US-12626927-B2 - Positive electrode material and battery

Abstract

A positive electrode material in one aspect of the present disclosure includes: a positive electrode active material; and a first solid electrolyte that covers the surface of the positive electrode active material. The first solid electrolyte contains Li, M1, O, and X1. M1 is at least one element selected from the group consisting of Nb and Ta. X1 is at least one element selected from the group consisting of Cl, Br, and I.

Inventors

• IZURU SASAKI
• Yoshiaki Tanaka
• Kazuya Hashimoto

Assignees

• PANASONIC INTELLECTUAL PROPERTY MANAGEMENT CO., LTD.

Dates

Publication Date

20260512

Application Date

20221005

Priority Date

20200428

Claims (13)

1. 1 . A positive electrode material comprising: a positive electrode active material; and a first solid electrolyte that covers a surface of the positive electrode active material, wherein the first solid electrolyte contains Li, M1, O, and X1, wherein M1 is at least one element selected from the group consisting of Nb and Ta, wherein X1 is at least one element selected from the group consisting of Cl, Br, and I, and wherein a molar ratio O/X1 of O to X1 in the first solid electrolyte is equal to or more than 0.16 and is equal to or less than 0.35.
2. 2 . The positive electrode material according to claim 1 , wherein X1 includes Cl.
3. 3 . The positive electrode material according to claim 1 , wherein M1 includes Ta.
4. 4 . The positive electrode material according to claim 1 , wherein a molar ratio Li/M1 of Li to M1 in the first solid electrolyte is equal to or more than 0.60 and is equal to or less than 2.4.
5. 5 . The positive electrode material according to claim 4 , wherein a molar ratio Li/M1 of Li to M1 in the first solid electrolyte is equal to or more than 0.96 and is equal to or less than 1.20.
6. 6 . The positive electrode material according to claim 1 , wherein the positive electrode active material contains Li, Ni, Co, Mn, and O.
7. 7 . The positive electrode material according to claim 1 , further comprising a second solid electrolyte, wherein the second solid electrolyte is represented by the following compositional formula: Li α M2 β X2 γ , wherein α, β, and γ are each independently a number larger than 0, wherein M2 is at least one element selected from the group consisting of metalloid elements and metallic elements other than Li, and wherein X2 is at least one element selected from the group consisting of F, Cl, Br, and I, wherein the positive electrode active material and the second solid electrolyte are each in a form of particles, and wherein the second solid electrolyte particle is in contact with the first solid electrolyte covering the surface of the positive electrode active material particle.
8. 8 . The positive electrode material according to claim 7 , wherein M2 includes yttrium.
9. 9 . The positive electrode material according to claim 7 , wherein, in the compositional formula, α, β, and γ satisfy 2.5≤α≤3, 1≤β≤1.1, and γ=6.
10. 10 . The positive electrode material according to claim 7 , wherein X2 includes at least one selected from the group consisting of Cl and Br.
11. 11 . The positive electrode material according to claim 10 , wherein X2 includes Cl and Br.
12. 12 . The positive electrode material according to claim 7 , wherein the second solid electrolyte contains Li 3 YBr 2 Cl 4 .
13. 13 . A battery comprising: a positive electrode containing the positive electrode material according to claim 1 ; a negative electrode; and an electrolyte layer disposed between the positive electrode and the negative electrode, wherein the electrolyte layer is a solid electrolyte layer containing a third solid electrolyte, and the third solid electrolyte meets one of the following requirements: (i) a halide solid electrolyte having the same composition as the first solid electrolyte, (ii) a halide solid electrolyte having a composition different from the first solid electrolyte, (iii) a sulfide solid electrolyte, (iv) an oxide solid electrolyte, (v) a polymer solid electrolyte, or (vi) a complex hydride solid electrolyte.

Description

BACKGROUND 1. Technical Field The present disclosure relates to a positive electrode material and a battery. 2. Description of the Related Art International Publication No. WO2018/025582 discloses a battery that uses a halide as a solid electrolyte. Journal of Power Sources 159 (2006), p 193-199 discloses a battery that uses a sulfide as a solid electrolyte. SUMMARY One non-limiting and exemplary embodiment provides a positive electrode material that can improve the charge/discharge efficiency of a battery. In one general aspect, the techniques disclosed here feature a positive electrode material including: a positive electrode active material; and a first solid electrolyte that covers a surface of the positive electrode active material. The first solid electrolyte contains Li, M1, O, and X1. M1 is at least one element selected from the group consisting of Nb and Ta, and X1 is at least one element selected from the group consisting of Cl, Br, and I. The present disclosure provides a positive electrode material that can improve the charge/discharge efficiency of a battery. Additional benefits and advantages of the disclosed embodiments will become apparent from the specification and drawings. The benefits and/or advantages may be individually obtained by the various embodiments and features of the specification and drawings, which need not all be provided in order to obtain one or more of such benefits and/or advantages. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view schematically illustrating the structure of a positive electrode material in embodiment 1; FIG. 2 is a cross-sectional view schematically illustrating the structure of a battery in embodiment 2; FIG. 3 is a schematic illustration of a press forming die used to evaluate the ionic conductivity of a solid electrolyte; and FIG. 4 is a graph showing a Cole-Cole plot obtained by the measurement of the impedance of a second solid electrolyte in Example 1. DETAILED DESCRIPTIONS (Findings Underlying the Present Disclosure) It is stated in International Publication No. WO2018/025582 that an all solid state secondary battery including a solid electrolyte composed of a halide containing Cl or Br can have good charge/discharge characteristics. Meanwhile, the inventors have conducted extensive studies and found that the ionic conductivity of the solid electrolyte of a battery that is in contact with the positive electrode active material contributes to the charge/discharge efficiency of the battery and that better charge/discharge characteristics are obtained by bringing a solid electrolyte having higher ionic conductivity into contact with the positive electrode active material. It is stated in Journal of Power Sources 159 (2006), p 193-199 that an all solid state secondary battery including a sulfide solid electrolyte can have good charge/discharge characteristics. Meanwhile, the inventors have conducted extensive studies and found that, when the sulfide solid electrolyte is in contact with the positive electrode active material, the sulfide solid electrolyte undergoes oxidative decomposition during charging. The oxidative decomposition of the solid electrolyte causes a reduction in the charge/discharge efficiency of the battery. According to the results of the studies by the inventors, by bringing a solid electrolyte having oxidation stability into contact with the positive electrode active material, the oxidative decomposition of the sulfide solid electrolyte during charging can be prevented. The inventors have thought that, by coating the surface of the positive electrode active material with a solid electrolyte having oxidation stability, the contact state between the positive electrode active material and the solid electrolyte can be achieved. Specifically, a solid electrolyte formed of a halide has higher oxidation stability than a sulfide solid electrolyte, and thus the oxidative decomposition of the sulfide solid electrolyte can be prevented. According to the above findings, the inventors have arrived at the following positive electrode material of the present disclosure that can improve the charge/discharge efficiency of a battery. Summary of Aspects of the Present Disclosure A positive electrode material according to a first aspect of the present disclosure contains: a positive electrode active material; anda first solid electrolyte that covers a surface of the positive electrode active material. The first solid electrolyte contains Li, M1, O, and X1, M1 is at least one element selected from the group consisting of Nb and Ta, andX1 is at least one element selected from the group consisting of Cl, Br, and I. In the positive electrode material in the first aspect, the surface of the positive electrode active material is covered with the first solid electrolyte. The first solid electrolyte may cover the entire surface of the positive electrode active material or may cover part of the surface of the positive electrode active materi