Dr. Stephen Campbell, Principal Scientist at Nano One, announced today that Nano One has developed coating technology that stabilizes cathodes for use in advanced lithium ion batteries and has applied for patent protection related to this coating technique.
“The innovation applies a coating to particles of cathode material without adding steps to our process,” explained Dr. Campbell, “and this reduces degradation and resistance between the cathode and the electrolyte in lithium ion batteries. We are encouraged by the preliminary results of our findings as this could help solve long-standing degradation mechanisms, enable energy dense battery designs, and increase the number of times that a battery can be recharged over its lifetime.”
“The improvements are pronounced under warmer operating conditions, such as those seen in electric vehicles,” added Dr. Campbell. “This is particularly suited to the commercialization of high energy and high voltage cathode materials, where the elimination or reduction of cobalt requires alternatives to enhance stability and durability.”
These advances have now enabled Nano One to increase its collaborative work with European and Asian commercial interests in the automotive supply chain, with the aim of developing materials for next generation solid state batteries. A detailed and technical explanation of the opportunity is provided below.
A stable, ion conducting coating on the surface of Nano One’s High Voltage Spinel (HVS) could solve interfacial problems for both liquid and solid ceramic electrolytes by inhibiting manganese dissolution in liquids and increasing conductivity with solid state electrolytes. Nano One has developed two types of coatings that stabilize the cathode when cycled at 55°C which could improve durability and stability without impacting capacity.
HVS has attracted attention in the lithium battery supply chain for two reasons. Firstly, the material contains no cobalt and based on cobalt supply constraints, HVS could reduce supply risk. The material contains primarily manganese and a small portion of nickel, and thereby measurably lower costs. Secondly, HVS has the highest and one of the most constant discharge voltages, measuring 4.7 volts which offsets its lower capacity. HVS also has high rate capability, which means that it can be charged and discharged rapidly without losing capacity.
On its own, HVS degrades rapidly when cycled at 55°C which is a design criterion for electric vehicles. Also, charging and discharging at 4.7 volts may cause the degradation of common liquid electrolytes which are considered unstable above 4.2 volts.
One solution to the electrolyte issue is to replace the liquid electrolyte with a solid polymer, glass or ceramic fast ion conductor. The Solid-State Electrolyte (SSE) makes dendritic cell failure and fire unlikely, and so enables the use of a lithium metal anode, replacing the bulky graphite with an ultra-thin anode and increasing the energy density of the cell. This solid-state design opens the opportunity for a safer, denser and high voltage lithium ion cell. Ceramic fast ion conductors such as Li3.25Ge0.25P0.75S4 (ref Kanno and Murayama J. Electrochem. Soc.;148(2001) A742) can have lithium conductivities as high as current liquid electrolyte.
Unfortunately, the physics of the HVS/SSE interface creates a highly resistive layer and high ionic conductivity is not realized when cells are constructed. Nano One has developed a coating that could increase ion conductivity with SSE’s and passivate manganese dissolution in liquid electrolytes while reducing electrolyte instability above 4.2 volts. This innovation has led Nano One to apply for patent protection.
CEO Dan Blondal added “We are encouraged by this innovation and we believe this technology could be of similar value to nickel-rich low-cobalt NMC’s where instabilities, voltage limitations and degradation are preventing commercial adoption in lithium ion batteries. Work initiated with commercial interests is growing and will focus on the integration of these materials with other advances in high energy and solid-state batteries. We look forward to sharing progress on these initiatives as they develop in the future.”
Nano One Materials Corp.