CN112968175B - Method for modifying positive electrode active material for lithium battery, modified positive electrode active material for lithium battery, positive electrode, and lithium battery - Google Patents
Method for modifying positive electrode active material for lithium battery, modified positive electrode active material for lithium battery, positive electrode, and lithium battery Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- 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
- H01M4/502—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese for non-aqueous cells
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- 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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- H—ELECTRICITY
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- 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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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a modification method of a lithium battery positive active material, a modified lithium battery positive active material, a positive electrode and a lithium battery, and relates to the technical field of lithium batteries, and the modification method of the lithium battery positive active material comprises the following steps: MnO is added to the positive active material of the lithium battery2Firstly, carrying out high-temperature treatment on the mixture by using LiOH solution, and then carrying out high-temperature treatment on the mixture by using oxalic acid solution to obtain a solid-liquid mixture; evaporating the water content of the solid-liquid mixture to obtain modified MnO2. The modification method of the lithium battery positive active material solves the problem of controlling MnO2Active site of (2) and MnO2Sulfate ions and sodium ions in the pore canal play a side effect, so that the lithium battery has low internal resistance, good stability of high-temperature storage internal resistance and high consistency of internal resistance, and the problem of high-temperature storage flatulence is obviously improved.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a modification method of a lithium battery positive active material, a modified lithium battery positive active material, a positive electrode and a lithium battery.
Background
A lithium battery is a device that directly converts chemical energy of its own electrode material into electric energy, and its negative electrode is lithium metal or lithium alloy having extremely high energy density. Compared with a secondary battery, the lithium battery has the advantages of high energy density, small self-discharge, high specific energy and the like, and is widely applied to daily life. The primary lithium manganese battery which takes manganese dioxide as the positive active material and lithium metal or lithium alloy as the negative material has higher specific energy and open-circuit voltage and long service life, and is one of the most popular lithium battery varieties in the market at present. However, the lithium manganese battery has the problems of fast increase of internal resistance in high-temperature storage, high internal resistance, easy flatulence in high-temperature soft package and the like, which limits the use of the lithium manganese battery.
In MnO2Lithium manganese cell as positive electrode active material due to MnO2Is a material with strong activity and rich pore canals, and MnO is formed after the battery is assembled2The active sites on the surface bring about a plurality of side reactions, and the products of the side reactions cause the problem of increasing the internal resistance of the lithium battery. Meanwhile, in the soft package battery, the internal resistance of the lithium battery is increased due to side reaction, and the gas generated by the side reaction can cause the problems of soft package flatulence and the like.
In addition, MnO is a positive electrode material for lithium manganese battery2Mostly MnO for electrolysis2In the production of electrolytic MnO2In the process, sulfate radicals, sodium ions and other substances are easily introduced. Electrolysis of MnO with sulfate radical and sodium ion2Narrow channels are difficult to remove easily. Thus, MnO containing sulfate and sodium ions2After the battery is made, sulfate ions and sodium ions are gradually transferred and diffused to the surface of a negative electrode along with the increase of high-temperature storage time, so that a coating film is formed, the internal resistance of the battery is increased, and the performance of the battery is influenced. Thus, MnO is controlled2Active site of (3) and electrolytic MnO2The side effect exerted by sulfate ions and sodium ions in the pore canal is an important measure for solving the problems of the increase of the internal resistance of the lithium manganese battery in high-temperature storage and the easy flatulence of soft packages.
In view of the above, the present invention is particularly proposed.
Disclosure of Invention
One of the objectives of the present invention is to provide a method for modifying a positive active material of a lithium battery, which can solve the problem of controlling MnO2Active site of (3) and electrolytic MnO2Sulfate ions and sodium ions in the pore channels play a side effect problem.
The second purpose of the invention is to provide a modified lithium battery positive electrode active material, so that the lithium battery has the advantages of low internal resistance, good stability of internal resistance in high-temperature storage, high consistency of internal resistance and the like, and the problem of easiness in flatulence in soft package high-temperature storage is obviously solved.
The invention also aims to provide a positive electrode which comprises the lithium battery positive active material and has the same advantages as the modified lithium battery positive active material.
The fourth purpose of the invention is to provide a lithium battery, which comprises the positive electrode and has the same advantages as the modified positive active material of the lithium battery.
In order to achieve the above purpose of the present invention, the following technical solutions are adopted:
in a first aspect, a method for modifying a positive active material for a lithium battery, the method comprising the steps of:
MnO is added to the positive active material of lithium battery2Firstly, carrying out high-temperature treatment on the mixture by using LiOH solution, and then carrying out high-temperature treatment on the mixture by using oxalic acid solution to obtain a solid-liquid mixture; evaporating the water content of the solid-liquid mixture to dryness to obtain modified MnO2；
Wherein, MnO2In terms of weight of MnO250-80% of the total weight of a solid-liquid mixture formed by the LiOH solution;
the temperature of the LiOH solution high-temperature treatment is 60-100 ℃;
the temperature of the oxalic acid solution high-temperature treatment is 60-100 ℃.
Further, the time of the LiOH solution high-temperature treatment is 4-8 h;
preferably, the high-temperature treatment time of the oxalic acid solution is 1-3 h.
Further, LiOH accounts for MnO20.1-2.0 wt%.
Further, oxalic acid accounts for MnO20.1-0.5wt% of (B).
Further, the MnO2Involving electrolysis of MnO2。
Further, the modification method comprises the following steps:
dissolving LiOH in water, and adding MnO2Reacting at 60-100 deg.C for 4-8h, wherein, MnO is2In terms of weight of MnO2Solid-liquid mixture formed by LiOH solution50-80% by weight; LiOH in MnO20.1-2.0 wt%; then adding MnO20.1 to 0.5 weight percent of oxalic acid, and continuously reacting for 1 to 3 hours at the temperature of between 60 and 100 ℃ to obtain a solid-liquid mixture; evaporating the water content of the solid-liquid mixture to dryness to obtain modified MnO2。
In a second aspect, a modified lithium battery positive active material prepared by the above modification method.
In a third aspect, a positive electrode includes the modified positive active material for a lithium battery.
In a fourth aspect, a lithium battery includes the positive electrode.
Further, the lithium battery further comprises a negative electrode, a separator and a nonaqueous electrolyte.
Preferably, the material of the negative electrode includes at least one of lithium and a lithium alloy.
Preferably, the housing of the lithium battery comprises at least one of a steel shell, an aluminum shell and an aluminum plastic film.
Compared with the prior art, the invention has the following beneficial effects:
the modification method of the lithium battery positive active material can solve the problem of controlling MnO2Active site of (2) and MnO2Sulfate ions and sodium ions in the pores play a side effect. Specifically, by adding MnO with a certain mass fraction2Ensure the transmission of ions during the reaction, make the reaction more uniform and more sufficient, and at a certain temperature, the lithium ions in the LiOH solution replace MnO2Sodium ions in the pore channels, and since LiOH is basic, sulfate ions in the pore channels generally exist as hydrogen sulfate, and basic lithium hydroxide easily reacts with acidic sulfate ions. Therefore, the bisulfate ions in the pore channel can be more dissociated before comparison, thereby achieving the effect of removing the sulfate ions in the pore channel and further solving the problem of MnO2Sulfate ions and sodium ions in the pore canal play a side effect; at a certain temperature, MnO is mixed with oxalic acid2The active sites are reacted away, thereby reducing side reactions.
The modified lithium battery positive active material provided by the invention has the advantages of low internal resistance, good stability of high-temperature storage internal resistance, high internal resistance consistency and the like, and obviously solves the problem of easy flatulence in soft package high-temperature storage.
The positive electrode provided by the invention has the same advantages as the modified positive electrode active material of the lithium battery, and the details are not repeated.
The lithium battery provided by the invention has the same advantages as the modified lithium battery positive active material, and the description is omitted.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1 is a lithium/MnO test of example 1 and comparative examples 1-42The internal resistance of the primary soft package battery changes with time.
Detailed Description
The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments, and it should be understood that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In MnO2Lithium manganese cell as positive electrode active material due to MnO2Is a material with strong activity and rich pore canals, and MnO is formed after the battery is assembled2The active sites on the surface bring about a plurality of side reactions, and the products of the side reactions cause the problem of increasing the internal resistance of the lithium battery. For example, in a pouch battery, a side reaction causes problems such as an increase in internal resistance of the lithium battery and a pouch gas generated by the side reaction. MnO containing sulfate radical and sodium ion2After the battery is made, the height is increasedThe temperature storage time is prolonged, sulfate ions and sodium ions are gradually transferred and diffused to the surface of the negative electrode, so that a coating film is formed, the internal resistance of the battery is increased, and the performance of the battery is influenced. Thus, MnO is controlled2Active site of (2) and MnO2The side effect exerted by sulfate ions and sodium ions in the pore canal is an important measure for solving the problems of the increase of the internal resistance of the lithium manganese battery in high-temperature storage and the easy flatulence of soft packages.
In view of the above, the present invention particularly provides a modification method of a lithium battery positive active material, which can solve the problem of controlling MnO2Active site of (2) and MnO2Sulfate ions and sodium ions in the pores play a side effect. The invention provides a modification method of a positive active material, which is characterized in that under a certain condition, MnO is replaced by lithium ions in LiOH solution2Sodium ions in the pore canal use hydroxide radical in LiOH solution to lead MnO to be MnO2Sulfate radicals in the pore passages are further dissociated, and MnO is then treated by oxalic acid2The active sites are reacted, so that the side reaction is reduced, the treatment process is simple and efficient, the condition is mild, and the method has a great application prospect.
According to a first aspect of the present invention, there is provided a method for modifying a positive active material for a lithium battery, comprising the steps of:
MnO is added to the positive active material of the lithium battery2Firstly, carrying out high-temperature treatment on the mixture by using LiOH solution, and then carrying out high-temperature treatment on the mixture by using oxalic acid solution to obtain a solid-liquid mixture;
evaporating the water content of the solid-liquid mixture to dryness to obtain modified MnO2；
Wherein, MnO2In terms of weight of MnO250-80% of the total weight of a solid-liquid mixture formed by the LiOH solution; typical but not limiting mass fractions thereof are for example 50%, 60%, 70%, 80%; the lithium hydroxide solution of manganese dioxide with certain solid content is subjected to high-temperature treatment, so that the transmission of ions during reaction is ensured, and the reaction is more uniform and sufficient;
the temperature of the LiOH solution high-temperature treatment is 60-100 ℃;
the temperature of the oxalic acid solution high-temperature treatment is 60-100 ℃.
Hair brushIn the modification method of the invention, the LiOH solution is treated at a high temperature of 60 to 100 ℃ typically but not limited to 60 ℃, 80 ℃ and 100 ℃, and at a certain temperature, lithium ions in the LiOH solution displace MnO2Sodium ions in the pore canal and the LiOH solution are easy to react with acid sulfate ions, so that MnO is enabled2Sulfate ions in the pore canal are further dissociated, so that MnO is removed2The sulfate ions in the pore canal act, thereby solving the problem of MnO2Sulfate ions and sodium ions in the pore canal play a side effect; in the modification method of the present invention, the oxalic acid solution is treated at a high temperature of 60 to 100 ℃ typically but not limited to 60 ℃, 80 ℃ and 100 ℃, and at a certain temperature, the oxalic acid solution converts MnO2The active sites are reacted away, thereby reducing side reactions.
In a preferred embodiment, the LiOH solution of the present invention is treated at elevated temperature for a period of time ranging from 4 to 8 hours, with typical but non-limiting periods of time being, for example, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours;
in a preferred embodiment, when the LiOH solution is treated at high temperature, LiOH occupies MnO20.1-2.0 wt%;
after the manganese dioxide containing sulfate radicals and sodium ions is made into a battery, the sulfate radicals and the sodium ions are gradually transferred and diffused to the surface of a negative electrode to form a coating film along with the increase of high-temperature storage time, so that the internal resistance of the battery is increased. Therefore, the present invention utilizes lithium ions in the LiOH solution to replace MnO2The sodium ions in the pore canal make MnO by utilizing the characteristic that LiOH solution is easy to react with acid sulfate ions2Sulfate ions in the pore canal are further dissociated, so that MnO is removed2Sulfate radical ions in the pore channels are used for removing sulfate radicals and sodium ions in the narrow pore channels of the manganese dioxide, so that the purpose of reducing the internal resistance of the battery and further improving the performance of the battery is achieved.
In a preferred embodiment, the oxalic acid solution of the invention is treated at high temperature for 1 to 3 hours, and typical but not limiting times are 1 hour, 2 hours and 3 hours.
In a preferred embodiment, the oxalic acid solution is at an elevated temperatureIn time, oxalic acid occupies MnO20.1-0.5wt% of (B).
Due to MnO2Is a material with strong activity and rich pore canals, and MnO is formed after the battery is assembled2The active sites on the surface cause many side reactions, and the products of the side reactions cause an increase in the internal resistance of the lithium battery. Meanwhile, in a soft package lithium battery, side reactions not only can lead to the increase of internal resistance of the lithium battery, but also can cause the problems of soft package flatulence and the like. Therefore, the present invention utilizes oxalic acid to convert MnO2The active sites are reacted, so that the aim of reducing side reactions is fulfilled, and the performance of the battery is improved.
In a preferred embodiment, the invention utilizes MnO2Including but not limited to electrolytic MnO2。
In a preferred embodiment, the method for modifying a positive active material for a lithium battery of the present invention comprises the steps of:
dissolving LiOH in water, and adding MnO2Reacting the slurry at 60-100 ℃ for 4-8h, wherein MnO is2In terms of weight of MnO250-80% of the total weight of the solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, wherein the LiOH accounts for MnO20.1-2.0 wt%; then adding MnO20.1 to 0.5 weight percent of oxalic acid, and continuously reacting for 1 to 3 hours at the temperature of between 60 and 100 ℃ to obtain a solid-liquid mixture; evaporating the water content of the solid-liquid mixture to dryness to obtain modified MnO2。
The modification treatment process is simple, efficient and mild in condition, and solves the problem of MnO of the positive active material of the lithium battery2Sulfate ions and sodium ions in active sites and pore channels play a side effect, so that the problems of increase of high-temperature storage internal resistance, soft package flatulence and the like of the lithium-manganese battery are solved. The modification method has a great application prospect.
According to a second aspect of the present invention, a modified lithium battery positive active material is provided, which is prepared by the above method, and the positive active material enables a lithium battery to have advantages of low internal resistance, good stability of internal resistance in high-temperature storage, high consistency of internal resistance, and the like, and obviously improves the problem of easy flatulence in soft package high-temperature storage.
According to a third aspect of the present invention, there is provided a positive electrode prepared from the above-described modified positive active material for a lithium battery.
The positive electrode provided by the invention has the same advantages as the modified positive electrode active material of the lithium battery, and is not repeated.
The positive electrode provided by the invention is MnO modified by the above2The active substance is prepared by pulping and coating a conductive agent, a binder and a water solvent.
Wherein the binder includes, but is not limited to, Polytetrafluoroethylene (PTFE) and LA-132; conductive agents include, but are not limited to, acetylene black, carbon black, graphite, and ketjen black; modified MnO285-93% of the mass of the solid material of the positive electrode, wherein the typical but non-limiting mass fraction is 85%, 90%, 93%; the binder accounts for 2-5% of the mass of the solid material of the positive electrode, and the typical but non-limiting mass fraction is 2%, 3%, 4%, 5%; the conductive agent accounts for 5% -8% of the mass of the solid material of the positive electrode, and the typical but non-limiting mass fraction thereof is 5%, 6%, 7%, 8%, for example.
According to a fourth aspect of the present invention, there is provided a lithium battery prepared from the above positive electrode. The lithium battery provided by the invention has the same advantages as the modified lithium battery positive active material, and the description is omitted.
The lithium battery comprises a positive electrode, a negative electrode, a diaphragm and a non-aqueous electrolyte;
wherein the electrolyte lithium salt of the non-aqueous electrolyte includes but is not limited to lithium perchlorate (LiClO)4) Lithium bistrifluoromethanesulfonylimide (C)2F6LiNO4S2) Lithium hexafluorophosphate and lithium tetrafluoroborate, lithium perchlorate (LiClO) being preferred in the present invention4) (ii) a Further, the concentration of the electrolytic lithium salt in the nonaqueous electrolytic solution is 0.6 to 1.5mol/L, preferably 0.7 to 1.0 mol/L; the organic solvent of the nonaqueous electrolytic solution of the present invention includes at least one of EC, PC, DME, and DMC.
In a preferred embodiment, the material of the negative electrode for a lithium battery of the present invention includes at least one of lithium and a lithium alloy;
in a preferred embodiment, the housing of the lithium battery of the present invention comprises at least one of a steel case, an aluminum case, and an aluminum plastic film.
lithium/MnO of the invention2The battery may use a metal lithium foil and/or a lithium alloy foil as a negative electrode as it is, or may use a metal lithium and/or a lithium alloy foil pressed on a current collector as a negative electrode.
The invention is further illustrated by the following examples. The materials in the examples are prepared according to known methods or are directly commercially available, unless otherwise specified.
Example 1
A method for modifying a positive active material of a lithium battery includes the following steps:
dissolving lithium hydroxide in deionized water, adding manganese dioxide, wherein MnO is2In terms of weight of MnO275% of the total weight of a solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, 0.5wt% of lithium hydroxide and 0.3 wt% of manganese dioxide are stirred for 6 hours at the temperature of 80 ℃, oxalic acid which accounts for 0.3 wt% of the manganese dioxide is added, the reaction is continued for 2 hours at the temperature of 80 ℃, and finally the whole solid-liquid mixture is transferred to the high temperature of 100 ℃ to evaporate water to obtain the modified manganese dioxide.
A preparation method of a lithium battery comprises the following steps:
firstly, uniformly mixing a certain amount of LA-132 glue, deionized water and absolute ethyl alcohol, adding acetylene black and graphite serving as conductive agents under the stirring state, stirring and dispersing for 1 hour, and slowly adding the active material modified MnO2After 2-3 hours, adding PTFE and slowly stirring to prepare anode slurry after the solid powder and the solvent are fully stirred;
and coating the obtained positive electrode slurry on an aluminum foil current collector, rolling, cutting into large pieces, and cutting into small pieces for assembling the battery. The positive plate is placed into a blast high-temperature box and a vacuum high-temperature box to remove moisture in the positive plate, then the baked positive plate is transferred into a glove box with the relative humidity lower than 1.0%, the positive plate, a cut negative lithium strip and a diaphragm are wound to prepare a battery cell, the battery cell is placed into a shell (a steel shell, an aluminum shell or an aluminum-plastic film), then liquid is injected, and finally lithium/MnO (manganese oxide) is assembled2A primary battery.
Example 2
A method for modifying a positive active material of a lithium battery includes the following steps:
dissolving lithium hydroxide in deionized water, adding manganese dioxide, wherein MnO is2In terms of weight of MnO275% of the total weight of a solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, wherein lithium hydroxide accounts for 2.0wt% of manganese dioxide, the mixture is stirred for 6 hours at the temperature of 80 ℃, oxalic acid accounting for 0.3 wt% of the manganese dioxide is added, the reaction is continued for 2 hours at the temperature of 80 ℃, and finally the whole solid-liquid mixture is transferred to the high temperature of 100 ℃ to evaporate water to obtain the modified manganese dioxide.
Lithium cell was prepared using modified manganese dioxide obtained in this example as positive active material, and the preparation method was the same as in example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Example 3
A method for modifying a positive active material of a lithium battery includes the following steps:
dissolving lithium hydroxide in deionized water, adding manganese dioxide, wherein MnO is2In terms of weight of MnO275% of the total weight of a solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, 0.5wt% of lithium hydroxide, stirring for 6h at 80 ℃, adding oxalic acid accounting for 0.1 wt% of manganese dioxide, continuing to react for 2h at 80 ℃, and finally transferring the whole solid-liquid mixture to a high temperature of 100 ℃ to evaporate water to obtain the modified manganese dioxide.
Lithium cell was prepared using modified manganese dioxide obtained in this example as positive active material, and the preparation method was the same as in example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Example 4
A method for modifying a positive active material of a lithium battery comprises the following steps:
dissolving lithium hydroxide in deionized water, adding manganese dioxide, wherein MnO is2In terms of weight of MnO275 percent of the total weight of solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, lithium hydroxide accounts for 0.5 percent of the weight of the manganese dioxide, the mixture is stirred for 6 hours at the temperature of 80 ℃, oxalic acid accounting for 0.5 percent of the weight of the manganese dioxide is added,and (3) continuing to react for 2h at 80 ℃, and finally transferring the whole solid-liquid to a high temperature of 100 ℃ to evaporate water to dryness to obtain the modified manganese dioxide.
Lithium cell was prepared using modified manganese dioxide obtained in this example as positive active material, and the preparation method was the same as in example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Example 5
A method for modifying a positive active material of a lithium battery comprises the following steps:
dissolving lithium hydroxide in deionized water, adding manganese dioxide, wherein MnO is2In terms of weight of MnO275% of the total weight of a solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, 0.5wt% of lithium hydroxide and 0.3 wt% of manganese dioxide are stirred for 6 hours at the temperature of 100 ℃, oxalic acid which accounts for 0.3 wt% of manganese dioxide is added, the reaction is continued for 2 hours at the temperature of 100 ℃, and finally the whole solid-liquid mixture is transferred to the high temperature of 100 ℃ to evaporate water to obtain the modified manganese dioxide.
Lithium batteries were prepared using the modified manganese dioxide obtained in this example as a positive active material in a manner consistent with example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Example 6
A method for modifying a positive active material of a lithium battery includes the following steps:
dissolving lithium hydroxide in deionized water, adding manganese dioxide, wherein MnO is2In terms of weight of MnO275% of the total weight of a solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, wherein lithium hydroxide accounts for 0.5wt% of manganese dioxide, the mixture is stirred for 4 hours at the temperature of 80 ℃, oxalic acid accounting for 0.3 wt% of the manganese dioxide is added, the reaction is continued for 2 hours at the temperature of 80 ℃, and finally the whole solid-liquid mixture is transferred to the high temperature of 100 ℃ to evaporate water to obtain the modified manganese dioxide.
Lithium cell was prepared using modified manganese dioxide obtained in this example as positive active material, and the preparation method was the same as in example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Example 7
A method for modifying a positive active material of a lithium battery includes the following steps:
dissolving lithium hydroxide in deionized water, adding manganese dioxide, wherein MnO is2In terms of weight of MnO275% of the total weight of a solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, 0.5wt% of lithium hydroxide, stirring for 8 hours at 80 ℃, adding oxalic acid accounting for 0.3 wt% of manganese dioxide, continuing to react for 2 hours at 80 ℃, and finally transferring the whole solid-liquid mixture to a high temperature of 100 ℃ to evaporate water to obtain the modified manganese dioxide.
Lithium cell was prepared using modified manganese dioxide obtained in this example as positive active material, and the preparation method was the same as in example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Example 8
A method for modifying a positive active material of a lithium battery includes the following steps:
dissolving lithium hydroxide in deionized water, adding manganese dioxide, wherein MnO is2In terms of weight of MnO275% of the total weight of a solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, 0.5wt% of lithium hydroxide, stirring for 6h at 80 ℃, adding oxalic acid accounting for 0.3 wt% of manganese dioxide, continuing to react for 1h at 80 ℃, and finally transferring the whole solid-liquid to a high temperature of 100 ℃ to evaporate water to obtain the modified manganese dioxide.
Lithium cell was prepared using modified manganese dioxide obtained in this example as positive active material, and the preparation method was the same as in example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Example 9
A method for modifying a positive active material of a lithium battery includes the following steps:
dissolving lithium hydroxide in deionized water, adding manganese dioxide, wherein MnO is2In terms of weight of MnO275 percent of the total weight of a solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, 0.5 percent of lithium hydroxide accounts for manganese dioxide, the mixture is stirred for 6 hours at the temperature of 80 ℃, oxalic acid accounting for 0.3 percent of the weight of the manganese dioxide is added, the reaction is continued for 3 hours at the temperature of 80 ℃, and finally the whole solid-liquid mixture is transferred to the high temperature of 100 ℃ to evaporate water to be dried, thus obtaining the modified solid-liquid manganese dioxideManganese dioxide.
Lithium cell was prepared using modified manganese dioxide obtained in this example as positive active material, and the preparation method was the same as in example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Example 10
A modification method of a lithium battery positive electrode active material comprises the following steps:
this embodiment is different from embodiment 1 in that MnO is present in this embodiment2In terms of weight of MnO2And the other steps are the same as those in example 1, and the modified manganese dioxide is obtained, wherein the total weight of the solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution is 60 percent.
Lithium cell was prepared using modified manganese dioxide obtained in this example as positive active material, and the preparation method was the same as in example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Comparative example 1
This comparative example used common manganese dioxide, unmodified according to the invention, as the positive electrode active material for the preparation of lithium batteries, giving lithium/MnO2The primary battery comprises the following specific steps:
the preparation of the positive electrode material mainly involves unmodified MnO as an active material2Acetylene black and graphite serving as conductive agents, LA-132 glue serving as a binder, PTFE, solvent water and absolute ethyl alcohol.
Firstly, uniformly mixing a certain amount of LA-132 glue, deionized water and absolute ethyl alcohol, adding acetylene black and graphite serving as conductive agents under the stirring state, stirring and dispersing for 1 hour, and slowly adding a certain amount of active material MnO2After 2-3 hours, adding PTFE and slowly stirring to prepare anode slurry after the solid powder and the solvent are fully stirred; coating the obtained positive electrode slurry on an aluminum foil current collector, rolling, cutting into large pieces, and cutting into small pieces of assembled batteries; the positive plate is placed into a blast high-temperature box and a vacuum high-temperature box to remove moisture in the positive plate, then the dried positive plate is transferred into a glove box with the relative humidity lower than 1.0%, the positive plate, a cut negative lithium strip and a diaphragm are wound to form a battery core, the battery core is placed into a shell (a steel shell, an aluminum shell or an aluminum-plastic film), then liquid is injected, and finally the battery core is filled with the lithium stripAssembled into lithium/MnO2A primary battery.
Comparative example 2
A method for modifying a positive active material of a lithium battery includes the following steps:
dissolving oxalic acid in deionized water, adding manganese dioxide, wherein MnO is2In weight of MnO2And (3) reacting for 2h at 80 ℃ with oxalic acid accounting for 0.3 wt% of manganese dioxide and accounting for 75% of the total weight of a solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, and finally transferring the whole solid-liquid mixture to a high temperature of 100 ℃ to evaporate water to obtain the modified manganese dioxide.
Lithium cell was prepared using the modified manganese dioxide obtained in this comparative example as a positive active material in accordance with example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Comparative example 3
A method for modifying a positive active material of a lithium battery includes the following steps:
dissolving lithium hydroxide in deionized water, adding manganese dioxide, wherein MnO is2In terms of weight of MnO275% of the total weight of a solid-liquid mixture formed by the solid-liquid mixture and the LiOH solution, and lithium hydroxide accounting for 0.5wt% of the manganese dioxide, stirring for 6h at 80 ℃, and finally transferring the whole solid-liquid mixture to a high temperature of 100 ℃ to evaporate water to obtain the modified manganese dioxide.
Lithium cell was prepared using the modified manganese dioxide obtained in this comparative example as a positive active material in accordance with example 1 to obtain lithium/MnO2The primary battery will not be described in detail.
Comparative example 4
A modification method of a lithium battery positive electrode active material comprises the following steps:
the comparative example is different from example 1 in that the comparative example is first treated with oxalic acid solution at high temperature and then treated with LiOH solution at high temperature, and other steps are the same as those of example 1 to obtain modified manganese dioxide.
Lithium cell was prepared using the modified manganese dioxide obtained in this comparative example as a positive active material in accordance with example 1 to obtain lithium/MnO2Primary battery, not described in detail。
Examples of the experiments
Evaluation of Battery Performance after high temperature storage
lithium/MnO prepared in examples 1-10 and comparative examples 1-42A primary pouch cell, having a capacity of 1200mA of CF502445, was pre-discharged at 500mA for 10min, followed by measurement of its internal resistance and thickness at a certain point (measurement of its gassing), and then placed in an oven at 60 ℃ to measure two indicators of the internal resistance and thickness at a certain point each day, FIG. 1 shows lithium/MnO obtained in example 1 and comparative examples 1-32Graph of internal resistance of primary pouch cell with time, and lithium/MnO obtained in examples 1-10 and comparative examples 1-4 are recorded in Table 12The internal resistance of the primary soft package battery changes after three days and the battery expands.
TABLE 1
As can be seen from FIG. 1, lithium/MnO prepared from manganese dioxide modified with both LiOH and oxalic acid2The internal resistance of the primary battery in high-temperature storage is more stable than that of a primary lithium manganese battery prepared by singly modifying LiOH, singly modifying oxalic acid and manganese dioxide without any modification. And the influence of LiOH on the modification of manganese dioxide is slightly larger than that of oxalic acid. The treatment of LiOH should precede the treatment of oxalic acid.
As can be seen from Table 1, the treatment of the positive electrode with LiOH and oxalic acid affects the stability of the internal resistance of the cell, and the solid content of manganese dioxide, the concentration of LiOH, the concentration of oxalic acid, the treatment time and the treatment temperature of the reaction system are all for lithium/MnO2The internal resistance of the primary battery in high-temperature storage is influenced, and the processing conditions related to LiOH have larger influence on the performance of the modified manganese dioxide. The treatment of LiOH should precede the treatment of oxalic acid.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.
Claims (8)
1. A method for modifying a positive active material of a lithium battery is characterized by comprising the following steps:
MnO is added to the positive active material of the lithium battery2Firstly, carrying out high-temperature treatment on the mixture by using LiOH solution, and then carrying out high-temperature treatment on the mixture by using oxalic acid solution to obtain a solid-liquid mixture; evaporating the water content of the solid-liquid mixture to dryness to obtain modified MnO2；
Wherein, the MnO is2Involving electrolysis of MnO2Replacement of MnO with lithium ions in LiOH solution2Sodium ions in the pore canal use hydroxide radical in LiOH solution to lead MnO to be MnO2Sulfate radicals in the pore canals are dissociated, and MnO is then treated by oxalic acid2The active site of (a) is reacted away;
MnO2in terms of weight of MnO250-80% of the total weight of a solid-liquid mixture formed by the LiOH solution;
the temperature of the LiOH solution high-temperature treatment is 60-100 ℃;
the temperature of the oxalic acid solution high-temperature treatment is 60-100 ℃;
LiOH in MnO20.1-2.0 wt%;
oxalic acid in MnO20.1-0.5wt% of (A);
the time for treating the LiOH solution at high temperature is 4-8 h;
the high-temperature treatment time of the oxalic acid solution is 1-3 h.
2. The modification method according to claim 1, characterized by comprising the steps of: dissolving LiOH in water, and adding MnO2Reacting at 60-100 deg.C for 4-8h, wherein, MnO is2In terms of weight of MnO250-80% of the total weight of a solid-liquid mixture formed by the LiOH solution; LiOH in MnO20.1-2.0 wt%; then adding MnO20.1 to 0.5 weight percent of oxalic acid, and continuously reacting for 1 to 3 hours at the temperature of between 60 and 100 ℃ to obtain a solid-liquid mixture(ii) a Evaporating the water content of the solid-liquid mixture to dryness to obtain modified MnO2。
3. A modified positive active material for a lithium battery, characterized in that it is modified by the modification method according to claim 1 or 2.
4. A positive electrode comprising the modified positive active material for a lithium battery according to claim 3.
5. A lithium battery comprising the positive electrode according to claim 4.
6. The lithium battery as claimed in claim 5, further comprising a negative electrode, a separator and a nonaqueous electrolytic solution.
7. The lithium battery of claim 6, wherein a material of the negative electrode includes at least one of lithium and a lithium alloy.
8. The lithium battery of claim 5, wherein the housing of the lithium battery comprises at least one of a steel shell, an aluminum shell, and an aluminum plastic film.
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| CN101157480A (en) * | 2007-09-18 | 2008-04-09 | 华东理工大学 | Manganese bioxide ionic sieve |
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