ADDITIVE FOR LITHIUM ION RECHAGEABLE BATTERY CELLS

• US 20130069601A1
• Filed: 06/07/2011
• Published: 03/21/2013
• Est. Priority Date: 06/07/2010
• Status: Active Grant

• Current Assignee: SK On Company Limited (SK Innovation Company Limited)
• Original Assignee: Nexeon Limited
• Inventors: Coowar, Fazlil, Lain, Michael Jonathan, Abdelsalam, Mamdouh Elsayed
• Granted Patent: US 8,945,774 B2
• Time in Patent Office: Days
• US Class Current: 320/162
• 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 10/056 characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
• CPC Class Codes: H01M 10/0566 Liquid materials
• CPC Class Codes: H01M 10/0567 characterised by the additives
• CPC Class Codes: H01M 10/0568 characterised by the solutes
• CPC Class Codes: H01M 10/0569 characterised by the solvents
• CPC Class Codes: H01M 10/44 Methods for charging or discharging circuits for charging H02J7/00
• CPC Class Codes: H01M 2300/0025 Organic electrolyte
• CPC Class Codes: H01M 2300/0034 Fluorinated solvents
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/38 of elements or alloys
• CPC Class Codes: H01M 4/386 Silicon or alloys based on silicon
• CPC Class Codes: H01M 4/387 Tin or alloys based on tin
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

The present invention claims the addition of vinylene carbonate (VC) and optionally also fluoroethylene carbonate to the electrolyte of lithium ion cells having a structural silicon composite anode, i.e. an anode containing fibres or particles of silicon. The additive significantly improves the cycling performance of the cells. A VC content in the range 3.5-8 wt % based on the weight of the electrolyte has been found to be optimum.

Claims

1. A lithium ion rechargeable battery cell comprising:

an anode comprising an electroactive material-containing particles selected from;

a) particles having spaced-apart structural elements on their surface, the smallest dimension of the structural elements on the particle surface being at least 10 nm and less than or equal to 10 μ

m and having an aspect ratio (defined as the ratio of the largest to smallest dimensions of the structural element) of at least 5;

b) particles that have pores or voids dispersed therein, each pore or void being defined by one or more walls having an average wall thickness of ≧

10 nm,

c) particles comprising fragments of particles that have pores or voids dispersed therein, each pore or void being defined by one or more walls having an average thickness of ≧

10 nm;

d) particles having a minimum dimension of at least 10 nm and an aspect ratio (ratio of the smallest to largest dimension) of at least 5;

e) particles comprising a columnar bundle of nano-rods having a diameter of 50 to 100 nm and a length of 2 to 5 μ

m, wherein each nano-rod has a diameter of at least 10 nm;

f) felt structures formed from particles as defined in (d) above;

g) scaffold structures formed from particles as defined in (d) above;

h) substrate particles comprising a dispersion of an electroactive material on a particulate substrate, wherein the particulate substrate is formed from a non-electroactive material, a conductive material or an electroactive material having a different composition to the electroactive material dispersed thereon;

i) or a mixture thereof;

a cathode comprising an active material capable of incorporating lithium and also of liberating lithium electrochemically and

an electrolyte;

wherein the electrolyte comprises 0 to 8 wt % of a cyclic carbonate including a vinyl group and 0 to 70 wt % of a fluorinated cyclic carbonate, with the proviso that the total amount of the cyclic carbonate including a vinyl group and the fluorinated cyclic carbonate is in the range 3.5 wt % to 70 wt % based on the total weight of the electrolyte solution.

2. A lithium ion rechargeable battery cell according to claim 1, where the electroactive material is a silicon-containing electroactive material.

3. A lithium ion rechargeable battery cell according to claim 1, said cell comprising:

an anode comprising active material comprising silicon-containing particles selected from;

a) particles having spaced-apart structural elements on its surface, the smallest dimension of the structural elements being at least 50 nm and less than or equal to 10 μ

m and having an aspect ratio (defined as the ratio of the largest to smallest dimensions of the element) of at least 5;

b) particles that includes at least one void defined by one or more walls having an average wall thickness of ≧

50 nm;

c) particles comprising fragments of particles that include at least one void, each void being defined by one or more walls having an average thickness of ≧

50 nm;

d) particles having a minimum dimension of at least 50 nm and an aspect ratio (ratio of the smallest to largest dimension) of at least 5;

e) particles comprising a columnar bundle of nano-rods having a diameter of 50 to 100 nm and a length of 2 to 5 μ

m, wherein each nano-rod has a diameter of at least 10 nm;

f) felt structures formed from particles as defined in (d) above;

g) scaffold structures formed from particles as defined in (d) above;

h) or a mixture thereof;

a cathode comprising an active material capable of incorporating lithium and also of liberating lithium electrochemically and

an electrolyte;

wherein the electrolyte comprises 0 to 8 wt % of a cyclic carbonate including a vinyl group and 0 to 70 wt % of a fluorinated cyclic carbonate, with the proviso that the total amount of the cyclic carbonate including a vinyl group and the fluorinated cyclic carbonate is in the range 3.5 wt % to 70 wt % based on the total weight of the electrolyte solution.

4. A cell according to claim 1, wherein the electrode material specified in paragraph (a) has a smallest dimension of no more than 1000 nm.

5. A cell as claimed in claim 1 wherein the electroactive material-containing particles are fibres selected from the group comprising tin-containing fibres, gallium containing fibres and silicon-containing fibres with a diameter of 10-500 nm and length of 1-150 μ

m, such fibres optionally being provided in the form of a scaffold or felt comprising such fibres.

6. A cell as claimed in claim 1, wherein the electroactive material-containing particles are fibres selected from the group comprising tin-containing fibres, gallium containing fibres and silicon-containing fibres with a diameter of 50-250 nm and length of 1-80 μ

m, such fibres optionally being provided in the form of a scaffold or felt comprising such fibres.

7. A cell as claimed in claim 1, wherein the electroactive material-containing particles are tubes selected from the group comprising tin-containing tubes, gallium containing tubes and silicon-containing tubes with a wall thickness of ≧

10 nm and length of ≧

1 μ

m.

8. A cell as claimed in claim 1, wherein the electroactive material-containing particles are tubes selected from the group comprising tin-containing tubes, gallium containing tubes and silicon-containing tubes with a wall thickness of ≧

50 nm and length of ≧

1 μ

m.

9. A cell as claimed in claim 1, wherein the electroactive material-containing particles are ribbons selected from the group comprising tin-containing ribbons, gallium containing ribbons and silicon-containing ribbons with a thickness of 50-200 nm, a width of 500 nm to 1 μ

m and a length of 1 μ

m or felts comprising such ribbons.

10. A cell as claimed in claim 1, wherein the electroactive material-containing particles are flakes selected from the group comprising tin containing flakes, gallium containing flakes and silicon-containing flake with a thickness of 50-200 nm and the two other dimensions in the range of 1-20 μ

m.

11. A cell as claimed in claim 1, wherein the silicon-containing particles are silicon-containing pillared particles consisting of a silicon-based particle core of diameter 5-25 μ

m with an array of silicon pillars attached thereto, the pillars having diameter of no more than 1000 nm and a length of 1-5 μ

m.

12. A cell as claimed in claim 1, wherein the silicon-containing particles are silicon-containing pillared particles consisting of a silicon-based particle core of diameter 5-25 μ

m with an array of silicon pillars attached thereto, the pillars having diameter of 50-250 nm and a length of 1-5 μ

m.

13. A cell as claimed in claim 1, wherein the silicon-containing particles are silicon containing pillared particles wherein the largest dimension of the whole particle, including the pillars, is less than 40 μ

m.

14. A cell as claimed in claim 1, wherein the silicon-containing particles are silicon-containing porous particles, each particle having a network of voids or pores extending therethrough.

15. A cell as claimed in claim 14 wherein at least some of the walls between adjacent pores have a thickness of ≧

10 nm and extend over a length of ≧

100 nm, and wherein the diameter of the porous particle is 1-30 μ

m.

16. A cell as claimed in claim 14, wherein at least some of the walls between adjacent pores have a thickness of ≧

50 nm and extend over a length of ≧

100 nm, and wherein the diameter of the porous particle is 1-30 μ

m.

17. A cell as claimed in claim 1, wherein the silicon-containing particles are columnar bundle of nano-rods having a diameter of 50 to 100 nm and a length of 2 to 5 μ

m, wherein each nano-rod has a diameter of at least 10 nm.

18. A cell as claimed in claim 1, wherein the silicon-containing particles are substrate particles comprising a dispersion of an electroactive material on a particulate substrate, where the particulate substrate is formed from a non-electroactive material having a different composition to the electroactive material dispersed thereon.

19. A cell as claimed in claim 1, wherein the anode includes an active material other than silicon that can reversibly react electrochemically with lithium.

20. A cell as claimed in claim 1, wherein the silicon is carbon coated.

21. A cell as claimed in claim 1, wherein the silicon particles have a silicon purity of 90-99.990% by weight, e.g. 95-99.80% by weight.

22. A cell as claimed in claim 1, wherein substantially all the active material in the anode comprises silicon.

23. A cell as claimed in claim 1 wherein the electrolyte includes both a cyclic carbonate including a vinyl group and a fluorinated cyclic carbonate.

24. A cell according to claim 1, wherein the fluorinated cyclic carbonate initially comprises 3.5 to 70 wt % of the total weight of the electrolyte solution.

25. A cell according to claim 1, wherein the electrolyte includes said fluorinated cyclic carbonate in an initial amount of 3.5-30 wt % based on the total weight of the electrolyte.

26. A cell according to claim 1, with the further proviso that when the amount of cyclic carbonate including a vinyl group comprise 0% of the electrolyte solution, the amount of the fluorinated cyclic carbonate comprises at least 12 wt % of the total weight of the electrolyte solution and the anode active silicon material includes unstructured silicon material as well as the structured silicon material referred to above.

27. A cell according to claim 1, wherein the electrolyte comprises at least 1%, 2%, 3%, 5%, 10% or 15% by weight of a cyclic carbonate including a vinyl group.

28. A cell according to claim 1, wherein the electrolyte comprises 3.5 to 8% by weight of a cyclic carbonate including a vinyl group.

29. A cell according to claim 1, wherein the cyclic carbonate including a vinyl group comprises, in an initial amount, 4.5-6 wt % based on the total weight of the electrolyte.

30. A cell according to claim 1, wherein the electrolyte comprises a mixture of a cyclic carbonate including a vinyl group and a fluorinated cyclic carbonate, the mixture being present in an initial amount of at least 3.5% based on the total weight of the electrolyte and optionally at least 5%.

31. A cell according to claim 1, wherein the electrolyte comprises at least 10% by weight of a fluorinated cyclic carbonate.

32. A cell according to claim 1, wherein the electrolyte comprises at least 15% by weight of a fluorinated cyclic carbonate.

33. A cell according to claim 1, wherein the electrolyte comprises at least 30% by weight of a fluorinated cyclic carbonate.

34. A cell according to claim 1, wherein the electrolyte comprises no more than 50% by weight of a fluorinated cyclic carbonate.

35. A cell according to claim 1, wherein the cyclic carbonate including a vinyl group is vinylene carbonate.

36. A cell according to claim 1, wherein the fluorinated cyclic carbonate is fluoroethylene carbonate, difluoroethylene carbonate or a mixture thereof.

37. A cell as claimed in claim 1, wherein the electrolyte initially includes 0.05 to 0.25 wt % dissolved CO₂.

38. A cell according to claim 1, wherein the electrolyte includes a cyclic carbonate including a vinyl group, a fluorinated cyclic carbonate and dissolved CO₂.

39. A cell according to claim 38, wherein the anode containing active material further comprises unstructured silicon material as well as structured silicon material.

40. A cell according to claim 38, wherein the cyclic carbonate including a vinyl group is vinylene carbonate and the fluorinated cyclic carbonate is fluoroethylene carbonate, difluoroethylene carbonate or a mixture thereof.

41. A cell according to claim 1, wherein the electrolyte solution further comprises a C_1-8 chain carbonate.

42. A cell according to claim 41, wherein the C_1-8 chain carbonate is selected from one or more of dimethylcarbonate, diethyl carbonate, ethyl methyl carbonate.

43. A cell according to claim 1, wherein the electrolyte solution further comprises a cyclic carbonate other than a cyclic carbonate including a vinyl group or a fluorinated cyclic carbonate.

44. A cell according to claim 43, wherein the cyclic carbonate is selected from one or more of the group comprising ethylene carbonate, propylene carbonate, butylene carbonate.

45. A cell according to claim 41, wherein the ratio of the cyclic carbonate (including a cyclic carbonate including a vinyl group and/or a fluorinated cyclic carbonate) to the C_1-8 chain carbonate is in the range 30:

70 to 50;

50.

46. A cell according to claim 41, wherein the C_1-8 chain carbonate is dimethyl carbonate or ethyl methyl carbonate or a mixture thereof.

47. A cell according to claim 41, wherein the cyclic carbonate is ethylene carbonate.

48. A cell according to claim 1 comprising a silicon-containing electroactive material, a cathode comprising an active material capable of incorporating lithium and also of liberating lithium electrochemically and an electrolyte, wherein (1) the electrolyte comprises 1 to 8 wt % of a cyclic carbonate containing a vinyl group, 3 to 70 wt % of a fluorinated cyclic carbonate and 0.05 to 0.25% of CO₂ and (2) the silicon containing material includes a non-structured silicon material as well as the structured silicon material specified in any one of claims 1 to 3.

49. A cell according to claim 1, wherein the electrolyte further comprises an electrolyte salt, wherein the electrolye salt is dissolved in the electrolyte solution to a concentration of between 0.7 to 2M.

50. A cell according to claim 49, wherein the electrolye salt is dissolved in the electrolyte solution to a concentration of 1M.

51. A cell according to claim 49, wherein the electrolyte comprises one or a mixture of lithium containing electrolyte salts selected from the group comprising LiPF₆, LiBOB, LiClO₄ or a mixture thereof.

52. A cell according to claim 51, wherein the electrolyte comprises LiPF6 at a concentration of 0.9M nd LiBOB at a concentration of 0.1M.

53. A method of charging a cell as claimed in claim 1, which comprises charging it to less than 80% and preferably no more than 60%, of the theoretical maximum charge of an anode active mass.

54. A method as claimed in claim 53, wherein the anode active mass is formed substantially wholly of silicon material and the method comprises charging the cell to less than 3,400 mAhr per gram of silicon, e.g. no more than 2,500 mAhr/g.