According to the present invention, there are provided a composite body that enables the formation of a lithium ion conductor that exhibits good lithium ion conductivity by a pressurization treatment without sintering at a high temperature (about 1,000° C.) while using a lithium-containing oxide having excellent safety and stability, as well as a lithium ion conductor, an all-solid state lithium ion secondary battery, an electrode sheet for an all-solid state lithium ion secondary battery, and lithium tetraborate. The composite body according to the embodiment of the present invention contains a lithium compound having a lithium ion conductivity of 1.0×10.sup.−6 S/cm or more at 25° C. and lithium tetraborate that satisfies the following requirement 1.

The requirement 1: In a reduced two-body distribution function G(r) obtained from an X-ray total scattering measurement of the lithium tetraborate, a first peak in which a peak top is located in a range where r is 1.43±0.2 Å and a second peak in which a peak top is located in a range where r is 2.40±0.2 Å are present, G(r) of the peak top of the first peak and G(r) of the peak top of the second peak indicate more than 1.0, and an absolute value of G(r) is less than 1.0 in a range where r is more than 5 Å and 10 Å or less.

According to the present invention, there are provided a composite body that enables the formation of a lithium ion conductor that exhibits good lithium ion conductivity by a pressurization treatment without sintering at a high temperature (about 1,000° C.) while using a lithium-containing oxide having excellent safety and stability, as well as a lithium ion conductor, an all-solid state lithium ion secondary battery, an electrode sheet for an all-solid state lithium ion secondary battery, and lithium tetraborate. The composite body according to the embodiment of the present invention contains a lithium compound having a lithium ion conductivity of 1.0×10.sup.−6 S/cm or more at 25° C. and lithium tetraborate that satisfies the following requirement 1.

The requirement 1: In a reduced two-body distribution function G(r) obtained from an X-ray total scattering measurement of the lithium tetraborate, a first peak in which a peak top is located in a range where r is 1.43±0.2 Å and a second peak in which a peak top is located in a range where r is 2.40±0.2 Å are present, G(r) of the peak top of the first peak and G(r) of the peak top of the second peak indicate more than 1.0, and an absolute value of G(r) is less than 1.0 in a range where r is more than 5 Å and 10 Å or less.

A solid-state battery that includes at least one battery constituent unit including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer, wherein each of the positive electrode layer and the negative electrode layer includes a side part having a terminal connection part and a terminal non-connection part; and an insulating part or a solid electrolyte part surrounding at least a part of the terminal non-connection part of at least one of the positive electrode layer and the negative electrode layer in a planar view of the at least one battery constituent unit such that the insulating part or the solid electrolyte part is in direct contact with the terminal non-connection part in a contact region and out of direct contact with the terminal non-connection part in a non-contact region.

A solid-state battery that includes at least one battery constituent unit including a positive electrode layer, a negative electrode layer, and a solid electrolyte layer interposed between the positive electrode layer and the negative electrode layer, wherein each of the positive electrode layer and the negative electrode layer includes a side part having a terminal connection part and a terminal non-connection part; and an insulating part or a solid electrolyte part surrounding at least a part of the terminal non-connection part of at least one of the positive electrode layer and the negative electrode layer in a planar view of the at least one battery constituent unit such that the insulating part or the solid electrolyte part is in direct contact with the terminal non-connection part in a contact region and out of direct contact with the terminal non-connection part in a non-contact region.

A battery includes: a power generating element that includes at least one solid-state battery cell that includes a positive electrode, a solid electrolyte layer, and a negative electrode which are laminated; a first pressurizing member in contact with a first principal surface of the power generating element; a second pressurizing member in contact with a second principal surface of the power generating element, the second principal surface being opposite to the first principal surface. The first pressurizing member includes a first void. The second pressurizing member includes a second void. The insulating member includes a side surface portion that covers a side surface of the power generating element, and an extending portion that extends from the side surface portion into each of the first void and the second void.

A battery includes: a power generating element that includes at least one solid-state battery cell that includes a positive electrode, a solid electrolyte layer, and a negative electrode which are laminated; a first pressurizing member in contact with a first principal surface of the power generating element; a second pressurizing member in contact with a second principal surface of the power generating element, the second principal surface being opposite to the first principal surface. The first pressurizing member includes a first void. The second pressurizing member includes a second void. The insulating member includes a side surface portion that covers a side surface of the power generating element, and an extending portion that extends from the side surface portion into each of the first void and the second void.

A battery cell includes an electrode assembly and a first conductive unit. The electrode assembly includes a plurality of first electrode plates, a plurality of second electrode plates, and a separator. The plurality of first electrode plates and the plurality of second electrode plates are alternately stacked. The separator includes a first separator and a plurality of second separators. Along a thickness direction of the electrode assembly, the plurality of first electrode plates are located on one side of the first separator. One of the second separators is disposed between each pair of adjacent first electrode plate and second electrode plate. The first separator includes a body portion and a protection portion protruding from an edge of the body portion. The protection portion overlays the first conductive unit.

A battery cell includes an electrode assembly, a housing, a cover plate, and a support member. The housing includes a first electrode plate and a second electrode plate. At least a part of the first electrode plate is stacked with the second electrode plate. The housing is provided with an opening and an accommodation cavity configured to accommodate the electrode assembly. The housing includes a side plate. The cover plate is perpendicular to the side plate and configured to close the opening. At least a part of the support member is disposed between the side plate and the electrode assembly, and the support member is configured to support the electrode assembly so that a spacing between an end, facing the side plate, of the first electrode plate and the side plate in a first direction is greater than a preset value. The first direction being a direction perpendicular to the side plate.

A battery cell includes an electrode assembly, a housing, a cover plate, and a support member. The housing includes a first electrode plate and a second electrode plate. At least a part of the first electrode plate is stacked with the second electrode plate. The housing is provided with an opening and an accommodation cavity configured to accommodate the electrode assembly. The housing includes a side plate. The cover plate is perpendicular to the side plate and configured to close the opening. At least a part of the support member is disposed between the side plate and the electrode assembly, and the support member is configured to support the electrode assembly so that a spacing between an end, facing the side plate, of the first electrode plate and the side plate in a first direction is greater than a preset value. The first direction being a direction perpendicular to the side plate.

An all-solid-state cell, having improved short-circuit resistance, comprises a first electrode layer, a first solid electrolyte layer, a second solid electrolyte layer, and a second electrode layer in this order, wherein the first solid electrolyte layer has a first surface, the second solid electrolyte layer has a second surface in contact with the first surface, and a maximum height Rz.sub.1 of the first surface and a maximum height Rz.sub.2 of the second surface satisfy the following relation (1):

0.15≤Rz.sub.1/Rz.sub.2≤0.25  (1)