Current-collector-free negative electrode and preparation method therefor, battery and electric device

Abstract

In order to overcome the problem of copper-lithium layering in an existing lithium metal negative electrode, reduce the mass of the lithium metal negative electrode and improve the electrochemical stability of the lithium metal negative electrode, the present application provides a current-collector-free negative electrode. The current-collector-free negative electrode comprises a first active material layer, and a first functional layer and a second functional layer, which are respectively arranged on two sides of the first active material layer, wherein the first active material layer is lithium metal, the first functional layer and / or the second functional comprises a lithium metal alloy Li-M and an artificial SEI material, M comprising one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth. The present application further discloses a preparation method for the current-collector-free negative electrode, a battery comprising the current-collector-free negative electrode, and an electric device. The current-collector-free negative electrode provided by the present application omits a current collector, and therefore the energy density of the negative electrode can be effectively increased; and the negative electrode has good mechanical strength and self-supporting performance.

Description

A current collector-free negative electrode, its preparation method, battery, and electrical device

[0001] This application claims priority to Chinese Patent Application No. 202410488243.8, filed on April 22, 2024, entitled "A current collector-free negative electrode and its preparation method, battery, and power device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of battery technology, specifically relating to a current collector-free negative electrode and its preparation method, a battery, and an electrical device. Background Technology

[0003] Due to its ultra-high theoretical specific capacity of 3860 mAh / g and the most negative standard reduction potential (-3.04V), along with its low density and small ionic radius, lithium metal batteries have become an important direction for high-energy-density battery research and development. Existing lithium metal anodes generally use lithium metal directly as the anode or combine lithium metal with copper current collectors to form a composite anode. However, due to copper's lithium-repellent properties, both traditional copper current collectors and composite current collectors face the technical challenge of separating the copper and lithium layers during long-term storage when using the rolling method to obtain copper current collector-lithium composite strips. Furthermore, the large mass of copper-based current collectors results in a large mass of lithium metal anodes, limiting the improvement of lithium metal battery energy density.

[0004] To address this issue, several solutions have been proposed in related technologies, but some shortcomings remain. For example, one solution uses a mesh current collector instead of copper foil, but this mesh current collector needs to be partially embedded in the lithium strip, making it impossible to simply prepare based on a finished lithium strip. Furthermore, the thickness of the lithium strip is limited because it must completely cover the thickness of the current collector mesh. Additionally, the current collector mesh has poorer cutability and weldability than pure metal, increasing the difficulty of subsequent electrode and battery fabrication. Another solution uses a polymer film instead of copper foil as the lithium metal support, but due to the use of a composite current collector, the lithium on both sides of the polymer film still needs to be transferred and soldered separately, increasing process complexity and introducing additional foil tab weight.

[0005] Furthermore, due to the high reactivity of lithium metal, whether used in liquid or solid systems, it reacts with the electrolyte due to its high electrochemical reactivity, consuming both lithium metal and electrolyte, which is detrimental to the battery's long-term cycling performance. Summary of the Invention

[0006] To address the problems of copper-lithium stratification, high lithium metal anode quality, and poor electrochemical stability in existing lithium metal anodes, this application provides a current collector-free anode, its preparation method, battery, and power device.

[0007] The technical solution adopted in this application to solve the above-mentioned technical problems is as follows:

[0008] On one hand, this application provides a current collector-free negative electrode, including a first active material layer and a first functional layer and a second functional layer respectively disposed on both sides of the first active material layer. The first active material layer is lithium metal, and the first functional layer and / or the second functional layer includes a lithium metal alloy Li-M and an artificial SEI material, wherein M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth.

[0009] Optionally, the first functional layer includes a second active material layer and a first artificial SEI layer, the second active material layer being located between the first active material layer and the first artificial SEI layer, the second active material layer including a lithium metal alloy Li-M, and the first artificial SEI layer including an artificial SEI material.

[0010] The second functional layer includes a third active material layer and a second artificial SEI layer. The third active material layer is located between the first active material layer and the second artificial SEI layer. The third active material layer includes a lithium metal alloy Li-M, and the second artificial SEI layer includes an artificial SEI material.

[0011] The artificial SEI material includes one or more of lithium-containing inorganic compounds and polymers.

[0012] Optionally, the lithium-containing inorganic compound includes one or more of lithium metal formed with one or more of fluorine, oxygen, sulfur, nitrogen, and phosphorus, LATP, LZO, LLTO, LLZO, LGPS, LPSC, Li3InCl6, and Li3YCl; the polymer includes one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and perfluorosulfonic acid (Nafion).

[0013] Optionally, the thickness of the first active material layer is 1–100 μm, the thickness of the second active material layer is 0.05–100 μm, the thickness of the third active material layer is 0.05–100 μm, the thickness of the first artificial SEI layer is 0.01–10 μm, and the thickness of the second artificial SEI layer is 0.01–10 μm.

[0014] Optionally, the lithium content in the first active material layer is greater than 90% by mass.

[0015] Optionally, the lithium content in the second and third active material layers is 0.05%-99.95% by mass.

[0016] Optionally, the artificial SEI material comprises a lithium-containing inorganic compound; by weight, the first functional layer and the second functional layer comprise 5-95% of mutually doped lithium-containing inorganic compounds and 95%-5% of lithium metal alloy Li-M.

[0017] Optionally, the lithium-containing inorganic compound includes one or more of lithium fluoride (LiF), lithium oxide (Li2O), lithium nitride (Li3N), lithium sulfide (Li2S), lithium phosphide (Li3P), LATP, LZO, LLTO, LLZO, LGPS, LPSC, LiPON, Li3InCl6, and Li3YCl.

[0018] Optionally, the thickness of the first functional layer is 0.1-100 μm, and the thickness of the second functional layer is 0.1-100 μm.

[0019] Optionally, it may also include a negative electrode tab, which is electrically connected to the first active material layer.

[0020] Furthermore, this application provides a method for preparing a current collector-free negative electrode as described above, comprising the following steps:

[0021] Lithium metal is provided as the first active material layer;

[0022] A first functional layer and a second functional layer are covered on both sides of the first active material layer. The first active material layer is lithium metal. The first functional layer and / or the second functional layer include lithium metal alloy Li-M and artificial SEI material. M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth.

[0023] Optionally, the first functional layer and the second functional layer are prepared by one or more of the following methods: roll forming, coating, physical vapor deposition, chemical vapor deposition, and atomic layer deposition.

[0024] Optionally, the first functional layer and the second functional layer are prepared by the following method:

[0025] A lithium metal alloy Li-M is coated on both sides of the first active material layer, wherein M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth, and the mass fraction of lithium metal is 0.05%-99.95% to obtain the second active material layer and the third active material layer.

[0026] The surfaces of the second and third active material layers are respectively covered with a first artificial SEI layer and a second artificial SEI layer.

[0027] Optionally, the first functional layer and the second functional layer are prepared by the following method:

[0028] MX layers are deposited on both sides of the first active material layer, wherein M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth; and X includes one or more of halogens, O, S, N and P.

[0029] During battery charging, lithium atoms (Li) from the positive electrode react to generate M and artificial SEI components containing lithium compounds (LiX). Metal M can undergo an alloying reaction with metal Li to produce Li-M alloys.

[0030] In another aspect, this application provides a battery comprising a current collector-free negative electrode as described above or a current collector-free negative electrode prepared by the preparation method described above.

[0031] In another aspect, this application provides an electrical device, including the battery described above.

[0032] According to the current collector-less negative electrode provided in this application, the use of traditional copper foil current collectors is omitted, and lithium metal in the first active material layer is directly used as the current collector. At the same time, a first functional layer and a second functional layer containing lithium metal alloy Li-M and artificial SEI material are formed on both sides of the first active material layer, respectively. This composite structure achieves weight reduction of the negative electrode. Since the first active material layer is both a source of lithium ions and a current collector, it can effectively increase the energy density of the negative electrode. On the other hand, the lithium metal alloy Li-M and artificial SEI material in the first and second functional layers can facilitate uniform deposition of lithium metal, avoid the formation of lithium dendrites and dead lithium, and the lithium alloy Li-M has better mechanical strength and self-supporting properties, which can effectively avoid the problems of easy wrinkling and breakage of pure lithium metal electrodes. Attached Figure Description

[0033] Figure 1 is a schematic diagram of an embodiment of the current collector-less negative electrode provided in this application.

[0034] Figure 2 is a schematic diagram of another embodiment of the current collector-less negative electrode provided in this application.

[0035] The reference numerals in the accompanying drawings are as follows: 1. First active substance layer; 2. First functional layer; 21. Second active substance layer; 22. First artificial SEI layer; 3. Second functional layer; 31. Third active substance layer; 32. Second artificial SEI layer. Detailed Implementation

[0036] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0037] Referring to Figures 1 and 2, this application provides a current collector-free negative electrode, including a first active material layer 1 and a first functional layer 1 and a second functional layer 3 respectively disposed on both sides of the first active material layer 1. The first active material layer 1 is lithium metal, and the first functional layer 1 and / or the second functional layer 3 include lithium metal alloy Li-M and artificial SEI material, wherein M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth.

[0038] The current collector-free negative electrode omits the use of traditional copper foil current collectors, directly employing lithium metal in the first active material layer 1 as the current collector. Simultaneously, a first functional layer 1 and a second functional layer 3, containing a lithium metal alloy Li-M and an artificial SEI material, are formed on both sides of the first active material layer 1. This composite structure achieves weight reduction of the negative electrode. Furthermore, since the first active material layer 1 serves as both a lithium ion source and a current collector, it effectively increases the energy density of the negative electrode. Moreover, compared to the softer lithium metal, the lithium metal alloy Li-M and the artificial SEI material in the first and second functional layers 1 and 3 have better stability, facilitating uniform lithium metal deposition and preventing the formation of lithium dendrites and dead lithium. Additionally, the lithium alloy Li-M has better mechanical strength and self-supporting properties, effectively avoiding the wrinkling and breakage problems inherent in pure lithium metal electrodes.

[0039] Referring to Figure 1, a current collector-free negative electrode structure is provided in one embodiment of this application, wherein the first functional layer 1 includes a second active material layer 21 and a first artificial SEI layer 22, the second active material layer 21 is located between the first active material layer 1 and the first artificial SEI layer 22, the second active material layer 21 includes a lithium metal alloy Li-M, and the first artificial SEI layer 22 includes an artificial SEI material.

[0040] The second functional layer 3 includes a third active material layer 31 and a second artificial SEI layer 32. The third active material layer 31 is located between the first active material layer 1 and the second artificial SEI layer 32. The third active material layer 31 includes a lithium metal alloy Li-M, and the second artificial SEI layer 32 includes an artificial SEI material.

[0041] The artificial SEI material includes one or more of lithium-containing inorganic compounds and polymers.

[0042] The second active material layer 21 and the third active material layer 31 provide initial protection for the intermediate first active material layer 1, preventing highly reactive metallic lithium from directly contacting and reacting with the electrolyte. At the same time, as the negative electrode lithium source active layer, the first artificial SEI layer 22 and the second artificial SEI layer 32 provide further protection. Furthermore, the second active material layer 21, the third active material layer 31, the first artificial SEI layer 22, and the second artificial SEI layer 32 can enhance the structural strength of the first active material layer 1.

[0043] In some embodiments, the lithium-containing inorganic compound includes one or more compounds formed from lithium metal and one or more of fluorine, oxygen, sulfur, nitrogen, and phosphorus, LATP, LZO, LLTO, LLZO, LGPS, LPSC, Li3InCl6, and Li3YCl; the polymer includes one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and perfluorosulfonic acid (Nafion).

[0044] In some embodiments, the compound formed by the lithium metal with one or more of fluorine, oxygen, sulfur, nitrogen, and phosphorus includes one or more of lithium fluoride (LiF), lithium oxide (Li2O), lithium nitride (Li3N), lithium sulfide (Li2S), and lithium phosphide (Li3P).

[0045] In some embodiments, the thickness of the first active material layer 1 is 1–100 μm, the thickness of the second active material layer 21 is 0.05–100 μm, the thickness of the third active material layer 31 is 0.05–100 μm, the thickness of the first artificial SEI layer 22 is 0.01–10 μm, and the thickness of the second artificial SEI layer 32 is 0.01–10 μm.

[0046] In a specific embodiment, the thickness of the first active material layer 1 can be 1um, 2um, 5um, 8um, 12um, 15um, 18um, 20um, 22um, 25um, 28um, 30um, 32um, 35um, 38um, 40um, 45um, 50um, 55um, 60um, 65um, 70um, 75um, 78um, 80um, 85um, 90um, 95um, or 100um. The thickness of the second active material layer 21 can be 0.05um, 0.1um, 1um, 2um, 5um, 8um, 12um, 15um, 18um, 20um, 22um, 25um, 28um, 30um, 32um, 35um, 38um, 40um, 45um, 50um, 55um, 60um, 65um, 70um, 75um, 78um, 80um, 85um, 90um, 95um, or 100um. The thickness of the third active material layer 31 can be 0.05um, 0.1um, 1um, 2um, 5um, 8um, 12um, 15um, 18um, 20um, 22um, 25um, 28um, 30um, 32um, 35um, 38um, 40um, 45um, 50um, 55um, 60um, 65um, 70um, 75um, 78um, 80um, 85um, 90um, 95um, or 100um. The thickness of the first artificial SEI layer 22 can be 0.01um, 0.05um, 0.08um, 0.12um, 0.15um, 0.18um, 0.2um, 0.22um, 0.25um, 0.28um, 0.3um, 0.32um, 0.35um, 0.38um, 0.4um, 0.45um, 0.5um, 0.55um, 0.60um, 0.65um, 0.7um, 0.75um, 0.78um, 0.8um, 0.85um, 0.9um, 0.95um, 1um, 5um, or 10um. The thickness of the second artificial SEI layer 32 can be 0.001um, 0.01um, 0.05um, 0.08um, 0.12um, 0.15um, 0.18um, 0.2um, 0.22um, 0.25um, 0.28um, 0.3um, 0.32um, 0.35um, 0.38um, 0.4um, 0.45um, 0.5um, 0.55um, 0.60um, 0.65um, 0.7um, 0.75um, 0.78um, 0.8um, 0.85um, 0.9um, 0.95um, 1um, 5um, or 10um.

[0047] Since the current collector-less negative electrode does not have an additional current collector, its mechanical strength is mainly determined by the first active material layer 1, the second active material layer 21, the third active material layer 31, the first artificial SEI layer 22, and the second artificial SEI layer 32. If the thickness of the second active material layer 21 and the third active material layer 31 is too low, the mechanical strength of the current collector-less negative electrode will be insufficient, and there is a risk of breakage. If the thickness of the first active material layer 1, the second active material layer 21, and the third active material layer 31 is too high, it will affect the ion conductivity of the current collector-less negative electrode.

[0048] If the thickness of the first artificial SEI layer 22 and the second artificial SEI layer 32 is too low, it will be difficult to protect the current-free negative electrode; if the thickness of the first artificial SEI layer 22 and the second artificial SEI layer 32 is too high, it will easily lead to an increase in the impedance of the current-free negative electrode, affecting the battery capacity retention rate.

[0049] In some embodiments, the mass content of lithium element in the first active material layer 1 is greater than 90%.

[0050] It should be noted that although the first active material layer 1 is lithium metal, certain impurities are allowed to exist therein. For example, in this embodiment, the impurity content of lithium metal in the first active material layer 1 is less than 0.05%.

[0051] In some embodiments, the lithium content in the second active material layer 21 and the third active material layer 31 is 0.05%-99.95% by mass. Correspondingly, the M content in the second active material layer 21 and the third active material layer 31 is 0.05%-99.95% by mass.

[0052] In a specific embodiment, the mass content of lithium element in the second active material layer 21 and the third active material layer 31 can be 0.05%, 0.1%, 0.5%, 1%, 2%, 5%, 8%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, 35%, 38%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 78%, 80%, 85%, 90%, 95%, or 99.95%.

[0053] In the second active material layer 21 and the third active material layer 31, the increased proportion of lithium and the decreased content of lithium-affinity alloying elements lead to an increased overpotential for lithium ion nucleation and a decreased effect on inducing uniform deposition of metallic lithium on the negative electrode side.

[0054] Referring to Figure 2, another embodiment of the current collector-free negative electrode structure provided in this application is shown, wherein the artificial SEI material comprises a lithium-containing inorganic compound; by weight, the first functional layer 1 and the second functional layer 3 comprise 5-95% parts of mutually doped lithium-containing inorganic compound and 95-5% parts of lithium metal alloy Li-M.

[0055] The first functional layer 1 and the second functional layer 3 contain mutually doped lithium-containing inorganic compounds and lithium metal alloy Li-M, which facilitates uniform lithium metal deposition, avoids the formation of lithium dendrites and dead lithium, thereby improving the battery's charge-discharge cycle stability, preventing battery capacity reduction due to active material consumption, and improving the battery's cycle performance. In this embodiment, the first functional layer 1 and the second functional layer 3 can be selected with relatively low thicknesses to avoid affecting the negative electrode energy density.

[0056] In some embodiments, the lithium-containing inorganic compound includes one or more of lithium fluoride (LiF), lithium oxide (Li2O), lithium nitride (Li3N), lithium sulfide (Li2S), lithium phosphide (Li3P), LATP, LZO, LLTO, LLZO, LGPS, LPSC, LiPON, Li3InCl6, and Li3YCl.

[0057] In some embodiments, the compound formed by the lithium metal with one or more of fluorine, oxygen, sulfur, nitrogen, and phosphorus includes one or more of lithium fluoride (LiF), lithium oxide (Li2O), lithium nitride (Li3N), lithium sulfide (Li2S), and lithium phosphide (Li3P).

[0058] Compared to the SEI layer generated by consuming lithium and electrolyte during the formation process of traditional batteries, the current collector-free negative electrode can achieve better protection for the current collector-free negative electrode by setting lithium-containing inorganic compounds as the first functional layer 1 and the second functional layer 3. At the same time, it can also reduce the irreversible consumption of lithium ions and electrolyte during the formation process and improve the battery capacity.

[0059] In some embodiments, the thickness of the first functional layer 1 is 0.1-100 μm, and the thickness of the second functional layer 3 is 0.1-100 μm.

[0060] In some embodiments, the current collector-free negative electrode further includes a negative electrode tab, which is electrically connected to the first active material layer 1.

[0061] The negative electrode tab is selected from a metallic material and is used for current extraction from the current-free negative electrode. It can be connected to the first active material layer 1 by welding.

[0062] Another embodiment of this application provides a method for preparing a current collector-free negative electrode as described above, comprising the following steps:

[0063] Lithium metal is provided as the first active material layer;

[0064] A first functional layer and a second functional layer are covered on both sides of the first active material layer. The first active material layer is lithium metal. The first functional layer and / or the second functional layer include lithium metal alloy Li-M and artificial SEI material. M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth.

[0065] By covering the first functional layer and the second functional layer on both sides of the first active material layer of lithium metal, direct contact between lithium metal and electrolyte can be avoided, thereby reducing side reactions. At the same time, this structure reduces the use of copper foil current collectors, thereby reducing weight and increasing energy density. Furthermore, the first and second functional layers can improve the support and mechanical strength of the current collector-less negative electrode, ensuring the strength requirements of the current collector-less negative electrode during winding and charge-discharge cycles, and avoiding breakage problems.

[0066] In some embodiments, the first functional layer and the second functional layer are prepared by one or more of the following methods: roll forming, coating, physical vapor deposition, chemical vapor deposition, and atomic layer deposition.

[0067] In some embodiments, when fabricating the current collector-free negative electrode shown in FIG1, the first functional layer and the second functional layer are prepared by the following method:

[0068] A lithium metal alloy Li-M is coated on both sides of the first active material layer, wherein M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth to obtain a second active material layer and a third active material layer.

[0069] The surfaces of the second and third active material layers are respectively covered with a first artificial SEI layer and a second artificial SEI layer.

[0070] When the second and third active material layers are prepared by roll forming, a lithium metal strip can be used as the first active material layer, and a strip-shaped lithium metal alloy Li-M can be used as the second and third active material layers. The second and third active material layers are respectively covered on both sides of the first active material layer, and then the first, second, and third active material layers are combined into one by roll forming.

[0071] When the second and third active material layers are prepared by physical vapor deposition, metal M can be deposited into the lithium metal of the first active material layer by magnetron sputtering or vacuum evaporation to form an alloy layer Li-M. Alternatively, metal M and lithium metal or alloy Li-M can be used as targets, and lithium metal alloy Li-M can be directly deposited on the surface of the first active material layer by magnetron sputtering or vacuum evaporation.

[0072] When performing vacuum evaporation, the target material is heated by resistance heating, electron beam evaporation, high frequency heating, or laser heating.

[0073] When the first artificial SEI layer and the second artificial SEI layer are prepared by roll forming, the prepared first artificial SEI layer and the second artificial SEI layer can be respectively covered on the surface of the second active material layer and the third active material layer. Then, the first artificial SEI layer is combined with the second active material layer and the second artificial SEI layer is combined with the third active material layer by roll forming.

[0074] When the first artificial SEI layer and the second artificial SEI layer are prepared by physical vapor deposition or atomic layer deposition, the target material of the corresponding element of the first artificial SEI layer and the second artificial SEI layer can be used for deposition; when chemical vapor deposition is performed, a certain reactive gas can be added, such as lithium phosphate Li3PO4 being magnetron sputtered in a nitrogen N2 atmosphere to generate lithium phosphorus oxynitride compound LiPON.

[0075] In some embodiments, when preparing the current collector-free negative electrode shown in FIG2, one or more of the methods described above, such as roll pressing, physical vapor deposition, chemical vapor deposition, and atomic layer deposition, can also be used.

[0076] In a preferred embodiment of this application, an in-situ method for generating the first functional layer and the second functional layer is provided. Specifically, the first functional layer and the second functional layer are prepared by the following method:

[0077] MX layers are deposited on both sides of the first active material layer, wherein M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth; and X includes one or more of halogens, O, S, N and P.

[0078] During battery charging, lithium atoms (Li) from the positive electrode react to generate M and artificial SEI components containing lithium compounds (LiX). Metal M can undergo an alloying reaction with metal Li to produce Li-M alloys.

[0079] By generating the first and second functional layers in situ, the bonding strength between the first and second functional layers and the first active material layer can be improved, preventing the first and second functional layers from pulverizing and detaching due to volume changes during charge-discharge cycles. Simultaneously, it also helps ensure the uniformity of doping of lithium-containing inorganic compounds LiX and lithium metal alloy Li-M in the first and second functional layers, achieving complete coverage of the first active material layer.

[0080] The following further explains the methods for generating the first and second functional layers in situ under different circumstances:

[0081] 1) The first functional layer and the second functional layer are a mixture of lithium halide and lithium metal alloy Li-M: metal halide M is deposited on both sides of the first active material layer respectively. x+ X - x The layer M is selected from one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; X is selected from one or more of F, Cl, Br, and I. Then, a metal halide M... x+ X - x During battery charging, lithium atoms (Li) originating from the positive electrode react to generate M and the artificial SEI component lithium halide (LiX). Metallic M can undergo an alloying reaction with metallic Li to produce Li-M alloys. The reactions involved in this process are as follows:

[0082] M x+ X - x +xLi=M+xLiX

[0083] M+Li = Li-M alloy

[0084] 2) The first functional layer and the second functional layer are a mixture of lithium oxide and metal alloy Li-M: metal oxide M is deposited on both sides of the first active material layer respectively. x+ O 2- x / 2 Layer M is selected from one or more of the following: gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; followed by a metal oxide M. x+ O 2- x / 2 During battery charging, lithium atoms (Li) from the positive electrode react to generate M and the artificial SEI component lithium oxide (Li₂O). Metallic M can then undergo an alloying reaction with metallic Li to produce a Li-M alloy. The reactions involved in this process are as follows:

[0085] M x+ O 2- x / 2 +xLi=M+x / 2Li2O

[0086] M+Li = Li-M alloy

[0087] Alternatively, the metal oxide M here x+ O 2- x / 2 These can be conductive metal oxides or non-conductive metal oxides. Conductive metal oxides can be classified into n-type conductive oxides (such as indium tin oxide (ITO), zinc aluminum oxide (AZO), fluorine-doped tin dioxide (FTO), indium tin zinc oxide (ITZO), zinc tin oxide (ZTO), zinc indium tin oxide (ZITO), etc.) and p-type conductive oxides (such as copper oxide (CuO), CuMO (M = Al, In, Ga, Mg), etc.); non-conductive metal oxides can be magnesium oxide (MgO), aluminum oxide (Al₂O₃), zinc oxide (ZnO), silicon oxide (SiO₂). x Tin oxide (SnO) and manganese oxide (MnO) x Zirconium oxide (ZrO), etc.

[0088] 3) The first functional layer and the second functional layer are a mixture of lithium sulfide and lithium metal alloy Li-M: metal sulfide M is deposited on both sides of the first active material layer. x+ S 2- x / 2 Layer M is selected from one or more of the following: gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; followed by a metal sulfide M. x+ S 2- x / 2 During the charging process of a lithium battery, lithium atoms (Li) originating from the positive electrode react to generate M and the artificial SEI component lithium sulfide (Li₂S). Metallic M can undergo an alloying reaction with metallic Li to produce a Li-M alloy. The reactions involved in this process are as follows:

[0089] M x+ S 2- x / 2 +xLi=M+x / 2Li2S

[0090] M+Li = Li-M alloy

[0091] 4) The first functional layer and the second functional layer are a mixture of lithium nitride and lithium metal alloy Li-M: metal nitride M is deposited on both sides of the first active material layer. x+ N 3- x / 3Layer M is selected from one or more of the following: gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; followed by a metal nitride M. x+ N 3- x / 3 During battery charging, lithium atoms (Li) from the positive electrode react to generate M and the artificial SEI component lithium nitride (Li3N). Metallic M can undergo an alloying reaction with metallic Li to produce a Li-M alloy. The reactions involved in this process are as follows:

[0092] M x+ N 3- x / 3 +Li=M+Li3N

[0093] M+Li = Li-M alloy

[0094] 5) The first functional layer and the second functional layer are a mixture of lithium phosphide and lithium metal alloy Li-M: metal phosphide M is deposited on both sides of the first active material layer respectively. x+ P 3- x / 3 Layer M is selected from one or more of the following: gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus, and bismuth; followed by a metal nitride M. x+ P 3- x / 3 During battery charging, lithium atoms (Li) from the positive electrode react to generate M and the artificial SEI component lithium phosphide (Li3N). Metallic M can then undergo an alloying reaction with metallic Li to produce a Li-M alloy. The reactions involved in this process are as follows:

[0095] M x+ P 3- x / 3 +Li=M+Li3P

[0096] M+Li = Li-M alloy

[0097] Another embodiment of this application provides a battery including a current collector-less negative electrode as described above or a current collector-less negative electrode prepared by the preparation method described above.

[0098] By adopting the current collector-free negative electrode as described above, the weight of the battery negative electrode can be reduced, and the battery energy density can be improved. At the same time, the current collector-free negative electrode has high electronic conductivity, mechanical strength and self-supporting performance, and can realize the function of traditional current collectors, thereby effectively avoiding the impedance problem and negative electrode strength problem caused by removing traditional current collectors.

[0099] In some embodiments, the battery is a stacked battery or a wound battery.

[0100] In some embodiments, the battery is a cylindrical battery or a square battery.

[0101] In some embodiments, the battery is a pouch battery or a hard-shell battery.

[0102] In one embodiment, the battery further includes an electrolyte layer and a positive electrode, the electrolyte layer being located between the positive electrode and the current collector-free negative electrode.

[0103] In the above different embodiments, the electrolyte layer is selected from one or more of a diaphragm, solid electrolyte, semi-solid electrolyte, or gel electrolyte. The diaphragm includes one or more of polypropylene (PP) and polyethylene (PE). The solid electrolyte includes one or more of oxide solid electrolyte, sulfide solid electrolyte, halogen solid electrolyte, polymer solid electrolyte, and composite solid electrolyte (inorganic filler + polymer matrix). The sulfide solid electrolyte includes at least one of Li6PS5X (X = F, Cl, Br, I), Li2S-SiS2, Li2S-P2S5, Li2S-GeS2, Li2S-SiS2-P2S5, Li2S-GeS2-P2S5, Li2S-SnS2-P2S5, and Li2S-AlS2-P2S5. The halide solid electrolyte includes at least one of Li2MnCl4, Li3InCl6, Li2ZnCl4, LiYbF4, LiAlF4, Li3YCl6, Li3BrCl6, and Li6CoCl8. The semi-solid electrolyte includes the solid electrolyte and the electrolyte solution, and the gel electrolyte includes a polymer matrix and the electrolyte solution, wherein the electrolyte solution and the polymer matrix form a gel state. When the electrolyte layer is selected from a separator, the battery also includes an electrolyte solution, and in this case, the battery is a liquid electrolyte battery; when the electrolyte layer is selected from a solid electrolyte, the battery is a solid-state battery; when the electrolyte layer is selected from a semi-solid electrolyte, the battery is a semi-solid-state battery; and when the electrolyte layer is selected from a gel electrolyte, the battery is a gel electrolyte battery.

[0104] The electrolyte comprises lithium salts, solvents, and additives; the solvents include one or more of the following: carbonates (ethylene carbonate EC, propylene carbonate PC, butene carbonate BC, dimethyl carbonate DMC, diethyl carbonate DEC, methyl ethyl carbonate EMC, γ-butyrolactone (BL), ethers (tetrahydrofuran THF, 2-methyl-tetrahydrofuran 2-Me-THF, dimethoxydimethyl ether DMM, 1,2-dimethoxyethane DOL-DME), and nitriles (acetonitrile AN, etc.); the lithium salts include lithium hexafluorophosphate LiPF6, lithium perchlorate LiClO4, lithium tetrafluoroborate LiBF4, lithium hexafluoroarsenate LiAsF6, and other organic lithium salts (such as lithium trifluoromethanesulfonate LiCF3SO, bis(2-methyl-3-methyl-4-methyl-3 ... One or more of the following: lithium trifluoromethanesulfonyl)imide LiTFSI, lithium difluorosulfonylimide LiFSI, lithium trifluoromethanesulfonyl-perfluorobutylsulfonylimide LiTNFSI, lithium fluorosulfonyl-perfluorobutylsulfonylimide LiFNFSI, lithium bis(oxalato)borate LiBOB, LiN(CF3SO2)2, and LiC(SO2CF3)3; additives include one or more of the following: film-forming additives, conductive additives, flame-retardant additives, overcharge protection additives, additives for controlling the water and HF content in the electrolyte, and general-purpose additives for improving low-temperature performance. They can also be additives for improving the stability of the electrode-electrolyte interface, such as fluoroethylene carbonate FEC and lithium nitrate LiNO3.

[0105] Another embodiment of this application provides an electrical device including the battery described above.

[0106] Because of the use of the battery as described above, the battery has a high energy density and low impedance, which can reduce the size and weight of the electrical device and alleviate the heat generation problem caused by the operation of the battery itself.

[0107] In some embodiments, the electrical devices include electric vehicles, electronic cigarettes, electronic vaporizers, wireless headphones, robotic vacuum cleaners, drones, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0108] The present application will be further illustrated by the following examples.

[0109] Example 1

[0110] This embodiment illustrates the method for preparing the current collector-free negative electrode and lithium battery disclosed in this application, including the following steps:

[0111] Lithium metal is provided as the first active material layer, and the thickness of the first active material layer is 20 μm;

[0112] Preparation of the second and third active material layers: A strip of lithium metal alloy Li-Mg is coated on both sides of the first active material layer and rolled to obtain the second and third active material layers. The thickness of the second active material layer is 2 μm and the thickness of the third active material layer is 2 μm. In the second and third active material layers, the mass content of Li element is 75% and the mass content of Mg element is 25%.

[0113] Preparation of the first and second artificial SEI layers: Using MgF2 metal halide as the target material, MgF2 alloy layers are deposited on the surfaces of the second and third active material layers, respectively, away from the first active material layer, by magnetron sputtering, to obtain a current collector-free negative electrode; the obtained current collector-free negative electrode is assembled with a positive electrode, a separator, and an electrolyte to obtain a lithium battery; the lithium battery is subjected to charge-discharge formation operation. During the formation process, MgF2 metal halide reacts with lithium atoms Li from the positive electrode during the charging process of the lithium battery to generate Mg and the artificial SEI component lithium halide LiF; metallic Mg reacts with metallic Li to produce Li-Mg alloy.

[0114] Example 2

[0115] This embodiment illustrates the method for preparing the current collector-free negative electrode and lithium battery disclosed in this application, including the following steps:

[0116] Lithium metal is provided as the first active material layer, and the thickness of the first active material layer is 10 μm;

[0117] The first and second functional layers are prepared in situ, namely, AgCl layers are deposited on both sides of the first active material layer. During battery charging, lithium atoms Li from the positive electrode react to generate Ag and artificial SEI component lithium-containing compound LiCl. Metallic Ag can undergo an alloying reaction with metallic Li to produce Li-Ag alloy.

[0118] Example 3

[0119] This embodiment illustrates the method for preparing the current collector-free negative electrode and lithium battery disclosed in this application, including most of the operational steps in Example 1, with the following differences:

[0120] In the preparation of the second and third active material layers, lithium alloy Li-Sn was used instead of lithium alloy Li-Mg in Example 1. SnCl2 was used instead of MgF2 in the first and second artificial SEI layers in Example 1.

[0121] Example 4

[0122] This embodiment illustrates the method for preparing the current collector-free negative electrode and lithium battery disclosed in this application, including most of the operational steps in Example 1, with the following differences:

[0123] In the preparation of the first and second artificial SEI layers: using Li2O metal oxide as the target material, Li2O metal oxide layers are deposited on the surfaces of the second and third active material layers away from the first active material layer by magnetron sputtering to obtain a current collector-free negative electrode; the obtained current collector-free negative electrode is assembled with a positive electrode, a separator, and an electrolyte to obtain a lithium battery.

[0124] Example 5

[0125] This embodiment illustrates the method for preparing the current collector-free negative electrode and lithium battery disclosed in this application, including most of the operational steps in Example 1, with the following differences:

[0126] In the preparation of the first and second artificial SEI layers: using LiF metal fluoride as the target material, LiF metal fluoride layers are deposited on the surfaces of the second and third active material layers, which are far from the first active material layer, by magnetron sputtering, to obtain a current collector-free negative electrode; the obtained current collector-free negative electrode is assembled with a positive electrode, a separator, and an electrolyte to obtain a lithium battery.

[0127] Comparative Example 1

[0128] This comparative example is used to illustrate the current collector-free negative electrode and the preparation method of lithium battery disclosed in this application. It includes most of the operation steps in Example 1, with the following differences:

[0129] Without preparing the first and second artificial SEI layers, the negative electrode without current collectors, obtained by directly combining the first active material layer, the second active material layer and the third active material layer, is assembled with the positive electrode, the separator and the electrolyte to obtain a lithium battery, and then a charge-discharge formation operation is performed.

[0130] Comparative Example 2

[0131] This embodiment illustrates the method for preparing the current collector-free negative electrode and lithium battery disclosed in this application, including most of the operational steps in Example 1, with the following differences:

[0132] Lithium metal is directly used as the current collector-less negative electrode. The current collector-less negative electrode is assembled with the positive electrode, separator and electrolyte to obtain a lithium battery, and then charge and discharge formation operation is performed.

[0133] Performance testing

[0134] The following performance tests were performed on the negative electrode and lithium battery prepared above:

[0135] Mechanical strength test of the negative electrode: For the above-mentioned examples and comparative examples, samples were prepared and Young's modulus was tested using a nanoindenter.

[0136] Electrochemical performance testing of lithium batteries: The negative electrode adopted the schemes in the above examples and comparative examples, respectively, and the positive electrode adopted commercial NCM811 with an areal capacity of 3mAh / cm². 2 Seven types of stacked batteries were fabricated in a dry room using commercially available DOL-DME (1:1 vol%, 1 mol LiTFSI) electrolyte. After pressure formation, the batteries underwent cycle testing at 0.1C rate.

[0137] The test results were all entered into Table 1.

[0138] Table 1

[0139] As can be seen from the test results in Table 1, the current collector-free negative electrode prepared by the preparation method provided in this application has good mechanical strength and self-supporting properties. At the same time, when it is applied to lithium batteries, it can effectively improve the capacity and cycle life of lithium batteries.

[0140] Comparing the test results of Example 1 with those of Comparative Examples 1 and 2, it can be seen that by setting the first functional layer and the second functional layer on both sides of the first active material layer, a protective effect can be formed on the negative electrode and the electrolyte, effectively reducing the consumption of electrolyte during battery cycling, thereby improving the cycle life of the lithium battery. At the same time, the first functional layer and the second functional layer can effectively improve the mechanical strength of the current collector-less negative electrode, suppress the deformation of the negative electrode, and play a certain protective role on the first active material layer, meeting the strength requirements of the current collector during the production process.

[0141] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A current collector-free negative electrode, characterized in that, It includes a first active material layer and a first functional layer and a second functional layer respectively disposed on both sides of the first active material layer. The first active material layer is lithium metal, and the first functional layer and / or the second functional layer includes a lithium metal alloy Li-M and an artificial SEI material. M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth.

2. The current collector-free negative electrode according to claim 1, characterized in that, The first functional layer includes a second active material layer and a first artificial SEI layer. The second active material layer is located between the first active material layer and the first artificial SEI layer. The second active material layer includes a lithium metal alloy Li-M, and the first artificial SEI layer includes an artificial SEI material. The second functional layer includes a third active material layer and a second artificial SEI layer. The third active material layer is located between the first active material layer and the second artificial SEI layer. The third active material layer includes a lithium metal alloy Li-M, and the second artificial SEI layer includes an artificial SEI material. The artificial SEI material includes one or more of lithium-containing inorganic compounds and polymers.

3. The current collector-less negative electrode according to claim 2, characterized in that, The lithium-containing inorganic compound includes one or more compounds formed from lithium metal and one or more of fluorine, oxygen, sulfur, nitrogen, and phosphorus, as well as LATP, LZO, LLTO, LLZO, LGPS, LPSC, Li3InCl6, and Li3YCl; the polymer includes one or more of polyethylene oxide (PEO), polyvinylidene fluoride (PVDF), polyvinyl alcohol (PVA), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), and perfluorosulfonic acid (Nafion).

4. The current collector-free negative electrode according to claim 2, characterized in that, The thickness of the first active material layer is 1–100 μm, the thickness of the second active material layer is 0.05–100 μm, the thickness of the third active material layer is 0.05–100 μm, the thickness of the first artificial SEI layer is 0.01–10 μm, and the thickness of the second artificial SEI layer is 0.01–10 μm.

5. The current collector-free negative electrode according to claim 1 or 2, characterized in that, In the first active material layer, the mass content of lithium element is greater than 90%.

6. The current collector-less negative electrode according to claim 2, characterized in that, In the second and third active material layers, the mass content of lithium element is 0.05%-99.95%.

7. The current collector-free negative electrode according to claim 1, characterized in that, The artificial SEI material comprises a lithium-containing inorganic compound; by weight, the first functional layer and the second functional layer comprise 5-95% of mutually doped lithium-containing inorganic compounds and 95%-5% of lithium metal alloy Li-M.

8. The current collector-less negative electrode according to claim 7, characterized in that, The lithium-containing inorganic compounds include one or more of lithium fluoride (LiF), lithium oxide (Li2O), lithium nitride (Li3N), lithium sulfide (Li2S), lithium phosphide (Li3P), LATP, LZO, LLTO, LLZO, LGPS, LPSC, LiPON, Li3InCl6, and Li3YCl.

9. The current collector-free negative electrode according to claim 7, characterized in that, The thickness of the first functional layer is 0.1-100um, and the thickness of the second functional layer is 0.1-100um.

10. The current collector-free negative electrode according to claim 1, characterized in that, It also includes a negative electrode tab, which is electrically connected to the first active material layer.

11. The method for preparing a current collector-free negative electrode according to any one of claims 1 to 10, characterized in that, The following steps are included: Lithium metal is provided as the first active material layer; A first functional layer and a second functional layer are covered on both sides of the first active material layer. The first active material layer is lithium metal. The first functional layer and / or the second functional layer include lithium metal alloy Li-M and artificial SEI material. M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth.

12. The method for preparing a current collector-free negative electrode according to claim 11, characterized in that, The first functional layer and the second functional layer are prepared by one or more of the following methods: roll forming, coating, physical vapor deposition, chemical vapor deposition, and atomic layer deposition.

13. The method for preparing a current collector-free negative electrode according to claim 11, characterized in that, The first functional layer and the second functional layer are prepared by the following method: A lithium metal alloy Li-M is coated on both sides of the first active material layer, wherein M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth, and the mass fraction of lithium metal is 0.05%-99.95% to obtain the second active material layer and the third active material layer. The surfaces of the second and third active material layers are respectively covered with a first artificial SEI layer and a second artificial SEI layer.

14. The method for preparing a current collector-free negative electrode according to claim 11, characterized in that, The first functional layer and the second functional layer are prepared by the following method: MX layers are deposited on both sides of the first active material layer, wherein M includes one or more of gold, indium, magnesium, zinc, chromium, nickel, molybdenum, tungsten, vanadium, titanium, niobium, zirconium, cobalt, manganese, aluminum, copper, boron, silver, tin, silicon, carbon, phosphorus and bismuth; and X includes one or more of halogens, O, S, N and P. During battery charging, lithium atoms (Li) from the positive electrode react to generate M and artificial SEI components containing lithium compounds (LiX). Metal M can undergo an alloying reaction with metal Li to produce Li-M alloys.

15. A battery, characterized in that, This includes the current collector-free negative electrode as described in any one of claims 1 to 10, or the current collector-free negative electrode prepared by the preparation method described in any one of claims 11 to 14.

16. An electrical appliance, characterized in that, Includes the battery as described in claim 15.

Images