Lithium-ion battery manufacturing method and lithium-ion battery

Abstract

To provide a novel manufacturing method for a lithium ion battery, capable of suppressing capacity deterioration after initial charging, and provide a lithium ion battery.SOLUTION: A method for manufacturing a lithium ion battery, disclosed herein, includes steps of: providing a positive electrode precursor layer at least containing a Li alloy of which a lithium (Li) alloy potential is 0.5 V(vs Li / Li+) or more and a positive electrode active material; obtaining a lithium ion battery precursor that includes the positive electrode precursor layer, a separator layer, and a negative electrode active material layer in this order, in which the lithium ion battery precursor is impregnated with an electrolyte; and converting the positive electrode precursor layer into a positive electrode active material layer by performing an initial charging to the lithium ion battery precursor.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to a method for manufacturing a lithium-ion battery, and to a lithium-ion battery. [Background technology]

[0002] Conventionally, in order to increase the capacity of lithium ion batteries, the active materials have been improved.

[0003] Patent Document 1 discloses an electrode used in a non-aqueous electrolyte secondary battery. The specific surface area of ​​the negative electrode active material of this electrode measured by the N adsorption method is 3.3 m 2 / g or more and 4.4m 2 The positive electrode active material of this electrode has a DBP oil absorption of 30 ml / 100 g or more and 47 ml / 100 g or less. The positive electrode density is 1.8 g / cm 3 or more and 2.2g / cm 3 The following is an explanation: Patent Document 1 discloses that the capacity of the negative electrode is increased by using a lithium (Li) alloy as the active material.

[0004] Nickel-cobalt-manganese (NCM) lithium oxide is widely used as a positive electrode active material, and improvements to its composition are being investigated. Specifically, Non-Patent Document 1 discloses that the capacity of a positive electrode can be increased by increasing the proportion of nickel (Ni) in NCM lithium oxide as a positive electrode active material. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-010991 Summary of the Invention [Problem to be solved by the invention]

[0006] When conventional electrodes such as the electrode of Patent Document 1 are used, a significant decrease in capacity is sometimes observed after the initial charge.

[0007] The present disclosure provides a novel method for manufacturing a lithium ion battery that can suppress a decrease in capacity after initial charging, and the lithium ion battery. [Means for solving the problem]

[0008] As a result of intensive research, the present inventors have found that the above problems can be solved by the following means, and have completed the present disclosure. That is, the present disclosure is as follows: <Mode 1> Lithium alloying potential is 0.5V (vs Li / Li + and a positive electrode precursor layer containing at least a lithium alloy having a composition of at least 100% by mass % or more and a positive electrode active material. providing a lithium ion battery precursor having the positive electrode precursor layer, a separator layer, and a negative electrode active material layer in this order and impregnated with an electrolyte; and performing initial charging on the lithium ion battery precursor to convert the positive electrode precursor layer into a positive electrode active material layer; A method for manufacturing a lithium-ion battery, comprising: <Aspect 2> The lithium alloy is Li3Bi, Li3Sb, and Li 2. The method of embodiment 1, wherein the .alpha.-tocopherol compound is selected from the group consisting of Sn. Aspect 3: The method according to Aspect 1 or 2, wherein the positive electrode active material is NCM lithium oxide. <Aspect 4> A positive electrode active material layer, a separator layer, and a negative electrode active material layer in this order, the positive electrode active material layer contains a positive electrode active material and at least one of bismuth element and antimony element; Lithium-ion battery. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to provide a novel method for manufacturing a lithium ion battery, and a novel lithium ion battery, which can suppress a decrease in capacity after initial charging. [Brief explanation of the drawings]

[0010]

Figure 1

[0011] <<Lithium-ion battery manufacturing method>> The disclosed method of manufacturing a lithium ion battery comprises: The lithium alloying potential (Li alloying potential) is 0.5V (vs Li / Li + and a positive electrode precursor layer containing at least a Li alloy having a composition of at least 100% by mass and a positive electrode active material. Obtaining a lithium ion battery precursor having the positive electrode precursor layer, the separator layer, and the negative electrode active material layer in this order and impregnated with an electrolytic solution; and performing initial charging on the lithium ion battery precursor to convert the positive electrode precursor layer into a positive electrode active material layer; Includes.

[0012] The present inventors have found that the cause of the decrease in battery capacity described in Patent Document 1 is that Li supplied in the initial positive electrode active material is consumed due to the formation of a solid electrolyte interphase (SEI) in the negative electrode during the first charge.

[0013] In response to this, the present inventors have found that the capacity can be improved by obtaining a lithium ion battery using the above-mentioned positive electrode precursor layer. Without wishing to be bound by theory, this is thought to be because Li from the Li alloy in the positive electrode precursor layer is released during the first charge and becomes Li consumed for SEI formation at the negative electrode, thereby suppressing the consumption of Li in the positive electrode active material for SEI formation. In addition, when the Li alloying potential of the Li alloy is 0.5 V (vs Li / Li + ) or more, it is believed that the occurrence of an electrochemical reaction inside the positive electrode precursor before the first charge can be suppressed.

[0014] Each component of the present disclosure will be described below.

[0015] <Preparation of Positive Electrode Precursor Layer> The positive electrode precursor layer is formed by using a Li alloying potential of 0.5 V (vs. Li / Li + ) or more, and a positive electrode active material. The positive electrode precursor layer may also contain other optional substances. Examples of other substances include a conductive additive and a binder.

[0016] The positive electrode precursor layer can be prepared by mixing the materials constituting the layer and applying the mixture.

[0017] (Li alloy) Li alloys have a Li alloying potential of 0.5V (vs Li / Li + ) or more. This Li alloying potential is 0.6V (vs Li / Li + ) or more, 0.7V (vs Li / Li + ) or more, or 0.8V (vs Li / Li + ) or more, and 1.5V (vs Li / Li + ) or less, 1.4V (vs Li / Li + ) or less, 1.3V (vs Li / Li + ) or less, 1.2V (vs Li / Li + ) or less, 1.1V (vs Li / Li + ) or less, 1.0V (vs Li / Li + ) or less.

[0018] Here, the Li alloying potential (vs Li / Li + ) is the electrode potential of the electrode reaction of formula (1) and is expressed based on the electrode potential of lithium of formula (2) below: xLi + +M+xe - ←→ Li x M (1) Li + +e - ←→ Li (2)

[0019] This Li alloying potential (vs Li / Li + ) can be measured as the monopolar potential obtained when the alloy is immersed in a salt solution of Li.

[0020] As such a Li alloy, for example, Li3Bi, Li3Sb, and Li Sn or the like can be used.

[0021] (Positive electrode active material) As the positive electrode active material, any arbitrary positive electrode active material can be used, and it is not particularly limited. For example, a lithium-containing oxide can be used.

[0022] The lithium-containing oxide as the positive electrode active material is not particularly limited, and for example, it may contain at least Li, at least one transition metal element selected from Co, Ni, and Mn, and O. As such a lithium-containing oxide, for example, lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), lithium manganate (LiMn2O4), nickel-cobalt-manganese (NCM) lithium oxide in which some of these elements are substituted with other elements can be used. The NCM lithium oxide is generally represented by the general formula of Li a Mn x Ni y Co z O 2±δ (0 < a ≤ 1.5, 0 ≤ x ≤ 1.5, 0 ≤ y ≤ 1.5, 0 ≤ z ≤ 1.5, 0 < δ(=x + y + z) < 1.5). The lithium-containing oxide as the positive electrode active material may, for example, have an O2-type structure, an O3-type structure, or a crystal structure other than these. As the positive electrode active material, only one type may be used alone, or two or more types may be used in combination.

[0023] (Conductive assistant) The conductive additive optionally contained in the positive electrode precursor layer may be a known conductive additive used in lithium ion batteries. Specifically, carbon materials such as ketjen black (KB), vapor grown carbon fiber (VGCF), acetylene black (AB), carbon nanotubes (CNT), carbon nanofibers (CNF), carbon black, coke, graphite, etc. may be used. Alternatively, metal materials that can withstand the environment during battery use may also be used. The conductive additive may be used alone or in combination of two or more. The conductive additive may be in various forms, such as powder or fiber. The amount of the conductive additive contained in the positive electrode active material layer is not particularly limited.

[0024] (binder) The binder optionally contained in the positive electrode precursor layer may be any binder known to be used in lithium ion batteries. For example, a styrene butadiene rubber (SBR)-based binder, a carboxymethyl cellulose (CMC)-based binder, an acrylonitrile butadiene rubber (ABR)-based binder, a butadiene rubber (BR)-based binder, a polyvinylidene fluoride (PVDF)-based binder, a polytetrafluoroethylene (PTFE)-based binder, etc. may be used. Only one type of binder may be used alone, or two or more types may be used in combination. The amount of binder contained in the positive electrode active material layer is not particularly limited.

[0025] <Preparation of Lithium-Ion Battery Precursor> The lithium ion battery precursor has a positive electrode precursor layer, a separator layer, and a negative electrode active material layer in this order, and is impregnated with a non-aqueous electrolyte solution. This lithium ion battery precursor may be produced by a known method.

[0026] The lithium ion battery precursor may further include a positive electrode current collector layer and a negative electrode current collector layer.

[0027] Each component of the lithium ion battery precursor will be described below.

[0028] (Positive electrode current collector layer) The positive electrode current collector layer may be made of a known metal that can be used as a positive electrode current collector for lithium-ion batteries. Examples of such metals include metal materials containing at least one element selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Pb, Co, Cr, Zn, Ge, In, Sn, and Zr. The shape of the positive electrode current collector is not particularly limited. It may take various forms, such as a foil, a mesh, or a porous form. The above metal may be deposited or plated on the surface of a substrate.

[0029] (separator) The separator may be a known separator used in lithium ion batteries. For example, the separator may be made of a resin such as polyethylene (PE), polypropylene (PP), polyester, or polyamide. The separator may have a single layer structure or a multi-layer structure. Examples of multi-layer separators include separators made of the above resins, such as a two-layer separator of PE / PP, or a three-layer separator of PP / PE / PP or PE / PP / PE. The separator may be made of a nonwoven fabric such as a cellulose nonwoven fabric, a resin nonwoven fabric, or a glass fiber nonwoven fabric. The thickness of the separator is not particularly limited and may be, for example, 5 μm or more and 1 mm or less.

[0030] (Negative electrode active material layer) The negative electrode active material layer contains a negative electrode active material. The negative electrode active material layer may also contain other optional components. Examples of the other components include a conductive additive and a binder. For the conductive additive and the binder, the description of the positive electrode active material layer can be referred to.

[0031] (Negative electrode active material layer: negative electrode active material) As the negative electrode active material, various substances may be used that have a lower potential (charge / discharge potential) for absorbing and releasing ions than the positive electrode active material. Examples of the negative electrode active material that may be used include silicon-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite, hard carbon, and various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, and the like. Only one type of negative electrode active material may be used alone, or two or more types may be used in combination.

[0032] (negative electrode current collector layer) The negative electrode current collector layer may be composed of a known metal or the like that can be used as a negative electrode current collector for a lithium-ion battery. Examples of such metals include a metallic material containing at least one element selected from the group consisting of Cu, Ni, Al, V, Au, Pt, Mg, Fe, Ti, Pb, Co, Cr, Zn, Ge, In, Sn, and Zr. The form of the negative electrode current collector layer is not particularly limited and may be various forms such as foil, mesh, or porous. The negative electrode current collector layer may be formed by plating or vapor-depositing the above-mentioned metal onto the surface of a substrate composed of any material. The surface of the negative electrode current collector layer may also be coated with a carbon material or the like.

[0033] (Non-aqueous electrolyte) The non-aqueous electrolyte may contain a non-aqueous solvent and an electrolyte, and the electrolyte may contain alkali metal ions, such as lithium ions, as carrier ions.

[0034] The non-aqueous solvent may be a solvent other than water, such as an organic solvent. Examples of the organic solvent include carbonate solvents such as ethylene carbonate (EC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and fluoroethylene carbonate (FEC). These organic solvents may be used alone or in combination.

[0035] The electrolyte is not particularly limited and may be, for example, a lithium salt, such as LiPF6.

[0036] <Preparation of Positive Electrode Active Material Layer> The positive electrode active material layer is produced by initially charging the lithium ion battery precursor to convert the positive electrode precursor layer into the positive electrode active material layer.

[0037] By initially charging the lithium-ion battery precursor having the positive electrode layer precursor layer, the Li in the Li alloy is consumed for SEI formation at the negative electrode. As a result, when the Li alloy contains at least one of LiBi and LiSb, the resulting positive electrode active material layer contains at least one of elemental bismuth and elemental antimony.

[0038] The initial charging conditions may be known conditions.

[0039] Lithium-ion battery The lithium ion battery of the present disclosure comprises: a positive electrode active material layer, a separator layer, and a negative electrode active material layer; The positive electrode active material layer contains a positive electrode active material and at least one of elemental bismuth and elemental antimony.

[0040] FIG. 1 schematically illustrates the configuration of a lithium-ion battery 100 according to one embodiment of the present disclosure. As illustrated in FIG. 1, the lithium-ion battery 100 may include a positive electrode 10, a separator 20, and a negative electrode 30. The positive electrode 10 may include a positive electrode active material layer 11 and a positive electrode current collector layer 12, and the negative electrode 30 may include a negative electrode active material layer 31 and a negative electrode current collector layer 32. In this case, the positive electrode active material layer 11 may contain the above-described positive electrode active material. Although not illustrated, an electrolyte may be contained in the positive electrode active material layer 11 and the negative electrode active material layer 31.

[0041] For each component of the lithium ion battery, the description of the manufacturing method can be referred to. [Example]

[0042] The present disclosure will be specifically explained with reference to examples and comparative examples, but the present disclosure is not limited to these.

[0043] <<Making a lithium-ion battery>> Example 1 92.3 mg of LiNi as the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, 8.4 mg of Li3Bi as a Li alloy, a conductive additive, and a binder were mixed in NMP to form a slurry, which was then applied to an Al foil and dried to obtain a positive electrode precursor layer.

[0044] The obtained positive electrode precursor layer was placed opposite a negative electrode active material layer containing graphite as an active material via a separator layer, and the resulting mixture was dried in a vacuum. A non-aqueous electrolyte solution was then poured into the resulting lithium ion battery precursor.

[0045] Examples 2 to 3 and Comparative Examples 1 to 3 Lithium ion battery precursors of Examples 2 to 3 and Comparative Examples 1 to 3 were obtained in the same manner as in Example 1, except that the content of the positive electrode active material and the type and content of the Li alloy were changed as shown in Table 1.

[0046] "evaluation" Based on the mass of the positive electrode active material contained in the cell, the current value at 210 mA / g is defined as a 1C rate, with 0.2C as the charge / discharge current value and 0.03C as the cut-off current value, and CCCV charging and CCCV discharging are performed. The upper limit voltage during charging is 4.25V, and the lower limit voltage during discharging is 2.50V. The obtained CCCV discharge capacity is the cell capacity and is used as an evaluation index in this disclosure.

[0047] Table 1 shows the configurations and evaluation results of the examples and comparative examples.

[0048] [Table 1]

[0049] From Table 1, the Li alloying potential is 0.5 V (vs Li / Li + It can be seen that the lithium ion battery of the present disclosure obtained from the Li alloy and positive electrode active material described above can suppress a decrease in the capacity of the positive electrode. [Explanation of symbols]

[0050] 10 positive electrode 11 Cathode active material layer 12 Positive electrode current collector 20 Separator 30 negative electrode 31 Negative electrode active material layer 32 Negative electrode current collector 100 Lithium-ion batteries

Claims

1. Lithium alloying potential is 0.5V (vs Li / Li ＋ ) or more, and a positive electrode active material; providing a lithium ion battery precursor having the positive electrode precursor layer, a separator layer, and a negative electrode active material layer in this order and impregnated with an electrolyte; and performing initial charging on the lithium ion battery precursor to convert the positive electrode precursor layer into a positive electrode active material layer; A method for manufacturing a lithium-ion battery, comprising:

2. The lithium alloy is Li ３ Bi, Li ３ 2. The method of claim 1, wherein the metal is selected from the group consisting of Sb, and LiSn.

3. 3. The method of claim 1, wherein the positive electrode active material is an NCM lithium oxide.

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