Battery, lithium manganese nickel composite oxide, and method of manufacturing, electrode sheet, device

Abstract

The application discloses a lithium ion battery, a lithium-manganese-nickel composite oxide and a preparation method thereof, a positive electrode sheet and an electric device. The lithium ion battery comprises a positive electrode sheet, a separator and a negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet to play a role of separation. The positive electrode sheet comprises a positive electrode material and a positive electrode current collector. The positive electrode material comprises a lithium-manganese-nickel composite oxide. The lithium-manganese-nickel composite oxide has a spinel type crystal form. The ratio of the peak intensity I 111 of a (111) peak to the peak intensity I 400 of a (400) peak in an X-ray diffraction spectrum of the lithium-manganese-nickel composite oxide is 2.1≤I 111 / I 400 ≤3.3. The (111) peak is a peak with a diffraction angle 2θ=18°-19.5°, and the (400) peak is a peak with a diffraction angle 2θ=43.5°-45°. In the above manner, the stability of the positive electrode active material can be improved, and the comprehensive performance of the battery can be improved.

Description

Technical Field

[0001] This application relates to the field of new energy technology, and in particular to lithium-ion batteries, lithium manganese-nickel composite oxides and their preparation methods, positive electrode sheets, and electrical devices. Background Technology

[0002] Lithium-ion batteries possess advantages such as high voltage, light weight, long cycle life, no memory effect, and good safety, making them widely applicable in digital products like mobile phones, digital cameras, and laptops, as well as power tools like electric vehicles and hybrid electric vehicles. A lithium-ion battery comprises positive electrode materials, negative electrode materials, a separator, electrolyte, and current collectors. Among these, the positive electrode material is crucial in determining the overall performance and cost of a lithium-ion battery. Spinel-type lithium manganese nickel composite oxides can be used as positive electrode materials in batteries; however, these oxides have a high lithium insertion / extraction potential, leading to severe side reactions between the positive electrode material and the electrolyte. This consumption of electrolyte generates a large amount of gas, increasing the risk of cell swelling and accelerating capacity decay. Simultaneously, the positive electrode material undergoes ion dissolution due to these side reactions, particularly affecting Mn. 2+ A significant amount of Mn was dissolved. 2+ It will deposit on the surface of the negative electrode, damaging the SEI film (Solid Electrolyte Interface) and accelerating the capacity decay of the negative electrode and the battery. Summary of the Invention

[0003] The main technical problem addressed by this application is to provide a lithium-ion battery, a lithium manganese nickel composite oxide and its preparation method, a positive electrode sheet and an electrical device, which can improve the stability of the positive electrode active material and thus increase the battery capacity.

[0004] To solve the above-mentioned technical problems, one technical solution adopted in this application is: to provide a lithium-ion battery, including: a positive electrode, a separator, and a negative electrode, wherein the separator is located between the positive electrode and the negative electrode and plays a role in isolation, the positive electrode includes a positive electrode material and a positive current collector, the positive electrode material includes lithium manganese nickel composite oxide; the crystal form of the lithium manganese nickel composite oxide is spinel type, and the peak intensity I of peak (111) in the X-ray diffraction pattern of the lithium manganese nickel composite oxide is... 111 Peak intensity I of (400) peak 400 The ratio 2.1 ≤ I 111 / I 400 ≤3.3, where peak (111) is the peak with a diffraction angle of 2θ = 18°-19.5°, and peak (400) is the peak with a diffraction angle of 2θ = 43.5°-45°. By adjusting the characteristic peak intensity ratio I of spinel-type lithium manganese nickel composite oxide 111 / I 400Within a preferred range, it is possible to improve the structural stability of the lithium manganese nickel composite oxide, thereby reducing its reactivity with the electrolyte when used as a cathode material and enhancing the overall performance of the battery.

[0005] In some embodiments, the average chemical composition of the lithium manganese nickel composite oxide is Li 1+a M x Ni 0.5+z Mn 1.5-x- z O 4-k , where 0 < a ≤ 0.3, 0 < x ≤ 0.2, -0.3 ≤ z ≤ 0.3, 0 ≤ k ≤ 0.2, and M includes one or more elements selected from Na, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta, and W. Increasing the Li content is beneficial for the spinel-type lithium manganese nickel composite oxide to have a thermodynamic tendency to grow towards a stable structure, and the doping of M elements can enhance the driving force for the spinel-type lithium manganese nickel composite oxide to grow towards a stable structure to compensate for the weakened growth driving force caused by the increase in Li content.

[0006] In some embodiments, the average chemical composition of the lithium manganese nickel composite oxide is Li 1+a M x N y Ni 0.5+ z Mn 1.5-x-y-z O 4-k-q Q q , where 0 < a ≤ 0.3, 0 < x ≤ 0.2, 0 ≤ y ≤ 0.3, -0.3 ≤ z ≤ 0.3, 0 ≤ k ≤ 0.2, 0 ≤ q ≤ 0.5, M includes one or more elements selected from Na, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta, and W, N includes one or more elements selected from Mg, Al, K, Sc, Ti, V, Cr, Fe, Co, Rb, Sr, Y, Zr, Rh, Sb, La, Sm, Gd, Yb, Lu, and Hf, and Q includes one or more elements selected from F, Cl, Br, and I. In this embodiment, the selected M element can, on the one hand, stabilize the crystal structure of the spinel-type lithium manganese nickel composite oxide, and on the other hand, capture hydrogen fluoride (HF) in the electrolyte, and the products of the side reaction are harmless to the battery system, significantly improving the overall performance of the battery.

[0007] In some embodiments, 1 ≤ a / x ≤ 20. In this embodiment, by controlling the doping amount of M elements and the Li content within this range, the improvement effect can be optimized, and the battery capacity, kinetic performance, and long-term use performance of the battery using this material can be taken into account, such as extending the service life of the battery.

[0008] In some embodiments, 0.03 ≤ a ≤ 0.15. In this embodiment, by controlling the doping amount of element M and the Li content within this range, the improvement effect can be optimized, and the battery capacity, kinetic performance, and long-term service performance of the battery using this material can be taken into account, such as extending the service life of the battery.

[0009] In some embodiments, 0.002 ≤ x ≤ 0.1. In this embodiment, by controlling the doping amount of element M and the Li content within this range, the improvement effect can be optimized, and the battery capacity, kinetic performance, and long-term service performance of the battery using this material can be taken into account, such as extending the service life of the battery.

[0010] In some embodiments, there is at least one peak in the X-ray diffraction pattern of the lithium manganese nickel composite oxide between diffraction angles 2θ = 21.5° - 24°, and the ratio of the intensity of the strongest peak between diffraction angles 2θ = 21.5° - 24° to the intensity of the (111) peak is 0 < I (21.5°-24°) / I 111 ≤ 3%. When regulating the doping type and doping amount of each element in the lithium manganese nickel composite oxide, considering the E value and the ratio of the intensity of the peak between 21.5° - 24° to the intensity of the (111) peak at the same time, the comprehensive performance of the battery can be better regulated.

[0011] In some embodiments, in a battery with a lithium manganese nickel composite oxide as the positive electrode material and Li as the negative electrode material, when charged under a charging rate of 0.1C, the ratio of the charging capacity of the battery in the 3.5 - 4.4V interval to the total charging capacity in the 3.5 - 4.95V interval is less than or equal to 15%. Regulating this ratio is beneficial to reducing the risk of Mn dissolution and energy density reduction.

[0012] In some embodiments, 0 < x + y + z ≤ 0.3. In this embodiment, the total cation doping amount is limited; by controlling the total cation doping amount within this range, the capacity, kinetic performance, and service life of the battery using this material can be taken into account.

[0013] In some embodiments, 2.4 ≤ I 111 / I 400 ≤ 2.8; 2 ≤ a / x ≤ 10; 0.05 ≤ a ≤ 0.12; 0.01 ≤ x ≤ 0.06; 0.005 ≤ y ≤ 0.05; 0.01 ≤ z ≤ 0.1; 0.01 ≤ x + y + z ≤ 0.1; 0.01 ≤ q ≤ 0.1; 0 ≤ k ≤ 0.1. At this time, the comprehensive performance of the battery is better.

[0014] In some embodiments, the lithium manganese nickel composite oxide includes one or more of single crystal particles, pseudo single crystal particles, and secondary particles. It is not easy to crack, which is beneficial to slowing down the surface side reaction.

[0015] In some implementations, the number of grains contained in a single secondary particle is 1 ≤ n ≤ 8. This is beneficial for improving the stability of lithium manganese nickel composite oxides.

[0016] In some embodiments, the grain shape includes one or more of the following: spherical, octahedral, octahedral with sharpened edges, rounded octahedral, and / or rounded octahedral with sharpened edges polyhedral. Among these, the grain surfaces of octahedral and octahedral with sharpened edges polyhedral are more favorable for Li... + The conductive crystal planes result in superior capacity and kinetic performance; the near-spherical grains mitigate cracking and corrosion caused by stress concentration, thus improving the material's subsequent processing performance and the long-term lifespan of batteries using it. The rounded octahedral and / or the rounded-edge polyhedral shapes combine the advantages of the first two types, balancing capacity, kinetic performance, and long-term stability.

[0017] In some embodiments, the volume median particle size of the lithium manganese nickel composite oxide is 2 μm ≤ D V50 ≤20 μm. When the particle size is controlled within this optimized range, parameters such as single crystal size, oxygen defects, and specific surface area can be better controlled.

[0018] In some embodiments, the pH of the lithium manganese nickel composite oxide powder is 10 ≤ pH ≤ 12. The spinel-type lithium manganese nickel composite oxide of this application has stronger alkalinity, which can neutralize the strong acid generated under high voltage and reduce damage to the surface of the cathode material.

[0019] In some embodiments, the specific surface area of ​​the lithium manganese nickel composite oxide is 0. <BET≤0.8 m 2 / g. A smaller specific surface area can mitigate surface side reactions.

[0020] In some embodiments, the lithium-ion battery further includes an electrolyte, the electrolyte solvent of which includes one or more of fluorocarbonates, fluorocarboxylic acids, sulfones, and fluoroethers. The selected electrolyte is a high-voltage resistant electrolyte, which reduces acidity under high voltage, significantly reducing surface side reactions and improving battery stability.

[0021] To solve the above-mentioned technical problems, another technical solution adopted in this application is: to provide a lithium manganese nickel composite oxide, wherein the crystal form of the lithium manganese nickel composite oxide is spinel type, and the peak intensity I of peak (111) in the X-ray diffraction pattern of the lithium manganese nickel composite oxide is... 111 Peak intensity I of (400) peak 400 The ratio 2.1 ≤ I 111 / I 400≤3.3, where peak (111) is the peak with a diffraction angle of 2θ = 18°-19.5°, and peak (400) is the peak with a diffraction angle of 2θ = 43.5°-45°. By adjusting the characteristic peak intensity ratio I of spinel-type lithium manganese nickel composite oxide 111 / I 400 Within a preferred range, the structural stability of lithium manganese nickel composite oxide can be improved, thereby reducing its reactivity with the electrolyte when used as a cathode material and improving the overall performance of the battery.

[0022] To solve the above-mentioned technical problems, another technical solution adopted in this application is: providing a method for preparing lithium manganese nickel composite oxide, comprising: providing raw materials for lithium manganese nickel composite oxide; and heat-treating the raw materials for lithium manganese nickel composite oxide in an oxygen-containing atmosphere to obtain the lithium manganese nickel composite oxide as described above. Through the above technical solution, lithium manganese nickel composite oxide can be obtained.

[0023] In some embodiments, heat-treating the raw material of lithium manganese nickel composite oxide in an oxygen-containing atmosphere includes: heating the raw material of lithium manganese nickel composite oxide to T1 and holding it at that temperature for 2-50 hours to obtain a lithium manganese nickel composite oxide intermediate; wherein, 850℃≤T1≤1100℃. A suitable temperature T1 and its holding time are important parameters to ensure grain size, oxygen defect content, elemental distribution, etc.

[0024] In some embodiments, the preparation method of lithium manganese nickel composite oxide further includes: heating the lithium manganese nickel composite oxide intermediate to T2 and holding it at that temperature for 0.5-20 h to obtain a lithium manganese nickel composite oxide preform; wherein T1-200℃≤T2≤T1 and T2≥800℃. Appropriate temperature T2 and holding time have a significant impact on the roundness of the grains, the oxygen defect content, and the R value.

[0025] In some embodiments, the preparation method of lithium manganese nickel composite oxide further includes: heating the lithium manganese nickel composite oxide preform to T3 and holding it at that temperature for 5-30 h to obtain the lithium manganese nickel composite oxide; wherein, 500℃≤T3≤800℃. Annealing helps to reduce the R value, reduce oxygen defects, and improve the stability of the material.

[0026] In some embodiments, the raw materials for providing the lithium manganese nickel composite oxide include: Li according to the target composition. 1+ a M x Ni 0.5+z Mn 1.5-x-z O 4-k Provide stoichiometric ratios of Li2CO3 and Ni 0.5+z Mn 1.5-x-z (OH) 4-2x M b O cPowders are mixed evenly to obtain raw materials for lithium manganese nickel composite oxides, where 0 < a ≤ 0.3, 0 < x ≤ 0.2, -0.3 ≤ z ≤ 0.3, 0 ≤ k ≤ 0.2, and M includes one or more elements selected from sodium (Na), silicon (Si), phosphorus (P), sulfur (S), niobium (Nb), molybdenum (Mo), ruthenium (Ru), tellurium (Te), cerium (Ce), tantalum (Ta), and tungsten (W). Increasing the Li content is beneficial for the spinel-type lithium manganese nickel composite oxides to have a thermodynamic tendency to grow towards a stable structure. The doping of M elements can improve the driving force for the spinel-type lithium manganese nickel composite oxides to grow towards a stable structure, so as to compensate for the weakening of the growth driving force caused by the increase in Li content.

[0027] To solve the above technical problems, another technical solution adopted in this application is: to provide a positive electrode sheet, including a positive electrode material and a positive electrode current collector, and the positive electrode material includes the lithium manganese nickel composite oxide of any one of the above. The stability of the positive electrode sheet is relatively high.

[0028] To solve the above technical problems, another technical solution adopted in this application is: to provide an electrical device, including the lithium ion battery of any one of the above.

[0029] The beneficial effect of this application is: different from the prior art situation, this application regulates the characteristic peak intensity ratio I 111 / I 400 Within a preferred range, it can improve the structural stability of the lithium manganese nickel composite oxide, thereby reducing its reactivity with the electrolyte when used as a positive electrode material and improving the overall performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the X-ray diffraction pattern of some embodiments and comparative examples of this application;

[0031] Figure 2 is the X-ray diffraction pattern of some embodiments and comparative examples of this application;

[0032] Figure 3 is the first-cycle charge curve of the coin cells of some embodiments and comparative examples of this application;

[0033] Figure 4 is the morphology diagram of the positive electrode active material of Example 3 of this application tested by scanning electron microscopy;

[0034] Figure 5 is the morphology diagram of the positive electrode active material of Example 36 of this application tested by scanning electron microscopy;

[0035] Figure 6 is the morphology diagram of the positive electrode active material of Example 46 of this application tested by scanning electron microscopy;

[0036] Figure 7 This is a scanning electron microscope (SEM) image of the positive electrode active material of Example 47 of this application.

[0037] Figure 8 This is a morphology image of the positive electrode active material of Comparative Example 1 of this application, as measured by scanning electron microscopy. Detailed Implementation

[0038] To make the purpose, technical solution and effects of this application clearer and more explicit, the following describes this application in further detail with reference to the accompanying drawings and embodiments.

[0039] As used herein, the term "about" is used to describe and indicate small variations. When used in conjunction with an event or situation, the term may refer to examples in which the event or situation occurred precisely or in examples in which the event or situation occurred very approximately. For example, when used in conjunction with numerical values, the term may refer to a range of variation less than or equal to ±10% of the numerical value, such as less than or equal to ±5%, less than or equal to ±4%, less than or equal to ±3%, less than or equal to ±2%, less than or equal to ±1%, less than or equal to ±0.5%, less than or equal to ±0.1%, or less than or equal to ±0.05%. Additionally, quantities, ratios, and other numerical values ​​are sometimes presented in range format herein. It should be understood that such range format is for convenience and brevity and should be interpreted flexibly to include not only numerical values ​​explicitly specified as range limits but also all individual numerical values ​​or subranges covered within the range, as if each numerical value and subrange were explicitly specified.

[0040] In the detailed description and claims, the list of items connected by the term "at least one of" can mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0041] With the widespread application of electrochemical devices (such as lithium-ion batteries), the requirements for their performance are becoming increasingly stringent, especially regarding battery safety, stability, and capacity. The expectation is for batteries to possess excellent overall performance in all aspects. Lithium-ion batteries include a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode comprises a positive current collector and the positive electrode material disposed on the current collector. Among these, the positive electrode material is crucial to the overall performance of the lithium-ion battery. However, currently used positive electrode materials are prone to severe side reactions with the electrolyte, leading to increased risk of cell swelling, accelerated negative electrode capacity decay, and overall battery capacity decay. These problems can typically be addressed through various methods, such as surface coating of the positive electrode material, structural control to reduce oxygen defects, increasing the particle size of the positive electrode material, reducing the specific surface area of ​​the positive electrode material, surface modification to stabilize the material surface, and reducing the contact between the electrolyte and the positive electrode material. However, these methods still have certain drawbacks.

[0042] To address the aforementioned technical issues, this application selects spinel-type lithium manganese-nickel composite oxide as the cathode material and improves its performance by controlling its crystal structure, elemental composition and content, and preparation process. This enhances the thermodynamic tendency and growth kinetics of the lithium manganese-nickel composite oxide towards a more stable structure, thereby improving its structural stability. Consequently, it significantly improves the overall performance of the lithium manganese-nickel composite oxide as a cathode material in batteries, specifically increasing battery capacity. Here, lithium manganese-nickel composite oxide refers to an oxide containing lithium manganese and nickel, meaning that the oxide may include other elements besides lithium manganese and nickel; therefore, it is also called a lithium manganese-nickel composite oxide.

[0043] This application provides a lithium-ion battery, including: a positive electrode, a separator, and a negative electrode. The separator is located between the positive and negative electrodes and serves as a separator. The positive electrode includes a positive electrode material and a positive current collector. The positive electrode material includes a lithium manganese nickel composite oxide. The lithium manganese nickel composite oxide has a spinel crystal form. The peak intensity I of peak (111) in the X-ray diffraction pattern of the lithium manganese nickel composite oxide is... 111 Peak intensity I of (400) peak 400 The ratio 2.1 ≤ I 111 / I 400 ≤3.3, (111) peak is the peak with diffraction angle 2θ=18°-19.5°, (400) peak is the peak with diffraction angle 2θ=43.5°-45°.

[0044] Lithium-manganese-nickel composite oxides can be tested using a CuKα1 powder X-ray diffractometer according to standard JIS K 0131-1996. In the X-ray diffraction (XRD) spectrum, the (111) peak (peak position 2θ=18°-19.5°) is the peak of the preferred growth basal plane of the lithium-manganese-nickel composite oxide crystal, and the (400) peak (peak position 2θ=43.5°-45°) is the peak of the growth end face of the lithium-manganese-nickel composite oxide crystal. The end face here is the theoretically grown end face. By controlling the intensity ratio of the characteristic peaks of the lithium-manganese-nickel composite oxide within this range, the structural stability of the lithium-manganese-nickel composite oxide can be improved, thereby reducing its reaction activity with the electrolyte when used as a positive electrode material and improving the overall performance of the battery.

[0045] In one embodiment, the first preferred growth crystal plane of the spinel-type lithium manganese nickel composite oxide is the (111) plane, that is, atoms spread and grow layer by layer along the (111) plane, so the packing quality of the (111) plane determines the stability of the crystal structure. A spinel-type lithium manganese nickel composite oxide grain can have multiple (111) planes (such as the eight lateral faces in the shape of an octahedral grain) growing simultaneously, and the crystal planes form (a00) lateral faces after contacting each other. Therefore, the (111) plane can be called the "basal plane" of the spinel structure, and the (a00) plane can be called the "end face" of the spinel structure. In the XRD spectrum, the ratio of the peak intensity of the basal plane (111) to the peak intensity of the end face (a00) is E=I. 111 / I a00 E indicates the preference of the (111) crystal plane; the larger the E value, the greater the preference of the (111) plane, the lower the energy of the (111) plane, resulting in smoother stacking of the (111) plane and a more stable overall structure of the spinel-type lithium manganese nickel composite oxide, thereby improving the stability of the battery using this material. However, when the E value is too large, the crystal structure is too stable, which can lead to lithium ions (Li... + Intercalation and deintercalation become difficult, which is detrimental to the kinetic performance and capacity utilization of the battery. Therefore, E can also be called the crystal plane preference index to characterize the stability of the crystal structure. In the conventional XRD spectrum, the (111) peak and the (400) peak are two of the three strong peaks with relatively large intensity. In this application, the (111) peak and the (400) peak are selected as characteristic peaks to consider the E value, that is, E=I 111 / I 400 .

[0046] In one embodiment, 2.3 ≤ I 111 / I 400 ≤3.0; further, 2.4≤I 111 / I 400 ≤2.8. For example, I 111 / I 400It can be 2.2, 2.5, 2.6, 2.7, 2.9, etc. By controlling the crystal plane preference index E value within this range, the reactivity of the lithium manganese nickel composite oxide with the electrolyte can be reduced, thereby improving the stability of the battery, while meeting the requirements of battery kinetic performance and capacity.

[0047] In some implementations, the crystal growth direction and structural stability of lithium manganese-nickel composite oxides can be controlled by adjusting the composition and content of elements contained in the oxides. In other words, the E value can be controlled by adjusting the composition and content of elements in the lithium manganese-nickel composite oxides.

[0048] In some embodiments, the average chemical composition of the lithium manganese nickel composite oxide is Li 1+a M x Ni 0.5+z Mn 1.5-x- z O 4-k Where 0 < a ≤ 0.3, 0 < x ≤ 0.2, -0.3 ≤ z ≤ 0.3, 0 ≤ k ≤ 0.2, and M includes one or more elements selected from sodium (Na), silicon (Si), phosphorus (P), sulfur (S), niobium (Nb), molybdenum (Mo), ruthenium (Ru), tellurium (Te), cerium (Ce), tantalum (Ta), and tungsten (W).

[0049] In the lithium manganese nickel composite oxide provided in this application, the Li content in the oxide is increased, that is, the molar ratio of Li sites to Ni / Mn sites is >0.5. Increasing the Li content is beneficial to the spinel-type lithium manganese nickel composite oxide having a thermodynamic tendency to grow towards a stable structure. Specifically, the increase in Li content can promote the improvement of the Mn valence state in the spinel structure, increase the Mn-O bond strength, and reduce the side reactions of the spinel-type lithium manganese nickel composite oxide with the electrolyte. That is, the added Li can enter the Mn site in an appropriate amount to form Li doping, improve the structural stability of the material, and thus reduce the side reactions with the electrolyte. However, there is a contradiction between the thermodynamic tendency of the spinel-type lithium manganese nickel composite oxide to grow towards a stable structure and the growth kinetics (i.e., the growth dynamics). Therefore, increasing the Li content will reduce the preference of the (111) plane, that is, reduce the E value, and reduce the kinetics of the spinel-type lithium manganese nickel composite oxide to grow into a stable structure. In other words, increasing the Li content can, on the one hand, enhance the thermodynamic tendency of spinel-type lithium-manganese-nickel composite oxides to grow towards a stable structure, and on the other hand, reduce the driving force for the growth of spinel-type lithium-manganese-nickel composite oxides towards a stable structure, that is, reduce the kinetic tendency.

[0050] Furthermore, this application introduces element M into the lithium manganese nickel composite oxide to modify it, thereby reconciling the contradiction between the thermodynamic tendency and growth motive force of spinel-type lithium manganese nickel composite oxide to grow towards a stable structure, thus significantly improving the stability of the spinel-type lithium manganese nickel composite oxide structure. In other words, the doping of element M can enhance the growth motive force of spinel-type lithium manganese nickel composite oxide towards a stable structure, compensating for the weakening of growth motive force caused by the increase in Li content.

[0051] In some embodiments, M includes one or more elements selected from sodium (Na), silicon (Si), phosphorus (P), sulfur (S), niobium (Nb), molybdenum (Mo), ruthenium (Ru), tellurium (Te), cerium (Ce), tantalum (Ta), and tungsten (W). In some embodiments, M includes one or more elements selected from Si, P, Ru, Te, Ce, and Ta; in other embodiments, M includes one or more elements selected from P, Ru, Te, and Ta. The element M may be distributed within the bulk phase of the spinel-type lithium-manganese-nickel composite oxide or on the surface of the material.

[0052] In this embodiment, the selected element M can stabilize the crystal structure of the spinel-type lithium manganese nickel composite oxide and capture hydrogen fluoride (HF) in the electrolyte. Furthermore, the products of the side reaction are harmless to the battery system, significantly improving the overall performance of the battery.

[0053] In some implementations, the doping amount x of element M needs to be matched with the Li content a to better balance the thermodynamic and kinetic trends of crystal growth, that is, to balance the Li content and the E value. To a certain extent, more Li may require more element M to achieve a balance.

[0054] In some implementations, 1 ≤ a / x ≤ 20. In some implementations, 2 ≤ a / x ≤ 10. For example, a / x can be 4, 6, 8, 11, 12, 15, 17, 19, etc.

[0055] In some implementations, 0.03 ≤ a ≤ 0.15; in other implementations, 0.05 ≤ a ≤ 0.12. For example, a can be 0.04, 0.06, 0.08, 0.09, 0.11, 0.13, 0.14, etc.

[0056] In some implementations, 0.002 ≤ x ≤ 0.1; in other implementations, 0.01 ≤ x ≤ 0.06. For example, x can be 0.005, 0.008, 0.02, 0.04, 0.05, 0.08, 0.09, etc.

[0057] In this embodiment, by controlling the doping amount of element M and the Li content within this range, the improvement effect can be optimized, and the battery capacity, dynamic performance and long-term performance of the battery using the material can be taken into account, such as extending the battery's service life.

[0058] In some embodiments, the average chemical composition of the lithium manganese nickel composite oxide is Li 1+a M x N y Ni 0.5+ z Mn 1.5-x-y-z O 4-k-q Q q Wherein, 0 < a ≤ 0.3, 0 < x ≤ 0.2, 0 ≤ y ≤ 0.3, -0.3 ≤ z ≤ 0.3, 0 ≤ k ≤ 0.2, 0 ≤ q ≤ 0.5, M includes one or more elements from Na, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta, and W, N includes one or more elements from magnesium (Mg), aluminum (Al), potassium (K), scandium (Sc), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), cobalt (Co), rubidium (Rb), strontium (Sr), yttrium (Y), zirconium (Zr), rhodium (Rh), antimony (Sb), lanthanum (La), samarium (Sm), gadolinium (Gd), ytterbium (Yb), lutetium (Lu), and hafnium (Hf), and Q includes one or more elements from fluorine (F), chlorine (Cl), bromine (Br), and iodine (I). Nitrogen (N) and phosphorus (Q) elements can be distributed in the bulk phase of spinel-type lithium-manganese-nickel composite oxides or on the surface of the material.

[0059] Wherein, element N is an element that can enter Li sites and / or Mn sites and / or Ni sites. In some embodiments, N includes one or more elements selected from K, Rb, Sr, Y, Rh, Sb, La, Sm, Gd, Yb, Lu, and Hf.

[0060] In this embodiment, nitrogen element is used as another cation to dope spinel-type lithium manganese nickel composite oxide. By introducing these elements, it is beneficial for E to reach the required range, improve the stability of the spinel-type lithium manganese nickel composite oxide structure, and reduce the side reactions between the material and the electrolyte. Among them, the preferred elements have the most obvious improvement effect.

[0061] In some implementations, 0 < y ≤ 0.3; in others, 0.001 ≤ y ≤ 0.1; and in still others, 0.005 ≤ y ≤ 0.05. For example, y can be 0.003, 0.008, 0.01, 0.07, 0.13, 0.19, 0.25, etc. Controlling the N doping amount within this range yields the best improvement, balancing battery capacity, kinetic performance, and long-term battery performance using this material.

[0062] In some implementations, 0.01 ≤ z ≤ 0.1. For example, z can be 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, etc. That is, the Ni content is also increased. The increased Ni is beneficial to improving the average valence state of Mn and stabilizing the structure. The increased Ni can also form a rock salt phase on the grain surface, protecting the manganese-rich phase and reducing the probability of Mn dissolution.

[0063] In some embodiments, 0 < x + y + z ≤ 0.3; in some embodiments, 0.005 ≤ x + y + z ≤ 0.2; and in some embodiments, 0.01 ≤ x + y + z ≤ 0.1. For example, x + y + z can be 0.008, 0.03, 0.06, 0.09, 0.16, 0.21, 0.27, etc. In this embodiment, the total cation doping amount is limited; by controlling the total cation doping amount within this range, the material's capacity, kinetic performance, and the lifespan of the battery using this material can be balanced.

[0064] In some implementations, 0 < q ≤ 0.5; in others, 0.001 ≤ q ≤ 0.2; and in still others, 0.01 ≤ q ≤ 0.1. For example, q can be 0.006, 0.03, 0.07, 0.13, 0.18, 0.24, 0.33, 0.42, etc. The doping amount of anions can be controlled, and the improvement effect is optimal when anions are within this range.

[0065] In some implementations, 0 ≤ k ≤ 0.1. For example, k can be 0.003, 0.005, 0.007, 0.009, etc. By controlling the oxygen content, the oxygen defects in the material can be reduced. Reducing oxygen defects helps improve the structural stability of the material and slows down the side reactions between the material and the electrolyte.

[0066] In some embodiments, the X-ray diffraction pattern of the lithium manganese nickel composite oxide has at least one peak between diffraction angles 2θ = 21.5° and 24°, and the ratio of the intensity of the strongest peak between diffraction angles 2θ = 21.5° and 24° to that of peak (111) is 0 < I. (21.5°-24°) / I 111 ≤3%; in some implementations, 0.2%≤I (21.5°-24°) / I 111 ≤2%, in some implementations, 0.5%≤I (21.5°-24°) / I 111 ≤1.5%. For example, I (21.5°-24°) / I 111 It can be 0.3%, 0.8%, 1.2%, 1.7%, 2.6%, etc.

[0067] The peak position and intensity of the peak between 21.5° and 24° can be controlled by adjusting the type, distribution, and doping amount of the modified elements (M, N, and Q). A higher peak intensity between 21.5° and 24° is more beneficial for extending the battery life using this material; however, the battery capacity drops sharply and lifespan deteriorates after the peak intensity exceeds a certain value. Therefore, in this application, when controlling the doping type and amount of each element in the lithium manganese nickel composite oxide, the E value and the ratio of the intensity of the peak between 21.5° and 24° to the intensity of the (111) peak must be considered simultaneously to better control the overall performance of the battery. The superior material composition and content are detailed above.

[0068] In some embodiments, in a battery using lithium manganese nickel composite oxide as the positive electrode material and Li as the negative electrode material, under a charging rate of 0.1C, the ratio R of the battery's charging capacity in the 3.5-4.4V range to its total charging capacity in the 3.5-4.95V range is less than or equal to 15%; in some embodiments, R is less than or equal to 10%; in some embodiments, 4% ≤ R ≤ 10%. For example, R can be 1%, 3%, 5%, 6%, 7%, 8%, 9%, 12%, 14%, etc.

[0069] In coin cells using spinel-type lithium-manganese-nickel composite oxide as the positive electrode and Li as the negative electrode, under constant current charging at a low rate of 0.1C, the ratio of the charging capacity in the 3.5-4.4V range to the total charging capacity in the 3.5-4.95V range is called the 4V plateau percentage. A larger 4V plateau percentage R indicates higher Mn content. 3+ A higher content of Mn also means a lower average charge / discharge voltage. 3+ Increased Mn content increases the risk of Mn leaching, and a decrease in average discharge voltage means a decrease in energy density. Therefore, the R value needs to be controlled to avoid being too large. However, when the E value of spinel-type lithium manganese-nickel composite oxides increases, it is often accompanied by an increase in R. To balance these two values, it is necessary to control the overall performance of the battery. Adjusting the doping type and amount of M element can balance the E and R values. Reasonable control of the doping type and amount of M element can increase the E value without increasing or even decreasing the R value. This results in a better material composition. For specific component contents, please refer to the description above.

[0070] In some embodiments, the lithium manganese nickel composite oxide includes one or more of single crystal particles, quasi-single crystal particles, and secondary particles.

[0071] In a single crystal, the particles inside the crystal body are arranged regularly and periodically in three-dimensional space. In other words, the entire crystal is composed of the same spatial lattice in three dimensions, and the arrangement of particles in space is long-range ordered. Single crystal particles are also called primary particles. Primary particles can agglomerate to form secondary particles. When a secondary particle contains only a few or a dozen crystal grains, it is called a quasi-single crystal particle.

[0072] In some embodiments, the grain shape of the lithium manganese nickel composite oxide includes one or more of the following: spherical, octahedral, regular octahedral shape with sharpened edges, rounded octahedral, and / or regular polyhedral shape with sharpened edges of rounded octahedral; in some embodiments, the grain shape is a regular octahedral shape with sharpened edges of rounded octahedral and / or regular polyhedral shape with sharpened edges of rounded octahedral.

[0073] Among them, the regular grain surfaces of octahedral and octahedral-shaped polyhedral grains with sharpened edges are more favorable for Li + The conductive crystal planes result in superior capacity and kinetic performance; the near-spherical grains mitigate cracking and corrosion caused by stress concentration, thus improving the material's subsequent processing performance and the long-term lifespan of batteries using it. The rounded octahedral and / or the rounded-edge polyhedral shapes combine the advantages of the first two types, balancing capacity, kinetic performance, and long-term stability.

[0074] In some embodiments, the lithium manganese nickel composite oxide further includes secondary particles, wherein the number of grains contained in a single secondary particle is 1 ≤ n ≤ 8, and in some embodiments, 1 ≤ n ≤ 3. For example, n can be 2, 4, 5, 6, 7, etc.

[0075] Among them, the surface of spinel-type lithium manganese nickel composite oxide particles is the region where side reactions are concentrated. The grain surface of spinel-type lithium manganese nickel composite oxide is the most stable crystal plane for Ni / Mn and Ni / Mn site elements, while the M element dissolved in spinel-type lithium manganese nickel composite oxide mainly enters the Ni / Mn site. Therefore, in single crystal particles, the M element entering the crystal lattice is the most stable, and the surface coating containing M element can also match well with the substrate surface, thereby maximizing the modification effect of M element.

[0076] Furthermore, compared to polycrystalline materials of the same size, single crystal particles have relatively stable crystal planes, smaller specific surface areas, and a lower probability of cracking and exposing unstable surfaces during processing and service, which helps to mitigate surface side reactions. Compared to polycrystalline materials of the same size, single crystals are more conducive to kinetic performance due to their smaller particle size and are also less prone to cracking.

[0077] In some embodiments, the volume median particle size of the lithium manganese nickel composite oxide is 2 μm ≤ D V50≤20 μm; in some implementations, 3 μm≤D V50 ≤15 μm, in some implementations, 5 μm≤D V50 ≤10 μm. For example, D V50 The particle size can be 4 μm, 6 μm, 8 μm, 13 μm, 18 μm, etc. When the particle size is controlled within this optimized range, parameters such as single crystal size, oxygen defects, and specific surface area can be better controlled.

[0078] In some embodiments, the pH of the lithium manganese nickel composite oxide powder is 10 ≤ pH ≤ 12. Compared to the conventional spinel-type lithium manganese nickel composite oxide with a pH of 7-10, the spinel-type lithium manganese nickel composite oxide of this application is more alkaline, which can neutralize the strong acid generated under high voltage and reduce damage to the surface of the cathode material; excessive alkalinity is not conducive to processing performance, and it is easy to absorb moisture and react with binders, thus deteriorating battery performance.

[0079] In some embodiments, the specific surface area of ​​the lithium manganese nickel composite oxide is 0 < BET ≤ 0.8 m². 2 / g; In some embodiments, 0 < BET ≤ 0.5 m 2 / g, in some embodiments, 0.1 ≤ BET ≤ 0.4 m 2 / g. For example, it could be 0.2m. 2 / g, 0.3 m 2 / g, 0.6 m 2 / g, 0.7 m 2 Specific surface area (S / g, etc.) can be measured using gas adsorption. A smaller specific surface area can mitigate surface side reactions. However, specific surface area is greatly affected by the coating state; for example, coating with nanoparticles significantly increases the specific surface area, but the active specific surface area actually decreases.

[0080] This application also provides a lithium manganese nickel composite oxide, wherein the crystal form of the lithium manganese nickel composite oxide is spinel type, and the peak intensity I of peak (111) in the X-ray diffraction pattern of the lithium manganese nickel composite oxide is... 111 Peak intensity I of (400) peak 400 The ratio 2.1 ≤ I 111 / I 400 The intensity ratio of the characteristic peaks of the lithium manganese nickel composite oxide is ≤3.3, where peak (111) is the peak with a diffraction angle of 2θ = 18°-19.5° and peak (400) is the peak with a diffraction angle of 2θ = 43.5°-45°. By controlling the intensity ratio of the characteristic peaks of the lithium manganese nickel composite oxide within this range, the structural stability of the lithium manganese nickel composite oxide can be improved, thereby reducing its activity in reacting with the electrolyte when used as a cathode material and improving the overall performance of the battery.

[0081] In some implementations, the crystal growth direction and structural stability of lithium manganese-nickel composite oxides can be controlled by adjusting the preparation process parameters. Specifically, the E value can be controlled by adjusting the preparation process parameters of the lithium manganese-nickel composite oxide.

[0082] In some embodiments, lithium manganese nickel composite oxides can be prepared using a solid-state synthesis method. The specific preparation method includes: providing raw materials for lithium manganese nickel composite oxides, and heat-treating the raw materials for lithium manganese nickel composite oxides in an oxygen-containing atmosphere to obtain the lithium manganese nickel composite oxides of any of the above embodiments.

[0083] The raw materials for the lithium manganese nickel composite oxide can be prepared according to the composition content of the target lithium manganese nickel composite oxide, and the specific raw materials used can be adjusted according to the type of doping element. For example, if the doped cation is a metal cation, the raw material used can be the metal oxide corresponding to that cation (M). b O c When the doped cation is an inorganic cation, it can be the corresponding ammonium salt, carbonate, etc., such as Li2CO3 or Ni. 0.5+z Mn 1.5-x-z (OH) 4-2x M b O c These are used as raw materials for lithium, manganese, and nickel.

[0084] After the raw material powders are mixed, they are heat-treated in an oxygen-containing atmosphere to obtain the corresponding lithium manganese nickel composite oxide. The structure of the obtained lithium manganese nickel composite oxide can be stabilized by controlling the heating temperature, time, and reaction atmosphere.

[0085] In some embodiments, the preparation method of lithium manganese nickel composite oxide includes:

[0086] S110: The raw material of lithium manganese nickel composite oxide is heated to T1 and sintered at temperature T1 to obtain lithium manganese nickel composite oxide intermediate.

[0087] S120: The lithium manganese nickel composite oxide intermediate is heated to T2 and sintered at temperature T2 to obtain the lithium manganese nickel composite oxide preform.

[0088] S130: The lithium manganese nickel composite oxide preform is heated to T3 and annealed to obtain the lithium manganese nickel composite oxide.

[0089] In some embodiments, 850℃≤T1≤1100℃, and in other embodiments, 900℃≤T1≤1000℃. For example, T1 can be 880℃, 930℃, 950℃, 980℃, 1000℃, 1060℃, etc. The sintering time is 2-50 h, specifically, the raw material of lithium manganese nickel composite oxide can be heated to T1 and held at T1 temperature for 2-50 h, for example, 8 h, 15 h, 23 h, 31 h, 42 h, etc.

[0090] In some embodiments, T1-200℃≤T2≤T1 and T2≥800℃; in other embodiments, 850+(T1-900) / 4℃≤T2≤T1-(T1-900) / 4℃. For example, T2 can be 820℃, 850℃, 880℃, 910℃, 960℃, 1000℃, etc. The sintering time is 0.5-20 h, specifically, the lithium manganese nickel composite oxide intermediate can be heated to T2 and held at T2 temperature for 0.5-20 h, for example, 2 h, 5 h, 8 h, 12 h, 15 h, 18 h, etc.

[0091] In some embodiments, 500℃≤T3≤800℃, and in others, 600℃≤T3≤700℃. For example, T3 can be 520℃, 560℃, 630℃, 680℃, 710℃, 750℃, etc. The annealing time can be 5-30 h, specifically, the lithium manganese nickel composite oxide preform can be heated to T3 and held at T3 temperature for 5-30 h, for example, 8 h, 14 h, 18 h, 23 h, 27 h, etc.

[0092] Among these parameters, the appropriate temperature T1 and its holding time are crucial for ensuring grain size, oxygen defect content, and elemental distribution. The appropriate temperature T2 and holding time significantly influence grain roundness, oxygen defect content, and the R-value. Annealing helps reduce the R-value, decrease oxygen defects, and improve material stability. In this embodiment, by rationally controlling the temperature ranges T1, T2, and T3, as well as the reaction times of steps S110, S120, and S130, the volumetric median grain size of the obtained material (2μm ≤ D) can be controlled. V50 ≤20 μm, low oxygen vacancy defects, high E value, low R value. For specific material performance parameters, please refer to the description of the above embodiments, which will not be repeated here.

[0093] In some implementations, steps S120 and S130 are not essential and may be performed only once or both may be omitted; S120 must be performed after cooling to a lower temperature following S110; S130 may be performed after cooling the preceding heat treatment process or may be performed directly together.

[0094] In some implementations, the oxygen-containing atmosphere can be air, oxygen, or a mixture of air and oxygen.

[0095] This application also provides a positive electrode sheet, which includes a positive electrode material and a positive electrode current collector. The positive electrode material is the lithium manganese nickel composite oxide described in any of the above embodiments.

[0096] In some embodiments, the positive electrode material further includes a positive electrode conductive material, thereby imparting conductivity to the electrode. The positive electrode conductive material can include any conductive material as long as it does not cause a chemical change. Non-limiting examples of positive electrode conductive materials include carbon-based materials (e.g., natural graphite, synthetic graphite, carbon black, acetylene black, Ketjen black, carbon fiber, etc.), metal-based materials (e.g., metal powder, metal fiber, etc., including, for example, copper, nickel, aluminum, silver, etc.), conductive polymers (e.g., polyphenylene derivatives), and mixtures thereof. In some embodiments, the positive electrode current collector may be aluminum (Al).

[0097] This application also provides an electrochemical device, which includes any device in which an electrochemical reaction occurs, and specific examples include all types of primary or secondary batteries. Lithium secondary batteries may include lithium metal secondary batteries, lithium-ion secondary batteries, lithium polymer secondary batteries, or lithium-ion polymer secondary batteries.

[0098] In some embodiments, the battery includes a positive electrode, a separator, and a negative electrode. The separator is located between the positive electrode and the negative electrode and serves to isolate them. The positive electrode includes the positive electrode described in any of the above embodiments.

[0099] In some embodiments, the negative electrode includes a current collector and a layer of negative electrode active material disposed on the current collector. The specific type of negative electrode active material is not specifically limited and can be selected according to requirements. For example, the negative electrode active material can be selected from natural graphite, artificial graphite, mesophase microcarbon spheres (MCMB), hard carbon, soft carbon, silicon, silicon-carbon composites, Li-Sn alloys, Li-Sn-O alloys, Sn, SnO, SnO2, and spinel-structured lithiated TiO2-Li4Ti5O. 12 One or more of Li-Al alloys.

[0100] In some embodiments, the electrolyte solvent includes one or more of fluorocarbonates, fluorocarboxylic acids, sulfones, and fluoroethers. The selected electrolyte is a high-voltage resistant electrolyte, which exhibits reduced acidity under high voltage, significantly reducing surface side reactions and improving battery stability.

[0101] In some embodiments, the application of the electrochemical device of this application is not particularly limited, and it can be used in any electronic device known in the prior art. That is, it provides an electrical device. In some embodiments, the electrochemical device of this application can be used in, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, household large storage batteries, and lithium-ion capacitors, etc.

[0102] The following uses a lithium-ion battery as an example and combines specific embodiments to illustrate the preparation of a lithium-ion battery. Those skilled in the art will understand that the preparation method described in this application is only an example, and any other suitable preparation method is within the scope of this application.

[0103] 1. Preparation of the positive electrode

[0104] Preparation of positive electrode active materials

[0105] Weigh the raw material powders according to the target composition of the positive electrode active material and the corresponding stoichiometric ratio. Mix the raw material powders evenly to obtain a raw material mixture powder. Heat the raw material mixture powder to T1 in air, hold it at that temperature for t1 time, and then cool it to room temperature to obtain a semi-finished product. Heat the semi-finished product to T2 in air, hold it at that temperature for t2 time, and then cool it to room temperature to obtain a pre-finished product. Heat the pre-finished product to T3 in air, hold it at that temperature for t3 time, and then cool it to room temperature to obtain a lithium nickel manganese composite oxide. For details on the specific target composition, raw materials used, and preparation process parameters, please refer to Tables 1 and 2.

[0106] 2. Battery (button cell) assembly

[0107] Using lithium foil as the counter electrode, the positive electrode material is assembled into a coin cell. Specifically, lithium nickel manganese composite oxide is mixed with conductive carbon black (Super P) and PVDF in a weight ratio of 90:5:5, and an appropriate amount of solvent N-methylpyrrolidone (NMP) is added. The mixture is stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry is coated onto aluminum foil and dried to obtain the positive electrode sheet. The loading of lithium nickel manganese composite oxide on the positive electrode sheet is 0.016 g / cm³. 2 Provide electrolyte. Using a 12 μm thick polypropylene film (Φ16 mm) as a separator, place the lithium sheet, separator, and positive electrode in sequence, ensuring the separator is positioned between the lithium metal sheet and the positive electrode to provide isolation. Inject electrolyte and assemble into a CR2030 coin cell. Let stand for 4 hours to obtain the coin cell.

[0108] The electrolytes used in Comparative Examples 1-8 and Examples 1-61 were mixed solutions of carbonates and fluorocarbonates containing 1 mol / L LiPF6, with a carbonate:fluorocarbonate ratio of 1:1.

[0109] The electrolytes used in Comparative Examples 9 and 10 contained only carbonate.

[0110] 3. Manufacturing of pouch batteries

[0111] The positive electrode active material is assembled into a pouch cell. Specifically, lithium nickel manganese composite oxide, conductive carbon black (Super P), and PVDF are mixed at a weight ratio of 96:2.5:1.5, and an appropriate amount of solvent N-methylpyrrolidone (NMP) is added. The mixture is stirred until homogeneous to obtain a positive electrode slurry. The positive electrode slurry is coated onto aluminum foil and dried to obtain a positive electrode sheet. The lithium nickel manganese composite oxide loading on the positive electrode sheet is 0.016 g / cm³. 2 Artificial graphite (negative electrode active material), carbon black (Super P) (conductive agent), styrene-butadiene rubber (binder), and sodium carboxymethyl cellulose (thickener) were mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 96:1:1:2 to form a uniform negative electrode slurry. This slurry was then uniformly coated onto the surface of the copper foil (negative electrode current collector). After drying and cold pressing, the negative electrode sheet was obtained. The loading of the negative electrode active material on one side of the negative electrode current collector was 0.007 g / cm³. 2 A mixed solution containing 1 mol / L LiPF6 in carbonates, fluorocarbonates, etc., is provided as the electrolyte. A 12 μm thick polypropylene film is used as the separator. The prepared positive electrode, separator, and negative electrode are arranged in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The mixture is then shaped and packaged in an aluminum-plastic bag. Electrolyte is injected, and after encapsulation, capacity formation is performed to obtain a soft-pack battery cell.

[0112] The electrolytes used in Comparative Examples 1-8 and Examples 1-61 were mixed solutions of carbonates and fluorocarbonates containing 1 mol / L LiPF6, with a carbonate:fluorocarbonate ratio of 1:1.

[0113] The electrolytes used in Comparative Examples 9 and 10 contained only carbonate.

[0114] 4. The relevant parameter testing process for the positive electrode active materials in the embodiments and comparative examples of this application is as follows:

[0115] (1) XRD test

[0116] Following the general rules of X-ray diffraction analysis in JIS K 0131-1996, the X-ray diffraction patterns of spinel-type nickel-manganese-lithium composite oxide materials were determined using CuK α1 rays.

[0117] (2) Element content test

[0118] The content of each element in spinel-type nickel-manganese-lithium composite oxide materials was measured according to EPA 6010D-2014 inductively coupled plasma atomic emission spectrometry.

[0119] (3) Morphological test

[0120] All positive electrode active materials of the examples and comparative examples were tested using a ZEISS Sigma 300 scanning electron microscope, and then the morphology of the samples was observed in accordance with the standard JY / T010-1996.

[0121] (4) Particle size test

[0122] Referring to GB / T19077-2016 Laser Particle Size Analyzer Diffraction Method, take a clean beaker, add an appropriate amount of the sample to be tested, add a surfactant and then a dispersant. After thorough dispersion, use a laser particle size analyzer to determine the particle size distribution characteristics (opacity: 8%-12%).

[0123] (5) Specific surface area test

[0124] According to GB / T 19587-2004 Gas Adsorption BET Method, after the sample is heated and degassed, the amount of gas adsorbed on the solid surface under different adsorption pressures is measured at a constant low temperature. Based on the BET multilayer adsorption theory and its formula, the amount of monolayer adsorption of the sample is obtained, and the specific surface area per unit mass of solid sample is calculated.

[0125] 5. Button charging test and R-value calculation for the 4V charging platform

[0126] At 25°C, the coin cells prepared with the positive electrode active materials of each embodiment / comparative example were charged at a constant current of 0.1C to a voltage of 4.95V. The charging capacity of 3.5-4.4V (C1) and the charging capacity of 3.5-4.95V (C2) were extracted from the original charging data.

[0127] The charging capacity of the 4V platform accounts for R = C1 / C2.

[0128] 6. Electrical performance testing of soft-pack packaging

[0129] (1) Test of the initial discharge energy density of positive electrode active material in pouch cell

[0130] The prepared pouch cell was used as the test object.

[0131] At 25°C, the pouch cell was charged at a constant current of 0.3C to a voltage of 4.8V, then charged at a constant voltage of 4.8V to a current of 0.05C. After resting for 5 minutes, the pouch cell was discharged at a constant current of 0.33C to a voltage of 3.5V. This discharge energy is the battery discharge energy. Dividing this energy by the mass of the positive electrode active material in the battery gives the initial discharge energy density of the positive electrode active material.

[0132] (2) High-temperature cycle performance test of soft-pack battery

[0133] The prepared pouch cell was used as the test object.

[0134] At 45℃, the pouch cell was charged at a constant current of 0.5C to a voltage of 4.8V, then charged at a constant voltage of 4.8V to a current of 0.05C. After resting for 5 minutes, the pouch cell was discharged at a constant current of 0.5C to a voltage of 3.5V. This constitutes one charging cycle, and the discharge capacity of this cycle is the discharge capacity of the first cycle. After performing the cycle charging test in the above manner, the cycle ends when the discharge capacity decays to 80% of the initial value. The total number of cycles is the high-temperature cycle life.

[0135] (3) High-temperature full-charge storage performance test of soft-pack battery

[0136] The prepared pouch cell was used as the test object.

[0137] At 25℃, the pouch battery was charged at a constant current of 0.3C to a voltage of 4.8V, and then charged at a constant voltage of 4.8V to a current of 0.05C. The battery was then placed at 45℃ and fully discharged every 10 days. Next, a full charge and discharge cycle was performed at 25℃, and the discharge capacity value Cn was extracted. The battery was then fully charged again and stored at 45℃. Storage continued until the discharge capacity Cn decreased to 80% of its initial value. The total storage time at 45℃ after a full charge is the high-temperature full-charge storage time.

[0138] Table 1: Preparation process parameters for each embodiment and comparative example

[0139]

[0140] Table 2: Composition and performance parameters of the cathode materials in each embodiment and comparative example

[0141]

[0142] Table 3: Battery performance parameters of each embodiment and comparative example

[0143]

[0144] The results show that when the average Li content in the spinel-type lithium-manganese-nickel composite oxide is greater than 1, it is modified by M element, and the E value (I) of the obtained active material is... 111 / I 400 When the coefficient of performance is greater than or equal to 2.3 and less than or equal to 3.0, the battery made with this material as the positive electrode active material has good overall performance, specifically good cycle performance, high storage performance, energy density and comprehensive electrical performance coefficient.

[0145] Please refer to the attached document. Figure 1 and attached Figure 2 , Figure 1 and Figure 2 These are X-ray diffraction patterns of some embodiments and comparative examples of this application. Specifically, they include the X-ray diffraction patterns of Comparative Example 1, Example 2, Example 3, Example 29, Example 42, and Comparative Example 7. Referring to the data in Tables 2 and 3, the E value of Comparative Example 1 is too small, resulting in poor stability of the cathode material, which in turn leads to poor cycle life and storage performance of the battery, and a lower overall electrical performance coefficient. As can be seen from Examples 1-2 and Comparative Example 1, when the E value is within the expected range (2.3-3.0), the energy density and storage performance of the battery are improved, but the improvement in storage performance and overall performance is not significant. This indicates that controlling the E value range can improve battery performance. However, due to the low lithium content in Examples 1-2, the overall performance of the battery is slightly lower, indicating that multiple parameters need to be balanced to improve the overall performance of the battery. Alternatively, controlling the E value range can solve the technical problems of improving the stability of the cathode material and increasing battery capacity proposed in this application. Furthermore, this application does not limit the Li content ratio to be greater than 1; when the Li content ratio is not greater than 1, the E value can still be within the predetermined range. As can be seen from Examples 3-4, when the E value is controlled within the expected range and the Li content ratio is greater than 1, the various performance characteristics of the battery are significantly improved, providing comprehensive performance.

[0146] As can be seen from Examples 5-21 and Comparative Examples 3-5, the doping of M, N and Q elements in lithium manganese nickel composite oxide can also regulate and improve the performance of the battery. The doping of M element can help regulate the E value within a predetermined range.

[0147] As can be seen from Examples 22-37 and Comparative Examples 6-7, by reasonably adjusting the Li content and M element content, the overall performance of the battery can be improved, resulting in good cycle performance, high storage performance, high energy density, and a high overall electrical performance coefficient.

[0148] As can be seen from Examples 38-58 and Comparative Example 2, the performance of the battery can be improved by controlling the preparation process of the lithium manganese nickel composite oxide, and the E value can be controlled within a predetermined range. As can be seen from Example 42, even high-temperature treatment can achieve an E value within the predetermined range, but the temperature is too high and the energy consumption is high. In other words, even if it is not the preferred process, the performance of the oxide can be controlled by simply adjusting the composition content.

[0149] Please see the appendix Figure 3 , attached Figure 3 These are the first-cycle charging curves of the coin cells in some embodiments and comparative examples of this application. Specifically, they include the first-cycle charging curves of Comparative Example 1, Comparative Example 2, Example 1, and Example 4. Referring to the data in Tables 2 and 3, it can be seen that the 4V platform ratio R value of the positive electrode active material provided in this application is within a reasonable range, resulting in good overall battery performance.

[0150] Please refer to the attached document. Figures 4-8 , Figure 4 This is a scanning electron microscope (SEM) image of the positive electrode active material of Example 3 of this application. Figure 5 This is a morphology image of the positive electrode active material of Example 36 of this application, obtained by scanning electron microscopy. Figure 6 This is a morphology image of the positive electrode active material of Example 46 of this application, obtained by scanning electron microscopy. Figure 7 This is a scanning electron microscope (SEM) image of the positive electrode active material of Example 47 of this application. Figure 8 This is a morphology image of the positive electrode active material of Comparative Example 1 of this application, obtained by scanning electron microscopy. The positive electrode active material provided in this application includes single crystal particles. Compared with polycrystalline materials of the same particle size, single crystal particles have relatively stable crystal planes on their surfaces, smaller specific surface areas, and a lower probability of cracking and exposing unstable surfaces during processing and service, which is beneficial for mitigating surface side reactions. Compared with polycrystalline materials of the same grain size, single crystals are more beneficial to kinetic performance due to their smaller particle size and are also less prone to cracking.

[0151] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A lithium-ion battery, characterized in that, Comprising: The device comprises a positive electrode, a separator, and a negative electrode. The separator serves as a separator between the positive and negative electrodes. The positive electrode includes a positive electrode material and a positive current collector. The positive electrode material includes a lithium manganese nickel composite oxide. The lithium manganese nickel composite oxide has a spinel crystal form. The peak intensity I of peak (111) in the X-ray diffraction pattern of the lithium manganese nickel composite oxide is... 111 Peak intensity I of (400) peak 400 The ratio 2.1 ≤ I 111 / I 400 ≤3.0, where peak (111) is the peak with a diffraction angle of 2θ = 18° - 19.5°, and peak (400) is the peak with a diffraction angle of 2θ = 43.5° - 45°; The X-ray diffraction pattern of the lithium manganese nickel composite oxide shows at least one peak between diffraction angles 2θ = 21.5° and 24°, and the ratio of the intensity of the strongest peak between diffraction angles 2θ = 21.5° and 24° to that of peak (111) is 0. (21.5°-24°) / I 111 ≤3%.​ 2. The lithium-ion battery according to claim 1, wherein The average chemical composition of the lithium manganese nickel composite oxide is Li 1+a M x Ni 0.5+z Mn 1.5-x-z O 4-k , where 0 < a ≤ 0.3, 0 < x ≤ 0.2, -0.3 ≤ z ≤ 0.3, 0 ≤ k ≤ 0.2, and M includes one or more elements of Na, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta, and W.

3. The lithium-ion battery according to claim 1 or 2, wherein The average chemical composition of the lithium manganese nickel composite oxide is Li 1+a M x N y Ni 0.5+z Mn 1.5-x-y-z O 4-k-q Q q , where 0 < a ≤ 0.3, 0 < x ≤ 0.2, 0 ≤ y ≤ 0.3, -0.3 ≤ z ≤ 0.3, 0 ≤ k ≤ 0.2, 0 ≤ q ≤ 0.5, M includes one or more elements selected from Na, Si, P, S, Nb, Mo, Ru, Te, Ce, Ta, W; N includes one or more elements selected from Mg, Al, K, Sc, Ti, V, Cr, Fe, Co, Rb, Sr, Y, Zr, Rh, Sb, La, Sm, Gd, Yb, Lu, Hf; and Q includes one or more elements selected from F, Cl, Br, I.

4. The lithium-ion battery according to claim 2 or 3, characterized in that, 1 ≤ a / x ≤ 20.

5. The lithium-ion battery according to any one of claims 2-4, characterized in that, 0.03≤a≤0.15。 6. The lithium-ion battery according to any one of claims 2-5, characterized in that, 0.002≤x≤0.1。 7. The lithium-ion battery according to any one of claims 2-6, characterized in that, 0 < x + y + z ≤ 0.

3.

8. The lithium-ion battery according to any one of claims 2-7, characterized in that, 2.4≤I 111 / I 400 ≤2.7;2≤a / x≤10;0.05≤a≤0.12;0.01≤x≤0.06;0.005≤y≤0.05;0.01≤z≤0.1;0.01≤x+y+z≤0.1;0.01≤q≤0.1;0≤k≤0.1。 9. The lithium-ion battery according to any one of claims 1-8, wherein In a battery with the lithium manganese nickel composite oxide as the positive electrode material and Li as the negative electrode material, when charged under the charging condition of a 0.1C charging rate, the ratio of the charging capacity of the battery in the 3.5-4.4V interval to the total charging capacity in the 3.5-4.95V interval is less than or equal to 15%.

10. The lithium-ion battery according to any one of claims 1-9, characterized in that, The lithium manganese nickel composite oxide includes one or more of single crystal particles, pseudo single crystal particles, and secondary particles.

11. The lithium-ion battery according to claim 10, characterized in that, The number of crystal grains contained in a single secondary particle is 1 ≤ n ≤ 8.

12. The lithium-ion battery according to claim 10 or 11, characterized in that, The crystal grain shape includes any one or more of quasi-spherical, octahedral, regular octahedral shape with sharpened and chamfered edges, octahedron with rounded edges, and / or regular polyhedron shape of octahedron with rounded edges and sharpened and chamfered edges.

13. The lithium-ion battery according to any one of claims 1-12, characterized in that, The median volumetric particle size of the lithium manganese nickel composite oxide is 2 μm ≤ D V50 ≤20 μm.

14. The lithium-ion battery according to any one of claims 1-13, characterized in that, The pH value of the powder of the lithium manganese nickel composite oxide is 10 ≤ pH ≤ 12.

15. The lithium-ion battery according to any one of claims 1-14, characterized in that, The specific surface area of ​​the lithium manganese nickel composite oxide is 0. <BET≤0.8 m 2 / g.

16. The lithium-ion battery according to any one of claims 1-15, characterized in that, The lithium-ion battery further includes an electrolyte, and the electrolyte solvent of the electrolyte includes one or more of fluorinated carbonates, fluorinated carboxylates, sulfones, and fluorinated ethers.

17. A lithium manganese nickel composite oxide, characterized in that, The lithium manganese nickel composite oxide has a spinel-type crystal structure, and the peak intensity I of peak (111) in the X-ray diffraction pattern of the lithium manganese nickel composite oxide is... 111 Peak intensity I of (400) peak 400 The ratio 2.1 ≤ I 111 / I 400 ≤3.0, where peak (111) is the peak with a diffraction angle of 2θ = 18° - 19.5°, and peak (400) is the peak with a diffraction angle of 2θ = 43.5° - 45°; The X-ray diffraction pattern of the lithium manganese nickel composite oxide shows at least one peak between diffraction angles 2θ = 21.5° and 24°, and the ratio of the intensity of the strongest peak between diffraction angles 2θ = 21.5° and 24° to that of peak (111) is 0. (21.5°-24°) / I 111 ≤3%.​ 18. A method for preparing a lithium manganese nickel composite oxide, characterized in that, Comprising: Providing raw materials for the lithium manganese nickel composite oxide; Performing heat treatment on the raw materials of the lithium manganese nickel composite oxide in an oxygen-containing atmosphere to obtain the lithium manganese nickel composite oxide as described in claim 17.

19. The method for preparing lithium manganese-nickel composite oxide according to claim 18, characterized in that, The performing heat treatment on the raw materials of the lithium manganese nickel composite oxide in an oxygen-containing atmosphere includes: Heating the raw materials of the lithium manganese nickel composite oxide to T1 and holding for 2-50 h to obtain an intermediate of the lithium manganese nickel composite oxide; wherein, 850°C ≤ T1 ≤ 1100°C.

20. The method for preparing lithium manganese-nickel composite oxide according to claim 19, characterized in that, Further comprising: Heating the intermediate of the lithium manganese nickel composite oxide to T2 and holding for 0.5-20 h to obtain a preform of the lithium manganese nickel composite oxide; where T1 - 200°C ≤ T2 ≤ T1 and T2 ≥ 800°C.

21. The method for preparing lithium manganese-nickel composite oxide according to claim 20, characterized in that, Further comprising: Heating the preform of the lithium manganese nickel composite oxide to T3 and holding for 5-30 h to obtain the lithium manganese nickel composite oxide; wherein, 500°C ≤ T3 ≤ 800°C.

22. The method for preparing lithium manganese nickel composite oxide according to any one of claims 18-21, characterized in that, The providing raw materials for the lithium manganese nickel composite oxide includes: According to the target component Li 1+a M x Ni 0.5+z Mn 1.5-x-z O 4-k Provide stoichiometric ratios of Li2CO3 and Ni 0.5+z Mn 1.5-x-z (OH) 4-2x M b O c The powder is mixed evenly to obtain the raw material for the lithium manganese nickel composite oxide; where 0 < a ≤ 0.3, 0 < x ≤ 0.2, -0.3 ≤ z ≤ 0.3, 0 ≤ k ≤ 0.2, and M includes one or more elements of sodium (Na), silicon (Si), phosphorus (P), sulfur (S), niobium (Nb), molybdenum (Mo), ruthenium (Ru), tellurium (Te), cerium (Ce), tantalum (Ta), tungsten (W).

23. A positive electrode plate, characterized in that, Comprising a positive electrode material and a positive electrode current collector, and the positive electrode material includes the lithium manganese nickel composite oxide as described in claim 17.

24. An electrical appliance, characterized in that, Comprising the lithium-ion battery according to any one of claims

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