Current efficiency in the lithium—water battery

The corrosion of Li was studied in 3-5M LiOH at 25~ and in 4.5M LiOI-I at 4~176The Arrhenius relationship is obeyed and the apparent activation energy for the Li corrosion reaction is found to be 15.5 kcal mole -1. An empirical relationship is derived from which the corrosion rate vf can be obtained at any molar LiOH. At 25~ ,f(kA m -2) ----0.31 ). An equation is also given which allows calculation of the Li corrosion rate when the metal is anodically polarized. The kinetics of the He evolution reaction (e.r.) on Li were determined, the transfer coefficient ~ has a value of 0.14. The rate-controlling process of the Li dissolution reaction is the highly polarized I-I2 evolution at cathodic sites. Based on the ~ value obtained, the enthalpy of activation for the He e.r. on Li at OCV is calculated to be 22.8 kcal mole -1. It is proposed that the protective film on Li has a duplex structure with a thin oxide/ hydroxide layer adjacent to the metal and an outer porous hydrated layer through which the reaction products and reactants can pass freely.The rapid dissolution of Li in alkaline aqueous solutions can be utilized electrochemically to produce high rate battery systems (1). This is possible because the corrosion (parasitic) reaction in 3-5M LiOH can be virtually eliminated if the metal is anodically polarized by about 300 mV. It has been found that the rate of the Li dissolution reaction Lt + H~O-> LiOH -5 Yz H2[i]is essentially constant at constant temperature from OCV to the above-mentioned polarization level. Unlike conventional batteries, in Li-H20 cells the current efficiency is governed by the ratio of two competing reactions, namely, the anodic dissolution reaction and the parasitic reaction (2, 3). The current, efficiency increases with an increase in the anodic dissolution rate (i.e., the current density), and if decreases at elevated temperatures where the corrosion reaction is stimulated. Since current efficiency is critical to cell performance, a fundamental understanding of the factors which influence the parasitic reaction is important.No prior investigations of the corrosion of Li immersed in aqueous electrolytes have been reported. Papers on the electrochemistry of the system have been concerned with anodic passivation and mathematical modeling. This corrosion study of Li in flowing electrolyte under conditions identical to battery operation was undertaken to gain knowledge of three aspects of the Li-H20 reaction.(i) Information on the reaction at various LiOH concentrations and temperatures provides data for the determination of the reaction rate constant. This then allows calculation of corrosion rates in practical battery systems.(it) To characterize the processes which occur across the oxide/hydroxide film in a Li-H20 cell, knowledge of the H20 activity at the active Li surface is necessary.The assumption of the previous mathematical modeling paper (2) was that the exchange current density for the parasitic hydrogen evolution reaction is proportional to the 0.5 power of water activity at the a...

mentioning

confidence: 99%

Corrosion of Lithium in Alkaline Solution

Littauer

Tsai

1977

“…Then Eq. [6] becomes CD = Co exp (--p'Xo) [7] The magnitude of i~ is strongly influenced by flow velocity and by contact pressure. Of interest is the relationship between i~ and film resistance or film thickness.…”

Section: Discussionmentioning

confidence: 99%

“…Determination of the current density depicted as ic is critical to the operation of the cell. It is at this point that the Li anode can be discharged with high current efficiency (i.e., 90%) (7). Also the concert- tration gradient within the diffusion layer remains constant.…”

Section: And 8 (R Values)mentioning

confidence: 97%

Anodic Behavior of Lithium in Aqueous Electrolytes: III . Influence of Flow Velocity, Contact Pressure, and Concentration

Littauer

Tsai

Hollandsworth

1978

The influence of electrolyte flow velocity, concentration, and contact pressure on the anodic behavior of lithium at constant temperatures in LiOH was studied. The experimental results reveal that, under constant load polarization, a steady-state i-E curve is obtained consisting of resistance and concentration polarization components. A method to accurately determine the film thickness was devised. It was found that the oxide film at the anode surface is quite thick, ca. 10 -2 cm, and its thickness remained constant irrespective of polarization level at constant electrolyte concentration, flow rate, and anode-cathode contact pressure. The effective diffusion layer at the Li active surface is thin, ca. 10 -3 cm. The fraction of active surface area was found to change significantly with LiOH concentration (ranging from 0.05 in 4.84M to 0.39 in 2.9UM), but it was virtually independent of flow velocity and contact pressure. Likewise, electrolyte concentration has far greater influence on film resistance than flow rate or contact pressure. Electrolyte flow velocity variation is, however, an effective means to alter power output from the cell. The oxide/hydroxide film which forms on Li anodes in aqueous, strongly alkaline electrolytes has some tmusual properties. For example, even though it is fairly thick (ca. 5 X 10 -2 cm) it will support high * Electrochemical Society Active Member.

“…318 To a great extent this is because unlike LIBs, which benefited from the military and portable electronics markets in the 1990's, VRFBs do not have a large market niche with a high profit margin and a low market penetration barrier, where they are clearly superior to existing alternatives from the customer viewpoint. (We are aware of the purchase of a flow battery startup SunCatalytix by Lockheed-Martin (NYSE: LMT) in 2014, 319 and of Lockheed's own attempts to develop RFBs for nuclear missile silos in the 1980's, [320][321][322][323] and of on-going US Department of Defense-funded work at Raytheon Technologies (NYSE: RTX) 324 and at Ameresco, Inc. (NYSE: AMRC) with Invinity Energy Systems (LSE:IES), 325 but these are exceptional events in a niche market rather than a real market trend).…”

Section: Vanadium Rfbs-the Technology Frontrunnersmentioning

confidence: 99%

Review—Flow Batteries from 1879 to 2022 and Beyond

Tolmachev

2023

We present a quantitative bibliometric study of flow battery technology from the first zinc-bromine cells in the 1870s to megawatt vanadium redox flow battery (RFB) installations in the 2020s. We emphasize that the cost advantage of RFBs in multi-hour charge-discharge cycles is compromised by the inferior energy efficiency of these systems, and that there are limits on the efficiency improvement due to internal cross-over and the cost of power (at low current densities) and due to acceptable pressure drop (at high current densities). Differences between lithium-ion and vanadium redox flow batteries are discussed from the end-user perspective.