CN220543945U - Pole piece and battery - Google Patents
Pole piece and battery Download PDFInfo
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- CN220543945U CN220543945U CN202321912949.XU CN202321912949U CN220543945U CN 220543945 U CN220543945 U CN 220543945U CN 202321912949 U CN202321912949 U CN 202321912949U CN 220543945 U CN220543945 U CN 220543945U
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- pole piece
- coating
- current collector
- active material
- recess
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- 239000011248 coating agent Substances 0.000 claims abstract description 132
- 239000011149 active material Substances 0.000 claims abstract description 43
- 239000003792 electrolyte Substances 0.000 claims abstract description 43
- 239000011148 porous material Substances 0.000 claims abstract description 33
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 14
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 14
- 230000005540 biological transmission Effects 0.000 abstract description 13
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 abstract description 8
- 238000001764 infiltration Methods 0.000 abstract description 8
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- 229910052744 lithium Inorganic materials 0.000 abstract description 8
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- 239000007773 negative electrode material Substances 0.000 description 6
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 5
- 239000006183 anode active material Substances 0.000 description 5
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- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
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- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
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- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 239000004677 Nylon Substances 0.000 description 1
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
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Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Landscapes
- Battery Electrode And Active Subsutance (AREA)
Abstract
The utility model provides a pole piece and a battery, wherein the pole piece comprises a current collector and an active substance coating arranged on the current collector; at least two concave parts are arranged on one side of the active material coating, which is away from the current collector, and pore channels are arranged between any two adjacent concave parts and are mutually communicated. The utility model ensures that the whole surface of the pole piece is uniformly distributed with the pore canal and the concave part, the pore canal can provide a transmission path for the electrolyte, the electrolyte infiltration efficiency is improved, the electrolyte is ensured to quickly infiltrate the whole pole piece, the pore canal can also shorten the transmission path of lithium ions, accelerate the transmission rate of the lithium ions in the pole piece, improve the rate capability of the battery and avoid the problem of lithium precipitation of the negative electrode under the condition of quick charge.
Description
Technical Field
The utility model relates to the technical field of batteries, in particular to a pole piece and a battery.
Background
The lithium ion battery has the advantages of high energy density, high cycle performance, high voltage, low self-discharge, light weight and the like, and is widely applied to portable electronic equipment (such as mobile phones, digital cameras, notebook computers and the like) and large and medium-sized electric equipment such as electric automobiles, electric bicycles, electric tools and the like. As the requirements for electronic products and new energy automobiles are higher, the requirements for the energy density of lithium ion batteries are also higher.
In order to pursue high energy density, the duty ratio of the inactive material in the battery core is reduced, and the effect of improving the energy density is achieved mainly by increasing the thickness of the pole piece coating so as to reduce the number of layers of the current collector and the diaphragm. However, the thickness of the coating is increased, so that the migration resistance of lithium ions in the coating and the infiltration efficiency of electrolyte are increased, the migration rate of lithium ions is low, the output power of the battery is low, the utilization rate of active materials is low, and the problems of lithium precipitation, capacity attenuation and the like are easily caused in the high-rate charging process of the battery. Therefore, in designing lithium ion batteries with high power density and energy density, reducing the duty ratio of inactive materials in the battery, when thicker electrodes are used, it is necessary to solve the problems of electrolyte transport, limited ion conduction and low active material utilization.
Disclosure of Invention
The utility model aims to solve the problems of low transmission rate of the existing pole piece electrolyte and low lithium ion transmission rate.
In order to solve the problems, a first aspect of the present utility model provides a pole piece, which comprises a current collector and an active material coating layer arranged on the current collector;
at least two concave parts are arranged on one side of the active material coating, which is away from the current collector, and pore channels are arranged between any two adjacent concave parts and are mutually communicated.
Further, the depth of the recess is 10% to 60% of the thickness of the active material coating, and/or the depth of the duct is 10% to 60% of the thickness of the active material coating.
Further, the active material coating comprises a first surface and a second surface which are oppositely arranged along the thickness direction of the pole piece, the first surface is connected with the current collector, and the concave part and the pore canal are arranged on the second surface;
the diameter of one side of the concave part, which faces away from the second surface, is larger than the diameter of one side of the concave part, which is close to the second surface;
and/or the diameter of the side of the pore canal away from the second surface is larger than the diameter of the side of the pore canal close to the second surface.
Further, the diameter of the recess portion is gradually reduced from a side close to the first surface to the second surface, and/or the diameter of the duct is gradually reduced from a side close to the first surface to the second surface.
Further, a projection area of the concave portion facing away from the second surface on the current collector is S1, a projection area of the concave portion located on the second surface on the current collector is S2, and a ratio of S1 to S2 is greater than 1 and less than or equal to 4.
Further, the projection area of the concave part on the current collector is larger than the projection area of the pore canal on the current collector.
Further, the size of the recess is in the range of 0.5 μm to 500 μm, and/or the size of the pore is in the range of 0.5 μm to 500 μm.
Further, the porosity of the active material coating on the side facing away from the current collector is greater than the porosity of the active material coating on the side adjacent to the current collector.
Further, the porosity of the active material coating layer near the current collector side is in the range of 10% to 35%, and/or the porosity of the active material coating layer away from the current collector side is in the range of 20% to 60%.
A second aspect of the present utility model provides a battery comprising a first pole piece, a second pole piece, and a separator disposed between the first pole piece and the second pole piece, the first pole piece and the second pole piece being of opposite polarity, at least one of the first pole piece and the second pole piece being the pole piece of any one of the first aspects.
Further, the electrolyte is infiltrated in the concave part of the pole piece and the pore canal.
According to the pole piece and the battery, through designing the structure of the pole piece, the concave parts and the pore channels which are communicated with each other are arranged on one side, deviating from the current collector, of the active material coating, all the pore channels are communicated with each other, so that the concave parts and the pore channels are uniformly distributed on the whole surface of the pole piece, a transmission path can be provided for electrolyte, the electrolyte infiltration efficiency is improved, the electrolyte can be ensured to quickly infiltrate the whole pole piece, the pore channels and the concave parts can also shorten the transmission path of lithium ions, the transmission rate of the lithium ions in the pole piece is accelerated, the multiplying power performance of the battery is improved, and the problem of lithium precipitation of a negative electrode under a quick charging condition is avoided.
Drawings
FIG. 1 is a schematic cross-sectional view of a pole piece provided in an embodiment of the present utility model;
fig. 2 is a schematic top view of a pole piece before rolling according to an embodiment of the present utility model;
FIG. 3 is a schematic cross-sectional view of FIG. 2;
FIG. 4 is an SEM image of a pole piece provided in an embodiment of the utility model;
FIG. 5 is an SEM image of a second coating provided in an embodiment of the utility model;
fig. 6 is an SEM image of the first and second coatings provided in an embodiment of the present utility model.
Reference numerals illustrate:
1-a current collector; 2-active substance coating;
21-a first coating; 22-a second coating;
221-coating bumps; 222 a-pore channel; 222 b-recesses.
Detailed Description
The technical scheme of the utility model is clearly and thoroughly described below with reference to the accompanying drawings. In the description of the present utility model, it should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present utility model and simplifying the description, and do not indicate or imply that the apparatus or element in question must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present utility model. Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more of the described features. Furthermore, in the description of the present utility model, the meaning of "at least one" means one or more, unless specifically defined otherwise.
In the description of the present specification, the term "on the basis of the above-described embodiment" means that a particular feature, structure, material or characteristic described in connection with the embodiment or example is included in at least one preferred embodiment or preferred example of the present utility model. In this specification, schematic representations of the above terms do not necessarily refer to the same implementations or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
As shown in fig. 1, in a first aspect of the present embodiment, there is provided a pole piece, which includes a current collector 1 and an active material coating 2 disposed on a surface of the current collector 1, the active material coating 2 being disposed on at least one surface of the current collector 1. The active material coating 2 includes a lower surface (i.e., a first surface) and an upper surface (i.e., a second surface) disposed opposite to each other in the thickness direction of the pole piece, and the upper surface of the active material coating 2 is a surface of the active material coating 2 facing away from the current collector 1. The upper surface of the active material coating 2 is provided with at least two concave portions 222b, a duct 222a is formed between any adjacent two concave portions 222b, the concave portions 222b and the duct 222a are communicated with each other, and the plurality of concave portions 222b are communicated through the duct 222a.
The recess 222b and the channel 222a in the present embodiment are non-penetrating structures, i.e. the depth of the recess 222b and the channel 222a is smaller than the thickness of the active material coating 2. As an alternative embodiment, the depth of the recess 222b is 10% to 60% of the thickness of the active material coating 2, and the depth of the pore 222a is 10% to 60% of the thickness of the active material coating 2.
For convenience of description below, the active material coating 2 is divided into a first coating layer 21 and a second coating layer 22, the second coating layer 22 is disposed on a side of the active material coating 2 facing away from the current collector 1, the first coating layer 21 is disposed between the second coating layer 22 and the current collector 1, that is, at least two recess portions 222b are disposed in the second coating layer 22, a duct 222a is formed between any adjacent two recess portions 222b, the recess portions 222b and the duct 222a communicate with each other, and the plurality of recess portions 222b communicate through the duct 222a.
As an alternative embodiment, before the second coating 22 is rolled, the second coating 22 includes a plurality of coating protrusions 221, the plurality of coating protrusions 221 may be uniformly disposed on the surface of the first coating 21, after the pole piece is rolled, the coating protrusions 221 may be connected together, but due to different stresses on two sides of the coating protrusions 221 during the rolling process, a recess 222b and a channel 222a are formed between the adjacent coating protrusions 221, the recess 222b and the channel 222a are mutually communicated, and the plurality of recesses 222b are communicated through the channel 222a. In this embodiment, the first coating 21 is a continuous active material coating, that is, the first coating 21 is not provided with the recess 222b or the pore 222a.
In this embodiment, the projection area of the recess 222b on the current collector 1 is larger than the projection area of the hole 222a on the current collector 1. As an alternative embodiment, the diameter of the recess 222b is greater than the diameter of the aperture 222a. As shown in connection with fig. 2, the cells 222a are formed by any adjacent two coating protrusions 221, and four coating protrusions 221 are disposed around the recess 222b, i.e., the recess 222b is the junction area of the cells 222a disposed in different directions. Illustratively, in fig. 2, the recess 222b is the intersection area of the cell 222a disposed in the horizontal direction and the cell 222a disposed in the vertical direction.
As an alternative embodiment, the plurality of coating bumps 221 may be arranged in a matrix on the surface of the first coating 21 before rolling. Fig. 4 is an SEM image of the pole piece in this example, and fig. 5 is an SEM image of the second coating layer. As can be seen from fig. 4 and 5, the recess 222b and the hole 222a communicating with each other are formed between the adjacent two coating protrusions 221, and the respective holes 222a communicate with each other.
As an alternative embodiment, the shape of the coating bump 221 may be the same, the pitch between the plurality of coating bumps 221 may be the same, and illustratively, the cross-sectional shape of the coating bump 221 may be at least one of rectangular, circular, elliptical, trapezoidal, or triangular. In other embodiments, the shape of the coating bump 221 may not be identical, and the spacing between the plurality of coating bumps 221 may not be identical. As a preferred embodiment, the plurality of coating protrusions 221 in the second coating 22 are uniformly distributed, so that the concave portions 222b and the pore channels 222a penetrate through the second coating 22, and the concave portions 222b or the pore channels 222a are uniformly distributed on the whole surface of the pole piece, thereby being beneficial to improving the efficiency of electrolyte infiltration and ensuring that the electrolyte rapidly infiltrates through the whole pole piece.
In this embodiment, each coating bump 221 may be disposed on the surface of the first coating 21 by gravure printing, silk-screen processing or 3D printing, so as to simplify the processing technology and improve the production efficiency. The first coating layer 21 may be formed by extrusion coating or transfer coating.
In the embodiment, by designing the structure of the pole piece, a first coating layer is continuously distributed on the surface of the current collector, a second coating layer is arranged on the surface of the first coating layer, concave parts and pore channels which are mutually communicated are arranged in the second coating layer, all pore channels are mutually communicated, the whole surface of the pole piece is distributed with concave parts or pore channels, the concave parts and the pore channels can provide a transmission path for electrolyte, the electrolyte infiltration efficiency is improved, and the electrolyte can be ensured to quickly infiltrate the whole pole piece, wherein the wetting rate of the electrolyte in the pole piece can reach 0.1mm/s -0.5 To 1.5mm/s -0.5 The method comprises the steps of carrying out a first treatment on the surface of the In addition, the pore canal and the concave part can also shorten the transmission path of lithium ions, quicken the transmission rate of the lithium ions in the pole piece, improve the rate capability of the battery and avoid the problem of lithium precipitation of the negative electrode under the condition of quick charge.
In this embodiment, each of the first coating layer 21 and the second coating layer 22 may include an active material, a binder, and a conductive agent, and the active material, the binder, and the conductive agent in the first coating layer 21 and the second coating layer 22 may be the same. In this embodiment, the specific kinds of the active material, the binder and the conductive agent are not further limited, and may be selected by those skilled in the art according to actual circumstances. If the pole piece is a positive pole piece, the active material is a positive pole active material, and if the pole piece is a negative pole piece, the active material is a negative pole active material.
As shown in fig. 1, the second coating 22 includes a lower surface (i.e., a first surface) and an upper surface (i.e., a second surface) opposite to each other in the thickness direction of the pole piece, the lower surface of the second coating 22 is connected to the first coating 21, the projected area of the lower surface of the coating bump 221 on the first coating 21 is smaller than the projected area of the upper surface of the coating bump 221 on the first coating 21, in other words, the coating bump 221 has a structure with a large upper side and a small lower side, so that the size of the recess 222b on the side close to the first coating 21 is larger than the size of the recess 222b on the side far from the first coating 21, and the size of the hole 222a on the side close to the first coating 21 is larger than the size of the hole 222a on the side far from the first coating 21. Therefore, the size of the pore canal 222a and the concave part 222b close to the first coating 21 is larger, the contact area between the electrolyte and the first coating 21 is increased, the electrolyte is favorable for fully infiltrating the first coating 21, and the infiltration efficiency of the electrolyte is improved.
In an alternative embodiment, the projected area of the coating bump 221 on the first coating 21 is gradually increased from the lower surface to the upper surface, in other words, the lower surface of the coating bump 221 is smoothly connected to the upper surface of the coating bump 221, and illustratively, the lower surface of the coating bump 221 and the upper surface of the coating bump 221 are arc-shaped, thereby gradually reducing the size of the recess 222b from the lower surface to the upper surface, gradually reducing the size of the channel 222a from the lower surface to the upper surface, and forming the shape of the channel 222a and the recess 222b into a horn shape.
In the present embodiment, the size of the recess 222b is larger than the size of the hole 222a, and the size of the hole 222a is in the range of 0.5 μm to 500 μm, and the size of the recess 222b is in the range of 0.5 μm to 500 μm. Illustratively, the dimension of the lower surface of the tunnel 222a is 300 μm, the dimension of the upper surface of the tunnel 222a is 20 μm, the dimension of the lower surface of the recess 222b is 500 μm, and the dimension of the upper surface of the recess 222b is 35 μm.
It should be noted that, the size of the hole 222a refers to the distance between the two opposite inner wall surfaces of the hole 222a, the size of the recess 222b refers to the distance between the two opposite inner wall surfaces of the recess 222b, and, for example, if the hole 222a and the recess 222b are circular, the size of the hole 222a refers to the diameter of the hole 222a, and the size of the recess 222b refers to the diameter of the recess 222 b.
Based on the above embodiment, the projection area of the concave portion 222b on the lower surface of the second coating 22 on the current collector 1 is S1, and the projection area of the concave portion 222b on the upper surface of the second coating 22 on the current collector 1 is S2, the ratio of S1 to S2 is greater than 1 and less than or equal to 4, i.e., 1 < S1/S2 is less than or equal to 4, thereby being beneficial to further improving the infiltration efficiency of the electrolyte.
In this embodiment, S1 is greater than S2 by rolling, and before rolling, the projected area of the lower surface of the coating bump 221 on the first coating 21 is equal to the projected area of the upper surface of the coating bump 221 on the first coating 21, and when rolling the coating bump 221, the upper surface of the coating bump 221 is pressed more than the lower surface of the coating bump 221, so that the coating bump 221 can form a structure with a large top and a small bottom, and the concave portion 222b between the coating bumps 221 forms a structure with a large top and a small bottom. The spacing between any two adjacent coating projections 221 is not further limited in this embodiment before the pair rolling, as long as it is ensured that the upper surfaces of any two adjacent coating projections 221 are not overlapped after the rolling.
In this embodiment, the thickness of the second coating layer 22 can be adjusted to adjust the areal density of the second coating layer 22, and the thicker the thickness of the second coating layer 22, the greater the areal density of the second coating layer 22. The surface density refers to the mass of all substances in the active substance coating 2 under the unit area of the surface of the pole piece, and all substances in the active substance coating 2 comprise active materials, binders, conductive agents and the like.
In fig. 6, the second coating layer 22 is located above the dotted line, the first coating layer 21 is located below the dotted line, and in this embodiment, the porosity of the second coating layer 22 is greater than that of the first coating layer 21, where the porosity of the first coating layer 21 ranges from 10% to 35%, and the porosity of the second coating layer 22 ranges from 20% to 60%, as shown in conjunction with fig. 6.
A second aspect of the present embodiment provides a battery, including a battery cell, a case, and an electrolyte, where the battery cell includes a positive electrode sheet (i.e., a first electrode sheet), a negative electrode sheet (i.e., a second electrode sheet), and a separator disposed between the positive electrode sheet and the negative electrode sheet, and at least one of the positive electrode sheet and the negative electrode sheet is the electrode sheet shown above; the cell is located in the housing, the electrolyte is injected into the housing with the cell mounted therein, and the electrolyte wets the recess 222b and the hole 222a of the pole piece as shown above.
In this embodiment, the negative electrode sheet is the electrode sheet shown above, and the positive electrode sheet is a sheet with a conventional structure. The negative plate adopts the pole piece with the structure, is favorable for shortening the transmission path of lithium ions, quickens the transmission rate of the lithium ions in the negative plate, improves the rate capability of the battery and avoids the problem of negative lithium precipitation under the condition of quick charge.
In order to illustrate the improvement of the battery performance by the second coating layer 22, this embodiment shows an example of a control experiment including four experimental groups and one control group, wherein the control group and the experimental group are identical in other variables such as positive electrode sheet and separator except for whether the second coating layer 22 and the active material coating layer 2 are provided with different surface densities, and the control group and the experimental group are specifically set as follows:
experiment group 1: the copper foil with the thickness of 6 mu m is used as a negative electrode current collector, a negative electrode active material coating is coated on two sides of the copper foil by adopting an extrusion coater, and the coating surface density is 6.95mg/cm 2 Rolling the coated pole piece to obtain a first coating 21; the negative electrode active material coating is applied to the surface of the first coating layer 21 by printing (including gravure printing or screen printing, etc.), a plurality of coating bumps 221 are arranged in a matrix on the surface of the first coating layer 21, and the coating surface density is 0.75mg/cm 2 Rolling the coated pole piece, and forming concave parts between adjacent coating convex blocks 221 after the coating convex blocks 221 are rolled222b and the pore canal 222a, the concave part 222b and the pore canal 222a are mutually communicated, and the plurality of concave parts 222b are communicated through the pore canal 222a, and the second coating 22 is formed on the surface of the first coating 21, so that the negative electrode sheet is obtained, wherein the thickness of the second coating 22 is 10% of the thickness of the negative electrode active material coating.
Experiment group 2: the areal density of the first coating 21 was 5.39mg/cm 2 The areal density of the second coating 22 was 2.31mg/cm 2 The remainder are the same as experimental group 1; the areal density of the first coating layer 21 and the second coating layer 22 can be adjusted by adjusting the coating thicknesses of the first coating layer 21 and the second coating layer 22, wherein the thickness of the second coating layer 22 is 30% of the thickness of the anode active material coating layer.
Experiment group 3: the areal density of the first coating 21 was 4.05mg/cm 2 The areal density of the second coating 22 was 3.65mg/cm 2 The rest is the same as in experiment 1, in which the thickness of the second coating layer 22 is 50% of the thickness of the anode active material coating layer.
Experiment group 4: the areal density of the first coating 21 was 3.36mg/cm 2 The areal density of the second coating 22 was 4.34mg/cm 2 The rest is the same as in experiment 1, in which the thickness of the second coating layer 22 is 60% of the thickness of the anode active material coating layer.
Control group: the copper foil with the thickness of 6 mu m is used as a negative electrode current collector, a negative electrode active material coating is coated on two sides of the copper foil by adopting an extrusion coater, and the coating surface density is 7.7mg/cm 2 And rolling the coated pole piece, and forming a negative electrode active material coating on the surface of the negative electrode current collector to obtain a negative electrode piece, wherein the negative electrode active material coating is free of a second coating.
The batteries prepared by the groups are subjected to the following performance tests, wherein the test process is as follows:
(1) Measurement of the wettability of the electrolyte in the pole piece:
(a) Testing the volatilization amount of the electrolyte to obtain the volatilization amounts of the electrolyte at different moments;
(b) Immersing the negative plate into electrolyte with the same amount and the same type as those in the step (a), and testing to obtain electrolyte reduction amounts at different moments after immersing;
(3) Subtracting the volatilization amount of the electrolyte in the step (a) at the same moment from the reduction amount of the electrolyte in the step (b) to obtain the actual liquid absorption amount delta m of the pole piece, and obtaining the actual wetting curve of the pole piece by using a Lucas-Washburn equation, wherein the slope of the actual wetting curve is the wetting rate of the electrolyte in the pole piece.
The wetting rate equation was measured based on the modified Lucas-Washburn equation as follows:
wherein: t is time, and Deltam is the change of the weight of the pole piece in the wetting process; ρsol is the electrolyte density; ae is the sectional area of the pole piece; k is the wetting rate of the electrolyte in the porous electrode; p is the porosity of the electrode;is the effective diameter of the electrode; r is (r) lv Is the surface tension of the electrolyte; θ is the contact angle of the electrolyte with the electrode; η is the viscosity of the electrolyte.
(2) Rate performance measurement:
and (3) completely discharging the sample at room temperature, and fully charging the sample with constant current and constant voltage of 0.2C/0.5C/1C/1.5C/2C, wherein the discharge is carried out according to the constant current discharge of 0.2C to the discharge cut-off voltage. The charging capacity at the constant current stage is respectively as follows: the total charge capacities of Cc1, cc2, cc3, cc4, cc5 are respectively C1, C2, C3, C4, C5, and the constant current charge ratios at the respective charge rates are respectively counted, and the constant current charge ratios are constant current charge capacities/total charge capacities.
(3) Lithium evolution measurement:
the sample battery is charged to 4.35V at constant current and constant voltage at 25 ℃ and 2C,2.5C and 3C respectively, kept stand for 10 minutes, then 0.7C is discharged to 3.0V, and each group of batteries is subjected to 20 times of cyclic tests, and the lithium precipitation condition of the battery is observed in an anatomic mode.
Table 1 experimental results of experimental and control groups
As can be seen from table 1, the second coating is disposed on the surface of the negative electrode sheet, the second coating includes a plurality of coating protrusions, so that a concave portion 222b and a hole 222a are formed between adjacent coating protrusions 221, the concave portion 222b and the hole 222a are mutually communicated, and the plurality of concave portions 222b are communicated through the hole 222a, and by disposing the second coating having the hole and the concave portion on the surface of the negative electrode sheet, the infiltration rate of the electrolyte can be increased, the risk of lithium precipitation of the negative electrode sheet can be reduced, and the charging rate performance of the battery can be improved; however, when the thickness of the second coating layer is more than 60% of the thickness of the anode active material coating layer, the increase of the wetting rate reaches an upper limit value, and when the thickness of the second coating layer is more than 60% of the thickness of the anode sheet, the volume density of the anode sheet is decreased, affecting the volume energy density of the battery.
In one specific embodiment, the battery may be manufactured as follows:
manufacturing a negative electrode sheet: the anode active material coating is graphite, CMC and SBR with the mass ratio of 96.5:2:1.5, dissolving the mixture in deionized water, adopting a double-planetary stirrer to rotate 1200r/min and revolve for 20r/min, stirring for 5 hours, and adopting an extrusion coater to coat the obtained negative electrode slurry on two sides of a copper foil with the thickness of 6 mu m, wherein the coating surface density is 7.7mg/cm 2 After drying, the coated pole piece is rolled, and the rolling compaction density is 1.69g/cm 3 The negative plate with the thickness of 96 μm is obtained.
The specific process for manufacturing the positive plate is as follows: taking 95% of lithium iron phosphate, 2% of polyvinylidene fluoride and 3% of Super P as positive electrode slurry, taking N-methyl pyrrolidone as a solvent, and the total solid content is 55%, coating the positive electrode slurry on two sides of a rolled aluminum foil with the thickness of 10 mu m according to a cell manufacturing process after preparing the positive electrode slurry, drying at 90 ℃ and the surface density of 14.5mg/cm 2 Then according to 4.0g/cm 3 The positive plate is obtained by rolling the positive plate with the compacted density of 81 mu m.
And (3) taking a Polyethylene (PE) porous polymeric film as an isolating film, sequentially stacking the positive plate, the isolating film and the negative plate, enabling the isolating film to be positioned between the positive plate and the negative plate to play a role of isolation, and winding to obtain the battery cell.
Preparation of electrolyte: in a dry argon atmosphere, adding lithium hexafluorophosphate (LiPF) into a solvent solution prepared by mixing Propylene Carbonate (PC), ethylene Carbonate (EC) and diethyl carbonate (DEC) in a weight ratio of 1:1:1 6 ) Uniformly mix, wherein LiPF 6 The concentration of (2) was about 1.12mol/L, and 10wt% fluoroethylene carbonate (FEC) was added thereto, and the mixture was uniformly mixed to obtain an electrolyte.
And packaging the battery cell into a punching pit of a packaging film (an aluminum plastic film comprises outer nylon layer, middle Al layer and inner PP layer), drying the battery cell, injecting electrolyte, packaging, performing formation, degassing and trimming to obtain a battery, and performing electrical property test on the obtained battery.
Although the present disclosure is described above, the scope of protection of the present disclosure is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the disclosure, and these changes and modifications will fall within the scope of the utility model.
Claims (11)
1. A pole piece, characterized by comprising a current collector and an active material coating arranged on the current collector;
at least two concave parts are arranged on one side of the active material coating, which is away from the current collector, and pore channels are arranged between any two adjacent concave parts and are mutually communicated.
2. A pole piece according to claim 1, characterized in that the depth of the recess is 10 to 60% of the thickness of the active material coating and/or the depth of the pore canal is 10 to 60% of the thickness of the active material coating.
3. The pole piece of claim 1, wherein the active material coating comprises a first surface and a second surface disposed opposite each other in a thickness direction of the pole piece, the first surface being connected to the current collector, the recess and the cell being disposed on the second surface;
the diameter of one side of the concave part, which faces away from the second surface, is larger than the diameter of one side of the concave part, which is close to the second surface;
and/or the diameter of the side of the pore canal away from the second surface is larger than the diameter of the side of the pore canal close to the second surface.
4. A pole piece according to claim 3, wherein the recess tapers in diameter from a side proximate the first surface to the second surface and/or the aperture tapers in diameter from a side proximate the first surface to the second surface.
5. The pole piece of claim 4, wherein the projected area of the recess facing away from the second surface on the current collector is S1, the projected area of the recess on the second surface on the current collector is S2, and the ratio of S1 to S2 is greater than 1 and less than or equal to 4.
6. A pole piece according to claim 3, characterized in that the projected area of the recess on the current collector is larger than the projected area of the aperture on the current collector.
7. A pole piece according to claim 6, characterized in that the size of the recess ranges from 0.5 μm to 500 μm and/or the size of the aperture ranges from 0.5 μm to 500 μm.
8. The pole piece of claim 1, wherein the active material coating on the side facing away from the current collector has a porosity greater than the active material coating on the side adjacent to the current collector.
9. A pole piece according to claim 8, characterized in that the porosity of the active material coating on the side close to the current collector ranges from 10% to 35% and/or the porosity of the active material coating on the side facing away from the current collector ranges from 20% to 60%.
10. A battery, characterized by comprising a battery cell, a shell and electrolyte, wherein the battery cell is positioned in the shell, and the electrolyte is injected into the shell provided with the battery cell; the battery cell comprises a first pole piece, a second pole piece and a diaphragm arranged between the first pole piece and the second pole piece, wherein the polarities of the first pole piece and the second pole piece are opposite, and at least one of the first pole piece and the second pole piece is the pole piece of any one of claims 1 to 9.
11. The battery of claim 10, wherein the electrolyte wets the recess of the pole piece and the aperture.
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| CN202321912949.XU CN220543945U (en) | 2023-07-20 | 2023-07-20 | Pole piece and battery |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202321912949.XU CN220543945U (en) | 2023-07-20 | 2023-07-20 | Pole piece and battery |
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