CN112666242A - Method for improving ion embedding/extracting rate of energy storage layered material - Google Patents
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Abstract
The invention discloses a method for improving ion intercalation/deintercalation rate in an energy storage layered material, which comprises the steps of preparing a layered anode material, placing the layered anode material in different electrolyte systems, analyzing lattice information of the layered anode material after ion intercalation and ion diffusion states under different conditions by means of electrochemical detection and theoretical calculation to obtain the relation between the difference between the interlayer spacing of the layered anode material and the size of electrolyte cations and the ion intercalation/deintercalation rate, and regulating and controlling the difference to improve the ion intercalation/deintercalation rate of the energy storage layered material to obtain a high-magnification anode material system. Through the mode, the method can obtain the key factors influencing the ion embedding/extracting rate, so that the method for improving the ion embedding/extracting rate in the energy storage layered material with universality and guiding significance is obtained, the method is favorable for guiding the experimental design to obtain a high-rate battery system, promotes the development of a power battery system, and has important social and economic significance.
Description
Technical Field
The invention relates to the technical field of high-rate layered material systems, in particular to a method for improving the ion intercalation/deintercalation rate of an energy storage layered material.
Background
The power battery is used as a core component of the electric vehicle and is a key factor for determining the performance and large-scale application of the new energy electric vehicle in the future. The most important performance indexes of the battery are two: energy density and rate capability. Wherein, the energy density determines how much energy can be loaded by the battery, and the characteristics of the battery are related to the intrinsic characteristics of a material system; the rate performance determines the charging and discharging speed, and the ion diffusion rate in the anode material is a key factor influencing the rate performance of the battery. Therefore, the improvement of the ion embedding/extracting rate has important research significance for improving the rate capability of the cathode material.
At present, the research at home and abroad aiming at the rate capability of the anode material is still in the stages of experimental observation, experience method and trial and error method improvement, and people think of various improvement methods, such as using a nano material as an electrode, preparing a 3D structure to improve the specific surface area of the electrode, and improving the internal structure and the diffusion speed of ions, thereby improving the rate capability of the electrode material. However, most of the research only floats on the performance analysis level of the nano material, the influence factors of the rate performance of the nano material are not deeply analyzed, and an effective way for improving the rate performance of the practical micron-sized commercial cathode material is lacked, so that the experimental conclusion cannot guide the industry to implement. On one hand, the nanoparticles have high specific surface area and light weight, and are difficult to be tightly combined, so that the compaction density of the electrode is reduced, and the volume energy density of the battery is limited; on the other hand, the nanoparticles may react with the electrolyte unnecessarily, reducing the lifetime. Also, the nanomaterial may greatly increase the cost of the battery. Therefore, compared with the method of simply analyzing and modifying the nano material, the method has the advantages that key factors influencing the rate performance of the battery are deeply researched, and an efficient material electrolyte system is designed, so that the method has important social and economic significance for developing high-performance energy storage layered materials.
In view of this, it is still necessary to perform theoretical calculation and related electrochemical performance analysis on the battery positive electrode material so as to obtain key factors influencing the ion intercalation/deintercalation rate in principle, and further obtain a method for improving the ion intercalation/deintercalation rate of the energy storage layered material with greater universality and guiding significance, thereby effectively improving the rate capability of the battery.
Disclosure of Invention
The invention aims to solve the problems and provides a method for improving the ion intercalation/deintercalation rate of an energy storage layered material.
In order to achieve the above object, the present invention provides a method for increasing ion intercalation/deintercalation rate of an energy storage layered material, comprising the following steps:
s1, preparing a layered positive electrode material;
s2, constructing a three-electrode system by taking the layered positive electrode material obtained in the step S1 as a positive electrode, an Ag/AgCl electrode as a reference electrode and a platinum sheet electrode as a counter electrode; immersing the three-electrode system into electrolyte for electrochemical performance test;
s3, obtaining the interlayer state of electrolyte cations in the electrolyte in the layered positive electrode material through theoretical calculation; analyzing by combining the electrochemical performance test result obtained in the step S2 to obtain the relationship between the difference between the interlayer spacing of the layered positive electrode material and the size of the electrolyte cations and the ion intercalation/deintercalation rate;
and S4, regulating and controlling the difference in the step S3, and increasing the ion embedding/removing rate of the energy storage layered material to obtain a high-magnification positive electrode material system.
Further, in step S3, the relationship between the difference between the interlayer distance of the layered positive electrode material and the size of the electrolyte cations and the ion intercalation/deintercalation rate means that the ion intercalation/deintercalation rate increases as the difference increases.
Further, in step S4, the method for adjusting the difference includes decreasing the size of the electrolyte cations and increasing the interlayer distance of the layered positive electrode material.
Further, the reduction in the size of the electrolyte cations and the increase in the interlayer spacing of the layered positive electrode material means that when the size of the electrolyte cations can be further reduced, the species of the electrolyte cations are replaced to reduce the size of the electrolyte cations; when the size of the electrolyte cation is reduced to the minimum, the layered positive electrode material is adjusted or the type of the layered positive electrode material is replaced to improve the interlayer spacing of the layered positive electrode material; the adjustment mode comprises changing the synthesis method of the layered positive electrode material, improving the oxidation degree of the layered positive electrode material and modifying or doping the layered positive electrode material.
Further, in step S3, the theoretical calculation is performed from the head calculation simulation package based on vienna, and the Kohn-Sham equation is solved within the framework of the density functional theory; the Kohn-Sham valence state expands on a plane wave basis with a cutoff energy of 400 eV.
Further, in step S3, the interlayer state includes the interlayer distance of the layered positive electrode material, the size of cations inserted between the layers, and the amount of ion-adsorbed water.
Further, in step S1, the layered positive electrode material is layered manganese dioxide, and the preparation method thereof is as follows: mixing potassium permanganate and manganese sulfate according to the molar ratio of 6:1, adding a predetermined amount of water, fully stirring, and placing at 150-170 ℃ for fully stirring and reacting for 10-14 h to obtain layered manganese dioxide.
Further, in step S2, the electrochemical performance test includes an open circuit voltage test, a cyclic voltammetry test, a charge and discharge test, and an in-situ ac impedance test.
Furthermore, the sweep rate range of the cyclic voltammetry test is 0.1-500 mV/s, and the sweep interval is-0.5-0V vs. OCP; the current range of the charge and discharge test is 0.2-20 mA, and the scanning interval is-0.5-0V vs. OCP; the frequency range of the in-situ alternating current impedance test is 0.01 Hz-10 MHz, the scanning interval is-0.5-0V vs. OCP, the voltage interval is 0.05V, and the voltage needs to be stabilized for 900s before each measurement.
Further, in step S2, the electrolyte is one or more of a lithium sulfate solution, a sodium sulfate solution, a potassium sulfate solution, a rubidium sulfate solution, a cesium sulfate solution, a tetramethylammonium chloride solution, or a tetraethylammonium chloride solution; the concentrations of the lithium sulfate solution, the sodium sulfate solution, the potassium sulfate solution, the rubidium sulfate solution and the cesium sulfate solution are 0.5mol/L, and the concentrations of the tetramethylammonium chloride solution and the tetraethylammonium chloride solution are 1 mol/L.
Compared with the prior art, the invention has the beneficial effects that:
1. according to the invention, the layered anode material is prepared and placed in different electrolyte systems, and the lattice information of the layered anode material after ion embedding and the ion diffusion states under different conditions are analyzed in an electrochemical detection and theoretical calculation mode, so that key factors influencing the ion embedding/extracting rate can be obtained and regulated, and the ion embedding/extracting rate in the energy storage layered material is increased, and a high-rate anode material system is obtained.
2. The invention starts from the ion embedding characteristic of the layered anode material, researches the influence of the rate characteristic and different ion states of the layered anode material in different electrolytes on the material interface transfer resistance by electrochemical test methods such as open-circuit voltage test, cyclic volt-ampere test, charge-discharge test, in-situ alternating current impedance test and the like aiming at the charge-discharge characteristic of the layered anode material in different electrolytes, obtains the interlayer ion state through theoretical calculation, combines the interlayer ion state and the cyclic volt-ampere test, the charge-discharge test, the in-situ alternating current impedance test and the like, is not only beneficial to guiding the experimental design to obtain a high-rate battery system, but also beneficial to knowing the influence factors of the rate performance of the material in principle to obtain the relation between the difference value of the interlayer spacing of the layered anode material and the size of the electrolyte cations and the ion embedding/extracting rate, thereby regulating and controlling the ion embedding/extracting rate in the energy, the effect of improving the multiplying power of the battery is achieved.
3. The method for improving the ion embedding/extracting rate in the energy storage layered material has universality, can be suitable for various layered positive electrode materials and electrolyte systems, has important significance for solving the design problem of the conventional high-rate battery system, is beneficial to improving the rate capability of a power battery and promotes the application of the power battery in different use conditions; the method is also beneficial to promoting the development of a power battery system, is expected to improve the competitiveness of battery energy storage products of related industrial companies, has remarkable social and economic benefit prospect, and has important theoretical and practical significance.
Drawings
FIG. 1 is a graph of electrochemical performance of a layered positive electrode material in different electrolytes;
FIG. 2 is the electrochemical impedance spectrum EIS and charge transfer resistance R of the layered positive electrode material in different electrolytesctA variation graph;
FIG. 3 is an in-situ AC impedance model of a layered positive electrode material and in-situ AC impedance test results;
fig. 4 is a hydration energy curve of corresponding layered positive electrode materials at different cation intercalation times;
FIG. 5 is a schematic view of the interlayer ionic state of a layered positive electrode material;
fig. 6 is a schematic diagram of interlayer spacing control of a layered positive electrode material in different electrolyte systems.
Detailed Description
The following detailed description of the preferred embodiments of the present invention, taken in conjunction with the accompanying drawings, will make the advantages and features of the invention easier to understand by those skilled in the art, and thus will clearly and clearly define the scope of the invention. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.
The invention provides a method for improving the ion embedding/extracting rate of an energy storage layered material, which comprises the following steps:
s1, preparing a layered positive electrode material;
s2, constructing a three-electrode system by taking the layered positive electrode material obtained in the step S1 as a positive electrode, an Ag/AgCl electrode as a reference electrode and a platinum sheet electrode as a counter electrode; immersing the three-electrode system into electrolyte for electrochemical performance test;
s3, obtaining the interlayer state of electrolyte cations in the electrolyte in the layered positive electrode material through theoretical calculation; analyzing by combining the electrochemical performance test result obtained in the step S2 to obtain the relationship between the difference between the interlayer spacing of the layered positive electrode material and the size of the electrolyte cations and the ion intercalation/deintercalation rate;
and S4, regulating and controlling the difference in the step S3, and increasing the ion embedding/removing rate of the energy storage layered material to obtain a high-magnification positive electrode material system.
In step S3, the relationship between the difference between the interlayer distance of the layered positive electrode material and the size of the electrolyte cations and the ion intercalation/deintercalation rate means that the ion intercalation/deintercalation rate increases as the difference increases.
In step S4, the method of modulating the difference includes decreasing the size of the electrolyte cations and increasing the interlayer spacing of the layered positive electrode material.
The reduction in the size of the electrolyte cations and the increase in the interlayer spacing of the layered positive electrode material means that when the size of the electrolyte cations can be further reduced, the species of the electrolyte cations are replaced to reduce the size of the electrolyte cations; when the size of the electrolyte cation is reduced to the minimum, the layered positive electrode material is adjusted or the type of the layered positive electrode material is replaced to improve the interlayer spacing of the layered positive electrode material; the adjustment mode comprises changing the synthesis method of the layered positive electrode material, improving the oxidation degree of the layered positive electrode material and modifying or doping the layered positive electrode material.
In step S3, the theoretical calculation is performed from the head calculation simulation package based on vienna, and the Kohn-Sham equation is solved within the framework of the density functional theory; the Kohn-Sham valence state expands on a plane wave basis with a cutoff energy of 400 eV.
In step S3, the interlayer state includes the interlayer spacing of the layered positive electrode material, the size of cations inserted between the layers, and the amount of ion-adsorbed water.
In step S1, the layered positive electrode material is layered manganese dioxide, and the preparation method thereof is as follows: mixing potassium permanganate and manganese sulfate according to the molar ratio of 6:1, adding a predetermined amount of water, fully stirring, and placing at 150-170 ℃ for fully stirring and reacting for 10-14 h to obtain layered manganese dioxide.
In step S2, the electrochemical performance test includes an open circuit voltage test, a cyclic voltammetry test, a charge-discharge test, and an in-situ ac impedance test.
The sweep rate range of the cyclic voltammetry test is 0.1-500 mV/s, and the sweep interval is-0.5-0V vs. OCP; the current range of the charge and discharge test is 0.2-20 mA, and the scanning interval is-0.5-0V vs. OCP; the frequency range of the in-situ alternating current impedance test is 0.01 Hz-10 MHz, the scanning interval is-0.5-0V vs. OCP, the voltage interval is 0.05V, and the voltage needs to be stabilized for 900s before each measurement.
In step S2, the electrolyte is one or more of a lithium sulfate solution, a sodium sulfate solution, a potassium sulfate solution, a rubidium sulfate solution, a cesium sulfate solution, a tetramethylammonium chloride solution, or a tetraethylammonium chloride solution; the concentrations of the lithium sulfate solution, the sodium sulfate solution, the potassium sulfate solution, the rubidium sulfate solution and the cesium sulfate solution are 0.5mol/L, and the concentrations of the tetramethylammonium chloride solution and the tetraethylammonium chloride solution are 1 mol/L.
Example 1
The embodiment provides a method for improving ion intercalation/deintercalation rate of an energy storage layered material, which comprises the following steps:
s1 preparation of layered positive electrode material
Adding 0.948g of potassium permanganate and 0.169g of manganese sulfate into a beaker, adding 120mL of water, stirring until the solution is clear, transferring the solution into a 200mL reaction kettle, and reacting and stirring at 160 ℃ for 12 hours to obtain layered manganese dioxide serving as a layered positive electrode material.
S2 electrochemical performance test and analysis
Taking the layered manganese dioxide obtained in the step S1 as a positive electrode, taking an Ag/AgCl electrode as a reference electrode, and taking a platinum sheet electrode as a counter electrode to construct a three-electrode system; and respectively immersing the three-electrode system into different types of electrolytes to test the electrochemical performance.
Wherein the different types of electrolyte comprise 0.5mol/L lithium sulfate solution, 0.5mol/L sodium sulfate solution, 0.5mol/L potassium sulfate solution, 0.5mol/L rubidium sulfate solution, 0.5mol/L cesium sulfate solution, 1mol/L tetramethylammonium chloride (TMAC) solution and 1mol/L tetraethylammonium chloride (TEAC) solution.
The electrochemical performance test comprises an open circuit voltage test (OCP), a cyclic voltammetry test (CV), a charge-discharge test (GCD) and an in-situ alternating current impedance test (in situ EIS), and the specific test method comprises the following steps:
a. open circuit voltage test (OCP)
And (4) respectively immersing the three-electrode system in the step S2 into the different types of electrolyte, and standing for 1 hour to obtain the open circuit voltage (OCP) in a stable state.
b. Cyclic voltammetry tests (CV)
Respectively immersing the three-electrode system in the step S2 into the different types of electrolytes, and testing the CV characteristics of the layered positive electrode material by adopting different sweep speeds; the scanning speed range is 0.1-500 mV/s, and the scanning interval is-0.5-0V vs.
c. Charge and discharge test (GCD)
Respectively immersing the three-electrode system in the step S2 into the different types of electrolyte, and testing the GCD characteristics of the layered positive electrode material by adopting different constant currents; the range of the different constant currents is 0.2-20 mA, and the scanning interval is-0.5-0V vs.
d. In situ AC impedance test (in situ EIS)
Respectively immersing the three-electrode system in the step S2 into the different types of electrolyte, and testing the EIS characteristics of the layered positive electrode material; the voltage amplitude is set to be 5mV, the frequency range is 0.01 Hz-10 MHz, the scanning interval is-0.5-0V vs. OCP, the voltage interval is 0.05V, and the voltage needs to be stabilized for 900s before each measurement.
By the above method, electrochemical performance maps of the layered positive electrode material in different electrolytes are measured, as shown in fig. 1. In fig. 1, a represents the open circuit voltage variation of the layered positive electrode material in different electrolytes, b represents the CV curve of the layered positive electrode material in different electrolytes, and c represents the rate characteristics of the layered positive electrode material in different electrolytes.
As can be seen from a diagram in FIG. 1, the open circuit voltage of the layered positive electrode material in each electrolyte is arranged from high to low in the order of Li2SO4＞Na2SO4＞K2SO4＞Rb2SO4＞Cs2SO4The open-circuit voltage of the layered positive electrode material in the TMAC solution and the TEAC solution is obviously lower than that of other electrolytes, mainly because cations and anions in other electrolytes can be embedded into the interlayer of the layered positive electrode material together to cause the increase of the open-circuit voltage, while cations in the TMAC solution and the TEAC solution cannot be embedded into the interlayer of the layered positive electrode material, and only the anions are embedded to cause the reduction of the open-circuit voltage. Meanwhile, as can be seen from the b diagram in fig. 1, when the electrolyte is a TMAC solution or a TEAC solution, the large molecules cannot be embedded between the layers of the layered positive electrode material, and the embedded capacitance is lacking, resulting in a lower capacity. As can be seen from the graph c in FIG. 1, when the electrolyte is Li2SO4、Na2SO4Or K2SO4When the positive electrode material is small in molecular weight, the interlayer of the layered positive electrode material has a vacant space for embedding more water, and the electrostatic action between cations and the interlayer under the action of water is reduced, so that the high rate performance is shown; when the electrolyte is Rb2SO4Or Cs2SO4When the cations are relatively large molecules, the surface water molecules are few, the interlayer electrostatic acting force is large, and the rate capability is relatively poor; when the electrolyte is an ultra-large molecule such as TMAC or TEAC, the molecule is too large to be embedded, resulting in poor rate capability.
According to the in-situ AC impedance test, the electrochemical impedance spectrum EIS and the charge transfer resistance R of the layered positive electrode material in different electrolytes are obtainedctThe graph of variation of (a) is shown in fig. 2. In fig. 2, a represents the layered positive electrode material at a test voltage of 0V vs. ocpElectrochemical Impedance Spectroscopy (EIS) in different electrolytes; b represents the electrochemical impedance spectrum EIS of the layered positive electrode material in different electrolytes when the test voltage is-0.5V vs. OCP; c represents the charge transfer resistance R of the layered positive electrode material under different electrolytes and different voltagesctAnd (5) a variation graph.
As can be seen from fig. 2, when the test voltage is 0V vs. ocp, it indicates that the layered positive electrode material is immersed in the electrolyte in a non-pressurized state, and the charge transfer is not driven by the potential, so the charge transfer resistance R isctIs large; when the test voltage is-0.5V vs. OCP, negative voltage is added, which is beneficial to the intercalation of cations, so that the charge transfer resistance in each corresponding electrolyte under the test voltage is relatively small.
Meanwhile, an in-situ ac impedance model and an in-situ ac impedance test result of the layered positive electrode material are shown in fig. 3. In fig. 3, a is an electrochemical impedance spectrum EIS of a layered positive electrode material tested in a lithium sulfate electrolyte; making fitting model semi-circle R according to a diagramctAdding a Valurg area and a diffusion area to obtain a theoretical model which is a b diagram; graphs c-i are respectively the layered positive electrode material in Li2SO4、Na2SO4、K2SO4、Rb2SO4、Cs2SO4Electrochemical impedance spectroscopy in TMAC, TEAC solutions.
As can be seen from FIG. 3, the layered positive electrode material is in Li2SO4、Na2SO4、K2SO4、Rb2SO4Or Cs2SO4The electrolyte containing monovalent alkali metal ions has better performance, and the performance of the electrolyte in organic electrolytes such as TMAC or TEAC is poorer.
S3, analyzing key factors influencing the ion embedding/extracting speed by combining theoretical calculation
Obtaining the interlayer state of electrolyte cations in the electrolyte in the layered positive electrode material through theoretical calculation; and analyzing by combining the electrochemical performance test result obtained in the step S2 to obtain the influence of the difference between the interlayer spacing of the layered positive electrode material and the size of the electrolyte cations on the ion intercalation/deintercalation rate.
Wherein the theoretical calculations are performed from a computational simulation program package (VASP) based on vienna and solved for Kohn-Sham equations within a Density Functional Theory (DFT) framework; the Kohn-Sham valence state expands on a plane wave basis with a cutoff energy of 400 eV.
Through the theoretical calculation, the supercell size and the interlayer spacing of the layered positive electrode material are fixed, cations with different sizes are embedded between the layers, then water molecules are gradually increased, the hydration energy is calculated, and the hydration energy change curve of the layered positive electrode material corresponding to the embedding of different cations is obtained, as shown in fig. 4.
In fig. 4, the hydration energy is negative to indicate that more water molecules can be inserted between the layers, and the hydration energy is regular to indicate that no water molecules can be inserted between the layers. Therefore, as can be seen from fig. 4, the smaller the size of the cations inserted between the layers of the layered positive electrode material is, the more the amount of water molecules that can be continuously inserted is; wherein, Cs+Inability to bind water molecules, Rb+Can bind 1 water molecule, K+Can combine 2 water molecules, Na+And Li+More than 4 water molecules can be combined.
A schematic view of the ion state between the layers of the layered positive electrode material is obtained according to the number of hydrated ions between the layers of the layered positive electrode material corresponding to each cation, as shown in fig. 5. As can be seen from fig. 5, as the size of the ion decreases, the number of water molecules that can be bound increases, the desolvation decreases, and the difference between the interlayer spacing and the ion size gradually increases; meanwhile, although Na can be derived from the hydration energy+And Li+More than 4 water molecules can be bonded, but Na is not enough to accommodate more water molecules due to interlayer spacing+And Li+Only 4 water molecules can be bound.
From the above analysis, it can be concluded that the difference between the interlayer spacing of the layered positive electrode material and the size of the electrolyte cations is a key factor affecting the ion intercalation/deintercalation rate. With the increase of the difference between the interlayer distance of the layered positive electrode material and the size of the electrolyte cations, more vacant space can be reserved between the layers to embed more water, so that the electrostatic action between the layers of the layered positive electrode material is reduced, and the ion embedding/extracting rate in the energy storage layered material is improved.
S4, regulating and controlling the difference value to improve the ion embedding/extracting rate of the energy storage layered material
According to the relation between the difference value and the ion embedding/extracting rate obtained in the step S3, the ion embedding/extracting rate of the energy storage layered material can be improved by regulating and controlling the difference value, and a high-magnification positive electrode material system is obtained.
A schematic diagram of layer spacing control of layered cathode materials in different electrolyte systems is shown in fig. 6. In FIG. 6, 2b in a denotes the interlayer spacing of layered manganese dioxide, 2a0The size of cations inserted between layers can be adjusted to obtain different b-a0Value, in turn, according to b-a being different0The state of ions between layers is obtained, so that the ion embedding/extracting rate of the energy storage layered material is improved. In FIG. 6, b is a schematic view showing a model in which cations are intercalated between layers of layered manganese dioxide; c is a schematic view of adjusting the interlayer spacing 2b of the layered positive electrode material; d is Li+、Na+And K+The solvating ions are embedded into the interlayer of the layered manganese dioxide, and the embedding of more bound water can be seen in the figure; e diagram is Rb+And Cs+The schematic diagram of the intercalation of such solvated ions into the layers of the layered manganese dioxide shows that it is more difficult to intercalate bound water.
Specifically, in this embodiment, ions with smaller ion sizes are selected as the electrolyte system, so that the ion sizes can be reduced, the difference between the interlayer distance and the ion size is increased, the ion intercalation/deintercalation rate of the energy storage layered material is increased, and the high-rate positive electrode system is obtained.
In other embodiments, the layered manganese dioxide can be changed into a layered cathode material with a larger interlayer spacing by changing the type of the layered cathode material, the interlayer spacing can be improved by modifying and doping the layered cathode material, and the interlayer spacing of the layered cathode material can be improved by changing the synthesis method or the oxidation degree of the layered cathode material. The oxidation degree can be regulated and controlled by a synthetic method or oxygen plasma treatment and the like, and the improvement of the oxidation degree is beneficial to increasing the interlayer spacing of the layered positive electrode material.
In addition, the cylindrical through hole has the same action mechanism as that of the layered material in microscopic size, and cations are transmitted along the hole or layer straight line, so that the effect similar to the adjustment of the interlayer spacing can be achieved by adjusting and controlling the pore diameter of the porous anode material. Wherein, the regulation and control of the pore diameter can be realized by adjusting the sintering temperature.
The regulating and controlling method can increase the difference value between the interlayer distance and the ion size by increasing the interlayer distance or reducing the cation size, thereby increasing the ion embedding/extracting rate of the energy storage layered material and obtaining a high-magnification positive electrode system.
Therefore, the method can obtain the relationship between the difference between the interlayer spacing of the layered positive electrode material and the size of the electrolyte cations and the ion intercalation/deintercalation rate by researching the key factors influencing the ion intercalation/deintercalation rate, and thus the method for improving the ion intercalation/deintercalation rate of the energy storage layered material is universal, and has important significance for guiding experimental design and promoting the development of a battery system.
In summary, the layered positive electrode material is prepared and placed in different electrolyte systems, lattice information of the layered positive electrode material after ion intercalation and ion diffusion states under different conditions are analyzed by means of electrochemical detection and theoretical calculation, so that the relationship between the difference between the interlayer spacing of the layered positive electrode material and the size of electrolyte cations and the ion intercalation/deintercalation rate is obtained, the difference is regulated and controlled, the ion intercalation/deintercalation rate of the energy storage layered material is increased, and the high-rate positive electrode material system is obtained. Through the mode, the method can obtain the key factors influencing the ion embedding/extracting rate, so that the method for improving the ion embedding/extracting rate in the energy storage layered material with universality and guiding significance is obtained, the method is favorable for guiding the experimental design to obtain a high-rate battery system, promotes the development of a power battery system, and has important social and economic significance.
The above description is only for the purpose of illustrating the technical solutions of the present invention and is not intended to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill 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; all the equivalent structures or equivalent processes performed by using the contents of the specification and the drawings of the invention, or directly or indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. A method for improving the ion intercalation/deintercalation rate of an energy storage layered material is characterized by comprising the following steps:
s1, preparing a layered positive electrode material;
s2, constructing a three-electrode system by taking the layered positive electrode material obtained in the step S1 as a positive electrode, an Ag/AgCl electrode as a reference electrode and a platinum sheet electrode as a counter electrode; immersing the three-electrode system into electrolyte for electrochemical performance test;
s3, obtaining the interlayer state of electrolyte cations in the electrolyte in the layered positive electrode material through theoretical calculation; analyzing by combining the electrochemical performance test result obtained in the step S2 to obtain the relationship between the difference between the interlayer spacing of the layered positive electrode material and the size of the electrolyte cations and the ion intercalation/deintercalation rate;
and S4, regulating and controlling the difference in the step S3, and increasing the ion embedding/removing rate of the energy storage layered material to obtain a high-magnification positive electrode material system.
2. The method for increasing the ion intercalation/deintercalation rate of the energy storage layered material as claimed in claim 1, wherein: in step S3, the relationship between the difference between the interlayer distance of the layered positive electrode material and the size of the electrolyte cations and the ion intercalation/deintercalation rate means that the ion intercalation/deintercalation rate increases as the difference increases.
3. The method for increasing the ion intercalation/deintercalation rate of the energy storage layered material as claimed in claim 1, wherein: in step S4, the method of modulating the difference includes decreasing the size of the electrolyte cations and increasing the interlayer spacing of the layered positive electrode material.
4. The method for increasing the ion intercalation/deintercalation rate of the energy storage layered material as claimed in claim 3, wherein: the reduction in the size of the electrolyte cations and the increase in the interlayer spacing of the layered positive electrode material means that when the size of the electrolyte cations can be further reduced, the species of the electrolyte cations are replaced to reduce the size of the electrolyte cations; when the size of the electrolyte cation is reduced to the minimum, the layered positive electrode material is adjusted or the type of the layered positive electrode material is replaced to improve the interlayer spacing of the layered positive electrode material; the adjustment mode comprises changing the synthesis method of the layered positive electrode material, improving the oxidation degree of the layered positive electrode material and modifying or doping the layered positive electrode material.
5. The method for increasing the ion intercalation/deintercalation rate of the energy storage layered material as claimed in claim 1, wherein: in step S3, the theoretical calculation is performed from the head calculation simulation package based on vienna, and the Kohn-Sham equation is solved within the framework of the density functional theory; the Kohn-Sham valence state expands on a plane wave basis with a cutoff energy of 400 eV.
6. The method for increasing the ion intercalation/deintercalation rate of the energy storage layered material as claimed in claim 1, wherein: in step S3, the interlayer state includes the interlayer spacing of the layered positive electrode material, the size of cations inserted between the layers, and the amount of ion-adsorbed water.
7. The method for increasing the ion intercalation/deintercalation rate of the energy storage layered material as claimed in claim 1, wherein: in step S1, the layered positive electrode material is layered manganese dioxide, and the preparation method thereof is as follows: mixing potassium permanganate and manganese sulfate according to the molar ratio of 6:1, adding a predetermined amount of water, fully stirring, and placing at 150-170 ℃ for fully stirring and reacting for 10-14 h to obtain layered manganese dioxide.
8. The method for increasing the ion intercalation/deintercalation rate of the energy storage layered material as claimed in claim 1, wherein: in step S2, the electrochemical performance test includes an open circuit voltage test, a cyclic voltammetry test, a charge-discharge test, and an in-situ ac impedance test.
9. The method for increasing the ion intercalation/deintercalation rate of the energy storage layered material as claimed in claim 8, wherein: the sweep rate range of the cyclic voltammetry test is 0.1-500 mV/s, and the sweep interval is-0.5-0V vs. OCP; the current range of the charge and discharge test is 0.2-20 mA, and the scanning interval is-0.5-0V vs. OCP; the frequency range of the in-situ alternating current impedance test is 0.01 Hz-10 MHz, the scanning interval is-0.5-0V vs. OCP, the voltage interval is 0.05V, and the voltage needs to be stabilized for 900s before each measurement.
10. The method for increasing the ion intercalation/deintercalation rate of the energy storage layered material as claimed in claim 1, wherein: in step S2, the electrolyte is one or more of a lithium sulfate solution, a sodium sulfate solution, a potassium sulfate solution, a rubidium sulfate solution, a cesium sulfate solution, a tetramethylammonium chloride solution, or a tetraethylammonium chloride solution; the concentrations of the lithium sulfate solution, the sodium sulfate solution, the potassium sulfate solution, the rubidium sulfate solution and the cesium sulfate solution are 0.5mol/L, and the concentrations of the tetramethylammonium chloride solution and the tetraethylammonium chloride solution are 1 mol/L.
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