WO2024016264A1 - 集流体、极片、电池单体、电池及用电装置 - Google Patents

集流体、极片、电池单体、电池及用电装置 Download PDF

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Publication number
WO2024016264A1
WO2024016264A1 PCT/CN2022/107037 CN2022107037W WO2024016264A1 WO 2024016264 A1 WO2024016264 A1 WO 2024016264A1 CN 2022107037 W CN2022107037 W CN 2022107037W WO 2024016264 A1 WO2024016264 A1 WO 2024016264A1
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Prior art keywords
current collector
battery
film layer
thickness
negative electrode
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PCT/CN2022/107037
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English (en)
French (fr)
Inventor
杜香龙
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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/CN2022/107037 priority Critical patent/WO2024016264A1/zh
Publication of WO2024016264A1 publication Critical patent/WO2024016264A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/70—Carriers or collectors characterised by shape or form
    • 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
    • H01M4/64—Carriers or collectors

Definitions

  • the present application relates to the field of battery technology, and in particular to a current collector, a pole piece, a battery cell, a battery and an electrical device.
  • secondary batteries In recent years, the application scope of secondary batteries has become more and more extensive. They are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aviation aerospace and other fields. As secondary batteries have achieved great development, higher requirements have been placed on their cycle performance, service life, etc.
  • This application was made in view of the above technical problems, and its purpose is to provide a current collector, pole piece, battery cell, battery and electrical device, wherein the current collector has a special structure that can effectively improve the performance of the pole piece.
  • the infiltration of the middle area during the battery cycle reduces the lithium precipitation phenomenon of the pole pieces, thereby improving the cycle performance and service life of the battery.
  • the present application provides a current collector.
  • the current collector includes: a first part, the first part is arranged along a first direction, and the first direction is the width direction of the current collector or the direction of the current collector. Length direction; a second part, the second part is disposed between the two first parts; wherein the first part and the second part are used to carry a film layer, and the first part has a first thickness, The second portion has a second thickness, the first thickness being greater than the second thickness.
  • the current collector provided by this application has a special structure of being thick on both sides and thin in the middle. Specifically, the current collector has a thicker first part and a thinner second part.
  • the film layer disposed on the first part can be made to have a higher density, while the film layer provided to the second part can have a lower density.
  • the membrane layer in the middle part of the pole piece can accommodate more electrolyte without changing the thickness of the pole piece, thereby improving the problem of the electrode piece being squeezed out due to the expansion of the electrode active material during charging and discharging.
  • the problem of lithium precipitation in the middle area effectively improves the battery cycle performance and service life, and helps improve the safety of the battery.
  • the ratio of the width of the second part in the first direction to the width of the first part and the second part in the first direction is 30%-70%, preferably Land is 40%-60%.
  • the proportion of the width of the second part in the entire first part and the second part is within an appropriate range, it is possible to make the third part disposed on the current collector without increasing the process difficulty.
  • the membrane layer on the two parts accommodates more electrolyte, thereby further helping to improve the problem of lithium precipitation in the middle area of the pole piece.
  • the current collector includes: a tab portion connected to at least one of the first portions in the first direction, and a thickness of the tab portion is less than or equal to the first portion. part thickness.
  • the tab part is connected to the first part.
  • the tab part and the first part can be formed at one time, which is helpful for the integrated processing of the pole piece;
  • the thickness of the lug part is smaller than the thickness of the first part, the thickness of the lug part after being flattened can be reduced by reducing the thickness of the lug part, thereby helping to improve the space utilization inside the battery.
  • the first thickness is 10 ⁇ m-20 ⁇ m, preferably 12 ⁇ m-18 ⁇ m; the second thickness is 1 ⁇ m-20 ⁇ m, preferably 6 ⁇ m-17 ⁇ m.
  • a film layer is provided on the first part and the second part, and the compaction density of the film layer in the first part is greater than the compaction density of the film layer in the second part.
  • the film layer disposed on the current collector in the first part by controlling the compaction density of the film layer disposed on the current collector in the first part to be greater than its compaction density in the second part, the film layer disposed on the second part can be compared with the first part. Accommodates more electrolyte, thereby effectively improving the lithium deposition problem in the middle area of the pole piece.
  • the current collector is a positive electrode current collector
  • the film layer is a positive electrode film layer
  • the compacted density of the positive electrode film layer in the first part is 2.3g/cm 3 -2.5g/cm 3 , preferably 2.4g/cm 3
  • the compacted density of the positive electrode film layer in the second part is 2.2g/cm 3 -2.4g/cm 3 , preferably 2.35g/cm 3 .
  • the current collector is a negative electrode current collector
  • the film layer is a negative electrode film layer
  • the compacted density of the negative electrode film layer in the first part is 1g/cm 3 -1.65g/cm 3 , Preferably it is 1.5g/cm 3
  • the compacted density of the negative electrode film layer in the second part is 0.9g/cm 3 -1.5g/cm 3 , preferably 1.45g/cm 3 .
  • the current collector with a special structure is used in the positive electrode and/or negative electrode of the battery, and the compaction density of the positive electrode film layer and/or the negative electrode film layer in the first part and the second part is controlled to an appropriate Within the range, the number of pores in the middle area of the positive electrode piece and/or the negative electrode piece can be effectively increased, so that the middle area can accommodate more electrolyte and effectively improve the lithium deposition problem of the electrode piece in the battery.
  • the sum of the thicknesses of the film layer and the current collector in the second part is greater than or equal to the sum of the thicknesses of the film layer and the current collector in the first part.
  • the thickness of the part of the pole piece with the film layer is equal, that is, The thickness of the entire electrode piece is uniform. Therefore, the distance between the electrode pieces in the battery is basically the same everywhere, which can avoid the battery polarity caused by the unequal distance between the positive electrode piece and the negative electrode piece during the battery cycle. ization, thereby helping to improve the lithium deposition problem of batteries.
  • the sum of the thicknesses of the membrane layer and the current collector in the second part is greater than the sum of the thicknesses of the membrane layer and the current collector in the first part, it means that ions migrate between the positive electrode piece and the negative electrode piece in the second part during the battery cycle.
  • the smaller distance helps to improve ion dynamics, thereby helping to reduce the polarization phenomenon in the middle part of the pole piece, thereby further improving the lithium deposition problem of the pole piece.
  • the sum of the thicknesses of the film layer and the current collector in the second part is 1%-3% greater than the sum of the thicknesses of the film layer and the current collector in the first part.
  • the first portion is obtained by thickening the current collector.
  • the second portion is obtained by thinning the current collector.
  • the current collector with a special structure can be realized through a variety of different processing methods, and the preparation method is flexible and diverse, which helps to improve the production efficiency of the current collector.
  • a second aspect provides a pole piece, which includes the current collector in any embodiment of the first aspect.
  • a third aspect provides a battery cell, which includes the current collector described in any embodiment of the second aspect.
  • a fourth aspect provides a battery, which includes the battery cell in any embodiment of the third aspect.
  • a fifth aspect provides an electric device, characterized in that the electric device includes at least one of the battery cell according to any embodiment of the third aspect or the battery according to any embodiment of the fourth aspect.
  • the battery cell and/or the battery are used to supply power to the electrical device.
  • Figure 1 is a schematic top view of a current collector according to an embodiment of the present application.
  • Figure 2 is a schematic cross-sectional view of a current collector according to an embodiment of the present application.
  • Figure 3 is another schematic cross-sectional view of a current collector according to an embodiment of the present application.
  • Figure 4 is a schematic structural diagram of a pole piece according to an 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 photo of the negative electrode piece after the cycle of Comparative Example 1 of the present application.
  • Figure 7 is a photo of the negative electrode piece after cycling in Example 1 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, and the selected lower and upper limits 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).
  • the positive electrode plate, negative electrode plate, electrolyte and separator are the basic elements that constitute a battery.
  • active ions are embedded and detached back and forth between the positive electrode piece and the negative electrode piece.
  • the electrolyte conducts active ions between the positive electrode piece and the negative electrode piece.
  • the separator is disposed between the positive electrode piece and the negative electrode piece to prevent the positive and negative electrodes of the battery from being short-circuited, while also allowing active ions to pass through.
  • the positive electrode piece and the negative electrode piece are collectively referred to as pole pieces.
  • the pole piece usually includes a current collector and a film layer disposed on the current collector, and the film layer includes an electrode active material.
  • 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 detached from the positive electrode, move and are embedded in the negative electrode; during the discharge process, lithium ions are detached 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 active 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.
  • the present application provides a current collector, a pole piece, a battery cell, a battery and a power device.
  • the current collector has a special structure of being thick on both sides and thin in the middle, so that the pole piece prepared by using the current collector has a relatively uniform thickness, and at the same time, the pressure density on both sides of the pole piece is higher, and the pressure density in the middle part is higher. Low.
  • the middle part of the pole piece can store more electrolyte, which can improve the polarization phenomenon in the middle area of the pole piece during the battery cycle, 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 top view of a current collector according to an embodiment of the present application.
  • Figure 2 is a schematic cross-sectional view of a current collector according to an embodiment of the present application.
  • the current collector 1 includes a first part 101 and a second part 102 .
  • the first part 101 is provided along the first direction k, and the first direction k is the width direction of the current collector 1 or the length direction of the current collector 1 .
  • the second part 102 is arranged between the two first parts 101 .
  • the first part 101 and the second part 102 are used to carry the film layer.
  • the first part 101 has a first thickness d1
  • the second part 102 has a second thickness d2
  • the first thickness d1 is greater than the second thickness d2.
  • the current collector 1 generally has two opposite surfaces along its own thickness direction, and the film layer is disposed on any one or both of the two opposite surfaces of the current collector 1 .
  • the structure of the current collector 1 shown in FIGS. 1 and 2 is a structure in which a film layer is provided on the surface of the current collector 1 .
  • the surface of the current collector 1 on which the film layer is provided has the structure shown in FIGS. 1 and 2 .
  • both surfaces of the current collector 1 have the structures of Figures 1 and 2.
  • the current collector 1 may be a positive electrode current collector or a negative electrode current collector.
  • the pole piece prepared using the current collector 1 can be used to form a wound electrode assembly or a laminated electrode assembly.
  • the first part 101 and the second part 102 of the current collector 1 form the coating area 10 of the current collector 1 , that is, the part of the current collector 1 used to carry the film layer.
  • the first direction k is preferably the width direction of the current collector 1 , and the first portion 101 is disposed along the first direction k to form both sides of the coating film area 10 .
  • the electrode active material is usually coated on the current collector, and then compacted, dried and other steps are performed to form a current collector with a film layer, that is, the pole piece.
  • the film layer obtained by cold pressing and drying has a higher density at the first part 101 than at the second part 102.
  • the pole piece is rolled along the second direction j to form a rolled electrode assembly.
  • the second direction j is perpendicular to the first direction k.
  • the second portion 102 is rolled to form the middle portion of the rolled electrode assembly.
  • compaction refers to the compacted density of the film layer.
  • the first direction k is preferably the length direction of the current collector l.
  • the preparation process of the pole pieces is similar to that of the pole pieces in the wound electrode assembly. After the pole pieces are prepared, the pole pieces are stacked alternately in sequence, and the separators are stacked in a Z-shape in the middle to form a laminated electrode assembly. Thus, the second portion 102 is laminated to form the middle portion of the laminated electrode assembly.
  • the thickness of the first part 101 of the current collector 1 is greater than the thickness of the second part 102 thereof, so that the film layers disposed on the coating area 10 of the current collector 1 have different pressure densities. That is, the density of the membrane layer in the first part 101 is greater than that in the second part 102 , so that the membrane layer located in the second part 102 can store more electrolytes, especially liquid electrolytes, than the first part 101 . Therefore, the middle part of the electrode assembly prepared by the current collector 1 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 active ions. conductivity, thereby improving the polarization phenomenon caused by insufficient.
  • the current collector 1 with a special structure, the occurrence of lithium precipitation can be effectively reduced, thereby improving the cycle performance and service life of the battery, and also helping to improve the safety performance of the battery.
  • the roller press can utilize By rolling the current collector and electrode active material with one pressure, pole pieces with uniform thickness and different compaction distribution can be obtained.
  • the thickness of the electrode piece obtained by one-time rolling with one pressure is uniform, which helps to equalize the spacing between the positive electrode piece and the negative electrode piece in whether it is a rolled electrode assembly or a laminated electrode assembly. , to avoid polarization caused by the large gap between the positive and negative electrodes of the battery.
  • pole pieces with different compaction distributions can be obtained by using only one pressure roller once, making the processing methods and steps of the pole pieces simpler, helping to improve the production efficiency of the pole pieces, thereby improving the battery While improving the cycle performance and service life of the battery, it also improves the production efficiency of the battery.
  • the ratio of the width of the second part 102 in the first direction k to the sum of the widths of the first part 101 and the second part 102 in the first direction k is 30%-70%, preferably 40%- 60%.
  • the second part 102 has a width h in the first direction k, and the sum of the widths of the first part 101 and the second part 102 in the first direction k is H.
  • the coating area 10 has a width H in the first direction k.
  • h/H 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 film layer disposed on the second part 102 of the current collector can accommodate as much electrolyte as possible without increasing the process difficulty. .
  • Figure 3 is another schematic structural diagram of the current collector 1 according to the embodiment of the present application.
  • the current collector 1 includes a tab portion 20 that is connected to the first portion 101 in the first direction k, and the thickness of the tab portion 20 is less than or equal to the first portion 101 thickness of.
  • the thickness of the tab portion 20 of the current collector 1 may be less than or equal to the thickness of the first portion 101 .
  • the thickness of the first part 101 is the thickness of the substrate itself used to prepare the current collector 1 .
  • the thickness of the tab portion 20 is equal to the thickness of the first portion 101 , that is, the thickness of the tab portion 20 is also equal to the thickness of the base material itself. This simplifies the process steps of processing the tab portion 20 of the current collector 1 .
  • the thickness of the second part 102 is the thickness of the base material itself used to prepare the current collector 1, This can also simplify the processing steps of the tab portion 20 .
  • the thickness of the first part 101 is greater than the thickness of the base material itself, which makes the thickness of the tab part 20 smaller than the thickness of the first part 101 .
  • the tab portion 20 is connected to the first portion 101 .
  • the thickness of the tab part 20 is equal to the thickness of the first part 101, the tab part 20, the first part 101 and the second part 102 can be integrally processed and formed, which helps to improve the production efficiency of the pole piece.
  • the thickness of the tab part 20 is smaller than the thickness of the first part 101 , it helps to reduce the thickness of the tab formed after the tab part 20 is flattened, helps save space inside the battery, and improves space utilization inside the battery. Rate.
  • the tab portion 20 of the current collector 1 can also be connected to the second portion 102 in the second reverse direction j.
  • the first thickness d1 is 10 ⁇ m-20 ⁇ m, preferably, d1 is 12 ⁇ m-18 ⁇ m.
  • d1 can be 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, or its value is within the range obtained by combining any two of the above values.
  • the second thickness d2 is 1 ⁇ m-20 ⁇ m, preferably, d2 is 6 ⁇ m-17 ⁇ m.
  • d2 can be 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, or a value thereof.
  • d2 can be 1 ⁇ m, 2 ⁇ m, 3 ⁇ m, 4 ⁇ m, 5 ⁇ m, 6 ⁇ m, 7 ⁇ m, 8 ⁇ m, 9 ⁇ m, 10 ⁇ m, 11 ⁇ m, 12 ⁇ m, 13 ⁇ m, 14 ⁇ m, 15 ⁇ m, 16 ⁇ m, 17 ⁇ m, 18 ⁇ m, 19 ⁇ m, 20 ⁇ m, or a value thereof.
  • the first part 101 is obtained by thickening the current collector 1 .
  • the first part 101 can be obtained by thickening both sides of the base material on which the current collector 1 is prepared. For example, ultrasonic welding can be performed on both sides of the base material to obtain the current collector 1 having the first portion 101 .
  • the first part 101 of the current collector 1 can be processed during the polishing process of the base material by changing the abrasive tool used to prepare the base material, so that the thickness of the tab part 20 of the current collector 1 is smaller than the thickness of the first part 101.
  • the second part 102 is obtained by thinning the current collector 1 .
  • the second part 102 can be obtained by thinning the middle part of the base material on which the current collector 1 is prepared.
  • the current collector 1 having the second portion 102 can be obtained by cutting the middle portion of the base material.
  • the second part 102 of the current collector 1 can be processed during the polishing process of the base material by changing the abrasive tool used to prepare the base material, so that the thickness of the tab part 20 of the current collector 1 is equal to the thickness of the first part 101 .
  • Figure 4 is a schematic structural diagram of a pole piece according to an embodiment of the present application.
  • the pole piece 3 includes a current collector 1 and a film layer 30 disposed on the current collector.
  • a film layer 30 is provided on the first part 101 and the second part 102, and the compaction density of the film layer 30 in the first part 101 is greater than the compaction density of the film layer 30 in the second part.
  • the film layer 30 disposed on the current collector 1 in the first part 101 is compared with the first part 102.
  • a part of the film layer can store more electrolyte, thereby effectively reducing the occurrence of polarization on the pole piece 3 and reducing lithium deposition on the pole piece 3 in the battery.
  • the sum of the thicknesses of the film layer 30 and the current collector 1 in the second part 102 is greater than or equal to the sum of the thicknesses of the film layer 30 and the current collector 1 in the first part 101 .
  • the film layer 30 has a thickness h1 in the first part 101
  • the film layer 30 has a thickness h2 in the second part 102
  • the current collector 1 has a thickness d1 in the first portion 101 and the current collector 1 has a thickness d2 in the second portion.
  • the thickness of the pole piece 3 in the second part 102 is greater than or equal to the thickness of the pole piece 3 in the first part 101 .
  • this equation is not absolute. Since the current collector is not a completely flat current collector and its surface has a special structure, the thickness of the pole piece 3 in the second part 102 may be slightly larger than that in the second part 102 . The thickness of the first part 101.
  • the sum of the thicknesses of the film layer and the current collector in the second part is 1%-3% greater than the sum of the thicknesses of the film layer and the current collector in the first part.
  • the thickness of the pole piece 3 in the second part 102 is slightly greater than the thickness of the pole piece 3 in the first part 101, specifically, greater than 1%-3%.
  • the sum of the thicknesses of the film layer 3 and the current collector 1 in the second part 102 is equal to the sum of the thicknesses of the film layer 3 and the current collector 1 in the first part 101, it means that the pole piece is in the entire coating area. 10
  • the thickness is uniform, so that after the electrode pieces are assembled into a battery, the distance between the positive electrode pieces and the negative electrode pieces in the battery is equal everywhere, effectively avoiding the problem caused by the unequal spacing between the positive and negative electrode pieces during the battery cycle.
  • the battery polarization effectively improves the lithium precipitation problem of the battery.
  • the second part 102 is the middle part of the pole piece. Most of the electrochemical reactions on the pole piece occur in the middle part of the pole piece. This helps to reduce the migration of active ions between the positive and negative pole pieces during the battery cycle. The distance helps improve ion dynamics, thereby reducing the polarization phenomenon in the middle part of the pole piece and improving the lithium precipitation problem of the pole piece.
  • 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 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 negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard 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 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 current collector 1 is a negative electrode current collector
  • the film layer 30 is a negative electrode film layer.
  • the compacted density of the negative electrode film layer in the first part 101 is 1g/cm 3 -1.65g/cm 3 , preferably 1.45g/cm 3 -1.6g/cm 3 , further preferably 1.5g/cm 3 -1.55g/cm 3 ;
  • the compacted density of the negative electrode film layer in the second part 102 is 0.9g/cm 3 -1.5g/cm 3 , preferably 1.3g/cm 3 -1.5g/cm 3 , further preferably 1.35g/cm 3 - 1.45g/cm 3 .
  • the negative electrode sheet can be prepared by forming the above-mentioned components for preparing the negative electrode sheet into a negative electrode slurry.
  • the negative active material, conductive agent, binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a negative electrode slurry.
  • the negative electrode slurry is coated on the current collector 1, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • the positive electrode sheet usually 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 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.
  • Composite current collectors 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 cathode active material may be a cathode active material known in the art for batteries.
  • the 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 (can also be abbreviated as NCM811), at least one of lithium nickel cobalt aluminum oxide (such as LiNi 0.85
  • 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 positive electrode material optionally 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 material layer optionally further contains 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 current collector 1 is a positive electrode current collector
  • the film layer 30 is a positive electrode film layer.
  • the compacted density of the positive electrode film layer in the first part 101 is 2.3g/cm 3 -2.5g/cm 3 , preferably 2.4g/cm 3 ; the compacted density of the positive electrode film layer in the second part 102 is 2.2g/cm 3 -2.4g/cm 3 , preferably 2.35g/cm 3 .
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the positive electrode sheet, such as positive active materials, conductive agents, binders, additives and any other components, are dispersed in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the current collector 1, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • 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 may optionally further include 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.
  • a spacer is included in the battery.
  • This application has no special restrictions on the type of separator, and any well-known porous structure separator with good chemical stability and mechanical stability can be selected.
  • the material of the isolator may be at least one selected from the group consisting of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation member may be an isolation film, and the isolation film may be a single-layer film or a multi-layer composite film, without any particular limitation.
  • the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there are no special restrictions.
  • 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 portion 21 of the positive electrode piece is rolled to form the positive tab 51 of the electrode assembly 5, and the tab portion 21 of the negative electrode piece is rolled to form the negative tab of the electrode assembly 5. 52. The coating area 10 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, laptop computers, ships, spacecraft, electric 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 two sides of the foil are thickened by ultrasonic welding to form the first part 101.
  • the final thickness of the first part 101 is 17 ⁇ m
  • the thickness of the second part 102 is 13 ⁇ m
  • the second part 102 is at The width in the first direction k accounts for 2/3 of the width of the coating film region 10 in the first direction k, thereby obtaining the positive electrode current collector 1 .
  • NMP solvent N-methylpyrrolidone
  • the positive electrode slurry was obtained.
  • the positive electrode slurry is evenly coated on the coating film area 10 of the positive electrode current collector 1, and then dried, cold pressed, and cut to obtain the positive electrode piece.
  • the density of the first part 101 of the positive electrode piece is 2.4g/cm 3 and the density of the second part 102 is 2.35g/cm 3 .
  • SBR binder styrene-butadiene rubber
  • CMC thickener sodium carboxymethylcellulose
  • the two sides of the foil are thickened by ultrasonic welding to form the first part 101.
  • the final thickness of the first part 101 is 9 ⁇ m
  • the thickness of the second part 102 is 6 ⁇ m
  • the thickness of the second part 102 The width in the first direction k accounts for 2/3 of the width of the coating film region 10 in the first direction k, thereby obtaining the negative electrode current collector 1 .
  • the negative active material graphite Dissolve the negative active material graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethylcellulose (CMC) in the solvent deionized water according to the mass ratio of 97:0.4:1.6:1. After mixing evenly, the negative electrode slurry is obtained. Then, the negative electrode slurry is evenly coated on the coating film area 10 of the negative electrode current collector, and then dried, cold pressed, and cut to obtain negative electrode pieces. Among them, the density of the first part 101 of the negative electrode piece is 1.5g/cm 3 and the density of the second part 102 is 1.45g/cm 3 .
  • Example 3 Compared with the battery cell of Example 1, Example 3 only changed the negative electrode current collector.
  • the negative electrode current collector in Example 3 changed the ordinary copper foil into the same negative electrode current collector 1 as in Example 2.
  • the positive electrode current collector of Example 4 is prepared using the same preparation method as that of Example 1 to prepare the positive electrode current collector 1.
  • SBR binder styrene-butadiene rubber
  • CMC thickener sodium carboxymethylcellulose
  • the battery cell 4 of Example 4 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.
  • Comparative Example 1 Compared with the battery cell of Example 1, Comparative Example 1 only changed the selection of the positive electrode current collector, and used ordinary aluminum foil as the positive electrode current collector 1.
  • the battery cell of Comparative Example 1 was prepared using the same preparation method as Example 1.
  • Comparative Example 2 uses ordinary aluminum foil as the positive electrode current collector.
  • 101 in Table 1 refers to the first part of the coating film area 10, and 102 refers to the second part of the coating film area 10.
  • 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 charged at a constant current rate of 0.33C. Discharge to the discharge cut-off voltage V2 and let it sit for 5 minutes. This is a charge and discharge cycle.
  • This method to perform a cycle charge and discharge test on the battery until the battery capacity decays to 80%. The number of cycles at this time is the cycle life of the battery.
  • the test results are shown in Table 2.

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Abstract

本申请提供了一种集流体、极片、电池单体、电池及用电装置。该集流体包括：第一部分，第一部分沿第一方向设置，第一方向为集流体的宽度方向或集流体的长度方向；第二部分，第二部分设置于两个第一部分之间；其中，第一部分和第二部分用于承载膜层，第一部分具有第一厚度，第二部分具有第二厚度，第一厚度大于第二厚度。该集流体具有特殊的结构，能够有效改善极片在电池循环过程中中间区域的浸润情况，减少极片的析锂现象，从而提高电池的循环性能和使用寿命。

Description

集流体、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，特别是涉及一种集流体、极片、电池单体、电池及用电装置。
背景技术
近年来，二次电池的应用范围越来越广泛，其广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次电池取得了极大的发展，因此对其循环性能、使用寿命等也提出了更高的要求。
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，提供一种集流体、极片、电池单体、电池及用电装置，其中，该集流体具有特殊的结构，能够有效改善极片在电池循环过程中中间区域的浸润情况，减少极片的析锂现象，从而提高电池的循环性能和使用寿命。
第一方面，本申请提供一种集流体，所述集流体包括：第一部分，所述第一部分沿第一方向设置，所述第一方向为所述集流体的宽度方向或所述集流体的长度方向；第二部分，所述第二部分设置于两个所述第一部分之间；其中，所述第一部分和所述第二部分用于承载膜层，所述第一部 分具有第一厚度，所述第二部分具有第二厚度，所述第一厚度大于所述第二厚度。
本申请提供的集流体具有两边厚、中间薄的特殊结构，具体来说，该集流体具有较厚的第一部分和较薄的第二部分。在使用该集流体制备极片时，能够使得设置于第一部分上的膜层压密较高，而设置于第二部分上的膜层压密较低。由此，能够在不改变极片厚度的情况下，使得极片中间部分的膜层能够容纳更多电解液，从而改善充放电过程中电解液因电极活性材料膨胀被挤出而导致的极片中间区域析锂问题，有效提高了电池循环性能以及使用寿命，并且帮助提升了电池的安全性。
在一些实施例中，所述第二部分在所述第一方向上的宽度与所述第一部分和所述第二部分在所述第一方向上的宽度的比值为30％-70％，优选地为40％-60％。
本申请的实施例中，通过设置第二部分的宽度在整个第一部分和第二部分中的占比在合适的范围内，能够在不增大工艺难度的情况下，使得设置于该集流体第二部分上的膜层容纳更多的电解液没从而进一步帮助改善极片中间区域析锂的问题。
在一些实施例中，所述集流体包括：极耳部分，所述极耳部分在所述第一方向上与至少一个所述第一部分连接，所述极耳部分的厚度小于或等于所述第一部分的厚度。
本实施例中，极耳部分与第一部分连接，在极耳部分的厚度等于第一部分的厚度的情况下，极耳部分和第一部分能够一次成型，有助于极片的一体化加工；在极耳部分的厚度小于第一部分的厚度的情况下，能够通过减小极耳部分的厚度来减小极耳揉平之后的厚度，从而帮助提高电池内部的空间利用率。
在一些实施例中，所述第一厚度为10μm-20μm，优选地为12μm-18μm；所述第二厚度为1μm-20μm，优选地为6μm-17μm。
在一些实施例中，所述第一部分和所述第二部分上设置有膜层，所述膜层在所述第一部分的压实密度大于所述膜层在所述第二部分的压实密度。
本申请的实施例中，通过控制设置于集流体上的膜层在第一部分的压实密度大于其在第二部分的压实密度，使得设置于第二部分的膜层相比于第一部分能够容纳更多的电解液，从而有效改善极片中间区域的析锂问题。
在一些实施例中，所述集流体为正极集流体，所述膜层为正极膜层，所述正极膜层在所述第一部分的压实密度为2.3g/cm 3-2.5g/cm 3，优选地为2.4g/cm 3；所述正极膜层在所述第二部分的压实密度为2.2g/cm 3-2.4g/cm 3，优选地为2.35g/cm 3。
在一些实施例中，所述集流体为负极集流体，所述膜层为负极膜层，所述负极膜层在所述第一部分的压实密度为1g/cm 3-1.65g/cm 3，优选地为1.5g/cm 3；所述负极膜层在所述第二部分的压实密度为0.9g/cm 3-1.5g/cm 3，优选地为1.45g/cm 3。
本申请的实施例中，在电池的正极和/或负极利用该具有特殊结构的集流体，通过将正极膜层和/或负极膜层在第一部分和第二部分的压实密度控制在合适的范围内，能够有效提高正极极片和/或负极极片中间区域的孔隙数量，从而使得中间区域容纳更多的电解液，有效改善电池中极片的析锂问题。
在一些实施例中，所述膜层和所述集流体在所述第二部分的厚度之和大于或等于所述膜层和所述集流体在所述第一部分的厚度之和。
本申请的实施例中，在膜层和集流体在第二部分的厚度之和等于膜层和集流体在第一部分的厚度之和的情况下，说明极片具有膜层的部分厚度相等，即整个极片的厚度均一，由此，电池中极片之间的间距基本上处处相等，能够避免电池的循环过程中，因正极极片和负极极片之间的间距不等而导致的电池极化，从而帮助改善电池的析锂问题。在膜层和集流体在第二部分的厚度之和大于膜层和集流体在第一部分的厚度之和的情况下，说明电池循环过程中正极极片和负极极片在第二部分处离子迁移的距离更小，有助于提高离子动力学，从而帮助减小极片中间部分的极化现象，从而进一步改善极片的析锂问题。
在一些实施例中，所述膜层和所述集流体在所述第二部分的厚度之和比所述膜层和所述集流体在所述第一部分的厚度之和大1％-3％。
在一些实施例中，所述第一部分通过加厚所述集流体得到。
在一些实施例中，所述第二部分通过减薄所述集流体得到。
本申请的实施例中，该具有特殊结构的集流体能够通过多种不同的加工手段实现，制备方法灵活多样，有助于提高该集流体的生产效率。
第二方面，提供一种极片，所述极片包括第一方面任一实施例中的集流体。
第三方面，提供一种电池单体，所述电池单体包括第二方面任一实施例所述的集流体。
第四方面，提供一种电池，所述电池包括第三方面任一实施例中的电池单体。
第五方面，提供一种用电装置，其特征在于，所述用电装置包括第三方面任一实施例所述的电池单体或第四方面任一实施例所述的电池中的 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。
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为本申请实施例一种集流体的示意性俯视图。
图2为本申请实施例一种集流体的示意性截面图。
图3为本申请实施例一种集流体的另一示意性截面图。
图4为本申请实施例一种极片的示意性结构图。
图5为本申请实施例一种电极组件的示意性结构图。
图6为本申请对比例1循环后的负极极片照片。
图7为本申请实施例1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。
在电池中，正极极片、负极极片、电解质以及隔离件是构成一个电池的基本元素。电池的充放电过程中，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进行活性离子的传导。隔离件设置于正极极片和负极极片之间，用于防止电池的正负极短路，同时还使得活性离子通过。其中，正极极片和负极极片统称为极片，极片通常包括集流体和设置于集流体上的膜层，该膜层包括电极活性材料。
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，由于电极活性材料在嵌锂、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活性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，本申请实施提供了一种集流体、极片、电池单体、电池以及用电装置。其中，该集流体具有两侧厚、中间薄的特殊结构，使得利用该集流体制备得到的极片具有较为均一的厚度的同时，极片两侧的压密较高，中间部分的压密较低。由此，极片的中间部分能够存储更多的电解液，在电池的循环过程中，能够改善极片中间区域的极化现象，从而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，本申请提供一种集流体。图1为本申请实施例一种集流体的示意性俯视图。图2为本申请实施例一种集流体的示意性截面图。
如图1和图2所示，集流体1包括包括第一部分101和第二部分102。
其中，第一部分101沿第一方向k设置于，第一方向k为集流体1的宽度方向或集流体1的长度方向。第二部分102设置于两个第一部分101之间。第一部分101和第二部分102用于承载膜层，第一部分101具有第一厚度d1，第二部分102具有第二厚度d2，且第一厚度d1大于第二厚度d2。
应理解，集流体1一般具有沿其自身厚度方向相对的两个表面，膜层设置在集流体1相对的两个表面的其中任意一者或两者上。图1和图2所示的集流体1结构为设置有膜层的集流体1表面的结构。换言之，在膜层仅设置于集流体1的一个表面上的情况下，集流体1设置有膜层的表面具有图1和图2所示的结构。在膜层设置于集流体1的两个表面上的情况下，集流体1的两个表面均具有图1和图2的结构。集流体1可以是正极集流体也可以是负极集流体。使用集流体1制备得到的极片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。
集流体1的第一部分101和第二部分102形成了集流体1的涂膜区域10，也就是集流体1上用于承载膜层的部分。
在卷绕式电极组件中，第一方向k优选地为集流体1的宽度方向，第一部分101沿第一方向k设置从而形成了涂膜区域10的两侧。在制备极片的过程中，通常将电极活性材料涂敷于集流体上，再经过压实、干燥等步骤形成设置有膜层的集流体，即极片。使用集流体1制备极片时，由于集流体1表面的特殊结构，使得通过冷压、干燥得到的膜层在第一部分101处的压密高于其在第二部分102处的压密。然后，将极片沿第二方向j卷绕形成卷绕式电极组件。第二方向j垂直于第一方向k。由此，第二部分102经过卷绕后形成卷绕式电极组件的中间部分。
应理解，压密指的是膜层的压实密度。
在叠片式电极组件中，第一方向k优选地为集流体l的长度方向。极片的制备过程与卷绕式电极组件中的极片类似。在制备好极片后，将极片依次交替叠放，中间由隔膜Z字叠绕形成叠片式电极组件。由此，第二部分102经过叠片后形成叠片式电极组件的中间部分。
本实施例中，该集流体1第一部分101的厚度大于其第二部分102的厚度，使得设置于集流体1涂膜区域10上的膜层具有不同的压密。即膜层在第一部分101的压密大于其在第二部分102的压密，使得位于第二部分102的膜层相比于第一部分101能够存储更多的电解质，尤其是液态电解质。由此，通过集流体1制备得到的电极组件的中间部分相比于其他部分具有容纳更多电解质的能力。在电池的循环过程中，尽管电极活性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，具有较好的活性离子传导能力，从而改善因不足导致的极化现象。通过使用该具有特殊结构的集流体1能够有效减少析锂的发生，由此，提高了电池的循环性能和使用寿命，还帮助提高了电池的安全性能。
另外，本申请提供的集流体1在制备极片的过程中，在压实的过程中，例如，通过辊压机压实的过程中，由于集流体1表面的特殊结构，使得辊压机利用一种压力去辊压集流体和电极活性材料即可获得厚度均一且具有不同压密分布的极片。一方面，通过一种压力一次性辊压得到的极片的厚度均一，不论是卷绕式电极组件还是叠片式电极组件中，均有助于正极极片和负极极片之间的间距相等，避免因电池正负极之间间距差异较大造成的极化现象。另一方面，仅使用一种压力辊压一次即可得到具有不同压密分布的极片，使得极片的加工方式、步骤更为简单，有助于提高极片的生产效率，从而在提高电池的循环性能和使用寿命的同时提高电池的生产效率。
可选地，第二部分102在第一方向k上的宽度与第一部分101和第二部分102在第一方向k上的宽度之和的比值为30％-70％，优选地为40％-60％。
具体来说，如图1所示，第二部分102在第一方向k上具有宽度h，第一部分101和第二部分102在第一方向k上的宽度之和为H，换言之，涂膜区域10在第一方向k上具有宽度H。30％≤h/H≤70％；优选地，40％≤h/H≤60％。h/H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。
本实施例中，通过设置第二部分102的宽度在合适的范围内，能够在不增大工艺难度的情况下，使得设置于该集流体第二部分102上的膜层尽可能多的容纳电解质。
图3为本申请实施例集流体1的另一示意性结构图。
可选地，如图2和图3所示，集流体1包括极耳部分20，极耳部分20在第一方向k上与第一部分101连接，极耳部分20的厚度小于或等于第一部分101的厚度。
具体来说，为了便于加工，集流体1的极耳部分20的厚度可以小于或等于第一部分101的厚度。例如，参见图3，在第二部分102是通过削薄集流体1加工制备的情况下，第一部分101的厚度即用于制备该集流体1的基材本身的厚度。此时极耳部分20的厚度等于第一部分101的厚度，即极耳部分20的厚度也等于该基材本身的厚度，由此，简化了加工集流体1的极耳部分20的工艺步骤。又例如，参见图2，在第二部分102是通过加厚集流体1的第一部分101加工制备的情况下，第二部分102的厚度即用于制备该集流体1的基材本身的厚度，由此也能够简化极耳部分20加工步 骤。此时第一部分101的厚度大于该基材本身的厚度，也就使得极耳部分20的厚度小于第一部分101的厚度。
本实施例中，极耳部分20与第一部分101连接。在极耳部分20的厚度与第一部分101的厚度相等的情况下，极耳部分20、第一部分101和第二部分102能够一体化加工成型，有助于提高极片的生产效率。在极耳部分20的厚度小于第一部分101的厚度的情况下，有助于减小极耳部分20在揉平后形成的极耳的厚度，帮助节省电池内部的空间，提高电池内部的空间利用率。
在另一些可能的实现方式中，例如，在叠片式电极组件中，集流体1的极耳部分20也可以在第二反向j上与第二部分102连接。
可选地，第一厚度d1为10μm-20μm，优选地，d1为12μm-18μm。
具体来说，d1可以为10μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm、18μm、19μm、20μm，或者其数值在上述任意两个数值组合所获得的范围之内。
可选地，第二厚度d2为1μm-20μm，优选地，d2为6μm-17μm。
具体来说，d2可以为1μm、2μm、3μm、4μm、5μm、6μm、7μm、8μm、9μm、10μm、11μm、12μm、13μm、14μm、15μm、16μm、17μm、18μm、19μm、20μm，或者其数值在上述任意两个数值组合所获得的范围之内。
可选地，如图2所示，第一部分101通过加厚集流体1得到。
具体来说，制备集流体1的过程中，第一部分101可以通过在制备集流体1的基材上加厚基材的两侧得到。例如，可以通过超声波焊接的方式在基材的两侧进行焊接以得到具有第一部分101的集流体1。又例如，还可以通过改变制备基材的磨具，在打磨基材的过程中即加工出集流体1的第一部分101，使得集流体1极耳部分20的厚度小于第一部分101的厚 度。
可选地，如图3所示，第二部分102通过减薄集流体1得到。
具体来说，制备集流体1的过程中，第二部分102可以通过减薄制备集流体1的基材的中间部分得到。例如，可以通过切削基材中间部分的方式得到具有第二部分102的集流体1。又例如，还可以通过改变制备基材的磨具，在打磨基材的过程中加工出集流体1的第二部分102，使得集流体1极耳部分20的厚度等于第一部分101的厚度。
图4为本申请实施例一种极片的示意性结构图。
如图4所示，极片3包括集流体1和设置于集流体上的膜层30。
可选地，第一部分101和第二部分102上设置有膜层30，膜层30在第一部分101的压实密度大于膜层30在第二部分的压实密度。
本实施例中，通过控制设置于集流体1上的膜层30在第一部分101的压实密度大于其在第二部分102的压实密度，使得设置于第二部分的膜层相比于第一部分的膜层能够存储更多的电解液，从而有效减小极片3上极化现象的发生，减少电池中极片3的析锂。
可选地，膜层30和集流体1在第二部分102的厚度之和大于或等于膜层30和集流体1在第一部分101的厚度之和。
请继续参见图4，膜层30在第一部分101具有厚度h1，膜层30在第二部分102具有厚度h2。集流体1在第一部分101具有厚度d1，集流体1在第二部分具有厚度d2。也就是说，d1+h1≤d2+h2。换言之，极片3在第二部分102的厚度大于或等于极片3在第一部分101的厚度。
具体地，理想状态下，经过一次性辊压得到的极片3具有均一的厚度，即d1+h1＝d2+h2。但在实际生产加工过程中，该等式并不绝对，由于该集流体不是完全平整的集流体，其表面具有特殊的结构，因此，极片3在第二部分102的厚度可能略大于其在第一部分101的厚度。
可选地，所述膜层和所述集流体在所述第二部分的厚度之和比所述膜层和所述集流体在所述第一部分的厚度之和大1％-3％。换言之，极片3在第二部分102的厚度略大于极片3在第一部分101的厚度，具体来说，大于1％-3％。
本实施例中，在膜层3与集流体1在第二部分102的厚度之和等于膜层3与集流体1在第一部分101的厚度之和的情况下，说明极片在整个涂膜区域10厚度均一，使得该极片在组装成电池后，电池中正极极片和负极极片之间的间距处处相等，有效避免电池循环过程中因正负极极片之间的间距不等而导致的电池极化，有效改善电池的析锂问题。若加工过程存在一定误差，在膜层3与集流体1在第二部分102的厚度之和大于膜层3与集流体1在第一部分101的厚度之和的情况下，由于较厚的是第二部分102，也就是极片的中间部分，极片上的电化学反应大多数均发生在极片的中间部分，由此，有助于减小电池循环过程中正负极极片之间的活性离子迁移距离，帮助提高离子动力学，从而减小极片中间部分的极化现象，改善极片的析锂问题。
下面对集流体1被用在负极极片、正极极片中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，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，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述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。所述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，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。
可选地，在一个实施例中，集流体1为负极集流体，膜层30为负极膜层。负极膜层在第一部分101的压实密度为1g/cm 3-1.65g/cm 3，优选为1.45g/cm 3-1.6g/cm 3，进一步优选为1.5g/cm 3-1.55g/cm 3；负极膜层在第二部分102的压实密度为0.9g/cm 3-1.5g/cm 3，优选为1.3g/cm 3-1.5g/cm 3，进一步优选为1.35g/cm 3-1.45g/cm 3。
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形成负极浆料。例如将负极活性材料、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。然后将负极浆料涂覆在集流体1上，经烘干、冷压等工序后，即可得到负极极片。
[正极极片]
正极极片通常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，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，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，正极材料还可选地包括粘结剂。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，正极材料层还可选地含有导电剂。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。
可选地，在一个实施例中，集流体1为正极集流体，膜层30为正极膜层。正极膜层在第一部分101的压实密度为2.3g/cm 3-2.5g/cm 3，优选为2.4g/cm 3；正极膜层在第二部分102的压实密度为2.2g/cm 3-2.4g/cm 3，优选为2.35g/cm 3。
可选地，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，例如正极活性材料、导电剂、粘结剂、添加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；将正极浆料涂覆在集流体1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，电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离件]
可选地，电池中还包括隔离件。本申请对隔离件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件。
可选地，隔离件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。隔离件可以是隔离膜，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， 正极极片的极耳部分21经过卷绕后形成了电极组件5的正极极耳51，负极极片的极耳部分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10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)正极集流体的制备
在厚度为13μm的铝箔两侧，通过超声波焊接加厚箔材的两侧区域以形成第一部分101，最终第一部分101的厚度为17μm，第二部分102的厚度为13μm，且第二部分102在第一方向k上的宽度占涂膜区域10在第一方向k上的宽度的2/3，由此，得到正极集流体1。
(2)正极极片的制备
将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集流体1的涂膜区域10上，再经过烘干、冷压、分切得到正极极片。其中，正极极片的第一部分101的压密为2.4g/cm 3，第二部分102的压密为2.35g/cm 3。
(3)负极极片的制备
将负极活性材料石墨、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97:0.4:1.6:1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上，再经过烘干、冷压、分切得到负极极片。
(4)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
(1)正极极片的制备
将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上，再经过烘干、冷压、分切得到正极极片。
(2)负极集流体的制备
在厚度为6μm的铜箔两侧，通过超声波焊接加厚箔材的两侧区域以形成第一部分101，最终第一部分101的厚度为9μm，第二部分102的厚 度为6μm，且第二部分102在第一方向k上的宽度占涂膜区域10在第一方向k上的宽度的2/3，由此，得到负极集流体1。
(3)负极极片的制备
将负极活性材料石墨、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97:0.4:1.6:1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的涂膜区域10上，再经过烘干、冷压、分切得到负极极片。其中，负极极片的第一部分101的压密为1.5g/cm 3，第二部分102的压密为1.45g/cm 3。
(4)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3
与实施例1的电池单体相比，实施例3仅改变了负极集流体，实施例3中的负极集流体将普通铜箔改变为与实施例2相同的负极集流体1。
实施例4
(1)正极集流体的制备
实施例4的正极集流体采用与实施例1相同的制备方法，制备得到正极集流体1。
(2)正极极片的制备
将正极活性材料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。随后将正极浆料均匀地涂覆于正极集流体1的涂膜区域10上，再经过烘干、冷压、分切得到正极极片。其中， 正极极片的第一部分101的压密为2.4g/cm 3，第二部分的压密为2.35g/cm 3。
(3)负极极片的制备
将负极活性材料硬碳、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97:0.4:1.6:1溶解于去离子水中，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上，再经过烘干、冷压、分切得到负极极片。
(4)电池单体的组装
实施例4的电池单体4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
对比例1与实施例1的电池单体相比，对比例1仅改变了正极集流体的选择，将正极集流体1改为使用普通铝箔。采用与实施例1相同的制备方法制备得到对比例1的电池单体。
对比例2
对比例2与实施例4的电池单体相比，区别仅在于对比例2采用普通铝箔作为正极集流体。
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 PCTCN2022107037-appb-000001
Figure PCTCN2022107037-appb-000002
表1中的101指涂膜区域10的第一部分，102指涂膜区域10的第二部分。
上述实施例1-4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 5527
2 5019
3 6231
4 5503
对比例1 4008
对比例2 3996
接下来，对上述电池的参数测试过程进行简单介绍。
1.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0.33C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。
由实施例1和对比例1、实施例2和对比例1的性能对比可以看出，通过使用本申请提供的具有特殊结构的集流体，不论是应用在正极还是负极中，均能够有效提高电池的循环性能，帮助延长电池的使用寿命。更进 一步地，通过实施例3和实施例1的性能对比、实施例3和实施例2的性能对比可以看出，若在电池的正负极同时使用该具有特殊结构的集流体，能够进一步抑制电池极化、提高电池的循环性能。通过实施例4和对比例2的性能对比能够看出，该具有特殊结构的集流体应用于钠离子电池时，同样能够有效提升电池的循环性能。
2.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6和图7所示。由图6和图7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. 一种集流体，其中，所述集流体包括：
    第一部分，所述第一部分沿第一方向设置，所述第一方向为所述集流体的宽度方向或所述集流体的长度方向；
    第二部分，所述第二部分设置于两个所述第一部分之间；
    其中，所述第一部分和所述第二部分用于承载膜层，所述第一部分具有第一厚度，所述第二部分具有第二厚度，所述第一厚度大于所述第二厚度。
  2. 根据权利要求1所述的集流体，其中，所述第二部分在所述第一方向上的宽度与所述第一部分和所述第二部分在所述第一方向上的宽度之和的比值为30％-70％，优选地为40％-60％。
  3. 根据权利要求1或2所述的集流体，其中，所述集流体包括：
    极耳部分，所述极耳部分在所述第一方向上与所述第一部分连接，所述极耳部分的厚度小于或等于所述第一部分的厚度。
  4. 根据权利要求1-3中任一项所述的集流体，其中，所述第一厚度为10μm-20μm，优选地为12μm-18μm；所述第二厚度为1μm-20μm，优选地为6μm-17μm。
  5. 根据权利要求1-4中任一项所述的集流体，其中，所述第一部分和所述第二部分上设置有膜层，所述膜层在所述第一部分的压实密度大于所述膜层在所述第二部分的压实密度。
  6. 根据权利要求5所述的集流体，其中，所述集流体为正极集流体，所述膜层为正极膜层，所述正极膜层在所述第一部分的压实密度为1.5g/cm 3-2.6g/cm 3，优选地为2.4g/cm 3；所述正极膜层在所述第二部分的压实密度为2.2g/cm 3-2.45g/cm 3，优选地为2.35g/cm 3。
  7. 根据权利要求5所述的集流体，其中，所述集流体为负极集流体，所述膜层为负极膜层，所述负极膜层在所述第一部分的压实密度为1g/cm 3-1.65g/cm 3，优选地为1.5g/cm 3；所述负极膜层在所述第二部分的压实密度为0.9g/cm 3-1.5g/cm 3，优选地为1.45g/cm 3。
  8. 根据权利要求5所述的集流体，其中，所述膜层和所述集流体在所述第二部分的厚度之和大于或等于所述膜层和所述集流体在所述第一部分的厚度之和。
  9. 根据权利要求8所述的集流体，其中，所述膜层和所述集流体在所述第二部分的厚度之和比所述膜层和所述集流体在所述第一部分的厚度之和大1％-3％。
  10. 根据权利要求1-9中任一项所述的集流体，其中，所述第一部分通过加厚所述集流体得到。
  11. 根据权利要求1-9中任一项所述的集流体，其中，所述第二部分通过减薄所述集流体得到。
  12. 一种极片，其中，所述极片包括如权利要求中1-11中任一项所述的集流体。
  13. 一种电池单体，其中，所述电池单体包括如权利要求12所述的极片。
  14. 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. 一种用电装置，其特征在于，所述用电装置包括如权利要求12所述的电池单体或如权利要求13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/CN2022/107037 2022-07-21 2022-07-21 集流体、极片、电池单体、电池及用电装置 WO2024016264A1 (zh)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001015146A (ja) * 1999-06-30 2001-01-19 Matsushita Electric Ind Co Ltd 電 池
JP2005038612A (ja) * 2003-07-15 2005-02-10 Ngk Spark Plug Co Ltd リチウムイオン二次電池およびその製造方法
CN101427414A (zh) * 2006-12-21 2009-05-06 丰田自动车株式会社 蓄电装置
JP2016096278A (ja) * 2014-11-15 2016-05-26 株式会社フジクラ 積層型蓄電池
CN111540910A (zh) * 2020-05-22 2020-08-14 江苏塔菲尔新能源科技股份有限公司 极片、电芯及电池
CN114551787A (zh) * 2022-02-18 2022-05-27 星恒电源股份有限公司 一种锂电池正极片及其制备方法

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001015146A (ja) * 1999-06-30 2001-01-19 Matsushita Electric Ind Co Ltd 電 池
JP2005038612A (ja) * 2003-07-15 2005-02-10 Ngk Spark Plug Co Ltd リチウムイオン二次電池およびその製造方法
CN101427414A (zh) * 2006-12-21 2009-05-06 丰田自动车株式会社 蓄电装置
JP2016096278A (ja) * 2014-11-15 2016-05-26 株式会社フジクラ 積層型蓄電池
CN111540910A (zh) * 2020-05-22 2020-08-14 江苏塔菲尔新能源科技股份有限公司 极片、电芯及电池
CN114551787A (zh) * 2022-02-18 2022-05-27 星恒电源股份有限公司 一种锂电池正极片及其制备方法

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