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CA-3141700-C - TITANIUM-NIOBIUM OXIDES AND ELECTRODES AND LITHIUM-ION SECONDARY CELLS EMPLOYING TITANIUM-NIOBIUM OXIDES

CA3141700CCA 3141700 CCA3141700 CCA 3141700CCA-3141700-C

Abstract

A titanium-niobium oxide according to the present invention contains less than 0.30 at% of an alkali metal element and at least one element selected from the group consisting of Al, Y, La, Ce, Pr, and Sm. The ratio of the total atomic weight of Al, Y, La, Ce, Pr, and Sm to the total atomic weight of Ti and Nb is equal to or more than 0.001.

Inventors

  • Kenji Higashi
  • Masafumi Yasuda
  • Hiroshi Okumura
  • Yoshiyuki Hirono

Assignees

  • KUBOTA CORPORATION

Dates

Publication Date
20260505
Application Date
20201225
Priority Date
20191226

Claims (5)

  1. CLAIMS [Claim 1] A titanium-niobium oxide containing the elements Ti, Nb, and O, comprising: less than 0.30 at% of an alkali metal element; at least one element selected from the group consisting of Al, Y, La, Ce, Pr, and Sm; a ratio of a total atomic weight of Al, Y, La, Ce, Pr, and Sm to the total atomic weight of Ti and Nb is equal to or more than 0.001, wherein when an aspect ratio given as a ratio of a major-axis length to a minor-axis length of primary particles of the titanium-niobium oxide is represented as a volume lognormal distribution, a proportion of the primary particles of which the aspect ratio is more than three is equal to or less than 11 vol%.
  2. [Claim 2] A titanium-niobium oxide containing the elements Ti, Nb, and O, comprising: less than 0.30 at% of an alkali metal element; at least one element selected from the group consisting of Al, Y, La, Ce, Pr, and Sm; a ratio of a total atomic weight of Al, Y, La, Ce, Pr, and Sm to the total atomic weight of Ti and Nb is equal to or more than 0.001, wherein when a major-axis length of primary particles of the titanium-niobium oxide is represented as a volume log-normal distribution, a proportion of the primary particles of which the major-axis length is more than 3 μm is equal to or less than 5 vol%.
  3. [Claim 3] The titanium-niobium oxide according to claim 1 or 2, wherein part of a surface of the titanium-niobium oxide is coated with a carbon material.
  4. [Claim 4] An electrode, comprising an electrode active material, wherein at least part of the electrode active material is the titanium-niobium oxide according to any one of claims 1 to 3.
  5. [Claim 5] A lithium-ion secondary cell, comprising a cathode and an anode, wherein one of the cathode and anode is the electrode according to claim 4.

Description

DESCRIPTION Title of Invention: TITANIUM-NIOBIUM OXIDES AND ELECTRODES AND LITHIUM-ION SECONDARY CELLS EMPLOYING TITANIUM-NIOBIUM OXIDES Technical Field [0001] The present invention relates to titanium-niobium oxides. The present invention also relates to electrodes that employ a titanium-niobium oxide as an electrode active material, and relates as well to lithium-ion secondary cells that employ such an electrode as a cathode or anode. Background Art [0002] For their high electric capacity and excellent cycle capacity retention ratio, titaniumniobium oxides are expected to be suitable for use as an active material in lithium-ion secondary cells (see, e.g., Patent Document 1 identified below). Citation List Patent Literature [0003] Patent Document 1: Japanese unexamined patent application publication No. 2010- [0004] 287496 Patent Document 2: Japanese unexamined patent application publication No. 2014- 225474 Summary of Invention Technical Problem For example, when a titanium-niobium oxide is synthesized through a solid reaction method, low calcination temperature leads to insufficient reaction, which leaves the intended product, TiNb2O1, adulterated with TiO2 and ThNb10O29. If a titaniumniobium oxide contains TiO2 and ThNb10O29, these degrade the charging-discharging performance of the titanium-niobium oxide. [0005] On the other hand, high calcination temperature, with a view to reducing Date Re9ue/Date Received 2021-11-23 adulteration with TiO2 and Ti2Nb10O29, leads to sufficient reaction, which induces growth of crystal grains (primary particles). Growth of crystal grains, for example, degrades the rate characteristics of lithium-ion secondary cells that employ a titaniumniobium oxide as an electrode active material. [0006] As a remedy, with the aim of achieving sufficient reaction at low calcination temperature, it has been proposed to add an alkali metal element to a titanium-niobium oxide, thereby to increase its reactivity (see, e.g., Patent Document 2 identified above). Inconveniently, simply adding an alkali metal element results in fiber-like growth of crystal grains. This exerts adverse effects such as low active material filling density in electrodes that employ a titanium-niobium oxide as an electrode active material. [0007] Against the background discussed above, an object of the present invention is to provide a titanium-niobium oxide characterized by suppressed adulteration with TiO2 and ThNb10O29 and suppressed growth of crystal grains, and to provide an electrode and a lithium-ion secondary cell that employ such a titanium-niobium oxide. [0008] Solution to Problem To achieve the above object, according to one aspect of the present invention, a titanium-niobium oxide contains: less than 0.30 at% (atomic percent) of an alkali metal element; and at least one element selected from the group consisting of Al, Y, La, Ce, Pr, and Sm. The ratio of the total atomic weight of Al, Y, La, Ce, Pr, and Sm to the total atomic weight of Ti and Nb is equal to or more than 0.001. (A first composition.) [0009] In the titanium-niobium oxide of the first composition described above, the ratio of the total atomic weight of Al, Y, La, Ce, Pr, and Sm to the total atomic weight of Ti and Nb may be equal to or more than 0.002. (A second composition.) [0010] In the titanium-niobium oxide of the first or second composition described above, the ratio of the total atomic weight of Al, Y, La, Ce, Pr, and Sm to the total atomic weight of Ti and Nb may be less than 0.024. (A third composition.) [0011] In the titanium-niobium oxide of the third composition described above, the ratio of the total atomic weight of Y to the total atomic weight of Ti and Nb may be equal to or more than 0.001 but equal to or less than 0.011. (A fourth composition.) [0012] In the titanium-niobium oxide of any of the first to fourth compositions described above, when the aspect ratio given as the ratio of the major-axis length to the minor- Date Re9ue/Date Received 2021-11-23 axis length of primary particles of the titanium-niobium oxide is represented as a volume log-normal distribution, the proportion of the primary particles of which the aspect ratio is more than three may be equal to or less than 11 vol%. (A fifth composition.) [0013] In the titanium-niobium oxide of any of the first to fifth compositions described above, when the major-axis length of primary particles of the titanium-niobium oxide is represented as a volume log-normal distribution, the proportion of the primary particles of which the major-axis length is more than 3 μm may be equal to or less than 5 vol% (volume percent). (A sixth composition.) [0014] In the titanium-niobium oxide of any of the first to sixth compositions described above, part of the surface of the titanium-niobium oxide may be coated with a carbon material. (A seventh composition.) [0015] To achieve the above object, according to another aspect of the present invention, an electrode includes an electrode ac