Multilayered firewall and battery pack comprising the same
Provided is a battery module including a multilayered firewall capable of controlling a heat transfer phenomenon due to a battery fire. The battery module includes a plurality of secondary battery cells accommodated in a housing member, wherein a secondary battery cell among the plurality of battery cells includes an electrode assembly in which a plurality of negative electrodes and positive electrodes are alternately stacked with a separator interposed therebetween and a pouch case encasing the electrode assembly, wherein a multilayered firewall is interposed between the plurality of secondary battery cells, and the multilayered firewall includes a heat absorption layer and fireproof layers stacked on opposing surfaces of the heat absorption layer.
1. A battery module including a plurality of secondary battery cells accommodated in a housing member,
wherein a secondary battery cell among the plurality of battery cells includes an electrode assembly and a pouch case encasing the electrode assembly,
wherein a multilayered firewall is interposed between the plurality of secondary battery cells, and the multilayered firewall includes a heat absorption layer and fireproof layers stacked on opposing surfaces of the heat absorption layer,
wherein a thickness of a central portion of the heat absorption layer is greater than a thickness of a central portion of the fireproof layers, wherein the central portion of the fireproof layers is a region in thermal contact with a region in which a composite layer of the secondary battery is formed, and
wherein a thickness of the outer portion of the heat absorption layer is equal to or less than a thickness of an outer portion of the fireproof layers and is less than the thickness of the central portion of the heat absorption layer, wherein the outer portion of the fireproof layers is a region in thermal contact with a peripheral of the plurality secondary battery cells.
2. The battery module of claim 1 , wherein the heat absorption layer includes at least one inorganic powder selected from a group consisting of aluminum hydroxide, talc, calcium carbonate, diatomaceous earth, titanium oxide, vermiculite, zeolite and white carbon.
3. The battery module of claim 1 , wherein the fireproof layer includes at least one flame retardant selected from a group consisting of a bromine-based flame retardant, a chlorine-based flame retardant, a phosphorus-based flame retardant, a boron-based flame retardant, a silicon-based flame retardant, and a nitrogen-based flame retardant.
4. The battery module of claim 1 , wherein the multilayered firewall has a thickness of 0.12 mm to 3 mm, and a thickness of the heat absorption layer is greater than a thickness of any one fireproof layer.
5. The battery module of claim 4 , wherein the heat absorption layer has a thickness of 0.1 mm to 1 mm, and the fireproof layer has a thickness of 10 μm to 1 mm.
6. The battery module of claim 1 , wherein the multilayered firewall has a thickness of 0.12 mm to 3 mm, a thickness of a central portion of the heat absorption layer is greater than a thickness of an outer portion of the heat absorption layer.
7. The battery module of claim 1 , wherein the multilayered firewall has an endothermic reaction at 110° C. to 150° C., and at least one structural change selected from a group consisting of phase change, expansion, foaming, and curing occurs by the endothermic reaction.
8. The battery module of claim 7 , wherein a weight reduction amount of the multilayered firewall due to the endothermic reaction is 20% to 40%.
9. The battery module of claim 1 , wherein the fireproof layers are made of a non-combustible material having a melting point higher than at least 1000° C.
10. The battery module of claim 1 , wherein the fireproof layers are each a sheet made of at least one selected from a group consisting of aluminum, iron, stainless steel, tin, lead, a tin-lead alloy, copper, and any combination thereof.
11. The battery module of claim 1 , wherein the fireproof layers are each a sheet made of inorganic fibers including at least one selected from a group consisting of glass fibers, rockwool fibers, ceramic wool fibers, gypsum fibers, carbon fibers, stainless steel fibers, slag fibers, alumina fibers, silica fibers, silica alumina fibers and zirconia fibers.
12. The battery module of claim 11 , wherein the inorganic fiber sheet is laminated on a metal foil.
13. The battery module of claim 3 , wherein the bromine-based flame retardant generates a bromine-based gas to block oxygen to thereby inhibit combustion, and includes at least one selected from a group consisting of tetrabromo bisphenol A, decabromo biphenyl, and pentabromo diphenyl ether.
14. The battery module of claim 3 , wherein the chlorine-based flame retardant inhibits combustion by generating a chlorine-based gas to block oxygen, and includes chlorine-based paraffin and chlorine-based polyethylene.
15. The battery module of claim 3 , wherein the phosphorus-based flame retardant blocks oxygen and heat by generating a carbonized layer on a surface of or inside the fireproof layers, and includes phosphate esters, and ammonium polyphosphates.
16. The battery module of claim 3 , wherein the boron-based flame retardant blocks oxygen and heat by generating a carbonized layer on the surface of or inside the fireproof layers, and includes sodium polyborate, sodium borate, and zinc borate.
17. The battery module of claim 3 , wherein the silicone-based flame retardant forms a Si—C inorganic heat insulating layer on the surface of or inside the fireproof layers, and includes a silicone resin.
18. The battery module of claim 3 , wherein the nitrogen-containing compound blocks oxygen by a nitrogen-based gas, and includes ammonium phosphate, a guanidine compound, and a melamine compound.
19. A battery module comprising:
a plurality of secondary battery cells stacked adjacent to each other inside a housing member, and
a plurality of multilayered firewalls, each firewall being interposed between a corresponding pair of adjacent secondary battery cells,
wherein the multilayered firewall includes fireproof layers and a heat absorption layer disposed between two fireproof layers,
wherein a thickness of a central portion of the heat absorption layer is greater than a thickness of a central portion of the fireproof layers, wherein the central portion of the fireproof layers is a region in thermal contact with a region in which a composite layer of the secondary battery is formed, and
wherein a thickness of the outer portion of the heat absorption layer is equal to or less than a thickness of an outer portion of the fireproof layers and is less than the thickness of the central portion of the heat absorption layer, wherein the outer portion of the fireproof layers is a region in thermal contact with a peripheral of the plurality secondary battery cells.