PRUSSIAN BLUE ANALOG HAVING CORE-SHELL STRUCTURE, PREPARATION METHOD THEREOF, AND SODIUM-ION SECONDARY BATTERY COMPRISING THE SAME

1 . A prussian blue analog having a core-shell structure, comprising a core and a cladding layer that dads the core, wherein

the chemical formula of the core is the following Formula 1,

Na x P[R(CN) 6 ] δ .z H 2 O  Formula 1

wherein the P and R are each independently selected from at least one of transition metal elements, 0<x≤2, 0<δ≤1, and 0≤z≤10,

the chemical formula of the cladding layer is the following Formula 2,

A y L[M(CN) 6 ] α .w H 2 O  Formula 2

wherein the A is an alkali metal or alkaline earth metal element other than sodium, and the L and M are each independently selected from at least one of transition metal elements, 0<y≤2, 0<α≤1, and 0≤w≤10.

2 . The prussian blue analog having a core-shell structure according to claim 1 , wherein P, R, L and M are each independently selected from Fe, Mn, Ni, Co, Cu and Zn.

3 . The prussian blue analog having a core-shell structure according to claim 1 , wherein

A is selected from Li, K, Rb, Cs, Be, Mg, Ca, Sr and Ba, optionally at least one of K, Rb, Cs, Mg and Ca, further optionally at least one of K, Rb and Cs.

4 . The prussian blue analog having a core-shell structure according to claim 1 , wherein

in Formula 1, the 0.7≤δ≤1, and/or

in Formula 1 and Formula 2, the x and y are each independently selected from 0.5-2, optionally 1.5-2.

5 . The prussian blue analog having a core-shell structure according to claim 1 , wherein

the thickness of the cladding layer is 100 nm or less, optionally 60 nm or less, more optionally 50 nm or less, and optionally in a range of 5 nm-40 nm, and further optionally in a range of 10 nm-20 nm.

6 . The prussian blue analog having a core-shell structure according to claim 1 , wherein the cladding amount of the cladding layer is 10 wt % or less, optionally 1 wt %-5 wt %.

7 . The prussian blue analog having a core-shell structure according to claim 1 , wherein the prussian blue analog has a particle size of 100 nm to 50 μm.

8 . A method for preparing a prussian blue analog having a core-shell structure, comprising the steps of:

1) adding a prussian blue analog particle to a solvent 1 and dispersing to obtain a suspension, the chemical formula of the prussian blue analog particle being the following Formula 1,

Na x P[R(CN) 6 ] δ .z H 2 O  Formula 1

wherein the P and R are each independently selected from at least one of transition metal elements, 0<x≤2, 0<δ≤1, and 0≤z≤10;

2) dissolving a soluble salt containing a transition metal element L in a solvent 2 to make a solution c;

3) dissolving a soluble salt containing an alkali metal or alkaline earth metal element A other than sodium and a soluble transition metal cyano complex containing a transition metal element M in a solvent 3 to make a solution d;

4) adding the solutions c and d dropwise to the suspension obtained in step 1) under stirring, and filtering the suspension to obtain a precipitate; and

5) washing and drying the precipitate obtained in step 4) to obtain a prussian blue analog having a core-shell structure, wherein the prussian blue analog having a core-shell structure has a core and a cladding layer that clads the core, the core is the prussian blue analog particle, and the chemical formula of the cladding layer is the following Formula 2,

A y L[M(CN) 6 ] α .w H 2 O  Formula 2

wherein the A is an alkali metal or alkaline earth metal element other than sodium, and the L and M are each independently selected from at least one of transition metal elements, 0<y≤2, 0<α≤1, and 0≤w≤10.

9 . The method according to claim 8 , wherein the prussian blue analog particle in step 1) is prepared by a method comprising the steps of:

i) dissolving a soluble salt containing P as a transition metal element and a slow-releasing agent containing Na in water to make a solution a;

ii) dissolving a soluble transition metal cyano complex containing R as a transition metal element in water to make a solution b;

iii) adding the solution a dropwise to the solution b under stirring, and after the completion of dropwise addition, aging and filtering to obtain a precipitate; and

iv) washing and drying the precipitate obtained in step iii) to obtain the prussian blue analog particle.

10 . The method according to claim 9 , wherein

the slow-releasing agent containing Na in step i) is at least one selected from sodium citrate, sodium ascorbate, disodium ethylenediamine tetraacetate, tetrasodium ethylenediamine tetraacetate, sodium chloride, sodium sulfate and sodium acetate.

11 . The method according to claim 9 , wherein

the soluble transition metal cyano complex in step ii) is a divalent transition metal sodium cyanide.

12 . The method according to claim 9 , wherein

in the step iii), the solution is maintained in a temperature range of 20° C.-120° C., optionally in a temperature range of 70° C.-90° C., and optionally at 80° C.

13 . The method according to claim 8 , wherein characterized in that

the respective solvents 1, 2 and 3 in steps 1), 2) and 3) may be the same or different, each being independently selected from at least one of deionized water and an organic solvent, optionally the organic solvent is selected from at least one of alcohol, ketone, and halogenated hydrocarbon, and optionally selected from at least one of methanol, glycerol, acetone, and ethanol.

14 . The method according to claim 8 , wherein

the soluble transition metal cyano complex in step 3) is a divalent transition metal sodium cyanide.

15 . The method according to claim 8 , wherein

in step 4), the rates of dropwise addition of the solution c and the solution d are each independently in a range of 0.1 ml/min-10 ml/min, optionally in a range of 0.1 ml/min-5 ml/min, and optionally in a range of 0.1 ml/min-2 ml/min; or

in step 4), the reaction system is maintained in a temperature range of 20° C.-120° C., optionally in a temperature range of 70° C.-90° C., and optionally at 80° C.

16 . The method according to claim 8 , wherein

the A is selected from at least one of Li, K, Rb, Cs, Be, Mg, Ca, Sr and Ba, optionally at least one of K, Rb, Cs, Mg and Ca, further optionally at least one of K, Rb and Cs.

17 . A sodium-ion secondary battery, comprising the prussian blue analog having a core-shell structure of claim 1 .

18 . A battery module, comprising the sodium-ion secondary battery of claim 17 .

19 . A battery pack, comprising the battery module of claim 18 .

20 . A powered device, comprising one or more of the sodium-ion secondary battery of claim 17 .