WO2024119495A1

WO2024119495A1 - Gel polymer electrolytes, and energy-storage cells and batteries made therewith

Info

Publication number: WO2024119495A1
Application number: PCT/CN2022/138014
Authority: WO
Inventors: Yedong WANG; Jiaoli WANG
Original assignee: Ses (Shanghai) Co. Ltd.
Filing date: 2022-12-09
Publication date: 2024-06-13

Abstract

Gel polymer electrolytes, preparation methods for the same, and electrochemical cells and batteries using the gel polymer electrolytes. In some embodiments, a gel polymer electrolyte is formed by polymerizing the gel precursor mixture composed of one or more monomers, one or more nonaqueous organic solvents, one or more salts, and/or one or more additives under certain conditions. A gel polymer electrolyte of the invention has good electrochemical redox stability, high ionic conductivity and certain mechanical strength, effectively inhibits the growth of lithium dendrites, and avoids the safety problems such as leakage, short circuit, and explosion caused by dendrites piercing through the diaphragm. It is suitable, for example, for lithium-ion battery and lithium-metal batteries.

Description

GEL POLYMER ELECTROLYTES, AND ENERGY-STORAGE CELLS AND BATTERIES MADE THEREWITH

FIELD OF THE INVENTION

The present invention generally relates to the field of electrochemical energy storage. In particular, the present invention is directed to gel polymer electrolytes, and energy-storage cells and batteries made therewith.

BACKGROUND

Energy-storage batteries are becoming more and more ubiquitous as electrification of vehicles and the proliferation of mobile devices and battery-powered sensors and other devices continue to increase. Lithium-ion and lithium-metal cells are two types of electrochemical cells that are prevalent and are becoming more prevalent. Liquid electrolytes and solid electrolytes are two types of electrolytes being deployed in many electrochemical cells, including lithium-ion and lithium-metal cells. However, these electrolytes have drawbacks.

Conventional liquid electrolytes are relatively thermodynamically unstable to lithium metal. The volume expansion that occurs in the plating-stripping processes that occur on a lithium-metal anode during charging-discharging usually causes cracks in the solid-electrolyte interphase (SEI) layer that forms on the anode. This leads to exposing fresh lithium metal to the liquid electrolyte, which results in unwanted side reactions. As a result, it is difficult to inhibit dendrite formation when deploying liquid electrolytes in lithium-metal batteries. In addition, organic-solvent-based liquid electrolytes in commercial lithium-ion batteries often impose safety hazards in practical applications due to the low flashpoints and flammability of carbon esters used as solvents. Other safety issues with liquid electrolytes include leakage, volatilization, and explosion.

All-solid-state batteries using all-solid-state electrolytes have attracted much attention because they are safer and more stable than liquid electrolytes. However, all-solid-state electrolytes have their own drawbacks, such as relatively low ionic conductivity, relatively high interfacial impedance between the solid-state electrolytes and the electrodes, and relatively high manufacturing costs, all when compared to liquid electrolytes. These drawbacks currently hinder widespread commercialization of all-solid-state batteries.

SUMMARY OF THE DISCLOSURE

In an implementation, the present disclosure is directed to a gel polymer electrolyte obtained by polymerizing a gel precursor mixture into a gel having a polymer matrix.

BRIEF DESCRIPTION OF THE DRAWINGS

For the purpose of illustration, the accompanying drawings show aspects of one or more embodiments of the invention (s) . However, it should be understood that the invention (s) of this disclosure is/are not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:

FIG. 1 is a graph of AC impedances of a liquid electrolyte and nine instantiations of gel polymer made in accordance with the present disclosure;

FIG. 2 is a graph of linear-sweep voltammograms of a liquid electrolyte and nine instantiations of gel polymer electrolyte made in accordance with the present disclosure;

FIG. 3 is a graph of cyclic voltammograms of a liquid electrolyte and nine instantiations of gel polymer electrolyte made in accordance with the present disclosure;

FIG. 4 is a graph of cell capacity retention of a liquid electrolyte and nine instantiations of gel polymer electrolyte made in accordance with the present disclosure;

FIG. 5A is a cross-sectional view of a simple electrochemical energy-storage cell made in accordance with the present disclosure;

FIG. 5B is a schematic diagram of an energy-storage battery made in accordance with the present disclosure;

FIG. 6 is a graph of linear-sweep voltammograms of a liquid electrolyte and two instantiations of gel polymer electrolyte made in accordance with the present disclosure; and

FIG. 7 is a graph of cyclic voltammograms of a liquid electrolyte and two instantiations of gel polymer electrolyte made in accordance with the present disclosure.

DETAILED DESCRIPTION Technical Problem

One purpose of the present disclosure is to provide gel polymer electrolytes, which can significantly improve the safety performance and cycling performance of lithium-ion batteries and lithium metal batteries.

Another purpose of the present disclosure is to provide methods of preparing gel polymer electrolytes.

Technical Solution

Throughout the present disclosure and in the appended claims, the term “about” when used with a corresponding numeric value refers to ±20%of the numeric value, typically ±10%of the numeric value, often ±5%of the numeric value, and most often ±2%of the numeric value. In some embodiments, the term “about” can mean the numeric value itself.

In order to achieve the above purpose, a technical solution adopted for gel polymer electrolytes of the present invention includes:

A gel polymer electrolyte composed of polymer matrix, one or more nonaqueous organic solvents, one or more salt (s) (e.g., lithium-based salt (s) ) and/or one or more additives, wherein the polymer matrix is composed of a monomer or any one or two combinations of monomer with initiator (s) and/or crosslinking agent (s) .

Each monomer, initiator, crosslinking agent, additive and lithium salt are dispersed in nonaqueous organic solvent to obtain a gel precursor mixture, and then the gel precursor mixture is polymerized to form gel polymer electrolyte.

The structural formula of a suitable monomer is shown in the following Formula 1:

wherein, in Formula 1:

R1, R2, R3 independently represent a hydrogen atom, a halogen atom, an alkyl, a cycloalkyl, a heterocyclic group, an aryl group, an alkoxyl group, an ester group, a carbonate group, a cyano group, or an heterocyclic aryl or acyl;

R4 represent a fluorine atom, an alkyl, a cycloalkyl, a heterocyclic group, an aryl group, an alkoxyl group, an ester group, a carbonate group, a cyano group, or a heterocyclic aryl or acyl;

the carbon atom of the alkyl, cycloalkyl, heterocyclic group, aryl group or heterocyclic aryl may be bonded to at least one substituent selected from a halogen, an alkoxyl group, an ester group, a cyano group, or a phenyl or phosphoric ester group;

the alkyl group comprises 1 to 10 carbon atoms, with a better choice being an alkyl with 1 to 4 carbon atoms;

preferably, the naphthenic group is a three to ten membered single ring, bridge ring, or spiro ring group;

preferably, the heterocyclic group is a five to ten membered heterocyclic group with one or more heteroatoms, preferably, wherein said heteroatom is selected from at least one of O, N, S, and P;

preferably, the substituent is a halogen or a C2 through C6 ester group; and

preferably, the halogen is at least one of F, Cl, and Br.

The structural formula of a suitable monomer is shown in the following Formula 2. This monomer can be used alone or in combination with a monomer of Formula 1, above.

wherein, in Formula 2:

the selection range of R1 through R3 in Formula 2 is the same as the range in Formula 1;

R4 independently represent alkyl, acyl or ester group; and

the carbon atom of the alkyl, acyl, or ester group may be bonded to at least one substituent selected from a halogen, an alkoxyl group, an ester group, a cyano group, or a phenyl or phosphoric ester group.

The monomer (s) account (s) for about 0.5%to about 100%of the weight of the polymer matrix.

Each crosslinking agent is a compound with one or more unsaturated carbon-carbon double bonds, with the crosslinking agent (s) accounting for about 0%to about 99.5%of the weight of the polymer matrix. Each crosslinking agent may be, but is not limited to, styrene, vinyl toluene, divinylbenzene, N, N'-methylene bisacrylamide, ethylene glycol dimethacrylate, poly (ethylene glycol) dimethacrylate, 1, 1, 1-trimethylol propane triacrylate, triallyl phosphate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, polydipentaerythritol hexaacrylate, and trihydroxymethyl propane triacrylate, among others.

The initiator (s) account (s) for about 0%to about 20%of the weight of the polymer matrix. Each initiator may be, but is not limited to, 2, 2-azodiisobutyronitrile, 2, 2'-azobis (2, 4-dimethyl) valeronitrile, dimethyl 2, 2'-azobis (2-methylpropionate) , benzoyl peroxide, potassium persulfate, dodecanoic peroxyanhydride, N, N-dimethylaniline, diisopropylbenzene peroxide, di tert butyl peroxide, tert butyl peroxybenzoate, 2-hydroxy-2-methyl-1-phenylacetone, 1-hydroxycyclohexylphenyl ketone, 2-methyl-2- (4-morpholinyl) -1- [4- (methylthio) phenyl] -1-acetone, 2, 4, 6-trimethylbenzoyl diphenylphosphine oxide, 2, 4, 6-trimethylbenzoyl phenyl phosphonate ethyl ester, 2-dimethylamino-2-benzyl-1- [4- (4-morpholinyl) phenyl] -1-butanone, 2-hydroxy-2-methyl-1- [4- (2-hydroxyethoxy) phenyl] -1-acetone, and methyl phenylglyoxylate, among others.

The polymer matrix accounts for about 0.5%to about 90%of the weight of gel polymer electrolyte.

To obtain a gel polymer electrolyte with good performance, a gel precursor mixture is prepared in a dry, inert (e.g., argon) protective atmosphere at a temperature of about -30℃ to about 40℃. In an example, the gel precursor mixture was sealed in a container, placed in an oven, and polymerized at a temperature in a range of about -15℃ to about 120℃ for about 1 hour to about 120 hours to obtain a gel polymer electrolyte.

To achieve a better dispersion effect of lithium salt in gel polymer electrolyte, the molar concentration of lithium salt in the gel precursor mixture is in a range of about 0.4 mol/L to about 4mol/L. Each lithium salt may be, but is not limited to, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis oxalate borate, lithium difluorosulfonylimide, lithium perchlorate, lithium hexafluoroarsenate, and lithium bis trifluoromethanesulfonylimide, or a combination of these, among others. If provided, the lithium salt (s) account (s) for about 5%to about 50%of the weight of the gel polymer electrolyte.

Each additive, if provided, may be selected from, but not limited to, vinyl carbonate, dimethyl phenyl phosphonate, potassium perfluorobutyl sulfonate, potassium perfluorooctane sulfonate, fluoroethylene carbonate, dimethyl sulfite, diethyl sulfite, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, trimethyl phosphite, triethyl phosphite, methyl vinyl sulfone, and lithium oxalate borate. If provided, the additive (s) account (s) for about 0%to about 20%of the weight of the gel polymer electrolyte.

Each nonaqueous organic solvent may be selected from, but not limited to, dimethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, methyl propyl carbonate, diethyl carbonate, dibutyl carbonate, methyl formate, ethyl acetate, methyl propionate, dipropyl carbonate, methyl acetate, acetonitrile, succinonitrile, butene carbonate, methyl isopropyl carbonate, methyl butyl carbonate, 1, 4-butyrolactone, dimethyl tetrahydrofuran, 1, 2-dimethoxyethane, ethyl propionate, methyl butyrate trifluoromethyl vinyl carbonate, dimethyl sulfoxide, sulfolane, 4-methyl-1, 3-butyrolactone, propane sulfolactone, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and compounds containing the structure shown in the following Formula 3, among others.

wherein, in Formula 3:

R5 represent an alkyl, a cycloalkyl, a heterocyclic group, an aryl group, an alkoxyl group, an ester group, a carbonate group, a cyano group, or a heterocyclic aryl or acyl; and

the carbon atom of the said alkyl, cycloalkyl, heterocyclic group, aryl group or heterocyclic aryl may be bonded to at least one substituent selected from a halogen, an alkoxyl group, an ester group, a cyano group, or a phenyl or phosphoric ester group.

The nonaqueous organic solvent (s) account (s) for about 3%to about 94.5%of the weight of the gel polymer electrolyte.

In some embodiments, a lithium secondary-battery cell may comprise:

A positive electrode. Positive electrode materials include, but are not limited to, lithium iron phosphate, triplets compound cathode materials, lithium manganate, and lithium cobalt oxide, among others.

A negative electrode. Negative electrode materials include, but are not limited to, carbon anode materials, silicon-based anode materials, lithium metal and its alloys, and/or tin based cathode materials, among others.

Any of the gel polymer electrolytes as described above.

A gel polymer electrolyte of the present disclosure and having high ionic conductivity, high oxidation decomposition potential, and good compatibility with electrode materials can significantly improve cycling performance and rate performance of, for example, lithium-ion batteries and lithium-metal batteries. A gel polymer electrolyte provided by the present disclosure has a solid-like morphology, which can effectively inhibit the growth of lithium dendrite, thereby improving the safety performance of the battery.

Example Modes of Execution

Modes for carrying out aspects of the present disclosure are further illustrated using the following embodiments and test examples.

Control 1

A liquid electrolyte is composed of nonaqueous organic solvent and a lithium salt. The nonaqueous organic solvent is composed of ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate with a volume ratio of 1: 1: 1. The lithium salt is lithium hexafluorophosphate, and its molar concentration in the nonaqueous organic solvent is 1.5 mol/L.

The liquid electrolyte was prepared in an Ar-atmosphere glovebox (water < 1 ppm, oxygen < 1 ppm) . The vinyl carbonate, dimethyl carbonate, and methyl ethyl carbonate were thoroughly mixed to obtain the nonaqueous organic solvent, and then dry lithium hexafluorophosphate was dissolved in the nonaqueous organic solvent and the nonaqueous organic solvent containing the salt was fully stirred to obtain the liquid electrolyte.

Embodiment 1

A gel polymer electrolyte is composed of polymer matrix, nonaqueous organic solvent, lithium salt. Said nonaqueous organic solvent is composed of ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate with a volume ratio of 1: 1: 1. The lithium salt is lithium hexafluorophosphate, and its molar concentration in nonaqueous organic solvent is 1.5 mol/L. The polymer matrix is composed of a monomer, initiator, and cross-linking agent, and the polymer matrix accounts for 9.5%of the weight of gel polymer electrolyte. The monomer is methyl vinyl sulfone, with the structural formula of methyl vinyl sulfone being shown in Formula 4, below, the crosslinking agent is pentaerythritol tetraacrylate, wherein the mass ratio of the monomer to the crosslinking agent is 1: 1. The initiator is azodiisobutyronitrile, and the initiator accounts for 3%of the weight of the polymer matrix.

The gel polymer electrolyte was prepared in an Ar-atmosphere glovebox (water <1 ppm, oxygen < 1 ppm) . The vinyl carbonate, dimethyl carbonate, and methyl ethyl carbonate were fully mixed to obtain nonaqueous organic solvent, and then the dry lithium hexafluorophosphate was dissolved in the nonaqueous organic solvent. After the nonaqueous organic solvent-containing lithium hexafluorophosphate was fully stirred, a monomer, a crosslinking agent, and an initiator were added to it to get the mixed solution. Then, the mixed solution was fully stirred to get the gel precursor mixture.

According to the process requirements of liquid injection into an electrochemical cell, an appropriate amount of gel precursor mixture was injected into the cell, sealed, and let it sit for 12 hours so that the gel precursor mixture could fully infiltrate electrode material and separator material. Then, the cell was placed in an oven at 45℃ for 24 hours to allow in situ polymerization to obtain a gel polymer electrolyte cell.

Embodiment 2

The implementation mode of Embodiment 2 is largely the same as the mode of Embodiment 1, above, with the difference being that the methyl vinyl sulfone is replaced by ethyl vinyl sulfone. The structural formula of ethyl vinyl sulfone is shown in the following Formula 5:

Embodiment 3

The implementation mode of Embodiment 3 is largely the same as the mode of Embodiment 1, with the difference being that the methyl vinyl sulfone is replaced by ethylene sulfonyl fluoride. The structural formula of ethylene sulfonyl fluoride is shown in the following Formula 6:

Embodiment 4

The implementation mode of Embodiment 4 is largely the same as the mode of Embodiment 1, with the difference being that the methyl vinyl sulfone is replaced by trifluoroethylene sulfonyl fluoride. The structural formula of trifluoroethylene sulfonyl fluoride is shown in the following Formula 7:

Embodiment 5

The implementation mode of Embodiment 5 is largely the same as the mode of Embodiment 1, with the difference being that the methyl vinyl sulfone is replaced by a mixture of N,N-dimethylacrylamide and ethylene sulfonyl fluoride, wherein the molar ratio of N, N-dimethylacrylamide to ethylene sulfonyl fluoride is 1: 1. The structural formula of N, N-dimethylacrylamide is shown in the following Formula 8:

Embodiment 6

A gel polymer electrolyte is composed of polymer matrix, nonaqueous organic solvent, lithium salt. The nonaqueous organic solvent is N, N-dimethylsulfonyl fluoride. The lithium salt is a mixture of lithium hexafluorophosphate and lithium difluorosulfonylimide with a mass ratio of 1: 1, and its molar concentration in the nonaqueous organic solvent is 2.5 mol/L. The polymer matrix is composed of a monomer, an initiator and a cross-linking agent, and the polymer matrix accounts for 9.5%of the weight of the gel polymer electrolyte. The monomer is methyl vinyl sulfone, with the structural formula of methyl vinyl sulfone as shown in Formula 4, above, the crosslinking agent is pentaerythritol tetraacrylate, wherein the mass ratio of the monomer to the crosslinking agent is 1: 1. The initiator is azodiisobutyronitrile, and the initiator accounts for 3%of the weight of the polymer matrix. The remaining implementation mode of Embodiment 6 is the same as the mode of Embodiment 1.

Embodiment 7

A gel polymer electrolyte is composed of a polymer matrix, a nonaqueous organic solvent, and lithium salts. The nonaqueous organic solvent is N, N-dimethylsulfonyl fluoride. The lithium salts are a mixture of lithium hexafluorophosphate and lithium difluorosulfonylimide with a mass ratio of 1: 1, and their molar concentration in nonaqueous organic solvent is 2.5 mol/L. The polymer matrix is composed of a monomer, an initiator and a cross-linking agent, and the polymer matrix accounts for 4.5%of the weight of the gel polymer electrolyte. The monomer is vinyl sulfonyl fluoride, with the structural formula of vinyl sulfonyl fluoride being shown in Formula 6, above, the crosslinking agent is pentaerythritol tetraacrylate, wherein the mass ratio of the monomer to the crosslinking agent is 1: 1. The initiator is dimethyl azodiisobutyrate, and the initiator accounts for 2.5%of the weight of the polymer matrix.

The remaining implementation mode of Embodiment 7 is the same as the mode of Embodiment 1.

Embodiment 8

The implementation mode of Embodiment 8 is largely the same as the mode of Embodiment 1, with the difference being that the methyl vinyl sulfone is replaced by trifluoroethyl -(trifluoromethyl) acrylate. The structural formula of trifluoroethyl - (trifluoromethyl) acrylate is shown in the following Formula 9:

Embodiment 9

The implementation mode of Embodiment 9 is largely the same as the mode of Embodiment 1, with the difference being that the methyl vinyl sulfone is replaced by 1- (trifluoromethylsulfonyl) ethene. The structural formula of 1- (trifluoromethylsulfonyl) ethene is shown in the following Formula 10:

Test Example 1

In this test, an AC impedance method is used to measure the conductivity of the liquid electrolyte of Control 1 and each of the gel polymer electrolytes of Embodiments 1 through 9. The conductivity test was carried out in two-electrode (stainless steel/stainless steel) analog batteries with an Autolab electrochemical workstation (Vantone, Switzerland) . The test temperature was 25℃, the scanning frequency range was from 1MHz to 1Hz, and the AC amplitude was 10 mV. The AC impedance diagram and calculation results are shown, respectively, in FIG. 1 and Table 1, below.

Table 1: Conductivity test results

According to the experimental data in Table 1, the gel polymer electrolyte prepared by the invention has high conductivity.

Test Example 2

This test tests the oxidation decomposition potential of electrolyte in the liquid electrolyte of Control 1 and each of the gel polymer electrolytes of Embodiments 1 through 9. Linear sweep voltammetry was conducted in two-electrode (Li/stainless steel) CR2032 coin cells with a Metrohm Autolab electrochemical workstation at 25 ℃. The scan rate was 1 mV/s from 3 V to 5.5 V. The test results are shown in FIG. 2. It can be seen from the experimental results in FIG. 2 that, compared with the liquid electrolyte (Control 1) , the example gel polymer electrolytes of the present disclosure (Embodiments 1 through 9) have wider electrochemical stability windows.

Test Example 3

This test tests the compatibility of electrolyte and electrode materials in the liquid electrolyte of Control 1 and each of the gel polymer electrolytes of Embodiments 1 through 9. Cyclic voltammograms was created using two-electrode (Li/N _0.8C _0.1M _0.1) CR2032 coin cells and a Metrohm Autolab electrochemical workstation at 25℃. The scan rate was 0.1 mV/sfrom 3 V to 4.3 V) . It can be seen from the experimental results in FIG. 3 that the example gel polymer electrolytes prepared in accordance with the present disclosure (Embodiments 1 through 9) have good compatibility with conventional intercalation electrodes.

Test Example 4

Charge-discharge performance testing was carried out in pouch cells composed of lithium metal/electrolyte/Ni _0.8Co _0.1Mn _0.1 at 0.33C rate, and the test temperature was 25 . After 100 cycles with each of the liquid electrolyte of Control 1 and the gel polymer electrolytes of Embodiments 1 through 9, the discharge capacity retention rate of the corresponding cells were recorded. The test results are shown in FIG. 4. It can be seen from FIG. 4 that after 100 cycles, the cells containing the gel polymer electrolytes prepared in accordance with the present disclosure (Embodiments 1 through 9) have higher retention rate of discharge capacity than the cell containing the liquid electrolyte (Control 1) . This indicates that the gel polymer electrolytes prepared according to the present disclosure have a stable structure and good compatibility with positive and negative electrode materials.

In accordance with the foregoing, in some aspects the present disclosure is directed to gel polymer electrolytes for use with energy-storage cells, such as electrochemical energy-storage cells based on alkali-metal chemistries, such as lithium chemistries, sodium chemistries, or potassium chemistries, among others. Gel polymer electrolytes of the present disclosure can be used with electrochemical cells containing any suitable type of electrodes, such as plating types (e.g., lithium-metal anodes) and intercalating types (e.g., lithium-ion anodes and cathodes) . Benefits of gel polymer electrolytes of the present disclosure include, but are not limited to the ability to completely and uniformly cover surfaces of the electrodes within the cells, good electrochemical redox stability (compared to liquid electrolytes of similar electrolyte chemistry) , high ionic conductivity (compared to all-solid-state electrolytes) , and, when used with plating-type electrodes, mechanical strength sufficient to effectively inhibit the growth of alkali-metal dendrites. Inhibiting dendrite growth greatly reduces the risks of cells short circuiting and exploding to provide cells deployed with such electrolytes with both good safety performance and good cycling performance. In addition, gel polymer electrolytes of the present disclosure reduce safety concerns caused by leakage of electrolyte. A further discussion of benefits of gel polymer electrolytes made in accordance with the present disclosure appears below following an example of making a gel polymer electrolyte and an energy-storage cell made therewith.

In some embodiments, a gel polymer electrolyte of the present disclosure includes an electrolyte solution and a polymer matrix formed from molecules of at least one monomer. The electrolyte solution includes one or more salts dissolved in a nonaqueous solvent. In some instantiations, the salt is selected based on the chemistry of the energy-storage cell in which the gel polymer electrolyte will be deployed. For example, when the chemistry is based on an alkali metal, such as lithium, sodium, or potassium, each salt is selected based on it including ions of the relevant alkali metal. For example, for lithium chemistries for either lithium-metal cells or lithium-ion cells, each salt may be a suitable lithium-based salt, such as any of the salts mentioned above, among others. The nonaqueous solvent may include any one or more suitable organic solvents, such as one or more of the solvents listed above. In some embodiments, the content of the organic solvent in the gel polymer electrolyte can reach as high as 90%by volume. It is noted that in some embodiments, the electrolyte solution contains only the salt (s) and nonaqueous solvent (s) , while in some embodiments, the electrolyte solution contains the salt (s) , the nonaqueous solvent (s) , and one or more additives, such as any one or more additives known in the art, such as one or more of the additives listed above, among others.

Each monomer is selected to form the desired polymer matrix when the molecules of the monomer cross link with one another and/or with other molecules, such as molecules of one or more additional monomers. Each monomer may be any suitable monomer, such as any of the monomers discussed above, among others. Regarding strength of the gel polymer electrolyte, despite the presence of the solvent in the gel polymer electrolyte, the polymer matrix is designed to provide enough strength, elasticity, and yield behavior to inhibit growth of alkali-metal dendrites in energy-storage cells having plating type electrodes. Consequently, some gel polymer electrolytes of the present disclosure can provide the same physical barrier effect as SEI layers in conventional liquid-electrolyte chemistries for inhibiting growth of alkali-metal dendrites, such as lithium dendrites.

In some embodiments, one or more crosslinking agents and/or one or more crosslinking initiators can be used to effect the desired crosslinking /polymerization of the molecules of the monomer (s) . Each crosslinking agent may be any suitable crosslinking agent compatible with the selected monomer (s) , such as, for example, any of the crosslinking agents listed above, among others. Similarly, each crosslinking initiator may be any suitable crosslinking initiator suitable for the crosslinking, such as, for example, any of the initiators noted above, among others. Those skilled in the art will be able to select the monomer (s) , crosslinking agent (s) , and/or crosslinking initiator (s) for the desired gel polymer electrolyte.

In some embodiments, a monomer-crosslinking agent-initiator system of the present disclosure is designed so that the gel polymer electrolyte can be made using a gel-polymer-electrolyte precursor that remains liquid until suitable crosslinking conditions are provided. In some embodiments, this allows the liquid precursor to be installed (e.g., by injection, gravity flow, etc. ) into an energy-storage cell prior to causing the liquid precursor to polymerize and form the final gel polymer electrolyte. Keeping the precursor liquid, preferably at room temperature (e.g., generally, 20℃) during and after installation allows liquid precursor to thoroughly and uniformly coat the electrodes and permeate and fill interstices within components inside the energy-storage cell, such as each porous separator and one or both types of the electrodes, such as each cathode and/or each anode, depending on whether each type has a porous construction. In some embodiments, the polymerization is effected by applying heat to the liquid precursor. Specific examples are described below.

As noted above, a gel polymer electrolyte formed by in-situ polymerization in an energy-storage cell can form a stable solid film on alkali-metal surfaces (e.g., of alkali-metal anodes) , similar to an SEI film in an energy-storage cell containing only liquid electrolyte. Such a stable solid film can prevent further contact between the salt solution and the electrode surface to avoid excessive decomposition of the salt solution on the electrode material surface, thus reducing excessive loss of the organic solvent, lithium salt (s) , and alkali-metal anode. Such a stable solid film can also control the deposition morphology of alkali metal on the surface of a plating-type anode so that alkali metal is evenly deposited on the anode surface. Therefore, the use of gel polymer electrolytes of the present disclosure for energy-storage cells that include plating-type electrodes based on alkali-metal chemistry can inhibit the generation and formation of alkali-metal dendrites at the source.

Also in accordance with the foregoing, in some aspects, the present disclosure is directed to energy-storage cells made using a gel polymer electrolyte, such as any of the gel polymer electrolytes described above. In some embodiments, an energy-storage cell of the present disclosure includes a housing and one or more of each of an anode, a separator, and a cathode. In some embodiments, multiple anodes, multiple separators, and multiple cathodes may be provided in a stacked construction as is well known in the art. In such stacked embodiments, the housing may comprise, for example, a flexible pouch or a hard shell. In some embodiments, a single set of anode, separator, and cathode may be rolled into a jelly-roll style roll, and the housing may be a cylindrical container housing the roll. Various forms of such energy-storage cells are well known, and any suitable form can be used. As noted above, the chemistry of an energy-storage cell of the present disclosure may be any suitable chemistry, such as an alkali-metal based chemistry, and the type of each anode and cathode may be any suitable type, such as a plating type or an intercalating type. The separator may be any suitable porous separator having interstices that allow ions in the salt solution within the gel polymer electrolyte to flow therethrough. As those skilled in the art will readily appreciate, an energy-storage cell of the present disclosure may further include other components, such as current collectors and one or more thermal shutdown layers, among others. Energy-storage cells made in this manner may be grouped together and electrically connected with one another in series and/or parallel so as to form an energy-storage battery. Techniques for making energy-storage batteries out of energy-storage cells are well known and do not need to be described herein for those skilled in the art to understand how to make energy-storage batteries from gel-polymer-electrolyte containing energy-storage cells of the present disclosure.

Further in accordance with the foregoing, in some aspects the present disclosure is directed to methods of making a gel polymer electrolyte. In some embodiments, such a method includes mixing together, so as to form a homogeneous mixture, a salt, a nonaqueous solvent selected for dissolving the salt, and molecules of at least one monomer selected for forming a polymer matrix. As discussed above, the salt may be any one or more suitable salts selected for the particular application of the gel polymer electrolyte at issue, such as an alkali-metal-based salt for an alkali-metal-based energy-storage cell. As also discussed above, the nonaqueous solvent may be any one or more suitable solvents, for example, one or more polar solvents, such as carbonate solvents, among others. The mixture is then provided with conditions that cause the molecules of the at least one monomer to crosslink so as to form the gel polymer electrolyte. In some embodiments, providing conditions that cause crosslinking include adding one or more crosslinking agents and/or one or more crosslinking initiators to the mixture. In some embodiments, providing conditions that cause crosslinking may additionally or alternatively include subjecting the mixture to one or more externally applied conditions, such as heating and/or irradiating with electromagnetic energy, such as light, for example ultraviolet and/or visible light, among others.

Still further in accordance with the foregoing, in some aspects the present disclosure is directed to methods of making an energy-storage cell. In some embodiments, such a method includes providing a cell structure that includes a housing containing an anode comprising an alkali metal, a cathode, and a separator located between the anode and the cathode, wherein the separator includes interstices that allow ions to flow through the separator. As discussed above, the cell structure may be any suitable cell structure for an energy-storage cell, such as a pouch-type structure or a rigid-shell-type structure, for example, a cylindrical housing or a button-cell housing, among others. This method further includes installing a gel-electrolyte precursor into the housing so that the gel-electrolyte precursor coats each of the anode and the cathode and fills the interstices of the separator. As mentioned above, the installing of the gel-polymer precursor may be performed in any suitable manner, such as injection or gravity flow, among others. The gel-electrolyte precursor comprises a salt containing ions of the alkali metal, a nonaqueous solvent for dissolving the salt, and molecules of at least one monomer selected for forming a polymer matrix. Each of the salt and nonaqueous solvent may be, for example, any one or more of each of the salts and the solvents mentioned above. After installing the gel-electrolyte precursor, the molecules of the at least one monomer are caused to crosslink so as to form the polymer matrix. As discussed above, causing crosslinking may include subjecting the mixture to one or more externally applied conditions, such as heating and/or irradiating with electromagnetic energy, such as light, for example ultraviolet and/or visible light, among others. In some embodiments, the installed gel-electrolyte precursor may additionally include one or more crosslinking agents and/or one or more initiators for effecting polymerization of the molecules of the at least one monomer.

Example Making of a Gel Polymer Electrolyte and an Energy-Storage Cell

Following is one example of making each of a gel polymer electrolyte and an energy-storage cell in accordance with aspects of the present disclosure. Those skilled in the art will readily understand that this example is merely illustrative and not limiting in any way, since they will understand, in light of the foregoing disclosure, the many ways in which a gel polymer electrolyte and an energy-storage cell can be made in accordance with this disclosure. In addition, those skilled in the art will readily understand that the parameters recited in this example are also merely illustrative and not limiting. These parameters include, but are not limited to the type of preparation site, the atmospheric makeup of the preparation site (inertness, water content, oxygen content, temperature, etc. ) , stirring and mixing speeds and times, gel-electrolyte precursor installation method, and heating time, among others. In this example, each of the specific materials (e.g., salt (s) , solvent (s) , monomer (s) , crosslinking agent (s) , and initiator (s) ) may be any one or more of the specific materials mentioned above and the cell structure may be any of the cell structures mentioned above or well known in the art, and the amounts of each may be any amount suitable to provide the desired salt-solution composition (e.g., molarity, etc. ) , the desired salt-solution-to-polymer-matrix ratio, and the desired mechanical properties (e.g., strength, elasticity, porosity, etc. ) of the resulting polymer matrix.

In this example, the gel-polymer precursor is prepared in a glovebox in an inert (e.g., argon) atmosphere having a water content of < 1 part per million (ppm) and an oxygen content of < 1 ppm and at room temperature. The salt is dissolved in an organic solvent and stirred thoroughly, for example, with a magnetic stirrer having a speed of 300 rpm and for a time of 12 minutes, to obtain a salt solution. One or more monomers, one or more crosslinking agents, and one or more initiators are combined with the salt solution, and the combination is mixed, for example, with a magnetic stirrer having a speed of 300 rpm and for a time of 30 minutes, to form a homogeneous mixture that is the gel-electrolyte precursor.

An appropriate amount of the gel-electrolyte precursor, which is at room temperature, is installed (e.g., by injection) into a cell structure having an anode (here, a plating-type anode) , a cathode (here, an intercalating-type cathode) , and a porous separator located between the anode and the cathode. The amount of gel-electrolyte precursor needed may be determined using conventional means for determining the amount of conventional liquid electrolyte. The cell structure is then sealed and left to sit for an amount of time so that the gel-electrolyte precursor fully penetrates the separator and the cathode. The filled and sealed cell is then placed into a heating chamber and heated to a temperature in a range of greater than about 20℃ to about 120℃ for about 1 hour to about 120 hours or in a range of about 50℃ to about 80℃ for about 48 hours to about 80 hours so as to effect polymerization and formation of the polymer matrix within the gel-electrolyte precursor so as to create the gel polymer electrolyte in situ within the cell structure to create the energy-storage cell.

Example Benefits of the Disclosed Gel Polymer Electrolytes

Some benefits of a gel polymer electrolyte of the present disclosure, such as any of the gel polymer electrolytes specifically mentioned and/or described herein and any made in accordance with methodologies described herein, are mentioned above. Following are more details on such and other benefits.

In some embodiments, the gel-electrolyte precursor of the gel polymer electrolyte uses a mixture that is liquid at room temperature and can be polymerized at higher temperatures or under other initiation conditions. The preparation method and the liquid state at room temperature of the gel-electrolyte precursor make it ideal for modifying production processes that were traditionally used for making liquid-electrolyte containing energy-storage cells. For example, a gel polymer electrolyte of the present disclosure can be installed into a suitable cell structure (e.g., pouch-type cell structure) using a conventional liquid-electrolyte injection method but instead for the gel-electrolyte precursor. Then the gel polymer-based energy-storage cell can be obtained by high-temperature polymerization. This is a simple, efficient, and low-cost production method.

Gel polymer electrolytes of the present disclosure can have high ionic conductivity and low interfacial impedance compared to conventional solid electrolytes. For example, the range of ion conductivity may be in a range of about 3 x 10 ^-3 S/cm to about 4 x 10 ^-3 S/cm. Ionic conductivity is a key factor in determining the internal resistance and multiplicative performance of an energy-storage cell, so a gel polymer-based energy-storage cell can have a longer cycle life and better multiplicative performance as compared to conventional solid electrolytes.

Compared with traditional liquid electrolytes, the gel polymer electrolyte of the present disclosure has a certain mechanical strength that can effectively inhibit the growth of lithium dendrites, thus avoiding safety problems such as short circuit and explosion caused by dendrites penetrating the separator. At the same time, the gel polymer electrolyte has the advantages of being non-flammable, non-volatile, and not easy to leak.

The gel polymer electrolyte covered by the present invention is effectively in a solid state, which can inhibit the growth of lithium dendrites, thus avoiding safety problems such as short circuit and explosion caused by dendrites penetrating the separator. Therefore, lithium-metal cells using polymer-based gel have higher safety performance. For example, the heating failure temperature of lithium-metal cells with gel polymer electrolytes is 200℃ higher than that of lithium metal batteries with liquid electrolytes (the heating failure temperature of liquid electrolytes is about 150℃) .

In some embodiments, a gel polymer electrolyte covered by the present disclosure has an oxidative decomposition potential of up to 5 V, which is much higher than that of the liquid electrolyte at 4.2 V. This indicates that the gel polymer electrolyte can be adapted to higher voltage ternary cathode materials.

Cyclic voltammetry shows that gel polymer electrolytes of the present disclosure have good compatibility and reversibility with electrode materials. Among them, compatible anode materials include, but are not limited to, carbon-based materials, silicon-based materials, lithium-metal, and lithium-metal alloys, and tin-based materials, among others. Cathode materials include, but are not limited to, lithium iron phosphate, ternary composite electrode materials, lithium manganate, and lithium cobalt oxide, among others.

Test results show significantly better safety performance and similar cycling performance compared to liquid electrolytes. Pouch-type (aka, “soft pack” ) energy-storage cells using a gel polymer electrolyte of the present disclosure have longer cycle life and higher safety performance. As noted above, a gel polymer electrolyte of the present disclosure can form a thin film on an electrode’s surface that provides a SEI-like function, e.g., to prevent further contact between the electrolyte and a lithium-metal anode, thus reducing the consumption of the lithium-metal anode and the electrolyte. Therefore, lithium-metal energy-storage cells using gel polymer electrolytes have higher discharge capacity retention than lithium metal batteries using liquid electrolytes. According to the test results, the discharge capacity retention rate of energy-storage cells using a gel polymer electrolyte of this disclosure is 3 to 4 percentage points higher than the discharge capacity retention rate of cells using liquid electrolyte during cell cycling, and therefore, the cycle life is longer.

FIG. 5A illustrates a simple example energy-storage cell 500 made in accordance with aspects of the present disclosure. Those skilled in the art will readily appreciate that the energy- storage cell 500 can be, for example, a battery cell (e.g., lithium-metal battery cell or cell based on another alkali metal chemistry, among others) or a supercapacitor cell. In addition, those skilled in the art will readily understand that FIG. 5A illustrates only some basic functional components of the cell 500 and that a real-world instantiation of the cell, such as a secondary battery or a supercapacitor, will typically be embodied in either a stacked construction containing multiple instantiations of the layered components or a wound construction. Further, those skilled in the art will understand that the energy-storage cell 500 will include other components, such as one or more seals, thermal shutdown layers, and/or vents, among other things, that, for ease of illustration, are not shown in FIG. 5A.

In this example, the cell 500 includes an anode 504 and a cathode 508 that are spaced apart from one another and include corresponding

active materials

504A and 508A and a pair of respective

current collectors

504C and 508C. The

current collectors

504C and 508C are electrically connected to corresponding electrical terminals 512 (1) and 512 (2) , such as tabs in a pouch-type construction. At least one porous dielectric separator 516 is located between the anode 504 and cathode 508 to electrically separate the anode and cathode but to allow ions of a gel polymer electrolyte 520 to flow therethrough. As will be appreciated, the gel polymer electrolyte 520 may be any gel polymer electrolyte described herein or able to be made by a skilled artisan without undue experimentation using only the present disclosure, including the claims, as a guide.

As those skilled in the art will understand, depending upon the type and design of the cell 500, each of the anode 504 and cathode 508 comprises one or more suitable materials that gain or lose ions via the gel polymer electrolyte 520 depending on whether the cell is being charged or discharged. Each of the

active materials

504A and 508A may be any suitable material for the anode 504 and the cathode 508, respectively. Examples of anode active materials 504A may include alkali-metal-based materials, such as pure lithium, pure sodium, pure potassium, and alloys thereof, among others. Examples of cathode-active materials 508A include crystalline oxides comprising various amounts of cobalt, nickel, and manganese, among many others. Each of the

current collectors

504C and 508C may be made of any suitable electrically conducting material, such as copper or aluminum, or any combination thereof. The porous separator 516 may be made of any suitable dielectric material, such as a polymer (e.g., PP, PE, a PP/PE hybrid, etc. ) , among others, and may be coated or uncoated as needed to meet a certain design. Various battery and supercapacitor constructions that can be used for constructing the cell 500 of FIG. 5A, are known in the art. If any of such known constructions is used, a novelty of the cell 500 lies in the gel polymer electrolyte 520 made in accordance with the present disclosure.

FIG. 5B illustrates an example multicell battery 550 made in accordance with the present disclosure. In this example, the battery 550 includes a plurality of electrochemical energy-storage cells 554 (1) through 554 (N) electrically connected with one another via suitable electrical connections 558. The number of the cells 554 (1) through 554 (N) provided may be any number, for example, 2 to 100 or more, needed to suit a particular application. The electrical connections 558 may be any connections needed to connect the cells 554 (1) through 554 (N) with one another such that the battery 550 meets the design requirements for the application at issue. For example, the electrical connections 558 may be either serial connections or parallel connections, or a combination of serial and parallel connections. In addition, the cells 554 (1) through 554 (N) may be grouped in one or more groups, and each such group may be part of a corresponding battery module. In such a case, the electrical connections 558 may include electrical connections among the modules. Those skilled in the art will readily understand the types and manners of effecting the physical connections needed for the electrical connections 558, which may include, but are not limited to, tab-to-tab connections, busbar connections, wiring connections, and wiring-harness connections, among others. Fundamentally, there are no limitations on the type (s) of electrical connections that can be part of the electrical connections 558. In this example, the electrical connections 558 are electrically connected to a pair of battery output terminals 562 (1) and 562 (2) that will be connected to an electrical load and/or electrical source (neither shown) during deployment of the battery. Not illustrated are the many other components of a battery that could be included aboard the example battery 550, such as, but not limited to, a battery management system, a sensor system, an emergency disconnect unit, and module controllers, among others.

FIG. 6 is a graph illustrating electrochemical stability windows for a conventional liquid electrolyte and two instantiations of a gel polymer electrolyte of the present disclosure. As seen in FIG. 2, each of the gel polymer electrolytes demonstrated a wider electrochemical stability window than the liquid electrolyte. The test conditions for generating this graph were that the linear sweep voltammograms were made using two-electrode (Li/stainless steel) CR2032 coin cells and a Metrohm Autolab electrochemical workstation at 25℃. The scan rate was 1 mV/sfrom 3V to 5.5V.

FIG. 7 is a graph illustrating that gel polymer electrolytes made in accordance with this disclosure can have good compatibility with conventional intercalating-type electrodes. Cyclic voltammetry was used to evaluate the Li-plating (negative scan) and Li-stripping (positive scan) behaviors in both a conventional liquid electrolyte and in two instantiations of a gel polymer electrolyte of the present disclosure. The test conditions for generating this graph were that the cyclic voltammograms were made using two-electrode ( (Li/N _0.8C _0.1M _0.1) CR2032 coin cells and a Metrohm Autolab electrochemical workstation at 25 ℃. The scan rate was 0.2 mV/sfrom 3V to 4.3V) .

In some aspects, the present disclosure is directed to a gel electrolyte for an energy-storage cell having an anode comprising an alkali metal, the electrolyte comprising: an electrolyte solution that includes a salt dissolved in a nonaqueous solvent, wherein the salt comprising cations of the alkali metal that will carry charge within the energy-storage cell during use; and a polymer matrix comprising at least one monomer, wherein the polymer matrix is formed within the gel electrolyte and contains the electrolyte solution.

In one or more embodiments of the gel electrolyte, the alkali metal is selected from the group consisting of lithium, sodium, and potassium.

In one or more embodiments of the gel electrolyte, the alkali metal is lithium and the salt comprises lithium bis (fluorosulfonyl) imide.

In one or more embodiments of the gel electrolyte, the nonaqueous solvent includes at least one carbonate solvent.

In one or more embodiments of the gel electrolyte, each of the at least one carbonate solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate.

In one or more embodiments of the gel electrolyte, the at least one monomer comprises a methacrylate monomer.

In one or more embodiments of the gel electrolyte, the methacrylate monomer is selected from the group consisting of methyl methacrylate, ethyl methacrylate, and hexafluoroisopropyl methacrylate.

In one or more embodiments of the gel electrolyte, the polymer matrix is formed with at least one crosslinker.

In one or more embodiments of the gel electrolyte, the at least one crosslinker is selected from the group consisting of pentaerythritol, tetraacrylate, and ethoxylated trimethylolpropane triacrylate.

In one or more embodiments of the gel electrolyte, the polymer matrix is formed with at least one initiator.

In one or more embodiments of the gel electrolyte, the at least one initiator is selected from the group consisting of 2, 2'-azobis (2-methylpropionitrile) , 2, 2'-azobis (2, 4-dimethyl) valeronitrile, and dimethyl 2, 2'-azobis (2-methylpropionate) .

In some aspects, the present disclosure is directed to an energy-storage cell, comprising: an anode comprising an alkali metal; a cathode; a separator located between the anode and the cathode, wherein the separator includes interstices that allow ions to flow through the separator; a housing containing the anode, the cathode, and the separator; and a gel electrolyte contained within the housing and in contact with the anode and cathode and permeating the interstices of the separator, wherein the gel electrolyte comprises: an electrolyte solution that includes a salt dissolved in a nonaqueous solvent, wherein the salt comprising cations of the alkali metal that will carry charge within the energy-storage cell during use; and a polymer matrix comprising at least one monomer, wherein the polymer matrix is formed within the gel electrolyte and contains the electrolyte solution.

In one or more embodiments of the energy-storage cell, the alkali metal is lithium.

In one or more embodiments of the energy-storage cell, the anode comprises lithium metal.

In one or more embodiments of the energy-storage cell, the anode is a plating-type anode.

In one or more embodiments of the energy-storage cell, the plating-type anode is configured to plate lithium metal.

In one or more embodiments of the energy-storage cell, the anode is an intercalating-type anode.

In one or more embodiments of the energy-storage cell, the intercalating-type anode is designed to intercalate lithium ions.

In one or more embodiments of the energy-storage cell, the alkali metal is lithium and the salt comprises lithium bis (fluorosulfonyl) imide.

In one or more embodiments of the energy-storage cell, the nonaqueous solvent includes at least one carbonate solvent.

In one or more embodiments of the energy-storage cell, each of the at least one carbonate solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate.

In one or more embodiments of the energy-storage cell, the at least one monomer comprises a methacrylate monomer.

In one or more embodiments of the energy-storage cell, the methacrylate monomer is selected from the group consisting of methyl methacrylate, ethyl methacrylate, and hexafluoroisopropyl methacrylate.

In one or more embodiments of the energy-storage cell, the polymer matrix is formed with at least one crosslinker.

In one or more embodiments of the energy-storage cell, the at least one crosslinker is selected from the group consisting of pentaerythritol, tetraacrylate, and ethoxylated trimethylolpropane triacrylate.

In one or more embodiments of the energy-storage cell, the polymer matrix is formed with at least one initiator.

In one or more embodiments of the energy-storage cell, the at least one initiator is selected from the group consisting of 2, 2'-azobis (2-methylpropionitrile) , 2, 2'-azobis (2, 4-dimethyl) valeronitrile, and dimethyl 2, 2'-azobis (2-methylpropionate) .

In one or more embodiments of the energy-storage cell, the gel electrolyte is polymerized in situ within the housing of the energy-storage cell.

In some aspects, the present disclosure is directed to a method of making a gel electrolyte, the method comprising: mixing together: a salt; a nonaqueous solvent selected for dissolving the salt; and molecules of at least one monomer selected for forming a polymer matrix; so as to form a mixture; and providing the mixture with conditions that cause the molecules of the at least one monomer to crosslink so as to form the gel electrolyte.

In one or more embodiments of the method, the salt comprises at least one lithium-based salt.

In one or more embodiments of the method, the at least one lithium-based salt is lithium bis (fluorosulfonyl) imide.

In one or more embodiments of the method, the nonaqueous solvent includes at least one carbonate solvent.

In one or more embodiments of the method, each of the at least one carbonate solvent is selected from the group consisting of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, and diethyl carbonate.

In one or more embodiments of the method, the at least one monomer comprises a methacrylate monomer.

In one or more embodiments of the method, the methacrylate monomer is selected from the group consisting of methyl methacrylate, ethyl methacrylate, and hexafluoroisopropyl methacrylate.

In one or more embodiments of the method, providing the mixture with conditions that cause the molecules of the at least one monomer to crosslink includes providing at least one crosslinker to the mixture.

In one or more embodiments of the method, the at least one crosslinker is selected from the group consisting of pentaerythritol, tetraacrylate, and ethoxylated trimethylolpropane triacrylate.

In one or more embodiments of the method, providing the mixture with conditions that cause the molecules of the at least one monomer to crosslink includes providing at least one initiator to the mixture.

In one or more embodiments of the method, the at least one initiator is selected from the group consisting of 2, 2'-azobis (2-methylpropionitrile) , 2, 2'-azobis (2, 4-dimethyl) valeronitrile, and dimethyl 2, 2'-azobis (2-methylpropionate) .

In one or more embodiments of the method, providing the mixture with conditions that cause the molecules of the at least one monomer to crosslink includes subjecting the mixture to heat.

In some aspects, the present disclosure is directed to a method of making an energy-storage cell, the method comprising: providing a cell structure that includes a housing containing: an anode comprising an alkali metal; a cathode; and a separator located between the anode and the cathode, wherein the separator includes interstices that allow ions to flow through the separator; installing a gel-electrolyte precursor into the housing so that the gel-electrolyte precursor coats each of the anode and the cathode and fills the interstices of the separator, wherein the gel-electrolyte precursor comprises a mixture that includes: a salt containing ions of the alkali metal; a nonaqueous solvent selected for dissolving the salt; and molecules of at least one monomer selected for forming a polymer matrix; and after installing the gel-electrolyte precursor, causing the molecules of the at least one monomer to crosslink so as to form the polymer matrix.

In one or more embodiments of the method, the alkali metal is lithium.

In one or more embodiments of the method, the anode comprises lithium metal.

In one or more embodiments of the method, the anode is a plating-type anode.

In one or more embodiments of the method, the plating-type anode is configured to plate lithium metal.

In one or more embodiments of the method, the anode is an intercalating-type anode.

In one or more embodiments of the method, causing the molecules of the at least one monomer to crosslink includes providing at least one crosslinker to the mixture.

In one or more embodiments of the method, causing the molecules of the at least one monomer to crosslink includes providing at least one initiator to the mixture.

In one or more embodiments of the method, causing the molecules of the at least one monomer to crosslink includes subjecting the gel-polymer precursor to heat.

Various modifications and additions can be made without departing from the spirit and scope of this disclosure. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments, what has been described herein is merely illustrative of the application of the principles of the present invention. Additionally, although particular methods herein may be illustrated and/or described as being performed in a specific order, the ordering is highly variable within ordinary skill to achieve aspects of the present disclosure. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.

Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.

Claims

A gel polymer electrolyte obtained by polymerizing a gel precursor mixture into a gel having a polymer matrix.
The gel polymer electrolyte of claim 1, wherein the gel precursor mixture comprises one or more monomers, one or more nonaqueous organic solvents, and one or more lithium salts or one or more additives or both one or more lithium salts and one or more additives.
The gel polymer electrolyte of claim 2, wherein the one or more monomers comprises any one or two combinations of a monomer with at least one initiator or at least one crosslinking agent or both at least one initiator and at least one crosslinking agent.
The gel polymer electrolyte of claim 3, wherein the one or more monomers comprise a compound represented by the following formula:

wherein:

R1, R2, R3 independently represent a hydrogen atom, a halogen atom, an alkyl, a cycloalkyl, a heterocyclic group, an aryl group, an alkoxyl group, an ester group, a carbonate group, a cyano group, or an heterocyclic aryl or acyl;

R4 represent a fluorine atom, an alkyl, a cycloalkyl, a heterocyclic group, an aryl group, an alkoxyl group, an ester group, a carbonate group, a cyano group, or a heterocyclic aryl or acyl;

the carbon atom of the alkyl, cycloalkyl, heterocyclic group, aryl group or heterocyclic aryl, when present, may be bonded to at least one substituent selected from a halogen, an alkoxyl group, an ester group, a cyano group, or a phenyl or phosphoric ester group;

the alkyl group, when present, comprises 1 to 10 carbon atoms;

the naphthenic group, when present, is a three to ten membered single ring, bridge ring, or spiro ring group;

the heterocyclic group, when present, is a five to ten membered heterocyclic group with one or more heteroatoms, preferably, wherein said heteroatom is selected from at least one of O, N, S, and P;

the at least one substituent, when present, is a halogen or a C2 through C6 ester group; and

the halogen, when present, is at least one of F, Cl and Br.
The gel polymer electrolyte of claim 3, wherein the one or more monomers comprise a compound represented by the following formula:

wherein:

the selection range of R1 through R3 is the same as the range of R1 through R3 of claim 61;

R4 independently represent alkyl, acyl, or ester group; and

the carbon atom of the alkyl, acyl or ester group may be bonded to at least one substituent selected from a halogen, an alkoxyl group, an ester group, a cyano group, or a phenyl or phosphoric ester group.
The gel polymer electrolyte of claim 3, wherein the one or more monomers account for about 0.5%to about 100%of the weight of the polymer matrix.
The gel polymer electrolyte of claim 3, wherein the at least one crosslinking agent comprises a compound with one or more unsaturated carbon-carbon double bonds.
The gel polymer electrolyte of claim 3, wherein the at least one crosslinking agent is selected from the group consisting of styrene, vinyl toluene, divinylbenzene, N, N'-methylene bisacrylamide, ethylene glycol dimethacrylate, poly (ethylene glycol) dimethacrylate, 1, 1, 1-trimethylol propane triacrylate, triallyl phosphate, pentaerythritol tetraacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate, polydipentaerythritol hexaacrylate, and trihydroxymethyl propane triacrylate.
The gel polymer electrolyte of claim 3, wherein the at least one crosslinking agent accounts for about 0%to about 99.5%of the weight of the polymer matrix.
The gel polymer electrolyte of claim 3, wherein the at least one initiator is selected from the group consisting of 2, 2-azodiisobutyronitrile, 2, 2'-azobis (2, 4-dimethyl) valeronitrile, dimethyl 2, 2'-azobis (2-methylpropionate) , benzoyl peroxide, potassium persulfate, dodecanoic peroxyanhydride, N, N-dimethylaniline, diisopropylbenzene peroxide, di tert butyl peroxide, tert butyl peroxybenzoate, 2-hydroxy-2-methyl-1-phenylacetone, 1-hydroxycyclo-hexylphenyl ketone, 2-methyl-2- (4-morpholinyl) -1- [4- (methylthio) phenyl] -1-acetone, 2, 4, 6-trimethylbenzoyl diphenylphosphine oxide, 2, 4, 6-trimethylbenzoyl phenyl phosphonate ethyl ester, 2-dimethylamino-2-benzyl-1- [4- (4-morpholinyl) phenyl] -1-butanone, 2-hydroxy-2-methyl-1- [4- (2-hydroxyethoxy) phenyl] -1-acetone, and methyl phenylglyoxylate.
The gel polymer electrolyte of claim 3, wherein the at least one initiator accounts for about 0%to about 20%of the weight of the polymer matrix.
The gel polymer electrolyte of claim 1, characterized in that the polymer matrix accounts for about 0.5%to about 90%of the weight of gel polymer electrolyte.
The gel polymer electrolyte of claim 2, characterized in that the one or more nonaqueous organic solvents are selected from the group consisting of dimethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, methyl propyl carbonate, diethyl carbonate, dibutyl carbonate, methyl formate, ethyl acetate, methyl propionate, dipropyl carbonate, methyl acetate, acetonitrile, succinonitrile, butene carbonate, methyl isopropyl carbonate, methyl butyl carbonate, 1, 4-butyrolactone, dimethyl tetrahydrofuran, 1, 2-dimethoxyethane, ethyl propionate, methyl butyrate trifluoromethyl vinyl carbonate, dimethyl sulfoxide, sulfolane, 4-methyl-1, 3-butyrolactone, propane sulfolactone, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and compounds containing the structure shown in the following formula:

wherein:

R5 represent an alkyl, a cycloalkyl, a heterocyclic group, an aryl group, an alkoxyl group, an ester group, a carbonate group, a cyano group, or a heterocyclic aryl or acyl; and

the carbon atom of the said alkyl, cycloalkyl, heterocyclic group, aryl group or heterocyclic aryl, when present, may be bonded to at least one substituent selected from a halogen, an alkoxyl group, an ester group, a cyano group, or a phenyl or phosphoric ester group.
The gel polymer electrolyte of claim 2, wherein the one or more nonaqueous organic solvents account for about 3%to about 94.5%of the weight of the gel polymer electrolyte.
The gel polymer electrolyte of claim 2, wherein said lithium salt is selected from, but not limited to, at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis oxalate borate, lithium difluorosulfonylimide, lithium perchlorate, lithium hexafluoroarsenate, and lithium bis trifluoromethanesulfonylimide.
The gel polymer electrolyte of claim 2, wherein the one or more lithium salts account for about 5%to about 50%of the weight of said gel polymer electrolyte.
The gel polymer electrolyte of claim 2, wherein the at least one additive is selected from the group consisting of vinyl carbonate, dimethyl phenyl phosphonate, potassium perfluorobutyl sulfonate, potassium perfluorooctane sulfonate, fluoroethylene carbonate, dimethyl sulfite, diethyl sulfite, trimethyl phosphate, triethyl phosphate, trioctyl phosphate, trimethyl phosphite, triethyl phosphite, methyl vinyl sulfone, and lithium oxalate borate.
The gel polymer electrolyte of claim 2, wherein the at least one additive accounts for about 0%to about 20%of the weight of said gel polymer electrolyte.
The gel polymer electrolyte of claim 1, wherein the polymerizing is performed by thermal initiated polymerization, plasma initiated polymerization, photoinitiated polymerization, microwave initiated polymerization, radiation initiated polymerization, electrochemical initiated polymerization, or a combination of two or more of thermal initiated polymerization, plasma initiated polymerization, photoinitiated polymerization, microwave initiated polymerization, radiation initiated polymerization, and electrochemical initiated polymerization.