Abstract
Improving one property without sacrificing others is challenging for lithium-ion batteries due to the trade-off nature among key parameters. Here we report 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.
Highlights
Improving one property without sacrificing others is challenging for lithium-ion batteries due to the trade-off nature among key parameters
As electric vehicles (EVs) have penetrated lithium-ion batteries (LIBs) markets, key electrochemical properties have imposed more challenging standards; while higher energy densities are desired for increased driving mileage, enhanced reaction kinetics are demanded for fast charging and high rate operations
In order to synthesize the popcornlike graphene ball (GB), we developed a chemical vapor deposition (CVD) process for graphene growth
Summary
Improving one property without sacrificing others is challenging for lithium-ion batteries due to the trade-off nature among key parameters. The modification of existing active materials by doping with foreign elements[9,10] or stoichiometric control[11,12,13] can increase the diffusivity of Li ions and the charging rate of conventional active materials with micrometer dimensions Most of those approaches are, effective at the expense of specific capacity. Beside energy density and fast charging, achieving long cycle life, especially at high temperatures (i.e., 60 °C), still remains a challenge for advanced LIBs that incorporate highcapacity electrode materials. Considering the efforts undertaken so far, one of the most realistic solutions for immediately achieving fast charging of cathode materials with a negligible loss in energy density and cycle life involves finding conductive protective materials that can be coated uniformly on the active materials with a minimal content. Finding advanced anode materials is essential because current graphite anodes suffer from Li metal deposition upon high rate charging
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