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A 2011 Stanford prototype showed how a lithium-ion battery could be made partly see-through by arranging its electrodes as fine grids in clear material. It did not demonstrate a commercial solar-window battery: pairing transparent storage with transparent solar cells was presented as a possible future use.
How does a transparent lithium-ion battery work?
Conventional battery electrodes are opaque. The Stanford team’s approach was to pattern the electrode materials into fine grids, leaving open areas through which light could pass. Chemistry World’s 2011 account describes the grids as trenches formed in clear polydimethylsiloxane (PDMS), a transparent polymer.
The reported cathode used LiMn₂O₄ nanorods, and the anode used Li₄Ti₅O₁₂ nanopowder. A 100 nm gold layer on the PDMS collected current. Water-based electrode slurries flowed into the patterned trenches by capillary action. The electrodes were stacked and aligned, with a clear electrolyte between them; a clear polymer bag enclosed the device, and aluminium strips served as terminals.
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In short, the device did not make the electrode materials themselves transparent. It reduced their visible footprint by arranging them in narrow patterned lines within a clear structure.
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How transparent was the prototype, and how much energy did it store?
Chemistry World reported three prototype configurations. Their measurements show a trade-off: the more transparent version stored less energy per unit of volume.
| Reported optical transparency | Reported energy density |
|---|---|
| 78% | 5 Wh/L |
| 60% | 10 Wh/L |
| 30% | 20 Wh/L |
These figures are the prototype results reported in the 2011 Chemistry World account, not specifications for a product sold today. The report also compared the 60%-transparent configuration with an average smartphone battery of around 100 Wh/L, saying it had about one tenth the energy density. That comparison was attributed to the account’s 2011 reporting and should not be read as a current, matched test of battery products.
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How should the 50 Wh/L and 150 Wh/L figures be understood?
Neither figure was a reported measurement of the prototype. They were forward-looking statements attributed to group leader Yi Cui in the 2011 account.
- About 50 Wh/L: Cui said this could be achievable at that stage through optimization and industrial approaches. It was an estimate, not a demonstrated device result.
- Up to 150 Wh/L: Cui associated this potential with advanced electrode materials. It was a projection, not an achieved result.
These historical estimates do not establish present-day battery benchmarks or the performance of a commercial transparent battery.
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Can solar windows store electricity?
The proposed idea was to combine a transparent battery with transparent solar cells. A window could then capture some incoming sunlight and store energy for later use, such as low-power lighting. Chemistry World described this as a possible application; it did not report an installed system, a product launch, an efficiency figure for an integrated window, or current market availability.
Transparent energy storage and transparent solar generation are separate components in this concept. The battery prototype alone does not show that a window can generate and store electricity as a functioning building product.
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What did the 2011 report establish—and what did it not?
The report documented a laboratory prototype and a method for reducing the visible area of opaque electrode materials. It also described a potential smart-window application. It did not establish that the prototype was ready for retail, that it had been integrated with transparent solar cells, or that a commercial solar-window battery is available today.
The account is Kate McAlpine’s Chemistry World article, published 26 July 2011. It cites Y. Yang et al., Proceedings of the National Academy of Sciences (2011), DOI 10.1073/pnas.1102873108. The construction details and reported performance figures above are attributed to the Chemistry World account.
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