Lithium ion battery without negative electrode
By generating the LiCF3SO3/LiF composite interface layer on the surface of the copper foil current collector, the problem of poor lithium dendrites growth and interface contact in negative electrode-free lithium-ion batteries is solved, and the performance improvement of lithium-ion batteries with high energy density and high stability is achieved.
Patent Information
- Application Number
- CN202510495034.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-21
- Publication Date
- 2025-07-01
AI Technical Summary
The problems of severe growth of lithium dendrites, poor circulation stability and poor interface contact in negative electrode-free lithium-ion batteries lead to reduced efficiency and safety risks.
The trifluoromethanesulfonic acid treatment process is introduced on the surface of the copper foil current collector to generate a lithium-philic interface layer rich in LiCF3SO3 and LiF, and an artificial SEI film is constructed to improve the uniformity of lithium deposition and inhibit dendrite generation, while optimizing the interface contact between the positive electrode material and the lithium metal.
It significantly improves the cycle life and safety of lithium-ion batteries, improves the uniformity of lithium deposition and interface stability, reduces interface impedance, and enhances the energy density and cycle efficiency of the battery.
Smart Images
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Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of lithium-ion batteries, and particularly relates to a lithium-ion battery without a negative electrode. Background Art
[0002] In a lithium-ion battery system without a negative electrode, since it does not require a pre-lithiated negative electrode material, it can maximize the energy density, and thus has received extensive attention. However, in the process of cycling, such battery systems generally have relatively serious problems of lithium dendrite growth and "dead lithium" formation, resulting in a decrease in Coulombic efficiency, a shortening of the cycle life, and being prone to safety accidents, which limits their practical applications. One of the core challenges is that the deposition process of lithium metal on traditional current collectors such as copper foils is usually accompanied by non-uniform nucleation and dendrite growth, and during long-term contact with the electrolyte, an unstable natural solid electrolyte interphase (SEI) is easily formed at the interface. This film layer often has a complex composition, uneven structure, and poor mechanical properties, and it is difficult to effectively inhibit side reactions, further exacerbating the irregular deposition and irreversible loss of lithium metal.
[0003] To solve the above problems, in recent years, the artificial construction of a stable, dense, and lithium-ion conductive SEI film has become one of the research hotspots. Compared with the naturally formed SEI film, the artificial SEI film has the advantages of strong controllability, clear composition, and uniform structure. It can effectively regulate the migration behavior of lithium ions at the interface, guide the uniform nucleation and deposition of lithium metal, and thus improve the cycle stability and safety of the battery. The key to constructing an artificial SEI film lies in selecting a suitable precursor and treatment process to effectively regulate the surface of the copper foil and significantly improve the battery performance without introducing excessive mass.
[0004] The present invention constructs an artificial SEI film by introducing trifluoromethanesulfonic acid to treat the surface of the copper foil current collector. During the treatment process, trifluoromethanesulfonic acid reacts with the lithium salt to form an interface layer rich in LiCF3SO3 and LiF. LiCF3SO3 has excellent ionic conductivity and electrochemical stability, while LiF, due to its high mechanical strength and chemical inertness, helps to inhibit interface side reactions and dendrite penetration. This composite modified layer not only has excellent lithium affinity but also can provide uniform nucleation sites during the deposition process of lithium metal, effectively inducing the dense deposition behavior of lithium and avoiding the formation of sharp dendrites. In addition, the artificial SEI film composed of LiCF3SO3 and LiF has good chemical stability to the electrolyte components, can maintain the integrity of the interface structure during the charge and discharge process of the battery, and further improves the interface stability and electrochemical performance during the cycling process.
[0005] More importantly, the construction of the trifluoromethanesulfonic acid modified layer not only improves the interfacial contact state between the copper foil negative electrode and lithium metal, but also promotes the stability of the cathode material. In the non-negative electrode lithium-ion battery system, the initial cycling process relies on the release of lithium ions from the cathode to complete the lithium deposition on the negative electrode. Therefore, the interfacial behavior between the cathode and lithium metal has a great impact on the overall performance. The artificial SEI film constructed by trifluoromethanesulfonic acid can effectively reduce the interfacial impedance during the lithium deposition / stripping process, which is beneficial to the efficient deintercalation and reinsertion of lithium ions in the cathode material, and improves the overall cycling efficiency and rate performance. In summary, the present invention uses trifluoromethanesulfonic acid to construct a LiCF3SO3 / LiF composite artificial SEI film, which not only optimizes the lithium metal deposition behavior, but also significantly improves the interfacial contact quality between the cathode material and lithium metal through interface engineering, providing important technical support for the development of high-energy density and high-stability non-negative electrode lithium-ion batteries. Summary of the Invention
[0006] The present invention provides a non-negative electrode lithium-ion battery and a method for preparing a non-negative electrode lithium-ion battery by constructing an artificial solid electrolyte interface film, which solves the problems of uneven lithium deposition, serious dendrite growth, poor cycle stability and poor interfacial contact in existing non-negative electrode batteries. By introducing a trifluoromethanesulfonic acid treatment process on the surface of the copper foil negative electrode current collector, a lithiumophilic interface layer rich in LiCF3SO3 and LiF is formed after lithium deposition, thereby artificially constructing a SEI film with high stability, high ionic conductivity and excellent wettability.
[0007] The present invention provides a non-negative electrode lithium-ion battery, which includes a positive electrode sheet, a negative electrode sheet, a microporous polypropylene separator and an electrolyte.
[0008] The positive electrode sheet includes a positive electrode active material of LiNi x Co y Mn zO2 (where x + y + z = 1), a conductive agent and a binder;
[0009] The negative electrode sheet is the surface of a thin lithium metal negative electrode formed by depositing lithium ions provided by the positive electrode material on the negative electrode current collector during charging, and does not contain a negative electrode active material. Then, a trifluoromethanesulfonic acid (CF3SO3H) treatment process is introduced on the surface of the copper foil to form a lithiumophilic interface layer rich in LiCF3SO3 and LiF;
[0010] The electrolyte is 0.6M LiBF4, 0.6M LiDFOB in DMC:FEC = 2:1 Vol%.
[0011] Further, the positive electrode material is LiNi x Co y Mn zO2(where x + y + z = 1), the particle size distribution is between 5 - 8 μm.
[0012] Furthermore, the conductive agent is acetylene black or carbon nanotubes, and the binder is polytetrafluoroethylene.
[0013] Furthermore, the mass ratio of the positive electrode active material, the conductive agent, and the binder is 8:1:1.
[0014] Furthermore, the negative electrode current collector is a copper foil with a thickness of 30 μm, and its surface is treated by electrochemical polishing.
[0015] Furthermore, the process of depositing lithium ions on the surface of the negative electrode current collector to form a thin lithium metal negative electrode is to charge to 4.4 V at a current density of 0.1C (1C = 200 mA g-1).
[0016] Furthermore, the process of introducing trifluoromethanesulfonic acid treatment on the surface of the copper foil is to drop 1 - 2 drops of 0.1 - 0.5 M trifluoromethanesulfonic acid on the surface of the negative electrode sheet for forming the thin lithium metal negative electrode. Then, reassemble with a new positive electrode sheet, a new separator, and electrolyte to obtain a non - negative electrode battery product.
[0017] Furthermore, the microporous polypropylene separator has a specification of a thickness of 25 μm and a porosity of 55%.
[0018] Furthermore, the electrochemical polishing process uses an electrolyte with a mass fraction of 85% phosphoric acid and absolute ethanol in a volume ratio of 1:1. Using a three - electrode system for electrochemical polishing: the working electrode is the copper foil, the counter electrode is the platinum electrode, and the reference electrode is the saturated calomel electrode. The selected electrolysis voltage range is 2.0 - 3.0 V, and the time is 5 - 10 min. After polishing, take out the copper foil, rinse it with deionized water, and dry it with N2.
[0019] The present invention provides the application of the above non - negative electrode lithium ion battery.
[0020] The LiCF3SO3 / LiF composite modified layer constructed by trifluoromethanesulfonic acid treatment in the present invention has excellent lithium affinity, mechanical stability, and ion - selective permeability, which can significantly improve the uniformity of lithium deposition and inhibit dendrite formation. At the same time, this artificial SEI film can improve the interfacial contact between the positive electrode material and the lithium metal, reduce the interfacial impedance, improve the intercalation and de - intercalation efficiency of lithium ions, and thus improve the overall electrochemical performance and energy density. The technical route has simple operation, can be compatible with the existing lithium battery process, and has good practicability and industrialization prospects.
[0021] In summary, the present invention provides a non - negative electrode lithium ion battery with high safety, high energy density, and excellent cycle life, and its preparation method. The interface regulation strategy adopted provides new ideas and key technical supports for the development of non - negative electrode batteries. Brief Description of the Drawings
[0022] Figure 1 XRD pattern of the positive electrode material in Example 1.
[0023] Figure 2 SEM image of the negative electrode sheet in Example 1.
[0024] Figure 3 Cycling performance graph of the non - negative electrode lithium - ion battery in Example 1.
[0025] Figure 4 SEM image of the negative electrode sheet in Comparative Example 1.
[0026] Figure 5 Cycling performance graph of the non - negative electrode lithium - ion battery in Comparative Example 1.
[0027] Figure 6 Cycling performance graph of the non - negative electrode lithium - ion battery in Example 2.
[0028] Figure 7 Cycling performance graph of the non - negative electrode lithium - ion battery in Example 3. Detailed Description of the Invention
[0029] To facilitate the understanding of the present invention, the following will describe the present invention in a more comprehensive and detailed manner in conjunction with the accompanying drawings of the specification and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.
[0030] Example 1
[0031] A method for preparing a non - negative electrode lithium - ion battery includes the following steps:
[0032] Step (1): Mix the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent acetylene black, and binder polytetrafluoroethylene in a mass ratio of 8:1:1, and use N - methylpyrrolidone as the solvent.
[0033] After mixing the above materials evenly, coat them on aluminum foil, dry and compact to obtain the positive electrode sheet.
[0034] In step (2), the copper foil is ultrasonically cleaned for 0.5 h. The cleaning solvents are 0.5 M hydrochloric acid in sequence, and the treatment time is 3 - 5 min. Then, it is washed multiple times with absolute ethanol and deionized water and left standing in a vacuum drying oven at 80 °C for 12 h to remove surface contaminants. Electrochemical polishing is performed on the cleaned copper foil. An electrolyte of phosphoric acid with a mass fraction of 85% and absolute ethanol in a volume ratio of 1:1 is used, and a three - electrode system is adopted for electrochemical polishing: the working electrode is the copper foil, the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode. The selected electrolysis voltage ranges from 2.0 - 3.0 V, and the time is 10 min. After polishing, the copper foil is taken out, rinsed thoroughly with deionized water, and dried with N2.
[0035] In step (3), the above - mentioned copper foil current collector is punched into a pole piece, and LiNi 0.8 Co 0.1 Mn 0.1 O2 is used as the positive electrode, the electrolyte is 0.6 M LiBF4, 0.6 M LiDFOB in DMC:FEC = 2:1 Vol%, and then the battery is charged to 4.4 V at a current density of 0.1 C (1 C = 200 mAg -1 ) for lithium deposition; when the lithium metal is completely deposited on the current collector, the battery is disassembled to obtain the pole piece with a thin lithium metal negative electrode.
[0036] In step (4), 1 - 2 drops of 0.5 M trifluoromethanesulfonic acid are dropped onto the pole piece with the thin lithium metal negative electrode, and the reaction lasts for 1 - 2 s. Then, it is reassembled using a new positive electrode pole piece, a new separator, and the electrolyte to obtain a non - negative electrode battery product. The coin - type battery is subjected to charge - discharge tests at 25 °C within a voltage range of 2.8 V - 4.4 V.
[0037] Figure 1 SEM image of the positive electrode material LiNi 0.8 Co 0.1 Mn 0.1 O2 for Example 1. It can be seen from the figure that its particle size is about 5 - 8 μm.
[0038] Figure 2 SEM image of the negative electrode pole piece for Example 1. It can be seen from the figure that after treatment with trifluoromethanesulfonic acid, its surface becomes flat.
[0039] Figure 3 Cycling curve of the non - negative electrode lithium - ion battery prepared in Example 1 at a current density of 100 mA / g. It can be seen from Figure 3 that within the voltage range of 2.8 V - 4.4 V, after 50 cycles, its discharge specific capacity decreases from 202 mAh g -1 to 105.1 mAhg -1 .
[0040] Comparative Example 1
[0041] A method for preparing a lithium-ion battery without a negative electrode includes the following steps:
[0042] Step (1): Mix the cathode active material LiNi 0.8 Co 0.1 Mn 0.1 O2, the conductive agent acetylene black, and the binder polytetrafluoroethylene in a mass ratio of 8:1:1, and use N-methylpyrrolidone as the solvent.
[0043] After mixing the above materials evenly, coat them on an aluminum foil, dry and press to obtain the cathode electrode sheet.
[0044] Step (2): Ultrasonically clean the copper foil for 0.5 h. The cleaning solvents are 0.5 M hydrochloric acid in turn, and the treatment time is 3 - 5 min. Then wash it with anhydrous ethanol and deionized water multiple times and leave it standing in an 80°C vacuum drying oven for 12 h to remove surface contaminants. Electrochemically polish the cleaned copper foil. Use an electrolyte with a mass fraction of 85% phosphoric acid and anhydrous ethanol in a volume ratio of 1:1. Adopt a three-electrode system for electrochemical polishing: the working electrode is the copper foil, the counter electrode is the platinum electrode, and the reference electrode is the saturated calomel electrode. The selected electrolysis voltage range is 2.0 - 3.0 V, and the time is 10 min. After polishing, take out the copper foil, rinse it with deionized water, and dry it with N2.
[0045] Step (3): Punch the above copper foil current collector into an electrode sheet, use LiNi 0.8 Co 0.1 Mn 0.1 O2 as the positive electrode, the electrolyte 0.6 M LiBF4, 0.6 M LiDFOB in DMC:FEC = 2:1 Vol%, and then charge the battery to 4.4 V at a current density of 0.1 C (1 C = 200 mAg -1 ) for lithium deposition; when the lithium metal is deposited on the current collector, disassemble the battery to obtain the electrode sheet forming a thin lithium metal negative electrode. Then reassemble it with a new cathode electrode sheet, a new separator, and an electrolyte to obtain a lithium-ion battery product without a negative electrode. The coin cell is charged and discharged at 25°C within a voltage range of 2.8 V - 4.4 V.
[0046] Figure 4 SEM image of the negative electrode sheet of Comparative Example 1. As can be seen from the figure, on the surface not treated with trifluoromethanesulfonic acid, the lithium metal shows dendritic growth.
[0047] Figure 5 Cycling curve of the lithium-ion battery without a negative electrode prepared in Comparative Example 1 at a current density of 100 mA / g. From Figure 5It can be seen that in the voltage range of 2.8V to 4.4V, after 50 cycles, its discharge specific capacity decreases from 199 mAh g -1 to 20.7 mAh g -1 .
[0048] Example 2
[0049] A method for preparing a non - negative electrode lithium - ion battery includes the following steps:
[0050] Step (1): Mix the positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the conductive agent acetylene black, and the binder polytetrafluoroethylene in a mass ratio of 8:1:1, and use N - methylpyrrolidone as the solvent.
[0051] After mixing the above materials evenly, coat them on the aluminum foil, dry and press to obtain the positive electrode sheet.
[0052] Step (2): Ultrasonically clean the copper foil for 0.5 h. The cleaning solvents are 0.5 M hydrochloric acid in sequence, and the treatment time is 3 - 5 min. Then wash it repeatedly with absolute ethanol and deionized water and leave it standing in an 80°C vacuum drying oven for 12 h to remove surface contaminants. Electrochemically polish the cleaned copper foil. Use an electrolyte with a mass fraction of 85% phosphoric acid and absolute ethanol in a volume ratio of 1:1. Adopt a three - electrode system for electrochemical polishing: the working electrode is the copper foil, the counter electrode is the platinum electrode, and the reference electrode is the saturated calomel electrode. The selected electrolysis voltage range is 2.0 - 3.0 V, and the time is 10 min. After polishing, take out the copper foil, rinse it with deionized water, and dry it with N2.
[0053] Step (3): Punch the above copper foil current collector into a sheet. Use LiNi 0.6 Co 0.2 Mn 0.2 O2 as the positive electrode, the electrolyte 0.6 M LiBF4, 0.6 M LiDFOB in DMC:FEC = 2:1 Vol%, and then charge the battery to 4.4 V at a current density of 0.1 C (1 C = 200 mA g -1 ) for lithium deposition; when the lithium metal is completely deposited on the current collector, disassemble the battery to obtain the sheet with a thin lithium metal negative electrode formed.
[0054] Step (4): Drop 1 - 2 drops of 0.3 M trifluoromethanesulfonic acid on the sheet with the thin lithium metal negative electrode formed, and react for 1 - 2 s. Then reassemble it using a new positive electrode sheet, a new separator, and the electrolyte to obtain the non - negative electrode battery product. The coin - type battery is subjected to charge - discharge tests at 25°C in the voltage range of 2.8V to 4.4V.
[0055] Figure 6 Cycling curve of the lithium metal-free anode lithium-ion battery prepared in Example 2 at a current density of 100 mA / g. It can be seen from Figure 6 that in the voltage range of 2.8 V to 4.4 V, after 50 cycles, its discharge specific capacity decreases from 185.9 mAh g -1 to 84.3 mAh g -1 .
[0056] Example 3
[0057] A method for preparing a lithium metal-free anode lithium-ion battery includes the following steps:
[0058] Step (1): Mix the cathode active material LiNi 0.6 Co 0.2 Mn 0.2 O2, the conductive agent acetylene black, and the binder polytetrafluoroethylene in a mass ratio of 8:1:1, and use N-methylpyrrolidone as the solvent.
[0059] After mixing the above materials evenly, coat them on aluminum foil, dry and press to obtain the cathode electrode sheet.
[0060] Step (2): Ultrasonically clean the copper foil for 0.5 h. The cleaning solvents are 0.5 M hydrochloric acid in sequence, and the treatment time is 3 - 5 min. Then wash it with anhydrous ethanol and deionized water multiple times and let it stand in an 80 °C vacuum drying oven for 12 h to remove surface contaminants. Electrochemically polish the cleaned copper foil. Use an electrolyte with a mass fraction of 85% phosphoric acid and anhydrous ethanol in a volume ratio of 1:1. Adopt a three-electrode system for electrochemical polishing: the working electrode is the copper foil, the counter electrode is the platinum electrode, and the reference electrode is the saturated calomel electrode. The selected electrolysis voltage range is 2.0 - 3.0 V, and the time is 10 min. After polishing, take out the copper foil, rinse it with deionized water, and dry it with N2.
[0061] Step (3): Punch the above copper foil current collector into an electrode sheet, use LiNi 0.6 Co 0.2 Mn 0.2 O2 as the positive electrode, the electrolyte 0.6 M LiBF4, 0.6 M LiDFOB in DMC:FEC = 2:1 Vol%, and then charge the battery to 4.4 V at a current density of 0.1 C (1 C = 200 mAg -1 ) for lithium deposition; when the lithium metal is completely deposited on the current collector, disassemble the battery to obtain the electrode sheet forming the thin lithium metal anode.
[0062] In step (4), 1-2 drops of 0.1 M trifluoromethanesulfonic acid are dropped onto the electrode sheet of the thin lithium metal anode, and the reaction is carried out for 1-2 s. Then, a new cathode electrode sheet, a new separator, and an electrolyte are reassembled to obtain a non-aqueous electrolyte battery product. The coin cell is subjected to charge-discharge tests at 25 °C within a voltage range of 2.8 V to 4.4 V.
[0063] Figure 7 It is the cyclic voltammogram of the non-aqueous electrolyte lithium-ion battery prepared in Example 3 at a current density of 100 mA / g. From Figure 7 it can be seen that within the voltage range of 2.8 V to 4.4 V, after 50 cycles, its discharge specific capacity decreases from 197 mAh g -1 to 63.1 mAh g -1 .
Claims
1. A method for preparing a negative electrode-free lithium-ion battery, characterized in that: The lithium-ion battery comprises: a positive electrode sheet, a negative electrode sheet, a microporous polypropylene diaphragm and an electrolyte. The positive electrode sheet includes a positive electrode active material of LiNi x Co y Mn z O2 (where x+y+z=1), conductive agent and binder; The negative electrode sheet is formed by the deposition of lithium ions provided by the positive electrode material on the negative electrode current collector during the charging process to form a thin lithium metal negative electrode surface, which does not contain negative electrode active materials. Then, a trifluoromethanesulfonic acid (CF3SO3H) treatment process is introduced on the copper foil surface to form a lithium-philic interface layer rich in LiCF3SO3 and LiF. The electrolyte is 0.6M LiBF4, 0.6M LiDFOB in DMC:FEC=2:1Vol%.
2. The negative electrode-free lithium ion battery according to claim 1, wherein the positive electrode material is LiNi x Co y Mn z O2 (where x+y+z=1), particle size distribution is between 5-8μm. 3 . The negative electrode-free lithium-ion battery according to claim 1 , wherein the conductive agent is acetylene black or carbon nanotubes, and the binder is polytetrafluoroethylene.
4. The negative electrode-free lithium ion battery according to claims 1 and 3, wherein the mass ratio of the positive electrode active material to the conductive agent and the binder is 8:1:
1. 5 . The negative electrode-free lithium ion battery according to claim 1 , wherein the negative electrode current collector is a copper foil with a thickness of 30 μm, and the surface of the copper foil is subjected to electrochemical polishing.
6. The negative electrode-free lithium ion battery according to claim 1, wherein the negative electrode current collector is copper foil, and the process of depositing lithium ions on the negative electrode current collector to form a thin lithium metal negative electrode surface is at a current density of 0.1C (1C = 200mAg -1 ) to 4.4V.
7. The negative electrode-free lithium-ion battery according to claim 1, wherein the process of introducing trifluoromethanesulfonic acid (CF3SO3H) on the surface of the copper foil is to drip 1-2 drops of 0.1-0.5M trifluoromethanesulfonic acid on the surface of the negative electrode sheet forming the thin lithium metal negative electrode, and then reassemble with a new positive electrode sheet, a new diaphragm and an electrolyte to obtain a negative electrode-free battery product. 8 . The negative electrode-free lithium-ion battery according to claim 1 , wherein the microporous polypropylene separator has a thickness of 25 μm and a porosity of 55%.
9. According to the negative electrode-free lithium-ion battery of claim 5, the electrochemical polishing process is to use an electrolyte of 85% by mass phosphoric acid and anhydrous ethanol electrolyte in a volume ratio of 1:1, and adopt a three-electrode system for electrochemical polishing: the working electrode is a copper foil, the counter electrode is a platinum electrode, and the reference electrode is a saturated calomel electrode. The selected electrolysis voltage range is 2.0-3.0V, and the time is 5-10min. After polishing, the copper foil is taken out, rinsed with deionized water, and blown dry with N2.
10. Use of a negative electrode-free lithium-ion battery as claimed in any one of claims 1 to 9.