Secondary battery and method for manufacturing secondary battery

Abstract

Disclosed are a secondary battery and a method for manufacturing the secondary battery. A secondary battery according to one aspect of the present invention comprises: a positive electrode unit; a negative electrode unit; and an electrolyte unit disposed between the positive electrode unit and the negative electrode unit, wherein the positive electrode unit comprises a positive electrode current collector made of a first metal material, a positive electrode active material including lithium, and a lithium alloy layer interposed between the positive electrode current collector and the positive electrode active material and formed by an alloy of the first metal of the positive electrode current collector and lithium.

Description

Secondary batteries and secondary battery manufacturing methods

[0001] The present invention relates to a secondary battery and a method for manufacturing the same. More specifically, it relates to a secondary battery using lithium metal and a method for manufacturing the same.

[0002]

[0003] With the rapid development of the electronics, communications, and computer industries, the application of energy storage technology is expanding to include camcorders, mobile phones, laptops, PCs, and even electric vehicles. Consequently, the development of lightweight, long-lasting, and highly reliable high-performance secondary batteries is underway.

[0004] In general, lithium metal is used in secondary batteries, and lithium metal has the advantage of being able to realize high energy density due to its low potential and large capacity.

[0005] However, when lithium metal is used in a secondary battery, a solid electrolyte interface (SEI) layer is formed on the negative electrode by accumulating decomposition products formed by chemical reactions with electrolytes, etc. The stable SEI layer has lithium ion conductivity and prevents lithium corrosion by blocking contact between the electrolyte and lithium. However, when lithium is deposited on the negative electrode where SEI has been formed, uniform lithium deposition does not occur and lithium deposition becomes concentrated in local areas. The growth of lithium dendrites can cause internal short circuits in the battery. Uneven lithium deposition, such as dendrite formation, can cause the formation of a new SEI layer and depletion of the electrolyte and lithium.

[0006] Additionally, there is a problem of lithium consumption due to various interfacial side reactions occurring between electrode materials, additives, and electrolytes at the positive and negative electrodes.

[0007]

[0008] An embodiment of the present invention is to provide a secondary battery and a method for manufacturing a secondary battery that can effectively compensate for lithium consumed in a secondary battery.

[0009]

[0010] According to one aspect of the present invention, a secondary battery is provided, which includes a positive electrode portion, a negative electrode portion, and an electrolyte portion disposed between the positive electrode portion and the negative electrode portion, wherein the positive electrode portion includes a positive electrode current collector made of a first metal material, a positive electrode active material containing lithium, and a lithium alloy layer interposed between the positive electrode current collector and the positive electrode active material and formed of an alloy of the first metal of the positive electrode current collector and lithium.

[0011] At this time, the cathode portion may include a cathode current collector made of a second metal material disposed on the electrolyte portion.

[0012] Additionally, the negative electrode portion may include a negative electrode current collector made of a second metal material and a negative electrode active material interposed between the negative electrode current collector and the electrolyte portion.

[0013] Additionally, the negative electrode portion may include a negative electrode current collector made of a second metal material and a thin film including a lithium layer interposed between the negative electrode current collector and the electrolyte portion.

[0014] Meanwhile, a secondary battery is provided, which includes a positive electrode part, a negative electrode part, and an electrolyte part disposed between the positive electrode part and the negative electrode part, wherein the positive electrode part includes a positive electrode current collector made of a first metal material and a positive electrode active material including lithium interposed between the positive electrode current collector and the electrolyte part, and a plurality of pores are formed on one surface of the positive electrode current collector that comes into contact with the positive electrode active material.

[0015] In addition, a secondary battery is provided, which includes a positive electrode portion, a negative electrode portion, and an electrolyte portion disposed between the positive electrode portion and the negative electrode portion, wherein the positive electrode portion includes a positive electrode current collector made of a first metal material and a positive electrode active material that is interposed between the positive electrode current collector and the electrolyte portion and includes lithium, and wherein one surface of the positive electrode current collector that comes into contact with the positive electrode active material is formed to have a higher surface roughness than the other surface of the positive electrode current collector.

[0016] In addition, a secondary battery is provided, which includes a positive electrode portion, a negative electrode portion, and an electrolyte portion disposed between the positive electrode portion and the negative electrode portion, wherein the positive electrode portion includes a positive electrode collector made of a first metal material and a positive electrode active material including lithium interposed between the positive electrode collector and the electrolyte portion, and wherein the positive electrode collector is formed of a first layer and a second layer, and the second layer of the positive electrode collector in contact with the positive electrode active material is formed to have a lower density than the first layer of the positive electrode collector.

[0017] At this time, the cathode portion may include a cathode current collector made of a second metal material disposed on the electrolyte portion.

[0018] Additionally, the negative electrode portion may include a negative electrode current collector made of a second metal material and a negative electrode active material interposed between the negative electrode current collector and the electrolyte portion.

[0019] Additionally, the negative electrode portion may include a negative electrode current collector made of a second metal material and a thin film including a lithium layer interposed between the negative electrode current collector and the electrolyte portion.

[0020] Meanwhile, according to another aspect of the present invention, a method for manufacturing a secondary battery is provided, including a positive electrode collector preparation step of preparing a positive electrode collector made of a first metal material, a lithium alloy layer forming step of forming a lithium alloy layer formed of an alloy of the first metal of the positive electrode collector and lithium on one surface of the positive electrode collector, and a positive electrode active material disposition step of disposing a positive electrode active material containing lithium on the lithium alloy layer.

[0021] At this time, the positive electrode current collector includes an aluminum thin film, and the lithium alloy layer forming step may include a thin film preparation step of interposing an electrolyte between the aluminum thin film and the lithium thin film, a lithiation step of contacting the aluminum thin film and the lithium thin film, and a thin film separation step of separating the aluminum thin film.

[0022] At this time, in the thin film preparation step, the electrolyte may contain a lithium salt.

[0023] Additionally, the lithiation step can be performed by pressing the aluminum thin film and the lithium thin film into contact.

[0024]

[0025] According to an embodiment of the present invention, lithium consumed by side reactions in a secondary battery can be effectively compensated for.

[0026]

[0027] Figures 1 to 3 are drawings showing a secondary battery according to one embodiment of one aspect of the present invention.

[0028] Figures 4 to 7 are drawings showing a lithium alloy layer in a secondary battery according to one embodiment of the present invention.

[0029] Figures 8 to 10 are drawings explaining charge and discharge characteristics in a secondary battery according to one embodiment of the present invention.

[0030] Figures 11 and 12 are drawings showing a secondary battery according to another embodiment of the present invention.

[0031] Figures 13 and 14 are drawings showing a secondary battery according to another embodiment of the present invention.

[0032] FIG. 15 is a flowchart showing a method for manufacturing a secondary battery according to an embodiment of another aspect of the present invention.

[0033]

[0034] The terminology used in this application is solely for the purpose of describing specific embodiments and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0035] In this application, when a part is said to "include" a component, unless otherwise specifically stated, this does not exclude other components, but rather implies the inclusion of additional components. Furthermore, throughout the specification, the term "on" means located above or below the target part, and does not necessarily mean located above the direction of gravity.

[0036] In addition, the term "coupling" is used as a concept that encompasses not only cases where each component is physically in direct contact with the other components in the contact relationship between each component, but also cases where another component is interposed between each component and each component is in contact with the other component.

[0037] Additionally, while terms such as "first," "second," etc. may be used to describe various components, these components should not be limited by these terms. These terms are used solely to distinguish one component from another.

[0038] The size and thickness of each component shown in the drawing are arbitrarily shown for convenience of explanation, and therefore the present invention is not necessarily limited to what is shown.

[0039] Hereinafter, embodiments of a secondary battery and a secondary battery manufacturing method according to the present invention will be described in detail with reference to the attached drawings. In describing with reference to the attached drawings, identical or corresponding components are assigned the same drawing numbers, and redundant descriptions thereof will be omitted.

[0040]

[0041] Figures 1 to 3 are drawings showing a secondary battery according to one embodiment of an aspect of the present invention. Figure 1 shows a state before initial charging of a secondary battery according to one embodiment of the invention.

[0042] Referring to FIG. 1, a secondary battery (100) according to one embodiment of the present invention includes a positive electrode portion (110), a negative electrode portion (150), and an electrolyte portion (190).

[0043] In the secondary battery (100) of this embodiment, charging occurs when lithium ions of the positive electrode (110) move to the negative electrode (150), and discharging occurs when lithium ions of the negative electrode (150) move to the positive electrode (110).

[0044] The positive electrode (110) supplies lithium ions required for the secondary battery (100) and includes a positive electrode current collector (120), a positive electrode active material (130), and a lithium alloy layer (140).

[0045] The positive electrode current collector (120) plays a role in transferring or exporting electrons from the outside to the positive electrode active material (130) during charging and discharging of the secondary battery (100). The positive electrode current collector (120) supports the positive electrode active material (130) and may be made of a first metal material having high conductivity without causing chemical changes in the secondary battery (100). For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., an aluminum-cadmium alloy, etc. may be used. In the present embodiment, a positive electrode current collector (120) made of aluminum may be used.

[0046] Referring to Fig. 1, an aluminum thin film can be used as the positive electrode collector (120) of the present embodiment.

[0047]

[0048] The cathode active material (130) is a material that participates in the electrode reaction of the secondary battery (100) in the cathode section (110). The cathode active material (130) contains lithium, and lithium may exist in the form of lithium oxide. For example, the cathode active material (130) may be LiCoO2, LiNiO2, LiMnO2, or LiNi x Co y A layered oxide system represented by LiMO2 (M is a metal) such as MnzO2 (x, y, z are the composition ratios, referred to as NCM), an olivine system represented by LiMPO4 (M is a metal) such as LiFePO4, a spinel system such as LiMn2O4, a complex metal chalcogen compound, sulfur, etc. may be used, but is not limited thereto, and various cathode active materials (130) may be used.

[0049] At this time, the positive electrode active material (130) may be mixed with a conductive agent, a binder, etc. The conductive agent may play a role in increasing the conductivity of lithium oxide, and the binder may play an adhesive role in helping the positive electrode active material (130) and the conductive agent to be well fixed to the positive electrode current collector (120), such as aluminum.

[0050] For example, a fluorine-containing binder such as PTFE or PVDF can be used as a binder, and carbon black (CB), conducting graphite, ethylene black, vertically-aligned carbon fiber, and carbon nanotube (CNT) can be used as a conductive material.

[0051]

[0052] The lithium alloy layer (140) supplies lithium required for pre-lithiation. That is, the lithium alloy layer (140) can serve as a lithium supply source that compensates for the irreversible consumption of lithium ions in the secondary battery (100). The lithium alloy layer (140) of the present embodiment is interposed between the positive electrode current collector (120) and the positive electrode active material (130), and can be formed of an alloy of the first metal of the positive electrode current collector (120) and lithium.

[0053] Referring to Fig. 1, in this embodiment, a positive electrode current collector (120) made of aluminum is used, and the lithium alloy layer (140) may be made of an alloy of aluminum and lithium.

[0054] At this time, the amount of lithium included in the lithium alloy layer (140) is set as the amount of lithium for pre-lithiation, and can be determined, for example, in the range of 10% to 200% of the active lithium in the positive electrode active material (130).

[0055] FIG. 4 to FIG. 7 are drawings showing a lithium alloy layer (140) in a secondary battery (100) according to one embodiment of the present invention.

[0056] FIG. 4 is a photograph showing a lithium alloy layer (140) formed on the surface of the positive electrode collector (120) of the present embodiment before pre-lithiation, and FIG. 5 is a photograph showing a cross-section of a lithium alloy layer (140) formed on the positive electrode collector (120) of the present embodiment before pre-lithiation.

[0057] Referring to FIG. 4, it can be confirmed that a lithium alloy layer (140) is formed on the surface of the aluminum thin film, which is the positive electrode collector (120) of the present embodiment, and that a cubic structure of the lithium alloy layer (140) is formed on the surface of the aluminum thin film.

[0058] In addition, referring to FIG. 5, it can be confirmed that an alloy of aluminum and lithium is formed on one side of the aluminum thin film of the present embodiment to a predetermined thickness, thereby forming an alloy layer distinct from the main body of the aluminum thin film. For example, in the present embodiment, the aluminum thin film and the lithium alloy layer (140) may have a total thickness of 24.4 μm, and the lithium alloy layer (140) formed on one side of the aluminum thin film may have a thickness of 5.61 μm.

[0059] FIG. 6 is a photograph showing a lithium alloy layer (140) formed on the surface of the positive electrode collector (120) of the present embodiment after pre-lithiation, and FIG. 7 is a photograph showing a cross-section of a lithium alloy layer (145) formed on the positive electrode collector (120) of the present embodiment after pre-lithiation.

[0060] Referring to FIG. 6, the lithium alloy layer (140) is formed in a cubic structure on the surface of the aluminum thin film before pre-lithiation, but after pre-lithiation, lithium ions escape from the lithium alloy layer (145), and a surface structure with many pores may be formed.

[0061] In addition, referring to FIG. 7, it can be confirmed that lithium ions escape from the lithium alloy layer (145) after pre-lithiation, thereby reducing its thickness. For example, in the present embodiment, before pre-lithiation, the aluminum thin film and the lithium alloy layer (140) had a total thickness of 24.4 μm, but it can be confirmed that the total thickness is reduced to 19.9 μm after pre-lithiation.

[0062] At this time, the lithium alloy layer (145) after pre-lithiation may exist in the form of an aluminum layer from which all lithium ions have been removed or an alloy layer from which some lithium ions remain.

[0063]

[0064] The negative electrode part (150) stores and releases lithium ions from the positive electrode part (110) while supplying electrons to the external circuit. The negative electrode part includes a negative electrode collector (150) made of a second metal material. The negative electrode collector (150) may be made of a second metal material that has high conductivity without causing chemical changes in the secondary battery (100). For example, copper, stainless steel, aluminum, nickel, titanium, palladium, sintered carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., aluminum-cadmium alloy, etc. may be used. In the present embodiment, a negative electrode collector (150) made of copper may be used.

[0065] The negative electrode portion of the present embodiment may not include a negative electrode active material and the negative electrode current collector (150) may be directly disposed on the electrolyte portion (190). For example, the secondary battery (100) of the present embodiment may be an anodeless lithium metal battery (AF-LMB) that does not include a negative electrode active material or a lithium thin film between the negative electrode current collector (150) and the electrolyte portion (190).

[0066]

[0067] The electrolyte (190) is a medium through which lithium ions can move between the positive electrode (110) and the negative electrode. The electrolyte (190) may include a material with high ionic conductivity to facilitate the movement of lithium ions.

[0068] The electrolyte portion (190) of the present embodiment may include an electrolyte and a separator.

[0069] The electrolyte may include a salt and a solvent. The salt serves as a passage for lithium ions to pass through, and the solvent may be an organic liquid used to dissolve the salt. In the electrolyte unit (190) of the present embodiment, the electrolyte may include a lithium salt. For example, the lithium salt may be LiCl, LiBr, LiFSI, LiI, LiClO4, LiAlO4, LiBF4, LiB 10Cl 10 , LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi, (C2F5SO2)2NLi, LiC4F9SO3, lithium chloroborane, lithium lower aliphatic carboxylic acid, lithium 4 phenylborate, etc., and can be used without limitation as long as it is used in the electrolyte.

[0070] The separator physically prevents the anode (110) and cathode from mixing with each other. Electrons do not flow directly through the electrolyte, and only ions can move through the microscopic pores of the separator.

[0071] Meanwhile, in this embodiment, an electrolyte part (190) including an electrolyte and a separator is presented, but it is not limited thereto, and various types of electrolyte parts (190), such as a solid electrolyte, may be used.

[0072]

[0073] Below, changes in operation and structure during initial charging and discharging of a secondary battery (100) according to the embodiment of the present invention described above are described.

[0074] FIG. 2 shows the initial charging state of a secondary battery (100) according to one embodiment of the invention, and FIG. 3 shows the structure of the secondary battery (100) after the initial charging.

[0075] Referring to FIG. 2, when the secondary battery (100) of the present embodiment having the above-described structure is initially charged, the lithium in the lithium alloy layer (140) becomes lithium ions and moves to the negative electrode together with the lithium ions supplied from the positive electrode active material (130). At this time, the lithium in the lithium alloy layer (140) is used to compensate for the active lithium loss occurring in the negative electrode. That is, the lithium in the lithium alloy layer (140) can be used for pre-lithiation. For example, the lithium in the lithium alloy layer (140) can be used to form a solid electrolyte interface (SEI) layer in the negative electrode.

[0076] Accordingly, a lithium layer (160) formed of lithium of the lithium alloy layer (140) and lithium of the positive electrode active material (130) can be formed on the negative electrode current collector (150) of the present embodiment.

[0077] After pre-lithiation, lithium ions may escape from the lithium alloy layer (145) of the present embodiment, thereby reducing its thickness. Accordingly, since the thickness of the lithium alloy layer (145) decreases after pre-lithiation, the overall thickness of the positive electrode may decrease. At this time, the decrease in the thickness of the positive electrode can accommodate the increase in thickness caused by the formation of the lithium layer (160) in the negative electrode, thereby effectively maintaining the volume of the entire secondary battery (100) and maintaining mechanical strength during charging.

[0078] In addition, in the secondary battery (100) of the present embodiment, there is an advantage in that, in the process of pre-lithiation with lithium supplied from the lithium alloy layer (140), no dead weight or other side reactions occur due to unnecessary gas formation.

[0079]

[0080] Referring to FIG. 3, when discharge occurs after pre-lithiation and initial charging, lithium may be ionized in the lithium layer (165) formed on the negative electrode current collector (150) and moved to the positive electrode active material (130). At this time, lithium is not recombined with the positive electrode current collector (120) and the lithium alloy layer (145), but is maintained in the state of active lithium. That is, the lithium that was in the lithium alloy layer (140) before pre-lithiation may exist as active lithium or the lithium layer (165) on the negative electrode current collector (150) after pre-lithiation. Accordingly, the lithium in the lithium alloy layer (140) may be used for irreversible consumption or may serve as a lithium storage during the remaining cycles, thereby preventing active lithium from being lost from the positive electrode active material (130).

[0081]

[0082] The secondary battery (100) of the present embodiment after pre-lithiation can be configured as part of the positive electrode current collector (120) with all lithium exhausted from the lithium alloy layer (145).

[0083] That is, the positive electrode portion (110) can be represented by a structure divided into a positive electrode current collector (120, 145) and a positive electrode active material (130). The positive electrode current collector (120, 145) is a structure in which the positive electrode current collector (120) before pre-lithiation and the lithium alloy layer (145) are integrally bonded, and lithium can escape from the lithium alloy layer (140) to form a thin film structure made of a single metal.

[0084] At this time, the positive electrode current collector (120, 145) may have a structure in which a plurality of pores are formed on one surface that comes into contact with the positive electrode active material (130). As described above, after pre-lithiation, lithium ions escape from the lithium alloy layer (145) to form a plurality of pores, so the portion of the positive electrode current collector (120, 145) where the lithium alloy layer (145) was previously formed may have a structure in which a plurality of pores are formed.

[0085] In other words, the surface of the positive electrode current collector (120, 145) that comes into contact with the positive electrode active material (130) may be formed to have a higher surface roughness than the other surface of the positive electrode current collector (120, 145). Since the portion of the positive electrode current collector (120, 145) that comes into contact with the positive electrode active material (130) is a portion where a lithium alloy layer (145) was previously formed, a void is created where lithium has escaped from the surface, and thus the surface may be formed unevenly and have a high surface roughness.

[0086] In other words, the positive electrode current collector (120, 145) may be formed of two layers in which the positive electrode current collector (120) prior to pre-lithiation and the lithium alloy layer (140) are combined, and may have a structure in which the density of the portion where the lithium alloy layer (145) was previously formed is formed low. That is, the positive electrode current collector (120, 145) may be formed of a first layer (120) and a second layer (145), and the second layer (145) in contact with the positive electrode active material (130) of the positive electrode current collector (120, 145) may be formed to have a lower density than the first layer (120) of the positive electrode current collector (120, 145).

[0087] FIGS. 8 to 10 are drawings explaining the charging and discharging characteristics of a secondary battery (100) according to one embodiment of the present invention.

[0088] Fig. 8 is a graph showing the initial charge and discharge profiles of LiAl-NCM622 / Cu AF-LMB and NCM / Cu AF-LMB. LiAl-NCM622 / Cu AF-LMB has a structure according to the present embodiment, and is a structure in which the lithium alloy layer (140) described above is added to the conventionally known NCM / Cu AF-LMB structure.

[0089] Referring to FIG. 8, it can be confirmed that the LiAl-NCM622 / Cu AF-LMB having the structure according to the present embodiment has an initial Coulombic efficiency (CE) of about 94%, which is significantly higher than the initial Coulombic efficiency (about 60-70%) of a typical NCM / Cu AF-LMB.

[0090] Referring to FIGS. 9 and 10, it can be confirmed that the LiAl-NCM622 / Cu AF-LMB having the structure according to the present embodiment has significantly improved cycling stability, as compared to the conventional NCM / Cu AF-LMB, with the capacity and coulombic efficiency maintained constant even after several cycles.

[0091]

[0092] Figures 11 and 12 are drawings showing a secondary battery according to another embodiment of the present invention. Figure 11 shows the secondary battery of the present embodiment before pre-lithiation, and Figure 12 shows the secondary battery of the present embodiment after pre-lithiation.

[0093] The secondary battery (200) according to the present embodiment differs from the above-described embodiment in that the negative electrode portion includes a negative electrode current collector (250) and a negative electrode active material (260). That is, the secondary battery (200) according to the present embodiment may be a LIB (Lithium-ion Battery).

[0094] Referring to FIGS. 11 and 12, the negative electrode portion of the present embodiment includes a negative electrode current collector (250) and a negative electrode active material (260) made of a second metal material.

[0095] The negative electrode current collector (250) may be made of a second metal material having high conductivity without causing chemical changes in the secondary battery (200). For example, copper, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, silver, etc., an aluminum-cadmium alloy, etc. may be used. In the present embodiment, a negative electrode current collector (250) made of copper may be used.

[0096] At this time, the negative electrode current collector (250) can form fine irregularities on the surface to strengthen the bonding strength with the negative electrode active material (260), and can have various forms such as a film, sheet, foil, mesh, net, porous body, foam, and non-woven body.

[0097] The negative electrode active material (260) is interposed between the negative electrode current collector (250) and the electrolyte unit (290), and is a material that participates in the electrode reaction of the secondary battery (200) in the negative electrode unit. When the battery is discharged, it can store and release lithium ions that have moved from the positive electrode to generate electrical energy. For example, the negative electrode active material (260) may include graphite, a mixture of graphite and silicon oxide, a mixture of graphite and silicon, silicon, lithium titanium oxide, tin, etc., but is not limited thereto, and various negative electrode active materials (260) may be used.

[0098] Referring to FIG. 11, as in the above-described embodiment, the positive electrode portion (210) includes a positive electrode current collector (220), a positive electrode active material (230), and a lithium alloy layer (240).

[0099] Referring to FIG. 12, as in the above-described embodiment, the lithium of the lithium alloy layer (240) is used to compensate for the active lithium loss occurring in the negative electrode. That is, the lithium of the lithium alloy layer (240) can be used for pre-lithiation.

[0100] In particular, the lithium of the lithium alloy layer (240) can minimize the volume expansion rate of the negative electrode by allowing pre-lithiation to occur in the negative electrode active material (260). By introducing lithium in advance into the negative electrode active material (260) such as silicon, the volume change of the negative electrode caused by the introduction of active lithium into the negative electrode during charging and discharging can be alleviated.

[0101] Meanwhile, in the present embodiment, the secondary battery (200) of the present embodiment after pre-lithiation may be configured such that all lithium is exhausted in the lithium alloy layer (245) and the lithium alloy layer (245) may be configured as a part of the positive electrode current collector (220).

[0102] That is, the positive electrode portion (210) may be structured as being divided into a positive electrode current collector (220, 245) and a positive electrode active material (230). The positive electrode current collector (220, 245) has a structure in which the positive electrode current collector (220) before pre-lithiation and the lithium alloy layer (245) are integrally bonded, and lithium may escape from the lithium alloy layer (245) to have a thin film structure made of a single metal.

[0103] At this time, the positive electrode current collector (220, 245) may have a structure in which a plurality of pores are formed on one surface that comes into contact with the positive electrode active material (230). As described above, after pre-lithiation, lithium ions escape from the lithium alloy layer (245) to form a plurality of pores, so the portion of the positive electrode current collector (220, 245) where the lithium alloy layer (245) was previously formed may have a structure in which a plurality of pores are formed.

[0104] In other words, the surface of the positive electrode current collector (220, 245) that comes into contact with the positive electrode active material (230) may be formed to have a higher surface roughness than the other surface of the positive electrode current collector (220, 245). Since the portion of the positive electrode current collector (220, 245) that comes into contact with the positive electrode active material (230) is a portion where a lithium alloy layer (240) was previously formed, a void is created where lithium has escaped from the surface, and thus the surface may be formed unevenly and have a high surface roughness.

[0105] In other words, the positive electrode current collector (220, 245) may be formed as two layers in which the positive electrode current collector (220) prior to pre-lithiation and the lithium alloy layer (245) are combined, and may have a structure in which the density of the portion where the lithium alloy layer (245) was previously formed is formed low. That is, the positive electrode current collector (220) may be formed as a first layer (220) and a second layer (245), and the second layer (245) in contact with the positive electrode active material (230) of the positive electrode current collector (220, 245) may be formed to have a lower density than the first layer (220) of the positive electrode current collector (220).

[0106]

[0107] Figures 13 and 14 are drawings showing a secondary battery according to another embodiment of the present invention. Figure 13 shows the secondary battery of the present embodiment before pre-lithiation, and Figure 14 shows the secondary battery of the present embodiment after pre-lithiation.

[0108] The secondary battery (300) according to the present embodiment differs from the above-described embodiment in that the negative electrode portion includes a negative electrode collector (350) and a lithium layer. That is, the secondary battery (300) according to the present embodiment may be an LMB (Lithium Metal Battery).

[0109] Referring to FIGS. 13 and 14, the negative electrode portion of the present embodiment includes a negative electrode current collector (350) made of a second metal material and a thin film (360) including a lithium layer interposed between the negative electrode current collector (350) and the electrolyte portion (390).

[0110] Referring to FIG. 13, as in the above-described embodiment, the positive electrode portion (310) includes a positive electrode current collector (320), a positive electrode active material (330), and a lithium alloy layer (340).

[0111] Referring to Fig. 14, as in the above-described embodiment, the lithium of the lithium alloy layer (340) is used to compensate for the loss of active lithium occurring in the negative electrode. That is, the lithium of the lithium alloy layer (340) can be used for pre-lithiation. Accordingly, in the present embodiment, the lithium of the lithium alloy layer (340) can be combined with a thin film including a lithium layer positioned in the negative electrode portion. Accordingly, the lithium of the lithium alloy layer (340) can be used for irreversible consumption or can serve as a lithium storage during the remaining cycles, thereby preventing the loss of active lithium from the positive electrode active material (330).

[0112] Meanwhile, in the present embodiment as well, the secondary battery (300) of the present embodiment after pre-lithiation can be configured as part of the positive electrode current collector (320) with all lithium exhausted in the lithium alloy layer (340).

[0113] That is, the positive electrode portion (310) may be structured as being divided into a positive electrode current collector (320, 345) and a positive electrode active material (330). The positive electrode current collector (320, 345) is a structure in which the positive electrode current collector (320) before pre-lithiation and the lithium alloy layer (345) are integrally bonded, and lithium can escape from the lithium alloy layer (340) to form a thin film structure made of a single metal.

[0114] At this time, the positive electrode current collector (320, 345) may have a structure in which a plurality of pores are formed on one surface that comes into contact with the positive electrode active material (330). As described above, after pre-lithiation, lithium ions escape from the lithium alloy layer (345) to form a plurality of pores, so the portion of the positive electrode current collector (320, 345) where the lithium alloy layer (340) was previously formed may have a structure in which a plurality of pores are formed.

[0115] In other words, the surface of the positive electrode current collector (320, 345) that comes into contact with the positive electrode active material (330) may be formed to have a higher surface roughness than the other surface of the positive electrode current collector (320, 345). Since the portion of the positive electrode current collector (320, 345) that comes into contact with the positive electrode active material (330) is a portion where a lithium alloy layer (340) was previously formed, a void is created where lithium has escaped from the surface, and thus the surface may be formed unevenly and have a high surface roughness.

[0116] In other words, the positive electrode current collector (320, 345) may be formed as two layers in which the positive electrode current collector (320) prior to pre-lithiation and the lithium alloy layer (345) are combined, and may have a structure in which the density of the portion where the lithium alloy layer (345) was previously formed is formed low. That is, the positive electrode current collector (320, 345) may be formed as a first layer (320) and a second layer (345), and the second layer (345) in contact with the positive electrode active material (330) of the positive electrode current collector (320, 345) may be formed to have a lower density than the first layer (320) of the positive electrode current collector (320).

[0117]

[0118] FIG. 15 is a drawing showing a flow chart of a secondary battery manufacturing method according to an embodiment of another aspect of the present invention.

[0119] Referring to FIG. 15, a method for manufacturing a secondary battery according to an embodiment of another aspect of the present invention includes a positive electrode current collector preparation step (S110), a lithium alloy layer formation step (S120), and a positive electrode active material arrangement step (S130).

[0120] In the positive electrode current collector preparation step (S110), a positive electrode current collector made of a first metal material is prepared.

[0121] In this embodiment, an aluminum thin film can be prepared as a cathode current collector. The aluminum thin film can have high conductivity without causing chemical changes in the secondary battery.

[0122]

[0123] In the lithium alloy layer forming step (S120), a lithium alloy layer formed of an alloy of the first metal of the positive electrode current collector and lithium is formed on one surface of the positive electrode current collector.

[0124] In this embodiment, an alloy of aluminum and lithium can be formed on one surface of an aluminum thin film. For example, an alloy of aluminum and lithium can be formed on one surface of the aluminum thin film by contacting a lithium thin film with the aluminum thin film.

[0125] Specifically, after interposing an electrolyte between an aluminum thin film and a lithium thin film, one side of the aluminum thin film can be lithiated by bringing the aluminum thin film and the lithium thin film into contact. At this time, the electrolyte may include a lithium salt. Additionally, to promote lithiation of the aluminum thin film, the aluminum thin film and the lithium thin film can be pressed and brought into contact.

[0126] In particular, when pressing an aluminum thin film and a lithium thin film in a state where an electrolyte is present, the amount of aluminum and lithium alloy formed can be controlled by controlling the pressing strength and contact time.

[0127] When lithiation of the aluminum thin film is achieved, the aluminum thin film can be separated from the lithium thin film to obtain an aluminum thin film having an alloy of aluminum and lithium formed on one surface.

[0128]

[0129] In the positive electrode active material arrangement step (S130), a positive electrode active material including lithium can be arranged on a lithium alloy layer to form a positive electrode portion of a secondary battery.

[0130]

[0131] Above, the preferred embodiments of the present invention have been described, but those of ordinary skill in the art will be able to modify and change the present invention in various ways by adding, changing, deleting or adding components, etc., within the scope that does not depart from the spirit of the present invention described in the claims, and this will also be considered to be included within the scope of the rights of the present invention.

[0132]

[0133] 100, 200, 300: Secondary batteries

[0134] 110, 210, 310: anode

[0135] 120, 220, 320: positive current collector

[0136] 130, 230, 330: Cathode active material

[0137] 140, 240, 340: Lithium alloy layer

[0138] 150, 250, 350: negative current collector

[0139] 190, 290, 390: Electrolyte section

Claims

1. Anode and cathode; and Including an electrolyte portion arranged between the positive electrode portion and the negative electrode portion, The above bipolar part is, A cathode current collector of a first metal material; A cathode active material comprising lithium; and A secondary battery comprising a lithium alloy layer formed of an alloy of the first metal of the positive electrode collector and lithium, and interposed between the positive electrode collector and the positive electrode active material.

2. In paragraph 1, The above cathode part, A secondary battery including a negative electrode current collector made of a second metal material disposed on the above electrolyte portion.

3. In paragraph 1, The above cathode part, A negative electrode current collector made of a second metal material; and A secondary battery comprising a negative electrode active material interposed between the negative electrode current collector and the electrolyte portion.

4. In paragraph 1, The above cathode part, A negative electrode current collector made of a second metal material; and A secondary battery comprising a thin film including a lithium layer interposed between the negative electrode collector and the electrolyte portion.

5. Anode and cathode; and Including an electrolyte portion arranged between the positive electrode portion and the negative electrode portion, The above bipolar part is, A positive electrode current collector made of a first metal material; and It is interposed between the positive electrode current collector and the electrolyte portion, and includes a positive electrode active material including lithium, A secondary battery, wherein a plurality of pores are formed on one surface of the positive electrode current collector that comes into contact with the positive electrode active material.

6. Anode and cathode; and Including an electrolyte portion arranged between the positive electrode portion and the negative electrode portion, The above bipolar part is, A positive electrode current collector made of a first metal material; and It is interposed between the positive electrode current collector and the electrolyte portion, and includes a positive electrode active material including lithium, A secondary battery, wherein one surface of the positive electrode current collector that comes into contact with the positive electrode active material has a higher surface roughness than the other surface of the positive electrode current collector.

7. Anode and cathode; and Including an electrolyte portion arranged between the positive electrode portion and the negative electrode portion, The above bipolar part is, A positive electrode current collector made of a first metal material; and It is interposed between the positive electrode current collector and the electrolyte portion, and includes a positive electrode active material including lithium, A secondary battery, wherein the positive electrode current collector is formed of a first layer and a second layer, and the second layer of the positive electrode current collector, which comes into contact with the positive electrode active material, is formed to have a lower density than the first layer of the positive electrode current collector.

8. In any one of paragraphs 5 to 7, The above cathode part, A secondary battery including a negative electrode current collector made of a second metal material disposed on the above electrolyte portion.

9. In any one of paragraphs 5 to 7, The above cathode part, A negative electrode current collector made of a second metal material; and A secondary battery comprising a negative electrode active material interposed between the negative electrode current collector and the electrolyte portion.

10. In any one of paragraphs 5 to 7, The above cathode part, A negative electrode current collector made of a second metal material; and A secondary battery comprising a thin film including a lithium layer interposed between the negative electrode collector and the electrolyte portion.

11. A step for preparing a cathode current collector of the first metal material; A lithium alloy layer forming step of forming a lithium alloy layer formed by an alloy of the first metal of the positive electrode current collector and lithium on one side of the positive electrode current collector; and A method for manufacturing a secondary battery, comprising a cathode active material arrangement step of arranging a cathode active material containing lithium on the lithium alloy layer.

12. In paragraph 11, The above positive electrode current collector comprises an aluminum film, The above lithium alloy layer forming step is, A thin film preparation step of interposing an electrolyte between the aluminum thin film and the lithium thin film; A lithiation step of bringing the aluminum thin film and the lithium thin film into contact; and A method for manufacturing a secondary battery, comprising a thin film separation step of separating the above aluminum thin film.

13. In paragraph 12, In the above thin film preparation step, A method for manufacturing a secondary battery, wherein the electrolyte comprises a lithium salt.

14. In paragraph 12, The above lithiation step is, A method for manufacturing a secondary battery, wherein the aluminum thin film and the lithium thin film are pressed and brought into contact with each other.

Images