A positive electrode capable of limiting lattice oxygen escape and a preparation method and application thereof

Abstract

The application discloses a positive electrode capable of limiting lattice oxygen escape, and a preparation method and application thereof. The specific method is to add a lattice oxygen inhibitor into the positive electrode in the secondary battery. The lattice oxygen inhibitor can not only play a role of a "physical passivation film" to constrain the particle volume change and prevent direct contact between the electrode and the electrolyte, but also play a role of an "electron reservoir" to inhibit the loss of the interface lattice oxygen and the conversion of the harmful interface phase transition in a way of interface charge compensation. The two aspects greatly inhibit the lattice oxygen release of the nickel-rich layered oxide, lithium cobaltate, lithium manganate, lithium-rich manganese-based and sodium-based layered oxide positive electrode material at high temperature, weaken the chemical crosstalk reaction between the active oxygen and the organic solvent and the lithiated negative electrode. Therefore, the heat accumulation of the thermal runaway trigger point can be effectively suppressed, the occurrence of the battery thermal runaway is delayed or avoided, and the safety of the battery is improved.

Description

Technical Field

[0001] This invention belongs to the field of secondary battery technology, specifically relating to a secondary battery positive electrode that restricts the escape of lattice oxygen, its preparation method, and its application. Background Technology

[0002] With the rapid development of electric vehicles and smart grids, the demand for high-energy-density lithium-ion batteries (LIBs) in these emerging fields has increased dramatically. High-capacity, low-cost nickel-rich layered oxides (LiNixCoyMnzO2) are considered one of the most promising candidates for high-energy-density LIBs. Unfortunately, the increased nickel content correspondingly increases the likelihood of thermal runaway (TR). Nickel-rich NCMs are prone to thermal runaway, leading to a large release of energy and raising the battery temperature to approximately 1000°C. In this situation, external auxiliary battery management systems (BMS) or fire suppression systems are essentially ineffective. The intense redox reaction between the strongly reducing lithiated graphite (LiCx) and the highly oxidizing nickel-rich dilithiated NCM is the key catalyst for triggering TR. Once the temperature exceeds the TR trigger point, many unique side reactions rapidly and simultaneously initiate within seconds. Simultaneously, the battery heating rate increases by several orders of magnitude, instantaneously reaching the catastrophic temperatures during TR. Therefore, suppressing the characteristic conversion flow between the cathode and anode at the TR trigger point is crucial for suppressing TR.

[0003] With increasing cycle count and temperature, delithiated nickel-rich layered oxides are prone to structural phase transitions. During this process, lattice oxygen in the bulk phase breaks free from its bonds, forming reactive oxygen species (ROS, O*). Research indicates that, in the absence of internal short circuits, crosstalk reactions induced by O* are the direct cause of thermal runaway in ternary lithium-ion batteries. Furthermore, the thermal runaway trigger temperature decreases with increasing nickel content. This is because the hybridization of Ni-O bonds increases with nickel content, further promoting the participation of oxygen anions in charge compensation within Ni-O bonds at high temperatures, thus driving the release of O*. Therefore, mitigating thermal runaway in ternary lithium-ion batteries can be achieved by weakening the charge compensation behavior of oxygen anions within Ni-O bonds, limiting the release of reactive oxygen species, and thus suppressing thermal runaway. The challenge lies in the fact that there is currently no effective strategy to address the TR problem caused by O*. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a positive electrode that can limit the escape of lattice oxygen and improve the safety of secondary batteries. This positive electrode can stabilize lattice oxygen in the bulk phase of the material, thereby limiting the release of active oxygen from the positive electrode material at high temperatures and inhibiting the continuous reaction between active oxygen and the electrolyte and the lithium graphite negative electrode, thus delaying thermal runaway and improving battery safety.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A positive electrode capable of limiting the escape of lattice oxygen, the positive electrode comprising an active material, a conductive agent, a binder, and a lattice oxygen inhibitor;

[0007] The lattice oxygen inhibitor is one or more of the following: phytate, α-glucohepanoate, tert-butyl ester compound, tetrasodium iminodisuccinate, sodium hexametaphosphate, sodium tripolyphosphate, oxalate, citric acid or citrate, aminocarboxylic acid compound, organic polyphosphonic acid, phosphate, and mercapto-(-SH) compound.

[0008] Furthermore, the active material accounts for 80-95% of the weight of the positive electrode; the conductive agent accounts for 1-10% of the weight of the positive electrode; the binder accounts for 1-10% of the weight of the positive electrode; and the lattice oxygen inhibitor accounts for 0.1-5% of the weight of the positive electrode.

[0009] Furthermore, the active material is a nickel-rich layered oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium-rich manganese-based oxide, and sodium-based layered oxide.

[0010] Furthermore, the phytate structure is shown in Formula I and Formula II:

[0011]

[0012] Wherein, R1 is at least one of monovalent metal ions such as lithium ion, sodium ion, and potassium ion;

[0013]

[0014] Wherein, R2 is at least one of the divalent metal ions such as barium ion, copper ion, calcium ion, zinc ion, cobalt ion, and magnesium ion;

[0015] The structure of the aminocarboxylic acid compound is shown in Formula III:

[0016]

[0017] Wherein, R3 is at least one of diacetamino, acetic acid, ethylenediaminetriacetyl, hydroxy, ethyl, phenyl, vinyl, acetoxy, acetoxyethyl, 3-acryloyl, 3-methacryloyl, and N,N-dipropyl.

[0018] The structure of the thiol compound is shown in Formula IV:

[0019]

[0020] Wherein, R4 is at least one of isooctyl acetate, propionic acid, 2-butanone, ethylamino, ethanol, butyric acid, acetaldehyde, succinic acid, 1,3,4-thiadiazolyl, acetate, mercapto, naphthyl, methyl acetate, acetylnaphthylamine, ethyl acetate, benzyl acetate, sodium pyruvate, thiadiazolyl, and benzoic acid.

[0021] In some specific embodiments, preferably, the phytate is at least one of lithium phytate, sodium phytate, potassium phytate, barium phytate, copper phytate, calcium phytate, zinc phytate, cobalt phytate, and magnesium phytate.

[0022] The aminocarboxylic acid compound is at least one of ethylenediaminetetraacetic acid, aziridine triacetic acid, diethylenetriaminepentaacetic acid, N-hydroxyethylethylaminetriacetic acid, and ethylene glycol-bis(B-aminoethyl ether)-N,N-tetraacetic acid.

[0023] The thiol compounds are at least one of the following: isooctyl thioglycolate, mercaptopropionic acid, 3-mercapto-2-butanone, β-mercaptoethylamine, mercaptoethanol, mercaptobutyric acid, mercaptoacetaldehyde, strontium thioglycolate, mercaptosuccinic acid, mercaptothiadiazole, magnesium thioglycolate, potassium thioglycolate, dimercaptomethane, 2-mercaptonaphthalene, methyl thioglycolate, mercaptoacetylnaphthylamine, benzyl thioglycolate, and 4-mercaptobenzoyl.

[0024] Furthermore, the chemical formula of the nickel-rich layered oxide is LiNi. x Co y Mn z O2(x+y+z=1);

[0025] The chemical formula of the lithium-rich manganese-based oxide is aLi2MnO3·(1-a)LiMO2 (M=Ni, Co, Mn);

[0026] The chemical formula of the sodium-based oxide is Na. b MO2 (where M represents transition metals such as nickel, cobalt, iron, and manganese), the value of b corresponds to the valence state of M.

[0027] Furthermore, the conductive agent is at least one of carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene.

[0028] Furthermore, the adhesive is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, polyvinyl alcohol, sodium carboxymethyl cellulose, styrene-butadiene rubber, and sodium alginate.

[0029] In some specific embodiments, preferably, the active material is Li[Ni] 0.8 Co 0.1 Mn 0.1O2, conductive agent is conductive carbon black, binder is polyvinylidene fluoride, lattice oxygen inhibitor is sodium phytate, and they are mixed in a mass ratio of 80:x:10:y, where x+y=10.

[0030] A method for preparing the above-mentioned positive electrode capable of restricting lattice oxygen escape includes the following steps:

[0031] The binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed. Then, the conductive agent, active material, and lattice oxygen inhibitor are added to the adhesive solution in sequence and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is coated onto an aluminum foil or carbon-coated aluminum foil current collector. Finally, the current collector coated with the positive electrode slurry is baked to remove the N-methylpyrrolidone, thus obtaining the positive electrode that can restrict the escape of lattice oxygen.

[0032] A secondary battery comprising the aforementioned secondary battery positive electrode that restricts lattice oxygen escape.

[0033] Furthermore, the secondary battery is a lithium-ion battery, a lithium metal battery, a sodium-ion battery, or a sodium metal battery.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention discloses a positive electrode that restricts lattice oxygen escape, its preparation method, and its application in improving the safety of secondary batteries. Specifically, the method involves adding a lattice oxygen inhibitor to the positive electrode of the secondary battery. The lattice oxygen inhibitor not only acts as a "physical passivation film" to constrain particle volume changes and prevent direct contact between the electrode and electrolyte, but also acts as an "electron bank" to suppress the loss of interfacial lattice oxygen and harmful interfacial phase transitions through interfacial charge compensation. These two aspects significantly suppress the release of lattice oxygen in nickel-rich layered oxide, lithium cobalt oxide, lithium manganese oxide, lithium-rich manganese-based, and sodium-based layered oxide positive electrode materials at high temperatures, weakening the chemical crosstalk reaction between active oxygen and organic solvents and the lithium-ionized negative electrode. More importantly, because the lattice oxygen inhibitor can passivate the positive electrode material, it delays the oxygen evolution process of the delithiated or desodium-ionized positive electrode at high temperatures, thereby postponing the participation of active oxygen in crosstalk reactions. Therefore, the heat accumulation at the thermal runaway trigger point can be effectively contained, delaying or avoiding the occurrence of battery thermal runaway and improving battery safety.

[0036] The positive electrode and electrolyte prepared by this invention have an exothermic temperature between -120 J / g and -250 J / g, with a higher initial exothermic temperature and a lower exothermic reaction temperature. This can delay or even block the thermal runaway of the battery and reduce the risk of thermal runaway. Assembling the electrolyte prepared by this invention into a pouch battery can significantly increase the trigger temperature of thermal runaway while reducing the maximum temperature during thermal runaway.

[0037] Full cells prepared using the cathode of this invention exhibit excellent cycle performance.

[0038] The preparation method of this invention is simple, requiring only simple stirring, mixing and filtration. The raw materials are readily available and inexpensive, making it suitable for widespread application. Attached Figure Description

[0039] Figure 1 The following are DSC curves of the positive electrodes of Comparative Example 1, Example 5, Example 10, and Example 15 compared to those in conventional carbonate electrolytes;

[0040] Figure 2 The DSC curves of the positive electrode and lithium graphite of Comparative Example 1 and Example 15 are shown.

[0041] Figure 3 The DSC curves for the positive electrode and conventional carbonate electrolyte in Comparative Example 3 and Example 30 are shown.

[0042] Figure 4 Temperature-time curves of the full cells assembled in Comparative Example 1, Example 5, and Example 15 during heating experiments;

[0043] Figure 5 Cycle capacity diagram of the full cell with the positive electrode of Comparative Example 1 and Example 5 assembled;

[0044] Figure 6 Cycle capacity diagram of the full cell with the positive electrode of Comparative Example 2 and Example 15 assembled;

[0045] Figure 7 Cycle capacity diagram of the full cell with the positive electrode of Comparative Example 4 and Example 30 assembled. Detailed Implementation

[0046] The present invention will now be described in further detail with reference to specific embodiments, so that those skilled in the art can more clearly understand the present invention.

[0047] Unless otherwise specified, all raw materials used in this invention are existing substances that can be purchased directly from the market. This invention provides a method for preparing a cathode that restricts lattice oxygen escape, comprising the following steps:

[0048] The binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed; then the conductive agent, active material, and lattice oxygen inhibitor are added to the adhesive solution in sequence and stirred evenly to obtain a positive electrode slurry; the positive electrode slurry is coated onto an aluminum foil or carbon-coated aluminum foil current collector; finally, the current collector coated with the positive electrode slurry is baked to remove N-methylpyrrolidone, thus obtaining the positive electrode that can restrict the escape of lattice oxygen;

[0049] The lattice oxygen inhibitor is one or more of the following: phytate, α-glucohepanoate, tert-butyl ester compound, tetrasodium iminodisuccinate, sodium hexametaphosphate, sodium tripolyphosphate, oxalate, citric acid or citrate, aminocarboxylic acid compound, organic polyphosphonic acid, phosphate, and mercapto-(-SH) compound.

[0050] In some specific embodiments, the active material accounts for 80-95% by weight in the positive electrode; the conductive agent accounts for 1-10% by weight in the positive electrode; the binder accounts for 1-10% by weight in the positive electrode; and the lattice oxygen inhibitor accounts for 0.1-5% by weight in the positive electrode.

[0051] The active material is one of nickel-rich layered oxides, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium-rich manganese-based oxides, and sodium-based layered oxides.

[0052] The conductive agent is one of carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene.

[0053] The adhesive is one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, polyvinyl alcohol, sodium carboxymethyl cellulose, styrene-butadiene rubber, and sodium alginate.

[0054] In some specific embodiments, the chemical formula of the nickel-rich layered oxide is LiNi. x Co y Mn z O2, x+y+z=1;

[0055] The chemical formula of the lithium-rich manganese-based oxide is aLi2MnO3·(1-a)LiMO2, where M is Ni, Co or Mn;

[0056] The chemical formula of the sodium-based oxide is Na. b In MO2 (where M represents transition metals such as nickel, cobalt, iron, and manganese), the value of b corresponds to the valence state of M.

[0057] In some specific embodiments, the active material is Li[Ni] 0.8 Co 0.1 Mn 0.1 O2, conductive agent is conductive carbon black, binder is polyvinylidene fluoride, lattice oxygen inhibitor is sodium phytate, and they are mixed in a mass ratio of 80:x:10:y, where x+y=10.

[0058] In some specific embodiments, the phytate structure is as shown in Formula I and Formula II:

[0059]

[0060] Wherein, R1 is at least one of monovalent metal ions such as lithium ion, sodium ion, and potassium ion;

[0061]

[0062] Wherein, R2 is at least one of the divalent metal ions such as barium ion, copper ion, calcium ion, zinc ion, cobalt ion, and magnesium ion;

[0063] The structure of the aminocarboxylic acid compound is shown in Formula III:

[0064]

[0065] Wherein, R3 is at least one of diacetamino, acetic acid, ethylenediaminetriacetyl, hydroxy, ethyl, phenyl, vinyl, acetoxy, acetoxyethyl, 3-acryloyl, 3-methacryloyl, and N,N-dipropyl.

[0066] The structure of the thiol compound is shown in Formula IV:

[0067]

[0068] Wherein, R4 is at least one of isooctyl acetate, propionic acid, 2-butanone, ethylamino, ethanol, butyric acid, acetaldehyde, succinic acid, 1,3,4-thiadiazolyl, acetate, mercapto, naphthyl, methyl acetate, acetylnaphthylamine, ethyl acetate, benzyl acetate, sodium pyruvate, thiadiazolyl, and benzoic acid.

[0069] More preferably, in some specific embodiments, the phytate is at least one of lithium phytate, sodium phytate, potassium phytate, barium phytate, copper phytate, calcium phytate, zinc phytate, cobalt phytate, and magnesium phytate.

[0070] The aminocarboxylic acid compound is at least one of ethylenediaminetetraacetic acid, aziridine triacetic acid, diethylenetriaminepentaacetic acid, N-hydroxyethylethylaminetriacetic acid, and ethylene glycol-bis(B-aminoethyl ether)-N,N-tetraacetic acid.

[0071] The thiol compounds are at least one of the following: isooctyl thioglycolate, mercaptopropionic acid, 3-mercapto-2-butanone, β-mercaptoethylamine, mercaptoethanol, mercaptobutyric acid, mercaptoacetaldehyde, strontium thioglycolate, mercaptosuccinic acid, mercaptothiadiazole, magnesium thioglycolate, potassium thioglycolate, dimercaptomethane, 2-mercaptonaphthalene, methyl thioglycolate, mercaptoacetylnaphthylamine, benzyl thioglycolate, and 4-mercaptobenzoyl.

[0072] Examples 1-5

[0073] This embodiment provides a method for preparing a positive electrode that can limit the escape of lattice oxygen, including the following steps:

[0074] The active material selected is Li[Ni 0.8 Co 0.1 Mn 0.1 The cathode slurry is prepared using O2 (NCM811), conductive carbon black as the conductive agent, polyvinylidene fluoride as the binder, and mercaptoacetylnaphthylamine as the lattice oxygen inhibitor, in a mass ratio of 80:x:10:y, where x+y=10. First, the binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed. Then, the conductive agent, active material, and lattice oxygen inhibitor are added sequentially to the adhesive solution and stirred until homogeneous to obtain the cathode slurry. The cathode slurry is then coated onto aluminum foil or carbon-coated aluminum foil current collectors. Finally, the current collector coated with the cathode slurry is baked to remove the N-methylpyrrolidone, yielding the cathode that restricts lattice oxygen escape. The specific material ratios in the cathode are shown in Table 1 below.

[0075] Examples 6-10

[0076] This embodiment provides a method for preparing a positive electrode that can limit the escape of lattice oxygen, including the following steps:

[0077] The active material selected is Li[Ni 0.8 Co 0.1 Mn 0.1 O2 (NCM811), conductive agent is conductive carbon black, binder is polyvinylidene fluoride, and lattice oxygen inhibitor is nitric acid triacetic acid, in a mass ratio of 80:x:10:y, x+y=10. First, the binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed; then, the conductive agent, active material, and lattice oxygen inhibitor are added to the above adhesive solution in sequence and stirred evenly to obtain a positive electrode slurry; the above positive electrode slurry is coated onto an aluminum foil or carbon-coated aluminum foil current collector; finally, the current collector coated with the positive electrode slurry is baked to remove N-methylpyrrolidone, obtaining the positive electrode that can restrict the escape of lattice oxygen. The specific material ratios in the positive electrode are shown in Table 1 below.

[0078] Examples 10-15

[0079] This embodiment provides a method for preparing a positive electrode that can limit the escape of lattice oxygen, including the following steps:

[0080] The active material selected is Li[Ni 0.8 Co 0.1 Mn 0.1The cathode slurry is prepared using O2 (NCM811), conductive carbon black as the conductive agent, polyvinylidene fluoride as the binder, and sodium phytate as the lattice oxygen inhibitor, in a mass ratio of 80:x:10:y, where x+y=10. First, the binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed. Then, the conductive agent, active material, and lattice oxygen inhibitor are added sequentially to the adhesive solution and stirred until homogeneous to obtain the cathode slurry. The cathode slurry is then coated onto aluminum foil or carbon-coated aluminum foil current collectors. Finally, the current collector coated with the cathode slurry is baked to remove the N-methylpyrrolidone, yielding the cathode that restricts lattice oxygen escape. The specific material ratios in the cathode are shown in Table 1 below.

[0081] Table 1. Details of active materials and lattice oxygen inhibitor content in lithium battery cathodes

[0082] Serial Number Active material content (%) Lattice oxygen inhibitor content (%) Example 1 80 0.1 Example 2 80 0.5 Example 3 80 1 Example 4 80 3 Example 5 80 5 Example 6 80 0.1 Example 7 80 0.5 Example 8 80 1 Example 9 80 3 Example 10 80 5 Example 11 80 0.1 Example 12 80 0.5 Example 13 80 1 Example 14 80 3 Example 15 80 5

[0083] Examples 16-20

[0084] This embodiment provides a method for preparing a cathode that can limit lattice oxygen escape, including the following steps:

[0085] The active material selected is NaNi 0.4 Fe 0.2 Mn 0.4 O2, conductive carbon black as the conductive agent, polyvinylidene fluoride as the binder, and diethylenetriaminepentaacetic acid as the lattice oxygen inhibitor, are prepared in a mass ratio of 80:x:10:y, where x+y=10. First, the binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed. Then, the conductive agent, active material, and lattice oxygen inhibitor are added sequentially to the adhesive solution and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then coated onto an aluminum foil or carbon-coated aluminum foil current collector. Finally, the current collector coated with the positive electrode slurry is baked to remove the N-methylpyrrolidone, yielding the positive electrode that restricts lattice oxygen escape. The specific material ratios in the positive electrode are shown in Table 2 below.

[0086] Examples 21-25

[0087] This embodiment provides a method for preparing a positive electrode that can limit the escape of lattice oxygen, including the following steps:

[0088] The active material selected is NaNi 0.4 Fe 0.2 Mn 0.4O2, conductive carbon black as the conductive agent, polyvinylidene fluoride as the binder, and 2-mercaptonaphthalene as the lattice oxygen inhibitor, are prepared in a mass ratio of 80:x:10:y, where x+y=10. First, the binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed. Then, the conductive agent, active material, and lattice oxygen inhibitor are added sequentially to the adhesive solution and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then coated onto an aluminum foil or carbon-coated aluminum foil current collector. Finally, the current collector coated with the positive electrode slurry is baked to remove the N-methylpyrrolidone, yielding the positive electrode that restricts lattice oxygen escape. The specific material ratios in the positive electrode are shown in Table 2 below.

[0089] Examples 26-30

[0090] This embodiment provides a method for preparing a positive electrode that can limit the escape of lattice oxygen, including the following steps:

[0091] The active material selected is NaNi 0.4 Fe 0.2 Mn 0.4 O2, conductive carbon black as the conductive agent, polyvinylidene fluoride as the binder, and cobalt phytate as the lattice oxygen inhibitor, are prepared in a mass ratio of 80:x:1:y, where x+y=10. First, the binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed. Then, the conductive agent, active material, and lattice oxygen inhibitor are added sequentially to the adhesive solution and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then coated onto an aluminum foil or carbon-coated aluminum foil current collector. Finally, the current collector coated with the positive electrode slurry is baked to remove the N-methylpyrrolidone, yielding the positive electrode that restricts lattice oxygen escape. The specific material ratios in the positive electrode are shown in Table 2 below.

[0092] Table 2. Details of active materials and lattice oxygen inhibitor content in sodium-ion cathodes.

[0093]

[0094]

[0095] Example 31

[0096] This embodiment provides a method for preparing a positive electrode that can limit the escape of lattice oxygen, including the following steps:

[0097] The active material is lithium manganese oxide, the conductive agent is conductive graphite, the binder is polytetrafluoroethylene, and the lattice oxygen inhibitor is barium phytate, all in a mass ratio of 80:x:10:y, where x+y=10. First, the binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed. Then, the conductive agent, active material, and lattice oxygen inhibitor are added sequentially to the adhesive solution and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then coated onto an aluminum foil or carbon-coated aluminum foil current collector. Finally, the current collector coated with the positive electrode slurry is baked to remove the N-methylpyrrolidone, yielding the positive electrode that restricts lattice oxygen escape. The specific material ratios in the positive electrode are shown in Table 3 below.

[0098] Example 32

[0099] This embodiment provides a method for preparing a positive electrode that can limit the escape of lattice oxygen, including the following steps:

[0100] The active material is lithium nickelate, the conductive agent is carbon fiber, the binder is sodium carboxymethyl cellulose, and the lattice oxygen inhibitor is β-mercaptoethylamine, all in a mass ratio of 80:x:1:y, where x+y=10. First, the binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed. Then, the conductive agent, active material, and lattice oxygen inhibitor are added sequentially to the adhesive solution and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then coated onto an aluminum foil or carbon-coated aluminum foil current collector. Finally, the current collector coated with the positive electrode slurry is baked to remove the N-methylpyrrolidone, yielding the positive electrode that restricts lattice oxygen escape. The specific material ratios in the positive electrode are shown in Table 3 below.

[0101] Example 33

[0102] This embodiment provides a method for preparing a positive electrode that can limit the escape of lattice oxygen, including the following steps:

[0103] The active material is lithium cobalt oxide, the conductive agent is carbon nanotubes, the binder is styrene-butadiene rubber, and the lattice oxygen inhibitor is tetrasodium iminodisuccinate, in a mass ratio of 80:x:1:y, where x+y=10. First, the binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed. Then, the conductive agent, active material, and lattice oxygen inhibitor are added sequentially to the adhesive solution and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is then coated onto an aluminum foil or carbon-coated aluminum foil current collector. Finally, the current collector coated with the positive electrode slurry is baked to remove the N-methylpyrrolidone, yielding the positive electrode that restricts lattice oxygen escape. The specific material ratios in the positive electrode are shown in Table 3 below.

[0104] Table 3. Details of active materials and lattice oxygen inhibitor content in sodium electrode cathodes.

[0105] Serial Number Active material content (%) Lattice oxygen inhibitor content (%) Example 31 80 1.5 Example 32 80 2 Example 33 80 4

[0106] Comparative Example 1

[0107] This comparative example provides a method for preparing a positive electrode that can limit the escape of lattice oxygen. The principle and steps are basically the same as those in experiment No. 1 in Example 1, except that the lattice oxygen inhibitor is removed.

[0108] Comparative Example 2

[0109] This comparative example provides a method for preparing a positive electrode that can limit the escape of lattice oxygen. The principle and steps are basically the same as those of the experiment in No. 1 of Example 1, except that the content of active material is 80% and the content of lattice oxygen inhibitor is 6%.

[0110] Comparative Example 3

[0111] This comparative example provides a method for preparing a positive electrode that can limit the escape of lattice oxygen. The principle and steps are basically the same as those in experiment No. 1 in Example 16, except that the lattice oxygen inhibitor is removed.

[0112] Comparative Example 4

[0113] This comparative example provides a method for preparing a positive electrode that can limit the escape of lattice oxygen. The principle and steps are basically the same as those in experiment No. 1 in Example 16, except that the content of active material is 80% and the content of lattice oxygen inhibitor is 6%.

[0114] Performance verification

[0115] To further verify the performance of the prepared cathode, the following performance tests were performed:

[0116] (1) The positive electrodes and electrolytes prepared in Examples 1-15 and Comparative Examples 1 and 2 were assembled into graphite|NCM811 full cells. The half cells were cycled 5 times at a current density of 0.1C to form a stable CEI film. After cycling, the cells were disassembled in an argon-filled glove box. The charged positive electrode sheets obtained from each example were cleaned with dimethyl carbonate to remove residual lithium salts and solvents on the electrode surface, and then dried in an argon-filled glove box. About 4 mg of charged positive electrode powder was scraped from the dried electrode sheet and placed in an aluminum crucible for a differential scanning calorimeter (DSC 4000, PerkinElmer). About 5 mg of electrolyte was added, and DSC test was performed to detect the exothermic reaction between the charged positive electrode powder and the electrolyte. The results of the exothermic reaction tests of the positive electrode and electrolyte prepared in Examples 1-15 and Comparative Examples 1 and 2 are shown in Table 4; the DSC curves of the charged positive electrode powder and electrolyte in Comparative Examples 1, 5, 10, and 15 are shown in Table 4. Figure 1 As shown.

[0117] Table 4. Results of heat release tests between the positive electrode and electrolyte prepared in Examples 1-15 and Comparative Examples 1 and 2.

[0118]

[0119]

[0120] Depend on Figure 1 It can be seen that the reaction heat release of the electrolyte in Comparative Example 1 with the conventional lithium battery cathode in the charging state is as high as -319.8 J / g, while after adding lattice oxygen inhibitor, the reaction heat release of Examples 5, 10 and 15 is reduced to -245.3, -200.2 and -121.6 J / g, respectively.

[0121] (2) The lithiated graphite electrode sheets and charged positive electrodes obtained from Comparative Example 1 and Example 15 were placed in two aluminum crucibles of different sizes. The charged positive electrode was placed in the small crucible, and the lithiated graphite sheets from Comparative Example 1 and Example 15 were placed in the large crucible. The bottom of the small crucible containing the charged positive electrode was pre-punched with a large number of small holes so that the generated active oxygen could reach the lithiated graphite smoothly. Figure 2 The DSC curves are for the positive electrode of Comparative Example 1 and Example 15 in the charged state, respectively.

[0122] Depend on Figure 2 It can be seen that using Example 15, which contains an inhibitor of reactive oxygen species, can significantly reduce the heat release of reactive oxygen species and lithiated graphite.

[0123] (3) Assemble the positive electrode and electrolyte prepared in Examples 16-30 and Comparative Examples 3 and 4 into hard carbon

[0124] |NaNi 0.4 Fe 0.2 Mn 0.4 The O2 full cell was used to cycle the half cell at a current density of 0.1C for 5 cycles to form a stable CEI film. After cycling, the cell was disassembled in an argon-filled glove box. The charged positive electrode sheets obtained from the disassembled examples were cleaned with dimethyl carbonate to remove residual sodium salts and solvents from the electrode surface, and then dried in an argon-filled glove box. Approximately 4 mg of charged positive electrode powder was scraped from the dried electrode sheet and placed in an aluminum crucible for DSC. Approximately 5 mg of electrolyte was added, and DSC testing was performed to detect the heat release of the reaction between the charged positive electrode powder and the electrolyte in each example. The heat release test results of the positive electrodes and electrolytes prepared in Examples 16-30 and Comparative Examples 3 and 4 are shown in Table 5; the DSC curves of the charged positive electrode powder and electrolyte in Comparative Example 3 and Example 30 are shown in Table 5. Figure 3 As shown.

[0125] Table 5. Results of heat release tests between the positive electrode and electrolyte prepared in Examples 16-30 and Comparative Examples 3 and 4.

[0126]

[0127]

[0128] Depend on Figure 3 It can be seen that the reaction heat released by the electrolyte of Comparative Example 3 with the conventional sodium electrode in the charged state is as high as -577.2 J / g, while after adding the lattice oxygen inhibitor, the reaction heat released in Example 30 is reduced to -302.2 J / g.

[0129] (4) Heating experiments were conducted using soft battery packs containing positive electrodes prepared in Example 5, Example 15, and Comparative Example 1, respectively. The temperature-time relationship was obtained, and the results are shown in [Figure 1]. Figure 4 .

[0130] Depend on Figure 4 It can be seen that the trigger temperature for thermal runaway in Comparative Example 1 was 154.1℃, while the trigger temperatures for thermal runaway in Examples 5 and 15 were 196.0℃ and 254.0℃, respectively. The highest temperature during thermal runaway in Comparative Example 1 was 1191.9℃, while the highest temperatures during thermal runaway in Examples 5 and 15 were 895.8℃ and 729.2℃, respectively. Using pouch cells containing the electrolytes of Examples 5 and 15 can significantly increase the trigger temperature for thermal runaway while reducing the highest temperature during thermal runaway.

[0131] (5) The positive electrode, electrolyte, negative electrode and separator prepared in Examples 1-15 and Comparative Examples 1 and 2 were assembled into NCM811|graphite full cells. The first discharge specific capacity (mAh / g) and the capacity retention rate after 100 cycles are shown in Table 6. Figure 5 , Figure 6 The graphs show the cycle performance of full cells containing cathodes from Comparative Example 1, Example 5, Comparative Example 2, and Example 15, respectively.

[0132] Table 6 contains full-cell discharge specific capacity and capacity retention data for the cathodes prepared in Examples 1-15 and Comparative Examples 1 and 2.

[0133]

[0134] Summary Table 6 Figure 5 , 6 It can be seen that the electrochemical performance of the cathode provided in the embodiments of the present invention is better than that of comparative examples 1 and 2, indicating that the addition of reactive oxygen species inhibitors in the embodiments of the present invention does not have a negative impact on electrochemical performance. However, once the amount of reactive oxygen species inhibitors added exceeds the weight percentage provided in the present invention, it will lead to poor cycle performance.

[0135] (7) The lithium battery positive electrode prepared in Examples 16-30, Comparative Examples 3 and 4 were assembled with electrolyte, negative electrode and separator to form NaNi 0.4 Fe 0.2 Mn 0.4The first discharge specific capacity (mAh / g) and capacity retention rate after 300 cycles of O2|hard carbon full battery are shown in Table 7. Figure 7 The graph shows the cycle performance of a full cell containing the cathodes of Comparative Example 4 and Example 16.

[0136] Table 7 contains full-cell discharge specific capacity and capacity retention data for the cathodes prepared in Examples 16-30 and Comparative Examples 3 and 4.

[0137]

[0138]

[0139] Summary Table 7 Figure 7 It can be seen that the electrochemical performance of the sodium cathode provided in the embodiments of the present invention is better than that of comparative examples 3 and 4, indicating that the addition of reactive oxygen species inhibitors in the embodiments of the present invention does not have a negative impact on electrochemical performance. However, if the amount of reactive oxygen species inhibitors added exceeds the weight percentage provided in the present invention, it will lead to poor cycling performance.

[0140] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A cathode capable of restricting the escape of lattice oxygen, characterized in that, The positive electrode includes an active material, a conductive agent, a binder, and a lattice oxygen inhibitor; The lattice oxygen inhibitor is one or more of phytates, aminocarboxylic acid compounds, and mercapto-containing compounds; The phytate structure is shown in Formula I or Formula II: Formula I Wherein, R1 is at least one of lithium ion, sodium ion, and potassium ion; Formula II Wherein, R2 is at least one of barium ion, copper ion, calcium ion, zinc ion, cobalt ion, and magnesium ion; The structure of the aminocarboxylic acid compound is shown in Formula III: Formula III Wherein, R3 is at least one of diacetamino, acetic acid, ethylenediaminetriacetyl, hydroxy, ethyl, phenyl, vinyl, acetoxy, acetoxyethyl, 3-acryloyl, 3-methacryloyl, and N,N-dipropyl. The structure of the thiol-based compound is shown in Formula IV: Formula IV Wherein, R4 is at least one of isooctyl acetate, propionic acid, 2-butanone, ethylamino, ethanol, butyric acid, acetaldehyde, succinic acid, 1,3,4-thiadiazolyl, acetate, mercapto, naphthyl, methyl acetate, acetylnaphthylamine, ethyl acetate, benzyl acetate, sodium pyruvate, thiadiazolyl, and benzoic acid.

2. The positive electrode according to claim 1, characterized in that, The active material is a nickel-rich layered oxide, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium-rich manganese-based oxide, or sodium-based layered oxide. The active material accounts for 80-95% of the weight of the positive electrode; the conductive agent accounts for 1-10% of the weight of the positive electrode; the binder accounts for 1-10% of the weight of the positive electrode; and the lattice oxygen inhibitor accounts for 0.1-5% of the weight of the positive electrode.

3. The positive electrode according to claim 1, characterized in that, The phytate is at least one of lithium phytate, sodium phytate, potassium phytate, barium phytate, copper phytate, calcium phytate, zinc phytate, cobalt phytate, and magnesium phytate. The aminocarboxylic acid compound is at least one of ethylenediaminetetraacetic acid, aziridine triacetic acid, diethylenetriaminepentaacetic acid, N-hydroxyethylethylaminetriacetic acid, and ethylene glycol-bis(B-aminoethyl ether)-N,N-tetraacetic acid. The thiol compounds are at least one of the following: isooctyl thioglycolate, mercaptopropionic acid, 3-mercapto-2-butanone, β-mercaptoethylamine, mercaptoethanol, mercaptobutyric acid, mercaptoacetaldehyde, strontium thioglycolate, mercaptosuccinic acid, mercaptothiadiazole, magnesium thioglycolate, potassium thioglycolate, dimercaptomethane, 2-mercaptonaphthalene, methyl thioglycolate, mercaptoacetylnaphthylamine, benzyl thioglycolate, and 4-mercaptotoluene.

4. The positive electrode according to claim 2, characterized in that, The chemical formula of the nickel-rich layered oxide is LiNi. x Co y Mn z O2, x+y+z=1; The chemical formula of the lithium-rich manganese-based oxide is aLi2MnO3·(1-a)LiMO2, where M is Ni, Co or Mn; The chemical formula of the sodium-based oxide is Na. b MO2, where M is nickel, cobalt, iron, or manganese, and the value of b corresponds to the valence state of M.

5. The positive electrode according to claim 1, characterized in that, The conductive agent is at least one of conductive carbon black, conductive graphite, carbon fiber, carbon nanotubes, and graphene; the binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, polyacrylic acid, polyvinyl alcohol, sodium carboxymethyl cellulose, styrene-butadiene rubber, and sodium alginate.

6. A positive electrode capable of restricting lattice oxygen escape according to any one of claims 1 to 5, characterized in that, The active material is Li[Ni] 0.8 Co 0.1 Mn 0.1 O2, conductive agent is conductive carbon black, binder is polyvinylidene fluoride, lattice oxygen inhibitor is sodium phytate, and they are mixed in a mass ratio of 80:x:10:y, where x+y=10.

7. A method for preparing a positive electrode as described in claim 6, capable of restricting lattice oxygen escape, characterized in that, Includes the following steps: The binder is dissolved in N-methylpyrrolidone and stirred until a clear adhesive solution is formed. Then, the conductive agent, active material, and lattice oxygen inhibitor are added to the adhesive solution in sequence and stirred evenly to obtain a positive electrode slurry. The positive electrode slurry is coated onto an aluminum foil or carbon-coated aluminum foil current collector. Finally, the current collector coated with the positive electrode slurry is baked to remove the N-methylpyrrolidone, thus obtaining the positive electrode that can restrict the escape of lattice oxygen.

8. A secondary battery, characterized in that, The secondary battery includes the positive electrode as described in claim 7, which can restrict the escape of lattice oxygen, and the secondary battery is a lithium-ion battery, a lithium metal battery, a sodium-ion battery, or a sodium metal battery.

9. The application of the positive electrode according to claim 6, which can limit the escape of lattice oxygen, in improving the safety of secondary batteries.

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