Breakthrough in Calcium-Ion Battery Technology
HONG KONG (AP) — Scientists at The Hong Kong University of Science and Technology have developed a quasi-solid-state calcium-ion battery that delivers a reversible specific capacity of 155.9 mAh g⁻¹ and retains more than 74.6% capacity after 1,000 cycles, according to a study published in Advanced Science. Led by Prof. Yoonseob Kim, the breakthrough came in collaboration with Shanghai Jiao Tong University and addresses longstanding issues in calcium-ion technology. Researchers announced the findings in February 2026, positioning the battery as a potential alternative to lithium-ion systems amid concerns over lithium scarcity.
The team employed redox-active covalent organic frameworks as electrolytes, achieving an ionic conductivity of 0.46 mS cm⁻¹ and a calcium ion transport number greater than 0.53 at room temperature, as reported by ScienceDaily and TechXplore. This design overcomes poor ion transport and cycling instability that have plagued calcium-ion batteries.
Prof. Yoonseob Kim's team at HKUST's Department of Chemical and Biological Engineering focused on carbonyl-rich covalent organic frameworks. These materials create aligned channels for rapid calcium ion movement, confirmed through experiments and simulations, according to Interesting Engineering and HKUST announcements.
Innovative Materials and Performance Details
The battery's full cell operates at 0.15 A g⁻¹ for the specific capacity and maintains performance at higher rates. After 1,000 cycles at 1 A g⁻¹, it retains over 74.6% of its capacity, TechXplore and ScienceDaily stated. The quasi-solid-state design reduces leakage risks compared to liquid electrolytes, offering safety benefits.
Here are the core specifications from the research:
- Ionic conductivity: 0.46 mS cm⁻¹ at room temperature.
- Calcium ion transport number: Greater than 0.53.
- Reversible specific capacity: 155.9 mAh g⁻¹ at 0.15 A g⁻¹.
- Capacity retention: More than 74.6% after 1,000 cycles at 1 A g⁻¹.
The publication, titled High-Performance Quasi-Solid-State Calcium-Ion Batteries from Redox-Active Covalent Organic Framework Electrolytes, appeared in Advanced Science around Feb. 13, 2026, based on ScienceDaily and HKUST releases. Sources noted minor variations in terminology, such as "anionic" versus "ionic" conductivity in some reports, but the data remained consistent across Interesting Engineering, ScienceDaily, TechXplore and HKUST.
Collaboration with Shanghai Jiao Tong University supported the work. No exact date for the study itself appeared in available excerpts.
Context in Sustainable Energy Storage
Calcium-ion batteries attract interest due to calcium's abundance and low cost compared to lithium, with a comparable electrochemical window, all sources reported. Lithium-ion batteries, commercialized in 1991, power electric vehicles, grid storage and electronics but face limits from finite lithium supplies and energy density plateaus, according to Interesting Engineering and ScienceDaily.
Historical challenges for calcium-ion systems included sluggish calcium ion transport and instability during cycling. The HKUST design uses structured pathways in covalent organic frameworks to enable practical use, HKUST and BatteriesNews stated.
Broader trends show a shift toward sustainable energy storage amid renewable energy growth. Calcium research has accelerated by 2026, aligning with green energy demands, sources added.
No direct comparisons to commercial lithium-ion batteries appeared in the research, such as energy density or cost per kilowatt-hour. Scalability details, including manufacturing feasibility and large-format cells, remained unaddressed.
Potential Implications for Future Applications
This breakthrough could position calcium-ion batteries as viable options for electric vehicles and grid storage, sources suggested. Calcium's abundance addresses lithium scarcity, potentially lowering costs and enhancing sustainability, according to ScienceDaily and TechXplore.
Prof. Yoonseob Kim said, "Our research highlights the transformative potential of calcium-ion batteries as a sustainable alternative to lithium-ion technology. By leveraging the unique properties of redox covalent organic frameworks, we have taken a significant step towards realizing high-performance energy storage solutions that can meet the demands of a greener future," as quoted in ScienceDaily, TechXplore and HKUST releases. A slight variation appeared in Interesting Engineering: "Our research underscores transformative potential calcium-ion as a alternative to lithium-ion technology."
The quasi-solid-state approach improves safety over liquid electrolytes, reducing risks in applications like grid storage, Interesting Engineering noted. Amid global renewable shifts, such alternatives support scalable storage needs, all primary sources reinforced.
No contradictions emerged among HKUST-related reports. Secondary sources like a 2019 CNBC article on flow batteries offered no specifics on calcium-ion tech, highlighting a disconnect in broader battery discussions.
Outlook for Advancing Calcium-Ion Innovation
Researchers described the development as a "major leap" in calcium-ion viability, according to ScienceDaily and HKUST. Future work may address gaps, including real-world testing for temperature ranges and safety certifications.
Competitive landscapes remain unclear, with no data on comparisons to sodium-ion or magnesium-ion batteries. Verification of long-term stability beyond 1,000 cycles is needed, sources indicated.
The announcement aligns with February 2026 press releases, amid urgency for next-generation batteries. No timelines for commercialization appeared in the research, but the innovation signals progress toward sustainable energy solutions.