News on China's scientific and technological development.

Chinese scientists created a rechargeable lithium-hydrogen gas battery for the first time in the world. It has a super high theoretical energy density of 2825 Wh/kg because Li and H are the lightest elements.

Paper in English:

The global clean energy transition and carbon neutrality call for developing high-performance batteries. Here we report a rechargeable lithium metal - catalytic hydrogen gas (Li−H) battery utilizing two of the lightest elements, Li and H. The Li−H battery operates through redox of H2/H+ on the cathode and Li/Li+ on the anode. The universal properties of the H2 cathode enable the battery to demonstrate attractive electrochemical performance, including high theoretical specific energy up to 2825 Wh kg−1, discharge voltage of 3 V, round-trip efficiency of 99.7 %, reversible areal capacity of 5–20 mAh cm−2, all-climate characteristics with a wide operational temperature range of −20–80 °C, and high utilization of active materials. A rechargeable anode-free Li−H battery is further constructed by plating Li metal from cost-effective lithium salts under a low catalyst loading of <0.1 mg cm−2. This work presents a route to design batteries based on catalytic hydrogen gas cathode for high-performance energy storage applications.

News in Chinese:

近日，中国科学技术大学化学与材料科学学院陈维教授课题组在国际期刊《德国应用化学》（Angew. Chem. Int. Ed）发表了题为“Rechargeable lithium-hydrogen gas batteries”的研究文章，首次报道了氢气电极作为正极的电池化学新体系，为基于氢气正极设计高性能电池提供了一种新途径。

氢气（H2）作为最具前景且经济高效的可再生资源之一，凭借其合适的氧化还原电位（0 V vs. SHE）、低过电位（约0 V）以及长期稳定性，可在与高活性电催化剂（如Pt/C）结合时，成为一种极具吸引力的电池电极材料。自20世纪60年代以来，可充电的镍-氢气（Ni-H）电池化学因其高稳定性、可靠性和耐久性，已被NASA成功应用于航空航天领域超过30年。近年来，中国科学技术大学陈维教授课题组聚焦于氢气电池，创制了不同类型的氢气电池体系(Adv. Mater. 2024, 2412108; Chem. Rev. 2022, 122, 16610-16751)，包括先进的镍-氢气电池(Adv. Mater. 2023, 2300502)、卤素-氢气电池(JACS 2023, 145, 25422-25430)、质子-氢气电池(JACS 2021, 143, 20302-20308)以及碳-氢气电池(Nat. Commun. 2022, 13, 2805)等，以其卓越的循环稳定性重新受到关注，并在大规模储能中展现出巨大潜力。这些体系均将氢气电极用作负极。然而，基于氢气负极的电池在0.8-1.4 V的有限工作电压下运行，能量密度相对较低。因此，作者提出，氢气的优异氧化还原特性不仅使其可作为负极，还可作为极具潜力的正极，与低电位负极配对。基于氢气正极的电池在与碱金属负极结合时，可展现出更高的能量密度和工作电压。其中，锂金属负极在高电压和高能量密度的氢气电池应用中具有巨大潜力。

该论文首次报道了一种可充电锂金属-氢气（Li-H）电池，该电池利用了最轻的两种元素Li和H。Li-H电池通过正极的反应H2/H+和负极的Li/Li+沉积溶解反应实现稳定运行。H2正极的优异特性使该电池展现出极具吸引力的电化学性能，包括高达2825 Wh kg-1的理论比能量、3 V的放电电压、99.7%的循环能量效率、5-20 mAh cm-2的可逆面容量、-20-80 ℃的宽工作温区及活性材料的高利用率。此外，作者进一步构建了一种无负极Li-H电池，在首次充电时从低成本的锂盐中沉积锂金属生成负极，进一步提升了电池的实际能量密度和经济适用性。该工作为基于氢气正极设计高性能储能电池提供了一种新途径。

Ultrabroadband integrated electro-optic frequency comb in lithium tantalate​

The integrated frequency comb generator based on Kerr parametric oscillation has led to chip-scale, gigahertz-spaced combs with new applications spanning hyperscale telecommunications, low-noise microwave synthesis, light detection and ranging, and astrophysical spectrometer calibration,,,,. Recent progress in lithium niobate (LiNbO3) photonic integrated circuits (PICs) has resulted in chip-scale, electro-optic (EO) frequency combs,, offering precise comb-line positioning and simple operation without relying on the formation of dissipative Kerr solitons. However, current integrated EO combs face limited spectral coverage due to the large microwave power required to drive the non-resonant capacitive electrodes and the strong intrinsic birefringence of LiNbO3. Here we overcome both challenges with an integrated triply resonant architecture, combining monolithic microwave integrated circuits with PICs based on the recently emerged thin-film lithium tantalate (LiTaO3). With resonantly enhanced EO interaction and reduced birefringence in LiTaO3, we achieve a fourfold comb span extension and a 16-fold power reduction compared to the conventional, non-resonant microwave design. Driven by a hybrid integrated laser diode, the comb spans over 450 nm (more than 60 THz) with more than 2,000 lines, and the generator fits within a compact 1-cm2 footprint. We additionally observe that the strong EO coupling leads to an increased comb existence range approaching the full free spectral range of the optical microresonator. The ultra-broadband comb generator, combined with detuning-agnostic operation, could advance chip-scale spectrometry and ultra-low-noise millimetre wave synthesis,,, and unlock octave-spanning EO combs. The methodology of co-designing microwave and photonics can be extended to a wide range of integrated EOs applications,,.


1月22日，中国科学院上海微系统与信息技术研究所研究员欧欣团队联合美国科罗拉多大学教授Gabriel Santamaria Botello、瑞士洛桑联邦理工学院教授Tobias J. Kippenberg团队，在基于绝缘体上钽酸锂单晶薄膜的电光频率梳芯片研究方面取得重要进展。相关研究成果以Ultrabroadband integrated electro-optic frequency comb in lithium tantalate为题，发表在《自然》（Nature）上。

光学频率梳技术在精密测量、微波合成和天文光谱观测等领域应用广泛。早期的光频梳系统体积大且成本昂贵。当前的研究前沿之一在于如何将这一技术在芯片尺度上实现，从而推动更广泛的应用。借助晶体的电光效应实现微波驱动的光频拓展是集成光频梳的主要技术方案之一，但由于传统电光材料存在双折射过强以及传统的微波电路设计能量利用率低的问题，导致集成电光频率梳光谱带宽较低，限制了这一技术的实际应用。

该研究基于上海微系统所和瑞士洛桑联邦理工学院前期共同构建的钽酸锂集成光子材料与工艺技术，挖掘了钽酸锂在低双折射效应特性方面的优势，并结合微波谐振电路的设计优化，实现了跨度超过450nm、谱线超过2000条的集成电光频率梳。与传统技术对比，钽酸锂电光频率梳将器件缩小至1cm2以内，并将谱宽拓展了4倍、功效提升了16倍。同时，研究证明了钽酸锂电光频率梳的启钥式开启，具有大范围的稳定可调性能。

超宽谱的钽酸锂电光频率梳下一代芯片级的多光源相干通信、芯片级光谱学和超低噪声毫米波合成为未来的相关研究提供了良好平台。