Topochemical Deintercalation of Li from Layered LiNiB: toward 2D MBene

Abstract

The pursuit of two-dimensional (2D) borides, MBenes, has proven to be challenging, not the least because of the lack of a suitable precursor prone to the deintercalation. Here, we studied room-temperature topochemical deintercalation of lithium from the layered polymorphs of the LiNiB compound with a considerable amount of Li stored in between [NiB] layers (33 at. % Li). Deintercalation of Li leads to novel metastable borides (Li∼0.5NiB) with unique crystal structures. Partial removal of Li is accomplished by exposing the parent phases to air, water, or dilute HCl under ambient conditions. Scanning transmission electron microscopy and solid-state 7Li and 11B NMR spectroscopy, combined with X-ray pair distribution function (PDF) analysis and DFT calculations, were utilized to elucidate the novel structures of Li∼0.5NiB and the mechanism of Li-deintercalation. We have shown that the deintercalation of Li proceeds via a “zip-lock” mechanism, leading to the condensation of single [NiB] layers into double or triple layers bound via covalent bonds, resulting in structural fragments with Li­[NiB]2 and Li­[NiB]3 compositions. The crystal structure of Li∼0.5NiB is best described as an intergrowth of the ordered single [NiB], double [NiB]2, or triple [NiB]3 layers alternating with single Li layers; this explains its structural complexity. The formation of double or triple [NiB] layers induces a change in the magnetic behavior from temperature-independent paramagnets in the parent LiNiB compounds to the spin-glassiness in the deintercalated Li∼0.5NiB counterparts. LiNiB compounds showcase the potential to access a plethora of unique materials, including 2D MBenes (NiB).

MBenes: progress, challenges and future

“…Firstly, 2D Ti 2 B, 27 Mo 2 B 51 and Hf 2 B 42 should be classified as new boron-containing MXenes since they have exactly the same structures and chemical formula as typical M 2 X MXene. Secondly, 2D LiB 52 and NiB 26 have no layered structures of alternate stacks of transition metal and B layers. Additionally, 2D MgB 2 , 53 FeB 2 , 54 TiB 2 , 25 and tetragonal Mn 2 B 2 (ref.…”

Few-layer Mg-deficient borophene nanosheets: I2 oxidation and ultrasonic delamination from MgB2

“…32 By performing topological chemical deintercalation of LiNiB at room temperature, a considerable amount of Li atoms stored between the [NiB] layers can be deintercalated and Li ∼0.5 NiB with a unique crystal structure is obtained and the deintercalation rate of Li atoms is about 50%. 37 On the other hand, the FBN can be obtained in the present work. An Mg 0.22 B 2 compound is obtained and up to 78% of Mg atoms can be deintercalated when the precursor MgB 2 is oxidized by I 2 in a mixture of CH 3 CN and HCl under nitrogen protection.…”

“…Moreover, Zaikina's group has also investigated the deintercalation of Li atoms from layered LiNiB to synthesise boron analogs of 2D MXenes, and a similar research result is obtained, in which Li atoms can't be completely deintercalated from layered LiNiB, otherwise it will cause the collapse of the two-dimensional structure of [NiB]. 37 Even for the layered MgB 2 , Mg atoms can't be completely deintercalated and up to 52% of Mg 2+ ions can be deintercalated by using a chelating agent 32 or an ion-exchange resin. 36 The reason why Mg atoms cannot be completely deintercalated will be further explained together with the theoretical calculation results.…”

Element‐Doped Mxenes: Mechanism, Synthesis, and Applications

“…[101,[243][244][245] Since the commercial application of lithiumion batteries (LIBs) in 1991, their important advantages such as high voltage, large capacity, long cycle life, and good safety performance have attracted much attention. [246,247] Compared with pristine MXenes, due to the adjustment of the interlayer distance by elemental doping, more abundant active sites are generated, which suppress the performance degradation due to the stacking of sheets and provide better electrochemical adsorption sites. [85,86,248,249] N, S codoping of V 2 CT x MXenes through rational structural design and optimization.…”