JP7054456B2 - Secondary battery - Google Patents

Description

The present invention relates to a secondary battery. More specifically, the present invention relates to the structure of a negative electrode current collector constituting the negative electrode of the secondary battery.

Since secondary batteries such as lithium-ion secondary batteries and sodium-ion secondary batteries are lighter and have higher energy density than existing batteries, in recent years, so-called portable power supplies such as personal computers and mobile terminals, as well as vehicle drive power supplies. Is preferably used as a battery. Secondary batteries such as lithium-ion secondary batteries for this purpose are becoming more and more popular as high-output power sources for driving vehicles such as electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid vehicles (PHVs). Is expected.

As one form of this kind of secondary battery, a battery (so-called all-solid-state battery) in which a powdered solid electrolyte is used instead of a liquid electrolyte (electrolyte solution) can be mentioned. A secondary battery of this type typically comprises an electrode body having a structure in which a positive electrode and a negative electrode are superposed with a solid electrolyte layer interposed therebetween.

As a current collector constituting the negative electrode of this type of secondary battery, a current collector made of copper (Cu) is generally adopted. However, the Cu negative electrode current collector is a material containing sulfur in any of the solid electrolyte layer, the positive electrode and the negative electrode (hereinafter, referred to as "electrode" when positive and negative are not particularly distinguished) (for example, sulfur containing sulfide). In the presence of the system solid electrolyte), there is a problem that a new sulfide may be generated by the reaction between the sulfur component and Cu. The generated sulfide is not preferable because it causes an increase in electron conduction resistance (hereinafter referred to as "interface resistance") at the interface between the negative electrode current collector and the negative electrode active material layer.
Regarding this problem, Patent Document 1 discloses a Cu-made negative electrode current collector main body coated with WC (tungsten carbide), Ti, Cr, or the like. By applying a coating as disclosed in Patent Document 1 to the surface of the negative electrode current collector made of Cu, the contact between the negative electrode current collector and the sulfur-containing material is prevented, so that the interfacial resistance particularly in the negative electrode is increased. There are advantages such as suppressing the increase and improving the battery performance.

Japanese Unexamined Patent Publication No. 2012-49023

However, in the technique disclosed in Cited Document 1, although the coating prevents the direct contact between the negative electrode current collector made of Cu and the material containing sulfur, the negative electrode current collector Fine Cu pieces generated in the processing step (particularly, cutting process) may remain on the negative electrode current collector. Therefore, it is difficult to completely eliminate the possibility that the Cu piece reacts with the sulfur-containing material and the interfacial resistance is increased by the generated sulfide. Further, when the entire surface of the negative electrode current collector is coated, the metal (for example, Ti) used for the coating and the metal (for example, simply referred to as “terminal”) for external connection (hereinafter, also simply referred to as “terminal”) are used. , Al), in these connecting portions, different metals are in direct contact. In such a case, due to the difference in recrystallization temperature between different metals, there is a possibility that the coated negative electrode current collector and the terminal cannot be efficiently ultrasonically welded. These are not preferable because it may hinder the improvement of the battery performance of the secondary battery and the maintenance of the secondary battery in a good condition.
Therefore, the present invention is a secondary battery provided with an electrode body containing a substance containing sulfur in order to fundamentally solve these problems, and a negative electrode having a configuration in which a reaction between copper and a sulfur component cannot occur at all. It is an object of the present invention to provide a secondary battery equipped with a current collector.

The present inventor has focused on configuring the negative electrode current collector with Al. Then, by forming a plating layer made of a metal element that does not easily react with the sulfur component on the portion of the surface of the current collector to which the negative electrode active material layer (negative electrode mixture layer) is applied, the negative electrode current collector made of Al is formed. I found that it could be adopted.
Further, the terminal for external connection is formed of Al, and the negative electrode current collector uncoated portion (that is, the negative electrode active material layer) corresponding to the portion to be connected to the terminal in the negative electrode current collector made of Al is coated. By not forming the above-mentioned plating layer on the non-existing part), ultrasonic welding of the same type of metal, that is, Al to Al can be performed, and easy and strong bonding between the negative electrode current collector made of Al and the terminal is realized. This led to the completion of the present invention.

That is, in order to realize the above object, the secondary battery disclosed here includes an electrode body having a structure in which a sheet-shaped positive electrode and a sheet-shaped negative electrode are alternately laminated with a solid electrolyte layer interposed therebetween. , A secondary battery containing a substance containing sulfur in at least a part of the electrode body.
The negative electrode includes a negative electrode current collector made of Al and a negative electrode active material layer formed on at least one surface of the negative electrode current collector. Further, a plating layer made of Ni and / or Cr is formed on the surface of the negative electrode current collector on which the negative electrode active material layer is formed.
An uncoated portion of the negative electrode current collector having neither the plating layer nor the negative electrode active material layer is formed at the end of the negative electrode current collector, and the uncoated portion of the negative electrode current collector is formed. Is characterized in that an external connection terminal made of Al is joined.

In the secondary battery having such a configuration, as a result of adopting a negative electrode current collector made of Al in the secondary battery containing a substance containing sulfur (for example, a sulfur-based solid electrolyte containing sulfide) in the electrode body, as described above. The problem of adopting a negative electrode current collector made of copper has been fundamentally solved. Further, since the plating layer is formed in the portion where the negative electrode active material layer is formed, the formation of sulfide due to the reaction between the constituent metal of the current collector body and the sulfur component is prevented, and the negative electrode due to the sulfide is prevented from forming. It is possible to suppress an increase in interfacial resistance.
Further, in the secondary battery disclosed here, since the same kind of metal (Al to Al) can be bonded between the uncoated portion of the negative electrode current collector and the external connection terminal made of Al, the negative electrode collection made of Al. Efficient bonding can be realized between the electric body and the terminal for external connection, and by these, the battery performance of the secondary battery can be improved.

It is sectional drawing of the main part schematically showing the electrode body constituting the secondary battery which concerns on one Embodiment. It is a top view which looked at the negative electrode constituting the secondary battery which concerns on one Embodiment from one side.

Hereinafter, an embodiment according to the present invention will be described with reference to the drawings. In the drawings described below, members and parts having the same function may be designated by the same reference numerals, and overlapping description may be omitted or simplified. Further, the dimensional relations (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relations. In addition, matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention can be grasped as design matters of those skilled in the art based on the prior art in the art.

As used herein, the term "secondary battery" generally refers to a power storage device that can be repeatedly charged and discharged, and is a term that includes a so-called storage battery such as a lithium ion secondary battery and a power storage element such as an electric double layer capacitor. Further, the "lithium ion secondary battery" refers to a secondary battery that uses lithium ions as a charge carrier and is charged and discharged by the movement of lithium ions between the positive and negative electrodes. Further, the "all-solid-state battery" means a secondary battery provided with a solid electrolyte.
Further, in the present specification, the “substance containing sulfur” refers to a substance that produces sulfur that can react with a current collector (particularly, a negative electrode current collector) when a battery is used.
Hereinafter, the present invention will be described in detail by taking a flat all-solid-state lithium-ion secondary battery as an example. It should be noted that the embodiments described below are not intended to limit the present invention to those described in such embodiments.

The all-solid-state lithium-ion secondary battery according to the present embodiment is a secondary battery having a closed structure in which the electrode body 20 is internally sealed by a laminated film (not shown).
FIG. 1 shows a cross-sectional view of a main part of an electrode body 20 constituting an all-solid-state lithium-ion secondary battery according to the present embodiment. Further, FIG. 2 is a plan view showing one surface of the negative electrode 50 constituting the electrode body 20.
As shown in FIG. 1, in the electrode body 20 according to the present embodiment, the sheet-shaped positive electrode 30 and the sheet-shaped negative electrode 50 are solid between the positive and negative electrodes in the sheet wide surface direction (Z direction in the figure). It is a laminated electrode body 20 formed by being alternately laminated with an electrolyte layer 40 interposed therebetween.

As shown in FIGS. 1 and 2, the negative electrode 50 in the laminated electrode body 20 includes a negative electrode current collector 52 and a negative electrode active material layer 54. The negative electrode current collector 52 is made of aluminum (Al).
The negative electrode active material layer 54 is a layer containing a negative electrode active material and a solid electrolyte, and may further contain a conductive material, a binder (binder), or the like, if necessary. As the negative electrode active material, a substance conventionally known in this type of battery can be used. Examples thereof include carbon-based negative electrode active materials such as graphite, mesocarbon microbeads, and carbon black. Further, a negative electrode active material containing silicon (Si) or tin (Sn) as a constituent element may be used. As the solid electrolyte contained in the negative electrode active material layer 54, the same kind of material as the solid electrolyte contained in the solid electrolyte layer 40 described later can be used.

As shown in FIG. 1, a plating layer 58 is formed on the surface of the negative electrode current collector 52 on which the negative electrode active material layer 54 is formed.
The plating layer 58 according to the present embodiment is a plating layer containing chromium (Cr) and / or nickel (Ni) as constituent metal elements. As a method for forming the plating layer 58, a conventionally known method can be used without particular limitation. For example, there is a method in which an appropriate pretreatment (for example, ginkating treatment or the like) is performed on the negative electrode current collector 52 made of Al, and then a plating treatment (for example, electroplating treatment, electroless plating treatment or the like) is performed. The content of the plating process itself does not constitute the present invention, and detailed description thereof will be omitted.

At one end of the negative electrode current collector 52, a negative electrode current collector uncoated portion 52a having neither a plating layer 58 nor a negative electrode active material layer 54 is formed. That is, in the present embodiment, the negative electrode current collector uncoated portion 52a protrudes in the left direction (L direction) in the drawing and is overlapped with the external connection terminal 56 (that is, the negative electrode current collector tab), which will be described later. A joint portion M joined by welding means is formed. The other end of the external connection terminal 56 is drawn out from a laminated film exterior body (not shown) to the outside of the battery, and is arranged so as to be electrically connectable to an external circuit, element, or the like. Since the external connection structure is not a part that characterizes the present invention, detailed description thereof will be omitted.

Further, as shown in FIG. 1, the positive electrode 30 according to the present embodiment includes a positive electrode current collector 32 and a positive electrode active material layer 34. Although not particularly limited, the positive electrode current collector 32 is usually composed of Al.
As the material or the like constituting the positive electrode active material layer 34 formed on at least one surface of the positive electrode current collector, the same materials as those used for the positive electrode of a conventional general secondary battery of this type can be used without limitation. Is. Since the configuration of the positive electrode does not particularly characterize the present invention, detailed description thereof will be omitted. Although not shown, uncoated portions of the positive electrode current collectors are formed at the right end (R direction) ends of the laminated positive electrode current collectors 32 in the drawings, respectively, as in the case of the negative electrode. , Overlaid and joined to an external connection terminal (ie, positive electrode current collector tab) by suitable welding means.

In the laminated electrode body 20, the solid electrolyte layer 40 formed between the positive and negative electrodes contains at least a solid electrolyte. The electrode body 20 according to the present embodiment contains a substance containing sulfur in at least a part of the electrode body, and as a suitable example as the substance containing such sulfur, positive and negative electrode active material layers 34 and 54 and the like. Examples thereof include conventionally known sulfide solid electrolytes that can be contained in the solid electrolyte layer 40. Examples of sulfide-based solid electrolytes are Li 2S-SiS ₂ series, Li ₂ SP ₂ S ₃ series, Li ₂ SP ₂ S ₅ series, Li _{2 SGeS 2} series, Li ₂ SB ₂ S. Examples include glass or glass ceramics such as ₃ series.

The laminated electrode body having the above-mentioned structure can be constructed in the same manner as the laminated electrode body used for a normal all-solid-state battery of this type, except that the Al current collector with the plating layer is prepared. That is, roughly speaking, a plating layer 58 made of Ni and / or Cr is formed in advance on a part of the surface of the negative electrode current collector 52 made of Al (that is, the part where the negative electrode active material layer 54 is formed). Next, the negative electrode active material layer 54 is formed on the plating layer 58 to manufacture the negative electrode 50. Next, the laminated electrode body 20 can be constructed by alternately superimposing the negative electrode 50 and the positive electrode 30 prepared separately while interposing the solid electrolyte layer 40.
After that, as shown in FIG. 1, the uncoated portions 52a of the negative electrode current collectors of each of the laminated negative electrodes 50 are overlapped in the stacking direction, and are superposed with the separately prepared external connection terminal (negative electrode current collector tab) 56. The joint portion M is formed by being joined by a welding means such as ultrasonic welding. Similarly, on the positive electrode side, the uncoated portion of the positive electrode current collector stacked in the stacking direction and the external connection terminal (positive electrode current collector tab) are joined by welding means such as ultrasonic welding.
Then, a desired secondary battery can be manufactured by sealing the electrode body constructed with an appropriate exterior body.

In the secondary battery according to the present embodiment, the negative electrode current collector and the sulfur-containing substance contained in the electrode body react with each other by forming a plating layer on the portion where the negative electrode active material layer is formed. Therefore, it is possible to prevent the formation of sulfides of Al, and it is possible to suppress an increase in interfacial resistance at the negative electrode. Further, by forming the above-mentioned uncoated portion on the negative electrode current collector made of Al, the negative electrode current collector can be efficiently connected between the external connection terminal made of Al and the same metal by a welding means such as ultrasonic welding. Can be joined. As a result, it is possible to provide a secondary battery having improved battery performance.

20 Electrode body 30 Positive electrode 32 Positive electrode current collector 34 Positive electrode active material layer 40 Solid electrolyte layer 50 Negative electrode 52 Negative electrode current collector 52a Negative electrode current collector uncoated part 54 Negative electrode active material layer 56 External connection terminal (negative electrode current collector tab) )
58 Plating layer M Joint L Left direction R Right direction Z Wide surface direction

Claims (1)

A secondary battery having an electrode body having a structure in which a sheet-shaped positive electrode and a sheet-shaped negative electrode are alternately laminated with a solid electrolyte layer interposed therebetween, and at least a part of the electrode body contains a substance containing sulfur. And,
The negative electrode includes a negative electrode current collector made of Al and a negative electrode active material layer formed on at least one surface of the negative electrode current collector.
A plating layer made of Ni and / or Cr is formed on the surface of the negative electrode current collector on which the negative electrode active material layer is formed.
Here, at the end of the negative electrode current collector, an uncoated portion of the negative electrode current collector having neither the plating layer nor the negative electrode active material layer is formed.
A secondary battery in which an external connection terminal made of Al is bonded to the uncoated portion of the negative electrode current collector.

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