Negative-electrode-free battery and preparation method thereof

Abstract

The invention provides a negative-electrode-free battery and a preparation method thereof. The negative-electrode-free battery comprises a positive electrode plate, a composite current collector, a diaphragm and an electrolyte, the composite current collector comprises a current collector and a coating compounded on the surface of the current collector, wherein the coating comprises a sulfur-containing fluorine compound; the electrolyte comprises a lithium salt, an additive and a solvent, wherein the additive comprises tripropargyl tri (trimethylsilyl) phosphate. The sulfur-containing fluorine compound is loaded by the carbon coating layer, so that excessive consumption of the additive in the initial stage can be avoided, and the action time is prolonged. Meanwhile, the alkynyl polymerization characteristic of TMS-TPP is combined, a dual-interface regulation and control mechanism is formed, a traditional single additive mode is broken through, triple synergy of interface pre-passivation, dynamic repair and dendritic crystal inhibition is achieved in a non-negative electrode system, the first effect is remarkably improved, the cycle life is remarkably prolonged, the safety is remarkably improved, the carbon-coated aluminum foil pre-modification technology is compatible with an existing electrode preparation production line, and the application prospect is wide. And complex equipment does not need to be newly added.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to an anode-free battery and a preparation method. BACKGROUND

[0002] An anode-free battery is a technology for forming a negative electrode by directly utilizing electrochemical deposition of lithium metal on a current collector. The core advantage of the anode-free battery is to greatly improve the energy density and reduce the production cost. By eliminating the redundant mass of the traditional graphite or silicon-based negative electrode, an energy density of 500-800 Wh / kg can be achieved (30%-50% higher than that of a lithium ion battery), meeting the urgent needs of electric vehicles, unmanned aerial vehicles and the like for lightweight and long endurance.

[0003] An anode-free battery (such as a lithium metal / copper current collector system) lacks a negative electrode lithium source and needs to release lithium from a positive electrode and deposit metal lithium on a negative electrode current collector (such as a carbon-coated aluminum foil). Since it completely relies on in-situ deposition of lithium ions on the negative electrode side, it faces challenges such as lithium dendrite growth, severe interface side reactions, short cycle life and the like. A SEI film with higher mechanical strength is required to inhibit lithium dendrite penetration. The prior art usually adds a silicon-based additive to the electrolyte to form a SEI film rich in silicate and lithium carbonate on the surface of the positive electrode, reduce the polarization voltage, and improve the cycle life and rate performance. At the same time, it generates a low-resistance coating on the surface of the negative electrode, suppresses self-discharge, and improves low-temperature and high-temperature performance. However, the interface stability, hydrolysis sensitivity and limited electrochemical stability of such an additive in the anode-free battery system application become the main restricting factors for further development, and it is difficult to adapt to the volume deformation during lithium deposition / stripping. In addition, the anode-free battery has higher requirements for the interface dynamic response speed of the electrolyte additive. The silicon-oxygen group of the conventional silicon-based electrolyte has a slow adsorption speed, which leads to the inability to quickly form a uniform SEI at the initial stage of lithium deposition, aggravates the local current density unevenness and dead lithium generation, and is insufficient to protect the structure collapse of the positive electrode material at high voltage (>4.5V). SUMMARY

[0004] The purpose of the present application is to provide an anode-free battery and a preparation method. The anode-free battery in the present application realizes directional deposition of lithium metal and self-adaptive regulation of volume expansion through the cooperation of the coating layer-electrolyte double path, solving the problems of interface failure and volume expansion of the anode-free battery.

[0005] The present application provides an anode-free battery, comprising a positive electrode sheet, a composite current collector, a separator and an electrolyte.

[0006] The composite current collector comprises a current collector and a coating layer composed of a sulfur-containing fluorine compound on the surface of the current collector.

[0007] The electrolyte includes lithium salt, additives and solvent, and the additive includes tripropargyl tris(trimethylsilyl) phosphate.

[0008] Preferably, the sulfur-fluorine compounds include sulfur-fluorine salts and / or sulfur-fluorine non-salt-based derivatives;

[0009] The sulfur-fluorine salt includes a sulfur-fluorine lithium salt;

[0010] The sulfur-containing fluorine-based non-salt derivative includes one or more of fluoroalkylsulfonyl fluoride, fluoroalkylsulfonic acid ester and fluoroalkylsulfonic acid.

[0011] Preferably, the sulfur-containing fluoride salt includes one or more of lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate and lithium fluorosulfonate;

[0012] The sulfur-containing fluorine-based non-salt derivative includes one or more of trifluoromethanesulfonyl fluoride, methyl trifluoromethanesulfonate, phenyl trifluoromethanesulfonate and trifluoromethanesulfonic acid.

[0013] Preferably, the coating further comprises a conductive agent and a binder, and the mass ratio of the sulfur-fluorine compound, the conductive agent and the binder in the coating is (1-5): (1-5): (1-5).

[0014] Preferably, when the sulfur-fluorine-containing compound is a sulfur-fluorine-containing non-salt-based derivative, the coating on the surface of the current collector further includes a lithium salt; the molar ratio of the lithium salt to the sulfur-fluorine-containing compound is 1:(0.5-2).

[0015] Preferably, the molar ratio of the S element in the sulfur-containing fluorine compound to tripropargyl tris(trimethylsilyl) phosphate is (2-5):1.

[0016] Preferably, the lithium salt in the electrolyte includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonylimide), lithium bis(fluorosulfonylimide), lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorobis(oxalatophosphate) and lithium tetrafluorooxalatophosphate.

[0017] Preferably, the solvent in the electrolyte includes one or more of organic ester solvents, ether solvents, sulfone solvents, nitrile solvents and amide solvents.

[0018] Preferably, the mass fraction of the additive in the electrolyte is 1-5%, the mass fraction of the lithium salt is 11-16%, and the mass fraction of the solvent is 79-88%.

[0019] The present invention provides a method for preparing a negative electrode-free battery as described above, comprising the following steps:

[0020] A) mixing the sulfur-containing fluorine compound, the conductive agent, the binder and the solvent to obtain a coating slurry, coating the coating slurry on the surface of the current collector to obtain a composite current collector;

[0021] B) assembling the positive electrode sheet, the separator and the composite current collector to obtain a battery cell, and injecting an electrolyte into the battery cell to obtain a negative electrode-free battery.

[0022] The application provides a negative electrode-free battery, which comprises a positive electrode sheet, a composite current collector, a separator and an electrolyte.

[0023] In the application, the sulfur-containing fluorine compound is introduced in the form of a pre-coating layer on the surface of the carbon-coated aluminum foil, and is combined with tripropargyl tri(trimethylsilyl) phosphate (TMS-TPP) (the highest unsaturation) in the electrolyte to form a space synergistic effect, thereby breaking through the limitation of traditional combination relying on the dissolution of the electrolyte. Compared with direct addition to the electrolyte, the carbon-coated layer can avoid initial excessive consumption of the additive and prolong the action time. Meanwhile, in combination with the alkyne polymerization property of TMS-TPP, a double-interface regulation mechanism is formed, thereby breaking through the traditional single-additive mode and realizing the triple synergy of interface pre-passivation-dynamic repair-branch inhibition in the negative electrode-free system, so that the initial efficiency, cycle life and safety are significantly improved, and the carbon-coated aluminum foil pre-modification process is compatible with the existing electrode preparation production line without the need to add complex equipment. DETAILED DESCRIPTION

[0024] The application provides a negative electrode-free battery, which comprises a positive electrode sheet, a composite current collector, a separator and an electrolyte.

[0025] The composite current collector comprises a current collector and a coating layer compounded on the surface of the current collector, and the coating layer comprises a sulfur-containing fluorine compound.

[0026] The electrolyte comprises a lithium salt, an additive and a solvent, and the additive comprises tripropargyl tri(trimethylsilyl) phosphate.

[0027] In the application, the current collector in the composite current collector is preferably an aluminum foil or a copper foil, the coating layer preferably comprises a sulfur-containing fluorine compound, a conductive agent and a binder, and further, the coating layer further comprises a lithium salt, such as LiPF6, which is combined with a sulfur-containing fluorine non-salt derivative to improve the conductivity of the coating layer.

[0028] In the application, the sulfur-containing fluorine compound comprises a sulfur-containing fluorine group, the sulfur-containing fluorine group is preferably one or more of -SO2F, -F and -SO2-, and simultaneously contains sulfur and fluorine elements; the sulfur-containing fluorine group in the sulfur-containing fluorine compound is strongly coordinated with lithium ions, thereby promoting the dissolution of lithium ions in the electrolyte.+ The uniform diffusion inhibits lithium dendrites; during the first charge, the coating layer is preferentially decomposed to generate a SEI film rich in LiF, improving the initial efficiency (reducing lithium irreversible loss). The sulfur-containing fluorine compound preferably includes a sulfur-containing fluorine salt and / or a sulfur-containing fluorine-based non-salt derivative, the sulfur-containing fluorine salt is preferably a sulfur-containing fluorine lithium salt, more preferably one or more of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate and lithium fluorosulfonate; the sulfur-containing fluorine non-salt derivative preferably includes one or more of fluorinated alkylsulfonyl fluoride, fluorinated alkyl sulfonate and fluorinated alkyl sulfonic acid, more preferably one or more of polyfluoroalkylsulfonyl fluoride, polyfluoroalkyl sulfonate and polyfluoroalkyl sulfonic acid, most preferably one or more of trifluoromethylsulfonyl fluoride, methyl triflate, phenyl triflate and triflic acid; when the sulfur-containing fluorine compound is a sulfur-containing fluorine non-salt derivative, the coating layer also includes a lithium salt, and the molar ratio of the lithium salt to the sulfur-containing fluorine non-salt derivative is preferably 1:(0.5-2), more preferably 1:(1-1.5), such as 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, preferably a range value with the above-mentioned any value as the upper limit or lower limit.

[0029] The sulfur-containing fluorine compound is blended with conductive carbon black and binder (PVDF) to coat the current collector, not directly added to the electrolyte. Compared with direct addition to the electrolyte, during the first charge, the coating layer is preferentially decomposed to generate a SEI film rich in LiF, improving the initial efficiency (reducing lithium irreversible loss), forming a pre-functional layer, and responding to the interface dynamics at a faster and more direct speed; compared with direct addition to the electrolyte, the carbon-coated layer can effectively avoid excessive consumption during formation, reduce the occurrence of side reactions, and avoid performance deterioration in the initial stage; the release rate of sulfur-containing fluorine-based substances can be adjusted by the carbon-coated layer density, and the "in-situ release" is approached.

[0030] In the present application, the conductive agent is preferably one or more of conductive carbon black, carbon nanotubes and graphene; the binder is preferably one or more of polyvinylidene fluoride, polytetrafluoroethylene, polymethyl methacrylate and hexafluoropropylene copolymer.

[0031] In the present application, the mass ratio of the sulfur-containing fluorine-based compound, the conductive agent and the binder in the coating is preferably (1-5):(1-5):(1-5), more preferably (1-3):(3-5):(2-4), and most preferably 2:5:3; that is, the mass of the sulfur-containing fluorine-based compound accounts for 10-50% of the total mass of the sulfur-containing fluorine-based compound, the conductive agent and the binder, more preferably 20-30%, such as 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, and preferably a range value with any of the above values as the upper limit or lower limit.

[0032] In the present application, the electrolyte includes a lithium salt, an additive and a solvent, and the additive includes tripropargyl tris(trimethylsilyl) phosphate. The present application uses tripropargyl tris(trimethylsilyl) phosphate (TMS-TPP) with the highest degree of unsaturation as the main additive of the electrolyte of the anode-free system. The strong electronegative coordination cluster formed by the sulfur-containing fluorine-based compound in the carbon coating and TMS-TPP is initially attached to the sulfur-containing fluorine-based compound in the carbon layer of the current collector, rather than TMS-TPP in the electrolyte. The strong electronegative coordination cluster must be formed at the interface of the current collector to have functional significance and achieve the purpose of regulating lithium deposition.

[0033] In the present application, the tripropargyl tris(trimethylsilyl) phosphate (TMS-TPP) has the structure shown in formula I. The propargyl group (-C≡CH) in the TMS-TPP undergoes electrochemical polymerization during lithium deposition, forming a flexible silicon-oxygen-carbon crosslinked network, enhancing the mechanical strength and ion permeability of the SEI, and providing a π electron cloud that is adsorbed on the active sites of the electrode surface through dynamic coordination; the siloxane group (Si-R-O) captures trace amounts of HF and H2O in the electrolyte through condensation reaction, reducing interfacial corrosion.

[0034]

[0035] In the present application, the molar ratio of the S element in the sulfur-containing fluorine-based compound to the tripropargyl tris(trimethylsilyl) phosphate is preferably (2-5):1, and more preferably (3-4):1.

[0036] In the present application, the lithium salt in the electrolyte includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium bis-trifluoromethylsulfonylimide, lithium bisfluorosulfonylimide, lithium bisoxalate borate, lithium difluoro oxalate borate, lithium difluoro di-oxalate phosphate and lithium tetrafluoro oxalate phosphate; the solvent in the electrolyte includes one or more of organic ester solvent, ether solvent, sulfone solvent, nitrile solvent and amide solvent, the organic ester is selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, methyl ethyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, ethyl formate, ethyl acetate, propyl acetate, propyl propionate, γ-butyrolactone, methyl trifluoroethyl carbonate, fluoroethylene carbonate (FEC), vinylene carbonate (VC) and di(2,2,2-trifluoroethyl) carbonate; the ether solvent is selected from one or more of dimethyl ether, diethyl ether, methyl ethyl ether, ethylene glycol dimethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether; the sulfone solvent is selected from sulfolane; the nitrile solvent is selected from acetonitrile; and the amide solvent is selected from 1-methyl-3-ethyl carbonyl quinoline di(trifluoromethylsulfonyl) imide.

[0037] In the present application, the mass fraction of the additive is 1-5%, more preferably 2-4%, such as 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, preferably a range value with any of the above values as the upper limit or lower limit; the mass fraction of the lithium salt is 11-16%, more preferably 12-15%, such as 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, preferably a range value with any of the above values as the upper limit or lower limit; and the mass fraction of the solvent is preferably 79-88%, more preferably 80-85%, such as 79%, 79.5%, 80%, 80.5%, 81%, 81.5%, 82%, 82.5%, 83%, 83.5%, 84%, 84.5%, 85%, 85.5%, 86%, 86.5%, 87%, 87.5%, 88%, preferably a range value with any of the above values as the upper limit or lower limit.

[0038] In the present application, the positive electrode tab preferably comprises a positive electrode current collector and a positive electrode coating layer compounded on the surface of the positive electrode current collector, the positive electrode coating layer comprising a positive electrode active material, a conductive agent and a binder, the positive electrode active material preferably being one or more of lithium cobaltate, lithium manganate, ternary nickel-cobalt-manganese lithium, nickel-manganese lithium, lithium iron phosphate, lithium manganese iron phosphate and lithium-rich manganese-based positive electrode material, the conductive agent preferably being one or more of conductive carbon black, carbon nanotube and graphene; the binder preferably being one or more of polyvinylidene fluoride, polytetrafluoroethylene, polymethyl methacrylate and hexafluoropropylene copolymer; the mass ratio of the positive electrode active material, the conductive agent and the binder preferably being (80-98):(1-5):(1-5), more preferably 94:3:3; and the positive electrode current collector preferably being an aluminum foil.

[0039] In the present application, the separator is preferably a polypropylene and / or ceramic-coated polyethylene separator.

[0040] The present application also provides a preparation method of the above-mentioned anode-free battery, comprising the following steps:

[0041] A) mixing a sulfur-containing fluorine compound, a conductive agent, a binder and a solvent to obtain a coating slurry, coating the coating slurry on the surface of a current collector to obtain a composite current collector;

[0042] B) assembling the positive electrode tab, the separator and the composite current collector to obtain a battery cell, and injecting an electrolyte into the battery cell to obtain an anode-free battery.

[0043] In the present application, the types and amounts of the sulfur-containing fluorine compound, the conductive agent and the binder are consistent with those described above, and will not be repeated here.

[0044] In the present application, the solvent used in the coating slurry is preferably N-methyl pyrrolidone, and the solid content of the coating slurry is preferably 45-55%, more preferably 50-52%.

[0045] In the present application, a positive electrode active material, a conductive agent, a binder and a solvent are mixed to obtain a positive electrode slurry, and then the positive electrode slurry is coated on the surface of a current collector to obtain a positive electrode tab through rolling and die cutting.

[0046] The types and amounts of the positive electrode active material, the conductive agent and the binder are consistent with those described above, and will not be repeated here.

[0047] In the present application, the solvent used in the positive electrode slurry is preferably N-methyl pyrrolidone, and the solid content of the positive electrode slurry is 50-60%, more preferably 51-53%.

[0048] In the present application, the components and the proportion of each component of the electrolyte are consistent with the components and the amount of each component of the electrolyte described above, and the present application will not be described here.

[0049] The present application selects tripropargyl tris(trimethylsilyl) phosphate (TMS-TPP) with the highest degree of unsaturated bond as the main additive of the anode-free electrolyte system, coats the sulfur-containing fluorine-based compound (sulfur-containing fluorine-based salt compound and / or sulfur-containing fluorine-based non-salt compound), conductive carbon black and binder (PVDF) on the current collector (copper foil / aluminum foil) to form a pre-function layer. Compared with direct addition to the electrolyte, the coating layer load can avoid the initial excessive consumption of the additive, prolong the action time. After the electrolyte is infiltrated, the sulfur-containing fluorine-based substance is gradually dissolved and released, which cooperates with TMS-TPP to regulate the interface, is suitable for new systems such as silicon-based anodes and sulfide solid electrolytes, and relieves the problem of coating rupture caused by volume expansion. The sulfur-containing fluorine-based substance in the carbon coating layer can be preferentially adsorbed in the lithium deposition hotspot area, and form a gradient passivation layer with TMS-TPP. At the same time, the sulfonyl (S=O) and fluorine atom (F) in the sulfur-containing fluorine-based derivative provide strong coordination sites, and form a dynamic coordination cage with TMS-TPP, which enhances the Li + The synergistic transmission reduces the solvation energy of Li + , accelerates the desolvation process, and reduces the decomposition side reaction of the electrolyte. In addition, the propargyl group in TMS-TPP undergoes electrochemical polymerization in the first cycle to generate an SEI film containing a silicon-oxygen skeleton (Si-R-O-R-Si), and the π electron cloud can form a gradient electron cloud matching with the decomposition products of the sulfur-containing fluorine-based substance, which enhances the compactness and ion selectivity of the SEI film, reduces the irreversible reaction of Li + with the electrolyte, and cooperates with the electron cloud of the silicon-oxygen-alkynyl-sulfur-containing fluorine-based multi-active site to break through the functional limitations of a single additive. The scheme in the present application provides a theoretically feasible path for solving the interface failure and volume expansion problems of the anode-free battery through material position reconstruction and functional synergy.

[0050] In order to further illustrate the present application, the following embodiments are used to describe the anode-free battery and the preparation method provided by the present application in detail, but it should not be understood as limiting the scope of protection of the present application.

[0051] Example 1 Preparation of tripropargyl tris(trimethylsilyl) phosphate (TMS-TPP)

[0052] A 50 mL three-necked flask was selected, and argon was continuously bubbled into the flask for 30 min. Trimethylsilyl propargyl alcohol (9.34 g, 0.073 mol), triethylamine (7.37 g, 0.073 mol), and tetrahydrofuran (20 mL) were weighed into the flask. Phosphorus oxychloride (4 g, 0.026 mol) was slowly added dropwise into the flask under ice-water bath. After the addition was completed, the reaction was allowed to proceed at room temperature. The reaction was allowed to proceed for 24 h. The reaction was quenched by adding water, and solid impurities were removed by filtration. The reaction mixture was extracted with THF three times. The organic phase was washed with saturated brine several times to remove triethylamine hydrochloride. The organic phase was dried over anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain a light yellow liquid.

[0053] Column chromatography was performed using pure petroleum ether as the eluent to obtain a light yellow transparent liquid (9.072 g, yield: 68%).

[0054]

[0055] Example 2 Preparation of tripropargyl tri(trimethylsilyl) phosphate (TMS-TPP)

[0056] A 50 mL three-necked flask was selected, and argon was continuously bubbled into the flask for 30 min. Trimethylsilyl propargyl alcohol (9.34 g, 0.073 mol), triethylamine (7.37 g, 0.073 mol), and tetrahydrofuran (20 mL) were weighed into the flask. Phosphorus oxychloride (4 g, 0.026 mol) was slowly added dropwise into the flask under ice-water bath. After the addition was completed, the reaction was allowed to proceed at room temperature. The reaction was allowed to proceed for 24 h. The reaction was quenched by adding water, and solid impurities were removed by filtration. The reaction mixture was extracted with THF three times. The organic phase was washed with saturated brine several times to remove triethylamine hydrochloride. The organic phase was dried over anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain a light yellow liquid. Column chromatography was performed using pure petroleum ether as the eluent to obtain a light yellow transparent liquid (9.453 g, yield: 71%).

[0057] Example 3 Preparation of tripropargyl tri(trimethylsilyl) phosphate (TMS-TPP)

[0058] A 50 mL three-necked flask was selected, and the environment was kept closed for continuous argon gas for 30 min. Trimethylsilyl propargyl alcohol (9.34 g, 0.073 mol), diisopropylethylamine (9.42 g, 0.073 mol), and acetonitrile (20 mL) were weighed into the flask. Under an ice-water bath, phosphorus oxychloride (4 g, 0.026 mol) was slowly added dropwise into the three-necked flask. After the addition was completed, the reaction was allowed to proceed at room temperature. The reaction was allowed to proceed for 24 h. The reaction was quenched with water, and solid impurities were removed by filtration. The mixture was extracted with acetonitrile three times. The organic phase was washed with saturated brine several times to further remove diisopropylethylamine hydrochloride. The organic phase was dried over anhydrous magnesium sulfate, filtered, and concentrated by rotary evaporation to obtain a light yellow liquid (9.771 g, yield: 73%).

[0059] Example 4

[0060] In a dry room environment with a dew point of -50°C, the positive electrode active material lithium cobaltate LiCoO2, conductive carbon black SP, and binder polyvinylidene fluoride PVDF were mixed in a mass ratio of 94:3:3. N-methylpyrrolidone (NMP) was added as a solvent, and the slurry was adjusted to a solid content of 52%. The slurry was then coated, rolled, and die-cut to prepare 56*63 mm positive electrode sheets for use.

[0061] The conductive carbon black (SP), polyvinylidene fluoride (PVDF), and sulfur-containing fluorine salt (LiFSI) were mixed in a mass ratio of 5:3:2. N-methylpyrrolidone (NMP) was added as a solvent, and the slurry was adjusted to a solid content of 50%. The slurry was then coated, rolled, and die-cut to prepare 58*65 mm negative electrode sheets for use.

[0062] The negative electrode sheet, the separator, and the positive electrode sheet were stacked in 13+12 layers, and the tabs were welded to prepare a 2.5 AH soft-pack battery. The naked cell was placed in a nitrogen circulation dry box, and the moisture content was controlled to be within 200 ppm for use.

[0063] In an argon atmosphere glove box with a water content of <10 ppm, non-aqueous organic solvents EC, DMC, EMC were mixed in a mass ratio of 25:40:30:5. Then 1.0 mol LiPF6 was added to the uniformly mixed non-aqueous organic solvent, dissolved and mixed uniformly. Then, the additives FEC (1%), VC (0.5%), and TMS-TPP (2%) prepared in Example 1 were added in a mass ratio of 1:0.5:2, and stirred uniformly to obtain an electrolyte.

[0064] The electrolyte prepared above was injected into the soft-pack battery prepared in the example, and the battery was vacuum packaged, rested, heat-pressed, and tested after being divided into two parts.

[0065] Comparative Example 4-1

[0066] The negative electrode sheet and the electrolyte in Comparative Example 4 were prepared according to the following procedures, and the battery to be tested was prepared according to the method in Example 4.

[0067] The negative electrode sheet: conductive carbon black (SP) and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 5:3, N-methyl pyrrolidone (NMP) was added as a solvent, and the slurry with a solid content of 50% was prepared. The slurry was coated, rolled, and die-cut to prepare a 58*65 mm negative electrode sheet for use.

[0068] The electrolyte: in an argon atmosphere glove box with a water content of <10 ppm, non-aqueous organic solvents EC, DMC, EMC, and DEC were mixed in a mass ratio of 25:40:30:5, then 1.0 mol LiPF6 was added to the uniformly mixed non-aqueous organic solvents, dissolved and mixed uniformly, then additives FEC (1%) and VC (0.5%) were added in a mass ratio of 1:0.5, and stirred uniformly to obtain the electrolyte.

[0069] Comparative Example 4-2

[0070] The negative electrode sheet and the electrolyte in Comparative Example 4-2 were prepared according to the following procedures, and the battery to be tested was prepared according to the method in Example 4.

[0071] The negative electrode sheet: conductive carbon black (SP) and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 5:3, N-methyl pyrrolidone (NMP) was added as a solvent, and the slurry with a solid content of 50% was prepared. The slurry was coated, rolled, and die-cut to prepare a 58*65 mm negative electrode sheet for use.

[0072] The electrolyte: in an argon atmosphere glove box with a water content of <10 ppm, non-aqueous organic solvents EC, DMC, EMC, and DEC were mixed in a mass ratio of 25:40:30:5, then 1.0 mol LiPF6 was added to the uniformly mixed non-aqueous organic solvents, dissolved and mixed uniformly, then additives FEC (1%), VC (0.5%), and TMS-TPP (2%) were added in a mass ratio of 1:0.5:2, and stirred uniformly to obtain the electrolyte.

[0073] Comparative Example 4-3

[0074] The electrolyte in Comparative Example 4-3 was prepared according to the following procedures, and the battery to be tested was prepared according to the method in Example 4.

[0075] Negative electrode sheet: conductive carbon black (SP), polyvinylidene fluoride (PVDF), and sulfur-containing fluorine salt compound (LiFSI) were mixed in a mass ratio of 5:3:2, N-methyl pyrrolidone (NMP) was added as a solvent, and the slurry with a solid content of 50% was prepared. The slurry was coated, rolled, and die-cut to prepare a 58*65mm negative electrode sheet for use.

[0076] Electrolyte: In an argon atmosphere glove box with water content <10ppm, non-aqueous organic solvents EC, DMC, EMC, DEC were mixed in a mass ratio of 25:40:30:5, then 1.0mol LiPF6 was added to the uniformly mixed non-aqueous organic solvent, dissolved and mixed uniformly, then additives FEC (1%), VC (0.5%) were added in a mass ratio of 1:0.5, stirred uniformly to obtain the electrolyte.

[0077] Comparative Example 4-4

[0078] The test battery was prepared according to the method in Example 4, and the negative electrode sheet and electrolyte in Comparative Example 4-4 were prepared according to the following steps:

[0079] Negative electrode sheet: conductive carbon black (SP), polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 5:3, N-methyl pyrrolidone (NMP) was added as a solvent, and the slurry with a solid content of 50% was prepared. The slurry was coated, rolled, and die-cut to prepare a 58*65mm negative electrode sheet for use,

[0080] Electrolyte: In an argon atmosphere glove box with water content <10ppm, non-aqueous organic solvents EC, DMC, EMC were mixed in a mass ratio of 25:40:30:5, then 1.0mol LiPF6 was added to the uniformly mixed non-aqueous organic solvent, dissolved and mixed uniformly, then additives FEC (1%), VC (0.5%), TMS-TPP (2%) and sulfur-containing fluorine salt (LiFSI) (2%) were added in a mass ratio of 1:0.5:2:2, stirred uniformly to obtain the electrolyte. The performance of the test battery obtained in Example 4 and Comparative Examples 4-1~4-4 was detected, and the results are shown in Table 1.

[0081] Initial efficiency test method / condition: the prepared electrolyte was soaked in a soft package at 45℃ for 24h, and the formation machine was set to 5kg / cm 2 , the temperature was set to 45℃, the maximum / minimum cutoff voltage was 4.1 / 2.9V, the rated capacity was 2.5AH, the 0.05C current constant charge was 2h, the 0.1C current constant charge was 1h, the 0.2C current constant charge was 2.5h, the room temperature aging was 24h, and the second sealing was performed. The sealed soft package was divided into several parts, the formation machine was set to 1.5kg / cm 2, temperature setting 25℃, 0.5C constant current discharge to 3.0V, after standing, 1.0C constant current constant voltage charging to 4.0V, 1.0C constant current discharge to 3.0V, record the discharge capacity.

[0082] Cycling test method / condition: after the soft package is placed in a common clamp, 1.0C constant current constant voltage charging to 4.0V, after standing, 1.0C constant current discharge to 3.0V, cycle number 1000 times, when the cycle capacity is lower than 80% of the initial value, the process stops.

[0083] Table 1 Performance data of the battery tested in Example 4 and Comparative Examples 4-1 to 4-4

[0084]

[0085] Example 5

[0086] In a dry room environment with a dew point of -50℃, the positive active material lithium cobaltate LiCoO2, conductive carbon black SP, and the binder polyvinylidene fluoride PVDF were mixed in a mass ratio of 94:3:3, N-methyl pyrrolidone (NMP) was added as a solvent, and the slurry was adjusted to a solid content of 52%. After coating, rolling, and die cutting, 56*63mm positive electrode sheets were prepared for use.

[0087] The conductive carbon black (SP), polyvinylidene fluoride (PVDF), and sulfur-containing fluorine non-salt compound (trifluoromethylsulfonyl fluoride) + LiPF6 (molar ratio 1:1) were mixed in a mass ratio of 5:3:2, N-methyl pyrrolidone (NMP) was added as a solvent, and the slurry was adjusted to a solid content of 50%. After coating, rolling, and die cutting, 58*65mm negative electrode sheets were prepared for use.

[0088] The negative electrode sheet, separator, and positive electrode sheet were laminated in 13+12 layers, and the tabs were welded to prepare 2.5AH soft package batteries. The naked battery was placed in a nitrogen circulating dry box, and the moisture content was controlled to be less than 200ppm before use.

[0089] In an argon atmosphere glove box with water content <10ppm, non-aqueous organic solvents DME, DEGDME were mixed in a mass ratio of 24.2:75.8, then 1.0mol LiPF6 was added to the uniformly mixed non-aqueous organic solvent, dissolved and mixed uniformly, then the additives FEC (1%), VC (0.5%), and TMS-TPP (2%) prepared in Example 1 were added in a mass ratio of 1:0.5:2, and stirred uniformly to obtain an electrolyte.

[0090] The above configured electrolyte was injected into the soft package battery prepared in the example, and after vacuum packaging, standing, heat pressing, discharging, and secondary sealing, the battery to be tested was obtained.

[0091] Comparative Example 5-1

[0092] The battery to be tested was prepared according to the method in Example 5, and the negative electrode sheet and electrolyte in Comparative Example 5-1 were prepared according to the following steps, respectively.

[0093] The negative electrode sheet: conductive carbon black (SP) and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 5:3, N-methyl pyrrolidone (NMP) was added as a solvent, and the slurry with a solid content of 50% was prepared. The slurry was coated, rolled, and die-cut to prepare a 58*65 mm negative electrode sheet for use.

[0094] The electrolyte: in an argon atmosphere glove box with water content <10 ppm, non-aqueous organic solvents DME and DEGDME were mixed in a mass ratio of 24.2:75.8, then 1.0 mol LiPF6 was added to the uniformly mixed non-aqueous organic solvent, dissolved and mixed uniformly, then additives FEC (1%) and VC (0.5%) were added in a mass ratio of 1:0.5, and stirred uniformly to obtain the electrolyte.

[0095] Comparative Example 5-2

[0096] The battery to be tested was prepared according to the method in Example 5, and the negative electrode sheet and electrolyte in Comparative Example 5-2 were prepared according to the following steps, respectively.

[0097] The negative electrode sheet: conductive carbon black (SP) and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 5:3, N-methyl pyrrolidone (NMP) was added as a solvent, and the slurry with a solid content of 50% was prepared. The slurry was coated, rolled, and die-cut to prepare a 58*65 mm negative electrode sheet for use.

[0098] The electrolyte: in an argon atmosphere glove box with water content <10 ppm, non-aqueous organic solvents DME and DEGDME were mixed in a mass ratio of 24.2:75.8, then 1.0 mol LiPF6 was added to the uniformly mixed non-aqueous organic solvent, dissolved and mixed uniformly, then additives FEC (1%), VC (0.5%), and TMS-TPP (2%) were added in a mass ratio of 1:0.5:2, and stirred uniformly to obtain the electrolyte.

[0099] Comparative Example 5-3

[0100] The battery to be tested was prepared according to the method in Example 5, and the negative electrode sheet and electrolyte in Comparative Example 5-3 were prepared according to the following steps, respectively.

[0101] Negative electrode sheet: Conductive carbon black (SP), polyvinylidene fluoride (PVDF), and trifluoromethylsulfonyl fluoride (+LiPF6) are mixed in a mass ratio of 5:3:2 (trifluoromethylsulfonyl fluoride to LiPF6 molar ratio of 1:1), and N-methylpyrrolidone (NMP) is added as a solvent to adjust the slurry to a solid content of 50%. The slurry is then coated, rolled, and die-cut to prepare a 58*65mm negative electrode sheet for use.

[0102] Electrolyte: In an argon atmosphere glove box with a water content of <10 ppm, the non-aqueous organic solvents DME and DEGDME were mixed in a mass ratio of 24.2:75.8, and then 1.0 mol LiPF6 was added to the evenly mixed non-aqueous organic solvent, dissolved and mixed evenly, and then additives FEC (1%) and VC (0.5%) were added in a mass ratio of 1:0.5 and stirred evenly to obtain the electrolyte.

[0103] Comparative Example 5-4

[0104] The battery to be tested was prepared according to the method in Example 5, and the negative electrode sheet and electrolyte in Comparative Example 5-4 were prepared according to the following steps:

[0105] Negative electrode sheet: Conductive carbon black (SP) and polyvinylidene fluoride (PVDF) are mixed in a mass ratio of 5:3, and N-methylpyrrolidone (NMP) is added as a solvent to adjust the slurry to a solid content of 50%. The slurry is then coated, rolled, and die-cut to prepare a 58*65mm negative electrode sheet for use.

[0106] Electrolyte: In an argon atmosphere glove box with a water content of less than 10 ppm, the non-aqueous organic solvents DME and DEGDME were mixed in a mass ratio of 24.2:75.8. 1.0 mol of LiPF6 was then added to the uniformly mixed non-aqueous organic solvent, dissolved, and mixed uniformly. Additives FEC (1%), VC (0.5%), TMS-TPP (2%), and trifluoromethylsulfonyl fluoride (+LiPF6) (2%) were then added in a mass ratio of 1:0.5 (molar ratio of trifluoromethylsulfonyl fluoride to LiPF6 was 1:1), and stirred uniformly to obtain an electrolyte. The electrolyte was then stirred uniformly to obtain an electrolyte.

[0107] The test batteries obtained in Example 5 and Comparative Examples 5-1 to 5-4 were subjected to performance testing using the same testing methods as those in Example 4 and Comparative Examples 4-1 to 4-4. The results are shown in Table 2.

[0108] Table 2 Performance data of the battery cells tested in Example 5 and Comparative Examples 5-1 to 5-4

[0109]

[0110]

[0111] From the data in Table 1 and Table 2, it can be seen that the functional synergy of the materials in the application and the material position reconstruction have a significant influence on the interface failure problem and the volume expansion problem of the negative electrode-free battery. Embodiments 4 and 5 have made significant progress and advantages in volume expansion and cycle performance compared with the comparative examples.

[0112] The above only describes the preferred embodiments of the present application, and it should be pointed out that for ordinary skilled persons in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A negative electrode-free battery, comprising a positive electrode sheet, a composite current collector, a separator and an electrolyte; The composite current collector comprises a current collector and a coating layer coated on the surface of the current collector, wherein the coating layer comprises a sulfur-containing fluorine compound; The electrolyte comprises a lithium salt, an additive and a solvent, wherein the additive comprises tripropargyl tris(trimethylsilyl) phosphate.

2. The negative electrode-free battery according to claim 1, characterized by, The sulfur-containing fluorine compound comprises a sulfur-containing fluorine salt and / or a sulfur-containing fluorine non-salt derivative; The sulfur-containing fluorine salt comprises a sulfur-containing fluorine lithium salt; The sulfur-containing fluorine non-salt derivative comprises one or more of fluorinated alkylsulfonyl fluoride, fluorinated alkyl sulfonate and fluorinated alkyl sulfonic acid.

3. The negative electrode-free battery according to claim 2, characterized by The sulfur-containing fluorine salt comprises one or more of lithium bisfluorosulfonylimide, lithium bis(trifluoromethylsulfonyl)imide, lithium trifluoromethylsulfonate and lithium fluorosulfonate; The sulfur-containing fluorine non-salt derivative comprises one or more of trifluoromethylsulfonyl fluoride, methyl trifluoromethyl sulfonate, phenyl trifluoromethyl sulfonate and trifluoromethyl sulfonic acid.

4. The negative electrode-free battery according to claim 1, characterized by, The coating layer further comprises a conductive agent and a binder, and the mass ratio of the sulfur-containing fluorine compound, the conductive agent and the binder in the coating layer is (1-5) : (1-5) : (1-5).

5. The negative electrode-free battery according to claim 1, characterized in that, When the sulfur-containing fluorine compound is a sulfur-containing fluorine non-salt derivative, the coating layer coated on the surface of the current collector further comprises a lithium salt, and the molar ratio of the lithium salt to the sulfur-containing fluorine compound is 1 : (0.5-2).

6. The negative electrode-free battery according to claim 1, characterized in that, The molar ratio of the S element in the sulfur-containing fluorine compound to tripropargyl tris(trimethylsilyl) phosphate is (2-5) :

1.

7. The negative electrode-free battery according to claim 1, characterized in that, The lithium salt in the electrolyte comprises one or more of lithium hexafluorophosphate, lithium perchlorate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide, lithium bisfluorosulfonylimide, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluoro bis(oxalato)phosphate and lithium tetrafluoro(oxalato)phosphate.

8. The negative electrode-free battery according to claim 1, characterized in that, The solvent in the electrolyte comprises one or more of an organic ester solvent, an ether solvent, a sulfone solvent, a nitrile solvent and an amide solvent.

9. The negative electrode-free battery according to claim 1, characterized in that, The mass fraction of the additive in the electrolyte is 1-5%, the mass fraction of the lithium salt is 11-16%, and the mass fraction of the solvent is 79-88%. 10.A method for preparing the negative electrode-free battery according to claim 1, comprising the following steps: A) mixing a sulfur-containing fluorine compound, a conductive agent, a binder and a solvent to obtain a coating slurry, coating the coating slurry on the surface of a current collector to obtain a composite current collector; B) assembling a positive electrode sheet, a separator and the composite current collector to obtain an electrode core, and injecting an electrolyte into the electrode core to obtain the negative electrode-free battery.

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