Limitations in Rechargeability of Li-O₂ Batteries and Possible Origins

Abstract

Quantitative differential electrochemical mass spectrometry (DEMS) is used to measure the Coulombic efficiency of discharge and charge [(e(-)/O2)dis and (e(-)/O2)chg] and chemical rechargeability (characterized by the O2 recovery efficiency, OER/ORR) for Li-O2 electrochemistry in a variety of nonaqueous electrolytes. We find that none of the electrolytes studied are truly rechargeable, with OER/ORR <90% for all. Our findings emphasize that neither the overpotential for recharge nor capacity fade during cycling are adequate to assess rechargeability. Coulometry has to be coupled to quantitative measurements of the chemistry to measure the rechargeability truly. We show that rechargeability in the various electrolytes is limited both by chemical reaction of Li2O2 with the solvent and by electrochemical oxidation reactions during charging at potentials below the onset of electrolyte oxidation on an inert electrode. Possible mechanisms are suggested for electrolyte decomposition, which taken together, impose stringent conditions on the liquid electrolyte in Li-O2 batteries.

A Comprehensive Study on Oxygen Reduction and Evolution from Lithium Containing DMSO Based Electrolytes at Gold Electrodes

“…the ratio of reduced to evolved oxygen) of less than 100%. 17,18 Similar results were also presented by Peng et al 19 Although the authors of that particular paper did not discuss that their DEMS measurements show that more oxygen is * Electrochemical Society Member.z E-mail: baltruschat@uni-bonn.de consumed during the cathodic scan than evolved in the subsequent anodic scan the fact remains. Electrochemical quartz crystal micro balance (eQCMB) measurements produced largely contradicting results.…”

Reversibility of anodic lithium in rechargeable lithium–oxygen batteries

“…At present, the studies on the cyclability and stability of Li-O 2 batteries have been primarily focused on the cathode catalysts [16][17][18][19][20][21][22][23][24][25][26][27][28][29] , electrolytes [30][31][32][33][34][35][36][37][38][39][40][41][42][43][44] , binder 45 and so on. For example, the electrolyte decomposition was found during the cycling of Li-O 2 batteries, which led to the formation of by-products such as H 2 O, CO 2 , insoluble Li salts, and the eventual degradation of the cathode and the separator [33][34][35][36][46][47][48][49][50][51] . Research on anode stability is challenging due to the high reactivity of metallic Li.…”

XPS Study of the Interface Evolution of Carbonaceous Electrodes for Li-O2Batteries during the 1st Cycle

“…1 The cell failure has been attributed to the gradual degradation of the electrolyte, which in turn leads to the passivation of the electroactive electrode area by solid side-products. 14 Although the detailed mechanisms of the parasitic side-reactions remain unclear, both the electrode and electrolyte solvent/salt have been demonstrated to partially react irreversibly with Li 2 O 2 during cycling to form more thermodynamically stable side-products, such as H 2 O, CO 2 , Li 2 CO 3 , LiF, R-CHO species, etc. 1 Porous carbons are widely used as electrode substrate materials due to their reasonable cost, high electrical conductivity, versatile morphology and high surface area, which enable significant amounts of Li 2 O 2 formation before electrode passivation.…”