Lewis acid-base complex additive modified ether-based electrolyte, preparation method thereof and application of lewis acid-base complex additive modified ether-based electrolyte in lithium metal battery

Abstract

The invention discloses a lewis acid-base complex additive modified ether-based electrolyte and a preparation method and application thereof in a lithium metal battery, and belongs to the technical field of a lithium secondary battery and an electrolyte used by the lithium secondary battery, and the preparation method comprises the following steps: directly adding a proper amount of lewis acid and lewis base into a basic electrolyte, uniformly stirring, standing, filtering, washing, and drying to obtain the lewis acid-base complex additive modified ether-based electrolyte. The lewis acid-base complex multifunctional additive is generated in situ in the basic electrolyte by utilizing a lewis acid-base coordination reaction between the ether electrolyte and the ether electrolyte, and then the ether electrolyte modified by the lewis acid-base complex multifunctional additive is prepared. According to the ether-based electrolyte optimized and modified through the Lewis acid-base complex additive prepared through the method, the functional attribute and stability of interface films (CEI and SEI) can be synergistically improved, side reactions, electrolyte consumption and active lithium loss are reduced, and positive electrode transition metal dissolution and lithium metal negative electrode (LMA) surface lithium dendrite growth are inhibited; and moreover, the lithium ion battery can also be adapted to a high-load positive electrode, so that the energy density, coulombic efficiency, cycle life and safety of the LMBs are further comprehensively improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium secondary batteries and electrolytes used therein, and in particular relates to an ether-based electrolyte modified with a Lewis acid-base complex additive, a preparation method thereof, and application in lithium metal batteries. Background Art

[0002] As a core component of new energy vehicles, power batteries have low energy density, short cycle life, high manufacturing costs, and potential safety hazards. These are the primary factors contributing to the current low range, short service life, high price, and frequent safety incidents of new energy vehicles. Therefore, the development of next-generation high-performance power batteries (high specific energy, low cost, long life, and high safety) is urgent.

[0003] Lithium metal batteries (LMBs) have a high energy density (theoretical specific capacity of 3860 mAh g -1 ) is considered the "ultimate solution" for next-generation battery technology, with enormous market potential, especially in electric vehicles, low-altitude economy, and energy storage. However, the development and application of LMBs based on current commercial organic electrolytes still face several technical bottlenecks. For example:

[0004] (1) Side reactions continuously occur between conventional liquid organic carbonate electrolytes and the positive electrode and highly active lithium metal anode (LMA), leading to unstable electrode / electrolyte interface, damage to electrode structure, and continuous consumption of electrolyte, resulting in low coulombic efficiency and short cycle life of the battery. (2) On the LMA side, the repeated rupture and reconstruction of the unstable solid electrolyte interface (SEI) further accelerates the loss of active lithium and significantly shortens the battery life. In addition, the uncontrollable growth of lithium dendrites caused by uneven lithium deposition will cause risks such as battery short circuit and thermal runaway. (3) On the positive electrode side, the stability and functional properties of the positive electrode / electrolyte interface (CEI) are poor, leading to the dissolution of positive electrode metal and structural damage, thereby affecting the positive electrode capacity and cycle durability, reducing battery capacity and shortening service life. This problem is particularly serious under practical conditions with high positive electrode load (>15 mg cm -2 ) becomes particularly significant. (4) The high volatility and flammability of liquid organic carbonate electrolytes lead to safety hazards such as leakage, fire, and even explosion in LMBs. These problems seriously restrict the development and application of high-performance LMBs and become a difficult problem for the development of high-energy-density, low-cost, long-life, and high-safety LMBs.

[0005] Ether-based electrolytes have excellent LMA compatibility, high ionic conductivity and excellent fast charging capability. When combined with additives, they can enhance SEI stability, form a functionalized SEI interface and inhibit dendrite growth. Among them, the most common additive is lithium nitrate (LiNO3). LiNO3 is added to the ether-based electrolyte to generate a functionalized SEI rich in Li3N through its preferential reduction characteristics, which can effectively improve SEI stability and improve LMBs performance. However, when using a high-load positive electrode, the above problems are still difficult to solve, resulting in the need to further improve the comprehensive performance of LMBs. Based on this, Li Chen et al. from Anhui University of Technology (Study on the interface regulation and electrochemical performance of lithium metal batteries by multifunctional electrolyte additives) simultaneously introduced two functional additives, LiNO3 and vinylene carbonate (VC), into a new fluorine-free electrolyte (1MLiBOB in DME) to further improve the flexibility and stability of SEI and improve the cycle performance of the battery. The Li-Li symmetric battery can be used at 0.5m Acm -2 , 0.5mAh cm -2 The stable cycle time was 1000 h under the conditions of -2 The LFP / / Li full battery matched with the lithium iron phosphate (LFP) positive electrode can stably cycle for more than 50 cycles. Obviously, this performance still needs to be greatly improved to achieve commercial application. Some other modification methods, such as Zhang Manshu et al. from China University of Geosciences (Study on the inhibition of lithium metal negative electrode dendrites and electrochemical properties by electrolyte additives), use a thin film substance as an additive to the electrolyte to inhibit the growth of lithium dendrites, thereby improving the cycle life and safety of the battery. However, its additive is a thin film made by electrospinning polyacrylonitrile (PAN), magnesium difluoride (MgF2) and NN dimethylformamide (DMF). The preparation process is complicated and there are too many pre-steps, which will undoubtedly lead to an increase in cost and is not conducive to large-scale production and application.

[0006] In summary, the existing technologies still have the following shortcomings: (1) Most of the electrolyte additives reported so far have a single function (lack of multifunctionality), which makes it difficult to synergistically solve the aforementioned problems; (2) Some additives need to be synthesized in advance and then added to the electrolyte to prepare the electrolyte containing the additive, which is a complicated process; (3) Although some multifunctional additives can be prepared through special design, their synthesis process is complex, costly, and time-consuming, which is not conducive to large-scale production and application.

[0007] Therefore, there is an urgent need to study new functionalized electrolytes to solve the aforementioned key problems faced in the development of high-performance LMBs. Summary of the Invention

[0008] In response to the above technical problems, the present invention proposes an ether-based electrolyte modified with a Lewis acid-base complex additive, a preparation method thereof, and an application in lithium metal batteries; the ether-based electrolyte is modified and optimized by using a Lewis acid-base complex multifunctional additive generated in situ in the electrolyte, and the preferential oxidation and reduction properties of the Lewis acid-base complex are utilized to simultaneously achieve in situ construction of highly stable functionalized CEI and SEI, inhibit the occurrence of side reactions and lithium dendrite growth, and adapt to high-load positive electrode systems, thereby achieving a comprehensive improvement in the energy density, coulombic efficiency, cycle life, and safety of LMBs.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] One of the technical solutions of the present invention

[0011] An ether-based electrolyte modified with a Lewis acid-base complex additive, the raw materials of which include a basic electrolyte, a Lewis acid, and a Lewis base;

[0012] The Lewis acid is selected from at least one of lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), boron trifluoride (BF3), zinc fluoride (SnF2), ferric chloride (FeCl3), fluoroethylene carbonate (FEC), aluminum chloride (AlCl3) and bisfluoroethylene carbonate (DFEC);

[0013] The Lewis base is at least one of lithium nitrate (LiNO3) and / or tris(2,2,2-trifluoroethyl)phosphite, triphenyl phosphite (TPPi), diphenyldimethoxysilane, hexamethyldisilazane, hexa(2,2,2-trifluoroethoxy)cyclotriphosphazene, tris(trimethylsilyl) phosphite (TMSP), trimethyl phosphite (TMPi), lithium triethanolamine, 4,5-dicyano-2-(trifluoromethyl)isopyrazole and phosphites, that is, the Lewis base is a single lithium nitrate, or tris(2,2,2-trifluoroethyl)phosphite, triphenyl phosphite (TPPi), diphenyldimethoxysilane, hexamethyldisilazane, hexa(2,2,2-trifluoroethoxy)cyclotriphosphazene, tris(trimethylsilyl) phosphite (TMSP), trimethyl phosphite (TMPi), lithium triethanolamine, 4,5-dicyano-2-(trifluoromethyl)isopyrazole and phosphites. at least one of (tris(2,2,2-trifluoroethyl)phosphite, triphenyl phosphite (TPPi), diphenyldimethoxysilane, hexamethyldisilazane, hexa(2,2,2-trifluoroethoxy)cyclotriphosphazene, tris(trimethylsilyl) phosphite (TMSP), trimethyl phosphite (TMPi), lithium triethanolamine, 4,5-dicyano-2-(trifluoromethyl)isopyrazole and phosphites); for example, the Lewis base is lithium nitrate, or tris(trimethylsilyl) phosphite (TMSP), or lithium nitrate + tris(trimethylsilyl) phosphite (TMSP);

[0014] The addition amount of the Lewis acid and the Lewis base is 0.5-10 wt % of the basic electrolyte respectively.

[0015] Beneficial Effects: The ether-based electrolyte optimized and modified with the Lewis acid-base complex additive prepared in this invention can synergistically enhance the functional properties and stability of the interfacial films (CEI and SEI), reduce side reactions, electrolyte consumption, and active lithium loss, and inhibit the dissolution of transition metals in the cathode and the growth of lithium dendrites on the LMA surface. Furthermore, it is compatible with high-load cathodes, comprehensively improving the energy density, coulombic efficiency, cycle life, and safety of LMBs.

[0016] Optionally, the basic electrolyte is prepared by dissolving an electrolyte salt in an ether solvent.

[0017] Furthermore, the electrolyte salt is at least one selected from lithium hexafluorophosphate, bisoxalatoborate, tetrafluoroborate, difluorooxalatoborate, bis(trifluoromethylsulfonyl)imide, bis(fluorosulfonyl)imide, difluorophosphate, and difluorooxalatophosphate.

[0018] Furthermore, the ether solvent is selected from at least one of 1,3-dioxolane (DOL), 1,3-dioxane (DOX), ethylene glycol dimethyl ether (DME), ethylene glycol ethyl ether, propylene glycol methyl ether, and propylene glycol ethyl ether.

[0019] Furthermore, the basic electrolyte is 1M LiTFSI (lithium bis(trifluoromethylsulfonyl)imide) / DME-DOL (1:1 v / v).

[0020] Furthermore, the concentration of the electrolyte salt in the basic electrolyte is 0.5-5.0M.

[0021] Optionally, the Lewis acid is 1 wt% LiBF4 and 5 wt% FEC; the Lewis base is 2 wt% LiNO3; or,

[0022] The Lewis acid is 10 wt% FEC, and the Lewis base is 0.5 wt% TMSP and 2 wt% LiNO3; or,

[0023] The Lewis acid is 5 wt% DFEC, and the Lewis base is 0.5 wt% TMSP and 2 wt% LiNO3; or,

[0024] The Lewis acid is 2 wt % SnF 2 and 4 wt % FEC, and the Lewis base is 1 wt % TPPi and 2 wt % LiNO 3 .

[0025] The second technical solution of the present invention:

[0026] A method for preparing an ether-based electrolyte modified with a Lewis acid-base complex additive comprises the following steps:

[0027] The above-mentioned Lewis acid and Lewis base are directly added to the basic electrolyte, stirred evenly, and allowed to stand. The Lewis acid-base complex additive is generated in situ in the basic electrolyte by utilizing the Lewis acid-base coordination reaction principle between the Lewis acid and the Lewis base, thereby preparing the ether-based electrolyte modified by the Lewis acid-base complex additive.

[0028] Optionally, the adding condition is: adding the Lewis acid and Lewis base to the basic electrolyte in an atmosphere of H2O <0.1 ppm, O2 <0.1 ppm, and the remainder being argon.

[0029] Optionally, the stirring is magnetic stirring, and the conditions are: stirring at a rotation speed of 500 rpm for 10 minutes.

[0030] Optionally, the standing time is 3-24 hours.

[0031] The third technical solution of the present invention:

[0032] Application of the above-mentioned Lewis acid-base complex additive-modified ether-based electrolyte in lithium metal batteries.

[0033] Optionally, the lithium metal battery is a half-cell or full-cell containing an ether-based electrolyte modified with a Lewis acid-base complex additive;

[0034] Wherein, the half-cell is a Li / / Cu and Li / / Li half-cell assembled from an ether-based electrolyte modified with a Lewis acid-base complex additive;

[0035] The full battery is assembled by assembling an ether-based electrolyte modified with a Lewis acid-base complex additive with LFP and LMA.

[0036] Furthermore, the loading amount of LFP is 15 mg cm -2 .

[0037] The fourth technical solution of the present invention:

[0038] A lithium metal battery comprises a positive electrode, a negative electrode and an electrolyte, wherein the electrolyte contains the above-mentioned Lewis acid-base complex additive.

[0039] Optionally, the positive electrode of the lithium metal battery is selected from at least one of lithium iron phosphate, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium cobalt oxide, lithium rich manganese base, lithium nickel manganese oxide, and lithium iron manganese phosphate.

[0040] Compared with the prior art, the present invention has the following advantages and technical effects:

[0041] Technological innovation:

[0042] 1. In situ generation of Lewis acid-base complexes in the electrolyte:

[0043] By rationally designing the structures and ratios of the selected Lewis acid and Lewis base and adding them to the ether-based electrolyte, a multifunctional Lewis acid-base complex is generated in situ in the electrolyte by utilizing the Lewis acid-base complex reaction principle between the two.

[0044] 2. Preferential redox properties of Lewis acid-base complex additives

[0045] The Lewis acid-base complex multifunctional additive generated by in-situ reaction in the electrolyte can undergo oxidation and reduction decomposition preferentially over the electrolyte solvent, and form a composite CEI and SEI rich in organic-inorganic functional components (LiF, Li3N or BO, etc.) with high ionic conductivity, high toughness and low impedance on the electrode surface;

[0046] 3. Multifunctional properties of Lewis acid-base complex additives:

[0047] Traditional electrolyte additives (such as LiNO3, fluoroethylene carbonate (FEC), etc.) usually exist in a single functional form, making it difficult to synergistically optimize the chemical stability and kinetic performance of CEI / SEI. The present invention introduces two or more specific types of additives (Lewis acid and Lewis base) into the electrolyte, causing them to react in situ in the electrolyte to form a Lewis acid-base complex multifunctional additive. This additive can synergistically improve the functional properties and stability of the interfacial film (CEI and SEI), reduce the occurrence of side reactions, electrolyte consumption and active lithium loss, and inhibit the dissolution of positive transition metals and the growth of lithium dendrites on the LMA surface.

[0048] 4. Ether-based electrolytes modified with Lewis acid-base complex additives are suitable for high-load cathodes, comprehensively improving the energy density, coulombic efficiency, cycle life, and safety of LMBs.

[0049] Industry value:

[0050] 1. The Lewis acid-base complex additive-modified ether-based electrolyte proposed in the present invention has a simple preparation method, low-cost and easily available raw materials, excellent electrochemical performance, and good market application prospects.

[0051] 2. The LMBs based on the ether-based electrolyte modified with the Lewis acid-base complex additive of the present invention perform well in terms of energy density, coulombic efficiency, cycle life and safety, and have the potential for further expansion of applications.

[0052] 3. The method of the present invention is compatible with the current industrialization route of lithium secondary batteries and has practical prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings:

[0054] Figure 1 The forward CV scanning curves of the electrolytes of Comparative Example 2 and Examples 5, 6, and 8 are shown;

[0055] Figure 2 Negative CV scanning curves of the electrolytes of Comparative Example 2 and Examples 5, 6, and 8;

[0056] Figure 3 EIS curves of the activated Li / / Cu half-cells assembled with the electrolytes of Comparative Example 2 and Examples 5, 6, and 8;

[0057] Figure 4 The Li / / Cu half-cell cycle test curves of the electrolytes assembled in Comparative Example 2 and Examples 5, 6, and 8;

[0058] Figure 5The Li / / Li half-cell cycle test curves of the electrolytes assembled from Comparative Example 2 and Examples 5, 6, and 8;

[0059] Figure 6 The LFP / / Li full cell rate test curves for the electrolytes of Comparative Example 2 and Examples 5, 6, and 8 are shown;

[0060] Figure 7 Cycling test curves of LFP / / Li full batteries assembled with the electrolytes of Comparative Example 2 and Examples 5, 6, and 8;

[0061] Figure 8 SEM images of the Cu surface of Li / / Cu half-cells assembled with the electrolytes of Comparative Example 2 and Examples 5, 6, and 8 after 100 cycles. DETAILED DESCRIPTION

[0062] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0063] It should be understood that the terms described herein are intended only to describe particular embodiments and are not intended to limit the present invention. In addition, for numerical ranges herein, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any intermediate value within a stated value or stated range and any other stated value or intermediate value within the stated range is also encompassed by the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0064] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0065] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0066] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0067] The present invention provides an ether-based electrolyte modified with a Lewis acid-base complex additive, a preparation method thereof, and an application in a lithium metal battery. The invention aims to improve the functional properties and stability of the interfacial films (CEI and SEI), reduce the occurrence of side reactions, electrolyte consumption, and active lithium loss, inhibit the dissolution of positive electrode transition metals and the growth of lithium dendrites on the LMA surface, and can be matched with a high-load positive electrode, thereby comprehensively improving the energy density, coulombic efficiency, safety, cycle life, and overall performance of the lithium metal battery.

[0068] The embodiment of the present invention discloses an ether-based electrolyte modified with a Lewis acid-base complex additive, comprising a basic electrolyte, a Lewis acid, and a Lewis base;

[0069] The Lewis acid is selected from at least one of lithium tetrafluoroborate (LiBF4), lithium hexafluorophosphate (LiPF6), boron trifluoride (BF3), zinc fluoride (SnF2), ferric chloride (FeCl3), fluoroethylene carbonate (FEC), aluminum chloride (AlCl3) and bisfluoroethylene carbonate (DFEC);

[0070] The Lewis base is selected from at least one of lithium nitrate (LiNO3), tris(2,2,2-trifluoroethyl)phosphite, triphenyl phosphite (TPPi), diphenyldimethoxysilane, hexamethyldisilazane, hexa(2,2,2-trifluoroethoxy)cyclotriphosphazene, tris(trimethylsilyl) phosphite (TMSP), trimethyl phosphite (TMPi), lithium triethanolamine and 4,5-dicyano-2-(trifluoromethyl)isopyrazole, and phosphites.

[0071] The Lewis acids and bases selected in the present invention have the following characteristics: good miscibility with conventional ether-based electrolytes; good film-forming properties and functional effects, such as accelerating interfacial ion conduction, inhibiting lithium dendrite growth, and inhibiting positive electrode metal dissolution; safety and environmental protection, low toxicity and high biodegradability, non-flammability, and a high flash point.

[0072] In some optional embodiments, the base electrolyte is 1M LiTFSI / DME-DOL (1:1 v / v) or 1M LiTFSI / DME-DOL (1:1 v / v) + 0.1-10 wt.% LiNO3.

[0073] In some optional embodiments, the added amount of Lewis acid and Lewis base is 0.5-10 wt % of the basic electrolyte respectively.

[0074] The present invention also discloses a method for preparing an ether-based electrolyte modified with a Lewis acid-base complex additive, comprising the following steps:

[0075] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), a Lewis acid and a Lewis base were simultaneously added to the base electrolyte, magnetically stirred (500rpm, 10min), and allowed to stand for 3-24h until a homogeneous, transparent solution was formed. The Lewis acid-base complex reaction between the Lewis acid and the Lewis base in situ generated a Lewis acid-base complex multifunctional additive.

[0076] In some optional embodiments, the Lewis acid-base complex multifunctional additive is used in an amount of 0.5-10 wt % of the base electrolyte.

[0077] In addition, the present invention also discloses the use of the ether-based electrolyte modified by the Lewis acid-base complex additive in a lithium metal battery.

[0078] The ether-based electrolyte modified with the Lewis acid-base complex additive of the present invention is suitable for various types of LMBs. LMBs containing the electrolyte of the present invention can be subjected to charge-discharge tests under high-load positive electrode conditions, demonstrating improved rate performance, longer cycle life, higher coulombic efficiency, and greater capacity retention.

[0079] 1. Enhance the compatibility between electrolyte and lithium metal anode:

[0080] Due to the characteristics of Lewis acid-base complexes, the side reactions between the electrolyte and the lithium metal negative electrode are effectively reduced.

[0081] 2. Improve the functional properties and stability of the interfacial film (CEI and SEI):

[0082] Through the preferential redox of Lewis acid-base complexes on the surface of the cathode and LMA, composite CEI and SEI with high ionic conductivity, high toughness and low impedance, which are rich in organic-inorganic functional components (LiF, Li3N or BO, etc.), are generated. This significantly improves the functional properties and stability of the interfacial film, reduces the interfacial impedance, effectively dissolves the cathode metal and inhibits the growth of lithium dendrites, thereby greatly improving the comprehensive electrochemical performance of LMBs.

[0083] 3. Improve the stability of the electrolyte under high positive load conditions:

[0084] Compared with conventional ether-based electrolytes, the electrolyte of the present invention has strong compatibility with high-load positive electrodes and can ensure the stability of battery cycle performance under high-load conditions.

[0085] 4. Compared with non-in-situ synthesized additives, it reduces costs and increases efficiency:

[0086] That is, the Lewis acid-base complex multifunctional additive of the present invention can be synthesized in situ in the electrolyte, eliminating the complex process and resource consumption required for preparing the additive in advance, making it more convenient and feasible, and significantly improving battery performance.

[0087] In summary, the present invention introduces Lewis acid and Lewis base additives of specific structures into conventional ether-based electrolytes, and utilizes the Lewis acid-base complex reaction between the two to in situ generate Lewis acid-base complex multifunctional additives. While maintaining the good basic performance of the electrolyte, it significantly inhibits the occurrence of side reactions and inhibits the dissolution of positive electrode metal and lithium dendrite growth, improves the interface stability and cycle performance of LMBs, and is suitable for high-load positive electrodes, which is of great significance for promoting the research and development of high-performance LMBs.

[0088] The raw materials used in the present invention are all purchased from the market.

[0089] The technical solution of the present invention is further illustrated by the following examples.

[0090] Comparative Example 1

[0091] In a glove box, 1 M LiTFSI / DOL-DME was prepared as the basic electrolyte A, and electrochemical tests and analyses were performed.

[0092] Li / / Cu and Li / / Li half-cells were assembled using basic electrolyte A and electrochemical tests were performed.

[0093] The basic electrolyte A was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0094] Comparative Example 2

[0095] Modified electrolyte B: basic electrolyte A + 2wt% LiNO3.

[0096] Li / / Cu and Li / / Li half-cells were assembled using modified electrolyte B and electrochemical tests were performed.

[0097] Modified electrolyte B was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0098] Comparative Example 3

[0099] Modified electrolyte C: basic electrolyte A + 2wt% TMSP.

[0100] Li / / Cu and Li / / Li half-cells were assembled with modified electrolyte C and electrochemical tests were performed.

[0101] The modified electrolyte C was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0102] Example 1

[0103] An ether-based electrolyte modified with a Lewis acid-base complex additive, comprising:

[0104] Modified electrolyte D: modified electrolyte B prepared in Comparative Example 2 + 0.5 wt% LiBF4.

[0105] A method for preparing an ether-based electrolyte modified with a Lewis acid-base complex additive comprises the following steps:

[0106] In an argon atmosphere glove box (H2O <0.1ppm, O2 <0.1ppm), a Lewis acid and a Lewis base were simultaneously added to a base electrolyte solution, magnetically stirred (500rpm, 10min), and allowed to stand for 3-24h to form a homogeneous, transparent solution. The Lewis acid-base complex reaction between the Lewis acid and the Lewis base in situ generated a Lewis acid-base complex multifunctional additive (the preparation process of the ether-based electrolyte modified with the Lewis acid-base complex additive in the following examples was the same as in Example 1).

[0107] Li / / Cu and Li / / Li half-cells were assembled using modified electrolyte D and electrochemical tests were performed.

[0108] The modified electrolyte D was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0109] Example 2

[0110] Modified electrolyte E: modified electrolyte B prepared in Comparative Example 2 + 0.5 wt% FEC.

[0111] Li / / Cu and Li / / Li half-cells were assembled using modified electrolyte E and electrochemical tests were performed.

[0112] The modified electrolyte E was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0113] Example 3

[0114] Modified electrolyte F: modified electrolyte C prepared in Comparative Example 3 + 10 wt% FEC.

[0115] Li / / Cu and Li / / Li half-cells were assembled using modified electrolyte F and electrochemical tests were performed.

[0116] The modified electrolyte F was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0117] Example 4

[0118] Modified electrolyte G: modified electrolyte B prepared in Comparative Example 2 + 10 wt% LiBF4.

[0119] Li / / Cu and Li / / Li half-cells were assembled using modified electrolyte G and electrochemical tests were performed.

[0120] The modified electrolyte G was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0121] Example 5

[0122] Modified electrolyte H: modified electrolyte B prepared in Comparative Example 2 + 2 wt% LiBF4.

[0123] Li / / Cu and Li / / Li half-cells were assembled with the modified electrolyte H and electrochemical tests were performed.

[0124] The modified electrolyte H was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0125] Example 6

[0126] Modified electrolyte I: modified electrolyte B prepared in Comparative Example 2 + 5 wt% FEC.

[0127] Li / / Cu and Li / / Li half-cells were assembled using modified electrolyte I and electrochemical tests were performed.

[0128] Modified electrolyte I was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0129] Example 7

[0130] Modified electrolyte J: modified electrolyte B prepared in Comparative Example 2 + 10 wt% LiBF4 + 0.5 wt% FEC.

[0131] Li / / Cu and Li / / Li half-cells were assembled using modified electrolyte J and electrochemical tests were performed.

[0132] The modified electrolyte J was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0133] Example 8

[0134] Modified electrolyte K: modified electrolyte B prepared in Comparative Example 2 + 1 wt% LiBF4 + 5 wt% FEC.

[0135] Li / / Cu and Li / / Li half-cells were assembled with the modified electrolyte K and electrochemical tests were performed.

[0136] The modified electrolyte K was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0137] Example 9

[0138] Modified electrolyte L: modified electrolyte B prepared in Comparative Example 2 + 0.5 wt% LiBF4 + 10 wt% FEC.

[0139] Li / / Cu and Li / / Li half-cells were assembled with the modified electrolyte L and electrochemical tests were performed.

[0140] The modified electrolyte L: was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0141] Example 10

[0142] Modified electrolyte M: modified electrolyte C prepared in Comparative Example 3 + 1 wt% LiBF4 + 8 wt% FEC.

[0143] The modified electrolyte M was used to assemble Li / / Cu and Li / / Li half-cells, and electrochemical tests were performed.

[0144] The modified electrolyte M was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0145] Example 11

[0146] Modified electrolyte N: modified electrolyte B prepared in Comparative Example 2 + 0.5 wt% LiBF4 + 0.5 wt% FEC.

[0147] Li / / Cu and Li / / Li half-cells were assembled with the modified electrolyte N and electrochemical tests were performed.

[0148] The modified electrolyte N was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0149] Example 12

[0150] Modified electrolyte O: modified electrolyte B prepared in Comparative Example 2 + 10 wt% LiBF4 + 10 wt% FEC.

[0151] Li / / Cu and Li / / Li half-cells were assembled with the modified electrolyte O and electrochemical tests were performed.

[0152] The modified electrolyte O was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0153] Example 13

[0154] Modified electrolyte P: modified electrolyte B prepared in Comparative Example 2 + 0.5 wt % TMSP + 10 wt % FEC.

[0155] Li / / Cu and Li / / Li half-cells were assembled with the modified electrolyte P and electrochemical tests were performed.

[0156] The modified electrolyte P was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0157] Example 14

[0158] Modified electrolyte Q: modified electrolyte B prepared in Comparative Example 2 + 0.5 wt % TMSP + 5 wt % DFEC.

[0159] The modified electrolyte Q was used to assemble Li / / Cu and Li / / Li half-cells, and electrochemical tests were performed.

[0160] The modified electrolyte Q was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0161] Example 15

[0162] Modified electrolyte R: modified electrolyte B prepared in Comparative Example 2 + 1 wt% TPPi + 2 wt% SnF2.

[0163] Li / / Cu and Li / / Li half-cells were assembled with the modified electrolyte R and electrochemical tests were performed.

[0164] The modified electrolyte R was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0165] Example 16

[0166] Modified electrolyte S: modified electrolyte B prepared in Comparative Example 2 + 1wt% TPPi + 2wt% SnF2 + 4wt% FEC.

[0167] Li / / Cu and Li / / Li half-cells were assembled with the modified electrolyte S and electrochemical tests were performed.

[0168] The modified electrolyte S was mixed with LFP (loaded with 15 mg cm -2 ) and LMA to assemble full batteries and perform electrochemical tests.

[0169] Effect verification: electrochemical performance test

[0170] 1. Three-electrode cyclic voltammetry (CV) test

[0171] The electrolytes of the comparative examples and embodiments were assembled into a three-electrode system, and CV tests were performed.

[0172] 2. Li / / Cu and Li / / Li half-cell tests

[0173] The electrolytes of the above comparative examples and embodiments were used to assemble Li-Cu and Li / / Li half-cells, and cycle tests were performed.

[0174] 3.LFP / / Li full battery test

[0175] The LFP / / Li half-cells assembled with the above comparative example and example electrolytes were subjected to rate and cycle tests.

[0176] 4.SEM testing

[0177] After the Li-Cu half-cells assembled with the electrolytes of the comparative examples and embodiments were cycled, the Cu surface morphology was tested.

[0178] Result analysis:

[0179] Compared with the commercial conventional ether-based electrolyte (Comparative Example 2), the ether-based electrolyte modified with the Lewis acid-base complex additive provided by the present invention exhibits significantly improved electrochemical performance. Specifically, the functionalized Lewis acid-base complex additive contained in the ether-based electrolyte modified with the Lewis acid-base complex additive provided by the present invention can be preferentially oxidized on the electrode surface (e.g. Figure 1 as shown) and restore (as Figure 2 As shown in Figure 2), an interfacial film (CEI and SEI) rich in functional components (LiF, Li3N and BO, etc.) is generated. These functional components can significantly improve the functional properties and stability of the interfacial film, and can effectively improve the interfacial ion conduction and reduce the interfacial impedance (as shown in Figure 2). Figure 3 At the same time, it can also effectively inhibit the side reaction between the electrolyte and LMA, reduce the decomposition of the electrolyte and the loss of active lithium, reduce the lithium nucleation overpotential and inhibit the growth of lithium dendrites and the corrosion and pulverization of active lithium (as shown). Figure 8 As shown), the Li / / Cu and Li / / Li half-cells exhibit higher coulombic efficiency and better cycle durability (as shown Figure 4 and 5As shown). In addition, the ether-based electrolyte modified with the Lewis acid-base complex additive provided in the embodiment of the present invention can match and be applied to high-load positive electrodes (LFP, 15 mg cm -2 ), the assembled LFP / / Li full battery has excellent rate performance and long cycle life. The capacity retention rate at 8C current can reach 65% (such as Figure 6 As shown), and the capacity retention rate after 300 cycles at 1C current is more than 90% (as shown Figure 7 The above test results show that the ether-based electrolyte modified with the Lewis acid-base complex additive provided by the present invention has excellent electrochemical properties and is suitable for LMBs with high-load positive electrode systems, and can achieve a comprehensive improvement in the overall performance of the battery.

[0180] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. An ether-based electrolyte modified with a Lewis acid-base complex additive, characterized in that: The raw materials include a basic electrolyte, a Lewis acid, and a Lewis base; Wherein, the Lewis acid is selected from one or more of lithium tetrafluoroborate, lithium hexafluorophosphate, boron trifluoride, zinc fluoride, ferric chloride, fluoroethylene carbonate, aluminum chloride and difluoroethylene carbonate; The Lewis base is at least one of lithium nitrate and / or tris(2,2,2-trifluoroethyl)phosphite, triphenyl phosphite, diphenyldimethoxysilane, hexamethyldisilazane, hexa(2,2,2-trifluoroethoxy)cyclotriphosphazene, tris(trimethylsilyl)phosphite, trimethyl phosphite, lithium triethanolamine, 4,5-dicyano-2-(trifluoromethyl)isopyrazole, and phosphites; The addition amount of the Lewis acid and the Lewis base is 0.5-10 wt % of the basic electrolyte respectively.

2. The ether-based electrolyte modified with a Lewis acid-base complex additive according to claim 1, characterized in that: The electrolyte salt in the basic electrolyte is lithium bis(trifluoromethylsulfonyl)imide; and the solvent is an ether solvent.

3. The ether-based electrolyte modified with a Lewis acid-base complex additive according to claim 2, characterized in that: The concentration of the electrolyte salt in the basic electrolyte is 0.5-5.0M.

4. The ether-based electrolyte modified with a Lewis acid-base complex additive according to claim 2, characterized in that: The ether solvent is selected from at least one of 1,3-dioxolane, 1,3-dioxane, ethylene glycol dimethyl ether, ethylene glycol ethyl ether, propylene glycol methyl ether, and propylene glycol ethyl ether.

5. A method for preparing an ether-based electrolyte modified with a Lewis acid-base complex additive according to any one of claims 1 to 4, characterized in that: The following steps are involved: The Lewis acid and Lewis base are added to the basic electrolyte, stirred evenly, and allowed to stand. A Lewis acid-base complex additive is generated in situ in the basic electrolyte by utilizing the Lewis acid-base coordination reaction principle between the Lewis acid and the Lewis base, thereby preparing an ether-based electrolyte modified with the Lewis acid-base complex additive.

6. The method for preparing an ether-based electrolyte modified with a Lewis acid-base complex additive according to claim 5, characterized in that: The adding condition is: adding the Lewis acid and Lewis base to the basic electrolyte in an atmosphere of H2O<0.1ppm, O2<0.1ppm, and the remainder being argon.

7. The method for preparing an ether-based electrolyte modified with a Lewis acid-base complex additive according to claim 5, characterized in that: The stirring was magnetic stirring, and the conditions were: stirring at a rotation speed of 500 rpm for 10 min.

8. The method for preparing an ether-based electrolyte modified with a Lewis acid-base complex additive according to claim 5, characterized in that: The standing time is 3-24h.

9. Use of an ether-based electrolyte modified with the Lewis acid-base complex additive according to any one of claims 1 to 4 in a lithium metal battery.

10. A lithium metal battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The electrolyte is an ether-based electrolyte modified by the Lewis acid-base complex additive according to any one of claims 1 to 4.

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