Tailoring Li–CO₂ Electrochemistry Based on 4,4′-Bipyridine Redox Cycle

Abstract

The aprotic Li–CO2 battery provides a tantalizing solution for simultaneous CO2 capture and electrical energy storage. Nevertheless, current Li–CO2 batteries based on ordinary reaction pathways, e.g., reducing CO2 to CO, oxalate, carbon, etc., often suffer from poor energy efficiency and severe parasitic reactions. Thus, exploring new Li–CO2 electrochemistry is of fundamental interest and practical importance. Herein, we report a new concept of a Li–CO2 battery that can realize both reversible capture/release of CO2 and highly efficient energy storage based on the redox cycle of 4,4′-bipyridine (BPD). Direct spectroscopic evidence coupled with theoretical calculations reveals that BPD first coordinates with CO2 to form a [BPD···2CO2] complex that can further be reduced via a two-electron pathway into Li2[BPD-2CO2] upon discharge; upon recharge the reaction is reversed, regenerating BPD and CO2. The BPD-assisted Li–CO2 battery minimizes the overpotential required to drive the discharge/charge reaction, eliminates the undesired parasitic reactions associated with pristine Li–CO2 batteries, and delivers a high discharge capacity (>1000 mAh/gc). This work represents a significant step forward toward truly reversible Li–CO2 batteries by the rational design of redox molecules that can participate in and regulate the conventional Li–CO2 electrochemistry.

A Li–O2/CO2 battery based on bio-inspired engineering of the Bi2S3/PVP cathode

“…The development of low-cost, high-energy, long-lived energy storage systems holds promise for the widespread use of renewable energy in power grids and cheap electric vehicles. 11–15 As the next generation of high specific energy electrochemical energy storage systems, lithium–air batteries have been widely studied in recent decades.…”

Unlock CO2 Reduction Reaction Pathways in Aprotic Li-CO2 Batteries with In Situ Isotope-Labeled Spectroscopy and Theoretical Calculations

“…Nevertheless, some essential questions and uncertainties behind the CO 2 RR still remain, including the identity of intermediates and products, the comprehensive understanding of primary and parasitic reaction pathways, and the determination of their controlling descriptors. The complexity arises from the involvement of gaseous, solid, and soluble intermediates and products in CO 2 RR in aprotic Li-CO 2 batteries . Extensive researches often relies on ex situ analysis, monitoring the pristine and cycled electrode and electrolyte components, and the in situ detection of CO 2 RR pathways often remains a formidable challenge .…”

“…Developing innovative energy generation technologies based on CO 2 capture and conversion is a promising solution to close the anthropogenic chemical carbon cycle and foster a more carbon-neutral and sustainable society. , Notably, the emerging aprotic Li–CO 2 batteries founded on the CO 2 redox cycle have recently garnered considerable research interest due to their potential in energy storage capability and CO 2 recyclability . However, since their initial development, the electrochemical performance has been primarily limited by poor reversibility and large overpotential, which relies on the CO 2 reduction reaction (CO 2 RR) upon discharge to form readily decomposable discharge products at low overpotentials and without any parasitic reactions. , To boost the energy capabilities and lifespan of aprotic Li-CO 2 batteries, understanding CO 2 RR processes and eliminating parasitic chemistries are the essential prerequisites …”

“…6,7 To boost the energy capabilities and lifespan of aprotic Li-CO 2 batteries, understanding CO 2 RR processes and eliminating parasitic chemistries are the essential prerequisites. 8 Over the past decade, significant efforts have been devoted to understanding CO 2 RR pathways. 9 Initially, most studies often presumed that the CO 2 RR proceeds via the reaction of 4Li + + 3CO 2 + 4e − → 2Li 2 CO 3 + C on various electrocatalyst surfaces (e.g., metal, 10−12 metal oxide, 13−15 carbon materials, 16,17 metal−organic framework, 18,19 etc.).…”

Steering the Orbital Hybridization to Boost the Redox Kinetics for Efficient Li–CO2 Batteries

“…The direct conversion of CO 2 into value-added chemicals or electricity offers a tempting route for the reduction or control of CO 2 concentration in the earth’s atmosphere and future exploration on Mars. − Among the proposed strategies, Li–CO 2 batteries, based on the reaction of 4Li + 3CO 2 ↔ 2Li 2 CO 3 + C can provide a high theoretical energy density (1876 W h kg 1– ) at theoretical output potential (2.8 V vs Li/Li + ), simultaneously realizing carbon capture and utilization. − Despite this, the development of Li–CO 2 batteries is still in its infancy and faces thorny problems, including the hysteretic kinetics of the CO 2 reduction reaction/CO 2 evolution reaction (CO 2 RR/CO 2 ER) processes. , Particularly, the sluggish CO 2 redox kinetics at the cathode side will result in incomplete dissociation of the discharge products (Li 2 CO 3 ) and piling up on the surface of the cathode, − which will prevent mass transfer and passivate the catalyst, leading to a low discharge platform, a large overpotential, and pitiful reversibility. , Therefore, the development of effective catalysts is a pressing matter.…”