JP7035643B2 - Lithium secondary battery - Google Patents

Lithium secondary battery Download PDF

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JP7035643B2
JP7035643B2 JP2018043340A JP2018043340A JP7035643B2 JP 7035643 B2 JP7035643 B2 JP 7035643B2 JP 2018043340 A JP2018043340 A JP 2018043340A JP 2018043340 A JP2018043340 A JP 2018043340A JP 7035643 B2 JP7035643 B2 JP 7035643B2
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current collector
electrolyte layer
secondary battery
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JP2019160491A (en
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勝春 肥田
純一 岩田
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Fujitsu Ltd
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Description

本発明は、リチウム二次電池に関する。 The present invention relates to a lithium secondary battery.

従来より、正極と、イオン伝導性電解質と、負極として金属リチウムを用いるリチウム二次電池において、該金属リチウム表面に絶縁性の多孔質薄膜を設けたことを特徴とするリチウム二次電池がある（例えば、特許文献１参照）。 Conventionally, in a lithium secondary battery using a positive electrode, an ionic conductive electrolyte, and metallic lithium as a negative electrode, there is a lithium secondary battery characterized in that an insulating porous thin film is provided on the surface of the metallic lithium (a positive electrode). For example, see Patent Document 1).

特開平０５－２７５１１８号公報Japanese Unexamined Patent Publication No. 05-275118

リチウム二次電池では、充電に伴って負極にリチウムが析出し、放電すると負極のリチウムがイオン伝導性電解質に戻る現象が繰り返し行われる。ところで、負極に析出したリチウムが均等にイオン伝導性電解質に戻るとは限らず、部分的に負極に残存することがある。部分的に負極に残存すると、負極とイオン伝導性電解質との間に空隙が生じた状態になる。 In a lithium secondary battery, lithium is deposited on the negative electrode as it is charged, and when discharged, the lithium on the negative electrode returns to the ionic conductive electrolyte. By the way, the lithium deposited on the negative electrode does not always return to the ion conductive electrolyte evenly, and may partially remain on the negative electrode. If it partially remains on the negative electrode, a void is formed between the negative electrode and the ion conductive electrolyte.

このようにリチウムが部分的に負極に残存すると、充放電に関与するリチウムイオンが減るため、リチウム二次電池の性能が低下するおそれがある。 When lithium partially remains in the negative electrode in this way, the lithium ions involved in charging and discharging are reduced, so that the performance of the lithium secondary battery may deteriorate.

そこで、性能低下を抑制可能なリチウム二次電池を提供することを目的とする。 Therefore, it is an object of the present invention to provide a lithium secondary battery capable of suppressing performance deterioration.

本発明の実施の形態のリチウム二次電池は、正極集電体と、前記正極集電体に重ねて設けられる正極と、前記正極に重ねて設けられ、リチウムイオンを含む固体電解質層と、前記固体電解質層の前記正極に面する第１面とは反対の第２面の一部分に設けられ、前記固体電解質層に対して不活性な絶縁材料製で、前記第２面に固着される固着部材と、前記固体電解質層の第２面と、前記固着部材とに重ねて設けられ、前記固着部材に固着され、前記固体電解質層との間に析出するリチウムを前記固体電解質層に向かう方向に付勢する負極集電体とを含み、前記固着部材の表面のうち、前記固体電解質層に接していない領域の全てが前記負極集電体に接している。 The lithium secondary battery of the embodiment of the present invention includes a positive electrode current collector, a positive electrode provided on the positive electrode current collector, a solid electrolyte layer provided on the positive electrode and containing lithium ions, and the above. A fixing member provided on a part of the second surface of the solid electrolyte layer opposite to the first surface facing the positive electrode, made of an insulating material inert to the solid electrolyte layer, and fixed to the second surface. And, lithium that is provided so as to be overlapped with the second surface of the solid electrolyte layer and the fixing member, is fixed to the fixing member, and precipitates between the solid electrolyte layer is attached in the direction toward the solid electrolyte layer. All of the regions of the surface of the fixing member that are not in contact with the solid electrolyte layer, including the negative electrode current collector, are in contact with the negative electrode current collector.

性能低下を抑制可能なリチウム二次電池を提供することができる。 It is possible to provide a lithium secondary battery capable of suppressing performance deterioration.

実施の形態のリチウム二次電池１００を示す平面図である。It is a top view which shows the lithium secondary battery 100 of embodiment. 図１のＡ－Ａ矢視断面を示す図である。It is a figure which shows the cross section of AA of FIG. リチウム二次電池１００の放電後と充電後の断面の様子を示す図である。It is a figure which shows the state of the cross-section after discharging and charging of a lithium secondary battery 100. リチウム二次電池１００のサイクル数と、充電容量の維持率との関係を表す実験結果である。This is an experimental result showing the relationship between the number of cycles of the lithium secondary battery 100 and the maintenance rate of the charge capacity.

以下、本発明のリチウム二次電池を適用した実施の形態について説明する。 Hereinafter, embodiments to which the lithium secondary battery of the present invention is applied will be described.

＜実施の形態＞
図１は、実施の形態のリチウム二次電池１００を示す平面図である。図２は、図１のＡ－Ａ矢視断面を示す図である。以下では、説明の便宜上、図２の断面に示す上下関係を用いて説明するが、普遍的な上下関係を表すものではない。 <Embodiment>
FIG. 1 is a plan view showing the lithium secondary battery 100 of the embodiment. FIG. 2 is a diagram showing a cross section taken along the line AA of FIG. Hereinafter, for convenience of explanation, the hierarchical relationship shown in the cross section of FIG. 2 will be used for explanation, but it does not represent a universal hierarchical relationship.

リチウム二次電池１００は、基板１０１の上に設けられており、正極集電体１１０、正極１２０、固体電解質層１３０、固着部材１４０、及び負極集電体１５０を含む。リチウム二次電池１００は、すべての構成要素が固体である全固体リチウム二次電池の一例である。 The lithium secondary battery 100 is provided on the substrate 101 and includes a positive electrode current collector 110, a positive electrode 120, a solid electrolyte layer 130, a fixing member 140, and a negative electrode current collector 150. The lithium secondary battery 100 is an example of an all-solid-state lithium secondary battery in which all the components are solid.

リチウム二次電池１００は、実際には、正極集電体１１０と負極集電体１５０にそれぞれ接続される正極端子及び負極端子に加えて、正極集電体１１０、正極１２０、固体電解質層１３０、固着部材１４０、及び負極集電体１５０を覆うケース等の構成要素を含むが、ここではリチウム二次電池１００の中身を示し、正極端子、負極端子、及びケース等の構成要素を省略する。 In the lithium secondary battery 100, in addition to the positive electrode terminal and the negative electrode terminal connected to the positive electrode current collector 110 and the negative electrode current collector 150, respectively, the positive electrode current collector 110, the positive electrode 120, and the solid electrolyte layer 130 Although the components such as the case covering the fixing member 140 and the negative electrode current collector 150 are included, the contents of the lithium secondary battery 100 are shown here, and the components such as the positive electrode terminal, the negative electrode terminal, and the case are omitted.

基板１０１は、シリコン層１０１Ａと絶縁層１０１Ｂを含む。基板１０１は、シリコンウェハの上面を酸化することによって、二酸化シリコン（ＳｉＯ２）製の絶縁層１０１Ｂを形成したものである。絶縁層１０１Ｂは、リチウム二次電池１００とシリコン層１０１Ａとを絶縁するために設けられている。 The substrate 101 includes a silicon layer 101A and an insulating layer 101B. The substrate 101 is formed by oxidizing the upper surface of a silicon wafer to form an insulating layer 101B made of silicon dioxide (SiO 2 ). The insulating layer 101B is provided to insulate the lithium secondary battery 100 and the silicon layer 101A.

基板１０１は、リチウム二次電池１００を作製するための基台として設けられており、基板１０１自体は、リチウム二次電池１００の構成要素に含まれなくてよいものである。このため、基板１０１は、シリコンウェハで作製されたものに限られず、リチウム二次電池１００との絶縁が確保可能なものであれば、どのようなものであってもよい。 The substrate 101 is provided as a base for manufacturing the lithium secondary battery 100, and the substrate 101 itself does not have to be included in the components of the lithium secondary battery 100. Therefore, the substrate 101 is not limited to that made of a silicon wafer, and may be any material as long as it can secure insulation from the lithium secondary battery 100.

正極集電体１１０は、絶縁層１０１Ｂの上に重ねて設けられ、平面視で矩形状である。正極集電体１１０は、正極１２０の正極活物質を保持し、電流を正極活物質に供給する機能を有する。正極集電体１１０は、一例として、チタン（Ｔｉ）層１１１Ａと、白金（Ｐｔ）層１１１Ｂとを有する。 The positive electrode current collector 110 is provided so as to be superposed on the insulating layer 101B, and has a rectangular shape in a plan view. The positive electrode current collector 110 has a function of holding the positive electrode active material of the positive electrode 120 and supplying an electric current to the positive electrode active material. The positive electrode current collector 110 has, for example, a titanium (Ti) layer 111A and a platinum (Pt) layer 111B.

チタン層１１１Ａは、絶縁層１０１Ｂと白金層１１１Ｂとの密着層として設けられている。また、白金層１１１Ｂには、正極１２０が面接続される。白金層１１１Ｂは、固体電解質層１３０の外部に表出している部分において、図示しない正極端子に接続される。チタン層１１１Ａ及び白金層１１１Ｂの厚さは、それぞれ、一例として、３０ｎｍ及び１７０ｎｍである。 The titanium layer 111A is provided as an adhesion layer between the insulating layer 101B and the platinum layer 111B. Further, the positive electrode 120 is surface-connected to the platinum layer 111B. The platinum layer 111B is connected to a positive electrode terminal (not shown) at a portion exposed to the outside of the solid electrolyte layer 130. The thicknesses of the titanium layer 111A and the platinum layer 111B are, for example, 30 nm and 170 nm, respectively.

正極１２０は、正極集電体１１０の上に重ねて設けられ、平面視で矩形状である。正極１２０は、平面視で正極集電体１１０の中に収まるように配置される。すなわち、正極１２０は、平面視で正極集電体１１０よりも小さい。 The positive electrode 120 is provided so as to be superposed on the positive electrode current collector 110, and has a rectangular shape in a plan view. The positive electrode 120 is arranged so as to fit inside the positive electrode current collector 110 in a plan view. That is, the positive electrode 120 is smaller than the positive electrode current collector 110 in a plan view.

正極１２０は、一例として、正極活物質としてコバルト酸リチウム（ＬｉＣｏＯ２）を用いて作製される。正極１２０の厚さは、一例として、３．０μｍである。 As an example, the positive electrode 120 is manufactured using lithium cobalt oxide (LiCoO 2 ) as the positive electrode active material. The thickness of the positive electrode 120 is, for example, 3.0 μm.

固体電解質層１３０は、リチウムイオンを含む固体状の電解質層であり、平面視で矩形状である。固体電解質層１３０のサイズは、一例として、四辺がそれぞれ５ｍｍである。固体電解質層１３０は、正極１２０及び正極集電体１１０を覆い、平面視で最外部の四辺が絶縁層１０１Ｂに接するように設けられている。なお、正極集電体１１０の一部分（図中の左端の部分）は、固体電解質層１３０に覆われずに表出する。正極端子に接続するためである。 The solid electrolyte layer 130 is a solid electrolyte layer containing lithium ions, and has a rectangular shape in a plan view. As an example, the size of the solid electrolyte layer 130 is 5 mm on each side. The solid electrolyte layer 130 covers the positive electrode 120 and the positive electrode current collector 110, and is provided so that the outermost four sides are in contact with the insulating layer 101B in a plan view. A part of the positive electrode current collector 110 (the leftmost part in the figure) is exposed without being covered with the solid electrolyte layer 130. This is to connect to the positive electrode terminal.

固体電解質層１３０は、一例として、固体電解質としてリン酸三リチウム（Ｌｉ３ＰＯ４）を形成した薄膜層であり、厚さは２．０μｍである。なお、固体電解質層１３０の下面（正極１２０に面する面）は第１面の一例であり、上面（固着部材１４０が設けられる面）は第２面の一例である。 The solid electrolyte layer 130 is, for example, a thin film layer on which trilithium phosphate (Li 3 PO 4 ) is formed as a solid electrolyte, and has a thickness of 2.0 μm. The lower surface of the solid electrolyte layer 130 (the surface facing the positive electrode 120) is an example of the first surface, and the upper surface (the surface on which the fixing member 140 is provided) is an example of the second surface.

固着部材１４０は、固体電解質層１３０の上面に設けられ、平面視で矩形環状の部材である。固着部材１４０は、平面視で負極集電体１５０の内部に収まるように設けられている。すなわち、固着部材１４０は、固体電解質層１３０の上面の一部分に設けられており、また、固体電解質層１３０の上面のうち、負極集電体１５０が位置する領域のうちの一部分に設けられている。 The fixing member 140 is provided on the upper surface of the solid electrolyte layer 130 and is a rectangular annular member in a plan view. The fixing member 140 is provided so as to fit inside the negative electrode current collector 150 in a plan view. That is, the fixing member 140 is provided on a part of the upper surface of the solid electrolyte layer 130, and is provided on a part of the upper surface of the solid electrolyte layer 130 in the region where the negative electrode current collector 150 is located. ..

これは、固体電解質層１３０と負極集電体１５０とが直接的に接する部分を確保するとともに、固着部材１４０が固体電解質層１３０と負極集電体１５０との間に位置するようにするためである。固着部材１４０は、固体電解質層１３０の上面に固着されている。 This is to secure a portion where the solid electrolyte layer 130 and the negative electrode current collector 150 are in direct contact with each other, and to ensure that the fixing member 140 is located between the solid electrolyte layer 130 and the negative electrode current collector 150. be. The fixing member 140 is fixed to the upper surface of the solid electrolyte layer 130.

固着部材１４０は、固体電解質層１３０に対して不活性な絶縁材料製である。固着部材１４０は、固体電解質層１３０の上面と、負極集電体１５０との両方に固着され、リチウム二次電池１００が充電されたときに固体電解質層１３０と負極集電体１５０との間にリチウムが析出（溶解析出）しても、固体電解質層１３０及び負極集電体１５０に固着した状態を保持可能な強度を有する。換言すれば、固着部材１４０は、固体電解質層１３０と負極集電体１５０とを固着している。固着部材１４０には、固体電解質層１３０に対して不活性な絶縁材料の中でも、特に金属酸化物のようなセラミックが適している。 The fixing member 140 is made of an insulating material that is inert to the solid electrolyte layer 130. The fixing member 140 is fixed to both the upper surface of the solid electrolyte layer 130 and the negative electrode current collector 150, and is between the solid electrolyte layer 130 and the negative electrode current collector 150 when the lithium secondary battery 100 is charged. Even if lithium is precipitated (dissolved and precipitated), it has a strength capable of retaining the state of being fixed to the solid electrolyte layer 130 and the negative electrode current collector 150. In other words, the fixing member 140 fixes the solid electrolyte layer 130 and the negative electrode current collector 150. Among the insulating materials inert to the solid electrolyte layer 130, ceramics such as metal oxides are particularly suitable for the fixing member 140.

固着部材１４０は、一例として、アルミナ（Ａｌ２Ｏ３）製であり、厚さは２０ｎｍである。なお、固着部材１４０の材料として、アルミナ（Ａｌ２Ｏ３）の代わりに、ジルコニア（ＺｒＯ２）を用いてもよい。 As an example, the fixing member 140 is made of alumina (Al 2 O 3 ) and has a thickness of 20 nm. As the material of the fixing member 140, zirconia (ZrO 2 ) may be used instead of alumina (Al 2 O 3 ).

固着部材１４０として、固体電解質層１３０に対して不活性な絶縁材料又は金属酸化物を用いるのは、固体電解質層１３０の上面と固着部材１４０との界面における還元反応が生じないようにして、リチウム二次電池１００の充電及び放電が繰り返されても、固着部材１４０と固体電解質層１３０の上面との固着状態を保持できるようにするためである。 The use of an insulating material or metal oxide that is inert to the solid electrolyte layer 130 as the fixing member 140 is such that a reduction reaction does not occur at the interface between the upper surface of the solid electrolyte layer 130 and the fixing member 140, and lithium is used. This is so that the fixed state of the fixing member 140 and the upper surface of the solid electrolyte layer 130 can be maintained even if the secondary battery 100 is repeatedly charged and discharged.

負極集電体１５０は、固着部材１４０の全体を覆うように、固体電解質層１３０の上面に設けられている。また、リチウム二次電池１００の充放電が繰り返し行われても、負極集電体１５０は、固着部材１４０の上面に固着された状態に保持される。充放電が繰り返し行われても、負極集電体１５０と固着部材１４０との間にリチウム又は他の物質が入り込むことはないからである。 The negative electrode current collector 150 is provided on the upper surface of the solid electrolyte layer 130 so as to cover the entire fixing member 140. Further, even if the lithium secondary battery 100 is repeatedly charged and discharged, the negative electrode current collector 150 is held in a state of being fixed to the upper surface of the fixing member 140. This is because lithium or other substances do not enter between the negative electrode current collector 150 and the fixing member 140 even if charging and discharging are repeated.

負極集電体１５０は、リチウム二次電池１００が充電されるときに固体電解質層１３０と負極集電体１５０との間にリチウムが析出すると、固着部材１４０によって下方向に固定された状態で、固着部材１４０に接していない部分が上方へ変形し、固体電解質層１３０の上面との間に生じる空間に、還元反応によって固体電解質層１３０から析出するリチウムが収まるようになっている。 When lithium is deposited between the solid electrolyte layer 130 and the negative electrode current collector 150 when the lithium secondary battery 100 is charged, the negative electrode current collector 150 is fixed downward by the fixing member 140. The portion not in contact with the fixing member 140 is deformed upward, and the lithium precipitated from the solid electrolyte layer 130 due to the reduction reaction is accommodated in the space generated between the portion not in contact with the fixing member 140 and the upper surface of the solid electrolyte layer 130.

この状態では、負極集電体１５０は、固着部材１４０によって下方向に引っ張られ、平面視で固着部材１４０に囲まれている部分には張力が掛かるため、析出したリチウムを固体電解質層１３０側に押し戻す（付勢する）。すなわち、負極集電体１５０が板バネのように作用し、復元力を発生する。 In this state, the negative electrode current collector 150 is pulled downward by the fixing member 140, and tension is applied to the portion surrounded by the fixing member 140 in a plan view, so that the precipitated lithium is transferred to the solid electrolyte layer 130 side. Push back (to urge). That is, the negative electrode current collector 150 acts like a leaf spring to generate a restoring force.

このように、析出したリチウムを負極集電体１５０が固体電解質層１３０側に押し戻す（付勢する）力を利用して、リチウム二次電池１００が放電されるときに、固体電解質層１３０と負極集電体１５０との間に析出しているリチウムを効率的に固体電解質層１３０に押し戻すことにより、固体電解質層１３０と負極集電体１５０との間にリチウムが残存することを抑制している。 As described above, when the lithium secondary battery 100 is discharged by utilizing the force that the negative electrode current collector 150 pushes back (urges) the precipitated lithium to the solid electrolyte layer 130 side, the solid electrolyte layer 130 and the negative electrode are used. By efficiently pushing the lithium deposited between the current collector 150 and the solid electrolyte layer 130 back to the solid electrolyte layer 130, it is possible to prevent the lithium from remaining between the solid electrolyte layer 130 and the negative electrode current collector 150. ..

そして、リチウム二次電池１００の充電時の還元反応及び放電時の酸化反応に関わるリチウムの量の減少をリチウム二次電池１００のライフサイクルにわたって抑制することにより、性能低下を抑制する。 Then, by suppressing the decrease in the amount of lithium involved in the reduction reaction during charging and the oxidation reaction during discharging of the lithium secondary battery 100 over the life cycle of the lithium secondary battery 100, the deterioration in performance is suppressed.

このような負極集電体１５０としては、一例として、銅（Ｃｕ）薄膜を用いる。厚さは、一例として、２００ｎｍである。負極集電体１５０は、リチウムよりもイオン化傾向が小さく、負極集電体に適した金属製であればよいため、銅以外には、例えばニッケルを用いることができる。 As such a negative electrode current collector 150, a copper (Cu) thin film is used as an example. The thickness is, for example, 200 nm. Since the negative electrode current collector 150 has a lower ionization tendency than lithium and may be made of a metal suitable for the negative electrode current collector, nickel can be used in addition to copper, for example.

以上のようなリチウム二次電池１００は、次のようにして作製することができる。まず、絶縁層１０１Ｂを有する基板１０１の上に、正極集電体１１０になるチタン層１１１Ａ及び白金層１１１Ｂをスパッタ法で成膜し、白金層１１１Ｂの上に、コバルト酸リチウムをスパッタ法で成膜し、６００℃で３０分間アニール処理を行うことによって正極１２０を形成する。 The lithium secondary battery 100 as described above can be manufactured as follows. First, a titanium layer 111A and a platinum layer 111B to be a positive electrode current collector 110 are formed on a substrate 101 having an insulating layer 101B by a sputtering method, and lithium cobalt oxide is formed on the platinum layer 111B by a sputtering method. The positive electrode 120 is formed by forming a film and performing an annealing treatment at 600 ° C. for 30 minutes.

さらに、正極１２０の上に、固体電解質層１３０としてのリン酸三リチウム及び固体電解質層１３０の上に固着部材１４０としてのアルミナをスパッタ法で成膜し、最後に固体電解質層１３０及び固着部材１４０の上に負極集電体１５０としての銅薄膜をスパッタ法で成膜することによって、リチウム二次電池１００が完成する。 Further, trilithium phosphate as the solid electrolyte layer 130 and alumina as the fixing member 140 are formed on the positive electrode 120 by a sputtering method, and finally the solid electrolyte layer 130 and the fixing member 140 are formed. The lithium secondary battery 100 is completed by forming a copper thin film as the negative electrode current collector 150 on the film by a sputtering method.

なお、ここでは、正極集電体１１０、コバルト酸リチウム、固着部材１４０としてのアルミナ、固体電解質層１３０としてのリン酸三リチウム及び負極集電体１５０としての銅薄膜をスパッタ法で成膜する形態について説明したが、スパッタ法の代わりに、蒸着法又はＰＬＤ(Pulsed Laser Deposition)法で成膜してもよい。 Here, a form in which a positive electrode current collector 110, lithium cobalt oxide, alumina as a fixing member 140, trilithium phosphate as a solid electrolyte layer 130, and a copper thin film as a negative electrode current collector 150 are formed by a sputtering method. However, instead of the sputtering method, a thin film may be formed by a vapor deposition method or a PLD (Pulsed Laser Deposition) method.

図３は、リチウム二次電池１００の放電後と充電後の断面の様子を示す図である。図３には、正極１２０、固体電解質層１３０、固着部材１４０、及び負極集電体１５０の部分を厚さ方向に拡大して示す。 FIG. 3 is a diagram showing a cross-sectional view of the lithium secondary battery 100 after discharging and charging. FIG. 3 shows the portions of the positive electrode 120, the solid electrolyte layer 130, the fixing member 140, and the negative electrode current collector 150 enlarged in the thickness direction.

図３（Ａ）には放電後の状態を示し、図３（Ｂ）には充電後の状態を示す。リチウム二次電池１００の充電状態は、ＳＯＣ(State of Charge)で表される。放電後とは、リチウム二次電池１００の仕様上の完全放電状態であり、ＳＯＣが０％の状態をいう。充電後とは、リチウム二次電池１００の仕様上の満充電状態であり、ＳＯＣが１００％の状態をいう。 FIG. 3A shows the state after discharging, and FIG. 3B shows the state after charging. The state of charge of the lithium secondary battery 100 is represented by SOC (State of Charge). After discharge is a completely discharged state according to the specifications of the lithium secondary battery 100, and means a state in which the SOC is 0%. After charging is a fully charged state according to the specifications of the lithium secondary battery 100, and means a state in which the SOC is 100%.

放電後は、図３（Ａ）に示すように、固体電解質層１３０と負極集電体１５０との間にリチウムは析出しておらず、負極集電体１５０は、固体電解質層１３０の上面に密着している。また、上述したように、負極集電体１５０としての銅薄膜は、固体電解質層１３０及び固着部材１４０の上に成膜されるため、図３（Ａ）に示す状態は、負極集電体１５０に応力が掛かっていない自然な状態である。 After the discharge, as shown in FIG. 3A, no lithium was deposited between the solid electrolyte layer 130 and the negative electrode current collector 150, and the negative electrode current collector 150 was placed on the upper surface of the solid electrolyte layer 130. It is in close contact. Further, as described above, since the copper thin film as the negative electrode current collector 150 is formed on the solid electrolyte layer 130 and the fixing member 140, the state shown in FIG. 3A is the negative electrode current collector 150. It is a natural state without stress.

また、リチウム二次電池１００が充電されても、固着部材１４０と負極集電体１５０との界面にリチウムは析出しないため、充電及び放電が繰り返されても、負極集電体１５０は、固着部材１４０に固着された状態である。 Further, even if the lithium secondary battery 100 is charged, lithium does not precipitate at the interface between the fixing member 140 and the negative electrode current collector 150, so that the negative electrode current collector 150 is a fixing member even if charging and discharging are repeated. It is in a state of being fixed to 140.

そして、図３（Ａ）に示す状態から充電を開始すると、負極集電体１５０との還元反応によって固体電解質層１３０からリチウムが析出し、満充電になると、図３（Ｂ）に示すように固体電解質層１３０と負極集電体１５０との間にリチウム１３０Ａが溜まった状態になる。リチウム１３０Ａは、負極として機能する。 Then, when charging is started from the state shown in FIG. 3 (A), lithium is precipitated from the solid electrolyte layer 130 by the reduction reaction with the negative electrode current collector 150, and when fully charged, as shown in FIG. 3 (B). Lithium 130A is accumulated between the solid electrolyte layer 130 and the negative electrode current collector 150. Lithium 130A functions as a negative electrode.

図３（Ｂ）に示す状態では、負極集電体１５０は、リチウム１３０Ａによって上向きに押されるとともに、固着部材１４０によって下向きに引っ張られるため、負極集電体１５０には、図３（Ａ）に示すように平坦な状態に戻ろうとする力が作用し、リチウム１３０Ａを下向き（固体電解質層１３０に向かう方向）に押す（付勢する）ことになる。 In the state shown in FIG. 3B, the negative electrode current collector 150 is pushed upward by the lithium 130A and pulled downward by the fixing member 140. Therefore, the negative electrode current collector 150 is shown in FIG. 3A. As shown, a force trying to return to a flat state acts to push (urge) the lithium 130A downward (toward the solid electrolyte layer 130).

このため、満充電の状態で図３（Ｂ）に示すようにリチウム１３０Ａが溜まった状態から放電が始まると、リチウム１３０Ａは、負極集電体１５０によって固体電解質層１３０に向かう方向に付勢されるので、固体電解質層１３０と負極集電体１５０との間にリチウム１３０Ａが残存することが抑制される。この結果、充電による還元反応と、放電による酸化反応に関与するリチウム（リチウムイオン）の量が減少することが抑制され、経時劣化によるリチウム二次電池１００の性能低下を抑制することができる。 Therefore, when the discharge starts from the state where the lithium 130A is accumulated as shown in FIG. 3B in the fully charged state, the lithium 130A is urged toward the solid electrolyte layer 130 by the negative electrode current collector 150. Therefore, the residual lithium 130A between the solid electrolyte layer 130 and the negative electrode current collector 150 is suppressed. As a result, it is possible to suppress a decrease in the amount of lithium (lithium ion) involved in the reduction reaction due to charging and the oxidation reaction due to discharge, and it is possible to suppress a deterioration in the performance of the lithium secondary battery 100 due to deterioration over time.

図４は、リチウム二次電池１００のサイクル数と、充電容量の維持率との関係を表す実験結果である。図４には、実線で実施の形態のリチウム二次電池１００の特性を示し、比較用に固着部材１４０を含まないリチウム二次電池の特性を破線で示す。 FIG. 4 is an experimental result showing the relationship between the number of cycles of the lithium secondary battery 100 and the maintenance rate of the charge capacity. In FIG. 4, the characteristics of the lithium secondary battery 100 of the embodiment are shown by a solid line, and the characteristics of a lithium secondary battery that does not include the fixing member 140 are shown by a broken line for comparison.

なお、充電は、定電流定電圧（CC-CV：constant current-constant voltage）方式で０．５ｍＡで行い、４．２Ｖで完了とした。放電は、定電流（CC：constant current）方式で０．５ｍＡで行い、２Ｖで完了とした。また、性能評価の実験は、室温で行った。 Charging was performed at 0.5 mA using a constant current-constant voltage (CC-CV) method, and was completed at 4.2 V. Discharge was performed at 0.5 mA by a constant current (CC) method and completed at 2 V. The performance evaluation experiment was conducted at room temperature.

固着部材１４０を含まないリチウム二次電池とは、リチウム二次電池１００から固着部材１４０を取り除いた構成を有し、リチウム１３０Ａが析出していない状態では、負極集電体１５０の下面の全体が固体電解質層１３０の上面と接している。 The lithium secondary battery that does not include the fixing member 140 has a configuration in which the fixing member 140 is removed from the lithium secondary battery 100, and in a state where the lithium 130A is not deposited, the entire lower surface of the negative electrode current collector 150 is covered. It is in contact with the upper surface of the solid electrolyte layer 130.

また、サイクル数とは、充放電の繰り返し回数である。充電容量の維持率は、新品の状態での充電容量に対する、サイクル数分だけ充放電を繰り返し行った状態での充電容量を百分率（％）で表す。 The number of cycles is the number of times charging / discharging is repeated. The maintenance rate of the charge capacity is expressed as a percentage (%) of the charge capacity in a state where charging and discharging are repeated for the number of cycles with respect to the charge capacity in a new state.

図４に示すように、実線で示す実施の形態のリチウム二次電池１００の特性と、破線で示す比較用のリチウム二次電池の特性とを比べると、両方ともサイクル数が数回くらいから１００％よりも低くなり、回数を経るにつれて、両者の差は開いている。 As shown in FIG. 4, when the characteristics of the lithium secondary battery 100 of the embodiment shown by the solid line and the characteristics of the lithium secondary battery for comparison shown by the broken line are compared, the number of cycles is about several to 100 in both cases. It is lower than%, and as the number of times goes by, the difference between the two becomes wider.

実線で示す実施の形態のリチウム二次電池１００の特性は、破線で示す比較用のリチウム二次電池の特性に比べて改善されており、サイクル数が１０回くらいまでは約１０％の改善であり、その後は約１５％程度の改善が見られた。 The characteristics of the lithium secondary battery 100 of the embodiment shown by the solid line are improved as compared with the characteristics of the comparative lithium secondary battery shown by the broken line, and the improvement is about 10% up to about 10 cycles. After that, an improvement of about 15% was seen.

このように、固着部材１４０を設けることにより、充放電を繰り返し行った場合の充電容量の低下が抑制されることを確認することができた。 In this way, it was confirmed that by providing the fixing member 140, the decrease in charge capacity when charging and discharging are repeated is suppressed.

従って、実施の形態によれば、性能低下を抑制可能なリチウム二次電池１００を提供することができる。すなわち、サイクル特性を改善したリチウム二次電池１００を提供することができる。 Therefore, according to the embodiment, it is possible to provide the lithium secondary battery 100 capable of suppressing the deterioration of performance. That is, it is possible to provide a lithium secondary battery 100 having improved cycle characteristics.

なお、以上では、固着部材１４０が平面視で矩形環状である形態について説明したが、固着部材１４０は、平面視で円環状、複数の直線状、又は、複数のドット状等であってもよい。固着部材１４０は、リチウム１３０Ａが析出した際に、負極集電体１５０がリチウム１３０Ａを固体電解質層１３０に向かう方向に付勢できるように、負極集電体１５０を固着して下向きに引っ張る力を発揮するものであればよい。 In the above, the form in which the fixing member 140 has a rectangular annular shape in a plan view has been described, but the fixing member 140 may have an annular shape, a plurality of linear shapes, a plurality of dot shapes, or the like in a plan view. .. The fixing member 140 fixes the negative electrode current collector 150 and pulls downward so that the negative electrode current collector 150 can urge the lithium 130A toward the solid electrolyte layer 130 when the lithium 130A is deposited. Anything that can be demonstrated will do.

また、以上では、固体電解質層１３０及び固着部材１４０の上に負極集電体１５０を直接的に設ける形態について説明したが、ＳＯＣが０％の状態でも、固体電解質層１３０と負極集電体１５０との間に負極としてのリチウム層が存在するようにしてもよい。 Further, although the embodiment in which the negative electrode current collector 150 is directly provided on the solid electrolyte layer 130 and the fixing member 140 has been described above, the solid electrolyte layer 130 and the negative electrode current collector 150 are described even when the SOC is 0%. A lithium layer as a negative electrode may be present between the two.

また、以上では、正極集電体１１０が白金層１１１Ｂを有する形態について説明したが、白金層１１１Ｂの代わりに金（Ａｕ）層を用いてもよい。 Further, although the form in which the positive electrode current collector 110 has the platinum layer 111B has been described above, a gold (Au) layer may be used instead of the platinum layer 111B.

また、以上では、正極１２０の作製に用いる正極活物質としてコバルト酸リチウム（ＬｉＣｏＯ２）を用いる形態について説明したが、代わりにリン酸鉄リチウム（ＬｉＦｅＰＯ４）又はマンガン酸リチウム（ＬｉＭｎ２Ｏ４）を用いてもよい。 Further, in the above, the embodiment in which lithium cobalt oxide (LiCoO 2 ) is used as the positive electrode active material used for producing the positive electrode 120 has been described, but instead, lithium iron phosphate (LiFePO 4 ) or lithium manganate (LiMn 2 O 4 ) has been described. May be used.

また、以上では、固体電解質層１３０がリン酸三リチウム（Ｌｉ３ＰＯ４）である形態について説明したが、代わりにリン酸リチウムオキシナイトライド（ＬｉＰＯＮ）を用いてもよい。 Further, although the form in which the solid electrolyte layer 130 is trilithium phosphate (Li 3 PO 4 ) has been described above, lithium phosphate oxynitride (LiPON) may be used instead.

以上、本発明の例示的な実施の形態のリチウム二次電池について説明したが、本発明は、具体的に開示された実施の形態に限定されるものではなく、特許請求の範囲から逸脱することなく、種々の変形や変更が可能である。 Although the lithium secondary battery of the exemplary embodiment of the present invention has been described above, the present invention is not limited to the specifically disclosed embodiment and deviates from the scope of claims. It is possible to make various modifications and changes.

以上の実施の形態に関し、さらに以下の付記を開示する。
（付記１）
正極集電体と、
前記正極集電体に重ねて設けられる正極と、
前記正極に重ねて設けられ、リチウムイオンを含む固体電解質層と、
前記固体電解質層の前記正極に面する第１面とは反対の第２面の一部分に設けられ、前記固体電解質層に対して不活性な絶縁材料製で、前記第２面に固着される固着部材と、
前記固体電解質層の第２面と、前記固着部材とに重ねて設けられ、前記前記固着部材に固着され、前記固体電解質層との間に析出するリチウムを前記固体電解質層に向かう方向に付勢する負極集電体と
を含む、リチウム二次電池。
（付記２）
前記固着部材は、平面視で矩形環状、円環状、複数の直線状、又は、複数のドット状である、付記１記載のリチウム二次電池。
（付記３）
前記絶縁材料は、アルミナ又はジルコニアである、付記１又は２記載のリチウム二次電池。
（付記４）
平面視で、前記固着部材が存在していない部分において、前記固体電解質層と前記負極集電体との間に設けられるリチウム製の負極をさらに含む、付記１乃至３のいずれか一項記載のリチウム二次電池。
（付記５）
前記負極集電体は、金属薄膜である、付記１乃至４のいずれか一項記載のリチウム二次電池。
（付記６）
前記負極集電体は、銅製である、付記１乃至５のいずれか一項記載のリチウム二次電池。
（付記７）
前記正極集電体は、前記正極に面接続される白金層を有する、付記１乃至６のいずれか一項記載のリチウム二次電池。 The following additional notes will be further disclosed with respect to the above embodiments.
(Appendix 1)
Positive current collector and
A positive electrode provided on the positive electrode current collector and a positive electrode
A solid electrolyte layer provided on the positive electrode and containing lithium ions,
It is made of an insulating material that is provided on a part of the second surface of the solid electrolyte layer opposite to the first surface facing the positive electrode and is inert to the solid electrolyte layer, and is fixed to the second surface. Members and
Lithium, which is provided so as to overlap the second surface of the solid electrolyte layer and the fixing member, is fixed to the fixing member, and precipitates between the solid electrolyte layer, is urged toward the solid electrolyte layer. Lithium secondary battery, including a negative electrode current collector.
(Appendix 2)
The lithium secondary battery according to Appendix 1, wherein the fixing member has a rectangular annular shape, an annular shape, a plurality of linear shapes, or a plurality of dot shapes in a plan view.
(Appendix 3)
The lithium secondary battery according to Appendix 1 or 2, wherein the insulating material is alumina or zirconia.
(Appendix 4)
2. Lithium secondary battery.
(Appendix 5)
The lithium secondary battery according to any one of Supplementary note 1 to 4, wherein the negative electrode current collector is a metal thin film.
(Appendix 6)
The lithium secondary battery according to any one of Supplementary note 1 to 5, wherein the negative electrode current collector is made of copper.
(Appendix 7)
The lithium secondary battery according to any one of Supplementary note 1 to 6, wherein the positive electrode current collector has a platinum layer surface-connected to the positive electrode.

１００ リチウム二次電池
１１０ 正極集電体
１１１Ａ チタン層
１１１Ｂ 白金層
１２０ 正極
１３０ 固体電解質層
１４０ 固着部材
１５０ 負極集電体 100 Lithium secondary battery 110 Positive electrode current collector 111A Titanium layer 111B Platinum layer 120 Positive electrode 130 Solid electrolyte layer 140 Sticking member 150 Negative electrode current collector

Claims (6)

正極集電体と、
前記正極集電体に重ねて設けられる正極と、
前記正極に重ねて設けられ、リチウムイオンを含む固体電解質層と、
前記固体電解質層の前記正極に面する第１面とは反対の第２面の一部分に設けられ、前記固体電解質層に対して不活性な絶縁材料製で、前記第２面に固着される固着部材と、
前記固体電解質層の第２面と、前記固着部材とに重ねて設けられ、前記固着部材に固着され、前記固体電解質層との間に析出するリチウムを前記固体電解質層に向かう方向に付勢する負極集電体と
を含み、
前記固着部材の表面のうち、前記固体電解質層に接していない領域の全てが前記負極集電体に接している、リチウム二次電池。 Positive current collector and
A positive electrode provided on the positive electrode current collector and a positive electrode
A solid electrolyte layer provided on the positive electrode and containing lithium ions,
It is made of an insulating material that is provided on a part of the second surface of the solid electrolyte layer opposite to the first surface facing the positive electrode and is inert to the solid electrolyte layer, and is fixed to the second surface. Members and
Lithium, which is provided so as to be overlapped with the second surface of the solid electrolyte layer and the fixing member, is fixed to the fixing member, and precipitates between the solid electrolyte layer, is urged toward the solid electrolyte layer. Including the negative electrode current collector
A lithium secondary battery in which all of the surface of the fixing member that is not in contact with the solid electrolyte layer is in contact with the negative electrode current collector . 前記固着部材は、平面視で矩形環状、円環状、複数の直線状、又は、複数のドット状である、請求項１記載のリチウム二次電池。 The lithium secondary battery according to claim 1, wherein the fixing member has a rectangular annular shape, an annular shape, a plurality of linear shapes, or a plurality of dot shapes in a plan view. 前記絶縁材料は、アルミナ又はジルコニアである、請求項１又は２記載のリチウム二次電池。 The lithium secondary battery according to claim 1 or 2, wherein the insulating material is alumina or zirconia. 平面視で、前記固着部材が存在していない部分において、前記固体電解質層と前記負極集電体との間に設けられるリチウム製の負極をさらに含む、請求項１乃至３のいずれか一項記載のリチウム二次電池。 The invention according to any one of claims 1 to 3, further comprising a lithium negative electrode provided between the solid electrolyte layer and the negative electrode current collector in a portion where the fixing member does not exist in a plan view. Lithium secondary battery. 前記負極集電体は、金属薄膜である、請求項１乃至４のいずれか一項記載のリチウム二次電池。 The lithium secondary battery according to any one of claims 1 to 4, wherein the negative electrode current collector is a metal thin film. 前記負極集電体は、銅製である、請求項１乃至５のいずれか一項記載のリチウム二次電池。 The lithium secondary battery according to any one of claims 1 to 5, wherein the negative electrode current collector is made of copper.
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