WO2024086986A1

WO2024086986A1 - Anisotropic positive electrode aluminum current collector and preparation method therefor, and electrochemical device

Info

Publication number: WO2024086986A1
Application number: PCT/CN2022/127104
Authority: WO
Inventors: 王成豪; 李学法; 张国平
Original assignee: 扬州纳力新材料科技有限公司
Priority date: 2022-10-24
Filing date: 2022-10-24
Publication date: 2024-05-02

Abstract

Provided in the present application is a method for preparing an anisotropic positive electrode aluminum current collector, the method comprising the following steps: providing an electrolytic aluminum solution, and adding an aluminum ingot to the electrolytic aluminum solution to obtain a melt, wherein the element components of the melt comprise Si, Fe, Cu, Mn, Ti, Ni, Cr and Al; adding a refining agent to the melt and refining same to obtain molten aluminum; casting and rolling the molten aluminum by using a casting-rolling mill to obtain a blank; cold-rolling the blank, and then subjecting same to homogenizing annealing to obtain a first intermediate; and subjecting the first intermediate to recrystallization annealing to obtain an anisotropic positive electrode aluminum current collector, wherein the anisotropic positive electrode aluminum current collector is provided with a first heat transfer body and a second heat transfer body. The anisotropic positive electrode aluminum current collector prepared in the present application has high safety. Further provided in the present application are an anisotropic positive electrode aluminum current collector and an electrochemical device.

Description

Anisotropic positive electrode aluminum current collector and preparation method thereof, and electrochemical device

Technical Field

The present application relates to the field of battery technology, and in particular to an anisotropic positive aluminum current collector and a preparation method thereof, and an electrochemical device.

Background technique

At present, high-purity aluminum foil is usually used as the positive electrode current collector of electrochemical devices (such as batteries). However, the thermal conductivity of aluminum foil prepared by traditional processes is almost the same in all directions. This characteristic causes the battery body to generate heat in all directions after the aluminum foil is used inside the battery, resulting in the heat inside the battery being unable to be discharged in time, increasing the safety risk of the battery.

Summary of the invention

Based on this, it is necessary to provide a method for preparing an anisotropic positive aluminum current collector that can improve safety.

In addition, it is also necessary to provide an anisotropic positive electrode aluminum current collector.

In addition, it is also necessary to provide an electrochemical device.

At least one embodiment of the present application provides a method for preparing an anisotropic positive aluminum current collector, comprising the following steps:

Providing an electrolytic aluminum solution, and adding an aluminum ingot to the electrolytic aluminum solution to obtain a melt, wherein the element components of the melt include: Si, Fe, Cu, Mn, Ti, Ni, Cr and Al;

adding a refining agent into the melt for refining to obtain aluminum liquid;

Using a casting and rolling machine to cast the aluminum liquid to obtain a billet;

cold rolling the blank and then performing homogenization annealing to obtain a first intermediate; and

Performing recrystallization annealing on the first intermediate to obtain an anisotropic positive electrode aluminum current collector;

Among them, in the processing direction, the anisotropic positive aluminum current collector is provided with a first heat transfer body, in the lateral direction perpendicular to the processing direction, the anisotropic positive aluminum current collector is provided with a second heat transfer body, and the anisotropic positive aluminum current collector is also provided with a heat insulator, and the heat insulator is perpendicular to the first heat transfer body and the second heat transfer body.

In some embodiments, the mass percentages of the elemental components of the melt are: Si: 0.1% to 0.15%, Fe: 0.45% to 0.5%, Cu: 0.1% to 0.15%, Mn: 1.1% to 1.2%, Ti: 0.02% to 0.04%, Ni: 0.02% to 0.04%, Cr: 0.02% to 0.04%, and the balance is Al.

In some embodiments, after the first intermediate is subjected to recrystallization annealing to obtain a second intermediate, the preparation method further comprises the following steps:

The second intermediate is rolled to a predetermined thickness to obtain the anisotropic positive electrode aluminum current collector.

In some embodiments, the preparation method comprises at least one of the following (1) to (4):

(1) The temperature of the homogenization annealing is 440° C. to 490° C.;

(2) The homogenization annealing time is 20h to 30h;

(3) The temperature of the recrystallization annealing is 270° C. to 330° C.;

(4) The recrystallization annealing time is 12h to 19h.

In some embodiments, after obtaining the aluminum liquid and before using a casting and rolling mill to cast the aluminum liquid, the preparation method further includes the following steps:

Pour the aluminum liquid into a static furnace, and control the temperature in the static furnace to be 750° C. to 760° C.;

The aluminum liquid in the static furnace is fed into a launder, and aluminum-titanium-boron wire is added in reverse to perform grain refinement;

Degassing the aluminum liquid in the launder with pure nitrogen or pure argon in a degassing box; and

The degassed aluminum liquid is filtered and purified.

At least one embodiment of the present application provides an anisotropic positive aluminum current collector, wherein the anisotropic positive aluminum current collector contains nickel metal and chromium metal, wherein a first heat transfer body is provided in the anisotropic positive aluminum current collector in a processing direction, and a second heat transfer body is provided in the anisotropic positive aluminum current collector in a lateral direction perpendicular to the processing direction, and an insulator is also provided in the anisotropic positive aluminum current collector, wherein the insulator is perpendicular to both the first heat transfer body and the second heat transfer body.

In some of the embodiments, the anisotropic positive electrode aluminum current collector further contains Fe, Cu, Mn, Ti and Al elements.

In some embodiments, the difference in thermal conductivity of the anisotropic positive aluminum current collector in various directions is greater than 0.5%.

In some of the embodiments, in the anisotropic positive aluminum current collector, the total mass fraction of the nickel metal and the chromium metal is less than 1%.

In some embodiments, the anisotropic positive aluminum current collector includes at least one of the following (1) to (2):

(1) The thickness of the anisotropic positive aluminum current collector is 4 μm to 20 μm;

(2) The surface dyne value of the anisotropic positive electrode aluminum current collector is greater than 20.

In some embodiments, the anisotropic positive aluminum current collector includes at least one of the following (1) to (5):

(1) The puncture strength of the anisotropic positive aluminum current collector is ≥50 gf;

(2) In the processing direction, the tensile strength of the anisotropic positive aluminum current collector is ≥100 MPa;

(3) In the transverse direction perpendicular to the processing direction, the tensile strength of the anisotropic positive electrode aluminum current collector is ≥100 MPa;

(4) In the processing direction, the elongation of the anisotropic positive aluminum current collector is ≥ 1%;

(5) In the transverse direction perpendicular to the processing direction, the elongation of the anisotropic positive electrode aluminum current collector is ≥ 1%.

At least one embodiment of the present application provides an electrochemical device, including the anisotropic positive aluminum current collector prepared by the preparation method or including the anisotropic positive aluminum current collector.

The present application dopes a certain amount of nickel metal and chromium metal into aluminum metal, and uses nickel metal and chromium metal to change the lattice arrangement direction of aluminum metal during the rolling process, so that the aluminum crystals are elongated in the machining direction (MD) and the transverse direction (TD), so as to respectively establish the first heat transfer body and the second heat transfer body, and establish the heat insulator perpendicular to both the first heat transfer body and the second heat transfer body. When the current collector of the anisotropic positive aluminum current collector is connected to the pole ear in the electrochemical device, the anisotropic positive aluminum current collector can not only reduce the heat conductivity at the pole ear position, but also can conduct the heat generated inside the battery through the first heat transfer body and the second heat transfer body, thereby avoiding excessive temperature inside the electrochemical device, thereby improving the safety of the electrochemical device.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better describe and illustrate the embodiments and/or examples of the present application, reference may be made to one or more drawings. The additional details or examples used to describe the drawings should not be considered as limiting the scope of the disclosed application, the embodiments and/or examples currently described, and any of the best modes of these applications currently understood.

FIG1 is a flow chart of the preparation of an anisotropic positive aluminum current collector provided in the present application.

Detailed ways

In order to facilitate the understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present application are given in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present application belongs. The terms used herein in the specification of the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application. The term "and/or" used herein includes any and all combinations of one or more related listed items.

Referring to FIG. 1 , at least one embodiment of the present application provides a method for preparing an anisotropic positive aluminum current collector, comprising the following steps:

Step S11, providing an electrolytic aluminum solution, and adding aluminum ingots into the electrolytic aluminum solution to obtain a melt.

Specifically, an electrolytic aluminum melt is provided, the electrolytic aluminum solution is sent to a smelting furnace, and aluminum ingots accounting for 20%-40% of the total weight of the electrolytic aluminum melt are added to the smelting furnace to obtain a melt, and the temperature of the melt is controlled to be 750°C to 780°C.

The elements of the melt include Si, Fe, Cu, Mn, Ti, Ni, Cr and Al. In one embodiment, the mass percentages of the elements of the melt are: Si: 0.1% to 0.15%, Fe: 0.45% to 0.5%, Cu: 0.1% to 0.15%, Mn: 1.1% to 1.2%, Ti: 0.02% to 0.04%, Ni: 0.02% to 0.04%, Cr: 0.02% to 0.04%, and the balance is Al.

Step S12: adding a refining agent into the melt for refining to obtain molten aluminum.

Specifically, pure nitrogen or pure argon is used to spray a refining agent into the melt for refining, and the melt is fully stirred for 8 minutes to 10 minutes to obtain aluminum liquid, which is then allowed to stand for 15 minutes to 25 minutes to remove scum on the surface of the aluminum liquid, and the aluminum liquid after removing the scum is poured into a standing furnace, and the temperature in the standing furnace is controlled to be 750°C to 760°C; the aluminum liquid in the standing furnace is sent to a flow trough, and aluminum-titanium-boron wire is added in reverse to refine the grains, and then the aluminum liquid in the flow trough is degassed with pure nitrogen or pure argon in a degassing box, and after degassing, the aluminum liquid is filtered and purified with a foam ceramic filter.

Step S13, using a casting and rolling machine to cast the aluminum liquid to obtain a billet.

Specifically, the purified aluminum liquid is sent to a casting and rolling mill for casting and rolling to produce billets with a thickness of 5.0 mm to 10.0 mm.

Step S14, cold rolling the blank and then performing homogenization annealing to obtain a first intermediate.

Specifically, the billet with a thickness of 5.0 mm to 10.0 mm is cold rolled to a thickness of 3.0 mm to 5.0 mm, and the cold rolled billet is subjected to homogenization annealing.

In one embodiment, the temperature of the homogenization annealing may be 440° C. to 490° C. In one embodiment, the time of the homogenization annealing may be 20 h to 30 h.

Step S15, performing recrystallization annealing on the first intermediate to obtain a second intermediate.

In one embodiment, before performing recrystallization annealing on the first intermediate, the first intermediate may be cold rolled to reduce the thickness of the first intermediate from 3.0 mm to 5.0 mm to 0.2 mm to 0.6 mm.

In one embodiment, the temperature of the recrystallization annealing may be 270° C. to 330° C. In one embodiment, the time of the recrystallization annealing may be 12 h to 19 h.

Step S16: rolling the second intermediate to a predetermined thickness to obtain an anisotropic positive electrode aluminum current collector.

The predetermined thickness can be set according to actual needs. In one embodiment, the predetermined thickness can be 4 μm to 20 μm. That is, the thickness of the anisotropic positive aluminum current collector can be 4 μm to 20 μm.

In which, in the processing direction (MD), the anisotropic positive aluminum current collector is provided with a first heat transfer body, in the transverse direction (TD) perpendicular to the processing direction (MD), the anisotropic positive aluminum current collector is provided with a second heat transfer body, and the anisotropic positive aluminum current collector is also provided with a heat insulator, and the heat insulator is perpendicular to both the first heat transfer body and the second heat transfer body.

During the rolling process of aluminum metal, the nickel metal and chromium metal inside the aluminum metal are compressed to form a layer interface in the thickness direction of the aluminum metal in advance, and then the aluminum crystals grow in the MD and TD directions instead of the previous growth in the thickness direction, forming the first heat transfer body and the second heat transfer body respectively. When the current collector of the anisotropic positive aluminum current collector is connected to the tab in the electrochemical device, the heat generated inside the electrochemical device will diffuse to the outside along the first heat transfer body and the second heat transfer body.

In one embodiment, the difference in thermal conductivity of the anisotropic positive aluminum current collector in various directions is greater than 0.5%.

In one embodiment, in the anisotropic positive aluminum current collector, the total mass fraction of the nickel metal and the chromium metal is less than 1%.

In one embodiment, the surface dyne value of the anisotropic positive electrode aluminum current collector is greater than 20.

In one embodiment, the puncture strength of the anisotropic positive aluminum current collector is ≥50 gf.

In one embodiment, in the machine direction (MD), the tensile strength of the anisotropic positive aluminum current collector is ≥100 MPa. In one embodiment, in the transverse direction (TD) perpendicular to the machine direction (MD), the tensile strength of the anisotropic positive aluminum current collector is ≥100 MPa.

In one embodiment, in the machine direction (MD), the elongation of the anisotropic positive aluminum current collector is ≥ 1%. In one embodiment, in the transverse direction (TD) perpendicular to the machine direction (MD), the elongation of the anisotropic positive aluminum current collector is ≥ 1%.

At least one embodiment of the present application provides an anisotropic positive aluminum current collector prepared by the above-mentioned preparation method, and the element components of the anisotropic positive aluminum current collector include: Si, Fe, Cu, Mn, Ti, Ni, Cr and Al.

In one embodiment, the mass percentages of the elemental components of the anisotropic positive aluminum current collector are: Si: 0.1% to 0.15%, Fe: 0.45% to 0.5%, Cu: 0.1% to 0.15%, Mn: 1.1% to 1.2%, Ti: 0.02% to 0.04%, Ni: 0.02% to 0.04%, Cr: 0.02% to 0.04%, and the balance is Al.

In one embodiment, the thickness of the anisotropic positive aluminum current collector is 4 μm to 20 μm.

At least one embodiment of the present application provides an electrochemical device, the electrochemical device comprising the anisotropic positive aluminum current collector prepared by the above preparation method or comprising the above anisotropic positive aluminum current collector. In one embodiment, the electrochemical device may be a battery. Specifically, the battery may be a secondary battery. More specifically, the secondary battery may be a non-aqueous secondary battery.

Specifically, the role of nickel metal and chromium metal in the present application is as follows: during the rolling process of aluminum metal, the nickel metal and chromium metal inside the aluminum metal are compressed to form a layer interface in the thickness direction of the aluminum metal in advance, and then the aluminum crystals grow in the MD and TD directions instead of the previous growth in the thickness direction, forming the first heat transfer body and the second heat transfer body respectively. When the current collector of the anisotropic positive aluminum current collector is connected to the pole ear in the electrochemical device, the heat generated inside the electrochemical device will diffuse to the outside along the first heat transfer body and the second heat transfer body.

In addition, the operating temperature of the battery prepared with the anisotropic positive aluminum current collector in the present application is 5°C to 10°C lower than the operating temperature of the battery prepared with traditional aluminum foil, which shows that the battery prepared with the anisotropic positive aluminum current collector in the present application has better safety and cycle life than the battery prepared with traditional aluminum foil.

The present application is further described below through specific examples and comparative examples.

Example 1

(1) The electrolytic aluminum melt is sent to a smelting furnace, and aluminum ingots accounting for 30% of the total weight of the electrolytic aluminum melt are added. The melt temperature is controlled to be 770°C, and the mass percentages of the elements in the melt are adjusted to Si: 0.13%, Fe: 0.45%, Cu: 0.14%, Mn: 1.1%, Ti: 0.025%, Ni: 0.027%, Cr: 0.021%, and the balance is Al.

(2) Use pure nitrogen or pure argon to spray refining agent into the melt for refining, stir it thoroughly and evenly, the refining time is 9 minutes, then let it stand for 20 minutes, remove the scum on the surface of the aluminum liquid, pour it into the standing furnace, and control the temperature in the standing furnace to 755℃.

(3) The aluminum liquid in the static furnace is sent into a flow trough, and aluminum titanium boron wire is added in reverse to refine the grains. Then, the aluminum liquid is degassed with pure nitrogen or pure argon in a degassing box. After degassing, the aluminum liquid is filtered and purified with a foam ceramic filter.

(4) The purified aluminum liquid is sent to a casting and rolling mill to cast and roll out a billet with a thickness of 8.0 mm.

(5) The above-mentioned billet with a thickness of 8.0 mm is cold rolled to obtain a billet with a thickness of 4.0 mm.

(6) The 4.0 mm thick blank in (5) is subjected to homogenization annealing, wherein the homogenization annealing temperature is 470° C. and the homogenization annealing time is 25 h.

(7) The annealed billet is cold rolled to a thickness of 0.5 mm, and then subjected to recrystallization annealing, wherein the temperature of the recrystallization annealing is 300° C. and the recrystallization annealing time is 15 h.

(8) The thickness of the billet after recrystallization annealing is rolled to 12 μm to obtain an anisotropic positive electrode aluminum current collector.

Comparative Example 1

(1) The electrolytic aluminum melt is sent to a smelting furnace, and aluminum ingots accounting for 30% of the total weight of the electrolytic aluminum melt are added. The melt temperature is controlled to be 770°C, and the mass percentages of the elements in the melt are adjusted to Si: 0.15%, Fe: 0.48%, Cu: 0.13%, Mn: 1.3%, Ti: 0.03%, and the balance is Al.

(8) The thickness of the billet after recrystallization annealing is rolled to 12 μm to obtain a positive electrode aluminum foil current collector.

The anisotropic positive aluminum current collector prepared in Example 1 and the positive aluminum foil current collector prepared in Comparative Example 1 were respectively prepared into ternary lithium batteries with a capacity of 100AH, and the cycle life and operating temperature of the ternary lithium batteries were tested respectively. The test results are shown in Table 1 below.

Table 1

As can be seen from Table 1 above, the ternary lithium battery prepared by the anisotropic positive aluminum current collector in Example 1 has a higher cycle life and a lower operating temperature than the ternary lithium battery prepared by the positive aluminum foil current collector in Comparative Example 1. This shows that compared with the ternary lithium battery prepared by the positive aluminum foil current collector in Comparative Example 1, the ternary lithium battery prepared by the anisotropic positive aluminum current collector in Example 1 has a better heat dissipation effect.

The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

A method for preparing an anisotropic positive aluminum current collector, characterized by comprising the following steps:

Providing an electrolytic aluminum solution, and adding an aluminum ingot to the electrolytic aluminum solution to obtain a melt, wherein the element components of the melt include: Si, Fe, Cu, Mn, Ti, Ni, Cr and Al;

adding a refining agent into the melt for refining to obtain aluminum liquid;

Using a casting and rolling machine to cast the aluminum liquid to obtain a billet;

cold rolling the blank and then performing homogenization annealing to obtain a first intermediate; and

Performing recrystallization annealing on the first intermediate to obtain an anisotropic positive electrode aluminum current collector;

Among them, in the processing direction, the anisotropic positive aluminum current collector is provided with a first heat transfer body, in the lateral direction perpendicular to the processing direction, the anisotropic positive aluminum current collector is provided with a second heat transfer body, and the anisotropic positive aluminum current collector is also provided with a heat insulator, and the heat insulator is perpendicular to the first heat transfer body and the second heat transfer body.
The method for preparing an anisotropic positive aluminum current collector according to claim 1, characterized in that the mass percentages of the elemental components of the melt are: Si: 0.1% to 0.15%, Fe: 0.45% to 0.5%, Cu: 0.1% to 0.15%, Mn: 1.1% to 1.2%, Ti: 0.02% to 0.04%, Ni: 0.02% to 0.04%, Cr: 0.02% to 0.04%, and the remainder is Al.
The method for preparing an anisotropic positive aluminum current collector according to any one of claims 1 to 2, characterized in that after the first intermediate is subjected to recrystallization annealing to obtain a second intermediate, the preparation method further comprises the following steps:

The second intermediate is rolled to a predetermined thickness to obtain the anisotropic positive electrode aluminum current collector.
The method for preparing an anisotropic positive aluminum current collector according to any one of claims 1 to 2, characterized in that the preparation method comprises at least one of the following (1) to (4):

(1) The temperature of the homogenization annealing is 440° C. to 490° C.;

(2) The homogenization annealing time is 20h to 30h;

(3) The temperature of the recrystallization annealing is 270° C. to 330° C.;

(4) The recrystallization annealing time is 12h to 19h.
The method for preparing an anisotropic positive aluminum current collector according to any one of claims 1 to 2, characterized in that after obtaining the aluminum liquid and before using a casting and rolling mill to cast the aluminum liquid, the preparation method further comprises the following steps:

Pour the aluminum liquid into a static furnace, and control the temperature in the static furnace to be 750° C. to 760° C.;

The aluminum liquid in the static furnace is fed into a launder, and aluminum-titanium-boron wire is added in reverse to refine the grains;

Degassing the aluminum liquid in the launder with pure nitrogen or pure argon in a degassing box; and

The degassed aluminum liquid is filtered and purified.
An anisotropic positive aluminum current collector, characterized in that the anisotropic positive aluminum current collector contains nickel metal and chromium metal, in a processing direction, a first heat transfer body is provided in the anisotropic positive aluminum current collector, in a lateral direction perpendicular to the processing direction, a second heat transfer body is provided in the anisotropic positive aluminum current collector, and the anisotropic positive aluminum current collector is also provided with a heat insulator, and the heat insulator is perpendicular to both the first heat transfer body and the second heat transfer body.
The anisotropic positive aluminum current collector according to claim 6, characterized in that the anisotropic positive aluminum current collector also contains Fe, Cu, Mn, Ti and Al elements.
The anisotropic positive aluminum current collector according to claim 6, characterized in that the difference between the thermal conductivity coefficients of the anisotropic positive aluminum current collector in various directions is greater than 0.5%.
The anisotropic positive aluminum current collector according to claim 6 is characterized in that, in the anisotropic positive aluminum current collector, the total mass fraction of the nickel metal and the chromium metal is less than 1%.
The anisotropic positive aluminum current collector according to any one of claims 6 to 9, characterized in that the anisotropic positive aluminum current collector comprises at least one of the following (1) to (2):

(1) The thickness of the anisotropic positive aluminum current collector is 4 μm to 20 μm;

(2) The surface dyne value of the anisotropic positive electrode aluminum current collector is greater than 20.
The anisotropic positive aluminum current collector according to any one of claims 6 to 9, characterized in that the anisotropic positive aluminum current collector comprises at least one of the following (1) to (5):

(1) The puncture strength of the anisotropic positive aluminum current collector is ≥50 gf;

(2) In the processing direction, the tensile strength of the anisotropic positive aluminum current collector is ≥100 MPa;

(3) In the transverse direction perpendicular to the processing direction, the tensile strength of the anisotropic positive electrode aluminum current collector is ≥100 MPa;

(4) In the processing direction, the elongation of the anisotropic positive aluminum current collector is ≥ 1%;

(5) In the transverse direction perpendicular to the processing direction, the elongation of the anisotropic positive electrode aluminum current collector is ≥ 1%.
An electrochemical device, characterized in that it comprises an anisotropic positive aluminum current collector prepared by the preparation method according to any one of claims 1 to 5 or comprises an anisotropic positive aluminum current collector according to any one of claims 6 to 11.