包括负极活性材料。
在一些实施例中，负极膜层的压实密度P g/cm 3、负极膜层的涂布重量CW g/1540.25mm 2之间满足：
Figure PCTCN2022105752-appb-000007
记
Figure PCTCN2022105752-appb-000008
负极膜层的压实密度P和涂布重量CW满足上述范围时，可以保证负极膜层在适当的厚度范围内，以此保证二次电池的能量密度；在二次电池充电过程中Z在上述范围时，铁电层可以影响极片整体结构包括极片下层的结构；并且极片具有合适的孔隙，电解液可以充分浸润极片，有利于锂离子的迁移。
在一些实施例中，负极膜层的压实密度P g/cm 3满足：1.1≤P≤1.85。
通过调节负极膜层的压实密度在合适的范围内，能够使得二次电池具有较高的能量密度。此外，通过调节压实密度在合适的范围内，还能使负极膜层在循环过程中具有较强的维持孔道结构的能力，由此负极极片521的电解液浸润性更好，能更好地提升二次电池的循环性能。可选地，1.3≤P≤1.8；示例性地，P g/cm 3可以为1.1g/cm 3、1.2g/cm 3、1.3g/cm 3、1.4g/cm 3、1.5g/cm 3、1.6g/cm 3、1.7g/cm 3或1.8g/cm 3；或者P的数值在上述任意两个数值范围内。
在本申请中，材料的压实密度为本领域公知的含义，可以用本领域已知的仪器及方法进行测试。例如可以参照标准GB/T24533-2009，通过电子压力试验机(例如UTM7305型)测试。示例性测试方法如下：称取1g材料，加入底面积为1.327cm 2的模 具中，加压至2000kg(相当于20000N)，保压30s，然后卸压，保持10s，然后记录并计算得到材料在20000N作用力下的压实密度。
在一些实施例中，负极膜层的涂布重量CW g/1540.25mm 2满足：0.1≤CW≤0.3。
通过调节负极膜层的涂布重量CW在合适的范围内，能够保证电芯的能量密度以及铁电层对负极膜层的效果。可选地，0.14≤CW≤0.17；示例性地，CW g/1540.25mm 2可以为0.1g/1540.25mm 2、0.12g/1540.25mm 2、0.13g/1540.25mm 2、0.14g/1540.25mm 2、0.15g/1540.25mm 2、0.16g/1540.25mm 2、0.17g/1540.25mm 2、0.18g/1540.25mm 2或0.19g/1540.25mm 2；或者是上述任意两个数值组成的组合。
涂布重量CW的测定方法：
基材冲片面积1540.25mm2，天平称重；冲小圆片(面积：1540.25mm2)，称重，减去基材重量即可得活性材料涂布重量；
在一些实施例中，负极膜层的厚度Lμm满足：30μm≤L≤200μm。
通过调节负极膜层的厚度L在合适的范围内，一方面能够保证负极活性材料的质量，从而保证二次电池的能量密度；另一方面可以与铁电层5213相配合，以使铁电层5213能够充分发挥压电效应，促进负极膜层中的金属离子均匀化分布。可选地，35μm≤L≤190μm。；示例性地，L可以为30、35、40、45、50、60、70、80、90、100、120、140、150、160、180、190或200；或者是上述任意两个数值组成的范围。
在本申请中，负极膜层的厚度为本领域公知的含义，可以采用本领域已知的仪器及方法进行测定。例如可以采用万分尺沿负极极片521的厚度方向测量至少12个不同位置的负极极片521的厚度，然后取平均值作为负极极片521的厚度h1；然后减去负极集流体的厚度即为负极膜层的厚度。
负极膜层的厚度还可以采用断层扫描，直接测定负极膜层的厚度，具体如下：利用离子抛光扫描可以测量出涂布重量1.制样：a.用陶瓷剪刀将极片剪成6mm*6mm大小，贴在涂抹石蜡的样品台上，将样品略突出(＜1mm)样品台边缘即可，b.设置抛光电压和时间抛光(厚度150um负极极片7.5KV下100min)；2.形貌分析：采用扫描电子显微镜，50倍左右移动样品位置，直至清晰为止，分别取12个位置标记5212的厚度，结束后取平均值，即可得到5212的厚度。
在一些实施例中，负极膜层可以包括本领域公知的用于二次电池的负极活性材料。作为示例，负极活性材料包括选自天然石墨、人造石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂中的一种或多种的组合。硅基材料可包括选自单质硅、硅氧化物、硅碳复合物、硅氮复合物和硅合金材料中的一种或多种的组合。锡基材料可包括选自单质锡、锡氧化物和锡合金材料中的一种或多种的组合。进一步可选地，负极活性材料包括硅碳复合物，在二次电池充电过程中，硅碳复合物中硅可能会发生体积膨胀，膨胀后的硅可能会给予铁电体颗粒以一定的压应力，从而进一步激发铁电体颗粒的压电效应，提高其均匀化金属离子浓度的能力。
在一些实施例中，负极膜层还可选地包括负极导电剂。本申请对负极导电剂的种类没有特别的限制，作为示例，负极导电剂可包括选自超导碳、导电石墨、乙炔黑、 炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或多种的组合。在一些实施例中，基于负极膜层的总质量，负极导电剂的质量百分含量在5％以下。
在一些实施例中，负极膜层还可选地包括负极粘结剂。本申请对负极粘结剂的种类没有特别的限制，作为示例，负极粘结剂可包括选自丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸类树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)和羧甲基壳聚糖(CMCS)中的一种或多种的组合。在一些实施例中，基于负极膜层的总质量，负极粘结剂的质量百分含量在5％以下。
在一些实施例中，负极膜层还可选地包括其他助剂。作为示例，其他助剂可包括增稠剂，例如，羧甲基纤维素钠(CMC-Na)、PTC热敏电阻材料等。在一些实施例中，基于负极膜层的总质量，其他助剂的质量百分含量在2％以下。
在一些实施例中，负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔或铜合金箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层，作为示例，金属材料可包括选自铜、铜合金、镍、镍合金、钛、钛合金、银和银合金中的一种或多种的组合，高分子材料基层可包括选自聚丙烯(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)和聚乙烯(PE)中的一种或多种的组合。
负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。负极浆料通常是将负极活性材料、可选的导电剂、可选地粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
负极极片521并不排除除了负极膜层之外的其他附加功能层。例如在某些实施例中，本申请的负极极片521还包括夹在负极集流体和负极膜层之间、设置于负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施例中，本申请的负极极片521还包括覆盖在负极膜层表面的保护层。
需要说明的是，上述针对负极极片521的各种参数测试，以负极活性材料作为测试样品为例进行说明，可以在涂布负极浆料前取样测试，也可以从冷压后的负极膜层中取样测试。当负极极片521测试样品是从经冷压后的负极膜层中取样时，作为示例，可以按如下步骤进行取样：任意选取一冷压后的负极膜层，对负极活性材料取样(例如可以选用刀片刮粉取样)；将上述收集到的负极活性材料粉末置于去离子水中，之后进行抽滤、烘干，再将烘干后的负极活性材料在一定温度及时间下烧结(例如400℃，2h)，去除粘结剂和导电剂，即得到负极活性材料测试样品。当铁电体颗粒作为测试样品时，同样地，可以在固化铁电浆料前取样测试，也可以在固化铁电浆料后进行取样测试。
[正极极片]
在一些实施例中，正极极片522包括正极集流体以及设置在正极集流体至少一个表面上的正极膜层。例如，正极集流体具有在自身厚度方向相对的两个表面，正极 膜层设置于正极集流体的两个相对表面中的任意一者或两者上。
正极膜层包括正极活性材料，正极活性材料可采用本领域公知的用于二次电池的正极活性材料。例如，正极活性材料可包括选自锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或多种的组合。锂过渡金属氧化物的示例可包括选自锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其各自的改性化合物中的一种或多种的组合。橄榄石结构的含锂磷酸盐的示例可包括选自磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的一种或多种的组合。
在一些实施例中，为了进一步提高二次电池的能量密度，正极活性材料可以包括式1所示的锂过渡金属氧化物及其改性化合物中的一种或多种的组合。
Li aNi bCo cM dO eA f      式1
在式1中，0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，1≤e≤2，0≤f≤1，M包括选自Mn、Al、Zr、Zn、Cu、Cr、Mg、Fe、V、Ti和B中的一种或多种的组合，A包括选自N、F、S和Cl中的一种或多种的组合。
在本申请中，上述各正极活性材料的改性化合物可以是对正极活性材料进行掺杂改性或表面包覆改性。
在一些实施例中，正极膜层还可选地包括正极导电剂。本申请对正极导电剂的种类没有特别的限制，作为示例，正极导电剂包括选自超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯和碳纳米纤维中的一种或多种的组合。在一些实施例中，基于正极膜层的总质量，正极导电剂的质量百分含量在5％以下。
在一些实施例中，正极膜层还可选地包括正极粘结剂。本申请对正极粘结剂的种类没有特别的限制，作为示例，正极粘结剂可包括选自聚偏氟乙烯(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-六氟丙烯共聚物和含氟丙烯酸酯类树脂中的一种或多种的组合。在一些实施例中，基于正极膜层的总质量，正极粘结剂的质量百分含量在5％以下。
在一些实施例中，正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔或铝合金箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层，作为示例，金属材料可包括选自铝、铝合金、镍、镍合金、钛、钛合金、银和银合金中的一种或多种的组合，高分子材料基层可包括选自聚丙烯(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)和聚乙烯(PE)中的一种或多种的组合。
正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。
[电解液]
本申请的电解液可采用本领域公知的用于二次电池的电解液。电解液包括锂盐 和有机溶剂。
作为示例，锂盐可包括选自六氟磷酸锂(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)和四氟草酸磷酸锂(LiTFOP)中的一种或多种的组合。
作为示例，有机溶剂可包括选自碳酸乙烯酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、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)和二乙砜(ESE)中的一种或多种的组合。
在一些实施例中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解液。
在一些实施例中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)和聚丁二酸丁二醇酯(PBS)中的一种或多种的组合。
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。如图2是作为一个示例的方形结构的二次电池5。
在一些实施例中，如图3所示，外包装可包括壳体51和盖板53。其中，壳体51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51具有与容纳腔连通的开口，盖板53用于盖设开口，以封闭容纳腔。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52。电极组件52封装于容纳腔。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，可根据需求来调节。
本申请的二次电池的制备方法是公知的。在一些实施例中，可将正极极片、隔离膜、负极极片和电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
在本申请的一些实施例中，根据本申请的二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为多个，具体数量可根据电池模块的应用和容量来调节。
图4是作为一个示例的电池模块4的示意图。如图4所示，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于 该容纳空间。
在一些实施例中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图5和图6是作为一个示例的电池包1的示意图。如图5和图6所示，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2用于盖设下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
用电装置
第二方面，本申请提供一种用电装置，用电装置包括本申请的二次电池、电池模块和电池包中的至少一种。二次电池、电池模块和电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。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。
用电装置可以根据其使用需求来选择二次电池、电池模块或电池包。
图7是作为一个示例的用电装置的示意图。该用电装置6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对高功率和高能量密度的需求，可以采用电池包1或电池模块。
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。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
制备二次电池的方法
第三方面，本申请还提出了一种制备二次电池的方法，该方法可以用于制备本申请第一方面任一实施例的二次电池。
所述方法包括：
S100，提供正极极片、负极极片和隔离膜，负极极片包括含有负极活性材料的负极膜层；
S200，将含有铁电体颗粒的铁电浆料提供至隔离膜，并于隔离膜的至少一个表面上固化形成铁电层；
S300，将正极极片、负极极片和设置有铁电层的隔离膜形成电极组件，其中，隔离膜设置于正极极片和负极极片之间；
S400，将电极组件装配至外包装内形成二次电池，
其中，负极膜层的压实密度为P g/cm 3；
负极膜层的涂布重量为CW g/1540.25mm 2；
铁电层的厚度为H μm；
铁电体颗粒的体积平均粒径Dv50为D μm，
所述二次电池满足：
Figure PCTCN2022105752-appb-000009
本申请实施例的方法制备工艺简单，只需在隔离膜上继续形成铁电层即可，不需更改原有的生产工艺路线，操作便捷；
在一些实施例中，步骤S200中，基于铁电层的总质量计，铁电体颗粒的质量含量b满足：90％≤a≤98％；可选地，95％≤a≤98％。
可以采用多种工艺将铁电浆料设置于隔离膜上，例如采用凹版工艺、涂布工艺等等。具体地，采用凹版工艺时，可以将铁电浆料置于凹版盘中，凹版辊通过辊缝携带铁电浆料，滚覆在隔离膜上，可以通过调节辊缝的尺寸控制铁电层的厚度。
铁电浆料的质量较少时，铁电浆料可能局部覆盖隔离膜，其所固化形成的铁电层可能呈现连续状态，也可能呈现不连续状态。随着铁电浆料的质量增加，铁电浆料可能全部覆盖隔离膜，其所固化形成的铁电层可能呈现连续整层结构，整层覆盖于隔离膜。在本申请中，铁电层覆盖隔离膜，是指铁电层沿其自身厚度方向的投影覆盖隔离膜。
可以通过调节铁电浆料中的铁电体颗粒的质量含量b，从而调整铁电体颗粒的质量。铁电体颗粒的质量含量b在上述范围时，铁电层和隔离膜的结合强度较高，铁电层不易剥落，且铁电层容易发挥压电效应，均匀化金属离子的分布。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
1、正极极片的制备
采用厚度为13μm的铝箔作为正极集流体。
将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2、导电炭黑、粘结剂聚偏二氟乙烯(PVDF)按98：1：1的重量比在适量的N-甲基吡咯烷酮(NMP)溶剂中充分搅拌混合，使其形成均匀的正极浆料；将正极浆料涂覆于正极集流体的表面上，经烘干等工序后，得到正极极片。
2、负极极片的制备
2.1负极活性材料的制备
将焦原料进行预处理去除杂质，热解造粒得到Dv50为11μm的二次颗粒；然后在3000℃下进行石墨化处理23h后，包覆沥青；在1000℃下高温炭化处理16h，得到人造石墨。
2.2负极极片的制备
采用厚度为8μm的铜箔作为负极集流体。
将负极活性材料人造石墨、导电炭黑、增稠剂羧甲基纤维素钠(CMC)、粘结剂丁苯橡胶乳液(SBR)按96.8:0.8:1.2:1.2重量比在适量的去离子水中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料涂覆于负极集流体上，经烘干等工序后，得到负极 极片。
3、电解液的制备
在含水量小于10ppm的环境下，将非水有机溶剂碳酸乙烯酯、碳酸甲乙酯、碳酸二乙酯按照体积比1:1:1进行混合得到电解液溶剂，随后将锂盐LiPF6溶解于混合后的溶剂中，配置成锂盐浓度为1mol/L的电解液。
4、隔离膜的制备
选择聚乙烯膜作为隔离膜，根据正极极片和负极极片的尺寸经分切得到合适的尺寸。
将40wt％钛酸钡、粘结剂丁苯橡胶(SR-1B)、分散剂羧甲基纤维素钠、丙烯酸酯乳液溶于去离子水中，在真空搅拌机作用下搅拌至体系呈均一状，得到固含量为40％的钛酸钡浆料。
将钛酸钡浆料涂覆于隔离膜的面向负极极片的表面，经110℃条件下烘干后，钛酸钡浆料在隔离膜上固化成型为铁电层。
5、锂离子电池的制备
将上述正极极片、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之间起到隔离作用，然后卷绕得到电极组件；将电极组件置于外包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，得到锂离子电池。
实施例2
实施例2-1至实施例2-7
与实施例1不同的是，实施例2-1至实施例2-4调整了“铁电层的厚度H”。
对比例
对比例1
与实施例1不同的是，对比例1未采用铁电层，S＝0。
对比例2
与实施例1不同的是，对比例2调整了“铁电层的厚度H”。
对比例3
与实施例1不同的是，对比例3的负极浆料中将负极活性材料和铁电体颗粒混合；具体地，负极活性材料、铁电体颗粒BaTiO 3、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)、导电剂炭黑按照质量比97：1：1:1在适量的溶剂去离子水中充分搅拌混合，形成均匀的负极浆料；将负极浆料均匀涂覆于负极集流体铜箔的表面上，经干燥、冷压后，得到负极极片。
实施例1、实施例2、对比例1至对比例3的参数如表1所示：
表1
Figure PCTCN2022105752-appb-000010
Figure PCTCN2022105752-appb-000011
在本文中，
Figure PCTCN2022105752-appb-000012
记
Figure PCTCN2022105752-appb-000013
实施例3
实施例3-1至实施例3-4
与实施例1不同的是，实施例3-1至实施例3-4调整了铁电体颗粒粒径D。
实施例1、实施例3-1至实施例3-4的参数如表2所示：
表2
Figure PCTCN2022105752-appb-000014
实施例4
实施例4-1至实施例4-4
与实施例1不同的是，实施例4-1至实施例4-4调整了铁电体颗粒的质量含量a％。
实施例1、实施例4-1至实施例4-4的参数如表3所示：
表3
Figure PCTCN2022105752-appb-000015
实施例5
实施例5-1至实施例5-5
与实施例1不同的是，实施例5-1至实施例5-5调整了负极膜层的压实密度P与涂布重量。实施例1、实施例5-1至实施例5-5的参数如表4所示：
表4
Figure PCTCN2022105752-appb-000016
实施例5
实施例6-1至实施例6-2
与实施例1不同的是，实施例6-1至实施例6-2调整了铁电体颗粒的种类。
对比例4
与实施例1不同的是，对比例4将铁电体颗粒替换为氧化铝颗粒。
实施例1、实施例6-1至实施例6-2以及对比例4的参数如表5所示：
表5
Figure PCTCN2022105752-appb-000017
测试部分
1、负极极片的测试部分
1.1负极膜层的涂布重量CW
取1540.25mm 2基材，天平称重W1；取冷压后的极片冲片，冲片面积1540.25mm2，天平称重，负极膜层的涂布重量CW＝W2-W1。
1.2负极膜层的厚度L
采用万分尺沿负极极片(不包含铁电层)的厚度方向测量至少12个不同位置的负极极片的厚度，然后取平均值作为负极极片的厚度h1；然后减去负极集流体的厚度即为负极膜层的厚度。
1.3负极膜片的压密P
负极膜层的压密可通过膜层的涂布重量CW与负极膜层的厚度L得到，计算公 式如下：P＝CW/L/1540.25。
1.3负极膜层的厚度L
采用万分尺沿负极极片的厚度方向测量至少12个不同位置的负极极片的厚度，然后取平均值作为负极极片的厚度h1；然后减去负极集流体的厚度即为负极膜层的厚度。
1.4铁电层的厚度H
采用万分尺沿隔离膜(不包含铁电层)的厚度方向测量至少12个不同位置的负极极片的厚度，然后取平均值作为隔离膜的厚度h1。然后采用万分尺沿隔离膜(包含铁电层)的厚度方向测量至少12个不同位置的隔离膜的厚度，然后取平均值作为总厚度h2，铁电层的厚度H＝h2-h1。
1.5铁电体颗粒的体积平均粒径Dv50
取一定量上述制备的铁电体颗粒样品，通过Mastersizer 2000E型激光粒度分析仪测试体积平均粒径Dv50。测试标准依据GB/T 19077-2016。
1.6铁电体颗粒的粒径的测试方法
材料的Dv90、Dv50、Dv10为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测试，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。Dv90为材料累计体积分布百分数达到90％时所对应的粒径；Dv50为材料累计体积分布百分数达到50％时所对应的粒径；Dv10为材料累计体积分布百分数达到10％时所对应的粒径。
2、二次电池的测试部分
2.1二次电池快速充电性能测试
在25℃下，将实施例和对比例制备得到锂离子电池以nC满充(例如n＝0.1、0.2、0.3、0.4、0.5)，以1C满放，如此循环10圈，再将锂离子电池以1C满充，然后拆解负极极片观察负极极片表面的析锂情况，若未析锂则以(n+0.1)C满充，再次进行测试，以此递增，直至负极表面析锂为止，以此时的倍率减去0.1C即为锂离子电池最大的充电能力。
2.2能量密度测试
在25℃下，将实施例和对比例制备得到锂离子电池以0.33C倍率满充、以0.33C倍率满放，循环3圈，取最后一圈放电能量(E)，使用电子天平称重锂离子电池的质量(m)，W＝E/m。
2.3存储寿命测试
将实施例和对比例制备得到锂离子电池满充至97％荷电状态(SOC)，在60℃下存储，容量衰减到80％截止，记录此时的存储时间，其中目标存储时间为280天，计算实施例与对比例分别与目标存储时间的比值，记为存储寿命。其中，目标存储寿命则为100％。
2.4循环性能测试：
在25℃下，将实施例和对比例制备的锂离子电池以3C倍率充电，以1C倍率放电，进行3％-97％SOC循环测试，直至锂离子电池的容量小于初始容量的80％，记录循环圈数。
测试结果
本申请的负极极片在改善二次电池的性能的作用如表6至表10所示。
表6
项目 充电能力 循环寿命 能量密度 存储寿命
实施例1 5.5C 2100 97.0％ 310
实施例2-1 5.1C 1900 99.0％ 300
实施例2-2 5.6C 2200 96.0％ 320
实施例2-3 5.7C 2400 95.0％ 325
实施例2-4 5.8C 2450 92.0％ 328
对比例1 4.0C 1700 100.0％ 280
对比例2 5.9C 2500 85.5％ 260
对比例3 4.5C 1800 99.5％ 290
由表6中的实施例2-1至2-5的测试结果可知，铁电层的厚度增加，可增强对锂枝晶的抑制效果，提高电芯充电能力，此外锂枝晶生长被抑制之后可明显改善电芯循环性能，减少循环跳水；从对比例1可知，无铁电层的电芯，负极极片锂枝晶会在循环过程中逐渐生长，恶化循环性能；从对比例2可知，铁电层过厚，对充电能力提升有限，反而会阻碍锂离子的穿梭，能量密度也大幅度恶化；从对比例3可知，物理混合负极活性材料与铁电体，提升充电能力的效果不如涂层，因为物混的铁电体，产生的反向电场方向不统一，相互干扰。
表7
项目 充电能力 循环寿命 能量密度 存储寿命
实施例1 5.5C 2100 97.0％ 310
实施例3-1 5.4C 2050 97.0％ 308
实施例3-2 5.2C 2000 97.0％ 305
实施例3-3 5.1C 1950 97.0％ 300
实施例3-4 4.9C 1900 97.0％ 290
由表7的实施例3-1至3-4的测试结果可知，铁电体粒径越小在涂层上分布的越均匀，对锂枝晶的生长越均衡，浓度极化越小，但是粒径越小，制备工艺越复杂，成本越高；粒径增大之后，成本降低，但是各粒径之间会产生干扰电场，影响抑制析锂的效果。
表8
Figure PCTCN2022105752-appb-000018
Figure PCTCN2022105752-appb-000019
由表8的实施例4-1至4-4的测试结果可知，铁电体含量增多，产生的反向电场强度增强，锂枝晶垂直生产速率减慢，大部分锂沉积为可逆的，充电能力提升，循环性能改善，但是铁电体含量过高，粘结力和分散剂含量减少，铁电体在负极膜层上的粘结力降低，极易脱落，本身的效果无法体现。
表9
项目 充电能力 循环寿命 能量密度 存储寿命
实施例1 5.5C 2100 97.0％ 310
实施例5-1 4.2C 1800 90.0％ 300
实施例5-2 4.5C 1850 92.0％ 305
实施例5-3 5C 1950 95.0％ 308
实施例5-4 5.1C 1940 96.0％ 310
实施例5-5 5.2C 1950 98.0％ 320
由表9中的实施例5-1至5-4的测试结果可知，3<P/(CW*1000)<19，可使铁电层产生的效果最佳，若P/(CW*1000)<3，极片厚度过大，铁电层对极片下层作用效果减弱，充电能力提升不明显，若P/(CW*1000)>19，极片的孔隙有可能被压实，电解液无法到达，铁电层的反向电场对极片没有影响，P/(CW*1000)在合适范围内，可使电芯充电能力、能量密度达到最优。
综合实施例5-1至5-4的测试结果可知，在二次电池充电过程中Z在上述范围时，铁电层可以影响极片整体结构包括极片下层的结构；并且极片具有合适的孔隙，电解液可以充分浸润极片，有利于锂离子的迁移，可使电芯充电能力、能量密度达到最优。
表10
项目 充电能力 循环寿命 能量密度 存储寿命
实施例1 5.5C 2100 97.0％ 310
实施例6-1 5.4C 2101 97.0％ 311
实施例6-2 5.5C 2101 97.0％ 309
对比例4 4.0C 1700 100.0％ 280
由表10中的实施例1、实施例6-1实施例6-2以及对比例4的测试结果可知，在二次电池充电过程中，铁电体材料可以显著改善二次电池的性能。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。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 (14)

  1. 一种二次电池，包括：
    正极极片；
    负极极片，其包括含有负极活性材料的负极膜层；
    隔离膜，其设置于所述正极极片和所述负极极片之间；
    铁电层，其设置于所述隔离膜的至少一个表面，所述铁电层包括铁电体颗粒，
    其中，
    所述负极膜层的压实密度为P g/cm 3；
    所述负极膜层的涂布重量为CW g/1540.25mm 2；
    所述铁电层的厚度为H μm；
    所述铁电体颗粒的体积平均粒径Dv50为D μm，
    所述二次电池满足：
    Figure PCTCN2022105752-appb-100001
    可选地，
    Figure PCTCN2022105752-appb-100002
  2. 根据权利要求1所述的二次电池，其中，
    所述铁电层的厚度Hμm满足：2≤H≤10；可选地，4≤H≤6。
  3. 根据权利要求1或2所述的二次电池，其中，
    所述铁电体颗粒的体积平均粒径Dv50满足：0.08≤D≤1；可选地，0.1≤D≤0.8。
  4. 根据权利要求1至3中任一项所述的二次电池，其中，
    基于所述铁电层的总质量计，所述铁电体颗粒的质量含量a满足：90％≤a≤98％；可选地，95％≤a≤98％。
  5. 根据权利要求1至4中任一项所述的二次电池，其中，
    所述铁电体颗粒包括选自钙钛矿结构氧化物、钨青铜型化合物和铋氧化物型层状结构化合物中的一种或多种；
    可选地，所述钙钛矿结构氧化物包括钛酸钡BTO、锆钛酸铅PZT、偏铌酸铅、铌酸铅钡锂PBLN和钛酸铅PT中的一种或多种。
  6. 根据权利要求1至5中任一项所述的二次电池，其中，
    所述铁电体颗粒的介电常数满足：100≤ε≤100000；可选地，1000≤ε≤10000。
  7. 根据权利要求1至6中任一项所述的二次电池，其中，
    所述负极膜层的压实密度P g/cm 3、所述负极膜层的涂布重量CW g/1540.25mm 2之间满足：
    Figure PCTCN2022105752-appb-100003
  8. 根据权利要求1至7中任一项所述的二次电池，其中，
    所述负极膜层的压实密度P g/cm 3满足：1.1≤P≤1.85；可选地，1.3≤P≤1.8。
  9. 根据权利要求1至8中任一项所述的二次电池，其中，
    所述负极膜层的涂布重量CW g/1540.25mm 2满足：0.1≤CW≤0.3；可选地， 0.14≤CW≤0.2。
  10. 根据权利要求1至9中任一项所述的二次电池，其中，
    所述负极膜层的厚度Lμm满足：30μm≤L≤200μm；可选地，35μm≤L≤190μm。
  11. 根据权利要求1至10中任一项所述的二次电池，其中，
    所述负极活性材料包括天然石墨、人造石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂中的一种或多种。
  12. 一种电池模块，包括如权利要求1至11中任一项所述的二次电池。
  13. 一种电池包，包括如权利要求12所述的电池模块。
  14. 一种用电装置，包括如权利要求1至11中任一项所述的二次电池、如权利要求12所述的电池模块或如权利要求13所述的电池包。
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