Team of Professor Feng Wei from Tianjin University: Lithophilic COF achieves uniform lithium deposition

Recently, the team of Professor Wei Feng of Tianjin University has made new progress in the organic covalent framework material ( COF ) inhibiting the growth of lithium dendrites , and explored the guiding effect of the lithium- philic COF structure on the uniform deposition of lithium ions in lithium metal batteries.
The design concept for the preparation of dendritic-free lithium metal batteries was published .
The related results were published in ACS Applied Materials & Interfaces under the title " Guiding Uniformly Distributed Li Ion Flux by Lithiophilic Covalent Organic Framework Interlayers for High-performance Lithium Metal Anodes .
Li Zihao , a doctoral student in the School of Materials Science and Engineering, Tianjin University, is the first author of the paper .
This research was supported by the National Natural Science Foundation of China .

Figure 1 Characterization of
COF materials .

( A ) Affinity of lithium COF synthesis step; ( B ) ^.
1
.
3
C solid NMR; ( C ) infrared spectroscopy; ( D ) X- ray diffraction, and ( E ) Analysis of the specific surface area

Experiments designed to give a reasonable ratio of monomers containing a triazine ring, and the synthesis of a large number of carbonyl groups COF structure, as shown in FIG 1 , by ¹ .

3
C solid NMR, IR, X- ray diffraction and other means of specific surface area proved COF Successful synthesis of materials

Figure 2 Lithophilic characterization of COF .

( A ) was added LiTFSI the COF pure LiTFSI in

By electrochemical measurement, the current density are 0 .

5 , 1 , and 2 mA cm & lt ^{- 2} and the capacities of 0 .
5 , 1 , and 2 mAh cm & lt ^{- 2} , the lithium-containing copper foil coated with an organic porous polymer test assembly obtained - copper half cell coulombic efficiency can be reached .
9 .

Figure 3 Characterization of a half-cell .

( A ) Comparison test of Coulomb efficiency; ( b ) Comparison of overpotential of lithium nucleation; Comparison of cycle stability of symmetric battery under current density ( c ) 1 mAcm ^{- 2} and ( d ) 4 mAcm ^{- 2} ; ( E ) symmetrical current density of the battery .

Figure 4 Schematic diagram of the mechanism of COF inhibiting the growth of lithium dendrites .

( A ) The growth of lithium dendrites on copper foil; ( b ) COF guides uniform ion current to achieve uniform lithium deposition

Figure 5 Test characterization of a full battery .

( A ) CV curve of lithium-sulfur battery ; ( b ) rate performance comparison of lithium-sulfur battery; ( c ) voltage-capacity curve of lithium-sulfur battery; ( d ) XPS characterization of adsorbed polysulfide ; ( e ) Comparison of rate performance of lithium-lithium iron phosphate batteries; ( f ) EIS characterization of lithium-lithium iron phosphate batteries ; ( g ) long-cycle comparison of lithium-lithium iron phosphate batteries ; ( h ) voltage of lithium-lithium iron phosphate batteries— Capacity curve

  Finally, a full battery was assembled with a lithium- philic COF material for testing.

As shown in Figure 5 , it can be found that whether in a lithium-sulfur battery or a lithium - lithium iron phosphate battery system, the introduction of lithium- philic COF can make the battery obtain Higher reversible capacity and more excellent rate performance, these results successfully proved that the design of lithium-philic structural framework has excellent versatility in lithium metal batteries

Original link
https://pubs.
acs.
org/10.
1021/acsami.
1c04517