Lithium secondary batteries capable of self-poisoning

Abstract

The present invention provides a self-poisoning lithium secondary battery that includes a positive electrode active material, a negative electrode active material, an electrolyte disposed between the positive electrode active material and the negative electrode active material to allow lithium ions to migrate therebetween, and a poisoning agent including a reaction initiator catalyst and a dopant. The dopant has a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond exposed at a free end, or a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond that is not exposed at a free end and is shielded by an organic or inorganic group. When the temperature of the lithium secondary battery reaches a first predetermined temperature, the dopant reacts with the reaction initiator catalyst to release at least one of the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond having a free radical or an unsaturated bond. Therefore, the dopant contaminates the positive electrode active material of the lithium secondary battery, rendering the lithium secondary battery harmless.

Description

[Technical Field]

[0001] The present invention relates to a lithium secondary battery, and more particularly to a lithium secondary battery capable of self-poisoning. [Background technology]

[0002] Lithium-ion batteries are widely used in a variety of products, including automobiles, consumer wearable products, industrial applications, portable devices, and energy storage devices, and are therefore applied in almost every area of ​​human daily life. However, accidents involving lithium-ion batteries, such as explosions and fires in mobile phone batteries and electric vehicles, still occur from time to time. All of this is due to the fact that lithium-ion batteries still lack comprehensive and effective solutions to safety issues.

[0003] Thermal runaway is the primary cause of fire or explosion safety issues in lithium secondary batteries. The primary cause of thermal runaway in lithium batteries is heat, which results from exothermic reactions caused by high temperatures in the SEI (solid electrolyte interface) film, electrolyte, binder, and positive and negative electrode active materials within the battery. Current thermal runaway suppression methods can be classified into two types: external and internal, depending on where the safety mechanism is activated. External methods utilize monitoring systems that utilize digital computational simulation. Internal methods can be further categorized into physical and chemical methods. External digital monitoring systems utilize dedicated protection circuits and management systems outside the battery to enhance battery safety monitoring during use. Internal physical types, such as thermal cutoff separators caused by a rise in the battery cell temperature, close the separator pores, blocking the passage of ions. Internal chemical types can be defined as scale control or electrochemical reaction types. In the scale control type, flame retardants are added to the electrolyte to prevent thermal runaway scaling. Examples of electrochemical reaction types include: 1) A monomer or oligomer is added to the electrolyte. As the temperature rises, polymerization occurs as the ion transfer rate slows. Therefore, as the temperature rises, ionic conductivity decreases, slowing the electrochemical reaction rate of the lithium secondary battery. 2) A positive temperature coefficient (PTC) resistance material is sandwiched between the positive or negative electrode layer and the adjacent current collecting layer. As the temperature of the lithium secondary battery rises, the electrical insulation capacity improves. This reduces the power transfer efficiency between the positive or negative electrode layer and the adjacent current collecting layer, as well as the electrochemical reaction rate. 3) A modification layer is formed on the surface of the positive electrode active material. As the temperature of the battery cell rises, the modification layer transforms into a dense film, increasing the resistance to charge transfer and slowing the electrochemical reaction rate.

[0004] However, the above methods only aim to passively block the ion / electron migration pathways to reduce heat generation, and do not aim to elucidate the fundamental reasons that cause thermal runaway in order to eliminate it.

[0005] Therefore, the present invention provides a lithium secondary battery capable of self-poisoning targeting the positive electrode active material in order to solve the problem of thermal runaway in the lithium secondary battery. Summary of the Invention

[0006] The main objective of the present invention is to provide a lithium secondary battery capable of self-poisoning. When the state of charge (SOC) of the lithium secondary battery is 50% or higher and the temperature of the lithium secondary battery approaches an abnormally high temperature due to self-heating, the poisoning agent is activated. Free radicals or unsaturated phosphorus-oxygen bonds, boron-oxygen bonds, or sulfur-oxygen bonds are released and contaminate the positive electrode active material of the lithium secondary battery. The poisoning agent is then rendered harmless by reducing the state of charge (SOC) of the lithium secondary battery to 10% or less.

[0007] To achieve the above, the present invention discloses a lithium secondary battery capable of self-poisoning, which includes a positive electrode active material, a negative electrode active material, an electrolyte disposed between the positive electrode active material and the negative electrode active material and allowing lithium ions to migrate between the positive electrode active material and the negative electrode active material, and a poisoning agent disposed within the lithium secondary battery that is activated when the temperature of the lithium secondary battery reaches a first predetermined temperature, where the state of charge of the lithium secondary battery is 50% or higher at the first predetermined temperature. The poisoning agent includes a reaction initiator catalyst and a dopant. The dopant has a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond exposed at a free end, or a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond that is not exposed at a free end and is shielded by an organic or inorganic group. Here, at the first predetermined temperature, the reaction initiator catalyst induces the dopant to release a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond having a free radical or an unsaturated bond, thereby contaminating the positive electrode active material and rendering the lithium secondary battery harmless.

[0008] The following detailed description of specific embodiments will make the objects, technical contents, features and effects of the present invention easier to understand. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a flow diagram showing a self-poisoning process of a self-poisoning capable lithium secondary battery according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] In order to more clearly understand the advantages, spirit and features of the present invention, the following examples will be described in detail and discussed. However, these examples are merely representative examples of the present invention and are not intended to limit the scope of the present invention or claims. These examples are presented to make the disclosure of the present invention clearer and easier to understand.

[0011] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the general inventive concept. Unless expressly indicated otherwise, words described in the singular also include the plural. Unless otherwise specified, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the exemplary embodiments belong. It will be further understood that terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly defined herein.

[0012] Throughout this specification, the phrase "an embodiment" or "a specific embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the invention. Thus, the appearances of the phrase "in an embodiment" or "in a specific embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment, but may. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments, as would be apparent to one of ordinary skill in the art from this disclosure.

[0013] The present invention relates to a lithium secondary battery capable of self-poisoning, mainly comprising a positive electrode active material, a negative electrode active material, an electrolyte disposed between the positive and negative electrode active materials, and a poison disposed within the lithium secondary battery. The positive electrode active material may be a positive electrode active material containing a lithium-cobalt-nickel-manganese-oxygen compound such as NCM811. The matrix of the negative electrode active material may be a material capable of forming an alloy with lithium, such as lithium metal or silicon, or a material capable of lithium intercalation and deintercalation, such as graphite. The electrolyte is disposed between the positive electrode active material and the negative electrode active material, allowing lithium ions to migrate between the positive and negative electrode active materials. The poison disposed within the lithium secondary battery is activated when the temperature of the lithium secondary battery reaches a first predetermined temperature. At this time, the lithium secondary battery's state of charge is 50% or higher.

[0014] The poison agent includes a reaction initiator catalyst and a dopant. The dopant may have a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond at its free end. These phosphorus-oxygen bonds, boron-oxygen bonds, or sulfur-oxygen bonds are bonded to a stable first group R1, i.e., an Ax1Oy2-R1 structure (where x1≧1, y1≧1, and A is selected from phosphorus, boron, or sulfur). The term "stable" as used above means that the first group R1 is more stable in the electrolyte than the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond. For example, the larger the molecular weight, the higher the stability. The dopant may also have a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond that is not exposed at a free end, and the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond is shielded by an organic or inorganic group such as R2-Ax2Oy2-R3 (x2≧1, y2≧1, A is selected from phosphorus, boron, or sulfur, and R2 and R3 can be organic or inorganic).

[0015] The reaction initiator catalyst induces or reacts with the dopant at a first predetermined temperature, causing the dopant to release at least one of a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond having a free radical or an unsaturated bond. These phosphorus-oxygen bonds, boron-oxygen bonds, or sulfur-oxygen bonds having a free radical or an unsaturated bond can contaminate the positive electrode active material of a lithium secondary battery. The charge state of the lithium secondary battery is reduced from 50% or more to 10% or less, thereby rendering the lithium secondary battery harmless and effectively suppressing thermal runaway of the lithium secondary battery. The first predetermined temperature is close to or lower than the critical temperature of the lithium secondary battery, i.e., the thermal runaway onset temperature, which is an abnormally high temperature caused by the lithium secondary battery itself. For example, the first predetermined temperature is 100°C or higher, preferably 120°C or higher. The electrolyte may be an inorganic solid electrolyte, an organic solid electrolyte, a liquid electrolyte, a gel electrolyte, a jelly electrolyte, or a solid-liquid mixed electrolyte.

[0016] The contamination referred to here refers to the reaction of free radicals or unsaturated phosphorus-oxygen, boron-oxygen, or sulfur-oxygen bonds with the composition of the positive electrode active material. This reaction may involve the creation of new bonds, such as bonding with the surface of the positive electrode active material to form a passivation layer, or it may involve the filling of lithium vacancies in the lattice of the positive electrode active material. After filling the vacancies, the positive electrode active material has higher lattice stability and / or lower oxygen release capacity than a lithium-deficient positive electrode active material, effectively suppressing thermal runaway in lithium secondary batteries. The state of charge of the lithium secondary battery is reduced to below 10%, achieving what is known as harmless charging.

[0017] Therefore, the self-poisoning process of the self-poisoning-capable lithium secondary battery of the present invention can be seen to include the following steps. First, in step S1, a lithium secondary battery containing a poisoning agent is provided. This poisoning agent includes a reaction initiator catalyst and a dopant. The lithium secondary battery is in a state where normal charging and discharging are possible. Next, in step S2, when the temperature of the lithium secondary battery reaches a first predetermined temperature due to abnormal heat generation, the reaction initiator catalyst induces the dopant to release free radicals or unsaturated boron-oxygen bonds, phosphorus-oxygen bonds, or sulfur-oxygen bonds, poisoning or contaminating the positive electrode active material of the lithium secondary battery and rendering the lithium secondary battery non-functional. The above-mentioned abnormal temperature rise of the lithium secondary battery can be caused by an internal short circuit of the lithium secondary battery during charging and discharging operations or discharge due to puncture by an external object. Furthermore, in order to distinguish the lithium secondary battery of the present invention from a lithium secondary battery that has lost its charging performance and is deemed to be discarded or invalid, it is further defined that the SOC (State of Charge) of the lithium secondary battery of the present invention is at least 50% when the self-poisoning process is induced.

[0018] The above-mentioned reaction initiator catalyst may be a compound containing a hydrohalic acid, for example, a first salt containing fluorine. The electrolyte is saturated with at least one dissolved second salt. The second salt is used to supply lithium ions for the charge / discharge operation of the lithium secondary battery, so the first salt is in an undissolved state in the electrolyte. Furthermore, the first salt and the second salt may be different. For example, the first salt may be lithium hexafluorophosphate (LiPF6). However, the hexafluorophosphate ion (PF6 -Compounds containing fluorine are relatively unstable and tend to form lower hydrocarbons such as alkanes and alkenes. Therefore, fluorine-containing first salts are often prepared from potassium tetrafluoroborate (KBF), sodium tetrafluoroborate (NaBF), lithium tetrafluorobismuthate (LiBiF), lithium hexafluoroborate (LiBF), lithium hexafluoroarsenate (LiAsF), or lithium heptafluorosulfide (LiSF), or from hexafluorophosphate ion (PF) rather than lithium (Li) or ammonium (NH). - ) can be more stabilized by potassium hexafluoroborate (KPF6) or sodium hexafluoroborate (NaPF6).

[0019] Another type of dopant is of the formula Ax3By3Cz3, where A is selected from lithium, sodium, potassium, and ammonium (NH4), and By3Cz3 is selected from phosphorus-fluorine or boron-fluorine bonds, and x3 ≥ 1, y3 ≥ 1, and z3 ≥ 1. For example, the dopant is lithium tetrafluoroborate (LiBF4), sodium tetrafluoroborate (NaBF4), potassium tetrafluoroborate (KBF4), lithium hexafluoroborate (LiBF6), lithium hexafluoroarsenate (LiAsF6), lithium heptafluorosulfide (LiSF7), or mixtures thereof.

[0020] For example, when the reaction initiator catalyst is lithium hexafluorophosphate and the dopant is lithium tetrafluoroborate, the following chemical reactions 1 to 5 occur, generating free radicals or unsaturated boron-oxygen bonds, which contaminate the positive electrode. LiPF6 → LiF+PF5....(1) PF5+H2O → POF3+HF ....(2) LiBF4+HF → BF3+LiF ....(3) BF3+3H2O → 3HF+H3BO3....(4) H3BO3 → H + +H2O+BO2 -....(5)

[0021] The water in the above chemical reaction may originate from trace amounts of water in the lithium secondary battery, or may be formed by the reaction of hydrofluoric acid (HF) with a carbonate ester organic solvent contained in the positive electrode active material, negative electrode active material, or electrochemical reaction system. For example, the carbonate ester organic solvent may be ethylene carbonate (EC) or propylene carbonate (PC). Furthermore, if the lithium secondary battery has a ceramic separator, the water in the above chemical reaction may originate from water produced by the reaction of hydrofluoric acid with the ceramic separator. The main material of the ceramic separator is an oxide material as the main structure, and the oxide material may be a good conductor of lithium ions, such as a solid electrolyte, or a non-lithium ion conductor. If the oxide is a solid electrolyte capable of conducting lithium ions, it may be lithium aluminum titanium phosphate (LATP), lithium aluminum germanium phosphate (LAGP), lithium lanthanum zirconium oxide (LLZO), or LiAlSiO4. If the oxide has poor lithium ion conductivity, it may be aluminum oxide. For example, if the oxide is aluminum oxide, it may release water after being attacked by hydrofluoric acid, as shown in Equation 6 below. Al2O3+6HF → 2AlF3+3H2O ....(6)

[0022] As described above, when the dopant releases a sulfur-oxygen bond having a free radical or an unsaturated bond and the sulfur-oxygen bond is located at the free end of the dopant, the dopant may be sodium trifluoromethanesulfinate (CF3SO2Na), perfluorobutanesulfonic acid (CF4F9SO3H), sodium perfluorobutanesulfonate (CF4F9SO3Na), or potassium perfluorobutanesulfonate (CF4F9SO3K). Furthermore, when the sulfur-oxygen bond is bonded to the first group R1, the first group R1 may be a compound having a carbon chain with at least one carbon atom, thereby allowing the dopant to exist relatively stably in the electrochemical reaction system before the first predetermined temperature is reached. Before the first predetermined temperature is reached, the reaction initiator catalyst is inactive in the lithium secondary battery. When the first predetermined temperature is reached, the reaction initiator catalyst is released, breaking the bond between the sulfur-oxygen bond and the first group R1, and forming a sulfur-oxygen bond having a free radical or an unsaturated bond. The first group R1 can be an alkyl group, an ether group, an aryl group, an aralkyl group, or an alkylaryl group. The structure of the first group R1 can determine whether the dopant is insoluble or soluble in different solvents. As used herein, "soluble" means that the dopant can be dissolved in a solvent (e.g., propylene carbonate) of a liquid electrolyte, a colloidal electrolyte, or a gel electrolyte, or can be dissolved in a plasticizer of a solid polymer electrolyte. When added to a lithium secondary battery, the amount of the dopant that dissolves in these solvents or plasticizers is greater than 1% by weight of the solvent or plasticizer.

[0023] The reaction initiator catalyst of the lithium secondary battery of the present invention may be selected from a boron fluoride compound or an aluminum halide compound. The boron fluoride compound may be potassium tetrafluoroborate (KBF), sodium tetrafluoroborate (NaBF), or ammonium tetrafluoroborate (NHBF), and the aluminum halide compound may be aluminum chloride (AlCl), aluminum bromide (AlBr), or the like.

[0024] The sulfur-oxygen bond with a free radical or unsaturated bond is located near the dopant and has the ability to contaminate the positive electrode active material. Because the first group R1 has a relatively stable molecular form, the presence of the first group can reduce the degree of sulfur-oxygen bond contamination of the positive electrode active material before the first predetermined reaction temperature is reached. However, this also means that the real-time inhibitory effect of the dopant having such a sulfur-oxygen bond on the lithium secondary battery is reduced before thermal runaway begins. In this regard, in this application, a reaction initiator catalyst with a bond-severing effect is used to sever the bond between the first group R1 and the sulfur-oxygen bond at the first predetermined temperature. With the first group R1 separated from the sulfur-oxygen bond, the sulfur oxide radical has a stronger mobility, thereby increasing the effect of contaminating the positive electrode active material. The reversibility / activity of the positive electrode active material is reduced, and thermal runaway of the lithium secondary battery is suppressed.

[0025] In the present invention, the sulfur-oxygen bond of the dopant is shielded, i.e., not exposed at the free end, e.g., LiFSi (lithium bis(fluorosulfonyl)imide) or sodium salt F—(SO2)—N - -(SO2)-FM +(where M represents lithium or sodium), 3-phenylsulfonylbenzenesulfonic acid, peroxydisulfuric acid, potassium peroxydisulfate, sodium peroxydisulfate, etc. These shielded or non-free-end forms are used to avoid or reduce the release of the dopant during normal charge and discharge operations of a lithium secondary battery or during related manufacturing processes after mixing with the lithium secondary battery, thereby affecting the utilization rate of the lithium secondary battery. In this embodiment, the dopant is a sulfur-oxygen bond having a second group R2 and a third group R3 attached to both ends thereof. R2 and R3 are the same or different organic or inorganic groups. The dopant is substantially chemically inert in a lithium secondary battery until a reaction-initiating catalyst attacks the dopant and cleaves the bond between R2 and / or R3 and the sulfur-oxygen bond, thereby leaving the sulfur-oxygen bond as a free radical or unsaturated bond that begins to contaminate the positive electrode active material. For example, when the dopant has a structure in which the sulfur-oxygen bond is not exposed at the free end, the structure of these dopants is a sulfinic acid group (

[0026] [ka] ) or sulfonyl group (

[0027] [ka] ), and R2 and R3 are organic or inorganic groups. Furthermore, the sulfur-oxygen bond is

[0028] [ka] or

[0029] [ka] For example,

[0030] [ka] Dopants having the structure of are sodium octyl sulfate, sodium hexyl sulfate, sodium ethyl sulfate, sodium 1-octanesulfonate monohydrate, sodium 1-octanesulfonate, sodium 1-heptanesulfonate, sodium hexanesulfonate, sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium 2-ethylhexyl sulfate, sodium ethyl sulfate, potassium nonafluoro-1-butanesulfonate, trifluoromethanesulfonyl chloride, 4-(3-butyl-1-imidazolio)-1-butanesulfonate, 3-(1-pyridinio)-1-propanesulfonate, dimethyl-2-hydroxyethylammonium propanesulfonate, 3-(decyldimethylammonio)propanesulfonate. The compound may be an inner salt, [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 1-ethyl-3-methylimidazolium ethyl sulfate, copper(I) trifluoromethanesulfonate-benzene complex, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate, 1-fluoropyridinium triflate, 4-formyl-1-methylpyridinium benzenesulfonate, 3-hydroxynaphthalene-2,7-disulfonic acid disodium salt, potassium benzene-1,2-disulfonate, lithium trifluoromethanesulfonate, potassium trifluoromethanesulfonate, sodium bisulfite solution, sodium metabisulfite, sodium thiosulfate, sodium 1-butanesulfonate, potassium diphenylsulfonesulfonate, potassium heptadecafluorooctanesulfonate), or a mixture of two or more of the above materials. For example,

[0031] [ka] The first compound having the structure may be phenyl vinyl sulfoxide, propyl sulfoxide, methyl phenyl sulfoxide, diisobutyl sulfoxide, dodecyl methyl sulfoxide, benzyl phenyl sulfoxide, dimethyl sulfite, sodium benzenesulfinate, sodium methanesulfinate, sodium p-toluenesulfinate, sodium bisulfite solution) or a mixture of two or more of the above materials. For example,

[0032] [ka] may be 4-(trifluoromethyl)benzenesulfonyl chloride, 4-chlorobenzenesulfonyl chloride, 3-(trifluoromethyl)benzenesulfonyl chloride, 4-fluorobenzenesulfonyl chloride, trifluoromethanesulfonic anhydride, methanesulfonyl chloride, p-toluenesulfonyl chloride, 4-toluenesulfonyl chloride, 3-hydroxynaphthalene-2,7-disulfonic acid disodium salt, isobutanesulfonyl chloride, cyclohexanesulfonyl chloride, 4-methoxybenzenesulfonyl chloride, 4-bromobenzenesulfonyl chloride, 4-(trifluoromethyl)benzenesulfonyl chloride, 4-iodobenzenesulfonyl chloride, 4-fluorobenzenesulfonyl chloride, 4-nitrobenzenesulfonyl chloride, biphenyl-4-sulfonyl chloride, biphenyl-4,4'-disulfonyl chloride, 4-(aminosulfonyl)benzenesulfonyl chloride), or a mixture of two or more of the above materials.

[0033] Compounds with phosphorus-oxygen bonds that function as dopants include copper(II) pyrophosphate hydrate, aluminum phosphate, dicalcium phosphate, disodium phosphate, monosodium phosphate, sodium phosphate, monopotassium phosphate, tripotassium phosphate, dipotassium phosphate, tetrasodium pyrophosphate, iron(III) pyrophosphate, sodium tripolyphosphate, potassium pyrophosphate, 1,10-decyldiphosphonic acid, (12-phosphonododecyl)phosphonic acid, dibutyl phosphite, dimethyl phosphite, diethyl phosphite, bis(2-ethylhexyl) phosphate, dibenzyl phosphite, triethyl phosphite, and phosphonium dioxide. The phosphate group may be selected from the group consisting of di-tert-butyl phosphate, triethyl phosphate, diethylallyl phosphate, diethyl allyl phosphonate, diethyl allylphosphonate, diethyl vinylphosphonate, dimethyl vinylphosphonate, diallyl phosphite, diethyl benzylphosphonate, diethylenetriaminepentakis(methylphosphonic acid), diethyl ethylphosphonate, diethyl isocyanomethylphosphonate, diethyl (methylthiomethyl)phosphonate, diethyl (difluoromethyl)phosphonate, tris(2,2,2-trifluoroethyl)phosphite, diethyl methylphosphonate, Eaton's reagent, or a mixture of at least two of the foregoing materials.

[0034] The compound having a boron-oxygen bond and functioning as a dopant may be 2-acetylaminophenylboronic acid pinacol ester, 3-acetyl-2-fluorophenylboronic acid, 3-acetylphenylboronic acid, 4-acetylphenylboronic acid, phenylboronic acid, 4-amino-3-nitrophenylboronic acid, 2-aminophenylboronic acid pinacol ester, 3-aminophenylboronic acid, 3-aminophenylboronic acid pinacol ester, 2-aminopyrimidine-5-boronic acid, bis(pinacolato)diboron, boric acid, 4-bromobutylboronic acid, 2-bromo-3-ethoxy-6-fluorophenylboronic acid, 4-bromomethylphenylboronic acid pinacol ester, n-butylboronic acid pinacol ester, borax, lithium bis(oxalato)borate, or a mixture of two or more of the above materials.

[0035] When the poison is in an insoluble form, the poison may be adjacent to or in direct contact with the positive electrode active material. For example, the poison may be mixed with particles of the positive electrode active material and randomly distributed among the particles, or the poison may be coated on the surface of the positive electrode active material. The electrolyte of a lithium secondary battery containing such a poison may be a solid electrolyte, a semi-solid electrolyte, a liquid electrolyte, or a mixture thereof.

[0036] If the poison is in a soluble form, it may be mixed into the electrolyte system. The electrolyte of this type of lithium secondary battery may be a pure liquid electrolyte, a pure gel electrolyte, a pure jelly electrolyte, a pure solid polymer electrolyte, or a mixture thereof. Furthermore, the above-mentioned electrolytes may be mixed with an oxide solid electrolyte.

[0037] Therefore, the present invention provides a lithium secondary battery capable of self-poisoning by adding a poisoning agent. When the temperature of the lithium secondary battery reaches a first predetermined temperature and the state of charge of the lithium secondary battery is 50% or higher, the poisoning agent releases free radicals or unsaturated phosphorus-oxygen bonds, boron-oxygen bonds, or sulfur-oxygen bonds, contaminating the positive electrode active material of the lithium secondary battery. The lattice of the positive electrode active material is stabilized, preventing or reducing the deposition of oxygen atoms. In addition, the SOC of the lithium secondary battery falls below 10%, exhibiting a poisoned state, losing charge and discharge capabilities, and effectively suppressing the occurrence of thermal runaway.

[0038] The above description is merely a preferred embodiment of the present invention, and is not intended to limit the scope of the claims. Therefore, all equivalent changes or modifications made in accordance with the features and spirit of the present invention should be included within the scope of the following claims.

Claims

1. A lithium secondary battery capable of self-poisoning, positive electrode active material, negative electrode active material, an electrolyte positioned between the positive electrode active material and the negative electrode active material so that lithium ions can move between the positive electrode active material and the negative electrode active material; and The lithium secondary battery includes a poisoning agent that is activated when the temperature of the lithium secondary battery reaches a first predetermined temperature, and the state of charge of the lithium secondary battery is 50% or more at the first predetermined temperature, and the poisoning agent is a reaction initiation catalyst, and the positive electrode active material includes a dopant having a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond that is exposed at a free end, or a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond that is not exposed at a free end and is shielded by an organic group or an inorganic group, and at the first predetermined temperature, the reaction initiator catalyst reacts with the dopant to release at least one of a phosphorus-oxygen bond, a boron-oxygen bond, or a sulfur-oxygen bond having a free radical or an unsaturated bond, thereby contaminating the positive electrode active material; A lithium secondary battery capable of self-poisoning, wherein the first predetermined temperature is 100° C. or higher.

2. 2. The self-poisoning lithium secondary battery according to claim 1, wherein the reaction initiator catalyst is a boron fluoride compound, an aluminum halide compound, or a hydrohalic acid compound.

3. When the reaction initiation catalyst is the boron fluoride compound, the reaction initiation catalyst is potassium tetrafluoroborate (KBF ４ ), sodium tetrafluoroborate (NaBF ４ ) or ammonium tetrafluoroborate (NH ４ BF ４ ), and when the initiation catalyst is the aluminum halide compound, the initiation catalyst is aluminum chloride (AlCl ３ ) or aluminum bromide (AlBr ３ 3. The self-poisoning capable lithium secondary battery according to claim 2, wherein the self-poisoning capable lithium secondary battery is a lithium secondary battery.

4. 2. The self-poisoning capable lithium secondary battery of claim 1, wherein when the reaction initiation catalyst is a hydrohalic acid compound, the reaction initiation catalyst is a first salt containing fluorine, the electrolyte is saturated with at least a second salt dissolved therein, the first salt is in an undissolved state in the lithium secondary battery, and the first salt is different from the second salt.

5. The first salt is lithium hexafluorophosphate (LiPF ６ 5. The self-poisoning capable lithium secondary battery according to claim 4, wherein

6. The dopant is A ｘ B ｙ F ｚ and A is lithium, sodium or ammonium (NH ４ ) and B ｙ F ｚ The self-poisoning capable lithium secondary battery according to claim 1 , wherein is selected from a phosphorus-fluorine bond or a boron-fluorine bond, and x≧1, y≧1, and z≧1.

7. The dopant is KBF ４ , NaBF ４ , LiBF ４ , LiBF ６ , LiSF ７ 7. The self-poisoning capable lithium secondary battery according to claim 6, characterized in that it is a mixture of at least two of the above materials.

8. 2. The self-poisoning capable lithium secondary battery of claim 1, further comprising a ceramic separator, wherein the reaction initiator reacts with the ceramic separator to release water.

9. 9. The lithium secondary battery capable of self-poisoning according to claim 8, wherein the main material of the ceramic separator is selected from an oxide solid electrolyte or an inert ceramic powder in which lithium ions cannot move.

10. 2. The self-poisoning lithium secondary battery according to claim 1, wherein the reaction initiator catalyst reacts with the carbonate organic solvent in the electrolyte to release water.

11. 2. The self-poisoning capable lithium secondary battery of claim 1, wherein when the dopant has the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond exposed at the free end, the sulfur-oxygen bond is bonded to a first group, the first group is a carbon chain having at least one carbon atom, and the reaction initiation catalyst triggers cleavage of the sulfur-oxygen bond and the first group.

12. The self-poisoning capable lithium secondary battery of claim 11, wherein the first group is an alkyl group, an ether group, an aryl group, an aralkyl group, or an alkylaryl group.

13. 2. The self-poisoning lithium secondary battery of claim 1, wherein the dopant has the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond that is not exposed at the free end, both ends of the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond are blocked by the organic group or the inorganic group, and the organic group or the inorganic group at both ends are the same, and the reaction initiator catalyst cleaves a bond between at least one of the organic group or the inorganic group and the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond, to generate a free radical or an unsaturated bond in the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond.

14. 2. The self-poisoning capable lithium secondary battery of claim 1, wherein the dopant has the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond that is not exposed at the free end, both ends are blocked with the organic group or the inorganic group, and the organic group or the inorganic group at both ends is different, and the reaction initiator catalyst cleaves a bond between at least one of the organic group or the inorganic group and the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond to generate a free radical or an unsaturated bond in the phosphorus-oxygen bond, the boron-oxygen bond, or the sulfur-oxygen bond.

15. 2. The self-poisoning lithium secondary battery according to claim 1, wherein the first predetermined temperature is 120[deg.] C. or higher.

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