WO2023184170A1 - 电化学装置及电子设备 - Google Patents

电化学装置及电子设备 Download PDF

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Publication number
WO2023184170A1
WO2023184170A1 PCT/CN2022/083802 CN2022083802W WO2023184170A1 WO 2023184170 A1 WO2023184170 A1 WO 2023184170A1 CN 2022083802 W CN2022083802 W CN 2022083802W WO 2023184170 A1 WO2023184170 A1 WO 2023184170A1
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WIPO (PCT)
Prior art keywords
coating
active material
current collector
material layer
electrochemical device
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PCT/CN2022/083802
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English (en)
French (fr)
Inventor
胡雨寒
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宁德新能源科技有限公司
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Priority to PCT/CN2022/083802 priority Critical patent/WO2023184170A1/zh
Publication of WO2023184170A1 publication Critical patent/WO2023184170A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers

Definitions

  • Some embodiments of the present application relate to the field of electrochemical technology, and in particular, to an electrochemical device and electronic equipment.
  • Electrochemical devices are the source of power for electronic equipment and are the key to ensuring the normal use of electronic equipment. With the gradual popularization of electronic devices such as mobile phones and laptop computers, the capacity requirements for electrochemical devices are becoming higher and higher.
  • the expansion of the electrochemical device can easily cause the active material layer to powder and fall off from the pole piece, causing the active material layer to lose electrical contact with the conductive network such as the current collector, ultimately leading to rapid attenuation and deterioration of the pole piece capacity. .
  • Some embodiments of the present application are intended to provide an electrochemical device and electronic equipment that can at least alleviate the expansion of the electrochemical device.
  • an electrochemical device including a current collector and an active material layer coated on the current collector.
  • the electrochemical device further includes a coating, the coating being disposed on the active material. layer.
  • the coating has a first end and a second end that are oppositely arranged, and along the width direction of the current collector, the coating has a third end that is opposite to each other and a second end that is opposite to each other.
  • Four ends The first end and the second end are connected to the current collector, and/or the third end and the fourth end are connected to the current collector.
  • the coating is opened with at least one through hole configured to communicate with the active material layer.
  • the coating is provided on the surface of the active material layer to reduce the free expansion space of the active material layer, so that the active material layer of the electrochemical device can still be in good contact with the current collector after long-term charge and discharge cycles. Opening through holes in the coating can allow more electrolyte to infiltrate deep into the active material layer, replacing the original solid-phase diffusion channel with a lower diffusion rate, providing a faster material transfer channel, and helping to reduce the electrochemical device's extreme The overall impedance of the chip. At the same time, the through holes provide a buffer space for the strain of the active material layer, which can reduce the expansion of the pole piece, which is beneficial to improving the long-term cycle life of the electrochemical device and maintaining high energy density.
  • the active material layer includes a first active material and a second active material, and the gram capacity of the first active material is greater than the gram capacity of the second active material.
  • the first active material includes at least one of elemental silicon, silicon oxide compounds, silicon carbon composites and silicon alloys; and/or the second active material includes graphite, soft carbon, hard carbon, carbon fiber and mesophase at least one of carbon microspheres.
  • the first active material is silicon, the second active material is carbon, and the mass content of the first active material in the active material layer is 1% to 45%.
  • the theoretical gram capacity of silicon is 4200mAh/g, which is greater than the gram capacity of carbon, 372mAh/g.
  • the use of silicon active materials can increase the capacity of the pole piece. Carbon active materials with a more stable structure are filled between the silicon active materials, which can be used as silicon active materials. The volume buffering matrix of the material.
  • the coating is provided with a plurality of through holes, and has a first surface and a second surface arranged oppositely along the thickness direction of the current collector. Compared with the first surface, the second surface is closer to the active material layer; based on the surface area of the first surface, the area ratio of the plurality of through holes is 10% to 30%.
  • the area of the through hole is within the aforementioned range, which can give the coating good dynamics while maintaining the original mechanical strength of the coating, which can effectively reduce irreversible plastic strain in the coating after long-term cycling.
  • a plurality of the through holes are distributed in the coating in an array. Multiple through holes are spaced apart. The uniform distribution of the array is conducive to the penetration of the electrolyte into various positions of the active material layer, and facilitates full contact between the active material layer and the electrolyte.
  • the through hole satisfies 0 ⁇ R ⁇ 5 ⁇ m, and R is the radius of the through hole.
  • the coating with a micron-scale porous structure can maintain a stable morphology for a long time during the charge and discharge cycle of the electrochemical device to reduce the volume expansion of the pole piece.
  • the tensile strength of the coating is greater than the tensile strength of the active material layer.
  • the coating has higher mechanical strength and tensile strength, and can withstand greater stress without producing plastic strain.
  • the coating covers the surface of the active material layer to reduce the free expansion space of the active material layer, thereby ensuring that the electrochemical device After long-term charge and discharge cycles, the active material layer can still be in good contact with the current collector.
  • the active material layer has a third surface and a fourth surface arranged oppositely; compared with the third surface, the fourth surface is closer to the The current collector; along the length direction of the current collector, the active material layer includes a first side and a second side arranged oppositely; along the width direction of the current collector, the active material layer includes a third side arranged oppositely The side and the fourth side; the coating includes a first portion provided on the third side; along the length direction of the current collector, the coating includes a first extension and a second extension that are oppositely arranged; along the In the width direction of the current collector, the coating includes a third extension portion and a fourth extension portion arranged oppositely; the first extension portion includes the first end and extends to the first side; the third extension portion includes the first end and extends to the first side; Two extension parts include the second end and extend from the second side.
  • Corresponding extension parts are provided in each direction of the active material layer, so that the coating covers the active material layer, wherein the first extension part, the second extension part, the third extension part and the fourth extension part can all be connected and fixed on on the current collector to limit the expansion of the active material layer.
  • the through hole is opened in the first part, and the through hole is opened in at least one of the first extension part, the second extension part, the third extension part and the fourth extension part.
  • Each extension part may be provided with through holes to facilitate the electrolyte to infiltrate into the active material layer from all directions.
  • the coating is provided with a plurality of through holes, including a first through hole and a second through hole; the first through hole is provided in the first part; and the second through hole is provided in the first extension part and on at least one of the second extension portions.
  • the third extension includes the third end and extends to the third side; and the fourth extension includes the fourth end and extends to the fourth side.
  • the coating meets at least one of the following conditions: (a), the first extension completely covers the first side of the active material layer; (b), the first extension The two extension parts completely cover the second side of the active material layer; (c), the third extension part completely covers the third side of the active material layer; (d), the fourth extension part completely Covering the fourth side of the active material layer.
  • the first extension part, the second extension part, the third extension part and the fourth extension part are all connected to the current collector.
  • the coating meets the following conditions: (a), along the length direction of the current collector, the thickness of the first extension part and the second extension part is 0.5 ⁇ m to 10 ⁇ m; ( b), along the width direction of the current collector, the thickness of the third extension part and the fourth extension part is 0.5 ⁇ m to 10 ⁇ m; (c), along the direction from the coating to the current collector , the thickness of the first part is 0.5 ⁇ m to 10 ⁇ m.
  • the coating meets the following conditions: (a), along the length direction of the current collector, the thickness of the first extension part and the second extension part is 1 ⁇ m to 8 ⁇ m; (b) ), along the width direction of the current collector, the thickness of the third extension part and the fourth extension part is 1 ⁇ m to 8 ⁇ m; (c), along the direction from the coating to the current collector, the thickness The thickness of the first part is 1 ⁇ m to 8 ⁇ m.
  • the coating needs to have a certain lower limit of thickness to ensure the coating's inhibitory effect on the expansion of the pole piece, and also to avoid the risk of excessive coating thickness deteriorating the energy density of the electrochemical device.
  • the thickness of the coating can be selected from 0.5 microns to 10 microns, and in some embodiments, 1 micron to 8 microns can be used.
  • the axis of the through hole is parallel to the direction from the coating to the active material layer to facilitate the entry and exit of the electrolyte.
  • the present application in a second aspect, also provides an electronic device, including the electrochemical device as described in any of the above embodiments.
  • Figure 1 is a schematic structural diagram of an electrochemical device according to some embodiments of the present application.
  • Figure 2 is a cross-sectional view along line A-A of Figure 1;
  • Figure 3 is a schematic structural diagram of a pole piece in some embodiments of the present application.
  • Figure 4 is an exploded view of a pole piece according to some embodiments of the present application.
  • Figure 5a is a schematic cross-sectional view of a pole piece in some embodiments of the present application.
  • Figure 5b is an exploded view of Figure 5a
  • Figure 6 is a schematic diagram of through hole arrangement in some embodiments of the present application.
  • Figure 7 is a schematic diagram of through hole arrangement in some embodiments of the present application.
  • Figure 8 is a schematic diagram of the relationship between the expansion of the electrochemical device and the number of cycles in some embodiments of the present application.
  • Figure 9 is a schematic diagram of the relationship between the expansion of the electrochemical device and the number of cycles in some embodiments of the present application.
  • Figure 10 is a schematic diagram of the relationship between the expansion of the pole pieces and the number of cycles in some embodiments of the present application.
  • Figure 11 is a schematic diagram of the relationship between the expansion of the pole piece and the energy density loss of the electrochemical device and the thickness of the coating in some embodiments of the present application;
  • Figure 12 is a schematic diagram of the relationship between discharge rate and discharge capacity in some embodiments of the present application.
  • Figure 13 is a schematic diagram of the relationship between the SOC state and DCR of the electrochemical device according to some embodiments of the present application.
  • Figure 14 is a schematic diagram of the relationship between the SOC state and Rss of the electrochemical device according to some embodiments of the present application.
  • Figure 15 is a schematic diagram of the relationship between the number of cycles and the capacity retention rate in some embodiments of the present application.
  • Figure 16 is a schematic diagram of the relationship between the number of cycles and the capacity retention rate in some embodiments of the present application.
  • Electrochemical device 100. Electrochemical device
  • 13a first part; 13a1, first surface; 13a2, second surface; 13b, first extension part; 13c, third extension part;
  • the most widely used negative active material for lithium-ion electrochemical devices is graphite material.
  • the gram capacity of graphite material is low (372mAh/g), making it difficult to meet the growing demand for high-capacity lithium-ion electrochemical devices.
  • Silicon is abundant in reserves and has a much higher gram capacity than graphite (4200mAh/g, based on Li 22 Si 4 alloy), so silicon is considered the most promising next-generation anode material.
  • the inventor of the present application noticed that during the charge and discharge process of the electrochemical device, the lithium deintercalation reaction of silicon is accompanied by a huge volume change (>300%, based on Li 22 Si 4 alloy), which easily causes the silicon active material to be removed from the pole piece. Powdering and falling off causes the active material layer to lose electrical contact with the conductive network such as the current collector, ultimately leading to rapid attenuation and deterioration of the capacity of the pole piece.
  • an embodiment of the present application proposes an electrochemical device 100.
  • the electrochemical device 100 is the smallest unit that constitutes an electrochemical device or an electrochemical device module. It is a place where the conversion of electrical energy and chemical energy is realized.
  • FIGS. 1 and 2 respectively show the structure of the electrochemical device 100 and the cross-section of the electrochemical device 100 .
  • the electrochemical device 100 includes a negative electrode piece 10, a positive electrode piece 20, and an isolation film 30.
  • the negative electrode piece 10 and the positive electrode piece 20 are spaced apart, and the isolation film 30 is provided between the negative electrode piece 10 and the positive electrode piece 20 to separate them.
  • the negative electrode piece 10, an isolation film 30, the positive electrode piece 20 and another isolation film 30 are stacked and wound into a bare cell of the electrochemical device 100; it is worth mentioning that in other embodiments, the bare cell
  • the core can also be a stacked structure.
  • the negative electrode piece 10 includes a current collector 11, an active material layer 12 and a coating 13.
  • the active material layer 12 is coated on at least one surface of the current collector 11, and the coating 13 is provided on the active material layer 12. superior.
  • the current collector 11 has a flat strip structure as a whole, and the thickness of each part of the current collector 11 is basically the same.
  • the thickness of the current collector 11 is usually between 3 microns ( ⁇ m) and 20 microns. between.
  • the current collector 11 has a long side 111 , a wide side 112 and a thickness side 113 .
  • the long side 111 is the side extending along the length direction (X direction) of the current collector 11 when it is unfolded into a flat state.
  • the wide side 112 is the side extending along the width direction (Y direction) of the current collector 11 when it is unfolded into a flat state.
  • the thickness side 113 is a side extending along the thickness direction (Z direction) of the current collector 11 when it is unfolded into a flat state.
  • the current collector 11 has two main surfaces 11a.
  • the two main surfaces 11a are jointly defined by the above-mentioned long side 111 and the wide side 112.
  • the two main surfaces 11a are arranged oppositely along the extension direction of the above-mentioned thickness side 113.
  • the two main surfaces 11a The active material layer 12 can be coated on both surfaces.
  • the current collector 11 is a pole piece made of a conductive base material. Depending on the type of pole piece, different materials can be selected as the current collector 11 of the pole piece. In this embodiment, the negative pole piece 10 is used, and the current collector 11 can be selected from copper foil.
  • the active material layer 12 is the core material layer of the electrochemical device 100.
  • the active material layer 12 is coated on at least one surface of the current collector 11, for example, coated on the above-mentioned current collector.
  • One of the two main surfaces 11 a of the fluid 11 or the two main surfaces 11 a of the current collector 11 are coated with the active material layer 12 .
  • the active material layer 12 includes active materials, conductive agents, adhesives, deionized water, etc. The above materials are mixed, stirred evenly, and coated on the surface of the current collector 11 to obtain the active material layer 12 .
  • the specific components of the active material are actually diverse.
  • the active material layer 12 includes a first active material and a second active material, wherein the gram capacity of the first active material is greater than the gram capacity of the second active material.
  • the first active material includes at least one of the group consisting of elemental silicon, silicon oxy compounds, silicon carbon composites, and silicon alloys.
  • the second active material includes at least one of the group consisting of graphite, soft carbon, hard carbon, carbon fiber, and mesocarbon microspheres.
  • the first active material is silicon
  • the second active material is carbon
  • the theoretical gram capacity of silicon is 4200 mAh/g, which is greater than the gram capacity of carbon 372 mAh/g.
  • the use of silicon active materials can increase the capacity of the electrochemical device. , filling the carbon active materials with a more stable structure between the silicon active materials, which can be used as a volume buffer matrix for the silicon active materials; wherein, the mass fraction of silicon in the active material layer 12 can be selected from 1% to 45%, and the mass fraction of silicon The content can be measured by Element Analysis.
  • the coating 13 is provided on the surface of the active material layer 12.
  • the coating 13 can partially or completely cover the active material layer 12.
  • the coating 13 is configured to limit the active material layer. 12, to reduce the powdering and falling off of the active material layer 12.
  • the coating 13 can be a high-strength and high-toughness organic coating film.
  • the coating 13 in order to ensure the mechanical strength of the coating 13, is a pure polymer, does not contain any active materials, and does not provide any charge and discharge. capacity. Compared with the active material layer 12, the coating 13 has higher mechanical strength and tensile strength, and can withstand greater stress without generating plastic strain.
  • the coating 13 covers the surface of the active material layer 12 to reduce the free expansion space of the active material layer 12, thereby ensuring that the active material layer 12 of the electrochemical device 100 can still be in good contact with the current collector 11 after long-term charge and discharge cycles. The cycle life of the electrochemical device 100 is improved.
  • the end of the coating 13 extends beyond the active material layer 12 to facilitate connection with the current collector 11 .
  • the coating 12 includes a first end 132 and a second end (not shown in the figure), and both the first end 132 and the second end are connected to the current collector 11 , so that the coating 13 limits the active material layer 12 in the length direction of the current collector 11 .
  • the coating 12 includes a third end 133 and a fourth end 134 , both of which are connected to the current collector 11 , or, The first end 132 , the second end 133 and the fourth end 134 are all connected to the current collector 11 , so that the coating 13 can react to the active material layer 12 in both the length direction and the width direction of the current collector 11 . to limit the expansion of the active material layer 12 .
  • the coating 13 is provided with at least one through hole 131, the through hole 131 penetrates the coating 13, and the through hole 131 is configured.
  • the electrolyte can directly enter the through hole 131 from the outside of the coating 13 and contact and react with the active material layer 12.
  • the through hole 131 serves as a material transfer channel for lithium ions, ensuring that the electrolyte can pass through the coating.
  • the layer 13 is in normal contact with the active material layer 12 on the current collector 11 so as to maintain the normal dynamics of the pole piece.
  • the electrolyte can also directly penetrate the coating 13 to contact and react with the active material layer 12 .
  • the coating 13 is a high-strength organic coating film with a porous structure, which can suppress the expansion of the pole piece and reduce the resistance of the active material layer 12 on the premise of ensuring that the pole piece has sufficient dynamics. Risk of powdering and demolding.
  • the coating 13 closely covers the surface of the active material layer 12. When the active material layer 12 expands due to lithium embedding, the coating 13 generates shrinkage stress, thereby reducing the expansion of the entire pole piece.
  • the coating 13 can be drilled using industrially mature LDP (laser drilling) technology. Through holes 131 are opened in the high-strength coating 13 so that the electrolyte can effectively infiltrate the internal active material layer 12 to successfully complete the electrochemical process. reaction, thereby improving the risk of kinetic deterioration caused by the high-strength coating 13; therefore, in this application, an active material layer 12 with a higher silicon mass content (less than 45%) can be used to increase the capacity of the electrochemical device.
  • the overall shape of the through hole 131 can be cylindrical, truncated cone, prism or pyramid shape, etc.
  • the through hole 131 can be circular, elliptical, rectangular or polygonal, etc. .
  • the number of through holes 131 can be set to multiple, and the multiple through holes 131 are arranged at intervals.
  • the through holes 131 can be evenly distributed on the coating 13.
  • the multiple through holes 131 are distributed in an array.
  • the uniform distribution is beneficial to the penetration of the electrolyte into the active material layer 12 from all positions, and facilitates full contact between the active material layer 12 and the electrolyte.
  • the distribution of the through holes 131 is not limited to the array distribution in this embodiment. In other embodiments, as shown in FIG. 7 , the through holes 131 can also be distributed on the coating 13 in a honeycomb shape.
  • the hole spacing can be set to be greater than twice the hole radius, and the hole spacing is equal to The distance between the centers of the through holes 131.
  • the coating 13 has a first surface 13a1 and a second surface 13a2 arranged oppositely. Compared with the first surface 13a1, the second surface 13a2 is closer to the active material layer 12. On the first surface 13a1, there are more The area ratio of each through hole is 10% to 30%.
  • the cross sections of the through holes 131 can be set to be equal, that is, the porosity of the coating 13 is 10% to 30%, which can give the coating 13 good dynamics and maintain the original properties of the coating 13 The mechanical strength can effectively reduce the irreversible plastic strain of the coating 13 after long-term cycling.
  • the through hole 131 is a micron-level through hole 131, and the radius of the through hole 131 can be set to less than 5 microns.
  • the axis of the through hole 131 can be set parallel to the thickness direction of the current collector 11. Since the outer surface of the coating 13 is usually flat, that is, the axis of the through hole 131 is set perpendicular to the outer surface of the coating 13 to facilitate the entry of the electrolyte.
  • vertical in this embodiment means that the angle between the axis of the through hole 131 and the outer surface of the coating 13 is between 80 degrees and 100 degrees.
  • the coating 13 with a micron-scale porous structure can maintain a stable morphology for a long time during the charge and discharge cycle of the electrochemical device 100 to reduce the volume expansion of the pole piece.
  • the active material layer 12 has a third face 12a and a fourth face 12d arranged oppositely. Compared with the third face 12a, The fourth surface 12d is disposed close to the current collector, and the third surface 12a is disposed away from the current collector 11.
  • the active material layer 12 includes a first side 12b and a second side (not shown in the figure).
  • the active material layer 12 also includes a third side 12c and a third side. Four sides (not shown in the figure).
  • the coating 13 includes a first part 13a and a first extension part 13b and a second extension part (not shown in the figure) connected to the first part 13a,
  • the first part 13a is disposed on the third surface 12a and closely fits the third surface 12a.
  • the first extension part 13b extends on the first side 12b
  • the second extension part extends on the second side
  • the first end part 132 is disposed on the third side.
  • An extension part, the above-mentioned second end part is arranged on the second extension part.
  • the active material layer 12 further includes a third extension portion 13c and a fourth extension portion (not shown in the figures) connected to the first portion 13a, the third extension portion 13c extending from the third side 12c, The fourth extension part extends to the fourth side surface, the third end part 133 is provided on the third extension part, and the fourth end part 134 is provided on the fourth extension part.
  • Corresponding extension portions are provided in each direction of the active material layer 12 so that the coating 13 covers the active material layer 12 , wherein the first end portion 132 , the second end portion , the third end portion 133 and the fourth end portion 134 can be connected and fixed on the current collector 11 to limit the expansion of the active material layer 12 .
  • the through hole 131 is opened in the first part 13a, and the electrolyte directly infiltrates into the active material layer 12 from the through hole 131 in the first part 13a.
  • the through hole 131 includes a first through hole 131a and a second through hole 131b.
  • the first through hole 131a is opened in the first part 13a, and at least one of the first extending part 13b and the second extending part is opened.
  • the through hole 131 further includes a third through hole 131c, and at least one of the third extension portion 13c and the fourth extension portion is provided with the third through hole 131c.
  • the electrolyte can be allowed to enter the active material layer 12 in all directions, so that the active material layer 12 is Fast soaking.
  • the thickness of the coating 13 will also have an impact on the technical effect of the present application, that is, the thickness of the coating 13 is related to the expansion of the pole piece.
  • the thickness of the coating 13 is related to the expansion of the pole piece.
  • 0 micron (no coating 13 ), 3 micron and 5 micron thickness coatings 13 are subjected to relevant tests to obtain the relationship between the thickness of the coating 13 and the expansion of the pole piece.
  • Figures 8 and 9 show the relationship between the expansion of the electrochemical device and the number of cycles, where L 1 is the test result curve when the thickness is 0 microns, and L 2 is the test result curve when the thickness is 3 microns. Test result curve, L 3 is the test result curve when the thickness is 5 microns.
  • L 1 is the test result curve when the thickness is 0 microns
  • L 2 is the test result curve when the thickness is 3 microns.
  • Test result curve L 3 is the test result curve when the thickness is 5 microns.
  • Figure 10 shows the relationship between the expansion of the negative electrode piece 10 and the number of cycles. Like the electrochemical device, the greater the number of cycles, the greater the expansion.
  • Figure 11 shows the relationship between the expansion of the pole pieces and the energy density loss of the electrochemical device and the thickness of the coating 13. As the thickness of the coating 13 increases, the expansion of the pole pieces becomes smaller and smaller, but the energy density of the electrochemical device 100 The losses are also increasing. According to Figure 11, it can be seen that the thickness of the coating 13 can be selected from a range of 1 micron to 8 microns.
  • coatings with thicknesses of 0 microns, 5 microns, and 5 microns + 30% LDP are used respectively (on the surface of the coating 13, the area ratio of the through hole 131 is 30%).
  • Coating 13 was tested, where L 4 is the test result curve at 0 micron thickness, L 5 is the test result curve at 5 micron thickness, and L 6 is the test result curve at 5 micron thickness + 30% LDP treatment.
  • Figure 12 shows the relationship between discharge rate and discharge capacity under different coating thicknesses. As the discharge rate increases, the discharge capacity of the electrochemical device 100 gradually decreases. According to Figure 12, it can be seen that after applying LDP technology to create the through hole 131 on the coating 13, as the discharge rate increases, the discharge capacity is similar to that without the coating 13, and the deteriorated kinetic parameters of the electrochemical device are effectively improve.
  • Figure 13 shows the relationship between the SOC state (state of charge) and DCR (high frequency impedance) of the electrochemical device under coating 13 with different thicknesses. According to Figure 13, it can be seen that as the state of charge of the electrochemical device decreases, the DCR gradually increases. After using LDP technology to create the through hole 131, as the state of charge of the electrochemical device decreases, its DCR is the same as that of the uncoated 13 Time is close.
  • Figure 14 shows the relationship between the SOC state of the electrochemical device and RSS (low frequency impedance) under coating 13 with different thicknesses.
  • RSS low frequency impedance
  • the dynamics and expansion rate of the pole piece can be accurately balanced.
  • a series of physical parameters such as the morphology, depth and distribution of the through holes can be accurately adjusted and controlled. , thereby balancing the improvement of pole piece dynamics and the loss of energy density.
  • the thickness of the coating 13 can be selected from 0.5 microns to 10 microns.
  • the thickness of the coating 13 can also be set to 1 micron to 8 microns. Based on the same inventive concept, the thickness of the first extension part 13b and/or the second extension part is 0.5 micron to 10 micron. In some other embodiments, it can also be set to 1 micron to 8 micron; along the width of the current collector 11 direction, the thickness of the third extension part 13c and/or the fourth extension part is 0.5 micron to 10 micron, and in some other embodiments, it can also be set to 1 micron to 8 micron; along the direction from the coating 13 to the current collector 11 , the thickness of the first part 13a is 0.5 micron to 10 micron, and in some other embodiments, it can also be set to 1 micron to 8 micron.
  • Rate is the charge and discharge rate, the larger the Rate, the better; HL is the high and low temperature test, the higher the value of HL, the better; DCR is the high frequency impedance test, the smaller the value of DCR, the better; Rss is the low frequency impedance test, the value of Rss Smaller is better.
  • Table 1 shows the parameter relationship between the structural parameters of the through hole 131 and the cyclic expansion/kinetics of the pole piece.
  • Table 1 describes the specific effects of the specific parameters of the through hole 131 on the dynamics-related parameters of the pole piece, according to "whether the through hole 131 exists", “whether the through hole 131 penetrates the coating 13" and "the distribution status of the through hole 131"
  • Class design determines the optimal parameters of the structure of the through hole 131.
  • Using the through hole 131 with a small aperture and a low area ratio will achieve an optimal balance between suppressing the expansion of the pole piece and maintaining the original dynamics of the pole piece.
  • the through hole 131 must penetrate the coating 13.
  • the radius is less than 5 microns, and the through hole 131 accounts for 10% to 50% of the area of the coating 13 surface.
  • the lower limit value gives the coating 13 good dynamics
  • the upper limit value maintains the original mechanical strength of the coating 13 to reduce irreversible plastic strain in the coating 13 after long-term cycling.
  • the same level in the table means that the two test values are the same or basically the same, for example, the difference is less than 0.1%.
  • the degree of difference in this application refers to the value obtained by subtracting the difference between the large object and the small object, divided by the small object, and multiplied by 100%.
  • Figures 15 and 16 show the relationship between the number of cycles and the capacity retention rate of the electrochemical device 100 under different coating 13 thicknesses, using no coating 13 and coating 13 with a thickness of 5 mm + 30% LDP treatment. Multiple test experiments. According to Figures 15 and 16, it can be seen that as the number of cycles increases, the capacity gradually decreases. Among them, the test curves are close to overlapping. The coating 13 treated with 5 mm thickness + 30% LDP increases with the number of cycles. , its capacity retention rate is approximately the same as that of uncoated 13, and the risk of cycle deterioration has not been observed.
  • micron-scale through holes 131 on the coating 13 by opening micron-scale through holes 131 on the coating 13, more electrolyte can be infiltrated into the depths of the pole piece, replacing the original solid-phase diffusion channel with a lower diffusion rate, and providing a faster material transfer channel. , which is beneficial to reducing the overall impedance of the pole piece.
  • the through hole 131 provides a buffer space for the strain of the active material layer 12, which can reduce the expansion of the pole piece, which is beneficial to improving the long-term cycle life of the electrochemical device 100 and maintaining high energy density.
  • an embodiment of the present application also provides an electronic device, including the electrochemical device 100 as described in any of the above embodiments.
  • the electrochemical device 100 disclosed in some embodiments of the present application can be used in, but is not limited to, electronic equipment such as vehicles, ships, or aircrafts.
  • the power supply system of the electronic device can be composed of the electrochemical device 100 disclosed in the present application. In this way, it is beneficial to increase the capacity of the electrochemical device 100, improve the endurance of the electronic device, and at the same time reduce the impedance of the electrochemical device 100. In order to meet the fast charging and fast discharging requirements of the electrochemical device 100 .
  • the electronic device may be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric vehicle, a ship, a spacecraft, etc.
  • electric toys can include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, electric airplane toys, etc.
  • spacecraft can include airplanes, rockets, space shuttles, spaceships, etc.

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  • Chemical Kinetics & Catalysis (AREA)
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Abstract

本申请一些实施例公开了一种电化学装置及电子设备，包括集流体、活性材料层和涂层，涂层设置于活性材料层上，沿集流体的长度方向，涂层具有相对设置的第一端部和第二端部，沿集流体的宽度方向，涂层具有相对设置的第三端部和第四端部；第一端部和第二端部连接于集流体，和/或，第三端部和第四端部连接于集流体；涂层开设有至少一个通孔。在涂层上开设通孔，可令更多的电解液浸润至活性材料层深处，取代原本扩散速率较低的固定扩散通道，提供更快速的物质传递通道，有利于降低电化学装置极片的整体阻抗，同时，通孔为活性材料层的应变提供了缓冲空间，可减小极片的膨胀，有利于电化学装置长期循环寿命的提高以及高能量密度的维持。

Description

电化学装置及电子设备 技术领域
本申请一些实施例涉及电化学技术领域，尤其涉及一种电化学装置及电子设备。
背景技术
电化学装置是电子设备的电源之源，是保证电子设备正常使用的关键。随着手机、笔记本电脑等电子设备的逐渐的普及，对电化学装置的容量要求也越来越高。
电化学装置在充放电的使用过程中，电化学装置膨胀易导致活性材料层从极片上粉化脱落，使得活性材料层与集流体等导电网络脱离电接触，最终导致极片容量的快速衰减恶化。
发明内容
本申请一些实施例旨在提供一种电化学装置及电子设备，以至少能够缓解电化学装置的膨胀。
本申请一些实施例为了缓解上述技术问题，采用以下技术方案：
第一方面，本申请的实施例提出了一种电化学装置，包括集流体和涂覆于所述集流体上的活性材料层，电化学装置还包括涂层，所述涂层设置于活性材料层上。沿所述集流体的长度方向，所述涂层具有相对设置的第一端部和第二端部，沿所述集流体的宽度方向，所述涂层具有相对设置的第三端部和第四端部。所述第一端部和所述第二端部连接于所述集流体，和/或，所述第三端部和所述第四端部连接于所述集流体。所述涂层开设有至少一个通孔，所述通孔被配置为与所述活性材料层连通。
涂层设置在活性材料层表面以减小活性材料层的自由膨胀空间，使得电化学装置在长期的充放电循环后活性材料层仍然能够与集流体良好接触。在涂层上开设通孔，可令更多的电解液浸润至活性材料层深处，取代原本扩散速率较低的固相扩散通道，提供更快速的物质传递通道，有利于降低电化学装置极片的整体阻抗。同时，通孔为活性材料层的应变提供了缓冲空间，可减小极片的 膨胀，有利于电化学装置长期循环寿命的提高以及高能量密度的维持。
根据本申请的一些实施例，所述活性材料层包括第一活性材料和第二活性材料，所述第一活性材料的克容量大于所述第二活性材料的克容量。所述第一活性材料包括单质硅、硅氧化合物、硅碳复合物和硅合金中的至少一种；和/或，所述第二活性材料包括石墨、软碳、硬碳、碳纤维和中间相碳微球的中的至少一种。所述第一活性材料为硅，所述第二活性材料为碳，所述第一活性材料在所述活性材料层的质量含量为1％至45％。
硅的理论克容量为4200mAh/g，大于碳的克容量372mAh/g，采用硅活性材料可提高极片的容量，在硅活性材料之间填充结构更为稳定的碳活性材料，可作为硅活性材料的体积缓冲基体。
根据本申请的一些实施例，所述涂层设置有多个通孔，沿所述集流体的厚度方向，所述涂层具有相对设置的第一面和第二面。相较于所述第一面，所述第二面靠近所述活性材料层；基于所述第一面的表面积，所述多个通孔的面积占比为10％至30％。通孔的面积处于前述范围，可赋予涂层良好的动力学，的同时，维持涂层原本的机械强度，可有效减少在长期循环后涂层出现不可逆的塑性应变。
多个所述通孔呈阵列分布于所述涂层。多个通孔间隔设置。阵列的均匀分布有利于电解液渗透到活性材料层的各个位置，便于活性材料层与电解液充分接触。
根据本申请的一些实施例，所述通孔满足0＜R≤5μm，R为所述通孔的半径。微米级多孔结构的涂层在电化学装置充放电循环过程中可长期保持形貌稳定，以减小极片的体积膨胀。
根据本申请的一些实施例，所述涂层的抗拉强度大于所述活性材料层的抗拉强度。涂层具有更高的机械强度及抗拉强度，可以承受更大应力而不产生塑性应变，涂层包覆在活性材料层表面以减小活性材料层的自由膨胀空间，从而保证电化学装置在长期的充放电循环后活性材料层仍然能够与集流体良好接触。
根据本申请的一些实施例，沿所述集流体的厚度方向，所述活性材料层具有相对设置的第三面和第四面；相较于所述第三面，所述第四面靠近所述集流体；沿所述集流体的长度方向，所述活性材料层包括相对设置的第一侧面和第二侧面；沿所述集流体的宽度方向，所述活性材料层包括相对设置的第三侧面 和第四侧面；所述涂层包括设置于所述第三面的第一部分；沿所述集流体的长度方向，所述涂层包括相对设置的第一延伸部和第二延伸部；沿所述集流体的宽度方向，所述涂层包括相对设置的第三延伸部和第四延伸部；所述第一延伸部包括所述第一端且延伸于所述第一侧面；所述第二延伸部包括所述第二端且延伸于所述第二侧面。
在活性材料层的每个方向均设置对应的延伸部，使得涂层包覆活性材料层，其中，第一延伸部、第二延伸部、第三延伸部和第四延伸部均可连接固定于集流体上，以限制活性材料层的膨胀。
根据本申请的一些实施例，所述通孔开设于所述第一部分，所述第一延伸部、第二延伸部、第三延伸部和第四延伸部中至少一个开设有所述通孔。各个延伸部均可设置通孔，以便于电解液从各个方向浸润至活性材料层。
所述涂层开设有多个通孔，包括第一通孔和第二通孔；所述第一通孔开设于所述第一部分；以及所述第二通孔开设于所述第一延伸部和所述第二延伸部中的至少一个上。所述第三延伸部包括所述第三端且延伸于所述第三侧面；和所述第四延伸部包括所述第四端且延伸于所述第四侧面。
根据本申请的一些实施例，所述涂层满足以下条件中的至少一个：(a)、所述第一延伸部完全覆盖于所述活性材料层的第一侧面；(b)、所述第二延伸部完全覆盖于所述活性材料层的第二侧面；(c)、所述第三延伸部完全覆盖于所述活性材料层的第三侧面；(d)、所述第四延伸部完全覆盖于所述活性材料层的第四侧面。所述第一延伸部、第二延伸部、第三延伸部和第四延伸部均连接于所述集流体。
根据本申请的一些实施例，所述涂层满足以下条件：(a)、沿所述集流体的长度方向，所述第一延伸部和第二延伸部的厚度均为0.5μm至10μm；(b)、沿所述集流体的宽度方向，所述第三延伸部和所述第四延伸部的厚度均为0.5μm至10μm；(c)、沿所述涂层至所述集流体的方向，所述第一部分的厚度为0.5μm至10μm。
根据本申请的一些实施例，所述涂层满足以下条件：(a)、沿所述集流体的长度方向，所述第一延伸部和第二延伸部的厚度均为1μm至8μm；(b)、沿所述集流体的宽度方向，所述第三延伸部和所述第四延伸部的厚度均为1μm至8μm；(c)、沿所述涂层至所述集流体的方向，所述第一部分的厚度为1μm至 8μm。
设计涂层厚度时，既需要涂层具有一定的厚度下限以保证涂层对极片膨胀的抑制效果，也要规避涂层厚度过大恶化电化学装置的能量密度风险，本申请的实施例中，涂层的厚度可选择0.5微米至10微米，在一些实施例中，可采用1微米至8微米。
根据本申请的一些实施例，所述通孔的轴线平行于所述涂层至所述活性材料层的方向，以便于电解液的进入进出。
根据本申请的一些实施例，第二方面，本申请还提出了一种电子设备，包括如上述任一实施例所述的电化学装置。
上述说明仅是本申请技术方案的概述，为了能够更清楚了解本申请的技术手段，而可依照说明书的内容予以实施，为了让本申请的上述和其它目的、特征和优点能够更明显易懂，以下特举本申请的具体实施方式。
附图说明
一个或多个实施例通过与之对应的附图进行示例性说明，这些示例性说明并不构成对实施例的限定，附图中具有相同参考数字标号的元件表示为类似的元件，除非有特别申明，附图中的图不构成比例限制。
图1为本申请一些实施例的电化学装置的结构示意图；
图2为图1的A-A剖视图；
图3为本申请一些实施例的极片的结构示意图；
图4为本申请一些实施例的极片的爆炸视图；
图5a为本申请一些实施例的极片的截面示意图；
图5b为图5a爆炸示图；
图6为本申请一些实施例的通孔排布示意图；
图7为本申请一些实施例的通孔排布示意图；
图8为本申请一些实施例的电化学装置膨胀与循环次数之间的关系示意图；
图9为本申请一些实施例的电化学装置膨胀与循环次数之间的关系示意图；
图10为本申请一些实施例的极片的膨胀与循环次数的关系示意图；
图11为本申请一些实施例的极片膨胀及电化学装置的能量密度损失与涂层厚度的关系示意图；
图12为本申请一些实施例的放电倍率与放电容量之间的关系示意图；
图13为本申请一些实施例的电化学装置SOC状态与DCR之间的关系示意图；
图14为本申请一些实施例的电化学装置SOC状态与Rss之间的关系示意图；
图15为本申请一些实施例的循环次数与容量保持率的关系示意图；
图16为本申请一些实施例的循环次数与容量保持率的关系示意图。
图中：
100、电化学装置；
10、负极极片；
11、集流体；111、长边；112、宽边；113、厚度边；
11a、主表面；
12、活性材料层；
12a、第三面；12b、第一侧面；12c、第三侧面；12d、第四面；
13、涂层；131、通孔；131a、第一通孔；131b、第二通孔；131c、第三通孔；132、第一端部；133、第三端部；134、第四端部；
13a、第一部分；13a1、第一面；13a2、第二面；13b、第一延伸部；13c、第三延伸部；
20、正极极片；
30、隔离膜。
具体实施方式
为了便于理解本申请，下面结合附图和具体实施例，对本申请进行更详细的说明。需要说明的是，当元件被表述“固定于”另一个元件，它可以直接在另一个元件上、或者其间可以存在一个或多个居中的元件。当一个元件被表述“连接”另一个元件，它可以是直接连接到另一个元件、或者其间可以存在一个或多个居中的元件。本说明书所使用的术语“上”、“下”、“内”、“外”以及类似的表述只是为了说明的目的。
除非另有定义，本说明书所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。在本申请的说明书中所使用的术语 只是为了描述具体的实施例的目的，不是用于限制本申请。本说明书所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。
此外，下面所描述的本申请不同实施例中所涉及的技术特征只要彼此之间未构成冲突就可以相互结合。本说明书中的“多个”，是指两个以上。
目前，应用最为广泛的锂离子电化学装置的负极活性材料采用的是石墨材料，石墨材料的克容量较低(372mAh/g)，难以满足日益增长的对高容量锂离子电化学装置的需求。硅储量丰富，且具有远高于石墨材料的克容量(4200mAh/g，基于Li 22Si 4合金)，因此硅被认为是最有潜力的下一代负极材料。本申请的发明人注意到，电化学装置在充放电过程中，硅的脱嵌锂反应伴随了巨大的体积变化(＞300％，基于Li 22Si 4合金)，易造成硅活性材料从极片上粉化脱落，使得活性材料层与集流体等导电网络脱离电接触，最终导致极片容量的快速衰减恶化。
为缓解上述问题，第一方面，本申请的实施例提出了一种电化学装置100，在本申请的实施例中，电化学装置100是组成电化学装置或电化学装置模组的最小单元，是具体实现电能和化学能转换的场所。请参照图1和图2，图1和图2分别示出了电化学装置100的结构及电化学装置100的截面。电化学装置100包括负极极片10、正极极片20和隔离膜30，负极极片10和正极极片20间隔设置，隔离膜30设于负极极片10和正极极片20之间以分隔两者。负极极片10、一隔离膜30、正极极片20以及另一隔离膜30层叠设置，并卷绕为电化学装置100的裸电芯；值得一提的是，在其他实施例中，裸电芯还可以是堆叠式结构。以负极极片10为例，负极极片10包括集流体11、活性材料层12和涂层13，活性材料层12涂覆于集流体11的至少一个表面，涂层13设置于活性材料层12上。
对于上述集流体11，请参照图3和图4，集流体11整体呈扁平的条状结构，其各部位的厚度基本一致，集流体11的厚度通常介于3微米(μm)至20微米之间。集流体11具有长边111、宽边112以及厚度边113。长边111是集流体11展开呈平整状态时沿其长度方向(X方向)延伸的边，宽边112是集流体11展开呈平整状态时沿其宽度方向(Y方向)延伸的边，厚度边113是集流体11展开呈平整状态时沿其厚度方向(Z方向)延伸的边。集流体11具有两个主表面11a，该两个主表面11a均由上述长边111和宽边112共同限定出，两主表面11a沿上述厚度边113的延伸方向相对设置，两个主表面11a上均可涂覆活性材 料层12。集流体11为极片为导电基材，根据极片种类的不同，可选择不同的材料作为极片的集流体11，在本实施例中，采用的是负极极片10，集流体11可选用铜箔。
对于上述活性材料层12，请参照图4和图5b，活性材料层12是电化学装置100的核心材料层，活性材料层12涂覆于集流体11的至少一个表面，例如涂覆于上述集流体11的两个主表面11a中的其中一个，或者上述集流体11的两个主表面11a均涂覆活性材料层12。活性材料层12包括活性材料、导电剂、粘接剂以及去离子水等，上述各材料混合后搅拌均匀并涂覆于上述集流体11的表面，从而得到活性材料层12。活性材料的具体成分实则是多样的，在本申请中，活性材料层12包括第一活性材料和第二活性材料，其中第一活性材料的克容量大于第二活性材料的克容量。
在一些实施例中，第一活性材料包括单质硅、硅氧化合物、硅碳复合物和硅合金的组中的至少一个。第二活性材料包括石墨、软碳、硬碳、碳纤维和中间相碳微球的组中的至少一个。
具体的，作为示例，第一活性材料为硅，第二活性物材料为碳，硅的理论克容量为4200mAh/g大于碳的克容量372mAh/g，采用硅活性材料可提高电化学装置的容量，在硅活性材料之间填充结构更为稳定的碳活性材料，可作为硅活性材料的体积缓冲基体；其中，硅在活性材料层12中的质量分数可选择1％至45％，硅的质量含量可通过可以通过Element Analysis元素分析测得。
对于上述涂层13，请参照图3至图5b，涂层13设置于活性材料层12的表面，涂层13可部分或者全部包覆活性材料层12，涂层13被配置为限制活性材料层12，以减少活性材料层12的粉化脱落。涂层13可采用高强度高韧性的有机包覆膜，在一些实施例中，为保证涂层13的机械强度，涂层13为纯粹的聚合物，不包含任何活性材料，不提供任何充放电容量。相较于活性材料层12，该涂层13具有更高的机械强度及抗拉强度，可以承受更大应力而不产生塑性应变。涂层13包覆在活性材料层12表面以减小活性材料层12的自由膨胀空间，从而保证电化学装置100在长期的充放电循环后活性材料层12仍然能够与集流体11良好接触，以提高电化学装置100的循环寿命。
为便于涂层13与集流体11固定，涂层13的末端超出活性材料层12以便于与集流体11连接。例如，沿集流体11的长度方向，涂层12包括第一端部 132和第二端部(未在图中示出)，第一端部132和第二端部均连接连接于集流体11，使得涂层13在集流体11的长度方向对活性材料层12进行限位。在其他实施例中，沿集流体11的宽度方向，涂层12包括第三端部133和第四端部134，第三端部133和第四端部134均连接于集流体11，或者，将第一端部132、第二端部、第三端部133和第四端部134均连接集流体11，使得涂层13在集流体11的长度方向以及宽度方向均能够对活性材料层12的进行限位，从而缓解活性材料层12的膨胀。
为便于电解液能够穿过涂层13以进入活性材料层12，请参照图3至图5b，涂层13上开设有至少一个通孔131，通孔131贯穿涂层13，通孔131被配置为与活性材料层12连通，电解液可从涂层13的外部直接进入该通孔131并与活性材料层12接触反应，通孔131作为锂离子的物质传递通道，保证电解液能够穿过涂层13以与集流体11上的活性材料层12正常接触，从而维持极片的正常动力学。在其他实施例中，电解液还可直接渗透涂层13以与活性材料层12接触反应。
在本申请的实施例中，涂层13为具有多孔结构的高强度有机包覆膜，在保证极片具备足够的动力学的前提下，可抑制极片的膨胀，减小活性材料层12的粉化脱模风险。涂层13紧密覆盖在活性材料层12的表面，当活性材料层12嵌锂膨胀时，涂层13产生收缩应力，从而减小极片整体的膨胀。涂层13可采用工业成熟的LDP(激光打孔)技术进行打孔加工，在高强度涂层13上开设通孔131，使得电解液可以有效浸润内部的活性材料层12，以顺利完成电化学反应，从而改善高强涂层13带来的动力学恶化风险；因此，本申请中，可采用硅质量含量更高的活性材料层12(45％以下)，以提高电化学装置的容量。
对于上述通孔131，通孔131的整体形状可采用圆柱状、圆台状、棱柱状或棱台状等，在涂层13的表面，通孔131的呈现圆形、椭圆形、矩形或多边形等。通孔131的数量可设置为多个，多个通孔131间隔设置，通孔131在涂层13上可采用均匀分布的方式，例如，如图6所示，多个通孔131呈阵列分布于涂层13上，均匀分布有利于电解液从各个位置渗透到活性材料层12，便于活性材料层12与电解液充分接触。值得一提的是，通孔131的分布并不限于本实施例中的呈阵列分布，在其他实施例中，如图7所示，通孔131也可呈蜂巢状分布于涂层13上。
请参照图4至图5b，通孔131为多个，相邻两个通孔131之间保持独立不相连的状态，其中孔间距可设置为大于两倍的孔半径，孔间距为相邻两个通孔131的中心之间的距离。沿集流体11的厚度方向，涂层13具有相对设置的第一面13a1和第二面13a2，相较于第一面13a1，第二面13a2靠近活性材料层12，在第一面13a1，多个通孔的面积占比为10％至30％。在一个实施例中，通孔131各处的横截面可设置为相等，即涂层13的孔隙率为10％至30％，可赋予涂层13良好的动力学，可维持涂层13原本的机械强度，可有效减少在长期循环后涂层13出现不可逆的塑性应变，并且，该通孔131为微米级通孔131，通孔131的半径可设置为5微米以下。通孔131的轴线可设置为平行于集流体11的厚度方向，由于涂层13的外表面通常为平面，即通孔131的轴线与涂层13的外表面垂直设置，以便于电解液的进入进出，本实施例中的垂直是指通孔131的轴线与涂层13的外表面的夹角在80度至100度。具有微米级多孔结构的涂层13在电化学装置100充放电循环过程中可长期保持形貌稳定，以减小极片的体积膨胀。
根据本申请的一些实施例，请参照图4至图5b，沿集流体11的厚度方向，活性材料层12具有相对设置的第三面12a和第四面12d，相较于第三面12a，第四面12d靠近集流体设置，第三面12a背离集流体11设置。沿集流体11的长度方向，活性材料层12包括第一侧面12b和第二侧面(未在图中示出)，沿集流体11的宽度方向，活性材料层12还包括第三侧面12c和第四侧面(未在图中示出)。为使得涂层13在多个方向抑制活性材料层12的膨胀，涂层13包括第一部分13a以及连接于第一部分13a的第一延伸部13b、第二延伸部(未在图中示出)，第一部分13a设置于第三面12a并与第三面12a紧密贴合，第一延伸部13b延伸于第一侧面12b，第二延伸部延伸于第二侧面，上述第一端部132设置于第一延伸部，上述第二端部设置于第二延伸部。在其他一些实施例中，活性材料层12还包括连接于第一部分13a的第三延伸部13c和第四延伸部(未在图中示出)，第三延伸部13c延伸于第三侧面12c，第四延伸部延伸于第四侧面，上述第三端部133设置于第三延伸部，上述第四端部134设置于第四延伸部。在活性材料层12的每个方向均设置对应的延伸部，使得涂层13包覆活性材料层12，其中，第一端部132、第二端部、第三端部133和第四端部134均可连接固定于集流体11上，以限制活性材料层12的膨胀。
通孔131开设于第一部分13a，电解液直接从第一部分13a的通孔131浸润活性材料层12。为提高电解液的浸润效率，通孔131包括第一通孔131a和第二通孔131b，第一通孔131a开设于第一部分13a，第一延伸部13b和第二延伸部中至少一个开设有第二通孔131b。在其他一些实施例中，通孔131还包括第三通孔131c，第三延伸部13c和第四延伸部中至少一个开设有第三通孔131c。当第一延伸部13b、第二延伸部、第三延伸部13c和第四延伸部均开设有通孔131时，可使得电解液全方位的进入活性材料层12，以使得活性材料层12被快速浸润。
本申请的发明人注意到，涂层13的厚度也会对本申请的技术效果产生影响，即涂层13的厚度与极片的膨胀有关，本申请的实施例通过对0微米(无涂层13)、3微米和5微米厚度的涂层13进行相关的测试，以得出涂层13厚度及极片膨胀之间的关系。
请参照图8至图10，图8和图9示出了电化学装置的膨胀与循环次数之间的关系，其中L 1为0微米厚度时的测试结果曲线，L 2为3微米厚度时的测试结果曲线，L 3为5微米厚度时的测试结果曲线。随着电化学装置100循环次数的增加，电化学装置的厚度逐渐增加，其膨胀率越来越大。图10示出了负极极片10的膨胀与循环次数的关系，同电化学装置一样，循环次数越多则膨胀越大。结合图8至图10可知，在加入涂层13后，电化学装置及极片的膨胀率明显下降，下降幅度随着涂层13厚度的增加而增加。随着涂层13厚度的增加，因极片膨胀而作用在涂层13上的载荷将等比例减小，令涂层13自身的应变值更小，最终抑制极片整体乃至整个电化学装置100的膨胀。理论计算结果表明，当涂层13处于弹性应变状态时，涂层13厚度与极片膨胀百分比为反比例关系，即涂层13厚度越大，则极片膨胀百分比越小。
图11示出了极片膨胀及电化学装置的能量密度损失与涂层13厚度的关系，随着涂层13厚度的增加，极片的膨胀越来越小，但电化学装置100的能量密度损失也越来越大。根据图11可知，涂层13厚度的范围可选择1微米至8微米。
请参照图12至图14，本实施例中分别采用厚度为0微米、5微米、5微米+30％LDP处理(在涂层13一个的表面，通孔131的面积占比为30％)的涂层13进行了测试，其中L 4为0微米厚度时的测试结果曲线，L 5为5微米厚度时的测试结果曲线，L 6为5微米厚度+30％LDP处理时的测试结果曲线。
图12示出了涂层在不同厚度下，放电倍率与放电容量之间的关系，随着放电倍率的增加，电化学装置100的放电容量逐渐减小。根据图12可知，在涂层13上应用LDP技术打造通孔131后，随着放电倍率的增加，其放电容量与无涂层13时的放电容量相近，恶化的电化学装置动力学参数得到有效改善。
图13示出了涂层在不同厚度的涂层13下，电化学装置的SOC状态(荷电状态)与DCR(高频阻抗)之间的关系。根据图13可知，随着电化学装置荷电状态的减小，DCR逐渐增大，采用LDP技术打造通孔131后，随着电化学装置荷电状态的减小，其DCR与无涂层13时相近。
图14示出了涂层在不同厚度的涂层13下，电化学装置的SOC状态与RSS(低频阻抗)之间的关系，随着电化学装置荷电状态的减小，Rss逐渐增大，采用LDP技术打造通孔131后，随着电化学装置荷电状态的减小，Rss阻抗与无涂层13时相近。结合图12至图14可知，采用厚度为5微米+30％LDP处理的涂层13，其放电容量与无涂层13时近似相同，但可明显减小电化学装置的阻抗。
通过调节涂层13厚度及通孔131的结构参数，可以精确平衡极片动力学与膨胀率，凭借成熟的LDP技术，通孔的形貌、深度及分布等一系列物理参数都可精确调整控制，从而平衡极片动力学的提升与能量密度的损失。设计涂层13厚度时，既需要涂层13具有一定的厚度下限以保证涂层13对极片膨胀的抑制效果，也要规避涂层13厚度过大恶化电化学装置100的能量密度风险，结合图8至图14可知，涂层13的厚度可选择0.5微米至10微米，在其他一些实施例中，涂层13的厚度也可设置为1微米至8微米。基于同样的发明构思，第一延伸部13b和/或第二延伸部的厚度为0.5微米至10微米，在其他一些实施例中，也可设置为1微米至8微米；沿集流体11的宽度方向，第三延伸部13c和/或第四延伸部的厚度为0.5微米至10微米，在其他一些实施例中，也可设置为1微米至8微米；沿涂层13至集流体11的方向，第一部分13a的厚度为0.5微米至10微米，在其他一些实施例中，也可设置为1微米至8微米。
为了获取通孔131的结构参数与极片的膨胀及动力学参数关系，以确定最佳的通孔131结构参数，本申请对不同通孔131结构参数下的极片膨胀和动力学进行了相关测试实验，测试结果如下表所示。其中Rate为充放电倍率，Rate越大越优；HL为高低温测试，HL的值越高越优；DCR为高频阻抗测试，DCR 的值越小越优；Rss为低频阻抗测试，Rss的值越小越优。
表1示出了通孔131的结构参数与极片循环膨胀/动力学的参数关系。
Figure PCTCN2022083802-appb-000001
表1描述了通孔131的具体参数对极片的动力学相关参数的具体效果，按照“通孔131是否存在”，“通孔131是否贯通涂层13”以及“通孔131分布状况”三类设计确定通孔131的结构的优选参数，使用孔径小面积占比低的通孔131，将在抑制极片膨胀与维持极片原有动力学两种需求上取得最优平衡。根据表1可知，本申请中必须是贯通涂层13的通孔131，在一些实施例中，半径小于5微米，通孔131在涂层13表面的面积占比10％至50％，也可采用10％至30％，下限值赋予涂层13良好的动力学，上限值维持涂层13原本的机械强度，以减少长期循环后涂层13出现不可逆的塑性应变。需要注意的是，表中同水平代表两个测试数值相同或基本相同，例如，差异度小于0.1％。本申请中差异度指的是大的对象减去小的对象得到的差值，除以小的对象，乘以100％，得到的数值。
图15和图16示出了不同涂层13厚度下，循环次数与电化学装置100容量保持率的关系，采用的是无涂层13以及5毫米厚度+30％LDP处理的涂层13进行了多次测试实验。根据图15和图16上可知，随着循环次数的增加，容量保持了逐渐降低，其中，各测试曲线接近重合，采用5毫米厚度+30％LDP处理的涂层13的随着循环次数的增加，其容量保持率与无涂层13的容量保持率近似同等水平，也尚未观察到循环恶化的风险。
本申请中，通过在涂层13上开设微米级的通孔131，可令更多的电解液浸润至极片深处，取代原本扩散速率较低的固相扩散通道，提供更快速的物质传递通道，有利于降低极片的整体阻抗。同时，通孔131为活性材料层12的应变 提供了缓冲空间，可减小极片的膨胀，有利于电化学装置100长期循环寿命的提高以及高能量密度的维持。
基于同样的发明构思，本申请的实施例还提出了一种电子设备，包括如上述任一实施例所述的电化学装置100。
本申请一些实施例公开的电化学装置100可以但不限用于车辆、船舶或飞行器等电子设备中。可以使用具备本申请公开的电化学装置100等组成该电子设备的电源系统，这样，有利于提高电化学装置100的容量，提高电子设备的续航能力，同时可减小电化学装置100的阻抗，以便于满足电化学装置100的快充快放要求。
本申请一些实施例提供一种使用电化学装置100作为电源的电子设备，电子设备可以为但不限于手机、平板、笔记本电脑、电动玩具、电动工具、电瓶车、电动汽车、轮船、航天器等等。其中，电动玩具可以包括固定式或移动式的电动玩具，例如，游戏机、电动汽车玩具、电动轮船玩具和电动飞机玩具等等，航天器可以包括飞机、火箭、航天飞机和宇宙飞船等等。
最后应说明的是：以上实施例仅用以说明本申请的技术方案，而非对其限制；在本申请的思路下，以上实施例或者不同实施例中的技术特征之间也可以进行组合，步骤可以以任意顺序实现，并存在如上所述的本申请的不同方面的许多其它变化，为了简明，它们没有在细节中提供；尽管参照前述实施例对本申请进行了详细的说明，本领域的普通技术人员应当理解：其依然可以对前述各实施例所记载的技术方案进行修改，或者对其中部分技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本申请各实施例技术方案的范围。

Claims (13)

  1. 一种电化学装置，包括集流体和涂覆于所述集流体上的活性材料层，其特征在于，所述电化学装置还包括涂层，所述涂层设置于所述活性材料层上；
    沿所述集流体的长度方向，所述涂层具有相对设置的第一端部和第二端部，沿所述集流体的宽度方向，所述涂层具有相对设置的第三端部和第四端部；
    所述第一端部和所述第二端部连接于所述集流体，和/或，所述第三端部和所述第四端部连接于所述集流体；
    所述涂层开设有至少一个通孔。
  2. 根据权利要求1所述的电化学装置，其特征在于，所述活性材料层包括第一活性材料和第二活性材料，所述第一活性材料的克容量大于所述第二活性材料的克容量。
  3. 根据权利要求2所述的电化学装置，其特征在于，所述活性材料层满足以下条件a)和b)中的至少一个：
    a)所述第一活性材料包括单质硅、硅氧化合物、硅碳复合物和硅合金中的至少一种；
    b)所述第二活性材料包括石墨、软碳、硬碳、碳纤维和中间相碳微球的中的至少一种。
  4. 根据权利要求2或3所述的电化学装置，其特征在于，基于所述活性材料层的质量，所述第一活性材料的质量含量为1％至45％。
  5. 根据权利要求1所述的电化学装置，其特征在于，所述涂层开设有多个通孔，沿所述集流体的厚度方向，所述涂层具有相对设置的第一面和第二面，相较于所述第一面，所述第二面靠近所述活性材料层，在所述第一面，所述多个通孔的面积占比为10％至30％。
  6. 根据权利要求1所述的电化学装置，其特征在于，所述通孔满足0＜R≤5μm，R为所述通孔的半径。
  7. 根据权利要求1所述的电化学装置，其特征在于，所述涂层的抗拉强度大于所述活性材料层的抗拉强度。
  8. 根据权利要求1所述的电化学装置，其特征在于，
    沿所述集流体的厚度方向，所述活性材料层具有相对设置的第三面和第四面，相较于所述第三面，所述第四面靠近所述集流体；
    沿所述集流体的长度方向，所述活性材料层包括相对设置的第一侧面和第二侧面；
    沿所述集流体的宽度方向，所述活性材料层包括相对设置的第三侧面和第四侧面；
    所述涂层包括设置于所述第三面的第一部分；
    沿所述集流体的长度方向，所述涂层还包括相对设置的第一延伸部和第二延伸部；
    所述第一端部设置于所述第一延伸部，所述第一延伸部延伸于所述第一侧面；所述第二端部设置于所述第二延伸部，所述第二延伸部延伸于所述第二侧面。
  9. 根据权利要求8所述的电化学装置，其特征在于，所述涂层开设有多个通孔，所述通孔包括第一通孔和第二通孔；所述第一通孔开设于所述第一部分；以及，所述第二通孔开设于所述第一延伸部和所述第二延伸部中的至少一个。
  10. 根据权利要求8所述的电化学装置，其特征在于，
    沿所述集流体的宽度方向，所述涂层还包括相对设置的第三延伸部和第四延伸部；
    所述第三端部设置于所述第三延伸部，所述第三延伸部延伸于所述第三侧面；所述第四端部设置于所述第四延伸部，所述第四延伸部延伸于所述第四侧面。
  11. 根据权利要求10所述的电化学装置，其特征在于，所述通孔还包括第 三通孔，所述第三通孔开设于所述第三延伸部和所述第四延伸部中至少一个。
  12. 根据权利要求10所述的电化学装置，其特征在于，所述第一部分、所述第一延伸部、所述第二延伸部、所述第三延伸部和所述第四延伸部中的至少一个的厚度为0.5μm至10μm。
  13. 一种电子设备，其特征在于，包括如权利要求1至12中任一项所述的电化学装置。
PCT/CN2022/083802 2022-03-29 2022-03-29 电化学装置及电子设备 WO2023184170A1 (zh)

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