Lithium secondary battery

Abstract

A lithium secondary battery according to embodiments of the present disclosure may comprise a positive electrode including a positive electrode active material which includes a lithium metal oxide in the form of a secondary particle in which a plurality of primary particles are aggregated, and is doped with a positive electrode doping element. In addition, the lithium secondary battery may comprise a negative electrode which includes a negative electrode active material including: a silicon-based active material, including silicon oxide; and a carbon-based active material, and faces the positive electrode. An aspect ratio of the primary particles may be 1.4-7.0, and an amount of the composite active material may be 1-50 wt% with respect to the total weight of the negative electrode active material.

Description

lithium secondary battery

[0001] The present disclosure relates to a lithium secondary battery. More specifically, it relates to a lithium secondary battery including a positive electrode and a negative electrode.

[0002] Secondary batteries, which can be repeatedly charged and discharged, are widely used as power sources for portable electronic communication devices such as camcorders, mobile phones, and laptops, thanks to the advancements in the information and communication and display industries. Furthermore, battery packs containing secondary batteries are being developed and applied as power sources for eco-friendly vehicles such as hybrid vehicles.

[0003] Examples of secondary batteries include lithium secondary batteries, nickel-cadmium batteries, and nickel-hydrogen batteries. Among these, lithium secondary batteries are actively being researched and developed due to their high operating voltage and energy density per unit weight, as well as their advantages in charging speed and weight reduction.

[0004] For example, a lithium secondary battery may include an electrode assembly including a positive electrode, a negative electrode, and a separator, and an electrolyte that impregnates the electrode assembly. The lithium secondary battery may further include an outer packaging material, for example, in the form of a pouch, that accommodates the electrode assembly and the electrolyte.

[0005] For example, the positive electrode may use lithium metal oxide as the positive electrode active material. The positive electrode active material may be damaged on the surface when charging / discharging is repeated, and a side reaction with the electrolyte may also occur.

[0006] For example, the negative electrode may use carbon-based or silicon-based active material particles as the negative electrode active material. When charging and discharging are repeated, the negative electrode active material may suffer mechanical and chemical damage, such as cracks in the particles, and may experience deterioration in contact between the active material particles and short-circuit problems.

[0007] An object of the present disclosure is to provide a lithium secondary battery having improved life characteristics and output characteristics.

[0008] A lithium secondary battery according to exemplary embodiments may include a positive electrode including a lithium metal oxide having a secondary particle form in which a plurality of primary particles are aggregated, and a positive electrode including a positive electrode active material doped or coated with a positive electrode doping element. In addition, the battery may include a silicon-based active material including silicon oxide and a carbon-based active material, and may include an anode facing the positive electrode. An aspect ratio of the primary particles may be 1.4 to 7.0, and a content of the silicon-based active material in the total weight of the negative electrode active material may be 1 wt% to 50 wt%.

[0009] In some embodiments, the aspect ratio of the primary particle may be 1.53 to 5.02.

[0010] In some embodiments, the lithium metal oxide includes nickel, and the mole fraction of nickel among the total moles of all elements excluding lithium and oxygen in the lithium metal oxide may be 0.5 to 0.99.

[0011] In some embodiments, the mole fraction of nickel among the total moles of all elements excluding lithium and oxygen in the lithium metal oxide may be 0.6 to 0.94.

[0012] In some embodiments, the doping element may include at least one of Al, Ti, Zr, Ba, Sr, W, Nb, Y, Mg, V, Ta, Mo, La, and B.

[0013] In some embodiments, the doping element may include at least one of Ti, Zr, Ba, Sr, W, Nb, and Ta.

[0014] In some embodiments, two or more doping elements may be used together.

[0015] In some embodiments, the content of the doping element may be from 100 ppm to 15,000 ppm of the total weight of the lithium metal oxide.

[0016] In some embodiments, the content of the doping element may be from 2,000 ppm to 12,000 ppm of the total weight of the lithium metal oxide.

[0017] In some embodiments, the silicon oxide may be doped or coated with a cathode doping element.

[0018] In some embodiments, the cathode doping element may include at least one of Li, Mg, Al, Ca, Fe, Ti, P, and V.

[0019] In some embodiments, the cathode doping element may include at least one of Li and Mg.

[0020] In some embodiments, the silicon oxide may include at least one of lithium silicate (Li2SiO3), lithium disilicate (Li2Si2O5), magnesium silicate (MgSiO3), and magnesium orthosilicate (Mg2SiO4).

[0021] In some embodiments, the content of the silicon-based active material among the total weight of the negative active material may be 1 wt% to 40 wt%.

[0022] Lithium secondary batteries according to exemplary embodiments of the present disclosure can have improved life characteristics and capacity characteristics.

[0023] Lithium secondary batteries according to exemplary embodiments may use lithium metal oxide doped with a doping element as the cathode active material. The doping element can suppress structural deterioration of the cathode active material during charge / discharge. Accordingly, deterioration of life and capacity characteristics due to damage to the cathode active material can be suppressed.

[0024] Lithium secondary batteries according to exemplary embodiments may utilize both silicon-based and carbon-based active materials as negative active materials. Accordingly, the deterioration of lifespan and capacity characteristics due to expansion of the silicon-based active material can be suppressed. Furthermore, the low capacity characteristics of the carbon-based active material can be improved by the silicon-based active material.

[0025] FIG. 1 and FIG. 2 are schematic plan views and cross-sectional views, respectively, showing lithium secondary batteries according to exemplary embodiments.

[0026] Figures 3 to 5 are images of cross-sections of positive electrode active material particles according to exemplary embodiments, respectively, measured using a scanning electron microscope (SEM).

[0027] According to exemplary embodiments of the present disclosure, a lithium secondary battery is provided, including a positive electrode including a lithium metal oxide having a secondary particle form in which a plurality of primary particles are aggregated, and a negative electrode including a silicon-based active material and a carbon-based active material.

[0028] Hereinafter, the present disclosure will be described in detail with reference to the attached drawings. However, these are merely exemplary and the present disclosure is not limited to the specific embodiments described as examples.

[0029] Hereinafter, unless otherwise specifically defined in the present disclosure, when a part such as a layer, film, thin film, region, or plate is said to be “on” another part, this may include not only the case where it is “directly above” the other part, but also the case where there is another part in between.

[0030] Hereinafter, the meanings of the terms “first” and “second” used in this specification do not limit the number or order of objects modified by “first” and “second,” but merely distinguish different objects modified from each other.

[0031] FIG. 1 and FIG. 2 are schematic plan views and cross-sectional views, respectively, illustrating a lithium secondary battery according to exemplary embodiments. For example, FIG. 2 is a cross-sectional view taken along line I-I' of FIG. 1.

[0032] Referring to FIGS. 1 and 2, a lithium secondary battery may include a positive electrode (100), a negative electrode (130) facing the positive electrode (100), and a separator (140) interposed between the positive electrode (100) and the negative electrode (130).

[0033] The positive electrode (100) may include a positive electrode current collector (105) and a positive electrode active material layer (110) disposed on at least one surface of the positive electrode current collector (105).

[0034] The positive electrode current collector (105) may include stainless steel, nickel, aluminum, titanium, or an alloy thereof. The positive electrode current collector (105) may also include aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver. The positive electrode current collector (105) may have a thickness of, but is not limited to, 10 μm to 50 μm, for example.

[0035] The positive electrode active material layer (110) may include a positive electrode active material. The positive electrode active material may include a compound capable of reversibly intercalating and deintercalating lithium ions.

[0036] According to exemplary embodiments, the positive electrode active material may include a lithium metal oxide having a secondary particle form in which a plurality of primary particles are aggregated.

[0037] According to exemplary embodiments, the aspect ratio of the primary particle may be 1.4 to 7.0.

[0038] If the aspect ratio of the primary particles is less than 1.4, the primary particles may not be stably aggregated. For example, cracks may occur in the secondary particles during repeated life tests, increasing the occurrence of gaps or voids within the secondary particles where the primary particles are aggregated, thereby reducing structural stability. Consequently, the life characteristics of the positive electrode active material may deteriorate.

[0039] If the aspect ratio of the above primary particles exceeds 7.0, the length of the long axis, which is the movement path of lithium ions, may become excessively long, resulting in a deterioration in output characteristics.

[0040] The above primary particle can be morphologically distinguished from a secondary particle. For example, the secondary particle may refer to a particle in which a plurality of primary particles are aggregated and are substantially observed or formed as a single particle. For example, in the case of the secondary particle, the boundary of the primary particles can be observed in a cross-sectional image of a scanning electron microscope (SEM).

[0041] FIGS. 3 to 5 are images of cross-sections of positive electrode active material particles according to exemplary embodiments, obtained by measuring them using a scanning electron microscope (SEM). Specifically, FIGS. 3a and 3b are images of cross-sections of any two positive electrode active material particles among positive electrode active material particles having a secondary particle structure in which primary particles having an aspect ratio of 2.58 are aggregated, respectively, obtained by measuring them using an SEM. FIGS. 4a and 4b are images of cross-sections of any two positive electrode active material particles among positive electrode active material particles having a secondary particle structure in which primary particles having an aspect ratio of 1.42 are aggregated, respectively, obtained by measuring them using an SEM. FIGS. 5a and 5b are images of cross-sections of any two positive electrode active material particles among positive electrode active material particles having a secondary particle structure in which primary particles having an aspect ratio of 6.51 are aggregated, respectively, obtained by measuring them using an SEM.

[0042] Referring to FIGS. 3 to 5, it can be seen that when the aspect ratio of the primary particles is 1.42 to 6.51, the primary particles are stably aggregated to form secondary particles.

[0043] The term "aspect ratio" as used herein refers to the ratio of the length of the major axis to the length of the minor axis of the primary particle. For example, it refers to the ratio of the length of the longest diameter to the length of the shortest diameter among the diameters of the cross section of the primary particle. For example, the closer the aspect ratio is to 1, the more spherical the particle is, and the larger the aspect ratio, the more rod-shaped the particle is.

[0044] In some embodiments, the aspect ratio of the primary particles may be 1.42 to 7.0, or 1.42 to 6.51. Within this range, the primary particles may aggregate to form stable secondary particles. Accordingly, the secondary morphology may be suppressed from collapsing due to repeated charging / discharging of the positive electrode active material, thereby improving both the lifespan characteristics and the output characteristics.

[0045] In some embodiments, the aspect ratio of the primary particles may be 1.5 to 6.51, 1.53 to 6.51, 2.0 to 6.51, 2.58 to 6.51, 2.58 to 6.0, or 2.58 to 5.02. In this range, the life characteristics and output characteristics may be further improved.

[0046] In exemplary embodiments, the positive electrode active material may include lithium metal oxide. For example, the primary particles may be lithium metal oxide, and the secondary particles formed by agglomeration of the primary particles may also be lithium metal oxide.

[0047] In some embodiments, the positive electrode active material or the lithium metal oxide may include nickel. For example, the positive electrode active material or the lithium metal oxide may include a layered structure or crystal structure represented by the following chemical formula 1.

[0048] [Chemical Formula 1]

[0049] Li x Ni a M b O 2+z

[0050] In chemical formula 1, 0.8≤x≤1.2, 0.5≤a≤0.99, 0.01≤b≤0.5, -0.2≤z≤0.2, a+b=1. M may include Co, Mn, and / or Al.

[0051] The chemical structure represented by Chemical Formula 1 represents the bonding relationship included in the layered structure or crystal structure of the positive electrode active material and does not exclude other additional elements. For example, M includes Co and / or Mn, and Co and / or Mn can serve as the main active element of the positive electrode active material together with Ni. Chemical Formula 2 is provided to express the bonding relationship of the above main active elements and should be understood as a formula encompassing the introduction and substitution of additional elements.

[0052] In one embodiment, auxiliary elements may be further included in addition to the main active element to enhance the stability of the positive electrode active material or the layered structure / crystal structure. The auxiliary elements may be incorporated into the layered structure / crystal structure to form bonds, and in this case, it should be understood that they are also included within the chemical structure range represented by Chemical Formula 1.

[0053] The auxiliary element may include, for example, at least one of Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, or Zr. The auxiliary element may also function as an auxiliary active element that contributes to the output activity of the positive electrode active material together with Co or Mn, for example, Al.

[0054] For example, the positive electrode active material or lithium metal oxide may include a layered structure or crystal structure represented by the following chemical formula 1-1.

[0055] [Chemical Formula 1-1]

[0056] Li x Ni a M1 b1 M2 b2 O 2+z

[0057] In Chemical Formula 1-1, M1 may include Co, Mn, and / or Al. M2 may include the auxiliary elements described above. In Chemical Formula 1-1, 0.8≤x≤1.2, 0.5≤a≤0.99, 0.1≤b1+b2≤0.5, -0.2≤z≤0.2, and a+b1+b2=1.

[0058] The above positive electrode active material may include a nickel-cobalt-manganese (NCM) lithium oxide. In this case, an NCM lithium oxide with an increased nickel content may be used.

[0059] Ni can be provided as a transition metal related to the output and capacity of a lithium secondary battery. Therefore, by employing a high-content (High-Ni) composition as described above in the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0060] However, as the Ni content increases, the long-term storage stability and lifespan stability of the cathode or secondary battery may relatively deteriorate, and side reactions with the electrolyte may also increase. However, according to an exemplary embodiment, the lifespan stability and capacity retention characteristics can be improved through the inclusion of Mn while maintaining electrical conductivity by including Co.

[0061] In some embodiments, the mole fraction of nickel among the total moles of all elements excluding lithium and oxygen in the lithium metal oxide (e.g., the mole fraction of nickel among the total moles of nickel, cobalt, and manganese) may be 0.5 to 0.99, 0.5 to 0.98, or 0.6 to 0.98. In this range, the output characteristics and life characteristics of the positive electrode active material may be improved together. For example, while the capacity characteristics may be improved by the nickel element, the structural stability may be improved by the remaining elements excluding nickel. For example, the capacity characteristics may be improved by increasing the content of the nickel element, and thus the amount of lithium metal oxide used may be reduced. Accordingly, the thickness of the electrode (e.g., the positive electrode) may be reduced, thereby improving the output characteristics.

[0062] In one embodiment, the mole fraction of nickel among the total moles of all elements excluding lithium and oxygen in the lithium metal oxide (e.g., the mole fraction of nickel among the total moles of nickel, cobalt, and manganese) may be 0.6 to 0.98, 0.6 to 0.94, or 0.7 to 0.94. In this range, the output characteristics of the positive electrode active material may be further improved.

[0063] In exemplary embodiments, the positive electrode active material (e.g., the lithium metal oxide) may further include a coating element or a doping element. In one embodiment, the coating element or the doping element may penetrate into the primary particle and be positioned inside the primary particle. In one embodiment, the coating element or the doping element may be formed on the surface of the primary particle (e.g., between the primary particles). In one embodiment, the coating element or the doping element may be positioned on the surface of the secondary particle where the primary particles are aggregated.

[0064] In some embodiments, the doping element or the coating element may include at least one of Al, Ti, Zr, Ba, Sr, W, Nb, Y, Mg, V, Ta, Mo, La, and B. Accordingly, the structural stability of the primary particles or the secondary particles in which the primary particles are aggregated may be improved due to the doping element, thereby improving the life characteristics. In addition, the electrical conductivity of the positive electrode active material may be improved, thereby improving the output characteristics.

[0065] In one embodiment, the doping element or the coating element may include at least one of Ti, Zr, Ba, Sr, W, Nb, and Ta. Accordingly, the life characteristics and output characteristics of the positive electrode active material may be further improved.

[0066] In some embodiments, the doping element or the coating element may be used in combination of two or more doping elements or coating elements. For example, a combination of Al and Y, Zr and Mo, Sr and W, Nb and Ti, Mg and B, Ta and Ba, or La and V may be used as the doping element or coating element. Accordingly, the life characteristics and output characteristics of the positive electrode active material may be further improved.

[0067] In one embodiment, the doping element or the coating element may be used in combination of three elements. For example, a combination of Ti, Sr, and Y, or Al, Zr, and W may be used. Accordingly, the life characteristics and output characteristics of the positive electrode active material may be further improved.

[0068] In some embodiments, the content of the doping element or the coating element may be 100 ppm to 15,000 ppm, 300 ppm to 15,000 ppm, or 1,000 ppm to 14,000 ppm based on the total weight of the positive electrode active material (e.g., lithium metal oxide). Within the content range, the doping element or the coating element may be positioned while maintaining an appropriate interval. Accordingly, the electrical conductivity of the positive electrode active material may be improved while suppressing side reactions caused by the doping element or the coating element. Accordingly, the life characteristics and output characteristics may be improved.

[0069] In one embodiment, the content of the doping element or the coating element may be 2,000 ppm to 12,000 ppm, 2,000 ppm to 10,000 ppm, 2,000 ppm to 8,000 ppm, 2,000 ppm to 6,000 ppm, or 2,000 ppm to 4,000 ppm based on the total weight of the positive electrode active material (e.g., lithium metal oxide). In the above content range, the output characteristics and life characteristics of the positive electrode active material may be further improved.

[0070] In some embodiments, the positive electrode active material may further include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium metal phosphate-based active material (e.g., LiFePO4) together with a lithium metal oxide.

[0071] In some embodiments, the positive electrode active material may further include a Mn-rich active material, a Li-rich Layered Oxide (LLO) / Over Lithiated Oxide (OLO) active material, or a Co-less active material having a chemical structure or crystal structure represented by the following Chemical Formula 2, together with a lithium metal oxide.

[0072] [Chemical Formula 2]

[0073] p[Li2MnO3]·(1-p)[LiqJO2]

[0074] In chemical formula 2, 0 <p<1이고, 0.9≤q≤1.2이며, J는 Mn, Ni, Co, Fe, Cr, V, Cu, Zn Ti, Al, Mg 및 B 중 적어도 하나의 원소를 포함할 수 있다.

[0075] For example, a cathode slurry can be prepared by mixing the above-described cathode active material in a solvent. The cathode slurry can be coated on a cathode current collector, and then dried and rolled to prepare a cathode active material layer (110). The cathode slurry can be coated on a cathode current collector, and then dried and rolled to prepare a cathode active material layer (110). The cathode slurry can be coated on a cathode current collector (105), and then dried and rolled to prepare a cathode active material layer (110). The coating process can be performed by a method such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc., but is not limited thereto. The cathode active material layer (110) can further include a binder, and optionally can further include a conductive material, a thickener, etc.

[0076] Non-limiting examples of solvents used in the manufacture of the positive electrode active material layer (110) include N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc.

[0077] The above binder may include polyvinylidenefluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylonitrile, polymethylmethacrylate, acrylonitrile butadiene rubber (NBR), poly(butadiene) rubber (BR), styrene-butadiene rubber (SBR), etc. In one embodiment, a PVDF series binder may be used as the positive electrode binder.

[0078] The conductive material may be added to enhance the conductivity of the positive electrode active material layer (110) and / or the affinity of lithium ions or electrons. For example, the conductive material may include, but is not limited to, a carbon-based conductive material such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), carbon fiber, etc., and / or a metal-based conductive material including a perovskite material such as tin, tin oxide, titanium oxide, LaSrCoO3, LaSrMnO3, etc.

[0079] The positive electrode active material layer (110) may further include a thickener and / or a dispersant. For example, the positive electrode active material layer (110) may include a thickener such as carboxy methyl cellulose (CMC).

[0080] The negative electrode (130) may include a negative electrode current collector (125) and a negative electrode active material layer (120) disposed on at least one surface of the negative electrode current collector (125).

[0081] Non-limiting examples of the negative electrode current collector (125) include copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, and a polymer substrate coated with a conductive metal. The negative electrode current collector (125) is not limited thereto, but may have a thickness of, for example, 10 μm to 50 μm.

[0082] The negative electrode active material layer (120) may include a negative electrode active material. A material capable of adsorbing and desorbing lithium ions may be used as the negative electrode active material.

[0083] According to exemplary embodiments, the negative electrode active material may include a silicon-based active material and a carbon-based active material. Capacity characteristics may be improved depending on the silicon-based active material included in the negative electrode active material, and life characteristics may be improved depending on the carbon-based active material included in the negative electrode active material.

[0084] In some embodiments, the silicon-based active material may include silicon oxide. For example, the silicon oxide may be SiO x (0 <x<2)일 수 있다. 상기 SiO x (0 <x<2)은 높은 이론 용량을 가지면서 순수한 규소(Si)에 비하여 충 / 방전에 따른 부피 변화가 감소하여 안정성이 향상될 수 있다.

[0085] In some embodiments, the silicon oxide may be doped with a cathode doping element or a cathode coating element. For example, the silicon oxide may be SiO doped with a cathode doping element. x (0 <x<2) 또는 음극 코팅 원소로 코팅된 SiO x (0 <x<2)일 수 있다. 이에 따라, 음극 활물질에 의한 수명 특성이 보다 향상될 수 있다.

[0086] In some embodiments, the cathode doping element or the cathode coating element may include at least one of Li, Ma, Al, Ca, Fe, Ti, P, and V. The cathode doping element or the cathode coating element may be positioned, for example, within the lattice structure of the silicon oxide. Accordingly, the electrical conductivity of the silicon oxide may be improved by the cathode doping element or the cathode coating element, and the charge / discharge lifespan may be improved. In addition, the cathode doping element or the cathode coating element may suppress the volume expansion of the silicon oxide due to charge / discharge, so that the lifespan characteristics may be improved.

[0087] In one embodiment, the cathode doping element or the cathode coating element may include at least one of Li and Mg. Accordingly, the life characteristics may be further improved.

[0088] In some embodiments, the silicon oxide may include at least one of lithium silicate (Li2SiO3), lithium disilicate (Li2Si2O5), magnesium silicate (MgSiO3), and magnesium orthosilicate (Mg2SiO4). The compound may have a stable structure in which silicon oxide is doped with Li or Mg. Accordingly, the life characteristics and charge / discharge capacity may be further improved.

[0089] In some embodiments, the silicon-based active material may include an additional material comprising silicon. For example, the silicon-based active material may include silicon (Si), a silicon-carbon composite, or the like.

[0090] In some embodiments, the carbon-based active material may include crystalline carbon, amorphous carbon, carbon composites, carbon fibers, and the like.

[0091] Examples of the above amorphous carbon include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), and mesophase pitch-based carbon fiber (MPCF).

[0092] Examples of the above crystalline carbon include graphite-based carbons such as natural graphite, artificial graphite, graphitized coke, graphitized MCMB, and graphitized MPCF.

[0093] For example, the carbon-based active material may include porous carbon including activated carbon, carbon nanotubes (CNTs), carbon nano-wires, graphene, carbon fibers, carbon black, graphite, microporous carbon, mesoporous carbon, and macroporous carbon, pyrolyzed cryogel, pyrolyzed xerogel, and pyrolyzed aerogel.

[0094] In some embodiments, the negative electrode active material may include additional negative electrode active materials in addition to the silicon-based active material and the carbon-based active material. For example, the negative electrode active material may further include lithium metal, a lithium alloy, a tin (Sn)-containing material, or the like. The lithium metal may be pure lithium metal or lithium metal with a protective layer formed thereon to suppress dendrite growth, etc.

[0095] According to exemplary embodiments, the content of the silicon-based active material in the total weight of the negative electrode active material may be from 1 wt% to 50 wt%.

[0096] The inclusion of a silicon-based active material in the negative electrode active material may improve capacity characteristics but deteriorate life characteristics. The deterioration of life characteristics can be suppressed by doping (or coating) the positive electrode active material with a doping element (or coating element). However, if the content of the silicon-based active material is less than 1 wt% of the total weight of the negative electrode active material, the effect of improving life characteristics by the positive electrode active material to which the doping element (or coating element) has been introduced may not be significant.

[0097] When the content of the silicon-based active material exceeds 50 wt% of the total weight of the negative electrode active material, the content of the silicon-based active material increases, which may increase the volume expansion rate of the negative electrode active material. Accordingly, cracks may occur in the negative electrode active material, which may deteriorate the life characteristics.

[0098] In some embodiments, the content of the silicon-based active material in the total weight of the negative active material may be 1 wt% to 45 wt%, 1 wt% to 40 wt%, 1 wt% to 35 wt%, or 1 wt% to 30 wt%. Within the above content range, both capacity characteristics and life characteristics may be improved.

[0099] For example, the negative electrode slurry can be prepared by mixing the negative electrode active material in a solvent. After coating / depositing the negative electrode slurry on a negative electrode current collector (125), drying and rolling can be performed to prepare a negative electrode active material layer (120). The coating process can be performed by methods such as gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, and casting, but is not limited thereto. The negative electrode active material layer (120) can further include a binder and optionally can further include a conductive material, a thickener, and the like.

[0100] Non-limiting examples of solvents for the negative electrode active material layer (120) include water, pure water, deionized water, distilled water, ethanol, isopropanol, methanol, acetone, n-propanol, t-butanol, etc.

[0101] The above-described materials that can be used in the manufacture of the anode as the binder, conductive agent and thickener can be used.

[0102] In some embodiments, a styrene-butadiene rubber (SBR)-based binder, a carboxymethyl cellulose (CMC)-based binder, a polyacrylic acid-based binder, a poly(3,4-ethylenedioxythiophene, PEDOT)-based binder, or the like may be used as the negative electrode binder.

[0103] A separator (140) may be interposed between the anode (100) and the cathode (130). The separator (140) may be configured to prevent electrical short-circuiting between the anode and the cathode and to allow ion flow. For example, the thickness of the separator (140) may be 10 μm to 20 μm, but the present disclosure is not limited thereto.

[0104] For example, the separator (140) may include a porous polymer film or a porous non-woven fabric. The porous polymer film may include a polyolefin polymer such as an ethylene polymer, a propylene polymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer. The porous non-woven fabric may include high-melting-point glass fibers, polyethylene terephthalate fibers, and the like. The separator (140) may also include a ceramic material. For example, inorganic particles may be coated on the polymer film or dispersed within the polymer film to improve heat resistance.

[0105] The separator (140) may have a single-layer or multi-layer structure including the above-described polymer film and / or non-woven fabric.

[0106] According to exemplary embodiments, an electrode assembly (150) may be formed by repeatedly arranging a positive electrode (100), a negative electrode (130), and a separator (140). In some embodiments, the electrode assembly (150) may be of a winding type, a stacking type, a z-folding type, or a stack-folding type.

[0107] An electrode assembly (150) may be housed together with an electrolyte within a case (160) to define a lithium secondary battery. According to exemplary embodiments, a non-aqueous electrolyte may be used as the electrolyte.

[0108] The non-aqueous electrolyte contains a lithium salt as an electrolyte and an organic solvent, and the lithium salt is, for example, Li + X - is expressed as and the anion of the lithium salt (X - ) as F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN- and (CF3CF2SO2)2N - Examples include the following. These may be used singly or in combination of two or more.

[0109] The organic solvent may include an organic compound that has sufficient solubility for the lithium salt and additives and does not exhibit reactivity within the secondary battery. For example, the organic solvent may include at least one of a carbonate solvent, an ester solvent, a ketone solvent, an alcohol solvent, and an aprotic solvent.

[0110] Examples of the carbonate solvent include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate, diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, ethyl propyl carbonate, dipropyl carbonate, vinylene carbonate, etc.

[0111] Examples of the ester solvent include methyl acetate (MA), ethyl acetate (EA), n-propyl acetate (n-PA), 1,1-dimethylethyl acetate (DMEA), methyl propionate (MP), ethyl propionate (EP), fluoroethyl acetate (FEA), difluoroethyl acetate (DFEA), trifluoroethyl acetate (TFEA), gamma-butyrolactone (GBL), decanolide, valerolactone, mevalonolactone, caprolactone, etc.

[0112] Examples of the ether organic solvent include dibutyl ether, tetraethylene glycol dimethyl ether (TEGDME), diethylene glycol dimethyl ether (DEGDME), dimethoxy ethane, diethoxy ethane, tetrahydrofuran (THF), and 2-methyltetrahydrofuran.

[0113] Examples of the above ketone solvent include cyclohexanone.

[0114] Examples of the alcohol solvent include ethyl alcohol, isopropyl alcohol, etc.

[0115] The aprotic solvent may include, for example, dimethyl sulfoxide, acetonitrile, sulfolane, and propylene sulfite.

[0116] In some embodiments, the electrolyte may further include additives. The additives may include, for example, cyclic carbonate compounds, fluorine-substituted carbonate compounds, sultone compounds, cyclic sulfate compounds, cyclic sulfite compounds, phosphate compounds, and borate compounds. These may be used alone or in combination of two or more.

[0117] The above cyclic carbonate compound may include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), etc.

[0118] The above fluorine-substituted cyclic carbonate compound may include fluoroethylene carbonate (FEC), etc.

[0119] The above sultone compounds may include 1,3-propane sultone, 1,3-propene sultone, 1,4-butane sultone, etc.

[0120] The above cyclic sulfate compound may include 1,2-ethylene sulfate, 1,2-propylene sulfate, etc.

[0121] The above cyclic sulfite compound may include ethylene sulfite, butylene sulfite, etc.

[0122] The above phosphate compound may include lithium difluoro bis-oxalato phosphate, lithium difluoro phosphate, etc.

[0123] The above borate compound may include lithium bis(oxalate) borate, etc.

[0124] For example, electrode tabs (positive electrode tab and negative electrode tab) may protrude from the positive electrode collector (105) and the negative electrode collector (125), respectively, and extend to one side of the case (160). The electrode tabs may be fused together with the one side of the case (160) and connected to electrode leads (positive electrode lead (107) and negative electrode lead (127)) that extend or are exposed to the outside of the case (160).

[0125] For example, a pouch-shaped case, a square case, a cylindrical case, a coin-shaped case, etc. can be used as the case (160).

[0126] The embodiments of the present disclosure described above include the following aspects and can be implemented through at least one of the following aspects.

[0127] A lithium secondary battery according to a first aspect of the present disclosure comprises: a positive electrode including a lithium metal oxide having a secondary particle form in which a plurality of primary particles are aggregated, a positive electrode including a positive electrode active material doped with a positive electrode doping element; and a negative electrode including a silicon-based active material including silicon oxide and a carbon-based active material, the negative electrode facing the positive electrode, wherein an aspect ratio of the primary particles is 1.4 to 7.0, and a content of the silicon-based active material in the total weight of the negative electrode active material is 1 wt% to 50 wt%.

[0128] In the first aspect, according to the second aspect, the aspect ratio of the primary particle may be 1.53 to 5.02.

[0129] In the first aspect or the second aspect, according to the third aspect, the lithium metal oxide includes nickel, and the mole fraction of nickel among the total moles of all elements excluding lithium and oxygen in the lithium metal oxide may be 0.5 to 0.99.

[0130] In any one of the first to third aspects, according to the fourth aspect, the mole fraction of nickel among the total moles of all elements excluding lithium and oxygen in the lithium metal oxide may be 0.6 to 0.94.

[0131] In any one of the first to fourth aspects, according to the fifth aspect, the anode doping element may include at least one of Al, Ti, Zr, Ba, Sr, W, Nb, Y, Mg, V, Ta, Mo, La and B.

[0132] In any one of the first to fifth aspects, according to the sixth aspect, the anode doping element may include at least one of Ti, Zr, Ba, Sr, W, Nb and Ta.

[0133] In any one of the first to sixth aspects, according to the seventh aspect, the anode doping element may be used in combination with two or more doping elements.

[0134] In any one of the first to seventh aspects, according to the eighth aspect, the content of the positive electrode doping element may be 100 ppm to 15,000 ppm of the total weight of the lithium metal oxide.

[0135] In any one of the first to eighth aspects, according to the ninth aspect, the content of the positive electrode doping element may be 2,000 ppm to 12,000 ppm of the total weight of the lithium metal oxide.

[0136] In any one of the first to ninth aspects, according to the tenth aspect, the silicon oxide can be doped with a cathode doping element.

[0137] In the above tenth aspect, according to the eleventh aspect, the cathode doping element may include at least one of Li, Mg, Al, Ca, Fe, Ti, P and V.

[0138] In the above tenth aspect or the eleventh aspect, according to the twelfth aspect, the cathode doping element may include at least one of Li and Mg.

[0139] In any one of the first to twelfth aspects, according to the thirteenth aspect, the silicon oxide may include at least one of lithium silicate (Li2SiO3), lithium disilicate (Li2Si2O5), magnesium silicate (MgSiO3), and magnesium orthosilicate (Mg2SiO4).

[0140] In any one of the first to thirteenth aspects, according to the fourteenth aspect, the content of the silicon-based active material in the total weight of the negative electrode active material may be 1 wt% to 40 wt%.

[0141]

[0142] Hereinafter, embodiments of the present disclosure will be further described with reference to specific experimental examples. The embodiments and comparative examples included in the experimental examples are merely illustrative of the present disclosure and do not limit the scope of the appended claims. It will be apparent to those skilled in the art that various changes and modifications to the embodiments are possible within the scope and technical idea of ​​the present disclosure, and it is natural that such changes and modifications fall within the scope of the appended claims.

[0143]

[0144] Examples and Comparative Examples

[0145] Comparative Example 1

[0146] (1) Manufacturing of anode

[0147] The aspect ratio is 2.58, the anode doping element is not doped, and LiNi 0.5 Co 0.2 Mn 0.3 Secondary particles (hereinafter, CAM-1) were prepared by agglomeration of primary particles having a composition of O2.

[0148] The above aspect ratio was calculated as the ratio of the longest diameter length to the shortest diameter length among the diameter lengths of the cross-section of the primary particle by measuring the cross-section of the primary particle using a scanning electron microscope (SEM).

[0149] A slurry was prepared by mixing CAM-1 as an active material, Denka Black as a conductive material, and polyvinylidene fluoride (PVDF) as a binder in a weight ratio of 92:5:3. The slurry was uniformly applied to a 15 μm thick aluminum foil, dried, and rolled to prepare a positive electrode for a lithium secondary battery.

[0150] (2) Manufacturing of cathode

[0151] A negative electrode active material was prepared by mixing SiO as a silicon-based active material and artificial graphite as a carbon-based active material in a weight ratio of 1:9.

[0152] An anode slurry containing 90 wt% of an anode active material, 4 wt% of a flake-type conductive agent KS6, 3 wt% of a styrene-butadiene rubber (SBR) as a binder, and 3 wt% of carboxymethyl cellulose (CMC) as a thickener was prepared. The anode slurry was uniformly coated on a 15 μm thick copper foil, dried, and rolled to prepare an anode for a lithium secondary battery.

[0153] (3) Manufacturing of lithium secondary batteries

[0154] The positive and negative electrodes manufactured as described above were each cut into a predetermined size and laminated, and a separator (polyethylene, thickness 15 ㎛) was interposed between the positive and negative electrodes to form a cell, and the tab portion of the positive electrode and the tab portion of the negative electrode were each welded. The welded positive electrode / separator / negative electrode assembly was placed in a pouch and sealed on three sides except for the electrolyte injection side. At this time, the part with the electrode tab was included in the sealing part. The electrolyte was injected through the remaining sides except for the sealing side, and the remaining sides were sealed, and then impregnated for more than 12 hours to manufacture a lithium secondary battery.

[0155] The above electrolyte was used as a mixed solvent of EC / EMC / DEC (25 / 45 / 30: volume ratio) in which 3 wt% of fluoroethylene carbonate (FEC), 1 wt% of 1,3-propenesultone (PRS), and 0.5 wt% of lithium bis(oxalato)borate (LiBOB) were added to a 1 M LiPF6 solution.

[0156] After this, pre-charging was performed for 36 minutes at a current (2.5 A) corresponding to 0.25 C. After 1 hour, degassed and aging was performed for more than 24 hours, and then chemical charge / discharge was performed (charge condition CC-CV 0.2C 4.2V 0.05C CUT-OFF, discharge condition CC 0.2C 2.5V CUT-OFF). After this, standard charge / discharge was performed (charge condition CC-CV 0.5C 4.2V 0.05C CUT-OFF, discharge condition CC 0.5C 2.5V CUT-OFF).

[0157] Examples 1 to 7 and Comparative Examples 2 to 7

[0158] A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that the composition of the positive electrode active material and the type and content of the positive electrode doping element were changed as shown in Table 1 below.

[0159] Experimental example

[0160] (1) Evaluation of life characteristics at room temperature (25 ℃)

[0161] After repeating 500 cycles of charging (CC-CV 0.5C 4.2V 0.05C CUT-OFF) and discharging (CC 0.5C 2.75V CUT-OFF) for lithium secondary batteries manufactured according to the examples and comparative examples, the room temperature life characteristics were measured by calculating the discharge capacity at 500 cycles as a % of the single discharge capacity.

[0162] Room temperature life characteristics (%) = (500 discharge capacity / 1 discharge capacity) × 100

[0163] (2) Output characteristics evaluation

[0164] The discharge output characteristics of the lithium secondary batteries manufactured according to the examples and comparative examples were measured using the HPPC (Hybrid Pulse Power Characterization by FreedomCar Battery Test Manual) method.

[0165]

[0166] The evaluation results are shown in Table 1 below.

[0167] Abbreviation for positive electrode active materialNi / Co / Mn(mol ratio)Anode doping elementDoping amount(ppm)Aspect ratioBlend ratio of negative electrode active material(carbon-based active material / silicon-based active material)(weight%)Lifetime characteristics(%)Power characteristics(W / kg)Example 1CAM-850 / 20 / 30Al2,0002.5890 / 1090.72,784Example 2CAM-960 / 20 / 20Al2,0002.5890 / 1092.72,801Example 3CAM-1070 / 15 / 15Al2,0002.5890 / 1096.62,827Example 4CAM-1180 / 10 / 10Al2,0002.5890 / 1080.72,851Example 5CAM-1290 / 5 / 5Al2, 0002.5890 / 1075.32, 906 Example 6CAM-1394 / 3 / 3Al2, 0002.5890 / 1071.92, 990 Example 7CAM-1498 / 1 / 1Al2, 0002.5890 / 1068.23, 005 Comparative Example 1CAM-150 / 20 / 30--2.5890 / 1089.62, 533 Comparative Example 2CAM-260 / 20 / 20--2.5890 / 1085.42, 565 Comparative Example 3CAM-370 / 15 / 15--2.5890 / 1078.62, 589 Comparative Example 4CAM-480 / 10 / 10--2.5890 / 1072.42,618Comparative example 5CAM-590 / 5 / 5--2.5890 / 1066.82,666Comparative example 6CAM-694 / 3 / 3--2.5890 / 1062.52,733Comparative example 7CAM-798 / 1 / 1--2.5890 / 1056.42,754

[0168]

[0169] Referring to Table 1, Examples 1 to 7 including anode doping elements had a lifespan characteristic of 68.2% or more and an output characteristic of 2,784 W / kg or more.

[0170] Figures 3a and 3b are images of the cross-sections of any two positive electrode active material particles according to Example 5, respectively, measured using a scanning electron microscope (SEM). Referring to Figures 3a and 3b, LiNi having an aspect ratio of 2.58 as a primary particle and doped with Al at a content of 2,000 ppm 0.9 Co 0.05 Mn 0.05 When O2 is used, it can be seen that the primary particles are stably aggregated to form secondary particles.

[0171] In Comparative Examples 1 to 7, which did not include anode doping elements, the life characteristics and output characteristics were deteriorated compared to the examples in which other conditions were maintained the same.

[0172]

[0173] Examples 8 to 36 and Comparative Examples 8 to 13

[0174] A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that the type and content of the positive doping element and the aspect ratio were changed as shown in Table 2 below.

[0175]

[0176] Cathode active material abbreviationNi / Co / Mn(mol ratio)Cathode doping elementDoping amount(ppm)Aspect ratioAnode active materialMixing ratio(carbon-based active material / silicon-based active material)(weight%)Life characteristics(%)Power characteristics(W / kg)Example 8CAM-1995 / 5 / 5Al1001.4290 / 1062.62,685Example 9CAM-2095 / 5 / 5Al1001.5390 / 1064.82,679Example 10CAM-2195 / 5 / 5Al1002.5890 / 1067.52,674Example 11CAM-2295 / 5 / 5Al1005.0290 / 1071.22,671Example 12 CAM-2395 / 5 / 5Al1006.5190 / 1073.32,540 Example 13 CAM-2495 / 5 / 5Al3001.4290 / 1062.72,865 Example 14 CAM-2595 / 5 / 5Al3001.5390 / 1069.62,862 Example 15 CAM-2695 / 5 / 5Al3002.5890 / 1073.22,853 Example 16 CAM-2795 / 5 / 5Al3005.0290 / 1077.92,850 Example 17 CAM-2895 / 5 / 5Al3006.5190 / 1080.82,653 Example 18 CAM-2995 / 5 / 5Al2, 0001.4290 / 1062.82, 920 Example 19 CAM-3095 / 5 / 5Al2, 0001.5390 / 1071.02, 918 Example 20 CAM-3195 / 5 / 5Al2, 0005.0290 / 1080.92, 901 Example 21 CAM-3295 / 5 / 5Al2, 0006.5190 / 1083.72, 746 Example 22 CAM-3395 / 5 / 5Al4, 0001.4290 / 1062.92, 943 Example 23 CAM-3495 / 5 / 5Al4, 0001.5390 / 1072.32, 942 Example 24CAM-3595 / 5 / 5Al4,0002.5890 / 1076.62,933Example 25CAM-3695 / 5 / 5Al4,0005.0290 / 1083.72,928Example 26CAM-3795 / 5 / 5Al4,0006.5190 / 1086.72,815Example 27CAM-3895 / 5 / 5Al12,0001.4290 / 1063.02,891Example 28CAM-3995 / 5 / 5Al12,0001.5390 / 1072.82,890 Example 29 CAM-4095 / 5 / 5Al12,0002.5890 / 1078.12,879 Example 30 CAM-4195 / 5 / 5Al12,0005.0290 / 1085.22,878 Example 31 CAM-4295 / 5 / 5Al12,0006.5190 / 1087.52,712 Example 32 CAM-4395 / 5 / 5Al15,0001.4290 / 1063.12,734 Example 33 CAM-4495 / 5 / 5Al15,0001.5390 / 1072.92,730 Example 34CAM-4595 / 5 / 5Al15,0002.5890 / 1078.32,719Example 35CAM-4695 / 5 / 5Al15,0005.0290 / 1085.22,717Example 36CAM-4795 / 5 / 5Al15,0006.5190 / 1087.42,543Comparative Example 8CAM-1595 / 5 / 5--1.4290 / 1062.52,677Comparative Example 9CAM-1695 / 5 / 5--1.5390 / 1064.32,675Comparative Example 10CAM-1795 / 5 / 5--5.0290 / 1070.32,661Comparative Example 11CAM-1895 / 5 / 5--6.5190 / 1072.22,506Comparative example 12CAM-9295 / 5 / 5Al2,0001.0590 / 1060.12,930Comparative example 13CAM-9395 / 5 / 5Al2,0007.0590 / 1084.72,650.

[0177]

[0178] Referring to Table 2, Examples 8 to 36, which included anode doping elements, had an aspect ratio of 1.4 to 7.0, and had a content of anode doping elements of 100 ppm to 15,000 ppm, had a lifespan characteristic of 62.6% or more, and an output characteristic of 2,540 W / kg or more.

[0179] Figures 4a and 4b are images of the cross-sections of any two positive electrode active material particles according to Example 18, measured using a scanning electron microscope (SEM). Referring to Figures 4a and 4b, LiNi having an aspect ratio of 1.42 as a primary particle and doped with Al at a content of 2,000 ppm 0.9 Co 0.05 Mn 0.05 When O2 is used, it can be seen that the primary particles are stably aggregated to form secondary particles.

[0180] Figures 5a and 5b are images of the cross-sections of any two positive electrode active material particles according to Example 21, measured using a scanning electron microscope. Referring to Figures 5a and 5b, LiNi having an aspect ratio of 6.51 as a primary particle and doped with Al at a content of 2,000 ppm 0.9 Co 0.05 Mn 0.05 When O2 is used, it can be seen that the primary particles are stably aggregated to form secondary particles.

[0181] In Examples 19 to 21, 23 to 26, and 28 to 31, in which the aspect ratio was 1.53 to 6.51 and the content of the anode doping element was 2,000 ppm to 12,000 ppm, the life characteristics and output characteristics were somewhat improved.

[0182] In comparative examples 8 to 11 that did not include anode doping elements, the life characteristics and output characteristics were deteriorated compared to the examples in which other conditions were maintained the same.

[0183] In Comparative Example 12, which includes a positive doping element but has an aspect ratio of less than 1.4, the life characteristics were deteriorated compared to the examples in which other conditions were maintained the same.

[0184] In Comparative Example 13, which includes a doping element but has an aspect ratio exceeding 7.0, the output characteristics were degraded compared to the examples in which other conditions were maintained the same.

[0185]

[0186] Examples 37 to 80

[0187] A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that the type and content of the positive doping element were changed as shown in Table 3 below.

[0188]

[0189] Abbreviation for positive electrode active materialNi / Co / Mn(mol ratio)Anode doping elementDoping amount(ppm)Aspect ratioBlend ratio of negative electrode active material(carbon-based active material / silicon-based active material)(weight%)Lifetime characteristics(%)Power characteristics(W / kg)Example 37CAM-4890 / 5 / 5Ti2,0002.5890 / 1075.62,933Example 38CAM-4990 / 5 / 5Ti4,0002.5890 / 1077.62,999Example 39CAM-5090 / 5 / 5Zr2,0002.5890 / 1075.52,959Example 40CAM-5190 / 5 / 5Zr4,0002.5890 / 1078.13,039Example 41 CAM-5290 / 5 / 5Ba2, 0002.5890 / 1075.82, 946 Example 42 CAM-5390 / 5 / 5Ba4, 0002.5890 / 1078.83, 039 Example 43 CAM-5490 / 5 / 5Sr2, 0002.5890 / 1076.02, 906 Example 44 CAM-5590 / 5 / 5Sr4, 0002.5890 / 1078.92, 981 Example 45 CAM-5690 / 5 / 5W2, 0002.5890 / 1076.62, 973 Example 46 CAM-5790 / 5 / 5W4, 0002.5890 / 1078.73, 050 Example 47 CAM-5890 / 5 / 5Nb2, 0002.5890 / 1075.32, 906 Example 48 CAM-5990 / 5 / 5Nb4, 0002.5890 / 1077.82, 951 Example 49 CAM-6090 / 5 / 5Y2, 0002.5890 / 1074.92, 879 Example 50 CAM-6190 / 5 / 5Y4, 0002.5890 / 1077.72, 919 Example 51 CAM-6290 / 5 / 5Mg2, 0002.5890 / 1073.92, 826 Example 52 CAM-6390 / 5 / 5Mg4, 0002.5890 / 1076.42, 893 Example 53CAM-6490 / 5 / 5V2,0002.5890 / 1074.12,933Example 54CAM-6590 / 5 / 5V4,0002.5890 / 1076.93,018Example 55CAM-6690 / 5 / 5Ta2,0002.5890 / 1076.32,906Example 56CAM-6790 / 5 / 5Ta4,0002.5890 / 1078.62,959Example 57CAM-6890 / 5 / 5Mo2,0002.5890 / 1074.02,879 Example 58 CAM-6990 / 5 / 5Mo4,0002.5890 / 1076.82,954 Example 59 CAM-7090 / 5 / 5La2,0002.5890 / 1075.22,933 Example 60 CAM-7190 / 5 / 5La4,0002.5890 / 1077.83,039 Example 61 CAM-7290 / 5 / 5B2,0002.5890 / 1075.42,879 Example 62 CAM-7390 / 5 / 5B4,0002.5890 / 1078.52,935 Example 63CAM-7490 / 5 / 5Al / Y1,000 / 1,0002.5890 / 1080.03,119 Example 64CAM-7590 / 5 / 5Al / Y2,000 / 2,0002.5890 / 1083.53,226 Example 65CAM-7690 / 5 / 5Zr / Mo1,000 / 1,0002.5890 / 1080.33,146 Example 66CAM-7790 / 5 / 5Zr / Mo2,000 / 2,0002.5890 / 1083.73,279 Example 67CAM-7890 / 5 / 5Sr / W1,000 / 1,0002.5890 / 1079.63,226 Example 68CAM-7990 / 5 / 5Sr / W2,000 / 2,0002.5890 / 1082.53,346 Example 69CAM-8090 / 5 / 5Nb / Ti1,000 / 1,0002.5890 / 1078.43,066 Example 70CAM-8190 / 5 / 5Nb / Ti2,000 / 2,0002.5890 / 1082.23,191 Example 71CAM-8290 / 5 / 5Mg / B1,000 / 1,0002.5890 / 1079.43,053 Example 72CAM-8390 / 5 / 5Mg / B2,000 / 2,0002.5890 / 1083.03,165 Example 73CAM-8490 / 5 / 5Ta / Ba1,000 / 1,0002.5890 / 1081.03,071Example 74CAM-8590 / 5 / 5Ta / Ba2,000 / 2,0002.5890 / 1084.53,207Example 75CAM-8690 / 5 / 5La / V1,000 / 1,0002.5890 / 1081.43,109Example 76CAM-8790 / 5 / 5La / V2,000 / 2,0002.5890 / 1084.73,162Example 77CAM-8890 / 5 / 5Ti / Sr / Y700 / 700 / 6002.5890 / 1079.33,034Example 78CAM-8990 / 5 / 5Ti / Sr / Y1,400 / 1,400 / 1,2002.5890 / 1082.23,087Example 79CAM-9090 / 5 / 5Al / Zr / W700 / 700 / 6002.5890 / 1080.73,063Example 80CAM-9190 / 5 / 5Al / Zr / W1,400 / 1,400 / 1,2002.5890 / 1082.83,149.

[0190]

[0191] Referring to Table 3, in Examples 37 to 80, in which at least one of Al, Ti, Zr, Ba, Sr, W, Nb, Y, Mg, V, Ta, Mo, La, and B was used as the anode doping element, and the content of the anode doping element was 2,000 ppm to 4,000 ppm, the life characteristics were 73.9% or more, and the output characteristics were 2,826 W / kg or more. In Examples 37 to 48, 55, and 56, in which at least one of Ti, Zr, Ba, Sr, W, Nb, and Ta was used as the anode doping element, the life characteristics and output characteristics were somewhat improved.

[0192] In Examples 63 to 80, in which two or more doping elements were used as the anode doping elements, the life characteristics and output characteristics were improved.

[0193]

[0194] Examples 81 to 86 and Comparative Examples 14 to 32

[0195] A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that the type and content of the positive electrode doping element and the mixing ratio of the negative electrode active material were changed as shown in Table 4 below.

[0196]

[0197] Abbreviation for positive electrode active materialNi / Co / Mn(mol ratio)Anode doping elementDoping amount(ppm)Aspect ratioBlending ratio of negative electrode active material(carbon-based active material / silicon-based active material)(weight%)Lifetime characteristics(%)Power characteristics(W / kg)Example 81CAM-1295 / 5 / 5Al2,0002.5899 / 186.82,854Example 82CAM-1295 / 5 / 5Al2,0002.5895 / 585.32,889Example 83CAM-1295 / 5 / 5Al2,0002.5880 / 2068.62,950Example 84CAM-1295 / 5 / 5Al2,0002.5870 / 3063.82,999Example 85CAM-1295 / 5 / 5Al2,0002.5860 / 4061.53,025Example 86CAM-1295 / 5 / 5Al2,0002.5850 / 5054.43,092Comparative Example 14CAM-595 / 5 / 5--2.58100 / 090.92,565Comparative Example 15CAM-595 / 5 / 5--2.5899.5 / 0.583.02,573Comparative Example 16CAM-595 / 5 / 5--2.5899 / 181.32,589Comparative Example 17CAM-595 / 5 / 5--2.5895 / 579.42,642Comparative Example 18CAM-595 / 5 / 5--2.5880 / 2059.72,693Comparative example 19CAM-595 / 5 / 5--2.5870 / 3056.22,746Comparative example 20CAM-595 / 5 / 5--2.5860 / 4054.22,773Comparative example 21CAM-595 / 5 / 5--2.5850 / 5047.52,826Comparative example 22CAM-595 / 5 / 5--2.5840 / 6044.52,879Comparative example 23CAM-595 / 5 / 5--2.5830 / 7041.22,933Comparative example 24CAM-595 / 5 / 5--2.5820 / 8037.72,986Comparative example 25CAM-595 / 5 / 5--2.5810 / 9034.43,066Comparative example 26CAM-595 / 5 / 5--2.580 / 10027.43,119Comparative example 27CAM-1295 / 5 / 5Al2,0002.5840 / 6047.73,147Comparative example 28CAM-1295 / 5 / 5Al2,0002.5830 / 7044.03,202Comparative example 29CAM-1295 / 5 / 5Al2,0002.5820 / 8039.93,266Comparative example 30CAM-1295 / 5 / 5Al2,0002.5810 / 9036.33,348Comparative example 31CAM-1295 / 5 / 5Al2,0002.580 / 10028.63,406Comparative example 32CAM-1295 / 5 / 5Al2,0002.5899.5 / 0.583.92,839.

[0198]

[0199] Referring to Table 4, in Examples 81 to 86 using a negative electrode active material including a positive doping element and a silicon-based active material content of 1 wt% to 50 wt% (a carbon-based active material content of 50 wt% to 99 wt% of the total weight of the negative electrode active material), the life characteristics were 54.4% or more, and the output characteristics were 2,854 W / kg or more.

[0200] In Examples 83 to 85, in which the silicon-based active material content was 10 wt% to 40 wt% of the total weight of the negative electrode active material (the carbon-based active material content was 60 wt% to 90 wt% of the total weight of the negative electrode active material), the life characteristics were 60% or more, and the output characteristics were 2,900 W / kg or more.

[0201] In comparative examples 14 to 20 that did not include anode doping elements, the life characteristics and output characteristics were deteriorated compared to the examples in which other conditions were maintained the same.

[0202] In Comparative Examples 22 to 26, which did not include a cathode doping element and used a cathode active material in which the silicon-based active material content exceeded 50 wt% of the total weight of the cathode active material, the life characteristics were less than 45%.

[0203] In Comparative Examples 27 to 31, which included a positive electrode doping element but included a silicon-based active material content exceeding 50 wt% of the total weight of the negative electrode active material, the life characteristics were less than 50%.

[0204] In Comparative Example 32, which included a positive doping element but contained a silicon-based active material content of less than 1 wt% of the total weight of the negative active material, the output characteristics were lowered compared to the examples in which other conditions were maintained the same.

[0205]

[0206] Examples 87 and 88, and Comparative Examples 33 and 34

[0207] A lithium secondary battery was manufactured in the same manner as in Comparative Example 1, except that the content of the positive doping element and the type of silicon-based active material were changed as shown in Table 5 below.

[0208]

[0209] Abbreviation for positive electrode active materialNi / Co / Mn(mol ratio)Anode doping elementDoping amount(ppm)Aspect ratioBlend ratio of negative electrode active material(carbon-based active material / silicon-based active material)(weight%)Type of silicon-based active materialLifetime characteristics(%)Power characteristics(W / kg)Example 87CAM-1295 / 5 / 5Al2,0002.5890 / 10Li 0.52 SiO77.02,884Example 88CAM-1295 / 5 / 5Al2,0002.5890 / 10Mg 0.16 SiO79.92,916Comparative example 33CAM-595 / 5 / 5--2.5890 / 10Li 0.52 SiO68.92,655Comparative example 34CAM-595 / 5 / 5--2.5890 / 10Mg 0.16 SiO71.92,661

[0210]

[0211] Referring to Table 5, SiO(Li) doped with Li or Mg as a silicon-based active material, which includes a cathode doping element 0.52 SiO or Mg 0.16 In Examples 87 and 88 using SiO, the life characteristics were 77.0% or more, and the output characteristics were 2,884 W / kg or more. Referring to Tables 1 and 5, SiO(Li) doped with Li or Mg as a silicon-based active material 0.52 SiO or Mg 0.16In Examples 87 and 88 using SiO, the life characteristics and output characteristics were improved compared to Example 5, which maintained the same conditions except that SiO was used as the silicon-based active material.

[0212] SiO(Li) doped with Li or Mg as a silicon-based active material 0.52 SiO or Mg 0.16 In Comparative Examples 33 and 34, which did not include anode doping elements, the life characteristics and output characteristics were deteriorated compared to the examples in which other conditions were maintained the same.

Claims

1. A cathode comprising a lithium metal oxide having a secondary particle form in which a plurality of primary particles are aggregated, and a cathode active material doped with a cathode doping element; and A silicon-based active material including silicon oxide and a negative electrode active material including a carbon-based active material are included, and a negative electrode is included opposite the positive electrode. The aspect ratio of the above primary particles is 1.4 to 7.0, A lithium secondary battery, wherein the content of the silicon-based active material among the total weight of the negative active material is 1 wt% to 50 wt%.

2. A lithium secondary battery according to claim 1, wherein the aspect ratio of the primary particles is 1.53 to 5.

02.

3. In claim 1, the lithium metal oxide contains nickel, A lithium secondary battery, wherein the mole fraction of nickel among the total moles of all elements excluding lithium and oxygen in the lithium metal oxide is 0.5 to 0.

99.

4. A lithium secondary battery according to claim 3, wherein the mole fraction of nickel among the total moles of all elements excluding lithium and oxygen in the lithium metal oxide is 0.6 to 0.

94.

5. A lithium secondary battery according to claim 1, wherein the positive electrode doping element includes at least one of Al, Ti, Zr, Ba, Sr, W, Nb, Y, Mg, V, Ta, Mo, La, and B.

6. A lithium secondary battery according to claim 5, wherein the positive electrode doping element includes at least one of Ti, Zr, Ba, Sr, W, Nb, and Ta.

7. A lithium secondary battery according to claim 5, wherein the positive electrode doping element is a lithium secondary battery in which two or more doping elements are used together.

8. A lithium secondary battery according to claim 1, wherein the content of the positive electrode doping element is 100 ppm to 15,000 ppm of the total weight of the lithium metal oxide.

9. A lithium secondary battery according to claim 8, wherein the content of the positive electrode doping element is 2,000 ppm to 12,000 ppm of the total weight of the lithium metal oxide.

10. A lithium secondary battery according to claim 1, wherein the silicon oxide is doped with a negative electrode doping element.

11. A lithium secondary battery according to claim 10, wherein the negative electrode doping element includes at least one of Li, Mg, Al, Ca, Fe, Ti, P, and V.

12. A lithium secondary battery according to claim 11, wherein the negative electrode doping element includes at least one of Li and Mg.

13. A lithium secondary battery according to claim 10, wherein the silicon oxide includes at least one of lithium silicate (Li2SiO3), lithium disilicate (Li2Si2O5), magnesium silicate (MgSiO3), and magnesium orthosilicate (Mg2SiO4).

14. A lithium secondary battery according to claim 1, wherein the content of the silicon-based active material among the total weight of the negative electrode active material is 1 wt% to 40 wt%.

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