Electrochemical reduction of nitro compounds derived from nitro compounds for high performance lithium ion batteries

【introduction】

As the demand for rechargeable lithium-ion batteries (LIBs) continues to increase, environmental friendliness and sustainability have become key factors in electrode materials. However, the manufacture of inorganic electrode materials such as LiCoO2 and graphite consumes a large amount of energy and releases a large amount of CO2. In addition, used batteries can cause more serious environmental problems by leaking toxic heavy metals from cobalt-based electrodes into the soil and water. In order to circumvent environmental and sustainability challenges, it is important to develop energy efficient, sustainable and recyclable battery materials.

[Introduction]

Recently, the team of Wang Chunsheng (communication author) of the University of Maryland designed a new chemical based on the electrochemical conversion of nitro compounds to high performance lithium ion battery azo compounds. Lithium 4-nitrobenzoate (NBALS) was selected as the model nitro compound, and the structure, lithiation/delithiation mechanism and electrochemical performance of the nitro compound were systematically studied. The initial capacity of NBALS at 0.5 C was 153 mAh g-1, maintaining a capacity of 131 mAh g-1 after 100 cycles. Detailed characterization indicates that the nitro group in the crystalline NBALS is irreversibly reduced to an amorphous azo compound during the initial electrochemical lithiation. Subsequently, the azo compound is reversibly lithiated/delithiated with high electrochemical performance in a charge/discharge cycle. The lithiation/delithiation mechanism of the azo compound was also verified by directly using an azo compound as an electrode material which exhibited electrochemical properties similar to those of the nitro compound while having a higher initial coulombic efficiency. Related results were published in Adv. under the title "Azo Compounds Derived from Electrochemical Reduction of Nitro Compounds for High Performance Li‐Ion Batteries". Mater. on.

[Graphic introduction]

Figure 1 How the organic molecules work in lithium-ion batteries

In the N-N reaction, two nitro groups are reduced to lithium by lithium ions to form Li2O.

Figure 2 Electrochemical performance of NBALS in lithium ion batteries

a) Constant current charging / discharging curve

b) Cyclic voltammogram of 0.1 mV s-1

c) Relationship between delithiation capacity and coulombic efficiency and cycle number at a current density of 0.5C

d) rate performance

Figure 3 Spectral analysis

a) Raman spectroscopy of NBALS electrodes before and after 1 cycle

b) Mass spectrometry of NBALS electrodes before and after 1 cycle

c) XRD spectra of NBALS electrodes before and after 1 cycle

d) Graphic and calculation of reduction from NBALS to azo compounds

[Summary] This work is an azo compound synthesized by lithiation of a nitro compound for use in a novel lithium ion battery active material for high performance LIBs. Detailed characterization indicates that during the initial lithiation process, the nitro compound is irreversibly converted to an azo compound and Li2O with a low ICE. The discovery of nitro and azo compounds for organic electrodes offers new opportunities for high performance LIBs.