A team at Sichuan University in China is proposing a novel lithium-ion/oxygen hybrid battery system that exploits the advantages and minimizes the disadvantages of both lithium-ion batteries (LIB) and lithium-oxygen batteries (LOB).

As described in a paper in the RSC journal Chemical Communications, the LOB-element supports high energy capacity (for extended vehicle range) and high power output, while the LIB component compensates for the shortcomings in cycle life of the LOB element.

Although lithium-ion battery (LIB) has played a vital role in the consumer market and the state-of-the-art LIB can deliver energy up to ~260 Wh kg^-1, it is still unsatisfactory for the future demands in some high-energy fields, such as electric vehicles (EVs). Development of beyond LIB systems is a way to meet the urgent need. Due to the ultra-high capacity (3860 mAh g^-1) and the lowest electrochemical potential (-3.04 V vs. standard hydrogen electrode) of lithium metal and the inexhaustible ambient oxygen, lithium-oxygen battery (LOB) has extremely high theoretical energy of ~ 3500 Wh kg^-1, which is 10 times higher than commercial LIB, showing great potential as a next-generation high-energy battery.

Nevertheless, its wide application is plagued by a series of existing problems, such as poor round-trip efficiency, unsatisfactory cycling life, anode corrosion, unstable cathodes and electrolytes, as well as the high-cost noble-metal-catalysts (Ag, Ru, Au, Pt and Pd) that are generally used to improve the charge transfer of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). In our view, based on current technologies, these problems will not be solved well for a long time.

… Herein, we propose a novel lithium ion/oxygen hybrid battery system by parallel connection of LIB and LOB, which possesses the characteristics of both LIB and LOB, compensating the disadvantages of one another.

—Mu et al.

Schematic diagrams of the proposed lithium ion/oxygen hybrid battery systems and their working mechanisms under different conditions: (a) low-rate discharge, (b) high-power output and (c) after that a spontaneous recovery process. Mu et al. Click to enlarge.

The Sichuan team used LiNi_1/3Co_1/3Mn1/3O₂ (NCM) and carbon materials as the cathodes of LIB and LOB respectively. The two cathodes are connected together by the external circuits as the cathode of the battery system, and share a common anode.

At low rate, when the LIB component could not meet the energy delivery, the LOB-part would automatically play an extended-range role via the ORR. At high rate, when the LIB-part could not meet the high-power delivery, the LOB-part could be also viewed as a LOC to automatically provide a transient high-power output through both EDLC and Faradaic pseudocapacitance (i.e., ORR) of absorbed O₂ on the surface of O₂-cathode-active-material due to its high surface area.

After high power, the LOC (LOB)-part could be charged spontaneously by the LIB- part, greatly facilitating the power regen of the hybrid system.

… considering the poor cyclability of LOB-part and the discharge-priority of LIB-part, we suggested that, in practical application, LIB-part should be used as much as possible to compensate the shortcoming of LOB-part. While, more researches are certainly necessary to improve the electrochemical performance of LOB.

This work demonstrates that our proposed lithium ion/oxygen hybrid battery system is a promising power device for future EVs.

—Mu et al.

Resources

• Shijia Mu, Ding Zhu, Ruixue Zhang, Kaifang Zhang, Zhendong Ding and Yungui Chen (2018) “A Lithium ion/Oxygen Hybrid Battery with High-Energy and High-Power” Chem Comm doi: 10.1039/C8CC03510E