Standard lithium-ion cells carry charge between electrodes using a freely flowing liquid electrolyte. When a cell is physically compromised, the internal separator can fail, triggering a short circuit. Heat breaks down the liquid, which flows and feeds the reaction: thermal runaway. Peer-reviewed battery manufacturing research confirms that liquid-electrolyte cells remain persistently vulnerable to this failure sequence under penetration or impact, per IOPscience.

Semi-solid-state cells interrupt that chain. The electrolyte is much thicker, closer to a gel, and largely immobile. Less liquid means less material available to heat and spread if something goes wrong. BMX's own explainer frames this precisely: the chemistry changes the failure mode rather than preventing failure entirely, and the company explicitly rejects "fireproof" and "non-flammable" as inaccurate descriptions of the product, according to BMX.

Two limits on the safety claim are worth stating directly. First, semi-solid-state chemistry does not confer any airline exemption; carry-on rules are set by watt-hour rating, not cell type. Second, the actual safety benefit depends on specific cell design and construction, not the category label alone. BMX acknowledges this too, noting that many products marketed under "semi-solid-state" or "solid-state" branding still fail standard safety tests, per the same explainer.

For context, this is still a bridge technology, not true solid-state. All-solid-state batteries, which eliminate liquid entirely, are not commercially available in consumer accessories. At the pilot-line level, all-solid-state cell yields run below 70-80% compared to over 95% for mature lithium-ion production, and manufacturing costs sit at $150-300 per kWh versus $70-100 for conventional lines, according to IOPscience. Semi-solid-state is the meaningful improvement achievable right now.

The SolidSafe Air measures 103 x 70 x 6.8mm and weighs 110g. It holds a 5,000mAh (18.5Wh) cell, supports 15W Qi2 magnetic wireless charging and 20W wired USB-C output when used separately, and recharges via USB-C at up to 15W. Running both outputs simultaneously drops performance to 10W USB-C and 5W Qi2, per Notebookcheck. Available in Titanium Gold, Black, and Silver at $59.99.

The 6.8mm thickness is the headline spec. Macworld called it the slimmest magnetic wireless power bank it had reviewed, noting that the iPhone Air is only marginally thinner at 5.6mm but carries a 3,149mAh battery against the SolidSafe Air's 5,000mAh. Whether the semi-solid-state chemistry specifically enables that thinness, or whether other construction choices account for it, has not been independently established.

The one concrete tradeoff is recharge speed. The 15W maximum input is slower than competing power banks that accept 18-30W, Macworld noted. Notebookcheck measured a full recharge at 1 hour 57 minutes, pulling 1.5A at 9V from the charger. Manageable overnight, less convenient mid-travel-day when time is short, according to Notebookcheck.

BMX also has a larger 10,000mAh lineup with color LCDs, 30W USB-C output, and a microSD variant in development, per Android Authority. Those are not on shelves yet.

The independent performance data is solid. Macworld's 89% result on an iPhone 16 Pro stands as one of the stronger outputs recorded in that lab's Qi2 power bank comparisons. Notebookcheck recorded 87% delivered to a 3,000mAh device, with case temperature rising from 28°C ambient to 34.2°C and holding steady throughout charging, a moderate thermal footprint for active output, per Notebookcheck.

The safety data is a different story. The recall figures and aircraft fire statistics cited in BMX's materials are vendor-originated. None of the early coverage reviewed here mentions UL, IEC, or comparable third-party certification for the SolidSafe line. That absence is a reporting observation, not a condemnation, but it is a gap.

What independent validation would look like in practice: standardized nail-penetration or crush tests conducted by a neutral lab, formal certification under recognized battery safety standards, or teardown analysis confirming the electrolyte composition claimed. None of that exists in the public record yet for this product.

The split for buyers is practical. On usability and size, the third-party evidence is reassuring. On the safety profile specifically, the record currently supports two narrower claims: the SolidSafe Air performs well in third-party charging tests, and BMX's fire-risk case remains largely self-reported.

Semi-solid-state chemistry is a recognized transitional technology between conventional lithium-ion and future all-solid-state cells, and the academic evidence supports the basic premise that less liquid electrolyte changes how a battery fails, as IOPscience confirms. At $59.99 with competitive real-world output, the SolidSafe Air sits in the premium-but-accessible tier of the Qi2 market, per Android Authority.

Safer portable battery chemistry is moving from lab demonstrations to consumer shelves at accessible prices. What comes next, whether that means independent certification, competitive responses, or wider third-party abuse testing, will determine whether BMX's safety claims hold under scrutiny or whether the SolidSafe Air is remembered mainly as the thinnest power bank Macworld ever reviewed.