CN110416528A - A kind of potassium ion battery - Google Patents

Abstract

The invention relates to the field of electrochemistry, in particular to a potassium ion battery. The potassium ion battery provided by the invention includes a positive pole, a negative pole and an electrolyte; the positive pole includes a positive electrode material of the potassium ion battery; the negative electrode active material layer of the negative pole is a GeP ₅ compound. The invention solves the problems of low specific capacity, low conductivity of elemental phosphorus and phosphide, and poor cycle performance of carbon-based negative electrode materials in potassium ion batteries in the prior art, and provides a new type of negative electrode material for potassium ion batteries.

Description

A kind of potassium ion battery

technical field

The invention relates to the field of electrochemistry, in particular to a potassium ion battery.

Background technique

With the increasing demand for electric vehicles and large-scale energy storage devices, lithium-ion batteries have dominated portable devices and electric vehicles in recent years. However, due to the limited resources of lithium elements, it is gradually becoming a trend to expand cost-effective battery alternatives. Sodium and potassium have attracted attention because of their similar properties to lithium and their abundance in soil. However, Na-ion batteries often suffer from insufficient operating voltage due to their low energy density. In the application of potassium-ion batteries, carbon-based anode materials are widely used in potassium-ion battery anodes because of their excellent cycle performance and reversible potassium storage capacity. However, there are still obstacles for its industrial application due to factors such as low specific capacity and low energy density due to its excessively high operating voltage. Phosphorus, as a substitute for anode materials, is considered to have a very broad application prospect due to its high theoretical specific capacity (2594mAh/g). However, the conductivity of elemental phosphorus is low and the volume expansion of potassium storage is large. In order to overcome these shortcomings, alloy-based phosphides such as NiP ₂ , Se ₄ P ₄ , Sn ₄ P ₃ and SnP ₃ , because of their metal characteristics and synergistic reaction mechanism and other characteristics have been introduced into the negative electrode material of potassium ion battery, but due to its low phosphorus content, the potassium ion battery using it as the negative electrode has low capacity and poor cycle performance.

Contents of the invention

In view of this, the present invention provides a potassium-ion battery, which solves the problem that the carbon-based negative electrode material in the potassium-ion battery in the prior art is too low in specific capacity and energy density due to its excessively high operating voltage, and that the alloy-based phosphorus The low phosphorus element in the compound leads to the technical problems of low capacity and poor cycle performance of the potassium ion battery.

The invention provides a potassium ion battery, comprising a positive pole, a negative pole and an electrolyte;

The positive electrode includes a potassium ion battery positive electrode material;

The negative electrode active material layer of the negative electrode is a GeP ₅ compound.

Preferably, the electrolyte of the electrolytic solution is potassium fluorosulfonimide.

Preferably, the solvent of the electrolyte includes ethylene carbonate and/or ethylene carbonate.

Preferably, the preparation method of the GeP ₅ compound includes mixing germanium powder and phosphorus powder at a molar ratio of 1:5 and performing ball milling.

Preferably, the ball-to-material ratio of the ball mill is 20:1.

Preferably, the ball milling time is 5-10 hours.

Preferably, the rotational speed of the ball mill is 900-1200r/min.

Preferably, the negative electrode further includes a binder and a current collector, and the negative electrode active material layer is bonded on the surface of the current collector through the binder.

Preferably, the binder is selected from polyvinylidene fluoride, polytetrafluoroethylene, lithium polyacrylate, polyvinyl alcohol, sodium carboxymethyl cellulose, polyurethane or styrene-butadiene rubber.

More preferably, the binder is lithium polyacrylate.

Preferably, the current collector is selected from copper foil, aluminum foil, nickel foil, copper mesh, aluminum mesh or nickel mesh.

More preferably, the current collector is copper foil.

The invention provides a potassium ion battery, the negative active material layer of which is GeP ₅ compound, because the P element content in GeP ₅ is relatively high, each phosphorus ion (P ^3- ) can store 3 potassium ions (K ⁺ ), When GeP ₅ is used as the negative electrode of potassium ion battery, it can store more potassium ions. Combined with its special layered structure and metal conductivity, it can significantly improve the theoretical specific capacity and reaction of potassium ion battery when it is used as the negative electrode of potassium ion battery. active. In addition, due to the strong electronegativity of phosphorus, GeP ₅ has higher potassium storage activity, which can further improve the performance of the battery.

The experimental results of the present invention show that the GeP ₅ compound prepared by the present invention has higher purity, and when it is used as the negative electrode active material of a potassium ion battery, its initial discharge capacity is 1400mAh/g, and after 2000 cycles at a high current density of 500mA/g , its potassium storage capacity remains at 200mAh/g, and the capacity retention rate is high, indicating that the potassium ion battery has good potassium storage performance and cycle stability.

Description of drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings that are required in the description of the embodiments or the prior art.

Fig. 1 is the X-ray diffraction figure of GeP ₅ compound of the present invention;

Fig. 2 is the scanning electron micrograph of GeP ₅ compound of the present invention;

Fig. 3 is the transmission electron microscope figure of GeP ₅ compound of the present invention;

Fig. 4 is a cycle performance test diagram of Example 2 of the present invention.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by persons of ordinary skill in the art without making creative efforts all belong to the protection scope of the present invention.

The invention provides a negative electrode material for a potassium ion battery, which is made into a negative electrode and used in a potassium ion battery, which solves the problem of low capacity and poor cycle performance of the potassium ion battery in the prior art due to too low a phosphorus element technical problem.

In order to further understand the present application, the lithium-ion/sodium-ion battery negative electrode material provided by the present application will be specifically described below in conjunction with examples.

Example 1

Add germanium powder with a purity of 99.9% and phosphorus powder with a purity of 99.8% to the ball mill tank at a molar ratio of 1:5, using a ball-to-material ratio of 20:1, and at a speed of 900-1200r/min, ball mill for 5- Obtain GeP ₅ compound after 10 hours, Fig. 1 is the X-ray diffraction pattern of GeP ₅ compound, as can be seen from the figure, its diffraction peak corresponds to standard card (PDF-24-0455), shows that the material synthesized is GeP ₅ and higher purity.

Figure 2 is a scanning electron microscope image of GeP ₅ compound, and Figure 3 is a transmission electron microscope image of GeP ₅ compound. It can be seen from Figure 2 and Figure 3 that the synthesized GeP ₅ compound is a bulk material with a small particle size of about 500nm, which is beneficial to relieve the stress caused by the volume expansion after potassium storage, thereby preventing the material from cracking.

Example 2

Lithium polyacrylate is used as binder, conductive carbon black is used as conductive agent, copper foil is used as current collector, and the prepared GeP ₅ compound is used as negative electrode active material layer, and lithium polyacrylate is bonded on the surface of copper foil to obtain Potassium ion battery negative electrode. In the electrochemical performance test of the potassium ion battery, the negative electrode of the above potassium ion battery and metal potassium were made into a GeP ₅ -K button battery, and potassium hexafluorophosphate-ethylene carbonate/diethyl carbonate (KPF ₆ - EC/DEC), potassium difluorosulfonimide-ethylene carbonate/ethylene carbonate (KFSI-EC/DEC), potassium hexafluorophosphate-ethylene carbonate/diethyl carbonate/fluoroethylene carbonate (KPF ₆ -EC/DEC/FEC), Potassium bisfluorosulfonimide-ethylene carbonate/ethylene carbonate/fluoroethylene carbonate (KFSI-EC/DEC/FEC) was used as the electrolyte to test its cycle performance.

Fig. 4 is a cycle performance test diagram of Example 2 of the present invention. It can be seen from the figure that the electrode mixed with the electrolyte of fluoroethylene carbonate (FEC) has a low initial specific capacity and decays rapidly after 800-1000 cycles. It shows that the addition of fluoroethylene carbonate (FEC) will lead to the formation of excess fluoride, resulting in a larger irreversible capacity. And in the case of not adding fluoroethylene carbonate FEC, in the electrolyte potassium hexafluorophosphate-ethylene carbonate/diethyl carbonate (KPF ₆ -EC/DEC), the battery capacity of the battery after 200 cycles Unstable changes appear, which indicates that the GeP ₅ electrode has poor cycle stability when an unstable SEI film is formed on the surface, which leads to excessive side reactions in the battery and deactivation of the battery.

When the potassium-ion battery uses KFSI-EC/DEC as the electrolyte, the first cycle of charge and discharge is carried out at a current density of 50mA/g, and its initial discharge capacity is 1400mAh/g, and then it is cycled at a current density of up to 500mA/g After 2000 cycles, its potassium storage capacity remained at 200mAh/g, indicating that when KFSI is used as the electrolyte, a uniform solid electrolyte interface layer can be formed on the electrode surface, thereby inhibiting the occurrence of side reactions, which makes the GeP ₅ compound a negative electrode for potassium-ion batteries The material has good potassium storage performance and cycle stability when used.

Apparently, the above-described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

Claims (10)

1. a kind of kalium ion battery, which is characterized in that including anode, cathode and electrolyte；

The anode includes kalium ion battery positive electrode；

The anode active material layer of the cathode is GeP₅Compound.

2. a kind of kalium ion battery according to claim 1, which is characterized in that the electrolyte of the electrolyte is fluorine sulphonyl Imines potassium.

3. a kind of kalium ion battery according to claim 1, which is characterized in that the solvent of the electrolyte includes carbonic acid second Enester and/or ethylene carbonate.

4. a kind of kalium ion battery according to claim 1, which is characterized in that the GeP₅The preparation method packet of compound Include that 1:5 is mixed and carried out ball milling in molar ratio by germanium powder and phosphorus powder.

5. a kind of kalium ion battery according to claim 4, which is characterized in that the ratio of grinding media to material of the ball milling is 20:1.

6. a kind of kalium ion battery according to claim 4, which is characterized in that the time of the ball milling is 5~10h.

7. a kind of kalium ion battery according to claim 4, which is characterized in that the revolving speed of the ball milling be 900~ 1200r/min。

8. a kind of kalium ion battery according to claim 1, which is characterized in that the cathode further includes binder and afflux Body, the anode active material layer are bonded on the surface of the collector by the binder.

9. a kind of kalium ion battery according to claim 8, which is characterized in that the binder be selected from Kynoar, Polytetrafluoroethylene (PTFE), Lithium polyacrylate, polyvinyl alcohol, sodium carboxymethylcellulose, polyurethane or butadiene-styrene rubber.

10. a kind of kalium ion battery according to claim 8, which is characterized in that the collector be selected from copper foil, aluminium foil, Nickel foil, copper mesh, aluminium net or nickel screen.