Paper ball-like particles

We have created a new form of ultrafine particles, resembling the shape of paper balls, and discovered their unique aggregation-resistant properties and excellent solvent processability. These particles are found useful for electrochemical energy storage, lubrication, and water treatment. 

Crumpling is a stochastic folding process that turns a flat sheet into a paper ball-shaped particle. This unusual morphology is fractal dimensional and not capable of forming tight contact with a surface or between each other, and can be strain hardened/stiffened under stress, which makes them remarkably aggregation-resistant. It is also a type of hollow structure, of which both the external and internal surface area are accessible. A major problem of ultrafine particles is their tendency to aggregate during processing and application due to strong van der Waals attraction. Particles with crumpled sheets shape represent a new type of ultrafine particles that does not easily aggregate.

We conceptualized the structure-properties relationship of paper ball-liked graphene particles, and using graphene oxide as a model system demonstrated their synthesis by capillary compression of their flat sheets in evaporating aerosol droplets. The resulting particles indeed exhibit nearly universal solution processability without the need of surface functionalization, and can redisperse in solvent even after being compressed into a pellet. Such properties have been found to be advantages for graphene applications in ultracapacitors, batteries, electrocatalysis, water treatment and lubrication.

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