JP7844292B2 - All-solid-state battery assembly - Google Patents

Description

This invention relates to an all-solid-state battery assembly, and more particularly to a structure for pressurizing a battery module.

The battery comprises multiple stacks connected in series or parallel, each stack including multiple cells, a pair of end plates that sandwich and secure the multiple cells, and multiple restraint bands that connect the pair of end plates (see Patent Document 1). The multiple cells are restrained by the pair of end plates and the multiple restraint bands while a restraining load is applied.

Japanese Patent Publication No. 2017-117636

When using all-solid-state battery cells, the volume expansion of the battery module during charging becomes significant. Therefore, to ensure the load from the end plates is appropriate, the end plates must be designed to move in accordance with the volume expansion of the battery module. In this case, a guide member is necessary to guide the movement of the end plates.

On the other hand, since battery modules composed of all-solid-state battery cells require high loads, the end plates bear a high load from the battery modules when they expand. This can cause the end plates to flex and detach from the guide members. This results in the end plates not being able to adequately secure the battery modules, making them prone to rattling due to external vibrations and shocks.

The problem that this invention aims to solve is to provide an all-solid-state battery assembly in which the end plate and guide member are less likely to separate when the battery module expands.

This invention solves the above problem by making the contact surface of the guide member with the pressure plate a curved surface that curves toward the pressure plate as it moves in the expansion direction of the battery module, and whose curvature increases as it moves in the expansion direction.

According to this invention, even if the pressure plate flexes due to the expansion of the battery module, the contact surface is a curved surface with a shape that corresponds to the deformation of the pressure plate, making it difficult for the pressure plate and the guide member to separate. As a result, the battery module becomes less prone to rattling, and the all-solid-state battery assembly can be made more resistant to vibration and shock.

Figure 1 is a front view showing an example of an embodiment of the all-solid-state battery assembly of the present invention. Figure 2 is a side view showing an example of an embodiment of the all-solid-state battery assembly of the present invention. Figure 3 is a cross-sectional view along the line III-III in Figure 1. Figure 4 is an enlarged view of section IV in Figure 1, and is an explanatory diagram illustrating the contact state between the movable end plate and the guide member according to the state of charge (SOC) of the all-solid-state battery. Figure 5(A) is a top view showing an excerpt of the portion of the guide member of the all-solid-state battery assembly in this embodiment in which the contact surface is formed, and Figure 5(B) is a top view showing an excerpt of the portion of the guide member of the all-solid-state battery assembly in the first modified example in which the contact surface is formed. Figure 6 is a cross-sectional view showing a first modified example of the all-solid-state battery assembly of the present invention. Figure 7 is a cross-sectional view showing a second modified example of the all-solid-state battery assembly of the present invention.

A solid-state battery assembly 1 according to an embodiment of the present invention will be described based on the drawings. Figure 1 is a front view showing an example of an embodiment of the solid-state battery assembly 1 of the present invention. Figure 2 is a side view showing an example of an embodiment of the solid-state battery assembly 1 of the present invention. Figure 3 is a cross-sectional view along line III-III in Figure 1.

The all-solid-state battery assembly 1 in this embodiment is not particularly limited, but is mounted in an automobile. As shown in Figure 1, this all-solid-state battery assembly 1 comprises a battery module 2 and a load application mechanism 3.

The battery module 2 is a battery pack containing multiple solid-state battery cells 21. In this battery module 2, the multiple solid-state battery cells 21 are stacked on top of each other along the Z-direction (stacking direction). Although not specifically shown in the figures, the electrodes of the multiple solid-state battery cells 21 are interconnected via busbars.

The all-solid-state battery cell 21, although not specifically shown, contains a power generation element in which a negative electrode, a negative electrode current collector, a solid electrolyte, a positive electrode, and a positive electrode current collector are stacked. The negative electrode is, for example, a lithium metal layer. The lithium metal layer is a layer that deposits on the negative electrode current collector during charging, increasing in volume, and decreases in volume during discharge. The negative electrode may also include layers other than the lithium metal layer; for example, it may include an auxiliary layer that assists in the deposition of the lithium metal layer. The negative electrode current collector is a metal foil, and copper foil is an example of this metal foil. As the solid electrolyte, for example, a sulfide solid electrolyte or an oxide solid electrolyte can be used, but the use of a sulfide solid electrolyte is preferred.

The positive electrode contains at least a positive electrode active material capable of releasing and storing lithium (Li), and is not particularly limited, but preferably contains a positive electrode active material containing sulfur. The sulfur-containing positive electrode active material can be any material that utilizes the oxidation-reduction reaction of sulfur to release lithium ions during charging and to store those lithium ions during discharge. The type of sulfur-containing positive electrode active material is not particularly limited, but particles or thin films of elemental sulfur (S), organic sulfur compounds, or inorganic sulfur compounds can be used. The positive electrode current collector is a metal foil, and copper foil is an example of this metal foil.

The battery module 2, composed of multiple all-solid-state battery cells 21, experiences significant volume changes in the lithium metal layer during charging and discharging. In this embodiment, the battery module 2 expands in the +Z direction during charging and contracts in the -Z direction during discharging. The +Z direction in this embodiment corresponds to an example of the "expansion direction" in the present invention, and the -Z direction in this embodiment corresponds to an example of the "contraction direction" in the present invention.

Such a battery module 2 is subjected to a load in the -Z direction by a load application mechanism 3. As shown in Figures 1 to 3, this load application mechanism 3 comprises a first fixed end plate 31, a second fixed end plate 32, a movable end plate 33, a restraint band 34, and a plurality of guide members 4a to 4c (in the following description, the plurality of guide members 4a to 4c may be collectively referred to as guide member 4). The movable end plate 33 in this embodiment corresponds to an example of a "pressure plate" in the present invention.

As shown in Figure 1, the first fixed end plate 31 is a rigid plate-shaped member. The first fixed end plate 31 is positioned below the battery module 2 and supports the battery module 2 from below. As shown in Figure 2, this first fixed end plate 31 is fixed to the guide member 4 by fastening bolts 35 and cannot be moved.

As shown in Figure 1, the second fixed end plate 32 is also a rigid plate-like member. The second fixed end plate 32 is positioned at the upper end of the load application mechanism 3. This second fixed end plate 32 is also fixed to the guide member 4 by fastening bolts 35 and cannot be moved.

The movable end plate 33 is also a rigid plate-like member. The movable end plate 33 is placed on the upper surface of the battery module 2. The movable end plate 33 applies pressure to the battery module 2 by transmitting the load applied from the restraint band 34 (described later) to the battery module 2.

This movable end plate 33 is in contact with the guide member 4, but is not fixed to the guide member 4. Therefore, it can move in the stacking direction (Z direction in the figure) in accordance with the expansion and contraction of the battery module 2 during charging and discharging.

As shown in Figure 3, the movable end plate 33 has a pair of wide sections 331 and a narrow section 333. The pair of wide sections 331 are located at both ends of the movable end plate 33 in the Y direction in the figure, and have a rectangular planar shape that is wider than the narrow section 333. The guide member 4 is in contact with a pair of ends 332 of these wide sections 331 in the X direction.

Figure 4 is an enlarged view of section IV in Figure 1, and is an explanatory diagram illustrating the contact state between the movable end plate 33 and the guide member 4a according to the charge level (SOC) of the battery module 2. The lower part of Figure 4 shows the relative positional relationship between the end 332 and the guide member 4a when the SOC (State of Charge) of the battery module 2 is 0%, while the upper part of Figure 4 shows the relative positional relationship between the end 332 and the guide member 4a when the SOC (State of Charge) of the battery module 2 is 100%.

As shown in Figure 4, the end portion 332 includes a curved end surface 322a. This end surface 322a is in direct contact with the guide member 4. If the end surface were flat, the end portion would include a corner, and if this corner contacted the guide member 4, stress would concentrate at the corner, causing the movable end plate 33 to become loose, and the battery module 2 to become loose as well. On the other hand, if the end surface 322a is curved, the contact area between the end surface 322a and the guide member 4 can be increased, making stress concentration less likely and reducing the looseness of the movable end plate 33. However, the end surface 322a is not limited to a curved surface; it may also be flat.

As shown in Figure 3, the narrow portion 333 is interposed between the pair of wide portions 331. The narrow portion 333 is the part that directly contacts the battery module 2 and presses it from above. A restraint band 34 is wrapped around this narrow portion 333.

As shown in Figure 1, the restraint band 34 is a stretchable, annular elastic member, though not particularly limited, and is wrapped around the first fixed end plate 31 and the movable end plate 33. Since the restraint band 34 is wrapped around the first fixed end plate 31 and the movable end plate 33 in an extended state from its natural length, the restoring force presses the movable end plate 33 in the -Z direction in the figure.

As shown in Figures 1 to 3, multiple guide members 4 (four in this example) guide the movement of the movable end plate 33 in both the expansion and contraction directions. In this embodiment, the guide members 4 are wall-shaped (flat plate-shaped) members extending along the Z-direction in the figures. By making the guide members 4 wall-shaped, the size of the guide members 4 can be reduced.

The shape of the guide member 4 is not limited to a wall shape. For example, the guide member 4 may be pole-shaped. In this case, the guide member 4 can be inserted through the through-hole formed in the movable end plate 33, and both ends of the guide member 4 can be fixed to the through-holes formed in the first and second fixed end plates 31 and 32 using fasteners or the like.

In such cases, it is preferable to increase the diameter of the through-hole to prevent the movable end plate from bending and interfering too much with the guide member. However, doing so makes the movable end plate prone to looseness. In contrast, in this embodiment, the movable end plate can be made less prone to looseness by forming a contact surface 41 on the guide member, as described later.

As shown in Figures 1 and 2, the guide members 4 are fixed to the first and second fixed end plates 31 and 32 by fastening bolts 35. As shown in Figure 3, the multiple guide members 4 are arranged to contact the respective end faces 332a of the end portion 332 of the movable end plate 33.

As shown in Figure 4, the guide member 4a includes a contact surface 41 that contacts the end face 332a of the movable end plate 33. The contact surface 41 is formed on the inner surface of the guide member 4a and includes an upper end 41a, a lower end 41b, a left end (the end furthest from the page in Figures 1 and 4) 41c, and a right end (the end furthest from the page in Figures 1 and 4) 41d.

As shown in Figure 4, the contact surface 41 is a curved surface that curves toward the movable end plate 33 side (the -X direction in the figure) as it moves in the expansion direction (the +Z direction in the figure). The curvature of this contact surface 41 increases in the expansion direction. In other words, the region on the upper end 41a side of the contact surface 41 is more curved than the region on the lower end 41b side, resulting in a larger protrusion toward the movable end plate 33 side.

As described above, a high load is applied to the movable end plate 33 in the expansion direction as the battery module 2 expands during charging. On the other hand, since the end face 332a of the movable end plate 33 is in contact with the contact surface 41 of the guide member 4a, the end face 332a receives a frictional force in the direction opposite to the expansion direction. Therefore, as shown in Figure 4, as the SOC increases, the movable end plate 33 gradually bends into a convex shape while rising.

At this time, the end face 332a also moves in the -X direction in the figure so as to gradually move away from the contact surface 41 of the guide member 4a. Furthermore, as the movable end plate 33 rises, the amount of movement of the end face 332a in the -X direction gradually increases.

As in conventional designs, when the end face separates from the contact surface of the guide member due to this movement, the movable end plate can no longer adequately secure the battery module. Furthermore, because the restraint band is an elastic material, when vibration or shock is applied to the all-solid-state battery assembly, it expands and contracts in accordance with the looseness of the battery module, preventing it from adequately securing the battery module.

In contrast, the contact surface 41 of the guide member 4a in this embodiment has a surface shape that curves more towards the movable end plate 33 as it approaches the upper end 41a, in order to accommodate the movement of the end face 332a caused by the movable end plate 33 as described above. In other words, the contact surface 41 is curved in the -X direction to accommodate the movement of the end face 332a in the -X direction. Therefore, during charging of the battery module 2, the end face 332a of the movable end plate 33 and the contact surface 41 of the guide member 4a are less likely to separate, and contact between the two can be maintained. As a result, the battery module 2 becomes less prone to rattling due to vibration and shock, and the all-solid-state battery assembly 1 becomes more resistant to vibration and shock.

Although not specifically shown in the diagram, the contact surfaces of guide members 4b to 4d are also curved surfaces that curve toward the movable end plate 33 as they move in the expansion direction, similar to guide member 4a. The curvature of these contact surfaces increases as they move in the expansion direction.

Figure 5(A) is a top view showing an excerpt of the portion of the guide member 4a of the all-solid-state battery assembly 1 in this embodiment where the contact surface 41 is formed. As shown in Figure 5(A), in this embodiment, the curvature of the contact surface 41 of the guide member 4a increases as it approaches the center of the battery module 2 (see Figure 3) in the direction perpendicular to the stacking direction of the all-solid-state battery cells (the Y direction in the figure). Therefore, as shown in Figures 5(A) and 4, the curvature of the contact surface 41 gradually increases in the width direction of the contact surface 41 from the right end 41d to the left end 41c, and the amount of protrusion of the contact surface 41 toward the movable end plate 33 gradually increases from the right end 41d to the left end 41c.

The amount of deflection of the movable end plate 33 is greater the closer it is to the center of the battery module 2 (see Figure 3). Therefore, the contact surface 41 described above can accommodate the change in deflection caused by the distance from the center of the battery module 2. Thus, the guide member 4a can contact the end face 332a of the movable end plate 33 along the Y direction, widening the contact range between the movable end plate 33 and the guide member 4a, and suppressing rattle of the battery module 2, including precession.

Furthermore, the curvature of the contact surfaces of guide members 4b to 4d (see Figure 3) also increases as it approaches the center of the battery module 2 in the direction perpendicular to the stacking direction. In other words, the contact surface of guide member 4b has a surface shape that is symmetrical with respect to the Y-axis to the contact surface of guide member 4a shown in Figure 5(A).

Furthermore, the contact surfaces of guide members 4c and 4d gradually increase in protrusion toward the movable end plate 33 from the left end (+Y direction in the figure) to the right end (-Y direction in the figure). In other words, the contact surface of guide member 4c has a surface shape that is line-symmetric with respect to the X-axis to the contact surface of guide member 4a, and the contact surface of guide member 4d has a surface shape that is point-symmetric with respect to the contact surface of guide member 4a (i.e., a surface shape that is line-symmetric with respect to the Y-axis to the contact surface of guide member 4c).

Furthermore, in this embodiment, the first coefficient of friction between the movable end plate 33 and the contact surface 41 when the movable end plate 33 moves in the expansion direction is greater than the second coefficient of friction between the movable end plate 33 and the contact surface 41 when the movable end plate 33 moves in the contraction direction.

Therefore, the frictional force acting on the movable end plate 33 in the contraction direction increases, which suppresses rattling and lifting of the battery module 2 in the expansion direction when shocks or vibrations are applied to the all-solid-state battery assembly 1.

Furthermore, in order to achieve the above-described relationship between the first and second friction coefficients, a minute surface shape like that shown in the lower right of Figure 4 can be formed, although this is not particularly limited. Note that in the lower right of Figure 4, for convenience, the end face 332a and the contact surface 41 are shown as being separated, but in reality, they are in contact with each other.

As shown in Figure 4, the end face 332a has a first minute inclined surface 334a that slopes toward the contact surface 41 as it moves in the expansion direction, and a first minute locking surface 334b that extends in a substantially horizontal direction. On the other hand, the contact surface 41 has a second minute inclined surface 411a that is substantially parallel to the first minute inclined surface 334a, and a second minute locking surface 411b that is substantially parallel to the first minute locking surface 334b.

When the movable end plate 33 moves in the expansion direction, the first minute locking surface 334b contacts the second minute locking surface 411b, thus relatively increasing the first coefficient of friction. Conversely, when the movable end plate 33 moves in the contraction direction, the first minute locking surface 334b does not contact the second minute locking surface 411b, thus relatively decreasing the second coefficient of friction.

In the all-solid-state battery assembly 1 of this embodiment, the contact surface 41 of the guide member 4a has a surface shape in which the curvature toward the movable end plate 33 increases as it approaches the upper end 41a. Therefore, during charging of the battery module 2, the end face 332a of the movable end plate 33 and the contact surface 41 of the guide member 4a are less likely to separate, and contact between the two can be maintained. As a result, the battery module 2 becomes less prone to rattling due to vibration and shock, and the all-solid-state battery assembly 1 becomes more resistant to vibration and shock.

In the above embodiment, four guide members 4 are arranged at both ends of the movable end plate 33, but the position and number of guide members 4 are not limited to this. As shown in the first modified example in Figure 6, a structure in which two guide members 4B are arranged in the center of the movable end plate 33B is also possible.

Figure 6 is a cross-sectional view showing a first modified example of an all-solid-state battery assembly. In this first modified example, the movable end plate 33B of the all-solid-state battery assembly 1B has a wide portion 331B in the center and narrow portions 333B at both ends.

The end portion 332B of the wide portion 331B is in contact with the guide member 4B. This guide member 4B also has a contact surface 41B that curves toward the movable end plate 33B 33B as it expands, and the curvature of this contact surface 41B increases as it expands. However, since the contact surface 41B is located closer to the center of the battery module 2 than the contact surface 41 in the above embodiment, the curvature of the contact surface 41B is smaller than the curvature of the contact surface 41.

Furthermore, in the first modified example, the change in curvature of the contact surface 41B in the direction perpendicular to the stacking direction (the Y direction in the figure) also differs from that of the above embodiment. Figure 5(B) is a top view showing an excerpt of the portion of the guide member where the contact surface of the all-solid-state battery assembly of the first modified example is formed. In the first modified example, since the guide member 4B is positioned to contact the central part of the movable end plate 33B, the curvature of the contact surface 41B gradually increases from the center of the contact surface 41B toward the left and right ends 41c and 41d.

Each narrow section 333B is wrapped with a restraining band 34. Therefore, in this first modification, the battery module 2 is pressurized via the movable end plate 33B by the two restraining bands 34.

Furthermore, as shown in the second modified example in Figure 7, the inner surface of the housing (battery pack 5) that contains the battery module 2 may be used as a guide member. Figure 7 is a cross-sectional view showing the second modified example of the all-solid-state battery assembly.

This second modified all-solid-state battery assembly 1C further comprises a battery pack 5. The battery pack 5 has a case portion 51 that houses a plurality of battery modules 2, and a lid portion 52 that covers the opening of the case portion 51. The lid portion 52 may be a floor panel of an automobile body.

In this modified example, the movable end plate 33 is in contact with the bottom surface of the case portion 51 and the bottom surface of the lid portion 52. The bottom surface of the case portion 51 and the bottom surface of the lid portion 52 function as guide members that guide the horizontal movement of the movable end plate 33 (in the X direction in Figure 7).

Therefore, contact surfaces _41C1 and _41C2 are formed on the bottom surface of the case portion 51 and the lower surface of the lid portion 52, respectively. These contact surfaces are curved and curve toward the movable end plate 33 as the battery module 2 expands. The curvature of these contact surfaces _41C1 and _41C2 increases as the expansion direction is approached, although this is not shown in the figure. The expansion direction of the battery module 2 on the left side of the figure is the -X direction, and the expansion direction of the battery module 2 on the right side of the figure is the +X direction.

In this second modification, the movable end plate 33 can be guided by a simple structure utilizing the battery pack 5, and rattling of the battery module 2 can be suppressed.

In the second modified example, a case portion 51 having an opening at the top is illustrated, but the position of the opening is not limited to this. The case portion 51 may also have an opening on the side, and this side opening may be covered by a lid.

1, 1B, 1C... All-solid-state battery assembly 2... Battery module 21... All-solid-state battery cell 3... Load application mechanism 31... First fixed end plate 32... Second fixed end plate 33, 33B... Movable end plate 331, 331B... Wide section 332... End section 332a... End face
334a...first minute slope
334b...First minute locking surface 333, 333B...Narrow section 34...Restraining band 35...Fastening bolt 4, 4B...Guide member 41, 41B, _41C1 , _41C2 ...Contact surface 41a, 41b...Upper and lower ends 41c, 41d...Left and right ends 411a...Second minute slope 411b...Second minute locking surface 5...Battery pack 51...Case section 52...Lid section

Claims (6)

A battery module comprising multiple all-solid-state battery cells stacked on top of each other,
A pressure plate is provided to pressurize the battery module and to move in the direction of expansion during charging of the battery module.
The system includes a guide member that guides the movement of the pressure plate,
The guide member has a contact surface that contacts the pressure plate,
The contact surface is a curved surface that curves toward the pressure plate side as it moves in the direction of expansion.
The curvature of the contact surface increases as it moves toward the expansion direction in the all-solid-state battery assembly. In the all-solid-state battery assembly according to claim 1,
The guide member is a wall-like member of the all-solid-state battery assembly. In the all-solid-state battery assembly according to claim 1,
The all-solid-state battery assembly further comprises a housing that houses the battery module inside,
A solid-state battery assembly in which the contact surface is formed on the inner surface of the housing. In the all-solid-state battery assembly according to claim 1,
The pressure plate has an end face that contacts the contact surface,
The end face of the all-solid-state battery assembly has a curved shape. In the all-solid-state battery assembly according to claim 1,
A solid-state battery assembly in which the curvature of the contact surface increases as it approaches the center of the battery module in a direction perpendicular to the stacking direction of the solid-state battery cells. In the all-solid-state battery assembly according to any one of claims 1 to 5,
A solid-state battery assembly in which the first coefficient of friction between the pressure plate and the contact surface when the pressure plate moves in the expansion direction is greater than the second coefficient of friction between the pressure plate and the contact surface when the pressure plate moves in the contraction direction during discharge of the battery module.