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Metallic potassium (K) is a desirable anode for potassium secondary batteries due to its low electrode potential in nonaqueous electrolytes and high theoretical capacity. Nevertheless, instability caused by dendritic growth, large volume changes, and parasitic side reactions hamper its practical application. Here, an anode containing metallic K is fabricated by infiltrating an aligned carbon nanotube membrane (ACM) with molten K because of its good wettability to molten K due to the strong capillary forces. The K metal is spatially distributed on the 3D ACM framework, which offers sufficient electrode/electrolyte contact for charge transfer. The robust ACM host provides a large number of K nucleation sites and physically confines the K deposited there, thus mitigating dimensional changes during cycling. The pathways for electrons and ions in the anode are associated to form a mixed conducting network, which is beneficial for the electrochemical redox. Consequently, the anode shows stable plating/stripping profiles with low polarization in symmetric cells using conventional carbonate‐based electrolytes. In addition, dendrite growth is suppressed, and the anode demonstrates excellent suitability when paired with a Prussian blue cathode in a full cell. This design strategy is expected to provide a way to address the problems with using metallic K anodes.

storage. [3] Recently, as a result of the abundance of K, potassium-ion batteries (PIBs) provide a cheaper alternative to LIBs and thus attract more attention. [4] The standard electrode potential of K/K + (−2.93 V vs E 0 ) is close to Li/Li + (−3.04 V vs E 0 ) in aqueous system, even lower than Li/Li + in nonaqueous electrolytes, [5] indicating that PIBs would potentially perform at a higher voltage/power operation. Additionally, recent studies have shown that high-energy metal-O 2 batteries based on K metal have higher round-trip efficiency than their Li and Na counterparts because potassium superoxide, the species generated in the O 2 cathode, is both thermodynamically and kinetically stable. [6] Using K metal anodes poses a particular challenge because K is highly reactive and reacts spontaneously with solvents and salt anions, forming a solid-electrolyte interphase (SEI) layer on the K surface. [7] However, the SEI layer is not optimized to accommodate large volume change during K plating/stripping, resulting in the unrecoverable cracking of the SEI layer. These phenomena will become serious especially at high deposition capacity. Furthermore, the resultant inhomogeneities in resistance and ion flux on SEI layer drive the morphologically nonuniform K growth (dendrite, granule, etc.) that could induce internal short-circuit and other serious safety hazards. [8] This highlights a compelling issue regarding safe cyclability of metal anode, that is, how to regulate the surface reactivity of metal toward organic electrolytes. However, the Secondary batteries based on earth-abundant potassium metal anodes are attractive for stationary energy storage. However, suppressing the formation of potassium metal dendrites during cycling is pivotal in the development of future potassium metal-based battery technology. Herein, a promising artificial solid-electrolyte interphase (ASEI) design, simply covering a carbon nanotube (CNT) film on the surface of a potassium metal anode, is demonstrated. The results show that the spontaneously potassiated CNT framework with a stable self-formed solid-electrolyte interphase layer integrates a quasi-hosting feature with fast interfacial ion transport, which enables dendrite-free deposition of potassium at an ultrahigh capacity (20 mAh cm −2 ). Remarkably, the potassium metal anode exhibits an unprecedented cycle life (over 1000 cycles, over 2000 h) at a high current density of 5 mA cm −2 and a desirable areal capacity of 4 mAh cm −2 . Dendrite-free morphology in carbon-fiber and carbon-black-based ASEI for potassium metal anodes, which indicates a broader promise of this approach, is also observed.

Duchenne muscular dystrophy (DMD) is an incurable neuromuscular degenerative disease, caused by a mutation in the dystrophin gene. Mdx mice recapitulate DMD features. Here we show that injection of wild-type (WT) embryonic stem cells (ESCs) into mdx blastocysts produces mice with improved pathology and function. A small fraction of WT ESCs incorporates into the mdx mouse nonuniformly to upregulate protein levels of dystrophin in the skeletal muscle. The chimeric muscle shows reduced regeneration and restores dystrobrevin, a dystrophin-related protein, in areas with high and with low dystrophin content. WT ESC injection increases the amount of fat in the chimeras to reach WT levels. ESC injection without dystrophin does not prevent the appearance of phenotypes in the skeletal muscle or in the fat. Thus, dystrophin supplied by the ESCs reverses disease in mdx mice globally in a dose-dependent manner.