Non-aqueous electrolyte and lithium ion battery containing same
阅读说明：本技术 一种非水电解液及含该非水电解液的锂离子电池 (Non-aqueous electrolyte and lithium ion battery containing same ) 是由 曾长安 李素丽 徐延铭 李俊义 于 2019-11-20 设计创作，主要内容包括：本发明提供一种非水电解液和含有该非水电解液的锂离子电池,所述电解液中含有锂盐、有机溶剂和添加剂,所述添加剂至少包括1,3,6-己烷三腈；另外,所述电解液中还含有稳定剂,所述稳定剂包括亚磷酸三苯酯、六甲基二硅胺烷、二异丙基碳二酰亚胺中的一种或几种。所述电解液通过稳定剂的加入,提高了电解液的热稳定性、延长了存储时间,通过所述稳定剂与1,3,6-己烷三腈添加剂之间的协同作用,有效改善了电池的循环和高温存储性能。(The invention provides a non-aqueous electrolyte and a lithium ion battery containing the same, wherein the electrolyte contains a lithium salt, an organic solvent and an additive, and the additive at least comprises 1,3, 6-hexanetricarbonitrile; in addition, the electrolyte also contains a stabilizer, and the stabilizer comprises one or more of triphenyl phosphite, hexamethyldisilazane and diisopropylcarbodiimide. The electrolyte improves the thermal stability of the electrolyte and prolongs the storage time by adding the stabilizer, and effectively improves the cycle and high-temperature storage performance of the battery by the synergistic action of the stabilizer and the 1,3, 6-hexanetricarbonitrile additive.)
1. A non-aqueous electrolyte, the electrolyte contains lithium salt, organic solvent and additive, characterized in that, the additive at least includes 1,3, 6-hexanetrinitrile; in addition, the electrolyte also contains a stabilizer, and the stabilizer comprises one or more of triphenyl phosphite, hexamethyldisilazane and diisopropylcarbodiimide.
2. The nonaqueous electrolytic solution of claim 1, wherein the 1,3, 6-hexanetricarbonitrile is present in an amount of 0.1 to 5% by weight based on the total mass of the electrolytic solution.
3. The nonaqueous electrolytic solution of claim 1 or 2, wherein the triphenyl phosphite accounts for 20 to 300ppm, preferably 50 to 150ppm, of the total mass of the electrolytic solution.
4. The nonaqueous electrolytic solution of any one of claims 1 to 3, wherein the hexamethyldisilazane is present in an amount of 20 to 300ppm, preferably 50 to 150ppm, based on the total mass of the electrolytic solution.
5. The nonaqueous electrolytic solution of any one of claims 1 to 4, wherein the diisopropylcarbodiimide accounts for 20 to 300ppm, preferably 50 to 150ppm, of the total mass of the electrolytic solution.
6. The nonaqueous electrolytic solution of any one of claims 1 to 5, wherein the additive further comprises one or more of Vinylene Carbonate (VC), vinyl sulfate (DTD), fluoroethylene carbonate (FEC), 1, 3-Propanesultone (PS), ethylene carbonate (VEC), vinyl sulfate, vinyl sulfite, methylene methanedisulfonate, vinyl sulfate, methylene methanedisulfonate, propylene sultone, Succinonitrile (SN), glutaronitrile, Adiponitrile (ADN), pimelonitrile, suberonitrile, sebaconitrile, etc., ethylene glycol bis (propionitrile) ether, 1, 2-bis (2-cyanoethoxy) ethane (DENE), 1, 2-bis (2-cyanoethoxy) ethane, 1,2, 3-tris- (2-cyanoethoxy) propane.
7. The nonaqueous electrolytic solution of claim 1, wherein the lithium salt is selected from lithium hexafluorophosphate (LiPF)6) Lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium difluoro (oxalato) borate (LiODFB), lithium difluoro (LiPO) phosphate2F2) Lithium tetrafluoroborate (LiBF)4) Lithium bis (oxalato) borate (LiBOB), lithium hexafluoroantimonate (LiSbF)6) Lithium hexafluoroarsenate (LiAsF)6) Lithium bis (trifluoromethylsulfonyl) imide (LiN (SO)2CF3)2) Lithium bis (pentafluoroethylsulfonyl) imido (LiN (SO)2C2F5)2) Tris (trifluoromethylsulfonyl) methyllithium (LiC (SO)2CF3)3) Or lithium bis (trifluoromethylsulfonyl) imide (LiN (CF)3SO2)2) One or more than two of them.
8. The nonaqueous electrolytic solution of any one of claims 1 to 7, wherein the organic solvent is at least one selected from the group consisting of carbonates (e.g., cyclic carbonates, chain carbonates), carboxylates (e.g., cyclic carboxylates, chain carboxylates), ether compounds (e.g., cyclic ether compounds, chain ether compounds), phosphorus-containing compounds, and sulfur-containing compounds; preferably, the organic solvent is at least one selected from the group consisting of cyclic carbonates, chain carbonates, cyclic carboxylates, and chain carboxylates.
9. The method for producing the nonaqueous electrolytic solution of any one of claims 1 to 8, characterized by comprising:
mixing an organic solvent, a lithium salt, an additive at least containing 1,3, 6-hexanetricarbonitrile and a stabilizer comprising one or more of triphenyl phosphite, hexamethyldisilazane and diisopropylcarbodiimide to prepare the non-aqueous electrolyte.
10. A lithium ion battery comprising the nonaqueous electrolytic solution of any one of claims 1 to 8.
Technical Field
The invention belongs to the technical field of electrolyte, and particularly relates to a non-aqueous electrolyte and a lithium ion battery containing the same.
Background
Since commercialization, lithium ion batteries have been widely used in the fields of digital, energy storage, power, military space and communication equipment, due to their portability, high specific energy, no memory effect, and good cycle performance. With the wide application of lithium ion batteries, consumers have made higher demands on the energy density, cycle life, high temperature performance, safety and other performances of lithium ion batteries.
The energy density can be improved mainly by the following methods, on one hand, the charging voltage of the battery can be improved, a positive electrode with higher charging voltage is adopted, the voltage of the existing battery is improved by adopting a process, or a high-nickel positive electrode or a lithium-rich positive electrode material with high capacity is adopted; on the other hand, negative electrode materials such as silicon carbon with high energy density can be adopted; the energy density is also increased by reducing or thinning the thickness of a main material such as an aluminum plastic film, a separator, an aluminum foil, or a copper foil, or by increasing the compacted density and/or the areal density of the positive and negative electrodes.
Increasing the charging voltage of a battery is a widely adopted method in the industry at present, but increasing the charging voltage of the battery brings the following hazards to the battery: firstly, when the anode is under high voltage, the surface transition metal ions are in a high oxidation state, and the electrolyte is easily oxidized; secondly, HF or HCl possibly generated by lithium salt in the electrolyte or residual substances in the additive can corrode transition metal ions, so that the transition metal ions are dissolved out, and the acidity of the electrolyte is influenced; and thirdly, the SEI film of the negative electrode is damaged due to the fact that the transition metal ions are dissolved out and transferred to the negative electrode to be reduced, and then the electrolyte is reduced again, so that gas generation of the battery can be caused.
The electrolyte is an important factor for improving the performance of the lithium ion battery, and the additive in the electrolyte is a key component. At present, the electrolyte of a high-voltage battery system is improved by adding protective additives or film-forming additives of a positive electrode and a negative electrode, and reducing the generation of side reactions so as to achieve the aim of stabilizing the positive electrode and the negative electrode, thereby improving the performance of the battery.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention aims to provide a nonaqueous electrolyte and a lithium ion battery containing the same. The non-aqueous electrolyte is prepared by adding one or more of stabilizers such as triphenyl phosphite, hexamethyldisilazane and diisopropylcarbodiimide into electrolyte containing 1,3, 6-hexanetricarbonitrile additive, and is used for stabilizing the electrolyte, improving the thermal stability and prolonging the storage time of the electrolyte, and the cycle and high-temperature storage performance of the battery can be improved through the synergistic effect of the stabilizers.
The inventor of the invention has found through a great deal of experimental researches that impurities including acrylonitrile or residual chlorine and the like are generated in the preparation process of 1,3, 6-hexanetricarbonitrile, 1,3, 6-hexanetricarbonitrile containing the impurities is added into an electrolyte as an additive, the chromaticity of the additive is high, in addition, the residual chlorine is combined with hydrogen radicals generated in a battery system to generate HCl, and lithium salt LiPF in the electrolyte6Will decompose to produce PF5And PF5HF can be generated by reaction with water, the acidity of the electrolyte is influenced, and side reaction can be generated with high-oxidation-state transition metal ions on the surface of the positive electrode, the transition metal on the surface of the positive electrode is corroded, the positive electrode is damaged, in addition, the transition metal ions dissolved out from the positive electrode are transferred to the negative electrode, the SEI film of the negative electrode can be damaged, and the performance of the battery is influenced.
According to the invention, one or more of triphenyl phosphite, hexamethyldisilazane, diisopropylcarbodiimide and other stabilizers are added into the electrolyte containing the 1,3, 6-hexanetricarbonitrile additive, so that the problems are effectively solved, and the cycle and high-temperature storage performance of the battery is improved.
The addition of triphenyl phosphite can prolong the shelf life of the electrolyte and has no negative influence on the electrochemical performance of the battery; the addition of hexamethyldisilazane can improve the storage stability and the thermal stability of the electrolyte; the addition of the diisopropylcarbodiimide can play a certain role in dehydration and deacidification, and has a good effect on inhibiting the chromaticity rise; the 1,3, 6-hexanetricarbonitrile is used as a nitrile additive and can be complexed with transition metal ions on the surface of the anode to stabilize the transition metal on the surface, so that the oxidation of the high-oxidation-state anode on the electrolyte under high voltage is reduced or inhibited, and the dissolution of the transition metal ions is reduced. One or more of stabilizers such as triphenyl phosphite, hexamethyldisilazane and diisopropylcarbodiimide are introduced into the electrolyte containing the 1,3, 6-hexanetricarbonitrile additive, so that the chromaticity or acidity of the electrolyte can be stabilized, the quality of the electrolyte is improved, the thermal stability of the electrolyte is improved, the storage time of the electrolyte is prolonged, and the cycle and high-temperature storage performance of the battery are effectively improved through the synergistic effect of the stabilizers and the 1,3, 6-hexanetricarbonitrile additive.
The purpose of the invention is realized by the following technical scheme:
a non-aqueous electrolyte, the electrolyte contains lithium salt, organic solvent and additive, characterized in that, the additive at least includes 1,3, 6-hexanetrinitrile; in addition, the electrolyte also contains a stabilizer, and the stabilizer comprises one or more of triphenyl phosphite, hexamethyldisilazane and diisopropylcarbodiimide.
According to the invention, the 1,3, 6-hexanetricarbonitrile accounts for 0.1-5 wt% of the total mass of the electrolyte.
According to the invention, the triphenyl phosphite accounts for 20-300ppm, preferably 50-150ppm of the total mass of the electrolyte.
According to the invention, the hexamethyldisilazane constitutes from 20 to 300ppm, preferably from 50 to 150ppm, of the total mass of the electrolyte.
According to the invention, the diisopropyl carbodiimide accounts for 20-300ppm, preferably 50-150ppm of the total mass of the electrolyte.
According to the invention, the additive also comprises one or more of Vinylene Carbonate (VC), vinyl sulfate (DTD), fluoroethylene carbonate (FEC), 1, 3-Propanesultone (PS), ethylene carbonate (VEC), vinyl sulfate, vinyl sulfite, methylene methanedisulfonate, vinyl sulfate, methylene methanedisulfonate, propylene sultone, Succinonitrile (SN), glutaronitrile, Adiponitrile (ADN), pimelonitrile, suberonitrile, sebaconitrile and the like, ethylene glycol bis (propionitrile) ether, 1, 2-bis (2-cyanoethoxy) ethane (done), 1, 2-bis (2-cyanoethoxy) ethane, 1,2, 3-tris- (2-cyanoethoxy) propane.
According to the invention, the lithium salt is selected from lithium hexafluorophosphate (LiPF)6) Lithium bis (fluorosulfonylimide) (LiFSI), lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium difluoro (oxalato) borate (LiODFB), bis (fluorosulfonato) imideLithium fluorophosphate (LiPO)2F2) Lithium tetrafluoroborate (LiBF)4) Lithium bis (oxalato) borate (LiBOB), lithium hexafluoroantimonate (LiSbF)6) Lithium hexafluoroarsenate (LiAsF)6) Lithium bis (trifluoromethylsulfonyl) imide (LiN (SO)2CF3)2) Lithium bis (pentafluoroethylsulfonyl) imido (LiN (SO)2C2F5)2) Tris (trifluoromethylsulfonyl) methyllithium (LiC (SO)2CF3)3) Or lithium bis (trifluoromethylsulfonyl) imide (LiN (CF)3SO2)2) One or more than two of them.
According to the present invention, the organic solvent is at least one selected from the group consisting of a carbonate (e.g., cyclic carbonate, chain carbonate), a carboxylate (e.g., cyclic carboxylate, chain carboxylate), an ether compound (e.g., cyclic ether compound, chain ether compound), a phosphorus-containing compound, and a sulfur-containing compound; preferably, the organic solvent is at least one selected from the group consisting of cyclic carbonates, chain carbonates, cyclic carboxylates, and chain carboxylates.
The method for producing the nonaqueous electrolytic solution is characterized by comprising the following steps:
mixing an organic solvent, a lithium salt, an additive at least containing 1,3, 6-hexanetricarbonitrile and a stabilizer comprising one or more of triphenyl phosphite, hexamethyldisilazane and diisopropylcarbodiimide to prepare the non-aqueous electrolyte.
A lithium ion battery comprises the non-aqueous electrolyte.
The invention has the beneficial effects that:
the invention provides a non-aqueous electrolyte and a lithium ion battery containing the same. The electrolyte is characterized in that one or more of stabilizers such as triphenyl phosphite, hexamethyldisilazane and diisopropylcarbodiimide are added into the electrolyte containing the 1,3, 6-hexanetricarbonitrile additive to stabilize the electrolyte, improve the thermal stability of the electrolyte and prolong the storage time of the electrolyte, and the circulation and high-temperature storage performance of the battery are effectively improved through the synergistic effect of the stabilizers and the 1,3, 6-hexanetricarbonitrile additive.
Detailed Description
As described above, the present invention provides a nonaqueous electrolytic solution containing a lithium salt, an organic solvent, and an additive, the additive including at least 1,3, 6-hexanetricarbonitrile; in addition, the electrolyte also contains a stabilizer, and the stabilizer comprises one or more of triphenyl phosphite, hexamethyldisilazane and diisopropylcarbodiimide.
In one embodiment of the invention, the 1,3, 6-Hexanetricarbonitrile (HTCN) constitutes 0.1 to 5 wt.%, for example 0.3 to 3 wt.%, for example 0.5 to 1.5 wt.%, based on the total mass of the electrolyte.
In one embodiment of the invention, the triphenyl phosphite accounts for 20 to 300ppm, preferably 50 to 150ppm, of the total mass of the electrolyte.
In one embodiment of the invention, the hexamethyldisilazane is present in an amount of 20 to 300ppm, preferably 50 to 150ppm, based on the total mass of the electrolyte.
In one embodiment of the invention, the diisopropyl carbodiimide accounts for 20 to 300ppm, preferably 50 to 150ppm, of the total mass of the electrolyte.
In one embodiment of the present invention, the additive further comprises one or more of Vinylene Carbonate (VC), vinyl sulfate (DTD), fluoroethylene carbonate (FEC), 1, 3-Propanesultone (PS), ethylene carbonate (VEC), vinyl sulfate, vinyl sulfite, methylene methanedisulfonate, vinyl sulfate, methylene methanedisulfonate, propylene sultone, Succinonitrile (SN), glutaronitrile, Adiponitrile (ADN), pimelonitrile, suberonitrile, sebaconitrile, etc., ethylene glycol bis (propionitrile) ether, 1, 2-bis (2-cyanoethoxy) ethane (done), 1, 2-bis (2-cyanoethoxy) ethane, 1,2, 3-tris- (2-cyanoethoxy) propane, in an amount of 0 to 5 wt% based on the total mass of the electrolyte.
In one embodiment of the present invention, the lithium salt is selected from lithium hexafluorophosphate (LiPF)6) Lithium bis (fluorosulfonyl) imide (LiFSI), lithium bis (trifluoromethylsulfonyl) imide (LiTFSI), lithium difluoro (oxalato) borate (LiODFB), lithium difluoro (LiPO) phosphate2F2) Lithium tetrafluoroborate (LiBF)4) Lithium bis (oxalato) borate (LiBOB), lithium hexafluoroantimonate (LiSbF)6) Lithium hexafluoroarsenate (LiAsF)6) Lithium bis (trifluoromethylsulfonyl) imide (LiN (SO)2CF3)2) Lithium bis (pentafluoroethylsulfonyl) imido (LiN (SO)2C2F5)2) Tris (trifluoromethylsulfonyl) methyllithium (LiC (SO)2CF3)3) Or lithium bis (trifluoromethylsulfonyl) imide (LiN (CF)3SO2)2) One or more than two of them.
In one embodiment of the present invention, the lithium salt is 10 to 18 wt% of the total mass of the electrolyte.
In one embodiment of the present invention, the organic solvent is at least one selected from the group consisting of a carbonate (e.g., cyclic carbonate, chain carbonate), a carboxylate (e.g., cyclic carboxylate, chain carboxylate), an ether compound (e.g., cyclic ether compound, chain ether compound), a phosphorus-containing compound, and a sulfur-containing compound. Preferably, the organic solvent is at least one selected from the group consisting of cyclic carbonates, chain carbonates, cyclic carboxylates, and chain carboxylates.
Wherein the carbonate is at least one selected from the group consisting of dimethyl carbonate, methylethyl carbonate, diethyl carbonate, methyl-n-propyl carbonate, ethyl-n-propyl carbonate, di-n-propyl carbonate, bis (fluoromethyl) carbonate, bis (difluoromethyl) carbonate, bis (trifluoromethyl) carbonate, bis (2-fluoroethyl) carbonate, bis (2, 2-difluoroethyl) carbonate, bis (2,2, 2-trifluoroethyl) carbonate, 2-fluoroethyl methyl carbonate, 2, 2-difluoroethyl methyl carbonate and 2,2, 2-trifluoroethyl methyl carbonate.
Wherein the carboxylic ester is at least one selected from methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, sec-butyl acetate, isobutyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, methyl isobutyrate, ethyl isobutyrate, methyl valerate, ethyl valerate, methyl pivalate and ethyl pivalate, methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, trifluoroacetic acid and 2,2, 2-trifluoroethyl ester.
Wherein the ether compound is at least one selected from tetrahydrofuran, 2-methyltetrahydrofuran, 1, 3-dioxolane, 2-methyl-1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 1, 3-dioxane, 1, 4-dioxane, dimethoxypropane, dimethoxymethane, 1-dimethoxyethane, 1, 2-dimethoxyethane, diethoxymethane, 1-diethoxyethane, 1, 2-diethoxyethane, ethoxymethoxymethane, 1-ethoxymethoxyethane and 1, 2-ethoxymethoxyethane.
Wherein the phosphorus-containing compound is selected from at least one of trimethyl phosphate, triethyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, ethylene methyl phosphate, ethylene ethyl phosphate, triphenyl phosphate, trimethyl phosphite, triethyl phosphite, triphenyl phosphite, tris (2,2, 2-trifluoroethyl) phosphate, and tris (2,2,3,3, 3-pentafluoropropyl) phosphate.
Wherein the sulfur-containing compound is at least one selected from sulfolane, 2-methylsulfolane, 3-methylsulfolane, dimethylsulfone, diethylsulfone, ethylmethylsulfone, methylpropylsulfone, dimethylsulfoxide, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, ethyl ethanesulfonate, dimethyl sulfate, diethyl sulfate and dibutyl sulfate.
In one embodiment of the invention, the organic solvent accounts for 60 wt% to 88 wt% of the total mass of the electrolyte.
As described above, the present invention also provides a method for producing the above nonaqueous electrolytic solution, the method comprising:
mixing an organic solvent, a lithium salt, an additive at least containing 1,3, 6-hexanetricarbonitrile and a stabilizer comprising one or more of triphenyl phosphite, hexamethyldisilazane and diisopropylcarbodiimide to prepare the non-aqueous electrolyte.
In one embodiment of the present invention, the mixing is not limited by the order of addition; or the organic solvent, the lithium salt, the additive and the stabilizer are added in sequence.
As described above, the present invention also provides a lithium ion battery comprising the above nonaqueous electrolytic solution.
In one aspect of the present invention, the lithium ion battery further includes a positive plate, a negative plate, and a separator, where the separator is disposed between the positive plate and the negative plate. The diaphragm arranged between the positive plate and the negative plate can prevent the current short circuit caused by the contact of the two plates and can allow lithium ions to pass through.
In one aspect of the present invention, the anode includes an anode current collector and an anode active material layer disposed on one or both surfaces of the anode current collector.
Wherein, the negative current collector is selected from copper foil, such as electrolytic copper foil or rolled copper foil.
Wherein the anode active material layer includes an anode active material and an anode binder.
In some embodiments, the negative electrode active material is any material capable of deintercalating metal ions such as lithium ions.
In some embodiments, the negative active material may be one or more of a carbon material, a silicon-based material, a tin-based material, or their corresponding alloy materials.
In some embodiments, the chargeable capacity of the negative active material is greater than the discharge capacity of the positive active material to prevent lithium metal from being precipitated on the negative electrode during charging.
In some embodiments, the negative electrode binder includes, but is not limited to, one or more of styrene-butadiene rubber, fluorine-based rubber, and ethylene propylene diene, hydroxyalkyl methyl cellulose.
The negative electrode active material layer may further include a conductive agent, and the conductive agent may be at least one of graphite, carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene.
In one aspect of the present invention, the positive electrode includes a positive electrode current collector and a positive electrode active material layer provided on one or both surfaces of the positive electrode current collector.
Wherein the positive electrode current collector is selected from aluminum foil.
Wherein the positive electrode active material layer includes a positive electrode active material and a positive electrode binder.
In some embodiments, the positive active material is one or more of layered lithium composite oxide, lithium manganate and lithium cobaltate mixed ternary material, and the general formula of the layered lithium composite oxide is Li1+xNiyCozM(1-y-z)Y2Wherein x is more than or equal to-0.1 and less than or equal to 1; y is more than or equal to 0 and less than or equal to 1, z is more than or equal to 0 and less than or equal to 1, and y + z is more than or equal to 0 and less than or equal to 1; wherein M is one or more of Mg, Zn, Ga, Ba, Al, Fe, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo and Zr; y is one or more of O, F, P.
In some embodiments, the positive electrode binder may be a polymeric material including, but not limited to, polyvinylidene fluoride and polyimide.
The positive electrode may further include a conductive agent, and the conductive agent may be at least one of graphite, carbon black, acetylene black, ketjen black, carbon nanotubes, and graphene.
In one embodiment of the present invention, the positive electrode active material has a compacted density of 17.04mg/cm when coated3The areal density of the alloy is 4.05mg/cm2(ii) a The negative electrode active material had a compacted density of 1.65mg/cm when applied3The areal density of the alloy is 9.5mg/cm2。
In one aspect of the invention, the separator is selected from porous films.
Wherein, the diaphragm is a porous film made of polymer.
In some embodiments, the polymers include, but are not limited to: polyethylene terephthalate, polybutylene terephthalate, polyether, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyether sulfone, polyphenylene ether, polyphenylene sulfide, polyethylene naphthalene, high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, and polypropylene.
In some embodiments, the separator further comprises an organic or inorganic coating disposed on one or both surfaces of the porous membrane.
In some embodiments, the inorganic material may specifically include, but is not limited toIn the following steps: BaTiO 23、Pb(Zr，Ti)O3(PZT)、Pb1-xLaxZr1-yTiyO3、PB(Mg3Nb2/3)O3-PbTiO3Hafnium oxide (HfO)2)、SrTiO3、SnO2、CeO2、MgO、NiO、CaO、ZnO、ZrO2、SiO2、Y2O3、Al2O3、SiC、TiO2And mixtures thereof.
In some embodiments, the organic material may specifically include, but is not limited to: cyanoethylpullulan, cyanoethylpolyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate butyrate and cellulose acetate propionate and mixtures thereof.
In one embodiment of the present invention, the charge cut-off voltage of the lithium ion battery is 4.25V or more.
The preparation method of the present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are only illustrative and explanatory of the present invention and should not be construed as limiting the scope of the present invention. All the technologies realized based on the above-mentioned contents of the present invention are covered in the protection scope of the present invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; reagents, materials and the like used in the following examples are commercially available unless otherwise specified.
Example 1
(1) Preparation of positive plate
Mixing a positive electrode active material 4.4V Lithium Cobaltate (LCO), a binder polyvinylidene fluoride (PVDF) and a conductive agent acetylene black according to a weight ratio of 97:1.5:1.5, adding N-methyl pyrrolidone (NMP), and stirring under the action of a vacuum stirrer until a mixed system becomes a uniform and fluid positive electrode slurry; uniformly coating the positive electrode slurry on an aluminum foil with the thickness of 10 mu m; baking the coated aluminum foil in 5 sections of baking ovens with different temperature gradients, drying the aluminum foil in a baking oven at the temperature of 100-130 ℃ for 4-10h, and then rolling and slitting to obtain the required positive plate.
(2) Preparation of negative plate
Mixing a negative electrode active material graphite, a thickening agent sodium carboxymethyl cellulose (CMC), a binder styrene butadiene rubber and a conductive agent according to a weight ratio of 97:1:1:1, adding deionized water, and obtaining negative electrode slurry under the action of a vacuum stirrer; uniformly coating the negative electrode slurry on a copper foil with the thickness of 9 mu m; and (3) airing the copper foil at room temperature, transferring the copper foil to an oven at 75-100 ℃ for drying for 6-12h, and then carrying out cold pressing and slitting to obtain the negative plate.
(3) Preparation of electrolyte
Uniformly mixing ethylene carbonate, propylene carbonate, diethyl carbonate and n-propyl propionate according to the mass ratio of 20:10:25:45 in a glove box filled with argon and qualified in water oxygen content (the solvent is finally normalized together with an additive and a lithium salt), and then quickly adding 14% of fully dried lithium hexafluorophosphate (LiPF)6) Dissolved in an organic solvent, and then 7 wt% FEC, 4 wt% PS, 2 wt% ADN, 1 wt% DENE, 1.3 wt% HTCN, 0.5 wt% DTD, 1 wt% LiFSI, 0.3 wt% LiPO were added2F2Finally, 100ppm of triphenyl phosphite is added, and the mixture is stirred uniformly to obtain the electrolyte with the required standard.
(4) Preparation of the separator
A polyethylene barrier film (available from Asahi chemical Co., Ltd.) having a thickness of 7 to 9 μm was selected.
(5) Preparation of lithium ion battery
Stacking the prepared positive plate, the prepared isolating membrane and the prepared negative plate in sequence to ensure that the isolating membrane is positioned between the positive plate and the negative plate to play an isolating role, and then winding to obtain a naked battery cell without liquid injection; placing the bare cell in an outer packaging foil, injecting the prepared electrolyte into the dried bare cell, and performing vacuum packaging, standing, formation, shaping, sorting and other processes to obtain the required lithium ion battery.
(6) Normal temperature cycling experiment at 25 ℃:
testing the thickness D0 of the fully charged battery cell before testing, placing the battery in an environment of (25 +/-3) DEG C, standing for 1.5-3 hours, when the battery cell body reaches (25 +/-3) DEG C, charging the battery to 4.25V according to 1C, then charging to 4.35V according to 0.7C, then charging to a cut-off current of 0.05C according to a constant voltage of 4.35V, then discharging to 3V according to 1C, recording an initial capacity Q0, when the cycle reaches the required times or the thickness exceeds the thickness required by the test, taking the previous discharge capacity as the capacity Q1 of the battery, then fully charging the battery, taking out the battery cell, standing for 1-3 hours at normal temperature, and testing the full-charge thickness D1. The results are reported in Table 2.
The formula used therein is as follows:
the thickness change rate (%) - (D1-D0)/D0%
Capacity retention (%) ═ Q1/Q0 × 100%
(7) High temperature cycling experiment at 45 ℃:
the thickness D0 of the full-electricity battery core is tested before the test, the battery is placed in the environment of (45 +/-3) DEG C and stands for 1.5 to 3 hours, when the battery core body reaches (45 +/-3) DEG C, the battery is charged and discharged according to 0.7C/0.5C, the cutoff current is 0.05C, then the battery is discharged at 0.5C, the initial capacity Q0 is recorded, when the cycle reaches the required times or the capacity decay rate is lower than 70 percent or the thickness exceeds the thickness required by the test, the previous discharge capacity is taken as the capacity Q1 of the battery, the battery is fully charged, the core is taken out and stands for 1 to 3 hours at normal temperature, and the full-electricity thickness D1 is tested. The results are reported in Table 2.
The calculation formula used therein is as follows:
the thickness change rate (%) - (D1-D0)/D0%
Capacity retention (%) ═ Q1/Q0 × 100%
(8)60 ℃ high temperature storage test
Charging the formed battery to 4.25V at 25 ℃ according to 1C, then charging to 4.35V at 0.7C, then charging to cutoff current of 0.05C at constant voltage of 4.35V, then discharging to 3.0V at constant current of 0.5C, then charging to 4.25V at 1C, then charging to 4.35V at 0.7C, then charging to cutoff current of 0.05C at constant voltage of 4.35V, and standing for 30 days at 60 ℃. The thickness expansion ratio calculation formula is as follows:
(D1-D0)/D0%
Where D1 is the cell thickness after high temperature storage and D0 is the cell thickness before high temperature storage. The results are reported in Table 2.
Other examples and comparative examples
Other examples and comparative examples were prepared in the same manner as in example 1 except that the components and contents of the additives in the electrolyte were different, as shown in table 1 below.
TABLE 1
TABLE 2 comparison of experimental results for examples and comparative examples
By comparing examples 1 to 3 with comparative examples 1 to 3/4, it was found that the addition of triphenyl phosphite can improve the capacity retention rate and thickness of the battery at 25 ℃ cycle and 45 ℃ cycle and improve the high temperature storage performance at 60 ℃ of the battery, but when the content is too low, the improvement effect is not significant, and when the content is too high, the cycle thickness and the storage thickness at 60 ℃ can be improved, but the cycle performance is deteriorated; comparing example 1 with comparative example 2, it can be seen that recycle and storage properties are significantly deteriorated by adding only triphenyl phosphite stabilizer without adding 1,3, 6-hexanetricarbonitrile; comparing example 5 with comparative example 1/5, it was found that the addition of hexamethyldisilazane to the electrolyte improved the cycle and high-temperature storage properties of the battery, but the low content had no effect; comparing example 6 with comparative example 1/6, it can be seen that the addition of diisopropylcarbodiimide can improve the cycle and high-temperature storage properties of the battery, but too high a content deteriorates the cycle properties.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.