Secondary battery module, secondary battery, and method for manufacturing secondary battery module

Abstract

This invention provides a secondary battery assembly that exhibits excellent cycle characteristics when used in a secondary battery. The secondary battery assembly comprises a metal complex represented by formula (1): where M is an n-valent metal, m is an integer of 0 or greater and (n-1) or less, Q is a ligand selected from: unsubstituted or substituted 8-hydroxyquinoline salts, unsubstituted or substituted 2-(2-pyridyl)phenol salts, and unsubstituted or substituted 2-(2',2''-bipyridin-6'-yl)phenol salts; and L is a ligand selected from phenol salts and naphthol salts.

Description

Technical Field

[0001] This disclosure relates to a secondary battery assembly, a secondary battery, and a method for manufacturing the secondary battery assembly. Background Technology

[0002] Of all types of anodes (negative electrodes) used in rechargeable Li-ion batteries, lithium (Li) metal offers the highest theoretical specific capacity (3860 mAh / g) and the lowest standard redox potential (-3.04 V relative to the standard hydrogen electrode). However, Li metal anodes still face problems of poor nucleation uniformity and uncontrolled Li dendrite growth during repeated deposition / stripping processes. These problems are typically accompanied by low coulombic efficiency (CE) and limited lifetime of lithium metal batteries (LMBs) due to Li anode pulverization losses and dendrite-induced burst internal short circuits. These drawbacks hinder the widespread use of LMBs in practical applications.

[0003] These obstacles are mostly related to the unstable interface between the anode and electrolyte caused by the high reducing activity and large volume changes of the Li metal anode. Conventional approaches to addressing these interface problems can generally be divided into two groups. According to the first group, conventional approaches involve constructing artificial interfaces on the Li anode to replace the unstable electrolyte-derived solid electrolyte interlayer (SEI). For example, artificial interfaces incorporating inorganic salts such as LiF (NPLs 1 and 2) have been proposed.

[0004] According to the second group, the decomposition of the electrolyte is controlled by adjusting the electron gain / loss and dissociation chemistry at the anolyte interface to spontaneously obtain a stable, lithium fluoride (LiF)-rich SEI. Therefore, electrolyte or interface engineering is employed to induce the formation of a stable SEI layer. For example, electrolyte engineering strategies have been proposed to improve the formation of the SEI intermediate layer (NPLs 3 to 10).

[0005] Reference List

[0006] Non-patent literature

[0007] NPL 1: Yin, Y.-C. et al. Metal chloride perovskite thin film basedinterfacial layer for shielding lithium metal from liquid electrolyte. NatureCommunications 11, 1761, doi:10.1038 / s41467-020-15643-9 (2020). NPL 2: Cheng, X.-B. et al. Implantable Solid Electrolyte Interphasein Lithium-Metal Batteries. Chem 2, 258-270, doi:https: / / doi.org / 10.1016 / j.chempr.2017.01.003 (2017). NPL 3: Ren, X. et al. Localized High-Concentration SulfoneElectrolytes for High-Efficiency Lithium-Metal Batteries. Chem 4, 1877-1892, doi:https: / / doi.org / 10.1016 / j.chempr.2018.05.002 (2018). NPL 4: Langdon, J. & Manthiram, A. Crossover Effects in Lithium-metalBatteries with a Localized High Concentration Electrolyte and High-nickelCathodes. Advanced Materials n / a, 2205188, doi:https: / / doi.org / 10.1002 / adma.202205188 (2022). NPL 5: Basile, A., Bhatt, A. I. & O’Mullane, A. P. Stabilizinglithium metal using ionic liquids for long-lived batteries. NatureCommunications 7, ncomms11794, doi:10.1038 / ncomms11794 (2016). NPL 6: Sun, H. et al. High-Safety and High-Energy-Density LithiumMetal Batteries in a Novel Ionic-Liquid Electrolyte. Advanced Materials 32,2001741, doi:https: / / doi.org / 10.1002 / adma.202001741 (2020). NPL 7: Yu, Z. et al. Molecular design for electrolyte solventsenabling energy-dense and long-cycling lithium metal batteries. Nature Energy5, 526-533, doi:10.1038 / s41560-020-0634-5 (2020). NPL 8: Fan, X. et al. All-temperature batteries enabled byfluorinated electrolytes with non-polar solvents. Nature Energy 4, 882-890, doi:10.1038 / s41560-019-0474-3 (2019). NPL 9: Zheng, J. et al. Electrolyte additive enabled fast chargingand stable cycling lithium metal batteries. Nature Energy 2, 17012, doi:10.1038 / nenergy.2017.12 (2017). NPL 10: Biswal, P. et al. The early-stage growth and reversibility ofLi electrodeposition in Br-rich electrolytes. Proceedings of the National Academy of Sciences 118, e2012071118, doi:10.1073 / pnas.2012071118 (2021). Summary of the Invention

[0008] Technical issues

[0009] However, the protective layers proposed by NPLs 1 and 2 may inevitably break down and are not regenerable during cycling, thereby triggering severe Li-electrolyte reactions at exposed surfaces, consuming active Li and electrolytes.

[0010] While using electrolytes proposed by NPLs 3 to 10 to form an SEI can reduce Li consumption, electrolyte consumption still occurs continuously. For example, the SEI layer thus formed is vulnerable to the mechanical regulation of irregular Li growth and undergoes continuous formation and destruction during cycling, further increasing electrolyte consumption. Therefore, an excess of electrolyte (electrolyte / capacity ratio > ~40 μL / mAh) and Li (negative electrode / positive electrode capacity ratio > 2) is required to ensure battery cycle stability, which reduces the battery's energy density.

[0011] To meet the energy density requirements of practical batteries, the negative electrode / positive electrode capacity ratio and the electrolyte / capacity ratio must be around 1 and below 10 μL / mAh, respectively. These requirements are met not only through a stable SEI layer (without unnecessary electrolyte loss) but also through a highly reversible Li stripping / deposition process to avoid the loss of active Li. Unfortunately, simultaneously tuning the SEI composition and Li stripping / deposition behavior remains challenging, especially under these practical operating conditions, due to the competitive multi-stage reaction kinetics of different solvents and salts. Therefore, a well-designed stable interface on the Li anode to induce SEI formation and stabilize the Li stripping / deposition process is crucial for achieving practically high-energy-density lithium-ion batteries (LMBs).

[0012] Solution

[0013] This disclosure aims to provide a secondary battery assembly that can provide excellent cycle characteristics when used in a secondary battery.

[0014] The inventors have invented a Li metal anode having a Li-rich molecular interface layer using specific metal complexes, including lithium 8-hydroxyquinoline (Liq). The inventors discovered that lithium 8-hydroxyquinoline (Liq), known as an electron injection layer material, can be deposited (e.g., thermal evaporation or transfer) to form a coating of defined thickness. When this coating is provided on the metal anode, the resulting dense interface effectively prevents oxidation by corrosive substances under environmental conditions (e.g., O2, CO2, H2O, N2, etc.), as confirmed by X-ray diffraction experiments. Thanks to the Li-rich dense packing structure and the abundant lithium-philic pyridine nitrogen in the Liq molecule, the Liq-Li anode is protected from parasitic reactions with the electrolyte, exhibiting excellent performance even during Li nucleation and stable deposition / stripping processes. Furthermore, combined measurements by X-ray photoelectron spectroscopy (XPS) and cryo-transmission electron microscopy (cryo-TEM) indicate that the Liq interface layer induces the precise formation of a stable fluorinated SEI. Therefore, the growth of Li dendrites during repeated deposition / stripping is significantly suppressed, while improved efficiency is achieved. This method is applicable not only to lithium metal batteries, but also to secondary batteries that use other metals as anodes.

[0015] Specifically, this disclosure is as follows: [1] A secondary battery assembly comprising a metal complex represented by formula (1):

[0016] in

[0017] M is an n-valent metal. m is an integer that is 0 or greater and (n-1) or less. Q is a ligand selected from the following: unsubstituted or substituted 8-hydroxyquinoline salts, unsubstituted or substituted 2-(2-pyridyl)phenol salts, and unsubstituted or substituted 2-(2',2''-bipyridin-6'-yl)phenol salts, and L is selected from the following ligands: phenol salts and naphthol salts.

[0018] [2] The secondary battery assembly according to [1] includes a layer comprising a metal complex represented by formula (1).

[0019] [3] The secondary battery assembly according to [1] or [2], wherein Q is an unsubstituted or substituted 8-hydroxyquinoline salt.

[0020] [4] The secondary battery assembly according to any one of [1] to [3], wherein m is 0.

[0021] [5] A secondary battery assembly according to any one of [1] to [4], wherein M is a monovalent metal.

[0022] [6] The secondary battery assembly according to [5], wherein M is Li, Na, K or Ag.

[0023] [7] A secondary battery assembly according to any one of [1] to [4], wherein M is a divalent metal.

[0024] [8] The secondary battery assembly according to [7], wherein M is Mg, Ca, Zn or Cu.

[0025] [9] A secondary battery assembly according to any one of [1] to [4], wherein M is a trivalent metal.

[0026]

[10] The secondary battery assembly according to [9], wherein M is Al.

[0027]

[11] The secondary battery assembly according to any one of [1] to [6], wherein the complex is represented by formula (2), (3) or (4):

[0028] in

[0029] R 21 R 22 R 23 R 24 R 25 and R 26 Each is independently selected from the group consisting of hydrogen atoms, halogen atoms, and hydroxyl groups. R 31 R 32 R 33 R 34 R 35 R 36 and R 37 Each is independently selected from the group consisting of hydrogen atoms, halogen atoms, and hydroxyl groups. R 41 R 42 R 43 R 44 R 45 R 46 R 47 R 48 R 49 and R 50 Each is independently selected from the group consisting of hydrogen atoms, halogen atoms, and hydroxyl groups.

[0030]

[12] The secondary battery assembly according to any one of [1] to

[11] , wherein the secondary battery assembly is a separator or an anode.

[0031]

[13] A secondary battery comprising a secondary battery assembly according to any one of [1] to

[12] .

[0032]

[14] The secondary battery according to

[13] is a lithium metal battery, a lithium-oxygen battery, a lithium-sulfur battery, a sodium metal battery, a sodium-oxygen battery, a sodium-sulfur battery, a potassium metal battery, a zinc metal battery, a magnesium metal battery, a calcium metal battery, an aluminum metal battery, an aluminum-sulfur battery, or a lithium-ion secondary battery.

[0033]

[15] A method for manufacturing a secondary battery assembly, comprising applying a metal complex represented by formula (1) to a substrate to obtain a secondary battery assembly according to any one of [1] to

[12] :

[0034] in

[0035] M is an n-valent metal. m is an integer that is 0 or greater and (n-1) or less. Q is a ligand selected from the following: unsubstituted or substituted 8-hydroxyquinoline salts, unsubstituted or substituted 2-(2-pyridyl)phenol salts, and unsubstituted or substituted 2-(2',2''-bipyridin-6'-yl)phenol salts. L is selected from the following ligands: phenol salts and naphthol salts.

[0036]

[16] The method for manufacturing a secondary battery assembly according to

[15] includes depositing a metal complex on a substrate.

[0037]

[17] The method for manufacturing a secondary battery assembly according to

[15] or

[16] , wherein the compound of formula (1) is deposited on a substrate by thermal evaporation under reduced pressure.

[0038]

[18] The method for manufacturing a secondary battery assembly according to

[15] or

[16] , wherein the compound of formula (1) is deposited on a substrate by transfer printing.

[0039] Beneficial effects

[0040] This disclosure provides a secondary battery assembly that can provide excellent cycle characteristics when used in a secondary battery. Attached Figure Description

[0041] In the attached diagram: Figure 1 a) Schematic diagram of the relative electron energies at the interface between the Li metal anode and the electrolyte to form a thermodynamically stable SEI layer. Eg is a window for the thermodynamic stability of the electrolyte.

[0042] b. Ultraviolet photoelectron spectrum of a pristine Li metal anode, including secondary electron cutoff (left) and valence band features (right).

[0043] Figure 2 :a, Schematic diagram of lithium 8-hydroxyquinoline (Liq) evaporating on the surface of lithium foil, which inhibits the reaction of H2O, O2 and CO2 in the air with the Li foil.

[0044] b. Photograph of a 10 nm Liq coated Li foil (thickness: ~0.17 mm) in air.

[0045] c, d, (c) schematic diagram of the SEI formation process on the original Li anode and (d) Liq-Li anode.

[0046] Figure 3 :af, simulated crystal and molecular structures of (a)LiOH, (b)Li2O, (c)Li2CO3, (d)LiF, (e)Li2S, and (f)Liq, and their corresponding structures after losing Li atoms.

[0047] Figure 4 :a, Size distribution of Li deposited on pristine Cu, LiF-Cu, and Liq-Cu.

[0048] Schematic diagrams of Li nucleation and growth on Cu surfaces: (b) Primitive Cu, (c) LiF-Cu, and (d) Liq-Cu.

[0049] Figure 5 :a, Schematic diagram of thermal evaporation of Liq on Li / Cu foil and polymer membrane.

[0050] Optical photographs of pristine (b)Cu and (c)Li in an argon glove box, 10 nm LiF on (d)Cu and (e)Li, and 10 nm Liq on (f)Cu and (g)Li.

[0051] Figure 6 a, b, UV photoelectron spectra of a Li metal anode with 5 nm Liq, including (a) secondary electron cutoff and (b) valence band characteristics as a function of Ar ion sputtering time.

[0052] c. Electron distribution at the interface between the Liq molecule and the Li metal anode.

[0053] d. Schematic diagram of the electronic structure at the interface between the Liq molecular layer and the Li metal anode.

[0054] Figure 7(a) Original Li foil, (b) 10 nm LiF-Li foil, and (c) 10 nm Liq-Li foil: In-situ XRD results of oxidation processes under ambient conditions (room temperature = ~25 °C, humidity = ~30%). The thickness of the Li foil was 0.17 mm.

[0055] Figure 8 a. 2D grazing-incidence wide-angle X-ray scattering pattern of a 10 nm Liq molecular intermediate layer on a Cu film.

[0056] b, the corresponding intensity and azimuth distribution of the plane (Qz = ~0.5).

[0057] Figure 9 a, Fixed current density 0.05 mA / cm 2 Below are a series of constant current Li electrodeposition voltage curves for Liq thickness.

[0058] b, with a Liq thickness ranging from 0 to ~50 nm and a fixed current density of 0.05 mA / cm² 2 The nucleation overpotential of Li was measured below.

[0059] Figure 10 Cryo-transmission electron microscopy images of Li nucleation on (a) the original Cu mesh, (b) the Cu mesh with deposited LiF mesophase, and (c) the Cu mesh with deposited Liq mesophase. The deposition thickness of the LiF and Liq molecular mesophase is approximately ~10 nm. Scale bar, 1 μm.

[0060] d, at 0.05 mA / cm 2 The Li nucleation overpotentials were measured for pristine Cu, LiF-Cu, and Liq-Cu at a fixed current density. The LiF and Liq thicknesses on the Cu current collector were approximately 10 nm.

[0061] e, the anodic current density in the cyclic voltammogram of Li|Cu under different scan cycles at a scan rate of 2 mV / s.

[0062] f, at 0.25 mA / cm 2 The change in CE with cycle number for pristine Cu / Li, LiF-Cu / Li, and Liq-Cu / Li asymmetric cells with 20 μL LiPF6 electrolyte (EC / DMC / DEC: 1:1:1 vol%) at a fixed current density.

[0063] g, at 0.5 mA / cm 2The change in CE (electrolysis coefficient) of a Liq-Cu / Li asymmetric cell with 10 μL LiPF6 electrolyte (EC / DMC / DEC: 1:1:1 vol%) with the number of cycles at a fixed current density.

[0064] Figure 11 a, b, cryo-TEM images of Li nucleation on Liq-Cu surfaces.

[0065] Figure 12 : a, b, (a) Li nucleation on a LiF-Cu surface and (b) corresponding frozen TEM images of fast Fourier transform (FFT).

[0066] High-resolution cryo-TEM images of c, d, (c)Li (002) and (d)Li2O (111).

[0067] Figure 13 Initial cyclic voltammograms of the original Li|Cu cell, LiF-Li|LiF-Cu cell, and Liq-Li|Liq-Cu cell at a scan rate of 2 mV / s and a scan window of -0.3 to 2.0 V.

[0068] Figure 14 Cyclic voltammetry curves of original (a) Li|Cu, (b) LiF-Li|LiF-Cu, and (c) Liq-Li|Liq-Cu asymmetric cells at a fixed scan rate of 2 mV / s.

[0069] Figure 15 a, at a fixed current density of 0.25 mA / cm 2 and capacity 0.5 mAh / cm 2 The voltage curves of the Liq-Li|Liq-Cu asymmetric cell at the 100th, 200th, 300th, 400th and 500th cycles are shown below.

[0070] b, Liq-Li|Liq-Cu asymmetric cells at different fixed current densities of 0.25, 0.5, 1 and 2 mA / cm 2 The corresponding capacities are 0.5, 1, 2, and 4 mAh / cm³. 2 The voltage curve below.

[0071] ce, at a fixed current density of 0.25 mA / cm 2 and area capacity 0.5 mAh / cm² 2 Surface morphology of (c) pristine Cu, (d) 10 nm LiF-Cu, and (e) 10 nm Liq-Cu after Li deposition.

[0072] Figure 16:ac, at a fixed current density of 0.2 mA / cm 2 and area capacity 4 mAh / cm 2 Surface morphology of (a) pristine Cu, (b) 10 nm LiF-Cu, and (c) 10 nm Liq-Cu after Li deposition.

[0073] df, at a fixed current density of 0.2 mA / cm² and an areal capacity of 6 mAh / cm² 2 Surface morphology of (d) pristine Cu, (e) 10 nm LiF-Cu, and (f) 10 nm Liq-Cu after Li deposition.

[0074] Figure 17 :ad, at a fixed current density of 0.2 mA / cm 2 Below, the deposition area capacity is (a) 4 mAh / cm² 2 and (b) 8mAh / cm 2 The subsequent LiF-Cu, and the deposition area capacity of (c) 4 mAh / cm² 2 and (d)8 mAh / cm 2 The cross-sectional morphology of the Liq-Cu.

[0075] e, with an area capacity of 4 mAh / cm² 2 and 8 mAh / cm 2 Below is a comparison of the Li deposition thickness on LiF-Cu and Liq-Cu.

[0076] Figure 18 X-ray photoelectron spectroscopy (XPS) results for the (a) C 1s, (b) Li 1s, (c) F 1s, and (d) O 1s regions of Li SEI formed on pristine Cu, 10 nm LiF-Cu, and 10 nm Liq-Cu.

[0077] ej, Cryo-TEM images of SEI layers formed on (eh) pristine Cu grids and (ik) 10 nm Liq-Cu grids.

[0078] Figure 19 The composition ratio of F1s in the SEI layer of Li deposits on pristine Cu, Cu with a LiF interlayer, and Cu with a Liq interlayer.

[0079] Figure 20 : ac, (a) original Cu grid, (b) 10 nm LiF-Cu grid, and (c) schematic diagram of Li and corresponding SEI layers deposited on 10 nm Liq-Cu grid.

[0080] df, at a fixed current density of 0.05 mA / cm 2 Frozen TEM images of Li deposited on a 10 nm LiF-Cu grid and a 10 nm Liq-Cu grid 20 min after deposition: (d) original Cu grid, (e) 10 nm LiF-Cu grid, (f) corresponding Li deposited on a 10 nm Liq-Cu grid.

[0081] Figure 21 (a) Cryo-TEM images of the SEI layer of Li deposited on a LiF-Cu grid and (b) corresponding Fast Fourier Transform images. (c) High-resolution cryo-TEM images of Li2CO3 (200) and Li2O (111), (d) Li (110) and LiF (220).

[0082] Figure 22 a, at a fixed current density of 0.25 mA / cm 2 and capacity 0.5 mAh / cm 2 Below are the galvanostatic Li electrodeposition / stripping voltage curves for pristine Li|Li, LiF-Li|LiF-Li, and Liq-Li|Liq-Li symmetric cells. The thickness of the Li anode is 0.6 mm.

[0083] be, the surface morphology of the original Li before cycling (b), and at a fixed current density of 0.25 mA / cm². 2 and capacity 0.5 mAh / cm 2 (c) Original Li after 1000 h of cycling, (d) LiF-Li after 1000 h of cycling, and (e) Liq-Li after 2000 h of cycling.

[0084] f, A Li|Li symmetric cell with a 10 nm Liq Celgard (registered trademark) separator at a fixed current density of 0.25 mA / cm² 2 and capacity 0.5 mAh / cm 2 Constant current Li electrodeposition / stripping voltage curves. Li anode thickness: 0.17 mm.

[0085] Nyquist plots of g, original Li|Li, LiF-Li|LiF-Li, and Liq-Li|Liq-Li symmetric cells.

[0086] h, galvanostatic Li electrodeposition / stripping voltage curves of a Li|Li symmetric cell with 10 nm Liq at different current densities and capacities. Thickness of the Li anode: 0.17 mm.

[0087] Figure 23 :af, at a fixed current density of 0.25 mA / cm 2and capacity 0.5 mAh / cm 2 The constant current Li electrodeposition / stripping voltage curves of a 10 nm Liq Li|Li symmetric cell at (a) 0–20 h, (b) 400–420 h, (c) 800–820 h, (d) 1200–1220 h, (e) 1600–1620 h, and (f) 1980–2000 h are shown below.

[0088] Figure 24 a, 10 nm Liq 60 μm Li|Li symmetric cells at different current densities of 0.5 mA / cm 2 1.0 mA / cm 2 , and 2.0 mA / cm 2 The constant current Li electrodeposition / stripping voltage curve corresponds to a continuous areal capacity of 1.0 mAh / cm² after 2000 h of cycling. 2 2.0 mAh / cm 2 , and 4.0 mAh / cm 2 At a fixed current density of 0.25 mA / cm 2 And capacity 0.5mAh / cm 2 .

[0089] bd, at a fixed current density of 0.5 mA / cm 2 And capacity 1.0 mAh / cm 2 The voltage curves are shown below: (b) 2000-2020 h, (c) 2200-2220 h, and (d) 2380-2400 h.

[0090] For example, at a fixed current density of 1.0 mA / cm² 2 And capacity 2.0 mAh / cm 2 The voltage curves are shown below: (e) 2400-2420 h, (f) 2600-2620 h, and (g) 2780-2800 h.

[0091] hj, at a fixed current density of 2.0 mA / cm 2 and capacity 4.0 mAh / cm 2 The voltage curves are shown below: (h)2820-2840 h, (i)3000-3020 h, and (j)3180-3200 h.

[0092] Figure 25 :af, Li|Li symmetric cells with a 10 nm Liq @ Celgard (registered trademark) separator at 0.25 mA / cm 2 The fixed current density and 0.5 mAh / cm2 The constant current Li deposition / stripping voltage curves at (a) 0–20 h, (b) 450–470 h, (c) 900–920 h, (d) 1350–1370 h, (e) 1800–1820 h, and (f) 2500–2520 h.

[0093] Figure 26 a, b, Nyquist plots of the original Li|Li, LiF-Li|Li and Liq-Li|Li symmetric cells after (a) 20 cycles and (b) 50 cycles, with an enlarged inset.

[0094] Figure 27 :ac, 10 nm Liq-Li|Li symmetric cell at 1 mA / cm 2 The fixed current density and 2.0 mAh / cm 2 Voltage curves at (a) 0-10 h, (b) 100-110 h, and (c) 270-280 h.

[0095] df, 10 nm Liq-Li|Li symmetric cell at 2 mA / cm 2 The fixed current density and 4 mAh / cm 2 Voltage curves at (d) 280-290 h, (e) 480-490 h, and (f) 670-680 h.

[0096] gi, 10 nm Liq Li|Li symmetric cell at 3 mA / cm 2 Fixed current density and 6 mAh / cm 2 Voltage curves at (g) 690–700 h, (h) 900–910 h, and (i) 1070–1080 h. Jl, 10 nm Liq Li|Li symmetric cells at 5 mA / cm 2 The fixed current density and 10 mAh / cm 2 Voltage curves at (j) 1090-1100 h, (k) 1300-1310 h, and (l) 1470-1480 h.

[0097] Figure 28 a. Discharge capacity cycling curves of pristine Li|LFP and Liq-Li|LFP full cells with excess Li, N / P ratio of ~5.0, and N / P ratio of ~1.9 at a charge / discharge rate of 2 C.

[0098] b. Cyclic curves of discharge specific capacity (left y-axis) and areal capacity (right y-axis) of 10 nm Liq on Li for LFP batteries under the conditions of a current density of 0.5 C, an N / P ratio of ~1.0 and a lean electrolyte of 10 μL / mAh.

[0099] c, d, Cyclic curves of discharge capacity (left axis) and areal capacity (right axis) of (c) Liq-Li|LFP and (d) Liq-Li|NCM-811 pouch batteries at charge / discharge rates of 0.2 C / 0.33 C and electrolyte ratio of 3.0 g / Ah.

[0100] Figure 29 :a, Discharge capacity cycling curves of pristine Li|LFP, 10 nm LiF-Li|LFP, and 10 nm Liq-Li|LFP full cells with excess Li at a charge-discharge rate of 2 C.

[0101] bd, (b) the corresponding discharge curves of pristine Li|LFP, (c) 10 nm LiF-Li|LFP and (d) 10 nm Liq-Li|LFP after initial and 270 cycles.

[0102] Figure 30 a. Discharge capacity cycling curve of a Liq-Li|LFP full cell with an N / P ratio of ~5.0 at a charge / discharge rate of 2 C.

[0103] b, c, (b) galvanostatic charge / discharge curves of 10 nm Liq-Li|LFP full cells at a fixed current density of 2 C, an N / P ratio of ~5.0 and an electrolyte ratio of 75 μL / mAh during the 1st, 50th, 100th, 150th and 220th cycles, and (c) the corresponding coulombic efficiency during the cycling process.

[0104] Figure 31 a. Discharge capacity cycling curve of a Liq-Li|LFP full cell with an N / P ratio of ~1.9 at a charge / discharge rate of 2 C.

[0105] b, c, (b) 10 nm Liq-Li|LFP full cell at a fixed current density of 2 C, an N / P ratio of ~1.9, and an electrolyte ratio of 75 μL / mAh during the 1st, 50th, 100th, 150th, and 220th cycles, and

[0106] (c) The corresponding coulombic efficiency during the cycle.

[0107] Figure 32(a) The constant current charge / discharge curves of a 10 nm Liq-Li|LFP full cell at a fixed current density of 0.5 C, an N / P ratio of ~1.0, and an electrolyte ratio of 10 μL / mAh at the 1st, 50th, 100th, 150th, and 220th cycles, and (b) the corresponding coulombic efficiency during the cycling process.

[0108] Figure 33 a. Cyclic curves of discharge specific capacity (left y-axis) and areal capacity (right y-axis) of Li deposited on a 10 nm Liq-Cu foil|LFP full cell at a fixed current density of 0.5 C, an N / P ratio of ~1.0 and an electrolyte ratio of 10 μL / mAh.

[0109] b, the corresponding constant current charge / discharge voltage curves at a fixed current density of 0.5 C during the 1st, 20th, 50th, 75th and 100th cycles.

[0110] c, the corresponding coulomb efficiency for 100 cycles.

[0111] Figure 34 a. Discharge capacity cycling curve of a Liq-Li|NCA full cell with an N / P ratio of ~1.0 at a charge / discharge rate of 0.2 C.

[0112] b, c, (b) galvanostatic charge / discharge curves of 10 nm Liq-Li|NCA full cells at a fixed current density of 0.2 C, an N / P ratio of ~1.0, and an electrolyte ratio of 10 μL / mAh during the 1st, 25th, 50th, 75th, and 100th cycles, and (c) the corresponding coulombic efficiency during the cycling process.

[0113] Figure 35 a) Photographs of a Liq-Li|NCM-811 pouch cell with a capacity of ~0.7 Ah and a Liq-Li|LFP pouch cell with a capacity of approximately 0.45 Ah. The electrolyte ratio of the pouch cells is ~3.0 g / Ah.

[0114] b, the initial coulombic efficiency of the pouch cell.

[0115] Figure 36 a, b, (a) Liq-Li|LFP pouch cell and (b) Liq-Li|NCM-811 pouch cell constant current charge / discharge voltage curves at 1, 20, 50, 75 and 100 cycles at a fixed charge rate of 0.2 C and a discharge rate of 0.33 C.

[0116] Figure 37a) Energy level alignment between Li molecules deposited with Liq, showing their highest occupied system orbitals (HOSO), lowest unoccupied system orbitals (LUSO), and vacuum level, as well as simulated reduction potentials relative to the vacuum level for different complexes in the reported electrolyte.

[0117] b. Energy diagram and electronic structure of a bare Li anode with an unavoidably oxidized surface and electrolyte. c. Energy diagram and electronic structure of a Liq-Li anode and electrolyte. E vac(s) Φ: Vacuum energy level at the surface. E: Work function. 还原电位 : Reduction potential relative to the vacuum level.

[0118] d, e, (d) the reaction between a Li anode with an oxidized surface and an electrolyte for SEI generation, and (e) the reaction between a Li anode coated with a Liq molecular layer and an electrolyte for SEI generation. Detailed Implementation

[0119] <Secondary Battery Assembly>

[0120] This disclosure relates to a secondary battery assembly comprising a metal complex represented by formula (1):

[0121] in

[0122] M is an n-valent metal. m is an integer that is 0 or greater and (n-1) or less. Q is a ligand selected from the group consisting of: unsubstituted or substituted 8-hydroxyquinoline salts, unsubstituted or substituted 2-(2-pyridyl)phenol salts, and unsubstituted or substituted 2-(2',2''-bipyridin-6'-yl)phenol salts. L is selected from the following ligands: phenol salts and naphthol salts.

[0123] In one embodiment, this disclosure relates to a secondary battery assembly comprising a layer including a metal complex represented by formula (1):

[0124] in

[0125] M is an n-valent metal. m is an integer that is 0 or greater and (n-1) or less. Q is a ligand selected from the following: unsubstituted or substituted 8-hydroxyquinoline salts, unsubstituted or substituted 2-(2-pyridyl)phenol salts, and unsubstituted or substituted 2-(2',2''-bipyridin-6'-yl)phenol salts. L is selected from the following ligands: phenol salts and naphthol salts.

[0126] The secondary battery assembly can be either an assembly incorporated into the secondary battery as is, or an assembly used to manufacture the secondary battery.

[0127] (Metal complex)

[0128] The following describes the metal complex represented by the above formula (1) (hereinafter also referred to as "metal complex").

[0129] In the definition of M, the variable "n" is an integer equal to or greater than 1, preferably an integer from 1 to 5, more preferably an integer from 1 to 3, and especially 1.

[0130] When n is 1, M is a monovalent metal, including Li, Na, K and Ag.

[0131] When n is 2, M is a divalent metal, including Mg, Ca, Zn and Cu.

[0132] When n is 3, M is a trivalent metal, including Al.

[0133] In terms of better interfacial compatibility and higher ionic conductivity, M is preferably Li.

[0134] The variable “m” in formula (1) is an integer of 0 or greater and (n-1) or less, preferably 0, that is, in terms of chemical stability and compatibility, it is preferred that the group L is not present in formula (1).

[0135] When n is 1, m is 0, that is, there is no group L in equation (1).

[0136] When n is 2, m is 0 or 1, preferably 0.

[0137] When n is 3, m can be 0, 1 or 2, preferably 0.

[0138] Q is a ligand selected from the following: unsubstituted or substituted 8-hydroxyquinoline salt, unsubstituted or substituted 2-(2-pyridyl)phenol salt, and unsubstituted or substituted 2-(2',2''-bipyridin-6'-yl)phenol salt, preferably unsubstituted or substituted 8-hydroxyquinoline salt.

[0139] Examples of substituents include halogen atoms (e.g., fluorine, chlorine, bromine), alkyl groups (e.g., alkyl groups having 1 to 4 carbon atoms), and hydroxyl groups, preferably fluorine atoms. When substituents are present, one or two substituents are preferred. The position of the substituents is preferably meta-positioned.

[0140] As Q, 8-hydroxyquinoline salt, 2-(2-pyridyl)phenol salt or 2-(2',2''-bipyridin-6'-yl)phenol salt is preferred, which is unsubstituted or meta-substituted with a fluorine atom.

[0141] L is a ligand selected from phenol salts and naphthol salts.

[0142] Where M is a metal complex of Li represented by formula (1), including the following:

[0143] in

[0144] R 21 R 22 R 23 R 24 R 25 and R 26 Each atom is independently selected from hydrogen atoms, halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms) and hydroxyl groups, preferably hydrogen atoms or halogen atoms, more preferably hydrogen atoms or fluorine atoms. R 31 R 32 R 33 R 34 R 35 R 36 and R 37 Each atom is independently selected from hydrogen atoms, halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms) and hydroxyl groups, preferably hydrogen atoms or halogen atoms, more preferably hydrogen atoms or fluorine atoms. R 41 R 42 R 43 R 44 R 45 R 46 R 47 R 48 R 49 and R 50 Each atom is independently selected from hydrogen atoms, halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms) and hydroxyl groups, preferably hydrogen atoms or halogen atoms, more preferably hydrogen atoms or fluorine atoms.

[0145] In some implementations, the lithium complex represented by formula (2) is preferred in terms of chemical stability, commercial availability and low cost.

[0146] Where M is a metal other than Li, the metal complexes represented by formula (1) include the following:

[0147] Where R 51 R 52 R53 R 54 R 55 and R 56 Each atom is independently selected from hydrogen atoms, halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms) and hydroxyl groups, preferably hydrogen atoms or fluorine atoms.

[0148]

[0149] Where M 2 Is it Mg, Zn, or Cu? R 61 R 62 R 63 R 64 R 65 R 66 R 61′ R 62′ R 63′ R 64′ R 65′ and R 66′ Each atom is independently selected from hydrogen atoms, halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms) and hydroxyl groups, preferably hydrogen atoms or fluorine atoms.

[0150]

[0151] Where R 71 R 72 R 73 R 74 R 75 R 76 R 71′ R 72′ R 73′ R 74′ R 75′ R 76′ R 71′′ R 72′′ R 73′′ R 74′′ R 75′′ and R 76′′ Each atom is independently selected from hydrogen atoms, halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms) and hydroxyl groups, preferably hydrogen atoms or halogen atoms, more preferably hydrogen atoms or fluorine atoms.

[0152] (Metal complex layer)

[0153] This secondary battery assembly includes a layer comprising a metal complex (hereinafter referred to as the "metal complex layer").

[0154] The metal complex layer may contain one, two or more metal complexes, preferably one.

[0155] Metal complex layers can be formed by deposition on a substrate contained in a secondary battery assembly.

[0156] For example, a metal complex layer can be formed on a substrate by thermal evaporation under reduced pressure. Alternatively, a metal complex layer can be formed by placing the substrate in a reduced-pressure container, allowing the powdered complex to evaporate, and then depositing it onto the substrate within the container.

[0157] The pressure inside the container can be 10. -2 Torr or lower. The preferred pressure is 10. -5 Torr or lower, more preferably 10 -6 Torr or lower. There is no specific limit to the lower limit of pressure; it can be 10. -11 Torr or more, for example, 10 -10 Torr or more. There are no temperature restrictions, as long as it is above the temperature at which the metal evaporates, and it depends on the pressure. For example, the temperature can be -50 °C or higher.

[0158] The evaporation rate can be from 0.1 to 100 Å / s. The evaporation rate is preferably 0.2 Å / s or more, more preferably 0.5 Å / s or more, and preferably 50 Å / s or less, more preferably 20 Å / s or less.

[0159] Another condition for thermal evaporation is the temperature of the substrate. The temperature of the substrate used for the metal complex layer can be less than or equal to 100 °C. The temperature is preferably 0 °C or more, more preferably 25 °C or more, and more preferably 80 °C or less, more preferably 50 °C or less.

[0160] Alternatively, the metal complex layer can be formed by transfer onto a substrate. An example of transfer is as follows: A second substrate, different from the substrate included in the secondary battery assembly, is prepared, and a layer including a metal complex is formed on the second substrate by thermal evaporation. The second substrate material with the metal complex layer is then pressed onto the substrate, bringing the metal complex layer of the second substrate material into contact with the substrate to obtain a laminate. The metal complex layer of the second substrate is in contact with the substrate. The second substrate is then peeled off from the laminate to obtain a substrate with the metal complex layer disposed on its surface.

[0161] There are no particular restrictions on the transfer conditions. Transfer is advantageous in terms of efficiency when the metal complex layer is a Li complex layer, such as a Liq molecular layer, especially when the substrate uses Li metal (e.g., a Li anode). Due to the electron-withdrawing nature of its molecular structure, Liq molecules exhibit stronger electrostatic interactions with Li metal (e.g., a Li anode) compared to interactions with polyolefins (such as polypropylene (PP) or polyethylene) typically used via physical adsorption. Specifically, the process is as follows: a polyolefin substrate (e.g., a PP membrane) having a Liq molecular layer (e.g., a 20 nm Liq molecular layer) is pressed onto the surface of a Li metal substrate (e.g., a Li anode) by thermal evaporation, and then peeled off to transfer the Liq molecular layer onto the Li metal substrate. The conditions described above for thermal evaporation can be applied to the transfer conditions. There are no particular restrictions on the pressure used to press the molecular layer onto the substrate; pressures from 0.1 MPa or higher to 100 MPa or lower can be used.

[0162] A clean Li metal substrate (e.g., Li anode) free of carbon contaminants can be provided, for example, through continuous Ar under ultra-high vacuum conditions. + Sputtering. According to this process, the transfer of the Liq molecular layer on the separator to the Li anode can be easily achieved during the stacking or compression process in the assembly of lithium metal batteries.

[0163] The above-described thermal evaporation and transfer methods are suitable for roll-to-roll processes and are therefore preferred industrial methods.

[0164] Methods for forming metal complex layers are not limited to those described above, and include PVD (physical vapor deposition) and coating metal complex solutions. Metal complex solutions can be prepared by derivatizing the metal complex to improve its solubility in a solvent.

[0165] The thickness of the metal complex layer can be less than or equal to 500 nm. The thickness is preferably 5 nm or more, more preferably 20 nm or more, and more preferably 300 nm or less, more preferably 100 nm or less.

[0166] (anode)

[0167] A secondary battery assembly can be an anode or a separator. When the secondary battery assembly is an anode, the anode material can be used as a substrate, and a metal complex layer can be disposed on the surface of the anode material. The anode material can be a metal foil containing a metal that serves as the anode active material of the secondary battery. The anode active material is a substance that acts as an anode component or anode component replenishment material when used in a secondary battery.

[0168] Examples of metal foils include foils made of lithium, sodium, potassium, magnesium, calcium, zinc, aluminum, or alloys containing at least one of these metals. For batteries with lithium as the anode active material, lithium foil is preferred.

[0169] The metallic material of the metal complex is preferably contained in the metal foil, and the metallic material of the metal complex and the metallic material of the metal foil are preferably the same. When the metallic material of the metal complex and the metallic material of the metal foil are different, it is preferable that the metallic material of the metal complex can form an alloy with the metallic material of the metal foil.

[0170] The thickness of the metal foil can be from 10 to 500 μm. The thickness is preferably 20 μm or more, more preferably 50 μm or more, and more preferably 400 μm or less, more preferably 200 μm or less.

[0171] Metal foils can have current collectors. Examples of current collectors include copper foil, carbon paper, and related fabrics.

[0172] In secondary batteries using metal anodes, the anode active material (metal) can be deposited on the current collector, which serves as the anode, via electrochemical methods or thermal evaporation. The substrate of the anode can be the current collector, and the metal complex layer can be disposed on the surface of the anode material or the current collector.

[0173] The anode material is not limited to metal foil; it can be a compound capable of storing and releasing ions. Anode active materials used in lithium-ion secondary batteries can be used. Carbon or silicon materials can be mentioned as examples. Carbon materials include graphite (natural graphite, artificial graphite, etc.), difficult-to-graphitize carbon, easily-graphitize carbon, nanotubes, etc. Silicon materials include SiO, Si, etc.

[0174] Using the aforementioned anode as a substrate, a pre-lithiated anode can be obtained by depositing a lithium complex layer (e.g., a Liq layer) on the substrate. This method is advantageous because the anode can be pre-lithiated by depositing the lithium complex on the anode surface rather than inserting lithium into the anode. Furthermore, the lithium complex is stable and unlikely to cause lithium oxidation problems.

[0175] The methods for preparing pre-lithiated anodes using Liq are not limited to those described above, and any known method can be used. For example, a pre-lithiated anode can be obtained by applying a lithium complex to a substrate. In preparing a pre-lithiated anode, Liq can be applied to the anode material, or Liq can be incorporated into the anode. Anode active materials and Liq can be mixed to form a pre-lithiated anode.

[0176] (Diaphragm)

[0177] When the secondary battery assembly is a separator, the separator material can be used as a substrate, and a metal complex layer can be disposed on the surface of the separator material. The separator material can be a porous membrane, a woven fabric, or a nonwoven fabric made of polymers including polyolefins, polypropylene, polyimide, polyvinylidene fluoride, poly(vinylidene fluoride-co-hexafluoropropylene), corn gluten, gelatin, and cellulose, or it can be made of glass fiber.

[0178] The thickness of the membrane material can be from 10 to 100 μm. The thickness is preferably 12 μm or more, more preferably 20 μm or more, and more preferably 80 μm or less, more preferably 40 μm or less.

[0179] A membrane with a deposited metal complex layer can be directly deposited on the anode surface as a component in a secondary battery. Alternatively, the deposited metal complex layer can be transferred onto the anode surface via membrane transfer.

[0180] Secondary batteries

[0181] This disclosure also relates to a secondary battery comprising a secondary battery assembly according to this disclosure. The secondary battery can be a secondary battery manufactured using the secondary battery assembly according to this disclosure. A secondary battery typically has a positive electrode, a negative electrode, and an electrolyte. The anode of this disclosure can be used as the negative electrode of the secondary battery.

[0182] The active material used for the positive electrode can be selected based on the type of battery. The positive electrode may have a cathode current collector. The electrolyte can be selected based on the type of battery.

[0183] A diaphragm can be placed between the positive and negative electrodes to prevent short circuits. The diaphragm can be the diaphragm disclosed herein.

[0184] Examples of secondary batteries include lithium metal batteries, lithium-oxygen batteries, lithium-sulfur batteries, sodium metal batteries, sodium-oxygen batteries, sodium-sulfur batteries, potassium metal batteries, zinc metal batteries, magnesium metal batteries, calcium metal batteries, aluminum metal batteries, and aluminum-sulfur batteries.

[0185] The following explanation uses lithium metal batteries as an example.

[0186] A lithium metal battery is a battery with a lithium metal anode, in which lithium metal is deposited on the negative electrode during charging and lithium ions are eluted from the negative electrode during discharging.

[0187] A lithium metal battery has a positive electrode, a negative electrode having a lithium metal layer, and an electrolyte. The anode of this disclosure can be used as a negative electrode or as a supplementary material to the negative electrode.

[0188] Active materials used for the cathode include lithium composite oxides. There are no particular limitations on lithium composite oxides; examples include LiCoO2, LiNiO2, LiMnO2, LiMn2O4, LiV2O5, and Li4Ti5O.12 LiNi x Co y Mn z M a O2 (where x + y + z + a = 1, 0 ≤ x < 1, 0 ≤ y < 1, 0 ≤ z < 1, 0 ≤ a < 1, and M is one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn, and Cr), LiV2O5, olivine-type LiMPO4 (where M is one or more elements selected from Co, Ni, Mn, Fe, Mg, and Cr), LiNi x Co y Al z O2 (where 0.9 < x + y + z < 1.1).

[0189] The positive electrode may have a current collector. Examples of current collectors include aluminum foil, carbon paper, or related fabrics.

[0190] Electrolytes can be liquid electrolytes or solid electrolytes.

[0191] Liquid electrolytes may contain non-aqueous organic solvents and lithium salts. There are no particular limitations on non-aqueous organic solvents; examples include carbonates (e.g., dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), ethylmethyl carbonate (EMC), methylethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC)); ethers (e.g., dimethyl ether, 1,2-dimethoxyethane, dibutyl ether, polyethylene glycol dimethyl ether, and tetrahydrofuran); esters (e.g., methyl acetate, ethyl acetate, n-propyl acetate, and γ-butyrolactone); ketones (e.g., hexanone); and alcohols.

[0192] There are no particular restrictions on lithium salts; examples include LiPF6, LiBF4, LiSbF6, LiAsF6, and lithium bis(fluorosulfonyl)imide (LiFSI).

[0193] The electrolyte can be impregnated in a porous membrane located between the negative and positive electrodes. There are no particular limitations on the membrane; examples include glass fiber, polyester, polyolefins (e.g., polyethylene, polypropylene), and polytetrafluoroethylene (PTFE). The membrane can be nonwoven or woven fabric. The membrane disclosed herein can be used.

[0194] Lithium metal batteries can be manufactured using any known method. There are no particular limitations on the shape of the battery; examples include cylindrical, rectangular, pouch, and button cells.

[0195] The secondary battery can be a lithium-ion secondary battery. For example, a lithium complex layer including a Liq layer can be deposited on an anode containing carbon or silicon material to obtain a pre-lithiated anode. The method for preparing a pre-lithiated anode using Liq is not limited to the above method, and any known method can be used. The components of the lithium-ion secondary battery other than the anode (cathode, electrolyte, separator, etc.) are not limited and can be any known components.

[0196] A lithium complex layer can be deposited on the separator. A pre-lithiated anode can be obtained by making the lithium complex layer and the anode face each other. The components of a lithium-ion secondary battery, excluding the separator (anode, cathode, electrolyte, etc.), are not limited and can be any known components.

[0197] <Design Principles of Metal Complex Interfaces on Metal Anodes>

[0198] The following example uses a Li metal anode and a Liq molecular layer to illustrate the design principle of metal complex interfaces on a metal anode.

[0199] During the initial charge / discharge cycle, excess electrons from the Li metal anode reach the electrolyte through the interface, leading to corrosion of the Li metal surface and degradation of the electrolyte.

[0200] Figure 1 a is a schematic diagram of the relative electronic energies at the interface between the Li metal anode and the electrolyte. The Fermi level of the Li metal anode is higher than the lowest unoccupied molecular orbital (LUMO) of the electrolyte. Ultraviolet photoelectron spectroscopy (UPS) was used. Figure 1 (b) It was found that unavoidable surface oxidation or organic contamination during manufacturing or long-term storage further reduces the work function (Wf) of the Li metal anode. The lower Wf of the Li metal anode indicates that more electrons from the Li metal anode can readily react with the electrolyte, leading to significant depletion of both the anode and electrolyte to achieve relative equilibrium.

[0201] Optimizing surface electron injection and transport at the interface between the Li metal anode and the electrolyte is considered an important factor affecting SEI evolution and the stability of the Li metal anode.

[0202] Lithium 8-hydroxyquinoline (Liq), commonly used as an electron injection layer in organic / hybrid light-emitting diode devices, can be precisely deposited on the surface of Li metal anode / copper (Cu) foil via thermal evaporation in a vacuum system. Figure 2 A is a schematic diagram of lithium 8-hydroxyquinoline (Liq) evaporated on the surface of a lithium foil, which inhibits the reaction of H2O, O2 and CO2 in the air with the Li foil.

[0203] As explained in the examples below, the Liq molecular layer on the Li metal anode can reduce the work function (Wf) of the Li metal anode through interfacial dipoles. Excess electrons from the lithium metal anode can be readily transferred to the interface, thereby participating in electrolyte decomposition and SEI formation.

[0204] As explained in the examples below, the continuous Li foil with the Liq molecular layer exhibits a metallic surface without significant oxidation. Furthermore, the Li ion conduction behavior of the interface layer is another key aspect of SEI formation and further Li deposition / stripping processes. Figure 2 As shown in a, the Liq molecule exhibits a lithium-loving chemical structure, which consists of lithium atoms bonded to hydroxyquinoline ligands.

[0205] The potential Li was evaluated + Conductivity characteristics show that the dissociation energy of the Liq molecule losing Li atoms is lower than that observed in common inorganic substances (Li₂O, Li₂CO₃, LiF, LiOH, and Li₂S) in Li metal anode SEI. Figure 3 (See Table 1). The low dissociation energy of the Liq molecule indicates that Li ions in the Liq molecule can easily migrate from the molecular framework, which is beneficial for tuning the Li content on the Li metal anode surface. + distributed.

[0206] Table 1: Calculated dissociation energies of a single Li atom from Li-containing crystals and molecules.

[0207]

[0208] Note: dis-Li indicates that Li is dissociated from the molecular or crystal structure.

[0209] Based on previous findings and key results, Figure 2 c and d depict the SEI evolution on the Li metal anode. Dissociated Li + Coordination with anions and solvent molecules produces numerous solvated Li in the liquid electrolyte. + Clusters. Solvated Li + The cluster shell, as a potential source of SEIs for formation on the Li anode, will solvate Li + The electrons are carried to the surface of the Li metal anode. For the pristine Li anode, spontaneous electron transfer occurs between the solvent / anion clusters and the active Li anode, leading to subsequent electrolyte decomposition and consumption of the Li anode to form the SEI region. Figure 2 c). Organic / inorganic decomposition precipitates from the electrolyte and Li metal anode are unevenly distributed in the SEI layer, forming a mosaic structure with crystalline and amorphous microphases.

[0210] In contrast, the Liq molecular interlayer enables efficient electron transfer through the interfacial dipoles at the interface between the Li anode and the electrolyte for Li + reduction / oxidation. The formation of the resulting SEI layer is regulated by avoiding the reaction between the solvent and the Li anode and subsequent corrosion of the Li anode surface ([ Figure 2 d). The SEI formed on the Liq-Li anode exhibits a multi-layer nanostructure with a uniform outer layer enriched in inorganic substances (e.g., Li2O, Li2CO3, and LiF) and an amorphous inner layer. In addition, due to the Li-rich and electron-conductive properties of the Liq molecules, the Liq molecular interlayer provides a uniform Li + concentration distribution and promotes the electron distribution on the Li anode surface. These features effectively reduce the interfacial polarization and local current density of the Li + concentration, resulting in a stable Li deposition / stripping process and the stability of the SEI layer.

[0211] <Mechanism of Liq or similar molecular layer protection for Li anode>

[0212] The possible mechanism of Liq-mediated SEI formation can be mentioned as follows ([ Figure 37 ). After injecting external electrons and physically contacting the Liq-Li with the electrolyte, spontaneous electron transfer occurs between the induced interface states of the Liq-Li and the E reduction energy levels of more substances in the electrolyte (i.e., the reduction potential relative to the vacuum level), resulting in the instantaneous formation of an initial SEI layer compared to using bare Li ([ Figure 37 b and c). This is because the Liq molecular layer effectively reduces the energy gap between Li and the electrolyte components at the Li / electrolyte interface through interfacial dipoles, enabling simpler and faster SEI formation with significantly reduced electrolyte and Li consumption compared to the formation process using bare Li. In addition, the reduction reactions of the solvent and salt mainly occur through interfacial electron transfer on the stacked dipole Liq molecular layer rather than on the Li metal surface, which helps reduce Li consumption during SEI formation and thus improve the Coulomb efficiency.

[0213]

[0214] Based on the results in the embodiments shown below, the deposition size distribution and growth mechanism of Li on different Cu surfaces are depicted in Figure 4 . Compared with the Li deposition on the original Cu surface and the surface with a LiF molecular layer, the average diameter of the Li deposition on the Cu grid with a Liq molecular interlayer is smaller and the distribution is relatively concentrated. Under the limited nucleation sites on the Cu surface, the Li deposits nucleate randomly on the Cu surface and grow freely in the vertical direction ([ ) Figure 4(b) For Li nucleation on a Cu surface with a LiF layer, initial Li nucleation and deposition preferably occur between LiF particles rather than beneath them due to poor conductivity and weak chemical bonding with the underlying Cu surface. Once nucleation occurs, further Li deposition tends to occur at the existing nucleation sites, forming dendritic microstructures vertically rather than creating additional Li nuclei. This low nucleation density leads to high initial nucleation barriers and subsequent non-uniform deposition.

[0215] For Li nucleation on Cu surfaces with a Liq molecular interlayer ( Figure 4 d) The Liq molecule is composed of a Li-rich chemical structure with a lithium-philic pyridine nitrogen, which provides numerous Li nucleation sites and sufficient Li. + In addition, thanks to the excellent electron transport capabilities of Liq molecules, the molecular intermediate layer provides ample electrons for Li nucleation and deposition. As the vertical Li growth barrier at the interface exceeds the surface energy for lateral growth, the Li deposits begin initial lateral growth to fill intergranular voids. By introducing the Liq molecular intermediate layer, a homogeneous Li nucleation process with both high density and initial lateral deposition is simultaneously achieved.

[0216] As described above, a design for a Li-rich molecular interface layer on a Li anode using lithium 8-hydroxyquinoline (Liq) with a defined thickness as an SEI precursor is provided.

[0217] Thanks to the Li-rich dense packing structure and the abundant lithium-loving pyridine nitrogen in the Liq molecule, the Liq-Li anode is protected from parasitic reactions with ambient air and electrolyte.

[0218] Furthermore, the Li interface layer improves interfacial electron transport and induces the precise formation of structurally stable fluorinated SEIs, thereby achieving uniform Li... + Nucleation, diffusion, and growth. In addition to the efficient and stable Li electroplating / stripping process, the utilization of the Liq molecular intermediate layer enables LMBs to cycle stably under conditions of low electrolyte, limited Li excess, and high capacity.

[0219] These forward-looking results allow for the simple and practical creation of a wide range and types of Liq molecular intermediates on commercially available Li / Cu foils or membranes, which enables the construction of reliable LMBs with contemporary cathode selection.

[0220] This method is applicable not only to lithium metal batteries, but also to secondary batteries that use other metals as anodes.

[0221] Example

[0222] More specific descriptions based on certain embodiments of this disclosure are provided in the following paragraphs.

[0223] <Experimental Methods>

[0224] (Material)

[0225] Lithium 8-hydroxyquinoline (Liq, >99.5%), polyvinylidene fluoride (PVDF), and lithium fluoride (LiF, >99.9%) were purchased from Sigma-Aldrich, USA. Lithium foil (Li, >99.9%) with a thickness of approximately 0.17 mm was manufactured by HONJO Chemical, Co. Lithium chips (Li, >99.9%) with a thickness of approximately 0.6 mm were manufactured by Xiamen TOB New Energy Technology Co., Ltd. Copper foil with a thickness of approximately 9 μm was purchased from MTI Co. Lithium hexafluorophosphate (LiPF6), ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) were all purchased from Sigma-Aldrich. Commercial Celgard (registered trademark) microporous monolayer membranes were purchased from Celgard LLC, USA. Lithium iron phosphate (LiFePO4) and LiNi... 0.815 Co 0.15 Al 0.035 O2 (NCA) was provided by BTR New Materials Group Co., Ltd. LiNi 0.8 Co0.1Mn0.1O2 (NCM) was provided by Changsha Research Institute of Mining and Metallurgy Co., Ltd. All chemicals are analytical grade and can be used without further purification.

[0226] (Evaporation of LiF / Liq on lithium anode / copper foil)

[0227] LiF / Liq powder was added to a quartz crucible and transferred to a vacuum evaporation system via a glove box. The vacuum level of the evaporation system was below 6 × 10⁻⁶ during thermal evaporation. -6 Torr. Through a mask (effective area: 1×1 cm) 2 LiF / Liq molecules were deposited on the surface of Li metal anodes / copper foils with varying deposition thicknesses ranging from 10 to 50 nm. The evaporation rate was controlled at approximately 0.3 Å / s. The samples were then transferred directly back into an Ar glove box, free from contamination from laboratory environmental conditions (~40% relative humidity).

[0228] (Evaporation of Liq on the polymer membrane)

[0229] Liq powder was added to a quartz crucible and transferred to a vacuum evaporation system via a glove box. The vacuum level of the evaporation system was below 6 × 10⁻⁶ during thermal evaporation. -6 Torr. For assembling a coin cell, Liq molecules pass through a mask (effective area: 1.8 × 1.8 cm). 2Liq molecules are deposited directly on the membrane surface. For assembling pouch cells, Liq molecules are deposited directly on the membrane surface without a mask. The evaporation rate is controlled at approximately 0.3 Å / s. The samples are then transferred directly to an Ar glove box, avoiding contamination from laboratory conditions.

[0230] (Characteristics)

[0231] The surface morphology of the lithium metal anode and lithium deposited on copper foil were examined using a scanning electron microscope (FEI Helios G3 UC), which features an Ar-protected transport support for protection during transport. The crystal structure of the Li metal and solid electrolyte interface was investigated using a Titan G2 transmission electron microscope (TEM, Thermo Fisher Scientific), equipped with a Gatan-613 cooling support. The TEM included a post-sample spherical aberration corrector (CEOS GmbH) for correcting TEM images. A 400-mesh Cu mesh coated with LiF / Liq molecules of a specific thickness was used as a support for Li deposition. The deposition rate was 0.25 mA / cm². 2 Li was deposited at a current density of 0.1 mAh / cm² with an areal capacity. After disassembly from a coin cell, the sample was washed with dioxane (DOL) and dried in an Ar glove box. The sample was then loaded into a cooling holder in the Ar glove box and subsequently sealed in a holder container filled with Ar. The holder was rapidly inserted into the TEM and placed in liquid nitrogen for cryogenic freezing at -180°C. All cryogenic TEM images were taken at -180°C with an operating voltage of 300 kV. X-ray photoelectron spectroscopy (XPS) (Al-Kα = 1486.6 eV) and ultraviolet photoelectron spectroscopy (UPS) (He-Iα = 21.22 eV) were collected using a photoelectron spectrometer (XPS-AXIS Ultra HAS, Kratos). The combined energy scale of XPS and UPS was obtained by measuring the Fermi edge (EF = 0 eV) and Au 4f on a clean Au surface. 7 / 2Calibration was performed at (84.0 eV). The energy resolutions of the UPS and XPS were 0.14 and 0.7 eV, respectively. UV and X-ray induced damage was examined by acquiring five consecutive spectra and further comparing them. If no significant changes were observed, the final spectrum was obtained by averaging the five individual spectra. Specimens were transferred to the XPS system using Ar-filled transfer containers to avoid air contamination. X-ray diffraction results were recorded using a Bruker D8 Discover diffractometer (Bruker AXS, Cu X-ray source). Li metal samples were assembled in Ar-filled sealed containers for further XRD measurements. Grazing-incidence wide-angle X-ray scattering (GIW AXS) measurements were performed on the Xeuss 3.0 SAXS / WAXS laboratory beamline at the Shanghai Synchrotron Radiation Facility (SSRF) using a Kα X-ray Cu source (operating at 50 kV, 0.06 mA, 1.542 Å). GIW AXS patterns were recorded using a two-dimensional X-ray detector (Eiger2 R 1M, Dectris). The incident angle is set to 0.18°.

[0232] (Electrochemical characterization)

[0233] Charge-discharge diagrams were plotted using a constant current charge-discharge station (Neware BTS-CT-3008-TC 5.X.). All coin cells (CR 2025 or CR 2032 type) were assembled and disassembled in an Ar glove box (H2O and O2 < 0.1 ppm). 1M lithium hexafluorophosphate (LiPF6) / EC:DMC:DEC (1:1:1 vol %) was used as the electrolyte.

[0234] Cyclic voltammetry and electrochemical impedance spectroscopy (EIS) were performed on an electrochemical workstation (Metrohm Autolab). EIS curves were obtained in the frequency range of 100 kHz to 0.01 Hz. For the Li|Cu half-cell, measurements were performed at room temperature at 0.25 and 0.5 mA / cm². 2 The current density is 0.5 or 1 mAh / cm² when electroplated / stripped onto the current collector. 2 The capacitance of Li, and the cutoff voltage (1.5V).

[0235] To investigate the deposition density, at 0.25 mA / cm² 2 The Li capacities were 4, 6, and 8 mAh / cm² at current densities of 0.25, 1, 2, 3, and 5 mA / cm². 2 At current densities of 0.5, 2, 4, 6, and 10 mAh / cm³, 2The areal capacity was tested using symmetrical Li|Li cells. The Li|NCA cells were activated at 0.1 C for the first three cycles to stabilize the solid electrolyte interface.

[0236] The working electrode is a mixture of LFP / NCA / NCM microparticles, polyvinylidene fluoride, and acetylene black in a weight ratio of 90:5:5. The average active masses of LFP, NCM, and NCA are approximately 18, 18, and 25 mg / cm³, respectively. 2 .

[0237] During full cell assembly, the capacity ratio (N / P ratio) of the negative electrode to the positive electrode was controlled. The electrolyte in each cell was controlled to be 40, 20, or 10 μL (for cells with a low electrolyte-to-cathode capacity (E / C) ratio). The operating potential windows for Li|LFP, Li|NCA, and Li|NCM full cells were 2.7–4.0 V, 2.8–4.3 V, and 2.8–4.2 V, respectively. All evaluations of the full cells were performed at room temperature.

[0238] By pairing 4 layers of LFP / NCM cathodes with corresponding dimensions of 4.7 × 7.7 cm 2 The pouch cell was assembled using a Li metal anode. The pouch cell was cycled at a charging rate of 0.2 C and a discharging rate of 0.33 C.

[0239] (Theoretical simulation)

[0240] DFT calculations were performed using the Vienna Ab-initio Simulation Package (VASP) and the all-electron projection enhanced wave (PAW) method. The Perdew-Burke-Ernzerhof (PBE) approximation with the generalized gradient approximation (GGA) was used to describe the exchange and correlation potentials. The cutoff energy of the plane-wave basis set was set to 450 eV. The dissociation of Li atoms was studied using three-layer supercells: 2×2 LiF (200), LiF (111), Li₂CO₃ (002), 3×3 Li₂O (111), and 2×3 LiOH (101). A 15 Å vacuum region was added above the supercell model to minimize interactions between adjacent systems. C₹H₆LiNO and Li₂S molecules were placed in a 30 Å × 30 Å × 30 Å vacuum chamber. A Gamma k-point grid of 6 was used, and geometry optimization was performed until the force acting on each ion decreased to below 0.01 eV / Å.

[0241] The dissociation energy of a Li atom is calculated using the following formula (1): Edis = E(dissociation) - E(pure)........................(1) Where E(dissociation) and E(pure) are the total energies of the dissociated system and the pure system, respectively.

[0242] <Example 1: Liq molecular layer on lithium anode / copper foil>

[0243] Using the above method, Liq or LiF is deposited on the surface of Li metal anode / copper foil by thermal evaporation.

[0244] Figure 2 b is a photograph of a Li foil coated with 10 nm Liq in air (thickness: ~0.17 mm). Figure 5 bg are optical photographs of the original (b)Cu and (c)Li, 10 nm LiF on (d)Cu and (e)Li, and 10 nm Liq on (f)Cu and (g)Li in an argon glove box.

[0245] The ultraviolet photoelectron spectroscopy (UPS) of a Li metal anode with 5 nm Liq was collected using the method described above. Figure 6 a, b show the ultraviolet photoemission spectra as a function of Ar ion sputtering time, including (a) secondary electron cutoff and (b) valence band characteristics.

[0246] Based on the emission secondary electron cutoff energy from the UPS results, the Li metal anode with a 5 nm Liq molecular interface layer exhibits a Wf of ~1.52 eV. Figure 6 a). The obtained Wf is similar to the simulated Wf of Li metal adsorbing gas molecules of different polarities, but much lower than that of clean Li metal (~2.9 eV). The highest occupied molecular orbital (HOMO) extracted from Liq molecules is ~2.13 eV ( Figure 6 b). As sputtering time increased from 5 min to 10 min, the HOMO energy of Liq molecules decreased from ~2.13 eV to ~2.05 eV. The corresponding Wf of the Li metal anode increased from ~1.52 eV to ~1.72 eV. With further sputtering, the occupied states in the UPS spectrum exhibited the Li metal Fermi level without the HOMO characteristics of Liq molecules. The Wf of the Li metal anode increased from ~1.72 eV to ~2.22 eV, which is still lower than the Wf of the clean Li metal surface, due to the remaining Li oxidation state. Combined with the charge density distribution at the Liq molecule-Li metal interface ( Figure 6 c) These results suggest that the Liq molecular layer on the Li metal anode can reduce the Wf of the Li metal anode through interfacial dipoles, such as Figure 6 As shown in d.

[0247] Due to its high chemical reactivity, Li metal anodes are susceptible to air contamination (e.g., O2, CO2, H2O), leading to capacity loss and even safety issues in practical storage and applications. In-situ X-ray diffraction analysis of Li metal anodes was performed under ambient air (room temperature, humidity ~30%). Figure 7 To further investigate the effectiveness of the molecular layer in protecting Li metal from air pollution. Figure 7 The in-situ XRD results of the oxidation process of (a) pristine Li foil, (b) 10 nm LiF-Li foil, and (c) 10 nm Liq-Li foil under ambient conditions (room temperature = ~25 °C, humidity = ~30%) are shown. The thickness of the Li foil is 0.17 mm.

[0248] For pristine Li and another Li coated with a 10 nm LiF molecular layer (LiF-Li), diffraction peaks indicating LiOH and Li₂O gradually appeared with exposure to air. In contrast, the Li metal anode with a 10 nm Liq molecular layer exhibited a stable chemical structure after 5 h of exposure to air.

[0249] <Example 2: Nucleation and Deposition of Li on Liq-Cu>

[0250] (2D Grazing Incidence Wide-Angle X-ray Scattering)

[0251] The orientation of Liq molecules was studied using 2D grazing incidence wide-angle X-ray scattering (GIWAXS) measurements. Figure 8 a shows a 2D grazing-incidence wide-angle X-ray scattering pattern of a 10 nm Liq molecular intermediate layer on a Cu film. Qz represents the out-of-plane direction, and Qxy represents the in-plane direction. The scattering vector Qz is associated with the diffraction angle 2θ by the following formula (2):

[0252] In a 2D GIWAXS image, isotropic orientation appears as a ring, while light spots represent strong molecular orientation. A 10 nm Liq molecular intermediate layer on a polycrystalline Cu substrate ( Figure 8 a) A ring is observed at Qz = 0.5 / nm, which is attributed to the stacking of Liq molecules with a spacing of ~1.26 nm. Furthermore, Figure 8 The corresponding intensity and azimuth distribution in the midplane (Qz = ~0.5) in b proves the obvious out-of-plane orientation of the Liq molecule.

[0253] (Li nucleation overpotential)

[0254] To further determine Li nucleation and deposition on the Liq molecule's intermediate layer, a galvanostatic nucleation overpotential test was performed on Li metal from a Li|Cu battery. The Li nucleation overpotential (μnuc) was calculated according to the following equation (1): μnuc = μmtc - μ 尖端 ........................(1) Among them μmtc and μ 尖端 These are the mass transfer control potential and the tip potential, respectively.

[0255] The following documents are available for reference in this regard.

[0256] Kim, MS et al. “Langmuir-Blodgett artificial solid-electrolyteinterphases for practical lithium metal batteries”. Nature Energy 3, 889-898, doi:10.1038 / s41560-018-0237-6 (2018). As the thickness of the Liq molecule increases, favorable nucleation sites appear, and μ... 尖端 Gradually increase. Based on the constant current-voltage curve and statistical data ( Figure 9 (See Table 2). The μnuc values ​​based on the Liq molecular intermediate layers with thicknesses ranging from 0 to ~50 nm are 44.6, 34.2, 33.1, 27.5, 31.2, and 27.2 mV, respectively. Figure 10 d) shows a trend towards a lower nucleation barrier for Li on the Cu surface. Compared to LiF-Cu (~37.2 mV), the Liq molecular layer with the same 10 nm thickness still exhibits a lower nucleation barrier (~34.2 mV). The use of ultrathin molecular layers is highly suitable for Li metal anodes, which is essential for constructing reliable LMBs.

[0257] Table 2: Tip potential and mass transfer control potential of Li nucleation on pristine Cu, LiF-Cu and Liq-Cu with different Liq molecular layers.

[0258]

[0259] (Cryo-TEM measurement)

[0260] Furthermore, cryo-TEM was used to compare and investigate the Li nucleation and deposition processes on pristine Cu meshes and Cu meshes with 10 nm LiF and Liq molecular layers. The stability and morphology of the deposited Li were mainly controlled by kinetics, due to the low diffusion activation energy at room temperature and the degree of time freedom before reaching favorable face-centered cubic vacancy sites on the Cu surface. Li nucleation on the pristine Cu surface exhibited vertical and whisker-like morphologies, with uneven distribution of nucleation sites. Figure 10 a). Under the same depositional conditions, Li nucleation on Cu surfaces with LiF layers exhibits a relatively dense and uniform nucleation microstructure with almost no whisker-like deposits. Figure 10 b). Li deposition on Cu surfaces with a Liq molecular layer exhibits a dense and flat microstructure. Figure 10 c). The deposits on Cu with Liq and LiF layers also consist of multiple Li nanocrystals with corresponding lattice spacings of ~0.18 nm, which are attributed to the (002) plane of metallic Li. Figure 11 and Figure 12 ).

[0261] (Cyclic Li stripping / electroplating process)

[0262] The regulatory and stabilizing role of the molecular intermediate layer on SEI formation and nucleation / deposition was further investigated using a cyclic Li stripping / electroplating process. The initial CV curves of the Li stripping / electroplating process on Cu surfaces with LiF and Liq molecular layers showed higher peak current densities and better symmetry than those of pristine Cu. Figure 13 ), corresponding to fast Li + Transport and reversible nucleation / deposition kinetics.

[0263] With the continuous Li stripping / electroplating process, due to the formation of the SEI layer and the corresponding Li + The conduction path shows a gradual increase in peak current density. For pristine Cu, even after 20 cycles, the corresponding stripping / electroplating process fails to reach thermodynamic equilibrium, likely due to the unstable stripping / electroplating process of the SEI layer itself or repeated breakage / regeneration. In contrast, the cyclic Li stripping process on Cu surfaces with Liq molecular layers reaches a stable and highest peak current density within several cycles. Figure 10 e) indicates that the Liq interlayer rapidly induces the formation of a stable SEI layer and enhances the electrochemical kinetics of the Li stripping / electroplating process. Furthermore, the overpotential on the Cu surface with the Liq molecular interlayer is stable and consistently lower than that on pristine Cu and Cu with the LiF interlayer. Figure 14 ).

[0264] (CE measurement in Li|Cu cells)

[0265] In addition, CE measurements were performed in Li|Cu batteries to further investigate the cycle stability of the Li stripping / electroplation process on the Cu surface. Figure 10 f). Specifically, the battery equipped with LiF and Liq molecular layers operates at 0.25 mA / cm². 2 The current density and 0.5 mAh / cm 2 At the areal capacity, the cells exhibited stable CEs of ~99.85% and ~99.99% respectively after 500 cycles. In contrast, the cell with pristine Cu showed poor lifetime, with the CE decaying to 77.36% after 60 cycles. Furthermore, even after 500 cycles, the cell with the Liq interlayer remained stable, with an overpotential of only ~13 mV. Figure 15 a). With increasing current density and corresponding Li stripping / plating capacity, the battery with the Liq interlayer still exhibits good stability and reversibility. Figure 15 b). Considering the inevitable polarization and consumption of Li and the electrolyte, the battery with the Liq interlayer was tested under a lean electrolyte (~10 μL) and controlled Li anode conditions to better predict the effect of the molecular interlayer on the stabilization of Li stripping / deposition under practical conditions. The battery with the Liq interlayer was tested at 0.5 mA / cm². 2 Current density and 1 mAh / cm 2 It still shows a stable CE of ~99.99% at the area capacity. Figure 10 g).

[0266] The main determinants of CEs are highly correlated with the morphology of Li deposits and SEI characteristics. When the deposition capacity is 0.5 mAh / cm³... 2 The fixed current density is 0.25 mA / cm². 2 At that time, Li deposits on the Cu surface with a Liq intermediate layer ( Figure 15 e) exhibits better performance than pristine Cu and Cu surfaces with LiF interlayers. Figure 15 c, d) More compact microstructure. Towards high-load cathodes (>4 mAh / cm²) 2 For Cu to be coupled, the deposition areal capacity of Li on Cu needs to be comparable to that of practical high-energy LMBs 34. ~4 mAh / cm³ 2 and ~8 mAh / cm 2 The high areal capacity of Li is 0.2 mA / cm². 2 Current density was deposited on different Cu surfaces. At ~4 mAh / cm² 2 Under the deposition capacity ( Figure 16The Li deposits on the Cu surface with the Liq interlayer exhibit a dense and flat morphology. Similarly, for the Cu surface with the LiF interlayer, the deposits also show a relatively compact morphology with distinct grain boundaries. In contrast, the deposits on the pristine Cu exhibit a moss-like structure with low penetration density. As the deposition capacity increases to 8 mAh / cm³, the deposition density increases. 2 ( Figure 16 The deposition on the Liq interlayer on the Cu surface is still more compact than that on the original Cu and Cu with the LiF interlayer.

[0267] (Cross-sectional morphology)

[0268] Furthermore, based on the thickness of the Cu foil, the deposition thickness can be estimated from the cross-sectional image of Li deposition on the LiF and Liq intermediate layers. Figure 17 (ad). Specifically, at 4 mAh / cm 2 At the given deposition capacity, the deposition thicknesses on the LiF and Liq interlayers are approximately 18.1 μm and 16.3 μm, respectively, corresponding to... Figure 17 The theoretical bulk Li metal in e (0.534 g / cm³) 3 The thickness was 90.5% and 81.5%. Similarly, as the deposition capacity increased to 6 mAh / cm³, the thickness also increased. 2 The deposition thicknesses of the LiF and Liq interlayers were approximately 35.0 μm and 25.8 μm, respectively, corresponding to 87.5% and 64.5% of the theoretical bulk Li metal thickness. These results indicate that dense Li deposition can be achieved by adjusting the Liq molecular interlayer.

[0269] <Example 3: Nanostructure and composition of the formed SEI>

[0270] The effects of different molecular intermediate layers on SEI layer formation were investigated using a combination of XPS and cryogenic TEM on Li deposits. In the C 1s spectrum ( Figure 18 a) Classified as CC, CO, (CH2CH2O) n , (CH2CH2OCH2O) n and CF x The peaks of the substances originate from the decomposition of the electrolyte and surface reactions with the molecular intermediate layer. In this work, all fluorinated substances originated from the decomposition of Li salts in the electrolyte and further subsequent reactions. Compared with the original and LiF intermediate layers, the SEI layer induced by the Liq intermediate layer exhibits emerging fluorinated carbon substances. Specifically, the F 1s spectra of different samples, after deconvolution, yielded four peaks for LiF and CFx substances (x = 1-). Figure 18 c and Figure 19For the SEI of Li deposits on pristine Cu, the relative proportions of LiF and fluorinated carbon were ~10.3% and ~16.2%, respectively. With the introduction of a LiF interlayer, the proportion of LiF in the SEI layer increased accordingly (~15.2%). In contrast, the fluorinated material in the Liq-induced SEI layer consisted mainly of fluorinated carbon (~23.2%) and a small amount of LiF (~3.9%).

[0271] These results indicate that the Liq molecular intermediate layer can effectively reduce the initial side reactions during the decomposition of Li salts in the electrolyte, which in turn promotes the fluorinated SEI by generating fluorinated carbon substances.

[0272] The nanostructure of the SEI on the Li deposit was further characterized by cryo-TEM analysis. For the original Cu surface, the Li deposit exhibited a porous structure with multiple pores. Figure 20 a, d). Li deposits on Cu surfaces with a LiF interlayer exhibit a randomly distributed columnar microstructure with no obvious porosity. Figure 20 b, e). In contrast, Li deposits on Cu surfaces with a Liq interlayer exhibit a dense and flat surface ( Figure 20 c, f).

[0273] Furthermore, the specific nanocrystalline structures of the SEI layers deposited by Li on different Cu surfaces were investigated using high-resolution TEM analysis. The SEI of Li deposited on pristine Cu exhibited a porous and mosaic structure, composed of amorphous phases and embedded Li, Li₂O, Li₂CO₃, and LiF nanocrystals. Figure 18 Furthermore, the SEI of Li deposited on Cu with a LiF interlayer also exhibits a mosaic structure with embedded nanocrystals (e.g., Li, Li₂O, Li₂CO₃, and LiF) without obvious voids. Figure 21 Notably, the SEI of Li deposits on the Cu surface with the Liq interlayer exhibits a continuous shell composed of LiF nanocrystals on an amorphous phase surface. Figure 18 XPS results and cryo-TEM observations synergistically confirmed the composition of the fluorinated SEI and the distribution of LiF nanocrystals in the Liq-induced SEI.

[0274] <Example 4: Stability of Li stripping / deposition in symmetric cells>

[0275] (Reversibility of long-term Li plating / stripping assessment 1)

[0276] A symmetrical Li|Li cell with different molecular intermediate layers (Li thickness: ~60 μm) was used at 0.25 mA / cm². 2Constant current cycling tests were used to evaluate the reversibility of long-term Li plating / stripping. Figure 22 a). Symmetrical cells with a Liq intermediate layer exhibited good plating / stripping cycle performance within 2000 h. Figure 23 The corresponding overpotential is only ~12 mV, far lower than that of the symmetric cell with the LiF interlayer (~40 mV). In contrast, the symmetric cell with the pristine Li anode exhibits a significantly increased overpotential and poor reversibility and cycling performance. After 2000 h of cycling, the symmetric cell with the Liq interlayer has an overpotential of 0.5 mA / cm². 2 1.0 mA / cm 2 and 2.0 mA / cm 2 Down( Figure 24 a) After continuous cycling for 400 h, it still showed stable cycling ability and reversibility. Figure 24 bj).

[0277] Furthermore, the advantages of the Liq interlayer were further investigated using the nanomorphology of the Li anode in the post-cycle symmetric cell. After long-term cycling, the Li anode with the Liq interlayer still maintained a smooth and dense surface compared to the original Li before cycling, without obvious dendrite growth. Figure 22 b, e). In contrast, the surfaces of both the pristine Li anode and the Li anode with a LiF interlayer exhibit a loose and porous structure. Figure 22 c, d), which is attributed to dendrite growth and the generation of inactive Li.

[0278] (Reversibility of long-term Li plating / stripping assessment 2)

[0279] To further demonstrate the practical feasibility of the Liq molecular intermediate layer, a symmetric Li|Li battery equipped with a Liq-modified separator was used, and the speed was 0.25 mA / cm². 2 Constant current cycling test was performed below. Figure 22 f). The resulting symmetrical cell operates at 0.25 mA / cm². 2 The fixed current density and 0.5 mAh / cm 2 It also exhibits a stable plating / stripping cycle capability of 2800 h at the same capacity. Figure 25 Furthermore, under non-cyclic conditions, the initial interfacial impedances of symmetrical cells with a pristine Li anode, a Li anode with a LiF interlayer, and a Li anode with a Liq interlayer are ~162 Ω, ~80 Ω, and ~98 Ω, respectively. Figure 22g). As the SEI layer forms and stabilizes, the interfacial impedance in the symmetric cell with LiF and Liq intermediate layers gradually decreases during cycling. After 50 cycles, the interfacial impedances of the symmetric cell with LiF and Liq intermediate layers decrease to ~41 Ω and ~53 Ω, respectively, which is much smaller than the interfacial impedance of the symmetric cell with pristine Li (~818 Ω). Figure 26 a, b).

[0280] Furthermore, even when the current density increases from 1 mA / cm² 2 Continuously increase to 5 mA / cm 2 Corresponding to 2 mAh / cm 2 Up to 10mAh / cm 2 At the area capacity, symmetric cells with a Liq intermediate layer still exhibit low overpotential and stable cycling capability above 1400 h. Figure 22 h and Figure 27 ).

[0281] <Example 5: Cyclic stability of LMBs under controlled N / P ratio and lean electrolyte conditions>

[0282] To further demonstrate the advantages and stability of the molecular intermediate layer, button-type LMBs with LFP cathodes and different Li anodes were cycled at a fixed current density of 2 C. Figure 28 a and Figure 29 After more than 250 cycles, the battery with a Liq interlayer on the Li anode exhibited a capacity retention of ~98.7%, which is significantly higher than batteries with pristine Li (~39.6%) and Li with a LiF interlayer (~80.5%). For practical LMBs, the capacity ratio (N / P ratio) of the anode to the cathode and the electrolyte content need to be controlled to further improve the energy density of LMBs. As the N / P ratio decreased from ~5.0 to ~1.9, under excess electrolyte conditions, the capacity retention of the Liq-Li|LFP battery after 200 cycles at 2 C was ~99.6% and ~98.2%, respectively. Figure 30 and Figure 31 To further control the N / P ratio (~1.0) and electrolyte content (10 μL / mAh), the Liq-Li|LFP battery exhibited a capacity retention of ~96.3% after more than 135 cycles at 0.5 C. Figure 28 b and Figure 32 Even with Li deposited on Liq-Cu as the anode, the Liq-Li|LFP cell exhibited a capacity retention of ~83.8% under conditions of a ~1 N / P ratio and a lean electrolyte (10 μL / mAh). Figure 33 ).

[0283] Furthermore, when using another typically unstable cathode, the Liq-Li|NCA cell exhibited a capacity retention of ~67.3% after 100 cycles at 0.2 C under the same well-controlled conditions. Figure 34 The potential practical application of the Liq interlayer on the Li anode was further demonstrated in pouch cells by pairing it with LFP and NCM-811 cathodes. The Liq-Li|LFP and Liq-Li|NCM-811 cells had capacities of ~0.45 Ah and ~0.7 Ah, respectively, with a fixed electrolyte ratio of ~3.0 g / Ah. Figure 35 a). The average initial CE of Liq-Li|LFP cells and Liq-Li|NCM-811 cells were ~89% and ~91%, respectively. Figure 35 b). The Liq-Li|LFP battery and the Li|NCM-811 battery exhibited excellent capacity retention of ~94.3% after more than 100 cycles and ~85% after more than 230 cycles, respectively, with charge / discharge rates of 0.33 C / 0.2 C. Figure 28 c, d). The corresponding voltage curves show a stable trend, i.e., a small or almost constant horizontal shift to the left. Figure 36 This indicates that the Liq-Li anode in the soft-pack form of LMBs has stable electrochemical performance.

[0284] Industrial applicability

[0285] According to this disclosure, a secondary battery assembly is provided that can provide excellent cycle characteristics when used in a secondary battery.

Claims

1. A secondary battery assembly comprising a metal complex represented by formula (1): in M is an n-valent metal. m is an integer that is 0 or greater and (n-1) or less. Q is a ligand selected from the following: unsubstituted or substituted 8-hydroxyquinoline salts, unsubstituted or substituted 2-(2-pyridyl)phenol salts, and unsubstituted or substituted 2-(2',2''-bipyridin-6'-yl)phenol salts, and L is a ligand selected from phenol salts and naphthol salts.

2. The secondary battery assembly according to claim 1, wherein the assembly comprises a layer comprising a metal complex represented by formula (1).

3. The secondary battery assembly according to claim 1 or 2, wherein Q is an unsubstituted or substituted 8-hydroxyquinoline salt.

4. The secondary battery assembly according to any one of claims 1 to 3, wherein m is 0.

5. The secondary battery assembly according to any one of claims 1 to 4, wherein M is a monovalent metal.

6. The secondary battery assembly according to claim 5, wherein M is Li, Na, K or Ag.

7. The secondary battery assembly according to any one of claims 1 to 4, wherein M is a divalent metal.

8. The secondary battery assembly according to claim 7, wherein M is Mg, Ca, Zn or Cu.

9. The secondary battery assembly according to any one of claims 1 to 4, wherein M is a trivalent metal.

10. The secondary battery assembly according to claim 9, wherein M is Al.

11. The secondary battery assembly according to any one of claims 1 to 6, wherein the complex is represented by formula (2), (3) or (4): Where R 21 R 22 R 23 R 24 R 25 and R 26 Each is independently selected from hydrogen atoms, halogen atoms, and hydroxyl groups. R 31 R 32 R 33 R 34 R 35 R 36 and R 37 Each is independently selected from hydrogen atoms, halogen atoms, and hydroxyl groups. R 41 R 42 R 43 R 44 R 45 R 46 R 47 R 48 R 49 and R 50 Each is independently selected from hydrogen atoms, halogen atoms, and hydroxyl groups.

12. The secondary battery assembly according to any one of claims 1 to 11, wherein the secondary battery assembly is a separator or an anode.

13. A secondary battery comprising a secondary battery assembly according to any one of claims 1 to 12.

14. The secondary battery according to claim 13, wherein the secondary battery is a lithium metal battery, a lithium-oxygen battery, a lithium-sulfur battery, a sodium metal battery, a sodium-oxygen battery, a sodium-sulfur battery, a potassium metal battery, a zinc metal battery, a magnesium metal battery, a calcium metal battery, an aluminum metal battery, an aluminum-sulfur battery, or a lithium-ion secondary battery.

15. A method for manufacturing a secondary battery assembly, comprising applying a metal complex represented by formula (1) to a substrate to obtain a secondary battery assembly according to any one of claims 1 to 12: in M is an n-valent metal. m is an integer that is 0 or greater and (n-1) or less. Q is a ligand selected from the following: unsubstituted or substituted 8-hydroxyquinoline salts, unsubstituted or substituted 2-(2-pyridyl)phenol salts, and unsubstituted or substituted 2-(2',2''-bipyridin-6'-yl)phenol salts, and L is a ligand selected from phenol salts and naphthol salts.

16. The method for manufacturing a secondary battery assembly according to claim 15, comprising depositing a metal complex represented by formula (1) on a substrate.

17. The method for manufacturing a secondary battery assembly according to claim 15 or 16, wherein the compound of formula (1) is deposited on a substrate by thermal evaporation under reduced pressure.

18. The method for manufacturing a secondary battery assembly according to claim 15 or 16, wherein the compound of formula (1) is deposited on a substrate by transfer printing.

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