CN111668547B - Nonaqueous electrolyte solution and electricity storage device using same - Google Patents
Nonaqueous electrolyte solution and electricity storage device using same Download PDFInfo
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- CN111668547B CN111668547B CN202010611242.XA CN202010611242A CN111668547B CN 111668547 B CN111668547 B CN 111668547B CN 202010611242 A CN202010611242 A CN 202010611242A CN 111668547 B CN111668547 B CN 111668547B
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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- Y02E60/10—Energy storage using batteries
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Abstract
The invention discloses a nonaqueous electrolyte and an electric storage device using the same. The non-aqueous electrolyte comprises a non-aqueous solvent, a lithium salt and an additive, wherein the additive comprises an isocyanate compound containing an unsaturated cyclic group. An electricity storage device according to the present invention includes a positive electrode, a negative electrode, a separator, and the nonaqueous electrolytic solution. The electric storage device using the non-aqueous electrolyte disclosed by the invention can realize the beneficial effects of electrode film formation, electrode performance improvement, gas inhibition of the battery and service life extension.
Description
Technical Field
Embodiments of the present invention relate to the field of battery manufacturing, and in particular, to a nonaqueous electrolyte solution and an electrical storage device using the same.
Background
Electric storage devices, particularly lithium secondary batteries, are widely used as power sources for mobile electronic devices, electric vehicles, energy storage devices, and the like.
On the other hand, the negative electrode of a lithium secondary battery includes lithium metal, a metal compound (a simple metal, a metal oxide, an alloy with lithium, or the like) capable of inserting and extracting lithium, and a carbon material. In particular, nonaqueous electrolyte secondary batteries using carbon materials capable of lithium intercalation and deintercalation, such as coke and graphite (artificial graphite and natural graphite), among carbon materials, are widely used. The negative electrode material stores and releases lithium and electrons at an extremely low potential equivalent to that of lithium metal, so that a large amount of the solvent is reductively decomposed, and a part of the solvent in the electrolyte is reductively decomposed on the negative electrode regardless of the kind of the negative electrode material, and the movement of lithium ions is inhibited by deposition of decomposed products, gas generation, and swelling of the electrode.
On the other hand, LiCoO used as a positive electrode material2、LiMn2O4、LiNiO2、LiFePO4And the material capable of inserting and extracting lithium stores and extracts lithium and electrons at a high voltage of 3.5V or more on the basis of lithium, and thus, regardless of the kind of the positive electrode material, a part of the solvent in the electrolyte solution is oxidatively decomposed on the positive electrode, and the resistance is increased by the deposition of the decomposed product, or the gas is generated by the decomposition of the solvent to swell the battery.
When the lithium secondary battery is mounted in the electronic device, the power consumption increases with the increase of the energy density, the temperature of the battery rises due to the heat generation of the electronic device, the electrolyte is in a state of being easily decomposed, the gas generated by the decomposition of the electrolyte swells the battery, and the service life of the battery is shortened.
Disclosure of Invention
An object of an embodiment of the present invention is to provide a nonaqueous electrolyte solution and an electricity storage device using the same, in which gas generation is suppressed and the battery life is prolonged.
In order to solve the above-described technical problem, an embodiment of the present invention provides a nonaqueous electrolytic solution including a nonaqueous solvent, a lithium salt, and an additive including an unsaturated cyclic group-containing isocyanate compound represented by general formula (I):
wherein R1 is selected from aralkyl with 7 to 13 carbon atoms, aryl with 6 to 12 carbon atoms and unsaturated ring with 5 to 12 carbon atoms, wherein, at least one hydrogen atom in the aralkyl with 7 to 13 carbon atoms, the aryl with 6 to 12 carbon atoms and the unsaturated ring with 5 to 12 carbon atoms can be substituted by halogen and/or alkyl with 1 to 4 carbon atoms.
In one embodiment, R1 in the unsaturated cyclic group-containing isocyanate compound represented by the above general formula (I) is selected from a phenyl group, a phenyl group in which at least one hydrogen atom is substituted with a halogen and/or an alkyl group having 1 to 4 carbon atoms, a cyclohexenyl group in which at least one hydrogen atom is substituted with a halogen and/or an alkyl group having 1 to 4 carbon atoms, a cyclohexadienyl group, and a cyclohexadienyl group in which at least one hydrogen atom is substituted with a halogen and/or an alkyl group having 1 to 4 carbon atoms.
In one embodiment, R1 in the unsaturated cyclic group-containing isocyanate compound represented by the general formula (I) is selected from a phenyl group, a phenyl group in which hydrogen atoms at the ortho-position and/or para-position of the isocyanate group are substituted with a halogen and/or an alkyl group having 1 to 4 carbon atoms, a cyclohexenyl group, and a cyclohexenyl group in which hydrogen atoms at the ortho-position and/or para-position of the isocyanate group are substituted with a halogen and/or an alkyl group having 1 to 4 carbon atoms.
In one embodiment, R1 in the unsaturated cyclic group-containing isocyanate compound represented by the general formula (I) is a six-membered cyclic group, and the degree of unsaturation is 1 to 3.
In one embodiment, R1 in the unsaturated cyclic group-containing isocyanate compound represented by the general formula (I) is selected from a phenyl group and a cyclohexenyl group.
In one embodiment, at least one hydrogen atom in the alkyl group having 1 to 4 carbon atoms may be substituted by an alkyl group having 1 to 4 carbon atoms.
In one embodiment, the non-aqueous solvent comprises Ethylene Carbonate (EC) and/or Ethyl Methyl Carbonate (EMC) and/or Propylene Carbonate (PC) and/or diethyl carbonate (DEC).
In one embodiment, R1 in the unsaturated cyclic group-containing isocyanate compound represented by the general formula (I) is selected from phenyl and cyclohexenyl, and when R1 is phenyl, the nonaqueous solvent is Ethylene Carbonate (EC): diethyl carbonate (DEC) 30: 70;
when R1 is cyclohexenyl, the nonaqueous solvent is Ethylene Carbonate (EC): ethyl Methyl Carbonate (EMC) was 30: 70.
In one embodiment, the additive further comprises:
cyclic carbonates having carbon-carbon double bonds or carbon-carbon triple bond unsaturated bonds;
and/or cyclic carbonates substituted with fluorine atoms;
and/or cyclic sultones;
and/or cyclic sultones.
In one embodiment, the cyclic carbonate having a carbon-carbon double bond or a carbon-carbon triple bond unsaturated bond is selected from Vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), or a combination thereof;
the cyclic carbonate substituted with fluorine atom is selected from fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), or a combination thereof;
the cyclic sulfated lactone is selected from vinyl sulfate (DTD), propylene sulfate lactone, or a combination thereof;
the cyclic sulfonic acid includes 1, 3-Propane Sultone (PS), 1, 4-butane sultone, propenyl-1, 3-sultone, or a combination thereof.
In one embodiment, the additive further comprises lithium difluorophosphate.
In one embodiment, the content of the compound represented by the general formula (I) is 0.1 to 10.0%.
In one embodiment, the content of the compound represented by the general formula (I) is 1.0% to 5.0%.
In one embodiment, the content of the cyclic carbonate having carbon-carbon double bond or carbon-carbon triple bond unsaturated bond is 0.01-10.00% by mass;
the mass percentage content of the fluorine atom substituted cyclic carbonate is 0.1-10.0%;
the mass percentage content of the cyclic sulfuric acid lactone is 0.1-10.0%;
the content of the cyclic sultone is 0.1-10.0% by mass.
In one embodiment, the content of the cyclic carbonate having carbon-carbon double bond or carbon-carbon triple bond unsaturated bond is 0.1-3.0 wt%;
the mass percentage content of the cyclic carbonate substituted by fluorine atoms is 0.5-5.0%;
the mass percentage content of the cyclic sulfuric acid lactone is 0.5-5.0%;
the mass percentage of the cyclic sultone is 0.5-5.0%.
In one embodiment, the content of the cyclic carbonate having carbon-carbon double bond or carbon-carbon triple bond unsaturated bond is 0.2-2.0 wt%;
the mass percentage content of the fluorine atom substituted cyclic carbonate is 1.0-2.0%;
the mass percentage content of the cyclic sulfuric acid lactone is 1.0-2.0%;
the mass percentage of the cyclic sultone is 1.0-2.0%.
In one embodiment, the lithium difluorophosphate is 0.01 to 10 mass percent.
In one embodiment, the lithium difluorophosphate is 0.1 to 5 mass percent.
In one embodiment, the water content in the nonaqueous electrolytic solution is not greater than 60 mg/l.
In one embodiment, the water content in the nonaqueous electrolytic solution is not greater than 35 mg/l.
In one embodiment, the water content in the nonaqueous electrolytic solution is not greater than 10 mg/l.
In one embodiment, the lithium salt includes LiPF6。
In one embodiment, the lithium salt is 0.1-50% by mass.
In one embodiment, the lithium salt is 0.1-10% by mass.
An embodiment of the present invention also provides an electricity storage device including a positive electrode, a negative electrode, a separator, and the above-described nonaqueous electrolytic solution.
In one embodiment, the positive electrode includes a positive electrode active material including a lithium-containing olivine-type phosphate or a composite metal oxide of lithium and at least one element selected from cobalt, manganese, and nickel.
In one embodiment, the negative electrode includes a negative electrode active material including at least one selected from the group consisting of lithium metal, a lithium alloy, a carbon material capable of deintercalating lithium, tin, a stannide, silicon, a silicon compound, and a lithium titanate compound as the negative electrode active material.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the embodiments of the present invention will be described in detail below. However, it will be appreciated by those of ordinary skill in the art that numerous technical details are set forth in order to provide a better understanding of the present application in various embodiments of the present invention. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments.
The nonaqueous electrolytic solution is characterized by comprising a nonaqueous solvent, a lithium salt and an additive, wherein the additive comprises an unsaturated cyclic group-containing isocyanate compound represented by the general formula (I).
Wherein R1 is selected from aralkyl with 7 to 13 carbon atoms, aryl with 6 to 12 carbon atoms and unsaturated ring with 5 to 12 carbon atoms, wherein, at least one hydrogen atom in the aralkyl with 7 to 13 carbon atoms, the aryl with 6 to 12 carbon atoms and the unsaturated ring with 5 to 12 carbon atoms can be substituted by halogen and/or alkyl with 1 to 4 carbon atoms.
The content of the unsaturated cyclic group-containing isocyanate compound represented by the general formula (I) in the nonaqueous electrolytic solution described in the present invention is in the range of 0.1 to 10.0%, preferably 1.0 to 5.0%, more preferably 0.01 to 5.00%, from the viewpoints of the advantageous effects of electrode film formation, electrode performance improvement, gas suppression of a battery, and life extension.
Further, there are 2 preferred embodiments of the nonaqueous electrolytic solution of the present invention.
[ MEANS FOR solving PROBLEMS ] A method for producing a catalyst
The first embodiment is an embodiment in which R1 is an aromatic group as the unsaturated cyclic group-containing isocyanate compound represented by the general formula (I).
More specifically, a nonaqueous electrolytic solution comprising a nonaqueous solvent, a lithium salt and an additive, wherein the additive comprises a compound of the following formula (I-1):
wherein at least one hydrogen atom on the phenyl group may be substituted with a halogen or an alkyl group having 1 to 4 carbon atoms, and at least one hydrogen atom on the aforementioned alkyl group having 1 to 4 carbon atoms may be substituted with an alkyl group having 1 to 4 carbon atoms.
[ MEANS FOR SECOND ]
Embodiment 2 is an embodiment in which R1 is cyclohexenyl or cyclohexadienyl as the unsaturated cyclic group-containing isocyanate compound represented by the above general formula (I).
More specifically, the nonaqueous electrolytic solution comprises a nonaqueous solvent, a lithium salt and an additive, wherein the additive comprises a compound shown in the formula:
wherein at least one hydrogen atom on the cyclohexenyl group or cyclohexadienyl group may be substituted with a halogen or an alkyl group having 1 to 4 carbon atoms, and at least one hydrogen atom on the aforementioned alkyl group having 1 to 4 carbon atoms may be substituted with an alkyl group having 1 to 4 carbon atoms.
The first mode is that the beneficial effects of film formation of the battery electrode, improvement of the electrode performance, gas inhibition of the battery and service life extension are based on the structural characteristics of unsaturated cyclic isocyanate, and the first mode has the effects of inhibiting the generation of bubbles and prolonging the service life of the battery according to the action mechanism that a product acted with solvent carbonate under high potential is polymerized and deposited on the surface of the positive electrode to form a passivation layer.
The second mode is that the beneficial effects of film formation of the battery electrode, improvement of the electrode performance, gas inhibition of the battery and service life extension are based on the structural characteristics of the unsaturated cyclic isocyanate, and the second mode has the effects of inhibiting the generation of bubbles and prolonging the service life of the battery according to the action mechanism that the product under the action of high potential and solvent carbonate is polymerized and deposited on the surface of the positive electrode to form a passivation layer.
In addition, in another embodiment of the invention, the nonaqueous electrolyte additive also comprises cyclic carbonate with carbon-carbon double bond or carbon-carbon triple bond unsaturated bond, and/or cyclic carbonate substituted by fluorine atom, and/or cyclic sultone.
As the cyclic carbonate having a carbon-carbon double bond or a carbon-carbon triple bond, the following are suitably listed: vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), and the like, and these cyclic carbonates having a carbon-carbon double bond or a carbon-carbon triple bond may be used in combination.
The cyclic carbonate substituted with a fluorine atom includes the following: fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), and the like, and cyclic carbonates substituted with these fluorine atoms may be used in combination.
Suitable cyclic sulfuric acid lactones include the following: vinyl sulfate (DTD), propylene sulfate lactone, and the like, and these cyclic sulfuric acid lactones may be used in combination.
Suitable examples of cyclic sultones include the following: 1, 3-Propane Sultone (PS), 1, 4-butane sultone, propenyl-1, 3-sultone, etc., and these cyclic sultones may be used in combination.
Based on the beneficial effects of electrode film formation, electrode performance improvement, gas inhibition of the battery and service life extension, the mass percentage content range of the cyclic carbonate with carbon-carbon double bonds or carbon-carbon triple bonds in the non-aqueous electrolyte described by the invention is as follows: 0 to 10.0%, preferably 1.0 to 5.0%, more preferably 0.01 to 5.00%.
The content of the fluorine atom-substituted cyclic carbonate is 0 to 10.0% by mass, preferably 0.1 to 3.0% by mass, and more preferably 0.2 to 2.0% by mass.
The content of the cyclic sultone is 0 to 10.0% by mass, preferably 0.5 to 5.0% by mass, and more preferably 1.0 to 2.0% by mass.
The content of the cyclic sultone is 0 to 10.0% by mass, preferably 0.5 to 5.0% by mass, and more preferably 1.0 to 2.0% by mass.
The content of the unsaturated cyclic group-containing isocyanate compound represented by the general formula (I) is 0.1 to 10.0%, preferably 0.5 to 5.0%, more preferably 1.0 to 2.0%.
In addition, in another embodiment of the present invention, the nonaqueous electrolyte additive further includes lithium difluorophosphate.
Based on the beneficial effects of electrode film formation, electrode performance improvement, gas suppression of the battery and service life extension, the mass percentage content of the lithium difluorophosphate in the non-aqueous electrolyte is 0.01-10%, preferably 0.1-5%, and more preferably 0.5-2%.
[ non-aqueous solvent ]
The nonaqueous solvent used in the nonaqueous electrolytic solution of the present invention may suitably be one or two or more selected from cyclic carbonates, chain esters, lactones, ethers, and amides. The resin composition preferably contains a chain ester, more preferably contains a chain carbonate, and most preferably contains both a cyclic carbonate and a chain carbonate.
The cyclic carbonates include the following: ethylene Carbonate (EC), Propylene Carbonate (PC);
the chain carbonates include the following: carbonates such as methyl ethyl carbonate (EMC), diethyl carbonate (DEC) and dimethyl carbonate (DMC).
When the isocyanate compound containing an unsaturated cyclic group represented by the general formula (I) of the present invention,
when R1 is phenyl, a preferred nonaqueous solvent system is Ethylene Carbonate (EC): diethyl carbonate (DEC) is mixed in a volume ratio, most preferably Ethylene Carbonate (EC) is mixed with diethyl carbonate (DEC) in a volume ratio EC: DEC of 30: 70.
When the isocyanate compound containing an unsaturated cyclic group represented by the general formula (I) of the present invention,
when R1 is cyclohexenyl, a preferable nonaqueous solvent system is Ethylene Carbonate (EC): ethyl Methyl Carbonate (EMC) is mixed in a volume ratio, most preferably Ethylene Carbonate (EC) is mixed with diethyl carbonate (DEC) in a volume ratio EC: DEC of 30: 70.
[ lithium salt ]
The electrolyte salt used in the present invention includes the following lithium salts.
The lithium salt includes the following: LiPF6、LiBF4、LiClO4、LiAsO4LiTFSI, LiFSI, preferably LiPF6。
[ preparation of nonaqueous electrolyte ]
One preparation method of the nonaqueous electrolyte solution is as follows: dissolving lithium salt in non-aqueous solvent, adding additive, mixing and stirring uniformly. Wherein the additive comprises an unsaturated cyclic group-containing isocyanate compound represented by the general formula (I):
wherein R1 is selected from one or more of aralkyl with 7 to 13 carbon atoms, aryl with 6 to 12 carbon atoms, unsaturated ring with 5 to 12 carbon atoms, wherein at least one hydrogen atom in the aralkyl with 7 to 13 carbon atoms, the aryl with 6 to 12 carbon atoms and the unsaturated ring with 5 to 12 carbon atoms can be substituted by halogen and/or alkyl with 1 to 4 carbon atoms, cyclic carbonate with carbon-carbon double bond or carbon-carbon triple bond unsaturated bond, cyclic carbonate substituted by fluorine atom, cyclic sultone and lithium difluorophosphate.
In the nonaqueous electrolytic solution, the required components may be added in the following mass percentage ratios. The isocyanate compound containing unsaturated cyclic groups described in the invention is 0.1-10% by mass, the cyclic carbonate with carbon-carbon double bonds or carbon-carbon triple bond unsaturated bonds is 0-10% by mass, the cyclic carbonate substituted by fluorine atoms is 0-10% by mass, the cyclic sultone is 0-10% by mass, the lithium difluorophosphate is 0-10% by mass, the lithium salt is 0.1-50% by mass, the solvent proportion is 50-99% by mass, and the sum of the mass fractions of all components is 100%.
The physical property index of the non-aqueous electrolyte after being mixed uniformly is measured and is in the following range:
conductivity (mS/cm) | Water content (ppm) | |
Characteristic value | 8.3 | 10.2 |
Range | 6-9 | ≤35 |
[ 1 st electric storage device ]
The electricity storage device described in the present invention includes a generic name of a lithium primary battery and a secondary battery, and is not limited to only a lithium secondary battery.
The lithium battery of the present invention comprises a positive electrode, a negative electrode, a separator and the nonaqueous electrolytic solution. Components other than the nonaqueous electrolytic solution, such as a positive electrode and a negative electrode, may be used without particular limitation.
The positive electrode active material of the power storage device described in the present invention may be a lithium-containing composite oxide. Specific examples of the lithium-containing composite oxide include LiMnO2、LiFeO2、LiMn2O4、Li2FeSiO4LiNi1/3Co1/3Mn1/ 3O2、LiNi5CO2Mn3O2、LizNi(1-x-y)CoxMyO2(x, y and z are values satisfying 0.01. ltoreq. x.ltoreq.0.20, 0. ltoreq. y.ltoreq.0.20, and 0.97. ltoreq. z.ltoreq.1.20, M represents at least one element selected from Mn, V, Mg, Mo, Nb and Al), LiFePO4And LizCO(1-x)MxO2(x and z are values satisfying 0. ltoreq. x.ltoreq.0.1 and 0.97. ltoreq. z.ltoreq.1.20, M represents at least one element selected from the group consisting of Mn, Ni, V, Mg, Mo, Nb, and Al).
Since the additive for nonaqueous electrolytic solution of the present embodiment can effectively cover the surface, the positive electrode active material may be LizNi(1-x-y)CoxMyO2(x, y and z are values satisfying 0.01. ltoreq. x.ltoreq.0.15, 0. ltoreq. y.ltoreq.0.15, and 0.97. ltoreq. z.ltoreq.1.20, M represents at least one element selected from the group consisting of Mn, Ni, V, Mg, Mo, Nb and Al) or LizCO(1-x)MxO2(x and z are values satisfying 0. ltoreq. x.ltoreq.0.1 and 0.97. ltoreq. z.ltoreq.1.20, and M represents at least one element selected from Mn, V, Mg, Mo, Nb, and Al). In particular, when a positive electrode active material having a high Ni ratio, such as LizNi (1-x-y) CoxMyO2 (where x, y, and z are values satisfying 0.01. ltoreq. x.ltoreq.0.15, 0. ltoreq. y.ltoreq.0.15, and 0.97. ltoreq. z.ltoreq.1.20, and M represents at least one element selected from the group consisting of Mn, Ni, V, Mg, Mo, Nb, and Al), is used, gas generation tends to be easily generated, but even in this case, gas generation can be effectively suppressed by the combination of the above-described electrolyte components.
As the negative electrode active material of the power storage device described in the present invention, a material capable of inserting and extracting lithium is used as the negative electrode active material. Including, but not limited to, carbon materials such as crystalline carbon (natural graphite, artificial graphite, and the like), amorphous carbon, carbon-coated graphite, and resin-coated graphite, and oxide materials such as indium oxide, silicon oxide, tin oxide, lithium titanate, zinc oxide, and lithium oxide. The negative electrode active material may also be lithium metal or a metal material that can form an alloy with lithium. Specific examples of metals that can be alloyed with lithium include Cu, Sn, Si, Co, Mn, Fe, Sb, and Ag. Binary or ternary alloys containing these metals and lithium may also be used as the negative electrode active material. These negative electrode active materials may be used alone, or two or more of them may be used in combination. From the viewpoint of high energy density, a carbon material such as graphite and an Si-based active material such as Si, an Si alloy, and an Si oxide may be combined as the negative electrode active material. From the viewpoint of both cycle characteristics and high energy density, graphite and an Si-based active material may be combined as the negative electrode active material. In the combination, the ratio of the mass of the Si-based active material to the total mass of the carbon material and the Si-based active material may be 0.5% to 95%, 1% to 50%, or 2% to 40%.
The battery separator is not particularly limited, and a single-layer or laminated microporous film, woven fabric, nonwoven fabric, or the like of polyolefin such as polypropylene or polyethylene can be used.
[ 2 nd electric storage device ]
The 2 nd power storage device of the present invention is an electric double layer capacitor that includes the nonaqueous electrolytic solution of the present invention and utilizes an interface between the electrolytic solution and an electrode. The power balance power supply and the vehicle starting power supply can be used as a hoisting device; the energy used as the traction energy of the vehicle can produce an electric automobile, replace the traditional internal combustion engine and transform the existing trolley bus; the energy storage device can be used as a pulse energy source of a laser weapon and can also be used as an energy storage source of other electromechanical equipment.
The unsaturated cyclic group-containing isocyanate compound represented by the general formula (I) of the present invention can be synthesized by the following method, but is not limited to this method.
Preparation of the phenyl isocyanate is exemplified:
aniline and CO are used as raw materials, the reaction is carried out in the presence of methanol, carboxyl is catalyzed and oxidized by a Pd-I compound catalyst to generate phenyl carbamate, and then phenyl isocyanate and alcohol are obtained through heating and decomposition.
[ preparation of lithium Secondary Battery ]
One of the preparation processes of the lithium secondary battery according to the present invention is given below, and it is to be understood that the method of preparing the lithium secondary battery is not limited thereto.
The first step is as follows: and (4) batching. The battery ingredients containing the non-aqueous electrolyte are mixed according to a certain proportion, and the material is stirred for 10 hours in a full-automatic way under high vacuum.
The second step is that: and (4) coating. And (3) adopting an automatic feeding system to uniformly coat the positive and negative pole pieces.
The third step: and (4) rolling the rolls. The positive and negative electrode materials are compacted by pressurization.
A fourth step of: and (6) slicing. According to the model of the battery, the positive and negative pole pieces are required to be cut into required widths.
The fifth step: and (4) tabletting and winding. And welding the positive and negative lugs on the positive and negative plates by using a full-automatic sheet making machine. And a full-automatic winding machine is adopted to wind the positive and negative pole pieces and the diaphragm into a cylindrical shape.
And a sixth step: and (5) dotting a bottom rolling groove and vacuum drying. The winding core is put into the steel shell, the negative pole lug is automatically welded, and the groove is automatically rolled. In addition, the mixture is baked at high vacuum and high temperature and dried to a small amount of moisture.
The seventh step: and (4) forming and grading. And performing charge and discharge tests on the sample.
Eighth step: and assembling the lithium battery.
The following lists experimental groups and experimental effect analysis, details the general experimental procedures.
To evaluate the excellent effect of the nonaqueous electrolytic solution of the present invention on the power storage device in the range described in the present invention, we tested the performance of the prepared battery as follows.
[ Battery Performance test ]
Each of the obtained nonaqueous electrolyte secondary batteries was charged to 4.2V at 25 ℃ with a current corresponding to 0.33C, and then aged while being kept at 45 ℃ for 24 hours. Then, at 25 ℃, the discharge was carried out to 2.8V with a current corresponding to 0.33C. Then, the battery was charged to 4.2V with a current corresponding to 0.233 and further discharged to 2.8V with a current corresponding to 0.33C, and this operation was repeated for 3 cycles to perform initial charge and discharge to stabilize the battery. Then, initial charge and discharge were performed by charging and discharging at a current corresponding to 1C, and the discharge capacity was measured. The obtained value is set as "initial capacity". Further, after the initial charge and discharge, the ac impedance was measured at 25 ℃ for the nonaqueous electrolyte secondary battery charged with a capacity of 50% of the initial capacity, and the obtained value was referred to as "initial resistance (Ω)".
[ measurement of discharge Capacity conservation Rate and resistance increase Rate ]
Each nonaqueous electrolyte secondary battery after initial charge and discharge was subjected to a charge-discharge cycle test, and 200 cycles were performed with a charge rate of 1C, a discharge rate of 1C, a charge termination voltage of 4.2V, and a discharge termination voltage of 2.8V. Then, the discharge capacity was measured by charging and discharging at 1C, and the obtained value was defined as "capacity after cycle". Further, after the cycle test, the ac impedance was measured in an environment at 25 ℃ for the nonaqueous electrolyte secondary battery charged with a capacity of 50% of the capacity after the cycle, and the obtained value was defined as "resistance (Ω) after the cycle". The discharge capacity retention rate and the resistance increase rate of each battery are shown in tables 2, 3, and 4. "discharge capacity retention rate" is represented by the formula: a value calculated by (capacity after cycle)/(initial capacity), "resistance increase rate" is represented by the formula: (resistance after cycle)/(initial resistance).
[ measurement of gas Generation ]
Unlike the batteries used for the evaluation of initial resistance, the evaluation of discharge capacity retention rate, and the evaluation of resistance increase rate, nonaqueous electrolyte secondary batteries of the same composition including each electrolyte of examples and comparative examples were prepared. The nonaqueous electrolyte secondary battery was charged to 4.2V at 25 ℃ with a current corresponding to 0.33C, and then aged while being kept at 45 ℃ for 24 hours. Then, at 25 ℃, the discharge was carried out to 2.8V with a current corresponding to 0.33C. Then, the battery was charged to 4.2V with a current corresponding to 0.33C, and further discharged to 2.8V with a current corresponding to 0.33C, and this operation was repeated for 3 cycles to perform initial charge and discharge, thereby stabilizing the battery. The volume of the nonaqueous electrolyte secondary battery after initial charge and discharge was measured by the archimedes method, and the obtained value was defined as "initial volume (cm3) of the battery". Further, the nonaqueous electrolyte secondary battery after initial charge and discharge was charged to 4.2V at 1C at 25 ℃ and then held at 60 ℃ for 168 hours. Then, it was cooled to 25 ℃ and discharged to 2.8V at 1C. Then, the volume of the nonaqueous electrolyte secondary battery was measured by the archimedes method, and the obtained value was defined as "volume after high-temperature storage (cm3) of the battery". The "gas generation amount" of each cell is shown. "gas generation amount" is represented by the formula: (volume after high-temperature storage) - (initial volume).
The present invention will be described in further detail with reference to the following examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Experimental procedures in the following examples, where no detailed conditions are indicated, are generally carried out according to conventional conditions, or according to conditions recommended by the manufacturer. Unless otherwise indicated, percentages and parts are by weight. The test materials and reagents used in the following examples are commercially available without specific reference.
A first embodiment of the present invention relates to a nonaqueous electrolytic solution. The core nonaqueous electrolyte additive of the present embodiment includes an unsaturated cyclic group-containing isocyanate compound represented by the general formula (I),
wherein R1 is phenyl. The following is a detailed description of the implementation of the present embodiment, and the following is provided only for the convenience of understanding and is not necessary to implement the present embodiment.
Ethylene Carbonate (EC) and diethyl carbonate (DEC) were mixed in a volume ratio of EC: DEC of 30:70 to obtain a mixed nonaqueous solvent.
LiPF is added to a concentration of 1.0mol/L6As an electrolyte, is dissolved in the mixed nonaqueous solvent.
A phenyl isocyanate compound, a vinylene carbonate compound (VC), fluoroethylene carbonate (FEC), and 1, 3-Propane Sultone (PS) were added to the obtained solution as additives for a nonaqueous electrolytic solution to prepare a nonaqueous electrolytic solution. The content of the phenyl isocyanate compound was 1.0%, the content of the vinylene carbonate compound (VC) was 0.2%, the content of the fluoroethylene carbonate (FEC) was 1.0%, the content of the 1, 3-Propane Sultone (PS) was 1.0%, and the content of the lithium difluorophosphate was 0.9%, based on the total amount of the nonaqueous electrolytic solution.
The positive electrode active material is LiNi0.8Co0.1Mn0.1O2And the negative electrode material is artificial graphite for preparing the lithium ion battery.
In other examples and comparative examples, a nonaqueous electrolytic solution and a lithium ion battery were prepared in the same manner as in the first embodiment, except that additives were used differently, as specifically shown in table 1 below:
TABLE 1
The test results of each example and comparative example are as follows:
the second embodiment of the present invention relates to a nonaqueous electrolytic solution, which has the same principle as the first embodiment, and is mainly different from the first embodiment in that phenyl isocyanate is replaced by cyclohexenyl isocyanate in the additive. The specific implementation mode is as follows:
ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC) were mixed at a volume ratio of EC: EMC of 30:70 to obtain a mixed nonaqueous solvent.
LiPF is added to a concentration of 1.0mol/L6As an electrolyte, is dissolved in the mixed nonaqueous solvent.
Cyclohexenylisocyanate, vinylene carbonate compound (VC), fluoroethylene carbonate (FEC), and 1, 3-Propane Sultone (PS) were added to the obtained solution as additives for a nonaqueous electrolytic solution to prepare a nonaqueous electrolytic solution. Based on the total amount of the nonaqueous electrolytic solution, the content of the cyclohexenyl isocyanate compound was 1.0%, the content of the vinylene carbonate compound (VC) was 0.2%, the content of the fluoroethylene carbonate (FEC) was 1.0%, the content of the 1, 3-Propane Sultone (PS) was 1.0%, and the content of the lithium difluorophosphate was 1.0%.
The positive electrode active material is LiNi0.8Co0.1Mn0.1O2And the negative electrode material is artificial graphite for preparing the lithium ion battery.
In other examples and comparative examples, a nonaqueous electrolytic solution and a lithium ion battery were prepared in the same manner as in the second embodiment, except that additives were used differently, as specifically shown in the following table 2:
TABLE 2
The test results of each example and comparative example are as follows:
by combining the test results of the first embodiment and the second embodiment of the present invention, it can be seen that
1) The additive for the non-aqueous electrolyte is added, wherein the additive comprises an isocyanate compound containing an unsaturated cyclic group and represented by a general formula (I),
in the formula, R1 is a six-membered ring group, the ring unsaturation degree is 1 to 3, especially phenyl and cyclohexenyl, which can significantly reduce the increase rate of the battery resistance and greatly reduce the gas generation amount, thereby achieving the effect of prolonging the battery life.
2) The additive for the non-aqueous electrolyte is added, wherein the additive comprises an isocyanate compound containing an unsaturated cyclic group and represented by a general formula (I),
wherein R1 is six-membered ring group, the ring unsaturation degree is 1 to 3, especially phenyl, cyclohexenyl, vinyl sulfate (DTD), vinylene carbonate compound (VC), fluoroethylene carbonate (FEC), 1, 3-Propane Sultone (PS), the additive generates synergistic action, which can further reduce gas generation amount and prolong the service life of the battery.
In addition, the inventors have found in their research that the addition of different types of additives to different solvents results in significantly different chemical and electrochemical stability of the battery system.
On the basis of the above, the present inventors have conducted a large number of screening experiments for combinations of solvents and additives.
The third embodiment of the present invention relates to a nonaqueous electrolytic solution, which has the same basic principle as the first embodiment, and is mainly distinguished in that a nonaqueous electrolytic solution system is prepared as shown in table 3:
TABLE 3
The test results of each example are shown in table 4:
TABLE 4
The fourth embodiment of the present invention relates to a nonaqueous electrolytic solution, which has the same basic principle as the second embodiment, and is mainly distinguished in that a nonaqueous electrolytic solution system is prepared as shown in table 5:
TABLE 5
The test results for each example are shown in table 6:
TABLE 6
By combining the test results of the third embodiment and the fourth embodiment of the present invention, it can be seen that
1) Ethylene Carbonate (EC): the addition of the additive package of example 1 of the present invention to a 30:70 nonaqueous solvent system of diethyl carbonate (DEC) resulted in the lowest gas generation.
2) Ethylene Carbonate (EC): the additive combination of example 3 of the present invention was added to a non-aqueous solvent system having 30:70 Ethyl Methyl Carbonate (EMC) to minimize gas generation.
It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in practice.
Claims (7)
1. A nonaqueous electrolytic solution comprising a nonaqueous solvent, a lithium salt and an additive, wherein the additive comprises an unsaturated cyclic group-containing isocyanate compound represented by the general formula (I),
wherein R1 is cyclohexenyl;
the nonaqueous solvent in the nonaqueous electrolyte comprises Ethylene Carbonate (EC) and/or Ethyl Methyl Carbonate (EMC) and/or Propylene Carbonate (PC) and/or diethyl carbonate (DEC);
the additive further comprises: vinyl sulfate, vinylene carbonate, fluoroethylene carbonate and 1, 3-propane sultone.
2. The nonaqueous electrolytic solution of claim 1, wherein the additive further comprises 0.01-10% by mass of lithium difluorophosphate.
3. The nonaqueous electrolytic solution of claim 1, wherein the content of the unsaturated cyclic group-containing isocyanate compound represented by the general formula (I) in the nonaqueous electrolytic solution is 0.1 to 10.0% by mass.
4. The nonaqueous electrolytic solution of claim 1, wherein the Vinylene Carbonate (VC) is contained in an amount of 0.01 to 10.00% by mass;
the fluoroethylene carbonate (FEC) accounts for 0.1-10.0% by mass;
the mass percentage content of the vinyl sulfate is 0.1-10.0%;
the mass percentage of the 1, 3-propane sultone is 0.1-10.0%.
5. An electricity storage device characterized by comprising a positive electrode, a negative electrode, a separator, and the nonaqueous electrolytic solution according to any one of claims 1 to 4.
6. The power storage device according to claim 5, wherein the positive electrode includes a positive electrode active material that includes a lithium-containing olivine-type phosphate or a composite metal oxide of lithium and at least one element selected from cobalt, manganese, and nickel.
7. The power storage device according to claim 5, wherein the negative electrode includes a negative electrode active material that includes at least one selected from the group consisting of lithium metal, a lithium alloy, a carbon material capable of deintercalating lithium, tin, a tin compound, silicon, a silicon compound, and a lithium titanate compound as a negative electrode active material.
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