Positive active material for all solid secondary battery, and all solid secondary battery including the same
A positive active material for an all-solid secondary battery, an all-solid secondary battery including the same, and a method of manufacturing the positive active material for an all-solid secondary battery, the positive active material including a secondary particle including a plurality of primary particles; and a buffer layer on a surface of the secondary particle; wherein the secondary particle includes a nickel lithium transition metal oxide represented by Formula 1, the buffer layer includes a copper compound represented by Formula 2, Li a Ni b M 1 c O 2-e A e <Formula 1> Li x Cu y X z . <Formula 2>
1 . A positive active material for an all-solid secondary battery, the positive active material comprising:
a secondary particle including a plurality of primary particles; and
a buffer layer on a surface of the secondary particle;
wherein:
the secondary particle includes a nickel lithium transition metal oxide represented by Formula 1,
the buffer layer includes a copper compound represented by Formula 2,
Li a Ni b M 1 c O 2-e A e <Formula 1>
in Formula 1,
M 1 is an element of Groups 4 to 14,
A is F, S, Cl, Br, or a combination thereof; and
a, b, c, and e satisfy the following relations: 0.9≤a≤1.3, 0.5≤b<1, 0<c<1, b+c=1, and 0≤e<1,
Li x Cu y X z <Formula 2>
in Formula 2,
X is a halogen, and
x, y, and z satisfy the following relations: 1≤x≤3, 1≤y≤5, and 1≤z≤5.
2 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein, in Formula 2, X is F, Cl, Br, I, or a combination thereof.
3 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein:
the copper compound represented by Formula 2 is represented by Formula 2b,
Li x Cu y Cl z <Formula 2b>
in Formula 2b, x, y, and z satisfy the following relations: 1≤x≤3, 1≤y≤5, 1≤z≤5.
4 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein the positive active material includes the copper compound in an amount of about 0.0005 mol % to about 0.2 mol %, based on 100 mol % of the nickel lithium transition metal oxide.
5 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein the positive active material includes the copper compound in an amount of about 0.005 mol % to about 0.1 mol %, based on 100 mol % of the nickel lithium transition metal oxide.
6 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein the copper compound is further included at interfaces between the plurality of primary particles.
7 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein the buffer layer is in a crystalline phase.
8 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein the buffer layer is in a mixed phase of a crystalline phase and an amorphous phase.
9 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein:
the nickel lithium transition metal oxide represented by Formula 1 is represented by Formula 1a,
Li a Ni b M 2 c M 3 d O 2-e A e <Formula 1a>
in Formula 1a,
M 2 is Co, Mn, Al, or a combination thereof;
M 3 is boron (B), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu)), zirconium (Zr), aluminum (Al), phosphorus (P), zinc (Zn), silicon (Si), niobium (Nb), cobalt (Co), or a combination thereof;
A is F, S, Cl, Br, or a combination thereof; and
a, b, c, d, and e satisfy the following relations: 0.8≤a≤1.2, 0.7≤b<1, 0<c<1, 0<d<1, b+c+d=1, and 1 23 e<1.
10 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein:
the nickel lithium transition metal oxide represented by Formula 1 is represented by Formula 1b,
Li a Ni b Co c M 4 d O 2 <Formula 1b>
in Formula 1b,
M 4 is Al, Mn, Zr, Mg, or a combination thereof; and
a, b, c, and d satisfy the following relations: 0.9≤a≤1.1, 0.7≤b<1, 0<c≤0.3, 0<d≤0.3, and b+c+d=1.
11 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein the nickel lithium transition metal oxide includes nickel in an amount of about 80 mol % to about 98 mol %, based on a total number of moles of transition metals in the nickel lithium transition metal oxide.
12 . The positive active material for an all-solid secondary battery as claimed in claim 1 , wherein the positive active material has a remainder of lithium of about 100 ppm or more.
13 . A cathode for an all-solid secondary battery, the cathode including the positive active material for an all-solid secondary battery as claimed in claim 1 .
14 . The cathode for an all-solid secondary battery as claimed in claim 13 , further comprising a solid electrolyte.
15 . The cathode for an all-solid secondary battery as claimed in claim 14 , wherein:
the solid electrolyte is a sulfide solid electrolyte, and
the sulfide solid electrolyte includes Li 2 S—P 2 S 5 , Li 2 S—P 2 S 5 —LiCl, Li 2 S—P 2 S 5 —LiBr, Li 2 S—P 2 S 5 —LiCl—LiBr, Li 2 S—P 2 S 5 —Li 2 O, Li 2 S—P 2 S 5 —Li 2 O—LiI, Li 2 S—SiS 2 , Li 2 S—SiS 2 —LiI, Li 2 S—SiS 2 —LiBr, Li 2 S—SiS 2 —LiCl, Li 2 S—SiS 2 —B 2 S 3 —LiI, Li 2 S—SiS 2 —P 2 S 5 —LiI, Li 2 S—B 2 S 3 , Li 2 S—P 2 S 5 —Z m S n , in which m and n are each independently a positive number, and Z is Ge, Zn, or Ga, Li 2 S-GeS 2 , Li 2 S-SiS 2 -Li 3 PO 4 , Li 2 S-SiS 2 -Li p MO q , in which p and q are each independently a positive number, and M is P, Si, Ge, B, Al, Ga, or In, Li 7-x PS 6-x Cl x , in which 0≤x≤2, Li z-x PS 6-x Br x , in which 0≤x≤2, and Li 7-x PS 6-x I x , in which 0≤x≤2.
16 . The cathode for an all-solid secondary battery as claimed in claim 14 , wherein the cathode includes the solid electrolyte in an amount of about 5 parts by weight to about 10 parts by weight, based on 100 parts by weight of the cathode.
17 . An all-solid secondary battery, comprising:
a cathode layer;
an anode layer; and
a sulfide solid electrolyte layer between the cathode layer and the anode layer;
wherein the cathode layer includes the cathode as claimed in claim 13 .
18 . The all-solid secondary battery as claimed in claim 17 , wherein, the sulfide solid electrolyte layer includes Li 2 S—P 2 S 5 , Li 2 S—P 2 S 5 —LiCl, Li 2 S—P 2 S 5 —LiBr, Li 2 S—P 2 S 5 —LiCl—LiBr, Li 2 S—P 2 S 5 —Li 2 O, Li 2 S—P 2 S 5 —Li 2 O—LiI, Li 2 S—SiS 2 , Li 2 S—SiS 2 —LiI, Li 2 S—SiS 2 —LiBr, Li 2 S—SiS 2 —LiCl, Li 2 S—SiS 2 —B 2 S 3 —LiI, Li 2 S—SiS 2 —P 2 S 5 —LiI, Li 2 S—B 2 S 3 , Li 2 S—P 2 S 5 —Z m S n , in which m and n are each independently a positive number, and Z is Ge, Zn, or Ga, LizS-GeS 2 , LizS-SiS 2 -Li 3 PO 4 , LizS-SiS 2 -LipMOq, in which p and q are each independently a positive number, and M is P, Si, Ge, B, Al, Ga, or In, i 7-x PS 6-x Cl x , in which 0≤x≤2, Li 7-x PS 6-x Br x , in which 0≤x≤2, and Li 7-x PS 6-x I x , in which 0≤x≤2.
19 . The all-solid secondary battery as claimed in claim 17 , wherein:
the anode layer includes a negative electrode current collector and a negative active material layer on the negative electrode current collector,
the negative active material layer includes a negative active material and a binder,
the negative active material is in a particle form, and
an average particle diameter of the negative active material is about 4 um or less.
20 . The all-solid secondary battery as claimed in claim 19 , wherein:
the negative active material includes a carbon negative active material, a metal negative active material, or a metalloid negative active material, and
the carbon negative active material includes amorphous carbon or crystalline carbon.
21 . A method of manufacturing the positive active material for an all-solid secondary battery as claimed in claim 1 , the method comprising:
coating a nickel lithium transition metal oxide represented by the following Formula 1 with a coating solution including a catalyst and LiOH, the catalyst including Cu n X m , in which X is a halogen and n and m satisfy the following relations: 1≤n≤5 and 1≤m≤5, and drying and heat-treating the coated nickel lithium transition metal oxide,
Li a Ni b M 1 c O 2-e A e <Formula 1>
wherein, in Formula 1,
M 1 is an element of Groups 4 to 14,
A is F, S, Cl, Br, or a combination thereof; and
a, b, c, and e satisfy the following relations: 0.9≤a≤1.3, 0.5≤b<1, 0<c<1, b+c=1, and 0≤e<1.