Composition, modified lithium metal negative electrode-diaphragm, preparation method of modified lithium metal negative electrode-diaphragm and battery

Abstract

The invention relates to a composition, a modified lithium metal negative electrode-diaphragm, a preparation method of the modified lithium metal negative electrode-diaphragm and a battery. Belongs to the technical field of batteries. The organic lithium borate can react with lithium metal to generate an SEI (solid electrolyte interface) layer of a polymer rich in boron; the chloride can react with lithium metal to generate an SEI layer rich in lithium chloride; wherein the mass of the organic lithium borate and the mass of the chloride are respectively not less than 1% of the mass of the polymer electrolyte precursor. The composition provided by the embodiment of the invention is applied to the battery, and in the charging and discharging process of the battery, a formed lithium metal negative electrode interface solid electrolyte layer has the advantages of stable electrochemical property, small lithium ion migration energy barrier and the like, so that a lithium metal negative electrode has a stable interface in the circulating process.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a composition, a modified lithium metal anode-separator and a preparation method thereof, and a battery. BACKGROUND

[0002] As an important candidate for the next generation of rechargeable batteries, polymer solid-state lithium metal batteries have the advantages of high energy density, low cost and high safety. However, in practical applications, polymer solid-state lithium metal batteries still face many challenges, among which the stability problem of the negative electrode interface is particularly prominent. The instability of the negative electrode interface can easily lead to the decline of the cycle performance of the battery, the capacity attenuation and the safety hazard.

[0003] In order to improve the stability of the negative electrode interface of the polymer solid-state lithium metal battery, researchers have been exploring the application of various electrolyte additives. Electrolyte additives can improve the performance of electrolyte, optimize the transmission channel of lithium ions, and reduce the occurrence of side reactions, thereby effectively improving the cycle stability and safety of the battery. SUMMARY

[0004] The present application provides a composition, a modified lithium metal anode-separator and a preparation method thereof, and a battery, to solve the technical problem of how to improve the electrochemical performance of the polymer electrolyte precursor. In a first aspect, the embodiments of the present application provide a composition, which comprises: A polymer electrolyte precursor, an organic lithium borate salt and a chloride, the organic lithium borate salt can react with lithium metal to generate a boron-rich polymer SEI layer; the chloride can react with lithium metal to generate a lithium chloride-rich SEI layer; wherein, The mass of the organic lithium borate salt and the mass of the chloride are each not less than 1% of the mass of the polymer electrolyte precursor.

[0005] Optionally, the mass of the organic lithium borate salt and the mass of the chloride are each 1% to 10% of the mass of the polymer electrolyte precursor.

[0006] Optionally, the organic lithium borate salt comprises at least one of lithium oxalate borate, lithium difluoro oxalate borate and lithium tetrafluoroborate; and / or, The chloride comprises at least one of tetrachloroethylene, sulfur dioxide chloride and indium trichloride.

[0007] Optionally, the raw materials of the polymer electrolyte precursor comprise an anion acceptor, an organic small molecule and an initiator.

[0008] Optionally, the anion acceptor comprises at least one of a borate ester molecule, a calixarene derivative and a nitrogen-containing heterocyclic compound; and / or, The organic small molecule includes: a metal salt and a skeleton material; and / or, The initiator includes at least one of phenyl bis (2, 4, 6-trimethyl benzoyl) phosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexyl benzophenone, benzophenone, 4-methyl benzophenone, 2, 4, 6-trimethyl benzophenone, thio propoxy thioxanthone, isopropyl thioxanthone.

[0009] Optionally, the anion acceptor is 2-20 parts by mass, the organic small molecule is 50-90 parts by mass, and the initiator is 0.1-5 parts by mass.

[0010] In a second aspect, the embodiments of the present application provide a preparation method of a modified lithium metal negative electrode-separator, the method comprises: attaching the separator to the surface of the lithium metal negative electrode to obtain a first lithium metal negative electrode-separator structure; immersing the surface of the separator of the lithium metal negative electrode-separator structure in the composition of any one of the first aspect to obtain a second lithium metal negative electrode-separator structure; carrying out a photopolymerization reaction on the second lithium metal negative electrode-separator structure to obtain a modified lithium metal negative electrode-separator.

[0011] Optionally, the volume of the composition is 10-20 μL.

[0012] In a third aspect, the embodiments of the present application provide a modified lithium metal negative electrode-separator, which is prepared by the method of any one of the second aspect.

[0013] In a fourth aspect, the embodiments of the present application provide a battery, which comprises the modified lithium metal negative electrode-separator of any one of the third aspect.

[0014] The above technical solutions provided by the embodiments of the present application have the following advantages compared with the prior art: The composition provided by the embodiments of the present application comprises: a polymer electrolyte precursor, organic lithium borate The salt and the chloride can react with lithium metal to form a SEI layer of a polymer rich in boron; the chloride can react with lithium metal to form a SEI layer rich in lithium chloride; wherein the mass of the organic lithium borate salt and the mass of the chloride are each not less than 1% of the mass of the polymer electrolyte precursor. The polymer electrolyte precursor is a basic raw material for forming a polymer electrolyte matrix; subsequent specific reaction mechanisms can be used to construct the main structure of the polymer electrolyte, provide a basic framework support for the entire electrolyte system, and carry other components to synergistically exert the functions of the electrolyte in the battery; the organic lithium borate salt can react with lithium metal to form a SEI layer of a polymer rich in boron, which can protect the lithium metal negative electrode and prevent further adverse reactions between lithium metal and other substances such as electrolyte, thereby reducing the consumption of lithium metal and the generation of side reactions; the chloride can react with lithium metal to form a SEI layer rich in lithium chloride, which has ionic conductivity and can act as a beneficial component for ion conduction in the SEI layer, helping lithium ions to move better at the interface between the negative electrode and the electrolyte, while also helping to enhance the stability of the SEI layer, further improving the protection effect on the lithium metal negative electrode, preventing the continuous erosion of the electrolyte on the lithium metal, and preventing the excessive development of adverse phenomena such as lithium dendrites; during the charging and discharging process of the battery, the organic lithium borate salt preferentially reacts with the lithium metal negative electrode to form a SEI layer of a polymer rich in B, and then tetrachloroethylene reacts at the negative electrode interface to form a SEI layer, forming an organic-inorganic double-layer SEI to synergistically improve the interface between the lithium metal negative electrode and the polymer solid-state electrolyte; and the mass of the organic lithium borate salt and the mass of the chloride are each ≥1% of the mass of the polymer electrolyte precursor, which can generate sufficient amounts of a SEI layer rich in boron and a SEI layer rich in lithium chloride, thereby enabling the composition to have excellent electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings, which are incorporated into and form a part of the specification, illustrate preferred embodiments of the present application and, together with the description, serve to explain the principles of the application.

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the accompanying drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0017] Figure 1 A flowchart of a modified lithium metal negative electrode-separator is provided for the embodiments of the present application. Figure 2Impedance plot of a solid-state polymer lithium metal symmetric cell provided for Example 1 of the present application; Figure 3 Long cycle voltage versus time curve of a solid-state polymer lithium metal symmetric cell provided for Example 1 of the present application. DETAILED DESCRIPTION

[0018] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0019] Various embodiments of the present application can exist in the form of a range; it should be understood that the description in the form of a range is merely for the convenience and brevity, and should not be understood as a hard limit on the scope of the present application; therefore, it should be considered that the described range has disclosed all possible sub-ranges and single values in the range. For example, it should be considered that the range description from 1 to 6 has disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers in the range, such as 1, 2, 3, 4, 5 and 6, which is applicable regardless of the range. In addition, whenever a numerical range is indicated in this document, it refers to any cited number (fraction or integer) in the indicated range.

[0020] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the drawing directions in the accompanying drawings. Furthermore, in the description of this application, terms such as "comprising" and "including" mean "including but not limited to." In this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. In this document, "and / or" describes the relationship between related objects, indicating that three relationships can exist; for example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. In this document, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can all represent: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple. "Parts representation" such as parts by weight or parts by mass indicates the proportional relationship between components. In the proportional relationships discussed in this article, parameters that need to be described by proportion should be understood as the first term of the proportion in the order of description, while the proportion figure should be understood as the second term. For example, if the mass ratio of substance A, substance B, and substance C is 1:2:3, then substances A, B, and C should correspond one-to-one with the proportion figure in the proportion in the order of description, i.e., the mass of substance A : the mass of substance B : the mass of substance C = 1 : 2 : 3.

[0021] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this application can be purchased from the market or prepared by existing methods.

[0022] In a first aspect, embodiments of this application provide a composition comprising: a polymer electrolyte. The mixture comprises a precursor, an organoboronate lithium salt, and a chloride, wherein the organoboronate lithium salt reacts with lithium metal to form a boron-rich polymer SEI layer; and the chloride reacts with lithium metal to form a lithium chloride-rich SEI layer. The mass of the organoboronate lithium salt and the mass of the chloride are each not less than 1% of the mass of the polymer electrolyte precursor.

[0023] In some embodiments, the mass of the organoboronate lithium salt and the mass of the chloride are 1% to 10% of the mass of the polymer electrolyte precursor, respectively.

[0024] In the embodiments of this application, the polymer electrolyte precursor serves as a key starting material for constructing the polymer electrolyte matrix. It forms the main structure of the polymer electrolyte through subsequent specific reactions (such as photopolymerization). This matrix not only provides physical support for the entire electrolyte system, ensuring the stability and integrity of the electrolyte within the battery, but also provides a site for the uniform dispersion and interaction of other functional components (such as lithium organoborate salts and chlorides). This allows them to synergistically perform key functions of the electrolyte in the battery, such as ion conduction and electrode isolation, thus providing a fundamental guarantee for the normal electrochemical operation of the battery.

[0025] Lithium organoborate salts can chemically react with lithium metal to form a boron-rich polymer SEI layer. Firstly, it forms a protective film on the surface of the lithium metal anode, effectively preventing direct contact between lithium metal and other active components in the electrolyte, thus significantly reducing unnecessary lithium metal consumption and the probability of various side reactions. This is crucial for maintaining the stability of the lithium metal anode and the overall performance of the battery, as the high reactivity of lithium metal makes it highly susceptible to adverse reactions without effective protection, leading to battery capacity decay and shortened lifespan. During battery charge-discharge cycles, lithium organoborate salts preferentially react with the lithium metal anode. This reaction sequence facilitates the rapid establishment of a preliminary SEI protective barrier during the initial operation phase of the battery. This boron-rich polymer SEI layer has a certain degree of elasticity, which can buffer the stress caused by volume changes on the lithium metal anode surface, making the SEI less prone to breakage. This lays the foundation for further optimization of the SEI structure and performance, making the entire SEI layer formation process more orderly and efficient, and contributing to improved battery stability and reliability during long-term cycling.

[0026] Chlorides can react with lithium metal to form a lithium chloride-rich SEI layer. This SEI layer has a low lithium-ion diffusion barrier, which facilitates rapid lithium-ion transport, reduces concentration polarization at the interface, and inhibits lithium dendrite growth. At the interface between the negative electrode and the electrolyte, lithium ions need to move rapidly and stably to achieve efficient charge and discharge processes. The presence of lithium chloride can reduce the resistance to ion transport and improve ion conduction efficiency. Simultaneously, the lithium chloride-rich SEI layer can enhance the stability of the entire SEI structure, further strengthening the protection of the lithium metal negative electrode. It can effectively resist the continuous erosion of lithium metal by the electrolyte and inhibit the growth of lithium dendrites, thereby reducing safety hazards such as battery short circuits caused by lithium dendrites and significantly improving battery safety and cycle life.

[0027] Synergistic effect of organoboronate lithium salts and chlorides: Chlorides can form a stable LiCl interface layer on the lithium metal surface. This interface layer can inhibit the growth of lithium dendrites and reduce the accumulation of dead lithium, thereby improving the cycle stability of the battery. However, the LiCl-rich SEI interface is prone to fracturing, leading to continuous side reactions between the electrolyte and the lithium metal anode. Therefore, organoboronate lithium salts can preferentially form a boron-rich polymer SEI on the lithium metal surface, which has a certain elasticity and can buffer the stress caused by the volume change of the lithium metal anode surface, making the SEI less prone to fracturing. However, the looseness of the boron-rich polymer SEI alone can also easily lead to continuous reactions between the electrolyte and lithium metal. Therefore, a dense LiCl SEI layer is also needed. The organoboronate lithium salt preferentially reacts with the lithium metal anode to form a boron-rich polymer SEI, and then the chloride reacts again at the anode interface to form an SEI, thus forming an organic-inorganic bilayer SEI that synergistically improves the interface between the lithium metal anode and the polymer solid electrolyte.

[0028] In summary, through the synergistic effect of organoboronate lithium salt and chloride, and their rational combination with the polymer electrolyte precursor, a composite system with unique structural and performance advantages was successfully constructed. This system can generate an organic-inorganic bilayer SEI structure, fully leveraging the respective advantages of the organic layer (boron-rich polymer SEI layer) and the inorganic layer (lithium chloride-rich SEI layer). The two layers complement and enhance each other, jointly improving the interfacial performance between the lithium metal anode and the polymer solid electrolyte. Ultimately, this composition possesses excellent electrochemical performance, providing a solid foundation for the development of high-performance polymer solid lithium metal batteries. It is expected to show promising application prospects in future battery applications, meeting the urgent needs of electric vehicles, portable electronic devices, and other fields for high-energy-density, long-life, and high-safety batteries.

[0029] In this embodiment, the mass of the organoborate lithium salt and the chloride can each be 1% to 10% of the mass of the polymer electrolyte precursor. The chloride forms a stable LiCl interface layer on the surface of the lithium metal anode, inhibiting the growth of lithium dendrites and reducing the accumulation of dead lithium. It synergistically forms an organic-inorganic bilayer solid electrolyte interface (SEI) with the organoborate lithium salt, improving the cycle stability and safety of the battery. If the chloride mass is too high (above 10%), the SEI layer formed at the anode interface may be too thick or structurally uneven, affecting the normal transport of lithium ions. If the chloride mass is too low (below 1%), it is difficult to form a sufficiently thick or stable LiCl interface layer on the anode surface, which may result in insufficient mechanical strength of the SEI layer, making it difficult to effectively inhibit the growth of lithium dendrites and the accumulation of dead lithium.

[0030] Lithium organoboronate salts preferentially react on the surface of lithium metal anodes to form a boron-rich polymer solid electrolyte interface. The SEI layer (Sediment Electrolyte) has a certain degree of elasticity, which can effectively buffer the stress generated by the volume change of the lithium metal anode during charging and discharging, preventing the SEI layer from cracking. If the proportion of organoborate lithium salt is too high and exceeds 10%, a thicker, loosely structured organic SEI layer may be formed, resulting in a lower overall mechanical strength of the SEI layer. This makes it difficult to effectively suppress the growth of lithium dendrites, which may trigger more side reactions and shorten the cycle life of the battery. If the proportion of organoborate lithium salt is too low and falls below 1%, it is difficult to form a sufficiently thick or stable boron-rich polymer SEI layer on the surface of the lithium metal anode, thus making it difficult to effectively buffer the volume change of the lithium metal anode, causing the SEI layer to be prone to cracking. For example, the mass of the organoborate lithium salt and chloride are 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10% of the polymer electrolyte precursor, respectively.

[0031] In some embodiments, the organoboronate lithium salt comprises at least one of the following: lithium oxalate borate, lithium difluorooxalate borate, lithium tetrafluoroborate; and / or, The chloride includes at least one of the following: tetrachloroethylene, sulfur dioxide acyl chloride, and indium trichloride.

[0032] In the embodiments of this application, the organoboronate lithium salt can be one or a combination of lithium oxalate borate, lithium difluorooxalate borate, and lithium tetrafluoroborate; the chloride can be one or a combination of tetrachloroethylene, sulfur dioxide acyl chloride, and indium trichloride.

[0033] In some embodiments, the raw materials for the polymer electrolyte precursor include: anion acceptors and small organic molecules. And initiators.

[0034] In some embodiments, the anion acceptor comprises at least one of the following: a borate ester molecule, a calixarene derivative, a nitrogen-containing heterocyclic compound; and / or, The organic small molecules include: metal salts and framework materials; and / or, The initiator includes at least one of the following: phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexylbenzophenone, benzophenone, 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, thiopropoxythionone, and isopropylthionone.

[0035] In this embodiment, the raw materials for the polymer electrolyte precursor include: anion acceptors and small organic molecules. And initiators. The anion acceptor unit can fix the anions in the lithium salt through non-covalent forces such as Lewis acid-base interaction, hydrogen bonding and π-π superposition, thereby increasing the lithium ion migration number in the polymer electrolyte. The anion acceptor can be one or more of borate ester molecules, calixarene derivatives, and nitrogen-containing heterocyclic compounds, which can interact with anions through various non-covalent forces, thereby fixing the anions in the lithium salt and increasing the lithium ion migration number. Among them, the calixarene derivatives can be one or more of urea-modified calix[4]arene, urea-modified calix[6]arene or calix[6]pyrrole; the nitrogen-containing heterocyclic compounds can be one or more of porphyrin, aminocrown ether, hematoporphyrin, dimethyl m-porphyrin, phthalocyanine, aminocrown ether, pyridine ring or pyrrole ring.

[0036] Organic small molecules serve as the skeletal support matrix for polymer electrolytes and provide lithium-ion transport pathways. Metal salts and framework materials also serve as the skeletal support matrix for polymer electrolytes and provide lithium-ion transport pathways. The metal salts can be one or more combinations of lithium trifluoromethanesulfonylimide, lithium bisfluorosulfonylimide, lithium perchlorate, lithium trifluoromethanesulfonate, sodium bis(trifluoromethanesulfonylimide), sodium perchlorate, and magnesium perchlorate, which share common properties such as high ion conductivity, electrochemical stability, thermal stability, and chemical stability. The framework materials can be vinylene carbonate and / or 4-vinyl-1,3-dioxolane-2-one, which possess certain antioxidant capabilities. As the polymer electrolyte matrix, they have weak interaction with lithium ions, facilitating lithium-ion transport. Initiators can initiate the polymerization reaction of polymer electrolyte precursors. Initiators can be one or more of the following: phenylbis(2,4,6-trimethylbenzoyl), phosphine oxide (IRGACURE819 photoinitiator), Darocur 1173 (2-hydroxy-2-methyl-1-phenylpropanone), Irgacure 184 (1-hydroxycyclohexylbenzophenone), benzophenone (BP), 4-methylbenzophenone, 2,4,6-trimethylbenzophenone, thiopropoxythioxanthrone, and isopropylthioxanthrone.

[0037] In summary, in polymer electrolyte precursors, anion acceptors can coordinate with anions in metal salts to form stable complexes. This coordination can affect the solubility and ion conductivity of the metal salt, thereby influencing the overall performance of the electrolyte. The backbone materials in small organic molecules contain unsaturated bonds or active groups, which can react with initiators to promote polymer formation.

[0038] In some embodiments, the anion acceptor is 2 to 20 parts by weight, the small organic molecule is 50 to 90 parts by weight, and the initiator is 0.1 to 5 parts by weight.

[0039] In the embodiments of this application, the anion acceptor can be 2 to 20 parts. The anion acceptor restricts the movement of anions by binding with them, thereby increasing the lithium ion migration number, which helps to reduce concentration polarization and improve the electrochemical performance of the battery. The organic small molecules can be 50 to 90 parts because: (1) forming a stable electrolyte structure: an appropriate amount of organic small molecules can ensure that the polymer electrolyte precursor forms a stable three-dimensional network structure, providing an effective transport path for lithium ions. (2) improving ionic conductivity: the high ionic conductivity of metal salts helps to improve the ionic conductivity of the electrolyte, thereby accelerating the migration speed of lithium ions. (3) enhancing electrochemical stability: the electrochemical stability of metal salts and framework materials can ensure that the electrolyte maintains stable performance during charging and discharging, and extend the battery's service life. (4) improving thermal and chemical stability: these organic small molecules can improve the thermal and chemical stability of the electrolyte, enabling it to maintain stability under high temperature or harsh environments. The initiator can be 0.1 to 5 parts. An appropriate amount of initiator can ensure that the polymer electrolyte precursor undergoes a rapid and efficient polymerization reaction under ultraviolet light irradiation, forming a stable polymer network structure, thereby improving the mechanical strength and ion conductivity of the electrolyte. For example, the anion acceptor can be 2 parts, 4 parts, 6 parts, 8 parts, 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, 20 parts, etc.; the small organic molecule can be 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, etc.; and the initiator can be 0.1 parts, 0.2 parts, 0.3 parts, 0.5 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, etc.

[0040] Secondly, embodiments of this application provide a method for preparing a modified lithium metal anode-separator, the method comprising: S1. The separator is attached to the surface of the lithium metal anode to obtain the first lithium metal anode-separator structure; S2. The composition described in any one of the embodiments of the first aspect is used to wet the surface of the separator of the lithium metal anode-separator structure to obtain a second lithium metal anode-separator structure. S3. The second lithium metal anode-separator structure is subjected to photopolymerization reaction to obtain a modified lithium metal anode-separator.

[0041] In the embodiments of this application, anion acceptors, small organic molecules and initiators are mixed together and stirred for 1 h to 20 h to obtain a polymer electrolyte precursor; organic borate and chloride are added to the homogeneously mixed polymer electrolyte precursor and stirred for 1 h to 20 h to obtain a composition; a separator is attached to the surface of a lithium metal anode, and then the composition is dripped to wet the surface of the separator; the second lithium metal anode-separator structure is subjected to ultraviolet light polymerization to obtain a modified lithium metal anode-separator.

[0042] In some embodiments, the volume of the composition is 10 μL to 20 μL.

[0043] In the embodiments of this application, the volume of the composition can be 10 μL to 20 μL, which ensures that the composition forms a uniform and dense coating on the separator, thereby improving the ion conductivity and mechanical strength of the electrolyte. If the volume of the composition is higher than 20 μL, the coating may be too thick, affecting the migration rate of ions and increasing the internal resistance of the electrolyte, thus reducing battery performance. If the volume of the composition is lower than 10 μL, it may be difficult to form a complete coating, resulting in uneven electrolyte distribution and performance degradation. For example, the volume of the composition can be 10 μL, 11 μL, 12 μL, 13 μL, 14 μL, 15 μL, 16 μL, 17 μL, 18 μL, 19 μL, 20 μL, etc.

[0044] The preparation method of the modified lithium metal anode-separator is based on the above composition. The specific raw materials of the composition can be referred to the above embodiments. Since the composition adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be repeated here.

[0045] Thirdly, embodiments of this application provide a modified lithium metal anode-separator, which is prepared by the method described in any one of the embodiments of the second aspect.

[0046] The modified lithium metal anode-separator is achieved based on the above-described preparation method of the modified lithium metal anode-separator. The specific steps of the preparation method of the modified lithium metal anode-separator can be referred to the above embodiments. Since the modified lithium metal anode-separator adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0047] Fourthly, embodiments of this application provide a battery comprising the modified lithium metal anode-separator as described in any one of the embodiments of the third aspect.

[0048] In the embodiments of this application, the modified lithium metal anode-separator is applied in a battery. During the charging and discharging process of the battery, the solid electrolyte layer formed at the lithium metal anode interface has advantages such as stable electrochemical properties and low lithium-ion migration barrier, so that the lithium metal anode has a stable interface during cycling.

[0049] The battery is based on the modified lithium metal anode-separator described above. The specific preparation steps of the modified lithium metal anode-separator can be referred to the above embodiments. Since the battery adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0050] The present application is further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the application. Experimental methods in the following embodiments that do not specify specific conditions are generally determined according to national standards. If there is no corresponding national standard, then generally accepted international standards, conventional conditions, or conditions recommended by the manufacturer are followed.

[0051] Example 1 The preparation method of the modified lithium metal anode-separator includes: In an argon-filled glove box, mixing 0.1 g of lithium bis(trifluoromethanesulfonyl)imide, 0.2 g of vinylene carbonate, 0.05 g of IRGACURE 819 photoinitiator, and 0.05 g of trimethyl borate and stirring at room temperature for 5 h. Adding 0.01 g of tetrachloroethylene and 0.01 g of lithium difluorooxalate borate to the polymer electrolyte precursor solution and stirring at room temperature for 1 h. Dropping 15 μL of the polymer electrolyte precursor containing tetrachloroethylene and lithium difluorooxalate borate onto a 35 μm thick, 2 cm diameter cellulose membrane disc. Performing an in-situ ultraviolet photopolymerization reaction on the lithium metal surface: attaching the thick cellulose membrane to a 50 μm thick, 1.4 cm diameter lithium metal disc and irradiating with ultraviolet light for 12 h to obtain the modified lithium metal anode-separator.

[0052] A lithium metal disc with a thickness of 50 μm and a diameter of 1.4 cm is attached to the other side of the in-situ polymerized electrolyte membrane to assemble it into a button cell.

[0053] Example 2 The preparation method of the modified lithium metal anode-separator includes: In an argon-filled glove box, mixing 0.1 g of lithium bis(trifluoromethanesulfonyl)imide, 0.2 g of vinylene carbonate, 0.05 g of IRGACURE 819 photoinitiator, and 0.05 g of trimethyl borate and stirring at room temperature for 5 h. Adding 0.02 g of tetrachloroethylene and 0.02 g of lithium difluorooxalate borate to the polymer electrolyte precursor solution and stirring at room temperature for 1 h. Dropping 15 μL of the polymer electrolyte precursor containing tetrachloroethylene and lithium difluorooxalate borate onto a 35 μm thick, 2 cm diameter cellulose membrane disc. Performing an in-situ ultraviolet photopolymerization reaction on the lithium metal surface: attaching the thick cellulose membrane to a 50 μm thick, 1.4 cm diameter lithium metal disc and irradiating with ultraviolet light for 12 h to obtain the modified lithium metal anode-separator.

[0054] A lithium metal disc with a thickness of 50 μm and a diameter of 1.4 cm is attached to the other side of the in-situ polymerized electrolyte membrane to assemble it into a button cell.

[0055] Example 3 The preparation method of the modified lithium metal anode-separator includes: In an argon-filled glove box, mixing 0.1 g of lithium bis(trifluoromethanesulfonyl)imide, 0.2 g of vinylene carbonate, 0.05 g of IRGACURE 819 photoinitiator, and 0.05 g of trimethyl borate and stirring at room temperature for 5 h. Adding 0.03 g of tetrachloroethylene and 0.03 g of lithium difluorooxalate borate to the polymer electrolyte precursor solution and stirring at room temperature for 1 h. Dropping 15 μL of the polymer electrolyte precursor containing tetrachloroethylene and lithium difluorooxalate borate onto a 35 μm thick, 2 cm diameter cellulose membrane disc. Performing an in-situ ultraviolet photopolymerization reaction on the lithium metal surface: attaching the thick cellulose membrane to a 50 μm thick, 1.4 cm diameter lithium metal disc and irradiating with ultraviolet light for 12 h to obtain the modified lithium metal anode-separator.

[0056] A lithium metal disc with a thickness of 50 μm and a diameter of 1.4 cm is attached to the other side of the in-situ polymerized electrolyte membrane to assemble it into a button cell.

[0057] Example 4: Synergistic effect of organoboronate lithium salt + chloride Polymer precursor: 0.1g LiTFSI + 0.2g VC + 0.05g IRGACURE819 + 0.05g trimethyl borate; Additives: 0.01g lithium oxalate borate (LiBOB) + 0.01g tetrachloroethylene (TCE); Preparation process: Same as in Example 1 (15 μL precursor, 35 μm cellulose membrane, UV light for 12 h).

[0058] Comparative Example 1 In an argon-filled glove box, 0.1 g of lithium bis(trifluoromethanesulfonyl)imide, 0.2 g of vinylene carbonate, 0.05 g of IRGACURE 819 photoinitiator, and 0.05 g of trimethyl borate were mixed and stirred at room temperature for 5 h. 15 μL of the polymer electrolyte precursor was dropped onto a 35 μm thick, 2 cm diameter cellulose membrane disc. In-situ UV-cured polymerization was then carried out on the lithium metal surface: the thick cellulose membrane was adhered to a 50 μm thick, 1.4 cm diameter lithium metal disc and irradiated with UV light for 12 h. A 50 μm thick, 1.4 cm diameter lithium metal disc was then attached to the other side of the in-situ polymerized thick electrolyte membrane, and a button cell was assembled.

[0059] Comparative Example 2 In an argon-filled glove box, 0.05 g of lithium bis(trifluoromethanesulfonyl)imide, 0.1 g of vinylene carbonate, 0.02 g of IRGACURE 819 photoinitiator, and 0.02 g of trimethyl borate were mixed and stirred at room temperature for 5 h. 15 μL of the polymer electrolyte precursor was dropped onto a 35 μm thick, 2 cm diameter cellulose membrane disc. In-situ UV-cured polymerization was then carried out on the lithium metal surface: the thick cellulose membrane was adhered to a 50 μm thick, 1.4 cm diameter lithium metal disc and irradiated with UV light for 10 h. A 50 μm thick, 1.4 cm diameter lithium metal disc was then attached to the other side of the in-situ polymerized thick electrolyte membrane, and a button cell was assembled.

[0060] Comparative Example 3 In an argon-filled glove box, 0.1 g of lithium bis(trifluoromethanesulfonyl)imide, 0.2 g of vinylene carbonate, 0.05 g of IRGACURE 819 photoinitiator, and 0.05 g of trimethyl borate were mixed and stirred at room temperature for 5 h. 20 μL of the polymer electrolyte precursor was dropped onto a 35 μm thick, 2 cm diameter cellulose membrane disc. In-situ UV-cured polymerization was then carried out on the lithium metal surface: the thick cellulose membrane was adhered to a 50 μm thick, 1.4 cm diameter lithium metal disc and irradiated with UV light for 12 h. A 50 μm thick, 1.4 cm diameter lithium metal disc was then attached to the other side of the in-situ polymerized thick electrolyte membrane, and a button cell was assembled.

[0061] Comparative Example 4 In an argon-filled glove box, 0.1 g of lithium bis(trifluoromethanesulfonyl)imide, 0.2 g of vinylene carbonate, 0.05 g of IRGACURE 819 photoinitiator, and 0.05 g of trimethyl borate were mixed and stirred at room temperature for 5 h. 25 μL of the polymer electrolyte precursor was dropped onto a 35 μm thick, 2 cm diameter cellulose membrane disc. In-situ UV-cured polymerization was then carried out on the lithium metal surface: the thick cellulose membrane was laminated onto a 50 μm thick, 1.4 cm diameter lithium metal disc and irradiated with UV light for 20 h. A 50 μm thick, 1.4 cm diameter lithium metal disc was then laminated onto the other side of the in-situ polymerized thick electrolyte membrane, and a button cell was assembled.

[0062] Comparative Example 5: Contains only lithium borate salt Polymer precursor: 0.1g LiTFSI + 0.2g VC + 0.05g IRGACURE819 + 0.05g trimethyl borate; Additive: 0.02g lithium dioxalate borate (LiBOB); Preparation process: Same as in Example 1 (15 μL precursor, 35 μm cellulose membrane, UV light for 12 h).

[0063] Comparative Example 6: Contains only chloride Polymer precursor: 0.1g LiTFSI + 0.2g VC + 0.05g IRGACURE819 + 0.05g trimethyl borate; Additive: 0.02g tetrachloroethylene (TCE); Preparation process: Same as in Example 1 (15 μL precursor, 35 μm cellulose membrane, UV light for 12 h).

[0064] Comparative Example 7: Blank Control (No additives added) Polymer precursor: 0.1g LiTFSI + 0.2g VC + 0.05g IRGACURE819 + 0.05g trimethyl borate; Additives: None; Preparation process: Same as in Example 1 (15 μL precursor, 35 μm cellulose membrane, UV light for 12 h).

[0065] The button batteries prepared in Examples 1-4 and Comparative Examples 1-7 were left to stand at 25°C for 12 h, and then subjected to charge-discharge cycles at a constant current of 5.4 mA, with a single cycle time of 48 min, for a total of 100 cycles. After the cycle test, electrochemical impedance spectroscopy (EIS) was performed on each battery, and the lithium deposition morphology of the negative electrode was characterized using scanning electron microscopy (SEM). Short circuits were determined by monitoring abnormalities in the charge-discharge curves. The test results are shown in Table 1. Table 1 Test Results

[0066] Figure 2 Impedance diagram of a solid polymer lithium metal symmetric battery provided in Embodiment 1 of this application; please refer to Figure 2 This indicates that the symmetrical battery is not short-circuited. Figure 3 This is a curve showing the long-cycle voltage versus time variation of a solid polymer lithium metal symmetric battery provided in Embodiment 1 of this application. Please refer to... Figure 3 The overpotential is stable, and there is no significant increase or decrease in polarization, indicating that the lithium metal symmetric battery is stable during cycling.

[0067] One or more technical solutions in the embodiments of this application have at least the following technical effects or advantages: (1) The composition provided in the embodiments of this application can form a stable solid electrolyte interface layer at the negative electrode interface. The solid electrolyte interface layer is an organic-inorganic bilayer SEI, namely a polymer layer rich in B and an inorganic layer SEI rich in LiCl. The organic borate salt preferentially reacts with the lithium metal negative electrode to generate a polymer SEI rich in B. Then the chloride reacts again at the negative electrode interface to generate SEI, thereby forming an organic-inorganic bilayer SEI to synergistically improve the interface between the lithium metal negative electrode and the polymer solid electrolyte. (2) The method of using the composition provided in the embodiments of this application has the advantages of simple operation, good industrial compatibility and low cost, and is suitable for the preparation of polymer solid lithium metal batteries.

[0068] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A composition comprising: A polymer electrolyte precursor, an organic lithium borate salt capable of reacting with lithium metal to form a boron-rich polymer SEI layer, and a chloride capable of reacting with lithium metal to form a lithium chloride-rich SEI layer; The mass of the organic lithium borate salt and the mass of the chloride are each not less than 1% of the mass of the polymer electrolyte precursor. The mass of the organic lithium borate salt and the mass of the chloride are each 1% to 10% of the mass of the polymer electrolyte precursor.

2. The composition of claim 1, wherein, The organic lithium borate salt includes at least one of lithium oxalate borate, lithium difluoro oxalate borate, and lithium tetrafluoroborate; and / or 3. The composition of claim 1, wherein, The chloride includes at least one of tetrachloroethylene, sulfur dioxide chloride, and indium trichloride. Raw materials of the polymer electrolyte precursor 4. The composition of claim 1, wherein, The anion acceptor includes at least one of borate molecules, calixarene derivatives, and nitrogen-containing heterocyclic compounds; and / or The organic small molecule includes metal salts and skeleton materials; and / or 5. The composition of claim 4, wherein, The initiator includes at least one of phenyl bis (2, 4, 6-trimethylbenzoyl) phosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexyl benzophenone, benzophenone, 4-methylbenzophenone, 2, 4, 6-trimethylbenzophenone, thio propoxy thioxanthone, and isopropyl thioxanthone. The anion acceptor is 2 to 20 parts by mass, the organic small molecule is 50 to 90 parts by mass, and the initiator is 0.1 to 5 parts by mass.

7. A preparation method of a modified lithium metal anode-separator, the method comprising:

6. The composition according to claim 4 or 5, characterized in that, attaching a separator to the surface of a lithium metal anode to obtain a first lithium metal anode-separator structure; immersing the surface of the separator of the lithium metal anode-separator structure in the composition of any one of claims 1 to 6 to obtain a second lithium metal anode-separator structure; subjecting the second lithium metal anode-separator structure to a photopolymerization reaction to obtain a modified lithium metal anode-separator. The volume of the composition is 10 to 20 μL.

9. A modified lithium metal anode-separator prepared by the method of claim 7 or 8.

8. The method of claim 7, wherein, 10. A battery comprising the modified lithium metal anode-separator of any one of claim 9. ​ ​

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