Active cathode material for lithium secondary batteries with suppressed side reactions with electrolyte and improved ionic conductivity

Abstract

FIELD: chemistry.SUBSTANCE: active material for a positive electrode for secondary lithium batteries with improved ionic conductivity and suppression of side reactions with the electrolyte. Positive active material contains a doping additive based on a titanium-containing transition metal, which is titanium isopropoxide, in an amount of 4 to 6 wt.% A positive active material for lithium-ion batteries containing the said alloying additive based on a titanium-containing transition metal suppresses side reactions with the electrolyte and provides increased ionic conductivity. EFFECT: improving the output power and service life of the lithium-ion battery, which is the technical result of the invention.3 cl, 1 dwg, 2 ex

Description

[0001] Technical field

[0002] The present invention relates to a cathode active material for lithium-ion batteries that suppresses side reactions with electrolyte and provides increased ionic conductivity. More specifically, the invention relates to a cathode active material for lithium-ion batteries that suppresses side reactions with electrolyte and has high ionic conductivity, thereby enabling the production of lithium-ion batteries with improved energy characteristics and high output power.

[0003] Prior Art

[0004] With the rapid development of the IT industry since the 2000s, cutting-edge IT devices combining the functions of personal computers, laptops, digital cameras, and other devices have been continuously entering the market. Rechargeable lithium-ion batteries, which are well suited for portable devices, are primarily used as the power source for their operation.

[0005] Modern IT devices are gradually improving and becoming more powerful in response to growing consumer demands. To achieve this high performance, ever-increasing energy is required. However, the capacity of lithium-ion batteries used in these devices has not increased significantly. Therefore, increasing the capacity of energy sources—particularly lithium-ion batteries—is considered a key issue for the further development of the IT industry. Therefore, over the past ten years, significant research and investment have been focused on the development of electrode materials for lithium-ion batteries with increased capacity.

[0006] A lithium-ion battery primarily consists of a cathode, anode, electrolyte, and separator. During charging, lithium ions released from the cathode active material are intercalated (integrated) into the anode active material. Conversely, during discharging, lithium ions are deintercalated (released) from the anode material and return to the cathode. Thus, lithium ions circulate between the cathode and anode, enabling energy storage and release during charging and discharging.

[0007] Recently, lithium-ion batteries have been facing increased demands for durability and fast charging capabilities. As a result, research is underway to develop cathode materials that can not only extend battery life but also ensure fast charging speeds and high output power.

[0008] However, traditional active cathode materials suffer from low electronic conductivity, which does not allow high charging speed to be realized, and are also prone to side reactions with the electrolyte, which reduces their durability.

[0009] Patent documents

[0010] Patent Document No. 1 Patent of the Republic of Korea No. 10-1478880 (Registration Date: 12 / 26 / 2014)

[0011] Patent Document No. 2 Patent of the Republic of Korea No. 10-2004457 (Registration Date: July 22, 2019)

[0012] Essence of the invention The technical problem to be solved

[0013] The object of the present invention is to provide a cathode active material for lithium-ion batteries that suppresses side reactions with electrolyte and provides improved ionic conductivity, thereby making it possible to create lithium-ion batteries with improved output power and cycle life.

[0014] Means of solving a technical problem

[0015] The said object is achieved by providing a cathode active material for lithium-ion batteries that suppresses side reactions with the electrolyte and has increased ionic conductivity, and a characteristic feature of the material is the content of an alloying additive based on a titanium-containing transition metal in an amount of 4 to 6% by weight.

[0016] According to a preferred embodiment of the invention, said titanium-containing transition metal-containing alloying additive is titanium isopropoxide.

[0017] According to a more preferred embodiment, said cathode active material for lithium-ion batteries, which suppresses side reactions with an electrolyte and has increased ionic conductivity, further contains a conductive polymer in an amount of 1 to 2% by weight.

[0018] According to an even more preferred embodiment, said conductive polymer is obtained by heat treating one or more components selected from the group consisting of polyacrylonitrile, cellulose and its derivatives, saccharides, chlorinated polyvinyl chloride (CPVC, Chlorinated Polyvinyl Chloride), polyaniline and polyvinyl alcohol.

[0019] According to a particularly preferred embodiment, the heat treatment is carried out at a temperature of 380 to 420°C for 25 to 35 minutes.

[0020] Furthermore, the aim of the present invention can also be achieved by providing a lithium-ion battery characterized in that it consists of a positive electrode consisting of a positive active material for a lithium-ion battery, in which side reactions with said electrolyte are suppressed and ionic conductivity is improved, a negative electrode and an electrolyte.

[0021] Invention Effect

[0022] The positive active material for a lithium-ion battery according to the present invention, which suppresses side reactions with the electrolyte and improves ion conductivity, exhibits an excellent effect of providing a lithium-ion battery with improved performance in output power and cycle life.

[0023] Brief description of drawings

[0024] Fig. 1 - Schematic representation of the process of obtaining a positive active material coated with a conductive polymer.

[0025] Implementation of the invention

[0026] Below, preferred embodiments of the present invention are described in detail, as well as the properties of individual components. This description is given with sufficient detail to enable a person skilled in the art with ordinary knowledge to easily implement the invention; however, this does not mean that the technical content and scope of the present invention are limited to the embodiments described.

[0027] The present invention relates to a positive active material for a lithium-ion battery, in which side reactions with an electrolyte are suppressed and ionic conductivity is improved, wherein said material contains a dopant based on a titanium-containing transition metal, preferably in an amount of 4 to 6% by weight.

[0028] A titanium-based transition metal alloying additive, preferably present in an amount of 4 to 6% by weight, is alloyed into the positive active material and serves to improve the structural stability of the lithium-ion battery during charging and discharging, thereby extending its service life. Titanium isopropoxide (TTIP) is the preferred alloying additive.

[0029] In general, the nickel content in positive active materials for lithium-ion batteries should be relatively high. However, the higher the nickel content, the lower the battery's structural stability during charge-discharge cycles and the worse its long-term performance. This problem can be solved by alloying with the aforementioned titanium-containing transition metal additive.

[0030] If the content of the titanium-containing transition metal alloying additive is less than 4% by weight, the effect achieved will be insignificant. On the other hand, if the content exceeds 6% by weight, no significant improvement will be observed, while the output power and capacity of the lithium-ion battery may decrease, which is undesirable.

[0031] Furthermore, the positive active material for a lithium-ion battery, in which side reactions with the electrolyte are suppressed and ion conductivity is improved, may additionally contain a conductive polymer in an amount of 1 to 2% by weight. Preferably, said conductive polymer is obtained by heat treatment of one or more components selected from the group consisting of polyacrylonitrile, cellulose and its derivatives, saccharides, chlorinated polyvinyl chloride (CPVC, Chlorinated Polyvinyl Chloride), polyaniline, and polyvinyl alcohol.

[0032] In more detail, the positive active material doped with a titanium-containing transition metal additive is mixed with 1-2% by weight of a carbonizable material such as polyacrylonitrile, cellulose and its derivatives, saccharides, chlorinated polyvinyl chloride (CPVC, Chlorinated Polyvinyl Chloride), polyaniline and polyvinyl alcohol, and heat treated for 25-35 minutes at a temperature of 380-420°C. In this way, a positive active material coated with a conductive polymer is obtained.

[0033] Figure 1 below shows the process of producing a positive active material coated with a conductive polymer, in particular using polyacrylonitrile.

[0034] The positive active material obtained through the process shown in Fig. 1 suppresses side reactions with the electrolyte and improves ion conductivity, thus achieving a lithium-ion battery with higher output power and longer service life.

[0035] If the conductive polymer content is 1% by weight, the effect achieved will be insignificant. However, if the conductive polymer content exceeds 2% by weight, no significant improvement will be observed, while the capacity of the lithium-ion battery may decrease, which is undesirable.

[0036] In addition, the positive active material for a lithium-ion battery composed of the above components can be used as a positive electrode in a lithium-ion battery and, together with a negative electrode and an electrolyte, form a lithium-ion battery.

[0037] The positive active material contained in the said positive electrode can be a common positive active material used in traditional lithium-ion batteries. Examples of such materials include lithium transition metal complex oxides such as LiM x O y(where M=Co, Ni, Mn or CoaNibMnc).

[0038] In addition, the negative active material contained in the negative electrode can be a common active material used in the negative electrodes of traditional lithium-ion batteries. Such materials include, but are not limited to, lithium metal, lithium alloys, carbon, petroleum coke, activated carbon, graphite, and other carbon materials, as well as lithium metal oxides used alone or in combination. Examples of lithium metal oxides include lithium transition metal complex oxides such as Li. x M γ Oz (where M is a transition metal such as V, an alkaline earth metal, a metalloid, or combinations thereof).

[0039] In addition, a foil made of aluminum, nickel, or a combination of them can be used as the positive electrode current collector, and a foil made of copper, gold, nickel, copper alloys, or a combination of them can be used as the negative electrode current collector.

[0040] In addition, generally accepted materials in the field can be used as the conductive additive. For example, these can be graphite materials such as natural or synthetic graphite; carbon blacks such as acetylene black carbon; conductive fibers such as carbon or metal fibers; metal powders such as aluminum powder; conductive materials such as zinc oxide fibers or conductive potassium titanate fibers; conductive metal oxides such as titanium oxide; and organic conductive materials such as phenylene derivatives. The conductive additive can be used either as a single component or as a combination of two or more components.

[0041] In addition, generally accepted materials in the field can be used as the binder used in the positive and negative electrodes. Examples of binders include: polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aramid resin, polyamide, polyimide, polyamideimide, polyacrylonitrile, polyacrylic acid, methyl polyacrylate, ethyl polyacrylate, polymethacrylic acid, methyl polymethacrylate, ethyl polymethacrylate, hexyl polymethacrylate, polyvinyl acetate, polyvinyl acetate, polyvinylpyrrolidone, polyester, polyethersulfone, hexafluoropolypropylene, styrene butadiene rubber, modified acrylic rubber and carboxymethyl cellulose.

[0042] In addition, the lithium-ion battery constructed from the above components can be applied to all types of lithium-ion batteries, including coin cells, pouch cells, prismatic batteries and cylindrical batteries.

[0043] Below, a method for producing a positive active material for a lithium-ion battery according to the present invention, in which side reactions with an electrolyte are suppressed and ionic conductivity is improved, as well as the characteristics of a lithium-ion battery into which the positive active material obtained by this method is introduced will be described using specific embodiment examples.

[0044] Example 1

[0045] Positive active material LiNiCoO5 doped with 5% by weight titanium isopropoxide, binder polyvinylidene fluoride, and carbon conductive additive were dispersed in N-methyl-2-pyrrolidone solvent at a weight ratio of 90:5:5 to obtain a positive electrode suspension. The resulting suspension was applied (coated) onto aluminum foil to form a thin electrode plate, which was then dried at 110°C for 2 hours and pressed to obtain a positive electrode.

[0046] Example 2

[0047] 1.5% by weight of polyacrylonitrile was added to 98.5% by weight of LiNiCoO2 positive active material doped with 5% by weight of titanium isopropoxide, stirred for 30 minutes at 200 rpm, and then heated at 400°C for 30 minutes to obtain LiNiCoCh coated with a conductive polymer. Then, the obtained positive active material, polyvinylidene fluoride (as a binder), and a carbon conductive additive were dispersed in N-methyl-2-pyrrolidone at a weight ratio of 90:5:5 to obtain a positive electrode suspension. The resulting suspension was applied to aluminum foil to form a thin electrode plate, which was dried at 110°C for 2 hours and pressed to obtain a positive electrode.

[0048] Comparative Example 1

[0049] The positive active material LiNiCoO2, polyvinylidene fluoride (as a binder), and a carbon conductive additive were dispersed in N-methyl-2-pyrrolidone at a weight ratio of 90:5:5 to obtain a positive electrode suspension. The resulting suspension was applied to aluminum foil to form a thin electrode plate, which was then dried at 110°C for 2 hours and pressed to obtain a positive electrode.

[0050] Therefore, the positive active material for a lithium-ion battery according to the present invention, in which side reactions with the electrolyte are suppressed and ion conductivity is improved, makes it possible to obtain a lithium-ion battery with an increased output power and an extended service life by suppressing side reactions with the electrolyte and improving ion conductivity.

Claims

1. A positive active material for a lithium-ion battery, characterized in that it contains an alloying additive based on a titanium-containing transition metal, which is titanium isopropoxide, in an amount of 4 to 6% by weight, suppresses side reactions with the electrolyte and has improved ionic conductivity.

2. An active cathode material for a lithium-ion battery, comprising a positive active material according to claim 1, characterized in that it further comprises a conductive polymer in an amount of 1 to 2% by weight, obtained by heat treatment at a temperature of 380 to 420°C for 25 to 35 minutes of at least one of the components selected from the group consisting of polyacrylonitrile, cellulose and its derivatives, saccharides, chlorinated polyvinyl chloride, polyaniline and polyvinyl alcohol, suppressing side reactions with the electrolyte and increasing ionic conductivity.

3. A lithium-ion battery, characterized in that it consists of a cathode made of an active cathode material for a lithium-ion battery according to paragraph 2, an anode and an electrolyte.

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