Importance Score: 65 / 100 🔴
Kuxiu S2: A Step Towards the Future with Semi-Solid State Power Bank Technology
Solid-state batteries represent a significant advancement, offering enhanced power, a more compact design, improved safety, and greater sustainability compared to lithium-ion options. However, the challenge lies in the cost-effective mass production of true all-solid-state batteries. Kuxiu addresses this issue with its semi-solid-state design, touting its S2 as potentially the “world’s safest” power bank and a first of its kind.
Kuxiu S2 Qi2 5000mAh MagSafe Power Bank: Features and Performance
The Kuxiu S2, priced at $79.99, is a 5000mAh MagSafe solid-state power bank that supports Qi2 for 15W wireless charging. Its 5,000mAh (19Wh) capacity provides ample energy to fully recharge the latest iPhone models, which have battery capacities ranging from 3,561mAh to 4,685mAh, at least once. Despite the marketing using the term “solid-state,” the company has confirmed that the battery is, in fact, a semi-solid-state type, a critical distinction.
Having used the Kuxiu S2 for several weeks under normal conditions, it has performed as expected.
The Nuances of “Solid State”
The definition of a solid-state battery is debated even within the battery industry, with classifications ranging from all-solid-state to semi-solid-state and quasi-solid-state. All-solid-state batteries, the future of battery technology, are completely liquid-free. However, achieving mass production necessitates intermediate steps.
Understanding Electrolyte Composition
Solid-state batteries employ a solid electrolyte—a component essential for transferring electrically charged particles between terminals. The key difference lies in the amount of liquid present. Batteries are typically classified as follows:
- Semi-Solid State: Liquid electrolyte comprises 5 to 10 percent of the battery’s active part weight.
- Quasi-Solid State: Less than 5 percent liquid electrolyte.
- All-Solid State: 0 percent liquid electrolyte.
The Kuxiu S2 utilizes a solid-liquid mixed electrolyte, giving it a gel-like consistency, classifying it as semi-solid state.
Lithium Polymer Battery: Examining the Label
The label on Kuxiu’s S2 power bank indicates “Battery Type: Li Polymer Battery.” Traditional LiPo batteries in power banks are known for shorter lifespans and lower energy densities, contrasting Kuxiu’s claims. However, solid electrolytes in solid-state batteries can be made from polymers. Thus, the S2 can be classified as a Li Polymer battery that is also a semi-solid-state battery, potentially making it the world’s first power bank of its kind.
Advantages and Comparisons
Standard lithium-ion batteries contain over 25% liquid, making them more susceptible to leakage and thermal issues than the S2. While the Kuxiu power bank doesn’t leverage all the advantages of all-solid-state batteries, such as even higher energy densities and superior safety, it represents progress. Importantly, Kuxiu can currently mass-produce the S2, helping reduce costs.
Typical 5,000mAh power banks degrade after 300–500 charging cycles, retaining only 60 to 80 percent of their original capacity. Kuxiu claims the S2 maintains 80 percent capacity after 1,000 cycles. While about 60 percent more costly than liquid-based power banks, the S2 should last twice as long before noticeable capacity degradation.
Design and Portability
The semi-solid state battery also increases the energy density. Kuxiu states 360Wh/kg compared to the 300Wh/kg of liquid cells. The S2 is compact and light (10.4 x 6.7 x 1.0cm / 145g), making it more portable than competing models. Anker provides an even smaller and lighter 5K option at 10.2 x 7.0 x 0.9cm / 120g, but that likely reflects material choices rather than energy density.
MagSafe Compatibility and Charging
The Kuxiu S2, as a MagSafe-compatible Qi2 power bank, magnetically snaps onto an iPhone 15 Pro and begins charging. The magnets are reliable, but the aluminum S2, with Corning Gorilla Glass and an “explosion-proof film,” is not immune to minor damage. Three weeks of use resulted in a small nick to the aluminum shell.
While compatible with MagSafe cases, their use may slightly increase heat, reducing efficiency.
Charging and Additional Features
The bottom USB-C port enables passthrough charging, allowing simultaneous charging of the power bank and attached devices. A full charge takes 90 minutes. The USB-C port also supports charging non-Qi2 devices up to 20W. It can even provide a slow charge to power-hungry devices like a 14-inch MacBook Pro.
A double-tap activates a low-current mode for charging small devices, bypassing automatic shutoff features. Though standard, this is a notable feature.
Wishlist
The addition of a kickstand, like those found on its competitors, would enhance the Kuxiu S2’s functionality.
Final Thoughts: Is the Kuxiu S2 Worth It?
Setting aside potentially misleading marketing, the Kuxiu S2 Qi2 5000mAh MagSafe “Solid-State” Power Bank is impressive. Despite a higher initial cost than comparable liquid electrolyte power banks, the S2’s semi-solid-state battery offers superior safety and a longer lifespan, ultimately proving more cost-effective over time.