CN105742708A - Electrolyte and lithium ion battery comprising same - Google Patents

Abstract

The application relates to the field of lithium batteries, in particular to electrolyte and a lithium ion battery comprising the electrolyte. The electrolyte includes an organic solvent, a lithium salt, and an additive including an acylketolithium-based compound and a lithium fluorophosphate compound. When the electrolyte simultaneously comprises the acyl ketone lithium compound and the fluoro lithium phosphate compound, the cycle performance of the lithium ion battery can be improved, and meanwhile, the storage performance of the electrolyte is also obviously improved.

Description

Electrolyte and include the lithium ion battery of this electrolyte

Technical field

The application relates to field of lithium, specifically, relates to a kind of electrolyte and includes the lithium ion battery of this electrolyte.

Background technology

In recent years, portable battery product, for instance photographing unit, DV, mobile phone, notebook computer etc. are widely used in daily life.Reducing size, alleviate weight, increasing the service life is development trend and the requirement of battery product industry.Therefore, exploitation and portable type electronic product think supporting power supply product, especially develop an urgent demand that the lightweight secondary cell that can provide high-energy-density is industry development.

Lithium ion battery, in initial charge process, can form one layer of SEI film in negative terminal surface.If the SEI film formed is too thick, membrane impedance is higher, then lithium ion cannot migrate through, and analysis lithium will occur；In cyclic process, if the SEI film formed is form compact and stable not, then SEI film can dissolve gradually or break, and causes that the negative pole exposed continues to react with electrolyte, while consuming electrolyte so that battery capacity reduces.It follows that the quality of SEI film is most important to the performance of lithium ion battery.Due to additives different in electrolyte or different amounts of same additive, the SEI film quality that all can result in is different, and membrane impedance is also different.Therefore, improve the quality of SEI film by control additive and amount and seem very necessary to realizing high performance lithium ion battery.

In consideration of it, special, the application is proposed.

Summary of the invention

In order to solve the problems referred to above, the applicant has carried out studying with keen determination, found that: when electrolyte includes acyl group ketone lithium compounds and fluorophosphate lithium simultaneously, it is possible to improve cycle performance and the memory property of lithium ion battery, thus completing the application.

The purpose of the application is in that to provide a kind of electrolyte, and including organic solvent, lithium salts and additive, described additive includes acyl group ketone lithium compounds and fluorophosphate lithium compound.

Preferably, described acyl group ketone lithium compounds is at least one in compound as shown in formula I:

Wherein, R₁₁、R₁₂、R₁₃、R₁₄、R₁₅、R₁₆Each independent it is respectively selected from hydrogen atom, halogen atom, cyano group, sulfonic group, substituted or unsubstituted C_1～20Alkyl, substituted or unsubstituted C_{2～ 20}Thiazolinyl, substituted or unsubstituted C_6～26Aryl, substituted or unsubstituted C_1～20Alkoxyl, substituted or unsubstituted C_6～26Aryloxy group, substituted or unsubstituted C_1～20Alkane sulfonyl, substituted or unsubstituted C_2～20Alkene sulfonyl, substituted or unsubstituted C_6～26Arylsulfonyl；

Substituent group is selected from halogen atom, cyano group, pyridine radicals, thienyl or sulfonic group；

Wherein, halogen atom is selected from F, Cl, Br, it is preferable that F, Cl.

Preferably, described acyl group ketone lithium compounds is at least one in compound as shown in formula II:

Wherein, R₂₁、R₂₂Each independent it is respectively selected from hydrogen atom, halogen atom, cyano group, sulfonic group, substituted or unsubstituted C_1～20Alkyl, substituted or unsubstituted C_2～20Thiazolinyl, substituted or unsubstituted C_6～26Aryl, substituted or unsubstituted C_1～20Alkoxyl, substituted or unsubstituted C_6～26Aryloxy group, substituted or unsubstituted C_1～20Alkane sulfonyl, substituted or unsubstituted C_2～20Alkene sulfonyl, substituted or unsubstituted C_6～26Arylsulfonyl；

Substituent group is selected from halogen atom, cyano group, pyridine radicals, thienyl or sulfonic group,

Wherein, halogen atom is selected from F, Cl, Br, it is preferable that F, Cl.

Preferably, R₂₁、R₂₂Each independent it is respectively selected from hydrogen atom, halogen atom, substituted or unsubstituted C_1～6Alkyl, substituted or unsubstituted C_2～6Thiazolinyl, substituted or unsubstituted phenyl, substituted or unsubstituted C_1～6Alkoxyl, substituted or unsubstituted phenoxy group；Substituent group is selected from halogen atom；

Preferably, R₂₁、R₂₂Each independent it is respectively selected from hydrogen atom, halogen atom, substituted or unsubstituted C_1～6Alkyl, substituted or unsubstituted C_1～6Alkoxyl；Substituent group is selected from halogen atom.

Preferably, R₂₁、R₂₂For identical substituent group.

Preferably, described acyl group ketone lithium compounds at least one in following compound:

Preferably, described fluorophosphate lithium compound at least one in single lithium fluophosphate or difluorophosphate.

Preferably, described acyl group ketone lithium compounds is 0.01%～5% in the mass percentage content of electrolyte, it is preferable that 0.1%～5%；And/or,

Described fluorophosphate lithium compound is 0.001%～2% in the mass percentage content of electrolyte, it is preferable that 0.1%～1%.

Preferably, described organic solvent is at least one in ethylene carbonate, Allyl carbonate, butylene, fluorinated ethylene carbonate, Ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonic acid ester, GBL, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate or ethyl n-butyrate..

Preferably, described lithium salts is selected from lithium hexafluoro phosphate, LiBF4, lithium perchlorate, hexafluoroarsenate lithium, fluorine oxalic acid lithium phosphate, LiN (SO₂R_F)₂、LiN(SO₂F)(SO₂R_F), double; two trifluoromethanesulfonimide lithium, double; two (fluorine sulphonyl) imine lithium, di-oxalate lithium borate, at least one in difluorine oxalic acid boracic acid lithium, wherein, R_F=C_nF_2n+1, n is the integer of 1～10, it is preferred to LiPF₆Or LiN (SO₂R_F)₂In at least one；

Preferably, described lithium salts concentration in the electrolytic solution is 0.5molL^-1～2molL^-1。

The another object of the application is in that to provide a kind of lithium ion battery, including the positive plate containing positive electrode active materials, containing the negative plate of negative active core-shell material, isolating membrane and electrolyte provided herein.

The technical scheme of the application at least has following beneficial effect:

In the electrolyte that the application provides, owing to including acyl group ketone lithium compounds mentioned above and fluorophosphate lithium simultaneously, therefore, it is possible to improve cycle performance and the memory property of lithium ion battery.It has been investigated that; when electrolyte includes acyl group ketone lithium compounds mentioned above and fluorophosphate lithium compound simultaneously; acyl group ketone lithium compounds will form passivating film on the surface of the pole piece of high-tension battery; thus electrolyte and electrode be obtained by reacting effective suppression; simultaneously; fluorophosphate lithium compound can effectively suppress lithium salts to decompose, and improves the membrane impedance of pole piece.Under the common synergism of the two, substantially increase the cycle performance of lithium ion battery, for instance lithium ion battery has the cycle performance of excellence under 4.4V high voltage and at 45 DEG C；Meanwhile, the memory property of electrolyte have also been obtained obvious raising.

Detailed description of the invention

Being described in detail below by the application, the feature of the application and advantage will illustrate along with these and become more apparent from, clearly.

The purpose of the application is in that to provide a kind of electrolyte, and including organic solvent, lithium salts and additive, described additive includes acyl group ketone lithium compounds and fluorophosphate lithium.

As a kind of improvement of the application electrolyte, acyl group ketone lithium compounds is at least one in compound as shown in formula I:

In formula I, R₁₁、R₁₂、R₁₃、R₁₄、R₁₅、R₁₆Each independent it is respectively selected from hydrogen atom, halogen atom, cyano group, sulfonic group, substituted or unsubstituted C_1～20Alkyl, substituted or unsubstituted C_2～20Thiazolinyl, substituted or unsubstituted C_6～26Aryl, substituted or unsubstituted C_1～20Alkoxyl, substituted or unsubstituted C_6～26Aryloxy group, substituted or unsubstituted C_1～20Alkane sulfonyl, substituted or unsubstituted C_2～20Alkene sulfonyl, substituted or unsubstituted C_6～26Arylsulfonyl；

Substituent group is selected from halogen atom, cyano group, pyridine radicals, thienyl or sulfonic group.

In formula I, it is preferred that R₁₁、R₁₂、R₁₃In to have at least a substituent group be hydrogen atom, R₁₄、R₁₅、R₁₆In to have at least a substituent group be hydrogen atom.

It is further preferred that the substituent group at acyl group ketone lithium compounds molecule two ends is identical.

As a kind of improvement of the application electrolyte, acyl group ketone lithium compounds is at least one in compound as shown in formula II:

In formula II, R₂₁、R₂₂Each independent it is respectively selected from hydrogen atom, halogen atom, cyano group, sulfonic group, substituted or unsubstituted C_1～20Alkyl, substituted or unsubstituted C_2～20Thiazolinyl, substituted or unsubstituted C_6～26Aryl, substituted or unsubstituted C_1～20Alkoxyl, substituted or unsubstituted C_6～26Aryloxy group, substituted or unsubstituted C_1～20Alkane sulfonyl, substituted or unsubstituted C_2～20Alkene sulfonyl, substituted or unsubstituted C_6～26Arylsulfonyl；

Substituent group is selected from halogen atom, cyano group, pyridine radicals, thienyl, sulfonic group or sulfonyl,

Wherein, halogen atom is selected from F, Cl, Br, it is preferable that F, Cl.

In this application, shown in substituent group, implication is as described below:

Carbon number is the alkyl of 1～20, and alkyl can be chain-like alkyl, it is possible to for cycloalkyl, the ring hydrogen being positioned at cycloalkyl can be replaced by alkyl, and in described alkyl, the preferred lower limit of carbon number is 2,3,4,5, it is preferred that higher limit is 3,4,5,6,8,10,12,14,16,18.Preferably, selecting carbon number is the alkyl of 1～10, further preferably, selecting carbon number is the chain-like alkyl of 1～6, and carbon number is the cycloalkyl of 3～8, still more preferably, selecting carbon number is the chain-like alkyl of 1～4, and carbon number is the cycloalkyl of 5～7.As the example of alkyl, specifically can enumerate: methyl, ethyl, n-pro-pyl, isopropyl, normal-butyl, isobutyl group, sec-butyl, the tert-butyl group, n-pentyl, isopentyl, neopentyl, cyclopenta, cyclohexyl.

Carbon number is the thiazolinyl of 2～20, can be cyclic alkenyl radical, it is possible to for chain thiazolinyl.It addition, the number of double bond is preferably 1 in thiazolinyl.In described thiazolinyl, the preferred lower limit of carbon number is 3,4,5, it is preferred that higher limit is 3,4,5,6,8,10,12,14,16,18.Preferably, selecting carbon number is the thiazolinyl of 2～10, it is further preferred that selecting carbon number is the thiazolinyl of 2～6, it is further preferred that selecting carbon number is the thiazolinyl of 2～5.As the example of thiazolinyl, specifically can enumerate: vinyl, pi-allyl, isopropenyl, pentenyl, cyclohexenyl group, cycloheptenyl, cyclo-octene base.

Carbon number is the aryl of 6～26, for instance phenyl, benzene alkyl, at least contain the aryl such as xenyl of a phenyl, condensed-nuclei aromatics base such as naphthalene, anthracene, phenanthrene, and xenyl and condensed-nuclei aromatics base also can be replaced by alkyl or thiazolinyl.Preferably, selecting carbon number is the aryl of 6～16, it is further preferred that selecting carbon number is the aryl of 6～14, it is further preferred that selecting carbon number is the aryl of 6～9.As the example of aryl, specifically can enumerate: phenyl, benzyl, xenyl, p-methylphenyl, o-tolyl, a tolyl.

Carbon number is the oxyalkyl of 1～20, and alkoxyl can be chain, it is possible to for ring-type.Preferably, selecting carbon number is the alkoxyl of 1～10, it is further preferred that selecting carbon number is the alkoxyl of 1～6, it is further preferred that selecting carbon number is the alkoxyl of 1～4.As the example of alkoxyl, specifically can enumerate: methoxyl group, ethyoxyl, positive propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, n-pentyloxy, isoamoxy, cyclopentyloxy, cyclohexyloxy.

When in the aryl that the aforementioned carbon number being previously mentioned is 6～26 containing oxygen atom, aryloxy group can be formed.Preferably, selecting carbon number is the aryloxy group of 6～16, it is further preferred that selecting carbon number is the aryloxy group of 6～14, it is further preferred that selecting carbon atom is the aryloxy group of 6～10.As the example of aryloxy group, specifically can enumerate: phenoxy group, benzyloxy, 4-methylphenoxy, 3,5-dimethyl phenoxies, 4-methylbenzyloxy, 3-methylbenzyloxy, 2,6-diisopropyl benzyloxies, 1-naphthoxy.

As the C being previously mentioned_1～20Alkyl, C_2～20Thiazolinyl, C_6～26Aryl, C_1～20Alkoxyl, C_{6～ 26}After aryloxy group is replaced by halogen atom, form C successively accordingly_1～20Haloalkyl, C_2～20Haloalkenyl group, C_6～26Halogenated aryl, C_1～20Halogenated alkoxy, C_6～26Haloaryloxy, wherein halogen atom is F, Cl, Br, it is preferred to F, Cl.In the halo group formed, part hydrogen atom or whole hydrogen atom are replaced by halogen atom, and the number of halogen atom can be 1,2,3 or 4.

Preferably, C is selected_1～10Haloalkyl, C_2～10Haloalkenyl group, C_6～16Halogenated aryl, C_{1～ 10}Halogenated alkoxy, C_6～16Haloaryloxy, it is further preferred that select C_1～6Halo chain-like alkyl, C_3～8Halogenated cycloalkyl, C_2～6Haloalkenyl group, C_6～14Halogenated aryl, C_1～6Halogenated alkoxy, C_{6～ 14}Haloaryloxy；It is further preferred that select C_1～4Halo chain-like alkyl, C_5～7Halogenated cycloalkyl, C_2～5Haloalkenyl group, C_6～10Halogenated aryl, C_1～4Halogenated alkoxy, C_6～10Haloaryloxy.

As the example of halo group, specifically can enumerate: trifluoromethyl (-CF₃null)、2-fluoro ethyl、3-fluorine n-pro-pyl、2-fluorine isopropyl、4-fluorine normal-butyl、3-fluorine sec-butyl、5-fluorine n-pentyl、4-fluorine isopentyl、1-is fluoride-based、3-fluorine pi-allyl、The fluoro-4-hexenyl of 6-、Adjacent fluorophenyl、To fluorophenyl、Between fluorophenyl、4-trifluoromethylphenyl、2,6-difluoromethyl phenyl、The fluoro-1-naphthyl of 2-、Fluoro-methoxy、1-fluorine ethyoxyl、The fluoro-positive propoxy of 2-、The fluoro-isopropoxy of 1-、The fluoro-n-butoxy of 3-、The fluoro-n-pentyloxy of 4-、2,2-difluoromethyl propoxyl group、The fluoro-positive hexyloxy of 5-、1,1,2-trifluoromethyl propoxyl group、The fluoro-n-heptyl oxygen base of 6-、The fluoro-n-octyl oxygen base of 7-、The fluoro-cyclopentyloxy of 3-、The fluoro-2-methylcyclopentoxy of 4-、The fluoro-cyclohexyloxy of 3-、3-fluorine ring oxygen in heptan base、4-fluoro-2-methyl ring oxygen in heptan base、3-fluorine ring octyloxy、4-fluorophenoxy、3-fluorophenoxy、2-fluorophenoxy、3,5-difluoro phenoxy group、2,6-difluoro phenoxy group、2,3-difluoro phenoxy group、2,The fluoro-4-methylphenoxy of 6-bis-、3-(2-fluoro ethyl) phenoxy group、2-(1-fluoro ethyl) phenoxy group、3,5-difluoro benzyloxy、2-fluorine benzyloxy、The fluoro-1-naphthoxy of 2-.In above-mentioned concrete example, F can be replaced by Cl and/or Br.

C_1～20Alkyl, C_2～20Thiazolinyl, C_6～26Aryl replaced by sulfonic group or sulfonyl after, corresponding form sulfonic group alkyl, sulfonic group thiazolinyl, sulfonic group aryl, alkyl sulphonyl, alkenylsufonyl, aryl sulfonyl.Part hydrogen atom in abovementioned alkyl, thiazolinyl, aryl or whole hydrogen atom can be replaced by sulfonic group; sulfonic number can be 1 or 2; same; part hydrogen atom in abovementioned alkyl, thiazolinyl, aryl or whole hydrogen atom can be replaced by sulfonyl, and the number of sulfonyl can be 1 or 2.

As containing sulfonyl example, specifically can enumerate: methyl sulphonyl, ethylsulfonyl, n-pro-pyl sulfonyl, isopropelsulfonyl, normal-butyl sulfonyl, iso-butylsulfonyl, tert. butylsulfonyl, n-pentyl sulfonyl, isopentyl sulfonyl, neopentyl sulfonyl, 2, 3-dimethyl propyl sulfonyl, 1-ethyl propyl sulfonyl, n-hexyl sulfonyl, Cyclopentylsulfonyl, cyclohexylsulfonyl, suberyl sulfonyl, ring octyl group sulfonyl, n-heptyl sulfonyl, n-octyl sulfonyl, suberyl sulfonyl, ring octyl group sulfonyl, acrylic sulfonyl, cyclobutenyl sulfonyl, pentenyl sulfonyl, hexenyl sulfonyl, heptenyl sulfonyl, octenyl sulfonyl, phenyl sulfonyl, 4-Methyl benzenesulfonyl base.

In addition contain sulfonic example, specifically can enumerate: sulfonomethyl, 2-sulfonic group ethyl, 3-sulfonic group n-pro-pyl, 4-sulfonic group normal-butyl, the sulfonic group tert-butyl group, 2-sulfonic group n-pentyl, 3-sulfonic group isopentyl, 6-sulfonic group n-hexyl, 2-sulfonic group cyclopenta, 4-sulfonic group cyclohexyl, sulfonic group acrylic, sulfonic group cyclobutenyl, sulfonic group pentenyl, sulfonic group hexenyl, sulfonic group heptenyl, sulfonic group octenyl, sulfonic group phenyl, 4-sulfonic acid methyl phenyl.

As a kind of improvement of the application electrolyte, R₂₁、R₂₂Each independent it is respectively selected from hydrogen atom, halogen atom, substituted or unsubstituted C_1～6Alkyl, substituted or unsubstituted C_2～6Thiazolinyl, substituted or unsubstituted phenyl, substituted or unsubstituted C_1～6Alkoxyl, substituted or unsubstituted phenoxy group；Substituent group is selected from halogen atom.

As a kind of improvement of the application electrolyte, R₂₁、R₂₂Each independent it is respectively selected from hydrogen atom, halogen atom, substituted or unsubstituted C_1～6Alkyl, substituted or unsubstituted C_1～6Alkoxyl；Substituent group is selected from halogen atom.

As a kind of improvement of the application electrolyte, R₂₁、R₂₂For identical substituent group.

A kind of as the application electrolyte improves, the example of acyl group ketone lithium compounds, shown in specific as follows:

As a kind of improvement of the application electrolyte, acyl group ketone lithium compounds is further selected from:

In this application, the acyl group ketone lithium compounds being previously mentioned can synthesize according to the synthetic method of existing routine, for instance is referred to patent: JP2000215913A.

As a kind of improvement of the application electrolyte, fluorophosphate lithium compound at least one in single lithium fluophosphate or difluorophosphate；The chemical formula of single lithium fluophosphate is Li₂PO₃F, difluorophosphate chemical formula be LiPO₂F₂。

In this application, the fluorophosphate lithium being previously mentioned can synthesize according to the synthetic method of existing routine, for instance is referred to document: Japan Patent 2008-140767.

A kind of improvement as the application electrolyte; acyl group ketone lithium compounds mass percent in the electrolytic solution is 0.01%～5%; upper limit value is 3%, 3.5%, 4%, 4.25%, 4.5%, 4.75%, lower limit value is 0.05%, 0.1%, 0.2%, 0.5%, 1wt%；Acyl group ketone lithium compounds mass percent in the electrolytic solution is 0.1%～3%.The scope of the mass percentage content of acyl group ketone lithium compounds can be made up of above-mentioned any upper limit value and lower limit value.If in the electrolytic solution, acyl group ketone lithium compounds or fluorophosphate lithium content are excessive, then can cause being formed on positive and negative plate surface thicker SEI film, reduce the conductive performance of lithium ion, worsen cycle performance and the memory property of lithium ion battery.

A kind of improvement as the application electrolyte, fluorophosphate lithium compound mass percent in the electrolytic solution is 0.001%～3%, upper limit value is 1%, 1.5%, 1.75%, 2%, 2.5%, and lower limit value is 0.005%, 0.01%, 0.05%, 0.1%, 0.5%；The mass percent in the electrolytic solution of described fluorophosphate lithium is preferably 0.001%～2%, more preferably 0.01%～1%.If in the electrolytic solution, acyl group ketone lithium kind compound content is too small, it is impossible to be effectively improved the cycle performance of lithium ion battery, cycle performance especially under high pressure；And the content of fluorophosphate lithium is too small, the effect of stable lithium salts can not be played equally, the performance of battery is not had effect.

As a kind of improvement of the application electrolyte, in above-mentioned electrolyte, the organic solvent in electrolyte can be non-aqueous organic solvent, and it is 1～8 and the compound containing at least one ester group that described organic solvent is preferably carbon number.

Example as organic solvent, can enumerate: ethylene carbonate, propene carbonate, butylene, fluorinated ethylene carbonate, Ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonic acid ester, GBL, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate, ethyl n-butyrate..

As a kind of improvement of the application electrolyte, the lithium salts in electrolyte can be organic lithium salt, it is possible to for inorganic lithium salt, specifically, can contain at least one in fluorine element, boron element, P elements in described lithium salts.Preferably, described lithium salts is selected from lithium hexafluoro phosphate (LiPF₆), LiBF4 (LiBF₄), lithium perchlorate (LiClO₄), hexafluoroarsenate lithium (LiAsF₆), LiTFOP (tetrafluoro oxalic acid lithium phosphate), LiN (SO₂R_F)₂、LiN(SO₂F)(SO₂R_F), double; two trifluoromethanesulfonimide lithium LiN (CF₃SO₂)₂(being abbreviated as LiTFSI), double; two (fluorine sulphonyl) imine lithium Li (N (SO₂F)₂) (being abbreviated as LiFSI), di-oxalate lithium borate LiB (C₂O₄)₂(being abbreviated as LiBOB), difluorine oxalic acid boracic acid lithium LiBF₂(C₂O₄) at least one in (being abbreviated as LiDFOB), wherein, substituent R_F=C_nF_2n+1Saturated perfluoroalkyl, n is the integer of 1～10, and the integer that 2n+1 is more than zero.It is particularly preferably LiPF₆And/or LiN (SO₂R_F)₂.Preferably, described lithium salts concentration in the electrolytic solution is 0.5M～2M (M=molL^-1)。

In this application, the preparation method of electrolyte selects conventional method, for instance can by organic solvent, lithium salts and additive mix homogeneously.

The another object of the application there are provided lithium ion battery, and described lithium ion battery includes electrolyte, the positive plate containing positive electrode active materials, the negative plate containing negative active core-shell material and isolating membrane.

In above-mentioned lithium ion battery, described positive plate also includes binding agent and conductive agent, is coated on plus plate current-collecting body by the anode sizing agent including positive electrode active materials, binding agent and conductive agent, treats that anode sizing agent obtains positive plate after drying.Same, the cathode size including negative active core-shell material, binding agent and conductive agent is coated on negative current collector, treats that cathode size obtains negative plate after drying.

Preferably, described positive electrode active materials is selected from cobalt acid lithium LiCoO₂, cobalt nickel lithium manganate ternary material, LiFePO 4, LiFePO4 (LiFePO₄), LiMn2O4 (LiMnO₂) at least one, for instance the mixture of cobalt acid lithium and lithium-nickel-manganese-cobalt ternary material can as positive electrode active materials.As the example of cobalt nickel lithium manganate ternary material, specifically can enumerate: LiNi_1/3Co_1/3Mn_1/3O₂, nickle cobalt lithium manganate LiNi_0.5Co_0.2Mn_0.3O₂、LiNi_0.6Co_0.2Mn_0.2O₂。

Preferably, described negative active core-shell material is graphite and/or silicon.

In above-mentioned lithium ion battery, the concrete kind of lithium battery diaphragm is not exposed to concrete restriction, can be any diaphragm material used in existing lithium ion battery, for instance polyethylene, polypropylene, Kynoar and their multilayer complex films, but be not limited only to these.

Embodiment

The application is further described below by way of instantiation.But these examples are only exemplary, the protection domain of the application do not constituted any restriction.

In following embodiment, comparative example and test example, reagent, material and the instrument used be not as having special explanation, being conventional reagent, conventional material and conventional instrument, all commercially available, wherein involved reagent obtains also by conventional synthesis process synthesis.

In following embodiment, comparative example and test example, used reagent is as follows:

Additive:

Acyl group ketone lithium compounds: the compound 1～compound 3 being previously mentioned.

Fluorophosphate lithium: the difluorophosphate being previously mentioned.

Lithium salts: lithium hexafluoro phosphate (LiPF₆)。

Organic solvent: ethylene carbonate (EC), Ethyl methyl carbonate (EMC).

Positive electrode active materials: cobalt nickel lithium manganate ternary material (LiNi1/3Co1/3Mn1/3O2).

Isolating membrane: using PE porous polymer film as isolating membrane.

The preparation of embodiment 1～19 lithium ion battery (following be all called for short battery) 1～19

Battery 1～19 is all prepared by the following method:

(1) prepared by negative plate

It is graphite by negative electrode active material graphite, conductive agent acetylene black, binding agent butadiene-styrene rubber, thickening agent sodium carboxymethyl cellulose according to weight ratio: acetylene black: butadiene-styrene rubber: sodium carboxymethyl cellulose=95:2:2:1 mixes, after adding deionized water, it is sufficiently stirred for mixing, forms uniform cathode size；This slurry is coated on negative current collector Copper Foil, then dries, cold pressing, obtain negative plate.

(2) prepared by positive plate

By positive electrode active materials lithium-nickel-manganese-cobalt ternary material, conductive agent acetylene black, binding agent polyvinylidene fluoride by weight for lithium-nickel-manganese-cobalt ternary material: acetylene black: polyvinylidene fluoride=96:2:2 mixes, add solvent N-methyl pyrilidone, after being sufficiently stirred for mixing, form uniform anode sizing agent；This slurry is coated on plus plate current-collecting body aluminium foil, then dries, cold pressing, obtain positive plate.

(3) prepared by electrolyte

Electrolyte 1～19 is all prepared by the following method:

< in the argon gas atmosphere glove box of 10ppm, it is after EC:EMC=3:7 mixes by EC, EMC according to weight ratio in water content, obtains mixed solvent then lithium salts LiPF that will be fully dry₆It is dissolved in above-mentioned mixed solvent, is then added thereto to acyl group ketone lithium compounds and difluorophosphate, after stirring, it is thus achieved that electrolyte, wherein LiPF₆Concentration be 1mol/L.

(4) preparation of battery

Battery 1～19 all prepares by the following method:

Positive plate, isolating membrane, negative plate being folded in order, make isolating membrane be between positive/negative plate to play the effect of isolation, then winding obtains naked battery core；Naked battery core is placed in outer package paper tinsel, the above-mentioned electrolyte prepared is injected in dried battery, is then passed through the operations such as Vacuum Package, standing, chemical conversion, shaping, it is thus achieved that battery.

In the above-mentioned process preparing battery, the kind of acyl group ketone lithium compounds used in electrolyte selected in each battery, each electrolyte and the content of content and fluorophosphate lithium thereof, as shown in table 1 below.

In table 1 below, the content of acyl group ketone lithium compounds and the content of fluorophosphate lithium are the percetage by weight that the total weight based on electrolyte obtains.

Table 1

Comparative example 1～17 lithium ion battery (following be all called for short battery) 1^#～17^#Preparation

Comparative example 1～17

Battery 1^#～17^#All it is prepared by the following method:

Repeating the preparation of battery 1 in embodiment 1, wherein in the preparation of electrolyte, change the kind of acyl group ketone lithium compounds, content and/or the content of change difluorophosphate, all the other conditions are all constant.

In the above-mentioned process preparing battery, the kind of acyl group ketone lithium compounds used in electrolyte selected in each battery, each electrolyte and the content of content and difluorophosphate thereof, as shown in table 2 below.

In table 2 below, the content of acyl group ketone lithium compounds and the content of difluorophosphate are the percetage by weight that the total weight based on electrolyte obtains.

Table 2

Note: in table 2, " " expression is not added with any kind of material.

Test case

(1) memory property test

The high-temperature storage performance of battery is characterized with the volume change before and after battery storage.

The battery prepared in embodiment and comparative example all carries out following test:

At 25 DEG C, first with the constant current of 0.5C, battery is charged to 4.4V, further with 4.4V constant-potential charge to electric current for 0.025C, then with drainage, battery is recorded in deionized water the initial volume of battery, using the initial volume of battery as the volume before battery storage, then battery is placed at 85 DEG C and stores 6h, after end to be stored, test battery volume after storage at high temperatures, then passes through following formula and calculates the volume change of battery.It addition, test result is as shown in Table 4 below.

The volume change (%) of battery=[volume before volume/battery storage after battery high-temperature storage] × 100%

(2) the normal-temperature circulating performance test of battery

The battery prepared in embodiment and comparative example all carries out following test:

At 25 DEG C, first with the constant current of 1C, battery is charged to 4.4V, further with 4.4V constant-potential charge to electric current for 0.025C, then with the constant current of 1C by battery discharge to 3.0V, this is a charge and discharge cycles process, and this discharge capacity is the discharge capacity of the 1st circulation.Battery carries out repeatedly cycle charge discharge electrical testing in a manner described, and detection obtains the discharge capacity of the 100th circulation, and is calculated the circulation volume conservation rate of battery by following formula.It addition, test result is as shown in Table 3 below.

Capability retention (%) after 100 circulations of battery=[discharge capacity of the discharge capacity/1st time circulation of the 100th circulation] × 100%

(3) the high temperature cyclic performance test of battery

The battery prepared in embodiment and comparative example all carries out following test:

At 45 DEG C, first with the constant current of 1C, battery is charged to 4.4V, further with 4.4V constant-potential charge to electric current for 0.025C, then with the constant current of 1C by battery discharge to 3.0V, this is a charge and discharge cycles process, and this discharge capacity is the discharge capacity of the 1st circulation.Battery carries out repeatedly cycle charge discharge electrical testing in a manner described, and detection obtains the discharge capacity of the 100th circulation, and is calculated the capability retention after the circulation of battery by following formula.It addition, test result is as shown in Table 3 below.

Capability retention (%) after 100 circulations of battery=[discharge capacity of the discharge capacity/1st time circulation of the 100th circulation] × 100%

Table 3

Related data from above-mentioned table 3, carries out analyzing as follows:

(1) 85 DEG C of memory property test result analysis

By to battery 2^#, battery 3^#And battery 3 and battery 1^#Test obtain as a result, it is possible to learn, when electrolyte contain difluorophosphoric acid lithium compound and acyl group ketone lithium compounds simultaneously, more only add acyl group ketone lithium compounds or only interpolation difluorophosphate or the situation without additive, memory property is good.

Being contrasted by the test result of the battery that battery 1-5 obtains, it is possible to learn, when the amount of fixing difluorophosphate is 0.5%, along with the addition of acyl group ketone lithium compounds increases, battery storage performance improves；

Being contrasted by the test result of the battery that battery 3 and battery 6-9 obtain, it is possible to learn, when the amount of fixing acyl group ketone lithium compounds is 1%, along with the addition of difluorophosphate coordination compound increases, battery storage performance improves；

Same, battery 10～19 memory property is analyzed, there is analysis result same as described above.

(2) test result analysis of cycle performance

Capability retention after the circulation obtained by battery 1～19 and battery 1^#Capability retention after the circulation obtained is it can be seen that containing acyl group ketone lithium compounds and difluorophosphoric acid lithium compound in electrolyte, battery has higher capability retention, and battery has the cycle performance of excellence at ambient and elevated temperatures.

By battery 1^#～9^#Capability retention after the circulation obtained, it is possible to learn, electrolyte 1^#In do not add any additive so that organic solvent can produce more side reaction in pole piece, causes that the capability retention of battery is low.

At battery 2^#With battery 3^#In; acyl group ketone lithium compounds, difluorophosphoric acid lithium compound is added respectively in respective electrolyte; the SEI film formed due to acyl group ketone lithium compounds can't stop the side reaction between active substance and electrolyte effectively; or difluorophosphate can not effectively stablize lithium salts, so that the cycle performance of battery can not get improving substantially.

Due at battery 4^#, battery 5^#With battery 7^#In; the weight percentage of acyl group ketone lithium compounds and/or difluorophosphoric acid lithium compound is very little; the SEI film formed due to acyl group ketone lithium compounds can not have the feature of compactness and stability concurrently; cannot effectively stop the side reaction between active substance and electrolyte; or difluorophosphate can not effectively stablize lithium salts, battery cycle performance at high temperature is made to can not get effective improvement.

At battery 6^#, battery 8^#, battery 9^#In, acyl group ketone lithium compounds and/or difluorophosphate compounds content are too much, and too much acyl group ketone lithium compounds and difluorophosphoric acid lithium compound remain in electrolyte, and acyl group ketone lithium compounds may proceed to react in pole piece, cause interface impedance to become big；Difluorophosphate can cause the hydraulic performance declines such as the electrical conductivity of electrolyte, thus worsening battery cycle performance at high temperature.

In battery 1～5; the content of difluorophosphoric acid lithium compound is 0.5%; add the acyl group ketone lithium compounds that content is 0.01%～5%; SEI film densification, stable can be formed; stop the side reaction between active substance and electrolyte, make battery have higher capability retention after circulating under high temperature and room temperature.

In battery 4 and battery 6～9; the content of acyl group ketone lithium compounds is 1%; add the difluorophosphoric acid lithium compound that content is 0.1%～2%; SEI film densification, stable can be formed; stop the side reaction between active substance and electrolyte, make battery have higher capability retention after circulating under high temperature and room temperature.Same, the capability retention after battery 10～19 is circulated is analyzed, and has analysis result same as described above.

It can be seen that when in electrolyte simultaneously containing acyl group ketone lithium compounds and difluorophosphoric acid lithium compound, improve the capability retention after battery circulates under high temperature and room temperature in from the above, battery has the cycle performance of excellence under high temperature and room temperature.

In sum: in the electrolytic solution; when the content of acyl group ketone lithium compounds is too small or excessive and it is too small or excessive to work as difluorophosphate compounds content; all can not form fine and close, stable, the good SEI film of interface performance; cannot effectively stablize lithium salts, thus the battery of good cycle under high temperature and room temperature cannot be obtained simultaneously.The acyl group ketone lithium compounds of 0.01%～5% and the difluorophosphoric acid lithium compound of 0.001%～2% is contained when electrolyte; especially containing the acyl group ketone lithium compounds of 0.1%～5% and the difluorophosphoric acid lithium compound of 0.1%～1%, battery cycle performance at high temperature is comparatively excellent.

Embodiment 20～33

Preparing electrolyte and lithium ion battery according to the method for embodiment 1, differ only in, in electrolyte, the composition of additive is as shown in table 4:

Table 4:

The storge quality of the lithium ion battery that embodiment 20～33 prepares, normal-temperature circulating performance and high temperature cyclic performance are similar to the aforementioned embodiment, and length is limit, and repeat no more.

Although the application is with preferred embodiment openly as above; but it is not for limiting claim; any those skilled in the art are under the premise conceived without departing from the application; can making some possible variations and amendment, therefore the protection domain of the application should be as the criterion with the scope that the application claim defines.

Claims (11)

1. an electrolyte, it is characterised in that include organic solvent, lithium salts and additive, described additive includes acyl group ketone lithium compounds and fluorophosphate lithium compound.

2. electrolyte according to claim 1, it is characterised in that acyl group ketone lithium compounds is at least one in compound as shown in formula I:

Wherein, R₁₁、R₁₂、R₁₃、R₁₄、R₁₅、R₁₆Each independent it is respectively selected from hydrogen atom, halogen atom, cyano group, sulfonic group, substituted or unsubstituted C_1～20Alkyl, substituted or unsubstituted C_{2～ 20}Thiazolinyl, substituted or unsubstituted C_6～26Aryl, substituted or unsubstituted C_1～20Alkoxyl, substituted or unsubstituted C_6～26Aryloxy group, substituted or unsubstituted C_1～20Alkane sulfonyl, substituted or unsubstituted C_2～20Alkene sulfonyl, substituted or unsubstituted C_6～26Arylsulfonyl；

Substituent group is selected from halogen atom, cyano group, pyridine radicals, thienyl or sulfonic group；

Wherein, halogen atom is selected from F, Cl, Br, it is preferable that F, Cl.

3. electrolyte according to claim 1, it is characterised in that described acyl group ketone lithium compounds is at least one in compound as shown in formula II:

Wherein, R₂₁、R₂₂Each independent it is respectively selected from hydrogen atom, halogen atom, cyano group, sulfonic group, substituted or unsubstituted C_1～20Alkyl, substituted or unsubstituted C_2～20Thiazolinyl, substituted or unsubstituted C_6～26Aryl, substituted or unsubstituted C_1～20Alkoxyl, substituted or unsubstituted C_6～26Aryloxy group, substituted or unsubstituted C_1～20Alkane sulfonyl, substituted or unsubstituted C_2～20Alkene sulfonyl, substituted or unsubstituted C_6～26Arylsulfonyl；

Substituent group is selected from halogen atom, cyano group, pyridine radicals, thienyl or sulfonic group,

Wherein, halogen atom is selected from F, Cl, Br, it is preferable that F, Cl.

4. an electrolyte according to claim 3, it is characterised in that R₂₁、R₂₂Each independent it is respectively selected from hydrogen atom, halogen atom, substituted or unsubstituted C_1～6Alkyl, substituted or unsubstituted C_2～6Thiazolinyl, substituted or unsubstituted phenyl, substituted or unsubstituted C_1～6Alkoxyl, substituted or unsubstituted phenoxy group；Substituent group is selected from halogen atom；

Preferably, R₂₁、R₂₂Each independent it is respectively selected from hydrogen atom, halogen atom, substituted or unsubstituted C_1～6Alkyl, substituted or unsubstituted C_1～6Alkoxyl；Substituent group is selected from halogen atom.

5. the electrolyte piece according to claim 3 or 4, it is characterised in that R₂₁、R₂₂For identical substituent group.

6. an electrolyte according to claim 1, it is characterised in that described acyl group ketone lithium compounds at least one in following compound:

7. electrolyte according to claim 1, it is characterised in that described fluorophosphate lithium compound at least one in single lithium fluophosphate or difluorophosphate.

8. electrolyte according to claim 1, it is characterised in that described acyl group ketone lithium compounds is 0.01%～5% in the mass percentage content of electrolyte, it is preferable that 0.1%～5%；And/or,

Described fluorophosphate lithium compound is 0.001%～2% in the mass percentage content of electrolyte, it is preferable that 0.1%～1%.

9. electrolyte according to claim 1, it is characterized in that, described organic solvent is at least one in ethylene carbonate, Allyl carbonate, butylene, fluorinated ethylene carbonate, Ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonic acid ester, GBL, methyl propionate, methyl butyrate, ethyl acetate, ethyl propionate or ethyl n-butyrate..

10. electrolyte according to claim 1, it is characterised in that

Described lithium salts is selected from lithium hexafluoro phosphate, LiBF4, lithium perchlorate, hexafluoroarsenate lithium, fluorine oxalic acid lithium phosphate, LiN (SO₂R_F)₂、LiN(SO₂F)(SO₂R_F), double; two trifluoromethanesulfonimide lithium, double; two (fluorine sulphonyl) imine lithium, di-oxalate lithium borate, at least one in difluorine oxalic acid boracic acid lithium, wherein, R_F=C_nF_2n+1, n is the integer of 1～10, it is preferred to LiPF₆Or LiN (SO₂R_F)₂In at least one；

Preferably, described lithium salts concentration in the electrolytic solution is 0.5molL^-1～2molL^-1。

11. a lithium ion battery, it is characterised in that include the positive plate containing positive electrode active materials, containing the electrolyte according to any one of the negative plate of negative active core-shell material, isolating membrane and claim 1～10.