CN107666011B

CN107666011B - Non-aqueous electrolyte and non-aqueous electrolyte secondary battery

Info

Publication number: CN107666011B
Application number: CN201610615091.9A
Authority: CN
Inventors: 申大卫; 钮博翔; 费震宇; 李林峰; 聂云华; 郑卓群
Original assignee: Microvast Power Systems Huzhou Co Ltd
Current assignee: Weihong Advanced Materials Co
Priority date: 2016-07-28
Filing date: 2016-07-28
Publication date: 2020-07-28
Anticipated expiration: 2036-07-28
Also published as: CN107666011A

Abstract

The present invention relates to a nonaqueous electrolyte solution and a nonaqueous electrolyte secondary battery; in particular to a nonaqueous electrolyte solution and a nonaqueous electrolyte secondary battery using carboxylic ester as a main solvent. A non-aqueous electrolyte comprises a solvent, an additive, an alkali metal salt and chain carboxylic ester with a special structure; the chain carboxylate of the present invention can be used as a main solvent in a nonaqueous electrolytic solution; and is particularly suitable for a nonaqueous secondary battery in which the negative electrode material is an alkali metal transition metal composite oxide or a transition metal oxygen/sulfur/nitride.

Description

Non-aqueous electrolyte and non-aqueous electrolyte secondary battery

Technical Field

The present invention relates to a nonaqueous electrolyte solution and a nonaqueous electrolyte secondary battery; in particular to a nonaqueous electrolyte solution and a nonaqueous electrolyte secondary battery using carboxylic ester as a main solvent.

Background

The non-aqueous electrolyte secondary battery is widely used for notebook computers, mobile phones, wearable equipment and the like, and is now widely used in the electric automobile industry, wherein L iPF is common non-aqueous electrolyte₆A system of mixed carbonate solvents; wherein the carbonate solvent is mainly a mixed solvent composed of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and Ethyl Methyl Carbonate (EMC). The EC dielectric constant in the carbonate solvent is large, so that lithium salt can be fully dissolved or ionized, and the conductivity of the electrolyte can be improved; EC thermal stability is high, and the EC can be decomposed after being heated to more than 200 ℃; the EC can form an SEI film on the surface of a carbon-based (particularly graphite) electrode, so that the charge-discharge efficiency of the battery is improved, and the cycle life of the battery is prolonged. The EC has high viscosity and high melting point (m.p.36.4 ℃), and can obtain excellent performance when being mixed with linear carbonate (DMC, EMC, DEC and the like) with low viscosity and low melting point to meet the application requirement of the secondary battery.

In the development of lithium secondary batteries, the negative electrode material is mainly a carbon-based material. Carbonate solvents are suitable for chemically inert carbon-based materials, sinceRecently, alkali metal transition metal composite oxides or transition metal oxides have attracted interest as anode materials, L i₄Ti₅O₁₂Is the only commercial material at present, and the potential of the material is about 1.55V (vs. L i/L i)⁺) The lithium ion diffusion coefficient was 2 × 10^-8cm²L i, an order of magnitude higher than conventional carbon-based materials₄Ti₅O₁₂The charge and discharge platform is stable, under the condition of high-rate charge and discharge, lithium ions are not easy to precipitate on the surface of the material, and L i₄Ti₅O₁₂Is a zero strain material, the crystal is very stable, although slight change occurs, but unlike the aforementioned carbon material (graphite), structural damage due to back-and-forth expansion and contraction of the electrode material during charge and discharge can be avoided, thereby having superior cycle performance, however, L i₄Ti₅O₁₂Besides the defects of low theoretical specific capacity (only 175mAh/g), low output voltage of the full battery and the like, the battery also has the defect of 'gas production' which influences the large-scale application of the battery. TiO 2₂、NiO、MoO₂、MoO₃、V₂O₅、Co₃O₄、CoO、Fe₃O₄、Fe₂O₃、FeO、Cu₂O, CuO, two materials based on vanadium have recently attracted interest in finding an ideal negative electrode material.chinese patent (CN 101154725B) discloses L iVO₂A new generation of anode material L i is firstly reported by Zhouhou cautions et al (Adv. EnergyMater.2013,3,428-₃VO₄. At present, research on lithium vanadium oxide materials is focused on modification of the materials, and no detailed report on compatibility/matching exploration with electrolytes is found. The experimental results of researchers of the invention show that the carbonate solvent is not suitable for being applied to the vanadium-based negative electrode material, and has the defects of large internal resistance, poor rate performance, unstable cycle and the like of a secondary battery. Different from carbon materials, the alkali metal transition metal composite oxide or the transition metal oxide is repeatedly desorbed in lithium ionWith accompanying change of valence state of transition metal during intercalation, e.g. Ti⁴⁺With Ti³⁺、V⁵ ⁺And V⁴⁺、V⁴⁺And V³⁺、Mo⁴⁺And Mo³⁺、Co³⁺And Co²⁺、Fe³⁺With Fe²⁺Interconversion between them. Carbon materials, which are composed mainly of carbon elements, have little oxidation or catalytic action on organic solvents and can be considered as chemically inert; transition metal elements such as Ti, V and Mo, which are in a high valence state, are highly oxidizable and, even in a low valence state, have catalytic decomposition or catalytic polymerization, which is complicated. The molecular structure determines the carbonate solvent, especially cyclic carbonates, which are not resistant to catalysis, and which are prone to decomposition on the surface of the active transition metal, releasing gases such as H₂、CO₂、CH₄、C₂H₆And the like. Gas is generated on the surface of the electrode, and the battery bulges and the internal resistance are increased (the physical distance between the positive electrode and the negative electrode is increased), so that the performance of the battery is deteriorated.

Besides the modification of the material itself, the search for the electrolyte matching with the material is also an important means for overcoming the bottleneck of the prior art. The present inventors have been working on finding an ideal nonaqueous electrolyte solvent to replace the carbonate solvent. The carboxylate solvent has a high dielectric constant and a low viscosity, and can significantly improve the low-temperature output characteristics of the secondary battery (j. electrochem. soc.,157(12) a1361-a1374 (2010)). However, it is usually mixed with the carbonate and the amount used in the mixing is relatively small, i.e., the carbonate solvent still predominates. The used carboxylic ester comprises micromolecular solvents such as methyl formate, ethyl acetate, methyl butyrate, ethyl propionate and methyl propionate, and the like, has a low boiling point and has poor high-temperature performance. The most interesting cyclic carboxylic ester is gamma-butyrolactone, the melting point of which is-43.5 ℃, the boiling point of which is 204 ℃, the liquid path is wide, and the prepared electrolyte can also obtain the conductivity equivalent to that of carbonate, but the gamma-butyrolactone can not be widely applied to the field of secondary batteries except for being used in primary batteries. The above shows that the use of a carboxylate solvent as a main solvent in a nonaqueous electrolyte secondary battery is still insufficient.

Disclosure of Invention

In order to solve the above technical problems, the present invention provides a nonaqueous electrolytic solution comprising a solvent and an alkali metal salt, characterized in that: the solvent comprises chain carboxylic ester with the following structure:

wherein R is selected from hydrocarbyl; r' is selected from alkyl with 1-8 carbon atoms.

The commonly used carbonate solvents are generally 5, namely Ethylene Carbonate (EC), Propylene Carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC), and the composition of the 5 solvents is changed to almost form the electrolyte system of the commercial lithium ion secondary battery at present. However, carbonates are chemically intrinsically more active solvents, for example DMC is a common methylating agent, which, under catalysis, gives a methyl substituent with the simultaneous release of the leaving methoxy and CO groups₂. In contrast, carboxylic acid esters are much less capable of alkylation and are generally used less frequently as alkylating agents. Up to now, carbonate has an irreplaceable position as a solvent of an electrolyte of a lithium ion secondary battery because, on the one hand, its electrochemical performance is excellent and, on the other hand, a chemically inert carbon-based material is dominant as a negative electrode active material. With the rise of alkali metal transition metal composite oxides and transition metal oxides as negative electrode active materials, nonaqueous electrolytes using carbonates as the main solvent have revealed a number of problems. The phenomena of more side reactions, gas generation of the battery, short cycle life and the like generally exist.

Compared with carbonate solvents, the carboxylate solvents are various in types and molecular structures, and can be prepared into electrolytes with various properties. The carboxylate has a high dielectric constant, a low viscosity, and a lower melting point than carbonate, and the low-temperature characteristics of the non-aqueous electrolyte can be improved by adding a small amount of the carboxylate, and is a second type of commercialized solvent other than carbonate solvents. Nevertheless, carboxylic acid esters are also used only as auxiliary solvents, and carbonates are the main solvents. The carboxylic acid esters used for improving the low-temperature characteristics are generally limited to small-molecule solvents such as methyl formate, ethyl acetate, methyl butyrate, ethyl propionate, and methyl propionate. The carboxylic ester has a plurality of varieties, has an industrial production basis, is cheaper than the carbonic ester, and provides a larger space for optimizing the electrolyte formula. The researchers of the invention find that the molecular structure of the carboxylate solvent has great influence on the electrolyte performance. For example, butyl acetate and ethyl hexanoate differ greatly in their ability to dissolve electrolyte salts; for another example, the viscosity of the electrolyte prepared from the isomers with the same molecular weight, namely methyl pivalate and butyl acetate, is greatly different.

If the carbon atoms connected with R' in the chain carboxylic ester are substituted by alkyl, secondary or tertiary carbenium ions are easily formed in the electrochemical process to promote the decomposition of carboxylic ester molecules; furthermore, carbocation stability: tertiary carbocation > secondary carbocation > primary carbocation, the more stable the carbocation is, therefore, the better the leaving group. Under electrochemical conditions, when the carbonyl group in the carboxylate molecule is attacked, the alkyl group is preferably a primary alkyl group in order to avoid the cleavage of the alkoxy group (the cleavage of the bond between the alkyl group and oxygen). In addition, if the carbon atom connected with R' is substituted by other alkyl, the carboxylic ester solvent has high viscosity (slow molecular movement speed) due to steric hindrance effect, and is injected into a battery to prepare an electrolyte, which is not favorable for the rate performance of the battery. The molecular structure of the preferred carboxylate is an important research content for developing a carboxylate-based electrolyte. According to the test results of the embodiment of the invention, the carboxylate with the special structure is matched with the negative electrode material graphite, the intermediate phase carbon, the amorphous carbon, the silicon-based material, the tin-based material, the transition metal oxide, the transition metal sulfide and the alkali metal transition metal composite oxide, especially the alkali metal transition metal composite oxide, so that excellent comprehensive performance of the battery can be obtained.

In the chain carboxylate provided by the invention, R can be selected from a hydrocarbon group with 1-20 carbon atoms, R 'is selected from a hydrocarbon group with a branched chain or without a branched chain with 1-8 carbon atoms, preferably, R' is selected from a hydrocarbon group with 3-8 carbon atoms, preferably, R is selected from a hydrocarbon group with a branched chain or without a branched chain with 1-7 carbon atoms, preferably, the total number of carbon atoms in the R and R 'groups is more than or equal to 3 and less than or equal to 10, further preferably, the total number of carbon atoms in the R and R' groups is more than or equal to 4 and less than or equal to 8, under the premise that the molecular weight is equivalent, the α -site carbon of the secondary carboxylate and the tertiary carboxylate have substituent groups, and the viscosity is higher due to steric hindrance effect, so that the primary carboxylate is preferred, namely, no substituent group exists on α -site carbon.

The chain carboxylate of the present invention can be used as a main solvent in a nonaqueous electrolytic solution; the volume of the chain carboxylic ester is preferably 70-100% of the total volume of the solvent; further preferably, the volume of the chain carboxylic ester is 85 to 100 percent of the total volume of the solvent; more preferably, the volume of the chain carboxylic ester is 90 to 100% of the total volume of the solvent. In another embodiment, the volume of the chain carboxylate is 70 to 95% of the total volume of the nonaqueous electrolytic solution. More preferably, the volume of the chain carboxylate is 85% to 95% of the total volume of the nonaqueous electrolytic solution. More preferably, the volume of the chain carboxylate is 90 to 95% of the total volume of the nonaqueous electrolytic solution.

In a preferred embodiment, the chain carboxylate is selected from methyl n-octanoate, ethyl n-octanoate, methyl n-hexanoate, ethyl n-hexanoate, propyl n-hexanoate, butyl n-hexanoate, isobutyl n-hexanoate, methyl pivalate, ethyl pivalate, propyl pivalate, butyl pivalate, isobutyl pivalate, n-pentyl pivalate, isoamyl pivalate, 2-methylbutanol pivalate, neopentyl pivalate, methyl butyrate, ethyl butyrate, n-propyl butyrate, n-butyl butyrate, isobutyl butyrate, n-pentyl butyrate, isoamyl butyrate, 2-methylbutanol butyrate, neopentyl butyrate, n-hexyl butyrate, methyl isobutyrate, ethyl isobutyrate, n-propyl isobutyrate, n-butyl isobutyrate, isobutyl isobutyrate, n-pentyl isobutyrate, isoamyl isobutyrate, 2-methylbutanol isobutyrate, neopentyl isobutyrate, At least one of n-hexyl isobutyrate, ethyl propionate, n-propyl propionate, n-butyl propionate, isobutyl propionate, n-pentyl propionate, isoamyl propionate, 2-methylbutanol propionate, neopentyl propionate, n-hexyl propionate, n-propyl acetate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, 2-methylbutanol acetate, neopentyl acetate, n-hexyl acetate, and n-octyl acetate.

The non-aqueous electrolyte may contain cyclic carboxylic acid ester in addition to linear carboxylic acid ester, and the solvent of the present invention may also contain cyclic carboxylic acid ester; the volume of the cyclic carboxylic ester is 0-50% of the total volume of the solvent. Preferably, the volume of the cyclic carboxylic ester is 0-30% of the total volume of the solvent. More preferably, the volume of the cyclic carboxylic ester is 10% to 30% of the total volume of the solvent. More preferably, the cyclic carboxylic acid ester is at least one selected from the group consisting of γ -butyrolactone, -valerolactone and-caprolactone.

In the non-aqueous electrolyte, the alkali metal salt is alkali metal lithium salt and/or alkali metal sodium salt, and the alkali metal lithium salt is selected from L iPF₆、LiBF₄、LiN(SO₂CF₃)₂、LiN(SO₂C₂F₅)₂、LiN(SO₂F)₂、LiPO₂F₂、LiCF₃SO₃、LiC(SO₂CF₃)₃、LiPF₃(CF₃)₃、LiPF₃(C₂F₅)₃、LiPF₃(iso-C₃F₇)₃、LiPF₅(iso-C₃F₇)、LiB(C₂O₄)₂、LiBF₂(C₂O₄) And L i₂B₁₂F₁₂At least one of (1); the alkali metal sodium salt is selected from NaPF₆、NaBF₄、NaN(SO₂CF₃)₂、NaN(SO₂C₂F₅)₂、NaN(SO₂F)₂、NaPO₂F₂、NaCF₃SO₃、NaC(SO₂CF₃)₃、NaPF₃(CF₃)₃、NaPF₃(C₂F₅)₃、NaPF₃(iso-C₃F₇)₃、NaPF₅(iso-C₃F₇)、NaBF₂(C₂O₄) And Na₂B₁₂F₁₂Preferably, the content of the alkali metal salt in the nonaqueous electrolytic solution is 0.5 mol/L to 3.0 mol/L, more preferably, the content of the alkali metal salt in the nonaqueous electrolytic solution is 0.8 mol/L to 2.5 mol/L, and still more preferably, the content of the alkali metal salt in the nonaqueous electrolytic solution is 0.9 mol/L to 1.5 mol/L.

In one embodiment, the solvent of the present invention further comprises at least one of a carbonate, a sulfite, a sulfonate, a sulfone, an ether, an organosilicon compound, an organoboron compound, a nitrile, an ionic liquid, and a phosphazene compound. Preferably, the solvent further comprises ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate, propylene methyl carbonate, propylene ethyl carbonate, phenol methyl carbonate, ethylene halo carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl methyl carbonate, ethylene sulfite, propylene sulfite, butylene sulfite, dimethyl sulfite, diethyl sulfite, sulfolane, dimethyl sulfoxide, ethylmethyl sulfoxide, 1, 3-propanesulfonate, 1, 4-butanesultone, dioxolane, dimethoxypropane, dimethyldimethoxysilane, pivalonitrile, valeronitrile, 2-dimethylvaleronitrile, ethoxypentafluorophosphazene, phenoxypentafluorophosphazene, N-methyl-N-butylpiperidine bis (trifluoromethylsulfonyl) imide salt and N-methyl-N- At least one propyl pyrrolidine bis (fluorosulfonyl) imide salt. Preferably, the carbonate includes cyclic carbonate and chain carbonate; the cyclic carbonate is at least one selected from ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate; the chain carbonate is at least one selected from dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

Preferably, the film-forming additive comprises an organic film-forming agent and/or an inorganic film-forming agent, the organic film-forming agent is selected from at least one of ionic liquid, sulfuric ester, sulfurous ester, sulfone, sulfoxide, sulfonic ester, carbonic ester, halogenated carbonic ester, carboxylic ester, halogenated carboxylic ester, phosphoric ester, halogenated phosphoric ester, phosphorous ester, halogenated phosphorous ester, unsaturated carbonic ester containing double bonds, nitrile, crown ether and organic boride, and the inorganic film-forming agent is selected from L iBOB, L iODBF, NaBOB, NaODBF, L i₂CO₃、Na₂CO₃、K₂CO₃And NH₄Further preferably, the organic film-forming agent is selected from at least one of Vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), phenyl ethylene carbonate (PhEC), phenyl vinylene carbonate (PhVC), Allyl Methyl Carbonate (AMC), Allyl Ethyl Carbonate (AEC), Ethylene Sulfite (ES), Propylene Sulfite (PS), dimethyl sulfite (DMS), diethyl sulfite (DES), 1, 3-propane sultone (1,3-PS), acrylonitrile (AAN), vinyl chlorocarbonate (ClEC), fluoroethylene carbonate (FEC), propylene carbonate Trifluoride (TFPC), bromo γ -butyrolactone (BrGB L), fluoro γ -butyrolactone (FGB L), Glutaric Anhydride (GA), and Succinic Anhydride (SA).

As one embodiment, the anti-overcharge additive of this invention comprises a redox shuttle additive and/or an electropolymerization additive. Preferably, the anti-overcharge additive comprises at least one of the following compounds:

in one embodiment, the flame retardant additive is at least one selected from the group consisting of phosphate esters, phosphonamides, phosphite esters, fluorophosphate esters, fluorophosphite esters, ionic liquids, and phosphazenes. Preferably, the flame retardant additive is selected from at least one of the following compounds:

wherein, X is₁，X₂，X₃，X₄，X₅，X₆Independently represent halogen OR independently represent OR_x；R_xRepresents a saturated aliphatic group with or without substituted hydrogen; or R_xRepresents a saturated aromatic group in which hydrogen is substituted or unsubstituted. The saturated aliphatic group or the saturated aromatic group may contain a halogen atom, a nitrogen atom, an oxygen atom, a sulfur atom, a silicon atom, or a boron atom.

As one embodiment, the conductive additive of the present invention includes at least one of a cationic ligand compound, an anionic ligand compound, and a neutral ligand compound; preferably, the conductive additive is selected from at least one of amines, crown ethers, cryptand compounds, fluoroalkyl borides, alkyl borides, and aza ethers.

In one embodiment, the wetting additive of the present invention is selected from at least one of quaternary ammonium surfactants, and carbonate compounds containing aromatic groups or long chain hydrocarbon groups. Preferably, the wetting additive is selected from methyl phenyl carbonate and/or bisoctyl carbonate.

In one embodiment, the mass of the additive is 0 to 15.0% of the mass of the nonaqueous electrolyte; preferably, the mass of the additive is 0-5.0% of the mass of the nonaqueous electrolyte; more preferably, the mass of the additive is 0 to 3.0% of the mass of the nonaqueous electrolytic solution. Preferably, the mass of the additive is 1.0-10.0% of the mass of the nonaqueous electrolytic solution.

The invention also provides a non-aqueous electrolyte secondary battery, which comprises a positive electrode, a negative electrode, a diaphragm and the non-aqueous electrolyte.

In one embodiment, the positive electrode material is at least one selected from the group consisting of lithium nickel cobalt manganese complex oxide, sodium nickel cobalt complex oxide, lithium nickel cobalt aluminum complex oxide, lithium manganese nickel complex oxide, olivine-type lithium phosphorus oxide, lithium cobalt oxide, sodium cobalt oxide, lithium manganese oxide, sodium manganese oxide, and sodium titanium nickel complex oxide.

In one embodiment, the negative electrode material is at least one selected from graphite, mesophase carbon, amorphous carbon, silicon-based material, tin-based material, transition metal oxide, transition metal sulfide, and alkali metal transition metal complex oxide. Preferably, the negative electrode material is selected from TiO₂、TiS₂、NiO、MoO₂、MoO₃、V₂O₅、Co₃O₄、CoO、Fe₃O₄、Fe₂O₃、FeO、Cu₂At least one of O and CuO.

Preferably, the negative electrode material is an alkali metal transition metal composite oxide, further preferably, the negative electrode material is selected from a lithium titanium oxide and/or a lithium vanadium oxide, further preferably, the negative electrode material is selected from a lithium titanium oxide and/or a modified lithium titanium oxide, the modification comprises doping and/or coating, and the modified lithium titanium oxide can be carbon-coated modified L i₄Ti₅O₁₂The mass of the carbon coating part is preferably 0.1-10.0% of the total mass of the anode material, and the modified lithium titanium oxide compound can also be L i doped with metal elements₄Ti₅O₁₂And/or metal element coated L i₄Ti₅O₁₂. The specific doping or cladding method is not limited, and other methods can be used to achieve the same effect as those described in the embodiments of the present invention.

As an embodiment, the doping or coating comprises employing at least one metal element pair L i of Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Al, Ga, In, Ge, Sn, Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Cd, W, L a, Ce, Nd, Sb and Sm₄Ti₅O₁₂And (5) carrying out modification treatment. Preferably, after doping or coatingThe metal element is in the form of metal oxide and L i₄Ti₅O₁₂The mass of the metal oxide is 0.1-49.0% of the total mass of the negative electrode material, for example, metal element Ti is selected to L i₄Ti₅O₁₂After coating, TiO is formed₂And L i₄Ti₅O₁₂In combination, the coating amount is in accordance with TiO₂Calculated as TiO₂The mass of the anode material is 0.1-49.0% of the total mass of the anode material.

As an embodiment, the titanium-based oxide for a negative electrode material of the present invention further comprises TiO₂-P₂O₅、TiO₂-V₂O₅、TiO₂-P₂O₅-SnO₂And TiO₂-P₂O₅-CuO, and the like.

In one embodiment, the negative electrode material of the present invention further includes a carbon material in addition to the lithium titanium oxide or the doped/coated modified lithium titanium oxide. The carbon material comprises graphite, mesophase carbon, soft carbon, hard carbon, graphene, vapor-grown carbon fiber and carbon black. The mass ratio of the lithium titanium oxide to the carbon material is (98:2) - (51: 49); preferably (90:10) to (70: 30).

As an embodiment, the metal sulfide used as the anode material of the present invention includes TiS₂、MoS₂、FeS、FeS₂Etc., metal nitrides such as L i_xCo_yN(0<x<4,0<y<0.5)。

As an embodiment, the separator is selected from a polyolefin melt-drawn separator; or the diaphragm is selected from at least one of polyethylene terephthalate, polyvinylidene fluoride, aramid fiber and polyamide as a base material; or the separator is selected from a separator coated with polyolefin on a high-softening-point porous base material; or the separator is selected from an inorganic solid electrolyte separator; or the separator is selected from an organic solid electrolyte separator; or the separator is selected from a composite separator in which an inorganic solid electrolyte is combined with an organic solid electrolyte. The high-softening-point porous base material refers to a porous base material with a softening point higher than 150 ℃.

The nonaqueous electrolyte secondary battery of the present invention is not limited to the binder, the conductive agent, and the like, and is not limited to the structure thereof, and is not limited to the manufacturing process thereof, except that the active material of the positive electrode material, the active material of the negative electrode material, the separator, and the nonaqueous electrolyte described in the present invention are used.

Drawings

FIG. 1 is a graph showing the cycle of a battery in example 4 of the present invention;

FIG. 2 is a graph showing the cycle of a battery according to example 11 of the present invention;

FIG. 3 is a comparison of the first charge curves of inventive example 15 and comparative example 7.

Detailed Description

The following specific examples are intended to describe the present invention in detail, but the present invention is not limited to the following examples.

The structure of the lithium ion secondary battery is not limited, and the lithium ion secondary battery can be cylindrical, square or button type, flexible package or steel shell or aluminum shell. In the embodiment of the invention, a laminated aluminum-plastic film flexible package battery is adopted, the design capacity is 10Ah, the diaphragm is a polyolefin melt-drawn diaphragm, and a button type half battery (2025 type) is also adopted.

The anode material of the 10Ah secondary battery adopts L iNi with high nickel content_0.5Co_0.2Mn_0.3O₂(NCM523), lithium cobaltate L iCoO₂And lithium manganate L iMn₂O₄(ii) a The negative electrode materials used were those exemplified in the examples.

As the conductive agent in the electrode sheet, for example, carbon, which may be amorphous carbon or crystalline carbon, including charcoal, coke, bone charcoal, sugar charcoal, activated carbon, carbon black, coke, graphitized mesocarbon microbeads (MCMB), soft carbon, hard carbon, graphite, and the like; the carbon can be carbon nano tube, graphite flake, fullerene, graphene and the like according to microstructure; from the aspect of micro morphology, the carbon can be carbon fiber, carbon tube, carbon sphere and the like. In the embodiment of the invention, one or more of graphene, VGCF, acetylene black and KS-6 are used. The binder plays a role of linking and fixing the positive electrode active material particles, and includes a hydrophilic polymer, that is, carboxymethyl cellulose (CMC), Methyl Cellulose (MC), Cellulose Acetate Phthalate (CAP), hydroxypropyl methyl cellulose (HPMC), hydroxypropyl methyl cellulose phthalate (HPMCP), polyvinyl alcohol (PVA), polyethylene oxide (PEO), and the like, and a hydrophobic polymer material, that is, a fluorine-based resin such as Polytetrafluoroethylene (PTFE), tetrafluoroethylene perfluoroalkyl vinyl ether copolymer (FEP), polyvinylidene fluoride (PVDF), polyethylene-tetrafluoroethylene copolymer (ETFE), and a rubber such as a vinyl acetate copolymer, styrene-butadiene block copolymer (SBR), acrylic modified SBR resin (SBR-based latex), and arabic rubber. PVDF was used in the examples of the present invention.

When evaluating the performance of the material and the electrolyte by using the button cell, mixing a negative electrode material, acetylene black serving as a conductive agent and polyvinylidene fluoride (PVDF) serving as a binder according to a mass ratio of 80:10:10, and adding N-methylpyrrolidone serving as a solvent to prepare slurry. The slurry was coated on an aluminum foil or a copper foil having a thickness of 20 μm, and then vacuum-dried at 120 ℃ and punched into a circular piece having a diameter of about 14mm to prepare an electrode. A sheet of lithium metal was used as the counter electrode. The separator was a porous polyethylene film with a thickness of 20 μm, assembled into a 2025 type button cell in an Ar-protected glove box. The preparation conditions and the battery test results referred to in the examples of the present invention are shown in tables 1 and 2.

Example 1

Electrolyte preparation

Preparing a non-aqueous mixed solvent of methyl pivalate (MTE, chain tertiary carboxylic ester) and Propylene Carbonate (PC) at a volume ratio of 70:30, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.3 mol/L.

Battery fabrication

The positive electrode material of the 10Ah laminated aluminum plastic film flexible package battery adopts L iNi_0.5Co_0.2Mn_0.3O₂(NCM523), negative electrode Material lithium titanium oxide L i₄Ti₅O₁₂(L TO), and a battery energy density at 1C discharge at ordinary temperature of about 85 Wh/kg.

Battery performance testing

(1) Under the condition of normal temperature, the flexible package battery is charged and discharged in the voltage range of 1.50V-2.80V, the constant current charging rate is 6C, the constant current discharging rate is 3C, and the high rate output characteristic and the charge-discharge cycle stability of the flexible package battery are examined.

(2) The flexible package battery is fully charged according to the multiplying power of 1C within the voltage range of 1.50V-2.80V, and then is placed for 30 days at the ambient temperature of 60 ℃, and whether the battery generates gas or bulges or not is observed.

Example 2

Electrolyte preparation

Preparing a non-aqueous mixed solvent of ethyl pivalate (ETE, chain tertiary carboxylic ester), methyl propionate (MP, chain primary carboxylic ester) and Ethylene Carbonate (EC) in a volume ratio of 50:30:20, adding a film-forming additive, namely Vinylene Carbonate (VC), wherein the content of the Vinylene Carbonate (VC) is 1.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

The secondary battery was fabricated and the battery performance was tested in the same manner as in example 1.

Example 3

Electrolyte preparation

Preparing a non-aqueous mixed solvent of butyl acetate (BA, chain primary carboxylic ester) and gamma-butyrolactone (gamma-B L, cyclic carboxylic ester) with a volume ratio of 90:10, and slowly adding electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Example 4

Electrolyte preparation

Preparing a non-aqueous mixed solvent of isobutyl acetate (IBA, chain primary carboxylic ester), methyl pivalate (MTE, chain tertiary carboxylic ester) and gamma-butyrolactone (gamma-B L, cyclic carboxylic ester) with a volume ratio of 70:20:10, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Example 5

Electrolyte preparation

Preparing a non-aqueous mixed solvent of propyl isobutyrate (PIB, chain secondary carboxylic ester) and Propylene Carbonate (PC) at a volume ratio of 70:30, adding film-forming additives of Vinylene Carbonate (VC) and 1, 3-propane sultone (1,3-PS) with the content of 2.0 wt% and 1.5 wt% of the mass of the non-aqueous electrolyte respectively, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 0.9 mol/L.

A secondary battery was fabricated in the same manner as in example 1.

The cell performance was tested as in example 1, except that the constant current charge rate was 3C and the constant current discharge rate was 3C.

Example 6

Electrolyte preparation

Preparing a non-aqueous mixed solvent of ethyl hexanoate (EH, chain primary carboxylic ester), ethyl propionate (EP, chain primary carboxylic ester) and gamma-butyrolactone (gamma-B L, cyclic carboxylic ester) in a volume ratio of 70:10:20, adding a film-forming additive of Vinyl Ethylene Carbonate (VEC) with the content of 1.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And L iBF₄And cooled to a molar ratio of 9:1 to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

A secondary battery was fabricated in the same manner as in example 1.

Example 7

Electrolyte preparation

Preparing a non-aqueous mixed solvent of hexyl acetate (HA, chain primary carboxylic ester) and gamma-butyrolactone (gamma-B L, cyclic carboxylic ester) according to a volume ratio of 80:20, adding additive succinonitrile (BDN) with the content of 2.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Battery fabrication

The positive electrode material of the 10Ah laminated aluminum plastic film flexible package battery adopts L iCoO₂(L CO), negative electrode Material Using lithium titanium oxide L i₄Ti₅O₁₂The cell energy density at 1C discharge at ambient temperature was about 85 Wh/kg.

Example 8

Electrolyte preparation

Preparing isobutyl acetate (IBA, chain primary carboxylic ester) solvent, accounting for 100% of the solvent volume, adding L iBOB (lithium bis (oxalato) borate) with the content being 0.5 wt% of the mass of the nonaqueous electrolyte, and slowly adding L iPF electrolyte salt₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Battery fabrication

The positive electrode material of the 10Ah laminated aluminum plastic film flexible package battery adopts L iMn₂O₄(L MO), negative electrode Material Using lithium titanium oxide L i₄Ti₅O₁₂The energy density of the battery at 1C discharge at room temperature was about 75 Wh/kg.

Battery performance testing

Under the condition of normal temperature, the flexible package battery is charged and discharged in the voltage range of 1.50V-2.80V, the constant current charging rate is 3C, the constant current discharging rate is 3C, and the high rate output characteristic and the charge-discharge cycle stability of the flexible package battery are examined.

Example 9

Electrolyte preparation

Preparing a non-aqueous mixed solvent of amyl acetate (PA, chain primary carboxylic ester) and valerolactone (-P L, cyclic carboxylic ester) at a volume ratio of 70:30, and slowly adding electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Battery fabrication

The positive electrode material of the 10Ah laminated aluminum plastic film flexible package battery adopts L iNi_0.5Co_0.2Mn_0.3O₂(NCM523) and L iMn₂O₄(L MO) composite material, negative electrode material using carbon-coated lithium titanium oxide L i₄Ti₅O₁₂C, carbon content about 2.0 wt%. The energy density of the battery during 1C discharge at normal temperature was about 82 Wh/kg.

Li₄Ti₅O₁₂The preparation of the/C material comprises weighing a lithium source compound L iOH & H according to the molar ratio of lithium to titanium of L i to Ti of 4:5₂O and TiO compound of titanium source₂And weighing the chelating agent and a carbon source compound glucose (the mass of the chelating agent is 10 percent of the total mass of the added materials), and slowly adding the chelating agent and the carbon source compound glucose into deionized water respectively, wherein the mass ratio of the added materials to the solvent medium is 40: 60. Then stirred for 4 hours. And transferring the uniformly mixed slurry to a spray drying system, roasting the spherical precursor powder obtained after spray drying for 4 hours at 450 ℃, and then roasting for 10 hours at 800 ℃, wherein the roasting atmosphere is nitrogen. After the baking and sintering, cooling, crushing and sieving.

Battery performance testing

Example 10

Electrolyte preparation

Preparing a non-aqueous mixed solvent of methyl pivalate (MTE, chain tertiary carboxylic ester), ethyl propionate (EP, chain primary carboxylic ester) and caprolactone (cyclic carboxylic ester-H L) in a volume ratio of 30:60:10, adding an additive of tris (trimethylsilane) borate (TMSB) with the content of 1.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Battery fabrication

The positive electrode material of the 10Ah laminated aluminum plastic film flexible package battery adopts L iNi_0.5Co_0.2Mn_0.3O₂(NCM523), negative electrode Material Using carbon-coated lithium titanium oxide L i₄Ti₅O₁₂C, carbon content about 2.0 wt%. The energy density of the battery during 1C discharge at normal temperature was about 85 Wh/kg.

The cell performance was tested as in example 1.

Example 11

Electrolyte preparation

Preparing methyl pivalate (MTE, chain tertiary carboxylic ester) and Butyl Acetate (BA)Chain primary carboxylic ester) and Propylene Carbonate (PC) in a volume ratio of 10:80:10, adding Succinic Anhydride (SA) as an additive in an amount of 1.0 wt% based on the mass of the nonaqueous electrolytic solution, and slowly adding L iPF parts of an electrolyte salt₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.3 mol/L.

Battery fabrication

The positive electrode material of the 10Ah laminated aluminum plastic film flexible package battery adopts L iNi_0.5Co_0.2Mn_0.3O₂(NCM523), negative electrode Material Using carbon-coated lithium titanium oxide L i₄Ti₅O₁₂C, carbon content about 5.0 wt%. The energy density of the battery during 1C discharge at normal temperature was about 83 Wh/kg.

The cell performance was tested as in example 1.

Example 12

Electrolyte preparation

Preparing a non-aqueous mixed solvent of butyl isobutyrate (BIB, chain secondary carboxylic ester), isobutyl acetate (IBA, chain primary carboxylic ester), gamma-butyrolactone (gamma-B L, cyclic carboxylic ester) and Propylene Carbonate (PC) in a volume ratio of 30:45:20:5, adding additives of succinonitrile (DBN) and Vinylene Carbonate (VC) with the content of 2.0 wt% of the mass of the non-aqueous electrolyte respectively, and slowly adding electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Button cell manufacture

The button cell (2025 type), the active material adopts zirconium doped lithium titanate, and is coated with carbon, the coating amount is 2.0 wt% (L i)₄Ti_4.95Zr_0.05O₁₂(L TZO)/C), and metallic lithium was used for the counter electrode.

Li₄Ti_4.95Zr_0.05O₁₂Preparation of an/C (2.0 wt%) material A lithium source compound L iOH. H was weighed out in a molar ratio of lithium, titanium and zirconium L i, Ti: Zr 4:4.95:0.05₂O and TiO compound of titanium source₂And nano-sized ZrO of a zirconium source compound₂Respectively and slowly adding chelating agent and carbon source compound glucose (the mass of the chelating agent is 10 percent of the total mass of the added materials) into deionized water, and adding the materials and a solvent mediumIn a mass ratio of 40: 60. Then stirred for 4 hours. And transferring the uniformly mixed slurry to a spray drying system, roasting the spherical precursor powder obtained after spray drying for 4 hours at 450 ℃, and then roasting for 10 hours at 800 ℃, wherein the roasting atmosphere is nitrogen. After the baking and sintering, cooling, crushing and sieving.

Battery performance testing

And (3) at normal temperature, charging and discharging the soft button cell in a voltage range of 1.0-2.5V, wherein the constant current charging rate is 0.2C, and the constant current discharging rate is 0.2C, and inspecting the specific capacity and the cycling stability of the soft button cell.

Example 13

Electrolyte preparation

Preparing a non-aqueous mixed solvent of isobutyl acetate (IBA, chain primary carboxylic ester), gamma-butyrolactone (gamma-B L, cyclic carboxylic ester) and fluoroethylene ester (F-EC) according to a volume ratio of 65:20:15, adding an additive Vinylene Carbonate (VC) with the content of 2.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding electrolyte salt L iPF₆And L iBF₄Cooling the mixture to obtain a nonaqueous electrolyte with a concentration of 1.1 mol/L according to a molar ratio of 8:2, and manufacturing the button cell

The active material of the button cell (2025 type) is cesium-doped lithium titanate and is coated by carbon, and the coating amount is 2.0 wt% (L i)_3.98Cs_0.02Ti₅O₁₂(L CTO)/C), and metallic lithium was used for the counter electrode.

Li_3.98Cs_0.02Ti₅O₁₂Preparation of an/C (2.0 wt%) material, a lithium source compound L iOH. H is weighed according to the molar ratio of lithium, cesium and titanium of L i, Cs, Ti of 3.98, 0.02 and 5 respectively₂O, cesium carbonate as a cesium source compound, and TiO as a titanium source compound₂And weighing the chelating agent and a carbon source compound glucose (the mass of the chelating agent is 10 percent of the total mass of the added materials), and slowly adding the chelating agent and the carbon source compound glucose into deionized water respectively, wherein the mass ratio of the added materials to the solvent medium is 40: 60. Then stirred for 4 hours. And transferring the uniformly mixed slurry to a spray drying system, roasting the spherical precursor powder obtained after spray drying for 4 hours at 480 ℃, and then roasting for 16 hours at 780 ℃ in the atmosphere of nitrogen. After the baking and sintering, cooling, crushing and sieving.

The cell performance was tested as in example 12.

Example 14

Electrolyte preparation

Preparing a non-aqueous mixed solvent of ethyl caprylate (EO, chain primary carboxylic ester), ethyl pivalate (ETE, chain tertiary carboxylic ester) and gamma-butyrolactone (gamma-B L, cyclic carboxylic ester) according to a volume ratio of 45:45:10, and slowly adding electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Button cell manufacture

Button cell (model 2025), active material using TiO with average particle size of about 500nm₂Metallic lithium was used for the counter electrode.

Battery performance testing

The battery test conditions are as follows: and (3) at normal temperature, the soft button cell is charged and discharged within the voltage range of 0.1-2.5V, the constant current charging rate is 0.1C, and the constant current discharging rate is 0.1C, and the charging and discharging curve and the first charging and discharging efficiency of the soft button cell are inspected.

Example 15

Electrolyte preparation

Preparing a non-aqueous mixed solvent of methyl pivalate (MTE, chain tertiary carboxylic ester), ethyl pivalate (ETE, chain tertiary carboxylic ester), Ethylene Carbonate (EC) and dimethyl carbonate (DMC) according to a volume ratio of 35:35:20:10, adding an additive 1, 3-propane sultone (1,3-PS) with the content of 2.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆A nonaqueous electrolytic solution was formed at a concentration of 1.1 mol/L.

Button cell manufacture

Button cell (model 2025), active material is vanadium oxide (V) with average particle size of about 300nm₂O₅And subjected to sanding treatment), and metallic lithium is used for the counter electrode.

Battery performance testing

Example 16

Electrolyte preparation

Preparing a non-aqueous mixed solvent of hexyl acetate (HA, chain primary carboxylic ester) and Propylene Carbonate (PC) according to a volume ratio of 85:15, adding an additive Vinylene Carbonate (VC) with the content of 2.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And L iTFSI, and cooling the mixture to obtain a nonaqueous electrolytic solution with a concentration of 1.2 mol/L, wherein the molar ratio of the two is 8.5: 1.5.

Button cell manufacture

Button cell (2025 type), active material adopts lithium titanium oxide L i₄Ti₅O₁₂The composite material with graphene (G) had a graphene content of 3.0 wt%, and metallic lithium was used for the counter electrode.

Li₄Ti₅O₁₂Preparing a composite material with graphene, namely weighing a lithium source compound L iOH & H according to the molar ratio of lithium to titanium of L i to Ti of 4:5₂O and TiO compound of titanium source₂And weighing a certain amount of graphene materials, respectively and slowly adding the graphene materials into deionized water, adding 1, 2-ethylene glycol and a small amount of cetyltrimethylammonium chloride to ensure that the graphene is uniformly dispersed, wherein the mass ratio of the total mass of the added materials to the solvent medium is 40: 60. Then stirred for 4 hours. And transferring the uniformly mixed slurry to a spray drying system, roasting the spherical precursor powder obtained after spray drying for 4 hours at 480 ℃, and then roasting for 8 hours at 800 ℃, wherein the roasting atmosphere is nitrogen. After the baking and sintering, cooling, crushing and sieving.

Battery performance testing

The battery test conditions are as follows: and (3) at normal temperature, charging and discharging the soft button cell in a voltage range of 1.0-2.5V, wherein the constant current charging rate is 0.2C, and the constant current discharging rate is 0.2C, and inspecting the charging and discharging curve and the charging and discharging cycle stability of the soft button cell.

Example 17

Electrolyte preparation

Preparing a non-aqueous mixed solvent of ethyl hexanoate (EH, chain primary carboxylic ester), ethyl propionate (EP, chain primary carboxylic ester) and gamma-butyrolactone (gamma-B L, cyclic carboxylic ester) in a volume ratio of 20:70:10Then adding a film-forming additive of Vinylene Carbonate (VC) and a flame-retardant additive of tris (trifluoroethyl) phosphate (TFP) with the contents of 2.0 wt% and 5.0 wt% of the mass of the non-aqueous electrolyte respectively, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.5 mol/L.

Button cell manufacture

Button cell (2025 type), active material adopts lithium titanium oxide L i₄Ti₅O₁₂And Hard Carbon (HC) at a mass ratio of 90:10, using lithium metal for the counter electrode.

Battery performance testing

The battery test conditions are as follows: and (3) at normal temperature, charging and discharging the soft button cell in a voltage range of 0.1-2.5V, wherein the constant current charging rate is 0.2C, and the constant current discharging rate is 0.2C, and inspecting the charging and discharging curve and the charging and discharging cycle stability of the soft button cell.

Example 18

Electrolyte preparation

Preparing a non-aqueous mixed solvent of isobutyl acetate (IBA, chain primary carboxylic ester), Ethylene Carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 70:20:10, adding a flame retardant additive of Ethoxy Pentafluorophosphonitrile (EPZ) with the content of 10.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.1 mol/L.

Battery fabrication

The positive electrode material of the 10Ah laminated aluminum plastic film flexible package battery adopts L iNi_0.5Co_0.2Mn_0.3O₂(NCM523), negative electrode Material with zirconium-doped lithium titanium oxide L i₄Ti_4.9Zr_0.1O₁₂(L TZO). the cell energy density at room temperature 1C discharge was about 85 Wh/kg.

Battery performance testing

And (3) under the normal temperature condition, the flexible package battery is charged and discharged in a voltage range of 1.5-2.8V, the constant current charging rate is 3C, and the constant current discharging rate is 3C, and the high rate output characteristic and the charge-discharge cycle stability of the flexible package battery are inspected.

Example 19

Electrolyte preparation

Preparing butyl acetate (BA, chain primary carboxylic ester), Propylene Carbonate (PC) and N-methyl-N-propyl pyrrolidine bis (trifluoro sulfonyl) imide salt (PP)_1,3TFSI) in a volume ratio of 70:15:15, slowly adding an electrolyte salt L iPF₆And L iTFSI, and cooling the mixture to obtain a nonaqueous electrolytic solution with a concentration of 0.9 mol/L, wherein the molar ratio of the two is 7: 3.

The cell was made as in example 18.

Battery performance testing

And (3) under the normal temperature condition, the flexible package battery is charged and discharged within the voltage range of 1.5-2.8V, the constant current charging rate is 2C, and the constant current discharging rate is 2C, and the high rate output characteristic and the charge-discharge cycle stability of the flexible package battery are inspected.

Example 20

Electrolyte preparation

Preparing a non-aqueous mixed solvent of butyl butyrate (BB, chain primary carboxylic ester), hexyl acetate (HA, chain primary carboxylic ester) and methyl pivalate (MTE, chain tertiary carboxylic ester) at a volume ratio of 30:30:40, adding an overcharge-preventing additive cyclohexylbenzene (HB) with the content of 2.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Battery fabrication

The positive electrode material of the 10Ah laminated aluminum plastic film flexible package battery adopts L iNi_0.5Co_0.2Mn_0.3O₂(NCM523), the cathode material uses nickel-doped lithium titanium oxide L i₄Ti_4.9Ni_0.1O₁₂(L TNO). the energy density of the battery at 1C discharge at ambient temperature was about 85 Wh/kg.

Battery performance testing

Example 21

Electrolyte preparation

Preparing a nonaqueous mixed solvent of hexyl acetate (HA, chain primary carboxylic ester), ethyl propionate (EP, chain primary carboxylic ester) and gamma-butyrolactone (gamma-B L, cyclic carboxylic ester) in a volume ratio of 70:10:20, adding a film-forming additive of Vinylene Carbonate (VC) with the content of 1.0 wt% of the mass of the nonaqueous electrolytic solution, slowly adding an electrolyte salt L iFSI, and cooling to form the nonaqueous electrolytic solution with the concentration of 2.0 mol/L.

Battery fabrication

The positive electrode material of the 10Ah laminated aluminum plastic film flexible package battery adopts L iNi_0.5Co_0.2Mn_0.3O₂(NCM523), negative electrode Material with sodium-doped lithium titanium oxide L i_3.8Na_0.2Ti₅O₁₂(L NTO). the cell energy density at 1C discharge at ambient temperature was about 85 Wh/kg.

Battery performance testing

Example 22

Electrolyte preparation

Preparing a non-aqueous mixed solvent of isobutyl acetate (IBA, chain primary carboxylic ester), Ethyl Octanoate (EO) and Propylene Carbonate (PC) in a volume ratio of 70:20:10, adding a film-forming additive of Vinylene Carbonate (VC) with the content of 1.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Button cell manufacture

Button cell (2025 type), active material adopts titanium disulfide TiS₂Metallic lithium was used for the counter electrode. Battery performance testing

The battery test conditions are as follows: and (3) at normal temperature, the soft button cell is charged and discharged within the voltage range of 0.1-2.5V, the constant current charging rate is 0.1C, and the constant current discharging rate is 0.1C, and the first charging and discharging curve and the first charging and discharging efficiency of the soft button cell are inspected.

Comparative example 1

Electrolyte preparation

Preparing a non-aqueous mixed solvent of dimethyl carbonate (DMC), Ethyl Methyl Carbonate (EMC) and Propylene Carbonate (PC) in a volume ratio of 33:33:34, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Comparative example 2

Electrolyte preparation

Preparing a non-aqueous mixed solvent of dimethyl carbonate (DMC), diethyl carbonate (DEC) and Ethylene Carbonate (EC) in a volume ratio of 33:33:34, adding a film-forming additive of Vinylene Carbonate (VC) with the content of 1.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Comparative example 3

Electrolyte preparation

Preparing a non-aqueous mixed solvent of Ethyl Acetate (EA), Methyl Propionate (MP), Ethylene Carbonate (EC) and Ethyl Methyl Carbonate (EMC) in a volume ratio of 30:40:20:10, adding a film-forming additive of Vinylene Carbonate (VC) with the content of 1.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

A secondary battery was fabricated in the same manner as in example 1.

Battery performance testing

The flexible package battery is charged and discharged in a voltage range of 1.50V-2.80V at the temperature of 45 ℃, the constant current charging rate is 3C, the constant current discharging rate is 3C, and the high rate output characteristic and the charge-discharge cycle stability of the flexible package battery are examined.

Comparative example 4

Electrolyte preparation

Preparing a non-aqueous mixed solvent of isobutyl acetate (IBA, chain primary carboxylic ester), Ethyl Methyl Carbonate (EMC) and Ethylene Carbonate (EC) in a volume ratio of 60:20: 20. However, the device is not suitable for use in a kitchenThen adding a film forming additive of Vinylene Carbonate (VC) with the content of 2.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆A nonaqueous electrolytic solution was formed at a concentration of 1.2 mol/L.

Secondary battery fabrication and battery performance testing were the same as in example 10.

Comparative example 5

Electrolyte preparation

Preparing a non-aqueous mixed solvent of hexyl acetate (HE, chain primary carboxylic ester), diethyl carbonate (DEC) and Propylene Carbonate (PC) in a volume ratio of 30:40:30, and slowly adding an electrolyte salt L iPF₆A nonaqueous electrolytic solution was formed at a concentration of 1.15 mol/L.

Comparative example 6

Electrolyte preparation

Preparing a non-aqueous mixed solvent of Ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC) and Ethylene Carbonate (EC) in a volume ratio of 33:33:34, adding an additive of Vinylene Carbonate (VC) with the content of 2.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Button cell fabrication and cell performance testing were the same as in example 13.

Comparative example 7

Preparing a non-aqueous mixed solvent of Ethyl Methyl Carbonate (EMC), dimethyl carbonate (DMC) and Ethylene Carbonate (EC) according to a volume ratio of 33:33:34, adding an additive 1, 3-propane sultone (1,3-PS) with the content of 2.0 wt% of the mass of the non-aqueous electrolyte, and slowly adding an electrolyte salt L iPF₆And cooled to form a nonaqueous electrolytic solution having a concentration of 1.2 mol/L.

Button cell fabrication and cell performance testing were the same as in example 15.

As is clear from the test results of example 1, example 2, example 3, example 4, example 5, example 6, example 10, example 11 and comparative example 1, comparative example 2, comparative example 4, comparative example 5 in Table 2, the nonaqueous electrolyte main solvent is selected from the group consisting of carboxylic acidWhen the acid ester solvent accounts for more than 70 percent of the total volume of the solvent, the acid ester solvent is used for a secondary battery taking the lithium titanium oxide as a cathode material, and the gas generation of the battery can be obviously inhibited. The higher the content of the carboxylic ester solvent is, the more obvious the effect of inhibiting gas production is, and when the carboxylic ester solvent accounts for 100 percent of the total volume of the solvent, the gas production is completely inhibited. Comparative example 3 shows that when a small molecular carboxylic acid ester (the total number of carbon atoms in the molecule is less than 5) is used in a large amount, the cycle performance of the battery at high temperature is deteriorated. FIG. 3 illustrates the application to metal oxide negative electrode materials such as V₂O₅In this case, the nonaqueous electrolytic solution containing a carboxylic acid ester as a main solvent also exhibits superior performance to that of a carbonate-based nonaqueous electrolytic solution, specifically, exhibits higher first charge-discharge efficiency and higher specific charge-discharge efficiency

The capacity exertion is higher.

TABLE 1

TABLE 2

Claims

1. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, a separator and a non-aqueous electrolyte, wherein the non-aqueous electrolyte comprises a solvent and an alkali metal salt, characterized in that: the solvent comprises chain carboxylic ester with the following structure:

wherein R is selected from hydrocarbyl; r' is selected from alkyl with 3-8 carbon atoms; the volume of the chain carboxylic ester is 95-100% of the total volume of the solvent; the negative electrode material is at least one selected from transition metal oxides, transition metal sulfides and alkali metal transition metal composite oxides.

2. The nonaqueous electrolyte secondary battery according to claim 1, wherein: the sum of the total number of carbon atoms contained in R and R' is not less than 3 and not more than 10.

3. The nonaqueous electrolyte secondary battery according to claim 2, wherein: the sum of the total number of carbon atoms contained in R and R' is not less than 4 and not more than 8.

4. The nonaqueous electrolyte secondary battery according to claim 1, wherein: and R' are both non-fluorine-containing hydrocarbon groups.

5. The nonaqueous electrolyte secondary battery according to claim 1, wherein: the chain carboxylic ester is selected from at least one of butyl n-hexanoate, isobutyl n-hexanoate, butyl pivalate, isobutyl pivalate, n-pentyl pivalate, isoamyl pivalate, n-butyl butyrate, isobutyl butyrate, n-pentyl butyrate, isoamyl butyrate, neopentyl butyrate, n-hexyl butyrate, n-butyl isobutyrate, isobutyl isobutyrate, n-pentyl isobutyrate, isoamyl isobutyrate, neopentyl isobutyrate, n-hexyl isobutyrate, n-butyl propionate, isobutyl propionate, n-pentyl propionate, isoamyl propionate, neopentyl propionate, n-hexyl propionate, n-butyl acetate, isobutyl acetate, n-pentyl acetate, isoamyl acetate, neopentyl acetate, n-hexyl acetate and n-octyl acetate.

6. The nonaqueous electrolyte secondary battery according to claim 1, wherein: the solvent further comprises a cyclic carboxylic acid ester; the volume of the cyclic carboxylic ester is 0-50% of the total volume of the solvent.

7. The nonaqueous electrolyte secondary battery according to claim 6, wherein: the volume of the cyclic carboxylic ester is 0-30% of the total volume of the solvent.

8. The nonaqueous electrolyte secondary battery according to claim 7, wherein: the volume of the cyclic carboxylic ester is 10-30% of the total volume of the solvent.

9. The nonaqueous electrolyte secondary battery according to claim 6, wherein: the cyclic carboxylic ester is at least one of gamma-butyrolactone, -valerolactone and-caprolactone.

10. The nonaqueous electrolyte secondary battery of claim 1, wherein the alkali metal salt is an alkali metal lithium salt and/or an alkali metal sodium salt, and the alkali metal lithium salt is L iPF₆、LiBF₄、LiN(SO₂CF₃)₂、LiN(SO₂C₂F₅)₂、LiN(SO₂F)₂、LiPO₂F₂、LiCF₃SO₃、LiC(SO₂CF₃)₃、LiPF₃(CF₃)₃、LiPF₃(C₂F₅)₃、LiPF₃(iso-C₃F₇)₃、LiPF₅(iso-C₃F₇)、LiB(C₂O₄)₂、LiBF₂(C₂O₄) And L i₂B₁₂F₁₂At least one of (1); the alkali metal sodium salt is selected from NaPF₆、NaBF₄、NaN(SO₂CF₃)₂、NaN(SO₂C₂F₅)₂、NaN(SO₂F)₂、NaPO₂F₂、NaCF₃SO₃、NaC(SO₂CF₃)₃、NaPF₃(CF₃)₃、NaPF₃(C₂F₅)₃、NaPF₃(iso-C₃F₇)₃、NaPF₅(iso-C₃F₇)、NaBF₂(C₂O₄) And Na₂B₁₂F₁₂At least one of them.

11. The nonaqueous electrolyte secondary battery according to claim 1, wherein the content of the alkali metal salt in the nonaqueous electrolyte is 0.5 mol/L to 3.0 mol/L.

12. The nonaqueous electrolyte secondary battery according to claim 11, wherein the content of the alkali metal salt in the nonaqueous electrolyte is 0.8 mol/L to 2.5 mol/L.

13. The nonaqueous electrolyte secondary battery according to claim 12, wherein the content of the alkali metal salt in the nonaqueous electrolyte is 0.9 mol/L to 1.5 mol/L.

14. The nonaqueous electrolyte secondary battery according to claim 1, wherein: the solvent further comprises at least one of carbonate, sulfite, sulfonate, sulfone, ether, an organosilicon compound, an organoboron compound, a nitrile, an ionic liquid and a phosphazene compound.

15. The nonaqueous electrolyte secondary battery according to claim 14, wherein: the solvent also comprises ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate and butylene carbonate, propylene methyl carbonate, propylene ethyl carbonate, phenol methyl carbonate, ethylene carbonate, ethylene halogen carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propyl methyl carbonate, ethylene sulfite, propylene sulfite, butylene sulfite, dimethyl sulfite, diethyl sulfite, sulfolane, dimethyl sulfoxide, ethylmethyl sulfoxide, 1, 3-propanesulfonate, 1, 4-butanesultone, dioxolane, dimethoxypropane, dimethyldimethoxysilane, pivalonitrile, valeronitrile, 2-dimethylpentanenitrile, ethoxypentafluorophosphononitrile, phenoxypentafluorophosphononitrile, N-methyl-N-butylpiperidine bis (trifluoromethylsulfonyl) imide salt and N-methyl-N-propylpyrile At least one of pyrrolidine bis (fluorosulfonyl) imide salts.

16. The nonaqueous electrolyte secondary battery according to claim 15, wherein: the carbonate ester comprises cyclic carbonate ester and chain carbonate ester; the cyclic carbonate is at least one selected from ethylene carbonate, fluoroethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate; the chain carbonate is at least one selected from dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

17. The nonaqueous electrolyte secondary battery according to claim 1, wherein: the non-aqueous electrolyte further comprises an additive; the additives include at least one of film forming additives, anti-overcharge additives, flame retardant additives, conductive additives, and wetting additives.

18. The nonaqueous electrolyte secondary battery according to claim 17, wherein: the film forming additive comprises an organic film forming agent and/or an inorganic film forming agent; the organic film forming agent is selected from at least one of ionic liquid, sulfate, sulfite, sulfone, sulfoxide, sulfonate, carbonate, halogenated carbonate, carboxylate, halogenated carboxylate, phosphate, halogenated phosphate, phosphite, halogenated phosphite, double-bond-containing unsaturated carbonate, nitrile, crown ether and organic boride; the above-mentionedThe inorganic film forming agent is selected from L iBOB, L iODBF, NaBOB, NaODBF, L i₂CO₃、Na₂CO₃、K₂CO₃And NH₄At least one of I.

19. The nonaqueous electrolyte secondary battery according to claim 18, wherein the organic film-forming agent is at least one selected from the group consisting of Vinylene Carbonate (VC), Vinyl Ethylene Carbonate (VEC), phenyl ethylene carbonate (PhEC), phenyl vinylene carbonate (PhVC), Allyl Methyl Carbonate (AMC), Allyl Ethyl Carbonate (AEC), vinyl sulfite (ES), Propylene Sulfite (PS), dimethyl sulfite (DMS), diethyl sulfite (DES), 1, 3-propane sultone (1,3-PS), acrylonitrile (AAN), vinyl chlorocarbonate (ClEC), fluoroethylene carbonate (FEC), propylene carbonate Trifluoride (TFPC), bromo γ -butyrolactone (BrGB L), fluoro γ -butyrolactone (FGB L), Glutaric Anhydride (GA), and Succinic Anhydride (SA).

20. The nonaqueous electrolyte secondary battery according to claim 17, wherein: the anti-overcharge additive includes a redox shuttle additive and/or an electropolymerization additive.

21. The nonaqueous electrolyte secondary battery according to claim 20, wherein: the anti-overcharge additive includes at least one of the following compounds:

22. the nonaqueous electrolyte secondary battery according to claim 17, wherein: the flame retardant additive is at least one selected from the group consisting of phosphate esters, phosphonamides, phosphite esters, fluorophosphate esters, fluorophosphite esters, ionic liquids, and phosphazenes.

23. The nonaqueous electrolyte secondary battery according to claim 22, wherein: the flame retardant additive is selected from at least one of the following compounds:

wherein, X is₁，X₂，X₃，X₄，X₅，X₆Independently represent halogen OR independently represent OR_x；R_xRepresents a saturated aliphatic group with or without substituted hydrogen; or R_xRepresents a saturated aromatic group in which hydrogen is substituted or unsubstituted.

24. The nonaqueous electrolyte secondary battery according to claim 17, wherein: the conductive additive includes at least one of a cationic ligand compound, an anionic ligand compound, and a neutral ligand compound.

25. The nonaqueous electrolyte secondary battery according to claim 24, wherein: the conductive additive is selected from at least one of amine, crown ether, cryptand compound, fluoro alkyl boride, alkyl boride and aza ether.

26. The nonaqueous electrolyte secondary battery according to claim 17, wherein: the wetting additive is at least one selected from quaternary ammonium surfactants and carbonate compounds containing aryl or long-chain hydrocarbon groups.

27. The nonaqueous electrolyte secondary battery according to claim 26, wherein: the wetting additive is selected from methyl phenyl carbonate and/or bisoctyl carbonate.

28. The nonaqueous electrolyte secondary battery according to claim 17, wherein: the mass of the additive is 0-15.0% of the mass of the nonaqueous electrolyte.

29. The nonaqueous electrolyte secondary battery according to claim 28, wherein: the mass of the additive is 0-5.0% of the mass of the nonaqueous electrolyte.

30. The nonaqueous electrolyte secondary battery according to claim 29, wherein: the mass of the additive is 0-3.0% of the mass of the nonaqueous electrolyte.

31. The nonaqueous electrolyte secondary battery according to claim 28, wherein: the mass of the additive is 1.0-10.0% of the mass of the nonaqueous electrolyte.

32. The nonaqueous electrolyte secondary battery according to claim 1, wherein: the positive electrode material is selected from at least one of lithium nickel cobalt manganese composite oxide, sodium nickel cobalt composite oxide, lithium nickel cobalt aluminum composite oxide, lithium manganese nickel composite oxide, olivine lithium phosphorus oxide, lithium cobalt oxide, sodium cobalt oxide, lithium manganese oxide, sodium manganese oxide and sodium titanium nickel composite oxide.

33. The nonaqueous electrolyte secondary battery according to claim 1, wherein: the negative electrode material is selected from TiO₂、TiS₂、NiO、MoO₂、MoO₃、V₂O₅、Co₃O₄、CoO、Fe₃O₄、Fe₂O₃、FeO、Cu₂At least one of O and CuO.

34. The nonaqueous electrolyte secondary battery according to claim 1, wherein: the negative electrode material is an alkali metal transition metal composite oxide.

35. The nonaqueous electrolyte secondary battery according to claim 34, wherein: the negative electrode material is selected from lithium titanium oxide and/or lithium vanadium oxide.

36. The nonaqueous electrolyte secondary battery according to claim 34, wherein: the negative electrode material is selected from lithium titanium oxide and/or modified lithium titanium oxide; the modification comprises doping and/or cladding.

37. The nonaqueous electrolyte secondary battery of claim 36, wherein the negative electrode material is carbon-coated L i₄Ti₅O₁₂。

38. The nonaqueous electrolyte secondary battery according to claim 37, wherein: the mass of the carbon coating part is 0.1-10.0% of the total mass of the negative electrode material.

39. The nonaqueous electrolyte secondary battery of claim 35, wherein the negative electrode material is L i doped with a metal element₄Ti₅O₁₂And/or metal element coated L i₄Ti₅O₁₂。

40. The nonaqueous electrolyte secondary battery of claim 39, wherein the doping or coating comprises employing at least one metal element pair of L i of Na, K, Rb, Cs, Mg, Ca, Sr, Ba, Al, Ga, In, Ge, Sn, Ti, V, Cr, Fe, Mn, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Cd, W, L a, Ce, Nd, Sb and Sm₄Ti₅O₁₂And (5) carrying out modification treatment.

41. The nonaqueous electrolyte secondary battery of claim 39, wherein the metal element is doped or coated in the form of a metal oxide with L i₄Ti₅O₁₂Combining; the mass of the metal oxide is 0.1-49.0% of the total mass of the negative electrode material.

42. The nonaqueous electrolyte secondary battery according to claim 1, wherein: the separator is selected from a polyolefin melt-drawn separator; or the diaphragm is selected from at least one of polyethylene terephthalate, polyvinylidene fluoride, aramid fiber and polyamide as a base material; or the separator is selected from a separator coated with polyolefin on a high-softening-point porous base material; or the separator is selected from an inorganic solid electrolyte separator; or the separator is selected from an organic solid electrolyte separator; or the separator is selected from a composite separator in which an inorganic solid electrolyte is combined with an organic solid electrolyte.