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CN-116338123-B - Method for judging bulk phase structural stability of positive electrode material of sodium ion battery

CN116338123BCN 116338123 BCN116338123 BCN 116338123BCN-116338123-B

Abstract

The invention provides a method for judging bulk phase structural stability of a positive electrode material of a sodium ion battery, which comprises the following steps of (1) dividing the positive electrode material of the sodium ion battery into 2 groups, respectively mixing the positive electrode material of the sodium ion battery with ultrapure water to obtain a suspension 1 and a suspension 2, (2) respectively stirring the suspension 1 and the suspension 2, carrying out one-step standing on the suspension 1, testing the pH of a supernatant, transferring the suspension 2 to a closed container, carrying out two-step standing on the supernatant, testing the pH of the supernatant, and judging the bulk phase structural stability of the positive electrode material of the sodium ion battery according to the pH difference of the suspension 1 and the suspension 2.

Inventors

  • ZHOU SHIBO
  • JIANG WEIJUN
  • CHEN SIXIAN
  • HE SHUANG

Assignees

  • 蜂巢能源科技股份有限公司

Dates

Publication Date
20260512
Application Date
20230322

Claims (9)

  1. 1. A method for determining bulk structural stability of a positive electrode material of a sodium ion battery, the method comprising the steps of: (1) Dividing the positive electrode material of the sodium ion battery into 2 groups, and respectively mixing with ultrapure water to obtain a suspension 1 and a suspension 2; (2) Respectively stirring the suspension 1 and the suspension 2, carrying out one-step standing on the suspension 1, testing the pH of the supernatant, carrying out two-step standing after the suspension 2 is transferred to a closed container, testing the pH of the supernatant, and judging the bulk phase structural stability of the positive electrode material of the sodium ion battery according to the difference value between the suspension 1 and the suspension 2 pH; the stirring treatment time in the step (2) is 8-12 min; the two-step standing time in the step (2) is 20-30 hours; And (3) the difference value between the suspension 1 and the suspension 2 pH in the step (2) is less than or equal to 1.1, and the bulk phase structural stability of the positive electrode material of the sodium ion battery is higher.
  2. 2. The method of claim 1, wherein the sodium ion battery positive electrode material of step (1) comprises a sodium ion battery transition metal layered oxide positive electrode material.
  3. 3. The method of claim 2, wherein the sodium ion battery transition metal layered oxide positive electrode material comprises one or more of sodium nickel iron manganese oxide, sodium nickel cobalt manganese oxide, sodium iron cobalt manganese oxide, sodium nickel copper iron magnesium acid.
  4. 4. The method of claim 1, wherein the mass concentration of the sodium ion battery cathode material in the suspension 1 and the suspension 2 in step (1) is the same.
  5. 5. The method of claim 1, wherein the mass concentration of the sodium ion battery positive electrode material in the suspension 1 and the suspension 2 is 50-150 g/L.
  6. 6. The method of claim 1, wherein the stirring process in step (2) is performed at a speed of 100 to 800rpm.
  7. 7. The method of claim 1, wherein the one-step standing time of step (2) is 20-40 min.
  8. 8. The method of claim 1, wherein the difference between the suspension 1 and the suspension 2 pH in step (2) is less than or equal to 0.5, and the bulk structural stability of the positive electrode material of the sodium ion battery is higher.
  9. 9. The method according to claim 1, characterized in that the method comprises the steps of: (1) Dividing the positive electrode material of the sodium ion battery into 2 groups, and respectively mixing the positive electrode material with ultrapure water to obtain a suspension 1 and a suspension 2 with the same mass concentration of 50-150 g/L; (2) And respectively stirring the suspension 1 and the suspension 2 at 500-600 rpm for 8-12 min, standing the suspension 1 for 20-40 min, testing the pH of the supernatant, transferring the suspension 2 to a closed container, standing for 20-30 h, testing the pH of the supernatant, and judging the bulk phase structural stability of the positive electrode material of the sodium ion battery according to the difference value between the suspension 1 and the suspension 2 pH.

Description

Method for judging bulk phase structural stability of positive electrode material of sodium ion battery Technical Field The invention belongs to the technical field of sodium ion batteries, and relates to a method for judging bulk phase structural stability of a positive electrode material of a sodium ion battery. Background Since the advent of lithium ion batteries in 1990, the performance of lithium ion batteries has been increasingly excellent as they have been studied intensively, and thus, lithium ion batteries are widely used in various fields such as 3C, electric vehicles, energy storage, and the like. With the increasing concern about pollution caused by fossil energy use and the global electromotive society, the use of highly reliable and highly stable chemical power sources by human beings is increasing. Although lithium ion batteries have a series of advantages of higher energy density, longer cycle life and the like, the global reserves of lithium resources are less (the relative abundance in the crust is only 20 ppm), and as the application amount increases, the lithium resources are more and more expensive, and the lithium ion batteries are more and more difficult to meet the demands of people for obtaining reliable, convenient and stable energy sources at low cost. As an alkali metal element, sodium ions have chemical characteristics similar to those of lithium ions, the sodium elements are low in cost and wide in global steps, and development and utilization of the sodium elements are not limited due to factors such as cost, insufficient resources and the like, so that the sodium ion battery can be used as a supplement of the lithium ion battery and can be widely applied to various application scenes with low energy density requirements. Currently, three main development directions of the positive electrode material of the sodium ion battery are transition metal layered oxides, polyanions and Prussian blue/white respectively. The transition metal oxide material has the characteristics of simple material preparation process, high operation voltage, high energy density, long cycle life and the like, so that the transition metal oxide material has the best development prospect. Although the material has many advantages, the material has problems in practical application, such as increased residual alkali on the surface, poor structural stability caused by proton exchange after contacting with water in the environment, and obviously deteriorated processing and electrical properties of the material, which is unfavorable for mass use. The conventional method for judging the stability of the transition metal layered oxide cathode material mainly comprises the steps of assembling the cathode material into a battery, performing cycle performance test, comparing through ① cycle life decay curves, performing XRD or dQ/dV test on the cathode material/pole piece subjected to different cycle times by ②, and representing the stability of different materials through the change of the characteristic peak intensity and displacement of the material. Although the two methods are more accurate, as the positive electrode materials are assembled into the buckling/battery and tested under a certain cycle life, XRD or dQ/dV test can be performed, the method is used for judging the bulk stability of the materials, which is not beneficial to widely screening and verifying a large number of transition metal layered oxide positive electrode materials, and is not beneficial to screening materials with better bulk structure stability for cell design and product development. Disclosure of Invention The invention aims to provide a method for judging bulk phase structural stability of a positive electrode material of a sodium ion battery, which does not need to assemble and buckling electricity, carry out cycle life, XRD and other project tests, can conveniently and rapidly judge whether the bulk phase stability of different sodium-electricity transition metal layered oxide positive electrode materials is good or not qualitatively, thereby shortening the screening time and the product development time of the positive electrode material, effectively reducing the cost required by product development and having better effect. In order to achieve the aim of the invention, the invention adopts the following technical scheme: In a first aspect, the present invention provides a method for determining bulk structural stability of a positive electrode material of a sodium ion battery, the method comprising the steps of: (1) Dividing the positive electrode material of the sodium ion battery into 2 groups, and respectively mixing with ultrapure water to obtain a suspension 1 and a suspension 2; (2) And respectively stirring the suspension 1 and the suspension 2, carrying out one-step standing on the suspension 1, testing the pH value of the supernatant, carrying out two-step standing after the suspension 2 is transferred to a closed co