Lithium transition metal oxide particles having lithium concentration gradients, methods for forming the same, and battery cathodes formed of the same
Previous hybrid-anion and cation-redox (HACR) cathodes were limited in cycling performance by irreversible anionic redox reactions caused by the loss of anions. To overcome this limitation, a lithium (Li) transition metal (M) oxide particle is described having a Li concentration gradient. In one example, the particle includes a Li-rich core region that provides capacity and energy density due anionic and cationic contributions and a Li-poor surface region surrounding the core region to inhibit anionic activity and thus substantially reduce the loss of anions. A gradient region disposed between the core and surface regions has a Li concentration profile that varies from a first Li concentration in the core region to a second Li concentration in the surface region. A high-temperature leaching method may be used to leach LiO from a Li-rich Li 1+x M 1−X O 2 particle, thus forming a coherent Li gradient with a stabilized layered structure.
1. A lithium (Li) transition metal (M) oxide particle comprising:
a core region having a first Li concentration greater than a stoichiometric Li concentration in the lithium transition metal oxide particle;
a surface region, surrounding the core region, having a second Li concentration less than the stoichiometric Li concentration in the lithium transition metal oxide particle; and
a gradient region, disposed between the core region and the surface region, having a Li concentration profile that varies from the first Li concentration to the second Li concentration,
wherein:
the core region enchances oxygen anion redox activity; and
the surface region suppresses oxygen anion redox activity and mitigates oxygen loss.
2. The particle of claim 1 , wherein the Li concentration profile varies from the first Li concentration to the second Li concentration in a smooth and continuous manner.
3. The particle of claim 1 , wherein:
the core region comprises a plurality of core region layers; and
the plurality of core region layers comprises:
at least one oxygen layer;
at least one Li ion layer; and
at least one M ion layer in which at least some M ions are substituted with Li ions.
4. The particle of claim 1 , wherein:
the surface region comprises a plurality of surface region layers; and
the plurality of surface region layers comprises:
at least one oxygen layer; and
at least one Li ion layer in which at least some Li ions are substituted with M ions.
5. The particle of claim 4 , wherein the M ions in the at least one Li ion layer provide structural support to the plurality of surface region layers so as to reduce structural degradation when Li ions are removed from the at least one Li ion layer.
6. The particle of claim 1 , wherein:
the transition metal oxide is of the form Li 1+X M 1−X O 2 ; and
M is at least one of nickel (Ni), cobalt (Co), or manganese (Mn).
7. The particle of claim 6 , wherein X is greater than 0 and less than or equal to 0.2 in the first Li concentration and X is greater than −0.1 and less than 0 in the second Li concentration.
8. The particle of claim 1 , wherein the core region, the surface region, and the gradient region form a coherent crystal lattice.
9. A transition metal (M) oxide particle comprising:
a core region having a first M concentration less than a stoichiometric M concentration in the transition metal oxide;
a surface region, surrounding the core region, having a second M concentration greater than the stoichiometric M concentration in the transition metal oxide; and
a gradient region, disposed between the core region and the surface region, having an M concentration profile that varies from the first M concentration to the second M concentration,
the first M concentration and the second M concentration being formed by at least one of substituting at least some M ions with alkali metal ions or at least some alkali metal ions with M ions.
10. The particle of claim 9 , wherein the M concentration profile varies from the first M concentration to the second M concentration in a smooth and continuous manner.
11. The particle of claim 9 , wherein:
the core region enhances oxygen anion redox activity; and
the surface region suppresses oxygen anion redox activity and mitigates oxygen loss.
12. The particle of claim 9 , wherein:
the alkali metal ions are lithium (Li) ions;
the core region comprises a plurality of core region layers; and
the plurality of core region layers comprises:
at least one oxygen layer;
at least one Li ion layer; and
at least one M ion layer in which at least some M ions are substituted with the Li ions.
13. The particle of claim 9 , wherein:
the alkali metal ions are lithium (Li) ions;
the surface region comprises a plurality of surface region layers; and
the plurality of surface region layers comprises:
at least one oxygen layer; and
at least one Li ion layer in which at least some Li ions are substituted with M ions.
14. The particle of claim 13 , wherein the M ions in the at least one Li ion layer provide structural support to the plurality of surface region layers so as to reduce structural degradation when Li ions are removed from the at least one Li ion layer.
15. The particle of claim 9 , wherein:
the transition metal oxide is of the form Li 1+X M 1−X O 2 ; and
M is at least one of nickel (Ni), cobalt (Co), or manganese (Mn).
16. The particle of claim 15 , wherein X is greater than 0 and less than or equal to 0.2 in the second M concentration and X is greater than −0.1 and less than 0 in the first M concentration.
17. The particle of claim 9 , wherein the core region, the surface region, and the gradient region form a coherent crystal lattice.
18. A cathode for a battery, the cathode comprising:
a plurality of particles, at least some of the plurality of particles comprising:
a core region having a first lithium (Li) concentration greater than a stoichiometric Li concentration in the transition metal oxide;
a surface region, surrounding the core region, having a second Li concentration less than the stoichiometric Li concentration in the transition metal oxide; and
a gradient region, disposed between the core region and the surface region, having a Li concentration profile that varies from the first Li concentration to the second Li concentration in a smooth and continuous manner,
wherein:
the core region enchances oxygen anion redox activity; and
the surface region suppresses oxygen redox activity and loss to an electrolyte of the battery, when the electrolyte is present in the battery.
19. The cathode of claim 18 , wherein the plurality of particles has a size distribution that is at least one of unimodal, bimodal, or uniform.
20. The cathode of claim 18 , wherein:
the transition metal oxide of at least some particles of the plurality of particles are of the form Li 1+X M 1−X O 2 ; and
M is at least one of the nickel (Ni), cobalt (Co), or manganese (Mn).