Electrolytes and their use in electrochemical cells

Abstract

A gel polymer electrolyte comprises a polymer matrix and a liquid electrolyte trapped and retained within the polymer matrix. The polymer matrix is ​​provided by a copolymer comprising linear polymer chains having monofunctional repeating units and a crosslinking agent that imparts polymer crosslinking functionality between the linear chains.

Description

[Technical Field]

[0001] This invention relates to electrolytes and their use in electrochemical cells. [Background technology]

[0002] Each lithium-ion battery cell contains lithium ions (Li + It is a type of rechargeable battery cell having two electrodes capable of reversibly storing lithium ions. When the cell is discharged, lithium ions move from the negative electrode (anode) to the positive electrode (cathode), and when the cell is charged, that direction is reversed.

[0003] The two electrodes must be kept separate to prevent short circuits. At the same time, ion transport between the electrodes must be facilitated, thereby keeping the cell's internal resistance at an acceptable level.

[0004] In certain cells, electrodes are separated and held by a separator such as a porous polymer membrane, and the ion conduction medium is provided by a liquid electrolyte. However, this configuration carries the risk of liquid electrolyte leakage.

[0005] Alternatively, a layer of ceramic electrolyte can be placed between the electrodes. Ceramic electrolytes typically contain sintered particles of ceramic ion-conducting material. However, this tends to increase interfacial resistance between particles, resulting in a decrease in ion transfer rate between particles and an increase in the battery's internal resistance.

[0006] In a further alternative, a polymer electrolyte can be placed between the two electrodes. This may include, for example, poly(ethylene oxide) in which lithium ions are distributed throughout the polymer network.

[0007] Generally, it is desirable to provide improved electrolyte materials that reduce the internal resistance of batteries and / or improve the safety of batteries.

[0008] Typically, a lithium-ion battery cell includes additional components such as current collectors and / or encapsulation bodies, and other protective elements. In certain cases, the negative electrode is not present within the battery cell immediately after cell assembly, but is instead provided as a lithium metal anode formed upon the first charge of the battery cell.

[0009] Also, rechargeable battery cells that use other charge-carrying metal ions instead of Li + ions are also known, for example, rechargeable battery cells that contain Na + or Mg 2+ as charge-carrying metal ions are known. SUMMARY OF THE INVENTION

[0010] In the case of certain polymer gel electrolytes based on poly(ethylene oxide) or ethylene glycol phenyl ether acrylate (EGPEA), Li + ions (or other charge-carrying metal ions) are thought to participate in the linking of polymer chains through interaction of the Li + ions with electro-negative functional groups on the chain (for example, FIG. 1 shows a polymer gel electrolyte based on EGPEA, having primary acrylate chains 10 and electro-negative ethylene glycol functional groups 12. Li + ions assist in the linking of polymer chains through interaction with the ethylene glycol groups). This generally has the effect of hindering the movement of Li + ions within the polymer gel electrolyte and reducing its ionic conductivity.

[0011] + In other polymer gel electrolytes, the polymer chains may be linked by polymer cross-linking. However, it has been found that if the degree of cross-linking is too high, the movement of Li

[0012] Thus, most generally, the present invention can provide a gel polymer electrolyte in which polymer chains are at least partially linked by polymer crosslinking, but the degree of polymer crosslinking is low enough not to pose an excessive barrier to the movement of charge-carrying metal ions in an electrochemical cell.

[0013] In a first aspect, the present invention provides a gel polymer electrolyte comprising a polymer matrix and a liquid electrolyte captured and held within the polymer matrix, wherein the polymer matrix is provided by a copolymer comprising linear polymer chains having monofunctional repeating units and a crosslinking agent that imparts a polymer crosslinking function between the linear polymer chains.

[0014] As used herein, the term "linear polymer chain having monofunctional repeating units" refers to a linear polymer chain formed by the polymerization of monomers each having one polymerizable group, i.e., monomers each binding to no more than two monomers in the polymerization process. Copolymers containing these linear polymer chains are thought to have an open structure in which the movement of charge-carrying metal ions such as Li + ions is relatively unhindered. An example of this type of open structure is schematically shown in FIG. 2, which shows linear acrylate chains 22 linked by a diacrylate crosslinking agent 20.

[0015] The linear polymer chains themselves may also be copolymers, provided that they are formed by the polymerization of monomers having one polymerizable group.

[0016] Generally, the molar ratio of the monofunctional repeating unit to the crosslinking agent is in the range of 50:50 to 99.9:0.1, preferably in the range of 80:20 to 99:1, more preferably in the range of 85:15 to 98:2. This is thought to provide a suitable level of crosslinking in the polymer network.

[0017] Generally, the ratio of the total mass of the linear chain with monofunctional repeating units to the total mass of the crosslinking agent is in the range of 30:70 to 95:5. In certain cases, the ratio is in the range of 40:60 to 90:10. In certain cases, the ratio is in the range of 50:50 to 85:15.

[0018] Typically, the polymer matrix is ​​present in an amount of 1 to 70% by volume, preferably 2 to 40% by volume, and more preferably 4 to 20% by volume, relative to the total volume of the gel polymer electrolyte.

[0019] Generally, the polymer matrix is ​​present in an amount of 1–25% by weight relative to the total mass of the gel polymer electrolyte. In certain cases, the polymer matrix is ​​present in an amount of 2–20% by weight relative to the total mass of the gel polymer electrolyte. In certain cases, the polymer matrix is ​​present in an amount of 3–15% by weight relative to the total mass of the gel polymer electrolyte.

[0020] The degree of crosslinking of the polymer network can be characterized by determining the storage modulus of the polymer. Therefore, the gel polymer electrolyte preferably has a storage modulus G' of 10 to 950 Pa at a frequency of 0.1 rad / s, more preferably 20 to 800 Pa at a frequency of 0.1 rad / s, and most preferably 40 to 750 Pa at a frequency of 0.1 rad / s.

[0021] The length of the polymer crosslinking agent generally affects the degree of separation of adjacent linear polymer chains, and therefore, Li + This also affects the extent to which charge-carrying metal ions can move freely within the gel polymer. Therefore, the polymer crosslinking agent is preferably in the range of 170 to 6000 Mw, more preferably 170 to 4000 Mw, and most preferably 170 to 2000 Mw. The weight-average molecular weight can be determined according to the protocol described in ISO 16014-2:2019.

[0022] Generally, at least 90% by weight of the polymer crosslinking agent has reactive ends selected from the group consisting of acrylic or methacrylic functional groups. In specific cases, at least 95% by weight of the polymer crosslinking agent has reactive ends selected from the group consisting of acrylic or methacrylic functional groups. In specific cases, at least 99% by weight of the polymer crosslinking agent has reactive ends selected from the group consisting of acrylic or methacrylic functional groups.

[0023] Typically, at least 90% by weight of the polymer crosslinking agent has a main chain and at least two reactive ends, the main chain comprising units selected from the group consisting of alkanes, polyethylene oxide (glycol), polypropylene oxide, bisphenol A ethoxylate, and siloxane. In certain cases, at least 95% by weight of the polymer crosslinking agent has this configuration. In certain cases, at least 99% by weight of the polymer crosslinking agent has this configuration.

[0024] In certain cases, at least 95% by weight of the polymer crosslinking agent has exactly two reactive ends. This limits the degree of crosslinking in the polymer gel, and Li + This is thought to reduce the barrier to the movement of charge-carrying metal ions. In certain cases, at least 97% by weight of the polymer crosslinking agent has exactly two reactive ends. In certain cases, at least 99% by weight of the polymer crosslinking agent has exactly two reactive ends.

[0025] Typically, at least 90% by weight of the polymer crosslinking agent is selected from the group consisting of poly(ethylene glycol) diacrylate, poly(propylene glycol) diacrylate, bisphenol A ethoxylate diacrylate, 1,10-bis(acryloyloxy)decane, polyethylene glycol dimethacrylate, organic polysiloxane dimethacrylate, and combinations thereof. In specific cases, at least 95% by weight of the polymer crosslinking agent is selected from this group. In specific cases, at least 99% by weight of the polymer crosslinking agent is selected from this group.

[0026] In certain embodiments, at least 90% by weight of the polymer crosslinking agent is poly(ethylene glycol) diacrylate. In certain embodiments, at least 95% by weight of the polymer crosslinking agent is poly(ethylene glycol) diacrylate. In certain embodiments, at least 99% by weight of the polymer crosslinking agent is poly(ethylene glycol) diacrylate.

[0027] In certain embodiments, at least 90% by weight of the monofunctional repeating units of the linear polymer chain are acrylate or methacrylate units. In certain embodiments, at least 95% by weight of the monofunctional repeating units of the linear polymer chain are acrylate or methacrylate units. In certain embodiments, at least 99% by weight of the monofunctional repeating units of the linear polymer chain are acrylate or methacrylate units.

[0028] Typically, at least 90% by weight of the monofunctional repeating units of a linear polymer chain contain alkane chains consisting of 1 to 8 carbon atoms. Repeating units with longer alkane chains may have poorer compatibility with liquid electrolytes. In certain cases, at least 95% by weight of the monofunctional repeating units of a linear polymer chain contain alkane chains consisting of 1 to 8 carbon atoms. In certain cases, at least 99% by weight of the monofunctional repeating units of a linear polymer chain contain alkane chains consisting of 1 to 8 carbon atoms.

[0029] Typically, at least 90% by weight of the monofunctional repeating units of a linear polymer chain are selected from the group consisting of methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, methyl methacrylate, butyl methacrylate, trifluoroethyl acrylate, hexyl methacrylate, and combinations thereof. In specific cases, at least 95% by weight of the repeating units are selected from this group. In specific cases, at least 99% by weight of the repeating units are selected from this group.

[0030] Typically, at least 90% by weight of the monofunctional repeating units of a linear polymer are provided by the following units: [ka] Here, R1 is H or CH3, and R2 is an alkane chain having 1 to 8 carbon atoms. In certain cases, at least 95% by weight of the monofunctional repeating units of the linear polymer are provided by these units. In certain cases, at least 99% by weight of the monofunctional repeating units of the linear polymer are provided by these units.

[0031] The choice of liquid electrolyte is not particularly limited. Typically, liquid electrolytes include solutions of lithium, sodium, or magnesium salts in a non-aqueous solvent. In certain cases, the solvent is aprotic.

[0032] Typically, the molar ratio of electrolyte salts (i.e., lithium, sodium, or magnesium salts) to monofunctional repeating units is in the range of 0.2:1 to 4:1. In certain cases, the molar ratio is in the range of 0.3:1 to 3:1.

[0033] Preferably, the solvent is a polar solvent. In certain cases, the solvent is a carbonate solvent, selected from the list consisting of, for example, ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, fluoroethyl methyl carbonate, fluoroethylene carbonate, diethyl carbonate, propylene carbonate, vinylene carbonate, and mixtures thereof.

[0034] Typically, liquid electrolytes have a volume of 0.03-0.55 nm in the desolvated state. 3 Includes lithium, sodium, or magnesium salts having anions in the range of [specify range].

[0035] In cases where the liquid electrolyte contains a solution of lithium salt, the lithium salt is typically selected from the group consisting of LiPF6, LiClO4, LiBr, LiNO3, lithium sulfonylimide salts, lithium borate salts, and mixtures thereof.

[0036] In a preferred embodiment, the liquid electrolyte comprises a solution of LiPF6 and / or lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0037] In a second embodiment, the present invention may provide an electrochemical cell comprising at least an electrode layer and an electrolyte layer disposed on one surface of the electrode layer, wherein the electrolyte layer contains a gel polymer electrolyte according to the first embodiment of the present invention.

[0038] To avoid any ambiguity, it should be clarified that the "electrolyte layer" refers to a component of an electrochemical cell that has the function of separating the anode and cathode of the electrochemical cell (as described in the background art, the anode may be present immediately after the cell is assembled or may be formed during the cell's first charge). Therefore, the electrolyte layer has the function of allowing ion movement in its thickness direction but preventing electron movement, and does not contain electrode active material. The electrolyte layer contains an ion-conducting component, but may additionally contain other non-ion-conducting components.

[0039] In certain cases, the electrolyte layer further comprises a porous spacer, which optionally comprises a material selected from the group consisting of polymer materials (e.g., polyethylene), electrical insulating materials, and composite materials having a polymer matrix and additionally containing ceramic electrolyte particles.

[0040] In certain cases, the electrolyte layer further comprises multiple ceramic electrolyte particles connected to provide a self-supporting network, with a gel polymer electrolyte present in at least some of the gaps between the ceramic electrolyte particles. The self-supporting network of ceramic electrolyte particles contributes to giving the electrolyte layer a defined minimum thickness and maintaining a defined minimum separation distance between opposing surfaces of the electrolyte layer. This helps to avoid short circuits across the electrolyte layer.

[0041] The self-supporting network of arranged ceramic electrolyte particles may be a sintered porous ceramic body. In certain cases, adjacent ceramic electrolyte particles are in direct bonding contact, e.g., direct sintering contact. In other cases, adjacent ceramic electrolyte particles are bonded together by different ceramic phases provided by inorganic sintering aids.

[0042] The choice of material for the ceramic electrolyte particles is not particularly limited. Preferably, the ceramic electrolyte particles are 10 -6 S / cm -1 It has an ionic conductivity exceeding 10. More preferably, the ceramic electrolyte particles are 10 -4 S / cm -1 It has an ionic conductivity exceeding 10. More preferably, the ceramic electrolyte particles are 10 -3 S / cm -1 It has an ionic conductivity exceeding [a certain value]. The ionic conductivity of ceramic electrolyte particles can be determined by analyzing the Nyquist plot obtained by electrochemical impedance spectroscopy when the material of the ceramic electrolyte particles supplied in bulk form is at 25°C.

[0043] Typically, the ceramic electrolyte particles contain a lithium-containing electrolyte material. For example, the ceramic electrolyte particles may contain a lithium garnet electrolyte material. In certain cases, the ceramic electrolyte particles may contain a lithium oxide material. For example, the ceramic electrolyte particles may contain a material selected from the group consisting of lithium lanthanum zirconium oxide (LLZO) and cation-added LLZO, and the cation dopant may be selected from the group consisting of tantalum, barium, yttrium, zinc, niobium, aluminum, germanium, strontium, gallium, titanium, and combinations thereof. The electrolyte material may have the formula Li 7-x La3Zr 2-x M x O 12 where 0 < x < 1, and M is selected from the group consisting of tantalum, barium, yttrium, zinc, niobium, aluminum, germanium, strontium, gallium, titanium, and combinations thereof. In certain cases, M is niobium or tantalum.

[0044] In cases where the self-supporting network contains an inorganic sintering aid in addition to the plurality of ceramic electrolyte particles, the inorganic sintering aid has a melting point lower than that of the ceramic electrolyte particles. The inorganic sintering aid typically has a melting point of 900 °C or lower. In certain cases, the inorganic sintering aid has a melting point of 850 °C or lower, such as 800 °C or lower or 750 °C or lower. In certain cases, the melting point of the inorganic sintering aid is 700 °C or lower.

[0045] The melting point of the inorganic sintering aid can be measured by differential scanning calorimetry of the inorganic sintering aid provided in bulk form.

[0046] When the inorganic sintering aid is present, it is typically provided by an ion-conductive material having an ionic conductivity exceeding 10 -10 S / cm -1 In certain cases, the inorganic sintering aid is 10 -9 S / cm -1The material is provided by an ion-conducting material having an ion conductivity exceeding 10. In certain cases, the inorganic sintering aid is 10 -8 S / cm -1 The material is provided by an ion-conducting material having an ion conductivity exceeding 10. In certain cases, the inorganic sintering aid is 10 -7 S / cm -1 The material is provided by an ion-conducting material having an ion conductivity exceeding 10. In certain cases, the inorganic sintering aid is 10 -6 S / cm -1 The material is provided by an ion-conducting material having an ion conductivity exceeding [a certain value]. In certain cases, the inorganic sintering aid is provided by an ion-conducting material having a lower ion conductivity than the ceramic electrolyte particles.

[0047] The ionic conductivity of inorganic sintering aids can be determined by analyzing the Nyquist plot obtained by electrochemical impedance spectroscopy when the inorganic sintering aid material, provided in bulk form, is at 25°C.

[0048] Sintering aids include oxides, carbonates (including Li2CO3), hydrides (including LiBH4), halides (including LiF, LiCl, LiBr, and LiI), and silicates (Li 2- The compound may include compounds selected from the group consisting of SiO2, alkali metal hydroxides (such as LiOH), and mixtures thereof.

[0049] In certain cases, the sintering aid may include a eutectic mixture of materials, such as a LiOH-NaOH eutectic mixture.

[0050] In certain cases, the sintering aid may contain lithium, boron, and optionally carbon as constituent elements. For example, the sintering aid may contain Li3BO3 (Li3BO3 is approximately 6.0 × 10⁻⁶). -8 It has been shown to have an ionic conductivity of S / cm and a melting point of approximately 800°C.

[0051] In certain cases, the sintering aid is Li 3-x B1-x C x may contain O3, where 0 < x < 1. For example, Li 2.2 C 0.8 B 0.2 BO3 has been shown to have an ionic conductivity of about 8.0×10 -7 S / cm and a melting point of about 685°C. Li 3-x B 1-x C x BO3 (0.5 < x < 0.99) has been shown to have a melting point in the range of 680°C to 750°C.

[0052] The inorganic sintering aid is typically present in an amount of 1 to 40% by weight based on the total amount of inorganic solids in the electrolyte layer. In certain cases, the inorganic sintering aid is present in an amount of 5 to 35% by weight based on the total amount of inorganic solids in the electrolyte layer. In certain cases, the inorganic sintering aid is present in an amount of 10 to 30% by weight based on the total amount of inorganic solids in the electrolyte layer.

[0053] To clarify to avoid ambiguity, the inorganic sintering aid is solid at 25°C.

[0054] Preferably, in the case where the electrolyte layer contains a plurality of ceramic electrolyte particles connected so as to provide a self-supporting network, the total amount of solid inorganic material in the electrolyte layer is 60% by volume or less with respect to the total volume of the electrolyte layer. This is considered to improve the degree to which the gel polymer electrolyte penetrates into the gaps between the ceramic electrolyte particles.

[0055] In such a case, the total amount of solid inorganic material present in the electrolyte layer may be 55% by volume or less with respect to the total volume of the electrolyte layer, and in certain cases, may be 50% by volume or less with respect to the total volume of the electrolyte layer.

[0056] Preferably, the amount of solid inorganic material present in the electrolyte layer is at least 30% by volume with respect to the total volume of the electrolyte layer, thereby ensuring that short circuits across the electrolyte layer are prevented.

[0057] Generally, the total amount of solid inorganic material present in the electrolyte layer is in the range of 30 to 60% by volume relative to the total volume of the electrolyte layer. In certain cases, the total amount of solid inorganic material present in the electrolyte layer is in the range of 35 to 60% by volume relative to the total volume of the electrolyte layer. In certain cases, the total amount of solid inorganic material present in the electrolyte layer is in the range of 40 to 55% by volume relative to the total volume of the electrolyte layer.

[0058] Preferably, the thickness of the electrolyte layer is 100 μm or less. This is thought to contribute to reducing the internal resistance of the electrochemical cell. More preferably, the thickness of the electrolyte layer is 60 μm or less. Most preferably, the thickness of the electrolyte layer is 40 μm or less.

[0059] In certain cases, the thickness of the electrolyte layer is in the range of 5 to 100 μm. In certain cases, the thickness of the electrolyte layer is in the range of 5 to 60 μm. In certain cases, the thickness of the electrolyte layer is in the range of 5 to 40 μm. In certain cases, the thickness of the electrolyte layer is in the range of 10 to 40 μm.

[0060] Typically, the electrode layer contains electrode-active particles. Generally, a gel polymer electrolyte is additionally present in at least some of the gaps between the electrode-active particles.

[0061] Therefore, gel polymer electrolytes can further contribute to improving ionic conductivity in the electrode layer.

[0062] Electrode-active particles contain electrode-active material.

[0063] The electrode layer may further contain ceramic electrolyte particles. These particles generally have the properties described above with respect to ceramic electrolyte particles that may be present in the electrolyte layer. In certain cases, the electrode layer may contain the same ceramic electrolyte particles as the electrolyte layer. However, in other cases, the electrode layer may contain ceramic electrolyte particles different from those optionally present in the electrolyte layer.

[0064] Typically, electrode-active particles and optionally ceramic electrolyte particles are connected to provide a self-supporting network. This self-supporting network may be a sintered porous ceramic body. In certain cases, adjacent electrode-active particles and / or ceramic electrolyte particles are in direct bonding contact, e.g., direct sintering contact. In other cases, adjacent electrode-active particles and / or ceramic electrolyte particles are bonded by different ceramic phases provided by inorganic sintering aids.

[0065] When an inorganic sintering aid is present, the electrolyte layer generally has the properties described above with respect to the optionally selected inorganic sintering aid. In certain cases, the electrode layer may contain the same inorganic sintering aid as the electrolyte layer. However, in other cases, the electrode layer may contain an inorganic sintering aid different from any of the inorganic sintering aids in the electrolyte layer.

[0066] Preferably, the total volume of the solid inorganic material (including electrode active particles, optionally selected ceramic electrolyte particles, and optionally selected inorganic sintering aids) within the electrode layer is 80% or less of the total volume of the electrode layer. This is because the volume of unoccupied space around the electrode active particles and optionally selected ceramic electrolyte particles is thought to promote the penetration of the gel polymer electrolyte into the electrode.

[0067] In certain cases, the total volume of solid inorganic material within the electrode layer is 70% or less of the total volume of the electrode layer. In certain cases, the total volume of solid inorganic material within the electrode layer is 60% or less of the total volume of the electrode layer.

[0068] If the total amount of solid inorganic material (including electrode active particles, optional ceramic electrolyte particles, and optional inorganic sintering aids) within the electrode is too small, it is likely to adversely affect the energy density of the cell. Therefore, it is preferable that the total volume of solid inorganic material within the electrode layer be at least 40% of the total volume of the electrode layer.

[0069] In certain cases, the total volume of solid inorganic material within the electrode layer is at least 45% of the total volume of the electrode layer. In certain cases, the total volume of solid inorganic material within the electrode layer is at least 50% of the total volume of the electrode layer. In certain cases, the total volume of solid inorganic material within the electrode layer is at least 55% of the total volume of the electrode layer.

[0070] Typically, the total volume of solid inorganic material within an electrode layer is 40-80% of the total volume of the electrode layer. In certain cases, the total volume of solid inorganic material within an electrode layer is 45-75% of the total volume of the electrode layer. In certain cases, the total volume of solid inorganic material within an electrode layer is 50-70% of the total volume of the electrode layer.

[0071] Typically, the electrode layer thickness is at least 10 μm. Preferably, the electrode layer thickness is at least 20 μm. This is thought to contribute to increasing the energy density of the electrochemical cell.

[0072] In certain cases, the electrode layer thickness is 10-100 μm. In certain cases, the electrode layer thickness is 10-80 μm. In certain cases, the electrode layer thickness is 20-50 μm.

[0073] In certain cases, the electrode layer is the cathode layer.

[0074] In such cases, the electrodes typically have a Li / Li ratio when measured at an ambient temperature of 25°C and an ambient pressure of 1 atmosphere. + The cathode active material has a potential of less than 5V relative to the ion. This is preferred because operating the cell at a higher potential can damage the gel polymer electrolyte. Examples of cathode active materials with specific potentials include lithium iron phosphate, lithium cobalt oxide, lithium nickel manganese oxide, nickel cobalt aluminum oxide, and LiNi x Mn y Co 1-x-y Examples include O2 (x=0.25~0.4, y=0.25~0.4) and mixtures thereof.

[0075] In such cases, the electrochemical cell typically also includes an anode layer, which is located on one surface of the electrolyte layer distal to the cathode layer. The anode layer may contain graphite, silicon, or lithium metal. Preferably, the anode layer contains graphite or silicon.

[0076] In certain cases, the anode is not present in the cell immediately after assembly, but is instead provided as a lithium metal anode formed during the cell's first charge. In such cases, the cell immediately after assembly may include a current collector layer that is in direct contact with one surface of the electrolyte layer distal to the cathode. The current collector layer may be provided by a metal sheet, such as a sheet of copper or a copper alloy.

[0077] In certain cases, the electrolyte layer may include a thin layer of excess gel polymer electrolyte present on one surface of the electrolyte layer distal to the cathode. This layer may contribute to adhesion between the electrolyte layer and its directly adjacent layer (e.g., the anode layer or current collector layer). The thickness of the excess gel polymer electrolyte layer is typically 0.5–5 μm.

[0078] In a third aspect, the present invention relates to a precursor composition for forming a gel polymer electrolyte according to a first aspect of the present invention, A specific amount of monofunctional monomer, A specific amount of crosslinking agent molecules, comprising crosslinking agent molecules having at least two reactive ends, Liquid electrolytes, Optionally, a polymerization initiator and This may provide a precursor composition containing the following:

[0079] A "monofunctional monomer" refers to a monomer that has one polymerizable group, that is, a monomer that combines with two or fewer other monomers during polymerization.

[0080] Typically, the molar ratio of monofunctional monomer to crosslinking agent molecule is in the range of 50:50 to 99.9:0.1, preferably in the range of 80:20 to 99:1, and more preferably in the range of 85:15 to 98:2.

[0081] Generally, a specific amount of monofunctional monomer includes acrylate or methacrylate monomers selected from the group consisting of methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, methyl methacrylate, butyl methacrylate, trifluoroethyl acrylate, hexyl methacrylate, and combinations thereof.

[0082] In certain cases, a certain amount of monofunctional monomer consists of at least 90% by weight of acrylate or methacrylate monomers. In certain cases, a certain amount of monofunctional monomer consists of at least 95% by weight of acrylate or methacrylate monomers. In certain cases, a certain amount of monofunctional monomer consists of at least 99% by weight of acrylate or methacrylate monomers.

[0083] Generally, at least 90% by weight of monomers constitute an alkane chain consisting of 1 to 8 carbon atoms. In certain cases, at least 95% by weight of monomers constitute an alkane chain consisting of 1 to 8 carbon atoms. In certain cases, at least 99% by weight of monomers constitute an alkane chain consisting of 1 to 8 carbon atoms.

[0084] Typically, polymerization initiators are thermal polymerization initiators. For example, the polymerization initiator may be a thermal radical polymerization initiator such as 2,2'-azobis(isobutyronitrile) (AIBN) or benzoyl peroxide.

[0085] In a fourth aspect, the present invention may provide a method for producing a gel polymer electrolyte according to a first aspect of the present invention, comprising providing a precursor composition according to a third aspect of the present invention and curing the precursor composition.

[0086] Typically, the step of providing a precursor composition according to a third aspect of the present invention includes physically mixing a specific amount of monofunctional monomer, a specific amount of crosslinking agent molecules, a liquid electrolyte, and (if used) a polymerization initiator within 30 minutes, preferably within 20 minutes, more preferably within 10 minutes.

[0087] Typically, the step of curing the precursor composition includes heating the composition to a temperature of, for example, 40 to 70°C.

[0088] During the curing process, monofunctional monomers polymerize to form linear polymer chains, and crosslinking agent molecules impart polymer crosslinking functionality between these linear chains. Typically, the polymerization process is a thermal polymerization process.

[0089] In a fifth aspect, the present invention may provide a method for manufacturing an electrochemical cell according to a second aspect of the present invention, comprising the steps of: providing a substrate containing an electrode active material; applying a precursor composition according to a third aspect of the present invention to an exposed surface of the substrate; and curing the precursor composition to provide a gel polymer electrolyte.

[0090] The substrate may comprise at least a first layer and a second layer arranged in a stacked configuration. The electrode active material is provided in the first layer. The second layer does not contain electrode active material and includes multiple ceramic electrolyte particles connected to provide a self-supporting network, providing an exposed surface for the substrate. [Brief explanation of the drawing]

[0091] The following drawings will be used to illustrate the present invention. [Figure 1] This is a schematic diagram of the molecular structure of a comparative example of polymer gel electrolytes. [Figure 2] This is a schematic diagram of the molecular structure of a polymer gel electrolyte according to one embodiment of the first aspect of the present invention. [Figure 3a]This graph shows the storage modulus and loss modulus as functions of angular frequency for the first comparative example of a polymer gel electrolyte. [Figure 3b] This graph shows the storage modulus and loss modulus as functions of angular frequency for a second comparative example of a polymer gel electrolyte. [Figure 3c] This graph shows the storage modulus and loss modulus as functions of angular frequency for a polymer gel electrolyte according to another embodiment of the first aspect of the present invention. [Figure 4] This figure shows the change in nominal discharge capacity with respect to the number of cycles during electrochemical cycling of battery cells containing different types of electrolytes. [Figure 5] This graph shows the storage modulus as a function of angular frequency for polymer gel electrolytes with different levels of crosslinking. [Figure 6] This graph shows the storage modulus as a function of angular frequency for polymer gel electrolytes with different types of crosslinking agents. [Modes for carrying out the invention]

[0092] Preparation of polymer gel precursors A polymer gel precursor was prepared by mixing the components shown in Table 1.

[0093] The PEGDA crosslinking agent monomers in Example 1 and Example 2 had a number-average molecular weight (Mn) of 700. [Table 1]

[0094] Rheology Test The precursors of Example 1 and Comparative Examples 1 and 2 were placed in a 55 mm diameter steel dish and cured in a 55°C oven for 60 minutes to prepare gels. After cooling to room temperature, the gels were subjected to rheological testing using a rotary rheometer (in this case, an Anton Paar MCR 302 model).

[0095] The procedure was as follows: A dish containing the hardened gel was fixed on a rotary rheometer, and a 50 mm diameter stainless steel upper parallel plate was lowered onto the sample surface, applying a steady-state force of 0.25 N. Vibrational rheology measurements were performed to determine the elastic modulus of the film as a function of shear strain (amplitude sweep test) and frequency (frequency sweep test).

[0096] Amplitude sweep: The linear viscoelastic region (LVR) for all samples was determined by amplitude sweep at a fixed frequency of 10 Hz while gradually increasing the shear strain (0.1 to 1000%).

[0097] After identifying appropriate stress and strain values ​​within the LVR range for each sample, frequency sweep tests were subsequently performed.

[0098] Frequency sweep: Frequency sweep measurements of film samples were performed while decreasing the vibration frequency in the range of 100 to 0.1 rad / s Hz. The mean modulus of elasticity (G': also called the storage modulus) and the viscous modulus of elasticity (G'': also called the loss modulus) were plotted against frequency.

[0099] All tests were conducted at 25±0.1℃.

[0100] The results of the frequency sweep test are shown in Figure 3a (Comparative Example 1), Figure 3b (Comparative Example 2), and Figure 3c (Example 1). Comparing Figures 3a and 3b with Figure 3c, it can be seen that the gels of Comparative Examples 1 and 2 have higher rigidity than the gel of Example 1.

[0101] Preparation of electrochemical cells For Example 2 and Comparative Examples 1 and 2, electrochemical cells were prepared using the following procedure. Two circular filter papers with a diameter of 13 mm (Whatman filter type 1001) were stacked to form a separator. 38 μl of polymer gel precursor was dropped onto the separator. An electrochemical cell was assembled from a separator (impregnated with a polymer gel precursor), a 13 mm diameter NMC111 cathode disk, and a 13 mm diameter graphite anode disk. The polymer gel precursor was cured in a 55°C oven for 60 minutes, and the cell was kept in a constant temperature bath at 25°C for 4 hours.

[0102] Following the protocol described above, but with a liquid electrolyte dropped onto a separator instead of a polymer gel precursor, and the curing step omitted, an additional cell was prepared. This was designated as Comparative Example 3.

[0103] The electrochemical cell was cycled using the following protocol: A full cycle was performed with a current value of 0.5C during charging and 1C during discharging. A value of 1C corresponds to discharging / charging the cell's total capacity in 1 hour. The voltage range was 2.7~4.2V (Li + The charging was limited to (Li-based), and no constant voltage process was added at the end of charging.

[0104] The results are shown in Figure 4. In Figure 4, the discharge capacity of each cell is shown relative to the discharge capacity obtained in the first cycle of Comparative Example 3. From Figure 4, it can be seen that the gel polymer electrolyte of Example 2 has a higher capacity retention rate than the gel polymer electrolytes of Comparative Examples 1 or 2.

[0105] Change in storage modulus G' depending on the degree of crosslinking Polymer gel precursors were prepared by mixing the components shown in Table 2. [Table 2]

[0106] The number-average molecular weight (Mn) of the PEGDA crosslinking agent monomer was 700.

[0107] Gel preparation and rheological testing were carried out as described above in relation to Example 1 and Comparative Examples 1 and 2. The results are shown in Figure 5. From Figure 5, it can be seen that Example 3 (lowest crosslinking density) exhibits the lowest storage modulus, and Example 5 (highest crosslinking density) exhibits the highest storage modulus.

[0108] Changes in storage modulus G' depending on the type of crosslinking agent Polymer gel precursors were prepared by mixing the components shown in Table 3.

[0109] Gel preparation and rheological testing were carried out as described above in relation to Example 1 and Comparative Examples 1 and 2. The results are shown in Figure 6. [Table 3]

Claims

1. A gel polymer electrolyte comprising a polymer matrix and a liquid electrolyte trapped and retained within the polymer matrix, wherein the polymer matrix is ​​provided by a copolymer comprising linear polymer chains having monofunctional repeating units and a crosslinking agent that imparts polymer crosslinking functionality between the linear chains.

2. The gel polymer electrolyte according to claim 1, wherein the molar ratio of the monofunctional repeating unit to the crosslinking agent is in the range of 50:50 to 99.9:0.

1.

3. The gel polymer electrolyte according to claim 2, wherein the molar ratio of the monofunctional repeating unit to the crosslinking agent is in the range of 80:20 to 99:

1.

4. The gel polymer electrolyte according to claim 3, wherein the molar ratio of the monofunctional repeating unit to the crosslinking agent is in the range of 85:15 to 98:

2.

5. The gel polymer electrolyte according to any one of claims 1 to 4, wherein the ratio of the total mass of the linear chain having monofunctional repeating units to the total mass of the crosslinking agent is in the range of 30:70 to 95:

5.

6. A gel polymer electrolyte according to any one of claims 1 to 5, wherein the storage modulus G' at a frequency of 0.1 rad / s is 10 to 950 Pa.

7. The gel polymer electrolyte according to claim 6, wherein the storage modulus G' at a frequency of 0.1 rad / s is 40 to 750 Pa.

8. The gel polymer electrolyte according to any one of claims 1 to 7, wherein the polymer matrix is ​​present in an amount of 1 to 70% by volume, preferably 2 to 40% by volume, and more preferably 4 to 20% by volume, relative to the total volume of the polymer gel electrolyte.

9. The gel polymer electrolyte according to any one of claims 1 to 8, wherein the polymer matrix is ​​present in an amount of 1 to 25% by weight relative to the total mass of the gel polymer electrolyte.

10. The gel polymer electrolyte according to claim 9, wherein the polymer matrix is ​​present in an amount of 2 to 20% by weight relative to the total mass of the gel polymer electrolyte.

11. The gel polymer electrolyte according to any one of claims 1 to 10, wherein the polymer crosslinking agent has a molecular weight in the range of 170 to 6000 Mw.

12. The gel polymer electrolyte according to claim 11, wherein the polymer crosslinking agent has a molecular weight in the range of 170 to 4000 Mw.

13. The gel polymer electrolyte according to claim 12, wherein the polymer crosslinking agent has a molecular weight in the range of 170 to 2000 Mw.

14. The gel polymer electrolyte according to any one of claims 1 to 13, wherein at least 95% by weight of the polymer crosslinking agent has reactive ends selected from the group consisting of acrylic or methacrylic functional groups.

15. The gel polymer electrolyte according to any one of claims 1 to 14, wherein at least 95% by weight of the polymer crosslinking agent has a main chain and at least two reactive ends, and the main chain comprises units selected from the group consisting of alkanes, polyethylene oxide (glycol), polypropylene oxide, bisphenol A ethoxylate, and siloxane.

16. The gel polymer electrolyte according to any one of claims 1 to 15, wherein at least 97% by weight of the polymer crosslinking agent has exactly two reactive ends.

17. The gel polymer electrolyte according to any one of claims 14 to 16, wherein at least 95% by weight of the polymer crosslinking agent is selected from the group consisting of poly(ethylene glycol) diacrylate, poly(propylene glycol) diacrylate, bisphenol A ethoxylate diacrylate, 1,10-bis(acryloyloxy)decane, polyethylene glycol dimethacrylate, organic polysiloxane dimethacrylate, and combinations thereof.

18. The gel polymer electrolyte according to any one of claims 1 to 17, wherein at least 95% by weight of the monofunctional repeating units of the linear polymer chain are acrylate or methacrylate units.

19. The gel polymer electrolyte according to any one of claims 1 to 18, wherein at least 95% by weight of the monofunctional repeating units of the linear polymer chain comprises an alkane chain consisting of 1 to 8 carbon atoms.

20. The gel polymer electrolyte according to claim 18 or 19, wherein at least 95% by weight of the monofunctional repeating units of the linear polymer chain is selected from the group consisting of methyl acrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, benzyl acrylate, methyl methacrylate, butyl methacrylate, trifluoroethyl acrylate, hexyl methacrylate, and combinations thereof.

21. The gel polymer electrolyte according to any one of claims 1 to 20, wherein the liquid electrolyte comprises a solution of lithium or sodium salt in a carbonate solvent.

22. The gel polymer electrolyte according to any one of claims 1 to 21, wherein the liquid electrolyte comprises a solution of lithium, sodium, or magnesium salt, and the molar ratio of the salt to the monofunctional repeating unit is in the range of 0.2:1 to 4:

1.

23. An electrochemical cell comprising at least an electrode layer and an electrolyte layer disposed on one surface of the electrode layer, wherein the electrolyte layer contains a gel polymer electrolyte according to any one of claims 1 to 22.

24. The electrochemical cell according to claim 23, wherein the electrolyte layer further comprises a porous spacer, and the porous spacer optionally comprises a material selected from the group consisting of a polymer material, an electrical insulating material, and a composite material having a polymer matrix and additionally containing ceramic electrolyte particles.

25. The electrochemical cell according to claim 23, wherein the electrolyte layer further comprises a plurality of ceramic electrolyte particles connected to provide a self-supporting network, and the gel polymer electrolyte is present in at least a portion of the gaps between the ceramic electrolyte particles.

26. A precursor composition for forming a gel polymer electrolyte according to any one of claims 1 to 22, A specific amount of monofunctional monomer, A specific amount of crosslinking agent molecules, which have at least two reactive ends, Liquid electrolytes, Optionally, a polymerization initiator and A precursor composition containing the above.

27. The precursor composition according to claim 26, comprising a polymerization initiator, wherein the polymerization initiator is a thermal polymerization initiator.

28. A method for producing a gel polymer electrolyte according to any one of claims 1 to 22, comprising providing a precursor composition according to claim 26 or claim 27, and curing the precursor composition.

29. A method for producing an electrochemical cell according to any one of claims 23 to 25, comprising the steps of: providing a substrate containing an electrode active material; applying a precursor composition according to claim 26 or claim 27 to an exposed surface of the substrate; and curing the precursor composition to provide a gel polymer electrolyte.

30. The substrate comprises at least a first layer and a second layer in which the substrate is stacked, The electrode active material is provided in the first layer, The method according to claim 29, wherein the second layer does not contain an electrode active material and includes a plurality of ceramic electrolyte particles connected to provide a self-supporting network, and provides an exposed surface of the substrate.

Images