JP2023128519A - Negative electrode of secondary battery, method for manufacturing the same, and secondary battery - Google Patents

Negative electrode of secondary battery, method for manufacturing the same, and secondary battery Download PDF

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JP2023128519A
JP2023128519A JP2022032897A JP2022032897A JP2023128519A JP 2023128519 A JP2023128519 A JP 2023128519A JP 2022032897 A JP2022032897 A JP 2022032897A JP 2022032897 A JP2022032897 A JP 2022032897A JP 2023128519 A JP2023128519 A JP 2023128519A
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active material
negative electrode
current collector
secondary battery
buffer layer
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貴柾 藪崎
Takamasa Yabuzaki
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Toyota Motor Corp
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/36—Accumulators not provided for in groups H01M10/05-H01M10/34
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
    • H01M4/42—Alloys based on zinc
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • 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

Abstract

To provide means for strengthening bonding between a negative electrode active material and a current collector.SOLUTION: A negative electrode 10 of a secondary battery includes: a current collector 11; an active material layer 12 composed of active material particles 13 laminated on the current collector 11; and a buffer layer 15 provided between the current collector 11 and the active material layer 12. The buffer layer 15 is composed of a hydrophilic composition 16 of either an organic polymer or an inorganic molecule. A method for producing the negative electrode 10 includes: forming the buffer layer 15 by applying the hydrophilic composition 16 containing no active material on the current collector 11; and forming the active material layer 12 by applying the active material particles 13 on the buffer layer 15. The secondary battery includes a positive electrode, the negative electrode 10, and an aqueous electrolyte.SELECTED DRAWING: Figure 1

Description

本発明は二次電池の負極及びその製造方法並びに二次電池に関する。 The present invention relates to a negative electrode for a secondary battery, a method for manufacturing the same, and a secondary battery.

特許文献１は水系亜鉛イオン電池を開示している。負極は負極活物質と導電助剤とバインダーとを含有する層からなる（特許文献１，段落[0022]）。特許文献２はニッケル－亜鉛の充電式バッテリセルを開示している。陰極電気化学的活性亜鉛源は、酸化亜鉛、亜鉛酸カルシウム、金属亜鉛、及び種々な亜鉛合金から選ばれる一種以上を含む（特許文献２，段落[0050]）。特許文献３は亜鉛二次電池を開示している。負極活物質は、酸化亜鉛（ＺｎＯ）及び亜鉛（Ｚｎ）である（特許文献３，段落[0030]）。 Patent Document 1 discloses a water-based zinc ion battery. The negative electrode consists of a layer containing a negative electrode active material, a conductive aid, and a binder (Patent Document 1, paragraph [0022]). US Pat. No. 5,001,202 discloses a nickel-zinc rechargeable battery cell. The cathodic electrochemically active zinc source includes one or more selected from zinc oxide, calcium zincate, metallic zinc, and various zinc alloys (Patent Document 2, paragraph [0050]). Patent Document 3 discloses a zinc secondary battery. The negative electrode active materials are zinc oxide (ZnO) and zinc (Zn) (Patent Document 3, paragraph [0030]).

特許文献４は非水電解質二次電池用負極を開示している。係る負極は、負極活物質層と集電体との界面の一部に、アミノ基を官能基として有するアゾ－ル化合物と、を有する（特許文献４，要約）。 Patent Document 4 discloses a negative electrode for a non-aqueous electrolyte secondary battery. Such a negative electrode includes an azole compound having an amino group as a functional group at a part of the interface between the negative electrode active material layer and the current collector (Patent Document 4, Abstract).

特開２０２０－０２４８１９号公報Japanese Patent Application Publication No. 2020-024819 特表２０１０－５４１１８３号公報Special Publication No. 2010-541183 特開２０２１－０７７５４３号公報JP2021-077543A 特開２０１５－１２８０７６号公報Japanese Patent Application Publication No. 2015-128076

本発明は負極活物質と集電体との結合を強固にする手段を提供することを課題とする。 An object of the present invention is to provide a means for strengthening the bond between a negative electrode active material and a current collector.

＜１＞ 集電体と、前記集電体上に積層された活物質粒子からなる活物質層を備え、
前記集電体と前記活物質層との間に設けられた緩衝層をさらに備え、
前記緩衝層は有機高分子及び無機分子のいずれかの親水性組成物からなる、
二次電池の負極。
＜２＞ 前記親水性組成物は繊維状の有機高分子である、
＜１＞の二次電池の負極。
＜３＞ 前記有機高分子はセルロースナノファイバー及びポリビニルアルコールの少なくともいずれかである、
＜２＞の二次電池の負極。
＜４＞ 前記活物質層はさらに、前記活物質粒子同士を結合するバインダーからなり、
前記バインダーは有機高分子からなり、
前記バインダーの前記有機高分子は、前記親水性組成物の前記有機高分子と異なる、
＜２＞又は＜３＞の二次電池の負極。
＜５＞ 前記活物質粒子は、亜鉛／酸化亜鉛からなる、
＜１＞～＜４＞のいずれかの二次電池の負極。
＜６＞ ＜１＞～＜５＞のいずれかの二次電池の負極の製造方法であって、
前記集電体上に、活物質を含有しない前記親水性組成物を塗布することで前記緩衝層を形成し、
前記緩衝層上に、前記活物質粒子を塗布することで前記活物質層を形成する、
二次電池の負極の製造方法。
＜７＞ 正極と＜１＞～＜５＞のいずれかの負極と水系電解液とを備える、
二次電池。
＜８＞ 前記集電体は、銅以外の金属でメッキされた銅からなる、
＜７＞の二次電池。
＜９＞ 前記正極は、ニッケル／水酸化ニッケルからなる活物質を有する、
＜７＞又は＜８＞の二次電池。 <1> comprising a current collector and an active material layer made of active material particles laminated on the current collector,
further comprising a buffer layer provided between the current collector and the active material layer,
The buffer layer is made of a hydrophilic composition of either an organic polymer or an inorganic molecule.
Negative electrode of secondary battery.
<2> The hydrophilic composition is a fibrous organic polymer,
Negative electrode of the secondary battery of <1>.
<3> The organic polymer is at least one of cellulose nanofibers and polyvinyl alcohol,
Negative electrode of the secondary battery of <2>.
<4> The active material layer further includes a binder that binds the active material particles to each other,
The binder is made of an organic polymer,
the organic polymer of the binder is different from the organic polymer of the hydrophilic composition;
The negative electrode of the secondary battery of <2> or <3>.
<5> The active material particles are made of zinc/zinc oxide,
The negative electrode of any of the secondary batteries <1> to <4>.
<6> A method for manufacturing a negative electrode of a secondary battery according to any one of <1> to <5>, comprising:
forming the buffer layer by applying the hydrophilic composition containing no active material on the current collector;
forming the active material layer by applying the active material particles on the buffer layer;
A method for manufacturing a negative electrode for a secondary battery.
<7> Comprising a positive electrode, one of the negative electrodes of <1> to <5>, and an aqueous electrolyte,
Secondary battery.
<8> The current collector is made of copper plated with a metal other than copper,
<7> Secondary battery.
<9> The positive electrode has an active material made of nickel/nickel hydroxide,
The secondary battery of <7> or <8>.

本発明は負極活物質と集電体との結合を強固にする手段を提供する。 The present invention provides a means for strengthening the bond between a negative electrode active material and a current collector.

負極の断面Cross section of negative electrode 緩衝層を有しない負極の断面Cross section of negative electrode without buffer layer 負極の製造の流れNegative electrode manufacturing flow

＜負極の構成＞ <Configuration of negative electrode>

図１は二次電池の負極１０の断面を表す。負極１０は集電体１１と活物質層１２とを備える。 FIG. 1 shows a cross section of a negative electrode 10 of a secondary battery. The negative electrode 10 includes a current collector 11 and an active material layer 12.

図１に示す集電体１１は一態様において金属箔、パンチングメタル及び発泡金属のいずれかからなる。集電体１１を構成する金属は一態様において銅、ニッケル及び銅ニッケル合金のいずれかである。集電体１１を構成する金属が銅を含有する場合、銅ではない金属、例えばスズでメッキされていることが好ましい。一態様において集電体１１は10μm～10mmの厚さを有する。 In one embodiment, the current collector 11 shown in FIG. 1 is made of metal foil, punched metal, or foam metal. In one embodiment, the metal constituting the current collector 11 is copper, nickel, or a copper-nickel alloy. When the metal constituting the current collector 11 contains copper, it is preferably plated with a metal other than copper, such as tin. In one embodiment, current collector 11 has a thickness of 10 μm to 10 mm.

図１に示すように活物質層１２は集電体１１上に積層されている。活物質層１２は活物質粒子１３とバインダー１４とを有する。一態様において活物質層１２は10μm～10mmの厚さを有する。 As shown in FIG. 1, the active material layer 12 is stacked on the current collector 11. The active material layer 12 includes active material particles 13 and a binder 14 . In one embodiment, active material layer 12 has a thickness of 10 μm to 10 mm.

活物質粒子１３は亜鉛／酸化亜鉛からなる。亜鉛／酸化亜鉛以外の負極活物質としては：
・水酸化亜鉛
・Siを含む有機材料で被覆された酸化亜鉛の粉体
・Zr、Si、Al、Ti、Sn、Bi、In、Zn、P、Oのいずれかの元素を含む無機材料で被覆した酸化亜鉛、ただし酸化亜鉛を被覆する時点で無機材料の構造の一部又は全体に上記元素が含まれているもの
が挙げられる。 The active material particles 13 are made of zinc/zinc oxide. Negative electrode active materials other than zinc/zinc oxide include:
- Zinc hydroxide - Zinc oxide powder coated with an organic material containing Si - Coated with an inorganic material containing any of the following elements: Zr, Si, Al, Ti, Sn, Bi, In, Zn, P, O zinc oxide, but those in which the above elements are included in part or the entire structure of the inorganic material at the time of coating the zinc oxide.

負極活物質は、その他の金属系の添加物を含有していてもよい。添加物としては、亜鉛酸カルシウム、水酸化カルシウム、酸化ビスマス、アルミニウム、酸化アルミニウム、水酸化アルミニウム、酸化インジウム、インジウム、金、酸化チタン（IV）（TiO2）、酸化チタン（III）（Ti2O3）、酸化ジルコン、鉄、スズ、酸化スズ、炭酸カリウム、フッ化カリウム、及び酸化カリウムが挙げられる。 The negative electrode active material may contain other metal-based additives. Additives include calcium zincate, calcium hydroxide, bismuth oxide, aluminum, aluminum oxide, aluminum hydroxide, indium oxide, indium, gold, titanium (IV) oxide (TiO 2 ), titanium (III) oxide (Ti 2 O 3 ), zircon oxide, iron, tin, tin oxide, potassium carbonate, potassium fluoride, and potassium oxide.

バインダー１４は活物質粒子１３同士を結合する。一態様においてバインダー１４は有機高分子からなる。好ましい態様において有機高分子は、カルボキシメチルセルロース（CMC）、スチレンブタジエンゴム（SBR）及びポリテトラフルオロエチレン（PTFE）の少なくともいずれかである。 The binder 14 binds the active material particles 13 together. In one embodiment, binder 14 is made of an organic polymer. In a preferred embodiment, the organic polymer is at least one of carboxymethyl cellulose (CMC), styrene butadiene rubber (SBR), and polytetrafluoroethylene (PTFE).

図１に示すように負極１０はさらに緩衝層１５を有する。緩衝層１５は集電体１１と活物質層１２との間に位置する。緩衝層１５は集電体１１と接する。緩衝層１５はさらに活物質層１２と接する。一態様において緩衝層１５は10nm～5mmの厚みを有する。緩衝層１５は親水性組成物１６を含有する。親水性組成物１６は有機高分子及び無機分子のいずれかからなる。親水性組成物１６は１種類の化合物からなる、又は２種類以上の化合物の混合物からなる。 As shown in FIG. 1, the negative electrode 10 further includes a buffer layer 15. Buffer layer 15 is located between current collector 11 and active material layer 12 . The buffer layer 15 is in contact with the current collector 11 . The buffer layer 15 further contacts the active material layer 12 . In one embodiment, buffer layer 15 has a thickness of 10 nm to 5 mm. Buffer layer 15 contains hydrophilic composition 16 . The hydrophilic composition 16 consists of either an organic polymer or an inorganic molecule. The hydrophilic composition 16 consists of one type of compound or a mixture of two or more types of compounds.

図１に示す親水性組成物１６として用いられる有機高分子の例はセルロースナノファイバー（CNF）、ポリビニルアルコール（PVOH）、SBR及びCMCである。CNF及びPVOHは繊維状であるため緩衝層１５の材料として望ましい。繊維状の有機高分子が親水性組成物１６として望ましいのはまず、繊維状の有機高分子がスラリーの材料活物質及び添加物同士の結着、またそれらと集電体との結着を担うバインダ本来の役割を果たすという理由による。それに加えて、繊維状の有機高分子は、活物質層１２と集電体１１との間の境界を経由して活物質層１２の集電体１１側に向けて電解液を積極的に引き込むことができる。このため、より多くの活物質粒子１３が電解液と接触できる点でも繊維状の有機高分子は親水性組成物１６として望ましい。 Examples of organic polymers used as the hydrophilic composition 16 shown in FIG. 1 are cellulose nanofibers (CNF), polyvinyl alcohol (PVOH), SBR, and CMC. CNF and PVOH are preferable as materials for the buffer layer 15 because they are fibrous. The reason why a fibrous organic polymer is desirable as the hydrophilic composition 16 is that the fibrous organic polymer binds the active material and additives of the slurry to each other and binds them to the current collector. This is because it plays the original role of a binder. In addition, the fibrous organic polymer actively draws the electrolyte toward the current collector 11 side of the active material layer 12 via the boundary between the active material layer 12 and the current collector 11. be able to. For this reason, fibrous organic polymers are desirable as the hydrophilic composition 16 in that more active material particles 13 can come into contact with the electrolytic solution.

これに対して後述する図２に示す負極２０では集電体１１と活物質層１２との組み合わせのみで電極が構成される。したがって、負極２０には繊維状の有機高分子からなる緩衝層１５が用いられない。このため活物質層１２と集電体１１との間の境界を経由して活物質層１２の集電体１１側に向けて電解液を積極的に引き込むことが難しい。結果として負極２０では活物質層１２の最表部の活物質粒子１３のみが電解液と接触する。 On the other hand, in the negative electrode 20 shown in FIG. 2, which will be described later, the electrode is composed only of the combination of the current collector 11 and the active material layer 12. Therefore, the buffer layer 15 made of a fibrous organic polymer is not used in the negative electrode 20. Therefore, it is difficult to actively draw the electrolytic solution toward the current collector 11 side of the active material layer 12 via the boundary between the active material layer 12 and the current collector 11 . As a result, in the negative electrode 20, only the active material particles 13 at the outermost portion of the active material layer 12 come into contact with the electrolyte.

図１に示す親水性組成物１６として用いられる無機分子の例は酸化ケイ素、酸化ジルコン、酸化チタン及び酸化スズである。 Examples of inorganic molecules used as the hydrophilic composition 16 shown in FIG. 1 are silicon oxide, zirconium oxide, titanium oxide, and tin oxide.

図１に示すように緩衝層１５は１層からなる。他の態様において緩衝層１５は相異なる親水性組成物からなる２以上の層からなる。一態様において親水性組成物１６とバインダー１４とは同じ組成物である。他の態様において親水性組成物１６とバインダー１４とは異種の組成物である。その一態様においてバインダー１４の有機高分子は、親水性組成物１６の有機高分子と異なる。 As shown in FIG. 1, the buffer layer 15 consists of one layer. In other embodiments, buffer layer 15 is comprised of two or more layers of different hydrophilic compositions. In one embodiment, hydrophilic composition 16 and binder 14 are the same composition. In other embodiments, hydrophilic composition 16 and binder 14 are dissimilar compositions. In one embodiment, the organic polymer of binder 14 is different from the organic polymer of hydrophilic composition 16.

＜緩衝層の機能＞ <Function of buffer layer>

図２は緩衝層を有しない負極２０の断面を表す。亜鉛／酸化亜鉛からなる活物質粒子１３は活物質層１２から脱落しやすい。活物質粒子１３は特に負極２０の端部２３から脱落しやすい。これに対して図１に示す緩衝層１５は、少なくとも負極１０の端部１８において、集電体１１を覆う。係る緩衝層１５は、活物質粒子１３が端部１８から脱落することを抑制する。緩衝層１５は、好ましくは負極１０の全体に渡って集電体１１を覆う。係る緩衝層１５は、活物質粒子１３が負極１０の全体のいずれかの箇所から脱落することを抑制する。活物質粒子１３の脱落の原因は明らかになっていないが、以下のような仮説を考慮すべきである。 FIG. 2 shows a cross section of a negative electrode 20 without a buffer layer. The active material particles 13 made of zinc/zinc oxide tend to fall off from the active material layer 12. The active material particles 13 are particularly likely to fall off from the end portion 23 of the negative electrode 20 . In contrast, the buffer layer 15 shown in FIG. 1 covers the current collector 11 at least at the end portion 18 of the negative electrode 10. Such a buffer layer 15 suppresses active material particles 13 from falling off from end portions 18 . The buffer layer 15 preferably covers the current collector 11 over the entire negative electrode 10 . The buffer layer 15 prevents the active material particles 13 from falling off from any part of the negative electrode 10 . Although the cause of the falling off of the active material particles 13 is not clear, the following hypothesis should be considered.

図２に示すように負極２０に緩衝層を設けない場合、活物質層１２の形成時に集電体１１と、活物質粒子１３及びバインダー１４との間の物理的な引っ掛かりが少ない。また集電体１１とバインダー１４との間の親和性が乏しい。このため集電体１１の表面と活物質層１２の表面とが十分に密着しない。これに対して図１に示す負極１０では、緩衝層１５が物理的な引っ掛かりを提供する。集電体１１とバインダー１４との間の親和性が乏しい場合でも、集電体１１の表面と活物質層１２の表面とが緩衝層１５を介して十分に密着する。このため活物質層１２が負極１０の表面から脱落することは抑制されている。 As shown in FIG. 2, when the negative electrode 20 is not provided with a buffer layer, there is less physical catching between the current collector 11, the active material particles 13, and the binder 14 when forming the active material layer 12. Furthermore, the affinity between the current collector 11 and the binder 14 is poor. Therefore, the surface of the current collector 11 and the surface of the active material layer 12 do not come into sufficient contact with each other. In contrast, in the negative electrode 10 shown in FIG. 1, the buffer layer 15 provides a physical hook. Even when the affinity between the current collector 11 and the binder 14 is poor, the surface of the current collector 11 and the surface of the active material layer 12 are in close contact with each other with the buffer layer 15 in between. Therefore, the active material layer 12 is prevented from falling off the surface of the negative electrode 10.

図２に示す負極２０では、集電体１１の表面に水系電解液が接触している状態で充電がされると水素ガスが集電体１１の表面から発生する。この水素ガスが活物質層１２に浸透することが活物質粒子１３の脱落の原因になっている可能性がある。これに対して図１に示す負極１０では、集電体１１の表面を緩衝層１５が覆っているため、水素ガスが集電体１１の表面から発生しにくい。一態様において負極１０は水系電解液を備える二次電池用の負極である。 In the negative electrode 20 shown in FIG. 2, hydrogen gas is generated from the surface of the current collector 11 when charging is performed while the surface of the current collector 11 is in contact with the aqueous electrolyte. There is a possibility that this hydrogen gas permeating into the active material layer 12 causes the active material particles 13 to fall off. On the other hand, in the negative electrode 10 shown in FIG. 1, since the buffer layer 15 covers the surface of the current collector 11, hydrogen gas is less likely to be generated from the surface of the current collector 11. In one embodiment, the negative electrode 10 is a negative electrode for a secondary battery including an aqueous electrolyte.

図１及び図２に示す一態様において集電体１１として銅又は銅合金が選択される。銅原子の拡散速度は比較的に高い。したがって集電体１１の表面が銅以外の金属、例えばスズでメッキされていたとしても集電体１１の表面への銅の露出を抑えきれない。集電体１１の表面に露出した銅は、水系電解液を電気分解することで水素ガスを発生させやすい。図１において緩衝層１５が水系電解液と銅との接触を妨げる。集電体１１として銅又は銅合金が選択された場合、水素ガスの発生の抑制には緩衝層１５の使用が有意義である。 In one embodiment shown in FIGS. 1 and 2, copper or a copper alloy is selected as the current collector 11. The diffusion rate of copper atoms is relatively high. Therefore, even if the surface of the current collector 11 is plated with a metal other than copper, such as tin, exposure of copper to the surface of the current collector 11 cannot be suppressed. The copper exposed on the surface of the current collector 11 tends to generate hydrogen gas by electrolyzing the aqueous electrolyte. In FIG. 1, a buffer layer 15 prevents contact between the aqueous electrolyte and the copper. When copper or a copper alloy is selected as the current collector 11, the use of the buffer layer 15 is significant in suppressing the generation of hydrogen gas.

さらに活物質粒子の脱落の抑制の他にも緩衝層の有意義な機能が見出されることを以下に説明する。図２に示す負極２０に水系電解液を適用した場合、集電体１１から遠い側の活物質粒子１３には水系電解液がよく行き渡る。しかしながら集電体１１に近い側の活物質粒子１３には水系電解液が行き渡らない。これに対して図１に示す負極１０は親水性組成物１６からなる緩衝層１５を有する。したがって水系電解液は、親水性の高い緩衝層１５に浸透することで、集電体１１に近い側の活物質粒子１３にも行き渡る。この作用をもたらす親水性組成物１６として繊維状の有機高分子が望ましいことは上述した通りである。 Furthermore, it will be explained below that the buffer layer has a significant function other than suppressing the falling off of active material particles. When an aqueous electrolyte is applied to the negative electrode 20 shown in FIG. 2, the aqueous electrolyte is well distributed over the active material particles 13 on the side far from the current collector 11. However, the aqueous electrolyte does not reach the active material particles 13 on the side closer to the current collector 11 . In contrast, the negative electrode 10 shown in FIG. 1 has a buffer layer 15 made of a hydrophilic composition 16. Therefore, the aqueous electrolyte permeates the highly hydrophilic buffer layer 15 and also spreads to the active material particles 13 on the side closer to the current collector 11 . As mentioned above, a fibrous organic polymer is desirable as the hydrophilic composition 16 that provides this effect.

＜負極の製造＞ <Manufacture of negative electrode>

図３は負極の製造の流れを示す。ステップＳ０１にて、図１に示す集電体１１上に親水性組成物１６を下地として塗布する。一態様において親水性組成物１６は活物質を含有しない。親水性組成物１６は予め分散媒中に分散させておく、又は溶媒中に溶解させておく。一態様において塗布は、集電体１１を、親水性組成物１６を含有する分散液に浸漬することで行う。図３に示すステップＳ０２にて、下地を乾燥することで、図１に示す緩衝層１５を集電体１１の表面に形成する。 FIG. 3 shows the flow of manufacturing the negative electrode. In step S01, a hydrophilic composition 16 is applied as a base onto the current collector 11 shown in FIG. In one embodiment, hydrophilic composition 16 does not contain an active material. The hydrophilic composition 16 is previously dispersed in a dispersion medium or dissolved in a solvent. In one embodiment, the coating is performed by immersing the current collector 11 in a dispersion containing the hydrophilic composition 16. In step S02 shown in FIG. 3, the buffer layer 15 shown in FIG. 1 is formed on the surface of the current collector 11 by drying the base.

図３に示すステップＳ０３にて、図１に示す緩衝層１５上に活物質粒子１３とバインダー１４との混合物を塗布する。一態様において塗布は集電体１１に活物質粒子１３とバインダー１４とを含有する分散液、例えばスラリーインクを塗布した後、分散液から分散媒を蒸発させることで行う。活物質粒子１３とバインダー１４とは予め分散媒中に分散させておく。 In step S03 shown in FIG. 3, a mixture of active material particles 13 and binder 14 is applied onto the buffer layer 15 shown in FIG. In one embodiment, the coating is performed by applying a dispersion containing the active material particles 13 and the binder 14, such as slurry ink, to the current collector 11, and then evaporating the dispersion medium from the dispersion. The active material particles 13 and the binder 14 are previously dispersed in a dispersion medium.

図３に示すステップＳ０４にて、図１に示す活物質粒子１３とバインダー１４とを乾燥することで、活物質層１２を緩衝層１５の表面に形成する。図３に示すステップＳ０５にて、図１に示す活物質層１２を緩衝層１５とともにプレスすることで負極１０を得る。 In step S04 shown in FIG. 3, the active material layer 12 is formed on the surface of the buffer layer 15 by drying the active material particles 13 and the binder 14 shown in FIG. In step S05 shown in FIG. 3, the negative electrode 10 is obtained by pressing the active material layer 12 shown in FIG. 1 together with the buffer layer 15.

＜二次電池＞ <Secondary battery>

ニッケル／水酸化ニッケルからなる活物質を有する正極と、上記酸化亜鉛／亜鉛からなる負極と、必要なセパレーターと、水系電解液とを組み合わせることでニッケル亜鉛二次電池を得る。ニッケル／水酸化ニッケル以外の正極活物質としては酸化亜鉛、酸化コバルト（II）（ＣｏＯ）、金属コバルト及び酸化ニッケルが挙げられる。 A nickel-zinc secondary battery is obtained by combining a positive electrode having an active material made of nickel/nickel hydroxide, a negative electrode made of zinc oxide/zinc, a necessary separator, and an aqueous electrolyte. Positive electrode active materials other than nickel/nickel hydroxide include zinc oxide, cobalt (II) oxide (CoO), metallic cobalt, and nickel oxide.

＜負極材料＞ <Negative electrode material>

負極材料としてスラリーインクを作製した。90重量部の酸化亜鉛の粉末と、10重量部の金属亜鉛の粉末と、1重量部のCMCの粉末と、3重量部のPTFEの粉末とを60重量部の水と混合した。混合物を公転-自転ミキサーにて15分間撹拌することでスラリーインクを得た。 Slurry ink was prepared as a negative electrode material. 90 parts by weight of zinc oxide powder, 10 parts by weight of metallic zinc powder, 1 part by weight of CMC powder, and 3 parts by weight of PTFE powder were mixed with 60 parts by weight of water. A slurry ink was obtained by stirring the mixture for 15 minutes using a revolution-rotation mixer.

＜集電体への緩衝層の付与＞ <Adding a buffer layer to the current collector>

集電体としてスズメッキ銅からなる発泡金属を選択した。係る集電体上に緩衝層を設けた。まず濃度１重量％のCNFの水分散液を作製した。係る水分散液に集電体を５秒間浸した後、水分散液から集電体を引き上げた。集電体を70℃で0.5時間乾燥させることでCNFからなる緩衝層を得た。 Foamed metal made of tin-plated copper was selected as the current collector. A buffer layer was provided on the current collector. First, an aqueous dispersion of CNF with a concentration of 1% by weight was prepared. After the current collector was immersed in the aqueous dispersion for 5 seconds, the current collector was pulled out of the aqueous dispersion. A buffer layer made of CNF was obtained by drying the current collector at 70°C for 0.5 hour.

＜集電体への塗工、集電体のプレス及び乾燥＞ <Coating on current collector, pressing and drying of current collector>

緩衝層上に上述のスラリーインクを塗布した。スラリーインクの固形分のロード量は103 mg/cm2を目標とした。集電体を70℃で0.5時間乾燥させることで活物質層を形成した。これらの層を付与した集電体を、さらに線圧1トンのロールプレスにてプレスすることで酸化亜鉛／亜鉛からなる負極を得た。 The slurry ink described above was applied onto the buffer layer. The solid content loading amount of the slurry ink was targeted at 103 mg/cm 2 . An active material layer was formed by drying the current collector at 70°C for 0.5 hour. The current collector provided with these layers was further pressed using a roll press with a linear pressure of 1 ton to obtain a negative electrode made of zinc oxide/zinc.

＜電池の作製＞ <Preparation of battery>

負極の上端に厚さ120μmの銅箔を抵抗溶接機で接合した。さらに親水性のPVA-セルロース混合不織布で負極全体を包んだ。ニッケル発泡金属と水酸化ニッケルとで複合化されている正極に対して正極端子を予め溶接した。包まれた負極に正極を重ねた。不織布で正極と負極の全体を包んだ。正極及び負極を電池筐体内に設置した。電解液として電池筐体内に6M KOHを滴下した。電池筐体に封止を行った後、以上によりSOC100%で140mAhの容量を有する電池を得た。 A 120 μm thick copper foil was bonded to the upper end of the negative electrode using a resistance welder. Furthermore, the entire negative electrode was wrapped in a hydrophilic PVA-cellulose mixed nonwoven fabric. A positive electrode terminal was welded in advance to a positive electrode made of a composite of nickel foam metal and nickel hydroxide. A positive electrode was placed on top of the wrapped negative electrode. The entire positive and negative electrodes were wrapped in nonwoven fabric. A positive electrode and a negative electrode were placed inside the battery housing. 6M KOH was dripped into the battery case as an electrolyte. After sealing the battery case, a battery having a capacity of 140 mAh at 100% SOC was obtained as described above.

＜電池の評価＞ <Battery evaluation>

下記表１に示す充放電パターンを電池に対して１サイクル適用した。1Cは満充電容量（140mAh）が1時間で全て放電されるのに必要な電流を示す。 The charge/discharge pattern shown in Table 1 below was applied to the battery for one cycle. 1C indicates the current required to fully discharge the full charge capacity (140mAh) in one hour.

＜表１ 活性化の充放電パターン＞ <Table 1 Charging and discharging pattern of activation>

［充電］ CC充電：0.2C（28mA），カットオフ電圧1.95V
CV充電：1.90V，カットオフ電流22mA
［休止］ 5分
［放電］ 0.2C（28mA），カットオフ電圧1.1V
［休止］ 5分 [Charging] CC charging: 0.2C (28mA), cutoff voltage 1.95V
CV charging: 1.90V, cutoff current 22mA
[Pause] 5 minutes [Discharge] 0.2C (28mA), cutoff voltage 1.1V
[Pause] 5 minutes

下記表２に示す充放電パターンを電池に対して２００サイクル適用した。 The charge/discharge pattern shown in Table 2 below was applied to the battery for 200 cycles.

＜表２ 試験用の充放電パターン＞ <Table 2 Charging/discharging pattern for testing>

［充電］ CC充電：1C（140mA），カットオフ電圧1.95V
CV充電：1.90V，カットオフ電流22mA
［休止］ 5分
［放電］ 1C（140mA），カットオフ電圧1.1V
［休止］ 5分 [Charging] CC charging: 1C (140mA), cutoff voltage 1.95V
CV charging: 1.90V, cutoff current 22mA
[Pause] 5 minutes [Discharge] 1C (140mA), cutoff voltage 1.1V
[Pause] 5 minutes

電池を分解して負極を取り出した。負極の表面を観察したところ、活物質粒子の脱落している面積の割合、負極脱落面積率、が下記表３に示すとおりであることが分かった。 The battery was disassembled and the negative electrode was taken out. When the surface of the negative electrode was observed, it was found that the ratio of the area where the active material particles had fallen off and the area ratio of the negative electrode falling off were as shown in Table 3 below.

＜表３ サイクル試験結果 負極脱落面積率＞ <Table 3 Cycle test results Negative electrode falling area rate>

［緩衝層無し］ 21.2[%]
［緩衝層有り］ 10.3[%] [No buffer layer] 21.2[%]
[With buffer layer] 10.3[%]

以上の結果は、緩衝層が、負極活物質の粒子、特に亜鉛を含有する負極活物質の粒子と集電体との結合を強固にすることを示す。 The above results indicate that the buffer layer strengthens the bond between the particles of the negative electrode active material, particularly the particles of the negative electrode active material containing zinc, and the current collector.

１０ 負極、 １１ 集電体、 １２ 活物質層、 １３ 活物質粒子、 １４ バインダー、 １５ 緩衝層、 １６ 親水性組成物、 １８ 端部、 ２０ 負極、 ２３ 端部、 Ｓ０１－Ｓ０５ ステップ 10 negative electrode, 11 current collector, 12 active material layer, 13 active material particles, 14 binder, 15 buffer layer, 16 hydrophilic composition, 18 end, 20 negative electrode, 23 end, S01-S05 steps

Claims (9)

集電体と、前記集電体上に積層された活物質粒子からなる活物質層を備え、
前記集電体と前記活物質層との間に設けられた緩衝層をさらに備え、
前記緩衝層は有機高分子及び無機分子のいずれかの親水性組成物からなる、
二次電池の負極。 comprising a current collector and an active material layer made of active material particles laminated on the current collector,
further comprising a buffer layer provided between the current collector and the active material layer,
The buffer layer is made of a hydrophilic composition of either an organic polymer or an inorganic molecule.
Negative electrode of secondary battery. 前記親水性組成物は繊維状の有機高分子である、
請求項１に記載の二次電池の負極。 the hydrophilic composition is a fibrous organic polymer;
A negative electrode for a secondary battery according to claim 1. 前記有機高分子はセルロースナノファイバー及びポリビニルアルコールの少なくともいずれかである、
請求項２に記載の二次電池の負極。 The organic polymer is at least one of cellulose nanofibers and polyvinyl alcohol,
A negative electrode for a secondary battery according to claim 2. 前記活物質層はさらに、前記活物質粒子同士を結合するバインダーからなり、
前記バインダーは有機高分子からなり、
前記バインダーの前記有機高分子は、前記親水性組成物の前記有機高分子と異なる、
請求項２又は３に記載の二次電池の負極。 The active material layer further includes a binder that binds the active material particles together,
The binder is made of an organic polymer,
the organic polymer of the binder is different from the organic polymer of the hydrophilic composition;
A negative electrode for a secondary battery according to claim 2 or 3. 前記活物質粒子は、亜鉛／酸化亜鉛からなる、
請求項１～４のいずれかに記載の二次電池の負極。 The active material particles are made of zinc/zinc oxide,
A negative electrode for a secondary battery according to any one of claims 1 to 4. 請求項１～５のいずれかに記載の二次電池の負極の製造方法であって、
前記集電体上に、活物質を含有しない前記親水性組成物を塗布することで前記緩衝層を形成し、
前記緩衝層上に、前記活物質粒子を塗布することで前記活物質層を形成する、
二次電池の負極の製造方法。 A method for producing a negative electrode for a secondary battery according to any one of claims 1 to 5, comprising:
forming the buffer layer by applying the hydrophilic composition containing no active material on the current collector;
forming the active material layer by applying the active material particles on the buffer layer;
A method for manufacturing a negative electrode for a secondary battery. 正極と請求項１～５のいずれかに記載の負極と電解液とを備える、
二次電池。 comprising a positive electrode, a negative electrode according to any one of claims 1 to 5, and an electrolyte;
Secondary battery. 前記電解液は水系電解液であり、
前記集電体は、銅以外の金属でメッキされた銅からなる、
請求項７に記載の二次電池。 The electrolyte is an aqueous electrolyte,
The current collector is made of copper plated with a metal other than copper,
The secondary battery according to claim 7. 前記正極は、ニッケル／水酸化ニッケルからなる活物質を有する、
請求項７又は８に記載の二次電池。 The positive electrode has an active material made of nickel/nickel hydroxide,
The secondary battery according to claim 7 or 8.
JP2022032897A 2022-03-03 2022-03-03 Negative electrode of secondary battery, method for manufacturing the same, and secondary battery Pending JP2023128519A (en)

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