| With extremely high theoretical capacity and low redox potential,new secondary metal battery systems based on Lithium/Zinc metal anodes are one of the most critical ways to solving future energy shortages and environmental problems.However,both lithium metal anodes and zinc metal anodes currently face tough challenges.In the case of lithium metal anode,lithium dendrites tend to grow on the surface of the anode during the lithium deposition.Zinc metal anode also suffers from the growth of dendrites,together with severe corrosion and hydrogen evolution side reactions between the zinc anode and the aqueous electrolyte.These aforementioned issues seriously restrict the commercial application of lithium/zinc metal anodes.Therefore,it is a key point to construct stable lithium/zinc metal anode for realizing highperformance lithium/zinc metal batteries.To overcome existing limitations of lithium/zinc metal anode,this paper developed three-dimensional host materials and two-dimensional protective layers to stabilize lithium/zinc metal anode from the perspective of structural design and interface modulation.The main research contents and results are as follows:（1）To eliminate the uncontrolled growth of dendrites in lithium metal anodes,a novel strategy of three-dimensional hollow-structure induced lithium deposition,i.e.,3D nitrogen-doped carbon cavity modified carbon cloth（named NPCM@CC）,was proposed as a host material for lithium metal to effectively regulate the lithium plating/stripping behavior.Firstly,porous NPCM@CC can reduce the local current density,which is beneficial to retard the formation of lithium dendrites.Secondly,the relatively high affinity of the nitrogen doping sites to lithium reduces the nucleation barrier of lithium.More importantly,the unique 3D cavity structure can induce and confine the deposition of lithium inside it due to its stronger electric field and sufficient space,which favors uniform and dendrite-free lithium deposition behavior in NPCM@CC even under a high deposition capacity.As a result,the NPCM@CC achieves an average coulombic efficiency of 99.1%for 150 cycles（2400 h in total）at a high areal capacity of 4 mAh cm-2,and is capable of cycling steadily for over 1800 h even at an ultra-high capacity of 8 mAh cm-2.（2）To address the issues of unstable native SEI film of lithium metal anode,a 3D fluorine-rich carbon cavity（named FNCS@CC）was designed as a host material for lithium metal based on the previous chapter to regulate the plating/stripping behavior of lithium and stabilize the SEI film.On the one hand,FNCS@CC is capable of regulating the lithium planting/stripping behavior based on its 3D cavity structure.On the other hand,the electrochemically active C-F bonds on the surface of FNCS@CC can effectively improve the lithium planting/s tripping kinetics by in situ derivatization of a LiF-rich SEI.The two have a synergistic effect in inhibiting the lithium dendrites and interface rupture.As a result,the cyclability and rate performance of the FNCS@CC-Li composite lithium anode are both enhanced,such as maintaining an average coulombic efficiency of 99.6%over 240 cycles,a cycle lifespan of more than 450 h at 6 mA cm-2 and 2 mAh cm-2（corresponding to a lithium utilization of 33.3%）,and excellent full-cell cycle performance at low negative/positive capacity ratio（1.5）and lean electrolyte（10 μL mAh-1）.（3）To tackle the issues of uncontrolled growth of dendrites and severe interfacial side reactions in zinc metal anode,an organic/inorganic multifunctional protective layer consisting of a metal-organic framework（ZIF8）modified graphene oxide filler and polyvinylidene fluoride（PVDF）matrix was constructed on the zinc anode surface to regulate the diffusion and deposition behavior of zinc ions and stabilize the electrode/electrolyte interface.The organic matrix of this protective layer can avoid direct contact between the active zinc and the electrolyte,minimizing the interfacial side reactions.Meanwhile,the inorganic filler accelerates the diffusion and desolvation process of zinc ions,ensuring a dendrite-free zinc deposition behavior.As a consequence,the assembled cells based on this protective layer show excellent electrochemical performance,such as a high average coulombic efficiency of 99.6%in 1450 cycles and the highest cumulative cycling capacity(12000 mAh cm-2)at 10 mA cm-2 that has been reported at that time.（4）Given the uneven distribution of ion flux and the easy growth of dendrites in the metal anode,silica nanosheets with abundant micro-mesopores and hydroxyl groups were constructed at the separator/electrolyte interface as an ion sieve for the metal anode to regulate the distribution,diffusion,and deposition behavior of ions.Taking zinc metal anode as an example,uniform micro-mesopores can redistribute the interfacial zinc ions and provide a homogeneous and fast zinc-ion flux for smooth zinc deposition.Meanwhile,the hydroxyl groups weaken the affinity between the ion sieve and the zinc metal to inhibit zinc deposition on the ion sieve,preventing the ion channels of the ion sieve from being blocked by the deposited zinc and failing.As a result,the hydroxylated silica ion sieve imparts the zinc metal anode with superior cycling stability(3400 h at 1 mA cm-2)and a cumulative capacity of up to 12500 mAh cm-2（about 20 times that of a bare zinc anode）.Moreover,this strategy can be conveniently extended to lithium metal anodes and is somewhat universal in terms of dendrite suppression. |
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