Patent Description:
Secondary batteries may be charged with and discharged of electricity and may be applied to devices within various fields such as mobile electronic devices having relatively small sizes to vehicles and power storage devices having medium and large sizes. Among such secondary batteries, lithium secondary batteries have advantages in terms of high operating voltages and energy density per unit weight, a high charging speed, as well as weight reduction.

A lithium secondary battery has a form in which an electrode assembly including a negative electrode, a positive electrode, and a separator interposed therebetween is accommodated in an external material and an electrolyte is injected. The external material may have various shapes such as a pouch shape, a prismatic shape, and a circular shape.

The negative electrode and the positive electrode of the lithium secondary battery may be formed by coating a slurry containing an electrode active material, a binder, a conductive material, and the like, on a surface of a current collector. While such a lithium secondary battery may be repeatedly charged and discharged, an electrode active material or particles constituting the electrode active material may repeatedly expand and contract due to an electrochemical action of lithium ions.

Although the amount of expansion and contraction of the negative electrode and the positive electrode varies depending on the type of an electrode active material, the repeated expansion and contraction of the negative electrode and the positive electrode may cause deformation of a case accommodating an electrode assembly.

That is, the present inventors have found that the above problems may be solved because the case may deal with expansion and contraction of an electrode accommodated in the case, inside the case. Also, it has been found that the exterior of the case may be prevented from deformation, even when charging and discharging are repeated.

<CIT> discloses a battery cell and module having an electrode assembly with a three-layer anode current collector, in which an elastic, electrically conductive middle layer is sandwiched between two copper foils in order to accommodate the thickness changes of the active material.

<CIT> discloses a battery cell and module having an electrode assembly with an an elastic, electrically conductive layer interposed between a current collector and an electrode, wherein the conductive layer comprises polyacetylene.

An aspect of the present disclosure is to deal with expansion and contraction of an electrode, accommodated in a case, inside the case.

Another aspect of the present disclosure is to prevent an exterior of a case from being deformed, even when charging and discharging are repeated.

According to an aspect of the present disclosure, a battery cell includes: a case provided with an accommodation space; and an electrode assembly accommodated in the accommodation space and contacting the case. The electrode assembly includes: a negative electrode including a plurality of negative electrode current collectors, on which a negative electrode mixture is coated, and a deformation absorbing member interposed between the plurality of negative electrode current collectors; a positive electrode including a positive electrode current collector on which a positive electrode mixture is coated; and a separator interposed between the negative electrode mixture and the positive electrode mixture. The deformation absorbing member is formed of a material including electrically conductive plastic having a porosity of <NUM>% or more to <NUM>% or less, and having elasticity, and the deformation absorbing member is interposed between surfaces, opposing a surface on which the negative electrode mixture is coated, of the negative electrode current collector and is pressurized or stretched by at least one of the negative electrode and the positive electrode to contract or expand.

The positive electrode may include a plurality of positive electrode current collectors, and the deformation absorbing member may be interposed between surfaces, opposing a surface on which the positive electrode mixture is coated, of the positive electrode current collector.

Each of the negative electrode and the positive electrode may be provided in plural, and the separator may be disposed between the negative electrode and the positive electrode.

The deformation absorbing member may be formed of a material containing polyacetylene.

The deformation absorbing member may be formed of conductive plastic including a carbon-base filler.

The deformation absorbing member may be bonded to at least one of the negative electrode current collector and the positive electrode current collector.

In the battery cell, c-c' = d(e-<NUM>), where c is an initial thickness of the deformation absorbing member, c' is a maximum deformable thickness of the deformation absorbing member, d is an initial thickness of the negative electrode mixture, and e is a ratio of an expanding thickness of the negative electrode mixture to an initial thickness of the negative electrode mixture.

The case may be provided to maintain an initial width of the accommodation space in a direction, in which the negative electrode, the separator, and the positive electrode are stacked, while the expanding thickness of the negative electrode mixture has a value of more than <NUM>% to <NUM>% or less of the initial thickness of the negative electrode mixture and the expanding thickness of the positive electrode mixture has a value of more than <NUM>% to <NUM>% or less of the initial thickness of the positive electrode mixture.

A sum of thicknesses of the plurality of negative electrodes, present in the accommodation space, may be <NUM> or more to <NUM> or less, and a sum of thicknesses of the plurality of positive electrodes, present in the accommodation space, may be <NUM> or more to <NUM> or less, a thickness of a separator interposed between the negative electrode and the positive electrode in the accommodation space may be at least <NUM>, and the initial width of the accommodation space in the direction, in which the negative electrode, the separator, and the positive electrode are stacked, may be <NUM> or more to <NUM> or less.

A thickness of one of the negative electrode current collectors of the electrode assembly may be at least <NUM>, the negative electrode mixture of the electrode assembly may be coated on one surface of the negative electrode current collector to have a thickness of at least <NUM>, and a thickness of one of the deformation absorbing members of the electrode assembly may be at least <NUM> or more to <NUM> or less.

According to another aspect of the present disclosure, a battery module includes: a module housing; and a battery cell including a case provided with an accommodation space and an electrode assembly accommodated in the accommodation space and contacting the case, the electrode assembly including a negative electrode including a plurality of negative electrode current collectors, on which a negative electrode mixture is coated, and a deformation absorbing member interposed between the plurality of negative electrode current collectors, a positive electrode including a positive electrode current collector on which a positive electrode mixture is coated, and a separator interposed between the negative electrode mixture and the positive electrode mixture, and the deformation absorbing member is formed of a material including electrically conductive plastic having a porosity of <NUM>% or more to <NUM>% or less, and having elasticity, and the deformation absorbing member is interposed between surfaces, opposing a surface on which the negative electrode mixture is coated, of the negative electrode current collector and is pressurized or stretched by at least one of the negative electrode and the positive electrode to contract or expand.

The battery cell may include a plurality of battery cells, and the plurality of battery cells may be stacked in the module housing and supported by the module housing.

The battery module may further include: at least one pad disposed between the battery cells and contacting the battery cell.

The case of the battery cell may be a pouch-type case.

The pad may be formed of a material having thermal conductivity of <NUM> W/mK or more to <NUM> W/mK or less.

Hereinafter, an X-axis illustrated in the accompanying drawings is a direction parallel to a width direction of a secondary battery, a Y-axis is a direction parallel to a thickness direction of the secondary battery, and a Z-axis is a direction parallel to a height direction of the secondary battery.

A structure of a battery cell <NUM> according to an exemplary embodiment is illustrated in <FIG>.

As illustrated of <FIG>, the battery cell <NUM> according to an exemplary embodiment may include a case101 provided with an accommodation space 101a. A negative electrode <NUM>, a positive electrode <NUM>, and a separator <NUM> may be disposed in the accommodation space 101a of the case101. The separator <NUM> may be interposed between the cathode <NUM> and the anode <NUM>, and an internal surface of the case101 may be in contact with the separator <NUM>. In addition, the accommodation space 101a may be filled with an electrolyte solution.

In an exemplary embodiment, the negative electrode <NUM> may include a plurality of negative electrode current collectors <NUM>, a deformation absorbing member <NUM> interposed between the plurality of negative electrode current collectors <NUM>, and negative electrode mixtures <NUM>, respectively applied to surfaces opposing surfaces, contacting the deformation absorbing member <NUM>, of the plurality of negative electrode current collectors <NUM>.

The plurality of negative electrode current collectors <NUM> may include a first negative electrode current collector 111a and a second negative electrode current collector 111b. The first negative electrode current collector 111a and the second negative electrode current collector 111b may be formed of a material including copper, gold, stainless steel, nickel, aluminum, titanium, or alloys thereof. However, the material is not limited by the present disclosure, and may be appropriately selected and applied according to the usage environment of the electrode assembly, specifications required for the electrode assembly, and/or the like.

The negative electrode mixture <NUM> is applied to each of one surface of the first negative electrode current collector 111a and one surface of the second negative electrode current collector 111b, and may be in the form of a slurry in which a negative electrode active material, a binder, a conductive material, a dispersant, and the like, are mixed and stirred. The negative electrode mixture <NUM> may be applied to one surface of the first negative electrode current collector 111a and the second negative electrode current collector 111b, and may then be compressed and dried.

The first negative electrode current collector 111a and the second negative electrode current collector 111b may be disposed such that surfaces thereof, on which the negative electrode mixture <NUM> is applied, do not face each other. In addition, the deformation absorbing member <NUM> may be interposed between the other surface of the first negative electrode current collector 111a and the other surface of the second negative electrode current collector 111b in a state in which the other surfaces of the first and second negative electrode current collectors 111a and 111b face each other.

In an exemplary embodiment, the deformation absorbing member <NUM> may be formed of a material having elasticity. The deformation absorbing member <NUM> may be attached to each of the first negative electrode current collector 111a and the second negative electrode current collector 111b. Accordingly, the deformation absorbing member <NUM> may be pressurized by at least one of the first negative electrode current collector 111a and the second negative electrode current collector 111b to contract in a direction, parallel to a Z-axis, when the negative electrode mixture <NUM> expands in the direction, parallel to the Z-axis.

When the negative electrode mixture <NUM> returns to an original state while contracting from the expanding state, during contraction of the negative electrode mixture <NUM>, the first negative electrode current collector 111a and the second negative electrode current collector 111b may be moved in different directions by the contraction of the negative electrode mixture <NUM> and a distance between the first negative electrode current collector 111a and the second negative electrode current collector 111b in the Z-axis direction may be gradually increased.

Accordingly, the volume of the deformation absorbing member <NUM> attached to each of the first negative current collector 111a and the second negative current collector 111b may expand in a direction, parallel to the Z-axis, to return to an original volume while the deformation absorption member <NUM> is stretched by the first negative electrode current collector 111a and the second negative electrode current collector 111b.

The battery cell <NUM> according to an exemplary embodiment may be a prismatic or cylindrical battery cell. The case <NUM> of the prismatic or cylindrical battery cell may be formed of a material containing aluminum, and a cross-sectional shape thereof may be prismatic or circular. Although the case <NUM> having a rectangular cross-sectional shape is illustrated in <FIG>, the case <NUM> may have a circular cross-section when the battery cell <NUM> is cylindrical.

When the battery cell <NUM> is prismatic or cylindrical, the case <NUM> of the battery cell <NUM> has a rigidity of a predetermined level or higher. Accordingly, in the case <NUM>, a width of the accommodation space 101a in the Z-axis direction may not be changed even when at least one of the negative electrode mixture <NUM> and the positive electrode mixture <NUM> expands in the Z-axis direction.

Accordingly, if the battery cell <NUM> has a structure in which the negative electrode, the positive electrode <NUM>, and the separator <NUM> contact each other and the separator contacts an internal surface of the case <NUM> having the rigidity of the predetermined level or higher, the deformation absorbing member <NUM> may contract or expand in the Z-axis direction when a thickness of at least one of <NUM> and the positive electrode mixture <NUM> expands or contracts.

Accordingly, when a battery module or battery pack is configured by providing a plurality of prismatic or cylindrical battery cells <NUM>, an additional member dealing with a change in the thickness of the case <NUM> of the battery cell <NUM> does not need to be provided in a module housing (not illustrated) or a pack housing (not illustrated) accommodating the battery cells <NUM>. This is because the battery cell <NUM> according to an exemplary embodiment may deal with a change in thickness of at least one of the negative electrode mixture <NUM> and the positive electrode mixture <NUM> in the case <NUM>. Therefore, when configuring the battery module (not illustrated) or the battery pack (not illustrated), materials required for assembling may be significantly reduced and assembly efficiency may be improved.

The deformation absorbing member <NUM> may be compressed by at least one of the negative electrode mixture <NUM>, the negative electrode current collector <NUM>, and the positive electrode <NUM> to expand or contract by the negative electrode current collector <NUM> while a state of charge (SOC) of the battery cell <NUM> changes from <NUM>% to <NUM>%.

SOC <NUM>%, a state of charge of <NUM>%, refers to a fully discharged state. SOC <NUM>%, a state of charge of <NUM>%, refers to a fully charged state.

In the cross-section of the negative electrode <NUM> in the Z-axis direction, the deformation absorbing member <NUM> may continuously contact the other surface of the first negative current collector 111a and the other surface of the second negative electrode current collector 111b in a width direction of the first negative electrode current collector 111a and the second negative electrode current collector 111b.

In an exemplary embodiment, the other surface of the first negative electrode current collector 111a and the other surface of the second negative electrode current collector 111b may contact an entire surface of the deformation absorbing member <NUM>.

In addition, in an exemplary embodiment, the deformation absorbing member <NUM> may be bonded to the first negative electrode current collector 111a and the second negative electrode current collector 111b by an adhesive.

Accordingly, the expansion and contraction of the negative electrode mixture <NUM> in a width direction of the entire first negative electrode current collector 111a and the second negative electrode current collector 111b may be dealt with, and binding between the deformation absorbing member <NUM> and the first and second negative electrode current collectors 111a and 111b may be firmly maintained.

In an exemplary embodiment, the deformation absorbing member <NUM> may be formed of a material including conductive plastic having a porosity of <NUM>% or more to <NUM>% or less.

In an exemplary embodiment, the first guide member <NUM> and the second guide member <NUM> may be formed of a material including low-density conductive plastic. The low-density conductive plastic may be a low-density conductive resin. A low-density plastic material has flexible properties, and thus, may facilitate an elastic behavior.

Pores, present in the deformation absorbing member <NUM>, may serve as a path along which an electrolyte of an electrolyte solution and may serve to enable expansion and contraction of the deformation absorbing member <NUM>. When a porosity of the deformation absorbing member <NUM> is <NUM>% or more to <NUM>% or less, the elastic behavior of the deformation absorbing member <NUM> may be facilitated while preventing durability of the deformation absorbing member <NUM> from being deteriorated.

In addition, when the porosity of the deformation absorbing member <NUM> is <NUM>% or more to <NUM>% or less, electrical conductivity of the deformation absorbing member <NUM> may be prevented from being reduced. In addition, when the porosity of the deformation absorbing member <NUM> is <NUM>% or more to <NUM>% or less, the deformation absorbing member <NUM> may be more easily expanded or contracted by the negative electrode mixture.

However, when the porosity is less than <NUM>%, electrical conductivity may be significantly reduced, and the ease of elastic behavior of the deformation absorbing member <NUM> may be relatively reduced. Accordingly, ability for the deformation absorbing member <NUM> to be contracted by expansion of at least one of the negative electrode <NUM> and the positive electrode <NUM> may be reduced.

In addition, when the porosity is greater than <NUM>%, the rigidity of the deformation absorbing member <NUM> may be relatively reduced and it may be difficult for the deformation absorbing member <NUM> to maintain a shape thereof.

In another exemplary embodiment, the deformation absorbing member <NUM> may be formed of a material containing polyacetylene. The polyacetylene may be iodized to have electrical conductivity, and a carbon-based filler may be mixed therewith to further improve electrical conductivity.

In an exemplary embodiment, the carbon-based filler may be carbon black (CB), carbon fiber (CF), carbon nanotubes (CNT), or the like.

As described above, the deformation absorbing member <NUM> has elasticity. Therefore, when the negative electrode mixture <NUM> contracts in the Z-axis direction, the deformation absorbing member <NUM> may be stretched by the first negative electrode current collector 111a and the second negative electrode current collector 111b to expand in the Z-axis direction and to recover an initial thickness thereof.

The positive electrode <NUM> may include a positive electrode current collector <NUM>, separated from the negative electrode <NUM> by the separator <NUM>, and a positive electrode mixture <NUM> applied to one surface and the other surface of the positive electrode current collector <NUM>.

The positive electrode mixture <NUM> is applied to each of one surface and the other surface of the positive electrode current collector <NUM> and may be in the form of a slurry in which a positive electrode active material, a binder, a conductive material, a dispersant, and the like, are mixed and stirred. The positive electrode mixture <NUM> may be applied to each of one surface and the other surface of the positive electrode current collector, and may then be pressurized and dried. The positive electrode active material may include a compound reversibly intercalating and deintercalating lithium ions.

The positive electrode current collector <NUM> may be formed of a material including aluminum, stainless steel, nickel, titanium, copper, or alloys thereof.

In a process of charging and discharging the battery cell <NUM>, not only the negative electrode <NUM> but also the positive electrode <NUM> may expand or contract. Therefore, deformation absorbing member <NUM> may be pressurized even by the expansion of the positive electrode mixture <NUM> and may be expanded by contraction of the positive electrode mixture <NUM>. Such a phenomenon may occur when the deformation absorbing member <NUM> is bonded to the first negative electrode current collector 111a and the second negative electrode current collector 111b, when the negative electrode mixture <NUM> included in the negative electrode <NUM> contacts the separator <NUM>, when the separator <NUM> contacts the positive electrode mixture <NUM> applied to the positive electrode current collector <NUM>, and when the separation membrane <NUM> contacts the case <NUM>.

A structure of a battery cell <NUM> according to another exemplary embodiment is illustrated in <FIG>.

As illustrated of <FIG>, in an exemplary embodiment, a deformation absorbing member <NUM> may also be provided on a positive electrode <NUM> to deal with a change in thickness of a positive electrode mixture <NUM>.

The deformation absorbing member <NUM> may be interposed between a pair of positive electrode current collectors <NUM> in the same principle as the negative electrode <NUM>, and may be bonded to the positive electrode current collector <NUM> by an adhesive.

In this case, the positive electrode mixture <NUM> may be applied to one surface of a single positive electrode current collector <NUM>, and the deformation absorbing member <NUM> may be bonded to the other surface of the single positive electrode current collector <NUM>. In addition, the deformation absorbing member may be bonded to another positive electrode current collector <NUM>, and a positive electrode mixture <NUM> may be applied to a surface, opposing a surface to which the deformation absorbing member <NUM> is adhered, of the positive electrode current collector <NUM>.

The deformation absorbing member <NUM> may continuously contact the positive electrode current collector <NUM> in a cross-section in the Z-axis direction. A principle of application and an effect thereof may be the same as the principle and effect in which the deformation absorbing member <NUM> is provided in the above-described negative electrode <NUM>.

<FIG> is a schematic view illustrating a structure of a battery cell <NUM> according to another exemplary embodiment.

As illustrated of <FIG>, the battery cell <NUM> according to another exemplary embodiment may include a plurality of negative electrodes <NUM> and a plurality of positive electrodes <NUM>, and a separator <NUM> may be interposed between the negative electrode <NUM> and the positive electrode <NUM>. The separator <NUM> may serve to prevent short-circuits.

The separator <NUM> may be present between the cathode <NUM> and the anode <NUM> in such a manner that a plurality of separators <NUM> are prepared and stacked between the cathode <NUM> and the anode <NUM>. Alternatively, the separator <NUM> may be present between the negative electrode <NUM> and the positive electrode <NUM> in a Z-folding manner in which a single separator <NUM> is prepared and disposed between the negative electrode <NUM> and the positive electrode <NUM> in a zigzag pattern. However, exemplary embodiments are not limited thereto.

When a plurality of negative electrodes <NUM> and a plurality of positive electrodes <NUM> are provided, both the negative electrodes <NUM> and the positive electrodes <NUM> present inside the case <NUM> may include a deformation absorbing member <NUM>, or only a portion of the negative electrodes <NUM> and only a portion of positive electrodes <NUM> may include the deformation absorbing member <NUM>. However, this is not limited by the present disclosure and may be appropriately selected and applied by physical properties of the negative electrode mixture <NUM> or the positive electrode mixture <NUM>, a usage environment of the battery cell <NUM>, and/or specifications required for the battery cell <NUM>.

In an exemplary embodiment, a width of the electrode assembly in a Z-axis direction in a state, in which all deformation-absorbing members <NUM> present in the accommodation space 101a expand by a maximum value in the Z-axis direction, may be at least the same a width H1 of the accommodation space 101a in the Z-axis direction. Accordingly, swelling of the case <NUM> may be prevented from occurring, and the case101 may be prevented from being deformed. The electrode assembly may include a positive electrode <NUM>, a negative electrode <NUM>, a separator <NUM>, and a deformation absorbing member <NUM>.

Electrode tabs (not illustrated) may be led out from the negative electrode <NUM> and the positive electrode <NUM> of the battery cell <NUM> to be exposed outwardly of the case <NUM>, respectively. Members such as a tape (not illustrated) for preventing insulation and damage may be additionally provided between an internal surface of the case <NUM> and the electrode tab (not illustrated).

<FIG> is a schematic view illustrating a structure of a battery cell <NUM> formed by stacking a negative electrode <NUM>, a positive electrode <NUM>, a separator <NUM>, and a deformation absorbing member <NUM> according to another exemplary embodiment.

The deformation absorbing member <NUM> may be provided on the negative electrode <NUM>. A plurality of negative electrodes <NUM> and a plurality of positive electrodes <NUM> may be provided and stacked in the Z-axis direction, and a separator <NUM> may be present between the negative electrode <NUM> and the positive electrode <NUM>.

The separator <NUM> may be present between the negative electrode <NUM> and the positive electrode <NUM> by a method of stacking a plurality of separators <NUM> or a method of folding a single separator <NUM> as described above.

In an exemplary embodiment, elements related to the negative electrode <NUM> may satisfy Equation <NUM>. <MAT>
where c is an initial thickness of the deformation absorbing member <NUM>, provided on the negative electrode <NUM>, in the Z-axis direction, c' is a maximum deformable thickness of the deformation absorbing member <NUM>, d is an initial thickness of a single negative electrode mixture <NUM> in the Z-axis direction, and e is a ratio of a thickness of the single negative electrode mixture <NUM> expanding in the Z-axis direction to an initial thickness of the single negative electrode mixture <NUM> in the Z-axis direction. The single negative electrode mixture <NUM> refers to a negative electrode mixture <NUM> coated on the first negative electrode current collector 111a or a negative electrode mixture <NUM> coated on the second negative electrode current collector 111b.

The initial thickness may have a thickness value when state of health (SOH) is <NUM>% and SOC is <NUM>%, and may be a thickness in a state in which a change amount of the thickness is zero (<NUM>). The SOH value is a value indicating a state of lifespan of a battery cell, and a unit thereof may be represented by [%]. The SOH value is a value which may be estimated using voltage, temperature, and current values of the battery cell, rather than a quantitatively measurable value. A decrease in the SOH value means that, when the battery cell is fully charged, a value of output current is decreased with respect to an initial value.

In Equation <NUM>, the maximum deformable thickness c' of the deformation absorbing member <NUM> in the Z-axis direction may be obtained using a volume change rate "g" depending on a porosity of low-density conductive plastic, constituting the deformation absorbing member <NUM>, and Equation <NUM>.

The porosity of the low-density conductive plastic constituting the deformation absorbing member <NUM> and the volume change rate "g" depending on the porosity may be inherent physical property values of the low-density conductive plastic, and may be values provided by a manufacturer of low-density conductive plastic.

In an exemplary embodiment, the porosity of the low-density conductive plastic constituting the deformation absorbing member <NUM> may be <NUM>%. In addition, when the porosity of the deformation absorbing member <NUM> is <NUM>%, the volume change rate "g" of the deformation absorbing member <NUM> may be <NUM>%. Even when materials have the same porosity, volume change rates of the materials may be different from each other due to inherent property values of the materials.

In an exemplary embodiment, when the thickness of the deformation absorbing member <NUM> in the Z-axis direction is set to <NUM> while allowing the thickness expansion amount of the negative electrode mixture <NUM> of the battery cell <NUM> to be <NUM>%, Equation <NUM> and Equation <NUM> may be used as follows. The thickness expansion amount is a value set more stably considering that the typical expansion amount of the negative electrode mixture <NUM> of the battery cell <NUM> is <NUM>% or more to <NUM>% or less.

The initial thickness c of the deformation absorbing member <NUM> in the Z-axis direction to be applied to Equation <NUM> and Equation <NUM> is <NUM>.

The maximum deformable thickness c' of the deformation absorbing member <NUM> is <NUM> × <NUM> because c' = cg as described in Equation <NUM>. According to the calculation, the deformation absorbing member <NUM> may contract by a maximum of <NUM> from the initial thickness c.

A ratio "e" of an expanding thickness of a single negative electrode mixture <NUM> in the Z-axis direction to an initial thickness of the single negative electrode mixture <NUM> in the Z-axis direction is <NUM>%. Therefore, the ratio "e" is <NUM>. Equation <NUM> may be used to obtain a thickness of the single negative electrode mixture <NUM> having a maximum expansion amount of <NUM> while satisfying the ratio "e.

A value of an initial thickness "d" of the single negative electrode mixture <NUM> in the Z-axis direction may be obtained by substituting the above values into Equation <NUM>. Therefore, the value of the initial thickness "d" of one negative electrode mixture <NUM> in the Z-axis direction may be set to <NUM>.

Since the above value is a thickness of the negative electrode mixture <NUM> coated on the first negative current collector 111a or the second negative current collector 111b, a thickness 2d of the negative electrode mixture <NUM> coated on each of the first negative current collector 111a and the second negative current collector 111b may be <NUM>. In this case, the initial thickness c of the deformation absorbing member <NUM> may be <NUM>, twice of the initial thickness c, to correspond to doubling of a thickness of the negative electrode mixture <NUM>.

When Equation <NUM> and Equation <NUM> are used to design the battery cell <NUM>, an initial thickness of the negative electrode mixture <NUM> which may prevent deformation of the case (<NUM> of <FIG>) of the battery cell <NUM> may be set.

The above-described Equation <NUM> and Equation <NUM> may be applied to the positive electrode <NUM>, provided with the deformation absorbing member <NUM>, in the same principle.

The deformation of the case (<NUM> of <FIG>) may include a phenomenon in which a width between the external surfaces of the case <NUM> in the direction, parallel to the Z-axis, is increased in <FIG>, a phenomenon in which the width between the external surfaces of the case <NUM> in the direction, parallel to the Z-axis, varies along the X-axis, a phenomenon in which the external or internal surface of the case <NUM> is curved, and the like.

In an exemplary embodiment, the deformation absorbing member <NUM> has a porosity of <NUM>%. When the porosity is <NUM>%, the deformation absorbing member <NUM> may be formed of a material including low-density plastic having a volume change rate of <NUM>%.

In an exemplary embodiment, a thickness of the entire negative electrode <NUM> present in the accommodation space 101a in the Z-axis direction may be <NUM> or more to <NUM> or less.

In an exemplary embodiment, the thickness of each of the first negative current collector 111a and the thickness of the second negative current collector 111b in the Z-axis direction may be <NUM>, and the negative electrode mixture <NUM> may be coated on each of the first negative current collector 111a and the thickness of the second negative current collector 111b to have a thickness of <NUM> in the Z-axis direction.

When a total thickness of the negative electrode mixture <NUM>, coated on each of the first negative electrode current collector 111a and the second negative electrode current collector 111b, is <NUM> and a thickness of the negative electrode mixture <NUM> when extending by a maximum value in the Z-axis direction is <NUM>% of the initial thickness, the initial thickness of the deformation absorbing member <NUM> present in the single negative electrode <NUM> according to Equation <NUM> and Equation <NUM> may be determined to be <NUM>.

Accordingly, the deformation absorbing member <NUM> may contract by a maximum value of the thickness change value of the negative electrode mixture <NUM> having an initial thickness of <NUM>. While the thickness of the negative electrode mixture <NUM> expands to <NUM>% from the initial thickness, the deformation absorbing member <NUM> may contract by the amount of expansion of the negative electrode mixture <NUM>. Therefore, a total thickness of the electrode assembly of the battery cell <NUM> in the Z-axis direction may not be changed.

When the width (H1 of <FIG>) of the accommodation space (101a of <FIG>) in the direction parallel to the Z-axis is designed in consideration of the above-described features, deformation of the case (<NUM> of <FIG>) caused by the electrode assembly of the battery cell <NUM> may be prevented. The above-described matters are equally applicable to the positive electrode <NUM>.

A thickness of the entire negative electrode mixture <NUM>, present in the accommodation space (101a of <FIG>), in the Z-axis direction may expand by about <NUM> to <NUM>% on average as compared with the initial thickness thereof while a state of charge (SOC) changes from <NUM>% to <NUM>% and SOH decrease from <NUM>%. The amount of increasing the total thickness of the negative electrode mixture <NUM> may be further increased as the amount of charge of the battery cell <NUM> is increased and as the battery cell <NUM> is deteriorated.

The amount of increasing the total thickness of the negative electrode mixture <NUM> may vary depending on the characteristics of the negative electrode active material and the degree of deterioration of the battery cell <NUM>, but the negative electrode mixture <NUM> may expand by an average of about <NUM> to <NUM>%. Therefore, as described above, when the expansion amount of the negative electrode mixture <NUM> is taken into consideration up to <NUM>%, the width H1 of the accommodation space 101a of the case <NUM> may be more stably designed.

As illustrated of <FIG>, when the deformation absorbing member <NUM> is present in only the negative electrode <NUM>, the width (H1 of <FIG>) of the accommodation space (101a of <FIG>) in a direction, parallel to the Z-axis direction, may have a value of <NUM> or more to <NUM> or less. This value may be an initial value when the SOH of the battery cell <NUM> is <NUM>% and the SOC of the battery cell <NUM> is <NUM>%, and the width (H1 of <FIG>) of the accommodation space (101a of <FIG>) in the direction, parallel to the Z-axis direction, may be maintained even while the SOH of the battery cell <NUM> is decreased and the SOC of the battery cell <NUM> is increased.

In an exemplary embodiment, when the width (H1 of <FIG>) of the accommodation space (101a of <FIG>) in the direction, parallel to the Z-axis direction, has a value of <NUM> or more to <NUM> or less, <NUM> positive electrodes <NUM> and <NUM> negative electrodes <NUM> may be provided in the accommodation space (101a of <FIG>). In addition, the deformation absorbing member <NUM> may be present in the negative electrode <NUM>, and <NUM> deformation absorbing members <NUM> may be provided. Then, a total thickness of the negative electrode <NUM> having the deformation absorbing member <NUM> in the Z-axis direction may have a value of <NUM> or more to <NUM> or less, and a total thickness of the positive electrode <NUM> in the Z-axis direction may have a value of <NUM> or more to <NUM> or less.

The separator <NUM> may be interposed between the negative electrode <NUM> and the positive electrode <NUM>, and a total thickness of the separator <NUM> in the accommodation space (101a of <FIG>) in the Z-axis direction may be <NUM> or more to <NUM> or less.

Accordingly, even when each of the negative electrode mixture <NUM> and the positive electrode mixture <NUM> expand by <NUM>% with respect to an initial thickness, the electrode assembly of the battery cell <NUM> and the internal surface of the case (<NUM> of <FIG>) may not be in contact with each other. Thus, deformation of the case (<NUM> of <FIG>) caused by expansion of the negative electrode <NUM> or the positive electrode <NUM> in the Z-axis direction may be prevented.

When the cross-sectional shape of the case (<NUM> of <FIG>) is not a rectangle, a maximum width, among widths of the accommodation space (101a of <FIG>) of the case (<NUM> of <FIG>) in the direction, parallel to the Z-axis direction, may be <NUM> or more to <NUM> or less.

A first initial thickness H2, at which a thickness deformation amount of the deformation absorbing member <NUM> is zero (<NUM>), may be a thickness in a state in which the negative electrode <NUM> and the positive electrode <NUM> do not expand or contract. In an exemplary embodiment, the width (H1 of <FIG>) of the accommodation space (101a of <FIG>) in the direction, parallel to the Z-axis direction, may have a value of <NUM> or more to <NUM> or less and, when the deformation absorbing member <NUM> is only present on the negative electrode <NUM>, the first initial thickness H2 of the single deformation absorbing member <NUM> may be <NUM> or more to <NUM> or less. The first initial thickness H2 of one of the deformation absorbing member <NUM> may be adopted within the above range in consideration of errors in processing of elements of the battery cell <NUM>, physical properties of the active material included in the negative electrode mixture <NUM> and the positive electrode mixture <NUM>, and the like.

A state, in which the deformation absorbing member <NUM> of <FIG> contracts, is schematically illustrated in <FIG>.

As illustrated of <FIG>, when the negative electrode mixture <NUM> expands to cause an increase in thickness, the thickness of one of the deformation absorbing members <NUM> may be a first deformation thickness H3. The first deformed thickness H3 may have a value obtained by subtracting an amount, by which the thickness of the single negative electrode mixture <NUM> has expanded, from the first initial thickness (H2 of <FIG>). Such a change in the thickness of the deformation absorbing member <NUM> may occur in all of the deformation absorbing members <NUM> provided in the plurality of negative electrodes <NUM>.

An enlarged view of "A" of <FIG> is illustrated in <FIG>.

As illustrated in <FIG>, the negative electrode mixture <NUM> may be coated on the first surface 111ab of the first negative electrode current collector 111a, and the deformation absorbing member <NUM> may be bonded to the second surface 111ac of the first negative electrode current collector 111a.

In addition, the deformation absorbing member <NUM> bonded to the second surface 111ac of the first negative electrode current collector 111a may be bonded to the first surface 111ba of the second negative electrode current collector 111b, and the negative electrode mixture <NUM> may be coated on the second surface 111ba of the second negative electrode current collector 111b.

In an exemplary embodiment, the negative electrode mixture <NUM> may be coated on end surfaces of the first negative electrode current collector 111a and the second negative electrode current collector 111b. In the first negative electrode current collector 111a and the second negative electrode current collector 111b, the deformation absorbing member <NUM> may be bonded to a surface on which the negative electrode mixture <NUM> is not coated. When a plurality of negative electrodes (<NUM> of <FIG>) are provided, the deformation absorbing member <NUM> may be present for each negative electrode (<NUM> of <FIG>).

A state illustrated in <FIG> is an initial state in which the negative electrode mixture <NUM> does not expand or contract. In this state, a thickness of the negative electrode mixture <NUM>, coated on the first negative electrode current collector 111a, and a thickness of the negative electrode mixture <NUM>, coated on the second negative electrode current collector 111b, may each have the second initial thickness H4.

<FIG> illustrates the case in which the thickness of the negative electrode mixture <NUM> applied to the first negative electrode current collector 111a and the thickness of the negative electrode mixture <NUM> applied to the second negative electrode current collector 111b have the same value, and exemplary embodiments are not limited thereto. In some cases, thickness of the negative electrode mixture <NUM>, coated on the first negative electrode current collector 111a, and the thickness of the negative electrode mixture <NUM>, coated on the second negative electrode current collector 111b, may be different from each other.

A thickness of the single separator <NUM> interposed between the single negative electrode (<NUM> of <FIG>) and the single positive electrode (<NUM> of <FIG>) may be at least <NUM>. In the accommodation space (101a of <FIG>), a total thickness of the separators <NUM> interposed between the respective negative electrodes (<NUM> of <FIG>) and the respective positive electrodes (<NUM> of <FIG>) may be <NUM> or more to <NUM> or less.

The above-described values are initial thickness values of the electrode assembly according to the width (H1 of <FIG>) of the accommodation space (101a of <FIG>) of the case (<NUM> of <FIG>) in an initial state, a state before the thickness deformation of the electrode assembly of the battery, and are summarized in the following Table <NUM>.

The number and thickness values of the above-described negative electrode (<NUM> of <FIG>), positive electrode (<NUM> of <FIG>), separator <NUM>, and deformation absorbing member <NUM> may be initial values of the negative electrode (<NUM> of <FIG>), the positive electrode (<NUM> of <FIG>), the separator (<NUM> of <FIG>), and the strain absorbing member (<NUM> of <FIG>) when the SOH value of the battery cell is <NUM>% and the SOC value of the battery cell is <NUM>%.

In this state, when the SOC reaches <NUM>%, a thickness of at least one of the negative electrode mixture <NUM> and the positive electrode mixture (<NUM> of <FIG>) expands. In the present disclosure, the deformation absorbing member <NUM> may contract by the thickness expansion amount.

Accordingly, in the present disclosure, even when the SOC reaches <NUM>%, a total thickness of the electrode assembly of the battery cell (<NUM> of <FIG>) in the Z-axis direction may not be changed. Therefore, the exterior of the case (<NUM> of <FIG>) of the battery cell (<NUM> of <FIG>) may be prevented from being deformed while the SOC reaches <NUM>% from <NUM>%. In the present disclosure, the electrode assembly refers to the negative electrode <NUM>, the positive electrode <NUM>, the separator <NUM>, and the deformation absorbing member <NUM>, as described above.

Accordingly, when the battery cell (<NUM> of <FIG>) is configured with the above-described values, swelling of the case (<NUM> of <FIG>) of the battery cell (<NUM> of <FIG>) may not occur even while the SOC reaches <NUM>% from <NUM>% SOC Ring phenomenon. Therefore, an additional member absorbing swelling of the case (<NUM> of <FIG>) does not need to be provided outside the case (<NUM> of <FIG>).

An enlarged view of "B" of <FIG> is illustrated in <FIG>.

<FIG> illustrates a state in which the SOH of the battery cell (<NUM> of <FIG>) is <NUM>% and the SOC thereof is <NUM>%.

The state illustrated of <FIG> is a state in which the negative electrode mixture <NUM> expands, and a thickness of the negative electrode mixture <NUM> coated on the first negative electrode current collector 111a and a thickness of the negative electrode mixture <NUM> coated on the second negative electrode current collector 111b may each have a second deformed thickness H5. The second deformation thickness H5 may have a value, greater than a value of the second initial thickness (H4 of <FIG>).

As the thickness of the negative electrode mixture <NUM> is increased, the thickness of the deformation absorbing member <NUM> may be decreased, so that the single deformation absorbing member <NUM> may have the first deformation thickness H3. The first initial thickness (H2 of <FIG>) may have a value, greater than a value of the first deformed thickness H3.

When the battery cell (<NUM> of <FIG>) enters a state in which the degree of deterioration is <NUM>% with respect to the initial state (<NUM>% of SOH) and SOC is <NUM>%, the thickness of the negative electrode mixture <NUM> may generally expands by about <NUM>%. In an exemplary embodiment, the width (H1 of <FIG>) of the accommodation space (101a of <FIG>) of the case (<NUM> of <FIG>) may have a value of <NUM> or more to <NUM> or less, which may be a value the same as and the width (H1 of <FIG>) of the accommodation space (101a of <FIG>) of the case (<NUM> of <FIG>) in a state in which SOH is <NUM>% and SOC is <NUM>%.

Deformation thicknesses of the thicknesses of the components of the electrode assembly, listed in Table <NUM>, are summarized in Table <NUM> below when the SOH is <NUM>% and the SOC is <NUM>%.

As illustrated in Table <NUM>, a total thickness of the electrode assembly of the battery cell (<NUM> of <FIG>) in the Z-axis direction may not be changed because the deformation absorbing member <NUM> contracts as much as the negative electrode mixture <NUM> expands.

In the battery cell (<NUM> of <FIG>) according to an exemplary embodiment, when the SOH has a value of <NUM>% or more to <NUM>% or less and the SOC has a value of <NUM>% or more to <NUM>% or less, the case (of <FIG>) <NUM>) may not be deformed by the electrode assembly of the battery cell (<NUM> of <FIG>).

<FIG> is a partially enlarged view of an electrode assembly of a battery cell according to another exemplary embodiment.

A state illustrated of <FIG> is a state of the positive electrode (<NUM> of <FIG>) when the SOH of the battery cell (<NUM> of <FIG>) is <NUM>% and the SOC thereof is <NUM>%. The positive electrode current collector <NUM> may include a first positive electrode current collector 131a and a second positive electrode current collector 131b.

A positive electrode mixture <NUM> may be coated on a first surface 131ab of the first positive electrode current collector 131a, and a deformation absorbing member <NUM> may be bonded to a second surface 131ac of the first positive electrode current collector 131a.

The deformation absorbing member <NUM> may be bonded to the first surface 131ba of the second positive electrode current collector 131b, and a positive electrode mixture <NUM> may be coated on the second surface 131bc of the second positive electrode current collector <NUM>.

In a cross-section of the positive electrode (<NUM> of <FIG>) in a thickness direction, the deformation absorbing member <NUM> may continuously contact the first positive electrode current collector 131a and the second positive electrode current collector 131b in a width direction of the positive electrode (<NUM> of <FIG>).

Accordingly, expansion and contraction of the positive electrode mixture <NUM> may be dealt with in width direction of the entire first and second positive electrode current collectors 131a and 131b, and binding between the deformation absorbing member <NUM> and the first positive electrode current collector 131a and the second positive electrode current collector 131b may be maintained to be firm.

When a plurality of positive electrodes (<NUM> of <FIG>) are provided, the deformation absorbing member <NUM> may be present for each positive electrode (<NUM> of <FIG>).

A third initial thickness H7 when SOH of the deformation absorbing member <NUM>, present in the positive electrode current collector <NUM>, is <NUM>% and SOC thereof is <NUM>% may be <NUM> or more to <NUM> or less. In this case, a thickness of a single first positive electrode current collector 131a and a thickness of a single second positive electrode current collector 131b may each have a fourth initial thickness H6, and a value of the fourth initial thickness H6 may be at least <NUM>.

A thickness of the positive electrode mixture <NUM>, coated on the first positive electrode current collector 131a, and a thickness of the positive electrode mixture <NUM>, coated on the second positive electrode current collector 131b, may each be at least <NUM>.

A thickness of a separator <NUM> interposed between one negative electrode (<NUM> of <FIG>) and one positive electrode (<NUM> of <FIG>) may be at least <NUM>.

A sum of thicknesses of the plurality of positive electrodes (<NUM> of <FIG>), present in the accommodation space (101a of <FIG>), may be <NUM> or more to <NUM> or less.

A width (H1 of <FIG>) of the accommodation space (101a of <FIG>) of the case (<NUM> of <FIG>) may be <NUM> or more to <NUM> or less.

<FIG> is a schematic view illustrating a state in which the deformation absorbing member <NUM> of <FIG> contracts. <FIG> illustrates a state of the positive electrode (<NUM> of <FIG>) when SOH is <NUM>% and SOC is <NUM>%.

As illustrated in <FIG>, the thickness of the deformation absorbing member <NUM> decreases from the third initial thickness (H7 of <FIG>) to the third deformation thickness H8, and the third deformation thickness H8 may be <NUM> or more to <NUM> or less.

A thickness of the positive electrode mixture <NUM>, coated on the first positive electrode current collector 131a, and a thickness of the positive electrode mixture <NUM>, coated on the second positive electrode current collector 131b, may each increase from the fourth initial thickness (H6 of <FIG>) to the fourth deformable thickness H9, and the fourth deformable thickness H9 may be at least <NUM>.

As described above, the deformation absorbing member <NUM> may be provided on at least one of the negative electrode (<NUM> of <FIG>) and the positive electrode (<NUM> of <FIG>). In this case, when the thicknesses of the negative electrode mixture (<NUM> of <FIG>) and the positive electrode mixture (<NUM> of <FIG>) are increased, the thickness of the deformation absorbing member <NUM> may be decreased. Meanwhile, when the thickness of the negative electrode mixture (<NUM> of <FIG>) and the positive electrode mixture (<NUM> of <FIG>) are decreased, the thickness of the deformation absorbing member <NUM> may be increased.

Therefore, a change in the thicknesses of the negative electrode mixture (<NUM> of <FIG>) and the positive electrode mixture (<NUM> of <FIG>) may be dealt with without changing the exterior of the case (<NUM> of <FIG>) of the battery cell (<NUM> of <FIG>). In addition, the change in the thicknesses of the negative electrode mixture (<NUM> of <FIG>) and the positive electrode mixture (<NUM> of <FIG>) may be dealt with inside the case (<NUM> of <FIG>), rather than outside the case (<NUM> of <FIG>).

In the battery cell (<NUM> of <FIG>) according to an exemplary embodiment, when the SOH has a value of <NUM>% or more to <NUM>% or less and the SOC has a value of <NUM>% or more to <NUM>% or less, the case (<NUM> of <FIG>) may not be deformed by an electrode assembly.

According to another aspect, a battery module including the battery cell according to the present disclosure is provided.

<FIG> is an exploded perspective view of a battery module <NUM> according to an exemplary embodiment. As illustrated in <FIG>, the battery module <NUM> may include a plurality of battery cells (<NUM> of <FIG> and <FIG>).

The battery module <NUM> may accommodate a plurality of the battery cells <NUM> in the module housing <NUM>. The module housing <NUM> may be formed of a material having a rigidity of a predetermined level or higher, and a shape thereof may be maintained while the battery cell <NUM> is accommodated therein.

A plurality of battery cells <NUM> may be stacked inside the module housing <NUM>, and a pad <NUM> may be provided between the battery cells <NUM>.

The pad <NUM> may contact the case <NUM> of the battery cell <NUM> to provide a surface pressure. In addition, in an exemplary embodiment, when the pad <NUM> is formed of a material having high thermal conductivity, the pad <NUM> may provide the surface pressure and may simultaneously perform a cooling function of the case <NUM>.

A positive electrode tab 100a of the battery cell <NUM> may be led out to one side of the case <NUM> of the battery cell <NUM>, and a negative electrode tab 100b may be led out to the other side of the battery cell <NUM>. A direction, in which the positive electrode tab 100a and the negative electrode tab 100b are led out to the case <NUM>, is not limited by the present disclosure, and the positive electrode tab 100a and the negative electrode tab 100b may have a form in which they are led out to only one side of the case <NUM>.

The positive electrode tab 100a and the negative electrode tab 100b may be welded to a busbar member <NUM> provided in a busbar frame <NUM>, and may be electrically connected to the busbar member <NUM>. The busbar frame <NUM> may be fixed to one side of the module housing <NUM>, and may support the busbar member <NUM>. The busbar frame <NUM> may be formed of a material including an insulating material.

In an exemplary embodiment, the case <NUM> of the battery cell <NUM> may be a pouch-type case. An external surface of the case <NUM> may be formed of a material containing an aluminum alloy, and an internal surface of the case <NUM> may be formed of a material containing polypropylene.

A negative electrode (<NUM> of <FIG>), a positive electrode (<NUM> of <FIG>), a separator (<NUM> of <FIG>), and a deformation absorbing member (<NUM> of <FIG>) are stacked in the case <NUM>, and the case <NUM> may be thermally sealed to seal the accommodation space (101a of <FIG>). In this case, the accommodation space (101a of <FIG>) may be filled with an electrolyte solution.

As described above, when at least one of the negative electrode (<NUM> of <FIG>) and the positive electrode (<NUM> of <FIG>) expands or contracts, the deformation absorbing member (<NUM> of <FIG>) may contract or expand to deal with a change in volume of at least one the negative electrode (<NUM> of <FIG>) and the positive electrode (<NUM> of <FIG>).

In this case, the module housing <NUM> has a rigidity of a predetermined level or higher, the cases <NUM> of the battery cells <NUM> may in close contact with each other in the Z-axis direction, or the case <NUM> and the pad <NUM> may be maintained in a state in close contact in the Z-axis direction. Accordingly, the case <NUM> may be supported by the module housing <NUM> or the pad <NUM> in a direction, parallel to a Z-axis.

Therefore, in the battery module <NUM> according to an exemplary embodiment, volumes of the negative electrode (<NUM> of <FIG>), the positive electrode (<NUM> of <FIG>), and the deformation absorbing member (<NUM> id <FIG>) may be changed inside the case <NUM> in the Z-axis direction. In addition, an external surface of the case <NUM> may not be deformed in the Z-axis direction even when the volumes of the positive electrode (<NUM> of <FIG>) and the deformation absorbing member (<NUM> of <FIG>) are changed in the Z-axis direction.

In another exemplary embodiment, a plurality of the battery modules <NUM> may be provided. The plurality of battery modules <NUM> may be accommodated in a pack housing (not illustrated) to form a battery pack (not illustrated).

As described above, expansion and contraction of an electrode, accommodated in a case, may be dealt with in the case.

Claim 1:
A battery cell comprising:
a case provided with an accommodation space; and
an electrode assembly accommodated in the accommodation space and contacting the case,
wherein the electrode assembly comprises:
a negative electrode including a plurality of negative electrode current collectors, on which a negative electrode mixture is coated, and a deformation absorbing member interposed between the plurality of negative electrode current collectors;
a positive electrode including a positive electrode current collector on which a positive electrode mixture is coated; and
a separator interposed between the negative electrode mixture and the positive electrode mixture,
wherein the deformation absorbing member is formed of a material including electrically conductive plastic having a porosity of <NUM>% or more to <NUM>% or less, and having elasticity, and wherein the deformation absorbing member is interposed between surfaces, opposing a surface on which the negative electrode mixture is coated, of the negative electrode current collector and is pressurized or stretched by at least one of the negative electrode and the positive electrode to contract or expand.