Positive electrode active material, sodium ion secondary battery comprising same and power consuming device

Patent metadata

Field	Value
Publication number	US-12500231-B2
Application number	US-202318529592-A
Country	US
Kind code	B2
Filing date	Dec 5, 2023
Priority date	Dec 31, 2021
Publication date	Dec 16, 2025
Grant date	Dec 16, 2025

Abstract

A positive electrode active material is granular and comprises a compound represented by formula 1: (NaxAy)a□bM1[M2(CN) 6 ] δ , wherein A is selected from at least one of alkali metal elements and has an ionic radius greater than that of sodium, M1 and M2 are each independently selected from at least one of transition metal elements, 0<y≤0.2, 0<x+y≤2, 0≤δ≤1, a+b=2, 0.85≤a≤0.98, □ represents a vacancy, and b represents the number of vacancies; and when the positive electrode active material is dissolved, at a temperature of 20° C., into an aqueous solution having a concentration of 5 g/100 g water, a pH value of the aqueous solution is in a range of 7.6 to 8.5. The positive electrode active material has good cycling and rate performance, and a high specific capacity.

First claim

What is claimed is:

1 . A positive electrode active material comprising a compound represented by Formula 1,
(Na x A y ) a□b M1[M2(CN) 6 ] δ   Formula 1
wherein A is selected from at least one of alkali metal elements and has an ionic radius greater than that of sodium, M1 and M2 are each independently selected from at least one of transition metal elements, 0<y≤0.2, 0<x+y≤2, 0<δ≤1, a +b=2, 0.85≤a≤0.98, □ represents a vacancy, and b represents the number of vacancies; and when the positive electrode active material is dissolved in water, an aqueous solution having a concentration of 5 g/100 g water is obtained, a pH value of the aqueous solution at a temperature of 20° C. is 7.6 to 8.5, wherein a particle of the positive electrode active material comprises: a gradient layer, in which a content of the A element gradually decreases in a direction from an external surface of the particle toward an interior portion of the particle, the gradient layer having a thickness in a range of 10 nm to 100 nm; an outermost layer, defined as a region from the external surface of the particle to a position within the particle where the content ratio of Na to A reaches 10 atom %:90 atom %, as measured by transmission electron microscopy-energy spectrum (TEM-EDS) line scan characterization, the outermost layer having a thickness in a range of 10 nm to 50 nm; and a vacancy layer, defined as a region from the external surface of the particle to a position within the particle where a total content by atom % of Na and A becomes less than a total content by atom % of M1 and M2, as measured by TEM-EDS line scan characterization, the vacancy layer having a thickness d2 in a range of 9 nm to 35 nm.

2 . The positive electrode active material according to claim 1 , wherein, the pH value of the aqueous solution at a temperature of 20° C. is 7.6 to 8.3.

3 . The positive electrode active material according to claim 1 , wherein the thickness of the gradient layer is in a range of 32-100 nm.

4 . The positive electrode active material according to claim 1 , wherein, in a radial direction of the particle, a distance from a position inside the particle where a content ratio of Na to A of Na:A=50 atom %:50 atom % to the surface of the particle is d1, and in a radial direction of the particle, a thickness of the vacancy layer of the particle is d2, and d2≤d1, the content by atom % of Na and A in the particle of the positive electrode active material is quantitatively measured by transmission electron microscopy energy spectrum line scan characterization.

5 . The positive electrode active material according to claim 1 , wherein, the A is independently selected from at least one of K, Rb, and Cs, optionally K.

6 . The positive electrode active material according to claim 1 , wherein, the M1 and M2 are each independently selected from at least one of Fe, Mn, Ni, Co, Cu, and Zn.

7 . The positive electrode active material according to claim 1 , wherein, the positive electrode active material has a volume median particle size D v 50 in a range of 1-5 μm.

8 . The positive electrode active material according to claim 1 , wherein, the positive electrode active material has a specific surface area in a range of 1-10 m 2 /g.

9 . A method for preparing a positive electrode active material, comprising the following steps:
1) Dissolving a soluble salt of transition metal element M1 together with an optional Na-containing slow release agent in a solvent to prepare a solution a; 2) Dissolving a soluble transition metal cyano complex of transition metal element M2 in a solvent to prepare a solution b; 3) Under a stirring state, dropwise adding the solution a to the solution b, followed by stirring and aging after the dropwise adding is finished; 4) adding a salt of A to a suspension obtained in step 3), followed by stirring and aging, wherein the A is selected from at least one of alkali metal elements and has an ionic radius larger than that of sodium; 5) Filtering a suspension obtained in step 4) and washing a filtered precipitate; 6) Mixing the washed precipitate obtained in step 5) and the soluble salt of the transition metal element M1 together in water, followed by stirring and aging to form a suspension d, wherein the amount of the soluble salt of the transition metal element M1 added is selected to obtain a pH value of the suspension d in a range of 8.1 to 9.0; and 7) Filtering the suspension d and washing a filtered precipitate to obtain the positive electrode active material, wherein the positive electrode active material is granular and comprises a compound represented by formula 1,
(Na x A y ) a □ b M1[M2(CN) 6 ] δ   Formula 1

wherein 0<y≤0.2, 0<x+y≤2, 0<δ≤1, a+b=2, 0.85≤a≤0.98, □ represents a vacancy, b represents the number of vacancies, and the A, M1, and M2 are defined as above; and when the positive electrode active material is dissolved in water, an aqueous solution having a concentration of 5 g/100 g water is obtained, a pH value of the aqueous solution at a temperature of 20° C. is 7.6 to 8.5, wherein a particle of the positive electrode active material comprises: a gradient layer, in which a content of the A element gradually decreases in a direction from an external surface of the particle toward an interior portion of the particle, the gradient layer having a thickness in a range of 10 nm to 100 nm; an outermost layer, defined as a region from the external surface of the particle to a position within the particle where the content ratio of Na to A reaches 10 atom %:90 atom %, as measured by transmission electron microscopy-energy spectrum (TEM-EDS) line scan characterization, the outermost layer having a thickness in a range of 10 nm to 50 nm; and a vacancy layer, defined as a region from the external surface of the particle to a position within the particle where a total content by atom % of Na and A becomes less than a total content by atom % of M1 and M2, as measured by TEM-EDS line scan characterization, the vacancy layer having a thickness d2 in a range of 9 nm to 35 nm.

10 . The method according to claim 9 , wherein, in step 6), an amount of the soluble salt of the transition metal element M1 added is selected to obtain a pH value of the suspension d in a range of 8.1 to 9.0.

11 . The method according to claim 9 , wherein, an amount of the precipitate added in step 6) is 5 g/100 g water to 15 g/100 g water.

12 . The method according to claim 9 , wherein, an anion of the salt of the A is the same as that of the soluble salt of the transition metal element M1 used in step 6).

13 . The method according to claim 9 , wherein, a molar ratio of the A element to the Na element in the precipitate added in step 6) is smaller than or equal to 1:9.

14 . The method according to claim 9 , wherein, before the salt of the A is added to the suspension obtained in step 3), the suspension is cooled to a temperature in a range of −20° C. to 25° C.

15 . The method according to claim 9 , wherein, an amount of the M1 in the precipitate added in step 6) is greater than or equal to 0.1 mol/L, relative to a volume of the suspension d.

16 . The method according to claim 1 , wherein, a molar ratio of the M1 in a total amount of the soluble salt of the transition metal element M1 to the M2 in the soluble transition metal cyano complex of the transition metal element M2 is in a range of 0.8:1 to 1:0.8.

17 . The method according to claim 9 , wherein,
in step 3), the solution is kept at a temperature in a range of 35° C.-120° C.

18 . A secondary battery

Assignees

• Contemporary Amperex Technology Hong Kong Ltd

Inventors

• Tian Jiarui
• Zhang Xinxin
• Ouyang Chuying
• Guo Yongsheng
• Wan Yuejuan
• Lin Wenguang
• Lan Jiadian
• Wang Jixiang

Classifications

• H01M2220/10

  Batteries in stationary systems, e.g. emergency power source in plant · CPC title

• H01M2004/028

  Positive electrodes · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M4/58

  of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates · CPC title

• H01M4/366 Primary

  as layered products · CPC title