Electrolyte, lithium-ion battery, electric device, and energy storage system

Abstract

An electrolyte (105), a lithium-ion battery (100), an electric device, and an energy storage system. The electrolyte (105) is suitable for a lithium-ion battery (100) comprising a lithium supplementing agent; the electrolyte (105) comprises an organic additive; the organic additive can be dissolved in the electrolyte (105); the oxidation-reduction potential of the organic additive is greater than the decomposition potential of the lithium supplementing agent. The organic additive can promote decomposition of the lithium supplementing agent and effectively reduce the decomposition potential of the lithium supplementing agent, thereby achieving the purpose of compensating for lithium loss of the lithium-ion battery. Moreover, the organic additive is easily dissolved in the electrolyte (105), diffuses to the surface of the lithium supplementing agent along with the electrolyte (105), and is in full contact with the lithium supplementing agent, thereby fully reducing the decomposition potential of the lithium supplementing agent, and increasing the utilization rate of the lithium supplementing agent.

Description

Electrolytes, lithium-ion batteries, electrical equipment, and energy storage systems

[0001] This application claims priority to Chinese Patent Application No. 202411189737.2, filed on August 27, 2024, entitled "Electrolyte, Lithium-ion Battery, Electrical Equipment and Energy Storage System", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, specifically to an electrolyte, a lithium-ion battery, an electrical device, and an energy storage system. Background Technology

[0003] The demand for lithium-ion batteries is increasing, and the performance requirements are also rising. Battery replenishment technology can compensate for the active lithium consumed during the initial formation of the SEI (Solid Electrolyte Interface) film, and is a promising technology for achieving long cycle life and high energy density batteries. Replenishment technology requires the lithium replenishing agent to fully decompose and provide active lithium to the battery. Currently used positive electrode lithium replenishing agents have relatively high decomposition potentials in the battery system. Under high voltage conditions, they are prone to side reactions such as electrolyte decomposition, which may cause gas generation and valve opening, leading to battery failure. It also reduces the utilization rate of the lithium replenishing agent, thus increasing battery costs. Summary of the Invention

[0004] Therefore, this application provides an electrolyte suitable for lithium-ion batteries containing lithium replenishing agents. The electrolyte includes an organic additive that is soluble in the electrolyte. The redox potential of the organic additive is greater than the decomposition potential of the lithium replenishing agent. By applying the organic additive to a lithium replenishment system containing a lithium replenishing agent, the organic additive, with its redox potential greater than the decomposition potential, can promote the decomposition of the lithium replenishing agent and effectively reduce its decomposition potential, thereby replenishing the lithium lost from the lithium-ion battery. Furthermore, the organic additive is easily soluble in the electrolyte and diffuses with the electrolyte to the surface of the lithium replenishing agent, ensuring sufficient contact and significantly reducing its decomposition potential, thus improving the utilization rate of the lithium replenishing agent.

[0005] The first aspect of this application provides an electrolyte suitable for lithium-ion batteries containing a lithium replenishing agent. The electrolyte includes an organic additive that is soluble in the electrolyte, and the redox potential of the organic additive is greater than the decomposition potential of the lithium replenishing agent.

[0006] In this embodiment of the application, the oxidation-reduction potential of the organic additive is 3.5V-4.5V, more preferably 4.0V-4.2V.

[0007] In this embodiment of the application, the organic additive has a mass percentage content of 0.01%-5% in the electrolyte.

[0008] In the embodiments of this application, the organic additives include one or more of piperidine oxide, phenothiazine compounds, thiazine compounds, organic amine compounds, aminobenzene compounds, phenothiazine compounds, anthracene compounds, thiaanthracene compounds, tetrathiofulvalene and its derivatives, benzoquinone and its derivatives, dimethoxybenzene and its derivatives, tetrathiofulvalene, N-methyl-N-propylpyrrolidine bromide, cobalt(II)porphyrin complex, ferrophthalocyanine, ethyl violetine, and ferrocene.

[0009] In this embodiment, the piperidine oxide includes 2,2,6,6-tetramethylpiperidine oxide; the phenothiazine compounds include 10-isopropylphenothiazine and 10-methylphenothiazine; the organic amine compounds include N,N,N',N'-tetramethyl-p-phenylenediamine, triethylenediamine, and triphenylamine; the aminobenzene compounds include tris(4-aminophenyl)amine and 1,4-bis(diphenylamino)benzene; the phenothiazine compounds include 5,10-dihydro-5,10-dimethylphenazine; the anthracene compounds include 9,10-dimethylanthracene; the thiaanthracene compounds include thiaanthracene; and the dimethoxybenzene and its derivatives include 2,5-di-tert-butyl-1,4-dimethoxybenzene.

[0010] In this embodiment of the application, the organic additive includes a first organic additive and a second organic additive, and the absolute value of the difference between the redox potentials of the first organic additive and the second organic additive is 0.01V-0.5V.

[0011] In this embodiment of the application, the mass ratio of the first organic additive to the second organic additive in the electrolyte is 1:(0.1-10).

[0012] In this embodiment of the application, the electrolyte further includes a lithium salt and a solvent; the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonate)imide, and lithium bis(fluorosulfonate); the solvent includes carbonate solvents, and the carbonate solvent includes one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate.

[0013] A second aspect of this application also provides a lithium-ion battery, the lithium-ion battery including a battery casing and a positive electrode, a negative electrode, a separator, and an electrolyte housed inside the battery casing, the separator and the electrolyte being disposed between the positive electrode and the negative electrode, the lithium-ion battery including a lithium replenishing agent, the electrolyte including the electrolyte provided in the first aspect of this application; the redox potential of the organic additive is higher than the decomposition potential of the lithium replenishing agent.

[0014] In this embodiment of the application, the mass ratio of the organic additive to the lithium supplement is 1:(1-1000).

[0015] In this embodiment of the application, the lithium supplement includes one or more of Li5FeO4, Li2NiO2, Li6CoO4, Li2Se, Li2CO3, Li2C2O4, Li2O, Li3N, Li2O2, Li2S, Li2S2, lithium borate, and lithium thioborate; preferably one or more of Li2CO3, Li2C2O4, Li2O, Li3N, Li2O2, Li2S, Li2S2, lithium borate, and lithium thioborate.

[0016] In this embodiment of the application, the positive electrode sheet includes a current collector and a positive electrode active layer disposed on the surface of the current collector, and the positive electrode active layer includes the lithium replenishing agent;

[0017] And / or the lithium-ion battery further includes a lithium replenishing layer, the lithium replenishing layer including the lithium replenishing agent.

[0018] In this embodiment of the application, the positive electrode sheet includes the positive electrode active material, and the positive electrode active material includes lithium iron phosphate.

[0019] A third aspect of this application also provides an electrical device, which includes the lithium-ion battery provided in the second aspect of this application.

[0020] The fourth aspect of this application also provides an energy storage system, which includes the lithium-ion battery provided in the second aspect of this application. Attached Figure Description

[0021] Figure 1 is a schematic diagram of the structure of a lithium-ion battery provided in an embodiment of this application;

[0022] Figure 2 shows the test results of the redox potential of the organic additive triphenylamine in Example 2;

[0023] Figure 3 shows the capacity-voltage curves of the lithium-ion batteries of Example 1 and Comparative Example 2.

[0024] Explanation of reference numerals in the attached diagram: 100-Lithium-ion battery; 101-Positive electrode; 102-Lithium replenishment layer; 103-Separator; 104-Negative electrode; 105-Electrolyte; 106-Battery casing. Detailed Implementation

[0025] The present application will be further described in detail below with reference to preferred embodiments, but the scope of protection of the present application is not limited to the following specific embodiments.

[0026] In this application, all technical terms have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of this application.

[0027] The demand for lithium-ion batteries is increasing, and the performance requirements are also rising. Battery replenishment technology can compensate for the active lithium consumed during the initial formation of the SEI (Solid Electrolyte Interface) film, making it a promising technology for achieving long cycle life and high energy density batteries. Replenishment technology requires the lithium replenishing agent to fully decompose and provide active lithium to the battery. Among various replenishment technologies, the commonly used positive electrode lithium replenishing agents in current battery systems have relatively high decomposition potentials. For example, the decomposition potentials of lithium carbonate and lithium oxide reach above 4.5V. Under high voltage conditions, the electrolyte is prone to decomposition, producing gases such as CO2, CO, and H2, which may cause the battery valve to open and lead to battery failure. Furthermore, the incomplete decomposition of lithium replenishing agents in existing battery systems also reduces the utilization rate of the replenishing agent, thus increasing battery costs.

[0028] To address the aforementioned problems with lithium replenishers, existing methods involve carbon coating the lithium replenisher particles to increase their conductivity and promote their decomposition. However, the decomposition efficiency remains unsatisfactory. This is because the lithium replenisher itself has poor conductivity, and the contact area between the solid lithium replenisher and the solid conductive carbon is small, resulting in a large overpotential during lithium replenisher decomposition. Furthermore, this may catalyze electrolyte decomposition, causing gas generation and valve opening in the battery, ultimately leading to battery failure.

[0029] To address the aforementioned technical problems, this application provides an electrolyte suitable for lithium-ion batteries containing lithium replenishing agents. The electrolyte includes an organic additive that is soluble in the electrolyte. The redox potential of the organic additive is greater than the decomposition potential of the lithium replenishing agent. By applying the organic additive to a lithium replenishment system containing a lithium replenishing agent, the organic additive, with its redox potential greater than the decomposition potential, promotes the decomposition of the lithium replenishing agent and effectively reduces its decomposition potential, thereby replenishing lithium loss from the lithium-ion battery. Furthermore, the organic additive is readily soluble in the electrolyte and diffuses with the electrolyte to the surface of the lithium replenishing agent, ensuring sufficient contact and significantly reducing its decomposition potential, thus improving the utilization rate of the lithium replenishing agent.

[0030] In this embodiment, the electrolyte is suitable for lithium-ion batteries containing lithium replenishing agents. The electrolyte includes organic additives that are soluble in the electrolyte. The redox potential of the organic additives is greater than the decomposition potential of the lithium replenishing agents. When this organic additive is applied to a lithium replenishment system containing lithium replenishing agents, controlling the redox potential of the organic additives to be greater than the decomposition potential of the lithium replenishing agents allows the organic additives to act as redox mediators that promote the decomposition of the lithium replenishing agents. This effectively reduces the decomposition potential of the lithium replenishing agents, solves problems such as the utilization rate of lithium replenishing agents in previous lithium replenishment system batteries, and also effectively alleviates the side reactions caused by lithium replenishing agents, thereby improving the battery capacity and service life.

[0031] The organic additive in this application is an organic redox mediator, also known as a redox shuttle or redox shuttle, which acts as a medium between the lithium replenisher and the electrode. When the battery is charged, the redox mediator is preferentially oxidized. The oxidized redox mediator diffuses to the surface of the lithium replenisher to further oxidize the lithium replenisher, while it is reduced to its initial state and can be recycled.

[0032] Based on the principle of "like dissolves like," compared to solid inorganic redox mediators, the organic additives in the electrolyte provided in this application have higher solubility and faster diffusion in the electrolyte, significantly improving the contact between the organic additives and the lithium replenisher. As organic additives that promote the decomposition of the lithium replenisher, they are more easily oxidized. After oxidation, the oxidized organic additive molecules diffuse to the surface of the lithium replenisher, spontaneously oxidizing and decomposing it. At this point, the organic additive changes from its oxidized state to its initial state, allowing for repeated recycling. Furthermore, unlike solid-phase organic additives that promote lithium replenisher decomposition, the organic additives in this application can dissolve in the organic electrolyte. As they diffuse to the surface of the lithium replenisher with the electrolyte, they effectively improve the utilization rate of the lithium replenisher without relying on a good conductive network. Simultaneously, they can reduce the proportion of inactive materials (such as solid-phase organic additives and conductive agents) in the battery electrodes, thereby further improving the battery's energy density.

[0033] In this application, the redox potential of the organic additive is 3.5V-4.5V. In some specific embodiments, the redox potential of the organic additive can be, for example, 3.5V, 3.6V, 3.7V, 3.8V, 3.9V, 4.0V, 4.1V, 4.2V, 4.3V, 4.4V, or 4.5V. By controlling the redox potential of the organic additive within the aforementioned suitable range, this application can accelerate the redox kinetics of the organic additive and promote the decomposition of the lithium supplement. Compared to inorganic redox mediators, which have a limited variety and fixed redox potentials, the organic additives in this application are diverse and their redox potentials can be adjusted through modification with different functional groups, thereby obtaining the desired target potential according to the different requirements of the lithium supplement.

[0034] In some embodiments of this application, the redox potential of the organic additive is 4.0V-4.2V. In some specific embodiments, the redox potential of the organic additive can be, for example, 4.0V, 4.1V, or 4.2V. In actual batteries, due to the poor conductivity and large particle size of the lithium replenishing agent, its decomposition process exhibits significant polarization. The greater the difference between the redox potential of the organic additive and the decomposition potential of the lithium replenishing agent, the easier it is for the lithium replenishing agent to decompose. However, when the redox potential of the organic additive is high, approaching the decomposition potential of the electrolyte, it can cause unnecessary side reactions. This application, by further controlling the redox potential of the organic additive within the above-mentioned range, can further effectively increase the driving force for the decomposition reaction of the lithium replenishing agent, further improve the lithium replenishment efficiency of the lithium replenishing agent, and also reduce side reactions in the battery system, thereby increasing cycle performance.

[0035] In some embodiments of this application, the mass percentage of the organic additive in the electrolyte is 0.01%-5%. In some specific embodiments of this application, the mass percentage of the organic additive in the electrolyte is 0.01%, 0.02%, 0.05%, 0.08%, 0.1%, 0.2%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and 5%. By controlling the concentration of the organic additive in the electrolyte within the above range, this application facilitates the dissolution of the organic additive in the electrolyte, promoting diffusion to the surface of the lithium supplement, enhancing the catalytic effect of the organic additive, and further reducing the decomposition potential of the lithium supplement while minimizing costs. In the embodiments of this application, the content of the organic additive in the organic electrolyte can be measured by ultraviolet spectrophotometer, nuclear magnetic resonance, liquid chromatography, etc.

[0036] In this application, the organic additives include one or more of piperidine oxides, phenothiazine compounds, thiazine compounds, organic amine compounds, aminobenzene compounds, phenothiazine compounds, anthracene compounds, thiaanthracene compounds, tetrathiofulvalene and its derivatives, benzoquinone and its derivatives, dimethoxybenzene and its derivatives, tetrathiofulvalene, N-methyl-N-propylpyrrolidine bromide, cobalt(II)porphyrin complexes, ferrophthalocyanine, ethyl violetine, and ferrocene. Compared to the limited variety of inorganic redox mediators, this application offers a rich selection of organic additives, such as piperidine oxides, phenothiazine compounds, thiazine compounds, organic amine compounds, aminobenzene compounds, phenothiazine compounds, anthracene compounds, thiaanthracene compounds, tetrathiofulvalene and its derivatives, benzoquinone and its derivatives, dimethoxybenzene and its derivatives, etc. These different types of organic compounds correspond to different ranges of redox potentials, and the organic additives can be selected according to the decomposition potential of the specific lithium supplement in the actual application. Furthermore, these organic additives can also adjust their redox potential through functional group modification, thereby achieving the desired target potential.

[0037] In the embodiments of this application, piperidine oxides include, but are not limited to, 2,2,6,6-tetramethylpiperidine oxides; phenothiazine compounds include, but are not limited to, 10-isopropylphenothiazine and 10-methylphenothiazine; organic amine compounds include, but are not limited to, N,N,N',N'-tetramethyl-p-phenylenediamine, triethylenediamine and triphenylamine; aminobenzene compounds include, but are not limited to, tris(4-aminophenyl)amine and 1,4-bis(diphenylamino)benzene; phenothiazine compounds include, but are not limited to, 5,10-dihydro-5,10-dimethylphenazine; anthracene compounds include, but are not limited to, 9,10-dimethylanthracene; thiaanthracene compounds include, but are not limited to, thiaanthracene; and dimethoxybenzene and its derivatives include, but are not limited to, 2,5-di-tert-butyl-1,4-dimethoxybenzene.

[0038] In this application, the organic additive includes a first organic additive and a second organic additive. In this application, the absolute value of the difference in redox potential between the first organic additive and the second organic additive is 0.01V-0.5V. In some specific embodiments of this application, the absolute value of the difference in redox potential between the first organic additive and the second organic additive can be, for example, 0.01V, 0.05V, 0.1V, 0.15V, 0.2V, 0.25V, 0.3V, 0.35V, 0.4V, 0.45V, or 0.5V. Due to differences in particle size and location of the lithium supplement in the lithium supplement system, the decomposition potential of the lithium supplement is not entirely consistent during the decomposition process. This application, by adding a combination of organic additives with different redox potentials, can perform graded decomposition of lithium supplements with different decomposition potentials, ensuring decomposition efficiency while minimizing the decomposition potential and reducing the occurrence of side reactions. Furthermore, even for lithium supplement particles of the same type, as the decomposition of the lithium supplement proceeds, the residual lithium supplement becomes increasingly difficult to decompose, requiring a higher voltage. Therefore, by selecting two organic additives with different redox voltages, the lithium supplement can be decomposed at low and high voltages respectively through their synergistic effect. In some specific embodiments of this application, the first organic additive may be, for example, 10-methylphenthiazide, and the second organic additive may be, for example, triphenylamine.

[0039] In this application, the mass ratio of the first organic additive to the second organic additive is 1:(0.1-10). In some specific embodiments of this application, the mass ratio of the first organic additive to the second organic additive can be, for example, 1:0.1, 1:0.2, 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, or 1:10. By controlling the mass ratio of the first organic additive to the second organic additive within a suitable range, the application requirements of different lithium supplementation systems can be met, and the utilization rate of the lithium supplementer can be improved.

[0040] In this embodiment, the electrolyte further includes lithium salts. In some embodiments, the lithium salts include, but are not limited to, one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonate)imide, and lithium bis(fluorosulfonate)imide. Adding the above-mentioned lithium salts to the electrolyte can further enhance its ion conductivity.

[0041] In this application, the electrolyte further includes a solvent. In some embodiments, the solvent includes carbonate solvents. In some specific embodiments, carbonate solvents include, but are not limited to, one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate. These solvents can promote the dissolution of organic additives and lithium salts in the electrolyte, further promote ion migration in the non-aqueous electrolyte and the catalytic decomposition of lithium supplementation agents by organic additives, thereby improving the electrochemical performance of the battery.

[0042] The electrolyte provided in this application uses an organic additive with a redox potential greater than the decomposition potential of the lithium replenisher as a redox mediator. When applied to a lithium replenishment system containing a lithium replenisher, it promotes the decomposition of the lithium replenisher and effectively reduces its decomposition potential, thereby replenishing the lithium lost from the battery. Furthermore, the organic additive in the electrolyte is easily soluble in the organic electrolyte and diffuses to the surface of the lithium replenisher, ensuring sufficient contact and promoting rapid and efficient decomposition, thus improving the utilization rate of the lithium replenisher. In addition, the organic additive can adjust its redox potential through functional group modification to achieve the desired target potential without reducing the proportion of active material in the electrode, resulting in a longer battery life and higher energy density.

[0043] This application also provides a lithium-ion battery, including a battery casing and a positive electrode, a negative electrode, a separator, and an electrolyte housed inside the battery casing. The separator and electrolyte are disposed between the positive and negative electrode. The lithium-ion battery includes a lithium replenishing agent, and the electrolyte includes the electrolyte provided above in this application. The redox potential of the organic additive in the electrolyte is higher than the decomposition potential of the lithium replenishing agent. In this application, the decomposition potential of the lithium replenishing agent specifically refers to the inherent decomposition potential of the lithium replenishing agent measured under ideal conditions, which can be obtained by referring to a table. By controlling the redox potential of the organic additive in the electrolyte to a range higher than the decomposition potential of the lithium replenishing agent, this application can promote the decomposition of the lithium replenishing agent, thereby achieving the purpose of replenishing the lithium loss of the battery. When the organic additive is oxidized, because the redox potential of the organic additive is higher than the decomposition potential of the lithium replenishing agent, the oxidized organic additive molecules diffuse to the surface of the lithium replenishing agent, which can spontaneously oxidize and decompose the lithium replenishing agent. The organic additive, acting as a redox mediator, becomes the initial state and can be recycled and reused.

[0044] In this application, the mass ratio of organic additive to lithium supplement is 1:(1-1000). In some specific embodiments of this application, the mass ratio of organic additive to lithium supplement can be, for example, 1:1, 1:2, 1:3, 1:4, 1:5, 1:10, 1:50, 1:100, 1:200, 1:300, 1:500, 1:800, or 1:1000. By controlling the mass ratio of organic additive to lithium supplement within a suitable range, this application ensures sufficient contact between the organic additive and the lithium supplement, further enhancing the promoting effect of the organic additive on the decomposition of the lithium supplement.

[0045] In this embodiment of the application, the content of lithium replenishing agent in the lithium-ion battery can be measured by XRD (X-ray Diffraction), chemical / electrochemical titration, electrochemical decomposition curves, etc.

[0046] In some embodiments of this application, the lithium replenishing agent includes one or more of Li5FeO4, Li2NiO2, Li6CoO4, Li2Se, Li2CO3, Li2C2O4, Li2O, Li3N, Li2O2, Li2S, Li2S2, lithium borate, and lithium thioborate. Different types of lithium replenishing agents can be applied to different battery lithium replenishment systems to increase the lithium replenishment effect. In some specific embodiments, the lithium replenishing agent includes one or more of Li2CO3, Li2C2O4, Li2O, Li3N, Li2O2, Li2S, Li2S2, lithium borate, and lithium thioborate.

[0047] In this application, the lithium replenishing agent includes intercalation-type lithium replenishing agents and / or conversion-type lithium replenishing agents. Different types of lithium replenishing agents are suitable for different battery lithium replenishment systems. Intercalation-type lithium replenishing agents include Li5FeO4, Li2NiO2, and Li6CoO4, while conversion-type lithium replenishing agents include one or more of Li2Se, Li2CO3, Li2C2O4, Li2O, Li3N, Li2O2, Li2S, Li2S2, lithium borate, and lithium thioborate. In this application, intercalation-type lithium replenishing agents refer to those in which lithium ions exist within the crystal framework of the material. When lithium is replenished, the material shrinks normally due to the release of lithium ions, leaving a residue of the lithium replenishing agent after replenishment. Conversion-type lithium replenishing agents refer to those in which lithium ions are not stored within the crystal framework of the material but exist in the form of an alloy or a compound composed of lithium and non-metallic elements. When lithium is replenished, the material gradually shrinks due to the release of lithium ions, leaving almost no residue of the lithium replenishing agent after replenishment.

[0048] In some embodiments of this application, the lithium replenishing agent is an intercalating lithium replenishing agent. When the lithium replenishing agent is an intercalating lithium replenishing agent, as the lithium replenishment process proceeds, the volume of the intercalating lithium replenishing agent will shrink, and the organic additives in the electrolyte can reach the reaction interface, ensuring sufficient contact between the lithium replenishing agent and the organic additives, and improving the catalytic efficiency of the organic additives for the decomposition of the lithium replenishing agent.

[0049] In some embodiments of this application, the lithium replenishing agent is a conversion-type lithium replenishing agent. When the lithium replenishing agent is a conversion-type lithium replenishing agent, its volume will continuously shrink as the lithium replenishment process proceeds, and some may even disappear. The organic additives in the electrolyte can continuously reach the reaction interface, ensuring real-time contact with the lithium replenishing agent and improving the catalytic efficiency of the organic additives for the decomposition of the lithium replenishing agent.

[0050] In some embodiments of this application, the lithium replenishing agent includes intercalation-type lithium replenishing agents and conversion-type lithium replenishing agents. When the lithium replenishing agent includes both intercalation-type and conversion-type lithium replenishing agents, the advantages of both can be utilized simultaneously, and the lithium replenishing effect can be further improved through their synergistic effect.

[0051] In some embodiments of this application, the positive electrode includes a current collector and a positive electrode active layer disposed on the surface of the current collector, the positive electrode active layer including the lithium supplement agent provided above. In some specific embodiments, the lithium supplement agent is uniformly dispersed in the positive electrode active layer.

[0052] In other embodiments of this application, the lithium-ion battery further includes a lithium replenishment layer, which includes the lithium replenishing agent provided above. In some specific embodiments, the lithium-ion battery 100, as shown in FIG1, includes a battery casing 106 and a positive electrode 101, a lithium replenishment layer 102, a separator 103, a negative electrode 104, and an electrolyte 105 housed within the battery casing 106, wherein the positive electrode 101, the lithium replenishment layer 102, the separator 103, and the negative electrode 104 are stacked sequentially. In some embodiments, the lithium replenishment layer is located between the positive electrode and the separator; in some embodiments, the lithium replenishment layer is located on the surface of the positive electrode closer to the separator; in some embodiments, the lithium replenishment layer is located on the surface of the separator closer to the positive electrode. Since the electrolyte is more abundant on the side of the separator closer to the positive electrode in the battery, placing the lithium replenishment layer between the positive electrode and the separator can further accelerate the diffusion rate of the organic additives, thereby further shortening the decomposition time of the lithium replenishing agent and increasing the battery production speed.

[0053] In some embodiments of this application, the lithium replenishment layer 102 further includes a conductive agent, a binder, and a dispersant. In these embodiments, the conductive agent can be any conductive agent known in the art, such as one or more of super P-Li, super P, acetylene black, graphene, and carbon nanotubes. In these embodiments, the binder and dispersant can also be any binder and dispersant known in the art.

[0054] In this embodiment, the positive electrode 101 includes a positive current collector and a positive active layer disposed on the positive current collector. The positive active material in the positive electrode material layer can be any positive active material for lithium-ion batteries known in the art. Exemplarily, in some embodiments, the positive active material includes at least one of phosphate-based positive active materials and transition metal oxide positive active materials. Phosphate-based positive active materials include, but are not limited to, one or more of doped or undoped lithium iron phosphate, lithium manganese iron phosphate, etc., while transition metal oxide positive active materials include, but are not limited to, one or more of doped or undoped ternary materials, lithium-rich layered oxides, etc. In some embodiments of this application, the positive active material includes lithium iron phosphate. Since lithium iron phosphate has a low stable voltage, high-voltage lithium replenishment can affect its stability. Therefore, selecting appropriate organic additives can effectively reduce the lithium replenishment decomposition potential of the lithium replenishment agent. Furthermore, the conductivity of lithium iron phosphate is lower than that of ternary materials, making it more prone to polarization of the lithium replenishment agent, leading to an increase in the lithium replenishment decomposition potential of the lithium iron phosphate material. Therefore, organic additives are needed to reduce the lithium replenishment decomposition potential.

[0055] In this embodiment, the separator 103 is a polymer film. In this embodiment, the negative electrode 104 includes a negative electrode current collector and a negative electrode active layer disposed on the negative electrode current collector. The negative electrode active material in the negative electrode material layer can be any negative electrode active material known in the art for lithium-ion batteries. In this embodiment, the negative electrode active material in the negative electrode material layer can be any negative electrode active material known in the art for lithium-ion batteries. For example, the negative electrode active material can be selected from one or more of carbon-based negative electrode active materials, silicon-based negative electrode active materials, tin-based negative electrode active materials, and lithium metal negative electrode active materials. Among them, carbon-based negative electrodes include, but are not limited to, natural graphite, artificial graphite, hard carbon, soft carbon, and graphene; silicon-based negative electrodes include, but are not limited to, silicon, silicon-carbon, and silicon-oxygen; tin-based negative electrodes include, but are not limited to, tin, tin-carbon, tin-oxygen, and tin metal compounds. In this embodiment, the battery casing 106 includes, but is not limited to, materials such as steel, aluminum, nickel-plated iron, or aluminum-plastic film.

[0056] The lithium-ion battery provided in this application uses an electrolyte containing organic additives in combination with a lithium replenishing agent in the battery. This effectively shortens the diffusion path of the organic additives, which act as redox mediators, accelerates the reaction rate that promotes the decomposition of the lithium replenishing agent, improves the battery's decomposition efficiency and capacity, and extends the battery's cycle life. This effectively solves the problems of low decomposition efficiency, high decomposition potential, and slow decomposition speed of previous lithium replenishing batteries.

[0057] This application also provides an electrical device that includes the lithium-ion battery described above. This electrical device may be, for example, an electric vehicle, a mobile phone, a tablet computer, a laptop computer, a wearable device (watch, bracelet), a digital camera, etc.

[0058] This application also provides an energy storage system comprising the lithium-ion battery described above.

[0059] The technical solution of this application will be described in detail below with reference to several embodiments.

[0060] Example 1

[0061] (1) Preparation of positive electrode sheet: The positive electrode active material (lithium iron phosphate), conductive agent (conductive carbon black), solvent (N-methylpyrrolidone), and binder (PVDF) are mixed, wherein the mass ratio of positive electrode active material, conductive agent, binder and solvent is 100:1.5:2.5:50; a positive electrode slurry with appropriate viscosity is prepared, coated on the positive electrode current collector (aluminum foil), and dried to obtain the positive electrode sheet;

[0062] (2) Preparation of the lithium replenishment layer: Lithium replenishing agent (Li2CO3), conductive agent (conductive carbon black), solvent (N-methylpyrrolidone), and binder (PVDF) are mixed to prepare a lithium replenishment slurry with appropriate viscosity, wherein the mass ratio of lithium replenishing agent: conductive agent: solvent: binder is 10:1:50:1. The prepared lithium replenishment slurry is coated on one side of the positive electrode sheet, and after drying, a lithium replenishment layer is obtained on one side of the positive electrode sheet; wherein the ratio of lithium replenishing agent to positive electrode active material is controlled to be 3:100.

[0063] (3) Preparation of negative electrode sheet: The negative electrode active material (graphite powder), conductive agent (conductive carbon black), binder (mixture of CMC and SBR), and solvent (water) are mixed to prepare a negative electrode slurry with appropriate viscosity. The mass ratio of positive electrode active material, conductive agent, binder and solvent is 100:0.8:2.5:50. The slurry is coated on the negative electrode current collector (copper foil) and dried to obtain the negative electrode sheet.

[0064] (4) Preparation of electrolyte: Add organic additive 10-methylphenthiazide to an electrolyte with a LiPF6 concentration of 1 mol / L (solvent is 15% DMC + 40% EMC + 15% DEC + 30% EC by mass ratio). The mass percentage of 10-methylphenthiazide in the electrolyte is 0.2%. After thorough mixing, let stand for 24 hours.

[0065] (5) Preparation of lithium-ion batteries: The prepared positive electrode sheet coated with lithium replenishment layer, the separator (PP film) and the prepared negative electrode sheet are stacked in sequence, with the lithium replenishment layer located on the side close to the separator. The soft pack battery is assembled, the prepared electrolyte is injected, and electrochemical tests are performed. The results are shown in Table 1.

[0066] Example 2

[0067] The difference from Example 1 is that the organic additive in step (4) is triphenylamine.

[0068] Example 3

[0069] The difference from Example 1 is that the organic additive in step (4) is 5,10-dihydro-5,10-dimethylphenazine.

[0070] Example 4

[0071] The difference from Example 1 is that the mass percentage of 10-methylphenothiazine in the electrolyte in step (4) is 0.05%.

[0072] Example 5

[0073] The difference from Example 1 is that the 10-methylphenothiazine in step (4) has a mass percentage content of 0.5% in the electrolyte.

[0074] Example 6

[0075] The difference from Example 1 is that the mass percentage of 10-methylphenothiazine in the electrolyte in step (4) is 1.5%.

[0076] Example 7

[0077] The difference from Example 1 is that the lithium replenishing agent is added to the positive electrode active material layer; specifically, in step (1), a positive electrode sheet with lithium replenishing agent is prepared: positive electrode active material (lithium iron phosphate powder), lithium replenishing agent (lithium carbonate), conductive agent (conductive carbon black), solvent (N-methylpyrrolidone), and binder (PVDF) are mixed, wherein the mass ratio of positive electrode active material, lithium replenishing agent, conductive agent, binder and solvent is 100:3:0.8:2.5:50; a positive electrode slurry with appropriate viscosity is prepared, coated on the positive electrode current collector (aluminum foil), and dried to obtain a positive electrode sheet with lithium replenishing agent.

[0078] Example 8

[0079] The difference from Example 1 is that the lithium replenishing agent is applied to the side of the separator closest to the positive electrode. Specifically, in step (2), the lithium replenishing layer is prepared by mixing the lithium replenishing agent (lithium carbonate), conductive agent (conductive carbon black), solvent (N-methylpyrrolidone), and binder (PVDF) to prepare a lithium replenishing slurry with appropriate viscosity, wherein the mass ratio of lithium replenishing agent: conductive agent: solvent: binder is 10:1:50:1. The prepared lithium replenishing slurry is coated on the side of the separator closest to the positive electrode active material layer, and after drying, a lithium replenishing layer is obtained on the side of the positive electrode. The ratio of lithium replenishing agent to positive electrode active material is controlled to be 3:100.

[0080] Example 9

[0081] The difference from Example 1 is that the organic additive in step (4) is 10-methylphenthiazide and triphenylamine in a mass ratio of 1:1.

[0082] Example 10

[0083] The difference from Example 1 is that the organic additive in step (4) is 10-methylphenthiazide and triphenylamine in a mass ratio of 1:10.

[0084] Example 11

[0085] The difference from Example 1 is that the organic additive in step (4) is 10-methylphenthiazide and triphenylamine in a mass ratio of 1:0.1.

[0086] Example 12

[0087] The difference from Example 1 is that the lithium replenishing agent is replaced with Li2C2O4, while the lithium replenishing capacity is the same.

[0088] Example 13

[0089] The difference from Example 1 is that the lithium replenishing agent is replaced with Li5FeO4, while the lithium replenishing capacity is the same.

[0090] Example 14

[0091] The difference from Example 1 is that the lithium replenishing agent is replaced with Li2NiO2, while the lithium replenishing capacity is the same.

[0092] Example 15

[0093] The difference from Example 7 is that the lithium replenishing agent is replaced with Li5FeO4, while the lithium replenishing capacity is the same.

[0094] Example 16

[0095] The difference from Example 7 is that the lithium replenishing agent is replaced with a mixture of Li5FeO4 and Li2CO3 in a mass ratio of 1:5, while the total lithium replenishment capacity remains the same.

[0096] Example 17

[0097] The difference from Example 7 is that the lithium replenishing agent is replaced with a mixture of Li5FeO4, Li2NiO2 and Li2CO3 in a mass ratio of 1:1:4, while the total lithium replenishment capacity is the same.

[0098] Example 18

[0099] The difference from Example 7 is that the positive electrode active material is a ternary material (NCM 622).

[0100] Example 19

[0101] The difference from Example 1 is that the organic additive in step (4) is 2,2,6,6-tetramethylpiperidine oxide.

[0102] Example 20

[0103] The difference from Example 1 is that the mass percentage of 10-methylphenothiazine in the electrolyte in step (4) is 0.01%.

[0104] Example 21

[0105] The difference from Example 1 is that the 10-methylphenothiazine in step (4) has a mass percentage of 5% in the electrolyte.

[0106] Example 22

[0107] The difference from Example 1 is that the organic additive in step (4) is 2-phenyl-4,4,5,5-tetramethylimidazoline-3-oxo-1-oxo.

[0108] Comparative Example 1

[0109] The difference from Example 1 is that no lithium replenishment layer is provided in the positive electrode, and no organic additives are added in step (4).

[0110] Comparative Example 2

[0111] The difference from Example 1 is that no organic additives were added in step (4).

[0112] Comparative Example 3

[0113] The difference from Example 1 is that the electrolyte organic additive in step (4) is lithium bromide.

[0114] Comparative Example 4

[0115] The difference from Example 7 is that no organic additives were added in step (4).

[0116] Comparative Example 5

[0117] The difference from Example 7 is that the electrolyte organic additive in step (4) is lithium bromide.

[0118] Comparative Example 6

[0119] The difference from Example 18 is that no organic additives were added to the electrolyte and no lithium replenishing agent was added to the positive electrode active material layer.

[0120] Comparative Example 7

[0121] The difference from Example 18 is that the electrolyte organic additive in step (4) is lithium bromide.

[0122] Table 1 shows the specific information regarding the mass percentage of organic additives in the electrolyte, the types of organic additives, the location of lithium replenishment, the types of lithium replenishment, and the types of positive electrode active materials for Examples 1-22 and Comparative Examples 1-7.

[0123] Electrochemical testing

[0124] (1) Test procedure for lithium iron phosphate batteries: Electrochemical tests were performed on Examples 1-17 and 19 and Comparative Examples 1-5;

[0125] Average decomposition potential and 0.1C discharge capacity after aging were tested: The lithium-ion batteries prepared in the examples and comparative examples were charged at room temperature at a rate of 0.05C for 2 hours, then charged at a rate of 0.33C to 3.8V, and then charged at a constant voltage of 3.8V with a cutoff current of 0.05C. After resting for 1 hour, they were charged again at a current of 0.006C to 4.6V. The average decomposition potential could be read from the testing software. After resting for 1 hour, they were discharged at 0.2C to 2.0V, and then charged at 0.33C to 3.8V. After venting, the batteries were aged at 45°C for 48 hours, then charged again at 0.33C to 3.8V, and then discharged at a current of 0.1C to 2.0V. The capacity of the aged batteries was obtained, and the results are shown in Table 2.

[0126] Cycle count test when capacity decays to 80%: Then, charge and discharge cycles were performed at 0.33C to test the number of cycles when capacity decays to 80%. The results are shown in Table 2.

[0127] (2) Ternary battery testing procedure: Electrochemical tests were performed on Example 18, Comparative Example 6 and Comparative Example 7;

[0128] Average decomposition potential and 0.1C discharge capacity after aging were tested: The lithium-ion batteries prepared in the examples and comparative examples were charged at a constant current of 0.02C for 10 hours at room temperature, followed by charging at 0.05C for 6 hours, and then charged at a constant current and constant voltage of 0.1C, with an upper limit voltage of 4.25V and a cutoff current of 0.05C. After standing for 1 hour, they were charged to 4.6V at a current of 0.006C, and the average decomposition potential could be read from the testing software. After that, the batteries were vented and then aged at 45°C for 48 hours. After that, they were charged to 4.25V at 0.33C, and then discharged to 2.0V at a current of 0.1C. The capacity of the aged batteries was obtained, and the results are shown in Table 2.

[0129] Cycle count test when capacity decays to 80%: Then, charge and discharge cycles were performed at 0.33C to test the number of cycles when capacity decays to 80%. The results are shown in Table 2.

[0130] Testing the redox potential of organic additives: An electrolyte containing 0.20% (w / w) of organic additives was prepared. A coin cell was then assembled using lithium metal as the negative electrode and carbon paper as the positive electrode. The coin cell was connected to an electrochemical workstation for electrochemical voltammetry scanning. The scanning program was: scanning from the open-circuit voltage forward to 4.6V, then backward to 3.0V, and then forward to 4.6V again, at a scan rate of 5mV / s. The position of the oxidation peak appearing in the second scan was recorded as the redox potential of the organic additive. If there were multiple redox peaks of the organic additive, the highest redox peak was considered the redox potential of the organic additive. Figure 2 shows the test results of the redox potential of the organic additive triphenylamine in Example 2. As can be seen from Figure 2, the redox potential of the organic additive triphenylamine in Example 2 was 4.1V.

[0131] Lithium replenishment agent utilization: The measured specific capacity of the positive electrode of the un-lithiated battery is X mAh / g, and the capacity of the battery after lithium replenishment is Y mAh / g. The added lithium replenishment agent can theoretically increase the battery capacity by Z mAh / g. Therefore:

[0132] The utilization rate of lithium supplementation agent = (YX) / Z*100%.

[0133] Table 1

[0134] Table 2

[0135] As shown in Table 1, compared to Comparative Examples 1-7 without added organic additives, Examples 1-7 of this application, by adding organic additives with redox potentials within a suitable range, significantly improved the cycle performance of the batteries while maintaining a high discharge capacity. This is because this application controls the redox potential of the organic additives in the electrolyte to a range higher than the decomposition potential of the lithium replenishing agent, which can promote the decomposition of the lithium replenishing agent, thereby replenishing the lithium loss of the battery and improving the overall electrochemical performance of the battery. Figure 3 shows the capacity-voltage curves of the lithium-ion batteries of Example 1 and Comparative Example 2. As can be seen from Figure 3, the organic additive 10-methylphenthiazide in Example 1 can effectively reduce the average decomposition potential, thereby promoting the decomposition of the lithium replenishing agent, reducing side reactions of the battery, and improving the electrochemical performance of the battery.

[0136] The above description is an exemplary embodiment of this application. It should be noted that those skilled in the art can make several improvements and modifications without departing from the principles of this application, and these improvements and modifications are also considered to be within the scope of protection of this application.

Claims

1. An electrolyte (105), characterized in that, The electrolyte (105) is suitable for lithium-ion batteries containing lithium replenishment agents. The electrolyte (105) includes organic additives that can be dissolved in the electrolyte (105). The redox potential of the organic additives is greater than the decomposition potential of the lithium replenishment agents.

2. The electrolyte (105) according to claim 1, characterized in that, The oxidation-reduction potential of the organic additive is 3.5V-4.5V, more preferably 4.0V-4.2V.

3. The electrolyte (105) according to claim 1 or 2, characterized in that, The organic additive has a mass percentage content of 0.01%-5% in the electrolyte (105).

4. The electrolyte (105) according to any one of claims 1-3, characterized in that, The organic additives include one or more of piperidine oxide, phenothiazine compounds, thiazine compounds, organic amine compounds, aminobenzene compounds, phenothiazine compounds, anthracene compounds, thiaanthracene compounds, tetrathiofulvalene and its derivatives, benzoquinone and its derivatives, dimethoxybenzene and its derivatives, tetrathiofulvalene, N-methyl-N-propylpyrrolidine bromide, cobalt(II)porphyrin complexes, ferrophthalocyanine, ethyl violetine, and ferrocene.

5. The electrolyte (105) according to claim 4, characterized in that, The piperidine oxide includes 2,2,6,6-tetramethylpiperidine oxide; the phenothiazine compounds include 10-isopropylphenothiazine and 10-methylphenothiazine; the organic amine compounds include N,N,N',N'-tetramethyl-p-phenylenediamine, triethylenediamine, and triphenylamine; the aminobenzene compounds include tris(4-aminophenyl)amine and 1,4-bis(diphenylamino)benzene; the phenothiazine compounds include 5,10-dihydro-5,10-dimethylphenazine; the anthracene compounds include 9,10-dimethylanthracene; the thiaanthracene compounds include thiaanthracene; and the dimethoxybenzene and its derivatives include 2,5-di-tert-butyl-1,4-dimethoxybenzene.

6. The electrolyte (105) according to any one of claims 1-5, characterized in that, The organic additives include a first organic additive and a second organic additive, wherein the absolute value of the difference between the redox potentials of the first organic additive and the second organic additive is 0.01V-0.5V; and / or in the electrolyte (105), the mass ratio of the first organic additive to the second organic additive is 1:(0.1-10).

7. The electrolyte (105) according to any one of claims 1-6, characterized in that, The electrolyte (105) further includes a lithium salt and a solvent; the lithium salt includes one or more of lithium hexafluorophosphate, lithium perchlorate, lithium bis(oxalato)borate, lithium bis(trifluoromethanesulfonate)imide, and lithium bis(fluorosulfonate); the solvent includes carbonate solvents, which include one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, and diethyl carbonate.

8. A lithium-ion battery (100), characterized in that, The lithium-ion battery (100) includes a battery casing (106) and a positive electrode (101), a negative electrode (104), a separator (103), and an electrolyte (105) housed inside the battery casing (106). The separator (103) and the electrolyte (105) are disposed between the positive electrode (101) and the negative electrode (104). The lithium-ion battery (100) includes a lithium replenishing agent, and the electrolyte (105) includes the electrolyte (105) as described in any one of claims 1-7. The redox potential of the organic additive is higher than the decomposition potential of the lithium replenishing agent.

9. The lithium-ion battery (100) according to claim 8, characterized in that, The mass ratio of the organic additive to the lithium supplement is 1:(1-1000).

10. The lithium-ion battery (100) according to claim 8 or 9, characterized in that, The lithium supplement includes one or more of Li5FeO4, Li2NiO2, Li6CoO4, Li2Se, Li2CO3, Li2C2O4, Li2O, Li3N, Li2O2, Li2S, Li2S2, lithium borate, and lithium thioborate; preferably one or more of Li2CO3, Li2C2O4, Li2O, Li3N, Li2O2, Li2S, Li2S2, lithium borate, and lithium thioborate.

11. The lithium-ion battery (100) according to any one of claims 8-10, characterized in that, The positive electrode (101) includes a current collector and a positive electrode active layer disposed on the surface of the current collector, the positive electrode active layer including the lithium supplement agent; And / or the lithium-ion battery (100) includes a lithium replenishing layer (102), the lithium replenishing layer (102) including the lithium replenishing agent.

12. The lithium-ion battery (100) according to any one of claims 8-11, characterized in that, The positive electrode (101) includes the positive electrode active material, which includes lithium iron phosphate.

13. An electrical appliance, characterized in that, The electrical device includes a lithium-ion battery (100) as described in any one of claims 8-12.

14. An energy storage system, characterized in that, The energy storage system includes a lithium-ion battery (100) as described in any one of claims 8-12.

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