Paintable battery

Abstract

If the components of a battery, including electrodes, separator, electrolyte and the current collectors can be designed as paints and applied sequentially to build a complete battery, on any arbitrary surface, it would have significant impact on the design, implementation and integration of energy storage devices. Here, we establish a paradigm change in battery assembly by fabricating rechargeable Li-ion batteries solely by multi-step spray painting of its components on a variety of materials such as metals, glass, glazed ceramics and flexible polymer substrates. We also demonstrate the possibility of interconnected modular spray painted battery units to be coupled to energy conversion devices such as solar cells, with possibilities of building standalone energy capture-storage hybrid devices in different configurations.

Figure 1. Paintable battery concept.

(a) Simplified view of a conventional Li-ion battery, a multilayer device assembled by tightly wound ‘jellyroll’ sandwich of anode-separator-cathode layers. (b) Direct fabrication of Li-ion battery on the surface of interest by sequentially spraying component paints stencil masks tailored to desired geometry and surface.

Figure 2. Electrochemical characterization of individual components of paintable Li-ion battery.

Composite electrodes: Charge-discharge curves and specific capacity vs. cycle numbers for spray painted (a, b), LCO/MGE/Li half-cell cycled between 4.2−3 V vs. Li/Li⁺ at C/8 and (c, d), LTO/MGE/Li half-cell cycled between 2-1 V vs. Li/Li⁺ at C/5. Both half cells show desired plateau potentials and good capacity retention. Polymer separator optimization: (e) Addition of DMF to polymer paint gave a mechanically robust separator but drastically reduced ionic conductivity. (f) Addition of SiO₂ (at ∼11% DMF) helped recover the ionic conductivity while maintaining mechanical robustness. Ionic conductivities were calculated from impedance spectra in supplementary Fig. S4. (g) High frequency region of electrochemical impedance spectrum of a typical optimized polymer measured at 23°C. The separator shows low ionic resistance, with ionic conductivity ∼1.24×10⁻³ S/cm.

Figure 3. Characterization of spray painted Li-ion cells.

(a) (Left) Glazed ceramic tile with spray painted Li-ion cell (area 5×5 cm², capacity ∼30 mAh) shown before packaging. (Right) Similar cell packaged with laminated PE-Al-PET sheets after electrolyte addition and heat sealing inside glove box. (b) Mass distribution of components in a typical painted battery. (c) Cross-sectional SEM micrograph of a spray painted full cell showing its multilayered structure, with interfaces between successive layers indicated by dashed lines for clarity (Scale bar is 100 µm). (d) Charge-discharge curves for 1^st, 2^nd, 20^th and 30^th cycles and (e) Specific capacity vs. cycle numbers for the spray painted full cell (LCO/MGE/LTO) cycled at a rate of C/8 between 2.7−1.5 V. (f) Capacities of 8 out of 9 cells fall within 10% of the targeted capacity of 30 mAh, suggesting good process control over a complex device even with manual spray painting.

Figure 4. Demonstrations of paintable battery.

Li-ion cell fabricated on (a), glass slide; (b) stainless steel sheet; (c) glazed ceramic tile. (d) (Left) A packaged and charged tile cell and (right) a similar tile cell charged with a photovoltaic panel mounted on the tile. (e) Fully charged battery of 9 parallely connected powering 40 red LEDs spelling ‘RICE’. (f) A flexible spray-painted Li-ion cell fabricated on a PET transparency sheet, powering LEDs. (g) Spray painted Li-ion cell fabricated on the curved surface of a ceramic mug, powering LEDs. The top electrode (LTO/Cu) was sprayed through a stencil mask to spell ‘RICE’. The cell area in a, b, c, f and g has been highlighted by dashed line for clarity.