CN115663286A - Lithium ion battery - Google Patents
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- CN115663286A CN115663286A CN202211570289.1A CN202211570289A CN115663286A CN 115663286 A CN115663286 A CN 115663286A CN 202211570289 A CN202211570289 A CN 202211570289A CN 115663286 A CN115663286 A CN 115663286A
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Abstract
In order to solve the problem of insufficient cycle performance caused by unstable passive film of the conventional lithium ion battery, the invention provides a lithium ion battery which comprises a positive electrode, a negative electrode, a non-aqueous electrolyte and a diaphragm arranged between the positive electrode and the negative electrode, wherein the positive electrode comprises a positive electrode material layer containing a positive electrode active material, the surface of the positive electrode material layer contains a first amphoteric oxide, the surface of the diaphragm contains a second amphoteric oxide, and the non-aqueous electrolyte comprises a non-aqueous organic solvent and PO (phosphorus oxide) 2 F 2 ‑ And a lithium salt comprising lithium hexafluorophosphate; the lithium ion battery meets the following conditions: m (10 b + c)/a is not less than 0.1 and not more than 30, and a is not less than 0.5 and not more than 1.5,0.01 and not more than 0.8,0.01 and not more than b and not more than 2,0.5 and not more than 30. The lithium ion battery provided by the invention has better cycle stability, and the cycle life of the battery is effectively prolonged.
Description
Technical Field
The invention belongs to the technical field of energy storage devices, and particularly relates to a lithium ion battery.
Background
The lithium ion battery has the advantages of high voltage platform, less self-discharge, high output power, no memory effect, long cycle life, less environmental pollution and the like, so that the lithium ion battery is widely applied to electric automobiles and consumer products. With the expansion of the application range, especially with the popularization of smart phones and electric vehicles, the demand for the cycle life of lithium ion batteries is increasing.
In the using process of the lithium ion battery, the anode active material with strong oxidation activity can easily oxidize the electrolyte, so that the electrolyte is decomposed to generate gas. In the prior art, lithium difluorophosphate is usually added into the electrolyte, and a passivation film can be formed on the surface of a positive electrode, so that the oxidation activity of a positive electrode active material is reduced, and the cycle life of a battery is improved. The additive typically has a Higher Occupied Molecular Orbital (HOMO) level than the electrolyte solvent and the lithium salt. Therefore, it is oxidized before the main electrolyte component in the charging process, and then forms a decomposition layer on the surface of the positive electrode to prevent the electrolyte from further decomposing, such a passivation film formed on the surface of the positive electrode is not stable enough to cause continuous oxidative decomposition during the cycling and storage of the lithium ion battery (especially at the end of cycling and storage), and the direct current internal resistance during the cycling and storage of the lithium ion battery is increased, which seriously affects the use of the lithium ion battery. More importantly, the introduction of conventional additives into the electrolyte results in an additional risk of increased moisture in the electrolyte, water and LiPF 6 HF is generated, which is detrimental to the cycling stability of the layered positive electrode active material, especially at high voltages.
Disclosure of Invention
The invention provides a lithium ion battery, aiming at the problem of insufficient cycle performance caused by unstable passivation film of the existing lithium ion battery.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention provides a lithium ion battery which comprises a positive electrode, a negative electrode, a non-aqueous electrolyte and a diaphragm arranged between the positive electrode and the negative electrode, wherein the positive electrode comprises a positive electrode material layer containing a positive electrode active material, the surface of the positive electrode material layer contains a first amphoteric oxide, the surface of the diaphragm contains a second amphoteric oxide, and the non-aqueous electrolyte comprises a non-aqueous organic solvent and PO 2 F 2 - And a lithium salt comprising lithium hexafluorophosphate;
the lithium ion battery meets the following conditions:
m (10 b + c)/a is not less than 0.1 and not more than 30, and a is not less than 0.5 and not more than 1.5,0.01 and not more than 0.8,0.01 and not more than b and not more than 2,0.5 and not more than c and not more than 30;
wherein a is the molar concentration of lithium hexafluorophosphate in the nonaqueous electrolyte and the unit is mol/L;
m is PO in the non-aqueous electrolyte 2 F 2 - The mass percentage of (a) is in unit;
b is the percentage content of the first amphoteric oxide in the mass of the positive electrode material layer, and the unit is;
and c is the percentage content of the second amphoteric oxide in the mass of the diaphragm, and the unit is%.
Optionally, the lithium ion battery satisfies the following conditions:
0.5≤m*(10*b+c)/a≤10。
optionally, the molar concentration a of lithium hexafluorophosphate in the nonaqueous electrolyte is 0.7 to 1.2mol/L.
Optionally, PO in the non-aqueous electrolyte 2 F 2 - The mass percentage content m is 0.05% -0.5%.
Optionally, the percentage content b of the first amphoteric oxide in the mass of the positive electrode material layer is 0.03-1%.
Optionally, the percentage content c of the second amphoteric oxide in the mass of the diaphragm is 3% -20%.
Optionally, the first amphoteric oxide and the second amphoteric oxide are each independently selected from at least one of alumina, zirconia, tungsten oxide, and titania.
Optionally, the positive active material comprises LiFe 1-x’ M’ x’ PO 4 、LiMn 2-y’ M y’ O 4 And LiNi x Co y Mn z M 1-x-y- z O 2 At least one of sulfide, selenide and halide, wherein M ' is at least one of Mn, mg, co, ni, cu, zn, al, sn, B, ga, cr, sr, V or Ti, M is at least one of Fe, co, ni, mn, mg, cu, zn, al, sn, B, ga, cr, sr, V or Ti, and 0 ≤ x ' < 1,0 ≤ y ' ≤ 1,0 ≤ y ≤1，0≤x≤1，0≤z≤1，x+y+z≤1。
Optionally, the nonaqueous electrolyte further comprises an additive, wherein the additive comprises at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, a phosphate compound, a borate compound and a nitrile compound;
the content of the additive is 0.01-30% based on the total mass of the nonaqueous electrolyte solution as 100%.
Optionally, the cyclic sulfate compound is selected from vinyl sulfate, allyl sulfate, methyl vinyl sulfate,
、
、
、
、
At least one of;
the sultone compounds are selected from 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone,
At least one of;
the cyclic carbonate compound is at least one of vinylene carbonate, ethylene carbonate, methylene ethylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate or a compound shown in a structural formula 1:
structural formula 1
In the structural formula 1, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from one of hydrogen atom, halogen atom and C1-C5 group;
the phosphate ester compound is at least one of tris (trimethyl silane) phosphate, tris (trimethyl silane) phosphite or a compound shown in a structural formula 2:
structural formula 2
In the formula 2, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated alkyl, unsaturated alkyl, halogenated alkyl, -Si (C) m H 2m+1 ) 3 M is a natural number of 1 to 3, and R 31 、R 32 、R 33 At least one of them is an unsaturated hydrocarbon group;
the borate compound is selected from at least one of tri (trimethyl silane) borate and tri (triethyl silane) borate;
the nitrile compound is at least one selected from succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetrinitrile, adiponitrile, pimelitrile, suberonitrile, nonanedionitrile and decanedionitrile.
According to the lithium ion battery provided by the invention, the surface of the positive electrode material layer contains the first amphoteric oxide, the surface of the diaphragm contains the second amphoteric oxide, and the first amphoteric oxide and the second amphoteric oxide can react with lithium hexafluorophosphate added in the electrolyte to generate a large amount of beneficial PO 2 F 2 - In the process of formation of the battery, PO 2 F 2 - The compound can be decomposed on the surface of the positive electrode and can be matched with the first amphoteric oxide to form a passive film, so that the oxidation activity of the positive electrode active material on the nonaqueous electrolytic solution is reduced, and more importantly, the inventor discovers through extensive research that the molar concentration a of lithium hexafluorophosphate in the nonaqueous electrolytic solution and the molar concentration a of PO in the nonaqueous electrolytic solution are 2 F 2 - When the mass percentage content m of the passivation film, the mass percentage content b of the first amphoteric oxide in the mass of the positive electrode material layer and the mass percentage content c of the second amphoteric oxide in the mass of the diaphragm meet the condition that m (10 b + c)/a is less than or equal to 0.1 and less than or equal to 30, and a is less than or equal to 0.5 and less than or equal to 1.5,0.01 and less than or equal to 0.8,0.01 and less than or equal to b and less than or equal to 2,0.5 and less than or equal to 30, the compactness of the passivation film generated on the surface of the positive electrode material layer can be effectively controlled to be in a more stable state, so that the rupture of the passivation film is avoided in the charge-discharge cycle of the battery, the cycle stability of the non-aqueous electrolyte and the positive electrode active material is ensured, and the cycle performance of the battery is effectively improved.
Detailed Description
In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not limit the invention.
The embodiment of the invention provides a lithium ion battery, which comprises a positive electrode, a negative electrode, a non-aqueous electrolyte and a diaphragm arranged between the positive electrode and the negative electrode, wherein the positive electrode comprises a positive electrode material layer containing a positive electrode active material, the surface of the positive electrode material layer contains a first amphoteric oxide, the surface of the diaphragm contains a second amphoteric oxide, and the non-aqueous electrolyte comprises a non-aqueous organic solvent and PO (phosphorus oxide) 2 F 2 - And a lithium salt comprising lithium hexafluorophosphate;
the lithium ion battery meets the following conditions:
m (10 b + c)/a is not less than 0.1 and not more than 30, and a is not less than 0.5 and not more than 1.5,0.01 and not more than 0.8,0.01 and not more than b and not more than 2,0.5 and not more than c and not more than 30;
wherein a is the molar concentration of lithium hexafluorophosphate in the nonaqueous electrolyte and the unit is mol/L;
m is PO in the non-aqueous electrolyte 2 F 2 - The mass percentage content of (A) is in units of;
b is the percentage content of the first amphoteric oxide in the mass of the positive electrode material layer, and the unit is;
and c is the percentage content of the second amphoteric oxide in the mass of the diaphragm, and the unit is%.
In the description of the present invention, the term "percentage content of the first amphoteric oxide to the mass of the positive electrode material layer" refers to the relative mass content of the first amphoteric oxide with respect to 100% by mass of the positive electrode active layer. The term "percentage content of the second amphoteric oxide with respect to the mass of the separator" means the relative mass content of the second amphoteric oxide with respect to 100% by mass of the separator.
The first amphoteric oxide on the surface of the positive electrode material layer and the second amphoteric oxide on the surface of the diaphragm can react with lithium hexafluorophosphate added in the electrolyte to generate a large amount of beneficial PO 2 F 2 - 。
The reaction equation is: 2Al 2 O 3 +3PF 6 - → AlF 3 + 3 PO 2 F 2 - 。
Al in the above amphoteric oxide 2 O 3 In order to explain the inventive concept of the present invention, it can be understood by those skilled in the art from the above mechanism that the object of the present invention can be also achieved when the material of the positive electrode material layer or the surface of the separator is other amphoteric oxide.
When the material of the positive electrode material layer and the surface of the separator is a non-amphoteric oxide, for example, magnesium oxide, boron oxide, silicon oxide, etc., the positive electrode material layer and the surface of the separator are formed of LiPF 6 Shows less reactivity or no reactivity, and thus generates no or very little PO 2 F 2 - And the condition limit of the application is not met, and the improvement of the cycle performance of the battery is not facilitated.
In the process of formation of the battery, PO 2 F 2 - The compound can be decomposed on the surface of the positive electrode and can be matched with the first amphoteric oxide to form a passive film, so that the oxidation activity of the positive electrode active material on the nonaqueous electrolytic solution is reduced, and more importantly, the inventor discovers through extensive research that the molar concentration a of lithium hexafluorophosphate in the nonaqueous electrolytic solution and the molar concentration a of PO in the nonaqueous electrolytic solution are 2 F 2 - M, the percentage content b of the first amphoteric oxide in the mass of the positive electrode material layer, and the second amphoteric oxidationWhen the content c of the material in the mass of the diaphragm meets the condition that m (10 + b + c)/a is not less than 0.1 and not more than 30, and a is not less than 0.5 and not more than 1.5,0.01 and not more than m and not more than 0.8,0.01 and not more than b and not more than 2,0.5 and not more than c and not more than 30, the compactness of the passivation film generated on the surface of the positive electrode material layer can be effectively controlled, so that the passivation film is in a more stable state, the rupture of the passivation film is avoided in the charge-discharge cycle of the battery, the cycle stability of the non-aqueous electrolyte and the positive electrode active material is ensured, and the cycle performance of the battery is effectively improved.
Meanwhile, the surface of the positive electrode material layer and the surface of the diaphragm both contain amphoteric oxide, so that the synergistic effect of the positive electrode material layer and the diaphragm can be more fully exerted, the cycle life of the battery can be prolonged, and when only one of the surfaces of the positive electrode material layer or the diaphragm contains amphoteric oxide, PO can be generated 2 F 2 - But PO it generates 2 F 2 - The amount is small, and the battery performance cannot be greatly improved.
In a preferred embodiment, the lithium ion battery satisfies the following condition:
0.5≤m*(10*b+c)/a≤10。
when the molar concentration a of lithium hexafluorophosphate in the nonaqueous electrolytic solution is equal to the PO in the nonaqueous electrolytic solution 2 F 2 - When the mass percentage content m of the first amphoteric oxide in the mass percentage content b of the positive electrode material layer and the mass percentage content c of the second amphoteric oxide in the mass percentage content c of the diaphragm meet the requirements, the dynamic performance and the cycle performance of the battery can be better improved on the premise of ensuring the energy density of the battery.
When the value of m (10 + b) + c)/a is too low, the side reaction of the nonaqueous electrolyte on the surface of the strong-oxidizing positive electrode material layer can not be effectively inhibited, and the PO is greatly reduced 2 F 2 - The internal resistance of the battery increases, causing insufficient high-temperature stability of the electrolyte, affecting the performance of the battery such as high-temperature cycle and storage, and deteriorating the cycle life of the battery.
When the value of m (10 + b) + c)/a is too high, the energy density and the dynamic performance of the battery are reduced, the conductivity of the electrolyte is too low, and the polarization of the battery is increased, so thatAffecting the normal use of the battery and simultaneously affecting the PO 2 F 2 - Is not beneficial to the improvement of the cycle life of the battery.
In some embodiments, the molar concentration a of lithium hexafluorophosphate in the nonaqueous electrolytic solution may be 0.5mol/L, 0.6mol/L, 0.7mol/L, 0.8mol/L, 0.9mol/L, 1.0mol/L, 1.1mol/L, 1.2mol/L, 1.3mol/L, 1.4mol/L, or 1.5mol/L.
In a preferred embodiment, the molar concentration a of lithium hexafluorophosphate in the nonaqueous electrolytic solution is 0.7 to 1.2mol/L.
When the content of lithium hexafluorophosphate in the nonaqueous electrolytic solution is too low, on the one hand, the content of the total electrolyte salt in the nonaqueous electrolytic solution is low, which affects the ion conductivity of the nonaqueous electrolytic solution, and on the other hand, the reactivity with the amphoteric oxide on the surface of the positive electrode material layer or the separator is also affected, thereby reducing the reactivity between the amphoteric oxide and the PF 6 - Anion reaction to PO 2 F 2 - The amount of (c); when the content of lithium hexafluorophosphate in the nonaqueous electrolyte is too high, the viscosity of the nonaqueous electrolyte increases and the conductivity decreases, which is also disadvantageous for improving the ionic conductivity of the nonaqueous electrolyte.
In some embodiments, PO in the nonaqueous electrolyte 2 F 2 - The content m may be 0.01%, 0.02%, 0.03%, 0.05%, 0.07%, 0.08%, 0.09%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.6%, 0.7%, or 0.8% by mass.
In a preferred embodiment, the PO in the non-aqueous electrolyte 2 F 2 - The mass percentage content m is 0.05-0.5%.
In the present invention, PO in the nonaqueous electrolytic solution 2 F 2 - Can be reacted with PF via amphoteric oxide 6 - The anion is generated by reaction, and can also be added into the non-aqueous electrolyte by an additional adding mode; when PO is used 2 F 2 - From amphoteric oxides and PF 6 - When anion is generated, PO in the non-aqueous electrolyte 2 F 2 - Influence of the amount of production ofIn addition to the content of the amphoteric oxide and the concentration of lithium hexafluorophosphate, the position of the amphoteric oxide and the contact area with the nonaqueous electrolyte solution, and the control voltage for the first formation of the battery, the amount of PO in the nonaqueous electrolyte solution is large 2 F 2 - The difference in the amount of produced PO, too little PO 2 F 2 - Excessive PO generation with insignificant performance improvement for lithium ion batteries 2 F 2 - The generation of lithium hexafluorophosphate, the main lithium salt, is reduced, and thus the ion conduction rate of the lithium ion battery is not improved.
In some embodiments, the percentage content b of the first amphoteric oxide to the mass of the positive electrode material layer may be 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.4%, 0.5%, 0.7%, 0.9%, 1.0%, 1.1%, 1.3%, 1.5%, 1.8%, or 2.0%.
In a preferred embodiment, the percentage content b of the first amphoteric oxide in the mass of the positive electrode material layer is 0.03% -1%.
The first amphoteric oxide is arranged on the surface of the positive electrode material layer, so that direct contact between the positive electrode active material with strong oxidizing property and the non-aqueous electrolyte can be isolated, side reaction of the non-aqueous electrolyte on the surface of the positive electrode material with strong oxidizing property is inhibited, gas quantity generated by decomposition of the non-aqueous electrolyte is reduced, and the service life of the battery is further prolonged well. Meanwhile, the amphoteric oxide can neutralize residual alkali on the surface of the positive electrode material layer, consume HF generated in the electrolyte or in the use process of the battery, inhibit the dissolution of transition metal in the positive electrode active material, improve the stability of the positive electrode active material and the electrolyte interface, ensure the acid-base balance of a battery system, and finally improve the electrochemical performance of the battery. The content b of the first amphoteric oxide in the mass of the positive electrode material layer is too low, which is not favorable for improving the structural stability of the positive electrode active material and PO 2 F 2 - Too high is not favorable for the improvement of the energy density and the reduction of the internal resistance of the battery.
In some embodiments, the percentage content c of the second amphoteric oxide with respect to the mass of the separator may be 0.5%, 0.7%, 0.9%, 1.0%, 1.1%, 1.3%, 1.5%, 1.8%, 2.0%, 2.3%, 2.7%, 3.0%, 3.3%, 3.7%, 4.0%, 4.3%, 4.7%, 5%, 8%, 10%, 13%, 15%, 16%, 18%, 21%, 23%, 24%, 26%, 27%, 29%, or 30%.
In a preferred embodiment, the percentage content c of the second amphoteric oxide in the mass of the diaphragm is 3% -20%.
The second amphoteric oxide on the surface of the diaphragm plays a key role in inhibiting or reducing the harmful crosstalk phenomenon generated by the positive electrode, can effectively reduce the side reaction products generated by the positive electrode from entering the negative electrode through the diaphragm, can further improve the electronic insulation property, the temperature resistance and the mechanical strength of the diaphragm, and is very important for realizing the lithium ion battery with long cycle life and high safety characteristic.
When the percentage content c of the second amphoteric oxide to the mass of the separator is in the above range, PO can be effectively promoted 2 F 2 - While improving the safety performance of the battery.
In some embodiments, the first amphoteric oxide and the second amphoteric oxide are each independently selected from at least one of alumina, zirconia, tungsten oxide, and titania.
In a preferred embodiment, the first amphoteric oxide and the second amphoteric oxide are each independently selected from at least one of alumina, zirconia, and titania.
In some embodiments, the separator is a polyolefin or non-woven porous composite film, and the second amphoteric oxide is coated on at least one side surface of the separator, and the separator includes, but is not limited to, one or more of polypropylene, polyethylene, polyimide and polyvinylidene fluoride.
In some embodiments, the positive active material comprises LiFe 1-x’ M’ x’ PO 4 、LiMn 2-y’ M y’ O 4 And LiNi x Co y Mn z M 1-x-y-z O 2 At least one of sulfide, selenide and halide, wherein M' is selected from Mn, mg, co, ni, cu, zn, al, sn, B, ga, cr, sr, V or TiAt least one, M is selected from at least one of Fe, co, ni, mn, mg, cu, zn, al, sn, B, ga, cr, sr, V or Ti, and 0 is more than or equal to x '< 1,0 is more than or equal to y' < 1,0 is more than or equal to y is more than or equal to 1,0 is more than or equal to x < 1,0 is more than or equal to z is more than or equal to 1, x + y + z is more than or equal to 1.
In some embodiments, the positive electrode material layer further comprises a positive electrode binder, and the positive electrode binder is selected from organic polymers, and the molecular weight of the organic polymers is 60 to 130 ten thousand.
When the positive electrode binder meets the conditions, the positive electrode material layer and the positive electrode current collector have good binding power and dynamic performance, and the battery is ensured to have excellent capacity and cycle life.
In some embodiments, the organic polymer includes thermoplastic resins such as polyvinylidene fluoride, copolymers of vinylidene fluoride, polytetrafluoroethylene, copolymers of vinylidene fluoride-hexafluoropropylene, copolymers of tetrafluoroethylene-perfluoroalkyl vinyl ether, copolymers of ethylene-tetrafluoroethylene, copolymers of vinylidene fluoride-trifluoroethylene, copolymers of vinylidene fluoride-trichloroethylene, copolymers of vinylidene fluoride-fluoroethylene, copolymers of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimides, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, and the like; an acrylic resin; sodium carboxymethylcellulose; at least one of nitrile rubber, butadiene rubber, ethylene-propylene rubber, styrene-butadiene-styrene block copolymer or its hydride, ethylene-propylene-diene terpolymer, polyvinyl acetate, syndiotactic-1,2-polybutadiene, and ethylene-vinyl acetate.
In some embodiments, the positive electrode material layer further comprises a positive electrode conductive agent comprising at least one of conductive carbon black, conductive carbon spheres, conductive graphite, conductive carbon fibers, carbon nanotubes, graphene, or reduced graphene oxide.
In some embodiments, the positive active material is selected from LiFe 1-x’ M’ x’ PO 4 、LiMn 2-y’ M y’ O 4 And LiNi x Co y Mn z M 1-x-y-z O 2 Wherein M ' is selected from at least one of Mn, mg, co, ni, cu, zn, al, sn, B, ga, cr, sr, V or Ti, M is selected from at least one of Fe, co, ni, mg, cu, zn, al, sn, B, ga, cr, sr, V or Ti, and 0 is more than or equal to x ' < 1,0 is more than or equal to y ' ≦ 1,0 is more than or equal to y 1,0 is more than or equal to x 1,0 is more than or equal to z is more than or equal to 1, x + y z is more than or equal to 1.
In a preferred embodiment, the positive active material may be selected from LiCoO 2 、LiFePO 4 、LiFe 0.8 Mn 0.2 PO 4 、LiMn 2 O 4 、LiNi 0.5 Co 0.2 Mn 0.3 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.5 Co 0.2 Mn 0.2 Al 0.1 O 2 、LiNi 0.5 Co 0.2 Al 0.3 O 2 At least one of (1).
In some embodiments, the positive electrode further includes a positive electrode current collector, and the positive electrode material layer is formed on a surface of the positive electrode current collector.
The positive electrode current collector is selected from metal materials capable of conducting electrons, preferably, the positive electrode current collector comprises at least one of Al, ni, tin, copper and stainless steel, and in a more preferred embodiment, the positive electrode current collector is selected from aluminum foil.
In some embodiments, the anode includes an anode material layer including an anode active material.
In a preferred embodiment, the anode active material comprises at least one of a carbon-based anode, a silicon-based anode, a tin-based anode, a lithium anode. The carbon-based negative electrode can comprise graphite, hard carbon, soft carbon, graphene, mesocarbon microbeads and the like; the silicon-based negative electrode can comprise silicon materials, silicon oxides, silicon-carbon composite materials, silicon alloy materials and the like; the tin-based anode may include tin, tin carbon, tin oxide, tin metal compounds; the lithium negative electrode may include metallic lithium or a lithium alloy. The lithium alloy may specifically be at least one of a lithium silicon alloy, a lithium sodium alloy, a lithium potassium alloy, a lithium aluminum alloy, a lithium tin alloy, and a lithium indium alloy.
In some embodiments, the negative electrode material layer further includes a negative electrode binder and a negative electrode conductive agent, and the negative electrode active material, the negative electrode binder and the negative electrode conductive agent are blended to obtain the negative electrode material layer.
The selectable ranges of the negative electrode binder and the negative electrode conductive agent are respectively the same as those of the positive electrode binder and the positive electrode conductive agent, and are not described again.
In some embodiments, the negative electrode further includes a negative electrode current collector, and the negative electrode material layer is formed on a surface of the negative electrode current collector.
The negative electrode current collector is selected from metal materials capable of conducting electrons, preferably, the negative electrode current collector comprises at least one of aluminum, nickel, tin, copper and stainless steel, and in a more preferred embodiment, the negative electrode current collector is selected from copper foil.
In some embodiments, the lithium salt further comprises LiBOB, liddob, liBF 4 、LiSbF 6 、LiAsF 6 、LiN(SO 2 CF 3 ) 2 、LiN(SO 2 C 2 F 5 ) 2 、LiC(SO 2 CF 3 ) 3 、LiN(SO 2 F) 2 、LiClO 4 、LiAlCl 4 、LiCF 3 SO 3 、Li 2 B 10 Cl 10 、LiSO 2 F. At least one of lipo, liDODFP, and a lithium salt of a lower aliphatic carboxylic acid.
In some embodiments, the concentration of the lithium salt in the nonaqueous electrolytic solution is 0.1mol/L to 8mol/L. In a preferred embodiment, the concentration of the lithium salt in the nonaqueous electrolytic solution is 0.5mol/L to 2.5mol/L. Specifically, the concentration of the lithium salt in the nonaqueous electrolytic solution may be 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L, or 2.5mol/L.
In some embodiments, the non-aqueous organic solvent includes at least one of an ether solvent, a nitrile solvent, a carbonate solvent, a carboxylate solvent, and a sulfone solvent.
In some embodiments, the ether solvent comprises a cyclic ether or a chainThe ether is preferably a chain ether having 3 to 10 carbon atoms or a cyclic ether having 3~6 carbon atoms, and the cyclic ether is not particularly limited to 1,3-Dioxolan (DOL), 1,4-Dioxolan (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH) 3 -THF), 2-trifluoromethyltetrahydrofuran (2-CF) 3 -THF); the chain ether may specifically be, but not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether. Dimethoxymethane, diethoxymethane, and ethoxymethoxymethane, which have low viscosity and can impart high ion conductivity, are particularly preferable because chain ethers have high solvating ability with lithium ions and can improve ion dissociation properties. The ether compound may be used alone, or two or more thereof may be used in combination in any combination and ratio. The content of the ether compound is not particularly limited, and is arbitrary within a range not significantly impairing the effect of the high-compaction lithium ion battery of the present invention, and is usually 1% by volume or more, preferably 2% by volume or more, and more preferably 3% by volume or more, and is usually 30% by volume or less, preferably 25% by volume or less, and more preferably 20% by volume or less, of the volume ratio of the nonaqueous solvent to the volume ratio of 100%. When two or more ether compounds are used in combination, the total amount of the ether compounds may be set to satisfy the above range. When the content of the ether compound is within the above-mentioned preferred range, the effect of improving the ionic conductivity by increasing the degree of dissociation of lithium ions and lowering the viscosity of the chain ether can be easily ensured. In addition, when the negative electrode active material is a carbon-based material, the co-intercalation phenomenon of the chain ether and the lithium ion can be suppressed, and thus the input/output characteristics and the charge/discharge rate characteristics can be set to appropriate ranges.
In some embodiments, the nitrile based solvent may specifically be, but is not limited to, at least one of acetonitrile, glutaronitrile, malononitrile.
In some embodiments, the carbonate-based solvent includes a cyclic carbonate or a chain carbonate, and the cyclic carbonate may be, but is not limited to, at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), γ -butyrolactone (GBL), and Butylene Carbonate (BC); the chain carbonate may be, but not limited to, at least one of dimethyl carbonate (DMC), ethyl Methyl Carbonate (EMC), diethyl carbonate (DEC) and dipropyl carbonate (DPC). The content of the cyclic carbonate is not particularly limited and may be any within a range not significantly impairing the effect of the lithium ion battery of the present invention, but when one is used alone, the lower limit of the content is usually 3% by volume or more, preferably 5% by volume or more, relative to the total amount of the solvent of the nonaqueous electrolytic solution. By setting this range, it is possible to avoid a decrease in conductivity due to a decrease in the dielectric constant of the nonaqueous electrolytic solution, and it is easy to make the large-current discharge characteristic, the stability with respect to the negative electrode, and the cycle characteristic of the nonaqueous electrolyte battery fall within a favorable range. The upper limit is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. Setting this range can improve the oxidation/reduction resistance of the nonaqueous electrolytic solution, and contributes to improvement of stability during high-temperature storage. The content of the chain carbonate is not particularly limited, and is usually 15% by volume or more, preferably 20% by volume or more, and more preferably 25% by volume or more, based on the total amount of the solvent of the nonaqueous electrolytic solution. The volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less. When the content of the chain carbonate is in the above range, the viscosity of the nonaqueous electrolytic solution is easily brought to an appropriate range, the decrease in the ionic conductivity is suppressed, and the content contributes to bringing the output characteristics of the nonaqueous electrolyte battery to a good range. When two or more kinds of chain carbonates are used in combination, the total amount of the chain carbonates may be set to satisfy the above range.
In some embodiments, chain carbonates having a fluorine atom (hereinafter simply referred to as "fluorinated chain carbonates") may also be preferably used. The number of fluorine atoms in the fluorinated chain carbonate is not particularly limited as long as it is 1 or more, but is usually 6 or less, preferably 4 or less. When the fluorinated chain carbonate has a plurality of fluorine atoms, the fluorine atoms may be bonded to the same carbon atom or may be bonded to different carbons. Examples of the fluorinated chain carbonate include a fluorinated dimethyl carbonate derivative, a fluorinated ethyl methyl carbonate derivative, and a fluorinated diethyl carbonate derivative.
The carboxylic ester solvent includes cyclic carboxylic ester and/or chain carbonate. Examples of the cyclic carboxylic acid ester include: at least one of gamma-butyrolactone, gamma-valerolactone and delta-valerolactone. Examples of the chain carbonate include: at least one of Methyl Acetate (MA), ethyl Acetate (EA), propyl acetate (EP), butyl acetate, propyl Propionate (PP), and butyl propionate.
In some embodiments, the sulfone-based solvent includes cyclic sulfones and chain sulfones, preferably, in the case of cyclic sulfones, compounds having carbon number 3~6, preferably carbon number 3~5, and in the case of chain sulfones, having carbon number 2~6, preferably carbon number 2~5. The content of the sulfone solvent is not particularly limited and is arbitrary within a range not significantly impairing the effect of the lithium ion battery of the present invention, and is usually 0.3% by volume or more, preferably 0.5% by volume or more, more preferably 1% by volume or more, and is usually 40% by volume or less, preferably 35% by volume or less, more preferably 30% by volume or less, relative to the total amount of the solvent of the nonaqueous electrolytic solution. In the case where two or more sulfone solvents are used in combination, the total amount of the sulfone solvents may be set to satisfy the above range. When the content of the sulfone-based solvent is within the above range, a nonaqueous electrolytic solution excellent in high-temperature storage stability tends to be obtained.
In a preferred embodiment, the non-aqueous organic solvent comprises at least one of ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, propylene carbonate, butyl acetate, gamma-butyrolactone, propyl propionate, ethyl butyrate, methyl acetate, ethyl acetate, fluoro ethyl acetate, and fluoro ether.
In a preferred embodiment, the non-aqueous organic solvent is a mixture of cyclic carbonates and chain carbonates.
In some embodiments, the additive comprises at least one of a cyclic sulfate-based compound, a sultone-based compound, a cyclic carbonate-based compound, a phosphate-based compound, a borate-based compound, and a nitrile-based compound;
the content of the additive is 0.01-30% based on the total mass of the nonaqueous electrolyte solution as 100%.
In some embodiments of the present invention, the, the cyclic sulfate compound is selected from vinyl sulfate, allyl sulfate, methyl vinyl sulfate,
、
、
、
、
At least one of;
the sultone compounds are selected from 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone,
At least one of;
the cyclic carbonate compound is at least one of vinylene carbonate, ethylene carbonate, methylene ethylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate or a compound shown in a structural formula 1:
structural formula 1
In the structural formula 1, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from one of hydrogen atom, halogen atom and C1-C5 group；
The phosphate ester compound is at least one of tris (trimethyl silane) phosphate, tris (trimethyl silane) phosphite or a compound shown in a structural formula 2:
structural formula 2
In the formula 2, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated alkyl, unsaturated alkyl, halogenated alkyl, -Si (C) m H 2m+1 ) 3 M is a natural number of 1 to 3, and R 31 、R 32 、R 33 At least one of which is an unsaturated hydrocarbon group;
in a preferred embodiment, the phosphate ester compound represented by the structural formula 2 may be at least one of tripropargyl phosphate, dipropargyl methyl phosphate, dipropargyl ethyl phosphate, dipropargyl propyl phosphate, dipropargyl trifluoromethyl phosphate, dipropargyl-2,2,2-trifluoroethyl phosphate, dipropargyl-3,3,3-trifluoropropyl phosphate, dipropargyl hexafluoroisopropyl phosphate, triallyl phosphate, diallyl methyl phosphate, diallyl ethyl phosphate, diallyl propyl phosphate, diallyl trifluoromethyl phosphate, diallyl-2,2,2-trifluoroethyl phosphate, diallyl-3,3,3-trifluoropropyl phosphate, diallyl hexafluoroisopropyl phosphate;
the borate compound is selected from at least one of tri (trimethyl silane) borate and tri (triethyl silane) borate;
the nitrile compound is at least one selected from succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetricarbonitrile, adiponitrile, pimelonitrile, suberonitrile, nonadinitrile and sebaconitrile.
In other embodiments, the additives may also include other additives that improve the performance of the battery: for example, additives for improving the safety performance of the battery, such as a flame retardant additive such as fluorophosphate ester and cyclophosphazene, or an anti-overcharge additive such as tert-amylbenzene and tert-butylbenzene.
It should be noted that, unless otherwise specified, in general, the content of any optional substance in the additive in the nonaqueous electrolytic solution is 10% or less, preferably 0.1 to 5%, and more preferably 0.1 to 2%. Specifically, the content of any optional substance in the additive may be 0.05%, 0.08%, 0.1%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, 2.2%, 2.5%, 2.8%, 3%, 3.2%, 3.5%, 3.8%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 7.8%, 8%, 8.5%, 9%, 9.5%, 10%.
In some embodiments, when the additive is selected from fluoroethylene carbonate, the content of fluoroethylene carbonate is 0.05% to 30% based on 100% of the total mass of the nonaqueous electrolytic solution.
The present invention will be further illustrated by the following examples.
Table 1 design of parameters of examples and comparative examples
Example 1
This example is intended to illustrate a lithium ion battery disclosed in the present invention, and includes a positive electrode, a negative electrode, a nonaqueous electrolytic solution, and a separator provided between the positive electrode and the negative electrode, in which:
the positive electrode comprises a positive active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 The conductive carbon black Super-P and the positive electrode binder are mixed to form a positive electrode material layer, and the surface of the positive electrode material layer contains a first amphoteric oxide with the mass shown in the table 1;
the negative electrode comprises a negative electrode material layer prepared by mixing a negative electrode active material artificial graphite, conductive carbon black Super-P, a binder styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) according to a mass ratio of 94;
the non-aqueous electrolyte comprises a non-aqueous organic solvent and PO 2 F 2 - And a lithium salt including lithium hexafluorophosphate, the organic solvent including Ethylene Carbonate (EC), diethyl carbonate (DEC) and Ethyl Methyl Carbonate (EMC) in a mass ratio of EC: DEC: EMC =1 6 ) Concentration and PO 2 F 2 - The contents are shown in Table 1.
The separator was a PE separator, the surface of which contained the mass of the second amphoteric oxide as shown in the example in table 1.
Examples 2 to 31
Examples 2 to 31 are for explaining a lithium ion battery disclosed in the present invention, and are mostly the same as in example 1, except that:
the positive electrode active materials and lipfs shown in examples 2 to 31 in table 1 were used 6 Concentration, PO 2 F 2 - The mass content of the first amphoteric oxide, the mass content of the second amphoteric oxide, and the mass content of the second amphoteric oxide.
Comparative examples 1 to 27
Comparative examples 1 to 27 are comparative illustrations of lithium ion batteries disclosed in the present invention, and are mostly the same as in example 1, except that:
the positive electrode active materials and lipfs shown in examples 1 to 27 in table 1 were used 6 Concentration, PO 2 F 2 - In a first amphoteric oxide/further oxide and the mass thereof, further additives and contents, a first amphoteric oxide/further oxide and the mass thereofContent, second amphoteric oxide/other oxide and mass content thereof.
The lithium ion batteries of the above examples and comparative examples may be prepared by a known method, and are not particularly limited. Examples thereof include: liPO to be synthesized by a known method 2 F 2 A method of adding to an electrolyte; the battery components such as active material, electrode plate, and separator are made to coexist in advance, and LiPF is included in the use 6 When the electrolyte of (2) is used for assembling the battery, PO is generated in the system 2 F 2 - The method of (1). In this embodiment, any method may be used.
As a measure of PO in the above-mentioned lithium ion batteries 2 F 2 - The method of content (c) is not particularly limited, and any known method may be used. Specific examples thereof include: ion chromatography, 19 F NMR, and the like.
Performance test
The following performance tests were performed on the lithium ion battery:
1. and (3) testing the cycle performance:
the lithium ion batteries of examples and comparative examples were charged at a rate of 1C, discharged at a rate of 1C at 25C, the battery capacity of the first charge and discharge was recorded, and a full charge discharge cycle test was performed at a charge and discharge cut-off voltage (e.g., 3V to 4.2V) until the capacity of the lithium ion battery had decayed to 80% of the initial capacity, and the initial capacity and the number of cycles of the battery were recorded.
2. And (3) testing the DCIR of the battery:
the DCIR test process of the battery comprises the following steps: the lithium ion secondary battery is left at 25 ℃ for 5 minutes, is subjected to constant current charging to an upper limit cut-off voltage (such as 4.2V) at a rate of 1C, is subjected to constant voltage charging until the current is less than or equal to 0.05C, the state of charge (SOC) of the battery is 100 percent, is left at 5 minutes, is subjected to constant current discharging at a rate of 1C, and is adjusted to 50 percent. After standing for 30min, the discharge was carried out at a rate of 1C for 10s, and the voltage before discharge was denoted as U1 and the voltage after discharge was denoted as U2. DCIR = (U1-U2)/1C of the battery.
(1) The test results obtained in examples 1 to 12 and comparative examples 1 and 14 to 27 are filled in Table 2.
TABLE 2
From the test results obtained in examples 1 to 12 and comparative examples 1, 14 to 27, it can be seen that the molar concentration a of lithium hexafluorophosphate in the nonaqueous electrolytic solution and the PO in the nonaqueous electrolytic solution 2 F 2 - The mass percent content m of the first amphoteric oxide in the mass percent content b of the positive electrode material layer and the mass percent content c of the second amphoteric oxide in the mass percent of the diaphragm satisfy the condition that m (10 b + c)/a is not less than 0.1 and not more than 30, and a is not less than 0.5 and not more than 1.5,0.01 and not more than m and not more than 0.8,0.01 and not more than b and not more than 2,0.5 and not more than 30, the obtained lithium ion battery has higher initial battery capacity, lower impedance and longer cycle life, and the conjecture is that lithium hexafluorophosphate can react to generate PO in the battery formation process 2 F 2 - ，PO 2 F 2 - Further decomposing the surface of the positive active material and matching the positive active material with the first amphoteric oxide to form a passive film, and controlling the content of lithium hexafluorophosphate and PO by regulating the first amphoteric oxide in the positive material layer and the second amphoteric oxide on the diaphragm 2 F 2 - The quality of the positive electrode material layer is adjusted, so that the positive electrode material layer has more stable property by adjusting the compactness of the passive film on the surface of the positive electrode material layer, further the rupture of the passive film is avoided in the charge-discharge circulation of the battery, the circulation stability of the non-aqueous electrolyte and the positive electrode active material is ensured, and the circulation performance of the battery is effectively improved.
From the test results of examples 1 to 12, it is found that the molar concentration a of lithium hexafluorophosphate in the nonaqueous electrolytic solution and the PO in the nonaqueous electrolytic solution 2 F 2 - M, the percentage content b of the first amphoteric oxide to the mass of the positive electrode material layer, and the percentage content of the second amphoteric oxide to the mass of the separatorThe percentage content c further satisfies the condition that m (10 x b + c)/a is not more than 0.5 and not more than 10, and a is not less than 0.7 and not more than 1.2,0.05 and not more than m and not more than 0.5,0.03 and not more than b and not more than 1,3 and not more than 20, which is favorable for further improving the initial capacity of the battery, reducing the battery impedance and prolonging the cycle life of the lithium ion battery, and the passivation film on the surface of the positive electrode material layer obtained at the moment is supposed to have better compactness and lower thickness, reduce the capacity loss of the lithium ion battery and improve the cycle performance of the lithium ion battery.
As is clear from the test results of comparative examples 14 to 27, even if the molar concentration a of lithium hexafluorophosphate in the nonaqueous electrolytic solution and PO in the nonaqueous electrolytic solution were used 2 F 2 - The percentage content m of the first amphoteric oxide in the mass of the positive electrode material layer, the percentage content b of the second amphoteric oxide in the mass of the diaphragm and the percentage content c of the second amphoteric oxide in the mass of the diaphragm meet the limit of a condition that m (10 + b + c)/a is less than or equal to 30, but when the value a, the value m, the value b or the value c does not meet the limit of the range, the lithium ion battery still does not have higher initial capacity and better cycle performance, and the value a, the value m, the value b or the value c has stronger relevance in the aspect of improving the performance of the lithium ion battery. Similarly, when the value of a, m, b, or c satisfies the range limits, but the value of m (10 + b + c)/a does not satisfy the above preset conditions, the improvement in the battery performance is not significant.
(2) The test results obtained for example 1 and comparative examples 5 to 13 are shown in Table 3.
TABLE 3
From the test results of example 1 and comparative example 5~6, it can be seen that the absence of either the first amphoteric oxide or the second amphoteric oxide results in PO 2 F 2 - A greater drop in the amount, at the same time, results in an increase in the impedance of the battery and a reduction in the number of cycles. From example 1And the test results of comparative examples 7 to 13, it can be seen that when other oxide is used in place of the first amphoteric oxide and/or the second amphoteric oxide, the LiPF is tested 6 Shows less reactivity or no reactivity, and thus generates no or very little PO 2 F 2 - And the condition limit of the application is not met, and the improvement of the cycle performance of the battery is not facilitated.
(3) The test results obtained in examples 1, 13 to 21 are shown in Table 4.
TABLE 4
From the test results of examples 1 and 13 to 21, it can be seen that when different amphoteric oxides or a combination thereof are used as the first amphoteric oxide and the second amphoteric oxide, as long as the value a, the value m, the value b or the value c satisfies the condition that 0.1 is not less than m (10 + b + c)/a is not more than 30, and 0.5 is not less than 1.5,0.01 is not less than m is not less than 0.8,0.01 is not less than b is not less than 2,0.5 is not less than 30, the obtained lithium ion battery has higher initial capacity and better cycle performance, which indicates that the lithium ion battery system provided by the invention has universality for different amphoteric oxides, and also indicates the necessity of using the amphoteric oxide for the lithium ion battery system of the application.
(4) The test results obtained for examples 1, 20 to 22 and comparative example 2~4 are filled in Table 5.
TABLE 5
From the test results of example 1 and comparative example 2~4, it can be seen that the battery enhancement effect of adding Vinylene Carbonate (VC), vinyl sulfate (DTD) or fluoroethylene carbonate (FEC) as a film forming additive to the electrolyte of lithium ion is significantly less than the performance enhancement of the battery system provided by the present application to the lithium ion battery.
As is clear from the test results of examples 1 and 20 to 22, the batteries provided by the inventionIn the system, vinylene Carbonate (VC), vinyl sulfate (DTD) or fluoroethylene carbonate (FEC) is additionally added, so that the impedance of the battery can be further reduced, the cycle life of the battery can be further prolonged, and the improvement mechanism of other additives on the performance of the battery and PO are illustrated 2 F 2 - Certain difference exists, and the two have complementary action on film formation, so that the quality of an interface film on the surface of the positive electrode material layer is improved.
(5) The test results obtained in examples 1, 23 to 31 are shown in Table 6.
TABLE 6
From the test results of examples 1 and 23 to 31, it can be seen that when the battery selects different positive active materials, and the value a, the value m, the value b or the value c satisfies the condition that m (10 b + c)/a is not less than 0.1 and not more than 30, and a is not less than 0.5 and not more than 1.5,0.01 and not more than m and not more than 0.8,0.01 and not more than b and not more than 2,0.5 and not more than 30, the battery has high initial capacity, lower battery impedance and excellent cycle performance, and can have both high energy density and long cycle life, which indicates that the battery system provided by the present invention is suitable for different positive active materials.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. A lithium ion battery is characterized by comprising a positive electrode, a negative electrode, a nonaqueous electrolyte and a diaphragm arranged between the positive electrode and the negative electrode, wherein the positive electrode comprises a positive electrode material layer containing a positive electrode active material, the surface of the positive electrode material layer contains a first amphoteric oxide, the surface of the diaphragm contains a second amphoteric oxide, and the nonaqueous electrolyte comprises a nonaqueous organic solvent and PO 2 F 2 - And a lithium salt comprising lithium hexafluorophosphate;
the lithium ion battery meets the following conditions:
m (10 b + c)/a is not less than 0.1 and not more than 30, and a is not less than 0.5 and not more than 1.5,0.01 and not more than 0.8,0.01 and not more than b and not more than 2,0.5 and not more than c and not more than 30;
wherein a is the molar concentration of lithium hexafluorophosphate in the nonaqueous electrolyte and the unit is mol/L;
m is PO in the non-aqueous electrolyte 2 F 2 - The mass percentage content of (A) is in units of;
b is the percentage content of the first amphoteric oxide in the mass of the positive electrode material layer, and the unit is;
and c is the percentage content of the second amphoteric oxide in the mass of the diaphragm, and the unit is%.
2. The lithium ion battery according to claim 1, wherein the lithium ion battery satisfies the following condition:
0.5≤m*(10*b+c)/a≤10。
3. the lithium ion battery according to claim 1, wherein the molar concentration a of lithium hexafluorophosphate in the nonaqueous electrolytic solution is 0.7 to 1.2mol/L.
4. The lithium ion battery of claim 1, wherein PO in the nonaqueous electrolyte solution 2 F 2 - The mass percentage content m is 0.05-0.5%.
5. The lithium ion battery of claim 1, wherein the percentage content b of the first amphoteric oxide in the mass of the positive electrode material layer is 0.03% -1%.
6. The lithium ion battery according to claim 1, wherein the percentage content c of the second amphoteric oxide to the mass of the separator is 3% to 20%.
7. The lithium ion battery of claim 1, wherein the first amphoteric oxide and the second amphoteric oxide are each independently selected from at least one of alumina, zirconia, tungsten oxide, and titania.
8. The lithium ion battery of claim 1, wherein the positive active material comprises LiFe 1-x’ M’ x’ PO 4 、LiMn 2-y’ M y’ O 4 And LiNi x Co y Mn z M 1-x-y-z O 2 At least one of sulfide, selenide and halide, wherein M 'is selected from at least one of Mn, mg, co, ni, cu, zn, al, sn, B, ga, cr, sr, V or Ti, M is selected from at least one of Fe, co, ni, mn, mg, cu, zn, al, sn, B, ga, cr, sr, V or Ti, and 0 is not less than 0 and not more than 1,0 and not more than y'. Ltoreq. 1,0 and not more than 1,0 and not more than x and not more than 1,0 and not more than z and not more than 1, x y + z is not less than 1.
9. The lithium ion battery of claim 1, wherein the nonaqueous electrolyte further comprises an additive comprising at least one of a cyclic sulfate-based compound, a sultone-based compound, a cyclic carbonate-based compound, a phosphate-based compound, a borate-based compound, and a nitrile-based compound;
the content of the additive is 0.01-30% based on the total mass of the nonaqueous electrolyte solution as 100%.
10. The lithium ion battery of claim 9, the cyclic sulfate compound is selected from vinyl sulfate, allyl sulfate, methyl vinyl sulfate,
、
、
、
、
At least one of;
the sultone compounds are selected from 1,3-propane sultone, 1,4-butane sultone, 1,3-propene sultone,
At least one of (a);
the cyclic carbonate compound is at least one of vinylene carbonate, ethylene carbonate, methylene ethylene carbonate, fluoroethylene carbonate, trifluoromethyl ethylene carbonate, difluoroethylene carbonate or a compound shown in a structural formula 1:
structural formula 1
In the structural formula 1, R 21 、R 22 、R 23 、R 24 、R 25 、R 26 Each independently selected from one of hydrogen atom, halogen atom and C1-C5 group;
the phosphate ester compound is at least one of tris (trimethyl silane) phosphate, tris (trimethyl silane) phosphite or a compound shown in a structural formula 2:
structural formula 2
In the formula 2, R 31 、R 32 、R 33 Each independently selected from C1-C5 saturated alkyl, unsaturated alkyl, halogenated alkyl, -Si (C) m H 2m+1 ) 3 M is a natural number of 1 to 3, and R 31 、R 32 、R 33 At least one of them is an unsaturated hydrocarbon group;
the borate compound is selected from at least one of tri (trimethyl silane) borate and tri (triethyl silane) borate;
the nitrile compound is at least one selected from succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetrinitrile, adiponitrile, pimelitrile, suberonitrile, nonanedionitrile and decanedionitrile.
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