KR102600145B1 - Positive active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same - Google Patents

Abstract

A cathode active material for lithium secondary batteries, a manufacturing method thereof, and a lithium secondary battery containing the same, comprising: a compound capable of reversible intercalation and deintercalation of lithium; and a coating layer located on at least a portion of the surface of the compound, wherein the coating layer includes P and S.

Description

Cathode active material for lithium secondary battery, manufacturing method thereof, and lithium secondary battery including the same

It relates to a positive electrode active material for lithium secondary batteries, a method of manufacturing the positive electrode active material for lithium secondary batteries, and a positive electrode active material for lithium secondary batteries.

In relation to the recent trend of miniaturization and weight reduction of portable electronic devices, the need for improved performance and larger capacity of batteries used as power sources for these devices is increasing.

A battery generates power by using materials capable of electrochemical reactions for the anode and cathode. A representative example of such batteries is a lithium secondary battery that generates electrical energy by changing the chemical potential when lithium ions are intercalated/deintercalated at the anode and cathode.

The lithium secondary battery is manufactured by using materials capable of reversible intercalation/deintercalation of lithium ions as positive and negative electrode active materials, and filling an organic electrolyte or polymer electrolyte between the positive and negative electrodes.

Lithium composite metal compounds are used as cathode active materials for lithium secondary batteries, and for example, composite metal oxides such as LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , and LiMnO ₂ are being studied.

Among the above cathode active materials, Mn-based cathode active materials such as LiMn ₂ O ₄ and LiMnO ₂ are easy to synthesize, relatively inexpensive, have the best thermal stability when overcharged compared to other active materials, and are attractive due to their low environmental pollution. However, it has the disadvantage of low capacity.

LiCoO ₂ has good electrical conductivity and a high battery voltage of about 3.7V, and has excellent cycle life characteristics, stability, and discharge capacity, so it is a representative cathode active material currently commercialized and sold. However, because LiCoO ₂ is expensive, it accounts for more than 30% of the battery price, which has the problem of low price competitiveness.

In addition, LiNiO ₂ exhibits battery characteristics of the highest discharge capacity among the above-mentioned positive electrode active materials, but has the disadvantage of being difficult to synthesize. In addition, the high oxidation state of nickel causes a decrease in battery and electrode lifespan, and there are problems with severe self-discharge and poor reversibility. In addition, commercialization is difficult because safety is not fully secured.

A positive electrode active material for a lithium secondary battery with excellent high capacity and high efficiency characteristics is provided, and a lithium secondary battery including a positive electrode containing the positive electrode active material is provided.

In one embodiment of the present invention, a compound capable of reversible intercalation and deintercalation of lithium; and a coating layer located on at least a portion of the surface of the compound, wherein the coating layer includes P and S.

The coating layer located on at least a portion of the surface of the positive electrode active material may include Li ₃ PO ₄ and Li-S compounds.

The lithium of Li ₃ PO ₄ and Li—S compounds contained in the composite coating layer originates from Li contained in a compound capable of reversible intercalation and deintercalation of lithium, or originates from a separate Li supply material. It can be.

Compounds capable of reversible intercalation and deintercalation of lithium include Li _a A _1-b X _b D ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5); _{Li a A 1 - b _ _ _ LiE 1 - b _ _ _ _ LiE 2 - b} Li _{a Ni 1 -b- c Co b Li a Ni 1 -b- c Co b _ _ Li a Ni 1 -b- c Co b _ _} Li _{a Ni 1 -b- c Mn b Li a Ni 1 -b- c Mn b _ _ Li a Ni 1 -b- c Mn b _ _} Li _a Ni _b E _c G _d O _{2 -e} T _e (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1, 0 ≤ e ≤ 0.05); Li _a Ni _b Co _c Mn _d G _e O _{2 - f} T _f (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1, 0 ≤ e ≤ 0.05); Li _a NiG _b O _{2 - c} T _c (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li _a CoG _b O _{2 - c} T _c (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li _a MnG` <sub>b</sub> O <sub>2 - c</sub> T <sub>c</sub> (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li <sub>a</sub> Mn <sub>2</sub> G <sub>b</sub> O <sub>2 - c</sub> T <sub>c</sub> (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li <sub>a</sub> MnG` _b PO ₄ (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); LiNiVO ₄ ; and Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2).

In the above formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

The content of the coating layer based on the total weight of the positive electrode active material may be 0.2 to 2.0% by weight.

In another embodiment of the present invention, preparing a compound capable of reversible intercalation and deintercalation of lithium; lithium source; phosphorus source; and preparing a sulfur source; the lithium source; phosphorus source; and dispersing a sulfur source in a solvent to prepare a coating solution; A lithium source is provided on the surface of the compound capable of reversible intercalation and deintercalation of lithium by stirring and mixing the compound capable of reversible intercalation and deintercalation of lithium into the coating solution; phosphorus source; and a sulfur source; uniformly attaching the; the lithium source; phosphorus source; and a sulfur source; drying a compound capable of reversible intercalation and deintercalation of attached lithium: and the lithium source; phosphorus source; and a sulfur source; by heat treating the compound capable of reversible intercalation and deintercalation of the attached lithium, reversible intercalation and deintercalation of the lithium formed on the surface of the coating layer containing P and S is achieved. It provides a method for producing a positive electrode active material for a lithium secondary battery, including the step of obtaining a possible compound.

the lithium source; phosphorus source; and a sulfur source; by heat treating the compound capable of reversible intercalation and deintercalation of the attached lithium, reversible intercalation and deintercalation of the lithium formed on the surface of the coating layer containing P and S is achieved. In the step of obtaining a possible compound, the heat treatment temperature may be 650 to 950°C.

the lithium source; phosphorus source; In the step of preparing a sulfur source, the lithium source may be lithium carbonate, lithium nitrate, lithium sulfate, lithium acetate, lithium phosphate, lithium chloride, lithium hydroxide, lithium oxide, or a combination thereof.

the lithium source; phosphorus source; and a sulfur source; in the step of preparing, the phosphorus source is (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , Li ₃ PO ₄ , P ₂ O ₅ or these. It can be a combination.

the lithium source; phosphorus source; and a sulfur source; in the step of preparing, the sulfur source may be (NH ₄ ) ₂ SO ₄ , NH ₄ H ₂ SO ₄ , Li ₂ SO ₄ , CoSO ₄ or a combination thereof.

In another embodiment of the present invention, a positive electrode comprising a positive electrode active material for a lithium secondary battery according to an embodiment of the present invention described above; A negative electrode containing a negative electrode active material; It provides a lithium secondary battery including; and an electrolyte.

A cathode active material having excellent battery characteristics and a lithium secondary battery containing the same can be provided.

1 is a schematic diagram of a lithium secondary battery.

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

In one embodiment of the present invention, a compound capable of reversible intercalation and deintercalation of lithium; and a coating layer located on at least a portion of the surface of the compound, wherein the coating layer includes P and S.

The coating layer located on at least a portion of the surface of the positive electrode active material may be a composite coating layer containing Li ₃ PO ₄ and a Li-S compound.

The compound in the coating layer may be a compound generated as a result of a heat treatment reaction.

The lithium of Li ₃ PO ₄ and Li—S compounds contained in the composite coating layer originates from Li contained in a compound capable of reversible intercalation and deintercalation of lithium, or originates from a separate Li supply material. It can be.

The positive electrode active material including a coating layer containing Li ₃ PO ₄ and Li-S can improve the battery characteristics of a lithium secondary battery. More specifically, it is possible to provide a positive electrode active material with improved efficiency characteristics and improved stability compared to existing positive electrode active materials.

Li ₃ PO ₄ in the coating layer serves as a driving force to increase the diffusivity of Li ions in the positive electrode active material, thereby improving battery characteristics by improving ionic conductivity that facilitates the movement of Li ions. In particular, it contributes to improving efficiency characteristics.

However, surface modification by the above P treatment may cause an excessive reduction reaction depending on the manufacturing conditions, so there is a possibility that structural defects may occur due to Li and oxygen deficiency on the surface of the anode material.

If these defects exist, swelling of the cell may occur, especially at high voltages, so complex processing is needed to offset the problems of P processing.

P and S have the effect of controlling the rocksalt structure and other surface defects formed on the surface of the anode material during the coating process (reduction reaction) with an anion coating material that is expected to have a Li acceptor effect.

In the case of S, the reducing power is relatively weaker than that of P, so when S is treated alone, it must be added in excess compared to P treatment to obtain a similar effect.

However, if S is added in excessive amounts, problems such as corrosion of the electrode plate may occur.

Accordingly, if a certain amount of S is added together with P, the degree of reduction of the surface of the active material during the coating process can be adjusted, and thus the effect of improving battery characteristics and controlling swelling can be expected at the same time.

In conclusion, the combined surface modification of P and S has the effect of improving the ionic conductivity of the anode material, controlling surface structural defects, and suppressing swelling by controlling excessive reduction reactions.

Specifically, the content of Li ₃ PO ₄ and Li-S compound in the coating layer may be 1/10 to 10/1 in terms of the molar ratio of Li-S to Li ₃ PO ₄ . If this range is satisfied, the desired effect can be achieved.

For specific examples, compounds _capable of reversible intercalation and _{deintercalation of} lithium _include Li _{a A} 1 - b _{Li a A 1 - b _ _ LiE 1 - b _ _ _ _ LiE 2 - b _ _ _ _} Li _{a Ni 1 -bc Co b Li a Ni 1 -bc Co b} Li _{a Ni 1 -bc Co b} Li _{a Ni 1 -b- c Mn b Li a Ni 1 -b- c Mn b _ _ Li a Ni 1 -b- c Mn b _ _} Li _a Ni _b E _c G _d O _{2 - e} T _e (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1, 0 ≤ e ≤ 0.05); Li _a Ni _b Co _c Mn _d G _e O _{2 - f} T _f (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1, 0 ≤ e ≤ 0.05); Li _a NiG _b O _2-c T _c (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li _a CoG _b O _{2 - c} T _c (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li _a MnG` <sub>b</sub> O <sub>2 - c</sub> T <sub>c</sub> (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li <sub>a</sub> Mn <sub>2</sub> G <sub>b</sub> O <sub>2 - c</sub> T <sub>c</sub> (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li <sub>a</sub> MnG` _b PO ₄ (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); LiNiVO ₄ ; and Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2). .

In the above formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; Q is selected from the group consisting of Ti, Mo, Mn, and combinations thereof; Z is selected from the group consisting of Cr, V, Fe, Sc, Y, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.

The weight ratio of the composite coating layer to the total weight of the positive electrode active material may be 0.2 to 2.0% by weight. If the weight ratio is less than 0.2, the role of the coating layer may be reduced, and if it is more than 2.0, initial capacity and charge/discharge efficiency may be reduced. However, it is not limited to this.

In another embodiment of the present invention, preparing a compound capable of reversible intercalation and deintercalation of lithium; lithium source; phosphorus source; and preparing a sulfur source; the lithium source; phosphorus source; and dispersing a sulfur source in a solvent to prepare a coating solution; A lithium source is provided on the surface of the compound capable of reversible intercalation and deintercalation of lithium by stirring and mixing the compound capable of reversible intercalation and deintercalation of lithium into the coating solution; phosphorus source; and a sulfur source; uniformly attaching the; the lithium source; phosphorus source; and a sulfur source; drying a compound capable of reversible intercalation and deintercalation of attached lithium: and the lithium source; phosphorus source; and a sulfur source; by heat treating the compound capable of reversible intercalation and deintercalation of the attached lithium, reversible intercalation and deintercalation of the lithium formed on the surface of the coating layer containing P and S is achieved. It provides a method for producing a positive electrode active material for a lithium secondary battery, including the step of obtaining a possible compound.

the lithium source; phosphorus source; and a sulfur source; by heat treating the compound capable of reversible intercalation and deintercalation of the attached lithium, reversible intercalation and deintercalation of the lithium formed on the surface of the coating layer containing P and S is achieved. In the step of obtaining a possible compound, the heat treatment temperature may be 650 to 950°C. In the above temperature range, the coating layer formed on the surface of the positive electrode active material can perform a stable role.

the lithium source; phosphorus source; In the step of preparing a sulfur source, the lithium source may be lithium carbonate, lithium nitrate, lithium sulfate, lithium acetate, lithium phosphate, lithium chloride, lithium hydroxide, lithium oxide, or a combination thereof.

the lithium source; phosphorus source; and a sulfur source; in the step of preparing, the phosphorus source is (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , Li ₃ PO ₄ , P ₂ O ₅ or these. It can be a combination.

the lithium source; phosphorus source; and a sulfur source; in the step of preparing, the sulfur source may be (NH ₄ ) ₂ SO ₄ , NH ₄ H ₂ SO ₄ , Li ₂ SO ₄ , CoSO ₄ or a combination thereof.

Since the description of the remaining configuration is the same as the above-described embodiment of the present invention, the description will be omitted.

In another embodiment of the present invention, a lithium secondary battery includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode includes a current collector and a positive electrode active material layer formed on the current collector, and the positive electrode active material layer includes the above-described positive electrode active material layer. A lithium secondary battery containing a positive electrode active material is provided.

The description related to the positive electrode active material will be omitted since it is the same as the above-described embodiment of the present invention.

The positive active material layer may include a binder and a conductive material.

The binder serves to attach the positive electrode active material particles to each other well and also to attach the positive electrode active material to the current collector. Representative examples include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, and polyvinyl alcohol. Chloride, carboxylated polyvinylchloride, polyvinylfluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene- Butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon, etc. can be used, but are not limited thereto.

The conductive material is used to provide conductivity to the electrode, and in the battery being constructed, 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, and Ketjen. Carbon-based materials such as black and carbon fiber; Metallic substances such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; Conductive polymers such as polyphenylene derivatives; Alternatively, a conductive material containing a mixture thereof may be used.

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

The negative electrode 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 lithium ions is a carbon material. Any carbon-based anode active material commonly used in lithium ion secondary batteries can be used, and a representative example is crystalline carbon. , amorphous carbon, or a combination of these can be used. Examples of the crystalline carbon include graphite such as amorphous, plate-shaped, flake, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon). Alternatively, hard carbon, mesophase pitch carbide, calcined coke, etc. may be mentioned.

The lithium metal alloy includes lithium and Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn. Any alloy of metals of choice may be used.

Materials capable of doping and dedoping lithium include Si, _SiO It is an element selected from the group consisting of rare earth elements and combinations thereof, but not Si), Sn, SnO ₂ , Sn-Y (Y is an alkali metal, alkaline earth metal, Group 13 element, Group 14 element, transition metal, rare earth elements selected from the group consisting of elements and combinations thereof, but not Sn), etc., and at least one of these may be mixed with SiO ₂ . The element Y includes 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, Ti, Ge, P, As, Sb, Bi, S, It may be selected from the group consisting of Se, Te, Po, and combinations thereof.

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

The anode active material layer also includes a binder and, optionally, may further include a conductive material.

The binder serves to adhere the negative electrode active material particles to each other and to the current collector, and representative examples include polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, polyvinyl chloride, and carboxylated Polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic Teed styrene-butadiene rubber, epoxy resin, nylon, etc. can be used, but are not limited thereto.

The conductive material is used to provide conductivity to the electrode, and in the battery being constructed, 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, and Ketjen. Carbon-based materials such as black and carbon fiber; Metallic substances such as metal powders such as copper, nickel, aluminum, and silver, or metal fibers; Conductive polymers such as polyphenylene derivatives; Alternatively, a conductive material containing a mixture thereof may be used.

The current collector may be selected from the group consisting of copper foil, nickel foil, stainless steel foil, titanium foil, nickel foam, copper foam, a polymer substrate coated with a conductive metal, and combinations thereof.

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

The negative electrode and positive electrode are manufactured by mixing an active material, a conductive material, and a binder in a solvent to prepare an active material composition, and applying this composition to a current collector. Since this electrode manufacturing method is widely known in the field, detailed description will be omitted in this specification. The solvent may be N-methylpyrrolidone, but is not limited thereto.

The electrolyte includes a non-aqueous organic solvent and a lithium salt.

The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can move.

The non-aqueous organic solvent may be carbonate-based, ester-based, ether-based, ketone-based, alcohol-based, or aprotic solvent. The carbonate-based solvents include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC), and ethylene carbonate ( EC), propylene carbonate (PC), butylene carbonate (BC), etc. can be used, and the ester solvents include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, and ethyl propionate. , γ-butyrolactone, decanolide, valerolactone, mevalonolactone, caprolactone, etc. can be used. The ether-based solvent may be dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, tetrahydrofuran, etc., and the ketone-based solvent may include cyclohexanone. there is. In addition, the alcohol-based solvent may be ethyl alcohol, isopropyl alcohol, etc., and the aprotic solvent may be R-CN (R is a straight-chain, branched, or ring-shaped hydrocarbon group having 2 to 20 carbon atoms. , may contain a double bond aromatic ring, or an ether bond), amides such as dimethylformamide, dioxolanes such as 1,3-dioxolane, and sulfolanes may be used.

The non-aqueous organic solvents can be used alone or in a mixture of one or more, and when used in a mixture of more than one, the mixing ratio can be appropriately adjusted according to the desired battery performance, which is widely understood by those working in the field. It can be.

In addition, in the case of the carbonate-based solvent, it is recommended to use a mixture of cyclic carbonate and chain carbonate. In this case, mixing cyclic carbonate and chain carbonate in a volume ratio of 1:1 to 1:9 may result in superior electrolyte performance.

The non-aqueous organic solvent according to an embodiment of the present invention may further include an aromatic hydrocarbon-based organic solvent in addition to the carbonate-based solvent. At this time, the carbonate-based solvent and the aromatic hydrocarbon-based organic solvent may be mixed at a volume ratio of 1:1 to 30:1.

As the aromatic hydrocarbon-based organic solvent, an aromatic hydrocarbon-based compound of the following formula (1) may be used.

[Formula 1]

(In Formula 1, R ₁ to R ₆ are each independently hydrogen, halogen, C1 to C10 alkyl group, haloalkyl group, or a combination thereof.)

The aromatic hydrocarbon-based organic solvent is benzene, fluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1,4-difluorobenzene, and 1,2,3-trifluorobenzene. , 1,2,4-trifluorobenzene, chlorobenzene, 1,2-dichlorobenzene, 1,3-dichlorobenzene, 1,4-dichlorobenzene, 1,2,3-trichlorobenzene, 1,2, 4-trichlorobenzene, iodobenzene, 1,2-diiodobenzene, 1,3-diiodobenzene, 1,4-diiodobenzene, 1,2,3-triiodobenzene, 1,2,4 -triiodobenzene, toluene, fluorotoluene, 1,2-difluorotoluene, 1,3-difluorotoluene, 1,4-difluorotoluene, 1,2,3-trifluorotoluene, 1,2,4-trifluorotoluene, chlorotoluene, 1,2-dichlorotoluene, 1,3-dichlorotoluene, 1,4-dichlorotoluene, 1,2,3-trichlorotoluene, 1,2,4 -Trichlorotoluene, iodotoluene, 1,2-diiodotoluene, 1,3-diiodotoluene, 1,4-diiodotoluene, 1,2,3-triiodotoluene, 1,2,4- It is selected from the group consisting of triiodotoluene, xylene, and combinations thereof.

The non-aqueous electrolyte may further include vinylene carbonate or an ethylene carbonate-based compound of the following formula (2) to improve battery life.

[Formula 2]

(In Formula 2, R ₇ and R ₈ are each independently hydrogen, a halogen group, a cyano group (CN), a nitro group (NO ₂ ), or a C1 to C5 fluoroalkyl group, and at least one of R ₇ and R ₈ is a halogen group, cyano group (CN), nitro group (NO ₂ ), or C1 to C5 fluoroalkyl group.)

Representative examples of the ethylene carbonate-based compounds include difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, cyanoethylene carbonate, or fluoroethylene carbonate. You can. When using more of these life-enhancing additives, the amount used can be adjusted appropriately.

The lithium salt is a substance that dissolves in an organic solvent and acts as a source of lithium ions in the battery, enabling the basic operation of a lithium secondary battery and promoting the movement of lithium ions between the anode and the cathode. Representative examples of such lithium salts include LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , 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 and LiB(C ₂ O ₄ ) ₂ (lithium bis(oxalato) borate (LiBOB) selected from the group consisting of It contains one or two or more supporting electrolyte salts. It is recommended that the concentration of lithium salt be used within the range of 0.1 to 2.0 M. When the concentration of lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity. It can exhibit excellent electrolyte performance and lithium ions can move effectively.

Depending on the type of lithium secondary battery, a separator may exist between the positive and negative electrodes. Such separators may be polyethylene, polypropylene, polyvinylidene fluoride, or a multilayer film of two or more layers thereof, such as polyethylene/polypropylene two-layer separator, polyethylene/polypropylene/polyethylene three-layer separator, polypropylene/polyethylene/poly. Of course, a mixed multilayer film such as a propylene three-layer separator can be used.

Lithium secondary batteries can be classified into lithium ion batteries, lithium ion polymer batteries, and lithium polymer batteries depending on the type of separator and electrolyte used, and can be classified into cylindrical, prismatic, coin, pouch, etc. depending on their shape. Depending on the size, it can be divided into bulk type and thin film type. The structures and manufacturing methods of these batteries are widely known in this field, so detailed descriptions are omitted.

Figure 1 schematically shows a representative structure of the lithium secondary battery of the present invention. As shown in Figure 1, the lithium secondary battery 1 is a battery containing an electrolyte solution impregnated in a positive electrode 3, a negative electrode 2, and a separator 4 present between the positive electrode 3 and the negative electrode 2. It includes a container (5) and an encapsulation member (6) that encloses the battery container (5).

Hereinafter, examples and comparative examples of the present invention will be described. However, the following example is only an example of the present invention, and the present invention is not limited to the following example.

Example

Example 1

A coating solution was prepared by wet mixing 0.037 g of LiOH powder, 0.465 g of (NH ₄ ) ₂ HPO ₄ powder, and 0.833 g of (NH ₄ ) ₂ SO ₄ powder in an ethanol solvent in a mixer. LiCoO ₂ positive electrode active material was mixed with the prepared coating solution, the coating solution was coated on the positive electrode active material and dried to prepare a mixture, and the mixture was heat treated at 800° C. for 6 hours to prepare a positive electrode active material.

Comparative Example 1

A common LiCoO ₂ positive electrode active material was used.

Comparative Example 2

It was prepared in the same manner as in Example 1, except that a coating solution was prepared by wet mixing 0.037 g of LiOH powder and 0.465 g of (NH ₄ ) ₂ HPO ₄ powder in an ethanol solvent in a mixer.

Comparative Example 3

It was prepared in the same manner as in Example 1, except that a coating solution was prepared by wet mixing 0.037 g of LiOH powder and 0.833 g of (NH ₄ ) ₂ SO ₄ powder in an ethanol solvent in a mixer.

Coin cell manufacturing

95% by weight of the positive electrode active material prepared in the above examples and comparative examples, 2.5% by weight of carbon black as a conductive agent, and 2.5% by weight of PVDF as a binder were mixed with N-methyl-2 pyrrolidone (NMP) as a solvent. A positive electrode slurry was prepared by adding 5.0% by weight. The positive electrode slurry was applied to an aluminum (Al) thin film, which is a positive electrode current collector, with a thickness of 20 to 40 μm, dried under vacuum, and then rolled pressed to prepare a positive electrode.

Li-metal was used as the cathode.

A coin cell type half cell was manufactured using the anode prepared in this way, Li-metal as the counter electrode, and 1.15M LiPF6EC:DMC (1:1 vol%) as the electrolyte.

Charging and discharging were carried out in the range of 4.5-3.0V, and lifespan was carried out at a rate of 1.0C.

Experiment example

Experimental Example 1: Confirmation of coating layer components

The coating layer components of the positive electrode active material prepared according to Example 1 were confirmed.

Experimental Example 2: Battery characteristic evaluation

Table 1 below shows the 4.5V initial formation, rate characteristics, 1cyle, 20cycle, and 30cycle capacity and life characteristic data of the examples and comparative examples above.

Formation
Discharge capacity (mAh/g) efficiency 1CY
Discharge capacity 20CY
Discharge capacity 30CY
Discharge capacity Life characteristics
(20CY/
1CY, %) Life characteristics
(30CY/
1CY, %) rate characteristics
(2.0/0.1C, %) Example 1 193.44 97.56 190.21 182.55 178.49 95.97 93.84 93.52 Comparative Example 1 193.22 93.57 189.45 168.27 148.47 88.82 78.37 88.24 Comparative example 2 193.57 97.44 191.26 181.44 176.95 94.87 92.52 92.46 Comparative Example 3 192.61 96.79 190.77 180.62 175.50 94.68 92.00 92.14

In Table 1, Example 1 was confirmed to have superior battery characteristics than Comparative Examples 1 to 3.

More specifically, Example 1, which includes a coating layer containing P and S, was confirmed to have superior characteristics in terms of efficiency and lifespan than Comparative Example 1, which does not include a coating layer.

Additionally, it was confirmed that Example 1, which includes a composite coating layer of P and S, is superior in battery characteristics when compared to Comparative Examples 2 and 3, which include a single coating layer containing P or S.

Experimental Example 3: Safety evaluation-swelling test

Figure 2 below shows the thickness change results of Example 1 and Comparative Example 2 on the 7th and 14th days of high temperature storage at 60°C. As can be seen in Figure 2 below, Comparative Example 2 containing a P-only coating layer was confirmed to have reduced stability due to the swelling phenomenon, and in Example 1 having a composite coating layer of P and S, it was confirmed that the stability that may occur during the coating process was confirmed. It can be confirmed that excessive reduction reaction is suppressed and the high-temperature storage effect is improved.

The present invention is not limited to the above-mentioned embodiments, but can be manufactured in various different forms, and those skilled in the art will be able to form other specific forms without changing the technical idea or essential features of the present invention. You will be able to understand that this can be implemented. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive.

Claims (12)

Compounds capable of reversible intercalation and deintercalation of lithium; and
It includes a coating layer located on at least a portion of the surface of the compound,
The coating layer contains P and S at the same time, is formed by direct contact with at least a portion of the surface of the compound, and is a single coating layer containing a Li-PS compound.
According to paragraph 1,
A positive electrode active material for a lithium secondary battery, wherein the single coating layer located on at least a portion of the surface of the positive electrode active material includes Li ₃ PO ₄ and a Li-S compound.
According to paragraph 2,
The content of Li ₃ PO ₄ and Li-S compound in the single coating layer is 1/10 to 10/1 in the molar ratio of Li-S to Li ₃ PO _4. A positive electrode active material for a lithium secondary battery.
According to paragraph 1,
The lithium of Li ₃ PO ₄ and Li-S compound contained in the single coating layer is,
A positive active material for a lithium secondary battery that is derived from Li contained in a compound capable of reversible intercalation and deintercalation of lithium, or derived from a separate Li supply material.
According to paragraph 1,
Compounds capable of reversible intercalation and deintercalation of lithium include Li _a A _1-b X _b D ₂ (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5); Li _{a A 1 - b LiE 1 - b LiE 2 - b} Li _a Ni _{1- bc Co b} Li _a Ni _{1 - bc Co b} Li _a Ni _{1 - bc Co b} Li _a Ni _{1- bc Mn b} Li _a Ni _{1 - bc Mn b} Li _a Ni _{1 - bc Mn b} Li _a Ni _b E _c G _d O _2-e T _e (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1, 0 ≤ e ≤ 0.05); Li _a Ni _b Co _c Mn _d G _e O _2-f T _f (0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤0.5, 0.001 ≤ e ≤ 0.1, 0 ≤ f ≤ 0.05); Li _a NiG _b O _2-c T _c (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li _a CoG _b O _2-c T _c (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li _a MnG` _b O _2-c T _c (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li _a Mn _2-b G _b O _4-c T _c (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1, 0 ≤ c ≤ 0.05); Li _a MnG _b PO ₄ (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); LiNiVO ₄ ; and Li _(3-f) J ₂ (PO ₄ ) ₃ (0 ≤ f ≤ 2). A positive electrode active material for a lithium secondary battery, which is at least one selected from the group consisting of:
In the above formula, A is selected from the group consisting of Ni, Co, Mn, and combinations thereof; X is selected from the group consisting of Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements, and combinations thereof; D is selected from the group consisting of O, F, S, P, and combinations thereof; E is selected from the group consisting of Co, Mn, and combinations thereof; T is selected from the group consisting of F, S, P, and combinations thereof; G is selected from the group consisting of Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, and combinations thereof; J is selected from the group consisting of V, Cr, Mn, Co, Ni, Cu, and combinations thereof.
According to paragraph 1,
A positive electrode active material for a lithium secondary battery, wherein the content of the single coating layer relative to the total weight of the positive electrode active material is 0.2 to 2.0% by weight.
Preparing a compound capable of reversible intercalation and deintercalation of lithium;
lithium source; phosphorus source; and preparing a sulfur source;
the lithium source; phosphorus source; and a sulfur source; dispersing them together in a solvent to prepare a coating solution;
A lithium source is provided on the surface of the compound capable of reversible intercalation and deintercalation of lithium by stirring and mixing the compound capable of reversible intercalation and deintercalation of lithium into the coating solution; phosphorus source; and a sulfur source; uniformly attaching the;
the lithium source; phosphorus source; and a sulfur source; drying the compound capable of reversible intercalation and deintercalation of the attached lithium: and
the lithium source; phosphorus source; and a sulfur source; heat-treating a compound capable of reversible intercalation and deintercalation of the attached lithium, thereby containing P and S at the same time, formed by direct contact with at least a portion of the surface of the compound, Li- Obtaining a compound capable of reversible intercalation and deintercalation of lithium formed on the surface of a single coating layer containing a PS compound;
A method for producing a positive electrode active material for a lithium secondary battery comprising a.
In clause 7,
the lithium source; phosphorus source; and a sulfur source; heat-treating a compound capable of reversible intercalation and deintercalation of the attached lithium, thereby containing P and S at the same time, formed by direct contact with at least a portion of the surface of the compound, Li- Obtaining a compound capable of reversible intercalation and deintercalation of lithium formed on the surface of a single coating layer containing a PS compound;
A method of producing a positive electrode active material for a lithium secondary battery, wherein the heat treatment temperature is 650 to 950°C.
In clause 7,
the lithium source; phosphorus source; and preparing a sulfur source,
The lithium source is lithium carbonate, lithium nitrate, lithium sulfate, lithium acetate, lithium phosphate, lithium chloride, lithium hydroxide, lithium oxide, or a combination thereof.
In clause 7,
the lithium source; phosphorus source; and preparing a sulfur source,
The phosphorus source is (NH ₄ ) ₂ HPO ₄ , NH ₄ H ₂ PO ₄ , (NH ₄ ) ₂ HPO ₄ , Li ₃ PO ₄ , P ₂ O ₅ , or a combination thereof. Manufacture of a positive active material for a lithium secondary battery. method.
In clause 7,
the lithium source; phosphorus source; and preparing a sulfur source,
The sulfur source is (NH ₄ ) ₂ SO ₄ , NH ₄ H ₂ SO ₄ , Li ₂ SO ₄ , CoSO ₄ or a combination thereof.
A positive electrode comprising the positive electrode active material for a lithium secondary battery according to any one of claims 1 to 6;
A negative electrode containing a negative electrode active material; and
electrolyte;
A lithium secondary battery containing.