ELECTRODE STRUCTURES

1 . A structure for use in an energy storage device, the structure comprising a population of microstructured anodically active material layers, wherein (a) members of the population comprise a fibrous or porous anodically active material and have (i) a surface that is substantially perpendicular to a reference plane, (ii) a thickness, T, of at least 1 micrometer measured in a direction parallel to the reference plane, (iii) a height, H A , of at least 50 micrometers measured in a direction orthogonal to the reference plane, and (iv) a void volume fraction of at least 0.1, and (b) the lineal distance, D L , between at least two members of the population, measured in a direction parallel to the reference plane, is greater than the maximum value of H A for the population.

2 . The structure of claim 1 wherein each member of the population comprises aluminum, tin, silicon or an alloy thereof.

3 . The structure of claim 1 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof.

4 . The structure of claim 1 wherein each member of the population comprises silicon or an alloy thereof and has a thickness of about 1 to about 100 micrometers.

5 . The structure of claim 1 wherein for each member of the population H A is greater than T.

6 . The structure of claim 1 wherein each member of the population comprises porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, and a thickness of about 1 to about 200 micrometers.

7 . The structure of claim 1 wherein the each member of the population is supported by a backbone having an electrical conductivity of less than 10 Siemens/cm.

8 . The structure of claim 1 wherein the maximum value of H A for the population is less than 5,000 micrometers.

9 . The structure of claim 1 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone having an electrical conductivity of less than 10 Siemens/cm, and the maximum value of H A for the population is less than 5,000 micrometers.

10 . The structure of claim 1 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone having an electrical conductivity of less than 1 Siemens/cm, and the maximum value of H A for the population is less than 1,000 micrometers.

11 . The structure of claim 1 wherein the population comprises at least 20 members.

12 . An electrochemical stack for use in an energy storage device, the electrochemical stack comprising, in a stacked arrangement, cathode structures, separator layers and anode structures, the separator layers being disposed between the anode structures and the cathode structures, the direction of stacking of the cathode structures, the separator layers, and the anode structures being parallel to a reference plane, the anode structures comprising a population of microstructured anodically active material layers wherein (a) members of the population comprise a fibrous or porous anodically active material and have (i) a surface that is substantially perpendicular to the reference plane, (ii) a thickness, T, of at least 1 micrometer measured in a direction parallel to the reference plane, (iii) a height, H A , of at least 50 micrometers measured in a direction orthogonal to the reference plane, and (iv) a void volume fraction of at least 0.1, and (b) the lineal distance, D L , between at least two members of the population, measured in a direction parallel to the reference plane, is greater than the maximum value of H A for the population.

13 . The electrochemical stack of claim 12 wherein the population comprises at least 20 members.

14 . The electrochemical stack of claim 12 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof.

15 . The electrochemical stack of claim 12 wherein each member of the population comprises silicon or an alloy thereof and has a thickness of about 1 to about 100 micrometers.

16 . The electrochemical stack of claim 12 wherein for each member of the population H A is greater than T.

17 . The electrochemical stack of claim 12 wherein each member of the population comprises porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, and a thickness of about 1 to about 200 micrometers.

18 . The electrochemical stack of claim 12 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone and the maximum value of H A for the population is less than 5,000 micrometers.

19 . The electrochemical stack of claim 12 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone having an electrical conductivity of less than 10 Siemens/cm, and the maximum value of H A for the population is less than 1,000 micrometers.

20 . The electrochemical stack of claim 12 wherein the anode structures comprise an anode current collector, the cathode structures comprise a cathode current collector, and the anode current collector or the cathode current collector comprises an ionically permeable conductor layer.

21 . The electrochemical stack of claim 12 wherein the anode structures comprise an anode current collector layer and the anode current collector layer is disposed between the anodically active material layer and a separator layer.

22 . The electrochemical stack of claim 21 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone and the maximum value of H A for the population is less than 5,000 micrometers.

23 . The electrochemical stack of claim 12 wherein the cathode structures comprise a cathode current collector layer and the cathode current collector layer is disposed between the cathodically active material layer and a separator layer.

24 . An energy storage device comprising carrier ions, a non-aqueous electrolyte and an electrochemical stack, the carrier ions being lithium, sodium or potassium ions, the electrochemical stack comprising, in a stacked arrangement, cathode structures, separator layers and anode structures, the separator layers being disposed between the anode structures and the cathode structures, the direction of stacking of the cathode structures, the separator layers, and the anode structures being parallel to a reference plane, the anode structures comprising a population of microstructured anodically active material layers wherein (a) members of the population comprise a fibrous or porous anodically active material and have (i) a surface that is substantially perpendicular to the reference plane, (ii) a thickness, T, of at least 1 micrometer measured in a direction parallel to the reference plane, (iii) a height, H A , of at least 50 micrometers measured in a direction orthogonal to the reference plane, and (iv) a void volume fraction of at least 0.1, and (b) the lineal distance, D L , between at least two members of the population, measured in a direction parallel to the reference plane, is greater than the maximum value of H A for the population.

25 . The energy storage device of claim 24 wherein the carrier ions are lithium ions.

26 . The energy storage device of claim 24 wherein the population comprises at least 20 members.

27 . The energy storage device of claim 24 wherein each member of the population comprises silicon or an alloy thereof and has a thickness of about 1 to about 100 micrometers.

28 . The energy storage device of claim 24 wherein for each member of the population H A is greater than T.

29 . The energy storage device of claim 24 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof.

30 . The energy storage device of claim 24 wherein each member of the population comprises porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, and a thickness of about 1 to about 200 micrometers.

31 . The energy storage device of claim 24 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone and the maximum value of H A for the population is less than 5,000 micrometers.

32 . The energy storage device of claim 24 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone having an electrical conductivity of less than 10 Siemens/cm, and the maximum value of H A for the population is less than 1,000 micrometers.

33 . The energy storage device of claim 24 wherein the anode structures comprise an anode current collector, the cathode structures comprise a cathode current collector, and the anode current collector or the cathode current collector comprises an ionically permeable conductor layer.

34 . The energy storage device of claim 24 wherein the anode structures comprise an anode current collector layer and the anode current collector layer is disposed between the anodically active material layer and a separator layer.

35 . The energy storage device of claim 34 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone and the maximum value of H A for the population is less than 5,000 micrometers.

36 . A secondary battery comprising carrier ions, a non-aqueous electrolyte and at least two electrochemical stacks, the carrier ions being lithium, sodium or potassium ions, each of the electrochemical stacks comprising, in a stacked arrangement, cathode structures, separator layers and anode structures, the separator layers being disposed between the anode structures and the cathode structures, the direction of stacking of the cathode structures, the separator layers, and the anode structures with each such electrochemical stack being parallel to a reference plane, the anode structures comprising a population of microstructured anodically active material layers wherein (a) members of the population comprise a fibrous or porous anodically active material and have (i) a surface that is substantially perpendicular to the reference plane, (ii) a thickness, T, of at least 1 micrometer measured in a direction parallel to the reference plane, (iii) a height, H A , of at least 50 micrometers measured in a direction orthogonal to the reference plane, and (iv) a void volume fraction of at least 0.1, the electrochemical stacks being stacked relative to each other in a direction that is orthogonal to the reference plane.

37 . The secondary battery of claim 36 wherein the carrier ions are lithium ions.

38 . The secondary battery of claim 36 wherein the population comprises at least 20 members.

39 . The secondary battery of claim 36 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof.

40 . The secondary battery of claim 36 wherein each member of the population comprises silicon or an alloy thereof and has a thickness of about 1 to about 100 micrometers.

41 . The secondary battery of claim 36 wherein for each member of the population H A is greater than T.

42 . The secondary battery of claim 36 wherein each member of the population comprises porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, and a thickness of about 1 to about 200 micrometers.

43 . The secondary battery of claim 36 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone and the maximum value of H A for the population is less than 5,000 micrometers.

44 . The secondary battery of claim 36 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone having an electrical conductivity of less than 10 Siemens/cm, and the maximum value of H A for the population is less than 1,000 micrometers.

45 . The secondary battery of claim 36 wherein the anode structures comprise an anode current collector, the cathode structures comprise a cathode current collector, and the anode current collector or the cathode current collector comprises an ionically permeable conductor layer.

46 . The secondary battery of claim 36 wherein the anode structures comprise an anode current collector layer and the anode current collector layer is disposed between the anodically active material layer and a separator layer.

47 . The secondary battery of claim 36 wherein each member of the population comprises nanowires of silicon or an alloy thereof, or porous silicon or an alloy thereof, has a void volume fraction of at least 0.1 but less than 0.8, a thickness of about 1 to about 200 micrometers, and is supported by a backbone and the maximum value of H A for the population is less than 5,000 micrometers.