WO2020007130A1

WO2020007130A1 - Negative electrode plate for lithium battery, and lithium battery

Info

Publication number: WO2020007130A1
Application number: PCT/CN2019/087216
Authority: WO
Inventors: 潘跃德; 李素丽; 李俊义; 徐延铭
Original assignee: 珠海冠宇电池有限公司
Priority date: 2018-07-06
Filing date: 2019-05-16
Publication date: 2020-01-09
Also published as: CN208385526U

Abstract

A negative electrode plate for a lithium battery, and a lithium battery. The negative electrode plate for a lithium battery comprises a current collector substrate that is a lithium ribbon, and further comprises a non-lithium metal foil extending in the length direction of the lithium ribbon and stacked on the lithium ribbon. One end of the non-lithium metal foil is exposed to the lithium ribbon in the width direction. The width of the portion of the non-lithium metal foil overlapping the lithium ribbon is greater than 1 mm and less than half of the width of the lithium ribbon. In the negative electrode plate of the present utility model, a lithium ribbon is used as a current collector substrate, and other non-lithium metal foils are stacked on at least one long side edge of the lithium ribbon, thereby enhancing the toughness and strength of the negative electrode plate, improving the processability of lithium metal negative electrodes, and also reducing the content of inactive materials in the negative electrode plate and improving the energy density of the lithium battery.

Description

Lithium battery negative sheet and lithium battery

Technical field

The utility model belongs to the technical field of lithium batteries, and more particularly, relates to a lithium battery negative plate and a lithium battery using the negative plate.

Background technique

With the gradual consumption of fossil energy and the intensification of environmental problems, the development of clean alternative energy sources has become an inevitable trend. Rechargeable batteries have been widely used in daily life, bringing convenience to people's lives, and also an important medium for solving energy problems and environmental problems. Among battery systems such as lead-acid batteries, nickel-metal hydride batteries, and lithium batteries, lithium batteries have the highest energy density. Graphite is currently the most widely used lithium battery anode material, but the theoretical capacity of graphite is only 372mAh / g. Lithium batteries using graphite as the anode material are gradually approaching the limit of energy density, and it is becoming increasingly difficult to meet people's requirements for high energy density. Demand for batteries.

Compared with graphite negative electrodes, the theoretical capacity of lithium metal negative electrodes is higher, which can reach 3860mAh / g. Using lithium metal negative electrodes to replace the current graphite negative electrodes to increase the energy density of lithium batteries is an important direction for the development of lithium battery technology. A lithium battery using a lithium metal negative electrode can obtain a higher energy density whether the positive electrode is matched with a currently mature positive electrode material system, a system using sulfur as a positive electrode active material, or a solid electrolyte system.

The active material of a lithium metal negative electrode is lithium metal. The lithium metal can be made into a lithium foil (belt) as a negative electrode sheet, or it can be combined with other metal foil materials to form a negative electrode sheet. For example, the Chinese invention patent application with the application number 201611205855.3, the Chinese invention patent application with the application number 201511031618.5, and the Chinese invention patent application with the application number 201611236487.9 all disclose negative electrodes containing lithium metal and are used in high energy density battery systems. . Among the above negative electrode sheets, some are formed by pressing a lithium band and a metal foil together to form a negative electrode sheet. The metal foil and the lithium band are equal in width or wider than the width of the lithium band. However, the metal foil is a non-active material of the negative electrode and has a large mass. It is not conducive to improving the energy density of lithium batteries; some use lithium foil as the current collector substrate of the negative electrode sheet directly, but because the lithium foil has a relatively soft texture, the use of the lithium foil as the negative electrode sheet in the subsequent cell manufacturing process is relatively large. The process is difficult. At the same time, there is also the problem of welding of the ears. The stability of the battery cell during use is poor and even easy to fail. How to further improve the existing lithium metal negative electrode, so that it has a higher energy density, and a more optimized structure are the key research and development contents of various battery manufacturers.

Utility model content

The object of the present invention is to provide a negative electrode sheet capable of improving the energy density of a lithium battery, and a lithium battery using the negative electrode sheet.

In order to achieve the above purpose, the present invention adopts the following technical solutions:

A lithium battery negative electrode sheet includes a current collector substrate, the current collector substrate is a lithium ribbon, and a non-lithium metal foil extending along the length direction of the lithium ribbon and stacked on the lithium ribbon, the non-lithium One end of a metal foil material is exposed to the lithium ribbon in a width direction, and a width of an overlapping portion of the non-lithium metal foil material and the lithium ribbon is greater than 1 mm and less than half of a width of the lithium ribbon.

More specifically, the current collector substrate is formed by stacking two lithium strips, and the non-lithium metal foil is located between the two lithium strips.

More specifically, the two ends of the lithium strip in the width direction are respectively stacked with the non-lithium metal foil.

More specifically, the lithium ribbon is a pure metal lithium foil or a foil made of a lithium composite material.

More specifically, the non-lithium metal foil is a copper strip, a carbon-coated copper strip, a nickel strip, or a carbon-coated nickel strip.

Preferably, the non-lithium metal foil is cut to form a foil tab connected to it as a whole.

Preferably, it further comprises an interlayer lithium band, the interlayer lithium band is stacked on the lithium band, and is arranged closely adjacent to the non-lithium metal foil, and the interlayer lithium band has a width equal to two non-lithium metal foils. The distance between the opposite trailing edges.

Preferably, a non-lithium metal foil is stacked at one end in the width direction of the lithium strip; further comprising an interlayer lithium strip, the interlayer lithium strip is stacked on the lithium strip and is in contact with the non-lithium metal foil Closely arranged, the width of the interlayer lithium strip is equal to the distance between the trailing edge of the non-lithium metal foil and the end edge of the lithium strip without the non-lithium metal foil.

Preferably, the thickness of the interlayer lithium ribbon is the same as the thickness of the non-lithium metal foil.

More specifically, the lithium ribbon has a single-layer structure, or a multilayer structure formed by stacking a lithium layer and a lithium composite material layer, or a multilayer structure formed by alternately stacking multiple lithium layers and lithium composite material layers , Or a multilayer structure formed by stacking lithium composite layers of different components.

A lithium battery includes a positive electrode sheet, a separator, and a negative electrode sheet, and the negative electrode sheet is the foregoing negative electrode sheet of a lithium battery.

It can be known from the above technical solutions that the negative electrode sheet of the present invention uses a lithium ribbon as a current collector substrate, and copper foil, nickel foil, and other non-metallic materials are stacked on the surface of at least one long side (at least one end in the width direction) of the lithium ribbon. Compared with lithium metal foil, which uses lithium foil as the current collector's negative electrode sheet alone, compounding other metal foil materials can make the negative electrode sheet have certain toughness, increase strength, and improve the processing performance of lithium metal negative electrode. At the same time, because the lithium ribbon is both the current collector and the negative electrode active material of the negative electrode sheet, other metal foils are only stacked on a part of the lithium ribbon along the length direction, and the width is smaller than the width of the lithium ribbon, thereby minimizing the battery negative electrode. The content of inactive materials has achieved an increase in the energy density of lithium batteries. In a preferred solution, the metal foil can also be die-cut to form the foil tabs, and the hard tabs are directly welded to the foil tabs when the electrodes are made. The integrated structure of the foil tabs and the metal foil solves the existing problem. Some lithium metal anodes have welding problems with the tabs.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to explain the embodiments of the present invention more clearly, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without paying creative labor.

FIG. 1 is a schematic structural diagram of Embodiment 1 of the present invention;

2 is a schematic diagram of applying the negative electrode sheet of Example 1 to a monopole winding process;

Figure 3 is a schematic diagram of the welding of foil tabs and hard tabs;

4 is a schematic diagram of applying the negative electrode sheet of Example 1 to a multi-pole winding process;

5 is a schematic diagram of the negative electrode sheet of Example 1 applied to a lamination process after die cutting;

6 is a cross-sectional view taken along line A in FIG. 5;

7 is a cross-sectional view taken along line B in FIG. 5;

8 is a schematic structural diagram of Embodiment 2 of the present invention;

9 is a sectional view of Embodiment 2 of the present invention;

10 is a schematic structural diagram of Embodiment 3 of the present invention;

FIG. 11 is a schematic structural diagram of Embodiment 4 of the present invention.

detailed description

The following describes the present utility model in detail with reference to the drawings. In detailing the embodiments of the present utility model, for convenience of explanation, the drawings showing the structure of the device will not be partially enlarged according to general proportions, and the schematic diagrams are merely examples, which are not shown here. The scope of protection of the utility model should be limited. It should be noted that the drawings are in simplified form and all use inaccurate proportions, which are only used to facilitate and clearly explain the purpose of the embodiments of the present invention.

Example 1

As shown in FIG. 1, the negative electrode sheet of a lithium battery includes a lithium band 1 and a non-lithium metal foil 2. The non-lithium metal foil 2 extends along the length of the lithium band 1 and is stacked on an edge portion of a long side of the lithium band 1. On the other hand, one end of the non-lithium metal foil is exposed to the lithium strip 1 in the width direction, and the lithium strip 1 is a current collector substrate of the negative electrode sheet of the lithium battery. There are two lithium strips 1 in this embodiment, and a non-lithium metal foil 2 is sandwiched between the two lithium strips 1. For the convenience of description, one end of the non-lithium metal foil 2 exposed on the lithium strip 1 is defined as a head, and the other end thereof is a tail, and the head is an area reserved for welding hard pole ears. The long side of the lithium band refers to the side of the lithium band on the same side as the tab, and the side opposite to the tab. Since the non-lithium metal foil 2 is stacked on the lithium strip 1, there is an overlap between the non-lithium metal foil 2 and the lithium strip 1. The width l of the overlapped portion is greater than 1 mm and less than half the width 10 of the lithium strip 1 (FIG. 7) . The width of the non-lithium metal foil 2 can be set to 10 mm to 100 mm as required, and preferably 20 mm to 100 mm.

The lithium strip itself, as a metal, has the function of a conductive element, can play the role of a negative electrode active material, and can also be used as a current collector substrate, thereby eliminating the copper foil, nickel foil and other foil materials used as a current collector substrate in a conventional negative electrode sheet. The content of the inactive material in the negative electrode sheet is reduced, which is beneficial to improve the energy density of the battery. The lithium strip of this embodiment may be a pure metal lithium foil or a foil made of a lithium composite material. The lithium composite material is metal lithium and aluminum, magnesium, boron, silicon, indium, zinc, silver, calcium, and manganese. In binary or multicomponent alloys formed by one or more of the elements, the mass percentage content of other elements in the lithium composite material may be 0.1% to 40%.

The non-lithium metal foil 2 stacked on the edge surface of the lithium strip may be a copper strip, a carbon-coated copper strip, a nickel strip, a carbon-coated nickel strip, or other metal strips. A composite structure composed of a lithium strip and other metal strips can improve lithium The processing performance of the belt, especially the processing performance of the tab part. Moreover, it is preferable to use a metal strip and a lithium strip that can be used to make foil tabs, and use die cutting to directly form non-lithium metal foil on the foil tabs, which is convenient for subsequent tab preparation. Welding of hard poles in the process. When non-lithium metal foils use copper or nickel strips, the thickness of the copper or nickel strips can be 3 to 20 microns; when non-lithium metal foils use carbon-coated copper strips or carbon-nickel strips, the metal strips are coated. The thickness of the carbon layer may be 0.1 μm to 3 μm. Use carbon coated copper tape or carbon coated nickel tape. After die-cutting the corresponding shape of the pole pieces, before welding the hard pole ears, wipe the carbon coating layer on the surface of the foil pole ears.

The negative electrode sheet of the lithium battery in this embodiment is formed by stacking two lithium strips and a non-lithium metal foil. The non-lithium metal foil is located between the two lithium strips, and the thickness of the lithium strip may be 1 micrometer to 100 micrometers. The thickness is preferably 10 micrometers to 50 micrometers, and the thickness difference between the two lithium ribbons does not exceed 10 micrometers. The thickness of the non-lithium metal foil is 3 to 20 microns. When preparing the negative electrode of a lithium battery, a lithium strip and a non-lithium metal foil (such as a copper strip) can be rolled together before rolling another lithium strip; or a lithium strip and a non-lithium metal foil ( After being rolled together, such as copper strips, another lithium strip is plated by vacuum coating.

FIG. 2 is a schematic diagram of an embodiment in which the negative electrode sheet of this embodiment is used to prepare a negative electrode sheet of a wound cell. As shown in FIG. 2, a foil is formed on a non-lithium metal foil by die cutting. Material pole 3, the negative electrode sheet is wound together with the separator and the positive electrode sheet to form a winding core. As shown in FIG. 3, after forming the foil tab 3 on the non-lithium metal foil, the hard tab can be directly welded to the foil tab 3. The hard pole ears include a metal strip 4 (a nickel strip or a copper-plated nickel strip) and a pole ear glue 5. The metal strip 4 is welded to the foil pole ears 3 by a laser welding process. FIG. 4 is a schematic diagram of another embodiment in which the negative electrode sheet of this embodiment is used to prepare a negative electrode sheet of a wound cell. As shown in FIG. 4, a plurality of non-lithium metal foils are formed by die cutting. The foil tabs 3 are evenly spaced, and the negative electrode sheet is wound together with the separator and the positive electrode sheet to form an electric core. FIG. 5, FIG. 6 and FIG. 7 are schematic diagrams of an embodiment in which the negative electrode sheet of this embodiment is used to prepare a negative electrode sheet of a laminated cell. As shown in FIG. 5, FIG. 6 and FIG. Die-cut into a plurality of small pole pieces, each of which has a foil tab 3 integrally connected with a non-lithium metal foil, and a negative electrode sheet, a separator, and a positive electrode sheet are sequentially stacked to form a battery core.

The battery is placed in a battery case (aluminum plastic case or metal case) and assembled with the electrolyte to form a battery. The positive electrode of the battery is a conventional positive electrode, including a positive current collector (aluminum foil or carbon-coated aluminum foil) and coated in Paste the positive electrode material on the surface of the current collector. The positive electrode material paste includes a positive electrode active material, a binder, and a conductive agent. The positive electrode active material may be lithium cobaltate, lithium iron phosphate, nickel cobalt aluminum ternary material, nickel cobalt manganese ternary material, vanadium pentoxide, elemental sulfur. Or air; the conductive agent can be graphite, graphene, carbon nanotubes, carbon fibers, conductive carbon black (SuperP), acetylene black, Ketjen black, etc .; the binder can be polyvinylidene fluoride (PVDF), polytetrafluoride Ethylene (PTFE), CMC / SBR, etc .; the electrolyte may be an electrolyte such as an ester electrolyte, an ether electrolyte, an ionic liquid, or a gel electrolyte or a solid electrolyte.

Example 2

8 and FIG. 9, this embodiment is different from Embodiment 1 in that in this embodiment, a non-lithium metal foil 2 and a non-lithium metal foil are stacked on the edge surfaces of the two long sides of the lithium strip 1 Both ends of the material 2 and the lithium ribbon 1 have overlapping portions.

Example 3

As shown in FIG. 10, this embodiment is different from Embodiment 1 in that this embodiment further includes an interlayer lithium band 6, and the interlayer lithium band 6 is stacked on the lithium band 1 and is closely related to the non-lithium metal foil 2 The interlayer lithium ribbon 6 and the non-lithium metal foil 2 are arranged between the lithium ribbons 1 on both sides of the interlayer lithium ribbon. The thickness of the interlayer lithium ribbon 6 is the same as that of the non-lithium metal foil 2 and the width is equal to the non-lithium metal foil The distance between the trailing edge of the material 2 and the end edge of the lithium strip 1 where the non-lithium metal foil is not provided. By providing the interlayer lithium ribbon 6 with the same thickness as the non-lithium metal foil 2, the surface flatness of the negative electrode sheet can be kept consistent, so that the unevenness of the surface of the negative electrode sheet will not adversely affect the battery performance.

Example 4

As shown in FIG. 11, this embodiment is different from Embodiment 2 in that this embodiment further includes an interlayer lithium band 6, and the interlayer lithium band 6 and the non-lithium metal foil 2 are disposed on one of the lithium bands 1 on both sides thereof. Meanwhile, the thickness of the interlayer lithium strip 6 is the same as the thickness of the non-lithium metal foil 2 and the width is equal to the distance between the opposite edges of the two non-lithium metal foils 2.

Example 5

This embodiment differs from Embodiment 1 in that the negative electrode of the lithium battery of this embodiment is composed of a lithium strip and a non-lithium metal foil, and the non-lithium metal foil is stacked on a long side of the lithium strip. . Preferably, when there is only one lithium belt, an interlayer lithium belt can also be stacked on the lithium belt, and the interlayer lithium belt and the non-lithium metal foil are closely adjacent to each other, so that the surface of the negative electrode sheet is kept flat.

Of course, the technical concept of the present invention is not limited to the above embodiments, and many different specific solutions can be obtained according to the concept of the present invention. For example, in the foregoing embodiment, the lithium ribbon has a single-layer structure, but the lithium ribbon may also be Multi-layer structure, for example, a lithium ribbon is formed by stacking a lithium layer and a lithium composite material layer, or alternately stacking multiple lithium layers and lithium composite material layers, or stacking lithium composite material layers of different components; such as this Such changes and equivalent transformations should be included in the scope of the present invention.

Claims

A negative electrode sheet for a lithium battery includes a current collector substrate, the current collector substrate is a lithium band, and further includes a non-lithium metal extending along the length of the lithium band and stacked on the lithium band. Foil, one end of the non-lithium metal foil is exposed to the lithium strip in a width direction, and a width of an overlapping portion of the non-lithium metal foil and the lithium strip is greater than 1 mm and less than half of a width of the lithium strip .
The negative electrode sheet for a lithium battery according to claim 1, wherein the current collector substrate is formed by stacking two lithium strips, and the non-lithium metal foil is located between the two lithium strips.
The negative electrode sheet for a lithium battery according to claim 1 or 2, wherein the two ends of the lithium strip in the width direction are respectively stacked with the non-lithium metal foil.
The negative electrode sheet for a lithium battery according to claim 1 or 2, wherein the lithium strip is a pure metal lithium foil or a foil made of a lithium composite material.
The negative electrode sheet for a lithium battery according to claim 1, wherein the non-lithium metal foil is a copper strip, a carbon-coated copper strip, a nickel strip, or a carbon-coated nickel strip.
The negative electrode sheet for a lithium battery according to claim 1 or 2, or 5, wherein the non-lithium metal foil material is cut to form a foil material tab connected to the non-lithium metal foil material.
The negative electrode sheet for a lithium battery according to claim 3, further comprising an interlayer lithium band, wherein the interlayer lithium band is stacked on the lithium band, and is arranged in close proximity to the non-lithium metal foil, The width of the interlayer lithium ribbon is equal to the distance between the opposite tail edges of the two non-lithium metal foils.
The negative electrode sheet for a lithium battery according to claim 7, wherein the thickness of the interlayer lithium ribbon is the same as the thickness of the non-lithium metal foil.
The negative electrode sheet for a lithium battery according to claim 1 or 2, characterized in that: a non-lithium metal foil is stacked on one end of the lithium strip in the width direction; further comprising an interlayer lithium strip, the interlayer lithium strip is stacked on The lithium strip is arranged close to the non-lithium metal foil, and the width of the interlayer lithium strip is equal to the tail edge of the non-lithium metal foil and the end edge of the lithium strip without the non-lithium metal foil. the distance between.
The negative electrode sheet for a lithium battery according to claim 9, wherein the thickness of the interlayer lithium ribbon is the same as the thickness of the non-lithium metal foil.
The negative electrode sheet for a lithium battery according to claim 4, characterized in that the lithium ribbon has a single-layer structure, or a multilayer structure formed by stacking a lithium layer and a lithium composite material layer, or a multiple lithium layer and A multilayer structure in which lithium composite material layers are alternately stacked, or a multilayer structure in which lithium composite material layers of different components are stacked.
A lithium battery includes a positive electrode sheet, a separator, and a negative electrode sheet, wherein the negative electrode sheet is the negative electrode sheet of a lithium battery according to any one of claims 1 to 11.