Stable cathode materials
Provided are electrochemically active particles suitable for use as an active material in a cathode of a lithium ion electrochemical cell that include: a plurality of crystallites including a first composition comprising lithium, nickel, and oxygen; and a grain boundary between adjacent crystallites of the plurality of crystallites and comprising a second composition comprising lithium, nickel, and oxygen; wherein the grain boundary has a higher electrochemical affinity for lithium than the crystallites. The higher electrochemical affinity for Li leads to increased Li retention in the grain boundaries during or at charge relative to the bulk crystallites and stabilizes the structure of the grain boundaries and crystallites for improved cycling stability with no appreciable loss in capacity.
1 . An electrochemically active particle for use in a cathode of an electrochemical cell, the particle comprising:
a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen;
a grain boundary between adjacent crystallites of the plurality of crystallites and comprising a second composition comprising lithium, nickel, and oxygen and further comprising one or more substitution elements selected from the group consisting of Mn, Nd, B, Ti, Cr, Fe, Y, Ga, Sb, W, Sc, Zr, Nb, Mo, Zn, Cu, In, Ge, Al, and any combination thereof, where the concentration of the substitution element in the grain boundary is greater than the concentration of the substitution element in the crystallites;
wherein the grain boundary has higher electrochemical affinity for Li than the crystallites.
2 . The particle of claim 1 , wherein the plurality of crystallites, the grain boundary or both, has an α-NaFeO 2 -type layered structure, a cubic structure, a spinel structure, a monoclinic structure, or a combination thereof.
3 . The particle of claim 1 , wherein the second composition is Li 1+x M′O 2+y , wherein M′ comprises said Ni, the amount of Ni on the basis of moles Ni per mole of M′ in the second composition is −0≤Ni≤0.99.
4 . The particle of claim 3 , wherein amount of Ni on the basis of moles Ni per mole of M′ of the second composition is 0.9 or less.
5 . The particle of claim 3 , wherein M′ comprises the substitution element Mn, Nd, B, Fe, Y, Ga, Al, or any combination thereof.
6 . The particle of claim 3 , wherein M′ comprises a substitution element having a higher oxidation potential than Ni.
7 . The particle of claim 6 , wherein the substitution element is capable of substituting for Ni in the 3b site of the Li 1+x M′O 2+y structure.
8 . The particle of claim 3 , wherein M′ comprises two or more substitution elements selected from the group consisting of Mn, Nd, B, Ti, Cr, Fe, Co, Y, Ga, Sb, W, Sc, Zr, Nb, Mo, Zn, Cu, In, Ge, and Al.
9 . The particle of claim 3 , wherein M′ comprises three or more substitution elements selected from the group consisting of Mn, Nd, B, Ti, Cr, Fe, Co, Y, Ga, Sb, W, Sc, Zr, Nb, Mo, Zn, Cu, In, Ge, and Al.
10 . The particle of claim 1 , wherein the first composition is defined by Li 1+x MO 2+y , wherein M comprises nickel at greater than or equal to 0.1 moles per mole M.
11 . The particle of claim 10 , wherein M comprises nickel at greater than or equal to 0.75 moles per mole M, optionally greater than or equal to 0.90 moles per mole M.
12 . The particle of claim 10 , wherein M further comprises an additional metal, wherein the additional metal is present in an amount of about 0.01 to about 0.90 moles per mole M;
the additional metal optionally selected from the group consisting of Mg, Sr, Co, Al, Ca, Cu, Zn, Mn, V, Ba, Zr, Ti, Cr, Fe, Mo, B, and any combination thereof.
13 . The particle of claim 1 , further comprising an outer coating on a surface of the particle, the outer coating comprising:
an oxide of one or more elements selected from Al, Zr, Y, Co, Ni, Mg, and Li;
a fluoride comprising one or more elements selected from Al, Zr, and Li;
a carbonate comprising one or more elements selected from Al, Co, Ni, Mn, and Li;
a sulfate comprising one or more elements selected from Al, Co, Ni, Mn, and Li; or
a phosphate comprising one or more elements selected from Al and Li.
14 . An electrochemically active particle, the particle comprising:
a plurality of crystallites comprising a first composition comprising lithium, nickel, and oxygen;
a grain boundary between adjacent crystallites of the plurality of crystallites and comprising a second composition comprising lithium, nickel, and oxygen and further comprising one or more substitution elements selected from the group consisting of Mn, Nd, B, Ti, Cr, Fe, Y, Ga, Sb, W, Sc, Zr, Nb, Mo, Zn, Cu, In, Ge, Al, and any combination thereof, where the concentration of the substitution element in the grain boundary is greater than the concentration of the substitution element in the crystallites;
wherein the grain boundary has higher electrochemical affinity for Li than the crystallites.
15 . An electrochemical cell comprising a cathode, an anode, and an electrolyte, the cathode comprising a cathode active material comprising the particle of claim 1 .