CR2032 button cell battery

Research on the Recycling of Anode Materials (RAM) from Waste CR2032 button cell battery

Currently, battery recycling mainly involves the recycling of precious metals such as cobalt, copper, and lithium salts, with a recovery rate of 3% of the total material usage. This inefficient recycling method has caused a huge waste of resources and generated a huge amount of waste.

With the increase in electronic products and electric vehicles, the output of lithium CR2032 button cell battery has gradually increased from 2.05 billion in 2005 to 5.86 billion in 2016. At present, the production capacity of lithium CR2032 button cell battery is expanding rapidly. Simply taking cylindrical CR2032 button cell battery as an example, an average of 45g of CR2032 button cell battery contains about 20% of graphite materials, so there are more than 52 million kilograms of anode materials waiting to be recycled. In the future, more and more lithium CR2032 button cell battery will fail and need to be recycled.

Currently, battery recycling mainly involves the recycling of precious metals such as cobalt, copper, and lithium salts, with a recovery rate of 3% of the total material usage. This inefficient recycling method has caused a huge waste of resources and generated a huge amount of waste.

The negative electrode of lithium battery is made by coating the active material, binder, conductive agent, etc. into a slurry with good consistency on copper foil to improve the bonding force and electrochemical performance of the material and the substrate.

The adhesion between graphite material and copper substrate is very weak, so an external binder is needed to improve its adhesion. For this reason, it is also very easy to peel graphite from the electrode. Julian E.C. Sabisch et al. selected waste CR2032 button cell battery to study the recycling of recycled negative electrode materials (RAM) and compared them with the initial unused negative electrode materials (VG) CR2032 button cell battery. The standard of waste CR2032 button cell battery selected is that the battery is in a fully discharged state and the capacity decays to less than 20% of the initial capacity. There are several advantages to selecting the negative electrode materials of waste CR2032 button cell battery for reuse:

1. Using the negative electrode materials of waste CR2032 button cell battery to make new CR2032 button cell battery not only does not require the need to find new sources, but also reduces the discharge of waste materials. RAM can be regarded as a special material after graphite has been pre-treated, and has a higher quality after being pre-circulated.

2. When the battery is charged and discharged for the first time, a passivation layer SEI will be formed on the surface of the negative electrode material, which is conducive to the transfer of lithium ions. The formation of SEI consumes some lithium ions, resulting in battery capacity loss. RAM has been stripped and inserted lithium, and contains a portion of SEI on the surface, which is equivalent to pre-lithiation of the negative electrode material using an external lithium source. When the recycled graphite material is recast into a battery, the amount of Li consumed by the lithium battery in forming a complete SEI will be reduced, improving the battery's initial efficiency.

(c) The negative electrode material is re-pulped and coated on copper foil to prepare for punching

The battery capacity is obtained using Maccor software by multiplying the current flowing through the battery by the time it flows. The current is generally C/40, which is given based on the weight of the negative electrode. Looking at the initial cycle voltage curve of VG in Figure 3a, it can be seen that it takes about 5s for the voltage to drop from 3V to 1.2V. When compared to the total amount of time the battery is cycled, it shows that the degree of pre-lithiation in the RAM battery is far less than 1% of the total capacity.

It can be seen from this that the degree of pre-lithiation is not enough to significantly affect the initial capacity of the RAM negative electrode. It should be emphasized that although the initial capacity loss does not change significantly due to the use of RAM, the overall capacity shown in Figure 3c is roughly equivalent to that of the VG battery.

Seeing this, many people probably have such questions. What will happen if the negative electrode materials come from different CR2032 button cell battery? Can the battery performance remain the same? In order to discuss the characteristics of different reused negative electrode materials, the negative electrode materials from different CR2032 button cell battery were recycled and remade into negative electrodes. The morphology was observed by SEM, as shown in Figure 4.

It can be seen that the morphology of VG and RAM is very different. The VG material is a stack of graphite layers with a sheet structure. The negative electrode after cycling is composed of smaller sheets. The surface is not as undulating as the VG material, but it does not affect the overall cycle performance.

In addition, a small-scale expansion test was conducted to prove the feasibility of recycling negative electrode materials from waste CR2032 button cell battery for lithium CR2032 button cell battery. Compared with experimental operations, in order to ensure safety during the disassembly process, the expansion test needs to be carried out in an inert atmosphere. The results show that the negative electrode materials in waste CR2032 button cell battery can be mechanically extracted from commercial CR2032 button cell battery, and the CR2032 button cell battery made with negative electrode materials obtained from exhausted CR2032 button cell battery have no obvious attenuation in the initial 10 weeks of cycling.

Using RAM, whose cycle history and manufacturing quality are unknown, can truly simulate the real-world LiB recycling conditions. The effect of putting RAM into new negative electrode manufacturing can be seen from SEM, and it also provides a new way to recycle waste lithium CR2032 button cell battery. Although the morphology of RAM varies, there is no significant difference in their performance.

Throughout the experiment, although not extensive, the phenomenon of pre-lithiation of graphite materials can be observed, which can prove the possibility of lithium embedding into carbon materials. Through the same treatment, negative electrodes made of RAM and VG show similar cycle stability, and RAM negative electrodes have higher first efficiency. The similar first cycle of RAM and VG CR2032 button cell battery shows that RAM still maintains crystallinity despite use and end of life.

The increase in first cycle capacity is mainly attributed to the negative electrode material after lithium ion embedding cycle, without causing consumption of Li content. However, further research is needed to confirm the extent to which pre-lithiation helps the reformation of SEI in RAM CR2032 button cell battery. In addition, more data needs to be tested, such as changes in long-term cycles, rate dependence, etc.

Analysis shows that during the charge and discharge process of lithium CR2032 button cell battery, the negative electrode material will inevitably undergo more or less crystal structure changes, and it is still impossible for the negative electrode material of the end-of-life battery to have the same performance structure as the unused negative electrode material. At the same time, the rationality of sampling in the test should be taken into account, and the electrochemical performance test is not comprehensive and needs further verification. Reusing negative electrode materials is a good way to deal with waste. Classifying different types of negative electrode materials and screening and grading them according to product use can ensure product quality and waste utilization efficiency.

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CR2032 button cell battery