JP2010219056A - Lithium battery - Google Patents
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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
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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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
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Abstract
Description
本発明はリチウム電池に関し、特に電極を改良したリチウム電池に関する。 The present invention relates to a lithium battery, and more particularly to a lithium battery having an improved electrode.
携帯電話やパーソナルコンピュータに代表される携帯機器の近年の目覚しい発達に伴い、その電源としての電池の需要も急速に増加している。特に、リチウム電池は原子量が小さく、かつイオン化エネルギーが大きなリチウムを使う電池であることから、高エネルギー密度を得ることができる電池として盛んに研究され、現在では携帯機器の電源をはじめとして広範囲に用いられるに至っている。 With the recent remarkable development of portable devices such as mobile phones and personal computers, the demand for batteries as a power source is rapidly increasing. In particular, lithium batteries are batteries that use lithium with a low atomic weight and high ionization energy, so they have been actively researched as batteries that can achieve high energy density, and are now widely used in power supplies for portable devices. Has come to be.
一般的に、リチウム電池は、正極活物質と炭素系導電剤を有機系バインダーで結着したシート状正極と、同じく負極活物質を有機系バインダーで結着したシート状負極がセパレータを介して捲回された極群を電槽缶内に挿入し、そこに有機電解液を注入して封口した構造となっている。 In general, in a lithium battery, a sheet-like positive electrode in which a positive electrode active material and a carbon-based conductive agent are bound with an organic binder, and a sheet-like negative electrode in which a negative electrode active material is bound with an organic binder are interposed through a separator. The rotated electrode group is inserted into a battery case can, and an organic electrolyte is injected into the battery case to seal it.
また、リチウム電池では、正極活物質としてコバルト酸リチウム（ＬｉＣｏＯ２）やマンガン酸リチウム（ＬｉＭｎ２Ｏ４）が一般的に用いられ、負極活物質には、コークスや炭素繊維などの炭素材料が用いられている。
これらの正極活物質と負極活物質を組み合わせることでリチウム電池は公称電圧３．５Ｖ以上の高電圧を達成している。
In lithium batteries, lithium cobaltate (LiCoO 2 ) and lithium manganate (LiMn 2 O 4 ) are generally used as the positive electrode active material, and carbon materials such as coke and carbon fiber are used as the negative electrode active material. It has been.
By combining these positive electrode active material and negative electrode active material, the lithium battery achieves a high voltage of a nominal voltage of 3.5 V or more.
しかしながら、電解質に有機電解液を用いるため、有機電解液に起因する漏液や作動温度範囲が狭いといった問題がある。 However, since an organic electrolyte is used as the electrolyte, there are problems such as leakage due to the organic electrolyte and a narrow operating temperature range.
さらに、負極活物質に炭素材料を用いるリチウム電池は炭素材料の充放電電圧が０Ｖ付近であることから、電池の充電過程でリチウム金属が負極表面に析出して内部短絡を引き起こす可能性があり、十分な信頼性を有しているとはいえない。 Furthermore, since a lithium battery using a carbon material as a negative electrode active material has a charge / discharge voltage of the carbon material of around 0 V, lithium metal may be deposited on the negative electrode surface during the battery charging process, causing an internal short circuit. It cannot be said that it has sufficient reliability.
かかる問題を解決する方法として、例えば特開平７−２９６８５０号公報では負極活物質にＮｂ２Ｏ４を用いると共に、正極活物質にＬｉ２ＭｎＯ３を用いた電池が提案されており、また特開平８−２２８４１号公報では正極および負極活物質にスピネル系リチウム含有金属酸化物を用いた電池が提案されている。 As a method for solving such a problem, for example, Japanese Patent Laid-Open No. 7-296850 proposes a battery using Nb 2 O 4 as a negative electrode active material and Li 2 MnO 3 as a positive electrode active material. Japanese Laid-Open Patent Publication No. 8-22841 proposes a battery using a spinel-based lithium-containing metal oxide as a positive electrode and a negative electrode active material.
このように、正極および負極活物質に酸化物を用いると、サイクル寿命や耐過放電特性が改善され、高信頼性を有するリチウム電池となるが、電解質に有機電解液を用いているため、やはり漏液や作動温度範囲が狭いといった電解液に起因する問題を解決することができない。 As described above, when an oxide is used for the positive electrode and the negative electrode active material, the cycle life and the overdischarge resistance are improved, and the lithium battery has high reliability. However, since the organic electrolyte is used as the electrolyte, Problems caused by the electrolyte such as leakage or a narrow operating temperature range cannot be solved.
そこで、これら安全上の問題を解決するために、不燃性の無機固体材料で構成される無機固体電解質を用いた耐熱性、信頼性に優れた全固体リチウム電池の開発が進められている。電解質に無機固体電解質を用いたリチウム電池の例としては、例えば特開平１１−７９４２号公報に開示されるように、固体電解質として硫化物ガラスを用いたものがある。しかし、硫化物ガラスは水分や酸素に対する安定性が乏しく電池製造コストの上昇につながるという問題がある。 Therefore, in order to solve these safety problems, development of an all-solid-state lithium battery excellent in heat resistance and reliability using an inorganic solid electrolyte composed of an incombustible inorganic solid material has been advanced. An example of a lithium battery using an inorganic solid electrolyte as an electrolyte is one using sulfide glass as a solid electrolyte, as disclosed in, for example, Japanese Patent Application Laid-Open No. 11-7942. However, there is a problem that sulfide glass has poor stability to moisture and oxygen and leads to an increase in battery manufacturing cost.
一方、リチウム電池に対する要求は安全性、信頼性だけに止まらず、携帯機器の小型化軽量化に伴い、さらなる高エネルギー密度化や高出力化が求められている。 On the other hand, demands for lithium batteries are not limited to safety and reliability, and with the miniaturization and weight reduction of portable devices, higher energy density and higher output are required.
かかる課題を解決するために、正極に含まれる導電剤の改良が種々試みられている。
例えば、黒鉛とカーボンブラックの混合物を用いたり（特開平８−２２２２０６号）、形状の異なる鱗片状黒鉛と繊維状炭素を混合したり（特開平９−２７３４４号）、炭素材料以外では遷移金属炭化物を用いたり（特開平５−２１７５８２号）、アルミニウム粉末やタンタル粉末を用いる（特開平８−７８０５４号）ことが提案されている。しかしながら、これらの導電剤はいずれも電池容量の増加には直接寄与しないため、導電剤を使用しないことで電池の高容量化、ひいては高エネルギー密度化を図る試みがなされている。
In order to solve this problem, various attempts have been made to improve the conductive agent contained in the positive electrode.
For example, a mixture of graphite and carbon black (JP-A-8-222206), flaky graphite and fibrous carbon having different shapes (JP-A-9-27344), transition metal carbides other than carbon materials (JP-A-5-217582) or aluminum powder or tantalum powder (JP-A-8-78054) has been proposed. However, none of these conductive agents directly contributes to an increase in battery capacity. Therefore, attempts have been made to increase the capacity of the battery and consequently to increase the energy density by not using the conductive agent.
特開平８−１４８１４１号では導電剤やバインダーなどの電池容量の低下を招く材料を使わずに活物質のみの焼成体を電極とすることで優れた充放電特性を有するリチウム電池を提案している。 Japanese Patent Laid-Open No. 8-148141 proposes a lithium battery having excellent charge / discharge characteristics by using a fired body of only an active material as an electrode without using a material that causes a decrease in battery capacity such as a conductive agent or a binder. .
しかしながら、前記提案では活物質層に結着剤を含まないために、電極が脆くて取扱が困難であるという問題がある。さらに、電極に導電性を付与していないために、活物質層の厚みが２０μｍを超えると充放電容量が極端に低下し、実用電池として充分なエネルギー密度が得られないという問題があることが明らかとなった。 However, the above proposal has a problem that the electrode is brittle and difficult to handle because the active material layer does not contain a binder. Furthermore, in order not to impart conductivity to the electrode, the thickness of the active material layer decreases 20μm the extremely ultra Ell and charge-discharge capacity, sufficient energy density is not be obtained as a practical battery Became clear.
そこで、本発明者らは酸化物ガラスを用いて活物質を結着した２０μｍ以上の厚みを有する電極に導電性を付与してリチウム電池の電極として使用することを鋭意研究した結果、導電剤としてＳｂ２Ｏ３ドープＳｎＯ２および／またはＳｎＯ２ドープＩｎ２Ｏ３、あるいはカーボンブラックおよび／または黒鉛を添加することで厚い電極が使用可能となることを見出した。しかしながら、電極内の導電剤の分布状態によって電極特性が大きく変化することが明らかとなり、最適な分布状態について研究することによって本発明を完成するにいたった。 Therefore, the present inventors have intensively studied to use an oxide glass as an electrode of a lithium battery by imparting conductivity to an electrode having a thickness of 20 μm or more obtained by binding an active material as a conductive agent. It has been found that thick electrodes can be used by adding Sb 2 O 3 -doped SnO 2 and / or SnO 2 -doped In 2 O 3 , or carbon black and / or graphite. However, it has been clarified that the electrode characteristics vary greatly depending on the distribution state of the conductive agent in the electrode, and the present invention has been completed by studying the optimal distribution state.
したがって、本発明は上述のような従来の技術に鑑みてなされたものであり、高エネルギー密度、高出力密度を有し、安全性および信頼性に優れたリチウム電池を提供することを目的とするものである。 Therefore, the present invention has been made in view of the conventional techniques as described above, and an object thereof is to provide a lithium battery having high energy density and high output density and excellent in safety and reliability. Is.
上記目的を達成するために、一対の電極間に、リチウムを含む無機固体電解質を介在させてなるリチウム電池において、前記一対の電極は、酸化物ガラスを介して結合された活物質と、前記活物質の粒子の間に配置された導電剤と、を含むことを特徴とするリチウム電池を提供する。 To achieve the above object, between a pair of electrodes, the lithium battery comprising by interposing an inorganic solid electrolyte containing lithium, wherein the pair of electrodes, and an active material coupled via an oxide glass, the active And a conductive agent disposed between the particles of the substance .
エネルギー密度が高く、出力密度、安全性、信頼性に優れたリチウム電池を提供できる。また、酸化物の充放電電圧は炭素材料の充放電電圧よりも貴な電位を示すことから、活物質、特に負極活物質に遷移金属酸化物を用いると、原理的にリチウムの析出反応が起こらず、電池の信頼性および安全性が向上する。 A lithium battery with high energy density and excellent power density, safety, and reliability can be provided. In addition, since the charge / discharge voltage of the oxide shows a higher potential than the charge / discharge voltage of the carbon material, when a transition metal oxide is used for the active material, particularly the negative electrode active material, a lithium precipitation reaction occurs in principle. Therefore, the reliability and safety of the battery are improved.
以下、本発明のリチウム電池の実施形態について説明する。図１は、本発明に係るリチウム電池の構成例を示す断面図である。図１において、１は正極、２は固体電解質、３は負極、４は正極電槽、５は負極電槽、６は封口樹脂である。 Hereinafter, embodiments of the lithium battery of the present invention will be described. FIG. 1 is a cross-sectional view showing a configuration example of a lithium battery according to the present invention. In FIG. 1, 1 is a positive electrode, 2 is a solid electrolyte, 3 is a negative electrode, 4 is a positive electrode battery case, 5 is a negative electrode battery case, and 6 is a sealing resin.
正極１および負極３は主として活物質と酸化物ガラスとで構成される。正極１および負極３に用いる活物質としては、次のような遷移金属酸化物が挙げられる。例えば、リチウムマンガン複合酸化物、二酸化マンガン、リチウムニッケル複合酸化物、リチウムコバルト複合酸化物、リチウムニッケルコバルト複合酸化物、リチウムバナジウム複合酸化物、リチウムチタン複合酸化物、酸化チタン、酸化ニオブ、酸化バナジウム、酸化タングステンなどとそれらの誘導体が挙げられる。 The positive electrode 1 and the negative electrode 3 are mainly composed of an active material and oxide glass. Examples of the active material used for the positive electrode 1 and the negative electrode 3 include the following transition metal oxides. For example, lithium manganese composite oxide, manganese dioxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium vanadium composite oxide, lithium titanium composite oxide, titanium oxide, niobium oxide, vanadium oxide , Tungsten oxide and the like and derivatives thereof.
上述の遷移金属酸化物のうち、特にＬｉ１＋ＸＭｎ２‐ＸＯ４（０≦Ｘ≦０．２）、ＬｉＭｎ２‐ＹＭｅＹＯ４（Ｍｅ＝Ｎｉ、Ｃｒ、Ｃｕ、Ｚｎ，０＜Ｙ≦０．６）、Ｌｉ４Ｔｉ５Ｏ１２およびＬｉ４Ｍｎ４Ｏ１２よりなる群は、充放電中の活物質の体積変化が小さい結晶系がスピネル系の活物質であり、酸化物ガラスで結着した場合に良好なサイクル特性を示すものである。 Among the transition metal oxides described above, Li 1+ XMn 2 -XO 4 (0 ≦ X ≦ 0.2), LiMn 2 -YMeYO 4 (Me = Ni, Cr, Cu, Zn, 0 <Y ≦ 0.6) ), A group consisting of Li 4 Ti 5 O 12 and Li 4 Mn 4 O 12 is a spinel-based active material in which the volume change of the active material during charge / discharge is small, and is bound by an oxide glass Exhibit good cycle characteristics.
ここで、正極活物質と負極活物質には明確な区別はなく、２種類の遷移金属酸化物の充放電電位を比較してより貴な電位を示すものを正極に、より卑な電位を示すものを負極にそれぞれ用いて任意の電圧の電池を構成することができる。 Here, there is no clear distinction between the positive electrode active material and the negative electrode active material, the charge and discharge potentials of the two types of transition metal oxides are compared, and the one showing the noble potential is shown as the positive electrode and the lower potential is shown. A battery having an arbitrary voltage can be formed by using each of the negative electrodes.
正極活物質と負極活物質に遷移金属酸化物を用いると、電池が過充電された場合にも金属リチウムの析出が起こらず、電池の信頼性が向上する。 When a transition metal oxide is used for the positive electrode active material and the negative electrode active material, metal lithium does not precipitate even when the battery is overcharged, and the reliability of the battery is improved.
本発明にかかる酸化物ガラスとしては、リン酸塩ガラスやホウ酸塩ガラス、ケイ酸塩ガラス、ホウケイ酸塩ガラスを中心とした多成分系酸化物ガラスを挙げることができる。
また、アルカリ金属元素の添加は体積抵抗を低減でき、特にリチウムを添加した場合にはリチウムイオン伝導性が期待されるので好ましい。
Examples of the oxide glass according to the present invention include a multicomponent oxide glass mainly composed of phosphate glass, borate glass, silicate glass, and borosilicate glass.
Addition of an alkali metal element is preferable because volume resistance can be reduced, and lithium ion conductivity is expected particularly when lithium is added.
電極の隙間に導電剤を後から添加するので、電池容量の低下を招くことなく電極に導電性を付与でき、厚みが２０μｍを超える電極でも優れた充放電特性が得られる。 Since a conductive agent is added to the gaps between the electrodes later, conductivity can be imparted to the electrodes without causing a decrease in battery capacity, and excellent charge / discharge characteristics can be obtained even with electrodes having a thickness exceeding 20 μm.
また、一般的に酸化物の充放電電圧は炭素材料の充放電電圧よりも貴な電位を示すことから、活物質、特に負極活物質にリチウム含有遷移金属酸化物を用いると、原理的にリチウムの析出反応が起こらず、電池の信頼性および安全性が向上する。 In general, since the charge / discharge voltage of an oxide shows a noble potential than the charge / discharge voltage of a carbon material, in principle, when a lithium-containing transition metal oxide is used for an active material, particularly a negative electrode active material, lithium No precipitation reaction occurs, and the reliability and safety of the battery are improved.
酸化物ガラスの組成は特に限定しないが、活物質粒子を結着するための熱処理は酸化物ガラスのガラス転移点以上、活物質の合成温度以下で行われるため、この温度範囲において流動性を示す酸化物ガラスを選定するのが好ましい。 The composition of the oxide glass is not particularly limited, but the heat treatment for binding the active material particles is performed at a temperature not lower than the glass transition point of the oxide glass and not higher than the synthesis temperature of the active material, and thus exhibits fluidity in this temperature range. It is preferable to select an oxide glass.
酸化物ガラスの添加量は、活物質と酸化物ガラスの組み合わせで種々最適値が異なると考えられるが、概して３０重量％以下が好ましい。３０重量％を超えると電極体積中に占める酸化物ガラスの体積が大きくなり、かえって活物質の充填率を下げることとなる。 Although the optimum amount of oxide glass is considered to vary in various optimum values depending on the combination of the active material and the oxide glass, it is generally preferably 30% by weight or less. When it exceeds 30% by weight, the volume of the oxide glass in the electrode volume increases, and the filling rate of the active material is lowered.
正極１は、正極活物質と酸化物ガラスに成形助剤を加えて加圧成形して熱処理した多孔質体から成り、負極３は、正極１中の正極活物質の充放電電位よりも卑な充放電電位を有する遷移金属酸化物を活物質とした多孔質体から成る。 The positive electrode 1 is composed of a porous body that is formed by adding a forming aid to a positive electrode active material and oxide glass, and is pressure-formed and heat-treated. The negative electrode 3 is lower than the charge / discharge potential of the positive electrode active material in the positive electrode 1. It consists of a porous body using a transition metal oxide having a charge / discharge potential as an active material.
正極１および負極３を作製するには、（１）活物質と酸化物ガラスを成形助剤を溶解させた水もしくは溶剤に分散させてスラリーを調製し、このスラリーを基材フィルム上に塗布して乾燥した後、加圧成形して裁断したものを熱処理する方法、あるいは（２）活物質と酸化物ガラスの混合物を直接あるいは成形助剤を加えて造粒して金型に投入し、プレス機で加圧成形した後、熱処理する方法、（３）造粒した混合物をロールプレス機で加圧成
形してシート状に加工した後、そのシートを裁断して熱処理する方法などが用いられる。（２）、（３）の造粒は、（１）の方法で述べたスラリーから造粒する湿式造粒であっても溶剤を用いない乾式造粒であっても構わない。
In order to produce the positive electrode 1 and the negative electrode 3, (1) a slurry is prepared by dispersing an active material and an oxide glass in water or a solvent in which a forming aid is dissolved, and this slurry is applied onto a base film. After drying, press-molded and cut, and then heat treated, or (2) granulate a mixture of active material and oxide glass directly or with a molding aid, put into mold, press A method of performing heat treatment after press molding with a machine, (3) a method of pressing the granulated mixture into a sheet by pressing with a roll press machine, and then heat-treating the sheet is used. The granulation of (2) and (3) may be wet granulation from the slurry described in the method of (1) or dry granulation without using a solvent.
次に、これら正極１および／または負極３に添加する導電剤には、導電性酸化物や炭素材料、金属粉を用いることができる。導電性酸化物では、例えばＳｎＯ２やＩｎ２Ｏ３、ＴｉＯ２‐Ｘ、ＺｎＯ、Ｆｅ３Ｏ４、ＲｅＯ３、ＭｏＯ２、ＲｕＯ２、ＶＯ、ＷＯ２など室温で大凡１×１０‐４Ω・ｍ以下の抵抗率を有する酸化物を用いることができる。さらに好ましくは、安定した低抵抗率を得るためにＳｂ２Ｏ３がドープされたＳｎＯ２とＳｎＯ２がドープされたＩｎ２Ｏ３が帯電防止や透明電極用に量産されており、これらを用いることが品質、コストの面からも有利である。 Next, as the conductive agent added to the positive electrode 1 and / or the negative electrode 3, a conductive oxide, a carbon material, or metal powder can be used. Examples of the conductive oxide include SnO 2 , In 2 O 3 , TiO 2 -X, ZnO, Fe 3 O 4 , ReO 3 , MoO 2 , RuO 2 , VO, and WO 2 , which are approximately 1 × 10 −4 Ω · An oxide having a resistivity of m or less can be used. More preferably, SnO 2 doped with Sb 2 O 3 and In 2 O 3 doped with SnO 2 are mass-produced for antistatic use and transparent electrodes in order to obtain a stable low resistivity. This is also advantageous in terms of quality and cost.
また、炭素材料では例えばファーネスブラックやアセチレンブラック、サーマルブラックなどのカーボンブラックと鱗片状や繊維状の天然黒鉛や人造黒鉛などを挙げることができる。なかでも一次粒子の平均粒径が０．０２５〜０．０７μｍのファーネスブラック、アセチレンブラックが充填性が良好でカーボンブラックとして適している。また、黒鉛には鱗片状の黒鉛をサブμｍまで微粉砕したものが充填性、導電性に優れ適当である。なお、これらの炭素材料は予めシランカップリング剤などで表面改質処理を施したものを用いることもできる。 Examples of the carbon material include carbon black such as furnace black, acetylene black, and thermal black, scaly and fibrous natural graphite, and artificial graphite. Of these, furnace black and acetylene black having an average primary particle size of 0.025 to 0.07 μm are suitable as carbon black because of good filling properties. In addition, graphite obtained by finely pulverizing scaly graphite to sub-μm is suitable for its excellent filling property and conductivity. Note that those carbon materials that have been surface-modified with a silane coupling agent or the like in advance can also be used.
また、金属粉では例えば、ＡｕやＡｇ、Ａｌ、Ｃｕ、Ｎｉ、Ｆｅなどを挙げることができる。 Examples of the metal powder include Au, Ag, Al, Cu, Ni, and Fe.
さらに、導電剤としてＳｂ２Ｏ３ドープＳｎＯ２および／またはＳｎＯ２ドープＩｎ２Ｏ３、あるいはカーボンブラックおよび／または黒鉛を用いると導電性が良好で優れた充放電特性が得られることとなる。 Further, when Sb 2 O 3 -doped SnO 2 and / or SnO 2 -doped In 2 O 3 , or carbon black and / or graphite is used as the conductive agent, good conductivity and excellent charge / discharge characteristics can be obtained.
添加方法としては、例えば活物質の平均粒径の１０分の１以下の平均粒径を持つ炭素材料の微粒子を水もしくは有機溶剤に分散させた懸濁液に熱処理して得られた正極１および／または負極３の多孔質体を浸漬して含浸する方法や電解質２を介して一括熱処理して一体化した発電要素を浸漬して含浸する方法がある。また、含浸を加速するために減圧あるいは減圧加圧含浸することも可能である。さらに、懸濁液を電極表面に滴下して導電剤を含浸する方法や吸引ろ過の方法を応用して電極を用いて懸濁液をろ過するような方法も可能である。一方、粒子を用いない方法としては、導電剤の出発材料を電極中に含浸しておいて熱分解反応を利用して導電剤を生成する方法が挙げられる。具体的には、ポリビニルアルコールなどの有機物を含浸しておいて熱分解して炭素材料を添加したり、ＳｎやＩｎなどの有機金属材料を含浸しておいて熱分解して導電性酸化物を電極内で合成する方法などが考えられる。なお、発電要素に含浸した場合は、発電要素の周縁部に付着した導電剤を除去するために周縁部を研磨あるいは切断加工することが必要である。 As an addition method, for example, the positive electrode 1 obtained by heat-treating a suspension in which fine particles of a carbon material having an average particle size of 1/10 or less of the average particle size of the active material are dispersed in water or an organic solvent, and There are a method of immersing and impregnating the porous body of the negative electrode 3 and a method of immersing and impregnating a power generation element integrated by batch heat treatment via the electrolyte 2. Further, in order to accelerate the impregnation, it is possible to impregnate under reduced pressure or under reduced pressure. Furthermore, a method of dropping the suspension onto the electrode surface and impregnating the conductive agent, or a method of filtering the suspension using the electrode by applying a suction filtration method is also possible. On the other hand, as a method that does not use particles, a method of impregnating a starting material of a conductive agent in an electrode and generating a conductive agent using a thermal decomposition reaction can be given. Specifically, it is impregnated with an organic substance such as polyvinyl alcohol and thermally decomposed to add a carbon material, or impregnated with an organic metal material such as Sn or In and thermally decomposed to form a conductive oxide. A method of synthesizing within the electrode is conceivable. When the power generation element is impregnated, it is necessary to polish or cut the peripheral portion in order to remove the conductive agent attached to the peripheral portion of the power generation element.
導電剤微粒子を分散させた懸濁液を用いて導電剤を含浸した場合導電剤粒子は溶媒と共に電極１、３内に侵入していくため、電極１、３の中心部へは染み込みにくい。これは電極１、３内の活物質粒子間に目詰まりしたように堆積し易いためで、これによって必然的に電極１、３表面近傍の導電剤濃度を高くすることができる。 When the conductive agent is impregnated using the suspension in which the conductive agent fine particles are dispersed, the conductive agent particles penetrate into the electrodes 1 and 3 together with the solvent, so that they do not easily penetrate into the central portions of the electrodes 1 and 3. This is because it is easy to deposit as clogged between the active material particles in the electrodes 1, 3, which inevitably increases the conductive agent concentration in the vicinity of the surfaces of the electrodes 1, 3.
Ｓｂ２Ｏ３ドープＳｎＯ２を分散した懸濁液に熱処理して得られた多孔質体電極を浸漬し、導電剤を含浸したのち、その断面をＸ線マイクロアナリシスで分析しＳｎの分布状態を評価したところ、電極表面近傍の濃度は中心部に比べ３から４倍高いことが確認された。だたし、電極が薄いためにＳｎの厚み方向での部分的な定量分析はできていない。ちなみに電極全体では電極重量の約３重量％のＳｂ２Ｏ３ドープＳｎＯ２が含浸される。 A porous electrode obtained by heat treatment is immersed in a suspension in which Sb 2 O 3 -doped SnO 2 is dispersed, impregnated with a conductive agent, and then the cross section is analyzed by X-ray microanalysis to determine the Sn distribution state. As a result of the evaluation, it was confirmed that the concentration in the vicinity of the electrode surface was 3 to 4 times higher than that in the central portion. However, since the electrode is thin, partial quantitative analysis in the thickness direction of Sn cannot be performed. Incidentally, the entire electrode is impregnated with Sb 2 O 3 -doped SnO 2 of about 3% by weight of the electrode weight.
一方、電極１、３に懸濁液を滴下して導電剤を含浸した場合には一方向からだけの含浸となるため、反対側の表面にまでは懸濁液が含浸しにくく、また含浸途中に活物質間に堆積してしまうため、導電剤濃度は必然的に特定の電極１、３の表面近傍で高くなる。 On the other hand, when the suspension is dripped onto the electrodes 1 and 3 and impregnated with the conductive agent, the impregnation is performed only from one direction. Therefore, the conductive agent concentration inevitably increases in the vicinity of the surfaces of the specific electrodes 1 and 3.
この現象を利用することで、特に集電体近傍に導電剤を高濃度に配置することができ、集電体と活物質間の電子の授受をスムーズに進行させる効果、つまり接触抵抗を低減する効果が得られる。 By utilizing this phenomenon, the conductive agent can be placed at a high concentration especially near the current collector, and the effect of smoothly transferring electrons between the current collector and the active material, that is, the contact resistance is reduced. An effect is obtained.
固体電解質２に用いられる酸化物系無機固体電解質には、例えばＬｉ１．３Ａｌ０．３Ｔｉ１．７（ＰＯ４）３やＬｉ３．６Ｇｅ０．６Ｖ０．４Ｏ４などの結晶質固体電解質、３０ＬｉＩ−４１Ｌｉ２Ｏ−２９Ｐ２Ｏ４や４０Ｌｉ２Ｏ−３５Ｂ２Ｏ３−２５ＬｉＮｂＯ３、１０Ｌｉ２Ｏ−２５Ｂ２Ｏ３−１５ＳｉＯ２−５０ＺｎＯなどの非晶質固体電解質、あるいは結晶質固体電解質と非晶質固体電解質の混合体もしくは焼成体を挙げることができる。 Examples of the oxide-based inorganic solid electrolyte used for the solid electrolyte 2 include Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 and Li 3.6 Ge 0.6 V 0.4 O 4 . crystalline solid electrolyte, 30LiI-41Li 2 O-29P 2 O 4 or 40Li 2 O-35B 2 O 3 -25LiNbO 3, 10Li 2 O-25B 2 O 3 -15SiO 2 -50ZnO amorphous solid electrolytes such as, or Examples thereof include a mixture or a fired body of a crystalline solid electrolyte and an amorphous solid electrolyte.
固体電解質２は、例えば上記製法（１）〜（３）と同様にして酸化物系無機固体電解質である結晶質固体電解質と非晶質固体電解質の混合体に成形助剤を加えて成形体を作製し、熱処理することで作製することができる。 The solid electrolyte 2 is formed by adding a molding aid to a mixture of a crystalline solid electrolyte and an amorphous solid electrolyte, which are oxide-based inorganic solid electrolytes, for example, in the same manner as in the above production methods (1) to (3). It can be manufactured by manufacturing and heat treatment.
上述の正極１、負極３および電解質層２を積層してなる発電要素を作製する方法としては、（イ）個別に熱処理して多孔質体とした正極１と負極３を電解質層２を介して積層する方法や、（ロ）熱処理後の正極１と負極３を熱処理前の電解質層２を介して積層して熱処理する方法や、（ハ）熱処理前の各層を積層して一括して熱処理する方法などが考えられる。ただし、各層の接触状態を考慮すると層間の接着が可能な（ロ）または（ハ）の方法が好ましい。 As a method for producing a power generation element formed by laminating the positive electrode 1, the negative electrode 3 and the electrolyte layer 2 described above, (a) the positive electrode 1 and the negative electrode 3 which are individually heat-treated to form a porous body are interposed via the electrolyte layer 2. (B) a method of laminating the positive electrode 1 and the negative electrode 3 after heat treatment via the electrolyte layer 2 before heat treatment, and (c) laminating each layer before the heat treatment and collectively heat treating. Possible methods. However, considering the contact state of each layer, the method (b) or (c) capable of bonding between the layers is preferable.
いずれにしても、ここで使用可能な成形助剤としては、例えばポリテトラフルオロエチレン、ポリアクリル酸、カルボキシメチルセルロース、エチルセルロース、ポリフッ化ビニリデン、ポリビニルアルコール、ジアセチルセルロース、ヒドロキシプロピルセルロース、ポリブチラール、ポリビニルクロライド、ポリビニルピロリドンなどの１種もしくは２種以上の混合物が挙げられる。 In any case, examples of the molding aid that can be used here include polytetrafluoroethylene, polyacrylic acid, carboxymethylcellulose, ethylcellulose, polyvinylidene fluoride, polyvinyl alcohol, diacetylcellulose, hydroxypropylcellulose, polybutyral, and polyvinyl chloride. 1 type, or 2 or more types of mixtures, such as polyvinylpyrrolidone.
基材フィルムとしては、例えばポリエチレンテレフタレート、ポリプロピレン、ポリエチレン、ポリテトラフルオロエチレンなどの樹脂フィルム、アルミニウム、ステンレス、銅などの金属箔などが使用可能である。 As the base film, for example, a resin film such as polyethylene terephthalate, polypropylene, polyethylene, polytetrafluoroethylene, or a metal foil such as aluminum, stainless steel, or copper can be used.
正極電槽４と負極電槽５に用いる金属製薄板は、ステンレス、アルミニウム、ニッケル、銅、コバール、４２アロイ、チタンあるいはアルミニウム合金などの金属材料であればよい。また、封口樹脂６は前記金属材料と接着性を有する接着性樹脂であればよく、封口にはヒートシーラーや熱板などを用いることができる。正極電槽４と負極電槽５の板厚は、電池のエネルギー密度の観点から薄いものを用いるのが望ましいが、ピンホールの有無や外装材としての強度の面から適当な厚みが選択されるべきである。例えば、アルミニウムの場合３０μｍ以上とすることが望ましい。一方、厚いほうでは、封止方法による制約や封止部の接着強度やエネルギー密度の観点から５００μｍ以下とするのが好ましい。 The metal thin plate used for the positive electrode case 4 and the negative electrode case 5 may be a metal material such as stainless steel, aluminum, nickel, copper, kovar, 42 alloy, titanium, or aluminum alloy. Moreover, the sealing resin 6 should just be adhesive resin which has adhesiveness with the said metal material, and a heat sealer, a hot plate, etc. can be used for sealing. The plate thicknesses of the positive electrode case 4 and the negative electrode case 5 are preferably thin from the viewpoint of the energy density of the battery, but an appropriate thickness is selected in view of the presence or absence of pinholes and the strength as an exterior material. Should. For example, in the case of aluminum, it is desirable to set it as 30 micrometers or more. On the other hand, when the thickness is thicker, the thickness is preferably 500 μm or less from the viewpoint of the restriction by the sealing method, the adhesive strength of the sealing portion, and the energy density.
正極電槽４および／または負極電槽５の極群収納部を予め凹状に成形してもよく、この凹状の成形方法には既存の従来技術を用いることができる。例えば成形金型によるプレス加工が一般的である。形状は、極群収納部から見て凹状であれば良く、深さや寸法は特に限定されないが、極群の厚みと封口樹脂７の厚みを考慮して極群と電槽が面で接触できる
寸法、形状にすべきである。また、成形方法によっては成形する際に凹状の極群収納部が台形となったり、屈曲部に曲面を設けたほうが好都合な場合があり、成形方法に適した任意の設計とすることで何ら問題はない。
The pole group storage part of the positive electrode case 4 and / or the negative electrode case 5 may be formed in a concave shape in advance, and an existing conventional technique can be used for this concave shape forming method. For example, press working with a molding die is common. The shape is not particularly limited as long as it is concave when viewed from the pole group storage part, and the depth and dimensions are not particularly limited. Should be in shape. Also, depending on the molding method, it may be more convenient for the concave pole group storage part to become trapezoidal or provide a curved surface at the bent part, and there is no problem with any design suitable for the molding method There is no.
封口樹脂６には、上記金属製電槽と接着性を有する接着性樹脂を用いることができる。例えば、変性ポリエチレンや変性ポリプロピレンなどの熱熔着性の接着性樹脂が取扱が簡便で適当である。 For the sealing resin 6, an adhesive resin having adhesiveness with the metal battery case can be used. For example, heat-weldable adhesive resins such as modified polyethylene and modified polypropylene are easy to handle and suitable.
本発明のリチウム電池の形状は、カード型、フィルム型、コイン型、円筒型および扁平型などの四角や三角、円形など特に限定されるものではない。 The shape of the lithium battery of the present invention is not particularly limited, such as a square shape such as a card shape, a film shape, a coin shape, a cylindrical shape, and a flat shape, a triangle shape, and a circular shape.
［実施例１］
水酸化リチウムと二酸化マンガンをＬｉとＭｎのモル比が１：２となるように混合し、この混合物を大気中、７００℃で１５時間加熱焼成することでリチウムマンガン複合酸化物（ＬｉＭｎ２Ｏ４）を調製し、これを正極活物質とした。
次に、水酸化リチウムと二酸化チタンをＬｉとＴｉのモル比が４：５となるように混合し、この混合物を大気中、７５０℃で１５時間加熱焼成することでリチウムチタン複合酸化物（Ｌｉ４Ｔｉ５Ｏ１２）を調製して負極活物質とした。
[Example 1]
Lithium hydroxide and manganese dioxide are mixed so that the molar ratio of Li and Mn is 1: 2, and this mixture is heated and fired at 700 ° C. for 15 hours in the air to prepare a lithium manganese composite oxide (LiMn 2 O 4). This was used as the positive electrode active material.
Next, lithium hydroxide and titanium dioxide are mixed so that the molar ratio of Li and Ti is 4: 5, and this mixture is heated and fired at 750 ° C. for 15 hours in the atmosphere to obtain a lithium titanium composite oxide (Li 4 Ti 5 was O 12) and was prepared as a negative electrode active material.
このＬｉＭｎ２Ｏ４とＬｉ４Ｔｉ５Ｏ１２のそれぞれと酸化物ガラス、ここでは５０Ｐ２Ｏ５−３０ＰｂＯ−２０ＺｎＯとを重量比８０：１０：１０で乾式混合して混合粉とした。この混合粉１００に対して成形助剤のエチルセルロースが重量比で１０となるように加え、さらにテレピネオールを加えてスラリーを調製した。このスラリーをポリエチレンテレフタレート（ＰＥＴ）フィルム上に塗布した後に乾燥させてシート状に成形したものをロールプレスで加圧圧縮成形して、正極、負極とも厚み０．２５ｍｍのシートとした。それぞれのシートを金型で打ち抜き２０ｍｍ角のシート状の正極および負極成形体を得た。 Each of LiMn 2 O 4 and Li 4 Ti 5 O 12 and an oxide glass, here 50P 2 O 5 -30PbO-20ZnO, were dry mixed at a weight ratio of 80:10:10 to obtain a mixed powder. A slurry was prepared by adding ethyl cellulose as a molding aid to the mixed powder 100 in a weight ratio of 10 and further adding terpineol. This slurry was applied onto a polyethylene terephthalate (PET) film, dried and formed into a sheet shape, and was pressure-compressed with a roll press to form a sheet having a thickness of 0.25 mm for both the positive electrode and the negative electrode. Each sheet was punched with a mold to obtain a 20 mm square sheet-like positive electrode and negative electrode molded body.
酸化物系無機固体電解質、ここでは１０Ｌｉ２Ｏ−２５Ｂ２Ｏ３−１５ＳｉＯ２−５０ＺｎＯとＬｉ１．３Ａｌ０．３Ｔｉ１．７（ＰＯ４）３を重量比５０：５０で混合した混合粉と成形助剤のエチルセルロースを重量比１００:１０で混合し、さらにテレピネオー
ルを加えてスラリーを調製し、ＰＥＴフィルム上に同じく成形して裁断することで２０ｍｍ角、厚み０．１ｍｍのシート状電解質成形体を作製した。
Oxide inorganic solid electrolyte, wherein the mixing in 10Li 2 O-25B 2 O 3 -15SiO 2 -50ZnO and Li 1.3 Al 0.3 Ti 1.7 (PO 4) 3 weight ratio of 50:50 Powder and molding assistant ethylcellulose are mixed at a weight ratio of 100: 10, and terpineol is further added to prepare a slurry, which is similarly molded on a PET film and cut to form a sheet-like electrolyte having a 20 mm square and a thickness of 0.1 mm. A molded body was produced.
上記正極成形体と負極成形体を電解質成形体を介して積層し、これを大気中、５５０℃で一括熱処理して正極１と負極３の間に固体電解質２を介した１８ｍｍ角、厚み０．５５ｍｍの発電要素を作製した。 The positive electrode molded body and the negative electrode molded body were laminated via an electrolyte molded body, and this was collectively heat-treated at 550 ° C. in the atmosphere, and the solid electrolyte 2 was interposed between the positive electrode 1 and the negative electrode 3, and the thickness was 0.1 mm. A power generation element of 55 mm was produced.
導電剤の添加は、次のようにして行った。導電剤にはＳｂ２Ｏ３ドープＳｎＯ２水分散体を用い、まずこれを純水で導電剤の濃度が約５重量％となるように希釈してＳｂ２Ｏ３ドープＳｎＯ２の懸濁液を調製した。次にこの懸濁液に一括熱処理して作製した発電要素を浸漬し、５分間放置してから取り出し、表面の液を拭き取った後、１２０℃で１０分間乾燥した。この浸漬と乾燥の操作を５回繰り返し、さらに発電要素の周囲を軽く研磨して不用部分の炭素材料を除去して発電要素とした。なお、化学分析の結果、このときの導電剤の添加量は発電要素から固体電解質の重量を引いた電極重量の約５重量％であった。 The addition of the conductive agent was performed as follows. As the conductive agent, an Sb 2 O 3 doped SnO 2 aqueous dispersion was used. First, this was diluted with pure water so that the concentration of the conductive agent was about 5% by weight, and a suspension of Sb 2 O 3 doped SnO 2 was obtained. Was prepared. Next, the power generation element produced by batch heat treatment was immersed in this suspension, left for 5 minutes, taken out, wiped off the liquid on the surface, and dried at 120 ° C. for 10 minutes. This operation of dipping and drying was repeated 5 times, and the periphery of the power generation element was lightly polished to remove the unnecessary carbon material to obtain a power generation element. As a result of chemical analysis, the amount of conductive agent added at this time was about 5% by weight of the electrode weight obtained by subtracting the weight of the solid electrolyte from the power generation element.
正極電槽４と負極電槽５には厚み０．１ｍｍのアルミニウムを２５ｍｍ角に裁断した金属薄板を用いた。ただし、正極電槽４には予めプレス成形で極群収納部を凹状に成形したものを用いた。負極電槽５には、予め幅５ｍｍの窓枠状に裁断加工しておいた電槽と接着
性を有する封口樹脂６をヒートシールしておいたものを用いた。
For the positive electrode case 4 and the negative electrode case 5, a thin metal plate obtained by cutting aluminum having a thickness of 0.1 mm into 25 mm squares was used. However, as the positive electrode battery case 4, a positive electrode group housing part formed in a concave shape by press molding in advance was used. As the negative electrode battery case 5, a battery case that was previously cut into a window frame shape having a width of 5 mm and a sealing resin 6 having adhesiveness were heat sealed.
最後に、電池の組み立ては負極電槽５の中央に上記発電要素を載置したのちに正極電槽４を被せて正極電槽４と負極電槽５をヒートシールして接着して表面近傍に高濃度に導電剤を含有した電極を用いたリチウム電池を作製した。 Finally, the battery is assembled by placing the power generation element in the center of the negative electrode case 5 and then covering the positive electrode case 4 with the positive electrode case 4 and heat-sealing and bonding the positive electrode case 4 and the negative electrode case 5 near the surface. A lithium battery using an electrode containing a conductive agent at a high concentration was produced.
［実施例２］
導電剤にカーボンブラックが導電粒子として配合された導電性インクを用い、これを専用溶剤でカーボンブラックの濃度が約３重量％となるように希釈した懸濁液を用いたこと以外は実施例１と同様にしてリチウム電池を組み立てた。なお、化学分析の結果、導電剤の添加量は電極重量の約２重量％であった。
[Example 2]
Example 1 except that a conductive ink in which carbon black is blended as conductive particles in a conductive agent is used, and a suspension obtained by diluting the carbon black with a special solvent so that the concentration of carbon black is about 3% by weight is used. A lithium battery was assembled in the same manner. As a result of chemical analysis, the amount of conductive agent added was about 2% by weight of the electrode weight.
［実施例３］
実施例２で作製したカーボンブラックの懸濁液に微粉砕した鱗片状天然黒鉛をカーボンブラックと黒鉛の重量比が４:１となるように添加して充分混合、分散してカーボンブラ
ックと黒鉛の混合懸濁液としたこと以外は実施例１と同様にしてリチウム電池を組み立てた。なお、化学分析の結果、導電剤の添加量は電極重量の約２重量％であった。
[Example 3]
The finely ground scaly natural graphite was added to the carbon black suspension prepared in Example 2 so that the weight ratio of carbon black to graphite was 4: 1, and was mixed and dispersed sufficiently. A lithium battery was assembled in the same manner as in Example 1 except that the mixed suspension was used. As a result of chemical analysis, the amount of conductive agent added was about 2% by weight of the electrode weight.
［比較例１］
炭素材料を後含浸する工程を省いたこと以外は実施例１と同様にしてリチウム電池を作製した。
[Comparative Example 1]
A lithium battery was produced in the same manner as in Example 1 except that the post-impregnation step with the carbon material was omitted.
［比較例２］
実施例1と同様にして作製したＬｉＭｎ２Ｏ４と結着剤としての酸化物ガラス５０Ｐ２
Ｏ５−３０ＰｂＯ−２０ＺｎＯ、導電剤としてのＳｂ２Ｏ３ドープＳｎＯ２と、バインダーとしてのポリテトラフルオロエチレンとを活物質、結着剤、導電剤およびバインダーの重量比が９０：１０：５：５になるように混合して混練した後、溶剤であるトルエンを加えて十分混練してロールプレスで厚み０．２５ｍｍの短冊状シートに成形した。
このシートを金型で打ち抜き２０ｍｍ角のシート状の正極成形体を得た。
[Comparative Example 2]
LiMn 2 O 4 produced in the same manner as in Example 1 and oxide glass 50P 2 as a binder
O 5 -30PbO-20ZnO, Sb 2 O 3 doped SnO 2 as a conductive agent, and polytetrafluoroethylene as a binder have a weight ratio of 90: 10: 5: active material, binder, conductive agent and binder. After mixing and kneading so as to be 5, the solvent toluene was added and sufficiently kneaded to form a strip-shaped sheet having a thickness of 0.25 mm by a roll press.
This sheet was punched with a mold to obtain a 20 mm square sheet-like positive electrode molded body.
次に、実施例1と同様にして作製したＬｉ４Ｔｉ５Ｏ１２と結着剤としての酸化物ガラ
ス５０Ｐ２Ｏ５−３０ＰｂＯ−２０ＺｎＯ、導電剤としてのＳｂ２Ｏ３ドープＳｎＯ２と、バインダーとしてのポリテトラフルオロエチレンとを活物質、結着剤、導電剤およびバインダーの重量比が８７：１３：５：８となるように混合して混練した後、溶剤であるトルエンを加えて十分混練してロールプレスで厚み０．２５ｍｍの短冊状シートに成形した。
このシートを金型で打ち抜き２０ｍｍ角のシート状の負極成形体を得た。
Next, Li 4 Ti 5 O 12 produced in the same manner as in Example 1, oxide glass 50P 2 O 5 -30PbO-20ZnO as a binder, Sb 2 O 3 doped SnO 2 as a conductive agent, and binder After mixing and kneading so that the weight ratio of the active material, the binder, the conductive agent and the binder is 87: 13: 5: 8, the solvent, toluene, is added and sufficiently kneaded. And it shape | molded into the strip-shaped sheet | seat of thickness 0.25mm with the roll press.
This sheet was punched out with a mold to obtain a 20 mm square sheet-like negative electrode molded body.
上記シート状正極成形体および負極成形体を用いたこと以外は実施例１と同様に発電要素を作製してＳｂ２Ｏ３ドープＳｎＯ ２ 導電剤が均一に分散した電極を用いたリチウム電池を作製した。 A lithium battery using an electrode in which a power generation element was produced in the same manner as in Example 1 except that the above sheet-like positive electrode molded body and negative electrode molded body were used, and the Sb 2 O 3 doped Sn O 2 conductive agent was uniformly dispersed. Was made.
［比較例３］
実施例１と同様にして正極、負極とも厚み０．２５ｍｍ、寸法２０ｍｍ角のシート状の正極および負極成形体を得た。これを大気中５５０℃で熱処理し、ついでＳｂ２Ｏ３ドープＳｎＯ２を実施例１と同様にして後含浸してそれぞれ正極１と負極３を得た。なお、化学分析の結果、導電剤の添加量は電極重量の約５重量％で実施例１とほぼ同じであった。
[Comparative Example 3]
In the same manner as in Example 1, a sheet-like positive electrode and negative electrode molded body having a thickness of 0.25 mm and dimensions of 20 mm square were obtained for both the positive electrode and the negative electrode. This was heat-treated at 550 ° C. in the atmosphere, and then post-impregnated with Sb 2 O 3 -doped SnO 2 in the same manner as in Example 1 to obtain a positive electrode 1 and a negative electrode 3, respectively. As a result of chemical analysis, the amount of conductive agent added was about 5% by weight of the electrode weight, which was almost the same as in Example 1.
次に、電解液は、プロピレンカーボネートと１，２―ジメトキシエタンが体積比で１：１の割合で混合された非水溶媒に電解質として過塩素酸リチウム（ＬｉＣｌＯ４）をその
濃度が１ｍｏｌ／ｌになるように溶解させて調製した。
Next, the electrolyte solution was lithium perchlorate (LiClO 4 ) as an electrolyte in a non-aqueous solvent in which propylene carbonate and 1,2-dimethoxyethane were mixed at a volume ratio of 1: 1, and the concentration thereof was 1 mol / l. It was dissolved and prepared.
上記正極を正極電槽に載置し、上記電解液を含浸させた厚み１００μｍのポリプロピレン製不織布からなるセパレータを、前記正極上に載せて上記負極ならびに負極電槽を積層して正極電槽と負極電槽をヒートシールして電解質に有機電解液を用いたリチウム電池を作製した。 A separator made of a nonwoven fabric made of polypropylene having a thickness of 100 μm impregnated with the electrolytic solution is placed on the positive electrode, and the negative electrode and the negative electrode battery are stacked on the positive electrode to form a positive electrode battery and a negative electrode The battery case was heat sealed to produce a lithium battery using an organic electrolyte as the electrolyte.
上記正極と負極を用いたこと以外は比較例２と同様にしてリチウム電池を作製した。 A lithium battery was produced in the same manner as in Comparative Example 2 except that the positive electrode and the negative electrode were used.
（導電剤の分布状態）
実施例１から３および比較例２と３のリチウム電池に用いた発電要素もしくは電極中の導電剤の分布状態を電子顕微鏡およびＸ線マイクロアナリシスで調査した。実施例１から３では、電極の集電体側に高濃度に導電剤が分散していることが確認された。これは電解質側からは懸濁液が含浸しにくかったためと推定される。比較例２では、電極全体に均一に導電剤が分布していることが確認された。比較例３の電極では電極の両側の表面近傍に導電剤が集中していることが分かった。
(Distribution state of conductive agent)
The distribution state of the conductive agent in the power generation elements or electrodes used in the lithium batteries of Examples 1 to 3 and Comparative Examples 2 and 3 was investigated by an electron microscope and X-ray microanalysis. In Examples 1 to 3, it was confirmed that the conductive agent was dispersed at a high concentration on the current collector side of the electrode. This is presumably because the suspension was difficult to impregnate from the electrolyte side. In Comparative Example 2, it was confirmed that the conductive agent was uniformly distributed over the entire electrode. In the electrode of Comparative Example 3, it was found that the conductive agent was concentrated near the surface on both sides of the electrode.
（電池特性評価）
上記実施例１から３および比較例１から３で作製した電池の放電容量測定を実施し、放電容量と放電平均電圧を求めた。なお、電池の放電容量は、充電終止電圧を２．８Ｖ、電流値を０．２ｍＡとして定電流充電した後、1時間放置して電流値１．０ｍＡでまず２．
０Ｖまで定電流放電し、４時間開回路状態で放置したのち引き続き電流値０．２ｍＡで２．０Ｖまで定電流放電して求めた。なお、０．２ｍＡ放電時の放電容量は１．０ｍＡ放電時の放電容量と引き続き行った０．２ｍＡ放電時の放電容量の合算値とした。放電平均電圧は、１．０ｍＡ放電時の放電容量の中間値での電圧とした。
(Battery characteristics evaluation)
The discharge capacities of the batteries prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were measured, and the discharge capacity and the discharge average voltage were obtained. The discharge capacity of the battery was as follows. First, the battery was charged at a constant current with a charge end voltage of 2.8 V and a current value of 0.2 mA, and then left for 1 hour, at a current value of 1.0 mA.
The constant current was discharged to 0 V, left in an open circuit state for 4 hours, and then continuously discharged to 2.0 V at a current value of 0.2 mA. The discharge capacity at the time of 0.2 mA discharge was the sum of the discharge capacity at the time of 1.0 mA discharge and the discharge capacity at the subsequent 0.2 mA discharge. The discharge average voltage was a voltage at an intermediate value of the discharge capacity at 1.0 mA discharge.
また、得られた１．０ｍＡ放電時の放電容量、放電平均電圧から体積エネルギー密度を算出したので、この結果も併せて表１にまとめて示す。なお、体積エネルギー密度の計算には電槽を含まない固体電解質２あるいは電解液を含浸したセパレータを介して一体化された正極１および負極３から成る発電要素のみの体積を分母に放電容量と放電平均電圧の積を分子に用いて求めた。 Moreover, since the volume energy density was computed from the discharge capacity | capacitance at the time of the obtained 1.0 mA discharge, and discharge average voltage, this result is collectively shown in Table 1. In calculating the volume energy density, the discharge capacity and discharge are calculated using only the volume of the power generation element composed of the positive electrode 1 and the negative electrode 3 integrated via a separator impregnated with a solid electrolyte 2 or an electrolyte solution not including a battery case. The product of the average voltage was obtained using the numerator.
実施例1から３と比較例１の１．０ｍＡ放電時の放電容量と放電平均電圧を比較すると
、実施例１から３では導電剤が添加されているために大きな放電容量を示したが、導電剤を含浸していない比較例１の電池は全く放電することができず放電容量は０ｍＡｈとなった。また、実施例の電池は電極の厚みが２００μｍ以上と厚いにもかかわらず充放電が可
能となった。このことから酸化物導電剤の添加が電池の充放電特性を大きく改善していることがわかる。
Comparing the discharge capacity and discharge average voltage at the time of 1.0 mA discharge of Examples 1 to 3 and Comparative Example 1
In Examples 1 to 3, since a conductive agent was added, a large discharge capacity was shown. However, the battery of Comparative Example 1 not impregnated with the conductive agent could not be discharged at all, and the discharge capacity was 0 mAh. It was. In addition, the batteries of the examples were able to be charged / discharged despite the electrode thickness being as thick as 200 μm or more. This indicates that the addition of the conductive oxide agent greatly improves the charge / discharge characteristics of the battery.
実施例１と比較例２を比較すると、導電剤として同じＳｂ２Ｏ３ドープＳｎＯ２をほぼ同量添加したにもかかわらず、高率放電時（１．０ｍＡ放電時）の放電容量に大きな差が現われ、電極表面近傍に集中的に導電剤を配置した方が出力特性に優れることが確認された。
これは実施例１のリチウム電池のほうが集電体、電極間の電子移動がスムーズであったためと推定できる。
Comparing Example 1 and Comparative Example 2, despite almost the same amount was added the same Sb 2 O 3 doped SnO 2 as a conductive agent, a large difference in discharge capacity at high rate discharge (at 1.0mA discharge) As a result, it was confirmed that the output characteristics were superior when the conductive agent was concentrated in the vicinity of the electrode surface.
It can be estimated that this was because the lithium battery of Example 1 was more smoothly moved between the current collector and the electrodes.
比較例３のリチウム電池は、実施例１と同様電極表面の導電剤濃度が高い電極を用いている上、電解質にイオン伝導性の高い有機電解液を用いているために高率放電時の放電平均電圧が高く、放電容量も大きくなり、結果として体積エネルギー密度が大きくなったものである。 The lithium battery of Comparative Example 3 uses an electrode having a high conductive agent concentration on the electrode surface as in Example 1, and uses an organic electrolyte having high ion conductivity for the electrolyte, so that discharge during high-rate discharge is performed. The average voltage is high, the discharge capacity is increased, and as a result, the volume energy density is increased.
（信頼性評価）
次に実施例１から３および比較例２、３の電池を使って高温（６０℃）サイクル試験を行った。サイクル試験は、充電電流値を０．２ｍＡ、放電電流値を同じ０．２ｍＡとして電圧範囲２．８から２．０Ｖで５０サイクルまで行った。表２に放電容量測定で得られた放電容量を初期放電容量とし、５０サイクル目の放電容量と合せて示す。
(Reliability evaluation)
Next, a high-temperature (60 ° C.) cycle test was performed using the batteries of Examples 1 to 3 and Comparative Examples 2 and 3. The cycle test was performed up to 50 cycles at a voltage range of 2.8 to 2.0 V with a charging current value of 0.2 mA and a discharging current value of 0.2 mA. Table 2 shows the discharge capacity obtained by the discharge capacity measurement as the initial discharge capacity, together with the discharge capacity at the 50th cycle.
表２の結果から、電解質に酸化物系無機固体電解質を用いた実施例１から３および比較例２のリチウム電池はほとんど容量低下がなく安定しているのに対し、有機電解液を用いた比較例３のリチウム電池は放電容量が約２分の１まで低下した。 From the results shown in Table 2, the lithium batteries of Examples 1 to 3 and Comparative Example 2 using an oxide-based inorganic solid electrolyte as the electrolyte are stable with almost no decrease in capacity, but are compared using an organic electrolyte. The lithium battery of Example 3 had a discharge capacity reduced to about one half.
サイクル試験が終了した電池の外観を目視で確認したところ、有機電解液を用いた比較例３の電池では、電池の膨れが確認された。これに対して固体電解質を用いた実施例１から３および比較例２の電池では外観上の変化はなかった。 When the appearance of the battery after the cycle test was visually confirmed, the battery of Comparative Example 3 using the organic electrolyte solution was confirmed to be swollen. In contrast, the batteries of Examples 1 to 3 and Comparative Example 2 using a solid electrolyte did not change in appearance.
これらのことから、高温において比較例２の電池は活物質と電解液がガス発生を伴う何らかの反応をして電池の内圧が上昇して電池が膨れたものと考えられる。 From these facts, it is considered that the battery of Comparative Example 2 was subjected to some reaction accompanied by gas generation at a high temperature, and the internal pressure of the battery increased to expand the battery.
以上のことから電解質に酸化物系無機固体電解質を用いた本発明にかかるリチウム電池
はエネルギー密度、出力密度、さらに安全性、信頼性が高次にバランスしていることが分かった。
From the above, it was found that the lithium battery according to the present invention using an oxide-based inorganic solid electrolyte as the electrolyte has a high balance between energy density, power density, safety, and reliability.
本実施例では正極活物質、負極活物質ともそれぞれ一種類の例しか開示しなかったが、電解質に酸化物系無機固体電解質を用いさらに導電剤を少なくとも一方の表面近傍に高濃度に含有した電極を用いれば、他の活物質や導電剤を用いてもエネルギー密度、出力密度、安全性ならびに信頼性の向上に同様の効果が得られることは明白である。 In this example, only one example of each of the positive electrode active material and the negative electrode active material was disclosed, but an electrode containing an oxide-based inorganic solid electrolyte as an electrolyte and containing a conductive agent in a high concentration near at least one surface. It is obvious that the same effect can be obtained in improving energy density, power density, safety and reliability even if other active materials and conductive agents are used.
１ 正極
２ 固体電解質
３ 負極
４ 正極電槽
５ 負極電槽
６ 封口樹脂
DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Solid electrolyte 3 Negative electrode 4 Positive electrode case 5 Negative electrode case 6 Sealing resin
Claims (5)
前記一対の電極は、酸化物ガラスを介して結合された活物質と、該活物質の粒子の間に配置された導電剤とを含むことを特徴とするリチウム電池。 In a lithium battery in which an inorganic solid electrolyte containing lithium is interposed between a pair of electrodes ,
The pair of electrodes includes an active material bonded through an oxide glass and a conductive agent disposed between particles of the active material .
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2012161055A1 (en) * | 2011-05-23 | 2012-11-29 | 国立大学法人名古屋工業大学 | Production method for material employed in energy device and/or electrical storage device, and material employed in energy device and/or electrical storage device |
| JP2018125260A (en) * | 2017-02-03 | 2018-08-09 | パナソニックＩｐマネジメント株式会社 | All-solid battery |
Citations (9)
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| Publication number | Priority date | Publication date | Assignee | Title |
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| WO2012161055A1 (en) * | 2011-05-23 | 2012-11-29 | 国立大学法人名古屋工業大学 | Production method for material employed in energy device and/or electrical storage device, and material employed in energy device and/or electrical storage device |
| JPWO2012161055A1 (en) * | 2011-05-23 | 2014-07-31 | 国立大学法人 名古屋工業大学 | Manufacturing method of material used for at least one of energy device and power storage device |
| JP2018125260A (en) * | 2017-02-03 | 2018-08-09 | パナソニックＩｐマネジメント株式会社 | All-solid battery |
| US11233269B2 (en) | 2017-02-03 | 2022-01-25 | Panasonic Intellectual Property Management Co., Ltd. | All-solid-state battery with varied binder concentration |
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