KR102328884B1 - Method of positive active material for rechargeable lithium battery - Google Patents

Abstract

A lithium metal compound and a phosphorus (P)-containing compound positioned on the surface of the lithium metal compound, wherein the phosphorus (P) content in the phosphorus-containing compound is 0.1 with respect to the total atomic weight of the elements present on the surface of the positive electrode active material Provided are a positive active material for a lithium secondary battery in atomic% to 10 atomic%, a method for preparing the same, and a lithium secondary battery including the same.

Description

Method of manufacturing a cathode active material for a lithium secondary battery

A cathode active material for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same.

Recently, with the development of the advanced electronic industry, miniaturization and weight reduction of electronic equipment are possible, and the use of portable electronic devices is increasing. As the need for a battery having a high energy density as a power source for such portable electronic devices is increasing, research on lithium secondary batteries is being actively conducted.

Such a lithium secondary battery includes a positive electrode including a positive electrode active material capable of intercalating and deintercalating lithium and a negative electrode including a negative electrode active material capable of intercalating and deintercalating lithium. It is used by injecting an electrolyte into a battery cell containing

As the cathode active material, LiCoO ₂ is most widely used. Recently, a substitute material, such as as a high-capacity and high-output and stable even required, performance and three-component system of LiCoO _2, up bingye as the use of a lithium secondary battery expansion by industries such as power tools, automobile by the mobile information electronic device Research on development is actively underway.

In particular, lithium nickel-based oxide having a high nickel content can have a high capacity and exhibit excellent electrochemical properties. However, due to the presence of a lot of residual lithium on the surface, cycle characteristics are deteriorated and stability is low, making it impossible to use for a long period of time.

One embodiment is to provide a positive electrode active material for a lithium secondary battery that exhibits a high capacity, has excellent lifespan characteristics, and has excellent stability due to a small amount of gas generation.

Another embodiment is to provide a method of manufacturing the positive active material.

Another embodiment is to provide a lithium secondary battery including the positive active material.

One embodiment includes a lithium metal compound, and a phosphorus (P)-containing compound positioned on the surface of the lithium metal compound, and the content of phosphorus (P) contained in the phosphorus-containing compound is the amount of elements present on the surface of the positive electrode active material. Provided is a positive active material for a lithium secondary battery in an amount of 0.1 atomic% to 10 atomic% based on the total atomic weight.

The phosphorus-containing compound may include lithium phosphate.

The phosphorus-containing compound is Li ₃ PO ₄ , Li ₂ HPO ₄ , LiH ₂ PO ₄ , LiMPO ₄ (M = Fe, Co, Mn, Ni, V, La, Ti, or Al), (NH ₄ ) ₂ HPO ₄ , (NH ₄ )H ₂ PO ₄ , AlPO ₄ , H ₃ PO ₄ , or a combination thereof.

The lithium metal compound may include a lithium nickel-based oxide represented by Formula 1 below.

[Formula 1]

Li _x Ni _y M _z O ₂

(In Formula 1,

M is Co, Mn, Al, Mg, Ti, Zr, or a combination thereof, and 0.95≤x≤1.00, 0.4≤y≤1.00, 0≤z≤0.6, and y+z=1.)

Another embodiment includes washing the first active material with an aqueous solution of a phosphorus (P)-containing material to obtain a second active material, wherein the first active material is a lithium metal compound and a lithium compound positioned on the surface of the lithium metal compound Including, wherein the lithium metal compound and the lithium compound are different, the second active material is a lithium metal compound, and a method for producing a cathode active material for a lithium secondary battery comprising a phosphorus-containing compound located on the surface of the lithium metal compound to provide.

The aqueous solution of the phosphorus-containing material may be an aqueous solution including phosphoric acid, phosphate, or a combination thereof, wherein the phosphate is Li ₃ PO ₄ , Li ₂ HPO ₄ , LiH ₂ PO ₄ , LiMPO ₄ (M = Fe, Co, Mn , Ni, V, La, Ti, or Al), (NH ₄ ) ₂ HPO ₄ , (NH ₄ )H ₂ PO ₄ , AlPO ₄ , H ₃ PO ₄ , or combinations thereof.

The amount of the phosphorus-containing material may be 0.01 to 20 mole parts based on 100 mole parts of the first active material.

The concentration of the aqueous solution of the phosphorus-containing material may be 0.01M to 10M. The lithium compound may include Li ₂ CO ₃ , LiOH, or a combination thereof.

Another embodiment provides a lithium secondary battery including a positive electrode including the positive electrode active material.

The details of other implementations are included in the detailed description below.

By providing the positive electrode active material, it is possible to realize a lithium secondary battery having a high capacity and excellent lifespan characteristics as well as excellent stability due to a small amount of gas generation.

1 is a schematic diagram showing a lithium secondary battery according to an embodiment.
FIG. 2 is an energy dispersive spectroscope (EDS) analysis picture of a scanning electron microscope (SEM) picture of the positive active material according to Example 1. FIG.
3 is a photograph by secondary ion mass spectroscopy (SIMS) of a cross section of the positive active material according to Example 1, and FIG. 4 is a phosphorus (P) element mapping for the same portion of FIG. ) is a picture.
5 is an X-ray photoelectron spectroscopy (XPS) analysis graph of the surface of the positive electrode active material according to Example 1. Referring to FIG.
6 is a graph showing the lifespan characteristics of lithium secondary batteries according to Examples 1 to 5 and Comparative Examples 1 and 2;

Hereinafter, embodiments of the present invention will be described in detail. However, this is provided as an example, and the present invention is not limited thereto, and the present invention is only defined by the scope of the claims to be described later.

Hereinafter, a positive active material for a lithium secondary battery according to an embodiment will be described.

The positive active material for a lithium secondary battery according to an exemplary embodiment may include a lithium metal compound and a phosphorus (P)-containing compound positioned on the surface of the lithium metal compound.

The lithium metal compound may include a lithium nickel-based oxide. Specifically, the lithium nickel-based oxide may be represented by the following formula (1).

[Formula 1]

Li _x Ni _y M _z O ₂

In Formula 1, M may be Co, Mn, Al, Mg, Ti, Zr, or a combination thereof. In addition, it may have a range of 0.95≤x≤1.00, 0.4≤y≤1.00, 0≤z≤0.6, and y+z=1. Specifically, the y value may be 0.5≤y≤1.00, 0.6≤y≤1.00, or 0.7≤y≤1.00.

When a lithium nickel-based oxide represented by Formula 1, specifically, a lithium nickel-based oxide having a high nickel content is used as a positive electrode active material, a lithium secondary battery having a high capacity and excellent electrochemical properties such as rate characteristics can be realized. have.

A phosphorus-containing compound is positioned on the surface of the lithium metal compound. The phosphorus-containing compound may be formed on the surface of the lithium metal compound by washing the synthesized lithium metal compound with a phosphorus (P)-containing aqueous solution. A method of manufacturing the positive active material including the cleaning treatment will be described later. Specifically, the phosphorus-containing compound may be formed by a reaction between the lithium compound remaining on the surface after synthesis of the lithium metal compound and the phosphorus-containing aqueous solution used for cleaning. When the phosphorus-containing compound is formed and positioned on the surface of the lithium metal compound, the capacity characteristics and cycle life characteristics of a lithium secondary battery are improved, and the amount of lithium remaining on the surface after the synthesis of the lithium metal compound is reduced due to The amount of gas generated during the charging/discharging process may be reduced, and thus battery stability may be improved.

Examples of the lithium compound include _{, but are not limited to, Li 2} CO ₃ , LiOH, or a combination thereof.

The phosphorus-containing compound positioned on the surface of the lithium metal compound may include lithium phosphate.

The lithium phosphate is specifically Li ₃ PO ₄ , Li ₂ HPO ₄ , LiH ₂ PO ₄ , LiMPO ₄ (M = Fe, Co, Mn, Ni, V, La, Ti, or Al), (NH ₄ ) ₂ HPO ₄ , (NH ₄ )H ₂ PO ₄ , AlPO ₄ , H ₃ PO ₄ , or a combination thereof.

The content of phosphorus (P) contained in the phosphorus-containing compound may be 0.01 atomic% to 10 atomic%, for example, 0.01 atomic% to 9 atomic%, 0.01 based on the total atomic weight of elements present on the surface of the positive electrode active material atomic % to 8 atomic %, 0.01 atomic % to 7 atomic %, 0.01 atomic % to 6 atomic %, 0.01 atomic % to 5 atomic %, 0.05 atomic % to 10 atomic %, 0.1 atomic % to 10 atomic %, 0.5 atomic % to 10 atomic %, or 1 atomic % to 10 atomic %. When the phosphorus (P) element present on the surface of the lithium metal compound has a content within the above range, a lithium secondary battery having a high capacity, excellent cycle life characteristics, and reduced gas generation and improved battery stability can be realized. The phosphorus content may be adjusted by changing the amount, concentration, etc. of the phosphorus-containing aqueous solution used in the cleaning treatment when the cathode active material is manufactured. The valence number of the phosphorus element may be measured by X-ray photoelectron spectroscopy (XPS) on the surface of the positive electrode active material.

The phosphorus-containing compound may be included in an amount of 0.01 parts by weight to 10 parts by weight based on 100 parts by weight of the lithium metal compound, for example, 0.01 parts by weight to 9 parts by weight, 0.01 parts by weight to 8 parts by weight, 0.01 parts by weight to 7 parts by weight. It may be included in parts by weight, 0.01 parts by weight to 6 parts by weight, 0.01 parts by weight to 5 parts by weight, 0.05 parts by weight to 10 parts by weight, 0.1 parts by weight to 10 parts by weight, or 0.2 parts by weight to 10 parts by weight. The weight range of the phosphorus-containing compound may be measured by inductively coupled plasma (ICP) emission spectroscopy. When the phosphorus-containing compound is present on the surface of the lithium metal compound within the above content range, a lithium secondary battery having high capacity and excellent cycle life characteristics as well as excellent battery stability may be realized.

In addition to the phosphorus-containing compound, a lithium compound remaining on the surface of the lithium metal compound after synthesis of the lithium metal compound may be additionally present on the surface of the lithium metal compound.

Hereinafter, a method of manufacturing a cathode active material according to another exemplary embodiment will be described.

The positive active material may be prepared by washing the first active material with an aqueous solution of a phosphorus (P)-containing material to obtain a second active material. In other words, the second active material corresponds to the positive active material according to the above-described exemplary embodiment.

The first active material is obtained after synthesizing a lithium metal compound, and the lithium compound remains on the surface of the synthesized lithium metal compound. In other words, the first active material may include a lithium metal compound and a lithium compound positioned on the surface of the lithium metal compound.

When the first active material obtained after the synthesis of the lithium metal compound is washed with an aqueous solution of a phosphorus-containing material, the lithium compound remaining on the surface reacts with the aqueous solution of the phosphorus-containing material to form the phosphorus-containing compound. amount can be reduced. Accordingly, when cleaning with an aqueous solution of a phosphorus-containing material, the amount of residual lithium is reduced while minimizing the change in the active material of the lithium metal compound, thereby improving battery stability such as gas generation as well as electrochemical properties such as capacity characteristics and cycle life characteristics. can be improved

As the lithium metal compound, lithium nickel-based oxide may be used as described above, and specifically, the compound represented by Chemical Formula 1 may be used. The lithium nickel-based oxide may be synthesized by a method known in the art, and accordingly, a description of the synthesis method will be omitted.

The aqueous solution of the phosphorus-containing material may be an aqueous solution containing phosphoric acid, phosphate, or a combination thereof. Examples of the phosphate include Li ₃ PO ₄ , Li ₂ HPO ₄ , LiH ₂ PO ₄ , LiMPO ₄ (M = Fe, Co, Mn, Ni, V, La, Ti, or Al), (NH ₄ ) ₂ HPO ₄ , (NH ₄ )H ₂ PO ₄ , AlPO ₄ , H ₃ PO ₄ , or a combination thereof.

* The amount of the phosphorus-containing material used for the washing may be 0.01 to 20 mole parts based on 100 mole parts of the first active material, for example, 0.01 mole part to 19.5 mole part, 0.01 mole part to 19 mole part, 0.01 mole part to 18 mole part 0.01 mol parts to 17 mol parts, 0.01 mol parts to 16 mol parts, 0.01 mol parts to 15 mol parts, 0.01 mol parts to 14 mol parts, 0.01 mol parts to 13 mol parts, 0.01 mol parts to 12 mol parts, 0.01 mol parts to 11 mol parts, 0.01 mol parts to 10 mol parts, 0.01 9 mole parts to 9 mole parts, 0.01 mole part to 8 mole part, 0.01 mole part to 7 mole part, 0.01 mole part to 6 mole part, 0.01 mole part to 5 mole part, 0.05 mole part to 10 mole part, 0.1 mole part to 10 mole part, or 0.2 mole part to 10 mole part . When the amount of the phosphorus-containing material is within the above range _{, a phosphorus-containing compound such as Li 3} PO ₄ may be formed on the surface of the lithium metal compound, thereby contributing to the improvement of the capacity characteristics and cycle life characteristics of the lithium secondary battery. In addition, since a positive active material including phosphorus (P) element within an appropriate atomic % range is prepared on the surface of the lithium metal compound, a lithium secondary battery having a high capacity and excellent cycle life characteristics and stability can be realized.

The concentration of the aqueous solution of the phosphorus-containing material may be 0.01M to 10M, for example, 0.01M to 9M, 0.01M to 8M, 0.01M to 7M, 0.01M to 6M, 0.01M to 5M, 0.05M to 10M , 0.1M to 10M, or 0.2M to 10M. When the concentration of the aqueous solution of the phosphorus-containing material used for cleaning is within the above range, a positive active material for realization of a lithium secondary battery having a high capacity and excellent cycle life characteristics and stability may be manufactured.

After the washing, a drying process may be further performed. The drying may be carried out by heat treatment at a temperature of 100° C. to 800° C., and may proceed for 1 hour to 20 hours.

Hereinafter, a lithium secondary battery according to another embodiment will be described with reference to FIG. 1 .

1 is a schematic diagram showing a lithium secondary battery according to an embodiment. Referring to FIG. 1 , a lithium secondary battery 100 according to an embodiment includes a positive electrode 114 , a negative electrode 112 opposite to the positive electrode 114 , and a separator disposed between the positive electrode 114 and the negative electrode 112 . 113, and an electrode assembly including an electrolyte (not shown) impregnated with the positive electrode 114, the negative electrode 112, and the separator 113, and the battery container 120 and the battery container containing the electrode assembly and a sealing member 140 sealing the 120 .

The positive electrode 114 includes a current collector and a positive electrode active material layer formed on the current collector. The positive active material layer includes a positive active material, a binder, and optionally a conductive material.

Al may be used as the current collector, but is not limited thereto.

The positive active material is the same as described above.

The binder serves to well adhere the positive active material particles to each other and also to adhere the positive active material to the current collector. Specific examples of the binder include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, and the like, but is not limited thereto.

The conductive material is used to impart conductivity to the electrode, and any electronically conductive material can be used as long as it does not cause chemical change. Examples include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, copper. , nickel, aluminum, metal powders such as silver, metal fibers, etc., may be used in combination with one or more conductive materials such as polyphenylene derivatives.

The negative electrode 112 includes a current collector and a negative active material layer formed on the current collector.

* The current collector may use Cu, but is not limited thereto.

The anode active material layer includes an anode active material, a binder, and optionally a conductive material.

The negative active material includes a material capable of reversibly intercalating/deintercalating lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and dedoping lithium, or a transition metal oxide.

The material capable of reversibly intercalating/deintercalating the lithium ions is a carbon material, and any carbon-based negative active material generally used in lithium secondary batteries may be used, and representative examples thereof include crystalline carbon, Amorphous carbon or these may be used together. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon). or hard carbon, mesophase pitch carbide, and calcined coke.

The lithium metal alloy includes lithium and a group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn. An alloy of a metal selected from may be used.

Examples of the material capable of doping and dedoping lithium include Si, SiO _x (0 < x < 2), Si-C composite, and Si-Q alloy (wherein Q is an alkali metal, alkaline earth metal, group 13 to group 16 element) , transition metal, rare earth element, or a combination thereof, not Si), Sn, SnO ₂ , Sn-C composite, Sn-R (wherein R is an alkali metal, alkaline earth metal, group 13 to 16 element, transition metal, A rare earth element or a combination thereof, but not Sn), and at least one of these and SiO ₂ may be mixed and used. Specific elements of Q and R include Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

Examples of the transition metal oxide include vanadium oxide and lithium vanadium oxide.

The binder well adheres the negative active material particles to each other and also serves to attach the negative active material to the current collector, representative examples of which include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, and carboxylation. polyvinyl chloride, polyvinyl fluoride, ethylene oxide-containing polymer, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene -Butadiene rubber, epoxy resin, nylon, etc., but are not limited thereto.

The conductive material is used to impart conductivity to the electrode, and any electronically conductive material can be used as long as it does not cause chemical change. Examples include natural graphite, artificial graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc. A conductive material including a conductive polymer such as a carbon-based material, a metal powder such as copper, nickel, aluminum, or silver, or a metal-based material such as a metal fiber, a polyphenylene derivative, or a mixture thereof may be used.

The negative electrode 112 and the positive electrode 114 are prepared by mixing an active material, a conductive material, and a binder in a solvent to prepare a slurry, and then applying the slurry to each current collector. As the solvent, an organic solvent such as N-methylpyrrolidone may be used, and an aqueous solvent such as water may be used depending on the type of binder, but is not limited thereto. Since such an electrode manufacturing method is widely known in the art, a detailed description thereof will be omitted herein.

The electrolyte includes an organic solvent and a lithium salt.

*The organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move. The organic solvent may be selected from carbonate-based, ester-based, ether-based, ketone-based, alcohol-based and aprotic solvents.

Examples of the carbonate-based solvent include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate ( ethylpropyl carbonate (EPC), ethylmethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. may be used.

In particular, when the chain carbonate compound and the cyclic carbonate compound are mixed and used, the dielectric constant can be increased and the solvent can be prepared with a low viscosity. In this case, the cyclic carbonate compound and the chain carbonate compound may be mixed and used in a volume ratio of about 1:1 to 1:9.

In addition, the ester solvent is, for example, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, ν-butyrolactone, decanolide (decanolide), valerolactone, me Valonolactone (mevalonolactone), caprolactone (caprolactone) and the like may be used. As the ether solvent, for example, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc. may be used, and as the ketone-based solvent, cyclohexanone, etc. may be used. have. In addition, ethyl alcohol, isopropyl alcohol, etc. may be used as the alcohol-based solvent.

The organic solvents may be used alone or in combination of one or more, and when one or more of the organic solvents are mixed and used, the mixing ratio may be appropriately adjusted according to the desired battery performance.

The electrolyte may further include an additive such as an overcharge inhibitor such as ethylene carbonate or pyrocarbonate.

The lithium salt is dissolved in an organic solvent, serves as a source of lithium ions in the battery, enables basic lithium secondary battery operation, and promotes movement of lithium ions between the positive electrode and the negative electrode.

Specific examples of the lithium salt include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiN(SO ₃ C ₂ F ₅ ) ₂ , LiC ₄ F ₉ SO ₃ , LiClO ₄ , LiAlO ₂ , LiAlCl ₄ , LiN(C _x F _2x+1 SO ₂ )(C _y F _2y+1 SO ₂ ), where x and y are natural numbers, LiCl, LiI, LiB(C ₂ O ₄ ) ₂ (lithium bis(oxalato) ) borate; LiBOB), or a combination thereof.

The concentration of the lithium salt is preferably used within the range of about 0.1M to about 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, excellent electrolyte performance may be exhibited, and lithium ions may move effectively.

The separator 113 separates the negative electrode 112 and the positive electrode 114 and provides a passage for lithium ions to move, and any one commonly used in a lithium battery may be used. That is, one having low resistance to ion movement of the electrolyte and excellent moisture content of the electrolyte may be used. For example, it is selected from glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in the form of a nonwoven fabric or a woven fabric. For example, a polyolefin-based polymer separator such as polyethylene or polypropylene is mainly used for lithium ion batteries, and a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and optionally single-layer or multi-layer structure can be used.

Hereinafter, specific embodiments of the present invention are presented. However, the examples described below are only for specifically illustrating or explaining the present invention, and the present invention is not limited thereto. In addition, since the content not described here can be sufficiently technically inferred by a person skilled in the art, the description thereof will be omitted.

(Manufacture of positive electrode active material)

Example 1

A 1M concentration of H ₃ PO ₄ aqueous solution is prepared. _{LiNi 0.80} Co _0.15 Al _0.05 O ₂ LiNi 0.80 Co 0.15 Al 0.05 O 2 50 g of the first active material having a lithium compound including _{Li 2} CO ₃ and LiOH on the surface prepared by synthesis _{was mixed with 50 g of the H 3} PO ₄ aqueous solution in a beaker. In this case, the H ₃ PO ₄ content was 9.6 mol parts based on 100 mol parts of the first active material.

The mixture was stirred on a hot plate with a magnetic stirrer for 20 minutes, filtered and separated, and the obtained material was dried in an oven at 120° C. for 12 hours or more to prepare a cathode active material.

Example 2

A positive active material was prepared in the same manner as in Example 1, except that in Example 1, a 1M (NH ₄ ) ₂ HPO ₄ aqueous solution was used instead of the H ₃ PO _{4 aqueous solution.}

Example 3

A positive active material was prepared in the same manner as in Example 1, except that in Example 1, _{an AlPO 4} aqueous solution having a concentration of 1M was used instead of the H ₃ PO _{4 aqueous solution.}

Example 4

Example 1 Except for using a mixture of Al(NO ₃ ) ₃ ㅇ9H ₂ O and (NH ₄ ) ₂ HPO ₄ aqueous solution (1:1 molar ratio) of 1M concentration instead of the H ₃ PO _{4 aqueous solution in Example 1, Example 1} A positive electrode active material was prepared in the same manner as in The content of the mixture of Al(NO ₃ ) ₃ o9H ₂ O and (NH ₄ ) ₂ HPO ₄ was 19.2 parts by mole based on 100 parts by mole of the first active material.

Example 5

A positive active material was prepared in the same manner as in Example 1, except that in Example 1, an aqueous solution _{of H 3} PO _{4 having a} concentration of 2M was used.

Example 6

A positive electrode active material was prepared in the same manner as in Example 1, except that 100 g of _{H 3} PO _{4 aqueous solution was used in Example 1.}

Comparative Example 1

The synthesized material LiNi _0.85 Co _0.10 Al _0.05 O ₂ was used as a cathode active material.

Comparative Example 2

A cathode active material was prepared in the same manner as in Example 1, except that distilled water was used instead of the H ₃ PO _{4 aqueous solution in Example 1.}

(Lithium secondary battery production)

92 wt% of the positive active material prepared in Examples 1 to 6 and Comparative Examples 1 and 2, 4 wt% of polyvinylidene fluoride (PVdF), and 4 wt% of acetylene black were mixed, and then N-methyl-2-p A slurry was prepared by dispersing in rollidone. Next, after coating the slurry on an aluminum foil, drying and rolling were performed to prepare a positive electrode.

A coin-type half-cell was manufactured using metallic lithium as a counter electrode of the positive electrode. At this time, an electrolyte solution in _{which 1.3M LiPF 6} was dissolved in a solvent of ethylene carbonate (EC), ethylmethyl carbonate (EMC) and dimethyl carbonate (DMC) (EC:EMC:DMC=3:4:3 volume ratio) was used.

Evaluation 1: EDS analysis of cathode active material

FIG. 2 is a photograph obtained by energy dispersive spectroscope (EDS) analysis of the positive active material according to Example 1. FIG. Referring to FIG. 2 , it can be seen that in the cathode active material obtained by washing according to Example 1, phosphorus (P) element is present on the surface of the NCA material having a high nickel content.

Evaluation 2: Cross-sectional SIMS analysis of positive electrode active material

3 is a photograph obtained by secondary ion mass spectroscopy (SIMS) analysis of a cross section of the positive electrode active material according to Example 1, and FIG. 4 is a phosphorus (P) element mapping photograph of the same portion of FIG. 3 . Referring to FIGS. 3 and 4 , it can be seen that in the cathode active material obtained by washing according to Example 1, phosphorus (P) element is present on the surface of the NCA material.

Evaluation 3: Surface XPS analysis of positive electrode active material

The surface of the positive active material according to Example 1 was analyzed by X-ray photoelectron spectroscopy (XPS), and the results are shown in FIG. 5 and Table 1 below. Referring to FIG. 5 , it can be seen that a _{Li 3} PO ₄ compound is formed on the surface of the positive electrode active material obtained by washing according to Example 1.

Table 1 below shows the composition of the elements present on the surface of the positive electrode active material of Example 1.

element Content (atomic%) O 43.9 Li 24.1 C 15.9 P 3.1 Ni 7.9 Co 1.8 S 2.7 Al 0.6

Referring to Table 1, it can be seen that the phosphorus (P) element is present in 3.1 atomic % on the surface of the positive electrode active material of Example 1, specifically, on the surface of the lithium metal compound. Evaluation 4: Lifespan characteristics of lithium secondary batteries

1C charging and 1C discharging were repeated for the lithium secondary batteries prepared in Examples 1 to 6 and Comparative Examples 1 and 2 to evaluate lifespan characteristics, and the results are shown in FIG. 6 .

Referring to FIG. 6 , in the case of Example 1 using the cathode active material obtained by washing with a phosphorus (P)-containing aqueous solution, it can be seen that the cycle life characteristics are remarkably excellent compared to Comparative Example 2 obtained by washing with distilled water.

Although preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also presented. It belongs to the scope of the invention.

100: lithium secondary battery
112: cathode
113: separator
114: positive electrode
120: battery container
140: sealing member

Claims (7)

Washing the first active material with an aqueous solution of a phosphorus (P)-containing material to obtain a second active material,
The first active material includes a lithium metal compound and a lithium compound positioned on the surface of the lithium metal compound, wherein the lithium metal compound and the lithium compound are different,
The second active material is a lithium metal compound, and a method of manufacturing a cathode active material for a lithium secondary battery comprising a phosphorus-containing compound positioned on the surface of the lithium metal compound. In claim 1,
The aqueous solution of the phosphorus-containing material is an aqueous solution containing phosphoric acid, phosphate, or a combination thereof, a method of manufacturing a cathode active material for a lithium secondary battery. In claim 2,
The aqueous solution of the phosphorus-containing material is an aqueous solution containing the phosphate,
The phosphate is Li ₂ HPO ₄ , LiH ₂ PO ₄ , LiMPO ₄ (M = Fe, Co, Mn, Ni, V, La, Ti, or Al), (NH ₄ ) ₂ HPO ₄ , (NH ₄ )H ₂ PO ₄ , AlPO ₄ , H ₃ PO ₄ , or a method of manufacturing a cathode active material for a lithium secondary battery comprising a combination thereof. In claim 1,
The amount of the phosphorus-containing material used is 0.01 to 20 mole parts based on 100 mole parts of the first active material. In claim 1,
The concentration of the aqueous solution of the phosphorus-containing material is 0.01M to 10M method of manufacturing a cathode active material for a lithium secondary battery. In claim 1,
The lithium metal compound is a method of manufacturing a cathode active material for a lithium secondary battery comprising a lithium nickel-based oxide represented by the following formula (1).
[Formula 1]
Li _x Ni _y M _z O ₂
(In Formula 1,
M is Co, Mn, Al, Mg, Ti, Zr or a combination thereof, and 0.95≤x≤1.00, 0.4≤y≤1.00, 0≤z≤0.6, and y+z=1.) In claim 1,
The lithium compound is Li ₂ CO ₃ , LiOH, or a method of manufacturing a cathode active material for a lithium secondary battery comprising a combination thereof.

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