【０００１】
【発明の属する技術分野】
本発明は固体電解質を用いた全固体電池の製造方法、特に正、負極合材層と固体電解質層からなる発電要素の成型方法及びそのためのの製造装置用金型に関する。
【０００２】
【従来の技術】
携帯電話やラップトップＰＣなどの普及とともにその主電源あるいはメモリーバックアップ電源として電池の高エネルギー密度化による小型化が強く要望されている。現在、この種の電源用電池は、リチウムと遷移金属の複合酸化物正極、カーボン負極、及び有機電解液を用いたリチウムイオン二次電池が主流であるが、電池エネルギー密度の向上につれて安全性の確保が困難となってきている。
またこのリチウムイオン二次電池は液体の電解液を用いるため、時として漏液が問題となる。リチウムイオン二次電池でのＬｉＰＦ６等のＬｉ塩を含むＥＣやＰＣ等の有機溶媒などは腐食性が高く、少量であっても環境に影響を及ぼすことが考えられるので電池メーカは電池からの漏液を完全になくすことに注力している。電池としての安全性を確保しつつ漏液を完全になくす１つの手段として、有機溶媒と溶質からなる液状電解液に代えて固体電解質を用いた全固体電池がある。
一般に、リチウムイオン導電性に優れる固体電解質としては結晶質或いは非晶質の硫化物が有望であるが、これらの多くが大気中の水分に反応し易く不安定であり、また酸素雰囲気で熱処理すると硫化物から酸化物への変化を起こすため、実際に電池を作製するためのプロセスは限られる。
例えば特許第３１９８８２８号によれば、ガラス系固体電解質の軟化点以上、ガラス転移点以下の温度で正極合材層・固体電解質層・負極合材層からなる粉体を加圧成形することで活物質と固体電解質の接触面積を増大させ、内部抵抗が低い電池が作製できることが提案されている。
このように一般的に硫化物を固体電解質に用いる全固体電池の作製には、発電要素部分の内部抵抗を下げるために正極合材層・固体電解質層・負極合材層の３層一体からなるペレットを作製する必要がある。この時、正極合材層、固体電解質層、負極合材層をそれぞれ個別にペレットとし最後に重ね合わせて３層とすると、各層の間の物理的接合が弱く、電気化学反応が円滑になされないため内部抵抗が非常に高くなる。また、予め正極合材層及び負極合材層をペレットとし、それらの間に固体電解質粉末を挟んでプレスを行うと、正極合材層及び負極合材層ペレットが過大な圧力を受けて機械的に破損する恐れがある。従って正極合材層・固体電解質層・負極合材層からなる３層ペレットを作製するためには、各粉体を一度に圧縮してペレットとする必要がある。
【０００３】
【特許文献１】
特開平９−３５７２４号公報
【０００４】
【発明が解決しようとする課題】
従来から用いられている電極ペレットの作製装置の模式図を図２に示す。これを用いて３層一体型ペレットからなる全固体電池の発電要素を作製するためには、まず、所定量の固体電解質粉末を中央に穴部を形成し、下型で穴の下側を塞いだシリンダー型金型に投入し、これを軽くプレスした後、さらに正極合材粉末を投入後、上型を入れて金型を上下反転させる。次に、下型を抜いて負極合材粉末を投入し、下型を穴部内に戻した後に油圧プレス等で上型と下型の間に圧力を加えてペレットを作製する。このペレットを金型から取り出す時は、下型を抜いた後、上型を押し込むことになる。しかし、ペレットを金型から取り出す時点でペレット端面が金型の内面に擦られ、図３のように正極または負極合材層から発生したバリ状物質が固体電解質層を貫いたり横切ったりする可能性がある。電池に用いられる活物質は、電子導電性の高いものが好ましく、また電子導電性が低い活物質を用いる場合はカーボンなどの導電助剤を添加するため、合材が固体電解質端面を貫いたり横切った場合、電池は内部短絡していることになる。
以上のように、シリンダー型金型を用いて正極合材層／固体電解質層／負極合材層の各界面が強固に接合された３層一体型ペレットを作製する場合、電池の内部短絡の可能性があり、信頼性に乏しかった。
この問題を解決するために、特開平９−３５７２４号公報では、一対の電極の少なくとも一方と固体電解質を電気絶縁性の枠内でペレット状に加圧成形することで、電極層や固体電解質層が直接金型と擦れ合うことがなくなり、ペレットを金型から取り出す際に固体電解質層を電極材料が貫いたり横切ったりすることによる電池の内部短絡を防ぐことが提案されている。しかしながら、高精度で耐摩耗性のある型枠を形成することは、コスト、材質面から大きな制約があった。
本発明は、ペレット部分での内部短絡を抑制しつつ、正極合材層／固体電解質層／負極合材層の各界面が強固に接合された少なくとも３層一体型からなるペレットを高い信頼性で製造する方法を提供することを目的とする。
【０００５】
【課題を解決するための手段】
本発明は、成型穴部をもつ外型と前記成型穴部に出入り可能な上型と下型とからなる金型を用い、前記成形穴部内に、正極層、固体電解質層および負極層の３層の粉体層を配置し、前記上型と下型により圧力をかけ、前記３層を一体化した圧粉体とし、前記圧粉体を前記成形穴部から取り出して、全固体電池の発電要素とする全固体電池の製造方法において、
前記成型外型は分離部において分離可能な２つの部分からなり、前記成形穴部内で、前記分離部に接する部分に前記固体電解質層が配された状態で、前記３層が一体化した圧粉体を形成し、前記成形外型を分離させて前記圧粉体を前記成形穴部から取り出すことを特徴とする全固体電池の製造方法に関する。
また、前記３層を一体化した圧粉体を形成する際、まず前記成形穴部内で前記分離部に接する部分に、前記固体電解質層のみを配置し、前記上型と下型により圧力Ｐ１により一次成形し、一次成形後の前記固体電解質層の一方側に前記正極層、他方側に前記負極層を配置し、前記上型と下型により圧力Ｐ２により二次成形して３層が一体化した圧粉体を形成するものであり、圧力Ｐ２は圧力Ｐ１よりも１．５倍以上大であることを特徴とする全固体電池の製造方法に関する。
また本発明は、成型穴部をもつ外型と前記成型穴部に出入り可能な上型と下型からなる金型であって、前記成型外型は分離部において分離可能な２つの部分からなることを特徴とする全固体電池の製造装置用金型に関する。
【０００６】
【発明の実施の形態】
以下、本発明の実施の形態について図面を参照しながら説明する。図１は本発明の全固体電池の製造方法を用いた成型製造装置の構成略図を示す。図１において、１は上型、２は下型、３は外型である。外型３は上下２つの相反する方向の部分に分離可能であり、外型３の内部には上型１及び下型２を挿入するための穴部が設けてある。次に、ペレット成型工程について説明する。下型２で下部を塞いだ前記外型３の穴部に固体電解質（例えばリチウムイオン導電性ガラスＬｉ３ＰＯ４−６３Ｌｉ２Ｓ−３６ＳｉＳ２）粉末を投入し、上型１を穴部に挿入して固体電解質粉末表面を軽く押さえることにより固体電解質粉末を平滑化する。穴部内の上型１と下型２に油圧ポンプを用いて圧力Ｐ１を加えることにより前記固体電解質粉末を圧縮する。次に固体電解質粉末の上部から正極活物質ＬｉＣｏＯ２、前記固体電解質、導電材としてのケッチェンブラック、及び結着材としてのポリテトラフルオロエチレン（ＰＴＦＥ）を混合した正極合材粉末を投入する。上型１を穴部に挿入し、正極合材粉末及び前記で圧縮された固体電解質粉末層の２層が動かないように押さえながら型部を上下反転させる。下型２を一旦引き抜いて外型３の穴部に負極活物質Ｌｉ４／３Ｔｉ５／３Ｏ４、前記固体電解質、前記導電材と前記結着材を混合した負極合材粉末を投入する。下型２を再度、外型３の穴部に挿入し上型１と下型２の間に油圧ポンプを用いて圧力Ｐ２を加えて正極合材層、固体電解質層、及び負極合材層からなる３層の圧粉体を構成する。この際、圧力Ｐ２は圧力Ｐ１よりも十分大きくした。続いて上型１及び下型２で加圧保持した状態のまま外型３を上下２つの相反する方向の部分に分離し、その後、圧粉体を保持した上型１と下型２を離反させて、下型２の上に位置した状態の圧粉体を型の上から取り出した。
この成型製造装置から取り出された成型体は、固体電解質層に外型３の分離部の痕跡が残る場合があるが、中央の電解質層に電極層による貫通等は生じないため、電池特性には影響しない。また、外型３を分離する際、成型体端面において固体電解質層が外型３内面に引きずられて正極合材層或いは負極合材層へバリ状等に伸びる可能性があるが、この場合も電池特性に悪影響は与えなく、電池の内部短絡の恐れもない。
【０００７】
【実施例】
以下に、本発明を実施例に基づいて具体的に説明する。
【０００８】
以下に述べる操作は全てアルゴンガス雰囲気のグローブボックス中で行った。
【０００９】
正極にＬｉＣｏＯ２、固体電解質にＬｉ３ＰＯ４−６３Ｌｉ２Ｓ−３６ＳｉＳ２で表されるリチウムイオン導電性ガラス、負極にＬｉ４／３Ｔｉ５／３Ｏ４を用いた。これらの粉体は予め、メノウ乳鉢を用いて粉砕した。
【００１０】
正極合材としてＬｉＣｏＯ２、固体電解質としてＬｉ３ＰＯ４−６３Ｌｉ２Ｓ−３６ＳｉＳ２、導電剤としてケッチェンブラック、及び結着材としてポリテトラフルオロエチレン（ＰＴＦＥ）を重量比で４９／４９／１／１となるようにメノウ乳鉢を用いて混合したものを用いた。負極合材も同様に、Ｌｉ４／３Ｔｉ５／３Ｏ４、固体電解質としてＬｉ３ＰＯ４−６３Ｌｉ２Ｓ−３６ＳｉＳ２、ポリテトラフルオロエチレン（ＰＴＦＥ）及びケッチェンブラックを重量比で４９／４９／１／１となるようにメノウ乳鉢を用いて混合した。
《実施例１》
全固体電池の製造装置は直径６．７５ ｍｍの棒状上型、内径６．８０ ｍｍ、高さ２０ ｍｍの上下重ね型のシリンダー形成をした外型が２つ、直径６．７５ ｍｍの棒状部分を持つ下型から構成されており、上型及び外型には加圧用の台座が付設している。本装置において、下型の上面が外型の上下分離部よりも０．１ ｍｍ低くなるように外型及び下型を設定し、外型の穴部に固体電解質２０ｍｇを投入し、上型を用いて表面を平らにした。引き続いて上型を引き抜いた後，正極合材６０ｍｇを穴部内の固体電解質の上へ投入し、上型を用いて正極合材を平らにした。上型の外型に対する位置を固定し、装置全体を上下反転させて下型を抜き、負極合材６０ｍｇを外型の穴部に投入した。下型を用いて負極合材層を平らにした後、下型を再度穴部へ挿入し、再度装置全体を上下反転させた。次いで、油圧プレス機を用いて上型と下型の間に３００ＭＰａ（３．０×１０８Ｐａ）の圧力を印加して正極合材層、固体電解質層、負極合材層の３層からなるペレットを作製した。続いて、上型と下型間に印加した圧力を常圧まで戻した後、上型と下型の間隔を保持した状態にて、外型を分離部から上下方向へ２つに分離し、次に上型と下型の間隔を広げることにより発電要素である直径６．８０ｍｍ、厚さ１．６ｍｍのペレットを下型の上から取り出した。取り出したペレットをケースに挿入し、ガスケットが嵌合された封口板を取り付け、ースと封口板をガスケットを介してかしめることにより全固体電池を作製した。このようにして作製した電池を電池Ａとする。
《実施例２》
実施例１で用いた全固体電池の製造装置を用いて、下型により下部が塞がれた外型の穴部に固体電解質を投入し、上型を用いて表面を平らにした後、油圧プレス機を用いて上型と下型の間に１００ＭＰａ（１．０×１０８Ｐａ）の圧力を印加した。上型を外型から引き抜き、引き続いて正極合材を穴部の固体電解質の上へ投入し、上型を用いて正極合材を平らにした。上型の外型に対する位置を固定し、装置全体を上下反転させて下型を抜き、負極合材を外型の穴部に投入した。下型を用いて負極合材層を平らにした後、再度下型を穴部に挿入し、再度装置全体を上下反転させた。油圧プレス機を用いて上型と下型の間に３００ＭＰａ（３．０×１０８Ｐａ）の圧力を印加して正極合材層、固体電解質層、負極合材層の３層からなる直径６．８０ｍｍ、厚さ１．５９ｍｍのペレットを作製した。以降、実施例１と同様の操作にて電池を作製した。このようにして作製した電池を電池Ｂとする。
《実施例３》
実施例１で用いた全固体電池の製造装置を用いて、外型の穴部に固体電解質を投入し、上型を用いて表面を平らにした後、油圧プレス機を用いて上型と下型の間に２００ＭＰａ（２．０×１０８Ｐａ）の圧力を印加した。引き続いて上型を抜き出し、正極合材を固体電解質の上へ投入し、上型を用いて正極合材を平らにした。上型の外型に対する位置を固定し、装置全体を上下反転させた後下型を抜き、負極合材を外型の穴部に投入した。ついで下型を用いて負極合材層を平らにした後、下型を挿入したまま、再度装置全体を上下反転させた。油圧プレス機を用いて上型と下型の間に３００ＭＰａ（３．０×１０８Ｐａ）の圧力を印加して正極合材層、固体電解質層、負極合材層の３層からなる直径６．８０ｍｍ、厚さ１．５８ｍｍのペレットを作製した。以後、実施例１と同様の操作にて電池を作製した。このようにして作製した電池を電池Ｃとする。
《比較例１》
次に、従来からペレットの作製に用いられている金型を用いた場合の比較例について説明する。下型を挿入した外型の穴部に固体電解質を投入し、上型を用いてその表面を平らにした。次に固体電解質層の上部から負極合材を投入し、再度、上型を用いてその表面を平らにした。外型に上型を挿入し、外型に対する上型の位置を固定して金型全体を上下反転させ、下型を引き抜き、外型の穴部から正極合材を投入し、下型を用いてその表面を平らにし、下型を挿入して金型全体を再度、上下反転させた。油圧プレス機を用いて上型と下型の間に３００ＭＰａ（３．０×１０８Ｐａ）の圧力を印加して正極合材層、固体電解質層、負極合材層の３層からなる直径６．８０ｍｍ、厚さ１．６０ｍｍのペレットを作製した。次に下型を引き抜き、金型全体を上下反転させて、油圧プレス機を用いて３００ＭＰａ（３．０×１０８Ｐａ）の圧力を印加して外型からペレットを押し出した。取り出したペレットをケースに挿入し、ガスケットが嵌合された封口板を取り付けてケースと封口板をガスケットを介してかしめることにより全固体電池を作製した。このようにして作製した電池を電池Ｄとする。
【００１１】
このように作製した電池ＡからＤはいずれも電池理論容量３．３ ｍＡｈ（負極容量を規制した電池）、作動電圧約２Ｖである。電池ＡからＤをそれぞれ２０個作製し、３３ μＡの電流にて電池電圧が３．３ Ｖになるか若しくは１５０時間充電し、１時間の休止の後、３３ μＡの電流にて電池電圧が１．０ Ｖになるまで放電した。内部短絡を起こしていた電池の個数を表１に示す。
【００１２】
【００１３】
電池Ａ、Ｂ、Ｃ では内部短絡を起こした電池は見られなかったが電池Ｄでは２０個のうち４個が短絡しており、これらの電池では放電容量は０であった。これら内部短絡していた電池のケースのカシメを外して分解したところ、ペレット端部において正極合材層の一部が固体電解質層を抜けて負極合材層まで達しているのが確認された。本発明による実施例である電池ＡからＣでは内部短絡のない信頼性の高い電池が得られた。
【００１４】
【発明の効果】
以上のように、本発明によれば、内部短絡を抑制しつつ、正極合材層／固体電解質層／負極合材層の各界面が強固に接合された３層からなるペレットを高い信頼性で製造することが可能となった。
【図面の簡単な説明】
【図１】本発明の全固体電池の発電要素製造装置の模式図
【図２】従来から用いられている電極ペレットの作製装置の模式図
【図３】従来から用いられている電極ペレット作製装置を用いて作製した電極ペレットの模式図
【符号の説明】
１ 上型
２ 下型
３ 外型
４ 発電要素
５ 正極合材層
６ 負極合材層
７ 固体電解質層[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing an all-solid battery using a solid electrolyte, and more particularly to a method for molding a power generation element including a positive / negative electrode mixture layer and a solid electrolyte layer, and a mold for a manufacturing apparatus therefor.
[0002]
[Prior art]
With the spread of mobile phones and laptop PCs, there is a strong demand for miniaturization by increasing the energy density of batteries as a main power source or memory backup power source. Currently, the mainstream of this type of power supply battery is a lithium-ion secondary battery using a lithium-transition metal composite oxide positive electrode, a carbon negative electrode, and an organic electrolyte. It is becoming difficult to secure.
In addition, since this lithium ion secondary battery uses a liquid electrolyte, liquid leakage sometimes becomes a problem. Organic solvents such as ECs and PCs containing Li salts such as LiPF 6 in lithium ion secondary batteries are highly corrosive, and even small amounts can affect the environment. Focusing on eliminating leaks completely. As one means of completely eliminating leakage while ensuring safety as a battery, there is an all-solid battery using a solid electrolyte instead of a liquid electrolyte composed of an organic solvent and a solute.
In general, crystalline or amorphous sulfides are promising as solid electrolytes having excellent lithium ion conductivity, but many of them are easily reacted with moisture in the atmosphere and are unstable. Due to the change from sulfide to oxide, the process for actually making the battery is limited.
For example, according to Japanese Patent No. 3198828, a powder composed of a positive electrode mixture layer, a solid electrolyte layer, and a negative electrode mixture layer is press-formed at a temperature not lower than the softening point of the glass-based solid electrolyte and not higher than the glass transition point, so as to be activated. It has been proposed that a contact area between a substance and a solid electrolyte can be increased to produce a battery having a low internal resistance.
As described above, in general, the production of an all-solid-state battery using a sulfide as a solid electrolyte is composed of a three-layer structure of a positive electrode mixture layer, a solid electrolyte layer, and a negative electrode mixture layer in order to reduce the internal resistance of a power generation element portion. It is necessary to make pellets. At this time, if each of the positive electrode mixture layer, the solid electrolyte layer, and the negative electrode mixture layer is individually pelletized and finally overlapped to form three layers, the physical bonding between the layers is weak, and the electrochemical reaction is not smoothly performed. Therefore, the internal resistance becomes very high. In addition, if the positive electrode mixture layer and the negative electrode mixture layer are pelletized in advance, and the solid electrolyte powder is sandwiched therebetween and pressed, the positive electrode mixture layer and the negative electrode mixture layer pellets are subjected to excessive pressure and mechanically May be damaged. Therefore, in order to produce a three-layer pellet composed of the positive electrode mixture layer, the solid electrolyte layer, and the negative electrode mixture layer, it is necessary to compress each powder at once to form a pellet.
[0003]
[Patent Document 1]
JP-A-9-35724
[Problems to be solved by the invention]
FIG. 2 is a schematic view of a conventional apparatus for producing an electrode pellet. In order to manufacture a power generating element of an all-solid-state battery comprising a three-layer integrated pellet using this, first, a hole is formed in the center with a predetermined amount of solid electrolyte powder, and the lower side of the hole is closed with a lower mold. After putting it into a cylindrical mold, pressing it gently, and further pouring the positive electrode mixture powder, put the upper mold and turn the mold upside down. Next, the lower mold is removed, the negative electrode mixture powder is introduced, the lower mold is returned into the hole, and then pressure is applied between the upper mold and the lower mold by a hydraulic press or the like to produce pellets. When removing the pellets from the mold, the upper mold is pushed in after the lower mold is removed. However, when the pellet is removed from the mold, the end face of the pellet is rubbed against the inner surface of the mold, and as shown in FIG. 3, the burr-like substance generated from the positive electrode or negative electrode mixture layer may penetrate or cross the solid electrolyte layer. There is. The active material used for the battery is preferably a material having high electron conductivity.If an active material having low electron conductivity is used, a conductive additive such as carbon is added, so that the mixture penetrates or crosses the solid electrolyte end face. If so, the battery is shorted internally.
As described above, when a three-layer integrated pellet in which the respective interfaces of the positive electrode mixture layer / solid electrolyte layer / negative electrode mixture layer are firmly joined using a cylinder mold, an internal short circuit of the battery is possible. And lacked reliability.
In order to solve this problem, Japanese Patent Application Laid-Open No. 9-35724 discloses that at least one of a pair of electrodes and a solid electrolyte are pressed into a pellet shape in an electrically insulating frame to form an electrode layer or a solid electrolyte layer. It has been proposed to prevent the battery from directly rubbing against the mold and to prevent an internal short circuit in the battery due to the electrode material penetrating or traversing the solid electrolyte layer when removing the pellet from the mold. However, forming a high-precision, wear-resistant mold has significant limitations in terms of cost and material.
The present invention provides a highly reliable pellet having at least a three-layer integrated structure in which the respective interfaces of the positive electrode mixture layer / solid electrolyte layer / negative electrode mixture layer are firmly joined, while suppressing internal short circuits at the pellet portion. It is intended to provide a method of manufacturing.
[0005]
[Means for Solving the Problems]
The present invention uses an outer mold having a molding hole and an upper mold and a lower mold that can enter and exit the molding hole, and includes a positive electrode layer, a solid electrolyte layer, and a negative electrode layer in the molding hole. A powder layer is disposed, and pressure is applied by the upper mold and the lower mold to make the three layers into a green compact. The green compact is taken out from the molding hole to generate power for the all-solid-state battery. In the method for manufacturing an all solid state battery as an element,
The molded outer mold is composed of two parts that can be separated in a separation part, and the three layers are integrated in a state where the solid electrolyte layer is arranged in a part in contact with the separation part in the molding hole. The present invention relates to a method for manufacturing an all-solid-state battery, comprising forming a body, separating the molded outer mold, and taking out the green compact from the molded hole.
Further, when forming a green compact in which the three layers are integrated, first, only the solid electrolyte layer is disposed in a portion in contact with the separating portion in the molding hole, and the pressure P1 is applied by the upper mold and the lower mold. After the primary molding, the positive electrode layer is disposed on one side of the solid electrolyte layer after the primary molding, and the negative electrode layer is disposed on the other side. The upper layer and the lower layer are secondarily molded by pressure P2 to integrate the three layers. The present invention relates to a method for manufacturing an all-solid-state battery, wherein the pressure P2 is 1.5 times or more greater than the pressure P1.
The present invention is also a mold comprising an outer mold having a molding hole, and an upper mold and a lower mold which can enter and exit the molding hole, wherein the molding outer mold is composed of two parts which can be separated at a separating part. The present invention relates to a mold for an all-solid-state battery manufacturing apparatus.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic diagram of a molding and manufacturing apparatus using the method for manufacturing an all solid state battery of the present invention. In FIG. 1, 1 is an upper mold, 2 is a lower mold, and 3 is an outer mold. The outer mold 3 is separable into two upper and lower opposite parts, and a hole for inserting the upper mold 1 and the lower mold 2 is provided inside the outer mold 3. Next, the pellet molding step will be described. Lower die second solid electrolyte (e.g. a lithium ion conductive glass Li 3 PO 4 -63Li 2 S- 36SiS 2) into the hole of the outer die 3 closes the lower powder was charged, insert the upper mold 1 in the hole The surface of the solid electrolyte powder is lightly pressed to smooth the solid electrolyte powder. The solid electrolyte powder is compressed by applying a pressure P1 to the upper mold 1 and the lower mold 2 in the hole using a hydraulic pump. Next, a positive electrode mixture powder obtained by mixing the positive electrode active material LiCoO 2 , the solid electrolyte, Ketjen black as a conductive material, and polytetrafluoroethylene (PTFE) as a binder is charged from above the solid electrolyte powder. The upper mold 1 is inserted into the hole, and the mold is turned upside down while holding the two layers of the positive electrode mixture powder and the solid electrolyte powder layer compressed as described above so as not to move. The lower mold 2 is once pulled out, and the negative electrode active material Li 4/3 Ti 5/3 O 4 , the solid electrolyte, the negative electrode mixture powder obtained by mixing the conductive material and the binder are charged into the hole of the outer mold 3. . The lower mold 2 is inserted into the hole of the outer mold 3 again, and a pressure P2 is applied between the upper mold 1 and the lower mold 2 using a hydraulic pump to remove the positive electrode mixture layer, the solid electrolyte layer, and the negative electrode mixture layer. Thus, a three-layer green compact is formed. At this time, the pressure P2 was sufficiently higher than the pressure P1. Subsequently, the outer die 3 is separated into two upper and lower portions in opposite directions while being pressed and held by the upper die 1 and the lower die 2, and then the upper die 1 and the lower die 2 holding the compact are separated from each other. Then, the green compact positioned on the lower mold 2 was taken out from the mold.
In the molded body taken out from the molding / manufacturing apparatus, traces of the separation part of the outer mold 3 may remain on the solid electrolyte layer, but since the central electrolyte layer is not penetrated by the electrode layer, etc., the battery characteristics may not be improved. It does not affect. Further, when the outer mold 3 is separated, the solid electrolyte layer may be dragged toward the inner surface of the outer mold 3 at the end face of the molded product and may extend to the positive electrode mixture layer or the negative electrode mixture layer in a burr-like manner. There is no adverse effect on battery characteristics, and there is no danger of internal short-circuit of the battery.
[0007]
【Example】
Hereinafter, the present invention will be specifically described based on examples.
[0008]
All the operations described below were performed in a glove box in an argon gas atmosphere.
[0009]
LiCoO 2 positive electrode, a lithium ion conductive glass represented by Li 3 PO 4 -63Li 2 S- 36SiS 2 the solid electrolyte, the Li 4/3 Ti 5/3 O 4 for the negative electrode was used. These powders were previously ground using an agate mortar.
[0010]
LiCoO 2 as a positive electrode material, Li 3 PO 4 -63Li 2 S -36SiS 2 as a solid electrolyte, ketjen black as a conductive agent, and polytetrafluoroethylene (PTFE) as a binder in a weight ratio of 49/49/1 / 1 was mixed using an agate mortar. Similarly, for the negative electrode mixture, Li 4/3 Ti 5/3 O 4 , Li 3 PO 4 -63Li 2 S-36SiS 2 as a solid electrolyte, polytetrafluoroethylene (PTFE) and Ketjen black were used in a weight ratio of 49/50. It mixed using the agate mortar so that it might be set to 49/1/1.
<< Example 1 >>
The manufacturing apparatus for the all-solid-state battery is a bar-shaped upper die having a diameter of 6.75 mm, two outer dies having an inner diameter of 6.80 mm and a height of 20 mm, each of which is formed as a vertically stacked cylinder. The upper and outer dies are provided with pressurizing pedestals. In this apparatus, the outer mold and the lower mold are set so that the upper surface of the lower mold is lower than the upper and lower separation parts of the outer mold by 0.1 mm, 20 mg of the solid electrolyte is charged into the hole of the outer mold, and the upper mold is placed. To flatten the surface. Subsequently, after the upper mold was pulled out, 60 mg of the positive electrode mixture was put on the solid electrolyte in the hole, and the positive electrode mixture was flattened using the upper mold. The position of the upper mold relative to the outer mold was fixed, the entire apparatus was turned upside down, the lower mold was removed, and 60 mg of the negative electrode mixture was put into the hole of the outer mold. After flattening the negative electrode mixture layer using the lower mold, the lower mold was inserted into the hole again, and the entire device was again turned upside down. Next, a pressure of 300 MPa (3.0 × 10 8 Pa) is applied between the upper mold and the lower mold by using a hydraulic press machine, and is composed of three layers of a positive electrode mixture layer, a solid electrolyte layer, and a negative electrode mixture layer. Pellets were made. Subsequently, after the pressure applied between the upper mold and the lower mold is returned to normal pressure, the outer mold is separated into two vertically from the separating part while maintaining the distance between the upper mold and the lower mold, Next, a pellet having a diameter of 6.80 mm and a thickness of 1.6 mm, which is a power generating element, was taken out from above the lower mold by increasing the distance between the upper mold and the lower mold. The taken-out pellet was inserted into a case, a sealing plate fitted with a gasket was attached, and the case and the sealing plate were crimped through a gasket to produce an all-solid-state battery. The battery thus manufactured is referred to as Battery A.
<< Example 2 >>
Using the apparatus for manufacturing an all-solid-state battery used in Example 1, the solid electrolyte was put into the hole of the outer mold whose lower part was closed by the lower mold, and the surface was flattened using the upper mold. Using a press machine, a pressure of 100 MPa (1.0 × 10 8 Pa) was applied between the upper mold and the lower mold. The upper mold was pulled out from the outer mold, and subsequently, the positive electrode mixture was charged onto the solid electrolyte in the hole, and the positive electrode mixture was flattened using the upper mold. The position of the upper die relative to the outer die was fixed, the entire device was turned upside down, the lower die was pulled out, and the negative electrode mixture was put into the hole of the outer die. After flattening the negative electrode mixture layer using the lower mold, the lower mold was inserted into the hole again, and the entire apparatus was again turned upside down. A pressure of 300 MPa (3.0 × 10 8 Pa) is applied between the upper mold and the lower mold using a hydraulic press machine, and a diameter 6 composed of three layers of a positive electrode mixture layer, a solid electrolyte layer, and a negative electrode mixture layer is applied. A pellet having a size of .80 mm and a thickness of 1.59 mm was produced. Thereafter, a battery was manufactured in the same manner as in Example 1. The battery manufactured in this manner is referred to as a battery B.
<< Example 3 >>
Using the all-solid-state battery manufacturing apparatus used in Example 1, the solid electrolyte was put into the hole of the outer die, the surface was flattened using the upper die, and the upper die and the lower die were pressed using a hydraulic press. A pressure of 200 MPa (2.0 × 10 8 Pa) was applied between the molds. Subsequently, the upper die was pulled out, the positive electrode mixture was put on the solid electrolyte, and the positive electrode mixture was flattened using the upper die. After fixing the position of the upper die with respect to the outer die, turning the entire apparatus upside down, the lower die was removed, and the negative electrode mixture was put into the hole of the outer die. Then, after the negative electrode mixture layer was flattened using the lower mold, the entire device was again turned upside down with the lower mold inserted. A pressure of 300 MPa (3.0 × 10 8 Pa) is applied between the upper mold and the lower mold using a hydraulic press machine, and a diameter 6 composed of three layers of a positive electrode mixture layer, a solid electrolyte layer, and a negative electrode mixture layer is applied. A pellet having a thickness of .80 mm and a thickness of 1.58 mm was produced. Thereafter, a battery was manufactured in the same manner as in Example 1. The battery fabricated in this manner is referred to as Battery C.
<< Comparative Example 1 >>
Next, a description will be given of a comparative example in which a mold conventionally used for producing pellets is used. The solid electrolyte was charged into the hole of the outer mold in which the lower mold was inserted, and the surface was flattened using the upper mold. Next, the negative electrode mixture was charged from above the solid electrolyte layer, and the surface was again flattened using the upper mold. Insert the upper mold into the outer mold, fix the position of the upper mold with respect to the outer mold, turn the whole mold upside down, pull out the lower mold, put the positive electrode mixture through the hole of the outer mold, use the lower mold Then, the surface was flattened, the lower mold was inserted, and the whole mold was again turned upside down. A pressure of 300 MPa (3.0 × 10 8 Pa) is applied between the upper mold and the lower mold using a hydraulic press machine, and a diameter 6 composed of three layers of a positive electrode mixture layer, a solid electrolyte layer, and a negative electrode mixture layer is applied. A pellet having a size of .80 mm and a thickness of 1.60 mm was produced. Next, the lower mold was pulled out, the whole mold was turned upside down, and a pressure of 300 MPa (3.0 × 10 8 Pa) was applied using a hydraulic press to extrude the pellets from the outer mold. The removed pellets were inserted into a case, a sealing plate fitted with a gasket was attached, and the case and the sealing plate were caulked via a gasket to produce an all-solid-state battery. The battery fabricated in this manner is referred to as Battery D.
[0011]
The batteries A to D thus produced all have a theoretical battery capacity of 3.3 mAh (a battery in which the negative electrode capacity is regulated) and an operating voltage of about 2V. 20 batteries A to D were prepared, and the battery voltage was 3.3 V at a current of 33 μA or charged for 150 hours. After a 1-hour pause, the battery voltage was 1 at a current of 33 μA. The battery was discharged until the voltage reached 0.0 V. Table 1 shows the number of batteries having an internal short circuit.
[0012]
[0013]
In the batteries A, B, and C, no battery having an internal short circuit was found, but in the battery D, 4 out of 20 batteries were short-circuited, and the discharge capacity was 0 in these batteries. When the internal short-circuited battery case was disassembled and disassembled, it was confirmed that a part of the positive electrode mixture layer at the end of the pellet reached the negative electrode mixture layer through the solid electrolyte layer. In the batteries A to C, which are examples according to the present invention, highly reliable batteries without internal short circuit were obtained.
[0014]
【The invention's effect】
As described above, according to the present invention, a three-layered pellet in which the respective interfaces of the positive electrode mixture layer / solid electrolyte layer / negative electrode mixture layer are firmly joined while suppressing internal short circuit with high reliability. It has become possible to manufacture.
[Brief description of the drawings]
FIG. 1 is a schematic view of an apparatus for manufacturing a power generation element of an all-solid-state battery according to the present invention. FIG. 2 is a schematic view of an apparatus for manufacturing an electrode pellet conventionally used. FIG. 3 is an apparatus for manufacturing an electrode pellet conventionally used. Schematic diagram of electrode pellets manufactured using SYN
DESCRIPTION OF SYMBOLS 1 Upper mold 2 Lower mold 3 Outer mold 4 Power generation element 5 Positive electrode mixture layer 6 Negative electrode mixture layer 7 Solid electrolyte layer
