Accurate chemical lithiation synthesis of over-lithium oxide positive electrode material and battery application
By precisely targeting aromatic lithium reagents with matching lithiation behavior and potential, chemical lithiation of lithium battery cathode materials is achieved, solving the problem of irreversible lithium consumption in existing lithium batteries and negative electrode-less lithium metal batteries. This results in improved energy density and cycle life, making it suitable for high-throughput industrial applications.
Patent Information
- Application Number
- CN202410740128.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-06-07
- Publication Date
- 2025-12-09
AI Technical Summary
Existing lithium batteries and negative electrode-free lithium metal batteries suffer from irreversible lithium-ion consumption during the first charge-discharge cycle, resulting in reduced energy density and cycle life. Existing pre-lithiation technologies suffer from over-lithiation and structural damage, making it difficult to achieve high-throughput industrial applications.
By precisely targeting aromatic lithium reagents that match the lithiation behavior and lithiation potential, conventional oxide cathode materials are chemically lithiated, and the endpoint of the lithiation reaction is controlled. Over-lithiation oxide cathode materials Li1+nNixCoyMn1-x-yO2, Li2Mn2O4, and Li1.5Ni0.5Mn1.5O4 are prepared, thus avoiding over-lithiation.
It has achieved a significant increase in energy density and cycle life of lithium-ion batteries and negative electrode-free lithium metal batteries, improved the utilization rate of positive electrode materials, and simplified the industrial production process.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of battery materials, and particularly relates to a controllable preparation method of a positive electrode material Li 1+ n Ni x Co y Mn 1-x-y O2, Li 1+n Mn2O4, Li 1+n Ni 0.5 Mn 1.5 O4 (0 < n < 1; 0 < x < 1; 0 < y < 1; 0 < x + y < 1) and its application, especially in lithium ion batteries and / or anode-free lithium metal batteries. BACKGROUND
[0002] In recent years, with the rapid development of new energy vehicles and smart grids, the market demand for high specific energy lithium batteries is increasing. The widely used lithium ion battery has the problem of low initial coulomb efficiency of the negative electrode material (graphite negative electrode material is 80-90%, silicon-based material is 70-80%), which means that a large amount of active lithium ions are irreversibly consumed in the first charge-discharge process, inevitably leading to a decrease in the energy density and cycle life of the full battery. The irreversible capacity loss can be compensated by pre-lithiation and other lithium supplement technologies.
[0003] In addition, people are also trying to explore lithium batteries with higher energy density. Lithium metal is considered an ideal anode material due to its ultra-high theoretical capacity (3860 mAh.g -1 ), low density and lowest redox potential, but its high cost and extreme sensitivity to moisture and air limit its industrial application. Based on this, researchers creatively removed the anode material in the lithium metal battery and only used copper foil instead, thereby proposing the concept of "anode-free lithium metal battery", which not only simplifies the battery production process, but also further increases the energy density to 400 Wh.kg -1 In recent years, it has attracted more and more attention. However, the anode-free battery also cannot avoid the inherent shortcomings of the lithium metal anode, such as uncontrolled dendrite growth, easy breaking of the SEI layer and formation of dead lithium, which leads to a large degree of consumption of reversible active lithium, which is undoubtedly a great challenge for the anode-free battery without Li compensation on the negative electrode side. Therefore, it is of great significance to compensate for the irreversible capacity loss through pre-lithiation technology for the further development of lithium ion full batteries and the industrialization of anode-free lithium metal batteries.
[0004] The existing pre-lithiation methods are mainly divided into two categories: negative electrode lithium supplement technology and positive electrode lithium supplement technology. Positive electrode lithium supplement technology is considered more likely to achieve industrial application due to its better process compatibility and higher safety. For example, Lin et al. (Energy Storage Mater. 2022, 45, 821) applied Li2Ni 0.5 Mn 0.5 O2to the anode-free battery, which can be successfully converted into LiNi 0.5 Mn 1.5 O4at the first charge and release a large amount of active Li + ion storage to replace the loss of Li in the next cycle, thereby prolonging the life of the anode-free battery (88% capacity retention after 50 cycles).
[0005] Layered transition metal oxide LiNi x Co y Mn 1-x-y O2(0≤x<1;0≤y<1;0<x+y≤1) has attracted more and more attention due to its high energy density and long-term cycle stability. Recent studies have shown that LiNi x Co y Mn 1-x- y O2can insert more than stoichiometric Li + ions to form a lithium-rich phase, and its pre-lithiation behavior varies greatly with the ratio of constituent elements. For example, Johnson et al. (ACS Appl. Mater. Interfaces 2016, 8, 15361-15368) found that when LiNi 0.5 Co 0.2 Mn 0.3 O2pre-lithiation is too high, the insertion of excess Li + ions will cause initial capacity deterioration and capacity decay, which is due to local structural distortion and intergranular cracks caused by lattice structure volume expansion due to the addition of excess lithium ions. In addition, Suo's team (Angew. Chem. Int. Ed. 2021, 60(15), 8289) used n-butyllithium as a lithiation reagent to chemically lithiate LiNi 0.8 Co 0.1 Mn 0.1 O2, and the lithium-rich Li2Ni 0.8 Co 0.1 Mn 0.1 O2was innovatively applied to prolong the cycle life of anode-free lithium metal batteries. The improved anode-free pouch battery can reach 447 Wh.kg -1The energy density and 84% capacity retention significantly improve cycle performance. However, they can only obtain the desired stoichiometric ratio of lithium-rich Li₂Ni by controlling the reaction time. 0.8 Co 0.1 Mn 0.1 O2 materials, and because n-butyllithium has a low lithiation potential, it is easy to over-lithiate the material into a metallic element and Li2O, which will damage the material structure and make it difficult to achieve high-throughput industrial applications.
[0006] Based on the above reasons, this application is hereby submitted. Summary of the Invention
[0007] Based on the above reasons, and in view of the problems or defects existing in the prior art, the purpose of this invention is to provide a controllable preparation method for lithium oxide cathode materials and their battery applications, thereby solving or at least partially solving the aforementioned technical defects existing in the prior art.
[0008] This invention appendix Figure 1 LiNi is a conventional metal oxide cathode material. 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (referred to as NCM111 in the diagram), LiNi 0.5 Co 0.2 Mn 0.3 O2 (referred to as NCM523 in the diagram), LiNi 0.8 Co 0.1 Mn 0.1 O2 (referred to as NCM811 in the diagram), LiMn2O4, LiNi 0.5 Mn 1.5 The over-discharge curve of O4 and its reduction potential with various aromatic lithium reagents were obtained. The inventors accurately located the matching lithiation potential range based on the overlithiation behavior of conventional oxide cathode materials, thereby selecting suitable aromatic lithium reagents.
[0009] For LiNi 0.5 Co 0.2 Mn 0.3 O2 to Li 1.7 Ni 0.5 Co 0.2 Mn 0.3 Lithium intercalation potential of O2 (1.55V vs. Li) + / Li) and to Li2Ni 0.5 Co 0.2 Mn 0.3 Over-lithiation potential of O2 (1.2V vs. Li) + / Li), due to experimental comparison of Li formed at the first over-lithiation platform. 1.7 Ni 0.5Co 0.2 Mn 0.3 O2 particle structure is more stable, and the application realizes the controllable synthesis of Li 1.7 Ni 0.5 Co 0.2 Mn 0.3 O2 (the potential of the reagent is required to be lower than 1.55V and higher than 1.2V vs.Li + / Li) positive electrode. Similarly, the application realizes the controllable synthesis of Li 1.35 Ni 0.8 Co 0.1 Mn 0.1 O2 (the potential of the reagent is required to be lower than 1.8V and higher than 1.2V vs.Li + / Li), Li 1.5 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (the potential of the reagent is required to be lower than 1.2V and higher than 0.8V vs.Li + / Li) positive electrode.
[0010] Similarly, the application realizes the controllable synthesis of spinel structure Li2Mn2O4 (the potential of the reagent is required to be lower than 2.9V and higher than 1.0V vs.Li + / Li), Li 1.5 Ni 0.5 Mn 1.5 O4 (the potential of the reagent is required to be lower than 2.7V and higher than 2.0V vs.Li + / Li) positive electrode.
[0011] The advantage of the application is that by adjusting the reducing ability of the lithiation reagent, the end point of the lithiation reaction is accurately controlled, the over-lithiated Li 1+n Ni x Co y Mn 1-x-y O2, Li2Mn2O4, Li 1.5 Ni 0.5 Mn 1.5 O4 is controllably prepared, and it is applied to lithium ion batteries and / or negative electrode-free lithium metal batteries, so that the energy density and cycle life are greatly improved.
[0012] In order to achieve the above-mentioned first purpose of the application, the technical scheme adopted by the application is as follows:
[0013] A controllable preparation method of an over-lithiated oxide positive electrode material, the chemical formula of the over-lithiated oxide positive electrode material is: Li 1+n Ni x Coy Mn 1-x-y O2, Li2Mn2O4, Li 1.5 Ni 0.5 Mn 1.5 O4; wherein: 0
[0014] First, the over-lithiation behavior of the conventional oxide cathode material in the lithium ion battery is accurately positioned by systematically studying the matching lithiation potential, and a suitable aromatic lithium reagent is selected; then the conventional layered transition metal oxide LiNi x Co y Mn 1-x-y O2 or spinel structure LiMn2O4, LiNi 0.5 Mn 1.5 O4 cathode material (material powder or cathode sheet) and the aromatic lithium reagent are subjected to a chemical lithiation reaction in an inert atmosphere, and the over-lithiated oxide cathode material is obtained after washing and drying.
[0015] Further, in the above technical solution, when the over-lithiated oxide cathode material is Li 1.7 Ni 0.5 Co 0.2 Mn 0.3 O2, the potential of the aromatic lithium reagent is required to be between 1.2-1.55V, without strict control of the reaction time, and the reaction is spontaneously terminated. For example, the aromatic lithium reagent can be any one or several of perylene lithium (single electron reduction potential 1.26V), benzophenone lithium (single electron reduction potential 1.50V), 9-fluorenone lithium (double electron reduction potential 1.25V), etc.
[0016] Further, in the above technical solution, when the over-lithiated oxide cathode material is Li 1.35 Ni 0.8 Co 0.1 Mn 0.1 O2, the potential of the aromatic lithium reagent is required to be between 1.2-1.8V, without strict control of the reaction time, and the reaction is spontaneously terminated. For example, the aromatic lithium reagent can be any one or several of perylene lithium (single electron reduction potential 1.26V), benzophenone lithium (single electron reduction potential 1.50V), p-terphenyl lithium (potential 1.70V), 9-fluorenone lithium (double electron reduction potential 1.25V), etc.
[0017] Further, in the above technical solution, when the over-lithiated oxide cathode material is Li 1.5 Ni 1 / 3 Co 1 / 3 Mn 1 / 3O2, the potential of the aromatic lithium reagent is required to be between 0.8-1.2V, without strict control of the reaction time, the reaction is spontaneously terminated. For example, the aromatic lithium reagent can be any one or several of anthracene lithium (potential 0.9V), perylene lithium (two-electron reduction potential 0.9V), benzophenone lithium (two-atom reduction potential 0.9V), etc.
[0018] Further, in the above technical solution, when the over-lithiated oxide positive electrode material is Li2Mn2O4, the potential of the aromatic lithium reagent is required to be between 1.0-2.9V, without strict control of the reaction time, the reaction is spontaneously terminated. For example, the aromatic lithium reagent can be perylene lithium (one-electron reduction potential 1.26V), benzophenone lithium (one-electron reduction potential 1.50V), p-terphenyl (potential 1.70V), 9-fluorenone lithium (one-electron reduction potential 2.0V, two-electron reduction potential 1.25V), phenoxazine lithium (potential 2.05V).
[0019] Further, in the above technical solution, when the over-lithiated oxide positive electrode material is Li 1.5 Ni 0.5 Mn 1.5 O4, the potential of the aromatic lithium reagent is required to be between 2.0-2.7V, without strict control of the reaction time, the reaction is spontaneously terminated. For example, the aromatic lithium reagent can be 9-fluorenone lithium (one-electron reduction potential 2.0V), phenoxazine lithium (potential 2.05V).
[0020] Further, in the preferred embodiment of the present application, the inert atmosphere is an argon atmosphere.
[0021] Further, in the above technical solution, the reaction of the lithium ion battery positive electrode material with the aromatic lithium reagent includes: spraying the aromatic lithium reagent on the surface of the positive electrode material, or immersing the positive electrode material powder or electrode sheet in the aromatic lithium reagent in an inert atmosphere.
[0022] Further, in the above technical solution, the reaction time of the aromatic lithium reagent with the positive electrode material is 1min-24h.
[0023] Further, in the above technical solution, the aromatic lithium reagent provided by the present application is prepared by chemical reaction of an aromatic compound with metallic lithium in an organic solvent; wherein: the organic solvent is an aprotic solvent, which can be any one of ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, methyl tetrahydrofuran, acetonitrile, N,N-dimethylformamide, etc.
[0024] Preferably, in the above technical solution, the aromatic lithium reagent is prepared by the following method, the steps are as follows:
[0025] The aromatic compound is dissolved in an organic solvent at room temperature, mixed, then lithium metal is added in a stoichiometric ratio of 1:1 of the aromatic compound to lithium metal, stirred until the reaction is complete, and a uniform solution is obtained, which is the aromatic lithium reagent.
[0026] More preferably, in the above technical solution, the concentration of the aromatic lithium reagent is 0.01-2 mol / L.
[0027] More preferably, in the above technical solution, the aromatic compound is one or more of anthracene, perylene, benzophenone, 9-fluorenone, p-terphenyl, phenoxazine, etc.
[0028] The second object of the present application is to provide the over-lithiated oxide positive electrode material prepared by the controllable preparation method described above.
[0029] Further, in the preferred embodiment of the present application, the over-lithiated oxide positive electrode material is Li 1.7 Ni 0.5 Co 0.2 Mn 0.3 O2, Li 1.35 Ni 0.8 Co 0.1 Mn 0.1 O2, Li 1.5 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2, Li2Mn2O4 or Li 1.5 Ni 0.5 Mn 1.5 O4.
[0030] The third object of the present application is to provide the application of the over-lithiated oxide positive electrode material prepared by the controllable preparation method described above in lithium ion batteries and / or anode-free lithium metal batteries.
[0031] The fourth object of the present application is to provide a lithium ion battery and / or anode-free lithium metal battery comprising the over-lithiated oxide positive electrode material prepared by the method described above.
[0032] Further, in the above technical solution, the lithium ion battery comprises a positive electrode sheet, a negative electrode sheet, a separator arranged between the positive and negative electrode sheets, an electrolyte, and a shell; the positive electrode sheet comprises a positive electrode active material, a conductive agent, and a binder, and the positive electrode active material is the over-lithiated oxide positive electrode material prepared by the controllable preparation method described above.
[0033] Further, in the above technical solution, the mass ratio of the positive electrode active material, the conductive agent, and the binder is (7-9):(0.5-2):(0.5-1).
[0034] Preferably, the above technical solution, the conductive agent is acetylene black, ketjen black, multi-walled carbon nanotube, Super P or one or several of the above materials.
[0035] Preferably, the above technical solution, the binder is one or several of polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), polyacrylic acid (PAA).
[0036] The reaction equation (not balanced) involved in the reaction mechanism of the present application is as follows:
[0037] LiNi x Co y Mn 1-x-y O2+Ar*-Li + →Li 1+n Ni x Co y Mn 1-x-y O2+Ar;
[0038] LiMn2O4+Ar*-Li + →Li2Mn2O4+Ar;
[0039] LiNi 0.5 Mn 1.5 O4+Ar*-Li + →Li 1.5 Ni 0.5 Mn 1.5 O4+Ar。
[0040] Compared with the prior art, the present application has the following beneficial effects:
[0041] (1) The present application uses potential-matched aromatic lithium reagent to chemically lithiate conventional layered transition metal oxide LiNi x Co y Mn 1-x-y O2 and spinel-structured LiMn2O4, LiNi 0.5 Mn 1.5 O4 cathode, realizing the controllable synthesis of over-lithiated Li 1+n Ni x Co y Mn 1-x-y O2, Li2Mn2O4, Li 1.5 Ni 0.5 Mn 1.5 O4. The lithiation reaction is limited by the potential of the lithiation reagent and thus spontaneously terminates, without the need for accurate control of reaction time, facilitating high-throughput industrial application.
[0042] (2) During the first week of charging, over-lithiated Li 1+n Nix Co y Mn 1-x-y O2, Li2Mn2O4, Li 1.5 Ni 0.5 Mn 1.5 O4 cathode can provide 0.3-1 times more active lithium source than conventional primary cathode materials, to compensate for the irreversible capacity loss of the anode, improve the utilization rate of the cathode material, and realize significant improvement in the reversible capacity and energy density of lithium ion full batteries and anode-free lithium metal batteries. BRIEF DESCRIPTION OF DRAWINGS
[0043] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained according to these drawings without creative labor for those skilled in the art.
[0044] Figure 1 LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (referred to as NCM111 in the figure), LiNi 0.5 Co 0.2 Mn 0.3 O2 (referred to as NCM523 in the figure), LiNi 0.8 Co 0.1 Mn 0.1 O2 (referred to as NCM811 in the figure), LiMn2O4, LiNi 0.5 Mn 1.5 O4 and the reduction potential of each aromatic lithium reagent;
[0045] Figure 2 is the cyclic voltammetry curve of the lithium benzophenone provided by the embodiment 1 of the present application;
[0046] Figure 3 is the first cycle charge-discharge curve of the LiNi 0.5 Co 0.2 Mn 0.3 O2 cathode sheet before and after the reaction of the lithium benzophenone provided by the embodiment 1 of the present application;
[0047] Figure 4 is the cyclic voltammetry curve of the lithium benzophenone provided by the embodiment 1 of the present application;
[0048] Figure 5 is the first cycle charge-discharge curve of the LiNi 0.8 Co0.1 Mn 0.1 First cycle charge-discharge curve of O2 cathode electrode sheet;
[0049] Figure 6 is the first cycle charge-discharge curve of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 First cycle charge-discharge curve of O2 cathode electrode sheet;
[0050] Figure 7 is the first cycle charge-discharge curve of LiMn2O4 cathode electrode sheet before and after the reagent reaction of the present application embodiment 4;
[0051] Figure 8 is the cyclic voltammetry curve of 9-fluorenone lithium provided by the present application embodiment 5;
[0052] Figure 9 is the first cycle charge-discharge curve of LiNi 0.5 Mn 1.5 O4 cathode electrode sheet before and after the reagent reaction of the present application embodiment 5;
[0053] Figure 10 is the LiNi 0.5 Co 0.2 Mn 0.3 O2 cathode matched with graphite anode lithium ion full cell cycle performance comparison;
[0054] Figure 11 is the LiNi 0.5 Co 0.2 Mn 0.3 O2 cathode matched with copper foil anode-free lithium metal battery cycle performance comparison. DETAILED DESCRIPTION
[0055] The application discloses a controllable preparation method of over-lithiated oxide cathode material and application thereof, and belongs to the technical field of battery materials. The method comprises the following steps: through the accurate positioning of the over-lithiation behavior of the over-lithiated oxide cathode material in a lithium ion battery and the matching of the lithiation potential, a suitable aromatic lithium reagent is selected, the cathode material is reacted with the aromatic lithium reagent, and the over-lithiated oxide cathode material is obtained through washing and drying. The application uses the potential-matched aromatic lithium reagent to chemically lithiate the conventional oxide cathode material, realizes the controllable synthesis of the over-lithiated oxide cathode material. Compared with other reagents such as lithium diphenyl, the aromatic lithium reagent is not easy to over-lithiate the material into metallic elements and Li2O and other substances, the reaction of the aromatic lithium reagent is limited by the potential of the reagent and can be spontaneously terminated, the aromatic lithium reagent is not easy to over-lithiate and does not need to accurately control the reaction time, and the aromatic lithium reagent is more convenient for realizing high-throughput industrial application.
[0056] The application will be further described in detail by the following examples. The examples are implemented on the premise of the application technology, and the detailed implementation and specific operation process are given to illustrate the creativity of the application, but the protection scope of the application is not limited to the following examples.
[0057] The equipment and raw materials used in the application can be purchased from the market or are commonly used in the field. The methods in the following examples are the conventional methods in the field, unless otherwise specified.
[0058] The aromatic lithium reagent provided by the application is prepared by chemical reaction of an aromatic compound (such as anthracene, perylene, benzophenone, 9-fluorenone, p-terphenyl, phenoxazine, etc.) with metallic lithium in an organic solvent (such as ethylene glycol dimethyl ether, tetrahydrofuran, N,N-dimethylformamide, etc.). The concentration of the aromatic lithium reagent is 0.01-2 mol / L.
[0059] Example 1
[0060] The embodiment provides a controllable preparation method of a lithium-rich oxide positive electrode material, which comprises the following steps:
[0061] (1) Equal-molar amounts of 0.02 mol of benzophenone and metallic lithium are mixed and dissolved in 100 mL of tetrahydrofuran (THF) solvent under the protection of argon gas, and stirred for 2 h to prepare a 0.2 mol / L benzophenone lithium reagent.
[0062] (2) LiNi 0.5 Co 0.2 Mn 0.3 O2, Super-P and polytetrafluoroethylene (PVDF) are mixed in a mass ratio of 8:1:1, N-methylpyrrolidone is added, homogenized, coated, and after drying, punched into LiNi 0.5 Co 0.2 Mn 0.3 O2 pole pieces are prepared.
[0063] (3) The LiNi 0.5 Co 0.2 Mn 0.3 O2 pole piece is immersed in 3 mL of the prepared benzophenone lithium reagent, and reacts for 10 min. After the reaction is completed, the pole piece is washed with THF for 3 times, and vacuum dried to obtain a lithium-rich Li 1.7 Ni 0.5 Co 0.2 Mn 0.3 O2 positive electrode.
[0064] Figure 2 is the cyclic voltammetry curve of the benzophenone lithium, and the reaction equilibrium potential is 1.50 V, which is in the range of the reaction equilibrium potential of the LiNi0.5 Co 0.2 Mn 0.3 O2 overdischarge between 1.55V and 1.2V lithium intercalation plateau, so the lithiation end point can be limited to Li 1.7 Ni 0.5 Co 0.2 Mn 0.3 O2 without further lithiation.
[0065] Figure 3 The first cycle charge-discharge curves of LiNi 0.5 Co 0.2 Mn 0.3 O2 cathode electrode sheet before and after the reaction of diphenyl ketone lithium. As can be seen from the figure, the open circuit voltage of the battery after prelithiation decreases from 3.31V to 1.50V, a new platform appears at 1.8V, the first cycle charge capacity increases from 180mAh / g to 318mAh / g, the reaction time is extended from 10min to 30min, and the first cycle charge-discharge curves of the battery are basically completely coincident, which confirms that diphenyl ketone lithium can effectively control the reaction end point at Li 1.7 Ni 0.5 Co 0.2 Mn 0.3 O2 without worrying about over-lithiation reaction.
[0066] Example 2
[0067] The embodiment provides a controllable preparation method of an over-lithiated oxide positive electrode material, comprising the following steps:
[0068] (1) Under the protection of argon atmosphere, equimolar amount of 0.02mol of perylene and metal lithium are mixed and dissolved in 100mL of tetrahydrofuran (THF) solvent, and stirred for 2h to prepare 0.2mol / L of perylene lithium reagent.
[0069] (2) LiNi 0.8 Co 0.1 Mn 0.1 O2, Super-P and polytetrafluoroethylene (PVDF) are mixed in a mass ratio of 8:1:1, N-methyl pyrrolidone is added, homogenized, coated, and after drying, LiNi 0.8 Co 0.1 Mn 0.1 O2 electrode sheet is prepared.
[0070] (3) The LiNi 0.8 Co 0.1 Mn 0.1 O2 electrode sheet is immersed in 3mL of prepared perylene lithium reagent and reacted for 10min. After the reaction is completed, it is washed with THF for 3 times and vacuum dried to obtain lithium-rich Li 1.35 Ni 0.8Co 0.1 Mn 0.1 O2 cathode.
[0071] Figure 4 The cyclic voltammogram of LiPc is shown in the figure, and the reaction equilibrium potential is 1.26 V, which is between the 1.80 V Li 0.8 Co 0.1 Mn 0.1 O2 over-discharge 1.80 V lithium intercalation platform and 1.20 V lithium intercalation platform, so that the lithiumation reaction end point can be limited to Li 1.35 Ni 0.8 Co 0.1 Mn 0.1 O2, without further lithiumation.
[0072] Figure 5 The first cycle charge-discharge curve of the Li-rich LiNi 0.8 Co 0.1 Mn 0.1 O2 cathode sheet after reaction with LiPc reagent. As can be seen from the figure, the open circuit voltage of the battery after prelithiation is significantly reduced to 1.33 V, a new platform appears at 2.1 V, the first cycle charge capacity increases from 219.1 mAh / g to 327.6 mAh / g, the reaction time is extended from 10 min to 30 min, and the first cycle charge-discharge curve of the battery is basically completely overlapped, which confirms that the Li 1.35 Ni 0.8 Co 0.1 Mn 0.1 O2 can be prepared controllably.
[0073] Example 3
[0074] The present embodiment provides a controllable preparation method of a superlithiated oxide positive electrode material, comprising the following steps:
[0075] (1) Under the protection of argon atmosphere, equimolar amount of 0.02 mol of anthracene and metal lithium are mixed and dissolved in 100 mL of ethylene glycol dimethyl ether (DME) solvent, and stirred for 2 h to prepare 0.2 mol / L of anthracene lithium reagent.
[0076] (2) LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, Super-P and polytetrafluoroethylene (PVDF) are mixed in a mass ratio of 8:1:1, N-methyl pyrrolidone is added, homogenized, coated, and after drying, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 electrode sheet is ready for use.
[0077] (3) LiNi 1 / 3 Co1 / 3 Mn 1 / 3 O2 cathode was immersed in 3 mL prepared anthracene lithium reagent, and reacted for 10 min. After reaction, the cathode was washed with DME for 3 times, and dried in vacuum to obtain Li 1.5 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O2 cathode.
[0078] Figure 6 The first cycle charge-discharge curve of LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 cathode after reaction with anthracene lithium reagent. As can be seen from the figure, the open circuit voltage of the battery after prelithiation is significantly reduced to 1.3 V, a new platform appears at 1.7 V, the first cycle charge capacity is increased from 168 mAh / g to 285 mAh / g, which confirms that anthracene lithium reagent can realize the controllable preparation of Li 1.5 Ni 1 / 3 Co 1 / 3 Mn 1 / 3 .
[0079] Example 4
[0080] The present embodiment provides a method for controllable preparation of over-lithiated oxide cathode material, comprising the following steps:
[0081] (1) Under the protection of argon gas, equimolar amount of 0.02 mol of p-terphenyl and lithium metal are mixed and dissolved in 100 mL of ethylene glycol dimethyl ether (DME) solvent, and stirred for 2 h to prepare 0.2 mol / L p-terphenyl lithium reagent.
[0082] (2) LiMn2O4, Super-P and polytetrafluoroethylene (PVDF) are mixed according to a mass ratio of 8:1:1, N-methyl pyrrolidone is added, homogenized, coated, dried, and then punched into LiMn2O4 cathode for standby.
[0083] (3) The LiMn2O4 cathode is immersed in 3 mL of prepared p-terphenyl lithium reagent, and after reaction, the cathode is washed with DME for 3 times, and dried in vacuum to obtain over-lithiated Li2Mn2O4 cathode.
[0084] Figure 7 The first cycle charge-discharge curve of LiMn2O4 cathode after reaction with p-terphenyl lithium reagent. As can be seen from the figure, the open circuit voltage of the battery after prelithiation is significantly reduced to 2.2 V, a new platform appears at 3.0 V, the first cycle charge capacity is increased from 146 mAh / g to 206.6 mAh / g, the reaction time is extended from 10 min to 30 min, and the first cycle charge-discharge curve of the battery is basically completely overlapped, which confirms that p-terphenyl lithium reagent can realize the controllable preparation of Li2Mn2O4.
[0085] Example 5
[0086] The present embodiment provides a controllable preparation method of a super-lithiated oxide cathode material, comprising the following steps:
[0087] (1) Under the protection of argon gas, equimolar amounts of 0.02 mol of 9-fluorenone and lithium metal are mixed and dissolved in 100 mL of tetrahydrofuran (THF) solvent, and stirred for 2 h to prepare a single-electron reduced 0.2 mol / L 9-fluorenone lithium reagent.
[0088] (2) LiNi 0.5 Mn 1.5 O4, Super-P and polytetrafluoroethylene (PVDF) are mixed in a mass ratio of 8:1:1, N-methyl pyrrolidone is added, homogenized, coated, and after drying, punched into LiNi 0.5 Mn 1.5 O4 electrode sheets for standby use.
[0089] (3) The LiNi 0.5 Mn 1.5 O4 electrode sheets are immersed in 3 mL of prepared 9-fluorenone lithium reagent, washed with THF for 3 times after the reaction is completed, and vacuum dried to obtain super-lithiated Li 1.5 Ni 0.5 Mn 1.5 O4 cathode.
[0090] Figure 8 The cyclic voltammetry curve of 9-fluorenone lithium is shown in the figure, and the reaction equilibrium potential is 2.0 V, which is between the 2.0 V lithium intercalation platform and the 2.7 V lithium intercalation platform of the over-discharged LiNi 0.5 Mn 1.5 O4, so the end point of lithiation reaction can be limited to Li 1.5 Ni 0.5 Mn 1.5 O4 without further lithiation.
[0091] Figure 9 The first cycle charge-discharge curve of the LiNi 0.5 Mn 1.5 O4 cathode electrode sheet after the reaction of the 9-fluorenone lithium reagent is shown in the figure. As can be seen from the figure, the open circuit voltage of the battery after prelithiation is significantly reduced to 2.0 V, a new platform appears at 3.0 V, and the first cycle charge capacity is increased from 185 mAh / g to 227.2 mAh / g, which confirms that the 9-fluorenone lithium reagent can realize the controllable preparation of Li 1.5 Ni 0.5 Mn 1.5 O4.
[0092] Application Example
[0093] The lithium-rich cathode prepared above was matched with carbon-coated aluminum foil to assemble into graphite full cells and anode-free lithium metal cells to evaluate the effect of cathode pre-lithiation on the energy density and cycle life of the cells. The test electrolyte of the graphite-based full cells was a commercial ternary electrolyte, and the test electrolyte of the anode-free lithium metal cells was 1 M LiTFSI dissolved in diethylene glycol dimethyl ether. CR2032 button cells were assembled in a glove box.
[0094] Figure 10 LiNi 0.5 Co 0.2 Mn 0.3 O2 cathodes matched with graphite anodes. As can be seen from the figure, the LiNi 0.5 Co 0.2 Mn 0.3 O2 cathode-based full cells decayed to 81.9 mAh / g after 100 cycles, and the capacity retention rate was 54.4%; while the Li 1.7 Ni 0.5 Co 0.2 Mn 0.3 O2 cathode-based cells can still have a capacity retention rate of 80.1% after 100 stable cycles, far exceeding the LiNi 0.5 Co 0.2 Mn 0.3 O2 cells.
[0095] Figure 11 LiNi 0.5 Co 0.2 Mn 0.3 O2 cathodes matched with copper foil before and after the reaction of the lithiation reagent of Example 1. As can be seen from the figure, the LiNi 0.5 Co 0.2 Mn 0.3 O2 cathode-based anode-free cells decayed to 30 mAh / g after 80 cycles, and the capacity retention rate was only 18.1%; while the Li 1.7 Ni 0.5 Co 0.2 Mn 0.3 O2 cathode-based cells can still have a capacity retention rate of 90.0% after 80 stable cycles, far exceeding the LiNi 0.5 Co 0.2 Mn 0.3 O2 cells.
Claims
1. A method for the controllable production of a lithium-excess-oxide cathode material, characterized by: The chemical formula of the over-lithiated oxide cathode material is: Li 1+n Ni x Co y Mn 1-x-y O2, Li2Mn2O4, Li 1.5 Ni 0.5 Mn 1.5 O4; wherein: 0 The method specifically comprises the following steps: The method comprises the following steps: firstly, through the systematic study on the over-lithiation behavior of the conventional oxide positive electrode material in the lithium ion battery, the matching lithiumization potential is accurately positioned, and a suitable aromatic lithium reagent is selected; then, the conventional oxide positive electrode material and the aromatic lithium reagent are subjected to a chemical lithiation reaction in an inert atmosphere, and the over-lithiated oxide positive electrode material is obtained through washing and drying.
2. The method of claim 1, wherein: when the over-lithiated oxide cathode material is Li 1.7 Ni 0.5 Co 0.2 Mn 0.3 O2, the potential of the aromatic lithium reagent is between 1.2-1.55V, and the aromatic lithium reagent is any one or several of lithium perylene, lithium benzophenone, lithium 9-fluorenone.
3. The method of claim 1, wherein: when the over-lithiated oxide cathode material is Li 1.35 Ni 0.8 Co 0.1 Mn 0.1 O2, the potential of the aromatic lithium reagent is between 1.2-1.8V, and the aromatic lithium reagent is any one or several of lithium perylene, lithium benzophenone, p-terphenyl, lithium 9-fluorenone.
4. The method of claim 1, wherein: When the over-lithiated oxide cathode material is Li 1.5 Ni 1 / 3Co 1 / 3 Mn 1 / 3 O2, the potential of the aromatic lithium reagent is between 0.8-1.2V, and the aromatic lithium reagent is any one or several of lithium anthracene, lithium perylene, lithium benzophenone.
5. The method of claim 1, wherein: When the over-lithiated oxide positive electrode material is Li2Mn2O4, the potential of the aromatic lithium reagent is between 1.0V and 2.9V, and the aromatic lithium reagent is any one or several of lithium perylene, lithium benzophenone, p-terphenyl, lithium 9-fluorenone or lithium phenazine.
6. The method of claim 1, wherein: when the over-lithiated oxide cathode material is Li 1.5 Ni 0.5 Mn 1.5 O4, the potential of the aromatic lithium reagent is between 2.0 and 2.7 V, and the aromatic lithium reagent is at least one of 9-fluorenyl lithium or phenazinyl lithium.
7. The method of claim 1, wherein: The concentration of the aromatic lithium reagent is 0.01-2mol / L, and the reaction time of the aromatic lithium reagent with the positive electrode material is 1min-24h.
8. The method of claim 1, wherein: The aromatic lithium reagent is prepared by the chemical reaction of an aromatic compound with metallic lithium in an organic solvent.
9. The application of the over-lithiated oxide positive electrode material prepared by the method in any one of claims 1-8 in a lithium ion battery and / or a negative electrode-free lithium metal battery.
10. A lithium-ion battery and / or a negative electrode-free lithium metal battery, characterized in that: The over-lithiated oxide positive electrode material prepared by the method in any one of claims 1-8.