CN109196691B

CN109196691B - Negative electrode for secondary battery

Info

Publication number: CN109196691B
Application number: CN201780033688.5A
Authority: CN
Inventors: 曹珍铉; 尹泫雄
Original assignee: LG Chem Ltd
Current assignee: LG Energy Solution Ltd
Priority date: 2016-10-14
Filing date: 2017-10-13
Publication date: 2022-01-04
Anticipated expiration: 2037-10-13
Also published as: CN109196691A; ES2955000T3; PL3444874T3; WO2018070843A3; HUE062853T2; WO2018070843A2

Abstract

The present invention relates to a negative electrode for a secondary battery. The anode for a secondary battery of the present invention includes an anode current collector and an anode active material bonded to at least a part of the surface of the anode current collector. The negative electrode current collector has a plurality of anti-stratification current collecting grooves formed thereon, in which the negative electrode active material is combined. The negative electrode active material is formed on an inner surface of the delamination prevention current collector to form a space portion in which the substance diffusion layer is formed in the delamination prevention current collector during charge and discharge.

Description

Negative electrode for secondary battery

Cross Reference to Related Applications

The present application claims the benefit of priority from korean patent application No. 10-2016-.

Technical Field

The present invention relates to a negative electrode for a secondary battery.

Background

Unlike the primary battery, the secondary battery is rechargeable and has a high possibility of compact size and high capacity. Therefore, many studies on secondary batteries have been recently conducted. As technology develops and the demand for mobile devices increases, the demand for secondary batteries as energy sources is rapidly increasing.

The secondary battery is classified into a coin type battery, a cylindrical type battery, a square type battery, and a pouch type battery according to the shape of a battery case. In such a secondary battery, the electrode group mounted in the battery case is a chargeable and dischargeable power generating device having a structure in which electrodes and separators are stacked.

The electrode group can be broadly divided into: a roll core type electrode group in which a separator is interposed between a positive electrode and a negative electrode (each provided in the form of a sheet coated with an active material), and then the positive electrode, the separator, and the negative electrode are wound; a stacked electrode group in which a plurality of positive and negative electrodes are sequentially stacked with separators therebetween; and a stack/folding type electrode group in which a stack type unit cell is wound together with a separation film having a long length.

When lithium metal is used for the negative electrode of the secondary battery, the following problems may occur. Lithium metal has high reactivity with electrolyte components. Therefore, when the electrolyte and the lithium metal are in contact with each other, the electrolyte may spontaneously decompose to form a passivation layer on the surface of the lithium metal. As the continuous charge and discharge of the lithium metal battery progresses, the passivation layer may be delaminated and fall off. Therefore, the passivation layer may be additionally generated in the gap generated due to the above phenomenon, forming so-called "dead lithium (Li)", thereby deteriorating the life characteristics of the battery. Further, when delamination and exfoliation of the passivation layer repeatedly occur, a local difference in current density may occur when charge and discharge are performed to unevenly distribute current, and lithium dendrite having a resin phase is formed. In addition, when the dendrite formed as described above continuously grows to contact the positive electrode through the separator, an internal short circuit may occur to explode the battery.

Disclosure of Invention

Technical problem

An aspect of the present invention is to provide a negative electrode for a secondary battery, which is capable of minimizing a phenomenon of shortening a life of the battery while charging and discharging the battery.

Technical scheme

The negative electrode for a secondary battery according to an embodiment of the present invention includes: and an anode current collector combined (integrated) with at least a portion of a surface of the anode current collector, wherein the anode current collector has a plurality of delamination prevention current collecting grooves, the anode active material is combined with the delamination prevention current collecting grooves, and the anode active material is disposed on an inner surface of each delamination prevention current collecting groove, thereby defining a space portion forming a passivation layer during charge and discharge.

Advantageous effects

According to the present invention, the anode active material may be bonded so that a space portion in which the passivation layer is formed in the delamination prevention current collecting groove formed in the anode to prevent the passivation layer from delaminating. Therefore, the life of the battery can be prevented from being shortened.

In particular, a passivation layer made of lithium metal and formed on the surface of the negative active material through charge and discharge may be supported by the inner wall of the delamination prevention current collecting groove, thereby preventing delamination of the passivation layer. Therefore, when charge and discharge are repeated, the peeling and generation of the passivation layer can be prevented from being repeated. Therefore, it is possible to prevent generation of dead lithium that grows unevenly with repetition of exfoliation and generation of the passivation layer. As a result, an increase in battery resistance and deterioration in cycle efficiency can be prevented. In addition, since the continuous growth of dendrites is prevented, it is possible to prevent the occurrence of short circuit due to the dendrites contacting the positive electrode through the separator, thereby preventing the battery from exploding due to internal short circuit.

Drawings

Fig. 1 is an exploded perspective view of a secondary battery to which a negative electrode for a secondary battery is applied according to an embodiment of the present invention.

Fig. 2 is a partial sectional view of a secondary battery negative electrode according to an embodiment of the present invention.

Fig. 3 is a partial sectional view showing a state in which a mass diffusion layer (mass diffusion layer) is provided on the negative electrode for a secondary battery according to the embodiment of the present invention.

Fig. 4 is a partial plan view showing an example of the negative electrode for a secondary battery of the embodiment of the invention.

Fig. 5 is a partial plan view showing another example of the negative electrode for a secondary battery of the embodiment of the invention.

Fig. 6 is a partial sectional view of a negative electrode for a secondary battery according to another embodiment of the present invention.

Detailed Description

The objects, specific advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the drawings. It should be noted that elements of the drawings of the present specification are denoted by the same numerals as much as possible even if they are shown in other drawings. Furthermore, the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the following description of the present invention, a detailed description of related art that may unnecessarily obscure the gist of the present invention will be omitted.

Fig. 1 is an exploded perspective view of a secondary battery to which an anode for a secondary battery is applied according to an embodiment of the present invention, and fig. 2 is a partial sectional view of the anode for a secondary battery of the embodiment of the present invention.

Referring to fig. 1 and 2, an anode 10 for a secondary battery according to an embodiment of the present invention includes an anode current collector 11 and an anode active material 12 bonded to the anode current collector 11.

Hereinafter, the anode for a secondary battery according to an embodiment of the present invention will be described in more detail with reference to fig. 1 to 5.

Referring to fig. 1, a secondary battery 100 to which the negative electrode for a secondary battery according to the embodiment of the present invention is applied includes an electrode group 120 and a battery case 110, and the battery case 110 includes a housing portion 111 that houses the electrode group 120.

The electrode group 120 may be a chargeable and dischargeable power generation element, and has a structure in which the electrodes 30 and the separators 40 are combined and alternately stacked.

The electrode 30 may include a positive electrode 20 and a negative electrode 10. Here, the electrode group 120 may have a structure in which the positive electrodes 20/the separators 40/the negative electrodes 10 are alternately stacked. Here, the separator 40 may be disposed between the cathode 20 and the anode 10, and outside the cathode 20 and outside the anode 10. Here, the separator 40 may be disposed to surround the entire electrode group 110, and the positive electrode 20/the separator 40/the negative electrode 10 are stacked in the electrode group 110.

The separator 40 is made of an insulating material to electrically insulate the positive electrode 20 from the negative electrode 10. Here, the separator is made of, for example, a polyolefin-based resin film having micropores such as polyethylene or polypropylene.

The electrode assembly 100 may include an electrode lead 50. Here, the electrode lead 50 may be electrically connected with a side surface of the electrode 30.

Fig. 3 is a partial sectional view showing a state in which a passivation layer is provided on a negative electrode for a secondary battery according to an embodiment of the present invention.

In more detail, referring to fig. 2 and 3, the anode 10 may include an anode current collector 11 and an anode active material 12 combined with the anode current collector 11.

The anode current collector 11 may be made of, for example, a foil containing a copper (Cu) material.

In addition, the negative electrode current collector 11 may have a plurality of delamination prevention current collectors 13, and the negative electrode active material 12 is combined with the delamination prevention current collectors 13.

The anode active material 12 may be bonded to at least a portion of the surface of the anode current collector 11.

In addition, the anode active material 12 may be made of, for example, a lithium (Li) metal material.

Further, the anode active material 12 may be disposed on the inner surface of the delamination prevention current collecting groove 13, thereby defining a space portion 13a forming the passivation layer S in the delamination prevention current collecting groove 13 while performing charge and discharge. Here, the passivation layer may be a Solid Electrolyte Interphase (SEI).

In particular, the negative electrode active material 12 is disposed at a lower portion of the delamination prevention collecting groove 13, and the space portion 13a may be defined at a portion other than the portion of the delamination prevention collecting groove 13 where the negative electrode active material 12 is disposed. Therefore, the passivation layer S formed in the space portion 13a of the delamination prevention layer current collecting groove 13 during charge and discharge can be supported while preventing delamination from the inner surface of the delamination prevention layer current collecting groove 13. That is, both sides of the passivation layer S may be supported by the inner wall 14 disposed on the inner side surface of the delamination prevention groove 13 to prevent the passivation layer S from delaminating. Therefore, the passivation layer S disposed on the surface of the anode active material 12 may serve as a kinetic barrier preventing further occurrence of the reduction reaction to significantly prevent or reduce the shortening of the battery life. In particular, dead lithium and a porous layer, which are generated due to repeated detachment and generation of the passivation layer S, may be stacked to prevent an increase in resistance of the battery and a reduction in cycle life.

In the negative electrode for a secondary battery according to the embodiment of the present invention, the passivation layer S may be disposed on the outer surface of the negative electrode active material 12 formed in the delamination prevention groove 13. Therefore, the passivation layer S may be disposed on the outer surface of the anode active material 12 from the initial stage of charge and discharge, thereby more effectively preventing the battery life from being shortened.

In the negative electrode for a secondary battery according to the embodiment of the present invention, when the width of the anti-stratification current collecting grooves 13 is a and the distance between the anti-stratification current collecting grooves 13 is B, the following conditional expression may be satisfied.

0.5<A/B<10 (1)

When the value is less than the range satisfying the conditional expression (1) (i.e., the value of a/B is less than 0.5), the flexibility of the side surface of the anode current collector 11 may deteriorate. That is, when the passivation layer S contracts and expands during charge and discharge while the flexibility of the inner wall 14 of the delamination prevention groove 13 defined in the negative electrode current collector 11 is deteriorated, the inner wall 14 may not contract and expand, thereby deteriorating the effect of the side surface of the passivation layer S.

Further, when the value is larger than the range satisfying the conditional expression (1) (i.e., the value of a/B is larger than 10), it cannot serve as a support because it is limited by the strength of the anode current collector 11 on the side surface of the passivation layer S. That is, the strength of the inner wall 14 of the delamination prevention groove 13 defined in the negative electrode collector 11 may be reduced, thereby deteriorating the supporting effect of the inner wall 14.

In the anode for a secondary battery of the embodiment of the invention, when the depth of the delamination prevention groove 13 is C and the total thickness of the anode current collector 11 is E, the following conditional expression may be satisfied.

0.2<C/E<0.8 (2)

When the value is less than the range satisfying the conditional expression (2) (i.e., the value of C/E is less than 0.2), the toughness of the passivation layer S due to the volume change of the passivation layer S may be deteriorated due to the deterioration of the flexibility of the anode current collector 11. That is, when the flexibility of the side surface of the delamination prevention collecting groove 13 defined in the negative electrode current collector 11 is deteriorated, the toughness of the passivation layer S may be deteriorated due to the volume change of the passivation layer S that shrinks and expands during charge and discharge. Therefore, the passivation layer S may be delaminated and peeled off from the surface of the negative electrode current collector 11 of lithium metal.

Further, when the value is larger than the range satisfying the conditional expression (1) (i.e., the value of C/E is larger than 0.8), the anode current collector 11 may have problems in terms of processing and resistance.

In the negative electrode for a secondary battery according to the embodiment of the present invention, when the depth of the space portion 13a of the layer separation preventing current collecting groove 13 is D, the following conditional expression may be satisfied.

0.05μm<D (3)

When the value is less than the range satisfying the conditional expression (3) (i.e., the depth D is less than 0.05 μm), the anode current collector 11 may not sufficiently serve as a lateral support for the growth of the passivation layer S to cause delamination of the passivation layer S. That is, the inner wall 14 of the anti-delamination flow collection groove 13 may not be sufficient to serve as a lateral support of the passivation layer S.

In the negative electrode for a secondary battery according to the embodiment of the present invention, when the width of the delamination prevention current collection grooves 13 is a, the distance between the delamination prevention current collection grooves 13 is B, and the depth of the delamination prevention current collection grooves 13 is C, the following conditional expression may be satisfied.

10 μm < A <1,000 μm,10 μm < B <1,000 μm, and 10 μm < C <1,000 μm

Here, in particular, the anode for a secondary battery of the embodiment of the invention may satisfy, for example, the following conditional expressions: 10 μm < a <100 μm,10 μm < B <100 μm, and 10 μm < C <100 μm.

Here, more particularly, the anode for a secondary battery of the embodiment of the invention may satisfy, for example, the following conditional expressions: 20 μm < a <60 μm,20 μm < B <60 μm, and 20 μm < C <60 μm.

As described above, in the anode 10 for a secondary battery according to an embodiment of the present invention, the copper (Cu) anode current collector 11 on which the pattern is formed may be used to adjust the passivation layer to reduce the size and form a support of the passivation layer S, thereby inhibiting delamination and peeling of the passivation layer S to form a more stable passivation layer S. This phenomenon can suppress a side reaction between the negative active material 12 containing lithium metal and the electrolyte to uniformly distribute current, thereby suppressing non-uniform dendritic growth and minimizing the generation of dead lithium.

Furthermore, when the Stable passivation Layer S is formed, the performance of the secondary battery can be improved as described in the paper published by Jianming Zheng [ High Stable Operation of Lithium Batteries Enabled by the format of a transformed High-conductivity Electrolyte Layer (2016) ]. That is, in a state in which the passivation layer S is delaminated and exfoliated and the passivation layer S in which the grown dead lithium is minimized is formed, the more the cycle is progressed, the higher the degree to which the degradation of the battery capacity is minimized, thereby maintaining the battery capacity.

< examples 1 to 10, comparative example 1>

When the width of the delamination-prevention collecting grooves 13 is a, the distance between the delamination-prevention collecting grooves 13 is B, and the depth of the delamination-prevention collecting grooves 13 is C, the lithium secondary battery may be constructed under the conditions shown in the following table.

[ Table 1]

	C (Unit μm)	A (unit μm)	B (Unit μm)
				Example 1	20	20	20
Example 2	40	40	40
				Example 3	60	60	60
Example 4	40	20	60
				Example 5	10	10	10
Example 6	100	100	100
				Example 7	200	200	200
Example 8	500	500	500
				Example 9	1000	1000	1000
Example 10	5000	5000	5000
				Comparative example 1 (collecting groove without formation of delamination prevention)	0	0	0

< Experimental example >

The apparent capacity and capacity retention when the pattern of table 1 was applied are shown in table 2 below. In addition, a battery in which Nickel Cobalt Manganese (NCM) was used as a positive electrode active material, lithium metal was used as a negative electrode active material, a PE separator was provided as a separator, and ethylene carbonate/ethyl methyl carbonate/dimethyl carbonate (EC/EMC/DMC)1M LiPF6 VC 0.5 wt% was used as an electrolyte was manufactured to be evaluated.

[ Table 2]

	Apparent capacity (mAh)	Capacity maintenance (%), cycle 200
			Example 1	5.25	88.57
Example 2	5.24	86.65
			Example 3	5.26	84.15
Example 4	5.28	86.57
			Example 5	5.28	70.57
Example 6	5.28	76.57
			Example 7	5.28	56.57
Example 8	5.28	46.57
			Example 9	5.29	35.78
Example 10	5.21	25.23
			Comparative example 1	5.24	20.46

As shown in table 2 above, when the capacity maintenance ratios of examples 1 to 10 in which the delamination prevention collecting grooves 13 were formed and the capacity maintenance ratio of comparative example 1 in which the delamination prevention collecting grooves 13 were not formed and thus no pattern was provided were compared, it was seen that the cycle performance was excellent when the delamination prevention collecting grooves 13 were formed.

Here, it can be seen that the capacity retention rates of examples 1 to 8 in which the delamination prevention current collecting grooves 13 were formed in a pattern having a size of 1000 μm or less were larger than that of comparative example 1 in which the delamination prevention current collecting grooves 13 were not formed and thus no pattern was provided.

Here, it can be seen that the capacity retention rates of examples 1 to 6 in which the anti-delamination flow collection groove 13 was formed in a pattern having a size of 10 μm to 100 μm were significantly larger than that of comparative example 1 in which the anti-delamination flow collection groove 13 was not formed and thus the pattern was not provided.

In particular, in the case of examples 1 to 4 in which the delamination prevention collecting grooves 13 were provided in a pattern having a size of 20 μm to 60 μm, it can be seen that the capacity retention rate was extremely excellent even after 200 cycles had elapsed.

Fig. 4 is a partial plan view showing an example of the negative electrode for a secondary battery of the embodiment of the present invention, and fig. 5 is a partial plan view showing another example of the negative electrode for a secondary battery of the embodiment of the present invention.

Referring to fig. 4, in the negative electrode 10 for a secondary battery of the embodiment of the present invention, the delamination prevention collecting groove 13 may have, for example, a rectangular shape.

Further, referring to fig. 5, in the negative electrode 10 'for a secondary battery of the embodiment of the present invention, the delamination prevention collecting groove 13' may have, for example, a circular shape.

Fig. 6 is a partial sectional view of a secondary battery negative electrode according to another embodiment of the present invention.

Referring to fig. 6, in the negative electrode 10 ″ for a secondary battery according to another embodiment of the present invention, a separation preventing part 15 may be further provided in the negative electrode collector 11.

The separation-preventing portion 15 may be disposed on the upper end of the separation-preventing layer current collector 13 of the negative electrode current collector 11 and protrude, thereby preventing the passivation layer S (see fig. 3) from being separated from the separation-preventing layer current collector 13. That is, the separation preventing portion 15 may extend from the upper end of the inner wall 14 of the negative electrode current collector 11 to the space portion 13a of the separation preventing layer collecting groove 13 to form a hole (hole) in the upper side surface of the passivation layer S, thereby preventing the passivation layer S from being separated from the separation preventing layer collecting groove 13.

For example, the separation-preventing portion 15 may have a shape protruding or stepped in a direction in which the separation-preventing portion 15 faces the upper end of the separation-preventing layer-collecting groove 13.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood that the scope of the invention is not limited to the negative electrode for a secondary battery described herein. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention.

Further, the scope of the invention will be apparent from the appended claims.

Claims

1. An anode for a secondary battery, comprising:

a negative electrode current collector; and

an anode active material bonded to at least a portion of a surface of the anode current collector,

wherein the negative electrode current collector has a plurality of delamination prevention current collecting grooves, the negative electrode active material is combined with the delamination prevention current collecting grooves, and

the negative electrode active material is disposed on an inner surface of each of the delamination prevention current collecting grooves to define a space portion where a passivation layer is formed during charge and discharge,

wherein the negative active material is disposed at the bottom of the anti-stratification current collecting groove,

the space portion is defined at a portion other than a portion where the negative electrode active material is disposed in the delamination prevention collecting groove, and

the passivation layer formed in the space portion of the delamination prevention current collecting groove during charge and discharge is supported to prevent delamination from the inner wall of the delamination prevention current collecting groove,

wherein, when the width of preventing layering collection groove is A, the distance between a plurality of preventing layering collection grooves is B, and the degree of depth of preventing layering collection groove is C, satisfies the following conditional expression: a is more than or equal to 20 mu m and less than or equal to 60 mu m, B is more than or equal to 20 mu m and less than or equal to 60 mu m, and C is more than or equal to 20 mu m and less than or equal to 60 mu m,

wherein, when the width of the delamination prevention current collecting groove is a, the distance between the plurality of delamination prevention current collecting grooves is B, the depth of the delamination prevention current collecting groove is C, the depth of the space portion of the delamination prevention current collecting groove is D, and the total thickness of the negative electrode current collector is E, the following conditional expression is satisfied: 0.05 μm < D, 0.2< C/E <0.8, and 0.5< A/B < 10.

2. The anode of claim 1, wherein the anode active material is made of lithium metal.

3. The anode according to claim 1 or 2, wherein the anode current collector is made of copper (Cu).

4. The anode of claim 1 or 2, wherein the passivation layer is disposed on an outer surface of the anode active material.

5. The anode according to claim 1 or 2, wherein the anode current collector further comprises a separation prevention portion protruding from an upper end of the delamination prevention current collection groove to prevent the passivation layer from being separated from the delamination prevention current collection groove.