US-12626906-B2 - Positive electrode and electricity storage device

US12626906B2US 12626906 B2US12626906 B2US 12626906B2US-12626906-B2

Abstract

Provided is a positive electrode including: a positive electrode current collector; and a positive electrode material mixture layer, the positive electrode material mixture layer including a positive electrode active material and dielectric particles, the positive electrode having a peak pore diameter smaller than or equal to the median diameter of the dielectric particles. Also provided is an electricity storage device including: the positive electrode; a negative electrode; and an electrolytic solution.

Inventors

Kazuki SAIMEN

Assignees

HONDA MOTOR CO., LTD.

Dates

Publication Date: 20260512
Application Date: 20220208
Priority Date: 20210212

Claims (5)

1 . A lithium-ion secondary battery, comprising: a positive electrode; a negative electrode; and a separator between the positive electrode and the negative electrode, the positive electrode comprising: a positive electrode current collector; and a positive electrode material mixture layer, the positive electrode material mixture layer comprising a positive electrode active material and dielectric particles, the positive electrode active material has a bimodal particle size distribution, the dielectric particles comprising BaZr 0.2 Ti 0.8 O 3 , KNbO 3 , or Li 0.33 La 0.55 TiO 3 , the positive electrode having a peak pore diameter of 0.1 μm or more and 0.6 μm or less, the peak pore diameter being smaller than or equal to a median diameter of the dielectric particles.
2 . The lithium-ion secondary battery according to claim 1 , wherein the positive electrode material mixture layer contains 0.1% by mass or more and 2% by mass or less of the dielectric particles.
3 . The lithium-ion secondary battery according to claim 1 , wherein the dielectric particles have a relative permittivity of 20 or more.
4 . The lithium-ion secondary battery according to claim 1 , wherein the positive electrode has a density of 3.4 g/cc or more.
5 . The lithium-ion secondary battery according to claim 1 , further comprising: an electrolytic solution.

Description

This application is based on and claims the benefit of priority from Japanese Patent Application 2021-020633, filed on 12 Feb. 2021, the content of which is incorporated herein by reference. BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a positive electrode and an electricity storage device. Related Art In the conventional art, lithium-ion secondary batteries are in widespread use as high-energy-density, electricity-storage devices. A typical lithium-ion secondary battery includes a positive electrode, a negative electrode, a separator provided between the electrodes, and an electrolytic solution with which the separator is impregnated. The positive electrode includes, for example, a positive electrode current collector and a positive electrode material mixture layer on the current collector. Patent Document 1 discloses a process that includes impregnating a positive electrode material mixture layer on a positive electrode current collection with a dispersion of dielectric particles having a relative permittivity of 500 or more and particle sizes of 200 nm or less so that the dielectric particles are placed inside the positive electrode material mixture layer. Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2016-119180 SUMMARY OF THE INVENTION Unfortunately, dielectric particles with particle sizes of 200 nm or less tend to aggregate, and the aggregation will cause a reduction in the rate of contact between the dielectric particles and an electrolytic solution if the dielectric particles are used in a large amount. As a result, even when the electric field generated inside the lithium-ion secondary battery acts on the dielectric particles, the dielectric polarization of the dielectric particles will be insufficiently effective in increasing the dissociation degree of the supporting salt in the electrolytic solution, which will cause the problem of an increase in cell resistance. Moreover, the dielectric particles will be insufficiently effective in trapping a small amount of an acid in the electrolytic solution and in interacting with and stabilizing the electrolytic solution, which may make it impossible to prevent the corrosion of the positive electrode active material or the decomposition of the electrolytic solution and lead to a reduction in the durability of the lithium-ion secondary battery. It is an object of the present invention to provide a positive electrode with which an electricity storage device can be produced having lower cell resistance and having higher durability. An aspect of the present invention relates to a positive electrode including: a positive electrode current collector; and a positive electrode material mixture layer, the positive electrode material mixture layer including a positive electrode active material and dielectric particles, the positive electrode having a peak pore diameter smaller than or equal to the median diameter of the dielectric particles. The positive electrode material mixture layer may contain 0.1% by mass or more and 2% by mass or less of the dielectric particles. The dielectric particles may have a relative permittivity of 20 or more. The positive electrode may have a peak pore diameter of 0.1 μm or more and 0.6 μm or less. The positive electrode may have a density of 3.4 g/cc or more. The positive electrode active material may have a bimodal particle size distribution. Another aspect of the present invention relates to an electricity storage device including: the positive electrode defined above; a negative electrode; and an electrolytic solution. The present invention makes it possible to provide a positive electrode with which an electricity storage device can be produced having lower cell resistance and having higher durability. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the results of measurement of the pore diameter distributions of electrodes obtained in Examples 1 to 5 and Comparative Examples 1 to 3; FIG. 2 is a scanning electron microscope (SEM) photograph of a cross-section of the positive electrode of Example 1; and FIG. 3 is an SEM photograph of a cross-section of the positive electrode of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION Hereinafter, embodiments of the present invention will be described. Positive Electrode A positive electrode according to an embodiment of the present invention includes a positive electrode current collector and a positive electrode material mixture layer, in which the positive electrode material mixture layer includes a positive electrode active material and dielectric particles. The positive electrode according to the embodiment has a peak pore diameter smaller than or equal to the median diameter of the dielectric particles. In an embodiment of the present invention, the positive electrode may have the positive electrode material mixture layer on one side of the positive electrode current collector or on each sid