WO2014168019A1 - リチウムイオン二次電池 - Google Patents
リチウムイオン二次電池 Download PDFInfo
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- WO2014168019A1 WO2014168019A1 PCT/JP2014/058937 JP2014058937W WO2014168019A1 WO 2014168019 A1 WO2014168019 A1 WO 2014168019A1 JP 2014058937 W JP2014058937 W JP 2014058937W WO 2014168019 A1 WO2014168019 A1 WO 2014168019A1
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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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
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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
- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/446—Composite material consisting of a mixture of organic and inorganic materials
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- the present invention relates to a battery, and more particularly to a lithium ion secondary battery that uses a ceramic separator and is excellent in economy and high in reliability.
- a lithium ion secondary battery includes, for example, a positive electrode formed by applying a positive electrode active material (lithium composite oxide) to a sheet-like current collector foil (such as an aluminum foil or a copper foil), and a negative electrode active material.
- a positive electrode active material lithium composite oxide
- a sheet-like current collector foil such as an aluminum foil or a copper foil
- a negative electrode active material such as an aluminum foil or a copper foil
- An electricity storage element constituted by laminating a negative electrode formed by coating a substance (activated carbon, carbon, etc.) via a separator for preventing a short circuit due to contact between the positive and negative electrodes, and an electrolytic solution, It has a structure accommodated in the exterior body.
- Patent Document 1 discloses a separator in which inorganic fine particles are dispersed in an organic polymer, instead of a conventionally used separator such as a polyolefin-based stretched film (hereinafter referred to as “polyolefin-based separator”). (Hereinafter also referred to as “ceramic separator layer”), a non-aqueous electrolyte battery in which the ceramic separator layer 111 is disposed between the positive electrode 101 and the negative electrode 102 as schematically shown in FIG. 4 is proposed. Has been.
- the ceramic separator layer 111 used in Patent Document 1 described above does not deform and shrink even at high temperatures. Therefore, even if the ceramic separator layer 111 is exposed to an unintended high temperature, the positive electrode and the negative electrode are not short-circuited by the contraction, heat generation, smoke generation, ignition, and the like are prevented, and safety can be improved. For example, the safety that does not ignite in the nail cutting test is due to this feature.
- Patent Document 2 as schematically shown in FIG. 5, a porous insulating layer (HRL) (substantially ceramic separator layer) 111 and a porous insulator ( A nonaqueous electrolyte battery has been proposed in which a generally used polyolefin separator 112 is provided.
- the porous insulating layer 111 is formed of a mixture of insulating inorganic fine particles and a binder (binder) made of an organic polymer, and is substantially the same as the ceramic separator layer.
- a porous insulating layer made of a mixture of a porous insulator 112, which is a polyolefin-based separator, and a binder (binder) made of insulating inorganic fine particles and an organic polymer.
- Layer 111 is interposed between the positive electrode 101 and the negative electrode 102, and a porous insulating layer (ceramic separator layer) 111 that does not shrink even at high temperatures is interposed, thereby suppressing and preventing short-circuiting, heat generation, and ignition of the positive electrode and the negative electrode.
- the porous insulator 112 which is a polyolefin-based separator with excellent electronic insulation, is able to ensure the electronic insulation between the positive and negative electrodes. Since the insulator 112 is used in combination, there are the following problems.
- the film thickness of the polyolefin-based separator is usually as thick as 20 to 30 ⁇ m, and there is a problem that the energy density per volume decreases, and a battery with a higher energy density can be designed as the separator film thickness decreases. It is very difficult to reduce the film thickness of the polyolefin separator due to handling problems.
- Patent Document 3 As schematically shown in FIG. 6, (a) a first insulating layer (ion-permeable gel) 113 and (b) a second insulating layer (between the positive electrode 101 and the negative electrode 102 (A lithium ion secondary battery including a ceramic separator layer 111 having lithium ion permeability and (c) a porous insulator (porous polyolefin separator) 112 has been proposed.
- Patent Document 3 since the ceramic separator layer (second insulating layer) 111 and the porous polyolefin-based separator (porous insulator) 112 are provided, the problem described above with respect to Patent Document 2 is applied as it is. Not only that, but one additional component, the ion-permeable gel (first insulating layer) 113, is added, which raises problems such as high cost, high resistance, reduced energy density, and reduced power density.
- a non-porous protective film made of, for example, a resin binder and solid particles having a thickness of 0.1 to 200 ⁇ m is formed on the surface of either the negative electrode active material coating layer or the positive electrode active material coating layer.
- a water electrolyte secondary battery (see Patent Document 4) or a negative electrode includes an active material layer containing particles of an active material containing Si or Sn, and a layer containing inorganic oxide particles is formed on the outermost surface.
- Non-aqueous electrolyte secondary batteries, and non-aqueous electrolyte secondary batteries having an outermost surface roughness of 0.1 to 3 ⁇ m as defined in JIS B0601 have been proposed (Patent Document 5). reference).
- a porous polyolefin-based separator is used as the separator, and there is actually a problem as described in Patent Documents 2 and 3 described above.
- JP 2006-164761 A International Publication No. 2005-098997 Pamphlet JP 2010-267475 A Japanese Patent Laid-Open No. 7-220759 JP 2009-164014 A
- the present invention solves the above-described problems, and can achieve high energy density and high power density at low cost without using a polymer separator such as a porous polyolefin separator, and safety.
- An object of the present invention is to provide a lithium ion secondary battery excellent in the above.
- the lithium ion secondary battery of the present invention is A positive electrode, a negative electrode, a ceramic separator layer disposed so as to be interposed between the positive electrode and the negative electrode, an electrode smoothing layer for smoothing at least one surface of the positive electrode and the negative electrode, and an electrolyte Including a battery element, and an exterior body that houses the battery element
- the electrode smoothing layer is formed from a composite material containing an active material and an organic material, and is provided on at least one surface of the positive electrode and the negative electrode.
- the ceramic separator layer is formed of a composite material including insulating inorganic fine particles and an organic material, has lithium ion permeability, and faces at least one of the positive electrode and the negative electrode through the electrode smoothing layer. It is characterized by being arranged.
- the electrode smoothing layer is provided on the surfaces of both the positive electrode and the negative electrode;
- the ceramic separator layer is preferably disposed so as to be positioned between the electrode smoothing layer provided on the surface of the positive electrode and the electrode smoothing layer provided on the surface of the negative electrode. .
- An electrode smoothing layer is provided on both surfaces of the positive electrode and the negative electrode, and a ceramic separator layer is located between the electrode smoothing layer provided on the surface of the positive electrode and the electrode smoothing layer provided on the surface of the negative electrode.
- the particle diameter of the active material constituting the electrode smoothing layer is preferably 0.03 to 5 ⁇ m.
- the particles constituting the electrode smoothing layer may include secondary particles in which a part of the primary particles is sintered or dissolved and recrystallized.
- the particle diameter of the active material constituting the electrode smoothing layer 0.03 to 5 ⁇ m, the surface of the electrode can be sufficiently smoothed, and the present invention can be further improved.
- the lithium ion secondary battery of the present invention is provided with an electrode smoothing layer made of a composite material containing an active material and an organic material on at least one surface of a positive electrode and a negative electrode, and made of a composite material containing insulating inorganic fine particles and an organic material. Since the lithium ion permeable ceramic separator layer is configured to face at least one of the positive electrode and the negative electrode through the electrode smoothing layer, the surface of the positive electrode or the negative electrode is uneven.
- the electrode smoothing layer absorbs the unevenness of the positive electrode or the negative electrode and makes it possible to smooth the surface, and the convex part of the positive electrode or the negative electrode is exposed to the surface of the ceramic separator layer, so that the counter electrode It is possible to suppress and prevent short-circuiting due to contact, and to ensure electronic insulation between the positive and negative electrodes with only the ceramic separator layer.
- the ceramic separator layer formed thereon has defects. Less likely to occur. As a result, it is possible to ensure electronic insulation between the positive and negative electrodes by using only the ceramic separator layer without using a polymer separator such as a porous polyolefin separator.
- the active material constituting the electrode smoothing layer for example, as the active material for the positive electrode, any lithium-containing metal oxide that is usually used in the art can be used.
- the negative electrode active material Li 4 Ti 5 O 12 , natural graphite, artificial graphite, coke, carbonaceous fiber such as carbon fiber, Li and alloy formation Examples are possible elements such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, and Ti, compounds containing these elements, or nitrides containing lithium.
- the active material is not limited to the above example, and other materials can be used.
- the electrode smoothing layer can further contain solid particles such as ceramic particles.
- solid particles such as ceramic particles.
- the solid particles for example, insulating fine particles such as alumina, SiO 2 , polyethylene resin, carbon particles having electron conductivity in consideration of electrode reaction, and the like can be used.
- the reason why it is possible to obtain the effect of ensuring the electronic insulation between the positive and negative electrodes with only the ceramic separator layer as described above is considered to be due to the following mechanism.
- the surface of the electrode (positive electrode or negative electrode) usually has irregularities, and when a ceramic separator layer is disposed so as to contact such an electrode, the ceramic separator layer has through-holes or the like due to the irregularities on the surface of the electrode. Defects are likely to occur, and these defects may reduce the safety of the lithium ion secondary battery.
- an electrode smoothing layer on the surface of the electrode (positive electrode or negative electrode) it becomes possible to reduce the influence of the unevenness on the surface of the electrode on the ceramic separator layer, which occurs in the ceramic separator layer.
- the lithium ion secondary battery of the present invention it is not necessary to use a polymer separator such as a porous polyolefin separator, and therefore the following effects can be obtained.
- porous polymer separator for example, a porous polyolefin separator
- a porous polyolefin separator occupies a high proportion of the cost of battery constituent materials. Reduction can be achieved.
- the thickness of the porous polymer separator (for example, a porous polyolefin separator) is usually 20 to 30 ⁇ m.
- the density can be increased (the presence of the porous polymer separator does not contribute to the development of energy (or capacity), and thus the energy density can be improved by eliminating the need for this polymer separator).
- the electrode smoothing layer contains an active material composed of a composite material containing an active material and an organic material, so that the battery capacity is also expressed from the electrode smoothing layer. It becomes possible to realize high energy density and high power density.
- FIG. 1 shows typically the structure of the lithium ion secondary battery (battery element) concerning Embodiment 1 of this invention. It is a figure which shows typically the lithium ion secondary battery (battery element) concerning Embodiment 2 of this invention. It is a figure which shows typically the modification of the lithium ion secondary battery (battery element) concerning embodiment of this invention. It is a figure which shows typically the structure of the conventional lithium ion secondary battery disclosed by patent document 1.
- FIG. It is a figure which shows typically the structure of the conventional lithium ion secondary battery disclosed by patent document 2.
- FIG. It is a figure which shows typically the structure of the conventional lithium ion secondary battery disclosed by patent document 3.
- each weighed material was put into a 1000 mL pot, and PSG grinding media having a diameter of 1.0 mm and 200 g of N-methylpyrrolidone (hereinafter referred to as NMP) as a solvent were added. Then, the mixture was dispersed by mixing at 150 rpm for 24 hours using a rolling ball mill. As a result, the secondary particles of lithium manganate were crushed, and the average particle diameter D 50 was 2.1 ⁇ m.
- NMP N-methylpyrrolidone
- Step 4 Production of Positive Electrode
- the positive electrode active material slurry produced in (Step 1) above was coated on a positive electrode current collector foil made of aluminum foil (Tokai Toyo Aluminum Sales Co., Ltd., thickness 20 ⁇ m) and dried.
- the positive electrode was produced by post-pressing. Further, an aluminum tab was attached to the exposed portion of the positive electrode current collector foil to produce a lead electrode.
- Step 5 Production of Negative Electrode
- the negative electrode active material slurry produced in (Step 2) above was coated on a negative electrode current collector foil made of rolled copper foil (manufactured by Nippon Foil Co., Ltd., thickness 10 ⁇ m) and dried.
- a negative electrode was produced by post-pressing. Further, a nickel tab was attached to the exposed portion of the negative electrode current collector foil to produce a lead electrode.
- Step 6 Preparation of electrode (negative electrode) smoothing layer
- the electrode smoothing layer slurry prepared in (Step 3) above was applied onto the negative electrode prepared in (Step 5) above, and the electrode (negative electrode) smoothing layer was applied. Formed.
- the electrode (negative electrode) smoothing layer is desirably formed to have a thickness of 10 ⁇ m or less, for example.
- Step 7 Formation of Ceramic Separator Layer
- 80 g of NMP as a solvent were charged. Further, PSZ grinding media having a diameter of 5 mm were put, and the mixture was dispersed by mixing at 150 rpm for 16 hours using a rolling ball mill.
- the prepared slurry for a ceramic separator layer was coated with a bar coater on the electrode (negative electrode) smoothing layer formed on the surface of the negative electrode in the above (Step 6), and then dried to form a ceramic separator layer having a thickness of 11 ⁇ m. Formed.
- Step 7 Production of Battery Cell
- the negative electrode 2 having the separator 11 is opposed to each other, and the electrode (negative electrode) smoothing layer 12 and the ceramic separator layer 11 are joined in such a manner as to be positioned between the positive electrode 1 and the negative electrode 2.
- a battery element 20 made of (positive electrode and negative electrode) was produced.
- the produced battery element was sandwiched between two laminates, and three sides were subjected to thermocompression bonding with an impulse sealer to produce a laminate package (exterior body) having an opening on one side.
- an electrolytic solution was injected into the package from the opening of the laminate.
- an electrolytic solution in which lithium hexafluorophosphate (LiPF 6 ) is dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3: 7 so as to be 1 M is used. did.
- a lithium ion secondary battery (battery cell) was produced by vacuum-sealing the opening of the laminate package.
- a lithium ion secondary battery (only a ceramic separator layer between the positive electrode and the negative electrode) produced by the same method except that the electrode (negative electrode) smoothing layer is not formed in (Step 6) above.
- the same evaluation was performed on the lithium ion secondary battery having the same. The results are also shown in Table 1.
- each weighed material was put into a 1000 mL pot, and PSG grinding media having a diameter of 1.0 mm and 200 g of N-methylpyrrolidone (hereinafter referred to as NMP) as a solvent were added. Then, the mixture was dispersed by mixing at 150 rpm for 24 hours using a rolling ball mill. As a result, the secondary particles of lithium manganate were crushed, and the average particle diameter D 50 was 2.1 ⁇ m. At this time, the secondary particles are not completely crushed, and some of the particles are present in the form of secondary particles formed by sintering or dissolving and recrystallizing the primary particles.
- NMP N-methylpyrrolidone
- Step 5 Production of positive electrode
- the positive electrode active material slurry produced in the above (Step 1) was coated on a positive electrode current collector foil made of aluminum foil (manufactured by Tokai Toyo Aluminum Sales Co., Ltd., thickness 20 ⁇ m) and dried.
- the positive electrode was produced by post-pressing. Further, an aluminum tab was attached to the exposed portion of the positive electrode current collector foil to produce a lead electrode.
- Step 6 Production of Negative Electrode
- the negative electrode active material slurry produced in (Step 2) above was coated on a negative electrode current collector foil made of rolled copper foil (manufactured by Nippon Foil Co., Ltd., thickness 10 ⁇ m) and dried.
- a negative electrode was produced by post-pressing. Further, a nickel tab was attached to the exposed portion of the negative electrode current collector foil to produce a lead electrode.
- Step 7 Preparation of electrode (positive electrode) smoothing layer
- the electrode (positive electrode) smoothing layer slurry prepared in the above (Step 3) was coated on the positive electrode prepared in the above (Step 5), and the electrode (positive electrode) ) A smoothing layer was formed.
- the electrode (positive electrode) smoothing layer is preferably formed to have a thickness of 10 ⁇ m or less, for example.
- Step 8 Preparation of electrode (negative electrode) smoothing layer
- the electrode (negative electrode) smoothing layer slurry prepared in (Step 4) above was applied onto the negative electrode prepared in (Step 6) above, and the electrode (negative electrode) ) A smoothing layer was formed.
- the electrode (negative electrode) smoothing layer is usually preferably formed to have a thickness of 10 ⁇ m or less.
- the prepared slurry for ceramic separator layer was coated with a bar coater on the negative electrode having the electrode (negative electrode) smoothing layer prepared in the above (Step 8), and then dried to form a ceramic separator layer having a thickness of 11 ⁇ m. . *
- Step 10 Production of Battery Cell
- the produced electrode (negative electrode) smoothing layer 12 (12b) and the negative electrode 2 having the ceramic separator layer 11 are opposed to each other, and the electrode (positive electrode) smoothing layer 12 (12a) and the electrode (negative electrode) smoothing layer 12 are provided.
- the ceramic separator layer 11 might be located, and the battery element 20 which consists of a pair of electrodes (a positive electrode and a negative electrode) was produced.
- the produced battery element was sandwiched between two laminates, and three sides were subjected to thermocompression bonding with an impulse sealer to produce a laminate package (exterior body) having an opening on one side.
- an electrolytic solution was injected into the package from the opening of the laminate.
- an electrolytic solution in which lithium hexafluorophosphate (LiPF 6 ) was dissolved in a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 3: 7 so as to be 1 M was used.
- a lithium ion secondary battery battery cell was produced by vacuum-sealing the opening of the laminate package.
- a lithium ion secondary battery (positive electrode and negative electrode) produced by the same method except that the electrode (negative electrode and positive electrode) smoothing layer is not formed in (Step 7) and (Step 8).
- the same evaluation was performed on a lithium ion secondary battery having only a ceramic separator layer between the two. The results are also shown in Table 2.
- the ceramic separator layer is formed on the electrode (negative electrode) smoothing layer provided on the negative electrode surface.
- the ceramic separator layer is provided on the electrode provided on the positive electrode surface ( It may be formed on the positive electrode) smoothing layer.
- the electrode (negative electrode) smoothing layer is provided only on the surface of the negative electrode.
- the electrodes (positive electrode and negative electrode) are smoothed on the surfaces of both the positive electrode and the negative electrode.
- the electrode (positive electrode) smoothing layer 12 may be formed only on the surface of the positive electrode 1.
- the parts denoted by the same reference numerals as those in FIGS. 1 and 2 indicate the same or corresponding parts.
- the present invention is not limited to the above embodiment, and relates to specific constituent materials and forming methods such as a positive electrode, a negative electrode, a separator protective layer, and a ceramic separator layer, and the type of electrolytic solution. It is possible to add various applications and modifications.
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Abstract
Description
なお、多孔質絶縁層111は、絶縁性の無機微粒子と有機高分子からなる結着剤(バインダ)との混合物から形成されており、実質的に、セラミックセパレータ層と同じものである。
(b)ポリオレフィン系セパレータは高抵抗でパワー特性の低下を招くため、その対策として、膜厚を薄くすることや、空隙率を高くすることが考えられるが、それらは容易ではなく、電池の高性能化を妨げる大きな要因となる。また、パワー特性を確保するために積層数を増加することが考えられるが、コストの増大を招く。
(c)ポリオレフィン系セパレータの膜厚は通常、20~30μmと厚く、体積当たりのエネルギー密度が低くなるという問題点があり、また、セパレータの膜厚が薄くなるほど高エネルギー密度の電池を設計できるが、ポリオレフィン系セパレータの膜厚をハンドリング上の問題などから薄くすることは非常に困難である。
しかし、特許文献4および5の電池の場合においても、セパレータとして、多孔質ポリオレフィン系セパレータが用いられており、上述の特許文献2,3などについて述べたような問題があるのが実情である。
正極と、負極と、前記正極と前記負極の間に介在するように配設されたセラミックセパレータ層および前記正極および負極の少なくとも一方の表面を平滑にするための電極平滑化層と、電解質とを含む電池要素と、前記電池要素を収容する外装体とを備え、
前記電極平滑化層は、活物質と有機物を含む複合材料から形成され、前記正極と前記負極の少なくとも一方の表面に設けられているとともに、
前記セラミックセパレータ層は、絶縁性無機微粒子と有機物を含む複合材料から形成され、リチウムイオン透過性を有し,前記正極および前記負極の少なくとも一方と、前記電極平滑化層を介して対向するように配設されていること
を特徴としている。
前記電極平滑化層が、前記正極および前記負極の両方の表面に設けられており、
前記セラミックセパレータ層は、前記正極の表面に設けられた前記電極平滑化層と、前記負極の表面に設けられた前記電極平滑化層との間に位置するように配設されていること
が好ましい。
ただし、活物質は上記の例に限定されるものではなく、さらに他の物質を用いることも可能である。
その場合、電極平滑化の効果を確保する見地から、固体粒子としては、粒子径が、0.03~5μmの粒子を用いることが望ましい。また、固体粒子としては、例えば、アルミナ、SiO2、ポリエチレン樹脂等の絶縁性微粒子や、電極反応を考慮して電子伝導性を有するカーボン粒子などを用いることができる。
電極(正極あるいは負極)の表面には、通常凹凸があり、このような電極と接するようにセラミックセパレータ層を配設した場合、電極の表面の凹凸により、セラミックセパレータ層には貫通ピンホールなどの欠陥が発生しやすく、これら欠陥はリチウムイオン二次電池の安全性を低下させる場合がある。
これに対し、電極(正極あるいは負極)の表面に電極平滑化層を形成することにより、電極の表面の凹凸の、セラミックセパレータ層への影響を緩和することが可能になり、セラミックセパレータ層に発生する欠陥を大幅に低減して、多孔質のポリマーセパレータを用いることを必要とせずに、安全で信頼性が高いリチウムイオン二次電池を得ることが可能になる。
<リチウムイオン二次電池の作製>
(工程1)正極活物質スラリーの作製
マンガン酸リチウム(戸田工業(株)製、HPM-7051、平均粒子径D50=6.1μm)88g、黒鉛(ティムカル社製、KS-6)2g、黒鉛(ティムカル社製、Super P Li)6gを秤量した。
グラファイト(三菱化学(株)製、GTR6、平均粒子径D50=11.0μm)85g、導電助剤(日立化成(株)製、SMSC10-4V3)15g、NMP100g、ポリフッ化ビニリデン((株)クレハ製、#7305)の10質量%NMP溶液53gを秤量し、プラネタリーミキサーで撹拌して負極活物質スラリーを作製した。
チタン酸リチウム(石原産業(株)製、XA-106、平均粒子径D50=6.8μm)80gを秤量して500mLのポットに入れて、さらに直径1.0mmのPSZ製粉砕メディアおよび溶媒としてNMP100gを加えて、転動ボールミルを用いて150rpmで16時間混合して分散を行った。これによりチタン酸リチウムの二次粒子は解砕され、平均粒径D50は0.8μmとなった。このとき、二次粒子は完全に解砕されているわけではなく、一部の粒子が、一次粒子が焼結または溶解再結晶結合されてなる二次粒子の形態で存在している。
上記(工程1)で作製した正極活物質スラリーをアルミ箔(東海東洋アルミ販売(株)製、厚さ20μm)からなる正極集電体箔上に塗工し、乾燥後プレスすることにより正極を作製した。さらに正極集電箔の露出した部分にアルミタブを取り付け、引き出し電極を作製した。
上記(工程2)で作製した負極活物質スラリーを圧延銅箔(日本製箔(株)製、厚さ10μm)からなる負極集電体箔上に塗工し、乾燥後プレスすることにより負極を作製した。さらに負極集電箔の露出した部分にニッケルタブを取り付け、引き出し電極を作製した。
上記(工程3)で作製した電極平滑化層用スラリーを、上記(工程5)で作製した負極上に塗工し電極(負極)平滑化層を形成した。なお、電極(負極)平滑化層は、例えば、10μm以下の厚みとなるように形成することが望ましい。
500mLのポットに、球状アルミナ粉末(電気化学工業(株)製、平均粒子径D50=0.3μm)100gと、溶剤としてNMP80gを投入した。さらに直径5mmのPSZ製粉砕メディアを入れ、転動ボールミルを用いて150rpmで16時間混合し、分散を行った。
図1に模式的に示すように、上記(工程4)で作製した正極1と、上記(工程7)で作製した、電極(負極)平滑化層12と、セラミックセパレータ11とを有する負極2とを対向させ、電極(負極)平滑化層12と、セラミックセパレータ層11とが正極1と負極2の間に位置するような態様で接合して、1対の電極(正極と負極)からなる電池素子20を作製した。
電解液としては、エチレンカーボネート(EC)とジエチルカーボネート(DEC)の体積比3:7の混合溶媒に、1Mになるように六フッ化リン酸リチウム(LiPF6)を溶解させた電解液を使用した。
上述のようにして作製したリチウムイオン二次電池(電池セル)の特性を評価するため、10個のリチウムイオン二次電池について、ショート不良の発生の有無を確認した。ショート不良の判断は、3.8Vまでセルを充電後1週間放置し、セルの電圧を測定して、電圧が3.7V以上のセルを良品、3.7V未満のセルをショート不良とした。その結果を表1に示す。
<リチウムイオン二次電池の作製>
(工程1)正極活物質スラリーの作製
マンガン酸リチウム(戸田工業(株)製、HPM-7051、平均粒子径D50=6.1μm)88g、黒鉛(ティムカル社製、KS-6)2g、黒鉛(ティムカル社製、Super P Li)6gを秤量した。
そして、プラネタリーミキサーを用いて撹拌することにより、正極活物質スラリーを作製した。
グラファイト(三菱化学(株)製、GTR6、平均粒子径D50=11.0μm)85g、導電助剤(日立化成(株)製、SMSC10-4V3)15g、NMP100g、ポリフッ化ビニリデン((株)クレハ製、#7305)の10質量%NMP溶液53gを秤量し、プラネタリーミキサーで撹拌して負極活物質スラリーを作製した。
マンガン酸リチウム(戸田工業(株)製、HPM-7051、平均粒子径D50=6.1μm)88g、黒鉛(ティムカル社製、KS-6)2g、黒鉛(ティムカル社製、Super P Li)6gを秤量した。
チタン酸リチウム(石原産業(株)製、XA-106、D50=6.8μm)80gを秤量して500mLのポットに入れて、さらに直径1.0mmのPSZ製粉砕メディアおよび溶媒としてNMP100gを加えて、転動ボールミルを用いて150rpmで16時間混合して分散を行った。これによりチタン酸リチウムの二次粒子は解砕され、平均粒径D50は0.8μmとなった。このとき、二次粒子は完全に解砕されているわけではなく、一部の粒子が、一次粒子が焼結または溶解再結晶結合されてなる二次粒子の形態で存在している。
上記(工程1)で作製した正極活物質スラリーをアルミ箔(東海東洋アルミ販売(株)製、厚さ20μm)からなる正極集電体箔上に塗工し、乾燥後プレスすることにより正極を作製した。さらに正極集電箔の露出した部分にアルミタブを取り付け、引き出し電極を作製した。
上記(工程2)で作製した負極活物質スラリーを圧延銅箔(日本製箔(株)製、厚さ10μm)からなる負極集電体箔上に塗工し、乾燥後プレスすることにより負極を作製した。さらに負極集電箔の露出した部分にニッケルタブを取り付け、引き出し電極を作製した。
上記(工程3)で作製した電極(正極)平滑化層用スラリーを、上記(工程5)で作製した正極上に塗工し、電極(正極)平滑化層を形成した。なお、電極(正極)平滑化層は、例えば、 10μm以下の厚みとなるように形成することが望ましい。
上記(工程4)で作製した電極(負極)平滑化層用スラリーを、上記(工程6)で作製した負極上に塗工し、電極(負極)平滑化層を形成した。なお、電極(負極)平滑化層についても、通常は、10μm以下の厚みとなるように形成することが望ましい。
500mLのポットに、球状アルミナ粉末(電気化学工業(株)製、平均粒子径D50=0.3μm)100gと、溶剤としてNMP80gを投入した。さらに直径5mmのPSZ製粉砕メディアを入れ、転動ボールミルを用いて150rpmで16時間混合し、分散を行った。
図2に模式的に示すように、上記(工程7)で作製した、電極(正極)平滑化層12(12a)を有する正極1と、上記(工程9)で作製した、電極(負極)平滑化層12(12b)と、セラミックセパレータ層11を有する負極2とを対向させ、電極(正極)平滑化層12(12a)と、電極(負極)平滑化層12(12b)の間に、セラミックセパレータ層11が位置するような態様で接合して、1対の電極(正極と負極)からなる電池素子20を作製した。
最後にラミネートパッケージの開口部分を真空シールすることによりリチウムイオン二次電池(電池セル)を作製した。
上述のようにして作製したリチウムイオン二次電池(電池セル)の特性を評価するため、10個のリチウムイオン二次電池について、ショート不良の発生の有無を確認した。ショート不良の判断は、3.8Vまでセルを充電後1週間放置し、セルの電圧を測定して、電圧が3.7V以上のセルを良品、3.7V未満のセルをショート不良とした。その結果を表2に示す。
上記実施形態1では、負極の表面にのみ電極(負極)平滑化層を設けるようにした場合につて説明し、実施形態2では、正極と負極の両方の表面に電極(正極および負極)平滑化層を設けるようにした場合について説明したが、場合によっては、図3に示すように、正極1の表面にのみ電極(正極)平滑化層12を形成するようにしてもよい。なお、図3において、図1および2と同一符号を付した部分は、同一または相当する部分を示す。
2 負極
11 セラミックセパレータ層
12(12a,12b) 電極平滑化層
20 電池素子
Claims (3)
- 正極と、負極と、前記正極と前記負極の間に介在するように配設されたセラミックセパレータ層および前記正極および負極の少なくとも一方の表面を平滑にするための電極平滑化層と、電解質とを含む電池要素と、前記電池要素を収容する外装体とを備え、
前記電極平滑化層は、活物質と有機物を含む複合材料から形成され、前記正極と前記負極の少なくとも一方の表面に設けられているとともに、
前記セラミックセパレータ層は、絶縁性無機微粒子と有機物を含む複合材料から形成され、リチウムイオン透過性を有し,前記正極および前記負極の少なくとも一方と、前記電極平滑化層を介して対向するように配設されていること
を特徴とするリチウムイオン二次電池。 - 前記電極平滑化層が、前記正極および前記負極の両方の表面に設けられており、
前記セラミックセパレータ層は、前記正極の表面に設けられた前記電極平滑化層と、前記負極の表面に設けられた前記電極平滑化層との間に位置するように配設されていること
を特徴とする請求項1記載のリチウムイオン二次電池。 - 前記電極平滑化層を構成する前記活物質の粒子径が、0.03~5μmであることを特徴とする請求項1または2記載のリチウムイオン二次電池。
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WO2019221146A1 (ja) * | 2018-05-17 | 2019-11-21 | 日本碍子株式会社 | リチウム二次電池 |
WO2019225077A1 (ja) * | 2018-05-24 | 2019-11-28 | 株式会社日立製作所 | 電池セルシート、電池 |
JP2020527833A (ja) * | 2017-09-15 | 2020-09-10 | エルジー・ケム・リミテッド | リチウム二次電池用負極及びこれを含むリチウム二次電池 |
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