Electrochemical behavior of Bi₄B₂O₉towards lithium-reversible conversion reactions without nanosizing

Abstract

Conversion type materials, in particular metal fluorides, have emerged as attractive candidates for positive electrodes in next generation Li-ion batteries (LIBs). However, their practical use is being hindered by issues related to reversibility and large polarization. To minimize these issues, a few approaches enlisting the anionic network have been considered. We herein report the electrochemical properties of bismuth oxyborate BiBO and show that this compound reacts with lithium via a conversion reaction leading to a sustained capacity of 140 mA h g when cycled between 1.7 and 3.5 V vs. Li/Li while having a surprisingly small polarization (∼300 mV) in the presence of solely 5% in weight of a carbon additive. These observations are rationalized in terms of charge transfer kinetics via complementary XRD, HRTEM and NMR measurements. This finding demonstrates that borate based conversion type materials display rapid charge transfer with limited carbon additives, hence offering a new strategy to improve their overall cycling efficiency.

Playing with the Redox Potentials in Ludwigite Oxyborates: Fe3BO5 and Cu2MBO5 (M = Fe, Mn, and Cr)

“…The voltage polarizations of 330 and 400 mV for the two reversible redox reactions in Fe 3 BO 5 oxyborate is lower compared to other Fe-based conversion materialsoxides in particularshowing voltage polarizations of more than 500 mV. ,, In analogy to kotoite-type M 3 B 2 O 6 (M = Co, Ni, and Cu), reversible cycling is expected to occur in the form of a conversion-type reaction between amorphous or nanocrystalline iron-based phases in a lithia matrix (made of Li 2 O and Li 3 BO 3 ) . The BO 3 polyanion in Fe 3 BO 5 seems to lower the voltage polarization compared to iron oxides, , as similar values were reported for other borates and oxyborates. ,, The reason for this relatively small voltage polarization is not fully understood and may, according to ref , be due to different reaction paths for lithiation and delithiation, linked to different mobilities of ionic species (here Li, O, BO 3 , and Fe).…”

“…20 The BO 3 polyanion in Fe 3 BO 5 seems to lower the voltage polarization compared to iron oxides, 13,32 as similar values were reported for other borates and oxyborates. 14,20,23 The reason for this relatively small voltage polarization is not fully understood and may, according to ref 23, be due to different reaction paths for lithiation and delithiation, linked to different mobilities of ionic species (here Li, O, BO 3 , and Fe).…”

“…20 Recently, bismuth oxyborate Bi 4 B 2 O 9 was identified as a conversion material with a low voltage polarization of only 300 mV. 23 Whereas the relatively low sustained capacity (140 mA h g −1 ) at intermediate voltages (1.7−3.5 V) has to be improved for commercial interest, the low voltage polarization shows some promise for conversion-type metal borates and oxyborates for use in LIB electrodes.…”

“…Indeed, after the initial lithiation, the transition metals are likely found to be dispersed in a lithia matrix (made of Li 2 O and Li 3 BO 3 ), and upon subsequent delithiation, the metallic copper is only partially reoxidized in Cu + with a concomitant decomposition of Li 2 O . Recently, bismuth oxyborate Bi 4 B 2 O 9 was identified as a conversion material with a low voltage polarization of only 300 mV . Whereas the relatively low sustained capacity (140 mA h g –1 ) at intermediate voltages (1.7–3.5 V) has to be improved for commercial interest, the low voltage polarization shows some promise for conversion-type metal borates and oxyborates for use in LIB electrodes.…”

Formation of bismuth metal in bismuth borate glass by reductive heat treatment and its electrochemical property as anode in lithium ion battery

“…This is supported by the report of Bi 4 B 2 O 9 crystal, Li 3 BO 3 formation starts in 1.9 V and then Li 2 O formation progresses at a lower potential. 24) At around 1.4 V and a gently potential drop at 1.30.9 V, a reaction for reducing of Bi 2 O 3 to Bi is progressing. Li et al reported that the reaction formula (3.2, 3.3 in which the monoclinic ¡-Bi 2 O 3 or tetragonal ¢-Bi 2 O 3 is reduced to Bi proceeds 1.2 or 1.4 V. 25) However, from the crystallization behavior of this glass system, cubic Bi 2 O 3 crystal was precipitated.…”