Separators for three-dimensional batteries

An electrode structure comprising a population of electrodes comprising an electrode active material layer and a population of counter-electrodes comprising a counter-electrode active material layer wherein

• the population of electrodes is arranged in alternating sequence with the population of counter-electrodes along a first direction,
• each member of the electrode population has a bottom, a top, a length LE, a width WE, a height HE, and a longitudinal axis AE extending from the bottom to the top of each such member and in a direction that is transverse to the first direction, the length LE of each member of the electrode population being measured in the direction of its longitudinal axis AE, the width WE of each member of the electrode population being measured in the first direction, and the height HE of each member of the electrode population being measured in a direction that is perpendicular to the longitudinal axis AE of each such member and the first direction, the ratio of LE to each of WE and HE of each member of the electrode population being at least 5:1, respectively, the ratio of HE to WE for each member of the electrode population being between 0.4:1 and 1000:1, respectively,
• the longitudinal axis AE of each member of the population of electrodes is surrounded by an electrically insulating separator layer, the electrically insulating separator layer comprising:
• (i) a first insulating material comprising a microporous separator material disposed in regions between opposing lateral surfaces of adjacent members of the electrode and counter-electrode populations, and
• (ii) a second insulating material along surfaces of one or more of the top and bottom of the members of the electrode population,
• the second insulating material comprising a lower conductivity for carrier ions than the first insulating material, and
• the microporous separator material comprises a particulate material and a binder, and has a void fraction of at least 20 vol %.