CN108063237A - Application of iron phosphate and iron phosphate composite material as negative electrode in potassium ion battery - Google Patents

Abstract

The invention relates to application of iron phosphate and an iron phosphate composite material as a negative electrode material in a potassium ion battery, wherein the iron phosphate composite material comprises an iron phosphate doped material and a coating material of the iron phosphate doped material or an iron phosphate coating material. The iron phosphate doped material is K_xFePO₄、Fe_xM_1‑xPO₄Or KFeMPO₄Wherein M is other metal or nonmetal element except K, and x is less than 1. The iron phosphate coating material is N @ FePO₄Wherein N is coated on FePO₄Metal or non-metal material on the surface of the material. The coating material of the ferric phosphate doped material is N @ K_xFePO₄、N@Fe_xM_1‑xPO₄Or N @ KFeMPO₄Wherein N is coated on K_xFePO₄、Fe_xM_1‑xPO₄Or KFeMPO₄The metal or non-metal material on the surface of the material. The ferric phosphate and ferric phosphate composite material provided by the invention has the function of storing potassium ions and then is converted into a ferric potassium phosphate or ferric potassium phosphate composite material, and the ferric potassium phosphate or ferric potassium phosphate composite material is converted into the ferric phosphate or ferric phosphate composite material by removing the potassium ions, so that the ferric phosphate and ferric phosphate composite material has the function of storing the potassium ions.

Description

Application of iron phosphate and iron phosphate composite materials as negative electrodes in potassium ion batteries

technical field

The invention belongs to the field of potassium ion batteries, and in particular relates to the application of iron phosphate and iron phosphate composite materials as negative electrodes in potassium ion batteries.

Background technique

In recent years, the energy crisis has become increasingly serious, and the demand for new energy has become increasingly urgent. Research and development of new alternative energy sources and energy conservation and emission reduction has important developmental strategic significance. As a green and environmentally friendly new energy source, lithium-ion batteries have attracted more and more attention. A new type of lithium-ion battery with high capacity, long life and high safety has become the goal pursued by people.

However, with the gradual shortage of lithium resources, lithium-ion batteries will gradually become expensive products. In this context, potassium-ion batteries will gradually increase, and their application fields will gradually expand. But the biggest problem in potassium-ion batteries is that there is no anode material that can match potassium-ion batteries. At present, there are many studies on potassium ion batteries, but there is no suitable negative electrode material to match, mainly because the diameter of potassium ions is larger than that of lithium ions. When the negative electrode material of lithium ion batteries is directly used as a negative electrode of potassium ions, it will be very unstable, and even The rapid degradation of materials occurs, leading to the rapid decay of electrochemical performance.

Therefore, it is necessary to develop a negative electrode material with a stable structure and suitable for potassium ion batteries, which can be matched with potassium ion positive electrodes to form potassium ion full batteries.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art, and provide the application of iron phosphate and iron phosphate composite materials as negative electrode materials in potassium ion batteries.

The iron phosphate and iron phosphate composite material provided by the present invention have the function of storing potassium ions, and then transform into iron potassium phosphate or iron potassium phosphate composite material, and iron potassium phosphate or iron potassium phosphate composite material are converted into iron phosphate or iron phosphate by removing potassium ions. Iron phosphate composite material, therefore has the function of storing potassium ions.

Another object of the present invention is to provide a negative electrode material for a potassium ion battery.

To achieve the above object, the present invention adopts the following technical solutions:

Application of iron phosphate and iron phosphate composite material in potassium ion battery as negative electrode material, said iron phosphate composite material includes iron phosphate doped material and coating material of iron phosphate doped material or iron phosphate coating material.

The iron phosphate and iron phosphate composite material provided by the present invention have the function of storing potassium ions, and then transform into iron potassium phosphate or iron potassium phosphate composite material, and iron potassium phosphate or iron potassium phosphate composite material are converted into iron phosphate or iron phosphate by removing potassium ions Iron phosphate composite material, therefore has the function of storing potassium ions. Both iron phosphate and iron potassium phosphate in the prior art are used as positive electrode materials. The present invention proposes for the first time that iron phosphate or iron phosphate composite materials are applied in negative electrode materials, and the obtained negative electrode materials have good electrochemical properties.

Taking iron phosphate as an example, when it is used as a negative electrode material, potassium element will be stored in the structure of iron phosphate and transformed into K _x FePO ₄ (x≤1). The K _x FePO ₄ ( _x ≤ 1) material is converted back to FePO ₄ as an electrochemical back reaction. Has the property of storing potassium. The following reaction formula can illustrate this process and is only used for the negative electrode.

FePO ₄ →K _x FePO ₄ (y≤1) Potassium storage process

K _x FePO ₄ ( _x ≤1)→FePO ₄ depotassiation process

The iron phosphate and the iron phosphate composite material provided by the invention can be used as a negative electrode, and form a potassium ion battery with other conventional positive electrode materials. Because iron phosphate and iron phosphate composite materials have the characteristics of stable structure, long cycle life, high safety and low cost, they can be widely used in potassium ion batteries and have good electrochemical performance.

It can be seen from the above that potassium can be stored and released through the basic structure of iron phosphate. If there is a negative electrode based on the basic structure of iron phosphate (the active material contains iron phosphate structure and stores potassium or partially stores potassium), it can be seen. For the scope of the present invention.

Iron phosphate contains various structures, including amorphous iron phosphate structure, olivine iron phosphate structure and other structures, all of which can be used to store potassium and be used on the negative electrode side, which should be within the protection scope of the present invention.

There are various production methods for iron phosphate, potassium iron phosphate and other derived materials, and the production methods and sources are not limited. It is considered as the scope of the present invention to apply to the negative electrode as the active material or one of the active materials.

Preferably, the iron phosphate doped material is K _x FePO ₄ , F _x M _1-x PO ₄ or KFeMPO ₄ , wherein M is other metal or non-metal material except K, and x<1. When x=1, potassium can no longer be directly stored as a negative electrode; only when the ratio of potassium in the pretreatment or synthesis process is lower than 1, the material of potassium iron phosphate (K _x FePO ₄ (where x<1)) can be Potassium is stored as an anode material.

Preferably, the iron phosphate coating material is N@FePO ₄ , wherein N is other metals or non-metallic elements coated on the surface of the FePO ₄ material.

Preferably, the coating material of the iron phosphate doped material is N@K _x FePO ₄ , N@ _Fex M _1-x PO ₄ or N@KFeMPO ₄ , wherein N is coated on K _x FePO ₄ , Other metal or non-metallic materials on the surface of Fe _x M _1-x PO ₄ or KFeMPO ₄ material.

Preferably, the ratio of M to Fe is not higher than 1:2.

Preferably, the ratio of N to Fe is not higher than 1:2.

Preferably, the N is one or more of carbon, silicon monoxide, aluminum oxide or copper oxide.

Preferably, KFeMPO ₄ or K _x FePO ₄ is subjected to depotassium treatment when preparing the negative electrode material. The depotassiation method can include electrochemical depotassiation method and chemical depotassiation method. The electrochemical method discharges the material to remove potassium ions to obtain iron phosphate; the chemical method uses an oxidant to oxidize iron potassium phosphate, the divalent iron is converted into trivalent iron, and the potassium metal is removed to obtain ferric phosphate. But the present invention is not limited to the potassium removal method.

In the present invention, the iron phosphate negative electrode material can also be obtained by depotassium, sodium and lithium treatment on potassium iron phosphate, sodium iron phosphate or lithium iron phosphate, and the potassium, sodium and lithium can be removed by electrochemical or chemical methods.

Replace the K element in potassium iron phosphate K _x FePO _{4 by} other metals _M to obtain _{Fex M 1-x PO 4} or KFeMPO ₄ ; Other metals or non-metallic elements) to extract M elements to obtain FePO ₄ . The above method can be used for potassium removal, but the present invention is not limited to the method for potassium removal.

It is also possible to replace lithium or sodium elements in lithium iron phosphate or sodium iron phosphate by other metals M to obtain iron phosphate-metal (MFePO ₄ , M is an element other than lithium and sodium metal) composite material. FePO ₄ is obtained by extracting M element from iron phosphate-metal (MFePO ₄ ) composite material. The present invention does not limit the method for removing M element from M FePO ₄ . The invention also protects a negative electrode material for a potassium ion battery. The negative electrode material includes iron phosphate or an iron phosphate composite material, and the iron phosphate composite material includes an iron phosphate doped material and a coating material of the iron phosphate doped material or iron phosphate cladding material.

Preferably, the iron phosphate doping material is K _x FePO ₄ , F _x M _1-x PO ₄ or KFeMPO ₄ , wherein M is other metal or non-metal element except K, and x<1.

One or more of the above-mentioned iron phosphate or iron phosphate composite materials are mixed with a conductive agent and a binder material and coated on a current collector to obtain a negative electrode of a potassium ion battery. The present invention has the characteristics of manufacturing the negative electrode, and the manufacturing method is the same as the manufacturing method of the negative electrode in the potassium battery, which is a general production method of the potassium ion battery.

Compared with the prior art, the present invention has the following beneficial effects:

The iron phosphate and iron phosphate composite material provided by the present invention have the function of storing potassium ions, and then transform into iron potassium phosphate or iron potassium phosphate composite material, and iron potassium phosphate or iron potassium phosphate composite material are converted into iron phosphate or iron phosphate by removing potassium ions Iron phosphate composite material, therefore has the function of storing potassium ions. The iron phosphate and the iron phosphate composite material provided by the invention can be used as a negative electrode, and form a potassium ion battery with other conventional positive electrode materials. Because iron phosphate and iron phosphate composite materials have the characteristics of stable structure, long cycle life, high safety and low cost, they can be widely used in potassium ion batteries and have good electrochemical performance.

Description of drawings

FIG. 1 is a charge-discharge curve diagram of the full battery prepared in Example 1.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments and drawings, but the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the technical field.

Unless otherwise specified, the reagents and materials used in the present invention are commercially available.

Example 1 Preparation of active material iron phosphate (FePO ₄ ) negative electrode

(1) Preparation of iron phosphate negative electrode

Mix according to the ratio (mass ratio) of iron phosphate (FePO ₄ ): carbon black: binder = 8:1:1. After mixing evenly, coat it on the current collector, dry it in vacuum and slice it to get the iron phosphate negative electrode. Electrodes are used in potassium ion batteries.

FIG. 1 is a charge-discharge curve diagram of the full battery prepared in this embodiment. A specific capacity of 121.1 mAh/g can be obtained during the first charging process, and a specific capacity of 120.6 mAh/g can be released during the first discharging process, and the first Coulombic efficiency is close to 99.8%.

Example 2 Preparation of iron phosphate negative electrode from sodium iron phosphate (Na _x FePO ₄ , x≤1) material

(1) Electrochemical method for sodium iron phosphate electrode removal

Mix according to the ratio (mass ratio) of sodium iron phosphate (Na _x FePO ₄ , x≤1): carbon black: binder = 8:1:1, after mixing evenly, apply it on the current collector, vacuum dry, After slicing, a sodium iron phosphate electrode is obtained. The sodium iron phosphate electrode and the sodium electrode are assembled into a half-cell, and the separator is a three-layer separator of PP/PE/PP, and electrolyte components are added. The structure of this battery is sodium iron phosphate positive electrode - sodium metal negative electrode. Charge the battery with a current of 0.1 C and charge the battery to 4 V. During the charging process, sodium is gradually released and transformed into iron phosphate (FePO ₄ ) or sodium iron phosphate (Na _x FePO ₄ , x≤0.2) material, the sodium content is less than 0.2.

(2) Chemical method to remove sodium iron phosphate electrode

Sodium iron phosphate (Na _x FePO ₄ , x≤1) was dissolved in acetonitrile, and excess NOBF ₄ was added for oxidation for 5 h. Remove unnecessary impurities to obtain iron phosphate (FePO ₄ ) or sodium iron phosphate (Na _x FePO ₄ , x≤0.2) material, the sodium content is less than 0.2.

(3) Mix the iron phosphate (FePO ₄ ): carbon black: binder = 8:1:1 ratio (mass ratio) prepared in (1) or (2), and coat it on the current collector after mixing evenly Above, after vacuum drying and slicing, the ferric phosphate negative electrode is obtained for the negative electrode of the potassium ion battery.

Example 3 Preparation of iron phosphate negative electrode from lithium iron phosphate (Li _x FePO ₄ , x≤1) material

(1) Electrochemical delithiation of lithium iron phosphate electrode

Mix according to the ratio (mass ratio) of lithium iron phosphate (Li _x FePO ₄ , x≤1): carbon black: binder = 8:1:1, after mixing evenly, coat it on the current collector, vacuum dry, After slicing, a lithium iron phosphate electrode is obtained. The lithium iron phosphate electrode and the lithium electrode are assembled into a half-cell, and the separator is a PP/PE/PP three-layer separator, and the electrolyte is added. The structure of this battery is lithium iron phosphate positive electrode-lithium metal negative electrode. Charge the battery with a current of 0.1 C and charge the battery to 4 V. During the charging process, lithium is gradually released and transformed into iron phosphate (FePO ₄ ) or lithium iron phosphate (Li _x FePO ₄ , x≤0.2) material, and the lithium content is lower than 0.2.

(2) Chemical delithiation of lithium iron phosphate electrode

Lithium iron phosphate (KFePO ₄ ) was dispersed in acetonitrile, and excess NOBF ₄ was added for oxidation for 5 h. Remove unnecessary impurities to obtain iron phosphate (FePO ₄ ) or lithium iron phosphate (Li _x FePO ₄ , x≤0.2) materials, and the lithium content is lower than 0.2.

(3) Mix the iron phosphate (FePO ₄ ): carbon black: binder = 8:1:1 ratio (mass ratio) prepared in (1) or (2), and coat it on the current collector after mixing evenly Above, after vacuum drying and slicing, the ferric phosphate negative electrode is obtained for the potassium ion negative electrode.

Example 4 Preparation of iron phosphate negative electrode from potassium iron phosphate (K _x FePO ₄ , x≤1) material

(1) Potassium Iron Phosphate Electrode Electrochemical Removal of Potassium

Mix according to the ratio (mass ratio) of potassium iron phosphate (K _x FePO ₄ , x≤1): carbon black: binder = 8:1:1, after mixing evenly, coat it on the current collector, vacuum dry, After slicing, a potassium iron phosphate electrode is obtained. The potassium iron phosphate electrode and the potassium electrode are assembled into a half-cell, and the separator is a three-layer separator of PP/PE/PP, and electrolyte components are added. The structure of this battery is iron potassium phosphate positive electrode-potassium metal negative electrode. Charge the battery with a current of 0.1 C and charge the battery to 4 V. During the charging process, potassium is gradually released and transformed into iron phosphate (FePO ₄ ) or iron potassium phosphate (K _x FePO ₄ , x≤0.2) material, and the potassium content is lower than 0.2.

(2) Chemical method for potassium iron phosphate electrode depotassiation

Potassium iron phosphate (KFePO ₄ ) was dispersed in acetonitrile, and excess NOBF ₄ was added for oxidation for 5 h. Remove unnecessary impurities to obtain iron phosphate (FePO ₄ ) or iron potassium phosphate (K _x FePO ₄ , x≤0.2) material, and the potassium content is lower than 0.2.

(3) Mix the iron phosphate (FePO ₄ ): carbon black: binder = 8:1:1 ratio (mass ratio) prepared in (1) or (2), and coat it on the current collector after mixing evenly Above, after vacuum drying and slicing, the ferric phosphate negative electrode is obtained for the potassium ion negative electrode.

Example 5 Preparation of Active Material Ferromanganese Phosphate (FeMnPO ₄ ) Negative Electrode

Mix according to the ratio (mass ratio) of ferromanganese phosphate (FeMnPO ₄ ): carbon black: binder = 8:1:1, after mixing evenly, coat on the current collector, vacuum dry and slice to obtain manganese phosphate Iron negative electrode.

Example 6 Preparation of active material carbon-coated iron phosphate (C@FePO ₄ ) negative electrode

Mix according to the ratio (mass ratio) of active material carbon-coated iron phosphate (C@FePO ₄ ): carbon black: binder = 8:1:1, after mixing evenly, coat it on the current collector, vacuum dry, After slicing, an iron phosphate negative electrode is obtained.

Example 7 Preparation of Active Material Carbon Coated Vanadium Iron Phosphate (C@FeVPO ₄ ) Negative Electrode

(1) Mix according to the ratio (mass ratio) of carbon-coated potassium vanadium iron phosphate (C@KFeVPO ₄ ): carbon black: binder = 8:1:1. After mixing evenly, coat it on the current collector, and pass through After vacuum drying and slicing, a negative electrode of potassium iron vanadium phosphate is obtained. The vanadium iron potassium phosphate electrode and the potassium electrode are assembled into a half-cell, and the separator is a three-layer separator of PP/PE/PP, and electrolyte components are added. The structure of this battery is Potassium Ferrovanadium Phosphate Positive Electrode - Potassium Negative Electrode. Charge the battery with a current of 0.1 C and charge the battery to 4 V. During the charging process, potassium is gradually released and transformed into ferrovanadium phosphate (FeVPO ₄ ) material.

(2) Mix the ferrovanadium phosphate (FeVPO ₄ ) prepared above: carbon black: binder = 8:1:1 ratio (mass ratio), mix evenly, coat on the current collector, and vacuum dry After slicing, the iron vanadium phosphate negative electrode is obtained.

The above summary of the invention and the present invention mainly solve the problem of using the prepared ferric phosphate material for the negative electrode and for the potassium ion battery. The electrochemical and chemical methods for delithiation, depotassium, and depotassium in the above examples are not within the scope of the present invention, and are only used as pretreatment methods for materials.

In the present invention, the ferric phosphate material is used to prepare the negative electrode of the potassium ion battery. The ferric phosphate and ferric phosphate-derived materials used are not limited to the production method, and the preparation method of the material does not belong to the content of the present invention. The content of the present invention is only to These materials are used to prepare negative electrodes and are used in the field of potassium ion batteries, solving the problem that there is no matching negative electrode material for potassium ion batteries before.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the scope of the present invention. Protection scope, within the spirit and principles of the present invention, any modification, equivalent replacement, improvement, etc., shall be included in the protection scope of the present invention.

Claims (10)

1. the application of ferric phosphate and phosphoric acid iron composite material as negative material in kalium ion battery, which is characterized in that described Phosphoric acid iron composite material includes ferric phosphate dopant material and the covering material of ferric phosphate dopant material or ferric phosphate covering material.

It 2. applies according to claim 1, which is characterized in that the ferric phosphate dopant material is K_xFePO₄、Fe_xM_1-xPO₄Or KFeMPO₄, wherein, M is other metals or nonmetalloid in addition to K, x ＜ 1.

It 3. applies according to claim 1, which is characterized in that the ferric phosphate covering material is N@FePO₄, wherein, N is bag Overlay on FePO₄The metal or nonmetallic materials of material surface.

It 4. applies according to claim 1, which is characterized in that the covering material of the ferric phosphate dopant material is N@ K_xFePO₄、N@Fe_xM_1-xPO₄Or N@KFeMPO₄, wherein, N is to be coated on K_xFePO₄、Fe_xM_1-xPO₄Or KFeMPO₄Material surface Metal or nonmetallic materials.

5. according to the application of claim 3 or 4, which is characterized in that the ratio of M and Fe is not higher than 1：2.

It 6. applies according to claim 4, which is characterized in that the ratio of N and Fe is not higher than 1：2.

7. according to the application of claim 3 or 4, which is characterized in that the N is charcoal, silicon monoxide, alundum (Al2O3) or oxidation One or more of copper.

It 8. applies according to claim 2, which is characterized in that when preparing negative material to KFeMPO₄Or K_xFePO₄It carries out De- potassium processing.

9. a kind of kalium ion battery negative material, which is characterized in that the negative material includes ferric phosphate or ferric phosphate composite wood Material, the phosphoric acid iron composite material include covering material or the ferric phosphate cladding of ferric phosphate dopant material and ferric phosphate dopant material Material.

10. kalium ion battery negative material according to claim 9, which is characterized in that the ferric phosphate dopant material is K_xFePO₄、Fe_xM_1-xPO₄Or KFeMPO₄, wherein, M is other metals or nonmetalloid in addition to K, x ＜ 1.