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Method for detecting SEI film on electrode surface of lithium ion battery

A lithium-ion battery and electrode surface technology, applied in the field of lithium-ion batteries, can solve the problems of affecting the content of SEI film, interference of heat signal of SEI film, complex chemical reaction, etc., and achieve the effects of low cost, small interference and simple detection method.

Pending Publication Date: 2022-04-22
TSINGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] Profatilova and Zhao et al. used the DSC method to study the thermal stability of Si anode materials, and observed that there was an exothermic reaction in the discharged Si material (LixSi) in the range of 80-130°C. Referring to the research on graphite-based anode materials, it was believed that This is caused by the transformation of the SEI film structure on the surface of the material, and the chemical reaction that occurs is more complicated
[0004] It should be noted that in the current literature reports on the thermal stability of graphite negative electrode materials, more electrolytes are added to simulate the real internal environment of the battery. reaction, which will interfere with the thermal signal of the SEI film, thus affecting the judgment of the content of the SEI film

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  • Method for detecting SEI film on electrode surface of lithium ion battery
  • Method for detecting SEI film on electrode surface of lithium ion battery
  • Method for detecting SEI film on electrode surface of lithium ion battery

Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0069] The test of SEI film in the graphite negative electrode lithium battery of embodiment 1

[0070] Disassemble graphite negative lithium-ion batteries whose SEI mass ranges from 0.54 to 0.93 mg, and then soak and wash the disassembled negative electrode with DMC for 3 times, and store the washed negative electrode in an argon atmosphere glove box. Vacuum dry in the transition chamber for 12 hours at a drying temperature of 30°C, and then cut the dried negative electrode sheet into a square of 1×1 cm as the electrode sheet to be tested.

[0071] Assemble the cut pole piece to be detected and the metal lithium piece into a button battery in a glove box, and 2 It is discharged under the current density to obtain the negative electrode sheet with the same charge state.

[0072] Disassemble the above-mentioned negative electrode sheet with the same charge state from the button battery, soak and wash it with DMC for 3 times, and vacuum-dry the washed negative electrode sheet i...

Embodiment 2

[0077] Example 2 The test of nanometer hollow silicon negative electrode (NHSi) lithium-ion battery SEI film

[0078] The charge and discharge cycles were 10 times, 20 times, 30 times, 50 times and 100 times respectively, and the charge and discharge voltage range was 0.05-1.5V (vs Li / Li + ), the activation current density was 100mA·g in the first three weeks -1 , the subsequent cycle current density is 500mA·g -1 Nano-hollow silicon anode (NHSi) lithium-ion battery with 100mA·g -1 Disassemble after discharging to 0.01V, soak and wash the disassembled negative electrode with DMC for 3 times, and vacuum-dry the washed negative electrode (circular electrode with a diameter of 10mm) in an argon atmosphere glove box transition chamber 12h, the drying temperature is 30°C.

[0079] Scrape off the sample powder from the negative plate and seal them all into a high-pressure gold-plated crucible. In order to prevent the material from reacting with the air during the test, the qualit...

Embodiment 3

[0081] The test of SEI film in the embodiment 3 nano silicon negative electrode (Nano Si) lithium-ion battery

[0082] Repeat the test process of embodiment 2, the difference is only: the negative electrode material to be tested is solid nano-silicon, and its DSC curve is as follows image 3 shown.

[0083] image 3The exothermic peak of the SEI film is at 50-150°C, and the exothermic peak area of ​​the SEI film in the Nano Si negative electrode sheet increases with the increase in the number of cycles, that is, the content and thickness of the SEI film continue to increase. Ordinary nano-solid silicon anodes undergo an alloying reaction with Li during charge and discharge, accompanied by a huge volume expansion, which can reach a maximum of 300%. Therefore, the SEI film on the surface of the material can never obtain a stable structure. With the expansion and contraction of the silicon material, it is constantly cracked and regenerated. This process continues to consume act...

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Abstract

The invention provides a lithium ion battery electrode surface SEI film detection method, which mainly analyzes the relationship between the SEI film quality and the heat release amount through a differential scanning calorimeter, and mainly comprises the following steps: firstly, disassembling, washing and drying a battery to be detected, then assembling the obtained electrode slices into a button cell for discharging, and finally detecting the SEI film on the surface of the lithium ion battery electrode. A DSC test is carried out on the fully discharged electrode plate, finally a DSC spectrogram is analyzed, an exothermic peak in the range of 100-150 DEG C is integrated to obtain the exothermic quantity of the SEI film, the exothermic quantity is in direct proportion to the content of the exothermic quantity, and therefore the exothermic quantity of the SEI film serves as semi-quantitative data of the content of the exothermic quantity. The SEI film testing method is simple, semi-quantitative detection of the SEI film can be achieved through a conventional DSC testing instrument, and the SEI film testing method has the advantages of being low in cost, small in environmental interference, high in accuracy and repeatability and the like.

Description

technical field [0001] The invention belongs to the field of lithium ion batteries, and in particular relates to a method for detecting an SEI film on the electrode surface of a lithium ion battery. Background technique [0002] The SEI film is a solid electrolyte film formed on the surface of the negative electrode during the first discharge of the battery. It can effectively prevent solvent molecules from intercalating into the negative electrode material while allowing lithium ions to pass through freely. The volume change of the negative electrode material during charging and discharging will cause the rupture of the SEI film, and a new SEI film will be formed on the surface of the active material exposed to the electrolyte. This process will lead to excessive growth of the SEI film and increase the internal resistance of the battery. The thickening of SEI is the main reason for the capacity fading of lithium-ion battery anode materials, which mainly affects the battery ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N25/20
CPCG01N25/20Y02E60/10
Inventor 邱新平徐涵颖韩策李杰
Owner TSINGHUA UNIV