WO2009050585A1 - Batterie secondaire au lithium - Google Patents

Batterie secondaire au lithium Download PDF

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Publication number
WO2009050585A1
WO2009050585A1 PCT/IB2008/003261 IB2008003261W WO2009050585A1 WO 2009050585 A1 WO2009050585 A1 WO 2009050585A1 IB 2008003261 W IB2008003261 W IB 2008003261W WO 2009050585 A1 WO2009050585 A1 WO 2009050585A1
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Prior art keywords
positive electrode
active material
electrode active
electrode layer
current collector
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PCT/IB2008/003261
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English (en)
Inventor
Hideki Nakayama
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Toyota Jidosha Kabushiki Kaisha
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Publication of WO2009050585A1 publication Critical patent/WO2009050585A1/fr

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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
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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 invention relates to a lithium secondary battery.
  • lithium secondary batteries as power sources are practically and widely used in the field of information-processing equipments and communication equipments because the lithium secondary batteries have high energy densities.
  • lithium secondary batteries as power sources are under consideration as power sources of electric motor vehicles in the field of motor vehicles because the development of electric motor vehicles is being hastened due to environmental and resource issues.
  • a positive electrode layer in which a positive electrode active material, a conductive material and a binder are uniformly dispersed are widely used.
  • JP-A-2005-50755 discloses a nonaqueous electrolyte battery-purpose electrode, which has a concentration gradient such that the concentration of the electrode active material is progressively increased from an electrode active material layer surface toward a current collector side in an electrode active material layer formed on the current collector.
  • This technology is intended to reduce the Li-ion diffusion resistance by improving the permeability of an electrolytic solution in the separator-side electrode active material layer, and to reduce the electronic resistance by improving a contacting area between the electrode active material and the current collector in the current collector-side electrode active material layer, so that the high rate characteristics will be improved.
  • the concentration of the positive electrode active material in the positive electrode layer is made higher on the positive electrode current collector side while being made lower on the separator side, the concentration of the positive electrode active material on the separator side becomes relatively low, thus giving rise to a problem of the capacity drop.
  • the concentration of the positive electrode active material in the positive electrode layer is made uniform in the direction of thickness, reaction proceeds only on the positive electrode current collector side of the positive electrode layer, resulting in non-uniform utilization rate of the positive electrode active material in the thickness direction of the positive electrode layer. As a result, the capacity drop may still occur.
  • the invention provides a lithium secondary battery in which the utilization rate of the positive electrode active material is made uniform in the direction of thickness of the positive electrode layer.
  • a lithium secondary battery has: a positive electrode body having a positive electrode current collector, and a positive electrode layer that is formed on the positive electrode current collector; a negative electrode body having a negative electrode current collector, and a negative electrode layer that is formed on the negative electrode current collector; a separator disposed between the positive electrode layer and the negative electrode layer; an organic electrolyte through which lithium ions are conducted between the positive electrode active material and the negative electrode active material.
  • a positive electrode current collector-side surface of the positive electrode layer has a higher Li-ion diffusivity than a separator-side surface of the positive electrode layer.
  • a first positive electrode active material inside which Li-ion diffusivity is high may be provided in the positive electrode current collector-side surface of the positive electrode layer while a second positive electrode active material inside which Li-ion diffusivity is lower than that of the first positive electrode active material may be provided in the separator-side surface of the positive electrode layer.
  • a difference of a diffusion coefficient between the first positive electrode active material and the second positive electrode active material may be equal to or greater than lxl ⁇ "7 cm 2 /s.
  • a crystal structure of the first positive electrode active material may differ from that of the second positive electrode active material.
  • the first positive electrode active material may be formed with a laminated structure; and the second positive electrode active material may be formed with a spinel structure.
  • the first positive electrode active material may be formed of LiNiO 2
  • the second positive electrode active material may be formed of LiMn 2 O 4 .
  • a transition metal forming the first positive electrode active material may differ from a transition metal forming the second positive electrode active material.
  • Each of the first positive electrode active material and the second positive electrode active material may have a laminated structure.
  • the Li-ion diffusivity in the positive electrode layer may decline in a stepwise manner from the positive electrode current collector-side surface toward the separator-side surface.
  • the positive electrode layer may be formed by superimposing a plurality of positive electrode layer-forming layers each of which has a different Li-ion diffusivity.
  • the Li-ion diffusivity in the positive electrode layer may decline in a continuous manner from the positive electrode current collector-side surface toward the separator-side surface.
  • a content of the positive electrode active material may be uniform in a thickness direction of the positive electrode layer.
  • the content of the positive electrode active material in the positive electrode layer may be 90 wt.% to 97 wt.%.
  • FIG. 1 schematically shows a sectional view of a lithium secondary battery according to an embodiment of the invention.
  • FIG. 2 schematically shows a sectional view of a positive electrode body according to the embodiment of the invention.
  • lithium secondary batteries according to embodiments of the invention will be described in detail.
  • a lithium secondary battery has a positive electrode body that has a positive electrode current collector, and a positive electrode layer formed on the positive electrode current collector, a negative electrode body that has a negative electrode current collector, and a negative electrode layer formed on the negative electrode current collector, a separator that is disposed between the positive electrode layer and the negative electrode layer, and an organic electrolyte through which lithium ions are conducted between the positive electrode active material and the negative electrode active material.
  • a positive electrode current collector-side surface of the positive electrode layer has a higher Li-ion diffusivity than a separator-side surface of the positive electrode layer.
  • a first positive electrode active material inside which Li-ion diffusivity is high is provided in the positive electrode current collector-side surface of the positive electrode layer while a second positive electrode active material inside which Li-ion diffusivity is lower than that of the first positive electrode active material is provided in the separator-side surface of the positive electrode layer.
  • a positive electrode active material having a high Li-ion diffusivity inside the positive electrode active material is disposed in the positive electrode current collector-side surface of the positive electrode layer, the Li-ion diffusivity can be made uniform in the thickness direction of the positive electrode layer. Therefore, for example, during the high-rate discharge as well, the utilization rate of the positive electrode active material can be made uniform in the thickness direction of the positive electrode layer can be made uniform, so that high capacity can be obtained.
  • the permeability of an electrolytic solution in the separator-side surface is improved by making low the concentration of the positive electrode active material in the separator-side surface of the positive electrode layer.
  • the concentration of the positive electrode active material in the separator-side surface is relatively low, thus giving rise to the capacity drop.
  • it is possible to achieve a high capacity because there is no need to make the concentration of the positive electrode active material in the separator-side surface of the positive electrode layer low.
  • the degree of utilization of the positive electrode active material is made uniform in the thickness direction of the positive electrode layer, local deterioration of the positive electrode active material may be prevented, and the cycle characteristics may be improved.
  • the uniformization of the degree of utilization of the positive electrode active material even when the electrode active material expands and shrinks in accordance with charging and discharging, the expansion and shrinkage may be alleviated over the whole positive electrode layer, and the stress concentration may be prevented.
  • the cycle characteristics can be further improved.
  • FIG. 1 schematically shows a lithium secondary battery according to the embodiment.
  • the lithium secondary battery shown in FIG. 1 has a positive electrode body 3 having a positive electrode current collector 1 and a positive electrode layer 2 formed on the positive electrode current collector 1, a negative electrode body 6 having a negative electrode current collector 4 and a negative electrode layer 5 formed on the negative electrode current collector 4, a separator 7 disposed between the positive electrode layer 2 and the negative electrode layer 5, and an organic electrolyte (not shown) through which lithium ions are conducted between the positive electrode active material 8 and the negative electrode active material 9.
  • a high-Li-ion-diffusivity positive electrode active material 8a as the first positive electrode active material in which the Li-ion diffusivity inside the positive electrode active material is high is used in the positive electrode current collector 1-side surface of the positive electrode layer 2
  • a low-Li-ion-diffusivity positive electrode active material 8b as the second positive electrode active material having a lower Li-ion diffusivity inside the positive electrode active material than the high-Li-ion-diffusivity positive electrode active material 8a is used in the separator 7-side surface of the positive electrode layer 2.
  • the positive electrode body according to the embodiment has a positive electrode current collector, and a positive electrode layer that is formed on the positive electrode current collector.
  • the positive electrode layer according to the embodiment contains at least a positive electrode active material, and may also contain a conductive material and a binder according to the needs. Furthermore, in this embodiment, a high-Li-ion-diffusivity positive electrode active material whose Li-ion diffusivity inside the positive electrode active material is high is used in the positive electrode current collector-side surface of the positive electrode layer, and a low-Li-ion-diffusivity positive electrode active material having a lower Li-ion diffusivity inside the positive electrode active material than the high-Li-ion-diffusivity positive electrode active material is used in the separator-side surface of the positive electrode layer. Therefore, the Li-ion diffusivity in the positive electrode current collector-side surface of the positive electrode layer is higher than the Li-ion diffusivity in the separator-side surface of the positive 5 electrode layer.
  • the active materials may be appropriately selected so that the Li-ion diffusivity in the positive electrode current collector-side surface of the positive electrode layer is made higher than the Li-ion diffusivity in the separator-side surface of the positive electrode layer.
  • the Li-ion diffusivities of the positive electrode current collector-side surface and the separator-side surface of the positive electrode layer can be evaluated from the
  • L 5 diffusion coefficient that is used for evaluation of the Li-ion diffusivity inside the positive electrode active material, and can also be evaluated from the content of the positive electrode active material, and other factors.
  • the diffusion coefficient will be described later.
  • FIG. 2 schematically shows a cross-sectional view of a positive electrode body according to the embodiment. As shown in FIG. 2, the positive electrode layer 2 is formed on a surface of the positive electrode current collector 1. The "positive electrode current collector-side surface of the positive electrode layer”
  • the "separator-side surface of the positive electrode layer” refers to a region in the positive electrode layer 2 (e.g., a region Y in FIG. 2) that spreads at most from the surface opposite from the positive electrode current collector-side surface to a location in the positive electrode layer 2 that is located at 30% of the thickness of the positive electrode layer 2 in the thickness direction of the positive electrode layer 2.
  • the thickness of the positive electrode layer depends on the use of the lithium secondary battery or the like. However, it is preferable that the thickness of the positive electrode layer be ordinarily within the range of 10 ⁇ m to 250 ⁇ m and, particularly, within the range of 20 ⁇ m to 200 ⁇ m and, more particularly, within the range of 30 ⁇ m to 150 ⁇ m.
  • the positive electrode layer according to the embodiment of the invention is not limited if the embodiment has the foregoing features.
  • the first aspect where crystal structures between the high-Li-ion-diffusivity positive electrode active material and the low-Li-ion-diffusivity positive electrode active material are different from each other
  • transition metals constructing the high-Li-ion-diffusivity positive electrode active material and the low-Li-ion-diffusivity positive electrode active material are different from each other.
  • the crystal structures between the high-Li-ion-diffusivity positive electrode active material and the low-Li-ion-diffusivity positive electrode active material are different from each other.
  • two or more kinds of positive electrode active materials inside which the Li-ion diffusivities are different from each other may be used.
  • positive electrode active materials a positive electrode active material inside which Li-ion diffusivity is relatively high may be regarded as the first positive electrode active material, and a positive electrode active material inside which Li-ion diffusivity is relatively low may be regarded as the second positive electrode active material.
  • the positive electrode active material according to the first aspect may include a laminated positive electrode active material, a spinel-structured positive electrode active material.
  • the Li-ion diffusivity of the laminated positive electrode active material is higher than that of the spinel-structured positive electrode active material.
  • the laminated positive electrode active material may include LiNiO 2 , LiCoO 2 , etc. In particular, LiNiO 2 is preferable.
  • the spinel-structured positive electrode active material may include LiMn 2 O 4 , LiCoMnO 4 , Li 2 NiMn 3 Os, etc. In particular, LiMn 2 O 4 is preferable.
  • the positive electrode active material may be used with a combination of the laminated positive electrode active material and spinel-structured positive electrode active material because the difference of the Li-ion diffusivity inside the positive electrode active material is large.
  • the first positive electrode active material may be a laminated positive electrode active material while the second positive electrode active material may be a spinel-structured positive electrode active material.
  • the first positive electrode active material may be LiNiO 2 while the second positive electrode active material may be LiMn 2 O 4 .
  • it is preferable that the difference of the diffusion coefficient of Li ion between the first positive electrode active material and the second positive electrode active material is within a predetermined range. The difference of the diffusion coefficients will be described later.
  • the average particle diameter of the positive electrode active material be, for example, within the range of 1 ⁇ m to 50 ⁇ m, and, particularly, within the range of 1 ⁇ m to 20 ⁇ m, and, more particularly, within the range of 3 ⁇ m to 5 ⁇ m. If the average particle diameter of the positive electrode active material is excessively small, handling the positive electrode active material may be poor. On the other hand, if the average particle diameter of the positive electrode active material is excessively large, a flat positive electrode layer may not be obtained. In addition, the average particle diameter of the positive electrode active material can be obtained by means of a scanning electron microscope (SEM) in such a manner that, for example, particle diameters of an active material carrier is measured, and then the measured particle diameters are averaged.
  • SEM scanning electron microscope
  • a positive electrode active material having different particle diameters may be used if the Li-ion diffusivity in the positive electrode current collector-side surface of the positive electrode layer is higher than the Li-ion diffusivity in the separator-side surface of the positive electrode layer.
  • two or more kinds of positive electrode active materials may exist in the positive electrode current collector-side surface and/or the separator-side surface.
  • the content of positive electrode active material in the positive electrode layer may be uniform in the thickness direction of the positive electrode layer. According to this construction, the capacity may be increased. Also, it is preferable that the content of the positive electrode active material in the entire positive electrode layer be, for example, within the range of 60 wt.% to 97 wt.%, and, particularly, within the range of 75 wt.% to 97 wt.%, and, more particularly, within the range of 90 wt.% to 97 wt.%.
  • the Li-ion diffusivity in the positive electrode current collector-side surface of the positive electrode layer is higher than the Li-ion diffusivity in the separator-side surface of the positive electrode layer, the Li-ion diffusivity in an intermediate region in the positive electrode layer is not limited.
  • the Li-ion diffusivity in the positive electrode layer may decline in a stepwise manner or in a continuous manner from the positive electrode current collector-side surface toward the separator-side surface. According to this construction, the degree of utilization of the positive electrode active material may be further made uniform.
  • the positive electrode layer be constructed of, for example, two to five positive electrode layer-forming layers, and in particular, be constructed of two or three positive electrode layer-forming layers.
  • the positive electrode layer may contain a conductive material.
  • the conductive material is not limited if the material may improve the electro-conductivity of the positive electrode layer.
  • Examples of the conductive material include carbon blacks, such as acetylene black, Ketjen black, etc.
  • the content of the conductive material in the positive electrode layer depends on the kind of the conductive material, it is preferably within the range of 1 wt.% to 10 wt.%.
  • the positive electrode layer may also contain a binder.
  • the binder include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), etc.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • the content of the binder in the positive electrode layer may be set to such an amount to be able to fix the electrode active material, for example, and a less content of the binder is preferable.
  • the content of the binder may be within the range of 1 wt.% to 10 wt.%.
  • the transition metals constructing the high-Li-ion-diffusivity positive electrode active material and the low-Li-ion-diffusivity positive electrode active material are different from each other. Due to different transition metals, two or more kinds of positive electrode active materials inside which the Li-ion diffusivities are different from each other may be used. Of these positive electrode active materials, a positive electrode active material inside which Li-ion diffusivity is relatively high may be regarded as the first positive electrode active material, and a positive electrode active material inside which Li-ion diffusivity is relatively low may be regarded as the second positive electrode active material.
  • the Li-ion diffusivity inside the positive electrode active material depends on the kind of the transition metal constructing the positive electrode active material.
  • the Li-ion diffusivity inside the positive electrode active material can be evaluated by means of a diffusion coefficient D (cm 2 /s).
  • the diffusion coefficient D of the positive electrode active material can be measured by, for example, a GITT method (Galvanostatic Intermittent Titration Technique), a PITT method (Potentionstatic Intermittent Titration Technique), or an EIS method (Electrochemical Impedance Spectroscopy).
  • the high-Li-ion-diffusivity positive electrode active material has a higher diffusion coefficient than the low-Li-ion-diffusivity positive electrode active material.
  • the difference of the diffusion coefficient between the high-Li-ion-diffusivity positive electrode active material and the low-Li-ion-diffusivity positive electrode active material may be, for example, equal to or above lxl0 '10 cm 2 /s, and, preferably, lxl ⁇ "7 cm 2 /s.
  • the diffusion coefficient of the high-Li-ion-diffusivity positive electrode active material may be, for example, within the range of lxl ⁇ "8 cm 2 /s to lxl ⁇ "6 cm 2 /s, and, in particular, within the range of lxl ⁇ '7 cm 2 /s to lxl ⁇ "6 cm 2 /s.
  • the diffusion coefficient of the low-Li-ion-diffusivity positive electrode active material may be, for example, within the range of lxl0 '10 cm 2 /s to lxl ⁇ "7 cm 2 /s, and, in particular, within the range of lxl ⁇ "lo cm 2 /s to l ⁇ l ⁇ ⁇ 8 cm 2 /s.
  • the high-Li-ion-diffusivity positive electrode active material depends on a combination with the low-Li-ion-diffusivity positive electrode active material.
  • the high-Li-ion-diffusivity positive electrode active material may be LiNiO 2 , LiCoO 2 , etc. In particular, LiNiO 2 is preferable.
  • the low-Li-ion-diffusivity positive electrode active material depends on the combination with the high-Li-ion-diffusivity positive electrode active material. Concretely, the low-Li-ion-diffusivity positive electrode active material may be LiMn 2 O 4 , LiCoMnO 4 , Li 2 NiMn 3 O 8 , etc. In particular, LiMn 2 O 4 is preferable.
  • the crystal structures between the high-Li-ion-diffusivity positive electrode active material and the low-Li-ion-diffusivity positive electrode active material may be the same, or may also be different from each other.
  • the crystal structure of the positive electrode active material in the second aspect is similar to that in the first aspect described above.
  • the high-Li-ion-diffusivity positive electrode active material and the low-Li-ion-diffusivity positive electrode active material may have a laminated structure because the laminated structure has an excellent Li-ion diffusivity inside the positive electrode active material.
  • the average particle diameter and the content of the positive electrode active material according to the second aspect as well as the layer construction of the positive electrode layer are similar to that in the first aspect described above, and therefore details will be omitted.
  • the positive electrode current collector according to the embodiment of the invention collects currents from the positive electrode layer.
  • aluminum, SUS, nickel, iron or titanium may be used as materials of the positive electrode current collector.
  • aluminum or SUS is preferable.
  • the positive electrode current collector may be formed with a foil shape, a plate shape or a mesh shape. In particular, the foil shape is preferable.
  • the method of manufacturing the positive electrode body according to the embodiment is not limited if the foregoing positive electrode body can be obtained.
  • a positive electrode body having a positive electrode layer in which the Li-ion diffusivity in the positive electrode layer declines in a stepwise manner from the positive electrode current collector-side surface toward the separator-side surface is to be formed
  • a first positive electrode layer-forming paste containing a positive electrode active material, a conductive material and a binder is first manufactured.
  • a second positive electrode layer-forming paste containing a binder, a conductive material, and another positive electrode active material having a different Li-ion diffusivity is prepared, and the first and second pastes are sequentially coated on the positive electrode current collector.
  • the positive electrode layer may be pressed in order to improve the electrode density of the positive electrode layer.
  • the manufacture method for the positive electrode body may use the differences in specific gravity between positive electrode active materials having a different Li-ion diffusivity.
  • the first positive electrode active material has a greater specific gravity than the second positive electrode active material
  • a positive electrode layer-forming paste containing these positive electrode active materials and having a predetermined fluidity is prepared, and is coated on the positive electrode current collector.
  • the positive electrode layer-forming paste when the positive electrode layer-forming paste is left at rest while the fluidity of the positive electrode layer is maintained, the first positive electrode active material having a greater specific gravity tends to sink whereas the second positive electrode active material having a smaller specific gravity tends to float.
  • the first positive electrode active material has a smaller specific gravity than the second positive electrode active material, the second positive electrode active material tends to sink whereas the first positive electrode active material tends to float.
  • the positive electrode layer may be pressed in order to improve the electrode density of the positive electrode layer.
  • a manufacture method for a positive electrode body can be provided by the foregoing method.
  • the foregoing definition of the "positive electrode current collector-side surface of the positive electrode layer” and the definition of the positive electrode separator-side surface of the positive electrode layer" may not be applied.
  • the negative electrode body according to the embodiment of the invention has a negative electrode current collector, and a negative electrode layer that is formed on the negative electrode current collector.
  • the negative electrode layer may contain at least a negative electrode active material, and may also contain a binder and a conductive material according to the needs.
  • the negative electrode active material is not limited if lithium ions can be stored and released.
  • metallic lithium, lithium alloys, metal oxides, metal sulfides, metal nitrides, carbon-based materials such as graphite may be used as the negative electrode active material.
  • the negative electrode active material may have a powder form, or a thin-film form. The content of the negative electrode active material contained in the negative electrode layer depends on the kind of the negative electrode active material.
  • the content of the negative electrode active material may be within the range of 60 wt.% to 97 wt.%, and, in particular, within the range of 75 wt.% to 97 wt.%, and, more particularly, with reference to 90 wt.% to 97 wt.%.
  • the binder and the conductive material in the negative electrode layer are similar to those in the foregoing positive electrode layer, and therefore details are omitted. Besides, the amount of the binder and the conductive material may be appropriately selected in accordance with the application of the lithium secondary battery. Besides, the membrane thickness of the negative electrode layer is not limited, and may be, for example, within the range of 10 ⁇ m to 100 ⁇ m, and, in particular, within the range of 10 ⁇ m to 50 ⁇ m.
  • Examples of the material of the negative electrode current collector include copper, SUS and nickel. In particular, copper is preferable.
  • the negative electrode current collector may be formed with a foil shape, a plate shape or a mesh shape. In particular, the foil shape is preferable.
  • the manufacture method for the negative electrode body according to the embodiment is not limited. For example, a negative electrode layer-forming paste containing a negative electrode active material, a binder and a solvent is first prepared. Then, the negative electrode layer-forming paste is coated on the negative electrode current collector, and the negative electrode layer is dried. In this case, the negative electrode layer may also be pressed in order to improve the electrode density of the negative electrode layer.
  • the separator according to the embodiment is disposed between the positive electrode layer and the negative electrode layer.
  • the separator normally prevents the positive electrode layer and the negative electrode layer from contacting each other, and retains the organic electrolyte.
  • the separator may be formed of resins such as polyethylene (PE), .polypropylene (PP), polyester, cellulose or polyamide, for example. In particular, polyethylene or polypropylene is preferable.
  • the separator may have a single-layer structure or may also have a multi-layer structure. As the multi-layer structure separator, double layer separator of polyethylene/polypropylene or triple layer separator of polypropylene/polyethylene/polypropylene may be used.
  • the separator may be made of a non-woven fabric such as a resin non-woven fabric or a glass fiber non-woven fabric.
  • the membrane thickness of the separator is not limited, and may be similar to that of a commonly-used lithium secondary battery.
  • lithium ions are conducted between the positive electrode active material and the negative electrode active material through the organic electrolyte.
  • the organic electrolyte include organic electrolytic solutions, polymer electrolytes or gel electrolytes.
  • a nonaqueous electrolytic solution containing a lithium salt and a nonaqueous solvent is used as the organic electrolytic solution.
  • the lithium salt is not limited if it is a lithium salt that is used in a common lithium secondary battery. Examples of the lithium salt include LiPF 6 , LiBF 4 , LiN(CF 3 SO 2 ) 2 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiC(CF 3 SOa) 3 , LiClO 4 , etc.
  • the nonaqueous solvent is not limited if it is capable of dissolving the lithium salt.
  • the nonaqueous solvent include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, acetonitrile, propionitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, 1,3-dioxolan, nitromethane, N,N-dimethyl formamide, dimethyl sulfoxide, sulfolan, ⁇ -butyrolactone, etc.
  • nonaqueous solvents a single species among the nonaqueous solvents may be used, or a mixture of two or more species among the nonaqueous solvents may also be used.
  • the nonaqueous electrolytic solution may use a room temperature molten salt.
  • the polymer electrolyte contains a lithium salt and a polymer.
  • the lithium salt used in the polymer electrolyte may be similar to that of the foregoing organic electrolytic solution.
  • the polymer is not limited if the polymer forms a complex together with a lithium salt. Examples of the polymer include polyethylene oxide, and the like.
  • the gel electrolyte contains a lithium salt, a polymer, .and a nonaqueous solvent.
  • the lithium salt and the nonaqueous solvent of the gel electrolyte may be similar to those of the foregoing organic electrolytic solution.
  • the polymer is not limited if the polymer is able to gelate. Examples of the polymer include polyethylene oxide, polypropylene oxide, polyacrylonitrile, polyvinylidene fluoride (PVDF), polyurethane, polyacrylate, cellulose, etc.
  • the shape of the battery case according to the embodiment is not limited if the battery case is capable of housing the foregoing positive electrode body, the foregoing negative electrode body, the foregoing separator, and the foregoing organic electrolyte.
  • examples of the shape of the battery case include a cylindrical shape, a square shape, a coin shape, a laminate shape, etc.
  • the lithium secondary battery according to the embodiment has an electrode body that is constructed of the positive electrode layer, the separator, and the negative electrode layer.
  • the shape of the electrode body is not limited. Concretely, examples of the shape of the electrode include a flat plate type, a rolled type, etc.
  • the lithium secondary battery of the embodiment may be manufactured by similar methods of manufacturing a commonly-used lithium secondary battery. For example, a positive electrode body, a negative electrode body and a separator are first housed in a battery case under an inert atmosphere. Then, an organic electrolyte is added into the battery case, and finally the battery case is sealed. Besides, in the embodiment, a lithium secondary battery manufacture method having a positive electrode body formation process by means of the foregoing positive electrode body manufacture method may be provided.
  • the Al current collector foil with the coated slurries was dried and pressed, and then ⁇ l ⁇ mm in diameter was punched thereon. Doing this, the manufacture of the positive electrode body was completed.
  • a negative electrode body graphite was prepared as a negative electrode active material, and polyvinylidene fluoride (PVDF) as a binder, and N-methyl-2-pyrrolidone as a solvent were also prepared. These materials were mixed to manufacture a negative electrode layer-forming slurry. In this case the ratio of negative electrode active material: binder was 92.5:7.5 by weight. Then, the negative electrode layer-forming slurry was coated on a Cu current collector foil of 15 ⁇ m in thickness, by means of a doctor blade to a thickness of 30 ⁇ m. After that, the Cu current collector foil with the coated slurries was dried and pressed, and then ⁇ l9 mm in diameter was punched thereon. Doing this, the manufacture of the negative electrode body was completed.
  • PVDF polyvinylidene fluoride
  • a CR2032-type coin cell was manufactured by using the positive electrode body and the negative electrode body obtained as described above. Incidentally, a polypropylene separator was prepared. As the electrolytic solution, lithium hexafluorophosphate (LiPF 6 ) as a supporting electrolyte was dissolved by a concentration of 1 mol/L to a mixture of EC (ethylene carbonate), DMC (dimethyl carbonate) and EMC (ethyl methyl carbonate) at a ratio of 3:3:4 by volume.
  • LiPF 6 lithium hexafluorophosphate
  • PVDF polyvinylidene fluoride
  • N-methyl-2-pyrrolidone as
  • PVDF polyvinylidene fluoride
  • the second positive electrode layer-forming slurry was coated on the electrode layer that was formed by using the first positive electrode layer-forming slurry, by means of a doctor blade to a thickness of 15 ⁇ m. After that, the Al current collector foil with the slurries was dried and pressed, and then ⁇ l ⁇ mm in diameter was punched thereon. Doing this, the manufacture of the positive electrode body was completed.
  • Comparative Example 1 coin cells were obtained in a similar manner to the forgoing Example 1, except that the first positive electrode layer- forming slurry obtained in Example 1 was only used, and coated on the Al current collector foil by means of the doctor blade to a thickness of 30 ⁇ m.
  • Comparative Example 2 coin cells were obtained in a similar manner to the forgoing Example 1, except that the second positive electrode layer-forming slurry obtained in Example 1 was only used, and coated on the Al current collector foil by means of the doctor blade to a thickness of 30 ⁇ m.
  • Comparative Example 3 coin cells were obtained in a similar manner to the forgoing Example 1, except that the second positive electrode layer-forming slurry obtained in Example 2 was only used, and coated on the Al current collector foil by means of the doctor blade to a thickness of 30 ⁇ m. Then, the high-rate capacity maintenance rates were respectively evaluated by using coin cells obtained in Examples 1 and 2 and Comparative Examples 1 to 3. First, the charging/discharging (upper and lower limit voltages of 4.1V to 3.0V) was performed at a current density of 0.1 mA/cm 2 . Then, the discharge capacity at the time of high rate was measured by increasing the discharge/charge current density in a stepwise manner. The high-rate capacity maintenance rate was evaluated by comparing the discharge capacity at the time of 20 mA/cm 2 with the discharge capacity at the time of 0.1 mA/cm 2 . Results are shown in Table 1. [Table 1]
  • Example 1 As shown in Table 1, it was confirmed in Example 1 that the capacity maintenance rate at the time of high rate was improved by changing the Li-ion diffusivity inside the positive electrode active material due to different crystal structures of positive electrode active materials. From the comparison of the results of Example 1 with the results of Comparative Example 1 and Comparative Example 2, it was confirmed that the capacity maintenance rate at the time of high rate was improved as compared with the cases where only one of the kinds of positive electrode active material in Example 1 was added into the positive electrode layer. Besides, if the discharging/charging was performed at the time of high rate, the contribution of the Li diffusivity in the electrolytic solution increased, in addition to the Li-diffusivity inside the solid (inside the positive electrode active material).
  • Comparative Example 1 it is considered that depletion of Li in the electrolytic solution at the time of high rate occurred at the time of high rate, so that it was not possible to extract sufficient capacity from the entire electrode. This is considered a reason why the results were better in Example 1 than in Comparative Example 1.
  • Example 2 it was confirmed that the capacity maintenance rate at the time of high rate was improved by changing the Li-ion diffusivity inside the positive electrode active material according to different kinds to transition metals that constitute the positive electrode active material. From the comparison of the results of Example 2 with the results of Comparative Example 1 and Comparative Example 3, it was confirmed that the capacity maintenance rate at the time of high rate was improved as compared with the cases where only one of the kinds of positive electrode active materials was added into the positive electrode layer.

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  • Manufacturing & Machinery (AREA)
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Abstract

Une batterie secondaire au lithium possède : un corps d'électrode positive (3) qui comprend un collecteur de courant d'électrode (1) et une couche d'électrode positive (2) formée sur le collecteur de courant d'électrode positive (1) ; un corps d'électrode négative (6) qui comprend un collecteur de courant d'électrode négative (4), et une couche d'électrode négative (5) formée sur le collecteur de courant d'électrode négative (4) ; un séparateur (7) disposé entre la couche d'électrode positive (2) et la couche d'électrode négative (5) ; et un électrolyte organique par lequel des ions de lithium sont conduits entre le matériau actif de l'électrode positive (8) et le matériau actif de l'électrode négative (9). La surface côté collecteur de courant d'électrode positive de la couche d'électrode positive possède une diffusivité d'ions de lithium supérieure à celle de la surface côté séparateur de la couche d'électrode positive.
PCT/IB2008/003261 2007-10-19 2008-10-15 Batterie secondaire au lithium WO2009050585A1 (fr)

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GB2507535A (en) * 2012-11-02 2014-05-07 Nexeon Ltd Multilayer electrode for metal ion battery
DE102015103598A1 (de) 2014-03-24 2015-09-24 Denso Corporation Lithium-Ionen-Sekundärbatterie
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US10077506B2 (en) 2011-06-24 2018-09-18 Nexeon Limited Structured particles
US10090513B2 (en) 2012-06-01 2018-10-02 Nexeon Limited Method of forming silicon
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US10396355B2 (en) 2014-04-09 2019-08-27 Nexeon Ltd. Negative electrode active material for secondary battery and method for manufacturing same
US10476072B2 (en) 2014-12-12 2019-11-12 Nexeon Limited Electrodes for metal-ion batteries
US10586976B2 (en) 2014-04-22 2020-03-10 Nexeon Ltd Negative electrode active material and lithium secondary battery comprising same
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KR101407085B1 (ko) * 2011-05-02 2014-06-19 주식회사 엘지화학 다층의 전극 활물질층을 포함하는 전극 및 이를 포함하는 이차 전지
JP2015011959A (ja) * 2013-07-02 2015-01-19 三菱マテリアル株式会社 リチウムイオン二次電池
JP6608615B2 (ja) * 2015-05-18 2019-11-20 株式会社アルバック 正極活物質膜、および、成膜方法
CN109244475B (zh) 2018-11-05 2024-06-21 宁德新能源科技有限公司 电化学装置及包含其的电子装置
KR20210031038A (ko) * 2019-09-10 2021-03-19 주식회사 엘지화학 리튬이차전지용 양극, 이의 제조방법 및 이를 포함하는 리튬이차전지

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WO2011116831A1 (fr) 2010-03-26 2011-09-29 Nokia Siemens Networks Oy Traitement de signaux relais dans des communications sans fil
US10077506B2 (en) 2011-06-24 2018-09-18 Nexeon Limited Structured particles
US10822713B2 (en) 2011-06-24 2020-11-03 Nexeon Limited Structured particles
US10388948B2 (en) 2012-01-30 2019-08-20 Nexeon Limited Composition of SI/C electro active material
US9548489B2 (en) 2012-01-30 2017-01-17 Nexeon Ltd. Composition of SI/C electro active material
US10103379B2 (en) 2012-02-28 2018-10-16 Nexeon Limited Structured silicon particles
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GB2507535B (en) * 2012-11-02 2015-07-15 Nexeon Ltd Multilayer electrode
GB2507535A (en) * 2012-11-02 2014-05-07 Nexeon Ltd Multilayer electrode for metal ion battery
DE102015103598A1 (de) 2014-03-24 2015-09-24 Denso Corporation Lithium-Ionen-Sekundärbatterie
US10396355B2 (en) 2014-04-09 2019-08-27 Nexeon Ltd. Negative electrode active material for secondary battery and method for manufacturing same
US10693134B2 (en) 2014-04-09 2020-06-23 Nexeon Ltd. Negative electrode active material for secondary battery and method for manufacturing same
US10586976B2 (en) 2014-04-22 2020-03-10 Nexeon Ltd Negative electrode active material and lithium secondary battery comprising same
US10593985B2 (en) 2014-10-15 2020-03-17 Sakti3, Inc. Amorphous cathode material for battery device
US10476072B2 (en) 2014-12-12 2019-11-12 Nexeon Limited Electrodes for metal-ion batteries
EP4246625A1 (fr) * 2022-03-16 2023-09-20 Ningde Amperex Technology Limited Appareil électrochimique et appareil électronique

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