Lin Chen,Jingwen Zhou,Junxiang Zhang,Guicai Qi,Bin Wang,Jianli Cheng
High energy density Li-CO 2 batteries have attracted much attention owing to the “two birds with one stone” feature in fixing greenhouse gas CO 2 and providing renewable energy. However, poor reversibility of the discharge product Li 2 CO 3 is one of the main problems that limit its application, resulting in poor cycling stability and severe polarization. Herein, copper indium sulfide (CIS), a semiconducting non-precious metal sulfide, is fabricated as cathode catalysts for high-performance Li-CO 2 batteries. Combined with the synergistic effect of bimetallic valence bonding and coordinated electron transfer, Li-CO 2 batteries using CIS cathodes exhibit high full specific discharge capacity, excellent rate capability and cycle stability, namely it delivers a high specific full discharge capacity of 8878 μAh cm −2 , runs steadily from 10 to 100 μA cm −2 , and performs a stable long-term cycling behavior (>1050 h) under a high energy efficiency of 84% and a low charge voltage of approximately 3.4 V at 20 μA cm −2 within 100 μAh cm −2 . In addition, a flexible Li-CO 2 pouch cell is constructed to reveal the potential of employing CIS to fabricate flexible high energy storage devices in practical applications. This work shows a promising development pathway toward next-generation sustainable energy storage devices.
In the past two decades, a lot of high-capacity conversion-type metal oxides have been intensively studied as alternative anode materials for Li-ion batteries with higher energy density. Unfortunately, their large voltage hysteresis (0.8–1.2 V) within reversed conversion reactions results in huge round-trip inefficiencies and thus lower energy efficiency (50%–75%) in full cells than those with graphite anodes. This remains a long-term open question and has been the most serious drawback toward application of metal oxide anodes. Here we clarify the origins of voltage hysteresis in the typical SnO 2 anode and propose a universal strategy to minimize it. With the established in situ phosphating to generate metal phosphates during reversed conversion reactions in synergy with boosted reaction kinetics by the added P and Mo, the huge voltage hysteresis of 0.9 V in SnO 2 , SnO 2 -Mo, and 0.6 V in SnO 2 -P anodes is minimized to 0.3 V in a ternary SnO 2 -Mo-P (SOMP) composite, along with stable high capacity of 936 mA h g −1 after 800 cycles. The small voltage hysteresis can remain stable even the SOMP anode operated at high current rate of 10 A g −1 and wide-range temperatures from 60 to −30 °C, resulting in a high energy efficiency of 88.5% in full cells. This effective strategy to minimize voltage hysteresis has also been demonstrated in Fe 2 O 3 , Co 3 O 4 -basded conversion-type anodes. This work provides important guidance to advance the high-capacity metal oxide anodes from laboratory to industrialization.
Flexible lithium–air batteries (LABs) with a redox mediator (RM) in the electrolyte demonstrate enhanced round-trip efficiency. However, their cycle performance is unsatisfactory due to severe corrosion of the Li metal anode. Herein, we propose a two step gelatinization strategy to fabricate a gradient RMs (including LiI, TMPD, and DMPZ) gel electrolyte, in which the bare electrolyte gelatinization on the Li surface and then the electrolyte contained RMs sequentially gelled on the formed gel. The RMs mainly distributed at the surface and anchored at the cathode side. By suppressing the shuttle of RMs in the electrolyte and alleviating the passivation of the Li anode, the mid-charging potentials can reach 3.44 and 4.08 V at the 15th cycle with and without the LiI mediator, respectively. The energy efficiency is 63% even at the 150th cycle, whereas the corresponding energy efficiency are only 47% and 51% for the LABs with liquid and normal gel electrolytes, respectively. Moreover, the cycle life of the battery containing the gradient gel electrolyte is three times longer than that with the liquid electrolyte. The gel electrolyte further offers the flexibility of the device, and the laminated cells thus fabricated can readily operate under harsh bending conditions.
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