CN117832614A - Secondary battery - Google Patents
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- CN117832614A CN117832614A CN202311857860.2A CN202311857860A CN117832614A CN 117832614 A CN117832614 A CN 117832614A CN 202311857860 A CN202311857860 A CN 202311857860A CN 117832614 A CN117832614 A CN 117832614A
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- 239000000654 additive Substances 0.000 claims abstract description 55
- 230000000996 additive effect Effects 0.000 claims abstract description 50
- 239000003792 electrolyte Substances 0.000 claims abstract description 36
- 239000007773 negative electrode material Substances 0.000 claims abstract description 25
- -1 cyclic silane compound Chemical class 0.000 claims abstract description 22
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 19
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000010703 silicon Substances 0.000 claims abstract description 17
- 239000013538 functional additive Substances 0.000 claims abstract description 7
- 125000000217 alkyl group Chemical group 0.000 claims description 28
- 125000004093 cyano group Chemical group *C#N 0.000 claims description 28
- 229910052736 halogen Inorganic materials 0.000 claims description 28
- 150000002367 halogens Chemical class 0.000 claims description 28
- 125000000392 cycloalkenyl group Chemical group 0.000 claims description 21
- 229910052739 hydrogen Inorganic materials 0.000 claims description 15
- 239000001257 hydrogen Substances 0.000 claims description 15
- 125000003118 aryl group Chemical group 0.000 claims description 14
- 125000001424 substituent group Chemical group 0.000 claims description 14
- 125000003342 alkenyl group Chemical group 0.000 claims description 12
- 239000010405 anode material Substances 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 9
- 238000006467 substitution reaction Methods 0.000 claims description 9
- 229910052717 sulfur Inorganic materials 0.000 claims description 9
- 125000003545 alkoxy group Chemical group 0.000 claims description 7
- 125000006651 (C3-C20) cycloalkyl group Chemical group 0.000 claims description 6
- 125000003358 C2-C20 alkenyl group Chemical group 0.000 claims description 6
- 239000006183 anode active material Substances 0.000 claims description 6
- 229910052799 carbon Inorganic materials 0.000 claims description 6
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- FSSPGSAQUIYDCN-UHFFFAOYSA-N 1,3-Propane sultone Chemical compound O=S1(=O)CCCO1 FSSPGSAQUIYDCN-UHFFFAOYSA-N 0.000 claims description 2
- FALRKNHUBBKYCC-UHFFFAOYSA-N 2-(chloromethyl)pyridine-3-carbonitrile Chemical compound ClCC1=NC=CC=C1C#N FALRKNHUBBKYCC-UHFFFAOYSA-N 0.000 claims description 2
- AYKYXWQEBUNJCN-UHFFFAOYSA-N 3-methylfuran-2,5-dione Chemical compound CC1=CC(=O)OC1=O AYKYXWQEBUNJCN-UHFFFAOYSA-N 0.000 claims description 2
- OBNDGIHQAIXEAO-UHFFFAOYSA-N [O].[Si] Chemical compound [O].[Si] OBNDGIHQAIXEAO-UHFFFAOYSA-N 0.000 claims description 2
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- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims 4
- 238000003860 storage Methods 0.000 abstract description 21
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- 230000000052 comparative effect Effects 0.000 description 4
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- 125000005913 (C3-C6) cycloalkyl group Chemical group 0.000 description 3
- UHOPWFKONJYLCF-UHFFFAOYSA-N 2-(2-sulfanylethyl)isoindole-1,3-dione Chemical compound C1=CC=C2C(=O)N(CCS)C(=O)C2=C1 UHOPWFKONJYLCF-UHFFFAOYSA-N 0.000 description 3
- 125000000882 C2-C6 alkenyl group Chemical group 0.000 description 3
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 3
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- 229910052782 aluminium Inorganic materials 0.000 description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 3
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- 239000002000 Electrolyte additive Substances 0.000 description 2
- 229910013716 LiNi Inorganic materials 0.000 description 2
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 2
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- 229910018540 Si C Inorganic materials 0.000 description 2
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- 229910008284 Si—F Inorganic materials 0.000 description 2
- DPXJVFZANSGRMM-UHFFFAOYSA-N acetic acid;2,3,4,5,6-pentahydroxyhexanal;sodium Chemical compound [Na].CC(O)=O.OCC(O)C(O)C(O)C(O)C=O DPXJVFZANSGRMM-UHFFFAOYSA-N 0.000 description 2
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- 229910002804 graphite Inorganic materials 0.000 description 2
- 239000010439 graphite Substances 0.000 description 2
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 2
- 229910003002 lithium salt Inorganic materials 0.000 description 2
- 159000000002 lithium salts Chemical class 0.000 description 2
- VDVLPSWVDYJFRW-UHFFFAOYSA-N lithium;bis(fluorosulfonyl)azanide Chemical compound [Li+].FS(=O)(=O)[N-]S(F)(=O)=O VDVLPSWVDYJFRW-UHFFFAOYSA-N 0.000 description 2
- QSZMZKBZAYQGRS-UHFFFAOYSA-N lithium;bis(trifluoromethylsulfonyl)azanide Chemical compound [Li+].FC(F)(F)S(=O)(=O)[N-]S(=O)(=O)C(F)(F)F QSZMZKBZAYQGRS-UHFFFAOYSA-N 0.000 description 2
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 2
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- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
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- LIVNPJMFVYWSIS-UHFFFAOYSA-N silicon monoxide Inorganic materials [Si-]#[O+] LIVNPJMFVYWSIS-UHFFFAOYSA-N 0.000 description 2
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- GEWWCWZGHNIUBW-UHFFFAOYSA-N 1-(4-nitrophenyl)propan-2-one Chemical compound CC(=O)CC1=CC=C([N+]([O-])=O)C=C1 GEWWCWZGHNIUBW-UHFFFAOYSA-N 0.000 description 1
- IFDLFCDWOFLKEB-UHFFFAOYSA-N 2-methylbutylbenzene Chemical compound CCC(C)CC1=CC=CC=C1 IFDLFCDWOFLKEB-UHFFFAOYSA-N 0.000 description 1
- USGDMCWUHFXPCY-UHFFFAOYSA-M C(C(=O)O)(=O)[O-].P(=O)(O)(O)O.[Li+] Chemical compound C(C(=O)O)(=O)[O-].P(=O)(O)(O)O.[Li+] USGDMCWUHFXPCY-UHFFFAOYSA-M 0.000 description 1
- 125000003601 C2-C6 alkynyl group Chemical group 0.000 description 1
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- 229910013275 LiMPO Inorganic materials 0.000 description 1
- 229910015643 LiMn 2 O 4 Inorganic materials 0.000 description 1
- AUBNQVSSTJZVMY-UHFFFAOYSA-M P(=O)([O-])(O)O.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.[Li+] Chemical compound P(=O)([O-])(O)O.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.C(C(=O)O)(=O)F.[Li+] AUBNQVSSTJZVMY-UHFFFAOYSA-M 0.000 description 1
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- 239000006182 cathode active material Substances 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 150000004759 cyclic silanes Chemical class 0.000 description 1
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Abstract
The invention provides a secondary battery. The functional additives in the electrolyte of the secondary battery include a first additive and a second additive; the first additive comprises a cyclic silane compound, and the second additive comprises a sulfonate compound. When the electrolyte contains the two additives, the two additives can jointly act on the surface of the electrode to form a stable low-impedance SEI film, so that the interface stability of the silicon negative electrode is obviously improved, the damage of the volume expansion of the silicon negative electrode material to the SEI film is reduced, and the high-temperature storage performance, the high-temperature cycle performance and the low-temperature discharge performance of the battery are obviously improved.
Description
Technical Field
The invention belongs to the technical field of batteries, and particularly relates to a secondary battery, in particular to a secondary battery capable of solving the problems of poor high-temperature cycle performance, poor high-temperature storage performance, poor low-temperature discharge performance and the like of the traditional silicon-based lithium ion battery.
Background
At present, people have more and more demands on high-energy density lithium ion batteries, and the theoretical specific capacity of the traditional graphite negative electrode is only 372mAh g -1 . In contrast, the theoretical specific capacity of the silicon-based anode material can reach 4200mAh g -1 The energy density of the lithium ion battery is expected to be greatly improved. At the same time, the silicon-based anode material also has lower lithium intercalation potential (about 0.4V vs. Li/Li + ) The lithium ion battery anode material has the advantages of abundant reserves and the like, and is a high-energy density lithium ion battery anode material with great potential. But howeverThe huge volume expansion effect of the silicon-based negative electrode leads to the fact that the circulation and storage performance of the silicon-based lithium ion battery can not meet the actual requirements, and the commercialized application of the silicon-based lithium ion battery is hindered. The electrolyte is used as an important component in the lithium ion battery, and plays an important role in the performance of the silicon-based anode material. Regulating the performance of silicon-based anode materials by means of a reasonably designed electrolyte additive is considered to be one of the most economically viable strategies. Although researchers have developed different silicon-based negative electrode additives, the industry requirements are still not well met at present. Therefore, it is necessary to continue active research and development in this respect.
Disclosure of Invention
In order to solve the problem that the high-temperature cycle performance, the high-temperature storage performance and the low-temperature discharge performance of the conventional secondary battery are poor, the invention provides a secondary battery which has the characteristics of good high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance.
The invention aims at realizing the following technical scheme:
a secondary battery including a negative electrode sheet and an electrolyte; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on one side or two side surfaces of the negative electrode current collector;
the electrolyte includes a functional additive including a first additive and a second additive; the first additive comprises a cyclic silane compound, and the second additive comprises a sulfonate compound;
the secondary battery satisfies the following relation:
1≤(0.5A+B)×1000/(3M)≤2.5；
A≥B；
wherein A is the mass ratio of a first additive in the electrolyte, B is the mass ratio of a second additive in the electrolyte, M is the surface density of a negative electrode active material layer on one side of a negative electrode plate, and the unit is mg/cm 2 。
According to an embodiment of the present invention, the secondary battery satisfies: the ratio of (0.5A+B) multiplied by 1000/(3M) is less than or equal to 1 and less than or equal to 2.5; illustratively, (0.5A+B) ×1000/(3M) is 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, or 2.5.
According to the embodiment of the invention, the secondary battery has the characteristics of good high-temperature cycle performance, good high-temperature storage performance and good low-temperature discharge performance, mainly because the cyclic silane compound serving as the first additive and the sulfonate compound serving as the second additive are introduced while ensuring that the secondary battery also meets 1 (0.5A+B) multiplied by 1000/(3M) multiplied by 2.5 and A is more than or equal to B, so that the additive can form enough SEI film on the surface of the negative electrode, provide enough protection for the negative electrode active material in unit area, and the obtained SEI film has moderate thickness, which is beneficial to improving the electrochemical performance of the secondary battery; meanwhile, the composition of the SEI film can be adjusted, so that the obtained SEI film comprises a large amount of N, O or S and other elements, the interface resistance of the battery is obviously reduced, and the high-temperature cycle performance and the low-temperature discharge performance of the battery are improved; further, si contained in the cyclic silane compound as the first additive has affinity for F, and bonds such as Si-C, si-N or Si-O are easily broken to form Si-F bonds, so that HF in the electrolyte is eliminated, stability of the SEI film and the CEI film is further facilitated to be protected, and high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance of the secondary battery are further facilitated to be improved. When the secondary battery does not satisfy A.gtoreq.B, the SEI film formed on the surface of the negative electrode is not significant for the improvement of electrochemical properties (such as at least one of high temperature cycle performance, high temperature storage performance and low temperature discharge performance) of the battery, although it can provide sufficient protection for the negative electrode active material per unit area. When the secondary battery satisfies (0.5a+b) ×1000/(3M) <1, the additive cannot form a sufficient SEI film on the surface of the anode, and cannot provide sufficient protection for the anode active material per unit area, which may exacerbate deterioration of electrochemical properties (such as at least one of high temperature cycle performance, high temperature storage performance, and low temperature discharge performance) of the secondary battery; when the secondary battery satisfies (0.5a+b) ×1000/(3M) >2.5, an SEI film formed on the surface of the negative electrode is too thick, affecting the dynamic properties of the secondary battery, thereby affecting the electrochemical properties (such as at least one of high temperature storage performance, high temperature cycle performance, and low temperature discharge performance) of the secondary battery.
According to an embodiment of the invention, 0.1% A.ltoreq.6%, preferably 3% A.ltoreq.5%.
According to an embodiment of the invention, 0.1% B.ltoreq.5%, preferably 1% B.ltoreq.4%.
According to an embodiment of the invention, 1mg/cm 2 ≤M≤15mg/cm 2 Preferably 5mg/cm 2 ≤M≤12mg/cm 2 Such as 5mg/cm 2 、8mg/cm 2 、10mg/cm 2 Or 12mg/cm 2 。
According to an embodiment of the invention, the first additive comprises at least one of the compounds of formula I:
R 1 、R 2 、R 3 、R 4 、R 6 、R 7 the same or different, independently of each other, selected from hydrogen, halogen, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted cycloalkenyl, substituted or unsubstituted aryl; when substituted, the substituent is halogen, cyano, alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, or aryl;
x is NR 5 O or S; r is R 5 Selected from hydrogen, halogen, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted cycloalkenyl; if substituted, the substituent is halogen, alkyl or cyano; y is C or Si; n is more than or equal to 0.
According to an embodiment of the invention, R 1 、R 2 、R 3 、R 4 、R 6 、R 7 Identical or different, independently of one another, from hydrogen, halogen, cyano, substituted or unsubstituted C 1-20 Alkyl, substituted or unsubstituted C 1-20 Alkoxy, substituted or unsubstituted C 3-20 Cycloalkyl, substituted or unsubstituted C 2-20 Alkenyl, substituted or unsubstituted C 3-20 Cycloalkenyl, substituted or unsubstituted C 6-20 An aryl group; in the case of substitution, the substituents are halogen, cyano, alkyl, C 3-20 Cycloalkyl, C 2-20 Alkenyl, C 3-20 Cycloalkenyl, C 2-20 Alkynyl or C 6-20 Aryl groups.
According to an embodiment of the invention, R 1 、R 2 、R 3 、R 4 、R 6 、R 7 Identical or different, independently of one another, from hydrogen, halogen, cyano, substituted or unsubstituted C 1-12 Alkyl, substituted or unsubstituted C 1-12 Alkoxy, substituted or unsubstituted C 3-12 Cycloalkyl, substituted or unsubstituted C 2-12 Alkenyl, substituted or unsubstituted C 3-12 Cycloalkenyl, substituted or unsubstituted C 6-12 An aryl group; in the case of substitution, the substituents are halogen, cyano, alkyl, C 3-12 Cycloalkyl, C 2-12 Alkenyl, C 3-12 Cycloalkenyl, C 2-12 Alkynyl or C 6-12 Aryl groups.
According to an embodiment of the invention, R 1 、R 2 、R 3 、R 4 、R 6 、R 7 Identical or different, independently of one another, from hydrogen, halogen, cyano, substituted or unsubstituted C 1-6 Alkyl, substituted or unsubstituted C 1-6 Alkoxy, substituted or unsubstituted C 3-6 Cycloalkyl, substituted or unsubstituted C 2-6 Alkenyl, substituted or unsubstituted C 3-6 Cycloalkenyl, substituted or unsubstituted C 6-10 An aryl group; in the case of substitution, the substituents are halogen, cyano, alkyl, C 3-6 Cycloalkyl, C 2-6 Alkenyl, C 3-6 Cycloalkenyl, C 2-6 Alkynyl or C 6-10 Aryl groups.
According to an embodiment of the invention, R 1 、R 2 、R 3 、R 4 、R 6 、R 7 Identical or different, independently of one another, from hydrogen, halogen, cyano, substituted or unsubstituted C 1-3 Alkyl, substituted or unsubstituted C 1-3 Alkoxy, substituted or unsubstituted C 3-5 Cycloalkyl, takeSubstituted or unsubstituted C 2-3 Alkenyl, substituted or unsubstituted C 3-5 Cycloalkenyl, substituted or unsubstituted C 6-8 An aryl group; in the case of substitution, the substituents are halogen, cyano, alkyl, C 3-5 Cycloalkyl, C 2-3 Alkenyl, C 3-5 Cycloalkenyl, C 2-3 Alkynyl or C 6-8 Aryl groups.
According to an embodiment of the invention, R 1 、R 2 、R 3 、R 4 、R 6 、R 7 Not simultaneously selected from hydrogen.
According to an embodiment of the invention, X is NR 5 O or S; r is R 5 Selected from hydrogen, halogen, cyano, substituted or unsubstituted C 1-20 Alkyl, substituted or unsubstituted C 3-20 Cycloalkyl, substituted or unsubstituted C 2-20 Alkenyl, substituted or unsubstituted C 3-20 A cycloalkenyl group; in the case of substitution, the substituent is C 1-20 Alkyl, halogen or cyano.
According to an embodiment of the invention, X is NR 5 O or S; r is R 5 Selected from hydrogen, halogen, cyano, substituted or unsubstituted C 1-12 Alkyl, substituted or unsubstituted C 3-12 Cycloalkyl, substituted or unsubstituted C 2-12 Alkenyl, substituted or unsubstituted C 3-12 A cycloalkenyl group; in the case of substitution, the substituent is C 1-12 Alkyl, halogen or cyano.
According to an embodiment of the invention, X is NR 5 O or S; r is R 5 Selected from hydrogen, halogen, cyano, substituted or unsubstituted C 1-6 Alkyl, substituted or unsubstituted C 3-6 Cycloalkyl, substituted or unsubstituted C 2-6 Alkenyl, substituted or unsubstituted C 3-6 A cycloalkenyl group; in the case of substitution, the substituent is C 1-6 Alkyl, halogen or cyano.
According to an embodiment of the invention, X is NR 5 O or S; r is R 5 Selected from hydrogen, halogen, cyano, substituted or unsubstituted C 1-3 Alkyl, substituted or unsubstituted C 3-5 Cycloalkyl, substituted or unsubstituted C 2-3 Alkenyl, substituted or unsubstituted C 3-5 A cycloalkenyl group; if it is substitutedThe substituent being C 1-3 Alkyl, halogen or cyano.
According to an embodiment of the invention, n is an integer between 0 and 5.
According to an embodiment of the invention, n is 0, 1, 2, 3, 4 or 5.
According to an embodiment of the present invention, the first additive includes at least one of the following compounds A1 to A7:
according to an embodiment of the invention, the first additive is present in an amount of 0.1wt% to 6wt%, preferably 3wt% to 5wt%, e.g. 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.2wt%, 1.3wt%, 1.5wt%, 1.6wt%, 1.8wt%, 2wt%, 2.2wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.8wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt%, 5wt%, 5.5wt% or 6wt% based on the total mass of the electrolyte.
According to an embodiment of the present invention, the first additive may be obtained commercially, or may be prepared by methods known in the art.
According to an embodiment of the invention, the second additive comprises at least one of 1, 3-Propane Sultone (PS), 1, 3-Propene Sultone (PST).
According to an embodiment of the invention, the second additive is present in an amount of 0.1wt% to 5wt%, preferably 1wt% to 4wt%, for example 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%, 0.6wt%, 0.7wt%, 0.8wt%, 0.9wt%, 1wt%, 1.2wt%, 1.3wt%, 1.5wt%, 1.6wt%, 1.8wt%, 2wt%, 2.2wt%, 2.4wt%, 2.5wt%, 2.6wt%, 2.8wt%, 3wt%, 3.5wt%, 4wt%, 4.5wt% or 5wt% based on the total mass of the electrolyte.
According to an embodiment of the invention, the functional additive further comprises a third additive comprising at least one of fluoroethylene carbonate (FEC), ethylene sulfate (DTD), maleic anhydride, citraconic anhydride, succinic anhydride, succinonitrile (SN), adiponitrile (ADN), ethylene glycol bis (propionitrile) ether (EGBE), 1,3, 6-Hexanetrinitrile (HTCN). By introducing the third additive, the third additive can act on the surfaces of the positive electrode and the negative electrode in preference to the first additive and the second additive and perform film forming reaction on the surfaces of the positive electrode and the negative electrode, so that the protection of the positive electrode and the negative electrode is better realized, the occurrence of side reaction is inhibited, and the high-temperature cycle performance, the high-temperature storage performance and the low-temperature discharge performance of the battery are improved.
According to an embodiment of the invention, the third additive is present in an amount of 1wt% to 15wt%, for example 1wt%, 2wt%, 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt% based on the total mass of the electrolyte.
According to an embodiment of the invention, the electrolyte further comprises an electrolyte salt.
According to an embodiment of the invention, the electrolyte salt comprises an electrolyte lithium salt.
According to an embodiment of the invention, the electrolyte lithium salt comprises lithium hexafluorophosphate (LiPF) 6 ) Lithium difluorophosphate (LiPF) 2 O 2 ) Difluoro lithium bis (oxalato) phosphate (LiPF) 2 (C 2 O 4 ) 2 ) Lithium tetrafluorooxalate phosphate (LiPF) 4 C 2 O 4 ) Lithium oxalate phosphate (LiPO) 2 C 2 O 4 ) Lithium bisoxalato borate (LiBOB), lithium difluorooxalato borate (LiODFB), lithium tetrafluoroborate (LiBF) 4 ) At least one of lithium bis (trifluoromethylsulfonyl) imide (LiTFSI) and lithium bis (fluorosulfonyl) imide (LiFSI).
According to an embodiment of the invention, the electrolyte salt is present in an amount of 10wt% to 15wt%, for example 10wt%, 11wt%, 12wt%, 13wt%, 14wt% or 15wt% based on the total mass of the electrolyte.
According to an embodiment of the invention, the electrolyte further comprises an organic solvent.
According to an embodiment of the present invention, the organic solvent includes at least one of Ethylene Carbonate (EC), propylene Carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), ethylpropionate (EP), propylpropionate (PP), ethylacetate (EA), ethyln-butyrate (EB) and γ -butyrolactone (GBL).
According to an embodiment of the present invention, the secondary battery is a lithium ion battery.
According to an embodiment of the present invention, the secondary battery further includes a positive electrode sheet.
According to an embodiment of the present invention, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer coated on one or both side surfaces of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material, a conductive agent, and a binder.
According to an embodiment of the present invention, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on one or both side surfaces of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material, a conductive agent, and a binder.
According to an embodiment of the present invention, the positive electrode active material layer comprises the following components in percentage by mass: 80 to 99.8 weight percent of positive electrode active material, 0.1 to 10 weight percent of conductive agent and 0.1 to 10 weight percent of binder.
Preferably, the positive electrode active material layer comprises the following components in percentage by mass: 90 to 99.6 weight percent of positive electrode active material, 0.2 to 5 weight percent of conductive agent and 0.2 to 5 weight percent of binder.
According to an embodiment of the present invention, the negative electrode active material layer comprises the following components in percentage by mass: 80 to 99.8 weight percent of negative electrode active material, 0.1 to 10 weight percent of conductive agent and 0.1 to 10 weight percent of binder.
Preferably, the mass percentage of each component in the anode active material layer is as follows: 90 to 99.6 weight percent of negative electrode active material, 0.2 to 5 weight percent of conductive agent and 0.2 to 5 weight percent of binder.
According to an embodiment of the present invention, the conductive agent includes at least one of conductive carbon black, acetylene black, ketjen black, conductive graphite, conductive carbon fiber, carbon nanotube, and metal powder.
According to an embodiment of the present invention, the binder includes at least one of sodium carboxymethyl cellulose, styrene-butadiene latex, polytetrafluoroethylene, and polyethylene oxide.
According to an embodiment of the present invention, the anode active material includes a silicon-based anode material; wherein the silicon-based negative electrode material comprises a silicon-carbon negative electrode material and/or a silicon-oxygen negative electrode material; preferably, the negative electrode active material includes a silicon-based negative electrode material and a carbon-based negative electrode material, wherein the carbon-based negative electrode material includes at least one of natural graphite, artificial graphite, mesophase carbon microspheres, hard carbon, and soft carbon. Preferably, the mass ratio of the silicon-based anode material to the carbon-based anode material is 5:95-95:5, for example, 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 70:30, 80:20, 90:10 or 95:5.
According to an embodiment of the present invention, the positive electrode active material includes a lithium transition metal composite oxide selected from LiMO 2 (M＝Ni、Co、Mn)、LiMn 2 O 4 、LiMPO 4 (M＝Fe、Mn、Co)、LiNi x M 1-x O 2 (M＝Co、Mn，0<x<1)、LiNi x Co y M 1-x-y O 2 (0.ltoreq.x, y.ltoreq.1 and x+y.ltoreq. 1;M = Mg, zn, ga, ba, al, fe, cr, sn, V, mn, sc, ti, nb, mo, zr, ta, W, B, F, si).
The invention has the beneficial effects that:
the invention provides a secondary battery, which comprises an electrolyte, wherein the electrolyte comprises electrolyte salt, an organic solvent and a functional additive, and the functional additive comprises a first additive and a second additive; the first additive comprises a cyclic silane compound, and the second additive comprises a sulfonate compound; when the electrolyte contains both the cyclic silane compound as the first additive and the sulfonate compound as the second additive, the mass ratio of the cyclic silane compound to the sulfonate compound and the ratio of the surface density of the anode active material layer satisfy: when (0.5A+B) multiplied by 1000/(3M) multiplied by 2.5 and A is more than or equal to B, the two additives can form a sufficient SEI film with high stability and low impedance, the interface stability of the cathode is obviously improved, the damage of the volume expansion of the cathode material to the SEI film is reduced, the sufficient and effective protection of the cathode active material in unit area is realized, the obtained SEI film has moderate thickness, the dynamic performance of lithium ions is not influenced, and the high-temperature cycle performance, the high-temperature storage performance and the low-temperature discharge performance of the secondary battery are improved.
Detailed Description
The present invention will be described in further detail with reference to specific examples. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the invention. All techniques implemented based on the above description of the invention are intended to be included within the scope of the invention.
The experimental methods used in the following examples are all conventional methods unless otherwise specified; the reagents, materials, etc. used in the examples described below are commercially available unless otherwise specified.
The batteries of examples and comparative examples were prepared by the following steps:
1) Preparation of positive plate
Lithium cobalt oxide (LiCoO) as a positive electrode active material 2 ) Mixing polyvinylidene fluoride (PVDF), SP (super P) and Carbon Nano Tube (CNT) according to the mass ratio of 96:2:1.5:0.5, adding N-methyl pyrrolidone (NMP), and stirring under the action of a vacuum stirrer until the mixed system becomes anode active slurry with uniform fluidity; uniformly coating anode active slurry on two surfaces of an aluminum foil; and drying the coated aluminum foil, and then rolling and slitting to obtain the required positive plate.
2) Preparation of negative plate
Mixing negative active substances silicon carbon/artificial graphite (containing 5% silicon carbon and 95% artificial graphite), sodium carboxymethylcellulose (CMC-Na), styrene-butadiene rubber, conductive carbon black (SP) and single-walled carbon nanotubes (SWCNTs) according to a mass ratio of 94.5:2.5:1.5:1:0.5, adding deionized water, and obtaining negative active slurry under the action of a vacuum stirrer; uniformly coating the anode active slurry on two surfaces of a copper foil; and (3) airing the coated copper foil at room temperature, transferring to an 80 ℃ oven for drying for 10 hours, and then carrying out cold pressing and slitting to obtain the negative plate.
3) Preparation of electrolyte
In a glove box filled with argon (H 2 O<0.1ppm，O 2 <0.1 ppm), the EC/PC/DEC/PP was uniformly mixed in a mass ratio of 10/20/40/30, and then sufficiently dried lithium hexafluorophosphate (LiPF) was rapidly added thereto 6 ) The final concentration is 1mol/L, fluoroethylene carbonate accounting for 12wt% of the total mass of the electrolyte is added after dissolution, adiponitrile accounting for 2wt% of the total mass of the electrolyte is added, a first additive accounting for the total mass A of the electrolyte and a second additive accounting for the total mass B of the electrolyte are added (the specific dosage and the selection are shown in the table 1), and the required electrolyte is obtained after the water and the free acid are detected to be qualified after uniform stirring.
4) Preparation of a Battery
Laminating the positive plate in the step 1), the negative plate in the step 2) and the isolating film according to the sequence of the positive plate, the isolating film and the negative plate, and then winding to obtain the battery cell; and (3) placing the battery cell in an outer packaging aluminum foil, injecting the electrolyte in the step (3) into the outer packaging, and performing the procedures of vacuum packaging, standing, formation, shaping, sorting and the like to obtain the battery. The charge and discharge range of the battery is 3.0-4.5V.
The obtained battery was subjected to a 60 ℃ high-temperature storage performance test, a 45 ℃ cycle performance test and a low-temperature discharge performance test, respectively.
1) 60 ℃ high-temperature storage performance test
The batteries of table 1 were charged to a cut-off voltage at 25 ℃ at a rate of 1C, a cut-off current of 0.025C, and left standing for 5 minutes, and the thickness of the lithium ion battery (this was taken as the thickness before storage) was measured. The fully charged battery is left open circuit for 35 days under the condition of (60+/-2) DEG C, and is left open circuit for 2 hours under the condition of room temperature after being stored for 35 days, the thickness after being stored is measured, and the thickness expansion rate of the lithium ion battery is calculated:
thickness expansion ratio = [ (thickness after storage-thickness before storage)/thickness before storage ] ×100%
2) 45 ℃ cycle performance test
The cells of Table 1 were subjected to charge and discharge cycles at 45℃in a charge and discharge cut-off voltage range at a rate of 1C, and the discharge capacity at week 1 was measured as x 1 mAh, discharge capacity of N-th circle is calculated as y 1 mAh; dividing the capacity at week N by the capacity at week 1 to obtain the cycle capacity retention rate R at week N 1 ＝y 1 /x 1 Recording cycle capacity retention rate R 1 The cycle number of the battery at 80%.
3) Low temperature discharge capacity retention test
The cells of Table 1 were subjected to 5 charge-discharge cycles at room temperature at 1C rate, then charged to 4.5V at 1C rate, and 1C capacity Q was recorded 0 After the battery in a full-charge state is placed at the temperature of minus 20 ℃ for 4 hours, the battery is discharged to 3V at the multiplying power of 0.2C, and the discharge capacity Q is recorded 1 The low-temperature discharge capacity retention rate was calculated.
Low-temperature discharge capacity retention (%) =q 1 /Q 0 ×100％。
Table 1 composition of electrolyte additives of examples and comparative examples
Table 2 results of performance test of the batteries of examples and comparative examples
As can be seen from comparison of performance tests of examples and comparative examples of table 2, the introduction of the cyclic silane-based compound as the first additive and the sulfonate-based compound as the second additive while ensuring that the secondary battery also satisfies 1.ltoreq.0.5a+b) ×1000/(3M). Ltoreq.2.5 and a.gtoreq.b, makes it possible for the additives to form a sufficient SEI film on the surface of the negative electrode, provides sufficient protection for the negative electrode active material per unit area, and has a moderate thickness of the obtained SEI film, which is advantageous for improving electrochemical performance of the secondary battery; meanwhile, the composition of the SEI film can be adjusted, so that the obtained SEI film comprises a large amount of N, O or S and other elements, the interface resistance of the battery is obviously reduced, and the high-temperature cycle performance and the low-temperature discharge performance of the battery are improved; further, si contained in the cyclic silane compound as the first additive has affinity for F, and bonds such as Si-C, si-N or Si-O are easily broken to form Si-F bonds, so that HF in the electrolyte is eliminated, stability of the SEI film and the CEI film is further facilitated to be protected, and high-temperature cycle performance, high-temperature storage performance and low-temperature discharge performance of the secondary battery are further facilitated to be improved. When the secondary battery does not satisfy A.gtoreq.B, the SEI film formed on the surface of the negative electrode is not significant for the improvement of electrochemical properties (such as at least one of high temperature cycle performance, high temperature storage performance and low temperature discharge performance) of the battery, although it can provide sufficient protection for the negative electrode active material per unit area. When the secondary battery satisfies (0.5a+b) ×1000/(3M) <1, the additive cannot form a sufficient SEI film on the surface of the anode, and cannot provide sufficient protection for the anode active material per unit area, which may exacerbate deterioration of electrochemical properties (such as at least one of high temperature cycle performance, high temperature storage performance, and low temperature discharge performance) of the secondary battery; when the secondary battery satisfies (0.5a+b) ×1000/(3M) >2.5, an SEI film formed on the surface of the negative electrode is too thick, affecting the dynamic properties of the secondary battery, thereby affecting the electrochemical properties (such as at least one of high temperature storage performance, high temperature cycle performance, and low temperature discharge performance) of the secondary battery.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiment. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A secondary battery, characterized in that the secondary battery comprises a negative electrode sheet and an electrolyte; the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer coated on one side or two side surfaces of the negative electrode current collector;
the electrolyte includes a functional additive including a first additive and a second additive; the first additive comprises a cyclic silane compound, and the second additive comprises a sulfonate compound;
the secondary battery satisfies the following relation:
1≤(0.5A+B)×1000/(3M)≤2.5；
A≥B；
wherein A is the mass ratio of a first additive in the electrolyte, B is the mass ratio of a second additive in the electrolyte, M is the surface density of a negative electrode active material layer on one side of a negative electrode plate, and the unit is mg/cm 2 。
2. The secondary battery according to claim 1, wherein 0.1% or less of A6% or less, 0.1% or less of B5% or less, 1mg/cm 2 ≤M≤15mg/cm 2 。
3. The secondary battery according to claim 1 or 2, wherein 3% or less of A5% or less, 1% or less of B4% or less, 5mg/cm 2 ≤M≤12mg/cm 2 。
4. The secondary battery according to any one of claims 1 to 3, wherein the first additive includes at least one of compounds represented by formula I:
R 1 、R 2 、R 3 、R 4 、R 6 、R 7 the same or different, independently of each other, selected from hydrogen, halogen, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted alkoxy, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted cycloalkenyl, substituted or unsubstituted aryl; when substituted, the substituent is halogen, cyano, alkyl, cycloalkyl, alkenyl, cycloalkenyl, alkynyl, or aryl;
x is NR 5 O or S; r is R 5 Selected from hydrogen, halogen, cyano, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted cycloalkenyl; if substituted, the substituent is halogen, alkyl or cyano; y is C or Si; n is more than or equal to 0.
5. The secondary battery according to claim 4, wherein R 1 、R 2 、R 3 、R 4 、R 6 、R 7 Identical or different, independently of one another, from hydrogen, halogen, cyano, substituted or unsubstituted C 1-20 Alkyl, substituted or unsubstituted C 1-20 Alkoxy, substituted or unsubstituted C 3-20 Cycloalkyl, substituted or unsubstituted C 2-20 Alkenyl, substituted or unsubstituted C 3-20 Cycloalkenyl, substituted or unsubstituted C 6-20 An aryl group; in the case of substitution, the substituents are halogen, cyano, alkyl, C 3-20 Cycloalkyl, C 2-20 Alkenyl, C 3-20 Cycloalkenyl, C 2-20 Alkynyl or C 6-20 An aryl group;
and/or X is NR 5 O or S; r is R 5 Selected from hydrogen, halogen, cyano, substituted or unsubstituted C 1-20 Alkyl, substituted or unsubstituted C 3-20 Cycloalkyl, substituted or unsubstituted C 2-20 Alkenyl, substituted or unsubstituted C 3-20 A cycloalkenyl group; in the case of substitution, the substituent is C 1-20 Alkyl, halogen or cyano;
and/or n is 0, 1, 2, 3, 4 or 5.
6. The secondary battery according to any one of claims 1 to 5, wherein the first additive includes at least one of the following compounds A1 to A7:
7. the secondary battery according to any one of claims 1 to 6, wherein the second additive includes at least one of 1, 3-Propane Sultone (PS), 1, 3-Propenesulfontone (PST).
8. The secondary battery according to any one of claims 1 to 7, wherein the functional additive further comprises a third additive comprising at least one of fluoroethylene carbonate (FEC), ethylene sulfate (DTD), maleic anhydride, citraconic anhydride, succinic anhydride, succinonitrile (SN), adiponitrile (ADN), ethylene glycol bis (propionitrile) ether (EGBE), 1,3, 6-Hexanetrinitrile (HTCN).
9. The secondary battery according to claim 8, wherein the content of the third additive is 1 to 15wt% based on the total mass of the electrolyte.
10. The secondary battery according to any one of claims 1 to 9, wherein the anode active material includes a silicon-based anode material; wherein the silicon-based negative electrode material comprises a silicon-carbon negative electrode material and/or a silicon-oxygen negative electrode material.
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