DE-112012006000-B4 - Secondary battery with non-aqueous electrolyte

Abstract

Secondary battery with non-aqueous electrolyte, comprising a positive electrode active material, the surface of which is coated with a film formed from an inorganic solid electrolyte, wherein the positive electrode active material is a lithium-containing composite oxide with a spinel structure, and contains at least one dopant consisting of Ti and Mg, the secondary battery with non-aqueous electrolyte operates at an electrical potential of 4.5 V or more, and the lithium-containing composite oxide is represented by the composition formula: LiNi 0.5 Mn 1.5 O 4 .

Inventors

• Takeshi, c/o TOYOTA JIDOSHA KABUSHIK Abe
• Yoshitomo, c/o TOYOTA JIDOSHA KABUSHIKI Takebayashi
• Ippei, c/o TOYOTA JIDOSHA KABUSHIKI KAIS Toyoshima

Assignees

• TOYOTA JIDOSHA KABUSHIKI KAISHA

Dates

Publication Date

20260513

Application Date

20120309

Claims (1)

1. Secondary battery with non-aqueous electrolyte, comprising a positive electrode active material whose surface is coated with a film formed from an inorganic solid electrolyte, wherein the positive electrode active material is a lithium-containing composite oxide with a spinel structure and contains at least one of Ti and Mg as a doping, the secondary battery with non-aqueous electrolyte operates at an electrical potential of 4.5 V or more, and the lithium-containing composite oxide is represented by the composition formula: LiNi 0.5 Mn 1.5 O 4

Description

Technical field The present invention relates to a secondary battery with a non-aqueous electrolyte, and more specifically to a secondary battery with a non-aqueous electrolyte having a positive electrode active material, the surface of which is coated with a film formed from an inorganic solid electrolyte. Technical background A conventional technique for producing a secondary battery with a non-aqueous electrolyte was known in which a decomposition reaction of an electrolyte solution at a positive electrode in a high-voltage state is suppressed by coating the surface of a positive electrode active material with a lithium-ion conductive glass in order to reduce a contact area between the positive electrode active material and the electrolyte solution (see patent literature 1). Patent literature 1 describes in examples a battery with a non-aqueous electrolyte and a method for producing a battery with a non-aqueous electrolyte, in which a decomposition reaction of an electrolyte solution in a high-voltage state is suppressed by coating positive electrode active material particles and a conductive material with a lithium-ion conductive glass using a sol-gel process, after a positive electrode plate, including mixed layers containing active materials on both surfaces, has been produced. In contrast, the inventors of the present invention conducted extensive studies regarding a technique for improving the battery characteristics of a secondary battery with a non-aqueous electrolyte by coating the surface of a positive electrode active material, which forms a positive electrode mixed layer, with an inorganic solid electrolyte prior to the fabrication of a positive electrode plate. This reduces the contact area between the positive electrode active material and an electrolyte solution, thereby suppressing a decomposition reaction of the electrolyte solution at the positive electrode. Specifically, the inventors of the present invention conducted studies regarding a coating process in which a precursor of an inorganic solid electrolyte, with which the surface of the positive electrode active material is to be coated, is coated with the precursor of the inorganic solid electrolyte, and undergoes a heat treatment (firing step) for a long time at a high temperature to increase the crystallinity of the coating. It was confirmed that the initial capacity of a battery produced by the high-temperature/long-duration firing step is reduced. The inventors of the present invention hypothesized that the reduction in the battery's initial capacity results from thermal damage to a positive electrode (li-vaporization), and they conducted studies on a novel coating process that replaces the high-temperature/long-duration firing step. As a result, the inventors found a coating process capable of increasing the crystallinity of an inorganic solid electrolyte with which the surface of the positive electrode active material is coated, and of reducing thermal damage to the positive electrode, thus enabling the production of a secondary battery with a non-aqueous electrolyte exhibiting superior battery characteristics compared to conventional batteries. The invention has already been filed (see publication). JP 2013-127 945 A with the priority number JP 2011-250 025 ). Furthermore, the US 6 337 158 B1 A lithium secondary battery with a positive electrode active material of the formula Li x Mn 2-yz Ni y M z O 4 , where M is one of Fe, Co, Ti, V, Mg, Zn, Ga, Nb, Mo and Cu; 0.02≤x≤1.10; 0.25≤y≤0.60; and 0<z≤0.10. The US 2008/020283 A1 describes a positive electrode active material whose surface is at least partially coated with an ion-conducting and electron-conducting layer. Saha H. et al. describe in Journal of Alloys and Compounds, 2011, 509 pp.4235-4241 a cathode active material coated on the surface with lithium borosilicate. Jung KH et al. describe in Journal of Alloys and Compounds, 2011, 509, pp. 4226-4232 the effects of a protective layer of [Li,La]TiO 3 on the electrochemical properties of LiMn 2 O 4 for lithium batteries. WU, H. et al. disclose in Journal of Power Sources, 2010, 195, 9, 2909-2913 “Surface modification of LiNi0.5Mn1.5O4 by ZrP2O7 and ZrO2 for lithium-ion batteries “. Locati, C. et al. describe in Journal of Power Sources, 2007, 174, 847-851 "Mg-doped LiNi0.5Mn1.5O4 spinel for cathode materials" . The US 2011/ 0 200 857 A1 describes further lithiu Ion batteries. The US 2011/ 0 104 553 A1 describes electrochemical cells with a lithium-containing cathode. Citation list Patent literature Patent literature 1: JP 2003-173770 A Summary of the invention Problem to be solved by the invention However, it was found that in the secondary battery with non-aqueous electrolyte obtained by the aforementioned invention, a film (or coating) formed from the inorganic solid electrolyte with which the surface of the positive electrode active material is coated decomposes (e.g., detaches) due to the expansion and contraction of the p