KR20180012149A - Safety-enhanced lithium secondary battery - Google Patents

Abstract

The present invention relates to a circular secondary battery with enhanced safety. More specifically, the present invention relates to a circular secondary battery with enhanced safety, which is capable of preventing explosion or ignition. To this end, the circular secondary battery includes a cooling member, which is made of a phase change material (PCM), in an inner wall of a can for the circular secondary battery, and the PCM lowers an internal temperature of the battery by changing phases when the internal temperature of the battery rises above a specific level.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a SAFETY-ENHANCED LITHIUM SECONDARY BATTERY

The present invention relates to a circular secondary battery with improved safety. Specifically, the present invention provides a cooling secondary member capable of absorbing heat in an inner wall of a can of the circular secondary battery to lower the internal temperature of the battery, To an improved circular secondary battery.

Recently, lithium secondary batteries, which are light and energy efficient and capable of achieving high capacity, are attracting attention as a demand for high capacity batteries for automobiles and electric power storage devices is increasing rapidly.

The circular lithium secondary battery, which is one of the lithium secondary batteries, includes a circular electrode assembly wound in a state where a center pin is coupled, a circular can to which the electrode assembly is coupled, And the like.

Such a high-capacity circular lithium secondary battery has a disadvantage that its heat generation is high and its safety is low when insulation is poor. In order to prevent an explosion upon overcharging, there is a safety vent which is deformed when the internal pressure is increased due to overcharging between the electrode assembly and the can assembly, a circuit board is deformed due to a change in shape of the safety vent, A current interruption means (CID), and a secondary protection element for breaking the circuit in response to a rise in temperature.

If the circular secondary battery is in an overcharged state, a local heat is generated and the battery temperature rapidly increases. In such a state, the internal pressure is rapidly increased due to the action of the electrolyte additive, . This internal pressure pushes the safety vent, which is a component of the cap assembly, outwardly, breaking the current interrupting means (CID) connected to the safety vane, thereby interrupting the current.

Unlike the pouch type outer casing, the can for the circular secondary battery is made of a metal material in order to prevent moisture penetration and to secure mechanical properties. Such a metal can has a disadvantage in that it can not rapidly release heat generated inside the can to the outside .

Therefore, when the temperature of the cell suddenly increases due to an internal short circuit in an abnormal situation such as an overload or an external short circuit when a physical shock is applied from the outside, or when the internal pressure of the battery rises to a certain level or more, There is a problem.

Korean Patent Publication No. 10-2015-0050150

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a cooling member made of a phase change material (PCM) on the inner wall of a can of a circular secondary battery, The present invention provides a circular secondary battery improved in safety by reducing the risk of ignition or explosion by keeping the internal temperature of the secondary battery constant by absorbing heat by the phase change material.

According to an embodiment of the present invention, there is provided a circular secondary battery including a cooling member made of a phase change material (PCM) on the inner wall of a can of a circular secondary battery.

Specifically, in one embodiment of the present invention

Cans for circular secondary batteries,

A jelly roll type electrode assembly accommodated in the can for the circular secondary battery; And

An electrolytic solution,

And a cooling member made of a phase change material is provided on the inner wall of the can for the circular secondary battery.

As described above, according to the present invention, when the temperature in the secondary battery rises above a certain level in an abnormal situation such as physical shock, overcharge or external short circuit, the cooling member provided on the inner wall of the can of the circular secondary battery generates heat The internal temperature of the secondary battery is kept constant, thereby solving the problem of ignition or explosion of the secondary battery. In addition, not only the temperature of the entire secondary battery cell is lowered during the high-temperature cycle, but also the temperature of the secondary battery cell is increased by releasing the heat absorbed by the cooling member during the low-temperature discharge. Therefore, Can be produced.

1 shows a structure in which a phase change material is provided on the inner wall of a can for a circular secondary battery according to an embodiment of the present invention.
2 is a graph showing the results of measurement of cyclic performance of the prototype secondary batteries of Examples 1 to 3 and the prototype secondary battery of Comparative Example 1 at high temperatures.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention. Herein, terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor may appropriately define the concept of the term to describe its own invention in the best way. It should be construed as meaning and concept consistent with the technical idea of the present invention.

Herein, terms and words used in the present specification and claims should not be construed to be limited to ordinary or dictionary meanings, and the inventor may appropriately define the concept of the term to describe its own invention in the best way. It should be construed as meaning and concept consistent with the technical idea of the present invention.

Hereinafter, the present invention will be described in detail in order to facilitate understanding of the present invention.

In one embodiment of the present invention,

Cans for circular secondary batteries,

A jelly roll type electrode assembly accommodated in the can for the circular secondary battery; And

An electrolytic solution,

And a cooling member made of a phase change material (PCM) is provided on the inner wall of the can for the circular secondary battery.

In general, a secondary battery can exhibit the highest performance at room temperature (20 to 30 ° C), and the lithium metal ion migration is not smooth at low temperatures, resulting in low capacity expression. At high temperatures, rapid deterioration in charge / .

The circular secondary battery according to an embodiment of the present invention includes a phase change material that absorbs heat at a high temperature and releases heat at a low temperature to maintain the internal temperature of the secondary battery within a predetermined range, And a high capacity retention rate can be realized.

1, a circular secondary battery 100 according to an embodiment of the present invention includes a circular battery case 20, a jelly roll-shaped electrode assembly 30 accommodated in a circular can, A cap assembly 40 coupled to an upper portion of the battery can, and an electrolyte (not shown).

The circular can 20 includes a circular side plate having a predetermined diameter and a bottom plate for sealing the bottom of the circular side plate so that a predetermined space for accommodating the electrode assembly 30 is formed. An upper portion of the circular side plate is opened to insert the electrode assembly 30.

The circular can 20 is generally formed of a metal material selected from the group consisting of steel, stainless steel, aluminum, and alloys thereof.

A jelly roll type electrode assembly 30 is accommodated in the circular can 20. The electrode assembly 30 includes a jelly roll type electrode assembly 30 with a separator 33 interposed between the anode 32 and the cathode 31, It is made up of a roll-wound structure.

The positive electrode 32 includes a positive electrode collector and a positive electrode active material layer coated on both surfaces of the positive electrode collector.

The cathode current collector is made of a metal thin plate having excellent conductivity, for example, aluminum foil, nickel foil, stainless foil or the like so that electrons can be collected from the cathode active material and transferred to an external circuit.

The positive electrode active material is a lithium-manganese-based oxide (for example, LiMnO _2, LiMn ₂ O and the like), lithium-cobalt oxide (e.g., LiCoO ₂ and the like), lithium-nickel-based oxide (for example, LiNiO ₂ and the like), lithium-nickel-manganese-based oxide (for example, LiNi _1-Y Mn _Y O ₂ (where, 0 <Y <1) in, LiMn _{2 -z} Ni _z O ₄ (where, 0 <z < 2) or the like), a lithium-nickel-cobalt-based oxide (for example, LiNi _{1 -Y} CoO ₂ (where 0 < for example, Li (Ni _P Co _Q Mn _R) O ₂ may represent (where, 0 <P <1, 0 <Q <1, 0 <R <1, P + Q + R = 1) , the As a typical example _{Li (Ni 1/3 Mn 1/3 Co 1/3} ) O 2, Li (Ni 0.6 Mn 0.2 Co 0.2) O 2, Li (Ni 0.5 Mn 0.3 Co 0.2) O 2, and Li (Ni _{0.8 Mn 0.1 Co 0.1) O 2)} , lithium-manganese-cobalt oxide (e.g., LiCo _1-Y Mn _Y O ₂ (where, 0 <Y <1), LiMn _2-z Co _z O ₄ (here in, 0 <Z <2), and so on), in response bingye oxide (LiFePO _4; LFP) and a lithium-nickel-cobalt - the transition metal (M) oxide (e.g., Li (in the Ni _P Co _Q Mn _R M _S) O ₂ (here, M is from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo 1, 0 <R <1, 0 <S <1, P + Q + R + 1, where P, Q, R and S are atomic fractions of independent elements, S = 1)), or a mixture of two or more thereof.

The cathode active material may also include a metal sulfide such as titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), niobium selenide (NbSe ₂ ), or vanadium oxide (V ₂ O ₅ ) Metal selenides, metal oxides, and the like.

The positive electrode active material may include a conductive material such as a carbon material and a binder such as polyvinylidene fluoride if necessary.

At both ends of the anode 32, a cathode current collector region where a cathode active material layer is not formed, that is, a cathode uncoated region is formed. A positive electrode tab 34 made of aluminum (Al) protruded by a predetermined length from the upper portion of the electrode assembly 30 is joined to one end of the positive electrode uncoated portion and connected to the cap assembly 40.

The negative electrode 31 includes a negative electrode collector made of a conductive metal thin plate such as copper (Cu) or nickel (Ni) foil, and a negative electrode active material layer coated on both surfaces thereof. The negative electrode active material layer includes a negative electrode active material, and may further include a conductive material, a binder, and the like, if necessary.

The negative electrode active material is a metal element or a semi-metal element capable of forming an alloy with lithium, and specifically includes magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In) (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr) , Palladium (Pd), platinum (Pt), and carbon materials such as natural graphite, artificial graphite, non-graphitized carbon, and reverse graphitized carbon.

At both ends of the cathode 31, a negative electrode current collector region where a negative active material layer is not formed, that is, a negative electrode uncoated portion is formed. A negative electrode tab 35 made of nickel (Ni) protruding to a predetermined length from the bottom of the electrode assembly 30 is attached to one end of the negative electrode uncoated portion and connected to the lower end of the can 20. The circular can 20 itself acts as a cathode by bonding the anode tab 35 of the electrode assembly 30 to the center of the bottom plate of the circular can 20

In addition, a center pin (not shown) may be inserted in the central hollow space of the jelly roll type electrode assembly to prevent loosening and serve as a movement path of the internal gas.

In addition, a lower insulating member (not shown) is provided between the lower surface of the electrode assembly and the lower surface of the electrode assembly so that the lower surface of the electrode assembly is not short-circuited with the bottom surface of the can, . In addition, an upper insulating member (not shown) is provided on the upper surface of the electrode assembly so that the upper surface of the electrode assembly and the cap assembly are not short-circuited.

In the can for a circular secondary battery, the electrode assembly may be inserted into the circular can, the electrolyte may be injected, and then the cap assembly 40 may be mounted on the upper opening of the can.

The cap assembly has a general structure in which a top cap 41 forming a positive electrode terminal, a circuit board 42, a safety vent 43, and a cap plate 45 are sequentially stacked. The safety vent is formed to shut off the current or exhaust gas when the pressure inside the battery rises. An insulation member 44 is formed between the vent and the cap plate to electrically isolate the vent from the cap plate.

In particular, the circular secondary battery according to the present invention may include a cooling member 21 made of a phase change material on the inner wall of a metallic material constituting the circular can 20.

The phase change material absorbs heat generated from the inside of the secondary battery through a phase change process in which the phase change material changes from a solid state to a liquid state, from a liquid state to a solid state, from a liquid state to a gas state, from a gas state to a liquid state, (20 占 폚 to 30 占 폚) at which the secondary battery can exhibit the optimum performance, and has a high latent heat of 180 kJ / kg to 195 kJ / kg at the phase change.

Moreover, since the volume change of the phase change material during the phase change from solid to liquid is small, the temperature can be maintained without significantly changing the thickness of the secondary battery. Therefore, even if the temperature inside the secondary battery rises abruptly to a certain temperature or higher, the phase change material absorbs heat, and the rise of the internal temperature can be effectively inhibited. Therefore, a dangerous state such as explosion or ignition can be prevented, and the safety of the battery can be secured even when exposed at a high temperature for a long time.

The phase change material may include, for example, any one selected from the group consisting of an inorganic substance in the form of a hydrate, a paraffinic hydrocarbon and an organic acid, or two or more thereof.

Specifically, the inorganic material of the hydrate _{forms, NaNH 4 SO 4 · 2H 2} O, Na 2 SO 4 · 10H 2 O, Na 2 SiO 3 · 5H 2 O, Na 3 PO 4 · 12H 2 O, Na (CH 3 COO) 3H ₂ O, NaHPO ₄ .12H ₂ O, K ₂ HPO ₄ .3H ₂ O, Fe (NO ₃ ) ₃ .9H ₂ O, FeCl ₃ .2H ₂ O, Fe ₂ O ₃ .4SO ₄ .9H ₂ O, Ca (NO ₃ ) ₂ .3H ₂ O, CaCl ₂ .6H ₂ O, K ₂ HPO ₄ .3H ₂ O and K ₃ PO ₄ .7H ₂ O, Or mixtures thereof.

The paraffinic hydrocarbon may be at least one selected from the group consisting of n-octanoic acid, n-heptanoic acid, n-pentanoic acid, n-tetracholic acid, n- n-nonadecane, n-octadecane, n-heptadecane, n-hexadecane, n-pentadecane, n-tetradecane and n-tridecane, or a mixture of two or more thereof .

In addition, the organic acid may include any one selected from the group consisting of n-octanoic acid, tartaric acid, oxalic acid, acetic acid, lactic acid, and chloroacetic acid, or a mixture of two or more thereof.

More specifically, the phase change material is selected from the group consisting of NaNH ₄ SO ₄ .2H ₂ O, Fe ₂ O ₃ .4SO ₄ .9H ₂ O, n-octanoic acid, n-eicosanoic acid, tartaric acid and oxalic acid A single substance or a mixture of two or more thereof.

In addition, the phase change material may include at least one metal particle selected from the group consisting of Fe, Ni, Zn, and Cr to improve the conductive effect.

At this time, the metal particles may be included in the total amount of the phase change material in an amount of about 30% by weight or less, specifically 0.01% by weight to 30% by weight. If the content of the metal particles exceeds 30% by weight, the volume of the battery increases and the surface of the inner wall may be uneven, resulting in deterioration of the safety of the battery.

The thickness of the cooling member is preferably about 50% or less of the total thickness of the can. When the thickness exceeds 50%, the entire thickness of the can becomes thick, so that the space between the can and the bottom surface of the electrode assembly becomes narrow, There is a disadvantage that welding is difficult.

The cooling member may be formed by dissolving the phase change material in a paste state or an organic solvent to form a solution state, spray coating, plating coating or dip coating, and curing.

At this time, the organic solvent may be a hydrocarbon solvent, a halogenated hydrocarbon solvent, an alcohol solvent, an aldehyde solvent, an ether solvent or an ester solvent.

Specifically, the hydrocarbon-based solvent is an aliphatic hydrocarbon solvent such as gasoline, kerosene (kerosene) or n-hexane; Alicyclic hydrocarbon solvents such as cyclohexanol, or methylcyclohexanol; And an aromatic hydrocarbon solvent such as benzene, toluene, or xylene, or a mixture of two or more thereof.

The halogenated hydrocarbon solvent may be an aliphatic hydrocarbon solvent such as dichloromethane, chloroform, dichloroethane, trichloroethane, tetrachloroethane, dichloroethylene, trichlorethylene or tetrachlorethylene; And aromatic chlorohydrocarbons such as chlorobenzene or olo-dichlorobenzene, or a mixture thereof.

The alcoholic solvent may include a single substance selected from the group consisting of 1-butanol, 2-butanol, isobutyl alcohol, isopentyl alcohol, and isopropyl alcohol, or a mixture thereof.

The ether-based solvent may include a single substance selected from the group consisting of ethyl ether, dioxane, and tetrahydrobutane, or a mixture thereof.

The ester solvent may include a single substance selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isobutyl acetate, pentyl acetate, and isopentyl acetate or a mixture thereof.

On the other hand, when the phase change material undergoes phase transition from solid to liquid at a high temperature, the liquid phase change material inside the secondary battery may adversely affect the inside of the cell.

Therefore, the cooling member for preventing such a disadvantage may further include a carrier.

The support may be one or more selected from the group consisting of carbon and polystyrene, which is inactive and does not cause a chemical reaction with other materials in the secondary battery in the internal resin layer.

When the carrier is additionally provided, even if the phase change material is phase-changed into a liquid phase in the battery, penetration into the battery can be prevented and stability can be secured.

As described above, in the case of the circular secondary battery of the present invention, by providing the cooling member made of the phase change material on the inner wall of the can, it is possible to absorb a large amount of heat radiated from the inside during the operation of the secondary battery, It is possible to prevent a rise in the temperature of the battery, thereby improving cycle life characteristics.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, It will be understood that various modifications and applications are possible. For example, each component specifically shown in the embodiments can be modified and implemented. It is to be understood that all changes and modifications that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Example

Example  One.

A phase change material-containing composition was prepared by dissolving Fe ₂ O ₃ .4SO ₄ .9H ₂ O, which is a phase change material, in isobutyl alcohol.

The above phase change material-containing composition was spray-coated on the inner wall of a stainless steel can made of stainless steel having a thickness of 0.01 mm and then cured to prepare a can for a circular secondary battery having a cooling member with a thickness of 0.005 mm.

Graphite as an anode active material, acetylene black as a conductive material, styrene-butadiene rubber (SBR) as a binder and carboxymethyl cellulose (CMC) as a thickener were mixed at a weight ratio of 96: 1: 2: And mixed with water (H ₂ O) to prepare a uniform negative electrode active material slurry. The prepared negative electrode active material slurry was coated on one side of the copper current collector to a thickness of 65 탆, dried and rolled, and punched to a predetermined size to prepare a negative electrode.

Subsequently, LiCoO ₂ as a cathode active material, acetylene black as a conductive material, and SBR as a binder were mixed at a weight ratio of 94: 3.5: 2.5 and then added to NMP to prepare a cathode active material slurry. The prepared slurry was coated on one side of an aluminum foil, dried and rolled, and then punched to a predetermined size to prepare a positive electrode.

A porous polyolefin separator was interposed between the positive electrode and the negative electrode, and then wound in a jelly roll state to produce an electrode assembly.

Then, the electrode assembly was inserted into a can for a circular secondary battery provided with the cooling member, and 1 M LiPF ₆ was added to a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 30:70 The dissolved electrolyte was injected, and then the cap assembly was mounted to produce a circular secondary battery.

Example  2.

A circular secondary battery was produced in the same manner as in Example 1, except that n-octacosane, which is a paraffinic hydrocarbon, was used instead of Fe ₂ O ₃ .4SO ₄ .9H ₂ O as a phase change material.

Example  3.

A circular secondary battery was produced in the same manner as in Example 1 except that oxalic acid was used as a phase change material.

Comparative Example  One.

(Circular battery manufacturing)

Graphite as an anode active material, acetylene black as a conductive material, styrene-butadiene rubber (SBR) as a binder and carboxymethyl cellulose (CMC) as a thickener were mixed at a weight ratio of 96: 1: 2: And mixed with water (H ₂ O) to prepare a uniform negative electrode active material slurry. The prepared negative electrode active material slurry was coated on one side of the copper current collector to a thickness of 65 탆, dried and rolled, and punched to a predetermined size to prepare a negative electrode.

Subsequently, LiCoO ₂ as a cathode active material, acetylene black as a conductive material, and SBR as a binder were mixed at a weight ratio of 94: 3.5: 2.5 and then added to NMP to prepare a cathode active material slurry. The prepared slurry was coated on one side of an aluminum foil, dried and rolled, and then punched to a predetermined size to prepare a positive electrode.

A porous polyolefin separator was interposed between the positive electrode and the negative electrode, and then wound in a jelly roll state to produce an electrode assembly.

Then, the electrode assembly was inserted into a stainless steel can, and an electrolytic solution in which 1 M LiPF ₆ was dissolved was injected into a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 30:70 Next, the cap assembly was mounted to manufacture a circular secondary battery.

Experimental Example

Experimental Example  One.

Five circular secondary batteries manufactured in Examples 1 to 3 and Comparative Example 1 were produced. Then, the temperature of these cells was raised to 5 캜 / minute, and maintained at 160 캜 for 1 hour to confirm whether or not the battery was ignited. Also, the battery was overcharged at 20 V / 1,680 mA (3C-rate; full charge rate of 20 minutes) to confirm whether or not the battery was exploded.

As a result, in the secondary battery according to Comparative Example 1, two or more batteries out of five were ignited or exploded, but none of the five circular secondary batteries according to the present invention were ignited and exploded.

Example Comparative Example One 2 3 One Whether ignited X X X O Explosion X X X X

Experimental Example  2.

The batteries prepared in Examples 1 to 3 and Comparative Example 1 were subjected to 300 cycles of charging and discharging at 60 DEG C at 1C, and the change in cycle capacity was measured. The results are shown in Fig.

Referring to FIG. 2, as the cycle progresses, the lithium secondary batteries of Examples 1 to 3 absorb a large amount of heat radiated from the inside of the battery as compared with the secondary battery of Comparative Example 1, , And the cycle life characteristics are improved.

20: Circular can (metal material)
21: cooling member
30: Electrode assembly
31: cathode
32: anode
33: Membrane
34: positive electrode tab
35: Negative electrode tab
40: cap assembly
41: Upper cap
42: circuit board
43: Safety vents
44: Insulation member
45: cap plate
100: secondary battery

Claims (12)

A can for a circular secondary battery;
A jelly roll type electrode assembly accommodated in the can for the circular secondary battery; And
An electrolytic solution,
Wherein a cooling member made of a phase change material is provided on the inner wall of the can for the circular secondary battery.
The method according to claim 1,
Wherein the can for a circular secondary battery is made of a metal material selected from the group consisting of steel, stainless steel, aluminum, and alloys thereof.
The method according to claim 1,
Wherein the phase change material comprises any one selected from the group consisting of an inorganic substance in the form of a hydrate, a paraffinic hydrocarbon and an organic acid, or a mixture of two or more thereof.
The method of claim 3,
The inorganic substance in the hydrate form is NaNH ₄ SO ₄ .2H ₂ O, Na ₂ SO ₄ .10H ₂ O, Na ₂ SiO ₃ .5H ₂ O, Na ₃ PO ₄ .12H ₂ O, Na (CH ₃ COO) ₂ O, NaHPO ₄ .12H ₂ O, K ₂ HPO ₄ .3H ₂ O, Fe (NO ₃ ) ₃ .9H ₂ O, FeCl ₃ .2H ₂ O, Fe ₂ O ₃ .4SO ₄ .9H ₂ O, Ca (NO ₃ ) ₂ .3H ₂ O, CaCl ₂揃 6H ₂ O, K ₂ HPO ₄揃 3H ₂ O, and K ₃ PO ₄揃 7H ₂ O, or a mixture of two or more thereof Wherein the secondary battery is a cylindrical secondary battery.
The method of claim 3,
The paraffinic hydrocarbon may be n-octanoic acid, n-heptanoic acid, n-pentanoic acid, n-tetracholic acid, Those containing any one selected from the group consisting of decane, n-octadecane, n-heptadecane, n-hexadecane, n-pentadecane, n-tetradecane and n-tridecane, or a mixture of two or more thereof / RTI &gt;
The method of claim 3,
Wherein the organic acid comprises any one selected from the group consisting of n-octanoic acid, tartaric acid, oxalic acid, acetic acid, lactic acid, and chloroacetic acid, or a mixture of two or more thereof.
The method of claim 3,
Wherein the phase change material further comprises at least one metal particle selected from the group consisting of Fe, Ni, Zn, and Cr.
The method of claim 7,
Wherein the metal particles are contained in an amount of 30 wt% or less in the total amount of the phase change material.
The method of claim 8,
Wherein the metal particles are contained in an amount of 0.01 to 30% by weight based on the total amount of the phase change material.
The method according to claim 1,
Wherein the thickness of the cooling member is 50% or less based on the total thickness of the can.
The method according to claim 1,
Wherein the cooling member is formed using a method including a step of making the phase change material into a paste state or a solution state, followed by spray coating, plating coating or dip coating, and curing.
The method according to claim 1,
Wherein the cooling member further comprises a carrier. .

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