Positive electrode material, electrochemical device, and electronic device
By doping Na into lithium transition metal composite oxides and controlling oxygen defects, the problem of low lithium-ion utilization in traditional cathode materials was solved, achieving high energy density and stable electrochemical performance, and improving the cycle performance of the battery.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2023-10-20
- Publication Date
- 2026-03-26
AI Technical Summary
Traditional nickel-containing cathode materials have low lithium-ion utilization rates, leading to increased battery usage costs and resource waste. Furthermore, lithium ions cannot be completely extracted or inserted during charging and discharging, affecting battery performance.
Lithium transition metal composite oxide is used as the cathode material. By doping with Na and regulating the oxygen defects inside the material, the redox properties of the transition metal are activated, thereby improving the energy density and kinetic performance of the material. At the same time, oxygen vacancies are formed on the surface to stabilize the material structure.
It improves the utilization rate of lithium ions, enhances the energy density and cycle performance of cathode materials, ensures the structural stability of materials in a highly delithiated state, and improves the cycle performance of electrochemical devices.
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Figure CN2023125761_26032026_PF_FP_ABST
Abstract
Description
A positive electrode material, an electrochemical device and an electronic device TECHNICAL FIELD
[0001] The present application relates to the field of energy storage, in particular to a positive electrode material, an electrochemical device and an electronic device. BACKGROUND
[0002] With the popularity of consumer electronics such as notebook computers, mobile phones, tablet computers, mobile power supplies and drones, the requirements for the batteries therein are becoming more and more stringent. For example, not only is the battery required to be light, but it is also required to have high capacity and a long working life. Lithium ion batteries have occupied a dominant position in the market due to their outstanding advantages such as high energy density, high safety, no memory effect and long working life.
[0003] For traditional positive electrode materials containing nickel, a large number of lithium ions cannot participate in the deintercalation / intercalation process during charging and discharging, and even if the voltage is greatly increased, the lithium ions in the positive electrode material cannot be completely deintercalated, because the lithium ions need to play a supporting role in the layered structure in the layered positive electrode material. Therefore, the low utilization of lithium ions in the traditional positive electrode material significantly increases the use cost of the battery and causes huge resource waste.
[0004] SUMMARY
[0005] In order to solve the problems in the prior art, the present application provides a positive electrode material in a first aspect, the positive electrode material comprises a lithium transition metal composite oxide, the lithium transition metal composite oxide comprises Li elements, Na elements and T elements, the T elements comprise at least one of Ni, Co or Mn; an electrode comprising the positive electrode material is assembled with a lithium sheet into a button cell, when the button cell is charged to 4.5V at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the molar ratio of Li elements to T elements in the lithium transition metal composite oxide is w1, which satisfies: w1≤0.2.
[0006] The inventors of the present application found that by introducing Na element doping in the lithium layer of the positive electrode material through an element doping method, and by controlling the oxygen defects in the material through synthesis means, a layered positive electrode material with extremely low lithium content in the charged state can be obtained. At the same time, the introduction of oxygen defects in the material can activate the redox of transition metals, which is beneficial to improve the energy density of the positive electrode material. Since the sodium ions doped in the lithium layer play a supporting role in the layered structure of the positive electrode material, the positive electrode material of the present application can maintain the stability of the material structure in a highly delithiated state. At the same time, the Na element with a larger ionic radius doped in the lithium layer can increase the lithium layer spacing, thereby improving the kinetic performance of the material. In addition, the oxygen vacancies formed on the surface of the positive electrode material of the present application can reduce the activity of the oxygen on the surface of the material and stabilize the outer layer oxygen ions of the positive electrode material, thereby improving the cycle performance of the material.
[0007] According to some embodiments of the present application, in the initial state, the molar ratio of Li element to T element in the lithium transition metal composite oxide is w2, and the molar ratio of Na element to T element is w3. In some embodiments, 0.55≤w2≤0.9. In some embodiments, 0.0005≤w3≤0.1. In some embodiments, 0.6≤w2+w3≤1.
[0008] In some embodiments, w1 / w2≤24%. In this way, it is indicated that the lithium ions in the positive electrode material can be fully deintercalated in the charged state, thereby improving the utilization rate of lithium ions in the positive electrode material.
[0009] According to some embodiments of the present application, an electrode comprising the positive electrode material is assembled with a lithium sheet into a button cell, and when the button cell is charged to 4.5V at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the molar ratio of Na element to T element in the lithium transition metal composite oxide is w4, and 0.0005≤w4≤0.1.
[0010] In some embodiments, 0.85≤w4 / w3≤1.1. In this way, it is indicated that the positive electrode material has good structural stability in the charged state, thereby being able to improve the cycle performance of the electrochemical device.
[0011] According to some embodiments of the present application, an electrode comprising the positive electrode material is assembled with a lithium sheet into a button cell, and when the button cell is discharged to 2.8V at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the molar ratio of Na element to T element in the lithium transition metal composite oxide is w5. In some embodiments, 0.55≤w5≤0.85.
[0012] In some embodiments, w1 / w5≤25.5%. In this way, it is indicated that the lithium ions in the positive electrode material can be reversibly fully deintercalated and inserted in the charging and discharging process, thereby improving the cycle performance of the electrochemical device while improving the utilization rate of lithium ions in the positive electrode material.
[0013] According to some embodiments of the present application, the molar ratio of Ni element to T element in the lithium transition metal composite oxide is 0.3 to 0.7.
[0014] According to some embodiments of the present application, the lithium transition metal composite oxide further comprises an M element, the M element comprising at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, K, Ca, Sr, Ca, Ba, Ta, Hf or Ce, and the molar ratio of the M element to the T element in the lithium transition metal composite oxide is 0.01 to 0.2.
[0015] According to some embodiments of the present application, the lithium transition metal composite oxide has a layered crystal structure.
[0016] According to some embodiments of the present application, in the initial state, the lithium transition metal composite oxide satisfies the general formula Li x Na y (Ni a Co b Mn c M d )O 2±e R e , wherein 0.55≤x / (a+b+c)≤0.9, 0.0005≤y / (a+b+c)≤0.1; 0.3≤a / (a+b+c)≤0.7, 0≤b / (a+b+c)≤0.7, 0≤c / (a+b+c)≤0.7, 0≤d / (a+b+c)≤0.2, 0≤e≤0.1, M comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, K, Ca, Sr, Ca, Ba, Ta, Hf or Ce, and R comprises at least one of F, Cl, Br, I or N.
[0017] According to some embodiments of the present application, an electrode comprising the positive electrode material is assembled with a lithium sheet into a button cell, and when the button cell is charged and discharged at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the obtained capacity voltage differential dQ / dV curve has a first oxidation peak and a first reduction peak in the interval of 4.2V to 4.5V and a second oxidation peak and a second reduction peak in the interval of 3.6V to 4.0V.
[0018] According to some embodiments of the present application, the peak height of the first oxidation peak is 500mAh / g / V to 2000mAh / g / V based on the mass of the positive electrode material.
[0019] According to some embodiments of the present application, the absolute value of the peak height of the first reduction peak is 500 mAh / g / V to 2000 mAh / g / V, based on the mass of the positive electrode material.
[0020] According to some embodiments of the present application, the peak voltage of the first oxidation peak is Vo1, the peak voltage of the first reduction peak is Vr1, and |Vo1-Vr1|≤0.2 V.
[0021] According to some embodiments of the present application, an electrode comprising the positive electrode material is assembled into a coin cell with lithium sheet, and when the coin cell is charged and discharged at a current of 0.04 C in a voltage interval of 2.8 V to 4.5 V, the discharge curve in the voltage capacity curve obtained has a platform in the interval of 4.2 V to 4.5 V. In some embodiments, the capacity of the discharge curve in the interval of 4.2 V to 4.5 V is Q1, and the total capacity in the interval of 2.8 V to 4.5 V is Qt, satisfying: 0.15≤Q1 / Qt≤0.35.
[0022] In a second aspect, the present application provides an electrochemical device comprising a positive electrode tab, wherein the positive electrode tab comprises the positive electrode material according to the first aspect of the present application.
[0023] According to some embodiments of the present application, in the X-ray diffraction spectrum of the lithium transition metal composite oxide in the full discharge state, the peak position of the (003) peak is in the range of 18° to 19°.
[0024] In a third aspect, the present application provides an electronic device comprising the electrochemical device according to the second aspect of the present application. BRIEF DESCRIPTION OF DRAWINGS
[0025] FIG. 1 shows the charge-discharge curves of the coin cells of Comparative Example 1 and Example 6.
[0026] FIG. 2 shows the capacity-voltage differential curves of the coin cells of Comparative Example 1 and Example 6.
[0027] FIG. 3 shows the X-ray diffraction (XRD) spectra of the electrode tabs of Comparative Example 1 and Example 6 in the full discharge state. DETAILED DESCRIPTION
[0028] For the purpose of clarity, technical solutions and advantages of the present application will be described in detail below with reference to embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments of the present application. The embodiments described herein are illustrative in nature and are used to provide a basic understanding of the present application. The embodiments of the present application should not be interpreted as a limitation of the present application.
[0029] For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any upper limit can be combined with any lower limit to create a range not explicitly recited; and any lower limit can be combined with any other lower limit to create a range not explicitly recited, and the same applies to any upper limit, which can be combined with any other upper limit to create a range not explicitly recited. Further, each individual disclosed point or singular value can be combined with any other point or singular value as a lower limit or upper limit to create a range not explicitly recited.
[0030] In the description herein, the terms "above" and "below" include the number itself, unless otherwise indicated.
[0031] Unless otherwise indicated, the terms used in this application have the meanings commonly understood by those of ordinary skill in the art. Unless otherwise indicated, the values of the parameters mentioned in this application can be measured using various measuring methods commonly used in the art (for example, can be tested according to the methods given in the examples of this application).
[0032] The list of items connected by the terms "at least one of," "at least one," "one or more of the following," or similar terms can mean any combination of the listed items. For example, if the items A and B are listed, the phrase "at least one of A and B" means only A; only B; or both A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; 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 can include a single component or multiple components. Item B can include a single component or multiple components. Item C can include a single component or multiple components.
[0033] In the context of the present application, the "initial state" of the positive electrode material refers to the state of the positive electrode material after initial synthesis, which has not undergone a charging process.
[0034] I. Positive electrode material
[0035] In a first aspect, the present application provides a positive electrode material, the positive electrode material comprising a lithium transition metal composite oxide, the lithium transition metal composite oxide comprising Li element, Na element and T element, the T element comprising at least one of Ni, Co or Mn; an electrode comprising the positive electrode material is assembled with a lithium sheet into a button cell, when the button cell is charged to 4.5V at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the molar ratio of Li element to T element in the lithium transition metal composite oxide is w1, which satisfies: w1≤0.2.
[0036] In some embodiments, the positive electrode material, in the initial state, has a molar ratio of Li element to T element w2, a molar ratio of Na element to T element w3, 0.55≤w2≤0.9, w2 being for example 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90 or any interval therebetween; in some embodiments, 0.0005≤w3≤0.1, w3 being for example 0.0005, 0.001, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 or any interval therebetween; in some embodiments, 0.6≤w2+w3≤1, for example the value of w2+w3 can be 0.60, 0.65, 0.70, 0.75, 0.80, 0.85, 0.90, 0.95, 1.0 or any interval therebetween; in some embodiments, wl / w2≤24%, for example the value of wl / w2 can be 24%, 20%, 18%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.8%, 0.6%, 0.4% or any interval therebetween.
[0037] In some embodiments, the electrode comprising the positive electrode material is assembled with a lithium sheet into a coin cell, the coin cell is charged at a current of 0.04C within a voltage interval of 2.8V to 4.5V to 4.5V, the coin cell has a molar ratio of Na element to T element w4 in the lithium transition metal composite oxide, 0.0005≤w4≤0.1, w4 being for example 0.0005, 0.001, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 or any interval therebetween; in some embodiments, 0.85≤w4 / w3≤1.1, the value of w4 / w3 can be 0.85, 0.86, 0.88, 0.90, 0.92, 0.94, 0.96, 0.98, 1.0, 1.02, 1.04, 1.06, 1.08, 1.1 or any interval therebetween.
[0038] The electrode comprising the positive electrode material is assembled into a coin cell with lithium sheet, the coin cell is discharged to 2.8V at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the molar ratio of Na element to T element in the lithium transition metal composite oxide is w5, 0.55≤w5≤0.85, w5 is for example 0.55, 0.60, 0.65, 0.70, 0.75, 0.80, 0.85 or any interval therebetween; in some embodiments, w1 / w5≤25.5%, for example the value of w1 / w5 can be 25.5%, 25%, 24%, 20%, 18%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6%, 5%, 4%, 3%, 2%, 1%, 0.8%, 0.6%, 0.4% or any interval therebetween.
[0039] In some embodiments, the molar ratio of Ni element to T element in the lithium transition metal composite oxide is 0.3 to 0.7, for example 0.30, 0.35, 0.4, 0.45, 0.5, 0.55, 0.60, 0.65, 0.7 or any interval therebetween.
[0040] In some embodiments, the lithium transition metal composite oxide further comprises M element, the M element comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, K, Ca, Sr, Ca, Ba, Ta, Hf or Ce, the molar ratio of M element to T element in the lithium transition metal composite oxide is 0.01 to 0.2, for example 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.10, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20 or any interval therebetween.
[0041] In some embodiments, the lithium transition metal composite oxide has a layered crystal structure. In some embodiments, the positive electrode material in the initial state, the lithium transition metal composite oxide satisfies the general formula Li x Na y (Ni a Co b Mn c M d )O 2±e R ewherein 0.55≤x / (a+b+c)≤0.9, 0.0005≤y / (a+b+c)≤0.1; 0.3≤a / (a+b+c)≤0.7, 0≤b / (a+b+c)≤0.7, 0≤c / (a+b+c)≤0.7, 0≤d / (a+b+c)≤0.2, 0≤e≤0.1, M comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, K, Ca, Sr, Ca, Ba, Ta, Hf or Ce, and R comprises at least one of F, Cl, Br, I or N.
[0042] In some embodiments, the electrode comprising the positive electrode material is assembled into a coin cell with lithium sheet, and when the coin cell is charged and discharged at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the obtained capacity-voltage differential dQ / dV curve has a first oxidation peak and a first reduction peak in the interval of 4.2V to 4.5V and a second oxidation peak and a second reduction peak in the interval of 3.6V to 4.0V.
[0043] In some embodiments, the peak height of the first oxidation peak is 500mAh / g / V to 2000mAh / g / V based on the mass of the positive electrode material, for example, the peak height of the first oxidation peak can be 500mAh / g / V, 600mAh / g / V, 700mAh / g / V, 800mAh / g / V, 900mAh / g / V, 1000mAh / g / V, 1100mAh / g / V, 1200mAh / g / V, 1300mAh / g / V, 1400mAh / g / V, 1500mAh / g / V, 1800mAh / g / V, 2000mAh / g / V or any interval therebetween.
[0044] In some embodiments, the absolute value of the peak height of the first reduction peak is 500mAh / g / V to 2000mAh / g / V based on the mass of the positive electrode material, for example, the peak height of the first reduction peak can be 500mAh / g / V, 600mAh / g / V, 700mAh / g / V, 800mAh / g / V, 900mAh / g / V, 1000mAh / g / V, 1100mAh / g / V, 1200mAh / g / V, 1300mAh / g / V, 1400mAh / g / V, 1500mAh / g / V, 1800mAh / g / V, 2000mAh / g / V or any interval therebetween.
[0045] In some embodiments, the peak voltage of the first oxidation peak is Vo1, the peak voltage of the first reduction peak is Vr1, and |Vo1-Vr1|≤0.2 V. In some embodiments, the value of |Vo1-Vr1| is, for example, 0.05 V, 0.06 V, 0.07 V, 0.08 V, 0.09 V, 0.10 V, 0.11 V, 0.12 V, 0.13 V, 0.14 V, 0.15 V, 0.16 V, 0.17 V, 0.18 V, 0.19 V, 0.20 V, or any interval therebetween.
[0046] In some embodiments, the electrode comprising the positive electrode material is assembled with a lithium sheet into a button cell, and when the button cell is charged and discharged at a current of 0.04 C in a voltage interval of 2.8 V to 4.5 V, a discharge curve in a voltage capacity curve obtained has a plateau in the interval of 4.2 V to 4.5 V. In some embodiments, the capacity of the discharge curve in the interval of 4.2 V to 4.5 V is Q1, and the total capacity in the interval of 3.0 V to 4.5 V is Qt, and 0.15≤Q1 / Qt≤0.35 is satisfied. In some embodiments, the value of Q1 / Qt is, for example, 0.15, 0.16, 0.17, 0.18, 0.19, 0.20, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, 0.32, 0.33, 0.34, 0.35, or any interval therebetween.
[0047] II. Electrochemical device
[0048] The electrochemical device provided in the present application comprises a positive electrode sheet, which comprises the positive electrode material described in the first aspect of the present application.
[0049] In some embodiments, the positive electrode sheet further comprises a conductive agent and a binder. In some embodiments, the binder comprises, but is not limited to, polyvinyl alcohol, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polytetrafluoroethylene, polyvinylidene fluoride, or vinylidene-hexafluoropropylene copolymer, etc. In some embodiments, the conductive agent comprises, but is not limited to, carbon-based materials, metal-based materials, conductive polymers, and mixtures thereof. In some embodiments, the carbon-based material is selected from carbon black, acetylene black, ketjen black, carbon fiber, carbon nanotube, graphene, or any combination thereof. In some embodiments, the metal-based material is selected from metal powder or metal fiber. In some embodiments, the conductive polymer is a polyphenylene derivative.
[0050] In some embodiments, the positive electrode further comprises a positive electrode current collector. In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, an aluminum foil can be used. The composite current collector can be formed by forming a metal material on a polymer substrate.
[0051] In some embodiments, the electrochemical device further comprises a negative electrode.
[0052] In some embodiments, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer disposed on a surface of the negative electrode current collector. In some embodiments, the negative electrode active material layer comprises a negative electrode active material. In some embodiments, the negative electrode active material comprises at least one of a carbon material or a silicon material. The carbon material comprises at least one of graphite, hard carbon, and the silicon material comprises at least one of silicon, silicon oxide, silicon carbide, or silicon alloy. In some embodiments, the negative electrode active material layer comprises a binder. In some embodiments, the binder comprises at least one of polyamide, polyacrylonitrile, acrylate polymer, polyacrylic acid, polyacrylic acid salt, sodium carboxymethyl cellulose, polyvinylpyrrolidone, polyvinyl ether, or styrene butadiene rubber. In some embodiments, the negative electrode active material layer further comprises a conductive material to improve the conductivity of the electrode. In some embodiments, the conductive material comprises at least one of conductive carbon black, acetylene black, carbon nanotube, ketjen black, or graphene.
[0053] In some embodiments, the electrochemical device further comprises an electrolyte or a solid-state electrolyte.
[0054] In some embodiments, the electrolyte that can be used in the embodiments of the present application can be an electrolyte known in the art.
[0055] In some embodiments, the electrolyte comprises an organic solvent and a lithium salt. In some embodiments, the organic solvent comprises, but is not limited to, ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), propylene carbonate, or ethyl propionate. In some embodiments, the lithium salt comprises at least one of an organic lithium salt or an inorganic lithium salt. In some embodiments, the lithium salt comprises, but is not limited to, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium difluorophosphate (LiPO2F2), lithium bis-trifluoromethanesulfonimide LiN(CF3SO2)2 (LiTFSI), lithium bis(fluorosulfonyl)imide Li(N(SO2F)2) (LiFSI), lithium bis(oxalato)borate LiB(C2O4)2 (LiBOB), or lithium difluoro(oxalato)borate LiBF2(C2O4) (LiDFOB).
[0056] In some embodiments, the electrochemical device includes a separator between the positive electrode and the negative electrode to prevent short circuit. The material and shape of the separator used in the embodiments of the present application are not particularly limited and can be any of the techniques disclosed in the prior art. In some embodiments, the separator includes a polymer or inorganic substance formed of a material stable to the electrolyte of the present application, and the like. For example, the separator can include a substrate layer and a surface treatment layer. The substrate layer is a nonwoven fabric, a film, or a composite film having a porous structure, and the material of the substrate layer includes at least one of polyethylene, polypropylene, polyethylene terephthalate, or polyimide. Specifically, a polypropylene porous film, a polyethylene porous film, a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, or a polypropylene-polyethylene-polypropylene porous composite film can be used. The surface treatment layer is provided on at least one surface of the substrate layer and can be a polymer layer or an inorganic layer, or a layer formed of a mixture of a polymer and an inorganic substance. The inorganic layer includes inorganic particles and a binder, and the inorganic particles include at least one of alumina, silica, magnesia, titania, hafnia, tin oxide, ceria, nickel oxide, zinc oxide, calcium oxide, zirconia, yttria, silicon carbide, boehmite, aluminum hydroxide, magnesium hydroxide, calcium hydroxide, or barium sulfate. The binder includes at least one of polyvinylidene fluoride, a copolymer of vinylidene fluoride-hexafluoropropylene, polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, a polyacrylic acid salt, polyvinylpyrrolidone, a polyvinyl ether, polytetrafluoroethylene, or polyhexafluoropropylene. The polymer layer includes a polymer, and the material of the polymer includes at least one of polyamide, polyacrylonitrile, an acrylate polymer, polyacrylic acid, a polyacrylic acid salt, polyvinylpyrrolidone, a polyvinyl ether, polyvinylidene fluoride, or a copolymer of vinylidene fluoride-hexafluoropropylene.
[0057] In some embodiments, the electrochemical device of the present application includes, but is not limited to, a primary battery or a secondary battery of all kinds. In some embodiments, the electrochemical device is a lithium secondary battery. In some embodiments, the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.
[0058] III. Electronic device
[0059] The electronic device of the present application can be any device using the electrochemical device according to the second aspect of the present application.
[0060] In some embodiments, the electronic device includes, but is not limited to: laptop computers, 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, large household batteries or lithium-ion capacitors, etc.
[0061] Examples and Comparative Examples
[0062] Examples 1-21
[0063] Preparation of cathode materials
[0064] (1) Prepare a mixed solution containing NiSO4 and MnSO4 according to the elemental molar ratio Ni:Mn = 50:50. Mix the mixed solution with a precipitant (NaOH solution) and a complexing agent (ammonia water) and react them. Control the reaction time to 60 hours, the ammonia water concentration to 1 mol / L, and the pH to 12.2 to obtain a nickel-manganese precursor TM(OH)2 (TM represents Ni / Mn) with an average particle size Dv50 of 11 μm.
[0065] (2) The above nickel-manganese precursor, lithium carbonate, and sodium carbonate are prepared according to the molar ratio of Li to transition metal element T(Ni+Mn) shown in Table 1. Li / (n Mn +n Ni And the molar ratio n of Na to T. Na / (n Mn +n Ni The powder was ground and mixed evenly, then calcined at 800℃ in a mixed atmosphere of air and ammonia for 20 hours. The volume percentages of air and ammonia in the mixed atmosphere were selected according to Table 1. The powder was cooled to room temperature at a rate of 3℃ / min, crushed, sieved, washed with deionized water, and vacuum filtered. It was then vacuum dried at 120℃ for 24 hours to obtain a dry powder. This powder was calcined in a N2 atmosphere for 6 hours (calcination temperatures are shown in Table 1), then quenched to room temperature at a rate of 10℃ / min. Finally, it was crushed and sieved to obtain the cathode material.
[0066] Comparative Example 1
[0067] The difference from Example 1 is that the cathode material is prepared according to the following steps:
[0068] (1) A mixed solution containing NiSO4 and MnSO4 is prepared according to the element molar ratio Ni:Mn = 50:50, and the mixed solution is mixed with a precipitating agent (NaOH solution) and a complexing agent (ammonia water) to react, with a reaction time of 60 hours, an ammonia water concentration of 1 mol / L, and a pH of 12.2, to obtain a nickel-manganese precursor NiMn (OH)2 with an average particle size Dv50 of 11 μm. 0.5 Mn 0.5 (OH)2;
[0069] (2) The nickel-manganese precursor and lithium carbonate are mixed uniformly at a molar ratio of Li:(Ni+Mn) of 1.05:1, and then calcined at 800°C in an air atmosphere for 20 hours, with a cooling rate of 10°C / min to room temperature, and finally crushed and sieved to obtain the positive electrode material.
[0070] Manufacture of button cell
[0071] - The positive electrode material, the binder polyvinylidene fluoride (PVDF), and the conductive agent conductive carbon black (Super P) are mixed at a weight ratio of 90:5:5, and then added into N-methyl pyrrolidone (NMP) to mix uniformly, to prepare a positive electrode slurry with a solid content of 0.7;
[0072] - The mixed positive electrode slurry is uniformly coated on an aluminum foil with a coating thickness of 40 μm, and single-sided coating is performed; after drying, rolling is performed to prepare the required electrode, wherein the electrode coating area density is 14 mg / cm 2 , and after drying, a positive electrode sheet is obtained, which is punched into a 14 mm round sheet to obtain a single-sided positive electrode sheet;
[0073] - The separator film is punched into an 18 mm round sheet; the negative electrode used is a lithium metal sheet with a diameter of 18 mm; the solvent is prepared by mixing propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) (PC:EC:DEC at a weight ratio of 1:1:1), and then LiPF6 is added to mix uniformly to obtain an electrolyte; the mass concentration of LiPF6 is 12.5% based on the total weight of the electrolyte; the positive electrode sheet, the separator paper, the negative electrode sheet (lithium sheet), the electrolyte, and the battery shell and other accessories are moved into a glove box (with a water content of less than 11 ppm);
[0074] The battery is assembled in the order of bottom to top and is injected with electrolyte: negative shell > flat pad + appropriate amount of electrolyte > metal lithium sheet + appropriate amount of electrolyte > one layer of separator paper + appropriate amount of electrolyte > positive electrode sheet + appropriate amount of electrolyte > flat pad + appropriate amount of electrolyte > spring > positive shell; the battery is packaged on a packaging machine to obtain a button cell.
[0075] Manufacture of lithium ion soft package battery
[0076] Preparation of the positive electrode: the positive electrode material, the binder polyvinylidene fluoride (PVDF), and the conductive agent conductive carbon black (Super P) in a weight ratio of 96:2:2 were mixed, added into N-methyl pyrrolidone (NMP), and uniformly mixed to prepare a positive electrode slurry with a solid content of 0.7; the positive electrode slurry was uniformly coated on one side surface of an aluminum foil, and after drying, the above step was repeated on the other side surface of the aluminum foil to obtain a double-sided coated positive electrode tab; after cold pressing, cutting, and welding of the tab, a positive electrode was obtained.
[0077] Preparation of the negative electrode: the artificial graphite, the styrene-butadiene rubber, and the sodium carboxymethyl cellulose (CMC) were mixed with deionized water in a mass ratio of 96:2:2, and uniformly stirred to obtain a negative electrode slurry. The negative electrode slurry was uniformly coated on one side surface of a copper foil, and after drying, the above step was repeated on the other side surface of the copper foil to obtain a double-sided coated negative electrode tab; after cold pressing, cutting, and welding of the tab, a negative electrode was obtained.
[0078] Preparation of the electrolyte: under a dry argon environment, LiPF6 was added into a solvent prepared by mixing propylene carbonate (PC), ethylene carbonate (EC), and diethyl carbonate (DEC) (PC:EC:DEC in a weight ratio of 1:1:1) to obtain an electrolyte, wherein the mass concentration of LiPF6 was 12.5% based on the total weight of the electrolyte.
[0079] Preparation of the separator: a porous polyethylene (PE) polymer film was used as the separator.
[0080] Assembly of the lithium ion soft package battery: the positive electrode, the separator, and the negative electrode were stacked in order, with the separator between the positive electrode and the negative electrode to play a separating role. The bare cell was obtained by winding, and was placed in an outer packaging aluminum plastic film, injected with the electrolyte, and packaged. After processes such as formation, degassing, and edge cutting, the lithium ion soft package battery was obtained.
[0081] Table 1 “ / ” represents the absence.
[0082] Test method
[0083] 1. X-ray diffraction test
[0084] After the lithium ion battery was fully discharged, the positive electrode tab was obtained, soaked and cleaned with dimethyl carbonate (DMC), dried, and then tested by an X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE, target material: Cu Kα; voltage and current: 40KV / 40mA, scanning angle range: 10° to 70°).
[0085] 2. Element content test
[0086] The positive electrode material sample is dissolved using a mixed solvent (for example, 0.4 g of the sample is dissolved using a mixed solvent of 10 ml of aqua regia (nitric acid and hydrochloric acid mixed at a ratio of 1:1) and 2 ml of HF), and the volume is made up to 100 ml. The content of each element in the positive electrode material is determined by inductively coupled plasma spectrometry (ICP).
[0087] 3. Cycle number test when the cycle capacity retention rate is 80% at 25°C: At 25°C, the lithium ion soft pack battery is charged to 4.35 V using a 1.5 C charging current to make the lithium ion battery reach the full charge state, and then discharged to a voltage of 2.8 V using a 4 C discharging current. The discharge capacity at this time is recorded as the initial discharge capacity. The above charging and discharging cycles are repeated until the cycle capacity retention rate is 80%, and the cycle number at this time is recorded. The cycle capacity retention rate = the discharge capacity of the Nth cycle / the initial discharge capacity.
[0088] 4. Cycle number test when the cycle capacity retention rate is 80% at 45°C: At 45°C, the lithium ion soft pack battery is charged to 4.35 V using a 1.5 C charging current to make the lithium ion battery reach the full charge state, and then discharged to a voltage of 2.8 V using a 4 C discharging current. The discharge capacity at this time is recorded as the initial discharge capacity. The above charging and discharging cycles are repeated until the cycle capacity retention rate is 80%, and the cycle number at this time is recorded. The cycle capacity retention rate = the discharge capacity of the Nth cycle / the initial discharge capacity.
[0089] Test results
[0090] The test results of the button cells and lithium ion soft pack batteries obtained in each example and comparative example are shown in Table 2.
[0091] As can be seen from the comparison of Examples 1-21 and Comparative Example 1 in Table 2, the positive electrode material of the examples of the present application has a molar ratio w1 of Li element to T element in the positive electrode material that satisfies w1≤0.2 when the button cell is charged to 4.5 V. It can be seen that the positive electrode material of the present application has a significantly reduced lithium content in the charged state, thereby greatly improving the utilization rate of lithium ions in the material. The lithium ion battery of the examples of the present application also has excellent cycle performance. The possible reason is that the sodium ions doped in the lithium layer play a supporting role in the layered structure of the positive electrode material, so that the positive electrode material of the present application can maintain the stability of the material structure in a highly delithiated state. At the same time, the oxygen vacancies formed on the surface of the positive electrode material of the present application can reduce the activity of the oxygen on the surface of the material and stabilize the outer layer oxygen ions of the positive electrode material, thereby improving the cycle performance of the material.
[0092] While certain example embodiments have been shown and described, the application is not limited to the disclosed embodiments. Rather, the application is intended to cover all modifications and alternatives that fall within the spirit and scope of the application as described by the appended claims.
Claims
1. A positive electrode material, characterized by, The positive electrode material comprises a lithium transition metal composite oxide, the lithium transition metal composite oxide comprises Li element, Na element and T element, the T element comprises at least one of Ni, Co or Mn; an electrode comprising the positive electrode material is assembled with a lithium sheet into a button cell, when the button cell is charged to 4.5V at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the molar ratio of Li element to T element in the lithium transition metal composite oxide is w1, and w1≤0.2 is satisfied.
2. The positive electrode material of claim 1, wherein, The positive electrode material satisfies at least one of the following conditions:
3. The positive electrode material according to claim 2, characterized in that, (1) the molar ratio of Li element to T element in the lithium transition metal composite oxide is w2, and the molar ratio of Na element to T element is w3, at least one of the following conditions is satisfied: (1) 0.55≤w2≤0.9; (2) 0.0005≤w3≤0.1; (3) 0.6≤w2+w3≤1; (4) w1 / w2≤24%.
4. The positive electrode material of claim 1, wherein, An electrode comprising the positive electrode material is assembled with a lithium sheet into a button cell, when the button cell is charged to 4.5V at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the molar ratio of Na element to T element in the lithium transition metal composite oxide is w4, at least one of the following conditions is satisfied: (1) 0.0005≤w4≤0.1; (2) 0.85≤w4 / w3≤1.
1.
5. The cathode material of claim 1, wherein, An electrode comprising the positive electrode material is assembled with a lithium sheet into a button cell, when the button cell is discharged to 2.8V at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the molar ratio of Na element to T element in the lithium transition metal composite oxide is w5, at least one of the following conditions is satisfied: (1) 0.55≤w5≤0.85; (2) w1 / w5≤25.5%. The positive electrode material satisfies at least one of the following conditions: (1) the molar ratio of Ni element to T element in the lithium transition metal composite oxide is 0.3 to 0.7; (3) the lithium transition metal composite oxide satisfies general formula Li x Na y (Ni a Co b Mn c M d )O 2±e R e wherein 0.55≤x / (a+b+c)≤0.9, 0.0005≤y / (a+b+c)≤0.1; 0.3≤a / (a+b+c)≤0.7, 0≤b / (a+b+c)≤0.7, 0≤c / (a+b+c)≤0.7, 0≤d / (a+b+c)≤0.2, 0≤e≤0.1, M includes at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, K, Ca, Sr, Ca, Ba, Ta, Hf or Ce, and R includes at least one of F, Cl, Br, I or N.
6. The cathode material of claim 1, wherein, (2) the lithium transition metal composite oxide further comprises M element, the M element comprises at least one of B, Mg, Al, Si, P, S, Ti, Cr, Fe, Cu, Zn, Ga, Y, Zr, Mo, Ag, W, In, Sn, Pb, Sb, V, Nb, La, Ge, K, Ca, Sr, Ca, Ba, Ta, Hf or Ce, the molar ratio of M element to T element in the lithium transition metal composite oxide is 0.01 to 0.2; 7. The positive electrode material according to claim 6, characterized in that, An electrode comprising the positive electrode material is assembled with a lithium sheet into a button cell, when the button cell is charged and discharged at a current of 0.04C in a voltage interval of 2.8V to 4.5V, a capacity voltage differential dQ / dV curve obtained has a first oxidation peak and a first reduction peak in an interval of 4.2V to 4.5V, and a second oxidation peak and a second reduction peak in an interval of 3.6V to 4.0V. The positive electrode material satisfies at least one of the following conditions: (1) the peak height of the first oxidation peak is 500mAh / g / V to 2000mAh / g / V based on the mass of the positive electrode material; (2) the absolute value of the peak height of the first reduction peak is 500 mAh / g / V to 2000 mAh / g / V based on the mass of the positive electrode material; (3) the peak voltage of the first oxidation peak is Vo1, the peak voltage of the first reduction peak is Vr1, and |Vo1-Vr1|≤0.2 V.
8. The positive electrode material of claim 6, wherein, The electrode comprising the positive electrode material is assembled into a button cell with lithium sheet, and when the button cell is charged and discharged at a current of 0.04C in a voltage interval of 2.8V to 4.5V, the discharge curve in the obtained voltage capacity curve satisfies at least one of the following conditions: (1) the discharge curve has a platform in the interval of 4.2V to 4.5V; (2) the capacity of the discharge curve in the interval of 4.2V to 4.5V is Q1, and the total capacity in the interval of 2.8V to 4.5V is Qt, satisfying: 0.15≤Q1 / Qt≤0.
35.
9. An electrochemical device, characterized by, The electrochemical device comprises a positive electrode sheet, and the positive electrode sheet comprises the positive electrode material according to any one of claims 1 to 8.
10. The electrochemical device of claim 9, wherein, The electrochemical device is in a full discharge state, and the peak position of the (003) peak in the X-ray diffraction spectrum of the lithium transition metal composite oxide is in the range of 18° to 19°.
11. An electronic device comprising the electrochemical device of claim 9 or 10.