Lithium secondary cell

• US 20040110068A1
• Filed: 12/05/2003
• Published: 06/10/2004
• Est. Priority Date: 06/07/2001
• Status: Abandoned Application

• Current Assignee: Mitsubishi Chemical Corporation (Mitsubishi Chemical Group Corp.)
• Original Assignee: Mitsubishi Chemical Corporation (Mitsubishi Chemical Group Corp.)
• Inventors: Saito, Hiroyuki, Yamamoto, Masaki, Kobayashi, Mitsuharu, Seki, Keiichi
• Application Number:
  US10/727,661
• Publication Number:
  US 20040110068A1
• Time in Patent Office: Days
• US Class Current: 429/326
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/0565 Polymeric materials, e.g. gel-type or solid-type
• CPC Class Codes: H01M 10/0567 characterised by the additives
• CPC Class Codes: H01M 10/42 Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells H01M10/60 takes precedence
• CPC Class Codes: H01M 10/4235 Safety or regulating additives or arrangements in electrodes, separators or electrolyte H01M10/4242 takes precedence
• CPC Class Codes: H01M 2004/028 Positive electrodes
• CPC Class Codes: H01M 2300/0085 Immobilising or gelification of electrolyte
• CPC Class Codes: H01M 4/13 Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
• CPC Class Codes: H01M 4/364 as mixtures
• CPC Class Codes: H01M 4/485 of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy H01M4/505, H01M4/525 take precedence
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/62 Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
• CPC Class Codes: H01M 50/124 having a layered structure
• CPC Class Codes: H01M 50/178 for pouch or flexible bag cells
• CPC Class Codes: H01M 50/55 on the same side of the cell
• CPC Class Codes: H01M 50/553 Terminals adapted for prismatic, pouch or rectangular cells
• CPC Class Codes: H01M 50/562 characterised by the material
• CPC Class Codes: H01M 50/566 by welding, soldering or brazing
• CPC Class Codes: H01M 6/40 Printed batteries , e.g. thin film batteries
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

A safe high-performance lithium secondary cell is provided whereby bulging of a lithium secondary cell during storage at a high temperature, which is particularly problematic when a casing accommodating a cell element is a variable shape casing, is suppressed.

The present invention provides a lithium secondary cell comprising a cell element which comprises a positive electrode, a negative electrode and an electrolyte comprising a non-aqueous solvent and a solute, and a variable shape casing which accommodates the cell element, wherein the cell element contains an additive α, and ΔEadd(AN) is smaller than ΔEsol(AN), where ΔEsol(AN) is the difference represented by Esol(A)−Esol(N), where Esol(N) is the enthalpy of a neutral molecule of the non-aqueous solvent, as obtained by a prescribed calculation method, and Esol(A) is the enthalpy of an anion radical formed by giving one electron to the neutral molecule, and ΔEadd(AN) is the difference represented by Eadd(A)−Eadd(N), where Eadd(N) is the enthalpy of a neutral molecule of the additive α, as obtained by a prescribed calculation method, and Eadd(A) is the enthalpy of an anion radical formed by giving one electron to the neutral molecule.

Claims

1. A lithium secondary cell comprising a cell element which comprises a positive electrode, a negative electrode and an electrolyte comprising a non-aqueous solvent and a solute, and a variable shape casing which accommodates the cell element, wherein the cell element contains an additive α

, and Δ

Eadd(AN) is smaller than Δ

Esol(AN), where Δ

Esol(AN) is the difference represented by Esol(A)−

Esol(N), where Esol(N) is the enthalpy of a neutral molecule of the non-aqueous solvent and Esol(A) is the enthalpy of an anion radical formed by giving one electron to the neutral molecule, as obtained by the following calculation method (#), and Δ

Eadd(AN) is the difference represented by Eadd(A)−

Eadd(N), where Eadd(N) is the enthalpy of a neutral molecule of the additive α and

Eadd(A) is the enthalpy of an anion radical formed by giving one electron to the neutral molecule, as obtained by the following calculation method (#),

Calculation method (#);

The enthalpy of a neutral molecule and the enthalpy of an anion radical are, respectively, obtained by quantum chemical calculations by an ab initio restricted Hartree-Fock molecular orbital method employing 6-31G* basis function system.

2. The lithium secondary cell according to claim 1, wherein Δ

Esol(AN)−

Δ

Eadd(AN), i.e. the difference between Δ

Esol(AN) and Δ

Eadd(AN), is at least 0.1 eV and at most 4 eV.

3. The lithium secondary cell according to claim 1, wherein the additive α

is a Lewis acid.

4. The lithium secondary cell according to claim 1, wherein the additive α

is a sulfur compound having at least one sulfur-oxygen double bond.

5. The lithium secondary cell according to claim 4, wherein the sulfur compound is represented by the following formula (1):

6. The lithium secondary cell according to claim 4, wherein the sulfur compound is represented by the following formula (2):

7. The lithium secondary cell according to claim 4, wherein the sulfur compound is at least one member selected from the group consisting of diethyl sulfoxide, diphenyl sulfoxide, tetramethylene sulfoxide, methyl methanesulfinate, ethyl ethanesulfinate, dimethyl sulfite, diethyl sulfite, 1,2-propylene glycol sulfite, 1,3-butylene glycol sulfite, diphenyl sulfite, ethylene sulfite, vinylene sulfite, dimethyl sulfone, diethyl sulfone, ethylmethyl sulfone, diphenyl sulfone, dibenzyl sulfone, sulfolane, 3-methyl sulfolane, 3-methyl sulfolene, methyl methane sulfonate, ethyl methanesulfonate, acetyl methanesulfonate, tetrahydrofurfuryl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, methyl propanesulfonate, methyl benzenesulfonate, 1,3-propanesultone, 1,4-butanesultone, dimethyl sulfate, diethyl sulfate, ethylmethyl sulfate, methylphenyl sulfate, ethylene glycol sulfuric acid ester, 1,3-propanediol sulfuric acid ester and 1,4-butanediol sulfuric acid ester.

8. The lithium secondary cell according to claim 4, wherein the sulfur compound is contained in an electrolyte.

9. The lithium secondary cell according to claim 4, wherein the sulfur compound is contained in an amount of at least 0.001 part by weight and at most 30 parts by weight, to the total amount of the solute and the non-aqueous solvent.

10. The lithium secondary cell according to claim 1, wherein the positive electrode contains a lithium-nickel compound oxide.

11. The lithium secondary cell according to claim 10, wherein the lithium-nickel compound oxide is represented by the following formula (3):

Li_aNi_XCo_YAl_ZO₂ 

 

(3)

(in the formula (3), a, X, Y and Z are, respectively, numbers which satisfy 0≦

a≦

1.1, 0.5≦

X≦

1, 0≦

Y≦

0.5, 0≦

Z≦

0.1, and 0.9≦

X+Y+Z1.1).

12. The lithium secondary cell according to claim 10, wherein the specific surface area of the lithium-nickel compound oxide is within a range of from 0.01 to 10 m²/g.

13. The lithium secondary cell according to claim 1, wherein the positive electrode contains an organic acid and/or a lithium salt of an organic acid.

14. The lithium secondary cell according to claim 13, wherein the organic acid is a bivalent or higher valent organic acid.

15. The lithium secondary cell according to claim 13, wherein the lithium salt of an organic acid is a lithium salt of a bivalent or higher valent organic acid.

16. The lithium secondary cell according to claim 13, wherein the positive electrode has a positive electrode material layer formed on a current collector, and the organic acid and/or the lithium salt of an organic acid is contained in an amount within a range of at least 0.1 wt % and at most 1 wt %, based on the weight obtained by deducting the weight of the organic acid and/or the lithium salt of an organic acid from the total weight of the positive electrode material layer.

17. The lithium secondary cell according to claim 1, wherein the electrolyte further contains a polymer.

18. The lithium secondary cell according to claim 17, wherein the polymer is a cross-linkable polymer.

19. The lithium secondary cell according to claim 18, wherein the cross-linkable polymer is an acrylic polymer.

20. The lithium secondary cell according to claim 1, wherein the variable shape casing is made of a laminated film comprising a gas barrier layer and a resin layer.