US-12620583-B2 - Electrochemical element, method for manufacturing same, and electrochemical device

Abstract

An electrochemical element includes a current collector, and an active material layer supported on the current collector, wherein the active material layer contains lithium silicate composite particles each including a lithium silicate phase, and silicon particles dispersed in the lithium silicate phase, and an electrically conductive carbon material, a first coating covers at least a portion of a surface of the lithium silicate composite particles and at least a portion of a surface of the electrically conductive carbon material, the first coating includes an oxide of a first element other than a non-metal element, and T1 A >T1 C is satisfied, where T1 A is an average thickness of the first coating that covers at least a portion of the surface of the lithium silicate composite particles, and T1 C is an average thickness of the first coating that covers at least a portion of the surface of the electrically conductive carbon material.

Inventors

• Yoshinori Satou
• Shuhei Uchida

Assignees

• PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.

Dates

Publication Date

20260505

Application Date

20201217

Priority Date

20200131

Claims (15)

1. 1 . An electrochemical element comprising a current collector, and an active material layer supported on the current collector, wherein the active material layer contains lithium silicate composite particles each including a lithium silicate phase, and silicon particles dispersed in the lithium silicate phase, and an electrically conductive carbon material, a first coating covers at least a portion of a surface of the lithium silicate composite particles and at least a portion of a surface of the electrically conductive carbon material, the first coating includes an oxide of a first element other than a non-metal element, and T1 A >T1 C is satisfied, where T1 A is an average thickness of the first coating that covers at least a portion of the surface of the lithium silicate composite particles, and T1 C is an average thickness of the first coating that covers at least a portion of the surface of the electrically conductive carbon material.
2. 2 . The electrochemical element of claim 1 , wherein the electrically conductive carbon material includes at least one selected from the group consisting of graphite, a hard carbon, and a soft carbon.
3. 3 . The electrochemical element of claim 1 , wherein the average thickness T1 A and the average thickness T1 C satisfy 0.02≤T1 C /T1 A <1.
4. 4 . The electrochemical element of claim 1 , wherein the first element is at least one element selected from the group consisting of Group 3 elements, Group 4 elements, Group 5 elements, and Group 6 elements of a periodic table.
5. 5 . The electrochemical element of claim 1 , wherein the first element includes at least one selected from the group consisting of Al, Ti, Si, Zr, Mg, Nb, Ta, Sn, Ni, and Cr.
6. 6 . The electrochemical element of claim 1 , wherein the average thickness TIA is 0.1 nm or more and 50 nm or less.
7. 7 . The electrochemical element of claim 1 , wherein the active material layer has a thickness TA, and T1b>T1t is satisfied, where T1b is a thickness of the first coating that covers the lithium silicate composite particles at a position of 0.25TA in the active material layer from the surface of the current collector, and T1t is a thickness of the first coating that covers the lithium silicate composite particles at a position of 0.75TA in the active material layer from the surface of the current collector.
8. 8 . The electrochemical element of claim 1 , wherein Cb>Ct is satisfied, where Cb is a concentration by atomic % of the first element that covers the surface of the lithium silicate composite particles at a position of 0.25T1 A in the first coating from the surface of the lithium silicate composite particles, and Ct is a concentration by atomic % of the first element at a position of 0.75T1 A from the surface of the lithium silicate composite particles.
9. 9 . The electrochemical element of claim 1 , wherein the first coating that covers at least a portion of the surface of the lithium silicate composite particles further contains carbon.
10. 10 . The electrochemical element of claim 1 , wherein at least a portion of the first coating that covers at least a portion of the surface of the lithium silicate composite particles is further covered with an electrically conductive second coating that is different in constituent element from the first coating.
11. 11 . The electrochemical element of claim 10 , wherein the electrically conductive second coating includes carbon atoms.
12. 12 . The electrochemical element of claim 10 , wherein the thickness TIA of the first coating that covers at least a portion of the surface of the lithium silicate composite particles and the thickness T2 A of the electrically conductive second coating satisfy the relation of 0<T1 A /T2 A <1500.
13. 13 . The electrochemical element of claim 11 , wherein Rb>Rt is satisfied, where Rb is an atomic ratio of the first element relative to the carbon atoms at a position of 0.25T1 A in the first coating that covers at least a portion of the surface of the lithium silicate composite particles from the surface of the lithium silicate composite particles, and Rt is an atomic ratio of the first element relative to the carbon atom at a position of 0.75T1 A from the surface of the lithium silicate composite particles.
14. 14 . An electrochemical device including a first electrode, a second electrode, and a separator interposed therebetween, wherein one of the first electrode and the second electrode is composed of the electrochemical element of claim 1 .
15. 15 . An electrochemical element comprising a current collector, and an active material layer supported on the current collector, wherein the active material layer contains lithium silicate composite particles each including a lithium silicate phase, and silicon particles dispersed in the lithium silicate phase, and an electrically conductive carbon material, a first coating covers at least a portion of a surface of the lithium silicate composite particles and at least a portion of a surface of the electrically conductive carbon material, the first coating includes an oxide of a first element other than a non-metal element, and T1 A >T1 C is satisfied, where T1 A is an average thickness of the first coating that covers at least a portion of the surface of the lithium silicate composite particles, T1 C is an average thickness of the first coating that covers at least a portion of the surface of the electrically conductive carbon material, at least a portion of the first coating that covers at least a portion of the surface of the lithium silicate composite particles is further covered with an electrically conductive second coating including carbon atoms, and the thickness T1A of the first coating that covers at least a portion of the surface of the lithium silicate composite particles and the thickness T2A of the second coating satisfy the relation of 0<T1A/T2A<1500.

Description

TECHNICAL FIELD The present disclosure relates mainly to an improvement in an active material layer. BACKGROUND ART Along with the diversification of electrochemical device applications, various performance improvements are required. In this regard, Patent Literature 1 proposes covering a surface of the positive electrode and negative electrode with a metal oxide. CITATION LIST Patent Literature PLT1: Japanese Laid-Open Patent Publication No. 2017-97999 SUMMARY OF INVENTION As one of the characteristics of electrochemical devices, a higher capacity is required. For example, in lithium ion secondary batteries, use of a silicon compound as a negative electrode material has been considered. It is also known that silicon compounds are more susceptible to erosion by side reactions during battery operation than when using a carbon material as the negative electrode material. Therefore, even when a silicon compound is used as the active material particles, it is required to suppress a decrease in the capacity retention rate of electrochemical devices. An aspect of the present disclosure relates to an electrochemical element including a current collector, and an active material layer supported on the current collector, wherein the active material layer contains lithium silicate composite particles each including a lithium silicate phase, and silicon particles dispersed in the lithium silicate phase, and an electrically conductive carbon material, a first coating covers at least a portion of a surface of the lithium silicate composite particles and at least a portion of a surface of the electrically conductive carbon material, the first coating includes an oxide of a first element other than a non-metal element, and T1A>T1C is satisfied, where T1A is an average thickness of the first coating that covers at least a portion of the surface of the lithium silicate composite particles, and T1C is an average thickness of the first coating that covers at least a portion of the surface of the electrically conductive carbon material. Another aspect of the present disclosure relates to an electrochemical device including a first electrode, a second electrode, and a separator interposed therebetween, wherein one of the first electrode and the second electrode is composed of the electrochemical device described above. Still another aspect of the present disclosure relates to a method of producing an electrochemical element including: a preparation step, of preparing lithium silicate composite particles each including a lithium silicate phase and silicon particles dispersed in the lithium silicate phase, and an electrically conductive carbon material; a supporting step, of allowing the lithium silicate composite particles and the electrically conductive carbon material to be supported on a surface of a current collector, and a coating formation step, following the supporting step, of allowing the lithium silicate composite particles and the electrically conductive carbon material to expose in a gas phase including a first element other than a non-metal element to form a first coating including an oxide of the first element, on at least a portion of a surface of each of them. With the present disclosure, chemical stability of the active material layer can be improved. Thus, the present disclosure can provide a long life electrochemical device. BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a schematic cross sectional view of a main portion of the electrochemical element of an embodiment of the present disclosure. FIG. 2 is a schematic cross sectional view of a further enlarged main portion of the electrochemical element shown in FIG. 1. FIG. 3 is a schematic cross sectional view illustrating the first active material of an embodiment of the present disclosure in detail. FIG. 4 is a schematic oblique cutaway view of a nonaqueous electrolyte secondary battery of an embodiment of the present disclosure. FIG. 5 is a flowchart illustrating a method of producing an electrochemical element of an embodiment of the present disclosure. DESCRIPTION OF EMBODIMENTS A. Electrochemical Element The electrochemical element of an embodiment of the present disclosure includes a current collector and an active material layer supported on the current collector. The active material layer includes lithium silicate composite particles and an electrically conductive carbon material. A first coating covers at least a portion of a surface of the lithium silicate composite particles and a surface of the electrically conductive carbon material. The first coating includes an oxide of the first element other than a non-metal element. The lithium silicate composite particles are covered with the first coating that is thicker than the electrically conductive carbon material. This allows for suppressing erosion of the lithium silicate composite particles, and their expansions can also be suppressed. Meanwhile, the first coating that covers the electrically conductive ca