KR20190059115A - Irreversible Additive Comprised in Cathode Material for Lithium Secondary Battery, Preparing Method thereof, and Cathode Material Comprising the Same - Google Patents

Abstract

The present invention relates to an irreversible additive contained in a positive electrode material for a lithium secondary battery, a method for manufacturing the same, and a positive electrode material comprising the additive. The irreversible additive comprises a lithium-excess transition metal oxide in a form of a secondary particle formed by aggregating a plurality of primary particles. A surface of the primary particles and a surface of the secondary particles are coated with at least one compound containing a metal element (M) and at least one compound containing boron (B), wherein M is any one selected from a group consisting of Al, Ti, Zr, and W.

Description

TECHNICAL FIELD The present invention relates to an irreversible additive contained in a cathode material for a lithium secondary battery, a method for producing the same, a cathode material containing the cathode material,

The present invention relates to an irreversible additive contained in a cathode material for a lithium secondary battery, a process for producing the same, and a cathode material containing the same.

As technology development and demand for mobile devices have increased, the demand for secondary batteries has increased sharply as an energy source. A lot of studies have been made on lithium secondary batteries with high energy density and discharge voltage among such secondary batteries, . Such a lithium secondary battery generally uses a lithium transition metal oxide as a cathode active material and a carbon-based material as an anode active material.

However, the theoretical maximum capacity of a negative electrode made of a carbon-based material is limited to 372 mAh / g (844 mAh / cc), which limits the capacity increase. Lithium metal, which has been studied as a cathode material, has a very high energy density and can realize a high capacity. However, there is a problem of safety due to dendrite and short cycle life during repeated charging and discharging.

Therefore, the use of an anode active material having a high energy density as a material capable of replacing a lithium metal with a high capacity has been inevitable, and many researches and proposals have been made on silicon, tin, or alloys thereof. For example, a silicon-based material reversibly intercalates and deintercalates lithium through a compound-forming reaction with lithium and has a theoretical maximum capacity of about 4200 mAh / g (9366 mAh / cc, specific gravity 2.23) Therefore, it is promising as a high capacity anode material.

For this reason, the use of the anode of the silicon oxide is inevitably prevented, but in the case of the anode including the silicon oxide, the capacity is large. However, since the initial efficiency is low, the consumed amount of Li is large during the initial charge and discharge.

It was confirmed that the energy density per unit volume and mass can be greatly increased by applying a sacrificial anode material that can provide Li as an additive to the silicon oxide cathode during the initial charge and discharge.

However, such a sacrificial anode material generally contains excessive Li and is liable to induce gelation in the battery due to a high Li by-product, and gas generation is relatively large, which is a serious problem in secondary cell performance.

Therefore, it is necessary to apply a coating layer capable of suppressing such Li by-products and protecting the secondary particles of the sacrificial anode material and the surfaces of the primary particles constituting the secondary particles.

In general, the formation of a coating layer forms a stable phase and surrounds the surface, or a material capable of forming a compound with lithium reacts with Li by-products located on the surface of the sacrificial anode material to form a new phase, have.

 In the case of such conventional coating techniques, a method of coating the materials to be coated by dry or wet mixing is adopted. In the dry process, the process ratio is generally lower than that of the wet process, and it is convenient and generally used. However, there is a limit in that coating is not performed well to the primary particle surface forming the secondary particles. On the other hand, although the wet process can coat the surface of the primary particles inside, an additional process of removing the solvent is required, and the process ratio is increased.

Accordingly, there is a high need for a coating method capable of uniformly coating the surface of primary particles in the secondary particles such as wet coating, while using a dry coating method that is simple in the manufacturing method if the process ratio is low.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and have found that when coating with tungsten oxide and aluminum oxide, which are stable coating sources at high voltage, coating with a raw material including boron, the irreversible additives And the surface of the primary particles in the secondary particles can be coated on the surface of the secondary particles of the secondary particles. Thus, the present invention has been accomplished.

Therefore, the irreversible additive of the present invention is an irreversible additive contained in a cathode material for a lithium secondary battery,

Wherein the irreversible additive comprises a lithium-excess transition metal oxide in the form of a secondary particle formed by aggregating a plurality of primary particles,

The surface of the primary particles and the surface of the secondary particles are coated with at least one compound containing a metal element (M) and at least one compound containing boron (B)

And M is any one selected from the group consisting of Al, Ti, Zr, and W.

Here, the irreversible additive is added to the cathode material so as to provide Li to the silicon oxide in order to supplement the consumption amount of Li of the initial silicon oxide in the lithium secondary battery using silicon oxide as the anode active material, Thereby solving the problem of capacity reduction of initial charge and discharge which may be a problem when used as a negative electrode active material.

However, as described above, since the irreversible additive is a Li overbased material, Li by-products are formed due to the nature of the Li irreversible additive, which may cause problems in battery performance.

For this purpose, a coating layer is formed on the surface of a Li-excess material. In the case of the dry coating method, the coating source can not penetrate into the secondary particles constituting the Li-excessive material, and the Li byproduct can not effectively be inhibited.

On the other hand, the irreversible additive according to the present invention has a structure in which a coating layer is uniformly formed not only on the surface of secondary particles but also on the surface of primary particles constituting secondary particles, on the surface of lithium-excess transition metal oxide composed of secondary particles , It is possible to effectively inhibit Li by-products present on the surface of the primary particles, thereby solving the problem of gelation or gas generation which may be caused by adding the lithium-excessive irreversible additive as described above.

Here, the lithium-excess transition metal oxide may be represented by any of the following formulas (1) to (4).

Li ₂ Ni _{1 - x} M _x O ₂ (1)

_{Li 2 Ni 1 - x M x} O 2 · Li 2 O · NiO (2)

Li ₆ Co _{1 - x} M _x O ₄ (3)

_{Li 6 Co 1 - x M x} O 4 · Li 2 O · Co y O z (4)

Wherein M is at least one anion selected from the group consisting of P, B, and F, or at least one transition metal selected from the group consisting of W, Ti, and Zr,

0? X <1, 1? Z / y? 2.

In detail, the M may be at least one transition metal selected from the group consisting of Ti, and Zr.

As described above, the lithium-excess transition metal oxide contains at least two times Li as a molar ratio relative to the transition metal. Therefore, it is used as an irreversible source which supplies extra Li to the cathode of silicon oxide, which consumes Li due to irreversible in the initial charge / discharge cycle. Therefore, it is possible to reduce the Li consumption of the cathode active material and to prevent the irreversible capacity of the actual anode from increasing, so that the energy density per unit volume and mass can be greatly increased.

On the other hand, the lithium-excess transition metal oxide may include a secondary particle type in which a plurality of primary particles are aggregated, wherein the secondary particles may be in the form of a coagulated phase in which the primary particles are slightly weakly aggregated , And it may be in the form of a single particle having a grain boundary because aggregation of the primary particles is firmly formed.

A coating layer for inhibiting Li by-products may be formed on the surface of the lithium-excess transition metal oxide of the secondary particles. According to the present invention, such a coating layer is formed on the surface of secondary particles, Can be evenly formed to the surface of the substrate

The coating layer may be coated with at least one compound containing a metal element (M) and at least one compound containing boron (B) by a manufacturing method described below.

Here, the compound containing the metal element (M) is stable at a high voltage and is not largely affected by the use environment of the lithium secondary battery using the cathode material containing the metal element (M), thereby securing the stability of the irreversible additive according to the coating , The compound containing boron (B) can lower the barrier energy due to the migration of Li ions, thereby increasing the efficiency and preventing the reactivity with the electrolyte solution, thereby ensuring the stability of the irreversible additive.

At this time, the compound containing the metal element (M) may be selected from the group consisting of a compound containing Al and a compound containing W. That is, the coating layer may include only one of the compound containing Al, W, or both compounds.

More specifically, the compound containing the metal element (M) may be selected from the group consisting of a lithium metal (M) oxide and a metal (M) oxide.

That is, the coating layer may include at least one selected from the group consisting of aluminum (Al) oxide, lithium aluminum oxide, tungsten (W) oxide, and lithium tungsten oxide.

The compound containing boron (B) may be selected from the group consisting of lithium boron oxide and boron oxide.

Thus, for example, the coating layer may be composed of lithium boron oxide, boron oxide, aluminum oxide, and lithium aluminum oxide, and may be composed of lithium boron oxide and lithium aluminum oxide, and lithium boron oxide, tungsten oxide, and lithium tungsten oxide And the combination of the above materials may be variously performed. At this time, the compound containing the metal element (M) can be determined depending on the coating source.

More specifically, the compound containing the metal element (M) is a lithium metal (M) oxide represented by the following formula (5), and the compound containing boron (B) is a lithium boron oxide Lt; / RTI &gt;

Li _a MO _b (5)

LiBO ₂ (6)

Li ₂ B ₄ O ₇ (7)

LiB ₃ O ₅ (8)

Here, M is any one selected from the group consisting of Al, Ti, Zr, and W;

1 ? A ? 5, and 2 ? B ? 5.

That is, the coating layer may be in an oxide form including Li. This is because, during the manufacturing process, the raw material containing the metal (M) and the raw material containing boron (B) are mixed with an excess lithium transition metal oxide and subjected to heat treatment so that the surface of the excess lithium metal oxide And reacts with Li by-products present therein to form an oxide including Li.

Therefore, the metal (M) oxide and the boron (B) oxide may be partially formed when the coating layer is likely to be formed in the form of an oxide containing Li, and a portion which remains unreacted partially with Li remains.

On the other hand, the structure of the coating layer may be a structure in which at least one compound containing the metal element (M) is coated in a particle form and a compound containing boron (B) is coated in a film form, May be a matrix-filler structure in which at least one compound containing a metal element (M) is uniformly distributed in the form of particles in a film of a compound containing boron (B).

Here, the term 'uniform' means that at least one kind of the compound containing the metal element (M) exists in a distributed rather than a localized manner.

This is due to the difference in melting point between the raw material containing the metal element (M) and the raw material containing boron (B) during the manufacturing process.

Basically, the raw material containing the metal element M has a melting point exceeding 1000 deg. C, while the melting point of the raw material containing boron (B) is as low as 300 deg. C or less. Therefore, , The raw material containing boron melts and is liquefied, and plays a role of moving the raw material including the metal element (M) so as to spread evenly on the surface of the particles.

At this time, the particle diameter of the compound including the metal element (M) may have an average particle diameter (D50) of 10 nm to 500 nm.

If the particle size is too small, it is not preferable because there is a problem in handling in the process, and when the particle size is too large, there is a problem of uniform distribution on the particle surface.

On the other hand, in one or more compounds containing at least one metal element (M) constituting the coating layer and at least one compound containing boron (B), the content of the metal element (M) is preferably 4000 (B) can be contained in the range of 400 to 2000 ppm, specifically in the range of 500 to 1500 ppm, based on the total weight of the irreversible additive have.

When the coating layer is formed so as to include the content of the metal element (M) and the content of the boron (B) in excess of the above range, it is not preferable to form a coating layer to achieve the desired effect, The thickness of the coating layer becomes thick, and accordingly, the supply of Li of the lithium-excess transition metal oxide may not be performed smoothly, which is not preferable.

Such an irreversible additive according to the present invention can be obtained, for example,

(a) an irreversible additive precursor comprising a lithium-excess transition metal oxide in the form of a secondary particle in which primary particles are aggregated, at least one raw material containing a metal element (M), and a raw material containing boron (B) Mixing the materials;

(b) heat treating the mixed mixture in the step (a) under an inert atmosphere;

. &Lt; / RTI &gt;

That is, the irreversible additive of the present invention can be produced by a dry coating method which is easy to manufacture and does not increase the process cost. That is, the mixing of the process (a) may be a dry mixing. Nevertheless, according to the present invention, the problem that only the surface of the secondary particles, which is the limit of the conventional dry coating method, is coated by mixing the raw materials containing boron (B) together and heat- It is possible to coat the surface of the primary particles inside, thereby more effectively suppressing Li by-products.

Here, the irreversible additive precursor may include a lithium-excess transition metal oxide, and the lithium-excess transition metal oxide may be a material represented by the general formulas (1) to (4) as described above.

The source material containing the metal element M may be an oxide including the metal element M and more specifically may be selected from the group consisting of Al ₂ O ₃ and WO ₃ .

When two or more kinds of raw materials are used as the raw material containing the metal element (M), the coating layer of the irreversible additive to be produced may be formed of two or more kinds of compounds including the metal element (M). For example, when Al ₂ O ₃ and WO ₃ are used together as a raw material containing a metal element (M), the coating layer may contain a compound containing Al and a compound containing W. Thus, the composition of the coating layer can be determined as necessary by adjusting the raw material.

The raw material containing the boron (B) may be H ₃ BO ₃ .

As described above, the raw materials including the metal element (M), for example, Al ₂ O ₃ and / or WO _3, have melting points of 2072 ° C for Al ₂ O ₃ and 1473 ° C for WO ₃ , These particles are coated only on the secondary particle surface of the lithium-excess transition metal oxide in the form of particles in the case of coating with the dry coating method using only these as a coating source.

However, according to the manufacturing method of the present invention, by using a raw material containing boron (B) together with a raw material containing the metallic element (M), the raw material containing boron (B) For example, since H ₃ BO ₃ has a melting point of 170.9 ° C. and is lower than a general coating temperature, the raw material including boron (B) is liquefied by the heat treatment in the above-mentioned process (b) ) Is dragged into the secondary particles of the lithium-excess transition metal oxide, so that these coating sources can all be coated to the inner primary particle surface.

At this time, at least one raw material containing the metal element (M) is mixed so that the content of M is 0.5 mol% based on the irreversible additive precursor, and the raw material containing boron (B) The content of B may be 1.0 mol%.

When mixed as described above, a coating layer can be formed by the content of the metal element (M) and boron (B) described above to form an appropriate amount of the coating layer.

Meanwhile, the heat treatment in the step (b) may include a step of forming a coating layer on the surface of the lithium-excess transition metal oxide by a raw material containing at least one starting material including the metal element M of the mixture and boron (B) , Whereby a compound containing at least one compound containing a metal element (M) to the surface of the secondary particle of the lithium-excess transition metal oxide and the primary particle surface inside the secondary particle, and a compound containing boron (B) A coating layer composed of one or more species can be formed.

At this time, the heat treatment may be performed under an inert atmosphere, specifically, in an atmosphere containing at least one element selected from the group consisting of N ₂ , Ar, and He.

In this way, it is necessary to carry out the reaction in an inert atmosphere to prevent the excess lithium transition metal oxide from being oxidized.

In addition, the conditions of the heat treatment for the coating may be performed at 350 to 450 degrees Celsius for 2 to 7 hours.

If the coating temperature is too low or the temperature is too short, the coating layer is not formed well. In addition, since the coating sources are not penetrated into the interior of the secondary particles, If the heat treatment temperature is too high or the heat treatment time is too long, the coating source is not formed as a coating layer but reacts with lithium-excessive transition metal oxide to form doping, It is possible to substitute to form a new substance, which is not preferable.

The present invention also provides a cathode material comprising at least one irreversible additive and a cathode active material. In addition, the cathode material may further include a conductive material and a binder.

The cathode active material may be, for example, a layered compound such as lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (LiNiO ₂ ) or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _{2 - x} O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ and LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; Formula _{LiNi 1 - x M x O 2} ( where, the M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, x = 0.01 ~ 0.3 Im) Ni site type lithium nickel oxide which is represented by; Formula LiMn _{2 -x} M _x O ₂ (where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); A lithium manganese composite oxide having a spinel structure represented by LiNi _x Mn _{2 - x} O ₄ ; LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ , and the like, but is not limited thereto.

The conductive material is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon black such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, and nickel powder; Conductive whiskey such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used. Concrete examples of commercially available conductive materials include acetylene black series such as Chevron Chemical Company, Denka Singapore Private Limited, Gulf Oil Company, etc.), Ketjenblack, EC (Armak Company), Vulcan XC-72 (Cabot Company), and Super P (Timcal).

The binder is a component which assists in bonding of the active material and the conductive material and bonding to the current collector, and is usually added in an amount of 1 to 30% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The positive electrode material according to the present invention can be manufactured as a positive electrode coated on the positive electrode collector and the electrode assembly in which the positive electrode and the negative electrode are stacked with the separator interposed therebetween is formed of lithium It can be used for a secondary battery.

At this time, the cathode material according to the present invention is more preferably used for a cathode including a specific anode active material.

As described above, when the silicon oxide is used as the negative electrode active material, although the capacity is large, since the initial efficiency is low, the consumed amount of Li is large at the time of initial charge-discharge and there is a problem in capacity development, It is possible to solve problems such as gelation and gas generation in the battery when silicon oxide is used as the negative electrode active material.

Therefore, silicon oxide may be used as an anode active material, which is a counter electrode of a cathode including a cathode material according to the present invention.

Further, the negative electrode active material is selected from the group consisting of crystalline artificial graphite, crystalline natural graphite, amorphous hard carbon, low crystalline soft carbon, carbon black, acetylene black, Ketjen black, super P, graphene, one or more carbon-based material, Si-based _{materials, Li x Fe 2 O 3 (} 0≤x≤1), Li x WO 2 (0≤x≤1), Sn x Me 1 is _{- x Me 'y O z (} Me : Mn, Fe, Pb and Ge; Me ': Al, B, P, Si, Group 1, Group 2 and Group 3 elements of the periodic table, Halogen: 0 < x &lt;8); Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, And Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials; Titanium oxide; Lithium titanium oxide, and the like, but the present invention is not limited thereto.

The negative electrode is prepared, for example, by coating a negative electrode slurry containing the negative electrode active material and drying the negative electrode collector. The negative electrode slurry may contain the above-described components as needed.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 300 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The electrolyte solution may be a lithium salt-containing non-aqueous electrolyte, and is composed of a non-aqueous electrolyte and a lithium salt. Non-aqueous organic solvents, organic solid electrolytes, inorganic solid electrolytes, and the like are used as the non-aqueous electrolyte.

Examples of the non-aqueous organic solvent include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl Methyl carbonate, gamma-butylolactone, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, But are not limited to, methyl ethyl ketone, methyl ethyl ketone, methyl ethyl ketone, methyl ethyl ketone, methyl ethyl ketone, cyclohexanone, cyclohexanone, cyclohexanone, An organic solvent such as an organic solvent such as an organic solvent such as an organic solvent such as an organic solvent such as an organic solvent such as an organic solvent such as toluene, Can be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, A polymer containing an ionic dissociation group and the like may be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF 6, LiCF 3 SO 3, LiCF 3 CO 2, LiAsF _{6, LiSbF 6, LiAlCl 4,} CH 3 SO 3 Li, CF 3 SO 3 Li, LiSCN, LiC (CF 3 SO 2) 3, (CF 3 SO 2) ₂ NLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium 4-phenylborate, imide and the like can be used.

The lithium salt-containing non-aqueous electrolyte may further contain, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxyethanol, trichloro-aluminum triflate, tetraethoxysilane, hexafluorophosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, Etc. may be added. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

In one specific _{example, LiPF 6, LiClO 4, LiBF} 4, LiN (SO 2 CF 3) 2 , such as a lithium salt, a highly dielectric solvent of DEC, DMC or EMC Fig solvent cyclic carbonate and a low viscosity of the EC or PC of And then adding it to a mixed solvent of linear carbonate to prepare a lithium salt-containing non-aqueous electrolyte.

INDUSTRIAL APPLICABILITY As described above, the irreversible additive of the present invention is characterized in that a coating layer composed of at least one compound containing a metal element (M) and at least one compound containing boron (B) By-products are effectively suppressed and the surface stability is excellent by having the constitution that is formed up to the surface of the inner primary particles of the secondary particles. When the battery is manufactured by incorporating the irreversible additive into the cathode material, Li can be provided to the active material to improve the energy density, while effectively preventing deterioration of battery performance.

In addition, since the irreversible additive is produced by the dry coating method, the manufacturing process is simplified and the manufacturing cost can be prevented from increasing.

1 is a graph showing the results of residual lithium amount according to Experimental Example 1;
2 is a graph showing the results of residual lithium amount according to Experimental Example 2. FIG.

Hereinafter, the present invention will be described in further detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

&Lt; Preparation Example 1 &

Then a solution of the Li ₂ O 50g and NiO 136g, N ₂ and then heat-treated at ° C 685 degrees for 18 hours in the atmosphere to cool the reaction of the results to give a non-reversible additive particles _{Li 2 NiO 2 · Li 2 O} · NiO.

&Lt; Preparation Example 2 &

After mixing 50 g of Li ₂ O and 37 g of Co (OH) ₂ , the mixture was heat-treated at 685 ° C. for 18 hours under an N ₂ atmosphere. The resultant reaction product was cooled to obtain irreversible additive particles Li ₆ CoO ₄ .Li ₂ O.Co ₂ O ₃ .

&Lt; Example 1 >

For the surface coating of the non-reversible additive particles prepared in Preparation Example 1, the 100g of _{Li 2 NiO 2 · Li 2 O} · NiO, 1.17g of WO _3, H ₃ BO ₃ 0.62g of dry mixing, and 450 degrees Celsius For 5 hours to prepare an irreversible additive.

&Lt; Comparative Example 1 &

The _{Li 2 NiO 2 · Li 2 O} · NiO prepared in Preparative Example 1 was used.

&Lt; Comparative Example 2 &

For the surface coating of the non-reversible additive particles prepared in Preparation Example 1, to the 100g of _{Li 2 NiO 2 · Li 2 O} · NiO, 0.62g of H ₃ BO _3, and dry-mixed, the heat treatment for 5 hours at 450 degrees Celsius Irreversible additives were prepared.

&Lt; Comparative Example 3 &

For coating the surface of a Li ₂ NiO ₂ prepared in Preparative Example 1, 100g of _{Li 2 NiO 2 · Li 2 O} · NiO, by dry mixing 1.17g WO _3, and the heat treatment for 5 hours at 450 degrees Celsius irreversible additives .

&Lt; Example 2 >

For the surface coating of the produced _{Li 6 CoO 4 · Li 2 O} · Co 2 O 3 in Preparative Example 2, 100g of _{Li 6 CoO 4 · Li 2 O} · Co 2 O 3, WO ₃ of 1.17g, 0.62g Of H ₃ BO ₃ were dry mixed and heat treated at 450 ° C. for 5 hours to prepare an irreversible additive.

&Lt; Comparative Example 4 &

Li ₆ CoO ₄ .Li ₂ O.Co ₂ O ₃ prepared in Preparation Example 2 was used.

&Lt; Comparative Example 5 &

For the surface coating of the produced _{Li 6 CoO 4 · Li 2 O} · Co 2 O 3 in Preparative Example 2, 100g of _{Li 6 CoO 4 · Li 2 O} · Co 2 O 3, 0.62g of the H ₃ BO ₃ Dry mixing and heat treatment at 450 DEG C for 5 hours to prepare an irreversible additive.

&Lt; Comparative Example 6 >

For the ₆ Li CoO · ₄ surface coating of Li ₂ O · Co ₂ O ₃ prepared in Preparative Example 2, mixed with 100g of _{Li 6 CoO 4 · Li 2 O} · Co 2 O 3, 1.17g of WO ₃ dry And heat treated at 450 DEG C for 5 hours to prepare an irreversible additive.

<Experimental Example 1>

In order to evaluate the residual amount of each of the manufactured Li irreversible additives in Example 1 and Comparative Examples 1 to 3 was measured, the content by using the titration method the Li residue form of LiOH and Li- ₂ CO ₃ in 0.1M HCl. 10 g of the coated or uncoated irreversible additive is added to 100 ml of water and stirred for 5 minutes. After stirring, the solution was filtered, and 0.1 M HCl was slowly added to the solution. The amount of residual HCl was calculated by changing the amount of HCl introduced through the changing pH.

The results are shown in Fig.

Referring to FIG. 1, it can be seen that the Li residual amount of the irreversible additive according to the present invention is remarkably reduced. In particular, the residual amount of Li was remarkably decreased as compared with the case of coating using only WO ₃ and H ₃ BO ₃ . It is believed that this is due to the coating on the primary particle surface.

<Experimental Example 2>

The evaluation was conducted in the same manner as in Experimental Example 1 to evaluate the Li residual amounts of the irreversible additives prepared in Example 2 and Comparative Examples 4 to 6, respectively.

The results are shown in Fig.

Similarly to FIG. 1, FIG. 2 also shows that the Li residual amount of the irreversible additive according to the present invention is remarkably reduced. In particular, the residual amount of Li was remarkably decreased as compared with the case of coating using only WO ₃ and H ₃ BO ₃ . It is believed that this is due to the coating on the primary particle surface.

&Lt; Example 3 >

The non-reversible additive prepared in Example 1 was added to NMP as a solvent at a weight ratio of 92: 2: 2: 4, using LiCoO ₂ as a positive electrode active material and a positive electrode active material: Super-P: binder (PVdF) A slurry was prepared, which was coated on aluminum foil at 70 [mu] m, dried and pressed at 130 [deg.] C to produce a positive electrode.

SiO2 was used as a negative electrode active material, and a binder (PVdF) of SiO2: conductive material (Super-P) was added to NMP as a solvent at a weight ratio of 95: 2.5: 2.5 to prepare an anode mixture slurry. Coated at 70 [micro] m, dried and pressed at 130 [deg.] C to prepare a negative electrode.

A liquid electrolyte in which 1 M LiPF ₆ was dissolved in a solvent in which the above-mentioned positive electrode and negative electrode were separated, a polyethylene film (Celgard, thickness: 20 μm) and ethylene carbonate, , A secondary battery was manufactured.

&Lt; Comparative Examples 7 to 9 &

Secondary batteries were prepared in the same manner as in Example 3 except that the irreversible additives prepared in Comparative Examples 1 to 3 were respectively used.

<Experimental Example 3>

The secondary batteries produced in Example 3, Comparative Examples 7 and 9 were measured for gas generation by the method described below.

More specifically, the cells prepared in each of the Examples and Comparative Examples were charged at 0.1 C to 4.25 V at 25 캜, and the gas collected in the pouch was analyzed by GC-TCD (gas chromatography-thermal conductivity detector). The results are shown in Table 1 below.

Example 3 Comparative Example 7 Comparative Example 9 Gas content CO ₂ 16 62 55 (Μl) CO 92 215 209 C ₂ H ₄ 6.5 13 12.1 Total amount 114.5 290 276.1

Experimental results show that when the irreversible additives of Example 1 are used, the amounts of byproducts and unreacted materials contained in the positive electrode material are reduced, and thus the amount of generated gas is greatly reduced compared with the case of using the additives of the comparative example.

Those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims (17)

As an irreversible additive contained in a cathode material for a lithium secondary battery,
Wherein the irreversible additive comprises a lithium-excess transition metal oxide in the form of a secondary particle formed by aggregating a plurality of primary particles,
The surface of the primary particles and the surface of the secondary particles are coated with at least one compound containing a metal element (M) and at least one compound containing boron (B)
Wherein M is any one selected from the group consisting of Al, Ti, Zr, and W.
The non-reversible additive according to claim 1, wherein the lithium-excess transition metal oxide is represented by any one of the following formulas (1) to (4)
Li ₂ Ni _{1 - x} M _x O ₂ (1)
Li ₂ Ni _{1 - x} M _x O _{2 -} Li ₂ O - NiO (2)
Li ₆ Co _{1 - x} M _x O ₄ (3)
Li ₆ Co _{1 - x} M _x O _{4 -} Li ₂ O - Co _y O _z (4)
Wherein M is at least one anion selected from the group consisting of P, B, and F, or at least one transition metal selected from the group consisting of W, Ti, and Zr,
0? X <1, 1? Z / y? 2.
The irreversible additive according to claim 1, wherein the compound containing the metal element (M) is selected from the group consisting of a compound containing Al and a compound containing W.
The method according to claim 1, wherein the compound containing the metal element (M) is selected from the group consisting of lithium metal (M) oxide and metal (M) oxide, and the compound containing boron (B) is selected from the group consisting of lithium boron oxide and boron Oxide. &Lt; / RTI &gt;
5. The compound according to claim 4, wherein the compound containing the metal element (M) is a lithium metal (M) oxide represented by the following formula (5), and the compound containing boron (B) An irreversible additive which is an oxide.
Li _a MO _b (5)
LiBO ₂ (6)
Li ₂ B ₄ O ₇ (7)
LiB ₃ O ₅ (8)
Here, M is any one selected from the group consisting of Al, Ti, Zr, and W;
1 ? A ? 5, and 2 ? B ? 5.
The irreversible additive according to claim 1, wherein at least one compound containing the metal element (M) is coated in a particle form, and the compound containing boron (B) is coated in a coating form.
The method of claim 6, wherein the at least one compound containing the metal element (M) is an irreversible additive coated with a matrix-filler structure uniformly distributed in the form of particles in a film of a compound containing boron (B) .
The irreversible additive according to claim 1, wherein the compound containing the metal element (M) has an average particle diameter of 10 nm to 500 nm.
The method of claim 1, wherein the metal element (M) is contained in a range of 4000 to 20000 ppm based on the total weight of the irreversible additive, and the boron (B) is contained in a range of 400 to 2000 ppm based on the total weight of the irreversible additive Irreversible additives.
A method for producing an irreversible additive according to claim 1,
(a) an irreversible additive precursor comprising a lithium-excess transition metal oxide in the form of a secondary particle in which primary particles are aggregated, at least one raw material containing a metal element (M), and a raw material containing boron (B) Mixing the materials;
(b) heat treating the mixed mixture in the step (a) under an inert atmosphere;
&Lt; / RTI &gt;
The method according to claim 10, wherein at least one of the raw materials including the metal element (M) is mixed so that the content of M is 0.5 mol% based on the irreversible additive precursor, and the raw material containing boron (B) And the content of B is 1.0 mol% based on the irreversible additive precursor.
The method for producing an irreversible additive according to claim 10, wherein the starting material containing boron (B) is H ₃ BO ₃ .
The method for producing an irreversible additive according to claim 10, wherein the starting material containing the metal element (M) is selected from the group consisting of Al ₂ O ₃ and WO ₃ .
The method for producing an irreversible additive according to claim 10, wherein the inert atmosphere is an atmosphere containing at least one element selected from the group consisting of N ₂ , Ar, and He.
11. The method of claim 10, wherein the heat treatment is performed at a temperature of 350 to 450 DEG C for 2 to 7 hours.
An anode material comprising at least one irreversible additive according to claim 1, and a cathode active material.
17. The cathode material according to claim 16, wherein the cathode material further comprises a conductive material and a binder.

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