A secondary battery comprising a battery enclosure, a non-aqueous electrolyte and an electrode structure, the 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 L E, a width W E, a height H E, and a longitudinal axis A E extending from the bottom to the top of each such member and in a direction that is transverse to the first direction, the length L E of each member of the electrode population being measured in the direction of its longitudinal axis A E, the width W E of each member of the electrode population being measured in the first direction, and the height H E of each member of the electrode population being measured in a direction that is perpendicular to the longitudinal axis A E of each such member and the first direction, the ratio of L E to each of W E and H E of each member of the electrode population being at least 5:1, respectively, the ratio of H E to W E for each member of the electrode population being between 0.4:1 and 1000:1, respectively, each member (21, 22) of the counter-electrode population comprises a bottom, a top, a length L CE, a width W CE, a height H CE, and a longitudinal axis A CE extending from the bottom to the top of each such member and in a direction that is transverse to the first direction, the length L CE of each member of the counter-electrode population being measured in the direction of its longitudinal axis A CE, the width W CE of each member of the counter-electrode population being measured in the first direction, and the height H CE of each member of the counter-electrode population being measured in a direction that is perpendicular to the longitudinal axis A CE of each such member and the first direction, the ratio of L CE to each of W CE and H CE of each member of the counter-electrode population being at least 5:1, respectively, the ratio of H CE to W CE for each member of the counter-electrode population being between 0.4:1 and 1000:1, respectively, the longitudinal axis A E of each member of the population of electrodes is surrounded by an electrically insulating separator layer, and between members of the electrode and counter-electrode populations, the electrically insulating separator layer comprises a microporous separator material comprising a particulate material and a binder, and having a void fraction of at least 20 vol.%. 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 L E, a width W E, a height H E, and a longitudinal axis A E extending from the bottom to the top of each such member and in a direction that is transverse to the first direction, the length L E of each member of the electrode population being measured in the direction of its longitudinal axis A E, the width W E of each member of the electrode population being measured in the first direction, and the height H E of each member of the electrode population being measured in a direction that is perpendicular to the longitudinal axis A E of each such member and the first direction, the ratio of L E to each of W E and H E of each member of the electrode population being at least 5:1, respectively, the ratio of H E to W E for each member of the electrode population being between 0.4:1 and 1000:1, respectively, each member (21, 22) of the counter-electrode population comprises a bottom, a top, a length L CE, a width W CE, a height H CE, and a longitudinal axis A CE extending from the bottom to the top of each such member and in a direction that is transverse to the first direction, the length L CE of each member of the counter-electrode population being measured in the direction of its longitudinal axis A CE, the width W CE of each member of the counter-electrode population being measured in the first direction, and the height H CE of each member of the counter-electrode population being measured in a direction that is perpendicular to the longitudinal axis A CE of each such member and the first direction, the ratio of L CE to each of W CE and H CE of each member of the counter-electrode population being at least 5:1, respectively, the ratio of H CE to W CE for each member of the counter-electrode population being between 0.4:1 and 1000:1, respectively, the longitudinal axis A E of each member of the population of electrodes is surrounded by an electrically insulating separator layer, and between members of the electrode and counter-electrode populations, the electrically insulating separator layer comprises a microporous separator material comprising a particulate material and a binder, and having a void fraction of at least 20 vol.%.