A high-heat-safe positive electrode active material

Abstract

The present invention provides a positive electrode active material, comprising lithium and a transition metal element; the transition metal element comprising nickel; a molar ratio of nickel to lithium of 0.5 to 0.96; a 100% SOC cutoff voltage of V1 for the positive electrode active material, a thermal decomposition peak temperature of T1 for the material under this voltage condition, and a voltage of V2 for the positive electrode active material, wherein V2 = V1 + 0.05, and a thermal decomposition peak temperature of T2, wherein T1 and T2 satisfy ‑15°C ≤ T1‑T2 ≤ 40°C. The positive electrode active material provided by the present invention can maintain the same good safety performance as under normal operating voltage conditions when the battery is overcharged, thereby reducing the probability of safety risks in the battery, and resolving the problem that battery materials are more susceptible to safety risks when overcharged, and the defect that some high-safety materials can only have good safety performance under limited voltages.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery positive electrode active materials, and relates to a positive electrode active material, in particular to a high-heat safety positive electrode active material. Background Art

[0002] Currently, during the use of positive electrode materials, due to continuous charging and discharging, overcharging may occur, causing battery heating and oxygen release from the materials, which can lead to thermal safety accidents. With the rapid development of lithium-ion batteries, safety performance has received more and more attention in the industry, especially for ternary positive electrode materials, whose thermal safety performance has received extensive attention. However, existing considerations on the safety performance of active materials have significant limitations.

[0003] Therefore, how to ensure the performance of active materials while ensuring that the positive electrode materials can better perform their performance in the battery while better improving safety performance has become one of the urgent problems to be solved by many front-line researchers in the industry.

[0004] In addition, the safety performance and cycle performance of lithium-ion batteries are two important performance indicators of batteries. By confirming these indicators, suitable battery materials can be screened out to meet battery usage. Summary of the Invention

[0005] In view of this, the technical problem to be solved by the present invention is to provide a positive electrode active material, particularly a high-heat-safe positive electrode active material. The positive electrode active material provided by the present invention can maintain the same excellent safety performance as under normal operating voltage conditions during overcharge, thereby reducing the possibility of battery safety risks.

[0006] The present invention provides a positive electrode active material, wherein the positive electrode active material includes lithium and a transition metal element;

[0007] The transition metal elements include nickel;

[0008] The molar ratio of the nickel element to the lithium element is 0.5 to 0.96;

[0009] The positive electrode active material has a cutoff voltage of V1 at 100% SOC, and a thermal decomposition peak temperature of T1 under this voltage condition. The positive electrode active material has a thermal decomposition peak temperature of T2 at a voltage of V2, where V2=V1+0.05, wherein T1 and T2 satisfy -15°C≤T1-T2≤40°C.

[0010] Preferably, T1 and T2 satisfy -10°C ≤ T1-T2 ≤ 40°C;

[0011] The positive electrode active material includes a positive electrode active material of a lithium ion battery.

[0012] Preferably, the 100% SOC specifically refers to the fully charged state of the lithium-ion battery composed of the positive electrode active material after the first charge;

[0013] At the 100% SOC, the positive electrode active material is in a lithium-deficient state.

[0014] Preferably, T1 and T2 satisfy 0°C≤T1-T2≤20°C;

[0015] The positive electrode active material has a thermal decomposition peak temperature of T3 at a voltage of V3, where V3=V1+0.1, wherein T1 and T3 satisfy 0°C≤T1-T3≤50°C.

[0016] Preferably, T1 and T3 satisfy 0°C≤T1-T3≤30°C, and T2 and T3 satisfy T2>T3.

[0017] Preferably, the positive electrode active material has a cutoff voltage of V1 at 100% SOC, and the thermal decomposition starting temperature of the material under this voltage condition is t1. The positive electrode active material has a thermal decomposition starting temperature of t2 at a voltage of V2, V2=V1+0.05, wherein t1 and t2 satisfy -15°C≤t1-t2≤40°C.

[0018] Preferably, t1 and t2 satisfy -10°C ≤ t1-t2 ≤ 20°C;

[0019] The positive electrode active material has a thermal decomposition starting temperature of t3 at a voltage of V3, V3=V1+0.1, wherein t1 and t3 satisfy -5°C≤t1-t3≤45°C.

[0020] Preferably, t1 and t3 satisfy 0°C≤t1-t3≤30°C.

[0021] Preferably, the positive electrode active material has a thermal conductivity of H1 at a voltage of V1, a thermal conductivity of H2 at a voltage of V2, and a thermal conductivity of H3 at a voltage of V3, wherein H1, H2 and H3 satisfy H1≥H2≥H3.

[0022] Preferably, H1, H2 and H3 satisfy 1.1H2≥H1≥H2.

[0023] Preferably, the positive electrode active material has the general formula shown in formula (I):

[0024] Li 1+a [Ni x Co y M z M1 bO2 (I);

[0025] where 0.5 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, 0 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1;

[0026] M includes Mn and / or Al;

[0027] M1 includes one or more of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y.

[0028] Preferably, the positive electrode active material further includes a coating layer;

[0029] The coating layer is an ion conductor layer;

[0030] The material of the coating layer includes metal lithium compounds and / or non-metal lithium compounds. [[ID=?]]

[0031] Preferably, the metal lithium compounds include one or more of lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganese oxide materials, lithium manganate, lithium nickelate, lithium titanate, lithium titanium aluminum phosphate, lithium lanthanum titanate, lithium lanthanum tantalate, lithium germanium aluminum phosphate, lithium lanthanum zirconium oxide, lanthanum zirconium aluminum lithium oxide, niobium-doped lithium lanthanum zirconium oxide, and tantalum-doped lithium lanthanum zirconium oxide;

[0032] The molar content of nickel in the lithium nickel cobalt manganese oxide material < 60%;

[0033] The non-metal lithium compounds include one or more of boron lithium compounds, sulfur lithium compounds, and phosphorus lithium compounds.

[0034] Preferably, the positive electrode active material is a positive electrode active material that can reduce the overcharge safety risk;

[0035] The method for reducing the overcharge safety risk includes making the positive electrode active material have a cut-off voltage of V1 at 100% SOC, and the peak temperature of thermal decomposition of the material at this voltage is T1. The positive electrode active material is at a voltage of V2, where V2 = V1 + 0.05, and the peak temperature of thermal decomposition of the material is T2. Among them, T1 and T2 satisfy -15°C ≤ T1 - T2 ≤ 40°C.

[0036] It should be noted that there seems to be an error in the original text where the tag [[ID=?]] is used instead of . This has been maintained in the translation for consistency with the original.The present invention provides a positive electrode active material comprising lithium and a transition metal element; the transition metal element includes nickel; the molar ratio of nickel to lithium is 0.5 to 0.96; the positive electrode active material exhibits a thermal decomposition peak temperature of T1 at a cutoff voltage of 100% SOC (V1); and a thermal decomposition peak temperature of T2 at a voltage of V2 (V2 = V1 + 0.05), wherein T1 and T2 satisfy the relationship -15°C ≤ T1 - T2 ≤ 40°C. Compared to the prior art, the present invention addresses the safety deficiencies of existing positive electrode active materials, although there are also improved technical solutions, by combining two different positive electrode active materials such that the thermal decomposition temperature of one positive electrode active material is higher than that of the other at 100% SOC. However, the present invention believes that this technical solution only limits the DSC of different materials, without considering that a material may have different DSC performance under different SOCs, and cannot protect the intrinsic performance of the material. Moreover, by setting a multi-layer structure, thereby improving the DSC performance of the battery, it cannot meet the performance requirements of high thermal safety.

[0037] Based on this, the present invention specially designs a positive electrode active material with specific performance. When the cut-off voltage of the positive electrode active material is V1 and V1+0.05 at 100% SOC, the difference in the corresponding thermal decomposition peak temperature is -10~40. When the difference is too large, the battery safety cannot be guaranteed. When the difference is too small, it means that the cut-off voltage of the material itself is set too small. If it is too small, it means that the material performance does not play a good role, or it is believed that less lithium ions are released. When the battery is overcharged, the positive electrode active material provided by the present invention can still maintain the same good safety performance as under normal operating voltage conditions, reducing the probability of safety risks in the battery, effectively solving the problem that the battery material is more prone to safety risks when overcharged, and also solving the defect that some current high-safety materials can only have good safety performance under limited voltage.

[0038] The positive electrode active material provided by the present invention has a smaller initial temperature difference, which further improves the safety performance of the battery produced with this material. Furthermore, under the condition of overcharging by 0.1V, the thermal decomposition difference of the material increases slightly, which overall demonstrates the stability of the material and further ensures battery safety. Furthermore, after overcharging, the thermal decomposition temperature decreases slightly, indicating a slight decrease in the decomposition temperature. However, this reduction in thermal decomposition temperature can ensure safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 These are the performance test results of Examples 1 to 30 of the present invention;

[0040] Figure 2These are the performance test results of Examples 31 to 50 of the present invention;

[0041] Figure 3 These are the performance test results of Comparative Examples 1 to 6 of the present invention;

[0042] Figure 4 1 is a DSC curve diagram at different voltages in Example 11 of the present invention. DETAILED DESCRIPTION

[0043] In order to further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention rather than limiting the patent claims of the present invention.

[0044] All raw materials of the present invention are not particularly limited in their sources and can be purchased from the market or prepared according to conventional methods well known to those skilled in the art.

[0045] There is no particular limitation on the purity of all raw materials in the present invention. The present invention preferably uses analytically pure materials or materials with conventional purity requirements in the field of lithium-ion battery positive electrode active material preparation.

[0046] All raw materials of the present invention, their brands and abbreviations are conventional brands and abbreviations in the field. Each brand and abbreviation is clear and unambiguous in the field of its relevant use. Those skilled in the art can purchase them from the market or prepare them by conventional methods based on the brand, abbreviation and corresponding use.

[0047] The abbreviations of the processes used in the present invention are all conventional abbreviations in the field. The specific steps and conventional parameters of each abbreviation are clear and definite in its relevant field. Those skilled in the art can implement them in a conventional manner based on the abbreviations.

[0048] The present invention provides a positive electrode active material, wherein the positive electrode active material includes lithium and a transition metal element;

[0049] The transition metal elements include nickel;

[0050] The molar ratio of the nickel element to the lithium element is 0.5 to 0.96;

[0051] The positive electrode active material has a cutoff voltage of V1 at 100% SOC, and a thermal decomposition peak temperature of T1 under this voltage condition. The positive electrode active material has a thermal decomposition peak temperature of T2 at a voltage of V2, where V2=V1+0.05, wherein T1 and T2 satisfy -15°C≤T1-T2≤40°C.

[0052] In the present invention, it should be noted that the active materials cannot be charged directly and are charged and discharged after being assembled into a battery. As is well known in the art, SOC refers to the battery state after the active materials are assembled into a battery and then charged and discharged. 100% SOC refers to the fully charged state after the active materials are assembled into a battery for the first time, at which point the positive electrode material is in a lithium-deficient state.

[0053] In the present invention, the 100% SOC is preferably a fully charged state of a lithium-ion battery composed of positive electrode active materials after first charging.

[0054] In the present invention, the difference may be negative because when the material exceeds the cutoff voltage, a small amount of lithium ions are released, and the c-axis decreases, thereby increasing the adsorption capacity for oxygen, so the thermal decomposition temperature is slightly increased, so the difference is negative.

[0055] In the present invention, the molar ratio of the nickel element to the lithium element is (0.5-0.96):1, preferably (0.6-0.9):1, and more preferably (0.7-0.8):1.

[0056] In the present invention, the positive electrode active material preferably includes a positive electrode active material for a lithium ion battery.

[0057] In the present invention, at the 100% SOC, the positive electrode active material is preferably in a lithium-deficient state.

[0058] In the present invention, T1 and T2 preferably satisfy -10°C ≤ T1-T2 ≤ 40°C, more preferably 0°C ≤ T1-T2 ≤ 20°C, and even more preferably 0°C ≤ T1-T2 ≤ 10°C.

[0059] In the present invention, the positive electrode active material has a thermal decomposition peak temperature of T3 at a voltage of V3, where V3 = V1 + 0.1. T1 and T3 preferably satisfy 0°C ≤ T1-T3 ≤ 50°C, more preferably 0°C ≤ T1-T3 ≤ 30°C, and even more preferably 0°C ≤ T1-T3 ≤ 20°C. Furthermore, T2 and T3 preferably satisfy T2 > T3.

[0060] In the present invention, the positive electrode active material has a cutoff voltage of V1 at 100% SOC, and a thermal decomposition starting temperature of t1 under this voltage condition. The positive electrode active material has a thermal decomposition starting temperature of t2 at a voltage of V2, where V2=V1+0.05, wherein t1 and t2 preferably satisfy -15°C≤t1-t2≤40°C, more preferably -10°C≤t1-t2≤20°C, and more preferably -5°C≤t1-t2≤10°C.

[0061] In the present invention, for the positive electrode active material, at voltage V3 where V3 = V1 + 0.1, the initial temperature of thermal decomposition of this material is t3, wherein t1 and t3 preferably satisfy -5°C ≤ t1 - t3 ≤ 45°C, more preferably satisfy 0°C ≤ t1 - t3 ≤ 30°C, and even more preferably satisfy 0°C ≤ t1 - t3 ≤ 20°C.

[0062] In the present invention, for the positive electrode active material, at voltage V1, the enthalpy value is H1, at voltage V2, the enthalpy value is H2, and at voltage V3, the enthalpy value is H3, wherein H1, H2, and H3 preferably satisfy H1 ≥ H2 ≥ H3, more preferably satisfy 1.1H2 ≥ H1 ≥ H2, and even more preferably satisfy 1.05H2 ≥ H1 ≥ H2.

[0063] In the present invention, the positive electrode active material preferably has a general formula as shown in formula (I):

[0064] Li 1+a [Ni x Co y M z M1 b O2 (I);

[0065] In the present invention, preferably 0.5 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, 0 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1.

[0066] Among them, preferably 0.5 ≤ x < 1, and more preferably 0.7 ≤ x ≤ 0.8.

[0067] Preferably 0 < y < 0.3, and more preferably 0.1 ≤ y ≤ 0.2.

[0068] Preferably 0 < z < 0.3, and more preferably 0.1 ≤ z ≤ 0.2.

[0069] Preferably 0 < a < 0.2, and more preferably 0.05 ≤ a ≤ 0.15.

[0070] Preferably 0 < b < 0.2, and more preferably 0.05 ≤ b ≤ 0.15.

[0071] In the present invention, M preferably includes Mn and / or Al, and more preferably includes Mn or Al.

[0072] In the present invention, M1 preferably includes one or more of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y, and more preferably includes Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, or Y.

[0073] In the present invention, the positive electrode active material preferably further includes a coating layer.

[0074] In the present invention, the coating layer is preferably an ion conductor layer.

[0075] In the present invention, the material of the coating layer preferably includes metal lithiation and / or non-metal lithiation, and more preferably includes metal lithiation or non-metal lithiation.

[0076] In the present invention, the metal lithium compound preferably includes one or more of lithium iron phosphate, lithium cobaltate, nickel cobalt manganate material, lithium manganate, lithium nickelate, lithium titanate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum tantalate, lithium germanium aluminum phosphate, lithium lanthanum zirconium oxide, lanthanum zirconium aluminum lithium oxide, niobium-doped lithium lanthanum zirconium oxide and tantalum-doped lithium lanthanum zirconium oxide, more preferably includes lithium iron phosphate, lithium cobaltate, nickel cobalt manganate material, lithium manganate, lithium nickelate, lithium titanate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum tantalate, lithium germanium aluminum phosphate, lithium lanthanum zirconium oxide, lanthanum zirconium aluminum lithium oxide, niobium-doped lithium lanthanum zirconium oxide or tantalum-doped lithium lanthanum zirconium oxide.

[0077] In the present invention, the molar content of nickel in the lithium nickel cobalt manganese oxide material is preferably less than 60%, more preferably ≤50%, and even more preferably ≤40%.

[0078] In the present invention, the non-metallic lithiate preferably includes one or more of a boron lithium compound, a sulfur lithium compound and a phosphorus lithium compound, and more preferably includes a boron lithium compound, a sulfur lithium compound or a phosphorus lithium compound.

[0079] In the present invention, coating means crushing the burnt material, screening it, and then mixing it with the corresponding material for 0.5h.

[0080] The specific coating and sintering temperature correspond to the following:

[0081] The boron-lithium coating agent H3BO3 / B2O3 is sintered at 280~320℃ / 8~12h.

[0082] Lithium sulfide uses sulfur / lithium sulfide 220~250℃ / 10~14h.

[0083] Lithium cobalt oxide uses Co2O3 / Co3O4 / hydroxide / cobalt oxyhydroxide at a temperature of 650~750℃ for 6~10h.

[0084] Lithium titanate is mixed with lithium titanate at 480~520℃ for 8~10h.

[0085] Lithium iron phosphate is mixed with lithium iron phosphate at 480~520℃ for 8~10h.

[0086] Lithium manganate is mixed with lithium manganate at 480~520℃ for 8~10h.

[0087] For lithium phosphate, use ammonium dihydrogen phosphate at 550~600℃ for 8~12h.

[0088] Multi-element coating corresponds to oxides at 600~700℃ for 8~15h.

[0089] In the present invention, the positive electrode active material is preferably a positive electrode active material that can reduce the safety risk of overcharging.

[0090] In the present invention, the method for reducing the safety risk of overcharging, that is, the present invention provides a method for reducing the safety risk of overcharging, preferably comprising the following steps:

[0091] The positive electrode active material has a cutoff voltage of V1 at 100% SOC, and a thermal decomposition peak temperature of T1 under this voltage condition. The positive electrode active material has a thermal decomposition peak temperature of T2 at a voltage of V2, V2=V1+0.05, wherein T1 and T2 satisfy -15°C≤T1-T2≤40°C.

[0092] In the above method of the present invention, its parameters are preferably compatible with the aforementioned corresponding parameters, and are not described one by one here.

[0093] The present invention is a complete and detailed overall technical solution to better ensure the safety performance of the positive electrode active material. Based on the comprehensive performance of the positive electrode active material, the safety performance during overcharging is further improved. The above-mentioned positive electrode active material can specifically be composed of the following:

[0094] A positive electrode active material is composed of a composite oxide of lithium and a transition metal element, wherein the transition metal element includes a nickel element, and the molar ratio of the nickel element to the lithium element is 0.5-0.96; the positive electrode active material has a cutoff voltage of V1 at 100% SOC, and a thermal decomposition peak temperature of T1 under this voltage condition; the positive electrode active material has a thermal decomposition peak temperature of T2 under a voltage of V2, where V2=V1+0.05, wherein -10°C ≤ T1-T2 ≤ 40°C.

[0095] Specifically, the preferred decomposition peak temperature difference is 0°C ≤ T1-T2 ≤ 20°C, and more preferably 0°C ≤ T1-T2 ≤ 10°C.

[0096] Specifically, the positive electrode active material has a cutoff voltage of V1 at 100% SOC, and the thermal decomposition starting temperature of the material under this voltage condition is t1. The positive electrode active material has a thermal decomposition starting temperature of t2 at a voltage of V2, V2=V1+0.05, wherein -15°C≤t1-t2≤40°C.

[0097] Specifically, the preferred decomposition starting temperature difference is -10°C ≤ t1-t2 ≤ 20°C, and more preferably -5°C ≤ t1-t2 ≤ 10°C.

[0098] Specifically, when the positive electrode active material is at a voltage V3, where V3 = V1 + 0.1, the peak temperature of thermal decomposition of this material is T3, and 0 °C ≤ T1 - T3 ≤ 50 °C.

[0099] Specifically, the preferred difference in peak temperature of decomposition is 0 °C ≤ T1 - T3 ≤ 30 °C, and more preferably 0 °C ≤ T1 - T3 ≤ 20 °C. At the same time, T2 > T3 needs to be satisfied.

[0100] Specifically, when the positive electrode active material is at a voltage V3, where V3 = V1 + 0.1, the initial temperature of thermal decomposition of this material is t3, and -5 °C ≤ t1 - t3 ≤ 45 °C.

[0101] Specifically, the preferred difference in initial temperature of decomposition is 0 °C ≤ t1 - t3 ≤ 30 °C, and more preferably 0 °C ≤ t1 - t2 ≤ 20 °C. Invention point 9: At a voltage V1, the heat content is H1, at a voltage V2, the heat content is H2, and at a voltage V3, the heat content is H3, and H1 ≥ H2 ≥ H3.

[0102] Specifically, preferably 1.1H2 ≥ H1 ≥ H2, and preferably 1.05H2 ≥ H1 ≥ H2.

[0103] Specifically, the general formula of the positive electrode active material is Li 1+a [Ni x Co y M z M1 b O2.

[0104] Where, 0.5 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, 0 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1.

[0105] Specifically, M is Mn and / or Al; M1 is one or more of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, Y.

[0106] Specifically, preferably M1 is one or more of Zr, Mg, Ti, Al, Sr, Nb, W, Mo.

[0107] Specifically, the positive electrode material further includes a coating layer, and the coating layer is an ion conductor layer; the ion conductor layer is lithium iron phosphate, lithium cobaltate, lithium nickel cobalt manganese oxide material (molar content of nickel < 60%), lithium manganate, lithium nickelate, lithium titanate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum tantalate, lithium germanium aluminum phosphate, lithium lanthanum zirconium oxide, lanthanum zirconium aluminum lithium oxide, niobium-doped lithium lanthanum zirconium oxide, tantalum-doped lithium lanthanum zirconium oxide and other metal lithium compounds; or boron lithium compounds, sulfur lithium compounds, phosphorus lithium compounds and other non-metal lithium compounds.

[0108] The above content of the present invention provides a high thermal safety positive electrode active material. The positive electrode active material with specific performance has a corresponding thermal decomposition peak temperature difference of -10~40 when the 100% SOC cut-off voltage is V1 and V1+0.05. When the difference is too large, the battery safety cannot be guaranteed. When the difference is too small, it means that the cut-off voltage of the material itself is set too small. If it is too small, it means that the material performance does not play a good role, or it is believed that less lithium ions are released. When the battery is overcharged, the positive electrode active material provided by the present invention can still maintain the same good safety performance as under normal operating voltage conditions, reducing the probability of safety risks in the battery, effectively solving the problem that the battery material is more prone to safety risks when overcharged, and also solving the defect that some current high-safety materials can only have good safety performance under limited voltage.

[0109] The positive electrode active material provided by the present invention has a smaller initial temperature difference, which further improves the safety performance of the battery produced with this material. Furthermore, under the condition of overcharging by 0.1V, the thermal decomposition difference of the material increases slightly, which overall demonstrates the stability of the material and further ensures battery safety. Furthermore, after overcharging, the thermal decomposition temperature decreases slightly, indicating a slight decrease in the decomposition temperature. However, this reduction in thermal decomposition temperature can ensure safety.

[0110] In order to further illustrate the present invention, a positive electrode active material provided by the present invention is described in detail below in conjunction with examples. However, it should be understood that these examples are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and specific operating processes are provided only to further illustrate the features and advantages of the present invention, rather than to limit the claims of the present invention. The scope of protection of the present invention is not limited to the following examples. Example

[0111] Examples 1 to 10

[0112] The positive electrode active material precursor [Ni 0.8 Co 0.1 Mn 0.1 ](OH)2, lithium hydroxide LiOH, and niobium pentoxide Nb2O5 are added to a high-speed mixer and mixed for 1 hour to obtain a mixed material. The molar ratio of the positive electrode active material precursor to lithium hydroxide (Li / Me) is 1.05, where Me represents the total molar amount of Ni, Co, and Mn in the positive electrode active material precursor. The mixed material is sintered in an atmosphere sintering furnace at a temperature of 820-850°C in an oxygen-containing atmosphere with an O2 concentration of 90% for 13-16 hours. The sintered product is crushed and sieved to obtain a high-nickel ternary positive electrode active material.

[0113] Examples 11 to 21

[0114] The positive electrode active material precursor [Ni 0.8 Co 0.1 Al 0.1 ](OH)2, lithium hydroxide LiOH and zirconium dioxide ZrO2.

[0115] Examples 22 and 28

[0116] The sintering temperature was 980℃, the sintering time was 15h, and the precursor was modified.

[0117] Examples 23 and 29

[0118] The sintering temperature is 950℃ and the time is 15h.

[0119] DSC test method:

[0120] The materials were mixed into a slurry, coated on the current collector, and dried; the negative electrode was assembled into a button cell using lithium sheets; the electrolyte used conventional lithium hexafluorophosphate, the battery was charged to a specific voltage condition, the battery was disassembled, and the electrode was cleaned with DMC and dried; the electrode DSC was tested, a certain amount of electrolyte was added, and the thermal decomposition curve was tested using a differential scanning calorimeter to obtain the corresponding thermal decomposition starting temperature, peak temperature, and heat; the heating rate was set to 10℃ / min.

[0121] 0.5<Ni<0.7, the cut-off voltage is 4.4V; 0.7≤Ni<0.8, the cut-off voltage is 4.35V; 0.8≤Ni<1, the cut-off voltage is 4.25V.

[0122] Overcharge performance test method: Prepare and assemble the materials into soft-pack batteries. According to the battery capacity, use 1C constant current to charge to the cut-off voltage, and then use the cut-off voltage constant voltage to charge to 0.05C. Then use 0.1C current for constant current charging. When the battery thermal runaway occurs, record the charging capacity and convert it into charging capacity.

[0123] Thermal runaway test: The materials are assembled into soft-pack batteries, which are charged to 100% SOC under the same conditions. A heating film is added to the battery surface, ensuring that it fits tightly against the battery. The temperature at which the battery experiences thermal runaway and the maximum temperature at which thermal runaway occurs are tested. The heating rate is set to 5°C / min.

[0124] See also Figure 1 , Figure 1 These are the performance test results of Examples 1 to 30 of the present invention.

[0125] See also Figure 2 , Figure 2 These are the performance test results of Examples 31 to 50 of the present invention.

[0126] See also Figure 3 , Figure 3 These are the performance test results of Comparative Examples 1 to 6 of the present invention.

[0127] The results of the examples show that H affects the maximum temperature: the lower the H, the lower the maximum temperature. The temperature difference affects the thermal runaway temperature: the larger the temperature difference, the lower the thermal runaway temperature. The starting temperature affects the overcharge performance: the larger the starting temperature difference, the lower the overcharge performance.

[0128] See also Figure 4 , Figure 4 1 is a DSC curve diagram at different voltages in Example 11 of the present invention, wherein the abscissa is temperature in °C, and the ordinate is heat flow (normalized) in W / g.

[0129] Depend on Figure 4 It can be seen that under the voltage of V1, T1 is 231.2℃ (green line, the middle peak line); under the voltage of V2, T2 is 239℃ (red line, the peak line on the right); under the voltage of V3, T3 is 222.8℃ (blue line, the peak line on the left); at the same time, from the peak area, it can be seen that the thermal conductivity H1 at V1 is the largest (peak area), the thermal conductivity H2 at V2 is the second, and the thermal conductivity H3 at V3 is H3.

[0130] The above describes in detail a high-heat safety positive electrode active material provided by the present invention. Specific examples are used herein to illustrate the principles and implementation methods of the present invention. The description of the above examples is intended only to facilitate understanding of the methods and core concepts of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including the manufacture and use of any device or system, and the implementation of any combined method. It should be noted that, without departing from the principles of the present invention, a person skilled in the art may make several improvements and modifications to the present invention, and such improvements and modifications fall within the scope of protection of the claims of the present invention. The scope of patent protection for the present invention is defined by the claims and may include other embodiments that can be conceived by a person skilled in the art. If these other embodiments have structural elements that are not different from the literal language of the claims, or if they include equivalent structural elements that are not substantially different from the literal language of the claims, then these other embodiments are also intended to be included within the scope of the claims.

Claims

1. A positive electrode active material, characterized in that The positive electrode active material includes lithium and transition metal elements; The transition metal elements include nickel element; The molar ratio of the nickel element to the lithium element is (0.5 - 0.96):1; When the cut-off voltage of the positive electrode active material at 100% SOC is V1, the peak temperature of thermal decomposition of this material under this voltage condition is T1. When the positive electrode active material is at voltage V2, where V2 = V1 + 0.05, the peak temperature of thermal decomposition of this material is T2. Among them, T1 and T2 satisfy -15°C ≤ T1 - T2 ≤ 40°C; The specific 100% SOC means the fully charged state after the first charge of the lithium-ion battery composed of the positive electrode active material; At 100% SOC, the positive electrode active material is in a lithium-deficient state.

2. The positive electrode active material according to claim 1, characterized in that T1 and T2 satisfy -10°C ≤ T1 - T2 ≤ 40°C.

3. The positive electrode active material according to claim 1, characterized in that The positive electrode active material includes the positive electrode active material of a lithium-ion battery.

4. The positive electrode active material according to claim 1, characterized in that T1 and T2 satisfy 0°C ≤ T1 - T2 ≤ 20°C; When the positive electrode active material is at voltage V3, where V3 = V1 + 0.1, the peak temperature of thermal decomposition of this material is T3. Among them, T1 and T3 satisfy 0°C ≤ T1 - T3 ≤ 50°C.

5. The positive electrode active material according to claim 4, characterized in that T1 and T3 satisfy 0°C ≤ T1 - T3 ≤ 30°C, and T2 and T3 satisfy T2 > T3.

6. The positive electrode active material according to claim 1, characterized in that When the cut-off voltage of the positive electrode active material at 100% SOC is V1, the initial temperature of thermal decomposition of this material under this voltage condition is t1. When the positive electrode active material is at voltage V2, where V2 = V1 + 0.05, the initial temperature of thermal decomposition of this material is t2. Among them, t1 and t2 satisfy -15°C ≤ t1 - t2 ≤ 40°C.

7. The positive electrode active material according to claim 6, characterized in that t1 and t2 satisfy -10°C ≤ t1 - t2 ≤ 20°C; When the positive electrode active material is at voltage V3, where V3 = V1 + 0.1, the initial temperature of thermal decomposition of this material is t3. Among them, t1 and t3 satisfy -5°C ≤ t1 - t3 ≤ 45°C.

8. The positive electrode active material according to claim 7, characterized in that t1 and t3 satisfy 0°C ≤ t1 - t3 ≤ 30°C.

9. The positive electrode active material according to claim 1, characterized in that When the positive electrode active material is at voltage V1, the magnitude of the heat content is H1. When at voltage V2, the magnitude of the heat content is H2. When at voltage V3, the magnitude of the heat content is H3. Among them, H1, H2, and H3 satisfy H1 ≥ H2 ≥ H3.

10. The positive electrode active material according to claim 9, characterized in that H1, H2, and H3 satisfy 1.1H2 ≥ H1 ≥ H2.

11. The positive electrode active material according to claim 1, characterized in that The positive electrode active material has a general formula shown in formula (I): Li 1+a [Ni x Co y M z M1 b ]O2(I); Among them, 0.5 ≤ x < 1, 0 < y < 0.3, 0 < z < 0.3, 0 < a < 0.2, 0 < b < 0.2, and x + y + z + b = 1; M includes Mn and / or Al; M1 includes one or more of Zr, Mg, Ti, Te, Al, Ca, Sr, Sb, Nb, Pb, V, Ge, Se, W, Mo, Zn, Ce, and Y.

12. The positive electrode active material according to claim 1, characterized in that The positive electrode active material further includes a coating layer; The coating layer is an ion conductor layer; The material of the coating layer includes metal lithium compounds and / or non-metal lithium compounds.

13. The positive electrode active material according to claim 12, characterized in that The metal lithium compound includes one or more of lithium iron phosphate, lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganese oxide, lithium nickel oxide, lithium titanate, lithium aluminum titanium phosphate, lithium lanthanum titanate, lithium lanthanum tantalate, lithium aluminum germanium phosphate, lithium lanthanum zirconium oxide, lanthanum zirconium aluminum lithium oxide, niobium-doped lithium lanthanum zirconium oxide and tantalum-doped lithium lanthanum zirconium oxide; The molar content of nickel in the lithium nickel cobalt manganese oxide material is less than 60%; The non-metallic lithiate includes one or more of a boron lithium compound, a sulfur lithium compound and a phosphorus lithium compound.

14. The positive electrode active material according to claim 1, characterized in that The positive electrode active material is a positive electrode active material that can reduce the safety risk of overcharging; The method for reducing the overcharge safety risk includes ensuring that the positive electrode active material has a 100% SOC cutoff voltage of V1, and the material has a thermal decomposition peak temperature of T1 under this voltage condition; the positive electrode active material has a thermal decomposition peak temperature of T2 under a voltage of V2, V2=V1+0.05, wherein T1 and T2 satisfy -15°C≤T1-T2≤40°C.

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