Electroactive Materials for Use in Metal-Ion Batteries

Abstract

This invention relates to particulate electroactive materials consisting of a plurality of composite particles, wherein the composite particles comprise: (a) a porous conductive particle framework including micropores and/or mesopores having a total volume of at least 0.4 to 2.2 cm.sup.3/g; (b) an electroactive material disposed within the porous conductive particle framework; and (c) a lithium-ion permeable filler penetrating the pores of the porous conductive particle framework and disposed intermediate the nanoscale silicon domains and the exterior of the composite particles.

Claims

1-41. (canceled)

42. A particulate material consisting of a plurality of composite particles, wherein the composite particles comprise: (a) a conductive porous particle framework comprising micropores and/or mesopores, wherein the micropores and/or mesopores have a total pore volume in the range from 0.4 to 2.2 cm.sup.3/g; (b) a plurality of nanoscale electroactive material domains disposed within the porous conductive particle framework; (c) a lithium-ion permeable filler penetrating the pores of the porous conductive particle framework and disposed intermediate the nanoscale electroactive material domains and the exterior of the composite particles.

43. A particulate material according to claim 42, wherein the total volume of micropores and mesopores in the conductive porous particle framework is at least 0.6 cm.sup.3/g.

44. A particulate material according to claim 42, wherein the total volume of micropores and mesopores in the conductive porous particle framework is no more than 1.8 cm.sup.3/g.

45. A particulate material according to claim 42, wherein the conductive porous particle framework has a PD.sub.50 pore diameter of no more than 10 nm.

46. A particulate material according to claim 42, wherein the volumetric ratio of micropores to mesopores in the conductive porous particle framework is from 90:10 to 55:45.

47. A particulate material according to claim 42, wherein the conductive porous particle framework is a conductive porous carbon particle framework.

48. A particulate material according to claim 42, wherein the conductive porous particle framework has a BET surface area of at least 750 m.sup.2/g and no more than 4,000 m.sup.2/g.

49. A particulate material according to claim 42, wherein the electroactive material is silicon.

50. A particulate material according to claim 49, wherein the weight ratio of silicon to the conductive porous particle framework in the composite particles is in the range from [0.5×P.sub.1 to 1.3×P.sub.1]: 1, wherein P.sub.1 is a dimensionless quantity having the magnitude of the total pore volume of micropores and mesopores in the conductive porous particle framework when expressed in cm.sup.3/g.

51. A particulate material according to claim 49, wherein the composite particles comprise from 0.35 wt % to 0.65 wt % of silicon.

52. A particulate material according to claim 49, wherein the composite particles comprise at least 80 wt %, or from 80 to 98 wt % in total of silicon and carbon.

53. A particulate material according to claim 42, wherein at least 85 wt %, more preferably at least 90 wt % of the electroactive material mass in the composite particles is located within the internal pore volume of the conductive porous particle framework.

54. A particulate material according to claim 42, wherein the lithium-ion permeable filler material is a conductive pyrolytic carbon material.

55. A particulate material according to any claim 42, wherein the lithium-ion permeable filler material is a lithium-ion permeable solid electrolyte.

56. A particulate material according to claim 55, wherein the lithium-ion permeable solid electrolyte also forms a coating over at least a portion of the outer surface of the porous carbon framework.

57. A particulate material according to claim 42, wherein the composite particles have a D.sub.50 particle diameter in the range from 1 to 30 μm.

58. A particulate material according to claim 42, wherein the composite particles have a BET surface area of no more than 200 m.sup.2/g and at least 0.1 m.sup.2/g.

59. A particulate material according to claim 42, wherein the volume of micropores and mesopores of the composite particles, as measured by nitrogen gas adsorption, is no more than (0.15×P.sup.1) cm.sup.3/g, wherein P.sub.1 is a dimensionless quantity having the magnitude of the total pore volume of micropores and mesopores in the conductive porous particle framework when expressed in cm.sup.3/g.

60. A particulate material according to claim 42, having specific capacity on lithiation of 1200 to 2340 mAh/g.

61. A process for preparing a composite material, the process comprising: (a) providing a plurality of conductive porous particles comprising micropores and/or mesopores, wherein the micropores and/or mesopores have a total pore volume in the range from 0.4 to 2.2 cm.sup.3/g; (b) depositing an electroactive material selected from silicon, tin, aluminium, germanium and alloys thereof into the micropores and/or mesopores of the porous carbon frameworks using a chemical vapour infiltration process, wherein the deposited electroactive material partially occupies the pore volume of the conductive porous particles; and (c) depositing a lithium-ion permeable filler material into some or all of the remaining pore volume of the conductive porous particles.

62. A process according to claim 61, wherein step (b) further comprises contacting the surface of the deposited electroactive material with a passivating agent prior to step (c), wherein the electroactive material is not exposed to oxygen prior to contact with the passivating agent, and, wherein the passivating agent is selected from one or more compounds of the formula:
R—CH═CH—R;  (i)
R—C≡C—R;  (ii)
O═CH—R; and  (iii)
HX—R;  (iv) wherein X represents O, S, NR or PR, and each R independently represents H or an optionally substituted aliphatic or aromatic hydrocarbyl group having from 1 to 20 carbon atoms, preferably from 2 to 10 carbon atoms, or wherein two R groups in formula (i) or (iv) form an unsubstituted or substituted hydrocarbyl ring structure.

63. A composition comprising a particulate material according to claim 42 and at least one other component selected from: (i) a binder; (ii) a conductive additive; and (iii) an additional particulate electroactive material.

64. An electrode comprising a particulate material according to claim 42 in electrical contact with a current collector, optionally wherein the particulate material is in the form of a composition according to claim 63.

65. A rechargeable metal-ion battery comprising: an anode, wherein the anode comprises an electrode as described in claim 64; (ii) a cathode comprising a cathode active material capable of releasing and reabsorbing metal ions; and (iii) an electrolyte between the anode and the cathode.

Description

EXAMPLE 1: SYNTHESIS OF COMPOSITE PARTICLES IN A FLUIDISED BED REACTOR

[0152] Composite particles containing silicon as the electroactive material and a pyrolytic carbon material as the lithium-ion permeable filler were prepared in a vertical bubble-fluidized bed reactor comprising an 83 mm internal diameter stainless steel cylindrical vessel. A 75 g quantity of a powder of porous carbon framework particles was placed in the reactor and the reactor was then sealed and purged with nitrogen gas for 30 mins at a flow rate of 2 L/min. A pneumatic vibrator system was used to agitate the particle bed.

[0153] The reactor is then heated to a reaction temperature of between 430° C. and 460° C. at a ramp rate of 10° C. per minute and 4% v/v monosilane gas diluted in nitrogen was supplied to the bottom of the reactor at a flow rate of 3 L/min. Silicon deposition was continued for 9 hours then the reactor was again purged with nitrogen for 15 minutes. The reactor temperature was then ramped to a target temperature of 675° C. under nitrogen flow. An excess amount of styrene was placed in a Dreschel bottle and heated in a water bath, up to 75° C. After 10 minutes of furnace temperature stabilisation, styrene was allowed to flow into the reactor tube for 30 to 90 minutes by bubbling nitrogen of 2 L/min into the Dreschel bottle. The reactor then was purged with nitrogen and cooled down to ambient temperature under nitrogen, resulting in a carbon coated material. The atmosphere is then switched over to air gradually over a period of two hours by incrementally switching the gas flow from nitrogen to air from a compressed air supply.