Lithium-ion batteries and power-consuming devices

Abstract

The present application relates to a lithium-ion battery, comprising a positive electrode and an electrolyte, wherein the positive electrode active material contains a doping element selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, in a content of 0.01%≦W1%≦0.5%, and the electrolyte contains an oligomer having general formula (I), in a content of 0.1%≦W2≦10%. The present application also relates to a power consuming device comprising the lithium-ion battery.

Description

[Technical Field]

[0001] The present application relates to the technical field of lithium batteries, and in particular to lithium-ion batteries, the positive electrode of which contains a positive electrode active material containing 0.01 to 0.5 wt % of a specific doping element and an electrolyte containing 0.1 to 10 wt % of an oligomer with a specific structure. The present application also relates to a power consumption device including a lithium-ion battery. [Background technology]

[0002] In recent years, with the continuous development of lithium ion batteries, lithium ion batteries have been widely applied in energy storage power systems such as hydroelectric power, thermal power, wind power and solar power plants, as well as in multiple fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. With the large-scale application of lithium ion batteries, higher requirements are being put forward in this field for their energy density, power supply performance and safety performance.

[0003] To improve the structural stability and power-saving performance of lithium-ion batteries, cathodes are typically doped with elements, such as W, Cu, Fe, V, Cr, Ti, Zr, Zn, and Al. However, these doping elements are prone to leaching in the acidic electrolyte environment, potentially destroying the cathode structure and further damaging the SEI film, potentially leading to thermal runaway in the battery. Therefore, cathode materials containing doping elements can seriously affect the cathode structure and the electrical and safety performance of the battery.

[0004] Therefore, there is still a need in the prior art to provide a lithium ion battery with high structural stability and good safety performance. Summary of the Invention [Problem to be solved by the invention]

[0005] The present application has been made in view of the above-mentioned problems, and its object is to provide a lithium-ion battery that has a positive electrode active material doped to obtain structural stability and also has good performance in preventing thermal runaway of the battery at high temperatures. and power consuming devices including lithium ion batteries The purpose is to provide [Means for solving the problem]

[0006] In order to achieve the above object, a first aspect of the present application provides a lithium ion battery, the lithium ion battery including a positive electrode and an electrolyte, wherein the positive electrode contains a positive electrode active material containing a doping element, the doping element including at least one selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and the content of the doping element is W1, and 0.01%≦W based on the weight of the positive electrode active material. 1 ≦0.5%, and the electrolyte solution contains an oligomer having the following general formula (I): [ka] p1 and q1 are the numbers of repeating units, p1 is an integer of 1 to 10, and q1 is an integer of 1 to 15. The content of the oligomer is W2, based on the total weight of the electrolyte, and is 0.1%≦W2≦10%.

[0007] In the present application, an oligomer having the above-mentioned specific functional group is added to the electrolyte solution, and the amino nitrogen atom and the ether-bonded oxygen atom in the specific functional group have a lone pair electron, which can bond with the proton hydrogen on the hydrogen fluoride to stabilize the hydrogen fluoride and have a certain deoxidizing effect. At the same time, the ester groups on both ends of the oligomer molecular structure stabilize the doping element at the positive electrode interface through a complexing action, thereby effectively suppressing the elution of the doping element and significantly reducing the risk of thermal runaway in the battery.

[0008] In any embodiment, the ratio W2 of the oligomer content to W1 of the doping element content satisfies 0.6≦W2 / W1≦250, optionally 3≦W2 / W1≦100, and further optionally 5≦W2 / W1≦50. When the doping element content in the positive electrode active material and the oligomer content in the electrolyte satisfy the above relationship, the elution of the doping element in the positive electrode material can be effectively suppressed, and the cycle performance and safety performance of the battery can be improved.

[0009] In any of the embodiments, the doping element content W1 is 0.01% to 0.4%, and optionally 0.02 to 0.3%. In any of the embodiments, the oligomer content W2 is 0.2% to 5%, and optionally 0.3 to 3%.

[0010] In any embodiment, in general formula (I), P1 is an integer of 2-8 and q1 is an integer of 2-10.

[0011] In any embodiment, the doping element is at least one selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B and Mo, and optionally at least one of Zr, Mg, Al and B.

[0012] In any embodiment, the positive electrode active material has the following general formula: Li x [Ni y Co z Mn w ]O2 as a positive electrode active material, and 0.8≦x≦1.2, 0.5≦y< 1.0 , 0 <z≦0.3、0<w≦0.3である。

[0013] In any embodiment, the solvent in the electrolyte is at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluorinated ethylene carbonate, ethyl acetate, and ethyl propionate.

[0014] In any embodiment, the lithium salt in the electrolyte is at least one selected from LiPF6 and lithium bis(fluorosulfonyl)imide, and optionally LiPF6.

[0015] In any of the embodiments, the lithium ion battery includes a negative electrode, and the negative electrode includes a negative electrode active material selected from the group consisting of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO, and lithiated TiO-LiTiO with a spinel structure. 12 , Li-Al alloy.

[0016] In any one of the embodiments, the electrolyte solution further contains an additive, which is at least one selected from vinylene carbonate, ethylene sulfate, lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium tetrafluoroborate, 1,3-propane sultone, lithium trifluoromethanesulfonate, and lithium bis(oxalato)borate.

[0017] A second aspect of the present application provides a power consuming device, the power consuming device including the lithium ion battery of the first aspect of the present application. [Brief explanation of the drawings]

[0018] In order to more clearly explain the technical solution of the present application, the following briefly introduces the drawings that need to be used in the embodiments of the present application. It is obvious that the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on the drawings without any creative efforts. [Figure 1] 1 is a schematic diagram of a lithium ion secondary battery according to one embodiment of the present application. [Figure 2] FIG. 2 is an exploded view of the lithium ion secondary battery according to the embodiment of the present application shown in FIG. [Figure 3] 1 is a schematic diagram of a battery pack according to one embodiment of the present application. [Figure 4] FIG. 4 is an exploded view of the battery pack shown in FIG. 3 according to one embodiment of the present application. [Figure 5] 1 is a schematic diagram of an apparatus in which a battery pack is used as a power source in one embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, specific embodiments of the present application will be described in detail with reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of actually identical structures may be omitted. This is to avoid the following description becoming unnecessarily long and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0020] For clarity, this application specifically discloses several numerical ranges. However, any lower limit may be combined with any upper limit to form an unspecified range, and any lower limit may be combined with another lower limit to form an unspecified range, and similarly, any upper limit may be combined with any other upper limit to form an unspecified range. In addition, each individually disclosed point or single numerical value may be combined with any other point or single numerical value as a lower limit or upper limit, or may be combined with another lower limit or upper limit to form an unspecified range.

[0021] In the development of lithium-ion batteries, doping the positive electrode active material with certain other elements is commonly used to stabilize the positive electrode structure and improve the battery's cycle performance and charge-dissipation performance. However, LiPF6 in the electrolyte is sensitive to water and easily hydrolyzes to produce hydrogen fluoride. LiPF6 is also susceptible to thermal decomposition, producing PF5, a Lewis acid that creates a certain acidic environment within the battery. The doping elements in the positive electrode material are easily dissolved from the positive electrode by the action of acid, potentially destroying the positive electrode structure. Furthermore, the deposition of the doping elements on the negative electrode can destroy the SEI film, exposing a fresh interface, further leading to reductive decomposition of the electrolyte and the consumption of active lithium. Furthermore, the destruction of the SEI film can accelerate the thermal runaway temperature of the battery core, potentially posing a safety issue. Therefore, there is a need in the art to develop a new lithium-ion battery that can improve stability and prevent thermal runaway by doping the positive electrode active material with certain elements.

[0022] Specifically, a first aspect of the present application provides a lithium-ion battery, comprising: a positive electrode; and an electrolyte; wherein the positive electrode active material comprises a doping element, the doping element being at least one selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo; and the content of the doping element is W1, and the content of the doping element is 0.01%≦W, based on the weight of the positive electrode active material. 1 ≦0.5%, and the electrolyte solution contains an oligomer having the following general formula (I): [ka] p1 and q1 are the numbers of repeating units, p1 is an integer of 1 to 10, and q1 is an integer of 1 to 15. The content of the oligomer is W2, based on the total weight of the electrolyte, and is 0.1%≦W2≦10%.

[0023] The inventors have discovered that adding an oligomer having the above-mentioned specific functional group to an electrolyte solution significantly reduces the safety risks posed by the doping element. Without being bound by any theory, the inventors believe that the amino nitrogen atom and ether-bonded oxygen atom in the specific functional group have a lone pair of electrons, which can bond with the proton hydrogen on the hydrogen fluoride to stabilize the hydrogen fluoride, thereby providing a certain deoxidizing effect. The ester groups at both ends of the oligomer molecular structure can stabilize the doping element at the positive electrode interface through complexation. The addition of the oligomer thus effectively prevents the doping element from leaching from the positive electrode material, thereby protecting the positive electrode structure and SEI film from destruction and further reducing the risk of thermal runaway at high temperatures in batteries.

[0024] On the other hand, by doping the cathode active material as described above, the stability of the cathode material can be improved, the thermal decomposition temperature of the material can be raised, and its electrical performance can be improved. In addition, the risks of doping elements can be avoided by adding the oligomer of general formula (I), thereby achieving both the stability of the cathode material and the safety of the battery.

[0025] In some embodiments, the ratio W2 of the oligomer content to W1 of the doping element satisfies 0.6≦W2 / W1≦250, optionally 3≦W2 / W1≦100, and even optionally 5≦W2 / W1≦50. When the doping element content in the positive electrode active material and the oligomer content in the electrolyte satisfy this relationship, the elution of the doping element from the positive electrode material can be more effectively inhibited, improving the cycle performance and safety performance of the battery. If the W2 / W1 ratio is too low, for example, less than 0.6, the oligomer's effect of inhibiting the elution of the doping element is insufficient. If the W2 / W1 ratio is too high, for example, greater than 250 or even as high as 400, not only the safety performance but also the cycle performance deteriorates.

[0026] The value of W2 / W1 can be changed by adjusting the doping amount in the positive electrode active material and the content of the oligomer in the electrolyte. In some embodiments, the content W1 of the doping element is 0.01 to 0.4%, and optionally 0.02 to 0.3%. The doping element is at least one selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo. In some embodiments, the doping element is at least one selected from Mg, Al, Zr, and B, and optionally at least one of Zr, Al, and B. Regarding doping of the positive electrode active material, for example, a doping precursor powder can be obtained by mixing a precursor powder of the positive electrode active material with a salt solution of the doping element, performing a liquid-phase diffusion reaction, and then drying. The doping element salt solution is a soluble metal solution containing the doping element. Its solute is one or more of the salts of the doping element, such as zinc sulfate, magnesium sulfate, aluminum chloride, or zirconium nitrate, and its solvent is an organic polar solvent, such as ethanol, methanol, or propanol, preferably ethanol. After mixing the solute and solvent, a doping element salt solution is obtained, whose concentration may be 0.5-5 mol / L. The precursor powder is then mixed with the doping element salt solution to carry out a liquid-phase diffusion reaction. The solids percentage of the mixture is 30%-50%. The doping element is uniformly infiltrated into the pores of the nickel-cobalt-manganese material through the solution by liquid-phase diffusion. Specific liquid-phase diffusion reaction process conditions can be selected and adjusted as needed, including the reaction temperature, reaction time, and stirring speed. An exemplary liquid-phase diffusion reaction process condition is a reaction temperature of 25-40°C, a reaction time of 30-90 min, and a stirring speed of 15-45 Hz. The doped precursor powder thus obtained can be further processed, for example, through processing steps such as sintering and grinding, to obtain the doped cathode active material.

[0027] In some embodiments, the content W2 of the oligomer is 0.2 to 5%, and optionally 0.3 to 3%. The oligomer may be uniformly mixed in addition to the non-aqueous organic solvent of the electrolyte solution. In some embodiments, in the general formula (I), p1 is an integer from 2 to 8, and q1 is an integer from 2 to 10. The weight average molecular weight Mw of the oligomer of the general formula (I) may be 1000 g / mol to 100000 g / mol, optionally 2000 g / mol to 20000 g / mol, and further optionally 3000 g / mol to 10000 g / mol. The weight average molecular weight Mw can be measured by gel permeation chromatography (GPC) based on the standard polystyrene conversion value using tetrahydrofuran as a solvent.

[0028] The positive electrode active material may be selected from any suitable material in the field of lithium-ion batteries, such as a ternary positive electrode material or a lithium iron phosphate material. In some embodiments, the positive electrode active material is the following general formula: Li x [Ni y Co z Mn w O2 as the positive electrode active material, where 0.8 ≦ x ≦ 1.2, 0.5 ≦ y < 1.0 , 0 < z ≦ 0.3, 0 < w ≦ 0.3, and optionally, in the general formula, 0.05 ≦ z ≦ 0.2 and 0.05 ≦ w ≦ 0.2. The positive electrode active material may be doped, and the doping method is as described above to obtain a doped positive electrode active material. The doping element is at least one selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, optionally at least one of Mg, Al, Zr, and B, and further optionally at least one of Zr, Al, and B. The positive electrode active material is, for example, LiNi 0.5 Co 0.2 Mn 0.3 O2, Li[Ni 0.9 Co 0.05 Mn 0.05 O2 or Li[Ni 0.8 Co 0.1 Mn0.1 ]O2, but is not limited to these.

[0029] In some embodiments, the solvent in the electrolyte solution is at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluorinated ethylene carbonate, ethyl acetate, and ethyl propionate. The solvent may be a mixture of two or more of the above solvents, such as a mixture of ethylene carbonate and ethyl methyl carbonate, in a weight ratio of 10:1 to 1:10, for example, 3:7.

[0030] In some embodiments, the lithium salt in the electrolyte is at least one selected from LiPF6 and lithium bis(fluorosulfonyl)imide, and optionally LiPF6. The concentration of the lithium salt in the electrolyte may be 0.5M to 5M, and optionally 1M to 3M.

[0031] In some embodiments, the lithium ion battery includes a negative electrode, and the negative electrode includes a negative electrode active material selected from the group consisting of natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and lithiated TiO2-Li4Ti5O with a spinel structure. 12 , Li-Al alloy.

[0032] In some embodiments, the electrolyte solution may further contain an additive to prevent decomposition of the non-aqueous electrolyte solution, improve the battery's stability at high temperatures, or suppress battery expansion. The additive is at least one selected from vinylene carbonate, ethylene sulfate, lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium tetrafluoroborate, 1,3-propane sultone, lithium trifluoromethanesulfonate, and lithium bis(oxalato)borate. The additive does not necessarily need to be added, and its content may be 0 to 5 wt %, or optionally 0.5 to 3 wt %, based on the total weight of the non-aqueous electrolyte solution.

[0033] A second aspect of the present application provides a power consuming device, comprising the lithium ion battery of the first aspect of the present application.

[0034] The materials for each assembly of the lithium-ion battery of the present application may be selected from a wide range. In some embodiments, the battery is specifically a lithium-ion secondary battery. The battery cells of the lithium-ion secondary battery are described in detail below.

[0035] Generally, a lithium-ion secondary battery includes a positive electrode plate, a negative electrode plate, a separator, and an electrolyte. During charging and discharging, active ions shuttle between the positive and negative electrodes, absorbing and releasing ions. The separator is located between the positive and negative electrodes to provide isolation. The electrolyte conducts ions between the positive and negative electrodes.

[0036] [Electrolyte] The electrolyte serves to conduct ions between the positive and negative electrodes and includes an electrolyte salt and a solvent.

[0037] In the present application, the electrolyte salt may be an electrolyte salt commonly used in lithium ion secondary batteries, such as a lithium salt, or may be the above-mentioned lithium salt as a highly thermally stable salt, a lithium salt as a low impedance additive, or a lithium salt that inhibits corrosion of aluminum foil. By way of example, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium hexafluoroarsenate (LiAsF), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoro(oxalato)borate (LiDFOB), lithium difluorophosphate (LiPOF), lithium difluorobis(oxalato)phosphate (LiDFOP), lithium fluorine sulfonate (LiSOF), difluorobis(oxalato) salt (NDFOP), LiF(SON)SOF, KFSI, CsFSI, Ba(FSI) and LiFSONSOCHCHCF.

[0038] The type of solvent is not particularly limited and can be selected according to actual needs. In some embodiments, the solvent is a non-aqueous solvent. Optionally, the solvent may include one or more of a linear carbonate, a cyclic carbonate, and a carboxylic acid ester. In some embodiments, the solvent may be selected from one or more of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluorinated ethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), tetrahydrofuran, sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0039] In some embodiments, the electrolyte solution optionally further includes other additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve certain battery performance characteristics, such as an additive that improves the overcharge performance of the battery, an additive that improves the high-temperature performance of the battery, or an additive that improves the low-temperature performance of the battery. For example, the additive may be at least one selected from the group consisting of cyclic carbonate compounds containing unsaturated bonds, halogen-substituted cyclic carbonate compounds, sulfate ester compounds, sulfite ester compounds, sultone compounds, disulfonic acid compounds, nitrile compounds, aromatic compounds, isocyanate compounds, phosphazene compounds, cyclic acid anhydride compounds, phosphite compounds, phosphate ester compounds, borate ester compounds, and carboxylic acid ester compounds.

[0040] [Positive electrode plate] The positive electrode plate 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, and the positive electrode active material layer includes a positive electrode active material and a conductive agent.

[0041] For example, the positive electrode current collector has two surfaces facing each other in the thickness direction thereof, and the positive electrode active material layer is disposed on one or both of the two facing surfaces of the positive electrode current collector.

[0042] In the lithium-ion secondary battery of the present application, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (e.g., aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer substrate (e.g., a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0043] The positive electrode active material layer disposed on the surface of the positive electrode current collector includes a positive electrode active material. The positive electrode active material used in the present application may include any common positive electrode active material used in secondary batteries. In some embodiments, the positive electrode active material may include one or more selected from lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and modified compounds thereof. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and modified compounds thereof. All of these materials are commercially available. The surface of the positive electrode active material may be coated with carbon. The positive electrode active material may be doped to obtain a doped positive electrode active material. The doping element may include at least one selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, but is not limited thereto.

[0044] The positive electrode active material layer may optionally include a conductive agent. However, the type of the conductive agent is not specifically limited, and a person skilled in the art may select the conductive agent according to actual needs. For example, the conductive agent used in the positive electrode material may be selected from one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0045] The positive electrode active material layer further includes an aqueous adhesive. The aqueous adhesive may be selected from one or more of soluble polysaccharides and their derivatives, and water-soluble or water-dispersible polymers. For example, the aqueous adhesive may be methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts, polyethyleneimine and its salts, polyacrylamide, acrylic acid copolymers and their derivatives.

[0046] In this application, the positive electrode plate may be manufactured according to a method known in the art. For example, a positive electrode active material to be coated with carbon, a conductive agent, and a water-based adhesive may be dispersed in a solvent (e.g., water) to form a uniform positive electrode slurry. The positive electrode slurry may be coated on a positive electrode current collector, and the positive electrode plate may be obtained after processes such as drying and cold pressing.

[0047] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector and a negative electrode material layer disposed on at least one surface of the negative electrode current collector, the negative electrode material layer including a negative electrode active material.

[0048] For example, the negative electrode current collector has two surfaces that face each other in the thickness direction thereof, and the negative electrode material layer is disposed on either one or both of the two facing surfaces of the negative electrode current collector.

[0049] In the lithium-ion secondary battery of the present application, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, a copper foil may be used as the metal foil sheet. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (e.g., copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer substrate (e.g., a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0050] In the lithium-ion secondary battery of the present application, the negative electrode material layer generally includes a negative electrode active material, an optional adhesive, an optional conductive agent, and other optional auxiliary agents, and is generally obtained by coating and drying a negative electrode slurry. The negative electrode slurry is generally formed by dispersing the negative electrode active material, the optional conductive agent, and the adhesive in a solvent and stirring the resulting mixture uniformly. The solvent may be N-methylpyrrolidone (NMP) or deionized water.

[0051] The specific type of the negative electrode active material is not limited, and may be any active material known in the art that can be used in the negative electrode of a lithium ion secondary battery, and those skilled in the art may select one according to actual needs. For example, the negative electrode active material may be selected from one or more of graphite, soft carbon, hard carbon, mesocarbon microbeads, carbon fiber, carbon nanotubes, silicone element, silicone oxide, silicone carbon composite, and lithium titanate.

[0052] By way of example, the conductive agent may be selected from one or more of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0053] By way of example, the adhesive may be selected from one or more 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).

[0054] Other optional auxiliaries include, for example, thickeners (eg, sodium carboxymethylcellulose (CMC-Na)).

[0055] [Separator] Lithium-ion secondary batteries using an electrolyte solution include a separator. The separator is disposed between the positive electrode plate and the negative electrode plate and serves to separate them. The separator of the present application is as described above, but the lithium-ion battery of the present application may further include a conventional separator. The type of the conventional separator is not particularly limited, and any known porous separator with good chemical and mechanical stability may be selected. In some embodiments, the material of the conventional separator may be selected from one or more of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without any particular limitation.

[0056] In some embodiments, the positive and negative electrodes and the separator can be fabricated into an electrode assembly by a winding or lamination process.

[0057] In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte.

[0058] In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The pouch may be made of plastic, such as polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0059] The present application does not particularly limit the shape of the secondary battery, and the secondary battery may be cylindrical, rectangular, or any other shape. For example, FIG. 1 shows an example of a lithium ion secondary battery having a rectangular structure. At the pond be.

[0060] In some embodiments, referring to FIG. 2, the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. ​​Lithium ion secondary battery In the pond The number of included electrode assemblies 52 may be one or more, which can be specifically selected by those skilled in the art according to actual needs.

[0061] In some embodiments, the lithium ion secondary batteries may be assembled into a battery module 4. The number of lithium ion secondary batteries included in the battery module 4 may be one or more, and the specific number can be selected by those skilled in the art depending on the application and capacity of the battery module 4. In the battery module 4, multiple lithium ion secondary batteries The pond The lithium ion secondary batteries may be arranged in a row along the longitudinal direction of the battery module. Of course, they may be arranged in any other manner. The pond Optionally, the battery module 4 may further include a housing having an accommodating space, and may accommodate a plurality of lithium ion secondary batteries. The pond , is accommodated in this accommodation space.

[0062] In some embodiments, the lithium ion secondary battery Ikemata The battery module 4 is a battery As a pack May be assembled with batteries In pack Included lithium-ion secondary battery Ikemata The number of battery modules 4 is determined by a person skilled in the art. Pack of It can be selected according to the application and capacity.

[0063] The lithium ion secondary battery of the present application may include a battery cell format, a battery module format, or a battery pack format. In some embodiments, the battery cells may be assembled as a battery module. In some embodiments, the battery cells may be assembled as a battery pack. In some embodiments, the battery modules may be assembled as a battery pack.

[0064] Figures 3 and 4 show an example of a battery pack. In Referring to Figures 3 and 4, the battery pack Ku may include a battery box and a plurality of battery cells installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 can cover the lower housing 3 to form an enclosed space for accommodating the battery cells.

[0065] The present application also provides a device, the device including a battery pack according to the present application. The battery pack may be used as a power source for the device or as an energy storage unit for the device. The device may be, but is not limited to, a mobile device (e.g., a mobile phone, a laptop, etc.), an electric vehicle (e.g., a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship, a satellite, an energy storage system, etc. The device may select a battery pack according to its usage needs.

[0066] An example device is shown in Figure 5. This device may be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the demand for high power and high energy density from lithium-ion secondary batteries, a battery pack or battery module may be employed. [Example]

[0067] Examples of the present application are described below. The examples described below are illustrative and are used only to interpret the present application, and should not be understood as limitations on the present application. If specific techniques or conditions are not specified in the examples, they will be performed according to the techniques or conditions described in literature in the field or according to the product instructions. If the manufacturer of the reagents or instruments used is not specified, they are all commercially available ordinary products.

[0068] [Doping of cathode materials] In this embodiment, the doping of the positive electrode active material is carried out as follows. The ternary positive electrode active material precursor powder is mixed with a salt solution of the doping element, followed by a liquid-phase diffusion reaction. After drying, the doped powder is obtained. The salt solution of the doping element is a soluble metal solution containing the doping element, with the solute being one of zinc sulfate, magnesium sulfate, aluminum chloride, or zirconium nitrate, and the solvent being ethanol. The solute and solvent are mixed to obtain a doping element salt solution. The ternary precursor powder is then mixed with the doping element salt solution to carry out a liquid-phase diffusion reaction, resulting in a solids percentage of 30% to 50% by weight. The doping element is uniformly infiltrated into the pores of the nickel-cobalt-manganese material through the solution via liquid-phase diffusion. Specific liquid-phase diffusion reaction process conditions are a reaction temperature of 25 to 40°C, a reaction time of 30 to 90 min, and a stirring speed of 15 to 45 Hz.

[0069] Example 1 (1) Manufacturing of positive electrode plates: Ternary positive electrode material LiNi 0.8 Co 0.2 Mn 0.2 O2 powder was mixed with a solution of zirconium nitrate in ethanol, and a liquid phase diffusion reaction was carried out, and the solid content of the mixture was 40% by weight. The zirconium element was uniformly infiltrated into the pores of the nickel-cobalt-manganese material through the liquid phase diffusion reaction method. The specific liquid phase diffusion reaction process conditions were: reaction temperature 35°C, reaction time 60 min, and stirring speed 35 Hz.

[0070] The doped positive electrode active material (the zirconium doping element was present at a content of 0.01 wt% based on the weight of the positive electrode active material), the conductive agent Super P (conductive carbon black), and the adhesive polyvinylidene fluoride (PVDF) were dissolved in N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The solids content of the positive electrode slurry was 50 wt%, and the mass ratio of the positive electrode active material, Super P, and PVDF in the solid components was 8:1:1. The positive electrode slurry was applied to an aluminum foil current collector, dried at 85°C, and then cold-pressed. After edge trimming, film cutting, and slitting, the positive electrode plate was dried at 85°C under vacuum for 4 hours to prepare a positive electrode plate.

[0071] [ Negative electrode plate manufacturing ] The negative electrode slurry was prepared by uniformly mixing the negative electrode active material graphite, the conductive agent Super P, the thickener CMC, and the adhesive styrene-butadiene rubber (SBR) in deionized water. The solids content of the negative electrode slurry was 30 wt%, and the mass ratio of graphite, Super P, CMC, and the adhesive styrene-butadiene rubber (SBR) in the solid components was 80:15:3:2. The negative electrode slurry was applied to a copper foil current collector, dried at 85°C, and then cold-pressed, edge-trimmed, film-cut, and slit. The negative electrode plate was then dried in a vacuum at 120°C for 12 hours.

[0072] [ Electrolyte production ] In an argon-filled glove box (water content <10 ppm, oxygen content <1 ppm), 2% vinylene carbonate was added to an organic solvent (EC:EMC = 3:7 wt% / wt%) and mixed uniformly. Then, 0.30 wt% of an oligomer (Mw = 5,000 g / mol, p1 = 5, q1 = 3) was added. 1M LiPF6 was slowly added to the non-aqueous organic solvent until the lithium salt was completely dissolved, yielding the target electrolyte.

[0073] [ Lithium-ion battery manufacturing ] A 16 μm polyethylene film (PE) was used as the separator. The fabricated positive electrode plate, separator, and negative electrode plate were stacked in this order, with the separator positioned between the positive and negative electrodes to isolate them. Then, the stack was wound to obtain a bare cell. The tabs were welded, the bare cell was placed in an outer casing, and the above-prepared electrolyte was injected into the dried battery core. The lithium-ion battery was then completed through packaging, standing, chemical formation, shaping, capacity testing, etc. (The pouch lithium-ion battery was 4.0 mm thick, 60 mm wide, and 140 mm long.)

[0074] Examples 2 to 16 Example 1 was repeated, with the differences being the type of positive electrode active material, the type of doping element in the positive electrode active material, the content of the doping element in the positive electrode active material, and the content of the oligomer in the electrolyte, as shown in Table 1.

[0075] Comparative Example 1 Example 1 was repeated, with the difference that the doping content in the positive electrode active material was 0.02%, and no oligomer of general formula (I) was added to the electrolyte.

[0076] [Table 1]

[0077] The lithium ion batteries manufactured in Examples 1 to 16 and Comparative Example 1 were tested, and the test methods were as follows.

[0078] (1) Hot box performance test of lithium-ion batteries.

[0079] The ambient temperature was adjusted to 25°C, and the lithium-ion battery was charged at 1C to 4.2V, then at a constant voltage of 0.05C. The lithium-ion battery was then placed in a heating furnace, which was heated at a rate of 10°C / min and held at that temperature for 10 minutes. When the lithium-ion battery began to show thermal runaway, the flow was terminated. The temperature monitored by the furnace during the lithium-ion battery's thermal runaway was recorded.

[0080] (2) Cycle performance test of lithium-ion batteries.

[0081] At 25°C, a lithium-ion battery was charged at a constant current of 1C to 4.2V, then charged at a constant voltage of 4.2V until the current reached 0.05C, and then discharged at a constant current of 1C to 2.8V. This constituted one charge-discharge cycle. The capacity retention of the lithium-ion battery after 500 cycles was calculated, assuming the capacity at the first discharge as 100%. The capacity retention (%) of the lithium-ion battery after 500 cycles = discharge capacity at 500th cycle / capacity at first discharge × 100%.

[0082] The test results of the lithium ion batteries manufactured in Examples 1 to 16 and Comparative Example 1 are summarized in Table 2 below.

[0083] [Table 2]

[0084] As can be seen from the test results in Table 2, compared with Comparative Example 1, Examples 1 to 16 of the present invention showed some improvement in both safety performance and cycle performance. This indicates that when the positive electrode active material contains a doping element, the electrolyte containing a certain amount of oligomer of general formula (I) can effectively inhibit the leaching of the doping element and improve the cycle performance and safety performance of the battery. Although the positive electrode material in Comparative Example 1 contained a doping element, the electrolyte did not contain an oligomer capable of complexing the doping element, and HF in the electrolyte could not be effectively removed. As a result, the doping element in the positive electrode material was leached out severely, destroying the positive electrode structure, causing the doping element to accumulate on the negative electrode, destroying the SEI film, and causing reductive decomposition of the electrolyte, resulting in relatively poor safety performance and cycle performance of the battery core.

[0085] Furthermore, as can be seen from a comparison between Examples 1 to 16, when the content of the doping element in the positive electrode active material and the content of the oligomer in the electrolyte satisfy a specific relationship, the elution of the doping element can be more significantly suppressed, thereby further improving the safety and cycle performance of the battery. For example, the W2 / W1 values ​​in Examples 9 and 10 exceed 250, and the content of the oligomer is relatively high, resulting in an increased viscosity of the electrolyte, which in turn leads to relatively poor overall performance. As can be seen from a comparison between Examples 5 to 10, by selecting a specific W2 / W1 ratio, batteries with better cycle performance and safety performance were obtained.

[0086] Although the present application has been described with reference to the above embodiments, various modifications may be made thereto and equivalents may be substituted for the components therein without departing from the scope of the present application. In particular, the technical features recited in the embodiments may be combined in any manner unless there is a structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims. [Explanation of symbols]

[0087] 1 battery pack 2 Upper housing 3 Lower housing 4 battery modules 5 Lithium-ion secondary battery 51 cases 52 electrode assembly 53 cover plate

Claims

1. A lithium ion battery including a positive electrode and an electrolyte, wherein a positive electrode active material included in the positive electrode contains a doping element, the doping element including at least one selected from W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and the content of the doping element is W1, and 0.01%≦W1≦0.5% based on the weight of the positive electrode active material, and the electrolyte contains an oligomer having the following general formula (I): 【Chemistry 1】 p1 and q1 are the numbers of repeating units, p1 is an integer from 1 to 10, and q1 is an integer from 1 to 15; the content of the oligomer is W2, based on the weight of the electrolyte, and 0.1%≦W2≦10%.

2. 2. The lithium ion battery according to claim 1, wherein the content W2 of the oligomer and the content W1 of the doping element satisfy 0.6≦W2 / W1≦250.

3. 2. The lithium ion battery according to claim 1, wherein the content W1 of the doping element is 0.01%≦W1≦∼0.4%.

4. The lithium ion battery according to any one of claims 1 to 3, wherein the content W2 of the oligomer is 0.2 to 5%.

5. 4. The lithium ion battery according to claim 1, wherein, in general formula (I), P1 is an integer of 2 to 8, and q1 is an integer of 2 to 10.

6. The lithium ion battery according to claim 1 , wherein the doping element comprises at least one selected from the group consisting of Mg, Al, Zr, and B.

7. The positive electrode active material includes a positive electrode active material of the following general formula: Li ｘ [Ni ｙ Co ｚ Mn ｗ ]O ２ 、 4. The lithium ion battery according to claim 1, wherein 0.8≦x≦1.2, 0.5≦y<1.0, 0<z≦0.3, and 0<w≦0.

3.

8. 4. The lithium ion battery according to claim 1, wherein the solvent in the electrolyte solution contains at least one selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, fluorinated ethylene carbonate, ethyl acetate, and ethyl propionate.

9. The lithium salt in the electrolyte solution is LiPF ６ 4. The lithium ion battery according to claim 1, further comprising at least one selected from the group consisting of lithium bis(fluorosulfonyl)imide and lithium bis(fluorosulfonyl)imide.

10. The negative electrode further includes a negative electrode active material, which may be natural graphite, artificial graphite, mesocarbon microbeads, hard carbon, soft carbon, silicon, a silicon-carbon composite, a Li—Sn alloy, a Li—Sn—O alloy, Sn, SnO, or SnO. ２ , lithiated TiO with spinel structure ２ -Li ４ Ti ５ O １２ 4. The lithium ion battery according to claim 1, wherein the lithium ion battery contains at least one selected from the group consisting of a Li-Al alloy and a Li-Al alloy.

11. 4. The lithium ion battery according to claim 1, wherein the electrolyte solution further contains an additive, and the additive includes at least one selected from the group consisting of vinylene carbonate, ethylene sulfate, lithium difluoro(oxalato)borate, lithium difluorophosphate, lithium tetrafluoroborate, 1,3-propane sultone, lithium trifluoromethanesulfonate, and lithium bis(oxalato)borate.

12. A power consuming device comprising a lithium ion battery according to any one of claims 1 to 3.

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