Lithium metal is one of the most attractive anode materials for next-generation lithium batteries due to its high specific capacity and low electrochemical potential. However, the poor cycling ...performance and serious safety hazards, caused by the growth of dendritic and mossy lithium, has long hindered the application of lithium metal based batteries. Herein, we reported a rational design of free-standing Cu nanowire (CuNW) network to suppress the growth of dendritic lithium via accommodating the lithium metal in three-dimensional (3D) nanostructures. We demonstrated that as high as 7.5 mA h cm–2 of lithium can be plated into the free-standing copper nanowire (CuNW) current collector without the growth of dendritic lithium. The lithium metal anode based on the CuNW exhibited high Coulombic efficiency (average 98.6% during 200 cycles) and outstanding rate performance owing to the suppression of lithium dendrite growth and high conductivity of CuNW network. Our results demonstrate that the rational nanostructural design of current collector could be a promising strategy to improve the performance of lithium metal anode enabling its application in next-generation lithium–metal based batteries.
Electrolyte engineering via fluorinated additives is promising to improve cycling stability and safety of high‐energy Li‐metal batteries. Here, an electrolyte is reported in a porous lithium fluoride ...(LiF) strategy to enable efficient carbonate electrolyte engineering for stable and safe Li‐metal batteries. Unlike traditionally engineered electrolytes, the prepared electrolyte in the porous LiF nanobox exhibits nonflammability and high electrochemical performance owing to strong interactions between the electrolyte solvent molecules and numerous exposed active LiF (111) crystal planes. Via cryogenic transmission electron microscopy and X‐ray photoelectron spectroscopy depth analysis, it is revealed that the electrolyte in active porous LiF nanobox involves the formation of a high‐fluorine‐content (>30%) solid electrolyte interphase layer, which enables very stable Li‐metal anode cycling over one thousand cycles under high current density (4 mA cm−2). More importantly, employing the porous LiF nanobox engineered electrolyte, a Li || LiNi0.8Co0.1Mn0.1O2 pouch cell is achieved with a specific energy of 380 Wh kg−1 for stable cycling over 80 cycles, representing the excellent performance of the Li‐metal pouch cell using practical carbonate electrolyte. This study provides a new electrolyte engineering strategy for stable and safe Li‐metal batteries.
Electrolyte engineering via fluorinated additives is promising to improve the cycling stability and safety of high‐energy Li‐metal batteries. The electrolyte in an active porous LiF nanobox involves the formation of a high‐fluorine‐content (>30%) solid electrolyte interphase layer to achieve a ≈3.5 Ah Li || LiNi0.8Co0.1Mn0.1O2 pouch cell with a specific energy of 380 Wh kg−1 under a practical carbonate electrolyte.
Ultrathick electrode design is a promising strategy to enhance the specific energy of Li‐ion batteries (LIBs) without changing the underlying materials chemistry. However, the low Li‐ion conductivity ...caused by ultralong Li‐ion transport pathway in traditional random microstructured electrode heavily deteriorates the rate performance of ultrathick electrodes. Herein, inspired by the vertical microchannels in natural wood as the highway for water transport, the microstructures of wood are successfully duplicated into ultrathick bulk LiCoO2 (LCO) cathode via a sol–gel process to achieve the high areal capacity and excellent rate capability. The X‐ray‐based microtomography demonstrates that the uniform microchannels are built up throughout the whole wood‐templated LCO cathode bringing in 1.5 times lower of tortuosity and ≈2 times higher of Li‐ion conductivity compared to that of random structured LCO cathode. The fabricated wood‐inspired LCO cathode delivers high areal capacity up to 22.7 mAh cm−2 (five times of the existing electrode) and achieves the dynamic stress test at such high areal capacity for the first time. The reported wood‐inspired design will open a new avenue to adopt natural hierarchical structures to improve the performance of LIBs.
Inspired by the vertical microchannels in natural wood as the highway for water transport, an ultra‐thick bulk LiCoO2 (LCO) cathode with vertical channels is fabricated to enhance the transport of Li+. Remarkably, the fabricated LCO cathode shows low tortuosity and high Li‐ion conductivity, and can deliver high areal capacity up to 22.7 mAh cm−2.
Lithium metal based anode with hierarchical structure to enable high rate capability, volume change accommodation, and dendritic suppression is highly desirable for all-solid-state lithium metal ...battery. However, the fabrication of hierarchical lithium metal based anode is challenging due to the volatility of lithium. Here, we report that natural diatomite can act as an excellent template for constructing hierarchical silicon-lithium based hybrid anode for high performance all-solid-state lithium metal battery. This hybrid anode exhibits stable lithium stripping/plating performance over 1000 h with average overpotential lower than 100 mV without any short circuit. Moreover, all-solid-state full cell using this lithium metal composite anode to couple with lithium iron phosphate cathode shows excellent cycling stability (0.04% capacity decay rate for 500 cycles at 0.5C) and high rate capability (65 mAh g
at 5C). The present natural diatomite derived hybrid anode could further promote the fabrication of high performance all-solid-state lithium batteries from sustainable natural resources.
Fast charging of lithium ion batteries is essential for next‐generation energy‐storage systems. However, the poor ionic and electronic transport of anodes with its rather high mass loading limits the ...practical applications of this technology. Herein, a multiscale design from niobium titanium oxide anode material to electrode structure is proposed for fast charging lithium ion batteries with a practical level of areal capacity (3 mAh cm−2). At the atomic scale, the introduction of oxygen vacancy and surface carbon coating enables niobium titanium oxide (TiNb2O7−x@C) to possess excellent ionic and electronic conductivity. For the microscopic electrode structure, 1D TiNb2O7−x@C fibers are tightly assembled to form a high‐speed transport network of ions and electrons throughout the electrode. As a result, the obtained TiNb2O7−x@C electrode shows excellent rate capability (1.83 mAh cm−2 at 1 C) and cycling stability under an areal capacity of 3 mAh cm−2 (2.35 mAh cm−2 after 100 cycles at 0.5 C) in half‐cells. Significantly, a full‐cell coupled with practical level mass loading of lithium cobalt oxide cathode is demonstrated to deliver 1.55 mAh cm−2 at 3 C for the first time.
A multiscale electrode design strategy is reported to achieve fast ionic and electronic transport for improving the electrochemical performance of TiNb2O7 electrodes at high mass loading (>11 mg cm−2). Moreover, a TiNb2O7–x@C/LiCoO2 full‐cell with practical level mass loading is fabricated, which displays excellent fast‐charging performance.
Natural polymer nanofibers are attractive sustainable raw materials to fabricate separators for high‐performance lithium ion batteries (LIBs). Unfortunately, complicated pore‐forming processes, low ...ionic conductivity, and relatively low mechanical strength of previously reported natural polymer nanofiber‐based separators severely limit their performances and applications. Here, a chemical modification strategy to endow high performance to natural polymer nanofiber‐based separators is demonstrated by grafting cyanoethyl groups on the surface of chitin nanofibers. The fabricated cyanoethyl‐chitin nanofiber (CCN) separators not only exhibit much higher ionic conductivity but also retain excellent mechanical strength in comparison to unmodified chitin nanofiber separators. Through density function theory calculations, the mechanism of high Li+ ion transport in the CCN separator is unraveled as weakening of the binding of Li+ ions over that of PF6− ions with chitin, via the cyanoethyl modification. The LiFePO4/Li4Ti5O12 full cells using CCN separators show much better rate capability and enhanced capacity retention compared to the cell using commercial polypropylene (PP) separators. Beyond this, the CCN separator can work very well even at an elevated temperature of 120 °C in the LiFePO4/Li cell. The proposed strategy chemical modification of natural polymer nanofibers will open a new avenue to fabricate sustainable separators for LIBs with superior performance.
A dense chitin nanofiber‐based separator with a high lithium ion transference number is achieved by a facile surface chemical modification method. This is a new type of separator that falls in between a traditional separator and gel electrolyte, and thus shows good comprehensive performance when compared with the liquid electrolyte‐based polyolefin separator and gel electrolyte.
The commercial ceramic nanoparticle coated microporous polyolefin separators used in lithium batteries are still vulnerable under external impact, which may cause short circuits and consequently ...severe safety threats, because the protective ceramic nanoparticle coating layers on the separators are intrinsically brittle. Here, a nacre‐inspired coating on the separator to improve the impact tolerance of lithium batteries is reported. Instead of a random structured ceramic nanoparticle layer, ion‐conductive porous multilayers consisting of highly oriented aragonite platelets are coated on the separator. The nacre‐inspired coating can sustain external impact by turning the violent localized stress into lower and more uniform stress due to the platelet sliding. A lithium‐metal pouch cell using the aragonite platelet coated separator exhibits good cycling stability under external shock, which is in sharp contrast to the fast short circuit of a lithium‐metal pouch cell using a commercial ceramic nanoparticle coated separator.
A nacre‐inspired coating is fabricated to improve the impact tolerance of the separator in a lithium battery via efficient energy dissipation. Remarkably, the pouch cell using the nacre‐inspired porous aragonite platelet coated separator performs with much lower instantaneous open‐circuit voltage change and faster voltage recovery than the cell using the commercial ceramic nanoparticle coated separator under external impaction.
High‐voltage spinel cobalt‐free LiNi0.5Mn1.5O4 (LNMO) is one of the most promising cathode candidates for next‐generation lithium‐ion batteries (LIBs) due to its high specific capacity, high ...operating voltage, and low cost. However, inferior electronic conductivity, transition metal dissolution, and fast capacity degradation of LNMO, especially in high mass loading for high areal capacity, are the critical material challenges for its practical application. Herein, trace multiple Cr‐Fe‐Cu elements doping of LiNi0.45Cr0.0167Fe0.0167Cu0.0167Mn1.5O4 (CFC0.5‐LNMO) cathode is achieved by a blow‐spinning strategy to exhibit very stable cycling at a practical level of areal capacity up to 3 mAh cm–2. It is demonstrated that the Cu, Fe, and Cr doping into the LNMO lattice can suspend the Mn dissolution and improve the Li ion diffusivity and electronic conductivity of the LNMO host. As a result, the obtained CFC0.5‐LNMO cathode exhibits an excellent rate performance (1.75 mAh cm–2 at 1C) and long cycling stability under an areal capacity of 3 mAh cm–2 (78% capacity retention over 300 cycles at 0.5C).
A trace multiple Cr‐Fe‐Cu co‐doping strategy in the high voltage LiNi0.5Mn1.5O4 (LNMO) cathode via a blow‐spinning technique is reported. The co‐modified LNMO can be charged to a high voltage of 4.95 V without structural collapse, exhibiting good rate capability and stable cycling performance under the areal capacity of 3.04 mAh cm−2 (78.2% capacity retention after 300 cycles at 0.5 C).
Gradient structures exist ubiquitously in nature and are increasingly being introduced in engineering. However, understanding structural gradient-related mechanical behaviors in all gradient ...structures, including those in engineering materials, has been challenging. We explored the mechanical performance of a gradient nanotwinned structure with highly tunable structural gradients in pure copper. A large structural gradient allows for superior work hardening and strength that can exceed those of the strongest component of the gradient structure. We found through systematic experiments and atomistic simulations that this unusual behavior is afforded by a unique patterning of ultrahigh densities of dislocations in the grain interiors. These observations not only shed light on gradient structures, but may also indicate a promising route for improving the mechanical properties of materials through gradient design.
Compared to conventional metals with homogeneous microstructures, heterogeneously structured materials with spatially gradient nanostructures exhibit superior mechanical properties, especially ...enhanced fatigue resistance under cyclic loading by suppressing the strain localization and damage accumulation. In this paper, the basic features of fatigue properties, cyclic deformation, and damage mechanism of gradient nanostructured metallic materials are reviewed. The challenges and prospects on exploring fatigue resistance of gradient nanostructured materials in the future are also addressed.
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