WO2024098886A1 - 复合电极及其制备方法、电池和用电设备 - Google Patents

复合电极及其制备方法、电池和用电设备 Download PDF

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WO2024098886A1
WO2024098886A1 PCT/CN2023/114471 CN2023114471W WO2024098886A1 WO 2024098886 A1 WO2024098886 A1 WO 2024098886A1 CN 2023114471 W CN2023114471 W CN 2023114471W WO 2024098886 A1 WO2024098886 A1 WO 2024098886A1
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active layer
active
composite electrode
layer
current collector
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PCT/CN2023/114471
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English (en)
French (fr)
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丁有才
吴怡祯
李彦朋
高鹏飞
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宁德时代新能源科技股份有限公司
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Publication of WO2024098886A1 publication Critical patent/WO2024098886A1/zh

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    • 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 technical field of lithium-ion batteries, and in particular to a composite electrode and a preparation method thereof, a battery and an electrical device.
  • the high energy density of batteries has always been a goal pursued in the battery field.
  • the stability of materials will decrease, so it is sometimes difficult to strike a balance between the high energy density of batteries and the safety of batteries.
  • the main purpose of the present application is to provide a composite electrode, aiming to provide a composite electrode with both high energy density and stability.
  • the present application proposes a composite electrode, which includes a current collector and a coating area formed on at least one side surface of the current collector, wherein the coating area includes a first active layer and a second active layer arranged along the same extension direction, and the thermal stability of the first active layer is different from the thermal stability of the second active layer.
  • the first active layer is disposed on the surface of the current collector and is close to a side of the current collector for setting a pole lug
  • the second active layer is disposed on the surface of the current collector and is located on a side of the first active layer away from the current collector for setting a pole lug, and the thermal stability of the first active layer is greater than the thermal stability of the second active layer.
  • the first active layer with high thermal stability on the side of the current collector for arranging the pole ear and arranging the second active layer with poor thermal stability on the side of the current collector away from the pole ear, the risk of the pole ear contacting the second active layer with poor thermal stability is reduced, and the heat generation of the second active layer with poor thermal stability during the heat dissipation of the pole ear and the risk of thermal runaway are reduced, thereby improving the stability of the composite electrode.
  • At least three coating areas are formed on the surface of the current collector, at least two coating areas are used to respectively set the first active layer and the third active layer, and at least another coating area is used to set the second active layer, and the second active layer is located between the first active layer and the third active layer, and the thermal stability of the third active layer is greater than the thermal stability of the second active layer.
  • burrs will inevitably appear on the edge of the current collector during the cutting process. Such burrs may pierce the diaphragm due to the change in the expansion force of the pole piece during the working process of the electrode, inducing a micro short circuit in the cell.
  • the micro short circuit will intensify the local reaction of the cathode, release a large amount of heat, and further cause the diaphragm to shrink, thereby causing a larger short circuit and heat generation, and even accidents such as fire and explosion.
  • the heat generated by the micro short circuit of the cell is not very high at the beginning, that is, for materials with good thermal stability around the burr, the heat generated by the micro short circuit of the cell at the beginning is difficult to cause heat generation and thermal runaway of the materials around the burr.
  • the risk of battery accidents is reduced, but for materials with poor thermal stability around the burr, the heat generated by the micro short circuit of the cell is easy to cause heat generation and even thermal runaway of the materials around the burr. In this way, it is easier to cause the local reaction of the cathode to intensify, release a large amount of heat, and produce more serious consequences. At this time, the risk of battery accidents increases.
  • the first active layer and the third active layer with high thermal stability are arranged on the sides of the current collector, and the second active layer with poor thermal stability is arranged near the middle of the current collector, so as to avoid the second active layer with poor thermal stability being arranged around the burrs, thereby reducing the above-mentioned risks.
  • the first active layer and the third active layer are made of the same material
  • the first active layer and the third active layer are made of different materials.
  • the thermal stability of the first active layer and the third active layer higher than that of the second active layer.
  • the materials of the first active layer and the third active layer can be the same or different.
  • a total heat release of the first active layer and a total heat release of the third active layer are respectively smaller than a total heat release of the second active layer.
  • the total heat release of the first active layer and the third active layer is selected to be smaller than the total heat release of the second active layer, thereby reducing the risk of large amounts of heat generation and the risk of fire caused by large amounts of heat generation.
  • the total heat release of the first active layer is in the range of 100 J/g-500 J/g
  • the total heat release of the third active layer is in the range of 100 J/g-500 J/g
  • the total heat release of the second active layer is in the range of 800 J/g-1500 J/g.
  • the total heat release of the first active layer and the third active layer is selected to be less than the total heat release of the second active layer, so as to reduce the risk of large amounts of heat generation and the risk of fire caused by large amounts of heat generation.
  • the total heat release of the first active layer ranges from 100J/g to 500J/g, for example, it can be 100J/g, 200J/g, 300J/g, 400J/g, 500J/g, and the range between any two of the above points.
  • the total heat release of the third active layer ranges from 100J/g to 500J/g, for example, it can be 100J/g, 200J/g, 300J/g, 400J/g, 500J/g, and the range between any two of the above points.
  • the range value between any two point values mentioned above, the range value of the total heat release of the second active layer is 800 J/g-1500 J/g, for example, it can be 800 J/g, 900 J/g, 1000 J/g, 1100 J/g, 1200 J/g, 1700 J/g, 1600 J/g, 1500 J/g, etc., as well as the range value between any two of the above point values.
  • the failure temperature of the battery cell formed by the first active layer is greater than the failure temperature of the battery cell formed by the second active layer; the failure temperature of the battery cell formed by the third active layer is greater than the failure temperature of the battery cell formed by the second active layer.
  • the failure temperature of the battery cell formed by the first active layer is 160°C-220°C
  • the failure temperature of the battery cell formed by the third active layer is 160°C-220°C
  • the failure temperature of the battery cell formed by the second active layer is 120°C-160°C.
  • the failure temperature of the battery cell composed of the first active layer is 160°C-220°C, for example, it can be 160°C, 170°C, 180°C, 190°C, 1200°C, 210°C, 220°C, etc., and the range value between any two of the above point values.
  • the failure temperature of the battery cell composed of the third active layer is 160°C-220°C, for example, it can be 160°C, 170°C, 180°C, 190°C, 1200°C, 210°C, 220°C, etc., and the range value between any two of the above point values.
  • the material of the first active layer or the third active layer can be lithium iron manganese phosphate or lithium iron phosphate and a mixture of the two.
  • the failure temperature of the battery cell composed of the second active layer is 120°C-160°C.
  • it can be 120°C, 130°C, 140°C, 150°C, 160°C, etc., and the range value between any two of the above point values.
  • the material of the second active layer can be a ternary material or lithium cobalt oxide, or a mixture of the two.
  • an insulating layer coating region is preset on one side of the current collector for arranging the pole lug, and the first active layer covers the insulating layer coating region.
  • An insulating layer coating area is provided on the side of the current collector located at the pole ear, for providing an insulating layer, so as to reduce the risk of the pole ear being bent and inserted into the active layer, thereby reducing the risk of causing the active layer to absorb the heat generated by the pole ear, causing the active layer to generate heat, and even thermal runaway.
  • the first active layer is provided close to the pole ear, thereby reducing the risk of the first active layer generating heat due to absorbing the heat of the pole ear. Therefore, by using the first active layer to cover the insulating layer coating area, the coating amount of the first active layer can be increased, thereby improving the energy density.
  • both sides of the current collector are defined to be used for setting pole lugs
  • the other side of the current collector for setting the pole lugs is preset with an insulating layer coating area
  • the third active layer covers the insulating layer coating area.
  • an insulating layer coating area is preset on the other side of the current collector for providing the tabs.
  • the third active layer covers the insulating layer coating area on the other side of the current collector.
  • the third active layer since the third active layer has good thermal stability, it helps to reduce the risk of heat generation by the third active layer due to absorbing heat from the tabs.
  • a width ratio of the first active layer to the second active layer is 0.25-4.
  • the width ratio of the first active layer to the second active layer is 0.25-4.
  • it can be 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4, etc., as well as the range value between any two of the above point values.
  • a width ratio of the sum of the first active layer and the third active layer to the second active layer is 0.25-4.
  • the width ratio of the sum of the first active layer and the third active layer to the second active layer is 0.25-4.
  • it can be 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4, etc., as well as the range value between any two of the above point values.
  • the width of the first active layer accounts for 20%-80% of the total width of the active layer
  • the width of the second active layer accounts for 20%-80% of the total width of the active layer.
  • the width of the first active layer accounts for 20%-80% of the total width of the active layer, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range between any two of the above points.
  • the width of the second active layer accounts for 20%-80% of the total width of the active layer, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range between any two of the above points.
  • the sum of the widths of the first active layer and the third active layer accounts for 20%-80% of the total width of the active layer
  • the width of the second active layer accounts for 20%-80% of the total width of the active layer.
  • the sum of the widths of the first active layer and the third active layer accounts for 20%-80% of the total width of the active layer, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range between any two of the above points.
  • the width of the second active layer accounts for 20%-80% of the total width of the active layer, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range between any two of the above points.
  • the width of the first active layer is greater than 3 mm.
  • the width of the first active layer is greater than 3 mm; on the other hand, the width of the insulating layer currently coated on the current collector is about 3 mm-3.5 mm. In order to make the first active layer cover the coating area of the insulating layer, the width of the first active layer is selected to be greater than 3 mm.
  • the width of the third active layer is greater than 3 mm.
  • the width of the third active layer is greater than 3 mm; on the other hand, the width of the insulating layer currently coated on the current collector is about 3 mm-3.5 mm. In order to make the third active layer cover the coating area of the insulating layer, the width of the third active layer is selected to be greater than 3 mm.
  • the gram capacity of the first active layer and the gram capacity of the third active layer are respectively smaller than the gram capacity of the second active layer.
  • the gram capacity of materials with good thermal stability is smaller than that of materials with poor thermal stability. Since the thermal stability of the first active layer and the third active layer is greater than that of the second active layer, the gram capacity of the first active layer and the third active layer is smaller than that of the second active layer.
  • a low-capacity first active layer is coated on the side of the positive electrode. In this way, the CB value on the side of the battery cell is low, reducing the lithium plating phenomenon on the side of the negative electrode.
  • the gram capacity of the first active layer and the gram capacity of the third active layer respectively account for 60%-80% of the gram capacity of the second active layer.
  • the thermal stability of the first active layer and the third active layer is greater than the thermal stability of the second active layer, the gram capacity of the first active layer and the third active layer is respectively less than the gram capacity of the second active layer, the gram capacity of the first active layer accounts for 60%-80% of the gram capacity of the second active layer, and the gram capacity of the third active layer accounts for 60%-80% of the gram capacity of the second active layer, for example, it can be 60%, 70%, 80%, if the gram capacity of the first active layer and the third active layer respectively accounts for too low the gram capacity of the second active layer, it will lead to too low energy density, and it cannot be too high, which will reduce thermal stability.
  • the materials of the first active layer and the third active layer can include lithium iron manganese phosphate, lithium iron phosphate, or a mixture of the two
  • the material of the second active layer can include ternary materials, lithium cobalt oxide, or a mixture of the two.
  • the average particle size Dv50 of the active material in the first active layer and the average particle size Dv50 of the active material in the third active layer are respectively 0.2 um-2 um.
  • the average particle size Dv50 of the material can be 0.2um, 0.3um, 0.4um, 0.5um, 0.6um, 0.7um, 0.8um, 0.9um, 1um, 1.2um, 1.4um, 1.6um, 1.8um, 2um, etc., and the range value between any two of the above point values.
  • the material can be lithium iron manganese phosphate material, which has poor ion conductivity. Setting the particle size within the above range is conducive to improving the kinetic performance of the material.
  • the average particle size Dv50 of the active material in the second active layer is in the range of 0.5 um to 20 um.
  • the average particle size Dv50 of the material in the second active layer can be 0.5um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um, 16um, 17um, 18um, 19um, 20um, and the range between any two of the above point values.
  • the first active layer, the second active layer, and the third active layer have the same thickness.
  • the first active layer, the third active layer and the second active layer are cold pressed to the same thickness after being cold pressed.
  • the thickness of the first active layer, the second active layer, and the third active layer is 80 ⁇ m-300 ⁇ m.
  • the thickness of the first active layer, the second active layer and the third active layer ranges from 80 ⁇ m to 300 ⁇ m, for example, 80 ⁇ m, 100 ⁇ m, 150 ⁇ m, 180 ⁇ m, 200 ⁇ m, 250 ⁇ m, 280 ⁇ m, 300 ⁇ m, etc., and the range between any two of the above point values.
  • the first active layer includes lithium manganese iron phosphate material.
  • the first active layer includes lithium manganese iron phosphate material, which is beneficial to not only improving stability but also improving energy density.
  • the lithium manganese iron phosphate material is provided with a conductive coating material.
  • a coating material is provided on the lithium manganese iron phosphate material.
  • the mass of the conductive coating material is 1%-10% of the mass of the lithium manganese iron phosphate material
  • the conductive coating material includes at least one of carbon or metal oxide.
  • the mass of the coating material is 1.0%-10.0% of the mass of the lithium manganese iron phosphate material, for example, it can be 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, and the range between any two of the above point values.
  • the conductive coating material includes at least one of carbon or metal oxide, for example, it can be carbon, it can also be metal oxide, or it can be a mixture of the two, without specific limitation, and of course it can also be other materials with conductive properties.
  • the first active layer further comprises a ternary material, and the mass of the lithium iron manganese phosphate material accounts for 20%-80% of the total mass of the first active layer.
  • the first active layer also includes a ternary material, and the mass of the lithium iron manganese phosphate material accounts for 20%-80% of the total mass of the first active layer.
  • the mass of the lithium iron manganese phosphate material can account for 20%, 30%, 40%, 50%, 60%, 70%, 80% of the total mass of the first active layer, and the range value between any two of the above point values.
  • the mass of the lithium iron manganese phosphate material cannot be too low or too high. If the mass of the lithium iron manganese phosphate material is too low, the mass of the ternary material will be too high, and the stability of the battery will be reduced. If the mass of the lithium iron manganese phosphate material is too high, the mass of the ternary material will be too low, and the energy density will be insufficient.
  • the general structural formula of the lithium manganese iron phosphate material is LiMnxFeyM1 -xyPO4 , wherein 0.4 ⁇ x ⁇ 0.8; 0.1 ⁇ y ⁇ 0.6; 0 ⁇ 1-xy ⁇ 0.2, and M represents a doping element, optionally including at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge.
  • the general structural formula of lithium iron manganese phosphate material is LiMn x Fe y M 1-xy PO 4 , wherein 0.4 ⁇ x ⁇ 0.8; 0.1 ⁇ y ⁇ 0.6; 0 ⁇ 1-xy ⁇ 0.2, and M represents a doping element, which may optionally include at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge.
  • the molar proportion of manganese in the lithium iron manganese phosphate material is 20%-80%, and the performance is relatively good.
  • the molar proportion of manganese in the lithium iron manganese phosphate material can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range value between any two of the above-mentioned points.
  • the second active layer includes at least one of a ternary material or lithium cobalt oxide.
  • Lithium cobalt oxide is an inorganic compound with the chemical formula LiCoO 2 , which is generally used as the positive electrode material of lithium-ion batteries.
  • the gram capacity of ternary materials is much higher than that of lithium iron manganese phosphate.
  • Using ternary materials as the second active layer can improve the overall energy density of the electrode. Energy density is the core indicator of power batteries, especially for lithium iron manganese phosphate systems. Only when the energy density exceeds that of lithium iron phosphate can it have application potential.
  • the general structural formula of the ternary material is LiNi a Co b N (1-ab) O 2 , wherein N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.35 ⁇ a ⁇ 1.0, 0 ⁇ b ⁇ 0.35, and 0 ⁇ 1-ab ⁇ 0.35.
  • the general structural formula of the ternary material is LiNi a Co b N (1-ab) O 2 , wherein N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.35 ⁇ a ⁇ 1.0, 0 ⁇ b ⁇ 0.35, and 0 ⁇ 1-ab ⁇ 0.35.
  • the ternary material can be divided into low-nickel ternary material, medium-nickel ternary material, and high-nickel ternary material.
  • the ternary material can also be divided into cobalt-free ternary material, wherein the cobalt element can be replaced by other metal elements.
  • the specific type of the ternary material is not limited.
  • the general structural formula of the ternary material is LiNi a Co b N (1-ab) O 2 , wherein 0.5 ⁇ a ⁇ 0.96.
  • the molar content of Ni element in the ternary material is selected to account for 50%-96% of the total molar content of other metal elements except lithium. For example, it can be 50%, 60%, 70%, 80%, 90%, 96%, etc., as well as the range value between any two of the above point values.
  • the ternary material includes at least one of 5-series single crystal ternary material, 5-series polycrystalline ternary material, 6-series single crystal ternary material, 6-series polycrystalline ternary material, 7-series single crystal ternary material, 7-series polycrystalline ternary material, 8-series single crystal ternary material, 8-series polycrystalline ternary material, 9-series single crystal ternary material, 9-series polycrystalline ternary material, and cobalt-free ternary material.
  • both the first active layer and the second active layer include ternary materials
  • the ternary materials in the first active layer and the second active layer are the same.
  • the ternary materials in the first active layer and the second active layer can be the same or different, but it is best if they are the same.
  • the advantage of being the same is that the lithium insertion amounts of the two active layers are similar and the expansion degrees are the same, which is beneficial to the stability of the electrode.
  • the first active layer includes a first active material, a conductive agent and a binder, the first active material includes a lithium iron manganese phosphate material, and the mass of the lithium iron manganese phosphate material accounts for 94%-97% of the total mass of the first active layer;
  • the second active layer includes a second active material, a conductive agent and a binder, the second active material includes a ternary material, and the ternary material accounts for 95%-98% of the total mass of the second active layer.
  • the first active layer includes a first active material, a conductive agent and a binder, the first active material includes a lithium iron manganese phosphate material, the mass of the lithium iron manganese phosphate material accounts for 94%-97% of the total mass of the first active layer, and the lithium iron manganese phosphate material is within this range (for example, it can be 94%, 95%, 96%, 97%, and the range value between any two of the above point values) to prepare an active layer with excellent performance, wherein the binder content can be 1.8%, 2%, 2.5%, 3%, etc., and the conductive agent content can be 1.8%, 2%, 2.5%, etc., and the range value between any two of the above point values.
  • the second active layer includes a second active material, a conductive agent and a binder.
  • the second active material includes a ternary material.
  • the ternary material accounts for 95%-98% of the total mass of the second active layer.
  • the ternary material is within this range (95%, 96%, 97%, 98%, and any two points between the above values).
  • an active layer with excellent performance can be prepared, wherein the binder content can be 1.5%, 2%, 2.5%, etc., and the conductive agent content can be 1.8%, 2%, 2.5%, etc.
  • the present application provides a method for preparing a composite electrode, comprising the following steps:
  • the thermal stability of the first active layer is different from the thermal stability of the second active layer.
  • the first active layer is close to the side of the current collector for setting the pole lug
  • the second active layer is located on the side of the first active layer away from the current collector for setting the pole lug
  • the thermal stability of the first active layer is greater than the thermal stability of the second active layer.
  • the first active layer with high thermal stability is arranged on the side of the current collector for setting the pole ear
  • the second active layer with poor thermal stability is arranged on the side of the current collector away from the pole ear, so as to reduce the risk of the pole ear contacting the second active layer with poor thermal stability, reduce the heat generation of the second active layer with poor thermal stability during the heat dissipation of the pole ear, and reduce the risk of thermal runaway, so as to improve the stability of the composite electrode.
  • the use of active layers with different thermal stabilities can solve the problem of reduced energy density of the active layer.
  • the following steps are included:
  • At least one first active material layer slurry, at least one third active material layer slurry and at least one second active material layer slurry are coated on the same surface of the current collector, the second active material layer slurry is arranged between the first active material layer slurry and the third active material layer slurry, and the thermal stability of the third active layer is greater than the thermal stability of the second active layer.
  • the first active layer and the third active layer with high thermal stability are arranged on the side of the current collector, and the second active layer with poor thermal stability is arranged near the middle of the current collector, so as to avoid the second active layer with poor thermal stability being arranged around the burrs, thereby reducing the above-mentioned risks.
  • the following steps are included:
  • the first active material layer slurry and the second active material layer slurry are simultaneously coated on the same surface of the current collector to form the first active layer and the second active layer on the current collector.
  • the first active material layer slurry and the second active material layer slurry need to be coated on the same side of the current collector at the same time. Because adjacent active layers are parallel, if one layer is coated and then another is coated, not only is the efficiency low, but the first layer will spread to the side, resulting in the width of the two layers being uncontrollable.
  • the third active material layer slurry needs to be coated, the first active material layer slurry, the third active material layer slurry, and the second active material layer slurry need to be coated at the same time.
  • the process of coating the first active material layer slurry and the second active material layer slurry on the same surface of the current collector further includes the following steps:
  • a primer is coated on one side of the current collector, and then the first active material layer slurry and the second active material layer slurry are coated on the primer.
  • a high-viscosity coating is applied on the current collector, and then the first active material layer slurry and the second active material layer slurry are applied to enhance the bonding force between the active material and the substrate.
  • the first active layer and the second active layer are cold pressed to the same thickness after being cold pressed, and the thickness is 80 ⁇ m-300 ⁇ m.
  • the first active layer and the second active layer are cold pressed to the same thickness, which is 80 ⁇ m-300 ⁇ m.
  • the drying temperature is 90°C-120°C
  • the cold pressing pressure is 20 tons-40 tons
  • the cold pressing temperature is 15°C-35°C.
  • the drying temperature is 90°C-120°C, for example, 90°C, 100°C, 110°C, 120°C.
  • the cold pressing pressure is 20 tons-40 tons, for example, 20 tons, 25 tons, 30 tons, 35 tons, 40 tons, and the range between any two of the above points. At the same time, cold pressing is performed at room temperature to simplify the operation.
  • the present application also provides a battery, comprising: a negative electrode plate, a positive electrode plate, a separator and an electrolyte, wherein the positive electrode plate is the composite electrode.
  • the battery prepared using the composite electrode has better cost performance.
  • the present application also provides an electrical device, which includes the battery.
  • the electrical equipment adopts the above cost-effective battery to improve the performance of the electrical equipment and increase its use value.
  • the composite electrode of the present application includes a current collector, a first active layer and a second active layer.
  • the first active layer is arranged on the surface of the current collector
  • the second active layer is arranged on the surface of the current collector and is located on the same surface of the current collector as the first active layer.
  • the thermal stability of the first active layer is different from the thermal stability of the second active layer. In theory, if the thermal stability of a material is high, the energy density of the material will be lower, and if the thermal stability of a material is poor, the energy density of the material will be higher.
  • the matching of active layers with different thermal stabilities can be achieved, avoiding the problem of simply using materials with high thermal stability, which will lead to reduced energy density although the thermal stability of the active layer is improved. At the same time, it also avoids the problem of simply using materials with high energy density, which will lead to poor thermal stability of the active layer although the energy density is improved.
  • the use of active layers with different thermal stabilities can solve the problem of reduced energy density of the active layer and improve stability at the same time.
  • FIG1 is a schematic diagram of a process for preparing a composite electrode of the present application.
  • FIG2 is a schematic flow chart of another method for preparing a composite electrode of the present invention.
  • FIG3 is a schematic diagram of the structure of the current collector of the present application.
  • FIG4 is a schematic diagram of the structure of the current collector of the present application.
  • FIG5 is a schematic structural diagram of an embodiment of a composite electrode of the present application.
  • FIG6 is a schematic structural diagram of another embodiment of the composite electrode of the present application.
  • FIG7 is a schematic diagram of the structure of the current collector of the present application.
  • FIG8 is a schematic structural diagram of another embodiment of the composite electrode of the present application.
  • FIG9 is a schematic structural diagram of another embodiment of the composite electrode of the present application.
  • FIG. 10 is a schematic structural diagram of another embodiment of the composite electrode of the present application.
  • connection can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined.
  • fixation can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined.
  • Batteries mentioned in this field can be divided into disposable batteries and rechargeable batteries according to whether they are rechargeable.
  • Common types of rechargeable batteries currently include: lead-acid batteries, nickel-metal hydride batteries and lithium-ion batteries.
  • Lithium-ion batteries are currently widely used in pure electric vehicles and hybrid vehicles. The capacity of lithium-ion batteries used for this purpose is relatively low, but they have larger output and charging current, and also have a longer service life, but the cost is higher.
  • the battery described in the embodiments of the present application refers to a rechargeable battery.
  • the embodiments disclosed in the present application will be described below mainly by taking a lithium-ion battery as an example. It should be understood that the embodiments disclosed in the present application are applicable to any other appropriate type of rechargeable battery.
  • the battery mentioned in the embodiments disclosed in the present application can be directly or indirectly applied to an appropriate device to power the device.
  • the battery mentioned in the embodiments disclosed in this application refers to a single physical module including one or more battery cells to provide a predetermined voltage and capacity.
  • Battery cells are the basic units in a battery, and can generally be divided into cylindrical battery cells, rectangular battery cells, and soft-pack battery cells according to the packaging method. The following will mainly focus on rectangular battery cells. It should be understood that the embodiments described below are also applicable to cylindrical battery cells or soft-pack battery cells in some aspects.
  • a battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator.
  • Lithium-ion battery cells mainly rely on the movement of lithium ions between the positive electrode sheet and the negative electrode sheet to work.
  • cylindrical battery cells the film structure of three layers of material is wound into a cylindrical electrode assembly, while in rectangular battery cells, the film structure is wound or stacked into an electrode assembly with a roughly rectangular shape.
  • the battery cell includes a shell, an electrode assembly and an electrolyte.
  • the electrode assembly is contained in the shell of the battery cell, and the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator.
  • the shell includes a shell and an end cap.
  • the shell includes a housing formed by a plurality of walls and an opening. The end cap is arranged at the opening to close the housing chamber.
  • the housing chamber also contains an electrolyte.
  • the positive electrode sheet and the negative electrode sheet in the electrode assembly include tabs. In order to ensure that a large current passes without melting, the number of positive tabs is multiple and stacked together, and the number of negative tabs is multiple and stacked together.
  • the tabs are electrically connected to the electrode terminals located outside the battery cell through connecting members, and the electrode terminals generally include a positive electrode terminal and a negative electrode terminal.
  • the electrode terminal is generally arranged at the end cap portion.
  • a plurality of battery cells are connected in series and/or in parallel via the electrode terminals for application in various applications.
  • the application of batteries includes three levels: battery cells, battery modules and batteries.
  • the battery module is formed by electrically connecting a certain number of battery cells together and placing them in a frame in order to protect the battery cells from external impact, heat, vibration, etc.
  • the battery refers to the final state of the battery system installed in the electric vehicle.
  • the battery generally includes a box for encapsulating one or more battery cells.
  • the box generally consists of a cover and a box shell.
  • a plurality of mounting points for connecting with the vehicle body are arranged on the frame of the box or in the middle of the box shell. In order to improve the stability of the connection between the vehicle body and the battery, mounting parts are often arranged at the mounting points.
  • multiple battery cells are first integrated into a battery module, and then the battery module is packaged in a battery box to form a battery pack/battery box.
  • Commonly used battery modules generally include two end plates, between which multiple battery cells are arranged.
  • the end plate with the output pole of the battery module is also called the output pole end plate, and the end plate without the output pole of the battery module is also called the non-output pole end plate.
  • a battery pack may contain multiple battery modules in one row or multiple rows.
  • the arrangement of multiple rows of multiple battery modules may be double rows and multiple columns, multiple rows and double columns, multiple rows and multiple columns, etc.
  • the first end plate of each column is generally a head output extreme plate
  • the two adjacent end plates between two rows of battery modules are middle non-output extreme plates
  • the last end plate of each column is a tail non-output extreme plate
  • the head output extreme plate and one of the middle non-output extreme plates belong to the first row of battery modules
  • one of the middle non-output extreme plates and the tail output extreme plate belong to the second row of battery modules.
  • the battery module needs to be packaged into the battery box with the help of tooling, which is generally equipped with a clamping mechanism for clamping the battery module, such as a clamping claw, a suction cup, etc.
  • a clamping claw groove that matches the clamping claw is generally provided on the side of the end plate away from the battery cell, so that the clamping claw can be inserted to clamp and transport the battery module.
  • the high energy density of batteries has always been a goal pursued in the battery field.
  • the stability of materials will decrease, so it is sometimes difficult to achieve both the high energy density and the stability of batteries.
  • the present application provides a composite electrode, aiming to provide a composite electrode that takes into account both high energy density and stability.
  • the composite electrode includes a current collector and a coating area formed on at least one side of the current collector.
  • the coating area includes a first active layer and a second active layer arranged along the same extension direction. The thermal stability of the first active layer is different from that of the second active layer.
  • Arranged along the same extension direction means that they can be arranged along the length direction of the current collector or along the width direction of the current collector, and there is no specific limitation.
  • the current collector refers to the structure or part that collects current. In lithium-ion batteries, it mainly refers to metal foil, such as copper foil and aluminum foil.
  • the current collector is used as a substrate to attach the positive or negative active material, and plays the role of collecting the current generated by the active material and outputting the current to the outside.
  • aluminum foil is used as the positive current collector
  • copper foil is used as the negative current collector.
  • the active layer refers to a coating structure including active materials, wherein the active material refers to the positive electrode active material involved in the positive electrode.
  • the positive electrode active material can use a compound that can reversibly embed and de-embed Li + (taking lithium secondary batteries as an example, of course, other types of secondary batteries can also be used).
  • the positive electrode active material may be a material that can reversibly intercalate and deintercalate Na + ).
  • the thermal stability of the active layer refers to the thermal stability of the material, which refers to the ability of the material to withstand temperature changes without being damaged. For example, below a certain temperature, the structure or composition of the active material in the active layer does not change, or the composition changes slightly, so that the active material can still maintain the corresponding function under the working environment. For example, for the cathode active material, the function of the material is to reversibly embed and deintercalate Li + ; above a certain temperature, the structure or composition of the active material in the active layer changes, for example, the structure collapses, or the material undergoes chemical changes, generating heat, making it difficult to maintain the normal function of the active material.
  • the thermal stability of the material can be tested by a differential scanning calorimeter (DSC).
  • the parameters of the differential scanning calorimeter are set as follows: under a nitrogen atmosphere, the purge gas is 50 ml/min, the protective gas is 20 ml/min, and the temperature rise program is 10°C/min, from 35°C to 600°C.
  • the sample preparation steps are: weigh about 10 mg of the sample in an Al 2 O 3 crucible and shake it flat.
  • the above test method can be used to obtain the changes in the structure and composition of the material. Under the same test conditions, the structure and composition of the two materials are more sensitive to temperature, indicating that the material has poor thermal stability.
  • high thermal stability refers to the material's ability to withstand temperature damage and high heat resistance.
  • the heat resistance temperature of materials with high thermal stability is higher than that of materials with poor thermal stability.
  • the thermal stability of the first active layer is greater than the thermal stability of the second active layer, which means that the heat resistance temperature of the active material in the first active layer is higher than the heat resistance temperature of the active material in the second active layer.
  • the composite electrode includes a current collector 10, a first active layer 20 and a second active layer 40.
  • the first active layer 20 is arranged on the surface of the current collector 10 and is close to the side of the current collector 10 for setting the pole ear 30.
  • the second active layer 40 is arranged on the surface of the current collector 10 and is located on the same surface of the current collector 10 as the first active layer 20, and is located on the side of the first active layer 20 away from the current collector 10 for setting the pole ear 30.
  • the thermal stability of the first active layer 20 is greater than the thermal stability of the second active layer 40.
  • the battery is divided into positive and negative poles, and the tabs are metal conductors that lead the positive and negative poles out of the battery cell.
  • the tabs at the positive and negative poles of the battery are the contact points during charging and discharging.
  • the thermal stability of the first active layer is greater than that of the second active layer, which means that the temperature at which the active material in the first active layer undergoes structural or property changes is higher than the temperature at which the active material in the second active layer undergoes structural or property changes.
  • the first active layer with high thermal stability on the side of the current collector for arranging the pole ear and arranging the second active layer with poor thermal stability on the side of the current collector away from the pole ear, the risk of the pole ear contacting the second active layer with poor thermal stability is reduced, and the heat generation of the second active layer with poor thermal stability during the heat dissipation of the pole ear and the risk of thermal runaway are reduced, thereby improving the stability of the composite electrode.
  • a tab 30 is provided on one side of the current collector 10 , and the first active layer 20
  • the second active layer 40 is arranged on one side of the current collector 10 close to the pole tab 30, and the second active layer 40 is arranged on the other side of the current collector to prevent the second active layer from directly contacting the pole tab 30. It is understandable that during the operation of the battery, the pole tab 30 will generate heat. If the active layer cannot withstand the heat generated by the pole tab 30, the active material in the active layer will change its structure or characteristics after receiving the heat generated by the pole tab 30, such as generating heat, or even thermal runaway, and the risk of fire.
  • At least three coating areas are formed on the surface of the current collector, at least two coating areas are used to respectively set the first active layer and the third active layer, and at least another coating area is used to set the second active layer, and the second active layer is located between the first active layer and the third active layer, and the thermal stability of the third active layer is greater than the thermal stability of the second active layer.
  • burrs will inevitably appear on the edge of the current collector during the cutting process. Such burrs may pierce the diaphragm due to the change in the expansion force of the pole piece during the working process of the electrode, inducing a micro short circuit in the cell.
  • the micro short circuit will intensify the local reaction of the cathode, release a large amount of heat, and further cause the diaphragm to shrink, thereby causing a larger short circuit and heat generation, and even accidents such as fire and explosion.
  • the heat generated by the micro short circuit of the cell is not very high at the beginning, that is, for materials with good thermal stability around the burr, the heat generated by the micro short circuit of the cell at the beginning is difficult to cause heat generation and thermal runaway of the materials around the burr.
  • the risk of battery accidents is reduced, but for materials with poor thermal stability around the burr, the heat generated by the micro short circuit of the cell is easy to cause heat generation and even thermal runaway of the materials around the burr. In this way, it is easier to cause the local reaction of the cathode to intensify, release a large amount of heat, and produce more serious consequences. At this time, the risk of battery accidents increases.
  • the first active layer and the third active layer with high thermal stability are arranged on the sides of the current collector, and the second active layer with poor thermal stability is arranged near the middle of the current collector, so as to avoid the second active layer with poor thermal stability being arranged around the burrs, thereby reducing the above-mentioned risks.
  • three active coating regions 13 are provided on the current collector 10, wherein the two active coating regions 13 located at the edges are used to coat the slurry of the first active layer 20 and the third active layer 50, and the middle active coating region 13 is used to coat the slurry of the second active layer 40.
  • This design can better balance the high energy density and stability issues. It can be understood that the width of the two first active layers 20 The degrees can be the same or different, and there is no specific limitation.
  • first active layer and the third active layer are made of the same material; or, the first active layer and the third active layer are made of different materials.
  • the thermal stability of the first active layer and the third active layer higher than that of the second active layer.
  • the materials of the first active layer and the third active layer can be the same or different.
  • the total heat release of the first active layer and the total heat release of the third active layer are respectively smaller than the total heat release of the second active layer.
  • the total heat release is a parameter obtained by testing the thermal changes of the material using a differential scanning calorimeter (DSC). It is obtained by integrating the heat release curve. A low total heat release indicates that the material has good thermal stability.
  • the parameters of the differential scanning calorimeter are set as follows: under nitrogen atmosphere, purge gas 50ml/min, protective gas 20ml/min, temperature rise program 10°C/min, from 35°C to 600°C.
  • the sample preparation steps are as follows: weigh about 10mg of the sample in an Al2O3 crucible and shake it flat.
  • the total heat release of the first active layer and the third active layer is selected to be smaller than the total heat release of the second active layer, thereby reducing the risk of large amounts of heat generation and the risk of fire caused by large amounts of heat generation.
  • the total heat release of the first active layer ranges from 100 J/g to 500 J/g
  • the total heat release of the third active layer ranges from 100 J/g to 500 J/g
  • the total heat release of the second active layer ranges from 800 J/g to 1500 J/g.
  • the range value of the total heat release of the first active layer is 100J/g-500J/g, for example, it can be 100J/g, 200J/g, 300J/g, 400J/g, 500J/g, etc., and the range value between any two of the above point values
  • the range value of the total heat release of the third active layer is 100J/g-500J/g, for example, it can be 100J/g, 200J/g, 300J/g, 400J/g, 500J/g, and the range value between any two of the above point values.
  • the second active layer is located in a relatively stable position in the current collector. Therefore, taking into account the need to increase energy density, the total heat release of the second active layer ranges from 800 J/g to 1500 J/g. For example, it can be 800 J/g, 900 J/g, 1000 J/g, 1100 J/g, 1200 J/g, 1300 J/g, 1400 J/g, 1500 J/g, etc., as well as the range between any two of the above point values.
  • the failure temperature of the battery cell formed by the first active layer is greater than the failure temperature of the battery cell formed by the second active layer; the failure temperature of the battery cell formed by the third active layer is greater than the failure temperature of the battery cell formed by the second active layer.
  • Failure temperature refers to the ambient temperature of the battery cell when it fails. The higher the failure temperature, the better the thermal stability of the material of the corresponding active layer.
  • the cell composed of active layer refers to the cell composed of electrodes composed of active layer, which are assembled into batteries under the same conditions, and the ambient temperature of the cell is tested when the cell has thermal runaway. Except for the positive electrode, the other conditions of the components of the cell are the same. For example, other conditions include electrolyte, negative electrode plate, etc. These components are the same.
  • the test method of the failure temperature of the battery can be that the battery is charged at a rate of 0.33C at room temperature until the voltage is equal to 4.2V, and then charged at a constant voltage CV to 0.05C current cutoff.
  • the single cell fixture is tightened, 5°C/min, placed in a 55°C environment for 2h, and then at a temperature rise rate of 5°C/min, maintained for 30min every 5°C, from 55°C to the cell runaway, and data is recorded for 1s.
  • the temperature when the cell runs away is recorded as Tf.
  • the failure temperature of the battery cell formed by the first active layer is 160°C-220°C
  • the failure temperature of the battery cell formed by the third active layer is 160°C-220°C
  • the failure temperature of the battery cell formed by the second active layer is 120°C-160°C.
  • the failure temperature of the first active layer is 160°C-220°C, for example, it can be 160°C, 170°C, 180°C, 190°C, 1200°C, 210°C, 220°C, etc., and the range value between any two of the above point values.
  • the failure temperature of the battery cell composed of the third active layer is 160°C-220°C, for example, it can be 160°C, 170°C, 180°C, 190°C, 1200°C, 210°C, 220°C, etc., and the range value between any two of the above point values.
  • the material of the first active layer and the third active layer can be lithium iron manganese phosphate or lithium iron phosphate and a mixture of the two.
  • the failure temperature of the battery cell composed of the second active layer is 120°C-160°C.
  • it can be 120°C, 130°C, 140°C, 150°C, 160°C, etc., and the range value between any two of the above point values.
  • the material of the second active layer can be a ternary material or lithium cobalt oxide, or a mixture of the two.
  • an insulating layer coating region is preset on one side of the current collector for arranging the pole ear, and the first active layer covers the insulating layer coating region.
  • An insulating layer coating area is provided on the side of the current collector located at the pole ear, for providing an insulating layer, so as to reduce the risk of the pole ear being bent and inserted into the active layer, thereby reducing the risk of causing the active layer to absorb the heat generated by the pole ear, causing the active layer to generate heat, and even thermal runaway.
  • the first active layer is provided close to the pole ear, thereby reducing the risk of the first active layer generating heat due to absorbing the heat of the pole ear. Therefore, by using the first active layer to cover the insulating layer coating area, the coating amount of the first active layer can be increased, thereby improving the energy density.
  • an insulating layer coating region 11 is preset on one side of the current collector 10 close to the electrode tab 30 , and the insulating layer 60 is disposed in the insulating layer coating region 11 .
  • the first active layer 20 is used to cover the insulating layer coating region 11 .
  • the coating area of the first active layer 20 is increased to improve the energy density of the composite electrode.
  • both sides of the current collector are used to set the pole lugs
  • the other side of the current collector for setting the pole lugs is preset with an insulating layer coating area
  • the third active layer covers the insulating layer coating area
  • an insulating layer coating area is preset on the other side of the current collector for providing the tabs.
  • the third active layer covers the insulating layer coating area on the other side of the current collector.
  • the third active layer since the third active layer has good thermal stability, it helps to reduce the risk of heat generation by the third active layer due to absorbing heat from the tabs.
  • the width ratio of the first active layer to the second active layer is 0.25-4.
  • the width ratio of the first active layer to the second active layer is 0.25-4.
  • it can be 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4, etc., as well as the range value between any two of the above point values.
  • the width ratio of the sum of the first active layer and the third active layer to the second active layer is 0.25-4.
  • the width ratio of the sum of the first active layer and the third active layer to the second active layer is 0.25-4.
  • it can be 0.25, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4, etc., as well as the range value between any two of the above point values.
  • the width of the first active layer accounts for 20%-80% of the total width of the active layer; and/or the width of the second active layer accounts for 20%-80% of the total width of the active layer.
  • the total width of the active layer refers to the sum of the widths of all active layers on one surface of the current collector.
  • the width of the first active layer accounts for 20%-80% of the total width of the active layer, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range between any two of the above points.
  • the width of the second active layer accounts for 20%-80% of the total width of the active layer, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range between any two of the above points.
  • the sum of the widths of the first active layer and the third active layer accounts for 20%-80% of the total width of the active layer; and/or the width of the second active layer accounts for 20%-80% of the total width of the active layer.
  • the sum of the widths of the first active layer and the third active layer accounts for 20%-80% of the total width of the active layer, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range between any two of the above points.
  • the width of the second active layer accounts for 20%-80% of the total width of the active layer, for example, it can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range between any two of the above points.
  • the width of the first active layer is greater than 3 mm.
  • the width of the first active layer is greater than 3 mm; on the other hand, the width of the insulating layer currently coated on the current collector is about 3 mm-3.5 mm. In order to make the first active layer cover the coating area of the insulating layer, the width of the first active layer is selected to be greater than 3 mm.
  • the width of the third active layer is greater than 3 mm.
  • the width of the third active layer is greater than 3 mm; on the other hand, the width of the insulating layer currently coated on the current collector is about 3 mm-3.5 mm. In order to make the third active layer cover the coating area of the insulating layer, the width of the third active layer is selected to be greater than 3 mm.
  • the gram capacity of the first active layer and the gram capacity of the third active layer are respectively smaller than the gram capacity of the second active layer.
  • the gram capacity of materials with good thermal stability is smaller than that of materials with poor thermal stability. Since the thermal stability of the first active layer and the third active layer is greater than that of the second active layer, the gram capacity of the first active layer and the third active layer is smaller than that of the second active layer.
  • lithium deposition refers to the lithium ions that reach the negative electrode from the positive electrode and directly form lithium on the negative electrode surface due to abnormal conditions. And lithium deposition is more likely to occur on the side of the negative electrode.
  • CB total capacity of the negative electrode / total capacity of the positive electrode.
  • this value is greater than 1.
  • This solution adopts coating the side of the positive electrode with a low-capacity first active layer. In this way, the CB value on the side of the battery cell is low, reducing the lithium deposition phenomenon on the negative electrode side.
  • the gram capacity of the first active layer and the gram capacity of the third active layer account for 60%-80% of the gram capacity of the second active layer respectively.
  • the thermal stability of the first active layer and the third active layer is greater than the thermal stability of the second active layer, the gram capacity of the first active layer and the third active layer is respectively less than the gram capacity of the second active layer, the gram capacity of the first active layer accounts for 60%-80% of the gram capacity of the second active layer, and the gram capacity of the third active layer accounts for 60%-80% of the gram capacity of the second active layer, for example, it can be 60%, 70%, 80%, if the gram capacity of the first active layer and the third active layer respectively accounts for too low the gram capacity of the second active layer, it will lead to too low energy density, and it cannot be too high, which will reduce thermal stability.
  • the materials of the first active layer and the third active layer can include lithium iron manganese phosphate, lithium iron phosphate, or a mixture of the two
  • the material of the second active layer can include ternary materials, lithium cobalt oxide, or a mixture of the two.
  • the average particle size Dv50 of the active material in the first active layer and the average particle size Dv50 of the active material in the third active layer are respectively 0.2 um-2 um.
  • the average particle size Dv50 of the material can be 0.2um, 0.3um, 0.4um, 0.5um, 0.6um, 0.7um, 0.8um, 0.9um, 1um, 1.2um, 1.4um, 1.6um, 1.8um, 2um, etc., and the range value between any two of the above point values.
  • the material can be lithium iron manganese phosphate material, which has poor ion conductivity. Setting the particle size within the above range is conducive to improving the kinetic performance of the material.
  • the average particle size Dv50 of the active material in the second active layer is in the range of 0.5 um to 20 um.
  • the average particle size Dv50 of the material in the second active layer can be 0.5um, 1um, 2um, 3um, 4um, 5um, 6um, 7um, 8um, 9um, 10um, 11um, 12um, 13um, 14um, 15um, 16um, 17um, 18um, 19um, 20um, and the range between any two of the above point values.
  • the first active layer, the second active layer, and the third active layer have the same thickness.
  • the first active layer, the third active layer and the second active layer are cold pressed to the same thickness after being cold pressed.
  • the thickness of the first active layer, the second active layer and the third active layer is 80 ⁇ m-300 ⁇ m.
  • the thickness of the first active layer, the second active layer and the third active layer ranges from 80 ⁇ m to 300 ⁇ m, for example, 80 ⁇ m, 100 ⁇ m, 150 ⁇ m, 180 ⁇ m, 200 ⁇ m, 250 ⁇ m, 280 ⁇ m, 300 ⁇ m, etc., and the range between any two of the above point values.
  • the first active layer includes lithium manganese iron phosphate material.
  • ternary lithium compounds There are currently two main types of cathode materials for commercial lithium-ion batteries: ternary lithium compounds and lithium iron phosphate LFP.
  • the advantage of ternary materials is high energy density, which is suitable for long-range vehicles, but the disadvantage is that elements such as cobalt and nickel are relatively expensive and are more likely to cause thermal runaway fires.
  • lithium iron phosphate does not contain rare transition metal elements and is cheaper.
  • the low energy density of lithium iron phosphate will result in a short driving range. In this context, it is particularly important to develop a material with high energy density and low cost. Lithium manganese iron phosphate LMFP is such a new material.
  • the crystal structure of lithium manganese iron phosphate material is the same as that of lithium iron phosphate, both of which belong to the olivine crystal type. The difference is that on the basis of lithium iron phosphate, Mn atoms are used to partially replace Fe atoms. Mn atoms are atoms with strong electrochemical activity and are often used in ternary lithium battery positive electrode materials. They have a higher voltage during the charging and discharging process, which means that storing the same number of lithium ions can provide more energy. The energy density of lithium manganese iron phosphate material is greatly improved compared to lithium iron phosphate.
  • the first active layer includes lithium manganese iron phosphate material, which is beneficial to improving energy density.
  • the lithium manganese iron phosphate material is provided with a conductive coating material.
  • Coating refers to coating the surface of a material with conductive material to improve conductivity.
  • the coating material refers to the material coated on the surface of lithium manganese iron phosphate, such as carbon material coated on the surface of lithium manganese iron phosphate particles.
  • a coating material is provided on the lithium manganese iron phosphate material.
  • the mass of the conductive coating material is 1%-10% of the mass of the lithium iron manganese phosphate material; and/or the conductive coating material includes at least one of carbon or metal oxide.
  • the mass of the coating material is 1.0%-10.0% of the mass of the lithium manganese iron phosphate material, for example, it can be 1.0%, 2.0%, 3.0%, 4.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, 10.0%, and the range between any two of the above point values.
  • the conductive coating material includes at least one of carbon or metal oxide, for example, it can be carbon, it can be metal oxide, or it can be a mixture of the two, without specific limitation, and of course it can also be other materials with conductive properties.
  • the first active layer also includes a ternary material, and the mass of the lithium manganese iron phosphate material accounts for 20%-80% of the total mass of the first active layer.
  • ternary positive electrode materials are layered nickel cobalt manganese (aluminum) lithium oxide composite materials.
  • Nickel, cobalt, and manganese are transition metal elements.
  • the solid solution formed can be mixed in any proportion.
  • the increase in the proportion of nickel elements can improve the battery specific energy
  • the increase in the proportion of manganese elements can ensure structural stability
  • the increase in the proportion of cobalt elements can stabilize the material layered structure, which is beneficial to the battery's cycle performance and rate performance.
  • ternary materials can also include materials that do not contain cobalt, for example, ternary materials obtained by using other metal elements instead of cobalt.
  • the first active layer also includes ternary materials, and the mass of lithium manganese iron phosphate material accounts for 20%-80% of the total mass of an active layer.
  • the mass of the lithium iron manganese phosphate material can account for 20%, 30%, 40%, 50%, 60%, 70%, 80% of the total mass of the first active layer.
  • the mass of the lithium iron manganese phosphate material cannot be too low or too high. If the mass of the lithium iron manganese phosphate material is too low, the mass of the ternary material will be too high. If the mass of the lithium iron manganese phosphate material is too high, the mass of the ternary material will be too low and the energy density will be insufficient.
  • the general structural formula of the lithium manganese iron phosphate material is LiMnxFeyM1 -xyPO4 , wherein 0.4 ⁇ x ⁇ 0.8; 0.1 ⁇ y ⁇ 0.6; 0 ⁇ 1-xy ⁇ 0.2, and M represents a doping element, optionally including at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge.
  • the general structural formula of lithium iron manganese phosphate material is LiMn x Fe y M 1-xy PO 4 , wherein 0.4 ⁇ x ⁇ 0.8; 0.1 ⁇ y ⁇ 0.6; 0 ⁇ 1-xy ⁇ 0.2, and M represents a doping element, which may optionally include at least one of Al, Cu, Mg, Zn, Ni, Ti, V, Zr, Co, Ga, Sn, Sb, Nb and Ge.
  • the molar proportion of manganese in the lithium iron manganese phosphate material is 20%-80%, and the performance is relatively good.
  • the molar proportion of manganese in the lithium iron manganese phosphate material can be 20%, 30%, 40%, 50%, 60%, 70%, 80%, and the range value between any two of the above-mentioned points.
  • the second active layer includes at least one of a ternary material or lithium cobalt oxide.
  • Lithium cobalt oxide is an inorganic compound with the chemical formula LiCoO 2 , which is generally used as the positive electrode material of lithium-ion batteries.
  • the gram capacity of ternary materials is much higher than that of lithium iron manganese phosphate.
  • Using ternary materials as the second active layer can improve the overall energy density of the electrode. Energy density is the core indicator of power batteries, especially for lithium iron manganese phosphate systems. Only when the energy density exceeds that of lithium iron phosphate can it have application potential.
  • ternary materials From the perspective of energy density alone, it would be more advantageous to use all ternary materials.
  • the crystal structure of ternary materials releases oxygen, which poses a high risk of thermal runaway.
  • the edges of the substrate are generally cut by laser or mechanical die-cutting, which inevitably results in some metal burrs, which can easily lead to micro-short circuits, thus inducing thermal runaway or even fire.
  • the energy density of the composite electrode is regulated by regulating the materials of the first active layer and the second active layer, thereby achieving a high energy density and low cost battery cell.
  • the second active layer includes at least one of a ternary material or lithium cobalt oxide.
  • the second active layer may include a ternary material or lithium cobalt oxide.
  • the second active layer may also include a mixture of a ternary material and lithium cobalt oxide. The specific details are not limited. Of course, in addition to the ternary material and lithium cobalt oxide, the second active layer may also include other high energy density positive electrode materials.
  • this design can improve the energy density of the battery cell and make the energy density customizable; in addition, compared with pure ternary materials, the increased LMFP content can reduce the risk of fire of ternary materials. At the same time, since the cost of ternary materials is relatively high, the composite electrode of the present application can also reduce costs and improve cost performance.
  • the general structural formula of the ternary material is LiNi a Co b N (1-ab) O 2 , wherein N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.35 ⁇ a ⁇ 1.0, 0 ⁇ b ⁇ 0.35, and 0 ⁇ 1-ab ⁇ 0.35.
  • the general structural formula of the ternary material is LiNi a Co b N (1-ab) O 2 , wherein N optionally includes at least one of Mn, Zr, Al, B, Ta, Mo, W, Nb, Sb, and La, wherein 0.35 ⁇ a ⁇ 1.0, 0 ⁇ b ⁇ 0.35, and 0 ⁇ 1-ab ⁇ 0.35.
  • the ternary material can be divided into low-nickel ternary material, medium-nickel ternary material, and high-nickel ternary material.
  • the ternary material can also be divided into cobalt-free ternary material, wherein the cobalt element can be replaced by other metal elements.
  • the specific type of the ternary material is not limited.
  • the general structural formula of the ternary material is LiNi a Co b N (1-ab) O 2 , wherein 0.5 ⁇ a ⁇ 0.96.
  • the molar content of Ni element in the ternary material is selected to account for 50%-96% of the total molar content of other metal elements except lithium. For example, it can be 50%, 60%, 70%, 80%, 90%, 96%, etc., as well as the range value between any two of the above point values.
  • the ternary material includes at least one of 5-series single crystal ternary material, 5-series polycrystalline ternary material, 6-series single crystal ternary material, 6-series polycrystalline ternary material, 7-series single crystal ternary material, 7-series polycrystalline ternary material, 8-series single crystal ternary material, 8-series polycrystalline ternary material, 9-series single crystal ternary material, 9-series polycrystalline ternary material, and cobalt-free ternary material.
  • 5 series ternary materials refer to ternary materials with a molar ratio of nickel metal greater than or equal to 50% and less than 60%.
  • 6 series ternary materials refer to ternary materials with a molar ratio of nickel metal greater than or equal to 60% and less than 70%.
  • 7 series ternary materials refer to ternary materials with a molar ratio of nickel metal greater than or equal to 70% and less than 80%.
  • 8 series ternary materials refer to ternary materials with a molar ratio of nickel metal greater than or equal to 80% and less than 90%.
  • 9 series ternary materials refer to ternary materials with a molar ratio of nickel metal greater than or equal to 90%, such as Ni90, Ni92, Ni95, etc. As the nickel content gradually increases, the battery energy density also increases.
  • the medium nickel ternary material has a relatively high nickel content, a low nickel content, and a high cobalt content, so the material stability is improved.
  • single crystal materials generate less heat and have high stability, so their stability performance is much higher than that of high nickel materials.
  • Nickel ternary in single crystals has currently achieved a good balance in multiple dimensions such as economy, stability, energy density, and cycle life.
  • Cobalt-free ternary materials refer to ternary materials that do not contain cobalt, for example, ternary materials in which the cobalt element can be replaced by other elements.
  • Single crystal ternary materials and polycrystalline ternary materials are named according to the morphology of the materials themselves. From the morphology point of view, single crystal is a single dispersed particle, while the corresponding polycrystalline ternary material is a secondary particle of primary particle agglomeration.
  • single crystal materials are more suitable for high voltage. At the same time, there are no grain boundaries inside single crystal materials, which can improve the circulation of ternary materials. Stability, for extending the cycle life of the battery. Under the same ratio of nickel, cobalt and manganese, the gram capacity of single crystal ternary materials is slightly lower than that of polycrystalline ternary materials, but because of its higher voltage, the overall energy density of the material is already similar to that of the current high-nickel ternary materials. The disadvantage of single crystal ternary materials is that the rate performance is not good, the production process is more complicated, and the material price is relatively high.
  • the ternary material in the present application is not specifically limited, and can be at least one of 5-series single crystal ternary material, 5-series polycrystalline ternary material, 6-series single crystal ternary material, 6-series polycrystalline ternary material, 7-series single crystal ternary material, 7-series polycrystalline ternary material, 8-series single crystal ternary material, 8-series polycrystalline ternary material, 9-series single crystal ternary material, 9-series polycrystalline ternary material, or cobalt-free ternary material.
  • both the first active layer and the second active layer include ternary materials
  • the ternary materials in the first active layer and the second active layer are the same.
  • the ternary materials in the first active layer and the second active layer can be the same or different, but it is best to be the same.
  • the advantage of being the same is that the lithium insertion amounts of the two active layers are similar and the expansion degrees are the same, which is beneficial to the stability of the electrode.
  • the first active layer includes a first active material, a conductive agent and a binder
  • the first active material includes a lithium iron manganese phosphate material
  • the mass of the lithium iron manganese phosphate material accounts for 94%-97% of the total mass of the first active layer
  • the second active layer includes a second active material, a conductive agent and a binder
  • the second active material includes a ternary material, and the ternary material accounts for 95%-98% of the total mass of the second active layer.
  • the first active layer includes a first active material, a conductive agent and a binder.
  • the first active material includes a lithium iron manganese phosphate material.
  • the mass of the lithium iron manganese phosphate material accounts for 94%-97% of the total mass of the first active layer.
  • the lithium iron manganese phosphate material is within this range (for example, it can be 94%, 95%, 96%, 97%, and the range value between any two of the above point values), and an active layer with excellent performance can be prepared, wherein the binder content can be 1.8%, 2%, 2.5%, 3%, etc., and the conductive agent content can be 1.8%, 2%, 2.5%, etc.
  • the second active layer includes a second active material, a conductive agent and a binder, the second active material includes a ternary material, the ternary material accounts for 95%-98% of the total mass of the second active layer, and the ternary material is within this range (95%, 96%, 97%, 98%, and the range value between any two of the above point values) to prepare an active layer with excellent performance, wherein the binder content can be 1.5%, 2%, 2.5%, etc., and the conductive agent content can be 1.8%, 2%, 2.5%, etc.
  • Too little conductive agent will lead to poor conductivity, and too much will lead to reduced energy density.
  • a moderate amount of binder can prevent the coating from falling off and has good heat resistance. Too little will lead to insufficient adhesion, and too much will lead to excessive slurry viscosity.
  • the present application also provides a method for preparing a composite electrode, comprising the following steps: coating a first active material layer slurry and a second active material layer slurry on the same surface of a current collector to form a first active layer and a second active layer on the current collector; after drying, cold pressing to obtain a composite electrode; wherein the thermal stability of the first active layer is different from the thermal stability of the second active layer.
  • the first active material layer slurry refers to a slurry used to prepare a first active layer
  • the second active material layer slurry refers to a slurry used to prepare a second active layer
  • Drying refers to the process of evaporating the solvent in the slurry and removing the solvent. This allows the pole piece to have a lower solvent content. If the solvent content is too high, the lithium battery will consume excessive lithium during the formation stage, causing irreversible loss of lithium, resulting in reduced capacity, battery bloating and other problems, affecting battery performance.
  • Cold pressing refers to compressing the electrode pole piece. After the positive electrode coating is dried, it is necessary to roll the pole piece during the process time. Rolling means compacting the pole piece.
  • Hot pressing compaction is higher than cold pressing, and the rebound rate is lower, which can reduce the rolling force; but the cold pressing process is relatively simple and easy to operate and control.
  • the main equipment of the roller reaches the following process values, compaction density, rebound rate, and elongation. At the same time, it should be noted that there are no brittle pieces, hard lumps, falling materials, wavy edges, etc. on the surface of the pole piece, and no fractures are allowed in the gap.
  • the pole piece rolling process can reduce the elongation and width of the pole piece during the rolling process, reduce the destruction rate of the pore structure of the pole piece coating material; improve the thickness consistency of the pole piece coating to improve the cross-sectional shape of the pole piece; improve the compaction density consistency of the electrode material after the pole piece is rolled; and reduce the rebound of the electrode material on the surface after the pole piece is rolled.
  • the pole piece rolling process can also ensure that the pole piece surface is smooth and flat, prevent burrs on the coating surface from piercing the diaphragm and causing a short circuit; compact the pole piece coating material to reduce the volume of the pole piece to increase the energy density of the battery; make the active material and conductive agent particles in closer contact to improve electronic conductivity; enhance the bonding strength between the coating material and the current collector, reduce the occurrence of powder loss of the electrode during the cycle, and improve the cycle life and stability of the battery.
  • two rollers can be used to compress the pole piece, so that friction is generated between the roller and the battery pole piece; the battery pole piece is pulled into the rotating roller pair, and the battery pole piece is compressed and deformed.
  • the rolling of the battery pole piece is the process of compacting the battery material on the positive and negative pole pieces, which can increase the compaction density of the positive or negative electrode material.
  • the appropriate compaction density can increase the discharge capacity of the battery, reduce the internal resistance, reduce the polarization loss, extend the cycle life of the battery, and improve the utilization rate of the lithium-ion battery.
  • FIG. 1 it is a schematic diagram of the process of preparing a composite electrode.
  • the first active material layer slurry and the second active material layer slurry are coated on the same surface of the current collector to form a During the process of forming the first active layer and the second active layer, the first active layer is close to the side of the current collector for setting the pole ear, and the second active layer is located on the side of the first active layer away from the current collector for setting the pole ear.
  • the thermal stability of the first active layer is greater than that of the second active layer.
  • FIG. 2 it is a schematic diagram of the process of preparing the composite electrode.
  • the first active layer with high thermal stability is set on the side of the current collector for setting the pole ear
  • the second active layer with poor thermal stability is set on the side of the current collector away from the pole ear, which reduces the risk of the pole ear contacting the second active layer with poor thermal stability, reduces the heat generation of the second active layer with poor thermal stability during the heat dissipation of the pole ear, and reduces the risk of thermal runaway.
  • the use of active layers with different thermal stabilities solves the problem of reduced energy density of the active layer.
  • the following steps are included: coating at least one first active material layer slurry, at least one third active material layer slurry and at least one second active material layer slurry on the same surface of the current collector, the second active material layer slurry is arranged between the first active material layer slurry and the third active material layer slurry, and the thermal stability of the third active layer is greater than the thermal stability of the second active layer.
  • the first active layer and the third active layer with high thermal stability are arranged on the side of the current collector, and the second active layer with poor thermal stability is arranged near the middle of the current collector, so as to avoid the second active layer with poor thermal stability being arranged around the burrs, thereby reducing the above-mentioned risks.
  • the following steps are included: simultaneously coating the first active material layer slurry and the second active material layer slurry on the same surface of the current collector to form the first active layer and the second active layer on the current collector.
  • the first active material layer slurry and the second active material layer slurry need to be coated on the same side of the current collector at the same time. Because adjacent active layers are parallel, if one layer is coated and then another is coated, not only is the efficiency low, but the first layer will spread to the side, resulting in the width of the two layers being uncontrollable.
  • the third active material layer slurry needs to be coated, the first active material layer slurry, the third active material layer slurry, and the second active material layer slurry need to be coated at the same time.
  • the process of coating the first active material layer slurry and the second active material layer slurry on the same surface of the current collector also includes the following steps: coating a primer on one surface of the current collector, and then coating the first active material layer slurry and the second active material layer slurry on the primer.
  • Primer refers to a high-adhesion coating used to enhance the adhesion between the active material layer and the current collector.
  • a high-viscosity coating is applied on the current collector, and then the first active material layer slurry and the second active material layer slurry are applied to enhance the bonding force between the active material and the substrate.
  • the first active layer and the second active layer are cold pressed to the same thickness, which is 80 ⁇ m-300 ⁇ m.
  • the first active layer and the second active layer are cold pressed to the same thickness, which is 80 ⁇ m-300 ⁇ m.
  • the drying temperature is 90°C-120°C
  • the cold pressing pressure is 20 tons-40 tons
  • the cold pressing temperature is 15°C-35°C.
  • the drying temperature is 90°C-120°C, for example, 90°C, 100°C, 110°C, 120°C.
  • the cold pressing pressure is 20 tons-40 tons, for example, 20 tons, 25 tons, 30 tons, 35 tons, 40 tons, and the range between any two of the above points. At the same time, cold pressing is performed at room temperature to simplify the operation.
  • the present application also provides a battery, including: a negative electrode sheet, a positive electrode sheet, a separator and an electrolyte, wherein the positive electrode sheet is the composite electrode described above. Since the composite electrode adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments, which will not be described one by one here.
  • the battery prepared using the composite electrode has better cost performance.
  • the present application also provides an electrical device, which includes the above-mentioned battery. Since the battery adopts all the technical solutions of all the above-mentioned embodiments, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiments, which will not be described one by one here.
  • the electrical equipment adopts the above cost-effective battery to improve the performance of the electrical equipment and increase its use value.
  • First active material layer slurry The positive electrode active material lithium manganese iron phosphate, conductive carbon black, binder PVDF and solvent N-methylpyrrolidone (NMP) are uniformly stirred at a weight ratio of 96:2:2:100 to obtain a uniformly mixed first active material layer slurry.
  • NMP solvent N-methylpyrrolidone
  • Second active material layer slurry The positive electrode active material five-series single crystal ternary material, conductive carbon black, binder PVDF and solvent N-methylpyrrolidone (NMP) are uniformly stirred at a weight ratio of 96:2:2:100 to obtain a uniformly mixed second active material layer slurry; the first active material layer slurry and the second active material layer slurry are uniformly coated on a 13um thick aluminum foil current collector at the same time, and then baked at 110°C Dry. After cold pressing at a pressure of 20-40 tons, a membrane with a coating thickness of about 90um can be obtained.
  • the width ratio of the first active layer to the width of the second active layer is 1:1, and the second active layer is located in the middle of the current collector, and the first active layer is located on both sides of the current collector.
  • Ethylene carbonate (EC), polycarbonate (PC), and dimethyl carbonate (DMC) are mixed in a volume ratio of 1:1:1, and then LiPF 6 is uniformly dissolved in the above solution to obtain an electrolyte.
  • the concentration of LiPF 6 is 1 mol/L.
  • the positive electrode sheets, separators, and negative electrode sheets in the above-mentioned embodiments or comparative examples are stacked and wound in order to obtain an electrode assembly; the electrode assembly is placed in an outer package, and the above-prepared electrolyte is added. After packaging, standing, formation, aging and other processes, a secondary battery is obtained.
  • Example 1 On the basis of Example 1, with other conditions unchanged, the experimental parameters were changed (as shown in Table 1) to obtain the experimental data of Examples 2 to 11 and Comparative Example 1.
  • Each battery is charged at a rate of 0.33C to a voltage of 4.2V at room temperature, and then discharged at a rate of 0.33C to a voltage of 2.0V.
  • the reversible capacity is measured as C0.
  • the total number of cycles is then recorded as X-Cycle.
  • the test was conducted by differential scanning calorimetry (DSC), and the parameters of the differential scanning calorimeter were set as follows: under nitrogen atmosphere, purge gas 50 ml/min, protective gas 20 ml/min, temperature rise program 10 ° C/min, from 35 ° C to 600 ° C.
  • the sample preparation steps are as follows: cut a certain amount of active layer, weigh about 10 mg of sample in an Al 2 O 3 crucible, and shake it flat.
  • the ternary material and the lithium manganese iron phosphate material are coated simultaneously to effectively improve the overall performance, indicating that the joint coating of the two comprehensively utilizes the advantages of both to improve the overall performance of the battery.
  • the use of a composite electrode structure can effectively improve the comprehensive performance of the composite electrode.

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Abstract

一种复合电极（100）及其制备方法、电池和用电设备，涉及锂离子电池技术领域。该复合电极（100）包括集流体（10）和形成于集流体至少一侧表面的涂布区域，涂布区域包括沿同一延伸方向排列设置的第一活性层（20）和第二活性层（40），第一活性层（20）的热稳定性不同于第二活性层（40）的热稳定性。不同热稳定性活性层的搭配，避免单纯采用热稳定性高的材料，虽然活性层的热稳定性得到改善，但会导致能量密度降低的问题，同时，也避免单纯采用高能量密度的材料，虽然能量密度提高，但会导致活性层热稳定性差的问题，搭配使用不同热稳定性的活性层，解决活性层能量密度的降低的问题，同时提高稳定性。

Description

复合电极及其制备方法、电池和用电设备
相关申请
本申请要求于2022年11月10日申请的、申请号为202211416838.X的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本申请涉及锂离子电池技术领域，特别涉及一种复合电极及其制备方法、电池和用电设备。
背景技术
电池的高能量密度是电池领域一直追求的目标，理论上，材料的能量密度提高，材料的稳定性会下降，所以电池的高能量密度和电池的安全性有时候难以兼顾。
发明内容
本申请的主要目的是提供一种复合电极，旨在提供一种兼顾高能量密度和稳定性的复合电极。
为实现上述目的，本申请提出的一种复合电极，所述复合电极包括集流体和形成于所述集流体至少一侧表面的涂布区域，所述涂布区域包括沿同一延伸方向排列设置的第一活性层和第二活性层，所述第一活性层的热稳定性不同于所述第二活性层的热稳定性。
可选地，所述第一活性层设于所述集流体的表面，并靠近所述集流体用以设置极耳的一侧，所述第二活性层设于所述集流体的表面，且位于所述第一活性层背离所述集流体用以设置极耳的一侧，所述第一活性层的热稳定性大于所述第二活性层的热稳定性。
通过将热稳定性高的第一活性层设置在集流体用以设置极耳的一侧，而将热稳定性差的第二活性层设置在集流体远离极耳的一侧，降低极耳接触热稳定性差的第二活性层的风险，降低极耳散热过程中引发热稳定性差的第二活性层产热，以及发生热失控的风险，如此来提高复合电极的稳定性。
可选地，所述集流体的表面至少形成三个涂层区域，至少两个涂层区域用以分别设置所述第一活性层和第三活性层，至少另一个涂层区域用以设置所述第二活性层，且，所述第二活性层位于所述第一活性层和所述第三活性层之间，所述第三活性层的热稳定性大于所述第二活性层的热稳定性。
考虑到集流体一般需要裁切以达到合适的尺寸，在裁切过程中集流体的边缘难免会产生毛刺，这种毛刺在电极工作过程由于极片膨胀力的变化可能会刺穿隔膜，诱发电芯微短路。微短路又会导致阴极局域反应加剧，释放大量热，进一步会导致隔膜收缩，从而引发更大的短路和产热，甚至发生起火和爆炸等事故。具体地，在毛刺刺穿隔膜的过程中，最开始电芯微短路产生的热量并不是很高，也即，对于毛刺周围热稳定性好的材料来说，最开始电芯微短路产生的热量难以引发毛刺周围材料的产热，以及热失控，此时电池发生事故的风险降低，但是对于毛刺周围热稳定性差的材料来说，电芯微短路产生的热量容易引发毛刺周围材料的产热，甚至热失控，如此，更易引发阴极局域反应加剧，释放大量热，以及产生更严重的后果，此时，电池发生事故的风险升高。
为此，为了降低因毛刺刺穿隔膜产热，引发毛刺周围材料产热以及热失控的风险，通过将热稳定性高的第一活性层和第三活性层设置在集流体的侧边，热稳定性差的第二活性层设置在集流体的靠近中部位置，避免热稳定性差的第二活性层设置在毛刺的周围，减少引发上述的风险。
可选地，所述第一活性层和所述第三活性层的材料相同；
或，所述第一活性层和所述第三活性层的材料不同。
理论上保持第一活性层和第三活性层的热稳定性高于第二活性层的热稳定性即可，并不对第一活性层和第三活性层的材料做限制，第一活性层和第三活性层的材料可以相同，第一活性层和第三活性层的材料也可以不同。
可选地，所述第一活性层的总放热量和所述第三活性层的总放热量分别小于所述第二活性层的总放热量。
由于需要将第一活性层和第三活性层设置在集流体容易产热的部位，为了减轻第一活性层和第三活性层在吸收热量后会大量产热，因此，选用第一活性层和第三活性层的总放热量小于第二活性层的总放热量，降低大量产热的风险，降低大量产热引发起火的风险。
可选地，所述第一活性层的总放热量的范围值为100J/g-500J/g，所述第三活性层的总放热量的范围值为100J/g-500J/g，所述第二活性层的总放热量的范围值为800J/g-1500J/g。
由于需要将第一活性层和第三活性层设置在集流体容易产热的部位，为了降低第一活性层在吸收热量后会大量产热的风险，因此，选用第一活性层和第三活性层的总放热量小于第二活性层的总放热量，降低大量产热的风险，降低大量产热引发起火的风险。第一活性层的总放热量的范围值为100J/g-500J/g，例如可以是100J/g、200J/g、300J/g、400J/g、500J/g，以及上述任意两个点值之间的范围值，第三活性层的总放热量的范围值为100J/g-500J/g，例如可以是100J/g、200J/g、300J/g、400J/g、500J/g，以及上 述任意两个点值之间的范围值，第二活性层的总放热量的范围值为800J/g-1500J/g，例如可以是800J/g、900J/g、1000J/g、1100J/g、1200J/g、1700J/g、1600J/g、1500J/g等，以及上述任意两个点值之间的范围值。
可选地，所述第一活性层构成的电芯的失效温度大于所述第二活性层构成的电芯的失效温度；所述第三活性层构成的电芯的失效温度大于所述第二活性层构成的电芯的失效温度。
电芯的失效温度越高说明活性层的热稳定性越好，基于第一活性层和第三活性层设置在集流体容易产热的部位，因此，第一活性层构成的电芯的失效温度和第三活性层构成的电芯的失效温度均大于第二活性层构成的电芯的失效温度。
可选地，所述第一活性层构成的电芯的失效温度为160℃-220℃，所述第三活性层构成的电芯的失效温度为160℃-220℃，所述第二活性层构成的电芯的失效温度为120℃-160℃。
为了降低第一活性层和第三活性层容易发生热失控，引发起火的风险，第一活性层构成的电芯的失效温度为160℃-220℃，例如，可以是160℃、170℃、180℃、190℃、1200℃、210℃、220℃等，以及上述任意两个点值之间的范围值，所述第三活性层构成的电芯的失效温度为160℃-220℃，例如，可以是160℃、170℃、180℃、190℃、1200℃、210℃、220℃等，以及上述任意两个点值之间的范围值，例如，第一活性层或第三活性层的材料可以是磷酸锰铁锂或磷酸铁锂以及两者的混合。同时，需要兼顾能量密度和发生热失控的风险，第二活性层构成的电芯的失效温度为120℃-160℃，例如，可以是120℃、130℃、140℃、150℃、160℃等，以及上述任意两个点值之间的范围值，例如，第二活性层的材料可以是三元材料或钴酸锂，以及两者的混合。
可选地，所述集流体用以设置极耳的一侧预设有绝缘层涂覆区域，所述第一活性层覆盖所述绝缘层涂覆区域。
在集流体位于极耳的一侧会设置绝缘层涂覆区域，用以设置绝缘层，以降低极耳弯折后插入活性层的风险，进而降低引发活性层吸收极耳产生的热量，引发活性层产热，甚至热失控的风险。本申请中，基于在集流体靠近极耳的一侧设置的是热稳定性好的第一活性层，采用将第一活性层靠近极耳设置，降低了第一活性层因吸收极耳的热量而发生产热的风险，因此，采用第一活性层覆盖绝缘层涂覆区域，可以增加第一活性层的涂覆量，提高能量密度。
可选地，定义所述集流体的两侧均用以设置极耳，所述集流体用以设置极耳的另一侧预设有绝缘层涂覆区域，所述第三活性层覆盖所述绝缘层涂覆区域。
考虑到集流体可在两侧均设置极耳，集流体用以设置极耳的另一侧预设有绝缘层涂覆区域，为了提高能量密度，第三活性层覆盖集流体另一侧的绝缘层涂覆区域，同时，由于第三活性层热稳定性好，有助于降低第三活性层因吸收极耳的热量而发生产热的风险。
可选地，所述第一活性层与所述第二活性层的宽度比为0.25-4。
理论上，第一活性层宽度越宽，热稳定性好的材料层越多，越有利于稳定性，但是能量密度会降低，第二活性层宽度越宽，热稳定性差的材料层越多，能量密度会增加，但是稳定性降低，为了平衡热稳定性和高能量密度，第一活性层与第二活性层的宽度比为0.25-4，例如，可以是0.25、0.5、1.0、1.5、2.0、2.5、3.0、3.5、4等，以及上述任意两个点值之间的范围值，通过第一活性层与第二活性层的宽度比设置，可以调节复合电极的不同稳定性和不同能量密度。
可选地，所述第一活性层和所述第三活性层之和与所述第二活性层的宽度比为0.25-4。
理论上，第一活性层与第三活性层的宽度之和越宽，热稳定性好的材料层越多，越有利于稳定性，但是能量密度会降低，第二活性层宽度越宽，热稳定性差的材料层越多，能量密度会增加，但是稳定性降低，为了平衡热稳定性和高能量密度，第一活性层和第三活性层之和与第二活性层的宽度比为0.25-4，例如，可以是0.25、0.5、1.0、1.5、2.0、2.5、3.0、3.5、4等，以及上述任意两个点值之间的范围值，通过第一活性层和第三活性层与第二活性层的宽度比设置，可以调节复合电极的不同稳定性和不同能量密度。
可选地，所述第一活性层的宽度占活性层的总宽度20％-80％；
和/或，所述第二活性层的宽度占活性层的总宽度的20％-80％。
为了平衡第一活性层与第二活性层的在集流体上的涂覆面积，以平衡活性层的能量密度与活性层稳定性，第一活性层的宽度占活性层的总宽度的20％-80％，例如，可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。同理，第二活性层的宽度占活性层的总宽度的20％-80％，例如，可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。
可选地，所述第一活性层和所述第三活性层宽度之和占活性层的总宽度20％-80％；
和/或，所述第二活性层的宽度占活性层的总宽度的20％-80％。
为了平衡第一活性层和第三活性层与第二活性层的在集流体上的涂覆面积，以平衡活性层的能量密度与活性层稳定性，第一活性层和第三活性层的宽度之和占活性层的总宽度的20％-80％，例如，可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。同理，第二活性层的宽度占活性层的总宽度的20％-80％，例如，可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。
可选地，所述第一活性层的宽度大于3mm。
一方面考虑到低于3mm的宽度，在涂覆工艺上的可操作性难度加大，为了方便涂覆，第一活性层的宽度大于3mm；另一方面，目前集流体上用于涂覆绝缘层的宽度在3mm-3.5mm左右，为了使第一活性层覆盖绝缘层的涂覆区域，因此，选择第一活性层的宽度大于3mm。
可选地，所述第三活性层的宽度大于3mm。
一方面考虑到低于3mm的宽度，在涂覆工艺上的可操作性难度加大，为了方便涂覆，第三活性层的宽度大于3mm；另一方面，目前集流体上用于涂覆绝缘层的宽度在3mm-3.5mm左右，为了使第三活性层覆盖绝缘层的涂覆区域，因此，选择第三活性层的宽度大于3mm。
可选地，所述第一活性层和所述第三活性层的克容量分别的克容量小于所述第二活性层的克容量。
理论上，热稳定性好的材料相比热稳定性差的材料，其克容量会小一些，基于第一活性层和第三活性层的热稳定性大于第二活性层的热稳定性，所以第一活性层和第三活性层的克容量小于第二活性层的克容量。
采用在正极的侧边涂覆低容量的第一活性层，如此，电芯侧边的CB值低，降低负极侧边的析锂现象。
可选地，所述第一活性层的克容量和所述第三活性层的克容量分别占所述第二活性层克容量的60％-80％。
第一活性层和第三活性层的热稳定性大于第二活性层的热稳定性，第一活性层和第三活性层的克容量分别小于第二活性层克容量，第一活性层的克容量占第二活性层克容量的60％-80％，第三活性层的克容量占第二活性层克容量的60％-80％，例如，可以是60％、70％、80％，若是第一活性层和第三活性层的克容量分别占第二活性层克容量太低，会导致能量密度太低，也不能太高，会使热稳定性降低。例如，第一活性层和第三活性层的材料可以包括磷酸锰铁锂、磷酸铁锂，或两者的混合，第二活性层的材料可以包括三元材料、钴酸锂，或两者的混合。
可选地，所述第一活性层中的活性材料的平均粒径Dv50和所述第三活性层中的活性材料的平均粒径Dv50分别为0.2um-2um。
材料颗粒太大，锂离子传输路径长，动力学性能差，若颗粒尺寸做的很小，动力学性能好，但是加工性差，很难在集流体上进行涂布，因此材料的平均粒径Dv50可以为0.2um、0.3um、0.4um、0.5um、0.6um、0.7um、0.8um、0.9um、1um、1.2um、1.4um、1.6um、1.8um、2um等，以及上述任意两个点值之间的范围值。例如，材料可以是磷酸锰铁锂材料，磷酸锰铁锂材料的离子传导能力很差，将粒径设置在上述范围内，有利于提高材料的动力学性能。
可选地，所述第二活性层中的活性材料的平均粒径Dv50的范围值为0.5um-20um。
可以理解的是，颗粒太大锂离子传输路径长，动力学性能差，若颗粒尺寸做的很小，动力学性能好，但是加工性差，很难在集流体上进行涂布。因此，第二活性层中材料的平均粒径Dv50可以为0.5um、1um、2um、3um、4um、5um、6um、7um、8um、9um、10um、11um、12um、13um、14um、15um、16um、17um、18um、19um、20um，以及上述任意两个点值之间的范围值。
可选地，所述第一活性层、所述第二活性层、所述第三活性层的厚度相同。
为了方便组装形成电芯，第一活性层、第三活性层和第二活性层在经过冷压后，冷压至相同的厚度。
可选地，所述第一活性层、所述第二活性层、所述第三活性层的厚度为80μm-300μm。
第一活性层、第二活性层、第三活性层的厚度的范围值为80μm-300μm，例如可以是80μm、100μm、150μm、180μm、200μm、250μm、280μm、300μm等，以及上述任意两个点值之间的范围值。
可选地，所述第一活性层包括磷酸锰铁锂材料。
采用第一活性层包括磷酸锰铁锂材料，不仅有利于提高稳定性还提高能量密度。
可选地，所述磷酸锰铁锂材料设有导电包覆材料。
为了提高磷酸锰铁锂材料的导电性，在磷酸锰铁锂材料设有包覆材料。
可选地，所述导电包覆材料的质量为所述磷酸锰铁锂材料质量的1％-10％；
和/或，所述导电包覆材料包括碳或金属氧化物中的至少一种。
包覆材料的量越多，导电性越好，电池的倍率性能就会越好。但是包覆材料含量进一步提高，实际 的活性材料含量就会降低，电极的能量密度也会损失。因此，包覆材料的质量为磷酸锰铁锂材料质量的1.0％-10.0％，例如可以是1.0％、2.0％、3.0％、4.0％、5.0％、6.0％、7.0％、8.0％、9.0％、10.0％，以及上述任意两个点值之间的范围值。同时导电包覆材料包括碳或金属氧化物中的至少一种，例如可以是碳，也可以是金属氧化物，还可以是两种的混合，具体不做限定，当然还可以是其他具有导电性能的材料。
可选地，所述第一活性层还包括三元材料，所述磷酸锰铁锂材料的质量占所述第一活性层总质量的20％-80％。
为了提高复合电极的能量密度，第一活性层还包括三元材料，且磷酸锰铁锂材料的质量占第一活性层总质量的20％-80％，例如，磷酸锰铁锂材料的质量可以占第一活性层总质量的20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。其中，磷酸锰铁锂材料的质量不能过低和过高，磷酸锰铁锂材料的质量过低会导致三元材料质量过高，电池的稳定性降低，磷酸锰铁锂材料的质量过高会导致三元材料质量过低，能量密度不足。
可选地，所述磷酸锰铁锂材料的结构通式为LiMnxFeyM1-x-yPO4，式中，0.4≤x≤0.8；0.1≤y≤0.6；0≤1-x-y≤0.2，M表示掺杂元素，可选地包括Al、Cu、Mg、Zn、Ni、Ti、V、Zr、Co、Ga、Sn、Sb、Nb和Ge中的至少一种。
磷酸锰铁锂材料的结构通式为LiMnxFeyM1-x-yPO4，式中，0.4≤x≤0.8；0.1≤y≤0.6；0≤1-x-y≤0.2，M表示掺杂元素，可选地包括Al、Cu、Mg、Zn、Ni、Ti、V、Zr、Co、Ga、Sn、Sb、Nb和Ge中的至少一种。磷酸锰铁锂材料中锰的摩尔占比为20％-80％，性能比较好，例如，磷酸锰铁锂材料中锰的摩尔占比可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。
可选地，所述第二活性层包括三元材料或钴酸锂中的至少一种。
钴酸锂是一种无机化合物，化学式为LiCoO2，一般使用作锂离子电池的正电极材料。三元材料的克容量远高于磷酸锰铁锂，采用三元材料作为第二活性层，可以提高电极整体的能量密度，能量密度是动力电池的核心指标，特别是对于磷酸锰铁锂体系，只有能量密度超过磷酸铁锂才有应用的潜力。
可选地，当所述第二活性层包括三元材料时，所述三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，N可选地包括Mn、Zr、Al、B、Ta、Mo、W、Nb、Sb、La中的至少一种，其中，0.35≤a<1.0，0≤b≤0.35，0≤1-a-b≤0.35。
三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，N可选地包括Mn、Zr、Al、B、Ta、Mo、W、Nb、Sb、La中的至少一种，其中，0.35≤a<1.0，0≤b≤0.35，0≤1-a-b≤0.35，根据镍含量的不同，三元材料可以分为低镍三元材料、中镍三元材料、高镍三元材料，以及根据是否含钴元素，三元材料还可以分为无钴三元材料，其中钴元素可由其他金属元素替代，本申请中，三元材料的具体类型不作限定。
可选地，当所述第二活性层包括三元材料时，所述三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，0.5≤a≤0.96。
镍元素比例上升可以提升电池比能量，因此，选择三元材料中Ni元素的摩尔含量占除锂以外的其他金属元素总摩尔含量的50％-96％，例如，可以是50％、60％、70％、80％、90％、96％等，以及上述任意两个点值之间的范围值。
可选地，所述三元材料包括5系单晶三元材料、5系多晶三元材料、6系单晶三元材料、6系多晶三元材料、7系单晶三元材料、7系多晶三元材料、8系单晶三元材料、8系多晶三元材料、9系单晶三元材料、9系多晶三元材料、无钴三元材料中的至少一种。
可选地，在所述第一活性层和所述第二活性层均包括三元材料时，所述第一活性层和所述第二活性层中的三元材料相同。
理论上，第一活性层和第二活性层中的三元材料可以相同也可以不同，但是最好是相同，相同的优势是两活性层的嵌锂量接近，膨胀程度一样，有利于极片的稳定。
可选地，所述第一活性层包括第一活性物质、导电剂和粘结剂，所述第一活性物质包括磷酸锰铁锂材料，所述磷酸锰铁锂材料质量占所述第一活性层总质量的94％-97％；
和/或，所述第二活性层包括第二活性物质、导电剂和粘结剂，所述第二活性物质包括三元材料，所述三元材料占所述第二活性层总质量的95％-98％。
第一活性层包括第一活性物质、导电剂和粘结剂，第一活性物质包括磷酸锰铁锂材料，磷酸锰铁锂材料质量占第一活性层总质量的94％-97％，磷酸锰铁锂材料在该范围内(例如可以是94％、95％、96％、97％，以及上述任意两个点值之间的范围值)，可以制备性能优异的活性层，其中，粘结剂含量可以为1.8％、2％、2.5％、3％等，导电剂含量可以是1.8％、2％、2.5％等，以及上述任意两个点值之间的范围值。
第二活性层包括第二活性物质、导电剂和粘结剂，第二活性物质包括三元材料，三元材料占第二活性层总质量的95％-98％，三元材料在该范围内(95％、96％、97％、98％，以及上述任意两个点值之间 的范围值)，可以制备性能优异的活性层，其中，粘结剂含量可以为1.5％、2％、2.5％等，导电剂含量可以是1.8％、2％、2.5％等。
本申请提供一种复合电极的制备方法，包括以下步骤：
在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在所述集流体上形成第一活性层和第二活性层；
烘干后，经过冷压，得到复合电极；
其中，所述第一活性层的热稳定性不同于所述第二活性层的热稳定性。
通过不同热稳定性活性层的搭配，实现不同能量密度的活性层的搭配，避免单纯采用热稳定性高的材料，虽然活性层的热稳定性得到改善，但会导致能量密度降低的问题，同时，也避免单纯采用高能量密度的材料，虽然能量密度提高，但会导致活性层热稳定性差的问题，搭配使用不同热稳定性的活性层，解决活性层能量密度的降低的问题，同时提高热稳定性。
可选地，在所述在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在所述集流体上形成第一活性层和第二活性层的过程中，所述第一活性层靠近所述集流体用以设置极耳的一侧，所述第二活性层位于所述第一活性层背离所述集流体用以设置极耳的一侧，所述第一活性层的热稳定性大于所述第二活性层的热稳定性。
将热稳定性高的第一活性层设置在集流体用以设置极耳的一侧，而将热稳定性差的第二活性层设置在集流体远离极耳的一侧，降低极耳接触热稳定性差的第二活性层的风险，降低极耳散热过程中引发热稳定性差的第二活性层产热，以及发生热失控的风险，如此来提高复合电极的稳定性。同时搭配使用不同热稳定性的活性层，解决活性层能量密度的降低的问题。
可选地，在所述在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在所述集流体上形成第一活性层和第二活性层的过程中，包括以下步骤：
在集流体的同一面涂覆至少一条第一活性物质层浆料、至少一条第三活性物质层浆料和至少一条第二活性物质层浆料，所述第二活性物质层浆料设置在所述第一活性物质层浆料和所述第三活性物质层浆料之间，所述第三活性层的热稳定性大于所述第二活性层的热稳定性。
由于集流体侧边因裁切容易产生毛刺，为了降低因毛刺刺穿隔膜产热，引发毛刺周围材料产热以及热失控的风险，通过将热稳定性高的第一活性层和第三活性层设置在集流体的侧边，热稳定性差的第二活性层设置在集流体的靠近中部位置，避免热稳定性差的第二活性层设置在毛刺的周围，减少引发上述的风险。
可选地，在所述在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在所述集流体上形成第一活性层和第二活性层的过程中，包括以下步骤：
在集流体的同一面同时涂覆第一活性物质层浆料和第二活性物质层浆料，在所述集流体上形成第一活性层和第二活性层。
为了方便控制多条活性层涂覆的宽度值，需要在集流体的同一面同时涂覆第一活性物质层浆料和第二活性物质层浆料，因为相邻的活性层是平行的，如果涂完一条再涂一条不仅效率低而且先涂的一层会往旁边扩散，导致两条宽度没法控制。当还需要涂覆第三活性物质层浆料时，第一活性物质层浆料、第三活性物质层浆料和第二活性物质层浆料需要同时涂覆。
可选地，在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料的过程中，还包括以下步骤：
在集流体的一面上涂覆一层底涂，再在底涂上涂覆第一活性物质层浆料和第二活性物质层浆料。
先在集流体上涂布一层高粘的涂层，再涂布第一活性物质层浆料和第二活性物质层浆料，用于增强活性材料与基材之间的粘结力。
可选地，在经过冷压的步骤中，所述第一活性层和所述第二活性层在经过冷压后，冷压至相同的厚度，所述厚度为80μm-300μm。
为了方便组装形成电芯，第一活性层和第二活性层在经过冷压后，冷压至相同的厚度，厚度为80μm-300μm。
可选地，在烘干后，经过冷压，得到复合电极的步骤中，所述烘干的温度为90℃-120℃，所述冷压的压力为20吨-40吨，所述冷压的温度为15℃-35℃。
为了有效去除浆料中的溶剂，采用烘干的温度为90℃-120℃，例如，可以是90℃、100℃、110℃、120℃。为了将活性层压实至合适密度，冷压的压力为20吨-40吨，例如可以是20吨、25吨、30吨、35吨、40吨，以及上述任意两个点值之间的范围值，同时，在常温下进行冷压，简化操作。
本申请还提供一种电池，包括：负极极片、正极极片、隔离膜及电解液，其中所述正极极片为所述的复合电极。
由于上述的复合电极具有高稳定、高能量密度和低成本的电芯的优势，采用该复合电极制备的电池性价比更好。
本申请还提供一种用电设备，所述用电设备包括所述的电池。
用电设备采用上述高性价比的电池，提高用电设备的使用性能，提高使用价值。
本申请的复合电极，包括集流体、第一活性层和第二活性层，第一活性层设于集流体的表面，第二活性层设于集流体的表面，并与第一活性层位于集流体的同一表面，第一活性层的热稳定性不同于第二活性层的热稳定性，理论上，材料的热稳定性高，材料的能量密度会低一些，材料的热稳定性差，材料的能量密度会高一些，通过不同热稳定性活性层的搭配，实现不同能量密度的活性层的搭配，避免单纯采用热稳定性高的材料，虽然活性层的热稳定性得到改善，但会导致能量密度降低的问题，同时，也避免单纯采用高能量密度的材料，虽然能量密度提高，但会导致活性层热稳定性差的问题，搭配使用不同热稳定性的活性层，解决活性层能量密度的降低的问题，同时提高稳定性。
附图说明
为了更清楚地说明本申请实施例或现有技术中的技术方案，下面将对实施例或现有技术描述中所需要使用的附图作简单地介绍，显而易见地，下面描述中的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据这些附图示出的结构获得其他的附图。
图1为本申请复合电极的制备方法流程示意图；
图2为本申请复合电极的另一制备方法流程示意图；
图3为本申请集流体的结构示意图；
图4为本申请集流体的结构示意图；
图5为本申请复合电极一实施例的结构示意图；
图6为本申请复合电极另一实施例的结构示意图；
图7为本申请集流体的结构示意图；
图8为本申请复合电极另一实施例的结构示意图；
图9为本申请复合电极另一实施例的结构示意图；
图10为本申请复合电极另一实施例的结构示意图。
附图标号说明：
本申请目的的实现、功能特点及优点将结合实施例，参照附图做进一步说明。
具体实施方式
下面将结合本申请实施例中的附图，对本申请实施例中的技术方案进行清楚、完整地描述，显然，所描述的实施例仅仅是本申请的一部分实施例，而不是全部的实施例。基于本申请中的实施例，本领域普通技术人员在没有作出创造性劳动前提下所获得的所有其他实施例，都属于本申请保护的范围。
需要说明，本申请实施例中所有方向性指示(诸如上、下、左、右、前、后……)仅用于解释在某一特定姿态(如附图所示)下各部件之间的相对位置关系、运动情况等，如果该特定姿态发生改变时，则该方向性指示也相应地随之改变。
在本申请中，除非另有明确的规定和限定，术语“连接”、“固定”等应做广义理解，例如，“固定”可以是固定连接，也可以是可拆卸连接，或成一体；可以是机械连接，也可以是电连接；可以是直接相连，也可以通过中间媒介间接相连，可以是两个元件内部的连通或两个元件的相互作用关系，除非另有明确的限定。对于本领域的普通技术人员而言，可以根据具体情况理解上述术语在本申请中的具体含义。
另外，在本申请中如涉及“第一”、“第二”等的描述仅用于描述目的，而不能理解为指示或暗示其相对重要性或者隐含指明所指示的技术特征的数量。由此，限定有“第一”、“第二”的特征可以明示或者隐含地包括至少一个该特征。另外，全文中出现的“和/或”的含义为，包括三个并列的方案，以“A和/或B为例”，包括A方案，或B方案，或A和B同时满足的方案。另外，各个实施例之间的技术方案可以相互结合，但是必须是以本领域普通技术人员能够实现为基础，当技术方案的结合出现相互矛盾或无法实现时应当认为这种技术方案的结合不存在，也不在本申请要求的保护范围之内。
本领域中所提到的电池按是否可充电可以分为一次性电池和可充电电池。目前常见的可充电电池的类型有：铅酸电池、镍氢电池和锂离子电池。锂离子电池目前广泛应用于纯电动车及混合动力车，用于这种用途的锂离子电池的容量相对略低，但有较大的输出、充电电流，也有较长的使用寿命，但成本较高。
本申请实施例中所描述的电池是指可充电电池。下文中将主要以锂离子电池为例来描述本申请公开的实施例。应当理解的是，本申请公开的实施例对于其他任意适当类型的可充电电池都是适用的。本申请中公开的实施例所提到的电池可以直接或者间接应用于适当的装置中来为该装置供电。
本申请公开的实施例中所提到的电池是指包括一个或多个电池单体以提供预定的电压和容量的单一的物理模块。电池单体是电池中的基本单元，一般按封装的方式可以分为：柱形电池单体、长方体电池单体和软包电池单体。下文中将主要围绕长方体电池单体来展开。应当理解的是，下文中所描述的实施例在某些方面对于柱形电池单体或软包电池单体而言也是适用的。
电池单体包括正极极片、负极极片、电解液和隔离膜。锂离子电池单体主要依靠锂离子在正极极片和负极极片之间的移动来工作。柱形电池单体中三层材料的薄膜结构被卷绕成柱形形状的电极组件，而在长方体电池单体中薄膜结构被卷绕或者叠置成具有大致长方体形状的电极组件。
在通常的电池单体结构中，电池单体包括外壳、电极组件和电解液。电极组件被容纳在电池单体的外壳中，电极组件包括正极极片、负极极片和隔离膜。外壳包括外壳和端盖。外壳包括由多个壁形成的容纳腔以及开口。端盖布置在开口处以封闭容纳腔。除了电极组件之外，容纳腔中还容纳有电解液。电极组件中的正极极片和负极极片包括极耳。为了保证通过大电流而不发生熔断，正极极耳的数量为多个且层叠在一起，负极极耳的数量为多个且层叠在一起。极耳通过连接构件与位于电池单体外部的电极端子电连接，电极端子一般包括正电极端子和负电极端子。对长方体电池单体而言，电极端子一般设置在端盖部分。多个电池单体经由电极端子而被串联和/或并联在一起以应用于各种应用场合。
在一些诸如电动车辆等的大功率应用场合，电池的应用包括三个层次：电池单体、电池模块和电池。电池模块是为了从外部冲击、热、振动等中保护电池单体，将一定数目的电池单体电连接在一起并放入一个框架中而形成的。电池则指的是装入电动车辆的电池系统的最终状态。电池一般包括用于封装一个或多个电池单体的箱体。箱体一般由盖体和箱壳组成。
箱体的边框上或箱壳中部设置有多个用于与车辆主体连接的挂载点，为提高车辆主体与电池连接的稳定性，多在挂载点设置挂载部。
在一些电池生产加工技术中，首先将多个电池单体先整合为电池模块，然后将电池模块封装于电池的箱体中，形成电池包/电池箱。
常用的电池模块一般包括两块端板，两块端板之间排布有多个电池单体。设置有电池模块输出极的端板又称输出极端板，未设置电池模块输出极的端板又称非输出极端板。
电池包内可封装一排多个电池模块，也可封装多排多个电池模块，多排多个电池模块的排列方式可以是双排多列、多排双列、多排多列等。以封装双排多列电池模块的电池包为例，每一列第一个端板一般为头部输出极端板，两排电池模块间相邻的两块端板为中部非输出极端板，每一列最后一个端板为尾部非输出极端板，头部输出极端板和其中一个中部非输出极端板属于第一排电池模块，其中一个中部非输出极端板和尾部输出极端板属于第二排电池模块。
电池模块封装入电池的箱体需要依托工装才可实现，工装上一般设置有夹持电池模块的夹持机构，如夹爪、吸盘等。当采用设置夹爪的工装封装电池模块时，一般会在端板背离电池单体一侧设置与夹爪适配的夹爪槽，以供夹爪插入实现对电池模块的夹持与转运。
电池的高能量密度是电池领域一直追求的目标，理论上，材料的能量密度提高，材料的稳定性会下降，所以电池的高能量密度和电池的稳定性有时候难以兼顾。
为了寻求性能较佳的电极，以平衡高能量密度和稳定性之间的矛盾，本申请提供一种复合电极，旨在提供一种兼顾高能量密度和稳定性的复合电极的。
复合电极包括集流体和形成于集流体至少一侧表面的涂布区域，涂布区域包括沿同一延伸方向排列设置的第一活性层和第二活性层，第一活性层的热稳定性不同于第二活性层的热稳定性。
沿同一延伸方向排列，指的是可以沿集流体的长度方向排列，也可以沿集流体的宽度方向排列，具体不作限定。
集流体，是指汇集电流的结构或零件，在锂离子电池上主要指的是金属箔，如铜箔、铝箔。集流体作为基材用于附着正极或负极活性物质，起到将活性材料产生的电流汇集，对外进行电流输出的作用。一般铝箔作为正极集流体，铜箔作为负极集流体。
活性层，是指包括有活性材料的涂层结构，其中的活性材料是指正极涉及的正极活性物质，正极活性物质可以使用能可逆地嵌入与脱嵌Li+的化合物(以锂二次电池为例，当然也可以是其他类型的二次 电池，例如，当是钠二次电池时，正极活性物质可以使用能可逆地嵌入与脱嵌Na+)。
活性层的热稳定性，热稳定性是指材料的热稳定性，是指材料承受温度的变化而不致破坏的能力，例如，在低于一定温度下，活性层中活性材料结构或成分不发生改变，或者是成分发生少量变化，以使得该活性材料在工作环境下仍能保持相应的功能，例如，对于阴极活性材料，该材料的功能是能可逆地嵌入与脱嵌Li+；在高于一定温度下，活性层中活性材料结构或成分发生改变，例如，结构坍塌，或材料发生化学变化，产生热量，使得难以保持该活性材料的正常功能。材料的热稳定性可以通过差示扫描量热测仪(DSC)来进行测试，例如，差示扫描量热仪的参数设置为：氮气气氛下，吹扫气50ml/min，保护气20ml/min，升温程序为10℃/min，从35℃升温至600℃。制样步骤为：称取10mg左右样品于Al2O3坩埚中，抖平。通过上述测试方法可得到材料的结构和成分变化情况，两种材料在相同的测试条件下，结构和成分受温度影响更敏感，说明该材料热稳定性差。
其中，热稳定性高，指的是材料承受温度破坏的能力强，耐热性高，相比于热稳定性差的材料，热稳定性高的材料的耐热温度高于热稳定性差的材料的耐热温度。例如，第一活性层的热稳定性大于第二活性层的热稳定性，指的是第一活性层中的活性材料的耐热温度高于第二活性层中的活性材料的耐热温度。
理论上，材料的热稳定性高，材料的能量密度会低一些，材料的热稳定性差，材料的能量密度会高一些，通过不同热稳定性活性层的搭配，实现不同能量密度的活性层的搭配，避免单纯采用热稳定性高的材料，虽然活性层的热稳定性得到改善，但会导致能量密度降低的问题，同时，也避免单纯采用高能量密度的材料，虽然能量密度提高，但会导致活性层热稳定性差的问题，搭配使用不同热稳定性的活性层，解决活性层能量密度的降低的问题，同时提高稳定性。
进一步地，复合电极包括集流体10、第一活性层20和第二活性层40，第一活性层20设于集流体10的表面，并靠近集流体10用以设置极耳30的一侧，第二活性层40设于集流体10的表面，并与第一活性层20位于集流体10的同一表面，且位于第一活性层20背离集流体10用以设置极耳30的一侧，第一活性层20的热稳定性大于第二活性层40的热稳定性。
极耳，电池是分正负极的，极耳就是从电芯中将正负极引出来的金属导电体，通俗的说电池正负两极的耳朵是在进行充放电时的接触点。
第一活性层的热稳定性大于第二活性层的热稳定性，指的是第一活性层中的活性材料发生结构或特性变化的温度要高于第二活性层中的活性材料发生结构或特性变化的温度。
通过将热稳定性高的第一活性层设置在集流体用以设置极耳的一侧，而将热稳定性差的第二活性层设置在集流体远离极耳的一侧，降低极耳接触热稳定性差的第二活性层的风险，降低极耳散热过程中引发热稳定性差的第二活性层产热，以及发生热失控的风险，如此来提高复合电极的稳定性。
例如，如图3至图9所示，集流体10的一侧设置有极耳30，第一活性层20
设置在集流体10靠近极耳30的一侧，而第二活性层40设于集流体的另一侧，避免第二活性层直接与极耳30接触。可以理解的是，电池在工作过程中，极耳30会产生热量，若是活性层不耐受极耳30产生的热量，则活性层中的活性材料在接收极耳30产生的热量后，其结构或特性会发生变化，例如会产热，甚至会热失控，以及起火的危险。
进一步地，集流体的表面至少形成三个涂层区域，至少两个涂层区域用以分别设置第一活性层和第三活性层，至少另一个涂层区域用以设置第二活性层，且，第二活性层位于第一活性层和第三活性层之间，第三活性层的热稳定性大于第二活性层的热稳定性。
考虑到集流体一般需要裁切以达到合适的尺寸，在裁切过程中集流体的边缘难免会产生毛刺，这种毛刺在电极工作过程由于极片膨胀力的变化可能会刺穿隔膜，诱发电芯微短路。微短路又会导致阴极局域反应加剧，释放大量热，进一步会导致隔膜收缩，从而引发更大的短路和产热，甚至发生起火和爆炸等事故。具体地，在毛刺刺穿隔膜的过程中，最开始电芯微短路产生的热量并不是很高，也即，对于毛刺周围热稳定性好的材料来说，最开始电芯微短路产生的热量难以引发毛刺周围材料的产热，以及热失控，此时电池发生事故的风险降低，但是对于毛刺周围热稳定性差的材料来说，电芯微短路产生的热量容易引发毛刺周围材料的产热，甚至热失控，如此，更易引发阴极局域反应加剧，释放大量热，以及产生更严重的后果，此时，电池发生事故的风险升高。
为此，为了降低因毛刺刺穿隔膜产热，引发毛刺周围材料产热以及热失控的风险，通过将热稳定性高的第一活性层和第三活性层设置在集流体的侧边，热稳定性差的第二活性层设置在集流体的靠近中部位置，避免热稳定性差的第二活性层设置在毛刺的周围，减少引发上述的风险。
例如，如图7至图9所示，在集流体10上设有三个活性涂层区域13，其中位于边缘的两个活性涂层区域13用于涂覆第一活性层20和第三活性层50的浆料，中间的活性涂层区域13用于涂覆第二活性层40的浆料，此种设计能更好的兼顾高能量密度和稳定性问题。可以理解的是，两第一活性层20的宽 度可以相同，也可以不同，具体不做限定。
进一步地，第一活性层和第三活性层的材料相同；或，第一活性层和第三活性层的材料不同。
理论上保持第一活性层和第三活性层的热稳定性高于第二活性层的热稳定性即可，并不对第一活性层和第三活性层的材料做限制，第一活性层和第三活性层的材料可以相同，第一活性层和第三活性层的材料也可以不同。
进一步地，第一活性层的总放热量和第三活性层的总放热量分别小于第二活性层的总放热量。
总放热量，是通过差示扫描量热仪(DSC)测试材料的热变化得到的参数，是根据放热曲线积分得到的，总放热量低，表明材料的热稳定性好。例如，差示扫描量热仪的参数设置为：氮气气氛下，吹扫气50ml/min，保护气20ml/min，升温程序为10℃/min，从35℃升温至600℃。制样步骤为：称取10mg左右样品于Al2O3坩埚中，抖平。
由于需要将第一活性层和第三活性层设置在集流体容易产热的部位，为了降低第一活性层和第三活性层在吸收热量后会大量产热的风险，因此，选用第一活性层和第三活性层的总放热量小于第二活性层的总放热量，降低大量产热的风险，降低大量产热引发起火的风险。
进一步地，第一活性层的总放热量的范围值为100J/g-500J/g，第三活性层的总放热量的范围值为100J/g-500J/g，第二活性层的总放热量的范围值为800J/g-1500J/g。
由于第一活性层和第三活性层设置在集流体容易产热的地方，且总放热量大存在较高的风险，因此，第一活性层的总放热量的范围值为100J/g-500J/g，例如，可以是100J/g、200J/g、300J/g、400J/g、500J/g等，以及上述任意两个点值之间的范围值，第三活性层的总放热量的范围值为100J/g-500J/g，例如可以是100J/g、200J/g、300J/g、400J/g、500J/g，以及上述任意两个点值之间的范围值。而第二活性层处于集流体中相对稳定的部位，因此，兼顾到能量密度需要提高，第二活性层的总放热量的范围值为800J/g-1500J/g，例如，可以是800J/g、900J/g、1000J/g、1100J/g、1200J/g、1300J/g、1400J/g、1500J/g等，以及上述任意两个点值之间的范围值。
进一步地，第一活性层构成的电芯的失效温度大于第二活性层构成的电芯的失效温度；第三活性层构成的电芯的失效温度大于第二活性层构成的电芯的失效温度。
失效温度，指的是电池失效时电芯所处的环境温度。失效温度越高表明相应的活性层的材料热稳定性越好。
活性层构成的电芯，指的是将活性层构成的电极组装成电芯，在相同的条件下组装成电池，测试电芯发生热失控情形下电芯所处的环境温度，其中电芯的各组成部分除了正极不同外，其他条件均相同，例如其他条件包括电解液、负极极片等，这些组成部分均相同。电池的失效温度的测试方法可以是，电池在常温下以0.33C倍率充电至电压等于4.2V后，再恒压CV充电至0.05C电流截止。单电芯夹具加紧，5℃/min，55℃环境放置2h，再以5℃/min温升速率，每5℃保持30min，从55℃温升至电芯发生失控，1s记录数据，电芯发生失控时的温度记为Tf。
失效温度越高说明活性层的热稳定性越好，基于第一活性层和第三活性设置在集流体容易产热的部位，因此，第一活性层和第三活性构成的电芯的失效温度均大于第二活性层的失效温度。
进一步地，第一活性层构成的电芯的失效温度为160℃-220℃，第三活性层构成的电芯的失效温度为160℃-220℃，第二活性层构成的电芯的失效温度为120℃-160℃。
为了降低第一活性层和第三活性层容易发生热失控，引发起火的风险，第一活性层的失效温度为160℃-220℃，例如，可以是160℃、170℃、180℃、190℃、1200℃、210℃、220℃等，以及上述任意两个点值之间的范围值，第三活性层构成的电芯的失效温度为160℃-220℃，例如，可以是160℃、170℃、180℃、190℃、1200℃、210℃、220℃等，以及上述任意两个点值之间的范围值，例如，第一活性层和第三活性层的材料可以是磷酸锰铁锂或磷酸铁锂以及两者的混合。同时，需要兼顾能量密度和发生热失控的风险，第二活性层构成的电芯的失效温度为120℃-160℃，例如，可以是120℃、130℃、140℃、150℃、160℃等，以及上述任意两个点值之间的范围值，例如，第二活性层的材料可以是三元材料或钴酸锂，以及两者的混合。
进一步地，集流体用以设置极耳的一侧预设有绝缘层涂覆区域，第一活性层覆盖绝缘层涂覆区域。
在集流体位于极耳的一侧会设置绝缘层涂覆区域，用以设置绝缘层，以降低极耳弯折后插入活性层的风险，进而降低引发活性层吸收极耳产生的热量，引发活性层产热，甚至热失控的风险。本申请中，基于在集流体靠近极耳的一侧设置的是热稳定性好的第一活性层，采用将第一活性层靠近极耳设置，降低了第一活性层因吸收极耳的热量而发生产热的风险，因此，采用第一活性层覆盖绝缘层涂覆区域，可以增加第一活性层的涂覆量，提高能量密度。
例如，如图4、图5和图9所示，集流体10靠近极耳30的一侧预设绝缘层涂覆区域11，绝缘层60设置在该绝缘层涂覆区域11，如图6和图8所示，采用第一活性层20覆盖该绝缘层涂覆区域11， 增大第一活性层20的涂覆面积，提高复合电极的能量密度。
进一步地，定义集流体的两侧均用以设置极耳，集流体用以设置极耳的另一侧预设有绝缘层涂覆区域，第三活性层覆盖绝缘层涂覆区域。
如图10所示，考虑到集流体可在两侧均设置极耳，集流体用以设置极耳的另一侧预设有绝缘层涂覆区域，为了提高能量密度，第三活性层覆盖集流体另一侧的绝缘层涂覆区域，同时，由于第三活性层热稳定性好，有助于降低第三活性层因吸收极耳的热量而发生产热的风险。
进一步地，第一活性层与第二活性层的宽度比为0.25-4。
理论上，第一活性层宽度越宽，热稳定性好的材料层越多，越有利于稳定性，但是能量密度会降低，第二活性层宽度越宽，热稳定性差的材料层越多，能量密度会增加，但是稳定性降低，为了平衡热稳定性和高能量密度，第一活性层与第二活性层的宽度比为0.25-4，例如，可以是0.25、0.5、1.0、1.5、2.0、2.5、3.0、3.5、4等，以及上述任意两个点值之间的范围值，通过第一活性层与第二活性层的宽度比设置，可以调节复合电极的不同稳定性和不同能量密度。
进一步地，第一活性层和第三活性层之和与第二活性层的宽度比为0.25-4。
理论上，第一活性层与第三活性层的宽度之和越宽，热稳定性好的材料层越多，越有利于稳定性，但是能量密度会降低，第二活性层宽度越宽，热稳定性差的材料层越多，能量密度会增加，但是稳定性降低，为了平衡热稳定性和高能量密度，第一活性层和第三活性层之和与第二活性层的宽度比为0.25-4，例如，可以是0.25、0.5、1.0、1.5、2.0、2.5、3.0、3.5、4等，以及上述任意两个点值之间的范围值，通过第一活性层和第三活性层与第二活性层的宽度比设置，可以调节复合电极的不同稳定性和不同能量密度。
进一步地，第一活性层的宽度占活性层的总宽度20％-80％；和/或，第二活性层的宽度占活性层的总宽度的20％-80％。
活性层的总宽度指的是在集流体一表面上所有活性层的宽度总和。
为了平衡第一活性层与第二活性层的在集流体上的涂覆面积，以平衡活性层的能量密度与活性层稳定性，第一活性层的宽度占活性层的总宽度的20％-80％，例如，可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。同理，第二活性层的宽度占活性层的总宽度的20％-80％，例如，可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。
进一步地，第一活性层和第三活性层宽度之和占活性层的总宽度20％-80％；和/或，第二活性层的宽度占活性层的总宽度的20％-80％。
为了平衡第一活性层和第三活性层与第二活性层的在集流体上的涂覆面积，以平衡活性层的能量密度与活性层稳定性，第一活性层和第三活性层的宽度之和占活性层的总宽度的20％-80％，例如，可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。同理，第二活性层的宽度占活性层的总宽度的20％-80％，例如，可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。
进一步地，第一活性层的宽度大于3mm。
一方面考虑到低于3mm的宽度，在涂覆工艺上的可操作性难度加大，为了方便涂覆，第一活性层的宽度大于3mm；另一方面，目前集流体上用于涂覆绝缘层的宽度在3mm-3.5mm左右，为了使第一活性层覆盖绝缘层的涂覆区域，因此，选择第一活性层的宽度大于3mm。
进一步地，第三活性层的宽度大于3mm。
一方面考虑到低于3mm的宽度，在涂覆工艺上的可操作性难度加大，为了方便涂覆，第三活性层的宽度大于3mm；另一方面，目前集流体上用于涂覆绝缘层的宽度在3mm-3.5mm左右，为了使第三活性层覆盖绝缘层的涂覆区域，因此，选择第三活性层的宽度大于3mm。
进一步地，第一活性层和第三活性层的克容量分别的克容量小于第二活性层的克容量。
理论上，热稳定性好的材料相比热稳定性差的材料，其克容量会小一些，基于第一活性层和第三活性层的热稳定性大于第二活性层的热稳定性，所以第一活性层和第三活性层的克容量小于第二活性层的克容量。
在负极极片中存在一种现象，即析锂现象，析锂现象指的是锂离子从正极到达负极因为异常情况直接在负极表面形成锂单质。而且析锂现象更容易在负极的侧边出现。
在设计电芯的时候会考虑一个重要的参数CB值，即CB＝负极的总容量/正极的总容量，一般这个值大于1，越大说明负极析锂的风险越低，但是太大又会造成负极过量，提高制造成本。本方案采用在正极的侧边涂覆低容量的第一活性层，如此，电芯侧边的CB值低，降低负极侧边的析锂现象。
进一步地，第一活性层的克容量和第三活性层的克容量分别占第二活性层克容量的60％-80％。
第一活性层和第三活性层的热稳定性大于第二活性层的热稳定性，第一活性层和第三活性层的克容量分别小于第二活性层克容量，第一活性层的克容量占第二活性层克容量的60％-80％，第三活性层的克容量占第二活性层克容量的60％-80％，例如，可以是60％、70％、80％，若是第一活性层和第三活性层的克容量分别占第二活性层克容量太低，会导致能量密度太低，也不能太高，会使热稳定性降低。例如，第一活性层和第三活性层的材料可以包括磷酸锰铁锂、磷酸铁锂，或两者的混合，第二活性层的材料可以包括三元材料、钴酸锂，或两者的混合。
进一步地，第一活性层中的活性材料的平均粒径Dv50和第三活性层中的活性材料的平均粒径Dv50分别为0.2um-2um。
材料颗粒太大，锂离子传输路径长，动力学性能差，若颗粒尺寸做的很小，动力学性能好，但是加工性差，很难在集流体上进行涂布，因此材料的平均粒径Dv50可以为0.2um、0.3um、0.4um、0.5um、0.6um、0.7um、0.8um、0.9um、1um、1.2um、1.4um、1.6um、1.8um、2um等，以及上述任意两个点值之间的范围值。例如，材料可以是磷酸锰铁锂材料，磷酸锰铁锂材料的离子传导能力很差，将粒径设置在上述范围内，有利于提高材料的动力学性能。
进一步地，第二活性层中的活性材料的平均粒径Dv50的范围值为0.5um-20um。
可以理解的是，颗粒太大锂离子传输路径长，动力学性能差，若颗粒尺寸做的很小，动力学性能好，但是加工性差，很难在集流体上进行涂布。因此，第二活性层中材料的平均粒径Dv50可以为0.5um、1um、2um、3um、4um、5um、6um、7um、8um、9um、10um、11um、12um、13um、14um、15um、16um、17um、18um、19um、20um，以及上述任意两个点值之间的范围值。
进一步地，第一活性层、第二活性层、第三活性层的厚度相同。
为了方便组装形成电芯，第一活性层、第三活性层和第二活性层在经过冷压后，冷压至相同的厚度。
进一步地，第一活性层、第二活性层、第三活性层的厚度为80μm-300μm。
第一活性层、第二活性层、第三活性层的厚度的范围值为80μm-300μm，例如可以是80μm、100μm、150μm、180μm、200μm、250μm、280μm、300μm等，以及上述任意两个点值之间的范围值。
进一步地，第一活性层包括磷酸锰铁锂材料。
目前商用锂离子电池的正极材料主要有两种：三元含锂化合物与磷酸铁锂LFP。三元材料的优点是能量密度高，适合长续航汽车，但缺点是钴镍等元素价格较高，更容易引发热失控起火。相比于三元材料，磷酸铁锂由于不含稀有过渡金属元素，成本也更低廉。然而，磷酸铁锂的能量密度较低，会导致续航里程短。在这个背景下，开发出一种高能量密度和低成本的材料尤为重要。磷酸锰铁锂LMFP就是这样的一种新型材料。
磷酸锰铁锂材料的晶体结构与磷酸铁锂相同，都属于橄榄石晶型，不同点在于在磷酸铁锂的基础上，使用Mn原子部分替代Fe原子。Mn原子是具有较强电化学活性的原子，常应用于三元锂电正极材料中，其在充放电过程中具有更高的电压，也就是说存储相同数量的锂离子可以提供更多的能量。磷酸锰铁锂材料的能量密度相比于磷酸铁锂大幅提高。
为此，采用第一活性层包括磷酸锰铁锂材料，有利于提高能量密度。
进一步地，磷酸锰铁锂材料设有导电包覆材料。
包覆，包覆是指在材料表面包覆导电物质，以提高导电性。
包覆材料，是指包覆在磷酸锰铁锂表面的材料，例如磷酸锰铁锂颗粒表面包覆碳材料等。
为了提高磷酸锰铁锂材料的导电性，在磷酸锰铁锂材料设有包覆材料。
进一步地，导电包覆材料的质量为磷酸锰铁锂材料质量的1％-10％；和/或，导电包覆材料包括碳或金属氧化物中的至少一种。
包覆材料的量越多，导电性越好，电池的倍率性能就会越好。但是包覆材料含量进一步提高，实际的活性材料含量就会降低，电极的能量密度也会损失。因此，包覆材料的质量为磷酸锰铁锂材料质量的1.0％-10.0％，例如可以是1.0％、2.0％、3.0％、4.0％、5.0％、6.0％、7.0％、8.0％、9.0％、10.0％，以及上述任意两个点值之间的范围值。同时导电包覆材料包括碳或金属氧化物中的至少一种，例如可以是碳，也可以是金属氧化物，还可以是两种的混合，具体不做限定，当然还可以是其他具有导电性能的材料。
进一步地，第一活性层还包括三元材料，磷酸锰铁锂材料的质量占第一活性层总质量的20％-80％。
三元材料，三元正极材料是层状镍钴锰(铝)酸锂复合材料，镍、钴、锰为过渡金属元素，所形成的固溶体可以任意比例混合，镍元素比例上升可以提升电池比能量，锰元素比例上升可以保证结构稳定性，钴元素比例上升可以稳定材料层状结构，有利于电池的循环性能和倍率性能。此外，还可以理解的是，三元材料还可以包括不含钴的材料，例如，采用其他金属元素代替钴得到的三元材料。
为此，为了提高复合电极的能量密度，第一活性层还包括三元材料，且磷酸锰铁锂材料的质量占第 一活性层总质量的20％-80％，例如，磷酸锰铁锂材料的质量可以占第一活性层总质量的20％、30％、40％、50％、60％、70％、80％，其中，磷酸锰铁锂材料的质量不能过低和过高，磷酸锰铁锂材料的质量过低会导致三元材料质量过高，磷酸锰铁锂材料的质量过高会导致三元材料质量过低，能量密度不足。
进一步地，磷酸锰铁锂材料的结构通式为LiMnxFeyM1-x-yPO4，式中，0.4≤x≤0.8；0.1≤y≤0.6；0≤1-x-y≤0.2，M表示掺杂元素，可选地包括Al、Cu、Mg、Zn、Ni、Ti、V、Zr、Co、Ga、Sn、Sb、Nb和Ge中的至少一种。
磷酸锰铁锂材料的结构通式为LiMnxFeyM1-x-yPO4，式中，0.4≤x≤0.8；0.1≤y≤0.6；0≤1-x-y≤0.2，M表示掺杂元素，可选地包括Al、Cu、Mg、Zn、Ni、Ti、V、Zr、Co、Ga、Sn、Sb、Nb和Ge中的至少一种。磷酸锰铁锂材料中锰的摩尔占比为20％-80％，性能比较好，例如，磷酸锰铁锂材料中锰的摩尔占比可以是20％、30％、40％、50％、60％、70％、80％，以及上述任意两个点值之间的范围值。
进一步地，第二活性层包括三元材料或钴酸锂中的至少一种。
钴酸锂是一种无机化合物，化学式为LiCoO2，一般使用作锂离子电池的正电极材料。三元材料的克容量远高于磷酸锰铁锂，采用三元材料作为第二活性层，可以提高电极整体的能量密度，能量密度是动力电池的核心指标，特别是对于磷酸锰铁锂体系，只有能量密度超过磷酸铁锂才有应用的潜力。
单从能量密度角度来说，全部应用三元材料会更有利。然而三元材料晶体结构存在释氧行为，热失控风险较高；另外，基材边缘一般是通过激光或者机械模切，难免会有一些金属毛刺，易导致微短路，从而诱发热失控甚至起火。
也即，通过调控第一活性层与第二活性层的材料来调控复合电极的能量密度，实现高能量密度的、低成本的电芯。
第二活性层包括三元材料或钴酸锂中的至少一种，例如，第二活性层可以包括三元材料或钴酸锂，第二活性层还可以包括三元材料与钴酸锂的混合，具体不做限定。当然，除了三元材料与钴酸锂之外，第二活性层还可以包括其他的高能量密度的正极材料。
相比于纯的LMFP电极而言，这种设计可以提高电芯的能量密度并实现能量密度可定制；另外，相比于纯的三元材料，LMFP含量提高可以实现降低三元材料的起火的风险。同时由于三元材料成本较高，采用本申请的复合电极还可以降低成本，提高性价比。
进一步地，当第二活性层包括三元材料时，三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，N可选地包括Mn、Zr、Al、B、Ta、Mo、W、Nb、Sb、La中的至少一种，其中，0.35≤a<1.0，0≤b≤0.35，0≤1-a-b≤0.35。
三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，N可选地包括Mn、Zr、Al、B、Ta、Mo、W、Nb、Sb、La中的至少一种，其中，0.35≤a<1.0，0≤b≤0.35，0≤1-a-b≤0.35，根据镍含量的不同，三元材料可以分为低镍三元材料、中镍三元材料、高镍三元材料，以及根据是否含钴元素，三元材料还可以分为无钴三元材料，其中钴元素可由其他金属元素替代，本申请中，三元材料的具体类型不作限定。
进一步地，当第二活性层包括三元材料时，三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，0.5≤a≤0.96。
镍元素比例上升可以提升电池比能量，因此，选择三元材料中Ni元素的摩尔含量占除锂以外的其他金属元素总摩尔含量的50％-96％，例如，可以是50％、60％、70％、80％、90％、96％等，以及上述任意两个点值之间的范围值。
进一步地，三元材料包括5系单晶三元材料、5系多晶三元材料、6系单晶三元材料、6系多晶三元材料、7系单晶三元材料、7系多晶三元材料、8系单晶三元材料、8系多晶三元材料、9系单晶三元材料、9系多晶三元材料、无钴三元材料中的至少一种。
5系三元材料，是指镍金属的摩尔比大于等于50％、小于60％的三元材料。6系三元材料，是指镍金属的摩尔比大于等于60％、小于70％的三元材料。7系三元材料，是指镍金属的摩尔比大于等于70％、小于80％的三元材料。8系三元材料，是指镍金属的摩尔比大于等于80％、小于90％的三元材料。9系三元材料，是指镍金属的摩尔比大于等于90％的三元材料，例如包括Ni90、Ni92、Ni95等。随着镍的含量逐步提高，电池能量密度也随之提升，镍越高，电芯能量密度越大，但钴被迫减少，材料的稳定性下降。中镍三元材料因镍含量相对高镍较低，且钴含量也较高，材料稳定性得到改善。再加上单晶材料产热较少，稳定性高，其稳定性性能要远高于高镍材料。单晶中镍三元目前在经济性、稳定性、能量密度、循环寿命等多个维度实现了较好的平衡。
无钴三元材料，是指不含有钴的三元材料，例如钴元素可以由其他元素替换构成的三元材料。
单晶三元材料和多晶三元材料是根据材料本身的形貌来命名的。从形貌上看，单晶为单个分散颗粒，而与之对应的多晶三元材料则是一次颗粒团聚的二次颗粒。
相对多晶材料，单晶材料更适合做高电压。同时，单晶材料内部没有晶界，可提升三元材料的循环 稳定性，对延长电池的循环寿命在镍钴锰比例相同的情况下，单晶三元材料克容量稍低于多晶三元材料，但由于其电压更高，因此材料整体能量密度已经和目前高镍三元材料差不多。单晶三元材料的缺点则在于倍率性能表现不佳，且生产工艺更为复杂，材料价格相对较高。
也即，本申请中的三元材料具体不做限定，可以是5系单晶三元材料、5系多晶三元材料、6系单晶三元材料、6系多晶三元材料、7系单晶三元材料、7系多晶三元材料、8系单晶三元材料、8系多晶三元材料、9系单晶三元材料、9系多晶三元材料、或无钴三元材料中的至少一种。
进一步地，在第一活性层和第二活性层均包括三元材料时，第一活性层和第二活性层中的三元材料相同。
理论上，在第一活性层和第二活性层均包括三元材料时，第一活性层和第二活性层中的三元材料可以相同也可以不同，但是最好是相同，相同的优势是两活性层的嵌锂量接近，膨胀程度一样，有利于极片的稳定。
进一步地，第一活性层包括第一活性物质、导电剂和粘结剂，第一活性物质包括磷酸锰铁锂材料，磷酸锰铁锂材料质量占第一活性层总质量的94％-97％；和/或，第二活性层包括第二活性物质、导电剂和粘结剂，第二活性物质包括三元材料，三元材料占第二活性层总质量的95％-98％。
第一活性层包括第一活性物质、导电剂和粘结剂，第一活性物质包括磷酸锰铁锂材料，磷酸锰铁锂材料质量占第一活性层总质量的94％-97％，磷酸锰铁锂材料在该范围内(例如可以是94％、95％、96％、97％，以及上述任意两个点值之间的范围值)，可以制备性能优异的活性层，其中，粘结剂含量可以为1.8％、2％、2.5％、3％等，导电剂含量可以是1.8％、2％、2.5％等。
第二活性层包括第二活性物质、导电剂和粘结剂，第二活性物质包括三元材料，三元材料占第二活性层总质量的95％-98％，三元材料在该范围内(95％、96％、97％、98％，以及上述任意两个点值之间的范围值)，可以制备性能优异的活性层，其中，粘结剂含量可以为1.5％、2％、2.5％等，导电剂含量可以是1.8％、2％、2.5％等。
导电剂过少导致导电效果变差，过多导致能量密度降低。粘结剂用量适中可以使得涂层不掉粉且耐热性较好，过少则粘结性不足，过多则导致浆料粘度超标。
本申请还提供一种复合电极的制备方法，包括以下步骤：在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在集流体上形成第一活性层和第二活性层；烘干后，经过冷压，得到复合电极；其中，第一活性层的热稳定性不同于第二活性层的热稳定性。
第一活性物质层浆料是指用来制备第一活性层的浆料，第二活性物质层浆料是指用来制备第二活性层的浆料。
烘干是指将浆料中的溶剂蒸发，去除溶剂的过程。使极片处于较低的溶剂含量，如果溶剂含量过多，锂电池在化成阶段会消耗过量的锂，造成锂的不可逆损失，导致容量降低，电池气胀等问题，影响电池性能。
冷压是指对电极极片进行压缩，正极涂布干燥完，需要在工艺时间内进行对辊。对辊即对极片进行压实，目前有热压和冷压两种工艺。热压压实相对冷压高，反弹率较低，可减少轧制力；但冷压工艺相对简单易操作控制。对辊主要设备到如下工艺值，压实密度、反弹率、延伸率。同时要注意极片表面无脆片、硬块、掉料、波浪边等现象且间隙处不允许断裂。极片轧制工艺可以降低极片在轧制过程中的延伸率和宽展率，降低极片涂层材料孔隙结构的破坏率；提高极片涂层的厚度一致性，以改善极片的横截面形状；提高极片轧制后电极材料的压实密度一致性；减少极片轧制后表面电极材料的反弹。极片轧制工艺还可以保证极片表面光滑和平整，防止涂层表面的毛刺刺穿隔膜引发短路；对极片涂层材料进行压实，降低极片的体积，以提高电池的能量密度；使活性物质、导电剂颗粒接触更加紧密，提高电子导电率；增强涂层材料与集流体的结合强度，减少电极片在循环过程中掉粉的情况发生，提高电池的循环寿命和稳定性能。
例如，可以利用两根棍轴来对极片做压缩活动，使轧辊与电池极片之间产生摩擦力；使电池极片拉进旋转的对辊之间，电池极片受压变形。电池极片的对辊是正负极片上电池材料压实的过程，可增加正极或负极材料的压实密度，合适的压实密度可增大电池的放电容量、减小内阻、减小极化损失、延长电池的循环寿命、提高锂离子电池的利用率。
如图1所示，为复合电极的制备方法流程示意图，通过不同热稳定性活性层的搭配，实现不同能量密度的活性层的搭配，避免单纯采用热稳定性高的材料，虽然活性层的热稳定性得到改善，但会导致能量密度降低的问题，同时，也避免单纯采用高能量密度的材料，虽然能量密度提高，但会导致活性层热稳定性差的问题，搭配使用不同热稳定性的活性层，解决活性层能量密度的降低的问题，同时提高热稳定性。
进一步地，在在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在集流体上形成 第一活性层和第二活性层的过程中，第一活性层靠近集流体用以设置极耳的一侧，第二活性层位于第一活性层背离集流体用以设置极耳的一侧，第一活性层的热稳定性大于第二活性层的热稳定性。
如图2所示，为复合电极的制备方法流程示意图，将热稳定性高的第一活性层设置在集流体用以设置极耳的一侧，而将热稳定性差的第二活性层设置在集流体远离极耳的一侧，降低极耳接触热稳定性差的第二活性层的风险，降低极耳散热过程中引发热稳定性差的第二活性层产热，以及发生热失控的风险。同时搭配使用不同热稳定性的活性层，解决活性层能量密度的降低的问题。
进一步地，在在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在集流体上形成第一活性层和第二活性层的过程中，包括以下步骤：在集流体的同一面涂覆至少一条第一活性物质层浆料、至少一条第三活性物质层浆料和至少一条第二活性物质层浆料，第二活性物质层浆料设置在第一活性物质层浆料和第三活性物质层浆料之间，第三活性层的热稳定性大于第二活性层的热稳定性。
由于集流体侧边因裁切容易产生毛刺，为了降低因毛刺刺穿隔膜产热，引发毛刺周围材料产热以及热失控的风险，通过将热稳定性高的第一活性层和第三活性层设置在集流体的侧边，热稳定性差的第二活性层设置在集流体的靠近中部位置，避免热稳定性差的第二活性层设置在毛刺的周围，减少引发上述的风险。
进一步地，在在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在集流体上形成第一活性层和第二活性层的过程中，包括以下步骤：在集流体的同一面同时涂覆第一活性物质层浆料和第二活性物质层浆料，在集流体上形成第一活性层和第二活性层。
为了方便控制多条活性层涂覆的宽度值，需要在集流体的同一面同时涂覆第一活性物质层浆料和第二活性物质层浆料，因为相邻的活性层是平行的，如果涂完一条再涂一条不仅效率低而且先涂的一层会往旁边扩散，导致两条宽度没法控制。当还需要涂覆第三活性物质层浆料时，第一活性物质层浆料、第三活性物质层浆料和第二活性物质层浆料需要同时涂覆。
进一步地，在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料的过程中，还包括以下步骤：在集流体的一面上涂覆一层底涂，再在底涂上涂覆第一活性物质层浆料和第二活性物质层浆料。
底涂是指高黏涂层，用于增强活性材料层与集流体之间的粘结力。
先在集流体上涂布一层高粘的涂层，再涂布第一活性物质层浆料和第二活性物质层浆料，用于增强活性材料与基材之间的粘结力。
进一步地，在经过冷压的步骤中，第一活性层和第二活性层在经过冷压后，冷压至相同的厚度，厚度为80μm-300μm。
为了方便组装形成电芯，第一活性层和第二活性层在经过冷压后，冷压至相同的厚度，厚度为80μm-300μm。
进一步地，在烘干后，经过冷压，得到复合电极的步骤中，烘干的温度为90℃-120℃，冷压的压力为20吨-40吨，冷压的温度为15℃-35℃。
为了有效去除浆料中的溶剂，采用烘干的温度为90℃-120℃，例如，可以是90℃、100℃、110℃、120℃。为了将活性层压实至合适密度，冷压的压力为20吨-40吨，例如可以是20吨、25吨、30吨、35吨、40吨，以及上述任意两个点值之间的范围值，同时，在常温下进行冷压，简化操作。
本申请还提供一种电池，包括：负极极片、正极极片、隔离膜及电解液，其中正极极片为上述的复合电极。由于复合电极采用了上述所有实施例的全部技术方案，因此至少具有上述实施例的技术方案所带来的所有有益效果，在此不再一一赘述。
由于上述的复合电极具有高稳定、高能量密度和低成本的电芯的优势，采用该复合电极制备的电池性价比更好。
本申请还提供一种用电设备，用电设备包括上述的电池。由于电池采用了上述所有实施例的全部技术方案，因此至少具有上述实施例的技术方案所带来的所有有益效果，在此不再一一赘述。
用电设备采用上述高性价比的电池，提高用电设备的使用性能，提高使用价值。
实施例
实施例1
正极极片的制备
第一活性物质层浆料：将正极活性物质磷酸锰铁锂、导电炭黑、粘结剂PVDF和溶剂N-甲基吡咯烷酮(NMP)按重量比96：2：2：100均匀搅拌，得到混合均匀的第一活性物质层浆料。
第二活性物质层浆料：正极活性物质五系单晶三元材料、导电炭黑、粘结剂PVDF和溶剂N-甲基吡咯烷酮(NMP)按重量比96：2：2：100均匀搅拌，得到混合均匀的第二活性物质层浆料；将第一活性物质层浆料和第二活性物质层浆料同时均匀的涂覆在厚13um的铝箔集流体上，然后在110℃下烘 干。经过压力20-40吨冷压处理后即可获得涂层厚度约为90um的膜片。其中，第一活性层的宽度与第二活性层的宽度比为1：1，且第二活性层位于集流体的中部，第一活性层位于集流体的两侧。
负极极片的制备
将人造石墨、导电炭黑、粘结剂羧甲基纤维素(CMC)和溶剂水按重量比95：2：3：100均匀混合，搅拌得到均匀的负极浆料；将负极浆料均匀的涂覆在厚6μm的铜箔集流体上，然后在100℃下烘干。经过压力20-40吨冷压处理后即可获得涂层厚度约为60μm的膜片。
电解液的制备
将碳酸亚乙酯(EC)、聚碳酸酯(PC)、碳酸二甲酯(DMC)按体积比1:1:1混合，然后将LiPF6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF6的浓度为1mol/L。
隔膜：以厚度为12μm的聚乙烯膜(PE)作为隔离膜。
二次电池的制备
将上述各实施例或对比例中的正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件放入外包装中，加入上述制备的电解液，经封装、静置、化成、老化等工序后，得到二次电池。
在实施例1的基础上，在其他条件不变的情况下，改变实验参数(如表1所示)，得到实施例2至实施例11、以及对比例1的实验数据。
二次电池性能测试
电池循环寿命测试
分别取五个上述各实施例和对比例中二次电池进行平行试验，每个电池在常温下以0.33C倍率充电至电压等于4.2V，然后再以0.33C倍率放电至电压等于2.0V，测得可逆容量为C0。不断重复充电放电，直到某一次循环的放电容量Cn/C0≤80％为止。那么总的循环次数记为X-Cycle。
电池高温稳定性测试
分别取五个上述各实施例和对比例中二次电池进行平行试验，每个电池在常温下以0.33C倍率充电至电压等于4.2V后，再恒压CV充电至0.05C电流截止。单电芯夹具加紧，5℃/min，55℃环境放置2h，再以5℃/min温升速率，每5℃保持30min，从55℃温升至电芯发生失控，1s记录数据，电芯发生失控时的温度记为Tf。
活性层总放热量测试
通过差示扫描量热测仪(DSC)来进行测试，差示扫描量热仪的参数设置为：氮气气氛下，吹扫气50ml/min，保护气20ml/min，升温程序为10℃/min，从35℃升温至600℃。制样步骤为：裁剪一定量的活性层，称取10mg左右样品于Al2O3坩埚中，抖平。
表1电池性能测试数据表

从表1中可以看出，对比例1的活性涂层为三元材料，其热稳定性和循环寿命差。
如实施例1至实施例11所示，同时涂布三元材料和磷酸锰铁锂材料，有效提高综合性能，说明两者的共同涂布综合利用两者的优势，以提高电池的综合性能。
综上所述，采用复合电极的结构，能有效提高复合电极的综合性能。
上仅为本申请的优选实施例，并非因此限制本申请的专利范围，凡是在本申请的申请构思下，利用本申请说明书及附图内容所作的等效结构变换，或直接/间接运用在其他相关的技术领域均包括在本申请的专利保护范围内。

Claims (42)

  1. 一种复合电极，其中，所述复合电极包括集流体和形成于所述集流体至少一侧表面的涂布区域，所述涂布区域包括沿同一延伸方向排列设置的第一活性层和第二活性层，所述第一活性层的热稳定性不同于所述第二活性层的热稳定性。
  2. 如权利要求1所述的复合电极，其中，所述第一活性层设于所述集流体的表面，并靠近所述集流体用以设置极耳的一侧，所述第二活性层设于所述集流体的表面，且位于所述第一活性层背离所述集流体用以设置极耳的一侧，所述第一活性层的热稳定性大于所述第二活性层的热稳定性。
  3. 如权利要求2所述的复合电极，其中，所述集流体的表面至少形成三个涂层区域，至少两个涂层区域用以分别设置所述第一活性层和第三活性层，至少另一个涂层区域用以设置所述第二活性层，且，所述第二活性层位于所述第一活性层和所述第三活性层之间，所述第三活性层的热稳定性大于所述第二活性层的热稳定性。
  4. 如权利要求3所述的复合电极，其中，所述第一活性层和所述第三活性层的材料相同；
    或，所述第一活性层和所述第三活性层的材料不同。
  5. 如权利要求3或4所述的复合电极，其中，所述第一活性层的总放热量和所述第三活性层的总放热量分别小于所述第二活性层的总放热量。
  6. 如权利要求5所述的复合电极，其中，所述第一活性层的总放热量的范围值为100J/g-500J/g，所述第三活性层的总放热量的范围值为100J/g-500J/g，所述第二活性层的总放热量的范围值为800J/g-1500J/g。
  7. 如权利要求3至6中任一项所述的复合电极，其中，所述第一活性层构成的电芯的失效温度大于所述第二活性层构成的电芯的失效温度；所述第三活性层构成的电芯的失效温度大于所述第二活性层构成的电芯的失效温度。
  8. 如权利要求7所述的复合电极，其中，所述第一活性层构成的电芯的失效温度为160℃-220℃，所述第三活性层构成的电芯的失效温度为160℃-220℃，所述第二活性层构成的电芯的失效温度为120℃-160℃。
  9. 如权利要求1至8中任一项所述的复合电极，其中，所述集流体用以设置极耳的一侧预设有绝缘层涂覆区域，所述第一活性层覆盖所述绝缘层涂覆区域。
  10. 如权利要求3至8中任一项所述的复合电极，其中，定义所述集流体的两侧均用以设置极耳，所述集流体用以设置极耳的另一侧预设有绝缘层涂覆区域，所述第三活性层覆盖所述绝缘层涂覆区域。
  11. 如权利要求1或2所述的复合电极，其中，所述第一活性层与所述第二活性层的宽度比为0.25-4。
  12. 如权利要求3至8、10中任一项所述的复合电极，其中，所述第一活性层和所述第三活性层之和与所述第二活性层的宽度比为0.25-4。
  13. 如权利要求1或2所述的复合电极，其中，所述第一活性层的宽度占活性层的总宽度20％-80％；
    和/或，所述第二活性层的宽度占活性层的总宽度的20％-80％。
  14. 如权利要求3至8、10中任一项所述的复合电极，其中，所述第一活性层和所述第三活性层宽度之和占活性层的总宽度20％-80％；
    和/或，所述第二活性层的宽度占活性层的总宽度的20％-80％。
  15. 如权利要求9、11、13中任一项所述的复合电极，其中，所述第一活性层的宽度大于3mm。
  16. 如权利要求10、12、14中任一项所述的复合电极，其中，所述第三活性层的宽度大于3mm。
  17. 如权利要求3至8、10、12、14、16中任一项所述的复合电极，其中，所述第一活性层的克容量和所述第三活性层的克容量分别小于所述第二活性层的克容量。
  18. 如权利要求17所述的复合电极，其中，所述第一活性层的克容量和所述第三活性层的克容量分别占所述第二活性层克容量的60％-80％。
  19. 如权利要求3至8、10、12、14、16至18中任一项所述的复合电极，其中，所述第一活性层中的活性材料的平均粒径Dv50和所述第三活性层中的活性材料的平均粒径Dv50分别为0.2um-2um。
  20. 如权利要求1至19中任一项所述的复合电极，其中，所述第二活性层中的活性材料的平均粒径Dv50的范围值为0.5um-20um。
  21. 如权利要求3至8、10、12、14、16至19中任一项所述的复合电极，其中，所述第一活性层、所述第二活性层、所述第三活性层的厚度相同。
  22. 如权利要求21所述的复合电极，其中，所述第一活性层、所述第二活性层、所述第三活性层的厚度为80μm-300μm。
  23. 如权利要求1至22中任一项所述的复合电极，其中，所述第一活性层包括磷酸锰铁锂材料。
  24. 如权利要求23所述的复合电极，其中，所述磷酸锰铁锂材料设有导电包覆材料。
  25. 如权利要求24所述的复合电极，其中，所述导电包覆材料的质量为所述磷酸锰铁锂材料质量的1％-10％；
    和/或，所述导电包覆材料包括碳或金属氧化物中的至少一种。
  26. 如权利要求23至25中任一项所述的复合电极，其中，所述第一活性层还包括三元材料，所述磷酸锰铁锂材料的质量占所述第一活性层总质量的20％-80％。
  27. 如权利要求23至26中任一项所述的复合电极，其中，所述磷酸锰铁锂材料的结构通式为LiMnxFeyM1-x-yPO4，式中，0.4≤x≤0.8；0.1≤y≤0.6；0≤1-x-y≤0.2，M表示掺杂元素，可选地包括Al、Cu、Mg、Zn、Ni、Ti、V、Zr、Co、Ga、Sn、Sb、Nb和Ge中的至少一种。
  28. 如权利要求1至27中任一项所述的复合电极，其中，所述第二活性层包括三元材料或钴酸锂中的至少一种。
  29. 如权利要求28所述的复合电极，其中，当所述第二活性层包括三元材料时，所述三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，N可选地包括Mn、Zr、Al、B、Ta、Mo、W、Nb、Sb、La中的至少一种，其中，0.35≤a<1.0，0≤b≤0.35，0≤1-a-b≤0.35。
  30. 如权利要求29所述的复合电极，其中，当所述第二活性层包括三元材料时，所述三元材料的结构通式为LiNiaCobN(1-a-b)O2，式中，0.5≤a≤0.96。
  31. 如权利要求30所述的复合电极，其中，所述三元材料包括5系单晶三元材料、5系多晶三元材料、6系单晶三元材料、6系多晶三元材料、7系单晶三元材料、7系多晶三元材料、8系单晶三元材料、8系多晶三元材料、9系单晶三元材料、9系多晶三元材料、无钴三元材料中的至少一种。
  32. 如权利要求28至31中任一项所述的复合电极，其中，在所述第一活性层和所述第二活性层均包括三元材料时，所述第一活性层和所述第二活性层中的三元材料相同。
  33. 如权利要求1至32中任一项所述的复合电极，其中，所述第一活性层包括第一活性物质、导电剂和粘结剂，所述第一活性物质包括磷酸锰铁锂材料，所述磷酸锰铁锂材料质量占所述第一活性层总质量的94％-97％；
    和/或，所述第二活性层包括第二活性物质、导电剂和粘结剂，所述第二活性物质包括三元材料，所述三元材料占所述第二活性层总质量的95％-98％。
  34. 一种复合电极的制备方法，其中，包括以下步骤：
    在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在所述集流体上形成第一活性层和第二活性层；
    烘干后，经过冷压，得到复合电极；
    其中，所述第一活性层的热稳定性不同于所述第二活性层的热稳定性。
  35. 如权利要求34所述的复合电极的制备方法，其中，在所述在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在所述集流体上形成第一活性层和第二活性层的过程中，所述第一活性层靠近所述集流体用以设置极耳的一侧，所述第二活性层位于所述第一活性层背离所述集流体用以设置极耳的一侧，所述第一活性层的热稳定性大于所述第二活性层的热稳定性。
  36. 如权利要求35所述的复合电极的制备方法，其中，在所述在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在所述集流体上形成第一活性层和第二活性层的过程中，包括以下步骤：
    在集流体的同一面涂覆至少一条第一活性物质层浆料、至少一条第三活性物质层浆料和至少一条第二活性物质层浆料，所述第二活性物质层浆料设置在所述第一活性物质层浆料和所述第三活性物质层浆料之间，所述第三活性层的热稳定性大于所述第二活性层的热稳定性。
  37. 如权利要求34至36中任一项所述的复合电极的制备方法，其中，在所述在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料，在所述集流体上形成第一活性层和第二活性层的过程中，包括以下步骤：
    在集流体的同一面同时涂覆第一活性物质层浆料和第二活性物质层浆料，在所述集流体上形成第一活性层和第二活性层。
  38. 如权利要求34至37中任一项所述的复合电极的制备方法，其中，在集流体的同一面涂覆第一活性物质层浆料和第二活性物质层浆料的过程中，还包括以下步骤：
    在集流体的一面上涂覆一层底涂，再在所述底涂上涂覆第一活性物质层浆料和第二活性物质层浆料。
  39. 如权利要求34至38中任一项所述的复合电极的制备方法，其中，在经过冷压的步骤中，所述第一活性层和所述第二活性层在经过冷压后，冷压至相同的厚度，所述厚度为80μm-300μm。
  40. 如权利要求34至39中任一项所述的复合电极的制备方法，其中，在烘干后，经过冷压，得到复合电极的步骤中，所述烘干的温度为90℃-120℃，所述冷压的压力为20吨-40吨，所述冷压的温度为15℃-35℃。
  41. 一种电池，其中，包括：负极极片、正极极片、隔离膜及电解液，其中所述正极极片为如权利要求1至33中任一项所述的复合电极。
  42. 一种用电设备，其中，所述用电设备包括如权利要求41所述的电池。
PCT/CN2023/114471 2022-11-10 2023-08-23 复合电极及其制备方法、电池和用电设备 WO2024098886A1 (zh)

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