阅读说明：本技术 一种无负极二次锂电池的电解液及无负极二次锂电池和化成工艺 (Electrolyte of non-negative secondary lithium battery, non-negative secondary lithium battery and formation process ) 是由 崔光磊 谢斌 许高洁 刘海胜 陆迪 于 2020-11-11 设计创作，主要内容包括：本发明属于锂电池技术领域,具体涉及一种无负极二次锂电池的电解液及无负极二次锂电池和化成工艺。液态电解液为以磺酰亚胺锂和氟代烷氧基三氟硼酸锂作为主锂盐,碳酸酯化合物-有机氟化合物作为有机溶剂体系,体系中加入功能添加剂。本发明还公开了一种无负极二次锂电池化成工艺,即将无负极二次锂电池在一定高温(40～100℃),一定压力(0～3MPa),一定真空度(0～-0.1MPa)中化成。本发明所提供的无负极二次锂电池具有高能量密度、高安全性和长循环寿命等优点。(The invention belongs to the technical field of lithium batteries, and particularly relates to an electrolyte of a non-negative secondary lithium battery, the non-negative secondary lithium battery and a formation process. The liquid electrolyte is an organic solvent system which takes lithium sulfonimide and lithium fluoroalkoxytrifluoroborate as main lithium salts and a carbonate compound-organic fluorine compound as an organic solvent, and functional additives are added into the system. The invention also discloses a formation process of the non-negative secondary lithium battery, namely the non-negative secondary lithium battery is formed at a certain high temperature (40-100 ℃), a certain pressure (0-3 MPa) and a certain vacuum degree (0-minus 0.1 MPa). The non-negative secondary lithium battery provided by the invention has the advantages of high energy density, high safety, long cycle life and the like.)

1. An electrolyte of a non-negative secondary lithium battery is characterized in that: the liquid electrolyte is an organic solvent system which takes lithium sulfonimide and lithium fluoroalkoxytrifluoroborate as main lithium salts and a carbonate compound-organic fluorine compound as an organic solvent, and functional additives are added into the system; wherein the final concentration of the main lithium salt in the electrolyte is 0.8-8 mol/L, and the functional additive accounts for 0.1-5% of the total mass of the electrolyte.

2. The electrolyte for a non-negative secondary lithium battery as claimed in claim 1, wherein: the molar concentration ratio of the lithium sulfonimide to the fluoroalkoxy trifluoroboric acid is 1: 9-9: 1; the volume ratio of the carbonate compound to the organic fluorine compound is 1: 9-9: 1.

3. The electrolyte for a non-negative secondary lithium battery as claimed in claim 1, wherein: the lithium sulfonimide is one of bis (trifluoromethylsulfonyl) imide lithium or bis (fluorosulfonyl) imide lithium; the lithium fluoroalkoxytrifluoroborate has the structure of formula 1:

wherein R is C₁-C₅Or C containing an aromatic ring₁-C₅A fluoroalkyl group.

4. The electrolyte for a non-negative secondary lithium battery as claimed in claim 1, wherein: the carbonate compound solvent is one or more of propylene carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diphenyl carbonate, dibutyl carbonate and butylene carbonate; the organic fluorine compound is one or more of fluoroethylene carbonate, propylene carbonate trifluoride, ethyl methyl 2,2, 2-trifluorocarbonate, diethyl 2,2, 2-trifluorocarbonate, ethyl propyl 2,2, 2-trifluorocarbonate, methyl isopropyl 2,2,2,2',2',2' -hexafluoro carbonate, methyl difluoroacetate, ethyl difluoroacetate, trifluoroethyl n-butyrate, methyl trifluoroacetate, ethyl trifluoroacetate, trifluoroethyl acetate, methyl pentafluoropropionate, 1,1,2, 2-tetrafluoroethyl-2, 2, 2-trifluoroethyl ether, 1,1,2, 2-tetrafluoroethyl-2, 2,3, 3-tetrafluoropropyl ether and 1,1,1,3,3, 3-hexafluoroisopropyl methyl ether; the functional additive is one or more of lithium difluorophosphate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium bis (perfluoropinanyl) borate, lithium fluoroalkoxytrifluoroborate, lithium perchlorate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium fluoride, lithium nitride, lithium oxide, lithium carbonate, lithium nitrate, potassium nitrate, sodium nitrate and cesium nitrate.

5. The utility model provides a no negative pole secondary lithium cell, includes negative pole mass flow body, liquid electrolyte, ceramic diaphragm, anode material and the anodal mass flow body, its characterized in that: the middle of the positive current collector and the negative current collector is separated by a ceramic diaphragm, wherein one side of the ceramic diaphragm facing the negative current collector is coated with a ceramic coating; the liquid electrolyte is the electrolyte according to claim 1.

6. A non-negative secondary lithium battery as claimed in claim 5, wherein: the ceramic diaphragm consists of a support substrate and a ceramic coating; the thickness of the ceramic coating is 1-15 mu m, the ceramic coating is composed of inorganic ceramic powder and a binder, and the mass ratio of the inorganic ceramic powder to the binder is (0.1-1): (1-0.1).

7. A non-negative secondary lithium battery as claimed in claim 6, wherein:

the support base material is one of a cellulose diaphragm, a polyamide non-woven fabric diaphragm, a polyimide non-woven fabric diaphragm, a polytetrafluoroethylene non-woven fabric diaphragm, a polyethylene terephthalate non-woven fabric diaphragm, a polybutylene terephthalate non-woven fabric diaphragm, a polyethylene single-layer diaphragm, a polyethylene-polypropylene-polyethylene multilayer diaphragm, a polypropylene single-layer diaphragm, a polypropylene-polyethylene-polypropylene multilayer diaphragm and a polyvinyl chloride non-woven fabric diaphragm.

8. A non-negative secondary lithium battery as claimed in claim 6, wherein: the inorganic ceramic powder is 0.01-2 mu m in diameter; the inorganic ceramic powder is one or more of silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, barium sulfate, boehmite, molybdenum disulfide, silicon carbide, calcium carbonate and diatomite; the binder is one or more of styrene butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, polyamide, polypropylene, polyacrylic acid, polyacrylonitrile, acrylate-acrylonitrile copolymer, polyvinyl ether, polyimide, styrene-butadiene copolymer, carboxymethyl cellulose, sodium carboxymethyl cellulose, polymethyl methacrylate, polypropylene carbonate, polyethylene carbonate, polystyrene carbonate, poly (epoxy cyclohexane carbonate) and polybutylene succinate.

9. A non-negative secondary lithium battery as claimed in claim 5, wherein: the negative current collector is a metal copper foil which is subjected to acid cleaning treatment and carbon coating treatment on the surface.

10. A method of manufacturing a non-negative secondary lithium battery according to claim 5, characterized in that: assembling a positive electrode material, a positive electrode current collector, a ceramic diaphragm, a negative electrode current collector subjected to acid washing and carbon spraying treatment and the double-main-salt electrolyte of claim 1 together to obtain the non-negative-electrode secondary lithium battery, wherein the pressure range is 0-3 MPa, the temperature range is 40-100 ℃, and the vacuum degree is-0.1-0 MPa during formation.

Technical Field

The invention belongs to the technical field of lithium batteries, and particularly relates to an electrolyte of a non-negative secondary lithium battery, the non-negative secondary lithium battery and a formation process.

Background

The lithium metal has extremely high theoretical specific capacity (3840mAh g)^-1) And has the lowest reduction potential, so the material is considered to be an ideal negative electrode material of a rechargeable battery. However, at present, the high energy density "holy cup" lithium metal secondary battery has short cycle life and poor safety performance, and the commercial development of the battery is limited by the problems of large volume expansion, rapid pulverization, serious dendritic crystal growth, large consumption of electrolyte and the like caused by excessive use of a metallic lithium negative electrode. Therefore, reducing the excessive use of the metallic lithium negative electrode is significant for improving the energy density and safety performance of the battery.

A solid film non-negative electrode battery composed of a positive electrode material, a solid electrolyte and a current collector is proposed in 2000 by B.J.Neudecker et al (see B.J.Neudecker et al, Journal of The Electrochemical Society,2000,147(2),517 and 523), The battery directly uses a negative electrode current collector as a negative electrode, when charging is carried out for The first time, metal lithium is deposited on The surface of The negative electrode current collector, and The metal lithium is converted into lithium ions to return to The positive electrode in The discharging process, so that cyclic charge and discharge are realized. In recent years, the research of non-negative secondary lithium batteries based on liquid electrolyte has been receiving attention because the advantages are obvious: 1. a metal lithium cathode with high chemical activity is not used, the requirements on production environment (such as humidity and temperature) are reduced, and the risk of safety production accidents is reduced; 2. the battery does not have voltage before first charging, can be stored for a long time without self-discharging, and has high safety index; 3. the volume energy density and the mass energy density are extremely high without using a negative electrode active material.

However, the development of the anodeless battery is limited due to its low coulombic efficiency and faster capacity fade during cycling, which is very difficult to achieve due to the uncontrollable electrochemical phenomena on the copper current collector. In addition to the concentration gradient and overpotential phenomena, the non-smoothness of the copper surface electrode during charging is a major cause of non-uniformity of Li deposition. Since convex surfaces have higher current densities, they are where Li deposits accumulate, leading to dendritic growth. Uncontrolled dendrite cycling growth leads to cracking of dead lithium and SEI. This in turn exposes more lithium to the electrolyte, causing lithium depletion and thickening of the SEI, resulting in low coulombic efficiency and rapid capacity fade.

Shuhailong, et al, physical research institute of the chinese academy of sciences, applied for a liquid electrolyte based button type non-negative secondary lithium battery in which a seed layer is deposited on the surface of a negative current collector and non-lithium metal ions are added to the electrolyte (shuhailong, et al, 201610685939.5, liquid electrolyte based non-negative secondary lithium battery). However, the conventional lithium hexafluorophosphate/carbonate electrolyte has poor compatibility with lithium metal, and lithium hexafluorophosphate is sensitive to water, is easy to hydrolyze, has poor thermal stability and is easy to thermally decompose. Ji-Guang Zhang et al successfully demonstrated a button type non-negative secondary lithium battery (Cu | | | LiFePO) using a high concentration lithium salt electrolyte (4M bis (fluorosulfonyl) imide Lithium (LiFSI) -diethylene glycol dimethyl ether (DME))₄) A key advantage of using such a high concentration electrolyte is its excellent reversibility of the lithium metal deposition/stripping process (coulombic efficiency)>99.8%) (see Ji-Guang Zhang et al, Advanced Functional Materials,2016,26(39), 7094-. Bing-Joe Hwang et al report a very stable double salt electrolyte, 2M bis (fluorosulfonyl) lithium imide (LiFSI) +1M bis (trifluoromethanesulfonyl) lithium imide (LiTFSI) -diethylene glycol dimethyl ether (DME)/1, 3-Dioxane (DOL), used in button Cu | | | LiFePO4 cathode-free batteries, where the average coulombic efficiency of 100 cycles of the battery can reach 98.9%. X-ray photoelectron spectroscopy (XPS) research shows that the SEI film of the copper cathode is rich in LiF and Li₂O and The like (see Bing-Joe Hwang et al, Journal of The Electrochemical Society,2019,166(8), A1501-A1509). Lithium salts of the sulphonimide type such as lithium bis (trifluoromethylsulphonyl) imide (LiTFSI), lithium bis (fluorosulphonyl) imide (LiFSI), despite thermal stabilityThe lithium ion battery has the advantages of good performance, no hydrolysis and high conductivity, but the short plate of the positive aluminum current collector is corroded, so that the lithium ion battery is difficult to be used as main salt in a secondary lithium battery with a cut-off charging potential higher than 4V; and the ether electrolyte system has insufficient oxidation resistance, which is not beneficial to the development of high-voltage high-capacity lithium battery materials. J.R.Dahn et al show a method of using a double salt liquid electrolyte (lithium difluorooxalato borate (LiDFOB)/lithium tetrafluoroborate (LiBF) for example₄) Fluoroethylene carbonate (FEC)/diethyl carbonate (DEC)) soft pack, non-negative secondary lithium battery of 250mAh with a residual capacity of 80% by continuously applying a pressure of 75kPa to the battery 90 times after charge-discharge cycles (see j.r. dahn et al, Nature Energy,2019,4(8), 683-. The boron salt is singly used as the main salt, although the low-temperature performance is good, the high-temperature performance is poor, the room-temperature conductivity is low, and all the boron salts singly used as the main salt also have certain defects.

The mixed use of boron salt and lithium salts of sulfonyl imide can effectively inhibit the corrosion of lithium salts of sulfonyl imide to the aluminum current collector of the positive electrode, so the lithium salts of sulfonyl imide and lithium fluoroalkoxy trifluoroborate are combined, and an organic fluorine compound solvent and a small amount of functional additives are matched for use, and the electrolyte belongs to a novel double-main-salt electrolyte system which has high ionic conductivity, wide electrochemical stability window and excellent electrode compatibility, and can effectively inhibit the negative electrode from generating lithium dendrite; and when the lithium ion battery is assembled into a non-negative secondary lithium battery, the lithium ion battery is used as a ceramic diaphragm, and then interacts with electrolyte to further reduce the risk of internal short circuit caused by lithium dendrites.

Disclosure of Invention

The invention aims to provide an electrolyte of a non-negative secondary lithium battery, the non-negative secondary lithium battery and a formation process.

In order to achieve the purpose, the invention adopts the technical scheme that:

the liquid electrolyte is an organic solvent system which takes lithium sulfonimide and lithium fluoroalkoxytrifluoroborate as main lithium salts and a carbonate compound-organic fluorine compound as an organic solvent, and functional additives are added into the system; wherein the final concentration of the main lithium salt in the electrolyte is 0.8-8 mol/L (preferably 1-3 mol/L), and the functional additive accounts for 0.1-5% (preferably 0.5-2%) of the total mass of the electrolyte.

The molar concentration ratio of the lithium sulfonimide to the fluoroalkoxytrifluoroborate is 1: 9-9: 1 (preferably 4: 6-6: 4); the volume ratio of the carbonate compound to the organic fluorine compound is 1: 9-9: 1 (preferably 2: 8-5: 5).

The lithium sulfonimide is one of bis (trifluoromethylsulfonyl) imide lithium or bis (fluorosulfonyl) imide lithium; the lithium fluoroalkoxytrifluoroborate has the structure of formula 1:

wherein R is C₁-C₅Or C containing an aromatic ring₁-C₅A fluoroalkyl group.

Preferably, said R is:

the carbonate compound solvent is one or more of propylene carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, diphenyl carbonate, dibutyl carbonate and butylene carbonate; preferably one or more of propylene carbonate, ethyl methyl carbonate, ethylene carbonate, dimethyl carbonate and diethyl carbonate.

The organic fluorine compound is one or more of fluoroethylene carbonate, propylene carbonate trifluoride, ethyl methyl 2,2, 2-trifluorocarbonate, diethyl 2,2, 2-trifluorocarbonate, ethyl propyl 2,2, 2-trifluorocarbonate, methyl isopropyl 2,2,2,2',2',2' -hexafluoro carbonate, methyl difluoroacetate, ethyl difluoroacetate, trifluoroethyl n-butyrate, methyl trifluoroacetate, ethyl trifluoroacetate, trifluoroethyl acetate, methyl pentafluoropropionate, 1,1,2, 2-tetrafluoroethyl-2, 2, 2-trifluoroethyl ether, 1,1,2, 2-tetrafluoroethyl-2, 2,3, 3-tetrafluoropropyl ether and 1,1,1,3,3, 3-hexafluoroisopropyl methyl ether; preferably one or more of fluoroethylene carbonate, propylene carbonate trifluoride, ethyl methyl 2,2, 2-trifluoro carbonate and diethyl 2,2, 2-trifluoro carbonate.

The functional additive is one or more of lithium difluorophosphate, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium bis (oxalato) borate, lithium difluorooxalato borate, lithium bis (perfluoropinanyl) borate, lithium fluoroalkoxytrifluoroborate, lithium perchlorate, lithium bis (fluorosulfonyl) imide, lithium bis (trifluoromethanesulfonyl) imide, lithium fluoride, lithium nitride, lithium oxide, lithium carbonate, lithium nitrate, potassium nitrate, sodium nitrate and cesium nitrate. Preferably one or more of lithium difluorophosphate, lithium hexafluorophosphate and lithium hexafluoroarsenate.

A non-negative secondary lithium battery comprises a negative current collector, liquid electrolyte, a ceramic diaphragm, a positive material and a positive current collector, wherein the positive current collector and the negative current collector are separated by the ceramic diaphragm, and one side of the ceramic diaphragm, which faces the negative current collector, is coated with a ceramic coating; the liquid electrolyte is the electrolyte.

The ceramic diaphragm consists of a support substrate and a ceramic coating; the thickness of the ceramic coating is 1-15 mu m, the ceramic coating is composed of inorganic ceramic powder and a binder, and the mass ratio of the inorganic ceramic powder to the binder is (0.1-1): (1-0.1).

The support base material is one of a cellulose diaphragm, a polyamide non-woven fabric diaphragm, a polyimide non-woven fabric diaphragm, a polytetrafluoroethylene non-woven fabric diaphragm, a polyethylene terephthalate non-woven fabric diaphragm, a polybutylene terephthalate non-woven fabric diaphragm, a polyethylene single-layer diaphragm, a polyethylene-polypropylene-polyethylene multilayer diaphragm, a polypropylene single-layer diaphragm, a polypropylene-polyethylene-polypropylene multilayer diaphragm and a polyvinyl chloride non-woven fabric diaphragm.

The inorganic ceramic powder is 0.01-2 mu m in diameter; the inorganic ceramic powder is one or more of silicon dioxide, titanium dioxide, aluminum oxide, magnesium oxide, barium sulfate, boehmite, molybdenum disulfide, silicon carbide, calcium carbonate and diatomite;

the binder is one or more of styrene butadiene rubber, polyvinyl alcohol, polytetrafluoroethylene, polyvinylidene fluoride, polyurethane, polyamide, polypropylene, polyacrylic acid, polyacrylonitrile, acrylate-acrylonitrile copolymer, polyvinyl ether, polyimide, styrene-butadiene copolymer, carboxymethyl cellulose, sodium carboxymethyl cellulose, polymethyl methacrylate, polypropylene carbonate, polyethylene carbonate, polystyrene carbonate, poly (epoxy cyclohexane carbonate) and polybutylene succinate.

The negative current collector is a metal copper foil which is subjected to acid cleaning treatment and carbon coating treatment on the surface.

The metal copper foil with the thickness of 5-50 mu m is ultrasonically soaked in an acid solution for 100-200 s, subjected to acid cleaning to remove oil and remove a surface oxide layer, then washed by deionized water and absolute ethyl alcohol to remove residual acid, dried in a room temperature environment, and then coated with a carbon material with the thickness of 0.5-5 mu m on the surface.

The acid used for the acid cleaning treatment is one or the combination of hydrochloric acid, hypochlorous acid, perchloric acid, hydrofluoric acid, sulfuric acid, carbonic acid, nitric acid, acetic acid and oxalic acid; the carbon material used for the surface carbon coating treatment is one or more of conductive carbon black, Ketjen black, acetylene black, single-walled carbon nanotubes, multi-walled carbon nanotubes, natural graphite, graphene and gas-phase carbon fibers (VGCF).

The positive electrode material comprises one or a combination of lithium iron phosphate, lithium iron manganese phosphate, lithium cobalt oxide, a lithium-rich manganese base, lithium nickel manganese cobalt oxide, lithium nickel aluminum cobalt oxide and lithium nickel manganese oxide; the positive current collector is a metal aluminum foil;

a preparation method of a non-negative secondary lithium battery comprises the steps of assembling a positive electrode material, a positive current collector, a ceramic diaphragm, a negative current collector subjected to acid washing and carbon spraying treatment and the double-main-salt electrolyte together to obtain the non-negative secondary lithium battery, wherein during formation, the pressure range is 0-3 MPa, the temperature range is 40-100 ℃, and the vacuum degree is-0.1-0 MPa.

The invention has the advantages that:

1) the fluoroalkoxy lithium trifluoroborate in the liquid electrolyte for the non-negative secondary lithium battery can effectively inhibit the corrosion of lithium sulfimide to the positive aluminum current collector, and the two lithium salts are matched with an organic fluorine compound solvent and a small amount of functional additives according to a certain proportion, so that the electrochemical stability window of lithium sulfimide salts can be widened; some fluorine atoms in the fluoride are combined with lithium ions, LiF is introduced into the SEI film, and the metal and the solvent are prevented from generating parasitic reaction and the growth of lithium dendrites is inhibited by improving the uniformity and the mechanical strength of the SEI film. Generally, the electrolyte has the advantages of excellent thermal stability, high ionic conductivity, wide electrochemical stability window, excellent electrode compatibility and the like, and can effectively inhibit the generation of lithium dendrites.

2) The electrolyte adopts the ceramic diaphragm, and the side of the diaphragm facing the negative current collector is coated with the ceramic coating which is matched with the SEI film rich in LiF generated under the action of the electrolyte, so that the short circuit risk of the non-negative secondary lithium battery can be effectively reduced;

3) after the metal copper foil of the negative electrode current collector of the non-negative secondary lithium battery is subjected to acid washing treatment and surface carbon coating treatment, the lithium affinity is enhanced, lithium is uniformly deposited on the surface of the current collector under the action of the electrolyte, and an SEI film rich in LiF (lithium phobic) is generated on the surface of the deposited lithium, so that the deformation of the SEI film along with the volume change can be minimized, the side reaction of the deposited lithium and the electrolyte can be reduced, and the lithium deposition/stripping efficiency in the non-negative secondary lithium battery is improved;

4) the formation process of the non-negative secondary lithium battery can enable the battery to form a compact, flat and stable SEI film, and prolong the cycle life of the battery;

5) the non-negative secondary lithium battery and the formation process thereof provided by the invention are suitable for large-scale production and manufacture of high-capacity non-negative secondary lithium battery products with the volume of more than 1Ah, and the products have the advantages of high energy density, high safety, long cycle life and the like.

Drawings

Fig. 1 is a graph showing the capacity change during the cycle at a charge and discharge rate of 0.1C in the soft-packed, non-negative secondary lithium batteries of examples 1 to 3 according to the present invention and comparative examples 1 to 2.

Fig. 2 is a graph showing the change in coulombic efficiency during the cycle at a charge-discharge rate of 0.1C in the soft-packed, non-negative secondary lithium batteries of examples 1 to 3 according to the present invention and comparative examples 1 to 2.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects solved by the present invention more apparent, the present invention is further described in detail below with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

According to the invention, a lithium salt of sulfonyl imide and lithium fluoroalkoxy trifluoroborate are combined to be used as a double-main-salt electrolyte for a non-negative secondary lithium battery, and an organic fluorine compound solvent and a small amount of functional additives are matched for use, so that the electrolyte belongs to a novel double-main-salt electrolyte system which has high ionic conductivity, wide electrochemical stability window and excellent electrode compatibility, and can effectively inhibit the negative electrode from generating lithium dendrites; when the lithium ion battery is assembled into a non-negative secondary lithium battery, the ceramic diaphragm is used and further interacts with electrolyte to further reduce the risk of internal short circuit caused by lithium dendrites; and further, the non-negative secondary lithium battery provided by the invention has the advantages of high energy density, high safety, long cycle life and the like.

Example 1

a. The manufacturing steps of the battery are briefly described as follows: mixing lithium nickel aluminum cobalt oxide (NCA) with conductive carbon black (Super P), Carbon Nano Tubes (CNT) and polyvinylidene fluoride according to the weight ratio of 93:2:2:3, adding N-methyl pyrrolidone, and uniformly stirring to prepare anode slurry. According to a single side of 27mg/cm²Coating the anode plate with the surface density, vacuum drying for 12 hours at 100 ℃, and then rolling and cutting the anode plate to obtain an anode plate; using a 10 μm copper foil as a negative current collector, the copper foil was ultrasonically cleaned in a 1% nitric acid aqueous solution for 3min to remove an oxide layer and dust impurities. And cleaning the copper foil subjected to acid treatment by using absolute ethyl alcohol, and drying after cleaning. Coating carbon nanotubes with the thickness of 1 mu m on the two sides of the copper foil, drying at room temperature, and then cutting to prepare the negative plate. Separating the positive and negative electrode plates with polypropylene (PP) ceramic diaphragm, wherein the side of the ceramic diaphragm facing the negative current collector is coated with ceramic coating (1 μm boehmite ceramic coating), wound into a cell, and encapsulated in aluminum plastic filmAnd (3) vacuum baking at 100 ℃ for 48h, injecting Propylene Carbonate (PC)/diethyl carbonate (DEC)/fluoroethylene carbonate (FEC) (wherein the volume ratio of PC/DEC/FEC is 1:1:1) electrolyte containing 0.6mol/L lithium bis (trifluoromethylsulfonyl) imide and 0.4mol/L lithium trifluoroethoxytrifluoroborate, and sealing to prepare the battery, wherein the functional additive is 1% of lithium difluorophosphate. And opening the battery after liquid injection and standing for 48 hours at 45 ℃ to ensure that the electrolyte is completely soaked.

b. Placing the battery in a fixture with the pressure of 1MPa, placing the fixture in a box with the temperature of 70 ℃ and the vacuum degree of-0.05 MPa, and carrying out vacuum formation, wherein the formation process comprises the following steps: and (3) performing constant current charging at 0.1 ℃ until the cut-off voltage is 4.2V, performing constant current discharging until the cut-off voltage is 3.4V, and circulating for 2 circles (see table 1).

c. And carrying out capacity cycle test on the battery after vacuum pumping and packaging at normal temperature.

Example 2

a. The manufacturing steps of the battery are briefly described as follows: mixing lithium nickel aluminum cobalt oxide (NCA) with conductive carbon black (Super P), Carbon Nano Tubes (CNT) and polyvinylidene fluoride according to the weight ratio of 93:2:2:3, adding N-methyl pyrrolidone, and uniformly stirring to prepare anode slurry. According to a single side of 27mg/cm²Coating the anode plate with the surface density, vacuum drying for 12 hours at 100 ℃, and then rolling and cutting the anode plate to obtain an anode plate; using a 24 μm copper foil as a negative current collector, the copper foil was ultrasonically cleaned in a 1% nitric acid aqueous solution for 3min to remove an oxide layer and dust impurities. And cleaning the copper foil subjected to acid treatment by using absolute ethyl alcohol, and drying after cleaning. Acetylene black with the thickness of 1 mu m is coated on the two sides of the copper foil, dried at room temperature and then cut to prepare the negative plate. And separating the positive plate and the negative plate by using a Polyethylene (PE) ceramic diaphragm, wherein one side of the ceramic diaphragm facing to a negative current collector is coated with a ceramic coating (1 mu m boehmite ceramic coating), the ceramic diaphragm is wound into a battery core, the battery core is encapsulated in an aluminum plastic film and is baked for 48h in vacuum at 100 ℃, 0.6mol/L of bis (trifluoromethyl sulfonyl) imide lithium and 0.4mol/L of Propylene Carbonate (PC)/diethyl carbonate (DEC)/fluoroethylene carbonate (FEC) (wherein the volume ratio of the PC/DEC/FEC is 1:1:1) electrolyte and 1% of lithium difluorophosphate are injected, and the battery is sealed. And opening the battery after liquid injection and standing for 48 hours at 45 ℃ to ensure that the electrolyte is completely soaked.

b. Placing the battery in a fixture with the pressure of 1MPa, placing the fixture in a box with the temperature of 70 ℃ and the vacuum degree of-0.1 MPa, and carrying out vacuum formation, wherein the formation process comprises the following steps: and (3) performing constant current charging at 0.1 ℃ until the cut-off voltage is 4.2V, performing constant current discharging until the cut-off voltage is 3.4V, and circulating for 2 circles (see table 1).

c. And carrying out capacity cycle test on the battery after vacuum pumping and packaging at normal temperature.

Example 3

a. The manufacturing steps of the battery are briefly described as follows: mixing lithium nickel aluminum cobalt oxide (NCA), conductive carbon black (Super P) and polyvinylidene fluoride according to the weight ratio of 95:2:3, adding N-methyl pyrrolidone, and uniformly stirring to prepare anode slurry. According to a single side of 27mg/cm²Coating the anode plate with the surface density, vacuum drying for 12 hours at 100 ℃, and then rolling and cutting the anode plate to obtain an anode plate; using a 10 μm copper foil as a negative current collector, the copper foil was ultrasonically cleaned in a 1% nitric acid aqueous solution for 3min to remove an oxide layer and dust impurities. And cleaning the copper foil subjected to acid treatment by using absolute ethyl alcohol, and drying after cleaning. Coating carbon nanotubes with the thickness of 1 mu m on the two sides of the copper foil, drying at room temperature, and then cutting to prepare the negative plate. And separating the positive plate and the negative plate by a polypropylene (PP) ceramic diaphragm, wherein one side of the ceramic diaphragm facing to a negative current collector is coated with a ceramic coating (1 mu m boehmite ceramic coating), the ceramic diaphragm is wound into a battery core, the battery core is encapsulated in an aluminum plastic film and is baked in vacuum at 100 ℃ for 48h, 0.6mol/L of bis (trifluoromethyl sulfonyl) imide lithium and 0.4mol/L of Propylene Carbonate (PC)/diethyl carbonate (DEC)/fluoroethylene carbonate (FEC)/methyl ethyl Fluorocarbonate (FEMC) (wherein the volume ratio of PC/DEC/FEC/FEMC is 1:1:1) electrolyte and 1% of lithium hexafluorophosphate serving as a functional additive are injected, and the battery is sealed. And opening the battery after liquid injection and standing for 48 hours at 45 ℃ to ensure that the electrolyte is completely soaked.

b. Placing the battery in a fixture with the pressure of 3MPa, placing the fixture in a box with the temperature of 50 ℃ and the vacuum degree of-0.05 MPa, and carrying out vacuum formation, wherein the formation process comprises the following steps: and (3) performing constant current charging at 0.1 ℃ until the cut-off voltage is 4.2V, performing constant current discharging until the cut-off voltage is 3.4V, and circulating for 2 circles (see table 1).

c. And carrying out capacity cycle test on the battery after vacuum pumping and packaging at normal temperature.

Comparative example 1

a. The manufacturing steps of the battery are briefly described as follows: mixing lithium nickel aluminum cobalt oxide (NCA) with conductive carbon black (Super P), Carbon Nano Tubes (CNT) and polyvinylidene fluoride according to the weight ratio of 93:2:2:3, adding N-methyl pyrrolidone, and uniformly stirring to prepare anode slurry. According to a single side of 27mg/cm²Coating the anode plate with the surface density, vacuum drying for 12 hours at 100 ℃, and then rolling and cutting the anode plate to obtain an anode plate; using a 10 μm copper foil as a negative current collector, the copper foil was ultrasonically cleaned in a 1% nitric acid aqueous solution for 3min to remove an oxide layer and dust impurities. And cleaning the copper foil subjected to acid treatment by using absolute ethyl alcohol, and drying after cleaning. Coating carbon nanotubes with the thickness of 1 mu m on the two sides of the copper foil, drying at room temperature, and then cutting to prepare the negative plate. And separating the positive plate and the negative plate by polypropylene (PP) ceramic, wherein one side of the ceramic diaphragm facing to the negative current collector is coated with a ceramic coating (1 mu m boehmite ceramic coating), the ceramic diaphragm is wound into a battery cell, the battery cell is packaged in an aluminum plastic film and is subjected to vacuum baking at 100 ℃ for 48h, 1mol/L electrolyte of Ethylene Carbonate (EC)/diethyl carbonate (DEC)/Ethyl Methyl Carbonate (EMC) of lithium hexafluorophosphate is injected, and the battery is sealed and manufactured. And opening the battery after liquid injection and standing for 48 hours at 45 ℃ to ensure that the electrolyte is completely soaked.

b. Placing the battery in a fixture with the pressure of 3MPa, placing the fixture in a box with the temperature of 70 ℃ and the vacuum degree of-0.05 MPa, and carrying out vacuum formation, wherein the formation process comprises the following steps: and (3) performing constant current charging at 0.1 ℃ until the cut-off voltage is 4.2V, performing constant current discharging until the cut-off voltage is 3.4V, and circulating for 2 circles (see table 1).

c. And carrying out capacity cycle test on the battery after vacuum pumping and packaging at normal temperature.

Comparative example 2

a. The manufacturing steps of the battery are briefly described as follows: mixing lithium nickel aluminum cobalt oxide (NCA) with conductive carbon black (Super P), Carbon Nano Tubes (CNT) and polyvinylidene fluoride according to the weight ratio of 93:2:2:3, adding N-methyl pyrrolidone, and uniformly stirring to prepare anode slurry. According to a single side of 27mg/cm²Coating the anode plate with the surface density, vacuum drying for 12 hours at 100 ℃, and then rolling and cutting the anode plate to obtain an anode plate; using a 10 μm copper foil as a negative current collector, copper was addedThe foil was ultrasonically cleaned in 1% aqueous nitric acid for 3min to remove oxide layers and dust impurities. And cleaning the copper foil subjected to acid treatment by using absolute ethyl alcohol, drying after cleaning, and then cutting to prepare the negative plate. And separating the positive plate and the negative plate by using a Polyethylene (PE) ceramic diaphragm, wherein one side of the ceramic diaphragm facing to a negative current collector is coated with a ceramic coating (1 mu m boehmite ceramic coating), the ceramic diaphragm is wound into a battery core, the battery core is encapsulated in an aluminum plastic film and is baked for 48h in vacuum at 100 ℃, 0.6mol/L of bis (trifluoromethyl sulfonyl) imide lithium and 0.4mol/L of Propylene Carbonate (PC)/diethyl carbonate (DEC)/fluoroethylene carbonate (FEC) (wherein the volume ratio of the PC/DEC/FEC is 1:1:1) electrolyte and 1% of lithium difluorophosphate are injected, and the battery is sealed. And opening the battery after liquid injection and standing for 48 hours at 45 ℃ to ensure that the electrolyte is completely soaked.

b. Placing the battery in a clamp with the pressure of 1MPa, placing the clamp in a room temperature environment with the temperature of 25 ℃ for formation, wherein the formation process comprises the following steps: and (3) performing constant current charging at 0.1 ℃ until the cut-off voltage is 4.2V, performing constant current discharging until the cut-off voltage is 3.4V, and circulating for 2 circles (see table 1).

c. And carrying out capacity cycle test on the battery after vacuum pumping and packaging at normal temperature.

Table 1 shows information on each of the examples and comparative examples:

the above examples and comparative examples were subjected to battery testing:

the test conditions were that the battery capacity was 1Ah, charge and discharge were performed at a current density of 0.1C, and the charge and discharge voltage of the battery was controlled to be 3.4 to 4.2V (see table 2, fig. 1 and 2).

TABLE 2

From table 2 and the discharge capacity graph of fig. 1 circulating 30 cycles, it can be seen that examples 1,2,3 have good circulation stability, and the capacity retention rate is above 70% after 30 cycles; comparative examples 1 and 2 had poor cycle stability, comparative example 1 exhibited incomplete capacity exertion, the capacity began to decay significantly after 15 cycles, and comparative example 2 exhibited cliff-type decay after 7 cycles.

From table 2 and the coulombic efficiency chart of fig. 2 for 30 cycles, it can be seen that examples 1,2, and 3 have higher coulombic efficiency and better stability, while comparative examples 1 and 2 have more stable coulombic efficiency in the initial cycle, but the coulombic efficiency in the subsequent cycle shows a decay tendency.

The comparative example 1 shows that the generated LiF-rich SEI layer of the double-salt electrolyte is beneficial to capacity maintenance and cycling stability of the non-negative-electrode battery through regulation, and the comparative example 2 shows that a compact, flat and stable SEI film can be formed through a high-temperature and high-pressure formation process, so that the cycling stability and the cycling efficiency of the non-negative-electrode battery are improved to a certain extent.

Finally, it is to be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing examples, those skilled in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced and improved; any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.