Electrolyte, lithium-ion battery, and electric device

Abstract

An electrolyte, a lithium-ion battery, and an electric device. The electrolyte comprises a borate additive, and the mass fraction w1 of the borate additive in the electrolyte falls within the range: 0.01%≤w1≤2%. The electrolyte further comprises a sulfur-containing additive, and the mass fraction w2 of the sulfur-containing additive in the electrolyte falls within the range: 0.01%≤w2≤2%. A ratio of the mass fraction w2 of the sulfur-containing additive to the mass fraction w1 of the borate additive falls within the range: 0.5≤w2 / w1≤1.2.

Description

Electrolyte, lithium-ion battery and electrical equipment

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on February 2, 2024, with application number 2024101471674 and application name “Electrolyte, lithium-ion battery and electrical equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of lithium-ion batteries, and in particular to an electrolyte, a lithium-ion battery, and electrical equipment. Background Art

[0003] With the rapid development of new energy technologies, the requirements for battery cycle life are becoming increasingly stringent. Adding a small amount of lithium ferrite (LFO), a lithium supplement, to the positive electrode material can effectively compensate for the consumption of active lithium during the cycle, thereby improving the battery's cycle performance. However, during the delithiation process, LFO undergoes an oxidation reaction between iron and oxygen, which easily produces oxygen and causes oxidation of the electrolyte at the positive electrode. This not only consumes the electrolyte but also makes the electrolyte system unstable, reducing the battery's cycle life and safety performance.

[0004] Summary of the Invention

[0005] In view of this, the present application provides an electrolyte, a lithium-ion battery and an electrical device, wherein the electrolyte has good stability.

[0006] The present application provides an electrolyte, which includes a borate additive. In the electrolyte, the mass fraction w1 of the borate additive is in the range of: 0.01%≤w1≤2%.

[0007] The present application also provides a lithium-ion battery, which includes: a negative electrode sheet, a separator, a positive electrode sheet and the electrolyte provided by the present application, wherein the separator is arranged on one side of the negative electrode sheet; the positive electrode sheet is arranged on the side of the separator away from the negative electrode sheet, the positive electrode sheet includes a positive electrode active layer and a positive electrode current collector layer, the positive electrode active layer is arranged on the surface of the positive electrode current collector layer, and the positive electrode active layer includes multiple lithium-supplementing particles; the electrolyte at least infiltrates a portion of the positive electrode sheet and a portion of the negative electrode sheet.

[0008] The present application also provides an electrical device, which includes: a device body and a lithium-ion battery provided in the present application, and the lithium-ion battery supplies power to the device body.

[0009] In the present application, the electrolyte is applied to a lithium-ion battery and the positive electrode of the lithium-ion battery includes lithium-replenishing particles. During the initial charge and discharge and continuous cycling of the lithium-ion battery, the active lithium ions in the positive electrode are continuously consumed, which may result in a loss of available energy of the lithium-ion battery. However, in the present application, the positive electrode includes lithium-replenishing particles. During the charging process of the lithium-ion battery, the lithium-replenishing particles can release lithium ions to timely replenish the active ions consumed in the electrolyte, thereby allowing the lithium-ion battery to have higher available energy. In addition, the lithium-supplementing particles release iron ions and oxygen anions while releasing lithium ions. The electrolyte includes borate additives, and the boron atoms in the borate additives are electron-deficient. The boron atoms easily combine with oxygen anions, thereby preventing the combination of iron ions and oxygen anions, thereby reducing the generation of oxygen, which is beneficial to reducing the solubility of oxygen in the electrolyte and reducing the side reaction between the oxygen and the electrolyte, which is beneficial to improving the stability of the electrolyte and improving the interface stability between the positive electrode and the electrolyte, and ultimately improving the cycle performance and safety performance of the lithium-ion battery when the electrolyte is applied to the lithium-ion battery.

[0010] Furthermore, when the mass fraction w1 of the borate additive satisfies the range of 0.01% ≤ w1 ≤ 2%, the mass fraction of the borate additive in the electrolyte is within a reasonable range. The borate additive has a sufficient amount of boron atoms and the boron atoms can combine with oxygen anions to reduce the amount of oxygen produced by the oxidation reaction between oxygen anions and iron ions, further slowing down the side reaction between the electrolyte and oxygen, improving the stability of the electrolyte and the interface stability between the positive electrode and the electrolyte, and ultimately improving the cycle performance and safety performance of the battery when the electrolyte is used in the battery. In addition, it can also avoid the increase in the interfacial impedance of the electrolyte caused by excessive borate additives in the electrolyte. When the mass fraction w1 of the borate additive is too large, in other words, the mass content of the borate additive in the electrolyte is too large, excess borate additive may adhere to the interface between the positive electrode sheet and the electrolyte or the interface between the negative electrode sheet and the electrolyte, undergo a reduction reaction, and generate decomposition products that adhere to the positive electrode sheet and / or the negative electrode sheet, thereby increasing the interfacial impedance, and then reducing the transmission speed and migration speed of active ions between the positive electrode sheet / negative electrode sheet and the electrolyte, thereby causing the energy efficiency of the lithium-ion battery to be low when the electrolyte is applied to the lithium-ion battery. When the mass fraction w1 of the borate additive is too small, in other words, the mass content of the borate additive in the electrolyte is too small, then when the electrolyte is applied to the lithium-ion battery, there are too few boron atoms in the borate additive, and the boron atoms can only combine with a small number of oxygen anions. When the lithium-ion battery is charged, the additional oxygen anions released by the lithium-supplementing particles react with the iron ions to produce oxygen, increasing the solubility of oxygen in the electrolyte and exacerbating side reactions between oxygen and the electrolyte, reducing the stability of the electrolyte. When this electrolyte is used in a lithium-ion battery, the battery's cycling performance is poor. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the implementation. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0012] FIG1 is a schematic cross-sectional view of a lithium-ion battery according to an embodiment of the present application;

[0013] FIG2 is a schematic cross-sectional view of a positive electrode sheet according to an embodiment of the present application;

[0014] FIG3 is a scanning electron microscope image of the lithium-supplementing particles after shrinkage according to an embodiment of the present application;

[0015] FIG4 is a scanning electron microscope image of the lithium-supplementing particles after shrinkage according to another embodiment of the present application;

[0016] FIG5 is a circuit block diagram of an electric device according to an embodiment of the present application;

[0017] FIG6 is a schematic structural diagram of an electrical device according to an embodiment of the present application.

[0018] Description of reference numerals:

[0019] 100-electrolyte, 200-lithium-ion battery, 210-negative electrode sheet, 220-diaphragm, 230-positive electrode sheet, 231-positive electrode active layer, 232-positive electrode current collector layer, 300-electrical equipment, 310-equipment body. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0021] The terms "first," "second," and the like in the specification and claims of this application and the accompanying drawings are used to distinguish between different objects, not to describe a particular order. Furthermore, the terms "including," "having," and any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, product, or apparatus comprising a series of steps or elements is not limited to the listed steps or elements but may optionally include steps or elements not listed, or may optionally include other steps or elements inherent to the process, method, product, or apparatus.

[0022] References herein to "embodiments" or "implementations" mean that a particular feature, structure, or characteristic described in connection with the embodiments or implementations may be included in at least one embodiment of the present application. The appearance of such phrases in various places in the specification does not necessarily refer to the same embodiment, nor do they constitute independent or alternative embodiments that are mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0023] With the rapid development of new energy technologies, the requirements for battery cycle life are getting higher and higher. Among them, adding a small amount of lithium supplement lithium ferrite (LFO) to the positive electrode material can effectively make up for the consumption of active lithium in the cycle process, thereby improving the cycle performance of the battery. However, during the delithiation process, lithium ferrite will undergo an oxidation reaction of iron and oxygen, which makes it easy to produce oxygen, causing the electrolyte to oxidize at the positive electrode plate, which not only consumes the electrolyte, but also makes the electrolyte system unstable, reducing the cycle life and safety performance of the battery. When lithium ferrite releases more lithium during the delithiation process, lithium ferrite will also release more oxygen at the same time, causing the positive electrode material and the electrolyte to have more side reactions, reducing the safety performance of the battery; when lithium ferrite releases fewer lithium ions during the delithiation process, it is difficult to make up for the consumption of active lithium in the cycle process, thereby reducing the cycle performance of the battery.

[0024] Referring to FIG. 1 , an embodiment of the present application provides an electrolyte 100 , wherein the electrolyte 100 includes a borate additive. In the electrolyte 100 , the mass fraction w1 of the borate additive is in the range of 0.01%≤w1≤2%.

[0025] Specifically, the mass fraction w1 of the borate additive can be, but is not limited to, 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.35%, 0.4%, 0.45%, 0.55%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 1.0%, 1.1%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.65%, 1.75%, 1.85%, 1.9% and 2%, etc.

[0026] It can be understood that the mass fraction w1 of the borate additive is the ratio of the mass of the borate additive to the mass of the electrolyte 100 .

[0027] It can be understood that the electrolyte 100 is applied to a lithium-ion battery 200, and the lithium-ion battery 200 also includes a negative electrode sheet 210, a separator 220, and a positive electrode sheet 230. The positive electrode sheet 230 includes a positive active layer 231 and a positive current collector layer 232. The positive active layer 231 is disposed on the surface of the positive current collector layer 232 and includes lithium-supplementing particles. The electrolyte 100 at least partially infiltrates the positive electrode sheet 230 and the negative electrode sheet 210. During the charge and discharge process of the lithium-ion battery 200, the electrolyte 100 acts as a transport medium for active ions, that is, a transport medium for lithium ions. On the one hand, it can provide some active lithium ions for use as conductive ions; on the other hand, the electrolyte 100 can provide ion channels to help lithium ions move freely in the lithium-ion battery 200. The lithium-replenishing particles can release lithium ions when the lithium-ion battery 200 is charged, thereby replenishing the active ions consumed in the electrolyte 100 in a timely manner.

[0028] It is understood that the borate additive includes boron, the nucleus of which is composed of 5 protons and 6 neutrons, and the outer electron configuration of boron is 1s 2 2s 2 2p 1 , where the number of electrons in the 2s energy level is 2, and the number of electrons in the 2p energy level is 1, then there is one electron missing in the electronic configuration of boron, and the boron atom has an electron-deficient characteristic.

[0029] In this embodiment, the electrolyte 100 is applied to a lithium-ion battery 200, and the positive electrode plate 230 of the lithium-ion battery 200 includes lithium-supplementing particles. During the initial charge and discharge and continued cycling of the lithium-ion battery 200, the active lithium ions in the positive electrode plate 230 are continuously consumed, which may result in a loss of available energy in the lithium-ion battery 200. However, in this embodiment of the present application, the positive electrode plate 230 includes lithium-supplementing particles. During the charging process of the lithium-ion battery 200, the lithium-supplementing particles can release lithium ions to timely replenish the active ions consumed in the electrolyte 100, thereby ensuring that the lithium-ion battery 200 has a higher available energy. In addition, the lithium-supplementing particles release iron ions and oxygen anions while releasing lithium ions, and the electrolyte 100 includes borate additives, and the boron atoms in the borate additives are electron-deficient. The boron atoms easily combine with oxygen anions, thereby preventing the combination of iron ions and oxygen anions, thereby reducing the generation of oxygen, which is beneficial to reducing the solubility of oxygen in the electrolyte 100 and reducing the side reaction of the oxygen and the electrolyte 100, which is beneficial to improving the stability of the electrolyte 100 and improving the interface stability between the positive electrode plate 230 and the electrolyte 100, and ultimately improving the cycle performance and safety performance of the lithium-ion battery 200 when the electrolyte 100 is applied to the lithium-ion battery 200.

[0030] Furthermore, when the mass fraction w1 of the borate additive satisfies the range of 0.01% ≤ w1 ≤ 2%, the mass fraction of the borate additive in the electrolyte 100 is within a reasonable range. The borate additive has a sufficient amount of boron atoms and the boron atoms can combine with oxygen anions to reduce the amount of oxygen produced by the oxidation reaction between oxygen anions and iron ions, further slowing down the side reaction between the electrolyte 100 and oxygen, improving the stability of the electrolyte 100 and the interface stability between the positive electrode plate 230 and the electrolyte 100, and ultimately improving the cycle performance and safety performance of the battery when the electrolyte 100 is used in the battery. In addition, it can also avoid the increase in the interfacial impedance of the electrolyte 100 caused by excessive borate additives in the electrolyte 100. When the mass fraction w1 of the borate additive is too large, in other words, the mass content of the borate additive in the electrolyte 100 is too large, excess borate additives may adhere to the interface between the positive electrode plate 230 and the electrolyte 100 or the interface between the negative electrode plate 210 and the electrolyte 100, and undergo a reduction reaction to generate decomposition products that adhere to the positive electrode plate 230 and / or the negative electrode plate 210, thereby increasing the interface impedance, and then reducing the transmission speed and migration speed of active ions between the positive electrode plate 230 / negative electrode plate 210 and the electrolyte 100, so that when the electrolyte 100 is applied to the lithium-ion battery 200, the energy efficiency of the lithium-ion battery 200 is low. When the mass fraction w1 of the borate additive is too small, in other words, the mass content of the borate additive in the electrolyte 100 is too low, then when the electrolyte 100 is applied to the lithium-ion battery 200, the boron atoms in the borate additive are too few, and the boron atoms can only combine with a small portion of the oxygen anions. When the lithium-ion battery 200 is charged, the other oxygen anions released by the lithium-supplementing particles react with the iron ions to produce oxygen, which increases the solubility of oxygen in the electrolyte 100 and exacerbates the side reactions between oxygen and the electrolyte 100, reducing the stability of the electrolyte 100. When the electrolyte 100 is applied to the lithium-ion battery 200, the cycle performance of the lithium-ion battery 200 is poor.

[0031] Preferably, the mass fraction w1 of the borate additive satisfies the range of 0.3%≤w1≤1.4%. Specifically, the mass fraction w1 of the borate additive can be, but is not limited to, 0.3%, 0.35%, 0.4%, 0.45%, 0.5%, 0.55%, 0.65%, 0.7%, 0.75%, 0.8%, 0.85%, 0.9%, 1.0%, 1.1%, 1.2%, 1.25%, 1.3%, 1.35%, 1.4%, etc.

[0032] In this embodiment, when the mass fraction w1 of the borate additive satisfies the range of 0.3% ≤ w1 ≤ 1.4%, the electrolyte 100 can bind the oxygen anions released by the lithium-supplementing particles to slow the generation of oxygen, while also preventing an excess of the borate additive in the electrolyte 100 from increasing the interfacial impedance of the electrolyte 100. When the electrolyte 100 is used in a battery, the lithium-ion battery 200 has both high cycle performance and high safety performance.

[0033] Optionally, the borate additive includes lithium ions.

[0034] In this embodiment, the borate additive includes lithium ions. When the electrolyte 100 includes the borate additive and is applied to the lithium-ion battery 200, the borate additive can serve as a lithium replenisher for the electrolyte 100. The borate additive can release lithium ions, thereby replenishing the lithium ions lost in the electrolyte 100, which is beneficial to improving the cycle performance of the electrolyte 100 when applied to the battery.

[0035] Optionally, the borate additive includes at least one of lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium tetrafluoroborate, lithium tetraborate, lithium tetracyanoborate, lithium difluoroborate, lithium tetrakis(trifluoromethyl)borate, lithium bis(trifluoromethyl)difluoroborate, lithium dicyanooxalatoborate, lithium pentafluoroethyl trifluoroborate, and lithium perfluoro-tert-butoxy trifluoroborate.

[0036] It can be understood that, in the terminology of this application, "at least one" means greater than or equal to one, and can be one, two, three or four, etc.

[0037] In this embodiment, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium tetrafluoroborate, lithium tetraborate, lithium tetracyanoborate, lithium difluoroborate, lithium tetrakis(trifluoromethyl)borate, lithium bis(trifluoromethyl)difluoroborate, lithium dicyanooxalatoborate, lithium pentafluoroethyl trifluoroborate, and lithium perfluoro-tert-butoxy trifluoroborate all include boron atoms. When the electrolyte 100 includes a borate additive, the boron atoms in the borate additive can combine with oxygen anions to reduce the amount of oxygen generated by the oxidation reaction between oxygen anions and iron ions, further slowing down the side reaction between the electrolyte 100 and oxygen, thereby improving the stability of the electrolyte 100 and the interface stability between the positive electrode sheet 230 and the electrolyte 100, and ultimately improving the cycle performance and safety performance of the battery when the electrolyte 100 is used in the battery. In addition, the cations of lithium fluorooxalatoborate, lithium bisoxalatoborate, lithium tetrafluoroborate, lithium tetraborate, lithium tetracyanoborate, lithium difluoroborate, lithium tetrakis(trifluoromethyl)borate, lithium bis(trifluoromethyl)difluoroborate, lithium dicyanooxalatoborate, lithium pentafluoroethyl trifluoroborate, and lithium perfluoro-tert-butoxy trifluoroborate are lithium ions. When the electrolyte 100 includes a borate additive and is applied to a lithium-ion battery 200, on the one hand, it can avoid the introduction of other cations into the electrolyte 100, which would cause excessive impurities in the electrolyte 100, thereby reducing the side reaction between the positive electrode sheet 230 / the negative electrode sheet 210 and the electrolyte 100 and improving the stability of the electrolyte 100. On the other hand, the borate additive can serve as a lithium replenisher for the electrolyte 100. The borate additive can release lithium ions, thereby replenishing the lithium ions lost in the electrolyte 100, which is beneficial to improving the cycle performance of the electrolyte 100 when applied to the battery.

[0038] In some embodiments, the electrolyte 100 further includes a sulfur-containing additive. In the electrolyte 100 , the mass fraction w2 of the sulfur-containing additive is in the range of 0.01%≤w2≤2%.

[0039] It can be understood that in the electrolyte 100 , the mass fraction of the sulfur-containing additive is the ratio of the mass of the sulfur-containing additive to the mass of the electrolyte 100 .

[0040] Specifically, the mass fraction w2 of the sulfur-containing additive can be, but is not limited to, 0.01%, 0.05%, 0.1%, 0.15%, 0.2%, 0.25%, 0.3%, 0.38%, 0.4%, 0.45%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.35%, 1.4%, 1.45%, 1.5%, 1.55%, 1.6%, 1.64%, 1.7%, 1.75%, 1.8%, 1.85%, 1.9% and 2%, etc.

[0041] In this embodiment, the electrolyte 100 further includes a sulfur-containing additive. When the electrolyte 100 is applied to the lithium-ion battery 200, during the initial charge and discharge and continued cycling of the lithium-ion battery 200, the negative electrode plate 210 and / or the positive electrode plate 230 form an interfacial film containing sulfur with the electrolyte 100. Active ions in the electrolyte 100 are transported more rapidly through the interfacial film containing sulfur. In other words, the interfacial film containing sulfur has excellent ion conductivity, thereby reducing the interfacial impedance between the negative electrode plate 210 and / or the positive electrode plate 230 and the electrolyte 100, thereby improving the energy efficiency of the lithium-ion battery 200 when the electrolyte 100 is applied to the lithium-ion battery 200. When the mass fraction w2 of the sulfur-containing additive satisfies the range of 0.01% ≤ w2 ≤ 2%, the mass content of the sulfur-containing additive in the electrolyte 100 is within a reasonable range, and the amount of sulfur in the interface film formed between the negative electrode plate 210 and / or the positive electrode plate 230 and the electrolyte 100 is within a reasonable range. This effectively improves the ion conductivity of the sulfur-containing additive, thereby compensating for the increased interfacial impedance caused by the addition of the borate additive. This results in faster transmission and migration speeds of active ions between the positive electrode plate 230 / negative electrode plate 210 and the electrolyte 100, thereby improving the energy efficiency of the lithium-ion battery 200 when the electrolyte 100 is used in the lithium-ion battery 200. Furthermore, decomposition of the sulfur-containing additive in the electrolyte 100 due to an excessively high mass fraction can be avoided, which is beneficial for improving the safety performance of the battery when the electrolyte 100 is used in the battery. When the mass fraction w2 of the sulfur-containing additive is too large, the sulfur-containing additive is prone to hydrolysis and acid generation in the electrolyte 100, thereby destroying the interface film between the positive electrode plate 230 / negative electrode plate 210 and the electrolyte 100. In the process of lithium ions continuously repairing the interface film, active lithium ions will be irreversibly lost, resulting in continuous attenuation of the capacity of the lithium-ion battery 200, thereby reducing the capacity retention rate, cycle performance and safety performance of the lithium-ion battery 200 when the electrolyte 100 is applied to the lithium-ion battery 200. When the mass fraction w2 of the sulfur-containing additive is too small, the amount of sulfur in the interface film formed by the negative electrode plate 210 and / or the positive electrode plate 230 and the electrolyte 100 is small, so that the improvement of the ion conductivity of the interface film by the sulfur-containing additive is very weak. In other words, the sulfur-containing additive is difficult to make up for the deficiency of the increase in the interfacial impedance of the electrolyte 100 caused by the addition of the borate additive, so that the transmission speed and migration speed of the active ions between the positive electrode plate 230 / negative electrode plate 210 and the electrolyte 100 are too slow, thereby making the energy efficiency of the lithium-ion battery 200 too low when the electrolyte 100 is applied to the lithium-ion battery 200.

[0042] Preferably, the mass fraction w2 of the sulfur-containing additive satisfies the range of 0.5%≤w2≤1.5%. Specifically, the mass fraction w2 of the sulfur-containing additive can be, but is not limited to, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.35%, 1.4%, 1.45%, and 1.5%.

[0043] In this embodiment, when the mass fraction w2 of the sulfur-containing additive satisfies the range of 0.5% ≤ w2 ≤ 1.5%, the amount of sulfur in the interfacial film formed between the negative electrode plate 210 and / or the positive electrode plate 230 and the electrolyte 100 is within a preferred range. This significantly improves the ion conductivity of the sulfur-containing additive, fully compensating for the increased interfacial impedance caused by the addition of the borate additive. This results in faster transmission and migration of active ions between the positive electrode plate 230 / negative electrode plate 210 and the electrolyte 100, thereby improving the energy efficiency of the lithium-ion battery 200 when the electrolyte 100 is used in the lithium-ion battery 200. Furthermore, decomposition of the sulfur-containing additive in the electrolyte 100 due to an excessively high mass fraction can be avoided, which is beneficial for improving the safety performance of the battery when the electrolyte 100 is used in the battery.

[0044] In some embodiments, in the electrolyte 100 , the ratio of the mass fraction w2 of the sulfur-containing additive to the mass fraction w1 of the borate additive satisfies the range: 0.5≤w2 / w1≤1.2.

[0045] Specifically, the value of w2 / w1 can be, but is not limited to, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.05, 1.1, 1.15 and 1.2, etc.

[0046] In this embodiment, when the ratio of the mass fraction w2 of the sulfur-containing additive to the mass fraction w1 of the borate additive satisfies the range of 0.5 ≤ w2 / w1 ≤ 1.2, the mass fractions of the borate additive and the mass fractions of the sulfur-containing additive are both within a reasonable range. On the one hand, the borate additive contains a sufficient amount of boron atoms that can combine with oxygen anions, and the sulfur-containing additive can compensate for the increased interfacial impedance caused by the addition of the borate additive. Thus, in the lithium-ion battery 200, the lithium-replenishing particles can promptly replenish lithium ions to the electrolyte 100, the borate additive can promptly inhibit the formation of oxygen, and the sulfur-containing additive can promptly compensate for the increased interfacial impedance caused by the borate additive. The lithium-replenishing particles, the borate additive, and the sulfur-containing additive cooperate with each other to achieve a higher stability of the electrolyte 100, thereby improving the cycle performance and safety performance of the lithium-ion battery 200 when the electrolyte 100 is used in the lithium-ion battery 200. When the value of w2 / w1 is too large, in the electrolyte 100, the mass fraction w2 of the sulfur-containing additive is much greater than the mass fraction of the borate additive. Although the sulfur-containing additive can make up for the deficiency of increased interfacial impedance caused by the addition of the borate additive, the amount of the sulfur-containing additive is too large, making it easy for the sulfur-containing additive to hydrolyze and generate acid in the electrolyte 100, thereby destroying the interface film between the positive electrode sheet 230 / negative electrode sheet 210 and the electrolyte 100, thereby reducing the electrolyte. In addition, if the content of the borate additive is too low, the boron atoms of the borate additive can only combine with a small portion of oxygen anions in the lithium ion battery 200, and most of the oxygen anions released by the lithium supplement particles react with iron ions to produce oxygen, thereby exacerbating the side reaction between the electrolyte 100 and oxygen, reducing the stability of the electrolyte 100, and thus reducing the cycle performance of the electrolyte 100 when applied to the lithium ion battery 200. When the value of w2 / w1 is too small, in the electrolyte 100, the mass fraction of the borate additive is much greater than the mass fraction w2 of the sulfur-containing additive. In other words, the sulfur-containing additive is difficult to make up for the insufficient interfacial impedance caused by the addition of the borate additive. The excess borate additive may adhere to the interface between the positive electrode sheet 230 and / or the negative electrode sheet 210 and the electrolyte 100 to increase the interfacial impedance, thereby reducing the transmission speed and migration speed of active ions between the positive electrode sheet 230 / negative electrode sheet 210 and the electrolyte 100, thereby causing the energy efficiency of the lithium-ion battery 200 to be low when the electrolyte 100 is applied to the lithium-ion battery 200.

[0047] Optionally, the sulfur-containing additive includes at least one of 1,3-propane sultone, vinyl sulfate, 1,3-propylene sultone, 1,4-butane sultone, 1,4-butene sultone, methylene disulfonate and pentaerythritol bicyclic sulfate.

[0048] In this embodiment, 1,3-propane sultone, vinyl sulfate, 1,3-propene sultone, 1,4-butane sultone, 1,4-butene sultone, methylene disulfonate, and pentaerythritol bicyclic sulfate all contain elemental sulfur. When these sulfur-containing additives are applied to the electrolyte 100 and the lithium-ion battery 200 undergoes initial charge and discharge and continuous cycling, the sulfur-containing additives release sulfur ions, and a sulfur-containing interface film is formed between the negative electrode plate 210 and / or the positive electrode plate 230 and the electrolyte 100. Active ions in the electrolyte 100 are transported more rapidly through the sulfur-containing interface film. In other words, the sulfur-containing interface film has excellent ion conductivity, thereby reducing the interfacial impedance between the negative electrode plate 210 and / or the positive electrode plate 230 and the electrolyte 100, thereby improving the energy efficiency of the lithium-ion battery 200 when the electrolyte 100 is applied to the lithium-ion battery 200.

[0049] Optionally, the electrolyte 100 further includes a solvent and a lithium salt, wherein the solvent is used to dissolve the lithium salt and the borate additive, and the lithium salt includes active ions, namely lithium ions.

[0050] Optionally, the solvent includes at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, ethyl methyl carbonate, dimethyl carbonate, ethyl acetate, ethyl propionate, propyl propionate, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, and ethylene glycol dimethyl ether.

[0051] Optionally, in some embodiments, in the electrolyte 100, the mass fraction w4 of the solvent is in the range of 75% ≤ w4 ≤ 84%. Specifically, the mass fraction w4 of the solvent may be, but is not limited to, 75%, 75.5%, 76%, 76.5%, 77%, 77.5%, 78%, 78.5%, 79%, 79.5%, 80%, 81%, 81.5%, 82%, 83%, 84%, etc.

[0052] Optionally, the lithium salt includes at least one of lithium hexafluorophosphate, lithium difluorosulfonyl imide, lithium difluorophosphate, lithium trifluoromethylsulfonyl imide, lithium trifluoromethanesulfonate, and lithium perchlorate.

[0053] Optionally, in some embodiments, in the electrolyte 100, the mass fraction w5 of the lithium salt is in the range of 10% ≤ w5 ≤ 15%. Specifically, the mass fraction w5 of the lithium salt may be, but is not limited to, 10%, 10.5%, 11%, 11.5%, 11.8%, 12%, 12.5%, 13%, 13.5%, 14%, 14.2%, 14.5%, 15%, etc.

[0054] Optionally, the electrolyte 100 further includes a film-forming additive. When the electrolyte 100 is applied to the lithium-ion battery 200, the film-forming additive can be used to promote the formation of the interface film of the positive electrode plate 230 and / or the negative electrode plate 210 and maintain the stability of the interface film.

[0055] Optionally, the film-forming additive includes at least one of fluoroethylene carbonate, vinylene carbonate, sulfur tris(trimethylsilyl)phosphate, tris(trimethylsilyl)borate, adiponitrile, succinonitrile, and 1,3,6-hexanetrinitrile.

[0056] Optionally, the mass fraction w6 of the film-forming additive is in the range of 1.5% ≤ w6 ≤ 3%. Specifically, the mass fraction w6 of the film-forming additive may be, but is not limited to, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, etc.

[0057] Please refer to Figure 2. An embodiment of the present application provides a lithium-ion battery 200, which includes: a negative electrode sheet 210, a separator 220, a positive electrode sheet 230, and an electrolyte 100 provided in this application. The separator 220 is arranged on one side of the negative electrode sheet 210; the positive electrode sheet 230 is arranged on the side of the separator 220 away from the negative electrode sheet 210, and the positive electrode sheet 230 includes a positive active layer 231 and a positive current collector layer 232. The positive active layer 231 is arranged on the surface of the positive current collector layer 232, and the positive active layer 231 includes multiple lithium-supplementing particles; the electrolyte 100 at least infiltrates a portion of the positive electrode sheet 230 and a portion of the negative electrode sheet 210.

[0058] It can be understood that the negative electrode plate 210 , the separator 220 and the positive electrode plate 230 are arranged in sequence.

[0059] It can be understood that in the lithium-ion battery 200, the electrolyte 100 includes lithium salt, and the electrolyte 100 includes active ions, i.e., lithium ions; the positive electrode plate 230 and the negative electrode plate 210 are at least partially immersed in the electrolyte 100. During the charging and discharging process of the lithium-ion battery 200, the electrolyte 100 serves as a transmission medium for active ions, i.e., a transmission medium for lithium ions. On the one hand, it can provide some active lithium ions for use as conductive ions; on the other hand, the electrolyte 100 can provide ion channels to help lithium ions move freely in the lithium-ion battery 200.

[0060] In the lithium-ion battery 200 provided in this embodiment, the positive active layer 231 of the positive electrode plate 230 includes lithium-replenishing particles. When the positive electrode plate 230 is applied to the lithium-ion battery 200 and the lithium-ion battery 200 is charged, the lithium-replenishing particles can release lithium ions. The lithium ions are transferred from the positive electrode plate 230 to the electrolyte 100 and then to the negative electrode plate 210, thereby replenishing the lithium ions in the lithium-ion battery 200 and improving the first efficiency, energy density and capacity retention rate of the lithium-ion battery 200. In addition, the lithium-ion battery 200 includes the electrolyte 100 provided in the present application, and the electrolyte 100 at least infiltrates a portion of the positive electrode plate 230 and a portion of the negative electrode plate 210. The electrolyte 100 includes a borate additive, and the boron atoms in the borate additive are electron-deficient. The boron atoms are easily combined with oxygen anions, thereby preventing the combination of iron ions and oxygen anions, thereby reducing the generation of oxygen, which is beneficial to reducing the solubility of oxygen in the electrolyte 100 and reducing the side reaction of the oxygen and the electrolyte 100, which is beneficial to improving the stability of the electrolyte 100 and improving the interface stability between the positive electrode plate 230 and the electrolyte 100, so that the lithium-ion battery 200 has higher cycle performance and safety performance. In some embodiments, the electrolyte 100 further includes a sulfur-containing additive. During the initial charge and discharge and continuous cycling of the lithium-ion battery 200, the sulfur-containing additive forms a sulfur-containing interface film between the negative electrode plate 210 and / or the positive electrode plate 230 and the electrolyte 100, thereby accelerating the transmission speed of active ions in the sulfur-containing interface film, thereby compensating for the excessive interface impedance caused by the addition of the borate additive, and enabling the lithium-ion battery 200 to have higher energy efficiency.

[0061] Optionally, the lithium-ion battery 200 can be a cylindrical battery, a square battery, a soft-pack battery, etc.

[0062] Optionally, the material of the diaphragm 220 is selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. In some embodiments, the diaphragm 220 is a single-layer film; in other embodiments, the diaphragm 220 is a multi-layer composite film. When the diaphragm 220 is a multi-layer composite film, the materials of each layer can be the same or different.

[0063] Optionally, the thickness of the diaphragm 220 ranges from 14 μm to 18 μm. Specifically, the thickness of the diaphragm 220 may be, but is not limited to, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, and 18 μm.

[0064] Optionally, the positive electrode active layer 231 further includes a positive electrode active material selected from at least one of a lithium transition metal oxide and a modified material thereof. In some embodiments, the positive electrode active material is lithium iron phosphate. The modified material may be a lithium transition metal oxide that has been doped and / or coated. Preferably, the lithium transition metal oxide may be, but is not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, or lithium nickel cobalt aluminum oxide.

[0065] Optionally, the material of the positive electrode current collector layer 232 is selected from aluminum.

[0066] Optionally, the positive electrode active layer 231 further includes a positive electrode binder and a positive electrode conductor. In the positive electrode active layer 231 , the positive electrode binder is used to bond the components in the positive electrode active layer 231 to improve the overall performance of the positive electrode plate 230 ; the positive electrode conductor can improve the conductivity of the positive electrode active layer 231 .

[0067] Optionally, the positive electrode binder is selected from at least one of polyvinylidene fluoride, polyvinylidene fluoride and polytetrafluoroethylene.

[0068] Optionally, the positive electrode conductive agent is selected from at least one of graphite, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0069] Optionally, the negative electrode plate 210 includes a negative electrode current collector layer (not shown) and a negative electrode active layer (not shown), wherein the negative electrode active layer is arranged on the surface of the negative electrode current collector layer, and the negative electrode active layer includes a negative electrode active material, and the negative electrode active material is selected from at least one of metallic lithium, artificial graphite, natural graphite, graphene and other composite materials.

[0070] Optionally, the negative electrode current collector layer is selected from copper.

[0071] Optionally, the negative electrode active layer further includes a negative electrode binder, a negative electrode conductive agent, and a negative electrode thickening agent. The negative electrode binder is used to bond the components in the negative electrode active layer to improve the overall performance of the negative electrode active layer; the negative electrode conductive agent is used to improve the electrical conductivity of the negative electrode active layer; and the thickening agent is used to improve the adhesion of the negative electrode active layer.

[0072] Optionally, the negative electrode conductive agent is selected from at least one of acetylene black, conductive carbon black, carbon nanotubes, carbon fibers, graphene, etc.

[0073] Optionally, the negative electrode binder includes at least one of asphalt binder, styrene-butadiene rubber (SBR), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl alcohol (PVA), polyacrylonitrile (PAN), polyacrylic acid (PAA), polyacrylate, carboxymethyl cellulose (CMC), sodium alginate, etc.

[0074] Optionally, the negative electrode thickening agent is selected from at least one of sodium carboxymethyl cellulose (CMC), polyacrylamide (PAM), polymethacrylate (PMA), etc.

[0075] Optionally, in some embodiments, the lithium supplement particles include a matrix and a coating layer, and the coating layer is disposed on the outer periphery of the matrix; wherein, the chemical formula of the matrix is Li 1+r M 1-p N p O 4-s B s , and 0.1 < r < 6.1, 0 ≤ p < 0.99, 0 ≤ s < 0.1 are satisfied; M and N are each independently selected from at least one of iron, cobalt, nickel, titanium, zinc, magnesium, aluminum, manganese, vanadium, chromium, zirconium, copper, niobium, tantalum, tungsten, yttrium, and lanthanum, and B is selected from at least one of sulfur, nitrogen, fluorine, chlorine, and bromine.

[0076] It can be understood that if the chemical formula of the matrix is Li 1+r M 1-p N p O 4-s B s , then the matrix is formed by Li 1+r M 1-p N p O 4-s B s .

[0077] In an embodiment of the present application, the lithium-supplementing particles include a matrix and a coating layer, and the coating layer is arranged on the periphery of the matrix. On the one hand, the coating layer can coat and protect the matrix, and can prevent the matrix from reacting with air and being oxidized, thereby ensuring that the lithium-supplementing particles can replenish lithium when the lithium-ion battery 200 is charged, which is beneficial to improving the performance of the lithium-supplementing particles; on the other hand, the coating layer has conductive properties. When the active ions in the matrix are deintercalated, they can enter the electrolyte 100 through the coating layer. The coating layer can reduce the impedance of the active ions deintercalated from the lithium-supplementing particles, which is beneficial to improving the rate performance of the lithium-ion battery 200 when the positive electrode plate 230 is applied to the lithium-ion battery 200. In this embodiment, the chemical formula of the matrix is ​​Li 1+r M 1-p N p O 4-s B s The matrix has a simple elemental composition, low material price, and simple synthesis process, which helps simplify the preparation process of the positive electrode plate 230 and saves the preparation cost of the positive electrode plate 230. In addition, the matrix has a high lithium content, so when the positive electrode plate 230 is applied to the lithium-ion battery 200 and the lithium-ion battery 200 is charged, the matrix can promptly release a large amount of lithium ions to timely replenish the lithium ions lost by the lithium-ion battery 200 during the charge and discharge cycle, thereby improving the initial efficiency and energy density of the lithium-ion battery 200.

[0078] Specifically, the value of r can be, but is not limited to, 0.2, 0.4, 0.7, 0.9, 1.0, 1.3, 1.5, 1.7, 2.2, 2.5, 2.8, 3.2, 3.5, 3.7, 4.5, 4.8, 4.9, 5.1, 5.3, 5.5, 5.6, 5.8, 5.9 and 6.0, etc.

[0079] Specifically, the value of p can be, but is not limited to, 0, 0.05, 0.09, 0.1, 0.15, 0.18, 0.22, 0.25, 0.28, 0.35, 0.39, 0.45, 0.48, 0.55, 0.59, 0.6, 0.65, 0.68, 0.7, 0.75, 0.79, 0.85, 0.88, 0.9, 0.94, and 0.98, etc.

[0080] Specifically, the value of s may be, but is not limited to, 0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, and 0.09.

[0081] Alternatively, in some embodiments, the matrix is ​​lithium ferrite, and the chemical formula of the matrix is ​​Li5FePO4. Alternatively, in other embodiments, the chemical formula of the matrix is ​​Li6CoO4.

[0082] Optionally, in some embodiments, the coating layer is a carbon coating layer, the coating layer is conductive, and the coating layer can protect the substrate it wraps, so as to improve the anti-oxidation performance of the lithium-supplementing particles.

[0083] Alternatively, in other embodiments, the chemical formula of the coating layer is: x O y @C, wherein Z is selected from at least one of iron, cobalt, nickel, titanium, zinc, magnesium, aluminum, manganese, vanadium, chromium, zirconium, copper, niobium, tantalum, tungsten, yttrium and lanthanum, and the type of Z is the same as the type of M in the matrix, and the coating layer also satisfies the relationship: 1≤x≤3, 1≤y≤5.

[0084] It can be understood that the chemical formula of the lithium supplement particles is Li 1+r M 1-p N p O 4-s B s @Z x O y @C, the lithium supplement particles are composed of Li 1+r M 1-p N p O 4-s B s 、Z x O y and C, the lithium supplement particles are formed with Li 1+r M 1-p N p O 4-s B s As the kernel, and Z x O y Wrapped around the outer periphery of the core, where Z x O y The oxide layer protects the core from external oxidation and corrosion. Carbon is then coated around the oxide layer to form a carbon layer, which improves the conductivity of the coating. In other words, the coating comprises an oxide layer and a carbon layer, disposed sequentially, with the oxide layer disposed between the carbon layer and the substrate.

[0085] Specifically, the value of x can be, but is not limited to, 1, 1.2, 1.3, 1.5, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.4, 2.6, 2.7, 2.8, 2.9, and 3.

[0086] Specifically, the value of y can be, but is not limited to, 1, 1.2, 1.4, 1.5, 1.6, 1.8, 2.0, 2.2, 2.4, 2.5, 2.7, 2.8, 2.9, 3.0, 3.2, 3.4, 3.6, 3.8, 4.0, 4.1, 4.3, 4.5, 4.6, 4.7, 4.9 and 5, etc.

[0087] In this embodiment, the chemical formula of the coating layer is Z x O y @C, the coating layer is composed of an oxide layer and a carbon layer, and the oxide layer is arranged closer to the substrate than the carbon layer. The oxide layer can be used to protect the substrate to prevent the substrate from being oxidized by oxygen in the air, thereby ensuring the substrate releases lithium ions to replenish lithium for the lithium-ion battery 200. In addition, the type of Z is the same as the type of M in the matrix, which can avoid the introduction of too many heteroatoms, thereby facilitating the improvement of the uniformity of the lithium-replenishing particles. Furthermore, the coating layer also includes carbon, which is coated on the periphery of the oxide layer to form a carbon layer, which is beneficial to improving the conductive properties of the lithium-replenishing particles and reducing the impedance of active ions entering the electrolyte 100 from the substrate and the coating layer, thereby facilitating the improvement of the energy efficiency of the lithium-ion battery 200.

[0088] Optionally, in the cross section of the positive electrode sheet 230, the area defined by the inner contour of the coating layer is S1, and after the lithium-supplementing particles release lithium ions, the area defined by the outer contour of the matrix is ​​S2, then the planar shrinkage rate of the matrix α = (S1-S2) / S1×100%.

[0089] It can be understood that the cross section of the positive electrode sheet 230 is obtained by cutting the positive electrode sheet 230 using an ion beam milling (CP) instrument.

[0090] In this embodiment, during the lithium-ion release process of the lithium-supplementing particle, the matrix shrinks due to a decrease in lithium content, while the shape of the coating layer remains unchanged. In this embodiment, the area S1 defined by the inner contour of the coating layer represents the area of ​​the matrix before shrinkage, and the area S2 defined by the outer contour of the matrix represents the area after shrinkage. The difference between S1 and S2 represents the area of ​​the matrix contracted during the shrinkage process. The planar shrinkage rate of the matrix can be used to characterize the amount of lithium released by a single lithium-supplementing particle during the lithium-supplementing process.

[0091] In some embodiments, in the positive electrode active layer 231 , the mass fraction of the lithium supplement particles is w3; the planar shrinkage rate of the matrix is ​​α; and the relationship is satisfied: 0.4≤α×w3 / w1≤0.85.

[0092] Specifically, the value of α×w3 / w1 can be, but is not limited to, 0.4, 0.42, 0.45, 0.48, 0.5, 0.52, 0.54, 0.56, 0.58, 0.59, 0.6, 0.63, 0.65, 0.68, 0.7, 0.72, 0.74, 0.76, 0.8, 0.82, 0.84 and 0.85, etc.

[0093] It can be understood that in the positive electrode active layer 231 , the mass fraction w3 of the lithium-supplementing particles is the ratio of the mass of the lithium-supplementing particles to the mass of the positive electrode active layer 231 .

[0094] It can be understood that when the lithium-supplementing particles release lithium ions, the matrix shrinks due to the release of lithium ions and the reduction of lithium content.

[0095] It can be understood that the product of the planar shrinkage rate α of the substrate and the mass fraction w3 of the lithium-supplementing particles can represent the total lithium release amount of the lithium-supplementing particles in the positive electrode active layer 231; the larger the value of α×w3, the greater the total lithium release amount of the lithium-supplementing particles; the smaller the value of α×w3, the smaller the total lithium release amount of the lithium-supplementing particles.

[0096] In this embodiment, when the in-plane shrinkage ratio α of the substrate, the mass fraction w3 of the lithium-supplementing particles, and the mass fraction w1 of the boric acid additive satisfy the relationship: 0.4 ≤ α × w3 / w1 ≤ 0.85, the total lithium release of the lithium-supplementing particles and the mass fraction of the borate additive are within a reasonable range. If the mass fraction of the lithium-supplementing particles and the in-plane shrinkage ratio of the substrate are within a reasonable range, the lithium-supplementing particles can release sufficient lithium ions during charging of the lithium-ion battery 200 to replenish the active ions consumed during the charge and discharge cycles of the lithium-ion battery 200, resulting in a high initial efficiency, energy density, and capacity retention rate. Furthermore, the borate additive is within a reasonable range, allowing it to promptly combine with the oxygen anions released by the lithium-ion supplementing particles, thereby preventing the generation of large amounts of oxygen and side reactions with the electrolyte 100. It also prevents excessive borate additive from increasing the interfacial impedance between the positive electrode 230 / negative electrode 210 and the electrolyte 100, ultimately enabling the lithium-ion battery 200 to achieve high cycle performance, safety, and energy efficiency. When the value of α×w3 / w1 is too large, the total lithium release from the lithium-ion supplementing particles is far greater than the mass fraction of the borate additive. In other words, the total lithium release from the lithium-ion supplementing particles is too large or the mass fraction of the borate additive is too small. During charging of the lithium-ion battery 200, the lithium-ion supplementing particles can release a large amount of lithium ions to replenish the active ions consumed in the electrolyte 100, resulting in a higher usable energy content in the lithium-ion battery 200. However, correspondingly, the lithium-supplementing particles release a large amount of iron ions and oxygen anions while releasing lithium ions. The iron ions and oxygen anions easily combine and undergo oxidation reactions, thereby increasing the amount of oxygen generated in the lithium-ion battery 200 and increasing the probability of side reactions between the electrolyte 100 and oxygen, thereby causing loss of the electrolyte 100 and reducing the stability of the electrolyte 100. In addition, the interface impedance between the electrolyte 100 and the positive electrode sheet 230 / negative electrode sheet 210 is increased, ultimately reducing the safety performance and energy efficiency of the lithium-ion battery 200. When the value of α×w3 / w1 is too small, the total lithium release amount of the lithium-supplementing particles is much smaller than the mass fraction of the borate additive. In other words, if the total lithium release amount of the lithium-supplementing particles is too small or the mass fraction of the borate additive is too large, then in the lithium-ion battery 200, the boron atoms in the borate additive can combine with the oxygen anions released by the lithium-supplementing particles to reduce the generation of oxygen, which is beneficial to reducing the solubility of oxygen in the electrolyte 100 and reducing the side reaction between oxygen and the electrolyte 100, thereby improving the safety performance of the lithium-ion battery 200.However, correspondingly, if the mass fraction of the lithium-supplementing particles is too small or the planar shrinkage rate α of the matrix is ​​too small, it is difficult for the lithium-supplementing particles to compensate for the lithium ions lost during the charge and discharge cycle of the lithium-ion battery 200, and the initial efficiency and energy density of the lithium-ion battery 200 are low. In addition, when the mass fraction of the borate additive is too large, in the electrolyte 100, part of the borate additive combines with oxygen anions, and the excess borate additive may adhere to the interface between the positive electrode plate 230 and / or the negative electrode plate 210 and the electrolyte 100, and undergo a reduction reaction and generate decomposition products, thereby increasing the interfacial impedance, and then reducing the transmission speed and migration speed of the active ions between the positive electrode plate 230 / negative electrode plate 210 and the electrolyte 100, thereby making the energy efficiency of the lithium-ion battery 200 low.

[0097] In some embodiments, the plane shrinkage ratio α of the substrate is in the range of 5%≤α≤40%.

[0098] Specifically, the planar shrinkage rate α of the substrate can be, but is not limited to, 5%, 8%, 9%, 10%, 12%, 14%, 15%, 18%, 20%, 21%, 23%, 25%, 26%, 27%, 28%, 30%, 32%, 33%, 34%, 35%, 36%, 38% and 40%, etc.

[0099] In this embodiment, as the lithium-replenishing particles release lithium ions, the matrix shrinks due to a decrease in lithium content. When the matrix's planar shrinkage rate α satisfies the range of 5% ≤ α ≤ 40%, the matrix's planar shrinkage rate is within a reasonable range. In other words, the lithium ions released by the lithium-replenishing particles are within a reasonable range. The lithium ions released by the lithium-replenishing particles can be replenished into the electrolyte 100 and, through the electrolyte 100, replenished into the negative electrode 210, thereby timely replenishing the active ions lost by the lithium-ion battery 200 during the charge and discharge cycle, thereby improving the initial efficiency, energy density, and capacity retention of the lithium-ion battery 200. When the planar shrinkage of the substrate is too large, the lithium-ion supplement particles release excessive lithium ions during charging of the lithium-ion battery 200, which can easily lead to local lithium deposition on the negative electrode 210, increasing the internal resistance of the lithium-ion battery 200 and reducing the energy efficiency of the lithium-ion battery 200. At the same time, the lithium-ion supplement particles release excessive oxygen anions and iron ions. The oxygen anions combine with the iron ions to generate oxygen, creating a safety hazard and shortening the service life of the lithium-ion battery 200. When the planar shrinkage of the substrate is too small, the lithium-ion supplement particles are unable to replenish the active ions lost by the lithium-ion battery 200 during the charge and discharge cycle, thereby reducing the initial efficiency and energy density of the lithium-ion battery 200.

[0100] Preferably, the plane shrinkage ratio α of the substrate is in the range of 10%≤α≤30%. Specifically, the plane shrinkage ratio α of the substrate can be, but is not limited to, 10%, 12%, 14%, 15%, 18%, 20%, 21%, 23%, 25%, 26%, 27%, 28%, 30%, etc.

[0101] In this embodiment, when the planar shrinkage rate α of the substrate satisfies the range of 10% ≤ α ≤ 30%, the planar shrinkage rate of the substrate is within the preferred range. When the lithium-replenishing particles are applied to the lithium-ion battery 200, the lithium ions released by the lithium-replenishing particles can be supplemented to the electrolyte 100, and supplemented to the negative electrode plate 210 through the electrolyte 100, so as to timely supplement the active ions lost by the lithium-ion battery 200 during the charge and discharge cycle, so that the lithium-ion battery 200 has better first efficiency, energy density and capacity retention rate. In addition, it can avoid excessive oxygen generation caused by excessive lithium-replenishing particles, reduce the probability of side reactions between the electrolyte 100 and oxygen, and the lithium-ion battery 200 has higher cycle performance and safety performance.

[0102] Optionally, the coating layer is a carbon coating layer, the coating layer has conductivity, and the coating layer can protect the substrate it wraps, so as to improve the anti-oxidation performance of the lithium-supplementing particles.

[0103] In some embodiments, in the lithium-ion battery 200 , the relationship: 20≤α / w1≤100 is satisfied.

[0104] Specifically, the value of α / w1 can be, but is not limited to, 20, 22, 25, 28, 30, 32, 36, 38, 40, 42, 45, 48, 50, 52, 55, 58, 60, 62, 65, 68, 70, 75, 78, 80, 82, 85, 88, 90, 92, 95, 98, and 100, etc.

[0105] In the lithium-ion battery 200 provided in this embodiment, when the value of α / w1 satisfies the range of 20≤α / w1≤100, the ratio of the planar shrinkage rate α of the substrate to the mass fraction w1 of the boric acid additive is within a reasonable range. On the one hand, the lithium ions released by the lithium-replenishing particles are within a suitable range, which can replenish the active ions lost by the lithium-ion battery 200 during the charge and discharge cycle; on the other hand, the borate additive can promptly combine with the oxygen anions released by the lithium-replenishing particles to reduce the generation of oxygen, thereby reducing the side reaction between the electrolyte 100 and oxygen, so that the lithium-ion battery 200 has both high first efficiency and good cycle stability. When the value of α / w1 is too large, the planar shrinkage rate α of the substrate is too large, or the mass fraction w1 of the boric acid additive is too small, then when the lithium-ion battery 200 is charged, the lithium-supplementing particles release too many lithium ions, which can easily lead to localized lithium deposition on the negative electrode 210 and release too many oxygen anions and iron ions. The mass fraction of boron atoms in the borate additive is too small, so it can only combine with a small number of oxygen anions, causing the lithium-ion battery 200 to produce a large amount of oxygen, increasing the probability of side reactions between the electrolyte 100 and oxygen and reducing the cycle performance of the lithium-ion battery 200. When the value of α / w1 is too small, the planar shrinkage rate α of the substrate is too small, or the mass fraction w1 of the boric acid additive is too large, then the lithium-supplementing particles are unable to replenish the active ions released by the lithium-ion battery 200 during the charge and discharge cycle, resulting in a low initial efficiency and energy density of the lithium-ion battery 200. In addition, excessive borate additives increase the interfacial impedance of the electrolyte 100 , thereby reducing the transmission efficiency of active ions in the lithium-ion battery 200 , and further reducing the cycle performance of the lithium-ion battery 200 .

[0106] In some embodiments, in the positive electrode active layer 231 , the mass fraction w3 of the lithium supplement particles is in the range of: 0.5%≤w3≤5%.

[0107] Specifically, the mass fraction w3 of the lithium supplement particles can be, but is not limited to, 0.5%, 0.6%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.1%, 2.3%, 2.4%, 2.5%, 2.7%, 2.8%, 2.9%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.3%, 4.5%, 4.6%, 4.7%, 4.8%, 4.9% and 5%, etc.

[0108] In this embodiment, when the mass fraction w3 of the lithium-supplementing particles satisfies the range of 0.5% ≤ w3 ≤ 5%, the mass fraction of the lithium-supplementing particles is within a reasonable range, and the lithium ions released by the lithium-supplementing particles can be replenished into the electrolyte 100 and replenished into the negative electrode plate 210 through the electrolyte 100, thereby timely replenishing the active ions lost by the lithium-ion battery 200 during the charge and discharge cycle, thereby improving the first efficiency, energy density, and capacity retention rate of the lithium-ion battery 200. When the mass fraction of the lithium-supplementing particles is too large, the lithium-supplementing particles release too many lithium ions during the charging process of the lithium-ion battery 200, which can easily lead to local lithium deposition on the negative electrode plate 210, and release too many oxygen anions and iron ions. The oxygen anions combine with the iron ions to generate oxygen, which creates a safety hazard and shortens the service life of the lithium-ion battery 200. When the mass fraction of the lithium-supplementing particles is too small, the lithium-supplementing particles are difficult to replenish the active ions lost by the lithium-ion battery 200 during the charge and discharge cycle, thereby reducing the first efficiency and energy density of the lithium-ion battery 200.

[0109] In some embodiments, at a magnification of 5K, within a rectangular area of ​​22 μm × 15 μm, in the cross section of the positive electrode sheet 230, the number of the lithium supplement particles is multiple; the sum of the areas defined by the inner contours of the multiple coating layers is S3, and after the lithium supplement particles release lithium ions, the sum of the areas defined by the outer contours of the multiple substrates is S4. Then, the shrinkage area S of the multiple lithium supplement particles during the lithium supplement process satisfies the relationship: S = S3-S4, and S satisfies the range: 1.5 μm 2 ≤S / w1≤8μm 2 .

[0110] Specifically, the value of S / w1 may be, but is not limited to, 1.5 μm. 2 , 1.8μm 2 , 2μm 2 , 2.2μm 2 , 2.5μm 2 , 2.8μm 2 , 3μm 2 , 3.2μm 2 , 3.5μm 2 , 4μm 2 , 4.5μm 2 , 4.8μm 2 , 5μm 2 , 5.2μm 2 , 5.6μm 2 , 6μm 2 , 6.5μm 2 , 7μm 2 , 7.5μm 2 and 8μm 2wait.

[0111] It can be understood that the rectangular area of ​​22 μm×15 μm is a rectangular area with a length of 22 μm and a width of 15 μm.

[0112] In this embodiment, at a specific magnification and in a specific area, the sum of the areas defined by the inner contours of the multiple coating layers S3 is the sum of the areas of the matrix of the multiple lithium supplement particles before shrinkage, and the sum of the areas defined by the outer contours of the multiple matrixes S4 is the sum of the areas of the matrix of the multiple lithium supplement particles after shrinkage. The difference between S3 and S4 is the shrinkage area S of the multiple lithium supplement particles during the lithium supplement process. When S / w1 satisfies the range of 1.5μm 2 ≤S / w1≤8μm 2When the value of S / w1 is within a reasonable range, the amount of lithium ions released by the multiple lithium-replenishing particles is within a reasonable range, so that the shrinkage area of ​​the multiple lithium-replenishing particles is within a reasonable range, and the lithium ions lost by the lithium-ion battery 200 during the charge and discharge process are replenished in time, so that the lithium-ion battery 200 has a higher first efficiency, energy density and capacity retention rate. In addition, the borate additive is within a reasonable range, so that the borate additive can be combined with the oxygen anions released by the lithium-replenishing particles in time to avoid the generation of a large amount of oxygen and side reactions with the electrolyte 100. It can also avoid the excessive borate additive and increase the interface impedance between the positive electrode plate 230 / negative electrode plate 210 and the electrolyte 100, and ultimately make the lithium-ion battery 200 have higher cycle performance, safety performance and energy efficiency. When the value of S / w1 is too large, the shrinkage area of ​​the multiple lithium-replenishing particles during the lithium-replenishing process is too large or the mass fraction of the borate additive is too small. During the charging process of the lithium-ion battery 200, the lithium ions released by the plurality of lithium-supplementing particles are too much, which can easily lead to local lithium deposition on the negative electrode 210, increase the internal resistance of the lithium-ion battery 200, and thus reduce the energy efficiency of the lithium-ion battery 200. At the same time, the lithium-supplementing particles will release too many oxygen anions and iron ions. The borate additive can only combine with a small number of oxygen anions, and then the oxygen anions combine with the iron ions to generate more oxygen, causing safety hazards and shortening the service life of the lithium-ion battery 200. When the value of S / w1 is too small, the shrinkage area of ​​the plurality of lithium-supplementing particles during the lithium replenishment process is too small or the mass fraction of the borate additive is too large. The lithium ions released by the plurality of lithium-supplementing particles are too few, and the plurality of lithium-supplementing particles are difficult to replenish the active ions lost by the lithium-ion battery 200 during the charge and discharge cycle, thereby reducing the initial efficiency and energy density of the lithium-ion battery 200. In addition, when the mass fraction of the borate additive is too large, in the electrolyte 100, part of the borate additive combines with oxygen anions, and excess borate additives may adhere to the interface between the positive electrode plate 230 and / or the negative electrode plate 210 and the electrolyte 100, and undergo a reduction reaction and generate decomposition products, thereby increasing the interface impedance, and then reducing the transmission speed and migration speed of active ions between the positive electrode plate 230 / negative electrode plate 210 and the electrolyte 100, thereby making the energy efficiency of the lithium-ion battery 200 low.

[0113] In some embodiments, the shrinkage area S of the plurality of lithium supplement particles during the lithium supplement process is in the range of: 0.1 μm 2 ≤S≤6μm 2 .

[0114] Specifically, the value of S may be, but is not limited to, 0.1 μm. 2 , 0.5μm 2 , 0.8μm2 , 1μm 2 , 1.2μm 2 , 1.5μm 2 , 2μm 2 , 2.2μm 2 , 2.5μm 2 , 3μm 2 , 3.2μm 2 , 3.5μm 2 , 3.8μm 2 , 4μm 2 , 4.5μm 2 , 4.8μm 2 , 5μm 2 , 5.2μm 2 , 5.6μm 2 , 5.8μm 2 and 6μm 2 wait.

[0115] In this embodiment, when the shrinkage area S of the plurality of lithium supplement particles during the lithium supplement process satisfies the range of 0.1 μm 2 ≤S≤6μm 2 When the lithium ions released by the multiple lithium-replenishing particles during the lithium-replenishing process are within a reasonable range and are replenished to the electrolyte 100, and are replenished to the negative electrode plate 210 through the electrolyte 100, so as to timely replenish the active ions lost by the lithium-ion battery 200 during the charge and discharge cycle, thereby improving the first efficiency, energy density and capacity retention rate of the lithium-ion battery 200. When the value of the shrinkage area S of the multiple lithium-replenishing particles during the lithium-replenishing process is too large, then during the charging of the lithium-ion battery 200, the multiple lithium-replenishing particles release too many lithium ions during the lithium-replenishing process, which can easily lead to local lithium deposition on the negative electrode plate 210, increase the internal resistance of the lithium-ion battery 200, and thus reduce the energy efficiency of the lithium-ion battery 200. At the same time, the lithium-replenishing particles will release too many oxygen anions and iron ions. The oxygen anions combine with the iron ions to generate oxygen, which creates a safety hazard and shortens the service life of the lithium-ion battery 200. When the shrinkage area S of the plurality of lithium-replenishing particles during the lithium-replenishing process is too small, the lithium-replenishing particles release too few lithium ions during the lithium-replenishing process, and the lithium-replenishing particles are unable to replenish the active ions lost during the charge and discharge cycles of the lithium-ion battery 200, thereby reducing the initial efficiency and energy density of the lithium-ion battery 200.

[0116] The technical solution of this application is further described below with reference to a number of embodiments.

[0117] Examples 1 to 17, Comparative Examples 1 to 8:

[0118] 1. Preparation of positive electrode sheet 230:

[0119] The positive electrode active material (for example, lithium iron phosphate), lithium supplement particles (for example, Li5FeO4 as a matrix, the chemical formula of the coating layer is Al2O3@C or Li6CoO4 as a matrix, the coating layer is a carbon coating layer), a positive electrode conductive agent (for example, conductive carbon black), and a positive electrode binder (for example, polyvinylidene fluoride) are dispersed in a solvent N-methylpyrrolidone and mixed uniformly to obtain a positive electrode slurry. In the positive electrode slurry, the mass fraction of the positive electrode active material: the mass fraction of the positive electrode conductive agent: the mass fraction of the positive electrode binder is 96%: 0.5%: 2.3%. The positive electrode slurry is coated on the positive electrode current collector layer 232 (for example, aluminum foil). The positive electrode slurry unit area (1540.25mm 2 ) with a coating weight of 254 mg to form a positive electrode active layer 231. After drying, cold pressing, slitting, and cutting, the positive electrode sheets 230 of Examples 1 to 17 and Comparative Examples 1 to 8 were obtained. The lithium-supplementing particles of Examples 1 to 16 and Comparative Examples 1 to 8 used Li₅FeO₄ as the matrix and the coating layer had the chemical formula of Al₂O₃@C. The lithium-supplementing particles of Example 17 used Li₆CoO₄ as the matrix and the coating layer was a carbon coating layer. The values ​​of the mass fraction w₃ of the lithium-supplementing particles, the planar shrinkage rate α of the matrix, and the shrinkage area S of the multiple lithium-supplementing particles during the lithium-supplementing process for Examples 1 to 17 and Comparative Examples 1 to 8 are shown in Table 1.

[0120] 2. Preparation of negative electrode sheet 210 and separator 220:

[0121] The negative electrode active material (for example, artificial graphite), the negative electrode conductive agent (for example, conductive carbon black), the negative electrode thickener (for example, carboxymethyl cellulose) and the negative electrode binder (for example, styrene-butadiene rubber) are dispersed in deionized water at a mass ratio of 96.5:0.5:1:2 and mixed evenly to obtain a negative electrode slurry. The negative electrode slurry is coated on the negative electrode current collector layer (for example, copper foil). The coating weight of the negative electrode slurry per unit area (1540.25 mm2) is 122 mg. After drying, cold pressing, slitting and cutting, the negative electrode sheets 210 of Examples 1 to 17 and Comparative Examples 1 to 8 are obtained.

[0122] A polyethylene separator 220 with a thickness of 16 μm was selected.

[0123] 3. Preparation of electrolyte 100:

[0124] In an argon atmosphere glove box with a moisture content of ≤1 ppm, ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate were mixed in a mass ratio of 1:1:1. Dried lithium hexafluorophosphate (LIPF), an electrolyte, was then dissolved in a solvent and stirred until completely dissolved. A borate additive, a sulfur-containing additive, and a film-forming additive were then added and mixed to obtain an electrolyte 100. The lithium salt concentration was 1 mol / L, and the mass fraction of the film-forming additive in electrolyte 100 was 3%. For the electrolytes 100 of Examples 1 to 17 and Comparative Examples 1 to 8, the type and mass fraction w1 of the borate additive, and the type and mass fraction w2 of the sulfur-containing additive are shown in Table 1.

[0125] 4. Assembly of lithium-ion battery 200:

[0126] The positive electrode sheets 230, separators 220, and negative electrode sheets 210 of Examples 1 to 17 and Comparative Examples 1 to 8 prepared above are stacked in sequence, with the separator 220 located between the positive electrode sheet 230 and the negative electrode sheet 210, and then wound to obtain a bare cell. The bare cell is placed in an outer package, dried, and injected with the above-mentioned electrolyte 100. After standing, forming, and packaging, implementing cells 1 to 15 and comparative cells 1 to 8 are obtained, wherein the positive electrode sheet 230 of Example 1 and the electrolyte 100 of Example 1 are arranged in implementing cell 1, the positive electrode sheet 230 of Example 2 and the electrolyte 100 of Example 2 are arranged in implementing cell 2, the positive electrode sheet 230 of comparative cell 1 and the electrolyte 100 of comparative cell 1 are arranged in comparative cell 1, and so on.

[0127] The test method for the plane shrinkage rate α of the substrate in the positive electrode sheet 230 is as follows:

[0128] Referring to Figures 3 and 4 , the positive electrode sheet 230 was assembled into a lithium-ion battery 200 and charged. The positive electrode sheet 230 was then disassembled and cut using an ion beam milling (CP) instrument to obtain a cross-section of the positive electrode sheet 230. The positive electrode sheet 230 was observed using a scanning electron microscope (SEM) and photographed at a magnification of 10K. Figure 3 is a scanning electron microscope image of the lithium-supplementing particles after shrinkage according to an embodiment of the present application. Figure 3 shows the situation of taking points along the inner contour of the coating layer. Using image analysis software and employing the polygon measurement function, points were taken along the inner contour of the coating layer. The image analysis software was used to calculate the area S1 defined by the inner contour of the coating layer. The area defined by the inner contour of the coating layer is the area of ​​the substrate before shrinkage. Figure 4 is a scanning electron microscope image of a lithium-supplemented particle after shrinkage, according to another embodiment of the present application. Figure 4 illustrates the situation of selecting points along the outer contour of the substrate. Using image analysis software, the area S2 defined by the outer contour of the substrate is calculated. The area defined by the outer contour of the substrate is the area of ​​the substrate after shrinkage. The in-plane shrinkage rate α of the substrate satisfies the equation: α = (S1 - S2) / S1 × 100%. The in-plane shrinkage rate α of the substrate is controlled by controlling the maximum voltage of the lithium-ion battery 200.

[0129] The test method for the shrinkage area S of the plurality of substrates in the positive electrode sheet 230 during the lithium replenishment process is as follows:

[0130] The positive electrode sheet 230 was assembled into a lithium-ion battery 200 and charged. The positive electrode sheet 230 was then disassembled and cut using an ion beam milling (CP) instrument to obtain a cross-section of the positive electrode sheet 230. The positive electrode sheet 230 was observed using a scanning electron microscope (SEM) and photographed at a magnification of 5K. Within a rectangular area measuring 22 μm × 15 μm, the sum of the areas defined by the inner contours of the multiple coating layers is S3, which is the total area of ​​the multiple lithium-replenishing particles before shrinkage. The sum of the areas defined by the outer contours of the multiple substrates is S4, which is the total area of ​​the multiple lithium-replenishing particles after shrinkage. Therefore, the shrinkage area S of the multiple substrates during the lithium replenishment process = S3 - S4.

[0131] Table 1 below shows the structural parameters of the electrolyte 100 and the lithium-ion battery 200 of Examples 1 to 17 and Comparative Examples 1 to 8.

[0132] Table 1: Electrolytes 100 and lithium-ion batteries of Examples 1 to 17 and Comparative Examples 1 to 8

[0133] Structural parameters of 200.

[0134] Performance test of lithium-ion battery 200:

[0135] The implementation batteries 1 to 17 and the comparative batteries 1 to 8 were placed at 25°C for 1 hour, charged to 3.65V at 0.5P, and then discharged to 2.5V at 0.5P. The initial discharge capacity C1 of the lithium ion battery 200 was recorded, and the initial discharge energy was E1. The implementation batteries 1 to 17 and the comparative batteries 1 to 8 were cycled for 500 cycles, and the discharge capacity C 500 , charging capacity C' 500 , discharge energy E 500 and charging energy E' 500 , the energy efficiency E=E of the implementation cells 1 to 17 and the comparative cells 1 to 8 is obtained. 500 / E' 500 × 100%, and the capacity retention rate Cf after 500 cycles of the implementation batteries 1 to 17 and the comparison batteries 1 to 8 is obtained. 500 The energy efficiency E and capacity retention rate Cf of the exemplary batteries 1 to 17 and the comparative batteries 1 to 8 after 500 cycles are shown in Table 2.

[0136] Table 2 below shows the performance parameters of Example Batteries 1 to 17 and Comparative Batteries 1 to 8.

[0137] Table 2: Performance parameters of Example Batteries 1 to 17 and Comparative Batteries 1 to 8.

[0138] Referring to Tables 1 and 2, in Examples 1 through 3, the mass fraction w3 of the lithium-supplementing particles, the shrinkage area S of the multiple lithium-supplementing particles during the lithium replenishment process, the mass fraction w1 of the borate additive, the mass fraction w2 of the sulfur-containing additive, and the value of S / w1 were all within reasonable ranges. However, in Examples 1 through 3, the ratio of the mass fraction w2 of the sulfur-containing additive to the mass fraction w1 of the borate additive gradually decreased, and the value w2 / w1 in Example 1 was greater than 1.2. Furthermore, in Examples 1 through 3, the shrinkage area S of the multiple lithium-supplementing particles during the lithium replenishment process continuously increased. The energy efficiency of Batteries 1 through 3 after 500 cycles decreased, but the capacity retention after 500 cycles increased. In other words, the cycling performance of Batteries 1 through 3 improved. This is because: when the mass fraction w2 of the sulfur-containing additive is much greater than the mass fraction of the borate additive, the sulfur-containing additive can compensate for the increased interfacial impedance caused by the addition of the borate additive. However, the excessive amount of the sulfur-containing additive makes it susceptible to hydrolysis and acid production in the electrolyte 100, thereby damaging the interfacial film between the positive electrode sheet 230 / negative electrode sheet 210 and the electrolyte 100 and reducing the cycle performance of the lithium-ion battery 200. In addition, the shrinkage area S of the multiple lithium-supplementing particles increases during the lithium-supplementing process, resulting in an increase in the release of oxygen and iron anions by the multiple lithium-supplementing particles. If the borate additive content is too low, the boron atoms in the borate additive can only combine with a small number of oxygen anions in lithium-ion battery 200. The majority of the oxygen anions released by the lithium-supplementing particles undergo oxidation reactions with iron ions to produce oxygen. This exacerbates the side reaction between electrolyte 100 and oxygen, reduces the stability of electrolyte 100, and thus reduces the cycle performance of electrolyte 100 when used in lithium-ion battery 200. Therefore, the cycle performance of embodiment battery 2 and embodiment battery 3 are both better than that of embodiment battery 1.

[0139] In Examples 4 to 6, the planar shrinkage rate α of the substrate, the mass fraction w3 of the lithium-replenishing particles, and the shrinkage area S of the multiple lithium-replenishing particles during the lithium-replenishing process remain unchanged, and the mass fraction w1 of the borate additive continues to increase, thereby causing the value of α×w3 / w1 to decrease successively. The energy efficiency of Implementation Battery 4 to Implementation Battery 6 after 500 cycles decreases successively, and the capacity after 500 cycles first decreases and then increases. This is because: when the amount of lithium released by the lithium-replenishing particles remains unchanged, as the mass fraction of the borate additive gradually increases, the borate additive can combine with the oxygen anions released by the lithium-replenishing particles, thereby preventing oxygen from reacting with the electrolyte 100 and reducing the stability of the electrolyte 100. However, the borate additive will increase the interfacial impedance between the electrolyte 100 and the positive electrode sheet 230 / negative electrode sheet 210, thereby reducing the cycle performance of the lithium-ion battery 200. Therefore, compared with Implementation Battery 4, the cycle performance of Implementation Battery 5 is slightly worse. Furthermore, the mass fraction of the sulfur-containing additive in the electrolyte 100 of the implementation battery 6 is greater than that in the electrolyte 100 of the implementation battery 5. The sulfur-containing additive in the electrolyte 100 of the implementation battery 6 can make up for the deficiency of the increase in interfacial impedance caused by the borate additive, thereby improving the cycle performance of the implementation battery 6.

[0140] In Examples 6 to 8, under the same other conditions, as the mass fraction w2 of the sulfur-containing additive continues to increase, the ratio w2 / w1 also continues to increase, and the value of w2 / w1 in Example 8 is greater than 1.2, so that the capacity retention rate of battery 8 after 500 cycles is lower than the capacity retention rates of batteries 6 and 7 after 500 cycles. This is because: as the mass fraction of the sulfur-containing additive increases, the sulfur-containing additive is easily hydrolyzed to produce acid in the electrolyte 100, thereby destroying the interface film between the positive electrode sheet 230 / negative electrode sheet 210 and the electrolyte 100, and then reducing the cycle performance of the lithium-ion battery 200.

[0141] In Examples 9 and 10, the value of w2 / w1 in Example 9 is larger, and the value of α×w3 / w1 is larger. This results in the energy efficiency of Example 9 being superior to that of Example 10, and the capacity retention of Example 9 being superior to that of Example 10. This is because, on the one hand, the borate additive can bind to the oxygen anions released by the lithium-supplementing particles, slowing the generation of oxygen and the side reaction between oxygen and the electrolyte 100, thereby improving the stability of the electrolyte 100. On the other hand, the sulfur-containing additive can fully compensate for the increased impedance caused by the borate additive, and avoids excessive mass fraction of the sulfur-containing additive causing hydrolysis and acid production, thereby preventing damage to the interface film between the positive electrode sheet 230 / negative electrode sheet 210 and the electrolyte 100 in Example 9. Therefore, compared to Example 10, Example 9 has better energy efficiency and better capacity retention.

[0142] In Examples 9 and 11, under the same other conditions, the type of borate additive in Example 9 is lithium difluorooxalatoborate, and the type of borate additive in Example 11 is lithium dicyanooxalatoborate. The energy efficiency of Example 9 is better than that of Example 11, and the capacity retention rate of Example 9 is better than that of Example 11. This shows that lithium difluorooxalatoborate has better performance in binding to oxygen anions of lithium supplement particles than lithium dicyanooxalatoborate.

[0143] In Examples 12 and 13, under the same other conditions, the type of sulfur-containing additive in Example 12 is 1,3-propene sultone, and the type of sulfur-containing additive in Example 11 is 1,4-butene sultone. The energy efficiency of Example 12 is better than that of Example 13. This shows that 1,3-propene sultone has better performance than 1,4-butene sultone in forming a sulfur-containing interfacial film to compensate for the excessive interfacial impedance caused by the borate additive.

[0144] In Examples 14 to 16, the planar shrinkage of the substrate in Example 16 was much greater than that of the substrates in Examples 14 and 15, resulting in a lower energy efficiency after 500 cycles of Example 16 than those of Example 14 and Example 15. This is because when Example 16 is charged, the lithium-supplementing particles release excessive lithium ions, which easily leads to localized lithium deposition on the negative electrode sheet 210. Furthermore, excessive oxygen anions and iron ions are released. The oxygen anions combine with the iron ions to generate oxygen, creating a safety hazard and increasing the internal resistance of Example 16. Consequently, the energy efficiency of Example 16 is lower than that of Example 14 and Example 15.

[0145] In Examples 9 and 17, the structural parameters of the electrolyte 100 and lithium-ion battery 200 are the same, but the materials of the lithium-supplementing particles in Examples 9 and 17 are different. Specifically, the lithium-supplementing particles in Example 9 use Li₅FeO₄ as the matrix and the coating layer has the chemical formula of Al₂O₃@C, while the lithium-supplementing particles in Example 17 use Li₆CoO₄ as the matrix and the coating layer is a carbon coating. As shown in Table 2, both Example 9 and Example 17 have high energy efficiency and capacity retention after 500 cycles. Therefore, the lithium-supplementing particles used in the lithium-ion battery 200 have a good lithium-supplementing effect, and the borate additive can be combined with lithium-supplementing particles made of different materials to maintain the cycling performance of the lithium-ion battery 200.

[0146] In Comparative Example 1 and Comparative Example 2, the planar shrinkage rate α of the substrate of Comparative Example 1 is much smaller than the planar shrinkage rate α of the substrate of Comparative Example 2, and the shrinkage area S of the multiple lithium-replenishing particles in Comparative Example 1 during the lithium replenishment process is much smaller than the shrinkage area S of the multiple lithium-replenishing particles in Comparative Example 2 during the lithium replenishment process. In addition, the value of α×w3 / w1 in Comparative Example 1 is less than 0.2, and the value of α×w3 / w1 in Comparative Example 2 is greater than 0.6, which makes the energy efficiency of Comparative Battery 1 higher than the energy efficiency of Comparative Battery 2, and the capacity retention rate of Comparative Battery 1 is lower than the capacity retention rate of Comparative Battery 2. This is because: the amount of lithium-supplementing particles in the comparative battery 1 is too small, and the mass content of the borate additive in the electrolyte 100 is too high. In the electrolyte 100, part of the borate additive combines with oxygen anions, and the excess borate additive may adhere to the interface between the positive electrode plate 230 and / or the negative electrode plate 210 and the electrolyte 100, and undergo a reduction reaction and generate decomposition products, thereby increasing the interface impedance, and then reducing the transmission speed and migration speed of active ions between the positive electrode plate 230 / negative electrode plate 210 and the electrolyte 100, resulting in lower energy efficiency of the comparative battery 1. The planar shrinkage rate α of the matrix in comparative battery 2 is larger, and the value of α×w3 / w1 is too large. Therefore, the lithium-supplementing particles release more oxygen anions and generate oxygen while releasing lithium ions, causing the electrolyte 100 to react with oxygen, thereby reducing the stability of the electrolyte 100 and increasing the interface impedance between the electrolyte 100 and the positive electrode sheet 230 / negative electrode sheet 210, thereby making the energy efficiency of comparative battery 2 lower.

[0147] In Comparative Examples 3 and 4, the mass fraction w1 of the borate additive in Comparative Example 3 is greater than 2%. In other words, the mass fraction w1 of the borate additive in Comparative Example 3 is too large, while the mass fraction w1 of the borate additive in Comparative Example 4 is 0. This makes the energy efficiency of Comparative Battery 3 lower than that of Comparative Battery 4, and the capacity retention rate of Comparative Battery 3 is higher than that of Comparative Battery 4. This is because: the mass fraction w1 of the borate additive in the electrolyte 100 of Comparative Battery 3 is too large, and the excess borate additive may adhere to the interface between the positive electrode sheet 230 and the electrolyte 100 or the interface between the negative electrode sheet 210 and the electrolyte 100, and undergo a reduction reaction to generate decomposition products that adhere to the positive electrode sheet 230 and / or the negative electrode sheet 210, thereby increasing the interfacial impedance, and then reducing the transmission speed and migration speed of the active ions between the positive electrode sheet 230 / negative electrode sheet 210 and the electrolyte 100, thereby making the energy efficiency of Comparative Battery 3 lower. In comparison battery 4, although the energy efficiency of comparison battery 4 is guaranteed, the lithium-supplementing particles release oxygen while releasing lithium ions, which increases the probability of side reactions between the electrolyte 100 and oxygen, reduces the stability of the electrolyte 100, and subsequently makes the capacity retention rate of comparison battery 4 low.

[0148] In Comparative Examples 5 and 6, the mass fraction w2 of the sulfur-containing additive in Comparative Example 5 is greater than 2%. In other words, the mass fraction w2 of the sulfur-containing additive in Comparative Example 5 is too large, while the mass fraction w2 of the sulfur-containing additive in Comparative Example 6 is 0. This results in the energy efficiency of Comparative Cell 5 being better than that of Comparative Cell 6, and the capacity retention rate of Comparative Cell 5 being lower than that of Comparative Cell 6. This is because the excessive mass fraction of the sulfur-containing additive in Comparative Cell 3 makes it easy for the sulfur-containing additive to hydrolyze and produce acid in the electrolyte 100, thereby destroying the interface film between the positive electrode sheet 230 / negative electrode sheet 210 and the electrolyte 100, reducing the stability of the electrolyte 100, and thus resulting in a lower capacity retention rate for Comparative Cell 3. In Comparative Cell 6, the electrolyte 100 does not include a sulfur-containing additive, so the problem of increased interfacial impedance caused by the addition of the borate additive to the electrolyte 100 cannot be alleviated, resulting in a lower energy efficiency for Comparative Cell 6.

[0149] In Comparative Examples 7 and 8, the mass fraction w3 of the lithium-supplementing particles in Comparative Example 8 is greater than the mass fraction w3 of the lithium-supplementing particles in Comparative Example 7, and the mass fraction w3 of the lithium-supplementing particles in Comparative Example 8 is greater than 3%, and the values ​​of w2 / w1 in Comparative Examples 7 and 8 are both greater than 1.2, and the values ​​of α×w3 / w1 in Comparative Examples 7 and 8 are both greater than 0.6. Compared with the capacity retention rates of Comparative Battery 2 and Comparative Battery 3, the capacity retention rates of Comparative Battery 7 and Comparative Battery 8 are too small. This is because: on the one hand, the value of α×w3 / w1 is too large, the total lithium release amount of the lithium-supplementing particles is much greater than the mass fraction of the borate additive, then when the lithium-supplementing particles release a large amount of iron ions and oxygen anions while releasing lithium ions, the borate additive is difficult to alleviate the generation of oxygen in the electrolyte 100, aggravating The side reaction between the electrolyte 100 and oxygen is reduced, the stability of the electrolyte 100 of the comparative battery 7 and the comparative battery 8 is reduced, thereby reducing the capacity retention rate of the comparative battery 7 and the comparative battery 8; on the other hand, in the electrolyte 100, the mass fraction w2 of the sulfur-containing additive is much larger than the mass fraction of the borate additive. Although the sulfur-containing additive can make up for the deficiency of the increase in interfacial impedance caused by the addition of the borate additive, the amount of the sulfur-containing additive is too much, which makes the sulfur-containing additive easy to hydrolyze and produce acid in the electrolyte 100, thereby destroying the interface film between the positive electrode sheet 230 / the negative electrode sheet 210 and the electrolyte 100, thereby reducing the stability of the electrolyte 100, resulting in a low capacity retention rate of the comparative battery 7 and the comparative battery 8.

[0150] Please refer to Figures 5 and 6. The embodiment of the present application further provides an electric device 300, which includes: a device body 310 and a lithium-ion battery 200 provided in the present application, and the lithium-ion battery 200 supplies power to the device body 310.

[0151] It can be understood that the lithium-ion battery 200 is electrically connected to the device body 310 .

[0152] In this embodiment, the lithium-ion battery 200 has good initial efficiency, cycle performance, and safety performance, resulting in a long service life for the lithium-ion battery 200. When the lithium-ion battery 200 is used to power the device body 310, the lithium-ion battery 200 can provide a stable power source for the device body 310, allowing the device body 310 to operate normally.

[0153] Optionally, the power-consuming device 300 in the embodiment of the present application may be, but is not limited to, a portable electronic device such as a mobile phone, tablet computer, laptop computer, desktop computer, smart bracelet, smart watch, e-reader, game console, or similar. It may also be a vehicle such as a car, truck, sedan, van, freight train, high-speed train, electric vehicle, or other similar vehicle. Furthermore, it may also be various household appliances. The power-consuming device 300 in the embodiment of FIG. 6 of the present application is an energy storage battery cabinet.

[0154] It can be understood that the electrical equipment 300 described in this embodiment is merely a form of the electrical equipment 300 used by the lithium-ion battery 200, and should not be understood as a limitation on the electrical equipment 300 provided in this application, nor should it be understood as a limitation on the electrical equipment 300 provided in each embodiment of this application.

[0155] Mentioning "embodiments" and "implementation methods" in this application means that the specific features, structures or characteristics described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrases in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments. In addition, it should be understood that the features, structures or characteristics described in the various embodiments of the present application can be arbitrarily combined to form another embodiment that does not deviate from the spirit and scope of the technical solution of the present application, unless there is a contradiction between them.

[0156] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the above preferred implementation modes, ordinary technicians in this field should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. An electrolyte, wherein The electrolyte includes a borate additive. In the electrolyte, the mass fraction w1 of the borate additive is in the range of 0.01%≤w1≤2%.

2. The electrolyte according to claim 1, wherein The electrolyte further includes a sulfur-containing additive. In the electrolyte, the mass fraction w2 of the sulfur-containing additive is in the range of 0.01%≤w2≤2%.

3. The electrolyte according to claim 2, wherein In the electrolyte, the ratio of the mass fraction w2 of the sulfur-containing additive to the mass fraction w1 of the borate additive satisfies the range: 0.5≤w2 / w1≤1.

2.

4. The electrolyte according to claim 1, wherein The borate additive includes at least one of lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium tetrafluoroborate, lithium tetraborate, lithium tetracyanoborate, lithium difluoroborate, lithium tetrakis(trifluoromethyl)borate, lithium bis(trifluoromethyl)difluoroborate, lithium dicyanooxalatoborate, lithium pentafluoroethyl trifluoroborate, and lithium perfluoro-tert-butoxy trifluoroborate.

5. The electrolyte according to claim 2, wherein The sulfur-containing additive includes at least one of 1,3-propane sultone, vinyl sulfate, 1,3-propylene sultone, 1,4-butane sultone, 1,4-butene sultone, methylene disulfonate and pentaerythritol bicyclic sulfate.

6. A lithium-ion battery, wherein: The lithium-ion battery comprises: negative electrode; A diaphragm, the diaphragm being arranged on one side of the negative electrode plate; A positive electrode sheet, the positive electrode sheet is arranged on the side of the separator away from the negative electrode sheet, the positive electrode sheet includes a positive electrode active layer and a positive electrode current collector layer, the positive electrode active layer is arranged on the surface of the positive electrode current collector layer, and the positive electrode active layer includes a plurality of lithium supplement particles; and The electrolyte according to any one of claims 1 to 5, wherein the electrolyte at least soaks a portion of the positive electrode sheet and a portion of the negative electrode sheet.

7. The lithium ion battery according to claim 6, wherein In the positive electrode active layer, the mass fraction of the lithium supplement particles is w3; the lithium supplement particles include a matrix and a coating layer, the coating layer is disposed on the outer periphery of the matrix, and the planar shrinkage rate of the matrix is α; then the relational expression is satisfied: 0.4 ≤ α × w3 / w1 ≤ 0.85; wherein, the chemical formula of the matrix is Li 1+r M 1-p N p O 4-s B s , and 0.1 < r < 6.1, 0 ≤ p < 0.99, 0 ≤ s < 0.1 are satisfied; M and N are each independently selected from at least one of iron, cobalt, nickel, titanium, zinc, magnesium, aluminum, manganese, vanadium, chromium, zirconium, copper, niobium, tantalum, tungsten, yttrium, and lanthanum, and B is selected from at least one of sulfur, nitrogen, fluorine, chlorine, and bromine.

8. The lithium ion battery according to claim 7, wherein In the cross section of the positive electrode sheet, the area defined by the inner contour of the coating layer is S1, and after the lithium-supplementing particles release lithium ions, the area defined by the outer contour of the matrix is S2. The planar shrinkage rate α of the matrix satisfies the relationship: α = (S1-S2) / S1×100%, and the range of the planar shrinkage rate α of the matrix is: 5%≤α≤40%.

9. The lithium ion battery according to claim 7, wherein In the lithium ion battery, the relationship: 20≤α / w1≤100 is satisfied.

10. The lithium ion battery according to claim 7, wherein In the positive electrode active layer, the mass fraction w3 of the lithium supplement particles is in the range of 0.5%≤w3≤5%.

11. The lithium ion battery according to claim 7, wherein At a magnification of 5K, within a rectangular area of 22 μm × 15 μm, in the cross section of the positive electrode sheet, the number of the lithium supplement particles is multiple; the sum of the areas defined by the inner contours of the multiple coating layers is S3, and after the lithium supplement particles release lithium ions, the sum of the areas defined by the outer contours of the multiple substrates is S4. Then, the contraction area S of the multiple lithium supplement particles during the lithium supplement process satisfies the relationship: S = S3 - S4, and the range of S is 1.5 μm. 2 ≤S / w1≤8μm 2 .

12. The lithium ion battery according to claim 11, wherein The range of the shrinkage area S of the plurality of lithium supplement particles during the lithium supplement process is: 0.1 μm 2 ≤S≤6μm 2 .

13. An electrical device, wherein: The electrical equipment includes: the device itself; and The lithium-ion battery according to any one of claims 6 to 12, wherein the lithium-ion battery is used to power the device body.

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