KR102673075B1 - Secondary battery and secondary battery module containing the same - Google Patents

Abstract

The present invention relates to a secondary battery including an electrode assembly and a case surrounding an outer peripheral surface of the electrode assembly, wherein the case has a shear thickening fluid layer, and a secondary battery module including the same.

Description

Secondary battery and secondary battery module including the same {SECONDARY BATTERY AND SECONDARY BATTERY MODULE CONTAINING THE SAME}

The present invention relates to secondary batteries and secondary battery modules containing the same.

Recently, as the use of secondary batteries has expanded, the demand for larger areas and higher capacities has become stronger. As the capacity of secondary batteries increases, the area of the electrode plate expands, and as more positive or negative active materials are placed in the same area, problems with battery safety arise.

In particular, there is a need for a means to prevent physical deformation of the secondary battery due to external shock or physical deformation due to internal elasticity.

For example, secondary batteries repeatedly experience swelling, in which secondary batteries expand and contract due to volume expansion of the negative electrode active material due to gases generated during charging and discharging or the reaction between the negative electrode active material and lithium ions. , there is a risk that the battery may expand and explode due to the generated gas.

Additionally, since the electrode assembly expands and contracts during the charging and discharging process, the heat-sealed portions of the upper and lower portions, especially on both sides, are prone to separation. When high pressure is generated inside the battery due to deterioration due to long-term use or abnormal operating conditions, the heat-sealed sealing surface may open and gas, electrolyte, etc. inside the battery may leak to the outside. Additionally, since the electrolyte is made of combustible materials, the risk of ignition is higher when it leaks.

In addition, it is difficult to predict the direction in which gas generated from a secondary battery will move to which part of the secondary battery, which may cause problems such as unexpected damage to the secondary battery.

In particular, in the case of pouch-type secondary batteries, it is difficult to suppress battery swelling because the strength of the exterior material is weak and cannot sufficiently withstand the pressure of the internal gas. In addition, when overcurrent flows due to overdischarge or short circuit, the temperature inside the battery rises and the liquid electrolyte turns into gas, which increases the pressure inside the battery and increases the risk of ignition.

Accordingly, there is a need for a secondary battery that can further improve the safety of the battery by preventing problems caused by shrinkage and expansion of electrodes or damage by external shock.

One aspect of the present invention seeks to provide a secondary battery capable of suppressing volume change due to volume expansion occurring inside an electrode assembly during charging and discharging.

In addition, one aspect of the present invention seeks to provide a secondary battery that can prevent damage to the secondary battery due to external impact.

In addition, one aspect of the present invention seeks to provide a secondary battery module that includes the secondary battery as a cell unit and is capable of buffering action to buffer swelling of the internal cell unit.

A secondary battery according to the present invention includes an electrode assembly and a case surrounding an outer peripheral surface of the electrode assembly, and the case has a shear thickening fluid (STF) layer.

The case according to one aspect of the present invention may further include one or two or more layers selected from a resin layer and a metal layer.

The shear thickening fluid layer according to one aspect of the present invention may include one having pores.

The shear thickening fluid layer according to one aspect of the present invention may include inorganic particles and polymers.

The shear thickening fluid layer according to one aspect of the present invention may include 5 to 50% by weight of inorganic particles and 50 to 95% by weight of polymer.

The inorganic particles according to one aspect of the present invention may have an average particle diameter of 5 nm to 1 μm.

When the secondary battery according to one aspect of the present invention has a state of charge (SOC) of 100%, the thickness change rate may satisfy Equation 1 below.

[Equation 1]

In equation 1 above,

The T ₁₀₀ is the thickness when the secondary battery has SOC 100%, and the T ₀ is the thickness when the secondary battery has SOC 0%.

The secondary battery module according to the present invention includes a plurality of secondary batteries as a cell unit,

It includes a cover surrounding the outer peripheral surface of the secondary battery,

The cover includes a shear thickening fluid layer containing a shear thickening fluid.

The cell units according to one aspect of the present invention may further include a spacer containing a shear thickening fluid between adjacent surfaces facing each other.

The cell unit according to one aspect of the present invention may include the above-described secondary battery.

The secondary battery according to one aspect of the present invention can further improve battery safety by suppressing external expansion of the secondary battery by absorbing volume expansion occurring inside the electrode assembly during charging and discharging.

In addition, the secondary battery according to one aspect of the present invention can prevent damage caused by the impact by absorbing the external impact when an external impact is applied.

In addition, internal short circuit due to swelling of the internal cell unit of the secondary battery according to one aspect of the present invention can be prevented.

Figure 1 illustrates cross-sections of the front and side of a secondary battery according to an embodiment of the present invention.
Figure 2 illustrates the top, front, and right side of a secondary battery module according to an embodiment of the present invention.
Figure 3 is a photograph observed with a scanning electron microscope showing the case surface (a) of a secondary battery according to an embodiment of the present invention and a cross-sectional view (b) of the shear thickening fluid layer junction within the case.

Hereinafter, the present invention will be described in more detail. However, the following examples are only for reference to explain the present invention in detail, and the present invention is not limited thereto, and may be implemented in various forms.

Additionally, unless otherwise defined, all technical and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains. The terminology used in the description herein is merely to effectively describe particular embodiments and is not intended to limit the invention.

The present invention relates to secondary batteries and secondary battery modules containing the same.

The secondary battery according to the present invention includes an electrode assembly 200 and a case 100 surrounding the outer peripheral surface of the electrode assembly, and the case 100 has a shear thickening fluid layer.

The present invention will be described in detail as follows.

The secondary battery according to the present invention includes a case 100; and an electrode assembly 200 including a plurality of electrode bodies stacked with a separator interposed therebetween. The case 100 accommodates the electrode assembly 200 and surrounds the outer peripheral surface, and the contact areas between the cases 100 are sealed and packaged.

The case of the secondary battery according to the present invention includes a case 100 having a shear thickening fluid layer.

The secondary battery according to the present invention includes a case 100 having a shear thickening fluid layer as described above, thereby absorbing shock applied from outside the secondary battery to prevent damage to the secondary battery and separation between the separator and electrodes in the secondary battery. This can be done, and battery safety can be further improved. In addition, it is possible to suppress the volume expansion of the secondary battery by absorbing the pressure generated due to the volume expansion that occurs during charging and discharging. In addition, by reducing the resistance inside the secondary battery, excellent electron transfer speed between the anode and the cathode can be provided, thereby significantly improving the output of the secondary battery.

According to one aspect of the present invention, the shear thickening fluid layer may include a shear thickening fluid (STF) that includes inorganic particles and polymers and may have non-Newtonian fluid characteristics. . By containing inorganic particles and polymers, the shear thickening fluid layer may have non-Newtonian flow characteristics in which viscosity changes depending on the shear rate. By having such flow characteristics, the secondary battery can be protected against forces such as pressure applied to the secondary battery.

Specifically, as it has non-Newtonian flow characteristics, when a strong impact is momentarily applied from the outside, the non-Newtonian flow characteristics reduce fluidity in response to the impact (shear), thereby absorbing the external shock and preventing ignition or rupture. Battery safety can be realized.

In addition, as it has non-Newtonian flow characteristics, the force applied from the volume expansion generated inside the secondary battery due to charging and discharging can be absorbed inside the secondary battery, thereby preventing volume expansion and reduction of the lifespan of the secondary battery.

In addition, when a strong impact is momentarily applied from the outside, excellent battery safety can be realized by absorbing the external shock and preventing ignition or rupture.

Preferably, the shear thickening fluid layer may include 5 to 50% by weight of inorganic particles and 50 to 95% by weight of polymer. Preferably, it may include a shear thickening fluid containing 5 to 45% by weight of inorganic particles and 55 to 95% by weight of polymer. When included in the above amount, it can have non-Newtonian flow characteristics, prevent damage to the secondary battery by absorbing force applied from inside or outside the secondary battery, and have better battery safety. In addition, by implementing low compressive strength, short circuit inside the battery can be prevented and excellent durability can be achieved.

According to one aspect of the present invention, the inorganic particles may include any one or two or more selected from silica, alumina, calcium carbonate, and zirconia. In terms of having non-Newtonian flow characteristics and absorbing pressure, the inorganic particles may preferably be silica.

More preferably, according to one aspect of the present invention, the inorganic particles may be porous inorganic particles having pores. The porous inorganic particles have active interfacial interactions on the surface, so non-Newtonian flow characteristics appear more clearly and battery safety can be further improved.

In particular, it is preferable to use porous silica because it can better exhibit non-Newtonian flow characteristics.

According to one aspect of the present invention, the porous silica may have a specific surface area of 100 to 800 m2/g, preferably 200 to 700 m2/g. When it has the above specific surface area, it has strong resistance to impact due to non-Newtonian flow characteristics and can prevent physical damage such as perforation or sinking.

According to one aspect of the present invention, the inorganic particles may have an average particle diameter of 1 to 100㎛. Preferably, the average particle diameter may be 6 to 50㎛. More preferably, the average particle diameter may be 6 to 30㎛. When the average particle diameter is as described above, the critical shear speed can be improved, and the safety of the secondary battery can be secured by absorbing not only a slowly applied force but also a strong force that is applied momentarily.

According to one aspect of the present invention, the polymer may be a polyalkylene glycol-based polymer. For a specific example, the polymer may include one or two or more selected from polyethylene glycol, polypropylene glycol, polybutylene glycol, polytetramethylene glycol, and copolymers containing these as repeating units. In terms of having non-Newtonian flow characteristics and absorbing pressure, the polymer may preferably be a polyethylene glycol-based polymer.

According to one aspect of the present invention, the polymer may have a weight average molecular weight of 100 to 100,000 g/mol. Preferably, the weight average molecular weight may be 100 to 50,000 g/mol. When the weight average molecular weight is as described above, the critical shear rate can be improved, damage to the secondary battery and separation between the separator and the electrode in the secondary battery can be prevented, and battery safety can be further improved.

According to one aspect of the present invention, the case 100 can be manufactured by hot melting a shear-thickening fluid slurry containing a shear-thickening fluid under carbon dioxide injection in a mold and then rapidly cooling it.

According to one aspect of the present invention, when manufacturing the case 100, a shear thickening fluid layer having pores can be formed by performing hot melt under carbon dioxide injection and then applying a rapid temperature change to quench it. Therefore, as described above, a shear-thickening fluid layer with pores can be formed according to a rapid temperature change under the injection of carbon dioxide.

According to one aspect of the present invention, the pores may occupy 1 to 50% by volume, preferably 5 to 30% by volume, relative to the total volume of the case. By including a shear-thickening fluid layer with pores as described above, the case 100 absorbs the force applied from the volume expansion caused by the rapid swelling phenomenon caused by the internal short circuit of the electrode assembly, thereby preventing volume expansion and reduction of the lifespan of the secondary battery. It can be prevented. In addition, when a strong shock is momentarily applied from the outside, excellent battery safety can be achieved by absorbing the shock and preventing physical damage, ignition, or rupture due to strong resistance to the external shock.

According to one aspect of the present invention, the hot melt may be performed at 250 to 500°C, and preferably at 300 to 500°C. After performing hot melt at the above temperature, it can be maintained for 1 to 5 minutes. When performed as above, the shear-thickening fluid slurry can be uniformly melted and carbon dioxide can foam at the same time to form pores in the shear-thickening fluid layer.

In addition, after performing the hot melt as described above, the molten shear thickening fluid slurry can be rapidly cooled to 5 to 30° C., thereby forming uniform pores and having non-Newtonian flow characteristics.

According to one aspect of the present invention, the shear thickening fluid layer in which pores are formed as described above absorbs shock while reducing the size of the pores due to external or internal force applied, thereby preventing damage to the secondary battery and the separator and electrode body in the secondary battery. It can prevent liver detachment, etc., and further improve battery safety.

According to one aspect of the present invention, the shear thickening fluid layer may be formed to have a thickness of 0.1 to 5 mm. Preferably, it can be formed to have a thickness of 0.5 to 3 mm. When manufactured with the above thickness, battery safety can be further improved through excellent absorption of external or internal forces.

According to one aspect of the present invention, the case 100 is not particularly limited, but may further include one or two or more layers selected from a resin layer and a metal layer to improve flexibility and insulation.

According to one aspect of the present invention, the resin layer is not particularly limited as long as it contains a resin capable of having mechanical strength and durability capable of protecting the secondary battery, but specifically, polyolefin-based, polyester-based, poly It may include any one or two or more selected from acrylic-based and polyamide-based polymers.

According to one aspect of the present invention, the metal layer may be included to miniaturize, reduce weight, and reduce thickness, while at the same time withstanding harsh thermal environments and mechanical shock. As a specific example, the metal layer may include one or a mixture of two or more selected from iron, chromium, manganese, nickel, copper, and aluminum, or an alloy thereof, but is not limited thereto.

In addition, according to one aspect of the present invention, an adhesive layer for providing adhesion and adhesion at the interface of two or more layers selected from the resin layer, metal layer, and shear thickening fluid layer may be further included, but is not limited thereto.

According to one aspect of the present invention, the thickness of the resin layer and the metal layer may vary depending on the characteristics of the electrode assembly 200 to be manufactured, for example, each may be independently manufactured to a thickness of 1 to 20㎛. It is not limited to this.

Therefore, the secondary battery according to the present invention has the advantage of significantly lowering the risk of fire or explosion of the secondary battery by primarily absorbing the force applied to the case when an unexpected accident such as penetration of the secondary battery occurs.

According to one aspect of the present invention, a first electrode tab and a second electrode tab may be formed on one or both ends of the electrode assembly 200. As shown in FIG. 1, electrode tabs protruding outwardly from the same side may be disposed at one end of the electrode assembly 200, but the configuration of the electrode tabs is not limited to this. One electrode tab may be attached to both ends of the electrode assembly 200, which are different sides, in a form that protrudes from both sides in the horizontal direction of the electrode assembly 200.

According to one aspect of the present invention, when an electrode tab is formed in the electrode assembly 200, the case surrounds the entire outer peripheral surface of the electrode assembly 200, and as shown in FIG. 1, the electrode tab is protruded to the outside. It may be in a shape that surrounds .

According to one aspect of the present invention, the secondary battery may include a plurality of electrode assemblies 200.

According to one aspect of the present invention, the plurality of electrode assemblies 200 may further include cooling plates 300 on surfaces adjacent to each other. A cooling plate 300 is interposed between the electrode assemblies 200 to prevent volume expansion and damage of the electrode assembly 200, and to quickly dissipate the heat generated in the electrode assembly to the outside to cool the electrode assembly. The cooling efficiency can be increased.

In addition, according to one aspect, the cooling plate 300 within the case allows complete adhesion when the side portion of the secondary battery is cooled by contacting the cooling plate 300, so as to have high heat dissipation efficiency with low thermal resistance. It may have a size corresponding to the electrode assembly 200.

The electrode assembly 200 according to one aspect of the present invention may be configured to include a plurality of electrode bodies stacked with a separator in between. Specifically, an electrode assembly 200 may be provided with a separator interposed between the anode and the cathode.

According to one aspect of the present invention, when the SOC of the secondary battery is 100%, the thickness change rate may satisfy Equation 1 below.

[Equation 1]

In equation 1 above,

T ₁₀₀ is the thickness when the secondary battery has SOC 100%, and T ₀ is the thickness when the secondary battery has SOC 0%. Preferably, Equation 1 may satisfy 0.03 or less.

At this time, the thickness refers to the total thickness of the secondary battery including the case 100 and the electrode assembly 200 including the separator, positive electrode, negative electrode, and non-aqueous electrolyte.

Specifically, when the secondary battery has a remaining capacity (state of charge, SOC) of 100%, lithium and the negative electrode active material are combined, and at this time, the volume of the negative electrode expands and the thickness of the secondary battery increases. do. As the volume expands like this, twisting may occur in the anode or cathode. When the twisting phenomenon occurs, a space may be created between the electrode and the separator, and the active material may be detached from the current collector. As a result, the internal resistance of the secondary battery may increase and the capacity may decrease.

Accordingly, according to one aspect of the present invention, the secondary battery has a small thickness change rate that satisfies Equation 1, thereby preventing the above-mentioned problems.

This problem can be prevented by including the case 100 including the shear thickening fluid layer according to the present invention.

Additionally, the materials for the anode, cathode, separator, and non-aqueous electrolyte of the secondary battery are not particularly limited in the present invention, and materials known in the art can be adopted depending on the type of secondary battery being adopted. Specific examples include:

According to one aspect of the present invention, the positive and negative electrodes are prepared by mixing and stirring the positive and negative electrode active materials with a solvent and, if necessary, a binder, a conductive material, a dispersant, etc., to prepare a mixture, and then applying the mixture to a current collector of a metal material. It can be manufactured by drying and pressing.

The positive electrode active material can be any active material commonly used in the positive electrode of secondary batteries. For example, Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga, B and combinations thereof. It may contain lithium metal oxide particles containing one or two or more metals selected from the group consisting of.

The negative electrode active material can be any active material commonly used in the negative electrode of secondary batteries. The negative electrode active material of a lithium secondary battery is preferably a material capable of lithium intercalation. As a non-limiting example, the negative electrode active material is lithium (metal lithium), easily graphitizable carbon, non-graphitizable carbon, graphite, silicon, Sn alloy, Si alloy, Sn oxide, Si oxide, Ti oxide, Ni oxide, Fe. It may be one or two or more materials selected from negative electrode active materials such as oxide (FeO) and lithium-titanium oxide (LiTiO ₂ , Li ₄ Ti ₅ O ₁₂ ).

As the conductive material, a typical conductive carbon material can be used without particular restrictions.

The current collector made of the metal material has high conductivity and is a metal to which the mixture of the positive electrode or negative electrode active material can easily adhere, and any metal material can be used as long as it is not reactive in the voltage range of the battery. Non-limiting examples of positive electrode current collectors include foils made of aluminum, nickel, or combinations thereof, and non-limiting examples of negative electrode current collectors include foils made of copper, gold, nickel, or copper alloys, or combinations thereof. It may be selected from foil, etc.

A separator is interposed between the anode and the cathode. Methods for applying the separator to a battery include lamination, stacking, and folding of the separator and the electrode, in addition to the general winding method.

According to one aspect of the present invention, the separator can be used without limitation as long as it is a microporous membrane adopted in the present technical field, and furthermore, any pore such as non-woven fabric, paper, and their microporous membrane containing inorganic particles on the inner pores or surface There is no particular limitation as long as it is a porous film that can be applied to a battery.

The separation membrane may be manufactured from any one or a mixture of two or more selected from homopolymers and copolymers derived from olefinic monomers. For specific examples, it may include any one or two or more selected from polyethylene, polypropylene, and copolymers thereof.

In addition, the separator may be manufactured using the polyolefin resin alone or with polyolefin resin as a main component and further containing inorganic particles or organic particles.

In addition, the separator can be used in a laminated form. For example, the polyolefin resin may be composed of multiple layers, and any one or all layers of the multi-layered base layer may contain inorganic particles and organic particles in the polyolefin resin. Doing so is not ruled out. Additionally, the separator may be in the form of a particle layer containing inorganic particles or organic particles laminated on one or both sides of a layer containing polyolefin resin, but is not limited thereto.

According to one aspect of the present invention, the thickness of the separator is not particularly limited, but may be 5 to 30 ㎛. The separator may mainly be a separator made through stretching, but is not limited thereto.

According to one aspect of the present invention, the separator has a tensile strength of 500 kgf/cm2 or more, specifically 500 to 1,000 kgf/cm2, in the transverse direction (TD) and machine direction (MD). It can be manufactured through biaxial stretching to uniformly improve the strength in the transverse direction (TD) and machine direction (MD). A separator made through uniaxial stretching has the advantage of increasing tensile strength in the stretched direction, but there is still stress to shrink in the stretched direction, which may cause shrinkage when the temperature increases.

According to one aspect of the present invention, the electrode assembly 200 is included in the case 100, and at this time, the case 100 may be coupled to the outer peripheral surface of the electrode assembly 200 by receiving it together with a non-aqueous electrolyte.

The non-aqueous electrolyte solution includes a lithium salt as an electrolyte and an organic solvent. The lithium salt may be those commonly used in electrolyte solutions for lithium secondary batteries without limitation, and can be expressed ^as Li ⁺

The anion of the lithium salt is not particularly limited and includes F ^- , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- , PF ₆ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , CF ₃ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , (SF ₅ ) ₃ C ^- , (CF ₃ SO ₂ ) ₃ C ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- , etc. Any one or more than two may be used.

The organic solvents include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, dipropyl carbonate, dimethyl sulfuroxide, acetonitrile, dimethoxyethane, diethoxyethane, sulfolane, gamma- Any one or a mixture of two or more selected from the group consisting of butyrolactone, tetrahydrofuran, etc. may be used.

The non-aqueous electrolyte solution can be injected into an electrode structure consisting of an anode, a cathode, and a separator interposed between the anode and the cathode.

The external shape of the secondary battery is not particularly limited, but may be selected from a cylindrical shape using a can, a square shape, a pouch shape, or a coin shape.

The secondary battery module according to the present invention includes a plurality of secondary batteries as a cell unit 500,

It includes a cover 400 surrounding the outer peripheral surface of the secondary battery,

The cover 400 includes a shear thickening fluid layer containing a shear thickening fluid.

The secondary battery module according to the present invention includes a shear thickening fluid layer in the cover 400 that protects the cell unit 500, thereby providing a buffering effect that can buffer swelling of the internal cell unit 500. As a result, shock applied from outside the secondary battery can be absorbed to prevent damage to the cell unit and separation between the separator and electrode body within the cell unit, and further improve battery safety. In addition, it is possible to prevent rapid changes in the volume of the cell unit by absorbing pressure generated due to internal volume expansion that occurs during charging and discharging, thereby preventing continuous discharge events such as internal short circuits.

The secondary battery module according to the present invention may include various numbers of cell units 500 for secondary batteries depending on the purpose, size, and capacity of the secondary battery, and the present invention is not limited thereto.

The description of the shear-thickening fluid layer in the secondary battery module according to the present invention is the same as described above in the description of the shear-thickening fluid layer in the secondary battery, so it is omitted.

According to one aspect of the present invention, the cell units 500 may further include a spacer containing a shear thickening fluid between adjacent surfaces facing each other. When a spacer is further included as described above, not only can the volume expansion of the cell unit 500 be absorbed, but also the safety inside the secondary battery module can be further improved by preventing collisions between the cell units 500.

Furthermore, the secondary battery module according to the present invention may include various numbers of secondary battery cell units 500 and spacers depending on the purpose, size, and capacity of the secondary battery, and the present invention is not limited thereto.

According to one aspect of the present invention, the cover 400 can be manufactured by hot melting a shear thickening fluid slurry containing a shear thickening fluid under carbon dioxide injection in a mold and then rapidly cooling it.

According to one aspect of the present invention, when manufacturing the cover 400, a shear thickening fluid layer with pores can be formed by performing hot melt under carbon dioxide injection and then applying a rapid temperature change to quench it. Therefore, as described above, a shear-thickening fluid layer with pores can be formed according to a rapid temperature change under the injection of carbon dioxide.

According to one aspect of the present invention, the pores may occupy 1 to 50% by volume, preferably 5 to 30% by volume, relative to the total volume of the cover. By including a shear thickening fluid layer with pores as described above, the cover 400 absorbs the force applied from the volume expansion due to the rapid swelling phenomenon caused by the internal short circuit of the cell unit, thereby preventing volume expansion and reduction of the lifespan of the secondary battery. It can be prevented. In addition, when a strong impact is momentarily applied from the outside, excellent battery safety can be realized by absorbing the external shock and preventing ignition or rupture.

According to one aspect of the present invention, the hot melt may be performed at 250 to 500°C, and preferably at 300 to 500°C. After performing hot melt at the above temperature, it can be maintained for 1 to 5 minutes. When performed as above, the shear-thickening fluid slurry can be uniformly melted and carbon dioxide can foam at the same time to form pores in the shear-thickening fluid layer.

In addition, after performing the hot melt as described above, the molten shear thickening fluid slurry can be rapidly cooled to 5 to 30° C., thereby forming uniform pores and having non-Newtonian flow characteristics.

According to one aspect of the present invention, the shear-thickening fluid layer in which pores are formed as described above not only reduces the size of the pores due to a force applied from the outside or inside, but also causes swelling of the inner cell unit 500 as well as penetration applied from the outside. By absorbing force from the cover 400 when an unexpected accident such as occurs, the risk of fire or explosion of the secondary battery can be significantly reduced and battery safety can be further improved.

In addition, it is possible to prevent rapid changes in the volume of the cell unit by absorbing pressure generated due to internal volume expansion that occurs during charging and discharging, thereby preventing continuous discharge events such as internal short circuits.

The cell unit 500 according to one aspect of the present invention may include the above-described secondary battery. As described above, by including a shear thickening fluid layer not only in the cover but also in the cell unit, a secondary battery with superior battery safety can be provided. Specifically, it is possible to prevent ignition or explosion due to deterioration of the cell unit by preventing an internal short that occurs due to volume expansion of the internal cell unit during charging and discharging.

In addition, it can absorb shock applied from the outside of the secondary battery module, and protect the cell unit when penetrated by metal, etc. in non-ideal situations, further improving battery safety against explosion.

As discussed above, the embodiments of the present invention have been described in detail, but those skilled in the art will understand the present invention without departing from the spirit and scope of the present invention as defined in the appended claims. The invention may be implemented by modifying it in various ways. Therefore, changes in future embodiments of the present invention will not depart from the scope of the present invention.

[Physical property measurement method]

1. Battery safety

In order to measure the safety of the battery, the secondary battery was dropped from a height of 1 m and physical shock was applied to the secondary battery to check for damage and classified as follows.

Preservation: There is no significant difference in overall appearance compared to before and after.

Good: External physical damage occurs without electrolyte leakage or smoke.

Damage: Internal short circuit occurs due to physical damage to the battery, resulting in smoke or electrolyte leakage.

To further compare the safety of the battery, a compression test was performed in the Z-axis direction, which is the thickness direction of the battery, using a round bar with a semi-diameter of 150 mm diameter.

L1: no change, L2: small explosion heat, L3: leakage, L4: smoke, L5: ignition, L1 to L3 were judged as OK, and L4 to L5 were judged as NG.

2. Cell thickness measurement

In order to check the phenomenon of lifting between the electrode plate and the separator and the deformation of the battery when charging and discharging the battery, the thickness of the battery was measured using Mitsutoyo's Thickness Gauge after charging and discharging 500 times, and then compared with the thickness before charging and discharging. The battery thickness increase rate according to Equation 1 was measured.

[Equation 1]

In equation 1 above,

The T ₁₀₀ is the thickness when the secondary battery has SOC 100%, and the T ₀ is the thickness when the secondary battery has SOC 0%.

3. Compressive strength measurement

When both sides of the cell are fixed with steel plates and charged and then discharged, the volume expands from SOC0 to SOC100. Force is generated as physical volume expansion is suppressed by the steel plate. At this time, the generated force was measured using a load cell from BONGSHIN.

4. Porosity

Porosity was measured using Autopore IV 9500 (Micromeritics).

[Example 1]

A suspension was prepared by mixing 40% by weight of porous silica (average particle diameter 10㎛, specific surface area 500 m2/g) and 60% by weight polyethylene glycol (weight average molecular weight 200g/mol) at 1,500 rpm using a ball mill. A shear thickening fluid slurry was prepared by mixing the suspension and methanol at a weight ratio of 1:3.

After adding the shear thickening fluid slurry into the mold, hot melt was performed at a temperature of 300°C for 3 minutes while injecting 40% by volume of carbon dioxide relative to the total volume of the slurry. Afterwards, it was rapidly cooled to 20°C to prepare a case for a secondary battery in which a 2㎛ thick shear thickening fluid layer was formed.

A secondary battery was manufactured by constructing a cooling plate on the adjacent surface of two electrode assemblies including an anode and a cathode with a separator (SK Innovation, ENPASS) in between, and sealing it to the manufactured secondary battery case. At this time, the secondary battery was completed by injecting electrolyte into some areas of the seal while being opened and resealing.

At this time, the positive electrode contains 94% by weight of LiCoMn111 as the positive electrode active material, 2.5% by weight of polyvinylidene fluoride as an adhesive, 3.5% by weight of Super-P (Imerys) as a conductive agent, and NMP (NMP) as an organic solvent. N-methyl-2-pyrrolidone) and stirred to prepare a uniform positive electrode slurry. The slurry was coated on a 20㎛ thick aluminum foil, dried at a temperature of 120°C, and then compressed to produce a 100㎛ thick positive electrode plate.

The negative electrode contains 95% by weight of artificial graphite as a negative electrode active material, 3% by weight of acrylic latex (ZEON, BM900B, solid content 20% by weight) with a T _g of -52°C as an adhesive, and 2% by weight of CMC (Carboxymethyl cellulose) as a thickener. % ratio was added to water as a solvent and stirred to prepare a uniform cathode slurry. The slurry was coated on 15㎛ thick copper foil, dried at a temperature of 120°C, and then pressed to produce a 100㎛ thick negative electrode plate.

[Example 2]

The same procedure as in Example 1 was performed except that the shear thickening fluid layer was prepared to be 1㎛ thick.

[Example 3]

The same procedure as in Example 1 was performed, except that the shear thickening fluid layer was prepared to be 0.1 μm thick.

[Example 4]

The same procedure as in Example 1 was performed except that the shear thickening fluid layer was prepared to be 5㎛ thick.

[Example 5]

The same procedure as in Example 1 was performed except that carbon dioxide was not injected during case manufacturing.

[Example 6]

The same procedure as in Example 1 was performed except that 10% by volume of carbon dioxide was added based on the total volume of the slurry.

[Example 7]

The same procedure as in Example 1 was performed except that carbon dioxide was added at 100% by volume based on the total volume of the slurry.

[Example 8]

Except that in Example 1, the content of the shear thickening fluid slurry was 5% by weight of porous silica (average particle diameter 10㎛, specific surface area 500 m2/g) and 95% by weight of polyethylene glycol (weight average molecular weight 200g/mol). The same procedure was performed.

[Example 9]

Except that in Example 1, the content of the shear thickening fluid slurry was 60% by weight of porous silica (average particle diameter 10㎛, specific surface area 500 m2/g) and 40% by weight of polyethylene glycol (weight average molecular weight 200g/mol). The same procedure was performed.

[Example 10]

In Example 1, the shear thickening fluid slurry was carried out in the same manner, except that porous silica with an average particle diameter of 10 ㎛ and a specific surface area of 50 m2/g was used.

[Comparative Example 1]

A general aluminum pouch battery that did not contain a shear thickening fluid layer was used.

The physical properties of the secondary batteries manufactured in Examples 1 to 10 and Comparative Example 1 were measured as shown in Table 1.

When the secondary battery of Example 1 was observed with a scanning electron microscope (HITACHI S-3700N) as shown in FIG. 3, it was confirmed that it was porous with pores.

Shear thickening
fluid layer
Thickness (㎜) compressive strength
SOC0→SOC100 Shear thickening
fluid layer
Porosity (%) thickness
rate of change
(Equation 1) Safety assessment fall compression Example 1 2.0 0N → 0.2kN 20.01 0.016 preservation OK(L2) Example 2 1.0 0N → 0.5kN 20.02 0.015 preservation OK(L2) Example 3 0.1 0N → 9.0kN 20.00 0.018 break OK(L3) Example 4 5.0 0N → 0.1kN 20.03 0.014 preservation OK(L2) Example 5 2.0 0N → 5.0kN 0.01 0.033 preservation OK(L2) Example 6 2.0 0N → 0.25kN 5.10 0.028 preservation OK(L2) Example 7 2.0 0N → 0.05kN 50.11 0.018 break OK(L2) Example 8 2.0 0N → 0.3kN 19.98 0.022 preservation OK(L2) Example 9 2.0 0N → 0.15kN 20.02 0.027 preservation OK(L3) Example 10 2.0 0N → 1.0kN 16.45 0.030 break NG(L4) Comparative Example 1 - 0N → 10.0kN 0.02 0.051 break NG(L4)

As shown in Table 1, it was confirmed that the secondary battery according to the present invention suppresses volume expansion during charging and discharging, has a significantly low thickness change rate, and has excellent safety even when subjected to strong impacts such as dropping or compression. In addition, it was confirmed that by implementing low compressive strength, excellent elasticity capable of absorbing external or internal force was achieved, resulting in better battery safety.

In addition, when comparing Examples 2 to 4 and Example 1, when the shear thickening fluid layer of the case is formed to a thickness of 0.1 to 5 mm, the rate of change in thickness occurring internally during charging and discharging is significantly low, Volume expansion can be suppressed. In addition, by implementing low compressive strength, short circuit inside the battery can be prevented and excellent durability can be achieved. Moreover, when formed to a thickness of 0.5 to 3 mm, not only can it prevent the expansion of the secondary battery against internal force, but also prevent damage, etc. from occurring when the secondary battery is subjected to a strong impact such as dropping or compressing. I was able to confirm that it didn't work.

In addition, when comparing Examples 5 to 7 with Example 1, when the porosity of the shear thickening fluid layer of the case accounts for 1 to 50% by volume, the rate of thickness change occurring internally during charging and discharging is significantly low, preventing volume expansion of the secondary battery. It can be suppressed. Furthermore, when the porosity is 5 to 30% by volume, low compressive strength can be achieved to prevent short circuits inside the battery, and it can be confirmed that no damage occurs when the secondary battery is subjected to strong impact such as dropping or compression. there was.

In addition, when comparing Examples 8 and 9 with Example 1, when the content of inorganic particles and polymers in the shear thickening fluid satisfies 5 to 45% by weight of inorganic particles and 55 to 95% by weight of polymers, the force due to volume expansion is increased. It was confirmed that the thickness change rate could be significantly reduced by absorbing a lot.

In addition, when comparing Example 10 with Example 1, when porous silica with a specific surface of 100 to 800 m2/g of the inorganic particles in the shear thickening fluid was used, resistance to external shock was strong, preventing physical damage. We have confirmed what can be prevented. Furthermore, it was confirmed that when porous silica satisfying 200 to 700 m2/g was used, the shock absorption effect was significantly improved, thereby further improving battery safety.

In addition, when the shear thickening fluid layer is not included as in Comparative Example 1, it can be seen that not only the volume expansion generated inside the secondary battery but also the shock applied from the outside cannot be absorbed, resulting in electrical damage, and the battery stability is significantly reduced. there was.

In addition, the secondary battery case manufactured in Examples 1 to 10 was applied as a cover for the secondary battery module, and the aluminum case was formed so that the electrodes face each other as shown in FIG. 2, and has a width of 400 mm, a length of 110 mm, and a thickness of 10 mm. It was confirmed that even when 10 lithium ion cell units with a capacity of 80 Ah were provided by stacking them in a cover, it had the same excellent physical properties as the secondary battery case according to the present invention.

As described above, in the present invention, the secondary battery and the secondary battery module including the same have been described through specific details and limited embodiments, but this is only provided to facilitate a more general understanding of the present invention, and the present invention is limited to the above embodiments. It is not limited to this, and various modifications and variations can be made by those skilled in the art from this description.

Accordingly, the spirit of the present invention should not be limited to the described embodiments, and the scope of the patent claims described later as well as all things that are equivalent or equivalent to the scope of this patent claim shall fall within the scope of the spirit of the present invention. .

100: case
200: Electrode assembly
300: cooling plate
400: cover
500: Cell monomer

Claims (10)

electrode assembly and
It includes a case surrounding the outer peripheral surface of the electrode assembly,
The case has a shear thickening fluid layer,
A secondary battery wherein the shear thickening fluid layer has pores. According to clause 1,
A secondary battery in which the case further includes one or two or more layers selected from a resin layer and a metal layer. delete According to clause 1,
The shear thickening fluid layer is a secondary battery containing inorganic particles and polymers. According to clause 4,
The shear thickening fluid layer is a secondary battery comprising 5 to 50% by weight of inorganic particles and 50 to 95% by weight of polymer. According to clause 4,
A secondary battery in which the inorganic particles have an average particle diameter of 5 nm to 1 μm. According to clause 1,
The secondary battery is a secondary battery whose thickness change rate satisfies Equation 1 below when SOC is 100%.
[Equation 1]

In equation 1 above,
The T ₁₀₀ is the thickness when the secondary battery has SOC 100%, and the T ₀ is the thickness when the secondary battery has SOC 0%. Containing a plurality of secondary batteries as a cell unit,
It includes a cover surrounding the outer peripheral surface of the secondary battery,
The cover includes a shear thickening fluid layer comprising a shear thickening fluid,
The shear thickening fluid layer is a secondary battery module having pores. According to clause 8,
A secondary battery module further comprising a spacer containing a shear thickening fluid between adjacent surfaces of the cell units facing each other. According to clause 8,
The cell unit is a secondary battery module including any one secondary battery selected from claims 1, 2, and 4 to 7.