CN111313008B - Magnesium-containing lithium-rich manganese-based positive electrode and preparation method thereof - Google Patents

Magnesium-containing lithium-rich manganese-based positive electrode and preparation method thereof Download PDF

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CN111313008B
CN111313008B CN202010145223.2A CN202010145223A CN111313008B CN 111313008 B CN111313008 B CN 111313008B CN 202010145223 A CN202010145223 A CN 202010145223A CN 111313008 B CN111313008 B CN 111313008B
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magnesium
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lithium
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CN111313008A (en
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董全峰
薛嘉熙
郑明森
范镜敏
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Xiamen University
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    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
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    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
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    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Abstract

The invention relates to a magnesium-containing lithium-rich manganese-based positive electrode and a preparation method thereof, wherein the magnesium-containing lithium-rich manganese-based positive electrode comprises a current collector and an active material, the active material is attached to the current collector, and the active material comprises: lithium-rich manganese-based positive electrode material xLi2MnO3·(1‑x)LiMO2M is a transition metal element, 0<x<1; magnesium simple substance or magnesium compound, conductive agent and binder; wherein the mass of the magnesium simple substance or the mass of magnesium in the magnesium compound is 0.1-10% of the mass of the lithium-rich manganese-based positive electrode material. The activation of manganese element in the first charging process of the lithium ion battery prepared from the magnesium-containing lithium-rich manganese-based anode is inhibited, and the lithium ion battery has extremely high cycle stability.

Description

Magnesium-containing lithium-rich manganese-based positive electrode and preparation method thereof
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a magnesium-containing lithium-rich manganese-based positive electrode and a preparation method thereof.
Background
Lithium ion batteries have been widely used in various industries, and the development of smart grids and electric vehicles is greatly restricted by the technical development of lithium ion batteries, and among the cathode materials of many lithium ion batteries, such as layered lithium cobaltate LiCoO2、LiNi1-x-yCoxMnyO2And lithium rich materials (xLi)2MnO3·(1-x)LiMO2M is a transition metal element, 0<x<1) The lithium-rich material has higher specific discharge capacity compared with other traditional anode materials (>250mAh/g) and high powerThe characteristic of electric voltage, and uses a large amount of cheap and nontoxic manganese element, compared with the LiCoO with higher content of toxic cobalt2And LiNi1-x-yCoxMnyO2The method has the characteristics of low cost, environmental friendliness and high safety. However, the working voltage of the lithium-rich material is higher than 4.5V (vs. Li)+Li), the material is faced with the problems of discharge voltage decay due to loss of lattice oxygen during cycling at high voltage, and gradual material deactivation due to side reactions of the electrolyte with the electrode material.
Metal magnesium element is used as doping element for lithium ion battery layered positive electrode material, and layered LiCoO is doped2And LiNi1-x-yCoxMnyO2The magnesium element in the anode materials has no electrochemical activity, so that the charge-discharge specific capacity of the materials can be obviously reduced when the doping amount is too large in industrial production, and the magnesium element is difficult to be uniformly distributed in the bulk phase or the surface phase of the materials when the doping amount is too low, so that the requirement on the production process is higher.
The Chinese patent application CN109904402A discloses a lithium-rich manganese-based material, which is a multi-phase heterostructure consisting of a layered structure and a spinel-shaped structure, and the molecular formula of the material is xLi2MnO3·(1-x)LiMO2·yLiNi0.5Mn1.5O4Wherein x is more than 0.3 and less than 1, and y is more than 0 and less than 0.1; m is one or more than two of ferrum, chromium, nickel, cobalt, magnesium, aluminum, zinc and copper; the microspheres are microscopically microspheres composed of layered structure nanoparticles, spinel structure nanoparticles and nanoparticles with a layered structure and spinel mutually embedded, the size range of the nanoparticles is 20-500 nanometers, and the diameter range of the microspheres is 5-20 micrometers. However, for the lithium-rich manganese-based material, the material itself is modified by means of doping, cladding and the like so as to achieve the purpose of improving the performance. From the current results, the effect of the modification of the lithium-rich manganese-based material is not ideal enough, the improvement of the cycle performance is limited, and the problem of structural change (crystal structure and electrode structure) of the lithium-rich manganese-based material in the charging and discharging process is difficult to be solved fundamentally) To a problem of (a).
Disclosure of Invention
The invention aims to overcome the problem that the capacity retention performance of the existing lithium-rich material is poor, and provides a magnesium-containing lithium-rich manganese-based positive electrode which has extremely high cycle stability.
The magnesium-containing lithium-rich manganese-based positive electrode comprises a current collector and an active material, wherein the active material is attached to the current collector and comprises: lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2M is a transition metal element, 0<x<1; magnesium simple substance or magnesium compound, conductive agent and adhesive.
The invention starts from an electrode manufacturing process, utilizes the process of the electrode preparation process, utilizes the magnesium element to realize the dynamic protection of the lithium-rich manganese-based material in the charging and discharging process, solves the problem of instability of the lithium-rich manganese-based material structure in the charging and discharging process from the electrode level, and improves the electrochemical performance.
In the invention, the magnesium element or the magnesium compound is uniformly mixed with other materials by a physical method, the magnesium element or the magnesium compound can be uniformly distributed in the electrode by an electrode preparation process, and the magnesium element dynamically acts with the lithium-rich manganese-based material in the charging and discharging process, so that the irreversible damage of the structure caused by excessive lithium removal during the first charging of the material is avoided by increasing the polarization in the charging process, and the lithium-rich manganese-based material can be protected in situ in the subsequent charging and discharging process, so that the side reaction caused by the direct contact of the material and the electrolyte is avoided. The invention has the advantages that the problem that the structure of the lithium-rich manganese-based material is unstable in the charging and discharging process is solved at the electrode level, and higher electrochemical performance is realized. The method avoids the use of a modification method which is only aiming at the complexity of the lithium-rich manganese-based material, needs precise regulation and control and has high process requirement, and the process method provided by the invention is simple and can easily realize large-scale batch production. The other key point of the invention is that the mass of the simple magnesium or the mass of magnesium in the magnesium compound is 0.1-10% of the mass of the lithium-rich manganese-based positive electrode material, preferably 1-7%, and the specific energy can be reduced due to the high content of the magnesium-containing compound, and the dynamic protection of the lithium-rich manganese-based material in the charging and discharging process can not be well realized due to the low content of the magnesium-containing compound. In the invention, the mass of the conductive agent is 0.1-15% of the mass of the lithium-rich manganese-based positive electrode material, and the mass of the binder is 0.1-15% of the mass of the lithium-rich manganese-based positive electrode material. The conductive agent and the binder respectively have the functions of increasing the conductive capacity and the tightness of the electrode, the content of the conductive agent and the binder must be regulated according to the characteristics of an actual battery so as to meet different use requirements, the improvement of the electrochemical performance by too much conductive agent is limited, extra mass can be increased unnecessarily, the transmission of charges is not facilitated by too little conductive agent, the electrochemical performance is often damaged by too much binder, and the good contact among the conductive agent, the lithium-rich material and the magnesium source is not facilitated by too little binder, so that the electrochemical performance is reduced.
The specific scheme is as follows:
a magnesium-containing lithium-rich manganese-based positive electrode comprising a current collector and an active material, the active material being attached to the current collector, the active material comprising: lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2M is a transition metal element, 0<x<1; magnesium simple substance or magnesium compound, conductive agent and binder; wherein the mass of the magnesium simple substance or the mass of magnesium in the magnesium compound is 0.1-10% of the mass of the lithium-rich manganese-based positive electrode material.
Further, the mass of the magnesium simple substance or the mass of magnesium in the magnesium compound is 0.1-10% of the mass of the lithium-rich manganese-based positive electrode material, and preferably 1-7%;
optionally, the mass of the conductive agent is 0.1-15% of that of the lithium-rich manganese-based positive electrode material;
optionally, the mass of the binder is 0.1-15% of the mass of the lithium-rich manganese-based positive electrode material.
Further, the magnesium compound is at least one of magnesium oxide, magnesium sulfide, organic magnesium salt or inorganic magnesium salt.
Further, the conductive agent is at least one of conductive carbon black, ketjen black or acetylene black.
Further, the binder is at least one of acrylonitrile multipolymer (LA), polyvinylidene fluoride (PVDF), sodium carboxymethyl cellulose (CMC), Polytetrafluoroethylene (PTFE), modified Styrene Butadiene Rubber (SBR) or Sodium Alginate (SA).
The invention also provides a preparation method of the magnesium-containing lithium-rich manganese-based positive electrode, which comprises the following steps: weighing the raw materials according to the mass percent, and then adding the lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2M is a transition metal element, 0<x<1, uniformly mixing a magnesium simple substance or a magnesium compound, a conductive agent and a binder by a physical method to obtain slurry, coating the slurry on the surface of the current collector, and then drying; the physical methods include stirring, milling or ball milling.
Further, adding solvent, preferably water, ethanol or isopropanol, during mixing, to facilitate stirring, grinding or ball milling, wherein the drying temperature is 50-120 deg.C, and the drying time is 1-20 h.
The invention also protects the magnesium-containing lithium-rich manganese-based anode prepared by the preparation method of the magnesium-containing lithium-rich manganese-based anode, and the activation of manganese element in the magnesium-containing lithium-rich manganese-based anode is inhibited in the first charging process.
The invention also protects a lithium ion/lithium battery which comprises a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode is the magnesium-containing lithium-rich manganese-based positive electrode, and the lithium ion battery has extremely high cycle stability.
Has the advantages that:
(1) in the magnesium-containing lithium-rich manganese-based positive electrode, activation of manganese in the active material in the first charging process is inhibited, oxygen precipitation is reduced, and the cycle stability is high.
(2) The magnesium-containing compound is dispersed in a solvent and physically mixed, such as stirring, grinding or ball milling, and then dried. Thereby achieving the effect that the magnesium element is uniformly distributed in the material and does not agglomerate.
(3) The preparation method of the magnesium-containing lithium-rich manganese-based positive electrode only needs simple mechanical mixing and drying treatment, and can be synthesized in a large scale.
Drawings
In order to illustrate the technical solution of the present invention more clearly, the drawings will be briefly described below, and it is apparent that the drawings in the following description relate only to some embodiments of the present invention and are not intended to limit the present invention.
FIG. 1 is the first charge and discharge curves of the lithium-rich manganese-based positive electrode and the magnesium-containing lithium-rich manganese-based positive electrode (magnesium source is magnesium sulfate, and the mass ratio of magnesium to the lithium-rich material is 2%) in example 1 at a current density of 20 mA/g;
FIG. 2 is a graph of the cycle performance of the lithium-rich manganese-based positive electrode and the magnesium-containing lithium-rich manganese-based positive electrode (magnesium source is magnesium sulfate, and the mass ratio of magnesium to the lithium-rich material is 2%) in example 1 after the first 20mA/g low-current activation, and then when the current density is 100 mA/g;
FIG. 3 is the first charge-discharge curve of the Mg-containing Li-rich Mn-based positive electrode of example 2 (Mg source is MgO, Mg accounts for 2% of Li-rich material) at a current density of 20 mA/g;
FIG. 4 is a graph of the cycle performance of the magnesium-containing lithium-rich manganese-based positive electrode of example 2 (magnesium oxide as the magnesium source, and 2% by mass of magnesium in the lithium-rich material) after being activated by a first low current of 20mA/g, and then at a current density of 100 mA/g;
FIG. 5 is the first charge-discharge curve of the Mg-containing Li-rich Mn-based positive electrode in example 3 (Mg source is magnesium sulfate, Mg accounts for 7% of the Li-rich material by mass) at a current density of 20 mA/g;
FIG. 6 is a graph of the cycle performance of the magnesium-containing lithium-rich manganese-based positive electrode of example 3 (magnesium source is magnesium sulfate, and the mass ratio of magnesium to lithium-rich material is 7%) after first activation with a small current of 20mA/g, and then at a current density of 100 mA/g.
Detailed Description
Preferred embodiments of the present invention will be described in more detail below. While the following describes preferred embodiments of the present invention, it should be understood that the present invention may be embodied in various forms and should not be limited by the embodiments set forth herein. The examples do not specify particular techniques or conditions, and are performed according to the techniques or conditions described in the literature in the art or according to the product specifications. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products commercially available. In the following examples, "%" means weight percent, unless otherwise specified.
The lithium-rich material used in the examples has the chemical formula of xLi2MnO3·(1-x)LiMO2M is nickel element, cobalt element and manganese element, and the stoichiometric ratio is 1: 1: 1, x is 0.5.
Example 1: magnesium sulfate is used as a magnesium source for the magnesium-containing lithium-rich manganese-based positive electrode, and the magnesium accounts for 2 percent of the mass of the lithium-rich material
This example relates to the preparation of a magnesium-containing lithium-rich manganese-based positive electrode using magnesium sulfate as the magnesium source, where the magnesium element accounts for 2% of the mass of the lithium-rich material, and the cycle performance was compared to a lithium-rich positive electrode prepared by the same preparation method but without the addition of magnesium sulfate.
The method comprises the following specific steps:
(1) taking a ball milling tank and a plurality of zirconium beads with different sizes. 50mg of lithium-rich material is added into the tank, magnesium sulfate accounts for 2% of the mass of the lithium-rich material, conductive carbon black accounts for 12% of the mass of the lithium-rich material, and LA binder accounts for 12% of the mass of the lithium-rich material.
(2) Dropping 300 μ L of water, sealing the pot, and ball milling for 6 h.
(3) The resulting slurry was coated on an aluminum foil and allowed to stand in a drying oven at 60 ℃ for 12 hours. And taking out after cooling, and tabletting by using the pressure of 10MPa to obtain the positive pole piece.
(4) And assembling the positive pole piece, the diaphragm, the electrolyte, the lithium piece and the motor shell into a half-cell in a glove box in an argon atmosphere, and standing for 12h for later use.
(5) And mounting the half battery to a charge-discharge test frame to perform constant current charge-discharge test of different currents.
Fig. 1 shows the first charge-discharge curves of a lithium-rich manganese-based positive electrode and a magnesium-containing lithium-rich manganese-based positive electrode (a magnesium source is magnesium sulfate, and the mass ratio of magnesium to the lithium-rich material is 2%) at a current density of 20 mA/g. The first-circle specific discharge capacities of the two electrodes are about 250mAh/g, and no obvious difference exists. However, the first-loop charging specific capacity of the magnesium-containing lithium-rich manganese-based positive electrode is 291.0mAh/g, the first-loop charging specific capacity of the lithium-rich manganese-based positive electrode is 321.4mAh/g, and the magnesium-containing lithium-rich manganese-based positive electrode has higher first-loop coulombic efficiency.
Fig. 2 is a cycle performance diagram of a magnesium-containing lithium-rich manganese-based positive electrode (magnesium source is magnesium sulfate, and the mass ratio of magnesium to the lithium-rich material is 2%) which is activated by a first small current and then is subjected to a current density of 100 mA/g. Under the low current of 20mA/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based positive electrode is 254.8mAh/g and is basically consistent with 253.0mAh/g of the lithium-rich manganese-based positive electrode. In the process of circulating 100 circles under the current density of 100mA/g, the first circle of the lithium-rich manganese-based anode has the specific discharge capacity of 213.8mAh/g, the 100 th circle of the lithium-rich manganese-based anode has the specific discharge capacity of 148.8mAh/g and the capacity retention rate of 69.6 percent, while the first circle of the magnesium-containing lithium-rich manganese-based anode has the specific discharge capacity of 213.7mAh/g, the 100 th circle of the lithium-rich manganese-based anode has the specific discharge capacity of 200.3mAh/g and the capacity retention rate of 93.7 percent, which are obviously superior to the. The activation of manganese is inhibited in the first charging process of the magnesium-containing lithium-rich manganese-based positive electrode, the voltage attenuation phenomenon is not obvious in the circulating process, and the circulating stability is improved.
Example 2: the magnesium oxide is taken as a magnesium source, and the magnesium accounts for 2 percent of the mass of the lithium-rich material
The embodiment relates to a cycle performance test of a magnesium-containing lithium-rich manganese-based positive electrode using magnesium oxide as a magnesium source, wherein magnesium accounts for 2% of the mass of a lithium-rich material.
This example differs from example 1 in that the magnesium source used for the magnesium-containing lithium-rich cathode is magnesium oxide.
FIG. 3 is a first-turn charge-discharge curve of a magnesium-containing lithium-rich manganese-based positive electrode (magnesium source is magnesium oxide, and the mass ratio of magnesium to lithium-rich material is 2%) at a current density of 20 mA/g. The charging specific capacity of the first ring is 298.9mAh/g, the discharging specific capacity of the first ring is 230.6mAh/g, and the first ring coulombic efficiency is higher.
Fig. 4 shows that the magnesium-containing lithium-rich manganese-based positive electrode (magnesium source is magnesium oxide, and the mass ratio of magnesium to the lithium-rich material is 2%) is subjected to first-loop low-current activation, and then a cycle performance test is performed at a current density of 100 mA/g. In the process of circulating for 30 circles under the current density of 100mA/g, the 1 st circle of the lithium-rich manganese-based anode has the specific discharge capacity of 202.0mAh/g, the 30 th circle of the lithium-rich manganese-based anode has the specific discharge capacity of 198.9mAh/g, the capacity retention rate is up to 98.4%, only little capacity attenuation exists, and excellent circulation stability is shown.
Example 3: magnesium sulfate is used as a magnesium source for the magnesium-containing lithium-rich manganese-based positive electrode, and the magnesium accounts for 7 percent of the mass of the lithium-rich material
The embodiment relates to a cycle performance test of a magnesium-containing lithium-rich manganese-based positive electrode by using magnesium sulfate as a magnesium source, wherein magnesium accounts for 7% of the mass of a lithium-rich material.
The difference between the present embodiment and embodiment 1 is that magnesium sulfate used in the magnesium-containing lithium-rich cathode accounts for 7% of the mass of the lithium-rich material.
FIG. 5 is a first-turn charge-discharge curve of a magnesium-containing lithium-rich manganese-based positive electrode (magnesium source is magnesium sulfate, and the mass ratio of magnesium to the lithium-rich material is 7%) at a current density of 20 mA/g. The charging specific capacity of the first circle is 254.8mAh/g, and the discharging specific capacity of the first circle is 205.4 mAh/g. FIG. 6 shows that the magnesium-containing lithium-rich manganese-based positive electrode (magnesium source is magnesium sulfate, and the mass ratio of magnesium to the lithium-rich material is 7%) is subjected to first-loop low-current activation, and then a cycle performance test is performed at a current density of 100 mA/g. In the process of circulating for 40 circles under the current density of 100mA/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based anode at the 1 st circle is 142.2mAh/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based anode at the 40 th circle is 141.6mAh/g, the capacity retention rate is up to 99.6%, almost no capacity attenuation can be considered, and the extremely high circulation stability is shown.
Example 4: the magnesium-containing lithium-rich manganese-based positive electrode takes magnesium citrate as a magnesium source, and the magnesium accounts for 6 percent of the mass of the lithium-rich material
The present example relates to cycle performance testing of a magnesium-containing lithium-rich manganese-based positive electrode using magnesium citrate as the magnesium source, wherein magnesium accounts for 6% of the mass of the lithium-rich material.
This example differs from example 1 in that the magnesium source used in the magnesium-containing lithium-rich cathode is magnesium citrate, the magnesium element of which accounts for 6% of the mass of the lithium-rich material. The conductive agent used by the magnesium-containing lithium-rich positive electrode is acetylene black, and the conductive agent accounts for 6% of the mass of the lithium-rich material. The binder used by the magnesium-containing lithium-rich positive electrode is PVDF binder, and accounts for 1% of the mass of the lithium-rich material.
And the magnesium-containing lithium-rich manganese-based positive electrode (the magnesium source is magnesium citrate, and the mass ratio of magnesium to the lithium-rich material is 6%) has a specific charge capacity of 237.6mAh/g and a specific discharge capacity of 194.4mAh/g in the first loop when the current density is 20 mA/g. After the first-turn low-current activation, the cyclic performance test is carried out at the current density of 100 mA/g. In the process of circulating for 40 circles under the current density of 100mA/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based anode at the 1 st circle is 126.3mAh/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based anode at the 40 th circle is 126.1mAh/g, the capacity retention rate is up to 99.8%, no capacity attenuation can be considered, and the extremely high circulation stability is shown.
Example 5: the magnesium-containing lithium-rich manganese-based positive electrode takes magnesium nitrate as a magnesium source, and magnesium accounts for 4 percent of the mass of the lithium-rich material
The embodiment relates to a cycle performance test of a magnesium-containing lithium-rich manganese-based positive electrode using magnesium nitrate as a magnesium source, wherein magnesium accounts for 4% of the mass of a lithium-rich material.
The difference between the present example and example 1 is that the magnesium source used in the magnesium-containing lithium-rich positive electrode is magnesium nitrate, and the magnesium element accounts for 4% of the mass of the lithium-rich material. The conductive agent used by the magnesium-containing lithium-rich positive electrode is conductive carbon black, and the conductive agent accounts for 12% of the mass of the lithium-rich material. The binder used by the magnesium-containing lithium-rich positive electrode is a CMC binder, and accounts for 12% of the mass of the lithium-rich material.
And the charge specific capacity of the first loop of the magnesium-containing lithium-rich manganese-based positive electrode (the magnesium source is magnesium nitrate, and the mass ratio of magnesium to the lithium-rich material is 4%) is 278.1mAh/g when the current density is 20mA/g, and the discharge specific capacity of the first loop is 226.2 mAh/g. After the first-turn low-current activation, the cyclic performance test is carried out at the current density of 100 mA/g. In the process of circulating 40 circles under the current density of 100mA/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based anode at the 1 st circle is 189.5mAh/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based anode at the 40 th circle is 185.9mAh/g, the capacity retention rate is up to 98.1%, the capacity retention rate is high, and the high-capacity lithium-rich manganese-based anode has extremely high circulation stability.
Example 6: the magnesium-containing lithium-rich manganese-based positive electrode takes a magnesium simple substance as a magnesium source, and the magnesium accounts for 0.1 percent of the mass of the lithium-rich material
The embodiment relates to a cycle performance test of a magnesium-containing lithium-rich manganese-based positive electrode using a magnesium simple substance as a magnesium source, wherein the magnesium element accounts for 0.1% of the mass of a lithium-rich material.
The difference between the embodiment and the embodiment 1 is that the magnesium source used by the magnesium-containing lithium-rich cathode is simple magnesium, and the magnesium element accounts for 0.1% of the mass of the lithium-rich material. The conductive agent used by the magnesium-containing lithium-rich positive electrode is Ketjen black, and the conductive agent accounts for 1% of the mass of the lithium-rich material. The binder used by the magnesium-containing lithium-rich positive electrode is a PTFE binder, and accounts for 15% of the mass of the lithium-rich material.
The magnesium-containing lithium-rich manganese-based positive electrode (the magnesium source is a magnesium simple substance, and the mass ratio of magnesium to the lithium-rich material is 0.1%) has a first-loop charging specific capacity of 290.4mAh/g and a first-loop discharging specific capacity of 217.8mAh/g when the current density is 20 mA/g. After the first-turn low-current activation, the cyclic performance test is carried out at the current density of 100 mA/g. In the process of circulating 40 circles under the current density of 100mA/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based anode at the 1 st circle is 122.7mAh/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based anode at the 40 th circle is 110.6mAh/g, the capacity retention rate is up to 90.1%, and the capacity retention rate is high.
Example 7: the magnesium-containing lithium-rich manganese-based positive electrode takes magnesium chloride as a magnesium source, and the magnesium accounts for 10 percent of the mass of the lithium-rich material
The embodiment relates to a cycle performance test of a magnesium-containing lithium-rich manganese-based positive electrode using magnesium chloride as a magnesium source, wherein magnesium accounts for 10% of the mass of a lithium-rich material.
The difference between the present embodiment and embodiment 1 is that the magnesium source used in the magnesium-containing lithium-rich positive electrode is magnesium chloride, and the magnesium element accounts for 10% of the mass of the lithium-rich material. The conductive agent used by the magnesium-containing lithium-rich positive electrode is conductive carbon black, and the conductive agent accounts for 10% of the mass of the lithium-rich material. The binder used by the magnesium-containing lithium-rich positive electrode is LA binder, and accounts for 10% of the mass of the lithium-rich material.
And the first-loop charging specific capacity of the magnesium-containing lithium-rich manganese-based positive electrode (the magnesium source is magnesium chloride, and the mass ratio of magnesium to the lithium-rich material is 10%) is 221.6mAh/g and the first-loop discharging specific capacity is 182.3mAh/g when the current density is 20 mA/g. After the first-turn low-current activation, the cyclic performance test is carried out at the current density of 100 mA/g. In the process of circulating for 40 circles under the current density of 100mA/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based anode at the 1 st circle is 130.8mAh/g, the specific discharge capacity of the magnesium-containing lithium-rich manganese-based anode at the 40 th circle is 130.4mAh/g, the capacity retention rate is up to 99.6%, the capacity retention rate is high, and excellent circulation stability is shown.
The preferred embodiments of the present invention have been described in detail, however, the present invention is not limited to the specific details of the above embodiments, and various simple modifications may be made to the technical solution of the present invention within the technical idea of the present invention, and these simple modifications are within the protective scope of the present invention.
It should be noted that the various features described in the above embodiments may be combined in any suitable manner without departing from the scope of the invention. The invention is not described in detail in order to avoid unnecessary repetition.
In addition, any combination of the various embodiments of the present invention is also possible, and the same should be considered as the disclosure of the present invention as long as it does not depart from the spirit of the present invention.

Claims (12)

1. A magnesium-containing lithium-rich manganese-based positive electrode is characterized in that: the magnesium-containing lithium-rich manganese-based positive electrode comprises a current collector and an active material, wherein the active material is attached to the current collector and comprises: lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2M is a transition metal element, 0<x<1; a compound of magnesium, a conductive agent and a binder; the mass of magnesium in the magnesium compound is 0.1-10% of the mass of the lithium-rich manganese-based positive electrode material, and the magnesium compound is at least one of magnesium sulfide, organic magnesium salt or inorganic magnesium salt; the preparation method of the magnesium-containing lithium-rich manganese-based positive electrode comprises the following steps: weighing the raw materials according to the mass percent, and then adding the lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2M is a transition metal element, 0<x<1, uniformly mixing a magnesium compound, a conductive agent and a binder by a physical method to obtain slurry, coating the slurry on the surface of the current collector, and then drying.
2. The magnesium-containing lithium-rich manganese-based positive electrode according to claim 1, characterized in that: the mass of magnesium in the magnesium compound is 1% -7% of the mass of the lithium-rich manganese-based positive electrode material.
3. The magnesium-containing lithium-rich manganese-based positive electrode according to claim 1, characterized in that: the mass of the conductive agent is 0.1-15% of that of the lithium-rich manganese-based positive electrode material.
4. The magnesium-containing lithium-rich manganese-based positive electrode according to claim 1, characterized in that: the mass of the binder is 0.1-15% of that of the lithium-rich manganese-based positive electrode material.
5. The magnesium-containing lithium-rich manganese-based positive electrode according to claim 1 or 2, characterized in that: the conductive agent is conductive carbon black.
6. The magnesium-containing lithium-rich manganese-based positive electrode according to claim 5, characterized in that: the conductive agent is at least one of Ketjen black or acetylene black.
7. The magnesium-containing lithium-rich manganese-based positive electrode according to claim 1 or 2, characterized in that: the binder is at least one of acrylonitrile multipolymer, polyvinylidene fluoride, sodium carboxymethylcellulose, polytetrafluoroethylene, modified styrene butadiene rubber or sodium alginate.
8. A method for preparing a magnesium-containing lithium-rich manganese-based positive electrode according to any one of claims 1 to 7, characterized in that: the method comprises the following steps: weighing the raw materials according to the mass percent, and then adding the lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2M is a transition metal element, 0<x<1, uniformly mixing a magnesium compound, a conductive agent and a binder by a physical method to obtain slurry, coating the slurry on the surface of the current collector, and then drying; the physical methods include stirring, milling or ball milling.
9. The method of claim 5, wherein the method comprises the steps of: adding solvent during mixing, and facilitating stirring, grinding or ball milling, wherein the drying temperature is 50-120 ℃, and the drying time is 1-20 h.
10. The method of claim 9, wherein the method comprises the steps of: the solvent is water, ethanol or isopropanol.
11. The magnesium-containing lithium-rich manganese-based positive electrode prepared by the method for preparing the magnesium-containing lithium-rich manganese-based positive electrode according to any one of claims 8 to 10 is characterized in that: the activation of the manganese element is inhibited in the first circle of charging process of the magnesium-containing lithium-rich manganese-based positive electrode.
12. A lithium ion/lithium battery, which consists of a positive electrode, a negative electrode and an electrolyte, is characterized in that: the positive electrode is the magnesium-containing lithium-rich manganese-based positive electrode in claim 11, and the lithium ion battery has excellent cycle stability.
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