Abdul-Rahman O. Raji, Tuqeer Nasir, Tuo Wang, Li He, William Ceren, Mina Moradnia, Sarathy Gopalakrishnan, Zeta Energy Corp., Houston, TX
Developing high energy density, fast-charging, and long cycle life lithium-metal batteries requires reversible deposition and dissolution of the lithium-metal anode without dendrite formation over many cycles in the battery cell. Dendrite formation is well-known to occur in lithium-metal deposited during electrochemical cycling of the anode, and its safety hazards are documented and severe. The resulting formation of dead lithium causes battery capacity degradation due to progressive deactivation of the lithium-metal, which is the active anode material. We hereby present a case for the use of a host structure with high specific surface area and porosity as a viable approach for addressing these fundamental issues. We demonstrate that vertically aligned carbon nanotubes (VACNT) coating is the ideal host material due to its high surface area, porosity, electrical conductivity, lightweight, and tunable properties; and we can reversibly deposit dendrite-free lithium-metal within the VACNT coating, thus forming a stable and practical Li-VACNT anode. The VACNT coating is deposited using vacuum processes via a combination of physical vapor deposition (PVD) and chemical vapor deposition (CVD). For the first time, we demonstrate not only that VACNT can be coated on both sides of the copper current collector, but also that the dual-sided coating can be achieved simultaneously over a large area. While vacuum coating of electrode materials is novel to the battery industry, we show that our processes are compatible with roll-to-roll coating, a requirement for battery material commercialization in the industry. With VACNT representing only a small fraction of the mass of the Li-VACNT anode, the advances presented here lay the foundation for the safe use of the ultimate lithium battery anode material, namely lithium-metal. The desirable combination of the tunable material properties, stable electrochemical performance, and commercial viability of the VACNT presents a model system for lightweight, compact, and fast-charging advanced lithium batteries.