A device and method for studying the dissolution of transition metals in lithium-ion batteries

Abstract

The present invention relates to the technical field of lithium-ion batteries, and specifically to a device and method for studying the dissolution of transition metals in lithium-ion batteries. The device comprises a lithium-ion battery, a buffer bottle, and a transition metal detection device. The housing of the lithium-ion battery is provided with an electrolyte outlet and an electrolyte inlet. The buffer bottle contains electrolyte, and the electrolyte in the buffer bottle is the same as the electrolyte in the lithium-ion battery. The buffer bottle is provided with: an inlet pipe with one end extending into the buffer bottle and connected to the electrolyte outlet; a first outlet pipe with one end extending below the liquid surface and connected to the electrolyte inlet; an air inlet pipe with one end extending above the liquid surface and connected to an air source; and a second outlet pipe with one end extending below the liquid surface and connected to a transition metal detection device. The device and method can realize real-time detection of the dissolution of transition metals in lithium-ion batteries under different conditions, which is of great significance for studying the performance degradation of batteries containing transition metals.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a device and method for studying the dissolution of transition metals in lithium ion batteries. Background Art

[0002] Lithium-ion batteries have many outstanding advantages and are widely used in many fields. As the most important cathode material in lithium-ion batteries, transition metals are an important element in the valence reaction. From the initial lithium manganese oxide (LiMn2O 4) , lithium iron phosphate (LiFePO4) to the most important nickel cobalt manganese (LiNi x Co y Mn y O2) ternary positive electrode materials, to the low-cobalt or cobalt-free manganese-rich positive electrode materials that may be developed in the future, but the positive electrode materials containing transition metals will inevitably experience the phenomenon of transition metal ion dissolution in the electrochemical environment. On the one hand, the dissolved transition metals destroy the structural stability of the original positive electrode material and thus affect the battery life. On the other hand, the dissolved transition metal ions will migrate and deposit on the surface of the negative electrode material, catalyzing the decomposition and regeneration of the SEI film, resulting in the continuous loss of reversible lithium ions, and ultimately leading to a decline in the overall performance of the battery.

[0003] Research on transition metal ion dissolution in batteries containing transition metal cathode materials helps qualitatively and quantitatively determine the impact of transition metal dissolution on battery performance and can provide effective solutions to mitigate transition metal dissolution. ICP-AES and ICP-AAS are the most common instruments and methods for detecting transition metal dissolution in batteries, but pre-treatment is complex, time-consuming, and unable to provide online, real-time data. Summary of the Invention

[0004] The purpose of the present invention is to provide a device and method for studying the dissolution behavior of transition metals in lithium-ion batteries, which is of great significance for studying the attenuation of battery performance in lithium-ion batteries containing transition metals, and effective battery life improvement measures can be proposed based on the research results.

[0005] Specifically, the present invention provides the following technical solutions:

[0006] A device for studying the dissolution of transition metals in lithium-ion batteries, comprising a lithium-ion battery, a buffer bottle, and a transition metal detection device;

[0007] The shell of the lithium-ion battery is provided with an electrolyte outlet and an electrolyte inlet;

[0008] The buffer bottle contains an electrolyte, and the electrolyte in the buffer bottle is the same as the electrolyte in the lithium-ion battery;

[0009] The buffer bottle is provided with: a liquid inlet pipe with one end extending into the buffer bottle and connected to the electrolyte outlet at the other end; a first liquid outlet pipe with one end extending below the liquid level of the electrolyte in the buffer bottle and connected to the electrolyte inlet at the other end; an air inlet pipe with one end extending above the liquid level of the electrolyte in the buffer bottle and connected to the gas source at the other end; and a second liquid outlet pipe with one end extending below the liquid level of the electrolyte in the buffer bottle and connected to the transition metal detection equipment.

[0010] Preferably, in the above-mentioned device for studying the dissolution of transition metals in lithium-ion batteries, the lithium-ion battery is a liquid lithium-ion battery or a quasi-solid-state lithium-ion battery.

[0011] Preferably, in the above-mentioned device for studying the dissolution of transition metals in lithium-ion batteries, the lithium-ion battery is a soft-pack lithium battery.

[0012] Preferably, in the above-mentioned device for studying the dissolution of transition metals in lithium-ion batteries, the electrolyte outlet is arranged on the upper side of the side wall of the shell, and the electrolyte inlet is arranged on the lower side of the side wall of the shell. Further preferably, the electrolyte outlet and the electrolyte inlet are arranged diagonally.

[0013] Preferably, in the above-mentioned device for studying the dissolution of transition metals in lithium-ion batteries, a first peristaltic pump is provided on the connecting pipeline between the electrolyte outlet and the liquid inlet pipe, and a second peristaltic pump is provided on the connecting pipeline between the electrolyte inlet and the first liquid outlet pipe.

[0014] In the above device, the internal core structure of the lithium-ion battery is exactly the same as that of the actual lithium-ion battery, which ensures the practical significance of the research results. The outer packaging is connected to hoses at the bottom and diagonally above the openings, and the hoses are connected to a peristaltic pump. The peristaltic pump controls the replacement speed of the lithium-ion battery electrolyte. The other end of the hose is connected to the two interfaces of the buffer bottle respectively. The buffer bottle contains the same electrolyte as the lithium-ion battery to form a replacement with the lithium-ion battery. The other two interfaces above the buffer bottle are connected to ultra-pure dry inert gas and transition metal ion detection equipment respectively. When performing transition metal ion testing, the peristaltic pump is turned off and a quantitative amount of the electrolyte to be tested is injected into the transition metal ion detection equipment through ultra-pure dry inert gas, thereby achieving the purpose of real-time detection of the dissolution status of transition metal ions.

[0015] Preferably, in the above-mentioned device for studying the dissolution of transition metals in lithium-ion batteries, the transition metal detection equipment is an ion chromatography or an inductively coupled plasma mass spectrometry.

[0016] The present invention also provides a method for studying the dissolution of transition metals in lithium-ion batteries using the above-mentioned device, comprising the following steps:

[0017] (1) placing the lithium-ion battery at a certain ambient temperature or supplying power to a load; turning on a first peristaltic pump to allow the electrolyte in the lithium-ion battery to flow into the buffer bottle through the liquid inlet pipe; turning on a second peristaltic pump to allow the electrolyte in the buffer bottle to flow into the lithium-ion battery through the first liquid outlet pipe;

[0018] (2) After a period of time, the lithium-ion battery is left at room temperature or stops supplying power to the load;

[0019] (3) After maintaining for a period of time, the first peristaltic pump and the second peristaltic pump are turned off, and then the inert gas is allowed to flow into the buffer bottle through the air inlet pipe, thereby forcing the electrolyte in the buffer bottle to flow into the transition metal detection device through the second liquid outlet pipe to detect the dissolution status of the transition metal in the electrolyte.

[0020] Preferably, in the above method for studying the dissolution of transition metals in lithium-ion batteries, the certain ambient temperature is -40 to 60°C.

[0021] Preferably, in the above-mentioned method for studying the dissolution of transition metals in lithium-ion batteries, the mass of the electrolyte in the buffer bottle is 5 to 10 times the mass of the electrolyte in the lithium-ion battery.

[0022] Preferably, in the above-mentioned method for studying the dissolution of transition metals in lithium-ion batteries, the flow rates of the first peristaltic pump and the second peristaltic pump are the same. Further preferably, the flow rates of the first peristaltic pump and the second peristaltic pump are both 0.1 to 100 mL / min.

[0023] The beneficial effects achieved by the present invention are:

[0024] The device and method provided by the present invention can realize real-time detection of transition metal dissolution conditions of lithium-ion batteries under different conditions (such as storage under different charge states, storage at different temperatures, normal high-temperature cycling, etc.), thereby providing reliable test results for studying transition metal dissolution in positive electrode materials. This is of great significance for studying the performance degradation of lithium-ion batteries containing transition metals, and effective battery life improvement measures can be proposed based on the research results. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the device described in Example 1 of the present invention; wherein, 1, lithium-ion battery, 2, buffer bottle, 3, transition metal detection equipment, 4, first peristaltic pump, 5, second peristaltic pump.

[0026] Figure 2 The electrolyte sample test results in Example 2; wherein, 1, Li + , 2. Fe 3+ 3. Ni2+ , 4. Co 2+ , 5, Mn 2+ , 6.Fe 2+ . DETAILED DESCRIPTION

[0027] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or the product instructions were used.

[0028] In the description of the present invention, unless otherwise specified, the terms "upper" and "lower" and the like indicate positions or state relationships based on the positions or state relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific position, be constructed and operate in a specific position, and therefore cannot be understood as a limitation on the present invention.

[0029] In the following examples, all instruments used without manufacturer indication are conventional products that can be purchased through regular channels. The methods described are conventional methods unless otherwise specified, and the raw materials described are commercially available unless otherwise specified.

[0030] Example 1 Research device

[0031] like Figure 1 As shown, Example 1 provides an apparatus for studying the dissolution of transition metals in lithium-ion batteries, comprising a lithium-ion battery 1, a buffer bottle 2, and a transition metal detection device 3. The lithium-ion battery 1 is a self-made 20Ah lithium-ion battery, with a positive electrode made of a ternary material of lithium nickel-cobalt-manganese oxide mixed with lithium iron phosphate, a negative electrode made of a silicon-based negative electrode, and an electrolyte composition of 1 mol / L LiPF6 in EC:EMC:DEC:FEC = 30:25:25:20. The electrolyte content in the battery is 2 g / Ah. The transition metal detection device 3 is an ion chromatograph.

[0032] The lithium-ion battery 1 is provided with an electrolyte outlet above the side wall of the housing and an electrolyte inlet diagonally below;

[0033] The buffer bottle 2 contains unused electrolyte, and the electrolyte in the buffer bottle 2 is the same as the electrolyte in the lithium-ion battery 1 ; the electrolyte in the buffer bottle 2 is 6 times the electrolyte in the lithium-ion battery 1 .

[0034] The bottle cap of the buffer bottle 2 is provided with four well-sealed plug-in tubes: one end is extended below the liquid level of the electrolyte in the buffer bottle 2, and one end is connected to the liquid inlet pipe of the electrolyte outlet through the first peristaltic pump 4; one end is extended below the liquid level of the electrolyte in the buffer bottle 2, and one end is connected to the first liquid outlet pipe of the electrolyte inlet through the second peristaltic pump 5; one end is extended above the liquid level of the electrolyte in the buffer bottle 2, and one end is connected to the air inlet pipe of the gas source Gas; one end is extended below the liquid level of the electrolyte in the buffer bottle 2, and one end is connected to the second liquid outlet pipe of the transition metal detection equipment 3.

[0035] Example 2 Research Methods

[0036] The method for studying the dissolution of transition metals in lithium-ion batteries using the device described in Example 1 comprises the following steps:

[0037] (1) subjecting the lithium-ion battery 1 to a 1C charge-discharge cycle at 45°C, turning on the first peristaltic pump 4 to allow the electrolyte in the lithium-ion battery 1 to flow into the buffer bottle 2 through the liquid inlet pipe; turning on the second peristaltic pump 5 to allow the electrolyte in the buffer bottle 2 to flow into the lithium-ion battery 1 through the first liquid outlet pipe; the flow rates of the first peristaltic pump and the second peristaltic pump are both 10 mL / min;

[0038] (2) After the lithium-ion battery 1 completes 100 cycles of charge and discharge, the cycle test is stopped, and the flow rates of the first peristaltic pump 4 and the second peristaltic pump 5 are increased to 50 mL / min;

[0039] (3) After 10 minutes, the first peristaltic pump 4 and the second peristaltic pump 5 are turned off, and dry inert gas is pressed in to pump 5 μL of electrolyte from the buffer bottle 2 into the transition metal detection device 3 to detect the dissolution of transition metals in the electrolyte. The results are shown in FIG. Figure 2 .

[0040] Figure 2 The electrolyte sample test results in Example 2 are as follows: 3+ 0.6ppm, Ni 2+ 1.2ppm, Co 2 + 0.8ppm, Mn 2+ 3.2ppm, Fe 2+ This indicates that under high-temperature cycling conditions, transition metals in the positive electrode of the battery will dissolve to a certain extent, especially Mn, which is the most significant.

[0041] By repeating the above steps (1) to (3), real-time and continuous detection of transition metal dissolution conditions in lithium-ion batteries under different conditions can be achieved, which provides a simple, accurate and intuitive method for studying the performance degradation of lithium-ion batteries containing transition metals.

[0042] Although the present invention has been described in detail above using general explanations, specific embodiments, and experiments, it will be apparent to those skilled in the art that modifications and improvements may be made based on the present invention. Therefore, such modifications and improvements, which do not depart from the spirit of the present invention, are intended to be within the scope of protection claimed herein.

Claims

1. A device for studying the dissolution of transition metals in lithium-ion batteries, characterized in that: including lithium-ion batteries, buffer bottles, and transition metal detection equipment; The shell of the lithium-ion battery is provided with an electrolyte outlet and an electrolyte inlet; The buffer bottle contains an electrolyte, and the electrolyte in the buffer bottle is the same as the electrolyte in the lithium-ion battery; The buffer bottle is provided with: a liquid inlet pipe with one end extending into the buffer bottle and the other end connected to the electrolyte outlet; One end is inserted below the liquid level of the electrolyte in the buffer bottle, and the other end is connected to the first liquid outlet pipe of the electrolyte inlet; one end is inserted above the liquid level of the electrolyte in the buffer bottle, and the other end is connected to the air inlet pipe of the gas source; one end is inserted below the liquid level of the electrolyte in the buffer bottle, and the other end is connected to the second liquid outlet pipe of the transition metal detection device; A first peristaltic pump is provided on the connecting pipeline between the electrolyte outlet and the liquid inlet pipe, and a second peristaltic pump is provided on the connecting pipeline between the electrolyte inlet and the first liquid outlet pipe; The transition metal detection equipment is an ion chromatography or an inductively coupled plasma mass spectrometer.

2. The device for studying the dissolution of transition metals in lithium-ion batteries according to claim 1, characterized in that: The lithium ion battery is a liquid lithium ion battery.

3. The device for studying the dissolution of transition metals in lithium-ion batteries according to claim 1 or 2, characterized in that: The lithium-ion battery is a soft-pack lithium battery.

4. The device for studying the dissolution of transition metals in lithium-ion batteries according to claim 1 or 2, characterized in that: The electrolyte outlet is arranged on the upper side of the side wall of the shell, and the electrolyte inlet is arranged on the lower side of the side wall of the shell. Preferably, the electrolyte outlet and the electrolyte inlet are arranged diagonally.

5. A method for studying the dissolution of transition metals in lithium-ion batteries using the device according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) placing the lithium-ion battery at a certain ambient temperature or supplying power to a load; starting a first peristaltic pump to allow the electrolyte in the lithium-ion battery to flow into the buffer bottle through the liquid inlet pipe; starting a second peristaltic pump to allow the electrolyte in the buffer bottle to flow into the lithium-ion battery through the first liquid outlet pipe; (2) After a period of time, the lithium-ion battery is left at room temperature or stops supplying power to the load; (3) After maintaining for a period of time, the first peristaltic pump and the second peristaltic pump are turned off, and then the inert gas is allowed to flow into the buffer bottle through the air inlet pipe, thereby forcing the electrolyte in the buffer bottle to flow into the transition metal detection device through the second liquid outlet pipe to detect the dissolution status of the transition metal in the electrolyte.

6. The method for studying the dissolution of transition metals in lithium-ion batteries according to claim 5, characterized in that: The certain ambient temperature is -40~60℃.

7. The method for studying the dissolution of transition metals in lithium-ion batteries according to claim 5, characterized in that: The mass of the electrolyte in the buffer bottle is 5 to 10 times the mass of the electrolyte in the lithium ion battery.

8. A method for studying the dissolution of transition metals in lithium-ion batteries according to any one of claims 5 to 7, characterized in that: The first peristaltic pump and the second peristaltic pump have the same flow rate.

9. The method for studying the dissolution of transition metals in lithium-ion batteries according to claim 8, characterized in that: The flow rates of the first peristaltic pump and the second peristaltic pump are both 0.1-100 mL / min.

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