Clamp type manganese complex electrolyte additive, electrolyte and lithium ion battery

Abstract

The invention provides a clamp-type manganese complex electrolyte additive, an electrolyte and a lithium ion battery. The clamp-type manganese complex electrolyte additive has a structure as shown in a formula I, the ligustrazine derivative is used as an electrolyte additive, the size of a pincerlike structure formed by the additive is similar to that of transition metal manganese ions, and the pincerlike structure has three active sites combined with metal ions and can form a stable structure with transition metal Mn; transition metal ions in the electrolyte are captured through complexation, so that the metal ions are prevented from participating in chemical reaction, the damage of dissolved manganese to the surface of the negative electrode is obviously slowed down, manganese deposition is effectively inhibited, and a negative electrode SEI film is protected; and meanwhile, the additive and the dissolved manganese form a stable structure which is dispersed in the electrolyte and does not generate precipitation, so that the integrity of the solution is kept, and the solvation structure of Li < + > ions is not influenced.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a clamp-type manganese complex electrolyte additive, an electrolyte and a lithium ion battery. Background Art

[0002] With the increasing popularity of electronic products such as electric vehicles and portable devices, the demand for high-energy-density lithium-ion batteries is becoming more and more urgent. This type of battery has broad application prospects in the fields of energy storage, aerospace, etc. How to improve the energy density of lithium batteries has become the focus of scholars' research.

[0003] The cost and safety of lithium manganese iron phosphate LMFP are at the same level as lithium iron phosphate LFP, and the energy density is at the same level as high-voltage ternary. In addition, LMFP has better power performance than LFP and ternary at low SOC; and higher low-temperature capacity retention rate than LFP and ternary. This shows that LMFP is currently a better positive electrode material because it has the advantages of low cost and high safety of LFP, while overcoming the pain points of low energy density and poor low-temperature performance of LFP.

[0004] The theoretical specific capacity of lithium nickel manganese oxide LNMO positive electrode is 147mAh / g. The battery assembled based on this electrode is expected to achieve an energy density greater than 250Wh / kg. The cost of LNMO particles is only about US$21,000 per ton. Its cost-effectiveness can surpass the current commercial power battery positive electrode and has good application prospects.

[0005] However, the two materials mentioned above have poor high-temperature cycling and storage performance due to the dissolution of transition metal manganese, and are prone to capacity drop in the late cycle. As manganese ions dissolve, they undergo a disproportionate reaction on the surface of the positive electrode material to generate divalent manganese, which migrates to the negative electrode surface and is reduced and deposited, which in turn destroys the SEI film, causing the SEI film to continue to grow and thicken, consume active lithium, increase electrode impedance, and produce gas at the negative electrode, ultimately leading to the continuous attenuation of battery capacity. Summary of the invention

[0006] The object of the present invention is to provide a clamp-type manganese complex electrolyte additive, an electrolyte and a lithium ion battery. The additive in the present invention can efficiently complex transition metal manganese ions in the electrolyte, effectively inhibit manganese deposition and protect the negative electrode SEI film.

[0007] The present invention provides a clamp-type manganese complex electrolyte additive having a structure shown in Formula I:

[0008]

[0009] In formula I, A is N or P, and R1 to R8 are independently selected from C1 to C5 alkyl groups, C6 to C12 aromatic groups, dimethylamino groups, methoxy groups or halogen groups.

[0010] Preferably, R1 to R8 are independently selected from methyl, ethyl, tert-butyl, phenyl, dimethylamino, methoxy or fluorine.

[0011] Preferably, the clamp-type manganese complex electrolyte additive has a structure shown in Formula I-1 to Formula I-10:

[0012]

[0013]

[0014] The present invention provides an electrolyte comprising a lithium salt, an organic solvent and the above-mentioned clamp-type manganese complex electrolyte additive.

[0015] Preferably, the mass fraction of the clamp manganese complex electrolyte additive in the electrolyte is 0.05-3%.

[0016] Preferably, the lithium salt includes one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate, lithium difluorooxalatoborate and lithium bis(oxalatoborate);

[0017] The concentration of the lithium salt in the electrolyte is 0.5-2 mol / L.

[0018] Preferably, the organic solvent includes one or more of carbonate solvents, carboxylate solvents, amine solvents, sulfone solvents and nitrile solvents.

[0019] Preferably, the carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, methyl propyl carbonate, butylene carbonate, methyl butyl carbonate and dibutyl carbonate;

[0020] The carboxylic acid ester solvent includes one or more of methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate and methyl propionate;

[0021] The amine solvent includes one or more of N-methylacetamide, N-methylformamide, dimethylformamide and diethylformamide;

[0022] The sulfone solvent includes one or more of dimethyl sulfide, dimethyl sulfoxide, cyclopentane, diphenyl sulfoxide, thionyl chloride, dipropyl sulfone, dimethyl sulfite, diethyl sulfite and tetramethyl sulfoxide;

[0023] The nitrile solvent includes one or more of acetonitrile, succinonitrile, adiponitrile, 3-methoxypropionitrile, 3-ethoxypropionitrile and 1,3,6-hexanetrinitrile.

[0024] The present invention provides a lithium ion battery, comprising a positive electrode, a negative electrode, a separator and the electrolyte described above.

[0025] The present invention provides the use of the clamp-type manganese complex electrolyte additive as described above in inhibiting manganese deposition at the negative electrode of a lithium-ion battery.

[0026] The present invention provides a clamp-type manganese complex electrolyte additive having a structure shown in Formula I. The present invention proposes a derivative of ligustrazine as an electrolyte additive, the clamp-shaped structure formed by the additive is similar in size to the transition metal manganese ion, and has three active sites for binding to the metal ions, and can form a stable structure with the transition metal Mn; the transition metal ions in the electrolyte are captured by complexation, thereby preventing the metal ions from participating in chemical reactions, significantly slowing down the damage of the dissolved manganese to the negative electrode surface, and effectively inhibiting manganese deposition to protect the negative electrode SEI film; at the same time, the additive forms a stable structure with the dissolved manganese and is dispersed in the electrolyte without precipitation, thereby maintaining the integrity of the solution without affecting Li + The solvation structure of the ion.

[0027] Furthermore, each molecule of the additive of the present invention has a structure of two complexed transition metals, which can significantly improve the complexation efficiency. A non-aqueous electrolyte containing a small amount of the additive of the present invention can significantly reduce manganese deposition at the negative electrode and improve the cycle performance of the battery cell. DETAILED DESCRIPTION

[0028] The present invention provides a clamp-type manganese complex electrolyte additive having a structure shown in Formula I:

[0029]

[0030] In formula I, A is N or P, and R1 to R8 are independently selected from C1 to C5 alkyl groups, C6 to C12 aromatic groups, dimethylamino groups, methoxy groups or halogen groups.

[0031] In the present invention, the four A groups in the formula I are N at the same time, or P at the same time. The N and P atoms have sp3 hybridization states, forming three covalent bonds, retaining a pair of lone electron pairs, and the molecular configuration is trigonal pyramidal. Compared with a single arc pair of electrons that binds to transition metal manganese but cannot maintain a stable structure, the N in ligustrazine in the present invention and the two A groups on the same side jointly provide three groups of lone pairs of electrons, and the pincer structure formed by these three groups of lone pairs of electrons is similar in size to the metal manganese ion, and can be complexed with the transition metal manganese ion without steric hindrance, thereby forming a more stable complex structure, as shown in formula II; if A is other elements such as C, S, the four valence electrons in the bond are fully utilized and evenly distributed in four orbitals, which belongs to completely symmetrical isotropic hybridization, and after bonding, it is a stable σ bond, and there is no lone electron pair, and it is impossible to complex the transition metal ion.

[0032]

[0033] In the present invention, R1-R8 are independently selected from C1-C5 alkyl, C6-C12 aromatic, dimethylamino, methoxy or halogen groups, preferably, R1-R8 are independently selected from methyl, ethyl, tert-butyl, phenyl, dimethylamino, methoxy or fluorine. The R groups (R1-R8) introduced in the present invention can further optimize the structure and function of the additives. For example, when R is a methoxy group, the PO bond can react with the free hydrogen in the electrolyte to achieve the effect of removing acid and water; when R is a F atom, LiF is generated after lithium removal, which is beneficial to the formation of negative electrode film, and the cycle performance of the battery cell is improved.

[0034] In the present invention, the clamp-type manganese complex electrolyte additive has a structure shown in Formula I-1 to Formula I-10:

[0035]

[0036] The present invention also provides a method for preparing the clamp-type manganese complex electrolyte additive described above, comprising the following steps:

[0037] Under a protective atmosphere, ligustrazine and a derivative of chlorophosphine / a derivative of chloramine are mixed in a solvent and reacted to obtain a compound shown in formula I.

[0038] The reaction equation is shown in Formula III:

[0039]

[0040] In formula III, A is N or P, R and R′ are in the same range as the group types of R1 to R8, and are independently selected from C1 to C5 alkyl, C6 to C12 aromatic, dimethylamino, methoxy or halogen groups, preferably independently selected from methyl, ethyl, tert-butyl, phenyl, dimethylamino, methoxy or fluorine.

[0041] The molar ratio of ligustrazine to the derivative of chlorophosphine / the derivative of chloramine is preferably 1:(4.4-5), more preferably 1:(4.5-4.8), such as 1:4.4, 1:4.5, 1:4.6, 1:4.7, 1:4.8, 1:4.9, 1:5, preferably a range value with any of the above values ​​as the upper or lower limit.

[0042] In the present invention, the protective atmosphere is preferably an inert atmosphere such as nitrogen or argon; the reaction temperature is preferably 15 to 30° C., more preferably 20 to 25° C.; the reaction time is preferably 8 to 12 hours, more preferably 10 to 11 hours.

[0043] In the present invention, the solvent is preferably an ether solvent, more preferably one or more of methyl ether, ethyl ether and methyl ethyl ether.

[0044] After the reaction is completed, the reaction product is subjected to necessary post-processing steps such as separation and purification, which are all commonly used steps for separating products and purifying in the art, and the present invention will not repeat them here.

[0045] The present invention also provides an electrolyte comprising a lithium salt, an organic solvent and the above-mentioned clamp-type manganese complex electrolyte additive.

[0046] In the present invention, the mass fraction of the clamp manganese complex electrolyte additive in the electrolyte is 0.05-3%, more preferably 0.1-2.5%, such as 0.05%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, preferably a range value with any of the above values ​​as the upper or lower limit.

[0047] In the present invention, the lithium salt preferably includes one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate, lithium difluorooxalatoborate and lithium bis(oxalatoborate); the concentration of the lithium salt in the electrolyte is preferably 0.5 to 2 mol / L, more preferably 1 to 1.5 mol / L.

[0048] In the present invention, the organic solvent includes one or more of carbonate solvents, carboxylic acid ester solvents, amine solvents, sulfone solvents and nitrile solvents; the carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, methyl propyl carbonate, butylene carbonate, methyl butyl carbonate and dibutyl carbonate; the carboxylic acid ester solvent includes methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate and methyl propionate. The amine solvent includes one or more of N-methylacetamide, N-methylformamide, dimethylformamide and diethylformamide; the sulfone solvent includes one or more of dimethyl sulfide, dimethyl sulfoxide, cyclopentane, diphenyl sulfoxide, thionyl chloride, dipropyl sulfone, dimethyl sulfite, diethyl sulfite and tetramethyl sulfoxide; the nitrile solvent includes one or more of acetonitrile, succinonitrile, adiponitrile, 3-methoxypropionitrile, 3-ethoxypropionitrile and 1,3,6-hexanetrinitrile. Specifically, in the embodiment of the present invention, a mixed solvent of ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC) is preferably used.

[0049] The present invention also provides a lithium ion battery, comprising a positive electrode, a negative electrode, a separator and the electrolyte described above.

[0050] In the present invention, the positive electrode includes a positive electrode collector and a positive electrode material layer arranged on the surface of the positive electrode collector, and the material of the positive electrode collector can be selected from aluminum, titanium or stainless steel; the positive electrode material layer includes a positive electrode active material, a conductive agent and a binder; the positive electrode active material can be lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), medium-high nickel ternary materials and their composite positive electrode materials; the conductive agent can be a carbon material, such as one or more of carbon black, conductive polymers, acetylene black, carbon fibers, carbon nanotubes and graphite; the binder can be one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride, carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), fluorine-based rubber, ethylene propylene diene monomer rubber and styrene butadiene rubber (SBR).

[0051] The negative electrode may include a negative electrode current collector and a negative electrode material layer on the surface of the negative electrode current collector, and the material of the negative electrode current collector may be selected from copper, nickel or stainless steel. The negative electrode material layer includes a negative electrode active material, a conductive agent and a binder; the negative electrode active material may be one or more of metallic lithium, lithium-embedded carbon material or lithium alloy; the conductive agent may be a carbon material, such as one or more of carbon black, conductive polymer, acetylene black, carbon fiber, carbon nanotube and graphite; the binder may be one or more of polyvinylidene fluoride (PVDF), polyvinylidene fluoride, carboxymethyl cellulose (CMC), polytetrafluoroethylene (PTFE), fluorine rubber, ethylene propylene diene monomer rubber and styrene butadiene rubber (SBR).

[0052] The isolation membrane may be polypropylene (PP), polyethylene (PE), a composite material of polypropylene (PP) and polyethylene (PE), glass fiber felt, or a composite membrane formed by welding or bonding wettable polyolefin microporous membranes.

[0053] The present invention also provides an application of the clamp-type manganese complex electrolyte additive described above in inhibiting manganese deposition at the negative electrode of a lithium-ion battery. The clamp-type manganese complex electrolyte additive of the present invention is applied to the electrolyte of a lithium-ion battery, and can efficiently complex transition metal manganese ions in the electrolyte, effectively inhibit manganese deposition and protect the negative electrode SEI film, thereby further improving the cycle performance of the lithium-ion battery.

[0054] The present invention provides a clamp-type manganese complex electrolyte additive having a structure shown in Formula I. The present invention proposes a ligustrazine derivative as an electrolyte additive, the clamp-shaped structure formed by the additive is similar in size to the transition metal manganese ion, and has three active sites for binding to the metal ions, and can form a stable structure with the transition metal Mn; the transition metal ions in the electrolyte are captured by complexation, thereby preventing the metal ions from participating in chemical reactions, significantly slowing down the damage of the dissolved manganese to the negative electrode surface, and effectively inhibiting manganese deposition to protect the negative electrode SEI film; at the same time, the additive forms a stable structure without precipitating solids, thereby maintaining the integrity of the solution without affecting Li + The solvation structure of the ion.

[0055] Furthermore, each molecule of the additive of the present invention has a structure of two complexed transition metals, which can significantly improve the complexation efficiency. A non-aqueous electrolyte containing a small amount of the additive of the present invention can significantly reduce manganese deposition at the negative electrode and improve the cycle performance of the battery cell.

[0056] In order to further illustrate the present invention, a clamp-type manganese complex electrolyte additive, electrolyte and lithium-ion battery provided by the present invention are described in detail below in conjunction with examples, but it should not be understood as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] At 15°C, under nitrogen atmosphere, 0.1 mol of ligustrazine was added to 40 ml of ether, and 0.45 mol of dimethylphosphonium chloride was slowly added under stirring. The reaction was continued for 8 hours. After the reaction was completed, the mixed solution was separated by flash chromatography to obtain compound A. GC-MS (m / z): calcd.for C 16 H 32 N2P4[M+1] + , 376.15, found 376.43.

[0059]

[0060] In a glove box, 30w% EC, 29.5w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 1.5w% compound A was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0061] Example 2

[0062] At 20°C, under nitrogen atmosphere, 0.1 mol of ligustrazine was added to 40 ml of methyl ether, and 0.45 mol of diethylphosphonium chloride was slowly added under stirring. The reaction was continued for 8 hours. After the reaction was completed, the mixed solution was separated by flash chromatography to obtain compound B. GC-MS (m / z): calcd. for C24H 48 N2P4[M+1] + , 488.28, found 488.69.

[0063]

[0064] In a glove box, 30w% EC, 30w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 1w% compound B was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0065] Example 3

[0066] At 30°C, under nitrogen atmosphere, 0.1 mol of ligustrazine was added to 40 ml of propyl ether, and 0.45 mol of di-tert-butylphosphonium chloride was slowly added under stirring. The reaction was continued for 12 hours. After the reaction was completed, the mixed solution was separated by flash chromatography to obtain compound C. GC-MS (m / z): calcd. for C 40 H 80 N2P4[M+1] + , 712.53, found 713.09.

[0067]

[0068] In a glove box, 30w% EC, 30.5w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 0.5w% compound C was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0069] Example 4

[0070] At 15°C, under nitrogen atmosphere, 0.1 mol of ligustrazine was added to 40 ml of ether, and 0.46 mol of dimethoxyphosphonium chloride was slowly added under stirring. The reaction was continued for 12 hours. After the reaction was completed, the mixed solution was separated by flash chromatography to obtain compound D. GC-MS (m / z): calcd.for C 16 H 32 N2O8P4[M+1] + , 504.11, found 504.43.

[0071]

[0072] In a glove box, 30w% EC, 30w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 1w% compound D was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0073] Example 5

[0074] At 20°C, under nitrogen atmosphere, 0.1 mol of ligustrazine was added to 40 ml of ether, and 0.46 mol of difluorochlorophosphine was slowly added under stirring. The reaction was continued for 10 hours. After the reaction was completed, the mixed solution was separated by flash chromatography to obtain compound E. GC-MS (m / z): calcd. for C8H8F8N2P4[M+1] + , 407.95, found 408.22.

[0075]

[0076] In a glove box, 30w% EC, 27w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 3w% compound E was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0077] Example 6

[0078] At 15°C, under nitrogen atmosphere, 0.1 mol of ligustrazine was added to 40 ml of propyl ether, and 0.5 mol of bis(dimethylamino)chlorophosphine was slowly added under stirring. The reaction was continued for 10 hours. After the reaction was completed, the mixed solution was separated by flash chromatography to obtain compound F. GC-MS (m / z): calcd. for C8H8F8N2P4[M+1] + , 407.95, found 408.22.

[0079]

[0080] In a glove box, 30w% EC, 30.95w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 0.05w% compound F was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0081] Example 7

[0082] At 30°C, under nitrogen atmosphere, 0.1 mol of ligustrazine was added to 40 ml of methyl ether, and 0.5 mol of methyl (phenyl) chlorophosphine was slowly added under stirring. The reaction was continued for 10 hours. After the reaction was completed, the mixed solution was separated by flash chromatography to obtain compound G. GC-MS (m / z): calcd.for C 36 H 40N2P4[M+1] + , 624.21, found 624.81.

[0083]

[0084] In a glove box, 30w% EC, 30.7w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 0.1w% compound G and 0.2w% compound D were further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; after 200 cycles, the battery was disassembled and the deposition content of Mn in the graphite negative electrode was analyzed.

[0085] Example 8

[0086] At 15°C, under nitrogen atmosphere, 0.1 mol of ligustrazine was added to 40 ml of ether, and 0.45 mol of dimethylammonium chloride was slowly added under stirring. The reaction was continued for 10 hours. After the reaction was completed, the mixed solution was separated by flash chromatography to obtain compound H. GC-MS (m / z): calcd. for C 16 H 32 N6[M+1] + , 308.27, found 308.59.

[0087]

[0088] In a glove box, 30w% EC, 30w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 1w% compound H was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0089] Example 9

[0090] At 15°C, under nitrogen atmosphere, 0.1 mol of ligustrazine was added to 40 ml of methyl ether, and 0.47 mol of diethylammonium chloride was slowly added under stirring. The reaction was continued for 10 hours. After the reaction was completed, the mixed solution was separated by flash chromatography to obtain compound I. GC-MS (m / z): calcd. for C 24 H 48 N6[M+1] + , 420.39, found 420.83.

[0091]

[0092] In a glove box, 30w% EC, 30.5w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 0.5w% compound I was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0093] Example 10

[0094] At 25°C, under nitrogen atmosphere, 0.1 mol of ligustrazine was added to 40 ml of ether, and 0.47 mol of difluorochloramine was slowly added under stirring. The reaction was continued for 10 hours. After the reaction was completed, the mixed solution was separated by flash chromatography to obtain compound J. GC-MS (m / z): calcd. for C8H8F8N6[M+1] + , 340.07, found 340.32.

[0095]

[0096] In a glove box, 30w% EC, 30w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 1w% compound J was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0097] Comparative Example 1

[0098] In a glove box, 30w% EC, 31w% DMC and 26w% EMC were mixed evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0099] Comparative Example 2:

[0100] In a glove box, 30w% EC, 29w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 1w% ligustrazine was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; after 200 cycles, the battery was disassembled and the deposition content of Mn in the graphite negative electrode was analyzed.

[0101] Comparative Example 3

[0102] In a glove box, 30w% EC, 29w% DMC and 26w% EMC were stirred evenly to form a mixed solution; 13w% LiPF6 was added to the mixed solution and stirred to fully dissolve to obtain a mixed salt solution; 1w% 1-aza-12-crown-4-ether (Formula IV) was further added to the mixed salt solution, and the obtained mixed solution was used as an electrolyte; the battery was disassembled after 200 cycles to analyze the deposition content of Mn in the graphite negative electrode.

[0103]

[0104] Application Examples

[0105] Take 95.5wt% LiMn 0.4 Fe 0.6 PO4, 2wt% PVDF and 2.5wt% conductive carbon black are mixed and dispersed evenly in NN dimethyl pyrrolidone to form a slurry, which is evenly coated on aluminum foil.

[0106] Cutting pieces; 94.8w% artificial graphite, 1.7w% CMC, 2.5w% SBR and 1wt% conductive carbon black were mixed and dispersed evenly in pure water to form a slurry, which was evenly coated on the copper foil and rolled (surface density was 2.6g / cm 3 ) Cutting pieces. The order of negative electrode shell - negative electrode sheet - polypropylene diaphragm - positive electrode sheet - gasket - spring sheet - positive electrode shell constitutes a 2032 button battery.

[0107] The button battery cycle test is 0.2C constant current and constant voltage to 4.4V, and 0.2C constant current discharge to 3V.

[0108] In order to study the complexation effect of additives on transition metal manganese, the point solution was disassembled after 200 cycles, and the graphite negative electrode of the button battery was taken for inductively coupled plasma (ICP) testing to analyze the deposition of transition metal manganese at the negative electrode. The results are shown in Table 1.

[0109] Table 1 Performance test data of batteries in embodiments and comparative examples

[0110]

[0111] By comparing Examples 1 to 10 with Comparative Example 1, it can be found that introducing the clamp-type manganese complex electrolyte additive of the present invention into the electrolyte can significantly improve the capacity retention rate and the first efficiency of the battery cell, and significantly reduce the deposition of manganese at the graphite negative electrode, thereby solving the industry pain points from the perspective of the electrolyte and having a wide range of application markets.

[0112] By comparing Example 4 with Comparative Example 2, it can be found that the introduction of a single nitrogen-containing heterocycle has a certain complexing effect on the transition metal ions, but the structure is unstable, and there is a certain improvement in the cycle, but it is not obvious; adding the clamp-type manganese complex electrolyte additive described in the present invention can form a stable structure with the transition metal, more significantly inhibit manganese deposition, and improve the cycle performance of the battery cell.

[0113] By comparing Example 4 with Comparative Example 3, it can be found that a 1-aza-12-crown-4-ether analysis can form a stable complex structure with a transition metal manganese ion, and the additive of the present invention can form a stable complex structure with two transition metal manganese ions. Under the same addition amount, the present invention can more significantly inhibit the deposition of manganese at the negative electrode; at the same time, since the additive introduces a PO bond, HF in the electrolyte can be eliminated, thereby improving the cycle performance of the battery cell.

[0114] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A clamp-type manganese complex electrolyte additive having a structure shown in Formula I: In Formula I, A is N or P, R 1 ~R 8 Independently selected from C1-C5 alkyl, C6-C12 aromatic, dimethylamino, methoxy or halogen groups.

2. The clamp-type manganese complex electrolyte additive according to claim 1, It is characterized in that R 1 ~R 8 are independently selected from methyl, ethyl, tert-butyl, phenyl, dimethylamino, methoxy or fluoro.

3. The clamp-type manganese complex electrolyte additive according to claim 1, It is characterized in that The clamp-type manganese complex electrolyte additive has structures shown in Formula I-1 to Formula I-10:

4. An electrolyte comprising a lithium salt, an organic solvent and the clamp-type manganese complex electrolyte additive according to any one of claims 1 to 3.

5. The electrolyte according to claim 4, It is characterized in that The mass fraction of the clamp-type manganese complex electrolyte additive in the electrolyte is 0.05-3%.

6. The electrolyte according to claim 4, It is characterized in that The lithium salt includes one or more of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate, lithium difluorooxalatoborate and lithium bis(oxalatoborate); The concentration of the lithium salt in the electrolyte is 0.5-2 mol / L.

7. The electrolyte according to claim 4, It is characterized in that The organic solvent includes one or more of carbonate solvents, carboxylate solvents, amine solvents, sulfone solvents and nitrile solvents.

8. The electrolyte according to claim 7, It is characterized in that The carbonate solvent includes one or more of dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, methyl propyl carbonate, butylene carbonate, methyl butyl carbonate and dibutyl carbonate; The carboxylic acid ester solvent includes one or more of methyl formate, ethyl formate, propyl formate, butyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate and methyl propionate; The amine solvent includes one or more of N-methylacetamide, N-methylformamide, dimethylformamide and diethylformamide; The sulfone solvent includes one or more of dimethyl sulfide, dimethyl sulfoxide, cyclopentane, diphenyl sulfoxide, thionyl chloride, dipropyl sulfone, dimethyl sulfite, diethyl sulfite and tetramethyl sulfoxide; The nitrile solvent includes one or more of acetonitrile, succinonitrile, adiponitrile, 3-methoxypropionitrile, 3-ethoxypropionitrile and 1,3,6-hexanetrinitrile.

9. A lithium ion battery comprising a positive electrode, a negative electrode, a separator and the electrolyte according to any one of claims 4 to 8.

10. Use of the clamp-type manganese complex electrolyte additive according to any one of claims 1 to 3 in inhibiting manganese deposition at the negative electrode of a lithium-ion battery.

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