Electrochemical device and electronic device

Abstract

An electrochemical device and an electronic device. The electrochemical device comprises a positive electrode sheet, a negative electrode sheet and an electrolyte, wherein the electrolyte comprises an additive A, the additive A comprising at least one of the compound represented by structural formula I or the compound represented by structural formula II; and the positive electrode sheet comprises a positive electrode material layer, the positive electrode material layer comprising manganese and iron. By applying both the electrolyte containing the additive A and the positive electrode sheet containing manganese and iron to the electrochemical device, the cycling performance and high-temperature storage performance of the electrochemical device are improved.

Description

An electrochemical device and an electronic device

[0001] This application claims priority to Chinese Patent Application No. 202410813568.9, filed on June 21, 2024, entitled "An Electrochemical Device and an Electronic Device", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of electrochemistry, and in particular to an electrochemical device and an electronic device. Background Technology

[0003] Lithium-ion batteries have attracted widespread attention and are widely used in energy storage due to their high energy density, low maintenance, relatively low self-discharge, long cycle life, lack of memory effect, stable operating voltage, and environmental friendliness. However, with the increasing demands of the energy storage market for longer battery cycle life and longer-term high-temperature storage, there is an urgent need to develop a long-cycle, highly stable lithium-ion energy storage battery and electronic device. Summary of the Invention

[0004] The purpose of this application is to provide an electrochemical device and an electronic device to improve the cycle performance and high-temperature storage performance of the electrochemical device. The specific technical solution is as follows:

[0005] It should be noted that the invention description in this application uses lithium-ion batteries as an example of electrochemical devices to explain this application, but the electrochemical devices in this application are not limited to lithium-ion batteries.

[0006] The first aspect of this application provides an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte; wherein the electrolyte includes an additive A, which includes at least one of a compound of formula I or a compound of formula II, and the mass percentage a of additive A is 0.05% to 4.0% based on the total mass of the electrolyte.

[0007] R1 to R9 are each independently selected from hydrogen atoms, fluorine atoms, unsubstituted or fluorinated C1 to C5 alkyl groups, unsubstituted or fluorinated C2 to C5 alkenyl groups, and unsubstituted or fluorinated C2 to C5 alkynyl groups. Fluorine substitution can be complete or partial. The positive electrode includes a positive electrode material layer, which includes manganese and iron elements. Based on the total mass of the positive electrode material layer, the mass percentage of manganese is W. Mn W Mn The condition 0.43 ≤ 100a / W is satisfied between and . Mn ≤170.94, preferably, 0.86≤100a / W Mn≤34.21. The mass percentage content a of additive A and the mass percentage content W of manganese element are compared. Mn The ratio 100a / W Mn Within the scope of this application, regulation is beneficial for additive A and manganese in the cathode material layer to exert a synergistic effect, effectively mitigating Mn. 3+ The uneven deposition at the negative electrode improves the kinetic performance of the electrochemical device, as well as its cycle performance and high-temperature storage performance.

[0008] In one embodiment of this application, the electrolyte includes additive B, which includes at least one of compound of formula III, formula IV, formula V or formula VI, and the mass percentage b of additive B is from 0.05% to 4.0% based on the total mass of the electrolyte.

[0009] Where R 11 R 12 R 16 R 19 Each is independently selected from hydrogen atoms, fluorine atoms, unsubstituted or fluorinated C1 to C5 alkyl groups, unsubstituted or fluorinated C2 to C5 alkenyl groups, and unsubstituted or fluorinated C2 to C5 alkynyl groups; R 10 R 15 R 18 Each is independently selected from oxygen atom, methylene, ethylene, methyleneoxy, and ethoxy; R 13 R 14 Each is independently selected from unsubstituted or fluorinated C1 to C5 alkylene groups; R 17 R 20 Each is independently selected from unsubstituted or fluorinated C1 to C8 alkylene groups, unsubstituted or fluorinated C2 to C8 alkenyl groups, and unsubstituted or fluorinated C2 to C8 alkyne groups; fluorination may be fully substituted or partially substituted.

[0010] In one embodiment of this application, the mass percentage of iron element is W based on the total mass of the positive electrode material layer. Fe And W Mn W Fe The condition between b and 0.13 ≤ 100b / (W) is satisfied. Fe +W Mn )≤11.41, preferably, 0.14≤100b / (W Fe +W Mn )≤5.49. 100b / (W Fe +W Mn) When the value is regulated within the above range, it is beneficial to construct a stable CEI film, improve the kinetic performance, reduce the side reactions of the electrolyte, and thus improve the cycle performance and high-temperature storage performance of the lithium-ion battery.

[0011] In one embodiment of the present application, the compound of formula I or the compound of formula II includes at least one of the following compounds:

[0012] In one embodiment of the present application, the compound of formula III, the compound of formula IV, the compound of formula V or the compound of formula VI includes at least one of the following compounds:

[0013] In one embodiment of the present application, the mass percentage ratio a / b of additive A to additive B satisfies 0.1 ≤ a / b ≤ 10. By regulating the mass percentage ratio a / b of additive A to additive B within the above range, the volume expansion of the lithium-ion battery during cycling can be reduced, the consumption of active lithium can be decreased, and the cycle performance of the lithium-ion battery can be improved.

[0014] In one embodiment of the present application, the positive electrode material layer includes a first positive electrode material and a second positive electrode material. The first positive electrode material is LiFePO4, and the second positive electrode material is a lithium manganese composite oxide; the chemical formula of the lithium manganese composite oxide is Li 1+r Mn 1- p T p O 2-s M s , where -0.1 < r < 0.2, 0 ≤ p < 0.2, 0 ≤ s < 0.2, T includes at least one of Co, Ni, Ti, Zn, Mg, Al, V, Cr or Zr, and M includes at least one of S, N, F, Cl or Br. The introduction of the first positive electrode material is beneficial for the lithium-ion battery to stably release and absorb lithium ions during the charge and discharge cycles. At the same time, the introduction of the second positive electrode material can play a role in lithium supplementation for the positive electrode and improve the cycle performance of the lithium-ion battery.

[0015] In one embodiment of the present application, based on the total mass of the positive electrode material layer, the mass percentage content W Mn of manganese element is 2.34% to 11.69%, and the mass percentage content W Fe of iron element is 27.05% to 32.71%. The mass percentage ratio W Mn / W Fe of manganese element and iron element is 0.072 to 0.432. By regulating the mass percentage ratio W Mn / W Fe Adjusting the parameters within the above range can improve kinetic performance, reduce battery impedance, and enhance the cycle performance and high-temperature storage performance of lithium-ion batteries.

[0016] In one embodiment of this application, the cathode material layer exhibits a first diffraction peak in the range of 18° to 19° and a second diffraction peak in the range of 15° to 16° in the XRD diffraction pattern (Cu target, Kα rays) at 3.6V. The presence of both the first and second diffraction peaks indicates higher stability of the cathode active material layer, which is beneficial for improving the cycle performance of lithium-ion batteries.

[0017] In one embodiment of this application, the electrolyte includes additive C, which includes at least one of lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium tetrafluoroborate (LiBF4), or lithium bis(oxalate borate) (LiBOB). Based on the mass of the electrolyte, the mass percentage c of additive C is from 0.01% to 2%. Controlling the mass percentage c of additive C within the above range can reduce interfacial impedance, improve the ion conduction capability of the positive electrode CEI, and enhance the rate performance and cycle performance of the lithium-ion battery.

[0018] A second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application.

[0019] The beneficial effects of this application are:

[0020] This application provides an electrochemical device and an electronic device. The electrochemical device includes a positive electrode, a negative electrode, and an electrolyte. The electrolyte includes a nitrogen-containing heterocyclic compound additive A. The positive electrode includes a positive electrode material layer containing manganese. The mass percentage of additive A (a) and the mass percentage of manganese (W) are... Mn 100a / W Mn Within the scope of this application, regulation facilitates the synergistic effect of additive A and manganese in the cathode material layer, effectively reducing Mn. 3+ The uneven deposition at the negative electrode improves the kinetic performance of the electrochemical device, as well as its cycle performance and high-temperature storage performance.

[0021] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Detailed Implementation

[0022] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. All other embodiments obtained by those skilled in the art based on this application are within the scope of protection of this application.

[0023] It should be noted that, in the specific embodiments of this application, lithium-ion batteries are used as an example of electrochemical devices to explain this application, but the electrochemical devices of this application are not limited to lithium-ion batteries.

[0024] By mixing and combining different cathode materials and utilizing the characteristics of their respective charge-discharge curves, the amount of active lithium can be increased, thus improving battery life. However, the use of different materials poses a challenge to the compatibility of the electrolyte. In order to stabilize high-valence transition metals, reduce electrolyte oxidation and decomposition at the cathode during full charging, and minimize the damage of transition metals to the anode, this application introduces novel cathode hybrid materials into lithium-ion batteries to improve their lifespan. Novel additives are introduced into the electrolyte of lithium-ion batteries, and the types and amounts of additives are adjusted for different transition metals to reduce lithium-ion battery impedance, enhance cycle life, and significantly improve the battery's high-temperature storage performance.

[0025] The first aspect of this application provides an electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte; wherein the electrolyte includes an additive A, the additive A being selected from nitrogen-containing heterocyclic compounds, the additive A comprising at least one of a compound of formula I or a compound of formula II, and the mass percentage a of the additive A is from 0.05% to 4.0% based on the total mass of the electrolyte.

[0026] R1 to R9 are each independently selected from hydrogen atoms, fluorine atoms, unsubstituted or fluorinated C1 to C5 alkyl groups, unsubstituted or fluorinated C2 to C5 alkenyl groups, and unsubstituted or fluorinated C2 to C5 alkynyl groups. Fluorine substitution can be complete or partial substitution. The positive electrode includes a positive electrode material layer, which includes manganese and iron elements. Based on the total mass of the positive electrode material layer, the mass percentage of manganese is W. Mn W Mn The condition 0.43 ≤ 100a / W is satisfied between and . Mn ≤170.94, preferably, 0.86≤100a / W Mn ≤34.21.

[0027] For example, the mass percentage 'a' of additive A can be 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or a range of any two of these values. Controlling the mass percentage 'a' of additive A within the above range can reduce Mn. 3+ Uneven deposition on the negative electrode improves kinetic performance and enhances the cycle performance of lithium-ion batteries.

[0028] For example, the ratio of the mass percentage 'a' of additive A to the mass percentage of manganese is 100a / W. Mn It can be 0.43, 1, 10, 20, 30, 50, 70, 90, 110, 130, 150, 170.94, or a range of any two of these values. 100a / W Mn If the ratio is too large, for example, exceeding the upper limit of this application, the relatively excessive amount of additive A will increase the interfacial impedance of the negative electrode, increase the side reactions of the additive itself in the electrolyte, and reduce the kinetic performance, high-temperature storage performance, and cycle performance of the electrochemical device; 100a / W Mn If the ratio is too small, for example, less than the lower limit of this application, a relatively small amount of additive A cannot effectively reduce Mn. 3+ Uneven deposition disrupts the graphite structure in the negative electrode, reducing the kinetic performance, high-temperature storage, and cycle performance of the electrochemical device. The mass percentage of additive A (a) and the mass percentage of manganese (W) are compared. Mn The ratio 100a / W Mn Within the scope of this application, regulation is beneficial for additive A and manganese in the cathode material layer to exert a synergistic effect, which can effectively reduce Mn 3+ The uneven deposition at the negative electrode improves the kinetic performance of the electrochemical device, as well as its cycle performance and high-temperature storage performance.

[0029] In one embodiment of this application, the electrolyte includes additive B, which is selected from sulfonate compounds or sulfate compounds. Additive B includes at least one compound of formula III, formula IV, formula V, or formula VI. Based on the total mass of the electrolyte, the mass percentage b of additive B is from 0.05% to 4.0%.

[0030] Where R 11 R 12 R 16 R 19 Each is independently selected from hydrogen atoms, fluorine atoms, unsubstituted or fluorinated C1 to C5 alkyl groups, unsubstituted or fluorinated C2 to C5 alkenyl groups, and unsubstituted or fluorinated C2 to C5 alkynyl groups; R 10 R 15R 18 Each is independently selected from oxygen atom, methylene, ethylene, methyleneoxy, and ethoxy; R 13 R 14 Each is independently selected from unsubstituted or fluorinated C1 to C5 alkylene groups; R 17 R 20 Each is independently selected from unsubstituted or fluorinated C1 to C8 alkylene groups, unsubstituted or fluorinated C2 to C8 alkenyl groups, and unsubstituted or fluorinated C2 to C8 alkyne groups; fluorination may be fully substituted or partially substituted.

[0031] For example, the mass percentage b of additive B can be 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, or a range of any two of these values. Controlling the mass percentage b of additive B within the above range can improve CEI stability and reduce Fe. 3+ and Mn 3+ The oxidation gas production improves kinetic performance and enhances the cycle performance and high-temperature storage performance of lithium-ion batteries.

[0032] In one embodiment of this application, the mass percentage of iron element is W based on the total mass of the positive electrode material layer. Fe And W Mn W Fe The condition between b and 0.13 ≤ 100b / (W) is satisfied. Fe +W Mn )≤11.41, preferably, 0.14≤100b / (W Fe +W Mn )≤5.49. For example, 100b / (W Fe +W Mn The value of ) can be 0.13, 1, 3, 5, 7, 9, 11.41, or a range of any two of these values. 100b / (W Fe +W Mn Controlling the value of ) within the above range is beneficial for the additives and the positive electrode to work together to build a stable CEI film and reduce Fe 3+ and Mn 3+ It reduces oxidation gas production, improves kinetic performance, and reduces electrolyte side reactions, thereby improving the cycle performance and high-temperature storage performance of lithium-ion batteries.

[0033] In one embodiment of this application, the compound of formula I or the compound of formula II includes at least one of the following compounds:

[0034] In one embodiment of the present application, the compound of Formula III, the compound of Formula IV, the compound of Formula V or the compound of Formula VI includes at least one of the following compounds:

[0035] In one embodiment of the present application, the mass percentage ratio a / b of Additive A to Additive B satisfies 0.1 ≤ a / b ≤ 10. For example, the mass percentage ratio a / b of Additive A to Additive B can be 0.1, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or a range composed of any two of these values. By controlling the mass percentage ratio a / b of Additive A to Additive B within the above range, a uniform SEI / CEI with a suitable proportion of organic and inorganic components can be obtained, reducing the volume expansion of the lithium-ion battery during cycling, reducing the consumption of active lithium, and improving the cycling performance of the lithium-ion battery.

[0036] In one embodiment of the present application, the positive electrode material layer includes a first positive electrode material and a second positive electrode material. The first positive electrode material is LiFePO4, and the second positive electrode material is a lithium manganese composite oxide; the chemical formula of the lithium manganese composite oxide is Li 1+r Mn 1- p T p O 2-s M s , where -0.1 < r < 0.2, 0 ≤ p < 0.2, 0 ≤ s < 0.2, T includes at least one of Co, Ni, Ti, Zn, Mg, Al, V, Cr or Zr, and M includes at least one of S, N, F, Cl or Br. The introduction of the first positive electrode material is beneficial to the stable release and absorption of lithium ions during the charge and discharge cycles of the lithium-ion battery. At the same time, the introduction of the second positive electrode material can play a role in lithium compensation for the positive electrode, improving the cycling performance of the lithium-ion battery.

[0037] In one embodiment of the present application, based on the total mass of the positive electrode material layer, the mass percentage content W Mn of manganese element is 2.34% to 11.69%, and the mass percentage content W Fe of iron element is 27.05% to 32.71%. The mass percentage ratio W Mn / W Fe of manganese element and iron element is 0.072 to 0.432. For example, the mass percentage content W Mn of manganese element can be 2.34%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 11.69% or a range composed of any two of these values; the mass percentage content W FeIt can be 27.05%, 28%, 29%, 30%, 31%, 32%, 32.71%, or a range of any two of these values; the mass percentage of manganese and iron (W) Mn / W Fe The value can be 0.072, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.432, or a range of any two values ​​therein. Not limited to any theory, the inventors of this application have discovered that the mass percentage ratio of manganese and iron elements W... Mn / W Fe Within the above range, regulation can significantly improve kinetic performance, enhance cycle performance and high-temperature storage gas production, and reduce Mn. 3+ Dissolution deposition reduces battery impedance and improves the cycle performance and high-temperature storage performance of lithium-ion batteries.

[0038] In one embodiment of this application, the cathode material layer exhibits a first diffraction peak in the range of 18° to 19° and a second diffraction peak in the range of 15° to 16° in the XRD diffraction pattern (Cu target, Kα rays) at 3.6V. The first and second diffraction peaks correspond to the diffraction peaks of the (111) and (010) crystal planes, respectively. The lithium-ion diffusion coefficients of the (111) and (010) crystal planes corresponding to these diffraction peaks are larger, resulting in higher stability of the cathode material layer and improving the cycle performance of the lithium-ion battery.

[0039] In one embodiment of this application, the electrolyte includes additive C, which includes at least one of lithium difluorophosphate (LiPO2F2), lithium difluorooxalate borate (LiDFOB), lithium tetrafluoroborate (LiBF4), or lithium bis(oxalate borate) (LiBOB). Based on the mass of the electrolyte, the mass percentage c of additive C is from 0.01% to 2%. For example, the mass percentage c of additive C can be 0.01%, 0.1%, 0.3%, 0.5%, 0.6%, 0.7%, 0.9%, 1.1%, 1.3%, 1.5%, 1.7%, 1.9%, 2%, or a range of any two of these values. Without being limited to any theory, the inventors of this application have found that controlling the mass percentage c of additive C within the above range is beneficial for forming a large amount of phosphides and borides on the positive electrode side, reducing interfacial impedance, improving the ion conduction capability of the positive electrode CEI, and enhancing the rate performance and cycle performance of the lithium-ion battery.

[0040] In this application, the electrolyte also includes a lithium salt. There are no particular limitations on the lithium salt used; any lithium salt known in the art can be used, as long as it achieves the purpose of this application. For example, the lithium salt can be selected from at least one of LiPF6, LiBF4, LiAsF6, LiClO4, LiB(C6H5)4, LiCH3SO3, LiCF3SO3, LiN(SO2CF3)2, LiC(SO2CF3)3, and LiPO2F2. Based on the mass of the electrolyte, the mass percentage of the lithium salt can be from 8% to 15%, for example, the mass percentage of the lithium salt can be 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, or a range consisting of any two of these values. There are no particular limitations on non-aqueous solvents used in this application, as long as they achieve the purpose of this application. For example, non-aqueous solvents can include, but are not limited to, at least one of carbonate compounds, carboxylic acid ester compounds, ether compounds, or other organic solvents.

[0041] The aforementioned carbonate compounds may include, but are not limited to, at least one of chain carbonate compounds, cyclic carbonate compounds, or fluorinated carbonate compounds. The aforementioned chain carbonate compounds may include, but are not limited to, at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), or methyl ethyl carbonate (MEC). The aforementioned cyclic carbonates may include, but are not limited to, at least one of ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), or vinyl ethylene carbonate (VEC). Fluorocarbonate compounds may include, but are not limited to, at least one of fluoroethylene carbonate (FEC), 1,2-difluoroethylene carbonate, 1,1-difluoroethylene carbonate, 1,1,2-trifluoroethylene carbonate, 1,1,2,2-tetrafluoroethylene carbonate, 1-fluoro-2-methylethylene carbonate, 1-fluoro-1-methylethylene carbonate, 1,2-difluoro-1-methylethylene carbonate, 1,1,2-trifluoro-2-methylethylene carbonate, or trifluoromethylethylene carbonate. The aforementioned carboxylic acid ester compounds may include, but are not limited to, at least one of methyl formate, methyl acetate, ethyl acetate, n-propyl acetate, tert-butyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, decanolactone, valproic acid lactone, or caprolactone. The aforementioned ether compounds may include, but are not limited to, at least one of dibutyl ether, tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1-ethoxy-1-methoxyethane, 2-methyltetrahydrofuran, or tetrahydrofuran. The aforementioned other organic solvents may include, but are not limited to, at least one of dimethyl sulfoxide, 1,2-dioxolane, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolium ketone, N-methyl-2-pyrrolidone, dimethylformamide, acetonitrile, trimethyl phosphate, triethyl phosphate, or trioctyl phosphate.

[0042] This application does not impose any particular limitation on the content of non-aqueous solvents in the electrolyte, as long as the purpose of this application can be achieved. For example, based on the mass of the electrolyte, the mass percentage of non-aqueous solvents can be 75% to 91.95%, such as 75%, 80%, 85%, 90%, 91.95%, or a range of any two of these values.

[0043] In one embodiment of this application, the electrolyte may include additive A, a lithium salt, and a non-aqueous solvent. The mass percentages of additive A and the lithium salt are as described above, and the mass percentage of the non-aqueous solvent is 81% to 91.95%. Lithium-ion batteries comprising the above-described electrolyte exhibit good cycle performance and high-temperature storage performance.

[0044] In one embodiment of this application, the electrolyte may include additive A, additive B, lithium salt, and a non-aqueous solvent. The mass percentages of additive A, additive B, and lithium salt are as described above, and the mass percentage of the non-aqueous solvent is 77% to 91.9%. Lithium-ion batteries comprising the above-described electrolyte exhibit good cycle performance and high-temperature storage performance.

[0045] In one embodiment of this application, the electrolyte may include additive A, additive C, lithium salt, and a non-aqueous solvent. The mass percentages of additive A, additive C, and lithium salt are as described above, and the mass percentage of the non-aqueous solvent is 79% to 91.94%. Lithium-ion batteries comprising the above-described electrolyte exhibit good cycle performance and high-temperature storage performance.

[0046] In one embodiment of this application, the electrolyte may include additive A, additive B, additive C, lithium salt, and a non-aqueous solvent. The mass percentages of additive A, additive B, additive C, and lithium salt are as described above, and the mass percentage of the non-aqueous solvent is 75% to 91.8%. Lithium-ion batteries comprising the above-described electrolyte exhibit good cycle performance and high-temperature storage performance.

[0047] In this application, the positive electrode includes a positive current collector and a positive electrode material layer disposed on at least one surface of the positive current collector. The phrase "positive electrode material layer disposed on at least one surface of the positive current collector" means that the positive electrode material layer can be disposed on one surface of the positive current collector along its thickness direction, or on two surfaces of the positive current collector along its thickness direction. It should be noted that "surface" here can refer to the entire surface area of ​​the positive current collector, or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved.

[0048] This application does not impose any particular restrictions on the positive electrode current collector, as long as it can achieve the purpose of this application. For example, it may include aluminum foil, aluminum alloy foil, or composite current collector (such as aluminum-carbon composite current collector).

[0049] In this application, the positive electrode material layer may further include a conductive agent and a binder. This application does not impose any particular restrictions on the types of conductive agents and binders, as long as they achieve the purpose of this application. This application does not impose any particular restrictions on the mass ratio of the positive electrode active material, conductive agent, and binder in the positive electrode material layer; those skilled in the art can select them according to actual needs, as long as the purpose of this application is achieved.

[0050] This application does not impose any particular limitation on the adhesive, as long as it can achieve the purpose of this application. For example, the adhesive may include, but is not limited to, adhesive polymers, such as at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyolefins, sodium carboxymethyl cellulose, lithium carboxymethyl cellulose, modified polyvinylidene fluoride, modified SBR rubber, or polyurethane, wherein polyolefin adhesives include at least one of polyethylene, polypropylene, polyolefin ester, polyolefin alcohol, or polyacrylic acid.

[0051] This application does not impose any particular limitation on conductive agents, as long as they can achieve the purpose of this application. For example, conductive agents may include, but are not limited to, carbon-based materials, metal-based materials, conductive polymers, or mixtures thereof; wherein carbon-based materials include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, or carbon fiber; metal-based materials include, for example, metal powders or metal fibers of copper, nickel, aluminum, silver, etc.; and conductive polymers include polyphenylene derivatives.

[0052] This application does not impose any particular limitations on the thickness of the positive electrode current collector and the positive electrode material layer, as long as the purpose of this application can be achieved. For example, the thickness of the positive electrode current collector can be 5 μm to 20 μm, and the thickness of the single-sided positive electrode material layer can be 30 μm to 120 μm.

[0053] Optionally, the positive electrode may further include a conductive layer located between the positive current collector and the positive electrode material layer. The composition of the conductive layer is not particularly limited and can be any conductive layer commonly used in the art. The conductive layer includes a conductive agent and a binder. This application does not impose any particular limitation on the conductive agent and binder in the conductive layer; for example, it can be at least one of the aforementioned conductive agents and binders.

[0054] In this application, the electrochemical device also includes a separator membrane. This application does not impose any particular limitation on the separator membrane, as long as it achieves the purpose of this application. For example, the material of the separator membrane may include, but is not limited to, at least one of polyethylene (PE), polyolefins (PO) primarily composed of polypropylene (PP), polyester (e.g., polyethylene terephthalate (PET) film), cellulose, polyimide (PI), polyamide (PA), spandex, or aramid. The type of separator membrane may include at least one of woven membrane, nonwoven membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0055] In some embodiments of this application, the separator may include a substrate layer and a surface treatment layer. The substrate layer may be a nonwoven fabric, membrane, or composite membrane with a porous structure, and the material of the substrate layer may include at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Optionally, a polypropylene porous membrane, a polyethylene porous membrane, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite membrane may be used.

[0056] Optionally, a surface treatment layer is provided on at least one surface of the substrate layer. The surface treatment layer may be a polymer layer or an inorganic layer, or a layer formed by mixing polymers and inorganic substances.

[0057] In some embodiments of this application, the inorganic layer comprises inorganic particles and a binder. This application does not particularly limit the inorganic particles; for example, the inorganic particles may include at least one selected from alumina, silicon oxide, magnesium oxide, titanium oxide, hafnium dioxide, tin oxide, cerium dioxide, nickel oxide, zinc oxide, calcium oxide, zirconium oxide, yttrium oxide, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. This application does not particularly limit the binder; for example, the binder may be at least one of the binders described above. In some embodiments of this application, the polymer layer comprises a polymer, the polymer material of which includes at least one selected from polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylate, polyvinylpyrrolidone, polyvinyl ether, or polyvinylidene fluoride or poly(vinylidene fluoride-hexafluoropropylene).

[0058] In some embodiments of this application, the inorganic layer may also include a thickener and a wetting agent. This application does not have any particular restrictions on the types of thickeners and wetting agents, as long as they can achieve the purpose of this application. For example, the thickener may include, but is not limited to, at least one of sodium carboxymethyl cellulose or lithium carboxymethyl cellulose; the wetting agent may include, but is not limited to, at least one of dimethylsiloxane, sodium dodecyl sulfate, trialkyl phosphate, methyl decanoate, and dodecyl acetate.

[0059] In this application, there is no particular limitation on the thickness of the separator, as long as it can achieve the purpose of this application. For example, the thickness of the separator can be from 4 μm to 30 μm.

[0060] In the present application, the electrochemical device further includes a negative electrode plate, which includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector. The above "the negative electrode active material layer is disposed on at least one surface of the negative electrode current collector" means that the negative electrode active material layer can be disposed on one surface of the negative electrode current collector along its own thickness direction, or can be disposed on two surfaces of the negative electrode current collector along its own thickness direction. It should be noted that the "surface" here can be the entire area of the surface of the negative electrode current collector, or a partial area of the surface of the negative electrode current collector. There is no special limitation in the present application, as long as the purpose of the present application can be achieved.

[0061] The present application does not particularly limit the negative electrode current collector, as long as the purpose of the present application can be achieved. For example, it can include copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam or composite current collector. Exemplarily, the composite current collector can be a lithium-copper composite current collector, a carbon-copper composite current collector, a nickel-copper composite current collector, a titanium-copper composite current collector, etc.

[0062] The negative electrode active material layer of the present application includes a negative electrode active material. The present application does not particularly limit the type of the negative electrode active material, as long as the purpose of the present application can be achieved. For example, the negative electrode active material can include natural graphite, artificial graphite, mesocarbon microbeads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, SiO x (0 < x < 2), Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, lithium titanate with a spinel structure Li4Ti5O 12 , Li-Al alloy or metallic lithium, or at least one of them.

[0063] The present application does not particularly limit the thickness of the negative electrode current collector and the negative electrode active material layer, as long as the purpose of the present application can be achieved. For example, the thickness of the negative electrode current collector is 4 μm to 12 μm, and the thickness of the negative electrode active material layer is 30 μm to 130 μm.

[0064] In some embodiments of this application, the negative electrode active material layer may further include a conductive agent and a binder. This application does not impose any particular restrictions on the types of conductive agents and binders, as long as they achieve the purpose of this application. For example, binders may include, but are not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene 1,1-difluoroethylene, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, or nylon, etc. Conductive agents may include, but are not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. Carbon-based materials are selected from natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or any combination thereof; metal-based materials are selected from metal powder, metal fiber, copper, nickel, aluminum, or silver; and conductive polymers are polyphenylene derivatives. This application does not impose any particular restrictions on the mass ratio of the negative electrode material, conductive agent, and binder in the negative electrode active material layer. Those skilled in the art can select according to actual needs, as long as the purpose of this application is achieved.

[0065] The electrochemical device also includes a housing for accommodating the positive electrode, separator, negative electrode, and electrolyte, as well as other components known in the field of electrochemical devices. This application does not limit the scope of these other components. This application does not impose any particular limitation on the housing; it can be a housing known in the art, as long as it achieves the purpose of this application. For example, the housing can be a rigid housing or a flexible housing. The material of the rigid housing can be metal; this application does not limit the type of metal and can use known metal rigid housings, as long as they achieve the purpose of this application. The flexible housing can be a metal-plastic film, such as aluminum-plastic film, steel-plastic film, etc.

[0066] The preparation process of the electrochemical device described in this application is well known to those skilled in the art, and this application does not impose any particular limitations. For example, the preparation process of the electrochemical device may include, but is not limited to, the following steps: stacking the positive electrode, the separator, and the negative electrode in sequence, and performing operations such as winding and folding as needed to obtain a wound electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the electrochemical device. Alternatively, stacking the positive electrode, the separator, and the negative electrode in sequence, and then fixing the four corners of the entire stacked structure with tape to obtain a stacked electrode assembly; placing the electrode assembly into a housing; injecting electrolyte into the housing and sealing it to obtain the electrochemical device. In addition, overcurrent protection elements, conductive plates, etc., may be placed in the housing as needed to prevent pressure rise and overcharging / discharging inside the electrochemical device.

[0067] A second aspect of this application provides an electronic device that includes the electrochemical device provided in the first aspect of this application.

[0068] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen-based computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries, and lithium-ion capacitors, etc.

[0069] Example

[0070] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0071] Test methods and equipment

[0072] Mn and Fe element content test

[0073] After discharging the lithium-ion battery to 2.5V at 0.5C, the positive electrode sheet was removed and cut into 10 small circular pieces with a diameter of 16mm. The positive electrode material layer was scraped off from the positive current collector of each small circular piece with a knife to obtain powder. 0.2g of the powder was weighed and digested with 10mL of aqua regia, and then diluted to 100mL in a volumetric flask with deionized water. The sample was tested using an inductively coupled plasma analyzer (ICP, model AVIO-200) with the radio frequency generator (RF) frequency set to 40.68MHz, argon secondary pressure set to 0.6MPa, RF power set to 1400W, and pump speed set to 1.0mL / min. The sample was then qualitatively analyzed based on the spectral wavelength, and quantitatively calculated based on the proportionality between the spectral intensity and concentration. The average of the elemental contents obtained from the 10 small circular pieces was taken as the mass percentage of iron and manganese in the positive electrode material layer.

[0074] Electrolyte composition testing

[0075] The lithium-ion battery was discharged to 2.5V at 0.5C and then disassembled to obtain positive and negative electrode plates. These plates were then centrifuged in centrifuge tubes to obtain the electrolyte. The percentage content of additives A and B in the centrifuged electrolyte was analyzed using gas chromatography-mass spectrometry (GC-MS).

[0076] XRD test

[0077] 1.0g of the binder sample prepared in each embodiment and comparative example was weighed and poured into the groove of the glass sample holder. It was then compacted and smoothed with a glass slide. The sample was tested using an X-ray diffractometer (model Bruker, D8) according to JJS K 0131-1996 "General Rules for X-ray Diffraction Analysis". The test voltage was set to 3.6V, the current to 30mA, the scanning angle range to 10° to 90°, the scanning step size to 0.0167°, and the time set for each step to 0.24s. The XRD diffraction pattern of the cathode material layer was obtained.

[0078] Cyclic performance test

[0079] At 45℃, the lithium-ion battery was charged at 1C to 3.6V, then charged at a constant voltage to 0.05C at 3.6V, and then discharged at 1C to 2.5V. This cycle was repeated for 3000 cycles. The discharge capacity after one cycle was recorded as the initial discharge capacity C0, and the discharge capacity after 3000 cycles was recorded as C1. The cycle capacity retention rate (%) = C1 / C0 × 100%.

[0080] High-temperature storage performance test

[0081] The lithium-ion battery was charged at 25℃ with a constant current of 0.5C to 3.6V, and then charged with a constant voltage to a current of 0.05C. The thickness of the lithium-ion battery was measured and recorded as d0. The battery was then placed in a 60℃ oven for 180 days, and the thickness at this point was recorded as d. The thickness expansion rate (%) of the lithium-ion battery after storage at 60℃ is calculated as (d - d0) / d0 × 100%.

[0082] 50% state-of-charge impedance test

[0083] At 25℃, the lithium-ion battery is discharged to 2.5V at a current of 0.5C, allowed to rest for 5 minutes, and then charged to 3.6V at a current of 0.5C. The battery is then held at 3.6V until a constant voltage of 0.025C is reached. After resting for 5 minutes, the battery is discharged to 2.5V at a current of 0.1C, and the discharged capacity is recorded as C1. The battery is then charged to 3.6V using 0.5C1 of the discharged capacity, held at 3.6V until a constant voltage of 0.025C1 is reached, allowed to rest for 5 minutes, and then discharged for 5 hours using a current of 0.1C1. The battery voltage at this point is recorded as V1. Finally, the battery is discharged for 1 second using a current of 1C, and the voltage at the end of the discharge is recorded as V2. The formula for calculating the 50% state-of-charge impedance is: 50% state-of-charge impedance (mΩ) = (V1 - V2) / (1C - 0.1C1).

[0084] Ratio Performance Test

[0085] At 25℃, the lithium-ion battery was charged to 3.6V at 0.3C, then charged at 3.6V at a constant voltage to 0.05C, allowed to rest for 5 minutes, and then discharged at 0.3C to 2.5V. The discharge capacity C at this point was recorded. (放电倍率) The discharge rate of the above process is successively adjusted to 0.5C, 1.0C, and 2.0C, and repeated once for each. The rate discharge capacity retention rate is then calculated. Rate discharge capacity retention rate (%) = C (2.0C) / C (0.3C) ×100%.

[0086] Example 1-1

[0087] <Preparation of the positive electrode>

[0088] The first positive electrode material LiFePO4, the second positive electrode material LiMnO2, conductive carbon black, and binder PVDF were mixed in a mass ratio of 86.5:10:2.0:1.5. N-methylpyrrolidone (NMP) was added, and the mixture was stirred until homogeneous to obtain a positive electrode slurry with a solid content of 70 wt%. The positive electrode slurry was uniformly coated onto one surface of a 12 μm thick aluminum foil current collector and dried at 120°C to obtain a positive electrode sheet with a single-sided coating of a 100 μm thick positive electrode material layer. The above steps were repeated on the other surface of the aluminum foil to obtain a positive electrode sheet with a double-sided coating of the positive electrode material layer. The sheet was dried under vacuum at 120°C, and then cold-pressed, cut, and slit to obtain a positive electrode sheet with dimensions of 74 mm × 867 mm. The mass percentage of manganese, W, is based on the total mass of the positive electrode material layers. Mn The iron content (W) is 5.85% by mass. Fe It is 30.59%.

[0089] <Preparation of Negative Electrode Sheets>

[0090] Artificial graphite (negative electrode active material), styrene-butadiene rubber (binder), and acetylene black (conductive agent) were mixed in a mass ratio of 97.4:1.4:1.2. Deionized water was added as a solvent to prepare a slurry with a solid content of 45 wt%. The slurry was stirred evenly in a vacuum mixer to obtain the negative electrode slurry. The negative electrode slurry was uniformly coated onto one surface of a 6 μm thick copper foil used as a negative electrode current collector and dried at 120°C to obtain a negative electrode sheet with a single-sided negative electrode material layer. The coating weight of the negative electrode material layer was 142 mg / 1540 mm². 2 Then, the above steps are repeated on the other surface of the copper foil to obtain a negative electrode sheet with a double-sided coating of negative electrode material. After drying at 120℃, it is cold-pressed, then cut and welded with tabs to obtain a negative electrode sheet with a size of 78mm×875mm for use. The thickness of the single-sided negative electrode material layer after cold pressing is 54.5μm.

[0091] <Preparation of Electrolyte>

[0092] In an argon-atmospheric glove box with a water content of <10ppm, ethylene carbonate (EC), propylene carbonate (PC), and diethyl carbonate (DEC) are mixed in a mass ratio of 1:1:1 to obtain a base solvent. Compound of formula I-1 and lithium salt LiPF6 are added, dissolved, and mixed evenly to obtain an electrolyte. The total mass of the electrolyte contains 12.5% ​​lithium salt LiPF6, 0.05% compound of formula I-1, and the remainder is the base solvent.

[0093] <Isolation membrane>

[0094] A single-layer PE porous polymer film with a thickness of 16μm, a porosity of 39%, an inorganic coating of Al2O3, and organic particles of polyvinylidene fluoride was used as the separator.

[0095] <Preparation of Lithium-ion Batteries>

[0096] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator acting as a separator between the positive and negative electrodes. The resulting battery is then wound to obtain a bare battery. The bare battery is placed in an outer packaging foil, and the prepared electrolyte is injected into the dried battery. After vacuum sealing, settling, formation, and shaping, the lithium-ion battery is complete. The formation process involves: charging at 45±5℃ with a constant current of 0.1C for 10 minutes, followed by constant current charging at 0.5C to a specified voltage Q = 4.5V, then constant voltage charging until the current is less than or equal to 0.05C, and finally constant current discharging at 0.5C to 2.5V.

[0097] Examples 1-2 to Examples 1-9

[0098] Except for adjusting the mass percentage of the first and second positive electrode materials according to Table 1 in the <Preparation of Positive Electrode Sheet>, keeping the mass percentage of conductive carbon black and binder PVDF unchanged, adjusting the mass percentage of additive A according to Table 1 in the <Preparation of Electrolyte>, changing the mass percentage of the base solvent accordingly, keeping the mass ratio of each component in the base solvent unchanged, and keeping the mass percentage of lithium salt LiPF6 unchanged, the rest is the same as in Example 1-1.

[0099] Examples 2-1 to 2-26

[0100] Except for adjusting the mass percentage of the first positive electrode material and the type and mass percentage of the second positive electrode material according to Table 2 in the <Preparation of Positive Electrode Sheet>, keeping the mass percentage of conductive carbon black and binder PVDF unchanged, adding additive B in the <Preparation of Electrolyte>, and adjusting the type and mass percentage of additive A and the type and mass percentage of additive B according to Table 2, changing the mass percentage of the base solvent accordingly, keeping the mass ratio of each component in the base solvent unchanged, and keeping the mass percentage of lithium salt LiPF6 unchanged, the rest is the same as in Example 1-1.

[0101] Examples 3-1 to 3-16

[0102] Except for adjusting the type of the second positive electrode material according to Table 3 in <Preparation of the positive electrode sheet>, adding additive C in <Preparation of the electrolyte> and adjusting the type and mass percentage of additive A, additive B, and additive C according to Table 4, changing the mass percentage of the base solvent accordingly, keeping the mass ratio of each component in the base solvent unchanged, and keeping the mass percentage of lithium salt LiPF6 unchanged, everything else is the same as in Example 2-1.

[0103] Comparative Example 1

[0104] Except that additive A is not added in the <Preparation of Electrolyte>, the mass percentage of the base solvent is changed accordingly, the mass ratio of each component in the base solvent remains unchanged, and the mass percentage of lithium salt LiPF6 remains unchanged, the rest is the same as in Example 1-1.

[0105] Comparative Example 2

[0106] Except for adjusting the mass percentage of the first and second positive electrode materials according to Table 1 in the <Preparation of Positive Electrode Sheet>, keeping the mass percentage of conductive carbon black and binder PVDF unchanged, adjusting the mass percentage of additive A according to Table 1 in the <Preparation of Electrolyte>, changing the mass percentage of the base solvent accordingly, keeping the mass ratio of each component in the base solvent unchanged, and keeping the mass percentage of lithium salt LiPF6 unchanged, the rest is the same as in Example 1-1.

[0107] Comparative Example 3

[0108] Except for adjusting the mass percentage of the first and second positive electrode materials according to Table 1 in the <Preparation of Positive Electrode Sheet>, and keeping the mass percentage of conductive carbon black and binder PVDF unchanged, the rest is the same as in Example 1-1.

[0109] Comparative Example 4

[0110] Except that in the <Preparation of Positive Electrode Sheet>, no second positive electrode material is added, only the first positive electrode material is added, and the mass percentage of conductive carbon black and binder PVDF remains unchanged, the rest is the same as in Example 1-1.

[0111] The preparation parameters and performance parameters of each embodiment and comparative example are shown in Tables 1 to 3.

[0112] As can be seen from Examples 1-1 to Examples 1-9 and Comparative Examples 1 to Comparative Examples 3, when the electrolyte and the positive electrode combination of the second positive electrode material with additive A are applied to lithium-ion batteries, the mass percentage a of additive A and 100a / W Mn When the value is within the range of this application, the lithium-ion battery exhibits a low 50% state-of-charge impedance, high cycle capacity retention, low thickness expansion rate at 60°C storage, and good rate discharge capacity retention, indicating improved cycle performance and high-temperature storage performance. The mass percentage content of additive A in Comparative Examples 1 to 3 and / or 100a / W Mn The values ​​are outside the scope of this application. The resulting lithium-ion battery has a high 50% state-of-charge impedance, low cycle capacity retention, and high thickness expansion rate at 60°C, indicating poor cycle performance and high-temperature storage performance. In Comparative Example 4, the positive electrode material layer does not contain manganese, resulting in a lithium-ion battery with a high 50% state-of-charge impedance and low cycle capacity retention, indicating low cycle performance.

[0113] The mass percentage b of additive B typically affects the cycle performance and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 2-1 to 2-7, when the mass percentage b of additive B is within the range of this application, the lithium-ion battery exhibits lower 50% state-of-charge impedance, higher cycle capacity retention, reduced thickness expansion rate at 60°C storage, and better rate discharge capacity retention, indicating improved cycle performance and high-temperature storage performance.

[0114] Iron content by mass W Fe Manganese content by mass W Mn 100b / (W) Fe +W Mn The ratios a and b typically affect the cycle performance and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 2-8 to 2-15, when the mass percentage of iron W... Fe Manganese content by mass W Mn 100b / (W) Fe +WMn When the values ​​of a and b are within the scope of this application, the lithium-ion battery has a lower 50% state-of-charge impedance, a higher cycle capacity retention rate, a lower thickness expansion rate at 60°C storage, and a better rate discharge capacity retention rate, indicating that the cycle performance and high-temperature storage performance of the lithium-ion battery are improved.

[0115] The type of additive A typically affects the cycle performance and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 2-1, 2-16 to 2-18, when the type of additive A is within the scope of this application, the lithium-ion battery has a low 50% state-of-charge impedance and a low thickness expansion rate at 60°C, and a high cycle capacity retention rate. Therefore, the lithium-ion battery in this application has good cycle performance and high-temperature storage performance.

[0116] The type of additive B typically affects the cycle performance and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 2-1, 2-19 to 2-21, when the type of additive B is within the scope of this application, the lithium-ion battery exhibits low 50% state-of-charge impedance and low thickness expansion rate at 60°C storage, as well as high cycle capacity retention. Therefore, the lithium-ion battery in this application possesses excellent cycle performance and high-temperature storage performance.

[0117] The a / b value typically affects the cycle performance and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 2-10 to 2-15 and Example 2-22, when the a / b value of the additive is within the range of this application, the lithium-ion battery exhibits lower 50% state-of-charge impedance and 60°C storage thickness expansion rate, and higher cycle capacity retention. In Examples 2-22, the a / b value is outside the range of this application, resulting in higher 50% state-of-charge impedance and 60°C storage thickness expansion rate, and lower cycle capacity retention. Therefore, the lithium-ion battery in this application possesses good cycle performance and high-temperature storage performance.

[0118] The type of second cathode material typically affects the cycle performance and high-temperature storage performance of lithium-ion batteries. As can be seen from Examples 2-1, 2-23 to 2-26, when the type of the second cathode material falls within the scope of this application, and the cathode material layer exhibits a first diffraction peak and a second diffraction peak in the XRD diffraction pattern (Cu target, Kα rays) at 3.6V, the lithium-ion battery exhibits lower 50% state-of-charge impedance and lower thickness expansion rate at 60°C storage, resulting in higher cycle capacity retention.

[0119] The type of additive C typically affects the cycle performance, high-temperature storage performance, and rate performance of lithium-ion batteries. As can be seen from Examples 3-1 to 3-13, when the electrolyte incorporating additive C is used in lithium-ion batteries, and the mass percentage c of additive C is within the range specified in this application, the 50% state-of-charge impedance of the lithium-ion battery is further reduced, the cycle capacity retention rate is further improved, the thickness expansion rate at 60°C storage is lower, and the rate performance is further enhanced. Therefore, the lithium-ion battery in this application possesses excellent cycle performance, high-temperature storage performance, and rate performance.

[0120] Different types of electrolytes and second cathode materials typically affect the cycle performance and high-temperature storage performance of lithium-ion batteries. Examples 3-14 to 3-16 demonstrate that when the electrolyte and second cathode material within the scope of this application are used in combination, the cycle capacity retention of the lithium-ion battery is further improved, and the 50% state-of-charge impedance and the thickness expansion rate at 60°C storage are further reduced, indicating that the lithium-ion battery possesses excellent cycle performance, high-temperature storage performance, and rate performance.

[0121] The terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, or article that comprises a list of elements includes not only those elements but also other elements not expressly listed or inherent to such process, method, or article.

[0122] The various embodiments in this specification are described in a related manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0123] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. An electrochemical device comprising a positive electrode, a negative electrode, and an electrolyte; wherein, The electrolyte includes additive A, which includes at least one of a compound of formula I or a compound of formula II, and the mass percentage a of additive A is from 0.05% to 4.0% based on the total mass of the electrolyte. R1 to R9 are each independently selected from hydrogen atoms, fluorine atoms, unsubstituted or fluorinated C1 to C5 alkyl groups, unsubstituted or fluorinated C2 to C5 alkenyl groups, and unsubstituted or fluorinated C2 to C5 alkynyl groups. The positive electrode sheet includes a positive electrode material layer, which comprises manganese and iron. Based on the total mass of the positive electrode material layer, the mass percentage of manganese is W. Mn ; W Mn The condition 0.43 ≤ 100a / W is satisfied between and . Mn ≤170.

94.

2. The electrochemical device according to claim 1, wherein, 0.86≤100a / W Mn ≤34.21。 3. The electrochemical device according to claim 1, wherein, The electrolyte includes additive B, which includes at least one of compound III, compound IV, compound V or compound VI, and the mass percentage b of additive B is from 0.05% to 4.0% based on the total mass of the electrolyte. Where R 11 R 12 R 16 R 19 Each is independently selected from hydrogen atoms, fluorine atoms, unsubstituted or fluorinated C1 to C5 alkyl groups, unsubstituted or fluorinated C2 to C5 alkenyl groups, and unsubstituted or fluorinated C2 to C5 alkynyl groups; R 10 R 15 R 18 Each is independently selected from oxygen atom, methylene, ethylene, methyleneoxy, and ethoxy; R 13 R 14 Each is independently selected from unsubstituted or fluorinated C1 to C5 alkylene groups; R 17 R 20 Each is independently selected from unsubstituted or fluorinated C1 to C8 alkylene groups, unsubstituted or fluorinated C2 to C8 alkenyl groups, and unsubstituted or fluorinated C2 to C8 alkyne groups.

4. The electrochemical device according to claim 3, wherein, Based on the total mass of the positive electrode material layer, the mass percentage of iron is W. Fe And W Mn W Fe The condition between b and 0.13 ≤ 100b / (W) is satisfied. Fe +W Mn )≤11.

41.

5. The electrochemical device according to claim 4, wherein, 0.14≤100b / (W Fe +W Mn )≤5.49。 6. The electrochemical device according to claim 1, wherein, The compound of formula I or the compound of formula II includes at least one of the following compounds:

7. The electrochemical device according to claim 3, wherein, The compound of formula III, formula IV, formula V or formula VI includes at least one of the following compounds:

8. The electrochemical device according to claim 3, wherein, The mass percentage ratio of additive A to additive B, a / b, satisfies 0.1 ≤ a / b ≤ 10.

9. The electrochemical device according to claim 4, wherein, The positive electrode material layer includes a first positive electrode material and a second positive electrode material. The first positive electrode material is LiFePO4, and the second positive electrode material is a lithium manganese composite oxide; the chemical formula of the lithium manganese composite oxide is Li 1+r Mn 1-p T p O 2-s M s , where -0.1 < r < 0.2, 0 ≤ p < 0.2, 0 ≤ s < 0.2, T includes at least one of Co, Ni, Ti, Zn, Mg, Al, V, Cr or Zr, and M includes at least one of S, N, F, Cl or Br.

10. The electrochemical device according to claim 4, wherein, Based on the total mass of the positive electrode material layer, the mass percentage W of the manganese element Mn The iron content (W) ranges from 2.34% to 11.69% by mass. Fe The mass percentage of manganese and iron is between 27.05% and 32.71% (W). Mn / W Fe The values ​​range from 0.072 to 0.

432.

11. The electrochemical device according to claim 1, wherein, In the XRD diffraction pattern of the cathode material layer at 3.6V, there is a first diffraction peak in the range of 18° to 19° and a second diffraction peak in the range of 15° to 16°.

12. The electrochemical device according to claim 1, wherein, The electrolyte includes additive C, which includes at least one of lithium difluorophosphate, lithium difluorooxalate borate, lithium tetrafluoroborate, or lithium bis(oxalate borate), and the mass percentage c of additive C is 0.01% to 2% based on the mass of the electrolyte.

13. An electronic device comprising the electrochemical device according to any one of claims 1 to 12.

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