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JP-7855520-B2 - Method for preparing negative electrode paste for lithium-ion batteries

JP7855520B2JP 7855520 B2JP7855520 B2JP 7855520B2JP-7855520-B2

Inventors

  • プレチェケンスキー， ミハイル ルドルフォビッチ
  • カシン， アレクサンダー アレクサンドロビッチ
  • ボブレノク， オレグ フィリッポビッチ
  • コソラポブ， アンドリー ゲナディエビッチ

Assignees

  • エムシーディ テクノロジーズ エス エー アール エル

Dates

Publication Date
20260508
Application Date
20210723
Priority Date
20201019

Claims (19)

  1. A method for preparing a negative electrode slurry for a lithium-ion battery, wherein the drying material of the negative electrode slurry contains more than 50% to less than 99.9% by weight of an active ingredient, which is a silicon phase or a silicon oxide ( SiO₂x , where x is a positive number of 2 or less) phase, or a combination of a silicon phase and a silicon oxide ( SiO₂x ) phase in which the total atomic ratio of oxygen:silicon content in the negative electrode material is greater than 0 to less than 1.8, and also contains more than 0.1% to less than 20% by weight of carbon nanotubes, and the method is A method comprising the steps of: (1) introducing a composition (C) comprising the silicon phase or the silicon oxide (SiO x , where x is a positive number of 2 or less) phase, or a combination thereof, wherein the total atomic ratio of oxygen to silicon in the combination of phases is greater than 0 to less than 1.8, into a liquid suspension (S) containing 0.01% to 5% by weight of carbon nanotubes, wherein more than 5% by weight of all carbon nanotubes in the suspension (S) are bundled single-layer and/or double-layer carbon nanotubes having a bundle length of more than 10 μm, and the mode of the hydrodynamic diameter distribution of the number of bundles of carbon nanotubes in the suspension (S) is less than 500 nm; and (2) mixing the mixture of the composition (C) in the suspension (S) until a uniform slurry is obtained.
  2. The method according to claim 1, wherein the hydrodynamic diameter distribution of the number of carbon nanotube bundles in the suspension (S) is bimodal.
  3. The method according to claim 1, comprising introducing the composition (C) containing the aforementioned combination of silicon and silicon oxide ( SiO₂x ) phases into the suspension (S) containing carbon nanotubes, while simultaneously introducing graphite and/or binder additives and/or dispersants and/or solvents.
  4. The method according to claim 1, further comprising one or more steps of introducing graphite and/or binder additives and/or dispersants and/or solvents into the suspension (S) containing carbon nanotubes, or into the mixture of the composition (C) in the suspension (S).
  5. The method according to claim 1, wherein the silicon and silicon oxide phases in the composition (C) are aggregated into bound aggregates having a diameter with a median distribution of more than 5 μm.
  6. The method according to claim 1, wherein the size of the X-ray coherent scattering domains in the silicon and silicon oxide phases is less than 10 nm.
  7. The method according to claim 1, wherein the surface of the silicon and silicon oxide aggregates is covered with a carbon layer, and the mass ratio of C:Si in the composition (C) is greater than 0.01 and less than 0.1.
  8. The method according to claim 1, wherein the carbon nanotubes in the suspension (S) are characterized by having a G/D band intensity ratio greater than 5 in the Raman spectrum at a wavelength of 532 nm.
  9. The method according to claim 8, wherein the carbon nanotubes in the suspension (S) are characterized by having a G/D band intensity ratio greater than 50 in the Raman spectrum at a wavelength of 532 nm.
  10. The method according to claim 1, wherein the carbon nanotube in the composite material contains more than 0.1% by weight of a functional group on its surface that includes an element having a higher Pauling electronegativity than carbon.
  11. The method according to claim 10, wherein the carbon nanotubes in the suspension (S) contain more than 0.1% by weight of a functional group on their surface, the functional group comprising at least one of the following elements: oxygen, fluorine, or chlorine.
  12. The method according to claim 11, wherein the carbon nanotubes in the suspension (S) contain more than 0.1% by weight of carboxyl groups on their surface .
  13. The method according to claim 1, wherein the suspension (S) containing 0.01 to 5% by weight of carbon nanotubes is an aqueous suspension or a suspension of a polar organic solvent having a bipolar moment greater than 1.5D.
  14. The method according to claim 13 , wherein the suspension (S) containing 0.01 to 5% by weight of carbon nanotubes is a suspension of n-methylpyrrolidone.
  15. A negative electrode slurry for lithium-ion batteries, (1) Silicon phase or silicon oxide (SiO x An active ingredient comprising a phase (wherein x is a positive number less than or equal to 2) or a combination of such phases, wherein the total atomic ratio of oxygen:silicon content in the combination of phases is greater than 0 and less than 1.8, (2) Carbon nanotubes, Of all the carbon nanotubes in the negative electrode slurry, more than 5% by weight of carbon nanotubes have a bundle length of more than 10 μm and are bundled single-layer and/or double-layer carbon nanotubes. The mode of the bundle length distribution of the number of carbon nanotube bundles in the negative electrode slurry is less than 5 μm. The dried material of the negative electrode slurry contains more than 50% by weight and less than 99.9% by weight of the active component. The total atomic ratio of oxygen to silicon content in the dry material of the negative electrode slurry is greater than 0 and less than 1.8. A negative electrode slurry wherein the dried material of the negative electrode slurry contains 0.1% to less than 20% by weight of carbon nanotubes.
  16. The negative electrode slurry according to claim 15, wherein the slurry comprises one or more binding polymer substances selected from polyvinylidene fluoride, styrene butadiene rubber, its latex, carboxymethylcellulose, its sodium salt, its Li salt, polyacrylic acid, its sodium salt, its Li salt, fluoroelastomers and their latex, and/or one or more dispersants selected from carboxymethylcellulose, its sodium salt, its Li salt, polyacrylic acid, its sodium salt, its Li salt, and polyvinylpyrrolidone .
  17. The negative electrode slurry according to claim 15, wherein the slurry differs in composition and structure from carbon nanotubes and comprises more than 0.1% by weight of one or more conductive additives selected from carbon black, graphite, and metals of groups 8 to 11 of the periodic table.
  18. A method for fabricating a negative electrode for lithium-ion batteries, (1) Silicon phase or silicon oxide (SiO x A step of introducing a composition (C) containing an active ingredient, which includes a phase (wherein x is a positive number less than or equal to 2) or a combination of such phases, wherein the total atomic ratio of oxygen:silicon in the combination of phases is greater than 0 to less than 1.8, into a liquid phase suspension (S) containing 0.01% to 5% by weight of carbon nanotubes, wherein more than 5% by weight of all carbon nanotubes in the suspension (S) are bundled single-layer and/or double-layer carbon nanotubes having a bundle length of more than 10 μm, and the mode of the hydrodynamic diameter distribution of the number of bundles of carbon nanotubes in the suspension (S) is less than 500 nm. (2) A step of mixing the mixture of composition (C) in the suspension (S) until a uniform negative electrode slurry is obtained, After step (2), the dried material of the uniform negative electrode slurry contains 50% to less than 99.9% by weight of the active ingredient. The total atomic ratio of oxygen to silicon content in the dry material of the homogeneous negative electrode slurry is greater than 0 and less than 1.8. The drying material of the homogeneous negative electrode slurry contains more than 0.1% by weight and less than 20% by weight of carbon nanotubes, in the process, (3) A step of coating the homogeneous negative electrode slurry onto the current collector of the lithium-ion battery, (4) A method comprising the steps of drying the coated uniform negative electrode slurry to form the negative electrode of the lithium-ion battery, and (5) compressing the negative electrode.
  19. A negative electrode for lithium-ion batteries, (1) Current collector and (2) Silicon phase or silicon oxide (SiO x An active ingredient comprising a phase (wherein x is a positive number less than or equal to 2) or a combination of such phases, wherein the total atomic ratio of oxygen:silicon content in the combination of phases is greater than 0 and less than 1.8, (3) Carbon nanotubes, Of all the carbon nanotubes in the negative electrode, more than 5% by weight of the carbon nanotubes have a bundle length of more than 10 μm and are bundled single-layer and/or double-layer carbon nanotubes. The mode of the bundle length distribution of the number of carbon nanotube bundles in the negative electrode is less than 5 μm. The active component constitutes more than 50% by weight and less than 99.9% by weight of the negative electrode, excluding the current collector. The total atomic ratio of oxygen to silicon content in the negative electrode is greater than 0 and less than 1.8. A negative electrode in which the carbon nanotubes constitute 0.1% to less than 20% by weight of the negative electrode, excluding the current collector.

Description

This invention relates to the electrical industry, particularly to lithium-ion batteries, and more specifically to lithium-ion batteries equipped with a silicon-containing anode, and to the anode of a lithium-ion battery. When used in lithium-ion batteries, silicon-containing anodes offer several advantages. The most significant of these is their high specific capacity, theoretically reaching 4200 mAh/g. However, the lifespan of such materials—that is, the number of charge-discharge cycles they can withstand while maintaining their capacity compared to carbon-based anodes—is generally lower. This is related to the fact that during battery charging, the interaction between silicon (density 2.33 g/cm³) and lithium forms a Li₂₂Si₅ phase (density 0.96 g / cm³ , silicon weight fraction 48 wt%), increasing the volume of the active component particles by 400% (5 times). After multiple charge-discharge cycles, voids form between the silicon particles constituting the anode composite material, and these voids bond together to form cracks. After several cycles, the anode loses its integrity, leading to insulation in parts of the anode and a decrease in battery capacity. Ultimately, the anode is completely destroyed. This is a major challenge limiting the widespread application of silicon and silicon-containing anodes in lithium-ion batteries. To ensure the efficiency of a silicon-containing anode over a sufficiently large number of charge-discharge cycles in a lithium-ion battery, both the integrity of the silicon-containing anode and the high conductivity of the material must be provided. Manufacturing a silicon-containing anode with a high specific capacity, such as 500 mAh/g, and capable of retaining that capacity over a sufficiently large number of charge-discharge cycles, such as maintaining over 80% of the initial capacity over more than 500 cycles, is a challenging technical problem, but the present invention provides a solution. As used herein, the term "negative electrode material" refers to a composite material of a negative electrode without a current collector. As used herein, the term "negative electrode active material" refers to a combination of materials within the negative electrode that chemically react with lithium during the battery charging process, such as graphite, silicon, or silicon oxide (SiO). To ensure reliable operation through multiple charge-discharge cycles without loss of battery capacity, several patents and research publications propose the use of silicon-carbon composites with relatively low volume change during the lithiumization process during charging as the anode active material. However, this approach does not solve these problems because it has inherent limitations related to the primary dependence of the specific capacity of the anode material on the relative volume change during lithiumization. Therefore, relatively low volume change means a low specific capacity of the battery. Another proposed solution involves pre-forming a porous structure in the silicon-containing anode material so that the formed lithium silicate fills the pores. This prevents the aggregation of composite aggregates over tens of charge-discharge cycles. Therefore, the disclosures [Patent Document 1] and [Patent Document 2] provide Si/C nanocomposites in which crystalline or amorphous carbon particles are embedded in pores derived from porous silicon particles. Disclosure [Patent Document 1] also provides a method for producing such a composite, comprising mixing an alkali metal or alkaline earth metal with a silicon oxide nanocomposite containing crystalline or amorphous carbon; a method for heat-treating such a composite to reduce silicon oxide; and a method for heat-treating the thus obtained composite in an acid to remove alkali metal oxides or alkaline earth metal oxides. The negative electrode material of the cited disclosure has an initial charge capacity of 847–855 mAh/g and retains 73–78% of the initial capacity after 50 cycles. The proposed solutions have two main drawbacks: (1) the complex method for obtaining the anode material, followed by its coating onto the anode current collector, requires an essential modification of existing processes for lithium-ion battery manufacturing; and (2) the insufficient increase in the useful life of the anode material, which remains short compared to graphite anode materials, due to the recrystallization of silicon in the Si/C composite and the gradual breakdown of the formed porous structure. Another solution for obtaining a negative electrode active material with a long useful life is to introduce fibrous carbon particles into the silicon-containing negative electrode material not only as a conductive additive but also as a reinforcing additive. It is known that reinforcement of composite materials can be achieved by introducing additives that have inherently high strength through the preferred use of elongated particles such as fibers. Furthermore, the