WO2024016127A1 - 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
WO2024016127A1
WO2024016127A1 PCT/CN2022/106318 CN2022106318W WO2024016127A1 WO 2024016127 A1 WO2024016127 A1 WO 2024016127A1 CN 2022106318 W CN2022106318 W CN 2022106318W WO 2024016127 A1 WO2024016127 A1 WO 2024016127A1
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active material
electrochemical device
material layer
pole piece
current collector
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PCT/CN2022/106318
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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/CN2022/106318 priority Critical patent/WO2024016127A1/zh
Publication of WO2024016127A1 publication Critical patent/WO2024016127A1/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
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • 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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • 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 embodiments of the present application relate to the field of electrochemistry 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 popularity of electronic devices such as mobile phones and laptop computers, the capacity requirements for electrochemical devices are becoming higher and higher.
  • the negative electrodes of traditional electrochemical devices are mostly graphite materials, and their theoretical gram capacity (372mAh/g) is low, which cannot meet the growing demand for high-capacity electrochemical devices.
  • Silicon has abundant reserves and has a much higher gram capacity (4200mAh/g) than graphite materials, so it is considered the most promising next-generation anode material.
  • the electron/ion conductivity of silicon material itself is lower than that of graphite material, and its overall dynamic parameters such as pole piece resistance/charge and discharge rate lag behind traditional graphite pole pieces, making it difficult to meet the rapid charge and discharge requirements of electrochemical devices.
  • Embodiments of the present application are intended to provide an electrochemical device and electronic equipment that can at least increase the capacity and charge and discharge rate of the electrochemical device.
  • an embodiment of the present application proposes an electrochemical device, including a pole piece, the pole piece including a current collector and an active material layer, the active material layer being disposed on the current collector, the active material
  • the layer includes a first active material and a second active material, the first active material having a gram capacity greater than the gram capacity of the second active material.
  • the active material layer has a first surface facing away from the current collector, the first surface is provided with at least one pore structure, and the ratio of the volume of all the pore structures to the volume of the active material layer is A, where, 2% ⁇ A ⁇ 20%.
  • the capacity of the electrochemical device can be increased, and the pore structure can be completely soaked and filled by the electrolyte, becoming a new lithium ion liquid phase transfer channel, replacing the solid phase channel with a lower diffusion coefficient, and lithium
  • the ions penetrate deep into the pole piece through the newly constructed pore structure.
  • a new transverse diffusion path at the pole piece pore structure is also added, effectively increasing the reaction area of the solid-liquid interface.
  • the solid-phase channel refers to a transmission channel for lithium ions on an active material layer without a pore structure. Lithium ions are mainly transmitted through the interior of solid particles and the interface.
  • the active material layer satisfies 2% ⁇ A ⁇ 20% to obtain the optimal parameters of the pore structure so as to achieve a balance between the capacity or energy density of the electrochemical device and the dynamic performance of the pole piece.
  • 4% ⁇ A ⁇ 14% is satisfied to further obtain the final parameters of the pore structure.
  • the balance between the capacity and energy density of the electrochemical device and the dynamic performance of the pole piece can be further achieved. .
  • the active material layer satisfies the following conditions:
  • N is the ratio of the depth of a single hole structure to the thickness of the active material layer.
  • R is the radius of the hole structure on the first surface.
  • R is the radius of the hole structure on the first surface.
  • R is the radius of the hole structure on the first surface.
  • the radius of the hole structure gradually increases, the thinned area with low depth at the edge position also gradually increases, which easily leads to a certain risk of deterioration of the dynamic enhancement effect of a single hole structure. Therefore, in this embodiment, the hole structure is required to The radius R ⁇ 200 ⁇ m, the preferred range is below 100 ⁇ m. That is, 10 ⁇ m ⁇ R ⁇ 200 ⁇ m, preferably, 30 ⁇ m ⁇ R ⁇ 100 ⁇ m.
  • D is the center distance between two adjacent hole structures.
  • D ⁇ 2R the center line connecting the three adjacent hole structures.
  • M is exactly 100%
  • the center line connecting the three adjacent hole structures forms an equilateral triangle.
  • the distance between the three adjacent hole structures is
  • D ⁇ 2R there is no risk of overlap between adjacent hole structures.
  • the hole structure is provided with a first section and a second section, the first section is close to the first surface, and the first section
  • the cross-sectional area of the segment is greater than the cross-sectional area of the second segment.
  • the pore structure has different cross-sectional sizes at different depths.
  • the overall structure is "wide on the outside and narrow on the inside". The "wide on the outside” structure is conducive to the rapid entry of the external electrolyte into the pore structure, while the "narrow on the inside” structure It is more conducive for the electrolyte in the pore structure to contact the active material layer.
  • the first active material includes at least one of silicon, silicon oxide, silicon carbon composite and silicon alloy.
  • the second active material includes at least one of graphite, soft carbon, hard carbon, carbon fiber and mesocarbon microspheres.
  • the first active material is silicon
  • the second active material is graphite
  • the theoretical gram capacity of silicon is 4200mAh/g, which is greater than the theoretical gram capacity of carbon, 372mAh/g.
  • the use of silicon active materials can increase the capacity of the electrochemical device. Carbon active materials with a more stable structure are filled between the silicon active materials, which can be used as silicon Volume buffer matrix of active material; wherein, the mass fraction of silicon in the active material layer can be selected from 1% to 45%. According to some embodiments of the present application, 1% ⁇ W ⁇ 45%, W is the mass content of the first active material in the active material layer.
  • the hole structure is one of a disc shape, a cylinder shape, a truncated cone shape, a cone shape, a prism shape or a pyramid shape.
  • laser drilling technology is used to form a hole structure on the surface of the active material layer. Due to process limitations, for example, because there is energy scattering and absorption of laser energy in the process of etching the active material layer, ultimately in the first
  • the pore structure formed on the active material layer is not a standard disk-shaped, cylindrical, truncated cone-shaped, cone-shaped, prism-shaped or pyramid-shaped, but is generally disk-shaped, cylindrical, truncated cone-shaped, cone-shaped, prism-shaped or Prismatic shape.
  • a plurality of the hole structures are distributed in an array.
  • the array distribution is conducive to the penetration of the electrolyte into the active material layer from various positions, making it easy for the active material layer to fully contact the electrolyte.
  • the angle between the axis of the hole structure and the thickness direction of the pole piece is 0 to 10 degrees to facilitate the rapid entry of electrolyte.
  • this application also provides an electronic device, including the electrochemical device as described in any of the above embodiments.
  • Figure 1 is an exploded view of a pole piece according to some embodiments of the present application.
  • Figure 2 is a schematic cross-sectional view of a pole piece in some embodiments of the present application.
  • Figure 3 is a schematic structural diagram of a pole piece in some embodiments of the present application.
  • Figure 4 is a top view of the pole piece of some embodiments of the present application.
  • Figure 5 is a top view of the pole piece of some embodiments of the present application.
  • Figure 6 is a top view of the pole piece of some embodiments of the present application.
  • Figure 7 is a diagram showing the relationship between the pole piece impedance and N in some embodiments of the present application.
  • Figure 8 is a diagram showing the relationship between M, pole piece dynamics and processing cost in some embodiments of the present application.
  • Figure 9 is a schematic diagram of the spacing between adjacent hole structures in some embodiments of the present application.
  • Figure 10 is a schematic diagram of the spacing between adjacent hole structures in some embodiments of the present application.
  • an embodiment means that a particular feature, structure or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application.
  • the appearances of this phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments.
  • inventions of the present application provide an electrochemical device. Please refer to Figures 1 and 2.
  • the electrochemical device includes a pole piece 100.
  • the pole piece 100 includes a current collector 10 and an active material layer 20.
  • the active material layer 20 is coated on the current collector 10 .
  • the electrode piece 100 is described as a negative electrode piece.
  • the electrochemical device also includes a positive electrode piece (not shown in the figure), a separator (not shown in the figure), and a casing (not shown in the figure).
  • the electrochemical device is the smallest unit that constitutes a battery or battery module, and is a place where the conversion of electrical energy and chemical energy is specifically realized.
  • the current collector 10 has a flat strip structure as a whole, and the thickness of each part of the current collector 10 is basically the same.
  • the thickness of the current collector 10 is usually between 3 microns ( ⁇ m) and 20 microns. between.
  • the current collector 10 has a long side 11 , a wide side 12 and a thickness side 13 .
  • the long side 11 is the side extending along the length direction (X direction) of the current collector 10 when it is unfolded into a flat state.
  • the wide side 12 is the side extending along the width direction (Y direction) of the current collector 10 when it is unfolded into a flat state.
  • the thickness side 13 is a side extending along the thickness direction (Z direction) of the current collector 10 when it is unfolded into a flat state.
  • the current collector 10 has two main surfaces 14, which are jointly defined by the above-mentioned long side 11 and the wide side 12.
  • the two main surfaces 14 are arranged oppositely along the extension direction of the above-mentioned thickness side 13.
  • the two main surfaces 14 The active material layer 20 can be coated on both.
  • the current collector 10 is a conductive base material for the pole piece 100. Depending on the type of the pole piece 100, different materials can be selected as the current collector 10 of the pole piece 100. In this embodiment, a negative pole piece is used, and the current collector 10 Copper foil is optional.
  • the active material layer 20 is the core material layer of the electrochemical device.
  • the active material layer 20 is coated on at least one surface of the current collector 10, for example, coated on the above-mentioned current collector.
  • One of the two main surfaces 14 of the current collector 10 , or both main surfaces 14 of the current collector 10 are coated with the active material layer 20 .
  • the active material layer 20 includes active materials, conductive agents, adhesives, deionized water, etc. The above materials are mixed and stirred evenly and then coated on the main surface 14 of the current collector 10 to obtain the active material layer 20 .
  • the specific components of the active material are actually diverse.
  • the active material layer 20 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 and the second active material is carbon.
  • the theoretical gram capacity of silicon is 4200 mAh/g, which is greater than the theoretical gram capacity of carbon 372 mAh/g.
  • the use of silicon active materials can improve the performance of the electrochemical device. Capacity, filling 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 content of silicon in the active material layer 20 can be selected from 1% to 45%, or higher The mass content of silicon can be measured by Element Analysis to increase the capacity of the electrochemical device.
  • the active material layer 20 has a first surface 21 facing away from the current collector 10 , and at least one hole structure 22 is formed on the first surface 21 .
  • the hole structure 22 extends from the active material layer 20 toward the current collector 10 , and the depth of the hole structure 22 may be set to 1% to 50% of the thickness of the active material layer 20 .
  • the hole structure 22 can be disk-shaped, cylindrical, truncated cone-shaped, conical, prism-shaped or pyramid-shaped, etc. (only part of the shape is shown in Figure 3).
  • the hole structure 22 On the surface of the active material layer 20, the hole structure 22 is in a circular, elliptical, rectangular or polygonal shape.
  • the number of hole structures 22 can be set to multiple, and the distance between two adjacent hole structures 22 can be a non-fixed value, thereby ensuring that the hole structures 22 can be set at any local position of the pole piece 100; in actual operation , please continue to refer to Figures 4 to 6.
  • multiple pore structures 22 On the end face of the active material layer 20, multiple pore structures 22 present a disk shape. Shape, step-like, wavy shallow pit shape.
  • multiple pore structures 22 are evenly distributed in the active material layer 20.
  • the multiple pore structures 22 are evenly distributed in an array. Uniform distribution is beneficial to The electrolyte penetrates into the active material layer 20 from all positions, so that the active material layer 20 and the electrolyte fully contact and react.
  • FIG. 5 shows a situation where the hole structures 22 with a circular front surface are distributed in a close-packed manner at equal intervals, and adjacent hole structures 22 maintain edge tangential contact.
  • the hole structure 22 is provided with a first section 221 away from the current collector 10 and a second section close to the current collector 10 .
  • Section 222 the first section 221 is the inlet of the hole structure 22
  • the second section 222 is the hole bottom of the hole structure 22
  • the cross-sectional area of the first section 221 is greater than the cross-sectional area of the second section 222, so that the hole
  • the entrance of the structure 22 is larger; in this embodiment, the hole structure 22 is at different depth positions and has different cross-sectional sizes.
  • the overall structure presents a "wide outside and narrow inside" structure.
  • the "wide outside” structure is conducive to the external The electrolyte quickly enters the pore structure 22, and the “inner narrow” structure is more conducive to the contact between the electrolyte in the pore structure 22 and the active material layer 20; wherein, the above-mentioned cross-section refers to the direction of the pore structure 22 perpendicular to the pole piece 100 In the cross section in the thickness direction, the hole structure 22 can penetrate into the active material layer 20 to a certain depth in the direction perpendicular to the current collector 10 to facilitate the rapid entry of the electrolyte.
  • the vertical in this embodiment refers to the axis of the hole structure 22 and the thickness of the pole piece 100 The angle between directions is 0 to 10 degrees.
  • the pore structure 22 can reach a depth of several microns inside the active material layer 20 and does not cause any morphological or structural impact on the active material layer 20 deeper in the pole piece 100.
  • the pore structure of the pole piece 100 after normal charge and discharge cycles 22 always maintains a stable morphology, without irreversible deterioration of morphology or structural parameters, and can maintain the kinetic improvement effect of the counterpole piece 100 for a long time.
  • the hole structure 22 can utilize industrially mature laser drilling technology to accurately etch the hole structure 22 to a certain depth on the first surface 21 of the active material layer 20 .
  • the pore structure 22 can be completely soaked and filled by the electrolyte, becoming a new liquid-phase transfer channel for lithium ions 30, replacing the solid-phase channel with a lower diffusion coefficient. Lithium ions 30 penetrate deep into the interior of the pole piece 100 through the newly constructed pore structure 22. In addition to the original longitudinal diffusion on the surface of the pole piece 100, a new transverse diffusion path at the pore structure 22 of the pole piece 100 is also added, effectively increasing the solid- The reaction area of the liquid interface.
  • the pore structure 22 makes it easier for the lithium ions 30 to be embedded into the active material layer 20 inside the pole piece 100, which reduces the difficulty of deintercalating the lithium ions 30 from the active material inside the pole piece 100, thereby reducing the impedance of the pole piece 100, thereby improving the pole piece. 100 overall dynamics to meet the rapid charge and discharge requirements of electrochemical devices.
  • More semiconductor silicon materials means poorer dynamics of the pole piece 100.
  • the structural parameters of the pore structure need to be improved.
  • a hole structure 22 with a larger radius and a shallower depth is used.
  • the hole structure 22 with a larger radius and a shallower depth is more suitable for negative electrode plates whose silicon material has poor processability and a high compaction density.
  • the dynamic parameter optimization of the shallow hole structure with a larger radius is close to the same level, and the risk of energy density deterioration is smaller.
  • the number of hole structures 22 can be set to be smaller, and the larger radius makes it easier to perform drilling processing.
  • the processing time t of the hole structure 22 has the following relationship with the radius R: t ⁇ 1/R 2 .
  • the radius of the hole structure 22 in this application is preferably R. >10 ⁇ m, the preferred range can be above 30 ⁇ m.
  • the radius R of the hole structure 22 is required to be ⁇ 200 ⁇ m, and the preferred range is less than 100 ⁇ m. That is, 10 ⁇ m ⁇ R ⁇ 200 ⁇ m, preferably, 30 ⁇ m ⁇ R ⁇ 100 ⁇ m.
  • the depth of the hole structure 22 (the depth of the hole structure 22 is defined as d), due to the local concentration of mechanical stress, the surface of the pole piece 100 after cold pressing will produce more severe plastic strain than the main body of the pole piece 100, resulting in supercooling. The surface layer is pressed, resulting in a smaller porosity of the active material layer 20, and there is a series of risks of kinetic deterioration such as deterioration of the electrolyte infiltration ability or weakening of the lithium ion 30 diffusion ability. The pore structure 22 needs to penetrate as much as possible through the area where the cold-pressed surface layer is located, thereby providing a fast transfer channel for the electrolyte or lithium ions 30 .
  • N the ratio of the depth of a single hole structure 22 to the thickness of the active material layer 20.
  • Figure 7 shows the relationship between the impedance Rss of the pole piece 100 and N, where L1, L2, and L3 are different respectively. Types of pole pieces have different compaction densities of corresponding pole pieces, L1 is 1.80 (unit g/cm 3 ), L2 is 1.74 (unit g/cm 3 ), L3 is 1.66 (unit g/cm 3 ), L1 , L2 and L3 have similar overall trends. As the ratio N between the depth of the hole structure 22 and the thickness of the active material layer 20 increases, the impedance of the pole piece 100 gradually decreases.
  • the compaction density of the pole piece also affects the impedance of the pole piece.
  • the distance between the particles of the active material layer decreases, the greater the contact probability, the larger the contact area between particles, the more conductive bridges and channels, and the pole The chip impedance decreases.
  • the greater the compaction density the more obvious the impedance decrease.
  • N is greater than 50%
  • the pole piece impedance decreases close to saturation.
  • the greater the compaction density the more obvious the impedance decrease. The smaller the value at which the pole piece impedance approaches saturation.
  • the depth d of the hole structure can be set to be greater than or equal to 1% of the thickness of the active material layer 20 , that is, N ⁇ 1%.
  • the depth of the hole structure 22 is more than 50% of the thickness of the active material layer 20 , as N increases, the impedance of the pole piece 100 does not decrease significantly and approaches the level. Therefore, in the embodiment of the present application, the hole structure 22
  • the ratio N of the depth of to the thickness of the active material layer 20 may be set to less than 50%, that is, N ⁇ 50%.
  • the impedance reduction effect of the pole piece 100 has not yet reached saturation, and there is still room for improvement.
  • 5% ⁇ N ⁇ 50% is preferably selected; and/or the depth of the hole structure 22 is d ⁇ 2 ⁇ m, and d ⁇ 2 ⁇ m is sufficient to allow the hole structure 22 to penetrate the cold-pressed surface layer; or, in some embodiments, , the larger value of 5% ⁇ N ⁇ 50% and d ⁇ 2 ⁇ m is selected.
  • the lower limit of the depth of 2 ⁇ m is set to meet the reverse requirements in the embodiment of the present application.
  • the volume of the hole structure 22 also affects the dynamics of the pole piece.
  • the balance of capacity reduction, in the embodiment of the present application, is 2% ⁇ A ⁇ 20%, preferably, 4% ⁇ A ⁇ 14%.
  • A is the ratio of the volume of all pore structures 22 to the volume of the remaining material of the active material layer (that is, the volume excluding all pore structures 22).
  • FIG. 8 shows the relationship between the area ratio M of all hole structures 22 on the first surface 21 and the dynamics and processing cost of the pole piece 100 , where L4 is the dynamics and L5 is the cost.
  • Figure 8 is divided into three stages.
  • the dynamics of the pole piece 100 increases approximately linearly with the area ratio M of the hole structure 22; in the second stage, with the area ratio M of the hole structure 22 As M increases, the dynamics of the pole piece 100 approaches saturation and the upper limit; in the third stage, the area ratio M of the hole structure 22 hardly changes the dynamics of the pole piece 100, but can lead to other risks.
  • the processing cost as the area ratio M of the hole structure 22 increases, the processing cost increases linearly. It can be seen from this that in the embodiment of the present application, the area ratio M of the hole structure 22 on the first surface 21 is ⁇ 50%, so as to ensure that the dynamics of the pole piece 100 is significantly improved after processing.
  • the upper limit of the area ratio M of the pore structure 22 on the first surface 21 is 100%, that is, the value range of M is 50% to 100%. Within this range, the dynamic enhancement effect of the pore structure 22 is sufficiently effective. .
  • M is close to 100%, the edge areas of two adjacent hole structures 22 overlap with each other.
  • the overlap of the hole structures 22 means that part of the pole piece 100 is repeatedly processed, which not only reduces the production efficiency of the pole piece 100 , and increases the time cost. Overlapping areas that have been impacted multiple times may also cause the local mechanical strength of the pole piece 100 to decrease, and even cause long-term cycle performance to deteriorate.
  • two adjacent hole structures 22 are just adjacent (tangent in Figure 9), and the center line connecting three adjacent hole structures 22 forms an equilateral triangle structure, and the active material
  • the surface structure of layer 20 is regarded as a repeated cycle of the equilateral triangle.
  • the equilateral triangle structure is composed of three 60° sectors 40 + the unprocessed area 211 at the center.
  • the hole structure in this limit state The area ratio of 22 on the first surface 21 Therefore, the area ratio M of the hole structure 22 on the first surface 21 should be less than or equal to 90%, that is, 50% ⁇ M ⁇ 90%; preferably, combined with Figure 7, it can be seen that when M is 70%, the pole piece The kinetics of 100 are improved to close to saturation, so the area ratio M of the hole structure 22 on the first surface 21 can be set to 70% ⁇ M ⁇ 90%. After the kinetics of the pole piece 100 is improved to close to saturation, it will not cause other performance deterioration. risks of.
  • the adjacent holes are The overlapping part of the structures 22 is reduced as much as possible.
  • M is exactly 100%
  • the center lines connecting the three adjacent hole structures 22 form an equilateral triangle.
  • the three 60° sectors 40 are in The centers of the equilateral triangles intersect, and there is clearly a spacing between adjacent hole structures 22
  • the non-overlapping area 41 accounts for approximately 79%
  • the overlapping area 50 accounts for approximately 21%.
  • the distance D between adjacent hole structures 22 can be set to The lower limit of this parameter range is calculated based on the most densely packed distribution of the hole structure 22.
  • the corresponding coverage area ratio is exactly 100%, which is the limit under which the depth d of the hole structure 22 can be measured.
  • the distance D outside this lower limit range It is difficult to accurately measure the depth d of the hole structure 22 , and a high-risk area where multiple hole structures 22 overlap will appear on the surface of the pole piece 100 .
  • the preferred range of the distance D between adjacent hole structures 22 is D ⁇ 2R. Obviously, under this condition, there is no risk of overlap between adjacent hole structures 22 at all.
  • the ratio of the volume of the hole structure 22 to the volume of the active material layer is A.
  • A the impedance and capacity retention rate of the electrochemical device are measured. test.
  • the measurement method of A is as follows.
  • punching the volume of the active material layer can be measured in advance.
  • the volume of the active material layer can be calculated by the amount of coating.
  • the punched volume is compared with the remaining volume. That is A; there are many testing methods for A, such as directly calculating the volume of the pore structure 22 and the volume of the active material layer.
  • the required pore structure 22 is a regular pore structure 22; or, filling the pore structure 22 , obtain the filler after filling and then calculate the volume of the filler; the calculation methods of A are actually diverse and will not be listed here.
  • the electrochemical devices in each embodiment and each comparative example are charged at a constant current of 0.1C at a rate of 0.1C under normal temperature (about 25°C) and normal pressure (0.1MPa) until the battery is fully charged.
  • the upper limit of the discharge cut-off voltage (4.2V) then rest for 5 minutes, then discharge at a constant current of 0.1C to the lower limit of the charge-discharge cut-off voltage (2V), and wait for 5 minutes.
  • the discharge capacity this time Record it as the first discharge capacity. After 400 charge and discharge cycles, the ratio of the discharge capacity after 400 charge and discharge cycles to the first discharge capacity is recorded as the capacity retention rate.
  • Rss is measured through the AC impedance method, which specifically applies a small amplitude phase to the electrode to obtain the complex impedance of the electrode. Then, based on the imagined equivalent circuit, the kinetic parameters of the electrode reaction are obtained through impedance spectrum analysis and parameter fitting.
  • Rate is the charge and discharge rate test, which refers to the battery cell in a fully charged state. , the ratio of the capacity released by constant current discharge to the cut-off voltage at different rates (0.1 to 2C) relative to the rated discharge capacity.
  • HL is the high and low temperature test.
  • the high and low temperature test is the ratio of the actual 0.2C discharge capacity of the battery core to the rated discharge capacity under different set ambient temperatures (generally fixed values in the range of -20°C to 60°C); DCR is high Frequency impedance test, DCR is mainly tested by using a charger and discharge machine in combination with a high and low temperature chamber.
  • the specific test method is to first adjust the temperature chamber to normal temperature, then leave it to thermal equilibrium and then conduct a 1C charge and discharge cycle test on the battery to obtain the actual test capacity C 0 , let it stand for 5 minutes, charge the battery to 4V with a current of 1C 0 capacity, then constant the voltage to I ⁇ 0.2C 0 , let it stand for 60 minutes, discharge it for 30 minutes at 1C 0 , adjust the battery to 50% SOC, and record the voltage at this time as V1 , after standing for 60 minutes, pulse discharge at 4C for 30 seconds in this state, and record the voltage at this time as V2.
  • Rss is a low-frequency impedance test; the temperature coefficient is defined as the ratio of the 0.2C discharge capacity of the battery at normal temperature (25°C) and high temperature (45°C). It is positively related to the battery dynamics. The higher the temperature coefficient, the lower the battery dynamics. The better.
  • Table 2 describes the specific effects of the specific structural parameters of the pore structure 22 on energy density and dynamic performance, according to "whether the pore structure 22 exists", “whether it satisfies 1% ⁇ N ⁇ 50%", “50% ⁇ M ⁇ 100”%” and “whether it satisfies "Four types of designs determine the preferred structural parameters of the pore structure 22.
  • M 100%
  • 50% ⁇ M ⁇ 100% is not satisfied, and the kinetics are not effective.
  • Example 1 the kinetic optimization is obvious, and the cycle capacity remains unobviously reduced and the expansion is small, which can achieve a balance between the capacity or energy density of the electrochemical device and the kinetic performance.
  • the same level means that the two test values are the same or basically the same, for example, the difference is less than 0.1%.
  • the difference in this application refers to the difference obtained by subtracting the small object from the large object, divided by the small object, multiplied by Value obtained at 100%.
  • the area ratio M of the pore structure 22 on the first surface 21 is 50% ⁇ M ⁇ 100%, preferably 70% ⁇ M ⁇ 90%; the depth of the pore structure 22 is consistent with the active material layer.
  • the thickness ratio N of 20 is 1% ⁇ N ⁇ 50%, preferably 5% ⁇ N ⁇ 50%; the center distance between two adjacent hole structures 22 Preferably D ⁇ 2R.
  • Table 3 describes the effects of M and N on impedance and capacity retention under different parameters. According to the results in Table 3, it can be seen that the effects in Examples 1 to 16 (while ensuring the reduction in impedance and making the capacity retention rate decrease smaller) are better than the effects in Comparative Examples 1 to 5.
  • the effects of Embodiments 3 to 12 are better than those of Embodiments 1, 2, 13 and 15. Therefore, the values of M and N can also be selected as 50% ⁇ M ⁇ 100% and 5% ⁇ N ⁇ 50%.
  • the effects of Embodiments 3 to 8 are better than those of Embodiments 9, 10 and 12.
  • the values of M and N can also be selected as 63% ⁇ M ⁇ 90% and 5% ⁇ N ⁇ 20%. . Furthermore, in Embodiments 3 to 8 and 11, the effects of Embodiments 6, 7 and 16 are due to those of Embodiments 3 to 5, 8 and 11, so you can also choose 80% ⁇ M ⁇ 86%, 8% ⁇ N ⁇ 16%. When 80% ⁇ M ⁇ 86% and 8% ⁇ N ⁇ 16%, the electrolyte can more easily enter the pore structure 22 to infiltrate the active material layer, and within this range, the electrochemical device can be recharged after multiple charges. After the discharge cycle, its capacity retention rate changes little, and a balance between impedance reduction and capacity retention rate can be achieved.
  • the gram capacity of the first active material is greater than the gram capacity of the second active material, and the capacity of the electrochemical device can be increased by adding the first active material with a larger gram capacity.
  • the pore structure 22 can be completely soaked and filled by the electrolyte, becoming a new liquid-phase transmission channel for lithium ions 30, replacing the solid-phase channel with a lower diffusion coefficient.
  • the lithium ions 30 penetrate deeply into the interior of the pole piece 100 through the newly constructed pore structure 22, In addition to the original longitudinal diffusion on the surface of the pole piece 100, a new transverse diffusion path at the pore structure 22 of the pole piece 100 is also added, effectively increasing the reaction area of the solid-liquid interface.
  • the pore structure 22 makes it easier for the lithium ions 30 to be embedded into the active material layer 20 inside the pole piece 100, which reduces the difficulty of deintercalating the lithium ions 30 from the active material inside the pole piece 100, thereby reducing the impedance of the pole piece 100, thereby improving the pole piece. 100 overall dynamics to meet the rapid charge and discharge requirements of electrochemical devices.
  • the hole structure 22 is also a space where the pole piece 100 can freely expand when it is strained, the pole piece 100 has the ability to undergo transverse strain in addition to longitudinal strain when the lithium embedded in it expands, and this new transverse strain can alleviate part of the longitudinal strain. pressure, thereby reducing the strain size of the pole piece 100 long-term cycles.
  • the active material layer 20 satisfies 2% ⁇ A ⁇ 20%, and satisfies 50% ⁇ M ⁇ 100% and 1% ⁇ N ⁇ 50% to obtain the optimal parameters of the pore structure 22, which is suitable for silicon mass content of 1 % to 45% of the negative electrode piece, in order to achieve a balance between the capacity or energy density of the electrochemical device and the kinetic performance of the pole piece 100.
  • An embodiment of the present application also provides an electronic device, including the electrochemical device described in any of the above embodiments.
  • the electronic device in the embodiment of the present application is not particularly limited and can be any electronic device known in the prior art.
  • electronic devices include but are not limited to Bluetooth earphones, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric vehicles, ships, 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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Abstract

本申请实施例公开了一种电化学装置及电子设备，包括极片，极片包括集流体和活性材料层，活性材料层设置于集流体上，活性材料层包括第一活性材料和第二活性材料，第一活性材料的克容量大于第二活性材料的克容量。活性材料层具有背离集流体的第一表面，第一表面开设有至少一个孔结构，全部孔结构的体积与活性材料层的体积的比值为A，其中，2％≤A≤20％。添加克容量更大的第一活性材料可提高电化学装置的容量，孔结构可成为新的锂离子液相传递通道，并且2％≤A≤20％，可令锂离子更加容易嵌入到极片内部的活性材料层，以降低极片的阻抗，便于满足电化学装置的快速充放电需求。

Description

电化学装置及电子设备 技术领域
本申请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普及，对电化学装置的容量要求也越来越高。传统的的电化学装置的负极多为石墨材料，其理论克容量(372mAh/g)较低，无法满足日益增长的对高容量电化学装置的需求。
硅储量丰富，且具有远高于石墨材料的克容量(4200mAh/g)，因此被认为是最有潜力的下一代负极材料。然而，硅材料自身的电子/离子的传导能力低于石墨材料，在极片阻抗/充放电倍率等动力学参数上整体落后于传统的石墨极片，难以满足电化学装置的快速充放电需求。
发明内容
本申请实施例旨在提供一种电化学装置及电子设备，以至少能够提高电化学装置的容量及充放电速率。
本申请实施例为了解决其技术问题，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，包括极片，所述极片包括集流体和活性材料层，所述活性材料层设置于所述集流体上，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。所述活性材料层具有背离所述集流体的第一表面，所述第一表面开设有至少一个孔结构，全部所述孔结构的体积与所述活性材料层的体积的比值为A，其中，2％≤A≤20％。
通过添加克容量更大的第一活性材料可提高电化学装置的容量，孔结构可被电解液完全浸润填充，成为新的锂离子液相传递通道，替代扩散系数较低的固相通道，锂离子通过新构建的孔结构，深入到极片内部，除了原有的极片表面纵向扩散，还加入了极片孔结构处的横向扩散新途径，有效增加了固-液界面的反应面积。所述固相通道是指不设置孔结构的活性材料层上，锂离子的传输 通道，锂离子主要通过固体颗粒内部以及界面传输。具体的，如，活性材料颗粒内部供锂离子传输的空位或间隙，活性材料颗粒与导电剂颗粒之间形成的有效连接界面等。孔结构令锂离子可以更加容易嵌入到极片内部的活性材料层，降低了极片内部活性材料脱嵌锂离子的难度，以降低极片的阻抗，从而提升极片整体动力学，以便于满足电化学装置的快速充放电需求。同时，活性材料层满足2％≤A≤20％，以取得孔结构的最优参数，以便于达到电化学装置的容量或能量密度与极片动力学性能的平衡。
根据本申请的一些实施例，满足4％≤A≤14％，以进一步取得孔结构的最后参数，在此范围内，可进一步达到电化学装置的容量及能量密度与极片动力学性能的平衡。
根据本申请的一些实施例，所述活性材料层满足以下条件：
(a)、50％≤M<100％，M为所有所述孔结构在所述第一表面的面积占比；
(b)、1％≤N<50％，N为单个所述孔结构的深度与所述活性材料层的厚度之比。
根据本申请的一些实施例，50％≤M<100％；5％≤N<50％。进一步的，63％≤M<90％；5％≤N<20％。更进一步的，80％≤M<86％；8％≤N<16％。
孔结构的深度与活性材料层的厚度之比N小于5％时，则极片阻抗的降低效果尚未达到饱和，仍然存在一定的提升空间，因此优选选用5％≤N<50％。当M为80％时，极片的动力学改善接近饱和；相邻两孔结构刚好邻接的极限状态下，所有孔结构在第一表面的面积占比M≈90％，因此，本实施例中，选用80％≤M<86％。
根据本申请的一些实施例，10μm<R<200μm，R为在所述第一表面，所述孔结构的半径。优选的，30μm<R<100μm。当孔结构的半径逐渐增大时，其边缘位置深度偏低的削薄区域也逐渐增大，易导致单个孔结构的动力学增强效果有一定的恶化风险，因此，本实施例中要求孔结构的半径R<200μm，优选范围为100μm以下。即10μm<R<200μm，优选的，30μm<R<100μm。
根据本申请的一些实施例，
Figure PCTCN2022106318-appb-000001
D为相邻两个孔结构的中心距。优选的，D≥2R。当M恰好为100％时，相邻三个孔结构的中心连线形成等边三角形，此时三相邻孔结构的间距
Figure PCTCN2022106318-appb-000002
当相邻孔结构的间距D的优选范围为D≥2R，相邻孔结构完全不存在重叠风险。
根据本申请的一些实施例，沿所述极片厚度方向，所述孔结构设置有第一区段和第二区段，所述第一区段靠近所述第一表面，所述第一区段的横截面积大于所述第二区段的横截面积。孔结构在不同的深度位置，其横截面的大小不同，整体呈现“外宽内窄”的结构，“外宽”的结构有利于外部的电解液快速进入孔结构，而“内窄”的结构则更有利于孔结构内的电解液与活性材料层接触。
根据本申请的一些实施例，所述第一活性材料包括硅、硅氧化物、硅碳复合物和硅合金中的至少一种。
根据本申请的一些实施例，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中的至少一种。
根据本申请的一些实施例，所述第一活性材料为硅，所述第二活性材料为石墨。
硅的理论克容量为4200mAh/g大于碳的理论克容量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，硅在活性材料层中的质量分数可选择1％至45％。根据本申请的一些实施例，1％≤W≤45％，W为所述第一活性材料在所述活性材料层中的质量含量。
根据本申请的一些实施例，所述孔结构为盘状、圆柱状、圆台状、圆锥状、棱柱状或棱台状中的一种。可以理解的是，采用激光打孔技术在活性材料层表面形成孔结构，由于工艺的限制，例如，因为激光能量在对活性材料层刻蚀的过程中，存在能量散射和吸收，最终在第一活性材料层上形成的孔结构不是标准的盘状、圆柱状、圆台状、圆锥状、棱柱状或棱台状，而是大体上为盘状、圆柱状、圆台状、圆锥状、棱柱状或棱台状。
根据本申请的一些实施例，在所述第一表面，多个所述孔结构呈阵列分布。阵列分布有利于电解液从各个位置渗透到活性材料层，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，所述孔结构的轴线与所述极片厚度方向之间的夹角为0度至10度，以方便电解液快速进入。
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，并且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极片的爆炸视图；
图2为本申请一些实施例的极片的截面示意图；
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俯视图；
图5为本申请一些实施例的极片的俯视图；
图6为本申请一些实施例的极片的俯视图；
图7为本申请一些实施例的极片阻抗与N之间的关系图；
图8为本申请一些实施例的M与极片动力学及加工成本之间的关系图；
图9为本申请一些实施例的相邻孔结构之间的间距示意图；
图10为本申请一些实施例的相邻孔结构之间的间距示意图。
图中：
100、极片；
10、集流体；11、长边；12、宽边；13、厚度边；14、主表面；
20、活性材料层；21、第一表面；211、未加工区域；22、孔结构；221、第一区段；222、第二区段；
30、锂离子；
40、扇形；41、未重合区域；
50、重合区域。
具体实施方式
下面将结合附图对本申请技术方案的实施例进行详细的描述。以下实施例仅用于更加清楚地说明本申请的技术方案，因此只作为示例，而不能以此来限制本申请的保护范围。
除非另有定义，本文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；本文中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请；本申请的说明书和权利要求书及上述附图说明中的术语“包括”和“具有”以及它们的任何变形，意图在于覆盖不排他的包含。
在本申请实施例的描述中，技术术语“第一”、“第二”等仅用于区别不同对象，而不能理解为指示或暗示相对重要性或者隐含指明所指示的技术特征的数量、特定顺序或主次关系。在本申请实施例的描述中，“多个”的含义是两个以上，除非另有明确具体的限定。
在本文中提及“实施例”意味着，结合实施例描述的特定特征、结构或特性可以包含在本申请的至少一个实施例中。在说明书中的各个位置出现该短语并不一定均是指相同的实施例，也不是与其它实施例互斥的独立的或备选的实施例。
第一方面，本申请的实施例提出了一种电化学装置，请参照图1和图2，该电化学装置包括极片100，极片100包括集流体10和活性材料层20，活性材料层20涂覆于集流体10上。本申请中，极片100均以负极极片进行描述，在其他实施例中，电化学装置还包括正极极片(图中未示出)、隔膜(图中未示出)、壳体(图中未示出)以及电解液(图中未示出)，负极极片、隔膜以及正极极片依次层叠或卷绕以形成电化学装置的电极组件，电极组件和电解液则收容于上述壳体内。需要说明的是，在本申请的实施例中，电化学装置是组成电池或电池模组的最小单元，是具体实现电能和化学能转换的场所。
对于上述集流体10，请参照图1和图2，集流体10整体呈扁平的条状结构，其各部位的厚度基本一致，集流体10的厚度通常介于3微米(μm)至20微米之间。集流体10具有长边11、宽边12以及厚度边13。长边11是集流体10展开呈平整状态时沿其长度方向(X方向)延伸的边，宽边12是集流体10展开呈平整状态时沿其宽度方向(Y方向)延伸的边，厚度边13是集流体10展开呈平整状态时沿其厚度方向(Z方向)延伸的边。集流体10具有两个主表面14，该两个主表面14均由上述长边11和宽边12共同限定出，两主表面14沿上述厚度边13的延伸方向相对设置，两个主表面14上均可涂覆活性材料层20。集流体10为极片100为导电基材，根据极片100种类的不同，可选择不同的材料作为极 片100的集流体10，在本实施例中，采用的是负极极片，集流体10可选用铜箔。
对于上述活性材料层20，请参照图1和图2，活性材料层20是电化学装置的核心材料层，活性材料层20涂覆于集流体10的至少一个表面，例如涂覆于上述集流体10的两个主表面14中的其中一个，或者上述集流体10的两个主表面14均涂覆活性材料层20。活性材料层20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10的主表面14，从而得到活性材料层20。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20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大于碳的理论克容量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20中的质量含量可选择1％至45％，更高的硅质量含量以提升电化学装置的容量，硅的质量含量可以通过Element Analysis(元素分析)测得。
硅材料自身的电子及离子的传导能力低于石墨材料，在极片100阻抗及充放电速率等动力学参数上整体落后于传统的石墨极片，为了改善极片100的阻抗提高电化学装置的充放电速率，在一些实施例中。请参照图1和图2，活性材料层20具有背离集流体10的第一表面21，第一表面21上开设有至少一个孔结构22。沿极片100的厚度反向(Z方向)，孔结构22从活性材料层20朝集流体10的方向延伸，孔结构22的深度可设置为活性材料层20厚度的1％至50％。
对于上述孔结构22的形状，请参照图3，孔结构22可采用盘状、圆柱状、圆台状、圆锥状、棱柱状或棱台状等(图3中仅示出了部分形状)，在活性材料层20的表面，孔结构22呈现圆形、椭圆形、矩形或多边形等。孔结构22的数量可设置为多个，相邻两个孔结构22之间的距离可以是非固定值，从而保证 在极片100的任意局部位置都能进行孔结构22的设置；在实际操作中，请继续参照图4至图6所示，孔结构22之间存在“相互独立、相互接触或者部分重合”的三种分布形态，在活性材料层20的端面，多个孔结构22呈现出盘状、台阶状、波浪状的浅坑形态。
在一些实施例中，多个孔结构22均匀分布于活性材料层20，例如，请参照图4，在活性材料层20的表面，多个孔结构22呈阵列式的均匀分布，均匀分布有利于电解液从各个位置渗透到活性材料层20，便于活性材料层20与电解液充分接触反应。图5则展示了正面形貌为圆形的孔结构22按照等间距密排方式分布，并且相邻孔结构22之间保持边缘相切接触的情况。
进一步的，在一些实施例中，请参照图3，沿极片100的厚度方向(Z方向)，孔结构22设置有背离集流体10的第一区段221和靠近集流体10的第二区段222，第一区段221为孔结构22的入口，第二区段222为孔结构22的孔底，第一区段221的横截面积大于第二区段222的横截面积，使得孔结构22的入口处较大；本实施例中，孔结构22在不同的深度位置，其横截面的大小不同，其整体呈现“外宽内窄”的结构，“外宽”的结构有利于外部的电解液快速进入孔结构22，而“内窄”的结构则更有利于孔结构22内的电解液与活性材料层20接触；其中，上述横截面是指孔结构22沿垂直于极片100厚度方向的截面，孔结构22可沿垂直于集流体10的方向深入活性材料层20一定深度，以方便电解液快速进入，本实施例中的垂直是指孔结构22的轴线与极片100厚度方向之间的夹角为0度至10度。
孔结构22可达到活性材料层20内部数微米的深度，并且未对极片100更深处的活性材料层20造成任何形貌或结构上的影响，正常充放电循环后的极片100，孔结构22始终保持形貌稳定，未出现不可逆的形貌或结构参数的恶化，可长期维持对极片100的动力学改善效果。
孔结构22可利用工业成熟的激光打孔技术，在活性材料层20的第一表面21精确溶蚀一定深度的孔结构22。孔结构22可被电解液完全浸润填充，成为新的锂离子30液相传递通道，替代扩散系数较低的固相通道。锂离子30通过新构建的孔结构22，深入到极片100内部，除了原有的极片100表面纵向扩散，还加入了极片100孔结构22处的横向扩散新途径，有效增加了固-液界面的反应面积。孔结构22令锂离子30可以更加容易嵌入到极片100内部的活性材料 层20，降低了极片100内部活性材料脱嵌锂离子30的难度，以降低极片100的阻抗，从而提升极片100整体动力学，以便于满足电化学装置的快速充放电需求。
越多的半导体硅材料意味着极片100动力学越差，为适应1％至45％的硅质量含量，需对孔结构的结构参数进行改善。
对于孔结构22的半径(定义半径为R)，孔结构22的半径R越大，则电解液更容易进入孔结构22，孔结构22的半径R越小，则越倾向于采用更深的孔结构22以浸润活性材料层20。本申请的实施例中，采用的是半径较大并且深度较浅的孔结构22，半径大深度浅的孔结构22更适用于硅材料加工性较差以及压实密度较大的负极极片。与半径较小的深孔结构相比，半径较大的浅孔结构的动力学参数优化接近同水平，能量密度恶化风险更小。
半径越大，孔结构22的数量可设置为更少，更大的半径更容易进行打孔加工。已知孔结构22的加工时间t与半径R呈现如下关系：t∝1/R 2，考虑到降低极片100加工速率或时间成本的生产需求，本申请中孔结构22的半径优选才有R>10μm，优选范围可采用30μm以上。而当孔结构22的半径逐渐增大时，其边缘位置深度偏低的削薄区域也逐渐增大，易导致单个孔结构22的动力学增强效果有一定的恶化风险，因此，本申请的实施例中要求孔结构22的半径R<200μm，优选范围为100μm以下。即10μm<R<200μm，优选的，30μm<R<100μm。
对于孔结构22的深度(定义孔结构22的深度为d)，由于机械应力的局部集中，冷压后的极片100表面附近将比极片100主体产生更为严重的塑性应变，形成过冷压表面层，导致活性材料层20的孔隙率偏小，存在电解液浸润能力恶化或锂离子30扩散能力减弱等一系列的动力学恶化风险。孔结构22需要尽可能穿透过冷压表面层所在的区域，从而提供电解液或锂离子30的快速传递通道。请参照图7，定义N为单个孔结构22的深度与活性材料层20的厚度之比，图7示出了极片100阻抗Rss与N之间的关系，其中L1、L2、L3分别为不同类型的极片，其对应极片的压实密度不相同，L1为1.80(单位g/cm 3)，L2为1.74(单位g/cm 3)，L3为1.66(单位g/cm 3)，L1、L2、L3的整体趋势走向相近，随着孔结构22的深度与活性材料层20的厚度之比N的增大，极片100的阻抗均为逐渐降低。同时极片的压实密度也影响极片的阻抗，压实密度 增大，活性材料层粒子间的间距减小，接触几率越大，粒子间接触面积也越大，导电桥梁和通道增多，极片阻抗降低。如图7所示，在N≤20％的范围内，压实密度越大，其阻抗降低越明显，当N大于50％时，极片阻抗降低趋近饱和，而压实密度越大，其极片阻抗趋近饱和的值越小。
只要存在孔结构22即可实现对极片100阻抗的降低，本申请的实施例中，孔结构的深度d可设置为大于或等于活性材料层20厚度的1％以上，即N≥1％。当孔结构22的深度为活性材料层20厚度的50％以上时，随着N的增大，极片100的阻抗降低不明显且趋近于水平，因此本申请的实施例中，孔结构22的的深度与活性材料层20的厚度之比N可设置为小于50％，即N<50％。
进一步的，根据图7可知，孔结构22的深度与活性材料层20的厚度之比N小于5％时，则极片100阻抗的降低效果尚未达到饱和，仍然存在一定的提升空间。本实施例中，优选选用5％≤N<50％；和/或，孔结构22的深度d≥2μm，d≥2μm足以使得孔结构22穿透过冷压表面层；或者，在一些实施例中，选用5％≤N<50％及d≥2μm两者中的较大值，设置2μm深度下限值是为了满足本申请实施例中的反向需求。
孔结构22体积同样影响极片的动力学，孔结构22的体积与活性材料层的体积的比值A越大，则极片的阻抗越小，但容量则会减小；为达到阻抗减小与容量减小的平衡，本申请的实施例中，2％≤A≤20％，优选的，4％≤A≤14％。需要说明，A是所有孔结构22的体积与活性材料层剩余材料的体积(即除去了所有孔结构22的体积)的比值。
对于所有孔结构22在第一表面21的面积占比(定义M为所有孔结构22在第一表面21的面积占比)，本申请的实施例旨在改善极片100的动力学性能，孔结构22在不引起其他风险的前提下，尽可能覆盖第一表面21的所有动力学恶化区域。请参照图8，图8示出了所有孔结构22在第一表面21的面积占比M与极片100动力学及加工成本之间的关系，其中L4为动力学，L5为成本。对于极片100动力学，图8分为三个阶段，第一阶段中，极片100动力学随孔结构22面积占比M近似线性提升；第二阶段中，随孔结构22的面积占比M的提升，极片100动力学接近饱和和上限；第三阶段中，孔结构22面积占比M几乎不改变极片100动力学，但可导致其余风险。对于加工成本，随着孔结构22面积占比M的提高，其加工成本线性提升。由此可知，在本申请的实施 例中，孔结构22在第一表面21的面积占比M≥50％，以保证加工后极片100动力学有明显的提升效果。
孔结构22的在第一表面21的面积占比M的上限值为100％，即M的取值范围为50％至100％，在此范围内，孔结构22的动力学增强效果足够有效。但在M接近100％时将出现相邻两孔结构22的边缘部分区域互相重叠的现象，孔结构22的重叠意味着极片100的部分位置被重复加工，这样不仅降低了极片100生产效率，并且提升了时间成本，多次受到冲击的重叠区域也可能导致极片100局部机械强度下降，甚至引起长期循环性能恶化。因此，在一些实施例中，如图9所示，相邻两孔结构22刚好邻接(图9中为相切)，相邻三个孔结构22的中心连线形成等边三角形结构，活性材料层20的表面结构视为该等边三角形的重复循环，等边三角形结构由三个60°的扇形40+中心处未加工区域211组成，因此，在本实施例中，此极限状态的孔结构22在第一表面21的面积占比
Figure PCTCN2022106318-appb-000003
由此，孔结构22在第一表面21的面积占比M应小于或等于90％，即50％≤M<90％；优选的，再结合图7可知，当M为70％时，极片100的动力学改善以接近饱和，因此孔结构22在第一表面21的面积占比M可设置为70％≤M<90％，在极片100动力学提升接近饱和后，不引起其他性能恶化的风险。
对于相邻孔结构22的间距(定义D为相邻孔结构22的中心之间的距离)，为了保证孔结构22在第一表面21的面积占比M足够大的前提下，使得相邻孔结构22的重叠部分尽可能减小，如图10所示，当M恰好为100％时，相邻三个孔结构22的中心连线形成等边三角形，此时三个60°的扇形40在等边三角形的中心相交，显然有相邻孔结构22的间距
Figure PCTCN2022106318-appb-000004
未重合区域41面积占比约为79％，重合区域50面积占比约为21％，由此可知，相邻孔结构22的间距D可设置为
Figure PCTCN2022106318-appb-000005
此参数范围下限值基于孔结构22的最密排分布情况计算，对应覆盖面积占比恰好为100％，是孔结构22深度d可被测量的极限情况，处于此下限范围以外的间距D，既难以精确测量孔结构22的深度d，也将在极片100表面出现多个孔结构22重叠的高风险区域。
进一步，在一些实施例中，相邻孔结构22的间距D的优选范围为D≥2R，显然此条件下，相邻孔结构22完全不存在重叠风险。
本申请的实施例中，以硅基阳极极片为例，孔结构22的体积与活性材料 层的体积的比值为A，在A不同的情况下，对电化学装置进行了阻抗及容量保持率的测试。其中，A的测量方法如下，采用冲孔时，可事先测量活性材料层的体积，活性材料层的体积可通过涂覆的量计算得到，冲孔后，将冲下来的体积比上剩余的体积即为A；A的测试方法还有很多，例如直接计算孔结构22的体积与活性材料层的体积，此时需要的孔结构22为规则的孔结构22；再或者，将孔结构22进行填充，填充后取得填充物再计算填充物的体积；A的计算方法实则多样，此处不一一列举了。
对于容量保持率的测试方法，本申请中，在常温(25℃左右)，常压(0.1MPa)下，将各实施例和各对比例中的电化学装置以0.1C倍率恒流充电至充放电截止电压上限(4.2V)，之后静止5分钟，再以0.1C倍率恒流放电至充放电截止电压下限(2V)，静置5分钟，此为一个循环充放电过程，此次的放电容量记为首次放电容量，以此充放电循环400圈，将充放电400圈的放电容量比上首次的放电容量记为容量保持率。Rss是通过交流阻抗法测试得到，其中交流阻抗法具体为在给电极施加一个小振幅的相、以此得到电极的复阻抗。然后根据设想的等效电路，通过阻抗谱的分析和参数拟合，得出电极反应的动力学参数。
测试的结果如下表1所示。
表1
Figure PCTCN2022106318-appb-000006
Figure PCTCN2022106318-appb-000007
根据表1的试验结果可知，A越大，则阻抗Rss越小，但容量保持率降低明显。对比例1和2中，A均小于2，虽容量保持率降低不明显，但阻抗较高；对比例3和4中，A均大于20，虽阻抗较低，但容量保持率降低较大。而实施例1至10中，阻抗明显降低，并且容量保持率降低幅度较小，因此，本申请的实施例中，选择2％≤A≤20％；根据表1中实施例1至10可进一步看出，实施例2至8的结果优于实施例1、9和10，因此，更优选的4％≤A≤14％。
为了得出孔结构22的结构参数与能量密度以及动力学性能之间的关系，本申请发明人进行了相关试验，其结果如下：其中，Rate为充放电倍率测试，指电芯满充状态下，以不同倍率(0.1至2C)的恒流放电至截止电压所释放的容量相对于额定放电容量的比值。HL为高低温测试，高低温测试为在设置的不同环境温度下(一般在-20℃至60℃范围固定取值)，电芯实际0.2C放电容量相对于额定放电容量的比值；DCR为高频阻抗测试，DCR主要是通过充放电机和高低温箱连用进行测试的，具体测试方法为先将温箱调至常温，搁置至热平衡后对电池进行1C充放电循环测试得到实际测试容量C 0，静置5min，用1C 0容量的电流将电池充电到4V后恒压至I≤0.2C 0，静置60min，1C 0放电30min，将电池调至50％SOC，记录此时的电压为V1，静置60min后在该状态下4C脉冲放电30s，记录此时的电压为V2，根据DCR＝(V1-V2)/4C 0可得到初次循环时电池50％SOC状态的内阻。Rss为低频阻抗测试；温度系数定义为电芯在常温(25℃)与高温(45℃)情况下0.2C放电容量的比值，与电芯动力学正相关，温度系数越高，电芯动力学越好。
表2孔结构22的结构参数与能量密度以及动力学性能之间的关系
Figure PCTCN2022106318-appb-000008
Figure PCTCN2022106318-appb-000009
表2描述了孔结构22的具体结构参数对能量密度以及动力学性能的具体效果，按照“孔结构22是否存在”、“是否满足1％≤N<50％”、“50％≤M<100％”以及“是否满足
Figure PCTCN2022106318-appb-000010
”四类设计确定孔结构22的优选结构参数。实施例4中，M＝100％，并且间距D＝1.7R，其动力学性能优化明显，但在循环后，其容量保持率较低，且电化学装置膨胀严重。实施例3中，不满足50％≤M<100％，其动力学有效不明显。实施例2中，动力学优化也不明显，是因为N＝2％，极片100阻抗的降低效果未达到饱和。实施例1中，动力学优化明显，且循环容量保持降低不明显以及膨胀较小，可达到电化学装置的容量或能量密度与动力学性能的平衡。需要说明的是，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。
综上，本申请的实施例中，孔结构22在第一表面21的面积占比M为50％≤M<100％，优选70％≤M<90％；孔结构22的深度与活性材料层20的厚度之比N为1％≤N<50％，优选5％≤N<50％；相邻两个孔结构22的中心距
Figure PCTCN2022106318-appb-000011
优选D≥2R。
为了得出孔结构22在第一表面的面积占比M以及孔结构22的深度与活性材料层的厚度之比N的最优参数，本申请的实施例再次进行了相关试验，阻抗及容量保持的测试方法可参照上述实施例，实验检测如下表3。
表3
Figure PCTCN2022106318-appb-000012
Figure PCTCN2022106318-appb-000013
表3描述了不同参数下的M和N对阻抗及容量保持率的影响。根据表3中的结果可知，实施例1至16中的效果(保证阻抗减小的同时，使得容量保持率减小幅度较小)优于对比例1至5的效果，本申请的实施例中，可选择50％≤M<100％，1％≤N<50％。实施例3至12的效果优于实施例1、2、13及15，因此，M和N的取值还可选择50％≤M<100％，5％≤N<50％。进一步，实施例3至12中，实施例3至8的效果优于实施例9、10及12，M和N的取值还可选择63％≤M<90％，5％≤N<20％。更进一步的，实施例3至8以及11中，实施例6、7、16的效果由于实施例3至5、8及11，因此还可选择80％≤M<86％，8％≤N<16％。当80％≤M<86％、8％≤N<16％时，电解液可更加容易的进入孔结构22以浸润活性材料层，并且，在此范围内，电化学装置的在经过多次充放电循环后，其容量保持率变化较小，可以达到阻抗减小与容量保持率减小的平衡。
本申请的实施例中，第一活性材料的克容量大于第二活性材料的克容量，通过添加克容量更大的第一活性材料可提高电化学装置的容量。孔结构22可被电解液完全浸润填充，成为新的锂离子30液相传递通道，替代扩散系数较低的固相通道，锂离子30通过新构建的孔结构22，深入到极片100内部，除了原有的极片100表面纵向扩散，还加入了极片100孔结构22处的横向扩散新途径，有效增加了固-液界面的反应面积。孔结构22令锂离子30可以更加容易嵌入到极片100内部的活性材料层20，降低了极片100内部活性材料脱嵌锂离子30的难度，以降低极片100的阻抗，从而提升极片100整体动力学，以便于 满足电化学装置的快速充放电需求。同时，考虑到孔结构22也是极片100应变时可以自由延展的空间，令极片100嵌锂膨胀时除了纵向应变以外拥有了横向应变的能力，并且这部分新的横向应变可以缓解一部分纵向应变的压力，从而降低极片100长期循环的应变大小。同时，活性材料层20满足2％≤A≤20％，并且满足50％≤M<100％以及1％≤N<50％，以取得孔结构22的最优参数，适用于硅质量含量为1％至45％的负极极片，以便于达到电化学装置的容量或能量密度与极片100动力学性能的平衡。
本申请的实施例还提出了一种电子设备，包括上述任一实施例所述的电化学装置。本申请实施例的电子设备没有特别限定，其可以是现有技术中已知的任何电子设备。例如，电子设备包括但不限于蓝牙耳极、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 (17)

  1. 一种电化学装置，包括极片，所述极片包括集流体和活性材料层，所述活性材料层设置于所述集流体上，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；
    所述活性材料层具有背离所述集流体的第一表面，所述第一表面开设有至少一个孔结构，全部所述孔结构的体积与所述活性材料层的体积的比值为A，其中，2％≤A≤20％。
  2. 根据权利要求1所述的电化学装置，其特征在于，4％≤A≤14％。
  3. 根据权利要求1所述的电化学装置，其特征在于，所述活性材料层满足以下条件：
    (a)、50％≤M<100％，M为所有所述孔结构在所述第一表面的面积占比；
    (b)、1％≤N<50％，N为单个所述孔结构的深度与所述活性材料层的厚度之比。
  4. 根据权利要求3所述的电化学装置，其特征在于，50％≤M<100％；5％≤N<50％。
  5. 根据权利要求4所述的电化学装置，其特征在于，63％≤M<90％；5％≤N<20％。
  6. 根据权利要求5所述的电化学装置，其特征在于，80％≤M<86％；8％≤N<16％。
  7. 根据权利要求1所述的电化学装置，其特征在于，10μm<R<200μm，R为在所述第一表面，所述孔结构的半径。
  8. 根据权利要求7所述的电化学装置，其特征在于，30μm<R<100μm。
  9. 根据权利要求7所述的电化学装置，其特征在于，
    Figure PCTCN2022106318-appb-100001
    D为相邻两个孔结构的中心距。
  10. 根据权利要求9所述的电化学装置，其特征在于，D≥2R。
  11. 根据权利要求1至10中任一项所述的电化学装置，其特征在于，沿所述极片厚度方向，所述孔结构设置有第一区段和第二区段，所述第一区段靠近所述第一表面，所述第一区段的横截面积大于所述第二区段的横截面积。
  12. 根据权利要求1至10任一项所述的电化学装置，其特征在于，所述第一活性材料包括硅、硅氧化物、硅碳复合物和硅合金中的至少一种。
  13. 根据权利要求12所述的电化学装置，其特征在于，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中的至少一种。
  14. 根据权利要求13所述的电化学装置，其特征在于，所述第一活性材料为硅，所述第二活性材料为石墨。
  15. 根据权利要求1至10中任一项所述的电化学装置，其特征在于，所述孔结构的轴线与所述极片厚度方向之间的夹角为0度至10度。
  16. 根据权利要求1至10中任一项所述的电化学装置，其特征在于，所述孔结构为盘状、圆柱状、圆台状、圆锥状、棱柱状或棱台状中的至少一种。
  17. 一种电子设备，其特征在于，包括如权利要求1至16中任一项所述的电化学装置。
PCT/CN2022/106318 2022-07-18 2022-07-18 电化学装置及电子设备 WO2024016127A1 (zh)

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JP2016058375A (ja) * 2014-09-10 2016-04-21 三菱マテリアル株式会社 リチウムイオン二次電池用負極及びリチウムイオン二次電池
CN112968148A (zh) * 2021-03-29 2021-06-15 欣旺达电动汽车电池有限公司 一种锂离子电池负极片和锂离子电池
CN113644231A (zh) * 2021-07-15 2021-11-12 恒大新能源技术(深圳)有限公司 复合负极片及其制备方法、二次电池

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2016058375A (ja) * 2014-09-10 2016-04-21 三菱マテリアル株式会社 リチウムイオン二次電池用負極及びリチウムイオン二次電池
CN112968148A (zh) * 2021-03-29 2021-06-15 欣旺达电动汽车电池有限公司 一种锂离子电池负极片和锂离子电池
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