Lithium ion battery and electric device comprising same

Abstract

A lithium ion battery and an electric device comprising same. The lithium ion battery comprises a positive electrode sheet and an electrolyte; the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material layer arranged on at least one surface of the positive electrode current collector, and the positive electrode active material layer comprises a positive electrode lithium replenishing agent; the electrolyte comprises a non-aqueous solvent and an additive; the additive comprises a sulfur-containing compound, and the non-aqueous solvent comprises an ether compound.

Description

Lithium-ion battery and power-consuming device containing same

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202310882920.X filed on July 19, 2023, entitled “A lithium-ion battery and an electrical device comprising the same,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the technical field of lithium-ion batteries, and in particular to a lithium-ion battery and an electrical device containing the same. Background Art

[0004] In recent years, the application scope of secondary batteries, represented by lithium-ion batteries, has become increasingly broad. Secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As secondary batteries have achieved great development, higher requirements have been placed on their performance.

[0005] During the initial charge and discharge process of a secondary battery, a solid electrolyte film (SEI film) forms on the negative electrode surface, depleting active ions and leading to a decrease in capacity. Although this can be improved by adding lithium to the electrode (for example, adding a small amount of high-capacity material as a lithium supplement during the positive electrode slurry process), the effect of this on the initial capacity is limited and difficult to meet the needs of practical applications.

[0006] Summary of the Invention

[0007] The purpose of the present application is to provide a lithium-ion battery and an electrical device containing the same. When a positive electrode lithium supplement is used and a corresponding electrolyte system is used, the lithium-ion battery can have good initial gram capacity, cycle stability and rate performance.

[0008] To this end, a first aspect of the present application provides a lithium-ion battery comprising a positive electrode sheet and an electrolyte;

[0009] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode lithium supplement;

[0010] The electrolyte includes a non-aqueous solvent and an additive; the non-aqueous solvent includes an ether compound, and the additive includes a sulfur-containing compound.

[0011] By incorporating both sulfur-containing compounds and ether compounds into the electrolyte, the interaction between the electrolyte and the positive electrode lithium supplement material interface is improved, thereby improving ion mobility at the positive electrode lithium supplement material interface, reducing the consumption of active lithium in side reactions, and playing a role in reducing polarization. This helps overcome the problem of insufficient initial gram capacity due to positive electrode polarization, and simultaneously improves cycle stability and rate performance.

[0012] In any embodiment, the ether compound includes a chain ether compound.

[0013] Compared with cyclic ether compounds, when chain ether compounds are used, they have stronger chelating ability with cations and can further reduce the viscosity of the electrolyte, which is beneficial to the improvement of ionic conductivity.

[0014] In any embodiment, the chain ether compound includes at least one of the following groups: ethylene glycol dimethyl ether (DME), ethylene glycol diethyl ether (DEE), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TRGDME), tetraethylene glycol dimethyl ether (TEGDME), dipropyl ether, dibutyl ether, etc.

[0015] In any embodiment, the mass percentage of the ether compound in the non-aqueous solvent is 15% to 30%.

[0016] When the mass proportion of ether compounds in non-aqueous solvents is 15% to 30%, a good solvent system can be provided, so that when the solvent dissolves higher concentrations of lithium salts and sulfur-containing compounds, it will not cause a significant increase in viscosity, which helps to increase the depolarization effect and expand the electrochemical stability window, maintaining better cycle stability and rate performance.

[0017] In any embodiment, the mass percentage of the ether compound in the non-aqueous solvent is 15% to 25%.

[0018] Optimizing the mass percentage of ether compounds in non-aqueous solvents can help further improve battery performance.

[0019] In any embodiment, the sulfur-containing compound comprises a sulfonate compound.

[0020] In any embodiment, the sulfonate compound includes at least one of the following group: 1,3 propane sultone, 1,3 propylene sultone, 1,4 butane sultone, methylene methane disulfonate, and the like.

[0021] Compared with the use of other sulfur-containing compounds such as sulfate compounds, the use of sulfonate compounds can promote the stable formation of SEI film, reduce the gas production and have low corrosiveness, which is more conducive to interface stability and safety.

[0022] In any embodiment, the mass percentage of the sulfur-containing compound in the electrolyte is 0.5% to 4%.

[0023] When the mass percentage of sulfur-containing compounds in the electrolyte is 0.5% to 4%, it is beneficial to improve the liquid phase conduction efficiency and the ion mobility at the interface of the positive electrode material, thereby improving the interface stability.

[0024] In any embodiment, the mass percentage of the sulfur-containing compound in the electrolyte is 1.5%-3.5%.

[0025] By optimizing the mass percentage of sulfur-containing compounds in the electrolyte, it is helpful to further improve battery performance.

[0026] In any embodiment, the electrolyte further comprises a lithium salt dissolved in the non-aqueous solvent; and in the electrolyte, the concentration of the lithium salt is 0.5 to 1.6 mol / L.

[0027] When the lithium salt concentration is 0.5-1.6 mol / L, it is beneficial for the electrolyte to maintain excellent ionic conductivity, thereby improving the ion mobility at the interface of the positive electrode lithium supplement material and optimizing the depolarization effect.

[0028] In any embodiment, the mass percentage of the sulfur-containing compound in the electrolyte is 1.5% to 3.5%; the mass percentage of the ether compound in the non-aqueous solvent is 15% to 25%; and the concentration of the lithium salt in the electrolyte is 1 to 1.4 mol / L.

[0029] When the amounts of the lithium salt, the sulfur-containing compound, and the ether compound all meet the above ranges, the battery performance can be further significantly improved.

[0030] In any embodiment, the positive electrode lithium supplement comprises at least one compound that meets the following formula: Li x M y O z , wherein M is one or more elements selected from Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Ni, Sb, Ti, V, Mo, and Sn, and 1≤x≤8, 0<y, 0<z<13.

[0031] In any embodiment, the positive electrode lithium supplement comprises at least one of the following: Li5FeO4, Li5Fe5O8, Li6CoO4, Li2NiO2, Li2O, Li2O2, Li6MnO4, Li6ZnO4, Li2CuO2, Li2CoO2, Li2MnO2, Li2C2O4, Li2Ni 0.5 Mn 1.5O4、Li(Ni 0.8 Co 0.1 Mn 0.1 ) 1.3 O2.

[0032] In a second aspect of the present application, an electrical device is provided, which includes the lithium-ion battery described in the first aspect of the present application.

[0033] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0034] This application utilizes an electrolyte containing both a sulfur-containing compound and an ether compound in a positive electrode lithium replenishment system with electrode polarization, thereby improving the liquid-phase conduction efficiency and the ion mobility at the positive electrode material interface, thereby reducing polarization. This helps overcome the problem of insufficient initial gram capacity due to positive electrode polarization and simultaneously improves the battery's cycle stability and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiment below. The accompanying drawings are for illustration purposes only and are not to be considered as limiting the present application. The same reference symbols are used throughout the drawings to represent the same components. In the drawings:

[0036] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0037] FIG2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG1 ;

[0038] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0039] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0040] FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;

[0041] 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application;

[0042] Description of reference numerals:

[0043] 1. Battery pack; 2. Upper case; 3. Lower case; 4. Battery module; 5. Lithium-ion battery; 5. Casing; 5. Electrode assembly; 5. Cover. DETAILED DESCRIPTION

[0044] The exemplary embodiments of the present disclosure will be described in more detail below. It should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. Instead, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0045] The "ranges" disclosed in this application are defined in the form of lower limits and upper limits, where a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of the particular range. Ranges defined in this manner can be inclusive or exclusive of the end values ​​and can be combined arbitrarily, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. In addition, if minimum range values ​​of 1 and 2 are listed, and maximum range values ​​of 3, 4, and 5 are listed, the following ranges are all contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" is an abbreviation for any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0047] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0048] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0049] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0050] To address the problem of capacity loss caused by active ion depletion during the initial charge and discharge of secondary batteries, electrode lithium supplements have been used to some extent. For example, a small amount of high-capacity material can be added as a lithium supplement during the cathode slurry mixing process to improve this problem. However, the effect of applying electrode lithium supplements on the initial capacity is limited, making it difficult to meet the needs of practical applications, thus limiting the application of secondary batteries.

[0051] The present application found that although the application of positive electrode lithium replenisher can improve the initial gram capacity to a certain extent, the positive electrode plate after lithium replenishment is prone to polarization, resulting in an unsatisfactory effect of improving the initial gram capacity. Therefore, the present application significantly improves the liquid phase conduction efficiency and the ion mobility at the interface of the positive electrode lithium replenisher material by simultaneously applying sulfur-containing compounds and ether compounds in the electrolyte of the lithium-ion battery, thereby achieving the effect of reducing polarization. As a result, the problem of insufficient initial gram capacity due to positive electrode polarization is effectively overcome, and the cycle stability and rate performance of the battery are improved at the same time.

[0052] The technical solutions described in the embodiments of the present application are applicable to lithium-ion batteries, battery modules using lithium-ion batteries, battery packs using lithium-ion batteries or battery modules, and electrical devices using at least one of lithium-ion batteries, battery modules and battery packs.

[0053] lithium-ion batteries

[0054] In some embodiments, a lithium-ion battery is provided, comprising a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte;

[0055] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode lithium supplement;

[0056] The electrolyte includes a non-aqueous solvent and an additive; the additive includes a sulfur-containing compound, and the non-aqueous solvent includes an ether compound.

[0057] By including both sulfur-containing compounds and ether compounds in the electrolyte, not only can the ionic conductivity of the electrolyte be improved, but it also helps improve the interaction between the electrolyte and the positive electrode material interface, thereby improving the ion mobility at the positive electrode material interface, reducing the consumption of active lithium in side reactions, and playing a role in reducing polarization. This helps to overcome the problem of insufficient initial gram capacity due to positive electrode polarization, and at the same time improves the cycle stability and rate performance of the battery.

[0058] In some embodiments, the ether compound includes a chain ether compound.

[0059] Compared with cyclic ether compounds, when chain ether compounds are used, they have stronger chelating ability with cations and can further reduce the viscosity of the electrolyte, which is beneficial to the improvement of lithium ion conductivity.

[0060] In some embodiments, the chain ether compound includes at least one of the following groups: ethylene glycol dimethyl ether (DME), ethylene glycol diethyl ether (DEE), diethylene glycol dimethyl ether (DEGDME), triethylene glycol dimethyl ether (TRGDME), tetraethylene glycol dimethyl ether (TEGDME), dipropyl ether, dibutyl ether, etc.

[0061] In some embodiments, the mass percentage of the ether compound in the non-aqueous solvent is 15% to 30%; for example, it can be about 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, etc.

[0062] When the mass proportion of ether compounds in non-aqueous solvents is 15% to 30%, a good solvent system can be provided, so that when the solvent dissolves higher concentrations of lithium salts and sulfur-containing compounds, it will not cause a significant increase in viscosity, which helps to increase the depolarization effect and expand the electrochemical stability window, maintaining better cycle stability and rate performance.

[0063] In some embodiments, the mass percentage of the ether compound in the non-aqueous solvent is 15% to 25%.

[0064] Optimizing the mass percentage of ether compounds in non-aqueous solvents can help further improve battery performance.

[0065] In some embodiments, the sulfur-containing compound includes a sulfonate compound.

[0066] In some embodiments, the sulfonate compound includes at least one of the following: 1,3 propane sultone, 1,3 propene sultone, 1,4 butane sultone, methylene methanedisulfonate, fluorosulfonates, and cyclic methylene disulfonate.

[0067] Compared with the use of other sulfur-containing compounds such as sulfate compounds, the use of sulfonate compounds can promote the stable formation of SEI film, reduce the amount of gas produced during formation, and have low corrosiveness, which is more conducive to electrochemical stability and high safety.

[0068] In some embodiments, the mass percentage of the sulfur-containing compound in the electrolyte is 0.5% to 4%; for example, it can be about 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, etc.

[0069] When the mass percentage of sulfur-containing compounds in the electrolyte is 0.5% to 4%, it is beneficial to further improve the liquid phase conduction efficiency and the ion mobility at the positive electrode material interface, thereby improving the interface stability. If the mass percentage of sulfur-containing compounds is greater than 4%, it may increase the interface impedance, thereby causing the charge rate and low-temperature performance to deteriorate. If the mass percentage of sulfur-containing compounds is less than 0.5%, the effect of improving the ionic conductivity of the electrolyte and the ion mobility at the positive electrode material interface is small, resulting in a weak depolarization effect and making it difficult to significantly improve the initial gram capacity.

[0070] In some embodiments, the mass percentage of the sulfur-containing compound in the electrolyte is 1.5%-3.5%.

[0071] By optimizing the mass percentage of sulfur-containing compounds in the electrolyte, it is helpful to further improve battery performance.

[0072] In some embodiments, the electrolyte further includes a lithium salt dissolved in the non-aqueous solvent; in the electrolyte, the concentration of the lithium salt is 0.5 to 1.6 mol / L; for example, it can be about 0.5 mol / L, 0.6 mol / L, 0.7 mol / L, 0.8 mol / L, 0.9 mol / L, 1 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, etc.

[0073] When the lithium salt concentration is 0.5-1.6 mol / L, the electrolyte maintains excellent ionic conductivity, thereby improving ion mobility at the cathode material interface and further optimizing the depolarization effect. Compared with concentrations less than 1 mol / L and greater than 1.4 mol / L, the improvement in depolarization and initial gram capacity is more significant when the lithium salt concentration is 1-1.4 mol / L.

[0074] In some embodiments, the mass percentage of the sulfur-containing compound in the electrolyte is 1.5% to 3.5%; the mass percentage of the ether compound in the non-aqueous solvent is 15% to 25%; and the concentration of the lithium salt in the electrolyte is 1 to 1.4 mol / L.

[0075] When the amounts of the lithium salt, the sulfur-containing compound, and the ether compound all meet the above ranges, the battery performance can be further significantly improved.

[0076] In some embodiments, the positive electrode lithium supplement comprises at least one compound conforming to the following formula: Li x M y O z , wherein M is one or more elements selected from Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Ni, Sb, Ti, V, Mo, and Sn, and 1≤x≤8, 0<y, 0<z<13.

[0077] In some embodiments, the positive electrode lithium supplement comprises at least one of the following: Li5FeO4, Li5Fe5O8, Li6CoO4, Li2NiO2, Li2O, Li2O2, Li6MnO4, Li6ZnO4, Li2CuO2, Li2CoO2, Li2MnO2, Li2C2O4, Li2Ni 0.5 Mn 1.5 O4、Li(Ni 0.8 Co 0.1 Mn 0.1 ) 1.3 O2, etc. It should be noted that some of the above compounds themselves can also be used as positive electrode active materials, such as Li2NiO2, Li2CuO2, Li2CoO2, Li2MnO2, Li2Ni 0.5 Mn 1.5 O4, etc., when its mass proportion in the positive electrode active material layer is about 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less or 3% or less, can be considered as a positive electrode lithium supplement rather than a positive electrode active material.

[0078] [Positive electrode]

[0079] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer includes a positive electrode lithium supplement; the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode active material layer is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0080] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0081] In some embodiments, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material may be a positive electrode active material for lithium ion batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.

[0082] In some embodiments, the positive electrode active material layer may further optionally include a binder. For example, the binder may include one or a combination of two or more selected from the group consisting of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0083] In some embodiments, the positive electrode active material layer may further include a conductive agent. For example, the conductive agent may include one or a combination of two or more selected from the group consisting of Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0084] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode active material layer, such as the positive electrode active material, the positive electrode lithium supplement, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the composite current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0085] [Negative electrode]

[0086] The negative electrode sheet 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. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two opposing surfaces of the negative electrode current collector.

[0087] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0088] In some embodiments, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material can be a negative electrode active material for a battery known in the art. For example, the negative electrode active material includes one or a combination of two or more selected from the following group: natural graphite, artificial graphite, mesophase microcarbon beads (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composite, Li-Sn alloy, Li-Sn-O alloy, Sn, SnO, SnO2, TiO2-Li4Ti5O 12 , Li-Al alloy. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for lithium-ion batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0089] In some embodiments, the negative electrode active material layer may further include a binder. For example, the binder may include one or a combination of two or more selected from the group consisting of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0090] In some embodiments, the negative electrode active material layer may further include a conductive agent. For example, the conductive agent may include one or a combination of two or more selected from the group consisting of Super P, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0091] In some embodiments, the negative electrode active material layer may further include other auxiliary agents, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0092] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode active material layer, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0093] [Electrolyte]

[0094] In some embodiments, the electrolyte includes a non-aqueous solvent and an additive; the additive includes a sulfur-containing compound, and the non-aqueous solvent includes an ether compound.

[0095] In some embodiments, the electrolyte further includes a lithium salt dissolved in the non-aqueous solvent.

[0096] In some embodiments, the lithium salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0097] In some embodiments, the non-aqueous solvent further comprises at least one selected from ethylene carbonate, ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0098] In some embodiments, the additives also include other additives in addition to sulfur-containing compounds; for example, the other additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain performance of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, etc.

[0099] [Diaphragm]

[0100] The diaphragm is provided between the positive electrode and the negative electrode to serve as an isolation. The present application has no particular restrictions on the type of diaphragm, and any well-known porous structure diaphragm with good chemical stability and mechanical stability can be selected. The material of the diaphragm can be selected from one or a combination of two or more of the following groups: glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride. The diaphragm can be a single-layer film or a multi-layer composite film, without particular restrictions. When the diaphragm is a multi-layer composite film, the materials of each layer can be the same or different, without particular restrictions.

[0101] [Preparation of lithium-ion batteries]

[0102] The positive electrode sheet, the negative electrode sheet and the separator can be made into an electrode assembly through a winding process or a lamination process, and then the electrolyte is injected after the outer packaging to prepare a lithium-ion battery.

[0103] The outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging can be a soft shell, such as a bag-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0104] The present application has no particular limitation on the shape of the lithium-ion battery, which can be cylindrical, square, or any other shape. For example, FIG1 shows a lithium-ion battery 5 having a square structure as an example.

[0105] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the diaphragm can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the lithium-ion battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0106] Battery modules and battery packs

[0107] In some embodiments, lithium-ion batteries can be assembled into a battery module. The number of lithium-ion batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art based on the application and capacity of the battery module.

[0108] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple lithium-ion batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple lithium-ion batteries 5 may be secured using fasteners.

[0109] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of lithium-ion batteries 5 are received in the receiving space.

[0110] In some embodiments, the lithium-ion batteries can also be assembled into battery packs.

[0111] In some embodiments, the battery modules 4 can also be assembled into a battery pack. The number of battery modules contained in the battery pack can be one or more. The specific number can be selected by those skilled in the art based on the application and capacity of the battery pack.

[0112] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0113] Electrical devices

[0114] The present application also provides an electric device, which includes the lithium-ion battery provided in the present application. In some embodiments, the electric device includes at least one of the battery modules or battery packs provided in the present application. The lithium-ion battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0115] As the electrical device, a lithium-ion battery, a battery module or a battery pack can be selected according to its usage requirements.

[0116] Figure 6 shows an example of an electric device. This device can be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of lithium-ion batteries, a battery pack or battery module can be used.

[0117] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a lithium-ion battery as a power source.

[0118] Example 1

[0119] A lithium-ion battery cell was prepared according to the following steps.

[0120] 1) Preparation of positive electrode sheet

[0121] Lithium iron phosphate as the positive electrode active material, lithium nickelate as the positive electrode lithium supplement, superconductive carbon black SP as the conductive agent and polyvinylidene fluoride (PVDF) as the binder are dispersed in N-methylpyrrolidone (NMP) as a solvent in a mass ratio of 93:3:2:2 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and after drying, cold pressing, slitting and cutting, the positive electrode sheet is obtained.

[0122] 2) Preparation of negative electrode sheet

[0123] The negative electrode active material graphite, superconductive carbon black SP as a conductive agent, SBR as a binder and CMC-Na as a thickener are dispersed in deionized water as a solvent in a mass ratio of 96:1:1:2 and mixed evenly to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil; after drying, cold pressing, slitting and cutting, the negative electrode sheet is obtained.

[0124] 3) Diaphragm

[0125] A polyethylene film was used as the separator.

[0126] 4) Preparation of electrolyte

[0127] Ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate are mixed in a ratio of 3:4:3 to obtain a first solvent; and the first solvent is mixed with an ether compound, ethylene glycol dimethyl ether, to obtain an organic solvent. The organic solvent comprises 20% by weight of the ether compound, ethylene glycol dimethyl ether.

[0128] Lithium hexafluorophosphate (LiPF6) as a lithium salt and 1,3-propane sultone (S-1) as a sulfur-containing compound were added to the organic solvent and mixed uniformly to prepare an electrolyte solution. The electrolyte solution had a concentration of 1.3 mol / L of LiPF6 and a mass percentage of 2.5% of 1,3-propane sultone.

[0129] 5) Preparation of lithium-ion batteries

[0130] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator being placed between the positive electrode sheet and the negative electrode sheet to serve as an isolation, and then the sheets are stacked to obtain a bare battery cell; the bare battery cell is placed in an outer packaging shell, dried, and then injected with electrolyte, and vacuum-sealed to obtain a lithium-ion battery cell.

[0131] The following performances of the lithium-ion battery cell were tested.

[0132] (1) Initial gram capacity

[0133] Use the Blue Electric test system to perform charge and discharge tests on the battery.

[0134] At 25°C, maintain the battery charge and discharge voltage range at 2.5-3.65V, cycle at a current density of 0.5C charge and 0.2C discharge, record the discharge capacity of the battery in the third cycle, and calculate the mass ratio of the discharge and active materials in the positive electrode. This ratio is the initial gram capacity (it should be noted here that the first cycle of the battery is the formation stage, and the third cycle is more stable than the second cycle, so the third cycle is selected as the first cycle in the actual sense).

[0135] The initial gram capacity of the lithium-ion battery cell of Example 1 is 153 mAh / g.

[0136] (2) Lithium ion conductivity of the electrolyte

[0137] The AC impedance method is used to monitor the ionic conductivity of the electrolyte (platinum black electrode). Two metal electrodes (Pb) are placed parallel and vertically in the electrolyte cell and connected to the measurement circuit. The AC impedance spectrum of the sample is measured on an electrochemical comprehensive tester. The experimental conditions are set as follows: frequency - 1-100000HZ. The electrolyte resistance is read from the intersection of the tail line and the real axis in the AC impedance spectrum, and the conductivity of the electrolyte is calculated.

[0138] The ion conductivity of the electrolyte in the lithium ion battery of Example 1 was 16.3 mS / cm.

[0139] (3) Capacity retention rate (500 cycles)

[0140] Use the Blue Electric test system to perform charge and discharge tests on the battery.

[0141] At 25°C, maintain the battery charge and discharge voltage range at 2.5-3.65V, cycle at a current density of 0.5C charge and 0.5C discharge, record the discharge capacity of the battery at the third cycle, recorded as the initial capacity C0, and then record a capacity after 500 cycles, recorded as capacity C500. The ratio of C500 to C0 is the retention rate of the current number of cycles (it should be noted here that the first cycle of the battery is the formation stage, and the third cycle is more stable than the second cycle, so the third cycle is selected as the first cycle in the actual sense).

[0142] The capacity retention rate (500 cycles) of the lithium ion battery of Example 1 was 94.5%.

[0143] (4) 100-cycle high-rate 10C retention rate (high-rate performance)

[0144] Use the Blue Electric test system to perform charge and discharge tests on the battery.

[0145] At 25°C, maintain the battery charge and discharge voltage range at 2.5-3.65V, cycle at a current density of 0.5C charge and 10C discharge, record the discharge capacity of the battery at the third cycle, recorded as the initial capacity C0, and then record a capacity after 100 cycles, recorded as capacity C500. The ratio of C500 to C0 is the retention rate of the current number of cycles (it should be noted here that the first cycle of the battery is the formation stage, and the third cycle is more stable than the second cycle, so the third cycle is selected as the first cycle in the actual sense).

[0146] The capacity retention rate (100 cycles) of the lithium-ion battery of Example 1 under high-rate (10C) cycling conditions is 84.6%.

[0147] Examples 2 to 10

[0148] The lithium salt concentration, the amount of the sulfur-containing compound, and the ether compound were changed to those shown in Table 1. Otherwise, the lithium-ion battery was prepared under the same conditions as in Example 1 and tested according to the method in Example 1.

[0149] Table 1

[0150] Examples 11 to 16

[0151] The amounts of the lithium salt, sulfur-containing compound, and ether compound were changed to those shown in Table 2. Otherwise, the lithium-ion battery was prepared under the same conditions as in Example 1 and tested according to the method in Example 1.

[0152] Table 2

[0153] By comparing the test results of the above embodiments, it can be seen that compared with Examples 11 to 16, Examples 1 to 10 have achieved further improvement in the capacity retention rate of the battery (especially the capacity retention rate under high-rate cycling conditions) by simultaneously optimizing and adjusting the dosage of lithium salts, sulfur-containing compounds and ether compounds.

[0154] Examples 17-18

[0155] The material of the positive electrode lithium supplement was changed to that shown in Table 3. Otherwise, the lithium-ion battery was prepared under the same conditions as in Example 1 and tested according to the method in Example 1.

[0156] Table 3

[0157] Examples 19-20

[0158] The sulfur-containing compound was changed to that shown in Table 4. Otherwise, the lithium-ion battery was prepared under the same conditions as in Example 1 and tested according to the method in Example 1.

[0159] Table 4

[0160] When different types of sulfonates are used as sulfur-containing compounds, the ionic conductivity of the electrolyte can be improved, and the lithium-ion battery can have good initial gram capacity and capacity retention.

[0161] Examples 21 to 23

[0162] The ether compound was changed to that shown in Table 5. Otherwise, the lithium-ion battery was prepared under the same conditions as in Example 1 and tested according to the method in Example 1.

[0163] Table 5

[0164] Examples 1 and 21 use chain ether compounds, which have further improved the initial gram capacity and capacity retention rate of the battery compared to Examples 22 to 23 using cyclic ether compounds.

[0165] Comparative Examples 1 to 4

[0166] The lithium salt concentration, the amount of the sulfur-containing compound, and the ether compound were changed to those shown in Table 6. Otherwise, the lithium-ion battery was prepared under the same conditions as in Example 1 and tested according to the method in Example 1.

[0167] Table 6

[0168] —Indicates that the value is missing because the corresponding component is not contained

[0169] By comparing the test results of Example 1 and Comparative Examples 1-2, it can be seen that the lack of either the sulfur-containing compound or the ether compound will significantly deteriorate the performance of the lithium-ion battery. The present application uses a sulfur-containing compound and an ether compound simultaneously in the electrolyte of a lithium-ion battery with a positive lithium supplement, and the two compounds synergistically enhance the efficiency, thereby significantly improving the initial gram capacity and capacity retention of the battery. By comparing the test results of Example 1 and Comparative Examples 3-4, it can be seen that when either the sulfur-containing compound or the ether compound is lacking, even if the concentration of the lithium salt in the electrolyte is adjusted, it is difficult to improve the initial gram capacity and capacity retention of the battery.

[0170] The above description is merely a preferred embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A lithium-ion battery comprising a positive electrode plate and an electrolyte; characterized in that: The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode active material layer includes a positive electrode lithium supplement; The electrolyte includes a non-aqueous solvent and an additive; the non-aqueous solvent includes an ether compound, and the additive includes a sulfur-containing compound; in the non-aqueous solvent, the mass percentage of the ether compound is 15% to 30%.

2. The lithium-ion battery according to claim 1, characterized in that The ether compounds include chain ether compounds.

3. The lithium ion battery according to claim 2, characterized in that The chain ether compound includes at least one of the following groups: ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, dipropyl ether, and dibutyl ether.

4. The lithium ion battery according to any one of claims 1 to 3, characterized in that: In the non-aqueous solvent, the mass percentage of the ether compound is 15% to 25%.

5. The lithium ion battery according to any one of claims 1 to 4, characterized in that: The sulfur-containing compounds include sulfonate compounds.

6. The lithium ion battery according to claim 5, characterized in that The sulfonate compound includes at least one of the following groups: 1,3 propane sultone, 1,3 propene sultone, 1,4 butane sultone, and methylene disulfonate.

7. The lithium ion battery according to any one of claims 1 to 6, characterized in that: In the electrolyte, the mass percentage of the sulfur-containing compound is 0.5% to 4%.

8. The lithium ion battery according to claim 7, characterized in that In the electrolyte, the mass percentage of the sulfur-containing compound is 1.5% to 3.5%.

9. The lithium ion battery according to any one of claims 1 to 8, characterized in that: The electrolyte further includes a lithium salt dissolved in the non-aqueous solvent; in the electrolyte, the concentration of the lithium salt is 0.5 to 1.6 mol / L.

10. The lithium ion battery according to claim 9, characterized in that In the electrolyte, the concentration of the lithium salt is 1 to 1.4 mol / L.

11. The lithium ion battery according to any one of claims 1 to 10, characterized in that: The positive electrode lithium supplement comprises at least one compound conforming to the following formula: Li x M y O z , wherein M is one or more elements selected from Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Ni, Sb, Ti, V, Mo, and Sn, and 1≤x≤8, 0<y, 0<z<13.

12. The lithium ion battery according to any one of claims 1 to 10, characterized in that: The positive electrode lithium supplement includes at least one of the following groups: Li5FeO4, Li5Fe5O8, Li6CoO4, Li2NiO2, Li2O, Li2O2, Li6MnO4, Li6ZnO4, Li2CuO2, Li2CoO2, Li2MnO2, Li2C2O4, Li2Ni 0.5 Mn 1.5 O4、Li(Ni 0.8 Co 0.1 Mn 0.1 ) 1.3 O2.

13. An electrical device, characterized in that: A lithium ion battery comprising any one of claims 1 to 12.

Images