Negative active material, preparation method thereof, electrode sheet, and battery

Abstract

The application provides a negative electrode active material and a preparation method thereof, a pole piece and a battery, and relates to the field of batteries. x TM y ChD b , wherein A is lithium and / or sodium, TM is a transition metal, Ch is a chalcogen element, D is O or B a C 1‑a , B is selected from at least one of a negative monovalent anion and a negative monovalent anion cluster, C is selected from at least one of a negative trivalent anion and a negative trivalent anion cluster, 0.5<=x<=8, 0.8<=y<=1.1, 0.25<=a<=0.75, 0.8<=b<=1.2; the negative electrode active material has an amorphous phase, and the mass ratio of the amorphous phase in the negative electrode active material is not less than 10%. The application can improve the technical problem that the existing negative electrode active material cannot simultaneously have high capacity, low expansion and high safety.

Description

Technical Field

[0001] This application relates to the field of batteries, and more specifically, to a negative electrode active material and its preparation method, an electrode sheet, and a battery. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics and new energy electric vehicles due to their advantages such as high energy density and long cycle life. However, the rapid development of electric transportation and large-scale energy storage has placed higher demands on lithium-ion batteries.

[0003] Currently, the energy density of lithium batteries is not high enough, resulting in poor driving range for electric vehicles and making it difficult to meet the requirements of medium- and long-distance transportation. Therefore, it is necessary to further improve the energy density of lithium batteries. Electrode active materials are key to determining the upper limit of battery energy density. Current research on anode materials mainly focuses on graphite anodes, lithium titanate anodes, and silicon-based materials. However, graphite anodes and lithium titanate anodes have low capacities; in particular, the actual usable capacity of graphite anodes does not exceed 350 mAh / g. -1 Furthermore, high-current charging can easily lead to lithium metal deposition, causing battery damage and safety issues. Lithium titanate anodes also have lower capacity, with actual capacities below 170 mAh / g. -1 Furthermore, titanium-based materials are relatively expensive. Silicon-based anode materials have a high theoretical specific capacity, reaching up to 3000 mAh g⁻¹. -1 However, high lithium intercalation can lead to severe volume expansion of the electrode, causing pulverization of the electrode material and continuous cracking and regrowth of the SEI film, resulting in a continuous decline in battery performance. Furthermore, regardless of whether it is graphite or silicon-based, on the one hand, it is extremely prone to safety accidents after thermal runaway and contact with water; on the other hand, after lithium intercalation, the activity is extremely high. In the case of battery damage or disassembly, the lithium-intercalated negative electrode will react with moisture in the air and release heat violently when exposed to air, which can also easily lead to thermal runaway and safety accidents. Summary of the Invention

[0004] In view of the above problems, this application provides a negative electrode active material and its preparation method, electrode sheet and battery, which can improve the technical problem that existing negative electrode active materials cannot simultaneously achieve high capacity, low expansion and high safety.

[0005] In a first aspect, embodiments of this application provide a negative electrode active material, the chemical formula of which is A. x TM y ChD b In the formula, A is lithium and / or sodium, TM is a transition metal, Ch is a chalcogenide, and D is O or B. a C 1-aB is selected from at least one class of monovalent anions and monovalent anion clusters, C is selected from at least one class of trivalent anions and trivalent anion clusters, 0.5≤x≤8, 0.8≤y≤1.1, 0.25≤a≤0.75, 0.8≤b≤1.2;

[0006] Among them, the negative electrode active material has an amorphous phase and the mass proportion of the amorphous phase in the negative electrode active material is not less than 10%.

[0007] In the technical solution of this application embodiment, the negative electrode active material has an amorphous phase and the mass ratio of the amorphous phase in the negative electrode active material is not less than 10%. On the one hand, the isotropic volume change characteristics of amorphous materials can significantly reduce stress concentration. At the same time, the microstructure is relatively loose, which can alleviate volume expansion. Furthermore, ions do not need to cross grain boundaries in amorphous materials and can move more easily in the amorphous structure, which is beneficial to improving the ion diffusion rate. Also, due to its amorphous structure, amorphous materials can accommodate more lithium / sodium ions, thereby increasing battery capacity. On the other hand, the above-mentioned general anti-perovskite or double anti-perovskite amorphous materials have good stability and safety in different lithium insertion / extraction states. They react mildly when exposed to water, do not burn or explode, and have no toxic or harmful products. They can be used in water-degradable batteries or water-soluble batteries in environments containing water or aqueous solutions, such as water-degradable batteries or water-soluble batteries in marine or humid environments.

[0008] In some embodiments, the mass percentage of the amorphous phase in the negative electrode active material is not less than 30%.

[0009] Optionally, the negative electrode active material is an amorphous phase.

[0010] In some embodiments, 1.9 ≤ x ≤ 2.1; and / or, 0.9 ≤ y ≤ 1.1; and / or, 0.45 ≤ a ≤ 0.55; and / or, 0.9 ≤ b ≤ 1.1.

[0011] In some embodiments, D is 0 and b = 1; or, D is B. a C 1-a , 1≤x≤2.5, can be chosen as 1.9≤x≤2.1.

[0012] In some embodiments, TM includes at least one of Fe, Co, Mn, Ni, Cu, Cr, V, Ti, W, Si, Sn, Nb, and Mg.

[0013] In some embodiments, Ch includes at least one of S, Se, and Te.

[0014] Optionally, B includes F. - Cl - ,Br - I- H - OH - BH4 - NH2 - NO2 - and CN - At least one of them.

[0015] Optionally, C includes N 3- (PO4) 3- (SbO4) 3- and (AsO4) 3- At least one of them.

[0016] In a second aspect, this application provides a method for preparing the negative electrode active material provided in the first aspect of this application, which includes: obtaining an anti-perovskite material characterized by a general chemical formula, subjecting the anti-perovskite material to amorphization treatment, and obtaining the negative electrode active material.

[0017] The amorphization process includes: fabricating a working electrode by mixing an anti-perovskite material and a conductive agent, assembling it with a counter electrode into a liquid half-cell, and then subjecting the liquid half-cell to constant current discharge to remove element A to obtain an amorphous phase, wherein element A is Li and the counter electrode is lithium metal, or element A is Na and the counter electrode is lithium metal.

[0018] In the technical solution of this application embodiment, the above method can be used to amorphize the anti-perovskite material, and the negative electrode active material obtained by the above method can stably exist and carry out electrochemical reactions compared with the negative electrode active material prepared by ball milling solid phase method, and the first coulombic efficiency is significantly improved, and the battery cycle stability is effectively enhanced.

[0019] In some embodiments, the preparation method further includes: performing constant current charging on the liquid half-cell that has obtained an amorphous phase to obtain a lithium / sodium-rich negative electrode active material.

[0020] Thirdly, this application provides an electrode sheet comprising an active material layer, wherein the active material layer includes the negative electrode active material provided in the above embodiments.

[0021] Fourthly, this application provides a battery that includes the electrode sheets described in the above embodiments.

[0022] Optionally, the battery includes a water-degradable battery.

[0023] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0024] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0025] Figure 1 The image shows the XRD pattern of the negative electrode active material prepared in Example 1.

[0026] Figure 2 The image shows the XRD pattern of the negative electrode active material prepared in Example 2.

[0027] Figure 3 The image shows the XRD pattern of the negative electrode active material prepared in Example 3.

[0028] Figure 4 The image shows the XRD pattern of the negative electrode active material prepared in Example 5.

[0029] Figure 5 Li2FeTe(N) in Example 7 0.5 Cl 0.5 The first charge-discharge curve of a Li half-cell;

[0030] Figure 6 The XRD pattern of Li₂FeSO₄ prepared in Comparative Example 1;

[0031] Figure 7 The XRD pattern of Li2FeSeO prepared in Comparative Example 2;

[0032] Figure 8 The XRD pattern of Li₂CoSeO prepared in Comparative Example 3;

[0033] Figure 9 The XRD pattern of LiFeSO4 prepared in Comparative Example 4;

[0034] Figure 10 The XRD pattern of LiFeSO₄ prepared in Comparative Example 5;

[0035] Figure 11 The charge-discharge curves of the first LiFeSO4||Li half-cell are shown.

[0036] Figure 12 The charge-discharge curves of the second LiFeSO4||Li half-cell are shown.

[0037] Figure 13 The charge-discharge curves for the third LiFeSO4||Li half-cell are shown.

[0038] Figure 14The first charge-discharge curve of the Li5FeSO4||Li half-cell;

[0039] Figure 15 The first charge-discharge curve of the Li5FeSO4||Na half-cell;

[0040] Figure 16 The first charge-discharge curve of the LiCoO2||Li3YCl3Br3||Li3FeSO all-solid-state full cell under test conditions of 60℃ and voltage range of 0.5-4.2V.

[0041] Figure 17 The first charge-discharge curve of the LiCoO2||Li3YCl3Br3||Li3FeSO all-solid-state full cell in the voltage range of 0-4.6V under test conditions of 60℃;

[0042] Figure 18 The graph shows the charge-discharge cycle curves of the LiCoO2||Li3YCl3Br3||Li3FeSO all-solid-state full cell under test conditions of 60℃ and voltage range of 0.5-4.2V. Detailed Implementation

[0043] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0045] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0046] The inventors discovered that for chemical formula A x TM y ChD b (A represents lithium and / or sodium, TM represents transition metals, Ch represents chalcogens, and D represents O or B) a C1-a B is selected from at least one class of monovalent anions and monovalent anion clusters, and C is selected from at least one class of trivalent anions and trivalent anion clusters. The crystalline phase of the compound (0.5≤x≤8, 0.8≤y≤1.1, 0.25≤a≤0.75, 0.8≤b≤1.2) is basically unable to insert A, but the crystalline phase can be transformed into an amorphous phase after de-insertion of A and the transformation is irreversible. The amorphous phase can reversibly insert and de-inserte A.

[0047] In view of the above, this application is hereby submitted.

[0048] This application provides a negative electrode active material, the chemical formula of which is A. x TM y ChD b In the formula, A is lithium and / or sodium, TM is a transition metal, Ch is a chalcogenide, and D is O or B. a C 1-a B is selected from at least one class of monovalent anions and monovalent anion clusters, C is selected from at least one class of trivalent anions and trivalent anion clusters, 0.5≤x≤8, 0.8≤y≤1.1, 0.25≤a≤0.75, 0.8≤b≤1.2; wherein, the negative electrode active material has an amorphous phase and the mass percentage of the amorphous phase in the negative electrode active material is not less than 10%.

[0049] The term "and / or" merely describes the relationship between related objects, indicating that three relationships can exist. "A is Li and / or Na" can represent: Li alone, Li and Na simultaneously, or Na alone. It is understood that the choice of A can be based on common choices in practical applications. When anti-perovskite materials are used as positive electrode active materials in batteries, A is Li when the battery is a lithium-ion battery, and A is Na when the battery is a sodium-ion battery. It should be noted that in this application, "alone / " indicates "or." For ease of description, the following description uses A as Li and the battery as a lithium-ion battery as an example.

[0050] Clusters are relatively stable microscopic or submicroscopic aggregates composed of several or even thousands of atoms, molecules or ions bound together by physical or chemical forces. Anionic clusters refer to clusters that ultimately exhibit a negative valence state.

[0051] The term B is selected from at least one class of monovalent anions and monovalent anion clusters. This means that B is a monovalent anion and / or a monovalent anion cluster. It can be understood that there are multiple types of monovalent anions and multiple types of monovalent anion clusters. B can be a combination of one or more of the multiple monovalent anions and multiple monovalent anion clusters. Similarly, C can be a combination of one or more of the multiple trivalent anions and multiple trivalent anion clusters.

[0052] The amorphous phase in the negative electrode active material, with a mass percentage of at least 10%, means that the entire negative electrode active material is amorphous, or that part of the negative electrode active material is anti-perovskite crystalline phase, and the remainder is amorphous phase, with a mass percentage of amorphous phase ≥ 10%. The mass percentage of amorphous phase can be determined by: normalizing the characteristic peaks of each phase and calculating the percentage of amorphous phase characteristic peaks as the percentage content of the corresponding phase; and simultaneously combining this with transmission electron microscopy (TEM) testing to determine the ratio of crystalline to amorphous phase structures through atomic-level morphology characterization.

[0053] It should be noted that after the negative electrode active material mentioned in this application is applied to the assembly of negative electrode sheets to form a battery, the amorphous phase can be reversibly de-lithiated and de-lithiated. At this time, as the negative electrode active material is delithiated during the discharge process of the battery, the crystalline phase will eventually be completely transformed into the amorphous phase, and this crystalline phase transformation is irreversible. That is, even if the negative electrode active material is delithiated in the future, it will not cause the amorphous phase to transform into the crystalline phase. However, when it is entirely crystalline, it is difficult to achieve lithium intercalation and cannot be used as a negative electrode active material. Therefore, the mass ratio of the amorphous phase in the negative electrode active material is not less than 10% refers to the initial state of the material, that is, the state before feeding. When the negative electrode active material is applied to the battery system, the content of the amorphous phase will change after charge and discharge cycles.

[0054] The negative electrode active material provided in this application utilizes the fact that the negative electrode active material has an amorphous phase and the mass proportion of the amorphous phase in the negative electrode active material is not less than 10%. On the one hand, the isotropic volume change characteristics of amorphous materials can significantly reduce stress concentration. At the same time, the relatively loose microstructure can alleviate volume expansion. Furthermore, ions do not need to cross grain boundaries in amorphous materials and can move more easily in the amorphous structure, which is beneficial to improving the ion diffusion rate. Also, due to its amorphous structure, amorphous materials can accommodate more lithium / sodium ions, thereby increasing battery capacity. On the other hand, the above-mentioned general anti-perovskite or double anti-perovskite amorphous materials have good stability and safety in different lithium insertion / extraction states. They react mildly when exposed to water, do not burn or explode, and have no toxic or harmful products. They can be used in water-degradable or water-soluble batteries in environments containing water or aqueous solutions, such as water-degradable or water-soluble batteries in marine or humid environments.

[0055] For example, x is any value of 1, 1.2, 1.5, 1.7, 2, 2.3, or 2.5 or between any two values; y is any value of 0.8, 0.9, 1, 1.1, or 1.2 or between any two values; a is any value of 0.25, 0.35, 0.45, 0.55, 0.65, or 0.75 or between any two values; and b is any value of 0.8, 0.9, 1, 1.1, or 1.2 or between any two values.

[0056] Optionally, the amorphous phase accounts for no less than 30% of the mass of the negative electrode active material, and may further be no less than 50%.

[0057] Optionally, the negative electrode active material is an amorphous phase.

[0058] That is, the active phase of the negative electrode is entirely amorphous.

[0059] In some alternative embodiments, 1.9 ≤ x ≤ 2.1; and / or, 0.9 ≤ y ≤ 1.1; and / or, 0.45 ≤ a ≤ 0.55; and / or, 0.9 ≤ b ≤ 1.1.

[0060] Within the aforementioned range, adjusting the structure of the negative electrode active material by adjusting the element ratio is beneficial to further improve the capacity of the battery made from the negative electrode active material.

[0061] Alternatively, D can be 0 and b = 1; or D can be B. a C 1-a , 1≤x≤2.5, can be chosen as 1.9≤x≤2.1.

[0062] That is, when D is O and b = 1, the general chemical formula of the negative electrode active material is A. x TM y ChO. When D is B a C 1-a At that time, the general chemical formula of the negative electrode active material is A x TM y Ch(B a C 1-a ) b Where 1≤x≤2.5, it can be selected as 1.9≤x≤2.1.

[0063] In some alternative embodiments, TM includes at least one of Fe, Co, Mn, Ni, Cu, Cr, V, Ti, W, Si, Sn, Nb, and Mg.

[0064] In some alternative embodiments, Ch includes at least one of S, Se, and Te.

[0065] Optionally, B includes F. - Cl - ,Br - I - H - OH - BH4 - NH2 - NO2 - and CN - At least one of them.

[0066] Optionally, C includes N 3- (PO4)3- (SbO4) 3- and (AsO4) 3- At least one of them.

[0067] The abundance of nitrogen (N) on Earth can reduce material costs and battery costs. The stable structures of the aforementioned anion clusters are beneficial for improving the stability of anti-perovskite materials.

[0068] Optionally, the negative electrode active material includes LiFeSO₄, Li₃FeSO₄, Li₅FeSO₄, or Li₂FeTe(N)₂ 0.5 Cl 0.5 ).

[0069] There are various methods for preparing the above-mentioned negative electrode active materials, such as ball milling solid-phase synthesis and mechanical alloy pre-lithiation.

[0070] Among them, the ball mill solid-state synthesis method refers to the process of preparing amorphous phase by using a high-energy or high-speed planetary ball mill to provide energy for chemical reactions. Taking LiFeSO as an example, Li2O, Fe2O3 and Fe2S3 are used as raw materials, weighed according to a certain stoichiometric ratio, and then mechanically ground in a high-energy or high-speed planetary ball mill to obtain amorphous phase lithium-poor anode LiFeSO.

[0071] The mechanical alloy pre-lithiation method includes: under inert gas protection, molten metallic lithium and crystalline active material are placed in a tantalum crucible, and ball milling / stirring reaction is carried out using a magnetic stirrer or ball mill to obtain an amorphous lithium-rich anode at the active material level.

[0072] However, the inventors discovered that the negative electrode active material prepared by ball milling solid-state synthesis has a relatively low degree of amorphization and a significant decrease in the initial coulombic efficiency of the battery. This may be because the material particles prepared by ball milling solid-state synthesis are small and have many surface defects. During the initial lithium insertion process, some lithium enters these defect sites and undergoes an irreversible reaction, resulting in a high initial lithium insertion amount and reduced initial coulombic efficiency. Furthermore, the mechanical alloy pre-lithiation method cannot prepare lithium-poor negative electrodes.

[0073] Therefore, this application also provides an electrochemical preparation method for the above-mentioned negative electrode active material, the preparation method comprising: obtaining an anti-perovskite material characterized by a general chemical formula, and subjecting the anti-perovskite material to an amorphization treatment to obtain the negative electrode active material;

[0074] The amorphization process includes: fabricating a working electrode by mixing an anti-perovskite material and a conductive agent, assembling it with a counter electrode into a liquid half-cell, and then subjecting the liquid half-cell to constant current charging to remove element A to obtain an amorphous phase, wherein element A is Li and the counter electrode is lithium metal, or element A is Na and the counter electrode is lithium metal.

[0075] Since the above-mentioned amorphization treatment involves using the prepared untreated anti-perovskite material with a good crystal structure as the positive electrode of the half-cell, the anti-perovskite material undergoes delithiation during the charging process of the half-cell, transforming from a crystalline phase to an amorphous phase, and this transformation is irreversible. Therefore, the above method can be used to amorphize the anti-perovskite material. Moreover, the negative electrode active material obtained by the above method can exist stably and carry out electrochemical reactions compared with the negative electrode active material prepared by ball milling solid-state method, and the initial coulombic efficiency is significantly improved, and the battery cycle stability is effectively enhanced.

[0076] It should be further noted that since the amorphous phase is prepared by the above-mentioned electrochemical delithiation method, the negative electrode active material obtained by the delithiation method is a lithium-poor / sodium phase. Therefore, in some optional embodiments, the preparation method further includes: performing constant current discharge on the liquid half-cell that has obtained the amorphous phase to obtain a lithium-rich / sodium negative electrode active material.

[0077] In other words, by performing constant current discharge on a liquid half-cell that has obtained an amorphous phase, lithium-poor / sodium-phase anode active material can be intercalated to obtain a lithium-rich / sodium-rich anode active material.

[0078] Understandably, after amorphization treatment, the liquid half-cell can be removed to obtain amorphous anti-perovskite material as the negative electrode active material. Typically, after removing the liquid half-cell, the conductive additives and the amorphous anti-perovskite are not sieved. Generally, when preparing electrode materials, a certain proportion of active material, conductive agent, and binder is required. Since the obtained amorphous anti-perovskite active material already contains a certain proportion of conductive additives, the proportion of conductive additives can be reduced during subsequent electrode material preparation.

[0079] Understandably, after amorphization treatment, the liquid half-cell can be removed to obtain a negative electrode containing amorphous anti-perovskite material, which can then be used for subsequent battery fabrication and testing. The liquid half-cell can be fabricated using a mold battery method, employing a specially customized mold with gaskets and springs to apply pressure and fix the battery materials and structure. In this case, no binder is added to the electrode material; whether or not a conductive agent is added depends on the material's electronic conductivity. If no conductive agent is added, after the mold battery test is completed, it can be disassembled, the electrolyte removed, and the amorphous anti-perovskite negative electrode material obtained.

[0080] Since it is difficult to directly synthesize the amorphous lithium-poor phase LiFeSO by high-temperature solid-state method, but it can be synthesized by low-temperature + ball milling, it indicates that LiFeSO is a metastable phase that is difficult to prepare by high-temperature solid-state method. Therefore, it can be reasonably expected that in addition to the electrochemical delithiation method mentioned above, the amorphization treatment can also be carried out by rapid cooling on the basis of high-temperature solid-state synthesis method, which can also stabilize the metastable phase.

[0081] This application also provides an electrode sheet, which includes an active material layer, wherein the active material layer includes the aforementioned negative electrode active material.

[0082] It is understandable that when the electrode is a negative electrode, the active material layer is a negative electrode active material layer, which includes the aforementioned negative electrode active material used as an electrode material.

[0083] This application also provides a battery, which includes the above-described negative electrode active material or the above-described electrode sheet.

[0084] It should be noted that in practical applications, when the negative electrode sheet contains the above-mentioned negative electrode active material, it can be determined according to A. x TM y ChD b The value of x is used to match the cathode material. For example, when it is lithium-poor LiFeSO, it needs to be matched with a lithium-containing cathode material, such as LiFePO4 or LiCoO2. When it is lithium-rich Li5FeSO, it can be matched with a lithium-poor or lithium-free cathode material, such as S cathode or FeF3.

[0085] The battery can be a primary battery or a secondary battery; it can be a sodium-ion battery or a lithium-ion battery; it can be a liquid battery, an all-solid-state battery or a semi-solid-state battery. When it is a liquid battery, since the negative electrode active material can dissolve in water, an anhydrous electrolyte should be selected.

[0086] Therefore, the battery may optionally include a water-degradable battery.

[0087] A water-degradable battery is one that can dissolve and become ineffective when exposed to water.

[0088] Based on the amorphous state of the negative electrode active material, it has good stability and safety under different lithium insertion / extraction states. It reacts mildly when exposed to water, does not burn or explode, and has no toxic or harmful products. Moreover, it is strongly alkaline after dissolving, forming a corrosive local environment in the solution. After a certain period of time, all battery materials (positive and negative electrodes, solid electrolyte, copper foil, and aluminum foil) dissolve or corrode, causing the entire battery to degrade and fail in water. Therefore, it can be used in water-degradable batteries in marine and humid environments.

[0089] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0090] It should be noted that the binder mainly binds the various components of the electrode, such as the active material, conductive agent, and current collector, together to form a stable electrode structure. In the following examples, the Li2FeSO4 / Li liquid half-cell, the first LiFeSO4||Li half-cell, the second LiFeSO4||Li half-cell, and the third LiFeSO4||Li half-cell are all assembled using molds. That is, unlike traditional coin cells, which require coating the electrode material onto the current collector, the active material is mixed with conductive carbon and pressed into the mold, so no binder is needed.

[0091] Example 1

[0092] This embodiment provides a negative electrode active material with the chemical formula LiFeSO. The preparation method of the negative electrode active material includes: using Li2O, Fe2O3 and Fe2S3 as raw materials, mixing 50% Li2O and 17% Fe2O3... 3、 33% Fe2S3 was weighed and ball-milled in a high-energy planetary ball mill at a speed of 500 rpm for 8 hours to obtain an amorphous lithium-poor anode, LiFeSO.

[0093] Figure 1 The image shows the XRD pattern of the negative electrode active material prepared in Example 1. Figure 1 It can be seen that the negative electrode active material prepared in Example 1 has an amorphous phase, which accounts for 60%.

[0094] Example 2

[0095] This embodiment provides a negative electrode active material with the chemical formula LiFeSO₄. The preparation method of the negative electrode active material includes:

[0096] The raw materials Li₂O, Fe powder, and S powder were weighed in equal proportions, placed in a mortar and ground and mixed for 30 minutes. The resulting powder was then pressed into sheets, placed in a quartz tube, and vacuumed to 100°C. -4 Pa was used to seal the tube with an oxyhydrogen flame and heat-treated in a closed environment under vacuum conditions at a temperature of 750℃, with a heating rate of 3℃ / min and a holding time of 10h. After the heat treatment, the resulting precursor was quenched to obtain Li2FeSO.

[0097] A Li₂FeSO₄ / Li liquid half-cell was assembled using a mixture of 90% Li₂FeSO₄ as the electrode active material and 10% conductive carbon as the working electrode, with lithium metal as the counter electrode. When the Li₂FeSO₄ / Li liquid half-cell was charged to 227 mAh / g using a charge-discharge apparatus, the positive electrode active material composition was amorphous lithium-poor LiFeSO₄.

[0098] Figure 2 The image shows the XRD pattern of the negative electrode active material prepared in Example 2. Figure 2 It can be seen that the negative electrode active material prepared in Example 2 has an amorphous phase, compared to Figure 1 , Figure 2 There are still a few weak diffraction peaks, indicating a relatively low degree of amorphization, with the amorphous phase accounting for 30%.

[0099] Example 3

[0100] This embodiment provides a negative electrode active material with the general chemical formula Li5FeSO. The only difference between the preparation method of this negative electrode active material and that of Example 2 is that when the Li2FeSO / Li liquid half-cell is discharged at a constant current to 965mAh / g on a charge-discharge instrument, the positive electrode active material is an amorphous lithium-poor negative electrode Li5FeSO.

[0101] Figure 3 The image shows the XRD pattern of the negative electrode active material prepared in Example 3. Figure 3 It can be seen that the prepared negative electrode active material has a very low degree of amorphization, with no obvious diffraction peaks, and the amorphous phase accounts for 90%.

[0102] Example 4

[0103] This embodiment provides a negative electrode active material with the general chemical formula Li3FeSO. The only difference between the preparation method of this negative electrode active material and that of Example 2 is that when the Li2FeSO / Li liquid half-cell is discharged at a constant current to 482mAh / g on a charge-discharge instrument, the positive electrode active material is an amorphous phase lithium-poor negative electrode Li3FeSO.

[0104] XRD pattern of the negative electrode active material prepared in Example 4 and Figure 3 Similarly, the prepared negative electrode active material has a very low degree of amorphization, with no obvious diffraction peaks, and the amorphous phase accounts for 90%.

[0105] Example 5

[0106] This embodiment provides a chemical formula Li 1.2The negative electrode active material of FeSO₄ differs from that of Example 2 only in that: when the Li₂FeSO₄ / Li liquid half-cell is discharged at a constant current to 185 mAh / g on a charge-discharge apparatus, the positive electrode active material is an amorphous phase lithium-poor negative electrode Li₂. 1.2 FeSO.

[0107] Figure 4 The image shows the XRD pattern of the negative electrode active material prepared in Example 5. The data shows that the prepared negative electrode active material has a high degree of amorphization and obvious diffraction peaks, with an amorphous phase ratio of 15%.

[0108] Example 6

[0109] This embodiment provides a mixed negative electrode active material with the general chemical formula Li₂FeSO₄ + Li₃FeSO₄. 80% Li₂FeSO₄ and 20% Li₃FeSO₄ are ball-milled at low speed for 300 minutes to ensure thorough mixing. During charge-discharge, Li₃FeSO₄ plays a major role in the initial lithium insertion stage, while Li₂FeSO₄ begins to play a role in the subsequent delithiation process. Furthermore, the crystalline phase of Li₂FeSO₄ gradually transforms into the amorphous phase of Li₂FeSO₄. 2-x FeSO.

[0110] Example 7

[0111] This embodiment provides a chemical formula of Li2FeTe(N) 0.5 Cl 0.5 The negative electrode active material is prepared by the following method: weighing raw materials LiCl, Li3N, Fe powder and Te powder according to the stoichiometric ratio, grinding and mixing them in a mortar for 30 minutes, pressing the resulting powder into sheets, placing them in a quartz tube, and evacuating to 10°C. -4 Pa was used to seal the tube using an oxyhydrogen flame, followed by heat treatment in a vacuum-sealed environment at 850℃, with a heating rate of 3℃ / min and a holding time of 10 hours. After heat treatment, the resulting precursor was quenched to obtain Li2FeTe(N) 0.5 Cl 0.5 ).

[0112] The negative electrode active material is assembled with lithium metal into a coin cell, denoted as _____.

[0113] Li2FeTe(N 0.5 Cl 0.5 The Li half-cell was charged and discharged using a 0.1C current. The charge / discharge curve is shown below. Figure 5 As shown, the first discharge capacity is 372mAh / g, the first charge capacity is 276mAh / g, and the coulombic efficiency is 74%.

[0114] Comparative Example 1

[0115] The method for preparing Li₂FeSO₄ provided in Comparative Example 1 includes:

[0116] The raw materials Li₂O, Fe powder, and S powder were weighed in equal proportions, placed in a mortar, and ground and mixed for 30 minutes. The resulting powder was pressed into 10mm round discs, placed in a quartz tube, and vacuumed to 1000°C. -4 Pa was used to seal the tube with an oxyhydrogen flame and heat-treated in a closed environment under vacuum conditions at a temperature of 750℃, with a heating rate of 3℃ / min and a holding time of 10h. After the heat treatment, the resulting precursor was quenched to obtain Li2FeSO.

[0117] Figure 6 The XRD pattern of Li2FeSO prepared in Comparative Example 1 shows that the Li2FeSO synthesized in Comparative Example 1 at high temperature has obvious diffraction peaks, high crystallinity, and is a typical anti-perovskite structure.

[0118] Comparative Example 2

[0119] The method for preparing Li2FeSeO provided in Comparative Example 2 includes:

[0120] The raw materials Li₂O, Fe powder, and Se powder were weighed in equal proportions, placed in a mortar and ground and mixed for 30 minutes. The resulting powder was pressed into 10mm round discs, placed in a quartz tube, and vacuumed to 1000 mm. -4 Pa was sealed using an oxyhydrogen flame and then heat-treated in a vacuum environment at a temperature of 750℃, with a heating rate of 3℃ / min and a holding time of 10h. After the heat treatment, the resulting precursor was quenched to obtain Li2FeSeO.

[0121] Figure 7 The XRD pattern of Li2FeSeO prepared in Comparative Example 2 shows that the Li2FeSeO synthesized in Comparative Example 2 at high temperature solid phase has obvious diffraction peaks, high crystallinity, and is a typical anti-perovskite structure.

[0122] Comparative Example 3

[0123] The method for preparing Li₂CoSeO provided in Comparative Example 2 includes:

[0124] The raw materials Li₂O, Co powder, and Se powder were weighed in equal proportions, placed in a mortar and ground and mixed for 30 minutes. The resulting powder was pressed into 10mm blanks, placed in a quartz tube, and vacuumed to 1000 mm. -4Pa was used to seal the tube with an oxyhydrogen flame and heat-treated in a closed environment under vacuum conditions at a temperature of 750℃, with a heating rate of 3℃ / min and a holding time of 10h. After the heat treatment, the resulting precursor was quenched to obtain Li2CoSeO.

[0125] Figure 8 The XRD pattern of Li2CoSeO prepared in Comparative Example 3 shows that the Li2CoSeO synthesized in Comparative Example 3 at high temperature solid phase has obvious diffraction peaks, high crystallinity, and is a typical anti-perovskite structure.

[0126] Comparative Example 4

[0127] The method for preparing amorphous LiFeSO4 provided in Comparative Example 4 includes:

[0128] The raw materials Li₂O, Fe powder, and S powder were weighed at 20%, 40%, and 40% respectively, and ground and mixed in a mortar for 30 minutes. The resulting powder was pressed into 10mm round discs, placed in a quartz tube, and vacuumed to 1000°C. -4 Pa was used to seal the tube with an oxyhydrogen flame and heat-treated in a closed environment under vacuum conditions at a temperature of 750℃, with a heating rate of 3℃ / min and a holding time of 10h. After the heat treatment, the resulting precursor was quenched to obtain LiFeSO4.

[0129] Figure 9 The XRD pattern of LiFeSO prepared in Comparative Example 4 shows that the LiFeSO synthesized in Comparative Example 4 at high temperature solid phase has obvious diffraction peaks. Comparative Example 4 contains more highly crystalline impurity phases, which means that it is difficult to directly synthesize lithium-poor phase LiFeSO by high temperature solid phase method, and the amorphization content is only 10%.

[0130] Comparative Example 5

[0131] The method for preparing Li₂FeSO₄ provided in Comparative Example 5 includes:

[0132] The raw materials Li₂O, Fe powder, and S powder were weighed in equal proportions, placed in a mortar, and ground and mixed for 30 min. The resulting powder was placed in a crucible and transferred to a tube furnace. A vacuum of -0.05 MPa was applied, and He gas was introduced at 60 ml / min. The temperature was increased to 750 °C at 3 °C / min and held at this temperature for 10 h. After the sintering process was completed and the furnace cooled to room temperature, the graphite crucible was quickly transferred to a glove box to avoid excessive air contact with the sample, yielding Li₂FeSO₄ powder.

[0133] Figure 10 The XRD pattern of Li₂FeSO₄ prepared in Comparative Example 5 shows obvious diffraction peaks, indicating high crystallinity and a typical anti-perovskite structure.

[0134] Experimental Example 1

[0135] The 90% LiFeSO4 prepared in Comparative Example 4 was mixed with 10% conductive carbon to form a working electrode, and lithium metal was used as the counter electrode to assemble a liquid half-cell, which is denoted as the first LiFeSO4||Li half-cell.

[0136] The LiFeSO4 prepared in Example 1 was mixed with conductive carbon at a mass percentage of 90% and 10% respectively to form a working electrode, and lithium metal was used as the counter electrode to assemble a liquid half-cell, which is denoted as the second LiFeSO4||Li half-cell.

[0137] Assembled in the same manner as described above, the LiFeSO prepared in Example 2 corresponds to the third LiFeSO||Li half-cell, and the Li3FeSO prepared in Example 4 corresponds to the Li3FeSO||Li half-cell.

[0138] Each of the above half-cells was charged and discharged at a constant current of 0.1C at 25°C.

[0139] Figure 11 The charge-discharge curves for the first LiFeSO4||Li half-cell are shown. Figure 11 As can be seen, the charge-discharge specific capacity is significantly lower than that of the second and third LiFeSO||Li half-cells, with a discharge specific capacity of only 85 mAh / g. The overall performance has declined significantly, indicating that the high-temperature solid-state method for preparing amorphous LiFeSO is very ineffective.

[0140] Figure 12 The charge-discharge curves of the second LiFeSO4||Li half-cell are based on... Figure 12 As can be seen, its first discharge capacity is relatively high, reaching 1144 mAh / g, but its charging capacity is only 886 mAh / g, and its first coulombic efficiency is low. This is because the amorphous lithium-poor phase LiFeSO in Example 1 is prepared by low-temperature ball milling. The material particles are small and have many surface defects. During the first lithium insertion process, some lithium will enter these defect sites and undergo irreversible reactions, resulting in a high lithium insertion amount in the first round and a low first efficiency of 77%.

[0141] Figure 13 The charge-discharge curve of the third LiFeSO4||Li half-cell is based on... Figure 13 As can be seen, the discharge capacity reaches 933 mAh / g, while the charging capacity is only 876 mAh / g. The coulombic efficiency is improved to 94% for the first time. When the half-cell is cycled for 20 cycles, the capacity retention rate is higher than 80%. The working electrode after cycling is tested by XRD. Compared with the uncycled amorphous material, the peak position and peak width are almost the same, indicating that the amorphous material prepared by electrochemical method can exist stably and carry out electrochemical reactions.

[0142] Figure 14 The first charge-discharge curve of the Li5FeSO||Li half-cell shows that its reversible capacity is as high as 800mAh / g or more in the voltage range of 0.1-3V.

[0143] In other words, the negative electrode active material prepared in the above embodiments has high capacity.

[0144] Experimental Example 2

[0145] A liquid half-cell was assembled using a mixture of 90% LiFeSO4 and 10% conductive carbon prepared in Example 2 as the working electrode and metallic sodium as the counter electrode, denoted as the LiFeSO4||Na half-cell. This half-cell was charged and discharged at a constant current of 0.1C at 25°C. A sodium electrolyte was used to transport Na+. + LiFeSO₄ does not contain sodium, but when assembled into a battery with metallic sodium, it can be charged and discharged normally, indicating that sodium can be reversibly inserted and extracted in this material.

[0146] Figure 15 The first charge-discharge curve of the Li5FeSO4||Na half-cell shows that its reversible capacity is as high as 340 mAh g in the voltage range of 0.1-2.8V. -1 above.

[0147] Experimental Example 3

[0148] Using Li3FeSO prepared in Example 4 as the negative electrode active material, Li3YCl3Br3 as the solid electrolyte, and LiCoO2 as the positive electrode active material, an all-solid-state full cell was assembled, denoted as LiCoO2||Li3YCl3Br3||Li3FeSO all-solid-state full cell.

[0149] The LiCoO2||Li3YCl3Br3||Li3FeSO all-solid-state full cell was charged and discharged at a constant current of 0.1C.

[0150] Figure 16 The first charge-discharge curves of the LiCoO2||Li3YCl3Br3||Li3FeSO all-solid-state full cell within a voltage range of 0.5-4.2V under test conditions at 60℃ are shown. Figure 16 It can be seen that the charging capacity is 3.05mAh, the specific capacity reaches 198.63mAh / g, the discharging capacity can reach 3.18mAh, the specific capacity is 227.00mAh / g, the first-cycle coulombic efficiency is 104%, and the average discharge voltage is 2.3214V.

[0151] Figure 17The graph shows the first charge-discharge curve of the LiCoO2||Li3YCl3Br3||Li3FeSO all-solid-state full cell under test conditions of 60℃ and a voltage range of 0-4.6V. Based on... Figure 17 It can be seen that its charging capacity is 3.34mAh, with a specific capacity of 209.27mAh / g, and its discharging capacity is 3.35mAh, with a specific capacity of 239.17mAh / g. The first-cycle coulombic efficiency is 114%, and the average discharge voltage is 2.1902V. Compared with the test conditions in the voltage range of 0.5-4.2V, the charging and discharging capacity is slightly improved.

[0152] Figure 18 The graph shows the charge-discharge cycle curves of the LiCoO2||Li3YCl3Br3||Li3FeSO all-solid-state full cell under test conditions of 60℃ and voltage range of 0.5-4.2V. It can be seen that under test conditions of 60℃ and voltage range of 0.5-4.2V, the capacity retention rate is 65% after 10 cycles, and the capacity retention rate can reach 53% after 20 cycles.

[0153] Experimental Example 3

[0154] Because the anti-perovskite electrode materials of Comparative Examples 1-4 and Examples 1-4 with different lithium insertion / extraction states react gently with water, do not burn or explode, the aqueous solution after the reaction is green, and the reaction product is tested as amorphous powder particles after drying.

[0155] Therefore, using Li3FeSO prepared in Example 4 as the negative electrode active material, anti-perovskite Li2OHCl as the solid electrolyte, and lithium cobalt oxide LiCoO2 as the positive electrode active material to assemble an all-solid-state battery LiCoO2||Li2OHCl||Li3FeSO, after immersing the all-solid-state battery LiCoO2||Li2OHCl||Li3FeSO in an aqueous solution, the solid electrolyte and negative electrode active material in the battery dissolve and fail. Since Li3FeSO and Li2OHCl dissolve in water and form a strong alkaline solution, they create a corrosive local environment in the solution. After a certain period, all materials of the all-solid-state battery LiCoO2||Li2OHCl||Li3FeSO (positive and negative electrodes, solid electrolyte, copper foil, and aluminum foil) dissolve or undergo corrosion reactions, causing the entire battery to degrade and fail in water.

[0156] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A negative electrode active material, characterized by, The chemical general formula of the negative electrode active material is A x TM y ChD b , wherein A is lithium and / or sodium, TM is a transition metal, Ch is a chalcogen element, and D is O or B a C 1-a , B is selected from at least one of a monovalent anion and a monovalent anion cluster, C is selected from at least one of a trivalent anion and a trivalent anion cluster, 0.5≤x≤8, 0.8≤y≤1.1, 0.25≤a≤0.75, and 0.8≤b≤1.

2. The negative electrode active material has an amorphous phase, and a mass ratio of the amorphous phase in the negative electrode active material is not less than 10%.

2. The negative electrode active material according to claim 1, characterized by The mass ratio of the amorphous phase in the negative electrode active material is not less than 30%.

3. The negative electrode active material according to claim 1, characterized by The negative electrode active material is an amorphous phase.

4. The negative electrode active material according to claim 1, characterized by 1.9≤x≤2.1; and / or, 0.9≤y≤1.1; and / or, 0.45≤a≤0.55; and / or, 0.9≤b≤1.

1.

5. The negative electrode active material according to claim 1, characterized by D is O, b = 1 ; or, D is B a C 1-a 1≤x≤2.

5.

6. The negative electrode active material according to claim 1, characterized by 1.9 ≤x ≤2.1。 7. The negative active material according to any one of claims 1 to 6, characterized in that, The TM includes at least one of Fe, Co, Mn, Ni, Cu, Cr, V, Ti, W, Si, Sn, Nb, and Mg.

8. The negative electrode active material according to any one of claims 1 to 6, characterized by, The Ch includes at least one of S, Se, and Te. and / or, the B comprises at least one of F - , Cl - , Br - , I - , H - , OH - , BH4 - , NH2 - , NO2 - , and CN - ; and / or, the C comprises N 3- , (PO4) 3- , (SbO4) 3- , and (AsO4) 3- .

9. The method of producing a negative electrode active material according to any one of claims 1 to 8, characterized by, The method comprises: Obtaining an inverse perovskite material as characterized by the chemical formula, and performing amorphous treatment on the inverse perovskite material to obtain the negative electrode active material; The amorphous treatment comprises: mixing the inverse perovskite material and a conductive agent to make a working electrode, assembling the working electrode and a counter electrode into a liquid half-cell, and performing constant-current discharge on the liquid half-cell to remove element A to obtain the amorphous phase, wherein element A is Li, and the counter electrode is a lithium metal, or element A is Na, and the counter electrode is a lithium metal. Alternatively, the amorphous treatment comprises: mixing the inverse perovskite material and a conductive agent to make a working electrode, assembling the working electrode and a counter electrode into a liquid half-cell, and performing constant-current charging on the liquid half-cell to obtain the lithium / sodium-rich negative electrode active material.

10. A pole piece characterized by, The battery comprises the electrode plate as claimed in claim 10.

11. A battery, characterized by The battery comprises a water-degradable battery.

12. The battery of claim 11, wherein, The battery comprises a water-degradable battery.

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