Electroactive Materials for Metal-Ion Batteries

Abstract

This invention relates in general to electroactive materials and a process for the preparation thereof. The electroactive particles comprise a comprise a porous particle framework, wherein the total pore volume of pores having pore diameter in the range from 3.5 to 100 nm is in the range from 0.3 to 2.4 cm3 per gram of the porous particle framework. The pores of the porous particle are at least partially occupied by a multilayer coating that is disposed on the internal pore surfaces of the porous particle framework. The multilayer coating comprises at least a first electroactive material layer, a second electroactive material layer, and a first interlayer material disposed between the first and second electroactive material layers.

Claims

1-36. (canceled)

37. A particulate material in the form of a plurality of composite particles, wherein the composite particles comprise: (a) a porous particle framework, wherein the total pore volume of pores having pore diameter in the range from 3.5 to 100 nm is P.sup.1 cm.sup.3 per gram of the porous particle framework, as determined by nitrogen gas adsorption, where P.sup.1 represents a number in the range from 0.3 to 2.4; (b) a multilayer coating disposed on the internal pore surfaces of the porous particle framework, wherein the multilayer coating comprises at least: (i) a first electroactive material layer; (ii) a second electroactive material layer; and (iii) a first interlayer material disposed between the first and second electroactive material layers.

38. The particulate material according to claim 37, wherein the porous particle framework is a conductive porous particle framework.

39. The particulate material according to claim 38, wherein the conductive porous particle framework is a conductive porous carbon particle framework, optionally wherein the conductive porous carbon particle framework comprises at least 80 wt % carbon.

40. The particulate material according to claim 37, wherein P.sup.1 is in the range from 0.8 to 2.3.

41. The particulate material according to claim 37, wherein the volume fraction of pores having a pore diameter in the range from 5 to 60 nm is at least 50 vol %, based on the total pore volume of pores having pore diameter in the range from 3.5 to 100 nm in the porous particle framework.

42. The particulate material according to claim 37, wherein the total volume of pores having diameter less than 3.5 nm in the porous particle framework, as determined by nitrogen gas adsorption, is P.sup.2 cm.sup.3/g, wherein P.sup.2 represents a number having a value of less than 0.25.

43. The particulate material according to claim 37, wherein the total volume of pores having diameter less than 3.5 nm in the porous particle framework, as determined by nitrogen gas adsorption, is P.sup.2 cm.sup.3/g, wherein P.sup.2 is no more than [0.5×P.sup.1].

44. The particulate material according to claim 37, wherein the porous particle framework has a BET surface area in the range from 250 m.sup.2/g to 2,500 m.sup.2/g.

45. The particulate material according to claim 37, wherein the first and second electroactive material layers independently comprise an electroactive material selected from elemental silicon, elemental tin, elemental germanium, elemental aluminium, and mixtures and alloys thereof.

46. The particulate material according to claim 37, wherein the first and second electroactive material layers both comprise elemental silicon.

47. The particulate material according to claim 37, wherein the first interlayer material comprises a passivation layer formed on the surface of the first electroactive material layer, wherein the passivation layer is an oxide, nitride, oxynitride or carbide of the first electroactive material.

48. The particulate material according to claim 37, wherein the first interlayer material comprises a passivation layer formed on the surface of the first electroactive material layer, wherein the passivation layer comprises a carbon-containing organic moiety covalently bonded to the surface of the first electroactive material layer.

49. The particulate material according to claim 37, wherein the first interlayer material comprises a conductive pyrolytic carbon material, a conductive metal layer, or a lithium-ion permeable solid electrolyte.

50. The particulate material according to claim 37, wherein the multilayer coating comprises n electroactive material layers and (n−1) interlayer materials disposed between each of the electroactive material layers, wherein n is an integer from 3 to 20.

51. The particulate material according to claim 50, wherein: (i) each of then electroactive materials is silicon; and (ii) each of the (n−1) interlayer materials is independently a passivation layer formed on the surface of the first electroactive material layer, wherein the passivation layer is an oxide, nitride, oxynitride or carbide of the first electroactive material or a carbon-containing organic moiety covalently bonded to the surface of the first electroactive material layer; or comprises a conductive pyrolytic carbon material, a conductive metal layer, or a lithium-ion permeable solid electrolyte.

52. The particulate material according to claim 37, wherein further comprising: (iv) a coating layer disposed on the surface of the outermost electroactive material layer.

53. The particulate material according to claim 37, wherein the amount of electroactive material in the composite particles of the invention is selected such that at least 25% and up to 80% of the internal pore volume of the porous particle framework is occupied by the electroactive material(s) and interlayer material(s).

54. The particulate material according to claim 37, wherein the composite particles comprise from 35 wt % to 75 wt % silicon.

55. The particulate material according to claim 37, wherein at least 85 wt %, more preferably at least 90 wt %, more preferably at least 95 wt %, more preferably at least 98 wt % of the electroactive material mass in the composite particles is located within the internal pore volume of the porous particle framework.

56. The particulate material according to claim 37, wherein the composite particles have a D.sub.50 particle diameter in the range from 0.5 to 200 μm.

57. A process for preparing composite particles, comprising: (a) providing a plurality of porous particles, wherein the total pore volume of pores having pore diameter in the range from 3.5 to 100 nm is P.sup.1 cm.sup.3 per gram of the porous particles, as determined by nitrogen gas adsorption, where P.sup.1 represents a number in the range from 0.3 to 2.4; (b) depositing a first electroactive material layer onto the internal pore surfaces of the porous particles; (c) forming a first interlayer material on the surface of the first electroactive material layer; (d) depositing a second electroactive material layer onto the surface of the first interlayer material.

58. A composition comprising a particulate material as defined in claim 37 and at least one other component.

59. An electrode comprising a particulate material as defined in claim 37 in electrical contact with a current collector.

60. A rechargeable metal-ion battery comprising: (i) an anode, wherein the anode comprises an electrode as described in claim 59 (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

Preparation of Composite Particles in a Fluidized Bed Reactor

[0270] 70 g of a particulate porous carbon framework was placed in a stainless steel fluidized bed reactor with a gas inlet consisting of 5 nozzles with 8×0.8 mm holes each, allowing for a disperse gas mixing. The cross sectional area of the fluidised bed is 0.058 m allowing for calculations of superficial velocities. The reactor was suspended from a frame and a vertically-oriented tube furnace was positioned such that the hot zone ran from the conical section to ¾ of the length of the cylindrical section (approx. 380 mm long). The minimum fluidization velocity was determined with a cold-flow pressure-drop test with nitrogen as an inert gas, ramping gas flow rate between 1 to 5 L/min. Once minimum fluidizing velocity was determined, the inert gas flow rate was held constant at or above the minimum fluidizing velocity. The furnace was ramped to the desired reaction temperature under constant inert gas flow rate. After stabilizing at a target temperature between 435-500° C., the fluidizing gas was switched from pure nitrogen to 4 vol % monosilane in nitrogen. The reaction progress was monitored by measuring pressure drop and furnace temperature difference between top and bottom. The gas flow rate was adjusted throughout the run to maintain a pressure drop consistent with continued fluidization and minimum temperature difference between the top and bottom of the bed of less than 100° C. was maintained. Dosing of monosilane is performed over a period of 6 hours or depending on the layer thickness, the reactor is then purged with nitrogen for 30 minutes to remove any excess monosilane. Then a pyrolytic carbon interlayer is formed by flowing through 30% Ethylene/Nitrogen mix for 30 minutes at temperatures between 300° C. — 500° C., then the reactor is purged with nitrogen for 30 minutes to remove any ethylene. The process of introducing monosilane and ethylene reactants was repeated depending on how many layers were needed. At the end of the layering technique the fluidizing gas was then switched to pure nitrogen whilst maintaining fluidisation, this purge lasted 30 minutes. Then the furnace was allowed to settle to ambient temperature over several hours. On reaching ambient temperature, the furnace atmosphere was switched to air gradually over a period of hours.