We are continuously looking at improving our ming, processing, and manufacturing processes. Some of the projects we are pursuing include:
Improvements in hydrometallurgy, with new methods for producing sulfates by leaching metal ores.
Polymer–inorganic solid–electrolyte interphase for stable lithium metal batteries
The solid–electrolyte interphase (SEI) is pivotal in stabilizing lithium metal anodes for rechargeable batteries. However, the SEI is constantly reforming and consuming electrolyte with cycling. The rational design of a stable SEI is plagued by the failure to control its structure and stability. A molecular-level SEI design using a reactive polymer composite, which effectively suppresses electrolyte consumption in the formation and maintenance of the SEI. The SEI layer consists of a polymeric lithium salt, lithium fluoride nanoparticles and graphene oxide sheets, as evidenced by cryo-transmission electron microscopy, atomic force microscopy and surface-sensitive spectroscopies. This structure is different from that of a conventional electrolyte-derived SEI and has excellent passivation properties, homogeneity and mechanical strength. The use of the polymer–inorganic SEI enables high-efficiency Li deposition and stable cycling of 4 V Li|LiNi0.5Co0.2Mn0.3O2 cells under lean electrolyte, limited Li excess and high capacity conditions. The same approach applies to design stable SEI layers for sodium and zinc anodes.
Use of graphene in the manufacturing of rechargeable battery cells.
Improving one property without sacrificing others is challenging for lithium-ion batteries due to the trade-off nature among key parameters. A chemical vapor deposition process to grow a graphene–silica assembly, called a graphene ball. Its hierarchical three-dimensional structure with the silicon oxide nanoparticle center allows even 1 wt% graphene ball to be uniformly coated onto a nickel-rich layered cathode via scalable Nobilta milling. The graphene-ball coating improves cycle life and fast charging capability by suppressing detrimental side reactions and providing efficient conductive pathways. The graphene ball itself also serves as an anode material with a high specific capacity of 716.2 mAh g−1. A full-cell incorporating graphene balls increases the volumetric energy density by 27.6% compared to a control cell without graphene balls, showing the possibility of achieving 800 Wh L−1 in a commercial cell setting, along with a high cyclability of 78.6% capacity retention after 500 cycles at 5C and 60 °C.
Solvent-free dry powder coating processes to reduce the cost of manufacturing of cathodes in lithium-ion batteries.
A solvent-free dry powder coating process for making LiNi1/3Mn1/3Co1/3O2 (NMC) positive electrodes in lithium-ion batteries. This process eliminates volatile organic compound emission and reduces thermal curing time from hours to minutes. A mixture of NMC, carbon black, and poly(vinylidene difluoride) was electrostatically sprayed onto an aluminum current collector, forming a uniformly distributed electrode with controllable thickness and porosity. Charge/discharge cycling of the dry-powder-coated electrodes in lithium-ion half cells yielded a discharge specific capacity of 155 mAh g−1 and capacity retention of 80% for more than 300 cycles when the electrodes were tested between 3.0 and 4.3 V at a rate of C/5. The long-term cycling performance and durability of dry-powder coated electrodes are similar to those made by the conventional wet slurry-based method. This solvent-free dry powder coating process is a potentially lower-cost, higher-throughput, and more environmentally friendly manufacturing process compared with the conventional wet slurry-based electrode manufacturing method
Improved Manufacturing Methods for Compositionally Gradient Layered Nickel-Rich NMC Cathode Materials Using a Combined Spray Pyrolysis and Fluidized-Bed Reactor
The materials and manufacturing costs of the battery components must be reduced significantly. This is especially true for the cathode materials and their manufacturing methods, which account for approximately 30% of the total cost of the state-of-the-art LIB. The large percentage of the total cost is due to the high cost of the components of the cathode materials and their complex manufacturing methods. Layered Ni-rich oxides of the type Li(Ni1-x-yMnxCoy)O2 with Ni greater than 0.6 (Ni-rich NMC) have recently gained prominence because of their high capacities (200 to 225 mAh/g), high-voltage cyclability (2.0 to 4.5 V), and low cost. Significantly improved performance of hierarchically structured (compositionally gradient) Ni-rich NMC (Ni equals 0.4) cathode powders exhibiting local elemental segregation have been reported through spray pyrolysis. We believe that both the chemistry (all-nitrate precursors) and the method (horizontal spray pyrolysis) can be further improved and developed into a scalable manufacturing method for the new generation of low-cost, high-capacity, high-voltage Ni-rich NMC cathode materials, such as Li(Ni1-x-yMnxCoy)O2 (Ni greater than 0.6). These cathode materials will contain the desired compositional gradient and surface chemistry that will enable superior long-term performance. A high-throughput and scalable manufacturing method for the production of Ni-rich NMC cathode materials of the type Li(Ni1-x-yMnxCoy)O2 (Ni greater than 0.6) by combining a vertically fed spray pyrolysis with a fluidized-bed reaction in a single reactor. This approach will mitigate the possibility of agglomeration, and uniform Ni-rich NMC cathode particles can be produced in a single reactor, making it a continuous production process. The Li(Ni1-x-yMnxCoy)O2 (Ni greater than 0.6) particles having a Ni-rich core, but with a Mn-rich surface, will be produced through rationally developed precursors for spray pyrolysis.
The proposed single solution precursors will use Li, Ni, Mn, and Co starting materials with similar decomposition temperatures (nitrates) along with minor components of Ni and Mn materials with increasing decomposition temperatures (carboxylates and fluorinated carboxylates) maintaining the overall stoichiometry. This novel inorganic–metalorganic composite precursor is expected to form particles with the targeted Ni-poor and Mn-rich surfaces upon spray pyrolysis. Amorphous powders formed during spray pyrolysis can be reacted further and crystallized to uniform particles with increased tap density through fluidized-bed reactor processing. The approach, combining spray pyrolysis and fluidized-bed reaction in a single reactor, using an inorganic–organic precursor, is novel and is expected to lead to a low-cost manufacturing method for the production of these next-generation cathode materials. Along with its high capacity, the Ni-rich NMC cathode particles of Li(Ni1-x-yMnxCoy)O2 (Ni greater than 0.6) produced by this combined method are expected to retain the compositional gradient favorable for the high voltage (2.0 to 4.5 V) and stable cycling performance.