Negative enthalpy collector coatings to enhance stability of metal anodes

Problem

Anodeless or anode-free liquid, solid and hybrid liquid-solid batteries hold tremendous promise, offering lower cost in parallel to over 50% higher energy by weight and by volume. However, because of the poor Coulombic efficiency (CE)—which leads to poor cathode utilization, rapid capacity fade during cycling, an unstable solid electrolyte interphase (SEI) and ultimately dendrites—such cells have not been commercially viable.

Solution

This invention discloses a modified current collector that improves metal plating/stripping and prevents dendrites. It may be used with an alkali metal anode or in “anodeless” “anode-free” configuration. The coating is designed to possess a negative enthalpy of solution with the plating metal (Li, Na, K, Zn, etc.) which promotes Frank–Van der Merwe growth (or FM growth) also known as “layer-by-layer growth.” This prevents geometrical roughening of the planting/stripping films, the perturbations being known to lead to dendrites and premature cell failure. The coating may be as thin as one or several atomic layers, up to microns in thickness. It may be placed onto a conventional planar, roughened, sponge-like, or hybrid current collector. It may be employed in a “Janus” configuration, coating both the current collector and its opposing membrane separator. It may also be employed to coat either one or both sides of a separator.

Features and benefits

Researchers employ planar Cu- and Al-based current collectors that offer only limited wetting by the electrolyte, which in turn results in dendrites during cycling. To attempt to overcome this problem, researchers employ exotic and expensive materials, such as graphenes or various surfactants, which promote improved wetting chemically. These solutions are expensive and poorly scalable. We overcome this problem through much less costly and more effective negative enthalpy thin films coating. These may be applied through a range of inexpensive process that can be readily scaled up through various existing deposition methods. This leads to improved Coulombic efficiency and suppression of dendrite growth, without having to modify the electrolyte or current collector chemistry. It represents a drop-in improvement to the existing process.