Cathode active material for secondary battery and secondary battery comprising same

Patent metadata

Field	Value
Publication number	US-11380891-B2
Application number	US-201716339638-A
Country	US
Kind code	B2
Filing date	Sep 29, 2017
Priority date	Oct 5, 2016
Publication date	Jul 5, 2022
Grant date	Jul 5, 2022

Abstract

A film-shaped coating layer including at least one lithium ion conductive compound having a band gap of 5.5 eV to 10 eV formed on the surface of a core including a lithium composite metal oxide to a thickness at which dielectric breakdown does not occur according to types of the lithium ion conductive compound and the lithium composite metal oxide under charge and discharge conditions. Thereby, an oxidation/reduction reaction is suppressed by blocking the movement of electrons at an interface between an active material and an electrolyte solution by the coating layer which surrounds the surface of particles and has lithium ion conductivity, and, as a result, a positive electrode active material for a secondary battery, which may improve energy density of an electrode and life characteristics of a battery, and a secondary battery including the same are provided.

First claim

The invention claimed is:

1. A lithium secondary battery comprising a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte solution,
wherein the positive electrode comprises a positive electrode active material,
wherein the negative electrode comprises a negative electrode active material, wherein the negative electrode active material comprises a metallic lithium thin film
wherein the electrolyte solution comprises an organic solvent and a lithium salt, and
wherein the positive electrode active material comprises:
a core including a lithium composite metal oxide; and
a film-shaped coating layer disposed to surround the core,
wherein the coating layer comprises at least one lithium ion conductive compound having a band gap of 5.5 eV to 10 eV,
wherein the lithium ion conductive compound is selected from the group consisting of LiBH 4 , LiBH 4 —LiI, and Li 2 NH, and
a thickness (d) of the coating layer satisfies X<d≤100X, where X is a maximum distance at which electrons are capable of passing through the coating layer by a dielectric breakdown electric field when charging to an open circuit voltage of the lithium composite metal oxide versus lithium, wherein X is determined by Equation 1, wherein d is less than 500 nm:
X=V/F b   [Equation 1]

wherein, in Equation 1, V is the open circuit voltage of the lithium composite metal oxide versus lithium, and F b is a dielectric breakdown electric field value calculated by Equation 2, and

F
b

=

24.442
⁢

⁢

exp
⁡

(

0.315
⁢

⁢

E

g
ω

⁢
max

)

[

Equation
⁢

⁢
2

]

wherein, in Equation 2, E g is a band gap, and ω max is a maximum phonon frequency.

2. The lithium secondary battery of claim 1 , wherein the thickness (d) of the coating layer satisfies X<d<X b , where X b is the thickness of the coating layer when bulk resistance of the coating layer is calculated by Equation 3 is 10Ω:
Bulk resistance of the coating layer=lithium ion conductivity of the lithium ion conductive compound×the thickness of the coating layer  [Equation 3].

3. The lithium secondary battery of claim 1 , wherein the lithium ion conductive compound has a band gap of 5.8 eV to 10 eV.

4. The lithium secondary battery of claim 1 , wherein the lithium ion conductive compound has a lithium ion conductivity at 25° C. of 1×10 −8 S/cm to 1×10 −2 S/cm and a density of 0.5 g/cm 3 or more.

5. The lithium secondary battery of claim 1 , wherein the lithium composite metal oxide is an oxide including lithium; and at least one metal selected from the group consisting of nickel, manganese, cobalt, and aluminum.

6. The lithium secondary battery of claim 1 , wherein the lithium composite metal oxide is doped with at least one element selected from the group consisting of tungsten (W), molybdenum (Mo), zirconium (Zr), titanium (Ti), magnesium (Mg), tantalum (Ta), aluminum (Al), iron (Fe), vanadium (V), chromium (Cr), barium (Ba), calcium (Ca), and niobium (Nb).

7. A method of preparing the lithium secondary battery of claim 1 , comprising: forming the film-shaped coating layer on the core including the lithium composite metal oxide to the thickness (d) satisfying X<d≤100X, where X is the maximum distance at which electrons are capable of passing through the coating layer by a dielectric breakdown electric field when charging to an open circuit voltage of the lithium composite metal oxide versus lithium, wherein X is determined by Equation 1 using at least one lithium ion conductive compound having a band gap of 5.5 eV to 10 eV, wherein the lithium ion conductive compound is selected from the group consisting of LiBH 4 , LiBH 4 —LiI, and Li 2 NH, wherein the thickness (d) of the coating layer is less than 500 nm, and
X=V/F b   [Equation 1]

wherein, in Equation 1, V is the open circuit voltage of the lithium composite metal oxide versus lithium, and F b is a dielectric breakdown electric field value calculated by Equation 2, and

F
b

=

24.442
⁢

⁢

exp
⁡

(

0.315
⁢

⁢

E

g
ω

⁢
max

)

[

Equation
⁢

⁢
2

]

wherein, in Equation 2, E g is a band gap, and ω max is a maximum phonon frequency.

Assignees

• Lg Chemical Ltd
• Lg Energy Solution Ltd

Inventors

• Park Eun Kyung
• Jang Min Chul
• Chung Chan Yeup
• Sung Da Young
• Park Chang Hun

Classifications

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• H01M4/525

  of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy · CPC title

• H01M4/0407

  by coating on an electrolyte layer · CPC title

• H01M4/505

  of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy · CPC title

• Y02E60/10

  Energy storage using batteries · CPC title