US2023299265A1PendingUtilityA1

Positive Electrode Active Material, Method for Manufacturing Positive Electrode Active Material, and Secondary Battery

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Assignee: SEMICONDUCTOR ENERGY LABPriority: Jul 5, 2016Filed: May 26, 2023Published: Sep 21, 2023
Est. expiryJul 5, 2036(~9.9 yrs left)· nominal 20-yr term from priority
Inventors:Teruaki OchiaiTakahiro KawakamiMayumi MikamiYohei MommaMasahiro TakahashiAyae Tsuruta
H01M 2300/0028H01M 10/0568H01M 4/366H01M 10/0525H01M 2004/028H01M 4/628H01M 4/131H01M 4/1315H01M 4/1391H01M 4/13915H01M 4/625H01M 2004/021Y02E60/50Y02E60/10Y02P70/50H01M 4/525H01M 4/134H01M 4/8657
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Claims

Abstract

A positive electrode active material which can improve cycle characteristics of a secondary battery is provided. Two kinds of regions are provided in a superficial portion of a positive electrode active material such as lithium cobaltate which has a layered rock-salt crystal structure. The inner region is a non-stoichiometric compound containing a transition metal such as titanium, and the outer region is a compound of representative elements such as magnesium oxide. The two kinds of regions each have a rock-salt crystal structure. The inner layered rock-salt crystal structure and the two kinds of regions in the superficial portion are topotaxy; thus, a change of the crystal structure of the positive electrode active material generated by charging and discharging can be effectively suppressed. In addition, since the outer coating layer in contact with an electrolyte solution is the compound of representative elements which is chemically stable, the secondary battery having excellent cycle characteristics can be obtained.

Claims

exact text as granted — not AI-modified
1 . A lithium-ion secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution,
 wherein the positive electrode comprises a positive electrode active material comprising lithium cobaltate,   wherein the positive electrode active material comprises a first region inside the positive electrode active material,   wherein the positive electrode active material comprises a second region and a third region in a superficial portion of the positive electrode active material,   wherein the first region comprises a layered rock-salt crystal structure,   wherein the second region comprises a rock-salt crystal structure,   wherein the third region comprises a rock-salt crystal structure,   wherein the third region is present in a region closer to a surface of the positive electrode active material than the second region,   wherein the first region comprises cobalt and lithium,   wherein the second region comprises cobalt and titanium,   wherein the third region comprises cobalt, magnesium, fluorine, and oxygen,   wherein at least part of the second region and at least part of the third region overlap with each other, and   wherein the third region comprises cobalt oxide which has a rock-salt crystal structure and magnesium oxide which has a rock-salt crystal structure.   
     
     
         2 . A lithium-ion secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution,
 wherein the positive electrode comprises a positive electrode active material comprising lithium cobaltate,   wherein the positive electrode active material comprises a first region inside the positive electrode active material,   wherein the positive electrode active material comprises a second region and a third region in a superficial portion of the positive electrode active material,   wherein the first region comprises a layered rock-salt crystal structure,   wherein the second region comprises a rock-salt crystal structure,   wherein the third region comprises a rock-salt crystal structure,   wherein the third region is present in a region closer to a surface of the positive electrode active material than the second region,   wherein the first region comprises cobalt and lithium,   wherein the second region comprises cobalt and titanium,   wherein the third region comprises cobalt, magnesium, fluorine, and oxygen,   wherein at least part of the second region and at least part of the third region overlap with each other,   wherein the third region comprises cobalt oxide which has a rock-salt crystal structure and magnesium oxide which has a rock-salt crystal structure, and   wherein fluorine is bonded to part of magnesium in the magnesium oxide.   
     
     
         3 . A lithium-ion secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution,
 wherein the positive electrode comprises a positive electrode active material comprising lithium cobaltate,   wherein the positive electrode active material comprises a first region inside the positive electrode active material,   wherein the positive electrode active material comprises a second region and a third region in a superficial portion of the positive electrode active material,   wherein the first region comprises a layered rock-salt crystal structure,   wherein the second region comprises a rock-salt crystal structure,   wherein the third region comprises a rock-salt crystal structure,   wherein the third region is present in a region closer to a surface of the positive electrode active material than the second region,   wherein the first region comprises cobalt and lithium,   wherein the second region comprises cobalt and titanium,   wherein the third region comprises cobalt, magnesium, fluorine, and oxygen,   wherein at least part of the second region and at least part of the third region overlap with each other,   wherein the third region comprises cobalt oxide which has a rock-salt crystal structure and magnesium oxide which has a rock-salt crystal structure,   wherein a degree of a mismatch between the layered rock-salt crystal structure in the first region and the rock-salt crystal structure in the second region is less than or equal to 0.12, and   wherein a degree of a mismatch between the rock-salt crystal structure in the second region and the rock-salt crystal structure in the third region is less than or equal to 0.12.   
     
     
         4 . The lithium-ion secondary battery according to  claim 1 ,
 wherein the electrolyte solution comprises an electrolyte comprising lithium hexafluorophosphate, and   wherein the electrolyte solution comprises ethylene carbonate, diethyl carbonate, and vinylene carbonate.   
     
     
         5 . The lithium-ion secondary battery according to  claim 1 ,
 wherein the electrolyte solution comprises vinylene carbonate.   
     
     
         6 . The lithium-ion secondary battery according to  claim 1 ,
 wherein a decomposition product of the electrolyte solution is present at the surface of the positive electrode active material.   
     
     
         7 . The lithium-ion secondary battery according to  claim 1 ,
 wherein a peak position of bonding energy with fluorine is higher than or equal to 682 eV and lower than or equal to 685 eV when an XPS analysis is performed on a vicinity of a surface of the positive electrode active material.   
     
     
         8 . The lithium-ion secondary battery according to  claim 1 ,
 wherein a thickness of the third region is greater than or equal to 0.5 nm and less than or equal to 50 nm.   
     
     
         9 . The lithium-ion secondary battery according to  claim 1 ,
 wherein a maximum of a distribution of titanium is present in a region from a depth of 0.2 nm or more to a depth of 10 nm or less from the surface of the positive electrode active material in EDX line analysis.   
     
     
         10 . The lithium-ion secondary battery according to  claim 1 ,
 wherein a maximum of a distribution of titanium is present in a region from a depth of 0.5 nm or more to a depth of 3 nm or less from the surface of the positive electrode active material in EDX line analysis.   
     
     
         11 . The lithium-ion secondary battery according to  claim 1 ,
 wherein the third region comprises a solid solution of the cobalt oxide and the magnesium oxide.   
     
     
         12 . The lithium-ion secondary battery according to  claim 1 ,
 wherein the first region further comprises magnesium.   
     
     
         13 . The lithium-ion secondary battery according to  claim 2 ,
 wherein the electrolyte solution comprises an electrolyte comprising lithium hexafluorophosphate, and   wherein the electrolyte solution comprises ethylene carbonate, diethyl carbonate, and vinylene carbonate.   
     
     
         14 . The lithium-ion secondary battery according to  claim 2 ,
 wherein the electrolyte solution comprises vinylene carbonate.   
     
     
         15 . The lithium-ion secondary battery according to  claim 2 ,
 wherein a decomposition product of the electrolyte solution is present at the surface of the positive electrode active material.   
     
     
         16 . The lithium-ion secondary battery according to  claim 2 ,
 wherein a peak position of bonding energy with fluorine is higher than or equal to 682 eV and lower than or equal to 685 eV when an XPS analysis is performed on a vicinity of a surface of the positive electrode active material.   
     
     
         17 . The lithium-ion secondary battery according to  claim 2 ,
 wherein a thickness of the third region is greater than or equal to 0.5 nm and less than or equal to 50 nm.   
     
     
         18 . The lithium-ion secondary battery according to  claim 2 ,
 wherein a maximum of a distribution of titanium is present in a region from a depth of 0.2 nm or more to a depth of 10 nm or less from the surface of the positive electrode active material in EDX line analysis.   
     
     
         19 . The lithium-ion secondary battery according to  claim 2 ,
 wherein a maximum of a distribution of titanium is present in a region from a depth of 0.5 nm or more to a depth of 3 nm or less from the surface of the positive electrode active material in EDX line analysis.   
     
     
         20 . The lithium-ion secondary battery according to  claim 2 ,
 wherein the third region comprises a solid solution of the cobalt oxide and the magnesium oxide.   
     
     
         21 . The lithium-ion secondary battery according to  claim 2 ,
 wherein the first region further comprises magnesium.   
     
     
         22 . The lithium-ion secondary battery according to  claim 3 ,
 wherein the electrolyte solution comprises an electrolyte comprising lithium hexafluorophosphate, and   wherein the electrolyte solution comprises ethylene carbonate, diethyl carbonate, and vinylene carbonate.   
     
     
         23 . The lithium-ion secondary battery according to  claim 3 ,
 wherein the electrolyte solution comprises vinylene carbonate.   
     
     
         24 . The lithium-ion secondary battery according to  claim 3 ,
 wherein a decomposition product of the electrolyte solution is present at the surface of the positive electrode active material.   
     
     
         25 . The lithium-ion secondary battery according to  claim 3 ,
 wherein a peak position of bonding energy with fluorine is higher than or equal to 682 eV and lower than or equal to 685 eV when an XPS analysis is performed on a vicinity of a surface of the positive electrode active material.   
     
     
         26 . The lithium-ion secondary battery according to  claim 3 ,
 wherein a thickness of the third region is greater than or equal to 0.5 nm and less than or equal to 50 nm.   
     
     
         27 . The lithium-ion secondary battery according to  claim 3 ,
 wherein a maximum of a distribution of titanium is present in a region from a depth of 0.2 nm or more to a depth of 10 nm or less from the surface of the positive electrode active material in EDX line analysis.   
     
     
         28 . The lithium-ion secondary battery according to  claim 3 ,
 wherein a maximum of a distribution of titanium is present in a region from a depth of 0.5 nm or more to a depth of 3 nm or less from the surface of the positive electrode active material in EDX line analysis.   
     
     
         29 . The lithium-ion secondary battery according to  claim 3 ,
 wherein the third region comprises a solid solution of the cobalt oxide and the magnesium oxide.   
     
     
         30 . The lithium-ion secondary battery according to  claim 3 ,
 wherein the first region further comprises magnesium.

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