COMPOSITION WITH SMALL MOLECULE ADDITIVES FOR IMPROVED SAFETY AND PERFORMANCE IN HIGH VOLTAGE BATTERIES

A battery cell may include an electrolyte, a first electrode including a first electrode layer and a first current collector, a second electrode including a second electrode layer and a second current collector, a separator interposed between the first electrode and the second electrode, and at least one protective layer. For example, a protective layer may be interposed between the first electrode layer and the first current collector, the second electrode layer and the second current collector, the separator and the first electrode, and/or the separator and the second electrode. When activated, the one or more protective layers may reduce or interrupt current flow through the battery cell. The composition of the one or more protective layers may include one or more small molecule additives to increase its stability and conductivity, thus improving the performance as well as the safety profile of the battery cell.

TECHNICAL FIELD

The subject matter described herein relates generally to battery cells and more specifically to a protective layer with small molecular additives for use in battery cells.

BACKGROUND

A battery cell can overcharge, overheat, and/or short circuit during operation. For example, an overcurrent can occur when the battery cell is overcharged and/or develops an internal short circuit. Overcurrent can cause irreversible damage to the battery cell. In particular, overcurrent can lead to thermal runaway, a hazardous condition in which undissipated heat from the overheating battery cell accelerates exothermic reactions within the battery cell to further increase the temperature of the battery. The consequences of thermal runaway can be especially dire including, for example, fire, explosions, and/or the like.

SUMMARY

Methods, systems, and articles of manufacture are provided for a protective layer for a battery cell. In one aspect of the current subject matter, a battery cell may include a protective layer configured to mitigate and/or eliminate the hazards that can arise during the operation of the battery cell. The protective layer may include one or more small molecule additives to facilitate cross linking and improve the stability and conductivity of the protective layer. Moreover, the protective layer may be configured to respond to an increase in temperature, voltage, and/or current by interrupting a flow of current within the battery cell. The protective layer may be disposed on one or both surfaces of at least one current collector or electrode of the battery cell. Accordingly, in some cases, a first protective layer may be interposed between a first current collector and a corresponding first electrode of the battery cell. Alternatively, and/or additionally, a second protective layer may be interposed between a second current collector and a corresponding second electrode of the battery cell.

In some cases, the protective layer may be part of a multifunctional layer that includes the protective layer and a sealing layer. The multifunctional layer may be interposed between an electrode and a current collector of the battery cell, with the sealing layer further being interposed between the electrode and the protective layer. The sealing layer may isolate the protective layer from the other components of the battery cell in particular the electrodes and the electrolyte included in the battery cell. As such, the presence of the sealing layer may lend flexibility to the choice of material used to form the protective layer. For example, the material forming the protective layer may be selected to maximize performance, with minimal consideration necessary for compatibility with the other components of the battery cell.

In another aspect, there is provided a battery cell that includes a protective layer with one or more small molecule additives. The battery cell may include: an electrolyte; a first electrode including a first electrode layer and a first current collector; a second electrode including a second electrode layer and a second current collector; a separator interposed between the first electrode and the second electrode; anda first protective layer reducing or interrupting a current flow within the battery cell upon activation, the first protective layer being formed from a composition that includes one or more small molecule additives combined with a functional material and/or a conductive material.

In some variations of the methods, systems, and articles of manufacture, one or more of the following features can optionally be included in any feasible combination.

In some variations, the one or more small molecule additives may include an aromatic amine, an aliphatic amine, an aliphatic carboxylic acid, an aromatic carboxylic acid, an aliphatic hydroxy compound, an aromatic hydroxyl compound, an aliphatic thiol compound, an aromatic thiol compound, an epoxy substituted aliphatic or aromatic compound, aromatic or aliphatic substituted pyrrole-2,5-dione, an ethylene substituted aliphatic or aromatic compound, and/or a free radical initiator.

In some variations, the composition of the first protective layer may include 0.1% to 90% of the one or more small molecule additive by weight, 1% to 50% of the one or more small molecule additive by weight, 1% to 10% of the one or more small molecule additive by weight, or 1% to 5% of the one or more small molecule additive by weight.

In some variations, the conductive material may be carbon black or a conductive polymer selected from poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT :PS S), polypyrrole (doped), poly(n-alkylthiophene), polyalylfluorene, and poly(3,4-ethylenedioxythiophene)-co-poly(ethyleneglycol) (PEDOT-PEG) (doped).

In some variations, the composition of the first protective layer may further include one or more base materials and/or binder materials.

In some variations, the first protective layer may be interposed between (i) the first electrode layer and the first current collector or (ii) the separator and the first electrode layer.

In some variations, the first protective layer may be coupled with a sealing layer that prevents a reaction between the first protective layer and at least one of the first electrode layer and the electrolyte of the battery cell until the sealing layer is activated by a second trigger.

In some variations, the battery cell may further include a second protective layer formed from the composition that includes the one or more small molecule additives combined with the functional material and/or the conductive material. The second protective layer may be interposed between (i) the second electrode layer and the second current collector or (ii) the separator and the second electrode layer.

In some variations, the second protective layer may be coupled with a sealing layer that prevents a reaction between the second protective layer and at least one of the second electrode layer and the electrolyte of the battery cell until the sealing layer is activated by at least one of a temperature trigger, a voltage trigger, a current trigger, and a physical damage to the battery cell.

In some variations, the first protective layer may be activated by at least one of a temperature trigger, a voltage trigger, a current trigger, and a physical damage to the battery cell.

In another aspect, there is provided a battery cell that includes: an electrolyte; a first electrode including a first electrode layer and a first current collector; a second electrode including a second electrode layer and a second current collector; a separator interposed between the first electrode and the second electrode; and a first protective layer reducing or interrupting a current flow within the battery cell upon activation, the first protective layer being formed from a composition that includes one or more metal salts, ceramic nano materials, and conductive nano additives.

In some variations of the methods, systems, and articles of manufacture, one or more of the following features can optionally be included in any feasible combination.

In some variations, the one or more metal salts may be organic salts selected from polyacid salts [—CR3—(CR2)0-100—COOM—]p, polymethacrylic salts [—CR2—(CR2)0-100—C(CR3)(COOM)—]p, polyacrylate salts [—CR2—(CR2)0-100—CR(COOM)—]p, polymethylmethacrylic salts [—CR(CR3)—(CR2)0-100—C(CR3)(COOM)-]p, polyols-M [—CR2—(CR2)0-100—CR—OM—]p, polysulfide-M [—CR2—(CR2)0-100—CR—SM—]p, and organic silicate [—R2Si—O—SiR2—]p, wherein M is selected from a group of metals including lithium (Li), sodium (Na), potassium (K), calcium (Ca), cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), titanium (Ti), nickel (Ni), zinc (Zn), manganese (Mn), lead (Pb), strontium (Sr), and zinc (Zn), and wherein

R is selected from H, —CH3, and —CH2CH3.

In some variations, the one or more ceramic nano materials may include a metal carbonate, a metal hydrogen carbonate, a metal oxide, a metal titanate, and/or a metal silicate.

In some variations, the one or more conductive nano additives may include a carbon nano material, a carbon fiber, single wall carbon nano tubes, multi wall carbon nano tubes, a metallic powder, and/or a combination of carbon and metallic powders

In some variations, the first protective layer may be interposed between (i) the first electrode layer and the first current collector or (ii) the separator and the first electrode layer.

In some variations, the first protective layer may be activated by at least one of a temperature trigger, a voltage trigger, a current trigger, and a physical damage to the battery cell.

In some variations, a second protective layer may be formed from the composition that includes the one or more small molecule additives combined with the functional material and/or the conductive material, the second protective layer being interposed between (i) the second electrode layer and the second current collector or (ii) the separator and the second electrode layer.

When practical, like labels are used to refer to same or similar items in the drawings.

DETAILED DESCRIPTION

A battery cell can include at least one protective layer to mitigate and/or eliminate the operational hazards of the battery cell including, for example, overcharging, overheating, short-circuiting, and/or the like. The overcharging, overheating, and/or short-circuiting of the battery cell can lead to thermal runaway, a dangerous condition in which the battery cell undergoes a precipitous increase in temperature. Accordingly, the protective layer can be configured to respond to an increase in temperature by interrupting a flow of current within the battery cell. For example, when the battery cell is exposed to temperatures exceeding a threshold value, the protective layer can undergo a phase transition that causes the protective layer to expand and/or contract. The expansion and/or contraction of the protective layer can cause an electric decoupling within the battery cell, for example, between an electrode of the battery cell and a corresponding current collector. The electric decoupling can interrupt the flow of current within the battery cell, thereby arresting exothermic reactions within the battery cell and any further increase in the temperature of the battery cell.

In some implementations of the current subject matter, the performance of the battery cell may be further enhanced by improving the stability and conductivity of the protective layer. For example, the stability and conductivity of the protective layer may be improved by forming the protective layer from a composition that includes one or more small molecule additives. In some cases, the composition forming the protective layer may include 1-90% small molecule additives relative to one or more functional materials such as polymers (e.g., polymethyl methacrylate (PMMA) and/or the like). As used herein, the term “small molecule additive” refers to an additives having a molecular weight that is below a threshold value such as, for example, 1000 Daltons, 600 Daltons, below 500 Daltons, below 400 Daltons, and/or the like. In some cases, a small molecule additive may be a micropolymer formed by multiple identical repeating units (e.g., monomers). Examples of small molecule additives include aromatic amines, aliphatic amines, aliphatic carboxylic acids, aromatic carboxylic acids, aliphatic hydroxy compounds, aromatic hydroxyl compounds, aliphatic thiol compounds, aromatic thiol compounds, epoxy substituted aliphatic or aromatic compounds, aromatic or aliphatic substituted pyrrole-2,5-dione, ethylene substituted aliphatic or aromatic compounds, free radical initiators, and/or the like (e.g., 1,5-Naphthalenediamine, 4,4′-(9-Fluorenylidene)dianiline, 2,6-diaminoanthracene, aliphatic diol, aliphatic diamine, aliphatic dicarboxylic acid, butane-1,2,3,4,-tetracarboxylic acid, pentaerythritol, biphenyl-4,4′-dicarboxylic acid, 2,6-naphthalene dicarboxylic acid, 4-(vinyloxy)aniline, 2-allylphenol, trimethylolpropane tris(3-mercaptopropionate), petaerytheritol tetrakis(3-mercaptoproprionate), 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H, 5H)-tri one, tris[2-(acryloyloxy)ethyl] isocyanurate, ethylene glycol bis -mercaptoacetate, 2,2′-(ethylene dioxy)diethanethiol, 4-aminothiophenol, tris(2,3-epoxypropyl) isocyanurate, 1-(4-aminophenyl)-1H-pyrrole-2,5-dione, and/or the like). It should be appreciated that small molecule additives may be used in place of large molecule additives at least because large molecule additives may be too cost prohibitive at the production scales typically associated with battery manufacturing.

To form the protective layer, the one or more small molecule additives may be combined with one or more active functional materials or inorganic materials along with one or more base materials (e.g., lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), and/or the like), binder materials, and/or conductive materials. Examples of functional materials include polyacrylic acid (PAA), crosslinked polyacrylic acid (PAA), carboxymethyl cellulose (CMC), poly(methyl acrylate) (PMA), poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), poly(2-hydroxyethyl methacrylate) (pHEMA), and/or the like. In some cases, the composition of the protective layer may include a conductive polymer. For example, in some cases, the composition of the protective layer may include 1-100% of the conductive polymer relative to the one or more conductive materials included therein or 1-100% of the conductive polymer relative to the one or more binder materials included therein. Alternatively, in some cases, the conductive polymer may be the sole conductive material and active functional material present in the composition of the protective layer. Examples of conductive polymers include poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), polypyrrole (doped), poly(n-alkylthiophene), polyalylfluorene, poly(3,4-ethylenedioxythiophene)-co-poly(ethyleneglycol) (PEDOT-PEG) (doped), and/or the like.

Exposing the protective layer to the other components of the battery cell, such as the electrodes and/or the electrolyte, may trigger undesirable reactions including degradation of the protective layer, premature activation of the protective layer, and/or the like. As such, in some implementations of the current subject matter, the protective layer may be a part of a multifunction layer that includes the protective layer and a sealing layer. The multifunction layer may be interposed between an electrode and a current collector of the battery cell, with the sealing layer further being interposed between the electrode and the protective layer. The presence of the multifunction layer including the protective layer may further improve the performance of the battery cell including the cell cycle (e.g., capacity retention) and high temperature stability of the battery cell.

In some implementations of the current subject matter, the sealing layer may be formed from one or more materials that are inert in the presence of the reactive components of the battery cell such as the electrodes and/or the electrolyte. The presence of the sealing layer may therefore lend flexibility in the choice of material forming the protective layer as the sealing layer may prevent the protective layer from being exposed to the reactive components of the battery cell. Moreover, the presence of the sealing layer may render the protective layer more tolerant to manufacturing processes (e.g., calendaring of the electrode and/or the like) as well as exposure to a high temperature environment such as during the coating and drying of the electrodes. Nevertheless, it should be appreciated that the sealing layer may be optional. For example, the multifunction layer including the protective layer and the sealing layer may be coupled with a first electrode of the battery cell whereas a second electrode of the battery cell may be coupled with the protective layer without the sealing layer.

Configuring a single protective layer to respond to multiple triggers may be challenging. Contrastingly, the sealing layer and the protective layer are configured to serve different purpose and may therefore be configured to activate upon different triggers such as, for example, a temperature trigger, a voltage trigger, a current trigger, and/or the like. For example, the sealing layer may be configured to respond to a more precise trigger point (e.g., a first threshold temperature, a first threshold voltage, a first threshold current, and/or the like) by exposing the protective layer whereas the protective layer may be configured to activate upon exposure and/or a less precise trigger point (e.g., a second threshold temperature, a second threshold voltage, a second threshold current, and/or the like).

In some implementations of the current subject matter, while the protective layer may exhibit instability towards the other components of the battery cell (e.g., electrodes, electrolyte, and/or the like), the sealing layer may be inert in the presence of these same components. For example, whereas the protective layer may become reactive in the presence of an electrolyte, the sealing layer may be immiscible and thus provide a physical separation between the protective layer, and a corresponding electrode in the battery cell. During normal operation (e.g., in the absence of any triggers), the presence of the sealing layer may prevent the protective layer from being exposed to the electrolyte and undergo an undesirable reaction. However, upon activation of a trigger associated with the sealing layer (e.g., a temperature trigger, a voltage trigger, a current trigger, and/or the like), the sealing layer may disintegrate to expose the protective layer, at which point a suitable reaction may take place to prevent thermal runaway at the battery cell. The protective layer may also be exposed by the sealing layer being broken due to application of mechanical stress.

This reaction may include a physical reaction (e.g., a swelling or other expansion of the protective layer) that causes an interruption in the electronic conduction pathway, akin to a positive temperature coefficient (PTC) composite. Alternatively and/or additionally, this reaction may include a chemical reaction such as a decomposition of the protective layer and/or a reaction between the electrode and the protective layer, which creates a nonconductive gap between the current collector and the electrode. This reaction may also include a chemical reaction between the protective layer and the electrolyte that lowers the ionic conductivity of the electrolyte.

In some implementations of the current subject matter, the sealing layer may be polymeric and applied by one or more of a solution-based spraying, coating, vapor deposition, and/or the like. Alternatively and/or additionally, the sealing layer may be metallic and applied by one or more of a metal evaporation, vapor deposition, and/or the like. Alternatively and/or additionally, the sealing layer may be formed from monomers, which are crosslinked by exposure to heat, ultraviolet light, x-ray, laser, and/or the like. Alternatively and/or additionally, the sealing layer may be formed from one or more conductive polymers and/or conductive ceramics (e.g., metal oxide, transition metal oxide, and/or the like). The sealing layer may also be formed by sputtering and/or atomic layer deposition.

In some implementations of the current subject matter, the protective layer, whether alone or as a part of a multifunction layer that further includes a sealing layer, may be coated on one or both current collectors of the battery cell. Depending on the application, such as the format of the battery cell, one or more of the current collectors may be formed from a metal foil or the case of the battery cell. Alternatively and/or additionally, the protective layer may be coated on one or both electrodes of the battery cell. The resulting battery cell may include a first protective layer interposed between a first electrode and a first current collector. Furthermore, in some cases, the battery cell may also include a second protective layer interposed between a second electrode and a second current collector.

FIGS.1A-Cdepict schematic diagrams illustrating examples of a battery cell100having one or more protective layers130consistent with implementations of the current subject matter. In some cases, the battery cell100may be a metal battery cell or a metal ion battery cell including, for example, a lithium (Li) ion battery cell, a sodium (Na) ion battery cell, an aluminum (Al) ion battery cell, a magnesium (Mg) ion battery cell, and/or the like. Moreover, the battery cell100may be in any format including, for example, a cylindrical battery cell, a button battery cell, a prismatic battery cell, a pouch battery cell, and/or the like. According to various implementations of the current subject matter, at least one protective layer130may be disposed on a surface of a separator140, an electrode layer120, and/or a current collector130of the battery cell100.

As shown inFIGS.1A-C, the battery cell100may include a first electrode layer120a, a first current collector130a, a second electrode layer120b, and a second current collector130b. The first electrode layer120aand the second electrode layer120bmay be opposite in polarity. For example, where the first electrode layer120aand the first current collector130aform a first electrode125a(e.g., the positive electrode) of the battery cell100, the second electrode layer120band the second current collector130bmay form a second electrode120b(e.g., the negative electrode) of the battery cell100. The separator140, which may be a polymeric film, may be interposed between the first electrode layer120aand the second electrode130b. In some cases, the first current collector130aand the second current collector130bmay be formed from a metal foil or a metallized foil including, for example, a copper (Cu) foil, an aluminum (Al) foil, an iron (Fe) foil, a titanium (Ti) foil, a nickel (Ni) foil, a carbon (C) foil, a metalized polymeric foil, and/or the like.

In the example of the battery cell100shown inFIG.1A, the battery cell100may include a first protective layer130binterposed between the first electrode layer120aand the first current collector120b. In the example of the battery cell100shown inFIG.1B, a second protective layer130bmay be further interposed between the second electrode120band the second current collector130b. In the example of the battery cell100shown inFIG.1C, the one or more protective layers110are coated on one or more surfaces of the separator140. Accordingly, in some cases, the first protective layer110amay be interposed between the separator140and the first electrode layer120a. Furthermore, in some cases, the second protective layer110bmay be interposed between the separator140and the second electrode layer120b.

FIGS.2A-Bdepict schematic diagrams illustrating examples of the battery cell100having one or more multifunction layers150consistent with implementations of the current subject matter. In some implementations of the current subject matter, each protective layer110of the battery cell100may be further coupled with a sealing layer155to form the one or more multifunction layers150. For example, inFIG.2A, a first multifunction layer150a, which includes the first protective layer110aand a first sealing layer155a, may be interposed between the first electrode layer120aand the first current collector130a. In the example shown inFIG.2A, the first protective layer110amay be interposed between the first electrode layer120aand the first sealing layer155awhile the first sealing layer155ais further interposed between the first protective layer110aand the first current collector130a.

FIG.2Bdepicts another example of the battery cell100including the first multifunction layer150ainterposed between the first electrode layer120aand the first current collector130aas well as a second multifunction layer150binterposed between the second electrode layer120band the second current collector130b. As shown inFIG.2B, the second multifunction layer150bmay include a second protective layer110band a second sealing layer155b, with the second protective layer110binterposed between the second electrode layer120band the second sealing layer155bwhile the second sealing layer155bis further interposed between the second protective layer110band the second current collector130b.

FIG.2Cdepicts another example of the battery cell100in which the multifunction layers150are interposed between the separator140and the first electrode layer120aand/or the second electrode layer120b. For example, in some cases, the first multifunction layer150amay be interposed between the separator140and the first electrode layer120awith the first protective layer110abeing interposed between the separator140and the first sealing layer155awhile the first sealing layer155ais further interposed between the first protective layer110aand the first electrode layer120a. Alternatively and/or additionally, the second multifunction layer150bmay be interposed between the separator140and the second electrode layer120bwith the second protective layer110bbeing interposed between the separator140and the second sealing layer155bwhile the second sealing layer155bis further interposed between the second protective layer110band the second electrode layer120b.

In some implementations of the current subject matter, the one or more protective layers110of the battery cell100may neutralize hazardous operating conditions such as overheating, overcharging, and/or internal short circuiting. For example, in some cases, the one or more protective layers110of the battery cell100may neutralize hazardous operating conditions by at least acting as a current limiter that reduces the flow of current through the battery cell100in the event of overheating, overcharging, and/or internal short circuiting. In some cases, the one or more protective layers110may reduce the flow of current through the battery cell100by at least exhibiting an increase in impedance when the temperature, voltage, and/or current through the battery cell100satisfies one or more threshold values, for example, by exceeding a temperature, a voltage, and/or a current associated with normal (or safe) operations. Alternatively and/or additionally, the one or more protective layers110of the battery cell100may neutralize hazardous operating conditions by at least acting as a current interrupter that eliminates the flow of current through the battery cell100in the event of overheating, overcharging, and/or internal short circuiting. For instance, in some cases, the one or more protective layers110may discontinue the flow of current through the battery cell100by at least creating a nonconductive gap when the temperature, voltage, and/or current through the battery cell100satisfies one or more threshold values, for example, by exceeding a temperature, a voltage, and/or a current associated with normal (or safe) operations.

In some implementations of the current subject matter, the one or more protective layers110of the battery cell100may be formulated to include one or more small molecule additives. The presence of the one or more small molecule additives in the composition of the one or more protective layers110may increase the stability and, in some cases, the conductivity of the one or more protective layers110. As such, the inclusion of the one or more small molecule additives may improve the performance of the battery cell100including, for example, cell cycle (e.g., capacity retention), high temperature stability, and/or the like. For example, in some cases, the stability of the one or more protective layers110may be increased as a result of a reaction between the one or more small molecule additives and other compounds (e.g., polymers) present in the one or more protective layers110. As noted, examples of small molecule additives include aromatic amines, aliphatic amines, aliphatic carboxylic acids, aromatic carboxylic acids, aliphatic hydroxy compounds, aromatic hydroxyl compounds, aliphatic thiol compounds, aromatic thiol compounds, epoxy substituted aliphatic or aromatic compounds, aromatic or aliphatic substituted pyrrole-2,5-dione, ethylene substituted aliphatic or aromatic compounds, free radical initiators, and/or the like. In some cases, the one or more protective layers110may include 0.1% to 90% of small molecule additives by weight, 1% to 50% of the small molecule additives by weight, 1% to 10% of the small molecule additives by weight, 1% to 5% of the small molecule additives by weight, and/or the like.

To form the one or more protective layers110, the one or more small molecule additives may be combined with one or more active functional materials or inorganic materials along with one or more base materials (e.g., lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), and/or the like), binder materials, and/or conductive materials. For example, in some cases, the composition of the one or more protective layers may include one or more metal salts (e.g., organic salts and/or the like), ceramic nano materials, and conductive nano additives. In some cases, the composition of the one or more protective layers may include 1-90% small molecule additives relative to other compounds such as the one or more functional materials. As shown inFIG.3C, examples of functional materials include polyacrylic acid (PAA), crosslinked polyacrylic acid (PAA), carboxymethyl cellulose (CMC), poly(methyl acrylate) (PMA), poly(methyl methacrylate) (PMMA), poly(ethyl methacrylate) (PEMA), poly(2-hydroxyethyl methacrylate) (pHEMA), and/or the like.

Examples of the one or more metal salts that may be present in the composition of the one or more protective layers100include polyacid salts [—CR2—(CR2)0-100—COOM—]p, polymethacrylic salts [—CR2—(CR2)0-100—C(CR3)(COOM—)-]p, polyacrylate salts [—CR2—(CR2)0-100—CR(COOM)—]p, polymethylmethacrylic salts [—CR(CR3)—(CR2)0-100—C(CR3)(COOM)—]p, polyols-M [—CR2—(CR2)0-100—CR—OM—]p, polysulfide-M [—CR2—(CR2)0-100—CR—SM—]p, and organic silicate [-R2Si—O—SiR2—]p, wherein M is selected from a group of metals including lithium (Li), sodium (Na), potassium (K), calcium (Ca), cadmium (Cd), cobalt (Co), copper (Cu), iron (Fe), titanium (Ti), nickel (Ni), zinc (Zn), manganese (Mn), lead (Pb), strontium (Sr), and zinc (Zn), and wherein R is selected from H, —CH3, —CH2CH3, and other organic substitutes. Where the one or more metal salts are present in the composition of the one or more protective layers110, the one or more metal salts may form 1% to 99% of the one or more protective layers110by weight, 10% to 90% of the one or more protective layers110by weight, 20% to 70% of the one or more protective layers110by weight, and/or the like.

As noted, the composition of the one or more protective layers110may further include one or more ceramic nano materials. In some cases, the one or more ceramic nano materials that may be present in the composition of the one or more protective layers110may exhibit certain dimensions such as, for example, at least one dimension that is less than 500 nanometers, at least one dimension that is less than100nanometers, and/or the like. Examples of the one or more ceramic nano materials that may be present in the composition of the one or more protective layers110may include metal carbonates (e.g., Li2CO3, Na2CO3, K2CO3, CaCO3, BeCO3, MgCO3, SrCO3, BaCO3, FeCO3, and/or the like), metal hydrogen carbonates (e.g., LiHCO3, NaHCO3, KHCO3, CsHCO3, Ca(HCO3)2, Mg(HCO3)2, and/or the like), metal oxides (e.g., CaO, MgO, SiO2, Al2O3, TiO2, ZrO2, CuO, SnO2, GeO2, Co3O4, ZnO, and/or the like), metal titanates (e.g., Li2TiO3, CaTiO3, MgTiO3, BaTiO3, ZnTiO3, and/or the like), and metal silicates (e.g., Li2SiO3, Na2SiO3, MgSiO3, CaSiO3, FeSO3, MnSiO3, K2SiO3, Zn2SiO4, Mg2SiO4, Fe2SiO4, Mn2SiO4, ZrSiO4, Be2SiO4, and/or the like). Where the one or more ceramic nano materials are present in the composition of the one or more protective layers110, the one or more ceramic nano materials may form 0.1% to 98.9% of the one or more protective layers110by weight, 5% to 80% of the one or more protective layers110by weight, and/or the like.

In some cases, the composition of the one or more protective layers110may include one or more conductive nano additives. For example, in cases where the one or more conductive nano additives are present in the composition of the one or more protective layers110, the one or more conductive nano additives may form 0.1% to 20% of the one or more protective layers110by weight, 0.5% to 10% of the one or more protective layers110by weight, and/or the like. At least one dimension of the one or more conductive nano additives may satisfy a corresponding threshold. For instance, in some cases, at least one dimension of the one or more conductive nano additives may be less than 100 nanometers, less than 500 nanometers, and/or the like. Examples of the one or more conductive nano additives include carbon nano materials and carbon fibers (e.g., graphene, graphene oxide, carbon black, and/or the like), single-wall or multi-wall carbon nano tubes, metallic powders (e.g., copper (Cu), aluminum (Al), silver (Ag), gold (Au), titanium (Ti), nickel (Ni), manganese (Mg), and/or the like), or a combination of carbon powders and metallic powders.

In some cases, the composition of the one or more protective layers110may include one or more conductive polymers. The composition of the protective layer110may include 1-100% of the conductive polymer relative to the one or more conductive materials included therein or 1-100% of the conductive polymer relative to the binder materials included therein. Alternatively, in some cases, the conductive polymer may be the sole conductive material and active functional material present in the composition of the protective layer. For example, in some cases, the composition of the protective layer110may include 1% to 90% of the conductive polymers by weight, 1% to 50% of the conductive polymers by weight, 1% to 10% of the conductive polymers by weight, and/or the like. Examples of conductive polymers shown inFIG.3Dinclude poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), polypyrrole (doped), poly(n-alkylthiophene), polyalylfluorene, poly(3,4-ethylenedioxythiophene)-co-poly(ethyleneglycol) (PEDOT-PEG) (doped), and/or the like.

In some implementations of the current subject matter, the protective layer110may be coupled with the sealing layer155to form the examples of the multifunction layers150shown inFIGS.2A-C. The sealing layer155may be formed from one or more materials that are inert in the presence of the reactive components of the battery cell100such as the electrodes (e.g., the first electrode layer110, the second electrode layer210, and/or the like), the electrolyte, and/or the like. In some cases, the materials forming the protective layer150may be electrically conductive. Examples of the materials forming the protective layer150may include poly (ethylene-Co-vinyl acetate) (PECVA), styrene-butadiene rubber (SBR), Polytetrafluoroethylene (PTFE)), wax, silicon (Si) rubber, polyacrylic polymer, poly propylene, polyethylene, ethylene propylene diene monomer (EPDM) rubber and its analog, materials exhibiting a negative thermal expansion (NTE) coefficient (such as zinc cyanide (ZnCN2) and so on), and materials that are reactive with the decomposition byproducts of electrolyte.

In instances where the sealing layer155is formed from a material having a negative thermal expansion (NTE) coefficient, the shrinkage of the protective layer1′ when the multifunctional safety layer150is exposed to higher temperatures (e.g., temperatures exceeding certain thresholds) may expose the protective layer110coupled with the sealing layer155. Alternatively, in instances where the sealing layer155is formed from materials that are prone to decompose at higher temperatures and/or voltages (e.g., temperatures and/or voltages exceeding certain thresholds), the corresponding protective layer110may become exposed when the multifunctional safety layer150is subj ected to higher temperatures and/or voltages. Once the protective layer110is exposed to the electrolyte, the electrode layers120, or other reactive components of the battery cell100, the reaction between them may neutralize hazardous operating conditions such as overheating, overcharging, and/or internal short circuiting. This reaction may include a physical reaction (e.g., a swelling or other expansion of the protective layer110) that causes an interruption in the electronic conduction pathway within the battery cell100. Alternatively and/or additionally, this reaction may include a chemical reaction such as a decomposition of the protective layer110and/or a reaction between the electrode layers120and the protective layer110, which creates a nonconductive gap between the current collector130and the corresponding electrode layer120. This reaction may also include a chemical reaction between the protective layer110and the electrolyte in the battery cell100that reduces the ionic conductivity of the electrolyte.

In some implementations of the current subject matter, the protective layer110and the sealing layer155may be activated by different triggers. For example, the sealing layer155may respond to a first trigger (e.g., a first temperature threshold, a first voltage threshold, a first current threshold, physical damage caused by metal penetration, crush and impact of the battery cell100, and/or the like) that is different and/or more precise than the second trigger activating the protective layer110. Accordingly, upon being activated by the first trigger, the sealing layer155may respond by at least exposing the protective layer110. The protective layer110may either be activated by this exposure (e.g., to the electrode120, the electrolyte, and/or other reactive components within the battery cell100) and/or the second trigger (e.g., a second temperature threshold, a second voltage threshold, a second current threshold, physical damage, and/or the like).

FIG.4depicts a flowchart illustrating an example of a process400for assembling a battery cell consistent with implementations of the current subject matter. Referring toFIG.4, in some cases, the process400may be performed to assemble the battery cell100to include the one or more protective layers110or, in some cases, the one or more multifunction layers150including the protective layer110coupled with the sealing layer155.

At402, a protective layer may be formed. In some implementations of the current subject matter, the one or more protective layers110of the battery cell100may be formed from a composite material that includes one or more small molecule additives combined with one or more functional materials (e.g., polymers and/or the like), base materials (e.g., a metal hydroxide such as lithium hydroxide (LiOH), sodium hydroxide (NaOH), potassium hydroxide (KOH), and/or the like), binder materials, and/or conductive materials (e.g., carbon black, conductive polymer, and/or the like). For example, in some cases, the composite material forming the one or more protective layers110of the battery cell100may include one or more metal salts, ceramic nano materials, and conductive nano additives. Moreover, in some cases, the composite material forming the one or more protective layers110may be a slurry that is then coated on one or more of the electrode120, the current collector130, and the separator140of the battery cell100. In some cases, the one or more protective layers110may be coupled with the one or more sealing layers155to form the one or more multifunction layers150. In those cases, the composite material forming the one or more protective layers110may be a slurry that is coated on the surface of the one or more sealing layers155or the materials forming the one or more sealing layers155may be coated on the surface of the one or more protective layers110to form the one or more multifunction layers150.

In some implementations of the current subject matter, subsequent to being coated, for example, on the surface of one or more of the electrode120, the current collector130, the separator140, and/or the sealing layer155, the slurry of the composite material forming the one or more protective layers110may be dried. In some cases, the slurry of the composite material forming the one or more protective layers110may undergo a high temperature treatment, for example, by being vacuum dried under high temperatures (e.g., between approximately 80° C. to 150° C.) for a long period of time (e.g., between approximately 8 hours to 24 hours). Subjecting the slurry of the composite material forming the one or more protective layers110to a high temperature treatment during formation may promote the reaction between the small molecule additives and the active functional polymers contained in the composite material. For example, the temperature and/or the duration of the high temperature treatment may be selected to ensure that all (or substantially all) of the small molecule additives react with the active functional polymers in order to eliminate the possibility of electrolyte contamination once the battery cell100is assembled.

At404, a first electrode may be formed. For example, the first electrode125a(e.g., the positive electrode) may be formed by coating the one or more materials (e.g., a slurry including the one or more materials) forming the first electrode layer120aon the surface of the first current collector130abefore the one or more materials are dried, for example, at 140° C. for 10 hours. The first electrode125aof the battery cell100may be further formed by punching the first electrode layer120ainto appropriately shaped and/or sized pieces. In some cases, the composite material forming the first protective layer110amay be coated on the surface of the first electrode layer120a. Moreover, in some cases, the material forming the first sealing layer155amay be interposed between the composite material forming the first protective layer110aand the material forming the first electrode layer120a.

At406, a second electrode may be formed. For example, the second electrode125b(e.g., the negative electrode) may be formed by coating the one or more materials (e.g., a slurry including the one or more materials) forming the second electrode layer120bon the surface of the second current collector130bbefore drying the one or more materials are dried, for example, at 125° C. for 10 hours. The second electrode125bof the battery cell200may be further formed by punching the second electrode layer120binto appropriately shaped and/or sized pieces. In some cases, the composite material forming the second protective layer110bmay be coated on the surface of the second electrode layer120b. Moreover, in some cases, the material forming the second sealing layer155bmay be interposed between the composite material forming the second protective layer110band the material forming the second electrode layer120b.

At408, a battery cell may be assembled to include the protective layer, the first electrode, the second electrode, a separator, and an electrolyte. For example, the battery cell100may be formed to include the one or more protective layer110, the first electrode125aincluding the first electrode layer120aand the first current collector130a, the second electrode125bincluding the second electrode layer120band the second current collector130b, the separator140, and an electrolyte. In instances where the battery cell100is a cylindrical cell, a layer of the separator140may be interposed between the first electrode125aand the second electrode125bof the battery cell100to form a sheet that is then wound, for example, around mandrel, to form a jellyroll before the jellyroll deposited inside a case. In instances where the battery cell100is a pouch cell, the first electrode125aand the second electrode125bmay be stacked with a layer of the separator140interposed therebetween. One or more such stacks may then be deposited inside a pouch. The battery cell100may be filled with the electrolyte before being sealed, aged (e.g., room temperature for 24 hours), and subjected to one or more charging and discharging cycles (e.g., at a C/20 charging rate). In some cases, in addition to and/or instead of the aforementioned high temperature treatment, the one or more protective layers110may also undergo radiation treatment (e.g., gamma ray such as X-ray, beta ray, ultraviolet (UV) light, and/or the like) as part of the formation process, which may further promote the crosslinking of the polymers contained in the composite material forming the one or more protective layers110.

As noted, the inclusion of the one or more protective layers110may improve the safety profile of the battery cell100including when the battery cell100. For example, the one or more protective layers110may act as a current limiter and/or a current interrupter to neutralize hazardous operating conditions at the battery cell100including, for example, overheating, overcharging, internal short circuiting, and/or the like. The performance of the battery cell100, including cell cycle (e.g., capacity retention), high temperature stability, and/or the like, may be further improved by forming the one or more protective layers110are formed from a composite material that includes one or more small molecule additives. To further illustrate,FIG.5Adepicts a graph comparing the cycle performance of a first battery cell including a protective layer having an additive, a second battery cell including a protective layer without any additives, and a third battery cell without any protective layers. The first battery cell, the second battery cell, and the third battery cell were each subjected to a cycling test that includes charging at 0.7 coulombs to a voltage of 4.48 volts and discharging at 0.5 coulombs to a voltage of 3 volts. The cycling performance of each battery cell may be evaluated based on the capacity retention of each battery cell after the batter cells undergo up to150charging and discharging cycles. As shown inFIG.5A, the first battery cell including the protective layer having the additive exhibited better cycling performance (e.g., a higher percentage of capacity retention over successive charging and discharging cycles) than the second battery cell whose protective layer does not include any additives. Moreover, the comparison inFIG.5Ashows that the inclusion of the additives in the protective layer of the first battery cell further renders the cycling performance of the first battery cell comparable to that exhibited by the third battery cell, which does not include any protective layers and is therefore more susceptible to hazardous operating conditions than the first battery cell. In other words, the presence of one or more additives, such as the small molecule additives described herein, may minimize the impact that the inclusion of one or more protective layers may have on the cycling performance of a battery cell while still retaining the safety benefits derived therefrom.

FIGS.5B-Cdepict graphs illustrating the safety profiles a battery cell that includes one or more protective layers formulated to include one or more additives, such as the small molecule additives described herein. InFIG.5B, for example, the battery cell may be overcharged but the one or more protective layers may reduce and/or disrupt the flow of current, such that the temperature and voltage of the battery cell remains stable and the battery cell does not overheat and undergo a thermal runaway.FIG.5Cdepicts the changes in the temperature and voltage of the battery cell after the battery cell undergoes physical damages such as penetration, deformation, impact, and/or the like. As shown inFIG.5C, the presence of the one or more protective layers prevents the physical damage to the battery cell from triggering any significant spikes in the temperature and voltage of the battery cell. Instead, the temperature and voltage of the battery cell remain stable, indicating that the presence of the one or more protective layers also prevents physical damages to the battery cell from causing overheating and a thermal runaway at the battery cell.

Example I

In some implementations of the current subject matter, the one or more protective layers110may be formed from a composite material including carbopol, lithium hydroxide (LiOH), super P, 4,4′-(9-fluorenylidene)dianiline, and water.

In some implementations of the current subject matter, the one or more protective layers may be formed from a composite material including carbopol (68.53%), lithium hydroxide (LiOH) (24.47%), super P (5%), 4,4′-(9-fluorenylidene)dianiline (2%), and water.

Example II

In some implementations of the current subject matter, the one or more protective layers110may be formed from a composite material including carbopol, lithium hydroxide (LiOH), super P, biphenyl-4,4′-dicarboxylic acid, and water.

In some implementations of the current subject matter, the one or more protective layers110may be formed from a composite material including carbopol (67.79%), lithium hydroxide (LiOH) (24.21%), super P (5%), biphenyl-4,4′-dicarboxylic acid (3%), and water.

Example III

In some implementations of the current subject matter, the one or more protective layers110may be formed from a composite material including carbopol, lithium hydroxide (LiOH), super P, petaerytheritol tetrakis(3-mercaptoproprionate), tris[2-(acryloyloxy)ethyl] isocyanurate, and water.

In some implementations of the current subject matter, the one or more protective layers110may be formed from a composite material including carbopol (68.53%), lithium hydroxide (LiOH) (24.47%), super P (5%), petaerytheritol tetrakis(3-mercaptoproprionate) (1%), tris[2-(acryloyloxy)ethyl] isocyanurate (1%), and water.