Key Takeaways & Executive Findings
- •• • The CrOx/10%eCFx composite achieves an energy density of 496.59 Wh kg−1 at a power density of 49.7 kW kg−1 (50 C), outperforming pure CrOx and CFx electrodes, indicating a significant enhancement in high-rate capability. • • The synergetic effect involves fluorine migration from CFx to CrOx, resulting in homogeneous LiF distribution and improved ionic/electronic conductivity, which is critical for mitigating the resistive accumulation of LiF that typically limits CFx rate performance. • • The composite cathode addresses the low practical capacity of CrOx (due to CrO3 fusion during calcination) and the poor rate capability of CFx, offering a balanced solution for high-energy, high-power lithium primary batteries. • • The work demonstrates a rational design strategy for composite cathodes by regulating discharge potential overlap, providing a pathway to revitalize lithium primary batteries for demanding applications.
Abstract
Chromium oxides (CrOx) and fluorinated graphite (CFx) are two typical cathode materials for lithium primary batteries. The former possesses the highest theoretical energy density but suffers from low practical capacity and inferior rate capability; the latter has the highest theoretical discharge capacity but fails to support fast discharge. Combining the merits of both cathodes via a composite design is desirable, yet the electrochemical performance of such composites remains unsatisfactory. In this work, we identified that by regulating the overlapped discharge potential of these two cathodes, fluorine atoms migrate from CFx to CrOx, leading to a homogeneous distribution of LiF and improved ionic and electronic conductivity, ultimately enhancing high-rate discharge performance. Benefiting from this synergetic effect, the CrOx/10%eCFx composite exhibits a considerably high energy density of 496.59 Wh kg−1 at a power density of 49.7 kW kg−1 (50 C), far superior to pure CrOx and CFx electrodes. We believe that the high-performance CrOx/eCFx composite cathode will justify its practical application in revitalizing advanced lithium primary batteries.
1. Introduction
Lithium primary batteries are indispensable in applications requiring high specific energy, long storage life, and instant readiness, such as medical implants, military electronics, and remote sensors. The cathode material is the primary determinant of electrochemical performance. While several cathodes like SOCl2, MnO2, CFx, and FeS2 have reached industrial scale, none dominate the market due to inherent limitations. Chromium oxides (CrOx) offer the highest theoretical energy density with an operating voltage of 3.0 V and a discharge capacity exceeding 350 mAh g−1, yet they suffer from low practical capacity and poor rate capability caused by the fusion of CrO3 during high-temperature calcination. Conversely, fluorinated graphite (CFx) boasts the highest theoretical discharge capacity but exhibits poor rate performance due to the accumulation of insulating LiF during discharge, which rapidly increases cell resistance.
To overcome these bottlenecks, this study introduces a composite cathode combining CrOx and CFx, leveraging their complementary discharge potentials. The key innovation lies in regulating the overlapped discharge potential to trigger fluorine migration from CFx to CrOx, which promotes homogeneous LiF distribution and enhances ionic and electronic conductivity. This synergetic effect enables the CrOx/10%eCFx composite to deliver an exceptional energy density of 496.59 Wh kg−1 at a power density of 49.7 kW kg−1 (50 C), far exceeding the performance of either pure component. This work not only provides a practical solution for high-rate lithium primary batteries but also offers a design principle for composite cathodes in other battery chemistries.
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Rui Yang, Qingfei Meng, Gengzhong Lin, Yuyang Qi, Shuwei Zhang, Zhongxue Chen, Yuliang Cao (2026). Revitalizing High-Performance Lithium Primary Batteries via the Synergetic Effect of CrOx and CFx. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-025-3647-4
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Frequently Asked Questions
What is the specific mechanism by which fluorine migration from CFx to CrOx improves the discharge performance of the composite cathode?
The fluorine migration occurs due to the overlapped discharge potential of CrOx and CFx. During discharge, fluorine atoms from CFx migrate to CrOx, leading to a homogeneous distribution of LiF. This prevents the accumulation of insulating LiF on the CFx surface, which typically causes a rapid rise in resistance. The homogeneous LiF distribution enhances both ionic and electronic conductivity, thereby improving the high-rate discharge capability.
How does the CrOx/10%eCFx composite compare to pure CrOx and CFx in terms of energy density and power density?
The CrOx/10%eCFx composite achieves an energy density of 496.59 Wh kg−1 at a power density of 49.7 kW kg−1 (50 C). This is far superior to pure CrOx and CFx electrodes, which suffer from low practical capacity and poor rate capability, respectively. The composite leverages the high energy density of CrOx and the high capacity of CFx while mitigating their individual drawbacks.
What are the practical implications of this composite cathode for industrial lithium primary battery applications?
The composite cathode enables high-rate discharge (up to 50 C) while maintaining high energy density, making it suitable for applications requiring instant high power, such as emergency power supplies, military devices, and medical equipment. The improved rate capability and energy density could extend the operational envelope of lithium primary batteries, potentially replacing multiple battery types in diverse scenarios.
What is the significance of the discharge potential overlap in the design of the composite cathode?
The discharge potential overlap is critical because it triggers the fluorine migration from CFx to CrOx. Without this overlap, the synergetic effect would not occur, and the composite would simply behave as a physical mixture with limited performance. By regulating the potential overlap, the researchers enabled a chemical interaction that enhances conductivity and LiF distribution, leading to superior electrochemical performance.
What are the potential scalability challenges for the CrOx/10%eCFx composite cathode?
Scalability challenges include the controlled synthesis of CrOx with consistent electrochemical properties, as CrOx is produced by thermal decomposition of CrO3, which can lead to particle fusion and reduced capacity. Additionally, the uniform mixing of CrOx and CFx at the 10% eCFx ratio must be achieved to ensure consistent performance. However, the composite approach is based on established materials and processes, suggesting that with proper engineering, industrial scale-up is feasible.
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