Electrode comprising electrode additive particles and secondary battery comprising same

Abstract

Disclosed in the present specification is a secondary battery comprising: a positive electrode including a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector; a negative electrode including a negative electrode current collector and a negative electrode active material layer formed on at least one surface of the negative electrode current collector; and an electrolyte layer interposed between the positive electrode and the negative electrode, wherein the positive electrode active material layer includes positive electrode active material particles and electrode additive particles dispersed on the positive electrode active material layer, the negative electrode active material layer includes negative electrode active material particles and electrode additive particles dispersed on the negative electrode active material layer, and the electrode additive particles include fumed silica and have an average diameter of 300 nm or less.

Description

Electrode comprising electrode additive particles and secondary battery comprising the same

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0079511, filed June 19, 2024, and Korean Patent Application No. 10-2025-0079756, filed June 17, 2025, the entire contents of which are incorporated herein by reference.

[0003] The present specification discloses an electrode comprising electrode additive particles and a secondary battery comprising the same.

[0004] With the recent rapid proliferation of battery-powered electronic devices such as mobile phones, laptops, and electric vehicles, demand for small, lightweight, and relatively high-capacity secondary batteries is rapidly increasing. In particular, lithium secondary batteries are attracting attention as a power source for portable devices due to their lightweight design and high energy density. Accordingly, active research and development efforts are underway to improve the performance of lithium secondary batteries.

[0005] Meanwhile, research to improve the rapid charge / discharge performance of secondary batteries is mainly focused on i) improving the ionic conductivity of the electrolyte and ii) improving the film at the electrolyte / active material interface.

[0006] However, in the actual lithium de-insertion / insertion process within the active material, the ionic conductivity of the electrolyte and the electrolyte / active material interfacial film is an important factor, but the concentration of free lithium ions at the interface when inserting lithium ions into the active material is also an important factor.

[0007] Therefore, there is an increasing need for research that can increase the concentration of free lithium ions on the surface of electrode active materials.

[0008] Accordingly, the inventors of the present invention intend to increase the concentration of free lithium ions at the interface when lithium ions are inserted into an active material by dispersing specific electrode additive particles capable of exerting surface charges within the electrode, thereby contributing to improving the performance of a secondary battery to which this is applied.

[0009] Hereinafter, secondary batteries and the like according to specific implementation examples of the present invention will be described.

[0010] Terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0011] The terminology used herein is for the purpose of describing exemplary embodiments only and is not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0012] In this specification, it should be understood that the terms “include,” “comprising,” or “having” are intended to specify the presence of a feature, number, step, component, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0013]

[0014] In one embodiment of the present invention, a secondary battery is provided, comprising: a positive electrode including a positive current collector and a positive active material layer formed on at least one surface of the positive current collector; a negative electrode including a negative current collector and a negative active material layer formed on at least one surface of the negative current collector; and an electrolyte layer interposed between the positive electrode and the negative electrode, wherein the positive active material layer includes positive active material particles and electrode additive particles dispersed on the positive active material layer, and the negative electrode active material layer includes negative active material particles and electrode additive particles dispersed on the negative electrode active material layer, and the electrode additive particles include fumed silica and have an average diameter of 300 nm or less.

[0015] In the above secondary battery, the positive and negative electrodes can be made of general ceramics having surface charges rather than oxide-based solid electrolyte particles containing a lithium source as electrode additive particles, and can have performance improvements similar to or greater than those of the case where oxide-based solid electrolyte particles are included.

[0016] In an exemplary embodiment, the electrode additive particles can increase the free lithium ion concentration at the surfaces of the positive electrode active material layer and the negative electrode active material layer. Meanwhile, the electrode additive particles may include a solid electrolyte and / or a general ceramic. For example, the electrode additive particles may include fumed silica as a general ceramic. In particular, the fumed silica is distinguished from silica fume, which have the greatest differences in particle size and the degree of impurities. Silica fume, which has a large particle size and contains a relatively large amount of impurities, may not significantly improve performance due to a relatively reduced contact area and attractive force with the electrolyte.

[0017] For example, the solid electrolyte may be at least one lithium metal oxide or lithium metal phosphate selected from a Nasicon-type solid electrolyte, a Lisicon-type solid electrolyte, a Garnet-type solid electrolyte, a Perovskite-type solid electrolyte, and a LiPON-type solid electrolyte, and more specific examples thereof may include at least one selected from the group consisting of a LAGP (lithium aluminum germanium phosphate) compound, an LLZO (lithium lanthanum zirconium oxide) compound, a LATP (lithium aluminum titanium phosphate) compound, an LLZTO (lithium lanthanum zirconium tantalum oxide) compound, an LLTO (lithium lanthanum titanium oxide) compound, a LSTP (lithium silicon titanium phosphate) compound, and a LGPO (lithium germanium phosphate) compound.

[0018] In an exemplary embodiment, the electrode additive particles may be included in an amount of 0.5 to 3 wt% based on the total weight of the positive or negative electrode, respectively. If the content is less than 0.5 wt%, the desolvation acceleration reaction due to the oxide may have a low contribution to the improvement of axial force, and if it exceeds 3 wt%, the output performance may be degraded due to a reduction in the reaction area and structural change due to the oxide.

[0019] In the present exemplary embodiment, the electrode additive particles may have an average diameter of 300 nm or less. Specifically, the electrode additive particles may have an average diameter in the range of 100 to 300 nm. As the particle diameter range and / or content range of the electrode additive particles are optimized, the free lithium ion concentration on the surface of the positive electrode active material layer and the negative electrode active material layer can be increased. On the other hand, if the particle diameter range of the electrode additive particles is excessively small, less than 100 nm, the surface of the nano ceramic particles may be covered with a polymer binder, and in this case, the performance improvement characteristics due to the interaction between the nano ceramic / liquid electrolyte may not be exhibited. In particular, fumed silica powder of 100 nm or less is difficult to apply to an actual process due to severe dust scattering, and even if fumed silica of 100 nm or less is added to the electrode slurry, it cannot actually exist at 100 nm or less unless additional processing is performed. These negative characteristics can be avoided by increasing the content of ceramic (electrode additive particles), but it is not desirable to increase it beyond 3 wt% because there are negative performances that come with increasing the ceramic content. Therefore, the effects according to the present invention can be obtained when the particle size range and content range of the electrode additive particles are included in the average diameter range of 100 to 300 nm and 0.5 to 3 wt%, respectively.

[0020] In an exemplary embodiment, the electrode additive particles may have an absolute value of zeta potential of 25 mV or more. In this range, the strength of electrostatic attraction is large, which may increase the concentration of free lithium ions on the surfaces of the positive and negative electrode active material layers.

[0021] In an exemplary embodiment, the negative active material particles may include one or more materials selected from the group consisting of carbonaceous materials, metallic compounds, and metal oxides.

[0022] At this time, a compound capable of reversible intercalation and deintercalation of lithium may be used as the negative electrode active material. Specific examples thereof include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium, such as Si, Al, Sn, Pb, Sb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; metallic oxides capable of doping and dedoping lithium, such as SiOβ (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metallic compounds and carbonaceous materials, such as Si-C composites or Sn-C composites, and any one or a mixture of two or more of these may be used. In addition, a metallic lithium thin film may be used as the negative electrode active material. In addition, both low-crystalline carbon and high-crystalline carbon may be used as the carbonaceous material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of high-crystalline carbon include natural graphite or artificial graphite in the form of amorphous, plate-like, flaky, spherical, or fibers, Kish graphite, pyrolytic carbon, mesophase pitch-based carbon fiber, meso-carbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0023] In an exemplary embodiment, the negative electrode active material layer may further include a binder and a conductive material in addition to the above-described negative electrode active material. The above binder is a component that assists in the bonding of the negative electrode active material and the conductive material and the bonding to the current collector, and includes, for example, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVdF / HFP), polyvinylacetate, polyvinyl alcohol, polyvinyl ether, polyethylene, polyethylene oxide, alkylated polyethylene oxide, polypropylene, polymethyl(meth)acrylate, polyethyl(meth)acrylate, polytetrafluoroethylene (PTFE), polyvinyl chloride, polyacrylonitrile, polyvinylpyridine, polyvinylpyrrolidone, styrene-butadiene rubber, acrylonitrile-butadiene rubber, ethylene-propylene-diene monomer (EPDM) rubber, sulfonated EPDM rubber, styrene-butylene rubber, fluororubber, carboxymethylcellulose (CMC), starch, One or more selected from the group consisting of hydroxypropyl cellulose, regenerated cellulose, and mixtures thereof may be used, but is not necessarily limited thereto.

[0024] The above binder may be used in an amount of 1 to 50 parts by weight, or 3 to 15 parts by weight, based on 100 parts by weight of the total weight of the negative electrode. As a result, the adhesive strength between the negative electrode active material and the current collector and the capacity characteristics of the secondary battery can be excellently maintained.

[0025] In addition, the conductive material included in the negative electrode is not particularly limited as long as it does not cause side reactions in the internal environment of the lithium secondary battery, does not cause chemical changes in the battery, and has excellent electrical conductivity. Representative examples thereof include graphite or conductive carbon, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, and lamp black; carbon-based materials having a crystal structure of graphene or graphite; conductive fibers such as carbon fiber and metal fiber; fluorinated carbon; metal powder such as aluminum powder and nickel powder; conductive whiskey such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which may be used alone or in combination of two or more thereof, but are not necessarily limited thereto.

[0026] The above-mentioned conductive material may be used in an amount of 0.5 to 50 parts by weight, or 1 to 30 parts by weight, based on 100 parts by weight of the total weight of the negative electrode. As a result, the electrochemical properties, such as conductivity and capacity, of the negative electrode and lithium secondary battery can be maintained excellently.

[0027] Additionally, a filler may be optionally added to the cathode as a component that suppresses its expansion. Such filler is not particularly limited as long as it can suppress the expansion of the electrode without causing chemical changes in the battery. Examples of fillers that can be used include olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber; and the like.

[0028] In addition, as the negative electrode current collector, platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS), copper (Cu), molybdenum (Mo), chromium (Cr), carbon (C), titanium (Ti), tungsten (W), ITO (In doped SnO2), FTO (F doped SnO2), and alloys thereof, as well as copper (Cu) or stainless steel surface-treated with carbon (C), nickel (Ni), titanium (Ti), or silver (Ag), but is not necessarily limited thereto. The negative electrode current collector may have a form such as a foil, a film, a sheet, a punched form, a porous body, or a foam body.

[0029] Meanwhile, in the lithium secondary battery of the other embodiment, the above-described positive electrode can be manufactured by, for example, dispersing and mixing the positive electrode active material, binder, and conductive agent in a dispersion medium (solvent) to make a slurry, applying the slurry on a positive electrode current collector, and then drying and rolling. At this time, the dispersion medium may be NMP (N-methyl-2-pyrrolidone), DMF (Dimethyl formamide), DMSO (Dimethyl sulfoxide), ethanol, isopropanol, water, and mixtures thereof, but is not necessarily limited thereto.

[0030] Accordingly, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector.

[0031] The above positive electrode active material is not particularly limited as long as it is a material capable of reversible insertion and de-insertion of lithium ions, and may include, for example, a lithium metal composite oxide including one or more metal elements selected from the group consisting of Co, Mn, Ni, W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, and Mo.

[0032] More specifically, as the positive electrode active material, a compound represented by any one of the following chemical formulas may be used: Li a A 1-b R b D2 (in the above formula, 0.90 ≤ a ≤ 1.8 and 0 ≤ b ≤ 0.5); Li a E 1-b R b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, and 0 ≤ c ≤ 0.05); LiE 2-b R b O 4-c D c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b R c D α (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α ≤ 2); Li a Ni 1-b-c Co b R c O 2-α Z α (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni 1-b-c Co b R c O 2-α Z2 (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni 1-b-c Mn b R c D α (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α ≤ 2); Li a Ni 1-b-c Mn bR c O 2-α Z α (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni 1-b-c Mn b R c O 2-α Z2 (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05 and 0 < α < 2); Li a Ni b E c G d O2 (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5 and 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d GeO2 (in the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5 and 0.001 ≤ e ≤ 0.1); Li a NiG b O2 (in the above formula, 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a CoG b O2 (in the above formula, 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a MnG b O2 (in the above formula, 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4 (wherein 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiTO2; LiNiVO4; and Li (3-f) J2(PO4)3(0 ≤ f ≤ 2).

[0033] In the above chemical formula, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, V or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0034] In addition, the positive electrode may further include a binder and a conductive material in addition to the positive electrode active material described above. The above binder is a component that assists in the bonding of the positive electrode active material and the conductive material and the bonding to the current collector, and includes, for example, polyvinylidene fluoride (PVdF), polyvinylidene fluoride-polyhexafluoropropylene copolymer (PVdF / HFP), polyvinylacetate, polyvinyl alcohol, polyvinyl ether, polyethylene, polyethylene oxide, alkylated polyethylene oxide, polypropylene, polymethyl(meth)acrylate, polyethyl(meth)acrylate, polytetrafluoroethylene (PTFE), polyvinyl chloride, polyacrylonitrile, polyvinylpyridine, polyvinylpyrrolidone, styrene-butadiene rubber, acrylonitrile-butadiene rubber, ethylene-propylene-diene monomer (EPDM) rubber, sulfonated EPDM rubber, styrene-butylene rubber, fluororubber, carboxymethylcellulose (CMC), starch, One or more selected from the group consisting of hydroxypropyl cellulose, regenerated cellulose, and mixtures thereof may be used, but is not necessarily limited thereto.

[0035] The above binder may be used in an amount of 1 to 50 parts by weight, or 3 to 15 parts by weight, based on 100 parts by weight of the total weight of the positive electrode. As a result, the adhesive strength between the positive electrode active material and the current collector and the capacity characteristics of the secondary battery can be excellently maintained.

[0036] In addition, the conductive material included in the positive electrode is not particularly limited as long as it does not cause side reactions in the internal environment of the lithium secondary battery, does not cause chemical changes in the battery, and has excellent electrical conductivity. Representative examples thereof include graphite or conductive carbon, and examples thereof include, but are not limited to, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, and the like; carbon-based materials having a crystal structure of graphene or graphite; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon; metal powders such as aluminum powder or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. These may be used alone or in combination of two or more, but are not necessarily limited thereto.

[0037] The above-mentioned conductive material may be used in an amount of 0.5 to 50 parts by weight, or 1 to 30 parts by weight, based on 100 parts by weight of the total weight of the positive electrode. As a result, the electrochemical properties, such as conductivity and capacity, of the positive electrode and lithium secondary battery can be maintained excellently.

[0038] Additionally, a filler may be optionally added to the positive electrode as a component that suppresses its expansion. Such filler is not particularly limited as long as it can suppress the expansion of the electrode without causing chemical changes in the battery. Examples of fillers that can be used include olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber; and the like.

[0039] In addition, the positive electrode current collector may be formed of, but is not limited to, platinum (Pt), gold (Au), palladium (Pd), iridium (Ir), silver (Ag), ruthenium (Ru), nickel (Ni), stainless steel (STS), aluminum (Al), molybdenum (Mo), chromium (Cr), carbon (C), titanium (Ti), tungsten (W), ITO (In doped SnO2), FTO (F doped SnO2), and alloys thereof, as well as aluminum (Al) or stainless steel surface-treated with carbon (C), nickel (Ni), titanium (Ti), or silver (Ag). The positive electrode current collector may be formed in the form of a foil, a film, a sheet, a punched body, a porous body, a foam, or the like.

[0040] In an exemplary embodiment, the positive electrode active material particles or negative electrode active material particles may have an average diameter in the range of 1 to 20 μm. In addition, the positive electrode active material particles or negative electrode active material particles may have a content of 50 to 99 wt% or 95 wt% or more, respectively, based on the total weight of the positive electrode active material layer or negative electrode active material layer.

[0041] In an exemplary embodiment, all or at least a portion of the outer surface of the positive electrode active material particle or the negative electrode active material particle may be coated with the electrode additive particle.

[0042] Meanwhile, the secondary battery may include an electrolyte layer interposed between the positive electrode and the negative electrode, and the liquid electrolyte included in the electrolyte layer may include a non-aqueous organic solvent and a lithium salt. At this time, the type of non-aqueous organic solvent that can be used is not particularly limited, and any organic solvent that has been previously known to be applicable to electrolytes of lithium ion batteries, etc. may be used. Examples of such organic solvents include at least one selected from the group consisting of carbonate solvents, ether solvents, nitrile solvents, phosphate solvents, and sulfone solvents.

[0043] More specifically, as the carbonate solvent, dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate, fluoroethylene carbonate, methyl propyl carbonate, ethyl methyl carbonate, ethyl propyl carbonate or methyl (2,2,2-trifluoroethyl) carbonate can be used, and as the phosphate solvent, trimethyl phosphate, triethyl phosphate or 2-(2,2,2-trifluoroethoxy)-1,3,2-dioxaphosphorane 2-oxide can be used.

[0044] In addition, as the ether solvent, dibutyl ether, tetraglyme, diglyme, dimethoxy ethane, or tetrahydrofuran derivatives such as 2-methyl tetrahydrofuran can be used, and as the nitrile solvent, succinonitrile, adiponitrile, sebaconitrile, acetonitrile, or propionitrile can be used. In addition, as the sulfone solvent, dimethyl sulfone, ethylmethyl sulfone, or sulforane can be used.

[0045] However, in terms of superior mechanical properties and safety of the composite electrolyte membrane, it is preferable to use a carbonate-based solvent, a sulfone-based solvent, or a phosphate-based solvent, which can be cured at least in part together with the crosslinked polymer and exhibit flame retardancy, as the organic solvent. In addition, it is more preferable to use a solvent that exhibits low volatility under curing conditions for forming the crosslinked polymer, for example, under thermal curing conditions of 60 to 80°C.

[0046] Meanwhile, the lithium salt dissolved or dispersed in the organic solvent may be any lithium salt that has been previously known to be applicable to the electrolyte of a lithium secondary battery, for example, LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis(trifluoromethanesulfonyl)imide), LiCl, LiBr, LiI, LiClO4, LiBF4, LiPF6, LiB 10 Cl 10 , LiCF3SO3, LiCF3CO2, LiC4BO8, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, (C2F5SO2)2NLi, (CF3SO2)3CLi, lithium chloroborane, lithium lower aliphatic carboxylic acid having 4 or less carbon atoms, lithium 4-phenylborate, and lithium imide, and one or more selected from the group consisting of these can be used.

[0047] Such lithium salt may be included in the organic solvent of the liquid electrolyte at a concentration of 0.8 M to 4.0 M, or 1.0 M to 2.0 M, thereby enabling the composite electrolyte membrane of one embodiment to exhibit excellent thermal stability and ionic conductivity.

[0048] Meanwhile, in the lithium secondary battery of the other embodiment, an electrolyte layer may be interposed between the positive and negative electrodes, for example, in the form of a layered membrane or film. In this case, the electrolyte layer may also function as a separator (i.e., electrically insulate the negative and positive electrodes while simultaneously allowing lithium ions to pass through). At this time, the electrolyte layer may be included in the secondary battery by being coated and attached in the form of a thin film on one surface of the positive or negative electrode. In addition, the electrolyte layer may be interposed independently between the positive and negative electrodes. In addition, the lithium secondary battery of the other embodiment may be a semi-solid battery that uses a liquid electrolyte and a solid electrolyte together.

[0049] In addition, when a porous separator is added to the electrolyte layer in the lithium secondary battery, the separator may be made of an olefin polymer such as polyethylene or polypropylene, glass fiber, or the like in the form of a sheet, multi-film, microporous film, woven fabric, or non-woven fabric, but is not necessarily limited thereto. However, it may be preferable to use porous polyethylene or porous glass fiber non-woven fabric (glass filter) as the separator, and it may be more preferable to use porous glass fiber non-woven fabric as the separator. The separator may be an insulating thin film having high ion permeability and mechanical strength, and the pore diameter of the separator may generally be in the range of 0.01 to 10 ㎛, and the thickness may generally be in the range of 5 to 300 ㎛, but is not limited thereto.

[0050] Meanwhile, the lithium secondary battery of the above-described other embodiment can be manufactured according to conventional methods in the art. For example, it can be manufactured by forming a composite electrolyte membrane or the like between the positive and negative electrodes, and optionally adding a porous separator or the like.

[0051] These lithium secondary batteries can be applied to battery cells used as power sources for small devices, and are particularly suitable for use as unit cells in battery modules that serve as power sources for medium- to large-sized devices.

[0052] As described above, the secondary battery according to the embodiment of the present invention can increase the concentration of free lithium ions on the surface of the electrode active material by including fumed silica as electrode additive particles in the positive and negative electrodes.

[0053] Figure 1 compares the charging DC resistance of secondary batteries according to Example 1 and Comparative Examples 1-2 of the present invention.

[0054] Figure 2 compares the discharge DC resistance of secondary batteries according to Example 1 and Comparative Examples 1-2 of the present invention.

[0055] Figure 3 shows the discharge DC resistance of samples in which silica fume and fumed silica were applied as electrode additive particles, respectively, in the secondary batteries of Comparative Examples 1 and 3 of the present invention.

[0056] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement them. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0057]

[0058] Example 1: Cell with 300 nm fumed silica anode / cathode application

[0059] A cathode slurry was prepared by mixing NCM with an average particle diameter (D50) of 10 ㎛ as a cathode active material and fumed silica with an average particle diameter (D50) of 300 nm as an electrode additive particle at a weight ratio of 99:1. Then, the cathode slurry was applied to an aluminum current collector with a thickness of 20 ㎛ and vacuum-dried at 120°C for 24 hours. Next, a rolling process was performed to form a cathode with a thickness of 80 ㎛.

[0060] A negative electrode slurry was prepared by mixing a natural / artificial graphite blend with an average particle size (D50) of 10 ㎛ as a negative electrode active material and fumed silica with an average particle size (D50) of 300 nm as an electrode additive particle at a weight ratio of 99:1. Then, the negative electrode slurry was applied to a copper current collector with a thickness of 20 ㎛ and vacuum dried at 120°C for 24 hours. Next, a rolling process was performed to form a negative electrode with a thickness of 80 ㎛.

[0061] The prepared positive and negative electrodes were positioned so that they face each other, a 15 μm thick polyethylene (PE) separator was interposed between them, and an electrolyte was filled to manufacture a bi-cell type lithium secondary battery. At this time, the electrolyte was prepared by dissolving 1.0 M LiFSI in an organic solvent composed of ethylene carbonate / ethyl methyl carbonate (EC / EMC mixing volume ratio of 3 / 7).

[0062]

[0063] Comparative Example 1: Cell with 300 nm fumed silica anode

[0064] The positive electrode was manufactured in the same manner as in Example 1.

[0065] To manufacture a negative electrode, a natural / artificial graphite blend having an average particle size (D50) of 10㎛ was used as a negative electrode active material, and the negative electrode active material: conductive material: binder was mixed at a weight ratio of 96.5:1.5:2, and the same process as for the positive electrode was performed to manufacture a negative electrode.

[0066] The prepared positive and negative electrodes were positioned so that they face each other, a 15 μm thick polyethylene (PE) separator was interposed between them, and an electrolyte was filled to manufacture a bi-cell type lithium secondary battery. At this time, the electrolyte was prepared by dissolving 1.0 M LiFSI in an organic solvent composed of ethylene carbonate / ethyl methyl carbonate (EC / EMC mixing volume ratio of 3 / 7).

[0067]

[0068] Comparative Example 2: Cell without electrode additive particles

[0069] A cell without electrode additive particles was manufactured in the same manner as in Comparative Example 1, except that no electrode additive particles were used in the positive electrode slurry ('Bare').

[0070]

[0071] Experimental Example 1: Layered DC Resistance

[0072] The cells manufactured in Example 1 and Comparative Examples 1-2 were repeatedly subjected to charge and discharge tests at room temperature (approximately 25°C) under the conditions of 1) 0.2C - 0.33C charging (cut-off: 4.2 V, 0.05 C), 2) 0.2C - 0.33C (cut-off: 2.5 V), and the resistance was measured according to the state of charge (SOC). Specifically, the charge and discharge tests were repeatedly performed under the SOC setting of 10% to 90%, and the DC resistance was measured after each charge and discharge (cut-off: 10 s or 4.5 V).

[0073] Figure 1 compares the charging DC resistance of the secondary batteries of Example 1 and Comparative Examples 1-2 of the present invention. Referring to Figure 1, the charging DC resistance can be confirmed according to the state of charge of the cell, and in particular, it can be confirmed that Example 1, in which fumed silica is applied to both the positive and negative electrodes, exhibits superior charging DC resistance characteristics compared to Comparative Example 1, in which fumed silica is applied only to the positive electrode.

[0074]

[0075] Experimental Example 2: Measurement of Discharge DC Resistance

[0076] The cells manufactured in Example 1 and Comparative Examples 1-2 were repeatedly subjected to charge and discharge tests at room temperature (approximately 25°C) under the following conditions: 1) 0.2C - 0.33C charge (cut-off: 4.2 V, 0.05 C), 2) 0.2C - 0.33C (cut-off: 2.5 V), and the resistance was measured according to the state of charge (SOC). Specifically, the charge and discharge tests were repeatedly performed under the SOC setting of 10% to 90%, and the DC resistance was measured after each charge and discharge (cut-off: 10 s or 2 V).

[0077] Figure 2 compares the discharge DC resistance of the secondary batteries of Example 1 and Comparative Examples 1-2 of the present invention. Referring to Figure 1, the discharge DC resistance can be confirmed according to the state of charge of the cell, and in particular, it can be confirmed that Example 1, in which fumed silica was applied to both the positive and negative electrodes, exhibits somewhat better charging DC resistance characteristics compared to Comparative Example 1, in which fumed silica was applied only to the positive electrode.

[0078]

[0079] Comparative Example 3: Cell with Silica Fume Anode Application

[0080] A silica fume cathode application cell was manufactured in the same manner as in Comparative Example 1, except that silica fume with an average particle diameter (D50) of 800 nm was used as the electrode additive particle ('Silica fumed').

[0081]

[0082] Experimental Example 3: Discharge DC Resistance - Comparison with Silica Fume

[0083] By applying Comparative Examples 1 and 3, the discharge DC resistance was measured in the same manner as Experimental Example 2, and the performance difference according to the application of fumed silica and silica fume was confirmed.

[0084] FIG. 3 compares the discharge DC resistance of samples using silica fume and fumed silica as electrode additive particles in secondary batteries using the positive electrodes according to Comparative Examples 1 and 3 of the present invention. The biggest difference between fumed silica and silica fume is the particle size and the degree of impurities. Referring to FIG. 3, it was confirmed that silica fume, which has a large particle size and contains relatively many impurities, does not significantly improve performance due to a relatively reduced contact area and attractive force with the electrolyte.

[0085]

[0086] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

Claims

1. A positive electrode including a positive electrode current collector and a positive electrode active material layer formed on at least one surface of the positive electrode current collector; A negative electrode comprising a negative current collector and a negative active material layer formed on at least one surface of the negative current collector; and An electrolyte layer interposed between the positive and negative electrodes; The positive electrode active material layer includes positive electrode active material particles and electrode additive particles dispersed on the positive electrode active material layer, and the negative electrode active material layer includes negative electrode active material particles and electrode additive particles dispersed on the negative electrode active material layer. A secondary battery, wherein the electrode additive particles include fumed silica and have an average diameter of 300 nm or less.

2. In paragraph 1, A secondary battery, wherein the electrode additive particles increase the concentration of free lithium ions on the surfaces of the positive electrode active material layer and the negative electrode active material layer.

3. In paragraph 1, A secondary battery, wherein the electrode additive particles are each included in an amount of 0.5 to 3 wt% relative to the total weight of the positive or negative electrode.

4. In paragraph 1, A secondary battery, wherein the electrode additive particles have an average diameter in the range of 100 to 300 nm.

5. In paragraph 1, A secondary battery, wherein the positive electrode active material particles or negative electrode active material particles have an average diameter in the range of 1 to 20 um.

6. In paragraph 1, A secondary battery, wherein the electrode additive particles have an absolute value of zeta potential of 25 mV or more.

7. In paragraph 1, A secondary battery, wherein the negative active material particles include at least one material selected from the group consisting of carbonaceous materials, metallic compounds, and metal oxides.

8. In paragraph 1, A secondary battery, wherein all or at least a portion of the outer surface of the positive electrode active material particle or the negative electrode active material particle is covered with the electrode additive particle.

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