Pole piece, preparation method thereof and lithium ion battery

Abstract

The invention discloses a pole piece and a preparation method thereof and a lithium ion battery, the pole piece comprises a current collector, a ceramic layer and an active material layer, the edge of the current collector is provided with a tab part, the ceramic layer is arranged on the surface of at least one side of the current collector and covers at least part of the surface of the tab part, the ceramic layer comprises ceramic particles, the particle size Dv50 of the ceramic particles is 0.2-1.5 [mu] m, and the active material layer is arranged on the surface of at least one side of the current collector and covers at least part of the surface of the tab part. The surface roughness of the ceramic layer is 1.2 microns to 2 microns, and the heat conductivity coefficient is 0.2 W / (m.K) to 1.0 W / (m.K); the active material layer is arranged on the surface of at least one side of the current collector and is adjacent to the ceramic layer or partially overlapped with the ceramic layer, so that the ceramic layer is arranged on at least part of the surface of the tab part of the pole piece, and the granularity of ceramic particles of the ceramic layer and the surface roughness and heat conductivity coefficient of the ceramic layer are strictly controlled; and the burr level of the laser tab die-cutting section on the pole piece can be effectively improved, and the processing yield, safety and reliability of the product pole piece are improved.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to an electrode, its preparation method, and a lithium-ion battery. Background Technology

[0002] Currently, in existing lithium-ion battery manufacturing technologies, active slurry is typically coated onto the current collector using methods such as transfer coating or spraying, followed by drying and laser cutting of the tabs to prepare the electrode sheets. This method is prone to generating burrs during laser cutting of the tabs, which can easily puncture or tear the separator during winding, assembly, or use, causing internal short circuits in the battery. This can lead to risks such as lithium battery fires and explosions, affecting product quality and safety. To address this issue, major manufacturers apply a ceramic coating near the tab cutting location to protect the tabs during die-cutting. However, the protective effect of this method is currently limited, and the resulting electrode sheets still pose safety hazards. When the burr size is larger than the thickness of the ceramic coating, there is still a risk of puncturing the separator, causing a short circuit, and potentially igniting the battery cell. Summary of the Invention

[0003] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes an electrode, a method for preparing the same, and a lithium-ion battery.

[0004] In a first aspect, the present invention provides an electrode comprising: A current collector, the edge of which has tabs; A ceramic layer is disposed on at least one side surface of the current collector and covers at least a portion of the surface of the electrode tab; the ceramic layer comprises ceramic particles with a particle size Dv50 of 0.2 μm to 1.5 μm; the surface roughness of the ceramic layer is 1.2 μm to 2 μm, and the thermal conductivity is 0.2 W / (m·K) to 1.0 W / (m·K); An active material layer is disposed on at least one side surface of the current collector and is adjacent to or partially overlaps with the ceramic layer.

[0005] According to embodiments of the present invention, the electrode sheet has at least the following beneficial effects: The electrode sheet has a ceramic layer disposed on at least a portion of the surface of the current collector's upper tab, which can protect the tab during die-cutting. The ceramic layer is controlled to have a low thermal conductivity (0.2 W / (m·K) ~ 1.0 W / (m·K)), which, compared to a ceramic layer with a high thermal conductivity, improves the layer's toughness, making it less prone to brittleness and mitigating burr levels after heat exposure. Furthermore, by controlling the ceramic layer to have a low surface roughness (i.e., 1.2 μm ~ 2 μm), the ceramic layer is more resistant to laser damage. During cutting, the ceramic layer exhibits high uniformity in deformation under heat, enabling even and rapid heat conduction to the current collector substrate. This shortens the heat-affected time of the substrate, further improving burr levels and reducing the probability of metal burrs. Furthermore, the use of low-particle-size (Dv50 0.2μm~1.5μm) ceramic particles in the ceramic layer results in tighter particle bonding and a more regular overall morphology. Under laser heat, this further shortens the heat-affected time of the current collector substrate, reducing the risk of metal burrs. Therefore, by setting a ceramic layer on at least a portion of the electrode tab surface and strictly controlling the ceramic particle size, surface roughness, and thermal conductivity of the ceramic layer, the burr level of the electrode tab die-cutting section after laser die-cutting can be effectively improved, enhancing the processing yield and reliability of the product electrode.

[0006] The thermal conductivity of the ceramic layer can be measured using the hot-wire method. Specifically, a metal wire (hot wire) is embedded in the sample, and after heating with electricity, the temperature rise over time is recorded. The thermal conductivity is calculated from the temperature rise rate. The surface roughness of the ceramic layer can be measured using a white light interferometer, referencing standard ISO 25178. The height difference on the coating surface is analyzed using the interference fringes of light to reconstruct the three-dimensional morphology. The particle size Dv50 of the ceramic particles can be measured using a laser particle size analyzer.

[0007] The particle size Dv50 of the ceramic particles can be any value or a range of any two of the following: 0.2μm, 0.3μm, 3.5μm, 0.4μm, 0.5μm, 0.55μm, 0.6μm, 0.65μm, 0.7μm, 0.75μm, 0.8μm, 0.85μm, 0.9μm, 1μm, 1.2μm, 1.35μm, 1.4μm, and 1.5μm. If the particle size Dv50 is too large (e.g., >1.5μm), the ceramic layer will be thicker and denser, increasing the cutting resistance during die cutting. This can lead to incomplete cutting and larger metal burrs on the current collector. If the particle size D50 is too small, the resulting ceramic layer will be too thin, reducing its mechanical strength and protective properties. It will not effectively protect the current collector, and during die cutting, the particles will act almost directly on the current collector, increasing the burrs. To address this, by controlling the particle size Dv50 of the ceramic particles within the above range, sufficient strength and protection of the ceramic layer can be ensured without excessively increasing the difficulty of cutting, thus effectively controlling burrs.

[0008] Furthermore, the surface roughness of the ceramic layer can be any value or a range of any two of the following: 1.2μm, 1.3μm, 1.45μm, 1.5μm, 1.6μm, 1.65μm, 1.7μm, 1.8μm, 1.9μm, and 2μm. If the surface roughness of the ceramic layer is too large, the laser energy cannot be absorbed and conducted evenly, which will lead to instability during laser cutting and increased burrs. If the surface roughness of the ceramic layer is too small, its heat conduction is rapid and concentrated, the interaction time between the laser and the material during die cutting is extremely short, the cutting process is difficult to control, and burrs are prone to increase.

[0009] The thermal conductivity of the ceramic layer can be any value or a range of any two of the following: 0.2 W / (m·K), 0.25 W / (m·K), 0.3 W / (m·K), 0.36 W / (m·K), 0.4 W / (m·K), 0.45 W / (m·K), 0.5 W / (m·K), 0.52 W / (m·K), 0.55 W / (m·K), 0.6 W / (m·K), 0.65 W / (m·K), 0.7 W / (m·K), 0.8 W / (m·K), 0.85 W / (m·K), 0.9 W / (m·K), 0.95 W / (m·K), and 1.0 W / (m·K). If the thermal conductivity of the ceramic layer is too high, the die-cutting time is extremely short, the process is difficult to control, burrs increase, and the ceramic layer's toughness deteriorates, making it prone to brittleness and cracking. When exposed to heat, even larger burrs will form. Conversely, if the thermal conductivity is too low, the die-cutting time increases, resulting in more heat exposure and larger burrs. Controlling the thermal conductivity of the ceramic layer to be low can improve these problems and reduce burr levels.

[0010] In some embodiments of the present invention, the product of the thermal conductivity (in W / (m·K)) of the ceramic layer and the particle size Dv50 (in μm) of the ceramic particles is less than or equal to the surface roughness (in μm) of the ceramic layer. From the perspective of die-cutting process input and output, surface roughness is affected by material particle size and material thermal conductivity. If the product of ceramic particle size D50 and ceramic layer thermal conductivity is too large, it means that either the heat conduction is too fast (thermal conductivity is too high), or the particles are too large (D50 is too large), or both. This will exacerbate the aforementioned adverse effects, resulting in excessively rapid heat loss and high cutting resistance. At this time, even if the surface roughness itself is within the acceptable range, it is usually difficult to offset the heat management imbalance and increased cutting difficulty caused by excessively high thermal conductivity and excessively large particles. This mismatch between parameters will disrupt the dynamic balance of heat conduction, absorption, and dissipation during laser cutting, ultimately leading to burr deterioration. Therefore, by limiting the thermal conductivity and thermal conductivity in the above manner to control the surface roughness of the ceramic layer, the burr level after die-cutting can be reduced.

[0011] In some embodiments of the present invention, the burr length of the cross section of the electrode tab die-cutting part is less than or equal to 3.5 μm.

[0012] In some embodiments of the present invention, the ceramic layer is disposed on one side surface of the current collector and covers at least a portion of the surface of the tab. Specifically, the ceramic layer may be designed to be disposed on one side surface of the current collector and cover part or all of the surface of the tab; wherein, the part of the surface of the tab may include the edge surface of the tab, so as to facilitate the action of the ceramic layer during laser die-cutting, thereby protecting the die-cut tab through the ceramic layer, improving the burr level, and reducing the probability of burr generation during die-cutting; if the ceramic layer is designed to cover the entire surface of the tab, heat conduction during laser cutting can be accelerated, shortening the heat-affected time of the current collector substrate and reducing the probability of burr generation. Further, in some embodiments, the ceramic layer may be designed to be disposed at the edge of the current collector and adjacent to or partially overlapping with the active material layer.

[0013] In some embodiments of the present invention, the ceramic layer is disposed on both sides of the current collector and covers at least a portion of the surface of the tab, thereby further improving the burr level at the tab die-cutting section and reducing the probability of burr generation. Specifically, the ceramic layer can be designed to be disposed on both sides of the current collector and cover part or all of the surface of the tab, wherein the part of the surface of the tab may include the edge surface of the tab. Alternatively, the ceramic layers on both sides of the current collector can be designed to cover part or all of the surface of the tab, or the ceramic layer on one side of the current collector can cover part of the surface of the tab, while the ceramic layer on the other side covers the entire surface of the tab.

[0014] In some embodiments of the present invention, the tab portion at the edge of the current collector is configured to connect to an external tab.

[0015] In some embodiments of the present invention, the tab portion at the edge of the current collector is configured as a tab.

[0016] In addition, the electrode tabs at the edge of the current collector can be one or more (such as 2, 3, 4, 5, 6, 8, etc.).

[0017] In some embodiments of the present invention, the ceramic particles include at least one of magnesium hydroxide particles, magnesium oxide particles, and aluminum oxide particles.

[0018] In some embodiments of the present invention, the ceramic layer further includes an adhesive.

[0019] In some embodiments of the present invention, the ceramic layer comprises 5 wt% to 25 wt% ceramic particles and 75 wt% to 95 wt% binder. For example, the content of ceramic particles in the ceramic layer may be any value or a range of any two of 5 wt%, 8 wt%, 10 wt%, 12 wt%, 13 wt%, 15 wt%, 16 wt%, 18 wt%, 20 wt%, 23 wt%, and 25 wt%; the content of binder may be any value or a range of any two of 75 wt%, 77 wt%, 80 wt%, 82 wt%, 84 wt%, 85 wt%, 87 wt%, 88 wt%, 90 wt%, 92 wt%, and 95 wt%.

[0020] In some embodiments of the present invention, the adhesive is selected from at least one of polyvinylidene fluoride (PTFE) and polyacrylonitrile (PAN).

[0021] In some embodiments of the present invention, the active material layer is disposed on both sides of the current collector.

[0022] In some embodiments of the present invention, the electrode is a positive electrode, the current collector is a positive current collector, and the active material layer is a positive active material layer.

[0023] The positive electrode current collector can be at least one of aluminum, copper, platinum, and silver. The positive electrode active material layer includes a positive electrode active material, which can be LiCoO2, LiMn2O4, Li2MnO3, Li2CrO4, LiNiO2, or LiNiO2. 0.5 Mn 1.5The positive electrode active material layer may include at least one of O4, LiFePO4, LiMnPO4, and LiCoPO4. The positive electrode active material layer may also include at least one of superconducting carbon black (super p), graphite, carbon black, carbon fiber, and carbon nanotubes; the positive electrode active material layer may also include at least one of polyvinylidene fluoride (PVDF), epoxy resin, styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC).

[0024] In some embodiments of the present invention, the electrode is a negative electrode, the current collector is a negative electrode current collector, and the active material layer is a negative electrode active material layer.

[0025] The negative electrode current collector can be at least one of copper, nickel, iron, silver, titanium, and platinum. The negative electrode active material layer includes a negative electrode active material, which can be a lithium-intercalable carbon material or a non-carbon material. The carbon material can be at least one of natural graphite, artificial graphite, soft carbon, hard carbon, or mesophase carbon microspheres. The non-carbon material can be at least one of lithium, elemental silicon, silicon compounds, elemental tin, tin compounds, lithium titanium phosphate, or lithium titanate. Furthermore, the negative electrode active material layer may also include a conductive agent, which can be at least one of graphite, carbon black, graphene, carbon nanotubes, or carbon nanofibers. The negative electrode active material layer may also include a binder, which can be at least one of styrene-butadiene rubber (SBR), carboxymethyl cellulose (CMC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or polyvinyl alcohol (PVA).

[0026] A second aspect of the present invention provides a method for preparing any of the aforementioned electrode sheets, comprising the following steps: Take a current collector substrate and mark the tab area on the current collector substrate; A ceramic slurry is prepared by mixing ceramic particles with a particle size Dv50 of 0.2 μm to 1.5 μm with a solvent. The ceramic slurry is then coated onto the surface of at least the tab region of the current collector substrate to prepare a ceramic layer. The surface roughness of the ceramic layer is controlled to be 1.2 μm to 2 μm, and the thermal conductivity is controlled to be 0.2 W / (m·K) to 1.0 W / (m·K). An active material layer is disposed on the current collector substrate, and the active material layer is adjacent to or partially overlaps with the ceramic layer; The tab area on the current collector substrate is die-cut using laser die-cutting.

[0027] In the above preparation method, by setting a ceramic layer on the surface of at least the tab area on the current collector substrate, the tab die-cutting can be protected, which helps to improve the burr level of the cross section at the tab die-cutting point, and even prevents burrs from being generated when cutting the tab. The use of low-particle-size ceramic particles to prepare the ceramic slurry for constructing the ceramic layer allows for tighter bonding of the ceramic particles and a more regular overall morphology. This shortens the heat-affected time of the current collector substrate during subsequent laser die-cutting of the electrode tabs, reducing the risk of metal burrs. Controlling the surface roughness of the ceramic layer to 1.2μm~2μm during preparation ensures high uniformity of deformation across different areas during laser cutting, allowing for uniform and rapid heat transfer to the current collector substrate, shortening the heat-affected time, further reducing the probability of burrs, and improving burr levels. Furthermore, controlling the thermal conductivity of the ceramic layer to 0.2 W / (m·K)~1.0 W / (m·K) improves the layer's toughness, making it less brittle and effectively reducing burr levels on the electrode tab die-cutting cross-section after laser cutting, thereby improving the processing yield and reliability of the product electrode.

[0028] In some embodiments of the present invention, the viscosity of the ceramic slurry is 2000 mPa·s to 7000 mPa·s, and the purity of the ceramic particles is 99.90% to 99.95%. For example, the viscosity of the ceramic slurry can be controlled to be any value or a range of any two of the following: 2000 mPa·s, 2300 mPa·s, 2500 mPa·s, 2800 mPa·s, 3000 mPa·s, 3600 mPa·s, 4000 mPa·s, 4500 mPa·s, 5000 mPa·s, 5200 mPa·s, 5500 mPa·s, 6000 mPa·s, 6300 mPa·s, 6500 mPa·s, 6800 mPa·s, and 7000 mPa·s. The purity of ceramic particles can be any value or a range of any two of the following: 99.90%, 99.92%, 99.93%, 99.94%, and 99.95%. If magnesium hydroxide particles are used, the purity of the ceramic particles is the mass fraction of magnesium hydroxide particles. The purity of ceramic particles can be determined by using XRD to analyze the phase structure of the ceramic material, detect the content of impurity elements in the material, and then remove the impurity elements to obtain the purity of the ceramic particles.

[0029] The above methods improve the burr level during laser die-cutting of electrode tabs by controlling the viscosity of the ceramic slurry to 4200 mPa.s ~ 5800 mPa.s and the surface roughness of the ceramic layer to 1.2 μm ~ 2 μm; and by controlling the purity of the ceramic particles to 99.90% ~ 99.95% and the thermal conductivity of the ceramic layer to 0.2 W / (m·K) ~ 1.0 W / (m·K).

[0030] Generally, for the above ceramic slurries, when the viscosity of the ceramic slurry is 5800 mPa·s, the surface roughness of the resulting ceramic layer is approximately 2 μm; when the viscosity of the ceramic slurry is 4700 mPa·s, the surface roughness of the resulting ceramic layer is approximately 1.5 μm; and when the viscosity of the ceramic slurry is 4200 mPa·s, the surface roughness of the resulting ceramic layer is approximately 1.2 μm. When the purity of the ceramic particles is 99.95%, the corresponding thermal conductivity of the resulting ceramic layer is approximately 1.0 W / (m·K); when the purity of the ceramic particles is 99.93%, the corresponding thermal conductivity of the resulting ceramic layer is approximately 0.6 W / (m·K); and when the purity of the ceramic particles is 99.90%, the corresponding thermal conductivity of the resulting ceramic layer is approximately 0.2 W / (m·K).

[0031] In some embodiments of the present invention, the ceramic layer raw material further includes a binder. Further, the ceramic layer raw material may include 5 wt% to 25 wt% ceramic particles and 75 wt% to 95 wt% binder.

[0032] In some embodiments of the present invention, the solvent is an organic solvent. For example, the solvent may be N-methylpyrrolidone (NMP) or other organic solvents.

[0033] In the process of preparing the ceramic layer, the ceramic slurry is coated on the surface of at least the tab area of ​​the current collector substrate. Specifically, the ceramic slurry can be coated on one or both sides of the tab area of ​​the current collector substrate, and the surface of the tab area can be partially or completely coated. If the surface of the tab area is partially coated, the coating area includes the tab die-cut position.

[0034] A third aspect of the present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode, and a separator, wherein the separator is sandwiched between the positive electrode and the negative electrode, and the positive electrode and / or the negative electrode are prepared by any of the electrode preparation methods described above or any of the electrode preparation methods described above. Detailed Implementation

[0035] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0036] Example 1 This embodiment proposes a positive electrode, which includes a current collector, an active material layer, and a ceramic layer. The current collector has tabs at its edge. The active material layer is disposed on both sides of the current collector, and the ceramic layer is disposed on the edge tab surface of the current collector and adjacent to the active material layer. The ceramic layer comprises 80 wt% ceramic particles and 20 wt% PVDF binder. The ceramic particles are magnesium hydroxide particles with a particle size Dv50 of 0.5 μm. The surface roughness of the ceramic layer is 2 μm, and its thermal conductivity is 0.5 W / (m·K).

[0037] The positive electrode is prepared by a method including the following steps: Take a copper foil substrate for the current collector and mark out the tab area on the copper foil substrate for the current collector; 80 wt% magnesium hydroxide ceramic particles (particle size Dv50 of 0.5 μm, purity of 99.90%) and 20 wt% PVDF binder were mixed with NMP solvent to prepare a ceramic slurry with a viscosity of 5800 mPa·s. The ceramic slurry was then coated on both sides of the tab region of the copper foil current collector substrate, with a single-sided coating thickness of 15 μm. After drying, a ceramic layer was obtained with a surface roughness of 2 μm and a thermal conductivity of 0.2 W / (m·K). Take 98wt% of active material lithium cobalt oxide, 1wt% of binder PVDF and 1wt% of conductive agent carbon black, mix with solvent to prepare active slurry; then coat the active slurry onto the current collector substrate and adjacent to the ceramic layer, and dry to obtain active material layer; Laser die-cutting was used to cut the tab area on the current collector substrate. The die-cutting power was controlled at 80W and the frequency was controlled at 1000Hz to obtain the positive electrode sheet.

[0038] The cross-section of the electrode tab die-cutting point on the positive electrode sheet was observed using a two-dimensional microscope, and the size of the metal burr protruding from the current collector substrate was detected. The burr length of the cross-section of the electrode tab die-cutting point on the positive electrode sheet in this embodiment was found to be 0.1 μm.

[0039] Example 2 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of the positive electrode sheet in this embodiment have a particle size Dv50 of 1 μm. Correspondingly, in the preparation method of the positive electrode sheet, magnesium hydroxide ceramic particles with a particle size Dv50 of 1 μm and a purity of 99.90% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Embodiment 1 during the preparation of the ceramic layer. Other material configurations, structures, and preparation methods are basically the same as in Embodiment 1.

[0040] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 0.2 μm.

[0041] Example 3 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of the positive electrode sheet in this embodiment have a particle size Dv50 of 0.8 μm. Correspondingly, in the preparation method of the positive electrode sheet, magnesium hydroxide ceramic particles with a particle size Dv50 of 0.8 μm and a purity of 99.90% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Embodiment 1 during the preparation of the ceramic layer. Other material configurations, structures, and preparation methods are basically the same as in Embodiment 1.

[0042] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 0 μm.

[0043] Example 4 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of the positive electrode sheet in this embodiment have a particle size Dv50 of 0.2 μm. Correspondingly, in the preparation method of the positive electrode sheet, magnesium hydroxide ceramic particles with a particle size Dv50 of 0.2 μm and a purity of 99.90% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Embodiment 1 during the preparation of the ceramic layer. Other material configurations, structures, and preparation methods are basically the same as in Embodiment 1.

[0044] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 2 μm.

[0045] Example 5 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of the positive electrode sheet in this embodiment have a particle size Dv50 of 1.3 μm. Correspondingly, in the preparation method of the positive electrode sheet, magnesium hydroxide ceramic particles with a particle size Dv50 of 1.3 μm and a purity of 99.90% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Embodiment 1 during the preparation of the ceramic layer. Other material configurations, structures, and preparation methods are basically the same as in Embodiment 1.

[0046] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 2 μm.

[0047] Example 6 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of this embodiment have a particle size Dv50 of 1 μm and a purity of 99.95%, and the thermal conductivity of the ceramic layer is 1 W / (m·K). Correspondingly, in the preparation method of the positive electrode sheet, magnesium hydroxide ceramic particles with a particle size Dv50 of 1 μm and a purity of 99.95% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Embodiment 1 during the preparation of the ceramic layer. Other material configurations, structures, and preparation methods are basically the same as in Embodiment 1.

[0048] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 2 μm.

[0049] Example 7 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of this embodiment have a particle size Dv50 of 1.3 μm and a purity of 99.95%, the surface roughness of the ceramic layer is 1.2 μm, and the thermal conductivity is 1 W / (m·K). Correspondingly, in the preparation method of the positive electrode sheet, magnesium hydroxide ceramic particles with a particle size Dv50 of 1.3 μm and a purity of 99.95% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 mm and a purity of 99.90% in Embodiment 1 during the preparation of the ceramic layer. Furthermore, the amount of NMP solvent used in preparing the ceramic slurry is adjusted so that the viscosity of the ceramic slurry is 4200 mPa·s. Other material configurations, structures, and preparation methods are basically the same as in Embodiment 1.

[0050] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 3 μm.

[0051] Example 8 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of this embodiment have a particle size Dv50 of 0.5 μm and a purity of 99.95%, and the thermal conductivity of the ceramic layer is 1 W / (m·K). Correspondingly, in the preparation method of the positive electrode sheet, magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.95% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 mm and a purity of 99.90% in Embodiment 1 during the preparation of the ceramic layer. Other material configurations, structures, and preparation methods are basically the same as in Embodiment 1.

[0052] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 0.2 μm.

[0053] Example 9 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of this embodiment have a particle size Dv50 of 0.5 μm and a purity of 99.95%, the surface roughness of the ceramic layer is 1.2 μm, and the thermal conductivity is 1 W / (m·K). Correspondingly, in the electrode sheet preparation method, magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.95% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Embodiment 1 during the ceramic layer preparation process. Furthermore, the amount of NMP solvent used in preparing the ceramic slurry is adjusted so that the viscosity of the ceramic slurry is 4200 mPa·s. Other material configurations, structures, and preparation methods are the same as in Embodiment 1.

[0054] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 0.3 μm.

[0055] Example 10 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the surface roughness of the ceramic layer in the positive electrode sheet of this embodiment is 1.2 μm and the thermal conductivity is 0.2 W / (m·K). Correspondingly, in the electrode sheet preparation method, the amount of NMP solvent used to prepare the ceramic slurry is adjusted during the ceramic layer preparation process so that the viscosity of the ceramic slurry is 4200 mPa·s. Other material configurations, structures and preparation methods are the same as in Embodiment 1.

[0056] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 1 μm.

[0057] Example 11 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of this embodiment have a particle size Dv50 of 1 μm and a purity of 99.95%, the surface roughness of the ceramic layer is 1.2 μm, and the thermal conductivity is 1 W / (m·K). Correspondingly, in the electrode sheet preparation method, magnesium hydroxide ceramic particles with a particle size Dv50 of 1 μm and a purity of 99.95% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 mm and a purity of 99.90% in Embodiment 1 during the ceramic layer preparation process. Furthermore, the amount of NMP solvent used in preparing the ceramic slurry is adjusted so that the viscosity of the ceramic slurry is 4200 mPa·s. Other material configurations, structures, and preparation methods are the same as in Embodiment 1.

[0058] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 0 μm.

[0059] Example 12 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of this embodiment have a particle size Dv50 of 1 μm and a purity of 99.90%, the surface roughness of the ceramic layer is 1.2 μm, and the thermal conductivity is 0.2 W / (m·K). Correspondingly, in the electrode sheet preparation method, magnesium hydroxide ceramic particles with a particle size Dv50 of 1 μm and a purity of 99.90% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Embodiment 1 during the ceramic layer preparation process. Furthermore, the amount of NMP solvent used in preparing the ceramic slurry is adjusted so that the viscosity of the ceramic slurry is 4200 mPa·s. Other material configurations, structures, and preparation methods are the same as in Embodiment 1.

[0060] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 0 μm.

[0061] Example 13 This embodiment provides a positive electrode sheet, which differs from Embodiment 1 in that: the ceramic particles in the ceramic layer of this embodiment have a particle size Dv50 of 0.8 μm and a purity of 99.93%, the surface roughness of the ceramic layer is 1.5 μm, and the thermal conductivity is 0.6 W / (m·K). Correspondingly, in the electrode sheet preparation method, magnesium hydroxide ceramic particles with a particle size Dv50 of 0.8 μm and a purity of 99.93% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Embodiment 1 during the ceramic layer preparation process. Furthermore, the amount of NMP solvent used in preparing the ceramic slurry is adjusted so that the viscosity of the ceramic slurry is 4700 mPa·s. Other material configurations, structures, and preparation methods are the same as in Embodiment 1.

[0062] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the positive electrode tab die-cutting point in this embodiment was found to be 2 μm.

[0063] Comparative Example 1 This comparative example provides a positive electrode sheet, which differs from Example 1 in that: the ceramic particles in the ceramic layer of this comparative example have a particle size Dv50 of 0.18 μm. Correspondingly, in the preparation method of the positive electrode sheet, magnesium hydroxide ceramic particles with a particle size Dv50 of 0.18 μm and a purity of 99.90% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Example 1 during the preparation of the ceramic layer. Other material configurations, structures, and preparation methods are basically the same as in Example 1.

[0064] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the upper tab die-cut of the positive electrode sheet in this comparative example was found to be 7 μm.

[0065] Comparative Example 2 This comparative example provides a positive electrode sheet, which differs from Example 1 in that: the ceramic particles in the ceramic layer of this comparative example have a particle size Dv50 of 1.7 μm. Correspondingly, in the preparation method of the positive electrode sheet, magnesium hydroxide ceramic particles with a particle size Dv50 of 1.7 μm and a purity of 99.90% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Example 1 during the preparation of the ceramic layer. Other material configurations, structures, and preparation methods are basically the same as in Example 1.

[0066] Using a burr inspection method similar to that in Example 1, the burr length at the die-cut section of the positive electrode sheet in this comparative example was found to be 12 μm.

[0067] Comparative Example 3 This comparative example provides a positive electrode sheet, which differs from Example 1 in that: the ceramic particles in the ceramic layer of this comparative example electrode sheet have a particle size Dv50 of 0.5 μm and a purity of 99.87%, the surface roughness of the ceramic layer is 2 μm, and the thermal conductivity is 0.17 W / (m·K). Correspondingly, in the electrode sheet preparation method, magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.87% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Example 1 during the ceramic layer preparation process. Other material configurations, structures, and preparation methods are the same as in Example 1.

[0068] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the upper tab die-cut of the positive electrode sheet in this comparative example was found to be 23 μm.

[0069] Comparative Example 4 This comparative example provides a positive electrode sheet, which differs from Example 1 in that: the ceramic particles in the ceramic layer of this comparative example electrode sheet have a particle size Dv50 of 0.5 μm and a purity of 99.98%, the surface roughness of the ceramic layer is 2 μm, and the thermal conductivity is 1.1 W / (m·K). Correspondingly, in the electrode sheet preparation method, magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.98% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Example 1 during the ceramic layer preparation process. Other material configurations, structures, and preparation methods are the same as in Example 1.

[0070] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the upper tab die-cut of the positive electrode sheet in this comparative example was found to be 10 μm.

[0071] Comparative Example 5 This comparative example provides a positive electrode sheet, which differs from Example 1 in that: the surface roughness of the ceramic layer in this comparative example electrode sheet is 1 μm and the thermal conductivity is 0.2 W / (m·K). Correspondingly, in the electrode sheet preparation method, the amount of NMP solvent used to prepare the ceramic slurry is adjusted during the ceramic layer preparation process so that the viscosity of the ceramic slurry is 4000 mPa·s. Other material configurations, structures, and preparation methods are the same as in Example 1.

[0072] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the upper tab die-cut of the positive electrode sheet in this comparative example was found to be 6 μm.

[0073] Comparative Example 6 This comparative example provides a positive electrode sheet, which differs from Example 1 in that: the ceramic particles in the ceramic layer of this comparative example electrode sheet have a particle size Dv50 of 0.5 μm and a purity of 99.95%, the surface roughness of the ceramic layer is 2.4 μm, and the thermal conductivity is 1 W / (m·K). Correspondingly, in the electrode sheet preparation method, magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.95% are used instead of magnesium hydroxide ceramic particles with a particle size Dv50 of 0.5 μm and a purity of 99.90% in Example 1 during the ceramic layer preparation process. Furthermore, the amount of NMP solvent used in preparing the ceramic slurry is adjusted so that the viscosity of the ceramic slurry is 7500 mPa·s. Other material configurations, structures, and preparation methods are the same as in Example 1.

[0074] Using a burr inspection method similar to that in Example 1, the burr length at the cross-section of the upper tab die-cut of the positive electrode sheet in this comparative example was found to be 16 μm.

[0075] The ceramic layer setup and preparation process control of the positive electrode sheets in the above embodiments and comparative examples, as well as the burr level of the cross-section at the die-cutting point of the positive electrode sheet, are shown in Table 1 below.

[0076] Table 1

[0077] As described above, the positive electrode preparation process of the above embodiments, by setting a ceramic layer on the surface of the tab region on the current collector substrate and strictly controlling the particle size of the ceramic particles in the ceramic layer, as well as the surface roughness and thermal conductivity of the ceramic layer, can effectively improve the burr level of the tab die-cutting section on the electrode after laser die-cutting, and improve the processing yield and safety reliability of the product electrode.

[0078] In some embodiments of the present invention, a negative electrode sheet is also set with a structure similar to that of the above embodiments, that is, a ceramic layer is set on the surface of the electrode area on the current collector electrode tab, and the particle size of the ceramic particles in the ceramic layer, as well as the surface roughness and thermal conductivity of the ceramic layer are strictly controlled. It can be understood that similar effects to the positive electrode sheets of the above embodiments can also be achieved. This can effectively improve the burr level of the electrode tab die-cutting section after laser die-cutting, and improve the processing yield and safety reliability of the product electrode sheet.

[0079] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. An electrode sheet, characterized in that, include: A current collector, the edge of which has tabs; A ceramic layer is disposed on at least one side surface of the current collector and covers at least a portion of the surface of the electrode tab; the ceramic layer comprises ceramic particles with a particle size Dv50 of 0.2 μm to 1.5 μm; the surface roughness of the ceramic layer is 1.2 μm to 2 μm, and the thermal conductivity is 0.2 W / (m·K) to 1.0 W / (m·K); An active material layer is disposed on at least one side surface of the current collector and is adjacent to or partially overlaps with the ceramic layer.

2. The electrode sheet according to claim 1, characterized in that, The product of the thermal conductivity of the ceramic layer and the particle size Dv50 of the ceramic particles is less than or equal to the surface roughness of the ceramic layer.

3. The electrode sheet according to claim 1, characterized in that, The ceramic layer is disposed on both sides of the current collector and covers at least a portion of the surface of the tab; and / or, the active material layer is disposed on both sides of the current collector.

4. The electrode sheet according to claim 1, characterized in that, The surface portion includes the edge surface of the tab portion.

5. The electrode sheet according to claim 1, characterized in that, The ceramic particles include at least one of magnesium hydroxide particles, magnesium oxide particles, and aluminum oxide particles.

6. The electrode sheet according to any one of claims 1 to 5, characterized in that, The ceramic layer also includes an adhesive.

7. The electrode sheet according to claim 6, characterized in that, The ceramic layer comprises 5 wt% to 25 wt% ceramic particles and 75 wt% to 95 wt% binder.

8. A method for preparing the electrode sheet according to any one of claims 1 to 7, characterized in that, Includes the following steps: Take a current collector substrate and mark the tab area on the current collector substrate; A ceramic slurry is prepared by mixing ceramic particles with a particle size Dv50 of 0.2 μm to 1.5 μm with a solvent. The ceramic slurry is then coated onto the surface of at least the tab region of the current collector substrate to prepare a ceramic layer. The surface roughness of the ceramic layer is controlled to be 1.2 μm to 2 μm, and the thermal conductivity is controlled to be 0.2 W / (m·K) to 1.0 W / (m·K). An active material layer is disposed on the current collector substrate, and the active material layer is adjacent to or partially overlaps with the ceramic layer; The tab area on the current collector substrate is die-cut using laser die-cutting.

9. The method for preparing the electrode according to claim 8, characterized in that, The viscosity of the ceramic slurry is 4200 mPa·s to 5800 mPa·s, and the purity of the ceramic particles is 99.90% to 99.95%.

10. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, and a separator, wherein the separator is sandwiched between the positive electrode and the negative electrode, and the positive electrode and / or the negative electrode are prepared by the preparation method of the electrode according to any one of claims 1 to 7 or the electrode according to claim 8 or 9.

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