CN116315033A - Secondary battery - Google Patents
Secondary battery Download PDFInfo
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- CN116315033A CN116315033A CN202111576303.4A CN202111576303A CN116315033A CN 116315033 A CN116315033 A CN 116315033A CN 202111576303 A CN202111576303 A CN 202111576303A CN 116315033 A CN116315033 A CN 116315033A
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- Prior art keywords
- formula
- positive electrode
- equal
- secondary battery
- compound
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- IAHFWCOBPZCAEA-UHFFFAOYSA-N succinonitrile Chemical compound N#CCCC#N IAHFWCOBPZCAEA-UHFFFAOYSA-N 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 229920006259 thermoplastic polyimide Polymers 0.000 description 1
- 229920005992 thermoplastic resin Polymers 0.000 description 1
- 239000002562 thickening agent Substances 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 239000011135 tin Substances 0.000 description 1
- XOLBLPGZBRYERU-UHFFFAOYSA-N tin dioxide Chemical compound O=[Sn]=O XOLBLPGZBRYERU-UHFFFAOYSA-N 0.000 description 1
- 229910001887 tin oxide Inorganic materials 0.000 description 1
- 238000009461 vacuum packaging Methods 0.000 description 1
- NQPDZGIKBAWPEJ-UHFFFAOYSA-N valeric acid Chemical compound CCCCC(O)=O NQPDZGIKBAWPEJ-UHFFFAOYSA-N 0.000 description 1
- 239000011787 zinc oxide Substances 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
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- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Secondary Cells (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
In order to overcome the problem of insufficient high-temperature cycle performance of the conventional lithium ion battery, the invention provides a secondary battery, which comprises a positive electrode, a negative electrode and nonaqueous electrolyte, wherein the positive electrode comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises compounds shown in a formula (B) and a formula (C): li (Li) 1+x Ni y Co z M 1‑y‑z O 2 Li (B) 1+c Mn 2‑d V d O 4 The nonaqueous electrolytic solution of formula (C) includes a solvent, an electrolyte salt, and an additive including a diisocyanate compound, and optionally a compound represented by formula (a); li [ M (C) 2 O 4 ) m R n ]The formula (A)The secondary battery satisfies the following conditions: 0.5-100 (a+b)/q-10, and a-2%, b-2.5%, 20-65%; the secondary battery provided by the invention can effectively inhibit and reduce divalent manganese ions dissolved out by the manganese-containing compound in the battery cycle process, optimize the positive and negative electrode interface structure, improve the capacity retention rate of the battery in high-temperature cycle and reduce the impedance growth rate.
Description
Technical Field
The invention belongs to the technical field of energy storage battery devices, and particularly relates to a secondary battery.
Background
The lithium ion battery has the advantages of high working voltage, long cycle life, high energy density, no memory effect and the like, and can be rapidly applied to the fields of mobile communication, notebook computers and the like after being put into the market in 1991. In lithium ion batteries, different positive electrode materials have different characteristics in structure and performance.
In the existing lithium ion battery, a common positive electrode material is a low-nickel layered ternary material, the volume energy density of the battery can be effectively improved, and the gram capacity of the material is increased along with the increase of the nickel content (for example, the NCM811 reaches 200 mAh/g). However, the reduction of the thermal decomposition temperature is extremely liable to cause the reduction of the safety of the low-nickel layered ternary material battery, and the surface activity enhancement accelerates the occurrence of side reactions with the electrolyte, causing the cycle capacity to be attenuated.
Compared with a low-nickel layered ternary material, the spinel lithium manganate material has more advantages in safety, and is excellent in low-temperature and rate capability, rich in resources and low in price. However, lithium manganate materials also suffer from disadvantages such as low gram capacity (110 mAh/g) resulting in lower energy densities.
Therefore, at present, two substances of lithium manganate and low-nickel layered ternary materials are mixed to be used as a positive electrode active material to prepare the lithium ion battery with high energy density and high safety performance. However, in the charge and discharge process of lithium manganate, trivalent manganese ions can undergo disproportionation reaction to generate soluble divalent manganese ions, so that the soluble divalent manganese ions are catalyzed to be oxidized and decomposed, in addition, manganese ions transferred to the surface of the negative electrode undergo reduction, the structure of the negative electrode SEI film is damaged, the electrolyte is catalyzed to be continuously decomposed on the surface of the negative electrode, and active lithium is lost, so that capacity attenuation is accelerated, the cycle performance of a lithium ion battery is deteriorated, and the influence of the lithium ion battery under the high-temperature condition is more serious. In addition, the compacted density of the lithium manganate is about 3.1g/cm 3 Lower than 3.4g/cm of ternary positive electrode material 3 Increase the polarization and advanceOne step promotes elution of manganese ions and deterioration of cycle performance.
On the other hand, as the common electrolyte salt of lithium ion battery electrolyte, lithium hexafluorophosphate is easy to decompose at high temperature to generate hydrofluoric acid, and the existence of hydrofluoric acid can not only catalyze the dissolution of divalent manganese ions in the lithium manganate positive electrode material, but also accelerate the decomposition of ternary positive electrode material active substances and electrolyte, and is also an important factor causing the shortage of high-temperature cycle performance of the battery.
Therefore, how to configure the electrolyte to improve the high-temperature cycle performance of the battery is a problem to be solved in the existing high-energy density manganese-containing battery system.
Disclosure of Invention
Aiming at the problem of insufficient high-temperature cycle performance of the existing lithium ion battery, the invention provides a secondary battery.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention provides a secondary battery, which comprises a positive electrode, a negative electrode and a nonaqueous electrolyte, wherein the positive electrode comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises a compound shown as a formula (B) and a formula (C):
Li 1+x Ni y Co z M 1-y-z O 2 (B)
Li 1+c Mn 2-d V d O 4 (C)
In the formula (B), x is more than or equal to-0.1 and less than or equal to 1, y is more than or equal to 0.5 and less 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 M comprises one or more than one of Mg, zn, ga, ba, al, fe, cr, sn, V, mn, sc, ti, nb, mo, zr;
in the formula (C), C is more than or equal to-0.05 and less than or equal to 0.2, d is more than or equal to 0 and less than or equal to 0.2, and V comprises one or more of Co, mg, al, ni, zn, ti, ca, sr, cr, ba;
the nonaqueous electrolytic solution includes a solvent, an electrolyte salt, and an additive including a diisocyanate compound, and optionally a compound represented by formula (a);
Li[M(C 2 O 4 ) m R n ](A)
In the formula (A), M is an integer more than or equal to 1, n is an integer more than or equal to 0, M is B or P, and R is halogen or halogenated alkane;
the secondary battery satisfies the following conditions:
0.5-100 (a+b)/q-10, and a-2%, b-2.5%, 20-65%;
wherein a is the mass percentage content of the diisocyanate compound in the nonaqueous electrolyte, and the unit is;
b is the mass percentage content of the compound shown in the formula (A) in the nonaqueous electrolyte, and the unit is;
q is the mass percentage content of Mn element in the positive electrode material layer, and the unit is%.
Alternatively, the secondary battery satisfies the following condition:
0.8≤100(a+b)/q≤4。
alternatively, the diisocyanate compound is selected from at least one of 4,4 '-dicyclohexylmethane diisocyanate, diphenylmethane-4, 4' -diisocyanate, toluene diisocyanate, and hexamethylene diisocyanate.
Alternatively, the compound represented by the formula (A) is selected from Li [ B (C) 2 O 4 ) 2 ]、Li[B(C 2 O 4 )F 2 ]、Li[P(C 2 O 4 ) 2 F 2 ]、Li[P(C 2 O 4 )F 4 ]At least one of them.
Optionally, the mass percentage of the compound shown in the formula (C) in the positive electrode material layer is more than or equal to 40%.
Optionally, the electrolyte salt comprises lithium hexafluorophosphate.
Optionally, the compound of formula (B) has a particle diameter D50 of 8-14 μm and a specific surface area of 0.2-0.8 m 2 /g；
The particle diameter D50 of the compound shown in the formula (C) is 10-18 mu m, and the specific surface area is less than or equal to 1.0m 2 /g。
Optionally, the mass percentage content a of the diisocyanate compound in the nonaqueous electrolyte is 0.02% -1.2%.
Optionally, the mass percentage content b of the compound shown in the formula (A) in the nonaqueous electrolyte is 0.1% -1.5%.
Optionally, the mass percentage q of Mn element in the positive electrode material layer is 25% -60%.
According to the secondary battery provided by the invention, the ternary material and the manganese-containing compound are adopted as the main components of the positive electrode active material, so that the energy density and the safety performance of the secondary battery can be effectively improved; meanwhile, in order to avoid the degradation of the high-temperature cycle performance of the battery, the inventor adds a diisocyanate compound and a compound shown in a formula (A) in a nonaqueous electrolyte, and discovers that the diisocyanate compound and the compound shown in the formula (A) have close relations with the addition amount of the diisocyanate compound and the mass percent of Mn element in a positive electrode material, and when the diisocyanate compound meets the relation of 0.5-100 (a+b)/q-10, the diisocyanate compound can effectively inhibit the dissolution of bivalent manganese ions in the positive electrode, and simultaneously generates oxidation-reduction reaction on the surface of the positive electrode to generate a compact protective layer, stabilize the positive electrode structure and reduce the oxidative decomposition of the electrolyte on the surface of the positive electrode; in addition, the compound shown in the formula (A) can effectively reduce the deposition of divalent manganese ions on a negative electrode, reduce the damage of dissolved manganese ions to a negative electrode SEI film structure, effectively inhibit the continuous decomposition of electrolyte at a negative electrode interface, reduce the loss of active lithium, improve the stability of the negative electrode interface, optimize a protective layer on the surface of a positive electrode, improve the initial effect and DCIR of a battery, and ensure lower interface impedance, thereby improving the capacity retention rate of the secondary battery in high-temperature circulation, reducing the impedance growth rate and ensuring excellent high-temperature circulation performance while ensuring higher safety performance of the secondary battery.
Detailed Description
In order to make the technical problems, technical schemes and beneficial effects solved by the invention more clear, the invention is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
The embodiment of the invention provides a secondary battery, which comprises a positive electrode, a negative electrode and a nonaqueous electrolyte, wherein the positive electrode comprises a positive electrode material layer, the positive electrode material layer comprises a positive electrode active material, and the positive electrode active material comprises a compound shown as a formula (B) and a formula (C):
Li 1+x Ni y Co z M 1-y-z O 2 (B)
Li 1+c Mn 2-d V d O 4 (C)
In the formula (B), x is more than or equal to-0.1 and less than or equal to 1, y is more than or equal to 0.5 and less 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 M comprises one or more than one of Mg, zn, ga, ba, al, fe, cr, sn, V, mn, sc, ti, nb, mo, zr;
in the formula (C), C is more than or equal to-0.05 and less than or equal to 0.2, d is more than or equal to 0 and less than or equal to 0.2, and V comprises one or more of Co, mg, al, ni, zn, ti, ca, sr, cr, ba;
the nonaqueous electrolytic solution includes a solvent, an electrolyte salt, and an additive including a diisocyanate compound, and optionally a compound represented by formula (a);
Li[M(C 2 O 4 ) m R n ](A)
In the formula (A), M is an integer more than or equal to 1, n is an integer more than or equal to 0, M is B or P, and R is halogen or halogenated alkane;
the secondary battery satisfies the following conditions:
0.5-100 (a+b)/q-10, and a-2%, b-2.5%, 20-65%;
wherein a is the mass percentage content of the diisocyanate compound in the nonaqueous electrolyte, and the unit is;
b is the mass percentage content of the compound shown in the formula (A) in the nonaqueous electrolyte, and the unit is;
q is the mass percentage content of Mn element in the positive electrode material layer, and the unit is%.
The ternary positive electrode material shown in the formula (B) has higher gram capacity, can provide high energy density for the battery, and the lithium manganate positive electrode material shown in the formula (C) can provide higher safety performance for the battery, and the ternary positive electrode material and the lithium manganate positive electrode material are matched for use, so that the lithium secondary battery with high energy density and high safety performance is obtained. Meanwhile, in order to avoid the degradation of the high-temperature cycle performance of the battery, the inventor adds a diisocyanate compound and a compound shown in a formula (A) in a nonaqueous electrolyte, and discovers that the diisocyanate compound and the compound shown in the formula (A) have close relations with the addition amount of the diisocyanate compound and the mass percent of Mn element in a positive electrode material, and when the diisocyanate compound meets the relation of 0.5-100 (a+b)/q-10, the diisocyanate compound can effectively inhibit the dissolution of bivalent manganese ions in the positive electrode, and simultaneously generates oxidation-reduction reaction on the surface of the positive electrode to generate a compact protective layer, stabilize the positive electrode structure and reduce the oxidative decomposition of the electrolyte on the surface of the positive electrode; in addition, the compound shown in the formula (A) can effectively reduce the deposition of divalent manganese ions on a negative electrode, reduce the damage of dissolved manganese ions to a negative electrode SEI film structure, effectively inhibit the continuous decomposition of electrolyte at a negative electrode interface, reduce the loss of active lithium, improve the stability of the negative electrode interface, optimize a protective layer on the surface of a positive electrode, improve the initial effect and DCIR of a battery, and ensure lower interface impedance, thereby improving the capacity retention rate of the secondary battery in high-temperature circulation, reducing the impedance growth rate and ensuring excellent high-temperature circulation performance while ensuring higher safety performance of the secondary battery.
In some embodiments, the diisocyanate compound has a mass percentage content a in the nonaqueous electrolytic solution of 0.02% to 2.0%.
If the content of the diisocyanate compound is too low, the dissolution of divalent manganese ions cannot be effectively inhibited, the stability of the anode-cathode interface is reduced, and if the content of the diisocyanate compound is too high, polymerization reaction easily occurs under the subsequent high-temperature condition, the generated polymer can cause impedance increase in the battery cycle process, and the improvement of the high-temperature cycle performance is also not facilitated.
Specifically, the mass percentage content a of the diisocyanate compound in the nonaqueous electrolytic solution may be 0.02%, 0.08%, 0.1%, 0.15%, 0.17%, 0.2%, 0.24%, 0.28%, 0.3%, 0.35%, 0.5%, 0.64%, 0.7%, 0.8%, 1.0%, 1.5%, 2.0% or the like.
In a preferred embodiment, the content of the diisocyanate compound a in the nonaqueous electrolytic solution is 0.02% to 1.2% by mass.
In some embodiments, the mass percentage content b of the compound shown in the formula (a) in the nonaqueous electrolyte is 0% -2.5%.
If the content of the compound represented by formula (a) is too high, it may cause an excessive thickness of the negative electrode SEI film and may increase the internal resistance of the battery.
Specifically, the mass percentage b of the compound represented by the formula (a) in the nonaqueous electrolytic solution may be 0.02%, 0.05%, 0.1%, 0.2%, 0.4%, 0.5%, 1.5%, 2.0%, 2.5%, or the like.
In a preferred embodiment, the mass percentage b of the compound represented by the formula (a) in the nonaqueous electrolyte is 0.1% to 1.5%, and if the content of the compound represented by the formula (a) is too low, the deposition of divalent manganese ions on the negative electrode cannot be effectively improved, and the effect of improving the cycle performance cannot be achieved.
In some embodiments, the mass percentage q of Mn element in the positive electrode material layer is 20% -65%;
if the mass percentage q value of Mn element in the positive electrode active material is too low, the safety performance of the secondary battery is reduced; if the q value of the Mn element in the positive electrode active material is too high, the capacity exertion and the high-temperature storage performance of the secondary battery are affected.
In a preferred embodiment, the mass percentage q of Mn element in the positive electrode material layer is 25% -60%.
In a preferred embodiment, the secondary battery satisfies the following conditions:
0.8≤100(a+b)/q≤4。
the mass percent of the diisocyanate compound a, the mass percent of the compound b shown in the formula (A) and the mass percent of the Mn element q in the positive electrode material are related, so that the design of the positive electrode material layer and the influence of the diisocyanate compound and the compound shown in the formula (A) on the battery performance can be combined to a certain extent, and the secondary battery with high safety and excellent high-temperature cycle performance can be obtained.
In some embodiments, the diisocyanate compound is selected from at least one of 4,4 '-dicyclohexylmethane diisocyanate (HMDI), diphenylmethane-4, 4' -diisocyanate (MDI), toluene Diisocyanate (TDI), hexamethylene Diisocyanate (HDI).
The isocyanate groups contained in the diisocyanate compound have the effects of removing water and acid, and effectively reduce hydrofluoric acid generated by decomposition of lithium hexafluorophosphate, so that dissolution of divalent manganese ions is inhibited, meanwhile, the diisocyanate compound can also generate a compact protective layer by oxidation-reduction reaction on the surface of the positive electrode, the structure of the positive electrode is stabilized, and the oxidative decomposition of electrolyte on the surface of the positive electrode is reduced, so that the high-temperature cycle performance of the battery is improved.
The above is only a preferred compound of the present invention, and does not represent a limitation of the present invention.
In some embodiments, the compound of formula (A) is selected from Li [ B (C) 2 O 4 ) 2 ]、Li[B(C 2 O 4 )F 2 ]、Li[P(C 2 O 4 ) 2 F 2 ]、Li[P(C 2 O 4 )F 4 ]At least one of them.
The oxalate ions contained in the compound shown in the formula (A) can form a complex with the dissolved divalent manganese ions, so that the deposition of the divalent manganese ions on a negative electrode is reduced, the damage of a negative electrode SEI film is reduced, and the high-temperature cycle performance of a battery is improved.
The above is only a preferred compound of the present invention, and does not represent a limitation of the present invention.
In some embodiments, the mass percentage of the compound shown in the formula (C) in the positive electrode material layer is greater than or equal to 40%.
If the weight percentage of lithium manganate in the positive electrode active material is too low, the safety performance of the secondary battery is lowered, and therefore, the mass percentage is preferably not less than 40%.
In some embodiments, the electrolyte salt comprises lithium hexafluorophosphate.
The lithium hexafluorophosphate LiPF 6 Has good conductivity and stable electrochemical performance, and can form proper SEI film and wider electrochemical stability window on the electrode. The diisocyanate compound can effectively remove hydrofluoric acid generated by decomposing lithium hexafluorophosphate, and reduce the dissolution of divalent manganese ions.
In some embodiments, the compound of formula (B) has a particle size D50 of 8 to 14 μm and a specific surface area of 0.2 to 0.8m 2 /g；
The particle diameter D50 of the compound shown in the formula (C) is 10-18 mu m, and the specific surface area is less than or equal to 1.0m 2 /g。
In general, the smaller the average particle diameter D50 of the positive electrode active material, the more advantageous is to improve the overall conductivity of the electrode, and further to improve the rate capability of the battery, however, too small particle diameter results in too low compaction density of the electrode material, which is disadvantageous to the improvement of energy density. Preferably, the compound of formula (B) has a particle diameter D50 of 8 to 14. Mu.m, and the compound of formula (C) has a particle diameter D50 of 10 to 18. Mu.m.
The electrode reaction is mostly concentrated on the electrode/electrolyte interface, the larger the specific surface area of the active material is, the larger the electrode/electrolyte interface is, the easier the electrode reaction is, the smaller the polarization is, the better the electrode performance is, but the larger the specific surface area is, the lower the structural strength of the positive electrode material layer is, and the problems of material falling and electrolyte decomposition are caused. Preferably, the specific surface area of the compound represented by formula (B) is 0.2 to 0.8m 2 Per gram, the specific surface area of the compound shown in the formula (C) is less than or equal to 1.0m 2 /g。
Preferably, the compound of formula (B) may have a particle diameter D50 of 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, and a specific surface area of 0.2m 2 /g、0.3m 2 /g、0.4m 2 /g、0.5m 2 /g、0.6m 2 /g、0.7m 2 /g、0.8m 2 /g。
Preferably, the compound of formula (C) may have a particle diameter D50 of 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, and a specific surface area of 0.2m 2 /g、0.3m 2 /g、0.4m 2 /g、0.5m 2 /g、0.6m 2 /g、0.7m 2 /g、0.8m 2 /g。
In some embodiments, the electrolyte salt may also be selected from LiPO 2 F 2 、LiBF 4 、LiSbF 6 、LiAsF 6 、LiCF 3 SO 3 、LiN(SO 2 CF 3 ) 2 、LiC(SO 2 CF 3 ) 3 、LiN(SO 2 C 2 F 5 ) 2 、LiN(SO 2 F) 2 、LiCl、LiBr、LiI、LiClO 4 、LiBF 4 、LiB 10 Cl 10 、LiAlCl 4 At least one of lithium chloroborane, lithium lower aliphatic carboxylate having 4 or less carbon atoms, lithium tetraphenyl borate, and lithium iminoborate. Specifically, the electrolyte salt may be LiBF 4 、LiClO 4 、LiAlF 4 、LiSbF 6 、LiTaF 6 、LiWF 7 An inorganic electrolyte salt; liPF (LiPF) 6 An isophosphoric acid electrolyte salt; liWOF 5 Isopolytics electrolyte salts; HCO (hydrogen chloride) 2 Li、CH 3 CO 2 Li、CH 2 FCO 2 Li、CHF 2 CO 2 Li、CF 3 CO 2 Li、CF 3 CH 2 CO 2 Li、CF 3 CF 2 CO 2 Li、CF 3 CF 2 CF 2 CO 2 Li、CF 3 CF 2 CF 2 CF 2 CO 2 Carboxylic acid electrolyte salts such as Li; CH (CH) 3 SO 3 Sulfonic acid electrolyte salts such as Li; liN (FCO) 2 ) 2 、LiN(FCO)(FSO 2 )、LiN(FSO 2 ) 2 、LiN(FSO 2 )(CF 3 SO 2 )、LiN(CF 3 SO 2 ) 2 、LiN(C 2 F 5 SO 2 ) 2 Cyclic 1, 2-perfluoroethanedisulfonimide lithium, cyclic 1, 3-perfluoropropanedisulfonylimide lithium, and LiN (CF) 3 SO 2 )(C 4 F 9 SO 2 ) Imide electrolyte salts; liC (FSO) 2 ) 3 、LiC(CF 3 SO 2 ) 3 、LiC(C 2 F 5 SO 2 ) 3 Isomethyl electrolyte salts; liPF (liquid crystal display) and LiPF 4 (CF 3 ) 2 、LiPF 4 (C 2 F 5 ) 2 、LiPF 4 (CF 3 SO 2 ) 2 、LiPF 4 (C 2 F 5 SO 2 ) 2 、LiBF 3 CF 3 、LiBF 3 C 2 F 5 、LiBF 3 C 3 F 7 、LiBF 2 (CF 3 ) 2 、LiBF 2 (C 2 F 5 ) 2 、LiBF 2 (CF 3 SO 2 ) 2 、LiBF 2 (C 2 F 5 SO 2 ) 2 And fluorine-containing organic electrolyte salts.
In general, the electrolyte salt in the electrolyte is a transfer unit of lithium ions, and the concentration of the electrolyte salt directly affects the transfer rate of lithium ions, which affects the potential change of the negative electrode. In the process of quick battery charging, the moving speed of lithium ions needs to be improved as much as possible, the formation of lithium dendrites caused by too fast negative electrode potential drop is prevented, potential safety hazards are brought to the battery, and meanwhile, the too fast attenuation of the circulating capacity of the battery can be prevented. Preferably, the total concentration of the electrolyte salt in the electrolyte may be 0.5 to 2.0mol/L, 0.5 to 0.6mol/L, 0.6 to 0.7mol/L, 0.7 to 0.8mol/L, 0.8 to 0.9mol/L, 0.9 to 1.0mol/L, 1.0 to 1.1mol/L, 1.1 to 1.2mol/L, 1.2 to 1.3mol/L, 1.3 to 1.4mol/L, 1.4 to 1.5mol/L, 1.5 to 1.6mol/L, 1.6 to 1.7mol/L, 1.7 to 1.8mol/L, 1.8 to 1.9mol/L, or 1.9 to 1.3mol/L, and preferably, 1.7 to 1.8mol/L, and more preferably, 0.7 to 1.8 mol/L.
In some embodiments, the nonaqueous electrolytic solution further includes an auxiliary additive including at least one of a cyclic sulfate compound, a sultone compound, a cyclic carbonate compound, and a nitrile compound;
and the mass percentage content of the auxiliary additive is 0.01-30% based on 100% of the total mass of the nonaqueous electrolyte.
In the nonaqueous electrolyte, the auxiliary additive can improve the conductivity of the electrolyte, improve the migration rate of lithium ions and improve the electrochemical reaction rate of the battery; meanwhile, the auxiliary additive is cooperated with the unsaturated phosphate compound shown in the structural formula 1, lithium hexafluorophosphate and lithium bis (fluorosulfonyl) imide, so that a more stable passivation film is produced on the surface of the positive electrode and the negative electrode, the stability of the electrolyte is improved, the corrosion of a positive electrode current collector is inhibited, and the cycle performance, the initial capacity exertion and the safety performance of the battery are improved.
In some embodiments, the cyclic sulfate compound is selected from at least one of vinyl sulfate, propylene sulfate, or vinyl methyl sulfate; the sultone compound comprises at least one of 1, 3-propane sultone, 1, 4-butane sultone or 1, 3-propylene sultone; the cyclic carbonate compound comprises at least one of ethylene carbonate, ethylene carbonate and fluoroethylene carbonate; the nitrile compound is at least one selected from succinonitrile, glutaronitrile, ethylene glycol bis (propionitrile) ether, hexanetrinitrile, adiponitrile, pimelic nitrile, suberonitrile, nonyldinitrile and decyldinitrile;
in nonaqueous electrolysis, a small amount of auxiliary additive is added to exert the effect, the addition amount of the auxiliary additive influences the conductivity of the electrolyte, the additive content is excessive, the cost of the electrolyte is increased, the additive content is too low to exert the effect, and the cycle performance and the safety performance of the battery cannot be better improved.
In general, the addition amount of any one of the optional substances in the auxiliary additive to the nonaqueous electrolytic solution is 10% or less, preferably 0.1 to 5%, and more preferably 0.1 to 2%, unless otherwise specified. Specifically, the addition amount of any optional substance in the auxiliary 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%, 8.5%, 9%, 9.5%, 10%.
In some embodiments, when the auxiliary additive is selected from fluoroethylene carbonate, the fluoroethylene carbonate is added in an amount of 0.05% to 30% based on 100% of the total mass of the nonaqueous electrolytic solution.
In some embodiments, the solvent comprises one or more of an ether solvent, a nitrile solvent, a carbonate solvent, and a carboxylate solvent.
In some embodiments, the ether solvent includes a cyclic ether or a chain ether, preferably a chain ether having 3 to 10 carbon atoms and a cyclic ether having 3 to 6 carbon atoms, and the cyclic ether may be specifically but not limited to 1, 3-dioxolane
(DOL), 1, 4-Dioxan (DX), crown ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-CH) 3 -THF), 2-trifluoromethyl tetrahydrofuran (2-CF) 3 -THF) one or more of; the chain ether may be, but not limited to, dimethoxymethane, diethoxymethane, ethoxymethoxymethane, ethylene glycol di-n-propyl ether, ethylene glycol di-n-butyl ether, diethylene glycol dimethyl ether. Since the chain ether has high solvation ability with lithium ions and can improve ion dissociation properties, dimethoxymethane, diethoxymethane and ethoxymethoxymethane, which have low viscosity and can impart high ion conductivity, are particularly preferable. The ether compound may be used alone, or two or more of them may be used in any combination and ratio. The amount of the ether compound to be added is not particularly limited, and is arbitrary within a range that does not significantly impair the effect of the highly compacted lithium ion battery of the present invention, and is usually 1% or more, preferably 2% or more, more preferably 3% or more in terms of the volume ratio of the nonaqueous solvent of 100%, and is usually 30% or less, preferably 25% or less, more preferably 20% or less in terms of the volume ratio. 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 amount of the ether compound is within the above preferred range, the effect of improving the ionic conductivity due to the increase in the dissociation degree of lithium ions and the decrease in the viscosity of the chain ether can be easily ensured. In addition, when the negative electrode active material is a carbon material, co-intercalation of the chain ether and lithium ions can be suppressed, and thus the input/output characteristics and the charge/discharge rate characteristics can be brought into appropriate ranges.
In some embodiments, the nitrile solvent may be, but is not limited to, one or more of acetonitrile, glutaronitrile, malononitrile.
In some embodiments, the carbonate-based solvent includes a cyclic carbonate or a chain carbonate, which may be specifically but not limited to one or more of Ethylene Carbonate (EC), propylene Carbonate (PC), gamma-butyrolactone (GBL), butylene Carbonate (BC); the chain carbonate may be, but is not limited to, in particular, one or more of dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dipropyl carbonate (DPC). The content of the cyclic carbonate is not particularly limited, and is arbitrary within a range that does not significantly impair the effect of the secondary battery of the present invention, but in the case where one is used alone, the lower limit of the content thereof 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 the range, it is possible to avoid a decrease in conductivity due to a decrease in dielectric constant of the nonaqueous electrolyte solution, and it is easy to achieve a good range of high-current discharge characteristics, stability with respect to the negative electrode, and cycle characteristics of the nonaqueous electrolyte battery. The upper limit is usually 90% by volume or less, preferably 85% by volume or less, and more preferably 80% by volume or less. By setting the range, the oxidation/reduction resistance of the nonaqueous electrolytic solution can be improved, thereby contributing to improvement of stability at high-temperature storage. The content of the chain carbonate is not particularly limited, but 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. In addition, the volume ratio is usually 90% or less, preferably 85% or less, and more preferably 80% or less. By setting the content of the chain carbonate in the above range, the viscosity of the nonaqueous electrolytic solution can be easily set to an appropriate range, and the decrease in the ionic conductivity can be suppressed, thereby contributing to the improvement in the output characteristics of the nonaqueous electrolyte battery. 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, it may also be preferable to use a chain carbonate having a fluorine atom (hereinafter simply referred to as "fluorinated chain carbonate"). 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. In the case where the fluorinated chain carbonate has a plurality of fluorine atoms, these fluorine atoms may be bonded to the same carbon or may be bonded to different carbons. Examples of the fluorinated chain carbonate include fluorinated dimethyl carbonate derivatives, fluorinated ethyl methyl carbonate derivatives, and fluorinated diethyl carbonate derivatives.
The carboxylic acid ester solvent includes a cyclic carboxylic acid ester and/or a chain carbonate. Examples of the cyclic carboxylic acid ester include: one or more of gamma-butyrolactone, gamma-valerolactone and delta-valerolactone. Examples of the chain carbonate include, for example: one or more 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 compounds having generally 3 to 6 carbon atoms, preferably 3 to 5 carbon atoms in the case of cyclic sulfones, and generally 2 to 6 carbon atoms, preferably 2 to 5 carbon atoms in the case of chain sulfones. The amount of the sulfone-based solvent to be added is not particularly limited, and is arbitrary within a range that does not significantly impair the effect of the secondary battery of the present invention, and is usually 0.3% or more, preferably 0.5% or more, more preferably 1% or more by volume, and is usually 40% or less, preferably 35% or less, more preferably 30% or less by volume, based on the total amount of the solvent of the nonaqueous electrolyte. When two or more sulfone solvents are used in combination, the total amount of sulfone solvents may be set to satisfy the above range. When the amount of the sulfone-based solvent added is within the above range, an electrolyte solution excellent in high-temperature storage stability tends to be obtained.
In a preferred embodiment, the solvent is a mixture of cyclic carbonates and chain carbonates.
In some embodiments, the positive electrode further comprises a positive electrode current collector, and the positive electrode material layer covers the surface of the positive electrode current collector.
The positive current collector is selected from a metal material that can conduct electrons, preferably, the positive current collector includes one or more of Al, ni, tin, copper, stainless steel, and in a more preferred embodiment, the positive current collector is selected from aluminum foil.
In some embodiments, the positive electrode material layer further comprises a positive electrode binder and a positive electrode conductive agent, and the positive electrode active material, the positive electrode binder and the positive electrode conductive agent are blended to obtain the positive electrode active material layer.
In some embodiments, the positive electrode binder includes a thermoplastic resin such as polyvinylidene fluoride, a copolymer of vinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene, a copolymer of tetrafluoroethylene-perfluoroalkyl vinyl ether, a copolymer of ethylene-tetrafluoroethylene, a copolymer of vinylidene fluoride-trifluoroethylene, a copolymer of vinylidene fluoride-trichloroethylene, a copolymer of vinylidene fluoride-fluoroethylene, a copolymer of vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene, thermoplastic polyimide, polyethylene, and polypropylene; an acrylic resin; and one or more of styrene butadiene rubber.
In some embodiments, the positive electrode conductive agent includes one or more of a metal conductive agent, a carbon-based material, a metal oxide-based conductive agent, and a composite conductive agent. Specifically, the metal conductive agent can be copper powder, nickel powder, silver powder and other metals; the carbon-based material may be a carbon-based material such as conductive graphite, conductive carbon black, conductive carbon fiber, or graphene; the metal oxide conductive agent may be tin oxide, iron oxide, zinc oxide, etc.; the composite conductive agent can be composite powder, composite fiber and the like. More specifically, the conductive carbon black may be one or more of acetylene black, 350G, ketjen black, carbon fiber (VGCF), and Carbon Nanotubes (CNTs).
In some embodiments, a separator is also included in the battery, the separator being located between the positive electrode and the negative electrode.
The separator may be an existing conventional separator, and may be a polymer separator, a non-woven fabric, etc., including but not limited to a single-layer PP (polypropylene), a single-layer PE (polyethylene), a double-layer PP/PE, a double-layer PP/PP, a triple-layer PP/PE/PP, etc.
The invention is further illustrated by the following examples.
Examples 1 to 16
This example is for illustrating the secondary battery and the method of manufacturing the same disclosed in the present invention, and includes the following steps:
1) Preparation of nonaqueous electrolyte
Mixing Ethylene Carbonate (EC), diethyl carbonate (DEC) and methyl ethyl carbonate (EMC) according to the mass ratio of EC: DEC: EMC=1:1:1, and then adding lithium hexafluorophosphate (LiPF) 6 ) To a molar concentration of 1mol/L, a diisocyanate compound having a mass content shown in Table 1 and a compound represented by formula (A) were further added.
2) Preparation of positive electrode plate
The positive electrode active material, the conductive agent Super-P and the binder polyvinylidene fluoride (PVDF) are mixed according to the weight ratio of LiNi 0.5 Co 0.2 Mn 0.3 O 2 +LiMn 2 O 4 : mixing conductive carbon black Super-P with a binder polyvinylidene fluoride=93:4:3, adding N-methyl pyrrolidone (NMP), and uniformly mixing to obtain lithium ion battery anode slurry; and coating the positive electrode slurry on two sides of a current collector aluminum foil, drying, calendaring and vacuum drying, and welding an aluminum outgoing line by using an ultrasonic welder to obtain the positive electrode plate of the lithium battery, wherein the thickness of the positive electrode plate is 120-150 mu m.
3) Preparation of negative electrode plate
Dispersing negative electrode active material graphite, conductive carbon black Super-P, binder styrene-butadiene rubber (SBR) and thickener carboxymethyl cellulose (CMC) in solvent deionized water according to the weight ratio of 94:1:2.5:2.5, and uniformly mixing to obtain negative electrode slurry; uniformly coating the negative electrode slurry on two sides of a negative electrode current collector copper foil; drying, calendaring and vacuum drying, and welding a nickel lead-out wire by an ultrasonic welder to obtain the lithium battery negative plate, wherein the thickness of the negative plate is 120-150 mu m.
4) Preparation of the cell
And placing a three-layer lithium battery diaphragm with the thickness of 20 mu m between the positive plate and the negative plate, winding a sandwich structure formed by the positive plate, the negative plate and the diaphragm, flattening the winding body, putting into an aluminum foil packaging bag, and baking for 48 hours at the temperature of 75 ℃ in vacuum to obtain the battery cell to be injected with the liquid.
5) Injection and formation of battery cell
In a glove box with water and oxygen contents below 20ppm and 50ppm respectively, the prepared electrolyte is injected into a battery cell, and the battery cell is subjected to vacuum packaging and is placed at 45 ℃ for 24 hours. Then the first charge is conventionally formed by the following steps: 0.05C constant current charging 180min,0.1C constant current charging 180min,0.2C constant current charging 120min, total charging capacity of C1, aging at 45 ℃ for 48h, secondary vacuum sealing, and then further charging to 4.2V with 0.2C constant current, wherein charging capacity of C2; constant current discharge to 3.0V was performed at a current of 0.2C, and the discharge capacity was dc.
Comparative examples 1 to 14
Comparative examples 1 to 14 are for illustrating the battery and the method for manufacturing the same disclosed in the present invention, and include most of the operation steps of example 1, which are different in that:
the electrolyte addition components and positive electrode parameters shown in table 1 were used.
Performance testing
The lithium ion battery prepared by the method is subjected to the following performance test:
high temperature cycle performance test of lithium ion battery: the formed battery was charged to 4.2V at 45 ℃ with a constant current of 1C, charged again with a constant current and constant voltage until the current was reduced to 0.05C, and discharged to 3.0V with a constant current of 1C, and so on, and the internal resistance of the discharge capacity at week 1 and the discharge capacity and internal resistance at week 500 were recorded.
The capacity retention and resistance increase rate for the high temperature cycle were calculated as follows:
capacity retention= (discharge capacity at 500 th week/discharge capacity at 1 st week) ×100%;
impedance increase rate= (500 th week impedance-1 st week impedance)/1 st week impedance×100%.
The test results are filled in table 1.
TABLE 1
Note that: HMDI refers to 4,4' -dicyclohexylmethane diisocyanate and LiODFB refers to Li [ B (C 2 O 4 )F 2 ]。
From the test results of examples 1 to 16 and comparative examples 1 to 14, when the mass percentage content a of the diisocyanate compound in the nonaqueous electrolytic solution, the mass percentage content b of the compound represented by the formula (a) in the nonaqueous electrolytic solution, and the mass percentage content q of the Mn element in the positive electrode material satisfy the following relationship: when the ratio of (a+b)/q is more than or equal to 0.5 and less than or equal to 100 and less than or equal to 10, the ratio of a is more than or equal to 0.02 and less than or equal to 2%, the ratio of b is more than or equal to 0 and less than or equal to 2.5%, and the ratio of q is more than or equal to 20 and less than or equal to 65%, the dissolution of divalent manganese ions can be effectively inhibited, the high-temperature cycle capacity retention rate of the battery is remarkably improved, and the impedance growth rate is reduced.
From the test results of examples 1 to 4, it can be seen that the addition of the diisocyanate compound alone can significantly improve the high-temperature cycle capacity retention rate of the battery, but the high-temperature cycle resistance increase rate improvement effect is slightly insufficient.
From the test results of comparative examples 5 to 11, it can be seen that the addition of the compound represented by the formula (a) alone also has an effect of improving the high-temperature cycle capacity retention rate of the battery, but the improvement effect is not as remarkable as that of the diisocyanate compound.
As can be seen from the test results of examples 5 to 13, the combination of the diisocyanate compound and the compound represented by the formula (A) further improves the high-temperature cycle capacity retention rate of the battery by combining the advantages of both, and the addition of the compound represented by the formula (A) further reduces the resistance increase rate and has a lower initial resistance, so that the battery has excellent comprehensive high-temperature performance.
As can be seen from the test results of comparative examples 3 and 13, even though the a value, the b value, and the q value all satisfy the parameter ranges thereof, the relation is not satisfied: when the initial impedance, the high-temperature circulation capacity retention rate and the high-temperature circulation impedance growth rate of the battery are not more than 0.5 and less than or equal to 100 (a+b)/q and less than or equal to 10, the good comprehensive level still cannot be achieved, which indicates that the interaction effect exists between the mass percent a of the isocyanate compound in the nonaqueous electrolyte, the mass percent b of the compound shown in the formula (A) in the nonaqueous electrolyte and the mass percent q of the Mn element in the positive electrode material, and the electrochemical performance of the battery at high temperature and the initial impedance of the battery can be improved if and only if the three components are in an equilibrium state. From the test results of comparative example 4, it is understood that when one of the parameters a, b, q is out of the limit range, even if the relation is satisfied: the requirement that the ratio of (a+b)/q is less than or equal to 0.5 and less than or equal to 100 is less than or equal to 10, and the effects of comprehensively improving the high-temperature circulation capacity retention rate, the high-temperature circulation impedance growth rate and the initial impedance of the battery cannot be achieved.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (10)
1. A secondary battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolytic solution, the positive electrode comprising a positive electrode material layer comprising a positive electrode active material comprising a compound represented by formula (B) and formula (C):
Li 1+x Ni y Co z M 1-y-z O 2 (B)
Li 1+c Mn 2-d V d O 4 (C)
In the formula (B), x is more than or equal to-0.1 and less than or equal to 1, y is more than or equal to 0.5 and less 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 M comprises one or more than one of Mg, zn, ga, ba, al, fe, cr, sn, V, mn, sc, ti, nb, mo, zr;
in the formula (C), C is more than or equal to-0.05 and less than or equal to 0.2, d is more than or equal to 0 and less than or equal to 0.2, and V comprises one or more of Co, mg, al, ni, zn, ti, ca, sr, cr, ba;
the nonaqueous electrolytic solution includes a solvent, an electrolyte salt, and an additive including a diisocyanate compound, and optionally a compound represented by formula (a);
Li[M(C 2 O 4 ) m R n ](A)
In the formula (A), M is an integer more than or equal to 1, n is an integer more than or equal to 0, M is B or P, and R is halogen or halogenated alkane;
the secondary battery satisfies the following conditions:
0.5-100 (a+b)/q-10, and a-2%, b-2.5%, 20-65%;
wherein a is the mass percentage content of the diisocyanate compound in the nonaqueous electrolyte, and the unit is;
b is the mass percentage content of the compound shown in the formula (A) in the nonaqueous electrolyte, and the unit is;
q is the mass percentage content of Mn element in the positive electrode material layer, and the unit is%.
2. The secondary battery according to claim 1, wherein the secondary battery satisfies the following condition:
0.8≤100(a+b)/q≤4。
3. the secondary battery according to claim 1, wherein the diisocyanate compound is selected from at least one of 4,4 '-dicyclohexylmethane diisocyanate, diphenylmethane-4, 4' -diisocyanate, toluene diisocyanate, hexamethylene diisocyanate.
4. The secondary battery according to claim 1, wherein the compound represented by the formula (a) is selected from Li [ B (C 2 O 4 ) 2 ]、Li[B(C 2 O 4 )F 2 ]、Li[P(C 2 O 4 ) 2 F 2 ]、Li[P(C 2 O 4 )F 4 ]At least one of them.
5. The secondary battery according to claim 1, wherein the mass percentage of the compound represented by the formula (C) in the positive electrode material layer is not less than 40%.
6. The secondary battery according to claim 1, wherein the electrolyte salt comprises lithium hexafluorophosphate.
7. The secondary battery according to claim 1, wherein the compound represented by the formula (B) has a particle diameter D50 of 8 to 14 μm and a specific surface area of 0.2 to 0.8m 2 /g；
The particle diameter D50 of the compound shown in the formula (C) is 10-18 mu m, and the specific surface area is less than or equal to 1.0m 2 /g。
8. The secondary battery according to claim 1, wherein the diisocyanate compound has a mass percentage a of 0.02% to 1.2% in the nonaqueous electrolytic solution.
9. The secondary battery according to claim 1, wherein the mass percentage b of the compound represented by the formula (a) in the nonaqueous electrolytic solution is 0.1% to 1.5%.
10. The secondary battery according to claim 1, wherein the mass percentage q of Mn element in the positive electrode material layer is 25 to 60%.
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| CN111916706B (en) * | 2018-11-28 | 2021-10-01 | 宁德时代新能源科技股份有限公司 | Lithium ion secondary battery, method for manufacturing same, and electric vehicle, consumer electronic product, and mechanical device including same |
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