Battery pole piece and preparation method thereof, battery and electric equipment

Abstract

The invention discloses a battery pole piece and a preparation method thereof, a battery and electric equipment. The battery pole piece comprises a current collector; the first active material layer is arranged on at least part of the surface of the current collector; the second active material layer is arranged on at least part of the surface, far away from the current collector, of the first active material layer; the third active material layer is arranged on at least part of the surface, far away from the first active material layer, of the second active material layer; the particle size Dv50 of the active material in the second active material layer is greater than the particle size Dv50 of the active material in the first active material layer, and the particle size Dv50 of the active material in the second active material layer is greater than the particle size Dv50 of the active material in the third active material layer. Different particle size distribution can meet the pore tortuosity of the thick electrode in the thickness direction of the electrode in the fast charging cycle process, the fast charging performance of the thick electrode is improved, the influence of concentration polarization on the electrochemical performance is reduced, and meanwhile the volume energy density of the electrode piece is improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of batteries, and particularly relates to a battery pole piece, a preparation method thereof, a battery, and a power utilization device. BACKGROUND

[0002] The lithium iron manganese phosphate positive electrode material improves the energy density on the basis of lithium iron phosphate, and therefore is widely concerned. However, similar to lithium iron phosphate, the lithium manganese iron phosphate material also faces the problem of slow electron / ion conduction rate. At present, the specific surface area of the lithium manganese iron phosphate material is increased, and the reaction active site is increased, so as to shorten the Li + transport distance. However, compared with the high-nickel ternary positive electrode material, the energy density is still a short board for the development of the lithium manganese iron phosphate battery.

[0003] From the perspective of technology and research and development cost, increasing the coating surface density and improving the compaction density is one of the shortcuts to improve the volume energy density of the lithium manganese iron phosphate material. However, the lithium manganese iron phosphate system battery is difficult to balance the two characteristics of high energy density and fast charging.

[0004] The existing scheme is to design the positive and negative pole pieces as multi-tab or full-tab with a gap structure, and to improve the energy density and fast charging performance by improving the diaphragm and electrolyte formula. However, these schemes still cannot meet the fast charging optimization of the thick electrode. SUMMARY

[0005] The present application aims to at least solve one of the technical problems in the related art. To this end, the purpose of the present application is to propose a battery pole piece, a preparation method thereof, a battery, and a power utilization device. In the present application, different particle size distributions can meet the pore tortuosity of the thick electrode in the thickness direction of the electrode in the fast charging cycle process, improve the fast charging performance of the thick electrode, reduce the influence of concentration polarization on the electrochemical performance, and also improve the volume energy density of the pole piece.

[0006] In one aspect of the present application, the present application proposes a battery pole piece. According to the embodiments of the present application, the battery pole piece comprises:

[0007] a current collector;

[0008] a first active material layer, the first active material layer being arranged on at least part of the surface of the current collector;

[0009] a second active material layer, the second active material layer being arranged on at least part of the surface of the first active material layer away from the current collector;

[0010] a third active material layer, the third active material layer being arranged on at least part of the surface of the second active material layer away from the first active material layer;

[0011] The particle size Dv50 of the active material in the second active material layer is greater than the particle size Dv50 of the active material in the first active material layer, and the particle size Dv50 of the active material in the second active material layer is greater than the particle size Dv50 of the active material in the third active material layer.

[0012] The battery pole piece according to the embodiments of the present application can meet the pore tortuosity of the thick electrode in the thickness direction of the electrode in the fast charging cycle process through the different particle size distributions, improve the fast charging performance of the thick electrode, reduce the influence of the concentration polarization on the electrochemical performance, and also improve the volume energy density of the pole piece.

[0013] In addition, the battery pole piece according to the above-mentioned embodiments of the present application can also have the following additional technical features:

[0014] In some embodiments of the present application, the difference between the particle size Dv50 of the active material in the second active material layer and the particle size Dv50 of the active material in the first active material layer is 0.1 μm to 29 μm.

[0015] In some embodiments of the present application, the difference between the particle size Dv50 of the active material in the second active material layer and the particle size Dv50 of the active material in the third active material layer is 0.1 μm to 29 μm.

[0016] In some embodiments of the present application, the particle size Dv50 of the active material in the first active material layer is 0.02 μm to 0.7 μm; preferably, the particle size Dv50 of the active material in the first active material layer is 0.3 μm to 0.7 μm.

[0017] In some embodiments of the present application, the particle size Dv50 of the active material in the second active material layer is 0.8 μm to 30 μm; preferably, the particle size Dv50 of the active material in the second active material layer is 0.8 μm to 1.5 μm.

[0018] In some embodiments of the present application, the particle size Dv50 of the active material in the third active material layer is 0.02 μm to 0.7 μm; preferably, the particle size Dv50 of the active material in the third active material layer is 0.3 μm to 0.7 μm.

[0019] In some embodiments of the present application, the width W1 of the first active material layer, the width W2 of the second active material layer, and the width W3 of the third active material layer satisfy: 0 < (W1-W2) / W1≤0.06; 0≤(W2-W3) / W2≤0.06.

[0020] In some embodiments of the present application, a relationship between the width W1 of the first active material layer, the width W2 of the second active material layer, and the width W3 of the third active material layer satisfies: (W1-W2) / W1>(W2-W3) / W2.

[0021] In some embodiments of the present application, a relationship between the thickness H1 of the first active material layer, the thickness H2 of the second active material layer, and the thickness H3 of the third active material layer satisfies: 0.1≤H1 / (H1+H2+H3)≤0.25; 0.1≤H3 / (H1+H2+H3)≤0.25; 0.5≤H2 / (H1+H2+H3)≤0.8.

[0022] In some embodiments of the present application, a relationship between the thickness H1 of the first active material layer and the thickness H3 of the third active material layer satisfies: H1=H3.

[0023] In some embodiments of the present application, a relationship between the areal density Q1 of the first active material layer, the areal density Q2 of the second active material layer, and the areal density Q3 of the third active material layer satisfies: 0.1≤Q1 / (Q1+Q2+Q3)≤0.2; 0.1≤Q3 / (Q1+Q2+Q3)≤0.2; 0.6≤Q2 / (Q1+Q2+Q3)≤0.8.

[0024] In some embodiments of the present application, the single-side areal density of the battery pole piece is 150g / m 2 ~300g / m 2 .

[0025] In some embodiments of the present application, the battery pole piece is a battery positive pole piece, the active material is a positive active material, and the current collector is a positive current collector; or, the battery pole piece is a battery negative pole piece, the active material is a negative active material, and the current collector is a negative current collector.

[0026] In some embodiments of the present application, the positive active material is a lithium manganese iron phosphate material LiMn x Fe 1-x PO4, wherein 0.5≤x≤0.9.

[0027] In a second aspect, the present application provides a method for preparing the battery pole piece described in the above embodiments. According to embodiments of the present application, the above method comprises:

[0028] forming a first active material layer on at least part of the surface of the current collector;

[0029] forming a second active material layer on the first active material layer away from at least part of the surface of the current collector;

[0030] A third active material layer is formed on a surface of the second active material layer distal to the first active material layer.

[0031] According to the method for manufacturing the battery pole piece, the different particle size distributions formed by the method can meet the pore tortuosity in the thickness direction of the thick electrode during fast charging cycles, improve the fast charging performance of the thick electrode, reduce the influence of concentration polarization on the electrochemical performance, and improve the volume energy density of the pole piece.

[0032] In a third aspect of the present application, a battery is provided. According to the embodiments of the present application, the battery has the battery pole piece of the above embodiments. Therefore, the volume energy density of the battery can be improved, and the fast charging performance of the battery is improved, and the influence of concentration polarization on the electrochemical performance is reduced.

[0033] In a fourth aspect of the present application, a power consuming device is provided. According to the embodiments of the present application, the power consuming device has the battery of the above embodiments. Therefore, the power consuming device has all the advantages of the battery, which will not be repeated here.

[0034] Additional aspects and advantages of the present application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0035] The above and / or additional aspects and advantages of the present application will become apparent and be readily appreciated from the following description, including the appended drawings, wherein:

[0036] Figure 1 The structure of the battery pole piece of the embodiments of the present application is shown in the figure.

[0037] REFERENCE NUMERALS

[0038] 100 - current collector, 200 - first active material layer, 300 - second active material layer, 400 - third active material layer. DETAILED DESCRIPTION

[0039] The embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below are exemplary and are intended to explain the present application, and cannot be understood as limiting the present application.

[0040] In the related art, from the perspective of technology and R&D cost, increasing the coating surface density and improving the compaction density is one of the shortcuts to improve the volumetric energy density of the lithium iron manganese phosphate material. However, the high tortuosity of the thick electrode can cause the electrons close to the interface between the current collector and the active material layer and the lithium ions close to the interface between the active material layer and the electrolyte to preferentially participate in the electrochemical reaction, thereby causing the uneven transmission of the electrons and ions along the thickness direction of the active material layer, the uneven distribution of the charge state, and the serious influence on the electrochemical reaction kinetics. In addition, for the application of the long electrode sheet such as the blade battery, according to the Joule law, the internal resistance is proportional to the length / thickness (the ratio of the length to the thickness), the internal resistance of the tab in the current collector on the thick electrode side is large, which is not conducive to the large-rate charging and discharging, and the thermal effect during fast charging and the double effect of the thick electrode can exacerbate the risk of thermal runaway at the tab. The above reasons cause the lithium iron manganese phosphate system battery to be difficult to balance the high energy density and the fast charging.

[0041] Therefore, in one aspect of the present application, the present application provides a battery electrode sheet. According to the embodiments of the present application, referring to the accompanying drawings, Figure 1 The battery electrode sheet includes: a current collector 100; a first active material layer 200, the first active material layer 200 is arranged on at least part of the surface of the current collector 100; a second active material layer 300, the second active material layer 300 is arranged on at least part of the surface of the first active material layer 200 away from the current collector 100; a third active material layer 400, the third active material layer 400 is arranged on at least part of the surface of the second active material layer 300 away from the first active material layer 200; the particle size Dv50 of the active material in the second active material layer 300 is greater than the particle size Dv50 of the active material in the first active material layer 200, and the particle size Dv50 of the active material in the second active material layer 300 is greater than the particle size Dv50 of the active material in the third active material layer 400. Therefore, the different particle size distributions of the present application can meet the pore tortuosity of the thick electrode in the thickness direction of the electrode during the fast charging cycle, improve the fast charging performance of the thick electrode, reduce the influence of concentration polarization on the electrochemical performance, and also improve the volumetric energy density of the electrode sheet.

[0042] The principle of the battery electrode sheet provided by the present application to achieve the above beneficial effects is described in detail as follows:

[0043] In the present application, the first active material layer, the second active material layer and the third active material layer are sequentially arranged on the current collector, and along the thickness direction of the active material layer, the particle size Dv50 of the active material first increases and then decreases. Among them, the packing density of the large particle active material in the middle layer (i.e. the second active material layer) is relatively low, and the volume energy density of this layer can be significantly improved by adjusting the compaction state of the pole piece, thereby improving the volume energy density of the pole piece as a whole. The packing density of the small particle active material in the first active material layer and the third active material layer is relatively high and the specific surface area is relatively large, so that the active material in the first active material layer and the third active material layer can provide multiple active sites, thereby facilitating the rapid diffusion of electrons close to the interface between the current collector and the active material layer, and ions (such as lithium ions) close to the interface between the active material layer and the electrolyte, thereby improving the fast charging performance of the thick electrode. Therefore, the different particle size distributions can meet the pore tortuosity of the thick electrode in the thickness direction of the electrode during the fast charging cycle, improve the fast charging performance of the thick electrode, reduce the influence of concentration polarization on the electrochemical performance, and also improve the volume energy density of the pole piece.

[0044] According to some specific embodiments of the present application, the difference between the particle size Dv50 of the active material in the second active material layer and the particle size Dv50 of the active material in the first active material layer is 0.1 μm-29 μm, thereby further meeting the pore tortuosity of the thick electrode in the thickness direction of the electrode during the fast charging cycle, further improving the fast charging performance of the thick electrode, and further reducing the influence of concentration polarization on the electrochemical performance.

[0045] According to still some specific embodiments of the present application, the difference between the particle size Dv50 of the active material in the second active material layer and the particle size Dv50 of the active material in the third active material layer is 0.1 μm-29 μm, thereby further meeting the pore tortuosity of the thick electrode in the thickness direction of the electrode during the fast charging cycle, further improving the fast charging performance of the thick electrode, and further reducing the influence of concentration polarization on the electrochemical performance.

[0046] According to still some specific embodiments of the present application, the particle size Dv50 of the active material in the first active material layer is 0.02 μm-0.7 μm, the particle size Dv50 of the active material in the second active material layer is 0.8 μm-30 μm, and the particle size Dv50 of the active material in the third active material layer is 0.02 μm-0.7 μm, thereby further meeting the pore tortuosity of the thick electrode in the thickness direction of the electrode during the fast charging cycle, further improving the fast charging performance of the thick electrode, further reducing the influence of concentration polarization on the electrochemical performance, and also further improving the volume energy density of the pole piece.

[0047] In addition, by limiting the particle size Dv50 of the active material in the third active material layer to the range of 0.02 μm to 0.7 μm, the effective specific surface area of the top layer (i.e., the third active material layer) can be effectively controlled, preventing the particles of the top layer from being too tightly packed to affect wettability, so that the side reaction of the top layer with the electrolyte and the lithium ion deintercalation capacity during fast charging can be effectively balanced. By limiting the particle size Dv50 of the active material in the second active material layer to the range of 0.8 μm to 30 μm, while ensuring high compaction to improve the volume energy density of the electrode sheet, the problem of redundant spacing between active material particles, which affects electron transfer and increases impedance, is avoided.

[0048] As some specific embodiments, when the positive active material is a lithium manganese iron phosphate material LiMn x Fe 1-x PO4, the particle size Dv50 of the active material in the first active material layer is 0.3 μm to 0.7 μm, the particle size Dv50 of the active material in the second active material layer is 0.9 μm to 1.2 μm, the particle size Dv50 of the active material in the third active material layer is 0.8 μm to 1.5 μm, and the particle size Dv50 of the active material in the third active material layer is 0.3 μm to 0.7 μm.

[0049] It should be noted that the particle size Dv50 of the active material in the first active material layer and the particle size Dv50 of the active material in the third active material layer can be the same or different.

[0050] In the present application, considering that the flow area at the tab is relatively small, forming a flow bottleneck, the ohmic impedance is large, and the thermal resistance is proportional to the thickness of the passing substance, the present application provides a stepped active material layer. Specifically, the width W1 of the first active material layer, the width W2 of the second active material layer, and the width W3 of the third active material layer satisfy: 0 < (W1-W2) / W1≤0.06; 0≤(W2-W3) / W2≤0.06. That is, the width W1 of the first active material layer is greater than the width W2 of the second active material layer, and the width W2 of the second active material layer is greater than or equal to the width W3 of the third active material layer. By setting a stepped active material layer, the thickness of the active material layer near the tab can be effectively thinned, thereby ensuring the shunt and heat diffusion at the tab under large current charging conditions, and also facilitating the wettability of the electrolyte to the multi-layer region of the active material layer from the side, ensuring efficient mass transfer of active ions (such as lithium ions) during high-rate charging and discharging, and further optimizing the fast charging performance.

[0051] Further, the first active material layer, the second active material layer and the third active material layer satisfy (W1-W2) / W1>(W2-W3) / W2, which can further effectively reduce the thickness of the active material layer near the tab, thereby ensuring the current distribution and heat diffusion of the tab under large current charging conditions, and also facilitating the infiltration of the electrolyte into the multi-layer region of the active material layer from the side, ensuring efficient mass transfer of active ions (such as lithium ions) during high-rate charging and discharging, and further optimizing the fast charging performance.

[0052] In addition, the tab can also be arranged in a diagonal arrangement of bipolar tabs, and the double-sided tabs can achieve large-rate current distribution to some extent, which has a positive effect on the temperature rise and uneven temperature distribution of fast charging, thereby further ensuring the current distribution and heat diffusion of the tab under large current charging conditions.

[0053] According to some specific embodiments of the present application, the first active material layer, the second active material layer and the third active material layer satisfy 0.1≤H1 / (H1+H2+H3)≤0.25; 0.1≤H3 / (H1+H2+H3)≤0.25; 0.5≤H2 / (H1+H2+H3)≤0.8, that is, the thickness of the second active material layer with large particle size and high energy density is large, and the thicknesses of the first active material layer and the third active material layer with small particle size are small, thereby ensuring a high volume energy density of the tab while further meeting the pore tortuosity of the thick electrode in the thickness direction during fast charging and discharging, further improving the fast charging performance of the thick electrode, further reducing the influence of concentration polarization on the electrochemical performance, and avoiding lithium precipitation caused by a thin top layer, thereby avoiding reducing the battery life.

[0054] Further, the thickness H1 of the first active material layer and the thickness H3 of the third active material layer satisfy H1=H3. It should be noted that the thickness H1 of the first active material layer and the thickness H3 of the third active material layer can be the same or different.

[0055] In the embodiments of the present application, the specific value of the thickness H1 of the first active material layer, the specific value of the thickness H2 of the second active material layer, and the specific value of the thickness H3 of the third active material layer are not particularly limited, and the specific values depend on the actual needs of the battery. As some specific embodiments, when the positive electrode material is a lithium manganese iron phosphate material LiMn x Fe 1-x PO4, the thickness H1 of the first active material layer is 6-27 μm, the thickness H2 of the second active material layer is 32-100 μm, and the thickness H3 of the third active material layer is 6-27 μm.

[0056] In embodiments of the present application, the thickness of the active material layer is in a positive proportion to the area density, and thus the area density Q1 of the first active material layer, the area density Q2 of the second active material layer, and the area density Q3 of the third active material layer satisfy: 0.1≤Q1 / (Q1+Q2+Q3)≤0.2; 0.1≤Q3 / (Q1+Q2+Q3)≤0.2; 0.6≤Q2 / (Q1+Q2+Q3)≤0.8.

[0057] It should be noted that the area density Q1 of the first active material layer and the area density Q3 of the third active material layer can be the same or different.

[0058] According to still some specific embodiments of the present application, the single-side area density of the battery pole piece is 150g / m 2 ~300g / m 2 , for example, can be 150g / m 2 , 200g / m 2 , 210g / m 2 , 220g / m 2 , 230g / m 2 , 240g / m 2 , 250g / m 2 , 260g / m 2 , 270g / m 2 , 280g / m 2 , 290g / m 2 , 300g / m 2 , etc. By limiting the single-side area density of the battery pole piece within the above range, the above battery pole piece can be further ensured to be a thick electrode, and the above battery pole piece can be further ensured to have a higher volumetric energy density.

[0059] According to still some specific embodiments of the present application, the compacted density of the battery pole piece is 2.2g / cm 3 ~3.8g / cm 3 By limiting the compacted density of the battery pole piece within the above range, the volumetric energy density of the active material layer can be significantly improved by increasing the compacted density of the pole piece.

[0060] In embodiments of the present application, the above battery pole piece can be a battery positive pole piece or a battery negative pole piece, and is not particularly limited. When the above battery pole piece is a battery positive pole piece, the active material is a positive active material, and the current collector is a positive current collector. When the above battery pole piece is a battery negative pole piece, the active material is a negative active material, and the current collector is a negative current collector.

[0061] Moreover, the specific type of the positive electrode sheet of the battery is not particularly limited, and for example, it can be a positive electrode sheet of a lithium ion battery or a positive electrode sheet of a sodium ion battery. Hereinafter, the positive electrode sheet of a lithium ion battery is taken as an example to be described, and the specific type of the positive electrode active material is not particularly limited, and as some specific examples, the positive electrode active material includes at least one of lithium iron phosphate, lithium iron manganese phosphate, lithium cobaltate, lithium nickelate, lithium cobalt phosphate, lithium manganese phosphate, lithium nickel phosphate, lithium manganate, a binary material, and a ternary material, and preferably a lithium manganese iron phosphate material LiMn x Fe 1-x PO4, wherein 0.5≤x≤0.9.

[0062] In some embodiments of the present application, the positive electrode active material layer can further include a positive electrode binder and a positive electrode conductive agent in addition to the positive electrode active material. As an example, the positive electrode binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. As an example, the positive electrode conductive agent can include at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0063] In some embodiments of the present application, the positive electrode current collector can include a metal foil or a composite positive electrode current collector. For example, the metal foil can be an aluminum foil. The composite positive electrode current collector can include a polymer material base layer and a metal layer formed on at least one side surface of the polymer material base layer, for example, the composite negative electrode current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, etc.) on a polymer material base material (such as a polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), etc. base material).

[0064] In a second aspect of the present application, a method for preparing the battery electrode sheet of the above embodiments is provided. According to the embodiments of the present application, the above method includes:

[0065] S100: forming a first active material layer on at least part of the surface of the current collector

[0066] In this step, a small particle size active material, a conductive agent, a binder, an optional dispersant, and a solvent in a set proportion can be uniformly mixed to obtain a first slurry, and then the first slurry is coated on at least part of the surface of the current collector and baked at a high temperature to form a first active material layer on at least part of the surface of the current collector.

[0067] S200: forming a second active material layer on at least part of the surface of the first active material layer away from the current collector

[0068] In this step, a set proportion of large-particle-size active material, conductive agent, binder, optional dispersant, and solvent are uniformly mixed to obtain a second slurry, which is then coated onto at least part of the surface of the first active material layer away from the current collector and baked at high temperature to form a second active material layer on at least part of the surface of the first active material layer away from the current collector. Moreover, the particle size Dv50 of the active material in the second active material layer is greater than the particle size Dv50 of the active material in the first active material layer.

[0069] S300: Forming a third active material layer on at least part of the surface of the second active material layer away from the first active material layer

[0070] In this step, a set proportion of small-particle-size active material, conductive agent, binder, optional dispersant, and solvent are uniformly mixed to obtain a third slurry, which is then coated onto at least part of the surface of the second active material layer away from the first active material layer and baked at high temperature to form a third active material layer on at least part of the surface of the second active material layer away from the first active material layer. Moreover, the particle size Dv50 of the active material in the second active material layer is greater than the particle size Dv50 of the active material in the third active material layer.

[0071] It should be noted that the first slurry can be coated onto the surface of the current collector, baked at high temperature to form the first active material layer, then the second slurry is coated onto the surface of the first active material layer, baked at high temperature to form the second active material layer, and finally the third slurry is coated onto the surface of the second active material layer, baked at high temperature to form the third active material layer, i.e., layer-by-layer baking at high temperature, which is beneficial to the solidification of the slurry during the coating process of the thick electrode and avoids the cracking of the electrode sheet. Alternatively, the first slurry, the second slurry, and the third slurry can be sequentially coated onto the surface of the current collector, and then baked at high temperature.

[0072] According to the method for preparing the battery electrode according to the embodiments of this application, a first active material layer, a second active material layer, and a third active material layer are sequentially formed on a current collector, and the particle size Dv50 of the active material first increases and then decreases along the thickness direction of the active material layer. The intermediate layer (i.e., the second active material layer) has a lower packing density of large active material particles, and the volumetric energy density of this layer can be significantly improved by adjusting the compaction state of the electrode, thereby improving the overall volumetric energy density of the electrode. The first and third active material layers have a higher packing density and a larger specific surface area of ​​small active materials, enabling the active materials in these layers to provide multiple active sites. This facilitates the rapid diffusion of electrons near the interface between the current collector and the active material layer, as well as ions (e.g., lithium ions) near the interface between the active material layer and the electrolyte, thereby improving the fast-charging performance of the thick electrode. Therefore, the different particle size distributions formed by this method can satisfy the porosity of the thick electrode in the electrode thickness direction during fast charging cycle, improve the fast charging performance of the thick electrode, reduce the influence of concentration polarization on electrochemical performance, and also improve the volumetric energy density of the electrode.

[0073] According to some specific embodiments of this application, the width of the coating die can be adjusted so that the width W1 of the first active material layer is greater than the width W2 of the second active material layer, and the width W2 of the second active material layer is greater than or equal to the width W3 of the third active material layer. By setting a stepped active material layer, the thickness of the active material layer near the tab can be effectively reduced, thereby ensuring the current shunting and heat diffusion at the tab under high current charging conditions. At the same time, it is also beneficial for the electrolyte to wet the multi-layer area of ​​the active material layer from the side, ensuring the efficient mass transfer of active ions (such as lithium ions) during high-rate charging and discharging, and further optimizing the fast charging performance.

[0074] In a third aspect, this application proposes a battery. According to an embodiment of this application, the battery has the battery electrodes described above. This improves the battery's volumetric energy density, enhances its fast-charging performance, and reduces the impact of concentration polarization on electrochemical performance.

[0075] In the embodiments of this application, the battery described above can be either a lithium-ion battery or a sodium-ion battery. The following explanation uses a lithium-ion battery as an example.

[0076] Specifically, the lithium-ion battery includes a positive electrode, a negative electrode, and a separator as described in the above embodiments, with the separator disposed between the positive and negative electrode. During battery charging and discharging, active lithium ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor of ions between the positive and negative electrode. The separator, disposed between the positive and negative electrode, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0077] The specific material of the diaphragm is not particularly limited. As some specific embodiments, the diaphragm includes at least one of PP diaphragm, PE diaphragm, single-sided ceramic diaphragm, double-sided ceramic diaphragm, non-woven fabric diaphragm, and glass fiber diaphragm.

[0078] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector. The negative electrode active material layer includes a negative electrode active material (e.g., graphite), optional negative electrode dispersant, negative electrode conductive agent, and negative electrode binder.

[0079] The preparation method of the negative electrode sheet includes: mixing the negative electrode active material, negative electrode dispersant, negative electrode conductive agent and negative electrode binder evenly according to the preset ratio, adding solvent and stirring evenly to form a negative electrode slurry, then coating it onto the current collector, drying it, and finally cutting it into a specific shape of negative electrode sheet for later use according to the different battery casings.

[0080] Cell preparation: The positive and negative electrode sheets are added to the separator and wound. After winding, the positive and negative electrode tabs are welded. Then, the bare cell is packaged in an aluminum-plastic film. After packaging, the cell is vacuum baked for 10-20 hours. Then, after liquid injection, standing, high temperature and high pressure formation, degassing and packaging, and capacity testing, a lithium-ion battery with a double-layer coated positive electrode is obtained.

[0081] The battery of this application may be in the form of a battery cell, a battery module, or a battery pack. In some embodiments, battery cells may be assembled into a battery module, and the number of battery cells contained in a battery module may be one or more, the specific number of which can be selected by those skilled in the art based on the application and capacity of the battery module. In some embodiments, battery modules may also be assembled into a battery pack, and the number of battery modules contained in a battery pack may be one or more, the specific number of which can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0082] In a fourth aspect, this application proposes an electrical device. According to an embodiment of this application, the electrical device includes the battery described in the above embodiments. Therefore, the electrical device possesses all the advantages of a battery, which will not be elaborated further here.

[0083] Specifically, the aforementioned electrical equipment can include, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Among them, electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc., and spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0084] It should be noted that the features and advantages described above for the battery also apply to this electrical device, and will not be repeated here.

[0085] The embodiments of this application are described in detail below. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. In addition, unless otherwise specified, all reagents used in the following embodiments are commercially available or can be synthesized according to the methods described herein or known methods. For reaction conditions not listed, they are also readily available to those skilled in the art.

[0086] Example 1

[0087] This embodiment provides a lithium-ion battery, the preparation method of which includes:

[0088] 1) Preparation of positive electrode sheet

[0089] Lithium manganese iron phosphate material (LiMn) with a mass ratio of 100:3:5:0.5:80 x Fe 1-x PO4 (x = 0.6), conductive carbon nanotubes, binder polyvinylidene fluoride, dispersant polyvinylpyrrolidone, and solvent NMP are uniformly mixed to obtain a first slurry. This first slurry is then coated onto the surface of an aluminum foil current collector with a coating width of 100 mm. After baking, a first active material layer is formed. The particle size Dv50 of the lithium manganese iron phosphate material in the first active material layer is 0.5 μm.

[0090] Lithium manganese iron phosphate material (LiMn) with a mass ratio of 100:3:5:0.5:80 x Fe 1-x PO4 (x = 0.6), conductive carbon nanotubes, binder polyvinylidene fluoride, dispersant polyvinylpyrrolidone, and solvent NMP are uniformly mixed to obtain a second slurry. This second slurry is then coated onto the surface of the first active material layer with a coating width of 100 mm. After baking, the second active material layer is formed. The particle size Dv50 of the lithium manganese iron phosphate material in the second active material layer is 1 μm.

[0091] Lithium manganese iron phosphate material (LiMn) with a mass ratio of 100:3:5:0.5:80 x Fe 1-x PO4 (x = 0.6), conductive carbon nanotubes, binder polyvinylidene fluoride, dispersant polyvinylpyrrolidone, and solvent NMP are uniformly mixed to obtain a third slurry. This third slurry is then coated onto the surface of the second active material layer with a coating width of 100 mm. After baking, the third active material layer is formed, resulting in the positive electrode. The particle size Dv50 of the lithium manganese iron phosphate material in the third active material layer is 0.5 μm.

[0092] The areal density of the above-mentioned positive electrode sheet is 220 g / m². 2The surface density of the first active material layer is 20% of the total surface density of a single side, the surface density of the third active material layer is 60% of the total surface density of a single side, and the surface density of the third active material layer is 20% of the total surface density of a single side.

[0093] 2) Preparation of negative electrode sheet

[0094] Preparation of the negative electrode sheet: Artificial graphite (anode active material), conductive carbon (SP), dispersant (CMC), and binder (SBR) are dispersed in deionized water at a mass ratio of 96.5:0.5:1:2 and mixed evenly to obtain a negative electrode slurry with a solid content of approximately 55%. The negative electrode slurry is coated onto a copper foil current collector, and after drying, cold pressing, slitting, and cutting, the negative electrode sheet is obtained.

[0095] 3) Preparation of electrolyte

[0096] In an argon atmosphere glove box with a moisture content ≤1ppm, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a mass ratio of 1:1:1. Then, the dried electrolyte lithium salt LiPF6 was dissolved in the solvent, with LiPF6 accounting for 16% of the mass of the electrolyte.

[0097] 4) Separating membrane

[0098] A polyethylene film with a thickness of 16 micrometers was selected as the diaphragm.

[0099] 5) Battery assembly

[0100] The prepared battery electrodes, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to separate them. After winding, a bare cell is formed. After welding the tabs, the bare cell is assembled into an outer packaging. After injecting the prepared electrolyte, the cell is encapsulated, left to stand, formed, shaped, and its capacity is tested, ultimately producing a lithium-ion battery.

[0101] Example 2

[0102] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 1, with the only difference being:

[0103] The coating width of the first active material layer is 100 mm, the coating width of the second active material layer is 95 mm, and the coating width of the third active material layer is 90 mm.

[0104] Example 3

[0105] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0106] The particle size Dv50 of lithium manganese iron phosphate in the first active material layer is 0.3 μm, the particle size Dv50 of lithium manganese iron phosphate in the second active material layer is 0.8 μm, and the particle size Dv50 of lithium manganese iron phosphate in the third active material layer is 0.3 μm.

[0107] Example 4

[0108] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0109] The particle size Dv50 of lithium manganese iron phosphate in the first active material layer is 0.4 μm, the particle size Dv50 of lithium manganese iron phosphate in the second active material layer is 0.9 μm, and the particle size Dv50 of lithium manganese iron phosphate in the third active material layer is 0.4 μm.

[0110] Example 5

[0111] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0112] The particle size Dv50 of lithium manganese iron phosphate in the first active material layer is 0.6 μm, the particle size Dv50 of lithium manganese iron phosphate in the second active material layer is 1.2 μm, and the particle size Dv50 of lithium manganese iron phosphate in the third active material layer is 0.6 μm.

[0113] Example 6

[0114] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0115] The particle size Dv50 of lithium manganese iron phosphate in the first active material layer is 0.7 μm, the particle size Dv50 of lithium manganese iron phosphate in the second active material layer is 1.3 μm, and the particle size Dv50 of lithium manganese iron phosphate in the third active material layer is 0.6 μm.

[0116] Example 7

[0117] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0118] The particle size Dv50 of lithium manganese iron phosphate in the first active material layer is 0.6 μm, the particle size Dv50 of lithium manganese iron phosphate in the second active material layer is 1.5 μm, and the particle size Dv50 of lithium manganese iron phosphate in the third active material layer is 0.7 μm.

[0119] Example 8

[0120] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0121] The coating width of the first active material layer is 100 mm, the coating width of the second active material layer is 98 mm, and the coating width of the third active material layer is 96 mm.

[0122] Example 9

[0123] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0124] The coating width of the first active material layer is 100 mm, the coating width of the second active material layer is 97 mm, and the coating width of the third active material layer is 94 mm.

[0125] Example 10

[0126] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0127] The areal density of the positive electrode is 220 g / m². 2 The surface density of the first active material layer is 15% of the total surface density on one side, the surface density of the third active material layer is 70% of the total surface density on one side, and the surface density of the third active material layer is 15% of the total surface density on one side.

[0128] Example 11

[0129] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0130] The areal density of the positive electrode is 220 g / m². 2 The surface density of the first active material layer is 10% of the total surface density of a single side, the surface density of the first active material layer is 80% of the total surface density of a single side, and the surface density of the third active material layer is 10% of the total surface density of a single side.

[0131] Example 12

[0132] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0133] The areal density of the positive electrode is 240 g / m². 2 .

[0134] Example 13

[0135] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0136] The particle size Dv50 of lithium manganese iron phosphate in the first active material layer is 0.05 μm, the particle size Dv50 of lithium manganese iron phosphate in the second active material layer is 1 μm, and the particle size Dv50 of lithium manganese iron phosphate in the third active material layer is 0.05 μm.

[0137] Example 14

[0138] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 2, except that:

[0139] The lithium manganese iron phosphate material in the first active material layer was replaced with ternary cathode material NCM, with a particle size Dv50 of 0.6 μm.

[0140] The lithium manganese iron phosphate material in the second active material layer was replaced with ternary cathode material NCM, with a particle size Dv50 of 1.5 μm.

[0141] The lithium manganese iron phosphate material in the third active material layer was replaced with ternary cathode material NCM, with a particle size Dv50 of 0.6 μm.

[0142] The areal density of the above-mentioned positive electrode sheet is 165 g / m². 2 .

[0143] Example 15

[0144] This embodiment provides a lithium-ion battery. The preparation method of this embodiment is basically the same as that of Embodiment 14, except that:

[0145] The particle size Dv50 of the ternary cathode material NCM in the first active material layer is 0.6 μm, the particle size Dv50 of the ternary cathode material NCM in the second active material layer is 28 μm, and the particle size Dv50 of the ternary cathode material NCM in the third active material layer is 0.6 μm.

[0146] Comparative Example 1

[0147] This comparative example provides a lithium-ion battery. The preparation method of this comparative example is basically the same as that of Example 1, except that:

[0148] 1) Preparation of positive electrode sheet

[0149] The lithium manganese iron phosphate material with a particle size Dv50 of 0.5 μm and 1 μm, carbon nanotubes as conductive agent, polyvinylidene fluoride as binder, polyvinylpyrrolidone as dispersant, and NMP as solvent used in Example 1 were uniformly mixed to obtain a slurry. The slurry was then coated onto the surface of an aluminum foil current collector with a coating width of 100 mm. After baking, a positive electrode sheet was formed with a single-sided areal density of 220 g / m². 2 Furthermore, the quality of each raw material used in this comparative example is the same as that in Example 1.

[0150] Comparative Example 2

[0151] This comparative example provides a lithium-ion battery. The preparation method of this comparative example is basically the same as that of Example 14, except that:

[0152] 1) Preparation of positive electrode sheet

[0153] The ternary cathode material NCM with a particle size Dv50 of 0.6 μm and NCM with a particle size Dv50 of 1.5 μm used in Example 14, the conductive agent carbon nanotubes, the binder polyvinylidene fluoride, the dispersant polyvinylpyrrolidone, and the solvent NMP were uniformly mixed to obtain a slurry. The slurry was then coated onto the surface of an aluminum foil current collector with a coating width of 100 mm. After baking, a cathode sheet was formed with a single-sided areal density of 165 g / m². 2 Furthermore, the quality of each raw material used in this comparative example is the same as that in Example 14.

[0154] The positive electrode sheets prepared in Examples 1-15 and Comparative Examples 1-2 were observed using SEM to obtain the thicknesses H1 of the first active material layer, H2 of the second active material layer, and H3 of the third active material layer in the positive electrode sheets. The results are shown in Table 1.

[0155] The Q1 / Q0*100 ratio of the lithium-ion batteries prepared in Examples 1-15 and Comparative Examples 1-2 were tested and calculated, and the results are shown in Table 1. Test procedure:

[0156] At 25℃, the battery is charged and discharged at 0.5C constant current and constant voltage until the cutoff voltage is reached. The cutoff current is 0.05C, and the discharge capacity is recorded as Q0. The battery is then charged at 3C until the upper limit voltage is reached, and the capacity after 20 minutes of charging is recorded as Q1. The result is Q1 / Q0*100.

[0157] At 25℃, the battery is charged to the cutoff voltage at 1 / 3C constant current and constant voltage with a cutoff current of 0.05C. The discharge capacity C and average voltage V are recorded. The cell energy density = C*V / cell weight, where the cell weight includes the positive and negative electrodes, separator, electrolyte, and current collector.

[0158] The temperature at the tab of the lithium-ion batteries prepared in Examples 1-15 and Comparative Examples 1-2 after double charging was tested, and the results are shown in Table 1.

[0159] The energy density of the lithium-ion batteries prepared in Examples 1-15 and Comparative Examples 1-2 was tested, and the results are shown in Table 1.

[0160] Table 1

[0161]

[0162]

[0163] As shown in Table 1, compared with Comparative Example 1, the Q1 / Q0*100% of Examples 1-13 is significantly improved. This indicates that the different particle size distributions of this application can satisfy the porosity tortuosity of the thick electrode in the electrode thickness direction during fast charging cycles, which is beneficial for the rapid diffusion of electrons near the interface between the current collector and the active material layer, as well as lithium ions near the interface between the active material layer and the electrolyte, thereby improving the fast charging performance of the thick electrode. In addition, the reduction in polarization is beneficial for battery capacity utilization and voltage drop, thus increasing energy density.

[0164] Compared to Example 1, the temperature at the tab in Example 2 is significantly lower, and the Q1 / Q0*100% ratio is also improved. This demonstrates that by setting a stepped active material layer, the thickness of the active material layer near the tab can be effectively reduced, thereby ensuring current shunting and heat diffusion at the tab under high-current charging conditions and significantly reducing the temperature at the tab. It also facilitates the side-wetting of the electrolyte into the multi-layered active material layer, ensuring efficient mass transfer of lithium ions during high-rate charging and discharging, further optimizing fast-charging performance.

[0165] Compared to Comparative Example 2, the Q1 / Q0*100% of Examples 14-15 is significantly improved. This demonstrates that the different particle size distributions of this application can satisfy the porosity tortuosity of the thick electrode in the electrode thickness direction during fast charging cycles, which is beneficial for the rapid diffusion of electrons near the interface between the current collector and the active material layer, as well as lithium ions near the interface between the active material layer and the electrolyte, thereby improving the fast charging performance of the thick electrode. Furthermore, compared to Comparative Example 2, the temperature at the tab in Examples 14 and 15 is significantly reduced. This shows that by setting a stepped active material layer, the thickness of the active material layer near the tab can be effectively reduced, thereby ensuring current shunting and heat diffusion at the tab under high current charging conditions, and significantly reducing the temperature at the tab.

[0166] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0167] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A battery electrode, characterized in that, include: current collector; A first active material layer is disposed on at least a portion of the surface of the current collector; A second active material layer is disposed on at least a portion of the surface of the first active material layer away from the current collector; A third active material layer is disposed on at least a portion of the surface of the second active material layer that is away from the first active material layer; The particle size Dv50 of the active material in the second active material layer is greater than that of the active material in the first active material layer, and the particle size Dv50 of the active material in the second active material layer is greater than that of the active material in the third active material layer.

2. The battery electrode according to claim 1, characterized in that, The difference between the particle size Dv50 of the active material in the second active material layer and the particle size Dv50 of the active material in the first active material layer is 0.1 μm to 29 μm.

3. The battery electrode according to claim 2, characterized in that, The difference between the particle size Dv50 of the active material in the second active material layer and the particle size Dv50 of the active material in the third active material layer is 0.1 μm to 29 μm.

4. The battery electrode according to claim 3, characterized in that, The particle size Dv50 of the active material in the first active material layer is 0.02 μm to 0.7 μm; Preferably, the particle size Dv50 of the active material in the first active material layer is 0.3 μm to 0.7 μm.

5. The battery electrode according to claim 3, characterized in that, The particle size Dv50 of the active material in the second active material layer is 0.8 μm to 30 μm; Preferably, the particle size Dv50 of the active material in the second active material layer is 0.8 μm to 1.5 μm.

6. The battery electrode according to claim 3, characterized in that, The particle size Dv50 of the active material in the third active material layer is 0.02 μm to 0.7 μm; Preferably, the particle size Dv50 of the active material in the third active material layer is 0.3 μm to 0.7 μm.

7. The battery electrode sheet according to any one of claims 1 to 6, characterized in that, The widths W1 of the first active material layer, W2 of the second active material layer, and W3 of the third active material layer satisfy the following: 0 < (W1 - W2) / W1 ≤ 0.06; 0≤(W2-W3) / W2≤0.

06.

8. The battery electrode according to claim 7, characterized in that, The widths W1 of the first active material layer, W2 of the second active material layer, and W3 of the third active material layer satisfy the following relationship: (W1-W2) / W1>(W2-W3) / W2.

9. The battery electrode sheet according to any one of claims 1 to 6, characterized in that, The thicknesses H1 of the first active material layer, H2 of the second active material layer, and H3 of the third active material layer satisfy the following relationship: 0.1≤H1 / (H1+H2+H3)≤0.25; 0.1≤H3 / (H1+H2+H3)≤0.25; 0.5≤H2 / (H1+H2+H3)≤0.

8.

10. The battery electrode according to claim 9, characterized in that, The thickness H1 of the first active material layer and the thickness H3 of the third active material layer satisfy the following relationship: H1 = H3.

11. The battery electrode sheet according to any one of claims 1 to 6, characterized in that, The areal density Q1 of the first active material layer, the areal density Q2 of the second active material layer, and the areal density Q3 of the third active material layer satisfy the following: 0.1≤Q1 / (Q1+Q2+Q3)≤0.2; 0.1≤Q3 / (Q1+Q2+Q3)≤0.2; 0.6≤Q2 / (Q1+Q2+Q3)≤0.

8.

12. The battery electrode according to claim 11, characterized in that, The single-sided density of the battery electrode is 150 g / m². 2 ~300g / m 2 .

13. The battery electrode sheet according to any one of claims 1 to 6, characterized in that, The battery electrode is a positive electrode, the active material is a positive electrode active material, and the current collector is a positive electrode current collector; Alternatively, the battery electrode is a negative electrode, the active material is a negative electrode active material, and the current collector is a negative electrode current collector.

14. The battery electrode according to claim 13, characterized in that, The positive electrode active material is lithium manganese iron phosphate (LiMn). x Fe 1-x PO4, where 0.5 ≤ x ≤ 0.

9.

15. A method for preparing the battery electrode sheet according to any one of claims 1 to 14, characterized in that, include: A first active material layer is formed on at least a portion of the surface of the current collector; A second active material layer is formed on at least a portion of the surface of the first active material layer away from the current collector; A third active material layer is formed on at least a portion of the surface of the second active material layer that is away from the first active material layer.

16. A battery, characterized in that, A battery electrode having any one of claims 1 to 14 or a battery electrode prepared by the method of claim 15.

17. An electrical appliance, characterized in that, It has the battery as described in claim 16.

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