Classifications

• • 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
  • H01M4/139—Processes of manufacture
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/621—Binders
  • H01M4/622—Binders being polymers
  • H01M4/623—Binders being polymers fluorinated polymers
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
  • H01M4/624—Electric conductive fillers
  • H01M4/625—Carbon or graphite
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/04—Processes of manufacture in general
  • H01M4/0402—Methods of deposition of the material
  • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • 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
  • H01M4/139—Processes of manufacture
  • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• • 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

Definitions

• the present disclosure relates to a method for manufacturing an electrode for a secondary battery using a non-aqueous electrolyte solution and a binder for a secondary battery electrode using a non-aqueous electrolyte solution.
• Patent Document 1 fibrillated polytetrafluoroethylene (PTFE) as a binder in an electrode of a lithium ion battery containing a non-aqueous electrolytic solution.
• Patent Documents 2 to 4 a uniform mixed powder obtained by mixing a conductive material with PTFE is obtained by spray drying.
• the present disclosure provides a method for manufacturing an electrode for a secondary battery and a binder so that the electric resistance value of the electrode can be lowered and the strength can be improved at the same time in the electrode using PTFE. be able to.
• composition for making an electrode which comprises a polytetrafluoroethylene resin and a conductive auxiliary agent as an essential component, and which is a powder containing no active material, is used to prepare a composition for producing an electrode which does not substantially contain a liquid medium. It is a method for manufacturing an electrode for a secondary battery using a non-aqueous electrolytic solution, which comprises the step (1).
• the binder preferably has a water content of 1000 ppm or less.
• the binder is preferably produced by a production method having a step (A) of mixing a polytetrafluoroethylene resin and a conductive auxiliary agent in the presence of a liquid medium.
• the liquid medium is preferably water.
• the binder is preferably obtained by a production method having a step (B) of drying the composition obtained by the step (A) by spray drying.
• the polytetrafluoroethylene resin preferably has a standard specific gravity of 2.11 to 2.20.
• the composition for producing an electrode preferably contains a positive electrode active material.
• the binder for a secondary battery is preferably a binder for a lithium ion secondary battery.
• the PTFE preferably has a fibrous structure having a fibril diameter (median) of 150 nm or less.
• the binder preferably has an elemental ratio (F / C ratio) of fluorine to carbon as measured by elemental analysis of 0.4 or more and 3.0 or less.
• the present disclosure comprises a composition for a secondary battery electrode using a non-aqueous electrolyte solution, which comprises a composition requiring a polytetrafluoroethylene resin and a conductive auxiliary agent and is a powder containing no electrode active material. It is also a dressing agent.
• the binder for the secondary battery electrode preferably has an elemental ratio (F / C ratio) of fluorine to carbon measured by elemental analysis of 0.4 or more and 3.0 or less.
• the present disclosure is also a binder for a secondary battery electrode using a non-aqueous electrolyte solution containing a mixed powder of a polytetrafluoroethylene resin and Ketjen black or carbon nanotubes.
• the present disclosure is also characterized by containing the above-mentioned binder for a secondary battery electrode.
• the present disclosure is also an electrode mixture characterized by containing the above-mentioned binder for a secondary battery electrode.
• the present disclosure is also an electrode characterized by having the above-mentioned electrode mixture.
• the present disclosure provides a method for manufacturing an electrode for a secondary battery and a binder so that the electric resistance value of the electrode can be lowered and the strength can be improved at the same time in the electrode using PTFE. be able to.
• An electrode mixture using PTFE as a binder may have a high resistance value of the electrode.
• the present disclosure provides a method for manufacturing an electrode, which solves such a problem and can obtain an electrode having a low resistance value.
• the electrode mixture using PTFE as a binder causes the action as a binder by fibrillating PTFE.
• the electrode when the electrode is manufactured by mixing PTFE and the conductive auxiliary agent as powders, the electrode may have high resistance. It is presumed that this is because the PTFE is unevenly distributed in the electrodes and therefore the conductive path is not sufficiently formed. Further, if the components are unevenly distributed in the electrode, it may cause a decrease in the strength of the electrode. On the other hand, if the kneading is vigorously carried out in order to lose the uneven distribution, the PTFE becomes excessively fibrillated, resulting in a decrease in flexibility and strength. Therefore, such a problem can be solved by using a binder that does not cause uneven distribution of PTFE and the conductive auxiliary agent.
• the method for manufacturing an electrode for a secondary battery using the non-aqueous electrolyte solution of the present disclosure requires a polytetrafluoroethylene resin and a conductive auxiliary agent, and uses a binder which is a powder containing no active material. It is a feature. Hereinafter, this will be referred to as the first binder of the present disclosure. Hereinafter, such a binder and the components to be blended in the binder will be described in detail.
• the active material if PTFE and the conductive auxiliary agent are to be mixed in advance, lithium is eluted from the active material due to moisture in the liquid medium, and the active material is deteriorated, resulting in a decrease in battery capacity and battery resistance. It is known to cause a problem of increase (Patent Document 5). Therefore, by using a binder composed of a composition that does not contain an active material and requires PTFE and a conductive auxiliary agent, the object of the present disclosure can be achieved without being limited to the active material. can.
• a mixed powder of polytetrafluoroethylene resin and Ketjen black or carbon nanotube is also disclosed. Can achieve the purpose of. Such an effect is an effect that cannot be obtained when other carbon-based conductive auxiliary agents such as acetylene black are used.
• a binder is referred to as a second binder of the present disclosure.
• the first method for manufacturing an electrode for a secondary battery using the non-aqueous electrolyte solution of the present disclosure comprises a composition comprising PTFE and a conductive auxiliary agent, and a binder which is a powder containing no active substance. Characterized by use. That is, the particles constituting the powder are not only composed of PTFE and a conductive auxiliary agent, but are composed of a composition containing both PTFE and a conductive auxiliary agent.
• the PTFE is not particularly limited, and may be a homopolymer or a copolymer that can be fibrillated, but a homopolymer is more preferable.
• examples of the fluorine atom-containing monomer as a comonomer include chlorotrifluoroethylene, hexafluoropropylene, fluoroalkylethylene, perfluoroalkylethylene, fluoroalkyl / fluorovinyl ether and the like.
• the PTFE used as a raw material for preparing the electrode mixture of the present disclosure preferably has a standard specific density of 2.11 to 2.20.
• the standard specific gravity is within the range, there is an advantage in that a high-strength electrode mixture sheet can be produced.
• the lower limit of the standard specific gravity is more preferably 2.12 or more.
• the upper limit of the standard specific gravity is more preferably 2.19 or less, and further preferably 2.18 or less.
• the PTFE used in the present disclosure may have a core-shell structure.
• the PTFE having a core-shell structure include a PTFE containing a core of high molecular weight PTFE and a shell of lower molecular weight PTFE or modified PTFE in the particles.
• examples of such PTFE include PTFE and the like described in JP-A-2005-527652.
• a powder-shaped PTFE that satisfies each of the above-mentioned parameters can be obtained by a conventional production method.
• it may be manufactured according to the manufacturing method described in International Publication No. 2015-080291, International Publication No. 2012-086710, and the like.
• a known conductive material can be arbitrarily used. Specific examples include metal materials such as copper and nickel, natural graphite, graphite such as artificial graphite (graphite), carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black, and needle coke. , Carbon nanotubes, carbon nanohorns, carbon nanofibers, fullerene and graphite, carbon materials such as amorphous carbon such as VGCF, and the like. In particular, Ketjen black, acetylene black, and carbon nanotubes are preferable. Among the carbon nanotubes, multi-walled carbon nanotubes are preferable.
• Examples of commercially available carbon black include Talker Black # 4300, # 4400, # 4500, # 5500 (Tokai Carbon Co., Furness Black), Printex L (Degusa Co., Furness Black), Raven7000, 5750, etc. 5250, 5000ULTRAIII, 5000ULTRA, etc., Conductex SC ULTRA, Conductex 975ULTRA, etc., PUER BLACK100, 115, 205, etc. 3350B, # 3400B, # 5400B, etc.
• VGCF examples include VGCF-H (manufactured by Showa Denko KK) and the like.
• examples of commercially available multi-walled carbon nanotubes include FT7000 (manufactured by CNano).
• the multi-walled carbon nanotubes preferably have an average outer diameter of 4 nm to 20 nm, more preferably 6 nm to 12 nm.
• the average fiber length is preferably 1 to 30 ⁇ m, more preferably 3 ⁇ m to 20 ⁇ m. Thereby, good conductivity can be obtained.
• a conductive auxiliary agent may be additionally mixed and used.
• the binder of the present disclosure preferably contains the above conductive auxiliary agent in a proportion of 1.0 to 60.0% by mass with respect to the total amount of the binder. Thereby, good conductivity and electrode strength can be obtained.
• the lower limit is more preferably 1.5 or more, and further preferably 2.0 or more.
• the upper limit is more preferably 55.0 or more, and further preferably 50.0 or less.
• the binder contains a conductive auxiliary agent, but when the electrode sheet is manufactured by the electrode mixture, PTFE and the conductive auxiliary agent are additionally mixed. It does not matter if it is used.
• the conductive auxiliary agent is usually 0.1% by mass or more, preferably 0.5% by mass or more, more preferably 0.8% by mass or more, and usually 50% by mass or less, preferably 50% by mass or more in the electrode mixture. Is preferably used so as to contain 30% by mass or less, more preferably 15% by mass or less. If the content is lower than this range, the conductivity may be insufficient. On the contrary, if the content is higher than this range, the battery capacity may decrease.
• Examples of the material to be added as necessary when mixing the conductive auxiliary agent and PTFE include a conductive material, a dispersant, a thickener and the like.
• a thickener celluloses such as carboxymethyl cellulose (CMC) and methyl cellulose (MC) can be preferably used.
• the blending amount of such components is preferably 5.0% by mass or less with respect to the total amount of the binder. If the above other components are blended in an amount of more than 5.0% by mass, the object of the present invention may not be sufficiently achieved.
• the binder used in the present disclosure is a composition in which PTFE and a conductive auxiliary agent are essential components in the form of powder. That is, the composition in which the PTFE and the conductive auxiliary agent are mixed is a powder, and does not include the mixture of the respective powders of the PTFE powder and the conductive auxiliary agent powder. Such a state is not particularly limited, but it is particularly preferable that the particles are in a state of being granulated by spray drying.
• the binder preferably contains PTFE and a conductive auxiliary agent in a weight ratio of 99: 1 to 50:50.
• the mixing ratio is preferably 95: 5 to 60:40, more preferably 90:10 to 65:35.
• the method for producing the binder is not particularly limited, and the binder can be produced by any method.
• a production method including a step (A) of mixing PTFE and a conductive auxiliary agent in the presence of a liquid medium. It is preferably manufactured by.
• a method of adding a conductive auxiliary agent as a powder to the liquid dispersion of PTFE and mixing the liquid dispersion a method of mixing the liquid dispersion of PTFE and the liquid dispersion of the conductive auxiliary agent, and the like can be mentioned.
• a mixing method a general method can be used. Examples thereof include, but are not limited to, mixers such as a dispenser, a homomixer, and a planetary mixer, homogenizers, and a wet jet mill.
• a dispersion that requires PTFE, a conductive auxiliary agent, and a liquid medium is used.
• the total amount of PTFE and the conductive auxiliary agent is preferably 1 to 60% by weight based on the total amount of PTFE, the conductive auxiliary agent and the liquid medium.
• the lower limit is more preferably 2% by weight or more, further preferably 3% by weight or more.
• the upper limit is more preferably 50% by weight or less, and further preferably 30% by weight or less.
• PTFE and the conductive auxiliary agent can be mixed with high uniformity.
• the liquid medium in such mixing is preferably water.
• PTFE used as a raw material
• the PTFE used as a raw material for the binder preferably has an average primary particle size of 150 nm or more because an electrode mixture sheet having higher strength and excellent homogeneity can be obtained. It is more preferably 180 nm or more, further preferably 210 nm or more, and particularly preferably 220 nm or more.
• the larger the average primary particle size of PTFE the more the increase in extrusion pressure can be suppressed when extrusion molding is performed using the powder, and the better the formability.
• the upper limit is not particularly limited, but may be 500 nm. From the viewpoint of productivity in the polymerization step, the upper limit is preferably 350 nm.
• the average primary particle diameter is the transmission of projected light at 550 nm with respect to the unit length of the aqueous dispersion whose polymer concentration is adjusted to 0.22% by mass using the aqueous dispersion of PTFE obtained by polymerization, and the transmission type.
• a calibration line with the average primary particle diameter determined by measuring the directional diameter in an electron micrograph can be created, the permeability of the aqueous dispersion to be measured can be measured, and the determination can be made based on the calibration line. ..
• the mixture of PTFE and the conductive auxiliary agent mixed in the liquid medium by the above step (A) is then dried by spray drying (step (B)) to remove the liquid medium.
• the drying method include a shelf type dryer, a vacuum dryer, a freeze dryer, a hot air dryer, a drum dryer, a spray dryer and the like. Particularly preferred is spray drying.
• Spray drying is a method of producing a dry powder by spraying a mixture of a liquid and a solid into a gas and rapidly drying the mixture. This makes it possible to obtain a binder in a powder state in which PTFE and a conductive auxiliary agent are uniformly mixed.
• Spray drying is a generally widely known technique and can be performed by any known device.
• the above step (B) can be performed by a general method using a known general device.
• the drying temperature is preferably in the range of, for example, 100 ° C. or higher and 250 ° C. or lower. At 100 ° C. or higher, the solvent can be sufficiently removed, and at 250 ° C. or lower, energy consumption can be further reduced, which is preferable.
• the drying temperature is more preferably 110 ° C. or higher, and more preferably 220 ° C. or lower.
• the amount of the supplied liquid may be, for example, in the range of 0.1 L / h or more and 2 L / h or less, although it depends on the scale of production.
• the nozzle size for spraying the prepared solution may be, for example, in the range of 0.5 mm or more and 5 mm or less in diameter, although it depends on the scale of production.
• the binder thus obtained preferably has a water content of 1000 ppm or less.
• the water content is 1000 ppm or less, it is preferable in that a secondary battery with less gas generation can be produced as an initial characteristic.
• the water content is more preferably 500 ppm or less.
• the water content of the binder is determined by using a Karl Fisher Moisture Meter (ADP-511 / MKC-510N manufactured by Kyoto Electronics Manufacturing Co., Ltd.) equipped with a boat-type water vaporizer and heating to 210 ° C with the water vaporizer. The vaporized water content was measured.
• As a carrier gas nitrogen gas was flowed at a flow rate of 200 mL / min, and the measurement time was set to 30 min. Chemaqua was also used as the curl fisher reagent. The sample amount was 1.5 g.
• the second binder of the present disclosure is a mixed powder of a polytetrafluoroethylene resin and Ketjen black and / or carbon nanotubes.
• a mixed powder is used as a binder, it is preferable to using a well-known carbon conductive auxiliary agent such as acetylene black in that electrode resistance can be reduced and battery characteristics are improved. It can be used in the same manner as the first binder described above.
• Ketjen black and / or carbon nanotubes used in the second binder are not particularly limited, and the above-mentioned ones can be used. Further, the carbon nanotubes are preferably multi-walled, and more specifically, those having an average fiber length of 1 to 20 ⁇ m are preferably used.
• the same polytetrafluoroethylene as the above-mentioned first binder can be used.
• the second binder may be obtained through the steps (A) and (B) described above in the same manner as the first binder described above, or these components may be simply mixed. It may be obtained.
• both the first binder and the second binder can be used in the same manner.
• composition for electrode fabrication means a composition containing all the essential components in an electrode. That is, it means a composition in a state where other electrode components such as an electrode active material are mixed with the above-mentioned binder.
• the composition for producing an electrode is a composition containing, in addition to the above-mentioned binder, an electrode active material, a conductive auxiliary agent to be additionally added, and the like.
• the positive electrode active material is not particularly limited as long as it can electrochemically store and release alkali metal ions, but for example, a substance containing an alkali metal and at least one transition metal is preferable. Specific examples include alkali metal-containing transition metal composite oxides, alkali metal-containing transition metal phosphoric acid compounds, and conductive polymers. Among them, as the positive electrode active material, an alkali metal-containing transition metal composite oxide that produces a high voltage is particularly preferable. Examples of the alkali metal ion include lithium ion, sodium ion, potassium ion and the like. In a preferred embodiment, the alkali metal ion can be a lithium ion. That is, in this embodiment, the alkali metal ion secondary battery is a lithium ion secondary battery.
• alkali metal-containing transition metal composite oxide examples include, for example.
• Formula: Ma Mn 2-b M 1 b O 4 (In the formula, M is at least one metal selected from the group consisting of Li, Na and K; 0.9 ⁇ a; 0 ⁇ b ⁇ 1.5; M 1 is Fe, Co, Ni, Alkali metal / manganese represented by (at least one metal selected from the group consisting of Cu, Zn, Al, Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge).
• MNi 1-c M 2 c O 2 (In the formula, M is at least one metal selected from the group consisting of Li, Na and K; 0 ⁇ c ⁇ 0.5; M 2 is Fe, Co, Mn, Cu, Zn, Al, An alkali metal / nickel composite oxide represented by (at least one metal selected from the group consisting of Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge), or Formula: MCo 1-d M 3 d O 2 (In the formula, M is at least one metal selected from the group consisting of Li, Na and K; 0 ⁇ d ⁇ 0.5; M 3 is Fe, Ni, Mn, Cu, Zn, Al, At least one metal selected from the group consisting of Sn, Cr, V, Ti, Mg, Ca, Sr, B, Ga, In, Si and Ge) Examples thereof include an alkali metal / cobalt composite oxide represented by. In the above, M is preferably one kind of
• MCoO 2 , MMnO 2 , MNiO 2 , MMn 2 O 4 , MNi 0.8 Co 0.15 Al 0.05 O 2 or MNi 1/3 Co 1/3 Mn 1/3 O 2 and the like are preferable, and the compound represented by the following general formula (3) is preferable.
• Examples of the alkali metal-containing transition metal phosphoric acid compound include the following formula (4).
• M4 is selected from the group consisting of V, Ti, Cr, Mn, Fe, Co, Ni and Cu.
• M is preferably one kind of metal selected from the group consisting of Li, Na and K, more preferably Li or Na, and even more preferably Li.
• the transition metal of the lithium-containing transition metal phosphoric acid compound V, Ti, Cr, Mn, Fe, Co, Ni, Cu and the like are preferable, and specific examples thereof are, for example, LiFePO 4 , Li 3 Fe 2 (PO 4 ). 3. Iron phosphates such as LiFeP 2 O 7 , cobalt phosphates such as LiCoPO 4 , and some of the transition metal atoms that are the main constituents of these lithium transition metal phosphate compounds are Al, Ti, V, Cr, Mn. , Fe, Co, Li, Ni, Cu, Zn, Mg, Ga, Zr, Nb, Si and the like substituted with other elements.
• the lithium-containing transition metal phosphoric acid compound preferably has an olivine-type structure.
• positive electrode active materials include MFePO 4 , MNi 0.8 Co 0.2 O 2 , M 1.2 Fe 0.4 Mn 0.4 O 2 , MNi 0.5 Mn 1.5 O 2 , and MV 3 .
• examples thereof include O 6 and M 2 MnO 3 (in the formula, M is at least one metal selected from the group consisting of Li, Na and K) and the like.
• the positive electrode active material such as M 2 MnO 3 and MNi 0.5 Mn 1.5 O 2 is used when the secondary battery is operated at a voltage exceeding 4.4 V or a voltage of 4.6 V or higher. , It is preferable in that the crystal structure does not collapse.
• an electrochemical device such as a secondary battery using a positive electrode material containing the positive electrode active material exemplified above does not easily decrease the residual capacity, the resistance increase rate does not change easily, and is high even when stored at a high temperature. It is preferable because the battery performance does not deteriorate even if it is operated by a voltage.
• M 2 MnO 3 and MM 6 O 2 are at least one metal selected from the group consisting of Li, Na and K, and M 6 is Co, Ni. , Mn, Fe, and other transition metals) and solid solution materials.
• the solid solution material is, for example, an alkali metal manganese oxide represented by the general formula M x [Mn (1-y) M 7 y ] Oz.
• M in the formula is at least one metal selected from the group consisting of Li, Na and K
• M 7 is composed of at least one metal element other than M and Mn, for example, Co, Ni. , Fe, Ti, Mo, W, Cr, Zr and Sn contains one or more elements selected from the group.
• the values of x, y, and z in the equation are in the range of 1 ⁇ x ⁇ 2, 0 ⁇ y ⁇ 1, 1.5 ⁇ z ⁇ 3.
• a manganese-containing solid solution material in which LiNiO 2 or LiCoO 2 is solid-dissolved based on Li 2 MnO 3 such as Li 1.2 Mn 0.5 Co 0.14 Ni 0.14 O 2 has a high energy density. It is preferable because it can provide an alkali metal ion secondary battery.
• lithium phosphate in the positive electrode active material because the continuous charging characteristics are improved.
• the use of lithium phosphate is not limited, it is preferable to use the above-mentioned positive electrode active material in combination with lithium phosphate.
• the lower limit of the amount of lithium phosphate used is preferably 0.1% by mass or more, more preferably 0.3% by mass or more, still more preferably 0.5% by mass, based on the total of the positive electrode active material and lithium phosphate. % Or more, and the upper limit is preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 5% by mass or less.
• Examples of the conductive polymer include a p-doping type conductive polymer and an n-doping type conductive polymer.
• Examples of the conductive polymer include polyacetylene-based, polyphenylene-based, heterocyclic polymers, ionic polymers, ladders, network-like polymers and the like.
• a substance having a composition different from that attached to the surface of the positive electrode active material may be used.
• Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide and other oxides, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate and calcium sulfate.
• Sulfates such as aluminum sulfate
• carbonates such as lithium carbonate, calcium carbonate, magnesium carbonate, carbon and the like.
• These surface-adhering substances are, for example, dissolved or suspended in a solvent, impregnated with the positive electrode active material, or added, and then dried, or the surface-adhering substance precursor is dissolved or suspended in the solvent to activate the positive electrode. It can be adhered to the surface of the positive electrode active material by a method of impregnating or adding the substance and then reacting by heating or the like, a method of adding to the positive electrode active material precursor and firing at the same time, or the like. In addition, when carbon is attached, a method of mechanically attaching carbonaceous material later in the form of activated carbon or the like can also be used.
• the amount of the surface adhering substance is preferably 0.1 ppm or more, more preferably 1 ppm or more, still more preferably 10 ppm or more, and the upper limit is preferably 20% or less, more preferably 0.1 ppm or more, more preferably 1 ppm or more, more preferably 10 ppm or more, in terms of mass with respect to the positive electrode active material. Is used at 10% or less, more preferably 5% or less.
• the surface-adhering substance can suppress the oxidation reaction of the electrolytic solution on the surface of the positive electrode active material, and can improve the battery life. If the amount of adhesion is too small, the effect is not sufficiently exhibited, and if it is too large, resistance may increase because it inhibits the entry and exit of lithium ions.
• Examples of the shape of the particles of the positive electrode active material include lumps, polyhedra, spheres, elliptical spheres, plates, needles, and columns as conventionally used. Further, the primary particles may be aggregated to form secondary particles.
• the tap density of the positive electrode active material is preferably 0.5 g / cm 3 or more, more preferably 0.8 g / cm 3 or more, and further preferably 1.0 g / cm 3 or more.
• the tap density of the positive electrode active material is lower than the above lower limit, the required amount of the conductive material and the binder required for forming the positive electrode active material layer increases, and the filling rate of the positive electrode active material in the positive electrode active material layer is restricted. , Battery capacity may be limited.
• the composite oxide powder having a high tap density a high-density positive electrode active material layer can be formed. Generally, the larger the tap density is, the more preferable it is, and there is no particular upper limit.
• the upper limit is preferably 4.0 g / cm 3 or less, more preferably 3.7 g / cm 3 or less, and further preferably 3.5 g / cm 3 or less.
• the tap density is the powder filling density (tap density) g / cm 3 when 5 to 10 g of positive electrode active material powder is placed in a 10 ml glass graduated cylinder and tapped 200 times with a stroke of about 20 mm. Ask as.
• the median diameter d50 (secondary particle diameter when the primary particles are aggregated to form secondary particles) of the particles of the positive electrode active material is preferably 0.3 ⁇ m or more, more preferably 0.5 ⁇ m or more, still more preferable. Is 0.8 ⁇ m or more, most preferably 1.0 ⁇ m or more, preferably 30 ⁇ m or less, more preferably 27 ⁇ m or less, still more preferably 25 ⁇ m or less, and most preferably 22 ⁇ m or less. If it is below the above lower limit, a high tap density product may not be obtained, and if it exceeds the upper limit, it takes time to diffuse lithium in the particles, which may cause a problem such as deterioration of battery performance.
• the filling property at the time of producing the positive electrode can be further improved.
• the median diameter d50 is measured by a known laser diffraction / scattering type particle size distribution measuring device.
• LA-920 manufactured by HORIBA is used as the particle size distribution meter
• a 0.1 mass% sodium hexametaphosphate aqueous solution is used as the dispersion medium used for the measurement, and the measured refractive index is set to 1.24 after ultrasonic dispersion for 5 minutes. Is measured.
• the average primary particle diameter of the positive electrode active material is preferably 0.05 ⁇ m or more, more preferably 0.1 ⁇ m or more, still more preferably 0. It is 2 ⁇ m or more, and the upper limit is preferably 5 ⁇ m or less, more preferably 4 ⁇ m or less, still more preferably 3 ⁇ m or less, and most preferably 2 ⁇ m or less. If it exceeds the above upper limit, it is difficult to form spherical secondary particles, which adversely affects the powder filling property and greatly reduces the specific surface area, so that there is a high possibility that the battery performance such as output characteristics will deteriorate. In some cases. On the contrary, if it is less than the above lower limit, problems such as inferior reversibility of charge / discharge may occur because the crystal is usually underdeveloped.
• the average primary particle size is measured by observation using a scanning electron microscope (SEM). Specifically, in a photograph at a magnification of 10,000 times, the longest value of the intercept by the left and right boundary lines of the primary particles with respect to the horizontal straight line is obtained for any 50 primary particles, and the average value is taken. Be done.
• the BET specific surface area of the positive electrode active material is preferably 0.1 m 2 / g or more, more preferably 0.2 m 2 / g or more, still more preferably 0.3 m 2 / g or more, and the upper limit is preferably 50 m 2 / g. It is g or less, more preferably 40 m 2 / g or less, still more preferably 30 m 2 / g or less. If the BET specific surface area is smaller than this range, the battery performance tends to deteriorate, and if it is large, there may be a problem that the tap density is difficult to increase.
• the BET specific surface area is large after pre-drying the sample at 150 ° C. for 30 minutes under nitrogen flow using a surface meter (for example, a fully automatic surface area measuring device manufactured by Okura Riken Co., Ltd.). It is defined by the value measured by the nitrogen adsorption BET 1-point method by the gas flow method using a nitrogen helium mixed gas accurately adjusted so that the value of the relative pressure of nitrogen with respect to the atmospheric pressure is 0.3.
• the particles of the positive electrode active material are mainly secondary particles.
• the particles of the positive electrode active material preferably contain 0.5 to 7.0% by volume of fine particles having an average particle size of secondary particles of 40 ⁇ m or less and an average primary particle size of 1 ⁇ m or less.
• a general method is used as a method for producing an inorganic compound.
• various methods can be considered for producing spherical or elliptical spherical active substances.
• a raw material for a transition metal is dissolved or pulverized and dispersed in a solvent such as water, and the pH is adjusted while stirring.
• a method of preparing and recovering a spherical precursor, drying it as necessary, adding a Li source such as LiOH, Li 2 CO 3 , or LiNO 3 and firing at a high temperature to obtain an active substance can be mentioned. ..
• the positive electrode active material may be used alone, or two or more kinds having different compositions may be used in any combination or ratio.
• Preferred combinations in this case include a combination of LiCoO 2 and a ternary system such as LiNi 0.33 Co 0.33 Mn 0.33 O 2 , LiCoO 2 and LiMn 2 O 4 or a part of this Mn. Examples thereof include a combination with a transition metal or the like, or a combination of LiFePO 4 and LiCoO 2 or a part of this Co substituted with another transition metal or the like.
• the content of the positive electrode active material is preferably 50 to 99.5% by mass, more preferably 80 to 99% by mass in the positive electrode mixture in terms of high battery capacity.
• the content of the positive electrode active material is preferably 80% by mass or more, more preferably 82% by mass or more, and particularly preferably 84% by mass or more.
• the upper limit is preferably 99% by mass or less, more preferably 98% by mass or less. If the content of the positive electrode active material in the positive electrode mixture layer is low, the electric capacity may be insufficient. On the contrary, if the content is too high, the strength of the positive electrode may be insufficient.
• the negative electrode active material is not particularly limited, and for example, lithium metal, artificial graphite, graphite carbon fiber, resin calcined carbon, thermally decomposed gas phase growth carbon, coke, mesocarbon microbeads (MCMB), full frill alcohol resin calcined carbon, Select from polyacene, pitch-based carbon fibers, vapor-grown carbon fibers, natural graphite, those containing carbonaceous materials such as refractory carbon, silicon-containing compounds such as silicon and silicon alloys, Li 4 Ti 5 O 12 and the like. Any one of them, or a mixture of two or more kinds, and the like can be mentioned. Among them, those containing at least a part of carbonaceous material and silicon-containing compounds can be particularly preferably used.
• the negative electrode active material used in the present disclosure preferably contains silicon as a constituent element. By including silicon as a constituent element, a high-capacity battery can be manufactured.
• Examples of the material containing silicon include silicon particles, particles having a structure in which silicon fine particles are dispersed in a silicon-based compound, silicon oxide particles represented by the general formula SiOx (0.5 ⁇ x ⁇ 1.6), or these. Mixtures are preferred. By using these, a negative electrode mixture for a lithium ion secondary battery having higher initial charge / discharge efficiency, high capacity, and excellent cycle characteristics can be obtained.
• Silicon oxide in the present disclosure is a general term for amorphous silicon oxides, and silicon oxide before disproportionation is represented by the general formula SiOx (0.5 ⁇ x ⁇ 1.6). As for x, 0.8 ⁇ x ⁇ 1.6 is preferable, and 0.8 ⁇ x ⁇ 1.3 is more preferable. This silicon oxide can be obtained, for example, by cooling and precipitating silicon monoxide gas produced by heating a mixture of silicon dioxide and metallic silicon.
• the particles having a structure in which silicon fine particles are dispersed in a silicon-based compound include, for example, a method of firing a mixture of silicon fine particles and a silicon-based compound, or silicon oxide particles before disproportionation represented by the general formula SiOx.
• the material obtained by the latter method is suitable because the microcrystals of silicon are uniformly dispersed.
• the size of the silicon nanoparticles can be set to 1 to 100 nm.
• the silicon oxide in the particles having a structure in which the silicon nanoparticles are dispersed in silicon oxide is preferably silicon dioxide. It can be confirmed by a transmission electron microscope that the silicon nanoparticles (crystals) are dispersed in the amorphous silicon oxide.
• the physical characteristics of the particles containing silicon can be appropriately selected depending on the target composite particles.
• the average particle size is preferably 0.1 to 50 ⁇ m, the lower limit is more preferably 0.2 ⁇ m or more, and even more preferably 0.5 ⁇ m or more.
• the upper limit is more preferably 30 ⁇ m or less, further preferably 20 ⁇ m or less.
• the average particle size in the present disclosure is represented by the weight average particle size in the particle size distribution measurement by the laser diffraction method.
• the BET specific surface area of the silicon-containing particles is preferably 0.5 to 100 m 2 / g, more preferably 1 to 20 m 2 / g.
• the BET specific surface area is 0.5 m 2 / g or more, there is no possibility that the adhesiveness when applied to the electrode is deteriorated and the battery characteristics are deteriorated. Further, when it is 100 m 2 / g or less, the ratio of silicon dioxide on the particle surface becomes large, and there is no possibility that the battery capacity is lowered when used as a negative electrode material for a lithium ion secondary battery.
• the method for imparting conductivity include a method of mixing with conductive particles such as graphite, a method of coating the surface of the particles containing silicon with a carbon film, and a method of combining both of them.
• a method of coating with a carbon film is preferable, and a method of chemical vapor deposition (CVD) is more preferable as a method of coating.
• the content of the negative electrode active material is preferably 40% by mass or more, more preferably 50% by mass or more, and particularly preferably 60% by mass or more in the electrode mixture in order to increase the volume of the obtained electrode mixture.
• the upper limit is preferably 99% by mass or less, more preferably 98% by mass or less.
• the electrode-making composition may further contain a thermoplastic resin.
• thermoplastic resin include vinylidene fluoride, polypropylene, polyethylene, polystyrene, polyethylene terephthalate, polyethylene oxide and the like. One type may be used alone, or two or more types may be used in any combination and ratio.
• the ratio of the thermoplastic resin to the electrode active material is usually 0.01% by mass or more, preferably 0.05% by mass or more, more preferably 0.10% by mass or more, and usually 3.0% by mass or less. It is preferably in the range of 2.5% by mass or less, more preferably 2.0% by mass or less.
• the mechanical strength of the electrode can be improved.
• the ratio of the electrode active material to the electrode mixture decreases, which may cause a problem that the capacity of the battery decreases or a problem that the resistance between the active materials increases.
• Method of manufacturing electrodes As the method for producing an electrode of the present disclosure, it is preferable to use a composition for producing an electrode obtained by mixing each of the above-mentioned components and to form a sheet thereof. In sheeting, the drying step can be omitted, so by applying shear stress to the electrode-making composition, which is a powder, without preparing a slurry, by reducing the amount of liquid medium used or not using it at all. The method used is preferred. Further, in order to reduce the load on the apparatus, a small amount of solvent may be added as a lubricant.
• the solvent is preferably an organic solvent, and the content of the solvent is preferably 10% by mass or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, based on the composition for producing an electrode. It is known that when a shearing force is applied to PTFE in a powder state, it easily becomes fibrillated. Taking advantage of such a fibrillating property, PTFE can be used as a binder. That is, the fibrillated PTFE is entangled with other powder components and the like to bind the powder components, whereby PTFE can act as a binder when molding the powder components.
• the fibrillated PTFE is subjected to an electrode mixture by performing a fine fibrillation process such that the fibril diameter (median value) (hereinafter, simply referred to as “fibril diameter”) has a fibrous structure of 20 nm or more. It can exhibit good performance as a binder for the purpose.
• the composition for producing an electrode does not substantially contain a liquid medium.
• the electrode has PTFE having a fibrous structure having a fibril diameter (median) of 20 nm or more as a component.
• the fibril diameter (median value) is 20 nm or more. That is, PTFE having such a small fibril diameter is present in the electrode, which is preferable in that it has an action of binding the powders of the components constituting the electrode to each other and has flexibility.
• the fibril diameter (median) is a value measured by the following method. (1) Using a scanning electron microscope (S-4800 type manufactured by Hitachi, Ltd.), an enlarged photograph (7000 times) of the electrode mixture sheet is taken to obtain an image. (2) Draw two lines on this image at equal intervals in the horizontal direction and divide the image into three equal parts. (3) For all the PTFE fibers on the upper straight line, the diameters of three points per PTFE fiber are measured, and the average value is taken as the diameter of the PTFE fiber. For the three points to be measured, select the intersection of the PTFE fiber and the straight line, and the location shifted up and down by 0.5 ⁇ m from the intersection. (Excluding unfibered PTFE primary particles).
• the fibril diameter is preferably 15 nm or more, preferably 20 nm or more, and more preferably 31 nm or more. Too much fibrilization tends to result in loss of flexibility.
• the upper limit is not particularly limited, but from the viewpoint of flexibility, for example, it is preferably 150 nm or less, more preferably 100 nm or less, and particularly preferably 75 nm or less.
• the method for obtaining PTFE having the above-mentioned fibril diameter is not particularly limited, but for example, Step of applying shearing force while mixing the above electrode-making composition (2)
• the electrode mixture obtained in the step (2) is formed into a bulk shape (3) and the bulk electrode mixture obtained in the step (3) is rolled into a sheet (4).
• the method can be mentioned.
• the step (2) is a step of applying a shearing force while mixing the composition for producing an electrode obtained by the step (1).
• the powder components for preparing the composition for producing an electrode may be mixed and mixed, and at the same time, a shearing force may be applied to fibrillate the PTFE to form an electrode mixture.
• the fibril diameter of PTFE can be 20 nm or more.
• step (5) of applying a larger load to the obtained rolled sheet and rolling it into a thinner sheet after the step (4). It is also preferable to repeat the step (5). Further, after the step (4) or the step (5), the fibril diameter is also adjusted by having a step (6) in which the obtained rolled sheet is roughly crushed, then molded into a bulk shape again, and rolled into a sheet shape. can do.
• the step (6) is preferably repeated, for example, once or more and 12 times or less.
• a shearing force is applied to fibrillate the PTFE, which is entangled with a powder component such as an electrode active material, whereby an electrode mixture can be produced.
• a powder component such as an electrode active material
• the content of PTFE is usually 0.1% by mass or more, preferably 0.5% by mass or more, and more preferably 1.0% by mass as the ratio of PTFE in the electrode mixture. It is usually 50% by mass or less, preferably 40% by mass or less, more preferably 30% by mass or less, and most preferably 10% by mass or less. If the proportion of the binder is too low, the active material cannot be sufficiently retained, the mechanical strength of the electrode is insufficient, and the battery performance such as cycle characteristics may be deteriorated. On the other hand, if it is too high, it may lead to a decrease in battery capacity and conductivity.
• the electrode mixture of the present disclosure can be used as an electrode mixture for a secondary battery.
• the electrode mixture of the present disclosure is suitable for a lithium ion secondary battery.
• the electrode mixture of the present disclosure is usually used in the form of a sheet when used in a secondary battery.
• the electrode mixture sheet is Step of preparing a mixture containing an electrode active material and, if necessary, a conductive auxiliary agent (0) Step (1) of preparing an electrode-making composition containing a binder in the mixture obtained in the step (0).
• Step of applying shearing force while mixing the electrode fabrication composition (2) The step (3) of forming the electrode mixture obtained by the step (2) into a bulk shape and the step (4) of rolling the bulk electrode mixture obtained by the step (3) into a sheet shape. It can be obtained by a method for manufacturing an electrode mixture sheet for a secondary battery having the above.
• the obtained electrode-making composition was determined only by the electrode active material, the binder, and the like. It exists in a shapeless state.
• Specific mixing methods include W-type mixer, V-type mixer, drum-type mixer, ribbon mixer, conical screw-type mixer, single-screw kneader, double-screw kneader, mix muller, stirring mixer, and planeta.
• a method of mixing using a Lee mixer or the like can be mentioned.
• the mixing conditions may be appropriately set to the rotation speed and the mixing time.
• the rotation speed is preferably 2200 rpm or less. It is preferably 10 rpm or more, more preferably 15 rpm or more, and even more preferably 20 rpm or more. Further, it is preferably in the range of 2000 rpm or less, more preferably 1800 rpm or less, and further preferably 1500 rpm. Below the above range, mixing will take longer and productivity will be affected. On the other hand, if it exceeds the limit, fibrillation may proceed excessively, resulting in an electrode mixture sheet having poor strength and flexibility.
• molding into a bulk shape means that the composition for producing an electrode is made into one mass.
• Specific methods for forming into a bulk form include extrusion molding and press molding.
• the "bulk shape" is not particularly specified in shape, and may be in a state of one lump, and includes a rod shape, a sheet shape, a spherical shape, a cube shape, and the like.
• the size of the mass is preferably 10,000 ⁇ m or more in diameter or the smallest side of the cross section. More preferably, it is 20000 ⁇ m or more.
• Specific examples of the rolling method in the above step (4) include a method of rolling using a roll press machine, a flat plate press machine, a calender roll machine, or the like.
• the number of steps (5) is preferably 2 times or more and 10 times or less, and more preferably 3 times or more and 9 times or less.
• Specific examples of the rolling method include a method of rotating two or a plurality of rolls and passing a rolled sheet between them to form a thinner sheet. It is desirable to heat during rolling.
• the lower limit of the temperature range is preferably 40 degrees or more, more preferably 50 degrees or more, still more preferably 60 degrees or more.
• the upper limit is preferably 300 degrees or less, more preferably 250 degrees or less, and even more preferably 200 degrees or less.
• step (6) in which the rolled sheet is roughly crushed, then molded into a bulk shape again, and rolled into a sheet shape.
• the number of steps (6) is preferably 1 or more and 12 times or less, and more preferably 2 or more and 11 times or less.
• step (6) specific methods for coarsely crushing the rolled sheet and forming it into a bulk form include a method of folding the rolled sheet, a method of forming it into a rod or a thin film sheet, and a method of forming chips.
• coarsely crushing means changing the form of the rolled sheet obtained in step (4) or step (5) to another form in order to roll into a sheet in the next step. This includes cases where the rolled sheet is simply folded.
• step (5) may be performed after the step (6), or may be repeated. Further, uniaxial stretching or biaxial stretching may be performed in steps (3) to (4), (5) and (6). The fibril diameter can also be adjusted by the degree of coarse crushing in the step (6).
• the rolling ratio is preferably 10% or more, more preferably 20% or more, preferably 80% or less, more preferably 65% or less, and further. It is preferably in the range of 50% or less. If it falls below the above range, it takes time as the number of rolling times increases, which affects productivity. On the other hand, if it exceeds the limit, fibrillation may proceed excessively, resulting in an electrode mixture sheet having poor strength and flexibility.
• the rolling ratio here refers to the reduction rate of the thickness after processing with respect to the thickness of the sample before rolling.
• the sample before rolling may be a bulk-shaped electrode-making composition or a sheet-shaped electrode-making composition.
• the thickness of the sample refers to the thickness in the direction in which a load is applied during rolling.
• the PTFE powder is fibrillated by applying a shearing force. Further, in order to have a fibrous structure having a fibril diameter of 20 nm or more, excessive shear stress may promote fibrillation too much, and the flexibility may be impaired. In addition, weak shear stress may not be sufficient in terms of strength. Therefore, by performing the steps of appropriately applying shear stress to the PTFE to promote fibrillation during mixing and rolling, rolling the resin and rolling it into a sheet, the fibril diameter is 20 nm or more. It can have a fibrous structure.
• the electrode mixture sheet of the present disclosure can be used as an electrode mixture sheet for a secondary battery. It can be either a negative electrode or a positive electrode. In particular, the electrode mixture sheet of the present disclosure is suitable for a lithium ion secondary battery.
• the positive electrode is composed of a current collector and an electrode mixture sheet containing the positive electrode active material.
• the material of the current collector for the positive electrode include metals such as aluminum, titanium, tantalum, stainless steel and nickel, or metal materials such as alloys thereof; carbon materials such as carbon cloth and carbon paper. Of these, metal materials, especially aluminum or alloys thereof, are preferable.
• Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, expanded metal, punch metal, foamed metal, etc. in the case of metal material, and carbon plate, carbon thin film, carbon in the case of carbon material. Examples include columns. Of these, metal foil is preferable.
• the metal foil may be appropriately formed in a mesh shape.
• the thickness of the metal foil is arbitrary, but is usually 1 ⁇ m or more, preferably 3 ⁇ m or more, more preferably 5 ⁇ m or more, and usually 1 mm or less, preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less. If the metal foil is thinner than this range, the strength required for the current collector may be insufficient. On the contrary, if the metal foil is thicker than this range, the handleability may be impaired.
• the conductive auxiliary agent is applied to the surface of the current collector from the viewpoint of reducing the electric contact resistance between the current collector and the positive electrode mixture sheet.
• the conductive auxiliary agent include carbon and precious metals such as gold, platinum and silver.
• the ratio of the thickness of the current collector to the positive electrode mixture sheet is not particularly limited, but the value of (thickness of the positive electrode mixture sheet on one side immediately before injecting the electrolytic solution) / (thickness of the current collector). Is preferably 20 or less, more preferably 15 or less, most preferably 10 or less, and more preferably 0.5 or more, more preferably 0.8 or more, and most preferably 1 or more. If it exceeds this range, the current collector may generate heat due to Joule heat during charging / discharging at a high current density. Below this range, the volume ratio of the current collector to the positive electrode active material may increase and the capacity of the battery may decrease.
• the positive electrode may be manufactured by a conventional method. For example, a method of laminating the electrode mixture sheet and the current collector via an adhesive and vacuum drying may be mentioned.
• the density of the positive electrode mixture sheet is preferably 3.00 g / cm 3 or more, more preferably 3.10 g / cm 3 or more, still more preferably 3.20 g / cm 3 or more, and preferably 3.80 g / cm 3 or more.
• the range is cm 3 or less, more preferably 3.75 g / cm 3 or less, still more preferably 3.70 g / cm 3 or less. If it exceeds this range, the permeability of the electrolytic solution to the vicinity of the interface between the current collector and the active material is lowered, and the charge / discharge characteristics are particularly lowered at a high current density, so that high output may not be obtained. If it is lower than that, the conductivity between active materials decreases, the battery resistance increases, and high output may not be obtained.
• the area of the positive electrode mixture sheet is preferably large with respect to the outer surface area of the battery outer case from the viewpoint of enhancing high output and stability at high temperatures.
• the total area of the electrode mixture of the positive electrode with respect to the surface area of the exterior of the secondary battery is preferably 15 times or more, and more preferably 40 times or more in terms of area ratio.
• the outer surface area of the battery exterior case is the total area calculated from the length, width, and thickness of the case part filled with power generation elements excluding the protrusions of the terminals in the case of a bottomed square shape. Say. In the case of a bottomed cylindrical shape, the geometric surface area approximates the case portion filled with the power generation element excluding the protruding portion of the terminal as a cylinder.
• the total area of the electrode mixture of the positive electrode is the geometric surface area of the positive electrode mixture layer facing the mixture layer containing the negative electrode active material, and the positive electrode mixture layer is formed on both sides via the collector foil. In the structure, it means the total area of each surface calculated separately.
• the thickness of the positive electrode is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the mixture sheet minus the thickness of the current collector is preferably 10 ⁇ m as the lower limit with respect to one side of the current collector. As described above, it is more preferably 20 ⁇ m or more, and the upper limit is preferably 500 ⁇ m or less, more preferably 450 ⁇ m or less.
• a substance having a different composition attached to the surface of the positive electrode may be used.
• Surface adhering substances include aluminum oxide, silicon oxide, titanium oxide, zirconium oxide, magnesium oxide, calcium oxide, boron oxide, antimony oxide, bismuth oxide and other oxides, lithium sulfate, sodium sulfate, potassium sulfate, magnesium sulfate and calcium sulfate.
• Sulfates such as aluminum sulfate
• carbonates such as lithium carbonate, calcium carbonate, magnesium carbonate, carbon and the like.
• the negative electrode is composed of a current collector and an electrode mixture sheet containing the negative electrode active material.
• the material of the current collector for the negative electrode include metals such as copper, nickel, titanium, tantalum, and stainless steel, or metal materials such as alloys thereof; carbon materials such as carbon cloth and carbon paper. Of these, metal materials, especially copper, nickel, or alloys thereof are preferable.
• Examples of the shape of the current collector include metal foil, metal cylinder, metal coil, metal plate, expanded metal, punch metal, foamed metal, etc. in the case of metal material, and carbon plate, carbon thin film, carbon in the case of carbon material. Examples include columns. Of these, metal foil is preferable.
• the metal foil may be appropriately formed in a mesh shape.
• the thickness of the metal foil is arbitrary, but is usually 1 ⁇ m or more, preferably 3 ⁇ m or more, more preferably 5 ⁇ m or more, and usually 1 mm or less, preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less. If the metal foil is thinner than this range, the strength required for the current collector may be insufficient. On the contrary, if the metal foil is thicker than this range, the handleability may be impaired.
• the negative electrode may be manufactured by a conventional method. For example, a method of laminating the electrode mixture sheet and the current collector via an adhesive and vacuum drying may be mentioned.
• the density of the negative electrode mixture sheet is preferably 1.3 g / cm 3 or more, more preferably 1.4 g / cm 3 or more, still more preferably 1.5 g / cm 3 or more, and preferably 2.0 g / cm / cm.
• the range is cm 3 or less, more preferably 1.9 g / cm 3 or less, still more preferably 1.8 g / cm 3 or less. If it exceeds this range, the permeability of the electrolytic solution near the interface between the current collector and the active material is lowered, and the charge / discharge characteristics are deteriorated especially at a high current density, so that high output may not be obtained. If it is lower than that, the conductivity between active materials decreases, the battery resistance increases, and high output may not be obtained.
• the thickness of the negative electrode is not particularly limited, but from the viewpoint of high capacity and high output, the thickness of the mixture sheet minus the thickness of the current collector is preferably 10 ⁇ m as the lower limit with respect to one side of the current collector. As described above, it is more preferably 20 ⁇ m or more, and the upper limit is preferably 500 ⁇ m or less, more preferably 450 ⁇ m or less.
• the binder of the present disclosure preferably has an elemental ratio (F / C ratio) of fluorine to carbon of 0.40 or more and 3.00 or less, and 0.50 or more and 2.50 or less in the electrode mixture sheet. Is more preferable. Within such a range, it is preferable in that an electrode having high strength and low electrode resistance can be manufactured.
• the elemental analysis is a value measured by a usual general method.
• F / C ratio for example, MICRO CORDER JM10 (manufactured by J Science Lab) is used, the sample amount is 2 mg, the combustion furnace is 950 ° C, the reduction furnace is 550 ° C, the helium flow rate is 200 mL / min, and the oxygen flow rate is 15. CHN simultaneous measurement is performed under the condition of ⁇ 25 mL / min, and it can be obtained from the average value of the values measured four times.
• F / C ratio average F (wt%) / average C (wt%)
• the electrode manufactured by the method for manufacturing an electrode for a secondary battery of the present disclosure can be used as a positive electrode or a negative electrode in various secondary batteries.
• the secondary battery is a battery that uses a non-aqueous electrolytic solution, and examples thereof include a lithium ion battery.
• Electrolytic solution As the non-aqueous electrolyte solution, a solution obtained by dissolving a known electrolyte salt in a known organic solvent for dissolving an electrolyte salt can be used.
• the organic solvent for dissolving the electrolyte salt is not particularly limited, but is not limited to propylene carbonate, ethylene carbonate, butylene carbonate, ⁇ -butyrolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, dimethyl carbonate, diethyl.
• Known hydrocarbon solvents such as carbonate and ethylmethyl carbonate; one or more of fluorosolvents such as fluoroethylene carbonate, fluoroether and fluorinated carbonate can be used.
• electrolyte salt examples include LiClO 4 , LiAsF 6 , LiBF 4 , LiPF 6 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 , etc., and are particularly good in terms of cycle characteristics. LiPF 6 , LiBF 4 , LiN (SO 2 CF 3 ) 2 , LiN (SO 2 C 2 F 5 ) 2 or a combination thereof is preferable.
• the concentration of the electrolyte salt needs to be 0.8 mol / liter or more, and further 1.0 mol / liter or more.
• the upper limit depends on the organic solvent for dissolving the electrolyte salt, but is usually 1.5 mol / liter or less.
• the electrode mixture group may be either a laminated structure in which the positive electrode and the negative electrode are formed via a separator, or a structure in which the positive electrode and the negative electrode are spirally wound via the separator.
• the secondary battery of the present disclosure preferably further comprises a separator.
• the material and shape of the separator are not particularly limited as long as they are stable to the electrolytic solution and have excellent liquid retention properties, and known ones can be used. Among them, resins, glass fibers, inorganic substances, etc., which are made of a material stable to the electrolytic solution of the present disclosure or the electrolytic solution used in the alkali metal secondary battery of the present disclosure, are used and have excellent liquid retention. It is preferable to use a porous sheet or a non-woven material.
• the material of the resin and the glass fiber separator for example, polyolefins such as polyethylene and polypropylene, aromatic polyamides, PTFE, polyether sulfone, glass filters and the like can be used.
• polyolefins such as polyethylene and polypropylene, aromatic polyamides, PTFE, polyether sulfone, glass filters and the like
• One of these materials such as polypropylene / polyethylene two-layer film and polypropylene / polyethylene / polypropylene three-layer film, may be used alone, or two or more of them may be used in any combination and ratio.
• the separator is preferably a porous sheet or a non-woven fabric made of a polyolefin such as polyethylene or polypropylene because the permeability of the electrolytic solution and the shutdown effect are good.
• the thickness of the separator is arbitrary, but is usually 1 ⁇ m or more, preferably 5 ⁇ m or more, further preferably 8 ⁇ m or more, and usually 50 ⁇ m or less, preferably 40 ⁇ m or less, further preferably 30 ⁇ m or less. If the separator is too thin than the above range, the insulating property and the mechanical strength may be deteriorated. Further, if it is too thick than the above range, not only the battery performance such as rate characteristics may be deteriorated, but also the energy density of the electrolytic solution battery as a whole may be lowered.
• the porosity of the separator is arbitrary, but is usually 20% or more, preferably 35% or more, still more preferably 45% or more. Further, it is usually 90% or less, preferably 85% or less, and further preferably 75% or less. If the porosity is too smaller than the above range, the film resistance tends to increase and the rate characteristics tend to deteriorate. On the other hand, if it is larger than the above range, the mechanical strength of the separator is lowered and the insulating property tends to be lowered.
• the average pore size of the separator is also arbitrary, but is usually 0.5 ⁇ m or less, preferably 0.2 ⁇ m or less, and usually 0.05 ⁇ m or more. If the average hole diameter exceeds the above range, a short circuit is likely to occur. Further, if it is below the above range, the film resistance may increase and the rate characteristics may deteriorate.
• oxides such as alumina and silicon dioxide
• nitrides such as aluminum nitride and silicon nitride
• sulfates such as barium sulfate and calcium sulfate are used, and those having a particle shape or a fiber shape are used. Used.
• a thin film such as a non-woven fabric, a woven fabric, or a microporous film is used.
• a thin film shape a thin film having a pore diameter of 0.01 to 1 ⁇ m and a thickness of 5 to 50 ⁇ m is preferably used.
• a separator formed by forming a composite porous layer containing the particles of the inorganic substance on the surface layer of the positive electrode and / or the negative electrode using a resin binder can be used.
• alumina particles having a 90% particle size of less than 1 ⁇ m may be formed on both sides of the positive electrode by using a fluororesin as a binder to form a porous layer.
• the ratio of the volume of the electrode mixture group to the internal volume of the battery (hereinafter referred to as the electrode mixture group occupancy rate) is usually the same. It is 40% or more, preferably 50% or more, and usually 90% or less, preferably 80% or less.
• the battery capacity may decrease. Further, if it exceeds the above range, the void space is small, and the internal pressure rises due to the expansion of the member due to the high temperature of the battery and the increase of the vapor pressure of the liquid component of the electrolyte, and the charge / discharge repetition performance as a battery. In some cases, various characteristics such as high temperature storage may be deteriorated, and further, a gas discharge valve that releases internal pressure to the outside may operate.
• the current collecting structure is not particularly limited, but in order to more effectively improve the charge / discharge characteristics of high current density by the electrolytic solution, it is preferable to have a structure that reduces the resistance of the wiring portion and the joint portion. When the internal resistance is reduced in this way, the effect of using the electrolytic solution is particularly well exhibited.
• the electrode mixture group has the above-mentioned laminated structure
• a structure formed by bundling the metal core portions of each electrode combination layer and welding them to the terminals is preferably used.
• the internal resistance becomes large. Therefore, it is also preferably used to reduce the resistance by providing a plurality of terminals in the electrode mixture.
• the internal resistance can be reduced by providing a plurality of lead structures on the positive electrode and the negative electrode and bundling them in the terminals.
• the material of the outer case is not particularly limited as long as it is a substance stable to the electrolytic solution used. Specifically, a nickel-plated steel plate, a metal such as stainless steel, aluminum or an aluminum alloy, a magnesium alloy, or a laminated film (laminated film) of a resin and an aluminum foil is used. From the viewpoint of weight reduction, aluminum or an aluminum alloy metal or a laminated film is preferably used.
• the metals are welded together by laser welding, resistance welding, or ultrasonic welding to form a sealed structure, or the above metals are used to form a caulking structure via a resin gasket. Things can be mentioned.
• the outer case using the above-mentioned laminated film include a case in which resin layers are heat-sealed to form a sealed and sealed structure.
• a resin different from the resin used for the laminated film may be interposed between the resin layers.
• the resin layer is heat-sealed via the current collecting terminal to form a closed structure, the metal and the resin are bonded to each other. Resin is preferably used.
• the shape of the secondary battery of the present disclosure is arbitrary, and examples thereof include a cylindrical type, a square type, a laminated type, a coin type, and a large size.
• the shapes and configurations of the positive electrode, the negative electrode, and the separator can be changed and used according to the shape of each battery.
• PTFE-A was obtained as an aqueous dispersion of PTFE (solid content: 31.2% by mass) with reference to Preparation Example 2 of International Publication No. 2015-080291. As a result of the measurement, the standard specific gravity was 2.16.
• Li-100 acetylene black
• ultrapure water was added as a solvent
• the mixture was stirred at 2000 rpm for 3 minutes using a mixer to prepare a conductive auxiliary agent dispersion liquid.
• 4.75 g of the aqueous dispersion PTFE-A was added as a solid content
• ultrapure water was further added to adjust the concentration of the solid content.
• the final amount of solvent was 45 g, and then the mixture was adjusted by stirring with a mix rotor for 1 hour.
• a dry powder was obtained using a spray dryer (manufactured by Tokyo Rika Kikai Co., Ltd.) (inlet temperature 140 ° C., air volume 0.60 cubic meters / min, flow rate 5.5 g / min). Further, vacuum drying (100 ° C., 8 hours) was carried out to obtain a binder 1.
• a spray dryer manufactured by Tokyo Rika Kikai Co., Ltd.
• vacuum drying 100 ° C., 8 hours
• binders 2 to 11 As a result of measuring the water content of the binders 1 to 11, all of them were 250 PPM or less.
• Example 1 ⁇ Preparation of positive electrode mixture sheet> Li (Ni 0.6 Mn 0.2 Co 0.2 ) O 2 (NMC622) as the positive electrode active material and Li- as the conductive auxiliary agent while adding the amount of the conductive auxiliary agent contained in the binder to be added later.
• 100 was weighed and stirred with a mixer at 1500 rpm for 10 minutes to give a mixture.
• the prepared binder 1 was added to a container containing the mixture, and the mixture was stirred with a kneader at 40 rpm for 2 hours to obtain a mixed powder composition.
• the obtained mixed powder composition was formed into a bulk shape and rolled into a sheet shape. Then, the rolled sheet obtained earlier is roughly crushed by folding it in two, molded into a bulk shape again, and then rolled into a sheet shape using a metal roll on a hot plate heated to 80 degrees. , The process of promoting fibrillation was repeated 4 times. Then, it was further rolled to obtain a positive electrode mixture sheet having a thickness of about 500 ⁇ m. Further, the positive electrode mixture sheet was cut into 5 cm ⁇ 5 cm, put into a roll press machine heated to 80 ° C., and rolled. Further, in order to promote fibrillation, a load of 2 kN was repeatedly applied to adjust the thickness. The gap was adjusted so that the final thickness of the positive electrode mixture layer was 90 ⁇ m and the density was 3.20 g / cc to obtain a positive electrode mixture sheet.
• the positive electrode mixture sheet is cut into squares having a width of 5.0 cm and a length of 10 cm to obtain test pieces.
• the four-terminal resistance of the positive electrode active material layer was measured according to JIS K7194; 1994 using a resistivity meter Loresta GP (manufactured by Mitsubishi Chemical Corporation). The smaller the resistance value, the better the battery characteristics.
• Example 2 A positive electrode mixture sheet was obtained in the same manner as in Example 1 except that the binder having the composition shown in Table 1 was used.
• Example 4 A positive electrode mixture sheet was obtained in the same manner as in Example 1 except that the conductive auxiliary agent to be mixed with NMC in a mixer was changed to Super-P Li (furness black) and the binder having the composition shown in Table 1 was used. rice field.
• Example 11 A positive electrode mixture sheet was obtained in the same manner as in Example 1 except that the conductive auxiliary agent to be mixed with NMC in a mixer was changed to carbon ECP (Ketchen Black) and the binder having the composition shown in Table 1 was used. ..
• Example 8 and 9 Li (Ni 0.8 Mn 0.1 Co 0.1 ) O 2 (NMC811) was used as the positive electrode active material, Li-100 was used as the conductive auxiliary agent, and the binder 8 was used.
• Example 10 Li (Ni 0.8 Mn 0.1 Co 0.1 ) O 2 (NMC811) was used as the positive electrode active material, Li-100 was used as the conductive auxiliary agent, and the binder 10 was used.
• a positive electrode mixture sheet was obtained in the same manner as in Example 1.
• the positive electrode mixture sheet was adhered to a 20 ⁇ m aluminum foil.
• As the adhesive a slurry in which polyvinylidene fluoride (PVDF) was dissolved in N-methylpyrrolidone (NMP) and carbon nanotubes (CNT) were dispersed was used.
• PVDF polyvinylidene fluoride
• NMP N-methylpyrrolidone
• CNT carbon nanotubes
• a coin battery was manufactured using the positive electrode sheet, the polyethylene separator, and Li metal as the negative electrode prepared above. Specifically, the separator was sandwiched between the positive electrode and the negative electrode in the dry room to form an electrode body battery.
• This electrode body battery was housed in a battery case (CR2032 type coin battery member) made of a stainless steel container. The electrolytic solution was injected into the battery case. The battery case was sealed with a caulking machine to obtain the non-aqueous electrolyte lithium ion secondary battery of the example.
• Example 1 A non-aqueous electrolyte lithium ion secondary battery was obtained in the same manner as in Example 1 except that the powdery PTFE-E containing no conductive auxiliary agent was used.
• Example 2 A non-aqueous electrolyte lithium ion secondary battery was obtained in the same manner as in Example 1 except that the powdery PTFE-E containing no conductive auxiliary was used and the conductive auxiliary was changed to Super-P Li.
• NMC811 as the positive electrode active material and Li-100 and FT7000 as the conductive auxiliary agent were weighed and stirred with a mixer at 1500 rpm for 10 minutes to obtain a mixture.
• the prepared powdery PTFE-E was added to a container containing the mixture, and the mixture was stirred with a kneader at 40 rpm for 2 hours to obtain a mixed powder composition.
• An electrode mixture sheet was prepared in the same procedure as in Example 8 to obtain a non-aqueous electrolyte lithium ion secondary battery.
• Example 8 Since it was seen as agglomerates in the dispersion before drying, spray drying was not performed, and the mixture was dried on a hot plate at 110 ° C. for 1 hour. Further vacuum drying (100 ° C., 8 hours) was carried out to obtain a mixed powder composition.
• An electrode mixture sheet was prepared in the same procedure as in Example 8 to obtain a non-aqueous electrolyte lithium ion secondary battery.
• the median fibril diameters of Examples 1 and 3 were 40 and 31 nm, respectively.
• the median fibril diameters of Examples 4 and 5 were 33 and 43 nm, respectively.
• the median fibril diameters of Examples 9, 10 and 11 were 51, 67 and 40 nm, respectively.
• Comparative Example 1 and Examples 1 to 3 it can be seen that an electrode having high tensile strength and low resistance can be produced. Further, a suitable range of the conductive material and PTFE was found from Comparative Example 2 and Examples 4 to 7. Further, from Comparative Examples 3 and 8, it was found that the battery characteristics can be improved by using a binder which is a powder containing no electrode active material.
• the method for manufacturing an electrode for a secondary battery using the non-aqueous electrolytic solution of the present disclosure can be used for manufacturing an electrode used for a battery such as a lithium ion secondary battery.

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