WO2024016122A1 - 一种极片、电池单体、电池及用电装置 - Google Patents

一种极片、电池单体、电池及用电装置 Download PDF

Info

Publication number
WO2024016122A1
WO2024016122A1 PCT/CN2022/106308 CN2022106308W WO2024016122A1 WO 2024016122 A1 WO2024016122 A1 WO 2024016122A1 CN 2022106308 W CN2022106308 W CN 2022106308W WO 2024016122 A1 WO2024016122 A1 WO 2024016122A1
Authority
WO
WIPO (PCT)
Prior art keywords
active material
pole piece
battery
lithium
specific surface
Prior art date
Application number
PCT/CN2022/106308
Other languages
English (en)
French (fr)
Inventor
杜香龙
Original Assignee
宁德时代新能源科技股份有限公司
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to PCT/CN2022/106308 priority Critical patent/WO2024016122A1/zh
Publication of WO2024016122A1 publication Critical patent/WO2024016122A1/zh

Links

Images

Classifications

    • 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
    • H01M4/139—Processes of manufacture
    • 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 battery technology, and in particular to a pole piece, a battery cell, a battery and an electrical device.
  • This application was made in view of the above technical problems. Its purpose is to provide a pole piece, a battery cell, a battery and an electrical device.
  • the pole piece has active materials with different specific surface areas, which can effectively improve the performance of the pole piece during the battery cycle.
  • the infiltration situation during the process improves the lithium precipitation problem in the middle area of the pole piece, thereby improving the cycle performance and service life of the battery.
  • the present application provides a pole piece.
  • the pole piece includes: a current collector.
  • the current collector includes a tab region and a coating film region.
  • the coating film region includes two components located at both edges of the coating film region. a first part and a second part located between the first part; a film layer, the film layer is disposed on the coating film area, the film layer includes a first active material and a second active material, wherein the film layer
  • the first active material is provided on the first part, the second active material is provided on the second part, and the specific surface area of the first active material is smaller than the specific surface area of the second active material.
  • the pole piece provided by this application has a first active material on both sides of the coating area and a second active material in the middle part.
  • the second active material has a larger specific surface area. Therefore, compared with the first active material, the pores in the second active material can absorb more electrolyte during the battery cycle, have a better infiltration effect, and can effectively improve the electrolyte absorption due to the expansion of the electrode plates during the battery cycle. Extruding the pole piece area increases the polarization of the pole piece and leads to the lithium deposition problem, thus improving the cycle performance and service life of the battery.
  • the middle part of the pole piece forms the middle part of the rolled electrode assembly after being rolled, which can store more electrolyte, thereby effectively solving the problem of the middle part of the rolled electrode assembly. Partial infiltration is difficult, and serious polarization and lithium precipitation occur during battery cycling.
  • the electrode assembly refers to the battery component including the positive electrode piece, separator, and negative electrode piece.
  • the D V 50 of the first active material is greater than the D V 50 of the second active material.
  • the first active material disposed on both sides of the electrode plate coating area has a larger average particle size
  • the second active material disposed on the middle part of the electrode piece coating area has a smaller average particle size.
  • the first active material is further disposed on the second part, and the second active material is disposed above the first active material.
  • the second active material in the middle part of the pole piece, is disposed above the first active material, so that during the preparation process of the pole piece, the first active material does not need to be coated in a complicated manner.
  • Zoned coating methods such as zebra coating can be achieved using conventional coating methods, which simplifies the preparation process of the pole piece.
  • the thickness of the second active material is greater than the thickness of the first active material.
  • the second active material in the middle part of the pole piece, by setting the thickness of the second active material to be greater than the thickness of the first active material, the second active material accounts for a larger proportion in the middle part of the pole piece, so that it can Holds more electrolyte.
  • the electrode piece preparation process is simplified, the electrode piece production efficiency is improved, and the problem of lithium precipitation from the electrode piece during the battery cycle is further improved.
  • the width of the second part is 30%-70% of the width of the coating film area, preferably 40%-60% of the width of the coating film area.
  • the amount of the second material can be controlled within an appropriate range, thereby improving the problem of lithium deposition while helping to save the cost of the pole piece.
  • the pole piece is a positive pole piece
  • the first active material is selected from the group consisting of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, a composite material of lithium iron phosphate and carbon, and a composite material of lithium manganese phosphate and carbon.
  • the second active material is selected from the group consisting of nano lithium iron phosphate, nano lithium manganese phosphate, nano lithium iron manganese phosphate, nano lithium iron phosphate and carbon.
  • the specific surface area of the first active material is ⁇ 11 m 2 /g
  • the specific surface area of the second active material is ⁇ 11 m 2 /g
  • the specific surface area of the second active material is ⁇ 16 m 2 /g.
  • the ability of the middle portion of the positive electrode sheet to accommodate ionic liquid can be further improved, thereby further improving the problem of lithium deposition in the middle area of the negative electrode sheet.
  • the DV50 of the first active material is >800 nm
  • the DV50 of the second active material is ⁇ 800 nm
  • the DV50 of the second active material is ⁇ 200 nm.
  • the carbon content of the first active material is ⁇ 1.5%
  • the carbon content of the second active material is ⁇ 1.5%
  • the carbon content of the second active material is ⁇ 2.5%.
  • the pole piece is a negative pole piece
  • the first active material is selected from at least one of artificial graphite, soft carbon, silicon-based materials, tin-based materials, and lithium titanate
  • the second The active material is selected from at least one of natural graphite, hard carbon, nano silicon-based materials, nano tin-based materials, and nano lithium titanate.
  • the specific surface area of the first active material is ⁇ 1.5m 2 /g
  • the specific surface area of the second active material is ⁇ 1.5m 2 /g.
  • the specific surface area of the second active material is ⁇ 4.5m 2 /g.
  • the ability of the middle part of the negative electrode sheet to accommodate ionic liquid can be further improved, thereby further improving the problem of lithium deposition in the middle area of the negative electrode sheet.
  • the Dv50 of the first active material is >10 ⁇ m
  • the Dv50 of the second active material is ⁇ 10 ⁇ m
  • the Dv50 of the second active material is ⁇ 7.5 ⁇ m.
  • a second aspect provides a battery cell, which includes the pole piece in any embodiment of the first aspect.
  • a third aspect provides a battery, which includes the battery cell in the second aspect.
  • an electrical device in a fourth aspect, includes at least one of the battery unit in the second aspect or the battery in the third aspect.
  • the battery unit and/or the battery are used. To provide power to the electrical device.
  • Figure 1 is a schematic structural diagram of a pole piece according to an embodiment of the present application.
  • Figure 2 is a schematic top view of a pole piece according to an embodiment of the present application.
  • Figure 3 is a schematic structural diagram of another pole piece according to the embodiment of the present application.
  • Figure 4 is a schematic structural diagram of another pole piece according to the embodiment of the present application.
  • FIG. 5 is a schematic structural diagram of an electrode assembly according to an embodiment of the present application.
  • Figure 6 is a diagram of DCR test results of the embodiments and comparative examples of the present application.
  • Figure 7 is a photo of the negative electrode piece after cycling in the comparative example of the present application.
  • Figure 8 is a photo of the negative electrode piece after cycling according to the 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
  • 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).
  • Batteries usually include positive electrode plates, negative electrode plates, electrolytes and separators. During the charging and discharging process of the battery, active ions are inserted and detached back and forth between the positive and negative electrodes. The electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the separator is arranged between the positive electrode piece and the negative electrode piece to prevent the positive and negative electrodes from being short-circuited and allows ions to pass through.
  • the positive electrode plate, the negative electrode plate and the separator are usually formed into an electrode assembly, and then the electrode assembly is placed in a casing containing the electrode assembly and the electrolyte to form a battery cell.
  • the electrode assembly can be a rolled structure or a laminated structure.
  • the battery includes at least one battery cell.
  • the battery may include a lithium-ion battery, a sodium-ion battery, a magnesium-ion battery, or the like.
  • the lithium-ion battery is a typical secondary battery. Because it relies on the chemical reaction of lithium ions as active ions to be deintercalated between the positive and negative electrodes for charging and discharging, the lithium-ion battery is also called It is a rocking chair type battery. During the charging process of a lithium-ion battery, lithium ions are released from the positive electrode, move and are embedded in the negative electrode; during the discharge process, lithium ions are released from the negative electrode, move and are embedded in the positive electrode.
  • the battery pole pieces will expand during the cycle. Due to various factors such as ion dynamics and battery energy density, the distance between the positive and negative electrodes is very small, which is usually not enough to accommodate the expansion of the electrode material or the damage of the structure.
  • the electrolyte especially the liquid electrolyte
  • the electrolyte will be squeezed out between the positive and negative electrode plates, so that there is not enough electrolyte between the positive and negative electrode plates for ion conduction, and the battery will undergo serious polarization, and the active ions (lithium ions) will ) precipitates on the surface of the negative electrode piece, that is, lithium precipitation occurs, which greatly affects the cycle performance and service life of the battery. In severe cases, it may also cause battery safety issues.
  • the pole piece is rolled into a cylindrical electrode assembly, and the middle area of the pole piece is rolled to form the middle part of the electrode assembly.
  • embodiments of the present application provide a pole piece, a battery cell, a battery and an electrical device, wherein a first active material with a smaller specific surface area is provided at the edge of the pole piece, and in the middle of the pole piece A second active material with a larger specific surface area is disposed at the middle position of the pole piece, so that the middle position of the pole piece can accommodate more electrolyte.
  • the pole piece, especially the middle area of the pole piece is polarized, thereby reducing the precipitation of lithium on the surface of the negative electrode piece.
  • lithium insertion and intercalation processes mentioned in this application refer to the process of lithium ions being embedded in the positive and negative electrode materials due to electrochemical reactions.
  • extraction, “delithiation” and “deintercalation” mentioned in this application are “The process refers to the process in which lithium ions are released from the positive electrode material and negative electrode material due to electrochemical reactions.
  • Figure 1 is a schematic structural diagram of a pole piece according to an embodiment of the present application.
  • Figure 2 is a schematic top view of a pole piece according to an embodiment of the present application.
  • the pole piece 1 includes a current collector 2 and a membrane layer 3.
  • the current collector 2 includes a tab area 21 and a coating film area 22, and the film layer 3 is disposed on the coating film area 22.
  • the coating film area 22 includes a first part 22a provided on both sides of the coating film area 22 and a second part 22b located between the first parts 22a.
  • the film layer 3 includes a first active material 31 and a second active material 32, wherein the first active material 31 is provided on the first part 22a, and the second active material 32 is provided on the second part 22b.
  • the film layer 3 is disposed on at least one surface of the current collector 2 .
  • the pole piece 1 can be a positive pole piece or a negative pole piece.
  • the pole piece 1 can be used to form a wound electrode assembly or a laminated electrode assembly.
  • the tab area 21 is connected to one end of the coating area 22 along the first direction O1, and the pole piece 1 is wound along the second direction O2 to form a rolled electrode assembly.
  • the first direction O1 is a direction perpendicular to the long side of the pole piece 1
  • the second direction O2 is a direction parallel to the long side of the pole piece 1.
  • the second portion 22b is rolled to form the middle portion of the rolled electrode assembly.
  • the tab region 21 may be connected to one end of the coating film region 22 along the first direction O1, or may be connected to one end of the coating film region 22 along the second direction O2.
  • the pole pieces are stacked alternately in sequence, and the separators are stacked in the middle in a Z-shape. Therefore, the second part 22b forms the middle part of the laminated electrode assembly after being laminated.
  • the first active material 31 is provided on both sides of the coating area 22 extending along the second direction O2
  • the second active material 32 is provided in the middle part
  • the ratio of the second active material 32 is The surface area is larger than that of the first active material 31, so that the second part 22b of the pole piece 1 can accommodate more electrolytes, especially liquid electrolytes, than the first part 22a. Therefore, the middle part of the electrode assembly assembled by the pole piece 1 also has the ability to accommodate more electrolytes than other parts.
  • the middle part of the electrode assembly can accommodate more electrolyte, the middle part still stores enough electrolyte and has better ion conductivity. , thereby improving the polarization phenomenon caused by insufficient electrolyte and effectively reducing the occurrence of lithium precipitation. Therefore, the cycle performance and service life of the battery are improved.
  • first active material 31 and the second active material 32 may be the same active material.
  • first active material 31 and the second active material 32 may be the same type of active material but have different specific surface areas.
  • the first active material 31 is lithium iron phosphate
  • the second active material 32 is nanolithium iron phosphate.
  • the first active material 31 and the second active material 32 may also be different active materials.
  • the first active material 31 and the second active material 32 may be different types of active materials with different specific surface areas.
  • the first active material 31 is lithium iron phosphate
  • the second active material 32 is nanometer lithium iron manganese phosphate.
  • the D V 50 of the first active material 31 is greater than the D V 50 of the second active material 32 .
  • DV50 refers to the particle size corresponding to the particles whose cumulative volume particle size distribution percentage reaches 50% in the active material. Represents the average particle size of the active material. Materials with smaller particle sizes usually have larger specific surface areas. Therefore, a material with a larger D V 50 can be selected as the first active material 31 , and an active material with a smaller D V 50 can be selected as the second active material 32 , so that the The specific surface area of one active material 31 is larger than that of the second active material 32 .
  • the average particle diameter of the first active material 31 by controlling the average particle diameter of the first active material 31 to be larger than the average particle diameter of the second active material 32, so that the specific surface area of the second active material 32 is larger than the specific surface area of the first active material 31, and at the same time, the second There are also more gaps between the particles of the active material 32, which can further accommodate more electrolyte, helping to further improve the lithium precipitation problem caused by polarization during the battery cycle, thereby further improving the cycle performance and service life of the battery.
  • Figure 3 is a schematic structural diagram of another pole piece according to the embodiment of the present application.
  • a first active material 31 is also provided on the second part 22b, and a second active material 32 is provided above the first active material 31.
  • the film layer 3 is usually provided on the current collector 2 by coating, and there are various coating methods.
  • the first active material 31 and the second active material 32 can be coated on the current collector 2 using zebra coating.
  • Zebra coating is a divided-area coating method that can coat different materials in different areas, or only coat materials in partially spaced areas. It has higher requirements on coating equipment.
  • a conventional coating device can be used to first coat the first active material 31 on the entire coating area 22, and then coat the second active material 32 on the second part 22b.
  • the requirements for coating equipment are not high and it is easy to implement.
  • the second portion 22b is provided with both the first active material 31 and the second active material 32 . It helps to simplify the production process of the pole piece 1 and improve the production efficiency of the pole piece 1.
  • the thickness of the second active material 32 is greater than the thickness of the first active material 31 .
  • the film layer formed by the first active material is thicker at the first part 22a and at the first part 22a.
  • the thickness of the second portion 22b is thinner.
  • the second active material 32 is coated at the second portion 22b, the thickness of the second active material is controlled to be greater than the thickness of the first active material 31.
  • the second active material 32 accounts for a larger proportion in the second portion 22b of the pole piece, so that the middle portion of the pole piece 1 can accommodate more electrolyte.
  • the production process of the pole piece 1 is simplified, the production efficiency is improved, and the problem of lithium deposition during the battery cycle is improved.
  • the thickness of the film layer 3 at the first portion 22a is equal to the thickness of the film layer 3 at the second hundred volts 22b.
  • the thickness of the film layer 3 is controlled to be uniform.
  • the thickness of the film layer 3 is controlled to be consistent, after the pole piece 1 is wound or laminated to form an electrode assembly, the distance between the positive pole piece and the negative pole piece is equal, and the ion conduction distances at different positions of the pole piece 1 are equal. , which helps to balance the electrochemical reaction and improve the problem of lithium precipitation in some areas caused by the uneven spacing between the positive electrode piece and the negative electrode piece.
  • the width of the second portion 22b is 30%-70% of the width of the coating film area 22, preferably 40%-60% of the width of the coating film area 22.
  • the second part 22b has a length d along the first direction O1
  • the coating film area 22 has a length D along the first direction O1, 30% ⁇ d/D ⁇ 70%; preferably, 40% ⁇ d/D ⁇ 60%.
  • d/D can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, or its value is within the range obtained by combining any two of the above values.
  • the width of the second part 22b within an appropriate range, the amount of the second active material 32 can be indirectly controlled within an appropriate range, which can improve the battery polarization phenomenon and reduce lithium deposition while also improving the battery polarization phenomenon and reducing lithium deposition. Save production costs of pole pieces.
  • Figure 4 is a schematic structural diagram of another pole piece according to the embodiment of the present application.
  • the coating area 22 also includes a thinned portion 22 c , one side of the thinned portion 22 c is connected to the tab area 22 , and the other side is connected to a first portion 22 a .
  • the first active material 31 is provided on the thinned portion 22c, and the thickness of the first active material 31 provided on the thinned portion 22c is smaller than the thickness of the first active material 31 provided on the first portion 22a.
  • a thinned portion 22c is provided at the connection between the coating film area 22 and the tab area 21, so that the pole piece 1 has a transition zone between the thickness of the coating film area 22 and the thickness of the tab area 21. This helps to maintain the integrity of the tabs and avoid mechanical damage to the tabs when the pole pieces 1 are rolled or stacked to form an electrode assembly.
  • pole piece 1 is used as a positive pole piece and a negative pole piece in a battery will be introduced below.
  • the negative electrode sheet usually 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 first negative electrode active material and a second negative electrode active material.
  • the negative electrode current collector has two surfaces facing each other in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector can be a metal foil or composite current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the first negative active material may be a negative active material for batteries known in the art.
  • the first negative active material may include at least one of the following materials: artificial graphite, soft carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the second negative electrode active material may also be a negative electrode material known in the art for batteries, as long as the specific surface area of the second negative electrode material is larger than the selected first negative electrode active material.
  • the second negative active material may include at least one of the following materials: natural graphite, hard carbon, nano silicon-based materials, nano tin-based materials, nano lithium titanate, and the like.
  • the nano-silicon-based material may be selected from at least one of nano-scale elemental silicon, nano-scale silicon oxide compounds, nano-scale silicon carbon composites, nano-scale silicon nitrogen composites and nano-scale silicon alloys.
  • the nanotin-based material may be selected from at least one of nanoscale elemental tin, nanoscale tin oxide compounds, and nanoscale tin alloys. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the specific surface area of the first negative active material is ⁇ 1.5m 2 /g
  • the specific surface area of the second negative active material is ⁇ 1.5m 2 /g
  • the specific surface area of the second negative active material is ⁇ 4.0m 2 / g.
  • artificial graphite is used as the first negative electrode active material
  • natural graphite is used as the second negative electrode active material.
  • the specific surface area of artificial graphite is less than 1.5 m 2 /g, and the specific surface area of natural graphite is greater than 4.0 m 2 /g.
  • the Dv50 of the first negative active material is >10 ⁇ m, and the Dv50 of the second negative active material is ⁇ 10 ⁇ m.
  • the Dv50 of the second negative active material is ⁇ 7.5 ⁇ m.
  • the specific surface areas of the active materials at different positions on the negative electrode sheet can be accurately controlled, thereby This allows the middle part of the negative electrode piece to further accommodate more electrolyte, effectively improving the phenomenon of easy lithium precipitation in the middle area of the negative electrode piece due to battery polarization.
  • the negative electrode film layer further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethyl At least one of acrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer also includes other auxiliaries, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethyl cellulose (CMC-Na)
  • CMC-Na sodium carboxymethyl cellulose
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet are separately formed into negative electrode slurry.
  • the first negative electrode active material, conductive agent, binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form negative electrode slurry 1 .
  • the second negative electrode active material, conductive agent, binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form negative electrode slurry 2 .
  • the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a first positive electrode active material and a second positive electrode active material.
  • the positive electrode current collector has two surfaces facing each other in its own 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 current collector can be a metal foil or composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the first cathode active material may be a cathode active material known in the art for batteries.
  • the first cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, 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 of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/3 Co 1/3 Mn 1/3 O 2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM811), at least one of lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15),
  • lithium-containing phosphates with an olivine structure can include but are not limited to lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), composite materials of lithium manganese phosphate and carbon, manganese phosphate At least one composite material of lithium iron, lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate
  • manganese phosphate At least one composite material of lithium iron, lithium iron manganese phosphate and carbon.
  • the second cathode active material may also be a cathode active material known in the art for batteries, as long as the specific surface area of the second cathode active material is larger than the selected first cathode active material.
  • the second cathode active material may include at least one of the following materials: an olivine-structured nanoscale lithium-containing phosphate, a nanoscale lithium transition metal oxide, and their respective modified compounds.
  • nanoscale lithium transition metal oxides may include, but are not limited to, nanometer lithium cobalt oxide, nanometer lithium nickel oxide, nanometer lithium manganese oxide, nanometer lithium nickel cobalt oxide, nanometer lithium manganese cobalt oxide, nanometer lithium At least one of nickel manganese oxide, nano-lithium nickel cobalt manganese oxide, nano-lithium nickel cobalt aluminum oxide and modified compounds thereof.
  • lithium-containing phosphates with nanoscale olivine structures may include, but are not limited to, nanolithium iron phosphate, composites of lithium iron phosphate and carbon, nanolithium manganese phosphate, composites of nanolithium manganese phosphate and carbon, nanoferromanganese phosphate At least one of composite materials of lithium, nano-lithium iron manganese phosphate and carbon. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • the specific surface area of the first cathode active material is ⁇ 11 m 2 /g
  • the specific surface area of the second cathode active material is ⁇ 11 m 2 /g
  • the specific surface area of the second cathode active material is ⁇ 16 m 2 /g.
  • lithium iron phosphate is used as the first cathode active material
  • nano-lithium iron phosphate is used as the second cathode active material.
  • the specific surface area of lithium iron phosphate is less than 11 m 2 /g
  • the specific surface area of nano-lithium iron phosphate is greater than 16 m 2 /g.
  • the Dv50 of the first cathode active material is >800 nm
  • the Dv50 of the second cathode active material is ⁇ 800 nm
  • the Dv50 of the second cathode active material is ⁇ 200 nm.
  • the specific surface areas of the active materials at different positions on the positive electrode sheet can be accurately controlled, thereby This allows the middle part of the positive electrode piece to further accommodate more electrolyte, further improving the lithium deposition problem of the battery.
  • the carbon content of the first positive active material is ⁇ 1.5%
  • the carbon content of the second positive active material is ⁇ 1.5%
  • the carbon content of the second positive active material is Carbon content ⁇ 2.5%.
  • the positive electrode film layer further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.
  • the positive electrode film layer further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the positive electrode sheet are separately formed into a positive electrode slurry.
  • the first positive electrode active material, conductive agent, binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form positive electrode slurry 1 .
  • the second positive electrode active material, conductive agent, binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form positive electrode slurry 2 .
  • the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte includes electrolyte salts and solvents.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, and trifluoromethanesulfonic acid.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, and butylene carbonate.
  • Ester fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, At least one of 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte also includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be at least one selected from the group consisting of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the wound electrode assembly can be cylindrical, square or any other shape.
  • FIG. 5 is a schematic diagram of a cylindrical electrode assembly 5 as an example. As shown in Figure 5, the tab area 21 of the positive electrode piece is rolled to form the positive tab 51 of the electrode assembly 5, and the tab area 21 of the negative electrode piece is rolled to form the negative tab of the electrode assembly 5. 52. The coating area 22 of the positive electrode piece and the negative electrode piece and the isolation film are rolled to form the middle part 53 of the electrode assembly 5.
  • An embodiment of the present application also provides a battery cell, which includes the pole piece in any embodiment of the present application.
  • the battery cell 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 battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the battery cells can also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • This application has no particular limitation on the shape of the battery cell, which can be cylindrical, square or any other shape.
  • An embodiment of the present application also provides a battery, which includes at least one battery cell in the embodiment of the present application.
  • multiple battery cells are first integrated into a battery module, and then the battery module is installed in a battery box to form a battery pack.
  • multiple battery cells can also be directly installed in the box to form a battery pack, eliminating the intermediate state of the battery module, thereby reducing the quality of the battery pack and increasing the energy density of the battery.
  • the second production and processing technology can also be called the packaging technology of battery cell to battery pack (cell to pack), and the battery pack is referred to as battery in this application.
  • the present application also provides an electrical device, which includes at least one of the battery cells or batteries in any embodiment of the present application.
  • the battery cells and batteries can be used as the power source of the electrical device or as the energy storage unit of the electrical device.
  • Power-consuming devices can include vehicles, cell phones, portable devices, laptops, ships, spacecraft, power toys and power tools, and more.
  • Vehicles can be fuel vehicles, gas vehicles or new energy vehicles, and new energy vehicles can be pure electric vehicles, hybrid vehicles or extended-range vehicles, etc.
  • spacecraft include aircraft, rockets, space shuttles, spaceships, etc.
  • electric toys include fixed Type or mobile electric toys, such as game consoles, electric car toys, electric ship toys, electric airplane toys, etc.
  • electric tools include metal cutting electric tools, grinding electric tools, assembly electric tools and railway electric tools, for example, Electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, electric planers, etc., but the application is not limited thereto.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery module or battery can be used as the power source.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a battery cell can be used as the power source.
  • the first negative electrode active material artificial graphite with D V 50 of 12.3 ⁇ m, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are mixed according to the mass ratio of 96.5:0.7: 1.8:1 was dissolved in solvent deionized water, and mixed evenly to obtain negative electrode slurry 1.
  • the specific surface area of artificial graphite in the negative electrode sheet is 1.1m 2 /g, and the specific surface area of natural graphite is 4.0m 2 /g.
  • Example 2 Compared with the battery cell of Example 1, Example 2 only changed the D V 50 of the second positive electrode active material. It should be understood that the specific surface area of the material will change as D V 50 changes. The specific parameters are detailed in Table 1.
  • Example 3 Compared with the battery cell of Example 1, Example 3 only changed the D V 50 of the second negative active material. See Table 1 for specific parameters.
  • Example 4 uses a composite material of lithium iron phosphate and carbon as the first positive electrode active material, and uses a composite material of nanometer lithium iron phosphate and carbon as the second positive electrode active material, wherein, The carbon content of the first positive active material is 1.18%, and the carbon content of the second positive active material is 2.01%.
  • the cathode slurry 1 is evenly coated on the first part 22a of the cathode current collector aluminum foil, and the cathode slurry 2 is evenly coated on the second part 22b of the cathode current collector aluminum foil, and then dried, cold pressed, and cut. Get the positive electrode piece.
  • the specific surface area of the first positive active material in the positive electrode sheet is 0.8 m 2 /g, and the specific surface area of the second positive active material is 1.15 m 2 /g.
  • the first negative electrode active material hard carbon with D V 50 of 6 ⁇ m, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are mixed in a mass ratio of 90:4:4 :2 is dissolved in the solvent deionized water and mixed evenly to obtain negative electrode slurry 1.
  • the second negative electrode active material hard carbon with D V 50 of 2 ⁇ m, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) are mixed in a mass ratio of 90:4:4 :2 is dissolved in the solvent deionized water and mixed evenly to obtain negative electrode slurry 2.
  • the negative electrode slurry is evenly coated on the negative electrode current collector copper foil one or more times, and then dried, cold pressed, and cut to obtain the negative electrode piece 2.
  • the negative electrode slurry 1 is evenly coated on the first part 22a of the negative electrode current collector copper foil, and the negative electrode slurry 2 is evenly coated on the second part 22b of the negative electrode current collector copper foil, and then dried, cold pressed, Cut the negative electrode piece into pieces.
  • the specific surface area of the first negative active material in the negative electrode sheet is 1.02m 2 /g, and the specific surface area of the second negative active material is 4.5m 2 /g.
  • the battery cell of Example 5 adopts the same preparation method as that of Example 1, except that a NaPF 6 electrolyte with a mass fraction of 11% is used, which will not be described again.
  • the first cathode active material lithium iron phosphate with a D V 50 of 10.1, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) in the solvent N-methylpyrrolidone (NMP) in a mass ratio of 97:0.8:2.2 ), stir thoroughly and mix evenly to obtain the positive electrode slurry. Then, the positive electrode slurry is evenly coated on the coating area 22 of the positive electrode current collector aluminum foil, and then dried, cold-pressed, and cut to obtain positive electrode pieces.
  • NMP N-methylpyrrolidone
  • the first negative electrode active material artificial graphite with D V 50 of 1.1 ⁇ m, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethylcellulose (CMC) are mixed according to the mass ratio of 96.5:0.7: Dissolve 1.8:1 in the solvent deionized water and mix evenly to obtain the negative electrode slurry. Then, the negative electrode slurry is evenly coated on the coating area 22 of the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain negative electrode pieces.
  • Comparative Example 1 adopts the same preparation method as Example 1, which will not be described again.
  • the negative active material hard carbon with D V 50 of 6 ⁇ m, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC) in a mass ratio of 90:4:4:2 Dissolve in the solvent deionized water and mix evenly to obtain the negative electrode slurry. Then, the negative electrode slurry is evenly coated on the coating area 22 of the negative electrode current collector copper foil, and then dried, cold pressed, and cut to obtain negative electrode pieces.
  • SBR binder styrene-butadiene rubber
  • CMC thickener sodium carboxymethyl cellulose
  • Comparative Example 2 and Example 5 adopt the same method and steps to prepare battery cells, which will not be described again.
  • positive active material 1 refers to the first positive active material
  • BET-1 refers to the specific surface area of the first positive active material
  • positive active material 2 refers to the second positive active material
  • BET-2 refers to is the specific surface area of the second positive active material
  • negative active material 1 refers to the first negative active material
  • BET-3 refers to the specific surface area of the first negative active material
  • negative material 2 refers to the second negative active material
  • BET-4 refers to the specific surface area of the second negative active material.
  • test method refers to the standard GB/T19587-2004 "Determination of specific surface area of solid materials by gas adsorption BET method".
  • the secondary batteries prepared in each Example and Comparative Example were charged at a constant current rate of 1C to the charging cut-off voltage V1, then charged at a constant voltage to a current ⁇ 0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 1C. to the discharge cut-off voltage V2 and let it sit for 5 minutes.
  • This is a charge and discharge cycle.
  • the test results are shown in Table 2.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Battery Electrode And Active Subsutance (AREA)

Abstract

本申请提供了一种极片、电池单体、电池及用电装置，极片包括：集流体，集流体包括极耳区域和涂膜区域，涂膜区域包括设置于涂膜区域两侧边缘的第一部分和位于第一部分之间的第二部分；膜层，膜层设置于涂膜区域上，膜层包括第一活性材料和第二活性材料，其中，第一部分上设置有第一活性材料，第二部分上设置有第二活性材料，第一活性材料的比表面积小于第二活性材料的比表面积。该极片能够有效改善极片在电池循环过程中的浸润情况，改善极片中间区域的析锂问题，帮助提高电池的循环性能和使用寿命。

Description

一种极片、电池单体、电池及用电装置 技术领域
本申请涉及电池技术领域，特别是涉及一种极片、电池单体、电池及用电装置。
背景技术
随着电池在储能系统、电动工具、电动自行车、电动汽车、军事装备、航空航天等众多领域中的应用，促进电池技术发展的同时也对其循环性能、使用寿命提出了更高的要求。
因此，如何提高电池的循环性能和使用寿命是一项亟待解决的技术问题。
发明内容
本申请是鉴于上述技术问题而进行的，其目的在于，提供一种极片、电池单体、电池及用电装置，该极片上具有比表面积不同的活性材料，能够有效改善极片在电池循环过程中的浸润情况，改善极片中间区域的析锂问题，从而提高电池的循环性能和使用寿命。
第一方面，本申请提供一种极片，所述极片包括：集流体，所述集流体包括极耳区域和涂膜区域，所述涂膜区域包括设置于所述涂膜区域两侧边缘的第一部分和位于所述第一部分之间的第二部分；膜层，所述膜层设置于所述涂膜区域上，所述膜层包括第一活性材料和第二活性材料，其中，所述第一部分上设置有所述第一活性材料，所述第二部分上设置有所述第二活性材料，所述第一活性材料的比表面积小于所述第二活性材料的比表面积。
本申请提供的极片在涂膜区域的两侧上具有第一活性材料，在中间部分具有第二活性材料，第二活性材料具有更大的比表面积。因此，与第一活性材料相比，第二活性材料中的孔隙在电池循环过程中能够吸附更多电解液，具有更好的浸润效果，能够有效改善电池循环过程中因极片膨胀电解液被挤出极片区域使得极片极化增大而导致的析锂问题，从而提高了电池的循环性能和使用寿命。尤其是在使用卷绕式电极组 件的电池中，极片的中间部分在卷绕后形成卷绕式电极组件的中间部分，能够存储更多的电解液，从而有效解决了卷绕式电极组件中间部分浸润困难，在电池循环过程中极化严重、析锂严重的问题。
应理解，第一活性材料和第二活性材料可以是相同的活性材料，也可以是不同的活性材料。电极组件指包括正极极片、隔离件、负极极片的电池部件。
在一些实施例中，所述第一活性材料的D V50大于所述第二活性材料的D V50。
本申请的实施例中，设置于极片涂膜区域两侧部分的第一活性材料具有更大的平均粒径，设置于极片涂膜区域中间部分第二活性材料具有更小的平均粒径，使得极片中间部分的活性材料颗粒之间具有更多的空隙，能够进一步容纳更多的电解液，从而通过在极片中间部分设置能够容纳更多电解液的第二活性材料进一步改善电池循环过程中极片的析锂问题，帮助进一步提升电池的循环性能和使用寿命。
在一些实施例中，所述第二部分上还设置有所述第一活性材料，所述第二活性材料设置于所述第一活性材料的上方。
本申请的实施例中，在极片的中间部分，通过将第二活性材料设置于第一活性材料上方的方式，使得极片在制备过程中，第一活性材料的涂布方式无需采用复杂的斑马涂布等分区涂布方式，采用常规的涂布方式即可实现，简化了极片的制备过程。
在一些实施例中，所述第二活性材料的厚度大于所述第一活性材料的厚度。
本申请的实施例中，在极片的中间部分，通过将第二活性材料的厚度设置为大于第一活性材料的厚度，使得第二活性材料在极片中间部分的占比更多，从而能够容纳更多的电解液。由此，在简化极片制备过程、提高极片生产效率的同时还进一步改善了电池循环过程中极片析锂的问题。
在一些实施例中，所述第二部分的宽度为所述涂膜区域的宽度的30％-70％，优选地为所述涂膜区域的宽度的40％-60％。
本申请的实施例中，通过设置第二部分的宽度在合适的范围内，能够控制第二材料的用量在合适的范围，改善析锂问题的同时帮助节省极片的成本。
在一些实施例中，所述极片为正极极片，所述第一活性材料选自磷酸铁锂、磷酸锰锂、磷酸铁锰锂、磷酸铁锂与碳的复合材料、磷酸锰锂与碳的复合材料、磷酸锰铁锂与碳的复合材料中的至少一种，所述第二活性材料选自纳米磷酸铁锂、纳米磷酸锰锂、纳米磷酸铁锰锂、纳米磷酸铁锂与碳的复合材料、纳米磷酸锰锂与碳的复合 材料、纳米磷酸铁锰锂与碳的复合材料中的至少一种。
在一些实施例中，所述第一活性材料的比表面积＜11m 2/g，所述第二活性材料的比表面积≥11m 2/g，优选地，所述第二活性材料的比表面积≥16m 2/g。
本申请的实施例中，通过选择比表面积范围合适的第二活性材料，能够进一步提高正极极片中间部分容纳离子液的能力，从而进一步改善负极极片中间区域析锂的问题。
在一些实施例中，所述第一活性材料的DV50＞800nm，所述第二活性材料的DV50≤800nm，优选地，所述第二活性材料的DV50≤200nm。
在一些实施例中，所述第一活性材料的含碳量＜1.5％，所述第二活性材料的含碳量≥1.5％，优选地，所述第二活性材料的含碳量≥2.5％。
在一些实施例中，所述极片为负极极片，所述第一活性材料选自人造石墨、软碳、硅基材料、锡基材料、钛酸锂中的至少一种，所述第二活性材料选自天然石墨、硬碳、纳米硅基材料、纳米锡基材料、纳米钛酸锂中的至少一种。
在一些实施例中，所述第一活性材料的比表面积＜1.5m 2/g，所述第二活性材料的比表面积≥1.5m 2/g，优选地，所述第二活性材料的比表面积≥4.5m 2/g。
本申请的实施例中，通过选择比表面积范围合适的第二活性材料，能够进一步提高负极极片中间部分容纳离子液的能力，从而进一步改善负极极片中间区域析锂的问题。
在一些实施例中，所述第一活性材料的Dv50＞10μm，所述第二活性材料的Dv50≤10μm，优选地，所述第二活性材料的Dv50≤7.5μm。
第二方面，提供一种电池单体，所述电池单体包括第一方面任一实施例中的极片。
第三方面，提供一种电池，所述电池包括第二方面中的电池单体。
第四方面，提供一种用电装置，所述用电装置包括第二方面中的电池单体或第三方面中的电池中的至少一种，所述电池单体和/或所述电池用于为所述用电装置供电。
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。在附图中，附图并未按照实际的比例绘制。
图1是本申请实施例一种极片的示意性结构图。
图2是本申请实施例一种极片的示意性俯视图。
图3是本申请实施例另一极片的示意性结构图。
图4是本申请实施例又一极片的示意性结构图。
图5是本申请实施例一种电极组件的示意性结构图。
图6是本申请实施例与对比例的DCR测试结果图。
图7是本申请对比例循环后的负极极片照片。
图8是本申请实施例循环后的负极极片照片。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的负极集流体、含有其的二次电池、电池模块以及电学装置的实施方式。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。
在本申请的描述中，需要说明的是，除非另有说明，“多个”的含义是两个以上；术语“上”、“下”、“左”、“右”、“内”、“外”等指示的方位或位置关系仅是为了便于描述本申请和简化描述，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的限制。此外，术语“第一”、“第二”、“第三”等仅用于描述目的，而不能理解为指示或暗示相对重要性。“垂直”并不是严格意义上的垂直，而是在误差允许范围之内。“平行”并不是严格意义上的平行，而是在误差允许范围之内。
下述描述中出现的方位词均为图中示出的方向，并不是对本申请的具体结构进行限定。在本申请的描述中，还需要说明的是，除非另有明确的规定和限定，术语“安装”、“相连”、“连接”应做广义理解，例如，可以是固定连接，也可以是可拆卸连接，或一体地连接；可以是直接相连，也可以通过中间媒介间接相连。对于本领域的普通技术人员而言，可视具体情况理解上述术语在本申请中的具体含义。
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，所述“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)。
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。
电池通常包括正极极片、负极极片、电解质和隔离件。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离件设置于正极极片和负极极片之间以防止正负极短路，同时可以使离子通过。
在电池的加工过程中，通常将正极极片、负极极片和隔离件组成电极组件，再将电极组件设置于容纳电极组件和电解质的壳体中以组成电池单体。电极组件可以是 卷绕式结构，也可以是叠片式结构。电池包括至少一个电池单体。
可选地，电池可以包括锂离子电池、钠离子电池、镁离子电池等。
本申请以锂离子电池为示例，锂离子电池是一种典型的二次电池，由于其依靠锂离子作为活性离子在正负极之间脱嵌的化学反应进行充放电，锂离子电池又被称为摇椅式电池。锂离子电池的充电过程中，锂离子从正极脱出，移动并嵌入到负极；而放电过程中，锂离子从负极脱出，移动并嵌入正极。
在锂离子电池的电化学反应中，由于电极材料在嵌锂、脱锂过程中的结构变化、活性材料的副反应等多种因素的影响，电池极片会在循环过程中发生膨胀。而出于离子动力学、电池能量密度等多种因素的考虑，正极极片和负极极片之间的间距非常小，通常不足以容纳电极材料的膨胀或结构的损坏。因此，会将电解质，尤其是液态的电解质挤出正负极极片之间，使得正负极极片之间没有足够的电解质进行离子传导，电池发生严重的极化现象，活性离子(锂离子)在负极极片的表面析出，即发生析锂，极大地影响了电池的循环性能以及使用寿命，严重时还会引发电池的安全问题。尤其是在卷绕式电极组件中，极片被卷绕成圆柱状的电极组件，极片的中间区域经卷绕后形成电极组件的中间部分。由于结构原因，圆柱状电极组件的中间部分浸润本身较为困难，存储的电解质有限。在电池的循环过程中，电极组件中间部分的电解质被挤出后，极化导致的析锂问题更为严重。
有鉴于此，本申请实施例提供了一种极片、电池单体、电池及用电装置，其中，该极片的边缘位置设置有比表面积较小的第一活性材料，该极片的中间位置设置有比表面积较大的第二活性材料，由此，该极片的中间位置能够容纳更多的电解质。在电池循环过程中，能够极片、尤其是极片的中间区域极化的现象，减少负极极片表面析锂的情况。
应理解，本申请所述“嵌锂”、“嵌入”过程指锂离子由于电化学反应在正极材料和负极材料中嵌入的过程，本申请所述“脱出”、“脱锂”、“脱嵌”过程指锂离子由于电化学反应在正极材料和负极材料中脱出的过程。
首先，本申请提供一种极片。图1为本申请实施例一种极片的示意性结构图。图2为本申请实施例一种极片的示意性俯视图。
如图1和图2所示，极片1包括集流体2和膜层3。其中，集流体2包括极耳区域21和涂膜区域22，膜层3设置于涂膜区域22上。涂膜区域22包括设置于涂膜区 域22两侧边缘的第一部分22a和位于第一部分22a之间的第二部分22b。
膜层3包括第一活性材料31和第二活性材料32，其中，第一部分22a上设置有第一活性材料31，第二部分22b上设置有第二活性材料32。
具体地，膜层3设置于集流体2的至少一个表面上。极片1可以是正极极片，也可以是负极极片。极片1可以用于组成卷绕式电极组件，也可以用于组成叠片式电极组件。
在卷绕式电极组件中，极耳区域21沿第一方向O1与涂膜区域22的一端连接，极片1沿第二方向O2卷绕形成卷绕式电极组件。第一方向O1为垂直于极片1长边的方向，第二方向O2为平行于极片1长边的方向。由此，第二部分22b经过卷绕后形成卷绕式电极组件的中间部分。在叠片式电极组件中，极耳区域21可以沿第一方向O1与涂膜区域22的一端连接，也可以沿第二方向O2与涂膜区域22的一端连接。极片依次交替叠放，中间由隔膜Z字叠绕，由此，第二部分22b经过叠片后形成叠片式电极组件的中间部分。
本实施例的极片1中，通过在涂膜区域22沿第二方向O2延伸的两侧边缘设置第一活性材料31，在中间部分设置第二活性材料32，而第二活性材料32的比表面积大于第一活性材料31，从而使得极片1的第二部分22b相比于第一部分22a能够容纳更多的电解质，尤其是液态电解质。由此，通过极片1组装得到的电极组件的中间部分相比于其他部分也具有容纳更多电解质的能力。在电池的循环过程中，尽管电极材料膨胀会导致部分电解质被挤出，但由于电极组件的中间部分能够容纳更多的电解质，使得中间部分仍存储有足够的电解质，具有较好的离子传导能力，从而改善了因电解质不足导致的极化现象，有效减少了析锂的发生。因此，提高了电池的循环性能和使用寿命。
应理解，第一活性材料31与第二活性材料32可以是相同的活性材料。换言之，第一活性材料31与第二活性材料32可以是同种类的活性材料只是拥有不同的比表面积。例如，第一活性材料31为磷酸铁锂，第二活性材料32为纳米磷酸铁锂。第一活性材料31与第二活性材料32也可以是不同的活性材料。换言之，第一活性材料31与第二活性材料32可以是不同种类且拥有不同比表面积的活性材料。例如，第一活性材料31为磷酸铁锂，第二活性材料32为纳米磷酸铁锰锂。
可选地，第一活性材料31的D V50大于第二活性材料32的D V50。
具体来说，DV50指的是活性材料中累计体积粒度分布百分数达到50％的粒子所对应的粒径。代表了活性材料的平均粒径。粒径更小的材料通常拥有更大的比表面积，因此，可以选择D V50较大的材料作为第一活性材料31，选择D V50较小的活性材料作为第二活性材料32，使得第一活性材料31的比表面积大于第二活性材料32。
本实施例中，通过控制第一活性材料31的平均粒径大于第二活性材料32的平均粒径，使得第二活性材料32的比表面积大于第一活性材料31的比表面积的同时，第二活性材料32的颗粒之间还具有更多的空隙，能够进一步容纳更多的电解液，帮助进一步改善电池循环过程中极化导致的析锂问题，从而进一步提高电池的循环性能和使用寿命。
图3为本申请实施例另一极片的示意性结构图。
可选地，参见图3，第二部分22b上还设置有第一活性材料31，第二活性材料32设置于第一活性材料31的上方。
具体来说，在极片1的生产过程中，通常以涂布的方式在集流体2上设置膜层3，而涂布的方式又分为多种。在图2所示的极片1中，可以采用斑马涂布的方式在集流体2上涂布第一活性材料31和第二活性材料32。斑马涂布是一种分区域的涂布方式，能够在不同区域涂布不同的物料，或者仅在部分间隔的区域涂布物料，对涂布设备的要求较高。而在图3所示的极片1中，可以通过常规的涂布装置先在整个涂膜区域22涂布第一活性材料31，再在第二部分22b上涂布第二活性材料32的方式进行涂布，对涂布设备的要求不高，容易实现。例如，通过凹版涂布的方式，使得第二部分22b上既设置有第一活性材料31，也设置有第二活性材料32。有助于简化极片1的生产过程，提高极片1的生产效率。
可选地，参见图3，在第二部分22b上，第二活性材料32的厚度大于第一活性材料31的厚度。
具体来说，通过凹版涂布或使用相应形状的模头等方法能够在涂膜区域22上涂布第一活性材料31时使得第一活性材料形成的膜层在第一部分22a处较厚，而在第二部分22b处的厚度较薄。在第二部分22b处涂布第二活性材料32时，控制第二活性材料的厚度大于第一活性材料31的厚度。由此，第二活性材料32在极片的第二部分22b的占比更多，使得极片1的中间部分能够容纳更多的电解液。本实施例中，在简化极片1的生产过程、提高生产效率的同时改善了电池循环过程中的析锂问题。
可选地，膜层3在第一部分22a处的厚度与膜层3在第二百伏嗯22b处的厚度相等。
换言之，在涂膜区域22上，不论采用哪种膜层的结构或使用哪种涂布方式，控制膜层3的厚度均一。通过控制膜层3的厚度一致，能够使得极片1在经过卷绕或叠片组成电极组件后，正极极片和负极极片之间的间距相等，在极片1不同位置的离子传导距离相等，有助于电化学反应的均衡性，改善因正极极片和负极极片之间因间距不等导致的部分区域容易发生析锂的问题。
可选地，继续参见图2，第二部分22b的宽度为涂膜区域22的宽度的30％-70％，优选地为涂膜区域22的宽度的40％-60％。
具体来说，第二部分22b沿第一方向O1具有长度d，涂膜区域22沿第一方向O1具有长度D，30％≤d/D≤70％；优选地，40％≤d/D≤60％。d/D可以为30％、31％、32％、33％、34％、35％、36％、37％、38％、39％、40％、42％、44％、46％、48％、50％、52％、54％、56％、58％、60％、62％、64％、66％、68％、70％，或者其数值在上述任意两个数值组合所获得的范围之内。
应理解，考虑到生产制备成本，粒径更小、比表面积更大的活性材料通常价格较为昂贵。本实施例中，通过将第二部分22b的宽度设置在合适的范围内，能够间接控制第二活性材料32的用量在合适的范围内，在改善电池极化现象，减少析锂的同时还能够节省极片的生产成本。
图4为本申请实施例又一极片的示意性结构图。
可选地，如图4所示，涂膜区域22还包括削薄部分22c，削薄部分22c的一侧与极耳区域22连接，另一侧与一个第一部分22a连接。削薄部分22c上设置有第一活性材料31，且设置于削薄部分22c上的第一活性材料31的厚度小于设置于第一部分22a上的第一活性材料31的厚度。
具体来说，在涂膜区域22与极耳区域21连接处设置了削薄部分22c，使得极片1在涂膜区域22的厚度与极耳区域21的厚度之间具有一个过渡区。由此，在卷绕或叠放极片1以形成电极组件时有助于保持极耳的完整性，避免极耳的机械性损坏。
下面对极片1在电池中作为正极极片、负极极片的具体实施例进行介绍。
[负极极片]
负极极片通常包括负极集流体以及设置在负极集流体至少一个表面上的负极膜 层，负极膜层包括第一负极活性材料和第二负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面的其中任意一者或两者上。
可选地，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。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材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、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。
可选地，第一负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，第一负极活性材料可包括以下材料中的至少一种：人造石墨、软碳、硅基材料、锡基材料和钛酸锂等。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负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。
可选地，第二负极活性材料也可以采用本领域公知的用于电池的负极材料，只要第二负极材料的比表面积大于选择的第一负极活性材料即可。作为示例，第二负极活性材料可以包括以下材料中的至少一种：天然石墨、硬碳、纳米硅基材料、纳米锡基材料和纳米钛酸锂等。纳米硅基材料可选自纳米级单质硅、纳米级硅氧化合物、纳米级硅碳复合物、纳米级硅氮复合物以及纳米级硅合金中的至少一种。纳米锡基材料可选自纳米级单质锡、纳米级锡氧化合物以及纳米级锡合金中的至少一种。这些负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。
可选地，第一负极活性材料的比表面积＜1.5m 2/g，第二负极活性材料的比表面积≥1.5m 2/g，优选地，第二负极活性材料的比表面积≥4.0m 2/g。
示例性地，人造石墨作为第一负极活性材料，天然石墨作为第二负极活性材料，人造石墨的比表面积小于1.5m 2/g，天然石墨的比表面积大于4.0m 2/g。
可选地，第一负极活性材料的Dv50＞10μm，第二负极活性材料的Dv50≤10μm，优选地，第二负极活性材料的Dv50≤7.5μm。
本实施例中，通过选择比表面积、平均粒径在一定范围内的活性材料分别作为第一负极活性材料、第二负极活性材料，能够准确控制负极极片上不同位置的活性材料的比表面积，从而使得负极极片的中间部分能够进一步容纳更多的电解质，有效改善电池极化导致负极极片中间区域容易析锂的现象。
可选地，负极膜层还包括粘结剂。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。
可选地，在一个实施例中，负极膜层还包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
可选地，负极膜层还包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分分别形成负极浆料。例如将第一负极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成负极浆料1。再例如将第二负极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成负极浆料2。然后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。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括第一正极活性材料和第二正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜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。
可选地，正极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。
可选地，第一正极活性材料可采用本领域公知的用于电池的正极活性材料。作 为示例，第一正极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))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、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中的至少一种。
可选地，第二正极活性材料也可以采用本领域公知的用于电池的正极活性材料，只要第二正极活性材料的比表面积大于选择的第一正极活性材料即可。作为示例，第二正极活性材料可以包括以下材料中的至少一种：橄榄石结构的纳米级含锂磷酸盐、纳米级锂过渡金属氧化物及其各自的改性化合物。其中，纳米级锂过渡金属氧化物的示例可包括但不限于纳米锂钴氧化物、纳米锂镍氧化物、纳米锂锰氧化物、纳米锂镍钴氧化物、纳米锂锰钴氧化物、纳米锂镍锰氧化物、纳米锂镍钴锰氧化物、纳米锂镍钴铝氧化物及其改性化合物等中的至少一种。纳米级橄榄石结构的含锂磷酸盐的示例可包括但不限于纳米磷酸铁锂、磷酸铁锂与碳的复合材料、纳米磷酸锰锂、纳米磷酸锰锂与碳的复合材料、纳米磷酸锰铁锂、纳米磷酸锰铁锂与碳的复合材料中的至少一种。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
可选地，第一正极活性材料的比表面积＜11m 2/g，第二正极活性材料的比表面积≥11m 2/g，优选地，第二正极活性材料的比表面积≥16m 2/g。
示例性地，磷酸铁锂作为第一正极活性材料，纳米磷酸铁锂作为第二正极活性材料，磷酸铁锂的比表面积小于11m 2/g，纳米磷酸铁锂的比表面积大于16m 2/g。
可选地，第一正极活性材料的Dv50＞800nm，第二正极活性材料的Dv50≤800nm，优选地，第二正极活性材料的Dv50≤200nm。
本实施例中，通过选择比表面积、平均粒径在一定范围内的活性材料分别作为第一正极活性材料、第二正极活性材料，能够准确控制正极极片上不同位置的活性材料的比表面积，从而使得正极极片的中间部分能够进一步容纳更多的电解质，进一步改善电池的析锂问题。
可选地，在正极活性材料含碳的情况下，第一正极活性材料的含碳量＜1.5％，第二正极活性材料的含碳量≥1.5％，优选地，第二正极活性材料的含碳量≥2.5％。
可选地，正极膜层还包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
可选地，正极膜层还包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，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别形成正极浆料。例如将第一正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料1。又例如，将第二正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料2。然后将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
可选地，电解质采用电解液。电解液包括电解质盐和溶剂。
可选地，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
可选地，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸 甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
可选地，电解液还包括添加剂。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]
在一些实施方式中，二次电池中还包括隔离膜。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。
可选地，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。
可选地，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。卷绕式电极组件可以是圆柱形、方形或其他任意的形状。例如，图5是作为一个示例的圆柱形的电极组件5的示意图。如图5所示，正极极片的极耳区域21经过卷绕后形成了电极组件5的正极极耳51，负极极片的极耳区域21经过卷绕后形成了电极组件5的负极极耳52，正极极片与负极极片的涂膜区域22以及隔离膜经过卷绕形成了电极组件5的中间部分53。
本申请实施例还提供一种电池单体，该电池单体包括本申请任一实施例中的极片。
在一些实施方式中，电池单体可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，电池单体的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。电池单体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，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。
本申请对电池单体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。
本申请实施例还提供一种电池，该电池包括至少一个本申请实施例中的电池单体。
在一些实施方式中，首先将多个电池单体(cell)先整合为电池模组 (module)，然后将电池模组安装于电池的箱体中，形成电池包(pack)。在另一些生产加工技术中，也可直接将多个电池单体安装设置于箱体中形成电池包，去除了电池模组这个中间状态，从而可降低电池包的质量并提高电池的能量密度。第二种生产加工技术也可以称之为电池单体至电池包(cell to pack)的封装技术，该电池包在本申请中简称为电池。
另外，本申请还提供一种用电装置，该用电装置包括本申请任一实施例中电池单体或电池中的至少一种。电池单体、电池可以用作该用电装置的电源，也可以用作用电装置的能量存储单元。用电装置可以包括车辆、手机、便携式设备、笔记本电脑、轮船、航天器、电动玩具和电动工具等等。车辆可以是燃油汽车、燃气汽车或新能源汽车，新能源汽车可以是纯电动汽车、混合动力汽车或增程式汽车等；航天器包括飞机、火箭、航天飞机和宇宙飞船等等；电动玩具包括固定式或移动式的电动玩具，例如，游戏机、电动汽车玩具、电动轮船玩具和电动飞机玩具等等；电动工具包括金属切削电动工具、研磨电动工具、装配电动工具和铁道用电动工具，例如，电钻、电动砂轮机、电动扳手、电动螺丝刀、电锤、冲击电钻、混凝土振动器和电刨等，但本申请不限于此。
作为一个示例的用电装置。该用电装置为纯电动车、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电池的高功率和高能量密度的需求，可以采用电池模块或电池作为电源。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用电池单体作为电源。
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
将D V50为1.05μm的第一正极活性材料磷酸铁锂、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比97:0.8:2.2溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料1，将D V50为0.78μm的第二正极活性材料纳米磷酸铁 锂、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比97:0.8:2.2溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料2。随后将正极浆料1均匀涂覆于正极集流体铝箔的第一部分22a上，将正极浆料2均匀涂覆于正极集流体铝箔的第二部分22b上，再经过烘干、冷压、分切得到正极极片。其中正极极片中磷酸铁锂的比表面积为10.1m 2/g，纳米磷酸铁锂的比表面积为16.2m 2/g。
(2)负极极片的制备
将D V50为12.3μm的第一负极活性材料人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比96.5:0.7:1.8:1溶解于溶剂去离子水中，混合均匀后得到负极浆料1，将D V50为7.5μm的第二负极活性材料天然石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比96.5:0.7:1.8:1溶解于溶剂去离子水中，混合均匀后得到负极浆料2。随后将负极浆料1均匀涂覆于负极集流体铜箔的第一部分22a上，将负极浆料2均匀涂覆于负极集流体铜箔的第二部分22b上，再经过烘干、冷压、分切得到负极极片。其中负极极片中人造石墨的比表面积为1.1m 2/g，天然石墨的比表面积为4.0m 2/g。
(3)电池单体的组装
将正极极片、隔离膜、负极极片按顺序叠放，使得隔离膜处于正极极片和负极极片之间并能够隔离正极极片与负极极片；然后将上述叠放好的部件卷绕得到电极组件；将电极组件设置于壳体中，干燥后注入质量分数为11％的LiPF 6电解液；经过化成、静置等工艺后得到电池单体。
实施例2
与实施例1的电池单体相比，实施例2仅改变了第二正极活性材料的D V50。应理解材料的比表面积会随D V50的变化改变。具体的参数详见表1。
实施例3
与实施例1的电池单体相比，实施例3仅改变了第二负极活性材料的D V50，具体的参数详见表1。
实施例4
与实施例1的电池单体相比，实施例4使用磷酸铁锂和碳的复合材料作为第一正极活性材料，使用纳米磷酸铁锂和碳的复合材料作为第二正极活性材料，其中，第一正极活性材料的含碳量为1.18％，第二正极活性材料的含碳量为2.01％。
实施例5
(1)正极极片的制备
将D V50为12μm的第一正极活性材料Na 0.85Ni 0.25Mn 0.75O 2、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比90:5:5溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料1。将D V50为8μm的第二正极活性材料Na 0.85Ni 0.25Mn 0.75O 2、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比90:5:5溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料2。随后将正极浆料1均匀涂覆于正极集流体铝箔的第一部分22a上，将正极浆料2均匀涂覆于正极集流体铝箔的第二部分22b上，再经过烘干、冷压、分切得到正极极片。该正极极片中第一正极活性材料的比表面积为0.8m 2/g，第二正极活性材料的比表面积为1.15m 2/g。
(2)负极极片的制备
将D V50为6μm的第一负极活性材料硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比90:4:4:2溶解于溶剂去离子水中，混合均匀后得到负极浆料1。将D V50为2μm的第二负极活性材料硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比90:4:4:2溶解于溶剂去离子水中，混合均匀后得到负极浆料2。将负极浆料一次或多次均匀涂覆在负极集流体铜箔上，再经过烘干、冷压、分切得到负极极片2。随后将负极浆料1均匀涂覆于负极集流体铜箔的第一部分22a上，将负极浆料2均匀涂覆于负极集流体铜箔的第二部分22b上，再经过烘干、冷压、分切得到负极极片。其中负极极片中第一负极活性材料的比表面积为1.02m 2/g，第二负极活性材料的比表面积为4.5m 2/g。
(3)电池单体的制备
实施例5的电池单体采用与实施例1相同的制备方法，区别仅在于使用质量分数为11％的NaPF 6电解液，在此不再赘述。
对比例1
(1)正极极片的制备
将D V50为10.1的第一正极活性材料磷酸铁锂、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比97:0.8:2.2溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料。随后将正极浆料均匀涂覆于正极集流体铝箔的涂膜区域 22上，再经过烘干、冷压、分切得到正极极片。
(2)负极极片的制备
将D V50为1.1μm的第一负极活性材料人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比96.5:0.7:1.8:1溶解于溶剂去离子水中，混合均匀后得到负极浆料。随后将负极浆料均匀涂覆于负极集流体铜箔的涂膜区域22上，再经过烘干、冷压、分切得到负极极片。
(3)电池单体的制备
对比例1采用与实施例1相同的制备方法，在此不再赘述。
对比例2
(1)正极极片的制备
将D V50为12μm的正极活性材料Na 0.85Ni 0.25Mn 0.75O 2、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按质量比90:5:5溶解于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料。随后将负正极浆料均匀涂覆于正极集流体铝箔的涂膜区域22上，再经过烘干、冷压、分切得到正极极片。
(2)负极极片的制备
将D V50为6μm的负极活性材料硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比90:4:4:2溶解于溶剂去离子水中，混合均匀后得到负极浆料。随后将负极浆料均匀涂覆于负极集流体铜箔的涂膜区域22上，再经过烘干、冷压、分切得到负极极片。
(3)电池单体的制备
对比例2与实施例5采用相同的方法和步骤制备电池单体，在此不再赘述。
不同实施例的产品参数详见表1。
表1：对比例及不同实施例的产品参数
Figure PCTCN2022106308-appb-000001
Figure PCTCN2022106308-appb-000002
表1中，正极活性材料1指的是第一正极活性材料，BET-1指的是第一正极活性材料的比表面积；正极活性材料2指的是第二正极活性材料，BET-2指的是第二正极活性材料的比表面积；负极活性材料1指的是第一负极活性材料，BET-3指的是第一负极活性材料的比表面积；负极材料2指的是第二负极活性材料，BET-4指的是第二负极活性材料的比表面积。
上述实施例1-5以及对比例1的电池性能测试结果详见表2。
表2：对比例及不同实施例循环寿命测试结果
实施例 循环寿命(圈)
1 4831
2 5356
3 5102
4 5228
5 4805
对比例1 3997
对比例2 3950
由实施例1和对比例1、实施例4和对比例1的数据比较可知，通过使用本申请提供的具有不同比表面积分布的正极极片和负极极片能够有效提高电池的循环寿命。通过实施例1和实施例2、实施例1和实施例3的数据对比可知，通过提高极片中间区 域的电极活性材料的比表面积能够进一步抑制析锂、提升电池的循环性能。
接下来，对上述电池的参数测试过程进行简单介绍。
1.BET测试
测试方法参考标准GB/T19587-2004《气体吸附BET法测定固态物质比表面积》。
取待测样品8～15g装到样品管中，记录待测样品的初始质量。将称重的待测样品装入设备NOVA2000e中。然后开始脱气，并将待测样品加热至200℃后，保持2h。之后记录脱气后待测样品的质量。然后将脱气后的待测样品重新装入设备中，倒入液氮进行BET测试。设定氮气压力0.08MPa-0.12MPa，加热温度为40℃-350℃。测试结束后，从测试结果中读取比表面积。
2.电池性能测试
25℃下，将各实施例和对比例制备得到的二次电池以1C倍率恒流充电至充电截止电压V1，之后恒压充电至电流≤0.05C，静置5min，再以1C倍率恒流放电至放电截止电压V2，静置5min，此为一个充放电循环。按照此方法对电池进行循环充放电测试，直至电池容量衰减至80％。此时的循环圈数即为电池的循环寿命。测试结果如表2所示。
3.DCR测试
取电池，进行充放电测试。先将电池在25℃条件下进行满充，满充后搁置30min。搁置后以1C放电倍率放电30min，调节至50％SOC，搁置10min。调节温箱温度为-20℃-10℃，搁置120min，测得放电初始电压。然后以3C放电速率放电10s，并记录放电过程中的最低电压，然后搁置10min，用3C放电初始电压与3C放电过程中最低电压差值除以电流值(放电倍率为3C，电流为78A)即得DCR。
其中，对比例1和实施例1的DCR测试结果如图6所示。由图6可知：实施例1与对比例1相比在-10℃条件下，DCR降低了6毫欧，25℃DCR降低了2毫欧，内阻明显降低，动力学明显提升。
4.析锂情况测试
在1C/1C(充放电条件)下，电池SOH达到70％时拆开实施例1和对比例1中的电池单体，得到负极极片的照片分别如图7和图8所示。由图7和图8可以看出，采用本申请提供的极片的实施例1经过充放电循环后，其负极极片表面没有锂金属析 出，而对比例1经过充放电循环后，其负极极片上有明显的锂金属析出。由此，充分说明本申请提供的极片能够有效降低电池在循环过程中的极化，抑制电池的析锂现象，从而提高了电池的循环性能、安全性能。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (15)

  1. 一种极片，其中，所述极片包括：
    集流体，所述集流体包括极耳区域和涂膜区域，所述涂膜区域包括设置于所述涂膜区域两侧边缘的第一部分和位于所述第一部分之间的第二部分；
    膜层，所述膜层设置于所述涂膜区域上，所述膜层包括第一活性材料和第二活性材料；
    其中，所述第一部分上设置有所述第一活性材料，所述第二部分上设置有所述第二活性材料，所述第一活性材料的比表面积小于所述第二活性材料的比表面积。
  2. 根据权利要求1所述的极片，其中，所述第一活性材料的D v50大于所述第二活性材料的D v50。
  3. 根据权利要求1或2所述的极片，其中，所述第二部分上还设置有所述第一活性材料，所述第二活性材料设置于所述第一活性材料的上方。
  4. 根据权利要求3所述的极片，其中，所述第二活性材料的厚度大于所述第一活性材料的厚度。
  5. 根据权利要求1-4中任一项所述的极片，其中，所述第二部分的宽度为所述涂膜区域的宽度的30％-70％，优选地为所述涂膜区域的宽度的40％-60％。
  6. 根据权利要求1-5中任一项所述的极片，其中，所述极片为正极极片，所述第一活性材料选自磷酸铁锂、磷酸锰锂、磷酸铁锰锂、磷酸铁锂与碳的复合材料、磷酸锰锂与碳的复合材料、磷酸锰铁锂与碳的复合材料中的至少一种，所述第二活性材料选自纳米磷酸铁锂、纳米磷酸锰锂、纳米磷酸铁锰锂、纳米磷酸铁锂与碳的复合材料、纳米磷酸锰锂与碳的复合材料、纳米磷酸铁锰锂与碳的复合材料中的至少一种。
  7. 根据权利要求6所述的极片，其中，所述第一活性材料的比表面积＜11m 2/g，所述第二活性材料的比表面积≥11m 2/g，优选地，所述第二活性材料的比表面积≥16m 2/g。
  8. 根据权利要求6或7所述的极片，其中，所述第一活性材料的D v50＞800nm，所述第二活性材料的D v50≤800nm，优选地，所述第二活性材料的D v50≤200nm。
  9. 根据权利要求6-8中任一项所述的极片，其中，所述第一活性材料的含碳量＜1.5％，所述第二活性材料的含碳量≥1.5％，优选地，所述第二活性材料的含碳量≥2.5％。
  10. 根据权利要求1-5中任一项所述的极片，其中，所述极片为负极极片，所述第一活性材料选自人造石墨、软碳、硅基材料、锡基材料、钛酸锂中的至少一种，所述第二活性材料选自天然石墨、硬碳、纳米硅基材料、纳米锡基材料、纳米钛酸锂中的至少一种。
  11. 根据权利要求10所述的极片，其中，所述第一活性材料的比表面积＜1.5m 2/g，所述第二活性材料的比表面积≥1.5m 2/g，优选地，所述第二活性材料的比表面积≥4.5m 2/g。
  12. 根据权利要求10或11所述的极片，其中，所述第一活性材料的D v50＞10μm，所述第二活性材料的D v50≤10μm，优选地，所述第二活性材料的D v50≤7.5μm。
  13. [根据细则91更正 09.08.2022]
    一种电池单体，其中，所述电池单体包括如权利要求1-12中任一项所述的极片。
  14. [根据细则91更正 09.08.2022]
    一种电池，其特征在于，所述电池包括至少一个如权利要求13所述的电池单体。
  15. [根据细则91更正 09.08.2022]
    一种用电装置，其特征在于，所述用电装置包括如权利要求13所述的电池单体或如权利要求14所述的电池中的至少一种，所述电池单体和/或所述电池用于为所述用电装置供电。
PCT/CN2022/106308 2022-07-18 2022-07-18 一种极片、电池单体、电池及用电装置 WO2024016122A1 (zh)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/CN2022/106308 WO2024016122A1 (zh) 2022-07-18 2022-07-18 一种极片、电池单体、电池及用电装置

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/CN2022/106308 WO2024016122A1 (zh) 2022-07-18 2022-07-18 一种极片、电池单体、电池及用电装置

Publications (1)

Publication Number Publication Date
WO2024016122A1 true WO2024016122A1 (zh) 2024-01-25

Family

ID=89616697

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/CN2022/106308 WO2024016122A1 (zh) 2022-07-18 2022-07-18 一种极片、电池单体、电池及用电装置

Country Status (1)

Country Link
WO (1) WO2024016122A1 (zh)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020145093A (ja) * 2019-03-07 2020-09-10 トヨタ自動車株式会社 リチウムイオン二次電池
CN112310344A (zh) * 2020-11-02 2021-02-02 珠海冠宇电池股份有限公司 一种正极片及含有该正极片的锂离子电池
CN113097427A (zh) * 2021-03-30 2021-07-09 珠海冠宇电池股份有限公司 一种负极片及电池
CN114597336A (zh) * 2022-03-23 2022-06-07 珠海冠宇电池股份有限公司 一种负极片和电池

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2020145093A (ja) * 2019-03-07 2020-09-10 トヨタ自動車株式会社 リチウムイオン二次電池
CN112310344A (zh) * 2020-11-02 2021-02-02 珠海冠宇电池股份有限公司 一种正极片及含有该正极片的锂离子电池
CN113097427A (zh) * 2021-03-30 2021-07-09 珠海冠宇电池股份有限公司 一种负极片及电池
CN114597336A (zh) * 2022-03-23 2022-06-07 珠海冠宇电池股份有限公司 一种负极片和电池

Similar Documents

Publication Publication Date Title
WO2022120833A1 (zh) 一种电化学装置和电子装置
WO2022041259A1 (zh) 二次电池及其制备方法与包含二次电池的电池模块、电池包及装置
WO2023185206A1 (zh) 一种电化学装置及包含其的电器
CN115810718A (zh) 负极极片及包含其的二次电池
WO2023029002A1 (zh) 负极集流体、含有其的二次电池、电池模块、电池包及用电装置
WO2024012166A1 (zh) 二次电池及用电装置
WO2023174050A1 (zh) 三元正极材料、其制造方法以及使用其的二次电池
WO2023071807A1 (zh) 隔膜及其制备方法、二次电池、电池模块、电池包和用电装置
WO2023133798A1 (zh) 一种用于锂离子二次电池的正极复合材料、正极和电池
WO2023137624A1 (zh) 二次电池、电池模块、电池包以及用电装置
WO2023060529A1 (zh) 锂离子电池
WO2023087218A1 (zh) 负极极片及其制备方法、二次电池、电池模块、电池包和用电装置
WO2024016122A1 (zh) 一种极片、电池单体、电池及用电装置
WO2024016264A1 (zh) 集流体、极片、电池单体、电池及用电装置
WO2023202238A1 (zh) 负极极片、二次电池、电池模块、电池包及用电装置
WO2024109530A1 (zh) 负极极片及包含其的二次电池
WO2024065726A1 (zh) 一种极片、电池单体、电池及用电装置
WO2023168553A1 (zh) 电池模组、电池包和用电装置
WO2023206140A1 (zh) 二次电池、电池模块、电池包和用电装置
WO2023044625A1 (zh) 复合人造石墨及其制备方法及包含所述复合人造石墨的二次电池和用电装置
WO2023230954A1 (zh) 二次电池、电池模块、电池包及用电装置
WO2023225937A1 (zh) 负极极片及其制备方法、二次电池、电池模块、电池包及用电装置
WO2023240595A1 (zh) 负极极片及其制造方法、电极组件、及二次电池
WO2024026675A1 (zh) 负极极片、二次电池、电池模块、电池包和用电装置
WO2023133805A1 (zh) 一种用于锂离子二次电池的正极复合材料、正极和电池

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 22951401

Country of ref document: EP

Kind code of ref document: A1