CN218647975U - Pole piece and battery beneficial to infiltration - Google Patents

Abstract

The utility model discloses a pole piece and battery that help infiltration, this pole piece include the mass flow body, at least one side of the mass flow body is equipped with the material district, the arch through-hole has been seted up in the material district in the one side of the mass flow body of laminating, the axial of arch through-hole is on a parallel with the mass flow body surface and be on a parallel with mass flow body coiling axis direction. The utility model has the advantages that the arrangement of the arched through holes in the pole piece material area can improve the liquid retention capacity of the lithium ion battery, thereby improving the cycle life of the battery; the through hole is filled with solid electrolyte, so that a film forming additive can be dynamically provided for the electrolyte and the electrolyte can be supplemented to improve the cycle performance of the battery; additionally, the utility model discloses the inlayer and the skin of accessible pole piece are infiltrated the pole piece jointly, promote infiltration efficiency and infiltration effect effectively, promote the uniformity and the homogeneity of filming.

Description

Pole piece and battery beneficial to infiltration

Technical Field

The utility model relates to a lithium ion battery technical field, concretely relates to pole piece and battery that help infiltration.

Background

Energy crisis and environmental issues have prompted the rapid development of the battery industry. The lithium ion battery has the characteristics of high energy density, good safety, long cycle life, no pollution and the like, and is widely applied to the fields of electronic products, electric tools, electric automobiles, energy storage and the like. The cycle life of a battery refers to the number of charge and discharge times that the battery undergoes under a certain charge and discharge regime when the capacity of the lithium battery falls to a certain specified value. At present, the cycle life of the polymer battery is commonly 500-700 times, and the main reason of the reduction of the cycle life is the exhaustion of the electrolyte in the battery. Along with the increase of energy density, the compaction density of the positive and negative pole pieces is increased in the manufacturing process of the lithium ion battery, and the positive and negative pole pieces are tightly attached to the diaphragm, so that the wettability of electrolyte is poor, the amount of residual electrolyte in the battery is reduced, and the cycle life of the battery is shortened.

Chinese patent CN109686918A discloses a lithium ion battery pole piece, in which through micropores are uniformly formed on a slurry membrane of the pole piece; chinese patent CN208797100U discloses a positive electrode plate and a secondary battery, in which concave-convex structures with different shapes are arranged on the surface of the electrode plate; chinese patent CN113644231A discloses a composite negative plate, a preparation method thereof, and a secondary battery, wherein the surface of the carbon active layer away from the current collector is provided with a plurality of micropores and filled with a second active material; although the technical scheme disclosed by the patent structurally improves the liquid retention capacity of the battery, the infiltration mode of the electrolyte on the pole piece is still a single path from outside to inside, so that the infiltration effect of the inner layer of the pole piece cannot be ensured, and the film forming condition can also be influenced. In the use process of the lithium ion battery, the protective films on the surfaces of the anode and the cathode are always in a dynamic repair state, and electrolyte, especially a film forming additive in the electrolyte, is always in a consumption state; in addition, the electrolyte is further consumed during charging and discharging of the battery, which causes a rapid decrease in the battery capacity and a decrease in the cycle life of the battery.

SUMMERY OF THE UTILITY MODEL

The utility model discloses a to the problem among the prior art, disclose a pole piece and battery that help infiltration, can not only increase electrolyte and protect the liquid measure, can also infiltrate in order to promote the uniformity and the homogeneity of filming through inlayer and skin common to the pole piece to improve the cycle life of battery from this, and help promoting the hardness and the portability of battery.

In particular, in one aspect, the utility model discloses a pole piece which is helpful for infiltration, the pole piece comprises a current collector; this at least one side of mass flow body is equipped with the material district, the arch through-hole has been seted up in the material district on the one side of the mass flow body of laminating, the axial direction of arch through-hole is on a parallel with the mass flow body surface, and be on a parallel with the mass flow body and roll up the axis direction.

The material area comprises a first material area and/or a second material area which are arranged on two sides of the current collector respectively, and the arch-shaped through hole is formed in at least one material area.

Wherein, on one side of the laminating anodal mass flow body in material district, set for: the surface area of the contact part of the material area and the current collector is C (unit: mm) ² ) The arch width of the arch-shaped through hole is H (unit: mm), the surface area of the arch curved surface on the arch through-hole of material district is D (unit: mm is ² ) Arch ratio a = D/C; the preferred range of the camber ratio A is 2-3%; the arch width H of the pole piece arch through hole is preferably 1 mm-3 mm.

Wherein a solid electrolyte coating is coated on the inner surface of the arched through hole. Further, the components of the solid electrolyte coating include one or more of EC, FEC, PS, PST, VC, VEC, preferably including EC.

In particular, in another aspect, the present invention discloses a cell that facilitates wetting, the cell including a pole piece that facilitates wetting as described above.

In particular, on the other hand, the utility model discloses a preparation method of the battery that helps infiltration as aforementioned, including the following steps:

s1: preparing the positive pole piece, including S1-1, dissolving a solid electrolyte and a binder in a solvent, and rotationally stirring to obtain a solid electrolyte coating material; s1-2, coating the prepared solid electrolyte coating material on an aluminum foil by adopting a gravure coating technology; s1-3, preparing anode slurry, coating the slurry on the aluminum foil with the solid electrolyte coating obtained in the step 2, and rolling, slitting, welding and other processes to prepare an anode piece;

s2: assembling the positive and negative pole pieces and the diaphragm into a battery cell by a winding machine or a laminating machine, manufacturing the battery cell into a dry battery cell by methods such as packaging or laser welding, and manufacturing the lithium ion battery by liquid injection and formation methods.

Wherein the preferable treatment temperature of the formation method is not more than 75 ℃, the preferable pressure is 0.1 MPa-1 MPa, and the preferable treatment time is 1 h-5 h.

Compared with the prior art, the utility model discloses a characteristics and beneficial effect do:

1. the arched through holes are formed in the surface, attached to the current collector, of at least one material area of the pole piece, so that the liquid retention capacity of the lithium ion battery can be improved, and the cycle life of the battery is prolonged; 2. solid electrolyte is filled in the through hole, a film forming additive is dynamically provided for the electrolyte and the electrolyte is supplemented, and the cycle performance of the battery is improved; 3. the axial direction of the arched through hole is parallel to the surface of the current collector and the direction of the current collector winding axis, so that the battery can be soaked from the inner layer and the outer layer of the pole piece together, the soaking efficiency and the soaking effect are effectively improved, and the consistency and the uniformity of film forming are promoted; 4. the arched through holes are formed in the surface, attached to the current collector, of the material area, so that the liquid retention amount is increased, the surface flatness of the pole piece is kept, and diaphragm deformation in subsequent lithium ion battery preparation is prevented; 5. parameters of the pole piece and the arched through hole are optimized, the arched through hole A is preferably 2% -3%, and the arched width is preferably 1 mm-3 mm, so that the comprehensive performances of the lithium ion battery, such as the rate performance, the cycle life and the like, are optimal.

Drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed for the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.

Fig. 1 is the structure schematic diagram of the positive plate of the lithium ion battery provided by the embodiment of the utility model.

Fig. 2 is a schematic structural diagram of a lithium ion battery negative plate provided by an embodiment of the present invention.

Fig. 3 is a schematic diagram of a cross-sectional structure of the battery cell after winding provided by the embodiment of the present invention.

Fig. 4A is the utility model discloses positive plate structure schematic diagram that comparative example 2 provided.

Fig. 4B is the utility model discloses positive plate planar structure schematic diagram that comparative example 2 provided.

Fig. 4C is a schematic diagram of a cross-sectional structure of the wound battery cell according to the comparative example 2 of the present invention.

Fig. 5 is a cycle test result of some examples and comparative examples provided by the present invention.

Fig. 6 shows the cycle test results of some embodiments provided by the present invention.

Wherein the figures include the following reference numerals:

1-1 positive pole lug, 1-2 positive pole current collector, 1-3 first positive pole material area, 1-4 second positive pole material area, 1-5 arch through hole, 2-1 nickel pole lug, 2-2 negative pole current collector, 2-3 negative pole material area, 3-1 comparative example 2 positive pole lug, 3-2 comparative example 2 positive pole current collector, 3-3 comparative example 2 positive pole material area, 3-4 micropore, H-arch width.

Detailed Description

In order to facilitate understanding of the present invention, it will be described more fully below, giving a preferred embodiment of the present invention. It should be understood that these examples are for the purpose of illustration only and are not to be construed as limiting the invention in any way, i.e., not as limiting the scope of the invention; relational terms such as "first" and "second," and the like, may be used solely to distinguish one element from another element having the same name, and do not necessarily require or imply any actual relationship or order between such elements.

The utility model relates to a help the exemplary structure of pole piece of infiltration is shown in figure 1, and this pole piece is positive pole piece, including anodal utmost point ear 1-1, anodal mass flow body 1-4 and anodal material district, wherein, anodal utmost point ear 1-1 and anodal mass flow body 1-2 are the aluminium foil, and anodal material district includes lithium cobaltate, lithium manganate, ternary, lithium iron phosphate, one or more in the rich lithium manganese, one or more and PVDF in CNTs, SP, GF-2, the graphite alkene. The positive material area comprises a first positive material area 1-3 and a second positive material area 1-4 which are respectively arranged on two sides of a positive current collector 1-2, and arch-shaped through holes 1-5 are oppositely arranged on one surface of the two material areas, which is attached to the positive current collector 1-2, and the axial direction of each arch-shaped through hole 1-5 is parallel to the surface of the current collector 1-2 and parallel to the winding axial direction of the current collector 1-2. Wherein, no special burr and sharp corner are arranged in the interface material area between the arched through holes 1-5 on the pole piece and the anode material area.

As shown in figure 1, on the side of the positive electrode material area, which is attached to a positive electrode current collector 1-2, the surface area of the contact part of the material area and the current collector is set as C (unit: mm) ² ) The arch width of the arch via hole is H (unit: mm), the surface area of the arch curved surface on the arch through-hole of material district is D (unit: mm (mm) ² ) The camber ratio A = D/C, and the preferred range of the camber ratio A of the positive pole piece is 2% -3%; preferably, the arch width H is 1mm to 3mm.

The inner surface of the arched through hole of the positive pole piece is coated with a solid electrolyte layer. The composition of the solid electrolyte layer comprises one or more of EC, FEC, PS, PST, VC and VEC. Among them, EC is an important component of the electrolyte and also has a film-forming function, and is an indispensable coating component in the arched through-hole, which helps the arched through-hole to promote the rapid entry of the electrolyte under a small size control.

It is noted that for the sake of brevity, the specific exemplary structural schematic diagram of the negative electrode plate is not shown in the embodiment of the present invention, but those skilled in the art will understand that the arched through-hole structure shown in fig. 1 can also be used for the negative electrode plate, which can be selected from a nickel tab and a copper foil current collector, and the negative electrode material component includes one or more of graphite, hard carbon, siO, one or more of CNtS, SP, GF-2, graphene, one or more of SBR, pAA, and CMC. Use the utility model discloses technical scheme's positive pole piece and/or negative pole piece to and loaded more than the lithium ion battery of positive pole piece and/or negative pole piece all be in the utility model discloses an in the protection range.

In order to further verify the technical effect of the technical solution of the present invention, a series of specific experiments are described as an implementation example below.

1. Preparation method

The lithium ion battery with the cell model number of 533450 is prepared as the battery used in the embodiment examples 1-23, and comprises a positive pole piece, a negative pole piece, electrolyte, a diaphragm and a shell. The structure of the positive pole piece is shown in fig. 1 and comprises a positive pole tab 1-1, a positive pole current collector 1-2 and a positive pole material area, wherein the positive pole tab 1-1 and the positive pole current collector 1-2 are aluminum foils, and the positive pole material area comprises 96% of lithium cobaltate, 1.5% of SP, 0.5% of graphene and 2% of PVDF. The structure of the negative pole piece is shown in fig. 2 and comprises a negative nickel tab 2-1, a negative current collector 2-2 and a negative material area 2-3, wherein the negative current collector 2-2 is copper foil, and the components of the negative material area 2-3 comprise 95.5% of graphite, 1.5% of SP, 1.5% of SBR and 1.5% of CMC. The utility model discloses do not specifically prescribe a limit to electrolyte, diaphragm, casing etc. in the concrete implementation, can select suitable material according to actual conditions.

For the sake of brevity, the specific implementation of the present invention will only explain the preparation method of the positive electrode plate in detail. The preparation method of the positive pole piece comprises the following steps:

step 1: a solid electrolyte-containing coating material is prepared. Different component materials and a binder PVDF are selected to be dissolved in a solvent NMP, and the solvent NMP is put into a 5L stirring tank to be stirred for 2 hours at the rotating speed of revolution of 25Hz and rotation of 1500 rpm. Wherein when the component material is EC, the ratio of EC to PVDF is 95; when the component material is FEC, the ratio of FEC and PVDF is 95.

Step 2: coating the inner surface of the arch-shaped through hole. And coating the prepared solid electrolyte coating material on the aluminum foil by adopting a gravure coating technology. The width of the gravure is the arched width H of the pole piece, and the surface area of the gravure is the surface area D of the arched through hole curved surface of the pole piece.

And step 3: and (3) preparing positive electrode slurry, coating the slurry on the aluminum foil obtained in the step (2), and rolling, slitting, welding and other processes to prepare the positive electrode piece.

Then, after the positive and negative pole pieces are isolated by a diaphragm, forming a battery cell by a winding machine, wherein the structure of the battery cell is shown in fig. 3; the dry cell is manufactured by methods such as packaging or laser welding, and after the electrolyte is injected, the lithium ion battery provided by the embodiment of the utility model is manufactured by a formation method. It is noted that the lamination machine can also be used for assembling the positive and negative pole pieces and the diaphragm to manufacture the battery core.

Comparative example 1 and comparative example 2 were set up simultaneously.

Comparative example 1 is a lithium ion battery using common positive and negative electrode sheets, and no micropores or through holes were formed in the positive and negative electrode sheets of the battery.

The structure of the positive pole piece of the comparative example 2 is shown in fig. 4A, and the positive pole piece comprises a positive pole tab 3-1 of the comparative example 2, a positive pole current collector 3-2 of the comparative example 2 and a positive pole material area 3-3 of the comparative example 2. Micropores 3-4 are uniformly formed in one surface of the positive electrode material area 3-3 of the comparative example 2, which is far away from the positive electrode current collector 3-2 of the comparative example 2, the opening depth of each micropore 3-4 is smaller than the thickness of the positive electrode material area 3-3 of the comparative example 2, and the plane structure of the positive electrode plate is shown in a figure 4B; the cross-sectional structure of the cell winding of the lithium ion battery provided in comparative example 2 is shown in fig. 4C. The other structural compositions and parameters of comparative example 1 and comparative example 2 were consistent with the examples.

Setting the liquid retention volume of the battery as B (g/(Ah)) and setting the volume as the final electrolyte remaining in the battery; the set rate performance is defined as the discharge capacity of the battery 1C divided by the discharge capacity of the battery 0.2C (i.e., 1C/0.2C), and is equivalent to the rate performance if the deviation between the experimental group and the comparative group is ± 1%.

2. Analysis of validation results

And (3) carrying out a solid electrolyte filling comparison experiment, setting a comparative example 1, a comparative example 2, an experiment 1 and an experiment 2, respectively measuring the liquid retention B and the infiltration time of the lithium ion battery, and carrying out a multiplying power test. The results of the experiment are shown in table 1 below.

Table 1

From table 1, it can be verified that the battery pole piece is provided with the micropores or the through holes to provide a retention space for the electrolyte in the pole piece, and the liquid retention amount of the battery can be improved. This was also confirmed by comparing the liquid retaining amounts B, which were significantly higher in comparative example 2 in which micropores were started in the positive electrode sheet region, in example 1 and example 2 in which arch-shaped through holes were opened in the positive electrode sheet region, and in comparative example 1 in which a common positive electrode sheet was used.

As can be verified by table 1, the arched through hole is formed in one surface, which is attached to the current collector, of the pole piece material area, and the axial direction of the arched through hole is parallel to the surface of the current collector and the winding axial direction of the current collector, as shown in examples 1 and 2, the battery can simultaneously infiltrate the pole piece with the inner layer and the outer layer, and the infiltration efficiency is improved; in contrast, although the comparative example 2 is provided with micropores, the micropores are perpendicular to the plane of the current collector, and only the pole piece can be infiltrated from the outer layer to the inner layer, and the infiltration time required by the method is close to that of the comparative example 1 using the common positive pole piece.

Comparing the soaking time, the soaking time of the example 1 and the example 2 is reduced by nearly 1 time compared with the comparative examples 1 and 2 in order to achieve the same rate test performance. In the preparation process of the lithium ion battery, the long-time soaking and infiltration not only reduces the production efficiency, but also possibly influences the adhesion effect, so that the material area and the current collector are stripped, and finally the performance and the cycle life of the lithium ion battery are reduced. Therefore, the utility model discloses a technical scheme can improve lithium ion battery industrialization production efficiency effectively, is favorable to the uniformity and the homogeneity of film forming, promotes battery performance and cycle life's promotion.

Different arch proportion comparison experiments were performed. With comparative example 1 and examples 2 to 7 having the same solid electrolyte composition but different camber ratios, the liquid retention amount B was measured and subjected to a rate test, respectively. The results of the experiment are shown in table 2 below.

Table 2

It can be verified from table 2 that when the arch ratio a of the lithium ion battery electrode piece is 1% -3%, the rate performance of the battery is better. It will be understood that an increase in the camber ratio a of the pole piece will provide a larger solid electrolyte fill space, and thus the retention B increases with an increase in the camber ratio a; it is noteworthy that an increase in pole piece camber over a indicates a decrease in charge area, which also affects cell performance. The multiplying power test shows that when the arch ratio A of the lithium ion battery pole piece is not more than 3%, the multiplying power influence of the battery is within 1%, namely the multiplying power performance is equivalent; and when the arch ratio A of the pole piece exceeds 3%, the multiplying power of the battery is obviously reduced. Therefore, in consideration of the comprehensive performance of the lithium ion battery, the camber ratio A of the pole piece can be set to be 1% -3%.

Analyzing the cycle performance of the lithium ion battery in combination with fig. 5, it can be confirmed that the increase of the liquid retention amount B improves the cycle life of the lithium ion battery, and the cycle life performance of comparative example 2 in which micropores start in the positive electrode sheet material region, and examples 2 to 5 and examples 8 to 9 in which the arch-shaped through holes are provided in the positive electrode sheet material region are significantly superior to that of comparative example 1; it is worth noting, however, that the cycle performance test of example 3 is consistent with the change trend of comparative example 2, and only shows weak cycle performance advantages, and therefore, the results of the rate test in table 2 can prove that the preferred camber ratio a of the lithium ion battery pole piece in the example of the present invention is 2% -3%.

Arch width H comparative experiments were performed. Comparative example 1, arching ratio a and example 5 and examples 8 to 14, which have the same solid electrolyte composition but different arching widths, were set, and liquid retention amount B was measured and subjected to a rate test, respectively. The results of the experiment are shown in table 3 below.

Table 3

The utility model discloses the size of a dimension of arch through-hole changes along with the change of arch width among the technical scheme, and is corresponding, and the flow cross section area that follow-up lithium ion preparation in-process electrolyte was soaked also changes along with it, and then influences the guarantor's liquid volume of battery, infiltration efficiency and infiltration effect. It will be appreciated that only the proper width of the dome will provide the cell with the best overall performance. From table 3, it can be confirmed that when the dome width does not exceed 3mm, the battery rate influence is within 1%; when the dome width exceeds 3mm, battery rate performance may be reduced. Therefore, in order to maintain the overall performance of the lithium ion battery, the arch width of the arch-shaped through hole on the pole piece is preferably set to be 1mm to 3mm.

And carrying out a lithium ion battery formation method treatment temperature comparison experiment. The camber ratio A and the camber width B of the pole piece were set to be the same, but the formation treatment temperatures were different in examples 5 and 15 to 23, and the liquid retention amount B was measured and the rate test was performed, and the experimental results are shown in Table 4 below.

Table 4

From table 4, it can be verified that the formation method is implemented in the temperature range below 75 ℃, and the effect of the rate capability of the lithium ion battery of the embodiment of the present invention is the best. Meanwhile, analysis in combination with fig. 6 proves that the formation method improves the cycle life of the lithium ion battery, and the formation effect is best at the treatment temperature of less than 75 ℃. In particular, the capacity of unformed example 5 remained greatly reduced as the number of cycles increased, and example 22, which was formed at 75 ℃, showed cycle test results nearly identical to example 5; with the increase of the cycle number, the examples 15-21 formed at the temperature of less than 75 ℃ show more stable capacity retention rate, and the reduction is obviously smaller than that of the examples 5 and 22. Therefore, in consideration of the comprehensive performance of the lithium ion battery, the preferable formation treatment temperature of the lithium ion battery can be set to be less than 75 ℃.

In addition, the lithium ion battery cycle tests of comparative example 1, comparative example 2 and some examples were also performed, and the specific test conditions were as follows: (1) standing for 5min; (2) 0.5C CC to 4.35V, CV to 0.05C; (3) standing for 5min; (4) 0.5C DC to 3.0V; (5) cycle 1000cls; and (6) ending. The test results are shown in fig. 5 and 6.

It should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and the present invention is not limited thereto, and any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (7)

1. A pole piece for facilitating wetting, wherein the pole piece comprises a current collector; at least one side of mass flow body is equipped with the material district, the material district has seted up the arch through-hole on the one side of the mass flow body of laminating, the axial direction of arch through-hole is on a parallel with the mass flow body surface and be on a parallel with mass flow body coiling axis direction.

2. The pole piece facilitating infiltration according to claim 1, wherein the material area comprises a first material area and/or a second material area respectively disposed on two sides of the current collector, and at least one material area is provided with the arched through hole.

3. The pole piece facilitating infiltration according to claim 1, wherein the ratio of the surface area of the arched through hole to the surface area of the material area is 2% to 3% of an arched ratio A; wherein arch ratio A = D/C, on the one side of laminating the anodal mass flow body in material district, D is the surface area of arch curved surface on the arch through-hole in material district, and C is the surface area of material district and mass flow body contact part.

4. The pole piece facilitating infiltration of claim 1, wherein the arched width H of the arched through hole is 1mm to 3mm.

5. The pole piece for facilitating infiltration of claim 1, wherein the inner surface of the arched through hole is coated with a solid electrolyte layer.

6. The pole piece for facilitating wetting of claim 5, wherein the composition of the solid electrolyte layer comprises one of EC, FEC, PS, PST, VC, VEC.

7. A lithium ion battery comprising the wetting facilitating pole piece of any of claims 1-6.

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