Insulating coating for improving quality of lithium ion battery

Abstract

The lithium ion battery includes a plurality of battery cells. Each battery cell includes an anode, a cathode, and a separator disposed between the anode and the cathode. The anode includes an anode active layer in contact with the current collector. The cathode includes a cathode active layer in contact with the current collector. The current collector from each cell contacts a tab located outside the cell. An electrically insulating coating is disposed on a portion of the tabs or on an outer edge of each anode or cathode. The anode and the cathode have different lengths.

Description

Technical Field

[0001] The present disclosure relates to insulating coatings for improving the quality of lithium-ion batteries. Background Art

[0002] Lithium-ion batteries have traditionally been used in a variety of small commercial applications, such as tablets and laptop computers, cellular phones, etc. Recently, lithium-ion batteries have been developed that exhibit high reversible charge capacities of greater than 200 milliampere hours per gram mass (mAh / g). This makes them useful in a variety of high-power applications, such as automobiles.

[0003] Although lithium-ion batteries exhibit the above-mentioned advantageous features, they have some disadvantages. These are listed below.

[0004] The surface of the electrode usually shows delamination between the electrode (anode or cathode) active layer and the corresponding electrode current collector. This delamination sometimes causes active materials from the electrode to contaminate the electrolyte in the battery. It sometimes also causes short circuits, which in turn causes the temperature of the battery to rise to uncomfortably high values. Unprocessed burrs or protrusions along the electrode surface may potentially cause damage to the separator during electrode stacking. These burrs and protrusions also adversely affect battery performance. Occasionally, there are cracks or breaks between the electrode and the current collector.

[0005] Therefore, it is desirable to design lithium-ion batteries that avoid some of these deficiencies or ameliorate the adverse effects of these deficiencies. Summary of the invention

[0006] The lithium-ion battery comprises a plurality of battery cells; wherein each battery cell comprises an anode, a cathode and a separator disposed between the anode and the cathode. The anode comprises an anode active layer in contact with an anode current collector, wherein the anode current collector from each battery cell contacts an anode tab located outside the battery cell. The cathode comprises a cathode active layer in contact with a cathode current collector, wherein the cathode current collector from each battery cell contacts a cathode tab located outside the battery cell. An electrically insulating coating is disposed on a portion of the anode tab in contact with the anode active layer, or on a portion of the cathode tab in contact with the cathode active layer, or on an outer edge of each anode and cathode. The anode and cathode have different lengths.

[0007] In one embodiment, an electrically insulating coating is disposed on a portion of an anode tab that contacts an anode current collector or on a portion of a cathode tab that contacts a cathode current collector; wherein the anode tab contacts the anode current collector at an outer edge of the anode, and wherein the cathode tab contacts the cathode current collector at an outer edge of the cathode.

[0008] In another embodiment, the electrically insulating coating is a cross-linked coating.

[0009] In yet another embodiment, the cross-linked coating is derived from the polymerization and cross-linking of repeating units comprising epoxies, acrylics, acrylates, phenolics, siloxanes, polyurethanes, or combinations thereof.

[0010] In yet another embodiment, the cross-linked coating disposed on the anode tab or on the cathode tab is derived from polymerization and cross-linking of repeating units comprising an epoxy resin.

[0011] In another embodiment, the cross-linked coating disposed on the outer edge of each anode or cathode is derived from the polymerization and cross-linking of repeating units comprising acrylic resins, acrylates, phenolic resins, siloxanes, polyurethanes, or combinations thereof.

[0012] In another embodiment, the electrically-insulative coating is cross-linked by ultraviolet radiation, thermal energy, or a combination thereof.

[0013] In another embodiment, the electrically insulating coating further penetrates into the anode active layer or the cathode active layer and prevents the active material from leaching out of the respective active layer.

[0014] In another embodiment, the electrically insulating coating contacts the anode current collector, forming a seal between the anode current collector and the anode active layer.

[0015] In yet another embodiment, the electrically insulating coating contacts the cathode current collector, forming a seal between the cathode current collector and the cathode active layer.

[0016] In another embodiment, the electrically insulating coating prevents the active material particles and the conductive material particles from peeling off from the anode active layer and the cathode active layer.

[0017] In yet another embodiment, the epoxy resin is bisphenol A diglycidyl ether or a cycloaliphatic epoxy resin.

[0018] A method for reducing damage to a lithium-ion battery comprising a plurality of battery cells comprises disposing a curable composition on the outer edge of an anode or cathode of at least one battery cell of the plurality of battery cells. The curable composition comprises a photoinitiator and a repeating unit of an epoxy resin, an acrylic resin, an acrylate, a phenolic resin, a siloxane, a polyurethane or a combination thereof. The curable composition is cured by subjecting it to electromagnetic radiation, thermal energy or a combination thereof. Each battery cell comprises an anode, a cathode and a separator disposed between the anode and the cathode. The anode comprises an anode active layer in contact with an anode current collector. The cathode comprises a cathode active layer in contact with a cathode current collector. The anode current collector from each battery cell contacts an anode tab located outside each battery cell, and the cathode current collector contacts a cathode tab located outside each battery cell.

[0019] In one embodiment, curing the curable composition forms an electrically insulating coating on an outer edge of at least one battery cell of the plurality of battery cells.

[0020] In another embodiment, the curable composition is disposed on a portion of the anode tab in contact with the anode current collector or on a portion of the cathode tab in contact with the cathode current collector, and wherein the curable composition is cured to form the electrically insulating coating.

[0021] In yet another embodiment, the curable composition is disposed on outer edges of an anode and a cathode of each battery cell of the plurality of battery cells.

[0022] In another embodiment, the electrically insulating coating further penetrates into the anode active layer or the cathode active layer and prevents the active material from leaching out of the active layer.

[0023] In another embodiment, the electrically insulating coating contacts the anode current collector, forming a seal between the anode current collector and the anode active layer.

[0024] In yet another embodiment, the electrically insulating coating contacts the cathode current collector, forming a seal between the cathode current collector and the cathode active layer.

[0025] In another embodiment, electromagnetic radiation is applied in a primary process and in a secondary process; wherein the secondary process follows the primary process; and wherein the electromagnetic radiation applied in the primary process is ultraviolet radiation.

[0026] In another embodiment, the electromagnetic radiation applied in the secondary process is different from the electromagnetic radiation applied in the primary process.

[0027] The above features and advantages and other features and advantages of the present disclosure are apparent from the following detailed description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Other features, advantages and details appear, by way of example only, from the following detailed description, which refers to the accompanying drawings, in which:

[0029] Figure 1A and 1B is a schematic diagram of an exemplary lithium-ion battery including a plurality of battery cells;

[0030] Figure 2A Depicted are the top edges of the battery cells before and after the insulating coating is applied. Figure 1A and 1B The cross section of the battery;

[0031] Figure 2B Depicted are the top edges of the battery cells before and after the insulating coating is applied. Figure 1A and1B a cross section of a battery; and

[0032] Figure 3 Before and after applying the insulating coating on the outer edge of each electrode and on a portion of the tab of each battery cell, along Figure 1A and 1B BB' and a side view of the exterior of the lithium-ion battery taken in the direction of arrow AA'. DETAILED DESCRIPTION

[0033] The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or use. According to an exemplary embodiment, a fast-curing electrically insulating polymer coating (hereinafter referred to as an "insulating coating") is disposed on the surface of an electrode of a lithium-ion battery to improve local mechanical strength and prevent active material particles and carbon black from being delaminated from the active layer of the electrode. Such delamination typically causes contamination of the electrolyte during battery cell assembly. The electrically insulating coating is a cross-linked coating and is applied to the area where the wiring tab of each battery cell contacts the current collector. It can also be applied to the outer edge of each electrode (current collector and corresponding active layer). This prevents a short circuit from forming when the lithium-ion battery is deformed during assembly or when it is incorporated into another device (e.g., an automobile). The electrically insulating coating can be applied locally by a nozzle (commonly referred to as nozzle spraying) or by printing, and then UV light is focused on the applied coating to promote rapid curing. The rapid curing process via ultraviolet light can be integrated into the electrode manufacturing process or the battery assembly process, thereby not causing any significant disturbances during the manufacturing process.

[0034] Figure 1A and 1B is a schematic exemplary cross-sectional view of a lithium ion battery 1000 including four battery cells 100A, 100B, 100C, and 100D having an insulating polymer layer 140 (insulating coating 140) disposed around the outer edge of each electrode. Figure 1A and 1B are identical figures. Due to the large number of reference numerals and to provide clarity to the reader, two figures have been selected to represent the lithium-ion battery. The features of each cell of battery 1000 will be described primarily with respect to cell 100A. Other features of the battery will be described in detail as needed to convey the appropriate amount of detail to the reader.

[0035] Although Figure 1A and Figure 1B The lithium-ion battery 1000 includes only 4 battery cells, but it may actually include a large number of battery cells. For example, the lithium-ion battery may include "n" battery cells, where n is an integer from 1 to 100.

[0036] exist Figure 1A and 1B In the embodiment, each battery cell 100A, 100B, 100C and 100D includes a cathode current collector, a cathode active layer, a separator, an anode active layer and an anode current collector. The anode and cathode in each battery cell are separated by a separator. Similarly, each battery cell is separated from its adjacent battery by a separator. Battery cell 100A includes a cathode 100A1 and an anode 100A2 separated by a separator 106A1. Figure 1A and 1B In the embodiment, separators with an odd coefficient "A" are used to separate the cathode from the anode (e.g., 106A1, 106A3, where coefficient A is 1, 3, etc.), and separators with an even coefficient A (e.g., 106A2, 106A4, where coefficient A is an even number) are used to separate one battery cell from another battery cell. Thus, the cathode (100A1, 100B1, 100C1, etc.) and anode (100A2, 100B2, 100C2, etc.) of each battery cell are separated by separators 106A1, 106A3, 106A5, 106A7, etc., and each battery cell 100A, 100B, 100C, 100D, etc. are separated from each other by separators 106A2, 106A4, 106A6, 106A8, etc.

[0037] The separators (106A1, 106A3, 106A5, 106A7, etc.) that separate the anode from the cathode and the separators (106A2, 106A4, 106A6, 106A8, etc.) that separate the battery cells from each other are larger in size than the anode and cathode. Figure 1A , where the respective separator protrudes beyond the borders of the anode and cathode. The larger size of the separator prevents short circuits between the anode and cathode. The separator typically comprises a porous electrically insulating polymer.

[0038] The battery cell 100A will now be described in detail. The description of the battery cell 100A can be applied to the battery cells 100B, 100C, 100D, etc. The battery cell 100A includes a cathode 100A1 and an anode 100A2. The cathode 100A1 includes two cathode active layers 104A1 and 104A2 disposed on opposite sides of a cathode current collector 112A1. The current collectors 112A1, 112B1, 112C1, 112D1, and 112E1 (for each cathode) extend outside the cathode and are welded to form a cathode tab 120A. The portion of each current collector that protrudes beyond the corresponding electrode is called a tab and is designated as 112A2, 112B2, 112C2, 112D2, 112E2, etc. In other words, the portion of the cathode current collector 112A1 that extends beyond the active layers 104A1 and 104A2 is called a tab (and is represented as 112A2). The corresponding tabs extend further away from the active layer and are welded to form a joint, which is typically in electrical communication with a load. The same nomenclature applies to each of the other cathode current collectors in a lithium-ion battery.

[0039] Anode 100A2 includes two anode active layers 108A1 and 108A2 disposed on opposite sides of anode current collector 114A1. Current collectors 114A1, 114B1, 114C1, and 114D1 (for each anode) protrude (beyond the corresponding anode active layer) to form tabs 114A2, 114B2, 114C2, and 114D2, which are welded together to form anode tab 120B. As described above, separator 106A1 separates cathode 100A1 from anode 100A2. In one embodiment, the anode current collector and tabs include copper, while the cathode current collector and tabs include aluminum.

[0040] In one embodiment, the anode and cathode have different lengths from each other. Figure 1A As shown, the length of the battery cell can be measured from the upper edge to the lower edge. The anode can be longer than the cathode and vice versa. Figure 1A In the illustrated embodiment, the cathode of each battery cell is slightly smaller in length than the anode. The use of different electrode sizes prevents lithium plating at the edge of the anode. Having the cathode and anode of different lengths prevents accidental contact between the cathode current collector and the anode active layer, and vice versa, thereby mitigating the effects of accidental thermal runaway. Using an insulating coating 140 on the cathode tab area prevents direct contact between the anode electrode (anode active layer) and the cathode current collector, even if a problem (such as a rupture) occurs in the separator. Therefore, by having anodes and cathodes of different lengths and by using an insulating coating on the edges of the corresponding batteries, thermal runaway can be mitigated.

[0041] Each electrode has an insulating coating 140 disposed on its outer edge. The insulating coating 140 extends around the periphery of the entire electrode. This prevents delamination and / or electrical shorting. Although the insulating coating is Figure 1A It is only shown as being provided on the periphery of each electrode (100A1 and 100A2) of the battery cell 100A, but it can be applied to the periphery of each electrode of other battery cells 100B, 100C, 100D, etc. in the battery 1000. In addition, a portion of each tab protruding from each electrode (cathode or anode) is coated with an insulating coating 160. The insulating coating can be applied to a portion of the tab (outside the electrode) at the point where the tab enters the electrode to serve as a current collector for each electrode. Some of these features and application points of insulating polymers will be discussed in detail below. Insulating coatings 140 and 160 may each have the same chemical composition, or may each have a different composition. In one embodiment, insulating coating 140 has a different chemical composition from insulating coating 160.

[0042] To describe the advantages of applying an insulating coating, select Figure 1A A section XX' (enclosed by a dashed line and indicated by numeral 130) is provided for detailed description. The section XX' includes two electrode active layers (in this case, cathode active layers 104A1 and 104A2) disposed on opposite surfaces of cathode current collector 112A1. Figure 2A and 2B express Figure 1A Magnified particle view of cross section XX' of a lithium-ion battery. Figure 2A and 2B Both depict cross section XX' at its upper edge 150 before and after application of insulating coating 140. Insulating coating 140 slightly penetrates into the active layer (anode or cathode active layer, as the case may be), contacts the active material and conductive particles (present in the active layer) and seals the edge of the cell. It also contacts current collector 112A1, forming a seal between current collector 112A1 and active layers (104A1 and 104A2), which prevents leaching of active material from the active layers and the cell.

[0043] Prior to the application of the insulating coating, the outer edges are exposed to environmental forces as well as various abrasive and deforming forces occurring during manufacturing, causing active material particles and other conductive particles to leach out of the corresponding active layers into the electrolyte and to the exterior of the battery cell. Such leaching of active material particles and conductive particles can result in short circuits, which in turn can result in undesirable elevated temperatures in lithium-ion batteries.

[0044] After the insulating coating 140 is applied to the outer edge of the electrode and allowed to cure, the heretofore loose active material particles and conductive particles are held in place by binding forces created by the insulating coating 140. These binding forces prevent leaching of the active particles and / or other conductive particles, thereby minimizing short circuits and other problems that have been described thus far.

[0045] The application of the insulating coating 140 improves local mechanical strength and reduces or prevents delamination of active material particles and conductive material particles, thereby reducing contamination during assembly. It also heals microcracks and prevents them from expanding into larger cracks that ultimately lead to interfacial delamination, especially when exposed to the slicing process. It should be noted that the insulating coating can be as Figure 1A It is shown applied along the entire outer edge of the electrode of the lithium ion battery, or alternatively may be applied in a coagulated form only in areas where the current collector contacts the active layer and an increased likelihood of delamination exists.

[0046] As described above, the insulating coating 160 may be applied to protect the cathode tabs 112A2, 112B2, 112C2, 112D2, 112E2, etc. or the anode tabs 114A2, 114B2, 114C2, 114D2, etc. (see Figure 1A and 1B ) from inadvertently contacting each other or other parts of the battery (e.g., opposing cathode or anode active layers) to create an electrical short. The insulating coating 160 can be applied to a portion of the cathode tabs 112A2, 112B2, 112C2, 112D2, 112E2 (protruding outside the cathode), etc., to a portion of the anode tabs 114A2, 114B2, 114C2, 114D2, etc. (protruding outside the anode), or to both the cathode tabs and the anode tabs (protruding outside the cathode and anode, respectively). Applying the insulating coating 160 to a portion of each tab mitigates the possibility of an accidental short circuit. The insulating coating is not applied to the joints 120A and 120B because metal-to-metal contact is desired for them to be welded to each other.

[0047] refer to Figure 1A and Figure 1B, the insulating coating 160 is applied only to the lower portion of the cathode tabs 112A2, 112B2, 112C2, 112D2, 112E2 (protruding outside the cathode), etc., or to the lower portion of the anode tabs 114A2, 114B2, 114C2, 114D2, etc. (protruding outside the anode), which are close to the corresponding current collectors (anode current collectors - 112A1, 112B1, 112C1, 112D1, 112E1, etc.) (cathode current collectors - 114A1, 114B1, 114C1, 114D1, etc.). The insulating coating 160 is usually applied to the cathode tabs and the anode tabs where the corresponding current collectors no longer contact the corresponding active layers. The upper portion of each tab (cathode tabs 112A2, 112B2, 112C2, 112D2, 112E2, etc., or anode tabs 114A2, 114B2, 114C2, 114D2, etc.) is not covered by the insulating coating 160, and the joints 120A and 120B are also not covered by the insulating coating 160. This is to facilitate welding of the corresponding tabs to form the corresponding joints. The lack of insulating coating 160 on each joint 120A and 120B also allows electrical communication with the load. The insulating coating 160 is applied with a thickness sufficient to prevent stray current from migrating from a tab to its adjacent tab.

[0048] In one embodiment, the thickness of the insulating coating 140 or 160 can be 200 nanometers to 50 microns. The electrically insulating and thermally stable coating applied to the tabs and electrode edges acts as a protective barrier against short circuits caused by separator failure, electrode misalignment, and overheating due to high current.

[0049] The materials used in the electrical insulating coating and the method of applying the coating will now be described in detail. The materials used in the insulating coating are essentially polymers. They are generally photosensitive polymer precursors, which can be cured using electromagnetic radiation to form an irreversible polymer network. Ultraviolet radiation is used to cure these photosensitive polymer precursors. Elevated temperatures can also be used to initiate or promote crosslinking. Therefore, they are able to handle high temperatures and potentially corrosive salts and electrolytes without experiencing any chemical degradation. Examples of photosensitive polymer precursors are epoxy resins, acrylic resins and acrylates, phenolic resins, silicone resins, polyurethane resins or combinations thereof. In other words, the insulating coating is derived from the polymerization and crosslinking of repeating units, and the repeating units include epoxy resins, acrylic resins, acrylates, phenolic resins, siloxanes, urethanes or combinations thereof. In one embodiment, the insulating coating 140 has a different chemical composition from the insulating coating 160.

[0050] Examples of epoxy resins are bisphenol A diglycidyl ether (BADGE) or cycloaliphatic epoxy resins. Epoxy resins are typically combined with a photoinitiator to react when exposed to ultraviolet radiation. The epoxy resin is used to form an insulating coating 160 disposed on the tab.

[0051] Examples of acrylics and acrylates are methyl methacrylate (MMA), ethyl methacrylate (EMA), butyl acrylate (BA), acrylic acid or a combination thereof. Examples of phenolic resins are phenol-formaldehyde resins. Examples of silicone polymers are vinyl terminated polysiloxanes, while examples of polyurethanes are isocyanate terminated prepolymers in combination with hydroxyl functional monomers and photoinitiators. Acrylics, acrylates, phenolic resins, silicone polymers and polyurethanes are commonly used as insulating coatings 140 on the edges of electrodes in lithium ion batteries. Suitable initiators for crosslinking can be used with each of the different repeating units detailed above.

[0052] In one embodiment, a curing composition comprising one of the aforementioned polymer precursors is mixed with an appropriate amount of an initiator, an optional crosslinking agent, an optional solvent, and other additives to form a reactive solution. The reactive solution is applied by a nozzle, by brushing, or by printing to form a layer of the precursor composition on the outer edge of each electrode in each battery cell of the lithium ion battery, such as Figure 1A In one embodiment, the precursor composition is applied to one or more outer edges of the electrode. It is generally applied to any electrode edge that is normally exposed to the ambient atmosphere without the insulating coating 140.

[0053] The precursor composition is optionally not applied to the outer edge of the separator, which generally tends to have a surface area greater than the surface of the electrode. The precursor composition is then cured by radiation and optional heat treatment. Radiation can be applied in one or two stages (e.g., primary process and / or secondary process). Radiation includes ultraviolet curing, x-ray curing, electron beam curing, microwave curing, or a combination thereof. In an exemplary embodiment, the radiation in the primary process includes ultraviolet curing.

[0054] In one embodiment, the precursor coating may be subjected to an optional secondary process to facilitate further curing. The secondary process may include thermal annealing at elevated temperatures and / or irradiation with a second form of electromagnetic radiation that is the same or different from the electromagnetic radiation used in the primary process. For example, if the primary curing process involves the use of ultraviolet radiation, the secondary curing process may optionally include thermal annealing at elevated temperatures, followed by curing optionally using additional ultraviolet radiation or electron beam radiation.

[0055] Annealing is performed at elevated temperatures to remove any residual solvent from the insulating coating and to promote additional curing. Annealing can be performed at elevated temperatures, which depend on the polymer precursor used. Typical annealing temperatures are 50 to 200°C for a period of 5 to 240 minutes.

[0056] Figure 3The insulating coating 160 is applied to the cathode tabs 112A2, 112B2, 112C2, etc. or the anode tabs 114A2, 114B2, 114C2, etc. (see Figure 1B ) before and after, the BB' of the lithium-ion battery 1000 (such as at Figure 1A An exemplary depiction of a side view of a cross section of the embodiment of the present invention (viewed in the direction of arrow AA'). Figure 3 It can be seen that before applying the insulating coating (see Figure 3 ), only the tab 120A and cathode active layer 104C2 are visible. After the insulating coating 160 is applied to the battery cell of the lithium-ion battery and cured and dried, the insulating coating 160 is also only visible on the lower portion of the tab 112C1 (which protrudes further upward to become part of the tab 120A). This can be seen in Figure 3 Seen to the right of the arrow in (facing the observer along the direction of arrow AA'). Figure 3 The side view to the right of the center arrow also shows an insulating coating 140 that is disposed on the outer edge of the electrode (on all sides) to prevent delamination.

[0057] The materials used in the anode and cathode current collectors, anode active layer, cathode active layer and separator will now be discussed in detail. The anode and cathode current collectors, tabs and tabs typically comprise metal. In one embodiment, the anode current collector comprises stainless steel, copper, nickel, iron, titanium or a combination thereof, and the cathode current collector comprises stainless steel, aluminum, nickel, iron, titanium or a combination thereof.

[0058] Figure 1A The anode active layers 108A1, 108A2, 108B1, 108B2, 108C1, 108C2, etc. and the cathode active layers 104A1, 104A2, 104B1, 104B2, 104C1, 104C1, etc. in the lithium ion battery shown each contain active materials (the anode active layer contains an anode active material, and the cathode active layer contains a cathode active material), conductive additives, and binders. Each of these is described below.

[0059] Anode active materials include some of the above carbonaceous materials, hard carbon, silicon, silicon mixed with graphite, silicon oxide mixed with graphite, carbon encapsulated silicon particles, Li4Ti5O 12 ; transition metals, such as tin, metal oxides, metal sulfides (such as TiO2, FeS, etc.), lithium metal and alloys, or combinations thereof. Exemplary active materials may include graphite, hard carbon, activated carbon, nanocarbon, silicon, silicon oxide, silicon oxide mixed with graphite, carbon-encapsulated silicon nanoparticles, or combinations thereof. In some such embodiments, the anode active material may be embedded with lithium (e.g., using pre-lithiation methods known in the art).

[0060] Hard carbon is a solid form of carbon that cannot be converted into graphite by heat treatment even at temperatures as high as 3000°C. It is also known as charcoal or non-graphitizable carbon. Hard carbon is produced by heating a carbonaceous precursor to about 1000°C in the absence of oxygen. Precursors of hard carbon include polyvinylidene chloride (PVDC), lignin, and sucrose. Other precursors, such as polyvinyl chloride (PVC) and petroleum coke, produce soft carbon or graphitized carbon. Soft carbon can be easily converted into graphite by heating to 3000°C.

[0061] In an exemplary embodiment, the anode active material includes silicon oxide mixed with graphite. The anode active material can be used in the anode active layer in an amount of 3 to 99 weight percent, respectively, based on the total weight of the anode active layer. In one embodiment, the anode active material can be used in the anode active layer in an amount of 4 to 60 weight percent, respectively, based on the total weight of the anode active layer.

[0062] The cathode active material may include lithium cobalt oxide (LCO, sometimes called "lithium cobaltate" or "lithium cobalt oxide" - one variant of which is LiCoO2); lithium nickel manganese cobalt oxide (NMC, with a variant of LiNiMnCo); lithium manganese oxide (LMO with variants of LiMn2O4, Li2MnO3, etc.); lithium nickel cobalt aluminum oxide (LiNiCoAlO2 and its variant as NCA) and lithium titanate oxide (LTO, one variant of which is Li4Ti5O 12 ); lithium iron phosphate oxide (LFP, a variant is LiFePO4), lithium nickel cobalt aluminum oxide (and its variant as NCA) and other similar materials, spinels (LiMn2O4, LiNi 0.5 Mn 1.5 O4), polyanion cathodes (LiV2(PO4)3) and other lithium transition metal oxides. Surface coated and / or doped cathode materials described above. For example, LiNbO3-coated LiMn2O4 and Al-doped LiMn2O4 may also be used. Low voltage cathode materials such as lithiated metal oxides / sulfides (e.g., LiTiS2), lithium sulfide, and sulfur may also be used.

[0063] Other variations of the foregoing may be included. In some embodiments where NMC is used as the active material, a nickel-rich NMC may be used. For example, in some embodiments, a variant of NMC may be LiNi x Mn y Co (1-x-y) O2、LiNi x Mn y Al (1-x-y) O2、LiNi x Mn (1-x) O2、Li (1+x)MO2, wherein x is equal to or greater than about 0.7, 0.75, 0.80, 0.85 or greater, and wherein y is less than 0.15. In one embodiment, y is less than 0.1. In some embodiments, NMC811 may be used, wherein in the foregoing formula, x is about 0.8 and y is about 0.1.

[0064] The cathode active material may be used in the cathode active layers 108A, 108B, and 108C in an amount of 50 to 98 wt % based on the total weight of each cathode active layer, respectively. In one embodiment, the cathode active material is used in the cathode active layer in an amount of 70 to 95 wt % based on the total weight of each cathode active layer.

[0065] Anode active layers 108A1, 108A2, 108B1, 108B2, 108C1, 108C2, etc. and cathode active layers 104A1, 104A2, 104B1, 104B2, 104C1, 104C1, etc. may all contain conductive additives. Conductive additives used in both anode active materials and cathode active materials include conductive carbonaceous materials. Examples of conductive carbonaceous materials include carbon nanotubes, carbon black, activated carbon, graphene, graphite, graphite oxide, carbon fibers, etc., or combinations thereof.

[0066] Carbon nanotubes include single-walled carbon nanotubes (SWNTs), double-walled carbon nanotubes (DWNTs), multi-walled carbon nanotubes (MWNTs) or a combination thereof, and have a diameter of 2 to 100 nanometers, wherein a diameter of 10 to 50 nanometers is desirable. They have a length of 20 to 10,000 nanometers, wherein a length of 200 to 5000 nanometers is desirable. Aspect ratios greater than 10, greater than 50, and greater than 100 are desirable.

[0067] Carbon blacks with high surface areas are preferred for use in electrodes. Carbon black (subtypes are acetylene black, channel black, furnace black, lamp black, and thermal black) is a material produced by the incomplete combustion of coal and coal tar, vegetable matter, or petroleum products (including fuel oil, fluid catalytic cracking tars, and ethylene cracking in a limited air supply). Carbon black is a form of semicrystalline carbon that has a high surface area to volume ratio, although lower than that of activated carbon. The surface area is 50 to 1000 m 2 / gm of carbon black can be used in the slurry for forming the electrode.

[0068] Activated carbon, also known as activated carbon, is a carbon with a surface area of ​​more than 3,000 m 2 / gm carbon form. It can be used in combination with other conductive carbonaceous elements listed herein. An example of carbon black or activated carbon that can be used in the electrode forming slurry is Keltjen TM Black or Super P.

[0069] Graphene is an allotrope of carbon consisting of a single layer of atoms arranged in a hexagonal lattice nanostructure. The graphene added to the slurry can be in the form of individual graphene sheets or in the form of multiple loosely connected graphene sheets. Each atom in the graphene sheet is connected to its three nearest neighbors by σ-bonds and delocalized π-bonds, which contribute to a valence band that extends across the sheet. This is the same type of bonding seen in carbon nanotubes and polycyclic aromatic hydrocarbons, as well as fullerenes and glassy carbon. The valence band contacts the conduction band, making graphene a semimetal with unusual electronic properties that are best described by the theory of massless relativistic particles.

[0070] Graphite particles can also be used in conductive compositions. Graphite is a natural manifestation of pure carbon with a hexagonal crystal structure arranged in several parallel levels, called graphene layers. In short, a graphite particle consists of a number of graphene sheets arranged parallel to each other. This anisotropic structure gives graphite special properties, such as electrical conductivity or specific strength along individual layers. It is very heat-resistant, with a sublimation point of over 3800°C, high thermal conductivity and chemical inertness.

[0071] Graphite oxide (GO) (sometimes called graphene oxide, graphite oxide or graphitic acid) is a compound of carbon, oxygen and hydrogen in variable ratios obtained by treating graphite with strong oxidants and acids to decompose additional metals. The most oxidized bulk product is a yellow solid with a C:O ratio between 2.1:1 and 2.9:1, which retains the layer structure of graphite, but with much larger and irregular spacing. The bulk material disperses spontaneously in alkaline solutions or can be dispersed in polar solvents by ultrasonic treatment to produce monomolecular sheets, similar to graphene (a single layer form of graphite) called graphene oxide. Graphene oxide sheets exist in the form of strong paper-like materials, films, thin films and composites, and can be used in electrode forming slurries for preparing electrodes.

[0072] Carbon fibers have a diameter of 5 to 10 microns and are composed primarily of carbon atoms. They can have a length greater than 1000 microns, with lengths greater than 10,000 microns being desirable. They are produced by stretching pitch or polyacrylonitrile polymer fibers at high pressures and temperatures in excess of 1500°C up to 2400°C. Carbon fibers are different from carbon nanotubes and do not have concentrically arranged cylindrical graphene sheets. Carbon fibers typically include high aspect ratio graphene sheets arranged in a parallel configuration to each other.

[0073] The above carbon nanotubes, carbon black, activated carbon, graphene sheets, graphite particles, graphite oxide particles or combinations thereof may be used alone or in any combination to form a conductive network. In an exemplary embodiment, carbon nanotubes are generally used in the largest amount when compared to other carbonaceous components.

[0074] Anode active layers 108A1, 108A2, 108B1, 108B2, 108C1, 108C2, etc. and cathode active layers 104A1, 104A2, 104B1, 104B2, 104C1, 104C1, etc. may contain a conductive additive in an amount of up to 30 wt%. Based on the total weight of the corresponding anode or cathode active layer, the conductive additive may be present in an amount of less than 20 wt%, with less than 10 wt% being desirable. In one embodiment, the anode or cathode active layer may contain a conductive additive in an amount of 1 wt% or more based on the total weight of the corresponding anode or cathode active layer.

[0075] The anode and cathode active layers may optionally contain a binder. The polymer binder generally comprises an organic polymer. Examples of organic polymers include poly(tetrafluoroethylene) (PTFE), styrene ethylene butylene styrene copolymer (SEBS), styrene butadiene styrene copolymer (SBS), acrylonitrile butadiene rubber (NBR), styrene-butadiene rubber (SBR), poly(propylene carbonate) PPC, sodium carboxymethylcellulose (CMC), poly(vinylidene fluoride) (PVDF), poly(vinylidene fluoride-to-hexafluoropropylene) (PVdF-HFP), polyacrylonitrile (PAN), poly(vinylidene fluoride-to-chlorotrifluoroethylene) (P(VDF-CTFE)), poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TeFE)), poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) terpolymer (P(VDF-TrFE-CFE)) or a combination thereof. In a preferred embodiment, the polymer binder used in the active layer is a poly(vinylidene fluoride-hexafluoropropylene) copolymer. The weight average molecular weight of the polymer binder is 5,000 to 1,000,000 g / mole. In one embodiment, the weight average molecular weight of the polymer binder is 50,000 to 750,000 g / mole. In another embodiment, the weight average molecular weight of the polymer binder is 75,000 to 500,000 g / mole. The weight average molecular weight is measured using gel permeation chromatography with polystyrene standards.

[0076] The polymer binder is optional and, if used in the anode active layer or cathode active layer, is present in an amount of less than 5 wt %. In one embodiment, it is used in an amount of less than 3 wt % based on the total weight of the corresponding anode or cathode active layer. In another embodiment, it is used in an amount of less than 1 wt % based on the total weight of the corresponding anode or cathode active layer.

[0077] The separators 106A1, 106A2, 106A3, etc. generally include a porous electrically insulating film. Examples of electrically insulating materials used as separators are polyolefins (e.g., polyethylene, polypropylene, or a combination thereof), polyimides, polyaramids, polyvinyl fluorides (e.g., polytetrafluoroethylene), polysiloxanes (e.g., polydimethylsiloxane), or a combination thereof.

[0078] In the preparation of the anode active layer 108A1, 108A2, 108B1, 108B2, 108C1, 108C2, etc. and the cathode active layer 104A1, 104A2, 104B1, 104B2, 104C1, 104C1, etc., the corresponding anode active material or cathode active material together with the conductive additive and the optional binder can be mixed with a suitable solvent to produce an anode active material slurry or a cathode active material slurry. The corresponding slurry is applied to an appropriate current collector (the anode active material slurry is applied to the anode current collector, and the cathode active material slurry is applied to the cathode current collector). The active material slurry is dried to form an active material layer.

[0079] Reference again Figure 1A , the anode active layers 108A1, 108A2, 108B1, 108B2, 108C1, 108C2, etc. together with the corresponding current collectors 114A1, 114B1, etc. form the anode of the lithium ion battery. The cathode active layers 104A1, 104A2, 104B1, 104B2, 104C1, 104C1, etc. together with the corresponding current collectors 112A1, 112B1, 112C1, etc. form the cathode of the lithium ion battery. As described above, the corresponding separators (having odd coefficients) 106A1, 106A3, 106A5 are arranged between the anode active layer and the cathode active layer, and the separators having even coefficients 106A2, 106A4, 106A6, etc. are arranged between the battery cells 100A, 100B, 100C, etc. to form a lithium ion battery. The electrolyte can be charged into the battery cell. Tabs 112A2, 112B2, 112C2, etc. are joined together and welded to form joint 120A. Tabs 114A2, 114B2, 114C2, etc. are joined together and welded to form joint 120B.

[0080] An insulating polymer layer 140 is then applied to the outer edge of each electrode (anode or cathode) in each battery cell by brushing, printing, or spraying (through a nozzle) as described above. Figure 1A and 1B , it can be seen that the insulating layer 140 contacts the outer edge of the electrode but does not contact the separator.

[0081] The insulating coating is then cured using radiation (UV) or thermal energy (heat). The insulating coating 160 may also be applied to tabs 112A2, 112B2, 112C2, etc., and / or to tabs 114A2, 114B2, 114C2, etc., via brushing, printing, or spraying (via a nozzle) as described above.

[0082] Disposing the insulating polymer layer 140 on the outer edge of the electrode and the insulating coating 160 on the tab prevents delamination and short circuits in the battery cells of the lithium-ion battery. It minimizes the leaching of active materials into the electrolyte and increases the life of the lithium-ion battery.

[0083] The terms "one" and "an" do not indicate a limitation of quantity, but rather indicate the presence of at least one of the referenced item. Unless the context clearly indicates otherwise, the term "or" means "and / or". References to "aspects" throughout the specification mean that a particular element (e.g., a feature, structure, step, or characteristic) described in conjunction with that aspect is included in at least one aspect described herein, and may or may not be present in other aspects. In addition, it should be understood that the described elements may be combined in any suitable manner in the various aspects.

[0084] When an element such as a layer, film, region, or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly on" another element, there are no intervening elements present.

[0085] Unless otherwise indicated herein, all test standards are the most current standards in effect as of the filing date of this application or, if priority is claimed, the filing date of the earliest priority application in which the test standards appear.

[0086] Unless defined otherwise, technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0087] Although the above disclosure has been described with reference to exemplary embodiments, it will be appreciated by those skilled in the art that various changes may be made and equivalents may be substituted for its elements without departing from its scope. In addition, many modifications may be made to adapt specific circumstances or materials to the teachings of the disclosure without departing from the basic scope of the disclosure. Therefore, it is intended that the disclosure is not limited to the specific embodiments disclosed, but will include all embodiments falling within its scope.

Claims

1. A lithium-ion battery comprising: a plurality of battery cells; Each battery cell includes: an anode; wherein the anode comprises an anode active layer in contact with an anode current collector; wherein the anode current collector from each battery cell contacts an anode tab located outside the battery cell; a cathode; wherein the cathode comprises a cathode active layer in contact with a cathode current collector; wherein the cathode current collector from each battery cell contacts a cathode tab located outside the battery cell; wherein the cathode has a different length than the anode; a separator; wherein the separator is disposed between the anode and the cathode; and An electrically insulating coating is disposed on a portion of the anode tab in contact with the anode active layer, or on a portion of the cathode tab in contact with the cathode active layer, or on an outer edge of each anode and cathode.

2. The lithium ion battery according to claim 1, wherein the electrically insulating coating is disposed on a portion of the anode tab that contacts the anode current collector or a portion of the cathode tab that contacts the cathode current collector; The anode tab contacts the anode current collector at an outer edge of the anode, and wherein the cathode tab contacts the cathode current collector at an outer edge of the cathode.

3. The lithium ion battery of claim 2, wherein the electrically insulating coating is a cross-linked coating, and wherein the cross-linked coating is derived from the polymerization and cross-linking of repeating units comprising epoxy resins, acrylic resins, acrylates, phenolic resins, siloxanes, polyurethanes, or combinations thereof.

4. The lithium ion battery of claim 1 , wherein the electrically insulating coating disposed on the outer edge of each anode or cathode is derived from the polymerization and cross-linking of repeating units comprising acrylic resins, acrylates, phenolic resins, siloxanes, polyurethanes, or combinations thereof.

5. The lithium ion battery of claim 3, wherein the electrically insulating coating is cross-linked via ultraviolet radiation, thermal energy, or a combination thereof. 6 . The lithium ion battery of claim 1 , wherein the electrically insulating coating further penetrates into the anode active layer or the cathode active layer and prevents active materials from leaching out of the corresponding active layer.

7. The lithium ion battery of claim 1 , wherein the electrically insulating coating contacts the anode current collector thereby forming a seal between the anode current collector and the anode active layer, or wherein the electrically insulating coating contacts the cathode current collector thereby forming a seal between the cathode current collector and the cathode active layer.

8. A method of reducing damage to a lithium-ion battery comprising a plurality of battery cells, the method comprising: disposing a curable composition on an outer edge of an anode or cathode of at least one battery cell in the plurality of battery cells; wherein the curable composition comprises a photoinitiator and repeating units of epoxy resin, acrylic resin, acrylate, phenolic resin, siloxane, polyurethane or a combination thereof; as well as curing the curable composition by subjecting the curable composition to electromagnetic radiation, thermal energy, or a combination thereof; wherein each battery cell comprises: an anode; wherein the anode comprises an anode active layer in contact with an anode current collector; a cathode; wherein the cathode comprises a cathode active layer in contact with a cathode current collector; and a separator; wherein the separator is disposed between the anode and the cathode; wherein the anode current collector from each battery cell contacts an anode tab located outside each battery cell, and wherein the cathode current collector contacts a cathode tab located outside each battery cell. 9 . The method of claim 8 , wherein curing the curable composition forms an electrically insulating coating on an outer edge of at least one battery cell in the plurality of battery cells.

10. The method of claim 8, further comprising disposing the curable composition on a portion of the anode tab in contact with the anode current collector or on a portion of the cathode tab in contact with the cathode current collector, and curing the curable composition to form an electrically insulating coating.

Images