Ti 3 C 2 T x supercapacitors with a hexagonal boron nitride separator manufactured by spray coating

Mobile electronic devices need electrochemical energy storage units to deliver high energy and power densities. Current efforts mostly focus on enhancing the performance of the electrode active materials. However, reducing the weight/volume fraction occupied by the passive components such as electrolyte, separator, and current collector can also dramatically improve the performance of the energy storage devices. Hexagonal boron nitride (h-BN) thin films have shown promising performance as separators in supercapacitor devices due to their electrically insulative character and high ionic conductivity. In this work, h-BN was used as an efficient separator in symmetric titanium carbide (Ti 3 C 2 T x ) MXene microsupercapacitors. The devices were fabricated using layer-by-layer deposition of h-BN nanosheets and Ti 3 C 2 T x via the spray coating method. The total thickness of the symmetric Ti 3 C 2 T x device with the h-BN separator was 20 times smaller than the control device with the Celgard separator. Significantly increased volumetric energy density, together with the facile fabrication procedure reported herein indicates that the sprayed all-2D symmetric supercapacitor devices are promising for microscale and flexible energy storage. Graphical abstract